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