i Abd Hamid

Characterization of Sn-3.5Ag-1.0Cu Lead-Free Solder Prepared via Powder Metallurgy Method

The toxicity in the Sn-Pb solder has promoted the development of Pb-free solder in the electronics industries. Among the Pb-solders, the Sn-3.5Ag-1.0Cu solder is considered a potential replacement and being studied by many researchers. In the present study, the characteristics of Sn-3.5Ag-1.0Cu lead-free solder were studied. The raw materials were tin, silver and copper powders in micron size. The solder was prepared using powder metallurgy route which includes blending, compacting and sintering. Four blending times and two compacting pressures were used to investigate for optimum condition. The melting temperature of the samples were studied using differential scanning calorimeter (DSC) and the presence of Sn Ag, Cu were confirmed using x-ray diffraction analysis (XRD). Finally the effect of variables on the hardness of the solders is reported.

Synthesis and Characterization of Strontium-Doped Lanthanum Cobaltite Cathode Material Prepared by a Modified Combined Complexing Method

A potential candidate for intermediate temperature solid oxide fuel cell (IT-SOFC) cathode material which is strontium-doped lanthanum cobaltite, La0.6Sr0.4CoO3-α (LSCO) has been synthesized by a complexing method. Citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) were used as a combined chelating agent and ethylene glycol (EG) was employed as surfactant. The obtained powder was characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). TGA results showed the thermal decomposition of the precursor gel was completed at 700 °C. A single perovskite phase of LSCO with cubic structure was obtained at calcination temperature of 1000 °C with heating/cooling rate of 10 °C min-1 as confirmed by XRD analysis. SEM result revealed that the morphology of the powder was spherical in shape with diameter ranging from 250 to 650 nm. Apparently, the bulk sample consists of almost homogeneous and identical particles.

Intermetallic Evolution of Sn-3.5Ag-1.0Cu-0.1Zn/Cu Interface under Thermal Aging

Due to environmental concerns, lead-free solders were introduced in replacing the lead-based solders in microelectronics devices technology. Although there are many lead-free solder available, the Sn-Ag-Cu is considered the best choice. But the solder has its draw backs in terms of melting temperature and intermetallic formations. To improve the solder, a fourth element Zn was added into the solder. The new composite solders were synthesized via powder metallurgy route. This research studies the effect of 0.1wt% Zn addition on the hardness and intermetallic formation on Cu substrate. For the hardness results, the micro Vickers values were reported. For intermetallic, the solders were melted at 250°C and aged at 150°C until 400 hours. The microhardness value for Zn based composites solder shows higher micro Vickers hardness compared to un-doped counterparts. The phases formed and its growth was studied under SEM and by energy dispensive x-ray (EDX). The SEM results show the presence of Cu6Sn5 and Cu3Sn intermetallics and the Cu5Zn8 intermetallic was not detected. The addition of 0.1wt% Zn has retarded the growth of the Cu3Sn intermetallic but not the total intermetallic thickness.

Effect of Ag addition on the intermetallic compound and joint strength between Sn-Zn-Bi lead free solder and copper substrate

This study investigated the effect of Ag addition on the formation of intermetallic compounds and joint strength of the Sn-Zn-Bi based alloys under liquid state aging. The intermetallic compounds were formed by reacting Sn-8Zn-3Bi and (Sn-8Zn-3Bi)-1Ag lead free solders on copper substrate. Scanning electron microscope (SEM) was used to see the morphology of the phases and energy dispersive x-ray (EDX) was used to estimate the elemental compositions of the phases. It was found that for Sn-8Zn-3Bi solder reacting with Cu substrate, the Cu₅Zn₈ intermetallic was formed. On the other hand, when 1% Ag was added into the solder, the Cu₃Sn and Cu₆Sn₅ IMC were formed. The morphology of the Cu₅Zn₈ intermetallic was flat whereas for Cu₃Sn and Cu₆Sn₅ were rather scallop. The addition of Ag into the Sn-Zn-Bi solder increases the shear strength of the solder joint. It is believed the scallop morphology of Cu-Sn contribute to strengthening the (Sn-8Zn-3Bi)-1Ag/Cu joints.

Intermetallic evolution between Sn-3.5Ag-1.0Cu-xZn lead free solder and copper substrate under long time thermal aging (x: 0, 0.1, 0.4, 0.7)

Due to environmental concern regarding toxicity of lead-based solder, the lead-free solders were introduced as a replacing solder in microelectronics devices technology. In this study, the effects of 0.1, 0.4 and 0.7 wt% Zn additions on the intermetallic formation and thickness of Sn-3.5Ag-1.0Cu solder on Cu substrate after long time aging were investigated. The X-Ray Diffraction (XRD) analysis shown that there were Cu6Sn5, Cu3Sn, β-Sn, CuZn and Ag3Sn phase formed after sintering process. The morphology of the intermetallic was observed under Scanning Electron Microscope (SEM) and the elemental distribution was confirmed by Energy Dispersive X-ray (EDX). The intermetallic thickness increases as the aging temperature increases while the addition of zinc into the system has suppressed the intermetallic formation.