Ternary Isotherms Research Articles

Elemental redistribution and interfacial reaction mechanism for the flip chip Sn-3.0Ag-(0.5 or 1.5)Cu solder bump with Al/Ni(V)/Cu under-Bump metallization during aging

In flip chip technology, Al/Ni(V)/Cu under-bump metallization (UBM) is currently applicable for Pb-free solder, and Sn−Ag−Cu solder is a promising candidate to replace the conventional Sn−Pb solder. In this study, Sn-3.0Ag-(0.5 or 1.5)Cu solder bumps with Al/Ni(V)/Cu UBM after assembly and aging at 150°C were employed to investigate the elemental redistribution, and reaction mechanism between solders and UBMs. During assembly, the Cu layer in the Sn-3.0Ag-0.5Cu joint was completely dissolved into solders, while Ni(V) layer was dissolved and reacted with solders to form (Cu1−y,Niy)6Sn5 intermetallic compound (IMC). The (Cu1−y,Niy)6Sn5 IMC gradually grew with the rate constant of 4.63 × 10−8 cm/sec0.5 before 500 h aging had passed. After 500 h aging, the (Cu1−y,Niy)6Sn5 IMC dissolved with aging time. In contrast, for the Sn-3.0Ag-1.5Cu joint, only fractions of Cu layer were dissolved during assembly, and the remaining Cu layer reacted with solders to form Cu6Sn5 IMC. It was revealed that Ni in the Ni(V) layer was incorporated into the Cu6Sn5 IMC through slow solid-state diffusion, with most of the Ni(V) layer preserved. During the period of 2,000 h aging, the growth rate constant of (Cu1−y,Niy)6Sn5 IMC was down to 1.74 × 10−8 cm/sec0.5 in, the Sn-3.0Ag-1.5Cu joints. On the basis of metallurgical interaction, IMC morphology evolution, growth behavior of IMC, and Sn−Ag−Cu ternary isotherm, the interfacial reaction mechanism between Sn-3.0Ag-(0.5 or 1.5)Cu solder bump and Al/Ni(V)/Cu UBM was discussed and proposed.

Determination of phase diagrams using the diffusion couple technique

It has been demonstrated that the diffusion couple technique is a powerful and efficient approach in establishing phase relationships of ternary systems. Accurate data on the phase equilibria can be obtained if the appropriate alloys are employed as end members of the diffusion couple. It is desirable to combine the diffusion couple technique with an investigation of the afterwards selected equilibrated alloys so that the precision and reliability of the obtained information about a ternary isotherm could be guaranteed.

Phase distribution and phase analysis in Cu6Sn5, Ni3Sn4, and the Sn-rich corner in the ternary Sn-Cu-Ni isotherm at 240°C

Metallurgical reactions between solders and under bump metallization (UBM) are key issues for the solder joint reliability in microelectronic packaging. A phase diagram consisting of solders and UBM materials are required to further understand the interfacial reactions and related phase transformation. In this study, series of ternary Sn-Cu-Ni alloys were designed, fabricated, and heat-treated at 240°C. Equilibrium phases of Sn, Ni3Sn4, and Cu6Sn5 were identified by XRD, and microstructure evidence in backscattered electron image (BEI) micrograph. Through detailed EPMA quantitative analysis, three acme compositions of the ternary region in the Sn-Cu-Ni isotherm near the Sn-rich corner were evaluated and determined. Furthermore, x-ray color mapping of tin, copper, and nickel were applied to study the phase distribution of the alloys with the aid of electron microprobe analysis (EPMA). According to the intensities of Sn, Cu, and Ni, collected by x-ray color mapping, special software was employed to map the corresponding concentrations on the Sn-Cu-Ni ternary isotherm. The degree of composition homogeneity and the phase distribution were further evaluated by phase-analysis techniques. Semiquantitative measurements by phase analysis can be extended to evaluate the phase boundaries with a statistical variation under 5% as compared to the quantitative analysis by EPMA. Finally, the isothermal section of the ternary Sn-Cu-Ni system near the Sn-rich corner at 240°C was constructed.

Effects of different printed-circuit-board surface finishes on the formation and growth of intermetallics at thermomechanically fatigued, small outline J leads/Sn-Ag-Cu interfaces

The effects of printed-circuit-board (PCB) surface finish and thermomechanical fatigue (TMF) on the formation and growth of intermetallic compounds (IMCs) between small outline J (SOJ) leads and Sn-3.0Ag-0.5Cu solder were investigated. The thickness of the IMC layer formed initially at the as-soldered SOJ/Sn-Ag-Cu interface over a Ni/Au PCB surface finish was about 1.7 times of that over the organic solderability preservative (OSP) PCB surface finish. The parabolic TMF-cycle dependence clearly suggests that the growth processes are controlled primarily by solid-state diffusion. The diffusion coefficient for the growth of the total IMC layer at the SOJ/Sn-Ag-Cu interface over the Ni/Au PCB surface finish is the same as that over the OSP PCB surface finish, and thus, the total IMC layer at the SOJ/Sn-Ag-Cu interface over the Ni/Au PCB surface finish is thicker than that over the OSP PCB surface finish. Using the Cu-Ni-Sn ternary isotherm, the anomalous phenomenon that the presence of Ni retards the growth of the Cu3Sn layer while increasing the initial growth of the Cu6Sn5 layer can be addressed.

Effects of different printed circuit board surface finishes on the formation and growth of intermetallics at thermomechanically fatigued small outline J leads/Sn–Pb interfaces

The effects of printed circuit board (PCB) surface finish and thermomechanical fatigue (TMF) on the formation and growth of intermetallic compounds (IMCs) between Small Outline J (SOJ) leads and Sn–37Pb solder were investigated. The thickness of the IMC layer formed initially at as-soldered SOJ/Sn–Pb interface over Ni/Au PCB surface finish was about 1.3 times of that over OSP PCB surface finish. The parabolic TMF cycle dependence clearly suggests that the growth processes are controlled primarily by solid-state diffusion. The diffusion coefficient for the growth of total IMC layer at SOJ/Sn–Pb interface over Ni/Au PCB surface finish is the same as that over OSP PCB surface finish and, thus, the total IMC layer at the SOJ/Sn–Pb interface over Ni/Au PCB surface finish is thicker than that over OSP PCB surface finish. Using the Cu–Ni–Sn ternary isotherm, the anomalous phenomenon that the presence of Ni retards the growth of the Cu 3Sn layer while increasing the initial growth of the Cu 6Sn 5 layer can be addressed.

Diffusion studies in the β (B2), β′ (bcc), and γ (fcc) Fe-Ni-Al alloys at 1000 °C

Diffusion studies were carried out in the Fe-Ni-Al system at 1000 °C with solid-solid diffusion couples assembled with β (B2), β′ (bcc), and γ (fcc) single-phase alloys for the development of diffusion structures, diffusion paths, and for the determination of interdiffusion and intrinsic diffusion coefficients. The diffusion structures were examined by optical and scanning electron microscopy, and the concentration profiles were determined by electron microprobe analysis. Diffusion couples included several series of β vs γ and β′ vs γ diffusion couples characterized by a common terminal alloy bonded to several terminal alloys with varying compositions. The development of planar and nonplanar interfaces, as well as two-phase layers, as observed in various couples, were related to the diffusion paths. The interdiffusion fluxes of individual components were calculated directly from the experimental concentration profiles, and the diffusional interactions among components were examined in the light of zero-flux planes (ZFPs) and flux reversals, which were identified in several couples. Ternary interdiffusion coefficients ( $$\tilde D_{i,j}^{Fe} $$ (i, j = Al, Ni)), with Fe considered as the dependent concentration variable, were evaluated at composition points of the intersection of diffusion paths of single-phase couples and of multiphase couples that developed planar interfaces. The interdiffusion coefficients were the largest in magnitude for the β′ alloys, especially near the β/β′ miscibility gap, and decreased for the β and γ alloys. In the β and γ phases, the main interdiffusion coefficient for Al was larger than those for Ni and Fe. Also, Fe interdiffused faster than Ni in the Fe-rich β and β′ phases. The cross-interdiffusion coefficients ( $$\tilde D_{AlNi}^{Fe} $$ and $$\tilde D_{NiAl}^{Fe} $$ ) were negative in all three phases. In general, the $$\tilde D_{AlNi}^{Fe} $$ coefficients were larger in magnitude than the $$\tilde D_{NiAl}^{Fe} $$ coefficients; however, the magnitude of $$\tilde D_{NiAl}^{Fe} $$ was greater than that of $$\tilde D_{AlNi}^{Fe} $$ near the β/(β + γ) phase boundary on the ternary isotherm. In the β phase, the magnitude of $$\tilde D_{i,j}^{Fe} $$ (i, j=Al, Ni) coefficients increased over 1 to 2 orders of magnitude with a decrease in the Al concentration and increase in the Fe/Ni concentration ratio. Interdiffusion coefficients, extrapolated from the ternary coefficients for binary alloys, were consistent with those in literature. Intrinsic diffusion coefficients were also determined at selected compositions. In addition, tracer diffusion coefficients were estimated for the binary Fe-Al and Ni-Al alloys at selected compositions, from an extrapolation of ternary interdiffusion coefficients.

Effect of Pharmaceutically Acceptable Glycols on the Stability of the Liquid Crystalline Gels Formed by Poloxamer 407 in Water

The ability of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) block copolymers (Poloxamers) to form “gels” (lyotropic liquid crystalline structures) in water is of interest to pharmaceutical applications. In such applications the presence of polar organic solvents is often desirable or required. The effect of such solvents on the stability of lyotropic liquid crystalline gels formed by PEO–PPO–PEO block copolymers was assessed by studying the phase behavior and structure in ternary isothermal (25°C) systems of pharmaceutical interest consisting of Poloxamer 407 (EO 100PO 70EO 100), water, and one of the following solvents (referred to here collectively as “glycols”): glycerol, propylene glycol, ethanol, polyethylene glycol 400, and glucose. Small-angle X-ray scattering was employed to establish the structure of the liquid crystals obtained and to determine their characteristic length scales. The stability range of the liquid crystalline gel phases in the systems studied was found to vary with the glycol type. For example, the micellar cubic structure can accommodate about 0.85 : 1 parts glucose per part water (in terms of weight) and up to as much as 5.5 : 1 parts propylene glycol per part water. A correlation between the glycol effects on the stability of the liquid crystalline phases and glycol physiochemical characteristics such as octanol/water partition coefficient or solubility parameter is proposed.

Prediction of K-Ca-Mg ternary exchange from binary isotherms in volcanic soils using the Rothmund-Kornfeld approach

The Gaines-Thomas formulation of the Rothmund-Kornfeld equation was used to predict the K-Ca-Mg exchange in variable surface charge soils. Binary and ternary equilibria were carried out at 25°C and at constant ionic strength of 0.050 mol/L. The selectivity sequence K > Ca > Mg was observed in binary isotherms. The experimental ternary isotherms are well described from binary data. When experimental v. calculated equivalent fractions were plotted, slopes between 0.901 and 1.051, and correlations between 0.970 and 0.986, were obtained. The design used assures in volcanic soils that no, or minor, changes in surface charge, cation exchange capacity, and selectivity occur, but the predicted ternary values are restricted to the same binary experimental conditions employed.

Determination and comparison of ternary competitive isotherms by frontal velocity analysis and rectangular pulse method

A new method, frontal velocity analysis, is applied to the determination of ternary competitive isotherms for benzyl alcohol, 2-phenylethanol and 3-phenylpropanol on ODS-silica 1∶1 methanol-water as mobile phase. Data obtained from the new method are in good agreement with results from the classic rectangular pulse method under the same conditions. This shows that the simpler and easier method, frontal velocity analysis can be used to determine ternary competitive isotherms accurately.

Interaction of poloxamer block copolymers with cosolvents and surfactants

The interactions of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) block copolymers (Poloxamers) with cosolvents and surfactants are addressed here. Ternary isothermal (25°C) systems of Pluronic F127 (Poloxamer 407) in the presence of water and polar water-miscible solvents (glycerol, propylene glycol or ethanol), a partially water-miscible solvent (glycerol triacetate), a non-ionic surfactant (tetraethylene glycol monooctyl ether, C 8(EO) 4), an anionic surfactant (sodium dodecyl sulfate, SDS), and a cationic surfactant (cetyltrimethyl ammonium bromide, CTAB) have been investigated by phase behavior studies and small angle x-ray scattering (SAXS). A number of regions with different lyotropic liquid crystalline structure have been identified in each ternary Poloxamer–water–cosolvent/surfactant system. For a given Poloxamer, the composition range over which a given self-assembled structure is stable varies according to the cosolvent/surfactant type (and properties). The effects that the different cosolvents or surfactants exhibit on the Poloxamer phase behavior are interpreted in terms of the preference of the cosolvent/surfactant molecules to locate in different domains of the PEO–PPO–PEO block copolymer self-assembly. Organic solvents, depending on their relative polarities, locate preferably in the PEO-rich or the PPO-rich domains of the microstructure. Some solvents (e.g. ethanol and glycerol triacetate) may show amphiphilic behavior and act as cosurfactants by preferably locating at the interface between the PEO-rich and the PPO-rich domains. The location of the solvents in the block copolymer assemblies is established by an analysis of the trends in the structure lattice spacing (obtained from SAXS) and the interfacial area per block copolymer molecule.

A double-serpentine diffusion path for a ternary diffusion couple

A double-serpentine diffusion path that crosses the straight line joining the terminal alloy compositions twice on a ternary isotherm is reported for a diffusion couple assembled with two β (B 2) Fe–Ni–Al alloys and annealed at 1000°C for 2 days. The couple developed a Ni concentration profile that exhibited two regions of mass loss separated by a region of mass gain on one side of the Matano plane. With an additional couple whose path intersected the double serpentine path, ternary interdiffusion coefficients were determined at the composition of intersection. Also, average values of the ternary interdiffusion coefficients, D ̃ ̄ ij Fe ( i, j= Al, Ni ), were determined over selected composition ranges of the couple and employed to model the concentration profiles. The cross D ̃ ̄ NiAl Fe coefficient was negative and comparable in magnitude to the main D ̃ ̄ NiNi Fe coefficient. The double-serpentine diffusion path was characterized by large diffusional interactions among the components and appreciable variations in the interdiffusion coefficients over different compositional ranges.

Effect of Glycols on the Self-Assembly of Amphiphilic Block Copolymers in Water. 1. Phase Diagrams and Structure Identification

The effects of cosolvents such as glycerol, propylene glycol, ethanol, or glucose (referred here as “glycols”) on the phase behavior of a representative poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO−PPO−PEO) triblock copolymer (Pluronic P105, (EO)37(PO)58(EO)37) are presented. Regions of lamellar, bicontinuous cubic, hexagonal, and micellar cubic lyotropic liquid crystalline structures (established from small-angle X-ray scattering measurements) have been delineated in the four ternary isothermal (25 °C) PEO−PPO−PEO−water−glycol phase diagrams. Pronounced effects on the concentration range of stability of the different phases were found when the glycol was varied from ethanol (the least polar glycol examined here) to glucose (the most polar). For example, glycerol and glucose swell the hexagonal phase to lower copolymer content, while propylene glycol and ethanol do not show this effect. Our experimental observations are discussed in terms of modification of the system “interfacial ...

Phase Diagrams in Volume, Mole Fraction Coordinates

For a binary mixture the V,x-diagram with isotherm and isobaric curves contains the complete information about the phase behavior of the system. In ternary mixtures isotherm and isobaric surfaces and additional information on the tie lines describe the complete phase behavior.For a binary mixture the V,x-phase diagrams corresponding to the classified P,T-phase diagrams are shown. The constitute binary V,x-phase diagrams and partly the critical V,x-surfaces of the ternary systems are shown for NH

Thermodynamic assessment of the Pu-U, Pu-Zr, and Pu-U-Zr systems

Based on thermodynamic and phase diagram data, the Gibbs energies of mixing of the solution phases in the Pu-U and Pu-Zr systems were calculated using an optimization procedure. The use of thermodynamic data in the optimization made it possible to accurately calculate thermodynamic properties as well as the phase diagrams, which were in good agreement with the respective experimental values. The Pu-U-Zr ternary isotherms were calculated by using the optimized parameters of the three binary subsystems. The results agreed reasonably well with the experimental ones.

Phase Relation in the Titanium-Rich Region of the Ge–Si–Ti Ternary System

The Ti-rich region of the Ge-Si-Ti ternary isotherm at 900°C was determined by metallography, X-ray diffraction, and electron microprobe analysis. The sample alloys were prepared by arc-melting. It was confirmed that at 900°C Ti 5 Si 3 and Ti 5 Ge 3 form a continuous solid solution Ti 5 (Si 1-x Ge x ) 3 with the hP16 crystal structure. The lattice constants for Ti 5 (Si 1-x Ge x ) 3 are linear functions of the composition variable x. This continuous solid solution also exists at 1100°C. There is another solid solution Ti 3 (Si 1-y Ge y ), that has the same crystal structure as Ti 3 Si (tP32), but this solid solution is stable only for y<0.44 at 900°C. It was also shown that there is not any other binary or ternary phase within the Ti-Ti 5 Si 3 -Ti 5 Ge 3 triangular region except Ti 5 (Si 1-x Ge x ) 3 and Ti 3 (Si 1-y Ge y ). In this region, there is one three-phase field Ti+Ti 5 (Si 1-x Ge x ) 3 +Ti 3 (Si 1-y Ge y ), and the compositions of these three phases are Ti 0.96 Si 0.03 Ge 0.01 , Ti 0.63 Si 0.08 Ge 0.29 , and Ti 0.75 Si 0.14 Ge 0.11 respectively. In addition, there are three two-phase fields within this region: Ti 5 (Si 1-x Ge x ) 3 + Ti 3 (Si 1-y Ge y ), Ti+Ti 3 (Si 1-y Ge y ), and Ti+Ti 5 (Si 1-x Ge x ) 3 .

The nitriding behavior of Ti-Al alloys at 1000 °C

The nitriding behavior of a series of alloys in the binary Ti-Al system has been determined at 1000 °C, under a controlled atmosphere of pure nitrogen gas, for times ranging between 7 and 100 hours. The scales and subscales were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive and wavelength dispersive X-ray analysis, electron energy loss spectroscopy, and optical microscopy. Upon formation of a surface nitride scale, the subscale became enriched in Al and resulted in the formation of a series of Al-rich intermetallic phases. This enrichment has been linked to the transport processes in the scale and subscale and a shifting of the diffusion path toward the Al-rich corner of the ternary isotherm. The formation of Al-rich intermetallic phases in the subscale was shown to result in rapid “breakaway” nitriding of the TiAl and TiAl2 alloys. The stoichiometry of the binary nitrides AlN and TiN was measured, as well as the composition of the ternary nitride “Ti2AlN.”

Phase equilibria of the Si-Ge-Ti system relevant to the reactions between SiGe alloys and Ti

The semiconductor-rich region of the Si-Ge-Ti ternary isotherm at 900°C was determined by metallography, x-ray diffraction, and electron microprobe analysis. The sample alloys were prepared by arc-melting. These alloys were brought to equilibrium by annealing at 900°C for 400 h. It was confirmed that at 900°C, TiSi2 and TiGe2 form a continuous solid solution Ti(Si1−yGey)2 with the C54 crystal structure. It was also shown that, other than Ti(Si1−yGey)2 and Si1−xGex, there is not any binary or ternary phase within the Si-Ge-TiGe2-TiSi2 trapezoid region. Between the Ti(Si1−yGey)2 and Si1−xGex single-phase fields is the Ti(Si1−yGey)2-Si1−xGex two-phase region. The tie-lines for this two-phase region were determined. The tie-lines tilt slightly toward the TiSi2 and Ge corners. In other words, at equilibrium, the silicon to germanium atomic ratio is larger in Ti(Si1−yGey)2 than in Si1−xGex (x>y). This tendency for tie-lines to tilt toward the TiSi2 and Ge corners had been proposed in the literature as the reason for the interesting microstructure evolution during the reactions between SiGe alloys and Ti. In addition, the possible diffusion paths for the reactions between SiGe alloys and Ti were discussed based on the obtained isotherm. Recognizing Si and Ge have higher mobilities in Ti(Si1−yGey)2, it is predicted that for SiGe the extent of concentration change is large but occurs over a shorter distance, and for TiSi2 the extent of concentration change is small but occurs over a longer distance.

A Record Nine Different Phases (Four Cubic, Two Hexagonal, and One Lamellar Lyotropic Liquid Crystalline and Two Micellar Solutions) in a Ternary Isothermal System of an Amphiphilic Block Copolymer and Selective Solvents (Water and Oil)

We report on a ternary isothermal system consisting of a poly(ethylene oxide)/poly(propylene oxide) (PEO/PPO) amphiphilic block copolymer, “water”, and “oil” (where “water” and “oil” are selective solvents for the different blocks), which exhibits the richest structural polymorphism ever observed (in equilibrium) in mixtures containing amphiphiles (such as block copolymers, surfactants, or lipids). The microstructure resulting from the self-assembly of the PEO/PPO block copolymer can vary from normal (oil-in-water) micelles in solution, through all types of normal and reverse (water-in-oil) lyotropic liquid crystals (normal micellar cubic, normal hexagonal, normal bicontinuous cubic, lamellar, reverse bicontinuous cubic, reverse hexagonal, reverse micellar cubic), to reverse micelles, as the relative volume fraction of the apolar (“oil”-like) components increases over that of the polar (“water”-like) components. The structure in the liquid crystalline phases has been established with small-angle X-ray sca...

Infrared joining of TiAl intermetallics using Ti-15Cu-15Ni foil—II. The microstructural evolution at high temperature

The microstructural evolution of TiAl joint during infrared joining at 1150°C under different holding times using Ti-15Cu-15Ni foil as brazing filler metal was investigated. Based on the observed microstructures, a five-step microstructural evolution mechanism at 1150°C joining temperature is proposed in this study. These time-dependent evolution steps including (a) β-Ti layer formation, (b) columnar α + β two-phase zone formation, (c) α2-phase nucleation, (d) high Al% α-phase formation and (e) α2-phase integration, are consistent with the multiphase diffusion theories in solid-state systems. Since different joining temperatures (Tw) have different corresponding ternary isotherms and stable phases, small variations of Tw can result in significant changes of the microstructural morphologies, especially concerning the microstructural evolution of zones of α2- and the high Al% α-phases. The mechanism proposed in this study has predicted such evolutions, which agree well with observed microstructures. All the observed microstructures at ambient temperatures can be clearly elucidated by this proposed mechanism.

Modification of the Microstructure in Block Copolymer−Water−“Oil” Systems by Varying the Copolymer Composition and the “Oil” Type: Small-Angle X-ray Scattering and Deuterium-NMR Investigation

The study addresses the effects of block composition on the self-assembly (and resulting microstructure) of amphiphilic block copolymers in the presence of selective solvents (“water” and “oil”) by examining the ternary phase behavior and structure of two copolymers, E20P70E20 and E100P70E100, having the same block architecture (ExPyEx) and P:poly(propylene oxide) middle-block size but different E:poly(ethylene oxide) end-block sizes (Pluronic P123, E20P70E20, contains 30% E and Pluronic F127, E100P70E100, 70% E). A characterization (using SAXS and deuterium NMR) of the ternary isothermal (25 °C) E20P70E20−butyl acetate−water and E20P70E20−butanol−water systems is presented first. A variety of lyotropic liquid-crystalline (LLC) phases are thermodynamically stable in the former (butyl acetate) system, both of the “normal” (oil-in-water) and of the “reverse” (water-in-oil) morphology. In the latter (butanol) system, the reverse LLC phases are not stable but are replaced by an extensive water-lean solution r...