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Sn–Zn-based alloys are promising low melting-point Pb-free solders, and it has been reported that their wetting properties and oxidation resistance can be improved with the addition of Cu. The interfacial reactions in the Sn–9 wt% Zn–xCu/Cu couples at 250 °C and Sn–9 wt% Zn–xCu/Ni at 280 °C were examined in this study. A thick γ–Cu5Zn8 phase layer and a very thin β′–CuZn phase layer were formed in both the Sn–9 wt% Zn/Cu and the Sn–9 wt% Zn–1 wt% Cu/Cu couples. The γ–Ni5Zn21 phase layer was formed in both the Sn–9 wt% Zn/Ni and Sn–9 wt% Zn–1 wt% Cu/Ni couples. With longer reaction time, the δ–Ni3Sn4 phase were formed in the Sn–9 wt% Zn/Ni couple as well. In both the Cu and Ni couples, the Zn-containing γ phases were uniform and planar and were the dominant reaction products. However, when the Cu content of the Sn–9 wt% Zn–xCu solders was 10 wt%, the interfacial reaction product becomes the η–Cu6Sn5 phase in both the Cu and Ni couples.

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Thermal inkjet technology is in widespread use for color printers. In the roofshooter thermal inkjet printhead, tantalum is often used as the diffusion barrier between the gold and the conduction layers, Al, Cu, and Al-Cu. This study investigated the contact stabilities of Al/Ta, Cu/Ta, and Al-Cu/Ta systems using the reaction couple technique. The couples were annealed in af urnace at 600°C, 750°C, 900°C, 1000°C, and 1200°C for various lengths of time. One reaction layer, the Al 3 Ta phase, was formed at the interface in the Al/Ta and Al-Cu/Ta couples heat treated at 750°C, 900°C, and 1000°C. No Cu is observed in the Al 3 Ta phase even in the Al-Cu/Ta couples; however, the reaction couples with Al-Cu have slower reaction rates. For the Al/Ta reaction couples annealed at 600°C and Cu/Ta couples annealed at 750°C, 900°C, 1000°C, and 1200°C, no noticeable interfacial reaction was observed. It was concluded that the contacts were very stable and Ta was av ery good barrier layer. In addition, phase equilibria studies of the Al-Ta system were carried out. The experimental results indicate that the Al 2 Ta phase was not stable at 850°C and higher. A revised Al-Ta phase diagram was proposed in this study.