Influence of Bump Diameter on the Growth of Intermetallic Compounds in Cu/Ni/Sn Copper Pillar Bump During Aging Process

In 3D electronic packaging, microbumps show great potential for vertical connection of stacked chips. The diameter of microbumps, which determines the surface/volume ratio, has great influence on the generation of Intermetallic Compounds (IMCs). To study the intermetallic reaction within different diameter microbumps during aging process, the 20 μm, 10 μm and 7 μm diameter Cu/Ni/Sn copper pillar bumps were prepared and reflowed. After aging treatment, the cross-section of microbumps was observed and analyzed. We observed sidewall Cu
₃
Sn around Cu pillar. Cu pillar was eroded into a cone in 10 μm and 7 μm diameter microbumps after aging treatment. We also found that the growth rate of sidewall Cu
₃
Sn increased with the microbumps diameter decreasing.