While this DRM is reasonably accurate in its effort to help with
understanding common SMT acceptability requirements, it is not intended
to be used as a standard as noted in the Introduction on page 2. The
IPC-A-610 committee has identified that some of the illustrations and
drawings used in the DRM (and the standard) fall short of what is really
needed, as in this discussion. The committee leaders/members would
appreciate industry support in providing high-quality photos or examples
that we can photograph to represent criteria for the next revision.
The pictures shown on page 35 of DRM-SMT-C and IPC-A-610C Figure 6-51
most likely do not represent rejectable nonwetting of solder. They most
likely are indicative of the kind of connection formed by some OSP/flux
combinations where solder wets only in the shape it was screened on the
land and does not "flow" over adjacent wettable areas. Please refer to
Figure 12-137 of IPC-A-610C for a somewhat better representation of
nonwetting, but there is room for improvement in the next Revision.
Work on IPC-A-610 Revision D is in progress, with a goal to publish at
the end of 2003 with enhanced area array and lead free support. 23 pages
of comments to IPC-A-610 have been reviewed in three separate two-day
meetings over the last year. The most efficient use of the committee's
time is for users to submit comments to IPC (me--I'm staff liaison to
this committee) using the format on the Product Improvement Form in the
back of every IPC standard. All received comments can then be compiled
and printed for committee review and to establish the paper trail
necessary for our ANSI audits. Meeting protocol is to review written
comments first and then accept walk-on comments as time permits. The
next committee meeting will be November 2-3 in New Orleans, in
conjunction with IPC's Annual Meeting; complete schedule at
http://www.ipc.org/html/2002annualmeeting.htm
Please contact me directly if you have some truly classic examples of
this or other anomalies that can be used in Revision D.
Cordially
Jack
Jack Crawford
Director, Professional Development and Assembly Technology
[log in to unmask]
847-790-5393
fax 847-504-2393
APEX 2003 March 31-April 2 Anaheim CA
www.goapex.org
IPC Printed Circuits EXPO March 25-27 Long Beach CA
http://www.ipcprintedcircuitexpo.org/
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Tempea, Ioan
Sent: Wednesday, October 23, 2002 1:23 PM
To: [log in to unmask]
Subject: [TN] Nonwetting on ImAu, REAL message
Sorry, the finger hit send too fast.
Hi Technos,
I just saw a copy of the desk reference manual IPC-DRM-SMT-C, in normal
language the Surface Mount Solder Joint Evaluation excerpt from
IPC-A-610C. I would need your opinions on the paragraph treating the
nonwetting (page 35).
The manual shows a fine pitch IC, on ImAu pads, with pretty uniform and
well wetted joints, but the solder does not go all the way to cover the
whole pad. The tips still show the gold. This is presented as a defect.
Is it really a defect? With extra large pads for fine pitch, we all
reduce the apertures of the stencils. In this situation, there will not
be enough solder to wet all the surface of the pads. What about the
homeplated apertures? No way that the chopped corners will be covered
with solder.
So, I guess you know, there are big issues with the inspection.
Please let me know what your experience is with non HASL finishes. Do
have the solder covering 100% of the pad after reflow?
Thank you,
Ioan
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