Homebrew PCBs

Hello,

I have finally got around to writing up a web page describing the things 
I've learned about cupric chloride etching at home (also having fun with 
my digital camera). This is pretty new, so I expect to find some things 
that will need changing. Criticizes are welcome. I hope its useful to 
somebody someday.

http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html

Hi Adam,

Very good work. Thanks for that very informative article. Definitely one 
to add to my bookmarks.

Thanks,
Les

Adam Seychell wrote:

>Hello,
>
>I have finally got around to writing up a web page describing the things 
>I've learned about cupric chloride etching at home (also having fun with 
>my digital camera). This is pretty new, so I expect to find some things 
>that will need changing. Criticizes are welcome. I hope its useful to 
>somebody someday.
>
>http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html
>
>  
>

Very nice site!  It would have been very helpfull when I was trying CuCl.

One question, you have a chart that shows AP as generally having about
1/4 the etching rate of CuCl and worse than 1/5 the rate of FeCl for a
given temperature.  What was your AP concentration?  My experiences
with AP and FeCl are significantly different from that.  Just
yesterday I etched a 2.5"X3.5" DS 1 oz board in 5 minutes.  1 L of AP
(250G/L per the directions on the package) heated to about 45C.  This
etchant is getting a bit old - I've done about 10 similar sized boards
in it so it may even be faster with fresh etchant.  This was
significantly faster than the FeCl etching that I have done at room
temp (12-14 minutes at 25C approx from memory).  I recall room temp AP
took a little longer than FeCl but not appreciably.  I'm mostly
curious since I'm very happy with AP.

Phil


--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
wrote:
> Hello,
> 
> I have finally got around to writing up a web page describing the
things 
> I've learned about cupric chloride etching at home (also having fun
with 

> my digital camera). This is pretty new, so I expect to find some things 
> that will need changing. Criticizes are welcome. I hope its useful to 
> somebody someday.
> 
> http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html

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\ufffdC. 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



Phil wrote:

> Very nice site!  It would have been very helpfull when I was trying CuCl.
> 
> One question, you have a chart that shows AP as generally having about
> 1/4 the etching rate of CuCl and worse than 1/5 the rate of FeCl for a
> given temperature.  What was your AP concentration?  My experiences
> with AP and FeCl are significantly different from that.  Just
> yesterday I etched a 2.5"X3.5" DS 1 oz board in 5 minutes.  1 L of AP
> (250G/L per the directions on the package) heated to about 45C.  This
> etchant is getting a bit old - I've done about 10 similar sized boards
> in it so it may even be faster with fresh etchant.  This was
> significantly faster than the FeCl etching that I have done at room
> temp (12-14 minutes at 25C approx from memory).  I recall room temp AP
> took a little longer than FeCl but not appreciably.  I'm mostly
> curious since I'm very happy with AP.
> 
> Phil
>

I can tell you for sure I'm using 1/1 oz material because I have
weighed it out.  I also have a bunch of .5/.5 and it is noticably
lighter.  Haven't etched it though.  I could have made up a weaker
batch of FeCl.  I followed the directions on the package but 12+ mins
at room temp sounds about right for what we are talking.  Your AP is a
bit weaker than the literature that came with mine recommends (80% of
mine - 250 g/L).

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
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
> 
> 
> 
> Phil wrote:
> 
> > Very nice site!  It would have been very helpfull when I was
trying CuCl.

> > 
> > One question, you have a chart that shows AP as generally having about
> > 1/4 the etching rate of CuCl and worse than 1/5 the rate of FeCl for a
> > given temperature.  What was your AP concentration?  My experiences
> > with AP and FeCl are significantly different from that.  Just
> > yesterday I etched a 2.5"X3.5" DS 1 oz board in 5 minutes.  1 L of AP
> > (250G/L per the directions on the package) heated to about 45C.  This
> > etchant is getting a bit old - I've done about 10 similar sized boards
> > in it so it may even be faster with fresh etchant.  This was
> > significantly faster than the FeCl etching that I have done at room
> > temp (12-14 minutes at 25C approx from memory).  I recall room temp AP
> > took a little longer than FeCl but not appreciably.  I'm mostly
> > curious since I'm very happy with AP.
> > 
> > Phil
> >

> 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\ufffdC. 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.htm
http://www.jtbaker.com/msds/englishhtml/f1060.htm

Russell Shaw wrote:
>>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\ufffdC. 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.
> 

yep, 5~6 minutes sounds ok for FeCl. But I didn't think AP at 45\ufffdC 
wouldn't be that fast as Phil is finding, maybe at 70\ufffdC however.

> http://www.jtbaker.com/msds/englishhtml/f1060.htm

Thats a good link on FeCl. They say diluting 1 part FeCl (sp.gr 1.47) to 
  2 parts water doesn't effect etch rate. I didn't try diluting it. I 
can't be bothered repeating all the experiments again :(.

Adam

Adam Seychell wrote:
> Russell Shaw wrote:
> 
>>>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\ufffdC. 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.
>>
> 
> yep, 5~6 minutes sounds ok for FeCl. But I didn't think AP at 45\ufffdC 
> wouldn't be that fast as Phil is finding, maybe at 70\ufffdC however.
> 
>>http://www.jtbaker.com/msds/englishhtml/f1060.htm
> 
> Thats a good link on FeCl. They say diluting 1 part FeCl (sp.gr 1.47) to 
>   2 parts water doesn't effect etch rate. I didn't try diluting it. I 
> can't be bothered repeating all the experiments again :(.
> 
> Adam

The msds says FeCl3 6H2O is crystals, so the liquid stuff you buy must
be mixed with water anyway. Maybe it etches faster with the extra
dilution just because it is less viscous and the copper can diffuse
away from the metal surface faster.