Hello Quyen Chu,

please read the information which R. Wayne Johnson provided on August 23 and
24; this was raising my interest strongly - especially his result that the
silver surface provided better protection through multiple solderings than
chemical tin. We will try and get sample boards with this surface for our
test runs soon.

Kind regards

Thomas Ahrens, D-24598 Boostedt

-----Ursprüngliche Nachricht-----
Von: Quyen Chu <[log in to unmask]>
An: [log in to unmask] <[log in to unmask]>
Datum: Freitag, 24. August 2001 17:59
Betreff: Re: [LF] Lead Free Board Finishes


>Hello All.
>
>Not to change topics, but does any have any experience in using ImAg as a
>board finish?  What are some of the advantages and disadvantages in using
>this finish?
>
>I understand that it is a less complex process vs NiAu or some of the other
>finishes that are under investigation.
>
>Thanks.
>
>qc
>
>
>
>
>
>-----Original Message-----
>From: Keith Sweatman [mailto:[log in to unmask]]
>Sent: Friday, August 24, 2001 6:45 AM
>To: [log in to unmask]
>Subject: Re: [LF] Lead Free Board Finishes
>
>
>Hi David,
>
>You asked about the stabilised Sn-0.7Cu eutectic to which I referred in an
>earlier contribution to the forum.
>
>As most people have found, the problem with the straight Sn-0.7Cu eutectic
>in
>wave soldering is the high incidence of bridges (shorts) and sometimes
rough
>and cracked joints.   There is some evidence that these problems are
>associated with the growth of the Cu6Sn5 intermetallic under the
>non-equilibrium conditions obtaining in the exit area of the wave in a way
>which interferes with the drainage of solder from the joint.   As you know
>it
>is inadequate drainage of solder in the exit area that results in shorts.
>A
>way has been found of controlling the nucleation and growth of the
>intermetallic so that it does not so detrimentally affect the drainage
>process.   The resulting joints are also smoother and brighter than those
>produced under comparable conditions with the straight eutectic.
>
>A paper on this alloy will be presented by Nihon Superior's Executive
>Director, Tetsuro Nishimura, at a conference in Hawaii later this year and
I
>am sure he will be happy to send you a copy after that conference.
>
>Regards
>Keith Sweatman
>Nihon Superior Co Ltd
>
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