Using Thermal Camera Fix iPhone 11 Pro Max Large Current
Large current is one of the common problems of phone repair. Today we will repair an iPhone 11 Pro Max Large current problems with the latest LINCSEEK Infrared Thermal Camera.

LINCSEEK Infrared Thermal Camera is used to check the temperature of components on the phone to see if the PCB is short-circuited.

Part 1: Overall Testing
An iPhone 11 Pro Max is unable to boot up. When lift the screen, disconnect the battery and connect the motherboard with a power cable, the ammeter shows a current of 1 ampere.

The phone has large current while the boot-up hasn’t been triggered. So it can be judged that the fault is on the main power supply circuit and related components.

Since there are lots of related components, the damaged component is hard to detect. An infrared thermal camera is typically used to quickly detect the faulty part.

Then, we use the thermal imager to fix an iPhone 11 Pro Max with large current.
The thermal imager can quickly detect faulty parts with simple operation. It can also quickly detect small current leakage of 5 milliampere and short-circuited capacitors without a microscope.

Remove the motherboard. Using the multimeter to measure the diode value of the battery connector. The diode value is 314, which is normal.

Put the motherboard on the thermal imager. Connect the motherboard with a power cable.

Areas around the NAND are getting hot seriously. We need to separate the motherboard for further testing since NAND is not on the main power supply circuit.
 
Remove the logic board with Heating Platform. Because the phone has been badly dropped before, we can see that there are a lot of missing pads on the pads.
 
Next, connect the logic board with a power cable. The logic board doesn’t have large current. The fault is probably on the signal board.

Part 2: Further Testing and Repair
Using the probes of the multimeter power up the signal board separately. Large current appears on the signal board, so it can be confirmed now that the fault is on the signal board.

Put the signal board on the thermal imager and supply power to it. It can be seen that the temperature of areas around U5000 reaches 80 °C quickly.

There is a short circuit when measure the capacitors around U5000 with the multimeter. Additionally, a capacitor was found to be burnt out during measurement.
Remove the capacitor. Apply some Paste Flux to the capacitor. Remove the capacitor with YIHUA 995D+ Hot Air Gun and replace it with a new one.

Measure with the multimeter again. The diode value returns to a normal value of 446.

There are still missing pads. Clean tin on the bonding pads of the signal board with Soldering Iron and Solder Wick.

Clean tin on the bonding pads of the logic board with the same method and then remove the thermal paste. Keep cleaning the bonding pads with PCB Cleaner.
 
Open Bitmap to determine the missing pads for repair. Since some missing pads are grounded, there is no need to repair them.

Scrape to show circuits of other missing pads with a Sculpture Knife. Apply tin to the bonding pads with a Soldering Iron.

Put the Soldering Lugs in position. Solder with a Soldering Iron at 380 °C. Apply some Solder Mask to the bonding pads that have been repaired. Then solidify with a UV Lamp for 5 minutes.

Then remove excess solder mask with a Sculpture Knife to show the pads. Next, we reball the signal board. Apply a layer of low-temperature Solder Paste evenly.
Put the signal board on the 170 °C Heating Platform to heat. After the solder balls are formed and the motherboard cools, apply some Paste Flux to the bonding pads.

Align the logic board and heating with the Heating Platform. After recombination and the motherboard cools, connect the motherboard with a Power Cable.
At this time, the motherboard no longer has a large current. Then trigger the boot-up with Tweezers. The boot current has returned to normal.

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