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Metal Films for Printed Electronics: Ink-substrate Interactions and Sintering
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.ORCID iD: 0000-0003-2340-2363
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A new manufacturing paradigm may lower the cost and environmental impact of existing products, as well as enable completely new products. Large scale, roll-to-roll manufacturing of flexible electronics and other functionality has great potential. However, a commercial breakthrough depends on a lower consumption of materials and energy compared with competing alternatives, and that sufficiently high performance and reliability of the products can be maintained. The substrate constitutes a large part of the product, and therefore its cost and environmental sustainability are important. Electrically conducting thin films are required in many functional devices and applications. In demanding applications, metal films offer the highest conductivity.

 

In this thesis, paper substrates of various type and construction were characterized, and the characteristics were related to the performance of inkjet-printed metal patterns. Fast absorption of the ink carrier was beneficial for well-defined pattern geometry, as well as high conductivity. Surface roughness with topography variations of sufficiently large amplitude and frequency, was detrimental to the pattern definition and conductivity. Porosity was another important factor, where the characteristic pore size was much more important than the total pore volume. Apparent surface energy was important for non-absorbing substrates, but of limited importance for coatings with a high absorption rate. Applying thin polymer–based coatings on flexible non-porous films to provide a mechanism for ink solvent removal, improved the pattern definition significantly. Inkjet-printing of a ZnO-dispersion on uncoated paper provided a thin spot-coating, allowing conductivity of silver nanoparticle films. Conductive nanoparticle films could not form directly on the uncoated paper.

 

The resulting performance of printed metal patterns was highly dependent on a well adapted sintering methodology. Several sintering methods were examined in this thesis, including conventional oven sintering, electrical sintering, microwave sintering, chemical sintering and intense pulsed light sintering. Specially designed coated papers with modified chemical and physical properties, were utilized for chemical low-temperature sintering of silver nanoparticle inks. For intense pulsed light sintering and material conversion of patterns, custom equipment was designed and built. Using the equipment, inkjet-printed copper oxide patterns were processed into highly conducting copper patterns. Custom-designed papers with mesoporous coatings and porous precoatings improved the reliablility and performance of the reduction and sintering process.

 

 

 

 

The thesis aims to clarify how ink-substrate interactions and sintering methodology affect the performance and reliability of inkjet-printed nanoparticle patterns on flexible substrates. This improves the selection, adaptation, design and manufacturing of suitable substrates for inkjet-printed high conductivity patterns, such as circuit boards or RFID antennas.  

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2014. , 72 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 210
Keyword [en]
inkjet printing, silver nanoparticles, paper, flexible substrates, sintering, printed electronics, IPL sintering, flash sintering, copper films, coatings, thin films, AgNP, conductive films, metal films
National Category
Physical Chemistry Materials Engineering Nano Technology Physical Sciences
Identifiers
URN: urn:nbn:se:miun:diva-23420ISBN: 978-91-87557-98-9 (print)OAI: oai:DiVA.org:miun-23420DiVA: diva2:763177
Public defence
2014-12-18, Mediacenter, Digital Printing Center, Järnvägsgatan 3, Örnsköldsvik, 10:00 (English)
Opponent
Supervisors
Available from: 2014-11-14 Created: 2014-11-13 Last updated: 2015-03-13Bibliographically approved
List of papers
1. The importance of surface characteristics for structure definition of silver nanoparticle ink patterns on paper surfaces
Open this publication in new window or tab >>The importance of surface characteristics for structure definition of silver nanoparticle ink patterns on paper surfaces
2010 (English)In: NIP26 and Digital Fabrication, Austin: The Society for Imaging Science and Technology, 2010, 309-313 p.Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Austin: The Society for Imaging Science and Technology, 2010
National Category
Materials Engineering
Identifiers
urn:nbn:se:miun:diva-12263 (URN)2-s2.0-79955715827 (Scopus ID)978-089208293-3 (ISBN)
Conference
26th International Conference on Digital Printing Technologies, NIP26 and 6th International Conference on Digital Fabrication 2010, DF 2010; Austin, TX; 19 September 2010 through 23 September 2010; Code 84729
Available from: 2010-11-22 Created: 2010-11-22 Last updated: 2016-10-05Bibliographically approved
2. Effect of Paper Properties on Electrical Conductivity and Pattern Definition for Silver Nanoparticle Inkjet Ink
Open this publication in new window or tab >>Effect of Paper Properties on Electrical Conductivity and Pattern Definition for Silver Nanoparticle Inkjet Ink
2012 (English)In: Proceedings of LOPE-C 2012, 2012, 115-119 p.Conference paper, Presentation (Refereed)
Abstract [en]

In this work, electrical conductivity and print pattern definition isstudied for silver nanoparticle ink, printed on ten commerciallyavailable paper substrates. Interrelations and correlations betweenelectrical conductivity, print pattern definition and a set ofmeasured paper properties are analyzed with a multivariatestatistical method. The papers are characterized in terms ofabsorption rate, porosity, apparent surface energy, surfaceroughness and surface material content. The statistical analysisshows that electrical conductivity and print pattern definition arecorrelated. Conductivity and print definition are correlatedpositively with absorption rate and negatively with surfaceroughness. A model based on projection to latent structures (PLS) isbuilt from the measurement data, showing adequate values of modelfit and predictive ability. This suggests that the chosen propertiesand methods for surface characterization are relevant in estimatingoverall performance of inkjet-printed conductors on paper.Additionally, a qualitative examination of the nanoparticle layercharacteristic is conducted with SEM cross section microscopy.Some of the properties and mechanisms of importance to theconductivity of the printed conductors are highlighted, of whichsome are crucial for achieving conductivity. Physical characteristicsof a suitable paper surface should ideally include large absorptioncapability for the ink carrier, but most importantly, a characteristicpore size and surface roughness amplitude that are both smallcompared to the dry ink layer thickness. If these criteria are met,paper media can be a low cost, comparably high performancealternative for metal nanoparticle inks in printed electronics applications.

Keyword
Inkjet, Nanoparticles, Sintering, printed electronics, paper, conductive inks, functional printing
National Category
Nano Technology
Identifiers
urn:nbn:se:miun:diva-16589 (URN)978-3-00-038122-5 (ISBN)
Conference
Large-area, Organic and Printed Electronics Convention (LOPE-C) 2012
Available from: 2012-06-27 Created: 2012-06-27 Last updated: 2014-11-14Bibliographically approved
3. Paper Surfaces for Metal Nanoparticle Inkjet Printing
Open this publication in new window or tab >>Paper Surfaces for Metal Nanoparticle Inkjet Printing
2012 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 259, 731-739 p.Article in journal (Refereed) Published
Abstract [en]

The widespread usage of paper and board offer largely unexploited possibilities for printed electronics applications. Reliability and performance of printed devices on comparatively rough and inhomogenous surfaces of paper does however pose challenges.Silver nanoparticle ink has been deposited on ten various paper substrates by inkjet printing. The papers are commercially available, and selected over a range of different types and construction. A smooth nonporous polyimide film was included as a nonporous reference substrate. The substrates have been characterized in terms of porosity, absorption rate, apparent surface energy, surface roughness and material content. The electrical conductivity of the resulting printed films have been measured after drying at 60°C and again after additional sintering at 110°C. A qualitative analysis of the conductivity differences on the different substrates based on surface characterization and SEM examination is presented. Measurable parameters of importance to the final conductivity are pointed out, some of which are crucial to achieve conductivity. When certain criteria of the surfaces are met, paper media can be used as low cost, but comparably high performance substrates for metal nanoparticle inks in printed electronics applications.

Keyword
printed electronics, inkjet printing, paper substrates, flexible substrates, nanoparticles, conductive inks
National Category
Nano Technology
Identifiers
urn:nbn:se:miun:diva-16448 (URN)10.1016/j.apsusc.2012.07.112 (DOI)000310436900110 ()2-s2.0-84866051319 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2012-06-14 Created: 2012-06-14 Last updated: 2016-10-20Bibliographically approved
4. Sintering Methods for Metal Nanoparticle Inks on Flexible Substrates
Open this publication in new window or tab >>Sintering Methods for Metal Nanoparticle Inks on Flexible Substrates
2009 (English)In: NIP 25: DIGITAL FABRICATION 2009, TECHNICAL PROGRAM AND PROCEEDINGS, The Society for Imaging Science and Technology, 2009, 614-617 p.Conference paper, Published paper (Refereed)
Abstract [en]

In this paper a number of selective sintering methods suitable for inkjet printed nanoparticles are demonstrated on two different coated papers. The selective methods demonstrated here are electric current heating, microwave sintering and photonic curing. As a reference, conventional heat chamber sintering is also included. Conductivity measurements and studies of sintered structures with optical and scanning electron microscopy are performed, as well as a qualitative evaluation of how the heat-sensitive substrates are affected. The purpose is to analyze characteristics of each method and gain insight in how different process parameters affect overall performance and reliability. With heat chamber sintering the best achievable conductivity without substrate deformation corresponded to less than 20% of pure silver. With some selective methods, conductivity reached well above 50% of pure silver.

 

 

Place, publisher, year, edition, pages
The Society for Imaging Science and Technology, 2009
Keyword
silver nanoink, sintering
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Other Materials Engineering
Identifiers
urn:nbn:se:miun:diva-10154 (URN)000279358900167 ()2-s2.0-77952635220 (Scopus ID)978-089208287-2 (ISBN)
Conference
NIP25: 25th International Conference on Digital Printing Technologies and Digital Fabrication 2009; Louisville, KY; 20 September 2009 through 24 September 2009; Code 80244
Available from: 2009-10-21 Created: 2009-10-21 Last updated: 2016-10-05Bibliographically approved
5. Assisted sintering of silver nanoparticle inkjet inks on paper with active coatings
Open this publication in new window or tab >>Assisted sintering of silver nanoparticle inkjet inks on paper with active coatings
Show others...
2015 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, 64841-64849 p.Article in journal (Refereed) Published
Abstract [en]

Inkjet-printed metal films are important within the emerging field of printed electronics. For large-scale manufacturing, low-cost flexible substrates and low temperature sintering is desired. Tailored coated substrates are interesting for roll-to-roll fabrication of printed electronics, since a suitable tailoring of the ink-substrate system may reduce, or remove, the need for explicit sintering. Here we utilize specially designed coated papers, containing chloride as an active sintering agent. The built-in sintering agent greatly assists low-temperature sintering of inkjet-printed AgNP films. Further, we examine the effect of variations in coating pore size and precoating type. Interestingly, we find that the sintering is substantially affected by these parameters.

Keyword
printed electronics, sintering, inkjet printing, silver nanoparticles, AgNP, thin films, paper, coatings, chemical sintering, mesoporous, flexible electronics
National Category
Materials Engineering Nano Technology Materials Chemistry Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-23418 (URN)10.1039/c5ra06626c (DOI)000359136500003 ()2-s2.0-84938717754 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2014-11-13 Created: 2014-11-13 Last updated: 2016-12-20Bibliographically approved
6. Inkjet Fabrication of Copper Patterns for Flexible Electronics: Using Paper with Active Precoatings
Open this publication in new window or tab >>Inkjet Fabrication of Copper Patterns for Flexible Electronics: Using Paper with Active Precoatings
Show others...
2015 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 33, 18273-18282 p.Article in journal (Refereed) Published
Abstract [en]

Low-cost solution-processing of highly conductive films is important for the expanding market of printed electronics. For roll-to-roll manufacturing, suitable flexible substrates and compatible postprocessing are essential. Here, custom-developed coated papers are demonstrated to facilitate the inkjet fabrication of high performance copper patterns. The patterns are fabricated in ambient conditions using water-based CuO dispersion and intense pulsed light (IPL) processing. Papers using a porous CaCO3 precoating, combined with an acidic mesoporous absorption coating, improve the effectiveness and reliability of the IPL process. The processing is realizable within 5 ms, using a single pulse of light. A resistivity of 3.1 ± 0.12 μΩ·cm is achieved with 400 μm wide conductors, corresponding to more than 50% of the conductivity of bulk copper. This is higher than previously reported results for IPL-processed copper.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2015
Keyword
intense pulsed light sintering, flash light sintering, printed flexible electronics, inkjet printing, paper coatings, copper patterns, IPL sintering, IPL processing, paper electronics, CuO reduction, inkjet fabrication
National Category
Physical Chemistry Materials Engineering Nano Technology Materials Chemistry Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-23419 (URN)10.1021/acsami.5b03061 (DOI)000360322000012 ()2-s2.0-84940528167 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2014-11-13 Created: 2014-11-13 Last updated: 2016-12-20Bibliographically approved

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