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Size and Surface Effects on Chemically-induced Joining of Ag Conductive Inks


Direct write (DW) technologies offer a potential avenue towards reducing existing long lead times required for fabrication of prototypes and evaluation of new materials and integrated circuit designs. Low-temperature interconnecting techniques are required to minimize the deleterious heat effects on the shape of printed conductive networks and electronic components. Therefore, the reduced melting temperatures characteristic of metallic nanomaterials offer opportunities to bridge this technological gap. Amongst reported low-temperature sintering approaches, the chemically-induced sintering method emerges as a readily scalable approach with relatively low energy input. By uncovering the underlying relationship between particle size effects and the role of the ionic salts used to induced sintering at ambient conditions, we aim to elucidate the compatible chemistries (i.e., size and salt) to achieve optimal chemically-induced sintering. A systematic study of the sintering of polyacrylic acid-modified Ag nanoparticle-based DW inks of different size distributions (bimodal vs. monodispersed distribution) and average sizes (e.g., 5 nm and 17 nm) was investigated to elucidate the role of a commonly used salt, NaCl in the chemically- induced sintering process. An observed enhancement of our ink conductivities by about 4 orders of magnitude for monodispersed 17 nm and bimodal distribution of 9 and 170 nm particles resulted mainly from the sintering between neighboring Ag nanoparticles. In the case of monodispersed 5 nm nanoparticles, a low electrical resistivity was observed despite a growth in grain size which indicated successful sintering. The low measured electrical resistivity was mainly due to significant AgCl formation that has a lower electrical conductivity. Our results show that the chloride ions played an active role in triggering first the oxidative decomposition of Ag to Ag+ resulting in AgCl formation which subsequently led to the sintering between neighboring Ag nanoparticles. The difference in results for the 5 nm and 17 nm monodispersed Ag nanoparticles was attributed to the difference in size-dependent surface reactivities and relative amount (i.e., packing density, thickness) of the polymeric PAA coating.

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Publication details

The article was received on 19 Jul 2018, accepted on 03 Sep 2018 and first published on 04 Sep 2018

Article type: Paper
DOI: 10.1039/C8CE01191E
Citation: CrystEngComm, 2018, Accepted Manuscript
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    Size and Surface Effects on Chemically-induced Joining of Ag Conductive Inks

    Y. Wu, Z. Wang, X. Zhao and M. C. Tan, CrystEngComm, 2018, Accepted Manuscript , DOI: 10.1039/C8CE01191E

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