A bonding technique for thin GaAs dice with via holes using gold-tin composites

100 mu m thin 2-mm-by-3-mm GaAs dice with via holes have been successfully bonded on alumina substrates using the technique of gold-tin multilayer composite. The bondings are near perfect, as confirmed by a scanning acoustic microscope. Scanning electron microscope images of cross sections reveal that the bonding layers are very uniform and the thickness is 1.5 mu m. EDX analysis shows that the composition of the bonding layer is nearly gold-tin eutectic. No die crackings were observed after the bonding. The specimens underwent 40 cycles of thermal shock test between -196 degrees C and 160 degrees C without incurring bonding degradation and die cracking.<
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