基于表面银膜修饰超疏水性铜微米层低温焊接技术

Low Temperature Welding Technology of Superhydrophobic Copper Micron Layer Based on Surface Silver Film Modification

研究了一种基于表面银膜修饰的铜微米层的低温焊接方法。采用电沉积方法获得表面银膜修饰的铜微米层,铜微米层表面次结构为纳米圆锥状突起,圆锥底部直径为500 nm~1μm,圆锥高为1~2μm,银膜厚度约为320 nm,用银膜修饰铜层可以有效防止铜层氧化。将两块银膜修饰的铜微米层面对面接触放置作为焊接偶,对接触区域施加一定的压力和较低的温度实现焊接互连。通过扫描电子显微镜、透射电子显微镜和焊点测试仪分析了焊接界面的形貌以及焊点的平均剪切强度。发现在焊接温度220℃、焊接压力20 MPa和焊接时间20 min的最优焊接参数条件下,铜微米层的纳米圆锥状凸起相互插入产生物理阻挡效果,圆锥状凸起结构由于纳米尺寸效应和尖端效应具有巨大的原子扩散界面,在界面处形成一定厚度的固溶强化区域,高度表面可熔化的银膜有效连接周围铜层作为中间缓冲层,减少焊接界面孔洞,显著提高焊点的平均剪切强度。热处理实验表明适当时间的热处理可以有效提高平均剪切强度,长时间受热对平均剪切强度影响不大。

A low temperature welding method of copper micron layer modified by surface silver film was studied. The copper micron layer modified by surface silver film was obtained by electrodeposition method. The surface substructure of the copper micron layer is nano conical protrusion, and the bottom diameter of the cone is 500 nm-1 μm, the cone height is 1-2 μm and the thickness of the silver film is about 320 nm. Modification of the copper layer with the silver film can effectively prevent the oxidation of the copper layer. The copper micron layers modified by two silver films were placed in face-to-face contact as a welding couple, and a certain pressure and lower temperature were applied to the contact area to realize welding interconnection. The morphology of the welding interface and average shear strength of the solder joint were analyzed by scanning electron microscope, transmission electron microscope and solder joint tester. It is found that under the optimal welding parameters conditions of 220 ℃ welding temperature, 20 MPa welding pressure and 20 min welding time, the nano conical protrusions of the copper micron layer are inserted into each other to produce physical barrier effect. Due to the nano size effect and tip effect, the conical protrusion structure has a huge atomic diffusion interface, and a solid solution strengthening region with a certain thickness is formed at the interface. The highly surface fusible silver film can effectively connect the surrounding copper layer as an intermediate buffer layer, reduce the welding interface holes and significantly improve the average shear strength of the solder joint. Heat treatment experiments show that the heat treatment with appropriate time can effectively improve the average shear strength, and long-time heating has little effect on the average shear strength.