Embedded Power Electronic Modules Realized by PCB Embedding

Abstract: Power electronics packaging with a high level of compactness, robustness and versatility has recently become the focus of many technology development projects. In Europe, main drivers for such efforts are e-mobility and “green” energy harvesting, which are promoted by European Commission and national authorities. One promising approach to realize a substantial level of size reduction and process flexibility in the packaging of power electronic systems is the embedding into the build-up layers of printed circuit boards. Conventional printed circuit board embedding, for low power applications, has meanwhile reached a considerable level of maturity and the numbers of products shipped per month are in the tens of millions. Using embedding technology for power electronic devices, however, is still challenging in many aspects.For power applications, the embedded system layout has to account for high currents and/or voltages and at the same time has to provide means to facilitate the power dissipation from the embedded components. PCB-substrates and modules therefore contain conductor traces with large cross sections and/or massive copper and ceramic structures in order to enable the required heat spreading. Such constructions are composed of materials with different CTEs. As a result, considerable stresses prevail in the buildup layers. In contrary to conventional PCBs, the build-up of power modules are non-symmetrical and a careful layout of embedded modules is necessary in order to avoid warpage of the package.

A large variety of embedded power electronic modules has been realized so far. Size and performance of the systems differ accordingly. They range from modules with lateral dimensions of a few square millimeters having a few components embedded for low voltage and currents of up to 50 Amperes, to complex assemblies with 24+ embedded semiconductors and a module area of several square decimeters for an operating Voltage of 600 V and a total power of 150 kW.

The present paper will give an overview of different developments and results in power electronic embedding using PCB technologies. A variety of results from recent projects dealing with embedded power modules will be presented.