A study on the effects of nanofiber anisotropic conductive adhesive (Nanofiber ACA) properties on fine pitch interconnection stability of ACA flip-chip assemblies

Abstract

Display related electronics such as cellular phones, laptops, and televisions have become an indispensable part of our lives. In line with this, as people are demanding images with high quality, the number of electrical paths from a display driver chip to display panel are increasing, resulting in a reduction of the electrode pitch, which is the center-to-center distance between nearby electrodes. The most critical issue facing current display devices is interconnecting the fine pitch driver chip on the display panel using anisotropic conductive adhesives (ACAs) without an electrical short circuit phenomenon, since conductive particles in the adhesives can be agglomerated between fine pitch electrodes during the bonding process, thereby causing electrical noise in the X-Y directions. In this study, we suggest and investigate a new concept of nanofiber ACA that incorporates conductive particles into nanofiber to suppress conductive particle movement and to obtain stable three-dimensional electrical properties of fine pitch electronics. Chapter 2 describes the effects of nanofiber structures on the electrical properties of ACAs. Two types of nanofiber ACAs are suggested and are electrically characterized. One type has randomly distributed nanofibers in an anisotropic conductive adhesive (ACA) resin, and the other has randomly distributed nanofibers coupled with conductive particles (Cp/nanofiber) in a non-conductive film (NCF) resin. The PS nanofiber ACAs had stable contact resistances due to the PS melting effect during the bonding process. The PAN nanofiber ACAs, however, showed slightly higher contact resistances about 20~30%. This is attributed to the PAN’s thermal stability at the bonding temperature, which means that it was more difficult to squeeze out the thicker nanofibers from the bonding area. Nevertheless, the PAN/Cp nanofiber ACAs had stable contact resistances (4 mΩ), with values similar to those of the conventional ACA. The results of measurement ...