Power Cycling Method for Power Modules With Low Thermal Resistance

Abstract

In this article, an advanced power cycling method for power modules with low thermal resistance is proposed. Thermal resistance of power module is getting smaller and smaller, and for power cycling test (PCT), it is more and more difficult to obtain the desired maximum junction temperature <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{\mathrm {vjmax}}$ </tex-math></inline-formula> and junction temperature swing <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta T_{\mathrm {vj}}$ </tex-math></inline-formula> under rated current. By analyzing the influencing factors of parameters in the PCT, this article proposes a new method to affect the parameters of the power cycle by changing the external thermal resistance so that the low thermal resistance module can perform the PCT at the rated current. Then, FZ750R65KE3 modules are selected to analyze the influence of different external thermal resistances on PCT parameters. Finally, PCTs are carried out using discrete devices and power modules to analyze the influence of changing the external thermal resistance on the typical failure modes bond wire liftoff and solder layer degradation. The new method enables power modules with low thermal resistance to perform PCT at rated current without changing lifetime and failure modes.