Conformal Coating is a special formula of paint, used to protect the circuit board and its related equipment from the erosion of the environment. Conformal Coating 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
Conformal Coating 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 corrode the conductor. We often see the PCB part of the metal board from the copper is not coated with Conformal Coating metal copper and water vapor, oxygen common chemical reaction caused.
The Conformal Coating 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 this paint can maintain its role in a satisfactory time, such as greater than the use of the product period, can be regarded as the purpose of its coating.
Conformal Coating ingredients
Acrylic Conformal Coating 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 clear. 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 Conformal Coating is the most widely used on the market is one of the most effective products.
Conformal Coating toxic?
Conformal Coating is toxic depends on the use of Conformal Coating thinner and the type of solvent, pcb proofing if the use of Conformal Coating with toluene, xylene as thinner, this chemical harmful to humans, if the use of lipids, alcohols Such as less harmful. Xylene with moderate toxicity, eye and upper respiratory tract irritation, high concentrations, the central system has anesthetic effect.
Although there are many known on the market called environmental protection Conformal Coating, but in actual use, we still need to do protective measures, the use of gas masks and so on.
Conformal Coating 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 Conformal Coating).
3, automatic dip coating - dip coating to ensure 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 corrosive residues are completely removed and the Conformal Coating are well adhered to the circuit board surface. Drying conditions: 60 ° C, 10-20 minutes, in the oven after taking out the hot coating 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 far 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 a high-quality natural fiber brush and gently brush the dip at room temperature. If you use machinery, you should measure the viscosity of the coating (with a viscosity agent 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. PCB design circuit board or components immersion speed should not be too fast, so as to avoid excessive bubbles.
6. After re-use after dip, 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, it should be placed at room temperature for more time to allow the solvent to flush out.
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 anti-welding 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 less than 75% relative humidity. PCB as a composite material will absorb moisture. If you do not go to the tide, Conformal Coating can not fully protect the role. Pre-drying, vacuum drying can remove most of the moisture.
Repair the coated device method
If you repair the already 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.