Conformation coating of PCBA components

Conformation coating of PCBA components

Everyone has repeatedly said that we should do a good job in quality, implement the quality control of PCBA, and let customers experience our good intentions for quality. But it is true to say that good quality is not empty talk. It requires us to put the inner part into practICe and the outer part into fine detail. Take the first link of PCBA processing as an example. If the conformal coating is not well done, it may increase the subsequent quality problems of the whole product.

Everyone has repeatedly said that we should do a good job in quality, implement the quality control of PCBA, and let customers experience our good intentions for quality. But it is true to say that good quality is not empty talk. It requires us to put the inner part into practice and the outer part into fine detail. Take the first link of PCBA processing as an example. If the conformal coating is not well done, it may increase the subsequent quality problems of the whole product.

1、 What is conformal coating?

In general, we all know that the coating is a transparent coating. In quality inspection, the coating of PCBA should be transparent with naked eyes first, rather than cloudy. In order to ensure the quality of the overall appearance, the conformal coating should be evenly covered on the surface of the printed board and components.

Then whether the coating layer is uniform and consistent. To some extent, it depends on the coating method. Different coating methods will affect the appearance of printed circuit board and the coating of edges and corners under different conditions. Although adopting different methods for different products may cause different problems, such as SMAll bubbles or fish eyes, the overall effect will not affect the use of PCBA products.

What is the conformal coating of PCBA components and what are the inspection methods

2、 Inspection method of coating

The most common inspection method for conformal coating. The SIMplest is visual inspection. Whether the coating layer on the PCB is uniform, whether there is peeling, etc. If it is the coating with fluorescent components, it is not easy to identify it with the naked eye, so it needs to be checked in dim light, and white light is often used as an auxiliary means of inspection.

3、 Goal of conformal coating

1. The conformal coating on PCBA components must have good adhesion; In addition, there should be no cavitation or small bubbles. The lowest evaluation standard is that there are not many small bubbles.

2. Through the detection of PCBA, it is usually necessary to check whether there are abnormalities in the content of powder particles, peeling condition, cracking wrinkles, ripples, fish eye size, etc.

3. In addition, for PCBA coating, we can not ignore the penetration of impurities; In addition, whether the curing is consistent.

4. For functional inspection, if there is obvious loss of adhesion at the jumper of PCB pad, which causes bridging reaction on the pad or adjacent conductor surface, it is a big problem for partial coating.

4、 Thickness of conformal coating

In many special environments, the requirements and reliability of products are very strict. Therefore, during the first article inspection of PCBA, certain requirements and inspections should be carried out on the thickness of the product coating. In particular, the wet film thickness measurement must be carried out. It can obtain the final coating thickness according to the known dry/wet film thickness conversion relationship. The evaluation of unqualified coating is given.