Adam,
In late 1999 there was a TechNet thread on pulse plating. You should be able to pick it up in the archives on IPC's website. They may contain some useful info for you.
Patty
Patricia J. Goldman
PPG Industries, Inc.
724-274-3417
[log in to unmask]
-----Original Message-----
From: Robert Peterson [mailto:[log in to unmask]]
Sent: Wednesday, January 30, 2002 7:47 AM
To: [log in to unmask]
Subject: Re: [TN] pulse plating - without additives
Hi,
I've never done it, but there is an article available at
http://dynatronix.com/copper.html
Hope this helps
Bob Peterson
Alternate Final Finishes, Inc.
-----Original Message-----
From: Adam Seychell [mailto:[log in to unmask]]
Sent: Wednesday, January 30, 2002 3:10 AM
To: [log in to unmask]
Subject: [TN] pulse plating - without additives
Hello platers. I am hoping someone here can share a few words
of wisdom about reverse pulse plating. I'm having difficulty
finding detailed information on the subject, as my local university
library showed to carry almost nothing. It seems that the
literature on reverse pulse plating is bound to research papers
only (which I latter learned can be quite costly and time
consuming to obtain). What I like to know is a method of plating
"standard" printed circuit boards in acid copper bath *without*
the use of additives. Pulse plating without additives has been
done or so I've been told, however most documents I have
read only talk about baths containing additives.
Normally, a pure DC in acid copper (200 g/l H2SO4, 20 g/l Cu)
would produce a rough and grainy deposit, especially when
thickness' become high ( >35 um). The problem is aggravated by
increasing current density. Even at current densities of
0.5A/dm2 the deposits still remain unacceptable. This is
something I have observed through experimentation.
A test panel was plated using reverse pulse technique to see
what effect it had compared to DC plating at an equivalent
average current density. Not having a proper pulse plating power
supply I constructed my own basic one, using standard DC supply
and an electronic circuit to periodically reverse the output. The
parameters of the plating were:
forward time = 5 ms
reverse time = 1.7 ms
forward & reverse current densities = 3 A/dm2
average current density = 1.5 A/dm2
The pulse plating deposits were only slightly improved over DC
plating. A rough and crystalline surface was clearly visible under a
40X microscope. This does not sound promising and I am hoping
this is due to incorrect characteristics of the current pulse. Most
reverse pulse plating systems tend to use forward/reverse current
ratios of around 3, forward times of 10~20ms and reverse times
1~2ms. Is important for the current reverse pulse to be short and
high ?
If anyone could guide me to right path I'd be greatly thankful. If
there is no such thing as additive free copper plating for PC
fabrication then kindly let me know as this could save me lot of
time doing what others have already attempted.
regards,
Adam Seychell.
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