Runny but fast-cure conductive epoxy?

Lots of good suggestions, but... nickel spray can maybe?

When I was into R/C flying, my mentor diluted epoxy with alcohol to paint the motor area to protect it from fuel. It worked beautifully.

My EMC "cure-all" spray can dried up but it wouldn't work anyhow, too much and too heavy. What so far works is this:

Seems graphite loaded and the joint looks ugly. But hey ... single-digit ohms.

The more expensive kind disappointed:

Sometimes a trace didn't make any connection, other times after laying it on real thick a connection had hundreds of ohms which is not useful in my case.

The silver (or whetever) particles in those things will look like basketballs next to 1 mil gold wire. Longterm, you may need a better way to bond things.

Oh, I know. This is only temporary and, also, this "Bare Paint" stuff does not have much holding strength to write home about. You can easily pull it apart. It's a kludge and only needed for a feasibility test. If I can make a device work for 15 minutes it'll be ok.

Does anyone know a bond house that can bond 0.001" gold wires to aluminum pads on already singulated ICs? The challenge is that these ICs are only 0.010" by 0.060" or so and sit on a tacky surface. So they aren't totally and rigidly anchored during bonding.

Mike Loskutoff

does a lot of interesting things, like custom hybrids, electro-optical hybrids, substrates, cool stuff. Lots of wire bonding.

Say hi for me.

Acetone seems to mix best. You can dump powder on top of epoxy, wet the powder with acetone, mix it, then put it in a vacuum chamber to boil off the acetone and remove air. Don't leave the acetone in epoxy because it turns it into a weak gel that slowly shrinks.

Does it have to be only one application? Strength from non-coductive epoxy. Then get conductivity from something not so strong?

Yup been there. So I don't know an epoxy, but I've soldered copper to thin gold.. I tin the piece of copper and then keep the soldering iron on the c opper, maybe 1/4- 1/2 inch from the end where I'll attach the gold. Bring gold into contact with the end and you're done. Or wrap the gold around th e tinned end and then put the soldering iron on the copper piece and slowly bring it towards the gold till you see it bond. How many do you have to d o?

George H.

Today about 10 wires, after the Fedex truck gets here. Problem is, ideally I should not lose any. So I am still debating whether to try soldering at 530F or use the Bareconductive pen.

Downside with the pen is that it needs some curing time and I'll have a bunch of folks watching via Internet, anxious to see measurement results.

chip quick wets metal, is solder, and melts way below 530F. You will need to add a variac or dimmer circuit to your trusty weller

in gold.. I tin the piece of copper and then keep the soldering iron on the copper, maybe 1/4- 1/2 inch from the end where I'll attach the gold. Brin g gold into contact with the end and you're done. Or wrap the gold around the tinned end and then put the soldering iron on the copper piece and slow ly bring it towards the gold till you see it bond. How many do you have to do?

Au has a pretty high melting point; it must be that it's dissolving into the solder. Same problem as soldering ultra-fine Cu wire.

Solder pre-saturated with gold would fix that .

Or maybe tin-plate the Au wires, then gentle, indirect heat? Or wrap in Au leaf, then heat?

Just a few wild ideas, for next time...

Cheers, James Arthur

thin gold.. I tin the piece of copper and then keep the soldering iron on t he copper, maybe 1/4- 1/2 inch from the end where I'll attach the gold. Br ing gold into contact with the end and you're done. Or wrap the gold aroun d the tinned end and then put the soldering iron on the copper piece and sl owly bring it towards the gold till you see it bond. How many do you have to do?

Oh, and conductive glue, of course. This explains how to make it with Liguid Tape(tm) and powdered graphite:

The guy has a web page somewhere that documents how he arrived at that recipe.

Cheers, James Arthur

Well, I just did it with "Bare Paint" from Radio Shack. It's messy, don't ever let that get onto any clothing or onto the carpet. With some training you can make a connection look like a genuine Chinese micro processor tar blob. And it works.

It would, but it would also be expensive. The Sn end of the system forms a eutectic at 217C, and the melting point (liquidus, to be precise) is back up at 260C at 78% Sn, 22% Au.

The most common Au-Sn alloy is Sn20Au80, with a 280C melting point. It's a eutectic between intermetallics, so it's rather brittle. Most often used for soldering ceramic ICs shut. Needless to say it's even more expensive...

Tim

Money is no object (Joerg is a famous big-spender).

Cheers, James Arthur

Hmm chip quik, 150C (300F) I wonder what is the alloy/ metal?

George H.

thin gold.. I tin the piece of copper and then keep the soldering iron on t he copper, maybe 1/4- 1/2 inch from the end where I'll attach the gold. Br ing gold into contact with the end and you're done. Or wrap the gold aroun d the tinned end and then put the soldering iron on the copper piece and sl owly bring it towards the gold till you see it bond. How many do you have to do?

Thanks, that makes sense. It was years ago for me, but I do sorta remember the gold just disappearing into the solder blob on the tip of the iron.

George H.

is

ms

Probably something with bismuth in it. Wood's metal (50Bi 26.7Pb 13.3Sn

Cheers

Phil