Homebrew PCBs

DJ Delorie wrote:
> I've found that ink blocks UV better than toner (8 steps vs 3 for
> toner).  I've heard that "photo" inks have an extra UV inhibitor in
> them, but I haven't tried mine to see if they work better than black.
> Inkjet is the way to go.

What do you mean by "steps"?

> I have a special target footprint I use on my boards - four square
> pads with a 1 mil gap between them.  Since I use negative prints, this
> results in a big sqare hole in the ink with a thin crosshair in it.  I
> pre-drill registration holes in the pcb, and line up both sides' films
> using the targets.

I've pretty much decided on Microtrak after spending most of the evening 
digging through MSDSes and datasheets. That's a positive-acting resist (i.e. 
on the transparency, black = copper, clear = blank FR4) which is developed in 
metasilicate.

I did get a reply from Mega, basically the difference is mainly down to 
Microtrak being an "inherited" product. Fotoboard is roller-coated, Microtrak 
is dip-coated. Other than that, the FR4 laminate is basically identical. The 
shelf life is a guaranteed minimum, not an absolute, so theoretically 
pre-coated MT should last a while, but will get harder to expose and develop 
as it ages.

This should be a fun week. :)

-- 
Phil.
ygroups@...
http://www.philpem.me.uk/