1. Check the few original pieces on the back of the WIFI chip and found that these pieces are still on the right position, as shown in picture 3-4-1.
2. Disassemble the WIFI chip and then measure the diode data of the pad by digital multimeter and found the signal of 51 pin WLAN_REG_ON has no data, as shown on picture 3-4-2, but in normally it should be 500+.
3. After check the circuit diagram and found this signal is directly connected to the power IC E11 pin, as shown in picture 3-4-3. So, we initially judge either the power chip was broken or the circuit board was disconnection.
4. Put the WIFI chip on the PCB holder, then remove the power chip and check the data between two points, the result is infinite, as shown in picture in 3-4-4 according to this we can prove the circuit board was disconnection.
5. This signal line is in the middle of the solder pad, and we measure it with multimeter, as shown in picture 3-4-5, we can see that these are normal.
7. Make the pin on Power IC, and clean it with chip graver tool, then assemble the WIFI module and power chip. As shown in picture 3-4-8, 3-4-9 and 3-4-10.
8. Test it, and all is fine, now just install the shield, then the problem of iPhone was resolved and you can use it normally