纳米铜银核壳焊膏脉冲电流快速烧结连接铜基板研究

Nano copper-silver core-shell particles (Cu@Ag NPs) are synthesized by a mild two-step solution method, many tiny Ag NPs with an average diameter of 6.9 nm fully covering the surfaces of medium-sized Cu NPs with the mean diameter of 57.5 nm, and scanning electron microscope (SEM), transmission electron microscope (TEM) and X-Ray diffraction (XRD) analysis are used to characterize the structure of as-synthesized Cu@Ag NPs. A simple screen-printing method is used to fabricate the sandwich structure of copper substrate/nano Cu@Ag paste/copper substrate. And the shear strength of the sandwich structure and the micro-structural features under the different pulse currents are studied. Experimental results show that a high shear strength and high intensity metallurgical joint structure can be obtained by pulse electric currents sintering nano Cu@Ag paste and connect Cu@Ag NPs and copper substrates in a less than 200 ms short time. The shear strength of the sandwich structure increases as the current increases, and the shear strength reach the highest value, i.e. 80 MPa at the pulsed current of 1.0 kA. Mechanism of pulse current sintering nano Cu@Ag paste was proposed by analyzing the nano Cu@Ag paste microstructural features after the pulse current sintering.