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Add your conducting adhesive here..

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LAN_403

Conundrum

Sat Jun 05 2010, 12:25PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Hi all.
Please add to this thread your best formulas for conducting paint "on the cheap".

So far my best one is Weldtite cycle repair compound (RTV) mixed 50/50 by volume with graphite lubricating powder.
(kudos to Island Lock & Safe for mentioning they had some in stock!)

supposedly if you add colloidal silver (obtainable from two silver electrodes placed in DI water with a periodic reversing power every minute or so) it makes it a lot more conductive.

interestingly with the increase in bicycle use over here there are a lot of shops selling this stuff for not much money.

If you need it to be more liquid e.g. for spin coating you can dilute it with various solvents including paint thinners (aka white spirit) and this helps a bit.

-A

"Bother" said Pooh, as he mistook hemlock for oregano...

IntraWinding

Sat Jun 05 2010, 02:06PM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

An early method for producing colloidal metal was to strike an arc between electrodes of the metal below water, but I don't know the technique you describe. Any links?

I started a thread in the Chemistry forum as I strove to make suitable silver powder:
Low cost conductive epoxy?

I hope to try a more sophisticated recipe one day, but I'm very interested in any info on this subject as silver conductive paints and adhesives are outrageously expensive compared to the value of metal they contain.

quicksilver

Sat Jun 05 2010, 08:29PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

When I was involved with rockets we made several bridge-wireless ignitors that would form resistance between to leg wires (stripped to 1/16") by dipping them into graphite, single micron powdered Al, conductive lampblack, PbO2, a nitrocellulose lacquer binder, & a chlorate. By altering the conductive lampblack & Al you could work from 10 ohms to zero. It seems that because of the nature of superfine materials the binder system would eventually form a bridge with no resistance what so ever.
The point being that given certain materials (especially conductive lampblack and ink-grade aluminum) capacity for micron sized particulate; you pretty much could "write your own ticket". My vote is for the conductive lampblack and Al.

Conundrum

Fri Dec 17 2010, 01:03PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

update:- if you can get Thixofix "improved" formula with S 1470 on the back this makes conductive adhesive when mixed with graphite powder, around 30K per cm after gentle drying with heat gun- watch out as it tends to swell up if overheated though.

Pinky's Brain

Sat Dec 18 2010, 03:22PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

quicksilver wrote ...

When I was involved with rockets we made several bridge-wireless ignitors that would form resistance between to leg wires (stripped to 1/16") by dipping them into graphite, single micron powdered Al, conductive lampblack, PbO2, a nitrocellulose lacquer binder, & a chlorate.

What's the lead oxide for?

Conundrum

Thu Dec 30 2010, 10:00AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Probably slightly off topic, but Humbrol "Liquid Poly" contains toluene and xylene.
Makes a truly awesome general purpose solvent for everything from conducting paints to EL phosphor.
Watch the fumes though guys...
DO *NOT* use any plastic bottle for really obvious reasons

the best thing I've found is one of those screw top glass test tubes the kitchen spices come in.

Tried mixing some with graphite (to get a more even mixture) then mixed the resulting thick liquid with RTV adhesive from a cyclerepair kit, have to test it but I expect it to work well.

I did have success "watering down" the silver conductor in the EL kits with it and the phosphor itself, to cover a wider area.
Managed to paint it onto a sheet of glass and then EL phosphor, Sellotape and more paint which works well.
Pics are on the EL thread.

EDIT:-

I also tried mixing the silver paint in the EL kits with conventional Araldite Instant Clear, and amazingly it does somewhat work although the resistance is over 50K/cm.

Perhaps this could be used to make Z-axis connections to LCDs and suchlike, just mask off the edges and PCB with Sellotape and apply carefully then peel off any excess with the tape when dry and panel properly supported.

The bare LCD I tried this on had extremely sucky performance and inter-segment leakover but the segments did switch OK.

-A

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