Genny,
I continue to see black pad failures in this laboratory. However, I
believe there is a kernel of truth in the statement that it is largely
understood and not as prominent as say 5 years ago.
Best regards,
Ed Hare, Ph.D.
VP SEM Lab, Inc.
---------------------------------------------------
SEM Lab, Inc.
Scanning Electron Microscopy and Failure Analysis
Snohomish, WA
Ph. (425)335-4400
Fax (603) 658-4519
http://www.semlab.com
---------------------------------------------------
Genny Gibbard wrote:
>Just listened to a Lead Free presentation by one of our assembly materials
>suppliers. They tested different pastes on different board finishes using a
>variety of different patterns, spacings, aperture sizes, etc,...
>By far and away, ENIG was the best finish for performance, for wetting,
>defects, voiding, ...
>The guy making the presentation said that he felt a lot of the initial
>concerns re ENIG - black pad being the biggest - have been resolved, and
>that they are no longer a concern, that they have determined what the cause
>of it is and eliminated it. Anyone want to comment on that? I'm not sure
>if he is correct, or just out of the loop.
>It was interesting as well: ImmAg got a very bad rating from them in
>performance, even though many on this forum really praise that finish. It
>exhibited dewetting (they printed solderpaste pads on an area with no
>soldermask, and the solder did not stay and spread where it was printed, it
>crept together with other pads into a big blob, like you might see a water
>drop do) and the amount of voiding was impressive!!
>About 4 years ago I joined this forum, and one of the reasons was because I
>was looking for info on ENIG. We had done a prototype run of a couple of
>boards and they failed miserably. They were never analyzed in depth, so it
>wasn't figured out what exactly caused the failure. It was the excuse we
>needed to not choose this finish and some of the extra costs associated with
>it.
>However, with the Pbfree push now, I don't know if we should re-examine
>whether to use the finish. For products where we needed a flat finish, we
>have gone to ImmSn, but we still use HASL wherever possible.
>
>Genny
>
>"Genius may have its limitations, but stupidity is not thus handicapped"
>Elbert Hubbard
>
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