Changdong Zou

Size-dependent melting properties of Sn nanoparticles by chemical reduction synthesis

Tin nanoparticles with different size distribution were synthesized using chemical reduction method by applying NaBH4 as reduction agent. The Sn nanoparticles smaller than 100 nm were less agglomerated and no obviously oxidized. The melting properties of these synthesized nanoparticles were studied by differential scanning calorimetry. The melting temperatures of Sn nanoparticles in diameter of 81, 40, 36 and 34 nm were 226.1, 221.8, 221.1 and 219.5 ℃, respectively. The size-dependent melting temperature and size-dependent latent heat of fusion have been observed. The size-dependent melting properties of tin nanoparticles in this study were also comparatively analyzed by employing different size-dependent theoretical melting models and the differences between these models were discussed. The results show that the experimental data are in accordance with the LSM model and SPI model, and the LSM model gives the better understanding for the melting property of the Sn nanoparticles.

Preparation Techniques and Characterization for Sn-3.0Ag-0.5Cu Nanopowders

Nanopowders of Sn-3.0Ag-0.5Cu (wt.%) alloy, which has the promising potential applications in microelectronics packaging as the lead free solder, were prepared under the protection of three various coolants. The oxidation of the nanopowders was measured by X-ray diffraction (XRD) and other relative methods to compare the protection of the nanopowders during their preparation. Moreover, the scanning electron microscope (SEM) was employed to measure the morphology and size of these nanopowders. It was observed that the Sn-based nanopowders were almost spherical in shape. In addition, the results showed that nearly the total powders are smaller than 100 nm.

Size control and its mechanism of SnAg nanoparticles

Abstract Sn3.5Ag (mass fraction, %) nanoparticles were synthesized by an improved chemical reduction method at room temperature. 1,10-phenanthroline and sodium borohydride were selected as the surfactant and reducing agent, respectively. It was found that no obvious oxidation of the synthesized nanoparticles was traced by X-ray diffraction. In addition, the results show that the density of primary particles decreases with decreasing the addition rate of the reducing agent. Moreover, the slight particle agglomeration and slow secondary particle growth can result in small-sized nanoparticles. Meanwhile, the effect of surfactant concentration on the particle size can effectively be controlled when the reducing agent is added into the precursor at an appropriate rate. In summary, the capping effect caused by the surfactant molecules coordinating with the nanoclusters will restrict the growth of the nanoparticles. The larger the mass ratio of the surfactant to the precursor is, the smaller the particle size is.

Investigating the formation process of sn-based lead-free nanoparticles with a chemical reduction method

Nanoparticles of a promising lead-free solder alloy (Sn3.5Ag (wt.%, SnAg) and Sn3.0Ag0.5Cu (wt.%, SAC)) were synthesized through a chemical reduction method by using anhydrous ethanol and 1,10-phenanthroline as the solvent and surfactant, respectively. To illustrate the formation process of Sn-Ag alloy based nanoparticles during the reaction, X-ray diffraction (XRD) was used to investigate the phases of the samples in relation to the reaction time. Different nucleation and growth mechanisms were compared on the formation process of the synthesized nanoparticles. The XRD results revealed different reaction process compared with other researchers. There weremany contributing factors to the difference in the examples found in the literature, with themain focus on the formation mechanism of crystal nuclei, the solubility and ionizability of metal salts in the solvent, the solid solubility of Cu in Ag nuclei, and the role of surfactant on the growth process. This study will help define the parameters necessary for the control of both the composition and size of the nanoparticles.

Recent advances in the synthesis of lead-free solder nanoparticle

Particles in the nano-meter size range present extraordinary properties, such as, large surface area per unit volume, large surface energy, low melting point, supermagnetism, self-purification and quantum size effects. These properties have attracted the attention of scientific and technological communities al over the world.In the area of electronics production, one major disadvantage of conventional lead-free solders is their relatively high melting temperatures. Higher melting temperatures result in higher reflow temperatures which in turn result in stress build-up and other defects occurring during reflow. The possibility to lower the melting temperature of solder alloys and to improve the mechanical properties of solder joints by decreasing the particle size to the nanometer range, has therefore, offered a potential solution to these problems. Nanoparticles of different solder alloys have, therefore, been manufactured using both top-down and bottom-up techniques. This paper presents the latest developments in the area of lead-free solder nanoparticles manufacturing. Both the manufacturing and characterization of solder nanoparticles are covered. This paper does not include, however, applications of such nanoparticles. Both work performed in our group and in other research groups, from all over the world, is included, and the results discussed.

Role of reactant concentration in size control of SnAgCu nanoparticles

Abstract Attributing to the melting temperature depressing resulted from the size effect of nanoparticles, the SnAgCu alloy system can be a promising candidate to replace the traditional toxic SnPb solder in the field of electronic packaging. Chemical reduction method was used to fabricate the Sn3.0Ag0.5Cu (SAC) (mass fraction, %) alloy nanoparticles. Sodium borohydride and 1,10-phenanthroline were chosen as the reducing agent and surfactant respectively. In addition, the morphology of the synthesized nanoparticles was investigated by field emission scanning electron microscopy (FE-SEM), and the size distribution of the as-prepared particles was obtained from the image analysis. It was found that the particle size increased with increasing the reactant concentration. Finally, theoretical analysis was employed to illustrate the influence of reactant concentration on the particle size.