Fix iPhone X Keeps Restarting – Logic Board Repair

The unique design and structure of its motherboard have made any repairs to iPhone X far more difficult than previous models. Especially logic board repairs. For every time. We need to desolder the double layer logic board before formal repair and resolder it back to after the repair was finished. Today we’ll fix the keep restarting issue by using our newly launched iPhone X motherboard soldering and desoldering rework station. Let’s begin our repair step by step.

Malfunction

Press the power button. And the Apple Logo appears on the screen(If you have met the issue about Apple logo, please check our special case for Fix iPhone 8 Stuck on Apple Logo). However, it keeps restarting. The motherboard of iPhone X is folded in half and soldered together. The upper layer mainly responsible for the phone boot up, and the lower layer mainly features baseband RF circuit. So the first thing we need to do is to detach the two layers from each other and check.

iPhone X logic board separation

Here comes our iPhone X heating platform. Heat the double-layer motherboard on the platform with temperature of 190℃ for 1 minute. Remove the upper layer with Sculpture Knife and tweezers. Then, remove tins on the two layers respectively.

Malfunction Troubleshooting

Connect the upper layer with display assembly. Then Connect it to DC Power Supply. And power up with trigger signal. The current reading on the ammeter is abnormal, which indicates that the fault is related to USB IC U6300. So we need to replace with a new USB IC and see how it works. Attach the upper layer to PCB Holder. Detach the USB IC from the upper layer with Hot Air Gun. We find that the USB IC has been replaced before and two empty pads have gone missing.

Repair

Let’s begin our repair. Remove tins on the bonding pad with rosin soaked Solder Wick. Then, apply some Paste Flux to the bonding pad. Get a new USB IC in position and solder with Hot Air Gun. Once done, clean with PCB Cleaner.

Test and check

Again, let’s measure boot current of the upper layer. Current reading on the ammeter is normal. The phone can get access to the home screen normally. Fault cleared.

Resolder the double layer motherboard

Now we need to resolder the two layers together. Reball the lower layer first. Then attach the reballed lower layer to the heating platform. Apply some BGA Paste Flux to bonding pads on the lower layer. And get the upper layer in position with the temperature of 150℃ and heat the two layers for 1 minute on the heating platform. Once the two layers have been soldered together. Wait for the double-stacked motherboard to cool for 15 minutes. Check the motherboard carefully. The motherboard has been soldered perfectly.

Test and check again

Now we can assemble the phone and test. Get the logic board and display assembly installed. Connect the battery and press power button. The phone turns on normally. iPhone X keeps restarting when turning on fixed perfectly.

Attaching the video for you for more details. For more repair information, please pay attention to REWA Official Youtube Channel.

Listing of the tools used. There is always one that you need or you are interested in. More cell phone replacement parts and tools please check REWA online store.

• iPhone X Motherboard Soldering/Desoldering Rework Station – RP200 
• Integrated Mobile Phone Repair Platform
• Electron Microscope
• Digital Multimeter
• Stainless Steel BGA Scraper
• Straight Tweezer
• Paste Flux Solder Wick
• Heat-resisting Adhesive Tape – 5.0mm
• Anti-static Plastic Pry Bar Soft Brush