Specifications and Requirements for Three-proof Paint Process
Ⅰ. Painting requirements
1. Spray paint thickness: the paint film thickness is controlled within 0.05mm-0.15mm. The dry film thickness is 25μm-40μm.
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. According to the requirements, one can determine whether to carry out the secondary coating.
3. Inspection and repair: worker should visually check whether the coated circuit board meets the quality requirements and repair the problem. For example, if the pins and other protective areas are stained with three-proof paint, worker can use tweezers to hold a cotton ball or clean cotton ball dipped in the washing board water to clean it. When scrubbing, one should be careful not to wash off the normal paint film.
4. Replacement of components:
After the paint film is cured, if want to replace the components, one can do as follows:
(1) Using electric ferrochrome to directly solder the components, and then using a cotton cloth dipped in the board water to clean the material around the pad.
(2) Welding substitute components.
(3) Using a brush to dip the three-proof paint to paint the welding part, and making the paint film surface dry and solidify.
Ⅱ. Operational requirements
1. Three anti-paint workplaces of pcba manufacturing manufacturers are required to be clean and dust-free, and there must be good ventilation measures, and irrelevant personnel are prohibited from entering.
2. Workers must wear masks or gas masks, rubber gloves, chemical protective glasses and other protective equipments during operation to avoid injury to the body.
3. After the work is completed, one 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 many pcb boards like aluminum circuit board, and the circuit boards should not be overlapped. During the coating process, the circuit boards should be placed horizontally.
Ⅲ. Quality requirements
1. The surface of many circuit boards like double sided circuit board must not have paint flow or dripping. When painting with brush, one must be careful not to drip 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 without chalking and peeling phenomenon must not have defects such as bubbles, pinholes, ripples, shrinkage holes, dust and so on. It is worth noting that 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.
5. Parts and components that cannot be coated with three anti-paint:
(1) Conventional non-coating devices: high-power radiators, heat sinks, power resistors, high-power diodes, cement resistors, code switches, potentiometers with adjustable resistors, buzzers, battery holders, fuse holders, ICs Sockets, light touch switches, relays and other types of sockets, pin headers, terminal blocks and DB9, plug-in or patch-type light-emitting diodes with non-indicating function, digital tubes, grounding screw holes.
(2) The parts and devices specified by the drawings that cannot be used with three-proof paint.
(3) According to the Non-Three-proof Components (Area) Catalogue, it is stipulated that devices with three-proof paint cannot be used.
6. If the conventional non-coatable devices in the regulations need to be coated, they can be coated by three-proof coating according to the requirements specified by the R&D department or the drawings.
