Reliability and Temperature Resistance of Solder–Metallic Mesh Composite Joints

Cu-to-Cu and Si-to-direct bonded copper (DBC) assemblies were bonded with SAC305 solder (reference) as well as with composite layers consisting of SAC305 solder matrices with integrated thin Cu and Ni meshes. The microstructural changes at the interfaces, such as the growth of intermetallic compound (IMC) layers and void formation, were monitored during annealing of the Cu-to-Cu samples at constant temperature of 150°C for 1000 h. All three types of sample exhibited sufficient shear strength above 40 MPa with preferable ductile fracture characteristics after annealing. The solder–mesh composite joints in the Si-to-DBC samples provided superior reliability against short-time temperature cycling between 80°C and 200°C. The cracking path was strongly distracted and branched through the mesh insert. The IMC growth rate was found to be reduced in the solder–mesh joints at the Si chip interface. Thermomechanical finite element simulations revealed that the mesh interacted with the solder matrix through plastic deformation and stretching, which could result in reduced thermal expansion of the composite overall.