Mechanical properties and ball shear strength of Sn-3.5Ag-Bi were investigated with Bi addition of 0-9 mass%. Solder characteristics of Sn-3.5Ag-Bi were improved with Bi addition to decrease the melting temperature, to promote wetting to Cu and Ni substrates, and to increase the tensile strength and fracture energy. Shear strength of Sn-3.5Ag-Bi solder bumps increased with Bi addition up to 5 mass%, and was kept almost unchanged with further increase of Bi addition. Shear strength exhibited a parabolic relationship with the tensile fracture energy of the solder alloys.

The shear strength and aging characteristics of 63Sn-37Pb solder bumps were characterized with variation in solder ball and UBM pad sizes. The shear strength increased with shorter effective crack size, a eff , which was determined with the solder ball and pad sizes. The shear strength of the solder bumps on Au/Ni/Cu and Ni/Cu did not change significantly with reflow time. Substantial decrease in the shear strength occurred for the solder bumps formed on Au/Ni/Cu with aging treatment, and the shear strength after aging was also related to the bump shape which was determined with the solder ball and pad sizes.

The mechanical properties of the 1-9 vol % Cu and Cu6Sn5-dispersed 63Sn-37Pb solder alloys were characterized with tensile test. Also, the Cu and Cu6Sn5-dispersed 63Sn-37Pb solder bumps of 760 μm size were fabricated on the Au(5 μm)/Ni(5 μm)/Cu(27 μm) BGA substrates by screen printing process, and their shear strength were characterized with variations of the dwell time at the reflow peak temperature(220°C) and aging time at 150°C. The yield strength and ultimate tensile strength of the 63Sn-37Pb solder alloy increased with dispersion of 1-9 vol % Cu and Cu6Sn5. In general, however, the Cu and Cu6Sn5-dispersed solder bumps exhibited lower shear strengths than those of the 63Sn-37Pb solder bumps The failure surface of the solder bumps after ball shear test could be divided into two regions of slow crack propagation and critical crack propagation, and the shear strength of solder bumps was inversely proportional to the slow crack propagation length.