Hi John - I can add a second negative vote to gold ball/wedge bonding to
Sn/Pb in addition to Steve's comments. A reliable bond can not be
established due to intermetallic formation issues, oxidation issues, and
material compatibility problems. As a general rule, gold wirebonding is not
conducted on Sn/Pb finishes.

Dave Hillman
Rockwell Collins
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Creswick <[log in to unmask]> on 06/24/99 08:09:42 AM

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Subject:  [TN] BALL BONDING




John,

From a metallurgical standpoint this is not a good idea.

However, the lower temperature your product operates at, the longer the
gold/tin/lead intermetallics will survive, but it is still a matter of time
before you see changes in interfacial resistance, strength, etc.  The wedge
(2nd) bond will typically fail before the ball (1st), due to the
differences
in cross-sectional gold thickness (volume) present in the bond.

Glob-top, and cure of the glob top, will also add additional stresses to
the
system.

Ultrasonic aluminum wedge bonding to the bare copper, or to nickel plating
is a far more reliable metallurgy - albeit slower bonding.  If given a
choice, I would flip chip it.

Steve