Thermal reliability & IMC behavior of low cost alternative Au-Ag-Pd wire bonds to Al metallization

To reduce material cost of Au bonding wire, Au-Ag alloy wire had been tried to use in electronic device, in alternative for Au wire. Nevertheless, Au-Ag alloy wire had not been applied to device due to failure problem during high humidity reliability test, like PCT(pressure cooker test) for a while. Recently, as the technology adding Pd element to conventional Au-Ag was developed, corrosive failure problem at interface between wire ball and Al pad (metallization) was solved in PCT. Finally, mass production of Au-Ag-Pd wire starts to grow up. The study on reliability and behavior of intermetallic compounds (IMC) have not been performed in terms of thermal aging or HTST (high temperature storage life test) yet. This study investigates IMC & voids behavior between Au-Ag-Pd wire and Al metallization under thermal aged condition (175´C). The chemical compositions of gold wires tested are 99.99% Au, Au-30wt.%Ag and Au-30wt.%Ag-5.5%wt.Pd, respectively. The wires are bonded on Al metallization by using thermosonic bonder, IMC behavior was characterized by FIB (focused ion beam), TEM (transmission electron microscope), EDS (energy dispersive X-ray spectrometer) The findings reveal that, interfacial reliability between Au-Ag-Pd wire and Al metallization is considerably improved, compared with 4N Au or Au-30%Ag, growth of IMCs as well as the voids formation are significantly suppressed.