Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

One of the things that I've been having trouble with on toner
transfer is smearing due to either incorrect pressure or too much
heat. My theory is that the smearing is happening because I have to
move the iron around to compensate for the holes in the iron. (for
various reasons, I'd prefer not to get a laminator) so I placed a
thin piece of aluminum (about 24 gauge) on top of the board between
the toner paper and the iron. The idea is to more uniformly
distribute the heat. It worked pretty well but I found I needed to
increase the iron temperature a bit over the direct contact
approach. This makes sense since the sheet metal is conducting heat
away from the board. I did move the iron a little during the heating
phase but much less than with out the al sheet.

I got much less smearing than before and much more uniform line
widths. Significantly reducing movement of the iron seemed to really
improve the quality of the product. This leads me to think that it
might work to just get two flat plates of steel, say 1/4 inch, heat
them in the oven to the correct temperature and then quickly
sandwitch the board/toner paper assembly between the plates. The
weight of the top plate may be sufficient to force toner-copper
contact. The thermal mass of the plates will need to be enough to
maintain the temp above the fusing point for 30 seconds or so.

Phil