Abstract
This study introduces a novel concept that uses composite structures of thin metallic meshes and Sn3.0Ag0.5Cu (SAC305) solder alloys to interconnect semiconductor chips to DBC substrates. The feasibility was proven by bonding Cu-to-Cu substrates. The averaged shear strength was measured as 44.1, 44.7 and 51.4 MPa for samples bonded with SAC305 (reference), Ni mesh/SAC305 and Cu mesh/SAC305 composites, respectively. The solder-mesh joints revealed a specific fracture behavior where crack propagation occurred partly within the solder and partly at the solder-mesh interface. Microstructural analyses confirmed that the metallic meshes were bonded by the formation of intermetallic compounds (IMC) while almost no (larger) defects were found. The solder-mesh concept was subsequently applied on Si-to-DBC assemblies. A very good resistance of Cu mesh/SAC305 composite joints against cyclic temperature between 80 and 200 °C was observed when the bonded area only reduced by 4.2 % after 8000 cycles. Thermal finite element (FE) simulations indicated that in particular Cu mesh/SAC305 composites can significantly reduce the thermal resistance of the interconnections which is equivalent to a better heat dissipation through the bonding layer. Thus, solder-mesh composite joints seem to be an attractive solution for high-temperature applications up to 200 °C.
