Power electronics modules consist of several layers of different materials according to their function. A base plate is necessary for mounting the module to the cooling unit, an insulating layer provides protection against high voltages, the power semiconductor chips with metal electrodes on both sides are used for switching currents, and finally passivation layers have to protect the chips against high electric fields and environmental impacts. The combination of semiconductors, metals and insulators and their different coefficients of thermal expansion leads to stresses and fatigue during temperature excursions. Some major trends require the use of new materials and joinings: higher voltages (up to 6.5 kV), higher currents (above 2000 A), and higher operating temperatures, e.g. in automotive applications (up to 200°C). To reduce the influence of the thermal mismatch between the base plate and the insulator (Alumina, AlN), metal matrix composites such as AlSiC have been used for several years in power modules. To minimize the partial discharge of the ceramics substrate, an amorphous coating (a-Si:H) was tested at high voltages up to 15 kV. A low-temperature joining technique based on silver powder processed under high pressure and at low temperatures works well at higher temperatures. Finally a concept for securing reliability is discussed.