Micro-nano interconnect between gold bond pads and copper nano-wires embedded in a polymer template

With the ongoing miniaturization and 3D integration trend in microelectronics packaging, a need exists to provide for denser chip interconnect than can be achieved with photolithography based processes. One way to achieve this is via a bumpless process using a S(ubmicron) W(ire) A(nisotropic) C(onductive) F(ilm) (SW-ACF) with a parallel array of submicron metal wires embedded in this film. This paper describes the first step of SW-ACF fabrication and bumped flip-chip bonding trials. The SW-ACF is based on a polycarbonate template filled with copper wires which is bonded onto a test chip with gold stud bumps. Electrical measurements showed that viable connections were made between the copper wires and the gold bond pads, and also that electrical insulation was maintained between bond pads. The concept worked for the smallest pad-pitch structure on the test chip which was 25 mum circular pads with 25 mum spacings.