Chosen Solution
I replaced the screen on my iPhone 6s a few days ago, I have done this for at least 80 phones before this one. Everything was going fine for about two days, now my backlight will not turn on. I did notice a few times that my screen wouldn’t respond to touch but I reset the phone and it fixed it. Now the screen is black, but the phone is recognized by my laptop.
You have a backlight issue but it’s hard to say wether it’s the screen or the backlight circuit on the logic board. If you have successfully replaced 80 6S screens, then it’s not unreasonable to expect to have one bad screen show up. Presumably, you have other screens to try or worst case, put back the original cracked screen. If the problem persists, then you have a blown backlight circuit and that requires a micro-soldering repair. Are you always disconnecting the battery before removing the screen? The 6S is prone to backlight circuit damage when the battery is connected during a screen replacement.
