Thermal expansion

About: Thermal expansion is a research topic. Over the lifetime, 21040 publications have been published within this topic receiving 349407 citations. The topic is also known as: heat expansion.

High-performance epoxy/binary spherical alumina composite as underfill material for electronic packaging

Abstract: In this study, epoxy (EP)/binary spherical alumina (S-Al2O3) composites with a high loading of 50 vol% were fabricated by incorporating different sizes of S-Al2O3 into EP to increase the thermal conductivity and yet retain the flowability of the composites. Notably, a distinctly reduced viscosity (21.8 Pa·s) and a highly increased thermal conductivity (1.364 W/m·K) were achieved by a binary S-Al2O3 mixture with 80% 30 μm and 20% 5 μm alumina that would have a theoretical maximum packing volume, thus permitting larger available free volume for the motion of particles and hence reducing the friction between them. Also, these EP/S-Al2O3 binary composites possessed superior electrical insulation, high thermal stability, significantly reduced thermal expansion coefficient and good mechanical properties. These combined desirable properties indicate that binary S-Al2O3 mixtures with an optimized size distribution and maximum packing volume are best candidates to develop high-performance epoxy-based underfill materials which would improve the flip-chip reliability.

Correlation of Properties of Materials to Debye and Melting Temperatures

Abstract: Many solid state properties are correlated to simple parameters like the atomic mass, the interatomic distance and some measure of the strength of the interatomic interaction, e.g. the melting temperature Tm or some Debye temperature θD. Such empirical relations are investigated for elastic properties, melting temperature, thermal expansion, vacancy formation energy, grain boundary and surface energy, cohesive energy, heat of fusion, activation energies for bulk, grain boundary, surface and dislocation pipe diffusion, viscosity, activation energy for creep, recrystallization temperature and other properties. When experimental data are available, both elements and diatomic compounds (alkali halides, oxides, carbides, III-V semiconductors) are considered. The correlations to Tm, θD(T = 0) and a high temperature effective θD are compared. It is found that for all practical purposes Tm gives the best correlation. For diatomic compounds, the average mass is not uniquely defined and various averages are discussed. The purpose of the paper is not only to present empirical relations but also to give a short account of the possibilities to calculate the considered parameters using solid state theory in its most advanced present state.

Thermal expansion of NaCl, KCl and CsBr by X‐ray diffraction and the law of corresponding states

Abstract: The coefficients of thermal expansion of NaCl, KCl and CsBr are determined accurately at different temperatures using a diffractometer, Geiger counter, chart recorder and a specially designed furnace. Equations are given for the variation of the lattice constants with temperature. The temperature dependence of the thermal expansion at high temperatures is shown to be related to the concentration of thermally generated Schottky defects. The energies of formation of Schottky pairs in the three halides are estimated and are found to be consistent with those deduced from ionic conductivity studies. The reduced parameters α/(α)M/2 and T/TM give a common curve for all the halides, TM being the melting point and (α)M/2 the value of α at T = ½ TM. The curve is a straight line in the limits ~ 0.30 < T/TM < ~ 0.65 and is found to deviate considerably at higher temperatures. Assuming that the deviation is due to defects, the energies of formation of Schottky defects for the varies halides of Li, Na, K, Rb and Cs are estimated and found to agree excellently with the experimental and theoretical values.