This is a valuable book giving a good overview as well as a state-of-the-art account of several topics related to thermal aspects of electronic packaging. Chapter I, by Nakayama, is entitled: "Thermal Management of Electronic Equipment: A Review of Technology and Research Topics." The role of heat transfer engineering and fundamental research, toward establishing design criteria are discussed. An exposition of natural convection, forced convection and advanced schemes of cooling follows. An interesting account of the heat load in Japanese computers caps up the section. Yovanovich and Antonetti wrote the next Section on the application of thermal contact resistance theory to electronic packages. The study surveys mechanical joints and the role of surface roughness, crucial, for example, to the performance of various electrical connectors. Direct air cooling of electronic components is discussed by Moffat and Ortega under two major headings, 1. Forced Convection and II. Natural Convection. Analytical and numerical methods, and experimental data are presented in the first part.
The effect of hydrostatic pressure on the energy gap of Bi2Te3 has been investigated in the pressure range one to 30 000 atm. From resistivity measurements as a function of temperature and pressure, it has been determined that the energy gap decreases from 0.171 ev at one atmosphere to 0.104 ev at 30 000 atm, corresponding to ∂Eg(0)/∂p=−2×10−6 ev/atm.
In the present study, the Eshelby theory of inclusions is applied to model the stresses arising after heat treatment at 400 °C in aluminum line metallizations, embedded in silicon/passivation matrix. The stresses obtained are about 200 MPa higher than the ones previously reported. Moreover, the stresses in the axial and width directions of the lines are shown to be on the same order, while the normal stress is smaller, especially in the lines of low thickness-to-width ratio. A modification of the familiar sin2 ψ method of x-ray stress measurement is presented to deal more accurately with the [111]-fiber texture present in the aluminum lines studied. The lateral and normal stresses in the aluminum metallizations after a heat treatment at 400 °C are measured in room temperature by x-ray diffraction from 4 h after the heat treatment at 400 °C up to 3 months. The experimental results are well in accord with predictions obtained from the Eshelby model. Particularly, the lateral stresses are found to be about equal, while the initial normal stress is smaller, but eventually becomes the largest stress component. Dislocation mechanisms to rationalize the present observations are discussed: at longer times, diffusion-controlled dislocation climb and void growth connected to it appear to be the most important mechanisms to relieve the stress, while during cooling dislocation glide is also significant.
Thermal stress-induced voiding in narrow aluminum-based metallizations used as interconnects in microelectronic circuits has recently become a serious reliability concern. Room-temperature stress relaxation and associated physical phenomena in passivated and unpassivated aluminum-based metallizations, subsequent to exposure to high temperatures, are analyzed based both on theoretically estimated and experimentally determined thermal stresses. It is shown that stress relaxation at longer times involves mainly dislocation climb, while short-term relaxation during cool down from higher temperatures, and immediately thereafter, involves significant dislocation glide. Void growth, frequently observed in passivated metallizations, provides a new source of atoms to feed stress relaxation by the same processes as in the absence of voiding.
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