Cross-Correlation of Interconnection Technologies—A Case Study of Reduced Wire Bond Quality after Ultrasonic Welding

In modern electronic modules, the packing density of components is increasing. This means that the points at which different assembly and connection technologies are used are moving closer and closer together. This significantly increases the probability of mutual interference. The negative effects of later process steps in particular can be critical here. In the present work, a typical case for power electronics production is considered, consisting of thick-wire bonding on the power semiconductor and subsequent ultrasonic welding of load terminals on the same substrate. The effect on the quality of the bond connections was investigated in setups with different load geometries, materials and load intensities. It was found that both wire damage due to cyclic mechanical alternating loading and a change in the interface between substrate and wire occurred. In the case of harder wire materials, complete breakage of the wire connections was observed after just 24 welds on terminals in typical geometries. However, the interface between the wire and the substrate was also damaged and lost 10% of its strength in this case. The investigations show how such effects can be minimized by the choice of wire material and geometry. This is another important building block in holistic process development, taking into account the interactions between different interconnection processes.