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[Display omitted] • The low-temperature bonding of Si 3 N 4 and Cu was achieved using Ti/Cu films. • It is an effective means of relieving stress caused by Si 3 N 4 /Cu CTE mismatch. • An efficient Cu-on-Si 3 N 4 structure for power devices is expected. A low-temperature bonding method of Si 3 N 4 /Si 3 N 4 homostructure and Si 3 N 4 /Cu heterostructure was developed in this work. The flawless interfaces were obtained by sputtered Ti/Cu thin films after bonding at 250 °C for 30 min under a uniaxial pressure of 20 MPa. The Ti film is able to improve the adhesion of the Cu film to Si 3 N 4 substrate, and the low-temperature bonding was achieved in view of high diffusion rates of Cu nanocrystalline film with (1 1 1) crystal plane. This proof-of-concept study on the low-temperature bonding of Si 3 N 4 ceramic to Cu is expected to address residual stress caused by ordinary active metal brazing (AMB) method, which provides insights for the further heterogeneous integrations of ceramics to metals. [ABSTRACT FROM AUTHOR]

• New method was proposed to modify the Si 3 N 4 surface by nanosecond laser. • A recast silicon layer formed on the Si 3 N 4 surface after laser irradiation. • Defect-free Si 3 N 4 /Al joints were obtained by surface modification of Si 3 N 4. In this study, a nanosecond laser was conducted to modify the Si 3 N 4 surface to realize the bonding of Si 3 N 4 to Al. The effects of nanosecond laser irradiation on the surface morphology and chemical compositions of Si 3 N 4 ceramic together with the bonding of Si 3 N 4 ceramic to Al were investigated. The laser irradiation induced the thermal decomposition of Si 3 N 4 ceramic, resulting in the formation of a recast silicon layer upon the ceramic surface. Then bonding of Si 3 N 4 ceramic and Al was achieved by the eutectic reaction between the recast silicon layer and Al at a bonding temperature of 600 °C under a uniaxial pressure of 10 MPa for 60 min. The nanosecond laser irradiation method proposed in this study provided a new idea to realize the direct bonding of ceramic to metal. [ABSTRACT FROM AUTHOR]

• W90 and Mg alloy were firstly bonded by ultrasonic-assisted soldering at 250 °C. • A semi-coherent interface was formed between Sn and W. • The joint strength treated with the ultrasonication time of 2 s reached 10.4 MPa. W90 tungsten heavy alloy (W90) and AZ31B Mg alloy were firstly bonded by ultrasonic-assisted soldering using Sn in atmospheric environment. The wetting angle of Sn on W90 decreased to 130.7° under the action of ultrasound. The microstructure of W90/Sn/Mg joint treated with 2 s of ultrasounication time was W90/Mg 2 Sn + Sn/Mg 2 Sn layer/Mg. As the ultrasonication time increased to 4 s, the joint width reduced and the thickness of Mg 2 Sn layer increased. The joint strength decreased from 10.4 MPa to 5.1 MPa as the ultrasonication time increased from 2 s to 4 s. A semi-coherent interface formed at the Sn/W interface as the ultrasound was applied. [ABSTRACT FROM AUTHOR]