[time-nuts] Fundamental limits on performance
richard at karlquist.com
Thu Sep 17 23:40:48 UTC 2009
Yes, we use that process for assembling hermetic optics. However, the
glass package in the bulova photo looks like it has a conventional
"tip off". Why are you thinking that they use the optical
Joseph M Gwinn wrote:
> time-nuts-bounces at febo.com wrote on 09/17/2009 01:10:32 PM:
>> "Rick Karlquist" <richard at karlquist.com>
>> "Discussion of precise time and frequency measurement" <time-
>> nuts at febo.com>
>> 09/17/2009 01:20 PM
>> Re: [time-nuts] Fundamental limits on performance
>> Sent by:
>> time-nuts-bounces at febo.com
>> Lux, Jim (337C) wrote:
>> >> impurities. The JHU crystals are apparently in some type of glass
>> >> enclosure which can take the high temperatures, and the
>> paper seemed to
>> The processing temperature is limited by the phase change of the
>> quartz. Above a certain temperature, it is permananently changed
>> to another form that is useless for oscillators. Is there any
>> evidence that these crystals are actually baked out at a higher
>> temperature than cold weld copper packaged ones? The link to
>> JHU was broken.
> There is a glass sealing approach that does not involve melting the glass.
> I forget the name of the process (ionophoresis?), but one prepares the
> surfaces to be sealed by grinding and polishing them to be optical flats
> (or nearly so). The pieces are held in contact, flat to flat, and the
> assembly is heated. When glass is above about 100 C, it becomes an
> electrical conductor. A current is then passed from one piece to the
> other through the contacted flats. This causes ionic migration and
> welding, yielding a hermetic seal with no messy epoxies or the like. I
> read the patent on this, but no longer recall the name of the inventor,
> but it was a big deal in the sealing of gas laser tubes.
> Found it. The founding patent is US 3,397,278.
> Here is a paper on the process: <
> FIELD ASSISTED GLASS SEALING, GEORGE WALLIS, Electrocomponent Science and
> Technology, 1975, Vol. 2, No. 1, pp. 45-53, printed in Great Britian.
> Joe Gwinn
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