Abstracts by Session

Session D: Power Electronics - New Materials
Wed   08:00 – 08:40 Manuel Gaertner SiC Power Devices: A Key Enabler for the Future E-Mobility

Wide Bandgap Materials are the perfect candidates for more efficient power electronic applications. Silicon Carbide (SiC) components have been used for many years in the industrial segment and now are progressively entering the automotive field. The first devices have been SiC diodes being used in on board charger PFC stages due to their excellent switching behavior. In the next wave now SiC MOSFETs are strongly entering the automotive domain in different applications like traction inverters, on board chargers and DCDC converters. Compared to well established Si components wide-bandgap materials are characterized by significant advantages especially considering a total cost of ownership approach, one key benefit is the strongly increased efficiency. New innovative power packages, optimized for fast switching and better thermal management, are introduced to the market to exploit the full capabilities of the new semiconductor material. Finally, an outlook on future automotive trends that are enabled by the SiC Technology is given, for example the increased DC bus voltage of nominal 800V that is a key enabler for future e-mobility.

Wed  08:40 – 09:00 Francesco Iannuzzo SiC Power MOSFETs Package-Level Testing and Issues in Normal-and Abnormal-Conditions
Thanks to the unprecedented potential in terms of efficiency compared with silicon counterparts, silicon carbide (SiC) devices have quickly become an enabling technology for power electronic applications, including the booming Electric Vehicles. However, the critical manufacturing process required to fabricate SiC MOSFETs raises concerns for long-term reliability. On top of that, short-circuit is one of the most critical aspects because of the huge power density compared to e.g., silicon IGBTs.
The speech presents first the degradation indicators under both wear and short-circuit conditions. Afterwards, an original mixed power-cycling/short-circuit test approach is presented, to investigate the implications of short-circuit events on the expected life. Results of failure analysis (lock-in thermography, focused ion beam, and scanning electron microscope) are also presented along with a transient thermo-mechanical simulation based on finite-element analysis. Finally, a mitigation strategy to enhance short-circuit robustness is proposed.
Wed  09:00 – 09:20 Giovanni Di Nuzzo Condition Monitoring of SiC Power Modules to Support Predictive Maintenance
The reliability of power modules plays a crucial role in developing safer and smarter generations of electric vehicles. Condition monitoring represents a possible solution to predict the possible occurrence of catastrophic failures and avoids unexpected breakdowns. More specifically, power modules for inverter applications are an emerging technology requiring condition monitoring indicators to detect ongoing degradation mechanisms. In this work, silicon carbide MOSFET power modules are thermally stressed through the application of a pulsed direct current until reaching end-of-life limits. As a result, two main failure modes occurring at the package level are observed: chip solder degradation and bond-wire damages. In addition, forward voltage, junction temperature, and thermal resistance are measured during the power cycling as promising parameters to monitor the device\’s state of health. After the test, the chip solder condition and bond-wires robustness are checked through scanning acoustic microscope images and optical inspections, respectively. The novelty of this work lies in refining health indicators for silicon carbide power modules.
Wed  09:20 – 09:40 Maximilian Podsednik Quantitative Aluminum Depth-Profile Measurements in SiC using Laser Assisted Methods
One method ideal for the characterization of novel materials is the recently presented online laser ablation of solids in liquids (online LASIL). In online LASIL a solid sample is ablated under a continuous stream of a liquid carrier medium, which is then introduced into the plasma of an ICP-MS. This approach circumvents the laborious sample digestion step required for conventional ICP-MS analysis but enables in contrast to other solid sampling techniques the use of liquid standards for quantification. In this work, the LASIL setup was further optimized by introducing segmented gas bubbles, that trap the generated nanoparticles in a single liquid segment. In this way, the washout behavior and the transport efficiency of the particles from the LASIL cell to the detection system could be improved drastically, enabling the accurate quantification of trace elements. To demonstrate the applicability of this method, the aluminum content of the hard to digest material silicon carbide was quantified. Those quantitative results can further be combined with qualitative LA-ICP-MS data of the same material, resulting in quantitative depth profiles with increased depth resolution.
Wed  09:40 – 10:00 Bianca Boettge Material Characterization of Cement Based Encapsulation
Wed  10:00 – 10:20 Christophe Fery Front Side Interconnection with Die Top System for Improved Reliability and High Temperature Performance
Facing a strong demand for car electrification, OEMs are pushed to develop more cost-effective vehicles. Beside batteries, the main inverter is also a key component that needs to become more efficient, smaller, and more reliable.
The adoption of SiC dies seems to be a suitable answer with demonstrated improvement of efficiency at system level, higher power densities and the ability to operate at higher temperatures.
However, the technologies for die assembly and interconnect need to match the enhanced performances. The use of Ag sintering, already established for die attach, also offers solutions for front side interconnect especially since Heraeus Electronics introduced the Die Top System (DTS®), which is a thin copper plate with pre-applied sinter paste.This materials system enables the bonding of thick copper wires, thus profiting further from the flexibility and maturity of wedge bonding. DTS® helps to maximize the power density and the reliability.
In the first part of the presentation, DTS® assembly process will be reviewed. Then, power cycling results will be discussed for DTS® either attached to Si-IGBT or to SiC-MOSFET with junction temperature up to 200°C.