Phil,
Thank you for a really detailed useful post!
One question: Do you worry about the conductivity of the
toner "screen print"? Seems that it could be an issue...
Ballendo
--- In Homebrew_PCBs@yahoogroups.com, "Phil" <phil1960us@y...> wrote:
> After trying lots of paper and making a few boards with magazine
> paper, I found just the right paper and a good technique. I'm very
> pleased with the results for both 1 and 2 sided boards. Up until
> now, I was pretty dissapointed with the quality of what i was
making -
> lots of trace blooming and areas of poor resist adhesion.. I know
> others have different techniques that work but this is getting darn
> near fool proof for me.
>
> The paper is general purpose good quality inkjet paper - less than
$5
> for 500. I use a canon personal copier to get toner onto the paper
> and crank the darkness up quite a bit. The toner goes on thick,
the
> paper absorbs the excess toner nicely and I get very very little
> blooming of my traces anymore.
>
> Copper substrate prep is pretty standard except I use emery cloth
at
> 220 grit to significanly increase the surface area to improve toner
> bonding. I'm going to try something finer than that. wash, degrease
> and dry in oven.
>
> I put the iron on just a touch back from the hottest setting
> (cotton). I also use children's construction paper between the
iron
> and the toner paper as a pad to even out the pressure which I apply
> quite liberally. I iron both sides for a minute at what my
bathroom
> scale says is 30 lbs of pressure. Finally, I leave the iron on top
> of the board/paper assembly and turn it off to let it cool down.
> This is an important step as it keeps the melted toner in strong
> contact with the copper substrate to ensure good bonding. Once
cool
> enough to handle, it goes into the water for a standard soak and
> rub. The paper falls apart very quickly and the toner doesn't
flake
> off at all so I can scrub pretty hard.
>
> Also, I am getting good results with legend printing (some times
> called silk screen). I use the above technique with 2 changes.
> First one is that after one minute of ironing, I use the edge of
the
> iron to "burnish" the toner paper into the board. This ensures
good
> contact of the hot toner to all surfaces including next to traces.
> The second one is that I do a hot peel of the toner paper. Enough
> toner stays on the board to be very legable but more importantly,
no
> soak-n-rub cycle and thus I can go right to drilling with no more
> than a 5 minute delay.
>
> some pix taken with a 10X microscope
> http://www.geocities.com/phil1960us/pcb/
>
> Phil