A reliability study of Au-Sn eutectic binding with Ga-As dice

GaAs test dice successfully bonded on alumina substrates using Au-Sn eutectic alloy with static pressure but without scrubbing are discussed. A scanning acoustic microscope (SAM) having a spatial resolution of 25 μm was used to examine the quality of the bondings. Nearly perfect bondings have been achieved consistently. After 100 cycles of thermal shock between -196° and +160°C, good specimens remain well bonded without die cracking, as confirmed by the SAM images. Specimens with voids near the edge of the dice incur vertical die cracking due to the concentrated stress at the voids. Shear tests have also been performed and 95% of the specimens tested passed the MIL-STD-883C test. The resulting shear strength correlates perfectly with the quality of the bondings determined by the SAM images