Segment wire bond

[egomon]

It seems that my texst is gone missing :)

So what is betetr to use to make the segment wire bond?

i found this two:

"bison electro" and "Silver Epoxy Kit-14 grams-CONDUCTIVE "

[/url]http://cgi.ebay.com/Silver-Epoxy-Kit-14-grams-CONDUCTIVE-when-cured_W0QQitemZ280211336497QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item413de5ad31[url]

[/url]http://www.bison.net/US/en/index.do[url]


Or is there eny other one that will work better then this ones.

Thank you

[bruce wegmann]

The material I use is made by MG Chemicals, out of Canada. The silver grains are as small as possible, being produced by chemical reduction/precipitation. You can order from their website at www.mgchemicals.com, or call them directly at 1-800-201-8822. It comes in a standard two-syringe, 14 gram package. I have had uniformly excellent results with this product.

[egomon]

Thank you. Will give it a try.

[Chris S.]

Hi Bruce. I've been looking for something like this for a while and have previously used CircuitWorks Conductive Epoxy with mixed results (but that may be me) so i was looking for something better. I've managed to find a supplier of the MG product in the UK but when I had a look at the relative data sheets the 'Volume Resistivity' surprised me as the CircuitWorks value was <0.0001 ohm/cm whereas the MG value was 0.38 ohm/cm which seems a big difference to me. Have you used the Circuitworks product and is it the flake size that is the most important factor. Your knowledge on this would be appreciated.

[bruce wegmann]

Never used the Circuitworks material, so can't make a direct comparison. I've talked to a couple friends who know more about the subtleties of this than I do, and they tell me two things. First, silver grain size is very important; the smaller, the better [this is especially true when applying it to very small surface areas, such as wire bonds,,,which is exactly what we're trying to do]. Some manufacturers make silver powder by abrasion [where a silver bar is essentially belt-sanded to dust]. They filter out the abrasive residue, and the larger silver particles, and go from there. The better method is chemical precipitation, where a silver compound is chemically decomposed, releasing the silver as ultrafine particles [micron-sized] in solution. The grain size is as small as you can get, and very uniform. The end result is you get a more uniform distribution of silver in the bond, and the highest probability that they will be in contact, forming a conductive path. Second, smaller particles do allow a greater percentage, by volume, of silver in the mix, without compromising bond strength. As for bulk resistance, that's the resistance you'd add by sending your signal through a centimeter-thickness of the material. Since the typical bond thickness is on the order of .004 inches [.01 cm], the actual increase in resistance is about a hundredth of the bulk value, or .0038 ohm, not much above a typical solder joint. So, that's the story, and I'm sticking to it .

[Chris S.]

Thanks for that. It makes sense as I have made what I thought were perfect bonds to the remains of broken wirebonds and have had no connection when its cured. Others have been fine so it may well be due to the luck of the draw with regard to where the particles are in the mix. I'll give the MG product a go and report back with a comparison (may be a while).

[azimuth_pl]

doubled post:
http://www.dwf.nu/viewtopic.php?t=3849

[Chris S.]

Hi......I managed to get some of the MG conductive epoxy and as promised here's my opinion :

Compared to the Circuitworks product, it is far superior in terms of success rate. There are still time when the contact fails to make after curing but this can be usually rectified with a little pressure. I'm very pleased with it and would recommend it, it's not perfect but best I've used so far. Thanks Bruce for the info!

[james_stan]

Chris

Are you able to post a photoof your success ? I'm sure interested
for one.

James

[Chris S.]

Hi James......I'll see what I can do (it may be a while) at the risk of embarrassing myself to the experts.

[james_stan]

Don't fret - I can't solder a crystal without burning chunks out of everything in sight
then it never works anyhow.

Why I think I can do it heaven only knows !

Cheers

james

[bruce wegmann]

You need a B&L StereoZoom and a Hakko soldering iron...the right tools for the job make it a lot easier... Works for me...