Thermal imaging of electronic devices with low surface emissivity

The technique of thermal imaging uses an infrared scanning imager to map the surface temperature of electronic devices and circuits. Often unrealistic thermal distributions are found in thermal images after emissivity correction, particularly where there are areas of low emissivity on the surface being studied. The background principles of temperature measurement are described using this technique and the reason these inconsistencies and errors may arise in measurements on devices having low surface emissivities is explained. A method of dealing with this problem is suggested and some results of measurements on a gallium arsenide MESFET with a very low surface emissivity are presented. These measurements give some guidance and warnings about the accuracy of this method for measuring thermal resistance