Hello Mark,
That is great to here!
I can't immediately think what is causing the pitting to be in lines or
streaks. If would have been great if you took a high resolution scan and put
it somewhere where it can be downloaded. I have web space if you need.
As for the opto sensor and registration, it may be worth mentioning that all
opto sensors are not created equal. The worst problem with the mechanical
flag type setup is that variations in movement from one activation to the
next is the main cause. A direct opto sensor setup without the pivoting
actuator is hundreds of times better.
The common garden variety sensor used most in domestic electronics is a
0.5mm. In other words the optical path is 0.5mm wide. These may be fine for
some boards but if you are working down to 2mil resolution then they may not
be so good.
Physically and electrically identical opto sensors are available that only
differ in optical path width. These go down to 0.01mm. If you can tell me
approximately where you are then I will find a supplier close to you.
You can get more registration reliability from the more common sensors by
reducing the influence of optical and electrostatic noise and bias. Just put
it in a metal shield to block out electrical interference and ambient light.
The darker the sensors environment the more consistent it will be. As the
actual sensor part of it is a semiconductor (photo transistor) it can also
be influenced by electrical noise.
The split board method will always solve this problem but I feel that it
causes unnecessary work. In my project (inkjet direct etch resist) I will be
drilling two registration holes in the board to clip onto pins in a truly
flat bed printer.
I am looking at my old laser printer now and wondering if I should bother to
buy a new inkjet printer. Perhaps after your success I should go directly to
laser direct etch resist.
I looked in the shed the other day and I have quite an amount of single side
laminate that is about 0.2 - 0.3mm thick along with plenty of single sided
FR4. Perhaps I should try the thinner laminate in the laser.
I have a spare image drum to, so perhaps my laser printer should be getting
nervous.
Keep up the good work, your getting excellent results, well capable for SMD
work.
My hobby work is digital so I need good resolution as well.
Thanks, Robert.
----- Original Message -----
From: "Mark Lerman" <mlerman@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Thursday, April 03, 2008 9:31 AM
Subject: Re: [Homebrew_PCBs] Direct Toner - First Try Results
Robert,
My second try was MUCH better. I noticed that the pitting was
actually more like streaks, all going in the same direction. Perhaps
caused by the gel?? Or not enough fusing?? Anyway, this time I used
no gel, then ran it through the laminator 4 times, once in each
direction. I etched it, and the results seem about perfect. No
pitting, no smearing. The 2 mil traces are perfect! I suspect I can
get them closer together than the 10 mil centers I am using now, but
these are pretty fine traces and more than adequate for what I usually do.
I used a precision optical sensor to find the leading edge of the
board as it enters the printer. I wonder if I can make double sided
boards with adequate registration? For now I think I'll stick with
what I have. A double sided board can easily be made using thinner
board and gluing two boards together using registration holes and pins.
Mark
At 06:59 PM 4/2/2008, you wrote:
>Hello Mark,
> An afterthought or two.
>
>I find that when I have to visually examine something in fine detail, it is
>easier to scan it on my scanner at maximum resolution and then scroll
>through the image on the PC screen. Perhaps you can do this with the fuser
>PCB to look for clues.
>
>If the problem is air pockets then it may pay to go over the PCB with very
>fine sand/emery paper (1200) before printing.
>
>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
>
>
>------------------------------------
>
>Be sure to visit the group home and check for new Links, Files, and Photos:
>http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>
>------------------------------------
>
>Be sure to visit the group home and check for new Links, Files, and Photos:
>http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
------------------------------------
Be sure to visit the group home and check for new Links, Files, and Photos:
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