Patent Description:
In power applications, especially for the ones with wide band gap devices, reducing the parasitic elements caused by the packaging and assembling techniques is critical in order to reduce the switching losses due to fast switching, to reduce the electromagnetic emissions and to obtain better current distribution in case of parallel connection of power modules.

The patent application <CIT> discloses a power module comprising at least one power die that is embedded in a multilayer structure.

The patent application <CIT> discloses a multilayer structure that is an assembly of at least two sub-modules.

The patent application <CIT> discloses a printed circuit board.

The patent <CIT> discloses an air or liquid colled computer module cold plate.

The patent application <CIT> discloses a power module and a busbar for cooling.

To that end, the present invention concerns a power module as set out in the appended claims <NUM> and <NUM>.

Thus, the present invention increases the power density of power modules and reduces the parasitic components in order to reduce the power losses and electromagnetic emissions.

According to the invention, the power module further comprises an inductor embedded in the multilayer structure.

According to an optional feature, each sub-module in the power module further comprises a magnetic material that is embedded in the multilayer structure, disposed or moulded on a surface of the multilayer structure.

Thus, the power module is compact and has lower tolerences.

According to the invention, only a part of the multilayer structure comprising the at least one power die is cooled by a liquid cooled system.

According to the invention, the electric power supply provided to the at least one power die is provided by the liquid cooled busbar.

Thus, the size and cost of a power module can be reduced thanks to the multifunctional busbar.

The present invention concerns also a method for manufacturing a power module as set out in the appended claims <NUM>-<NUM>.

According to an optional feature, each sub-module is obtained by performing the successive steps of:.

Thus, the power dies connected within the module have low parasitic inductance due to packaging.

According to an optional feature, after the assembling of the sub-modules, the at least one capacitor is placed in a hole in the assembled sub-modules.

Thus, the capacitor is placed as close as possible to the switching power devices in order to reduce the switching loop, thus, the loop inductance.

According to an optional feature, the at least one capacitor is electrically connected after the assembling of the sub-modules between a top layer of a top sub-module and a bottom layer of a bottom sub-module.

Thus, the capacitor is used as bus capacitor of the switching power stage.

The characteristics of the invention will emerge more clearly from reading of the following description of the embodiment, the said description being produced with reference to the accompanying drawings, among which:.

<FIG> is a diagram representing an example of an electric circuit of a power module according to the present invention.

Each power module comprises a gate driver <NUM> that provides gate signals to the power dies D1 and D2.

The drain of the power die D1 is connected to the positive power supply DC+ provided, for example, by a liquid cooled busbar. The source of the power die D1 is connected to the drain of the power die D2 and to a first terminal of an inductor L1.

The source of the power die D2 is connected to the negative power supply DC-provided, for example, by the liquid cooled busbar.

The second terminal of the inductor L1 is the ouptut of the power module.

<FIG> is a diagram representing a power module according to the present invention that is cooled by a liquid cooled busbar.

The power module is an assembly of plural sub-modules, for example two sub-modules which have a multilayer structure like PCBs. Each sub-module has at least one embedded semiconductor power die such as SiC MOSFET, IGBT or other. The power module assembly will be disclosed in more details in reference to <FIG> and <FIG>.

Very close to the power dies which form the power stage of the power module, capacitors are embedded within the multilayer structure composed of the sub-modules of the power module as bus capacitors in order to smooth the bus voltage.

Each capacitor is connected between the top layer of the top sub-module and the bottom layer of the bottom sub-module. Each capacitor is electrically connected after the assembling of the sub-modules. Each capacitor is placed in a verticle hole formed by drill and is connected by soldering.

The part comprising the power dies is cooled by a liquid cooled busbar composed of two bars 20a and 20b. The bar 20a is used to convey a negative DC power to the dies of the power module and the bar 20b is used to convey a positive DC power to the dies of the power module.

In the example of <FIG>, each bar 20a and 20b comprises one channel that is splited to <NUM> sub-channels in order to increase the thermal exchange.

The channel noted 23a of the bar 20a is connected to the channel 23b of the bar 20b as other channels shown in <FIG>.

In the multilayer structure, additional components can also be embedded like control integrated circuits noted <NUM>, inductors, transformers, sensors, additional capacitors or resistors noted <NUM>.

Also, embedded into the multilayer structure or mounted on the outer surface of the multilayer structure, additional components can be attached by soldering or other to include additional or complementary functionalities to the power module. The surfaces of the multilayer structure above and under the power dies are made of copper with or without finishing in order to enable the bus connections of the power modules.

<FIG> is a method for manufacturing a power module according to the present invention.

The power module is composed of two sub-modules which have a multilayer structure like PCBs, the differents steps of <FIG> represent different stages of the manufacturing of one of the sub-modules.

At step S30, a base layer is cut, for example by laser cut in order to form a cavity of the size of a power die. The power die is then placed in the cavity. An example of the formed base layer is given in <FIG>.

<FIG> represents different stages of the manufacturing of a power module according to the present invention.

The <FIG> represents a base layer <NUM> that is an electrically non-conductive and thermally conductive material. For example the base layer <NUM> is made of FR4. The base layer <NUM> is cut, for example by laser cut in order to form a cavity of the size of a power die <NUM>. The power die <NUM> is then placed in the cavity. The base layer may be divided intwo or several layers separated by at least one higher thermally conductive layer <NUM> such as metal, like copper in order to increase heat spreading.

At step S31, isolation and conducting layers are laminated on the base layer formed at step S30. An example is given in <FIG>.

The <FIG> represents the base layer <NUM> and the power die <NUM> on which a thin isolation layer <NUM> is laminated on the top of the base layer <NUM> and a thin isolation layer <NUM> is laminated on the bottom of the base layer <NUM>. Electrically conducting layers <NUM> and <NUM>, for example made of copper, are laminated also on the thin isolation layers <NUM> and <NUM>. Insulation and conducting layers are laminated together in a single step.

It has to be noted here that the same operation is performed of the other sub-module.

At step S32, laser drilling and metallization are then made in order to connect the power die <NUM> to the conductor layer. An example is given in <FIG>.

Laser drilling and metallization <NUM>, <NUM> and <NUM> are then made in order to connect the power die <NUM> to the conductor layer. The power die contact to the conductor layers can cover completely the power die top and bottom surface, or partially, by using multiple via connections or other shapes.

At step S33, through hole vias are mechanically drilled and a further metallization is performed in order to connect the different conductor layers at different spots according to a layout.

At step S34, the conductor layers are etched, for example by a chemical or a mechanical process in order to obtain the desired layout like for example the one noted <NUM> on the thin conductor layer.

At step S35, if the number of conductor layers is not reached, the process returns to step S31. Otherwise, the process moves to step S36.

<FIG> is an example wherein only two conductor layers are needed. According to this example, the process moves to step S31 and executes again the steps S31 to S34 one time.

Additional thin isolation layers and a thick conductor layers are laminated on both sides. An example is given in <FIG>.

Additional thin isolation layers <NUM> and <NUM> and thick conductor layers <NUM>, <NUM> are laminated on both sides of the sub-module as obtained at step S34.

Laser drilling and metallization are then made in order to connect the thin conductors layers and the thick conductor layers. An example is given in <FIG>.

Laser drilling and metallization <NUM> and <NUM> are then made in order to connect the thin conductors layers <NUM> and <NUM> and the thick conductor layers <NUM> and <NUM>. The connection can be made through multiple via connections or through other shapes like mettalized copper squares. The conductor layers are etched in order to obtain the desired layout on layers <NUM> and <NUM> and vias are formed. An example is given in <FIG>.

Through hole vias <NUM> are made by drilling then metallizing. Also, board machining or drilling is performed in order to place capacitors <NUM> and magnetic materials.

Note that in some particular cases where the conductor layers <NUM> and <NUM> are very thick, they can be pre-etched before lamination.

At step S36, machining and drilling are performed in order to obtain any desired module shape or drills on the module for any mechanical features sweeted to the final application. Machining and drilling can also be made in order to assemble later on additional components such as capacitors, magnetic materials for inductors or other.

At step S37, the two sub-modules are then assembled with thermally and electrically conductive materials in order to form the multilayer structure.

At step S38, external component soldering, attachment and magnetic material moulding is performed.

Very close to the power dies which form the power stage of the power module, capacitors are embedded within the two sub-modules of the power module as bus capacitors in order to smooth the bus voltage.

Each capacitor is connected between the top layer of the top sub-module and the bottom layer of the bottom sub-module. Each capacitor is electrically connected after the assembling of the sub-modules. Each capacitor is placed in a verticle drill and is connected by soldering.

Also, embedded into the assembled sub-modules or mounted on the outer surface of the assembled sub-modules, additional components like control integrated circuits inductors, transformers, sensors, magnetic material, additional capacitors or resistors can be attached by soldering or other on a surface of the multilayer structure to include additional or complementary functionalities to the power modules. <FIG> represents the different areas of a power module according to the present invention.

The power module according to the present invention is decomposed into plural areas.

In the area noted <NUM>, gate drivers of the power dies are located.

In the area noted <NUM>, the decoupling or bus capacitors and power dies are located and in the area noted <NUM>, an external inductor is located.

Claim 1:
A power module decomposed into plural areas, comprising at least two semiconductor power dies (<NUM>), wherein the power module is composed of two sub-modules assembled with thermally and electrically conductive materials, each sub-module having a multilayer structure, each sub-module having at least one semiconductor power die (<NUM>), each sub-module having at least one cavity where one semiconductor power die (<NUM>) is placed, each sub-module being formed of isolation and conductor layers and each sub-module further comprises at least one capacitor (<NUM>) embedded the multilayer structure of a sub-module for decoupling an electric power supply to the at least one semiconductor power die (<NUM>) embedded in the multilayer structure and at least one driving circuit of the at least one semiconductor power die (<NUM>) that is disposed on a surface of the multilayer structure or embedded completly or partially in the multilayer structure, the at least one driving circuit is located in a first area (<NUM>), the at least one capacitor (<NUM>) is located in a second area (<NUM>) and an external inductor is located in a third area (<NUM>), only a part of the multilayer structure comprising the at least one semiconductor power die (<NUM>) is cooled by a liquid cooled busbar (20a, 20b) and the electric power supply provided to the at least one semiconductor power die (<NUM>) is provided by the liquid cooled busbar (20a, 20b).