Homebrew PCBs

I am following up on a comment in an earlier thread, to the effect that starting with 2 parts drug store hydrogen peroxide + 1 part Muriatic acid, one cannot ever get to the point of having CuCl2. (BTW, please forgive & correct if I do not get the chemical formulas right. Chemistry was a LONG time ago!)

I am concerned / disappointed, because I have been saving my used etchant, made from the above, thinking that I would eventually build a tank to bubble in air to regenerate it, etc. But now it sounds like I would do better to neutralize what I have and start over.

1) Is that right, or is there any way to use the used etchant I now have on hand?

2) What do I need to do to make up an etchant mix that WOULD serve as the base for CuCl2?

Many thanks ...

Andy

If you actually want to use air to regenerate it that could work. You
might have to fine some CuCl to add, it could take a long long time
otherwise.

I don't think many people are patient enough to use air regeneration,
concentrated H2O2 is such a nice quick fix.

ST

On Sat, Feb 13, 2010 at 10:47 PM, awakephd <a_wake@...> wrote:
> I am following up on a comment in an earlier thread, to the effect that starting with 2 parts drug store hydrogen peroxide + 1 part Muriatic acid, one cannot ever get to the point of having CuCl2. (BTW, please forgive & correct if I do not get the chemical formulas right. Chemistry was a LONG time ago!)
>
> I am concerned / disappointed, because I have been saving my used etchant, made from the above, thinking that I would eventually build a tank to bubble in air to regenerate it, etc. But now it sounds like I would do better to neutralize what I have and start over.
>
> 1) Is that right, or is there any way to use the used etchant I now have on hand?
>
> 2) What do I need to do to make up an etchant mix that WOULD serve as the base for CuCl2?
>
> Many thanks ...
>
> Andy
>
>
>

I don't see why it would not regenerate with air.  However, because the drug store H202 is only 3% you resultant solution is going be fairly weak in CuCl, you may need to evaporate the saved etchant to up the concentration.  I have seen posts suggest 30% H202 is available at beauty supply outlets, used for hair bleaching.

I was able to find a gallon of 3% H202 at my local Smart and Final  
warehouse grocery store, was fairly low cost.  Its used in the food service industry as a sanitize.  I don't worry about regeneration and just make up new each time but I have been evaporating the spent etchant and saveing the resulting CuCl for future use. Not sure I will use it as I am thinking of going back to ammonium persulfate because its nice and clean with no corossive fumes. You do have to heat the AP to make it work.


--- In Homebrew_PCBs@yahoogroups.com, "awakephd" <a_wake@...> wrote:

>
> I am following up on a comment in an earlier thread, to the effect that starting with 2 parts drug store hydrogen peroxide + 1 part Muriatic acid, one cannot ever get to the point of having CuCl2. (BTW, please forgive & correct if I do not get the chemical formulas right. Chemistry was a LONG time ago!)
> 
> I am concerned / disappointed, because I have been saving my used etchant, made from the above, thinking that I would eventually build a tank to bubble in air to regenerate it, etc. But now it sounds like I would do better to neutralize what I have and start over.
> 
> 1) Is that right, or is there any way to use the used etchant I now have on hand?
> 
> 2) What do I need to do to make up an etchant mix that WOULD serve as the base for CuCl2?
> 
> Many thanks ...
> 
> Andy
>

"awakephd" <a_wake@...> writes:
> I am following up on a comment in an earlier thread, to the effect
> that starting with 2 parts drug store hydrogen peroxide + 1 part
> Muriatic acid, one cannot ever get to the point of having CuCl2.

This is wrong - I did exactly that.  I started with two parts 3%
(drugstore) peroxide and one part 37% (hardware store) HCl, added
copper, and now have a tank of gleaming green CuCl etchant.

It's not instant - I dumped the copper in the tank, turned on the air
bubbler, and waited - it took a few days to completely convert (3
liters solution, 0.5 lb copper).  Probably would have gone faster if I
had put the copper in right away, but I didn't figure that part out
until a few days had past, and most of the H2O2 was decomposed, so I
had to pour more in.

Okay, it sounds like I'm back to plan A -- saving the etchant and making a bubbler tank down the road. A followup question -- now that you have the CuCl, how long does it take to etch a board with it?

BTW, is it CuCl or CuCl2?? I think I've seen it both ways on this forum??

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:

>
> 
> "awakephd" <a_wake@...> writes:
> > I am following up on a comment in an earlier thread, to the effect
> > that starting with 2 parts drug store hydrogen peroxide + 1 part
> > Muriatic acid, one cannot ever get to the point of having CuCl2.
> 
> This is wrong - I did exactly that.  I started with two parts 3%
> (drugstore) peroxide and one part 37% (hardware store) HCl, added
> copper, and now have a tank of gleaming green CuCl etchant.
> 
> It's not instant - I dumped the copper in the tank, turned on the air
> bubbler, and waited - it took a few days to completely convert (3
> liters solution, 0.5 lb copper).  Probably would have gone faster if I
> had put the copper in right away, but I didn't figure that part out
> until a few days had past, and most of the H2O2 was decomposed, so I
> had to pour more in.
>

"awakephd" <a_wake@...> writes:
> Okay, it sounds like I'm back to plan A -- saving the etchant and
> making a bubbler tank down the road. A followup question -- now that
> you have the CuCl, how long does it take to etch a board with it?

Usually 3-6 minutes depending on how long I let it warm up first, and
if I manually swish it around in the etchant or let the bubbler do the
work.

> BTW, is it CuCl or CuCl2?? I think I've seen it both ways on this forum??

http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/#Chemistry_of_cupric_chloride_etchant