This study investigates interfacial reactions of (Sn–9Zn) + xCu/Ni systems. Ni5Zn21, Cu5Zn8, (Ni,Zn,Cu)3Sn4, (Cu,Ni,Zn)6Sn5, and Cu6Sn5 phases were formed on the Sn–9Zn/Ni interface at 240–270 °C, when 0–10 wt% Cu was added to the Sn–9Zn solder. Experimental results indicate that changing the concentration of Cu in the Sn–9Zn solder dramatically changes the formation of intermetallic compounds (IMCs) in the (Sn–9Zn) + xCu/Ni system. Different diffusion and segregation rates of elements are the main reasons for a change in the IMC evolution.
This study investigates the effects of various reaction times and Cu contents on the interfacial reactions between Sn-9Zn-xCu alloys and Ni substrates. After aging at 255°C for 1 h to 3 h, the Ni 5 Zn 21 and Cu 5 Zn 8 phases formed at the interface of Sn-9Zn/Ni and Sn-9Zn-1wt.%Cu/Ni couples, respectively. The (Ni,Zn) 3 Sn 4 phase was found in the Sn-9Zn-4wt.%Cu/Ni couple, and the (Cu,Ni) 6 Sn 5 and Cu 6 Sn 5 phases formed, respectively, in the Sn-9Zn-7wt.%Cu/ Ni and Sn-9Zn-10wt.%Cu/Ni couples. As the reaction time was increased from 5 h to 24 h, the (Cu 5 Zn 8 + Ni 5 Zn 21 ) phases replaced the Cu 5 Zn 8 phase to form in the Sn-9Zn-1wt.%Cu/Ni couple; the (Ni,Zn) 3 Sn 4 phase formed in the Sn-9Zn-4wt.%Cu/Ni couple, and (CuZn + Cu 6 Sn 5 ) formed in the Sn-9Zn-10wt.%Cu alloys. Experimental results indicate that intermetallic compound (IMC) formation in Sn-9Zn-xCu/Ni couples changes dramatically with reaction time and Cu content. The Sn-Zn-Ni, Sn-Cu-Ni, and Sn-Zn-Cu ternary isothermal sections greatly help us to understand the IMC evolutions in the Sn-9Zn-xCu/Ni couples.
This study investigates the interfacial reactions between Sn-3.0wt.% Ag-0.5wt.%Cu (SAC) and Sn-0.7wt.%Cu (SC) on In/Ni/Cu multilayer substrates using the solid-liquid interdiffusion bonding technique. Samples were reflowed first at 160°C, 180°C, and 200°C for various periods, and then aged at 100°C for 100 h to 500 h. The scalloped Cu 6 Sn 5 phase was formed at the SAC/In/Ni/Cu and SC/In/Ni/Cu interfaces. When the reflowing temperatures were 160°C and 180°C, a ternary Ni-In-Sn intermetallic compound (IMC) was formed when the samples were further aged at 100°C. This ternary Ni-In-Sn IMC could be the binary Ni 3 Sn 4 phase with extensive Cu and In solubilities, or the ternary Sn-In-Ni compound with Cu solubility, or even a quaternary compound. As the reflow temperature was increased to 200°C, only one Cu 6 Sn 5 phase was formed at the solder/substrate interface with the heat treatment at 100°C for 500 h. Mechanical test results indicated that the formation of the Ni-In-Sn ternary IMC weakened the mechanical strength of the solder joints. Furthermore, the solid-liquid interdiffusion (SLID) technique in this work effectively reduced the reflow temperature.Key words: Sn-3.0wt.%Ag-0.5wt.%Cu and Sn-0.7wt.%Cu, lead-free solder, In/Ni/Cu multilayer substrates, solid-liquid interdiffusion bonding technique
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