Investigations on TS bondability of different Au wires down to room temperature

The presentation shows results of Au wire thermosonic (TS) bonding from 125 °C down to room temperature. One topic was the proof of room temperature bondability of different kinds of Au wires (standard, doped, Pd alloyed) on different Al bond pad metallizations and a PCB substrate with Cu/Ni/Pd/flash-Au metallization. Investigations include mechanical tests of Au loops and ball contacts as well as investigations of the microstructure of the contacts (FIB, SEM, TEM). Au/Al intermetallic phases with thicknesses of a few hundred nanometers were found below the Au ball contacts on Al metallization directly after bonding at room temperature (without curing). The Au wedge contacts were exclusively established with flash Au as finish metallization of the PCB