Russ,

The excess foaming during and after plating is an indication that the bath
is over activate and unstable. The foaming is caused by the plating reaction
and should subside once the parts are removed. If it continues then that
means that the bath is continuing to plate and that plating is occurring on
the tank walls. If you are not filtering your bath than you will introducing
particulate material from board debris as well as from the environment, that
will react with the plating solution,  specially if the material is
metallic.

I would agree with Dennis and you should check the specific gravity and
other components as well as send samples to your vendor. I would also offer
one further recommendation that might be a reach but it caused me sleepless
nights many years ago. I had a problem with very much the same thing  and
after checking all of the normal chemical parameters we were stuck for an
answer. We were able to scrap off some of the nodules and etched them in a
watch glass and look at them under a microscope. When the copper etched away
we could see that there was something under the copper. We could not figure
out what it was and no analysis that we performed gave us any glue. We went
back to the line and look in to all of the tanks and we could see something
floating in all of them We could not figure out what it was and than we saw
something had changed. There was a water line coming from the etcher which
was the discharge from the cooling coil. In an attempt to reduce water
consumption the company had installed a line from the etcher to the PTh line
to recycle the cooling water and was using it in the rinse tanks on the
electroless plating line. We cut a piece of the pipe and inside the pipe it
was half the diameter of what it should have been. It was filled with algae.
If the lines are stagnate for a period of time the algae grows like crazy.
We then looked at the rinse tanks and all of the process tanks after the
rinses and could see material floating in all of them but not in any of the
tanks before the introduction of the etcher's cooling water. This might be a
stretch but look in the tanks before EC and see if you can see any material
floating around. If you were closed during the holidays and this problem
occurred during or after your start up it might be a cause. Check the basics
first, such as chemistry and filtration. And of course get your vendor
involved.

Regards

Scott Westheimer
Colonial Circuits
----- Original Message -----
From: "Russell Burdick" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, January 15, 2004 3:39 PM
Subject: [TN] eless copper


> Hello everybody,
>
> Today's chemistry question concerns electroless copper plating.
>
> Problem is small nodules of copper deposited on the surface of the board
and
> in the holes at the electroless copper bath. Noticable differences in bath
> operation is more foaming during plating and more foam present after
plating
> is completed. Also, a noticable black/dark green particulate visible on
the
> foam surface and eventually on the tank wall and equipment.
>
> Have previously found and corrected excessive EDTA conc. ( indicating
higher
> than wanted proprietary bath chemicals ). Problem still exists but to a
> lesser extent.
>
> Thanks for all help.
>
> Russ
>
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