I would add
- slow cool down, this can give a coarser grain structure which can show as
dull/grainy.
- it's possible your component finish has changed (without notification is
not unknown) for Pb-free compliance.
- finally, disturbed joints of course, but I am sure you will have checked
that before coming on 'net.
Sometimes it a combination of things, so that if any one becomes marginal
the combined effect will tip you over.
Regards
Mike Fenner
Indium Corporation
We are at Productronica
click for details
www.indium.com/productronica/
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: 08 November 2005 19:22
To: [log in to unmask]
Subject: Re: [TN] Grainy Solder Joints
Hi Kevin! There are a number of metallurgical and microstructural reactions
that can result in a solder joint not having a "bright and shiny"
appearance. The majority of the time the lack of a "bright and shiny"
appearance results in absolutely no change in solder joint integrity. The
other minority instances, such as too much gold in a solder joint resulting
in a grainy appearance, the solder joint integrity is impacted. If you had
"bright and shiny" solder joint appearance before then something has changed
in your process - the change may not impact the solder joint integrity but
you should trace down what is now different. The use of Pbfree solder alloys
is going to make the "bright and shiny" solder joint appearance follow the
dinosaurs into extinction! JSTD-001 committee removed the "bright and shiny"
appearance criteria several years ago. The
IPC-HDBK-001 has some good information on "bright and shiny" that may be of
use.
Dave Hillman
Rockwell Collins
[log in to unmask]
Kevin Glidden
<[log in to unmask]
COM> To
Sent by: TechNet [log in to unmask]
<[log in to unmask]> cc
Subject
11/08/2005 11:59 [TN] Grainy Solder Joints
AM
Please respond to
[log in to unmask]
om
We are experiencing dull / grainy TH solder joints, made by hand soldering
w/ iron @ 500F. At first, it appeared to be residue on the surface, so I
started chasing the cleaner. But all checked out OK. I refluxed (water
soluble, ORH0) and reflowed (iron @ 600F). This improved the finished
appearance, but not 100%. While eutectic, the joint is perfect. Then when
I draw the iron away, it cools and the surface finish is no longer smooth or
shiny. What can cause this?
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