Ingemar,

You raise an interesting point.  Although I can not say we have duplicated
your findings, it would be logical to expect the 'already made' wire bonds
to act as miniature antennae.

The good/bad news is that usually all the package leads are shorted together
by tie bars, etc. at this point in the process, and the package and leads
are firmly mechanically clamped into a thermally (and capacitively) massive
heat stage - which is at ground potential.

I might caution that possibly your scope probe either by physical location
or size does not realistically represent a wire bond - one way or another.

Many times we will bond the Vss & Vdd pads first.  One could probably take
both sides of the argument as to whether that really makes a difference in
all cases.

Keeping the EFO away from the work is ultimately limited by machine mechanics.

Just think of all the ga-zillion IC's bonded in this manner in the last
15-20  years.

Maybe we should go back to the ol' hydrogen gas flame-off. Can you imagine
the bonding rate reduction that would make - and all the liability and
safety issues that it would raise nowadays??

Keep us posted.

Steve Creswick - CTS




At 12:50 PM 5/31/00 +0200, you wrote:
>Anyone in the club who have heard if the flameoff can induce voltage in the
material that you bond on?. E.g. we have checked with an osc probe and found
peaks up to 50V when the flame goes off. Some semi chips without I/O guards
seem to get dizzy. Anyone with experience?
>Ingemar Hernefjord
>Ericsson Microwave Systems
>
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