A printed circuit board is a core part of several devices and equipment, and hence its structural and functional accuracy is crucial to the functioning of the end product. This is why PCBs have a conformal coat on them, which is basically a thin layer of polymer film applied on the board to protect the components mounted on them from any kind of contamination, dirt, and so on. So, this works as an insulation layer. Conformal coating is of various types based on its chemical composition. There are many benefits of PCB conformal coating and types of it. This post discusses the details of conformal coating, its types, benefits, and more.
Types of Conformal Coating
There are five main types of conformal coating based on their composition or chemical makeup. Each has its own sets of advantages and disadvantages. Here are the types explained at length.
Epoxy resins: These are mostly two-part formulations with excellent heat, abrasion, and moisture resistance. This shields the board in harsh environments. However, it may be tedious if this coating requires any repairs or changes.
Urethane resins: These are either single-part or double-part compositions. However, once applied they are not easy to remove and poses the risk of peeling a component or wire when removing. It offers excellent resistance to chemicals, humidity, and heat.
Acrylic resins: These are mostly solvent-based one-part formulations. They can be easily reworked upon or even removed safely if required. However, these coatings cannot withstand high temperatures and harsh industrial conditions.
Silicone resin: This is a single-component formulation usually suitable for high temperature applications. This coating once applied is hard to remove. However, these resins offer excellent corrosion, humidity, and heat resistance.
Parylene resin: Parylene evaporates into a gas when heated, and later is allowed to cool in a vacuum chamber. Once cooled, it polymerizes into a thin film which is placed on the board. This heating and polymerization process requires specific equipment and this process is called chemical vapor deposition.
Aspects to Consider When Choosing the Conformal Coating Type
As mentioned, conformal coating is done to shield the boards from outside parameters. There are various types of conformal coating types and selecting the right one depends on your application needs. Here are some pointers.
While a UL listing or the required certification plays a huge role in deciding the conformal coating type, it is mainly your application environment that matters. This is because the coating composition or type must be able to withstand the same and safeguard the board inside from corrosion, spills, heat, and so on.
If your application requires constant high temperature or has heat producing processes, silicone conformal coating may be the most suitable one for you. On the other hand, if the working environment is normal while the board may need periodic upgrades, the conformal coating should come off easily. In this case, acrylic conformal coating may be the best option.
Polyurethane may be suitable for low temperature but low- to medium-volume applications.
Parylene may be useful if your application has very specific requirements such as electrical insulation and a homogenous film throughout the board. However, this may be expensive as it required specialized equipment, and hence is used for specific applications.
A board used in outdoor operating environments may require more heat, humidity, and corrosion resistance than the ones used indoor. This is also an important criterion in terms of selecting the conformal coating type.
If you are an OEM looking for PCBs for your product, ensure you partner with a reliable PCB manufacturer and service provider who can understand your requirements. Also, ensure you discuss each detail of your requirement such as the materials used for PCBs, number of layers, components, conformal coating type, and the other aspects of PCB design. ABP Electronics is a custom circuit board manufacturer offering end-end services. The company offers custom solutions and offers assistance regarding every detail of the PCB materials.