The Materials and Reliability of Power Electronics Devices

Small signal commercial electronics have traditionally been designed to operate at temperatures from 0°C to 70°C.  Increased temperature often compromises performance and when combined with the higher voltages, current densities, and heat dissipations associated with power electronics can result in an increased susceptibility to oxide breakdown, electromigration, and other catastrophic on-chip failure mechanisms.  Furthermore, the large temperature swings of extreme environments and the rapid temperature cycles resulting from turning on and off large amounts of power can cause fatigue of the die, wires, die attach, and substrate in the package. The course sequence focuses on understanding the device technologies, and developing packaging and thermal management strategies that mitigate risks related to the operating temperatures and large temperature cycles common in extreme temperature and power electronics. 

      Included will be issues related to the effect of high and low operating temperatures on device and packaging reliability, power device (IGBT, MOSFET, BJT) and material (Si, SiC, GaN) selection, passive component and packaging materials selection, thermal management, and assembly of reliable high power and extreme temperature electronic systems. Finally, failure mechanism models for high temperature and power electronics will be presented together with a discussion of design options to mitigate failure. 

Topics covered : Reliable design and manufacture of power semiconductor components; Reliable design of power inverters and converters; Effects of temperature on device performance and reliability; Reliable packaging of power modules and assemblies.

     The development of robust and reliable power electronic systems for sustainable energy systems requires an understanding of the fundamental degradation processes that can cause failure at the device, interconnection, and packaging level in the environments encountered in a wide range of energy systems applications.  The course sequence will present the dominant failure mechanisms at each of these levels, along with selected models and reliability assessment methodologies.  Mechanisms to be covered include degradation in GaN and SiC devices; fatigue and fracture of wirebonds, die attach, and substrates in power electronic modules; corrosion and conductive filament formation in boards; and fatigue of solder joints.

    Wide bandgap semiconductors are extremely attractive for the gamut of power electronics applications. Of the various materials and device technologies, the AlGaN/GaN high-electron mobility transistor has been developed and has reached the market. While GaN device and circuit technology is poised to break out in the commercial arena, certain risks or barriers to entry in the market should not be overlooked. The relative technology immaturity of GaN with respect to Silicon and GaAs leave issues like long-term reliability unanswered. The courses also present the main degradation mechanisms of GaN-based HEMTs devices.