Preparation of Oxidation-Resistant Ag-Cu Alloy Nanoparticles by Polyol Method for Electronic Packaging

Ag or Cu metal nanoparticle paste can be used as a bonding material for electronic packaging applications. However, Ag nanoparticle paste has some drawbacks including high cost and being prone to ion migration in high-humidity conditions. The main obstacle to using Cu nanoparticle paste is rapid oxidation in air during heating. In this work, we describe a method to prepare Ag-Cu alloy nanoparticle paste by a polyol chemical reduction method combined with subsequent concentration. Characterization with ultraviolet–visible spectroscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and energy dispersive spectrometry confirm the formation of the Ag-Cu alloy structure. During the synthesis of Ag-Cu alloy nanoparticles, an Ag core forms initially, followed by codeposition of Ag and Cu. Most of the Ag-Cu alloy nanoparticles have a truncated octahedral shape with twin structures located at the edges. This Ag-Cu alloy nanoparticle paste has a good oxidation resistance up to 350°C in air atmosphere. Using the Ag-Cu alloy nanoparticle paste, joints were formed at a low sinter-bonding temperature of 160°C. Shearing tests confirm the formation of robust joints, with an average shear strength of 50 MPa.