Chosen Solution
Hi friends, I wanted an opinion, unfortunately iPhone 7 with audio chip problem there are really too many around, although I have a good success rate with a Reflow this time it went wrong. The phone does not turn on, I have an absorption of 0.4A from the cable but nothing appears on the display. Disassembled I noticed that the lines “PP_Soc_Var” “PP_CPU_Var” and “PP_GPU_Var” are all in short. So I think the processor is the problem … I had used a high temperature tape to cover the rest of the logic board leaving only the Audio chip uncovered, with a temperature of 310C. I’m really baffled, I didn’t think it could go so bad …
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).
“PP_Soc_Var”, “PP_CPU_Var” and “PP_GPU_Var” are not shorted they are supposed to have a low resistance. After any audio IC work on the iPhone 7 a 0.4A draw will most likely be a VDD_BOOST line short. Check these caps first for bridging if you cannot see any bridging you will probably need to remove the audio IC. Pay attention to the cap circled.
