An Assessment of Mechanical Inter-Locking Effects on Bump/Pad Contact Surface Characteristics of a Flip Chip on Flex with Non-Conductive Adhesive

• Main Authors: Ji-Chung Chen, 陳一中
• Other Authors: Yu-Hsing Chao
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/06718483371298085574

碩士 === 國立臺灣海洋大學 === 機械與機電工程學系 === 96 === This paper focuses on the mechanical interlocking effects on the bump/pad interfacial contact surface of a flip chip on flex with non-conductive adhesive under thermal cycling loads after the bonding/curing process of packaging. The aim of improvement for the bump/pad interfacial contact characteristics was to enhance the reliability of chip set package through a well maintained contact surface. Comparisons of the normal stress on the interfacial contact surface with varied roughness for the true-shaped bump geometric parameters, revealed the mechanical interlocking effects, and induced the increase of equivalent contact stresses. Finite Element Code ANSYS was used to analyze the package, and a 2D model was adopted to proceed with a parametric sensitivity analysis for the material properties of non-conductive adhesive and bump geometric dimensions varied. The results of aging by using thermal cycling showed that the bonding force between bump/pad will be improved by moderate increase of Young’s modulus and thermal expansion coefficient of non-conductive adhesive. A so-called “saw-tooth” fractal surface will raise the normal compressive force, and surpassed the flat surface by the effect of mechanical interlocking. A case-by-case interfacial stress analysis was suggested for the investigation of any realistic microelectronic package due to the complexity among all the interrelated parameters.