Stackable SiC-Embedded Ceramic Packages for High-Voltage and High-Temperature Power Electronic Applications

This study encompasses the development of a high-voltage and high-temperature–capable package for power electronic applications based on the embedding of silicon carbide (SiC) semiconductor devices in the ceramic circuit carrier such as the direct bonded copper (DBC) substrate. By sealing semiconductor devices into DBC substrates, high temperature, high voltage, and high current capability as well as high corrosion resistance can be achieved compared with the state-of-the-art printed circuit board (PCB) embedding technology. The power devices are attached with high-temperature stable solder and sinter material and are surrounded by thermal conductive ceramic and high-temperature–capable potting materials that enable the complete package to operate at 250°C or above. Furthermore, the single embedded packages can be stacked together to multilevel DBC topologies with increased voltage blocking characteristics. Thus, current limits of the PCB and low-temperature cofired ceramic–based multilayer solutions are exceeded and will be confirmed in the course of this study. This package is designed to carry out the maximal performance of SiC and future wide bandgap devices. It is a promising solution not only for applications in harsh ambient environments such as aerospace and turbine, geothermal well logging, and downhole oil and gas wells but also for hybrid electric/electric vehicle and energy conversion.

Stackable SiC Embedded Ceramic Packages for High Voltage and High Temperature Power Electronics Applications

This paper encompasses the development of a high voltage and high temperature capable package for power electronic applications based on the embedding of SiC (silicon carbide) semiconductor devices in ceramic circuit carrier such as direct bonded copper (DBC) substrate. By sealing the semiconductor devices into DBC substrates, high temperature, high voltage and high current capability as well as high corrosion resistance can be achieved compared to state-of-the-art PCB (printed circuit board) embedding technology. The power devices are attached with high temperature stable solder and sinter material, and are surrounded by thermal conductive ceramic and high temperature capable potting materials that enable the complete package to operate at 250 °C or above. Furthermore, the single embedded packages can be stacked together to multilevel DBC topologies with increased voltage blocking characteristics. Thus, current limits of PCB and LTCC (low-temperature co-fired ceramic) based multilayer solutions are exceeded and will be confirmed in the course of this study. This package is designed to carry out the maximal performance of SiC and future WBG (wide band-gap) devices. It is a promising solution for applications in harsh ambient environment such as aerospace and turbine, geothermal well logging, down hole-well oil & gas, but also applicable for HEV/EV (hybrid electric/electric vehicle) and energy conversion.

Strength assessment for direct-sintered Al2O3-to-Cu joints based on damage modeling

Metal-to-ceramics direct sintering was carried out with Al2O3 and Cu / 3 μm Ni / 1 μm Au substrates. The bonding paste consisted of micron-sized Ag2O particles and a reducing solvent that provokes Ag2O-to-Ag reduction during processing accompanied by the formation of Ag nano particles. Five different sets of process parameters resulted in different joint microstructure and strength. The experimental data was used to calibrate an elasto-visco-plastic finite element model of the sintered assembly which yielded a quantitative damage function and criterion to predict the strength of direct-sintered joints. The developed ductile damage formulation introduced a parameter ξ, i.e. the product of equivalent creep strain and stress triaxiality, that controls the tolerable plastic strain at fracture. An extended numerical parameter study subsequently revealed the complex interaction between the joint strength and microstructural joint features. Thinner joints were found to provide a slightly higher strength while the amount of sinter material and costs is significantly reduced. Moreover, it is recommended to aim at a higher level of densification at the edges and corners of sintered joints since these areas apparently contribute more to the overall mechanical strength. The developed concept is capable of tailoring the microstructure of direct-sintered joints according to the requirements or vice versa.

Friction mechanism and lock-up friction coefficient prediction for sinter bronze friction materials

Purpose – This research investigated the mechanism of wet friction plates of engagement and solved the problem that the lock-up friction coefficient of sinter material could not be obtained but from experiments for a long time. The paper aims to discuss these issues. Design/methodology/approach – Including four steps: surface topology sampling and reconstruction, fractal parameters obtaining and fractal surface simulating, micro-contact mechanics model and friction coefficient fractal model, and experimental verification. Findings – After running in stage of the friction plates, the fractal dimension would reach a dynamically stable stage for a long time. The proportional coefficient K expresses the correlation between the base hardness and the asperities shear strength. The model could be property for one or more working condition via adjusting the coefficient K. The experiment data of friction coefficient are increased as the load magnified both in the model prediction and experiment practice. The trend is different from other models. Originality/value – This research is original and it is supported by national defense project. It would be served for tracked vehicles to solve the defect in transmission system. The friction coefficient is obtained via solving the tangential force in MB model. The surface topography could be reconstructed by laser topography instrument and the parameters could be received by program.