Smitty Two wrote in
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In article ,
Al wrote:

In article
,
Smitty Two wrote:

In article ,
"Michael A. Terrell" wrote:

Smitty Two wrote:

Yes there are many alloys of solder. 60/40 was the standard for
some time but was replaced 20 years ago by 63/37. That is the
only tin/lead ratio that is eutectic and has been the industry
standard for all soldering AFAIK, for at least 20 years. You
may have used 80/20 for some reason, but it certainly isn't
eutectic.


I never claimed that it was.

Well, you wrote:

"80/20 is used for wave soldering, because it has a very narrow
temperature range where it is in a plastic state. this reduces
cold solder joints, by not giving the leads a chance to move while
the solder passes through this state."



If that isn't the definition of eutectic, than you have my apology
for being wrong yet again.

Defintion of eutectic:

"The lowest temperature at which a mix of two materials will melt.
Often the temperature is an anomaly, that is, it is much lower than
the melting temperatures of only slightly different mixtures.
Lead-tin solder is an example. Lead melts at 327C, tin at 231C. The
lowest melting combination is 67 lead, 33 tin (180C). Non-eutectic
mixtures have a melting or softening range. Such mixtures do not flow
well until thoroughly heated past the softening range."

Jeesh, get a dictionary.

Al


Exactly: "Non-eutectic mixtures have a melting or softening range."
This is what causes the "cold solder" problem when components are
moved slightly as the solder cools. In the eutectic (63/37) alloy of
tin and lead, the melting temperature and the freezing temperature are
the same. THAT is the relevant part of the definition as it relates to
soldering.

Sheesh, learn how to read and comprehend your dictionary.

Jon


That is how Tektronix explained it to it's techs when they converted from
60/40 to eutectic 63/37 solder.Eutectic has a narrower plastic range.
Now,that is for repair work,I do not know what TEK used in its
wavesoldering lines.it makes sense ot use a eutectic alloy on them,too,as
motion would have a greater effect on a partially soldified joint.

for REMOVING that relay,I'd use ChipQuik or similar alloy,the joint would
melt at around 200 something degrees F,MUCH less chance to apply too much
heat to the PCB.

You would think that solder makers would offer an alloy similar to ChipQuik
for this purpose,at a more reasonable price,maybe in a 1/2 lb spool.

--
Jim Yanik
jyanik
at
kua.net