Solid State Relays generate thermal energy during their on state conduction at approximately the rate of 1.0 to 1.5 watts per ampere of load current depending upon their design. For reliable operation of the Solid State Relay, this energy must be dissipated into the surrounding air in order to maintain a safe operating temperature. The most common method to accomplish this dissipation to the air is through the use of a heat sink. However, the proper sizing of the heat sink is not the only consideration when creating an SSR assembly. Another critical consideration if the proper mounting of the Solid State Relay to the heat sink itself, which can greatly effect the efficiency of the “thermal system” and therefore the operation and reliability of the assembly. This paper discusses the use of thermal interface materials that are placed between the SSR and the Heat Sink to improve thermal performance and the proper mounting techniques to ensure reliable operation of the Solid State relay.