In view of power electronics applications, baseplates made from metal diamond composites have been manufactured and characterised. The surface contours of the baseplates were measured during thermal loads up to 180°C starting at room temperature with help of the TherMoiré technique. X-ray analysis investigation was performed to detect porosity and local inhomogeneities of the baseplates. Al- and Cu-based diamond composite baseplates were Ni-plated and used for manufacturing of 3.3 kV IGBT modules. The solder layer between AlN AMB (active metal brazing) substrates and baseplates was investigated by ultrasonic and X-Ray analyses. Thermal resistance of the manufactured IGBT modules was characterised and compared to that of IGBT modules with AlSiC or Cu baseplates. The influence of thermal cycling on the solder layer and thermal resistance of the manufactured module was investigated.