Power density improvement in power conversion modules is essential for development of highly integrated drivetrain in an automotive application. Wide-bandgap semiconductor devices are efficient in power conversion, however, still generate power losses and heat in small volume in comparison to Silicon counterparts. In automotive systems, the thermal management of the module is provided by liquid-cooled heat sinks to ensure the desired operation of the devices for the considered high-power density applications.

The power semiconductor die layout in power module substrates is generally optimized for minimum electrical parasitic (e.g. stray inductance) considering minimum spacing between dies for thermal decoupling. The layout assumes a thick base plate which provides enhanced heat spreading and transfer from dies to the cooling structure. For module designs utilizing direct substrate cooling method, the base plate is removed, leading to a steady-state thermal asymmetry in the power module due to insufficient heat spreading/transfer causing significant temperature differences among the devices. The semiconductor device characteristics vary with their temperature, and hence the steady state temperature difference leads to asymmetry in power conversion among devices, that is, a few devices taking higher share of power conversion than others. This power conversion asymmetry may lead to reliability and package failure issues in long operational time frame.

This paper proposes a thermal imbalance mitigation method which utilizes evolutionary optimized liquid-cooled heat sinks. The heat sink structure is optimized for the targeted power module such that the steady-state temperature imbalance among devices is minimum while minimizing the overall max. junction temperature and the pressure drop across the heat sink. The optimization procedure utilizes population-based evolutionary algorithms to optimize the geometry for specified objectives.

In the full paper, the authors will present the problem formulation, an optimization scheme for the considered problem using evolutionary algorithm, consider a case-study and present the heat sink optimization, and finally compare the thermal performance of the heat sink with existing literature.

Power density improvement in power conversion modules is essential for development of highly integrated drivetrain in an automotive application. Wide-bandgap semiconductor devices are efficient in power conversion, however, still generate power losses and heat in small volume in comparison to Silicon counterparts. In automotive systems, the thermal management of the module is provided by liquid-cooled heat sinks to ensure the desired operation of the devices for the considered high-power density applications.

The power semiconductor die layout in power module substrates is generally optimized for minimum electrical parasitic (e.g. stray inductance) considering minimum spacing between dies for thermal decoupling. The layout assumes a thick base plate which provides enhanced heat spreading and transfer from dies to the cooling structure. For module designs utilizing direct substrate cooling method, the base plate is removed, leading to a steady-state thermal asymmetry in the power module due to insufficient heat spreading/transfer causing significant temperature differences among the devices. The semiconductor device characteristics vary with their temperature, and hence the steady state temperature difference leads to asymmetry in power conversion among devices, that is, a few devices taking higher share of power conversion than others. This power conversion asymmetry may lead to reliability and package failure issues in long operational time frame.

This paper proposes a thermal imbalance mitigation method which utilizes evolutionary optimized liquid-cooled heat sinks. The heat sink structure is optimized for the targeted power module such that the steady-state temperature imbalance among devices is minimum while minimizing the overall max. junction temperature and the pressure drop across the heat sink. The optimization procedure utilizes population-based evolutionary algorithms to optimize the geometry for specified objectives.

In the full paper, the authors will present the problem formulation, an optimization scheme for the considered problem using evolutionary algorithm, consider a case-study and present the heat sink optimization, and finally compare the thermal performance of the heat sink with existing literature.


Liquid-Cooled Heat Sink Optimization for Thermal Imbalance Mitigation in Wide-Bandgap Power Modules

Division / Sponsors: 
Electronic & Photonic Packaging Division (EPPD)

Paper Proceedings: https://asmedigitalcollection.asme.org/InterPACK/InterPACK2020/volume/84041

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