GB2565071A

GB2565071A - Semiconductor module

Info

Publication number: GB2565071A
Application number: GB1712272.2A
Authority: GB
Inventors: David Hart Simon
Original assignee: Yasa Ltd
Current assignee: Yasa Ltd
Priority date: 2017-07-31
Filing date: 2017-07-31
Publication date: 2019-02-06
Anticipated expiration: 2037-07-31
Also published as: GB2565071B; GB201712272D0

Abstract

A semiconductor module comprises a semiconductor device 100 between two heat spreaders 150. The heat spreaders 150 are connected to opposing faces of the semiconductor device 100 and extend beyond the semiconductor device 100 to form overlapped regions. A housing 300 for housing the semiconductor device 100 and heat spreaders 150 comprises inlets 450 for receiving a cooling fluid. Each of the inlets 450 directs cooling fluid towards one of the heat spreaders 150. Outlets 460 expel the cooling fluid from the housing 300. The inlets are spaced from the heat spreaders 150. The heat spreaders 150 comprise through holes 160 to permit the cooling fluid to flow through the through holes 160 and into the overlapped regions between the heat spreaders 150 and to the outlets 460. A second housing comprises a chamber flooded with a cooling fluid and one or more of the semiconductor modules 100.

Description

Semiconductor Module

FIELD OF THE INVENTION

The present invention relates to a semiconductor module and a power module incorporating the semiconductor module. More specifically, the present invention relates to the cooling of the same. Such arrangements are advantageous in the field of power inverters due to high power losses and associated heat generated by such devices.

BACKGROUND OF THE INVENTION

Electrical and electronic components generate heat as a by-product when they are in use. Overheating usually impacts performance and component lifetime and therefore electrical and particularly electronic components are typically cooled to prevent overheating.

Devices have limitations on the upper temperature at which they may be effectively operated and as limit temperatures are breached so devices may become less efficient and may fail. In most instances devices are unable to recover from failures due to overheating and the whole system in which they are a part becomes unusable, requiring repair or in many cases “burnt out” modules / systems are replaced.

Many different approaches have been used to address overheating limitations: Some have sought to increase the operating temperature of devices using wide band gap semiconductors such as silicon carbide. SiC semiconducting devices are able to tolerate higher ambient temperature of operation, though they still generate heat through use and though self tolerant, associated local passive and silicon devices still require thermal management. The majority effort however has been focussed on silicon and removal of heat from devices, sub-modules and systems. In many power electronics applications, heatsinks are used in instances where efficient heat dissipation is required. Heatsinks absorb and dissipate heat from electrical components by virtue of close thermal contact. For example, a heatsink may be soldered, bonded or otherwise mounted to a power electronic device such as a semiconductor module to improve heat removal by providing a large thermal capacity into which waste heat can flow.

In high power applications the heatsink may be enlarged to improve thermal capacity. However increasing the size of a heatsink increases the weight and volume of a power supply and correspondingly the cost. In many instances the available space, particularly for automotive applications is decreasing rather than the reverse.

Considerable effort has been applied to cooling of electronic components in computing systems wherein central processing units (CPUs) have many millions of semiconducting devices integrated onto the surface of a silicon die. Though heat loss from any one device is small, integration density has led to total heat dissipation being high and can be a severe limitation on speed and lifetime of CPUs.

Some technologies for cooling electronic components in computing systems have also been applied in cooling of high power single or low level integration semiconducting switch devices such as those used in power inverters and particularly immersion cooling is being employed using single phase dielectric liquids or alternatively phase change evaporable liquids.

In US2011/0122583 there is described a liquid tight enclosure providing immersion double sided flow cooling to semiconductor power modules having finned heatsinks aligned with coolant flow direction for improved thermal transfer. Multiple modules may be assembled within a flow through housing with multiple connectors extending through the housing wall.

US2016/0351468 describes integrated double sided cooled power modules with direct copper bonded heat spreaders to which are attached pin-finned heat exchangers immersed in a coolant flow. The approach requires access to bare die and direct-bondcopper technology to gain improved heat spreading.

Delphi Technologies US2009/0057882 has taken a similar approach cooling semiconducting power modules attached to a fluid guiding base and cover such that modules are double sided cooled. A post array may be formed on the outward facing surfaces of the power modules to improve heat transfer to flowing coolant. Coolant may be passed across multiple semiconducting power module arrays in a generally zig-zag fashion thereby cooling both sides of the semiconductor modules.

DE10146558 teaches atomised coolant sprays directed towards semiconducting devices mounted on a double sided insulating substrate. Advantage is taken of evaporative cooling and though the mounting substrate (circuit board) is double sided semiconductor device switches are cooled from one side only.

To address increasing power demands from electric machines particularly for use in land vehicles, but for transportation generally, double sided semiconductor module cooling has been the subject of cooling developments. In this instance semiconducting modules comprising at least semiconducting switches are planarised and interconnected and sandwiched between thermally dissipating substrates usually metallic such as direct-bond-copper onto which are mounted high surface area heat dissipating fins or pins / posts. Thermally dissipating substrates are electrically isolated from the semiconducting module. Electrical connection to semiconducting modules is through a narrow end section, the modules being of thin aspect in one axis from which connections are made.

A practical example of a double sided cooled semiconducting module was presented in 2008 at the 5th International Conference on Integrated Power Electronics Systems. Proceedings : 11.03.2008 - 13.03.2008, Nuremberg, Germany ISBN: 978-3-80073089-6. There is described a semiconducting module consisting of an Insulated Gate Bipolar Transistor (IGBT) and diodes with direct liquid cooling from the top and bottom side. A complex lamination of semiconducting devices with interconnection on chip, sandwiched by copper and aluminium nitride (electrical insulation) layers and finally capped by copper provide electrical isolation of high voltage regions from coolant as well as providing a low thermal resistance to heat generating devices in the silicon surface. Water is used to cool the module and DC link capacitors are mounted on the module’s exterior taking advantage, through thermal conduction, of the coolant circuit.

In Hitachi Review Vol. 63 (2014) No.2 page 98 there is described Hitachi’s Generation III double sided cooling module where IGBT devices similar to those described above have heat dissipating fins directly attached to a monolithically formed sandwich containing the IGBT devices. Power density of an inverter using this technology is

35kW/L which is 5.6 times that of first generation inverters using single sided indirect cooled IGBT modules.

The demand for ever greater power density and consequential improved thermal management continues and we have therefore appreciated the need for an improved cooling arrangement.

SUMMARY OF THE INVENTION

The present invention therefore provides a semiconductor module, comprising: a semiconductor device sandwiched between two heat spreaders, the heat spreaders being thermally and mechanically connected to opposing faces of the semiconductor device and extending beyond the semiconductor device to form overlapped regions of the two heat spreaders, a housing for housing the semiconductor device and heat spreaders, the housing comprising: inlets for receiving a cooling fluid into the housing to flood the housing with the cooling fluid, each of the inlets being arranged to direct cooling fluid towards a respective one of each of the heat spreaders, and outlets for expelling the cooling fluid from the housing, each of the outlets being in fluid communication with a respective one of the overlapped regions of the heat spreaders, wherein each of the walls having inlets located therein are spaced from the respective heat spreaders to permit cooling fluid to flow over the surface of the respective heat spreader, wherein each of the heat spreaders comprise through holes extending from one face of the heat spreader to the opposing face of the heat spreader to permit the cooling fluid to flow therethrough, the respective through holes being arranged to receive the cooling fluid from the surface of the heat spreader receiving the cooling fluid and pass the cooling fluid through the through holes into the overlapped region between the heat spreaders to the outlet.

When cooling fluid flows from the housing inlet, the through holes in the heatspreaders receive the cooling fluid from the surface of the heat spreader and pass the cooling fluid through the through holes into the overlapped region between the heat spreaders to the housing outlet. Using this arrangement of module, a very effective cooling strategy of the semiconductor device is possible.

The inlets may be provided in opposing walls of the housing, each of the opposing walls facing a respective one of the heat spreaders. Each of the inlets may comprise a plurality of through holes in the wall of the housing.

Each of the respective inlets may be arranged to direct cooling fluid to impinge on the outer surface of the respective one of the heat spreaders, the outer surface of the heat spreader being the surface of the heat spreader opposing the surface of the heat spreader in contact with the semiconductor device. Each of these respective inlets may be arranged to direct cooling fluid to impinge on the outer surface of the respective one of the heat spreaders in the region of the heat spreader devoid of through holes.

The respective gap between the respective housing wall and respective heat spreader may form a plenum chamber in fluid communication with the inlet and through holes in the heat spreader.

The outlets may be provided in opposing walls of the housing, each of the opposing walls being adjacent a respective one of the overlapped regions of the heat spreaders.

In any of the above, the through holes may be configured to provide a turbulent flow of the cooling fluid.

In any of the above, one or both of the heat-spreaders comprise a cooling fluid distributor for distributing the cooling medium.

The through holes may be arranged in the form of an array of holes surrounding the periphery of each of the semiconductor devices coupled to the heat spreader.

The present invention also provides a power module, comprising: a housing comprising a chamber flooded with a cooling fluid, and an inlet in fluid communication with the chamber to supply the chamber with the cooling fluid, and an outlet in fluid communication with the chamber for outputting the cooling fluid from the chamber; one or more semiconductor modules, as described above, located in the chamber, the semiconductor modules being immersed in the cooling fluid, the semiconductor module inlets being in fluid communication with the chamber, and the semiconductor module outlets being in fluid communication with the power module outlet.

One or more of the semiconductor modules may be mounted to a Printed Circuit Board (PCB), the PCB providing electrical connections between the semiconductor devices, the PCB being located in the chamber and immersed in the cooling fluid.

The power module may also comprise lower power electrical and electronic components located within the chamber and immersed in the cooling fluid. The semiconductor modules may be co-located within the chamber, and the lower power electrical and electronic components may be co-located within a different area of the chamber to the semiconductor modules.

The cooling fluid may be caused to flow more favourably in the areas of the chamber occupied by the semiconductor modules. 51% to 99% of the cooling fluid flow may be caused to flow in the areas of the chamber occupied by the semiconductor modules, preferably 95% of the cooling fluid flow.

The respective semiconductor device of each of the one or more semiconductor modules may be electrically connected to the respective heat spreaders of the semiconductor module, the respective heat spreaders of each of the semiconductor modules forming a respective bus bars to electrically connect the semiconductor devices to other devices to transmit power between the semiconductor devices and other devices.

When there are two or more semiconductor modules located within the chamber of the power module, the semiconductor modules may be arranged in series such that the inlet of the first semiconductor module is in fluid communication with the power module chamber, the outlet of the first semiconductor is in fluid communication with the inlet of the next semiconductor module, and the outlet of the last semiconductor module is in fluid communication with the outlet of the power module. In this arrangement, at least two semiconductor modules may also be in parallel with each other such that the at least two semiconductor modules share an inlet and share an outlet.

When there are two or more semiconductor modules located within the chamber of the power module, the semiconductor modules may be arranged parallel to one another, such that each of the semiconductor module inlets are in fluid communication with the chamber, and each of the semiconductor module outlets are in fluid communication with the power module outlet.

The cooling fluid may be pumped so as to cause the fluid to flow between the inlet port and the outlet port. So long as there is a pressure differential in the cooling fluid between the inlets and outlets, cooling fluid will flow through the power module and flow through the semiconductor module(s).

The inlet port of the power module and outlet port of the power module may be coupled to a cooling circuit comprising a heat exchanger, the heat exchanger for removing heat from the cooling fluid.

The semiconductor modules of the power module may be connected and configured to form an inverter for converting between DC and AC. When the inverter is configured to convert DC to AC, the inverter comprises one or more electrical inputs for receiving one or more DC voltages, and one or more electrical outputs for outputting one or more AC voltages. The output of the inverter is configured to power an electric motor.

When the inverter is configured to convert AC to DC, the inverter comprises one or more electrical inputs for receiving one or more AC voltages, and one or more electrical outputs for outputting one or more DC voltages. The output of the inverter is configured to charge a battery or other electrical storage device.

The inverter may be configurable as a bidirectional inverter for converting DC to AC and AC to DC, the bidirectional inverter comprising one or more DC ports for receiving or outputting one or more DC voltages, and one or more AC ports for inputting or outputting one or more AC voltages.

Semiconductor modules of the power module may be connected and configured to form an inverter for converting DC to DC. The inverter, in this configuration, comprises one or more electrical inputs for receiving one or more DC voltages, and one or more electrical outputs for outputting one or more DC voltages.

In any of the above examples of semiconductor modules and power modules, the semiconductor module may comprise an IGBT, Silicon carbide (SiC) semiconducting switch devices, metal oxide semiconducting field effect transistors (MOSFETs), or power diodes.

In any of the above examples of semiconductor modules and power modules, wherein the cooling fluid is a dielectric cooling fluid.

LIST OF FIGURES

The present invention will now be described, by way of example only, and with reference to the accompanying figures, in which:

Figures 1 a and 1 b show a semiconductor power device;

Figure 2 shows an arrangement of a semiconductor power device and heat spreaders;

Figure 3 is a perspective view of a semiconducting assembly;

Figure 4 is a second perspective sideways view of a semiconducting assembly;

Figure 5a and 5b show different views of the semiconducting power device;

Figure 6 shows an end-on view of a semiconducting assembly;

Figure 7 shows a view of a semiconductor module;

Figure 8 shows a view of a semiconductor module;

Figure 9 shows a view of a semiconductor module;

Figure 10 shows a view of a semiconductor module;

Figure 11 shows a power device incorporating semiconductor modules; and

Figure 12 shows an example electrical arrangement of a power device incorporating the semiconductor modules.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In brief, the present invention relates to a semiconductor module that is cooled using a cooling fluid. The semiconductor module comprises a semiconductor device (such as a semiconductor power device) sandwiched between two heat spreaders, which extend beyond the package of the power device and overlap each other in those regions. The heat spreaders are thermally and mechanically connected to opposing faces of the semiconductor device, which can be a so-called double-sided semiconductor power device. A housing surrounds the semiconductor device and heat spreaders. The housing is provided with inlets and outlets so that the semiconductor module can be flooded with a cooling fluid. The inlets are arranged to direct cooling fluid towards a respective one of each of the heat spreaders. The heat spreaders comprise through holes that extend from one face of the heat spreader to the opposing face of the heat spreader. These through holes permit the cooling fluid to flow therethrough. When cooling fluid flows from the housing inlet, the through holes in the heatspreaders receive the cooling fluid from the surface of the heat spreader and pass the cooling fluid through the through holes into the overlapped region between the heat spreaders to the housing outlet. Using this arrangement of module, a very effective cooling strategy of the semiconductor device is possible.

Double sided semiconducting modules are preferably characterised by being built so as to enhance thermal conductivity between silicon active junctions, i.e. junctions of diffused devices in the silicon surface and the module outer surface which is usually a high thermal conductivity metal - typically copper, tinned copper, aluminium or solderable aluminium. To reduce thermal resistance between active i.e. heat generating silicon switch devices and the module surface, various intervening layers are thin, typically a few microns to a few tens of microns thickness and because of this aspect, preferred power semiconducting modules have thin of the order of a few millimetres thickness in one axes and typically of several tens of millimetres in the other two axes. It is through the large area faces that heat is removed and typically electrical connections are made through the thin aspect edges.

Double sided power semiconductor modules are normally electrically isolated from the large area surface layers. Electrical connection to the semiconducting module is made via pins or screws to isolated connectors along edges. However special advantage may be taken in the present invention from using the large surface area of modules as electrical connection regions.

Whereas double sided semiconductor power modules described above are usually cooled by means of heatsinks attached or bonded to the two opposing large surface areas available, the heatsinks being air or more effectively direct liquid cooled, the present invention employs direct liquid immersion cooling of the modules without use of pinned or finned heatsinks, utilising the surprising advantage of localised turbulent flow caused by submerged liquid jets. In effect submerged liquid jets are surprisingly advantageous analogues of heatsink pins or fins.

The following example provides explanation of a preferred embodiment of the present invention and of the benefits and advantages provided:

With reference to Figure 1a and 1b semiconductor power device 100 is an integrated semiconductor switching device often found in power supplies where voltage/current transformations are required to provide power to motors, or from generators. Transformations are usually from DC to AC (AC to DC) and often from DC to multiphase AC, typically 3-phase.

To provide an appropriate switching signal to achieve for instance a sinusoidal AC output, gate driver circuitry is required to operate switching devices in semiconductor power device 100 and in some instances the gate driver circuitry may be integrated into the semiconductor power device 100 to form a so called integrated power module.

Double sided semiconducting power modules 100 with or without gate drivers are designed to maximise dissipation of heat from switch, diode and other integrated components and so have a “flat-plate” format being thin when viewed on end as shown in Figure 1 a which is a view of the cross-section A-A’ seen in Figure 1. Thickness of the module is of the order of a few millimetres thickness in one direction and several 10s of millimetres in the other two orthogonal axes. Input and output connections 110 are typically along one edge so as to leave clear the central heat dissipating zones 120 on either side of the module.

Whereas heat dissipating zones 120 are frequently fitted with finned heatsinks which may be air or direct liquid cooled, the latter e.g. by way of water channels within the heatsink, the present invention with reference to Figure 2, uses dual heat spreading plates 150 having perforated end zones 160 made up of multiple holes 170 that traverse the heat spreading plates 150. The heat spreading plates 150 having central regions 180 which coincide with central regions 120 of the double sided semiconducting module 100. The combination of a double sided semiconducting power device 100 sandwiched between two perforated heat spreader plates 150 forms a semiconducting assembly 200.

Attachment of semiconductor power modules to holed heat-spreader plates is preferably by bonding via solder or brazing or amalgam type or similarly thin and high thermal conductivity joining technologies. A less thermally efficient route is via mechanical clamping using a thermal conducting paste or fluid to fill air gaps.

Figure 3 is a perspective view of a semiconducting assembly 200 showing two heat spreader plates 150 sandwiching a semiconducting power device 100.

Figure 4 is a second perspective sideways view of a semiconducting assembly 200 showing through holes 170 in perforation regions 160. Heat spreader plates 150 may be attached to double sided semiconducting module 100 by a low melting point solder alloy or compound, by a thermally conducting grease or by a thermally conducting adhesive compound, but which ever technique is used a good thermal contact is preferred with no entrapped air at the boundary 190 between heat spreader plates 150 and semiconducting module 100.

Figures 5a,b, 6 and 7 show the build of a semiconductor module.

Figure 5a is an elevation view of a semiconducting module 100 and Figure 5b is a plan view of the same module 100.

Figure 6 is an end-on view of a semiconducting assembly 200 showing input/output connector region 110, thermal interface regions 190.

Heat flow arrows 210 show route of heat flow from semiconducting module 100 across thermal interface 190 into heat spreader 150 and so towards perforated regions 160 and additional heat flow paths 220 showing heat flow from semiconducting module 100 across thermal interface 190 in to heat spreaders 150 and towards the surface 230 of the heat spreaders 150.

With reference to Figures 7 to 10, Figure 7 shows a cut through schematic of a semiconductor assembly 200 with surrounding housing 300, which together form semiconductor module. The housing 300 comprises perforated plates 310 which lay parallel to and separated from heat-spreader plates 150 by gap 320 to form plenums 330 either side of the semiconducting assembly, the plenums being bounded on the one side by the perforated housing plates 310 and on the other by the heat spreader plates 150 both of which are co-joined at their edges 400. The housing 300 comprising inlet 450 and outlet 460 ports, both in fluid communication with the plenum 330 for receiving and outputting a cooling medium. The inlet ports 450 may comprise an array of multiple through-hole perforations 470 through housing plates 310.

Plenums 330 are flooded with a cooling fluid (not shown) to cool the semiconducting assemblies 200, perforations 470 in the housing plates 310 generating cooling fluid jets 500 which impinge perforation free regions 180 of the heat-spreader plates 150.

Heat-spreaders 150 comprise heat exchanging elements 160 in the form of a plurality of holes 170 in the heat spreader overlapping regions and a hole-free region 180 to which the semiconductor power device 100 is coupled. With suitable pressure differential between region P1 and outlet region P2 cooling fluid flows through the holes in housing plates 310 to impinge on hole-free regions 180 of heat spreader plates 150 and thereafter cooling medium progresses laterally along the surface of heat spreader plates 150 to flow through the through holes 170 in the peripheral region 160 of the heat spreader 150 to extract heat from the heat-spreader 150. The cooling fluid then flows to one or more housing outlets 460.

With reference to Figure 10, semiconducting power device 100 mounted to heat spreaders 150 and housing plates 310 in combination form a semiconducting cooling arrangement 600. One or more semiconductor modules 200 may be surrounded by perforated housing plates 310 thereby enabling double sided coolant fluid immersion and coolant fluid jet impingement on the semiconductor assemblies 200.

As discussed above, the inlets generate cooling fluid jets which impinge perforation free regions of the heat-spreader plates.

High velocity low friction flow is preferable through the perforations in the housing plates so as to produce high velocity impinging jets on the solid surface of the heat spreader plates attached to the power module. High velocity submerged coolant jets produce local turbulent flow that effectively removes heat from the surface on which jets impinge.

Rate of flow of coolant and heat transfer coefficient between coolant and hot surface provides an overall thermal transfer coefficient that surprisingly exceeds that of direct liquid cooled pinned or finned heatsinks similarly bonded to a double sided power module. Thermal transfer in the latter being limited by the weakest link i.e. thermal resistance of the heatsink, a function of thermal conductivity and distance travelled i.e. higher thermal resistance for high aspect ratio pins and fins. In contrast submerged liquid jets have a much higher effective thermal conductivity and approaching zero thermal resistance: Thermal transfer coefficient between coolant and substrate being common to both cooling approaches.

Coolant fluid is delivered from the housing perforated plates generally orthogonally to the faces of the heat-spreader holed flanged plates and leaves generally parallel to the heat spreader region taking a route towards the holed flanged regions in the heat spreader plates. Because of pressure differential, coolant medium traverses the holes in the flanges of the heat-spreader plates and by virtue of the size and shape of holes and coolant flow rate, heat is further removed from the heat-spreader plates and hence from the semiconductor device. Coolant fluid exits the housing through outlets, which may be connected to a low pressure coolant fluid sink.

With reference to Figure 11, which shows a power module comprising one or more semiconductor modules 600. The semiconducting modules 600 may be mounted to a circuit board 620 for electrical interconnection along with other active and passive devices e.g. 670 and 680 and the whole being mounted in a liquid tight chamber 630, which chamber further has inlet port 640 which traverses the chamber wall allowing coolant fluid 700 to flood the chamber and thereby supplying coolant fluid 700 to the semiconducting cooling arrangements and outlet port 650 taking coolant 700 to an external heat exchanger (not shown). Pressure of coolant medium P1 being greater than pressure P2 which causes the coolant medium to flow through semiconducting cooling arrangements 600 to out let 650.

Whilst the cooling of the semiconductor modules 600 is shown in parallel, that is each of the inlets of the semiconductor modules 600 is in fluid communication with the flooded chamber of the power device, and each of the outlets of the semiconductor modules are in fluid communication with the outlet 650, other arrangements are also possible.

For example, the cooling of the semiconductor modules 600 may instead be in series, that is the inlet of a first semiconductor module is in fluid communication with the inlet or chamber of the power device and its outlet feeds cooling fluid to the next semiconductor module. That is the outlet of the first semiconductor module is in fluid communication with the inlet of the next semiconductor module. This arrangement continues for sequent semiconductor modules in the series chain, and the final semiconductor module is arranged such that its outlet is in fluid communication with the outlet of the outlet 650 of the power device.

Furthermore, some semiconductor modules may be in series, and some may be grouped in parallel.

In any of the above arrangements, coolant fluid is a dielectric fluid. Its flow may be split predominantly towards semiconducting modules, because these typically have the highest heat dissipating load. The additional active and passive devices that together form a power supply, require much less cooling. Flow maybe split between 51:49 and 99:1 semiconductor module proportion to other component proportion. Other ratios are possible. A preferred ratio for the present invention is 95:5.

Power connector 690 provides a liquid sealed means of input and output power from the liquid filled chamber 630

Though the above may use the usual electrical configuration of semiconductor power modules i.e. wherein heat dissipating surfaces are electrically isolated, special advantage may be gained from using semiconducting modules in which a normally electrically isolating layer is omitted thereby causing the outward facing module surface(s) to be electrically live, usually at a high working voltage. Whereas electrically live semiconductor power modules is normally to be avoided, in the present invention using the module double outer surfaces as both heat spreaders and “collector” (versus emitter and gate) connections improves heat dissipation by removing normally present thermally resistant, electrically isolating layers and reduces inductive losses by utilising the heat-spreader plates as combined heatsink busbars.

Figure 12 shows a two level inverter power supply 800, a format widely used by industry to provide a controlled 3-phase power output 820 from a DC source 810. Three semiconducting cooling arrangements 600, one for each power phase U,V, W are situated within a liquid tight chamber 630 the chamber being fitted with an inlet port 640 and an outlet port 650. Chamber 630 is flooded with a dielectric fluid coolant 700 which fluid coolant is caused to flow by means of a pressure differential across the semiconducting cooling arrangement 600. A pressure differential may be achieved through an external pump (not shown) and heat removed from the two level inverter power supply 800 is exchanged with the ambient environment through an externally mounted heat exchanger (not shown).

The present invention may be used to cool double sided semiconducting modules for use in a power inverter for converting DC to AC (for example when powering a motor) or AC to DC (for example when receiving power from a generator), comprising: one or more inputs for receiving one or more DC voltages; one or more outputs for outputting one or more AC voltages; and a plurality of double sided semiconductor modules with cooling housings as described above, the plurality of double sided semiconductor modules being coupled to the one or more inputs and one or more outputs, the semiconductor modules being mounted to a Printed Circuit Board (PCB), the PCB providing electrical connections between the semiconductor devices, the one or more inputs and the one or more outputs.

In this inverter, the input DC voltages may comprise a +DC input voltage and/or a -DC input voltage, and wherein the AC output may comprise an AC phase output voltage.

Alternatively, the power inverter may be used as a DC to DC converter.

Each of the plurality of double sided semiconductor modules with cooling housings and heat-spreader plates has a longitudinal axis, and wherein each module may be mounted on the PCB such that the longitudinal axes of the modules are parallel to one another. The modules may be arranged on the PCB so as to be symmetrical in at least one axis.

The modules may be electrically arranged to provide a three level T-type topology or a two level topology. When configured as a three level T-type topology, the inverter may comprises a second DC output at a DC/2 voltage.

The electrical arrangement between the modules may be configurable via the PCB if the double sided semiconductor modules are electrically isolated. In case of semiconducting modules being electrically live, they may be configurable by one or more connector bars, each of the one or more connector bars connecting the electrically live heat-spreader plate, bus bars of two modules together in order to provide a three level T-type topology or a two level topology.

The inverter may comprise four modules arranged in a three level T-type configuration, and wherein the heatsink bus bars of two of the four modules are electrically connected together using a connector bar. In this arrangement, the heatsink bus bars of the second and third of the modules, located on the PCB between the first and fourth modules, may be electrically connected together using the connector bar. An alternative electrical connection arrangement using the PCB is used for electrically isolated double sided semiconducting power modules.

In any of the above, the inverter may comprise two or more pluralities of semiconductor cooling arrangement modules, each of the two or more pluralities of semiconductor cooling arrangement modules providing one phase of a multiphase output AC voltage.

The output of the inverter may be configured to power an electric motor. The cooling circuit of the inverter may be in fluid communication with a cooling circuit of the electric motor.

No doubt many other effective alternatives will occur to the skilled person. It will be understood that the invention is not limited to the described embodiments and encompasses modifications apparent to those skilled in the art lying within the scope of the claims appended hereto.

Claims

CLAIMS:

1. A semiconductor module, comprising:

a semiconductor device sandwiched between two heat spreaders, the heat spreaders being thermally and mechanically connected to opposing faces of the semiconductor device and extending beyond the semiconductor device to form overlapped regions of the two heat spreaders, a housing for housing the semiconductor device and heat spreaders, the housing comprising:

inlets for receiving a cooling fluid into the housing to flood the housing with the cooling fluid, each of the inlets being arranged to direct cooling fluid towards a respective one of each of the heat spreaders, and outlets for expelling the cooling fluid from the housing, each of the outlets being in fluid communication with a respective one of the overlapped regions of the heat spreaders, wherein each of the walls having inlets located therein are spaced from the respective heat spreaders to permit cooling fluid to flow over the surface of the respective heat spreader, wherein each of the heat spreaders comprise through holes extending from one face of the heat spreader to the opposing face of the heat spreader to permit the cooling fluid to flow therethrough, the respective through holes being arranged to receive the cooling fluid from the surface of the heat spreader receiving the cooling fluid and pass the cooling fluid through the through holes into the overlapped region between the heat spreaders to the outlet.

2. A semiconductor module according to claim 1, wherein inlets are provided in opposing walls of the housing, each of the opposing walls facing a respective one of the heat spreaders.

3. A semiconductor module according to claim 1 or 2, wherein each of the inlets comprise a plurality of through holes in the wall of the housing.

4. A semiconductor module according to claim 1, 2 or 3, wherein each of the respective inlets is arranged to direct cooling fluid to impinge on the outer surface of the respective one of the heat spreaders, the outer surface of the heat spreader being the surface of the heat spreader opposing the surface of the heat spreader in contact with the semiconductor device.

5. A semiconductor module according to claim 4, wherein each of the respective inlets is arranged to direct cooling fluid to impinge on the outer surface of the respective one of the heat spreaders in the region of the heat spreader devoid of through holes.

6. A semiconductor module according to any preceding claim, wherein the respective gap between the respective housing wall and respective heat spreader forms a plenum chamber in fluid communication with the inlet and through holes in the heat spreader.

7. A semiconductor module according to any preceding claim, wherein the outlets are provided in opposing walls of the housing, each of the opposing walls being adjacent a respective one of the overlapped regions of the heat spreaders.

8. A semiconductor module according to any preceding claim, wherein the through holes are configured to provide a turbulent flow of the cooling fluid.

9. A semiconductor module according to any preceding claim, wherein one or both of the heat-spreaders comprise a cooling fluid distributor for distributing the cooling medium.

10. A semiconductor module according to any preceding claim, wherein the through holes are arranged in the form of an array of holes surrounding the periphery of each of the semiconductor devices coupled to the heat spreader.

11. A power module, comprising:

a housing comprising a chamber flooded with a cooling fluid, and an inlet in fluid communication with the chamber to supply the chamber with the cooling fluid, and an outlet in fluid communication with the chamber for outputting the cooling fluid from the chamber;

one or more semiconductor modules according to any one of claims 1 to 10 located in the chamber, the semiconductor modules being immersed in the cooling fluid, the semiconductor module inlets being in fluid communication with the chamber, and the semiconductor module outlets being in fluid communication with the power module outlet.

12. A power module according to claim 11, wherein one or more of the semiconductor modules are mounted to a Printed Circuit Board (PCB), the PCB providing electrical connections between the semiconductor devices, the PCB being located in the chamber and immersed in the cooling fluid.

13. A power module according to claim 11 or 12, wherein the power module comprises lower power electrical and electronic components located within the chamber and immersed in the cooling fluid.

14. A power module according to claim 13, wherein the semiconductor modules are co-located within the chamber, and the lower power electrical and electronic components are co-located within a different area of the chamber to the semiconductor modules.

15. A power module according to any one of claims 11 to 14, wherein the cooling fluid is caused to flow more favourably in the areas of the chamber occupied by the semiconductor modules.

16. A power module according to claim 15, wherein 51% to 99% of the cooling fluid flow is caused to flow in the areas of the chamber occupied by the semiconductor modules, preferably 95% of the cooling fluid flow.

17. A power module according to any one of claims 11 to 16, wherein the respective semiconductor device of each of the one or more semiconductor modules is electrically connected to the respective heat spreaders of the semiconductor module, the respective heat spreaders of each of the semiconductor modules forming a respective bus bars to electrically connect the semiconductor devices to other devices to transmit power between the semiconductor devices and other devices.

18. A power module according to any one of claims 11 to 17, wherein, when there are two or more semiconductor modules located within the chamber, the modules are arranged in series such that the inlet of the first semiconductor module is in fluid communication with the power module chamber, the outlet of the first semiconductor is in fluid communication with the inlet of the next semiconductor module, and the outlet of the last semiconductor module is in fluid communication with the outlet of the power module.

19. A power module according to claim 18, wherein at least two semiconductor modules are in parallel with each other such that the at least two semiconductor modules share an inlet and share an outlet.

20. A power module according to any one of claims 11 or 17, wherein, when there are two or more semiconductor modules located within the chamber, the modules are arranged parallel to one another, such that each of the semiconductor module inlets are in fluid communication with the chamber, and each of the semiconductor module outlets are in fluid communication with the power module outlet.

21. A power module according to any one of claims 11 to 20, wherein the cooling fluid is pumped so as to cause the fluid to flow between the inlet port and the outlet port.

22. A power module according to any one of claims 11 to 21, wherein the inlet port and outlet port are coupled to a cooling circuit comprising a heat exchanger, the heat exchanger for removing heat from the cooling fluid.

23. A power module according to any one of claims 11 to 22, wherein the semiconductor modules are connected and configured to form an inverter for converting between DC and AC.

24. A power module according to claim 23, wherein, when the inverter is configured to convert DC to AC, the inverter comprises one or more electrical inputs for receiving one or more DC voltages, and one or more electrical outputs for outputting one or more AC voltages.

25. A power module according to claim 24, wherein the output of the inverter is configured to power an electric motor.

26. A power module according to claim 23, wherein, when the inverter is configured to convert AC to DC, the inverter comprises one or more electrical inputs for receiving one or more AC voltages, and one or more electrical outputs for outputting one or more DC voltages.

27. A power module according to claim 26, wherein the output of the inverter is configured to charge a battery or other electrical storage device.

28. A power module according to claim 23, wherein the inverter is configurable as a bidirectional inverter for converting DC to AC and AC to DC, the bidirectional inverter comprising one or more DC ports for receiving or outputting one or more DC voltages, and one or more AC ports for inputting or outputting one or more AC voltages.

29. A power module according to any one of claims 11 to 22, wherein the semiconductor modules are connected and configured to form an inverter for converting DC to DC.

30. A power module according to claim 29, wherein the inverter comprises one or more electrical inputs for receiving one or more DC voltages, and one or more electrical outputs for outputting one or more DC voltages.

31. A semiconductor module according to any one of claims 1 to 10 or a power module according to any one of claims 11 to 30, wherein the semiconductor module comprise an IGBT, Silicon carbide (SiC) semiconducting switch devices, metal oxide semiconducting field effect transistors (MOSFETs), or power diodes.

32. A semiconductor module according to any one of claims 1 to 10 and 31 or a power module according to any one of claims 11 to 31, wherein the cooling fluid is a dielectric cooling fluid.