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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To temporarily stop delivery of Leadree for vacation breaks send: SET Leadfree NOMAIL
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Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
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