Shear strength of Cu/In–48Sn/Cu diffusion soldered interconnections

Abstract

This paper presents the results of shear tests performed on Cu/In–48Sn/Cu diffusion soldered interconnections at the room and elevated temperatures of 373 and 423 K. Before the tests, the microstructure characterisation and chemical microanalysis of the joint area were performed. Termination of the diffusion soldering process led to the significant increase in the ultimate shear strength values. These values differed because of the type of the intermetallic phase that fulfilled the joined area: 11·2 MPa for [Cu6(Sn,In)5] and 28·5 MPa for [Cu41(Sn,In)11] phase. The shear tests performed at higher temperatures revealed a very good strength of the joints (9·8 MPa), especially for those with only the [Cu41(Sn,In)11] phase where fracture occurred inside the copper substrate. In the case of joints where unconsumed solder, [Cu6(Sn,In)5] and/or [Cu41(Sn,In)11], phases were present, the fracture surfaces observations allowed concluding that the crack propagated mostly through the intermetallic/solder interface or inside the intermetallic phase.

Keywords:

• Diffusion soldering
• Intermetallics
• Shear strength
• SEM

This work was performed in the frame of the European Action COST 531 on lead free solder materials.