PCB before applying HumiSeal

Proper PCB preparation is the most critical step before applying HumiSeal conformal coating, produced by Chase Corporation. In PCB Assembly, SMT Assembly, and Turnkey PCB Assembly, poor preparation is the leading cause of coating failure such as delamination, bubbles, or corrosion.

Remove all contaminants

After soldering, PCBs often have residues that must be eliminated:

• Flux residues (especially no-clean flux)
• Oils from handling
• Dust and particles
• Ionic contamination

Cleaning methods:

• Solvent cleaning (IPA or dedicated cleaners)
• Ultrasonic cleaning for complex assemblies
• Deionized (DI) water cleaning systems

A clean surface ensures proper adhesion of Conformal Coating.

Dry the PCB completely

Moisture trapped on the board can cause serious issues:

• Poor coating adhesion
• Blistering or bubbles
• Corrosion under the coating

Best practices:

• Air dry or use compressed air
• Bake PCB at 50–80°C for 30–60 minutes if needed
• Ensure no moisture remains under components

Inspect before coating

Before coating, perform a visual and quality inspection:

• Check for solder defects (bridges, cold joints)
• Ensure no residues remain
• Verify components are properly mounted

Fixing issues after coating is much more difficult in SMT Assembly.

Mask critical areas

Certain areas must not be coated:

• Connectors and edge contacts
• Test points
• Switches and mechanical interfaces

Use masking tape, boots, or removable latex to protect these zones during PCB Assembly.

Surface activation (optional but recommended)

For high-reliability applications:

• Use plasma cleaning to improve surface energy
• Enhances coating adhesion
• Common in aerospace and automotive Turnkey PCB Assembly

Control handling and environment

• Wear gloves to avoid fingerprints
• Work in a clean, dust-free environment
• Maintain controlled humidity and temperature

Contamination during handling can compromise coating quality.

Final readiness checklist

Before applying HumiSeal:

• PCB is clean and contamination-free
• Fully dry with no trapped moisture
• Masking is correctly applied
• Inspection is completed
• Environment is controlled

Conclusion

Preparing the PCB properly is essential for successful HumiSeal coating. In PCB Assembly, SMT Assembly, and Turnkey PCB Assembly, thorough cleaning, drying, inspection, and masking ensure strong adhesion, reliable protection, and long-term performance.

We support HumiSeal and equivalent conformal coating solutions for your PCBA projects.

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