Nonlinear dynamic behavior of thin PCB board for solder joint reliability study under shock loading

Solder joint reliability under shock loading condition has been a concern over the years especially with constant reductions in the characteristic dimensions of the package and the solder joint. With the impeding transition to lead free solder, attention has moved from temperature cycle failure to mechanical shock failure. A method has been developed that employs a specially designed shock test board (STB) to characterize the solder joint performance as a function of board surface strain. This unique test board can be adapted to a wide range of test and boundary conditions. Using this board, a range of shock inputs is tested to establish correlation of the dynamic response and solder joint damage severity. This method can be used to characterize solder joint performance at the component level, early in development. One can also provide board strain based design limits guide system design and prevent late discovery of solder joint issues. Modal analysis based and explicit time integration finite element models have been used to supplement understanding of the board response after shock loading. The shock model demonstrates good correlation of the strain on the thick board while thin board shows challenges in modeling prediction where nonlinear behavior observed. The modeling data also suggested that the maximum principal stress at the solder joint interface is a good failure criterion as it maps well with the actual failure region found.