Homebrew PCBs

----- Original Message ----- 
From: "tboneuk_2000" <a_reynolds@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, February 08, 2004 8:29 PM
Subject: [Homebrew_PCBs] Image but no etch


> Hello all
> After three working boards using the photo resist method I seem to
> have run into a problem.
> I was using fotoboard 2 pre coated laminates
> Sodium metasilicate Developer solution (first batch was diluted 10:1
> but found developed far to quickly so I am now using around 15:1 and
> 20:1 dilution to slow down the developing process)
> Feric chloride etching solution mixed 1:1 with water
>
> After exposure for a minuite (more than 2 mins causes the developer
> to completly remove all resist), I developed the board and all seems
> fine. I get a good positive image of the artwork from transparent
> film to the board but when I try to etch the board nothing happens.
>
> To test my etchent I made a quick test using copper clad board and
> an etch resistant pen, this worked no problems at all, a perfect
> board.
>
> I've tried both my first batch of developer (10:1 dilution) and my
> second batch (20:1) but both gave the same result.

Try moving the UV source a lot further from the artwork and PCB, so that the
exposure takes about 10 minutes. You aren't using enough exposure, so you
are leaving a very thin film of resist on the tracks and with the 2 minutes
exposure you don't have enough latitude to get it right. With about 10
minutes exposure do some more testing to find the optimum exposure. I had
some problems getting everything right when using Fotoboard 2, but now I get
excellent results every time. I use 13 minutes exposure with two UV tubes at
a distance of about 20 cm.

Leon
--
Leon Heller, G1HSM
Email: aqzf13@...
My low-cost Philips LPC210x ARM development system:
http://www.geocities.com/leon_heller/lpc2104.html