Tadao Matsunaga

Acceleration switch with extended holding time using squeeze film effect for side airbag systems

Bulk micromachined silicon mechanical acceleration switches have been designed, fabricated, and characterized for the purpose of crash sensing for side airbag systems in which high-speed response is required for triggering the airbag. In order to inflate the airbag, collision should be recognized by analyzing the output signals of the electrical accelerometer and the acceleration switch to prevent mis-operation caused by an electromagnetic noise. The ON-state duration of the acceleration switch is designed to convert to the acceleration magnitude, and for this purpose squeeze film effect is utilized. The acceleration switch consists of an electrical contact part suspended from the surrounding seismic mass which performs holding of the ON-state using the squeeze film effect. A reliable and sticking-free switching operation was realized by Au microspring contact. The contact resistance achieved was 600 mΩ. It responded quickly and held the ON-state up to 6 ms depending on the acceleration amplitude.