Three anti-paint is a special formula of paint, used to protect the circuit board and its related equipment from the erosion of the environment. Three anti-paint has a good resistance to high and low temperature performance; its curing into a layer of transparent protective film, 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, leakage, dust, corrosion, anti-aging, anti-mildew, anti-parts loose and anti-corona and other properties The
Three anti-paint effect
Moisture is the most common and most damaging main factor for PCB boards. Excessive moisture will significantly reduce the insulation resistance between the conductors, accelerate the high-speed decomposition, reduce the Q value, and corrosion the conductor. We often see the PCB part of the metal board from the copper is not coated with three anti-paint metal copper and water vapor, oxygen common chemical reaction caused.
The three anti-paint coating on the printed circuit board and components, when the operating environment may be affected by unfavorable factors, you can reduce or eliminate the electronic operating performance of the decline. If the drape can maintain its effect for a satisfactory time, such as greater than the product life, can be regarded as the purpose of its coating.
Three anti-paint ingredients
Acrylic products
Acrylic three anti-paint flexibility can provide comprehensive protection. Because it is a one-component system, with good adhesion, simple operation, the equipment and conditions are not demanding, easy construction, high transparency, high brightness, short operating cycle and other characteristics, so they are easy to use and easy to remove. Some acrylic products meet the military standards, they dry quickly and not dry, can be used to clear the organic solvent to clear, so this type of circuit board three anti-paint is the most widely used on the market is one of the most effective products.
Three anti-paint toxic?
Three anti-paint is toxic depends on the use of three anti-paint thinner and solvent type, if the three anti-paint with toluene, xylene to do thinner, this chemical harmful to humans, if the use of lipids, alcohols and other hazards Smaller. Xylene with moderate toxicity, eye and upper respiratory tract have a stimulating effect, high concentrations, the central system has anesthetic effect.
Although there are many known on the market called environmental protection three anti-paint, but in actual use, we still need to do protective measures, the use of gas masks and so on.
Three anti-paint use of the following four methods:
1, brushing - the use of universal, can be produced in the smooth surface of the excellent coating effect.
2, spray - the use of spray cans products can be easily used in maintenance and small-scale production use, the gun is suitable for large-scale production, but these two spray methods for the accuracy of the operation requirements are high, and may produce Shadow (the lower part of the component is not covered with three anti-paint).
3, automatic dip coating - dip coating to ensure that the complete film, and will not cause excessive spraying caused by waste of material.
4, selective coating of the film - coating accurate and not waste material, suitable for large quantities of film, but the coating equipment requirements are higher. Most suitable for large quantities of film. Use a prepared XY table to reduce the cover. PCB board painting, there are many connectors without painting. Adhesive tape is too slow and tear when there are too many residual glue, consider the shape of the connector, size, location, do a combination of cover, with the installation hole positioning. Cover without paint parts.
Three anti - paint operation process requirements
1, clean and bake, remove moisture and moisture. Must first want to paint the surface of the dust, moisture and oil in addition to clean, so that it can give full play to its protective performance. Thorough cleaning ensures that the corrosive residue is completely removed and the three anti-paint is well adhered to the circuit board surface. Drying conditions: 60 ° C, 10-20 minutes, in the oven after taking out the hot coating effect better;
2, with the brush coating method, the brush area should be larger than the area occupied by the device to ensure that all cover devices and pads;
3, brush the plate as much as possible flat, brush should not have drops of dew, brush should be flat, there can not be exposed part, 0.1-0.3mm between the appropriate.
4. Before brushing and spraying, keep the diluted product fully agitated and place for 2 hours before brushing or spraying. Use high-quality natural fiber brush, gently brush at room temperature dip coating. If you use machinery, you should measure the viscosity of the coating (with a viscosity or flow cup), you can use the diluent to adjust the viscosity.
5. The circuit board assembly should be immersed vertically in the paint. Do not immerse the connector, unless carefully covered, the circuit board should be immersed for 1 minute until the bubble disappears, and then slowly out. The circuit board surface will form a layer of uniform film. So that most of the paint residue from the circuit board back to the film machine. TFCF has different coating requirements. Circuit board or component immersion speed should not be too fast, so as to avoid excessive bubbles.
6. After the end of dip coating, if the surface crust phenomenon, the skin removed, you can continue to use.
7. After brushing flat on the bracket, ready to cure, you need to use the heating method is to accelerate the curing coating. If the coating is uneven or contains air bubbles, the curing in the high temperature furnace should be done at room temperature for some time to allow the solvent to flush out.
Precautions:
1 If it is desired to obtain a thicker coating, it is best to obtain it by applying a thin coating of two layers - and it is required that the second layer be allowed to be applied after the first layer has been completely dried.
2, in the coating on the PCB, the general connector, software sockets, switches, radiators, heat dissipation area, the board area is not allowed to have a coating material, it is recommended to use tearable plastic cover.
3. Thickness of the film: The thickness of the film depends on the application method. The amount of thinner added, the viscosity of the glue is low, the thickness of the coating is thin; conversely, the viscosity of the glue is high and the thickness of the coating is thick.
4. All coating operations should be carried out under conditions of not less than 16 ° C and relative humidity below 75%. PCB as a composite material will absorb moisture. If you do not go to the tide, three anti-paint can not fully protect the role. Pre-drying, vacuum drying can remove most of the moisture.
Repair the already coated device method
If you repair the coated device, simply connect the soldering iron directly to the coating to remove the component, install the new components, and then the area with a brush or solvent cleaning, and then dry, re-use paint Coated well.