Novel Bi-based High Temperature Solder for Power Semiconductor Joining

Conference: CIPS 2006 - 4th International Conference on Integrated Power Systems
06/07/2006 - 06/09/2006 at Naples, Italy

Proceedings: CIPS 2006

Pages: 6Language: englishTyp: PDF

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Yamada, Yasushi; Yagi, Yuji; Nishibe, Yuji (Power Device Lab., Toyota Central Research and Development Laboratories, Inc., 41-1, Yokomichi, Nagakute, Nagakute-cho, Aichi 470-0205 Japan)
Takaku, Yoshikazu; Ohnuma, Ikuo; Ishida, Kiyohito (Department of Material Science, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-02, Sendai 980-8579 Japan)

A novel high temperature solder for power semiconductor joining of hybrid and fuel-cell vehicle's inverter has been studied. The melting temperatures of well-known lead-free solders such as Sn-based alloys are around 220 °C, that are not sufficient for high temperature operation of compound power semiconductor device such as GaN and SiC. New Bi-based solders; Bi with CuAlMn particles whose melting temperature is 270 °C are developed to improve the brittleness of Bi. The CuAlMn particles were prepared by gas-atomizing method, then they were mixed with Bi melt. According to mechanical property measurements, it was found that the tensile strength of the fabricated solder was almost 2 times higher than that of pure Bi. Consequently, joining samples were fabricated using metal plates and their reliabilities were examined by thermal cycling test. After almost 2000 cycles of -40/200 °C test, almost no intermetallic compounds and cracks were observed for Cu interface of CTE (Coefficient of Thermal Expansion) matched sample, on the contrary, certain amount of brittle Bi3Ni was found for Ni interface sample. In addition, joining samples using Sn-Cu solder were peeled off during -40/250 °C test, however no degradations were found on the samples using the fabricated solders. In conclusion, the developed solder seems to have a capability for high temperature operation of power semiconductor device.