Methods for reliability assessment of MEMS devices — Case studies of a MEMS microphone and a 3-axis MEMS gyroscope

Despite the fact that MEMS devices have become common in many electronic products, methods for their reliability assessment are still undeveloped. One significant difference to the reliability assessment of conventional electronic component boards is that MEMS devices require a stimulus or means to measure an output in order to monitor their health while the MEMS assemblies are exposed to loadings. Challenges are faced particularly when the instruments to perform the stimulus or measurements will also be exposed to the loading condition. Furthermore, for MEMS devices simple functional/not-functional failure criteria are often not sufficient and health monitoring during loading must cover several characteristics, each of which have their own application specific acceptance limits. Solutions to these challenges are discussed with the help of two case studies: i) a MEMS microphone and ii) a 3-axis MEMS gyroscope. The number of different failure modes in MEMS devices is also large and some of the failures are transient, such as those caused by temporary sticking of moving parts. The small length scale and complexity of the MEMS structures together with the fact that many of the failure modes are transient make the employment of new methods for their failure analyses necessary. Methods of failure analyses, the role of Finite Element Modeling in failure analyses, and some typical failure modes are also discussed.