Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "txtom2" <unknown2@...> wrote:
>
> I just mixed up some Muriatic Acid and Hydrogen Peroxide (1:2) and tried etching a very small piece of PC board (cleaned and with no mask)to see how long it takes to etch thru (room temp about 75 degrees F). I saw a change in surface color in a couple of minutes, but no etch thru after 15 minutes. I changed the ratio to 2:2 to increase the acid content and after 15 minutes, no further apparent progress. 
> 
> Can someone please tell me what I'm doing wrong ? About how long should it take to etch ??
> 
> Thanks,  Tom
>

Heating the solution makes a huge difference. I use a vertical etching tank I made of plexiglass with an aquarium heater and a bubbler to agitate the solution. PCBs normally finish etching in a few minutes depending on the peroxide concentration. I find that the faster the etch, the less chance of pitting or other damage to areas under the resist.