The interfacial reaction between lead-free solders (Sn, Sn-3.0Ag-0.5Cu (SAC305), and Sn-9Zn (SZ)) and substrate Cu-4.3 at% Ti (C1990HP) was investigated using the reaction couple technique at 240, 255, and 270 oC. The results show that the Cu6Sn5 and small precipitated Ti2Sn3 phase formed at the Sn/C1990HP and SAC305/C1990HP interface. Meanwhile, the driving force clearly seen for Cu6Sn5 in the SAC305 solder to spall massively from the interface originates from prolonged the reaction time. The content of Ti substantially increased the amount of IMC at the interface which separated parts of Cu6Sn5 compounds with the inner region containing more Ti than the outer for Sn/C1990HP and SAC305/C1990HP system. The existence of Sn/C1990HP and SAC305/C1990HP on the liquid/solid state reaction indicates that spalling occurred with changes in reaction time and temperature. With increased reaction temperature and time, the grain produced an abnormal condition resulting in Cu6Sn5 not accumulating at the interface and spalling into the solder in addition to grain ripening and an increase in total layer thickness. The hexagonal prism-shaped Cu6Sn5 phase is found on the top of the C1990HP substrate when the Cu6Sn5 layer detaches for Sn/C1990HP and SAC305/C1990HP system. However, a continuous and laminar IMC layer was occurred in SZ/C1990HP reaction couple. The new IMC grains grew and gradually merged together to compose a continuous IMC layer. The planar CuZn5 and Cu5Zn8 layer formed in almost reaction. An IMC Cu5Zn8 serves as a diffusion barrier in the SZ/C1990HP system. However, the CuZn5 phase is disappeared when increased time and temperature. For Sn/C1990HP, SAC305/C1990HP, and SZ/C1990HP systems, the thickness of the IMCs layer increases when the reaction time and temperature increase.
Further investigation, the mechanical test of joint strength in Sn/C1990HP revealed in this study. The fracture mode for 240, 255, and 270 oC are ductile, brittle & ductile, and brittle, respectively. The tensile strength enhances with increasing reflow temperature. However, it weakens with increasing aging time.

The interfacial reaction between lead-free solders (Sn, Sn-3.0Ag-0.5Cu (SAC305), and Sn-9Zn (SZ)) and substrate Cu-4.3 at% Ti (C1990HP) was investigated using the reaction couple technique at 240, 255, and 270 oC. The results show that the Cu6Sn5 and small precipitated Ti2Sn3 phase formed at the Sn/C1990HP and SAC305/C1990HP interface. Meanwhile, the driving force clearly seen for Cu6Sn5 in the SAC305 solder to spall massively from the interface originates from prolonged the reaction time. The content of Ti substantially increased the amount of IMC at the interface which separated parts of Cu6Sn5 compounds with the inner region containing more Ti than the outer for Sn/C1990HP and SAC305/C1990HP system. The existence of Sn/C1990HP and SAC305/C1990HP on the liquid/solid state reaction indicates that spalling occurred with changes in reaction time and temperature. With increased reaction temperature and time, the grain produced an abnormal condition resulting in Cu6Sn5 not accumulating at the interface and spalling into the solder in addition to grain ripening and an increase in total layer thickness. The hexagonal prism-shaped Cu6Sn5 phase is found on the top of the C1990HP substrate when the Cu6Sn5 layer detaches for Sn/C1990HP and SAC305/C1990HP system. However, a continuous and laminar IMC layer was occurred in SZ/C1990HP reaction couple. The new IMC grains grew and gradually merged together to compose a continuous IMC layer. The planar CuZn5 and Cu5Zn8 layer formed in almost reaction. An IMC Cu5Zn8 serves as a diffusion barrier in the SZ/C1990HP system. However, the CuZn5 phase is disappeared when increased time and temperature. For Sn/C1990HP, SAC305/C1990HP, and SZ/C1990HP systems, the thickness of the IMCs layer increases when the reaction time and temperature increase.
Further investigation, the mechanical test of joint strength in Sn/C1990HP revealed in this study. The fracture mode for 240, 255, and 270 oC are ductile, brittle & ductile, and brittle, respectively. The tensile strength enhances with increasing reflow temperature. However, it weakens with increasing aging time.

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