Page 9 - Wire Bonding in Microelectronics

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4B.5 The Current Status of the NDPT (2008)
for Critical Space Applications . . . . . 125
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
5 Gold-Aluminum Intermetallic Compounds and
Other Metallic Interface Reactions in Wire
Bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
5.1 Gold-Aluminum Intermetallic Compound
Formation and Classical Wire-Bond
Failures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
5.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . 131
5.1.2 Intermetallic Compound Formation in
the Au-Al System . . . . . . . . . . . . . . . . 132
5.1.3 The Classical Au-Al Compound
Failure Modes . . . . . . . . . . . . . . . . . . . 139
5.1.4 Reversing the Au-Al Metallurgical
Interfaces . . . . . . . . . . . . . . . . . . . . . . . 144
5.1.5 The Effect of Diffusion Inhibitors and
Barriers . . . . . . . . . . . . . . . . . . . . . . . . . 146
5.2 Impurity-Accelerated Au-Al
Bond Failures . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
5.2.1 The Effect of Halogens on the Au-Al
Bond System . . . . . . . . . . . . . . . . . . . . 148
5.2.2 Recommendations for Removing or
Avoiding Halogen Contamination . . . 151
5.2.3 Nonhalogen Epoxy Outgassing
Induced Bond Failures . . . . . . . . . . . . 153
5.2.4 Green Mold Compound Problems . . . 153
5.3 Nongold-Aluminum Bond Interfaces . . . . . . . 154
5.3.1 Aluminum-Copper Wire-Bond
System . . . . . . . . . . . . . . . . . . . . . . . . . . 154
5.3.2 Aluminum Bond Pads Containing Copper,
Causing Bonding
Problems . . . . . . . . . . . . . . . . . . . . . . . . 156
5.3.3 Copper-Gold Wire Bond
System . . . . . . . . . . . . . . . . . . . . . . . . . . 157
5.3.4 Palladium-Au and -Al Bonding
System (Used Primarily for
Lead Frames) . . . . . . . . . . . . . . . . . . . . 158
Ball Bonding with Pd Wire . . . . . . . . . . . . . . 160
5.3.5 The Silver-Aluminum Wire
Bond System . . . . . . . . . . . . . . . . . . . . 160
5.3.6 Aluminum-Nickel Wire Bond
System . . . . . . . . . . . . . . . . . . . . . . . . . . 163