Microstructural evolution of Sn single grain microbumps for 3D-TSV high density solder interconnection under thermal aging tests

As I/O number increases continually, the 3D-TSV packaging technology rises. Lead-free solder interconnection is one important technology for 3D-TSV stacked packaging. In order to deal with rising TSV density, solder joint volume is getting smaller. In the present paper, a high-density Sn micro-bump arrays for 30×30μm pitch were fabricated by photolithography, electroplating and reflow. The diameter and height of obtained Sn micro bumps are about 10μm and 8μm, respectively. It is found that the bulk of the micron bumps contains only one Sn grain due to the volume constraint. Also, the microstructural evolution of these single Sn grain microbumps under isothermal aging was investigated using scanning electron microscope (SEM).