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April 2008

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Subject:
From:
Joe Hughes <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Joe Hughes <[log in to unmask]>
Date:
Tue, 29 Apr 2008 10:40:47 -0700
Content-Type:
text/plain
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text/plain (82 lines)
It looks like skip nickel plating or residue tarnish.  If you have an XRF
measure the discolored pads and the shinny gold pads.  You should see a
difference in Nickel thickness if it was skip plating.  If you don't have a
XRF, try using a pencil eraser on the dark pads, if they become shinny like
the others around them it might just be Soldermask or other residue that
leached out during the hot water DI final rinse.

Are the holes around the dark pads open or closed with Soldermask?  You'll
see this problem a lot if you have one side of the hole covered with mask,
and the other side open.  Or if you have small holes which are partially
open partially closed, allowing some ENIG solutions in but not good flow in
and out.


Joe


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Tuesday, April 29, 2008 10:19 AM
To: [log in to unmask]
Subject: [TN] ENIG PCB Problem...

Hi All!
 
We just got some boards in this morning that we were supposed to be
building on a quick turn. The lot was supposed to be 25 assemblies, but
we only got 11 boards.
 
We noticed something at a few pads of a device footprint that looked
pretty bad. Check out:
 
http://stevezeva.homestead.com/Dark_Pads.jpg
 
http://stevezeva.homestead.com/Dark_Pads_Close.jpg
 
If it isn't obvious, the boards are ENIG. These pads stood out right
away with the naked eye, and when we started looking closely at the
boards, we noticed other dark looking pads, but not nearly as bad as
what you see in the photo.
 
If I've been paying attention correctly, I can't call this black pad.
Black pad needs more than just a visual indication such as this, right?
We looked at all 11 boards, but only found 4 of them with any problems.
Only one of four had the problem as bad as what is in the photo.
 
My feeling is that we shouldn't run any of them, no matter if we can see
a problem or not... 
 
Of course we're getting in touch with our fab house about this, but we
haven't heard back from them yet. This just happened a couple of hours
ago.
 
Thanks!
 
Steve 
 

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