I teach people how to do soldering under a microscope, so I was unconcerned on doing a screen replacement and didn't want Apple touching my wife's phone. (They replaced my iPhone 6 battery and jacked it up, I had to fix it myself.) After replacing my wife's screen, again, this time it didn't power up. I can confirm if it seems bricked (won't turn on, no charge indication, won't connect to iTunes) that removing one of the battery leads for about 30 seconds, then reattaching it, can fix your problem. The battery for an iPhone 6s is not soldered into place, its just a connecter. Be sure to try that before taking it to a phone repair shop.