I had problem getting good quality etching using ferric chloride if the
pattern wasn't top quality. Using a mixture of 30 % Hydr.peroxide, 30%
hydrochloric acid and 40% water gave a significantly better result. The
etching process here is MUCH quicker, around 30 secs, guess the shorter time
means that the photoresist isn't affected that much ? (my personal theory).

Wear rubber gloves and eye protection !

Regards
Attila - SM4RAN
----- Original Message -----
From: "Mike Harrison" <mike@whitewing.co.uk>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Tuesday, September 26, 2006 1:52 PM
Subject: Re: [EE]Homemade PCB


> On Tue, 26 Sep 2006 12:21:25 +0100, you wrote:
>
> >I do not know if this is a good procedure or not, but you can read it on
> >Maplin's site:
> >
> >Single and double-sided copper clad SRBP and glass fibre boards coated
with
> >a positive photo-resist suitable for use with our UV exposure box. The
> >boards are covered with light proof protective film, which should not be
> >removed until the board is used. The PCB should be exposed using our UV
> >exposure box and a circuit overlay transparency. Exposure time will be
from
> >8 to 15 minutes. Mix together 0.5l approx with one teaspoonful of sodium
> >hydroxide (available from most chemists) and pour into a tray (CH38R).
>
> NO NO NO. DO Not use Sodium Hydroxide - it totally sucks ( see my page for
why), and is the primary
> reason for homemade PCBs having a reputation for unreliability & poor
repeatability.
> Get some silicate stuff. You'll be glad you did.
>
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