Effects of thermal aging on Cu nanoparticle/Bi-Sn solder hybrid bonding

• Autores: M. Usui, T. Satoh, Hidehiko Kimura, S. Tajima, Y. Hayashi, D. Setoyama, Masashi Kato
• Localización: Microelectronics reliability, ISSN 0026-2714, Nº. 78, 2017, págs. 93-99
• Idioma: inglés
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• Resumen

  • Abstract The effects of high-temperature aging on a novel hybrid bonding layer were investigated. The hybrid layer, which consisted of Cu nanoparticles and a eutectic Bi-Sn solder powder, was formed by a sintering reaction of the solid-phase Cu nanoparticles and a chemical reaction involving the liquid-phase Bi and Sn in combination. The layer was used to bond a SiC chip to a direct bonded aluminum substrate. A conventional Cu nanoparticle-based bonding layer was also prepared as a reference. Samples with these bonding layers were evaluated using the thermal aging test (225 or 250 °C, 100 h). Bonding strength and synchrotron radiation computed laminography (SRCL) measurements were performed both before and after the thermal aging test. It was observed that thermal aging greatly decreased the bonding strength of the conventional layer. In contrast, the bonding strength of the hybrid layer was reduced only slightly by the thermal aging treatment. SRCL images showed that the conventional layer exhibited numerous cracks, which acted as passages for oxidation. On the other hand, in the hybrid layer, the liquid-phase Bi and Sn densified the Cu sintering phase through the formation of an alloyed Cu-Sn phase. As a result, the hybrid layer contained fewer passages for oxidation as compared to the conventional layer and maintained its bonding strength even against thermal aging. Therefore, the hybrid layer, which is highly stable against thermal aging, will be useful for the high-temperature operation of intelligent power modules.