Aftershock effects on the reliability of electronic components under shock test

Shock test is one of the significant reliability tests for electronics products. JEDEC test standards regulate only the first controlled-pulse by defining a variety of conditions such as the pulse peak acceleration, pulse duration and velocity change during the drop impact processes. In reality, a practical test showed that not only was one pulse produced, but also a series of two or more aftershocks are encountered. Hence, it is doubtful on whether and how the aftershocks influence results of components´ reliability. The purpose of this study is to investigate the aftershocks´ effect on the test products and to predict the time interval of its occurrence as well as the relating acceleration responses. The investigations include experimental, theoretical and finite element analysis methods. The severity of aftershock and the time instant it happens were first tested and modeled precisely. This model was then used as input both for theoretical and numerical calculations to solve system´s response. Good consistencies among results of all three methods are observed, it is then possible to use the theoretical and FEA methods for the shock design of electronic systems prior to the manufacturing of the prototypes. Most importantly, the corresponding outcomes have taken the aftershock into consideration instead of only the primary pulse. It is believed to be more accurate in the reliability analysis of electronic products.