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

Did another board today; the lines were big enough to use toner
transfer so I did it that way, to try out the hotter laminator too.

Things that didn't go so well:

First time, I put the TT paper on the board and ran it through. Came
out curly, I suspect the paper and board have different heat-expansion
amounts. Second time I ran just the board through once, seemed to
help. Since the first time through some of the toner came off,
perhaps the pulling stress was a factor.

First time, I put the hot board into the cold water. Not sure if
stress was a factor here too. Second time I cooled the board first
(see details below).

First time through, the laminator had been at temperature for 7
minutes. By the second time, it was plenty "warmed up". I also
boosted the temperature from 350 F to 360 F.

The green TRF seems to want to put down foil over the spaces beween
close-together lines. This resulted in some micro-shorts. Not sure
if the hotter temperature is causing this, but I sent my whole process
to Frank (Pulsar) to see if he had any ideas.

What worked:

Board was prepped with soap and green scrubbie, as usual. Sanded with
2000 grit paper under running water until the water no longer beaded
off. Dried the board.

Artwork on TT paper as usual, nothing special here. Smallest details
are 11 mil lines with 8.66 mil spaces. The printer doesn't seem to
have a problem printing this.

Laminator at 360 F. At least 10 minutes warmup, probably more like
15. Run board through once to preheat (cover copper with blank paper
in case there's junk on the rollers), then three times with TT paper
on it - short edge first, then long edge first, then diagonally. Once
might have been enough, but I wanted to compensate for cheap rollers ;-)

Place board on table saw (cold cast iron), board side down. Press on
top (paper side) with push block, which has rubber sole. This held
the TT paper and hot toner against the copper while cooling it, which
took only a few seconds as the cast iron sucked away the heat.

Put in cold water. DON'T POKE AT THE PAPER! It will come off on its
own. I poked it the first time, again, that may have been a factor in
the toner detachment.

Dry. It was fairly well stuck; I could gently wipe it with a paper
towel and nothing came off.

Green TRF - one pass, short edge. Cool as above, peel. 100%
coverage, aside from the issue with the micro-shorts it was nearly
perfect.

Etch, 4-5 minutes heated CuCl. Strip toner, tin plate.

Cleaned up micro-shorts with an x-acto knife.

To those who use TT without TRF: comments on how well toner alone
blocks etchant? Do you get pinholes in the copper?