時間：2026-07-03(五) 14:10 pm

講題：Slightly Oxidized Copper Particle Stable Pastes: Pioneering Low Temperature Sintering Techniques

講者 :  Prof. Tetsu Yonezawa

服務單位：Division of Materials Science and Engineering, Faculty of Engineering, Hokkaido University  

地點：4樓創意講堂

主持人：張鑑祥教授

摘要：

          In the realm of SDGs, the demand for efficient power modules, particularly for applications like inverters, has surged in recent years. Power semiconductors, crucial components in electronic devices spanning from household appliances to transportation systems, necessitate effective heat control mechanisms, especially as the prevalence of wide bandgap semiconductors escalates, leading to operational temperatures exceeding 200 °C. However, the conventional lead-free solder, typically employed in joining materials, becomes impractical due to its high melting point under such conditions.

To overcome this issue, sintering-based joining / electroconductive materials have emerged as a promising solution. While silver has desirable properties such as high electronic and thermal conductivity, its prohibitive cost and issues related to ion migration limit its widespread use in high-end electronics packaging. Copper, with its extremely lower cost than silver and reduced migration concerns, presents an important alternative. Nonetheless, the susceptibility of copper to oxidation, particularly in the case of fine particles or nanoparticles, poses significant hurdles, including combustion in ambient air without appropriate passivation layers.

In this study, we have controlled the oxidative state and crystalline structure of copper nanoparticles prepared by ourselves. Using alkylcarboxylic acid molecules, we protected the particles, enabling their dispersion in high concentrations (up to 80 wt%) in a high boiling temperature liquid medium. Surface analysis with HR-TEM and XRD revealed the presence of interesting Cu₆₄O phase, which readily transformed into metallic copper at temperatures below 100 °C during sintering. The resulting pastes were employed as low temperature sintering conductive and die-attach materials. Notably, even at 150°C, these particles exhibited significant necking, demonstrating robust bonding capabilities. Furthermore, die-attach joints exhibited shear strengths exceeding 20 MPa, while the conductivity of the conductive materials reached 10^-5 Ω•cm. 

These findings underscore the potential of copper nanoparticles in the development of advanced materials for diverse applications, offering a pathway towards efficient, cost-effective, and environmentally sustainable solutions in the realm of power electronics and beyond

學經歷：

詳情請參見附檔