Hi ….. and of course, there was an OCXO that used a beryllium oxide substrate in pretty much the same way (inner oven in a double oven). Same basic issues and not exactly cost effective.
The alumina substrate lives on in a number of miniature oven designs. Bob > On Nov 1, 2020, at 5:20 AM, Bernd Neubig <[email protected]> wrote: > > > > -----Tobias wrote----- >> Also an interesting material when high thermal conductivity is considered > is boron nitride. It is around five times better than copper, comparable to > diamond and can be sintered to a ceramic material. >> Of course the Wiedemann-Franz-Lorenz law doesn't apply here as it is a very > good electrical insulator. >> A boron nitride OCXO would indeed be interesting! :-) > > About 30 years ago, in my previous job as head of TeleQuarz oscillator > division (now Vectron->...Microchip), we had used AlN hybrid substrates > replacing the FR4 PCB in OCXO. We had built up a complete hybrid > manufacturing line for that. Aluminum Nitride has an extremely high thermal > conductivity while being an isolator. The thermal performance was excellent. > However it was nearly impossible to solder on it manually (e.g. to change > components for fine tuning purposes) because the solder literally was > freezing on the substrate and even a special soldering iron with temperature > regulation directly in thee tip (Metcal) was not able to deliver sufficient > heat fast enough. After a few years we stopped this line. > > Have a nice Sunday. > Bernd > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
