Eutectic arrays

Since the work of Edwards et al. a vast array of molten salts has been studied, including mixtures and eutectics [2-5]. Beyond the binary ionic melt there are two important factors affecting the local order of the system, namely, the covalency of the interaction between unlike ions and the stoichiometry... 

Metal-metal eutectics have been studied for many years due to their excellent mechanical properties. Recently, oxide-oxide eutectics were identified as materials with potential use in photonic crystals. For example, rodlike micrometer-scaled microstructures of terbium-scandium-aluminum garnet terbium-scandium per-ovskite eutectics have been solidified by the micro-pulling-down method (Pawlak et al., 2006). If the phases are etched away, a pseudohexagonally packed dielectric periodic array of pillars or periodic array of pseudohexagonally packed holes in the dielectric material is left. 

Question Consider the eutectic solidification of a liquid to a + where the volume fraction of the / phase is relatively low. In this case, rather than solidifying in a lamellar structure, the phase may solidify as a series of rods embedded in a matrix of the a phase. Assuming that the rods are evenly spaced in a square array in the a matrix, calculate the critical 0-phase volume fraction (0 ) below which the rodlike morphology is more energetically stable than the lamellar morphology. 

A great many short-chain surfactants do not display either the hexagonal or lamellar liquid crystal as the separating phase above the Krafft eutectic they exhibit a cubic phase instead. Because the hexagonal liquid crystal is often found next to this cubic phase (at higher compositions), it may be presumed that this cubic phase has the discontinuous phase structure. The discontinuous cubic-phase structure consists of discrete micelle-like structural elements arrayed in various ways to form isotropic phase structures having cubic symmetry. A large family of such cubic structures exists [81,82]. 

FIG. 79 Ceramic column grid array (CCGA) configurations, a) Single melt eutectic Pb-Sn fillet, b) cast column with eutectic Pb-Sn on card pad, c) column last attach solder process (CLASP) with Pd-doped solder on chip-carrier pad and eutectic Pb-Sn fillet on card pad. 

Seiko-Epson also investigated utilizing Sn-Ag-Cu to attach area array packages such as EGAs and CSPs. ATC testing (-40 °C to 125°C, 30 min/cycle) confirmed that parts attached with Sn-Ag-Cu exhibited more than three times the fatigue life compared to conventional eutectic Sn-Pb solder. 

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