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Conductive epoxy for very small contact area

Hi, Joerg.

Good timing -- I just did a bit of research for my niece Maggie, who is experimenting with "wearable electronics" while waiting to hear back on her post-graduation job applications.

It turns out that conductive ink/paint is getting a lot of attention these days from those interested in "wearables":

Bare Conductive Paint - 50mL ($25)

Naturally, given the price of the stuff, people are experimenting with creating their own using powdered conductive material (e.g. graphite or charcoal) in a glue or paint base:

Be sure to read the comments, both for additional ideas and so that you're aware of the health risks of using powdered metal as your conductor.

Some research results:

Hope something in all this helps...

Frank McKenney

--
  What I've learned, above all, is to keep marching forward, because the 
  best news is that since chance does play a role, one important factor 
  in success _is_ under our control: the number of at bats, the number of 
  chances taken, the number of opportunities seized.  For even a coin 
  weighted toward failure will sometimes land on success.  Or as the IBM 
  pioneer Thomas Watson said, "If you want to succeed, double your 
  failure rate."      -- Leonard Mlodinow / The Drunkard's Walk
Reply to
Frnak McKenney
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Again, I have done somthing this small bit wicking away was no issue. Now it is.

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

63 37 solder melts at 217 Degrees C.

we have very thin stuff. Way less than the usual

BGA solder balls are available on Ebay from .3 mm to .76 mm diameter.

I have soldered .002 wire from Ney with a regular soldering iron. But it was to a copper wire that was maybe 24 gauge.

A quick look on the internet finds a company Deringer Ney. Probably the same company. It was a long time ago.

Dan

Reply to
dcaster

That's the stuff I've use a lot lately. My question would be how to reduce the "highly viscous" characteristic mentioned in the datasheet without destroying conductivity. I don't need a very low resistance, low tens of ohms is fine.

I'd like to buy off the shelf, cost isn't an issue in my case.

Thanks. It kind of does but I know the Bare Paint stuff quite well, went through several tubes by now. And maybe there just isn't any better solution out there.

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

No, about 183C, 217C is more like a lead free solder, for example Sn96C.

Cheers

--
Syd
Reply to
Syd Rumpo

For best results I keep my iron in the 360-370C range. It can be done with less but gets dicey.

Those are boulders :-)

I just ordered a bunch of stuff, MG Chemicals 840 nickel paint, their

835 thinner and some more black Bare Paint. Had to order today because this stuff isn't allowed on aircraft so has to come ground. 
--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

If this is just for wafer testing, why not use a more suitable substrate and bonding pad?

RL

Reply to
legg

Wafers do not generally contain Kapton :-)

It is for testing singulated microscopically small sensors. We are using all the space there is.

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

...The other issue is to dispense such a

There are other ways to dispense solder; diodes used to be made by plating the solder onto a cat's-whisker contact, pressing it against the semiconductor, and heating the assembly.

The solder (indium, I believe) was the dopant for a Germanium alloy diode.

More practical might be to use a sticky flux, dip the wire in it, then touch it to a little pile of pulverized solder... kinda do-it-yourself solder paste. Study the nut-topping procedure at your local Baskin-Robbins for inspiration.

Reply to
whit3rd

On Sun, 13 Sep 2015 20:40:12 +0100, Syd Rumpo Gave us:

Colder than that, and one may experience icicling problems on the assembly. So melting point and a reasonable flow point are separated a bit..

Reply to
DecadentLinuxUserNumeroUno

Been ages; used to determine solvent by smell; in this case i think it is butyl alcohol. Use only minimal amount as too much will kill the conductivity.

Reply to
Robert Baer

Hi Joerg, I'm kinda late to this thread, and I didn't read all of it so this may be redundant. It sounds like you want silver paint. Maybe from here?

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I'm not sure who makes the best stuff. For really small pads I've seen people make brushes with a single camel hair... or something like that. (It's not something I've done a lot of.)

Of course the shelf life of the paint is very short.... use it or lose it. :^)

George H.

Reply to
George Herold

...and all the inerconnection methods intended for the final application? It doesn't seem that one will be much use without the other.

RL

Reply to
legg

On Mon, 14 Sep 2015 03:36:16 -0700, Robert Baer Gave us:

You are all idiots if you think you can "thin" epoxy formulations.

Reply to
DecadentLinuxUserNumeroUno

epotek.com - H20E and variants. 1:1 mix, small dots or dabbing easy, will oven cure at 80C in 3 hours, 120C in 15 mins. No creep. No guessing. Could be used for production work - 40 year pedigree.

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--
Grizzly H.
Reply to
mixed nuts

Doesn't the solvent all evaporate?

--

Rick
Reply to
rickman

On Mon, 14 Sep 2015 10:47:35 -0400, mixed nuts Gave us:

I suggested this days ago. Used it for years too.

Reply to
DecadentLinuxUserNumeroUno

You have to read the data sheet. H20E is 3 hours at 80c. H20E-FC cooks in 45 minutes. It's also good practice to include a test coupon of the same materials you're using to prove adequate cure without having to poke at expensive stuff - batches vary. I've gotten a couple of batches that needed considerably more time for low temp. curing even though they were normal at higher temps.

--
Grizzly H.
Reply to
mixed nuts

I have done so many times. I use the epoxy diluted with alcohol to paint the engine compartments of my R/C models.

Reply to
John S

Thanks, I'll look into that. But running out of time I ordered a bunch of MG 840, thinner, and several tubes of bare electric paint. That should get us going at least for prototypes.

Production is another matter and then we may have to look at SPI, Epotek or something similar. Maybe MG-Chemicals. Then we'd sit down with an engineer there.

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

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