Industrial/PHD Course: Modern Power Semiconductors and their Packaging

The main component of modern Power Electronics circuits is the semiconductor power switch. This course presents the fundamentals of Power Switches operations from a physical point of view, together with the specific peculiarities and the reason to use them in a special application.

An overview on different packaging technologies and their properties, advantages and disadvantages, is also given. Requirements from the applications and possibilities to tackle them with a semiconductor package solution will be proposed.

Part I) semiconductor theory

This part aims to give an understanding of semiconductor power switch operations. A preliminary introduction to the PN junction and fundamentals of bipolar junction and field-effect transistors will be given. Then, a comparison between traditional semiconductor technologies, like Silicon, and emerging technologies like GaN and SiC will follow. Successively, referring to MOSFETs and IGBTs, several details about the structure of the elementary cell will be introduced together with the explanation of the fundamental mechanisms taking place during operations, like the Miller plateau, voltage/current overshoot and voltage/current tail. An overview of abnormal operations, like unclamped inductive switching (UIS) and short circuit, together with typical unstable phenomenon like current crowding and thermal runaway, will be also discussed. Finally, modern driving strategies, including two-level turn off and anti-desaturation will be introduced.

Part II) packaging theory

This part aims to introduce, analyze and discuss packaging techniques for modern semiconductor power switches. The present challenges in terms of power density, stray inductance and resistance, and reliability issues will be broadly discussed from a physics point of view, together with several sample applications. Modern interconnection solutions will be presented together with the research challenges in the field of power electronics packaging like copper bond wires, low-profile packaging, bondless packaging, etc.

Task: The participants will be grouped and asked to team work on a real design. A final 1-day lecture is included where groups will compare and deeply discuss the achievements and the design choices.