The circuit board is coated with a conformal coating. But why do they bond tightly together to form a thin film, providing essential protection for the board?

　　The attraction between the contacting parts of two different substances is a manifestation of molecular forces, which only become significant when the molecules of the two materials are extremely close. Typically, the surfaces of two solids cannot make tight contact, so the adhesive forces between them remain ineffective. However, liquids and solids can achieve intimate contact, allowing their adhesive forces to take effect—for instance, the adhesion that exists between a coating and the object it’s applied to.

　　This refers to the strength of adhesion between the paint film and the coating surface. Such bonding is formed by the interaction between polar groups in the polymer of the paint film (such as hydroxyl or carboxyl groups) and the polar groups on the coating surface. If the coating surface is contaminated or contains moisture, or if the conformal coating itself has a significant tendency to shrink—and due to cross-linking of the polymer during curing, reducing the number of available polar groups—these factors can all contribute to decreased film adhesion.

　　The adhesion of the three-proof coating can only be measured indirectly. Currently, there are three primary methods specifically designed to assess coating adhesion: the comprehensive approach, which includes techniques like the cross-cut test and circle-drawing method; the peel test, based on the pull-off method; and the solvent-softener combined with water immersion test method.

　　The reason for reduced adhesion is that low-molecular-weight substances within the coating migrate to the coating surface and accumulate between the paint film and the coating interface, weakening the attractive forces between the polymer's polar groups in the paint film and the polar groups on the coating surface. The purpose of surface corona treatment is to eliminate (remove) these low-molecular-weight substances adhering to the coating surface, as they could otherwise impair the paint film's adhesion.

　　Specializing in the production of moisture-proof, corrosion-resistant, and salt-spray-resistant adhesives for a wide range of electronic products. Analysis of abnormal phenomena during the application process:

　　What is the whitening issue that occurs when applying conformal coating?

　　1. Problem description: The film contains water or other liquids, causing it to appear lighter and whiter than the original artwork, with the film taking on a white, hazy appearance.

　　Reason:

　　(1) The wood board has excessive moisture content, causing prolonged water evaporation and extended residence time within the paint film, which leads to whitening. (2) The ambient humidity is too high. (3) Water has inadvertently mixed into the application surface, containers, or paint itself. (4) The thinner is evaporating too quickly. (5) Moisture remaining in the primer film hasn’t been fully removed. (6) The paint has been applied too thickly. (7) The hardener was incorrectly mixed and is incompatible with the paint, resulting in whitening.

　　Solution: (1) Dry the boards before construction, ensuring their moisture content is kept below 12%; (2) Avoid applying thick layers of paint at once; (3) Do not work in high-humidity conditions—use an appropriate slow-drying retarder if necessary; (4) Ensure the surface to be painted is clean and completely free of moisture; (5) Never mix water into the paint or containers; (6) Use the specified thinner and hardener.