DUAL LAYER MATCHING (20 MHZ) PIEZOELECTRIC TRANSDUCERS WITH GLASS ANDPARYLENE

This study describes a method of applying very thin broadband matching layers to 2 mm diameter 20 MHz transducers. Dual layer acoustic match ing between tile ceramic and the medium at the front face of the trans ducer was accomplished by selecting 1/4 wavelength glass layers from a commercial source, epoxying them to the ceramic, and vapor depositing parylene to 1/4 wavelength thickness on the glass. A 6 dB fractional bandwidth of 0.75 and insertion loss of -10 dB was found on the averag e for these transducers, This method allowed fabricating probes that p erformed well, were reproducible, provided both a matching and protect ion coating, and could be fabricated in a practical manner.