Development of an AlN HTCC multilayer system with a tungsten cofiring metallization

The shrinkage behaviour aluminium nitride HTCC multilayer with a tungsten cofiring metallization was investigated. A new investigation method was used to characterize the shrinkage values of AlN tape and tungsten paste individually. Unlike to common methods small cylinders of dried tungsten paste were manufactured by instrumental pressing, as well as pure AlN laminates were investigated. The tungsten cylinders and the AlN substrates were debindered at 700°C and sintered pressureless in sintering interruption experiments at several peak temperatures up to 1830°C under nitrogen atmosphere. The adaption of the shrinkage mismatch between AlN and tungsten metallization was reached by the use of a variation of the grain sizes of the tungsten metal powders and by the addition of ceramic powders. A bimodal grain size distribution of the tungsten metal powders lead to the shift of shrinkage behaviour above 1400°C. By the variation of ceramic powders (AlN and Y2O3) an increase in shrinkage above 1700°C was observed. The tungsten carbide formation due to residues of carbon in the tape after debindering is observed.