Resonators encapsulated in all glass holders have existed for many years.
Prior to reliable Cold Weld Technology, all glass sealing was the method of choice when the best performance was required.
The combination of a reliable high vacuum seal coupled with high temperature processing, providing high Q Factors and desirable long term stability.

What’s Unique About This Technology Today?

The base and cover of the resonator are literally fused together in a controlled and focused heat cycle. The quartz blank has been exposed to hard vacuum and very high heat during this process. Upon completion, the quartz is only exposed to the glass envelope and the mounting structure thus reducing the chances of contamination over time.

The Method

Years ago, the Pyrex cover or “ bulb “ was sealed using an open flame much like the methods used to seal vacuum tubes.
The current method uses RF heating to excite an embedded Kovar ring in the base while under vacuum.
This ring melts the surrounding glass including the bulb forming a perfect seal.
The high temperatures involved need careful control as the heat can be sufficient to damage the quartz blank through conduction.
This however has the benefit of vaporizing any volatile substances that might be present during the process.

Advantages:

• Resonators constructed in glass are the most heat resistant available. They can be conditioned to resist temperatures up to 300o C without damage.
• High Q factors result from sealing in a hard vacuum.
• The materials are non conductive so can interact with other components without shorting.
• For precision applications glass sealed resonators can be heat conditioned more aggressively than metal ones thus reducing stabilization time.
• The low magnetic signature of this type of assembly can have an advantage in certain applications.
• The transparent envelope allows for mechanical inspection at any time.