On 14 Apr 2014 12:10:34 -0700, you wrote:
>"H2O2 can degrade with temperature and time."
>
>- I wondered about that shelf life thing, but didn't know if my acid was the one that had gone bad. The past few etches have turned out OK, but seemed to take forever. When I first got attached to that method I was really impressed by how fast it worked and how forgiving it was about conditions and agitation. I remember etching outside in the late fall or winter (I think it was even rainy) and it would burn away so fast that I had to rip it out of the solution after a couple minutes or it would eat through the thinner traces.
That's too fast, you don't get enough control.
The reaction is essentially an oxidization of copper, so the more
oxygen (and warmer the solution) the faster.
The normal way is to add oxygen by bubbling, your option on using the
H2O2, but you don't want to dilute the solution.
The normal etch time on a board has been mentioned to be about 12
minutes.
>
>I need to get that going again. I'll probably start with all new chemicals and if that doesn't do it, I'll track down the stronger H2O2 you guys are talking about.
All new chemicals will etch faster because of the increased oxygen.
That's why the brushing of the board with a brush works, (as long as
the resist stays on the board, that is).
Agitation keeps a fresh flow of etchant to the board, one reason why
spray etching works well, as long as it is even.
Harvey
>
>George