Multidisciplinary Approach for Robust Package Design of MEMS Accelerometers

Micro-electro-mechanical systems (MEMS) packaging is becoming increasingly critical and plays a major role in the successful commercialization of MEMS products. The packaging system should enable the MEMS to perform the sensing function and at the same time protect it from environmental exposure. The design of the package should be robust enough to be able to withstand minor handling and manufacturing induced defects. Failures due to these defects are not unusual, one of our accelerometers in a small outline integrated circuit package has experienced a low ppm occurrence of device fracture. A multidisciplinary approach inclusive of vibration analysis, electrical response determination, stress analysis, and fracture mechanics are utilized to determine the appropriate package design. It is demonstrated here on a MEMS package for automotive airbag deployment. Along with the usual temperature exposure, this package also has to withstand a harsh vibration environment. The package is designed to avoid exciting MEMS resonance frequency to protect the transducer from sticking or clipping. At the same time, it delivers a reliable and intact transducer with no device fracture failures or output signal offset.