Melting Point Of Sn Research Articles

Further optimization of ITO films at the melting point of Sn and configuration of Ohmic contact at the c-Si/ITO interface

Progressive improvement in the TCO characteristics of ITO (In2O3:Sn) thin films grown at substrate temperature (TS ∼ 232 °C) near the melting point of Sn has been pursued via optimization of gas pressure in the RF magnetron sputtering system. The optical transmission characteristics virtually remain consistently impressive on varying the gas pressure; however, crystallinity improves with significant dominance along 〈222〉 crystallographic orientation at an optimum gas pressure of 10 mTorr. Simultaneously, enhanced doping of the In2O3 network by Sn4+ active dopants along with optimum reducing condition attained at 10 mTorr pressure in the magnetron plasma provide maxima of both concentration and mobility of the charge carriers in the ITO films prepared at each substrate temperature in the range 200–350 °C and lead to a very high TCO figure of merit characteristics. At lower gas pressure below 10 mTorr, although dopant incorporation increases, formation of enhanced number of electrically inactive dopants (Sn2+) (reduced Sn4+/Sn2+ ratio) deteriorates the electrical characteristics of the ITO films. On lowering of gas pressure beyond the optimum reducing condition in the plasma, changes in the nature of decay of the concentration and mobility of the charge carriers depend sensitively on the substrate temperature. The carrier concentration reduces rapidly at higher TS while carrier mobility diminishes significantly at lower TS. Accordingly, dopant concentration and the oxidation state of the In2O3:Sn matrix together control the carrier characteristics in a complex manner which is again sensitively influenced by the substrate temperature and the working gas pressure of the magnetron plasma. Significantly superior ohmic contact of the optimum ITO film with c-Si wafer evolves due to narrowing of the junction barrier height (φB) arising by virtue of increased carrier concentration in ITO, thanks to effective doping by Sn4+. Improved c-Si/ITO junction characteristics admit supplementary application feasibility of ITO films in devices fabrication, particularly as transparent electrodes in c-Si p-n junction solar cells.

Microstructures and thermal properties of Sn–Bi–Pb–Zn alloys as heat storage and transfer materials

Low-melting-point alloy has the characteristics of high thermal conductivity, low solidus temperature and the wide range of use temperature, which is a potential heat transfer medium. The microstructure and thermal properties of Sn–Bi–Pb–Zn alloys as heat transfer and storage material were investigated in this paper. The phase compositions, microstructure and thermal properties were investigated by X-ray diffusion (XRD), electron probe microanalysis (EPMA) and differential scanning calorimeter (DSC) analysis, respectively. The results show that the phases of Sn–Bi–Zn and Sn–Pb–Zn alloys are mainly eutectic formed by solid solution, while the formation of Pb7Bi3 intermetallic compounds decreases the melting point of Sn–Bi–Pb and Bi–Pb–Zn. The thermal properties of the zinc-containing alloys are better than that of Sn–Bi–Pb, but the weight of the zinc-containing alloys significantly reduces above 900 °C. As the density, specific heat capacity and thermal diffusivity change with temperature and physical state, the thermal conductivity of the alloys first decreases and then increases. These results demonstrate the feasibility of using low-melting alloys as the heat transfer and storage material.

Optimization of Nano-structured Tin Doped Indium Oxide Films Grown at Substrate Temperature close to the Melting Point of Tin

Abstract For efficient utilization of In2O3:Sn (ITO) films in device structures, a low-temperature growth is always preferred. However, optical transparency and electrical conductivity of the transparent-conducting-oxide (TCO) films always hold a trade-off relation in-between. For accommodating all such stringent requirements, ITO films in the present investigation has been deposited on glass substrates using 13.56 MHz RF magnetron sputtering and optimized at temperature close to the melting point of Sn as a dopant to the In2O3 network, in order to utilize its best favorable contribution to the growth of properly doped films having balanced combination of relevant optical, electrical and nano-structural properties. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Nanotechnology: Ideas, Innovations & Initiatives-2017 (ICN:3i-2017).

Core-Shell Transformation-Imprinted Solder Bumps Enabling Low-Temperature Fluidic Self-Assembly and Self-Alignment of Chips and High Melting Point Interconnects.

We demonstrate the realization of core-shell transformation-imprinted solder bumps to enable low-temperature chip assembly, while providing a route to high-temperature interconnects through transformation. The reported core-shell solder bump uses a lower melting point BiIn-based shell and a higher melting point Sn core in the initial stage. The bumps enable fluidic self-assembly and self-alignment at relatively low temperatures (60-80 °C). The bumps use the high surface free energy of the liquid shell during the self-assembly to capture freely suspended Si dies inside a heated (80 °C) water bath, leading to well-ordered defect-free chip arrays; the molten liquid shell wets the metal contact (binding site) on the chips and yields self-aligned and electrically connected devices. The solid core provides the anchor point to the substrate. After the completion of the assembly, a short reflow raises the melting point, yielding a solid electrical connection. The low melting point liquid diffuses into the high melting point core. The tuning of the material ratios leads to tailored transformation-imprinted solders with high melting points (160-206 °C) in the final structure.

Understanding of Void Formation in Cu/Sn-Sn/Cu System During Transient Liquid Phase Bonding Process Through Diffusion Modeling

Transient Liquid Phase (TPL) bounding of Sn foil sandwiched between two Cu foils involves, in the temperature range above the melting point of Sn (232 °C) and below 350 °C, the formation and the growth of two intermetallic compounds (IMCs) Cu6Sn5 and Cu3Sn and mostly unintended micro-pores. The present study aims to analyze the mechanism of void development during the soldering process through an experimental and modeling approach of diffusion-controlled IMC transformation. This modeling couples the diffusion process and the interface motion with the volume shrinkage induced by the difference of partial molar volumes of atoms between each phase. We also consider two types of inter-diffusion transports: (i) inter-diffusion based on the exchange of Cu and Sn atoms and (ii) inter-diffusion of Sn atoms with vacancies allowing Kirkendall void formation. The simulations of IMC growth performed correspond to a sequence of planar phase layers, where the distinctive scallop morphology of the Cu6Sn5 layer is described through an analytical function allowing to quantify the grain boundary diffusion pathway. We take into account of the volume diffusion mechanism for Cu3Sn intermetallic. For Cu6Sn5 intermetallic two mechanisms are considered, volume diffusion and grain boundary diffusion, limited by grain growth. The simulations of IMC growth kinetics, for different transport scenarios, are compared to the experimental evolving morphologies to determine the most likely mechanism of micro-void formation.

Melting point of Sn as the optimal growth temperature in realizing the favored transparent conducting properties of In2O3:Sn films

At substrate temperature (TS) close to melting point of Sn (TSn) rapid incorporation of metallic dopants in significant amount introduces sharp rise in mobility (μ) and concentration (ne) of charge carriers, leading to substantial reduction in resistivity (ρ); simultaneous sharp widening in optical gap (Eg) results in optimum Figure-of-Merit (Φ). The Eg vs. ne2/3 plot demonstrates two distinct regimes of TS across TSn, leading to higher reduced effective mass of charge carriers, mvc∗ by 0.072m0 owing to rapid incorporation of Sn4+ at substitutional site of In3+ in In2O3 matrix. Consequently, the self-energy due to electron-impurity scattering rises and/or the material self-converts to an alloy-like ensemble. On further increase in TS, Φ reduces due to enhanced optical absorption by metallic dopants and dopant induced defects, as noted by enhanced Urbach-energy (EU). Rather than any arbitrary TS, TSn has been demonstrated as an optimal growth temperature for ITO films grown by RF magnetron sputtering.

In situ imaging of the soldering reactions in nanoscale Cu/Sn/Cu and Sn/Cu/Sn diffusion couples

The soldering reactions of three-segmented Sn/Cu/Sn and Cu/Sn/Cu diffusion couples are monitored by in-situ transmission electron microscopy to reveal the metallurgical reaction mechanism and the associated phase transformation pathway. For Sn/Cu/Sn diffusion couples, there is no ε-Cu3Sn formation due to the relatively insufficient Cu as compared to Sn. Kirkendall voids form initially in the Cu segment and then disappear due to the volume expansion associated with the continued intermetallic compound (IMC) formation as the reaction progresses. The incoming Sn atoms react with Cu to form η-Cu6Sn5, and the continuous reaction then transforms the entire nanowire to η-Cu6Sn5 grains with remaining Sn. With continued heating slightly above the melting point of Sn, an Sn-rich liquid phase forms between η-Cu6Sn5 grains. By contrast, the reaction in the Cu/Sn/Cu diffusion couples results in the intermetallic phases of both Cu3Sn and Cu6Sn5 and the development of Cu6Sn5 bulges on Cu3Sn grains. Kirkendall voids form in the two Cu segments, which grow and eventually break the nanowire into multiple segments.

Hybrid Printing Metal-mesh Transparent Conductive Films with Lower Energy Photonically Sintered Copper/tin Ink

With the help of photonic sintering using intensive pulse light (IPL), copper has started to replace silver as a printable conductive material for printing electrodes in electronic circuits. However, to sinter copper ink, high energy IPL has to be used, which often causes electrode destruction, due to unreleased stress concentration and massive heat generated. In this study, a Cu/Sn hybrid ink has been developed by mixing Cu and Sn particles. The hybrid ink requires lower sintering energy than normal copper ink and has been successfully employed in a hybrid printing process to make metal-mesh transparent conductive films (TCFs). The sintering energy of Cu/Sn hybrid films with the mass ratio of 2:1 and 1:1 (Cu:Sn) were decreased by 21% compared to sintering pure Cu film, which is attributed to the lower melting point of Sn for hybrid ink. Detailed study showed that the Sn particles were effectively fused among Cu particles and formed conducting path between them. The hybrid printed Cu/Sn metal-mesh TCF with line width of 3.5 μm, high transmittance of 84% and low sheet resistance of 14 Ω/□ have been achieved with less defects and better quality than printed pure copper metal-mesh TCFs.

Numerical Modeling of Fracture-Resistant Sn Micropillars as Anode for Lithium Ion Batteries

Sn possesses three times higher capacity in comparison to graphite anode (372 mAhg–1) that makes it a promising candidate for enhanced performance Li ion batteries. Contrary to Si, Sn is compliant and ductile in nature and thus is expected to readily relax the Li diffusion-induced stresses. The low melting point of Sn additionally allows for stress relaxations from time-dependent or creep deformations even at room temperature. In this study, numerical modeling is used to reveal the significance of plasticity and creep-based stress relaxations in the Sn working electrode. The maximum elastic tensile hoop stresses for 1 μm micropillar size with 1C charging rate conditions reduces down from ∼1 GPa to ∼200 MPa when Sn is allowed to plastically deform at a yield strength of ∼150 MPa. After experimentally determining the creep response of Sn micropillars, creep deformations are incorporated in numerical modeling to show that the maximum tensile hoop stress is further reduced to ∼0.45 MPa under the same conditio...

Discussion on Local Spark Sintering of a Ceramic-Metal System in an SR-CT Experiment during Microwave Processing.

In this paper, local spark sintering of a ceramic-metal system (SiO2-Sn) during microwave processing was examinedby means of synchrotron-radiation-computed tomography technology. From the reconstructed 3-D and cross-section images of the specimen, adensification process was observed below the melting point of Sn, and then the specimen came into a rapid densification stage. These results may be due to the local spark sintering induced by the high-frequency alternating microwave electric fields. As the metallic particles Sn were introduced, the microstructure of “ceramic-metal” will lead to a non-uniform distribution and micro-focusing effect from electric fields in some regions (e.g., the neck). This will result in high-intensity electric fields and then induce rapid spark sintering within the micro-region. However, in the subsequent stage, the densification rate declined even when the specimen was not dense enough. The explanation for this is that as the liquid Sn permeated the gaps between SiO2, the specimen became dense and the micro-focusing effect of electric fields decreased. This may result in the decrease or disappearance of spark sintering. These results will contribute to the understanding of microwave sintering mechanisms and the improvement of microwave processing methods.

Formation of novel rice-like intermetallic phases and changes in the mechanical, microstructural and electrical properties of Sn–5Sb alloys with addition Ag and Bi

In the present study, the effects of Ag and Bi additions (1 wt.%) on the microstructural, thermal, mechanical and electrical properties of Sn–5Sb solder alloys were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), microhardness tests, and four probe measurements. It was observed that the melting point of Sn–5Sb solder alloy decreased with the addition of Ag and Bi. It was found that the final microstructure of rapidly solidified Sn–5Sb-1X (X = Ag and Bi) alloys was strictly dependent upon the wheel speeds; the microstructures changed from a coarse dendritic and needle-like structure to a refined ultra fine dendritic and rice-like structure with increasing wheel speed. Cooling rate was also effective on both the mechanical and electrical properties. It was found that all of the alloys exhibit higher mechanical properties with increasing cooling rate and/or decreasing testing temperature. Similarly, significant improvements of 32% and 9% in electrical conductivity of both of the alloys were obtained with the addition of Ag and Bi, respectively. The microstructural evolution of the Sn–5Sb based alloys plays a crucial role in influencing the mechanical properties of these alloys.

Thermal cycle reliability of Cu-nanoparticle joint

The improvement of the performance of power electronic devices requires the development of new Pb-free joint materials that are capable of enduring high temperatures more than 200°C. Cu-nanoparticle joints are considered to be promising for this purpose owing to their low cost, high melting point, and good thermal conductivity. There have, however, been few studies on the thermal cycle reliability of such joints. In the present study, thermal cycle tests involving up to 1000 cycles of −40/150°C and −40/200°C, respectively, were conducted on Cu-nanoparticle and soldered Sn–0.7wt.%Cu joints between an Al2O3 chip and Cu–65wt.%Mo plate. The Cu-nanoparticle joint was found to be undamaged by the −40/150°C thermal cycles at a joint temperature of 300°C, but completely broken at the joint interface by the −40/200°C thermal cycles. The Cu-nanoparticle joint interface was subsequently strengthened by increasing the joint temperature to 350°C, and this enabled endurance of the −40/200°C thermal cycles. However, the soldered joint was completely broken by −40/200°C thermal cycles owing to the melting point of Sn–0.7wt.%Cu (227°C) being much lower than that of Cu (1085°C). The Cu-nanoparticle joint thus exhibited superior thermal reliability compared to the soldered joint.

Ultra-Low Temperature (~180°C) Solid-Phase Crystallization of GeSn on Insulator Triggered by Laser-Anneal Seeding

Solid-phase crystallization (SPC) of amorphous-GeSn (a-GeSn) films on insulating substrates has been developed combining with laser-annealed seeding, to realize next generation thin-film devices. By this technique, we have realized crystallization of GeSn (>10%) at low temperatures (~180oC), which is applicable for flexible thin-film devices on low cost plastic substrates with low softening temperatures (~200oC). In addition, the starting point of crystallization can be controlled by seeding, which is big advantage in device designing. Introduction In order to realize next generation flexible devices, novel functional materials have to be crystallized at controlled positions on insulating substrates below the softening temperature of low cost plastic substrates (~200oC). GeSn is attracting material for this purpose, since GeSn has higher carrier mobility than Si or Ge, and moreover, GeSn shows direct band structure by introducing substitutional Sn concentration more than 8%. Under such background, we have investigated solid-phase crystallization (SPC) of GeSn [1] and realized growth of GeSn at 180oC. However, to initiate the SPC at controlled positions, the samples have to be annealed above the melting point of Sn (~232oC) to form seeding regions, which is not applicable on flexible plastic substrates. In line with this, we propose an idea to use laser-annealing (LA) to form crystal seeds. By forming seeds by LA, lateral SPC is expected at process temperature below 200°C. Moreover, by decreasing the process temperature, we can expect that GeSn crystals with high substitutional Sn concentration should be obtained. Experimental Procedure In the experiment, amorphous Ge0.8Sn0.2 layers (100 nm thickness) were deposited on quartz substrates by a molecular beam technique. The samples were irradiated with a KrF excimer laser (wavelength: 248 nm, energy: 160 mJ/cm2) with 100 pulses in 1 sec to form seed regions, followed by thermal annealing (180 - 220 oC) for lateral SPC as shown in Fig. 1. Results and Discussion Nomarski images of samples as LA and after annealing at 180oC for 48h are shown in Figs. 2(a) and 2(b), respectively. The laser annealed seed region is formed as shown in Fig. 2(a). From the seed, a bright region spreads after 180oC annealing. The Raman spectra obtained at points A, B, and C in Figs. 2(a) and 2(b) are shown in Fig. 2(c). From these spectra, we can clearly say that lateral SPC is initiated from only the seed and no spontaneous nucleation occurs. From the length of lateral SPC region, growth rates of GeSn at various annealing temperatures (180, 200, 220 oC) are evaluated. It is found that the growth rate is about 1 μm/h at 180 oC, which is nearly 106 time as large as that of Ge [2]. The activation energy of the growth rate of Ge0.8Sn0.2 was estimated to be ~1.5 eV, which was smaller than that of Ge (~2.0 eV). This is attributed to the weakening atomic bonds by Sn atoms. This is a very useful technique to realize next generation flexible thin-film devices. Substitutional Sn concentration in grown layer obtained after annealing at 180oC for 48h is evaluated by Raman measurement, which is shown in Fig. 3. Substitutional Sn concentration in SPC region shows higher value (>10%) than that of LA region (~7.5%), which is attributed to difference of non-equilibrium conditions between SPC and LA. Interestingly, substitutional Sn concentration shows very high values exceeding 15% near the growth edge. The Sn concentration decreases with increasing distance from the edge. Decrease in the Sn concentration from >15% to ~10% is attributed to the post annealing effect of grown regions. Detailed physics will be discussed at the presentation.

Near-infrared light absorption by polycrystalline SiSn alloys grown on insulating layers

High-Sn-content SiSn alloys are strongly desired for the next-generation near-infrared optoelectronics. A polycrystalline growth study has been conducted on amorphous SiSn layers with a Sn-content of 2%–30% deposited on either a substrate of SiO2 or SiN. Incorporating 30% Sn into Si permits the crystallization of the amorphous layers at annealing temperatures below the melting point of Sn (231.9 °C). Composition analyses indicate that approximately 20% of the Sn atoms are substituted into the Si lattice after solid-phase crystallization at 150–220 °C for 5 h. Correspondingly, the optical absorption edge is red-shifted from 1.12 eV (Si) to 0.83 eV (Si1−xSnx (x ≈ 0.18 ± 0.04)), and the difference between the indirect and direct band gap is significantly reduced from 3.1 eV (Si) to 0.22 eV (Si1−xSnx (x ≈ 0.18 ± 0.04)). These results suggest that with higher substitutional Sn content the SiSn alloys could become a direct band-gap material, which would provide benefits for Si photonics.

Experimental investigations on the soldering performances of the joints for Bi-2223/Ag tapes

In this paper, we have fabricated Bi-2223/Ag jointed tapes and evaluated its joint resistance at liquid nitrogen temperature (77K). The tapes were joined by the conventional resistive joint method using five kinds of solders with different melting points. The lower melting point Bi–Sn–Pb and high melting point Sn–Ag–Cu solders have lower joint resistances. In addition, two different joining processes were compared by joining the copper sheet. The joint resistances were measured at lower temperature and the resistance appears comparable to each other. It indicated that the direct-jointing is more effective method for high temperature superconductor (HTS) joining.

Submicron Cu/Sn Bonding Technology With Transient Ni Diffusion Buffer Layer for 3DIC Application

A submicron Cu/Sn bonding with transient Ni buffer layer at 225 °C is demonstrated to overcome current 5- \(\mu \) m Cu/Sn physical limitation. The 10-nm Ni layer suppresses immense Cu/Sn interdiffusion during heating step prior to major bonding process. When the temperature is close to the Sn melting point, the Ni layer dissolves and molten Sn gives successful submicrometer Cu/Sn bonding. The excellent mechanical strength and electrical performance of this scheme show the great potential for future and highly dense 3D interconnects.

Formation of Cu2SnSe3 from stacked elemental layers investigated by combined in situ X-ray diffraction and differential scanning calorimetry techniques

Stacked elemental layers of Mo/Cu/Sn and Mo/Cu/Sn/Se were employed as samples for investigating the formation reaction of Cu–Sn intermetallic compounds as well as Cu2SnSe3 phases by in situ technique of X-ray diffraction and differential scanning calorimetry. The use of a combined in situ technique allows a real-time observation on solid-state reactions as well as any crystalline phase changes during annealing towards the crystallization of Cu2SnSe3. It is found that Cu and Sn form intermetallic compounds of Cu6Sn5, Cu3Sn and Cu41Sn11 as the annealing temperature rises from 30 to 550°C. The reaction of Se with Cu to form a CuSe phase dominates the binary phase formation at a low annealing temperature. The annealing of a stacked Mo/Cu/Sn/Se layer suggests that only Cu6Sn5 intermetallic compound directly acts as a reactant for the Cu-selenide phase formation. A SnSe phase mostly forms from a liquid-state reaction of Sn and Se above the Sn melting point. The in situ investigation also reveals a complete set of Cu-selenide peritectic decompositions of CuSe2→CuSe→Cu1.8Se at 360 and 412°C. The formation of Cu2SnSe3 phase starts at 450°C as a product from a reaction between Cu1.8Se and SnSe in a presence of liquid Se. Comparisons on the initial formation temperatures of all involved phases and on the formation pathways between Cu2SnSe3 and Cu2SnS3 are discussed as well.

Liquid immiscibility and core-shell morphology formation in ternary Al–Bi–Sn alloys

Abstract The effects of composition on liquid immiscibility, macroscopic morphology, microstructure and phase transformation in ternary Al–Bi–Sn alloys were investigated. Three types of morphology, the core-shell type, the stochastic droplet type and uniform dispersion type, of Al–Bi–Sn particles prepared by a jet breakup process were distinguished, and the relationships between which were discussed. The phase transformation behaviors of the Al–Bi–Sn alloys were studied by thermal analysis, in agreement with the microstructural observation and microanalysis. The liquid immiscibility and formation of the core-shell morphology in Al–Bi–Sn alloys are easily achieved when the composition lies in the liquid miscibility gap. The particles exhibit a high melting point Al-rich core with a low melting point Sn–Bi-rich solder shell, showing promise for application as high-density electronic packaging materials.

Uniform Nano-Sn/C Composite Anodes for Lithium Ion Batteries

Nano-Sn/C composites are ideal anode materials for high energy and power density Li-ion batteries. However, because of the low melting point of Sn and the tendency of grain growth, especially during high temperature carbonization, it has been a significant challenge to create well-dispersed ultrasmall Sn nanoparticles within a carbon matrix. In this paper, we demonstrate an aerosol spray pyrolysis technique, as a facile and scalable method, to synthesize a nano-Sn/C composite with uniformly dispersed 10 nm nano-Sn within a spherical carbon matrix. The discharge capacity of nano-Sn/C composite sphere anodes maintains the initial capacity of 710 mAh/g after 130 cycles at 0.25 C. The nano-Sn/C composite sphere anodes can provide ~600 mAh/g even at a high rate of 20 C. To the best of our knowledge, such high rate performance for Sn anodes has not been reported previously. The exceptional performance of the nano-Sn/C composite is attributed to the unique nano-Sn/C structure: (1) carbon matrix offers mechanical support to accommodate the stress associated with the large volume change of nano-Sn, thus alleviating pulverization; (2) the carbon matrix prevents Sn nanoparticle agglomeration upon prolonged cycling; and (3) carbon network provides continuous path for Li ions and electrons inside the nano-Sn/C composite spheres.

Melting of Sn to 1 Mbar

The melting point of Sn was determined between 20-105 GPa using laser-heated diamond anvil cell experiments, coupled with in situ synchrotron X-ray diffraction studies. In agreement with previous LH-DAC speckle experiments, we observe a flattening of the melting slope between P = 40–60 GPa. However, we also observe that this plateau is followed by a further increase in the melting slope above P ∼ 70 GPa, leading to a remarkably high melting point of Tm = 5500 K by P = 105 GPa.