FLIP-CHIP INTERCONNECTION TO VARIOUS SUBSTRATES USING ANISOTROPIC CONDUCTIVE ADHESIVE FILMS

Abstract

Flip-chip interconnection to various substrates using ACF was investigated. It was demonstrated that the interconnection resistance of the joints made between gold bumps of the chip and Ni/Au coated pads on FR-4 boards was lower than 10 mΩ depending upon the kinds of conducting particles, although the interconnection was due to the mechanical contact between conducting particles and conductor surfaces. The current–voltage characteristics of the interconnection exhibited an ohmic behavior up to currents of 2000 mA per bump. In attaching bumpless chips to various substrates, the interconnection resistance strongly depended on the kinds of conducting particles and substrates. It was demonstrated that Ni particles were favorable for making good electrical contacts between Al pads of the bumpless chip and substrate electrodes. It was also demonstrated that low interconnection resistance in the range of 2 mΩ to 7 mΩ was obtained as well as with bumped chips, when FR-4 boards with Ni/Au bumped pads were used as substrates for interconnecting bumpless chips.