TO-3 at Motorola around 1955. The lead spacing was originally intended to allow plugging the device into a then-common tube socket. The metal package can be attached to a heat sink, making it suitable for devices dissipating several watts of heat. Thermal compound is used to improve heat transfer between the device case and the heat sink. Since the device case is one of the electrical connections, an insulator may be required to electrically isolate the component from the heatsink. Insulating washers may be made of mica or other materials with good thermal conductivity. The case is used with high-power and
Liquid metal (Fr)(estimated at 27 °C [81 °F]), and gallium (Ga)(30 °C [86 °F]). Alloy systems that are liquid at room temperature have thermal conductivity far superior to ordinary non-metallic liquids, allowing liquid metal to efficiently transfer energy from the heat source to the liquid. They also have a higher electrical conductivity that allows the liquid to be pumped by more efficient, electromagnetic pumps. This results in the use of these materials for specific heat conducting and/or dissipation applications. Another advantage of liquid alloy systems is their inherent high densities. Once oxides have been removed from the substrate surface, most liquid metals