I looked at the pictures. They bring back a bad memory or a real life work
experience depending on your perspective.

The Bad:
Once, after having taught the IPC-A-610 to a number of co-workers (at a
former place of employment). We decided boards, not too different in
appearance from those you have submitted for our consideration, we
acceptable. Later it turned out cause was a circumferential crack at the
junction of the plated through hole barrel and the copper on the land
(sometimes called the Knee). The assemblies presented latent intermittent
failures.

The Good:
At another place of employ I was asked to offer up an opinion on another
such board. This time we had a micro-section of the PTH with lead installed.
There was good evidence of wetting to the PTH. We recommended using the
boards. They performed normally and to my knowledge continued to operate in
their service environment.

The key to evaluating this condition, in my opinion, is evidence of wetting.
If this condition is not the normal output of your soldering process proceed
with caution. If you have a low contact angle on the PTH wall, the condition
is probably acceptable. If the contact angle is high and the PTH wall is not
solderable, because it is cracked or poorly plated the condition is
unacceptable.

My casual observation, from the images, is things look bad. There is a
pretty clear line around the PTH. The solder contact angle at the PTH looks
convex.



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Bill Kasprzak
Sent: Friday, May 20, 2005 10:25 AM
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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