The red screen usually means there is a fault with the front camera / proximity sensor flex. Try disconnecting it, then boot the phone. If it boots as normal you will need to replace this part. iPhone 5s 前置摄像头和传感器排线更换
Do any of the capacitors seem dark or burnt up on these lines? PP_SOC_VAR, PP_CPU_VAR & PP_GPU_VAR have very low resistance, most multimeters will beep on both sides because of this. So you may not have short. There is a still possibility heat has gotten through to the other side of the board and caused a short under the CPU or baseband CPU. I would never reflow an audio IC on the iPhone 7. The problem normally is a broken trace between I2S_AP_TO_CODEC_MCLK and pad C12 on the audio IC (usually caused by a drop or a bend). Reflowing the IC normally wouldn’t reconnect this trace. I always remove the audio IC and repair the trace at pad C12 (also check F12, H12 & J12). Then reball, then resolder the IC. Repairing this trace provides more strength and would stop the problem for occurring again (in most cases).
This connector can be replaced, although it is difficult. You would need to send it to a microsoldering specialist. I would recommend this option rather than replacing the motherboard. This way you can keep all your data on the phone.
Did you disconnect the battery prior to fitting the screen assembly? If it was still attached, you have most likely blown a filter beside the connectors. Have a look around the connectors, usually the filter will look darkened compared to the others or burnt up. It would need to be replaced in order to get the touch working again.
Take the board back out and inspect the WIFI / Bluetooth IC and surrounding components. It’s the one marked in orange. Check for any cracks, damage or missing components. It may have been damaged if there was something loose underneath it when the board was put back in while replacing the charging port. In my experience after replacing this IC the WIFI should work again.
Unfortunately this is not a modular component. It requires soldering to replace. Similar to the iPad Air and Mini charging ports. Here is a long tutorial if you want to attempt it. https://www.youtube.com/watch?v=Ia2VkdfX...
After removing the charging IC (U1401), reballing and re-soldering back onto the motherboard. Now the phone is working perfectly. The phone no longer reboots after I power it off. I hope this will help anyone else with the same problem. I guess replacing this with a new component would work also.
I had the same issue after a screen replacement. I disconnected each connector on the board then reattached them one by one to see which part was causing it to red screen. I noticed that it red screened when the power button / top sensor flex was attached. It must have been damaged in the process of removing the screen. Changing this flex cable solved the problem and now its booting as normal. Hopefully this will help anyone else that has the same issue. As I couldn't find any other solutions on the internet.