Testing and multi-scale modeling of drop and impact loading of complex MEMS microphone assemblies

Failure under dynamic mechanical stresses caused by impact and drop loading is a critical concern for reliability of surface mount components in portable electronic products. This study focuses on drop-induced failures in system-in-package (SIP) COTS Micro-Electro-Mechanical Systems (MEMS) components that are mounted on PWAs. In particular, we are interested in the effects of secondary impacts that can occur between the PWB and neighboring structures (such as the product case, battery packs, displays or other adjacent PWBs) in portable electronic products. Drop tests are conducted under highly accelerated drop conditions with ultra-high accelerations (10,000-30,000 Gs) that generate stress levels well beyond those expected in actual use, or in conventional qualification tests. Furthermore, secondary impacts are allowed between the test specimen and the fixture, resulting in additional amplifications of stress and accelerations. Due to the geometric complexity, a hierarchical, multi-scale global-local modeling approach is used to assess the stress levels at critical failure sites in the MEMS. The modeling is based on 3D transient Finite element analysis (FEA).