A simple reset can fixed your bricked iPhone and allow you to switch it on. Here is how: Hold the Power key and theHome button simultaneously for about five to fifteen seconds. Then the Apple logo should appear. Give it five to ten minutes to power on and then proceed in using your device normally. To reduce battery related issues, reset your phone when having the device plugged into a power source. If your bricked iPhone switches on but promptly shuts down or fails to get past the Apple logo after 10 minutes and above, you will need to restore the device. The next step is how to restore your phone.
Step 3. Restore Your Phone
Plug your phone into your computer > Open iTunes on your computer > Choose the device from the program window > Click the "Restore" button. iTunes will regain all the files in your iPhone and reset its firmware at the same time. Once this step is finished, iTunes will ask if you would like to restore your iPhone from a previous backup. If there is no backup, just set up your device as new.
Step 4. Try Another PC If you cannot restore your iPhone/iPad, try another computer with iTunes installed. But sometimes there can be a conflict or a driver problem that prevents your PC from recognizing your device. In that case, jump to step 5.
Step 5. Downgrade Your iOS Version