Cross-supported planar MEMS vector hydrophone for high impact resistance

The high g shock resistance and sensitivity are two dominant factors to impact the airdropped sonobuoy reliability. In order to improve the high g shock resistance and sensitivity of MEMS vector hydrophones for airdropped application, cross-supported planar MEMS vector hydrophone is presented in this paper. The planar-shaped vibration unit with the Wheatstone bridge is defined on the wafer, and stress concentration region (SCR) is etched on the back of wafer. After theoretical and numerical calculation, the acceleration shock reaches up to 2000 m/s2 when the sonobuoy is thrown in the sea and contacted the water. According to the simulation, the max equivalent stresses respectively are 91.3 MPa (along the direction of X axis), 92.3 MPa (along the direction of Y = X axis) and 16.2 MPa (along the direction of Z axis), whereas the fracture strength of Si is reported 175 MPa. Optimum parameters are determined in view of the sensitivity, frequency and impact resistance of hydrophone. The test results demonstrated the hydrophone has favorable sensitivity and directivity. In brief, the cross-supported planar MEMS vector hydrophone was fabricated and its superiority was preliminarily confirmed.