[time-nuts] OCXO housings - Why copper and not iron/steel?

[Bob kb8tq]

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 <BNeubig at t-online.de> 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 -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.