Conductive pen technique and substrate

Mon Jan 30, 2012 3:53 am   

Our lab will be evaluating fractal-like antenna. For the initial
(simple) designs, we are considering to use conductive ink pens,
primary to save artwork/fabrication time and cost.

Does anyone have firsthand experience with these, ie. the best pen
brands, and what type of substrate material to use so the tracks stay
put.

Ken Marsh

Mon Jan 30, 2012 4:14 am   

Ken Marsh wrote:


You'll be happier with copper tape and scissors, I think.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

Mon Jan 30, 2012 5:52 am   

In article <4F260B2D.41B282A_at_electrooptical.net>,
Phil Hobbs <pcdhSpamMeSenseless_at_electrooptical.net> wrote:


What Phil said. "conductive" ink is often a poor conductor, and very
expensive compared to either copper tape or attacking a bare copper
board with an Xacto knife (or paint and ferric chloride - if you can
paint the pattern you want, you can paint it on copper with a paint
marker or a brush and etch the copper you don't want off, and have a
real conductor.)

I do have firsthand experience, and I hate the stuff.

--
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.

Mon Jan 30, 2012 6:13 am   

On Jan 30, 2:53 am, kenma...@interlect.com (Ken Marsh) wrote:


Limited experience with those things tells me their resistance is
high, and reliabliity and longevity low. Colloidal carbon makes a far
more reliable conductive ink, but has much more R.


NT

Mon Jan 30, 2012 6:15 am   

On Mon, 30 Jan 2012 02:53:29 GMT, kenmarsh_at_interlect.com (Ken Marsh)
wrote:


Jeez, just use tin or copper alarm foil. It comes with the adhesive
already on it.

Mon Jan 30, 2012 6:18 am   

On Sun, 29 Jan 2012 23:52:23 -0500, Ecnerwal
<MyNameForward_at_ReplaceWithMyVices.Com.invalid> wrote:


Well,if he were to go that route, the silver filled conductive epoxy
would be the choice. Mill tiny groves in G-10 plates (milling is cheap)
and fill them with it. Makes for precise uniformity of trace dimensions.

You can get grooves down to 0.035 easy. Some will do 0.015 for you.
Those are mils.

Mon Jan 30, 2012 10:54 am   

Pueblo Dancer <Kachina_at_allhopiislost.org> wrote:
: Well,if he were to go that route, the silver filled conductive epoxy
: would be the choice. Mill tiny groves in G-10 plates (milling is cheap)
: and fill them with it. Makes for precise uniformity of trace dimensions.

: You can get grooves down to 0.035 easy. Some will do 0.015 for you.
: Those are mils.

Do you really mean 0.9um and 0.4um (metric)? We do have a milling machine
(FEI Helios) that can do it, but I would not call this easy, or a subtitute
for an xacto knife. Filling the grooves with epoxy would be even more
difficult. A typo maybe?

One would need a squeegee of some sort to remove the extra
epoxy even if you meant 35 mils i.e. 0.035 inch grooves - sounds a bit
messy.

Regards,
Mikko

Mon Jan 30, 2012 11:53 am   

On Sun, 29 Jan 2012 21:15:57 -0800, Pueblo Dancer
<Kachina_at_AllHopiIsLost.org> wrote:




Yes, it might be fine for straight lines, but we are wanting to do
tight curves, zig zags, crosses, etc. That could be tricky with tape.

Won't bend uniformly. Have to solder cross-overs, etc.

If anyone ever came up with a laser printer cartridge that deposited
(real) conductive ink on flexible plastic sheet, they would make a
fortune.

Ken

Mon Jan 30, 2012 3:15 pm   

On Mon, 30 Jan 2012 10:54:26 +0200 (EET), Okkim Atnarivik
<Okkim.Atnarivik_at_twentyfour.fi.invalid> wrote:


That would make each trace uniform, Hell, you could pull solder paste
into the grooves. And no, it would not be difficult to apply.

It makes uniform traces. Hand cut foil does not. Foil requires
attachment. Epoxy would get "laid up" in the cracks with a single, easy
swipe.

Mon Jan 30, 2012 3:17 pm   

On Mon, 30 Jan 2012 10:53:29 GMT, kenmarsh_at_interlect.com (Ken Marsh)
wrote:


You can buy printers that use food coloring for printing images on
cakes. I am quite sure you could make an epoxy mix that it would print
just fine.

Mon Jan 30, 2012 4:39 pm   

Ken Marsh wrote:

Don't piece the tape, use wide stuff and cut it to shape. (I'm assuming
this is a microwave antenna.) I have 3-inch wide Cu tape in my drawer,
as well as a roll of 12-inch-wide copper-plated Kapton.

If you need something really complicated, if your time's worth anything
you'd be much better off making Gerber files and having it made on
flex. A good board house can do big flexes with 4-mil lines and spaces.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

Mon Jan 30, 2012 8:47 pm   

On Mon, 30 Jan 2012 10:53:29 +0000, Ken Marsh wrote:


But there are already a number of good ways to do fast prototyping of
circuit boards. Unless there's a good reason why FR-4 doesn't work as a
substrate for you, your best bets, IMHO, all revolve around leveraging
everything that has been learned about circuit board fabrication in the
last 60 years, instead of messing around with reinventing the wheel.

Paint then etch, or direct etch with an X-Acto knife and peel the rest
off (heating with a soldering iron does wonders for making the copper
debond from the substrate), drawing up what you want in a PCB program and
sending it off to a quick-turn PCB house, and getting one of those PCB
prototyping milling machines are all viable answers to your problem.
Furthermore, all of them give you an antenna with a known and
controllable conductivity, and some of them give you an easy way to
duplicate antennas and/or carefully control what gets laid down.

That having been said, I think that your best bet for doing this
according to your preconceptions is to use silver-filled epoxy, thinned
with 99% isopropyl alcohol until it flows nicely, and painted on with a
brush. But -- check your conductivity, because you might not like the
result.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

Mon Jan 30, 2012 10:23 pm   

In article <kJednZQHWo5MbrvSnZ2dnUVZ_vGdnZ2d_at_web-ster.com>,
Tim Wescott <tim_at_seemywebsite.com> wrote:


Conductive particles have a problem with working in an electrostatic process - the fact that the toner is non-conductive plastic is not irrelevant to the process working. Some fairly crude efforts in inkjet have been made, as I recall. Perhaps they have even got a bit less crude - here's one.

http://www.conductiveinkjet.com/

http://www.printedelectronicsworld.com/articles/conductive-inkjet-printable-ink-prints-circuits-directly-on-polyesters-00002405.asp?sessionid=1

http://www.novacentrix.com/product/metalon.php

But any of these are likely to provide a result that is not going to behave the same way that copper on FR4 (or flex if that's what you are prototyping for) will. So they may be of limited value as prototypes, anyway.

Tim left out (though I find it horribly crude - it's quick) Print out the pattern you want in reverse, and iron it onto a board, then etch (soaking the paper off first.) Laser printer toner is actually decent resist (though pinholes are an issue.)

You could also probably have your local screen-printing place zap out a quick screen of your design and print that onto boards for etching.

In the "old tech you'd be lucky to find working" line, one of our labs used to plot resist pen directly on copper-clad with a flatbed pen plotter. The rise of the pesky roll and inkjet plotters makes that harder to manage now. Optimists would then think that a conductive ink pen in such a plotter would solve all your issues - good luck with that if you head there.

Or the old way - printout a laserprinter transparency and expose a photo-resist board, develop, then etch - but that's work, and more importantly in many places these days, a bunch of moderately nasty chemicals. One reason quick-turn board houses get so much business - in any regulated work environment, setting up to be compliant for handling and disposing of and having all the chemistry on hand costs the company more than letting the quickturn house deal with all that. The good ones really are quick, too.

You're not going to get terribly precise geometry hand-painting the things, that's for sure. And the "conductivity" needs the quotation marks, and costs the earth with all that silver that's mostly not touching all that other silver, so it mostly doesn't conduct much.

--
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.

Tue Jan 31, 2012 12:32 am   

On 30 Jan., 20:47, Tim Wescott <t...@seemywebsite.com> wrote:

snip

I think even easier would be to stick some copper foil on a bare piece
of fr4
or what ever backing that has the right properties, then cut and peel
digikey has adhesive copperfoil up to several feet wide

-Lasse

Tue Jan 31, 2012 5:58 am   

"Ken Marsh" <kenmarsh_at_interlect.com> wrote in message
news:4f2604ad.6173421_at_news.tpg.com.au...

http://www.techniks.com/

Press-n-peel blue. Stick it in a laser printer, print, then iron onto
copperclad board. Etch.

Cheers