Hello Dave,
Thanks for the info. on solder joint contamination issues in your recent
message.
With regard to the Zn and Co contamination issue, in both cases these
elements were present in the plated deposit of SMT connectors which had been
solder paste reflowed onto the board (one connector had Zn present in the
deposit; another sample had Co present in the deposit). Problems were
reported, and it was theorized that perhaps the Zn and the Co had dissolved
from the plated coating into the solder joint.
Rob Schetty
LeaRonal Inc.
----------
From: David D Hillman
Sent: Thursday, October 30, 1997 7:00 AM
To: [log in to unmask]
Subject: Re: Assembly (Sn-Pb Solder Joint Contamination)
Hi Rob - Zn and Co solder joint contamination? Wow, what was the substrate
that you were soldering? It is pretty hard to get Zn to stay in the solder
joint unless you are specifically using a solder that contains Zn. The Zn
tends to "dross out" of a solder alloy. I am still looking for any Co info
that might be available. The maximum % P that a solder alloy can have is
one of those confusing questions - both JSTD-001 and JSTD-006 (except for
ultra pure alloys, paragraph 3.2.4) are silent on %P allowed. Several
solder alloy manufacturers use P additions to solder alloys for a number of
proprietary reasons - typical claims are that P makes solder more fluid,
stronger solder joints, reduces drossing of solder pots, etc. I know
several people using solder alloys that contain P and they are quite
satisfied with the results. I haven't worked with any of the P containing
solder alloys so I can't substantiate the improvement claims either true or
false. Hope that helps.
Dave Hillman
Rockwell Collins
[log in to unmask]
[log in to unmask] on 10/27/97 10:08:36 AM
To: [log in to unmask]
cc: [log in to unmask], [log in to unmask], David D
Hillman/CedarRapids/Collins/Rockwell
Subject: Re: Assembly (Sn-Pb Solder Joint Contamination)
Thanks Alexander, Charles, and Dave for recent responses to my inquiry
about
the max. % Zn and Co in Sn-Pb solder joints and industry specs. related to
same. With regard to your specific questions:
Charles - I'm located at LeaRonal's world headquarters in Freeport,
NY,
USA.
Dave - Yes, in two separate instances, Zn and Co may have been present
unintentionally in the surface finish and thereby are suspected to have
contaminated the solder joint.
==> I have one more question for Technet - what about the maximum % P
allowable in a Sn-Pb solder joint?
Thanks.
Rob Schetty
LeaRonal Inc.
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