Homebrew PCBs

If the only problem I was having is to fill in an occasional pinhole, 
I'd call it good.  Given the amount of manual fussing you have to do, 
that seems a pretty minor point.

I've been experimenting with this technique but have yet to get a 
laminator becuase I've gotten reasonably good results from the iron 
approach.  It seems to me that there are a number of variables you 
have to deal with.  each one can ruin the process.

1) fusing temperature
1a) toner fusing point
1b) fusing time
2) fusing pressure
3) thickness of toner
4) quality and cleanliness of copper substrate

I think 2) is a huge issue in that there is fine line between too 
much and not enough.  I found that even modest pressure causes some 
smearing of toner (and the widening of traces). Its my opinion that 
little pressure is needed, you just have to ensure that the toner 
makes contact with the substrate for a long enough time at the fusing 
temperature.  i.e., it has to melt and be in contact with the 
substrate long enough.  I've gotten good results with letting the 
iron be all the weight needed.  I also do not apply ANY lateral force 
as that seems to cause smearing.

Since I print on an inkjet and then use a copier for my toner 
deposition, I am able to control the amount of toner pretty well.  I 
tried a non-scientific range of toner densities and found that you 
want it to be fairly thick, especialy for large ground areas.  How 
ever, the thicker the toner, the easier it is to get smearing.  less 
pressure is needed in that case.

It probably goes without saying but preparation the the board is 
critical.  I've gotten good results with a very fine emery cloth to 
create a rough surface (i.e. significantly increase total surface 
area to allow better toner bonding). 

Toner fusing temperature is tricky because different toners have 
different fusing points and it appears the substrate material type is 
a factor as well.  For example, ricoh has a lower temperature toner 
to allow shorter warm up times for their printers.  does anyone have 
pointers to information on fusing temperatures for varous toners?  
I've googled until my eyeballs hurt and found only scraps of info.  I 
may just have to try an experiment.


Phil



--- In Homebrew_PCBs@yahoogroups.com, "Leon Heller" 
<leon_heller@h...> wrote:
> 
> >From: "joshdewinter" <joshdewinter@y...>
> >Reply-To: Homebrew_PCBs@yahoogroups.com
> >To: Homebrew_PCBs@yahoogroups.com
> >Subject: [Homebrew_PCBs] AHHH!!!!  Thermography looking like a 
better 
> >option
> >Date: Wed, 11 Feb 2004 17:35:49 -0000
> >
> >   I'm getting frustrated.  I've tried all night (for several 
nights)
> >to perfect my toner transfer process.  I keep getting marginal
> >results.  I started with an iron.  Eventually, I got a laminator,
> >albeit a cheesy, low grade one.
> >   My results are not production grade, and it's frustrating me.
> 
> [deleted]
> 
> You are probably using the wrong printer, some are better than 
others at 
> toner transfer.
> 
> Leon
> --
> Leon Heller, G1HSM Tel: +44 1424 423947
> Email: aqzf13 at dsl dot pipex dot com
> WWW: http://www.geocities.com/leon_heller
> 
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