Direct measurement of hot-spot temperature in flip-chip solder joints with Cu columns under current stressing using infrared microscopy

In this study, the temperature map distribution in the Sn3.0Ag0.5Cu solder bump with Cu column under current stressing is directly examined using infrared microscopy. It is the radiance changes between the different materials of the surface that cause the unreasonable temperature map distribution. By coating a thin layer of black optical paint which is in order to eliminate the radiance changes, we got the corrected temperature map distribution. Under a current stress of 1.15 × 10⁴ A/cm² at 100°, the hot-spot temperature is 132.2°C which surpasses the average Cu column temperature of 129.7°C and the average solder bump temperature of 127.4°C. It is interesting that there are two modes of temperature distribution in the Cu column and in the solder bump, respectively.