Finite element modelling of failures in thick film chip resistor solder joints

In this paper, thick film chip resistors with two different types of solder alloys namely SnPb and SnAgCu have been evaluated for the effects of the solder alloy elemental composition on the solder joint failures under cyclic temperature loading conditions. The creep properties of both solders have been modelled using the Garofalo equation and the creep strain energy density has been extracted and used as the damage indicator for lifetime prediction. Three thick film chip resistors of different sizes have been modelled and the effect of device size on the failures in the solder joints has been analysed. In addition, both thermal cycling and thermal shock conditions have been modelled in order to simulate effects of extreme harsh conditions and the total damage has been calculated using the Miner´s law of linear damage accumulation. Based on the modelling results, the most vulnerable places in the solder joints where the failures may originate and propagate have been identified. Empirical lifetime models have used to predict the life time of the resistor solder joints.