Abstract Preview

Here is the abstract you requested from the IMAPS_2016 technical program page. This is the original abstract submitted by the author. Any changes to the technical content of the final manuscript published by IMAPS or the presentation that is given during the event is done by the author, not IMAPS.

Spurious Turn-On inside a Power Module of Paralleled SiC MOSFETs
Keywords: Paralleled SiC module, crosstalk and spurious turn-on, layout symmetry and parasitics
Silicon carbide (SiC) dice are often paralleled to realize power modules with high-current rating. Package parasitics significantly impact the switching performance of SiC module [Chen][Kim][Li] [Liang][Mantooth][Peftitsis]. Owing to the large network of interconnect (parasitic) impedances, terminal waveforms could appear benign while the dice experience detrimental fault currents generated by spurious cross-turn-on [Heer][Xu][Zhang]. This paper will quantify the nonuniform distribution of current stress and switching energy among the dice, as well as the penalty caused by cross-turn-on, versus layout symmetry, number of dice, gate resistance, input voltage, load current, and free-wheeling diode. A reliable model for the package is essential. This is demonstrated for a commercial power module with 16 dice, 124 layout inductances, and the companion parallel resistances extracted from finite-element simulation. For a module tested at 800 V / 300 A and carrying six paralleled dice per switch, the cross-turn-on induced current spikes simulated without and with package model differ by as much as 11.75 times. Factors that lead to the increased cross-turn-on current will be identified. Asymmetrical and symmetrical modules following commercial layouts are tested by a double pulse tester that switches the low side on and off while maintaining the high side off. Cross-turn-on currents inside a module increase the high-side switching energy and total switching energy by 44% and 20%, respectively, under nominal condition (800 V / 300 A and 2.5 Ω gate resistance). Terminal currents, peak cross-turn-on currents, low-side, high-side, and total switching energies of the asymmetrical module and symmetrical module corresponding to various input voltages (200 V to 800 V), low-side gate resistances (2.5 Ω to 25 Ω), and load currents (60 A to 360 A) are normalized for comparison. Peak cross-turn-on current of symmetrical module is always lower and only 16% of that of asymmetrical module under nominal condition. Symmetrical layout greatly decreases the cross-turn-on currents without increasing the total switching energy. One-Die, two-die, four-die, and six-die modules are modeled on the asymmetrical layout to explore how number of dice influences cross-turn-on and switching energy. Gate resistance and load current of each die of the modules are kept the same. Peak cross-turn-on current and total switching energy which are divided by the number of dice for fair comparison increase with the number of dice. The peak cross-turn-on current and switching energy of the six-die module are 134% and 36% higher than those of the one-die module, respectively. Severity of cross-turn-on soars as number of dice increases. Besides symmetrical layout, paralleling SiC Schottky diode is effective to reduce cross-turn-on current to 48% and total switching energy to 65% of the original values. Decreasing the gate-loop inductance to half, which is difficult in reality due to areas occupied by the dice for bond-wire structure, has little influence on the problem and increasing external gate resistance suppresses cross-turn-on at the expense of higher switching energy.
Zichen Miao, Graduate research assistant
Virginia Tech
Blacksburg, Virginia

  • Amkor
  • ASE
  • Canon
  • EMD Performance Materials
  • Honeywell
  • Indium
  • Kester
  • Kyocera America
  • Master Bond
  • Micro Systems Technologies
  • MRSI
  • Palomar
  • Plexus
  • Promex
  • Qualcomm
  • Quik-Pak
  • Raytheon
  • Specialty Coating Systems