The SSR heat sink is designed around a pair of SCR's mounted on a heat-spreading metal base to eliminate thermal fatigue failures. To dissipate the heat developed naturally in a solid state relay due to a nominal voltage drop across the device, it must be mounted on a Finned Heat Sink (FHS), or on a metal plate of adequate size. It is advisable to install a solid state relay where the ambient temperature is relatively low because its current-switching rating is decreased as its temperature increases.

       The solid state relay is a series of single-pole, normally open, solid state switching devices with no moving parts, capable of tens of millions of cycles of operation. It is designed to control 120V, 240V or 480V (up to 660V) alternating current (VAC), and provides zero voltage switching and 2500VAC isolation between the load terminals and the control signal. A control signal causes the SSR heat sink to switch the AC load ON or OFF just as a conventional mechanical contact switch does but with none of the problems associated with moving contact relays, such as corrosion, pitting, arcing, radio frequency interference (RFI) and bounce. Therefore, the solid state relay is able to sustain a much longer life.

       In electronic systems, a heat sink is a passive component that cools a device by dissipating heat into the surrounding air. Heat sinks are used to cool electronic components such as high-power semiconductor devices, and optoelectronic devices such as higher-power lasers and light emitting diodes (LEDs). A heat sink is a heat exchangers such as those used in refrigeration and air conditioning systems, or the radiator in an automobile.