Abstract:

A simple solution method to synthesize Cu nanoparticles with the mean diameter of 57.5 nm is developed, and as-synthesized Cu nanoparticles are characterized systematically, including scanning electron microscope(SEM), transmission electron microscope(TEM), X-ray diffraction(XRD), thermal gravity analysis(TGA) and differential thermal analysis(DTA). The nano copper paste is prepared by dispensing as-prepared Cu nanoparticles into deionized water with the assistance of ultrasonic. The sandwich structure of nickel/nano copper paste/copper is fabricated using a simple screen-printing method and the shear strength of the sandwich structure, the cross-sectional microstructure and fracture micro-structural features under the different pulsed current sintering processes is studied. Experimental results show that the shear strength of the sandwich structure increase as the current increase, and the shear strength reach the highest value, i.e. 46.3 MPa, when the current is 0.8 kA, also the pulse electric current sinter nano copper paste and connect nanometer copper particles and nickel as well as copper substrates in a short time (less than 200 ms) to obtain a high density and high performance joint structure. Mechanism of pulse current sintering nano copper paste is proposed by analyzing the nano-copper solder paste microstructural features after the pulse current sintering.

Key words: pulsed electric current sintering, rapid joining, Cu nanoparticles