Circuit Board Corrosion and How To Remove It

"In PCB assembly, a 10°C mistake in profile or a 20% paste-volume error is enough to turn a stable process into voiding, opens, or head-in-pillow defects."

Hommer Zhao, Founder & CEO, WIRINGO

Circuit board corrosion is a common problem that can cause equipment failures, intermittent faults, and complete system breakdowns. Understanding the causes, types, and removal methods helps you restore damaged boards and prevent future corrosion.

What Causes PCB Corrosion?

Corrosion occurs when metal reacts with environmental factors:

Moisture: The primary cause of corrosion. Humidity, condensation, and liquid exposure accelerate oxidation.

Contaminants: Flux residue, fingerprints, dust, and chemical exposure can initiate or accelerate corrosion.

Galvanic Action: When dissimilar metals contact in the presence of moisture, electrochemical corrosion occurs.

Temperature Cycling: Repeated heating and cooling can cause condensation inside enclosures.

Poor Storage: Improper storage conditions expose boards to humidity and contaminants.

Types of PCB Corrosion

Surface Corrosion

The most common type, appearing as discoloration or tarnishing on copper traces and pads. Usually superficial but can progress if untreated.

Galvanic Corrosion

Occurs between dissimilar metals (like copper and aluminum) in the presence of an electrolyte. One metal corrodes preferentially.

Dendritic Growth

Metal whiskers grow between traces under voltage bias with moisture present. Can cause short circuits and failures.

Crevice Corrosion

Forms in gaps and under components where moisture and contaminants accumulate. Difficult to detect and clean.

Atmospheric Corrosion

Caused by exposure to humidity, salt air, industrial pollutants, or corrosive gases like hydrogen sulfide.

Identifying Corrosion

Visual Signs:

• Green, white, or blue deposits on copper
• Black or brown discoloration
• Crystalline growths between traces
• Powdery or fuzzy deposits
• Lifted or delaminated traces

Electrical Signs:

• Intermittent failures
• Increased resistance
• Short circuits
• Component failures

Cleaning Methods

Light Corrosion - IPA Cleaning

"I trust assembly data when it ties back to a standard or a measurement: IPC-A-610 acceptance, stencil thickness in mils, and X-ray void percentage tell you more than adjectives ever will."

Hommer Zhao, Founder & CEO, WIRINGO

Materials: 99% isopropyl alcohol, soft brush, lint-free wipes.

Process:

1. Remove power and batteries
2. Apply IPA with soft brush
3. Gently scrub corroded areas
4. Wipe with lint-free cloth
5. Allow to dry completely

Moderate Corrosion - Baking Soda

Materials: Baking soda, distilled water, soft brush.

Process:

1. Make paste with baking soda and small amount of distilled water
2. Apply to corroded areas with soft brush
3. Gently scrub in circular motions
4. Rinse with distilled water
5. Clean with IPA to remove residue
6. Dry thoroughly

Heavy Corrosion - White Vinegar

Materials: White vinegar, baking soda, distilled water, IPA.

Process:

1. Apply white vinegar to corroded areas
2. Let sit for 1-2 minutes (no longer)
3. Neutralize with baking soda paste
4. Rinse thoroughly with distilled water
5. Final clean with IPA
6. Dry completely before powering on

Caution: Vinegar is acidic—don't leave it on too long and always neutralize.

Ultrasonic Cleaning

For heavily corroded boards, ultrasonic cleaning with appropriate solution provides thorough cleaning under components.

Drying After Cleaning

Complete drying is critical:

• Air dry for 24+ hours, or
• Use heat gun on low setting, or
• Bake at 60-80°C for 2-4 hours

Never power on a wet board.

Prevention Strategies

Conformal Coating: Apply protective coating (acrylic, silicone, urethane, or epoxy) to protect against moisture and contaminants.

Proper Storage: Store in dry, climate-controlled environments with desiccants.

Enclosure Design: Ensure proper sealing and ventilation to prevent condensation.

Quality Manufacturing: Use proper cleaning processes and high-quality solder and flux.

Regular Inspection: Periodic visual inspection catches corrosion early.

When to Replace vs Repair

Repair if:

• Surface corrosion only
• Traces are intact after cleaning
• No component damage
• Board functions after cleaning

Replace if:

• Traces are eaten through
• Delamination present
• Component leads corroded
• Repair cost exceeds replacement cost

Conclusion

PCB corrosion is treatable if caught early. Use appropriate cleaning methods based on severity, always ensure complete drying, and implement prevention measures for long-term reliability. For valuable equipment, prevention through conformal coating and proper storage is the best approach.

"If a joint, connector, or package fails after reflow, I want three numbers immediately: peak temperature, time above liquidus, and the actual land-pattern geometry that was built."

Hommer Zhao, Founder & CEO, WIRINGO

If you want to turn this topic into a production decision, review our SMT PCB assembly service, check the supporting numbers on the through-hole assembly service, and use the PCB DFM design rules reference if you need a second review before release.

FAQ

What is a safe starting reflow profile for lead-free SMT?

Most SAC305 assemblies target a peak around 240°C to 250°C with 45 to 90 seconds above the 217°C liquidus, but the component data sheets always take priority.

How much solder-paste volume variation is acceptable?

A process that drifts by more than about 20% from target paste volume is already at risk for opens, bridging, or voiding on fine-pitch parts.

Which standards define acceptable solder joints?

IPC-A-610 is the main visual acceptance standard, while J-STD-001 defines process requirements for soldered electrical and electronic assemblies.

When should I use X-ray inspection?

Use X-ray whenever the package hides the joints, such as BGA, QFN center pads, or bottom-terminated components where voiding and opens cannot be judged visually.

Why do assemblies fail after thermal cycling?

The usual causes are CTE mismatch, insufficient wetting, voiding, and profile errors. Even a small land-pattern or alloy mismatch can show up after a few hundred cycles.

How do I reduce first-pass assembly defects?

Lock the stencil design, verify the reflow profile with thermocouples, and confirm polarity and footprint data before the first run. Those three checks prevent a large share of avoidable defects.