Patent Description:
Power converters for example for oil and gas applications, traction drives and high-power conversion equipment, for example rectifiers and inverters, typically include press-pack power devices.

A press-pack power device includes for example insulated gate bipolar transistors IGBTs.

Such a power converter further comprises heatsinks to dissipate the heat generated by the press-pack power devices. For example, <CIT>, <CIT> disclose heatsinks with two plates on both sides of a semiconductor plate. <CIT> discloses a presspack device with a cooling piece inside.

The press pack devices and the heatsinks are typically sandwiched to form a stack, the stack being compacted between two compaction plates to apply an homogeneous compaction pressure on the press-pack power devices.

Moreover, power signals delivered by the power converter flow through the press pack devices and the heatsinks generally made of an aluminium alloy.

A liquid cooled heatsink is generally made of one piece comprising a massive part sandwiched between two cooling parts comprising cooling channels.

Such a liquid cooled heatsink is disposed at each end of the stack so that a first surface of a cooling part is in contact with a press pack device and the second surface of the cooling part opposite to the first surface is in contact with a compaction plate.

As the temperature of the first and second surfaces are different, a temperature gradient is generated for the heatsinks at the ends of the stack.

These heatsinks are subjected to thermal expansion so that the heatsinks at the ends of the stack are deformed according to a "banana shape".

The deformation of the heatsinks generate excessive inhomogeneous stresses on the IGBTs in the center of press pack devices in the contact with the said heatsinks and causes a lack of pressure between the said heatsinks and the IGBTs at the edge of the press pack devices preventing an electrical contact between the said heatsinks and the IGBTs at the edge of the press pack devices.

Inhomogeneous stresses deteriorate some of the IGBTs and deteriorate the quality of the power supplied by the power converter and lead to failures of the power converter.

It is therefore proposed to remedy some of the disadvantage related to heatsinks according to the prior art.

In view of the foregoing the invention proposes a heatsink for cooling at least one electronic device package having an upper contact surface and a lower contact surface, the heat sink comprising a first cooling piece and a support piece comprising a first surface and a second surface opposite to the first surface, the first cooling piece comprising an inlet configured to receive a coolant and an outlet configured to exhaust the coolant, a first surface of the first cooling piece being configured to be in direct contact with one of the upper and lower contact surfaces, the first surface of the support piece being in direct contact with a second surface of the cooling piece.

The support piece and the first cooling piece are two independent pieces so that the interface between the first surface of the support piece and the second surface of the first cooling piece allows a relative movement between the support piece and the first cooling piece along a direction parallel to the interface between the first cooling piece and the support piece.

Advantageously, the heatsink further comprises a wedge having the same dimensions as the first cooling piece, the wedge being in direct contact with the second surface of the support piece.

Preferably, the wedge and the support piece are made in a single piece.

Preferably, the heatsink further comprises a second cooling piece comprising an inlet configured to receive the coolant and an outlet configured to exhaust the coolant, a first surface of the second cooling piece being configured to be in direct contact with one of the upper and lower contact surfaces of another second electronic device package, the second surface of the support piece being in direct contact with a second surface of the second cooling piece, the support piece and the second cooling piece are two independent pieces so that the interface between the second surface of the support piece and the second surface of the second cooling piece allows a relative movement between the support piece and the second cooling piece along a direction parallel to the interface between the second cooling piece and the support piece.

Advantageously, each cooling piece comprises a first side surface and a second side surface opposite to the first side surface, the first and second side surfaces extending between the first and the second surfaces of the said cooling piece, the inlet and the outlet of each cooling piece being disposed on a same side surface of the said cooling piece.

Preferably, the inlet and the outlet of the first and second cooling pieces are disposed on the same side surface of the heatsink comprising one of the first and second side surfaces of the first and second pieces, the side surface of the heatsink extending between the first surfaces of the first and second cooling pieces.

Advantageously, the inlet of each cooling piece comprising an inlet connecting part and the outlet of each cooling piece comprising an outlet connecting part, the support piece comprises two recesses on the surface in direct contact with the second surface of the said cooling piece, a first recess lodging with a clearance the inlet connecting part or the outlet connecting part and the second recess lodging with a clearance the outlet connecting part or the inlet connecting part.

Preferably, the inlet and the outlet of the first cooling piece are disposed on the second surface of the first cooling piece, the support piece comprising an inlet and an outlet disposed on a side face of the support piece extending between the first and second surfaces of the support, a first and a second apertures, and a first and a second channels, the first channel fluidly connecting the first aperture to the inlet of the support piece and the second channel fluidly connecting the second aperture to the outlet of the support piece, the first and second apertures being disposed on the first surface of the support piece so that the fluid flows from the inlet of the support piece to the inlet of the first cooling piece and flows from the outlet of the first cooling piece to the outlet of the support piece.

Advantageously, the inlet and the outlet of the second cooling piece are disposed on the second surface of the second cooling piece, the support piece further comprises a third and a fourth apertures, and a third and a fourth channels, the third channel fluidly connecting the third aperture to the inlet of the support piece and the fourth channel fluidly connecting the fourth aperture to the outlet of the support piece, the third and fourth apertures being disposed on the second surface of the support piece so that the fluid flows from the inlet of the support piece to the inlet of the second cooling piece and flows from the outlet of the second cooling piece to the outlet of the support piece.

Preferably, each aperture is surrounded by a groove, a gasket being inserted in the groove.

Advantageously, the heatsink further comprises centring means configured to assemble each cooling part on the support part.

Preferably, the centring means comprise a plurality of pins or holes disposed on the second surface of each cooling part and a plurality of holes or pins disposed on the surface of the support part in direct contact with the second surface of the said cooling part, each pin been inserted in a different hole with a clearance.

Another object of the invention relates to a packaging stack comprising at least two electronic device packages, each electronic device package comprising an upper and a lower contact surfaces, each upper surface and each lower surface of the electronic device packages being associated to one heatsink as defined above.

Advantageously, the electronic device packages and the heatsinks are compacted between two compaction plates.

Preferably, the packaging stack further comprises an inlet manifold and an outlet manifold, the inlet manifold being configured to supply the inlet of each cooling piece with coolant and the outlet manifold being configured to receive the cooling from the outlet of each cooling piece.

Advantageously, the inlet of a first or second cooling piece is connected to the inlet manifold, the outlet of the said first or second cooling piece is connected to the inlet of an adjacent first or second cooling piece to the said first or second cooling piece, the outlet of the adjacent first or second cooling piece is connected to the outlet manifold.

Other characteristics and advantages of the invention will emerge on reading the following description of embodiments of the invention, provided solely by way of non-limiting examples and with reference to the drawings in which:.

The power converter comprises a packaging stack <NUM> compacted between two compacting devices <NUM>, <NUM>.

Each compacting device <NUM>, <NUM> comprises a compaction plate <NUM>, <NUM>, a pressure cone <NUM>, <NUM>, and a clamping plate <NUM>, <NUM>.

The pressure cone <NUM>, <NUM> is sandwiched between the compaction plate <NUM>, <NUM> and the clamping plate <NUM>, <NUM>.

A plurality of tie rods <NUM> connect the two clamping plates <NUM>, <NUM> to maintain the packaging stack <NUM> compacted between the two compaction plates <NUM>, <NUM>.

The compacting devices <NUM>, <NUM> may be done differently, for example the compacting devices <NUM>, <NUM> may comprise the compaction plates <NUM>, <NUM> and the pressure cones <NUM>, <NUM>, the pressure cones <NUM>, <NUM> being connected by a clamping bar to maintain compacted the packaging stack <NUM> compacted between the two compaction plates <NUM>, <NUM>.

The packaging stack <NUM> comprises a plurality of electronic device packages <NUM>, <NUM>, <NUM>, <NUM>, a plurality of heatsinks <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, an inlet manifold <NUM>, and an outlet manifold <NUM>.

Each electronic device package <NUM>, <NUM>, <NUM>, <NUM> may be cylindrical and comprises an upper contact surface 12a, 13a, 14a, 15a and a lower contact surface 12b, 13b, 14b, 15b.

Each electronic device packages <NUM>, <NUM>, <NUM>, <NUM> may comprise a field effect transistor, for example an insulated gate bipolar transistor IGBT, integrated gate commutated thyristors IGCT or thyristors and gate turn-off thyristor GTO.

The packaging stack <NUM> further comprises cables (not represented) to connect the electronic device packages <NUM>, <NUM>, <NUM>, <NUM> and control circuits (not represented) to control the electronic device packages <NUM>, <NUM>, <NUM>, <NUM>.

Each end of the packaging stack <NUM> is connected to a supply device (not represented), for example a grid, to supply the converter with a voltage, the voltage flowing through the electronic device packages <NUM>, <NUM>, <NUM>, <NUM> and the heatsinks <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

A first heatsink <NUM> is disposed between a first compaction plate <NUM> and a first electronic device packages <NUM>, a second heatsink <NUM> is disposed between the first electronic device packages <NUM> and a second electronic device packages <NUM>, a third heatsink <NUM> is disposed between the second electronic device packages <NUM> and a third electronic device packages <NUM>, a fourth heatsink <NUM> is disposed between the third electronic device packages <NUM> and the fourth electronic device packages <NUM>, and the fifth heatsink <NUM> is disposed between the fourth electronic device packages <NUM> and the second compaction plate <NUM>.

An electrical insulating (not represented) is inserted between the first compaction plate <NUM> and the first heatsink <NUM>, and the second compaction plate <NUM> and the fifth heatsink <NUM>.

The first and fifth heatsinks <NUM>, <NUM> have a same architecture, and the second, third and fourth heatsinks <NUM>, <NUM>, <NUM> are identical.

The packaging stack <NUM> may comprise more than four device packages and five heatsinks as represented, the heatsinks and the electronic device packages being alternately arranged, and the device packages at the end of the packaging stack <NUM> being separated from the compaction plates by a heatsink having the same architecture as the first and fifth heatsinks <NUM>, <NUM>.

Each heatsink <NUM>, <NUM>, <NUM>, <NUM>, <NUM> comprises a support piece <NUM> comprising a first surface 23a and a second surface 23b opposite to the first surface 23a, and a first cooling piece <NUM> comprising a first surface 24a and a second surface 24b opposite to the first surface 24a.

The first surface 24a of the first cooling piece <NUM> is in direct contact with one of the upper and lower contact surfaces 12a, 13a, 14a, 15a, 12b, 13b, 14b, 15b so that any element such as thermal grease is inserted between the first surface 24a and the upper contact surface or the lower contact surface.

The first surface 23a of each support piece <NUM> is in direct contact with the second surface 24b of the associated cooling piece <NUM> so that that any element such as thermal grease is inserted between the first surface 23a of each support piece <NUM> and the second surface 24b of the associated cooling piece <NUM>.

The support piece <NUM> and the first cooling piece <NUM> are two independent pieces.

The support piece <NUM> and the first cooling piece <NUM> are stacked one on the other.

The interface between the first surface 23a of the support piece <NUM> and the second surface 24b of the first cooling piece <NUM> allows a relative movement between the support piece <NUM> and the first cooling piece <NUM> along a direction parallel to the interface between the first cooling piece <NUM> and the support piece <NUM>.

As the support piece <NUM> can have a relative movement compared to the first cooling piece <NUM>, under the thermal expansion of the support piece <NUM> resulting from a gradient temperature between the first and second surfaces of the support piece <NUM>, the support piece <NUM> can move freely in the direction parallel to the interface without generating constraints on the electronic device package <NUM>, <NUM>, <NUM>, <NUM>.

As no constraints are generated by thermal expansion, the duration of the electronic device packages <NUM>, <NUM>, <NUM>, <NUM> is extended and the electrical contact between the electronic device packages <NUM>, <NUM>, <NUM>, <NUM> and the heatsinks <NUM> is enhanced.

The heatsinks may have a rectangular section or may have another shape, and are designed to cover at least the upper contact surface and the lower contact surface of the electronic device packages <NUM>, <NUM>, <NUM>, <NUM>.

It is assumed that the heatsinks have a rectangular section.

Each first cooling piece <NUM> comprises an inlet 24c receiving a coolant and an outlet 24d exhausting the coolant.

The inlet 24c is intended to be connected to the inlet manifold and the outlet 24d is intended to be connected to the outlet manifold.

The first cooling piece <NUM> comprises a cooling circuit connected to the inlet 24c and the outlet 24d.

The cooling circuit evacuates the thermal losses generated by the electronic device package <NUM>, <NUM>, <NUM>, <NUM> in the coolant.

Each second, third and fourth heatsinks <NUM>, <NUM>, <NUM> further comprises a second cooling piece <NUM> having the same architecture and the same dimensions as the first cooling piece <NUM>.

The second cooling piece <NUM> comprises a first surface 25a, a second surface 25b, an inlet 25c receiving the coolant, and an outlet 25d exhausting the coolant.

The second cooling piece <NUM> further comprises the cooling circuit connected to the inlet 25c and outlet 25d.

The first surface 25a of the second cooling piece <NUM> is in direct contact with the lower surface 12b, 13b, 14b, 15b of the electronic device package <NUM>, <NUM>, <NUM>, <NUM>.

In variant, the first surface 25a of the second cooling piece <NUM> may be in direct contact with the upper surface 12a, 13a, 14a, 15a.

The second surface 23b of the support piece <NUM> is in direct contact with the second surface 25b of the second cooling piece <NUM>.

The support piece <NUM> and the second cooling piece <NUM> are two independent pieces so that the interface between the second surface 23b of the support piece <NUM> and the second surface 25b of the second cooling piece <NUM> allows a relative movement between the support piece <NUM> and the second cooling piece <NUM> along a direction parallel to the interface between the second cooling piece <NUM> and the support piece <NUM>.

Each of the first and fifth heatsinks <NUM>, <NUM> further comprises a wedge <NUM> having the same dimensions as the first cooling piece <NUM>.

The wedge <NUM> is sandwiched between the electrical insulating and the support piece <NUM> of the first and fifth heatsinks <NUM>, <NUM>, the wedge <NUM> being in direct contact with the second surface 23b of the support piece <NUM>.

The first and fifth heatsinks <NUM>, <NUM> comprising the wedges <NUM> have the same thickness as the second, third and fourth heatsinks <NUM>, <NUM>, <NUM>.

The support pieces <NUM>, the first cooling pieces <NUM>, the second cooling pieces <NUM>, and the wedges <NUM> are made of an electrically conductive material, for example an aluminium alloy.

In variant, the wedge <NUM> and the support piece <NUM> are made in a single piece permitting to ease the manufacturing of the packaging stack <NUM>.

The thickness of the first and second cooling parts may be equal and may be one third of the thickness of the support part <NUM>.

Each of the first and second rectangular cooling pieces <NUM>, <NUM> comprises a first side surface and a second side surface opposite to the first side surface.

The first and second side surfaces of the first cooling piece <NUM> extend between the first and the second surfaces 24a, 24b.

The first and second side surfaces of the second cooling piece <NUM> extend between the first and the second surfaces 25a, 25b.

As represented, the inlet 24c and the outlet 24d of the first cooling pieces <NUM> are disposed on the same side surface of the first cooling pieces <NUM>, and the inlet 25c and the outlet 25d of the second cooling pieces <NUM> are disposed on the same side surface of the second cooling pieces <NUM>.

The localisation of the inlet and the outlet on the same side surface of a cooling piece simplify the connection of the inlet and the outlet to the inlet and outlet manifolds <NUM>, <NUM>.

In variant, the inlet 24c, 25c and the outlet 24d, 25d of the first and second cooling pieces <NUM>, <NUM> may be disposed on different side surfaces.

Each heatsink <NUM>, <NUM>, <NUM>, <NUM>, <NUM> further comprises a first side surface and a second side surface extending between the first surfaces 24a, 25a of the first and second cooling pieces <NUM>, <NUM>.

Further, as represented, the inlet 24c, 25c and the outlet 24d, 25d of the first and second cooling pieces <NUM>, <NUM> are disposed on the same side surface of the heatsinks <NUM>, <NUM>, <NUM>, <NUM>, <NUM> to simplify even more the connection of the inlet and the outlet to the inlet and outlet manifolds <NUM>, <NUM>.

In variant, the inlet 24c, 25c and outlet 24d, 25d of the first and second cooling pieces <NUM>, <NUM> are disposed on different side surfaces of the heatsinks <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

An inlet 24c, 25c of a first or second cooling piece <NUM>, <NUM> is connected to the inlet manifold for example through an input duct 21a, 21b, 21c, 21d.

The outlet 24d, 25d of the said first or second cooling piece <NUM>, <NUM> is connected to the inlet 24c, 25c of an adjacent first or second cooling piece <NUM>, <NUM> for example through an intermediary duct <NUM>.

The outlet 24d, 25d of the adjacent first or second cooling piece <NUM>, <NUM> is connected to the outlet manifold <NUM> for example through an output duct 22a, 22b, 22c, 22d.

Two adjacent cooling pieces are fluidly connected together in series reducing the number of input and output ducts to simplify even more the connection of the inlet 24c, 25c and the outlet 24d, 25d to the inlet and outlet manifolds <NUM>, <NUM>.

Two adjacent cooling pieces may be fluidly connected together in series even if the inlets and the outlets of the first and second cooling pieces <NUM>, <NUM> are not disposed on the same side surface of the heatsinks <NUM>, <NUM>, <NUM>, <NUM> and even if the inlet and outlet of each first and second cooling pieces <NUM>, <NUM> are not disposed on the same side surface of the said cooling piece.

<FIG> illustrates schematically a second example of the first and fifth heatsinks <NUM>, <NUM> at the ends of the packaging stack <NUM> and <FIG> illustrates a second example of the second, third and fourth heatsinks <NUM>, <NUM>, <NUM> sandwiched between two electronic device packages <NUM>, <NUM>, <NUM>, <NUM>.

The second examples, the inlet 24c of the first cooling piece <NUM> comprises an inlet connecting part <NUM> and the outlet 24d of the first cooling piece <NUM> comprises an outlet connecting part <NUM>.

The inlet connecting part <NUM> and the outlet connecting part <NUM> protrude from the first cooling piece <NUM>.

In order to have a constant thickness of the heatsink, the support piece <NUM> comprises two recesses <NUM>, <NUM> on the first surface 23a.

A first recess <NUM> lodges the inlet connecting part <NUM> with a clearance and the second recess <NUM> lodges the outlet connecting part <NUM> with clearance.

Equivalently, as illustrated on <FIG>, the inlet 25c of the second cooling piece <NUM> comprises an inlet connecting part <NUM> and the outlet 25d of the second cooling piece <NUM> comprises an outlet connecting part <NUM>, the inlet connecting part <NUM> and the outlet connecting part <NUM> protruding from the second cooling piece <NUM>.

The support piece <NUM> comprises two recesses <NUM>, <NUM> on the second surface 23b.

A first recess <NUM> lodges the inlet connecting part <NUM> with a clearance and the second recess <NUM> lodges the outlet connecting part <NUM> with a clearance.

The values of the clearances are determined so that a relative displacement between each cooling piece <NUM>, <NUM> and the support piece <NUM> does not create an interference between the inlet and outlet connecting parts and the support piece to avoid constraints in the support part <NUM>.

<FIG> illustrates schematically a partial longitudinal section of a third example of the heatsinks <NUM>, <NUM>, <NUM> sandwiched between two electronic device packages <NUM>, <NUM>, <NUM>, <NUM>.

In this example, the inlet and outlet 24c, 24d of the first cooling piece <NUM> are disposed on the second surface 24b of the first cooling piece <NUM>, and the inlet and outlet 25c, 25d of the second cooling piece <NUM> are disposed on the second surface 25b of the second cooling piece <NUM>.

The inlet and outlet 25c, 25d of the second cooling part <NUM> are connected to the cooling circuit <NUM> having for example a spiral shape.

The support piece <NUM> comprises an inlet <NUM> connected to the input duct 21a, 21b, 21c, 21d and an outlet <NUM> connected to the output duct 22a, 22b, 22c, 22d, the inlet <NUM> and outlet <NUM> been disposed on a side surface of the support part <NUM>.

The support piece <NUM> further comprises a first aperture <NUM> and a second aperture <NUM> disposed on the first surface 23a, and a third aperture <NUM> and a fourth aperture <NUM> disposed on the second surface 23b.

The support piece <NUM> comprises a first aperture <NUM> and a second aperture <NUM> disposed on the first surface 23a, and a third aperture <NUM> and a fourth aperture <NUM> disposed on the second surface 23b.

The support piece <NUM> further comprises a first channel <NUM>, a second channel <NUM>, a third channel <NUM> and a fourth channel <NUM>.

The first channel <NUM> fluidly connects the inlet <NUM> to the first aperture <NUM>, the second channel <NUM> fluidly connects the outlet <NUM> to the second aperture <NUM>, the third channel <NUM> fluidly connects the inlet <NUM> to the third aperture <NUM>, the fourth channel <NUM> fluidly connects the outlet <NUM> to the fourth aperture <NUM>.

The coolant flows from the inlet <NUM> of the support piece <NUM> to the inlets 24c, 25c of the first and second cooling parts <NUM>, <NUM>, and exhausts the first and second cooling parts <NUM>, <NUM> through the outlets 24d, 25d of the first and second cooling parts <NUM>, <NUM> and the outlet <NUM> of the support part <NUM>.

In this example, the intermediary ducts are suppressed simplifying the coolant circulation in the packaging stack <NUM>.

The first, second, third, and fourth apertures <NUM>, <NUM>, <NUM>, <NUM> of the support piece <NUM> may be surrounded by a groove <NUM> and a gasket <NUM> inserted in the groove <NUM> as illustrated on <FIG>.

The groove <NUM> and a gasket <NUM> inserted in the groove <NUM> enhance the sealing between the support party <NUM> and the first and second cooling parts <NUM>, <NUM>.

If the heatsink comprises only the first cooling part <NUM>, the support part <NUM> may not comprise the third and fourth apertures <NUM>, <NUM> and the third and fourth channels <NUM>, <NUM>.

In variant, the support part <NUM> comprises the third and fourth apertures <NUM>, <NUM> and the third and fourth channels <NUM>, <NUM>, and further comprises plugs to obstruct the third and fourth apertures <NUM>, <NUM>.

The disclosed examples of heatsinks <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may further comprise centring means to assemble the first and second cooling parts <NUM>, <NUM> on the support piece <NUM>.

<FIG> illustrates schematically an example of the centring means.

The centring means may comprise a plurality of pins <NUM> disposed on the second surface 24b, 25b of the cooling part <NUM>, <NUM> and a plurality of holes <NUM> disposed on the corresponding surface 23a, 23b of the support piece <NUM>.

Each pin <NUM> is inserted in a different hole <NUM> with a clearance.

The value of the clearance is determined so a relative displacement between each cooling piece <NUM>, <NUM> and the support piece <NUM> does not create an interference between the inlet and outlet connecting parts and the support piece to avoid constraints in the support part <NUM>.

Claim 1:
Heatsink (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) for cooling at least one electronic device package (<NUM>, <NUM>, <NUM>, <NUM>) having an upper contact surface (12a, 13a, 14a, 15a) and a lower contact surface (12b, 13b, 14b, 15b), the heat sink comprising a first cooling piece (<NUM>) and a support piece (<NUM>) comprising a first surface (23a) and a second surface (23b) opposite to the first surface, the first cooling piece (<NUM>) comprising an inlet (24c) configured to receive a coolant and an outlet (24d) configured to exhaust the coolant, a first surface (24a) of the first cooling piece being configured to be in direct contact with one of the upper and lower contact surfaces, the first surface (23a) of the support piece (<NUM>) being in direct contact with a second surface (24b) of the cooling piece, characterized in that the support piece (<NUM>) and the first cooling piece (<NUM>) are two independent pieces so that the interface between the first surface of the support piece and the second surface of the first cooling piece allows a relative movement between the support piece and the first cooling piece along a direction parallel to the interface between the first cooling piece and the support piece.