Abstract
The microstructure and micro-hardness of Sn-3.5wt.5%Ag, Sn-3.5wt.%Ag-0.27wt.%Ti and Sn-3.5wt.%Ag-0.27wt.%Cd treated at 75, 100, 125 and 150oC were studied. The microstructure characteristics of the tested alloys had been investigated using optical microscope (OM), scanning electron microscope (SEM) and x-ray diffraction (XRD). The impression creep had been carried out using Vickers micro-hardness indenter under different loads (10, 50 and 100gm). The stress exponent values were found to be varied from 3.2 to 8.4. The energy activating the creep processes support dislocation climb as the rate controlling mechanism. The dislocation mobility was restricted due to the agglomerations of the Ag3Sn eutectic phase in the above three solders. Whereas; the presence of the twinning of ?-Sn phase, and the dispersion of fine CdSn1.9 IMCs throughout Sn-3.5wt.%Ag-0.27wt.%Cd made strongly blockage of the dislocation motion.
Highlights
A global movement away from using lead in the manufacture of industrial parts had led researchers to develop new lead-free solders [1,2,3]
Since the properties of the binary Pb-free solders cannot fully meet the requirements for applications in electronic and packaging; additional alloying elements were added to improve the performance of the lead-free solder alloys
The present work is devoted to study (i) the effect of aging temperatures on the eutectic SnAg specimens ranging from 75°C to 150°C and cooled in a switched off furnace to room temperature, (ii) the characterization of separate minor additions of Ti and/ or Cd on the indentation creep behavior of eutectic Sn3.5Ag lead-free solder alloys by measuring creep exponent n and activation energies Q, (iii) comparison with the previous work is given
Summary
A global movement away from using lead in the manufacture of industrial parts had led researchers to develop new lead-free solders [1,2,3]. Shen Jun et al [32] studied the effect of cooling rates on microstructure and micro-hardness of Sn-3 5%Ag leadfree solder alloys They found that the hardness of Ag3Sn eutectic phase formed in furnace-cooled specimen is about three or four times larger than that of the investigated solders solidified under different cooling conditions. The present work is devoted to study (i) the effect of aging temperatures on the eutectic SnAg specimens ranging from 75°C to 150°C and cooled in a switched off furnace to room temperature, (ii) the characterization of separate minor additions of Ti and/ or Cd on the indentation creep behavior of eutectic Sn3.5Ag lead-free solder alloys by measuring creep exponent n and activation energies Q, (iii) comparison with the previous work is given. To estimate the activation energy, the variation of minimum creep rate in terms of 1000/T are drawn at different loads and alloys [40]
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