PCBA conformal paint general process

PCBA conformal paint spraying is an extremely important means of protection in the field of electronic manufacturing, which has an irreplaceable and important role. It aims to improve the moisture, mildew, and dust resistance of PCBA boards, enhance stability and durability, and ensure the stable operation of electronic devices in various harsh environments. In the entire operation process of PCBA conformal paint, there are strict regulations in terms of process specifications, quality requirements, storage and precautions. The process specification contains basic content such as the scope of operation, the use of materials and tools, and clarifies the technical requirements, such as testing, cleaning, drying plates and other conditions before painting, painting, curing and other steps in the painting process, as well as the treatment of different components. In terms of operational requirements, it pays attention to the safety and independence of the working environment, emphasizing personnel protection and the correct use and maintenance of equipment and tools.

"General Process Specification for PCBA Conformal Coatings"

 1. Content and scope of application This operating procedure clearly stipulates the operation specifications, process requirements and quality requirements of all types of PCBA board coating of the company.

 2. Materials and tools used Conformal paint, paint box, rubber gloves, masks or gas masks, brushes, American tape, tweezers, ventilation equipment, drying racks, ovens.

 3. Technical requirements

    1. The application of three-coat paint protection must be carried out only after testing, inspection approval, and thorough cleaning before PCBA assembly.

2.The brush used should be kept clean and should not be used for other operations; When painting the brush, pay attention to avoid dripping into the parts that do not need to be painted; After use, the brush should be cleaned with thin materials.

3.The coating layer should be transparent, covering the PCB board and components evenly, and the color and consistency should be uniform and consistent.

4.The process steps are: painting the A side→ the surface is dry→ the B side is painted→ curing at room temperature.

5.Spraying thickness: 0.1mm - 0.3mm.

6.All coating operations should be carried out under conditions not lower than 16°C and relative humidity below 75%. Since PCB is a composite material that will absorb moisture, if it is not dehumidified, the conformal paint cannot give full play to the protective effect, and pre-drying and vacuum drying can remove most of the moisture. 4. Requirements for the process of brushing and applying three-conformal paint

7.Clean and dry the plate to remove moisture and moisture. Before brushing, the dust, moisture and rosin on the surface of the PCBA board must be removed first, so that the conformal paint can adhere well to the surface of the circuit board. Baking plate conditions: 60°C, 30 - 40 minutes, after removing from the oven, it is better to paint while it is hot.

8.According to the product size and board component layout, the brush is correctly selected, the conformal paint is poured into the container, and then the brush is dipped in an appropriate amount of glue to evenly brush the circuit board.

9.The brushing area should be larger than the area occupied by the device to ensure complete coverage of the device and pads.

10.When brushing, the PCBA board should be laid flat as much as possible, there should be no drip after brushing, the brushing should be flat, and there should be no exposed parts, and the brushing thickness should be 0.1 - 0.3mm.

11.After brushing, the side with more plug-in elements is placed horizontally on the air drying rack for surface dry curing (the heating method can accelerate the curing of the coating).

12.When applying conformal paint to the PCB, all connected devices, sockets, switches, heat sinks (pieces), heat dissipation areas, etc. (see the note for components that cannot be coated with conformal paint) are not allowed to be brushed with conformal paint, and masking paper should be used to cover and protect them when painting.

13.If a thicker coating is desired, this can be achieved by applying two thinner coats (the requirement is that the first coat must be completely dry before the second coat is allowed). 5. Operational requirements

14.The three-prevention work should be carried out in a separate closed room, and the operation room must have good ventilation facilities.

15.Smoking, eating, and drinking are prohibited in the operation room, and alcoholic beverages should not be consumed before work.

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

17.After the work is completed, the used utensils should be cleaned in time, the tools and equipment should be sorted out and wiped, and the containers containing conformal paint should be tightly covered.

18.The workplace should be clean and dust-free, free of flying dust, and irrelevant personnel should not be allowed to enter.

19.Tools and equipment should be fully grounded and electrostatic protection measures should be taken.

20.Do not place PCBA on top of each other during operation; The PCB board should be placed horizontally.

21.Before each batch of raw materials is used, a small sample curing test (3 - 5PCS) should be carried out. 6. Quality requirements

22.The surface of the PCB should not have flowing paint, dripping, or semi-wetting.

23.The conformal paint layer should be flat, bright, and uniform in thickness, which can protect the surface of the pad, sticker components or conductors.

24.The surface of the paint layer should not have orange peel, bubbles, pinholes, or ripples.

25.Devices or components that do not require protection do not need to be painted with conformal paint.

26.The printed board after the three-proof should be clean and tidy, and there should be no damage to components.

27.There are no defects and foreign substances such as dirt, handprints, corrugations, shrinkage holes, dust and other defects and foreign objects on the board surface and components, and there is no powdering and peeling. 7. Storage requirements The purpose of storage requirements is to ensure the safe storage of raw materials and prevent risks caused by improper storage. The precautions are to give countermeasures for special situations that may arise, such as the treatment of expired paint, emergency treatment of splashes into the eyes, etc. These comprehensive and detailed regulations help the PCBA conformal coating work to be carried out smoothly, improve the protective performance of PCBA boards, and ensure the stable operation of electronic equipment in complex environments.

28.Raw materials should be stored in a cool, dry warehouse (room temperature should not exceed 30 degrees), with explosion-proof ventilation systems and equipment, and away from heat sources.

29.It should be stored separately from other types of chemicals, with clear material labeling, and must not be mixed.

30.Pay attention to fire prevention and be equipped with firefighting equipment.

31.The storage room should be equipped with leak emergency equipment and reasonable containment materials (e.g., sand).

32.The warehouse should be ventilated to prevent accidents caused by the accumulation of leaking gases.

33.The storage container should be marked with an expiration date.

34.Storage shelves or equipment should be well grounded, and equipment and tools that are prone to sparks should be prohibited. 8. Precautions

35.Conformal paint exceeds the shelf life and is prohibited from use.

36.The storage container should be kept tightly closed after opening.

37.It is forbidden to pour the remaining conformal paint back into the original storage container, and it should be stored separately and closely.

38.If the workshop or storage room is not opened for a long time (more than 12 hours), it should be ventilated for 15 minutes before entering.

39.If it accidentally splashes into the eyes, immediately open the upper and lower eyelids, rinse with running water or saline, and then seek medical treatment.

40.If you feel uncomfortable while brushing, you should quickly leave the work site to a fresh air, give oxygen if you have difficulty breathing, and then seek medical treatment.

Remarks Elements that cannot be painted with conformal paint:

41.High power band heat sink surface or heat sink element, power resistor, power diode, cement resistor.

42.DIP switches, adjustable resistors, buzzers, battery holders, fuses (tubes), IC holders, tactile switches.

43.All types of sockets, pin headers, terminal blocks and DB headers.

44.plug-in or stick-on light-emitting diodes, digital tubes.

45.Other parts and devices that cannot use insulating paint as specified in the drawings.

46.The screw holes of PCBA boards cannot be brushed with conformal paint. The quality requirements strictly control the state of the PCB board after painting to ensure that the surface is free of defects and the protection is in place.