The role of PCB three anti-paint
Tri-proof paint is a specially formulated paint used to protect circuit boards and related equipment from bad environment. The three-proof paint has good high and low temperature resistance; after curing, it becomes a transparent protective film, which can be used under conditions such as chemical substances (such as fuel, coolant, etc.), vibration, moisture, salt spray, humidity and high temperature. Protect the circuit from damage. Under these conditions, the circuit board may be corroded, mold growth and short circuit, etc., with excellent insulation, moisture resistance, leakage resistance, dustproof, corrosion resistance, aging resistance, mildew resistance, parts loosening and insulation corona resistance and other properties .
Three anti-paint effect
Moisture is the most common and destructive main factor for PCB circuit boards. Too much moisture will greatly reduce the insulation resistance between conductors, accelerate high-speed decomposition, reduce Q value, and corrode conductors. We often see that the patina on the metal part of the PCB circuit board is caused by the chemical reaction between the copper and the water vapor and oxygen that are not coated with the three-proof paint.
Applying three anti-paints to printed circuit boards and components can reduce or eliminate the decline of electronic operation performance when it may be affected by adverse factors in the operating environment. If this coating varnish can maintain its effect for a satisfactory period of time, such as greater than the service life of the product, it can be regarded as having achieved its coating purpose.
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There are the following four kinds of three anti-paint use process:
1. Brushing-universal use, can produce excellent coating effect on a smooth surface.
2. Spraying-the use of spray can products can be easily applied to maintenance and small-scale production. The spray gun is suitable for large-scale production, but these two spraying methods require higher accuracy of operation and may produce Shadow (where the lower part of the component is not covered with the three-proof paint).
3. Automatic dip coating-dip coating can ensure complete coating, and will not cause material waste caused by excessive spraying.
4. Selective coating of film-coating is accurate and does not waste materials. It is suitable for large-scale coating, but it has higher requirements for coating equipment. It is most suitable for large-volume coating. Using a compiled XY table can reduce the cover. When PCB boards are painted, many connectors do not need to be painted. The adhesive tape is too slow and there is too much residual adhesive when tearing. Consider forming a combined cover according to the shape, size and position of the connector, and use the mounting holes to locate it. Cover parts that are not to be painted.
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Precautions:
1. If you want to get a thicker coating, it is best to get two thinner coatings-and it is required that the first layer must be completely dried before the second layer is allowed to be applied.
2. When applying paint to the PCB, general connectors, software sockets, switches, heat sinks, heat dissipation areas, plug-in areas, etc. are not allowed to have coating materials. It is recommended to use tear-proof solder mask to cover.
3. Thickness of the film layer: the thickness of the film layer depends on the application method. The added amount of thinner is large, the viscosity of the glue is low, and the thickness of the glue is thin; on the contrary, the viscosity of the glue is high and the thickness of the glue is thick.
4. All coating operations should be carried out under the conditions of not less than 16℃ and relative humidity less than 75%. PCB as a composite material will absorb moisture. If the moisture is not removed, the three-proof paint cannot fully protect. Pre-drying and vacuum drying can remove most of the moisture.