الفهرس 
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Abstract
Sn-Pb solder alloy for metal interconnections has a long history,
dating back 2000 years. These alloys are the dominant solders used
widely in manufacture because of their unique combination of material
properties, such as low cost, availability, low melting temperatures,
ductility and excellent wetting on Cu and its alloys. It is well known that
conventional Pb- containing solders are harmful to both people’s health
and environment, so the exploration of lead-free solders as substitute of
lead-tin alloys is paid more attention, especially with the arrival of
legislative restriction on the use of lead solders by European Union to
pass legislation prohibiting or restricting the use of Pb–Sn solders. The
lead-free solders used in electronic industry need to meet a series of
standards: good wettability, low melting point, low cost and adequate
strength. At present, a number of investigations have been carried out on
such promising lead-free solder alloys as Sn-Ag, Sn-Ag-Cu, Sn-Cu, Sn-
Zn, Sn-Bi and Sn-In. Among these alloys, the Sn-Ag-Cu system solder
becomes one of the most future solders because of its excellent wetting
and mechanical properties. However, it also has some disadvantages,
such as poor creep-rupture.
Minor alloying addition to solders has been an important strategy to
improve the integrity and reliability of Pb-free solders joint. In this study,
the effects of 0.06Ni and 0.5Sb additives on the microstructure and
solidification behavior as well as the creep and tensile properties of Sn–
1.0Ag–0.5Cu (SAC105) alloys were investigated. The microstructure was
examined by optical microscopy (OM), scanning electron microscopy
(SEM) and energy dispersive X-ray spectrometer (EDS). Phase
identification of the alloy samples was carried out by X ray
diffractometry (XRD). The basic features of thermal properties of the the
selected solder alloys have been studied by using the differential scanning
calorimetry (DSC). Tensile stress-strain and creep tests were performed at
constant temperatures 25, 70 and 110 ºC after waiting time of 5 min for
the test temperatures to determine the effect of Ni and Sb additions on the
mechanical properties of the examined alloy.
Results showed that the Ag3Sn, η-Cu6Sn5 IMC particles and the β-Sn
phase were detected in SAC (105) solder. Addition of Ni resuted in the
formation of Ni3Sn4 IMC, but no new IMCs are detected with the
addition of Sb to the SAC (105) solder alloy. Moreover, microstructural
analysis revealed that addition of both Ni and Sb refines the
microstructure of SAC (105) solder alloy.
The DSC results showed that melting temperature of SAC105
(226.0 oC) is slightly increased by 0.6 and 1.4 oC for the SAC105 doped
with .06wt% Ni and 0.5wt% Sb, respectively. The pasty range for
SAC105, SAC105 (0.06Ni) and SAC105 (0.5Sb) was 18.1, 16.6 and 18.1
oC, respectively. So, the pasty range also was slightly decreased or quite
similar to the lead-free SAC105 solder. In the onset-to onset method,
undercooling was 35.6, 26.4 and 26.8 oC for SAC105, SAC105 (0.06Ni)
and SAC105 (0.5Sb) solders, respectively.
It is known that, creep is an important deformation mechanism, which
must be analyzed in order to understand the reliability characteristics of
solder joints. In this study the steady state creep behavior of the three
solder alloys were also investigated under the effect of three different
ranges of stress (16.9 - 30.2, 16.3 - 20.5 and 13.9 - 18.1 MPa);. each
range was conducted at constant temperature of 25, 70 and 110 ºC,
respectively. The lead-free SAC105(0.5Sb) solder shows superior creep
performance over the other two solders in terms of the combination of
much higher creep resistance and vastly elongated creep fracture lifetime.
It was found that Sb and Ni are beneficial to improve the creep strength
of the SAC105 solder and could enhance its creep resistance due to solid
solution hardening of Sb and precipitation hardening of Ni3Sn4 IMC
reinforced SAC105 solder alloy. The activation energies (Q) of SAC 105,
SAC105 (0.06Ni) and SAC105 (0.5Sb) alloys are 40.7, 46.0 and 54.4
kJ/mol, respectively. As the temperature increases from 25 to 110 oC, the
stress exponent parameter (n) was decreased from 7.0 to 5.3, 8.4 to 6.4
and 9.3 to 7.2 for SAC105, SAC105 (0.06Ni), and SAC105 (0.5Sb)
alloys, respectively.
Typical tensile stress-strain tests for SAC105, SAC105 (0.06Ni) and
SAC105 (0.5Sb) solder alloys were performed under the effect of
different strain rates ranged from 8.8 x 10-4 to 1.02 x 10-2 s-1 at constant
temperatures of 25, 70 and 110 ºC to determine the effect of separate
addition of Ni and Sb contents on the mechanical properties of the
examined alloys as well as to determine the effect of strain rate on
strength of the tested solder alloy. The tensile tests revealed that all alloys
demonstrated an increase in both ultimate tensile strength (UTS) and
yield stress with increasing strain rate and/or decreasing testing
temperature, suggesting that the tensile behavior of the three alloys is
strain rate and temperature dependence. Alloying of Ni and Sb resulted in
an increase in both the yield and the ultimate tensile strength compared to
the original solder. The SAC105 (0.5Sb) alloy was found to have
surprising and good combination of high strength and ductility. Sb seems
to have dissolving effect on the Sn matrix and subsequently strengthens
the alloy by solid solution hardening.