1. In PCBA processing, generally for products with special purposes, such as high temperature, high humidity, high salinity, and high corrosion, the printed circuit board will be sprayed with three anti-paints, then in electronic processing, the three anti-paints What are the requirements? let's see it together:
①It has the characteristics of waterproof, anti-dust, anti-dust, anti-acid, alkali, alcohol, anti-mildew, anti-aging, anti-friction.
②A dense protective film can be generated on the surface of various printed circuit boards, component packaging materials, metal and non-metal materials, and solder joints.
③The protective film after stabilization has stable physical and chemical properties, high insulation resistance, high breakdown voltage and good high frequency characteristics.
④The color is transparent, quick-drying, and the curing temperature is low.
⑤Simple operation, spraying, painting and dipping.
⑥ Non-toxic, harmless to human body and environment.
Coated with three anti-paint
Two, three types of anti-coating materials, applications and development
Three anti-paint materials are usually acrylic, silicone, polyurethane, epoxy resin, and alkyd resin. The process selection is generally determined by the different viscosity of the product (different concentrations have different solid content).
Three anti-coating materials can be divided into insulating protective glue, moisture-proof adhesive, and three anti-adhesives according to the use: according to whether they can be re-soldered after curing, they can be divided into two types: solderable and non-solder solder; according to the wind coating material solvent, they can be divided into traditional There are three types of solvent-based coating materials, water-based coating materials and new solvent-free coating materials.
(1) Solderable three anti-adhesive
Some electronic products may require repair or replacement of components after SMT patch processing and three-proof treatment, which requires the use of solderable three-proof glue. This three-proof paint is required to be transparent and quick-drying, and can generate protective films on various printed circuit boards to prevent leakage and short circuit. The protective film of solderable three-proof can prevent the erosion of weak acid, alkali, alcohol and moisture. It is resistant to high temperature and will not drip when heated. It can be tinned after curing. The main components of the solderable three-proof adhesive are acrylic resin or silicone resin. The solvents are methyl propane acetate, ketone solution, acetone, xylene, and a small amount of additives.
(2) Non-explosive tin three anti-adhesive
Most of the non-solderable three-proof adhesives use epoxy resin materials, single-component or two-component transparent liquids, which can also be cured by heating at room temperature. After the glue is cured, an elastic glue layer is formed, which is dustproof and waterproof. Moisture, salt spray, corrosion, vibration, surface aging, leakage resistance, etc., can work for a long time under the conditions of -60 ~ 180 ℃, suitable for brushing, dipping and spraying.
Non-solder three-proof adhesives are mainly used for high-reliability products used in harsh environments such as high temperature, low temperature, humidity, salt spray and mold, high speed, vibration, etc., such as military weapons and equipment, aerospace, navigation, power supply, electricity, automobiles, And all the electronic equipment working in the harsh environment in the wild.
(3) Traditional solvent-based coating materials
The use rate of traditional solvent-based coating materials is 95% in the European Union and 506 in the United States. At present, most SMT patch processing plants in China use solvent-based coating materials. The two coating materials described above are all solvents. Type coated shoe material.
Since environmental protection legislation restricts the solvents that people are used to using, non-volatile solvent (OC-FREE) legislation has been implemented in the United States and Eurasian, and other solvents may also be banned.
(4) Water-based coating materials
At present, only a small part of special smt processing plants use water-based coating materials. The main reason is that the water-based coating material requires a longer curing time. Although the coating material can be completed within 15mi (solvent-based coating material is completed in 10-12min), it needs 24h to remove the internal moisture, so the PCB Performance testing cannot be performed immediately after curing. For mass production, this is unacceptable. therefore. Water-based coating materials have been produced in small batches. Especially suitable for PCBA production of military products.
(5) New solvent-free coating materials
This technology means that 1009% of the material is coated on the PCB, which is 100% converted into a film without volatility through the process, and the transportation requirements are not high, and the storage and operation are convenient. In the United Kingdom, silicon-based coating materials are mainly used, but the technology has not been well resolved due to process problems, excessive thickness and other problems, so it has not been widely adopted so far.
