Homebrew PCBs

grantfair2001 wrote:
 > Wow, you have been hard at work. Congratulations on your findings.
 >
 > I just bought a new Grade B burette on the weekend and it shipped
 > today <g>. (I had decided to put off procrastinating . . .)

The price here in Australia for basic class B burette is about AUD$55
http://www.brand.de/images/download/prospekte/cat_engl/2%20gk600eng_81-108_vol-instr.pdf

 >
 > So - to start out, if I get this right, I can prepare a 
solution of
 > 0.1 to 0.5 Moles/liter (0.4% to 1.6% w/v HCl) and start etching?

plus the 150 g/l of dissolved copper(II) as copper chloride :)


I'm still not sure on the best way to prepare the etchant. Weigh 
some scrap copper wire for about 150 g/l final etch solution.
Place in yor ready to go etching tank and pour in some 10% HCl so 
the copper is half immersed. Leave it for a few days, You'll see 
the copper form thick coating of  blue copper hydroxide on bits 
exposed to air. The liquid will go dark brown and the copper 
immersed will be reddish and partially etched. Add more 
concentrated HCl (30% to 37% wt) and dissolve the blue copper 
hydroxide. Keep adding some HCl every day, the solution should be 
very dark brown.
After about 3 ~4 days, and the copper is fully immersed with acid 
then turn on the air sparger. The idea is to etch the remaining 
copper. Its a bit tricky to know when to add more acid and/or 
water, I guess you can do a copper(I) chloride test as I 
described in my previous post. If very high copper(I) is evident 
after 10 hours of sparging then it means there is low acid. The 
bubbling may take 1 or 2 days to dissolve all the copper. You 
don't want too high of acid during the preparation. If you can't 
do titrations and keep the HCl below 3.7%,  then there are other 
signs to look for, such as irritating HCl fuming from the 
sparger, or if too low, there will be excessive copper(I), or 
even signs of copper hydroxide precipitate on the surface of the 
solution, when the HCl has reached to zero.
When all the copper is dissolved then you need to add the 
necessary water and HCl to bring up the desired volume.
Check with hydrometer for sp.gr about 1.26 ~ 1.29