Apologies to the O.P. I missed the exposed resist and was thinking toner transfer.
Donald.
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----- Original Message -----
> From: "Eddie Stassen" <estassen@...>
> To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
> Sent: Monday, March 5, 2012 6:01:43 AM
> Subject: Re: [Homebrew_PCBs] Etching problem - Help please
> I presume this is positive photoresist, in which case it looks like either
> over exposure or transparencies that are not dense enough. Try adjust you
> exposure a bit or double up on your transparencies if possible.
>
> On Mon, Mar 5, 2012 at 12:45 AM, Pete <pete@...> wrote:
>
> > ∗∗
> >
> >
> > Hi,
> >
> > I am trying to etch a small PCB and finding it etches unevenly
> > leaving a
> > small area of copper which is stubborn to remove. Just leaving in
> > the
> > etchant for longer starts to undermine the tracks that etched ok.
> >
> > Here's what I do:
> >
> > 1. Print the track layout on inkjet printer using transparency film.
> >
> > 2. Lay the film ink side down onto a 3" x 2" single sided photo
> > resist
> > coated copper clad board (cut from a Maplin Size 4 ref KU14)
> >
> > 3. Expose in a home made LED Light box for 4 minutes
> >
> > 4. Develop in Universal Developer (PBD2) Sodium Metasilicate for 1
> > minute.
> >
> > 5. Etch in Ferric Chloride track side down for 16 mins, agitating
> > every
> > minute or so.
> >
> > The result is most of the copper dissolves after 10 mins then it
> > leaves a
> > small area which refuses to disappear after waiting a further 5
> > minutes.
> >
> > A photo of the etched board is here
> >
> > https://picasaweb.google.com/109391378120539635298
> >
> > On close inspection of the board the unetched copper is left as
> > stripes.
> > So I am wondering if this is a board problem or the process.
> >
> > Any help is appreciated.
> >
> > Thanks
> > Pete
> >
> >
> >
>
>
> [Non-text portions of this message have been removed]
>
>
>
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