Copper micro and nano particles mixture for 3D interconnections application

A novel copper paste with copper micro particles mixed with copper nanoparticles is proposed in this study. The mixed ratio between the two kinds of particles is simulated based on the Monte Carlo method. The copper micro particles are assumed to have a Face-Centered-Cubic (FCC) structure and the nanoparticles are filled randomly in the interstices between micro particles. The nanoparticles arrangement with maximum occupancy in the interstitial space is calculated, which enable its weight percentage estimation. Based on the simulation results, experiments are carried out to examine the micro paste, nano paste and mixed paste quality by optical microscope, contact angle measurements and thermogravimetric analysis (TGA). The experimental results reveal that the mixed paste is denser in structure and has a lower transition temperature.