What Are the Three Core Protections?

PCB conformal coating is widely used in electronic manufacturing to protect circuit boards and related components from environmental erosion. It enhances the operational stability of electronic devices and extends their service life significantly, making it an indispensable protective material in industries such as industrial automation, automotive electronics, and aerospace. This article will detail the core protections, additional advantages, types, and application guidelines of conformal coating to help professionals make informed decisions in practical operations.

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1. What is PCB Conformal Coating?

Conformal coating, also known as protective coating, is a specially formulated functional paint designed to shield circuit boards and electronic equipment from environmental damage. It forms a dense, transparent protective film on the surface of components, which adheres tightly to the PCB and components to resist various harsh environmental factors, ensuring stable operation of electronic devices in complex working conditions.

2. The Three Core Protections of Conformal Coating

The term “three protections” refers to the core protective functions of conformal coating, targeting the most common environmental risks faced by PCBs. Here is a detailed breakdown:

2.1 Moisture Protection

Moisture is one of the primary threats to electronic devices. Humidity in the air can easily penetrate into the internal structure of electronic products, leading to short circuits, component corrosion, and insulation failure. Conformal coating effectively blocks moisture infiltration by forming a seamless protective film on the PCB surface. This function is particularly critical in high-humidity environments such as outdoor equipment, marine facilities, and bathroom-related electronics, preventing moisture-induced electrical faults.

2.2 Salt Spray Protection

In coastal areas, marine climates, or industrial environments with salt mist, the salt in the air will adhere to the surface of electronic devices through moisture absorption, causing severe corrosion to metal components such as pins, pads, and connectors. This corrosion gradually degrades the electrical performance of the device and even leads to permanent damage. Conformal coating acts as an isolation barrier to prevent direct contact between salt particles and PCBs, effectively extending the service life of electronic equipment in salt spray environments.

2.3 Mold Protection

Mold thrives in humid and dark environments. When the surface of electronic components gets damp, it provides an ideal breeding ground for mold. Mold not only damages the stability of electrical connections but also erodes the mechanical structure of the device, resulting in equipment failure. The special chemical components in conformal coating inhibit mold growth and reproduction, eliminating mold-related risks and ensuring the reliability of electronic devices in humid and hot working conditions.

3. Additional Advantages of Conformal Coating

High-quality conformal coating offers more than just the three core protections; it also provides multiple additional advantages to enhance device performance and reliability:

• Leakage Protection: Excellent insulation performance reduces leakage in high-power and high-voltage applications, minimizing the risk of electrical failures and ensuring safe operation.
• Dust Protection: The protective film covers the component surface to prevent dust and debris accumulation, avoiding interference with electrical contacts and maintaining smooth circuit operation.
• Anti-static Protection: It effectively suppresses static accumulation, preventing electrostatic discharge from damaging sensitive components such as chips and sensors.

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4. Main Types of Conformal Coating

Conformal coating is classified into three main types based on chemical composition: silicone conformal coating, polyurethane conformal coating, and acrylic conformal coating. All three types provide basic protections such as dustproof, moistureproof, moldproof, salt spray resistance, and aging resistance, but they differ in characteristics and application scenarios. The key differences are summarized as follows:

Acrylic conformal coating cures quickly, enabling high construction efficiency and easy rework, making it suitable for applications with high production rhythm requirements and medium protection needs. Polyurethane conformal coating offers a long service life, excellent wear resistance, and moisture resistance, ideal for outdoor equipment and industrial devices requiring high durability. Silicone conformal coating resists extreme temperatures (from low to high temperature cycles) and has good flexibility, which is suitable for harsh working conditions such as aerospace and automotive electronics. Epoxy conformal coating features outstanding chemical corrosion resistance, applicable to equipment exposed to acids, alkalis, solvents, and other harsh chemical environments.

5. Application Specifications and Requirements of Conformal Coating

Standardized application operations are essential to ensure the protective effect of conformal coating. The following guidelines cover spraying specifications, operational requirements, and quality standards:

5.1 Spraying Specifications

• Thickness Control: The wet film thickness should be controlled between 0.05mm and 0.15mm, and the dry film thickness should be 25um to 40um. This range balances protective performance and circuit compatibility.
• Secondary Coating: For products with high protection requirements, a second coating can be applied after the first film is fully cured, depending on actual needs.
• Inspection and Repair: Visually inspect the coated circuit board to ensure it meets quality standards. If conformal coating adheres to pins or protected areas, clean the affected parts with degreased cotton dipped in circuit board cleaner using tweezers, taking care not to damage the normal film.
• Component Replacement: To replace components after film curing, first solder off the old component with a soldering iron and clean the area around the pad with cotton dipped in circuit board cleaner. After soldering the new component, apply conformal coating to the soldering area with a brush and let it dry and cure.

5.2 Operational Specifications

• The workplace must be clean and dust-free with good ventilation. Unauthorized personnel are prohibited from entering to avoid dust contamination and solvent accumulation.
• Operators must wear protective equipment such as masks (or gas masks), rubber gloves, and chemical safety goggles to protect against solvent hazards.
• Clean tools immediately after operation and seal the conformal coating container tightly to prevent solvent evaporation and paint deterioration.
• Implement anti-static measures for circuit boards. Do not stack circuit boards and keep them horizontal during the coating process to avoid electrostatic damage and physical scratches.

5.3 Quality Requirements

• No running or dripping of the coating is allowed on the circuit board surface. Avoid dripping on locally isolated areas during brush coating.
• The conformal coating film should be flat, bright, and evenly thick, fully covering pads, surface mount components, and conductor surfaces. There should be no bubbles, pinholes, wrinkles, shrinkage cavities, dust, or other defects on the film surface and components, and no chalking or peeling. Do not touch the film before it is dry.
• Components or areas requiring local isolation (such as connectors, switches, grounding screw holes, and heat sinks) should not be coated with conformal coating. Use masking measures to ensure the functionality of these key parts is not affected.

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Choosing the right conformal coating and following standardized application processes can effectively mitigate environmental risks and improve the stability and safety of electronic devices. For high-reliability PCB assembly and conformal coating solutions, FUMAX is your trusted partner. We provide customized protective coating services tailored to industrial automation, automotive electronics, and other industries, ensuring your products perform stably in harsh environments.

Visit our official website for more details: www.fumaxtech.com

Contact us directly via email: sales10@fumaxtech.com