Homebrew PCBs

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