Development and Testing of Cold gas Sprayed Circuit Boards for Power Electronics Applications
Within the framework of the presented project, new mounting concepts for power electronics were implemented by applying Al/Cu coat systems to insulators by means of cold gas spraying (CGS). The layers sprayed with cold gas were investigated and good material properties are observed. The applied metallizations show an extremely small porosity, no thermally induced phase conversions or process-related oxides and a high adhesive strength. Also the processing of assemblies with standard processes such as a soldering, adhesive bonding and heavy wire bonding is possible. The temperature shock stability of the new substrates was determined in temperature cycle experiments and it was compared with the temperature shock stability of the DCB substrates. The substrates were tested actively but also passively in bicameral temperature shock chamber and in power cycling experiments at power electronic function samples. The accomplished reliability investigations showed that the characteristic lifetime of the cold gas sprayed substrates is approximately 80% of the characteristic lifetime of the DCB substrates. These demonstrate that the substrates produced in cold-gas technology can be used for power electronic applications.
New implementation of RSFQ superconductive digital gates
We present additional RSFQ superconductive digital electronics logic gates that have been developed to complement already existing gates. These gates are the NOR, NAND and XNOR. The gates were designed, simulated and laid out for fabrication in both IPHT's FLUXONICS 1 kA/cm 2 and Hypres' 4.5 kA/cm 2 processes. Layout circuit parameters such as inductance were extracted to compare these with design values. Good working margins were obtained after several steps of manual circuit optimisation during the design and simulation stages. NioPulse , superconductor circuit design software developed by NioCAD in South Africa, was used and evaluated during the design process.
THERMALLY SPRAYED SOLDER / BRAZE FILLER ALLOYS FOR THE JOINING OF LIGHT METALS
Generally the established thermal spray technologies like flame or arc spraying can be used for the defined deposition of solder/braze filler metal layers. But for those processes used under atmospheric conditions the achieved quality of the solder/braze joints is low. A high density of defects like inclusions or oxides, pores and contaminations are not avoidable. The novel technique of the cold gas spraying (CGS) works with very low process temperatures. Therefore the heating of spray particles is reduced to a minimum. The produced coatings are free of oxides and show very low porosity. So investigations concerning the potential of CGS for the application of solder/braze filler metals are self-evident.