Effect of High-Temperature Processing on the Aging Behavior of Precision 5-MHz Quartz Crystal Units

The influence of contamination level on the aging behavior of quartz crystal resonators has been studied. Resonators were made using high-temperature bonding techniques and were baked prior to sealing in both dry hydrogen and under high vacuum in order to minimize the level of contamination within the enclosure. The initial stabilization period for the frequency drift rate to reach 3 parts per 1010/month and the period to restabilize after power interruption to oven and oscillator is usually less than a week for these units. The time periods to reach the same drift rate for units made using the current state-of-the-art fabrication tecnhiques range from one to six months. The difference in aging behavior is discussed in terms of a possible aging mechanism.