On Sat, 24 Nov 2007, Dennis Waggoner wrote:
> My first attempt at a double sided board using smt and PLCC hardward.
> Using a max resolution of .010" traces with .010" between them I
> managed (using PressNPeel) to successfully create this board. The
> technique I used to locate the top transfer to the bottom is outlined
> below
I've never used Press-n-Peel (always used inkjet photo paper for toner
transfer) so I don't know how much light it lets through - but I've found
that optically lining up the sides (i.e. a bright light behind the
transfer sheets, face in - using vias to make sure it's lined up), taping
the ends of the two sheets to form a hinge, then putting the board between
and just ironing the whole lot (turning over halfway through to iron the
other side - the heat transferring through the board gets the other side
to basically stick well enough for turning the board over) is extremely
accurate. I usually get it absolutely spot on with this method - most the
time, after etching and holding the board up to the light, there is no
detectable mismatch between the two sides.
It's really fast to do as well.
A light box is probably the easiest way to do it, but during daytime, I
just use sunlight and at night, a table lamp.