Effects of Boundary Conditions and Source Dimensions on the Effective Thermal Conductivity of a Printed Circuit Board
The heat conduction equation and its boundary conditions were used to show that the planar and normal thermal conductivities of an orthotropic model of a printed circuit board were functions of source to board size ratio, top and bottom side boundary conditions, and thickness and thermal conductivity of each layer. Numerical solutions of the heat conduction equation were used to quantify the dependence on source to board size ratio and top and bottom boundary conditions. It was shown that the thermal conductivities were stronger functions of the source to board size ratio for smaller values of this ratio. This dependence was more pronounced for boards with stronger convection heat transfer on their top side, and for boards with thicker component side copper layer. The thermal conductivities were less sensitive to the variation of the convection heat transfer on the bottom side of the board.Copyright © 2003 by ASME
This paper describes a novel technique for studying structure-transport correlations in nanoscale multilayer thin films. Here, local current-voltage characteristics from simplified magnetic tunnel junctions are measured in situ on cross-sectional transmission electron microscopy (TEM) samples and correlated directly with TEM images of the microstructure at the tunneling site. It is found that local variations in barrier properties can be detected by a point probe method, and that the tunneling barrier height and width can be extracted.