Long life and reliable operation are key requirements of many electronic systems. Excessive heat dissipation in components can cause them to degrade or fail sooner than would normally be expected. Good thermal design results in power converters with lower component temperatures, higher reliability and longer life.

Conduction Cooling - Conduction is a heat transfer mechanism used in every electronics design. Even if a system is designed for convection cooling of the circuit boards, conduction is still the dominant heat transfer mechanism within the component devices and on the circuit board. This is especially true of power electronics, where concentrations of heat are developed in components such as power silicon and magnetics. This heat must be transferred via conduction to the component case, the circuit board or a heatsink before it can be handled by the system-level cooling mechanism(s). Consequently, all electronics designers must be conversant with the techniques of thermal conduction and its analysis.

Conduction is defined as the transfer of heat through a static (non-moving) material. Heat will flow through the material if there is a temperature differential across it. The heat flow will be in the direction from the higher temperature to the lower temperature. The rate of heat flow will depend upon the temperature differential and the thermal conductivity of the material. The overall relationships are analogous to current flow in an electric circuit, where temperature differential is equivalent to voltage differential, thermal conductivity is equivalent to electrical conductivity, and the rate of heat flow is equivalent to electrical current.

Heat generated by a semiconductor must be removed to the ambient environment to maintain the junction temperature of the component within safe operating limits. Often this heat removal process involves conduction from a package surface to a heat spreader that can more efficiently transfer the heat to the ambient environment. The spreader has to be carefully joined to the package to minimize the thermal resistance of this newly formed thermal joint.