Thermal Conductivity of Power Semiconductors—When Does It Matter?

Abstract

A study comparing the interaction between wide bandgap (WBG) materials, chip thickness, and heat sink selection on the total temperature rise in a standard power electronics package was performed. The thermal calculations, using the ARL ParaPower tool, showed that chips with thermal conductivities of less than 150 W/mK (including β-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) had a dominant effect on total temperature rise, whereas thermal conductivities greater than 400 W/mK (including SiC and diamond) had little impact. In designs with devices having thermal conductivities between 150 and 400 W/mK (including GaN) the temperature rise resulting from the chip is a significant fraction of the total rise for heatsinks with heat transfer coefficients of 50,000 W/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> K or higher. For chips with thermal conductivities less than Si, the thickness of the chip can be a significant factor affecting the overall temperature rise.