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Operating Procedures for Applying Three-Proof Coating

Release time:

2025-05-09 16:31

Operating Procedures for Applying Three-Proof Coating
Operating Procedures for Applying Three-Proof Coating

In the manufacturing and maintenance of electronic products, the coating process for conformal coatings is of paramount importance. Conformal coatings—also known as three-proof coatings or electrical protective adhesives—are special coating materials endowed with properties such as moisture resistance, dust resistance, mold resistance, and insulation. They effectively protect printed circuit boards from environmental degradation. This article will provide a comprehensive introduction to three common conformal coating application methods: spray coating, dip coating, and brush coating.

I. Spray Coating Method

The spray coating method is one of the most commonly used techniques for applying conformal coatings. Its working principle is based on liquid atomization. As the conformal coating passes through the nozzle of a spray gun, it is atomized into tiny droplets under the action of high-pressure gas. These droplets are then sprayed onto the surface of the object being coated at high speed, forming a uniform coating. The spray coating method is suitable for large-area coating applications and allows for selective spraying, meeting the requirements of various application scenarios.

Operation Procedure

Equipment Calibration: Inspect the atomization performance of the spray gun, the pressure of the paint supply system, and the exhaust system to ensure that the equipment is in optimal condition.

Workpiece Preprocessing: Ultrasonic cleaning technology is employed, in conjunction with a neutral detergent, to remove oil stains and oxide layers, followed by drying. For areas that need to retain conductivity or avoid coating, professional masking materials are used for protection.

Spraying three-proof paint:

Automatic machine spraying: Suitable for large-scale production, featuring high efficiency and stable quality. It requires precise control of the spray gun’s movement trajectory, spray rate, and droplet size.

Hand spraying: Suitable for small-batch production or repairs, offering high flexibility. Operators must master spraying techniques to ensure an even coating.

Curing: Perform stepwise curing according to the established temperature profile, with strict control over temperature fluctuations.

Quality Inspection: Visually inspect the appearance of the paint finish, and use specialized instruments to test key parameters such as insulation performance and temperature resistance.

II. Dip Coating Method

The dip-coating method is suitable for applications requiring comprehensive and uniform coating, particularly for printed circuit boards with large or complex structures. The principle behind this method relies on the capillary action and gravity of the liquid to ensure that the coating material adheres evenly to the surface of the object being coated.

Operation Procedure

Preparatory work:

Clean the circuit board: Remove contaminants such as oil stains, dust, and rust.

Prepare the coating solution: Select an appropriate three-proof coating, dilute it according to the specified ratio, and pour it into a clean container.

Cover non-coated areas: Use anti-static tape to cover areas that do not require coating.

Dipping operation: Slowly immerse the object into the paint liquid, ensuring that all areas are fully submerged. Lift it out at a uniform speed, and carefully control the lifting angle.

Drying and Curing: Use natural drying or thermal curing to enhance coating quality.

Inspection and Repair: Check the coating for smoothness and thickness, and promptly repair any defects.

III. Brush Coating Method

The brush-coating method is simple to operate and highly flexible, making it particularly suitable for small-batch production and PCB boards with complex structures. It uses a brush to evenly apply the diluted three-proof coating onto the surface of the PCB board.

Operating steps

Preprocessing: Remove dust, moisture, and oil stains from the surface of the PCB board; if necessary, perform rust removal and then dry it thoroughly.

Dilute the three-proof coating: Dilute to the appropriate viscosity according to the specified ratio and stir thoroughly.

Choose the right brush: Select a high-quality brush made of natural fibers or synthetic fibers, tailored to the size and shape of the PCB board.

Apply the three-proof coating following a specific sequence and direction, controlling the pressure and speed of application to ensure an even coating.

Curing Treatment: Perform the curing treatment at an appropriate temperature according to the conformal coating model and requirements.

IV. Conclusion

The spray coating, dip coating, and brush coating methods each have their own advantages and disadvantages and are suitable for different production scenarios and requirements. Spray coating is efficient and provides uniform coverage, making it ideal for large-scale production; dip coating ensures comprehensive and even coverage, making it well-suited for large or complex structures; and brush coating is simple to operate, making it appropriate for small-batch production and complex PCB boards. In practical applications, the appropriate coating method should be selected based on the PCB board’s structure, production volume, and coating requirements, and operators must strictly adhere to the operational guidelines to ensure both coating quality and operational safety. By rationally selecting and applying these coating processes, the stability and reliability of electronic products can be effectively enhanced.

Bossin Related Product Recommendations

UV-resistant, moisture-proof, and anti-corrosion coating

Product Type

Product Features

Application areas

B-02 (Phosphate Acrylate)

Enhance adhesion to substrates such as metal, glass, and plastic.

Vacuum-plated UV coatings, metallic UV varnishes, UV adhesives, UV inks

B-404 (Aliphatic Polyurethane Acrylate)

Good adhesion, moisture-cured

UV-resistant, anti-corrosion, and anti-moisture coating; self-adhesive; dual-curing

B-405 (Aliphatic Polyurethane Acrylate)

Good adhesion, moisture-cured

UV-resistant, three-proof coating, dual-cure

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