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iPhone 12 Pro Max Not Booting? How to Fix with CPU Pad Repair

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A no-boot issue in an iPhone 12 Pro Max is a challenge for repair technicians, especially when caused by missing CPU pads. This guide explains how to diagnose, repair, and restore functionality to the device by skillfully repairing the CPU pads through wire jumping and other intricate methods.

iphone 12 pro max

Device Details

Model: iPhone 12 Pro Max

Announced: 2020, October 13

Defect Phenomenon

Device: iPhone 12 Pro Max

Symptoms:

  1. The device was unable to boot.
  2. Previous repair attempts failed.
  3. Customer feedback identified missing CPU pads.

Repair Process

Initial Inspection

  • Disassembled the phone and found the motherboard already separated.
  • Inspected the CPU under a microscope and confirmed repair traces on the pads.
01 Received the phone the mothebroard has been separated already

Root Cause

  • Missing pads on the CPU were preventing proper connections, including three critical and challenging pads located close to one another.

Repair Process

Step 1: Remove the CPU

  • Carefully remove the CPU from the motherboard.
02 Remove the CPU and check under the microscope

Step 2: Locate the Missing Pads

  • Inspected under a microscope to identify missing or damaged pads.
  • Removed the solidified UV mask covering the pads.

Step 3: Root Identification

  • Patiently scratched the pad areas with a sculpture knife to locate the roots.
  • Strengthened the roots by applying solder flux and curing with a UV lamp.
04 the 3 missing pads
05 remove the UV mask
06 After removing the UV mask the root of the pads cannot be found
07 keep slightly scraching with sculpture knife till we can see a little pads as marked below
09 Root searching

Step 4: Prepare for Wire Jumping

  • Cleaned the roots and applied a minimal amount of tin paste to each.
10 UV solidify the pads and the roots
11 Scratch out the roots
13 finished
12 Tin paste

Step 5: Wire Jumping for Missing Pads

  • Soldered one side of the wire to the roots.
  • Created a loop on the other side for a secure connection.
  • Applied a UV mask to stabilize the wires and cured them with a UV lamp.
14 Then lets jump wires like what we do on the motherboard
CPU Repair
16 Jump wire other pads

Step 6: Reball the CPU

  • Re-balled the CPU with solder balls to ensure proper connection with the motherboard.
17 Solder back the CPU

Step 7: Reassemble the Motherboard

  • Soldered the CPU back to the motherboard and recombined the two motherboard layers using a heating platform.

Summary

The issue finally gets fixed by CPU pads jump wire repair. As mentioned, CPU chip missing pad repair requires rich experience, excellent stable handwork, and great patience.

Do more practice and then you can repair similar issues like this with confidence.

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