The core principle for addressing PCB corrosion is "prevention first, with repair as a supplement." This is because once corrosion occurs, the loss of the metal layer is irreversible. Repair can only mitigate faults and cannot restore original performance. Severe corrosion necessitates PCB replacement. Compared to post-failure maintenance, lifecycle prevention offers lower costs, better results, and greatly extends the service life of both the PCB and the entire device.
I. Design Optimization: Building the First Line of Defense Against Corrosion
Optimization during the design phase is fundamental to corrosion prevention, following the principles of "corrosion-resistant material selection, rational layout, and enhanced protection."
Material Selection: For standard applications, FR-4 epoxy fiberglass boards are preferred. For high-humidity, high-temperature, or outdoor environments, use specialized substrates with high Tg, low moisture absorption, and chemical resistance, such as PTFE-based laminates, which can reduce moisture absorption by over 50%.
Surface Finish Selection: Choose based on the application. Ordinary consumer electronics may use OSP (Anti-Oxidation) + HASL (Hot Air Solder Leveling) composite processes. For high-reliability scenarios (automotive, medical, industrial), prioritize ENIG (Electroless Nickel Immersion Gold), which offers salt spray resistance exceeding 96 hours. For fine-pitch circuits, immersion silver is recommended, providing oxidation resistance three times greater than standard HASL.
Layout and Structure: Appropriately increase trace spacing and creepage distance. Avoid ultra-fine, high-density layouts to reduce the risk of dendritic corrosion. Use via plugging processes to block moisture ingress channels. Avoid pits, blind vias, and other structures that trap liquids. Design drainage and thermal management channels to prevent moisture and contaminant accumulation. Increase insulation between metals of different potentials to eliminate galvanic corrosion. Design protective covers for key areas like connectors to minimize contact with external media.
II. Strict Control of Manufacturing Processes: Eliminating Residues and Process Defects
The manufacturing stage requires strict control of process quality to thoroughly eliminate inherent corrosion risks.
Soldering Process: Use low-residue, halogen-free, low-chloride environmentally friendly fluxes. Avoid highly active rosin-based fluxes. Post-soldering professional cleaning is mandatory, employing ultrasonic cleaning followed by deionized water rinsing. Pass ion cleanliness tests (e.g., ROSE test) to ensure ionic contamination meets industry standards (typically below 1.56 µg/cm² NaCl equivalent). Operators must wear lint-free gloves and anti-static wrist straps throughout; bare-hand contact with PCB surfaces is strictly prohibited to prevent sweat contamination.
Coating and Protection: Solder mask ink must be applied uniformly, ensuring complete coverage without misses, bubbles, or pinholes, and fully cured. For high-reliability applications, conformal coating is essential. Select the type based on the environment: acrylic for dry indoor settings (low cost, easy rework); polyurethane for outdoor, humid, or temperature-variable environments; silicone or parylene for the most demanding conditions (high temp, high humidity, strong corrosion), offering the best protection. Post-coating, perform adhesion and salt spray tests to ensure coating integrity. Strictly control plating and etching processes to ensure uniform plating thickness, strong adhesion, and absence of pinhole defects. Use high-purity electrolytic copper foil to reduce micro-galvanic corrosion induced by impurities.
III. Standardized Storage and Transportation: Isolating Corrosive Media
Finished PCBs must be stored in a standardized warehouse environment equipped with temperature and humidity monitoring. Control temperature between 20-25°C and relative humidity between 40-50%. Keep the storage area away from sources of corrosive gases (chemical plants, boiler rooms) and maintain a ventilated, dry environment. Use vacuum-sealed moisture-barrier aluminum foil bags for packaging, with silica gel desiccant and VCI (Vapor Corrosion Inhibitor) paper placed inside. Ensure an adequate amount of desiccant per bag and inspect/replace expended desiccant regularly. Use shock-resistant, pressure-resistant packaging for transportation to avoid damage to protective layers from vibration/friction. Open-air transportation is prohibited to prevent rain and sun exposure. For long-term inventory (exceeding 6 months), conduct visual inspections and ion cleanliness re-tests before storage and after retrieval to prevent corrosion during storage.
IV. Usage and Maintenance Protection: Scenario-Adaptive Reinforcement
Reinforcing protection based on the specific usage scenario of the equipment is a key link in corrosion prevention.
Indoor General Electronics: Maintain a dry, ventilated operating environment. Avoid placement near water sources or grease fumes. Regularly clean internal dust.
Outdoor, Automotive, Industrial Equipment: Must use sealed, waterproof enclosures. Add waterproof gaskets, and dust/heat dissipation filters to block moisture, dust, and salt spray ingress. In coastal salt-laden environments, apply additional anti-corrosion coatings and perform regular salt spray protection treatments. In humid environments, place small desiccant packs inside the equipment and replace them periodically.
Daily Maintenance: Strictly avoid cleaning PCBs with water or common alcohol. For cleaning, use dedicated electronic-grade isopropyl alcohol (IPA) or anhydrous ethanol. Gently brush with a soft-bristle brush. After cleaning, ensure the board is thoroughly air-dried or oven-dried at low temperature (not exceeding 40°C) before powering on. Periodically inspect the PCB for visual defects: check for solder mask/conformal coating peeling, discoloration of traces, or oxidation of solder joints. Address minor issues promptly. Avoid prolonged overload operation of equipment to reduce thermal cycling stress that can crack protective layers, thereby extending PCB lifespan.
V. Quality Inspection and Reliability Verification: Proactively Identifying Hidden Defects
Establish a comprehensive quality inspection system. Conduct reliability tests such as salt spray testing, damp heat testing, and THB (Temperature Humidity Bias) testing before shipment and storage to verify corrosion resistance under simulated harsh conditions. Regularly perform sampling inspections for ion cleanliness, plating thickness, and protective coating adhesion to ensure all metrics meet industry standards. This proactive testing helps identify process defects and potential issues early, preventing corrosion problems at the source.
Home > 
