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Structure Inheritance in Nanoparticle Ink Direct-Writing Processes and Crack-Free Nano-Copper Interconnects Printed by a Single-Run Approach

1
School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Wenhua West Road 2, Weihai 264209, China
2
Department of Mechanical Engineering, Harbin University of Science and Technology at Rongcheng, Xueyuan Road 2006, Rongcheng 264300, China
3
Department of Mechanical Engineering, State Key Laboratory of Tribology, Key Laboratory for Advanced Manufacturing by Materials Processing Technology, Ministry of Education of PR China, Tsinghua University, Beijing 100084, China
*
Authors to whom correspondence should be addressed.
Materials 2019, 12(9), 1559; https://doi.org/10.3390/ma12091559
Received: 4 April 2019 / Revised: 7 May 2019 / Accepted: 8 May 2019 / Published: 13 May 2019
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Abstract

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/□. View Full-Text
Keywords: nano-copper conductive ink; interconnects; structure inheritance; crack-free; direct-writing nano-copper conductive ink; interconnects; structure inheritance; crack-free; direct-writing
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Liu, S.; Li, Y.; Xing, S.; Liu, L.; Zou, G.; Zhang, P. Structure Inheritance in Nanoparticle Ink Direct-Writing Processes and Crack-Free Nano-Copper Interconnects Printed by a Single-Run Approach. Materials 2019, 12, 1559.

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