Hi Mark,
I may offer some limited suggestions to some of your questions.
Q: 1 - Should I have run the board through the laminator more than
once?
A: It may possibly help to run the PCB through a second time if the
laminators temperature is to low or the roller speed too fast but this is
less than an ideal solution. If it is one of these problems then it is best
for reduce the roller speed or increase the temperature as each pass of the
PCB through the laminator introduces more pressure on the PCB and may cause
additional smearing.
Q: 2 - Would I be better off using an oven or hotplate to fuse the
toner? I can control the temperature quite well, but will the toner
fuse well without the pressure?
A: Two parts to your question.
1) Better temperature regulation should yield better results irrespective of
the method apart from what is said in part 2.
2) In a printer, paper is porous and the textured surface is irregular.
Fuser pressure forces the toner into the surface causing a strong bond. A
PCB is not porous and has a distinctly regular surface so this is not
required for this reason. However there is a second function that may be
necessary depending on your etch process. Toner can have pockets of air
underneath and the fuser will most likely expel this air. Correct
temperature by non-pressure methods should work just as well but a fuser
leaves more room for temperature error. None of this will matter unless
capillary action takes etch into the resist-to-copper gap and even this will
probably make no difference depending on the etch process. I use Ferric
Chloride and exposure to air. As the exposure to air accelerates the
process, air deprived etch that may be in the gaps has less opportunity to
make any difference or pitting. Other etches may behave differently.
Q: 3 - What causes the pitting? Too long in the etching? Toner not
completely fused? All the traces and pads seem equally pitted, so I
don't think it's the trace width.
A: See two above. Also insufficient toner or too high a fusing temperature
will cause this problem. Or too low a temperature that causes air to be
trapped. Too long in the etch can cause it too but most people monitor the
etching and take the board out as soon as the etch is complete.
Hope this helps, Robert
----- Original Message -----
From: "Mark Lerman" <mlerman@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Thursday, April 03, 2008 7:16 AM
Subject: [Homebrew_PCBs] Direct Toner - First Try Results
I just made my first (single sided) board using my modified laser
printer that deposits toner directly on the board. A few observations
and questions:
1- I used the Eagle Demo2 board, but inserted four 2 mil traces
between 2 of the dip pads, each connecting to one of 4 adjacent pads.
These are 2 mil traces on 10 mil centers, with the traces on the
sides being 7.5 mils from the pads.
2 - I used some of Dave's gel on the 1/32 inch thick board - will try
without it later.
3 - I then ran the board through a laminator once - no carrier.
4- I etched using muriatic acid / peroxide, room temperature, a
little agitation by hand rocking the board.
The board came out okay, but there is some pitting that I am not
happy with. All four 2 mil traces are intact, none of them are
shorted. Questions:
1 - Should I have run the board through the laminator more than
once? I bought the laminator at Staples, no model number on the box,
but I believe it is one of those recommended on the laminator link.
I'll have to measure the temperature sometime. Any other thoughts re
the laminator?
2 - Would I be better off using an oven or hotplate to fuse the
toner? I can control the temperature quite well, but will the toner
fuse well without the pressure?
3 - What causes the pitting? Too long in the etchant? Toner not
completely fused? All the traces and pads seem equally pitted, so I
don't think it's the trace width.
Lots of questions, but I realize that I am on somewhat uncharted
territory here. It's going to take time and experimentation to work
it all out, but I'm excited by the possibilities of this technique.
Mark
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