GB2536051A

GB2536051A - Heatsink

Info

Publication number: GB2536051A
Application number: GB1503788.0A
Authority: GB
Inventors: Elliott Thornton Warren; Mikhail O'dell-Vnukov Andrew
Original assignee: Hiflux Ltd
Current assignee: Hiflux Ltd
Priority date: 2015-03-06
Filing date: 2015-03-06
Publication date: 2016-09-07
Also published as: GB201503788D0

Abstract

A heat sink 18 for power electronic applications comprises a first plate member 38, an opposing second member 40 and side walls 44 defining a fluid space 20. A fluid inlet and a fluid outlet allow fluid to be passed through the fluid space. Internal fluid passageways within the fluid space allow fluid to circulate through or around a plurality of pins, fins or projections 42 that extend from, and that are attached to, or are integral with, the first plate member. The first plate member has a thickness in at least 50% of the areas between the pins, fins or projections, not exceeding 1mm and no less than 0.2 mm. The first plate is thin, which allows a quick transfer of heat from the power electronic device 12. The structural rigidity of the device is maintained by the projections 42 and the second plate 40. A method of manufacturing the heatsink comprises attaching at least 50% of the pins, fins or projections to both the first plate member and the opposing second member. A method of cooling power electronics, a battery or an IGBT arrangement comprises mounting the respective arrangement on the heatsink and passing fluid through the heatsink.

Description

Heatsink The present invention relates to a heatsink and a method of manufacturing a heatsink, plus methods of using heatsinks in power electronics and IGBT (insulated gate bipolar transistor) arrangements.

Heatsinks for IGBT and other power electronics (PE) devices need rapidly to transfer heat away from those devices. Most commonly the heatsinks used for this purpose facilitate a rapid heat transfer away from the device by using a fluid, usually air, water or water/glycol that passes through or around the heatsink The present invention seeks to improve upon existing heatsinks.

Figure 1 shows a standard PE device 12 for mounting on a heatsink and for the connection of PE or IGBT devices. The device 12 has electrical terminals 10 on one side and a baseplate 14 on the opposite side. The baseplate 14 is for mounting the device to a heat sink and to provide the start of a thermal pathway for heat to be transferred away from PE/IGBT devices. This thermal pathway passes, typically through conduction, through the baseplate 14 to connect with the heatsink 18 (see Figures 2 and 3 for prior art examples, as discussed below).

Conventionally the baseplate 14 of the PE device 12 is thermally coupled to the heatsink 18 via thermal paste 28. One example of this is shown in Figures 2 and 3, with a fluid space 20 being incorporated into the heatsink 18 by means of which fluid can be pumped through the heatsink from an inlet 22 and out through an outlet 24.

Further improvements in the heat transfer away from the PE/IGBT device can also be provided by incorporating pins 42 onto the heatsink 18 -to increase the surface area for engagement by the fluid. These pinned heatsinks can then be further improved by capping the pins with a housing 36 -the housing can be sealed thereover to allow the fluid to be pumped past the pins, and thus in effect "through" the heatsink.

Further improvements in the heat transfer away from the PE device 12 is still desirable, however, and the present invention seeks to achieve this.

According to the present invention, therefore, there is provided a heatsink for power electronics applications comprising: a first plate member, an opposing second member and side walls defining therebetween a fluid space; a fluid inlet and a fluid outlet for allowing fluid to be passed through the fluid space; and internal fluid passageways within the fluid space, which fluid passageways circulate through or around a plurality of pins, fins or projections that extend from, and that are attached to, or are integral with, the first plate member, the plurality of pins, fins or projections being within the fluid space. A first embodiment is shown in Figure 4. A close-up view of the internal pins is shown in Figure 6.

It is preferred that the first plate member has a thickness in at least 50% of the areas between the pins, fins or projections, not exceeding 1mm and no less than 0.2 mm.

Where the pins, fins or projections extend perpendicular to the first plate member, the thickness of the first plate member is measured parallel to the axes of those pins, fins or projections.

Preferably the thickness of the first plate member between the pins, fins or projections does not exceed 1mm, and is no less than 0.2 mm, throughout the full extent of the plate that has such pins, fins or projections, although instead of this 100%, or the earlier 50 %, the percentage may be at least 75% or at least 90%.

Preferably the pins, fins or projections are laser welded onto the first plate member.

Generally the first plate member will be flat or planar. However, it might be curved, for example to fit to curved devices.

It can be double sided, an example of which is shown in Figure 5, and it might have various shapes too.

It is preferably flat, for a flat device for example.

Instead of laser welding, the pins, fins or projections may be etched into a first plate member so as to leave the spaces between the pins, fins or projections at the thickness claimed above. An example of this is shown in Figure 7. This arrangement preferably comprises a top plate and bottom plate.

One or both plates could feature a fluid space provided by etching material away, leaving pins or profiles. They may be regularly or irregularly shaped and/or tapered. They may be chamfered or filleted. They can extend as an array or pin-set along at least 50% of the plate from which they extend. They can be provided with a side wall 54 to enclose the fluid space. Figure 8 shows a close-up view of one example of such an arrangement.

Other methods of manufacturing could be to cast the first plate member with the pins therein, to use 3D printing, to use forging, to use routing, or to use metal injection moulding. These methods would typically result in a base plate thickness well over imm, and it thus may be the second member -the first plate member thus caps these to still provide a heat sink that falls within the scope of the present invention.

Another example of second member is shown in figure 9 -it has tapered, round, frustoconical pins.

The pins, fins or projections may range in length from 0.2mm to 20mm. For etching they might be no longer than 1mm. If they are welded, they might be between 3mm and 10mm long. If the fins are formed from plates, or if the gaps between the pins or fins or projections are formed via routing, they may be as long as 2cm long.

Preferably the chosen method is laser welding of pins.

To facilitate the laser welding of pins, fins or projections onto the first plate member, especially where the pins, fins or projection, and the first plate member, are made of copper, that first plate member is preferably a sheet that is nickel plated, oxidized, blackened or otherwise surface treated prior to the welding step. Nickel plating reduces the reflection of the laser, compared to copper, thus facilitating the welding process. A consequence can be faster welding of pins, fins or projections onto the first plate member, thus reducing manufacturing costs.

The nickel plating may be on one or both sides of the first plate member. It may be put thereon specifically for the laser processing step and then removed therefrom (e.g. by abrasive, chemical or polishing techniques) to facilitate the later attachment of the PE device thereto, i.e. on the outside surface thereof. This removal might be only on that outside surface, or on both the inside an so far as it is accessible) and outside surfaces.

The first plate member is typically made from metal, and is preferably made of copper.

Alternative materials to copper may include, but are not limited to, aluminium, brass, steel, stainless steel, steel alloys, silver, gold, other precious metals and various mixtures or alloys thereof. The material might even include or comprise other thermally conductive materials, such as thermally conductive ceramics or plastics, or thermally conductive composites. Metals, however, are the preferred materials due to their commonly inherent useful thermal conductivity and laser weldability.

The first plate member is preferably a top sheet of the heatsink and by being thin, i.e. being between 0.2mm and 1mm, it more quickly allows the transfer of heat from the PE device, or some other such item to be cooled, to the pins, fins or projections within the fluid space. Therefore, fluid passing through the fluid space between or around those pins, fins or projections, i.e. along the fluid passageways, can more quickly transfer heat away from the item to be cooled. Prior art heatsinks have not had such a thin top sheet, or first plate member, interfacing between the fluid space and the item to be cooled (i.e. the baseplate of the PE device), generally because such thin sheets would not function in the prior art arrangements -they would flex too much, or too easily.

The present inventors, however, have realised that such a thin first plate member can still be used while still having adequate structural integrity for the heatsink when the pins, fins or projections extend from them within a defined fluid space to an opposing second member since the heatsink as a whole provides the structural integrity, i.e. the two opposing members and the pins cooperate as a single structure, preferably with all or most of the pins welded or otherwise joined to those members at both ends thereof The sidewalls may also be used in this structure further to increase structural rigidity.

It is believed that to go thinner than 0.2 mm is not worthwhile, however, since that could risk compromising that structural integrity.

The side walls for defining the edges of the fluid space can be provided by a variety of materials. For example it might be a potting compound applied between the edges of two overlying plates, or it may be a solder wall applied between such plates, or it can be provided by side wall plates welded to the other members and plates, or it can be a flange applied to either the first plate member or the opposing second member, e.g. through a pressing process.

The opposing second member is preferably a further plate member and may likewise be welded to the fins, pins or projections. Alternatively, the fins, pins or projections may be formed on the opposing second member with the first plate member then being laser welded onto those pins, fins or projections.

It may have similar, or the same, thickness requirements as the first plate member, or it can have the same or similar thickness as that first plate member. As such, preferably the opposing second member is a further plate member and it preferably has a thickness in at least 50% of the areas between the pins, fins or projections, not exceeding 1mm and no less than 0.2 mm. Further, where the pins, fins or projections extend perpendicular to the further plate member, the thickness of the further plate member is preferably measured parallel to the axes of those pins, fins or projections.

Further, preferably the thickness of the further plate member between the pins, fins or projections does not exceed 1mm, and is no less than 0.2 mm, throughout the full extent of the plate that has such pins, fins or projections, although instead of this 100%, or the earlier 50 chi, the percentage may be at least 75% or at least 90%.

Further, preferably the pins, fins or projections are laser welded onto the further plate member.

Further, preferably the first plate member is flat or planar, or most preferably confirming to the shape of the first plate member.

Instead of laser welding, the pins, fins or projections may be etched into the further plate member so as to leave the spaces between the pins, fins or projections at the thickness claimed above. Yet further, other methods of manufacturing could be to cast the further plate member with the pins therein, to use 3D printing, to use forging, to use routing, or to use metal injection moulding.

It is possible for some of the pins, fins and projections to be formed or fabricated on the first plate member and for others to be formed or fabricated on the opposing second member, such that they intermesh, and upon joining the two together, for example using laser welding, the combination of the two sets of pins, fins or projections provide the bridging members between the first plate member and the opposing second plate member with the internal fluid passageways extending between those combinations of the fins, pins and projections.

Preferably all the pins are joined at both ends, i.e. to the first plate member and the opposing second member, thus maximising the structural integrity of the assembly of the heatsink. The joining of at least 50% of the pins at both ends, however, would also offer good structural integrity.

Preferably the thickness of the opposing second member at the space between the pins, fins and projections of the opposing second member, or at that opposing second member (i.e. for pins extending from the first plate member), is also between 0.2mm and 1mm, and more preferably it is about the same thickness as that of the first plate member. The opposing second member thus provides a second thin member onto which to mount a PE device, or other device to be cooled. The heatsink is thus then a dual sided heatsink with two thin skins.

The present invention therefore provides a heatsink, a heatsink with a power electronics unit mounted on a first side thereof and a heatsink provided with a power electronics unit mounted on both sides thereof, each utilising a heatsink design as described above (or below).

The present invention also provides a method of manufacturing such a heatsink, plus methods of using such heatsinks in power electronics and IGBT (insulated gate bipolar transistor) arrangements.

The present invention has been described above purely by way of example, and in relation to power electronic applications. However, it might alternatively be a heatsink for use in battery cooling applications, or other high temperature transfer requirement applications, e.g. batteries or high load electronics used in the transport industry, especially in electric cars, electric trains or aircraft, such as those comprising hybrid or plug-in electrical systems.

The temperatures of use for the present invention can vary widely, with suitably chosen materials being used for the application in suit, i.e. the materials are chosen such that at the temperatures involved in the specific application, they do not soften or melt during use in a manner that allows the structural integrity of the heatsink to be compromised. For example, temperatures above 300°c may require steel rather than copper as the primary material of choice for the pins and plates/members.

The interface temperature between the fluid and the inside surface of the first plate member, however, can be reduced below those operating temperatures of the components -it will typically be somewhere between 50 and 100°C, although the actual temperature can vary since it is controlled through the appropriate control of the fluid flow, and the specifics of the fluid used (such as its boil-point in the case of a liquid). As such other temperatures ranges are also available.

Preferably the pin density between the first plate member and the opposing second member is constant across the plate -at least in the area located under the item to be cooled. However, where higher temperature regions are expected next to lower temperature regions, on the same PE device, or where more than one PE device is attached, each having different cooling requirements, higher or lower density pin arrangements may be provided in the relevant areas, i.e. for aligning with the cooling need of the component lying in registration therewith. Higher pin densities can increase manufacturing costs, but can also increase thermal transfer efficiency.

Where pins are used and where they are laser welded onto the first plate member or the opposing second member, they are preferably about 1mm diameter. They are preferably of a round section. Typically their diameter will be no less than 0.5mm and no more than 2mm. Other sections, such as tear shaped, diamond shaped, square shaped or rectangular shaped (and other geometric shapes) are also usable for such pins.

Bigger surface areas in contact with the fluid flow can also give increased heat transfer efficiency. Generally speaking the laser welding step can increase the surface area of the pins -the laser welding will create surface aberrations on the pin wall, and these increase the surface area in contact with the fluid, thus further increasing the heat transfer efficiency. It is not essential, however, to make use of this feature.

Where forging is used for forming the pins, fins or projections, typically the diameter or size of the pins would be no less than 2mm at their base. They may also be tapered, for example as shown in figure 9.

Tapered pins, fins or projections might also be desirable in general.

If the pins or fins or projections are cast then they will most likely be tapered -to facilitate their removal from the die (e.g. for reusable dies).

If etched or machined or otherwise fabricated, other sizes are also achievable.

If 3D printed, such as using direct metal laser sintering, or DMLS, other shapes and forms are also achievable Since the pins, fins or projections are generally arranged internally of the heatsink, they might collectively be referred to as the internal heat-transfer elements. It will be appreciated, however, that external heat-transfer elements might also be present, and they might be continuous in at least some arrangements with some of the internal heat-transfer arrangements.

These and other features of the present invention will now be described in further detail, purely by way of example, with reference to the accompanying drawings in which: Figures 1 to 3, as described above, define prior art arrangements; Figure 4 shows a first embodiment of the present invention with a standard PE device mounted onto the top plate of the heatsink; Figure 5 shows a second embodiment of the present invention in which two standard PE devices are mounted to the heatsink, one on the top surface and one on the bottom surface; Figure 6 shows a closeup section view of the inside of the embodiment of Figure 4; Figure 7 shows a third embodiment of the present invention where projections have been formed by etching and joined to an opposing plate by laser-welding. These and similar projections could also be formed by metal injection moulding, forging, casting, electrochemical machining or spark erosion techniques.

Figure 8 shows a close-up cutaway section of the third embodiment.

Figure 9 shows a further possible second member for the present invention wherein the opposing second member is formed with tapered pins extending upwardly therefrom for welding to the underside of the first plate member. This version might be manufactured by forming the pins using a metal injection moulding process; Figure 10 shows an embodiment where the wall used to enclose the fluid space is welded to the top and bottom sheets Figure 11 shows an embodiment where the wall used to enclose the fluid space is soldered to the top and bottom sheets.

Figures 12 to 15 show an alternative mode of assembly and manufacture of the heatsink, in which arrays of pins are welded onto first and second plate members, with those pins then being intermeshed upon joining the plates together and welding the intermeshed pins onto the opposing plates so as to retain the heatsink in an assembled form; and Figures 16 to 19 show another mode of assembly where all the pins are initially joined or formed on a first plate (usually using laser welding), and a second plate is then joined onto the free ends of those pins in opposition to that first plate..

Figures 1 to 3 have already been discussed above so a further discussion herein is not provided. Referring thus instead first to Figure 4, a first embodiment of the present invention is disclosed. This embodiment is a rectangular or square heatsink, cut away for showing the detail of the pins therein. The shape, however, could be any shape. As can be seen, the heatsink 18 has an inlet 22 and an outlet 24 for passing fluid through a fluid space 20 within the heatsink 18. This fluid space is defined or bordered by a first plate member 38 and an opposing second member 40, also in the form of a plate member, and also a side wall 44 surrounding the circumference of the two plate members 38, 40. This side wall is shown to be located between the two plate members, but instead it may cap the outsides of those members. As such many alternative forms of fluid tight sealing member could be used. Figure 6 presents a close-up view of the cutaway section with the PE device omitted.

In the preferred embodiments, the sealing member is a wall connected to the sheet by means of a solder boundary, a welded edge or adhesive.

The plate members are parallel to one another in this embodiment. They are also flat or planar. Other shapes are possible instead, however, including non-flat shapes, non-corresponding shapes, and non-square/rectangular shapes.

Extending between the first plate member and the opposing second member 38, 40 is a plurality of pins, fins or projections -in this heatsink it is an array of pins extending perpendicularly to both the first plate member 38 and the second plate member 40. In this embodiment, these pins are straight and round, although other pin forms or sections will also be workable.

Mounted to the outside of the first plate member, which in this embodiment is the upper plate member, there is attached a PE device 12. The PE device, as per Figure 1, has connectors 10, and a baseplate 14. The baseplate 14 is mounted onto the first plate member 38. The space between the baseplate 16 and plate 38 is filled with a thermal paste 28, which has a high thermal conductivity. Any known mode of mounting, however, can similarly be used.

As for the inlet and outlet 22, 24, in this embodiment these are in the form of standard pipe mounts, although other arrangements can also be provided such as internally or externally threaded bosses. In this embodiment these are soldered onto the first plate member on the face of the plate member, but they may be otherwise bonded or formed thereon, or they might even be edge mounted or mounted to the opposing second member instead. They are simply shown on the first plate member for simplicity of illustration.

Figure 5 then shows a further embodiment in which two PE device 12 are mounted onto the heatsink 18. In this embodiment, the two PE devices 12 are on the first plate member 38 and the opposing second member 40 respectively. Such double sided, thin walled heatsinks are particularly useful for space saving applications since they can use the fluid to cool two power electronic devices at the same time.

Referring next to Figures 7 and 8, further examples of pins, fins or projections are shown, again rising from an opposing second member. As can be seen, in these embodiments the pins are tear or round or oval shaped and are again provided in a regular array across the majority of the array. Some of the pins could have a different orientation, size or shape to the rest if desired, e.g. to improve fluid flow in, for example, corner areas, especially for non-round versions, since they can then be angled to lie optimally for the direction of fluid flow. For example, for shapes such as oval pins, this may be so that they lie more close to parallel to the convex rounding of the wall in the corners.

Other shapes for the pins, fins or projection, including combinations of different shapes, are also usable.

Referring next to Figure 9, another possible form for the opposing second member is shown. In this example, the opposing second member 40 has formed thereon the plurality of pins 42. These pins are tapered so as to be narrow at their top and wider at their base. In this embodiment, the opposing second member 40 is also thicker than the required 1mm. The plate to be welded onto the top of the pins will thus be the thin plate, i.e. the first plate member, and it can be welded thereon using laser welding, thus forming a heatsink of the present invention once the side walls, inlet and outlet are applied thereto.

To further improve this version, the base of this second member 40 could also be made thinner, i.e. between 0.2 and 1mm, inclusive.

As with the embodiment of Figure 7, a thin first plate member can be welded on top of this opposing second member to form a heatsink of the present invention once the side walls, inlet and outlet are applied thereto.

Referring next to Figure 10, a view of an embodiment similar to that of Figure 6 is shown -prior to the application of the PE device to the top thereof. The side walls are welded between the plates and take the form of rectangular sectioned plates.

The inlet and outlet are also attached -to the upper plate. These may be affixed thereto using soldering. Inside the heatsink are the plurality of pins -in this case laser welded between the plates.

Figure 11 is similar to Figure 10, but instead shows soldered plates forming the sidewalls.

Other forms of sidewall are also possible -pure solder or polymer/potting compound are two examples of this.

In these two embodiments of Figures 10 and 11, the pins are round pins having a lmm diameter. They are positioned in a regular square array, but they might instead be positioned in a staggered array to densify their array compared to a square array.

The array of pins can be seen to be regular and with approximately a 1.0mm space between adjacent pins. Pin spacings of between 0.5mm and 5mm are considered to be of most benefit with respect to the present invention since such spacings permit fluid flow and efficient heat transfer. Wider spaces can also be used if desired, but may reduce the efficiency of the heat transfer. Likewise smaller spacings can be used, but the fluid pressures needed to pump the water through the heatsink might then increase undesirably.

Referring next to Figures 12 to 15, there is shown one mode for the assembly of a heatsink, involving two plate members, each with arrays of pins welded thereon. These two plate members can be joined together through an intermeshing of those pins and then a welding process is applied to the respective external walls of the first plate member and the opposing second member so as to weld the free ends of the respective pins to the correspondingly engaged first plate member or opposing second member. Laser welding is the preferred mode for this welding due to its controllability and applicability to welding such 1mm pins to the plates through the backs of those plates.

Referring next to Figures 16 to 19, an alternative mode of assembly is shown. In this the pins are all applied to the first plate member -via laser welding in this instance, and then a blank second plate is brought into engagement with the free ends of those pins. The pins are then laser welded to the inside surface of that second plate -via the outside surface, to join the structure of the heatsink into one. This thus then provides a strong structure, like the previous embodiment.

Either of these two construction methods could equally be applied to an etched construction (where the projections are created by etching material away from one sheet and then joined to a second sheet) and to a welded construction (where pins are welded to a sheet at each end).

These examples and other features of the present invention have therefore been described above purely by way of example. Modifications in detail may be made to the invention within the scope of the claims appended hereto.

Claims

CLAIMS: 1. A heatsink for power electric applications comprising: a first plate member, an opposing second member and side walls defining therebetween a fluid space; a fluid inlet and a fluid outlet for allowing fluid to be passed through the fluid space; and internal fluid passageways within the fluid space, which fluid passageways circulate through or around a plurality of pins, fins or projections that extend from, and that are attached to, or are integral with, the first plate member, the plurality of pins, fins or projections being within the fluid space; wherein the first plate member has a thickness in at least 50% of the areas between the pins, fins or projections, not exceeding lmm and no less than 0.2 mm.
2 The heatsink of claim 1, wherein the thickness of the first plate member between the pins, fins or projections does not exceed 1mm, and is no less than 0.2 mm, throughout the full extent of the plate that has such pins, fins or projections.
3. The heatsink of any one of the preceding claims, wherein the first plate member is made predominantly from metal.
4. The heat sink of any one of the preceding claims, wherein the first plate member is made predominantly from copper.The heatsink of any one of claims 1 to 3, wherein the first plate member is made predominantly from one or more of the following materials: aluminium, brass, steel, stainless steel, steel alloys, silver, gold, other precious metals and various mixtures or alloys thereof 6. The heatsink of claim 5, wherein the pins, plate and second member are made predominantly of copper.7. The heatsink of any one of the preceding claims, wherein the pins, fins or projections are laser welded onto the first plate member.8 The heatsink of claim 7, wherein to facilitate the laser welding of pins, fins or projections onto the first plate member, that first plate member is a sheet that is nickel plated, oxidized, blackened or otherwise surface treated prior to the welding step.9 The heatsink of any one of the preceding claims, wherein the first plate member is flat or planar.10. The heatsink of any one of the preceding claims, wherein the heatsink is double sided.11. The heatsink of any one of the preceding claims, wherein one or both of the first plate member or the opposing second member feature a fluid space provided by etching material away, leaving pins or profiles.12. The heatsink of any one of the preceding claims, wherein the pins, fins or projections range in length from 0.2mm to 20mm.13. The heatsink of any one of the preceding claims, wherein the pins are welded to the first plate member or the opposing second member, and they are between 3mm and 10mm long.14. The heatsink of claim 9, wherein to facilitate the laser welding of pins, fins or projections onto the first plate member, or the opposing second member, or both, that first plate member, that opposing second member, or both members is/are a sheet that is nickel plated, oxidized, blackened or otherwise surface treated prior to the welding step.15. The heatsink of any one of the preceding claims, wherein the first plate member is a top sheet of the heatsink 16. The heatsink of any one of the preceding claims, wherein the sidewalls are also used in the heatsink's structure further to increase structural rigidity thereof.17. The heatsink of any one of the preceding claims, wherein the opposing second member is a further plate member.18. The heatsink of claim 17, wherein the further plate member is welded to the fins, pins or projections.19. The heatsink of any one of the preceding claims, wherein the opposing second member is a further plate member having a thickness in at least 50% of the areas between the pins, fins or projections, not exceeding 1mm and no less than 0.2 mm.20. The heatsink of any one of the preceding claims, wherein all the pins, fins or projections are joined at both ends respectively to the first plate member and the opposing second member.21. The heatsink of any one of the preceding claims, wherein the pins, fins or projections are pins and they are laser welded onto the first plate member or the opposing second member, the pins having a diametrical dimension of no less than 0.5mm and no more than 2mm.22. The heatsink of claim 21, wherein the pins have a round section, the diametrical dimension being their diameter.23. A heatsink substantially as hereinbefore described with reference to any one of Figures 4 to 19.24. A method of manufacturing a heatsink according to any one of the preceding claims comprising attaching at least 50% of the pins, fins or projections to both the first plate member and the opposing second member.25. The method of claim 24, comprising attaching all of the pins, fins or projections to both the first plate member and the opposing second member.26. The method of claim 24 or claim 25, wherein the attachment of at least one of the ends of each pin, fin or projection to its respective first plate member or opposing second member is by laser welding.27 The method of any one of claims 24 to 26, wherein some of the pins, fins and projections are formed or fabricated on the first plate member and others are formed or fabricated on the opposing second member, such that they intermesh, and upon joining the two members together, the combination of the two sets of pins, fins or projections provide the bridging members between the first plate member and the opposing second plate member with the internal fluid passageways extending between those combinations of fins, pins and projections.28. The method of any one of claims 24 to 26, wherein all of the pins, fins and projections are formed or fabricated on the first plate member and the opposing second member is then subsequently joined to the free ends of those pins, fins and projections.29. The method of any one of claims 24 to 26, wherein all of the pins, fins and projections are formed or fabricated on the opposing second member and the first plate member is then subsequently joined to the free ends of those pins, fins and projections.30. A method of cooling power electronics, a battery or an IGBT arrangement comprising mounting the power electronics, battery or IGBT arrangement on a heatsink according to any one of claims 1 to 23, and passing fluid through the heatsink.