Drop qualification of MEMS components in handheld electronics at extremely high accelerations

Failures under dynamic mechanical stresses caused by impact and drop loading are an important concern when assessing the durability of portable, hand-held electronic products. This study focuses on failures in COTS MEMS packages on PWAs, due to repeated drop and impact events. This MEMS component uses a system-in-package (SIP) configuration, consisting of a MEMS microphone chip and an ASIC signal processing chip, both wire bonded and packaged on an organic substrate under a soldered metal lid. Highly accelerated qualification techniques are investigated by using ultra-high accelerations (10,000 - 30,000 Gs) that generate stress levels significantly beyond those encountered in conventional qualification tests or in actual use. By quantitatively evaluating the durability of the MEMS packages, this study also provides valuable insights regarding the acceleration amplifications that are generated from secondary impacts in portable electronic products. This study uses two hierarchical levels of secondary impacts. The first secondary impact is between the specimen fixture base and the drop table, and is generated with a commercially available Dual Mass Shock Amplifier (DMSA) accessory on a commercial drop tower, to get accelerations as high as 30,000 Gs. The next level of secondary impact is between the test specimen and the fixture, and is generated by using finite clearances between the PWB and the fixture base to further magnify accelerations in the test PWA. By conducting failure analysis, multiple failure modes under these highly accelerated tests ranging from package level failures to failures of the MEMS device are identified.