PCB potting is a process where a printed circuit board or electronic component is immersed or coated with a protective material, usually a liquid or gel-like substance called potting compound. Depending on applications, there are three commonly used materials: epoxy, polyurethane and silicone.
In the potting process, an electronic assembly is carefully placed inside a mold, often referred to as the “pot”. This mold acts as a temporary container and shaping tool during the potting process. The “pot” is then filled with the selected potting compound. This compound, once cured or hardened, permanently encapsulates and shields the electronic assembly, providing the desired protective characteristics.
Figure 1: PCB potting example
Advantages of PCB Potting
The filled compound is helpful to prevent moisture and corrosive agents from reaching the components, and it also provides shock and vibration protection. For example, potting helps to prevent bubbles and air pockets from forming in electronic components. Bubbles and air pockets can reduce the thermal conductivity, mechanical strength, and electrical insulation of the potting material. They can also create voids that can trap moisture and other contaminants.
Applications of PCB Potting
The applications of PCB potting are diverse and widespread across various industries. In the automotive sector, potting is utilized to protect sensitive electronics in vehicles from extreme temperatures, vibrations, and corrosive substances encountered on the road. In aerospace and marine applications, potting is essential for ensuring the functionality and longevity of electronics exposed to demanding environmental conditions.
How does potting compare to conformal coating?
As an alternative of potting, some PCBs or components are directly applied with a thin layer of transparent conformal coating. So, both act as the barrier providing protection, how to weigh up the two protective solutions?
Protection Strength: Thickness is a key factor that determines the protection strength of both conformal coating and potting. Conformal coatings are typically applied at a thickness of 25-250 micrometers and common materials for this coating include acrylics, silicones, urethanes, and epoxies. While potting materials are typically applied at a thickness of 1-10 millimeters. This means that potting provides better protection than conformal coating, but it also adds more weight and volume to the device. For example, conformal coating is common with mobile and handled electronics while potting can provide additional protection and is applied into more extreme conditions.
Flexibility and Rework:
In terms of flexibility, conformal coating offers greater adaptability and ease of modification compared to potting. The thinner coating layer allows for rework, repair, or modifications if needed, making it a suitable choice for applications where changes may be anticipated. Solvent-based, mechanical, thermal and chemical stripping are all available rework methods. On the other hand, potting, once cured, forms a rigid and immovable protective casing around the components. It's less flexible and more challenging to modify or rework after the encapsulation process.
In summary, potting is preferred when maximum protection is crucial, especially in harsh or extreme environmental conditions. On the other hand, conformal coating strikes a balance between protection and flexibility, making it suitable for applications where modifications and adaptability are important, and weight and volume are constraints. The choice ultimately depends on the specific needs and priorities of the application.
