Effect of Adding Indium on Wetting Behavior, Microstructure and Physical Properties of Tin- Zinc Eutectic Alloy

International Journal of Science and Engineering Applications
Volume 4 Issue 4, 2015, ISSN-2319-7560 (Online)
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Effect of Adding Indium on Wetting Behavior, Microstructure
and Physical Properties of Tin- Zinc Eutectic Alloy
Abu Bakr El- Bediwi
Metal Physics Lab.,
Physics Department,
Faculty of Science,
Mansoura University
Mansoura, Egypt
Mohammed Munther
Jubair
Ministry of Education
Iraq
Rizk Mostafa Shalaby
Metal Physics Lab.,
Physics Department,
Faculty of Science,
Mansoura University
Mansoura, Egypt
Mustafa Kamal
Metal Physics Lab.,
Physics Department,
Faculty of Science,
Mansoura University
Mansoura, Egypt
Abstract: Effect of adding indium on microstructure, wetting process, thermal, electrical and mechanical properties of tin- zinc eutectic alloy
have been investigated. Microstructure (started base line, lattice parameters, unit cell volume, crystal size and the shape of formed crystalline
phases) and measured physical properties of tin- zinc eutectic alloy changed after adding different ratio of indium content. A little variation
occurred in thermo-graph (Endo-thermal peaks) of Sn91Zn9 alloy after adding indium. The contact angle, melting temperature and specific heat of
Sn91Zn9 alloy decreased after adding indium content. Also elastic modulus and internal friction values of Sn91Zn9 alloy decreased after adding
indium content. But electrical resistivity and Vickers hardness values of Sn91Zn9 alloy increased after adding indium content. The SnZn9In5 alloy
has adequate properties for solder applications.
Key words: tin- zinc eutectic alloy, thermal and mechanical properties, electrical resistivity, wetting process
1. INTRODUCTION
Over the past few years the study of lead free solder has
become a hot subject. New lead free solder alloy has great attention
from researchers around the world. Lead free solders fall into two
groups: first has lower melting points and chiefly includes alloys of tin
and bismuth. Second is group of alloys, those with higher melting
points than tin-lead. The leading choice seems to be a tin-silver-copper
alloy. There is a tin-rich ternary eutectic at about 217 °C. These alloys
at 30 °C higher melting point are a challenge to use. Sn-Zn solder
alloys are quite capable in terms of mechanical integrity but have poor
oxidation and corrosion resistance. Many studies have been made on
various alloy system solders based on Sn such as SnZn9, SnAg3.5,
SnAg3Cu0.5, etc. as possible replacements [1, 2]. T. Ohoak et al
investigated the dependence of frequency over a range of 0-3 Hz on
Young’s modulus and internal friction in SnZn9 and SnAg3.5 eutectic
lead free solder alloys [3[. Several researchers [4- 7] operated to
improve the properties of Sn-Zn lead free alloy by adding small
amount of alloying elements such as Bi, Cu, In, Ag, Al, Ga, Sb, Cr, Ni,
Ge to develop ternary and even quaternary Pb free alloys. The
microstructures of the tin- zinc- aluminum lead free solder alloys,
which prepared from the Zn-5Al master alloy and Sn, using scanning
electron microscopy were investigated [8]. The microstructures and
mechanical properties of SnZn8.55AgxAl0.45Ga0.5 (x= 0.5-3 wt. %) lead
free solder alloys were studied [9]. Small additions of Ag decreased
the melting point of the SnZn8.55AgxAl0.45Ga0.5 solder alloys while
maintaining the same strength and ductility as the Sn63b37 solder alloy.
The effects of adding alloying elements such as Ag, Al, and Ga, on
melting temperature, microstructures and mechanical properties of the
SnZn9 lead free solder alloy were studied [10]. The results show,
SnZn9Ga0.5 alloy has very good UTS and elongation, which are better
than both those of the SnZn9Ag0.5 and SnZn9Al0.45 alloys. Also effect
of adding Al and Cu on microstructural and mechanical properties as
well as thermal behavior of SnZn9 lead free solder alloy was
investigated [11]. The results indicate the microhardness of the
SnZn9Al0.5 alloy was also higher than that of the SnZn9Cu0.5 alloy.
Tin- zinc is desired to have a lead free solder with a melting
temperature close to the eutectic temperature of the tin- lead alloy.
Aluminum has a high melting temperature and good electrical
conductivity. It may form solid solutions with tin and zinc. . So that,
adding aluminum to tin- zinc solder alloy retain the melting point as
low as possible but the soldering temperature higher than that eutectic
tin- lead alloy. The aim of this work was to investigate the effect of
adding different ratio from indium on microstructure, wetting
behavior, thermal, electrical and mechanical properties of tin- zinc
eutectic lead free solder alloy.
2. EXPERIMENTAL WORK
The alloys Sn91-xZn9Inx (X=0, 1, 2, 3, 4 and 5 wt. %) which
used tin, zinc and indium elements with a high purity, more than
99.95%, were molten in the muffle furnace. The resulting ingots were
turned and re-melted several times to increase the homogeneity of the
ingots. From these ingots, long ribbons of about 3-5 mm width and ~
80 m thickness were prepared as the test samples by directing a
stream of molten alloy onto the outer surface of rapidly revolving
copper roller with surface velocity 31 m/s giving a cooling rate of 3.7
× 105
k/s. The samples then cut into convenient shape for the
measurements using double knife cuter. Structure of used alloys was
performed using an Shimadzu x–ray diffractometer (Dx–30, Japan) of
Cu–K radiation with =1.54056 Å at 45 kV and 35 mA and Ni–filter
in the angular range 2 ranging from 20 to 100° in continuous mode
with a scan speed 5 deg/min. Scanning electron microscope JEOL
JSM-6510LV, Japan was used to study microstructure of used
samples. The melting endotherms of used alloys were obtained using
a SDT Q600 V20.9 Build 20 instrument. A digital Vickers micro-
hardness tester, (Model-FM-7- Japan), was used to measure Vickers
hardness values of used alloys. Internal friction Q-1
and the elastic
constants of used alloys were determined using the dynamic resonance
method [12- 14].

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3. RESULTS AND DISCUSSIONS
Microstructure
X-ray diffraction patterns of Sn91-xZn9Inx (x= 0, 1, 2, 3, 4, 5
wt. %) rapidly solidified alloys show that sharp lines of body centered
tetragonal Sn and hexagonal Zn phases as presented in Figure 1. From
x-ray analysis, adding In content to SnZn9 alloy produced a change in
its matrix microstructure (lattice parameters, unit cell volume and
crystal size) and the shape of formed phases such as peak intensity,
peak broadness and peak position. That is because In atoms dissolved
in Sn91Zn9 matrix formed a solid solutionor and some In atoms formed
a traces of undetected phases (In or In intermetallic phases). Also the
calculated lattice parameters, (a and c), unit volume cell and crystal
size of tetragonal tin phase in Sn91-xZn9Inx (x= 0, 1, 2, 3, 4, 5 wt. %)
alloys are listed in Table 1. The results illustrated that, adding In
content to Sn91Zn9 alloy caused a little variation in lattice parameters
and unit cell volume with a significant variation in crystal size of
tetragonal tin phase of Sn91Zn9 alloy after adding In content.
Figure 1:- x-ray diffraction patterns of Sn91-xZn9Inx alloys
Table 1:-lattice parameters, unit cell volume and crystal particle
size of β-Sn in Sn91-xZn9Inx alloys
Samples a Å c Ǻ V Å3
 Å
SnZn9 5.82 3.183 107.83 681.943
SnZn9In1 5.801 3.182 107.11 454.054
SnZn9In2 5.805 3.188 107.45 465.097
SnZn9In3 5.814 3.189 107.78 707.90
SnZn9In4 5.812 3.189 107.70 593.691
SnZn9In5 5.821 3.180 107.76 658.568

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Scanning electron micrographs, SEM, of Sn91-xZn9Inx (x= 0, 1, 2, 3, 4,
5 wt. %) alloys show heterogeneous structure (different features) as
seen in Figure 2 and it's agreed with x-ray analysis.
.
Figure 2:- SEM of Sn91-xZn9Inx alloys
Soldering properties
Wettability
Wettability is quantitatively evaluated by the contact angle
formed at the solder substrate’s flux triple point. The contact angles
of Sn91-xZn9Inx (x= 0, 1, 2, 3, 4, 5 wt. %) alloys on Cu substrate in air
are shown in Table 2. The results show that, the contact angle of
Sn91Zn9 alloy is variable decreased after adding In content. The
Sn86Zn9In5 alloy has low contact angle value and also adequate for
solder applications.
Table 2:-contact angles of Sn91-xZn9Inx alloys
Samples Contact angle (°)
SnZn9 46
SnZn9In1 42.5
SnZn9In2 45.75
SnZn9In3 45
SnZn9In4 42
SnZn9In5 38.25

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Thermal properties
The amounts of thermal properties depend on the nature of
solid phase and on its temperature. The DSC thermographs were
achieved with heating rate 10 C /min in the temperature range 0- 400
C. The DSC thermographs of Sn91-xZn9Inx (x= 0, 1, 2, 3, 4, 5 wt. %)
alloys are shown in Figure 3. From these graphs the melting point,
pasty range and other thermal parameters (specific heat, Cp, enthalpy,
ΔH, entropy, ΔS) of Sn91-xZn9Inx (x= 0, 1, 2, 3, 4, 5 wt. %) alloys are
identified and then listed in Table 3. A little variation occurred in
thermo-graph (Endo-thermal peaks) of Sn91Zn9 alloy after adding
indium. That is because In atoms dissolved in matrix alloy changed
its structure and that is agreed with x-ray diffraction analysis. The
melting temperature of Sn91Zn9 alloy decreased after adding indium
content. Also the pasty range and other thermal parameters of Sn91Zn9
alloy varied after adding indium content.
Figure 3:- DSC graphs of Sn91-xZn9Alx alloys
Table 3:- melting point and other thermal parameters of
Sn91-xZn9Alx alloys
Samples Melting
point ºK
CP
J/g. ºK
∆ S
J/g. ºK
ΔH
J/g
SnZn9 471.43 2.716 130.772 62.40
SnZn9In1 469.13 2.558 130.155 61.81
SnZn9In2 465.89 2.45 139.889 65.97
SnZn9In3 463.12 2.46 127.025 59.91
SnZn9In4 462.17 2.392 127.256 59.80
SnZn9In5 460.37 2.271 151.858 71.45

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Electrical resistivity
Crystalline imperfections and plastic deformation
raises the electrical resistivity as a result of the increased
number of electron scattering centers. The measured electrical
resistivity of Sn91-xZn9Inx (x= 0, 1, 2, 3, 4, 5 wt. %) alloys at
room temperature using double bridge method are shown in
Table 4. Electrical resistivity of Sn91Zn9 alloy variable
increased after adding indium content. That is because indium
atoms dissolved in the Sn91Zn9 matrix, formed solid
solution/or and some traces, played as scattering center for
conduction electrons increased electrical resistivity value.
Table 4:- electrical resistivity of
Sn91-xZn9Inx alloys
ρx10-8
Ω.mSamples
33.65SnZn9
35.6SnZn9In1
39.94SnZn9In2
40.83SnZn9In3
38.27SnZn9In4
39.39SnZn9In5
Mechanical properties
Elastic moduli
The elastic constants are directly related to atomic bonding
and structure. It is also related to the atomic density. The measured
elastic modulus and calculated bulk modulus, B, and shear modulus,
, of Sn91-xZn9Inx (x= 0, 1, 2, 3, 4, 5 wt. %) alloys are listed in Table
5. Elastic modulus value of Sn91Zn9 alloy is variable decreased after
adding indium content as shown in Table 5. That is because the
dissolved indium atoms, formed solid solution or stick on grain
boundary/ or formed small cluster from phases in Sn91Zn9 matrix,
affected on bond matrix strengthens.
Internal friction and thermal diffusivity
Internal friction is a useful tool for the study of structural
aspects of alloys. Resonance curves of Sn91-xZn9Inx (x= 0, 1, 2, 3, 4, 5
wt. %) alloys are shown in Figure 4 and the calculated internal friction
values are presented in Table 5. Also from resonance frequency at
which the peak damping occur using the dynamic resonance method
the thermal diffusivity value was calculated and then listed in Table 5.
The results show that, internal friction value of Sn91Zn9 alloy is
variable decreased by adding indium content.
.
Table 5:- elastic moduli, internal friction and thermal diffusivity
of Sn91-xZn9Inx alloys
Samples E GPa µ
GPa
B
GPa
Q-1
Dth x10-7
m2
sec
SnZn9 44.34±3.1 16.42 49.30 0.085 4.476
SnZn9In1 30.75±1.2 11.39 34.05 0.052 3.392
SnZn9In2 29.53±1.2 10.95 32.57 0.054 2.947
SnZn9In3 33.04±2.1 12.25 36.3 0.081 3.484
SnZn9In4 32.9±2.19 12.20 35.99 0.057 2.773
SnZn9In5 30.09±1.6 11.17 32.80 0.059 2.316
Figure 4:- resonance curves of Sn91-xZn9Alx alloys
Vickers microhardness and minimum shear stress
The hardness is the property of material, which gives it the
ability to resist being permanently deformed when a load is applied.
The greater of material hardness is the greatest of the resistance to
deformation. The Vickers hardness number of Sn91-xZn9Inx (x= 0, 1,
2, 3, 4, 5 wt. %) alloys at 10 gram force and indentation time 5 sec are
shown in Table 6. Also calculated minimum shear stress of Sn91-
xZn9Inx (x= 0, 1, 2, 3, 4, 5 wt. %) alloys are listed in Table 6. Vickers
hardness value of Sn91Zn9 alloy is variable increased by adding indium
content.
Table 6:- Vickers hardness and minimum shear stress of
Sn91-xZn9Inx alloys
µn kg/mm2
Hv kg/mm2
Alloys
7.50822.75±1.1SnZn9
7.76623.53±1SnZn9In1
9.17427.8±1.23SnZn9In2
10.13130.7±1.9SnZn9In3
8.70126.37±1.2SnZn9In4
12.14936.82±2.5SnZn9In5
4. CONCLUSIONS
1. Adding indium content to SnZn9 alloy produced a change
in its matrix microstructure (lattice parameters, unit cell
volume and crystal size) and the shape of formed phases
2. The contact angle, melting temperature, elastic modulus and
internal friction values of SnZn9 alloy are variable decreased
after adding indium content. The SnZn9In5 alloy has low
contact angle and melting point values.
3. The electrical resistivity and Vickers hardness values of
SnZn9 alloy are variable increased after adding indium
content.
4. The SnZn9In5 alloy has adequate properties for solder
applications
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Effect of Adding Indium on Wetting Behavior, Microstructure and Physical Properties of Tin- Zinc Eutectic Alloy

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Effect of Adding Indium on Wetting Behavior, Microstructure and Physical Properties of Tin- Zinc Eutectic Alloy