--- 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