CPB fcCSP BGA Package Reliability assessment via the study of Bump Cross Section Morphology after Product Realiability stress testing

Abstract

In this paper we study and assess fine-pitch CPB fcCSP BGA package reliability via the study of bump cross section morphology after product reliability stress testing. The IMC formation and progression in copper pillar bump was studied in Mass Production destined SoC Controller to predict the health and life time left for the CPB. In particular we are interested in the reliability of fine-pitch oblong copper pillar bumps arranged in Omni-directional patterns. During product reliability testing, CPB cross-section analysis (Via P-FIB) was performed on CPB bumps strategically located in different sections of the fcCSP BGA package after each reliability test read point. JEDEC standard suite of package related tests were performed. IMC formation and progression under the effect of abovementioned environmental stresses as well as different assembly line variations and materials, including molding compound and substrate, were taken into account. We also compare IMC formation from two different bumping technologies. By assessing the various IMC, void and crack formations, we propose that the product reliability engineer should consider verifying health of product physically in addition to ATE final test. This paper also provides feedback to package technology development from product reliability point of view.