Epoxy as an electrical potting compound
Regular epoxy can be used for thermal insulation but it can trap heat in electronic assemblies that can affect the performance of temperature sensitive parts. The 832TC which is a thermally conductive epoxy, encapsulating and potting compound has the ability to protect circuits by reducing the risks of heat buildup. For printed circuit assemblies where thermal management is an issue, 832TC can be used as an electrical potting compound. When 832TC is cured, it improves reliability, operational range and prolongs the life of the electrical and electronic parts. This electric grade epoxy can also be used to restrict access to proprietary design elements. The 832TC epoxy has strong chemical resistance against brine, acids, based and aliphatic hydrocarbons and superb protection against corrosion, fungus, thermal shock, physical impact, water and static.
Urethanes as electric potting compound
Urethanes are known for their properties of flexibility, elongation and abrasion resistance which is an advantage for devices with large stresses due to mismatch of component composition and dimensions. Urethanes have low Tgs that is why they can be used to provide protection to components in consumer electronics with an operating range of -40C to 105C. Urethane formulations can be adjusted if there is a need for fast gel times at room temperature or for slow gel times with very low exotherms. The chemistry of urethanes is a two-component system with one side polyol and the other isocyanate which is sensitive to moisture in the air. However, to purge air, it is suggested to protect unused material with a layer or nitrogen gas in the container.
Silicones as electric potting compound
Silicone when used as an electric potting compound is similar to urethane’s properties of flexibility and elongation. However, it is different from urethane because silicones do not have enough strength to withstand abrasion. High strength silicone potting compound is available but it has too high viscosity that is not necessary in most applications. On the other hand, silicone has the advantage of providing the widest range of temperatures for an electric potting compound. Specialty silicone polymers can handle up to 200C operating temperature with the material staying soft throughout the temperature ranges so that protection can be provided to components with minimal stress. From the aspect of health and environment, silicone is the safest of the three potting compounds.
There are two types of silicones that can be used as an electric potting compound: vinyl polymer-based material that is platinum-catalyzed and the other is condensation type that uses salt as a catalyst. Platinum can be neutralized by sulfur, amine and tin salts so that the potting compound will have areas of cured material where contamination is located. The formulations of condensation type silicone offer better adhesion but it is not suggested for large masses because of the unevenness of cure.