Homebrew PCBs

I'm not so sure that a 7 mil trace is going to come out that well on 
a 300 dpi device.  that is basically 2 dots wide (2.1 to be exact but 
it doesn't do partial dots). that isn't very much toner. 10 mils is 3 
dots and that's still kind of light.

Also, I'm not sure its a unit conversion problem.  300 dpi means each 
dot is 3.33 mils wide (or .3 dots/mil).  You dont get exact alignment 
except on 10 dot/3 mil boundaries (for whole mil alignment).  So, for 
example, a 7 mil trace width starting at 5 mils will have .5 dot, 1 
dot, .6 dot (in a row).  Depending on how the printer driver software 
handles this you could get 1, 2 or 3 dots. if three, you've got a 10 
mil trace, if 2, you've got a 6.66 mil trace.   Using metric, you can 
see similar alignment issues though the math is messier.  I know 
later HP printers do some sort of resolution enhancement so there are 
probably more subtle issues but I always turn that stuff off.

Bottom (and quite obvious) line: you need more DPI for better 
printing of your artwork.  I'd skip 600 and get a 1200 DPI printer. 

--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
<stefan_trethan@g...> wrote:
> 
> > A cheap old epson stylus 400 colour will do 8mil tracks/spacing 
smoothly 
> > in
> > 600x720dpi mode. It's the printer technology and ink/transparency 
> > combination
> > that makes the most difference.
> >
> >
> 
> You don't understand the problem.
> Even a 300dpi unit can do traces of 7 mil but _not_ metric spaced 
smd 
> parts.
> the printer works in inches and if you print metric spacing you get 
a 
> variations in
> line width and space.
> 
> ST