Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

----- Original Message -----
From: "dl5012" <dl5012@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, February 07, 2006 7:41 PM
Subject: [Homebrew_PCBs] Re: Toner transfer experiments and a fix for cheap,
low-temp laminators


> Hi Leon,
>
> What resist (positive or negative) are you using and where do you buy
> it? How do you apply it to boards? When I was in junior college, we
> used to spin it on. How long will presensitized boards keep? How do
> you dispose of your expended chemicals? I'm on a septic system and am
> very careful about what I put down the drain because I or my neighbors
> will eventually end up drinking some of it...

I use pre-coated FPC-16 board (positive-working resist) from Mega
Electronics:

http://www.megauk.com/

The board is best used within six months, I've found.

I simply pour the NaOH and any exhausted etchant down the drain. The small
amounts I use don't matter.


>
> I'd like to try doing boards with a positive resist. It would
> probably give more predictable results, once you got exposure and
> developing times down, with less pitting.

My UV exposure takes 13 minutes, but I can get on with something else during
that time. Etching is in hot FeCl3 with continuous manual agitation; it
takes about 5 minutes with fresh etchant. I use a large plastic container
half-filled with hot water, with a smaller container in it holding the
etchant and PCB. The etchant lasts for several weeks if I occasionally add a
little HCl. I dispose of it when the etching time gets to about 15 minutes.

Leon

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