Preparation of PVP coated Cu NPs and the application for low-temperature bonding

There is an increasing interest in developing a low temperature interconnection process using nanoparticles. Some studies focus on bonding using Ag nanoparticles (Ag NPs). However, few studies investigate a bonding process using Cu nanoparticles (Cu NPs) due to the easy oxidation in air. Here we achieve a robust bonding of Cu wires to Cu pads with polyvinylpyrrolidone (PVP) coated Cu NPs at a low temperature of 170 °C. The PVP coating can effectively prevent the oxidation of Cu NPs when heated in air. The bonding is formed through the sintering of Cu NPs and direct metallic bonding between the sintered Cu particles and Cu pads. Electrical measurements of the Cu NPs demonstrate that Cu NPs have a low resistivity of 8.6 × 10−5 Ω cm after being sintered under pressure. This method has the potential to be used in the electrical packaging industry due to its economic cost, easy operation, and high conductivity.