Papers by Keyword: Lead-Free

Abstract: The properties of modified Bi_0.5Na_0.5TiO₃ (BNT) based lead-free ceramics were investigated. The BNT-based ceramics were prepared by a solid-state mixed oxide method Phase formation was determined by X-ray diffraction technique (XRD). The X-ray diffraction analysis of the ceramics suggested that all samples exhibited a perovskite structure without second phase. The value of dielectric constant increased with increasing in sintering temperature. Moreover, high sintering temperatures could improve ferroelectric properties of BNT base lead-free ceramics.

Abstract: In this research, the effects of bismuth zinc zirconate (BZZ) additive on phase formation, microstructural and mechanical properties of bismuth sodium potassium titanate (BNKT) ceramics were investigated. The BZZ-doped BNKT ceramics were prepared using solid state reaction technique. The pure phase of BZZ-doped BNKT powders were achieved for a calcinations temperature of 850 °C for 4h. The obtained powders were pressed into small pellets and sintered at optimum temperature to from dense ceramics. The XRD analysis of the ceramics shows that all ceramic samples exhibited a pure phase perovskite structure. The bulk densities of samples were about 5.82-6.03 g/cm³ which measured using the Archimedes method. The mechanical properties were measured using micro hardness tester. The microstructural of sintered surface was investigated using scanning electron microscopy (SEM). Average grain size increased with increasing BZZ content. The relations of these results were discussed and compared to the previous works.

Abstract: In this research, the physical and electrical properties of 0.8K_0.5Na_0.5NbO₃-0.2Ba_0.5Ca_0.5Zr_0.5Ti_0.5O₃ (0.8KNN-0.2BCZT) were characterized. Lead-free material, 0.8KNN-0.2BCZT with and without alkaline excess was synthesized via solid state reaction method. KNN and BCZT were calcined at 700°C and 1200°C for 2 hours respectively and mixed by planetary milling. The mixed powder was recalcined at 1250°C for an hour then sintered at 1150°C, 1200°C and 1250°C for 2 and 4 hours. XRD analysis of 0.8KNN-0.2BCZT for excessive (8% Na, 2% K) sample sintered at 1150°C for 4 hours has single phase showing ABO₃ structure (A=K, Na, Ba, Ca and B=Ti, Zr, Nb) and multi phases for the other ones. The microstructure analysis (SEM) showed cubic-like grain shape in which excessive sample possessed greater average grain size than other. Dielectric properties and Curie temperature of single phase sample in this research were higher than those of pure KNN. The conductivity analysis reveals two regimes. The first regime (<300°C) showed no significant role of BCZT in KNN and the second one (>300°C) showed that BCZT increased conductivity of KNN and factor dissipation as well.

Abstract: This research has investigated the properties of low-silver Sn-1.0Ag-0.7Cu (SAC107) alloy. Different weight percentages (0, 0.25, 0.5, 0.75 and 1 wt. %) of silicon nitride (Si₃N₄) were used as reinforcement particles. The SAC107 - Si₃N₄ composite solder was fabricated via powder metallurgy (PM) technique. The results showed that homogeneous distribution of Si₃N₄ particles along the grain boundaries has increased the hardness of the SAC107 - Si₃N₄ composite solders compared to monolithic SAC107 solder alloy. The melting temperature is maintained at the SAC107 level, indicating that the novel composite solder is suitable for existing soldering process.

Abstract: The effect of Si particulate addition on the commercial Sn-Cu-Ni solder system (SN100C) solder alloy has been investigated. The SN100C/Si composite solder was fabricated via powder metallurgy (PM) technique. In this study five different Si composition chosen were (0 wt. %, 0.25 wt. %, 0.5 wt. %, 0.75 wt. %, and 1.0 wt. %). The results indicated that adding a small amount of Si particulate can slightly improve the physical properties of the composite solder compared to monolithic solder alloy. Microstructural analysis revealed the reinforcement seen well distributed between the grains boundaries with additions of 1.0 wt. % resulted with highest hardness value.

Abstract: This research has investigated the solder performances of Sn-0.7Cu lead-free solder reinforced with silicon nitride (Si₃N₄). The Sn-0.7Cu + Si₃N₄ composite solder were fabricated via powder metallurgy (PM) technique with five different weight percentages (0, 0.25, 0.5, 0.75 and 1.0). Results showed that distribution of Si₃N₄ along the grain boundaries has increased the hardness of the Sn-0.7Cu + Si₃N₄ composite solders compared to monolithic Sn-0.7Cu solder alloy. Addition of Si₃N₄ reinforcement had no significant effect to the melting temperature of the solder. Overall, the entire range of Sn-0.7Cu + Si₃N₄ composition greatly improves the microhardness of the eutectic solder.

Abstract: The effect of micron-size silicon nitride (Si₃N₄) particles additions, up to 1.0 wt. % on Sn-Cu-Ni (SN100C) solder alloy was investigated. Sn-Cu-Ni composite solder were prepared via powder metallurgy (PM) technique. Different percentages of Si₃N₄ (0, 0.25, 0.5, 0.75 and 1.0 wt. %) were added into the alloy. Result revealed that reinforcement was well distributed between the grain boundaries which could positively affect the properties of the composite solder.

Abstract: Composite solder has drawn attention improvement in microstructural modification and mechanical properties. This research was done to investigate the influence of activated carbon (AC) particulate on the commercial Sn-Cu-Ni solder system (SN100C) solder alloy. The SN100C+AC composite solder was fabricated via powder metallurgy (PM) technique. In this study, five different AC compositions were chosen; (0, 0.25, 0.5, 0.75 and 1.0 wt. %. This study has shown that composite solder has better properties compared to the monolithic solder alloy. A small amount of AC particulate had improved the physical properties of the composite solder. Microstructural analysis showed that the reinforcement was well distributed along the grain boundaries and no significant influence on the melting point of SN100C. Apart from that, 1.0 wt. % of AC additions results with the highest hardness value compared to the other composition.

Abstract: The research on a new low-Ag lead-free solder has become a hot spot in the field of electronic packaging. In this work, the effects of Bi addition on microstructure, melting temperature, wettability of low-Ag solder, shear strength of solder joint and the growth of interfacial intermetallic compound (IMC) before and after thermal cycling were investigated. A moderate amount of Bi element resulted in the microstructural refinement and melting temperature reduction of Sn-0.2Ag-0.7Cu solder. Wetting test results showed that a small amount of Bi produced the significant effect on improving the wettability. In addition, it is shown that the thickness of interfacial IMC during thermal cycling decreased first and then increased; the shear strength of solder joint increased with the increase of Bi.

Abstract: Submicron-structured (Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ (BNBT6) dense ceramics, from nanometric powder synthesized by sol gel auto-combustion at 500°C and obtained by hot-pressing (800°C-2h) and subsequent recrystallization at moderate temperature (1000-1050°C-1h), have been studied. In-situ measurements at the shear mode of electromechanical resonance of non-standard thickness-poled shear plates as a function of the temperature show higher depolarization temperature than measurements at the radial mode of thin disks. Shear mode related material coefficients are measurable up to 160°C, being k₁₅≈30% and d₁₅≈250 pC.N^-1 at 130°C. Depolarization is a complex phenomena caused by a ferroelectric (FE) macrodomains thermal randomization and a phase transition from the field-induced FE phase to a relaxor phase. The early stage of such a transition involves a non-negligible piezoelectricity arising most probably by the percolative coexistence of ferroelectric macrodomains in the resonator under the given stress field for each resonance mode.