Stress production and relief in the gold/silicon eutectic die-attach process

Eutectic braze thickness and package cooling rate for stress relief in eutectically bonded die were evaluated. Two package types, a 30 pin leadless chip carrier and a 28 pin flat pack were used as models in finite element stress calculations to study these parameters on the maximum principal stress, maximum circumferential stress, and maximum shear stress. Bonding temperature, creep rate, silicon tensile strength, and the effects of surface defects on silicon tensile strength were studied to evaluate their effects on stresses in the die. It is indicated that with a thicker eutectic braze and a slower cooling rate, die can be eutectically attached without excessive stress.