Technique for measuring thermal resistance of semiconductor packages and

Abstract

A thermal test apparatus for measuring the thermal heat transfer characteristics of semiconductor packaging material as well as the thermal characteristics of the package design is disclosed comprising a substrate having the size and shape of a semiconductor die. The substrate is in contact with the semiconductor packaging material. A heating source for heating the substrate is located within the apparatus, along with a temperature sensitive element for which the voltage drop across the element is a function of temperature. The element is connected in series via a first set of conductive traces to forcing pads used to force current through the element. Sensing pads for measuring the forward voltage drop of the diode are connected in parallel via a second set of conductive traces across the element to two points very close to the element in order to greatly reduce the thermal resistance measurement error due to the resistance in the conductive trace material. In another aspect of the present invention the thermal measurement error is reduced by connecting the sensing pads via a second set of conductive traces to two points across the diode such that those two points are located not more than two microns from the diode. Once the voltage drop across the element is measured, the temperature of the element and the junction surrounding the element can be determined and standardized to indicate the relative thermal conductive properties of the various semiconductor designs and packaging materials used.