Apply HumiSeal conformal coating

Applying HumiSeal conformal coating, produced by Chase Corporation, requires controlled processes to ensure proper protection, adhesion, and reliability. In PCB Assembly, SMT Assembly, and Turnkey PCB Assembly, correct application is critical to achieve consistent coating performance.

Surface preparation (most important step)
Before applying Conformal Coating, the PCB must be thoroughly prepared:

• Remove flux residues, oils, dust, and contaminants
• Use approved cleaning methods (solvent cleaning, ultrasonic, or deionized water)
• Ensure the board is completely dry

Poor cleaning is one of the main causes of coating defects in PCB Assembly.

Masking (protect no-coat areas)
Certain areas must not be coated:

• Connectors and sockets
• Test points
• Switches and contact surfaces

Use tapes, boots, or masking materials to protect these areas during SMT Assembly.

Choose the application method

HumiSeal coatings can be applied using several methods depending on production volume:

Spray coating (manual or automated)

• Most common method in PCB Assembly
• Provides uniform coverage
• Suitable for both low and high volumes

Selective coating (automated)

• High precision using programmable machines
• Ideal for Turnkey PCB Assembly production lines
• Reduces masking requirements

Dip coating

• PCB is immersed in coating liquid
• Ensures full coverage
• May result in thicker coating

Brush coating

• Used for small batches or rework
• Less consistent than automated methods

Control coating thickness

Maintain proper thickness (typically 25–75 µm):

• Avoid too thin (insufficient protection)
• Avoid too thick (risk of cracking or heat issues)

Thickness control is essential for consistent quality in SMT Assembly.

Curing process

After application, the coating must be cured:

• Air drying (common for acrylic coatings)
• Heat curing (for urethane or epoxy)
• UV curing (for UV-curable HumiSeal coatings)

Follow manufacturer specifications for time and temperature to ensure full curing.

Inspection and quality control

After curing, inspect the coating:

• Use UV light to verify coverage (if UV tracer is present)
• Check for bubbles, voids, or missed areas
• Ensure no overcoating on masked areas

Inspection ensures coating quality in Turnkey PCB Assembly.

Best practices

• Maintain clean working environment
• Control humidity and temperature during application
• Use proper equipment calibration
• Train operators on coating techniques

Conclusion

Applying HumiSeal conformal coating involves careful surface preparation, proper masking, controlled application, and thorough curing. In PCB Assembly, SMT Assembly, and Turnkey PCB Assembly, following these steps ensures optimal protection, improved reliability, and long-term performance of electronic products.

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

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