posted on 2020-03-24, 16:33authored byQiang Jia, Guisheng Zou, Wengan Wang, Hui Ren, Hongqiang Zhang, Zhongyang Deng, Bin Feng, Lei Liu
Ag–Cu
bimetallic nanoparticles, combining the advantages of both Ag and
Cu, are a promising material for power electronic packaging. In this
work, a supersaturated Ag–7.3 wt % Cu alloy nanoparticle film
was developed by using pulsed laser deposition. Unlike Cu nanoparticles,
the supersaturated Ag–Cu alloy nanoparticles can conduct bonding
in air without the assistance of a reduction agent. The shear strength
was >20 MPa when the bonding temperature reached 300 °C, which
was above the die shear standard (MIL-STD-883 K, 7.8 MPa) and compatible
with the typical die attach process. The Cu separating behavior was
accompanied by the bonding process at 250–400 °C, which
was discussed systematically. Neck formation was delayed to about
250 °C because of the hindering effect of the thin oxide shell
of the Ag–Cu alloy. The necking networks provide volume diffusion
paths despite the growth of surface oxide, resulting in compact densification.
The bondline under the SiC die consisted of a porous Ag–Cu
alloy matrix with a dispersed secondary phase of Cu2O/CuO,
which is supposed to have improved electrochemical migration resistance.