Eutectic Melting Point Research Articles

Packaging Technology for Electronic Applications in Harsh High-Temperature Environments

Silicon-on-insulator (SOI) integrated circuits have been demonstrated for use at temperatures up to 300 °C. However, to build functional electronics, multiple devices must be interconnected to provide the desired functionality. A system-in-package approach has been developed using thick-film technology on Si3N4 ceramic substrates. Si3N4 has a near coefficient-of-thermal-expansion match to Si and a higher flexural modulus than Al2O3, which is commonly used for thick-film applications. The conductor metallization is Au. For 300 °C operation, eutectic Au-Ge die attach was used with a Ti/Ti:W/Au backside die metallization. After 3000 h at 325 °C, the mean die shear strength decreased from 3.96 to 3.33 kg/mm2, a decrease of only 16%. Formation of Au-Si-Ge ternary eutectic (melting point 326 °C) was observed and limits the use of Au-Ge die attach to 300 °C. SOI dies typically have Al wire bond pads that are not compatible with Au thermosonic wire bonding for high-temperature applications. Two plating processes have been examined: electroless Ni/immersion Au/electroless Au and electroless Ni/electroless Pd/immersion Au. The plating processes provide a barrier layer (Ni) and a wire-bondable finish (Au or Pd-Au) over the Al wire bond pads. After 10 000 h at 300 °C, the wire pull force for the Ni/Au samples decreased by ~30% due to annealing of the Au wire, while the ball shear force increased by ~35%. The daisy-chain electrical resistance remained relatively constant. For the Ni-Pd-Au samples, after 2000 h at 320 °C, the ball shear force remained constant or increased slightly, the wire pull force decreased by ~25% due to annealing of the Au wire, and the daisy-chain resistance remained relatively constant. After 3000 h, however, cratering of the Si wire bond pad was observed corresponding to some first bond pad lifts and increased daisy-chain resistance. Optimization of the wire-bonding parameters for bonding to the harder Ni/Pd/Au bond pad is required to eliminate cratering.

Liquid phase-enabled reaction of Al–Ga and Al–Ga–In–Sn alloys with water

The water-reactivity of Al–Ga and Al–Ga–In–Sn alloys is investigated as a means to utilize the chemical potential energy of Al to split water for the production of H 2. Al in bulk quantities of these alloys participates in a heterogeneous reaction with water to produce H 2 and α-Al(OH) 3 (bayerite). Low melting point phases in these alloys are believed to enable the observed reaction upon liquefaction by providing a means of transport for Al in the alloys to reach a reaction site. In the Al–Ga binary system, this reaction-enabling phase is shown to form at a temperature corresponding to the system’s eutectic melting point. In the Al–Ga–In–Sn quaternary system this reaction-enabling phase liquefies at 9.38 °C, as shown using differential scanning calorimetry (DSC). Alloys with the composition 50 wt% Al-34 wt% Ga-11 wt% In-5 wt% Sn are reacted with distilled water in a series of controlled experiments, and H 2 yield from these reactions is measured as a function of time and temperature. Applying kinetic analysis to the yield data shows the apparent activation energy for the reaction process to be 43.8 kJ/mol. A physicochemical model for the alloy–water reaction is presented in the context of the observed experimental results and relevant scientific literature.

Synthesis of LiNi1/3Co1/3Al1/3O2 cathode material with eutectic molten salt LiOH-LiNO3

A lithium-ion battery cathode material, LiNi1/3Co1/3Al1/3O2, with excellent electrochemical properties was prepared by three-phase temperature sintering, using eutectic lithium salts (0.38LiOH.H2O-0.62LiNO3) mixed with the precursor Ni1/3Co1/3Al1/3(OH)2. This method was simple and inexpensive, and the materials could be mixed uniformly at the eutectic melting point without any grinding. A well-layered α-NaFeO2 structure was confirmed by X-ray diffraction (XRD). The ratio of characteristic diffraction peaks I(003)/I(104) reached 1.73. Charge–discharge testing of the synthesized powder showed an initial charge–discharge capacity of 151.5mAh.g–1 at a specific current of 0.2C in the range 2.8–4.3V up to 20 cycles with no noticeable capacity-fading (94.5% of the first discharge capacity), and reversible capacities of 133.7 and 120.9mAh.g–1 for specific currents of 1C and 2C at room temperature. The discharge capacity and capacity retention at 55°C were substantially better than at room temperature.

Microstructural Evolution during Friction Stir Processing of Magnesium Alloy Castings

Friction stir processing (FSP) of cast AM60 magnesium alloy has been studied using the breaking pin method, freezing the microstructure during the process. Strong evidence is seen that partial melting plays a key role in removing the β-Mg17Al12, whereas the manganese rich intermetallics persist during FSP. This is consistent with temperature predictions made using a process model adapted to FSP of AM60 castings that show the eutectic melting point is exceeded.

Diffusion in Al-Ni and Al-NiCr Interfaces at Moderate Temperatures

The diffusion couples for experimental study were prepared by HVOF spraying of nickel and nickel with 20 wt.% of chromium powders onto an aluminium sheet surface. The interfaces with sharp gradients of chemical concentration of these elements were prepared. Annealing at temperatures of 600°C and 630°C, close to the Al + Al3Ni eutectic melting point (639.9°C), with different dwell times were used. During annealing, the reactants diffuse and form layers of Al3Ni2 and Al3Ni intermediate phase compositions. Moreover, nickel without the assistance of chromium diffuses preferably along the grain boundaries into aluminium substrate and produces the strengthening of the substrate by stable Al3Ni and metastable Al9Ni2 particles. The microstructures were obtained by scanning electron microscopy. Layer thickness measurements were realized by means of image analyses. Chemical composition was estimated by energy dispersive microanalysis measurements. According to the results of the analyses performed the average chemical interdiffusion coefficients and Wagner’s integral interdiffusion coefficients were calculated.

Eutectic melting behavior of polyamide 10,T-co-6,T and 12,T-co-6,T copolyterephthalamides

Abstract Semi-aromatic polyterephthalamides 10,T and 12,T were synthesized with 0–60 wt-% PA-6,T comonomer by a melt polycondensation process. Molecular weights of the copolymers ranged from 12,000 to 27,000 g/mol and all produced tough melt-pressed films. The substituted aromatic carbon of the 13 C NMR spectra revealed that comonomer sequences are statistical; e.g., 50:50 wt-% PA-12,T-co-6,T copolymer had 12,T-12,T:12,T-6,T:6,T-6,T sequence ratios of approximately 1:2:1. Copolymers of both PA-10,T and 12,T exhibited a eutectic melting point at 30 wt-% PA-6,T, with melting points decreasing linearly from 315 and 292 °C to minima of 280 and 272 °C, respectively. Melting enthalpies showed similar minima at ca. 35 wt-% PA-6,T. WAXD and DMA were used to further characterize the eutectic behavior, and a comprehensive analysis of PA-6,T copolymer melting behavior is given.

Effects of hydrothermal aging on SiC-DPF with metal oxide ash and alkali metals

The silicon carbide used to make diesel particulate filters (SiC-DPF) has a maximum temperature of use, which is not the melting point of the filter material itself but rather the eutectic melting points of the ash materials and alkali metals deposited on the filter wall. Chemical reactions between the SiC filter and the other materials, i.e. ash materials and/or alkali metals, decrease the filtration efficiency and catalytic reactivity of engine out emission. The objective of this study is to understand the effect of hydrothermal aging on the SiC-DPF, and on the SiC-CDPF (catalyzed diesel particulate filter) deposited with ash materials and/or alkali metals. Hydrothermal aging simulated for the extreme condition of uncontrolled regeneration in DPF is carried out by using H 2O at high temperature. The surface change of the SiC filter was characterized in terms of the geometric microstructure and metal composites of the filter by using the SEM-EDS, BET and XRD. The accumulated ash materials and alkali metals in the SiC-DPF were an admixture, and the SiC-DPF after-treatment system always contained H 2O. According to the results, H 2O in the after-treatment system can be regarded as an influential factor of SiC-DPF durability even though the SiC itself has a very high melting point. The regeneration temperature has to be controlled under a critical value to ensure the durability of SiC-DPF in the after-treatment system, considering the fact that large quantities of ash materials, alkali metals and H 2O components are included in the exhaust gas.

Cobalt: a universal barrier metal for solderable under bump metallisations

Published data augmented by new work suggests that cobalt is a suitable constituent of many under bump metallisations, its function being as the barrier metal. This stems from the combination of cobalt’s high wettability by and low solubility in, molten solders, together with the slow rate of growth and favourable mechanical properties of the interfacial intermetallic compounds formed. Although other metals and alloys exhibit similar characteristics, the range of compatible solders is always limited. Cobalt appears to be suitable for use with low melting point bismuth- and indium-based filler metals, lead–tin eutectic, lead-free and high melting point lead-based alloys, as well as the gold-rich solder family.

Conditions for subeutectic growth of Ge nanowires by the vapor-liquid-solid mechanism

The requirement of the presence of a liquid for the widely accepted vapor-liquid-solid (VLS) mechanism suggests that nanowire growth should be carried out at temperatures above the catalyst-nanowire eutectic melting point. In this paper, we examine the nanowire growth at the deep subeutectic temperatures often employed for germanium nanowire growth with Au catalyst nanoparticles. The effects of germane partial pressure on the low temperature limit for Au-catalyzed Ge nanowire growth by chemical vapor deposition from GeH4(g) were studied thoroughly, both with and without initial heating above the bulk eutectic temperature. A model to explain the temperature and pressure limits of subeutectic VLS nanowire growth was developed. The interdependence of the pressure and temperature required for good quality germanium nanowire growth may also apply in other cases of nanowire growth, beyond the Au–Ge system.

LiF-LiVO3-Li2SO4-Li2MoO4 four-component system

The LiF-LiVO3-Li2SO4-Li2MoO4 four-component system was studied using differential thermal analysis. The eutectic composition was determined (mol %): LiF, 25.0; LiVO3, 43.8; Li2SO4, 14.8; Li2MoO4, 16.5. The eutectic melting point is 428°C; the enthalpy of melting is 260 J/g.

Characteristics of a near-net-shape formed Al–Al 3Fe eco-functionally graded material produced over its eutectic melting temperature

With the concept of an eco-material in mind, this work looks into the possibility of manufacturing Al–Al 3Fe functionally graded material (FGM) products by semi-solid extrusion. For this purpose, an Al–Al 3Fe FGM thick-walled tube of 90 mm outer diameter × 90 mm long × 15 mm thickness was fabricated utilizing a vacuum centrifugal method. Al–Al 3Fe FGM billets of 40 mm diameter × 12 mm thickness, with graded distribution from 0 to 40 vol% of coarse brittle Al 3Fe particles in the thickness direction, were machined from the thick-walled FGM tube. The billets were pressed in the container at temperatures of 660, 670 and 680 °C, where Al alloy melt and solid Al 3Fe particles co-existed. A near-net-shape product of Al–Al 3Fe FGM, in the form of a cup, was successfully fabricated through the semi-solid backward extrusion process during which lower test temperatures produced better results. The volume fraction concentration of Al 3Fe appears to be independent of the test temperature and over 60 vol% around the bottom cup region, decreasing gradually towards the cup wall region. The shape of coarse Al 3Fe particles changes to a more fine fibrous shape at some locations whilst remaining unchanged in others. The shape change mechanism appears not to be due to melt flow erosion, dissolution and/or re-crystallization, but rather due to viscous melt flow splitting of coarse particles. The brittleness of the coarse Al 3Fe intermetallic compound that makes the application of conventional plastic deformation methods impossible appears not to be the case during near-net-shape forming over eutectic melting point. Shore hardness increases with increasing volume fraction of Al 3Fe particles and following semi-solid forming the product appears to be harder than before. This appears to be the result of refining of Al 3Fe particles through shear stress introduced by liquid Al flow during semi-solid forming. Fabrication of FGMs having fine fibrous Al 3Fe phase, appears to be possible if the forming process is carried out at an optimum condition.

Solid–liquid equilibria of mixtures containing tert-butanol, m-chlorophenol, and p-chlorophenol and development of adductive crystallization processes

The solid–liquid equilibria data of the ternary system consisting of tert-butanol (A), m-chlorophenol (B), and p-chlorophenol (C) and the three constituent binary systems were experimentally studied by means of the solid-disappearance method. The binary system consisting of m-chlorophenol and p-chlorophenol was observed to exhibit one eutectic point. However, the tert-butanol + m-chlorophenol and tert-butanol + p-chlorophenol mixtures behave differently, each exhibiting two eutectic points and one congruent melting point; the mole fraction of tert-butanol in the congruent melting complexes, which are represented, respectively, by the formula A 2B and A 2C, are 0.6602 and 0.6690. All the experimental melting temperature data can be satisfactorily represented by the empirical equations of Ott and Goates. Several ternary mixtures with specified mole ratios of m-chlorophenol to p-chlorophenol (pseudo-binary mixtures) were also studied. They all exhibit two eutectic points and one congruent melting point near the tert-butanol mole fraction of 0.6667. This implies that the mixtures of the congruent melting complexes A 2B and A 2C were formed during freezing. A ternary phase diagram showing the projections of all eutectic and congruent melting points is prepared. Based on the information contained in this diagram, a conceptually feasible process using tert-butanol as an adductive agent is proposed to separate the eutectic mixture of m-chlorophenol and p-chlorophenol.

Microstructure and Conduction of Composites Bi2CuO4-Bi2O3 Near the Eutectic Melting Point

Microstructure and conduction of ceramic composites Bi2CuO4 + xBi2O3 (x = 5, 10, 15, 20 wt %) near the eutectic melting point (770°C) are studied. Bismuth oxide, initially randomly distributed over the ceramics bulk, after quenching from temperatures exceeding the eutectic melting point, becomes localized at triple junctions and grain boundaries in Bi2CuO4, which is caused by wetting grain boundaries and forming a liquid-channel structure. The jumpwise change in the composites’ conductivity near 730 and 770°C caused by polymorphic transformation of Bi2O3 and the eutectic melting with simultaneous formation of a liquid-channel structure. Transport numbers of the oxygen ion are measured at 770°C by coulomb-volumetric method. The conduction by oxygen ions increases in the composites with decreasing average size of Bi2CuO4 crystallites.

Growth of boron nitride nanotubes and iron nanowires from the liquid flow of FeB nanoparticles

The growth of hexagonal boron nitride (BN) nanotubes and nanocages from the liquid flow of iron boride (FeB) nanoparticles has been achieved by the nitrogen plasma treatment of FeB nanoparticles at temperature close to the eutectic melting point of the alloy (<1000 °C). In addition to BN nanotubes (5–10 nm diameter), BN nanotubules (100–200 nm diameter) created by interconnected chains of BN nanocages, as well as BN hollow microspheres can be grown. The recrystallization of iron from smaller FeB particles results in crystalline iron nanowires encapsulated by BN. These observations suggest that nanostructure formation can be controlled by the liquid flow of nanoparticles where interfacial wetting behaviour and surface tension play a key mechanistic role.

Crystallization of D-mannitol in binary mixtures with NaCl: phase diagram and polymorphism.

To study the crystallization, polymorphism, and phase behavior of D-mannitol in binary mixtures with NaCl to better understand their interactions in frozen aqueous solutions. Differential scanning calorimetry, hot-stage microscopy, Raman microscopy, and variable-temperature X-ray diffractometry were used to characterize D-mannitol-NaCl mixtures. NaCl and D-mannitol exhibited significant melt miscibility (up to 7.5% w/w or 0.20 mole fraction of NaCl) and a eutectic phase diagram (eutectic composition 7.5% w/w NaCl; eutectic temperature 150 degrees C for the alpha and beta polymorphs of D-mannitol and 139 degrees C for the delta). The presence of NaCl did not prevent mannitol from crystallizing but, depending on sample size, affected the polymorph crystallized: below 10 mg, delta was obtained; above 100 mg, alpha was obtained. Pure mannitol crystallized under the same conditions first as the delta polymorph and then as the a polymorph, with the latter nucleating on the former. KCl showed similar eutectic points and melt miscibility with D-mannitol as NaCl. LiCl yielded lower eutectic melting points, inhibited the crystallization of D-mannitol during cooling, and enabled the observation of its glass transition. Despite their structural dissimilarity, significant melt miscibility exists between D-mannitol and NaCl. Their phase diagram has been determined and features polymorph-dependent eutectic points. NaCl influences the polymorphic behavior of mannitol, and the effect is linked to the crystallization of mannitol in two polymorphic stages.

Design and fabrication of thin film resistive heaters for hybrid optoelectronic packaging

This paper presents the technology for the design and fabrication of planar resistive heaters made from vacuum deposited nichrome thin films on a quartz substrate. These heaters are suitable as isolated local heat sources for melting solder to attach discrete components on a hybrid optoelectronic integration platform. Numerical simulations are performed using the Finite Element Method (FEM) to determine the geometry of the heaters in order to deliver adequate thermal performance. Multiple heater elements are batch processed on a 3.0 in polished fused quartz wafer using standard photolithographic techniques. Use of polyimide as a reliable insulation layer between the nichrome thin film and the solder has improved the thermal uniformity over the heater surface. Individual heaters can reach temperatures close to 300/spl deg/C drawing 7.1 W of power on an uncooled alumina platform and 12.0 W on an uncooled copper platform. This temperature is high enough to melt gold-tin (AuSn) solder (with eutectic melting point of 280/spl deg/C), typically used for attaching different optoelectronic components on a substrate.

Crystallization behaviour of metal-nonmetal monotectic alloys; succinonitrile-pyrene system

The phase-diagram of succinonitrile-pyrene system determined by the thaw-melt method shows the formation of a monotectic (melting point, 143.3°C) and a eutectic (melting point, 55.3°C) at 0.025 and 0.744 mole fractions of succinonitrile respectively. The critical solution temperature is 48.7°C above the monotectic horizontal. Growth behaviour of the parent components, eutectic and the monotectic studied by measuring the rate of movement of the growth front in a capillary suggests the applicability of Hillig-Turnbull equation for the system.

Phase equilibria of water and ionic liquids [emim][PF 6] and [bmim][PF 6

In this work, solid–liquid and liquid–liquid equilibria of [emim][PF 6]+water and liquid–liquid equilibria of [bmim][PF 6]+water are studied using DSC, Karl–Fischer analysis, UV and DSC. An eutectic melting point for [emim][PF 6]+water is found at 314 K with about 5 wt.% of water. The solubility of [emim][PF 6] in water increases from about 5 wt.% at 308 K to 8 wt.% at 323 K. The solubility of water in liquid [emim][PF 6] is around 5 wt.% and relatively independent of temperature. The solubility of [bmim][PF 6] in water measured by UV increases from 2.4 wt.% at 303 K to 3.7 wt.% at 323 K. The solubility of water in [bmim][PF 6] measured by Karl–Fischer increases from 2.67 wt.% at 303 K to 3.70 wt.% at 323 K.

Phase diagram for the mixtures of ibuprofen and stearic acid

The binary mixtures of ibuprofen and stearic acid have been tested on the DSC at a heating rate of 5°C min −1. All temperatures reported here are for endothermic peak temperatures. The heating curves are employed to construct a phase diagram. The resultant phase diagram shows the existence of a compound formed between the two materials and is essentially two simple eutectic systems compressed into one equilibrium diagram. The component in excess melts at a lower temperature than its single entity. There are two eutectic melting points at 42% ibuprofen and 65% ibuprofen. It would seem probable that the “condensed phase compound” has the formula AB 2, where A is stearic acid (C 18H 36O 2) and B is ibuprofen (C 13H 18O 2). A relationship between the enthalpy of melting (Δ H m) and %composition is found. However, the overlapped endothermic peaks pose difficulty in peak integration resulting in a deviation from a typical plot. DSC is a fast, useful, and reliable analytical tool to detect and investigate the eutectic compound in this study.

Physical chemistry of binary organic eutectic and monotectic alloys; 1,2,4,5-tetrachlorobenzene−β-naphthol and 1,2,4,5-tetramethylbenzene-succinonitrile systems

Phase diagrams of 1,2,4,5-tetrachlorobenzene–β-naphthol and 1,2,4,5-tetramethylbenzene–succinonitrile systems which are organic analogues of a nonmetal–nonmetal and a nonmetal–metal system, respectively, show the formation of a simple eutectic (melting point 103.7°C) with 0.71 mole fraction of β-naphthol in the former case and a monotectic (melting point 76.0°C) with 0.07 mole fraction of succinonitrile and a eutectic (melting point 52.5°C) with 0.97 mole fraction of succinonitrile in the latter case. The growth behaviour of the pure components, the eutectics and the monotectic studied by measuring the rate of movement of the solid–liquid interface in a capillary, suggests that the data obey the Hillig–Turnbull equation, v= u(Δ T) n , where v is the growth velocity, Δ T is the undercooling and u and n are constants depending on the nature of the materials involved. From the values of enthalpy of fusion determined by the DSC method using Mettler DSC-4000 system, entropy of fusion, interfacial energy, enthalpy of mixing and excess thermodynamic functions were calculated. The optical microphotographs of pure components and polyphase materials show their characteristic features.