Tutorial 3

T03. Reliability and Qualification of Wide Bandgap Automotive Power Semiconductors

Description of the Tutorial Proposal

Wide bandgap devices are increasingly penetrating the automotive market and are becoming prime candidates for implementation in applications like traction inverters or battery chargers for electric vehicles. The mission profile of the Electric vehicle traction inverter is a particularly aggressive one since the electrothermal stresses on the power devices vary significantly in amplitude and frequency as the motor drive goes through various stages of the drive cycle including acceleration, deceleration, stalling etc. Historically, the traction converter has been implemented using silicon devices (insulated gate bipolar transistors) where the performance and reliability is well known and understood. However, recently, wide bandgap power devices like silicon carbide MOSFETs and Gallium Nitride High electron mobility transistors are being considered for automotive applications due to their improved energy conversion efficiency. Application of these WBG devices in automotive applications requires understanding of the reliability and qualification procedures especially according to the automotive standard. SiC and GaN power devices have varying internal physics and modes of operation with vastly varying robustness and reliability performance compared to silicon devices. Given the sensitive nature of the application, these devices must pass stringent automotive reliability tests and guidelines defined by the Automotive Electronics Council (AEC), the Joint Electron Device Engineering Council (JEDEC-

JC70) and the European Centre of power electronics (AQG). The objectives of this tutorial are:

i) Introduce the reliability and robustness requirements of automotive power devices. 

ii) Understand the role of packaging and how it affects electrothermal and thermo-mechanical performance. 

iii) Understand the physics of degradation and failure of power devices. 

iv) Understand the peculiarities of robustness and reliability in WBG devices (SiC and GaN). 

v) Understand test methods and circuits used in assessing the reliability and robustness of power devices.

Abstract

Power semiconductor devices are at the heart of electric vehicle power converters. These converters include the main traction converter as well as the DC/DC converter for on-board and off-board charging. They perform DC to AC conversion during traction mode and AC to DC conversion during regenerative braking and battery charging. Power semiconductor devices, depending on their internal physics, have conduction and switching losses which dissipate as heat thereby requiring thermal management solutions. Historically, these devices have been silicon IGBTs however, the advent of SiC MOSFETs means that higher switching frequencies can be used without suffering from high switching losses. The reliability of these power devices is crucial for the EV. SiC MOSFETs have different electrothermal and thermos-mechanical failure mechanisms due to different material properties and device physics. This tutorial will take attendees through the physics of failure of power semiconductors and how to ensure devices meet the automotive reliability requirements for EVs.

Biography

Layi ALATISE is currently a Professor and Royal Society Industry Fellow in Power Electronics at the University of Warwick. He received the B.Eng. (first class Hons.) degree in electrical/electronic engineering and the Ph.D. degree in microelectronics and semiconductors from Newcastle University, Newcastle upon Tyne, U.K., in 2005 and 2008, respectively. In June 2008, he joined the Innovation R&D Department, NXP Semiconductors, as Development Engineer where he designed, processed, and qualified discrete power trench MOSFETs for automotive applications and switched-mode power supplies. In November 2010, he joined the University of Warwick as Science City Research Fellow to investigate advanced power semiconductor materials and devices for improved energy conversion efficiency. Since February 2019, he has been a Professor in Electrical Engineering with the University of Warwick, Coventry, U.K. He has led several EPSRC projects in Power Electronics and is currently working on an UK government funded Project with a major automotive manufacturer for the development of automotive powertrains based on Silicon Carbide traction inverters. He was a recipient of the 2021 best paper award in the IEEE Transactions in Industrial Electronics. He has the authored or co-authored more than 100 publications in journals and international conferences. Prof. Alatise is a Chartered Engineer, Fellow of the IET and a Senior member of the IEEE.