The Many Markets for Nanotechnology september/october 2011
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INDUSTRIAL + SPECIALTY PRINTING September/October 2011 • Volume 02/Issue 05
16 Prescription for Change: A Look at New Regulations in the Label Industry
Kathy Magyar, MACtac Standardization, printing technologies, and legislation will have an impact on pharmaceutical labels in the coming year. Find out what this means for you.
20 Nameplate Knowledge
Ben P. Rosenfield This panel discussion brings to light the challenges and successes of six experienced nameplate producers.
24 Nanotechnology and Printed Electronics
Alan Rae, Ph.D., TPF enterprises LLC Discover what can be accomplished using nanomaterials and how to avoid common problems when using them.
30 Printing an Electrocardiogram Electrode
Andy Greene, FLEXcon Product design is critical to functionality in medical electronics. This article focuses on EKG electrodes and related adhesives.
34 Predictable Print Quality Using Rz Wim Zoomer, Technical Language
Stencil smoothness is a gateway to consistency and repeatability in screen printing. Learn how to set up a system to measure it.
COLUMNS 10 Business Management
Ross Bringans, Ph.D., PARC Read about developing strategic partnerships with companies supplying practical R&D, with materials suppliers, tech specialists, and other manufacturers to help close the gap between R&D and production.
14 Printing Methods
Joe Clarke, Clarke Product Renovation Shear is an important quality in screen printing. This column explains how it’s used to minimize print variations and decrease setup times.
38 Industry Insider
by Mary Boone, Plextronics, Inc The author describes how printed, carbon-based, organic photovoltaics can make products that harvest readily available energy.
40 Shop Tour
AP Industrial/Phoenix Interface Technology Take a look at how this Tempe, AZbased company makes membrane switches, graphic overlays, and other printed-electronics products.
DEPARTMENTS 4 Editorial Response 6 Product Focus 37 Industry News ON THE COVER
INDUSTRIAL + SPECIALTY PRINTING, (ISSN 2125-9469) is published bi-monthly by ST Media Group International Inc., 11262 Cornell Park Dr., Cincinnati, OH 45242-1812. Telephone: (513) 421-2050, Fax: (513) 362-0317. No charge for subscriptions to qualified individuals. Annual rate for subscriptions to non-qualified individuals in the U.S.A.: $42 USD. Annual rate for subscriptions in Canada: $70 USD (includes GST & postage); all other countries: $92 (Int’l mail) payable in U.S. funds. Printed in the U.S.A. Copyright 2011, by ST Media Group International Inc. All rights reserved. The contents of this publication may not be reproduced in whole or in part without the consent of the publisher. The publisher is not responsible for product claims and representations. POSTMASTER: Send address changes to: Industrial + Specialty Printing, P.O. Box 1060, Skokie, IL 60076. Change of address: Send old address label along with new address to Industrial + Specialty Printing, P.O. Box 1060, Skokie, IL 60076. For single copies or back issues: contact Debbie Reed at (513) 4219356 or Debbie.Reed@STMediaGroup.com. Subscription Services: ISP@halldata.com, Fax: (847) 763-9030, Phone: (847) 763-4938, New Subscriptions: www.industrial-printing.net/subscribe.
Nanotubes can make for an interesting geometric shape conceptually, but the money and products currently in the mix make the importance of nanotube very real. Turn to page 24 to get a handle on practical ideas for using printed nanotechnology materials. Cover design by Keri Harper.
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Girl Scout Cookies at $15 Billion a Box GAIL FLOWER
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In August 2011, Mike Williams of Rice University’s news staff wrote an article about how graduate students at Houston, TX-based Rice showed local Girl Scouts how a shortbread cookie could serve as a carbon source for graphene. And graphene is worth lots more than cookies. How did they do it? When Girl Scout Troop 25080 came to Rice’s Smalley Institute for Nanoscale Science and Technology (YouTube video: http://tinyurl .com/3tngrnk), Rice graduate students Gedeng Ruan, Zengzong Sun, Zhiwei Peng, and their professor, James Tour, showed the girls that graphene can be made from any carbon source, including the cookies they were then eating. The commercial rate for pristine graphene runs at $250 for a 2-in. square, making an entire box of traditional shortbread cookies worth about $15 billion in profit after processing. The researchers made high-quality graphene by carbon deposition on copper foil. The crumbled cookie took 15 minutes to re-cook in a furnace flowing with argon and hydrogen gas at a temperature of 1050°C. When it came out, it looked like a small, clear piece of flexible material. As the cookie cooked, a single-atom-thick layer of graphene formed on the oppositeside of the foil, leaving other residues on the original side. If you can make bulk graphene, you might be able to make graphene-based transparent electrodes by combining graphene with a fine metallic mesh. And if you can do that, you might have a challenging product for replacing indium tin oxide as a necessary element for flat-panel
and touchscreen displays, solar cells, and LED lighting. But first, you have to back up a bit to what it takes to make indium. ITO (tindoped indium tin oxide) is a transparent conducting film that is deposited on surfaces using electron beam, physical vapor deposition, or a range of sputter-deposition techniques. It is widely used, limited in supply, and expensive to deposit because it traditionally requires the use of vacuum techniques. If you want lots of indium, you commonly get it as a byproduct of processing zinc, and then you must purify it. It’s complicated. Enter graphene. It’s based on carbon—the most common element around. Researchers at Rice University have made graphene out of cockroaches, chocolate, grass, and many other unusual, carbonbased sources. Results were the same. A tiny film of graphene formed on the opposite side of copper foil. The advantage is that graphene makes for a transparent, flexible product that’s close to the end use. Therefore, solar cells need not be made of glass, and printing on flexible, roll-to-roll substrates can make the end product for a lower price. By the time the Girl Scouts of Troop 25080 make it to Rice University, chances are they’ll have made cookies at some point rather than graphene; however, they won’t long forget the point that physical things can change forms and that research is fun. I’d be willing to bet that each will own devices with flat-panel displays using graphene in the future. I’ll bet you that based on the cost of a cookie—before processing, please.
4 | INDUSTRIAL + SPECIALTY PRINTING www.industrial-printing.net
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The latest equipment and materials for industrial printing
Polyester Film Autotex Soft Touch is the newest polyester film from MacDermid Autotype (macdermidautotype.com). The company says it developed the matte, textured material to provide a uniquely soft, tactile finish, combined with excellent resistance to surface wear, abrasion, and a wide range of chemicals and solvents. It is designed for surface applications such as membrane touch switches, fascia panels, and other tactile applications. MacDermid Autotype explains that the film can be embossed easily and used for creating domed switches that can withstand more than five million actuations and maintain formability and flexibility. The film is compatible with conventional and specialized screen inks. Autotex Soft Touch is available in roll or sheet format in either 150- or 200-μm gauges.
Fluid-Deposition System Fujifilm Dimatix (www.dimatix.com) recently announced the launch of its DMP-5005 Materials Printer, a large-format, non-contact, fluid-deposition system capable of jetting a wide range of materials using the Fujifilm Dimatix 16-jet, 1- or 10-pl, user-fillable cartridges for product and process development and up to five sequentially operating 128-jet, 1- or 10-pl printheads with up to five different functional fluids. The system supports a printable area of 19.7 x 19.7 in. (500 x 500 mm) and is engineered to maintain positional accuracy and repeatability of ± 5 and ± 1 μm, respectively. The printer uses a temperaturecontrolled vacuum platen to register and thermally manage substrates during printing, including plastic, glass, ceramics, and silicon, as well as flexible substrates such as membranes, gels, thin films, and paper products. An integrated drop-visualization system captures droplet formation images dynamically as droplet-ejection parameters are adjusted to produce a tuned printhead and fluid combination. The system also supports printhead calibration on a pernozzle basis. A second camera system facilitates observation of fluid-drying behavior, assessment of print-location precision, and more. 6 | INDUSTRIAL + SPECIALTY PRINTING www.industrial-printing.net
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Upgraded WebFed Screen Press UV-LED curing technology is the latest upgrade to the K61 from Kammann (www. kammann.com). The K61 ECO UV-LED is a roll-to-roll, web screen-printing system that features a complete servomotor drive system and modular design that allows combinations of screen printing, die cutting, laminating, stamping, and finishing. According to Kammann, UV-LED curing uses an average of 8 w/lamp for web systems, eliminates noise pollution from exhaust blowers, emits low amounts of heat, has a compact footprint, and supports more than 10,000 hours of manufacturing use. Other system upgrades include digital web- and tension-control features designed to allow the machine to print color-to-color registration in the range of ± 50 µm based on material thickness and ink viscosities.
Gerber Scientific Products (www.gspinc.com) recently introduced LexEdge II 5-mil a semi-rigid Lexan material that has a customformulated print surface designed specifically for use with Gerber Edge series printers. According to Gerber, LexEdge II 5-mil is ideally suited for the production of dynamic, sub-surface graphics such as membrane switches, keyboard overlays, architectural signs, instrument panels, and exhibit/display work. Gerber also says it is dimensionally stable and resists tearing, abrasion, and heat—and is an excellent material option for producing small decals with a low profile for thinner, smooth-touch label applications. LexEdge II 5-mil is 15 in. (381 mm) wide and available in lengths of 10 and 50 yd (9.2 and 45.8 m).
Screen USA (www.screenusa.com) has added features to the newest version of the HQ-510 RIP designed to increase prepress productivity and drive more Screen brand output devices. The PostScript-language-compatible RIP is based on Harlequin technology, and Screen says HQ-510 RIP v8.3 incorporates all the advances of PostScript 3 and PDF, supports the company’s recently launched PlateRite HD 8900 series thermal platesetter, and is compatible with Windows 2003 Server, Windows 2008 Server 32-bit, Windows 7 32-bit, and Windows XP with Service Pack 2. The RIP engine processes native PostScript, PDF, and XPS files. Version 8.3 accepts PDF/X-4, PDF 1.7, and HD Photo file types. The RIP’s PDF retained-raster feature is designed to accelerate the processing of variable printing jobs, even if they are delivered as basic PDF files. Shared image data are identified and rendered only once, then returned to the RIP process and merged with variable content when required. Optional tools include specialized color management, screening, trapping, TIFF/IT-P1 input, postRIP imposition, and in-RIP OPI.
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Fluorosilicone Gel NuSil Technology’s (www.nusil.com) new FS-3502-1 is a 100 mol%, two-part, white, fluorosilicone gel available in a 1:1 mix ratio. The gel is designed to fill small gaps and backfill electronics in applications that require solvent and/or fuel resistance, and it’s formulated to bond aggressively with most surfaces. According to NuSil, the gel’s cure can be heataccelerated and notes that FS-3502-1 is hydrocarbon-resistant for components exposed to aviation fuels, such as JP-8; chemicals; and solvents used in automotive, electronics, and aircraft applications. According to NuSil, a low Type 00 durometer allows the gel to exhibit low modulus and absorb stresses incurred during thermal cycling. FS-3502-1 is controlled in accordance with applicable ITAR regulations and is RoHS compliant. The gel comes standard in white. Translucent or color-matched gels can be produced.
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Printing equipment used in manufacturing News & Trends
• Automating Your Pad-Printing Operation Automation is an important part of efﬁcient, consistent pad printing. Find out about some of the options designed to enhance speed and precision for industrial applications. • Membrane Switch: Screen Printing 101 The membrane-switch market has experienced dramatic growth and soared to an unprecedented level. • Industry Insider The Importance of Printed Electronics to P&G
www.twitter.com/iSPmag printing photovoltaics P. 22
Top Stories • Printing Photovoltaics Screen printing photovoltaic cells is the most reliable method and fastest growing application in industrial printing.
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Au Co De Fin Ho InInk
TECHNIQUES, TIPS & APPLICATIONS
Collaborating with Industry on Printed Electronics Ross Bringans
PARC, a Xerox company
Building blocks Transistors—the building blocks of many electronic circuits—can now be fabricated with inkjet and traditional printing technologies such as gravure and offset (Figure 1). But what about the performance of these printed transistors compared to those fabricated by conventional methods? A common figure of merit is the carrier mobility—amorphous-silicon thin-film
Printing enables low-cost advantages and novel form factors not easily attained by other electronics-manufacturing methods. The applications, from consumer electronics to biomedical devices, are endless. A great deal of progress has been made recently in printed electronics, but why don’t we see printed devices around us everyday, everywhere? The electronics industry, while continually advancing per Moore’s Law, has been limited in some ways. It is not easy or cost-effective to realize new applications enabled by novel form factors, low-cost volume fabrication, and very large-area electronics such as bendable electronics, smart tags, disposable billboard-size displays, respectively. So the ability to create electronic devices using printing methods similar to those used to print words and images on paper presents many opportunities. For example, such a capability would allow us to make custom circuits that could be different for every copy—analogous to every-page-is-different digital printing. Or, we could print circuits on a wider range of substrates than those used now for electronics, which are usually high-quality semiconductor crystals or glass.
data line 680 µm
Pixel Pad Figure 1 A variety of printing processes are suitable for the manufacture of transistors.
Figure 2 Operational circuit elements printed with inkjet
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transistors (TFTs) used to switch individual pixels in most liquid-crystal-display (LCD) backplanes have a mobility of around 1 in units of sq cm/V sec. Printed transistors using organic semiconductors and printed metals have been demonstrated with mobilities of somewhat greater than 1. However, the polycrystalline arrays used in specialty displays have a mobility of around 100, and the single crystal silicon that is used in most chip applications has mobility much greater than 100. So, while printed electronics is not likely to replace traditional technologies for microprocessors or digital signal processors, it can replace large-area backplanes for displays and create other applications such as control circuitry for sensors and inexpensive identification circuits. How are these transistor building blocks built? The exciting thing about printed electronics is that a device can first be designed in a computer file and then printed directly with an inkjet printer. Think of the semiconductor, metal, and insulator inks as analogous to image printing with cyan, magenta, yellow, and black—just as proofs can be created using digital printers, TFTs can be built by combining the different layers according to the device design. The advantage in both the electronic and the paper cases is rapid trial-and-error in the design phase, which prevents costly mistakes later. Once a circuit has been designed, the printer will be able to choose whether to manufacture using digital techniques when short runs are important, or migrate to gravure or offset for high-volume manufacturing. Compared to inkjet, the latter approaches promise custom circuits, finer features, and enhanced yield, as well as more compatibility with roll-to-roll (R2R) processing techniques. From materials to device design, the capabilities of printed TFTs have improved considerably over the past 10 years. For materials, most work has been done using inkjet-printable materials and especially organic semiconductors, and in the case of the metal layers, most work has been done with nano-particles of silver that have modified surfaces to keep the layers from clumping together before the printing process takes place. For device designs, key work has included getting controllable layers of—and controllable interfaces between—the materials. Ink formulations,
printed sensors, memory and electronics
Figure 3 PARC produced the sensors, amplifiers, logic circuitry, and memory components for DARPA’s blast dosimeter.
for example, must take into account that an initial layer cannot be adversely affected by the solvents in the subsequent layers. It also turns out that the best device results occur for semiconductors that form crystalline arrangements of the organic molecules after they are printed. With these experiences and TFT building blocks, it is now possible to create printed circuits in a wide range of complexities. TFTs can be uniformly arrayed, as is the case for display backplanes where each pixel has just one TFT; or, they can be arranged in a more complex manner, as is the case with circuit elements such as amplifiers (Figure 2). These elements can,
in turn, be arranged into even more complex circuits that enable a variety of applications. Applications More attention was paid initially to display applications enabled by printed electronics, with the hope that R2R printing would facilitate cheaper manufacturing. But more recently, there has been an emphasis on other application directions, ranging from lighting and photovoltaics to ID systems, batteries, memory, and sensors. One example of a challenging application that PARC, a Xerox company, developed was for the U.S. Defense Advanced Research Projects Agency (DARPA). Because we had a september/october 2011 | 11
• PRODUCT CONCEPT • OPPORTUNITY DISCOVERY
• OPPORTUNITY DISCOVERY • PRODUCT CONCEPT
LAB SCALE PROTOTYPES
GAP MATERIALS PROCESS EQUIPMENT
MATERIALS PROCESS EQUIPMENT
Figure 4 Developing strategic partnerships with materials suppliers, tech specialists, and manufacturers can help close the gap between R&D and production.
long-standing capability in printed, flexible, and organic electronics—as well as a comprehensive on-site fabrication and prototyping infrastructure—DARPA chose us to create an all-printed blast dosimeter that could sense and record explosive impacts to prevent traumatic brain injury for field personnel. Furthermore, DARPA required the dosimeter to be low-cost, flexible, and disposable, yet robust enough in the field for useful life lasting more than a oneweek period. Such a system involves sensors, amplifiers, logic circuitry, and memory components—all of which were built at PARC (Figure 3). To achieve the necessary electronic performance, both n-type and p-type TFTs were developed to yield the advantages of CMOS circuitry; these were then combined to produce, for example, the ring oscillators and shift registers that would help process the data. The resulting components achieved the necessary performance and cost advantages, demonstrating that printing technology could play an important part for these types of applications. This experience led us to conclude that moderate-sized circuit elements could be routinely fabricated for a wide range of applications. Furthermore, this moderate level of complexity made it more likely that applications could reach the market sooner than those requiring either
very large numbers of devices or those requiring very high performance—highresolution displays and high-speed logic, for example. THE MISSING ECOSYSTEM Taking such component technologies to the next step—applications in the marketplace— requires an ecosystem. For today’s electronics, there is an established and understood value chain for getting a product to market. If one has a product concept, then the sequence of researchdevelopment-productization-product ramp already exists, whether inside one company or within the infrastructure created by many companies. The frequent looping back amongst these stages, such as redefining the concept after research results are obtained, is also well understood. In the case of printed electronics, however, the necessary ecosystem is only now beginning to be connected. What is missing? Technology is still in flux. One aspect is that the materials, processes, and associated equipment used in research and to develop lab-scale prototypes are still evolving. And these may or may not be the same as those being optimized for production scale-up. To progress, we must ensure that the materials used in early prototyping are capable of the required performance at an application level. One way PARC has been
12 | INDUSTRIAL + SPECIALTY PRINTING www.industrial-printing.net
addressing this gap is by working with chemical and substrate companies to validate and help optimize their materials for particular devices and applications. This typically benefits from a joint or collaborative innovation activity in which the supplier company and the prototype developer go through the process in several iterations to optimize the combination of material, process, and device or circuit design. DIFFICULTY TRANSITIONING FROM PROTOTYPING TO EARLY MANUFACTURING To address this gap (Figure 4), there needs to be an infrastructure partnership in which different technology capabilities are combined to make a more manufacture-compatible product. This could be a technology partnership to add more capabilities to an existing product. As an example, PARC is working with ThinFilm, who has a printed memory product, and by partnering, we are developing a more capable memory for the market. A more universal issue is the availability of matched prototyping and manufacturing. Currently, companies developing a concept or a prototype do not have direct access to a manufacturing capability to take their product to market. Meanwhile, the companies developing the manufacturing capabilities do not have the full range of prototyping and design that will match the need. The two sides
need to work together. In an example of such an approach, PARC has been working with Soligie to streamline and provide this path from concept to production. For a company with a novel product concept or design, this arrangement ensures a greater likelihood of successfully manufacturing the design and prototyping while leveraging shared expertise. This type of collaboration is a step towards what we expect will become more commonplace once the printed electronics technology matures with more standard components and manufacturing processes, and the industry looks more like the existing electronic ecosystem in which it is much more straightforward to hand off research to prototyping and manufacturing.
PARC, a Xerox Company Ross Bringans, Ph.D., is VP and director of the Electronic Materials and Devices Laboratory research organization at PARC, a Xerox company. His organization focuses on novel printed, flexible, organic, and large-area electronics for various applications; MEMS; optoelectronic systems; and other activities. The infrastructure within the organization includes both silicon and optoelectronic fabrication lines for prototype devices.
Once a circuit has been designed, the printer will be able to choose whether to manufacture using digital techniques when short runs are important, or migrate to gravure or offset for highvolume manufacturing. Summary Printed electronics has a very exciting future. Its capabilities enable novel applications in displays, sensors, flexible electronics, and smart devices, as well as entirely new applications that will emerge once companies explore the opportunities further for their customer needs and future growth. This very exciting early stage of the technology means that we are missing an established infrastructure to move ideas seamlessly to products realized in the marketplace. The good news is that we are beginning to see approaches towards creating the necessary ecosystem to address these infrastructure and value-chain gaps. As the field matures, we expect the printed-electronics industry to transform into a stable and accessible set of capabilities where anyone with a great idea can rapidly get it to market. After all, that is one of the key attractions of replacing the complexity of the current electronics business with the advantages of printing. september/october 2011 | 13
High-Shear Printing Joe Clarke
Clarke Product Renovation
There has been a gross misconception in the screen-printing industry that if one wants quality, slow and steady wins the race. Nothing could be further from the truth. Why do the ink mavens tell us to stir some shear into our ink? We go to press only to find that restrictive on-press settings force us to print slowly. If you want impeccable quality and consistency, you must first adjust your product processing to permit high-shear-rate printing. Shear is a direction of the force applied to the ink. Shear stress is force over area— for our purposes, physical pressure on the ink, not the mesh. Shear rate is clearance over velocity. It would be called printstroke speed in any one-print scenario. A sticky wicket The free-radical, UV inks you’d love to print run about 20,000-30,000 cP. Conversely, IMD/IML inks have to adhere to low-energy stocks to be water and high-heat resistant and thermoformable. This requires them to be as high as 70,000 90,000 cP. But it gets worse. They bring with them the arch-enemy of screen printing: high tack or intrinsic cohesion. The press must have four parallel planes: carriage, blade, mesh, and bed or cylinder. The mesh dictates the ink-film thickness but restricts its volume. Most stencils limit edge-acuity at the stock level only. And the ink is notoriously shear-rate thinning. Then all you’ll need to upgrade to high-shear printing is configure the blade to meet the parameters defined below. The need for speed If the ink gurus wanted us to apply shear
stress—physical pressure on the fluid— they’d ship ink in toothpaste tubes instead of insisting we stir it vigorously before use. To upgrade to shear-rate printing, you’ll adjust the blade for maximum stroke speed so that the ink fills the mesh consistently, free of distortion, and seals the mesh as the ink wets-out the low-energy PC or PP and then releases the screen immediately, allowing the ink to level absent wet or dry artifacts. This sequenced list reviews the nine pre-requisites of the printing blade: Convert variable static to consistent dynamic tension. The blade must adapt seamlessly in both stroke and perpendicular directions to convert resting screen tension to consistent printing tension at all points on the image from center to edge and be neither too hard nor too soft. Apply minimal drag on the screen mesh. The PUR polymer should have a very low coefficient of friction and have a conformal edge to fit the mesh with minimal force. It must survive exothermic heat, abrasion, and chemical attack—and maintain its edge during the press run. Meter the requisite ink volume precisely. If the funnel or angle formed between the plane of the mesh and the face of the blade is too long, the ink is broadcast, transferring prematurely and causing wet artifacts—blurring, gain, filling, or sag. If it is too short for its edge and speed, fluid pressure drops resulting in dry-artifacts— pinholes, mesh marks, or streaks. Fill the mesh at maximum stroke speed. It’s like skipping a rock across a pond. Don’t allow a drop in fluid pressure as the edge of the blade reaches the mesh openings. For accurate fluid volume, you
14 | Industrial + Specialty Printing www.industrial-printing.net
Maximum Pressure Dimensional Error
Minimum Speed Dry Artifacts
BOTH ENDS Maximum Funnel Wet Artifacts Slow Speed
Maximum Footprint Slow Speed
Maximum Pressure (on stock) Surface Flaws/ Press Peel
Figure 1 Slow-speed, shear-stress printing with wide-angle blades A 90,000 cP viscosity • Prints lean, dry artifacts, poor release and cleaning • Runs faster, loses volume, sticks, and has poor transfer • Runs slower, may improve release B Narrow window of opportunity for quality C 20,000 cP viscosity • Prints fat, wet artifacts, poor wetting and leveling • Runs faster, gains volume, has surface flaws • Runs slowly, may reduce filling
must stroke fast. Slow speed is the underpinning cause of most surface-appearance flaws such as blotchiness, mottling, filtering, texture, or orange peel. Form a tight upper seal with minimal area and pressure. Screen printing is a pumping process, wherein we must
create a pressure differential between the topside and underside of the screen. This requires the proper dynamic edge, just large enough to eliminate dry artifacts at the best speed and yet small enough to prevent broadcasting and wet artifacts. Eliminate fluid constrictions proximate to the vertex. The vertex is the angle formed where the edge meets the mesh surface. This must be the precise point where the ink reaches sufficient fluid pressure to transfer. Transfer earlier and wet artifacts will arise; later and youâ&#x20AC;&#x2122;ll get dry artifacts. Apply zero net pressure on the stock. The instant the blade puts pressure on the stock, the interface area between blade and mesh increases; therefore, the interface pressure drops in direct proportion. As a result, wet and dry artifacts ensue along with a multitude of surfaceappearance flaws. Develop an immediate lower seal. The best stencil ever made can instantly be rendered useless given sufficient lag
time between ink transfer and the lower stencil to stock seal. For this reason, and to prevent ink broadcasting, it is critical to print at a minimal angle. Enable minimal press peel or offset to crown. Peel and offset not only ruin the mesh, but also the image along with it. Surface-appearance flaws and dry artifacts are exacerbated by peel or offset to crown. With the settings described herein, the need for either mesh-wrenching setting will be between zero and minimum. Figure 1 shows how shear-stress printing has underpinned every flaw in screen printing for decades. Viscous inks (A) climb an angled or buckled blade while lower viscosity inks (C) flow too fast or too soon and parallel to the screen mesh. Between the two is a dangerously narrow window of opportunity (B). Conversely, high-shear-rate printing uses a minimum angle, minimum pressure, maximum flood and print speeds, and minimum peel/offset. Flatbed rates are the limit of feed and cure speeds, while cylinder-press speeds
with IMD/IML inks typically run flaw-free between 1800-2600 pieces/hr with highshear-rate printing. To upgrade to shear-rate printing, match the polymer to the mesh count, match the dynamic edge to the speed limit of the press, and match the profile to the volume required. Always minimize the angle to eliminate wet artifacts. Always minimize the pressure (downward force) to maintain dimensional accuracy, and always maximize the speed to meter the ink accurately and eliminate wet artifacts. Then you can minimize peel/offset, setup times, and variations in your prints.
Clarke Product Renovation Joe Clarke is the president of Clarke Product Renovation (CPR), a company that specializes in solutions for PTF circuitry, biomedical apps, PV, IMD/IML windows, gradients, and more. He can be reached at email@example.com.
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PRESCRIPTION FOR CHANGE: A Look at New Regulations in the Label Industry
Find out how standardization, printing technologies, and legislation will have an impact on pharmaceutical labels in the coming year. Gail Magyar MACtac
16 | INDUSTRIAL + SPECIALTY PRINTING www.industrial-printing.net
he prescription-labeling industry evolves continuously. From advancing technology to improving regulations, prescription labelers must be educated about the ongoing changes and look for solutions to improve prescription-labeling safety as required by the prescription-labeling industry. In 2012, the industry can expect even more changes in printed prescription labels. Because the increased elderly population fi nds labels difficult to read and many patients think the labeling system is too complex, demands for improved labeling are increasing. LABEL STANDARDIZATION To increase patient safety, the U.S. Pharmacopeia Convention drafted a proposal to standardize label regulations, which could be the fi rst standardized requirements ever established specifically for prescription labels. The proposal suggests that each label include 12-pt font size, prioritized information, clear descriptions, and additional white space. The overarching problem is whether or not stakeholders can bear the burden of these changes, because along with these standard requirements comes a series of necessary adaptations. As for the labeling industry, the problems are most likely minimal and will not affect the quality of labels produced by suppliers and converters. The adjustment to the changes simply requires suppliers and converters to be able to have enough material to support the changes. The larger font sizes and additional white space increase the amount of label material needed, which results in increased manufacturing capacity. Because pharmacies must conform to the changes, purchasing larger labels from suppliers and converters will most likely become a bigger burden on their budgets. Although these are minor adjustments, the changes could take a toll on the parties involved. Larger labels and clearer descriptions for prescription labels are the latest priorities, but the question is: Are they the only changes scheduled for prescription labels in the future?
LABELING TECHNOLOGY Prior to the new label regulations, the prescription-labeling industry already witnessed a series of changes, leading pharmacies to change from toner fusion printing to direct thermal printing. In the future, a possible shift from direct thermal to another print-on-demand technology could also occur. The important thing for all parties involved to remember is that all print methods available for prescription labeling today have their challenges. It becomes a tradeoff for the pharmacy based on what is most important. Toner-fusion printers provide a very clear image. And because of the tonerâ&#x20AC;&#x2122;s bond to the paper, the image is extremely durable and less sensitive to heat, water, and UV exposure. However, toner fusion printers are sheet-fed, so they can curl
diminishing. With todayâ&#x20AC;&#x2122;s technology, UV overcoats can actually be counterproductive to printing because they can inhibit the labelâ&#x20AC;&#x2122;s ability to reach its full image density. The advanced thermal chemistry of direct thermal printing is erasing this problem and has become the preferred printing method at some large retail pharmacies. As we look to the future, one potential printing technology the market could shift toward is thermal-transfer printing. Thermal-transfer printing is a type of variable printing similar to direct thermal. It uses the same printers used for direct thermal but instead the printhead heats a ribbon to produce durable images on a wide variety of materials. It is less sensitive to light, heat, and abrasion, which increases the lifespan of the printed material.
As for the labeling industry, the problems are most likely minimal and will not affect the quality of labels produced by suppliers and converters. The adjustment to the changes simply requires suppliers and converters to be able to have enough material to support the changes and cause issues with paper jamming. Toner-fusion printer cartridges are messy, and printers are much larger than direct thermal printers, taking up much-needed space in pharmacies. Many prescription labels are currently printed with a technique called direct thermal printing. The change to direct thermal printing was implemented mainly due to ease of use of the print method. This method uses a print head that applies heat to the chemicals on the surface of the paper without the use of a toner cartridge or ribbon. Direct thermal printing eliminates the need for toner cartridges and ribbons in the printer, reducing the timeconsuming and messy hassle of changing them after the toner or ribbon is used up. Previously, limitations on the durability of direct-thermal label stocks required a press-applied UV coating to enhance environmental protection. However, with the advancement in direct thermal technology, the need for press-applied UV overcoats is
Thermal-transfer printing has demonstrated the ability to be durable in other markets. However, Health Insurance Portability and Accountability Act (HIPAA) laws mandate that personal information be destroyed. Because printing methods such as thermal transfer use ribbon technology and imprint reverse images of the printed information on the ribbon, ribbons need to be changed often and destroyed after use. Destroying the ribbons is an additional step pharmacies would need to implement, which adds cost and complexity. The additional burden of destroying the ribbon is a tradeoff that needs to be weighed against the durability advantages of the labels themselves. For today, the simplicity of direct thermal printing, the lack of ribbons and its small printer size make it the print method of choice for pharmacies nationwide. Until the technology advances further, label-stock suppliers and converters have to understand the stability issues SEPTEMBER/OCTOBER 2011 | 17
Test length ranges from 24 hours to 30 days (Figures 1 and 2). At the end of the exposure process, the sample labels are measured for readability, as well as measuring the density level of the remaining image.
Figure 1 Heat (82° C/ 180° F) 20-day endurance-test results
Figure 2 Initial activation after day one of testing
surrounding the products currently used and provide the best assurance they can to pharmacies and patients. Responsible testing All pharmacies, however, do require products to meet certain expectations such as IPA resistance, hand sanitizer, heat and humidity. To address the pharmacy requirements, label suppliers and converters conduct a variety of endurance tests on their labels under various conditions. They ensure their labels hold up to extreme exposure in heat, humidity, UV exposure, water, and multiple household products, among others. Some tests are more robust than others, pro-
ducing different results and varying label life spans. By determining common storage areas for prescription bottles—bathrooms and kitchens being the most common—it’s easy to understand the types of environmental exposures labels needed to best withstand, which also dictate the type of simulated real-world environmental tests that are required for testing. An example of a test procedure uses image samples from a typical direct thermal printer at default settings. Labels are then exposed to varying environmental conditions and common household products, water, heat, humidity, UV light, hydrogen peroxide, and more for a specific period of time.
18 | Industrial + Specialty Printing www.industrial-printing.net
New legislation The state of California implemented standards for prescription labeling that were in full effect January 1, 2011. The goal of the standardization was to increase patient compliance when taking medication to improve outcomes and patient safety. Because the changes were patient centered, California has the potential to be a model for streamlining standards from state to state. Although California has taken the reins in terms of looking out for patients, its patient-centered approach may be difficult to implement across the border. It seems clear that patient safety involves more than the information on the label. Expiration dates of prescriptions are supposed to last for one year. But it is not uncommon for patients to keep them around longer. Therefore, maintaining image quality over an extended period of time is critical for label suppliers and converters, and the type of label supplied contributes to longevity. Continuous upgrades in prescription labeling put pressure on the label suppliers and pharmacies. All of those involved in the supply chain must be prepared to handle changes, whether they will be applied immediately or put into effect over time, especially in regard to the multiple directions prescription labeling can go in upcoming years.
gail Magyar MACtac Kathy Magyar, marketing manager, MACtac Roll Label, has more than 16 years of experience with a concentration on the development of prime papers and thermal products. Her expertise lies in the area of direct thermal imaging, and she is responsible for managing direct-thermal and thermal-transfer products and handling strategic product development and introduction
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This roundtable discussion gives insight into the business of nameplate production and what it takes to be successful in the marketplace. Ben P. Rosenfield
ameplates are key components. They’re among the most prominent types of brand or product identifiers and can be used to enhance the appeal, usefulness, and safety of a variety of equipment types (Figure 1). They must also, in most cases, last as long as the items to which they’re affi xed. In addition, nameplates are as functional as they are decorative, which may explain why many specialty printers also produce tags, faceplates, panel fronts, and graphic overlays (Figure 2), all of which share similar performance requirements. The following conversation presents the perspectives of six industry experts, reveals some of their most common challenges, and offers tips that any nameplate business can use to boost its bottom line. The panel includes: ALAN DAVIS President, Tapecon www.tapecon.com BRANDON RICH Graphics Manager, Hallmark Nameplate www.hallmarknameplate.com DONALD RUDNICK President, Nameplates for Industry www.nameplatesforindustry.com LISA SAVEGNAGO President, Nameplate and Panel Technology www.nptec.com JOSH SHELTON Nameplate Sales Director, Holland 1916 www.holland1916.com
DEBORAH WARNER President, Graphic Label Solutions www.graphiclabelsolutions.com
What types of customers or industry segments approach you for nameplate production? DAVIS Business machines, electronics, power controls, medical—industrial OEM—those are the main segments. RICH Mostly medical, military, a lot of scientific-measurement equipment, some appliances, and a lot of transportation— trains, aerospace, and others. That’s the core of it. RUDNICK We’re selling generally to manufacturers of medical devices and instruments, industrial equipment and devices, a lot of handheld instruments, as well as food-service equipment. SAVEGNAGO Medical industries, automotive, telecommunications, and others. SHELTON Industrial equipment, a lot in the energy marketplace—from oil and gas to other types of production equipment—and aerospace, lifting and rigging, and other industrial applications. WARNER OEMs in automotive, medical, consumer electronics, and industrial equipment.
What types of equipment do you use in the production process?
20 | INDUSTRIAL + SPECIALTY PRINTING www.industrial-printing.net
DAVIS For printing, we have clamshell, cylinder, and roll-to-roll screen printing. We also have flexo and digital. We’re starting to do more nameplates and faceplates with inkjet. We even do a few in digital eletrophotography because we’ve gotten into some serializing and sequential numbering and variable printing. In finishing, we use laminating, diecutting—roll-to-roll and sheet fed—and embossing RICH Most of it is screen printing. We do some digital printing with inkjet and offset. As far as finishing, we use steel-rule dies in clamshell presses, and we also do digital plotter cutting and laser cutting. RUDNICK Traditionally, it was all screen printing in our facility. Today, it’s a combination of screen printing and digital— probably half of the products we make are a combination of both digital and screen printing. We’ve been using digital offset for 12 years, and we also have flatbed UV inkjet technology. We do steel-rule diecutting and laser cutting, and we’ve been doing urethane doming for quite a number of years. SAVEGNAGO In screen printing, we use semiautomatic, 3/4 automatic, and fully automatic presses. We use a photoprocessor for photosensitive aluminum and a variety of finishing equipment for metal nameplates. SHELTON We use screen-printing presses— no digital equipment at this time—and in finishing we have punch presses, shears, and other tools.
WARNER Flexo, sheet-fed and roll-to-roll screen printing, letterpress, and several types of digital printers—sheet fed, roll-toroll, and UV.
What is the most common misconception customers have about nameplates, and how do you educate them? DAVIS Sometimes customers think you just push a button and it just spits out nameplates, but there’s a lot of preparation involved. You have color matching, different finishing operations, and other special processing considerations. Our sales force is very experienced and successful in working with customers in design aspects and helping them understand idiosyncrasies of nameplates and faceplates. RICH We get a lot of raster graphics, and people ask us to manipulate those. For example, they think changing a word that’s placed on a gradient is as easy as clicking on text and typing, but we have to match that gradient. A lot of people also assume they can achieve certain colors on certain materials. People will tell you to match a color that’s meant to be printed on coated paper, but when you just lay a sheet of plastic over the paper, you get a totally washed out color. We find that calling customers and educating them by phone can make them happy. RUDNICK The most common misconception is that we just press a button and the product comes out the other end. We teach customers that a nameplate is a custom manufactured product and that five-day turnaround in our industry is really quick—especially when the average is eight to ten days.
Figure 1 Nameplates combine aesthetics, functionality, and durability. Photo courtesy of Graphic Label Solutions and Empire Screen Printing.
they say it’s a pretty simple product. We use this as an opportunity to educate them about lead time, selecting the right type of nameplate for their environments, and ways we can help them with their businesses. We do a lot with our Website and social media. We have a lot of phone conversations and see a lot of value in faceto-face interactions.
WARNER We have a whole training program for our customers. Too few are going into lean manufacturing, so we go in and do a complete analysis on the way they currently purchase. It gives us an opporSAVEGNAGO Customers think we put the job tunity to come back and offer value-engiin a computer and all of sudden we get an neered solutions. I think it’s really good to end product, like printing a mailing label. A work with customers to help them develop lot of people need to be educated about the an accurate forecast of their needs. substrates, adhesives, and application surfaces. That’s extremely important. You have These days, everyone wants to educate them about surface energy and to commoditize printing and other qualities. You get people who don’t demand the cheapest prices. have any engineering background. How do you address pricing as
part of customer education?
SHELTON There are very few nameplate experts out there, so customers often see a printed or etched stainless-steel tag and
DAVIS We’re more successful with customers who are looking for our ex-
pertise to add to theirs to design a unit. When you talk about internal engineering resources or design resources, those carry some additional overhead that you have to cover. You have to evaluate the inquiry and what type of customer it is so that, in a way, you’re picking the customers in the industries in which you want to be successful. RICH Customers will be referred to me and will ask why they’re being charged double what they paid last time just for artwork? I’ll have to explain that we had to rebuild their art file. If we were to print it, we know they would reject it. They’re usually pretty understanding. RUDNICK You try to explain the differences in base materials that can be used, the types of adhesives, the printing process itself, and the influence of how the product is being used. You get customers who buy the cheapest, and it’s not unheard of for them to come back to us, explaining that they didn’t realize there was such a difference.
SEPTEMBER/OCTOBER 2011 | 21
Figure 2 Faceplates (left), panel fronts, overlays (right), and other products share enough similarities to nameplates that some producers specialize in them as well. Photos courtesy of Nameplates for Industry (left) and Tapecon (right).
Savegnago Everything we do is custom. We have to color match everything in screen printing. That takes expertise, as does getting the tolerance and the tight registration in our printing. If you want to go to China and get a cheaper price, you go right ahead. Good luck. As far as pricing, sometimes people think it’s too expensive. They leave, and eight months later I get a phone call asking me to make that product because it didn’t turn out as expected. Shelton Sometimes people don’t understand how the nameplate reacts in the field. Or maybe lead time is a huge problem for them. We ask these types of questions. We try to talk to people about reducing inventory; we’re definitely a big proponent of lean manufacturing. We also have a strong lead time, and that can lead into auxiliary savings that customers can see compared to just the price of the job. The commodity battle is definitely a battle we all have to face. Warner We look at the total piece of business. We don’t look at it from the entryway; we look at it from 20,000 feet away. We develop what’s called linear pricing. It doesn’t matter whether they want to order one piece or 10,000 pieces. We can control cost that way.
What are some of the challenges you face in prepress, printing, finishing, or other areas of your business, and how do you overcome them? Davis It’s always a challenge to keep up as prepress changes and gets better. There’s a lot of digital equipment out there, but how much of the equipment is geared toward nameplates and faceplates? You have do a full range of tests to make sure you still have the durability, that you can emboss it if you need to, that you are getting full adhesion of the ink onto the plastic substrates. Rich Number one is the files customers send us. They’ll just use whatever fonts they want, but they’ll only put on a note and tell us what font they used. Or they’ll use a proprietary font that isn’t for sale to the public. We also get a lot of conflicting information between the art file and the engineering file. Another problem is not having any dimensions to go by. If they don’t know the dimensions, we can output a line-art version of their product 1:1 on film, send it to them, and they can lay it over their part to see how it fits.
22 | Industrial + Specialty Printing www.industrial-printing.net
Rudnick Customers will often come in with a design that looks nice but isn’t suitable for the process. They take time to create art without taking into account the limitations of the process, whether it’s the relationship of print to cut or the fineness of lines. On our end, one challenge is working on a nameplate that must fit in a recess—getting the tolerance right so it fits without hanging up or having too much space around it. We put up a red flag for production when there’s a recess so we can take steps necessary to understand the tolerances involved. Savegnago Art files. Customers take images they like off of the Internet and don’t understand that the resolution they have is too low. We give them a list of what’s best. In screen printing, we have to watch ink viscosity, and the technicians have to be really well trained and watch what they’re doing so they can respond right away if something goes wrong. Shelton We have approved art formats we can use, and we work really hard to get our customers to give us those formats. We can make it with a bar napkin, but we’d really prefer not to. From a sales standpoint, we set expectations with our customers regarding what we need, and we work on the
front end to get it. Sometimes customers don’t understand what we’re trying to accomplish in the proofing stage and don’t always understand the whole process. As a sales team, we try to educate up front. That’s probably our main challenge. NEW from Chromaline®
Warner The biggest challenge was going to lean manufacturing and analyzing the flow from prepress to getting on press to taking the work to finishing. We get the process owners very involved in tracking what they currently do, looking at it, finding opportunities for improvement, and making those recommendations. They are empowered to control their own processes.
What other advice can you give nameplate producers to help them improve their best practices and customer interactions? Davis You have to document procedures, have standard operating procedures, learn from your mistakes, and have consistency throughout production. Experimentation is important so that as things change, you have some R&D going on—some testing—to know that everything still performs the way it should. Rich Educating the customer about their own product is a big part of it. As far as best practices go, keeping a really detailed database of a customer and all of the different parts they have is very helpful. They make come back ten years later with a new part and want to know what material they used and what colors they had so they can make everything the same. That’s something that comes up a little more frequently than you’d think. Rudnick Give the customer what they want, not what they ask for. Work on lean manufacturing. Standardize so that all of your presses have the same setup—squeegees are in a particular spot, and tape, scissors, and whatever tools the operator needs are at every workstation and set up identically. The printer can then move from one press to the another and not have to look for anything.
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Savegnago Work with contractors who can meet your tolerances. I’ve gotten plates back that have shear marks on them. Contractors will work within a tolerance, but the tolerance I specify is so high that it’s blatantly obvious when they don’t cut a piece within the tolerance that I like. Shelton Be proactive in asking good questions. Learn how customers use the products you manufacture. Warner You have to listen to the people who own the process— who do it every day. They know it better than anyone, so you listen to find out what they think can be improved.
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Nanotechnology and Printed Electronics This article demystifies the expansive landscape of printable nanomaterials and describes their many uses in modern applications. Alan Rae, Ph.D.
TPF Enterprises LLC
24 | INDUSTRIAL + SPECIALTY PRINTING www.industrial-printing.net
anotechnology and printed electronics are business and technology areas that have been hyped mercilessly in the last 10 to 15 years, with the promise of markets of literally trillions of dollars and the opportunity to give a shot in the arm to traditional industries suffering great structural change, such as the printing industry. A lot of money has been thrown at nanotechnology worldwide—nearly $2 billion this year in the U.S., according to the National Nanotechnology Initiative, with matching funds in Asia and Europe and an equivalent amount again being spent by industry. Most of the government funds in the U.S. have gone to universities and to set up outstanding National Science Foundation centers, such as the Center for High-Rate Nano Manufacturing (www. nano.neu.edu), small-business grants have stimulated partnerships and spinoffs, and there has been groundbreaking work in developing new materials and systems. The new-materials businesses, like many others, did not escape the recession—many went down. The intellectual property (IP) they generated, however, is being regenerated in new ventures and in larger companies that bought the IP or the small companies. Pixelligent is one company that made it out of Chapter 11 successfully, making nanosized semiconductors to enhance LED performance. PRINTING IN ELECTRONICS There is a great deal of printing already in use in electronics, ranging from photolithography to screen printing. The target of roll-to roll printing has been hampered by materials issues and competition from other forms of circuit formation that are mature, low cost, and improved incrementally. Companies with great technology in roll-to-roll processing, such as Polaroid and Kodak, have created the technology base for companies such as Konarka to thrive in printed electronics—in Konarka’s case, in flexible solar cells. The traditional route to circuit-board manufacture involves glass cloth impregnated by resin sandwiched between layers of thin copper foil, itself formed by continuously plating copper on a cylindrical electrode. The copper is patterned using photolithography and etched to produce conductive paths, and then the laminates
are joined together with intermediate glass-epoxy layers, aligned and densified in laminating presses not unlike those used to manufacture plywood. Layer-to-layer interconnections are drilled using mechanical drills or lasers and plated to form interlayer connections. The fi lling may be completed using further plating or screened conductive paste, and subsequent layers may be built up by sequential deposition of epoxy and copper patterns using photolithography. Protective surface fi nishes such as OSP (Organic Solderability Preservative) solder or silver are applied by liquid coating, hot-metal dipping, electroless plating, or plasma techniques, and the board is ready to receive its solder mask—patterned by photolithography—and solder paste, patterned by stencil printing. Integral resistors or inductors may be printed or plated. Embedded capacitors are normally developed by etch, revealing dielectric layers sandwiched between copper foil. Board manufacturing is a complex process with many steps. The idea of using an alternative additive process is attractive, with a great deal of success in relatively large-area applications such as the solar-cell and display markets, as well as membrane switches for keyboards. But there has been very limited penetration in mainstream electronics. Nanomaterials can have a wide range of compositions and morphologies, as shown in Figure 1 for conductive materials. CHALLENGES IN USING NANOMATERIALS Economic sensibility requires the use of low-cost substrate materials massproduced for other applications, such as polyesters. The materials available to form circuits on these low-temperature substrates (organic semiconductors or
conductive adhesives) do not have enough electron mobility or conductivity. Many application markets, such as current displays, are flat in format. Roll-to-roll processing is not an obvious candidate for production. Sputtering and other vapor-deposition techniques are cost-effective and have been used widely in the production of RFID antennae, displays, solar cells, and other applications in flat markets. The potential use of nano-based inks in cleanroom environments makes production engineers anxious. Great care must be taken to prevent the dispersion of aerosols during processing or of dried materials in post processing, but proper techniques eliminates such issues Nano hype in Europe has been followed by nano pushback, particularly from environmental groups and NGOs. As with any new material, there is no epidemiological information, and toxicological information is sparse. Much of the early work on toxicology of nanomaterials was allegedly carried out on impure materials such as carbon nanotubes containing up to 30% Ni or other catalyst residue, as well as amorphous carbon or buckyballs that had been dispersed in a toxic, organic solvent. It is almost impossible to deconflate the effects of the impurities and the actual material. Silver has also received enhanced attention due to its widespread use in antimicrobials—it is the leading antimicrobial agent in burn dressings—despite its widespread use for centuries as colloidal silver and in photographic films. Silver appears to be relatively toxic to aquatic life whether present as an ionic species or a finely dispersed material. At present, there is no smoking gun that shows that nanomaterials per se are more toxic than conventionally sized materials or salts, but they have shown a capability to cross biological barriers in the (NanoDynamics Inc.)
Figure 1 Examples of conductive nanomaterials—Ag particles, Ag platelets, and C nanotubes SEPTEMBER/OCTOBER 2011 | 25
Vr (Microohm-cm) Figure 2 Volume resistivity of 80-nm Ag after sintering (NanoDynamics Inc.)
Figure 3 LaserJob NanoWork stencil compared to a standard stencil after print
• Metal, organic based • Sub-micron particulates • Bulk conductivity >104 S/m • Low processing temperature (<200 °C)
• Polymeric or Nano particulate based • Electrical resistivity >1014 W-em • Film thickness <5 µm • Permittivity (2-20), low loss • Semiconductor compatible band gap • Low processing temperature (<200 °C) • Organic, inorganic, hybrid • Electron mobility 10-2 -102 cm2/V s • Low processing temperature (<200 °C) • Organic, metal, or inorganic • Resistance (10-100K W/=} • ±10% Nominal resistance tolerance
Light emitting Photovoltaic Table 1 Classes of Functional Inks and Critical Attributes (iNEMI Roadmap, 2011)
26 | Industrial + Specialty Printing www.industrial-printing.net
same way as ionic materials do. Caution is appropriate if there is a potential for exposure. NIOSH and others have carried out studies, and it appears that normal plant-engineering controls, such as respirators, are effective in the production environment; in normal use electronic products are designed not to shed nanoparticles in coatings and composites; and at disposal, most materials would be destroyed by incineration or be encapsulated and relatively inert in landfills. Recovery of valuable metals would take place by dissolution or incineration. Careful monitoring and dust collection is required during shredding or grinding of circuits where dust might be generated. At present, there are no specific requirements for manufacturers to disclose that their products contain nanomaterials. The U.S. EPA is keeping a special watch on nano silver for antimicrobial use only and on carbon nanotubes for all applications that manufacturers need to specify in advance. Other restrictions have been discussed but not implemented, but a few local governments, such as in Cambridge, MA, have taken things into their own hands and require disclosure that companies process nanomaterials. If in doubt, consult with your local environmental agencies. The opportunity for nanomaterials in printed electronics The generally accepted definition of nanotechnology is the understanding and control of matter at dimensions between approximately 1-100 nm, where unique phenomena enable novel applications (NNI/ISO). Not every material exhibits unique properties at this scale—ionic materials such as salt, for example—and not every nanomaterial stays nano after it is processed, such as nano solder coalescing into larger particles. Low-temperature reactivity of metals, primarily Ag, Sn, and Cu, is caused by the fact that a nano metal particle may have a few hundred to a few thousand atoms present. Many of the atoms are surface atoms that are not fully coordinate and so are reactive and willing to bond to another metal atom in another particle at a much lower temperature than the classical melting point—nano Ag at less than 200°C, for example, whereas normal silver melts at more than 900°C (Figure 2). Companies such as Ames Goldsmith have commercialized technology developed at universities— in this case, Dr. Dan Goia’s group at Clarkson University—to produce a range of interesting materials. In the case of enhanced electron mobility in adhesives, coatings, and composites through the incorporation of nanoparticles, flakes, or fibers—including silver nanowires, carbon nanotubes, and graphene—a small percentage addition can have a huge affect because of the large number of particles present. For example, in a 1-m3 space, a 1 volume % space divided into 100-nm cubes would generate 1018 particles, each 10 -6 m—1 μm—apart. Dramatic conductivity improvements are typically seen at a 1 or 2% content of well-dispersed particles, often in combination with more conventionally sized particles. Endicott Interconnect Technologies has been a pioneer in the use of materials of this type in via fills. Electromagnetic effects range from semiconductor properties, such as light emission and modification (quantum dots) to solarpower collection (CdTe) to inability to interact with light (alumina, silica, etc.). Fillers to modify hardness, strength, wear resistance,
SUBSTRATE Current = Glass • Plastic (PET, PEN, PI) • Metal (Steel)
BACKPLANE (TETs) Current = PECVD a Si Organic Printed Si Printed Metal Oxides Carbon Nanotubes Epitaxial Lift Off
FRONTPLANE (Active Material) Current = Liquid Crystals Small-Molecule OLED Polymer OLED Quantum-Dot LED Electrophoretics Electrowetting Electrochrome
TRANSP. CONDUCTIVE FILM (TCF) Current = Indium Tin Oxide (ITO) Metal Nanoparticules Metal Nanowires Carbon Nanotubes Conductive Polymers Graphene
Figure 4 Display construction and materials (Lux Research) dielectric constant, and thermal expansion can be incorporated invisibly. Nanoscale structures can also be used to modify surfaces. The lotus-leaf structure combines hydrophobic, waxy crystal with hairs that prevent surface wetting. Non-wetting is a key component in printing processes, and this phenomenon is being exploited commercially. THE INEMI ROADMAP The large-area/flexible-electronics section of the 2011 iNEMI roadmap (www.inemi. org) was written by more than 50 participants in the global supply chain. Participant companies and universities worldwide included Printovate, A*STAR, Binghamton University, Western Michigan University, Rotadyne, Henkel, DuPont, Kodak, Polyera, Corning, H.C. Starck, Speedline, Cornell University, Endicott Interconnect, NIST, Kyocera, and the Ukrainian Academy of Sciences. It spans 151 pages with more than 250 references and analyzes the technology and supply chain for printed electronics worldwide. Display and other applications are increasing in volume, and government funded work under the EU 7th Framework, Singapore, Japan, Korea, China, and the U.S. is increasing as access to high-performance materials increases. The availability of functional inks and processes, as well as characterization techniques, are seen as key enablers for this market, and there is much work to be done in this emerging business sector. Table 1 shows the classes of electrically functional inks and their
critical attributes. Inks are required for both passive and active devices. TYPES OF INKS AND FUNCTIONAL ATTRIBUTES Each practical printing technology— gravure, flexography, offset lithography, screen, drop-on-demand inkjet, and aerosol jet—has specific viscosity and other demands. Low-viscosity inks have real difficulty suspending dense materials like silver (specific gravity 10.5). Conducting and semiconducting polymers usually have a limited range of effective solvents available with restricted drying characteristics. A key sentence in the roadmap says that the “rate of commercialization of materials ... is occurring too slowly to meet the cost/performance/utility demands to enable near-term product launches.” Inkjet inks usually have a low solids content, so drying times may be protracted. Many ink-process aids can interfere with electrical properties. Conductive and capacitive inks based on nanomaterials already show significantly higher performance than organic conductors such as PAN (polyacrylonitrile) or PEDOT (polyethylenedioxythiophene). Resistive inks are often based on nano or near-nano carbon. Active inks are improving rapidly with the best electron mobility based on pentacene systems with inorganic nanomaterials based inks catching up rapidly. NANO AND NEAR-NANOMATERIALS IN PRINTING AND PRINTABLE MATERIALS The applications are not necessarily in totally new systems; rather, we see im-
provements to existing materials systems to allow them to compete more effectively. Users won’t see the nanotechnology—they will just see a stencil that prints better (LaserJob), or an ink that conducts at a lower process temperature (Nanomas) enabling a product than can now be made flexible rather than rigid. Plate-based printing is the domain of many of these products because that is where the installed infrastructure base is technically, but there is no reason why many or most of these materials could not be applied in roll-to-roll processing, given the normal challenges of roll-printing functional materials. A process time of minutes is fine for a plate structure but is unacceptable in roll-to-roll manufacture, where seconds are more appropriate. A combination of the two will be necessary until techniques like flash sintering as developed by Oak Ridge National Laboratories and NovaCentrix are adapted for roll-to-roll applications. EQUIPMENT Lotus-leaf structures have been emulated by scientists for many years using a combination of hydrophobic materials, such as fatty compounds or fluorine compounds, textured to create biomimetic hydrophobic and oleophobic surfaces for clothing, paints, and other applications. Stencils are now being treated for improved release properties being commercialized by LaserJob (NanoWork, www.laserjob.de) and Dek (NanoPro-Tek, www.dek.com) with impressive performance improvements claimed. SEPTEMBER/OCTOBER 2011 | 27
Metal nanowires Graphene 3
Conductive polymers Carbon Nanotubes
Likely Losers 1
Incremental advances 3 Maturity
Figure 5 Value vs. maturity for transparent conductive materials (Lux Research) Copper and solderable surface finishes for copper Copper, whether plated or printed, will be an essential ingredient of future circuits. Nanostructured copper is readily produced by pulse plating (www.mnt-era.net/mntera-net-success-stories/nanocopper-2006) and has been successfully printed and flash sintered on flexible substrates by NovaCentrix Inc. (www.novacentrix.com/ product/metalon.php). Novel surface finishes have been commercialized by Enthone (Cookson Electronics Inc., www.enthone.com/pwb/index. aspx). This surface finish, originally developed by Ormecon in Germany, combines a conductive polymer with silver to combine the best features of OSP and silver. This product is potentially a substitute for ENIG, as well as other surface finishes, due to its superior, aging, oxidation, and solderability properties coupled to multiple reflow capability. Imagable solder mask using nanomaterials has also been developed (UV-Curable Compositions and Method of Use Thereof in Microelectronics, U.S. Patent Application, 20030138733, IBM). Displays: the biggest potential market for printable nanomaterials? Printing volumes and value are related
to area. Displays are arguably the largest potential users of nano-enabled inks. Lux Research (www luxresearchinc. com) published a study of the new display market in January, 2011, “Sorting Hype from Reality in Printed, Organic, and Flexible Display Technologies,” in which the group outlined the components of displays and the materials of interest in each element. Figure 4 outlines the existing and potential materials of construction in a display, including carbon nanotubes, printable metals, semiconductors, quantum dots, nanowires, and graphene. Within specific areas, such as conductors, Lux ranked the individual nanomaterials usable as transparent conductive fillers (TCFO) for commercial desirability. The results, shown in Figure 5 show that some materials heavily supported for years may be less effective than current materials (metal nanoparticles) or upstarts like graphene. Final thoughts While we haven’t touched the other huge potential area market for roll-to-roll printing—solar cells—many companies, such as NanoSolar, Global Solar, and Konarka, use a combination of printing and vapor deposition on substrates such as stainless-steel
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foil to produce new cell designs. Expect to see future articles on this topic. You will also notice that RFID tags were not addressed. Nearly five years ago I was astounded by the work done by Marc Chason, Dan Gamota, Paul Brazis, and the team at Motorola Laboratories. They had printed literally miles of functioning electronic devices—RFID tags—on flexible substrates on roll-to-roll presses. It can be done, it has been done, and it will be done again! A wide range of functional, economical nanomaterials will be critical to this future success. To follow developments in this field, I’d recommend the comprehensive iNEMI roadmap and the work done by the FlexTech Alliance (www.flextech.org), whose Website has links to the workshops and conferences worldwide showcasing new developments. How will the industry shake off the reputation of being an industry of the future whose future never comes? Just as in nanotechnology, which has the same stigma, applications quietly develop that will gain significant market share, when the right market drivers are in place—for example, the growing adoption of solar power or changes in smart-phone configuration requiring additional flexible circuits. The evolution of a supply chain is also critical to meet manufacturers’ needs reliably. Don’t expect revolution, but rather a gradual evolution of a technology whose day will come when the technical needs and the cost effectiveness drivers intersect with a capable supply chain.
Alan Rae, Ph.D.
TPF Enterprises LLC Alan Rae, Ph.D., has worked in the electronics, ceramics, nanotechnology and “clean tech” industries for more than 25 years in the UK and U.S., managing global businesses and technology development at a startup, operating company and at the corporate level. He currently runs TPF Enterprises LLC, a technology commercialization and business development company he founded in 2009, based at the UB Technology Incubator. He is active in electronics industry associations and standards work. He holds director and VP positions with four new companies and consults for two Fortune 100 companies in alternative energy. He also is technical editor for Global Solar Technology.
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Printing an Electrocardiogram Electrode This article describes the important role adhesives play in the construction and efficacy of biomedical sensors. Andy Greene FLEXcon
s medical devices become smaller and smaller, the individual patient has become empowered to monitor his or her own health condition. The increased accuracy and availability of medical devices, such as hand-held electrocardiograms (abbreviated as EKG or ECG) enable immediate feedback. The most common causes of heart disease are widely debated, but improvements in treatment for heart attacks and other cardiovascular emergencies are universally acknowledged. These improvements have saved countless lives. Biomedical sensors are a newer product category for printed, flexible electronics within the medical industry, an industry that has historically been dominated by conventional, rigid electronics. Products such as EKG electrodes require highly specialized coatings to be applied for accurate signal reception and transmission. Cardiovascular disease is the leading cause of death in many developed nations. An EKG diagnostic test has become a necessary analysis in determining the cardiovascular health of a patient in numerous situations, including clinical trials, stress tests, exercise tests, and shortterm and long-term monitoring. There are an estimated 165 million EKG tests
conducted every year in the U.S. alone. As can be expected with an aging population, the worldwide market is rapidly expanding. The total market for biomedical electrodes is forecast to reach close to $1 billion in 2015. Healthcare cost is also increasing rapidly. Healthcare providers may seek to cut costs with commodity products to make up for rising labor costs. EKG electrodes are a very mature, commodity-based market. As the market expands due to the reasons mentioned above, there will be increased competition from non-traditional medical suppliers. The newer competitors may offer greater economies of scale and material expertise not seen in the niche medical field. PRODUCT REQUIREMENTS EKG electrodes are built in two general designs: tab and snap (Figure 1). In a snap style, electrode metal clasps bind the EKG electrode via leads to the monitor and to the patient with either hydrogel or pressuresensitive adhesive. In a tab electrode, the EKG monitor is connected directly to the adhesion layer face stock, which is coated with either hydrogel or pressure-sensitive adhesive.
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The adhesion layer between the patient and the electrode must fulfill a combination of objectives: achieve a strong physical bond between the patientâ&#x20AC;&#x2122;s skin and the EKG tab and transmit the electrical activity of the heart (biopotentials) to the EKG monitoring device. Hydrogel is responsible for transmitting the biopotentials in the majority of EKG electrodes. The hydrogel layers work in conjunction with a printed electronic circuit that may contain silver/ silver chloride. Hydrogels are made of a colloidal cross-linked gel dispersed in a water medium (more than 95% water). When coated, the gel behaves as a liquid and can be coated on many surfaces. After cross-linking, the hydrogel behaves as a viscoelastic layer that posesses excellent stretching properties. This enables the gel to conform well to an uneven skin surface and to not yield easily when under mechanical duress. There are disadvantages, however, to this material. Hydrogel is costly to produce and requires moisture-proof packaging to maintain its ionic properties. The EKG layout has long been standardized. Electrode placement must be very precise. A 12-wire lead layout has 10 electrodes placed on the body. Six are on the chest as
the V (precordial) electrodes. Four are on the extremities. It is called a 12-lead EKG because there are 12 different angles by which the EKG biopotentials are measured. This frame of reference is designated by a vector between two electrodes. The importance of signal clarity and which vectors to read are dictated by the cardiographer. Signal clarity is most important when monitoring the waveform. A particular vector signal will be under examination when examining an ischemia or other malady. For high signal fidelity, the medical electrode must function well with the connected circuitry for signal analysis, known as the EKG monitor. A cardiac biopotential is a signal with amplitude between 0.5-10 mV with a frequency between 0.01-250 Hz. Analyzing a small signal requires effective shielding. There are sources of noise in the hospital environment and from competing signals in the patient’s body. The electrode manufacturer needs to focus on maximizing output of the cardiac signal. There must be as few signal losses as possible in this electrical circuit. The adhesion layer of the electrode can be fulfilled by a pressure-sensitive adhesive (PSA). Traditional pressure-sensitive material is most often an acrylic material that will hold the physical bond. This is a clear advantage over the degrading performance of the atmosphere-sensitive, hydrogel-based coating. An unmodified dielectric pressure-sensitive adhesive cannot transmit an EKG biopotential and, therefore, does not enhance the signal fidelity for the given contact area. This adhesive, however, is much less costly to produce and is omnipresent across many industries outside of the medical field. (For more information about printing adhesives, visit www. industrial-printing.net/content/stickingwith-printable-adhesives). The sensitive nature of this application requires the EKG-electrode adhesive to fulfill a long list of electrical and material requirements. Pressure-sensitive adhesives come in many formulations to achieve the desired physical properties. Adhesive chemistry is tailored to a specified substrate to survive for a given duration. The chosen polymer system will also have to be verified as biocompatible with the human skin by a certified testing organization. A new material will have to be FDA approved before market introduction.
Tab Style Facestock
Face Stock Adhesive/hydrogel
Figure 1 EKG electrode designs
Figure 2 Signal-transmission directions Duration of skin contact could vary from one minute to several days, depending on the intended market of an EKG electrode. For this reason, formulating an adhesive with good green strength that can acquire a quick signal by forming a quick mechanical bond), yet with the capability of maintaining its hold over the long term—high shear strength and peel—is integral. The molecular weight and degree of branching of the polymer determine the peel, tack, and shear properties of a given material. The chosen cross-linking mechanism and additives can further modify the adhesive performance to bond securely to a patient’s skin. All of these components must interact well together in the coating system and must not irritate or injure the
patient during use. The adhesive’s viscoelastic nature enables it to respond well to flexing. The acrylic material does not dry out as rapidly as hydrogel. The real trick is balancing the ability to achieve a stable bond quickly and, thereby acquiring an electrical signal while still making the adhesive formulation suitable for pain-free removal. The technician will need to reapply the electrode for precise positioning in an emergency situation; therefore, the bond needs to have high tack; a low, stable peel to avoid patient pain; and be repositionable without premature or accidental removal. . Choosing an electrode substrate that is light, comfortable, breathable, and bonds well to the adhesion layer is another unique september/october 2011 | 31
Typical sheet resistances (W/SQ) 100 1000 10,000+
Values are approximate These are exceptions to this general classification
Figure 3 Ranges of gel-sheet resistance measured in Ω/sq challenge. The material must exhibit soft, cloth-like properties without damaging the electrical signal. Some material advances have brought conductive textiles and polymers into the fold. Fulfilling both mechanical and electrical requirements requires careful design considerations. On the electrical side, the adhesion layer must transmit the biopotential from the patient’s body to the EKG electrode with good signal fidelity. Good signal fidelity means that the physiological signal is transmitted accurately. This requires a good signal-to-noise ratio, achievable by limiting triboelectric and ambient noise either by shielding or through adhesive formulation. Association for the Advancement of Medical Instrumentation (AAMI) requires that an EKG adhesive or gel conforms to AAMI EC12, EC11, EC38, and EC53 standards. A large portion of these requirements relates to the inherent electrical resistance and electrical response time of the electrode materials. The electrical receptor must polarize (Figure 2) in response to a given input signal and translate the signal to the EKG monitor. The fidelity (attenuation) and speed (response time quantified by RC constant) of the signal transfer need to be tightly controlled by ionic or capacitive signal transmission. The EKG monitor’s electrical design affects the design properties of the adhesive. Properties like DC offset, common mode rejection ratio, biasing current, and input impedance can vary widely between monitor manufacturers and product models. These variables can also impact the adhesive’s acceptable attenuation and polarization targets. Manufacturing Hydrogel-based adhesives are polymer-infused dispersions where the majority binder is water. Water has a very high surface
energy material and is almost impossible to bond to polymers without the addition of polymers for cross-linking. The substrates that are coated often need physical (roughening) and chemical treatment to promote bonding. The hydrogel may undergo a variety of curing techniques to hold a stable post cross-linking matrix including electron beam, gamma irradiation, and UV curing. Chemical coagulants and stabilizers may also be used to ensure a stable rheology. The binding acrylate of an acrylic-based adhesive possesses an inherently lower surface energy, making it easier to bond to a given substrate. The cross-linking mechanism is usually either thermal cure or UV activated. Having a more versatile and stable coating allows different product substrates to further appeal to patient comfort. The coating stability produces flexibility in the coating area. There are a number of well-established roll-to-roll flood-coating methods for the PSA industry allowing an economy of scale not before seen in the EKG electrode industry. These continuous processes enable mass production the likes of which are seen in other commodity industries where a very high manufacturing efficiency is a necessity. Hydrogel-based adhesives dry out and rarely are the best for long-term application. That period of time depends on the environment in which it is used. However, drying out is not an issue in an adhesive system where water is not the primary ingredient. Hydrogel storage is another consideration. Once a packet is opened, unused electrodes may be thrown away, adding waste. Hydrogel-based adhesive systems are notorious for having incredible initial tack. However, the technician will not normally achieve optimal placement every time—especially on the first try. Therefore, shortterm removability is important. Designing
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an adhesive system with the potential tack to transmit the electrical signal without difficult removal can be an advantage for the technician and the patient. Summary Adhesives can be formulated to tranmit a biopotential across a given surface. Biomedical-adhesive transmissions are accomplished by capacitive means (Figure 3) in a higher impedance (as compared to hydrogel) polymer system. Anisotropic adhesive enables new design possibilities where the signal can be transmitted over a highly localized location only, while ignoring all other areas, via a Z-axial capacitive structure where the signal isn’t transmitted in the X-Y direction. Abandoning the low-impedance-transmission strategy has its benefits. It allows the designer the option of omitting costly, low-resistance materials such as Ag/AgCl, the price of which has skyrocketed in recent years. A conductive adhesive and a hydrogel generally fall in different realms of sheet resistance based on the materials used in the adhesive system. As mentioned earlier, the largest component of hydrogel is water, which is conductive. The most common element found in the PSA is the base polymer, which is a dielectric material. Filler material and additives in the interstitial space between the dielectric filler can bring the sheet resistance down significantly, but not as low as hydrogel in terms of sheet resistance. While established by AAMI, the practical conductivity needed in the adhesive system should be determined by those designing the EKG monitoring system. Creating a unique EKG electrode design could yield real benefits by increasing the signal fidelity and reducing the cost of materials and manufacturing. These can be accomplished while fulfilling the extensive list of medical qualifications and, finally, by making the device a more enjoyable experience than traditional EKG electrodes.
andy greene FLEXcon
Andy Greene is a technical service engineer involved in pilot product development for the flexible-electronics-business team at FLEXcon.
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Predictable Print Quality Using Wim Zoomer
iner lines and spaces in printed electronics demand correspondingly higher requirements in resolution and edge sharpness from printed line work. To get finer lines and spaces, the printer must apply direct emulsion to produce the highest resolution for the best possible edge sharpness. Consequently, stencil quality has to meet more stringent requirements. The screen maker is expected to guarantee the expected stencil quality. The printer, in turn, should evaluate stencils to predict print quality of the screen concerned before it goes to press. Using an eye glass and illumination, he is able to determine the presence of pinholes and edge defects. However, there is also a way to measure the stencil’s surface smoothness to ensure a perfect screen-printed edge sharpness. Besides capillary film, many companies use a direct emulsion to coat their screens. Direct emulsions are water-based systems with a solids content of approximately 50%. After drying, the coating should
be 50% thinner compared to the previously applied wet coat. During drying, the water evaporates from the emulsion. The emulsion shrinks in the mesh openings and creates a concave shape. This concave shape prevents the creation of a good seal between the screen and the substrate. A good seal ensures a perfectly printed edge sharpness. However, during printing, besides filling the screen’s image, the ink will also flow into the concave shape. Eventually, a printed image with bulges will be the result. But do not confuse bulges with another regular defect pattern called saw tooth (Figures 1 and 2). Bulges are outside image defects, whereas a saw tooth is an inside image defect. The actual image becomes smaller. The size of the bulges depends on several factors, such as: the quality of the seal, the angle of the image on the screen, the depth of the concave and the viscosity of the ink.
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SURFACE ROUGHNESS R Z MEASUREMENT The smoother the surface, the better the seal, and consequently, the better printed edge sharpness. The smoothness of the emulsion’s surface can be measured, which acts as a measure for the predicted edge sharpness. The lower the number, the smoother the surface, and the better gasket-like seal between substrate and screen. Result: a sharper edge. The stencil’s smoothness is measured with a surface roughness measurement device expressed in R z (in microns). Several devices are available. Using a probe with very fine needle with a 2µm diameter, pull it automatically over a specified distance to determine the stencil’s surface roughness. The path of the needle is divided into five equal zones. The device records the surface profile and calculates the average surface roughness per five zones (difference between max and minimum roughness value per zone). Here is the calculation:
Rz = (Rz1 + Rz2 + Rz3 + Rz4 + Rz5) 5 Since R z is measured in microns, the higher the numeric value, the deeper the undulation in the stencil. Lower values indicate a smoother surface. An R z of 12 µm means that a stencil with a concave depth in the emulsion in center between two knuckles of 12 µm. It is very likely that this concavity allows ink to flow underneath the stencil’s edges causing bulges along the image’s edges, as depicted in Table 1. The optimum R z is between 3 and 7 µm (Figure 3). PROCEDURE 1. Place the screen on a stable surface with the print side up. 2. Position the measurement probe of the surface roughness tester at 22.5° angle to the threads. This angle ensures a correct impression of the surface condition, since the probe travels across the deepest (center of mesh openings) and the highest (the fabric’s knuckles) areas of the stencil’s surface. 3. Taken the factors influencing the size of the bulges into account, if R z is more than 7 µm, ink may leak into the concaves. The resulting bulges will affect printed image quality. A lower R z results in a smoother stencil and a better printed edge sharpness. On the other hand, if R z is less than 3, during the print stroke at the end of the image, this stencil does not allow the forward driven air to escape. The consequence will be air entrapment in the ink deposit. PRACTICE Quite often the screen maker and the printer rely on the printed results as a reliable means to evaluate stencil quality. We know that this statement is partly correct since many other factors, such as squeegee pressure, squeegee hardness, substrate, ink viscosity, and mesh selection, affect print quality. This means that a perfect stencil can produce an unacceptable print quality. This is an interesting subject of discussion between the printer and the screen maker. To start with, the best possible stencil quality factors besides line width, EOM (emulsion over mesh), R z belongs to the most relevant stencil parameters affecting print quality. EOM is the thickness of the
Figure 1 Printed line with Rz = 3-µm stencil
Figure 2 Printed line with Rz = 12-µm stencil
D C Figure 3 Examples of high and low Rz A Stencil with a high Rz is not able to create sufficient seal. B Stencil with a high Rz causes ink flow underneath the stencil’s edges, causing a printed image with bulges. C Stencil with a low Rz prevents undesired ink flow underneath the stencil’s edges. D Image with excellent edge sharpness caused by stencil with low Rz.
emulsion on the face of print side of the mesh. R z value provides the screen maker with a very useful method of measuring stencil quality parameter, before the screen goes to press. These parameters should be measured and recorded in a log book. Later the collected data serves for adequate feed-back. Generally, R z changes with the emulsion build-up. The thicker the stencil, the smoother the emulsion’s surface and, therefore, the lower the R z. Since the sten-cil
thickness is an optimized parameter per print application, it is possible to im-prove the stencil’s smoothness independently from the stencil’s thickness. EOM and sur-face roughness R z values can only be measured using special measurement devices. COATING METHODS The most accurate and consistent way to apply emulsion onto a screen is an automatic coating machine with coating SEPTEMBER/OCTOBER 2011 | 35
Relative EOM and Rz
Multiple Coating Affecting EOM and Rz
troughs. We distinguish different basic methods providing totally different stencil quality results. The shape of the lip of the coating trough strongly affects the amount of the deposited emulsion during each pass of the coater. On most fabrics we use coating troughs with round edges. As we know from round edge squeegees, these will deposit relatively large amounts of material. On the other hand, a sharp coating trough will leave just a little emulsion on the fabric. The emulsion is another very important factor. Emulsions with a high solid content easily reach the required R z range. At the same time, a high EOM may be achieved. Emulsions with a low-solids content and low viscosity are especially suited for the second coating method: wet on dry to manufacture a stencil with a low OEM and a low R z. Wet-on-wet Coating wet-on-wet implies that each successive pass with the coating deposits fresh emulsion in addition to the emulsion which is still wet on the mesh. Wet-on-wet coated emulsion accumulates on the side opposite the coating trough. We start coating from print side of the mesh and add as many times from print side as necessary. Subsequently turn the screen around and continue coating from squeegee side to build up an EOM. Each pass with the coating trough the wet emulsion continues to build up proud on the mesh. Since drying is only applied after weton-wet depositing all emulsion it may be clear that the emulsion shows substantial
shrinkage, especially in the holes of the fabric. As a result, wet-on-wet coating results in the expected EOM, but the Rz value will remain relatively high and probably causes the concave effect. Wet-on-wet coated emulsion using a sharp coating trough, rather than a round one, deposits less emulsion. Sharper edge coating troughs result in less emulsion built up on the mesh and a relatively high R z. Wet-on-dry Also called coating with intermediate drying, using time consuming drying after each additional coating step. The quality wet-on-dry coating method is applied for the preparation of thin stencils for fine detail printing with excellent edge sharpness. The EOM is quite low and the Rz-value is low enough to ensure an excellent print result. Wet-on-dry coating is done with a sharp-edged coating trough. Each coat of emulsion is (except the first one) applied on print side followed by drying with print side up. At each pass this coating method deposits a minimum amount of emulsion proud on the mesh and step by step decreases Rz by filling the concave. After all the coating trough makes a scraping movement on the knuckles of the fabric and leaves emulsion only in the low spots. After depositing the first coat wet-onwet (one print side and one squeegee side) combination the screen with emulsion is being dried. Next coats are being applied wet-on-dry. On a 380 mesh fabric the EOM and R z development may be as follows in Table 1. After exposure and development R z will in-
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crease a couple of microns, due to removal of unexposed emulsion, the absorption of water followed by successively drying again. Saw tooth The defect caused by R z should not be confused with a saw tooth defect. Figures 1 and 2 depict that a concave effect is caused by too high a R z. High R z values cause bulges connected to the printed image. This concave defect is an outside image defect causing line gain. A saw-tooth defect is not caused by high R z values but by too low EOM. The moment, the printing squeegee passes during making the print stroke, the gap between the fabric’s threads and the substrate is not high enough. As a consequence the threads block the flow of the ink with a regular pattern we recognize as ‘saw tooth’. More emulsion is not better. Too much emulsion on the face of the screen causes a difficult ink transfer. A recommendation is an EOM ratio of 10-20% of the fabric thickness. Currently the minimum requirements in printed electronics are a consistent ink deposit and a fine line width combined with excellent edge sharpness (Figure 3 D). A measurement device to control EOM is a necessary tool. A combination of the EOM with the stencil’s surface roughness R z, provides the printed electronics manufacturer with a set of non-destructive measurable stencil parameters to predict print quality, The EOM and the R z measurement are variables to optimize stencil quality, applying the methods described before. Without any doubt, the EOM and Rz measurement devices belong in the screenmaker’s toolbox.
Technical Language Wim Zoomer (firstname.lastname@example.org) is owner of Nijmegen, Netherlands-based Technical Language, a consulting and communication business that focuses on flatbed and reel-to-reel rotary screen printing and other printing processes. He has written numerous articles for international screen-printing, art, and glass-processing magazines and is frequently called on to translate technical documents, manuals, books, advertisements, and other materials in English, French, German, Spanish, and Dutch. He is also the author of the book, “Printing Flat Glass,” as well as several case studies that appear online. He holds a degree in chemical engineering. You can visit his Website at www.technicallan guage.eu.
Market movements and association updates
INDUSTRY NEWS Ne
U.S. Photovoltaics Project Pipeline Soars w
ey 2% o Tex 2% as 2% Me
N e v ad
The U.S. non-residential photovoltaics pipeline now exceeds 17 gigawatts as reported by Solarbuzz in the United States Deal Tracker. In Europe, feed-in tariffs have been trimmed, but growth opportunities for photovoltaics California 62% investment, manufacturing, and installation have improved in the U.S. market.
In the U.S. there are 601 projects from 50 kW to 500 MW in size with installation dates from this year through 2015. Most of the development has been in the state of California, followed by Arizona , Nevada, New Jersey , New Mexico, and Texas, though as many as 40 states contribute to the pipeline. Other 18%
For the projects that are in process, the top suppliers of PV modules are First Solar, SunPower Corp., and Suntech Power. Advanced Energy and SatCon Technology are the leading inverter suppliers to the pipeline, according to the report.
Bend Me an Electron
Cambridge, MA-based MC10 was founded in 2008 with the intention of developing the next generation of electronic systems through its conformal electronics platform. MC10’s platform enhances and enables new applications by allowing high-performance electronics to occupy spaces and geometries not possible in their traditional, rigid form. Backed by an extensive patent portfolio secured through in-licensing and continued developments at the company, the main goals are to apply bendable, conformable electronics in consumer electronics, medical devices, and defense systems. The company uses standard tools and processes to combine the performance of traditional semiconductors with the mechanical properties of elastomeric (stretchable) materials. The combination offers reliable sensing and actuation for unusual devices. Professor John Rogers of UIUC and professor George Whitesides of Harvard grew MC10 out of their own research with backing by North Bridge Venture Partners and Osage University Partners. In June 2011, the company raised a $12.5 million Series B round lead by Braemar Energy Ventures. MC10 also has a deal with Reebok to develop a wearable product that’s still in the secrecy stage, but one can only guess that involves footwear and printed electronics. Other projects underway include collaboration with Massachusetts General Hospital and other institutions to develop a new type of balloon catheter with sensors to make heart procedures easier to perform/conform. Another project underway at MC10 is a curved image sensor to mimic the shape of a human retina and leading to thinner cell-phone cameras. The home health-monitoring market is another twinkle in the company’s eye. SEPTEMBER/OCTOBER 2011 | 37
Harvesting Energy from Available Sources Mary Boone
You’ve likely heard a great deal lately about energy harvesting—the idea that you can capture, possibly store, and use the energy that already exists all around you to power things. This relatively new field focuses on using ambient lighting, heat, vibration, and/or any of dozens of other sources to power small electronic devices to make our lives better and simpler in some way. While there is work underway to harvest body heat from people in buildings or the vibrations of passing vehicles on a road, it is photovoltaic (PV) technology—the conversion of light into electricity—that has started to see real traction in energy harvesting. We use approximately 20% of all the power produced in the U.S. to light our homes, offices, and shopping malls. Think about that—20% of our national power budget goes to lighting, much of which is wasted and/or never really used during the course of the day. That’s where energy harvesting comes into play. By using a PV device, it is possible to harvest some of that wasted light and use it to power walkway lights, charge your cell phone, or run the thermostat on your furnace. Not only could this eliminate the need to ever change a battery, saving the cost of new batteries, but it also prevents all those batteries from ending up in a landfill. Energy harvesting can be both cheaper and easier for the consumer and better for the environment. The energy-harvesting market comprises a number of different technologies serving an even larger number of end applications. Experts claim that the total market for all energy harvesting applications in 2010 was approximately $623 million. It was also estimated that approximately 40% of the companies working on an EH source were focused on PV applications, by far the majority of the potential EH options. By
2015, the EH market is projected to grow to $1.7 billion, and to grow to a staggering $4 billion by 2019. Furthermore, $2.4 billion of the 2019 market opportunity are projected to be PV-based applications. Keys to the future of EH The key to unlocking these markets is to find the best way to integrate the right product into the right application, whether it be a charger for your cell phone or a pharmaceutical package that is smart enough to know if you’ve taken your medicine or not. It’s the “fit it and forget it” mentality. While PV is getting a lot of attention for energy harvesting applications, one class in particular, organic photovoltaics (OPV), has a unique set of features that may make integration into everyday products easier. Unlike other photovoltaic technologies that are based on the same kinds of materials and processes used to make computer chips, OPVs, as their name implies, are made from carbon-based organic materials. Because they are made from different materials, they perform differently than traditional PV devices and, at the lower light levels found indoors, OPVs can actually produce more power than conventional PV technologies. Another game-changing aspect of OPVs is how they are made. OPV materials are typically supplied as inks, meaning that instead of having scientists in clean suits working on multi-million-dollar pieces of semiconductor fabrication equipment processing wafers one at a time, making an OPV device looks a lot more like printing a newspaper with inks being laid down using familiar printing and coating equipment in a continuous roll-to-roll process that is measured in meters per minute. Not having to buy that entire expensive capital equipment means that the unit cost for the modules
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can end up being significantly lower than other PV technologies. OPV modules can also be flexible and conformable and can be made in many shapes and sizes other than just standard rectangles seen in PV for outdoor solar applications. That flexibility to design all sorts of different shapes and sizes is critical because, unlike the sprawling solar farms situated in the desert with row after row of identical modules, your computer keyboard and your furnace’s thermostat and the blinking promotional display at the end of the grocery aisle are all very different sizes and shapes. That means that each device has very different power needs, yet all three of them are prime candidates for energy harvesting. OPV is the technology that will enable these applications along with many more, and the printing industry is the missing link that will bring these applications from the lab to the consumer. So, while the technologists perfect the materials and the processes to make a myriad of OPV devices, how can your organization jump-start the manufacturing and integration of OPV into these applications? Take a minute to look around at the things you do every day and ask yourself, “Could I use an OPV module to harvest a little bit of the light around me to run this?” If the answer is yes, a new product opportunity awaits us all.
Plextronics, Inc. Mary Boone is the director of inks business development at Pittsburgh, PA-based Plextronics, Inc. The author would like to thank contributing authors Mark Storch and Ritesh Tipnis.
American Ultraviolet Co.
AWT World Trade Inc.
Franmar Chemical Inc.
Graphic Parts International
Specialty Graphic Imaging Assn
ST Book Division
5, 39 29
shop tour 1
AP Industrial/Phoenix Interface Technologies
location Tempe, AZ other info Located in Tempe, AZ, the All Pro family of companies includes AP Industrial and Phoenix In-
terface Technologies divisions. Phoenix Interface Technologies is a manufacturer of membrane switches, graphic overlays, and printed flexible circuits. It also specializes in challenging, custom-made, small- and medium-run projects. AP Industrial is an industrial-surface-finishing business that specializes in liquid and powder coatings. AP Industrial also provides sand blasting, masking, and pretreatment (yellow and RoHS-compliant chem-film) services. The two divisions enable the company to occupy unique niches and lucrative industrial markets, including military, medical, aviation, industrial, instrumentation, and solar.
1 Main office in Tempe, AZ 4 Die cutting in the finishing area area dedicated to printed flexible circuits and and powder coatings for a variety of 2 An 5 Liquid membrane-switch manufacturing industrial surfaces 3 Laser cutting for quick-turn prototyping 40 | Industrial + Specialty Printing www.industrial-printing.net