Dice on the cheap

This IS done regularly in "throw-away" consumer products. I'm not sure what kind of wire-bonding is used... my best guess would be ultrasonic.

...Jim Thompson

Unless you're talking about power chips, e.g., power transistors, MOSFETs, rectifiers, wirebonding best done using gold wire and thermosonic ball/wedge methods. On circuit board end, best done using 'soft gold' plating, also called 'five 9s' gold, since thermosonic bonding produces best results with pure gold. In a pinch, you can also bond to recently cleaned copper and less pure gold, but reliability will be much, much lower.

Please reply with what equipment you're intending to use.

Paul Mathews

Joel Kolstad wrote:

Hi Paul,

I'm mainly concerned with RF devices... diodes, FETs, mixers, switches, etc. -- many 'desirable' ones now only come in dice.

Thanks, I'll keep that in mind. I don't have any equipment yet, but the idea was to find a used manual wire bonder in the ballpark of the "low thousands of dollars" to use.

---Joel

Look around for an old K&S thermosonic bonder and a small supply of 1 mil Au bond wire. You will need functioning electronics, preheating stage, and a stereo microscope. Some of the used ones are missing parts of the above. pm

Thanks, will do!

I haven't done it now for ~25 years, but in 1980 I can recall rummaging around a San Jose "used" equipment warehouse and bought 3 K&S bonders so I could get ONE workable bonder on-the-cheap ;-)

Also bought a probe station the same way.

...Jim Thompson

Hmm... not a bad idea!

I would have to guess that bonder ended up in a company somewhere rather than your garage?

Omnicomp/GenRad Portable Tester Division

...Jim Thompson

I don't remember now, other than the wafer platform moved and the probe card and tips were stationary.

...Jim Thompson

Do you remember which probe station? Not the old manual Cascade Microtech Model 42 one?

Robert

That's standard on all the ones I know of. The old manual Model 42 had a vertical cylinder grease chuck on top of which the wafer sat under a vacuum pull. You grabbed the vertical cylinder with two hands and moved what you wanted to probe under the center line of the stereozoom microscope. It had a lever that would lift the top plate of the station (with the magnetically clamped DC needle and CPW probes) up a certain amount measured in mils. Then you'd grab the cylinder and try and slide it on the grease while looking through the microscope to where you wanted to probe. Then lower the plate and gently adjust your probes vertically for contact plus 2-4 mils of overtravel.

At that point you could hit the lever, the probes would all come up, you grab the chuck and move it to the next die, and when you moved the lever to come back down you'd have the same amount of overtravel at the new location. Repeat for next die, etc.

I sure was happy when they finally got electric driven screws that moved the chuck. Then it could be computer controlled as well.

Still some of the old manual ones made.

Such as these guys:

Robert

The one I bought had micrometer-style adjustments and the stage was electrically raised and lowered. It also stepped X-Y for automatic testing.

...Jim Thompson