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Conductive silver tracing and epoxy — Parallax Forums

Conductive silver tracing and epoxy

kelvin jameskelvin james Posts: 531
edited 2006-11-01 07:14 in General Discussion
I haven't seen anyone post about this yet, so after a simple test to make a small circuit, it does work. Adheres well to fr4 and negligable resistance through traces. Components can be epoxied right to the board or through holes. Must have patience to work with it. Heat curing will produce a working circuit in less than a half hour. It is normally used to repair circuits, but thought it would be worth playing around with.

kelvin

Comments

  • TiboTibo Posts: 81
    edited 2006-10-08 14:11
    neat. Can you show us a picture ? How big is the circuit ? Do you think this can be used for small components ?
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  • BeanBean Posts: 8,129
    edited 2006-10-08 15:18
    Where did you get it ? What is the part number ?
    I would like to use it to connect vias on double sided board. Have you tried that ?

    Bean.

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  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2006-10-08 19:18
    If this is what I'm thinking of, the Company is called "Circuit Works" and they make a conductive epoxy pen also as well as a two part solution.

    Here is some one who carries the pen (quick Google search)
    http://www.wassco.com/chemcirworpe.html

    Keep in mind, that once the epoxy dries, it becomes very brittle, ...and don't expect to push a lot of current through
    your "wires" either.

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  • Washer MedicWasher Medic Posts: 39
    edited 2006-10-09 02:18
    Radio Shack carries’s the pens we use them to repair damaged traces
    Catalog #: 64-4339

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  • kelvin jameskelvin james Posts: 531
    edited 2006-10-09 05:54
    I wouldn't go rushing out to buy this stuff, it isn't cheap. I just wanted to see if it was possible to make a circuit with it. My original test was with a proto board with the copper pads. I made small jumpers between the pads to create the circuit, just the old standard resistor / led thing because i wanted to generate some current on it. Since the jumpers are only about 1/16 in. long, there is next to no resistance. Upon futher testing, a trace approx. 1/16 in. wide by an inch long will show about 2 ohms. So, to construct a circuit using only the silver trace would be problem, but looks okay to jumper pads with. As far as the epoxy not holding up, i haven't done any destuctive testing yet, but i will to see what happens. Obviously, it isn't going to be as strong as solder. This whole thing will probably wind up being an exercise in futility, but it is always interesting to experiment. It is made by Circuitworks, as Beau pointed out. I included a picture i took after the first attempt, a little messy, takes practice, but shows the idea. Now that i gone this far, i am going to try a fairly complicated circuit to see what happens.

    Bean, i made a via with the pen and it looks okay. The trace solution seems to bond well to the fr4. But, at this point, i couldn't guarantee it is the type of thing you would want to use.

    kelvin
    test.jpg
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  • GadgetmanGadgetman Posts: 2,436
    edited 2006-10-09 08:22
    Just one point everyone should be aware of...

    We all know that the pen is expensive because it contains a lot of silver. But you should also be aware of the 'Use by' date on it. I think it's about 6months or so. And it may be a lot shorter if the shop doesn't sell too many of them...

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  • kelvin jameskelvin james Posts: 531
    edited 2006-10-10 06:52
    Well, i don't have an expiry date on mine, so i guess i won't know if it is good or not. I threw together an i2c circuit tonite, 64k eeprom and some smt resistors. Had to route the clock line to the back side and back up to bypass sda to a common vdd. Did not turn out as " pretty " as i wanted, but hooked it up and ran no problem. All ground lines from eeprom pins were done on back of board, and then back up to vss line.

    kelvin
  • GadgetmanGadgetman Posts: 2,436
    edited 2006-10-10 21:54
    Well, mine WAS a 'Circuitworks Flex Conductive Pen' by Chemtronics.

    I think the expiration date was on the packaging, though...
    (Who remembers to keep that?)

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  • MaryMc2009MaryMc2009 Posts: 6
    edited 2006-10-13 01:52
    It will dry out fast, even with the cap on so don't plan on keeping this around in a tool box for that once a year use. For the expense, it's great when doing your own etching, and forget a trace or get some erosion on the pads. Vias it works as a quick fix as long as the number is kept down (I drill the hole a size larger and add a small copper wire in the hole with the component)
  • UVNETUVNET Posts: 2
    edited 2006-10-13 20:36
    I had a few circuitworks pens, and they dried out, some even before I opened it.

    I found a bottle of stuff called Wire Glue and I will try that out.

    Small viles of conductive copper paint maybe sold at DIY auto parts shops for fixing rear mirror defrost conductor traces.

    All similar products I've tried tend to go bad fast.

    If fine copper wool and filings could be tinned and mixed with a flux glue that sets with a soldering iron I think that might work nice.
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  • John BondJohn Bond Posts: 369
    edited 2006-10-16 13:06
    Hi Guys

    There are a couple of other options, high solids paints (I've worked with 98% "zink rich"), some tins and tin based compounds and the silver based products you discuss above. Here is a company thet make paints that can be used to screen print a PCB

    http://spraylat.com/gentextlong.asp?miKey=189

    Interesting hey

    By the way (as an after thought hence the edit). Some of there compounds can be a bit toxic.

    John Bond
  • kelvin jameskelvin james Posts: 531
    edited 2006-10-28 06:56
    It can be done. This is a 5 piece smt led and resistor circuit using the silver stuff on a perf board. It measures around 1/2 by 3/4 of an inch, minus the headers. I used a hot mix of the epoxy on the headers, they are there to stay, the board will break before the headers come off. The smt leds' are nasty little critters to work with, a tiny bit of epoxy and a heat cure makes them pretty solid.

    kelvin
    led1.jpg
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    led2.jpg
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  • Sparks-R-FunSparks-R-Fun Posts: 388
    edited 2006-10-31 20:08
    Anyone know if this (or something else) can be used to make connections to aluminum?
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2006-10-31 21:43
    Sparks-R-Fun,

    How many connections?· For small applications, the Conductive silver Epoxy would work just fine.

    You can use Silver-solder to solder to aluminum, but it takes more heat than a regular soldering iron (<- Butane torch) and there is
    a trick involved... to get a good solder flow, both materials should be right at or just below the point of glowing red.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • T ChapT Chap Posts: 4,223
    edited 2006-10-31 21:55
    If this hasn't already been mentioned, LPKF has a silver paste that you can buy in small packet of silver paste. It is expensive but nice in a jam to get something done in a day. You will have to build or buy a small vacuum box to pull the paste from one side of the via to the other. I used to flip the board several times pulling the paste each direction to get a good coating of the via/holes. The paste is solderable if you are very careful and at low temp/low time. In a thousand vias I'd experience 1% malfunction, usually associated with soldering over a plated hole.

    http://www.lpkf.com/products/rapid-pcb-prototyping/through-hole-plating/proconduct/index.htm
  • kelvin jameskelvin james Posts: 531
    edited 2006-11-01 07:14
    One note with the epoxy is, you have to treat it like any other bonding compound, the surface must be prepared properly. Epoxies or cements like a porous surface to adhere to. Even with the perfboard, i used some acetone and emery cloth to kind of rough up the surface a bit. The heat cure is important for bonding and conductivity, i just used a suspended blow dryer on high heat, about a half inch away from the material. I have an ir thermometer to read the temp. Just don't over-cook it.

    kelvin
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