Electronic circuit board components as the core of PCBA, should have good resistance to environmental adaptability and electrical parameters. Conformal coating is the process of spraying a dielectric material onto a device component to protect it from moisture, fungus, dust, corrosion, abrasion, and other environmental stresses.
Three normal ways to do conformal coating process
1. Brush coating works by flow coating the material onto the board and is suitable for low volume application, finishing and repair.
The finish tends to be inferior cosmetically and can be subject to many defects such as bubbles. The coating also tends to be thicker and unless skilled operators used the coating, highly subjective in quality. And in this way you can add some fluorescent material to your coating liquid and when you work under a fluorescent lamp you can easily to find out which area or space is not covered the coating.
conformal coating brush
2. Spray application coating can be completed with a spray aerosol or dedicated spray booth with spray gun and is suitable for low and medium volume processing.
The quality of the surface finish can be superior to all other methods when a trained skilled operator completes ，the process, as long as the circuit board is clean and the coating has no adhesion issues. The coating application may be limited due to 3D effects but masking requirements are more “shield” than “barrier” since the penetration is less effective. However, the lack of penetration can be an issue where coating is desired to penetrate under devices.
3. Conformal coating dipping is a highly repeatable process and if the PCB is designed correctly can be the highest volume technique.
Coating penetrates everywhere, including under devices, and therefore any masking must be perfect to prevent leakage. Therefore, many PCBs are completely unsuitable for dipping due to design. The issue of “thin tip coverage” where the material slumps around sharp edges can be a problem especially in a highly condensing atmosphere. This tip coverage effect can be eliminated by double dipping the PCB, using several thin layers of anatomist spraying to achieve good coverage without exceeding coating thickness recommendations or a combination of the two techniques.
Moisture + dust + salt spray is an important factor in PCBA failure. Electronic circuit board components coated with three anti (anti-salt spray, anti-heat, anti-mold) paint can withstand the impact of harsh environments on the circuit and components, increase the mechanical strength and reliability, to prevent sudden changes in temperature caused by condensation Wire leakage between the short circuit and even breakdown, for working in high voltage and low pressure conditions of the printed circuit board can improve the wire between the creepage, breakdown phenomenon, thereby enhancing the reliability of the product.
