Homebrew PCBs

In a message dated 11/14/2003 11:23:07 AM Central Standard Time, 
alienrelics@... writes:
Before anyone starts typing, read that again, if you find yourself
very upset now you should type "dihydrogen monoxide" into a search
engine and read up on it.
Careful, Steve!  Some bureacrat will write a bill in the U.S. Congress 
banning it from the public!  (It is particularly uncomfortable in inhaled!)        
Jan Rowland


[Non-text portions of this message have been removed]

This something that I found on Ferric Chloride.

www.artmondo.net/printworks/articles/ferric.htm

My chemicals finally arrived today so I made up a batch of cupric 
chloride etchant. The ingredients I used were:

250g copper oxide
790 ml 35% hydrochloric acid. This is probably not as accurate as going 
by weight but there is no way I am letting that stuff near the kitchen 
scales :-)
enough water to make up 2.5 litres

I added the acid to about 1 litre of water a little at a time, stirring 
all the time. Once all the acid was in the solution reached 30 deg 
centigrade, from 13 deg C when I started. I then added the copper oxide 
and stirred well. I dumped the whole lot into a 2.5 litre container and 
topped it up with water.

The end result was a fairly deep green solution. In my etch tank at 35 
deg C it took 20 minutes to etch a board which seems slightly slower 
than new ferric but a lot quicker then the manky old ferric I was using 
:-) It does not seem to be as agressive as ferric. The board I used was 
an old board that was over exposed and has been lying around for about a 
year. Some areas took a while to start etching due to accumulated 
oxides, fingerprints etc. A piece of the same board dunked in ferric 
seemed to etch more evenly.

35% HCl is pretty nasty stuff. I mixed up the solution outdoors in 
fairly damp conditions and there were clouds of fumes coming from the 
container of acid.

All I need to do is get the new light box sorted out and I will be able 
to try the etchant properly.

Les

You can put more copper oxide to increase etch rate. From memory 
I think its around 140 g/L of copper(II) ions is good concentration.
What copper oxide did you get, the black stuff or red ?
Black is more common which is copper(II) oxide.
100 g copper(II) oxide (black) = 66g copper
100 g copper(I) oxide (red) = 89g copper




Les Newell wrote:

> My chemicals finally arrived today so I made up a batch of cupric 
> chloride etchant. The ingredients I used were:
> 
> 250g copper oxide
> 790 ml 35% hydrochloric acid. This is probably not as accurate as going 
> by weight but there is no way I am letting that stuff near the kitchen 
> scales :-)
> enough water to make up 2.5 litres
> 
> I added the acid to about 1 litre of water a little at a time, stirring 
> all the time. Once all the acid was in the solution reached 30 deg 
> centigrade, from 13 deg C when I started. I then added the copper oxide 
> and stirred well. I dumped the whole lot into a 2.5 litre container and 
> topped it up with water.
> 
> The end result was a fairly deep green solution. In my etch tank at 35 
> deg C it took 20 minutes to etch a board which seems slightly slower 
> than new ferric but a lot quicker then the manky old ferric I was using 
> :-) It does not seem to be as agressive as ferric. The board I used was 
> an old board that was over exposed and has been lying around for about a 
> year. Some areas took a while to start etching due to accumulated 
> oxides, fingerprints etc. A piece of the same board dunked in ferric 
> seemed to etch more evenly.
> 
> 35% HCl is pretty nasty stuff. I mixed up the solution outdoors in 
> fairly damp conditions and there were clouds of fumes coming from the 
> container of acid.
> 
> All I need to do is get the new light box sorted out and I will be able 
> to try the etchant properly.
> 
> Les
> 
> 
> 
> 
> 
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
> 
> To unsubscribe from this group, send an email to:
> Homebrew_PCBs-unsubscribe@yahoogroups.com
> 
>  
> 
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ 
> 
>

Thanks Adam,

Sounds like my solution is quite low in copper. If I had realised this I 
would have used less acid and made up less etchant. I bought 250g of 
copper (II) oxide and based my calcs on the information I found here:
http://www.pacificsun.ca/~robert/pcb/cucl.htm
Never mind, the copper level will build up by itself so it does not 
really matter. This is only hobby stuff so an extra 5 minutes or so 
makes no difference anyway.

Les

>You can put more copper oxide to increase etch rate. From memory 
>I think its around 140 g/L of copper(II) ions is good concentration.
>What copper oxide did you get, the black stuff or red ?
>Black is more common which is copper(II) oxide.
>100 g copper(II) oxide (black) = 66g copper
>100 g copper(I) oxide (red) = 89g copper
>
>
>
>
>  
>

--- In Homebrew_PCBs@yahoogroups.com, Les Newell <lesnewell@f...> 
wrote:
> Thanks Adam,
> 
> Sounds like my solution is quite low in copper. If I had realised 
this I 
> would have used less acid and made up less etchant. I bought 250g 
of 
> copper (II) oxide and based my calcs on the information I found 
here:
> http://www.pacificsun.ca/~robert/pcb/cucl.htm
> Never mind, the copper level will build up by itself so it does not 
> really matter. This is only hobby stuff so an extra 5 minutes or so 
> makes no difference anyway.
> 
> Les
> 
> 
> >You can put more copper oxide to increase etch rate. From memory 
> >I think its around 140 g/L of copper(II) ions is good 
concentration.
> >What copper oxide did you get, the black stuff or red ?
> >Black is more common which is copper(II) oxide.
> >100 g copper(II) oxide (black) = 66g copper
> >100 g copper(I) oxide (red) = 89g copper
> >
got a question
is it attack only copper or also tin (tin as resist after patern
plating)

gr. Roel

> 
> got a question
> is it attack only copper or also tin (tin as resist after patern
> plating)
> 
> gr. Roel


To my knowledge the only etchants known to be compatible 
with tin metal plating resists is the ammonia alkaline type.

ALKALINE AMMONIA CHLORIDE ETCHANT:

* cupric chloride
* aqua ammonia
* ammonium chloride

pH > 8
If it has a slight ammonia smell at room temp then pH is 
high enough. Copper content is monitored by specific gravity 
and must be kept between an upper and lower limit during 
normal operation.
Sorry, I don't have the S.G. numbers or concentrations of 
ammonium chloride at the moment.
This etchant cannot be regenerated via electrolysis, due to 
chloride content. Regeneration is by dissolved air, ammonium 
chloride, and ammonia. The ammonium chloride and ammonia is 
required by regeneration reaction of dissolved oxygen (from 
air). This etchant is very fast, comparable to fresh ferric 
chloride.


CONTROL:

When solution stops smelling or pH < 8 then add some 25% 
aqua ammonia.

When S.G. goes too high, you add water.

When etchant slows down and pH > 8 and S.G. is in range then 
you add ammonium chloride. There are probably better ways to 
identify when ammonium chloride is required. I don't have 
the experience with this etchant to know. I've only "played" 
around with it in small beakers.

FURTHER READING:

see http://www.pcbfab.com/iepart5.html
see http://www.pcbfab.com/iepart3.html