Shearing tests of solder joints on tape ball grid array substrates

Shearing behavior of Sn-37Pb, Sn-3Ag-0.5Cu, and Sn-3Ag-0.5Cu-8 in solder joints on tape ball grid array (TBGA) substrates were investigated with different shearing speeds from 7 mu m/s to 700 mu m/s and over a wide temperature range from -25 degrees C to 150 degrees C. Both shearing speed and testing temperature were found to have strong effects on the shearing strength and fracture mechanisms of the solder joints. At certain temperature, the shearing force increases sharply with the increase of shearing speed due to a small amount of grain boundary deformation and incomplete dislocation movement as well as more work hardening at a high strain rate. With a fixed speed, the shearing force decreases dramatically with the increase of shearing temperature as a result of a small amount of work hardening and more dynamic recovery, as well as a reduction in Young's modulus at elevated temperatures. Two lead-free solder joints were much stronger than the tin-lead solder joints under any given shearing condition. At a low temperature of -25 degrees C, the tin-lead solder joints failed with a combination of intermetallic compounds (IMC) fracture and solder/IMC interface detachment, whereas both lead-free solder joints failed by IMC/Ni interfacial separation. From 25 degrees C to 150 degrees C, the fracture mode of all solder joints was complete ball cut through the bulk solder with a ductile rupture. The underlying mechanisms for different shearing performance are interpreted in relation to the properties of the interconnecting materials.