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October 2004

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Subject:
From:
"Ingemar Hernefjord (KC/EMW)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ingemar Hernefjord (KC/EMW)
Date:
Mon, 4 Oct 2004 09:20:56 +0200
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Steve & netters,

so TN is also forum for debating and analysing historical events..interesting. I have 25 heavy books from TIME about all time's such episodes, and it seems to be in man's nature to twist and turn retrospectivly to see if one can't find something that noone observed before. The simple truth didn't satify... So...nothing new at all. While others bring remarkable stories, I may perhaps say something trivial about wirebonding.

The problem we had was apparently connected to the argon plasma cleaning. The high energetic argon ions bombarded sites far from the gold thickfilm conductors that were to be the target for cleaning, thus releasing a lot of atoms and ions of all kinds (probably organic compounds)from soldered connectors and glued components. So, there was a re-deposition of contaminations on the very gold we wanted to be cleaned! We covered the suspected sources with aluminium foil, and found a considerable improvement of bondability. We also skipped the whole plasma cleaning in some cases, and found better results even there. So, dear Steve, plasma cleaning has to be handled, not as a microwave oven for heating coffee, nor as a magic all-stuff-wonderbox, but as a machine that demands a skilled and experienced operator.

Thanks for giving the right impetus.

Ingemar Hernefjord
Ericsson Microwave Systems

PS. Brian Ellis, a sly fox, think it was him....gave me these words, applicable in the case of the 911 newsmaker:  Te audire no possum. Musa sapientum fixa est in aure. Ha-ha...the ancient romans had a good sence of humour..





-----Original Message-----
From: Ingemar Hernefjord (KC/EMW)
Sent: den 23 september 2004 11:59
To: 'TechNet E-Mail Forum'; 'Creswick, Steven'
Subject: RE: [TN] Strange wirebonding problem



Hi all,
thanks for offline advice, have now many red threads, will tell all in the end what caused bond problem. Targets e.g.
* LPD (Light Point Defects)
* Plasma Cleaner re-deposition contaminations
* capillary tip epoxy residues
* thickfilm delaminations
* micro hardness variations
* cleaning agent residues
* pad metallisation process salts imbedded
* too thin pad metallisation
* distance to Kovar frame or cavities can affect mechanical wave response

mental strengtheners e.g.
* hangglider tour frees mind, better thinking (XX )

At the moment, we go for Plasma Cleaner something...logic choice.

Thanks again

Ingemar






Good Morning or Afternoon,

saw movie about the Amtrak incident on Mobile bridge. Terrible. So many unusual failures were involved to cause that accident. The detective work to reconstruct was impressive, they found the sources. Now, need detective work on micro problem, which can also make grey hair. Ordinary aluminium pads, Silicon chip, Autobonded, 25um Au wire, ball, chips silver epoxied, workpiece +150 Centigrades.
One side of chip have normal bonds, other side get oftenly bad bondings with following symptoms: aluminium metallisation bubbles and ball doesn't fasten, the bond pad get what looks like chipouts, but without classic look. Have checked everything: autobonder program, ceramic capillary, chip epoxy bond line, looked after bond pad contaminations, MCM fixture, ball formation, wire quality and a lot more...without finding the reason.  Aluminium looks like it has been boiling, but how on earth could it, the machine just adds U/S power.

Maybe Phil, jk  or other microguru can whet the neurons and propose some idea? Will post two photos to Steve's headache gallery, one with normal chip before bonding, the other after bonding.

In advance thanks giving I am (Yoda)

Ingemar Hernefjord
Ericsson Microwave Systems

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