Homebrew PCBs

With a lot of help from this list and a lot of experimentation, I'm having
much better success with my toner transfers.  The process that finally ended
up working for me for creating my first usable double-sided board went like
this:

1) Discard overused boards.  It's true you can transfer toner onto a board
and then clean it back off and try again if it doesn't come out the first
time.  I had diminishing returns after my seventh or eighth try, and found
it better to stop trying to salvage the board.

2) Line up the both sides of the board.  I held the two sheets of magazine
paper up to a worklight to line everything up, and then taped them together
on one side with ordinary Scotch tape.

3) Clean board blank with acetone, scour with Scotchbrite pad, clean with
dish-soap and hot water.

4) Pre-heat board to about 200F.

5) Place the board between the taped-together patterns, using the taped-edge
as a guide.

6) Provide 1-minutes of constant pressure with the iron, then about
5-minutes of moving pressure.

7) Flip the board and repeat.

8) Drop the still-hot board immediately into hot water for 10-minutes.

9) Remove paper.  Touch up any broken traces with a sharpie (industrial
permanent ink, micro-fine point).  Break any shorted traces with an x-acto
knife.

10) To ensure that both surfaces of the board get evenly etched, I put small
squares of foam mounting tape in inconspicuous corners of the bottom of my
board.  I use the 3M kind - this stuff's about 3-4mm thick, which gives
enough clearance from the bottom of the tank. I left the paper on one side
so it wouldn't stick to the tank.

11) I submerged the board in FeCl in a simple closeable plastic container.
I held it over the stovetop on medium heat and hand-agitated the tank...I
didn't measure the temperature here, but it was just cool enough to be able
to easily hold the tank without gloves.

I checked the progress of the etching intermittently, and found it barely
took 5 minutes to get complete removal of unwanted copper without any
etching into my traces.  I dunked the board in cool water in a separate
plastic container to stop the etching, and now have a nice looking,
perfectly aligned double-sided board ready for drilling.

-Andrew

On Sun, Apr 18, 2010 at 7:03 PM, andrewmv@... <andrewmv@...>wrote:

>
>
> I've just started attempting my first PCBs with the toner transfer method,
> and I'm consistently getting terrible results.
>
> Some sections of the pattern transfer flawlessly to the board, while others
> stay on the paper. I've tried varying heat, pressure, and ironing time, but
> my results are always similar.
>
> It never seems to be the same parts of the pattern that come though, but I
> never get the whole thing.
>
> My current process is:
>
> 1) Print the patterns in black toner on medium-gloss photo paper with a
> Dell 5310n laser printer at my office.
> 2) Scour the board blank in two orthogonal directions with 150 grit
> sandpaper
> 3) Clean the board blank with pure acetone
> 4) Preheat the board to about 150 degrees Fahrenheit with an electric
> clothes iron. I'm measuring with a handheld infrared HVAC thermometer.
> 5) With the iron at about 400 degrees, I place the pattern toner-side down
> on the board, and apply pressure with the iron. The pattern almost
> immediately fuses to the copper, as I've seen suggested it should, and I
> move the iron around the pattern regularly, applying a least two full
> minutes of heat and pressure to every part of the board.
> 6) I immediately place the board and paper into a bowl of hot water, and
> let it soak for 10-20 minutes.
>
> I've tried variations on this...I initially skipped the scouring, cleaning,
> or preheating the board. I've tried using mild pressure all the way up to my
> full body weight. None of these significantly improved or worsened results.
>
> I tried letting the board fully cool before placing it into COLD water, as
> I've seen suggested, and found that there was virtually no toner transfer
> whatsoever.
>
> Any tips or ideas?
>
>  
>


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