In the manufacturing process of electronic devices, the PCB board, being a critical component, can be affected by environmental factors during use. To enhance the reliability and extend the lifespan of PCB boards, conformal coating is a common solution that should be considered. This article will provide a detailed analysis of the conformal coating process, quality control requirements, and the challenges and solutions encountered in practical applications.
Overview of Conformal Coating Methods
Depending on the production scale, quality requirements, and application needs, common coating methods include brushing, spraying, dipping, and selective coating. Each method is dedicated to suit different scenarios due to its uniqueness. Below is a detailed introduction to four coating methods:
Brushing
Brushing is a simple and cost-effective coating method widely used in repairs, rework, and low-volume production. The coating is applied evenly to the circuit board using a brush. Although it is easy to operate, its coating uniformity is relatively poor, which may result in brush marks. Therefore, brushing is suitable for situations where coating quality is less demanding or where only partial repairs are needed. When using this method, the coating thickness must be carefully measured to match quality standards.
Spraying
Spraying can be done manually or automatically. Manual spraying uses a spray can or spray gun and is suited for low-volume production. While easy to operate, it may lead to uneven coating, and masking is required to protect areas that should not be coated, also resulting in complexity and time-consuming.
Automatic spraying systems use programmed control to achieve high-speed and efficient coating. The PCB board is transported on a conveyor belt, and the spray nozzles apply the coating along a predefined path. This method is particularly suited for large-volume production, especially in production lines where coating uniformity is critical. Automatic spraying equipment can significantly improve production efficiency and ensure consistency in coating, but masking of non-coating areas is still required.
Selective Conformal Coating
Selective coating is a more automated coating method that precisely controls a robotic nozzle to apply the coating only to specific areas of the circuit board. This method is especially beneficial for mass production, as it avoids the need to mask areas that do not require coating. Selective coating can be instantly cured with built-in UV lamps, improving both production efficiency and coating quality control. It is ideal for applications requiring high precision in coating.
Dipping
Dipping involves immersing the circuit board in a transparent coating solution, particularly used for larger circuit boards that require high coating uniformity. The coating thickness can be adjusted by controlling the immersion speed, time, and the viscosity of the solution. This method is suitable for large-volume production and ensures a uniform coating, but extensive masking is required for areas that do not need coating. Dipping is commonly used in applications where full coverage of the circuit board’s surfaces is essential.
Quality Control after Conformal Coating
Post-coating quality inspection includes checking the coating thickness, uniformity, and common defects.
- Thickness and Uniformity
The coating thickness should meet the manufacturer’s specifications. LCSC typically applies a coating thickness of 50 to 200 microns. Coatings that are too thick or too thin can affect the protective performance. The uniformity of the coating directly impacts its protective capabilities, so it is essential to ensure there are no bubbles, drips, or other defects.
- Common Defects
Bubbles, drips, and brush marks are common issues encountered during coating. Visual inspections, ultrasonic testing, and other methods are used to ensure the quality of the coating. The coating should be smooth, flat, and have no obvious defects.
LCSC Shipping Protection
The final step after PCBA conformal coating is transportation. LCSC provides shipping protection to ensure that the PCBA is effectively protected during transit.
LCSC‘s standard packaging uses red anti-static bubble wrap to prevent electrostatic damage to components. For customers with specific requirements, we offer dividers in the packaging to enhance the compression resistance, or an “anti-static bag and divider” dual packaging solution. This packaging solution is especially suitable for protecting high-value or fragile components.
Advantages:
- PCBA is inserted vertically to enhance compression resistance.
- Effectively reduces the mutual pressure between finished
- Ensures the safety of components during transport.
As shown in the image, the PCBA is packaged in an anti-static bag, then wrapped in red bubble wrap to prevent movement during transportation. It is placed in a dedicated slot to ensure secure transport.
