| Summary: | 碩士 === 國立中興大學 === 化學工程學系所 === 100 === In this study, the Bi-xSn(x=2,5,10wt.%Sn) alloys joined with the Cu and Ni substrates are used to investigate the interfacial reactions and shear strength of the high-Bi/Cu and high-Bi/Ni solder joint systems. For the high-Bi/Cu joints, there is only Cu3Sn formed at the interface. The Cu3Sn phase detached from the Cu substrate, and a Bi-rich layer existed between the Cu substrate and the Cu3Sn phase. We propose a possible mechanism to explain the detachment phenomenon of the Cu3Sn phase based on the ternary Sn-Bi-Cu isothermal section. For the high-Bi/Cu joints under solid-state aging, the Cu3Sn phase grew with increasing the aging time. At the same time, part of the Cu3Sn phase was transformed into the Cu6Sn5 phase. In the Bi-2wt.%Sn/Ag/Cu system, the Cu3Sn phase also detached from the Cu substrate after reflow for 15 sec. The Ag layer disappeared at the interface and dissolved into the high-Bi alloy and the intermetallic compound (IMC). The interfacial reaction of the Bi-2wt.%Sn/Ag/Cu is similar to the high-Bi/Cu aging reaction. Therefore, it is concluded that the addition of an Ag layer has no significant influence on the interfacial reactions of the high-Bi/Cu joints.
In the Bi-2wt.%Sn/Ni system, the product of the reflow reaction is the Ni3Sn2 phase, and this phase grew with increasing the reflow time. In the Bi-5wt.%Sn and Bi-10wt.%Sn/Ni systems, the product of the reflow reaction is the Ni3Sn4 phase, and the IMC became thicker as the reflow time increased. For the solid-state aging, the Ni3Sn4 phase grew with increasing the aging time. In the Bi-2wt.%Sn/Au/Ni system, the Au layer dissolved into the molten alloy and the IMC during the reflow reaction and aging reaction. Compared with the Bi-2wt.%Sn/Au/Ni and high-Bi alloy/Ni interfacial reactions, the interfacial morphologies are similar for these two systems.
According to the data of interfacial shear strength, the strength of the high-Bi alloy/Cu and Ni substrates are better than the Pb-5wt.%Sn/Cu and Ni substrates, so the high-Bi alloys have high potential to replace the high-lead solder
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