Looks like nickel skip to me. The shiny part in the middle of the pad could
be where the test probe made contact at E.T. 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dan Skweres
Sent: Tuesday, April 29, 2008 1:40 PM
To: [log in to unmask]
Subject: Re: [TN] ENIG PCB Problem...

Steve,
What are the shiny spots in the center of the pads? Two things come to mind
depending on what your seeing. If those shiny spots happen to be small
remnants of solder than possibly some one did a HASL coat, tried
(unsuccessfully ) to solder strip and ENIG. If they're just a reflection
then another possibility comes to mind. Poor rinsing of chemical clean or
tin strip prior to solder mask leaving chemistry trapped within via holes
causing a reaction preventing ion exchange during plating process. Are the
pads exhibiting the anomaly all in the same net? I have experienced this
first hand. As a matter of fact there is a thread in the archives about
this.
Dan S.
----- Original Message ----- 
From: "Steve Gregory" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, April 29, 2008 1:19 PM
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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