Liu Shujie, Li Yujie, Xing Songling, Liu Lei, Zou Guisheng, Zhang Peng
School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Wenhua West Road 2, Weihai 264209, China.
Department of Mechanical Engineering, Harbin University of Science and Technology at Rongcheng, Xueyuan Road 2006, Rongcheng 264300, China.
Materials (Basel). 2019 May 13;12(9):1559. doi: 10.3390/ma12091559.
When nanoparticle conductive ink is used for printing interconnects, cracks and pores are common defects that deteriorate the electrical conductivity of the printed circuits. Influences of the ink solvent, the solid fraction of the ink, the pre-printing treatment and the sintering parameters on the interconnect morphology and conductivity were investigated. It was found that the impacts of all these factors coupled with each other throughout the whole procedure, from the pre-printing to the post-printing processes, and led to a structure inheritance effect. An optimum process route was developed for producing crack-free interconnects by a single-run direct-writing approach using home-made nano-copper ink. A weak gel was promoted in the ink before printing in the presence of long-chain polymers and bridging molecules by mechanical agitation. The fully developed gel network prevented the phase separation during ink extrusion and crack formations during drying. With the reducing agents in the ink and slow evaporation of the ink solvent, compact packing and neck joining of copper nanoparticles were obtained after a two-step sintering process. The crack-free interconnects successfully produced have a surface roughness smaller than 1.5 μm and the square resistances as low as 0.01 Ω/□.
当使用纳米颗粒导电油墨印刷互连线路时，裂纹和孔隙是常见的缺陷，会降低印刷电路的导电性。研究了油墨溶剂、油墨的固体含量、印刷前处理以及烧结参数对互连线路形态和导电性的影响。研究发现，在从印刷前到印刷后的整个过程中，所有这些因素相互影响，并导致了一种结构继承效应。通过使用自制的纳米铜油墨，采用单次直写方法，开发出了一种用于生产无裂纹互连线路的最佳工艺路线。在长链聚合物和桥接分子存在的情况下，通过机械搅拌在印刷前促进油墨中形成弱凝胶。充分发展的凝胶网络可防止油墨挤出过程中的相分离以及干燥过程中的裂纹形成。借助油墨中的还原剂以及油墨溶剂的缓慢蒸发，经过两步烧结工艺后，铜纳米颗粒实现了紧密堆积和颈部连接。成功制备的无裂纹互连线路表面粗糙度小于1.5μm，方阻低至0.01Ω/□。
