Bill,

Partially filled PTHs are a risk. Small diameter, high aspect ratio vias are sometimes due to poor copper plating, which can result in voids, cracks, dewetting and other named matters near the opening. Would make cross section asap to identify exact cause, which ought to be obvious quite easily.

Ingemar Hernefjord
Ericsson Microwave Systems

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Bill Kasprzak
Sent: den 20 maj 2005 16:25
To: [log in to unmask]
Subject: [TN] Plating problem at the "Knee"


Morning Technetters,

I thought I would try to get this in before the Friday Follies (NTC)
begins.

I have a board that we have wave soldered and I have a number of joints
where the solder reaches the top side pad then stops as if though there
was a barrier. Upon closer examination, I noticed that there is something
not quite right near the edge of the  hole on the top side. I remember
reading about "Knee" problems on PTH's on this forum and searched the IPC
archives for more information. I couldn't find anything.

So I'm asking the community at large to comment about this condition at
the "knee" and the causes for it. We are certainly able to do touch up on
these joints but I'd like to try and see this before we process the board.
There are a couple of pictures that Steve G has graciously placed on his
"Picturepallooza" site.

Go to: http://www.stevezeva.homestead.com

The picture names are, "Topside Fillet and Topside Fillet 2".

Let me know what you think. Thanks.

Bill Kasprzak
Moog Inc

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Process Engineer, Electronic Assembly

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