日本金属学会誌

J. Japan Inst. Metals, Vol. 41, No. 11 (1977),
pp. 1161-1165

High-speed Thermocompression Bonding of Au Wires to Al Electrodes on Semiconductor Devices

Seiichi Iwata1, Akitoshi Ishizaka1 and Hiroshi Yamamoto1

1Central Research Laboratory, Hitachi Ltd., Kokubunji

Abstract:

In the realization of high-speed and highly reliable thermo-compression bonding of Au wire to Al electrodes, the two most important factors were found to be the deformation of Au wire, which breaks the oxide film on Al, and the surface cleanliness of Al. Furthermore, it was found that the bond time (the time during which a load is applied to the bond) could be shortened to about 20 ms (formerly about 200 ms).
The amount of deformation or strain of Au wire was measured, and compared with the bond breaking force. The latter quantity was newly introduced in this study to facilitate the evaluation of bond integrity, and was found to be directly related to the bond failure rate. The bond breaking force was found to increase with the strain, provided the surface cleanliness and the bond time were constant. At the same strain and the bond time, the Al oxide film thickness and the amount of surface contamination were the factors influencing the bond breaking force.
The bond time was found to be determined by the sum of the time required for the plastic deformation of Au and Al and that for the reaction of Au and Al, the former being much greater than the latter. In this study, by increasing the strain rate of Au by applying higher load, the bond time as short as 20 ms was realized.


(Received 1977/04/16)

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