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eMMC Chip Removal and Reballing Guide

IoTSRG Team
November 22, 2023
3 min read
#eMCP#IoT#Hardware Security#Penetration Testing#Dumping#eMMC

Step 1: Secure the PCB in a Holder

Before proceeding with eMMC chip removal, stabilize the board to prevent accidental damage.

  • Method: Use a sturdy mechanical holder.
  • Why? Affordable, reliable support, minimizes movement during desoldering/reballing.

Step 2: Identifying Faulty BGA (Ball Grid Array) Chips

Inspect for faulty eMMC chips before removal:

  • Visual Inspection: Check for cracks, discoloration, or misalignment.
  • Thermal Imaging: Detect hotspots indicating poor connections.
  • Multimeter/Continuity Test: Identify open/short circuits.
  • X-ray (if available): Examine solder ball integrity non-destructively.

Step 3: Cleaning the Area Around the eMMC

Goal: Remove dust/flux residues for better heat distribution.

  1. Surface Cleaning: Wipe with isopropyl alcohol (IPA) and lint-free cloth.
  2. Chip Cleaning: Post-removal, clean residual solder with solder wick.
  3. PCB Cleaning: Use desoldering braid + IPA on pads for fresh solder adhesion.

Step 4: Applying Minimal Flux

Purpose: Prevents oxidation, ensures proper solder wetting.

  • Tools: Flux pen/syringe.
  • Technique:
    1. Apply thin, even layer on eMMC.
    2. Avoid overapplication (prevents solder bridges).
    3. Keep flux confined to target area.

Step 5: Applying Kapton Tape

Why? Protects nearby components from heat damage.

  • Steps:
    1. Cut tape to size, wrap around eMMC.
    2. Smooth for adhesion (no gaps).
    3. Verify tape doesn’t obstruct soldering area.

Step 6: Removing the BGA (eMMC) Chip

Tools: Hot air rework station, thermocouple, tweezers.

  1. Heating:
    • Monitor temperature (solder melts at 138°C or 183°C).
    • Bubbles at 110–120°C indicate low-temp solder.
  2. Lifting:
    • Use tweezers/vacuum tool when solder is molten.
    • Avoid force to prevent pad damage.

Step 7: Desoldering Process

Goal: Clean PCB pads for reballing.

  1. Soldering Iron: Set to 300–350°C.
  2. Desoldering Wick:
    • Place on pads, heat with iron.
    • Move wick in a "7:30" clockhand motion.
  3. Inspect Pads: Clean with IPA; ensure flat, residue-free surface.

Step 8: Cleaning with Haired Brush & IPA

Steps:

  1. Dip soft brush in 99% IPA.
  2. Gently scrub pads/chip in circles.
  3. Wipe dry with lint-free cloth.

Step 9: Reballing the eMMC Chip

9a. Applying Flux

  • Thin layer on chip pads. Avoid excess.

9b. Stencil Placement

  • Align BGA stencil (use magnetic holder for precision).
  • Tool Tip: RB-01 reballing station recommended.

9c. Solder Ball Placement

Method 1: Pre-made Solder Balls

  • Fill stencil openings with balls.

Method 2: Solder Paste

  1. Press paste on lint-free cloth to dry.
  2. Apply paste in "4:00" motion, remove excess at "10:00".

Final Checks:

  • Reheat to shape balls if needed.
  • Ensure no bridges (critical for adapter compatibility).