Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

----- Original Message -----
From: "lcdpublishing" <lcdpublishing@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Saturday, May 06, 2006 10:10 PM
Subject: [Homebrew_PCBs] Ferric Chloride - muck at bottom of tank question


> Hi guys,
>
> I use Ferric Chloride for my etchant, I know there is "neater" stuff
> out there, but this works okay for me - plus I have a couple more
> bags of the stuff to use up.
>
> I have a couple questions regarding useage of it...
>
> 1) I don't know why I started doing this, but, before etching a
> board, I stir up all the muck at the bottom of the tank. Then I drop
> in my bubble rock and etch my boards. Is the mucky stuff at the
> bottom the Ferric Chloride crystals or is it just useless muck? If
> I don't have to stir it up before use - that would save me a bit of
> messy work.
>
> 2) I have lost count of how many boards I have etched with the batch
> I am using right now. If I were to guess, I would have to say
> probably in the area of 20-25 8" x 10" boards. Most of those board
> were single sided and all copper removed except for the traces and
> pads. It currently takes about 20~25 minutes to etch a board with
> the chemicals at around 68 degrees F. To be honest, I have no idea
> how long it took when I first mixed up the batch :-) So, I am just
> trying to get a feel for the "Status" of this batch as to whether
> it's time to dump it or keep using it?
>
> 3) I know that for some chemical etchants, you use heaters to speed
> up the process. I recall someone telling me not to use a heater
> with Ferric Chloride so I never did. However, I did buy a fish tank
> heater, but never used it. I don't mind waiting 20 minutes to etch
> a board if it is safer than doing it faster with the heater. If a
> heater is okay to use with this stuff, at what temperature should I
> shoot for? (SAFELY!)

Try adding some HCl, that should get rid of the sludge. Adding H2O2 will
also help, with the HCl it will convert cuprous chloride into cupric
chloride. Doing that should allow you to use the solution indefinitely, if
you wish. Heating to about 50C will speed things up a lot. I always heat my
FeCl3 etchant by putting the etchant container inside a larger one
containing hot water.

Leon

Leon