Hi Steve,

These pictures are classic examples of dewetting for sure!  You are right
that it is from contamination on the copper.  The contamination could be
several things.

The most common dewet problems seen at HAL come from:
1.  A soldermask process problem that leaves a residue on the surface of the
exposed copper, such as incomplete developing or baking in an oven  that is
not properly vented. These residues often do not have pigmentation so they
are difficult to see.
2.  A preclean line that has insufficient etch or bad rinse.
3.  Incomplete tin / solder strip is another common problem, but usually
much worse in the holes than on the surface.

Then there are a host of other possibilities.  Virtually any process prior
to outer layer manufacturing prior to HAL Could contribute to Dewetting.
That goes all the way to excessive brighteners in the copper plating line.
Anything that prevents the solder from coming in contact with the copper can
cause dewetting or non-wetting.

Fortunately, these were coated with solder at HAL and you did not find out
you had a solderability problem after you loaded the boards with components!

Hope this helps
Sherry

----- Original Message -----
From: Stephen R. Gregory <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, September 06, 2000 11:31 AM
Subject: [TN] HASL Dewetting...


> Hi All!!
>
> Got some boards in at receiving that are exhibiting dewetting on the pads.
> You can see what I mean at:
>
> http://www.driveway.com/share?sid=e25a88c4.8e904&name=Pictures
>
> I'm rejecting them of course, but what would be the most likely cause of
> something like that? I'm pretty sure it's some form of contamination, but
> what?
>
> Thanks!
>
> -Steve Gregory-
>
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