What is three-proof paint?

1. What is conformal paint, and what is conformal paint? Conformal paint is a specially formulated coating that protects circuit boards and their related equipment from environmental aggression. Conformal paint has good high and low temperature resistance; After curing, a transparent protective film will be formed, which has excellent insulation, moisture-proof, leakage-proof, shockproof, dustproof, anti-corrosion, anti-aging, corona resistance and other properties. Conformal coatings are widely used in the electronics manufacturing industry, and there are many conformal coatings with different compositions such as acrylic and polyurethane on the market. Conformal paint is also known as PCB electronic circuit board protection oil, protective oil, electronic waterproof adhesive, circuit board coating oil, circuit board moisture-proof paint, conformal coating, insulation paint, anti-corrosion paint, anti-salt spray paint, dustproof paint, protective paint, coating paint, conformal adhesive, etc.

So what exactly is the conformal paint? In the strict sense, there is no definition, the word "three" is taken from the ancient meaning of "more", that is, the meaning of multi-directional protection, in daily application the conformal paint basically has the "three-proof" performance of waterproof, moisture-proof, dust-proof, in addition, it also has cold and heat shock resistance, aging resistance, radiation resistance, salt spray resistance, ozone corrosion resistance, vibration resistance, good flexibility, strong adhesion and other properties, because of its low technical content, cheap price, in the application of low-end products is more common.

2. The role of anti-paint Conformal paint is a specially formulated coating used to protect circuit boards and their related equipment from environmental erosion, thereby improving and extending their service life and ensuring the safety and reliability of use. Under real conditions, such as chemical environment (fuel, coolant, etc.), vibration, high dust, salt spray, humidity and high temperature, the circuit board may have corrosion, softening, deformation, mildew and other problems, resulting in circuit board circuit failure. Conformal paint is applied to the surface of the circuit board to form a flexible film with a thickness of about 50 - 100 microns, which can protect the circuit from damage under relatively harsh conditions.

3. Anti-paint characteristics

One-component, low-viscosity resin, suitable for brushing, spraying, dipping, pouring and other processes, with good adhesion.

It has good high and low temperature resistance; After curing, it forms a transparent protective film, which has the properties of insulation, moisture-proof, leakage-proof, shockproof, dustproof, anti-corrosion, anti-salt spray, anti-mildew, anti-aging, and corona resistance.

4. The use of conformal paint

Conformal paint covers the surface of the circuit board, creating a 50 - 100 micron thick film. It protects circuits from damage such as chemicals (e.g. fuel, coolant, etc.), shock, moisture, salt spray, humidity and high temperatures. Under these conditions, the circuit board may be corroded, mold growing, and short circuits, leading to failures in circuits without conformal paint. Conformal paint is mainly used in daily applications to protect the integrated circuits of ordinary household appliances and electronic products such as color TVs, refrigerators, washing machines, microwave ovens, air conditioners, telephones, electric water heaters, etc., with strong adhesion, waterproof, lightning protection, rust resistance, corrosion resistance, etc., which can greatly improve the performance stability of home appliances.

5. Process requirements for conformal paint

(1) Conformal paint construction technology

Brushing – This is the simplest conformal coating process that produces excellent coating results on smooth surfaces.

Spraying - spraying method is the most commonly used coating method in the industry, and is divided into two types: automatic spraying by machine and manual spraying. Machine spraying can realize automatic feeding, save labor and material costs, improve production efficiency, and ensure product consistency, product quality and surface spraying effect.

Dip coating – Dip coating ensures complete lamination and does not cause material waste due to overspray.

Selective coating film – accurate application without wasting material, suitable for large batches of lamination, but with high requirements for coating equipment, is most suitable for large batches of lamination. Use a compiled XY table to reduce occlusion. When painting the PCB board, there are many connectors that do not need to be painted, the adhesive tape is too slow and there is too much glue left when tearing, you can consider making a combined cover according to the shape, size and position of the connector, and use the mounting hole to position it to cover the part that does not need to be painted.

(2) Precautions during operation

Clean and dry the plate to remove moisture and moisture. The dust, moisture and oil stains on the surface of the object to be painted must be removed first, so that it can give full play to its protective effect. Thorough cleaning ensures that corrosive residues are completely removed, allowing the conformal paint to adhere well to the surface of the board. Baking conditions: 60°C, 10 - 20 minutes, apply while hot after removing from the oven for better effect.

When applying conformal paint using the brush method, the brush area should be larger than the area occupied by the device to ensure complete coverage of the device and pads.

When brushing the conformal paint, the circuit board should be laid flat as much as possible, there should be no drip after brushing, and the brushing should be flat, and there should be no exposed parts, which should be 0.1 - 0.3mm.

Before brushing and spraying conformal paint, ensure that the diluted conformal paint is well stirred and left for 2 hours before brushing or spraying. Use a high-quality natural fiber brush and apply the dip gently at room temperature. If using machinery, the viscosity of the paint should be measured (using a viscosity agent or flow cup), and the viscosity can be adjusted using a thinner.

The circuit board assembly should be immersed vertically into the paint tank. Do not immerse the connector, unless carefully covered, the circuit board should be immersed for 1 minute until the bubbles disappear, and then slowly take it out, a uniform film layer will form on the surface of the circuit board. Most of the paint residue should flow from the circuit board back to the dipping machine, and the immersion speed of the circuit board or components should not be too fast to avoid excessive bubbles.

When using again after dipping, if there is a crust on the surface, remove the epidermis and continue to use.

If the coating surface is uneven or contains bubbles, it should be placed at room temperature for more time before curing in a high-temperature furnace, so that the solvent can flash out.

(3) Operating environment requirements

The application of conformal paint should be carried out in a separate closed room, and the operation room must have good ventilation facilities.

Smoking, eating, and drinking are prohibited in the operation room, and alcoholic beverages should not be consumed before work.

Wear masks or gas masks, rubber gloves, chemical protective glasses and other protective equipment during operation to avoid injury to the body.

After the work is completed, wash the used utensils in time, organize and wipe the tools and equipment, and cover the containers with conformal paint tightly.

The workplace should be clean and dust-free, free of flying dust, and irrelevant personnel should not be allowed to enter.

Tools and equipment should be fully grounded and electrostatic protection measures should be taken.

Do not place circuit boards on top of each other during operation; The PCB board should be placed horizontally.

Before each batch of raw materials is used, a small sample curing test should be done.

(4) Places where conformal paint cannot be coated

1.High power band heat sink surface or heat sink element, power resistor, power diode, cement resistor.

2.DIP switches, adjustable resistors, buzzers, battery holders, fuses (tubes), IC holders, tactile switches.

3.All types of sockets, pin headers, terminal blocks and DB headers.

4.plug-in or stick-on light-emitting diodes, digital tubes.

5.Other parts and devices that cannot use insulating paint as specified in the drawings.

6.The screw holes of the circuit board board cannot be painted with conformal paint.

(5) PCB board requirements coated with conformal paint

1.The surface of the circuit board should not have flowing paint, dripping, or semi-wetting.

2.The conformal paint layer should be flat, bright, and uniform in thickness to protect the surface of the pad, sticker component or conductor.

3.The surface of the paint layer should not have orange peel, bubbles, pinholes, or ripples.

4.Conformal coating is not required on devices or components that do not need to be protected.

5.The printed board after the three-proof should be clean and tidy, and there should be no damage to components.

6.There are no defects and foreign substances such as dirt, handprints, corrugations, shrinkage holes, dust and other defects and foreign objects on the board surface and components, and there is no powdering and peeling.

6. The difference between conformal paint and PCB nano-coating Although conformal paint also has many characteristics and advantages, which can make electronic products have moisture-proof, anti-leakage, shockproof, dustproof and other performances, but with the development of science and technology and the increasing improvement of people's material living standards, consumers have put forward more requirements for product quality. Regulatory efforts in relevant countries and economies have also increased, the barrier to entry has increased, and manufacturers using low-end materials to produce low-quality products are facing greater survival challenges. More and more high-end manufacturing industries are aware of this and are constantly investing in research and development to improve quality, starting to use more advanced and cutting-edge materials and technologies. Nano moisture and anti-corrosion coating is an advanced representative of PCB waterproof, moisture-proof and salt spray corrosion materials, nano coating not only has the basic protective characteristics of conformal coating, but also solves some problems that conformal coatings cannot solve, greatly improving protection and environmental protection performance. As an industry pioneer of PCB nano-coating, nano-moisture-proof coating has always led the market direction, and its products have been tested by many domestic listed companies.

Through the above detailed explanation of conformal paint, the following can be summarized:

<！--[if！支持列表]-->·       <！--[endif]-->Definition and protective performance: Conformal paint is a special coating that protects circuit boards and related equipment from environmental erosion, although there is no strict definition of "three-proof", but it basically has waterproof, moisture-proof, dust-proof functions in daily life, and also has a variety of other properties, because of the low technical content and low price in the low-end products are widely used.

Function: Protect the circuit board and its related equipment from harsh environmental erosion, improve and extend its life, and ensure the safety and reliability of use.

Features: One-component, low-viscosity resin, suitable for a variety of processes and good adhesion, cured into a transparent protective film, with a variety of protective properties.

Usage: Used for integrated circuit protection of various home appliances and electronic products, improving product performance stability.

Process requirements

Construction process: including brushing, spraying, dipping, and selectively coating film, each with its own characteristics and applicable scenarios.

Operation precautions: cleaning the drying board, specific requirements for different coating methods, treatment when re-use, etc.

Operating environment requirements: separate closed room operation, good ventilation, wearing protective equipment, cleaning after work, etc.

Uncoated places: such as high-power heat dissipation components and other specific components and parts.

Requirements after coating: the surface should not have a variety of undesirable phenomena, protect the relevant components and keep the board surface clean, etc.

Difference from PCB nano coating: conformal paint has many properties, but with the increase in demand, nano moisture and anti-corrosion coating, as an advanced representative, in addition to the basic protective characteristics, it also solves the problems that conformal coating cannot solve, improve protection and environmental protection performance, high-end manufacturing gradually began to use this more advanced technology.