On Sat, 12 Dec 2009 13:43:54 -0500, Nathan House wrote:

> Unfortunately, I still can't make PCBs. I can't get the toner to transfer
> from the paper to the board for the life of me. But that's another post :-)

Evening Nathan.

Lots and lots of scrubbing - before you put your layout to the board, that is.
The copper clad board needs to be spotless.  I use a pan scrub (nylon ?) for
this, with washing-up liquid - that takes away the grease and layer of
oxidation; the water ends up black afterwards, unless it is a new piece of
board.  After that I dry the board with kitchen roll (doesn't leave bits of
fluff or other particles behind) and then give the board a wipe with some
meths, again using a piece of kitchen roll.  Keep wiping with meths until
there is no blackness on the kitchen roll from the board.

After that I'm ready to press.  After attaching the schematic (a bit of
masking tape does the trick, but be careful where you put it - it will melt
and the adhesive will not come off easily; it's also etch resistant, so don't
get it on the copper side !) I put the board onto a hard and flat surface
between two pieces of grease-proof paper - this is to protect the iron mainly.
I then put the iron in place on the board and lean heavily onto it for one
minute without moving it, then after that I'll 'iron' the board - side to
side, up and down, using the edge of the iron mainly.  This bit takes about
another minute or so.

Once the ironing's done, I chuck the (very hot) board into some cold water
(no soap or anything - some people say it makes the paper peel better, but
I've had mixed results).  After a minute or two soaking, most of the paper
peels away; what's left can be scrubbed off with a toothbrush.  The brushing
can be done with a little pressure, but don't overdo it; if there is no
pressure and the toner is peeling away, your board probably wasn't clean
enough or the toner is not the right sort.  

The paper does not have to be completely removed; in fact, I tend to stop
brushing even when there are still plenty of gaps covered by a layer of paper
since too much brushing will eventually start to lift the toner.  When the
board dries out after taking it out of the water, the bits between the tracks
will turn white and brittle; they're easily removed with a scalpel.  The bits
of paper left over the toner are of no concern.  Take the opportunity to touch
up any holes with an indelible marker pen too; some types of paper will bleed
the ink though, but if you've chosen the right type of paper then you should
be fine.  You should now be ready for etching.

The paper I use is the glossy stuff from advertising pamphlets, brochures,
etc. that's pushed through my door.  I tried quite a few different types, but
this works a treat and is free.  I try to find some that is mainly white; any
printing already on the paper doesn't tend to affect the etching, but it's not
good when you're trying to spot pinholes, defects, etc. after ironing.  This
paper peels peels nicely too (photo paper seemed to be impossible to remove,
regular paper seemed to be very fibrous but peeled OK, for example).

Also, when you tell your printer to print, make sure that you set it up
accordingly; for example, I tell mine that I'm printing on transparencies
even though I'm not - this is because it lowers the fixing temperature when
printing IIRC, so the toner should lift easier.  I also set the print density
to maximum, toner saving mode to off, page protection of, and I use 1200dpi
resolution (not the interpolated '1200HQ' mode either).

I've been using this method a fair while, and the last four weekends or so
I've been knocking up some quick test fixtures for my current project; the
copper clad board I am using for these is over 20 years old and black, but it
scrubs up brilliantly and etches fine with how I've outlined above.  I've
also done double-sided boards with this method too.  The key is getting it
really clean I believe.

A few months ago I posted some queries on toner transfer and some of my
findings to the piclist; search the archives and you might find the thread.
I seem to remember Vitaliy making some good suggestions at the time that I
didn't try - you may want to give them a whirl.

Also, make sure you use an old iron.  For my first few attempts I decided
to spice things up with a bit of 'Danger PCB-ing' and used the girlfriend's
best iron.  I broke it by leaning on it too hard, and then had to buy her a
brand-spanking-new super-deluxe (and pricey) model...

Regards,

Pete Restall
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