Short circuit on the motherboard after chip replacement on an iPhone

I've an SE and I changed a U2/Tristar chip on it because the phone didn't charge up. After chip replacement the motherboard has PP_GPU and PP_CPU short. I used kapton tape to cover other parts and I used the hot air station on 350C. I think I did a good job but just in case I removed the IC (all pads look good) but the motherboard still has short circuit. The phone never had water damage. Can anyone tell me why has the phone short circuit and how can I fix it please? Thanks in advance.