Abstract In gravure offset printing, ink is transferred with the help of an offset material from a patterned gravure plate to a substrate. This thesis is concerned with the study and further development of this printing process for electronics; on alumina, glass and polymers. The work has been divided into five parts. In the first section, the printing process is described. The second section describes the composition of the inks for gravure offset printing and the resulting ink properties. It also presents the ink transfer mechanism; the model that explains how the ink is transferred between an offset material and a substrate. The third chapter details the printing process explained by a solvent absorption mechanism. The forth chapter describes the firing/curing of printed samples and their properties. The last chapter describes applications of the method. The inks used to produce conductors on ceramics (ceramic inks) and conductors on polymers (polymer inks) contain silver particles, and were under development for gravure offset printing. The major achieved properties were the high ink pickup to the offset blanket and high transfer percentage to the substrate. 100% ink transfer from blanket to substrate for ceramic inks and almost 100% ink transfer for polymer inks was obtained. The printing of ceramic inks was able to produce 8 μm of relatively thick, 300 μm wide lines with < 10 mΩ/sq. resistance. The minimum line width for conducting lines was 35 μm, with one printing. Multi printing was applied producing as many as 10 times wet-on-wet multiprinted lines with 100 % ink transfer from blanket to substrate resulting in a square resistance of 1mΩ/sq. Polymer inks were able produce a square resistance of 20 mΩ/sq. for 300 μm wide lines after curing at 140 °C for about 15 min, and the minimum width was down to 70 μm. In the optimised manufacturing process, the delay time on the blanket was reduced to 3 s. In addition to ultra-fine-line manufacturing of conductors, the method enables the manufacture of special structures e.g. laser-solder contact pads with 28/28 μm lines/spaces resolution. With industrial printing equipment it is possible to produce 100 m2/h with the demonstrated printing properties.

Today’s state of the art additive manufacturing (AM) systems have the ability to fabricate multi-material devices with novel capabilities that were previously constrained by traditional manufacturing. AM machines fuse or deposit material in an additive fashion only where necessary, thus unlocking advantages of mass customization, no part-specific tooling, near arbitrary geometric complexity, and reduced lead times and cost. The combination of conductive ink micro-dispensing AM process with hybrid manufacturing processes including: laser machining, CNC machining, and pick & place enables the fabrication of printed electronics. Printed electronics exploit the integration of AM with hybrid processes and allow embedded and/or conformal electronics systems to be fabricated, which overcomes previously limited multi-functionality, decreases the form factor, and enhances performance. However, AM processes are still emerging technologies and lack qualification and standardization, which limits widespread application, especially in harsh environments (i.e. defense and industrial sectors). This dissertation explores three topics of electronics integration into AM that address the path toward qualification and standardization to evaluate the performance and repeatable fabrication of printed electronics for resilience when subjected to harsh environments. These topics include: (1) the effect of smoothing processes to improve the as-printed surface finish of AM components with mechanical and electrical characterization—which highlights the lack of qualification and standardization within AM printed electronics and paves the way for the remaining topics of the dissertation, (2) harsh environmental testing (i.e. mechanical shock, thermal cycling, die shear strength) and initiation of a foundation for qualification of printed electronic components to demonstrate survivability in harsh environments, and (3) the development of standardized methods to evaluate the adhesion of conductive inks while also analyzing the effect of surface treatments on the adhesive failure mode of conductive inks. The first topic of this dissertation addresses the as-printed surface roughness from individually fusing lines in AM extrusion processes that create semi-continuous components. In this work, the impact of surface smoothing on mechanical properties and electrical performance was measured. For the mechanical study, surface roughness was decreased with vapor smoothing by 70% while maintaining dimensional accuracy and increasing the hermetic seal to overcome the inherent porosity. However, there was little impact on the mechanical properties. For the electrical study, a vapor smoothing and a thermal smoothing process reduced the surface roughness of the surfaces of extruded substrates by 90% and 80% while also reducing measured dissipative losses up to 24% and 40% at 7 GHz, respectively. The second topic of this dissertation addresses the survivability of printed electronic components under harsh environmental conditions by adapting test methods and conducting preliminary evaluation of multi-material AM components for initializing qualification procedures. A few of the material sets show resilience to high G impacts up to 20,000 G’s and thermal cycling in extreme temperatures (-55 to 125ºC). It was also found that coefficient of thermal expansion matching is an important consideration for multi-material printed electronics and adhesion of the conductive ink is a prerequisite for antenna survivability in harsh environments. The final topic of this dissertation addresses the development of semi-quantitative and quantitative measurements for standardizing adhesion testing of conductive inks while also evaluating the effect of surface treatments. Without standard adhesion measurements of conductive inks, comparisons between materials or references to application requirements cannot be determined and limit the adoption of printed electronics. The semi-quantitative method evolved from manual cross-hatch scratch testing by designing, printing, and testing a semi-automated tool, which was coined scratch adhesion tester (SAT). By cross-hatch scratch testing with a semi-automated device, the SAT bypasses the operator-to-operator variance and allows more repeatable and finer analysis/comparison across labs. Alternatively, single lap shear testing permits quantitative adhesion measurements by providing a numerical value of the nominal interfacial shear strength of a coating upon testing while also showing surface treatments can improve adhesion and alter the adhesive (i.e. the delamination) failure mode of conductive inks.

Ce projet vise à développer de nouvelles encres à base de nanofils d’argent et de nanocellulose pour des applications conductrices et transparentes. Les nanocelluloses, nanoparticules issues de la cellulose, sont de deux types : les nanocristaux de cellulose (NCC) et les nanofibrilles de cellulose (NFC) et possèdent des propriétés bien spécifiques. Ce travail a consisté d’une part (i) à utiliser la forme tubulaire et rigide des NCC pour produire des nanotubes d’argents par synthèse chimique, avant leur formulation en encre et d’autre part (ii) à utiliser les propriétés d’enchevêtrement des NFC flexibles pour stabiliser des nanofils d’argent commerciaux, habituellement instables en suspension. Les divers résultats de ce projet ont permis d’aboutir à la formulation brevetée et à la commercialisation d’une encre conductrice à base d’une faible quantité d’argent et de NCC et de deux encres conductrices et transparentes à base de NFC et de nanofils d’argent. Les interactions physico-chimiques et la stabilité colloïdale de ces suspensions hybrides ont été étudiée de manière fondamentale, tout en développant des formulations adaptées à divers procédés d’impression, que ce soit à échelle laboratoire mais aussi industrielle. / This project aims at developing new conductive inks based on nanocellulose and silver nanowires for transparent and conductive applications. Nanocellulose are nanoparticles extracted from the cellulose and two kinds currently exist: the cellulose nanocrystals (CNC) and the cellulose nanofibrils (CNF). This project have evaluated on one hand the ability of using tubular rigid CNC as template for producing silver nanorods, prior their formulation into conductive inks. On the other hand, the ability of using flexible and entangled CNF to stabilize commercial silver nanowires, usually unstable in suspension, was investigated. The results of this project lead to the patented formulation and commercialization of one low silver content conductive ink based on silver and CNC and two conductive transparent ink based on CNF and silver nanowires. Physico-chemical interactions and colloidal stability of such hybrid suspension have been scientifically studied meanwhile printing process adapted formulation have been successfully designed and tested at laboratory scale but also industrial scale.

Le potentiel des procédés d’impression dans les applications électroniques sur des supports en céramique a été démontré dans ce travail. Plusieurs techniques d’impression ont été étudiées : sérigraphie, flexographie, héliogravure et jet d’encre. Les propriétés de surface de plusieurs types de céramique ont été caractérisées avant et après frittage : taille des pores, rugosité et énergie de surface. Ces analyses ont permis de sélectionner les matières premières des encres les mieux adaptées à ces supports, ainsi qu’aux procédés d’impression considérés. Des formulations aqueuses à base de particules d’argent ont été privilégiées. Les propriétés de ces encres, rhéologie et tension de surface, ont été analysées et leurs effets sur la qualité des lignes imprimées (largeur, épaisseur et rugosité) ont été évalués. Après impression, les motifs ont été frittés. Des résistivités proches de celle de l’argent ont été obtenues (2 à 12x10-8 Ohm.m). L’originalité de ce travail réside notamment dans l’utilisation d’encres sérigraphiques à base d’eau et l’impression d’encres flexographiques sur des supports en céramique. Cette étude ouvre donc des perspectives pour l’industrialisation et la production de masse de composants électroniques sur supports céramiques souples. / This work demonstrates the printing processes potential for manufacturing ceramic based electronic devices. Several printing techniques were studied: screen printing, flexography, rotogravure and inkjet. Ceramic tapes surface properties were characterised: surface pore size, roughness and surface energy. These analyses allowed the selection of the inks raw materials adapted to the substrates and the printing processes. Water-based silver inks were formulated. Inks properties, rheology and surface tension, were analysed and their effect on line properties was investigated. Printed substrates were afterwards sintered. Resistivity values close to that of bulk silver were reached (2 to 12x10-8 Ohm.m). These work novelties are mainly the formulation of water-based environmentally friendly screen printing pastes and the flexography printing of silver inks onto ceramic substrates. This study offers new perspectives for the industrialisation and the mass production of electronic components on flexible ceramic substrates.

Ces travaux examinent le potentiel d’un papier à fort lissé pour la production de masse de tags RFID-HF imprimés. Les caractérisations menées sur le papier Powercoat HD mettent en évidence une haute tolérance à la température et une faible rugosité. De fait, il se présente ainsi comme une sérieuse alternative à l’utilisation des films polymères (PET, PEN, PI, etc.), permettant de développer pleinement les performances électriques d’encres conductrices métalliques.Deux procédés d’impression industriels ont été considérés, la flexographie et la sérigraphie ayant tout deux fait leurs preuves depuis plusieurs décennies pour l’impression graphique à hautes cadences. Le potentiel de leur utilisation pour l’impression à grande échelle de dispositifs électroniques à bas-coût est discuté dans ces travaux. De plus, les performances électriques d’encres commerciales à base d’argent sont étudiées en fonction de la taille des particules qui les composent. En effet, l’utilisation de particules métalliques à l’échelle nanométrique pourra faciliter l’activation des mécanismes de diffusion atomique, améliorant ainsi le contact physique entre les particules et favorisant la conduction électrique. En parallèle, les encres à microparticules sont moins coûteuses et leurs conditions d’utilisation moins contraignantes. Toutefois, la coalescence des particules métalliques après l’impression ne pourra être initiée sans un traitement thermique de recuit.Le recuit est usuellement réalisé dans une étuve ou un tunnel à air chaud, la température doit alors rester inférieure à la tolérance du substrat. Cela permet d’atteindre des performances électriques qui restent limitées pour des durées de procédé de l’ordre de plusieurs minutes. Afin de tenir compte des contraintes industrielles d’une production à grande échelle et de permettre d’obtenir les meilleures performances électriques en un temps réduit, l’un des principaux axes de recherche exploré consiste au déploiement des technologies émergentes de recuit photonique proche infrarouge (NIR) et lumière intense pulsée (IPL). Ces dernières sont basées sur l’absorption de l’énergie lumineuse par le film d’encre provoquant ainsi sont échauffement rapide. L’important différentiel d’absorption entre les encres et le substrat contribue, en outre, à une sélectivité de ces procédés permettant de limiter la dégradation du support tout en atteignant au niveau de l’encre, des températures pouvant être supérieures à 300°C. Pour chaque procédé de recuit, l’influence des différents paramètres sur les performances électriques finales a pu être étudiée par la mise en place d’un suivi in-situ de la résistance, permettant un échantillonnage allant jusqu’à 250 kHz.Finalement, des boucles RFID-HF ont été imprimées, recuites dans les conditions précédemment optimisées puis caractérisées. Une estimation des coûts de production a été menée afin de distinguer les contributions liées à l’encre, au support et à la puce électronique en silicium. Les résultats obtenus mettent en évidence le potentiel du papier Powercoat HD, couplé à une impression en flexographie et à un recuit proche infrarouge, permettant alors la production à grande échelle de tags RFID-HF pour un coût matière de l’ordre de 5 centimes d’euros. / This work examines the potential of a very smooth paper for the mass production of printed RFID-RF tags. Characterizations on Powercoat HD paper demonstrate high temperature tolerance and very low roughness. It thus represents a serious alternative to the use of polymeric films (PET, PEN, PI, etc.), enabling the electrical performance of metallic conductive inks to be fully developed.Two industrial printing processes have been considered, flexography and screen printing, and their use were discussed for the printing of low-cost electronic devices. Moreover, the electrical performances of commercial silver based inks are studied according to the size of their particles. Indeed, the use of metal particles at the nanometric scale can facilitate the activation of the atomic diffusion mechanisms, thus improving the physical contact between the particles and promoting electrical conduction. In parallel, microparticles inks are cheaper and their conditions of use less restrictive. In any case, the coalescence of the metal particles after printing cannot be initiated without a thermal sintering treatment.Sintering is usually carried out in an oven or hot air tunnel, the temperature must therefore remain below the tolerance of the substrate. This leads to limited electrical performances for long process duration of several minutes. In order to take into account the industrial constraints of large-scale production and to achieve the best electrical performance in a short time, one of the main explored research areas is the deployment of emerging near-infrared (NIR) and intense pulsed light (IPL) photonic technologies. These latter are based on the absorption of light energy by the ink film thus causing rapid heating. The important absorption differential between the inks and the substrate allows high heating selectivity which makes it possible to limit the degradation of the substrate while the ink temperatures may be greater than 300 ° C. For each sintering process, the influence of the various parameters on the final electrical performance has been studied by setting up an in-situ resistance monitoring, allowing sampling frequency up to 250 kHz.Finally, RFID-HF loops were printed, sintered under previously optimized conditions and then characterized. An estimate of the production costs was carried out in order to distinguish the contributions related to the ink, the substrate and the silicon chip. The obtained results demonstrate the potential of Powercoat HD paper, coupled with flexographic roll-to-roll printing and near-infrared technology, enabling the large-scale production of RFID-HF tags at a material cost of the order of 5 euros cents.