The easiest is adhesive tape, because it comes off in one piece and
you know it will resist.
But you must make sure to rub it on well, especially the edges.
You can overlap multiple strips of tape, but the junction is tricky to
get completely tight.
There are also wide rolls of this sticky plastic for protecting
schoolbooks from dirt.
Laquer also works, as long as you get a good continous layer. You
could use colophony resin dissolved in alcohol (used as a protective
coating/solder flux), or some other coating you might have around
anyway to coat your finished boards.
ST
On Wed, Jun 11, 2008 at 7:51 AM, lnphoenix <Lnphoenix@...> wrote:
> I'm about to make a microwave test PCB for the first time, using tone
> transfer. The PCB size is about 4"x4" with the bottom layer is served
> as a ground plane. How do I mask the bottom layer so the copper
> remained intact during contact with ferric chloride? Vaseline? Masking
> tape? Huge tip marking pen? Some kind of chemical etching resist?
>
> TIA
> Lanny
>
>
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