On pre-etch boards. I read some time ago that PCB board manufacturers
oxidize the copper before adhering it to the fiberglass substrate. Bare copper
is difficult to bond to, but a thin oxide layer bonds well. I use cheap board
that often have defects and I clean them with 400 grit sand paper on an orbital
sander. Then I clean the board with lacquer thinner. What ever is in lacquer
thinner creates a thin oxide layer, and aid in adhering the toner to the board.
Found this also allows a lower laminator temperature, and less distortion of the
toner.
Think this pre-etch may also be applicable to the acetone transfer method
that has been documented here recently.
RD