On Mon, Mar 29, 2010 at 04:24:26AM -0400, Roger wrote:
> Steve Thompson wrote:
> > There's also something known as 'purple plague' - not migration,
> > but reaction between gold and aluminium that showed up when gold
> > metallised die were bonded with aluminium wires.
> That I'm not familiar with. I would not expect Gold and Aluminum to
> readily bond with out creating some kind of interface.
NASA is, for some unfathomable reason, interested in wire bonding and
wire bonding failure modes, and has some very interesting things up on
the web:
http://nepp.nasa.gov/wirebond/intermetallic_creation_and_growt.htm
and
http://nepp.nasa.gov/wirebond/Literature.htm
and
http://nepp.nasa.gov/wirebond/
and in particular this reference:
Chen, G.K.C., On the Physics of Purple-Plague Formation, and the
Observation of Purple Plague in Ultrasonically-Joined Gold-Aluminum
Bonds, IEEE Trans. on PMP, Vol. 3, 1967, pp. 149-155.
It appears that In-Au bonds have problems with intermetallic compounds,
too.
--
Mike Andrews, W5EGO
mikea@mikea.ath.cx
Tired old sysadmin
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