On Sun, 30 Aug 2015, Paul Koning wrote:
On Aug 30, 2015, at 1:55 PM, Chuck Guzis <[email protected]> wrote:
On 08/30/2015 09:47 AM, Tothwolf wrote:
If repair of the core memory in CHM's IBM 1620 is ever attempted, I
think either low-tin solder alloy with 1-2% added copper or possibly a
more modern indium-lead solder alloy would probably be the best choice
for the enamel wire to terminal connections since that would greatly
reduce the likelihood of any future wire breakage.
Wouldn't solderless bonding/welding be a better alternative?
That's what the IBM IEEE article mentions.
I'm still a bit puzzled by the dissolving of copper wire by conventional
solder. The wire used in core memories is thin, but not outrageously so
by the standards of, say, Litz wire, and that is soldered routinely.
See the other paper I mentioned earlier in the thread:
https://app.aws.org/wj/supplement/WJ_1975_10_s370.pdf
On page 5, they describe 0.0031" 40 AWG magnet wire being reduced to 0.002"
after soldering with 60/40 tin-lead solder. That 0.0011" reduction is
basically 1/3 of the diameter of the wire. This explains the failures of
the enamel wires in CHM's IBM 1620.
Copper erosion from tin is something I'd never really given a lot of
thought to, but it will certainly be something I keep in mind from now on.
