Hi Larry! The addition of copper by the solder manufacturers seems absolutely
backwards but you need to remember an important rule: do things in moderation
and not in excess (this rule works for a most things outside of work too). Many
metal alloys (solder is a metal alloy is material terms) contain small amounts
of other elements to enhance the overall alloy properties. Some of these
additions change the alloy melting point, some add strength, some refine grain
structure, some enhance corrosion properties, etc. The addition of copper to a
solder alloy is just part of the solder manufacturer's recipe for getting the
metal alloy properties they desire. Unlike many manufacturing operations, the
electronics industry uses a metal alloy in its molten form and we have to deal
with the "unintentionally" changing  of the alloy composition as we do
processing. Too much of an element results in the degradation of an alloys
properites. Copper, gold, nickel and tin tend to be the problem elements from
circuit boards as described by other technet responses. Hope this helps.

Dave Hillman
Rockwell Collins
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Larry Tawyea <[log in to unmask]> on 10/08/99 07:51:56 AM

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Subject:  Re: [TN] HASL-contaminated solder pot



Sherry,

I very good summation of the HASL process.  There is one thing though that
has been bothering me for some time now.  Why is it that some of the solder
manufactures of no lead solders, such as Castin, are adding copper to the
formulations?  This flies in the face of what process engineering's have been
taught for years.

Larry

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