Deformation Behavior and Microstructure Evolution of the Cu-2Ni-0.5Si-0.15Ag Alloy During Hot Compression
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TRODUCTION
THE lead frame is the foundation of the integrated circuits, which plays the main role of supporting the chip, along with electrical signal transmission and heat dissipation in the integrated circuit. Thus, the lead frame is very important for the microelectronics industry.[1] The lead frame material should be adequate heat and electrical conductor, have high strength and heat resistance, along with excellent processing properties. Many experts have conducted a lot of research to obtain the desired material for the lead frame. Due to the high electrical conductivity, Cu alloys are widely used as the lead frame materials, including Cu-Ni-Si, Cu-Fe, Cu-Fe-P, Cu-Cr-Zr, and Cu-Ag alloys. Among these alloys, Cu-Ni-Si has become a research focus due to its high strength and hardness, good processing properties, and modest electrical conductivity.[2–13] Cu-Ni-Si alloy is one of the age-hardening alloys. Corson had been the first to find the hardening behavior of this alloy in 1927, and attributed this age-hardening behavior to the precipitation of the d-Ni2Si phase.[14] The
YI ZHANG, Associate Professor, is with the School of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471003, China and also Visiting Professor in the Department of Mechanical Engineering, University of South Florida, Tampa 33620. Contact e-mail: [email protected] ALEX A. VOLINSKY, Associate Professor, and HAI T. TRAN, Ph.D. Graduate Student, are with the Department of Mechanical Engineering, University of South Florida. Conatct e-mail: [email protected] QIAN-QIAN XU and ZHE CHAI, Ph.D. Graduate Students, and BAOHONG TIAN, Professor, are with the School of Materials Science and Engineering, Henan University of Science and Technology. Manuscript submitted April 12, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS A
microalloyed technology has been used to further improve the comprehensive performance of the Cu-Ni-Si alloy, and then the Cu-Ni-Si-Ag alloy was developed. The strength and hardness of the Cu-Ni-Si alloy can be enhanced significantly by adding a small quantity of silver. Silver atoms dissolve in the matrix and induce obvious hardening. Solid solution strengthening tends to decrease the electrical conductivity of the Cu alloys, since lattice distortions induced by the solute atoms increase electron scattering.[15,16] However, the solid solution of Ag atoms does not cause a clear decline in the electrical conductivity of the Cu-Ni-Si alloy, since Ag addition promotes Ni2Si phase precipitation. The Ni2Si phase precipitation weakens the lattice distortion, which is induced by the Ni and Si atoms, so it can be said that the precipitation of the Ni2Si phase offsets the adverse effects of Ag addition on the electrical conductivity. There are many similar results of Ag affecting precipitation of copper alloys.[17,18] In the previous study, it was found that the comprehensive performance of the Cu-2Ni-0.5Si alloy can be improved by the addition of 0.15 wt pct Ag, and the hardness, electrical conductivity, and s
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