Homebrew PCBs

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.

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.

On Wed, 05 May 2004 15:51:57 -0000, cpexed <cpexed@...> 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.


some (me included) do like CuCl etchant very much.
It is made up of HCl, water, and H2O2.
It can be regenerated.
It works well without any agitation/heating in a tupperware container.

(and it does work with toner transfer)

More common is FeCl and persulphates.

>
> Also what is the proper way of disposing any used etchant?  Are there
> places to bring used etchant, neutralizing solutions?

Neutralize it, and bring it to the local "hazardous waste disposal place"
no idea how you call it. The problem is not the acidity, but the copper.

It was suggested to mix it with concrete cement and dump it, the copper is 
contained then.
some let it evaporate and dispose of the residue properly.

I myself am not too sure about this whole stuff, I simply can't imagine 
that
copper should be more dangerous than some other chemicals that are put 
down the
drain in huge amounts. I wonder if there is no copper washed of copper 
roofs by acidic
rain.

There is also the saying "the solution to pollution is dilution".

ST

--- 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

> 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.

That's strange. In Austria 90% of all roof runoff goes into the same sewer 
as
the household wastewater. Now that you say it i am really suspicious how 
the
wastewater plant processes this huge amount...

Only in the last years people startet to let rainwater seep away in the 
garden because
they charge you more sewer fees if you run the water from the roof down 
the drain.
(depending on sq. meters of the house)

But then you have the farmers who put copper sulphate (i think) on the 
plants, to
keep the bugs off. (See it is obviously poisonous). maybe you should 
dilute it and
spray your garden with it ;-).


I think it is a good idea to set up electrolysis electrodes and see what 
happens,
so far the copper content in my etchant is much too low and i can't try 
them out
but i will let you know what happens when i can finally try.
I'm very curious what will happen with the HCl molarity, because i do not 
fully understand
the chemistry involved. i hope the electroplating takes the second copper 
away from the CuCl2 and
this way generates CuCl which etches again, not sure. If this is the case
and there is no clorine gas escaping then you should not need any 
chemicals to keep it
going. (chemical process: copper in at the pcb, solid copper out at the 
electrode,
no gas escaping -> great. Disadvantage: stop dreaming, it isn't going to 
be that easy)

ST

Steve wrote:
> --- 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...

New FeCl diluted 1:1 etches double-sided boards in 6 mins at room temp
for me (boards vertical in a simple bubble etcher), and has no undercutting
problems. Much longer etching is needed if the pcb isn't first cleaned
of preservatives.