Ultrafast formation of unidirectional and reliable Cu3Sn-based intermetallic joints assisted by electric current

摘要

High-temperature-stable Cu3Sn-based joints were selectively fabricated using electric current-assisted bonding process within an extremely short time (similar to 200 ms) and under a low pressure of 0.08 MPa in a Cu/Sn/Cu interconnection system at ambient temperature. The experimental results showed that the imposed electric current density (similar to 10(4) A/cm(2)) resulted in sharply increased local temperature as well as accelerated growth of Cu3Sn intermetallic compounds (IMCs). Under the effects of electron wind force induced electromigration and joule heat-induced temperature, the transient formation of Cu3Sn-based joints can thus be obtained across the interfaces. Furthermore, highly unidirectional 1 0 0 growth of Cu3Sn IMCs was achieved along the direction of electron flow. By calculating the planar atomic densities of projected images on different planes, the particular growth direction was confirmed to represent the low-scattering path for tile traveling electron flow. The oriented Cu3Sn-based joints exhibited more reliable shear properties than the Sn-based joints. (C) 2016 Elsevier Ltd. All rights reserved.