That's an interesting one. Sounds like something is used to promote the
copper adhesion to Teflon. Probably dissolved away during etching and
also attacked by the alkaline Vigon. Do you know the copper treatment?
If it's yellow, it might be zinc, which could conceivably be attacked by
a strong alkali, being amphoteric. Brown-blue--reddish sounds like
copper oxide. I suggest an urgent e-mail to Dr Wack and to the laminate
maker.

Brian

Ingemar Hernefjord (KC/EMW) wrote:
> Hi all,
> anyone who have this experience?
> A. Peel fresh PWB: high force needed, white stuff left on board. Soft like butter. Copper underside yellowish.
> B. Peel used PWB: much lower force needed, no white stuff left on board. Copper underside brown-blue-redish.
>
> Reason for asking is this. We suspect that something bleeds out from beneath the copper traces during the
> VIGON cleaning. Not much, but sometimes creating kind of 'grease' along the copper traces. Therefore, I'm
> interested in the interface between the copper and the teflon. What stuff can there be that changes from white to colourless, and may be dissolved by VIGON.
>
> Sending two pics to the always and amazingly tolerant, patient and positive S.G.
>
> Ingemar Hernefjord
> Ericsson Microwave Systems
>
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