Influence of the pad design on the reliability of PCB/BGA assemblies under drop excitation

Abstract

In this work, the influence of the copper pad geometry on the reliability of printed circuit board/ball grid array (PCB/BGA) assemblies under drop impact is assessed. The method employed is based on drop experiments combined with finite element simulations. For the experimental part, various test PCBs with three different pad designs were manufactured and tested under drop impact loading conditions. The lifetime of each BGA component was obtained by using suitable daisy chain circuits. For the numerical part, simulation models were implemented in Ansys v14.5 and the stresses at the critical locations of the PCB were evaluated with the help of the submodeling technique. From the experimental and simulation results, a clear dependency of the reliability of the tested samples on the copper pad geometry can be deduced. Moreover, using a lifetime model developed in a previous work [1] describing the relationship between the applied stress on the board and the number of drop to failure, predictions regarding the lifetime of the tested samples can be made. A very good correlation between the predicted and measured results can be shown. With the findings of this research work, it is therefore possible to define guidelines for the design of electronic packages with fine pitch area array interconnections.