Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "cpexed" <cpexed@y...> wrote:
> Hello,
> 
> I am just diving into to PCB design. What etchant do you recommend 
> for starting out using toner transfer methods. I am not wanting to 
> buy any hotplates or special tanks just use some old plastic 
> tupperware.

Look here in Files and in Links under Acid Etching.

FeCl is that rust colored stuff that Radio Shack and others carry. I
have used it in the past and still have about 5 pounds of dry FeCl.
But I hate it so much I may not use what I have left. It must be used
pretty hot, and it takes a long time to etch. Longer etch times mean
more undercutting and more time for something to go wrong. It also
stains horribly. It's renewable by electroplating the copper out, but
it's a touchy process.

I've used some variety of Ammonia based etchant before and liked the
speed of etch. I don't recall which it was (there are two or three)
but it was blue.

However, since you can make your own CuCl etchant cheap, why no try
it? You can make it from stuff you get from drug stores and hardware
stores or pool supply stores. Check those Files and Links pages for
more info. It's also constantly renewable, either by adding hydrogen
peroxide, or just by bubbling air through it.

One gentleman here posted his mix using regular 3% hydrogen peroxide
(off the shelf at a drugstore) and 30% muriatic acid (off the shelf
from a hardware store, also used as brick cleaner, wood bleach, and as
a pool chemical). I formatted it as HTML and saved it to
Files/Acid_Etch area.

An excerpt, written by dkesterline:

"I have successfully used 2 parts 3% medical H2O2 with one part 31%
acid - no additional water. It's pretty close to the same mix when
you're done. Etching times of 7-10 minutes."

"With stronger H2O2 (30% or more) you can just add a little more to
regenerate the mix. With the 3% stuff it has too much water and if you
add enough to regenerate the CuCl it dilutes the mix to much. To get
around that I usualy just regenerate with a bubbler. (aquarium pump
and a plastic "air stone")"

The only problem with CuCl seems to be that when you renew it, you are
making more of it. You should have a local pollution control listed in
your phone book, I think they take most stuff for free. I do -not-
advocate dumping down the drain.

> Also what is the proper way of disposing any used etchant?  Are there 
> places to bring used etchant, neutralizing solutions?
> I live in an apartment and dont think it would be a good idea to put 
> it down the drain :) The neighbors below probably wont appreciate it.

Copper is toxic in large quantities. Runoff from a roof goes into your
yard and is filtered (and diluted) by the soil. In the US, it's
illegal to run your roof gutters directly into the sewer. Dumping used
etchant in the drain means it goes right to the sewage treatment
plant, killing the bacteria used to treat sewage. If you have a septic
tank, it kills the bacteria there and you'll end up with a huge bill
to have it dug up and cleaned out sooner.

It may be sufficient to simply let it dry out and dispose of it in the
landfill as a dry waste. Check your local laws.

Steve