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In PCB manufacturing, even with strict in-process controls, small amounts of electroplating defects (typically ≤1%) are inevitable. To minimize scrap loss, manufacturers must apply targeted repair methods while clearly defining when a defect is not repairable. Effective cost control requires balancing “repair feasibility” and “final product reliability”—minor plating inconsistencies may be repairable, but severe defects such as large-area voids or complete copper-loss in vias should be scrapped.

This guide provides a complete overview of common PCB electroplating defect repair methods, post-repair inspection standards, and scrap criteria to help factories establish a reliable “Repairable vs. Scrap” decision system.

1. Common PCB Electroplating Defects and Repair Methods

PCB electroplating defects vary in mechanism and severity. Using the right tools and repair steps ensures minimal damage and prevents new defects such as trace scratches or over-polishing.

1.1 Via Wall Without Copper / Thin Copper: Local Re-Plating

Typical cause: Insufficient activation, poor cleaning, inconsistent current density
Repairable when: Small quantity (≤5 vias per PCB)
Recommend scrap when: >10 vias per PCB show no copper

Tools

• Plating pen (copper anode)

• Acidic copper electroplating solution

• 800-grit sandpaper

• Isopropyl alcohol, degreasing cotton

Repair Procedure

1. Clean Via Wall: Light sanding + IPA wipe

2. Surface Activation: 10% sulfuric acid, 1–2 minutes

3. Local Re-Plating:

• Current density: 0.5–1 A/dm2

• Plate until copper thickness ≥25 μm

4. Rinse & Dry: Followed by continuity test

Key Requirements

• Final via copper thickness ≥25 μm

• Via resistance ≤100 mΩ

1.2 Plating Peeling / Blistering: Local Re-Plating

Repairable for: Defects ≤10 mm2
Scrap if: Peeling area >20 mm2 (poor adhesion, unreliable after re-plating)

Tools

• Heat gun (300–320°C)

• 1000-grit sandpaper

• Local nickel-gold plating pen or small re-plating equipment

Repair Procedure

1. Remove Residual Plating: Heat + slight sanding

2. Clean Surface: IPA wipe

3. Re-Plate:

• Copper layer: 20–25 μm

• Nickel: 5–8 μm, Gold: 0.1–0.3 μm (for ENIG/ENEPIG pads)

4. Adhesion Testing: Tape test and optional salt spray test (48 hours)

Key Requirements

• Adhesion must pass tape test (no peeling)

• Thickness deviation ≤10%

1.3 Pinholes / Bubbles: Fill and Re-Plate

Repairable when:

• Pinhole ≤0.03 mm

• Bubble ≤0.1 mm
  Not repairable: Penetrated pinholes affecting insulation

Tools

• Copper-based conductive paste

• Cotton swabs

• Heat gun (150–180°C)

Repair Procedure

1. Cleaning

2. Fill pinhole with conductive paste

3. Heat-cure (5–10 seconds)

4. Local copper re-plating (5–10 μm)

5. Microscopic inspection (200x)

Key Requirements

• Insulation resistance ≥1011 Ω

• Surface flatness, no over-plating

1.4 Copper Nodule / Burrs: Mechanical Polishing

Repairable for: Surface nodules not causing short circuits
If short-circuited: Polish first, then retest continuity

Tools

• 1200–1500 grit sandpaper

• Micro grinder (5,000–8,000 rpm)

• 100x magnifier

• Isopropyl alcohol

Repair Procedure

1. Identify defect location

2. Light sanding for small nodules (≤0.05 mm)

3. Micro-grinding for larger burrs (≥0.08 mm)

4. Clean and test spacing + electrical isolation

Key Requirements

• Remaining copper thickness ≥80% of design

• Adjacent line resistance ≥1000 Ω

2. Post-Repair Inspection Standards

After completing any repair, the PCB must undergo comprehensive quality verification.

2.1 Appearance Inspection

• 200x microscope

• No discoloration, scratches, or noticeable bumps

2.2 Thickness Measurement

• Permitted deviation: ±10%

• Verified by X-ray plating thickness tester

2.3 Adhesion Test

• Tape test (3M 610): No peeling

• Bend test: Radius 5 mm, 10 cycles, no cracking

2.4 Electrical Performance

• Via resistance ≤100 mΩ

• Line insulation resistance ≥1011 Ω

• Critical areas: Must pass thermal shock test (260°C / 10s) + salt spray test

3. Scrap Standards for PCB Electroplating Defects

A PCB should be scrapped if repair cost is too high or performance cannot be guaranteed.

3.1 Via Wall Without Copper

• 10 affected vias per PCB (or >5 in multilayer boards)

• Copper thickness after re-plating <20 μm

• Via resistance >500 mΩ

3.2 Plating Peeling / Blistering

• Single defect area >20 mm2

• Total peeling >5% of PCB area

• Fail tape test after re-plating

3.3 Pinholes / Bubbles

• Penetrated pinholes affecting insulation

• 5 pinholes per cm2

• Bubble diameter >0.2 mm or total area >3%

3.4 Copper Nodule / Burrs

• Trace width reduced >10% after polishing

• Line spacing still <0.05 mm

• Cannot restore insulation (resistance <1000 Ω)

3.5 Severe Plating Abnormalities

• Thickness deviation >30%

• Metal impurity levels causing resistivity >2.5×10?? Ω·m

Conclusion

A robust PCB electroplating repair strategy requires accurate defect classification, minimal-damage repair techniques, and strict post-repair testing. At the same time, well-defined scrap criteria prevent unreliable boards from entering downstream processes and eliminate wasted labor and material costs. By building a clear “Repair vs. Scrap” decision model, PCB manufacturers can significantly improve both production yield and cost efficiency.