New assembly and packaging technologies for high power and high temperature GaN and SiC devices Zusammenfassung: This thesis work is aimed at investigating the assembly and packaging technologies for GaN and SiC based high power and high temperature electronic devices. The die attachment and interconnection methods have been in the focus of investigations. For mounting SiC and GaN devices Ag sintering and foil based Transient Liquid Phase (TLP) bonding were selected as die attachment techniques. For TLP bonding process the TLP interlayer material was produced in the form of electroplated multilayer foils which were based on Ag Sn and Ag In binary systems. Two design variants of multilayer foils consisting of a 3 layer sandwich structure and a 9 layer structure were successfully produced. The 9 layer structure provided the benefit of avoiding the post bonding annealing step. The novel multi layer foil can be utilized as a commercial product for TLP interlayer material. For both Ag sintering and foil based TLP bonding a complete process parameter optimization was performed. Various characterizations methods such as Differential Scanning Calorimetry (DSC) Energy Dispersive X ray (EDX) Spectroscopy Infrared (IR) Thermography Digital Image Correlation (DIC) and Die Shear Tests were used to determine the properties of the die attachments. Subsequently electrical thermal and mechanical properties of both die attachment types were compared to the current state of the art high temperature die attachments such as Au80Sn20 Au88Ge12 etc. It was found that both Ag sintering and TLP bonding exhibited better thermal and electrical properties. The thermo mechanical stresses in Ag sintered and TLP bonded joints were considerably low in a wide range of temperatures i.e. 30 – 400 ºC. The GaN on Si High Electron Mobility Transistors (HEMTs) from Fraunhofer IAF Freiburg were used during the investigations. These devices feature high breakdown voltages lower specific on state resistances and achieve higher performances on smaller area as compared to their Si counterpart. A systematic electrical characterization of GaN on Si HEMTs was performed from on wafer devices to the final assembly. The objective was to investigate the assembly related thermal and thermo mechanical influences on the electrical characteristics of the devices. A major emphasis was given to the thermal characterization of the GaN assemblies. The surface temperatures of the devices were measured using IR thermography and surface mounted Pt 1000 temperature sensors. The actual channel tem ...