Sinter kinetics and interface reactions of silver thick films on aluminium nitride

The aim of this study is to get an insight into the silver film sinter kinetics and the interface formation on aluminium nitride (AlN). Therefore, systematic variations in the paste recipe where carried out and the resulting film shrinkage, blister behaviour, solderability and adhesion strength where correlated with the sintering kinetics and the microstructure of the films. The influence of the glass and bismuth(III)-oxide volume fractions on the glass-viscosity, sintering behaviour of silver pastes as well as the interfacial reactions with aluminium nitride were investigated by means of thermomechanical analysis and FESEM-cross sections of fired films. A significant role in this process play the inorganic components bismuth(III)-oxide and glass. This is because of the ability of bismuth(III)-oxide to dissolve into the glass matrix, lowering the viscosity of the glass phase. Also the surface of the film changes in accordance to the glass - bismuth(III)-oxide ratio due to the changed softening behaviour and this is critical for the solderability.