-----Original Message-----
From: Ingemar Hernefjord (EMW)
Sent: den 7 juni 2000 10:10
To: 'Creswick'; TechNet E-Mail Forum.
Subject: RE: [TN] wirebonding EFO


Thanx MCM bro Steve,
we use Delvotec and K&S 25micron Au balls on GaAs MMICs. We had some ideas about cratering, bad silverepoxy joint under chip or EFO induction. My hypotalamus says cratering is most likely to cause hidden troubles, because GaAs 80um chips are fragile, others suspect the glue joint for not cooling enough, and finally there are some guys that believe more in the EFO hazardous model. Now, Watt do you feel for U/S ball bonding in principle yourself? Some chipmakers recommend thermosonic or wedgebonding and don't mention U/S, must be something behind that. The later method has more than one disadvantage, I think of placing 1st bond on top of chip and then 2nd down on conductor. Should be vice versa.  Guess you buy MMICs from same suppliers as we do, not many in that club. Never got a warning from them concerning U/S ball bonding?

I'll keep you informed

Ingemar Hernefjord
Ericsson Microwave Systems

-----Original Message-----
From: Creswick [mailto:[log in to unmask]]
Sent: den 2 juni 2000 06:02
To: TechNet E-Mail Forum.; Ingemar Hernefjord (EMW)
Subject: Re: [TN] wirebonding EFO


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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