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November 1999

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Subject:
From:
Ted Stern <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 29 Nov 1999 10:13:59 -0600
Content-Type:
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Dear Ms. Menard:

I was interested in your reply, and specifically your description of "modified
polarization characteristics" on the board.  Being a novice in periodic reverse pulse
plating theory, I was wondering if you could further elaborate on the mechanism?

I have been told the copper "stipping" associated with the reverse pulse has to due
with the disruption of the cuprous diffusion barrier at the surface of the cathode.  Do
you believe this is accurate?

Thanks,
Ted Stern

Stephane Menard wrote:

>  Dear Mr. Savard,
>
> 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 ....
>
> Sincerely,
> Stephane Menard
> Micropulse Plating Concepts
>
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