eMMC Chip Removal and Reballing Guide
IoTSRG Team
November 22, 2023
3 min read
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.
- Surface Cleaning: Wipe with isopropyl alcohol (IPA) and lint-free cloth.
- Chip Cleaning: Post-removal, clean residual solder with solder wick.
- 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:
- Apply thin, even layer on eMMC.
- Avoid overapplication (prevents solder bridges).
- Keep flux confined to target area.
Step 5: Applying Kapton Tape
Why? Protects nearby components from heat damage.
- Steps:
- Cut tape to size, wrap around eMMC.
- Smooth for adhesion (no gaps).
- Verify tape doesn’t obstruct soldering area.
Step 6: Removing the BGA (eMMC) Chip
Tools: Hot air rework station, thermocouple, tweezers.
- Heating:
- Monitor temperature (solder melts at 138°C or 183°C).
- Bubbles at 110–120°C indicate low-temp solder.
- 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.
- Soldering Iron: Set to 300–350°C.
- Desoldering Wick:
- Place on pads, heat with iron.
- Move wick in a "7:30" clockhand motion.
- Inspect Pads: Clean with IPA; ensure flat, residue-free surface.
Step 8: Cleaning with Haired Brush & IPA
Steps:
- Dip soft brush in 99% IPA.
- Gently scrub pads/chip in circles.
- 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
- Press paste on lint-free cloth to dry.
- 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).