Packaging of power module

In power electronics, components are integrated into housings adapted to each specific need. A package with a single chip inside is called a "discrete component", and a package with several chips is called a "module".

These power modules are one of the elementary parts of a power converter. Depending on how they are built and how they are combined, they perform a wide range of electrical functions, such as a switchgear cell, a bidirectional current switch, an inverter or a bridge rectifier.

A power module is made up of seven elementary components: electronic chips called "semiconductor chips", a metallized ceramic substrate, a baseplate, solder joints, internal connection elements, electrical terminals and an encapsulant.

In many fields, such as automotive and aeronautics, new requirements call for the development of power modules with higher power density and capable of operating at high temperatures (over 200°C) over long periods of time.

In the automotive industry, the need to reduce the cost of electrical systems means that they have to be brought closer to the mechanical devices they control. As a result, some systems have to operate at ambient temperatures ranging from – 40 to 160°C.

In aeronautics, the aim is to reduce the complexity of (hydraulic) wiring on commercial aircraft, which means bringing converters as close as possible to the actuators they control. As a result, some devices will have to operate at ambient temperatures ranging from – 55 to 225°C.

To meet these needs, the 2D planar integration of power modules based on component transfer by soldering and interconnections via wire bonding needs to be reviewed. Improvements are needed in power module packaging, notably through the use of new 3D interconnection technologies as an alternative to wire bonding, and new materials capable of withstanding high thermal stresses.

In this article, the various power module components are presented in detail, along with their implementation procedures, performance and limitations. Technological solutions for increasing power density in power modules and high temperature are also presented.