Your expectations are not too high, you just need to iron out some
problems in your process.
It is not unreasonable to achieve a perfect transfer every time, it
can be done with a low failure rate. A total loss (=redo transfer) is
very rare with my setup, surely lower than 5%. Sometimes i will get a
broken trace, usually close to the edge (say each 10th board). I know
why that happens and i know how to avoid it, but i just can't be
bothered with boards where it don't matter.
My procedure is very quick, a rub of the PCB with 1000grit sandpaper
(dry). Just enough to have the whole surface with a sanding pattern,
only a few seconds work. Then i wipe the board with acetone, once,
using a piece of toilet paper. That's board preparation done. If i do
a very large board or it must be perfect i might wipe it twice,
sometimes even using another piece of toilet paper ;-).
Then i cut the printout to size, usually a few mm larger than the PCB,
but can also be smaller. Apply printout, feed fuser. While it passes
through the fuser i go and fill a plastic container with warm water.
The PCB takes ~20 seconds to pass through the fuser, i'll usually be
back in time to catch it as it comes out. When i feel like it i'll
pass it through the fuser a second time, sometimes not. Doesn't seem
to make much of a difference really.
Next step is scratching the back of the paper to allow the water in
quicker. I use a wire brush or some coarse sandpaper. Then the PCB is
immersed in the water. If i have time i let it sit for a while, but
usually i begin rolling off the paper immediately, starting in the
center and working outside. It hepls to dunk the PCB a couple of times
for more water. The residue is removed easily by wiping with a sponge
or foam rubber piece. Takes a minute or two. I'll check the transfer
at this point.
Now the board goes in the etcher, and a very long wait begins,
especially if the etchant is cold and hasn't been topped up with H2O2
and HCl for a long time. It can take an hour to etch now that i have
moved the setup to a room that isn't heated in winter. I could keep a
more agressive etchant, or heat it, but since i don't make so many
boards any more i can usually find something to do and don't mind the
wait. Often this involves watching TV, which often results in me
missing when the board is finished. Doesn't seem to matter much, i
haven't lost one due to overetching yet (i use 8 or 10 mil traces most
of the time, more rarely 6.6mil).
Obviously now the board is washed with plenty of water, and drilled,
and cut to size, and the toner removed. This takes another 15 minutes
or so.
Now look at the time, i could have made another board since i started
writing this (etching time excluded).
Once you get your process sorted out you'll be just fine.
ST
On Feb 11, 2008 11:51 PM, Chuck Kelsey <wb2edv@...> wrote:
> Thanks guys for all the tips.
>
> Is anyone doing toner transfers and consistently getting perfect results?
> Maybe my expectations are too high and I'll have to live with some "hand
> drawn" missing traces.
>
> My last attempt was a 4x6" board that actually had 6 circuit boards on it
> that I'll cut apart. Out of the 6, there was only
> 1 with no flaws and 2 with a minor flaw.
>
> Chuck
> WB2EDV
>
>
>
> ----- Original Message -----
> From: "Ben Buxton" <bb@...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Sunday, February 10, 2008 11:43 PM
> Subject: Re: [Homebrew_PCBs] Trouble producting transfers
>
>
> >
>
> > I had this problem initially where some toner would still lift off the
> > cpper with the paper.
> >
> > The solution I have found is novel, but works surprisingly well - in
> > fact I can now reliably transfer and etch to smaller than SOIC traces.
> >
> > All I do is let the board + paper soak for a few minutes after the
> > initial 10 or so laminator passes. Then, whilst the paper is still wet,
> > I run it again through the laminator. It hisses and steams, but after a
> > few passes the paper dries and the toner really sticks to the copper.
> >
> > When the peper and board are wet, the paper holds to the board until I
> > manually pull it off. And the toner sticks firm enough that I can run a
> > fingernail across without lifting the toner.
> >
> > Note that if you want to do this, for safety you MUST make sure that the
> > electricals in the laminator are far enough from where you pass the wet
> > board through - I figure if you're making PCBs, you're also able to
> > safely open up your laminator to check this out.
> > It may take careful paper placement to prevent the laminator from
> > tearing the wet paper+toner away from the board.
> >
> > Also, the way to verify that the copper is clean is that when you wet
> > the board, water actually stays wet across the whole surface. If the water
> > retreats from areas of copper and pools up, your board is dirty. When it's
> > clean, air-dry it, don't wipe it down. I use Jif for the final clean -
> > rubbed across the board, the abrasive action cleans the copper, and the
> > built in soaps remove the oils.
> >
> > FYI, my setup uses an HP laserjet4 (found on the street), a k-mart
> > laminator, and IJ-84 matte paper. A home made bubble tank (using an
> > aquarium pump + air stone) etches a 5x7mm board in under 10 minutes.
> >
> > BB
> >
> > Chuck Kelsey <wb2edv@...> uttered the following thing:
> >> I picked up a new GBC 9" personal desktop laminator and tried some boards
> >> with no luck.
> >>
> >> I'm using a 4" x 6" board with 1 oz. copper and it has a thickness of
> >> 0.032". I clean it with a brillo pad and rinse thoroughly while wiping
> >> with
> >> a wet paper towel, then dry with a paper towel.
> >>
> >> The laser printer is a Lexmark 4039 10plus set at the darkest setting.
> >> Using
> >> the Pulsar toner transfer paper.
> >>
> >> The first attempt I ran the board (with the paper on the bottom) for 8
> >> passes in different directions. The laminator ready light had been on for
> >> 15-20 minutes before I began. I also pre-heated the board with a hair
> >> dryer.
> >>
> >> I dropped the board with the paper into a container of water and let it
> >> rest
> >> until the paper floated off on its own. Right away I could see pieces of
> >> black toner floating in the water as I lifted the paper out.
> >>
> >> My second attempt was done the same way, except I ran the board through
> >> 16
> >> times. Same problem - toner pieces floating around in the water.
> >>
> >> This is very discouraging and I'm at a loss. Anyone have any suggestions?
> >>
> >> Chuck
> >> WB2EDV
> >>
> >
> > --
> > Ben Buxton - Random Network Person
> >
> >
> >
> > Be sure to visit the group home and check for new Links, Files, and
> > Photos:
> > http://groups.yahoo.com/group/Homebrew_PCBs
> > Yahoo! Groups Links
> >
> >
> >
> >
>
>
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBs
> Yahoo! Groups Links
>
>
>
>
>