Novel low-volume solder-on-pad (SoP) material and process for flip chip bonding using Au stud bumps

A novel solder bumping material and process for low-volume solder-on-pad (SoP) have been developed to be applied in the flip chip bonding using Au stud bumps. It features a maskless, low-cost, and lead-free material. The thicknesses of the solder bumps on pads on a substrate were measured about 10 μm. With this material and optimized process, as well as, fluxing underfill, a 3D IC module composed of a GPU, two SRAM, two Si interposer with TSVs, and passives were successfully developed.