Low Temperature Cu/Ga Solid–Liquid Inter-Diffusion Bonding Used for Interfacial Heat Transfer in High-Power Devices

Abstract

Interfacial heat transfer is essential for the development of high-power devices with high heat flux. The metallurgical bonding of Cu substrates is successfully realized by using a self-made interlayer at 10 °C, without any flux, by Cu/Ga solid-liquid inter-diffusion bonding (SLID), which can be used for the joining of heat sinks and power devices. The microstructure and properties of the joints were investigated, and the mechanism of Cu/Ga SLID bonding was discussed. The results show that the average shear strength of the joints is 7.9 MPa, the heat-resistant temperature is 200 °C, and the thermal contact conductance is 83,541 W/(m2·K) with a holding time of 30 h at the bonding temperature of 100 °C. The fracture occurs on one side of the copper wire mesh which is caused by the residual gallium. The microstructure is mainly composed of uniform θ-CuGa2 phase, in addition to a small amount of residual copper, residual gallium and γ3-Cu9Ga4 phase. The interaction product of Cu and Ga is mainly θ-CuGa2 phase, with only a small amount of γ3-Cu9Ga4 phase occurring at the temperature of 100 °C for 20 h. The process of Cu/Ga SLID bonding can be divided into three stages as follows: the pressurization stage, the reaction diffusion stage and the isothermal solidification stage. This technology can meet our requirements of low temperature bonding, high reliability service and interfacial heat transfer enhancement.

Low‐Temperature Solidifiable Liquid Metal with Ultrahigh Thermal Conductivity Enabled by Spontaneous Phase Transition for Electronics’ Safety and Long‐Life Cooling

“…However, it was reported that the CuGa 2 and Cu 9 Ga 4 phases will form between liquid metal and copper substance below 200 °C. [43,44] In the phase analysis of EGaInSn/Cu joint using transmission electron microscopy, a thin layer of Cu 9 Ga 4 was actually present between the CuGa 2 and copper substance, and this finding is consistent with thermodynamic studies previously published. [45,46] In our study, the Cu 9 Ga 4 layers should be too thin to be detected even by SEM, which may attribute to the low solidifying temperature and the short reaction time.…”

Interfacial Intermetallic Compounds Growth Kinetics and Mechanical Characteristics of Ga-Cu Interconnects Prepared Via Transient Liquid Phase Bonding

“…However, big voids and cracks were observed in the phase in joints. Furthermore, Mu et al [20] reported successful bonding using a self-made Ga interlayer at 100 • C by Cu/Ga SLID bonding, but the strength was only 5-8 MPa, underscoring the imperative for significant improvement. These studies imply that there exists substantial room for improvement in Ga-Cu interconnection technology, rendering it well-suited for practical applications.…”

Sintering Bonding of SiC Particulate Reinforced Aluminum Metal Matrix Composites by Using Cu Nanoparticles and Liquid Ga in Air

“…Typically, the decrease of melting point and increase of diffusion coefficient are remarkable compared with that of bulk state [ 20 , 21 , 22 , 23 ]. Based on the character of liquid Ga and Cu nanoparticles, it would be promising to use liquid Ga and Cu nanoparticle as filler metal to join SiC p /Al MMCs without flux [ 24 ]. Furthermore, the understanding of sintering bonding, interaction between liquid Ga and Cu nanoparticles is still limited.…”