Versa Electronics has extensive experience with ruggedized electronic products and assemblies. Conformal coating and potting are two methods of enhancing or ensuring an assembly is protected in harsh environments and insulated against contamination. Conformal coating is the application of a protective chemical or polymer film that conforms to the PCA’s topology. Potting is a process of filling an enclosure or mold with a compound that hardens to provide shock, vibration, moisture and corrosive protection to its enclosed electronics. Versa’s Contract Manufacturing Services experience includes 100’s of thousands of these ruggedized assemblies!
The conformal coating provides a level of protection to printed circuit assemblies in harsh environments where moisture, chemicals or foreign material may be present. PCA’s can be coated in part, or in their entirety, depending on the device’s needs and interface requirements. OEM customers documentation package specifies which areas are to be coated and those that should be masked.
The primary conformal coating materials include acrylics, polyurethanes, and silicone. An acrylic conformal coating is the most preferred given its performance, ease of application and ability to be reworked. Polyurethane coatings provide a durable finish; however, they have a short shelf life and can be difficult to repair. Silicone conformal coating provides a flexible overlay for complex assemblies but, is high in cost and can require special application environments to control material migration when atomized.
Conformal coating application methods include dip, spray, and brushing. Dipping is simply immersing and removing the assembly in a vat of coating material followed by drying. This method provides the quickest form of application but can be challenging when masking of components is required. The most common form of application is spraying. It achieves a very uniform coating and allows for good masking opportunities. The brushing of the conformal coating is primarily for locational applications and in touch up or repair of coated assemblies.
Potting is a process where an enclosure, or form, containing an electronic assembly is filled with a liquid compound that hardens permanently protects the assembly. Potting is frequently done to provide resistance to shock and vibration and to prevent moisture and corrosive materials from affecting the assembly. In addition, potting may provide a level of visual intellectual property protection.
The primary compounds used in potting include epoxy, polyurethane and silicon-based products. Epoxy resins provide material stability before and after processing, are easy to use, and have high temperature and chemical resistance. Cracking can be an issue and some high acids are problematic. Polyurethanes provide a wide range of hardness specifications and are easily modified to meet specific requirements. Ongoing high temperature (266 F) excursions and resistance to chemicals when the assembly is immersed can be problematic. Silicon potting provide a wide range of temperature properties, but the cost is a greater factor with these compounds. In each case, the specific recipe comprising the given potting compound can be dialed in for the application’s requirements.