solder in space

[bill platt]

http://science.nasa.gov/headlines/y2004/16aug_solder.htm

Edited: 28 Mar 2006, 2:53 p.m.

[Katie Wasserman]

Interesting. This could be important if one of us gets a seat on the Mars mission and takes along a bunch of broken HP calculators to fix in his/her spare time.

[bill platt]

:-D

[Ed Look]

Get 'em fixed FAST. I don't think it has to be the thirteenth mission in a series named after a Greek god to suffer a systemwide computer failure...

... oh, and bring a freshman physics text (HP manuals aren't what they used to be); even advanced spacefarers can use that to get home!

[Howard Owen]

That's terrible! I mean, don't we have enough of war here on Earth without shipping our solders off...

Oh, wait ..

[David Smith]

Another neat thing solder can do in space is grow huge tin "whiskers". This phenomnon has damaged saveral satellites. Hughes, in particular, had a bunch of relays short out because the whiskers shorted out the relay contacts.

[Ed Look]

That's fascinating! What causes the precipitation of tin from the solidified melt, the reduced pressure?

[bill platt]

Whiskers grow here on earth, too. They are a major problem with some galvanized steel computer room platforms--you know the ones, with the perforated floors. They also grow inside electronics. The end result is shorting out of stuff. Can be very expensive.

What causes them? Thermodynamics!:-)

[Ed Look]

Yes, yes, of course it's thermodynamics. But I am not all that familiar with the long term chemistry of solders.

I am somewhat familiar with the chemistry of semiconductors. I am surprised that whiskers would segregate and grow in, say a chip or a component. Or, do you mean at the contacts or junctions?