Technical requirements and precautions for application of PCBA three proofing paint

What is three proof paint coating machine

We know that the circuit board is a very fine product. The dust, mold and moisture in the air are enough to cause damage to it, which will lead to electric leakage, signal distortion and other problems of the circuit board. Therefore, the way people think of is to add a layer of protective clothing on the circuit board, just as we wear raincoats on rainy days. However, this layer of clothes is not so easy to wear. How to control the uniformity and thickness of coating is a great knowledge. At first, it was operated manually, which was time-consuming and laborious. Later, the three proofing paint coating machine appeared, that is, the machine specially used to dress the circuit board. There are many names of the coating materials, such as three proofing paint, three proofing glue, waterproof oil and so on. The use of the coating machine with this protective layer will greatly enhance the service life of the circuit board and improve the mechanical strength and insulation characteristics of the product.

1、 What are the application methods of PCBA three proofing paint?

1. Dipping: it is more economical for large equipment, but the thickness after coating will be affected by factors such as immersion temperature, time, extraction speed, vertical flow time, whether to add air knife... And sometimes by the characteristics of some components, so it can not be impregnated.

2. Spraying: it is more economical for small and medium-sized equipment. When using spraying, just like painting, the uniformity of coating depends on the relative moving speed, spraying position, spraying pressure and whether there are high parts. In addition, the bottom of the part cannot be sprayed and may need additional treatment.

3. Brushing: it is more economical for small equipment. When coating, it is easy to cause uneven coating due to the skill of coating. In addition, pay attention to the problem of hair loss of the brush. The bottom of the part is also difficult to coat.

4. Selective coating: Although coating has many advantages, it is often time-consuming and labor-consuming. You can also choose to apply at some positions where necessary. Some three proof paint spraying machines can carry out selective coating through program setting, which is much more convenient than manual coating.

2、 What are the operation requirements for applying PCBA three proofing paint?

1. The three prevention work should be carried out in a separate room, but it can not be completely sealed. There must be good ventilation facilities.

2. Smoking, eating and drinking are prohibited in the operation room. Do not use alcoholic beverages before work.

3. During operation, wear masks or gas masks, rubber gloves, chemical protective glasses and other protective equipment to avoid injury to the body, which also depends on the selected three anti paint products. If it is a product containing stupid, pay great attention to protection and fire prevention. If it is a tis-nm environmental protection three anti paint product, it has much higher safety and will not have the risk of combustion.

4. After the work is completed, clean the used utensils in time, sort out and wipe the test tools and equipment, and cover the container with three proofing paint tightly.

5. The workplace shall be clean and free of dust, and irrelevant personnel are prohibited from entering.

6. Tools and equipment shall be fully grounded and electrostatic protection measures shall be taken.

7. Do not overlap PCBA during operation; The PCB board shall be placed horizontally.

8. Small sample curing test (3-5pcs) shall be conducted for each batch of raw materials before use.

3、 What tools are needed to apply PCBA three proofing paint?

III. paint proof, paint box, rubber gloves, mask or gas mask, brush, American adhesive tape, tweezers, ventilation equipment, drying rack and oven.

4、 What are the process requirements for applying PCBA three proofing paint?

1. Clean and dry the board to remove moisture and moisture. Before brushing, the dust, moisture and rosin on the surface of PCBA board to be brushed must be removed to make the three proofing paint adhere to the surface of circuit board well. Drying plate condition: 60 ° C, 30-40 minutes. The effect of coating is better when it is hot after being taken out of the oven.

2. Correctly select and use the brush according to the product size and the layout of board components, pour the three proofing paint into the container, and then use the brush to stick appropriate glue solution to evenly brush and coat the circuit board.

3. The brushing area shall be larger than the area occupied by the device to ensure that all devices and pads are covered.

4. The PCBA Board shall be placed as flat as possible during brushing. There shall be no drip after brushing. The brushing shall be flat and free of exposed parts. The brushing thickness should be between 0.1-0.3mm.

5. After brushing, the side with many plug-in components shall be placed horizontally upward on the air drying frame for surface drying and curing (the coating can be accelerated by heating).

6. When painting three proofing paint on PCB, all connecting plug-in devices, sockets, switches, radiators (fins), heat dissipation areas, etc. (see remarks for components that cannot be painted with three proofing paint) are not allowed to be painted with three proofing paint, which shall be covered and protected with textured paper.

7. If a thicker coating is desired, it can be obtained by applying two thinner coatings (the second coating is allowed only after the first layer is completely dry).

5、 What are the technical requirements for applying PCBA three proofing paint?

1. The three proofing paint shall be applied for protection after passing the test, inspection and thorough cleaning before PCBA assembly.

2. The brush used shall be kept clean and shall not be used for other operations; When painting with the brush, pay attention not to drip to the parts that do not need to be painted; The used brush shall be cleaned with thinner.

3. The coating layer shall be transparent and cover the PCB board and components evenly, with uniform color and consistency.

4. The process steps are: painting surface a → surface drying → painting surface B → curing at room temperature

5. Spraying thickness: the spraying thickness is 0.1mm-0.3mm (the dry film thickness is generally 30-100um)

6. All coating operations shall be carried out at a temperature of not less than 16 ℃ and a relative humidity of less than 75%. As a composite material, PCB will absorb moisture. If the moisture is not removed, the three proofing paint can not fully protect it. Pre drying and vacuum drying can remove most of the moisture.

6、 What are the precautions for applying PCBA three proofing paint?

1. The three proofing paint is forbidden to be used if it exceeds the shelf life.

2. The storage container shall be sealed after being opened.

3. It is forbidden to pour the remaining three proofing paint back into the original storage container and keep it separately and sealed.

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

5. If the glasses are accidentally splashed, open the upper and lower eyelids immediately, rinse them with flowing water or normal saline, and then seek medical treatment.

6. If you feel unwell during brushing, you should quickly leave the operation site to a place with fresh air. If you have difficulty breathing, give oxygen and then seek medical treatment.

7、 What are the quality requirements for applying PCBA three proofing paint?

1. The PCB surface shall be free of paint flow, dripping and leakage, and semi wetting.

2. The three proofing paint layer shall be flat, bright and uniform in thickness, and protect the surface of pad, paste component or conductor.

3. The surface of the paint layer shall be free of orange peel, bubbles, pinholes and ripples.

4. The devices or components that do not need protection do not need to be painted with three proofing paint.

5. The printed board after three proofs shall be clean and tidy, and there shall be no damage to components.

6. There are no dirt, fingerprints, corrugations, shrinkage cavities, dust and other defects and foreign objects on the board surface and components, and there is no pulverization and peeling.

8、 Which components of PCBA cannot be coated with three proofing paint?

1. High power with radiating surface or radiator module, power resistor, power diode and cement resistor.

2. Dial switch, adjustable resistance, buzzer, battery base, fuse base (tube), IC base, touch switch.

3. All types of sockets, pins, terminals and DB heads.

4. Plug in or paste led, nixie tube.

5. The insulating paint and other parts specified in the drawing shall not be used.

6. The screw holes of PCBA board cannot be painted with three proofing paint.

9、 What are the storage requirements for applying PCBA three proofing paint?

1. Raw materials shall be stored in a cool and dry warehouse (room temperature shall not exceed 30 ℃), equipped with explosion-proof ventilation system and equipment, and shall be far away from heat source.

2. It shall be stored separately from other kinds of chemicals, with clear material identification, and mixed storage shall be avoided.

3. Pay attention to fire prevention and provide fire-fighting equipment.

4. The storage warehouse shall be equipped with leakage emergency equipment and reasonable storage materials (such as sand).

5. The warehouse shall be ventilated to prevent accidents caused by leakage gas accumulation.

6. The storage container shall be marked with the effective use date.

7. Storage shelves or equipment shall be well grounded. It is forbidden to use equipment and tools that are easy to produce sparks.