title: Highly Conductive Cu-Cu Joint Formation by Low-Temperature Sintering of Formic Acid-Treated Cu Nanoparticles.
abstract: Highly conductive Cu-Cu interconnections of SiC die with Ti/Ni/Cu metallization and direct bonded copper substrate for high-power semiconductor devices are achieved by the low-temperature sintering of Cu nanoparticles with a formic acid treatment. The Cu-Cu joints formed via a long-range sintering process exhibited good electrical conductivity and high strength. When sintered at 260 °C, the Cu nanoparticle layer exhibited a low resistivity of 5.65 μΩ·cm and the joints displayed a high shear strength of 43.4 MPa. When sintered at 320 °C, the resistivity decreased to 3.16 μΩ·cm and the shear strength increased to 51.7 MPa. The microstructure analysis demonstrated that the formation of Cu-Cu joints was realized by metallurgical bonding at the contact interface between the Cu pad and the sintered Cu nanoparticle layer, and the densely sintered layer was composed of polycrystals with a size of hundreds of nanometers. In addition, high-density twins were found in the interior of the sintered layer, which contributed to the improvement of the performance of the Cu-Cu joints. This bonding technology is suitable for high-power devices operating under high temperatures.
authors.affiliation: State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology , Harbin 150001, China.|Department of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen Graduate School , Shenzhen 518055, China.
authors.forename: Jingdong
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen Graduate School , Shenzhen 518055, China.
authors.forename: Hongtao
authors.initials: H
authors.lastname: Chen
authors.affiliation: Department of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen Graduate School , Shenzhen 518055, China.
authors.forename: Hongjun
authors.initials: H
authors.lastname: Ji
authors.affiliation: State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology , Harbin 150001, China.|Department of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen Graduate School , Shenzhen 518055, China.
authors.forename: Mingyu
authors.initials: M
authors.lastname: Li
keywords: Cu nanoparticles; high conductivity; low-temperature bonding; power electronic packaging; sintering