M Kumar wrote:-
>1. What is the reliability of hole wall plating thickness meauring
>instruments like CAVIDERM ( based on barrel resistance )? How does one
>counter the inherent uncertainties of this measuring technique?

I have not seen any response to your question but perhaps these were
off-line. We used to use a Caviderm some 15?? years ago which required
the hole to be electrically isolated from the rest of the panel. This
meant the readings could only be taken after etching, or by milling
around a test hole outside the circuit area. The probes had to contact
both sides of the panel which made it a little awkward to use.

I expect that Caviderm now have newer machines with much more
capability, but my experience has been with the CMI unit, CMI being the
company. This works by inducing small electrical fields in the copper
and readings can be taken with a single probe anywhere on the panel in
holes larger than 0.85mm. It is possible to ahieve much greater control
of plating distribution and tight hole size tolerances by getting
instant feedback after plating.

The machine is hand size and can be connected to a printer. It is very
accurate and consistent, we do sections daily and verify the readings
are always within +/-2 microns. After many years of use and several
software upgrades, our original unit is still working well and I can
thoroughly recommend it. In fact I would not attempt to copper plate
without one.

Best Regards
Paul Gould
Teknacron Circuits Ltd
[log in to unmask]
Isle of Wight,UK

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