> Phil wrote:
>
>
>>Very nice site! It would have been very helpfull when I was trying CuCl.
...
Adam Seychell wrote:
> Thats interesting your experience were different than what I measured in
> my test. The bubbles agitation for my test was very vigorous, so maybe
> that had something to do with it. The FeCl3 was full strength as sold
> industrially (sp.gr=1.47), the AP was 200g/l almost fresh (very faint
> blue color due to previous tests). For AP I was getting about 9 minutes
> with 1oz copper at 42°C. 5 minutes sounds fast! Two possible reasons:
> you unknowingly have "1/2 oz" PCB material, or the ferric chloride you
> were using was for some reason not very potent which made it slow in
> comparison. I'm equally curious becuase it could mean my test results
> are botched.
>
> If you have access to a micrometer caliper, you can peal copper away
> from the board using a heat gun and pair of pliers, burn off the
> remaining epoxy stuck to the back of the foil, and measure its thickness
>
> Adam
Ferric chloride works faster if it is diluted with water (to 1 part or 2
parts water). A properly cleaned 35um copper pcb should etch in 5 minutes
at room temperature with gentle/moderate bubble agitation.
Diluted ferric chloride:
Fe(3+) + 3.Cl(-) + 2.H(+) + O(-) ions in solution
When in contact with Cu metal, the Cu goes into solution as Cu(2+),
so two electrons need to go somewhere. These are consumed to make
ferric into ferrous or Fe(3+) -> Fe(2+):
2.(Fe(3+) + 3.Cl(-) + 2.H(+) + O(-)) + Cu(2+) + 2.e(-)
-> 2.Fe(2+) + 6.Cl(-) + 4.H(+) + 2.O(-) + Cu(2+)
Water is therefore ∗required∗ for fast etching.
http://www.artmondo.net/printworks/articles/ferric.htmhttp://www.jtbaker.com/msds/englishhtml/f1060.htm