On 11 Jul 2003 13:24:02 -0700, the renowned
(six-toes) wrote:

i want to etch some printing plates ,first starting with a design in
Coral say and then outputting to a printer to make a etch mask.
i am not sure what method to use to make the mask and how to apply to
the copper using a printer ..
any ideas ?
how long to imerse in the ferric chloride or similar solution?
say to etch of 1/16" of metal.

I've never tried this on thick copper, but as someone else mentioned,
this is one possibility:

1) I assume you just need to etch away a thou or two of copper
(1-oz copper PCBs have 0.0014" thick copper on them)

2) You can buy coated paper that does toner transfer. It's a bit
of a dubious process in my experience, but it does work for
coarse resolution. You print using a LASER printer or
photocopy an inkjet printout onto the paper, then IRON the
paper onto the very well cleaned, slightly roughened and dried
copper. The toner (facing the copper) should melt (might have
problems with such a thick piece of copper, maybe you have
to preheat the copper first), and being a polymer should
stick to the copper.

3) You then soak the whole thing in water until the backing
paper comes off.

4) Then etch in hot FeCl or other etchant, for maybe 10-15min,
preferably with bubble aeration or agitation.

5) Clean off the toner with solvent like laquer thinner.

You'd want to find some way to cover the back of the copper to
avoid wasting most of your etchant (masking tape?), or maybe just
suspend it on the surface of the etchant.

The paper costs $2.50 US a sheet, and you can get it from Digikey and
others.

Some have had luck using ordinary heavyweight (clay) coated stock as
might be used for posters, but I've not tried it.

----

If that doesn't work, and it may well NOT, (one of) the RIGHT way(s)
to do it would be to LAMINATE dry-film photoresist onto the copper,
expose with UV light, develop and etch. Think and Tinker has the film
in relatively reasonable lot sizes last I looked (50' for around $70
as opposed to around $300 for a full roll).

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
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