Flip-Chip Interconnects Based on Single Metal-Coated Polymer Spheres

Abstract

In microelectronics packaging, minimizing thermomechanical stresses is crucial to achieve high reliability. This paper presents a novel approach for flip-chip interconnects, utilizing individual metal-coated polymer spheres at a low bonding temperature. The method involves selectively depositing individual conductive particles onto a polydimethylsiloxane (PDMS) carrier and then transferring the particles to electrical pads on substrate using Ag sintering followed by die placement and introducing underfill material. The deposition process achieved a high yield of 98.8% on the PDMS carrier, while the transferring process resulted in well-defined ink dots with a yield of 96.2%. The sintered Ag formed good bonds between the particles and electrical pads, leading to moderate interconnect resistance (as low as 0.57 Ω). This work has demonstrated the feasibility of interconnects based on a single metal-coated polymer sphere with low thermomechanical stress induced, thanks to the low bonding temperature (140 °C) and pressure (0.1 MPa) as well as the mechanical compliance of polymer particles.