Ultrasound Transducers for High Pressure Environments Up to 1000 Bar

This paper studies the influence of high ambient pressure on ultrasound transducers where the piezoelectric layer is bonded to the acoustic matching layer by two different methods: Au-Sn solid-liquid interdiffusion and standard polymer adhesives. The transducers were fabricated by bonding 6 MHz piezoelectric elements to silicon matching layers. Electrical impedance was measured on the transducers during exposure to 1000 bar pressure at 15 °C in a silicone oil filled pressure vessel. The bondlines of the transducers were characterized before and after pressure exposure by scanning acoustic microscopy and optical microscopy. The exposure to high pressure was found to have noticeable effects on the piezoelectric material of the transducers, whereas no degradation was observed in the bondlines.