Introduction of a New Metric for the Solder Joint Reliability Assessment of BGA Packages on System Level

The reliability assessment of ball grid array (BGA) components on system level for automotive applications requires a detailed simulation model, which describes the warpage behavior over temperature very accurately, for a credible reliability assessment [1]. However, in the product development process, detailed models of these complex components are not always available for a numerical investigation due to various reasons, e.g. missing information about material properties or stack up. The work presented in this paper advances the state of the art in solder joint reliability assessment under thermomechanical load by introducing a new load based metric. This approach facilitates the process of ensuring the reliability of BGA type packages on system level by aiming to use the easier accessible and experimentally quantifiable displacements of BGA component and printed circuit board (PCB) over temperature. To develop this metric, in a first step the deformations of individual solder joints, due to displacements from BGA and PCB, are investigated. A parameter related to the deformation of the solder joints is introduced and then correlated with crack growth data from a passive temperature cycling test. By showing the correlation between the deformation related parameter and experimental crack growth data, the basis is established to further develop the method and use displacements, measured on top of component and PCB, for the correlation with cycles to failure. The accuracy of the new metric is assessed by comparison with results from the state of the art reliability assessment approach on the basis of strain based damage related parameters obtained by means of the finite element method.