Abstract
This thesis focuses on the miniaturization of power electronics devices and the development ofmultifunctional components. The main objective is to develop materials with specific electrical properties to reducesystem size, with particular emphasis on power modules. The work focuses on the production of a functionalizedsubstrate with a capacitor function inside the package. The study begins by defining the specifications for thefunctionalized substrate, and considering an architecture capable of integrating a decoupling capacitor. A single-layercapacitor based on SPS-sintered barium titanate was chosen for its high permittivity. Alumina was chosen as the substratematerial, for areas requiring a material with good fracture field, mechanical and thermal properties. Nickel is chosen asthe metallic material for metallization. The thesis explores different forms of co-sintering, including cermet composites,multi-layers and function gradient materials (FGM) for the BaTiO3/Ni and Al2O3/Ni material couples. Mastery of thevarious stages in the synthesis of nanometric BaTiO3 powder is demonstrated, and sintering parameters are optimized toobtain high-density ceramics with controlled dielectric properties. Different geometries for ceramic/ceramic co-sinteringare examined, taking into account the advantages and challenges of co-sintering depending on the application of pressure.The study points to a T-shaped geometry as the preferred choice, given the electrical interconnections required betweenthe housing components. Co-sintering tests on Al2O3/Ni/BaTiO3 multilayers revealed stresses at the interfaces. A cermetbasedcomposition gradient was used to obtain the multilayer. At the same time, two BaTiO3/Ni and Al2O3/Ni subassemblieswere produced for dielectric characterization. A BaTiO3/Ni FGM was developed with the addition of anintermediate composite layer. No diffusion or phase formation is visible in this system. The use of a sacrificial materialduring the sintering process has demonstrated its value in achieving reproducible sintering, limiting nickel creep and thetemperature gradient within the sintering mould. An FGM with a diameter of 15 mm and a thickness of 2 mmreproducibly exhibits permittivities close to 105 with losses of less than 10%. The associated capacitance is greater than100 nF. These parameters correspond to the values targeted at the start of the project. It is possible to obtain a Ni/Al2O3/NiFGM, but to limit thickness and improve the system's heat dissipation capacity, a multilayer approach is moreappropriate. A Ni/Al2O3/Ni sandwich was developed using nickel foil and sacrificial alumina powder. This approachdemonstrated the formation of a bonding zone between the two materials. The sintering of this device is reproducible,and the dielectric properties of the systems are close to those of pure alumina. The sub-systems were assembled bybrazing and bonding, and a "capacitor-substrate" prototype was obtained with satisfactory mechanical properties, bothin terms of pulling and shearing. In conclusion, the thesis demonstrates that it is possible to go from powder synthesisto the prototype to be integrated into a power module, while optimizing each stage to guarantee both the high degree ofintegration of the solutions and the desired properties.