Nanowire, ACF, for, ultrafine-pitch, flip-chip, interconnection

Advanced microelectronic packaging, driven by the multiple benefits of system performance, power, size and cost, has moved into a three-dimensional (3D) era. One of the bottlenecks to 3D IC integration is the high-density interconnections to be formed between stacked dies. Prevailing solder-based interconnect encounters constraints including high process temperature, increasing process cost and intermetallic compound (IMC) reliability issues related to the ever-decreasing pad/pitch size. Anisotropic conductive film (ACF) and anisotropic conductive adhesive (ACA) technology are two of the fine-pitch, low-temperature flip-chip material bonding options, which have been considered as potential replacements for solder interconnections. However, conventional ACF or Anisotropic conductive paste (ACP) with spherical conductive particles have limitations in terms of unpredictable numbers of trapped particles in the interconnections and the occurrence of particle agglomeration in the small gaps between interconnections. To tackle these limitations, a nanowire ACF (NW-ACF) with vertically configured, high aspect ratio metallic nanowires has been fabricated utilizing a nanoporous template and an electrodeposition method to create a novel nano-ACF material. The NW-ACF has been structurally and electrically characterized to demonstrate its feasibility as a fine-pitch and low-temperature interconnection solution for future 3D die-/wafer-level interconnection applications.