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An Analytical Method to Calculate the Heat Flow and Temperatures Within the Structure of A VLSI Integrated Circuit
V. Lakshminarayanan and N. Sriraam

The density of active devices per unit area of the die has been increasing with the increase in the number of functions integrated into single package integrated circuits, such as microprocessors and microcontrollers. The device operation leads to an increase in die temperature, which has to be kept within limits by managing the heat flow out of the package. This paper analyzes the heat flow mechanisms in a typical VLSI integrated circuit package, in the structure of the composite device at various points and boundary interfaces. The mathematical analysis considers all the interfaces from the die to the ambient and gives equations for estimating the temperature at any point between the die and the ambient. The analysis will be useful to estimate the temperature at various internal points in the composite device structure.

Keywords: Heat flux, Fourier’s law, Boundary conditions, Heat flow in composite media, VLSI integrated circuit, microprocessor, thermal interface material, heat spreader, heat sink, thermal conductivity, conduction, convection, radiation.

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