Making a conductive adhesive

Well, I was trying to solder some extra thick peizo material, having very little luck when I realized that this could be solved very easily with some sort of conductive adhesive. So I set out to make some. I’m posting the steps for making a conductive adhesive for posterity and in case anyone needs to know. It’s not difficult though I have tried a few different methods and this one is the best.

1. Find your glue, preferably one that requires drying or curing, not anaerobic adhesives like Loctite (cyanoacrylate). I tried a couple of versions of Loctite and found that the conductive medium would merely clump together, making an oatmeal-glue. You can use adhesives like Rubber cement, 2 part epoxy or even white glue (polyvinyl acetate).

In this case I used two-part epoxy. It has a long cure time and its fairly rigid.

A small sample of the epoxy

A small sample of the epoxy

Nothing much to see there, since I wanted to use only a few drops of actual adhesive, I only mixed a gram or so of the stuff.

2. Prepare the medium. In this case I used a conductive graphite powder and iron filings. If you’re going to use iron filings, magnetize them first by letting them rub on a magnet, then force them off and into the graphite mixture. Beware that using a water based glue can make the iron filings oxidize.

Anyways, if you don’t have any graphite on hand you can crush up some pencil leads in a crucible or on something that will allow you to make the graphite as fine as possible. And in the event of not having any iron filings, like me, do what I did, grind or file down a piece of steel or an iron nail. make sure they’re magnetic.

This is the graphite/iron mixture

This is the graphite/iron mixture

Now, you may ask “Why iron, and why magnetize it?” Well, the iron provides low resistance paths through the adhesive and when you apply a magnetic field to the iron filings, they align themselves to the field, thus you can create a lower resistance path. I’ve reduced the resistance with this method by tens of KOhms based on the little I’ve done this so far, your results may vary.

3. Mix the glue and medium. Well this is a pretty simple step. The only thing you’ll many though is to add enough of the medium to make the overall adhesive almost clumpy, mixed to the point of saturation. This way you can ensure conductance.

This is the mixed version of the glue/graphite/iron filings

This is the mixed version of the glue/graphite/iron filings

4. Application of the glue. Simply apply the glue however you want, wherever you want. You’ll get less resistance if you place the two conductors as close to each other as possible though. Also, you’ll want to place one or two magnets, polarity aligned to the connections zones, near the adhesive. This will make the iron (if you used it) move slowly into lengthwise position between the two conductors.

This is the peice of peizo material attached with epoxy.

This is the peice of peizo material attached with epoxy.

Anyways, to be honest, I’ve only tried this formula a few times and did it entirely by eye, therefore I can’t give any exact values. But, thus far it works for me. If it works or doesn’t work for anyone else, feel free to comment. 🙂

  1. Alexander
    January 2nd, 2012 at 01:44
    Reply | Quote | #1

    I’ve wanted to make some liquid conductive material for some time. Cannot find exact places online to purchase conductive pens from, will try this when I have time to go down to the hardware store. Thank you Steve. 🙂

  2. Lukas
    April 19th, 2012 at 14:06
    Reply | Quote | #2

    hey dude,
    i find it quite awesome that you did these instructions as it’s sumthin i really seeked after startin with arduino and e-clothes; it’s a missing part in my collection.
    But could you add sum info about how much of the graphite powder you used? I mean what i’d need is a relation between graphite and iron filings.

    Greetz from Germany,

  3. Jeff
    October 14th, 2012 at 18:09
    Reply | Quote | #3

    Hi, I was also wondering about the ratios of graphite, iron filing, and epoxy. Can you give me a rough place to start?

  4. smackaay
    October 26th, 2012 at 23:31
    Reply | Quote | #4

    Well, to be honest, I just did it by mixing until it felt right. Use a fixed amount of epoxy and add graphite or filings until the consistency was still malleable but had enough conductivity. Too thick and you won’t be able to apply it, too thin and it may not conduct very well.

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