RFID tags for cryogenic applications: Experimental and numerical analysis of thermo-mechanical behaviour

International audienceRFID solutions will improve the traceability of biological samples stored at low temperature (77 K) in biobanks. To achieve this goal, the reliability of RFID tags is essential. In this paper, we focus on the reliability aspect of RFID tags in harsh environment and more specifically to assembly design optimization through numerical simulations and accelerated life tests. A package-dimensioned model and a wire-interconnect centered model have been used to assess stress distribution in the package and wire bonds. We also develop a specific versatile test bench to apply thermal cycling while monitoring the functionality of the tags. We investigate three different tag configurations and demonstrate that the main failure mode is related to wire breaks. The occurrence of this failure depends mainly on the nature and thickness of the encapsulant resin which induce compressive and tensile stresses during thermal cycling. FEM results are in good agreement with observed failures

Tailoring the Crystallographic Texture and Electrical Properties of Inkjet-printed Interconnects for Use in Microelectronics

International audienceIn this paper, silver nanoparticles with a mean diameter of 40 nm are studied for future applications in microelectronic devices. The enhanced diffusivity of nanoparticles is exploited to fabricate electrical interconnects at low temperature. Sintering condition has been tuned to tailor the grain size so that electrical resistivity can be lowered down to 3.4 µOhm∙cm. In this study, a {111}-textured gold thin film has been used to increase diffusion routes. The combined effects of the substrate crystalline orientation and the sintering condition have been demonstrated to have a significant impact on microstructures. In particular, a {111} fiber texture is developed above 300°C in printed silver only if the underlying film exhibits a preferential orientation. This condition appeared as essential for the efficiency of the gold wire-bonding process step. Thus, inkjet-printed interconnects show a prospective potential compared to conventional subtractive technique and offers new opportunities for low cost metallization in electronics packaging

Impact of variable frequency microwave and rapid thermal sintering on microstructure of inkjet-printed silver nanoparticles

International audienceThe effect of thermal profile on microstructure is studied in the frame of thin films deposited by inkjet-printing technology. The role of sintering temperature and thermal ramp is particularly investigated. Fast heating ramps exhibit coarse grains and pores, especially when a hybrid microwave curing is performed. This enhanced growth is attributed to the quick activation of densifying sintering regimes without undergoing thermal energy loss at low temperature. Microstructural evolution of various sintered inkjet-printed films is correlated with electrical resistivity and with the Young's modulus determined by nanoindentation. A strong link between those three parameters is highlighted during experiments giving credit to either a surface or a fully volumetric sintering, according to the process. Sintering is then mainly triggered by surface mass transfer or by grain boundary diffusion respectively. Silver thin-films with an electrical resistivity 4 to 5 times higher than the bulk has been reached in a few minutes and with a Young's modulus of 38 GPa

Microstrain and residual stress in thin-films made from silver nanoparticles deposited by inkjet-printing technology

Abstract. Colloidal suspensions of nanoparticles are increasingly employed in the fabrication process of electronic devices using inkjet-printing technology and a consecutive thermal treatment. The evolution of internal stresses during the conversion of silver nanoparticle-based ink into a metallic thin-film by a thermal sintering process has been investigated by in-situ XRD using the sin 2 ψ method. Despite the CTE mismatch at the film/substrate interface, the residual stress in silver films (below 70 MPa) remains lower than in conventional PVD thin-films, as a result of the remaining porosity. A Warren-Averbach analysis further showed that the crystallite growth is associated with a minimization of the twin fault density and the elastic microstrain energy above 150°C. A stabilization of the microstructure and internal stress is observed above 300°C. Inkjetprinting technology thus appears as a good alternative to conventional metallization techniques and offers significant opportunities asset for interconnect and electronic packaging

Chip integration using inkjet-printed silver conductive tracks reinforced by electroless plating for flexible board packages

International audienceInkjet-printing of interconnects is a maskless technology that has attracted great interest for printed electronics and packaging applications. Gemalto is expecting by motivated and developing skills and knowledge in this area to be at the forefront of European Security innovation and to answer to a continuous market pressure for higher security, lower cost and more secure complex systems. With an increasing need for flexible and mass deliveries of advanced secure personal devices such as: electronic passports, ID cards, driver licenses, other smartcards, e-documents and tokens. EMSE is seeing in these new developments an exciting brand new area of research situated between material science and electronics. In this frame, deposit and pattern creation for chip interconnection require specific behaviors which have to be scientifically understood to pursue industrial harmonious implementation. Both groups collaborated on inkjet-printed electronic routing from deposition to sintering and characterization, using collaborative means provided on Micro-PackS platform

Microstructuration des dépôts imprimés par jet d'encre de la coalescence des nanoparticules d'argent vers la réalisation d'interconnexions de composants électroniques.

Several challenges are still holding back the technological transfer of printed electronics to industry in spite of recent progresses. In this thesis work, the printing method of inks based on silver nanoparticles (=25 nm) was optimized according to its rheology and to the fluid/substrate interactions for the fabrication of electrical interconnections with a thickness of 500 nm. These lines were printed on silicon or flexible substrates and annealed either by conventional (oven or infrared) or selective methods (microwave) at temperatures comprised between 100 and 300 °C.A better understanding of the relationship between process and microstructure of these printed thin films, based on several crystallographic equipments (XRD, EBSD and EDX), led to the optimization of nanocrystallites growth with an activation energy of about 3 to 5 kJ•mol-1. In addition to the low residual stress (70 MPa), this optimization is used to achieve low electrical resistivity (3.4 μOhm•cm) associated with a greater coherence of the crystal lattices at grain boundaries. The probability of electron scattering at such interfaces can be further reduced using an innovative approach of oriented crystallite growth by atomic interdiffusion from the substrate.The low mechanical stiffness (E=25 nm) en fonction de sa rhéologie et des interactions fluide/substrat a permis de réaliser des interconnexions électriques d’une épaisseur de 500 nm. Ces lignes imprimées sur des substrats silicium ou flexibles sont ensuite recuites par des méthodes conventionnelles (étuve ou infrarouge) ou sélectives (micro-onde) à des températures comprises entre 100 et 300°C.Une meilleure compréhension de la relation procédé/microstructure des couches minces imprimées, via plusieurs caractérisations cristallographiques (DRX, EBSD et EDX), a permis d’optimiser la croissance des domaines nanocristallins, activée pour des énergies de l’ordre de 3 à 5 kJ•mol-1. Outre les faibles contraintes résiduelles (70 MPa), cette optimisation permet d’atteindre de faibles résistivités électriques (3.4 µOhm•cm) associées à un accroissement de la cohérence des réseaux cristallins aux joints de grains. La probabilité de réflexion des électrons à ces interfaces peut être davantage réduite, grâce à une approche innovante de croissance orientée des cristallites par interdiffusion atomique à partir du substrat.La faible rigidité mécanique (E<50 GPa) de ces lignes initialement poreuses nécessite une étape de renforcement par texturation ou par croissance electroless pour résister aux étapes de micro-assemblage et de soudure filaire. La réalisation d’un démonstrateur fonctionnel a ainsi permis de valider la technologie d’impression pour la fabrication de composants électroniques

Microstructuration des dépôts imprimés par jet d'encre de la coalescence des nanoparticules d'argent vers la réalisation d'interconnexions de composants électroniques.

Plusieurs défis subsistent pour la migration de l électronique imprimée vers l industrie, malgré des avancées récentes. Dans ces travaux de thèse, l optimisation du procédé d impression d encres à base de nanoparticules d argent (=25 nm) en fonction de sa rhéologie et des interactions fluide/substrat a permis de réaliser des interconnexions électriques d une épaisseur de 500 nm. Ces lignes imprimées sur des substrats silicium ou flexibles sont ensuite recuites par des méthodes conventionnelles (étuve ou infrarouge) ou sélectives (micro-onde) à des températures comprises entre 100 et 300C.Une meilleure compréhension de la relation procédé/microstructure des couches minces imprimées, via plusieurs caractérisations cristallographiques (DRX, EBSD et EDX), a permis d optimiser la croissance des domaines nanocristallins, activée pour des énergies de l ordre de 3 à 5 kJ mol-1. Outre les faibles contraintes résiduelles (70 MPa), cette optimisation permet d atteindre de faibles résistivités électriques (3.4 Ohm cm) associées à un accroissement de la cohérence des réseaux cristallins aux joints de grains. La probabilité de réflexion des électrons à ces interfaces peut être davantage réduite, grâce à une approche innovante de croissance orientée des cristallites par interdiffusion atomique à partir du substrat.La faible rigidité mécanique (E=25 nm) was optimized according to its rheology and to the fluid/substrate interactions for the fabrication of electrical interconnections with a thickness of 500 nm. These lines were printed on silicon or flexible substrates and annealed either by conventional (oven or infrared) or selective methods (microwave) at temperatures comprised between 100 and 300 C.A better understanding of the relationship between process and microstructure of these printed thin films, based on several crystallographic equipments (XRD, EBSD and EDX), led to the optimization of nanocrystallites growth with an activation energy of about 3 to 5 kJ mol-1. In addition to the low residual stress (70 MPa), this optimization is used to achieve low electrical resistivity (3.4 Ohm cm) associated with a greater coherence of the crystal lattices at grain boundaries. The probability of electron scattering at such interfaces can be further reduced using an innovative approach of oriented crystallite growth by atomic interdiffusion from the substrate.The low mechanical stiffness (E<50 GPa) of these porous lines requires a reinforcement step either by crystalline texturation or by electroless growth to withstand the assembly and wire-bonding steps. The fabrication of a functional demonstrator thus validated the printing technology for the manufacture of electronic components.ST ETIENNE-ENS des Mines (422182304) / SudocGARDANNE-Centre microélec. (130412301) / SudocSudocFranceF

Impression et recuit de nanoparticules métalliques pour l’électronique imprimée

National audienceThe recent progress in functionalized inks based on metal nanoparticles and their subsequent deposition by inkjet-printing technologies promoted the emergence of printed electronics. Such printed structures can be treated by selective sintering techniques that enable the sintering of 20 nm-nanoparticles at process temperatures compatible with flexible plastic substrates. This article discusses the various aspects related to the production of metal tracks on flexible substrates, from the deposition using direct printing technologies, to the relationship between microstructural characteristics and electrical properties of such structures for the fabrication of devices such as antennas, interconnectsor electrodes.Le développement récent d’encres fonctionnalisées constituées de nanoparticules métalliques, associé à la maîtrise du procédé d’impression par jet d’encre, a rendu possible l’émergence de l’électronique imprimée. Les structures imprimées peuvent être traitées par des techniques de recuit sélectif qui permettent de réaliser la coalescence de nanoparticules de 20 nm à une température de procédé compatible avec les substrats plastiques flexibles. Cet article aborde les différents aspects liés à la réalisation de pistes métalliques sur substrat souple, depuis les technologies d’impression directes, jusqu’à l’adéquation entre les caractéristiques microstructurales et les propriétés électriques de telles structures pour la fabrication de dispositifs tels que des antennes, des pistes de routage ou des électrodes

Selective Sintering of Inkjet-Printed Silver Inks Using Variable Frequency Microwave

International audienceWith the recent development of printed electronics on flexible substrate, urge for low temperature sintering process has emerged. In the frame of temperature sensitive substrates like plastics (PET, ABS, PC, etc.) conventional convective oven cannot be suitably used to achieve near‐bulk electrical resistivity. Consequently, several alternative sintering technologies have been reported and tested. In this present work, the prospective advantage of variable frequency sintering is studied for selective and fast sintering of metal inks. This variable frequency mode (VFM) improves the distribution of the electromagnetic field within the cavity and impedes arcing phenomena that could happen on metal surface. Inkjet-printed devices were processed using a VFM mode with a central frequency of 6.425 GHz with a bandwidth of 1.15 GHz and a sweep rate of 0.1 second has been used. A solid calibration step is required for temperature measurements and control during the process. The procedure includes a camera-based observation coupled with a pyrometer and an optic fiber. A reliable determination of the substrate and ink emissivity is compulsory to tailor the temperature feedback so as to not overcome the substrate's glass transition. The direct impact of microwave has been analyzed comparatively to conventional sintering assisted sintering where a thermally conductive susceptor or matrix is exploited. A huge shrink in electrical resistivity is particularly observable for samples prepared with conventional rapid thermal annealing (RTA), while those prepared in VFM quickly exhibit resistivities below 8 μΩ.cm, about 6 time the silver bulk resistivity. The electrical resistivity shrinkage is mainly originating from the contribution of the grain size. Through a strong coupling between microwave and silver nanoparticle, selective sintering of metallic parts is achieved on low temperature substrates enabling very low electrical resistivity without damaging the plastic substrate. These promising results open ways to successful implementation of microwave sintering in industrial process for flexible electronic application