Liquid Tin Research Articles

Spreading Dynamics of Tin, Bismuth and Some Lead-Free Solders over Copper Substrate

The spreading of a liquid on a solid surface is very important in a number of practical applications. Many interesting physical phenomena can be observed when a small drop of a fluid spreads on a solid surface. These phenomena are related to spreading dynamics, which can be classified as spontaneous and forced wetting. In this work spreading dynamics of liquid metals and solders alloys were established to determine the mechanism of spreading. The spreading dynamics of bismuth, tin, 99.3wt%Sn-0.7wt%Cu alloy, 99.8 wt%Bi-0.2wt%Cu alloy and 60wt%Sn-40wt%Pb were studied by using sessile droplet method. Tests were carried out at a temperature range from 280oC to 350oC over a copper substrate. Results showed a discontinuous decrease of spreading velocity as a function of time. For example, spreading velocity of liquid tin at 320oC decreased from 234.86 mm/s at 0.0025 s to 4.62 mm/s at 0.0225 s, after that increased up to 9.24 mm/s at 0.025 s, then down back to 6.07 mm/s at 0.03 s, and finally reached to the end of spreading after 0.04 s.

ＮｂＣ晶出を伴うＦｅ‐３６％Ｎｉ合金溶接金属における凝固過程の解析

Numerical model to calculate the fraction of liquid phase which takes into account the formation of crystallized phase during welding solidification was proposed in order to predict the solidification cracking susceptibility of high Ni steel weld metals. For evaluating the validity of the proposed model, changes in the fraction of residual liquid phase on solidification process for Fe-36%Ni-0.02%C-1%Nb weld metal solidifying at nearly γ phase and Fe-36%Ni-0.2%C-1%Nb weld metal solidifying with niobium carbide during γ solidification were quantitatively investigated as follows. After each quenched solidification microstructure of these weld metals was made by liquid tin, the change in the fraction of residual liquid phase for Fe-36%Ni-0.02%C-1%Nb weld metal was quantitatively evaluated by analyzing the region corresponding to residual liquid phase in SEM (Scanning Electron Microscope) image of the quenched weld metal. Also, Fe-36%Ni-0.2%C-1%Nb weld metal was quantitatively evaluated by separating NbC from residual liquid phase by using the mapping data of Nb and C by EPMA (Electron Probe Micro Analyzer). These experimental data coincided with the fractions of liquid phase obtained by using the model for Fe-36%Ni-0.02%C-1%Nb and Fe-36%Ni-0.2%C-1%Nb weld metals and the morphology of niobium carbide predicted by the model also corresponded to TEM (Transmission Electron Microscope) observations. Furthermore, the effects of niobium and carbon contents on the solidification cracking susceptibility of Fe-36%Ni weld metal was able to be explained by using the model.

Incident-mass dependence of temperature-enhanced ion-induced sputtering in liquid metals

The sputtering yield of liquid tin due to heavy-ion bombardment has been found to have significantly reduced dependence on the sample temperature than that of light-ion bombardment. These results, combined with previous light-ion data, show that the mechanisms that increase the sputtering yield of materials under ion irradiation are diminished or surpassed by the effects of heavy-ion bombardment. Beams of 700eV Ne+ and 500–1000eV Ar+ ions irradiated high-purity tin at temperatures from 20–340°C at oblique incidence; a pair of quartz–crystal microbalances performed real-time measurement of the mass ejected from the surface. Monte Carlo atomistic simulations were also performed for comparison and to help interpret the experimental results. We discuss the results of this series of experiments and the lack of a comprehensive understanding of the mechanisms behind temperature-dependent sputtering in light of these results.

Electrochemical nitriding of Sn in LiCl–KCl–Li 3N systems

Electrochemical nitriding of a liquid phase tin metal has experimentally been confirmed by using the oxidation of nitride ions in molten LiCl–KCl–Li 3N melts according to the following reactions: N 3 − = N ads + 3 e − N ads + Sn = SnN x From the XPS analysis, N 1s signal and Sn 3d signals are observed, which corresponds to the formation of SnN x , after conducting argon ion sputtering for 1000 s. This showed that a thick and stable nitride film was formed by electrochemical nitriding.

Temperature dependence of liquid Sn sputtering by low-energy He + and D + bombardment

Absolute sputtering yields of liquid tin from 240 to 420 °C due to irradiation by low-energy helium and deuterium have been measured. For ion energies ranging from 300 to 1000 eV, temperature enhancement of liquid tin sputtering was noted. These measurements were obtained by IIAX (the Ion-surface InterAction eXperiment) using a velocity-filtered ion beam at 45° incidence to sputter material from a liquid tin target onto deposition monitors. Sputtering yields from 500 eV ion bombardment at 45° incidence increase from 0.1 ± 0.03 and 0.019 ± 0.008 Sn particles/ion at room temperature, for He + and D + ions respectively, to 0.30 ± 0.12 and 0.125 ± 0.05 Sn particles/ion for 380 °C. Temperature enhanced sputtering has been seen in other liquid metals (namely lithium, tin–lithium, and gallium) using both ion beam and plasma irradiation.

Pressure dependence of the structure of liquid group 14 elements

X-ray diffraction has been measured for liquid group 14 elementsat high pressures using synchrotron radiation. Static structure factorsS(Q) and pair distributionfunctions g(r) show different pressure dependences for liquid silicon, liquid germanium and liquid tin. Inliquid silicon, a significant change in the local structure occurs between 8 and 14 GPa. Inliquid germanium, an anisotropic contraction of local structure occurs continuouslywith increasing pressure. In liquid tin, the structure contracts almost uniformly.These pressure dependences are discussed in relation to the pressure-inducedphase transitions in crystalline phases and the changes in bonding between atoms.

In Situ Characterization of Interfaces between Liquid Tin–Vanadium Alloys and Alumina by Neutron Reflection Spectroscopy

The composition and structure of interfaces between single crystal Al2O3 (sapphire) samples and liquid Sn–V alloys, containing 1% and 3% V, have been characterized in situ at high temperature using neutron reflection spectroscopy. Measurements made at 900°C are shown to be consistent with a thin (10–25 nm) AlV2O4 layer forming at the solid/liquid interface, with possibly a thinner layer of enhanced V content adjacent to the liquid, to promote wetting. After longer time exposure to temperature this interface layer roughens and a more complex interface structure occurs.

Characterisation of Interfaces Between Liquid Tin and Alumina in the Presence of Titanium Alloy Additions

Neutron reflection spectroscopy has been used to characterise the composition of interfaces between liquid Sn-Ti alloys and Al2O3. The reflectivity profiles for both 1% and 3% Ti alloys are consistent with the presence of a layer approximately 2 nm thick at the liquid/solid interface, showing extensive segregation of Ti. The composition of this layer is not pure Ti but shows a greater Ti content than any known Ti oxide composition. In all interfaces exposed to liquid metals at elevated temperature (including pure Sn) there is a layer of thickness 20–100 nm on the alumina surface with slightly lower neutron scattering length density than pure alumina. This is interpreted as evidence for surface roughening of the Al2O3 surface during exposure to the liquid metal.

Thickening kinetics of interfacial Cu6Sn5 and Cu3Sn layers during reaction of liquid tin with solid copper

Thickening behavior of interfacial η (Cu6Sn5) phase and ɛ (Cu3Sn) phase intermetallic layers was investigated in liquid tin/solid copper reaction couples over reaction times from 30 sec to over 4,000 min and temperatures from 250°C to 325°C. A scanning electron microscope (SEM) was used to quantify the interfacial microstructure at each processing condition. The η developed with a scalloped morphology, while the ɛ always grew as a somewhat undulated planar layer in phase with the η. The thickness of each phase was quantitatively evaluated from SEM micrographs using imaging software. Thickening kinetics of the ɛ and η compounds were modeled using time- and temperature-dependent empirical power-law equations. From the model, values for the kinetic exponent, rate constant, and activation energy were established for each intermetallic layer. Measured values for the kinetic exponents and activation energies suggest that thickening of the η is controlled by a grain-boundary diffusion mechanism, and growth of the ɛ occurs by solid-state diffusion, probably grain-boundary diffusion.

Experiments on interaction of liquid tin with solid copper

The reaction of liquid tin with solid copper has been studied by heating small volumes ofpure tin on copper coupons at various temperatures and times, and evaluating the resulting reaction metallographically. Three reaction temperatures were used:260,400,and450 ° C. Specimen geometry was chosento simulate a typical solder joint. The reaction was observed to occur in two stages: an initial fast stage with copper/liquid tin interface movement rates from 0.2 μm s-1 at260 ° C to 0.8 μm s-1 at 450 ° C, followed by a much slower stage. It was concluded that the first stage corresponds to direct dissolution of copper in liquid tin up to or beyond the liquidus concentration for the reaction temperature used.This is followed by the formation of an intermetallic compound layer atthe copper/liquid interface. Subsequent copper dissolution then occurs by solid state diffusion through the compound layer, a much slower process than direct dissolution.

Experimental Measurements of Velocity, Potential, and Temperature Distributions in Liquid Aluminum During Electromagnetic Stirring

An experimental technique has been developed to measure both axial and transverse velocities and temperature distribution in molten aluminum. Couette flow of liquid aluminum, lead, tin, and low melting alloy in cylindrical container was chosen for calibration of the experimental technique and the magnetic probe. Velocity and temperature profiles for liquid aluminum rotating in cylindrical container at different angular velocities are obtained for two different values of the depth. We determined that the velocity values increase with magnetic induction.

Dynamic surface tension measurements on molten metal-oxygen systems: model validation on molten tin

A theoretical model on oxygen transport at the surface of liquid metals has been validated by dynamic surface tension measurements performed on liquid tin as test metal. The oxygen contamination conditions have been obtained at different oxygen partial pressures under low total pressure conditions (Knudsen regime), confirming that an oxide removal regime occurs under an oxygen partial pressure much higher than the equilibrium one (the “Effective Oxidation Pressure”). Experimental results are reported which give a new insight on the relative importance of the various processes due to the oxygen mass transport between the liquid metal and the gas phase. The critical aspects involved in surface tension measurements of liquid metals, related to the problem of liquid metal–oxygen interactions, are also carefully underlined.

D +, He + and H + sputtering of solid and liquid phase tin

Absolute sputtering yields of Sn in the solid and liquid phases for incident H +, D +, and He + ions with energies of 300 to 1000 eV were determined via a series of experiments using the ion-surface interaction experiment (IIAX), a facility designed to measure such ion-surface interactions. IIAX incorporates an ion source with an array of ion beam filters and optics to bring a near mono-energetic beam of ions to the target, in this case at 45° to the surface normal. A pair of quartz crystal microbalances record the amount of mass collected from both sputtering and evaporation from the target. VFTRIM-3D modeling results of tin sputtering best fit the experimental data when the bulk of pure tin was modeled with 60% SnO coverage in the top three monolayers most likely indicating the presence of a very thin oxide layer during experimentation.

Measurements of the Thermal Diffusivity and Thermal Conductivity of Metals Near the Melting Point

A pulsed technique for measuring the thermal diffusivity a and thermal conductivity λ of spherical samples with an allowance for the spatial–time energy distribution over the laser-beam cross section is described. The measured temperature dependences а(Т) and λ(Т) for solid and liquid tin near the melting point of samples are presented. The a and λ measurement accuracies are 5 and 15%, respectively.

Surface Phenomena and Interfacial Interaction at the Glass–Liquid Tin–Gas Phase Interface

We used the sessile drop method to study the temperature dependences of the density and surface tension of tin and liquid glass. We have studied the effect of the composition of the gas phase on the surface tension of the glass. We used the method of adjoining drops to determine the temperature dependence of the interfacial tension at the glass horbar; tin melt boundary. We have studied the effect of silicon, aluminum, iron, nickel, and manganese on the interfacial tension in the glass ― tin system. We have shown that in this system, these additives are not interface-active.

Deviation from Wiedemann-Franz law for the thermal conductivity of liquid tin and lead at elevated temperature

The thermal conductivities of tin and lead in solid and liquid states have been determined using a nonstationary hot wire method. Measurements on tin and lead were carried out over temperature ranges of 293 to 1473 K and 293 to 1373 K, respectively. The thermal conductivity of solid tin is 63.9±1.3 W⋅m−1⋅K−1 at 293 K and decreases with an increase in temperature, with a value of 56.6±0.9 W⋅m−1⋅K−1 at 473 K. For solid lead, the thermal conductivity is 36.1±0.6 W⋅m−1⋅K−1 at 293 K, decreases with an increase in temperature, and has a value of 29.1±1.1 W⋅m−1⋅K−1 at 573 K. The temperature dependences for solid tin and lead are in good agreement with those estimated from the Wiedemann–Franz law using electrical conductivity values. The thermal conductivities of liquid tin displayed a value of 25.7±1.0 W⋅m−1⋅K−1 at 573 K, and then increased, showing a maximum value of about 30.1 W⋅m−1⋅K−1 at 673 K. Subsequently, the thermal conductivities gradually decreased with increasing temperature and the thermal conductivity was 10.1±1.0 W⋅m−1⋅K−1 at 1473 K. In the case of liquid lead, the same tendency, as was the case of tin, was observed. The thermal conductivities of liquid lead displayed a value of 15.4±1.2 W⋅m−1⋅K−1 at 673 K, with a maximum value of about 15.6 W⋅m−1⋅K−1 at 773 K and a minimum value of about 11.4±0.6 W⋅m−1⋅K−1 at 1373 K. The temperature dependence of thermal conductivity values in both liquids is discussed from the viewpoint of the Wiedemann–Franz law. The thermal conductivities for Group 14 elements at each temperature were compared.

Metallographic Study On Alloying of Nickel-Tin Films From Stacked Single Layers Through Heating

SUMMARYAn alloying process for nickel-tin surface films from stacked single layers through heating was investigated from the metallographic viewpoint using X-ray analysis (XRD) and SEM-EDX. Nickel and tin films were produced separately on the steel surface in this order. The thickness of each layer was about 10 μm. The specimens were then heated in an ambient atmosphere or in vacuum using an electronic furnace. The treatment temperatures were 623, 723, 823 and 1123K and the treatment time was 10.8 ks. Once the tin phase on the top of the surface was melted by heating, nickel atoms began to diffuse into the liquid tin phase and various nickel-tin intermetallic compound phases, Ni3Sn4, Ni3Sn2, Ni3Sn were formed. At higher temperatures, tin oxides were formed and, due to the consumption of tin during the oxide formation, the tin content of the intermetallic compounds for tin and nickel was decreased. In vacuum, the oxide did not form.

Liquid metal embrittlement of tensile specimens of En19 steel by tin

Liquid metal induced embrittlement (LMIE) of En19 steel was investigated by tensile testing specimens coated with liquid pure tin. Testing was carried out over a range of steel hardnesses and test temperatures, and for each material hardness the temperature above which recovery of the unembrittled tensile behaviour of the specimens occurred was measured. Metallographic examination of each of the specimens was carried out and the results of this examination were compared with the mechanical behaviour. This work illustrates the importance of dissolution of the steel by tin on the behaviour of the specimens tested at the higher temperatures.

Diffusion soldering for stable high-temperature thin-film bonds

Diffusion soldering is a special bonding technique to produce joints at a moderate temperature that are subsequently stable at higher temperatures. The search for material systems extending the upper-temperature limit of stability requires information from the pertinent phase diagrams and the reaction kinetics. Combining experimental studies on phase equilibration in powder samples with bulk and thin-film diffusion couples is a useful approach for a systematic search. Promising candidates for dsoldering are Pt-In or Pd-In, and molybdenum is also an effective diffusion barrier against the attack of liquid tin.

Component lifetime comparison and waste volume in CLiFF Sn/Flibe and Sn/LiPb blankets

The thin Convective Liquid Flow First Wall (CLiFF) concept is one of the liquid FW concepts investigated in the Advanced Power Extraction (APEX) study for high power density application. Liquid tin has been suggested as the 2 cm thick front flowing liquid layer because of its low vapor pressure. Two choices were selected for the conventional blanket that follows the thin liquid wall (LW), namely: (1) LiPb/SiC blanket, and (2) Flibe/SiC blanket. Lithium is enriched to 90% Li-6 in the first blanket option and to 25% Li-6 in the second option (with 10 cm-thick beryllium front zone). Due to the superior attenuation characteristics of Flibe over LiPb, this impacted the lifetime of the SiC structure used in both options. In this paper, we assessed the lifetime of the SiC structure in the FW/Blanket and the shield in both blanket options. The end-of-life limit of 200 dpa is assumed (corresponding to ∼3% burn-up). The frequency of replacement of each component is estimated based on 30-years plant lifetime. Comparison is made for the waste volume of replaced components in each option. It is shown that the shield can last the plant lifetime in the Flibe blanket while part of the shield in the LiPb blanket will require replacement. The frequency of replacing the FW/Blanket with the LiPb blanket option is twice as much as in the Flibe blanket option. This is translated to a total volume of disposed structure at plant end-of-life from the entire FW/B/shield system that is larger by ∼60%.