Title :
Failure mode analysis for TAB inner lead bonding
Author :
Jee, Yong ; Andrews, Marshall
Author_Institution :
Microelectron. Comput. Technol. Corp., Austin, TX, USA
Abstract :
The performance of tape-automated inner-lead gang bonding in the interconnection of VLSI devices was studied, using failure modes, failure probability curves, and Weibull distribution curves. 129-lead tin-plated copper tapes were bonded to annealed gold bumps with a thermode at 450°C and 40 psig and pull-tested with a micro-pull tester. Several different failure modes were observed during the pull test: lead break in span, lead break at pad, lead separation from bump, bump fracture, bump lift, and silicon substrate cratering. The major failure mode (half of the failures) was lead break, which indicates good bonding. Lead separation from bump was related to nonuniformity of the eutective layer, uneven bonding pressure caused by inadequate planarization, and surface roughness or contamination of leads and bumps. High bonding pressure and uneven leads produced deformation and bump fractures during pulling. The frequency of bump lift was very low. Thermal stress and microcracks are proposed as factors affecting bump lift and silicon substrate cratering. Failure probability curves showed the distribution of pull strength and failure probability, and Weibull distribution curves indicated the dispersion of pull strength data
Keywords :
VLSI; circuit reliability; failure analysis; lead bonding; probability; statistical analysis; surface mount technology; thermal stress cracking; 129-lead tin-plated copper tapes; 450 degC; Cu-Sn-Au; SMT; Si; TAB; VLSI device interconnection; Weibull distribution curves; annealed gold bumps; bump fracture; bump lead separation; bump lift; bumps contamination; eutective layer nonuniformity; failure mode analysis; failure modes; failure probability curves; inadequate planarization; leads contamination; micro-pull tester; microcracks; pad lead break; pull strength; pulling bump fractures; pulling deformation; silicon substrate cratering; span lead break; surface roughness; tape-automated inner-lead gang bonding; thermal stress; thermode; uneven bonding pressure; Annealing; Bonding; Copper; Failure analysis; Gold; Silicon; Testing; Thermal stresses; Very large scale integration; Weibull distribution;
Conference_Titel :
Electronic Components Conference, 1989. Proceedings., 39th
Conference_Location :
Houston, TX
DOI :
10.1109/ECC.1989.77767
