Homebrew PCBs

Stefan Trethan wrote:
> On Sat, 12 Feb 2005 02:30:57 -0000, Bob_xyz <bob_barr@...> wrote:
> 
> 
>>Having read up a bit on CuCl2 etching, I can see that there are
>>quite a few advantages to using it, especially versus FeCl. I'm
>>wondering, though, about how critical the chemistry aspects of it
>>are to getting good results.
>>How difficult is it to determine that you've gotten the
>>concentrations of the various chemicals involved correct? How
>>difficult is it to maintain the etching solution in good condition?
>>Thanks, Bob
> 
> 
> It is harder than just mixing FeCl, but not that much.
> It depends on how you like to work. If you are a person that likes to do  
> stuff "by gut feeling" then you needn't do any analysis and just go by  
> color and etchrate. If you are a person that likes to have 3 plans before  
> starting anything then you should get some analysis gear. You'd want a  
> hydrometer for density and the "two eyedropper" method for molarity (see  
> one page in the links). This gives you accurate information about the  
> bath, and you can maintain it without having any experience.
> The hydrometer measures S.G., the molarity stuff measures how much HCl  
> you've got, and the color itself is a strong indicator of when to  
> regenerate.
> 
> There are some pages in the links section that describe overly complicated  
> stuff, like stirrers and so on. You neend't have any of that.
> 
> Even if you go for the simple analysis gear, it won't be very expensive.  
> As a hydrometer you might get away with using a car battery tester (the  
> thing with the rubber ball to suck up acid), but check if the range is OK  
> and keep in mind a real hydrometer would be more accurate.
> 
> ST
> 

Having used the etchant for few months now, I would agree with 
everything said above. A hydrometer, and a some droppers will get you 
out of the dark when things aren't working right. Fortunately, the 
accepted acid concentration range is very broad, so any capability of 
measuring within a +-%33 error, will be good enough.


Adam