Aging of Coldweld-Sealed Quartz Crystal Units

摘要

Design considerations for making reliable military coldweld holders are reviewed along with information on precautions to be taken for achieving reliable seals. Data is presented to show the improvement in aging of coldwelded general-purpose military crystal units over similar units in glass- and solder-sealed metal holders. Similarly, comparison of the aging of miniature crystal units in coldwelded HC-18/U and TO-5 military type holders shows the substantially improved performance of the units in the TO-5 type. The results of aging tests made on SSB crystal units in various metal coldweld holder configurations are reviewed and compared with similar units in glass holders. The two to one improvement in the aging of the coldwelded units is indicated to be due in part to the coldweld method of sealing but mainly to vacuum baking and coldweld sealing in the same high-vacuum environment. Data is also shown to indicate the effect of the bonding agent and holder configuration on the frequency-time stability of coldweld SSB crystal units. Single sideband crystal units in coldwelded HC-6/U holders are shown to be more stable than those in other metal holder configurations. Their average weekly aging rate indicates that the average frequency change in a 20,000-hour reliability period would be 12 x 10 to the minus 8th power. (Author)