Homebrew PCBs

Thanks for the advice folks, a great response to my question and all  much appreciated.

I'll do some more trials and report back soon.

Thanks
Pete

--- In Homebrew_PCBs@yahoogroups.com, "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
>