On Tue, 21 Mar 2006, Peter Todd wrote:

> On Tue, Mar 21, 2006 at 09:40:23PM +0200, Peter wrote:
>>> That's a very good point... Anyone got any sure info how are glass
>>> encapsulated diodes encapsulated? I'm very curious.
>>
>> They use low temperature glass. You can melt it in a lighter's flame.
>> Melts at about 350-450 deg. C or so afaik. Some soldering irons can get
>> that hot.
>
> Are there any thing about this glass that are different than normal
> glass? Especially weak?

'weak' and 'low melting temperature' are not necessarily related. At 
normal temperature they are as hard as ... glass. But you can take a 
1N4148 and hold it into the gas flame of a lighter for a couple of 
seconds and see the glass melt.

> See, I'm thinking you could easilly make Nixie tubes with this stuff...
> The fabrication would be fairly easy at low temperature, and aparently
> the requierments for Nixie tubes in terms of gasses and purity are very
> similar to neon tubes. It'd be nice to be able to assemble a stack of
> glass with the electrodes in it, and then seal it at the edges.

You have to study things like outgassing and adsorbtion and Invar (to 
make the glass passthroughs) and getting the process under control 
because the pressure at sealing time will be higher than when the object 
cools off, and it may take some special magic to stabilize the 
conditions in the tube enough to make it work reliably. I am not sure 
whether the seal on diodes is hermetic. I do not think it is.

Peter
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist