Flip-chip interconnects based on single metal-coated polymer spheres

In modern microelectronics packaging, minimizing thermo-mechanical stresses is crucial to achieve high reliability. This paper presents a novel approach for flip-chip interconnects, utilizing individual conductive particles 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. 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 a good bond between the particles and electrical pads, leading to moderate interconnect resistance (as low as 0.57 Ω). This work demonstrates the feasibility of low thermo-mechanical stress interconnects, thanks to the low bonding temperature (140 °C) and pressure (0.1 MPa) requirements.