Silver Ink Formulations for Sinter-free Printing of Conductive Films

Abstract

Inkjet printing offers an attractive method for the deposition of metal interconnects in electronic systems and enables a low-cost, environmentally friendly route to manufacture. However, virtually all current metal inkjet processes require post-deposition sintering treatments to achieve the optimum electrical conductivity, because the growth mechanism involves coalescence of discrete nanoparticles. A manufacturing process that reduces the number of steps by directly printing silver, removing the need to sinter the printed metal, would be highly advantageous. Here we describe a, sinter-free process that results in the direct printing of crystalline silver. This process exploits the chemistries developed for Atomic Layer Deposition (ALD), to form the basis of a new ink formulation, which we term; Reactive Organometallic inks (ROM). These ROM ink formulations are capable of depositing low temperature, high conductivity metal films, without the need for subsequent sintering treatments. To reduce the temperature for direct formation of metallic Ag, we have added an alcohol as a catalytic reducing agent to dissociate the organometallic component. Silver films printed from our novel ROM ink, on a glass substrate at 120 °C, are electrically conductive with a typical resistivity as low as 39.2% that of bulk silver, without the need for sintering.

Low-Cost Printed Flexible Antenna by Using an Office Printer for Conformal Applications

“…The invention of chemically cured conductive inks has opened a new era of inkjet printing technology enabling the use of office inkjet printers without any postprocessing of printed conductive layers [17]. Chemical curing of the AgNP ink in printed antenna fabrication requires special treatment of the surface of the substrate so that a conduction path could be formed instantly at room temperature [18]. The comparison between our low-cost printed technique and the commercially available Dimatix printer technique is done in Table 1.…”

EGaIn‐Assisted Room‐Temperature Sintering of Silver Nanoparticles for Stretchable, Inkjet‐Printed, Thin‐Film Electronics

“…Sinter‐free Ag inks are of particular interest because they do not require heating, plasma treatment, or other postprocessing steps that could damage the circuit substrate or surface‐mounted microelectronics . This includes atomic layer deposition (ALD) for direct printing of crystalline Ag and a commercially available AgNP ink that is specialized for inkjet printing (Mitsubshi‐NBSIJ‐FD02). While promising for room temperature circuit printing, this latter ink requires a specialized, solvent‐compatible, microporous substrate with a chemical reacting agent (e.g., Mitsubishi Resin Coated Paper NB‐RC‐3GR120) to eliminate crack formation and create percolating networks of AgNP.…”

Room temperature sintering of polar ZnO nanosheets: I-evidence

“…); the fact that the specific surface area of the particles may suffer an unexpected variation during storage inevitably leads to a misinterpretation of the experimental results when this alteration is not considered. Besides, the control of this process may have potential applications, such as the fabrication of ZnO ink formulations for sinter-free printing of semiconductive films, in a similar way as silver nanoparticles are currently being used for printing conductive circuits [11][12][13]. The purpose would be to produce an ink of polar ZnO nanoparticles, stabilized by an appropriate organic agent, whose removal upon deposition of the printed pattern would trigger the spontaneous sintering of the ZnO nanoparticles under the appropriate moist atmosphere at room temperature to form the semiconductive film.…”