Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
wrote:
> Phil wrote:
...
> > One other thing I haven't seen discussed is the effect of etching
> > speed on pinholing with TT.  I think (though have no way to prove it)
> > that pinholing is proportional to etch time.  It seems to work out
> > that way.  The last batch (the one I mentioned) had almost no
> > pinholing at all.  I was very pleased with the result.  Even under the
> > microscope, it looked suprisingly clean for TT.   
> > 
> 
> As I understand the "pinholes" are just small voids in the toner
coating 
> the copper. How can this effect etching rate , which is governed by a 
> chemical reaction ?

The other way around - etch time affects pinholing.  Shorter time,
less pinholing.  At least that's what I have noticed.  

It may have to do with the fact that I suplimented, as usual, the
toner resist on the larger areas with an etch resist pen.  perhaps it
is this resist that breaks down in the etchant and the faster the
etching time, the less breakdown occurs.   However, even the areas
that i didn't supliment look amazingly good, too. 

What ever the reason, I am very happy with the latest results.

Phil