Development of Embedded High Power Electronics Modules for Automotive Applications

Abstract

The automotive industry has a strong demand for highly reliable and cost-efficient electronics. Especially the upcoming generations of hybrid cars and fully electrical vehicles need compact and efficient 400 V power modules. Within the engine compartment installation space is of major concern. Therefore small size and high integration level of the modules are needed. Conventionally IGBTs and diodes are soldered to DCB (Direct Copper Bond) ceramics substrates and their top contacts are connected by heavy Al wire bonds. These ceramic modules are vacuum soldered to water-cooled base plates. Embedding of power switches, and controller into compact modules using PCB (Printed Circuit Board) technologies offers the potential to further improve the thermal management by double-sided cooling and to reduce the thickness of the module. In the recently started “HI-LEVEL” (Integration of Power Electronics in in High Current PCBs for Electric Vehicle Application) project, partners from automotive, automotive supplier, material supplier, PCB manufacturer and research teamed up to develop the technology, components and materials to realize high power modules. The following topics of the development will be addressed in detail in this paper:Assemble of power dies (IGBT and diode) using new sinter die attach materials:The deployment of new no pressure, low temperature sinter paste for the assembly of the power dies is a mayor development goal. Here the development of a reliable process to realize a defect free bonding of large IGBT dies (up to 10x14mm2) is essentially. These pastes are applied by stencil printing or dispensing and the sintering will take place after die placement at temperatures of around 200 °C.Thick copper substrate technology:To handle the high switching current, suitable copper tracks in the PCB are required. The realization of such thick copper lines (up to 1mm thickness) requires advanced processing, compared to conventional multilayer PCB production. In this paper the essential development steps towards a 10 kW inverter module with embedded components will be described. The process steps and reliability investigations of the different interconnect levels will be described in detail.