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Runny but fast-cure conductive epoxy?

Folks,

Need to contact thin litz wire strands to 0.001" gold bond wires. Yes, no kidding, 1mil. Soldering is iffy because the gold wires vaporize above 500F ... poof ... gone.

Can anyone recommend a conductive epoxy that cures in much less than 1h at room temperature, is runny enough to wet a wire end for dabbing it onto the bond wire, and has reasonable life time once the pot or tube is closed again?

I can't heat-cure the stuff because the devices to be contacted are on an adhesive backing so our usual Prima-Bond EG8020 won't work here. Resistivity isn't critical, if the glue joint ends up having a few ohms that's fine.

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg
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52 years ago, a guy in the machine shop at MIT's Research Lab for Electronics WELDED such small wires to thermistors that went into my blood-flow-rate apparatus. ...Jim Thompson 
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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
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I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Too bad someone doesn't make a UV curable conductive epoxy.

tm

Reply to
Tom Miller

Yeah. Someone has a patent though but that's all I know about it:

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But UV-curable dielectric are available:

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--
Regards, Joerg 

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

That's how bonding is sometimes done. But I neither have the equipment nor the time for lengthy science experiments. I don't mind the soldering but the bond strength on these experimental devices is so weak that merely touching the gold wires with a Weller tip can (and have) make the bond fail. It's like trying to attach a postage stamp with the bucket of a Caterpillar.

--
Regards, Joerg 

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

Why not use a gold-plated FFC jumper and wire-bond directly to that? Thermal conductance and flexibility will be reasonably similar.

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 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

FFC cable is much too stiff and mechanically heavy. I have strands of really thin litz wire that work nicely. I'd just like to bond them without using heat.

Maybe some solder with a really low melting point would work although the Weller won't go below 350F which is still similar to a hot barbecue.

--
Regards, Joerg 

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

Well, the idea may be toast anyhow because I need it tomorrow morning and it seems there's air shipping restrictions placed on such stuff now:

formatting link 

--
Regards, Joerg 

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

We've used these

MFR1 LOCTITE 3880 10.6G SYRINGE RS HUGHES MFR2 TRA CON TRA-DUCT 2902 2G 2-PART PACKETS MFR3 HYSOL KS4008 5.6 OZ. WOLCOTT PARK

and you might try the Trace Technologies 2505-N conductive pen, intended to repair PCB traces.

--

John Larkin         Highland Technology, Inc 

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin

You might give MasterBond a call.

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They have an applications engineer available by phone.

Reply to
Tom Miller

Just for the hell of it, could you ask for something _normal_ from time to time?

:)

--

Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com
Reply to
Tim Wescott

I can ship you the Trace conductive pen, for tomorrow AM delivery.

It will cost you, in a liquid currency.

--

John Larkin         Highland Technology, Inc 

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin

You can buy bismuth solder paste with a melting point down around 140 C. You should be able to melt all your junctions at once by passing a heat gun over them for a second.

Reply to
Kevin McMurtrie

Ultrasonic bonder, followed by a hydrogen torch to 'cut' the Au wire and make a small ball for the next bond

Reply to
RobertMacy

Ugh! Most conductive epoxies are NOT terribly conductive. If you want to drain off static charges, it works, but for conducting any real current, it usually doesn't work well. Part of it may be not breaking through oxides on the wires. I have gotten some silver paint that sort of worked better. The stuff we've used most recently was MG Chemicals Silver Conductive Epoxy, but as I say, good for draining static charges only. I doubt you'll get anywhere near a few Ohms with any conductive epoxy.

Jon

Reply to
Jon Elson

The serious silver-filled stuff is pretty good, numbers like 0.001 ohm-cm.

--

John Larkin         Highland Technology, Inc 

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin

It's nearly standard to bond gold wire to a PCB pad (like a lot of chip-on-board items); can you use an intermediary circuit board?

Reply to
whit3rd

That would be no problem :-)

But what is conductive pen? Can that hold a couple of very thin wires together at a point where they cross, like solder?

--
Regards, Joerg 

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

Ah, this is what a Trace pen is:

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I think those won't hold wires together that are in the air though. Also it should not be shipped for next day air because it's not legal to be carried on aircraft for safety reasons.

Is any of the other three real runny and somewhat fast curing? I only need it to hold the wires together in the air, no additional component weight snce that is going to be on a mechanically supported carrier.

--
Regards, Joerg 

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

Yeah: Can I have fries with that? :-)

Just came back from our local Mexican place, had a nice burger with Jalapenos, home made fries and the whole nine yards. And a Negra Modelo from tap.

--
Regards, Joerg 

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

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