Process-dependent Thermal-Mechanical Behaviors of an Advanced Thin-Flip-Chip-on-Flex Interconnect Technology with Anisotropic Conductive Film Joints

User experiences for electronic devices with high portability and flexibility, good intuitive human interfaces and low cost have driven the development of semiconductor technology toward flexible electronics and display. In this study proposes, an advanced flexible interconnect technology is proposed for flexible electronics, in which an ultra-thin IC chip having a great number of micro-bumps is bonded onto a very thin flex substrate using an epoxy-based anisotropic conductive film (ACF) to form fine-pitch and reliable interconnects or joints (herein termed ACF-typed thin-flip-chip-on-flex (TFCOF) technology). The electrical and thermal -mechanical performances of the micro-joints are the key to the feasibility and effectiveness of the technology. Thus, the main goal of the study is to assess the process-induced thermal-mechanical behaviors of the interconnect technology during the bonding process. To undertake the process modeling, a process-dependent simulation methodology that integrates both thermal and non-linear thermal-mechanical finite element (FE) analyses together with ANSYS (R) birth-death modeling technique is proposed. The validity of the process modeling is confirmed through various temperature and warpage measurements. Subsequently, the contact behaviors of the ACF joints under four-point bending and static bending tests are characterized through FE modeling. The simulated contact stresses are further correlated with the measured electrical resistance data using four-point probe method, by which the minimum threshold contact stress for achieving a reliable contact electrical performance is determined.