Introduction to Conformal Coating Application and Process

1. What is Conformal coating ？

2. Main Applications of Conformal Coating

• Moisture / fog / mold resistance
• Thermal shock resistance, aging resistance, radiation resistance
• Salt‑fog and ozone corrosion resistance
• Vibration resistance, good flexibility, and strong adhesion

Typical Application Scenarios

1. Civil & Commercial Use

   Protects electronic circuits in household appliances against water, detergents, harsh outdoor environments, chemicals, and indoor pollutants.

   Applicable to washing machines, dishwashers, LED screens, alarms, air conditioners, computers, induction cookers, etc.
2. Automotive Industry

   Protects circuits from fuel vapors, salt fog, brake fluid, etc. Essential for long‑term reliability of automotive electronics.
3. Aerospace

   Withstands extreme pressure changes and harsh environments; ensures stable circuit performance under rapid pressurization / depressurization.
4. Marine

   Protects equipment against fresh and saltwater corrosion, even for submerged devices.
5. Medical Devices

   Shields electronics from chemicals and special operating environments for stable performance.
6. Outdoor Electronic Products

3. Process Specifications and Requirements

Spraying Requirements

• Coating thickness: 0.05 mm – 0.15 mm; cured film thickness: 25 μm – 40 μm
• Secondary coating: Apply after full curing for high‑protection products (optional)
• Inspection & repair: Visually check quality; clean unwanted coating from pins / protected areas with board cleaner
• Component replacement: Desolder → clean pads → replace → re‑coat and cure

Coating Process Flow

1. Preparation

   Prepare boards, coating, tools; define areas for masking and key process parameters.
2. Cleaning

   Clean immediately after soldering to remove flux residues.

• Identify contaminant polarity to select proper cleaner
• Alcohol cleaners: Ensure ventilation and drying to prevent explosion risk
• Water cleaning: Use alkaline emulsifier → rinse with pure water

3. Masking Protection (for non‑selective coating)

• Use non‑transfer adhesive tape
• Anti‑static tape for ICs
• Mask components per drawing requirements

4. Pre‑Baking / Dehumidification
   PCBA must be pre‑baked before coating to remove moisture.

5. Coating Methods

• Manual Brushing

  Widely used; ideal for small batches, complex dense PCBs, strict masking. Low material consumption; suitable for expensive two‑part coatings. Requires skilled operators.
• Manual Dipping

  Delivers uniform, continuous film. Not suitable for adjustable capacitors, trimmers, potentiometers, poorly sealed components.

  Key parameters: adjust viscosity; pull‑out speed < 1 m/s to avoid bubbles.
• Spraying
  • Manual Spraying: For complex, low‑volume, multi‑type products. Mask connectors, IC sockets, contacts.
  • Automatic Spraying: Selective coating equipment; high volume, consistent, precise, eco‑friendly. increasingly replacing manual methods.

4. Key Coating Requirements (per IPC‑A‑610E)

Zones

• Must NOT be coated:
  Electrical contacts (gold pads, gold fingers, vias, test points); batteries; connectors; fuses; heatsinks; jumpers; optical lenses; potentiometers; sensors; unsealed switches; performance‑sensitive areas.
• Must be coated:
  All solder joints, pins, and conductive parts of components.
• Optional:
  Solder‑mask covered areas.

Thickness Standards

Thickness Measurement

• Cured film: Micrometer (IPC‑CC‑830B), dry‑film gauge
• Wet film: Measure with wet‑film gauge → calculate dry thickness based on solid content

Quality Requirements

• No runs, drips, or leaks
• Film: smooth, glossy, uniform
• No bubbles, pinholes, wrinkles, shrinkage, dust, chalking, or peeling
• Do not touch before surface dry
• Masked areas must remain coating‑free

5. Summary