Chosen Solution
I changed the screen because it broke. Got a new screen but it had lcd damage where you see rainbow colors. Bought a new one, replaced and it worked. Now when i was putting back the shield plate screws which is the last part, the phone turned off. I thought it was just the cable connector. I unscrewed it to see if one of the cable came off the base, before i got to take out the plate, it turned on. So i screwed it back and it turned off while i was putting the last 2 of the screw. After that it never turned on even after putting back the rainbow defective screen. Charged it for 30mins, did the power button and home trick, connected it to a computer to see if it turns on, none. Connecting to computer nothing shows up thats says iphone connected or any. Did it short around the power button?
Did you put a long screw in one of the two screw holes near the bottom of the screen connector area? If yes, it is probably long screw damage as these screw holes sit right on the logic board and over-tightening / putting longer screws can damage the circuit layers of the board at that spot which may cause this issue. Damage for that is hard to spot without a microscope, usually you would see exposed copper or exposed wiring in the screw hole or traces of copper on the screw to indicate long screw damage.
This sounds a LOT like long screw damage—which is really a misnomer. You don’t have to actually mix up the screws, simply overtightening the bottom left lcd screw can drill it into the logic board and rip up traces underneath.
HOWEVER, your phone should still turn on and be detected by iTunes. The common problem with iphone 6 LSD is tearing the lcd reset or image power enable lines that run from the connector under the screw hole to the rest of the board. In other words, common LSD in iPhone 6 = no image, not no power.
The second possibility that this could be is backlight filter blown. That is pretty uncommon on the 6, but I believe that you have been working on the device multiple times without disconnecting the battery. You mentioned putting back the lcd shield as “the last part”, but of course the real last part is reconnecting the battery. You do not want to be connecting any cables into their connectors while the battery is still connected since you will have live battery voltage present inside the connector. All it takes to cause a temporary short and therefore a rush of current is to graze any metal ground across the hot pin in the connector.
My guess is that you either have a backlight or an image problem and that your phone not being detected by the computer is just a troll. In either case, this is a job for your local microsolderer or mail in repair service.
Next time be sure to disconnect the battery and only just tighten the screws, don’t grind on them and you’ll be okay in the future.
