Substrate stresses for double load copper wire bonding

Copper wire is increasingly used in microelectronics packaging manufacturing. The double load bonding process reduces the under pad damages during Cu wire bonding; however, the mechanism is not yet well understood. A non-linear 3D finite element model was used to study the Cu wire bonding procedure to analyze the stress distributions, especially in the silicon substrate, for conventional and double load wire bonding. For the same ultrasound power and the same copper ball deformation, the compressive stress under the pad with double load wire bonding is much larger than with the conventional bonding procedure, the tensile stresses are almost the same, and the shear stresses under the pad are less with double load wire bonding. The reduced damage under the pad for double load wire bonding is related to the reduced stresses.