Homebrew PCBs

On Mon, 12 Mar 2012 09:48:12 +0100, you wrote:

>Hi all,
>
>After a hiatus of many years I'm getting back into electronics (robotics 
>in particular). I have made a couple of PCBs using the photo transfer 
>method.
>I am now venturing into SMD components and want to use the toner 
>transfer method as I have discarded my UV lightbox.
>So I'd like to know what methods you guys use to get very thin traces 
>reliably.

clean board, good paper, good laminator.

>What are the limits of this method?

I find that 10 mil traces are reliable, but somewhat picky to get
right.  0.5 mm spacing on a VQFP-100 flatpack is about the limit for
me, and the board still needs a bit of hand rework at times.


>What are the things to look out for to get reliable thin traces?

clean the board well.  proper temperature and pressure in the
laminator.  For large (5x7) boards I run through 8 to 10 times with
the laminator I have.  You will need to experiment.  Green foil helps
a lot, but I have had instances where it simply does not adhere at
all, ever.  Then it may ruin the board.  Odd.  Best boards have green
foil done properly.  Photoresist is actually a better process when
done with a good negative.

You will need a laser printer with 1200 DPI, dense toner, and one that
the toner softens at the proper temperature (that of the laminator).
600 DPI does not work for fine traces.

Harvey

>
>Thanks.
>
>Bert