Etude et caractérisation d'une nouvelle connectique adaptée à l'intégration tridimensionnelle pour l'électronique de puissance

L'intégration tridimensionnelle est une voie prometteuse permettant d'améliorer simultanément des performances électriques (réduction des inductances et résistances parasites) et performances thermiques (refroidissement double face) des modules de puissance. Nous proposons d'un assemblage à base d'enchevêtrement de nano fils de cuivre. Le principe réside en une structure constituée de deux surfaces métalliques sur lesquelles sont électro-déposées des nano-poteaux de cuivre en utilisant des membranes de nano filtration en alumine. Un assemblage se réalise par compression à froid jusqu'à interpénétration et enchevêtrement des nano-poteaux créant ainsi une liaison électrique, thermique et mécanique. Dans le cadre de cette thèse, l'étude, dans une première phase, a porté sur l'amélioration d'un procédé de fabrication des assemblages nano scratch pré-existant. La mise en œuvre de la technologie et l'application à des composants de puissance sont ensuite présentés. La connexion a alors été caractérisée d'un point de vue mécanique, électrique et thermo-mécanique. Les résultats de ces caractérisations ont été utilisés pour optimiser les conditions de dépôt dans une démarche itérative. Enfin, nous avons démontré la faisabilité des dépôts des nano poteaux sur la face avant des composants de puissance. Cela permet d'imaginer une nouvelle structure packaging 3D compacte. Il est ainsi possible d'envisager une simplification des technologies de type contact pressé.Three-dimensional integration is a promising issue which allows improving simultaneously electrical performances (reduction of inductance stray and parasitic resistances) and thermal management (double sides' cooling) of power electronic modules. We propose a hybrid assembly method based on entanglement of copper nano wires. Its principle resides in the structure composed of two metallic surfaces on which nano copper wires are electroplated by template method using alumina membranes. Electro-thermo-mechanical interconnection is then achieved by pressing both surfaces together, thus leading to the permeation and the entanglement of the nano-wires. The study focuses, firstly, on improvement of making process of nano scratch assemblies. The implementation of process and its application on power components are presented. The connection is then characterized in mechanical, electrical, thermo-mechanical points of view. The results of these characterizations were used to optimize electrodeposition condition in an iterative approach. Finally, we demonstrated the feasibility of electrodeposition on the front side of power components. This allows imagining a new compact packaging 3D structure. It is, thus, possible to consider a simplification of pressured contact technology

Development and reliability of a direct access sensor using flip chip on flex technology with anisotropic conductive adhesive

Technological developments in biomedical microsystems are opening up new opportunities to improve healthcare procedures. Swallowable diagnostic sensing capsules are an example of these. In none of the diagnostic sensing capsules, is the sensor’s first level packaging achieved via Flip Chip Over Hole (FCOH) method using Anisotropic Conductive Adhesive (ACA). In a capsule application with direct access sensor (DAS), ACA not only provides the electrical interconnection but simultaneously seals the interconnect area and the underlying electronics. The development showed that the ACA FCOH was a viable option for the DAS interconnection. Adequate adhesive formed a strong joint that withstood a shear stress of 120N/mm2 and a compressive stress of 6N required to secure the final sensor assembly in place before encapsulation. Electrical characterization of the ACA joint in a fluid environment showed that the ACA was saturated with moisture and that the ions in the solution actively contributed to the leakage current, characterized by the varying rate of change of conductance. Long term hygrothermal aging of the ACA joint showed that a thermal strain of 0.004 and a hygroscopic strain of 0.0052 were present and resulted in a fatigue like process. In-vitro tests showed that high temperature and acidity had a deleterious effect of the ACA and its joint. It also showed that the ACA contact joints positioned at around or over 1mm would survive the gastrointestinal (GI) fluids and would be able to provide a reliable contact during the entire 72hr of the GI transit time. A final capsule demonstrator was achieved by successfully integrating the DAS, the battery and the final foldable circuitry into a glycerine capsule. Final capsule soak tests suggested that the silicone encapsulated system could survive the 72hr gut transition