Genny,
I agree with part of your belief: I too believe Black Pad failures are as prominent as they were 4 to 5 years ago primarily because the chemistry suppliers were forced by the users having Black Pad failures to improve their chemistry and I think they have responded appropriately. However, I don't believe that they largely understand the failure mechanism because if they did they should be able to produce Black Pad failures and all of the studies I've seen where investigators tried to create Black Pad failures didn't create Black Pad failures.
Regards,
George
George M. Wenger
Reliability / FMA Engineer
Base Station and Subsystems Group
Andrew Corporation, 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Ed Hare
Sent: Thursday, April 14, 2005 12:04 PM
To: [log in to unmask]
Subject: Re: [TN] ENIG - no more problems?
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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