10. Thermal management

10.1 Heat origin and heat transfer mechanisms

During the operation of a power module, semiconductor chips dissipate a certain amount of electrical power (conduction and switching losses) in the form of heat. This heat is transferred to the cooler body by two main transfer mechanisms: conduction and convection. In addition, to encourage heat flow, the materials beneath the chips need to have very high lateral thermal conductivity.

• Conduction is the transmission of heat by direct contact between two elements, or by propagation within the same material. A heat flow through a wall made of a single material of thermal conductivity λ, thickness e and surface area S, is defined using Fourier's law: