Microwave Tech - Why do we need to spray paint on the fingerprint recognition soft and hard board?

Why do we need to spray paint on the fingerprint recognition soft and hard board?

1. What is the three-proof paint?

Three anti-paint is a kind of specially formulated paint, used to protect circuit boards and related equipment from environmental erosion. The three-proof paint 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 real conditions, such as chemical, vibration, high dust, salt spray, humidity and high temperature, the circuit board may have corrosion, softening, deformation, mildew and other problems, which may cause the circuit board to malfunction.

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

Under conditions such as chemical substances (for example: fuel, coolant, etc.), vibration, humidity, salt spray, humidity and high temperature, the circuit board that is not used with the three-proof paint may be corroded, mold growth and short circuit, etc., leading to the circuit In the event of a failure, 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. Thereby, the purpose of miniaturization of components can be met.

2, the specifications and requirements of the three anti-paint process

Painting requirements:

1. Spray paint thickness: The paint film thickness is controlled within 0.05mm-0.15mm. The dry film thickness is 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 (determine whether to carry out the secondary coating according to the requirements).

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

4. Replacement of components: After the paint film is cured, if you want to replace the components, you can do as follows:

(1) Solder the components directly with electric chromium iron, and then use a cotton cloth dipped in the board water to clean the material around the pad

(2) Welding alternative components

(3) Use a brush to dip the three anti-paint to brush the welding part, and make the paint film surface dry and solidify

Operation requirements:

1. Three anti-paint workplaces are required to be clean and dust-free, and there must be good ventilation measures, and irrelevant personnel are prohibited from entering.

2. Wear masks or gas masks, rubber gloves, chemical protective glasses and other protective equipment during operation to avoid injury to the body.

3. After the work is completed, clean the used tools in time, and close and tightly cover the container with the three-proof paint.

4. Anti-static measures should be taken for the fingerprint recognition soft and hard combination board, 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 fingerprint recognition soft and hard board must not have the phenomenon of flow paint or dripping. When the paint is painted, pay attention to not dripping to the partially isolated part.

2. The three-proof paint layer should be flat, bright, and uniform in thickness to protect the surface of the pad, patch component or conductor.

3. The surface of the paint layer and components must not have defects such as bubbles, pinholes, ripples, shrinkage holes, dust, etc. and foreign objects, no chalking, no peeling phenomenon, note: before the paint film is dry, do not touch the paint at will membrane.

4. Partially isolated components or areas cannot be coated with three-proof paint.