Bismuth Content Research Articles

Using Machine Learning to Construct the Blood-Follicle Distribution Models of Various Trace Elements and Explore the Transport-Related Pathways with Multiomics Data.

Permeabilities of various trace elements (TEs) through the blood-follicle barrier (BFB) play an important role in oocyte development. However, it has not been comprehensively described as well as its involved biological pathways. Our study aimed to construct a blood-follicle distribution model of the concerned TEs and explore their related biological pathways. We finally included a total of 168 women from a cohort of in vitro fertilization-embryo transfer conducted in two reproductive centers in Beijing City and Shandong Province, China. The concentrations of 35 TEs in both serum and follicular fluid (FF) samples from the 168 women were measured, as well as the multiomics features of the metabolome, lipidome, and proteome in both plasma and FF samples. Multiomics features associated with the transfer efficiencies of TEs through the BFB were selected by using an elastic net model and further utilized for pathway analysis. Various machine learning (ML) models were built to predict the concentrations of TEs in FF. Overall, there are 21 TEs that exhibited three types of consistent BFB distribution characteristics between Beijing and Shandong centers. Among them, the concentrations of arsenic, manganese, nickel, tin, and bismuth in FF were higher than those in the serum with transfer efficiencies of 1.19-4.38, while a reverse trend was observed for the 15 TEs with transfer efficiencies of 0.076-0.905, e.g., mercury, germanium, selenium, antimony, and titanium. Lastly, cadmium was evenly distributed in the two compartments with transfer efficiencies of 0.998-1.056. Multiomics analysis showed that the enrichment of TEs was associated with the synthesis and action of steroid hormones and the glucose metabolism. Random forest model can provide the most accurate predictions of the concentrations of TEs in FF among the concerned ML models. In conclusion, the selective permeability through the BFB for various TEs may be significantly regulated by the steroid hormones and the glucose metabolism. Also, the concentrations of some TEs in FF can be well predicted by their serum levels with a random forest model.

Terbium(III) oxide as rare earth metal modifier in PbO/Bi2O3 sodium borate glasses for highly efficient optoelectronic devices: Synthesis, characterization, and applications

This paper explores the incorporation of Terbium(III) oxide as a rare earth metal modifier in sodium borate glasses containing PbO/Bi2O3, aiming to enhance the efficiency of optoelectronic devices. The synthesis and characterization of these glasses are detailed, highlighting the unique properties introduced by Terbium(III) oxide. The study investigates the regularities in the characteristics such as physical, XRD, UV, FTIR, and optical properties of 70B2O3–15Na2O – 15PbO – (5-x)Bi2O3 – xTb2O3, where x = 0; 1; 2; 3; 5 mol% prepared glassy samples, considering varying concentrations of bismuth and the modifier (e.g. Tb2O3), and examines their mutual impact on the borate glass matrix involved. It is found that there are sharp peaks on the diffraction pattern, which increase in width and intensity with increasing Terbium concentration from 3 to 5 mol% in the glass matrices, e.g. two-phase structures, amorphous and crystalline, are observed. Moreover, a wide excitation band in the glass matrix is also observed in the region of 200–320 nm. The study delves into the potential applications of these modified glasses in highly efficient optoelectronic devices, contributing valuable insights to the advancement of materials for technological applications.

The Production of Smalt and Other Cobalt Compounds at the Blaafarveværket, Modum, Norway

Forensic analysis of fine art and objet d’art uses accurately determined pigment compositions to confirm or deny provenance, dating and attribution. Some of the most important pigments in this respect are those associated with cobalt. The Blaafarveværket, or Blue Colour Works, based near Modum in Norway, was a producer of cobalt products (especially smalt and zaffre) during the eighteenth and nineteenth, exploiting local cobalt ores and other raw materials locally sourced and brought in from more distant areas. century. The Blue Colour Works is now a museum and study of its archive has detailed type and quantity of its production, showing that it was perhaps the most important producer of cobalt products in the early nineteenth century, and the largest mining operation in Norway. The archive gives details of the production processes for some of the products and shows that these processes changed through time. The museum preserves samples of different parts of the intermediate and end products, showing that the output was a smalt very low in manganese and zinc, with some nickel, significant iron and arsenic and relatively raised bismuth and uranium contents. REE element analysis combined with lead isotopes shows that different sources of silica were probably used, since both are quite variable, supporting archive suggestions that external sources of silica and plant ash were employed on occasions.

Reporting the Bismuth Promotion for Green Methanol Synthesis by CO2 Hydrogenation over MgO-Supported Cu-Zn Catalysts

Due to the effective exploitation of carbon resources and concurrent decrease in the concentration of atmospheric carbon dioxide (CO2), the thermochemical conversion of CO2 into high-value chemical compounds has emerged as a significant research field. In this article, we report on the effective thermochemical conversion of CO2 for the synthesis of methanol by using Bi-promoted Cu-Zn/MgO catalysts. Cu-Zn bimetallic catalysts supported by MgO were created using the coprecipitation technique. The catalysts that were produced were subjected to varying concentrations of bismuth in order to examine their potential enhancing properties. Several analytical methods were applied to examine the physicochemical profile of the calcined catalysts. ICP-OES confirmed the actual bulk concentration of bismuth in each bismuth-supported Cu-Zn/MgO catalysts. X-ray diffraction studies revealed crystalline form of MgO catalysts support on one hand and high dispersion of Cu and Zn metal oxide on the MgO surface on the other. The study employed scanning electron microscopy (SEM) to examine the morphology of produced catalysts with uniform distribution, since this revealed their nanosize. The mesoporosity characteristic of Bi-promoted Cu-Zn/MgO catalysts was demonstrated by BET surface investigations. The catalytic performance of Bi-promoted Cu-Zn/MgO catalysts for methanol production by CO2 hydrogenation was revealed by activity data in liquid phase slurry reactor. The active profile of Bi could be further justified by comparative studies conducted for the current work with literature.

Fabrication and characterization of TeO2–Na2O–BaO glass doped with Yb2O3 for optical and particulate-radiation shielding applications: Role of Bi2O3/WO3

In this research, transparent 64TeO2–15Na2O–5BaO-(10-x)Bi2O3-(x+5)WO3-1Yb2O3 glasses were prepared and analysed for their optical, structural, and radiation protection potentials. Samples of the novel glasses were produced in the laboratory, starting with the melting-quenching process. The glasses were characterised using standard laboratory procedures and dedicated software. The influence of replacing WO3 with Bi2O3 on the investigated properties was highlighted. The values of the glass density increase from 5.42 g/cm3 to 5.67 g/cm3 as the bismuth oxide concentration increases from 0 to 10 mol%. XRD spectrograms of the glass samples reveal that they have an amorphous structure. The glasses had high optical transparency, which was reduced when WO3 was replaced by Bi. The photoluminescence decay showed that the luminescence lifetime of Yb3+ decreases with increasing bismuth concentration. For electrons, the mass stopping powers (Sp) were within 1.253–8.918 MeV cm2/g, 1.241–8.721 MeV cm2/g, and 1.232–8.549 MeV cm2/g for samples containing 0, 5, and 10 mol% of Bi2O3. Generally, Sp of electrons, protons, alpha particles, and 12C ions were in the order, (Sp)TWBi−0>(Sp)TWBi−5>(Sp)TWBi−10. Increasing the concentration of Bi atomic density in the glasses improved the total interaction probability of thermal neutrons but reduced the ability of the glasses to moderate fast neutrons.

Acrylonitrile‐butadiene‐styrene‐based composites for the manufacture of anthropomorphic simulators

AbstractThe development of functional compounds for extrusion applied in the additive manufacturing of anthropomorphic simulators is interesting, as it guarantees the manufacture of a 3D model similar to the patient. These simulators find applications in therapies or laboratory tests involving x‐rays. In order to replicate human conditions in these tests, it is essential to create materials that closely match the properties of human tissue, including the smoothness of soft tissues and the hardness of the bone tissue. This study developed ceramic‐polymeric composites, where the tomography intensity of each mixture was measured experimentally. Combinations of acrylonitrile butadiene styrene (ABS) with zirconium oxide and basic bismuth carbonate allowed imitation of bone tissue. The samples containing zirconium oxide and basic bismuth carbonate presented results that exceeded the minimum limit and reached a value close to 2000 Hounsfield units (HU) with 12% basic bismuth carbonate content. Combinations of ABS with hydroxyapatite and aluminum oxide can imitate soft tissues. The use of a surfactant facilitated the mixing of ceramic filler with polymer. Finally, 3D printing of a physical model was performed using a dual extruder printer, allowing simultaneous printing of bone and soft tissue components.Highlights Material mimicking x‐ray attenuation similar to bone tissue. Relation between 3D printing porosity and intensity in Hounsfield unit. Computed tomography tests on a 3D printed anthropomorphic phantom. Creating a 3D model from a Computed Tomography scan. Double extruder for 3D printing of two tissue simultaneously.

Pharmacokinetic and Safety Study of Bismuth Potassium Citrate Formulations in Healthy Subjects.

Potassium bismuth citrate is a gastric mucosal protector and a key drug for treating peptic ulcers. To evaluate the pharmacokinetic characteristics and safety of 120-mg bismuth potassium citrate formulations administered orally under fasting conditions in healthy Chinese subjects. A single-center open two-cycle trial was conducted on 12 healthy subjects who received a single oral dose of 120 mg of bismuth potassium citrate. The plasma concentration of bismuth was determined using a validated inductively coupled plasma mass spectrometry (ICP‒MS) method. The pharmacokinetic parameters, including maximum serum concentration (Cmax) and area under the curve concentration-time curve (AUC0-t and AUC0-∞), and safety were evaluated via noncompartment analysis. The ratios of the least square geometric mean ratio between the test (T) and reference (R) formulations for Cmax, AUC0-t, and AUC0-∞ were 44.8%, 55.5%, and 64.4%, respectively; the bilateral 95% confidence intervals (Cis) for these parameters were 20.2-99.6%, 24.1-127.5%, and 23.7-175.0%, respectively, and the non-inferior limits for these parameters were 169.4%, 198.8%, and 200.5%, respectively. The upper limits of the one-sided 97.5% confidence interval for the least squares geometric mean ratio (T/R) were lower than the non-inferior limits. No serious adverse reactions or adverse reactions leading to detachment were observed among the subjects. The concentration of bismuth in the blood of healthy subjects in the T formulation was not greater than that in the R formulation. Similarly, the safety of oral administration of 120 mg of bismuth potassium citrate formulations to healthy subjects was good. The trial registration number (TRN) was [2018] 013, 6 December 2018.

Properties of AlxGa1-xAs grown from a mixed Ga-Bi melt.

Thick smoothly graded AlxGa1-xAs layers (50-100µm) are used in light-emitting diode structures and also for creation of high-power photovoltaic converters with side-input of laser radiation. To achieve the required thickness of the AlxGa1-xAs layer the high temperature LPE growth technique is required. However high epitaxial temperature increases the unintentional doping level. Epitaxy from mixed Ga-Bi melts was investigated as a way to solve this problem. It was found that for growing relatively thick AlxGa1-xAs layers, it is expedient to use Ga-Bi melts with 20 at% or less bismuth content. SIMS and Hall characterization of AlxGa1-xAs layers revealed that the growth of AlxGa1-xAs from mixed Ga-Bi melts reduces the background doping level (including carbon) and influences the native defect formation keeping the n-type conductivity. This effect is explained by the changes of the group III and V elements concentrations in the melt as well as Bi incorporation in the lattice.

Synthesis of Pure and Bi‐Doped Lead Oxides via Microwave‐Assisted Solvothermal Methodology and their Electrochemical Characterization

AbstractIn this study, we have reported the synthesis of both pure and bismuth‐doped lead oxide nanoparticles using solvothermal method. The synthesized nanomaterials were analyzed to assess their structure, crystallinity, phase, maximum absorption and band gap. The electrical characteristics of the fabricated nanostructures were evaluated using cyclic voltammetry (CV) and electron impedance spectroscopy (EIS). The maximum specific capacitance and energy density, 349.96 F/g and 95.27 Wh/g respectively, were attained at a scan rate of 200 mV/s in pure lead oxide. The synthesized pure lead oxide has displayed remarkable cyclic stability, retaining approximately 83 % of its performance even after undergoing 2000 cycles. The addition of bismuth to the lead oxide appeared to inhibit the electrochemical properties of lead oxide due to bismuth ion adsorption. This effect is directly concerned with the amount of dopant which predicted the increase in bismuth contents potentially suppressed the performance of the lead oxide. Our study provides insights into the possible uses of lead oxides in energy storage and conversion devices by revealing a previously unexplored method for optimizing their electrochemical characteristics. The understanding of oxide‐based materials in materials science and electrochemistry is expected to advance with the use of this novel technology.

Pd-Bi-Based Catalysts for Selective Oxidation of Glucose into Gluconic Acid: The Role of Local Environment of Nanoparticles in Dependence of Their Composition

Palladium–bismuth nanomaterials are used in various chemical applications such detectors, electrodes, and catalysts. Pd-Bi catalysts are attracting widespread interest because these catalysts enable the production of valuable products quickly and efficiently, and are environmentally friendly. However, the composition of the catalyst can have a significant impact on its catalytic performance. In this work, we identified a correlation between the composition of the catalyst and its efficiency in converting glucose into sodium gluconate. It was found that the conversion decreases with increasing bismuth content. The most active catalyst was the 0.35Bi:Pd sample with a lower bismuth content (glucose conversion of 57%). TEM, SEM, EXAFS, and XANES methods were used to describe, in detail, the surface properties of the xBi:Pd/Al2O3 catalyst samples. The increase in particle size with increasing bismuth content, observed in the TEM micrographs, was associated with the low melting point of bismuth (271 °C). The SEM method showed that palladium and bismuth particles were uniformly distributed over the surface of the support in close proximity to each other, which allowed us to conclude that an alloy of non-stoichiometric composition was formed. The EXAFS and XANES methods established that bismuth was located on the surface of the nanoparticle predominantly in an oxidized state.

High bismuth-doped germanosilicate fiber for efficient E + S-band amplification.

Bismuth-doped germanosilicate fiber (BGSF), the active media of fiber amplifiers, has attracted widespread attention. Here, we report a BGSF with a high bismuth concentration of 0.075 wt. % and achieve high-efficiency E + S-band amplification, which was prepared by the modified chemical vapor deposition (MCVD) process. The small signal absorption (SSA) and unsaturated loss (UL) of BGSF at 1310 nm are 1.32 and 0.11 dB/m, respectively. The results show a record with only 45 m BGSF was created, to the best of our knowledge, which provides a maximum gain of 39.24 dB with an NF of 6.2 dB at 1430 nm under -20 dBm input signal power.

Co-sputtering strategy to construct robust sodiophilic interfaces for anode-less sodium metal batteries.

A copper-bismuth composite coating was fabricated by a facile co-sputtering strategy to enhance the sodiophilicity and structural stability of the substrate. The composite coating with lower bismuth content can maintain the sodiophilicity and form a thin and dense SEI during cycling, thus improving the reversibility of the anode-less sodium metal batteries.

Effluent toxicity study using biomarkers for ciprofloxacin photoelectrocatalytic degradation by bismuth-doped titanium dioxide nanotubes

ABSTRACT Ciprofloxacin hydrochloride (CIP) is a broad-spectrum synthetic antibiotic often found in domestic sewage and industrial waste due to the inefficiency of conventional treatments. Given the potential risk of drug accumulation, this study presents coatings of titanium dioxide nanotubes (TiO2) doped with different bismuth (Bi) concentrations to degrade CIP through photocatalytic and photoelectrochemical processes. Characterization studies revealed that bismuth (Bi) doping affected the morphology of the materials, with concentrations of 0.01 and 0.05 mol L−1, resulting in collapsed materials with a smaller active surface area. Photocatalysis tests for all the materials exhibited a similar degree of efficiency to photolysis, approximately 33%. Ecotoxicity tests using the biomarkers Lactuca sativa L., Lemna minor, and Artemia salina indicated that, although they were similar to photolysis in terms of efficiency, the effluents generated when employing the doped catalysts showed lower levels of toxicity, with the best results achieved for the material doped with 0.005 mol L−1 of Bi, with a toxicity level approximately 40% lower. Photoelectrocatalysis proved to be the most efficient CIP degradation technique. The highest degradation rate was observed for materials doped with 0.005 mol L−1 of Bi, with an efficiency of 46%, which is 1.4 times more efficient than photolysis. These results demonstrate that materials doped with low amounts of Bi can be effectively used as photoanodes for drug degradation, as their performance is superior, and the final product generated exhibits low toxicity to living organisms.

Effects of parabolic barrier design for multiple GaAsBi/AlGaAs quantum well structures

The results of a comparative study on how the design of multiple quantum structures containing a parabolic barrier profile affects optical properties are presented. All quantum well (QW) structures were grown by molecular beam epitaxy (MBE) on semi-insulating GaAs substrates. The investigated samples consisted of (i) double parabolic quantum wells (type A) or (ii) multiple (two or three) rectangular quantum wells surrounded by parabolic barriers (type B). The optical quality of samples was characterized performing room-temperature (RT-PL) and temperaturedependent photoluminescence (TD-PL) measurements. The investigation aimed at the optimization of a multiple quantum well (MQW) structure design for application in the gain region of near infrared (NIR) laser diodes (LDs) revealed benefits of both double parabolic quantum wells and a mixed design (rectangular MQW with parabolic barriers). The PL band position for all samples was registered in the vicinity around 1.19 eV, which corresponds to the Bi content in QW of ~4.4%. It was shown that all structures of type A exhibit an intense emission, while the intensity of photoluminescence measured for the samples of type B depends on the number of QWs. The weaker intensity of the PL signal from two QWs inserted between parabolic barriers was explained by a larger point defect density at low temperature grown inner GaAs barriers. The room-temperature PL intensity of the structure with three GaAsBi QWs embedded in one parabolic AlGaAs barrier was the highest one. The shift of PL peak position to lower energies (1.16 eV) was attributed to the slightly higher bismuth concentration, 4.9%.

Semi-empirical growth model of InSbBi grown by molecular beam epitaxy

The molecular beam epitaxy growth of bump-free indium antimonide-bismide (InSbBi) necessitates precise control of group III and V stoichiometry, as well as the growth temperature and rate. In this research, we propose a semi-empirical growth model approach to enhance our understanding of the involved growth kinetics and predict the bismuth (Bi) content and surface quality of InSbBi films. The model combines the impact of growth rate and the maximum incorporation rate of Bi on the Bi content of InSbBi. Our findings indicate that bump-free InSbBi requires a minimum Bi incorporation rate to Bi adatoms arrival rate (or Bi flux) ratio of 0.96, which closely approaches the ideal value of 1.0. By employing this growth model, we can optimize the growth conditions for achieving high-quality InSbBi films with controlled Bi content.

Cubic AgBiS2 Powder Prepared Using a Facile Reflux Method for Photocatalytic Degradation of Dyes.

The ternary chalcogenide AgBiS2 has attracted widespread attention in the field of photovoltaic and photoelectric devices due to its excellent properties. In this study, AgBiS2 powders with an average diameter of 200 nm were prepared via a simple and convenient reflux method from silver acetate, bismuth nitrate pentahydrate, and n-dodecyl mercaptan. The adjustment of the ratios of Ag:Bi:S raw materials and of the reaction temperatures were carried out to investigate the significance of the synthesis conditions toward the composition of the as-synthesized AgBiS2. The results of XRD indicated that the powders synthesized at a ratio of 1.05:1:2.1 and a synthesis temperature of 225 °C have the lowest bismuth content and the highest purity. The synthesized AgBiS2 crystallizes in a rock salt type structure with the cubic Fm3¯m space group. Scanning and transmission electron microscopy, thermogravimetric analysis, ultraviolet-visible-near-infrared spectra, and photocatalytic degradation performance were employed to characterize the as-synthesized samples. The results demonstrated that AgBiS2 powders display thermal stability; strong absorption in the ultraviolet, visible, and partial infrared regions; and an optical bandgap of 0.98 eV. The obtained AgBiS2 powders also have a good degradation effect on the methylene blue solution with a degradation efficiency of 58.61% and a rate constant of 0.0034 min-1, indicating that it is an efficient strategy for sewage degradation to reduce water pollution.

Ferroelectric relaxor behaviour in Bi and K/Na-substituted solid solutions of tetragonal tungsten bronze PbNb2O6

Lead metaniobate (PbNb2O6 or PNO) belongs to the tetragonal tungsten bronze (TTB) family. There are three polymorphic forms of PNO: tetragonal (stable at high temperature), rhombohedral (stable at room temperature), and the metastable orthorhombic phase, which has ferroelectric properties. The metastable orthorhombic phase is formed by quenching from the high temperature tetragonal phase due to the reconstructive/sluggish tetragonal to rhombohedral phase transition. A suitable ionic substitution can also lead to the stable ferroelectric orthorhombic phase. Stabilization of the ferroelectric orthorhombic phase by ionic substitution, and the formation of ferroelectric relaxors with increased amounts of dopants is hereby reported for the compositions Pb(1-x)Bi(x/2K(x/2)Nb2O6 and Pb(1-x)Bi(x/2)Na(x/2)Nb2O6. The solid solutions of PNO showed evidence of linked dielectric relaxation and ferroelectricity, validating the distinctive ferroelectric relaxor behaviour for the compositions Pb0.6Bi0.2K0.2Nb2O6 and Pb0.6Bi0.2Na0.2Nb2O6. As the concentrations of bismuth (Bi) and potassium/sodium (K/Na) dopants increased, the Curie temperature (Tc), or the temperature corresponding to the maximum dielectric permittivity (Tm), dropped. By using the Uchino-Nomura relation as a modification of the Curie-Weiss law, it was established that the Pb0.6Bi0.2K0.2Nb2O6 solid solution exhibit higher degree of diffuseness than Pb0.6Bi0.2Na0.2Nb2O6 at the transitions. The width of the ferroelectric hysteresis loop increased as the percentage of dopants increased, from x = 0.1 to x = 0.3. At x = 0.4, a narrow ferroelectric hysteresis loop and a frequency-dependent Tm abruptly formed, which is indicative of a ferroelectric relaxor.

Effect of trace bismuth on the solidification structure of hypereutectic Al–22Si alloys

The effect of trace Bi on the solidification structure of the Al–22Si alloy was studied by optical microscopy, scanning electron microscopy, field emission transmission electron microscopy, X-ray diffraction, and differential scanning calorimetry. Trace amounts of Bi were found to have an inhibitory effect on the growth of primary silicon in the Al–22Si alloy. The average size and area fraction of primary silicon reached a minimum when 0.05 wt% Bi was added. As the bismuth content gradually increased, the average size and area fraction of primary silicon continued to increase. The addition of Bi improved the morphology of eutectic silicon in the Al–22Si alloy, as it gradually changed from long needle flakes to short needle flakes. Stacking faults formed in eutectic silicon may have resulted in its morphogenesis.

Physical, microstructural, and radiation energy absorption properties of recycled CRT-screen glass doped with Bi2O3

In this study, pristine TV-CRT screen glass (TVS) and those doped with 10% (TVS-Bi10) and 20% (TVS-Bi20) by weight of Bi2O3 were prepared and analyzed for their physical, microstructural, radiation dosimetry quantities, and shielding features. The glass samples were fabricated using the cold isostatic press method. The surface microstructure and the chemical composition of the glass ceramics were probed with the aid of the scanning electron microscopy-energy dispersive X-ray (SEM-EDX) system. Photon absorption and scattering quantities were estimated using standard procedures. The mean density values determined by Archimedes principle were calculated as 2.614, 2.788, and 3.056 gr/cm3 for the TVS, TVS-Bi10, and TVS-Bi20 samples, respectively. SEM images of samples showed that the increase in bismuth content increased sample crystallization and surface pores. The estimated mass energy absorption coefficients of the samples varied from 0.0177 to 11.7578 cm2/g for TVS, 0.0182–14.5218 cm2/g for TVS-Bi10, and 0.0187–17.7615 cm2/g for TVS-Bi20 for photon energies between 15 keV and 15 MeV. At 1 mm glass thickness and for 100 keV gamma rays, the dose rate was 13 MR/h, 17 MR/h, and 22 MR/h for TVS, TVS-Bi10, and TVS-Bi20, respectively. The mass stopping powers of electrons at 15 keV have values of 12.37 MeV cm2/g 12.21 MeV cm2/g, and 12.03 MeV cm2/g for TVS, TVS-Bi10, and TVS-Bi20, respectively. Generally, the ranges of the CPs were such that those of TVS > TVS-Bi10>TVS-Bi20. Bi2O3 increases the electron, proton, alpha particle, and carbon ion absorbing features of the TVS-BiX samples. Bi2O3 suppresses photon scattering, makes the TVS glass more sensitive to photon and charged particle interaction and absorption. The investigated glasses are useful for gamma-radiation, light, and heavy ion absorption and protection technology.

Properties of Mixing SAC Solder Alloys with Bismuth-Containing Solder Alloys for a Low Reflow Temperature Process

The subject of extensive research has been the establishing of lower temperature soldering of electronic assemblies that are similar to the once common yet still preferred eutectic Tin-Lead (SnPb) soldering processes that are below 217˚C. This research measured and compared the mixing mechanisms of paste and ball dissolution. Mixed soldered assemblies will have different dissolution results that are dependent on the peak reflow temperature. The hypothesis for this experiment was to determine the relationship of various times above the melting point of low temperature solders containing Bismuth. The results measured are from solder joints of both SAC305 and Bismuth containing solders formed at lower process temperatures compared to the standard high temperatures which peak at 230˚C-260˚C. The Bismuth containing solders evaluated start with the highest to lowest weight percentage of Bismuth, the eutectic 58Bismuth/42Tin (58Bi/42Sn), 57Bi/42Sn/1Ag and a propriety alloy that has a lower Bismuth content along with various micro alloys, defined as 40-58Bi/Sn/X (X representing proprietary micro alloys or doping). The assembly was with an 18mil 96.5Tin/3.0Silver/0.5Copper (SAC305) solder ball mixed with each solder paste. These solder alloys were exposed to three different peak temperatures 180˚C, 195˚C, 205˚C. Another reflow profile attribute of focus was times above 138˚C - the melting point of the eutectic Sn58Bi alloy, this term used throughout the study is referred to Time Above Melting (TAM). The ball and paste assembly used the times above melting of 120sec and 240sec to represent process extremes and verify their significance on improving mixing level results. The average mixing % levels were recorded and compared for each solder joint combination to test the theory that the solder paste solidifies during the time above melting (TAM) within the reflow oven. [1] This experiment effectively demonstrates that the reflow profile parameter for time above melting has limited effectiveness in additionally mixing the paste with the BGA solder ball. Optimization of mixing percentages will need to be achieved by optimizing the paste and ball volumes.