Module packaging effects on MEMS airbag sensor performance for automobiles

In this paper, the effects of the packaging module housing of MEMS airbag sensor for signal generation is studied. Conventional airbag sensor packaging module for automobiles is composed of the accelerometer MEMS sensor mounted on a printed circuit board, which is assembled inside a plastic housing. And the entire module is mechanically installed by bolts on the automobile frame structure to capture the acceleration from the structure vibration. In this case, the signal path from the frame to the sensor is complex, and the frame vibration is interacted with the module vibration, which may delay and distort the original signal pattern. To remove housing vibration effects, a new sensor packaging on the flexible circuit board was introduced to attach directly on the frame structure surface using adhesive. For the signal characterization, impact tests were performed for the conventional sensor packaging and the directly attached sensor using an aluminum channel and automobile side frame. Numerical analyses were also carried out to understand the vibration effects of the packaging module and the structure. It was found that the vibration behaviors of the frame structure and the module housing, and the module installation location had significant influence on the impact signal generations. The results indicated that the design of the airbag sensor packaging system for proper airbag explosion requires comprehensive engineering considerations.