纳米铜银核壳焊膏脉冲电流快速烧结连接铜基板研究

Rapid Sintering of Nano Copper-Silver Core-Shell Paste and Interconnection of Copper Substrates by Pulse Current

一种温和的两步液相法制备的纳米铜银核壳颗粒,实现了均径为6.9 nm的小尺寸纳米银颗粒包覆在均径为57.5 nm的纳米铜颗粒的表面,采用扫描电子显微镜、透射电子显微镜和高分辨率射像对其结构进行了表征。采用模板印刷法制备铜基板/纳米铜银核壳焊膏/铜基板三明治结构,研究了脉冲电流对三明治结构的剪切强度大小和微结构特征的影响。试验结果表明脉冲电流烧结纳米铜银核壳焊膏连接Cu-Cu基板可在短时间(小于200 ms)内快速获得高致密度且实现冶金连接的高强度焊点结构。三明治结构的剪切强度随脉冲电流的增加而增大,在1.0 kA的脉冲电流下,可获得高达80 MPa的剪切强度。经研究脉冲电流烧结后的纳米铜银核壳焊膏内部显微组织结构,提出双脉冲电流下纳米铜银核壳焊膏烧结连接的机理。

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.