Dual-mode SC-cut resonator hysteresis and aging study

Abstract

This paper presents recent measurements and theoretical predictions for dual-mode quartz 20 MHz, third overtone, SC-cut resonators. Fabricated lots of such resonators have f-T hysteresis below 50 parts per billion (ppb), with the best resonators demonstrating only a few ppb over the entire temperature range. Process and fabrication control have shown to be critical elements in reducing both hysteresis and mounting stress. Aging rates have also been measured, and the effects of absolute and mode-to-mode differential aging have been modeled. When both modes age at the same rate, no change in the thermometric frequency is predicted. However, the predictions show thermometric errors versus temperature for differential aging rates. These lead to both a "tilt" and an offset in the temperature sensing error versus temperature