Comparative analysis of complex liquids based on a multi-experimental approach.
A parallel analysis is here presented between the results gathered by the author by means of three different experimental approaches--Dielectric analysis, Thermally Stimulated Depolarization (TSD) and Differential Scanning Calorimetry (DSC)--on some multi-component complex liquids consisting of association structures of self-assembling amphiphiles as, water-in-oil microemulsions. The highly dispersed nature of these systems was evidenced with the dielectric study: a Maxwell-Wagner relaxation was found to characterize this type of systems. The structural evolution of the system, against water addition, was well described by the orientational processes induced in the liquid samples by a nearly static electric field as in the TSD method. The investigation by DSC, besides offering a basic picture of the system's thermodynamics, allowed the measure of the specific heat, at constant pressure, at the higher order percolative phase transition. The comparison between the results obtained on samples processed with identical thermal cycles, once under the action of an impressed electric field as in TSD, and, once in the absence of any impressed electric field as in DSC, did help distinguish three main concentration intervals within which structurally different systems form namely, isotropic microemulsions and two liquid crystalline structures of lyotropic type.
Experimental Evidence of Interphasal Water in Water-in-Oil Microemulsions
By means of thermal analysis (DSC) applied to water-in-oil microemulsions, the experimental evidence is presented that, in the above systems, the water may exist in at least two different configurations, namely: interphasal and free, distinguished by the melting temperatures of respectively 263 K and 273 K. The role of both water and interphase in governing the microemulsion stability and structural changes upon water addition, are analysed. It is also shown that the enthalpic contribution associated with the thermal events ascribed to the dispersed phase (interphasal chorona + water core of the spherical droplet), are not particularly affected by the change of the continuous, hydrocarbon dispersing medium, provided that all the other components of the system as well as their mutual proportions are kept unchanged. The title system is, therefore, presented as a useful tool for studying the properties of water and interphasal water from both a scientific and a practical point of view, with particular regard to the forms of water in biosystems.
Ultrathin Wafer Pre-Assembly and Assembly Process Technologies: A Review
Ultrathin silicon wafer technology is reviewed in terms of the semiconductor applications, critical challenges, and wafer pre-assembly and assembly process technologies and their underlying mechanisms. Mechanical backgrinding has been the standard process for wafer thinning in the semiconductor industry owing to its low cost and productivity. As the thickness requirement of wafers is reduced to below 100 μm, many challenges are being faced due to wafer/die bow, mechanical strength, wafer handling, total thickness variation (TTV), dicing, and packaging assembly. Various ultrathin wafer processing and assembly technologies have been developed to address these challenges. These include wafer carrier systems to handle ultrathin wafers; backgrinding subsurface damage and surface roughness reduction, and post-grinding treatment to increase wafer/die strength; improved wafer carrier flatness and backgrinding auto-TTV control to improve TTV; wafer dicing technologies to reduce die sidewall damage to increase die strength; and assembly methods for die pick-up, die transfer, die attachment, and wire bonding. Where applicable, current process issues and limitations, and future work needed are highlighted.