Thermal management solution for power stage comprising top-cooled power semiconductor switching devices
A power stage assembly for improved thermal dissipation and EMC for top-cooled semiconductor power switching devices, e.g. high voltage, high current lateral GaN power transistors in embedded die packages. The power switching devices are mounted on a PCB substrate, with electrical connections between a bottom side of each device package and the PCB. Each device package has a thermal pad on the top-side. A heat-spreader is secured in thermal contact with the thermal pads of each device, and a heatsink is in thermal contact with the heat-spreader. The heat-spreader is a multilayer structure comprising: a thermally conductive metal substrate layer in contact with the heatsink; a conductive layer providing an EMC layer which is connected to power ground; a conductive layer defining large area thermal pads in thermal contact with thermal pads of each die; and dielectric material electrically isolating conductive layers of the heat-spreader.
1. A power stage assembly for top-cooled semiconductor power switching devices comprising:
a PCB substrate
a plurality of embedded die packages, each die package comprising a semiconductor power switching device comprising at least one power transistor, having electrical contact areas on a front-side of the embedded die package and a thermal pad on the back side of the embedded die package;
the plurality of embedded die packages being mounted on the PCB substrate with electrical connections between conductive traces of the PCB and the electrical contact areas on the front-side of each die package;
a heat-spreader in thermal contact with the thermal pads on the back-side of each die package; the heat-spreader being secured to the PCB substrate; and a heatsink in thermal contact with the heat-spreader;
wherein the heat-spreader is a multilayer structure comprising:
a first layer comprising a thermally conductive metal substrate layer in contact with the heatsink;
a second layer comprising a thermally conductive dielectric layer;
a third layer comprising an electrically conductive and thermally conductive material defining an electromagnetic compatibility (EMC) shielding layer;
a fourth layer comprising a thermally conductive dielectric layer;
a fifth layer comprising an electrically conductive and thermally conductive material defining thermal pads in thermal contact with thermal pads of each die package;
the dielectric layers providing electrical isolation between said conductive layers; and the EMC shielding layer being interconnected to power ground; and the thermal pads of the fifth layer having an area larger than an area of the thermal pad of each embedded die package to provide lateral heat-spreading.
2. The power stage assembly of claim 1 , wherein said layers of the heat-spreader are provided by a multi-layer insulated metal substrate (IMS).
3. The power stage assembly of claim 1 , wherein the top-cooled power switching devices are GaN power switching devices.
4. The power stage assembly of claim 1 , configured for a half-bridge switch topology, a full-bridge switch topology, or other switch topology comprising a plurality of power switching devices.
5. The power stage assembly of claim 1 , wherein the thermal pads of the embedded die packages have an area A D and the thermal pads of the heat-spreader have an area A H , and wherein an area ratio of A H :A D is in a range of 3:1 to 10:1.
6. The power stage assembly of claim 1 , wherein the thermal pads of the embedded die packages have an area A D and the thermal pads of the heat-spreader have an area A H , and wherein an area ratio of A H :A D is greater than 5:1.
7. The power stage assembly of claim 1 , configured for a half-bridge switch topology, wherein:
the embedded die packages are arranged to provide a high-side switch comprising one power switching device or a plurality of power switching devices electrically connected in parallel and a low-side switch comprising one power switching device or a plurality of power switching devices electrically connected in parallel, and
said thermal pads of the fifth layer of the heat-spreader comprise a first thermal pad for the low-side switch and a second thermal pad for the high-side switch, and wherein the first thermal pad is interconnected through the fourth layer to the EMC shielding layer.
8. The power stage assembly of claim 1 , configured for a full-bridge switch topology, wherein:
the embedded die packages are arranged to provide a high-side switch comprising one power switching device or a plurality of power switching devices electrically connected in parallel and a low-side switch comprising one power switching device or a plurality of power switching devices electrically connected in parallel, and said thermal pads of the fifth layer of the heat-spreader comprise a first thermal pads for each for the low-side switch and second thermal pads for each of the high-side switch, and wherein the first thermal pads are interconnected through the fourth layer to the EMC shielding layer.
9. The power stage assembly of claim 1 , configured for a full-bridge switch topology, wherein:
the embedded die packages are arranged to provide a high-side switch comprising one power switching device or a plurality of power switching devices electrically connected in parallel and a low-side switch comprising one power switching device or a plurality of power switching devices electrically connected in parallel, and
said thermal pads of the fifth layer of the heat-spreader comprise a first thermal pad for the low-side switch and second thermal pad for the high-side switch.
10. A heat-spreader for a power stage assembly configured for a half-bridge switch module, wherein a plurality of embedded die packages are arranged to provide a high-side switch comprising one power switching device or a plurality of power switching devices electrically connected in parallel and a low-side switch comprising one power switching device or a plurality of power switching devices electrically connected in parallel,
the heat-spreader comprising a multilayer insulated metal substrate (IMS) structure comprising:
a first layer comprising a thermally conductive metal substrate layer;
a second layer comprising a thermally conductive dielectric layer;
a third layer comprising an electrically conductive and thermally conductive material defining an electromagnetic compatibility (EMC) shielding layer;
a fourth layer comprising a thermally conductive dielectric layer;
a fifth layer comprising an electrically conductive and thermally conductive material defining thermal pads in thermal contact with thermal pads of each die package;
the dielectric layers providing electrical isolation between said conductive layers; and the EMC shielding layer being interconnected to power ground;
the thermal pads of the fifth layer having an area larger than an area of the thermal pad of each embedded die package to provide lateral heat-spreading; said thermal pads of the fifth layer of the heat-spreader comprising a first thermal pad for the low-side switch and a second thermal pad for the high-side switch, and wherein the first thermal pad is interconnected through the fourth layer to the EMC shielding layer.
11. A power stage assembly for top-cooled semiconductor power switching devices comprising:
a PCB substrate
a plurality of embedded die packages, each embedded die package comprising a semiconductor power switching device comprising at least one power transistor, having electrical contact areas on a bottom-side of the die package and a thermal pad on a top-side of the die package;
the plurality of embedded die packages being mounted on the PCB substrate with electrical connections between conductive traces of the PCB substrate and the electrical contact areas on the back-side of each die package;
a heat-spreader in thermal contact with the thermal pads on the back-sides of each of each die package;
the heat-spreader being secured to the PCB substrate; and
a heatsink in thermal contact with the heat-spreader;
wherein the heat-spreader is a multilayer structure comprising:
a first layer comprising a thermally conductive metal substrate layer in contact with the heatsink;
a second layer comprising a thermally conductive dielectric layer;
a third layer comprising an electrically conductive and thermally conductive material defining thermal pads in contact with thermal pads of each die package;
the dielectric layer providing electrical isolation between the first and second layers of the heat-spreader;
the thermal pads of the third layer having an area larger than an area of the thermal pad of each embedded die package to provide lateral heat-spreading.
12. The power stage assembly of claim 11 , wherein said layers of the heat-spreader are provided by a multi-layer insulated metal substrate.
13. The power stage assembly of claim 11 , wherein the top-cooled power switching devices are GaN power switching devices.
14. The power stage assembly of claim 11 , configured for a half-bridge switch topology, a full-bridge switch topology, or other switch topology comprising a plurality of power switching devices.
15. The power stage assembly of claim 11 , wherein the thermal pads of the embedded die packages have an area A D and the thermal pads of the heat-spreader have an area A H , and wherein an area ratio of A H :A D is in a range of 3:1 to 10:1.
16. The power stage assembly of claim 11 , wherein the thermal pads of the embedded die packages have an area A D and the thermal pads of the heat-spreader have an area A H , and wherein an area ratio of A H :A D is greater than 5:1.
17. The power stage assembly of claim 11 , configured fora half-bridge switch topology, wherein:
the embedded die packages are arranged to provide a high-side switch comprising one power switching device or a plurality of power switching devices electrically connected in parallel and a low-side switch comprising one power switching device or a plurality of power switching devices electrically connected in parallel, and
said thermal pads of the fifth layer of the heat-spreader comprise a first thermal pad for the low-side switch and a second thermal pad for the high-side switch.