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TECHNICAL PAPERS

Plastic Deformation Kinetics of 95.5Sn4Cu0.5Ag Solder Joints

[+] Author and Article Information
Z. Guo, H. Conrad

Materials Science & Engineering Department, North Carolina State University, Raleigh, NC 27695-7907

Yi-Hsin Pao

Material Systems Reliability Department, Ford Research Laboratory, 20000 Rotunda Drive, P.O. Box 2053 (MD 2313/SRL), Dearborn, MI 48121-2053

J. Electron. Packag 117(2), 100-104 (Jun 01, 1995) (5 pages) doi:10.1115/1.2792074 History: Received August 01, 1994; Revised March 31, 1995; Online November 06, 2007

Abstract

The plastic deformation kinetics of 95.5Sn4Cu0.5Ag solder joints were determined in monotonic loading shear over the temperature range of 25°–150°C using three types of tests: (a) constant shear rate, (b) constant shear stress (creep), and (c) differential tests (changes in shear rate or temperature during an otherwise isothermal constant shear rate test). The deformation kinetics were evaluated in terms of the Dorn high temperature plastic deformation equation γ̇p = A(μb/kT) D(b/d)P (τ/μ)n where γ̇p is the shear rate, μ the shear modulus, b the Burgers vector, D the appropriate diffusion coefficient, d the grain size and τ the shear stress. A, p, and n are constants whose values depend on the rate controlling mechanism. It was found that n increased with stress from ~4 at 2 MPa to ~20 at 25 MPa, relatively independent of temperature. The activation ΔH was determined to be 21.1 ± 2 kcal/mole. The constant A, however, decreased with temperature from a value of ~1018 at 25°C to ~1010 at 150°C. The values of n and ΔH suggest that dislocation glide and climb is the rate controlling mechanism and hence that p ≈ 0. It is speculated that the large decrease in A with temperature may be the result of an effect on the microstructure.

Copyright © 1995 by The American Society of Mechanical Engineers
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