Thanks for the input. I don't think toner sticking is my problem.
I have to clean the board between attempts. I use acetone and have
to scrape it off with my fingernail. It's stuck really well.
Problem is that the clay coating of the picture paper is also stuck
really well. Clay comes off big areas easily. Can rub it off with
a wet thumb in the denser areas. But for 5 mil spaces between traces,
I just can't get it out. For a few spaces, I could dig it out with a sharp knife. This board is almost all 5 mil spaces.
As for cleaning, I've been using a nylon scrubber followed by tarn-x
followed by alcohol. Tarn-X is a copper/silver cleaner containing
thiourea. Been using it for decades with excellent results on pen-plotted boards.
As for ironing, I've only made 5 tries so far. Longer time has
been worse as has been lower temperature. My first attempt,
2-minutes at 450F seemed to be the best so far. The copper surface
is starting to take on the texture of the fiberglass. Time for a new
chunk of board.
I tried cooling the board then putting back the iron for a few
seconds and hot peeling the paper. That was a disaster.
Seems like the thing to do would be to put some conformal material between the iron and board to even out the pressure.
High temperature thin rubber sheet?
Had another thought. What about a a thin sheet ot teflon.
Print the image on that. Teflon oughta peel right off.
I'm off to buy some other paper.
mike
--- In Homebrew_PCBs@yahoogroups.com, "Phil" <phil1960us@y...> wrote:
>
> --- In Homebrew_PCBs@yahoogroups.com, "gettingalongwouldbenice"
> <gettingalongwouldbenice@y...> wrote:
> >
> > I've done some more ironing experiments. The toner is sticking to the
> > board very well in most areas. With a little practice, it should be
> > fine. Problem is that I can't get the paper off without tearing off
> > the traces. I've got a TQFP64 package with a bunch of parallel runs
> > with 5 mils between them. The toner looks fine, but the paper is
> > stuck in the spaces between runs. I soaked it for an hour, but can't
> > get the paper out of the cracks without tearing off the runs.
> > Larger traces with more space are no problem.
> > Suggestions?
> >
>
> Toner coming off could be one of several things: rough handling, board
> prep issues, insufficient fusing time/temp, fusing pressure or paper
> issues.
>
> To get the paper off, try extra soaking. Be gentle with the toner.
> Soft rubbing with your thumb should get it off pretty easily. Dont
> force it.
>
> Board prep, for me at least, is crucial. You not only need to
> degrease it but remove oxides and "activate" the copper. There are
> lots of ways to do this. Think-n-tinker has a good process
> http://www.thinktink.com/stack/volumes/volvi/cleaning.htm My
> technique is to use 600 grit wet-or-dry sandpaper and wipe with
> acetone on a paper towel. The 600 grit removes the crud layer and
> creates more surface area for the toner to bind to (IMO, this is
> crucial for good toner transfer). The acetone degreases and removes
> the debris from the sanding. The negative is that you loose a little
> copper.
>
> Fusing temperature is pretty important but so is time. I'd try
> doubling your ironing time.
>
> Pressure is also important. With an iron, I would iron the board and
> when it was done, turn off the iron and leave it on the board/paper
> assembly. This ensures good physical paper/copper contact while the
> toner goes from liquid to solid. I also have used a metal wall paper
> roller on the cooling board to good effect.
>
> paper, what can I say that hasn't been already said? I like inkjet
> paper but get accused of pedantry when I mention it. Still, its ultra
> cheap and works really well.
>
> > Also, what do people use to touch up missing trace segments, pinholes,
> > etc.??? Lumocolor 313-2 would do it except that the pen tip is way
> > too large. If I could find a pen that would do the touch up, I'd just
> > plot with the pen and be done with it.
> >
> > What I need is a finepoint system 0.1 pen with etch resistant ink.
> >
> > How do the various etchants affect different inks? I've only used
> > FeCl. Are other etchants easier on the resist?
> >
> > Thanks, mike