A new method for flux-free diffusion joining of aluminum matrix composites reinforced with SiC particles (SiCp/Al MMCs) in atmosphere environment has been developed. Liquid gallium and nano-copper particles were employed as filler metal under joining temperatures ranging between 400 °C to 480 °C, with a holding time of 2 h and pressure of 3 MPa. The results showed that 65 vol.% SiCp/6063 Al MMCs were successfully joined together. X-ray diffraction (XRD) analysis confirmed the presence of Ga2O3 at the fracture. Meanwhile, neither copper oxide nor aluminum oxide was detected. The formation of Ga2O3 can protect nano-copper particles and SiCp/6063 Al MMCs from oxidation. The width of weld seam tended to be narrowed from 40 μm to 14 μm gradually with increasing temperature from 400 °C to 480 °C. The maximum shear strength level of 41.2 MPa was achieved with a bonding temperature of 450 °C. The change of the strength was due to the adequate elements’ mutual diffusion and solution, as well as the change of the quantity and morphology of intermetallic compounds in the weld seam, such as Al2Cu and Cu3Ga. When the diffusion joining temperature reached 440 °C or above, the leak rate of the specimen remained under 10−10 Pa·m3/s.

The vacuum brazing of dissimilar electronic packaging materials has been investigated. In this research, this applies silicon particle-reinforced aluminum matrix composites (Sip/Al MMCs) to Kovar alloys. Active melt-spun ribbons were employed as brazing filler metals under different joining temperatures and times. The results showed that the maximum joint shear strength of 96.62 MPa was achieved when the joint was made using Al-7.5Si-23.0Cu-2.0Ni-1.0Ti as the brazing filler metal at 580 °C for 30 min. X-ray diffraction (XRD) analysis of the joint indicated that the main phases were composed of Al, Si and intermetallics, including CuAl, TiFeSi, TiNiSi and Al3Ti. When the brazing temperature ranged from 570 °C to 590 °C, the leakage rate of joints remained at 10−8 Pa·m3/s or better. When the joint was made using Al-7.5Si-23.0Cu-2.0Ni-2.5Ti as the brazing filler metal at 580 °C for 30 min, the higher level of Ti content in the brazing filler metal resulted in the formation of a flake-like Ti(AlSi)3 intermetallic phase with an average size of 7 µm at the interface between the brazing seam and Sip/Al MMCs. The joint fracture was generally in the form of quasi-cleavage fracture, which primarily occurred at the interface between the filler metal and the Sip/Al MMCs. The micro-crack propagated not only Ti(AlSi)3, but also the Si particles in the substrate.

Using friction stir welding, the electronic container box and lid made from aluminium matrix composites with reinforcement of SiC particle (15 vol% SiCp/Al-MMCs) was welded successfully with T-joint. The temperature distribution of box during the process, mechanical property and microstructure of the joint as well as gas tightness of welded box was investigated. The experimental results indicated that the satisfactory T-joint can be obtained under appropriate friction stir welding parameters. During the welding process, the bottom center, which was used to place the electronic component, reached a quite lower temperature of 100°C. That can ensure safety of components in the box. After the welding process, the microstructure in stir zone was better than in base material due to the refining and homogeneous distribution of the SiC particles. The experimental results showed that the electronic container box after friction stir welding had gas tightness. The He-leakage rate was under 10-8 Pa•m3/s.