Phase diagram of Au-Al-Cu at 500 °C

Jyun Lin Li,Pei Jen Lo,Ker-Chang Hsieh,Ming Chi Ho

doi:10.1007/s13404-014-0140-2

Abstract

Diffusion couples and equilibrated alloys were used to construct the isothermal phase diagram of Au-Al-Cu at 500 °C. Electron microprobe analyses were performed to determine the phase compositions and phase relationships. Two ternary phases and 10 three-phase equilibriums were determined in this study. Four additional three-phase equilibriums were estimated to meet the criteria for phase relationships. The δ (Au2Al) phase exhibited a wide range of solubility, and the lattice parameters were examined by X-ray. The solubility ranges of the binary intermetallic phases were also determined.

Highlights

Gold wire has been used as bonding wire in IC packages because of its ductility and anticorrosion characteristics
The increase in the I/O number of ICs from 200 to 300 has required diameter of gold wires to decrease from 25 μm to less than 20 μm to match the decrease in the area of the Al pad
A two-phase layer (AlCu+ε) was in contact with the Al2Cu phase layer; the Al2Cu-ε-AlCu three-phase equilibrium was generated. The existence of this three-phase equilibrium was confirmed through the alloy sample A1 and the equilibrium microstructure (Fig. 4)

Summary

Introduction

Gold wire has been used as bonding wire in IC packages because of its ductility and anticorrosion characteristics. The increase in the I/O number of ICs from 200 to 300 has required diameter of gold wires to decrease from 25 μm to less than 20 μm to match the decrease in the area of the Al pad. The stiffness of gold wire must be enhanced to avoid short circuits derived from wire sweep. Au-Cu alloy wire is one of the new alloy bonding wires that has been developed. The bonding wire reacts with the Al pad and forms intermetallic phases to maintain the electrical connection. A low-temperature Au-Al-Cu phase diagram could provide essential information to understand the reactions between the Au-Cu alloy wire and

Results

Discussion

Conclusion