Moisture, dust, and corrosion can often compromise the performance and lifespan of PCBA due to the diverse environments. Conformal coating technology effectively enhances PCBA stability and prolongs its lifespan by providing a shield against mold, moisture, and salt spray.
Basic Composition and Protective Functions of Conformal Coating
Conformal coatings provide robust environmental protection for PCBA, contributing to extending product lifespans and improving stability:
- Mold Resistance
The mold-resistant feature in conformal coating prevents mold growth in humid environments. Mold is prone to developing on the surface of circuit boards in damp conditions, potentially damaging the PCB or causing short circuits. Conformal coatings form a protective layer on the PCB surface, effectively isolating moisture and preventing mold growth, ensuring long-term stable operation.
- Moisture Resistance
Moisture resistance is one of the most critical functions of conformal coatings. Moisture and water are primary causes of PCB failures, especially in humid environments where moisture can lead to short circuit and corrosion of components. Conformal coatings form a moisture-proof layer on the PCB, preventing water penetration and effectively mitigating electrical failures caused by humidity, ensuring the normal operation of the circuit board.
- Salt Spray Resistance
In certain environments, salt mist/salt spray corrosion can severely impact electronic components. This is particularly evident in coastal areas or regions with heavy salt spray pollution. The longer a circuit board is exposed to a salt spray environment, the stronger the corrosive effect, potentially leading to component failure. Corrosion occurs when environmental factors such as oxygen, humidity, and pollutants cause material degradation or deterioration.
Salt spray corrosion is a common and highly destructive form of corrosion, primarily caused by chlorides in marine environments, such as sodium chloride (NaCl). These chlorides are transmitted through the air and, upon contacting metal surfaces, chloride ions penetrate protective oxide layers and coatings. This triggers electrochemical reactions, resulting in metal surface corrosion. Furthermore, chloride ions exhibit strong hydration capabilities, easily adhering to surface pores and cracks in metals. They displace oxygen in the oxide layer, making the metal surface more reactive and accelerating corrosion.
Conformal coating effectively prevents salt spray corrosion by creating an additional barrier on the PCB surface. This significantly enhances the strength of anti-corrosion, safeguarding both the board and its components.
Basic Process Requirements
To ensure a stable and high-quality conformal coating, the following conditions must be met:
- Cleaning Requirements
Before applying the conformal coating, you must thoroughly clean the PCB to remove solder residues, dust, grease, and other contaminants. Special attention must be paid to protecting the electronic components when coating, ensuring no unwanted exposure to the coating material.
- Environmental Conditions
The application should take place in a dust-free, oil-free, and water-free environment, with temperature and humidity within specified ranges to prevent fluctuations that could affect the quality of the coating.
- Spraying Equipment Selection
Using appropriate spraying equipment, such as spray guns and nozzles, can ensure an even and fine coating. You must precisely control the speed, angle, and distance during the spraying process to avoid coating drips or sagging.
- Coating Thickness Requirements
The coating thickness is typically between 50 and 200 microns. An overly thick layer can result in uneven drying, while a thin layer may compromise the protective effect.`
- Curing Requirements
After spraying, the PCB must undergo drying and curing. Strict controls of temperature, humidity, and time during the curing process are essential to ensure the coating performs optimally.
Coating Methods
There are several methods to apply conformal coatings: brushing, spraying, and dipping.
- Brushing
This method is simple and suitable for partial repairs and small-scale. The coating is applied with a brush, and after curing, a protective layer forms. However, due to human factors, brushing can result in uneven coatings, brush marks, and non-coating areas, making it less suitable for demanding applications.
- Spraying
This method can be either manual or automatic. Manual spraying is ideal for small-scale production, while automatic spraying is suitable for large-volume production and ensures even coating with high efficiency. This method is appropriate for applications where coating quality is a high priority.
- Dipping
The PCB is immersed in the conformal coating, creating an even protective layer. This method is ideal for large PCBs, providing thorough sealing and ensuring coating uniformity. A disadvantage is that the layer may be thicker, leading to longer drying.
Conformal Coating Spraying Service
LCSC offers high-quality PCBA conformal coating spraying services that effectively protect circuit boards from environmental impact. As a leading provider of electronic components and PCBA services, LCSC offers a one-stop solution, from design to production, ensuring product quality and delivery efficiency.
- Materials
LCSC uses UV-curable conformal coating, which is suitable for a wide range of environmental conditions.
- Thickness Requirements
The coating thickness ranges from 50 to 200 microns, with the default coating applied to the front side. The sides of components and leads do not require coating. If necessary, increasing the thickness to 201~300 microns or 301~400 microns is feasible.
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