High acceleration board level reliability drop test using Dual Mass Shock Amplifier

The advance of mobile electronics applications has been demanding higher drop/shock reliability performance under more severe drop/shock impacts. This in turn is requiring the board level reliability (BLR) drop test to be able to reach higher peak acceleration, particularly higher than 5000 G. One method to reach this high acceleration is to use an apparatus called Dual Mass Shock Amplifier (DMSA) attached onto a conventional drop tester. The conventional drop tester typically generates a primary impact in the range of 1000 ~ 2000 G, and the DMSA, which hangs above the drop table of the drop tester and continues to fall down immediately following the primary impact, is capable to generate a secondary impact with the drop table with magnitude 2~5x of the primary impact in terms of peak acceleration. In this study, the mechanics of drop test and DMSA was introduced and modeled with Newton physics. Two DMSAs with various different features were custom-designed, fabricated, assembled, and tested. Various aspects of the DMSA, including materials, layout, weight, gap height, holding mechanism, were evaluated and addressed. The effects of drop height, weight of DMSA, and gap height on the change of velocity and peak acceleration of secondary impact were studied. The strain on BLR drop test board under high acceleration impact was measured and discussed. Consistency of the shock amplification characterized by C pk was studied and method to improve the consistency was discussed. It is demonstrated through this study that using DMSA can be a simple, economical, and consistent method to achieve high acceleration for BLR drop test.