Low Ag Content Research Articles

Microstructure, Wettability and IMC Formation of Low-Ag SAC Solder on Cu Substrate

This Paper Reports the Microstructure, IMC Evaluation and Wettability of Low-Ag Sn-Ag-Cu(SAC) (0.3 Wt% Ag and 0.5 Wt% Ag) and SAC305 Solder Alloys in Reflowed and Agedconditions. Reflow was Done at 250°C and Thermal Aging at 150°C For100 Hours. Microstructure of Bulk Solder and the IMC Formed at Interfacebetween Solder and Cu Substrate were Observed Using SEM Equipped with EDX. Microstructureobservation Showed Finer β-Sn Dendrites at 0.3%Ag Indicating a Possiblerefining Effect of Lower Ag on Bulk Solder Microstructure. SEM Result Showedfiner Ag3Sn Distributed in the Solder but the IMC Thickness of Bothreflowed and Aged Solder Joint Seems to Increase with Decreasing Ag Content.This could be due to Finer β-Sn Dendrites which Provide more Diffusion Paththrough Grain Boundaries and Increase IMC Thickness. Similarly, Lower Ag Content Appears to have Detrimental Effect on Wettability and Wetting Angle Ofsolder Joint.

Comparison of silver nanoparticles stored under air or argon with respect to the induction of intracellular free radicals and toxic effects toward keratinocytes

Bacterial infections decreased considerably after the discovery of antibiotics. Nevertheless, because of the rising rate of infections caused by antibiotic-resistant bacteria strains, the search for new bactericidal agents has again become a crucial topic in clinical medicine. Silver nanoparticles (AgNP) have a huge potential in dermatology and wound care management because of their ability to release silver ions (Ag+ ions) in a prolonged and sustained way. However, negative effects of silver on the patient’s cells should not be underestimated. Furthermore, it has been controversially discussed whether AgNP are responsible for nanoparticle-specific outcomes or not. In this study, we investigated the effects of AgNP on human skin keratinocytes (HaCaT) in order to better understand the mechanisms of cytotoxicity and to improve the use of this highly reactive biocide in wound healing. We found that most of the cells with internalized AgNP displayed the typical morphological signs of apoptosis. The cell viability assay (XTT) showed concentration-dependent toxic effects of the AgNP toward HaCaT cells. The generation of reactive oxygen species (ROS) induced by AgNP was investigated in cell suspensions by means of electron paramagnetic resonance (EPR) spectroscopy. In order to distinguish between the effects of Ag+ ions released during AgNP storage and those of Ag+ ions released after nanoparticle application, we compared AgNP stored under air (O2) with AgNP stored under argon (Ar). Dispersions of AgNP stored under Ar have a low content of Ag+ ions because of the absence of oxygen which is needed for oxidative dissolution. The results show that Ag+ ions released during particle storage are responsible for most of the ROS produced during 1h incubation with the cells. AgNP (Ar) also induced intracellular ROS but to a much smaller extent compared to AgNP (O2). These findings highlight the complexity of experiments to assess the toxicity of AgNP and suggest the possibility of reducing AgNP toxic effects by storing AgNP formulations and even silver-containing wound dressing under an inert gas atmosphere.

A highly sensitive non-enzymatic glucose sensor based on bimetallic Cu–Ag superstructures

Bimetallic Cu–Ag superstructures were successfully fabricated for the first time by using the natural leaves as reducing agent through a facile one-step hydrothermal process. Morphology, structure and composition of the Cu–Ag superstructures were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and inductively coupled plasma-optical emission spectroscopy (ICP-OES), respectively. The results reveal that the Cu–Ag superstructure is bimetallic nanocomposite constructed by nanoparticles with low Ag content and shows a rough surface and porous flexural algae-like microstructure. By using a three-dimensional nickel foam as the scaffold, a novel non-enzymatic glucose sensor based on Cu–Ag nanocomposites has been fabricated and applied to non-enzymatic glucose detection. The as-prepared Cu–Ag nanocomposites based glucose sensor displays distinctly enhanced electrocatalytic activity compared to those obtained with pure Cu nanomaterials prepared with a similar procedure, revealing a synergistic effect of the matrix Cu and the doped Ag. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy indicate that the Cu–Ag superstructures based glucose sensor displays a fascinating sensitivity up to 7745.7μAmM−1cm−2, outstanding detection limit of 0.08μM and fast amperometric response (<2s) for glucose detection. Furthermore, the sensor also exhibits significant selectivity, excellent stability and reproducibility, as well as attractive feasibility for real sample analysis. Because of its excellent electrochemical performance, low cost and easy preparation, this novel electrode material is a promising candidate in the development of non-enzymatic glucose sensor.

Improved electrochemical performance of Ag-modified Li4Ti5O12 anode material in a broad voltage window

Li4Ti5O12/Ag composites were synthesized by a solid-state method. The effect of Ag modification on the physical and electrochemical properties is discussed by the characterizations of X-ray diffraction, scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, cycling and rate tests. The lattice parameter of Li4Ti5O12 with a low Ag content is almost not changed, but the lattice parameter becomes larger due to the high content of Ag. Li4Ti5O12/Ag material has a uniform particle size which is about 1 \(\upmu\)m. Modification of appropriate Ag is beneficial to the reversible intercalation and deintercalation of Li + . Modification of Ag not only decreases the charge transfer resistance of Li4Ti5O12 material, but also improves the diffusion coefficient of lithium ion. Li4Ti5O12/Ag (3 mass%) material has the lowest charge transfer resistance, the highest diffusion coefficient of lithium ion and the best rate cycling performance. Li4Ti5O12/Ag composites were synthesized by a solid-state method, and the remarkably improved rate properties of the Ag-modified samples are due to high conductivity of Ag at the surface of Li4Ti5O12, and faster kinetics of both the Li+ diffusion and the charge transfer reaction.

Effect of the composition on the ionic motion in an In-rich chalcopyrite ingot of the Cu–Ag–In–Se system

A Cu0.9Ag0.1In3Se5 ingot with a length of 31mm and 10mm of diameter was grown from the pure elements using the Bridgman method. The ingot appeared broken in two separate parts that were cut in several slices 2mm thick. A S1 region, from the bottom to 13.6mm, where the composition varies markedly along its length, but the surface composition is homogeneous in all slices; and a S2 non homogenous region, from 13.6 to the end of the ingot. Composition, X-ray diffraction and Laue diffractogram data of S1 region show the formation of an In rich chalcopyrite single crystal. All homogenous samples have a lower Ag content than that corresponding to the expected composition. The low Ag solubility in the chalcopyrite lattice is possibly due to its larger ionic size as compared to that of Cu. The electrical properties have been analyzed in three samples with different composition by forming a graphite paint/sample/graphite paint solid state device. The sample potential drop, Vm, the current intensity, I, and the Vm(t)/I(t) ratio vary with time when a constant potential is applied to such device. The no reproducibility of the electrical measurements has been observed. Therefore, these compounds are mixed ionic and electronic conductors. This behavior is associated with ionic motion and their subsequent accumulation at the graphite paint/sample interface that leads to the formation of a new potential. The different composition in In rich chalcopyrites indicates a different number of (InCu2++2VCu) defect pairs, DADPs. A relation between the interface potential and the number of DADPS and Ag content has been established. The existence of such interface potential is supported by the discharge processes observed when the solid state device under study is set in short- and open-circuit configurations.

Study on low-Ag content Sn–Ag–Zn/Cu solder joints

The eutectic Sn–Ag–Cu solder is the most popular lead free solder. But reliability and cost issues limit its application. On the other hand, Sn–Ag–Zn system has many advantages comparing with Sn–Ag–Cu. In this paper, interfaces of Sn–xAg–1Zn/Cu and Sn–2Ag–xZn/Cu (x=1, 2, 3), Sn–2Ag–2.5Zn/Cu and Sn–1.5Ag–2Zn/Cu solders joints were studied to understand effects of Ag and Zn contents. Results show that shearing strength of as-reflowed Sn–2Ag–2Zn/Cu and Sn–1.5Ag–2Zn/Cu joints is higher than other joints. Because of the strong Cu–Sn reaction and the formation of Ag3Sn, the Sn–Ag–Zn series solder joints are not suitable for use above 150°C temperature. After 250°C soldering for 4h, while the Zn content increased from 1wt% to 2wt%, the interfacial IMC of Sn–Ag–Zn/Cu altered from Cu6Sn5 to Cu5Zn8. The Cu5Zn8 interface has higher shearing strength than Cu6Sn5 interface. Relationships among microstructure, strength and aging condition are discussed.

Core–shell-structure Ag–BaTiO3 composite nanopowders prepared directly by flame spray pyrolysis

Core–shell-structure Ag–BaTiO3 composite nanopowders are prepared directly by flame spray pyrolysis. The single-crystalline Ag was located in the core part of the composite powder, and the Ba and Ti components are uniformly distributed in the shell part. The X-ray diffraction (XRD) patterns of the Ag–BaTiO3 composite powders have the main crystal peaks of Ag and broad peaks at around 28°. The Ag–BaTiO3 pellets with low Ag contents (below 20 wt%) have a dense structure and fine grain size. Abnormal grain growth of the Ag(30 wt%)–BaTiO3 pellets occurs even at a low sintering temperature of 1000 °C. The Ag–BaTiO3 pellet had a mixed crystal structure of BaTiO3 and Ag phases. Silver is uniformly distributed in the BaTiO3 matrix without phase separation. The dielectric constants of the BaTiO3, Ag(10 wt%)–BaTiO3, and Ag(30 wt%)–BaTiO3 pellets are 830, 2130, and 4680, respectively.

Investigation of microstructure and mechanical properties of novel Sn–0.5Ag–0.7Cu solders containing small amount of Ni

This work investigates the effects of small additions (0.05 and 0.1wt.%) of Ni on the microstructure and mechanical properties of low Ag content Sn–0.5Ag–0.7Cu (SAC (0507)) lead-free solder alloy. The addition of 0.05Ni resulted in the microstructural refinement, uniform distribution of the Ag3Sn and (Cu,Ni)6Sn5 intermetallic compounds (IMCs) and small primary β-Sn grains. This apparently enhances the mechanical strength and microhardness. However, the addition of 0.1Ni leads to the formation of relatively high fraction of the primary β-Sn phase and the IMCs appeared abrasive within the matrix. As a result, the SAC (0507)–0.1Ni solder exhibits low tensile strength, microhardness and large elongation, which produce a soft and highly compliant bulk solder. In addition, the strength of all studied alloys increases with increasing strain rate and decreasing testing temperature, showing strong strain rate and temperature dependence. Based on the obtained stress exponents and activation energies, it is proposed that the dominant deformation mechanism in SAC (0507) solders is dislocation climb over the whole temperature range investigated.

Robust Synthesis of Gold Cubic Nanoframes through a Combination of Galvanic Replacement, Gold Deposition, and Silver Dealloying

A facile, robust approach to the synthesis of Au cubic nanoframes is described. The synthesis involves three major steps: 1) preparation of Au-Ag alloyed nanocages using a galvanic replacement reaction between Ag nanocubes and HAuCl4 ; 2) deposition of thin layers of pure Au onto the surfaces of the nanocages by reducing HAuCl4 with ascorbic acid, and; 3) formation of Au cubic nanoframes through a dealloying process with HAuCl4 . The key to the formation of Au cubic nanoframes is to coat the surfaces of the Au-Ag nanocages with sufficiently thick layers of Au before they are dealloyed. The Au layer could prevent the skeleton of a nanocage from being fragmented during the dealloying step. The as-prepared Au cubic nanoframes exhibit tunable localized surface plasmon resonance peaks in the near-infrared region, but with much lower Ag content as compared with the initial Au-Ag nanocages.

Elemental distribution, solute solubility and defect free volume in nanocrystalline restricted-equilibrium Cu–Ag alloys

In this article we study the elemental distribution and solute solubility in nanocrystalline alloys of immiscible components near restricted equilibrium for the case of the binary Cu–Ag system. As predicted from thermodynamic considerations, a grain boundary segregated monophase alloy is observed in the annealed mechanically alloyed state for low Ag content by using atom probe tomography. From the detected Ag solute grain boundary enrichment the segregation free enthalpy is estimated to range between −25 and −49 kJ mol−1 following the McLean equation, in agreement with values reported for coarse-grained Cu–Ag. The extension of the alloying range is described by a two-domain thermodynamic model that considers the excess free volume in the grain boundaries and the strain in the grain interior on the basis of the universal equation of state at negative pressure. To access the grain boundary volumetric strain experimentally, a method based on a combination of density measurements and microscopical quantification of closed pore areas is presented. Moreover, we apply x-ray diffraction line broadening analysis to determine the local strain amplitude, which yields a root-mean-square microstrain of ∼0.3% for a grain size of ∼30 nm. It is shown that the grain boundary free volume represents the major origin for the global solubility enhancement in nanocrystalline Cu–Ag at 503 K.

Improved strength of Ni and Zn-doped Sn–2.0Ag–0.5Cu lead-free solder alloys under controlled processing parameters

The Sn–Ag–Cu (SAC) solders with low Ag or Cu content have been identified as promising candidates to replace the traditional Sn–Pb solder for flip-chip interconnects. The changes in microstructure, microhardness and mechanical properties associated with the alloying of Ni and Zn to the Sn–2.0Ag–0.5Cu(SAC205) solders were explored in this work. Furthermore, correlations between the mechanical behavior and controlled processing parameters such as temperature, strain and strain rate were analyzed and established. Microstructure analysis showed that additions of Ni and Zn to SAC(205) alloy not only suppressed the formation of brittle Ag3Sn IMC phase but also refined the large β-Sn dendrites, and promoted the formation of new (Cu,Ni)6Sn5 and Cu5Zn8 intermetallic compounds (IMCs) in the SAC(205) solder. Besides, the IMC particles were uniformly distributed in the β-Sn matrix. Accordingly, the mechanical properties, the microhardness and total elongation of Ni and Zn-doped SAC(205) solders were significantly improved. Both the yield strength (YS) and ultimate tensile strength (UTS) were observed to increase with increasing strain rates and decreasing temperature. This behavior was attributed to the competing effects of work hardening and dynamic recovery processes. The Zn-doped solder consistently displayed the highest mechanical properties and ductility due to the formation of hard Cu5Zn8 IMC particles and the refinement of β-Sn grain size, which could provide more obstacles for dislocation pile up in the adjacent grains.

Electrochemical Migration of Micro-alloyed Low Ag Solders in NaCl Solution

The reliability investigation of the lead-free solders is still a current issue. In this paper, Electrochemical Migration (ECM) behavior of novel lead-free micro-alloyed low Ag content solders were investigated by water drop test in NaCl solution. The results were compared to commonly used lead-free and lead bearing solder alloys. It was found that some micro-alloyed solders can have similar low ECM susceptibility than lead bearing ones. X-ray photoelectron spectroscopy was also carried out to find the root cause of different ECM behaviour of micro-alloyed solders. The results of water drop test and x-ray photoelectron spectroscopy were in good agreement relating electrochemical migration susceptibility. Since SAC0807 solder alloy has shown higher corrosion rate than SAC0307 and has also higher ability for ECM as well. It is concluded, that some lead-free micro-alloyed low Ag content solder alloy (e.g.: SAC0807) could have a high reliability risk in the electronic devices during operation.

Finite element analysis of the effect of silver content for Sn–Ag–Cu alloy compositions on thermal cycling reliability of solder die attach

Thermal performance of a chip-scale packaged power device can be improved by attaching a heat spreader to the backside of the heat generating silicon die via solder thermal interface materials [STIMs]/solder die-attach. Driven by government legislation, electronics industry has advanced to lead (Pb)-free solders due to environmental and health concerns emanating from the use of Pb-based solders. Though solder compositions in the form of Sn–Ag–Cu (SAC) ternary system have been widely accepted and preferred by the electronic industry as replacements for the traditional Pb-based solder alloys, debate continues over the optimal silver content in the Sn–Ag–Cu (SAC) solder alloys. Apparently, the effect of silver (Ag) content on thermo-mechanical reliability of SAC alloy compositions as small area solder joints (flip chip solder bump or ball grid array (BGA)) has been extensively studied but not enough information exist on the effect of Ag percentage in SAC solder alloys when employed as large area solder joint (die-attach application). In this study, non-linear finite element method (FEM) is used for a comparative analysis of the effect of Ag content on the thermal fatigue performance of Sn–3Ag–0.5Cu (SAC305) and Sn–4Ag–0.5Cu (SAC405) when used in die-attach applications under three different thermal cyclic loading cases. The results show that Von-Mises stresses and strain energy in each of the two different SAC solder joints were strong function of the thermal cycle profiles, increasing in the order −55–80°C<−55–125°C<−65–150°C. In addition, this study suggests that the range of stress was relatively greater for the SAC alloy with higher Ag content (SAC405) while the lower Ag content SAC solder (SAC305) experiences a comparatively larger accumulated plastic work under the same thermal cycling condition. Further failure analysis via visual inspection reveals that for all cases of thermal cyclic loading employed in this study, maximum values of strain energy were all located in the corner regions (critical regions) of the solder joints at the side next to the silicon die independent of the Ag content of the solder joints. This paper also highlights the concerns as regards the implementation of conventional thermal fatigue models for accurate life time prediction of large area solder joint.

Co x Ag1−x core–shell nanoparticles: magnetic and magneto-optical studies

The magneto-optical properties of 14-nm Co x Ag1−x core–shell nanoparticles (x=0.7, 0.8, and 0.35) deposited on different substrates are investigated at room temperature in the photon-energy range from 0.8 to 4.8 eV. Particles with low Ag content show spectra very similar to pure Co nanoparticles while particles with high Ag content have totally different features, where the Ag plasma edge dominates the spectra. The spectral features of the polar Kerr rotation depend on particle composition. The ageing process and development of an oxide layer influence the particles’ core–shell structures and magnetization curves. Co-rich particles exhibit lower resistance to the oxidation process as compared to Ag-rich ones. The quality of the nanoparticles was checked by transmission electron microscopy in respect of time scale.

Lead in Ancient Peru: the Curamba Smelter and Lead Sling Bullets

Since the 16th century, the Inca site of Curamba, in southern Peru, has been interpreted as a metallurgical center for processing silver ore. Yet, aside from the many shallow pits, interpreted as hornos for smelting silver, there was no physical evidence for the use of huayras or tocochimbos, which were the structures traditionally used for precontact silver smelting in the ancient Andes. Geochemical analyses (inductively coupled plasma) of scoria excavated from the hornos at Curamba indicate low Ag (<0.3 ppm to 0.4 ppm), Au (<2 ppm), and Cu (18 ppm to 31 ppm) contents, whereas Pb (155 ppm to 234 ppm) and Zn (125 ppm to 259 ppm) contents were high. This suggests that nonargentiferous galena (PbS) was smelted to obtain lead. A lead-zinc signature is also indicated by the presence of As, Ba, Fe, Mn, and V, yet no ore minerals such as PbS or sphalerite [(Zn,Fe)S] have been found at the site. Several precontact lead artifacts from ancient Peru have been described as bars (lingotes) or weights (pesos). However, alternatively, these artifacts might be more accurately described as: (a) biconic to ovoid (30 mm to 60 mm, 30 g to 40 g) or (b) spherical (35 mm, 80 g to 160 g); therefore, in composition, dimensions, form, and weight, these ancient Peruvian lead artifacts from the north coast are strikingly similar to ancient Roman and Celtic lead sling ammunition from first-century BC battle sites, and are herein interpreted to have served a similar function in ancient Andean warfare.

Study on melt properties, microstructure, tensile properties of low Ag content Sn–Ag–Zn Lead-free solders

Sn–Ag solders have been regarded as the most promising solders to replace Sn–Pb solders in the future, but the reliability and cost issues limit its use. Therefore a low-Ag content Sn–Ag–Cu solder, SAC105 was researched, which still has some problems. Sn–Ag–Zn solders are obviously superior in many aspects in comparison to Sn–Ag–Cu solders, but the low-Ag Sn–Ag–Zn solders were rarely studied. In this paper, properties of Sn–xAg–yZn (x=1, 1.5, 2, 3; y=1, 1.5, 2, 2.5, 3, 4) solders, including melt properties, microstructure, and tensile properties were investigated. It was found that reduction of Ag content in Sn–Ag–Zn solders leads to the same problems as in Sn–Ag–Cu solders in melt properties and tensile properties. Although Sn–xAg–1Zn solders have higher strength, the elongation is lower. Results show that melt properties and tensile properties can be improved by the optimization of Zn content, but excessive Zn additon could lead to worse properties as well. Sn–2Ag–2.5Zn and Sn–1.5Ag–2Zn solders were found to have optimized properties. In addition, relations between melt properties and microstructure, as well as microstructure and tensile properties, were discussed.

Sn-Ag-Cu-X 무연솔더로 솔더링 된 접합부의 진동파괴 거동

Environmental and health concerns over the lead have led to investigation of the alternative Pb-free solders to replace commonly used Pb-Sn solders in microelectronic packaging application. The leading candidates for lead-free solder alloys are presently the near eutectic Sn-Ag-Cu alloys. Therefore, extensive studies on reliability related with the composition have been reported. However, the insufficient drop property of the near eutectic Sn-Ag-Cu alloys has demanded solder compositions of low Ag content. In addition, the solder interconnections in automobile applications like a smart box require significantly improved vibration resistance. Therefore, this study investigated the effect of alloying elements (Ag, Bi, In) on the vibration fatigue strength. The vibration fatigue was conducted in 10~1000Hz frequency and 20Grms. The interface of the as-soldered cross section close to the Cu pad indicated the intermetallic compound () regardless of solder composition. The type and thickness of IMC was not significantly changed after the vibration test. It indicates that no thermal activities occurred significantly during vibration. Furthermore, as a function of alloying composition, the vibration crack path was investigated with a focus on the IMCs. Vibration crack was initiated from the fillet surface of the heel for QFP parts and from the plating layer of chip parts. Regardless of the solder composition, the crack during a vibration test was propagated as same as that during a thermal fatigue test.

Dual Screen Printing Featuring Novel Framed Busbar Screen Layout and Non-Contacting Ag Busbar Paste

Screen printing has been the dominant technology for the metallization of silicon solar cells up to date. Many efforts have been made to further optimize the process focusing on economical profitability and electrical performance. The aim of this work is to improve the cell performance while reducing the costly consumption of Ag paste at the same time.A dual printing approach is presented for the font side metallization of Si solar cells. A new non-contacting paste with lower Ag content is introduced for the busbars along with a novel screen layout featuring framed busbars. The paste and layout are compared to regular single and dual printing of a standard front side paste. The utilization of a low Ag containing and non-contacting busbar paste yields Ag savings of 15%. Simultaneously, the cell efficiency is improved by 0.2%abs. compared to standard single printing.

The Morphology and Evolution of Cu&lt;sub&gt;6&lt;/sub&gt;Sn&lt;sub&gt;5&lt;/sub&gt; at the Interface of Sn-2.5Ag-0.7Cu-0.1RE/Cu Solder Joint during the Isothermal Aging

The morphology and growing behavior of Cu6Sn5intermetallic compound (IMC) of low Ag content Sn-2.5Ag-0.7Cu-0.1RE/Cu solder joint interface are investigated by adopting the X-ray diffraction, JSM-5610LV scanning electronic microscope and energy spectrum analysis. The results show that the cross-section morphology Cu6Sn5of the solder joint interface is scallop-like and its section morphology is circle-like grain. With the aging time increasing, the cross-section Cu6Sn5morphology of the solder joint interface can be changed from the scallop-like to the shape-layer, and the growing kinetics is coincidence with the law of parabola and its growing behavior is controlled by diffusion. With adding a small amount of rare earth elements in the Sn-2.5Ag-0.7Cu solder alloy, the growing rate of the Cu6Sn5can be reduced.

Geology, mineral chemistry and tourmaline B isotopes of the Córrego Bom Sucesso area, southern Serra do Espinhaço, Minas Gerais, Brazil: Implications for Au–Pd–Pt exploration in quartzitic terrain

The Palaeo-Mesoproterozoic metasiliciclastic rocks of the southern Serra do Espinhaço, Minas Gerais, Brazil, are host to historically important alluvial deposits of diamonds and gold. Detrital gold grains often comprise Au–Pd–Pt intermetallic compounds, with low Ag contents, which contain inclusions of tourmaline and titaniferous hematite (up to ~ 6 wt.% TiO 2). The latter minerals connect the alluvial mineralisation to the rutile–hematite–quartz veins and tourmalinisation observed in the quartzitic country rocks of the alluvial gravel. The quartzite (Sopa-Brumadinho Formation of lacustrine to fan-deltaic origin) is affected by pervasive B metasomatism with F-bearing tourmaline replacing the recrystallised quartz fabric. The tourmaline belongs to the alkali group, with Mg/(Mg + Fe) and X/(X + Na) ratios in the ranges from 0.5 to 0.7 and 0.18 to 0.29, respectively, where X represents vacancies in the X site. Boron-isotopic values of tourmaline vary from ~ 1 to − 10.4‰ δ 11B. The B-isotope range, in conjunction with the Na–Mg-rich tourmaline composition, and the widespread occurrence of tourmalinite in the Sopa-Brumadinho Formation suggest a derivation from non-marine evaporitic brines. Brines are capable of transporting otherwise immobile Ti and explain, under oxidising conditions, the fractionation of Ag from Pd to precipitate palladiferous gold with extremely high Pd/Ag ratios. Zirconium-in-rutile and Ti-in-quartz temperatures for a variety of hematite-rich veins suggest episodic vein emplacement over a temperature range from around 500 °C to ~ 350 °C. Cross-cutting relationships and episodic vein emplacement indicate a late-Brasiliano age.