Homebrew PCBs

"derekhawkins" <eldata@...> writes:
> Still guessing after all these years? (Apologies to Paul Simon).

In my case, variations in etch are due to two primary factors:

1. Mapping the pattern onto discrete toner dots sometimes results in
   slightly wider traces, and sometimes slightly narrower, depending
   on how it falls on dot boundaries.  A 6 mil trace is sometimes 5
   mil (three dots) and sometimes 6.67 mil (four dots).

2. My toner and drum are old, so the edges of the toner aren't crisp.
   I'm getting new ones tomorrow, maybe I'll do some test prints.

I suspect that variations in the iron transfer may cause
discrepancies, but I use a laminator because of that.  Also, the etch
itself causes differences.  I use the sponge wipe method, so I can
manually control how fast each part of the board etches.  However, the
sideways motion causes more etch creep under the toner.