Three proof paint is a specially formulated coating used to protect circuit boards and related equipment from environmental erosion. Three proofing paint has good resistance to high and low temperatures; After solidification, it forms a transparent protective film that can protect the circuit from damage in situations such as vibration, moisture, salt mist, humidity, and high temperatures containing chemicals (such as fuel, coolant, etc.). Under these conditions, circuit boards may be corroded, mold may grow, and short circuits may occur. They have superior insulation, moisture resistance, anti leakage, dust prevention, corrosion resistance, aging resistance, mold resistance, anti loosening of parts, and insulation resistance to corona.

The function of three anti paint

Moisture is the most common and destructive factor affecting PCB circuit boards. Excessive moisture can significantly reduce the insulation resistance between conductors, accelerate high-speed decomposition, reduce Q values, and corrode conductors. We often see copper green on the metal part of PCB circuit boards, which is caused by the chemical reaction of copper, water vapor, and oxygen without coating with three anti paint.

Applying three proofing paint to printed circuit boards and components can reduce or eliminate the performance degradation of electronic products when they may be affected by adverse operating environment factors. If this type of three proof paint can maintain its function for a satisfactory period of time, such as exceeding the product's service life, it can be considered as having achieved its coating purpose.

Composition of three proofing paint

Acrylic products

Acrylic three proof paint has strong flexibility and provides comprehensive protection. Due to its single component system, good adhesion, simple operation, low requirements for equipment and conditions, convenient construction, high transparency, high brightness, and short operating cycle, they are easy to use and easy to remove. Some acrylic products meet military standards, and they dry quickly without drying. They can be removed with matching organic solvents, so this type of circuit board three proofing paint is one of the most widely used and effective products on the market.

Is the three prevention paint toxic

The toxicity of the three proofing paint depends on the type of diluent and solvent used. If toluene and xylene are used as diluents for the three proofing paint, these chemicals are harmful to human health. If lipids, alcohols, and other chemicals are used, the harm is relatively small. Xylene has moderate toxicity and is irritating to the eyes and upper respiratory tract. At high concentrations, it has an anesthetic effect on the central system.

Although many so-called environmental protection three proofing paints appear on the market now, it is still necessary for us to take protective measures in actual use, such as wearing gas mask when using.

There are four types of processes for using three proofing paint:

1. Brush coating - widely used and can produce excellent coating effects on smooth surfaces.

3. Automatic dip coating - dip coating ensures complete film coverage and does not cause material waste due to excessive spraying.

Requirements for the operation process of three proofing paint

1. Clean and dry the board to remove moisture and moisture. It is necessary to first remove dust, moisture, and oil stains from the surface of the object to be coated, in order to fully utilize its protective effect. Thorough cleaning can ensure that corrosive residues are completely removed and that the three proofing paint adheres well to the surface of the circuit board. Drying conditions: 60 ° C, 10-20 minutes, take it out in the oven and apply it while it is hot;

2. Apply using a brush coating method, with a brush coating area larger than the area occupied by the device to ensure full coverage of the device and solder pad;

3. When brushing, the board should be placed as flat as possible, and there should be no dripping after brushing. The brushing should be flat and there should be no exposed parts, preferably between 0.1 and 0.3mm.

4. Before brushing and spraying, ensure that the diluted product is thoroughly stirred, and let it stand for 2 hours before brushing or spraying. Use a high-quality natural fiber brush to gently brush and dip at room temperature. If using machinery, the viscosity of the coating should be measured (using a viscosity agent or flow cup), and a diluent can be used to adjust the viscosity.

6. If there is any skin formation on the surface after the dip coating is completed and reused, remove the skin and continue to use.

7. After brushing, lay it flat on the bracket and prepare for curing. The method of heating is to accelerate the curing of the coating. If the surface of the coating is uneven or contains bubbles, it should be left at room temperature for more time to allow the solvent to flash out before curing in a high-temperature furnace.

matters needing attention:

1. If you want to obtain a thicker coating, it is best to apply two thinner layers - and it is required that the first layer be completely dried before the second layer can be applied.

2. When applying paint to a PCB, it is generally not allowed to have coating materials on connectors, software sockets, switches, heat sinks, heat dissipation areas, and plug-in board areas. It is recommended to use tearable solder tape to cover them.

3. Film thickness: The thickness of the film depends on the application method. The amount of diluent added is large, the viscosity of the adhesive is low, and the thickness of the coating is thin; On the contrary, the viscosity of the adhesive is high, and the thickness of the coating is thick.

4. All coating operations should be carried out under conditions of no less than 16 ℃ and a relative humidity of less than 75%. PCB as a composite material will absorb moisture. If the moisture is not removed, the three proofing paint cannot provide sufficient protection. Pre drying and vacuum drying can remove most moisture.

Method for repairing coated devices

If repairing a component that has already been coated, simply contact the soldering iron directly with the coating to remove the component. After installing a new component, clean the area with a brush or solvent, then dry and recoat with the coating.