Intermetallic compounds formed during interfacial reactions between liquid Sn-8Zn-3Bi solders and Ni substrates

The morphology and growth kinetics of intermetallic compounds (IMCs) formed at the interfaces between liquid Sn-8Zn-3Bi solders and nickel substrates in the temperature range from 225°C to 400°C are investigated for the applications in bonding recycled sputtering targets to their backing plates. The results show that a continuous single layer of Ni₅Zn₂₁ IMC appears at temperatures below 325°C, while a double layer containing Ni₅Zn₂₁ and Ni₃₅Zn₂₂Sn₄₃ IMCs is formed at temperatures above 325°C. In both cases, the growth kinetics of IMCs is interface-controlled. During the growth of IMCs, their reaction fronts migrate in the direction of the solder much more rapidly than toward the nickel substrate, and erosion of the Ni substrate is quite slight.