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Subject: Re: [Homebrew_PCBs] Metalized holes

From: adam Seychell <adam_seychell@...>
Date: 2003-05-11

Markus Zingg wrote:

[deleted]
>The main advantage
> however is independancy and the possibility to have a four layer PCB
> completed within say 2 - 3 hours....

Multilayer in 2 - 3 hours ! No offense, but that statement
made me laugh. Even if you had a fully automated machines
that did everything from drill to the final dry, it will
take much longer than 3 hours.
With your experience of the pattern plated through hole, you
must of learned to appreciate the complex nature of the
process. As you said earlier its not easy, so unless the
hobbyist wants convert to PCB making as their primary
interest then plated through holes will be best left to
professionals or semi-professionals.

I appreciate your enthusiasm in attempting to make plated
through hole boards at home. I've always had a interest in
chemistry and find the inner workings of the PCB process
quite fascinating. I'm interested in the basic method you
are using or plan to use. Is it the pattern plating process
or the "tent and etch" or the "etch back" process ?

In the "etch back" process you take a thin copper clad board
18 um or less (1/2 oz/ft^2), apply photoresist, expose,
develop, and copper plate the tracks so an additional 35um+
is added. Remove the photoresists and etch the whole board
until the original 18 um copper cladding is completely
etched and so the thicker tracks are not etched. Obviously
this requires an etching apparatus capable of uniform etch,
something much better than simple bubble tank.

Adam