ACF bonding technology for paper- and PET-based disposable flexible hybrid electronics

Abstract

In light of the necessity to introduce reliable interconnection technologies for the development of disposable diagnostic kits, fine-pitch flip-chip integration of bare silicon dies on the paper and polyethylene terephthalate (PET)-based substrates have gained increasing importance. As the key-enabler of a hybrid electronic system, the interconnection technology should provide reliable electrical and mechanical properties. Paper and PET are temperature- and pressure-sensitive, and are not compatible with the conventional flip-chip bonding technologies, i.e., soldering and thermo-compression bonding. In this study, the feasibility of implementing Anisotropic Conductive Films (ACF) in hybrid integration was assessed, in which bare silicon dies with the thicknesses of 30 mu m and 730 mu m were bonded to screen-printed paper and PET substrates. As an alternative to direct bare die bonding, the integration of PET- and paper-based interposers to printed substrates was also addressed here. Correspondingly, the long-term reliability of the ACF-bonded samples was assessed via dynamic bend cycling tests. It was shown that ACF provides robust and reliable interconnects on both substrates with a failure cycle of more than 45,000 cycles.