Homebrew PCBs

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. 

Anybody have any idea where I am going wrong

Best regards
Tbone

----- 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

>
> 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
>


i too think there is still resist left due to not enough exposing.

try by scratching on a spot. if yu dip it in the etchant
and this spot gets dull and the "exposed" areas not then it is
as leon says...

ST

I agree that the exposure time needs to be longer, you are most 
likely still leaving a thin layer of resist on the board.

I use 4 15 watt blacklite tubes at about 7-8" and expose for about 5 
mins. that is using M.G. Chemical Series 600 boards.

Also when developing use a foam brush to wipe the board down.


Ben