Coated materials have a long and storied history on printed circuit boards. A good conformal coating protects PCB components from moisture, corrosion, contaminants, and other factors such as vibration and thermal shock. Coating materials is a complex science, and there is no one best coating or application method for every job. These choices depend on the PCB design, materials used and assembly. For example, hand-brushing PCB coating materials is a slow, cumbersome process; But for small batch applications, it is still quite suitable.

No matter which method is chosen, basic application errors can occur, leading to defects forming in the coating and ultimately limiting the functional life of the PCB.

The most common problem in the application of coating materials

The printed circuit board industry is growing rapidly. Think of all the tremendous technological advances we've seen in the last 30 years! PCBA is growing at a similar pace. Through this evolution, we have noticed two important trends that lead to possible problems in the application of coated materials.

1. Components are becoming more complex and facing more demanding performance requirements

2. The size of the PCB continues to shrink, resulting in smaller components and more dense placement

The second point makes the application of coating materials extremely challenging. Due to the small working space, coating material characteristics can limit the performance of the PCB: the coating material needs to flow and distribute evenly over the component, but when the space is small, the surface tension, adhesion and cohesion of the material can prevent the correct distribution of the coating material.

This is just a growing potential challenge. When we look at the issues that lead to design failure, we notice three specific pain points. In no particular order, they are:

1. Bubbles are formed in the coating

2. Too much or too little coating around acute angles

3. Defects occur in the process of extreme thermal aging

These are the three biggest killers in coating material applications. So how do we solve this problem?

Solve common application problems of PCB coating materials

The short answer is: Science - lots of complex, boundary-pushing science. The HumiSeal research team is working tirelessly on the latest breakthroughs in coating material science. This includes redesigning traditional application methods as well as working on creating new coating materials.

UV curable coating material for PCBS

More and more research shows the promise of UV LED curing coating materials. When dealing with sharp part edges, fast-curing coatings have advantages because they cure before the liquid flows to the bottom of the part. As a result, they hold their expected shape very well.

We recommend the use of UV-curable coatings over other fast-curing coatings (such as two-component coatings) because it is relatively simple and easy to use. Two-component materials usually require specialized mixing equipment and a lot of preparation. Uv-curable coating materials also have their drawbacks. Due to the limited penetration of ultraviolet light (UV) through materials, they often require multilayer applications. However, there is hope that the problem can be solved.

UVA spectral light waves have a larger penetration range, enabling thicker coating and curing. In addition, UVA cured coating materials exhibit higher heat shock resistance and physical stability. These are not the only new coating materials being developed.

Sharp edges covered with coating

One of the latest breakthroughs in coating materials comes in the form of sharp edge coverage (SEC). The new coating can adhere tightly to sharp component surfaces. This allows the coating to be distributed more evenly than ever before, reducing cracks caused by the material being too thick or failing to hold glue around corners, ensuring that every point of the component is fully protected.

previous: none

next: none