Ni Sn Intermetallics Research Articles

Ultrasound-induced interinhibitive dissolution-precipitation evolution and significantly improved mechanical properties of Kovar/SnSb10 assembly

Ultrasound-assisted Kovar/SnSb10 assemblies are promising candidates for high-precision electronic devices; however, limited research has been conducted on the effect of ultrasonication on its interfacial evolution and mechanical properties. In this study, the microstructure evolution, orientation relationships (ORs), interinhibitive dissolution-precipitation mechanism, and mechanical properties of a Kovar/SnSb10 assembly with/without ultrasonication were systematically investigated. The morphology of the intermetallics (IMCs) evolved from a newly-formed, lash-type to a block-type morphology with an increasing reflow duration, and dentation-type IMCs appeared after ultrasonication. The interfacial IMC without ultrasonication mainly contained FeSn2 and a minority of Ni3Sn2, whereas the strong disturbance caused by ultrasound led to the formation of FeSn in the peripheral FeSn3 and NiSn IMCs. Furthermore, high-resolution transmission electron microscopy (HRTEM) analysis revealed that the ORs of IMC/solder and IMC/Kovar transformed from coherent and semi-coherent to incoherent relationships after ultrasonic treatment. The ORs of the IMC/solder growth front after ultrasonication were [0 1¯ 1]Sn∥[1 1 0]FeSn3, (0 1 1)Sn∥(0 0 1¯)FeSn3 and [0 1¯ 1]Sn∥[5¯ 1 0]NiSn, (0 1 1)Sn∥(0 1¯ 0)NiSn. Additionally, 60 s ultrasonic treatment promoted the growth of IMCs, and increased the ultimate shear strength by approximately 20 MPa, despite the emergence of incoherent interfaces. This phenomenon was primarily attributed to the dispersion strengthening effect of the abundant ultrasound-induced nano-Ni3Sn2 precipitates. This study substantiates the feasibility of ultrasonication-assisted Kovar/SnSb10 assemblies and introduces a novel concept for low-cost, high-efficiency, and high-performance packaging.

Mechanochemical preparation of NiCuSn nanoparticles and composites in presence of cetyltrimethylammonium bromide (CTAB) and the catalytic application of the products in homocoupling and hydration of terminal alkynes

We report the synthesis of the NiCuSn nanoparticles and nanocomposites in mechanochemical route using CTAB as milling additive. The study of grinding intensity (frequency) and time interval drew up the importance of the well-chosen operation parameters. The mild milling resulted in formation of NiSn intermetallics, while the intense ones aided the evolution of bronze and copper(I) oxide phases. The utilization of CTAB proved to be the key factor to prevent or slow down the process of mechanical alloying and to fritter the metal grains into the nanodimensions. The dynamic light scattering data demonstrated positively charged particles with average solvodynamic diameters of around 70 nm applying intense or long-term millings. Without CTAB or with relatively short or weak grindings, these values remained between 230 and 550 nm, as in the case of the surface areas getting around 20 m2/g with and 1 m2/g without CTAB. The catalytic transformation of p-methoxyphenylacetylene in dimethyl sulfoxide showed that the copper, copper(I) oxide and bronze particles managed the reaction toward the evolution of 1,3-diyne in Glaser-Hay homocoupling without base addition, while the Sn and SnO2 phases assisted to the Markovnikov-type hydration of alkyne groups. The formation of α-diketone signed that the anti-Markovnikov route was also occurred. The use of CTAB was found to exert a profound effect on the quality of catalytic end-products through the controlled generation of bronze and tin oxide phases and the solid solution of nickel atoms.

High-temperature stability of Ni-Sn intermetallic joints for power device packaging

In this study, the feasibility and high-temperature stability of Ni-Sn bonded joints fabricated by transient liquid phase sintering (TLPS) were investigated for high-temperature power electronics applications. A 30Ni-70Sn (wt%) TLPS paste was fabricated with micro-sized pure Ni and Sn powders, and chip bonding was performed on a direct bonded copper (DBC) substrate. During TLPS bonding, Sn particles melted and reacted with Ni particles, which resulting in the formation of stable Ni-Sn TLPS intermetallic joints. During aging treatments at 150 and 200 °C, the formed Ni3Sn4 phases were transformed into the Ni3Sn2. With increasing aging treatments, the reactions between Ni3Sn4 intermetallics and remaining Ni particles increased, which resulted in the formation of the Ni-rich Ni-Sn intermetallics. Even after 1000 h at an aging temperature of 200 °C, there is no significant difference in the stable and dense microstructure of Ni-Sn TLPS joints. In addition, their mechanical strengths did not vary significantly even after long-term treatment for 1000 h at 150 and 200 °C. This means that the Ni-Sn TLPS joints have a good long-term microstructural stability and mechanical reliability at high temperatures up to 200 °C. Therefore, we conclude that the Ni-Sn paste is a promising candidate as a die-attach material for high-temperature electronic assemblies.

Ni–Sn intermetallics as an efficient buffering matrix of Si anodes in Li-ion batteries

High-capacity Si-based anodes with good coulombic efficiency and long-cycle life are achieved by embedding silicon nanoparticles in dual Ni3Sn4/Ni3Sn2 active/inactive intermetallic matrix.

Ab initio study of the cohesive properties, electronic structure and thermodynamic stability of the Ni–In and Ni–Sn intermetallics

A comprehensive study of the structural, cohesive and electronic properties of several stable, metastable and non-stable intermetallic phases (IPs) of the Ni–In and Ni–Sn systems have been performed by ab initio density-funcional-theory (DFT) methods. Using the projector augmented wave method we have performed systematic spin polarized calculations with the exchange and correlation functions of Perdew and Wang in the generalized gradient approximation (GGA), as well as those by Ceperley and Alder in the local-density-approximation (LDA). Structural properties, the energy-of-formation (EOF) from the elements and the cohesive properties of the various phases have been established by minimizing the internal structural parameters. We present trends at 0 K in the composition dependence of the molar volumen, bulk modulus and its pressure derivative, electronic density of states, magnetic moments and the EOF of several stable and metastable IPs reported in the Ni–In and Ni–Sn systems as well as various non-stable (hypothetical) compounds which are relevant in connection with the thermodynamic analysis of the Ni–In and Ni–Sn systems using Gibbs energy models and the so-called CALPHAD techniques. The results are compared with the available experimental data and with previously reported theoretical results. The present study of the thermodynamic and cohesive properties of Ni–In/Sn intermetallic phases should contribute to the understanding of the phase-stability systematics in the Ni–In–Sn system and the design of new soldering alloys.

Effects of Zn-Containing Flux on Sn-3.5Ag Soldering with an Electroless Ni-P/Au Surface Finish: Microstructure and Wettability

The microstructure resulting from Sn-3.5Ag soldering on an electroless Ni-P/Au pad using flux containing Zn(II) stearate was investigated. The content of zinc compound in the flux was 0 wt.% (Z-0), 20 wt.% (Z-20) or 50 wt.% (Z-50). A study of the interfacial microstructure revealed that both Z-20 and Z-50 fluxes yielded a thinner P-rich layer at the interface than did the Z-0 flux. In addition, compared with the bulky Ni–Sn intermetallics of the Z-0 joint interface, refined interfacial intermetallic compounds (IMCs) were observed when using Zn-containing fluxes, Z-20 and Z-50. Based on qualitative analyses of both Z-20 and Z-50 joint interfaces, it was presumed that their intermetallic layers would consist of Ni, Zn, and Sn. Additionally, the Ni content in the IMC layer of the Z-50 joint was lower than that of the Z-20 joint. Electron probe microanalysis (EPMA) of the initial Z-50 joint interface revealed Zn in the interfacial reaction layer, suggesting that Zn participated in the reaction between solder and the surface finish at an early stage of soldering. Consequently, the supply of Zn from the flux diminished Ni diffusion into the molten solder during heating. This effect may have caused a thin P-rich layer to form at the joint interface.

First-Principles Calculation of Phase Stability and Cohesive Properties of Ni-Sn Intermetallics

The cohesive properties of Ni-Sn intermetallics (stable, metastable, and virtual), hitherto unexplored by density-functional theory (DFT) methods, are reported. Specifically, the total energies and cohesive properties of Ni, Sn, and 27 Ni-Sn intermetallics are calculated from first-principles, using ultrasoft pseudopotentials (USPP) and both local-density approximation (LDA) and generalized-gradient approximation (GGA) for the exchange-correlation functional. Among the intermetallics considered, the ground-state structures are consistent with experimental observations; however, not all of them are registered in the equilibrium-phase diagram. An important result of this systematic study, using both USPP-LDA and USPP-GGA, is that oC20-NiSn4 is predicted to be the ground-state structure. Only recently, this phase has been observed as a product of the interfacial reaction in Ni/Sn diffusion couples. In addition, we find that the thermodynamic stability of a tetragonal phase, tP10-NiSn4, is very similar to that of oC20-NiSn4. The elastic stability of both tP10-NiSn4 and oC20-NiSn4 is confirmed by calculating their single-crystal elastic constants. The calorimetric data for the enthalpy of formation of stable intermetallics show an agreement that is better for those calculated with USPP-LDA than those calculated with USPP-GGA. In general, the experimental lattice parameters of stable and metastable phases are found to lie between those calculated using USPP-LDA and those calculated using USPP-GGA; however, in several cases, the values calculated using USPP-GGA agree to within 1 pct of the experimental data. The Ni3Sn2(ht) ⇌ Ni3Sn2(lt) transformation is discussed in terms of supergroup-subgroup relations. The bonding between the Ni and the Sn is discussed based on the analyses of the density of states (DOS) and the charge densities.

Correlation between Ni3Sn4 intermetallics and Ni3P due to solder reaction-assisted crystallization of electroless Ni–P metallization in advanced packages

Ni3Sn4 intermetallic was formed by the depletion of Ni from electroless Ni–P, and a Ni3P layer was formed simultaneously due to solder reaction-assisted crystallization during solder reflow. Both Ni3Sn4 and Ni3P grew rapidly due to the solder reaction-assisted crystallization and their growth was diffusion controlled during the first 15 min of annealing at 220 °C. After that, the growth rate of Ni3Sn4 was greatly reduced and the crystallization of electroless Ni–P to Ni3P was no longer induced. Based on kinetic data and scanning electron microscope morphology observations, underlying mechanisms causing this specific phenomenon are proposed. This finding is indeed very crucial since we may control the growth of Ni–Sn intermetallics by monitoring the solder reaction-assisted crystallization of electroless Ni–P.

Design and tailoring of Ni–Sn–W composites for bonded abrasive applications

Abstract The combination of properties ideal for metal bonds in abrasive products can rarely be achieved in a monolithic material. This research demonstrates a successful approach for producing a composite bond with higher elastic modulus without a significant increase in wear resistance, by taking advantage of the reaction between matrix and reinforcement to produce intermetallics. Composites comprised of a Ni–Sn matrix with continuous W fiber and/or W powder dispersoid were prepared by powder metallurgy methods. Composite specimens densified by hot pressing were characterized with a combination of scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyses, measurements of wear resistance, and measurements of Young's modulus and hardness by both bulk and nanoindentation methods. A significant stiffening effect was observed; the elastic modulus of the composites was up to 30% greater than that predicted by a rule of mixtures based on the moduli of the unreacted fiber and matrix constituents alone. As desired, the wear resistance of the composite was approximately equal to that of the Ni–Sn matrix. One contribution to this combination of properties is believed to be the high elastic moduli and likely low fracture toughness of the Ni–W and Ni–Sn intermetallics that are formed. Properties of the Ni–Sn–W composites are contrasted with those of a Ni–Sn matrix reinforced with WC particulate, where no reaction occurs at the interface.

The use of shape memory alloy NiTi particles in SnPbAg matrix: interfacial chemical analysis and mechanical characterisation

Abstract Uncoated and copper electroless coated fine NiTi superelastic particles have been incorporated into a liquid SnPbAg matrix. The wettability of the Cu coating by the molten alloy was determined with a wetting balance. The composite interfaces have been investigated by Auger electron spectroscopy (AES). Uncoated NiTi reacted with the matrix to form Ni–Sn intermetallics, whereas the Cu layer of coated particles behaved as a sacrificial layer, leading to a small interfacial zone containing neither Cu–Sn nor Ni–Sn intermetallics. The mechanical characterisation of Cu-coated NiTi/SnPbAg composites shows a reinforcement of the composite material compared to the monolithic matrix, and also an unusual increase of the elongation at rupture. These results can be interpreted with the superelastic properties of the NiTi shape memory alloy (SMA) particles.

Electrochemically Deposited Ni-Sn Alloys: A 119 Sn Mössbauer Study

Equiatomic electrodeposition of Ni-Sn alloys is known for its corrosion resistance. Mossbauer spectra of Ni-Sn layers and Ni-Sn intermetallics are best interpreted by the coexistence of Ni3Sn2, Ni3Sn4 and SnO in varying amounts. The presence of an intermetallic &";NiSn&'; has not yet been verified. XRD and STM exhibit the nanostructure of the electrodeposited substrate.

Interfacial studies of uncoated and coated NiTi particles in SnPbAg matrix

Uncoated and copper electroless coated fine NiTi superelastic particles have been incorporated into liquid SnPbAg matrix. The wettability of the Cu coating by the molten alloy was determined with a wetting balance. The composite interfaces have been investigated by Auger Spectroscopy. Uncoated NiTi reacted with the matrix to form Ni-Sn intermetallics, whereas the Cu layer of coated particles behaved as a sacrificial layer, leading to a small interfacial zone containing neither Cu-Sn nor Ni-Sn intermetallics. The mechanical characterisation of Cu-coated NiTi/SnPbAg composites shows a reinforcement of the composite material compared to the monolithic matrix, and also an unusual increase of the elongation at rupture. These results can be interpreted in terms of the superelastic properties of the NiTi SMA particles.

Formation Kinetics and Thin Film Stress of Tin Containing Intermetallic Compounds

AbstractThin film reactions and its influence on mechanical stress have been investigated in Cr/Cu/Sn and Cr/Ni/Sn multilayer structures. Thin film stresses of different intermetallic compounds in each material system were evaluated using substrate bending technique. Stress state in the thin film structures was round directly related to formation kinetics and thermal properties of intermetallics. In Cu-Sn system, a large internal stress increase in tension was generally observed after being heat treated at high temperatures. In Ni-Sn systems, formation of intermetallics is a relatively slow reaction at elevated temperatures as compared to that of Cu-Sn samples. Contrary to that of Cu-Sn system, formation of Ni-Sn intermetallics causes a decrease in stress in the thin film structure. The correlation of thin film stress state and the structure evolution at the interface is studied and discussed in details.