Homebrew PCBs

I'm glad that you guys are clear about using 2% H202. I would have
thought more is better too. I finally have some use for that gallon of
32% HCL in the garage.

Mike



--- In Homebrew_PCBs@yahoogroups.com, "fenrir_co" <fenrir@...> wrote:
>
> --- In Homebrew_PCBs@yahoogroups.com, garydeal <garydeal@> wrote:
> >
> > 
> >      This afternoon I finally got around to mixing up a small batch 
> >of 
> > the 1/3 HCl + 2/3 H2O2. I've read the positive reviews on that 
> >recipe 
> > here, but was really surprised/impressed at the results.
> >      My usual initial test is to cut a small strip of .005" brass 
> >and 
> > wave the end around in the solution, and it dissolved in record 
> >time. So, 
> > I set up a sheet with some photoresist (laminated dry-film), burned 
> >my 
> > favorite test file into the resist, developed it and popped it into 
> >the 
> > beaker. I hesitate to say that it took minutes to etch, it would 
> >make 
> > more sense to describe it as seconds. Since the test file has two 
> >parts 
> > panels, I dropped the second one in and it was nicely finished in 
> >short 
> > order. The guy that craves these parts is going to be really 
> >pleased, as 
> > am I.
> > 
> >      Question:
> >      The solution total was about 225 ml, and the brass sheet was 
> >etched 
> > one sided with an etch area of a couple of square inches. Afterward 
> >the 
> > solution was quite hot and bubbling like soda pop on the stove. I 
> >put it 
> > in a cold water bath to cool it down, but I have to wonder - is 
> >there the 
> > possibility of a runaway reaction and what is the result?
> > 
> >      Oh, and I'm sure this is common knowledge to the rest of you, 
> >but on 
> > say, a 1 oz and 2 oz board, what are the copper thicknesses?
> > 
> >      Thanks,
> >      -Gary
> >
> 
> Your mixture is far too strong, you need to add more water (add acid 
> to water, not water to acid, though with regular muriatic the danger 
> isn't nearly as bad as adding water to lab grade sulfuric acid). The 
> 40 volume H2O2 adds some water, but not enough, it seems. You don't 
> want the stuff etching so fast that you can't even get it out in time, 
> plus the fumes, heat, etc, might melt the container it's in.
> 
> Also, you want a bucket with a /lot/ of baking soda dissolved in it to 
> neutralize the etchant. During my one trial run with this process, I 
> discovered that sharpies and other permanent markers are useless as a 
> resist with this process, so you'd need to touch up with tough paint 
> on a fine brush. I'm sticking with FeCl3 so that if I /have/ an 
> accident I won't burn myself instantly.
>