Homebrew PCBs

Thank you Ned for the warnings of copper toxicity. Yes, copper is
a toxic heavy metal that is only required by life in trace
quantities, somewhere around fraction of ppm levels.
All copper compounds will be nasty, and that includes copper
sulfate and of course spent ferric chloride etchants.
Its common sense that the chemicals we hobbyist use should be 
well understood and properly handled.

For those wanting to make up a copper chloride etchant then the
following may be the easiest and cheapest preparation method
available to the average hobbyist.

1) According to the famous cupric chloride web page
http://users.rcn.com/rexa/Projects/CuCl_ech.html ,the suggested
composition is;

cupric chloride dihydrate @ 200g/L = 1.17 Moles/L
35 %wt hydrochloric acid  @ 100g/L = 0.95 Moles/L

The copper concentration is therefore;
	1.17 * 63.6 = 75 g/L

2) Take a tray or large bucket and place in 75 grams * V_tank of
scrap copper metal, where V_tank is final volume of etchant in
liters.

3) With the help of atmospheric oxygen the copper metal can be
made to react with HCl and produce cupric chloride. Once some
cupric chloride is formed it then aids in oxidation of the copper
metal provided atmospheric oxygen and excess HCl are present. The
precise volume in litres of 35% HCl acid to completely react with
all the copper plus have a free HCl concentration of 0.95 Moles/L
in final etchant may be calculated;

35% HCl volume  = V_tank * (1.17 * 2 + 0.95) / 11.3
		= V_tank * 0.3

4) Measure out V_tank *0.3 liters of acid and dilute it about
down to %50 with water. Pour some of the diluted acid into the
container holding the copper metal so that copper pieces are
about half way immersed. Leave it to stand for about 2 days
outside until some of the copper has oxidized and a green/brown
solution is formed. At this point enough cupric chloride will of
formed to start the etching reaction.

5) pour in the remaining diluted acid and slowly air agitate the
solution until all (or nearly all) the copper has dissolved.

6) Make up the final etchant volume with water.

---------------------
I have not done this exact same method myself, but it should
work. There will be some loss of HCl during the preparation so
the theoretical amount (V_tank * 0.3) is probably not enough to
reach final HCl concentration of 0.95 M/liter. I don't think more
acid will hurt so I'd be inclined to try (V_tank * 0.4) liters or
more.

Let me know if you have any questions.
		
Adam.




Ned Konz wrote:

 > On Tuesday 04 March 2003 11:57 am, kenneth magers wrote:
 >
 >>as for myself i will stick with feric chloride
 >>years ago i spent a week in the hospital from
 >>cooper poisening not much fun plus in the usa
 >>it is classified hazzardus materials
 >
 >
 > As is ferric chloride when it's been used to etch copper.
 >