Piezoelectric device for controlling the frequency-temperature shift of piezoelectric crystals and method of making same

A piezoelectric device for selectively reducing the frequency-temperature shift of piezoelectric crystals, comprising:

• a substrate having at least one substantially upwardly facing surface:
• a piezoelectric element having an upwardly facing surface and a downwardly facing surface, and a left side and a right side;
• a temperature dependent interface structure for beneficially stressing the piezoelectric element at a predetermined temperature range comprising a substantially conductive and compliant material coupling the left and right side of the piezoelectric element with the substrate;
• the temperature-dependent interface structure having a glass transition temperature between about 50 degrees C. to about 80 degrees C;
• and
• the substrate, piezoelectric element and temperature-dependent interface structure defining a piezoelectric package having a predetermined non-compensated third order Bechmann curve having a low temperature and high temperature end, with an inflection temperature of about 25 degrees C. or less, whereby the frequency-temperature shift is reduced on the third order Bechmann curve due to the beneficial stresses imparted to the piezoelectric element by the temperature-dependent interface.

A piezoelectric device, comprising:

• a substrate;
• a piezoelectric element having an upwardly facing surface including a top electrode and a downwardly facing surface including a bottom electrode, and a left side and a right side;
• a temperature dependent interface structure for beneficially stressing the piezoelectric element at a predetermined temperature range comprising a substantially conductive and compliant adhesive material bonding the left and right sides of the downwardly facing surface of the piezoelectric element with the substrate, the interface structure having a glass transition temperature ranging from about 50 degrees C. to about 80 degrees C.;
• and
• the substrate, piezoelectric element and temperature dependent interface structure defining a piezoelectric package having a predetermined non-compensated third order Bechmann curve having a low temperature end and a high temperature end, with an inflection temperature of about 25 degrees C. or less, the interface structure being more compliant in proximity to and above the glass transition temperature than below the glass transition temperature, defining a beneficially stressed piezoelectric element which has a substantially reduced frequency-temperature shift at the low temperature end of the third order Bechmann curve due to the reduced compliance of the interface structure below the glass transition temperature.