Abstract
The highest density of various electronic packaging is flip chip bonding technology. The non-conductive adhesive (NCA) and anisotropic conductive film (ACF) are the major candidates of the high density packaging methods among various flip chip technologies. Both bonding methods depend on the constrictive stress to let the bump of IC or conductive particle of ACF become deformed, which induces the electrical connection between the IC’s bump and the substrate’s electrode. The contact resistance decreases as the bonding stress increases. However, too large stress will damage the bonding structure. Thus, as long as the stress is under control, stable electric and physical properties can be maintained. The subject of this research is to study the relationship between the stress and connection qualities, such as connection resistance, power-up test, and mechanical failure. The research method is from the derivation of mathematic model to real case study, which could predict the effect of the different bumps, adhesives, and process conditions on joining quality. Finally, experiments are used to verify it indirectly. There are three real case studies in this work. (1)The application of micro-bump-bonding for Chip-on-glass: From stress evaluation to experiment verification, we find that the compliant bump COG has lower and more stable contact resistance than Au bump COG. (2)The application of non-conductive adhesive for chip-on-film: From stress evaluation to experiment verification, we find that the thermal stress decreases and the connection quality improves, as the coefficient of thermal expansion (CTE) mismatch between selected adhesive and Au bump decreases. (3)The application of anisotropic-conductive-film for chip-on-film: From stress concept to experiment verification, we find that the curing percentage of adhesive increases and the connection resistance decreases, while the bonding temperature or bonding time increases. From the aforementioned stress analytic model cases to indirect experiment verification, we find that the connection quality improves while the intrinsic stress increases and the thermal stress decreases.