>  1. The dimension of the positive photoresist coated PCB was 3"x4".
>  2. I put the inkjet printed transparency on top of the PCB and
>  exposed under
>  UV light for 7 minutes.
>  3. I put the PCB into developer solution and used a brush to
>  help removing
>  the photoresist, within less than a minute, all unwanted blue colored
>  photoresist was gone, but I still leave the PCB soaked in the
>  solution for
>  another 2 more minutes,
>  4. The developed PCB was then put into slightly warmed Ferric Chloride
>  solution, again I used a brush to remove the copper until all unwanted
>  copper is cleared, the whole process took about 20 minutes.
>
>  I want to know what causes the problem:-
>  excessive UV-exposure, developed or etched the board too long, Ferric
>  Chloride solution too concentrated, or what?

I suspect a major part of your problem is using a brush at any stage. I have
always done these sort of things by bubbling air through the liquid to
agitate it as using a brush is too likely to lift the resist, and I do not
see that it would speed up the etching any more than air bubbles. Using a
brush in the developing tank is likely to lift the resist exactly where you
want it to stay.

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