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Bond cratering is the damage of the silicon layer under the bond pad that is induced by overbonding. This study explores the reason behind the occurrence of cratering in relation to secondary ball bond parameters, namely, the pre-ultrasonic ball power, the ball power compensation, and the ball delay force. The optimization of these parameters
to prevent bond cratering was accomplished through Taguchi Design of Experiment. This study showed that an increase in both pre-ultrasonic ball power and ball power compensation will increase ball shear strength, but will also increase the tendency for bond cratering. The study also showed that the ball delay force is best set to zero. The optimized setting of these secondary bonding parameters resulted in the elimination of bond cratering without negative effects on the ball shear strength and ball bond size. |
