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October 1998

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Subject:
From:
David D Hillman <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 23 Oct 1998 05:35:45 -0500
Content-Type:
text/plain
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text/plain (80 lines)
Hi Earl - I think the jury is still out as to the impact of Phosphorus on
the integrity of the solder joint for immersion gold/electroless nickel
finishes. The latest information published by M. Zei of HP ( "The Effect of
Electroless Ni/ Immersion Au Plating Parameters on PBGA Solder Joint
Attachment Reliability) at the IPC Surface Finishes Conference in Austin
Texas last month (prior to Texas becoming an extension of the Gulf of
Mexico) was that "no clear relation between the P content and attachment
strength". Zei also looked at some of the plating variables and reached the
same conclusion. Looks like more testing and investigation is needed to
uncover the answers. I have been using immersion gold/electroless nickel
finishes on a couple of CSP applications successfully but I have talked
with other folks who are having problems.


Dave Hillman
Rockwell Collins
[log in to unmask]





Earl Moon <[log in to unmask]> on 10/22/98 07:42:39 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
      to Earl Moon <[log in to unmask]>

To:   [log in to unmask]
cc:
Subject:  [TN] Percent Phosphorous in plating solution causing excess
      intermetal              lics in Au/Ni/Cu solder joints




Folks,

Does anyone have information concerning the amount as percentage of
phosphorous in electroless nickel solutions that correlates to excess
intermetallic formations in electroless gold over electroless nickel
over copper solder termination areas leading to SMT solder joint
failure?

Am I really seeing some people addressing this issue by saying under 7%
is the maximum limit to ensure long term SMT solder joint reliability?
Am I seeing some people saying this is possible and still provide an
adequate nickel barrier between copper pads and the gold protecting
them? Is there an answer to ensuring reliable solder joints using
electroless Au/Ni or a much better alternative to it and HASL?

Thank you,

Earl Moon

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