Re: OT: Old Ge power transistor internal bonding solder - what's in it?

Bob Koller <testtech@...>

Is the solder soft? If so, it may be an indium alloy, or two with different melting temperatures. If it is relatively hard, it is a brazing alloy of some kind. I wouldn't worry about it being toxic.

On Wednesday, November 5, 2014 6:05 PM, "Brad Thompson [TekScopes]" <> wrote:

On 11/5/2014 8:46 PM, [TekScopes] wrote:

I just junked out some early 1960s power supplies, which yielded a
dozen of the old-style TO-36 doorknob transistors - the real old kind
with tall solid copper cases, not the later lower profile ones. I
always save these for possible use in making high current feedthroughs
for vacuum or hermetic use. I can't ID the JEDEC number - they're
marked only with a Kepco number - but I'm sure they are a common type.

I cut off the top of one to see the internal construction - it's a Ge
alloy type, I presume, with a die about 1 cm square. The contacts are
soldered onto the metallized areas, and also to the steel E&B pin
posts. I presume it's a fairly low temperature solder alloy, so it
should be easy to remove the guts and re-use the package.

But, I'm wondering what's in the solder - I'd prefer not to have Cd or
anything else hazardous in there to deal with. I hope it's maybe a
Sn-In-Bi-Pb-Ag type alloy with no Cd. There may even be two different
types used. The luster of the stuff bonding the emitter ring at the
center is silvery, with no hint of yellowish that sometimes shows with
Cd, while the stuff bonding the outer base ring, the pin tops and
sleeves to the case is dull gray, almost porous-looking, like
tarnished pig-Pb or very old regular solder. Some areas of that seem
to have a yellowish or greenish cast, but I think it's because of the
reflection color from the Ni plating inside the case. The emitter
solder is directly lighted from above, and doesn't show this at all,
nor do the well-lit areas of the grayish stuff. I can't see any of the
solder that holds the backside of the die (collector) to the case.

Does anyone know what they used for putting these together back then?
I don't need to know any exact compositions, but mostly whether
there's Cd in it or not. I would imagine that certain elements may
have been incompatible with the semiconductor alloys too, so would not
have been used.
Hello, Ed--

You might want to post an inquiry to the Yahoo newsgroup...

...Which may have readers knowledgeable about older materials.

You might also visit...

...And see what's available there.


Brad AA1IP

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