MEMS Accelerometer Fabricated Using Printed Circuit Processing Techniques

This paper reports a MEMS capacitive-type accelerometer fabricated using printed circuit processing techniques. A Kapton polymide film is used as the structural layer for fabricating the MEMS accelerometer. The accelerometer proof mass along with four suspension beams are defined in the Kapton polyimide film. The proof mass is suspended above a Teflon substrate using a spacer. The deflection of the proof mass is detected using a pair of capacitive sensing electrodes. The top electrode of the accelerometer is defined on the top surface of the Kapton film. The bottom electrode is defined in the metallization on the Teflon substrate. The initial gap height between the bottom electrode and the Kapton film is approximately 40 mum. For an applied external acceleration/deceleration (normal to the proof mass), the proof mass deflects towards or away from the fixed bottom electrode due to inertial force. This deflection causes either a decrease or increase in the air gap height thereby either increasing or decreasing the capacitance between the top and the bottom electrodes. An example PCB MEMS accelerometer with a square proof mass of membrane area 6.4 mm times 6.4 mm is reported. The measured resonant frequency of 375 Hz and the Q-factor in air is 1.5.