Introduction To Conformal Coating

Conformal coating is a protective non conductive dielectric layer that is applied onto the printed circuit board assembly to protect the electronic assembly from damage due to contamination, salt spray, moisture, fungus, dust and corrosion caused by harsh or extreme environments.

It is usually used in products that are used in outdoor environments where heat and moisture are prevalent. Coating also prevents damage from rough handling, installation, reduction of mechanical and thermal stress. It also prolong the lifeof the product during its operation. At the same time, it helps to increase the dielectric strength between conductors enabling the design of the PCB to be more compact and small. It also acts to protect circuitry and components from abrasionand solvents.

When coated, it is clearly visible as a clear and shiny material. Some coatings are hard, while others have a slightly rubbery texture. Most coatings include a marker that appears greenish white when view under UV light. This marker enables easy inspection of the coating thoroughness checking during production.

In the past, coatings are only applied to military and life/medical products as the cost and the process of doing this washigh then. In recent years, the development in material and new processes has enabled consumer electronics products to be coated as well. This will be becoming more common and will become a norm as circuitry and electronic components continueto shrink in size and dimension.

Types Of Conformal Coating

Commonly used conformal coatings are silicone, epoxy, acrylic, urethane and Paraxylene. The chemical and physical properties of the materials differs and therefore offer different degree of protection. The basic characteristicsof the materials are described below.