关键词: 纳米银颗粒制备, 微纳米银焊膏, 高温封装

Abstract: With the rapid development of third-generation wide bandgap semiconductors, it puts forward higher requirements for high-temperature packaging materials. Ag nanoparticles (Ag NPs) solder paste is regarded as one of the most promising bonding materials due to its "low-temperature sintering and high-temperature service" characteristic. However, after sintering, it still confronts the problem of high porosity. One of the effective ways to solve it is to mix Ag NPs and Ag microparticles (Ag MPs). Accordingly, the controllable preparation of Ag NPs and the sintering properties of the mixture of Ag NPs and Ag MPs were investigated. In the preparation of Ag NPs, this work probed into the influence of the mass ratio of polyvinylpyrrolidone (PVP) to silver nitrate (AgNO₃) and the pH value of the reaction solution on the particle size of Ag NPs. It was found that when the mass ratio of PVP to AgNO₃ is 1:4, and the pH value of the reaction solution is 10, the well-dispersed Ag NPs with an average particle size of approximately 143 nm can be obtained. After that, the prepared Ag NPs were mixed with Ag MPs at different mass ratios to fabricate the Ag microparticles/nanoparticles (Ag MPs/Ag NPs) mixed solder paste, which was subsequently used for bare Cu bonding. The results showed that Ag MPs can improve the initial packing density of particles in the solder paste. Meanwhile, based on the "low-temperature sintering" characteristic of Ag NPs, the connection among Ag NPs and between Ag NPs and Ag MPs was achieved through sintering. As a result, it significantly reduced the porosity and enhanced the shear strength of Cu-Cu joints. When the mass ratio of Ag MPs to Ag NPs is 1:5, the porosity of the sintered joint is 0.6%, and the shear strength is 21.8 MPa. The research results provide a reference for further promoting the application of Ag solder paste in high-temperature packaging.

Key words: preparation of Ag nanoparticles, micro- and nano-silver solder paste, high-temperature packaging