Investigation of the characteristics of overhang bonding for 3-D stacked dies in microelectronics packaging

It is indicated that the impact and deflection of overhang die during overhang bounding process results in considerable impact of performance of bonding in this paper. Specifically, the deflection is unstable and up to 27 μm for the given parameters, which results in low shear force strength and low success rate of overhang bonding. To improve the performance of the overhang bonding, an effective and novel approach, overhang bonding with thick Al, is presented. The approach decreases hardness of bonding die, which makes the bonding die more compliant during bonding process than that in the traditional approach, thus the shear strength and bonding success rate of overhang bonding will be improved. Finally, effects of ultrasonic and force to overhang bonding indicates that excessively low or excessively high ultrasonic power results in weak bonding performances, and so did the force.

► The deflection of overhang bonding results in low shear strength.
► Since a novel approach is more compliant, the shear strength will be improved.
► Excessively low or high ultrasonic power results in weak bonding performances.