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Intermetallics"Effects of α-Fe_2O_3 Additions on Assembly Reliability of Electroplated Sn-Based Solder Cap on Cu Pillar Bump During Thermal Cycling"Authors: Lijun Liu, et al; zhaoxiuchen@bit.edu.cn.Abstract: Composite solder alloys reinforced by different nominal concentrations of α-Fe_2O_3 nanoparticles are examined, and the performance of corresponding copper (Cu) pillar bumps during thermal cycling (TC) tests is investigated. First, spherical α-Fe_2O_3 nanoparticles (50nm in diameter) were successfully prepared by a chemical method. Then, Sn-xFe_2O_3 composite solders with different concentrations of α-Fe_2O_3 were deposited on the surface of Cu pillar bumps by electroplating. During electroplating, the concentration of α-Fe_2O_3 nanoparticles in the plating solution ranged from 0 to 0.04g/L. TC tests of fabricated joints were conducted from -65° to 150℃ for different numbers of cycles. The microstructure, evolution of interfacial intermetallic compounds (IMCs) and shear strength of the solder joints were investigated following TC tests. Cross-sectional analysis indicates that adding α-Fe_2O_3 nanoparticles can remarkably suppress the overgrowth of interfacial IMCs. Compared to the strength of joint without nanoparticles after the TC test, joint strength increases with the addition of α-Fe_2O_3, and an optimum nominal concentration of 0.032g/L in the electroplating solution was identified. (Journal of Electronic Materials, Dec. 4, 2018)