Experimental thermal characterization of VLSI packages

To insure optimum performance of circuits, highly accurate measurements are needed to characterize the thermal performance of very large-scale integrated circuit (VLSI) packages. To do this, a temperature-sensitive device inside the package is measured after calibrating the devices with respect to temperature variations. The different methodologies used to calibrate packaged devices are described. The method used as a basis is: to apply a constant forward current to a p-n junction and to measure the change in voltage across the junction due to a change in temperature. This p-n junction voltage is referred to as the temperature-sensitive parameter (TSP). The range of temperatures was limited to a 100°C range. Equipment used included current sources, thermocouples, thermal measurement instrumentation, thermal environment controllers, and test devices. It was concluded that the voltage measured across a conducting semiconductor junction can serve as an excellent temperature-sensitive parameter for the thermal characterization of VLSI packages. It is easily measured and well behaved, i.e., linear with temperature change over a wide range