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Recently, the application of Ag bonding wires in electronic devices has been attempted as alternative to Au bonding wires to reduce the material cost of Au. Nevertheless, Ag bonding wires have not been applied to devices due to interface corrosion problems between the Ag wire and Al pad during humidity reliability tests, such as the PCT (Pressure Cooker Test). As the technology for alloying Pd element in Ag wire has developed recently, the corrosive failure problem at the interface in the PCT has been improved significantly. This study examined the behavior of IMCs(intermetallic compounds) and interface corrosion between an Ag wire and Al metallization under humidity conditions (100%RH, 121'C). The chemical compositions of the Ag wires tested were pure Ag, Ag — 1wt%Pd and Ag-3%Pd. These wires are bonded to Al and noble metal(Au, Pd) metallization using a thermo-sonic bonder. The interfaces were characterized by FIB(Focused ion beam), HRTEM (High Resolution Transmission Electron Microscope) and EDS (Energy Dispersive X-ray Spectroscopy) The findings show that, (1) the interfacial reliability between the Ag wire and Ag metallization was improved considerably. The interface corrosion was suppressed significantly as the Pd content was increased. (2) Ag wires on a noble metal(Au, Pd) pad have stable reliability in PCT.

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.