I dont think so, pure quartz melts at, I think, 1440C but glasses (like lead-glass) melt at much lower temperatures 500 to 600C. Remember the chemical glass-blowing skill of the technicians.
The glass mix has to be formulated to match the expansion rate of the lead seals. A iron alloy with a small expansion coeff. whose name I dont recall was used for the leads. Glasses soften well below melting temperature (I remember "sucked in" 807 and 6146 tubes that had dissipated a few watts to many) Then the softened glass is "rolled" onto the lead. If you look carefully at some glass wire-ended diodes you will see a slight waist where this happened. The seal and adhesion is a thin metal/oxide/glass interface. Soldering temps rarely cause trouble but bending the lead wire close to the glass should be avoided. I used an oxy-hydrogen flame micro-welder for making connections for high temp life tests, so the wires got quite hot, but not close to the metal-glass seal. I only had peripheral knowledge of glass technology but most of the technology was developed in the lamp and valve (tube ) industries. I guess there are great references in the web now :-)) Alan G3NYK --- On Mon, 26/3/12, Chuck Harris <cfhar...@erols.com> wrote: > From: Chuck Harris <cfhar...@erols.com> > Subject: Re: [time-nuts] Distribution amp - Use a video amp unit ? > To: "Discussion of precise time and frequency measurement" > <time-nuts@febo.com> > Date: Monday, 26 March, 2012, 15:10 > Yes, but.... > > The glass used to make the body of the diode melts at > something like 1500C! > > -Chuck Harris > > ALAN MELIA wrote: > > Si juctions are formed at temps of 1000C or more. > Thermal failure is more likely > > to be due to alloying of metal contact areas. I used to > lifetest transistors up to > > 360C for 20 hours with power applied!! and anything up > to 6 months at 200C. You > > cant get those temps with plastic encalsulations though > glass (double dummet) > > diodes will stand 300C easily > > > > Alan G3NYK > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.