Au-Ag Heat-Press Bonding Technology for Multi-LSI Package.

The Au-Ag heat-press bonding process was applied to the micro bonding process for Multi-LSI package. The Auplated Cu lead was bonded on the Ag-plated Cu frame.In the case of bonding temperatures above 325°C and pressures from 150MPa to 300MPa, the bonding strength was about 8N/mm and the fracture occured at the neck of Cu lead. However, when the bonding pressure was higher than 300MPa, the strengths were reduced. On the other hand, when the bonding pressure was less than 100MPa, the strengths were reduced rapidly and the fracture occured at the Au/Ag interface.By observing the structure on the cross section, several non-bonding areas were found at the Au/Ag interface. On the other hand, non-bonding areas were not found at the interface of Cu lead fractured bonding. According to the AES analysis of the surface of the bonding fractured at Au/Ag interface, it was assumed that this bonding was achieved by the Au-Ag slight mutual diffusion at the interface. In the case of the bonding done at more than 300MPa, deformation of Cu lead caused the reduction of the bonding strength.