Experiment and Simulation in Design of the Board-Level Drop Testing Tower Apparatus

Abstract

Solder joint reliability is of great concern to semiconductor and electronic product manufacturers. Due to rapid advancements in the electronic industry, packages with fine pitch ball grid array have been increasingly used in portable electronic devices. The mechanical shock resulting from mishandling during transportation or custom usage may lead to malfunction of product. A Joint Electron Device Engineering Council (JEDEC) standard (JESD22-B111) for a board-level drop test of handheld electronic products was released to specify the drop test procedure and conditions in 2003. The purpose of this paper is to design and analyze the performance of a drop test apparatus created in an in-house laboratory in terms of research basis. The specified impact shock with a sine wave accompanied by peak acceleration and pulse duration is a core requirement. The impact pulse is a complex function of various tester parameters. However, this is a unique characteristic based on the infrastructure design of each drop tester. Once the main frame of the drop tester is established, the drop height, strike surface material, and thickness are the major factors to evaluate the performance of drop tester. Therefore, many time-consuming experimental trial-and-error steps are required to calibrate and characterize a drop tester to achieve the required impact pulse. The most serious conditions B, G and H are achieved, also for condition A, which satisfies the JESD22-B111 test conditions. To provide design guidelines, the dynamic simulation using finite element model by ANSYS LS-DYNA code was performed in terms of drop height, strike surface material, and thickness. This study observed that (1) the peak acceleration and pulse duration are significantly affected by strike surface thickness; (2) the peak acceleration is strongly affected by strike surface modulus, but less so on the pulse duration; (3) the drop height affects the peak acceleration, but is insignificant on the pulse duration. The results between experiment and simulation are well correlated at certain levels. An empirical relationship is developed to determine the different design parameters of peak acceleration and pulse duration. In real applications, the designed parameters that can be varied to achieve the desired impact pulse are strike surface modulus and thickness because the drop height is standard.