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Unit Circuits Co., Limited
Address: No.3 Shatouxiang Industrial Zone,Changzhen Community,
Gongming,Shenzhen,China 518106
Conformal Coating?

Conformal Coating is a special formula of paint, used to protect circuit boards and related products from environmental erosion. Conformal Coating has good resistance to high and low temperature; it forms a transparent protective film after curing, which has excellent insulation, moisture resistance, leakage resistance, shock resistance, dust resistance, corrosion resistance, aging resistance, corona resistance and other properties.


Under realistic conditions, such as environment with chemical, vibration, high dust, salt spray, humidity and high temperature, the circuit board may have problems like corrosion, softening, deformation, mildew and so on, which may cause the circuit board to malfunction.

The three-proof paint is coated on the surface of the circuit board to form a layer of three-proof protective film (three-proof refers to anti-moisture, anti-salt spray and anti-mildew).


Under conditions of containing chemical substances (such as fuel, coolant, etc.), vibration, humidity, salt spray, humidity and high temperature, without Conformal Coating PCB may be corroded, mold growth and short circuit, etc., which leads to failure of circuit. The use of three-proof paint can protect the circuit from damage, thereby improving the reliability of the circuit board, increasing its safety factor, and ensuring its service life.

In addition, because the three-proof paint can prevent leakage, it allows higher power and closer printed board spacing. So as to meet the purpose of miniaturization of components.

Specifications and requirements of Conformal Coating

1.The paint film thickness:0.05mm-0.15mm.The dry film thickness:25um-40um.

2.Secondary coating: In order to ensure the thickness of the product with high protection requirements, the secondary coating can be carried out after the paint film is cured (the secondary coating is determined according to the requirements).

3.Inspection and repair: visually inspect whether the coated circuit board meets the quality requirements, and check if the problem solved. For example, if the pins and other protective areas are stained with three-proof paint, to clean areas by using tweezers to hold a cotton ball or clean cotton ball dipped in the washing board water. When scrubbing, be careful not to wash off the normal paint film.

4.Component replacement: After the paint film is cured, if you want to replace the component, you can do as follows: (1) Directly take off the component with electric ferrochrome, and then clean areas around the pad with a cotton cloth dipped in water for cleaning PCB (2) Solder the substitute component (3) Use a brush to dip the three-proof paint to brush the welding part, and make the paint film surface dry and solidify.


Operation requirements

1.Workplaces are required to be clean and dust-free with good ventilation measures, and prohibit irrelevant personnel from entering.

2.Wearing masks, gas masks, rubber gloves, chemical protective glasses and other protective equipment during operation to avoid injury.

3.After the work is completed, cleaning tools in time, closing and covering paint container tightly. 

4.Anti-static measures should be taken for the circuit boards, and the circuit boards should not be overlapped. During the coating process, the circuit boards should be placed horizontally.


Quality Requirements

1.The surface of the circuit board must not have any flow of paint or dripping. When painting with a brush, be careful not to drip to the isolated part areas.

2.The three-proof paint layer should be flat, bright and even, which could protect the surface of the pad, SMD component or conductor.

3.The surface of the paint layer and components must not have defects and foreign objects such as bubbles, pinholes, ripples, shrinkage holes, dust, etc., same time no chalking, no peeling. Note: Do not touch the paint film before the paint film is going to dry.

4.Isolated components areas cannot be coated with conformal paint.

Components that cannot be coated with conformal paint 

1.Conventional non-coatable components: paint high-power radiator, heat sink, power resistor, high-power diode, cement resistor, code switch, potentiometer (adjustable resistor), buzzer, battery holder, fuse holder, IC Sockets, touch switches, relays and other types of sockets, pin headers, terminal blocks and DB9, plug-in or patch-type light-emitting diodes (non-indicating function), digital tubes, ground screw holes.


图片5.jpg2.The components specified by the drawings that cannot be used with three anti-paints.

Precautions for Conformal Coating

1.PCBA frame width >5mm

2.10*10mm<PCBA Size <410*410mm

3. PCBA Components height<80mm

4.PCBA distance from conformal coating are to Non Conformal coating area >3mm

5.Clean enough to reach better coating. Coating thickness: 0.1-0.3mmBaking conditions:60°C,10-20mins

6.Pay attention to components which cannot be coated.

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