Flip chip process using mushroom bumps and interlocking bumps

Abstract

For flip chip applications, Sn bumps, Cu mushroom bumps, and interlocking bumps were fabricated by electrodeposition to characterize the contact resistance. Average contact resistance of Sn bump joints was lowered from 34mΩ to 27.5mΩ with increasing bonding stress from 40 MPa to 95 MPa, which was much smaller than a few hundred mΩ of flip-chip joints processed with anisotropic conductive film. Substantial improvement of the surface roughness was achieved by surface heat-treatment at 300° for 10 sec due to the local surface melting. To improve the contact resistance characteristics in flip chip process, mushroom bumps and interlocking bumps were examined in this study.