Mechanical analysis of Ultra-Thin-Chip-on-Flex (UTCOF) with anisotropic conductive adhesive (ACA) joints

The work attempts to investigate the thermal-mechanical behaviors of an advanced flexible electronics technology during the bonding process and under four-point bending (FPB) and static bending (SB). The flexible technology implements an epoxy-based anisotropic conductive film (ACF) to form fine-pitch and reliable interconnects of Integrated circuits (IC) bumps on flex substrates. The paper starts from exploring its process-induced thermal-mechanical behaviors through process modeling using a proposed process-dependent simulation methodology. The validity of the process-modeling is confirmed through various experiments. Subsequently, the contact behaviors of the ACF joints in the flexible technology under FPB and SB are also characterized using FE modeling and a four-point probe method. The simulated contact stress is correlated with the measured contact electrical resistance.