Les systèmes Cu /Ni-P/Au sont utilisés comme contacts électriques car ils présentent une conductivité électrique élevée, alliée à un bon comportement mécanique et une résistance à la corrosion. Le Cu possède une conductivité électrique unique qui en a fait le métal le plus utilisé en électronique. Cependant, sa faible résistance à la corrosion nécessite l’application de revêtements protecteurs. Les sous couches de Ni (généralement Ni-P) permettent essentiellement d’éviter la diffusion entre Cu et Au. Enfin, la couche de finition en Au est utilisée pour garantir la durée de vie des contacts électriques. Pour des raisons économiques, ce film de faible épaisseur est poreux, entrainant ainsi un couplage galvanique entre l’Au et le Ni au détriment du nickel. Ainsi ce travail est dédié à l’identification et la mise en œuvre des stratégies visant à améliorer la durée de vie des contacts électriques et plus globalement des modules électroniques.Lors de cette thèse, nous avons développé 3 stratégies : (1) améliorer les propriétés de la couche barrière de Ni, (2) remplacer l’or par un métal moins onéreux, (3) sceller les pores de la couche d’Au les propriétés du film barrière Ni-P améliorées notamment par des additifs tels que la glycine. Sn a également imposé un effet similaire. D’autres couches de finition nobles NiAg et NiPd ont été étudiées. Bien que des films hautement adhésifs aient été formés par potentiel pulsé, ces films poreux n'offraient pas un comportement correct à la corrosion. Enfin, il a été découvert que les pores de la couche de finition en Au peuvent être efficacement scellés par électrodéposition de poly méthacrylate de méthyle / Cu/Ni(Ni-P)/Au systems are used as electrical contacts due to their combination of electrical conductivity, corrosion resistance, and mechanical behavior. Cu has a unique electrical conductivity that made it the most used metal in electronics. However, protective coatings must be applied on Cu due to its poor corrosion resistance. Au films are used to secure a proper lifetime of electrical contacts. Ni films are essential to avoid the diffusion of Cu into Au. Electrodeposition is the method of choice to form these multi-layer systems. The Au top-coat is notably thin and hence porous. The corrosive media penetrate through these pores, hence electrical contacts are suffering from a galvanic coupling. This work is dedicated to identify and test the strategies to enhance the lifetime of electrical contacts and electronic modules. Three strategies were detected, (1) improve the properties of the Ni barrier layer, (2) replacing the Au film with a thicker but cheaper alternative metal, and (3) seal the pores of Au top-coat using a post-treatment process. It was found out that the properties of the Ni-P barrier film can be notably improved by additives such as glycine. Sn also found to be highly advantageous for forming NiSn barrier coatings. NiAg and NiPd noble top-coats were investigated as alternatives to Au thin films. Although highly adhesive films were formed using the pulse deposition, the films were porous and thus did not offer a proper corrosion behavior. And finally, a cathodic electropolymerization was employed as a post-treatment method. It was found out that the pores of Au top-coat can be effectively sealed by the electrodeposition of polymethyl methacrylate

Almost all electronic devices require efficient conversion of electrical power from one form to another. Electrical power is used world wide at the rate of approximately 12 billion kW per hour. The Center for Power Electronics Systems at Virginia Tech was established with a vision to develop an integrated systems approach via integrated power electronic modules (IPEMs) to improve the reliability, cost-effectiveness, and performance of power electronics systems. IPEMs are multi-layered structures based on embedded power technology and offer the advantage of three-dimensional (3D) packaging of electronic components in a small and compact volume, replacing the traditional wire bonding technology. They have the potential to offer reduced time and effort associated with developing and manufacturing power processors. However, placing multiple heat generating chips in a small volume also makes thermal management more challenging. With the steady increase in the heat density of the electronic packages during the last few decades, thermal management is becoming a key enabling technology for the future growth of power electronics. The focus of this work is on using computational analysis tools and experimental techniques to assess fundamental and practical cooling limitations on IPEMs, developing both passive and active integrated thermal management strategies, and creating design guidelines for IPEMs based on both thermal and thermo-mechanical stress considerations. Specifically, a commercially available finite element package is used to create a 3D geometric layout of the electronic module. The baseline finite element numerical model is validated using bench-top wind tunnel experiments. The experimental setup is also employed to characterize the thermal behavior of chips in the multi-chip package and test the applicability of superposition methodology for temperature fields of chips within multi-chip modules. Using numerical models, both passive and active integrated thermal management strategies are investigated. The passive cooling strategies include advanced ceramic materials, copper trace thickness, and structural enhancements. Active cooling strategies include double-sided cooling using traditional heat sinks, and an extension of double-sided cooling concept using microchannels integrated with the module on both sides of embedded chips. The overall result of the work presented here is the better understanding of thermal issues and limitations with IPEM technology, and development of thermal design guidelines for cooling strategies that take into consideration both thermal and thermo-mechanical performance. / Ph. D.