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Indium solder & solar cells

I contacted Dave Scheiner at Kester for some input (his comments are
attached). I would highly suggest that these specific questions be sent
directly to Indium's technical support at:  askus@indium.com

You would be surprised of the feedback that you will get when they
understand this is a student satellite project !

Gregory Beat


Greg -

Their specific question is outside Kester's core competency/products.
Here's what I understand about soldering to gold.  These comments are in
regards to tin/lead solders
and soldering to a gold over nickel surface.

If the gold is thicker than 40-50 micro-inches, the solder most likely
not dissolve all the gold and bond to it.  The solder will be dull
and, if the gold content in the solder exceeds about 5%, the solder
will be brittle.

If the gold is thin, less than 20 micro-inches, it easily dissolves into
solder, making the solder joint look grainy.  If the metal that was
the gold is not oxidized, the gold-contaminated solder will bond to it.
However, as gold plates usually in a columnar structure, the gold should
at least 10 micro-inches thick to protect the base metal ( in most cases

nickel) from oxidation.

Now then back to your solar cells, if the gold is over a non solderable
substrate (alumina for example) then you will need a gold - indium
Kester does not make any indium solders.  I would refer you to
www.indium.com <http://www.indium.com> .


Dave Scheiner
dscheiner@littonkester.com <mailto:dscheiner@littonkester.com>

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