Evaluation of Bond Pad Structures by using Harsh Wire Bonding

Abstract

IC bond pad structures having Al metallization and SiO₂ insulator are historically designed with full plates in underlying metallization layers, connected by vias. Additionally, pads having bond over active electronic equipment (BOAC) that square measure way more sensitive to pad cracks, square measure possible gift within the same IC. Cracks within the pad insulator weaken the bond dependableness and will cause electrical outpouring or shorts to electronic equipment beneath the pad. Cracks square measure additional possible to occur throughout metallic element wire bond thanks to higher bonding stress as compared to Au alloy wire bonding. Experimental knowledge from bonding with 1mil Au or metallic element wires reveals dramatic variations in pad hardiness against cracking, relying upon the underlying metal structures and patterns. A “harsh” Au wire bond formula is additionally developed to supply the strain effects of metallic element wire bond in experiments while not having to upgrade older bonding instrumentation for metallic element wire. Cratering check once wire bond is employed to judge pad cracking. Ball shear checking followed by a cratering test any reveals pad cracking tendencies. Style principles for exaggerated pad hardiness to cracking square measure developed supported the information. Dependableness knowledge verifies the effectiveness of the planning principles. Correct style of interconnects at a lower place the pad will greatly increase pad hardiness to cracking, permitting way more margin in bonding stress, sanctionative the choice of Au or metallic element wire bond on an equivalent IC while not pad cracking.