Homebrew PCBs

----- Original Message ----- 
From: <Linux_Rules@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, January 18, 2004 2:47 PM
Subject: [Homebrew_PCBs] Problems with HCL/H2O2 etchant.


>
>
> Several weeks ago there was a thread about using HCL
> & H2O2 as an etchant. That was a god-send for
> this newbie/lurker. I have used A.P. mostly but am
> unhappy with the cost. F.C. is so nasty that I avoid it
> if possible. The HCL/H2O2 looked perfect.
>
> Last week, I finished my bubble tank (1 gal capacity) so
> I diluted the 30% HCL with an equal amount of D.I.
> water. Due to a brain fart, I don't remember how much
> H2O2 that I added - about 1-2oz, I think..? (Too much?)
>
> The solution was clear so I put in my first board and the
> etch was perfect after about 15 minutes (room temp). The
> etchant turned bright, clear green by the end of the etch.
> I left the bubbler on for about 1/2 hour after the etch. No
> visible color change after the etch.
>
> Since it worked so well for the first board, I assumed that
> I had it "made". Two days ago, I put in my second board
> (4"x6"). After 30 minutes, there was no visible removal of
> the copper, however the toner was sluffing off in the areas
> of large toner (copper flow areas). I pulled the board and
> dunked in a junk board. After 45 minutes, no etch.
>
> Hmmmm.......
>
> I haven't a hint of a suspicion of a clue as to what happened!
> It worked so well for one board, then failed miserably
> Does anyone on the list have any idea why this would fail?
> Unhappily, being a beginner with this, I have no equipment
>  to chemically analyze the etchant.

It only works when it is fresh. You'll have to add H2O2 to get it going
again, until the acid gets too dilute.

Leon
--
Leon Heller, G1HSM
Email: aqzf13@...
My low-cost Philips LPC210x ARM development system:
http://www.geocities.com/leon_heller/lpc2104.html