Sorry Mr. Menard,
I should have been more detailed in my response.
The actual 2 phases are:
1- Forward current phase (Current is lower then on reverse phase, Duration
about 20 milliseconds and that can vary quite a bit): Where the panel is a
cathode and is plated with ionic copper from the solution.
2- Reverse current phase (Current is higher then ogn the forward phase,
Duration about 0.5 milliseconds, that may also vary but not quite as
much):The panel becomes an anode, effectively an electro-stripping
situation. Since the lenght of this process is rather short is allows for a
redistribution of ions near the plated surfaces, it MAY cause some stripping
if the phase is extended too much. (B the way I am not convince that
actually NO stripping is hapening, bu it would be micro-stripping and very
hard to detect)
Pulse plating is more indiscriminate than standard plating in the sence that
it is less affected by board design.
About the:
"One last thing, if it would be based on pure 'stripping' of the copper, we
could assume that it would work with any chemistry. Believe me, it is not
...."
- You could also try to use diesel in a regular car and it also would not
work... Like any chemical process, the chemistry involved must be right.
Now if you would kindly answer the original post by Brian Carlson and tell
us what do you think the "benefits or possible disadvantages to pulse
plating" would be.
Alain Savard, B.Sc.
Chemical Process Analyst
CAE Electronics Ltd.
e-mail: [log in to unmask]
-----Original Message-----
From: Stephane Menard
I am sorry to say that I do not agree with your short summary on the
mechanism of pulse periodic reverse technology for copper plating on PCB and
especially what you call the 'stripping' phase.
I do not believe that you want to strip the copper. This would induce
unsatisfactory roughness of the deposit and probably unappropriate
metallurgical properties (for the PCB specs).
The very short and very intense reverse pulse is actually designed to modify
the polarization characteristics on the boards (basically increasing
polarization at high current density area). Of course, the chemistry will
then play a very important role also because she needs to be able to
'respond' to the pulse and this, at a quite high frequency
Without going into details, this proposed theory has been demonstrated and
is
based on electrochemical studies which clearly showed the influence of such
pulses on polarization.
One last thing, if it would be based on pure 'stripping' of the copper, we
could assume that it would work with any chemistry. Believe me, it is not
....
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