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October 1998

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Subject:
From:
Werner Engelmaier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 2 Oct 1998 12:21:19 EDT
Content-Type:
text/plain
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text/plain (44 lines)
In a message dated 10/2/98 1:47:14, you wrote:

>The problem I am seeing is that when I am wave soldering this switch to
>the PCB I am seeing poor wetting around the leg of the switch.  When I
>solder dip test the switch leg I see areas which haven't wetted (You are
>right with your first question it is NOT DE-wetting).  When I found that
>the two legs had a different finish I attempted to find out which leg
>was the worse but both seem to be pretty poor at accepting solder.
>
>You say in your reply "With this much Au/Ag underplating with nickel
>will NOT help"  Should these finishes be solderable?  What can I ask the
>supplier to do to his finish to eliminate these problems?
>
>Thanks for you reply,
>
>Neil
 Hi Neil,
From your further description, it sounds like that the brass of the leads is
not solderable for whatever reason; so covering this surface with Au and/or Ag
may promote solder coverage giving the appearance of wetting withou any real
wetting having taken place. This problem could be solved with a Ni-overplate
over the brass followed by Au, not Ag. However the Aulayer thickness need to
be controlled to avoid the possibility of 'gold embrittlement.'

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask]

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