الفهرس 
Introduction And Literature ReviewOnly 14 pages are availabe for public view
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Abstract
because of the understanding of the harmful effect of lead and lead containing alloys on the environment and human health, many Pb-free solder-alloys have been developed to replace Sn-Pb solders in electronic applications. The European community, US Environmental Protection Agency (EPA), and electronics industries have started initiatives to diminish lead usage. Many lead-free solders have been studied as replacements for Sn–Pb solders. The lead-free solders used in electronic industry should meet a series of standards: good wettability, low melting point, low cost and adequate strength. At the present time, 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.
The present work mainly aims to:
1. Prepare non-toxic and cheap solder alloys based on Sn-Zn alloy.
2. Improve its wetting behaviour and corrosion resistance by decreasing Zn-content.
3. Decrease its melting temperature by adding In as the ternary element.
So, Sn-6.5Zn-3In alloy has been choosen as the based alloy in this work. Additionally, ZnO was added to this alloy for improving its mechanical properties.
Summery
119
The present work mainly covers studying the effect of adding ZnO nano-particles on the structural, thermal and tensile properties of Sn- 6.5 wt% Zn - 3 wt% In (SZI653) solder alloy.
Thermal analysis and microstructure evolutions of both the plain SZI653 and SZI653–0.3 wt% nano-sized ZnO composite solders were discussed. Thermal properties of these solder alloys have been studied by using the differential scanning calorimetry (DSC). The microstructure was examined by 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 results showed that the observed endothermic peak of the SZI653 plain solder was found shifted from 194.06 to 194.72 oC for SZI653 composite solder. So, the melting temperature of the SZI653 composite solder was found slightly higher than that of the plain SZI653 solder by about 0.6 oC. Microstructural analysis discovered that β-Sn ,α-Zn and In3Sn IMCs were detected in both SZI653 plain and SZI653 composite solders. The addition of 0.3 wt% ZnO nano-particles refined β-Sn and In3Sn IMCs which distributed within the eutectic regions, because these nanoparticles act as pinning centers which inhibited the mobility of dislocation that concentrated around grain boundaries.
Tensile creep tests of the SZI653 plain and SZI653 composite solder were carried out at the temperatures ranging from 20 to 110 oC under the effect of different applied stresses ranged from 9.1 to 18.1 MPa.
Summery
120
It can be noticed that isothermal creep curves of both solders showed a monotonic shift towards higher strains and lower fracture times with increasing testing temperature and/or applied stress. In addition, the level of creep strain for SZI653 composite is generally lower than that of SZI653 plain solder under the same testing conditions. Creep parameters were found to be increased with increasing temperature and the addition of ZnO nanoparticles. It is also seen that under the same test conditions SZI653 composite solder yields low minimum (steady state) creep rate ε•st and high creep life time compared with those of the SZI653 plain solder. This can be rendered to the decrease of the grain sizes in the composite solder compared with those in the SZI653 and the finer microstructure of the In3Sn IMCs. The obtained activation energy Q was found to be 0.46 and 0.41 eV for the SZI653 plain and composite solders respectively. These values suggest that the creep process is controlled by grain boundary sliding or migration mechanisms.
Stress-strain tests for SZI653 plain and SZI653 composite solder alloys were performed under the effect of different strain rates ε• ranged from 1.33 x 10-3 to 1.611x 10-2 s-1 at different testing temperatures ranging from 35 to 110 oC. The results showed that increasing strain rates or decreasing the testing temperatures with the existence of the nano-sized ZnO particles resulted in increasing the work hardening parameter (WHP) ultimate tensile stress UTS, yield stress y and modulus of elasticity Y. The activation energy Q of 37.2 kJ/mol is obtained for SZI653 plain and of 45.8 kJ/mol for SZI653 composite solder alloys. These values were found to be close to those reported for the dislocation motion mechanism in Sn-based alloys.