Homebrew PCBs

One point to make here, when I mentioned fluorescent tubes, I was not
refering to the white, like what you see overhead in office buildings. You
will want to use the blacklight type of tubes. Also, if you are having a
problem with undercutting, are you using transparency with artwork on the
same side as the pcb or is it on the top side? If your artwork (emulsion) is
against the pc board and it is opaque, you should not experience
undercutting from a tube type bulb or a set of tubes. You should use a hard
surface below the board so that it will be even and the glass should be held
down with some pressure to insure that there are no gaps between the copper
and emulsion. If all the above are true, then it could be too much exposure
time. I have used a table with 4 such tubes for years and I can easily
produce 12"X12" panels with tight mil specs, no problem. I do not know of
any of the professional board shops that use round bulbs for exposure. Also,
if you get into larger boardwork, the round bulbs will cause shadowing on
the outer traces. This is not noticable on small boards but on larger
boards, your traces will be bigger than the actual artwork on the outer
areas of the board due to the angle of the light. And lastly, in my area, I
can buy these blacklight tubes for next to nothing as opposed to the price
of those UV round bulbs.
-Mike

----- Original Message -----
From: "Adam Seychell" <adam_seychell@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, May 18, 2003 7:52 PM
Subject: Re: [Homebrew_PCBs] How I make my PCBs


> Fluro tubes have disadvantage producing of wide angled light. In
> my experience this light source produces problems with light
> under cutting the photomask and giving inconsistent track widths.
> A bulb lamp at distance far enough so the uniformity is