Fabrication of extremely conductive high-aspect silver traces buried in hot-embossed polycarbonate films via the direct gravure doctoring method

• Published in: Advanced powder technology : the international journal of the Society of Powder Technology, Japan Vol. 32; no. 3; pp. 764 - 770
• Main Authors: Kusaka, Yasuyuki, Kawamura, Tadaharu, Nakagawa, Masatoshi, Okamoto, Kazuki, Tanaka, Keizo, Fukuda, Nobuko
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2021
• Subjects: Conductive paste; Flexible electronics; Printing; Silver nanoparticles; Suspension; Traces; Printing; Suspension; Traces; Flexible electronics; Conductive paste; Silver nanoparticles
• ISSN: 0921-8831; 1568-5527
• DOI: 10.1016/j.apt.2021.01.027

[Display omitted] •High-aspect flexible conductive traces are produced by a simple hot-embossing/blading technique.•Binary-sized Ag pastes enable extremely conductive traces with a good structural integrity.•Large particles provide pathway for volatile solvents to smoothly escape from the filled ink.•Small particles served as glues and conductive connections enable low resistivity at low sintering temperature. Depositing inks on a planar substrate by printing is a facile way to fabricate conductive traces and other complicated functional devices. However, irrespective of the printing methods used, the thickness of the inks has an upper limit due to their fluidic property and subsequent wetting on the substrates. Herein, we present a method for creating high-aspect ratio conductive traces by combining hot-embossing and gravure doctoring techniques. Binary-sized colloidal pastes containing Ag nanoparticles and micrometer-sized spherical Ag powder additives were filled using a doctor blade in the grooves of polycarbonate (PC) films inscribed via hot-embossing to create buried traces. Under optimal mixing conditions in which the minimum resistivity was achieved, voids between the microparticles provided a pathway for the volatile solvents to smoothly escape from the filled ink and minimized thickness reduction during the thermal sintering process. A fabricated trace buried in the PC film with an aspect ratio of around 3:1 and a linewidth of 55 μm showed extremely low resistance of less than 10 Ω/m. A flexible transparent heater was developed using the reported binary colloidal paste.