WIrebonds - lets learn about them together.

[retroleds]

Let's talk about wire bonds...I want to learn more myself. This seemed like a really good starting article.

http://nepp.nasa.gov/wirebond/Basic%20Info.htm

[f.e.a.r]

i was under the impression that the wire bond was made out of lead? i think this was also mentioned in a deleted thread. but now i come to think of it, is it lead as it has low conductivity?. your linked article lists gold, silver, aluminium and copper as materials used.

http://en.wikipedia.org/wiki/Wire_bonding

seems i was wrong, aluminium seems more likely.

[retroleds]

The wire bonds themselves weren't made of lead, but for someone fashioning one by hand, lead is not a terrible choice. If you start with the .015 fine solder(solid core, obviously) and pull a piece gently between two hands you can stretch it to about 1/2 that diameter before it snaps - and it will be much stiffer too. Easier to work with than copper(IMO), as it's easy bendability makes it a good candidate for first attaching one end and then coming back later(after first bond is hardened) to bend the second end into position. Copper has more "spring back" to it, which can make it frustrating to get to the close contact you need before starting to think about gluing down with the silver epoxy. All becomes a bit crazy at that scale.

[abem]

Looks like you need something like this nifty semi-luggable Hughes TSB-460 Wire Bonder:
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... _500wt_810

Mmm, even comes with a Leica GZ6...

-abe.

[retroleds]

Looks like you need something like this nifty semi-luggable Hughes TSB-460 Wire Bonder:
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... _500wt_810

Mmm, even comes with a Leica GZ6...

-abe.

Tempting, tempting..

[f.e.a.r]

after many hours of practice (and casualties) i now consider myself capable of wire bonding. all done on a budget set up, i bought a secondhand stereo microscope from ebay for 45gbp, with x20/x40 magnification it works a treat. bought some silver epoxy and i was ready to tackle the job. my success rate and techniques are improving but there are no guarantees when working in that minuscule environment. at times, very frustrating but when you do get that dormant segment back to life...

[retroleds]

after many hours of practice (and casualties) i now consider myself capable of wire bonding. all done on a budget set up, i bought a secondhand stereo microscope from ebay for 45gbp, with x20/x40 magnification it works a treat. bought some silver epoxy and i was ready to tackle the job. my success rate and techniques are improving but there are no guarantees when working in that minuscule environment. at times, very frustrating but when you do get that dormant segment back to life...

Excellent. You'd probably agree that it is a lot easier fixing a bond that is still there, then replacing a bond that is gone or beyond repair. That's where the wire bonding machine would be nice. The price gets balanced against the grim reality that frequently the mashed wire-bonds weren't the original sin. The module had failed internally(in some percentage of these), which is why someone pulled it out and tinkered with it. Have to break a few eggs....

Yeah, it is cool to have that little light come on. I get a bit giddy when I slip a module under the scope and see a perfect bond that is only loose by a hair, giving it sporadic function - success is so close at hand. Unless your hand slips.

[f.e.a.r]

Excellent. You'd probably agree that it is a lot easier fixing a bond that is still there, then replacing a bond that is gone or beyond repair. That's where the wire bonding machine would be nice. The price gets balanced against the grim reality that frequently the mashed wire-bonds weren't the original sin. The module had failed internally(in some percentage of these), which is why someone pulled it out and tinkered with it. Have to break a few eggs....

Yeah, it is cool to have that little light come on. I get a bit giddy when I slip a module under the scope and see a perfect bond that is only loose by a hair, giving it sporadic function - success is so close at hand. Unless your hand slips.

haha yeah, there are different levels of bonding... as you say, the hardest one is totally replacing the wire and having to bond both ends. i take the wire from a broken module and transfer it to the repairable one, the journey from A to B is stressful. once you get it there, thats when the fun starts, manipulating it into position and bonding both ends .

so true ed, such joy at the simple "touch down", or even better, the "touch down" that lights several segments at once, a loose wire from the brain chip