Ultrasonic microscope investigations of die attach quality and correlations with thermal resistance

In the semiconductor industry the use of ultrasonic microscopes for evaluating the integrity of the bond between adjacent surfaces has increased dramatically over the last few years. These instruments are rapidly becoming an acceptable diagnostic tool in the QC laboratory and new specifications have been written incorporating them into MIL requirements. Especially in the non-destructive investigation of plastic encapsulated ICs for delaminations, cracks, voids, and die-bonding faults ultrasonic microscopy has great advantages. The main equipment used is SLAM (or through transmission mode acoustic microscope) with a frequency range of 10–200 MHz and C-SAM (or reflective mode acoustic microscope) working in the range 5–100 MHz. In this paper, standard measurements of die attach quality and thermal resistance are correlated with C-SAM results. A general correlation between the amount of delamination and the measured thermal resistance was found.