On Sun, 3 Mar 2019 15:13:46 -0600, you wrote:

On 3/3/2019 1:35 PM, Kevin Byrne via Groups.Io wrote:

Green TRF protects your traces from any and all etchant. It works real 
good with Apache AL13P as that is my way. It should work with other 
laminators but doesn't with household iron. Other? foil is also sold 
on E-Bay.

Many people use toner transfer.  The basic idea is to print on paper,
then using heat transfer, get it to stick to the PC board.  Toner is
plastic with graphite (more or less, it needs to be black).  The fuser
in a laser printer liquifies the toner and that seeps into the paper.

The idea behind toner transfer is that you print on something where
the toner does NOT seep into the paper.  Clay coated paper is one
answer.  Glossy magazine paper is another.  Specially coated paper
(it's detrose, like sugar, water soluable)is another.

Print on the paper.  Toner adheres (however minimally) to the paper.

Invert it and put on a PC board...  Run that through a laminator (or
heat source with pressure)...  that melts the toner and it glues it
*AND* the paper attached to the pc board.

Now soak that in water.  For most paper, the paper fibers weaken and
can be scrubbed off.... how well depend on the paper....

With the paper, the dextrose dissolves and the paper floats off.

Now the good news is that it's on the board, the bad news is that
there might be gaps and holes in the toner layer.

Green foil fills some of those blanks, and the additional material
(the green dust that adheres to the melted toner during the phase
where you heat the green foil) tends to seal the toner surface.

That is why you're using it.

Too little heat and pressure and there are gaps in the traces because
the toner doesn't stick (also if there is grease or oil on the PC
board).  Lots of debate on how clean to make the board and how to
clean the board.

Too much pressure tends to flatten the traces and cause them to
spread.  Generally not as much of an issue as you might think until
you start doing 100 pin chips with 0.5 mm pin spacing (and the nominal
size of the trace is 10 mils, with a 10 mil gap. best that I'd been
able to do).

Lots of variables here, so it does take some experimentation.

Harvey

I have some yellow paper from ebay to try. Otherwise magazine paper I 
wanted to try too. And parchment and glossy etc... :) I never knew about 
the Green TRF though. Best place to buy?