Effect of Ag addition on the creep characteristics of Sn–8.8 wt%Zn solder alloy

Abstract Full implementation of the new generation of lead-free solders requires detailed knowledge and understanding of their mechanical behavior. The materials used in the present study are Sn–8.8 wt%Zn (binary) and Sn–8.8 wt%Zn–1.5 wt%Ag (tertiary) alloys. Effect of Ag addition, deformation temperature T and the applied stress, σ , on the creep characteristics have been studied. Creep tests were performed under the effect of different stresses ranged from 17.8 to 26 MPa at the deformation temperatures 291, 303, 323 and 343 K. The transient creep parameters β and n were found to be markedly affected by the creep test conditions, T and σ . The parameter β was found to be decreased by increasing T and/or σ while n was found to increase by increasing T irrespective of the applied stress σ . The steady-state creep rate έ st was found to increase with increasing both T and σ in both solder alloys. The steady-state creep rate έ st was related to the stress σ with the relationship έ st  =  Cσ m where m  = (∂ln  έ st /∂ln  σ ) is the stress exponent. This exponent is decreased with increasing T in both alloys. Addition of 1.5 wt%Ag to the binary alloy increased its creep resistance. This behavior was attributed to the formation of the intermetallic compounds (IMCs) AgZn and Ag 3 Sn during solidification. These IMCs played the role of pinning action for the moving dislocations and consequently leading to the increase of its creep resistance. Micro-structural changes were investigated by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis.

[1]  Tao-Chih Chang,et al.  Effect of aging on the growth of intermetallic compounds at the interface of Sn–9Zn–xAg/Cu substrates , 2003 .

[2]  Creep behavior of eutectic Sn-Cu lead-free solder alloy , 2002 .

[3]  A. A. El-khalek.  The variation of work-hardening characteristics of Al–1 wt% Si and Al–1 wt% Si–0.1 wt% Zr–0.1 wt% Ti alloys , 2002 .

[4]  A. A. El-khalek,et al.  Effect of Cu additions on the structural and mechanical properties of Sn–Zn alloy , 2007 .

[5]  K. Suganuma.  The Development and Commercialization of Lead-Free Soldering , 2001 .

[6]  C. Thwaites,et al.  Tin and its alloys and compounds , 1983 .

[7]  G. S. Al-Ganainy,et al.  Effect of Phase Transformation on Creep Characteristics of Sn—5 wt% Bi Alloy , 1996 .

[8]  Effect of Zn addition on steady state creep characteristics of Sn–3·3Ag solder alloy , 2008 .

[9]  Min-Hsiung Hon,et al.  Phase transformation and morphology of the intermetallic compounds formed at the Sn–9Zn–3.5Ag/Cu interface in aging , 2008 .

[10]  Tao-Chih Chang,et al.  Electrochemical Behaviors of the Sn-9Zn-xAg Lead-Free Solders in a 3.5 wt % NaCl Solution , 2004 .

[11]  Sungho Jin,et al.  New, lead-free solders , 1994 .

[12]  J. W. Morris,et al.  Anomalous creep in Sn-rich solder joints , 2002 .

[13]  J. Jones,et al.  Effect of addition of molybdenum or niobium on creep-rupture properties of Fe_3Al , 1992 .

[14]  R. Ramanujan,et al.  Hot hardness and indentation creep studies of a Fe–28Al–3Cr–0.2C alloy , 2000 .

[15]  M. Hon,et al.  Microstructure and adhesion strength of Sn–9Zn–1.5Ag–xBi (x = 0 wt% and 2 wt%)/Cu after electrochemical polarization in a 3.5 wt% NaCl solution , 2008 .

[16]  A. Fawzy,et al.  Effect of silver addition on the creep parameters of Sn-7 wt.% Bi alloy during transformation , 2008 .

[17]  K. Suganuma,et al.  Oxidation behavior of Sn–Zn solders under high-temperature and high-humidity conditions , 2008 .

[18]  A. Fawzy.  Effect of Zn addition, strain rate and deformation temperature on the tensile properties of Sn–3.3 wt.% Ag solder alloy , 2007 .

[19]  R. Messler,et al.  Modelling the creep rates of eutectic Bi–Sn solder using the data from its constitutive phases , 1998 .

[20]  M. Otsuka,et al.  Effect of bismuth on the isothermal fatigue properties of Sn-3.5mass%Ag solder alloy , 1998 .