Thermal spreader, heat sink, and filling rig

Abstract

There is described a filling rig for filling a chamber located on a plate, the filling rig comprising: a connector, the connector comprising: a sealing component for sealing the filling rig to the plate at a location of a filling hole on the plate; a fill tube for injecting a working fluid into the chamber via the filling hole; a pump connected to the connector, the pump being arranged to extract air from the chamber so as to provide a low pressure in the chamber; and a working fluid reservoir, the reservoir being connected to the fill tube so as to be able to provide working fluid to the chamber via the fill tube.

Description

[0001] Thermal spreader, heat sink, and filling rig

[0002] Field of the invention

[0003] The present invention relates to a thermal spreader and to a heat sink comprising the thermal spreader. The present invention further relates to a method of manufacturing a thermal spreader and a heat sink.

[0004] Background to the Disclosure

[0005] Referring to Figure 1a, there is shown a radio access network (RAN) that is arranged to facilitate communication between computer devices. Typically, such a RAN is used in a system that comprises a plurality of RANs, where a first user is able to send information to a first RAN over a first wireless network, this information is transferred to a second RAN (e.g. via a wired or optical network), and the second RAN then sends the information to a second user over a second wireless network.

[0006] This system enables users to communicate with each other over a wide area, where a device of each user communicates wirelessly with a nearby RAN, and where a plurality of RANs communicate with each other over a (more efficient / speedy) wired or optical connection.

[0007] Older systems typically operate at relatively low transmission frequencies; with these frequencies, antennas and radio units are typically located separately and are then connected with radio frequency (RF) cable to facilitate communication between these components with minimal losses. However, with more recent standards there has been a move to higher transmission frequencies and to large active antenna arrays (that is, arrays of antennas that can steer a transmission beam to an individual user), and these changes place a physical limit on how far the antenna can be from related processing electronics without having unacceptable levels of signal degradation.

[0008] Therefore, newer technologies, such as those used in 5G, typically use massive multiple-input, multiple-output antennas (m-MIMOs) to facilitate communications with user devices, as shown in Figure 1 b. An example of a m-MIMO radio is shown in Figure 1 b, which illustrates how within these m-MIMOs the antennas are integrated with a radio unit, with the integrated unit then being mounted at the top of the RAN mast. These, newer technologies have greater functionality and typically need to dissipate higher thermal power than their predecessors.

[0009] Problematically, conventional heat sinks that might have been sufficient for cooling previous componentry of RANs can be insufficient for cooling this newer componentry.

[0010] Summary of the Disclosure

[0011] According to at least one aspect of the present disclosure, there is described a filling rig for filling a chamber located on a plate, the filling rig comprising: a connector, the connector comprising: a sealing component for sealing the filling rig to the plate at a location of a filling hole on the plate; a fill tube for injecting a working fluid into the chamber via the filling hole; a pump connected to the connector, the pump being arranged to extract air from the chamber so as to provide a low pressure in the chamber (e.g. a pressure below atmospheric pressure and / or a vacuum); and a working fluid reservoir, the reservoir being connected to the fill tube so as to be able to provide working fluid to the chamber via the fill tube.

[0012] Preferably, the filling rig comprises a hole-forming tool for forming the filling hole in the plate following the sealing of the filling rig to the plate.

[0013] Preferably, the filling rig comprises a sealing mechanism for sealing the hole using a cold weld. Preferably, the sealing mechanism is arranged for sealing the hole prior to the releasing of the sealing component from the plate.

[0014] Preferably, the pump is arranged to extract air from the chamber via the fill tube.

[0015] Preferably, the filling rig comprises a hole-forming tool (e.g. a punch or a slicing tool) for forming the filling hole in the plate.

[0016] Preferably, the filling rig comprises a sealing mechanism for sealing the filling hole, preferably for sealing the filling hole while the chamber is at a low pressure. Preferably the sealing mechanism comprises a cold weld sealing mechanism.

[0017] Preferably, the filling rig comprises a connector chamber located at a first end of the fill chamber, preferably wherein the connector chamber comprises one or more of: a widened portion, a cut-out, and a recess of the fill chamber.

[0018] Preferably, the filling rig comprises a seal die and a seal punch that are arranged to interact in order to deform material around a filling hole located between the seal die and the seal punch so as to seal the filling hole. Preferably, the connector comprises the seal die.

[0019] Preferably, the seal punch comprises an end stop.

[0020] Preferably, the working fluid reservoir is connected to the connector via a fill chamber. Preferably, the reservoir is connected to the fill chamber via a valve, preferably a needle precision valve.

[0021] Preferably, the fill chamber comprises a triangular measurement chamber.

[0022] Preferably, the filling rig comprises a sensor for determining a volume of fluid in the fill chamber.

[0023] Preferably, the filling rig comprises a sensor for determining a volume of fluid in the working fluid reservoir.

[0024] Preferably, the filling rig comprises a working fluid hopper that is arranged to provide working fluid to the reservoir. Preferably, the hopper is connected to the reservoir via a valve.

[0025] Preferably, the pump is arranged to provide a vacuum or a near vacuum in the chamber. Preferably, the pump is arranged to provide a pressure of no more than 10-4mBar, no more than 10-5mBar, and / or no more than 10-6mBar.

[0026] Preferably, the filling rig comprises a pump for providing a low pressure (e.g. a vacuum) between the sealing component and the plate so as to seal the sealing component to the plate.

[0027] Preferably, the filling rig comprises a sensor for monitoring a degassing process in the reservoir, preferably a sensor for detecting quantities of bubbles in the reservoir.

[0028] Preferably, the filling rig comprises a temperature loop for altering a temperature of one or more components of the filling rig (and / or for altering a temperature of one or more fluids within the one or more components), preferably for altering a relative temperature between two of the components of the filling rig (and / or for altering a relative temperature between two or more fluids in the two or more components).

[0029] Preferably, the temperature loop comprises a fluid loop and / or a water loop.

[0030] Preferably, the filling rig comprises one or more of: a high temperature loop for increasing the temperature of a component of the filling rig; and a low temperature loop for decreasing the temperature of a component of the filling rig.

[0031] Preferably, the filling rig comprises one or more liquid jackets located around one or more of: the connector; the reservoir; and the fill chamber.

[0032] Preferably, the filling rig comprises a controller, preferably a proportional integral derivative controller, for controlling the temperature loop.

[0033] Preferably, the sealing component comprises an O-ring and / or a suction cup.

[0034] Preferably, the filling rig comprises a degassing mechanism for degassing a working fluid in the working fluid reservoir. According to another aspect of the present disclosure, there is described a method of operating the filling rig of any preceding claim.

[0035] According to another aspect of the present disclosure, there is described a method of operating a filling rig so as to transfer a working fluid to a chamber of a plate, the method comprising: sealing a connector to the plate via a sealing component such that a fill tube of the connector is located adjacent a filling hole of the plate; creating a low pressure in the chamber, preferably using a pump of the filling rig, more preferably wherein the pump is connected to the chamber via the fill tube; and injecting a working fluid into the chamber via the fill tube.

[0036] Preferably, sealing the connector to the plate comprises creating an area of low pressure between the sealing component and the plate, preferably using a pump.

[0037] Preferably, the method comprises forming the filling hole, preferably using a punch and / or a hole-forming tool of the filling rig.

[0038] Preferably, the method comprises pressurising the chamber prior to the forming of the filling hole.

[0039] Preferably, the method comprises transferring working fluid from a working fluid hopper to a working fluid reservoir.

[0040] Preferably, the method comprises degassing the working fluid in the working fluid reservoir. Preferably, the method comprises degassing the working fluid by: reducing a pressure in the working fluid reservoir such that the working fluid starts to boil; sealing the working fluid reservoir to enable gases to collect at the top of the reservoir; and removing the gases from the working fluid reservoir.

[0041] Preferably, the degassing steps are repeated, preferably the degassing steps are performed at least three times.

[0042] Preferably, the method comprises transferring the working fluid from the working fluid reservoir to a fill chamber. Preferably, the method comprises heating the working fluid reservoir relative to the fill chamber so as to create a pressure gradient between the working fluid reservoir and the fill chamber.

[0043] Preferably, the method comprises transferring the working fluid from the fill chamber to the chamber of the plate. Preferably, the method comprises heating the fill chamber so as to create a pressure gradient between the fill chamber and the chamber of the plate.

[0044] Preferably, the method comprises sealing the filling hole. Preferably, the method comprises sealing the filling hole while the chamber of the thermal spreader remains at a low pressure.

[0045] Preferably, the method comprises: locating a seal die on a first side of the plate adjacent the filling hole; locating a seal punch on a second side of the plate; and moving the seal punch relative to the seal die (e.g. moving the seal punch towards the seal die or the seal die towards the seal punch) so as to deform the plate in the region of the filling hole so as to seal the filling hole.

[0046] Preferably, the method comprises moving the seal punch until an end stop is reached.

[0047] Preferably, the method comprises forming a chamber in the plate using the seal die and the seal punch, Preferably, the method comprises dividing a first chamber into a plurality of sub-chambers using the seal die and the seal punch.

[0048] Preferably, the method comprises removing the sealing component of the connector from the plate after the filling hole has been sealed.

[0049] Thermal spreader

[0050] According to another aspect of the present disclosure, there is described a thermal spreader for a heat sink, the heat sink being arranged to be located adjacent to components so as to cool the components, the thermal spreader comprising one or more heat transfer structures, wherein each heat transfer structure is arranged to provide a thermal connection between a plurality of components with similar operating temperatures

[0051] Preferably, the heat transfer structures are an integral part of the thermal spreader.

[0052] Preferably, the thermal spreader comprises thermosyphons and / or heat pipes that are integral to the thermal spreader.

[0053] Preferably, the thermal spreader is formed by a roll bonding process and / or a laser welding process.

[0054] Preferably, the heat transfer structures comprise inflated chambers. Preferably, the inflated chambers comprise a working fluid (e.g. a fluid that promotes heat transfer and / or a fluid with a heat capacity of at least 4,000 J / kg.K).

[0055] Preferably, the inflated chambers comprise wicks.

[0056] Preferably, one or more layers of the thermal spreader comprises paint arranged to separate adjacent layers during a roll bonding process.

[0057] Preferably, the thermal spreader comprises one or more structural inflated chambers. Preferably, the structural inflated chambers contain (e.g. are filled with) a fluid, preferably a pressurised gas or a non- compressible liquid or a (e.g. non-compressible) solid.

[0058] Preferably, the thermal spreader is formed of a plurality of sheets (e.g. two or more sheets), preferably a plurality of sheets of different composition and / or material.

[0059] Preferably, the thermal spreader comprises a first, outer, sheet, a second, inner, sheet, and a third, outer, sheet, wherein the second, inner, sheet is located between the first and third outer sheets. Preferably, the second, inner, sheet is formed of a stiffer material than the first and third outer sheets.

[0060] Preferably, the thermal spreader comprises a first heat transfer structure and a second heat transfer structure. Preferably, the first heat transfer structure overlaps the second heat transfer structure. Preferably, a first inflated chamber of the first heat transfer structure overlaps a second inflated chamber of the second heat transfer structure, wherein, at the point of overlap, the first inflated chamber is formed between the first, outer, sheet and the second, inner, sheet and the second inflated chamber is formed between the third, outer, sheet and the second, inner, sheet.

[0061] Preferably, each of the inflated chambers comprises a flattened outer surface.

[0062] Preferably, the thermal spreader comprises a plurality of inflated chambers of different heights and / or thicknesses.

[0063] Preferably, each of the inflated chambers is of a similar, and / or the same, height.

[0064] Preferably, the inner sheet comprises one or more holes, wherein each hole connects: a first inflated chamber located between the inner sheet and the first outer sheet; and a second inflated chamber located between the inner sheet and the second outer sheet.

[0065] Preferably, the thermal spreader comprises a stiffening structure arranged around at least a portion of the perimeter of the thermal spreader. Preferably, the stiffening structure comprises a structural inflated chamber.

[0066] Preferably, the thermal spreader comprises one or more walls that extend (at least partially) perpendicular to a base of the thermal spreader. Preferably, the thermal spreader comprises one or more structural inflated chambers on an exterior face of a wall. Preferably, one or more of said structural inflated chambers are connected, via a hole on the inner plate, to one or more structural inflated chambers on the base of the interior face of thermal spreader.

[0067] Preferably, the inflated chambers comprise additional elements, preferably one or more of: a wick, and a mesh. Preferably, the inflated chambers comprise a looped heat pipe.

[0068] Preferably, the thermal spreader comprises one or more structural components arranged to provide structural rigidity to the thermal spreader.

[0069] Preferably, the structural components comprise the heat transfer components.

[0070] Preferably, the thermal spreader comprises one or more insulating components for thermally isolating components with differing operating temperatures.

[0071] Preferably, the heat transfer structures comprise heat pipes and / or thermosyphons.

[0072] Preferably, the thermal spreader is formed of a plurality of layers. Preferably, each layer is separated by a thermal interface material (TIM).

[0073] Preferably, the thermal spreader comprises a trunk and one or more branches that extend from the trunk, the branches comprising the heat transfer components.

[0074] Preferably, the thermal spreader is formed using a constructal theory design.

[0075] According to another aspect of the present disclosure, there is described a heat sink comprising the thermal spreader of any preceding claim.

[0076] Preferably, the heat sink further comprises a housing. Preferably, the housing is arranged to provide electromagnetic interference (EMI) protection and / or weather protection.

[0077] Preferably, the heat sink comprises one or more heat dissipation structures, preferably one or more fins.

[0078] Preferably, the heat dissipation structures comprise a trunk and one or more branches that extend from the trunk.

[0079] Preferably, the heat dissipation structures comprise extruded heat dissipation structures.

[0080] Preferably, the heat dissipation structures are formed from a folded sheet of material, preferably a folded sheet of metal.

[0081] Preferably, the folded sheet comprises holes.

[0082] Preferably, the heat dissipation structures each comprise a trunk that extends away from the heat sink and one or more branches that extend from the trunk.

[0083] Preferably, the heat dissipation structures are formed using a constructal theory design.

[0084] Preferably, a first heat transfer component of the thermal spreader is arranged to transfer heat to a first surface of the heat sink, the first surface being adjacent a first heat dissipation structure; and a second heat transfer component of the thermal spreader is arranged to transfer heat to a second surface of the heat sink, the second surface being adjacent a first heat dissipation structure.

[0085] Preferably, the first surface and the second surface are thermally isolated surfaces.

[0086] According to another aspect of the present disclosure, there is described a telecoms device comprising the aforesaid heat sink.

[0087] Preferably, the telecoms device comprises a massive multiple-input, multiple-output antenna (m-MIMO).

[0088] According to another aspect of the present disclosure, there is described a radio access network comprising one or more of the aforesaid telecoms devices.

[0089] According to another aspect of the present disclosure, there is described a method of manufacturing the aforesaid thermal spreader.

[0090] According to another aspect of the present disclosure, there is described a method of manufacturing a thermal spreader for a heat sink, the method comprising: providing a first sheet and a second sheet; applying a paint to a surface of the first sheet; locating the first sheet adjacent the second sheet with the painted surface of the first sheet being in contact with the second sheet; feeding the first sheet and the second sheet into a rolling machine (and / or a static press) to bond the first sheet and the second sheet so as to form a thermal spreader; and inflating the thermal spreader so as to form inflated chambers between the first sheet and the second sheet at the locations of the paint.

[0091] Preferably, the method comprises: inflating the thermal spreader so as to provide a plurality of connected inflated chambers; and separating the plurality of chambers so as to form multiple separate chambers. Preferably, separating the plurality of chambers comprises deforming the thermal spreader so as to seal one or more channels connecting the inflated chambers.

[0092] Preferably, the method comprises locating a stop nearthe thermal spreader priorto the inflation of the thermal spreader so as to form inflated chambers that have flatted surfaces. Preferably, a subset of the plurality of chambers have different heights.

[0093] Preferably, the method further comprises annealing the thermal spreader.

[0094] Preferably, the method further comprises providing a working fluid to the inflated chambers. Preferably, providing the working fluid comprises creating a vacuum in the inflated chambers so as to pull the working fluid into the inflated chambers.

[0095] Preferably, the method comprises sealing the inflated chambers.

[0096] Preferably, the method comprises providing wicks in the inflated chambers.

[0097] Preferably, the inflated chambers comprise one or more of: heat transfer structures, thermosyphons, and heat pipes.

[0098] Preferably, a set (e.g. a first set) of the inflated chambers comprises heat transfer structures.

[0099] Preferably, a set (e.g. a second set) of the inflated chambers comprises structural chambers. Preferably, the structural chambers contain a pressurised fluid (e.g. gas) and / or a reinforcement structure. Preferably, the method comprises injecting a pressurised fluid into the structural chambers.

[0100] Preferably, a set (e.g. a third set) of the inflated chambers forms a channel for moving fluid (e.g. a liquid and / or a coolant) around the thermal spreader. Preferably, the channel is connected to an edge of the thermal spreader so as to enable the transfer of fluid into and / or out of the set of inflated chambers that forms a channel for moving fluid around the thermal spreader.

[0101] Preferably, the method further comprises: providing a third sheet; locating the third sheet adjacent the second sheet with the painted surface of the third sheet being in contact with the second sheet; feeding the first sheet, the second sheet, and the third sheet into a rolling machine to bond the first sheet, the second sheet, and the third sheet so as to form the thermal spreader; and inflating the thermal spreader so as to form inflated chambers between the first sheet and the second sheet and between the second sheet and the third sheet at the locations of the paint.

[0102] Preferably, the method comprises providing holes in the second sheet prior to the bonding of the first sheet, the second sheet, and the third sheet. Preferably, the method comprises drilling holes in the third sheet.

[0103] Preferably, the holes are arranged (e.g. at positions of paint on the first sheet and the second sheet) so as to provide connections between inflated chambers located between the first sheet and the second sheet and inflated chambers located between the second sheet and the third sheet.

[0104] Preferably, the method comprises providing additional elements on one or more of the sheets prior to the bonding of the sheets. Preferably, the additional elements comprise a wick and / or a mesh structure. Preferably, the sheets are combined so that the additional elements are located between the first sheet and the second sheet and / or between the second and the third sheet.

[0105] Preferably, the method further comprises manipulating the thermal spreader so as to form walls on the thermal spreader. Preferably, the method comprises deep drawing, cutting, and / or welding the thermal spreader to form the walls.

[0106] Preferably, the method further comprises adding strengthening structures to the thermal spreader, preferably strengthening embossments and / or ribs.

[0107] Preferably, the method comprises adding a working fluid to the inflated chambers.

[0108] Preferably, the method comprises adding a fluid that encourages the transfer of heat to a set of inflated chambers that comprise heat transfer structures.

[0109] Preferably, the method further comprises adding a pressurised fluid to a set of inflated chambers that comprise structural chambers.

[0110] According to another aspect of the present disclosure, there is described a method of manufacturing the aforesaid heat sink.

[0111] According to another aspect of the present disclosure, there is described a method of manufacturing a heat sink, the method comprising: locating thermal dissipation structures so as to receive heat from a thermal spreader; and combining the thermal dissipation structures with the thermal spreader.

[0112] Preferably, the heat sink comprises the aforesaid thermal spreader.

[0113] Preferably, the thermal spreader of the heat sink is manufactured using the aforesaid method.

[0114] Preferably, the method comprises: providing a housing; locating thermal dissipation structures adjacent the housing; locating the thermal spreader inside the housing; and applying pressure to the sides of the housing so as to combine the housing, the thermal dissipation structures, and the thermal spreader.

[0115] Preferably, the method comprises applying a thermal interface material to an inner surface of the heat dissipation structures prior to the locating of the thermal dissipation structures adjacent the housing.

[0116] Preferably, the method comprises applying a thermal interface material to the thermal spreader prior to the locating of the thermal spreader in the housing.

[0117] Preferably, the method comprises affixing heat transfer structures, preferably heat pipes, to the thermal spreader.

[0118] Preferably, the method comprises applying a thermal interface material to the heat transfer structures prior to the affixing of the heat transfer structures to the thermal spreader.

[0119] Preferably, the method comprises inserting attachment structures through the layers of the heat sink so as to secure together the layers of the heat sink.

[0120] Preferably, the method comprises injecting a working fluid into the chambers.

[0121] Preferably, the method comprises providing a housing for the heat sink.

[0122] Preferably, the housing comprises one or more attachment options for mounting electronics within the housing.

[0123] Preferably, the housing comprises one or more clearance structure for enabling the use of the heat sink with components of various sizes.

[0124] Preferably, the housing comprises one or more selective welds and / or selective cuts for controlling the flow of heat through the heat sink. Preferably, the housing comprises one or more thermally segregated zones, preferably wherein the thermally segregated zones are formed by providing areas of selective thinning and / or wherein the thermally segregated zones comprise their own cooling fins.

[0125] Preferably, a side wall of the housing comprises one or more sections for mounting weld studs and / or drilling or tapping holes.

[0126] Preferably, a side wall of the frame comprises a recess for accommodating a sealing component.

[0127] Preferably, the method comprises forming a side wall of a housing of the heat sink by: extruding a section of material; cutting notches into the extruded section; bending the cut section; and securing the ends of the bent section in order to form a continuous side wall, preferably wherein securing the ends comprises welding the ends. Preferably, the cuts are formed so as to not fully penetrate the extruded profile of the section.

[0128] Any feature described as being carried out by an apparatus, an application, and a device may be carried out by any of an apparatus, an application, or a device. Where multiple apparatuses are described, each apparatus may be located on a single device.

[0129] Any feature in one aspect of the disclosure may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied to apparatus aspects, and vice versa.

[0130] Furthermore, features implemented in hardware may be implemented in software, and vice versa. Any reference to software and hardware features herein should be construed accordingly.

[0131] Any apparatus feature as described herein may also be provided as a method feature, and vice versa. As used herein, means plus function features may be expressed alternatively in terms of their corresponding structure, such as a suitably programmed processor and associated memory.

[0132] It should also be appreciated that particular combinations of the various features described and defined in any aspects of the disclosure can be implemented and / or supplied and / or used independently.

[0133] The disclosure extends to methods and / or apparatus substantially as herein described with reference to the accompanying drawings.

[0134] The disclosure will now be described, by way of example, with reference to the accompanying drawings.

[0135] Description of the Drawings

[0136] Figure 1 a shows a radio access network RAN.

[0137] Figure 1 b shows an example of an m-MIMO radio.

[0138] Figure 1 c shows a die cast heat sink.

[0139] Figures 2a and 2b show a heat sink comprising a thermal spreader according to the present disclosure.

[0140] Figure 3 shows exemplary fins of the heat sink.

[0141] Figures 4a and 4b show an embodiment of the thermal spreader.

[0142] Figure 5 shows a method of manufacturing the thermal spreader.

[0143] Figures 6a, 6b, and 6c show further embodiments of the thermal spreader.

[0144] Figure 7 shows a further embodiment of a method of manufacturing the thermal spreader.

[0145] Figures 8a, 8b, and 8c show an embodiment of the thermal spreader that comprises a thinned section.

[0146] Figures 9a, 9b, 9c, and 9d shows a mould for manufacturing the thermal spreader.

[0147] Figures 10a and 10b show an embodiment of the thermal spreader that comprises integrated heat transfer structures. Figure 11 shows a method of manufacturing an embodiment of the thermal spreader.

[0148] Figures 12a and 12b show a method of forming a corner of the thermal spreader.

[0149] Figure 13 shows an alternate arrangement of fins for the heat sink.

[0150] Figure 14 shows an embodiment of the thermal spreaderthat comprises an additional structure, e.g. a structure formed of wicking material.

[0151] Figure 15 shows a method of manufacturing a thermal spreader that includes additional elements.

[0152] Figure 16 shows another method of manufacturing a thermal spreader that includes additional elements.

[0153] Figure 17 shows a method of including wicking material in a heat transfer structure of the thermal spreader.

[0154] Figure 18 shows another method of including wicking material in a heat transfer structure of the thermal spreader.

[0155] Figures 19 shows a filling hole that can be used to transfer a working fluid to a chamber of the thermal spreader.

[0156] Figures 20a, 20b, 20c, 20d, 20e, and 20f show aspects of a filling rig for transferring a working fluid to a chamber of the thermal spreader.

[0157] Figures 21 a, 21 b, 21 c, and 21 d show aspects of a method of transferring a working fluid to a chamber of the thermal spreader.

[0158] Figures 22a and 22b show aspects of a method of transferring a working fluid to a chamber of the thermal spreader.

[0159] Figures 23a - 23h show further aspects of a filling rig for transferring a working fluid to a chamber of the thermal spreader.

[0160] Figures 24a - 24b, 25, 26, 27, 28, and 29a - 29g show aspects of a housing of a heat sink.

[0161] Description of the preferred embodiments

[0162] Referring to Figure 1 c, a heat sink may be used in order to cool the componentry of the RAN (e.g. in order to cool a m-MIMO radio). Typically, the componentry is located in, or adjacent, the heat sink so that the heat sink can receive heat from the componentry and then transfer this heat to the environment surrounding the heat sink. This enables the componentry associated with the heat sink to be kept at a temperature that is within a desired operating range.

[0163] Figure 1 c shows a die cast heat sink that comprises a plurality of fins 102 that are located on a shared wall 104. As shown in Figure 1 c, in use heat is transferred from a first component 106-1 associated with the heat sink to the shared wall, and this heat thereafter passes into the fins before being transferred to the environment surrounding the heat sink. Such a heat sink can enable the temperature of the first component to be kept within an acceptable operating range.

[0164] In order to manufacture the die cast heat sink, liquid metal (e.g. aluminium) is injected into a reusable mould. A benefit of die casting the heat sink is that once the reusable mould has been formed it is possible to efficiently produce large numbers of heat sinks. However, there are a few drawbacks of using a die cast heat sink.

[0165] One such drawback is that, since the liquid metal has to be able to flow through the mould filling the entire internal volume, die casting by its very nature provides a single structure in which the fins 102 are an integral part of the shared wall 104 and in which each part of the die cast structure requires a certain thickness. As such, the fins are typically thicker than they need to be from a thermal or mechanical perspective. This increases the weight and the volume of the die cast heat sink beyond that which is necessary to provide a given amount of cooling. Additionally, there is a minimum viable thickness of the shared wall, since smaller channels restrict the flow of liquid metal, and this again leads to a higher weight heat sink than might be achieved without die casting.

[0166] Yet further, die cast structures need to be releasable from the reusable mould, and therefore all parts of the structure need a taper in the geometry. Notably, this leads to fins 102 that taper from a maximum width at the base (at the shared wall 104) to a minimum width at the tip. Such a shape is often undesirable from a heat transfer perspective as compared to, say, a fin of constant width it adds unnecessary weight not needed for strength or thermal reasons. Such a shape also limits the amount of fins that can fit on a base plate of a given size and so limits the amount of heat transfer that can be achieved using such a base plate.

[0167] Regarding the material of the die cast heat sink, this typically comprises a liquid aluminium mix that includes additives such as silicon. These additives ensure the liquid aluminium mix flows freely through the mould; problematically, these additives can reduce the thermal conductivity of the liquid aluminium mix resulting in the need for greater material thickness to achieve the same thermal spreading resistance as conventional aluminium.

[0168] Finally, and considering now the use of the die cast heat sink with reference to Figure 1 c, the heat sink is typically associated with a plurality of components 106-1 , 106-2 so as to cool each of these components. Using a single heat sink to cool a plurality of components enables the provision of compact devices with broad functionality (e.g. the first component 106-1 may comprise a base band processors and the second component 106-2 may comprise a beam forming integrated circuit). However, as shown in the detailed view of Figure 1 c, one drawback with a die cast heat sink with a shared wall 104 is thermal cross talk. That is, where the first component is operating at a higher temperature than the second component, heat may transfer from this first component to the second component as well as to the fins 102. In practice, this thermal cross talk leads to each of the components needing to be kept at the operating temperature of the component with the lowest operating temperature range to avoid overheating this lowest-temperature component.

[0169] An example of the drawbacks of thermal cross talk is found when temperature tolerant components (such as power amplifiers) are placed within range of temperature sensitive components (such as pluggable optical transducers, e.g. small form-factor pluggable (SFP) transducers). Most power amplifiers can tolerate a temperature of over 125°C, whereas SFP optical components are limited to around 85°C. Due to thermal cross talk, where the die cast heat sink is arranged to cool each of these components, the die cast heat sink must typically maintain a temperature in each component of around 85°C. This means adding extra material in the base of the heat sink to spread the heat effectively and elongating the cooling fins to reduce the temperature. And this adds unnecessary weight and volume to the die cast heat sink (since one or more of the components 106-1 , 106-2 is being cooled below its max operating temperature - this can be referred to as overcooling).

[0170] One alternative to a die cast heat sink is a bonded fin heat sink. Bonded fin heat sinks comprise a common base plate, where a plurality of separate fins can be slotted into this common base plate. Typically, the common base plate is die cast. By providing a base plate into which fins can be slotted, it is possible to use different designs of fins, e.g. fins that are punched from metal sheet so that they do not taper. This enables the use of fins that provide greater cooling than is possible with a heat sink that is a single die cast structure, since it is possible to fit more fins within the same space if the fins are thinner, thus increasing the cooling surface area within a given volume.

[0171] However, bonded fin heat sinks still have many of the drawbacks of die cast heat sinks. For example, there is still a requirement for a common base plate, which increases weight and volume and leads to thermal cross talk. Furthermore, the interface between the common base plate and the fins typically provides a region of reduced heat transfer; this can be compensated for by providing longer fins, but this again increases weight and volume. Yet further, the relative complexity of bonded fin heat sinks increases the cost and difficulty of manufacturing a bonded fin heat sink. Therefore, the present disclosure considers a heat sink that addresses, in certain embodiments, at least some of these drawbacks; for example, by thermally segregating components with different temperature operating ranges. By thermally segregating components in this way, a heat sink of the present disclosure can reduce the need for overcooling of certain components, where this enables the provision of an efficient low weight and low volume heat sink.

[0172] Referring to Figures 2a and 2b, there is shown a heat sink 200 according to the present disclosure. The heat sink comprises one or more heat dissipation structures (e.g. fins 210) that are arranged to transfer heat from one or more components associated with the heat sink to the environment surrounding the heat sink so as to maintain a temperature of these components. These fins are typically located on a housing 220 of the heat sink. The heat sink further comprises a thermal spreader 230 (that may equally be termed a ‘plate’ or an ‘adaptor plate’) that is arranged to provide a thermal connection between the components and the fins, where the thermal spreader is typically located in the housing. The housing of the heat sink may also be a housing of the components being cooled by the heat sink (e.g. both of the thermal spreader and the components may be located inside the housing of the heat sink. Equally, the heat sink may be a component that is entirely separate from the components being cooled, where this heat sink can then be attached to these components. Typically, the heat sink comprises one or more heat pipes 240 to transfer heat about the heat sink, though it will be appreciated that other heat transfer structures may be used to transfer heat about the heat sink.

[0173] Typically, the heat dissipation structures comprise fins 210 that are extruded and then cut to a desired length. This provides a simple and cheap method of providing fins. The fins may, for example, be 30mm, 50mm, or 70mm tall and may have a fin pitch of around 10mm. But it will be appreciated that various arrangements of fins are possible. The pitch of the fins may be fixed as the orientation of the fins may transition from a vertical orientation to an angled or chevron configuration so that the extrude length from a thermal point of view never exceeds a certain threshold size (e.g. 250mm). This enables the optimizing of the fin spacing for a heat sink of this threshold size so as to cover a wide range of enclosure sizes.

[0174] Referring to Figure 3, in some embodiments, the shape of the fins is based on constructal theory. Figure 3 shows exemplary shapes of fins generated in this manner. Such shapes provide increased cooling per unit weight as compared to conventional parallel fins.

[0175] More generally, in some embodiments, one or more of the fins comprises a trunk and a plurality of branches, wherein the trunk extends away from the heat sink and wherein the branches extend away from the trunk. The branches thus extend, at least partially, in a direction parallel to an external surface of the heat sink. The fins may comprise a tree structure comprising a hierarchy of one or more trunks, with each trunk comprising one or more branches that extend from the trunks, and with the branches themselves comprising one or more subbranches that extends from the branches (and so on). The fins may have: at least one tier of branches, at least two tiers of branches, at least three tiers of branches, and / or at least five tiers of branches. In some embodiments, one or more of the branches connects to a plurality of trunks (e.g. the branches may connect with adjacent branches or trunks).

[0176] The housing 220 seals a device associated with the heat sink and provides protections to the components of this device (e.g. protection from the elements and / or electromagnetic interference (EMI) and / or protection to and from any radio frequency (RF) hardware inside the housing). The housing may, for example, be formed of aluminium and may be laser cut and welded. Equally, the housing may be deep drawn or the housing may be die cast.

[0177] Referring to Figure 4a and 4b, the thermal spreader 230 comprises a plurality of heat transfer structures (e.g. thermal bridges) that are arranged to provide a thermal connection between components of the device that have similar operating temperatures. These thermal bridges typically further provide a connection between said components with similar operating temperatures and the housing 220 and / orthe fins 210 of the heat sink. By providing such a thermal spreader it is possible to provide a plurality of isolated regions that require different operating temperatures. This reduces the need for overcooling of any components and so enables the provision of smaller fins than is possible with a die cast heat sink.

[0178] The thermal spreader 230 is also arranged to thermally isolate two or more components with different operating temperatures. Typically, this thermal isolating comprises of thermally insulating these components from each other, e.g. by increasing the thermal resistance between said components. This may comprise separating the heat transfer structures associated with the different components using air (which is a thermal insulator). In this regard, the thermal spreader may comprise a plate of conductive metal, where sections are cut out of the metal to thermally isolate components from each other with the remaining portions of the metal providing the thermal bridges. The removal of sections from the adapter sheet provides both thermal isolation between regions with different operating temperatures and reduced weight.

[0179] Typically, the two or more components with different operating ranges are thermally isolated using an air gap. Equally, these components may be isolated using a thermally insulating material, such as a foam (or any other material with a low thermal conductivity).

[0180] These components with different operating temperatures may be cooled by different heat dissipation structures, such as the fins 210, where these different heat dissipation structures may be located on separate (e.g. thermally isolated) sections of the housing. Such an arrangement further reduces the possibility of thermal cross-talk.

[0181] Specifically, the thermal spreader 230 is arranged to contact a first component at a first contact point and a second component having at a second contact point and to provide a first thermal bridge connecting these first and second contact points at the first component and the second component. The first thermal bridge is arranged to connect the first component and the second component to a first shared portion of the surface of the heat sink 200 and / or to a first shared number of the fins 210 of the heat sink.

[0182] The thermal spreader 230 is similarly arranged to make contact with a third component and a fourth component and to provide a second thermal bridge connecting these contact points at the third component and the fourth component. The second thermal bridge is arranged to connect the third component and the fourth component to a second shared portion of the surface of the heat sink 200 and / or to a second shared number of the fins 210 of the heat sink.

[0183] The first component and the second component comprise components with similar operating temperatures (e.g. relatively low operating temperatures). Similarly, the third component and the fourth component comprise components with similar operating temperatures (e.g. relatively high operating temperatures). Therefore, the thermal spreader 230 may comprise a first thermal bridge for connecting components at a relatively low operating temperature (this may be termed a low-temperature thermal bridge) and a second thermal bridge for connecting components at a relatively high temperature (this may be termed a high-temperature thermal bridge). The first thermal bridge and the second thermal bridge may be separated and / or thermally isolated. Similarly, the first surface of the heat sink and the second surface of the heat sink (or the first shared number of the fins and the second shared number of the fins) may be separated and / or thermally isolated.

[0184] The first thermal bridge may be arranged to transfer heat to a first section of the housing and / or to a first heat dissipation structure. The second thermal bridge may be arranged to transfer heat to a second section of the housing and / or to a second heat dissipation structure. The first section of the housing and the second section of the housing or the first heat dissipation structure and the second heat dissipation structure may be thermally isolated.

[0185] The thermal spreader 230 is typically designed using constructal theory, so that the thermal spreader efficiently utilises material to form the thermal bridges without adding excessive weight.

[0186] As with the fins 210, the thermal spreader 230 may comprise a trunk and a plurality of branches, where the branches extend from the trunk. The branches extend, at least partially, in a direction away from the trunk (e.g. the branches extend, at least partially, in a direction perpendicular to the trunk). As with the fins, the thermal spreader may comprise a tree structure comprising a hierarchy of one or more trunks, with each trunk comprising one or more branches that extend from the trunks, and with the branches themselves comprising one or more sub-branches that extends from the branches (and so on). The thermal spreader may comprise: at least one tier of branches, at least two tiers of branches, at least three tiers of branches, and / or at least five tiers of branches.

[0187] The thermal spreader 230 is typically arranged to also provide structural strength to the heat sink (e.g. to the housing 220 of the heat sink). Therefore, the thermal spreader may be arranged to extend between the walls of the housing and to resist the deformation of these walls. The thermal spreader may comprise rigid components, such as thin metal sheet structures and bends, that are located around the perimeter of the thermal spreader so as to increase the rigidity of the thermal spreader.

[0188] The thermal bridges of the thermal spreader 230 may be formed of a conductive metal; therefore, these thermal bridges are able to serve the dual purposes of heat transfer and structural support to reduce the need for dedicated support structures.

[0189] Typically, the heat sink 200 comprises one or more heat pipes 240, where the heat pipes provide the thermal bridges (that is, the thermal bridges and / or the heat transfer structures may comprise heat pipes).

[0190] The heat pipes comprise a wick, an evaporator section, a heat transport section (e.g. an adiabatic section), and a condenser section. The evaporator section is located next to a heat source (e.g. next to one of the components being cooled), where the evaporator receives heat from this heat source that acts to evaporate a fluid in the heat pipe. The evaporated fluid flows through the heat transport section towards the condenser section, where heat is released . As the fluid releases heat, it condenses and soaks into the wick. The liquid then moves along the wick so as to return to the evaporator section. Heat pipes provide an efficient method of transferring heat.

[0191] The thermal spreader 230 may comprise one or more of these heat pipes 240, where the heat pipes may be arranged to form the thermal bridges; for example, a first heat pipe may be arranged with its evaporator section near the first component and a second heat pipe may be arranged with its evaporator section near the second component, where the condenser ends of each of the first and second heat pipe are located by the first shared portion of the heat sink so as to transfer heat from each of the first component and the second component to this first shared portion.

[0192] The heat pipes 240 may, for example, be welded onto the thermal spreader 230 or attached using an adhesive. Equally, the heat pipes may be attached to the thermal spreader by using attachment structures (such as screws), by pressure, by soldering, or by brazing.

[0193] It will be appreciated that various other structures and / or mechanisms may be used to transfer heat through the heat sink 200. For example, the heat sink may comprise one or more thermosyphons (e.g. heat pipes that contain no wick and that rely on gravity to return the condensed liquid to the evaporator section) and / or may comprise a high conductivity material such as metal or graphene that conducts heat through the heat sink.

[0194] The heat sink 200 typically comprises passive heat transfer structures that do not need to consume energy to function, such as the heat pipe. Equally, the heat sink may comprise active heat transfer mechanisms, such as fans, where an input power is provided to these active mechanisms so as to encourage the transfer of heat from the heat sink.

[0195] In some embodiments, the heat sink 200 comprises a pump (e.g. a liquid pump), where an input power is provided to the pump to move a working fluid around tubes located in the thermal spreader. Such a pump may encourage the transfer of heat from the heat sink. In some embodiments, the heat sink 200 comprises an active heat transfer mechanism that is located external to the heat sink and that acts to increase airflow over the fins so as to achieve a higher heat transfer rate from the heat sink.

[0196] The various layers of the heat sink may be joined together using an adhesive, a structural bond (such as a weld, solder, or braze) and / or attachment structures. For example, the components may be connected using rivets, or the components may be connected by pressing together the layers of the heat sink to flatten these layers together. In some embodiments, the components are connected using a clinching or cold welding process (or more generally by deforming adjacent layers of the heat sink so as to form a secure structure between these layers). Such connection methods also provide a strong thermal connection between the layers.

[0197] Prior to the joining of the layers, a thermal interface material (TIM) may be provided that fills any imperfections existing on the surfaces of the layers so as to provide an improved thermal connection between the layers. The thermal interface material may also provide adhesion between surfaces (e.g. the thermal interface may comprise a thermal epoxy). In some embodiments, the thermal interface is metal based (e.g., the thermal interface may comprise a soldered or brazed interface). Typically, thermal interface layers have a lower thermal conductivity than the material used for the fins 210, the housing 220, or the thermal spreader 230, so it is desirable to use as thin a layer of thermal interface material as possible.

[0198] Referring to Figure 5, the method of forming the heat sink 200 may comprise one or more of:

[0199] In a first step 11 , applying a thermal interface material to an inner surface of the fins 210.

[0200] In a second step 12, locating the housing 220 adjacent the fins 210 (so the housing is connected to the fins by the thermal interface material on the inner surface of the fins).

[0201] In a third step 13, applying a thermal interface material to the heat pipes 240.

[0202] In a fourth step 14, affixing the heat pipes 240 to the thermal spreader 230.

[0203] In a fifth step 15, applying a thermal interface material to the thermal spreader 230.

[0204] In a sixth step 16, locating the thermal spreader inside the housing 220.

[0205] In a seventh step 17, applying pressure to the sides of the housing 220 (which typically surround the thermal spreader 230) to press the various layers together and to minimise the thickness of the various thermal interface layers.

[0206] In an eighth step 18, inserting attachment structures through the layers of the heat sink to hold the various layers together more securely.

[0207] In a ninth step 19, removing any excess thermal interface material.

[0208] It will be appreciated that these steps may be carried out in a different order and that certain steps (in particular the first step 11 , the third step 13, the fifth step 15, the eighth step 18, and the ninth step 19) are optional.

[0209] Referring to Figures 6a and 6b, there is shown an embodiment of the thermal spreader 230 in which the heat pipes 240 (or thermosyphons, or more generally the heat transfer structures) are an integral part of the thermal spreader.

[0210] More specifically, this embodiment of the thermal spreader 230 comprises a plurality of chambers (e.g. contoured chambers or inflated chambers), which chambers comprise heat transfer structures such as thermosyphons or heat pipes.

[0211] Referring to Figures 6b and 6c, the thermal spreader 230 may comprise a wall that is also a part of the thermal spreader, where this wall provides the functions of the enclosure 220. More generally, the thermal spreader may comprise structural elements that allow it to be integrated into another component with the thermal spreader forming both thermal and structural elements of the overall device. Therefore, this thermal spreader may be used without the enclosure. The wall may be formed, for example, by drawing the thermal spreader.

[0212] Such a thermal spreader may be formed using a roll bonding technique as described with reference to Figure 7. Equally, this embodiment of the thermal spreader could be formed by soldering or brazing or gluing or welding two plates together.

[0213] In a first step 21 , a paint is applied to a first (typically metal) sheet; for example, a graphite paint is silk screened onto an aluminium sheet. The paint defines areas of the first metal sheet that will not be bonded together in the later steps of the roll bonding method.

[0214] In a second step 22, a second (typically metal) sheet is placed on top of the first sheet with the painted side of the first sheet being in contact with the second sheet.

[0215] In a third step 23, the two sheets are fed into a (hot or cold) rolling machine to bond the two sheets into a combined plate (e.g. to form the thermal spreader 230). Typically, the combined plate (hereafter referred to as the thermal spreader) is annealed following the rolling process to reduce any stresses that have built up during the rolling process. The thermal spreader typically comprises the thermal spreader and it should be appreciated that any concepts disclosed herein with reference to the ‘thermal spreader’ may similarly be implemented for the ‘thermal spreader’ (and vice versa).

[0216] Equally, the two sheets may be bonded using a static press or another bonding technique such as welding, brazing, gluing, sintering, or soldering.

[0217] In a fourth step 24, the thermal spreader 230 is inflated using a high pressure fluid (e.g. a liquid or gas) so that each of the areas that have been painted expand. This provides a plate with each of flat areas and inflated areas / inflated chambers (e.g. where the inflated chambers provide the heat transfer or structural structures).

[0218] Following this fourth step 24, individual chambers are typically sealed off from an inflation line to form individual chambers on the same thermal spreader.

[0219] In this regard, the paint is typically applied so as to form connected areas and to provide a channel to an edge of the thermal spreader. This enables the inflating fluid to be provided via the channel so as to inflate each of the painted areas. Separate inflated chambers may then be formed by sealing the channel and by sealing the connections between the various inflated areas from each other (e.g. by deforming the thermal spreader to close any channels connecting adjacent inflated chambers). Such a method of forming and separating inflated chambers enables each chamber to be inflated from a single inflation point before these chambers are separated.

[0220] In a (optional) fifth step 25, a (e.g. small amount of) working fluid is provided to the inflated areas (e.g. to the ‘chambers’). The method may comprise, prior to the provision of the working fluid, creating a vacuum in the chambers to remove undesirable gasses and contaminants. Thereafter, the working fluid is transferred into the chambers, and then the chambers are sealed to create a thermosyphon.

[0221] In some embodiments, wicks are added to the chambers; for example, by inserting scrolled up fine metal meshes (that act as wicks) through holes that have been drilled into the thermal spreader 230. Equally, metal powders may be inserted into these holes. Where a metal powder is used, a vibration plate may then be used to level the powder, with the thermal spreader then being placed in a high temperature oven to sinter the metal powder so as to form a sintered wick. Equally, the powdered metal could be pressed externally to fix it in place.

[0222] More generally, in some embodiments, the paint and inflation process is implemented so as to provide heat pipes within the thermal spreader, which heat pipes comprise wicking sections.

[0223] In some embodiments, in the fifth step 25, a thermally conductive material is added to the chambers to promote higher heat transfer rates compared to the base materials; for example, materials such as graphite may be injected into the chambers. In some embodiments, phase change materials are inserted into the chambers to absorb heat and to manage thermal power peaks.

[0224] Typically, the above-described method is used to provide a thermal spreader comprising a plurality of thermosyphons, vapour chambers, or heat pipes - and this method enables a quick, effective, efficient, and cheap method of providing a thermal spreader that can efficiently transfer heat between regions of the thermal spreader.

[0225] Typically, each of the first and second sheets comprises an aluminium sheet. It will be appreciated that other materials can be used and that while the first and second sheets are typically made of different grades of the same material, these sheets may be made of different materials and / or compositions.

[0226] Furthermore, the integral heat transfer structures typically provide structural rigidity to the thermal spreader 230 to improve the amount of support provided to the housing 220 by the thermal spreader.

[0227] It will be appreciated that the formation of the chambers may be achieved using methods other than roll bonding. For example, the chambers may be formed by stamping chambers on one or more first sheets and then combining these first sheets with a second sheet to provide the chambers between the first and second sheets. Other methods of forming the thermal spreader 230 include welding, brazing, soldering, and / or gluing together a plurality of sheets.

[0228] The heights of the chambers of the thermal spreader 230 are typically selected so as to minimise the thickness of the thermal interface material that is present between the thermal spreader and the components and to contour to features on the adjacent electronics boards. In particular, the method of Figure 7 is typically performed so as to obtain a plurality of inflated chambers of variable (or different) height (or thickness) so that there is no necessity to compensate for differences in height using thermal interface material. Furthermore, the thermal spreader is typically inflated so as to obtain inflated chambers with flattened surfaces, to improve a thermal connection between said chambers and components located adjacent said chambers. This may involve the thermal spreader (and a mould used to form the thermal spreader) being formed so as to provide inflated chambers of differing heights.

[0229] In order to accurately control the size and shape of the inflated chambers, two different grades, thicknesses, or types of metal may be used for the first and second metal sheets. This can be used to ensure that the inflation occurs only in one location (e.g. if the first sheet is much thicker than the second sheet, then the first sheet will stay roughly unchanged as the second sheet deforms to form the inflated chambers).

[0230] Therefore, the first metal sheet may be: thicker, stiffer, and / or harder than the second metal sheet (or vice versa).

[0231] In some embodiments, chambers of different heights are achieved by modifying (e.g. machining) the first sheet, the second sheet, and / or the thermal spreader 230 before inflation so as to change the thickness of a section of the first sheet, the second sheet, and / or the thermal spreader.

[0232] An exemplary process for obtaining inflated chambers of a desired height is described below with reference to Figures 8a - 8c.

[0233] Referring to Figure 8a, in a first step, a portion 802 of the thermal spreader 230 is machined (or otherwise modified) before inflation in order to decrease the thickness of this portion of the plate and to form a thinned portion. This thinned portion will deform at a lower force than the other, un-thinned, portions of the thermal spreader. The thinned portion typically relates to one of the chambers that will be inflated during the inflation step. Where a uniform force is placed on all of the chambers during this inflation step, the thinned portion will deform more than the other chambers and so the corresponding chamber will be of a greater height than the other chambers. The exact height of the chamber that corresponds to the thinned portion will depend on the amount of material removed. Referring to Figures 8b and 8c, the thinned portion 802 is shown alongside an un-thinned portion 804 after the inflation step has been performed. Figure 8c shows a cross-section of the thermal spreader 230, which shows how the thinned portion is associated with a taller (or thicker) chamber than the un-thinned portion.

[0234] In some embodiments, the thinned portion 802 corresponds to a contact portion, which contact portion is arranged to contact a component to be cooled. The thermal spreader may comprise a plurality of thinned portions to provide a plurality of contact portions, these portions each being associated with a component to be cooled (which component may be placed in contact with the contact portion a substantial time after the manufacture of the thermal spreader). This enables a number of relatively tall (and typically flat-topped) contact points to be provided that receive heat from the components and then transfer this heat to relatively short heat transfer structures that move the heat through the heat sink. The use of thinned material for the contact points also reduces the force needed to flatten a surface of these contact points.

[0235] The shape of the chambers themselves may also be used to control the height of the chambers, e.g. wider channels inflate more than narrow channels. Combining shaping of the chambers with the selective thinning of the chambers provides an improved ability to profile the inflated chambers to mate with the electronics to be cooled.

[0236] A mould that may be used to provide a combined plate (e.g. the thermal spreader 230) of desired thickness is shown in Figures 9a - 9d, which figures show the mould in both open and closed positions as well as showing cross sections of the mould.

[0237] The mould comprises a plurality of channels corresponding to the painted sections of the sheets, where these channels provide space for the chambers to inflate. The mould further comprises one or more stops that are located so as to be above the (e.g. second sheet of the) thermal spreader 230 prior to the inflation of the inflated chambers. The stops prevent the full inflation of the inflated chambers so as to provide inflated chambers with flattened surfaces (as opposed to the rounded surfaces that are obtained when the chambers are inflated without any external forces being place onto the chambers. In particular, the stops may be located so as to be adjacent thinned portions of the thermal spreader; with such an arrangement, the stops can be used to provide flattened contact points that can be placed next to components so as to receive heat from these components.

[0238] The mould of Figures 9a - 9d both controls the height of the inflated chambers as well as flattening the areas where the thermal spreader 230 will make contact with the components of the device being cooled (e.g. through a thermal interface material). As described above, two different grades or thicknesses of metal may be used to make sure the inflation goes in one direction and / or to ensure that inflation is resisted by one half of the mould. At the end of this inflation step, the thickness of the thermal spreader, and the heights of the inflated chambers, are accurately set ready for an electronic board to be attached with the need for only a minimal amount of thermal interface material.

[0239] Furthermore, performing the inflation stage between a contoured and featured mould allows additional surface structural or thermal features to be integrated in the inflation step. Details on the mould, such as structural ribs / indentations will be transferred to the expanding aluminium sheet within.

[0240] The thermal spreader 230 comprises inflated (or contoured) chambers that are used to provide the heat transfer structures. The thermal spreader may equally (or alternatively) comprise structural chambers, or structural inflated chambers, that are arranged to increase the rigidity and structural strength of the thermal spreader. The structural chambers may be filled with a pressurised fluid (e.g. a pressurised gas or liquid) so that the fluid stiffens the structure and resists any deformation of the structural chambers and / or the thermal spreader. Equally, a structural mesh, or another reinforcing structure, may be located in the structural chambers to resist deformation. This enables the provision of a stiff thermal spreader so that the thickness of the (separate) housing 220 may be reduced or the housing may even be removed completely since the thermal spreader can provide structural rigidity for the heat sink (e.g. as shown in Figure 6c). The thermal spreader with removed ‘housing’ may have the side walls formed by e.g. deep drawing or cut and welding in order to form the housing. Alternatively, the thermal spreader may be combined with e.g. an extruded or cast or roll bond frame and welded, bonded or brazed to the thermal spreader to form the housing.

[0241] Referring to Figure 10a and 10b, there is shown another embodiment of the thermal spreader 230. In this embodiment, the thermal spreader is combined with the housing 220.

[0242] The embodiment of the thermal spreader 230 of Figures 10a and 10b comprises three (or more) layers. This enables heat transfer structures to be routed through the different layers of the thermal spreader so as to cross over the thermal spreader 230. For example, the three layer (e.g. bonded) plate enables a working fluid within an inflated chamber to pass along a first inflated chamber 235 that is located between the first sheet 231 and the second sheet 232 of the plate, to pass through a first hole 236 in the second sheet of the plate, and to pass into a second inflated chamber 237 that is located between the second sheet 232 and the third sheet 233 of the plate. The fluid may then pass through a second hole 238 in the second sheet and into a third inflated chamber 239 that is again located between the first sheet and the second sheet of the plate.

[0243] This embodiment of the thermal spreader 230 therefore allows thermal bridges to be built more efficiently between various regions of the thermal spreader. For example, the above structure enables a heat transfer structure comprised of the first inflated chamber 235, the second inflated chamber 237, and the third inflated chamber to pass from a first side of the second sheet 232 (between the first sheet 231 and the second sheet) to a second side of the second sheet (between the second sheet and the third sheet 233), and back to the first side of the second sheet. This enables a first heat transfer structure to cross over a second heat transfer structure without interfering with the operation of that second heat transfer structure. This also enables the avoidance of clashes with any high-profile components on the electronics board.

[0244] Such an inflated chamber that passes through the second sheet may also be used to provide a structural chamber.

[0245] In other words, a first inflated chamber may overlap a second inflated chamber, wherein, at the point of overlap, the first inflated chamber is formed between the first, outer, sheet and the second, inner, sheet and the second inflated chamber is formed between the third, outer, sheet and the second, inner, sheet.

[0246] An exemplary method for forming the thermal spreader 230 of Figures 10a and 10b is described with reference to Figure 11 .

[0247] In a first step 31 that occurs prior to the bonding and inflation of the layers, holes are provided in the second (middle) sheet, e.g. holes may be drilled through this second sheet, so as to provide the connections between the first and third (outer) sheets of the thermal spreader 230 that will be formed after the bonding and inflation processes.

[0248] In a second step 32, a third step 33, a fourth step 34, a fifth step 35, and a sixth step 36 that correspond to the first step 21 , second step 22, third step 23, fourth step 24, and fifth step 25 of the method of forming the second embodiment of the thermal spreader 230, paint is applied to one or more of the sheets (typically to the first sheet and the third sheet), the sheets are located together with the second sheet placed between the first and third sheets, and the sheets are then inflated to form the inflated chambers.

[0249] The holes that are drilled in the second sheet in the first step 31 are located so as to join inflated chambers located between the first and second sheets and inflated chambers formed between the second and third sheets. Typically, the holes in the second sheet are provided to overlap with paint that is provided on the first and third sheets.

[0250] Typically, the second sheet is stiffer, thicker, and / or of a higher grade material (e.g. a material with a higher Young's modulus) than the first sheet and the third sheet so that when the inflation step occurs the second sheet remains substantially unchanged and the first and third sheets deform and stretch to either side of the second sheet. Typically, the first sheet and the third sheet are formed of the same material, although equally different materials may be used for the first and the third sheet, e.g. to provide an asymmetric plate.

[0251] With this embodiment of the thermal spreader 230 in particular (but also with the other embodiments described herein), the housing 220 and the thermal spreader may be integrated so that the walls of the thermal spreader 230 provide the functionality that is otherwise provided by the walls of the housing 220.

[0252] The integration of the thermal spreader 230 with the housing 220 enables the inflated chambers that form the heat transfer structures to be located near the exterior of the heat sink. This has the effect of lowering the thermal resistance between the component that requires cooling and the surface that is removing the heat, e.g. a convection surface that transfers the heat to the surrounding air. Therefore, the heat transfer structures enable the transfer of heat to the environment as well as between locations on the thermal spreader. This further increases the overall cooling performance provided by the heat sink.

[0253] To provide structural strength to the thermal spreader 230, a skeleton structure of structural inflated chambers may be formed that is separate to the inflated chambers of the heat transfer structures. This skeleton structure may be filled with a pressurised fluid to provide rigidity. For example, during the formation of the plate, structural inflated chambers may be formed around the perimeter of the thermal spreader with these chambers then being filled with pressurised fluid (e.g. pressurised gas) to provide structural strength. In one embodiment, an inflated ring may be formed around the perimeter of the thermal spreader to provide walls.

[0254] Equally, the skeleton structure may be combined with the heat transfer structures, where the inflated chambers may be used to provide both heat transfer and structural rigidity.

[0255] Typically, following the inflation process, the structural inflated chambers are filled with a pressurised fluid such as pressurised air or a non-compressible liquid, where this provides increased rigidity. It will be appreciated that numerous other substances could be used to fill the chambers (e.g. shock absorbing substances, elastomers, cross-bracing, phase change materials, etc. Furthermore, the structural chambers could be used for further purposes, such as for protecting components of a heat sink, and / or to provide wire / cable routing conduits, etc.).

[0256] Referring to Figures 12a and 12b, for the purposes of forming strong walls, the method of forming the plate may comprise forming holes in the second sheet to enable the formation of one or more structural (e.g. pressurised) chambers that extend from the interior of the heat sink (e.g. from an inflated chamber located between the first and second sheets) to the exterior of the heat sink (e.g. to an inflated chamber located between the second and third sheets). Such an arrangement provides a thermal spreader with tightly bent corners that are not substantially kinked. This technique may also be used to form heat transfer elements that effectively transfer the heat from electronic components across the base plate and up the walls of the enclosure.

[0257] Forming the thermal spreader 230 may comprise drilling a hole in the second sheet at a corner location where, subsequent to the inflation step, the thermal spreader of the thermal spreader 230 is then bent at the corner location to form a thermal spreader with walls. The walls are typically at the edge of the thermal spreader and, as shown in Figures 12a and 12b, the thermal spreader may comprise a first inflated chamber on the interior side of a first wall and a second inflated chamber on an exterior side of a second wall that is attached to, and perpendicular to, the second wall, where the first inflated chamber is joined to the second inflated chamber via a hole in the second sheet of the thermal spreader.

[0258] Referring to Figure 13, there is shown an alternate embodiment of the heat dissipation structures, e.g. the fins 210, that is of particular use with the latter-described embodiments of the thermal spreader 230 (those embodiments comprising inflated chambers and in particular those embodiments comprising overlapping inflated chambers). While the fins may be formed by extrusion, various other methods of forming the fins are possible. As an example that is shown in Figure 13, the fins may comprise folded fins in which a sheet is folded into a concertina shape and thereafter attached to the body of the heat sink. With such a method of forming the fins, holes can be punched into the sheet prior to the folding process so as to provide clearance for the inflated chambers (e.g. the structural chambers of the heat transfer structures). This can facilitate, for example, the overlapping of multiple heat transfer structures.

[0259] Referring to Figure 14, there is shown an embodiment of the plate in which additional elements are added to the heat transfer structures before the bonding of the sheets and the inflation. In this embodiment, wick sections are added to the heat transfer structures prior to the inflation so that, following the inflation, the heat transfer structures comprise heat pipes. The wick sections may, for example, comprise sintered particles or a mesh structure. While this embodiment considers the use of heat pipes for the heat transfer structures, as has been described above, the heat transfer structures may comprise heat pipes, thermosyphons, vapour chambers, or any other type of heat transfer structure.

[0260] The use of such additional elements enables the inflated sections to be arranged to provide additional heat transfer, additional rigidity, or more generally additional functionality. For example, the addition of the wick sections increases the thermal performance of (wickless) thermosyphons.

[0261] In some embodiments, the method of bonding the sheets comprises including a looped heat pipe (e.g. a looped heat pipe evaporator) in the inflated sections, where this looped heat pipe may be added before or after the inflation of the chambers. The use of a looped heat pipe provides additional functionality where the gravity driven return of a fluid in the heat transfer structures is not guaranteed, e.g. in aerospace contexts.

[0262] Referring to Figure 15, there is described a method of forming such a thermal spreader with additional elements. The method of forming the thermal spreader 230 may comprise any one or more of the below steps:

[0263] In a first step 41 , holes are stamped into a second (inner) sheet (or ‘layer’) of the plate.

[0264] In a second step 42, paint is applied to a first (outer) sheet and a third (outer) sheet of the plate. Equally, paint may be applied to the second (middle) sheet.

[0265] In a third step 43, additional elements, such as an internal mesh or the wicking structures, are added to one or more of the sheets.

[0266] In a fourth step 44, the sheets are combined with the second sheet being located between the first and third sheets and the additional elements being located between the first and second sheets or between the second and third sheets. The sheets are then (e.g. roll) bonded to form the thermal spreader 230.

[0267] In a fifth step 45, the plate is deep drawn (or cut and welded, or combined with a frame that is extruded, cast, or roll bonded) to form the walls of the plate, which walls provide certain functionality of the housing 220.

[0268] In a sixth step 46, the plate is inflated to form the inflated chambers (or ‘channels’) of the thermal spreader 230. Additional features such as strengthening embossments, ribs etc. can be added to the inflated plate through detailing on the inflation mould.

[0269] In a seventh step 47, working fluid is added to the chambers. For example, a fluid is added to the heat transfer structures that encourages the transfer of heat between the ends of these structures, and pressurised fluid is added to the structural chambers to increase the rigidity of the thermal spreader 230. In general, mechanical (or structural) channels may have additional material / fluid / etc added to provide enhancement such as strength, vibration damping, thermal reasons etc. Thermal channels may be filled with working fluid.

[0270] In an eighth step 48, the inflated chambers are sealed (typically sealed under vacuum).

[0271] Figure 16 shows another, detailed embodiment of a method for forming the thermal spreader. The formation of the thermal spreader 230 with additional elements enables a yet further improvement in the cooling capabilities of the thermal spreader at the cost of some additional complexity in the manufacture process.

[0272] As described above, wicking material may be included in the thermal spreader 230 in order to provide heat pipes that form the heat transfer structures. Wicking material provides a capillary pumping pressure for a working fluid of the heat pipes so that a heat pipe is less reliant on gravity than a thermosyphon (that does not contain wicking material). Providing heat pipes therefore improves the reliability and versatility of the heat sink. An exemplary method of adding wicking material to the chambers so as to form heat pipes is described below with reference to Figures 17a-17e.

[0273] Referring to Figure 17a, there is shown a plate that comprises an inflated chamber 302 (e.g. as may be formed after the fourth step 24 of the method of Figure 7.

[0274] Referring to Figure 17b, in order to insert a wicking material (such as a wire wool, a wire mesh, sintered or non-sintered fine particles, etc.) into the chamber 302, a method of manufacturing the thermal spreader 230 may comprise forming (e.g. machining) a hole 304 in the chamber and then inserting a wicking material 306 into the chamber via the hole. The size of the hole is typically dependent on the material that is to be added, where different materials may be used for different contexts (e.g. based on thermal requirements of the heat sink).

[0275] As examples of the addition of wicking materials: wire mesh may be compressed before being inserted into the hole, where the mesh would then expand to form the wick of a heat pipe; wire wool may be positioned to the side of the inflated chamber and then the tube pressed to secure the wool in a desired position; fine metal particles may be introduced into the chamber and then, optionally, sintered afterwards in order to bond the particles together; a mandrel may be positioned in the centre of the roll bond tube with fine metal particles then being packed around the mandrel before the plate is placed in a furnace, the particles are sintered to bond the particles together, and finally the mandrel is removed.

[0276] Referring to Figure 17c, once the wicking material 306 has been added to the chamber 302, a portion 308 of the chamber may be pressured or deformed in order to fix the wicking material in place. Equally, a fixing structure may be placed in, or inserted through, the chamber to fix the material in place. For example, where the wicking material is a single structure, opposing ends of this structure may be fixed to opposing ends of the chamber in order to ensure that the wicking material extends through the whole chamber.

[0277] Referring to Figure 17d, once the wicking material 306 is inserted in the tube and is in a desired position, the chamber 302 is sealed. Sealing the chamber may comprise one or more of: applying a sealing component, such as a cap, to the hole 304; pinching the end 310 of the chamber so as to close the hole; and welding the chamber so as to close the hole.

[0278] Referring to Figure 17e, an exemplary operation of the heat pipe is shown. In this embodiment, multiple heat sources 312-1 , 312-2 (e.g. components) are positioned at different positions on the evaporator section of the heat pipe. These heat sources transfer heat to the working fluid of the heat pipe, which working fluid carries the heat towards a condenser end 314 of the heat pipe. The working fluid then condenses and moves along the wicking material towards an opposite, evaporator, end 316 of the heat pipe, where the working fluid is then heated by the heat sources. This causes the working fluid to heat and to evaporate and to move back towards the condenser end of the heat pipe.

[0279] A further exemplary method of locating a wicking material in a chamber is described with reference to Figures 18a-18d. These figures illustrate an embodiment of forming the thermal spreader that provides looped heat pipes.

[0280] Referring to Figure 18a, there is provided a thermal spreader that comprises a looped chamber 322. Typically, the chamber comprises an outer loop as well as a plurality of columns linking opposing sides of the outer loop (where each column may be associated with a different heat source). In some embodiments, the chamber is arranged to extend to the edge of the thermal spreader, e.g. to an inflation point at which air can be inserted into the thermal spreader to inflate the chambers. With such an arrangement, the wicking material 326 may be added to the chamber at the inflation point 324; this avoids the need to form a separate hole in the chamber to insert the wicking material.

[0281] Referring to Figure 18b, once the wicking material 326 has been added to the chamber 322, a bottom section 328 of the chamber is pressed to push a channel into the surface of the chamber and to secure the wicking material in place. This step further ensures there are no large gaps between the wicking material (e.g. gaps larger than the porosity of the wick) so as to ensure that the working fluid can only flow in one direction along the wick.

[0282] Referring to Figure 18c, the open end 324 of the chamber 322 is then sealed and working fluid is added to the chamber.

[0283] The operation of this multi heat source looped heat pipe is shown in Figure 18d. As shown in this figure, multiple heat sources 330 (e.g. components) are located along different sections of the looped heat pipe. These components transfer heat to the working fluid in the heat pipe, which causes a change of phase of that working fluid (e.g. which vaporises the working fluid). The ensuing vapour flows vertically along the looped heat pipe towards a condenser end 332 of the heat pipe, at which point the working fluid condenses and then flows back towards the evaporator end 334 of the heat pipe. The wicking material 336 then pulls the fluid back to the heat sources via capillary action completing the loop.

[0284] It will be appreciated that the shape of the looped heat pipe shown in Figures 18a-18d is exemplary and that any looped shape is possible. Furthermore, the heat sources may be located at different levels with the wicking material being used to supply these heat sources (or rather the portion of the heat pipe adjacent these heat sources) with condensed working fluid via capillary action.

[0285] As shown by Figures 18b and 18c, the looped heat pipe may be provided so that only the evaporator end 334 of the looped heat pipe comprises inflated chambers on each of the component sheets of the thermal spreader with the remaining chambers of the looped heat pipe being located on only a single side of the thermal spreader (e.g. on the side that will contact the components that will be cooled by the heat sink).

[0286] Filling rig

[0287] In order to provide a thermal spreader, and heat transfer structures, with a high heat transfer capacity, it is desirable to ensure that the chambers are filled with working fluid and are free from contaminants (e.g. dust and dirt and non-condensable gasses). Therefore, the chambers are typically sealed under vacuum after being filled with working fluid.

[0288] Referring to Figure 19, there is shown a first side of a thermal spreader that comprises an inflated chamber 302 that is created, e.g. using a roll bonding process as well as a second side of that same thermal spreader that comprises a filling hole 402. In this regard, in order to provide a working fluid to the chamber, a hole may be formed that enables access to the chamber (the hole may be formed on either side of the chamber).

[0289] Typically, the thermal spreader 230 is formed so that only one side of the thermal spreader comprises inflated chambers. This provides a flat surface on the second side of the thermal spreader on which the filling rig can be placed. Using the filling rig on a flat surface simplifies the process of sealing the filling rig to the surface so as to prevent the ingress of contaminants and non-condensable gases as the working fluid is injected into the chamber. It will be appreciated that the filling rig could equally be used to fill a contoured surface with inflated chambers on both sides of the thermal spreader, e.g. where the filling rig comprises a similarly contoured surface so that it rests on top of the contoured surface of the thermal spreader). Typically, the hole 402 is drilled, punched, or sliced in the thermal spreader 230. Beneficially, if a punching or slicing method is used, no swarf is created and no material is removed from the thermal spreader (if created, swarf might lead to blockages or might necessitate more regular cleaning of the filling rig thereby decreasing the effectiveness and efficiency of the filling rig, and not removing material is beneficial when it comes to resealing the hole after filling). The hole may be created using a separate tool or may be created using a punch that is connected to the part of the filling rig that injects fluid into the chambers.

[0290] In some embodiments, the chamber is pressurized prior to the forming of the hole. This prevents collapse of the chamber when the hole is formed. The chamber may, for example, be pressurized by injecting a pressurizing fluid into the chambers via the inflation point (where this inflation point may then be sealed before the filling rig is attached to the thermal spreader and the filling hole 402 is formed.

[0291] Referring to Figure 20a, there is shown an embodiment of a filling rig that may be used to inject a working fluid into the chamber.

[0292] The filling rig comprises: a low vacuum pump 401 , a first valve 404 connecting the vacuum pump to a connector 410, and a second valve 406 connecting the connector to the atmosphere. The first valve and the second valve are typically connected to the same inlet of the connector.

[0293] The connector 410 comprises a sealing component 412 for sealing the connector onto the thermal spreader. The sealing component may, for example, comprise an O-ring seal and / or a suction cup. The connector further comprises a temperature control inlet 414-1 and a temperature control outlet 414-2 that are described further below. The connector further comprises a fill tube 416 and a vacuum tube 418, where the vacuum tube is connected to the vacuum pump.

[0294] The connector 410 is arranged to be attached to the thermal spreader via the sealing component 412, e.g. via the suction cup with the fill tube 416 of the connector being aligned with the filling hole 402 on the thermal spreader. Once the connector is attached to the thermal spreader, the first valve 404 is opened and the second valve 406 is closed and the vacuum pump 401 is operated so as to create a vacuum that pulls the connector into the plate (thereby sealing the connector and the plate). This forms an airtight seal about the sealing component and the filling hole. The first valve 404 can then be closed and the low vacuum pump 401 can be switched off (or even disconnected from the filling rig).

[0295] In some embodiments, the filling rig further comprises a punch or slicing tool (or more generally a hole-forming tool) for forming the filling hole 402 in the thermal spreader. By combining the hole-forming tool with the filling rig, it can be ensured that the fill tube 416 is always aligned with the hole.

[0296] Typically, the hole-forming tool is arranged to form the hole while the connector and the fill tube 416 are at low pressure (e.g. under vacuum). Any contaminants formed during the formation of the hole (and any contaminants that are present in the chamber) are then drawn out of the chamberdue to the vacuum. Typically, this formation of the hole occurs without any oxidization of the exposed metal since any air and contaminants in the chamber that might cause oxidation are removed from the chamber rapidly due to the substantial pressure difference between the inflated chamber and the fill tube 416 at the time of forming the hole (it is at least for this reason that the low pressure is provided in the fill tube prior to the formation of the hole). This lack of oxidation simplifies the closure of the hole after a working fluid has been transferred into the chamber.

[0297] Beneficially, the use of the hole-forming tool enables a hole to be formed at any point in the chamber (so this avoids the need to align the filling rig with a pre-existing hole). Furthermore, the use of a piercing, punching, or slicing tool provides a hole without removing substantial amounts of material from the thermal spreader (as would occur if, for example, a drill were used to form the hole). This hole-forming tool thus simplifies the closure of the hole after a working fluid has been transferred into the chamber (as will be described further below), since this remaining material is usable to seal the hole. Referring to Figure 20b, once the connector 410 is firmly attached to the thermal spreader via the sealing component 412 (so as to form a seal), a high vacuum pump 422 is attached to the connector. The high vacuum pump is connected to the connector via a third valve 434 and a fourth valve 436 that are located in series. A fifth valve 438 connects the central portion of this attachment (the portion between the third and fourth valves) to the atmosphere.

[0298] In order to remove contaminants and non-condensable gases from the chamber 302, the third valve 434 and the fourth valve 436 are opened and the high vacuum pump 422 is then operated so as to remove air and other non-condensables from the chamber. Typically, the fill tube 416 doubles as a high vacuum tube, where the high vacuum pump is connected to the fill tube so as to extract non-condensables and any contaminants via the fill tube.

[0299] Typically, the high vacuum pump 422 is arranged to achieve a pressure in the chamber 302 of no more than 10-4mBar, no more than 10-5mBar, or no more than 10-6mBar. Higher vacuums can be used (e.g. ~10mBar - 10-4mBar, but these may leave some non-condensables within the chamber after sealing); higher vacuums may be used in situations where a rapid production / filling speed is prioritised over maximising the performance of the thermal spreader. Once this pressure has been obtained, the fourth valve 436 is closed and the third valve 434 and the fifth valve 438 can then be opened to return the high vacuum pump to atmospheric pressure.

[0300] In some embodiments, a vacuum chamber is provided between the fourth valve 434 and the high vacuum pump 422. Such a vacuum chamber can act as a vacuum capacitor where the vacuum pump is able to pull a low vacuum in the chamber so that when a part is attached to the connector 410, the filling rig is able to quickly pull the desired vacuum. Where such a vacuum chamber is provided, the volume of the vacuum chamber is typically arranged to be at least 5 times, at least 10 times, and / or at least 20 times the volume of the part.

[0301] Referring to Figure 20c, after the non-condensables and contaminants have been removed from the chamber 302, a working fluid reservoir 442 is attached to the connector 410. Typically, the working fluid reservoir is connected to the connector via a fill volume chamber 444. Typically, the working fluid reservoir is also connected to a working fluid hopper 446, where the working fluid hopper is able to provide working fluid to the reservoir via a sixth valve 448, the reservoir is able to provide working fluid to the fill chamber 444 via a seventh valve 450, and the fill chamber is able to provide working fluid to the connector (e.g. to the fill tube 416 of the connector) via an eighth valve 452. A fill vacuum pump 454 is connected to the reservoir via a ninth valve 456 and to the atmosphere via a tenth valve 458.

[0302] In operation (assuming that all valves are initially closed and all chambers are initially empty), the fill vacuum pump 454 is turned on and the ninth valve 456 and the seventh valve 450 are opened. When a sufficient vacuum is achieved in the reservoir 442 and the fill volume chamber 444 then the ninth valve 456 and the seventh valve 450 are closed. The hopper 446 is then filled with working fluid, and the sixth valve 448 is opened. The vacuum in the reservoir 442 pulls the working fluid into the reservoir from the hopper 446. When sufficient fluid is in the reservoir, the sixth valve 448 is closed. This provides a reservoir that contains a desired amount of working fluid.

[0303] Typically, before the working fluid is injected into the chamber 302, the working fluid is degassed (e.g. to remove dissolved gases and any non-condensables from the working fluid).

[0304] In order to degas the working fluid, in some embodiments, the ninth valve 456 is opened with the other valves being closed. The fill vacuum pump 454 is then activated so that the pressure in the working fluid reservoir 442 reduces until the working fluid in the reservoir starts to boil. The ninth valve 456 is then closed. Such a method enables non-condensable gases to escape the working fluid and to collect at the top of the reservoir over time. Once the non-condensable gasses have fully escaped from the working fluid (as may be determined by the cessation of bubbling of the working fluid) the ninth valve 456 is opened so that the pressure in the working fluid reservoir drops and fluid boiling occurs pulling the non-condensable gasses out of the working fluid reservoir. This process may be repeated until the working fluid is sufficiently degassed. For example, the process may be repeated at least 3 times and / or at least 5 times.

[0305] In order to provide feedback to a controller and to determine the point at which the non-condensable gases have escaped the working fluid, the working fluid reservoir 442 may comprise a sensor and / or a camera. In particular, the working fluid reservoir may comprise a camera that is arranged to identify a rate of production of bubbles in the working fluid reservoir (e.g. using image tracking software).

[0306] More generally, the filling rig may be arranged to pressurise and then depressurise the working fluid reservoir 442 in order to degas a working fluid in the working fluid reservoir.

[0307] In particular, a pump of the filling rig may be used to provide a vacuum above the working fluid in the working fluid reservoir 442, the working fluid reservoir is then sealed so that non-condensable gases gather above the working fluid (and can thereafter be removed from the reservoir, e.g. using the pump).

[0308] It will be appreciated that other methods of degassing the working fluid are possible, e.g. freeze-pump-thaw methods, or bubbling an inert gas such as nitrogen through the working fluid.

[0309] Referring to Figure 20d, there is described a temperature control system that may be implemented to assist the transfer of working fluid about the filling rig.

[0310] The filling rig typically comprises one or more liquid cooled pumped loops that are arranged to move fluid around the various components of the filling rig by altering the working fluid temperature and therefore the pressures within these chambers. Equally, the filling rig may comprise one or more high temperature loops or low temperature loops that are arranged to alter a temperature in a component of the filling rig so as to achieve a desired working fluid temperature and thus pressure in that component. Raising the temperature in a component with a fixed volume (e.g. raising the temperature of a fluid in this component) leads to a higher working fluid pressure in that component, and lowering the temperature leads to a lower working fluid pressure. Therefore, a pressure difference that drives the movement of the working fluid can be achieved using temperature control in selected parts of the filling rig.

[0311] In some embodiments, liquid jackets are wrapped around the working fluid reservoir 442, the fill volume chamber 444, and / or the connector 410. These jackets can be configured to either heat or cool these components. By heating one component and / or by cooling another component it is possible to generate a pressure gradient in the working fluid so that, when a valve between these two components is opened, the working fluid flows along the pressure gradient.

[0312] While Figure 20d shows the use of hot water and cold water loops, it will be appreciated that other fluids may be used in these loops and, more generally, that other methods of providing heating and / or cooling are possible (e.g. using resistive heating loops that provide heat in dependence on the application of a current, or using, e.g. thermoelectric devices to provide heating or cooling).

[0313] Typically, the filling rig comprises one or more controllers (e.g. proportional integral derivative controllers) that are arranged to control one or more temperature loops in order to provide a temperature gradient between two components of the filling rig.

[0314] Referring to Figure 20e, typically the rig comprises the fill volume chamber 444, which fill volume chamber is arranged to provide a precise volume of working fluid to a chamber of the thermal spreader. Typically, the quantity of working fluid to be added to a chamber of the thermal spreader is determined a percentage of the cavity volume or wick volume of that chamber.

[0315] The fill volume chamber 444 may, for example, be arranged to provide volumes of working fluid ranging from 0.1 ml to 5ml, such volumes enable the provision of a suitable amount of working fluid to most thermosyphon applications (it will be appreciated that other volumes of the fill volume chamber are possible). In order to fill the fill volume chamber 444, the seventh valve 450 is opened and then the working fluid reservoir 442 is heated and / or the fill volume chamber 444 is cooled. This relative heating / cooling generates a pressure gradient that acts to move working fluid from the reservoir into the fill volume chamber. Typically, this process is performed after the working fluid has been degassed.

[0316] It will be appreciated that forthe fill volume chamber 444 (and forthe other components of the filling rig) various methods of moving fluid are possible (e.g. using a temperature gradient, using a pump / compressor, and / or using gravity).

[0317] The seventh valve 450 typically comprises a (e.g. needle) precision valve that limits the rate at which working fluid passes through the valve. This enables the close control of the volume of working fluid that enters the valve from the working fluid reservoir 442. This volume may be determined based on the time for which the valve is open. Equally, the volume of working fluid in the fill volume chamber 444 may be determined by measuring the height of fluid in this chamber (e.g. using a sensor in the fill volume chamber and / or an optical sensor that views the fill volume chamber).

[0318] Once the fill volume chamber 444 contains a desired volume of working fluid, the seventh valve 450 is closed. The working fluid can then be provided to a chamber of the thermal spreader via the eighth valve 452.

[0319] Typically, in order to provide the working fluid to a chamber of the thermal spreader, the temperature control loops are operated in order to heat the fill volume chamber 444 and the connector 410 (and to increase the pressure in these components). In some embodiments, the chamber of the thermal spreader has a lower pressure than the fill volume chamber due to the above-described use of the vacuum pumps 402, 422, so that this pressure gradient acts to transfer working fluid from the fill volume chamber to the chamber of the thermal spreader.

[0320] Referring to Figure 20e, the fill volume chamber 444 may comprise one or more of: a window 502 for enabling a volume of working fluid present in the fill volume chamber to be determined; a window clamp 504 for sealing the fill volume chamber; one or more securing structures 506 (e.g. bolts) for fixing the window clamp in place; a sealing component (e.g. an O-ring seal 508) for sealing the window; a working fluid inlet 510 and a working fluid outlet 512 for enabling the transfer of the working fluid into and out of the fill volume chamber; and a temperature loop inlet 514 and a temperature loop outlet 516 for enabling the passage of a heated or cooled fluid through a channel of the fill volume chamber (or, e.g. the passage of electrical wires that may be used to provide heat to the fill volume chamber). In some embodiments, proportional integral derivative (PID) controlled resistive heaters are used to control the temperature of the fill volume chamber.

[0321] Typically, the fill volume chamber 444 comprises a measurement chamber 518 that is triangular in shape in order to decrease the measurement uncertainty for smaller fills. In this regard, the use of a triangular shape increases the fluid height drop to fluid volume ratio as compared to a rectangular arrangement so as to decrease measurement uncertainty.

[0322] Once the desired volume of working fluid has been transferred to the chamber of the thermal spreader, the filling hole 402 is sealed so that the filling rig can be disconnected from the thermal spreader. Typically, this process is performed while the chamber remains under vacuum so as to ensure that no non-condensable gases or contaminants enter the chamber.

[0323] In order to seal the filling hole 402, the filling rig may be arranged to deform the filling hole. More specifically, the filling rig may comprise a punch and a die that can be pressed together deforming the metal around the hole to form a cold weld joint thus sealing the chamber.

[0324] Referring to Figure 20f, there is described another embodiment of the fill volume chamber 444. In this embodiment, the fill volume chamber comprises a tube 520 for transferring fluid into and out of the fill volume chamber 444, where the tube is arranged to receive fluid from, and / or transfer fluid to, the connector 410 and the reservoir 442. The tube typically comprises a temperature-tolerant tube, e.g. made from borosilicate or Pyrex, that is sealed at a top end 524 of the tube and is open at a bottom end 522 of the tube.

[0325] The fill volume chamber 444 of Figure 20f comprises a heating element 526 that is located near (e.g. adjacent) the top end 524 of the tube 520; the heating element may, for example, be a PID controlled heater. The fill volume chamber may also comprise one or more cartridge heaters 528 and / or temperature sensors 530 to enable precise control the temperature in the top end of the tube.

[0326] In operation, the heating element 526 is operable to raise the temperature at the top end 524 of the tube 520, e.g. to raise this temperature to a predetermined temperature such as 70°C. This increase in the temperature at the top end of the tube provides an increase in the pressure of the fill volume chamber 444. Therefore, when the eighth valve 452 that separates the fill volume chamber 444 from the connector 410 is opened, the pressure in the fill volume chamber drops and a vapour bubble grows at the top end of the tube and a fluid in the tube is pushed out of the fill volume chamber and into the connector 410. The volume of the fluid that has exited the fill volume chamber can then be determined by determining a drop in a height of a fluid line in the tube.

[0327] Furthermore, since the working fluid in the fill volume chamber 444 typically has a low thermal conductivity, the operation of the heating element 526 typically causes a temperature gradient in the tube 520 between the top end 524 and the bottom end of the tube 522 (which temperature gradient works to push the working fluid out of the fill volume chamber and into the connector 410).

[0328] This drop in the height of the fluid line may, for example, be measured using an optical sensor, a capacitive sensor, or by a user viewing a scale on the fill volume chamber 444.

[0329] Once a desired amount of fluid has been transferred to the connector 410, the eighth valve 452 is closed and the connector may then be heated to ensure that all of the fluid that has been received from the fill volume chamber 444 evaporates into the chamber (e.g. instead of remaining in the connector 410). Once the chamber has been filled, the device can be sealed and removed from the filling rig.

[0330] Typically, in order to fill the tube 520, the fluid reservoir 442 is heated to generate a pressure difference between this reservoir and the fill volume chamber 444. Then the seventh valve 450 is opened (while the eighth valve 452 is closed) to enable an amount of fluid to pass to the tube of the fill volume chamber and, once a desired amount of fluid has been transferred to this tube (e.g. when the tube is full), the seventh valve is closed. The fill volume chamber can then be operated as described above to transfer the fluid to the connector 410.

[0331] When the fill is complete - that is, when the working fluid has been transferred to the connector 410 (and thereafter to the chamber of the plate 606) - a vapour space will be left at the top end 524 of the tube 520. The heating element 526 can then be switched off to lower the temperature, and therefore pressure, in the tube (though, in any event, the heating element will typically become thermally decoupled from the working fluid naturally since this vapour space isolates the heating element from any working fluid in the tube).

[0332] When a user wishes to refill the tube 520, this user is able to open the seventh valve 450 thereby joining the tube with the (higher pressure) reservoir 442. This causes the collapse of the vapour space at the top end 524 of the tube. The tube 520 then fills with working fluid with no wasting of this working fluid.

[0333] Such a process is shown in Figures 21 a - 21 d.

[0334] Referring to Figure 21 a, the connector 410 comprises a seal die 602 that is typically machined into the connector. This seal die is arranged to interact with a seal punch 604 in order to seal the filling hole 402.

[0335] Referring to Figure 21 b, in order to seal the filling hole 402, the connector 410 is placed on a first side of a plate 606 (e.g. the thermal spreader) at the location of the filling hole 402 and the seal punch 604 is placed on the second side of this plate with the seal punch being aligned with the seal die. Referring to Figure 21 c, the seal punch 604 is then moved towards the seal die 602, which movement results in a deformation of the plate at the location of the filling hole 402. This deformation of the plate leads to a sealing of the filling hole.

[0336] In order to ensure correct alignment between the punch and die, the filling may comprise a support such as a heavy duty C shaped support. Equally, correct alignment may be ensured using, for example, optical sensors.

[0337] Typically, the seal punch 604 comprises an end stop that indicates when the seal punch has been pressed into the seal die 602 enough to seal the filling hole 402. Therefore, after the seal punch has reached the end stop, the seal punch is retracted and both of the seal punch and the connector 410 are removed from the plate 606.

[0338] The seal die 602 and the seal punch 604 may also be used without the remainder of the filling rig in order to separate a plurality of chambers of the thermal spreader before the filling of these chambers. In this regard, in order to allow all of the chambers of the thermal spreader to be inflated simultaneously, these chambers must have a connecting channel. The seal die and the seal punch may be used to deform this connecting channel in order to form a plurality of separated chambers. Equally, a laser weld or a spot weld may be used to seal and separate the chambers of the thermal spreader.

[0339] In order to remove the thermal spreader from the filling rig, the sealing component 412 is removed from the thermal spreader (e.g. by providing, e.g. via the low vacuum pump 401 or via a positive pressure compressor, a positive pressure so as to break the seal between the sealing component and the thermal spreader). After the connector 410 has been removed from the thermal spreader, a further seal may be added to the filling hole (e.g. by using a sealing component) to reduce the risk of the cold weld seal leaking during use of the heat sink.

[0340] Referring to Figures 22a and 22b, there is shown a section of the thermal spreader after the sealing of the filling hole 402. These figures show a seal die impression 608 and a seal punch impression 610 that are left by the seal die 602 and the seal punch 604 respectively. These impressions seal a chamber 612 of the thermal spreader.

[0341] As shown in Figure 20c, each of the low vacuum pump 401 , the high vacuum pump 422, and the fluid reservoir may be connected to the connector 410 simultaneously. Not least due to this, the disclosed filling rig enables the chambers to be rapidly filled, where: the connector is attached to the thermal spreader, a vacuum is achieved by the low vacuum pump to seal the connector to the thermal spreader; a vacuum is achieved by the high vacuum pump to extract contaminants from the chamber, working fluid is then degassed and injected into the chamber, and the chamber is then sealed. The filling rig may then be disconnected (e.g. by the low vacuum pump or a positive pressure compressor operating to break the seal between the connector and the thermal spreader) and connected to another thermal spreader or another section of the thermal spreader.

[0342] It will be appreciated that the low vacuum pump 401 , the high vacuum pump 422, and the fill pump 454 may be implemented as a single component (or as two components), where a single pump may be attached to the connector 410 and then used to create suction for various purposes.

[0343] It will be appreciated that the arrangements of valves described with reference to the above figures is purely exemplary and that, in its simplest form, the filling rig may comprise a connector, which connector comprises: a sealing component arranged to form a seal with a surface; a tube arranged to align with a filling hole on the surface; a pump arranged to extract contaminants from the filling hole; and a working fluid reservoir arranged to inject a working fluid into the filling hole.

[0344] It will be appreciated that references to a ‘vacuum’ in the above description refer more generally to an area of low pressure (e.g. an area of pressure that is lower than atmospheric pressure, lower than l OmBar, lower than 10-3mBar, or lower than 10-6mBar). Referring to Figures 23a - 23h, there are described further aspects of an apparatus and a method for transferring a working fluid into a chamber of the thermal spreader. The below description supplements the previous description of the filling of the chamber and so it will be appreciated that any aspects described with reference to Figure 23a - 23h may be combined with the aspects described above (e.g. with reference to Figures 17a - 22b). In particular, the below description provides further detail of the formation of a hole that supplements the description for Figure 20a.

[0345] Similarly to Figures 17a and 19, Figure 23a shows an inflated chamber 302 into which a user is seeking to introduce a working fluid.

[0346] Referring to Figure 23b, in a first step the filling rig is positioned above the inflated chamber 302 with the punch 604 positioned above the chamber at a location of a desired hole (which hole may be located at any point of the chamber). Typically, the punch is associated with (or connected to) the connector 410 of the sealing rig so that locating the punch in a desired position typically involves aligning the connector with the desired position.

[0347] The punch 604 is typically arranged to pass along the filling tube 416, where this ensures that the filling tube is aligned with the hole after the hole has been formed. In some embodiments, the filling rig further comprises a seal alignment structure 614 where this structure can be used to ensure that the seal die 602 is aligned with the punch when the hole is formed. Each of the connector 410 and the alignment structure 614 are typically connected to a shared structure of the filling rig such that they can be placed to either side of the inflated chamber 302 while remaining aligned.

[0348] In some embodiments, the seal die 602 is integrated with the connector 410 of the filling rig. This enables each of the active components of the filling rig to be located on one side of the inflated chamber 302 with a simple anvil-type plate being located on the other side of this chamber. This type of arrangement is particularly desirable where there are obstructions, e.g. cooling fins, located on one side of the chamber; with such a situation the anvil can easily slot between the fins and then the connector with the integrated seal die is able to connect to the unobstructed side of the chamber in order to transfer the working fluid into the chamber and to seal the chamber.

[0349] As shown in Figure 23c, once the filling rig (and the punch 604) is correctly located, the connector 410 is lowered onto the inflated chamber 302 and the seal alignment structure 614 is raised so that the sealing component 412 of the connector (e.g. an o-ring) - forms a vacuum tight seal with the inflated chamber 302. This typically comprises attaching the sealing component to the inflated chamber with sufficient force to compress the sealing component (while ensuring that the force is not large enough to substantially deform or crush the inflated chamber - in some embodiments, the sealing component may be attached with sufficient force to cause some deformation, where this can help to ensure a seal is formed, but this force remains small enough to avoid completely collapsing the inflated chamber). A vacuum is then achieved by drawing air out of the filling tube 416 in order to securely attach the connector to the inflated chamber 302.

[0350] Once the connector 410 is attached to the inflated chamber 302, the punch 604 is lowered and penetrates the surface of the inflated chamber 302 so as to form a hole 402 in the inflated chamber (while maintaining the seal and the vacuum between the inflated chamber and the connector 410).

[0351] As shown in Figure 23d, once the hole 402 has been formed, the punch 604 is removed. Any air or contaminants within the inflated chamber are then drawn out of the empty inflated chamber via the filling tube 416. Typically, the filling rig is arranged to provide a vacuum (or substantially a vacuum) so as to draw the air out of the chamber rapidly and thus to prevent any oxidisation of surfaces that are exposed by the hole forming process. Typically, the filling rig is arranged to provide a pressure of less than 1 millibar (mbar) in the filling tube 416 prior to the formation of the hole so as to achieve this rapid extraction of air once the hole has been formed. Following the formation of the hole, the filling rig is then able to fill the inflated chamber 302 with a precise volume of working fluid. Methods of filling the chamber have been described above, e.g. with reference to Figures 20a - 20f.

[0352] Referring to Figure 23e, once the inflated chamber 302 has been filled with the desired amount of working fluid, the inflated chamber is sealed to retain the fluid in the chamber. Typically, this comprises sealing the chamber with a sealing structure that is a part of the filling rig and / or sealing the chamber with a cold weld seal.

[0353] Integrating the sealing structure into the filling rig enables the sealing to be performed while the filling rig remains under vacuum and the hole 402 remains isolated (so that contaminants cannot enter the hole prior to the sealing of the hole).

[0354] Typically, at the sealing stage a known volume of working fluid has already been introduced into (e.g. evaporated into) the inflated chamber 302. The filling rig remains under vacuum at this point and the connector 410 remains heated to ensure no working fluid can leaves the inflated chamber.

[0355] As shown in Figures 23f and 23g, in order to seal the inflated chamber 302, the seal die 602 and / or the seal alignment structure 614 is raised in order to deform (e.g. crush) the inflated chamber in the region of the hole 402. Typically, the filling rig is arranged to fully crush the chamber in the region of the hole so that when the seal die 602 is operated the material around the hole has nowhere to flow other than into the seal die (which seal die is aligned with the hole).

[0356] As shown in Figure 23f, in some embodiments the seal die 602 is offset from the fill hole 402. By offsetting the seal die from the fill hole, the material in the region of the seal die (as the seal die moves relative to the fill hole) flows and fills both the fill hole itself and a connector chamber 103 immediately above the fill hole in the connector 410. More specifically, the connector and the seal alignment structure 614 act together to restrict the flow of the deformed material so that this material fills both the fill hole and the small chamber. In this way, providing the connector chamber causes a thickening of the material around the fill hole to ensure a permanent seal is formed by the movement of the seal die.

[0357] Typically, the connector chamber 103 comprises a widened portion, a cut out, and / or a recess in the connector 410, which portion provides a chamber into which material of the inflated chamber 302 can move as this chamber is deformed by the seal die 602. This connector chamber is typically located at a first end of the connector with this first end being located adjacent the inflated chamber in use. For example, the connector chamber may be formed at an end of the fill tube 416 of the connector.

[0358] Once the hole has been sealed, as shown in Figure 23h, the connector 410 and the seal alignment structure 614 are opened and the filled and sealed enclosed chamber 302 can then be removed from the filling rig. The surface of the inflated chamber will typically be left with a seal die impression 610 and a protrusion 608 at the location of the hole, which protrusion relates to the material that has moved into the space provided by the connector chamber 103, and which protrusion ensures that the inflated chamber 302 is securely sealed.

[0359] This process is typically repeated a plurality of times in order to inject working fluid into each enclosed chamber 302 of the thermal spreader. Equally, a filling rig may be provided with a plurality of connectors 410 and punches 604, etc. so that numerous inflated chambers can be filled simultaneously. This may involve manufacturing a filling rig that is adapted to a specific thermal spreader (and such a filling rig may provide rapid filling of a specific type of thermal spreader).

[0360] Housing

[0361] As described above, the heat sink described herein typically comprises a housing, which housing may provide EMI protection, weather protection, mount points for the components of the heat sink, and / or a means for mounting input / output hardware. Figures 24a and 24b show a front view and a rearview of an embodiment of such a housing, where the housing comprises a clamshell assembly.

[0362] This housing comprises one or more of: walls 702 that provide a structure of the housing; a rear heat sink 704 that typically comprises a plate (e.g. the thermal spreader 300 and / or a plate connected to the thermal spreader 300) and fins; fins 706 (e.g. sheet metal fins) that encourage the cooling of the heat sink; a radio frequency filter 708 that filters the incoming and outbound signal; a mounting bracket 710 that enables the housing to be mounted onto a desired structure (e.g. a telecoms mast); a front heat sink 712, which front heat sink may be removable; and a connection structure 714 for receiving inputs and / or outputs, e.g. for connecting a component inside the housing to an electrical source of inputs / outputs so that power and instructions can be provided to this component and readings can be received from this component.

[0363] Figure 25 shows a detailed view of a housing that may be used for the heat sink. In particular, Figure 25 shows a cross-section of the housing adjacent the rear heat sink 704. This figure also illustrates that the housing may be composed of two (e.g. thin) sheets of metal that are joined together (e.g. bonded, welded, and / or brazed).

[0364] As shown in these figures, each sheet of the housing may comprise (e.g. have embossed upon it) features that provide multi-phase chambers 720 for providing cooling to the heat sink. Furthermore, the housing may comprise a first set and a second set of attachment structures 716, 718 for mounting electronics within the housing and / or for ensuring adequate positioning and pressure between heated components and the heat sink. For example, the housing may comprise weld studs that pull the heat sink into contact with a component to be cooled and / or the housing may comprise a clincher nut for this purpose. Furthermore, the attachment options may comprise threaded weld nuts for mounting onto a cooling channel, internally threaded weld nuts for PCB standoffs, and / or press-fit threaded nuts.

[0365] In some embodiments, the housing comprises one or more clearance structures (e.g. ‘cans’) that are located on the sheets of the housing so as to extend the sheets and enable the use of the heat sink for components with various sizes.

[0366] The attachment options and the clearance structures are designed to not compromise the outer skin of the assembly so as to ensure that the weather protection and EMI sealing of the assembly is maintained.

[0367] As shown in Figure 25, the housing typically comprises one or more of: one or more mounting locations (e.g. chambers) for mounting components within the housing; a cut-out or semi cut-out region 722 for providing thermal control; and an EMI seal lip and gasket 724 for providing EMI protection to the components within the housing.

[0368] Referring to Figure 26, there is shown a base plate of the housing, which base plate may be used for mounting the fins 706 (e.g. the base plate may comprise one of the sheets of the housing of Figure 25). This base plate may comprise a part of the wall 702 of the housing. This figure shows, moving from Detail A through to Detail H, various features that may be included in the base plate. Typically, the base plate comprises the thermal spreader 300 that has been described above.

[0369] Referring to Detail A, the base plate is typically formed of an inner wall 732 and an outer wall 734. The outer wall may comprise an internally threaded weld stud 738 (e.g. this stud may be attached to the outer wall). In particular, the inner wall may comprise a clearance 736, which clearance comprises a cut-away section of the inner wall, so that the stud can be mounted on the outer wall so as to extend into an interior section of the base plate. The outer wall may comprise a deflected portion 740 so as to accommodate the stud.

[0370] Referring to Detail B, the base plate may comprise a threaded insert 744, which threaded insert allows compression between a component on a board located within the housing and a chamber (e.g. an inflated chamber of the thermal spreader 300) without compromising this chamber. In this regard, the base plate may comprise a chamber 742, which may be a chamber of the thermal spreader and / or which may be a chamber of a separate base plate of the housing. Referring to Detail C, the base plate may comprise a threaded insert 746 that is located between the inner wall 732 and the outer wall 734 of the housing, which threaded insert may be mounted to an outer surface of the inner wall (with the inner wall comprising a deflected portion 748 at which the inner wall diverges from the outer wall to make room for this threaded insert).

[0371] Referring to Detail D, the base plate may be arranged for use with a printed circuit board (PCB) 750 that comprises a board component 752, which board component requires an amount of clearance. To provide this clearance, the base plate may comprise a protrusion 756 the extends from the base plate, which protrusion may be an integral part of the base plate or may be a separate part that is attached to the base plate. In particular the protrusion may comprise a cap that is placed on top of a part that would otherwise extend through the base plate. The base plate typically comprises a securing structure 758, e.g. a weld, a clip, or an adhesive, that secures the protrusion (e.g. the cap) onto the base plate. The base plate may further comprise a seal 754 (e.g. to provide weatherproofing or EMI protection) at an attachment point at which the protrusion is attached to the base plate.

[0372] Referring to Detail E, the base plate may be arranged for use with an externally mounted device 768, such as a radio filter., . The externally mounted device may be connected to an internal component such as a PCB. To enable the externally mounted device to connect to the internally mounted component at a controlled spacing, the base plate may comprise threaded holes 760 that provide a through passage through the inner wall 732 and the outer wall 734. Typically, the threaded holes are associated with a securing structure 762, such as a weld, a clip, or an adhesive and a sealing structure 764 that provides weatherproofing and EMI protection to the base plate. The externally mounted device may comprise a hole or cavity allowing a radio frequency or electrical connection between an interior of the base plate and an interior of the externally mounted device. The e.g. radio filter needs to be positioned a known and tightly controlled distance from the PCB. To this end, the externally mounted device may be precisely manufactured using e.g. CNC milling and screwed into one of the threaded holes in order to insert the externally mounted device into the base plate.

[0373] Referring to Detail F, there is shown a structure for preventing thermal cross-talk between components mounted in the housing. The structure comprises a thinned notch region 774 that throttles heat flow between adjacent sections of the housing. Each section may comprise dedicated fins 772 that cool a component within that section of the housing (e.g. these dedicated fins may provide cooling to an optical connector independently of a main heat sink). These fins may be created by cutting into the outer wall 734 to form the fin bodies, and bending the fins from the wall into position. Pin fins could also be used. Detail F shows an embodiment in which the thinned region comprises a notch 774, which may for example be sliced, machined, punched, etc.

[0374] Referring to Detail G, there is shown a further structure for preventing thermal cross-talk in which the thinned region comprises deflected regions 775 of the inner wall 732 and the outer wall 734. Deflecting of the material automatically thins the material while stretching it, increasing the resistance to heat transfer.

[0375] Referring to Detail H, the base plate may comprise a shield can, whereby an inner-mounted component 776 is mounted so as to be spaced from the outer wall 734 of the base plate and so to provide a sealed zone 778. Typically, this comprises the inner wall comprising a deflected portion 782 that diverges from the outer wall so as to provide the sealed zone. Furthermore, the base plate typically comprises a sealing structure 784 that provides a seal between the inner mounted component and the deflected portion.

[0376] While in the illustrated example, in Detail B, the outer wall 734 is pushed together with the inner wall at the threaded insert location, in a different embodiment these surfaces could be separated. Similarly, in other embodiments the threaded insert could be replaced by a thermal coupling component to thermally attach the chamber 742 to either a printed circuit board or a further component via a thermally conductive pillar section. Where a thermal coupling component is used, having a depression in the inner wall 732 may help to increase the evaporative surface area in the vicinity of the thermal coupling component. Referring to Figure 27, there is shown an embodiment of the fins 706 that shows various features that may be included as a part of the fins of the base plate.

[0377] Referring to Detail A, there is shown a fin 706 that comprises a cut-out 802 to provide clearance for components that protrude through each of the inner wall 734 and the outer wall 732 of the base plate.

[0378] Referring to Detail B, there is shown a fin 706 that comprises a cut-out section 804 that prevents the flow of heat along the fin through the cut-out section. Such a cut-out section may be used to provide thermally- segregated sections on the fin.

[0379] Referring to Detail C, there is shown a fin that comprises a v-shaped cut-out 806. This cut-out provides flexibility in the fin to allow the base plate to flex during use. The fin may also comprise a weld 808 at the base of the fin so as to secure the fin to the outer wall 732 of the base plate (e.g. at the end of the v). Numerous different types of cut out could be used to achieve the same end result.

[0380] Referring to Detail D, there is shown a fin 706 that comprises a cut-out region 810 that accommodates a deflection in an inner wall 734 or an outer wall 732 of the base plate, e.g. that accommodates a deflected portion 812 of the inner wall or the outer wall.

[0381] Referring to Detail E, there is shown a fin 706 that comprises a cut-out region 814 that controls (e.g. prevents) the flow of heat through a portion of the fin. Such a cut-out region is useable to control the portions of the fin that receives heat so as to, e.g., avoid heating of the fin in certain sections.

[0382] Referring to Detail F, there is shown a fin 706 that comprises a selective weld 816. The selective weld controls the locations of heat transfer through the fin; in particular, the selective weld causes heat transfer to occur at the welded points, and not at the unwelded points. Other methods of selective fin adhesion to cause heat transfer to occur only at selected points along the fin include using adhesives, brazing, or soldering along specific portions of the join between the fin and the outer wall.

[0383] Referring to Figure 28, there is shown an embodiment of a frame that may form the wall 702 of the housing. The frame comprises one or more frame bends 832 that form the corners of the frame. Typically, the frame is formed of a section, e.g. an extruded section, that is folded so as to form a continuous frame. The frame may comprise a single attachment point 834 (e.g. a weld, a bond, or a braze) that connects the ends of the extruded section so as to form the frame and so as to ensure that the frame is weatherproof and provides EMI protection.

[0384] The frame may comprise one or more mounting blocks 836 (e.g. internal, threaded, sealed, mounting blocks) that provide an attachment structure for mounting hardware 838 (e.g. where the mounting hardware is useable to attach the housing to a structure such as a telecoms mast). The frame (and, e.g. the extruded section that is bent to form the frame) may further comprise clearance holes 840 for providing input and / or output connections.

[0385] In order to enable the bending of the extruded section, the extruded section typically comprises notch cutouts 842, that enable the bending of the extruded section. The extruded section comprises a continuous section 844 that continues beneath the cutouts in order to ensure that the frame is weatherproof and provides EMI protection and ease of bending.

[0386] As shown in Detail A and Detail B, typically, the extruded section and / or the frame comprises a groove 846, e.g. a machined groove, for a sealing structure such as an O-ring. The groove may be machined into the frame after the extruded section has been bent to form the frame. Equally, the groove 846 may be a part of the extruded section (e.g. the groove may exist before the section is bent to form the frame).

[0387] Detail C shows a detail of the mounting blocks 836. Typically, these mounting blocks comprise a mount frame 848 that is attached to a mount bracket 852 via a section 850 of the frame via a mount bolt 854. The frame may further comprise a sealing structure 856 located adjacent the connection point to provide weatherproofing and EMI protection at the location of the mounting block. Also shown in Figure 28 is a cross section of a part of the frame, which cross section shows an integrated groove 846 for a sealing structure as well as a first mounting surface 860 (e.g. for a rear heat sink) and a second mounting surface 862 (e.g. for a front heat sink). The frame may comprise a thickened wall section 858 for bolting inputs, outputs, handles, wall mounts, etc. to the frame via clearance holes 840.

[0388] Referring to Figures 29a - 29g, there is described a method of manufacturing the housing. Figure 29a shows a finished version of an embodiment of a housing, Figures 29b - 29g show steps of manufacturing a housing.

[0389] This method of manufacturing provides tight tolerances by exploiting the inherent flexibility of the thin metal sheets that are used to form the base plate of the housing.

[0390] Referring to Figure 29b, in a first step, a fin notch 902 can be cut into a fin 706 of the housing. This fin notch enables some (e.g. localised) flex in the housing to prevent deformation of the fins when a bending force is applied to the housing. The fin is attached to a thin metal sheet base 904 of the frame, which sheet base forms a part of the housing frame 908. The sheet base comprises an inflated chamber 910 (e.g. a two-phase chamber).

[0391] The sheet base 904 may comprise the thermal spreader 300 where this inflated chamber 910 comprises a chamber of the thermal spreader).

[0392] The sheet base further comprises board mount hardware 906 for mounting a PCB or an electrical component to the frame.

[0393] Furthermore, the sheet base 904 comprises clearance holes 913 through the rear housing (which enable securing structures to be placed through the sheet base, as described below.

[0394] Referring to Figure 29c, a circuit board 912 may then be placed adjacent the sheet base 904 (e.g. being secured using the board mount hardware 906), with a component 914 of the circuit board being located adjacent the chamber 910 of the sheet base 904. The component may be thermally connected to the chamber 910 using a thermal interface material 916 so as to aid the transfer of heat away from the component via the chamber.

[0395] In this regard, as has been described above, the sheet base typically comprises the thermal spreader 300, where the chambers of the thermal spreader are arranged to provide heat transfer that moves heat from the components 914 of the board 912 to the environment (e.g. via the fins 706 of the housing).

[0396] Optionally, the component (or another component 918) may be coated in the thermal interface material 916 so as to be thermally connected to a further surface of the housing.

[0397] In this regard, the housing typically comprises a front section and a rear section. The board 912 may comprise a nearside and a farside, where components are mounted on both sides of the board. The nearside components may then transfer heat out of a front side of the housing and the farside components may transfer heat out of a rear side of the housing. Therefore, components on opposing sides of the board may each be coated with a thermal interface material and may be located adjacent respective inflated chambers located on opposing sides of the housing. These inflated chambers may each be parts of a single frame. Equally, a plurality of frame components may be provided with separate components providing inflated chambers for the front and rear of the housing.

[0398] Referring to Figure 29d, an EMI shield 920 may then be added to the housing to provide EMI protection. The EMI shield may be made to tightly controlled tolerances to provide dimensional accuracy to the positioning of PCB and other hardware components.

[0399] Referring to Figure 29e, the various components of the housing may then be secured together using securing structures 922, such as bolts that are attached to the board mount hardware 906 or to separate securing structures. For example, the board mount hardware may comprise threaded inserts or end stops 924 to receive the bolts. Securing structures, e.g. bolts, pull the slightly flexible base plate towards the component to be cooled, bottoming out a known position relative to the components.

[0400] Referring to Figure 29f, the front heat sink 926 can then be attached to the housing. As described above, the housing typically comprises a front side and a rear side, where components located on different sides of the board 912 are arranged to be cooled by a front heat sink or a rear heat sink depending on the side of the board on which they are mounted.

[0401] Referring to Figure 29g, e.g. EM l / weather sealing bolts (928) can be used to pull the rear base plate to a known position relative to the PCB, aided by the stand offs in the local region.

[0402] This method of manufacturing the housing provides an arrangement in which the front heat sink and the rear heat sink are able to deflect. Therefore, the tolerances between the components and the heat sink are very tight so as to maintain a thermal connection between each component and a respective heat sink, and to thereby require a reduce thickness of thermal interface materials, providing optimal cooling.

[0403] Various aspects of the housing that have been described above are now described in more detail below.

[0404] As described with reference to Figure 27, in order to control the flow of heat through the heat sink and into the fins, selective welding may be used during the manufacture of the heat sink. Such use of selective welding ensures that there is effective transfer of heat to the fins of the heat sink where the weld is present and that substantially lower amounts of heat transfer occur where welds are not present. Furthermore, heat flow through the fins may be controlled by selective fin cuts.

[0405] Selective welding of the fins significantly speeds up the welding process. In particular, by using selective welding, it is possible to provide comparable thermal performance to fully welded fins while using a fraction of the weld, e.g. using 50% less weld. This greatly accelerates fin attachment during production of the housing since continuous welds in thin sheet metal are problematic due to heat buildup, which can result in material buckling. Alternative selective fin attachment methods may also be used, such as brazing, soldering, adhesives, or further attachment methods known in the art.

[0406] In a similar manner, heat flow through the base of the housing may be controlled by selective thinning of the base, such as by creating notches like notch 774 shown in Figure 26, detail F, to create thermal zones that are isolated from the heat flow in the main body of the heat sink. The selective thinning may involve pressing a shape into the base sheet 904 that locally draws the material to be very thin. Equally, this thinning may be performed using a CNC machine removing material (or by using some combination of these processes).

[0407] As described above, the housing may comprise thermally segregated zones that may be created by providing areas of selective thinning in the housing. As also described above, these thermally segregated zones may have their own cooling fins. For example, the cooling fins may be provided to cool a low temperature tolerant optical plug.

[0408] In a practical example, a housing for a heat sink of a low temperature tolerant component (e.g. optical transceiver) may have dedicated fins for cooling away from the main fins. With this example (or indeed with heat sinks for other purposes), thermal cross talk in a thermally segregated zone may be controlled (e.g. throttled) by selectively cutting a notch in one or more sheets of the housing. This notch effectively creates a thermally isolated heat sink within the main heat sink. In general, the housing may comprise one or more notches arranged to form thermally segregated zones of the housing (and the heat sink).

[0409] As described above, the frame of the housing typically comprises a side wall, e.g. an extruded, bent, and butt welded side wall. The side wall comprises one or more cuts (or ‘notches’) which enable the side wall to bend at the locations of these cuts.

[0410] EMI and weather protection may be achieved by this side wall by not cutting though the wall in order to form the side wall, but by instead cutting the notches and bending the side wall into shape. Specifically, the side wall may be extruded (into a line), before the notches are cut into the side wall, and the side wall is bent in order to form the continuous side wall.

[0411] A shaped tool may be used to cut the notches at correct spacing intervals that will later allow the frame to be folded into a desired shape. Typically, these cuts are formed such that they do not fully penetrate the extruded profile of the side wall and instead leave a continuous piece of material (e.g. metal), where this ensures EMI / weather proofing of the housing. The cuts are typically formed such that the material at the locations of the cuts joins seamlessly at the corners of the side wall once the side wall is bent into place. Equally, in some embodiments, the cuts are formed so as to provide clearance at these corners, which clearance may enable the introduction of an additional seal and / or sealant at these corners.

[0412] In order to seal the joint and secure the side wall in a continuous shape, the side wall may be welded and / or an adhesive may be used to connect two ends of the side wall.

[0413] Furthermore, the side wall may comprise threaded holes or weld studs to provide mounting structures for mounting the sides (e.g. the ‘lid’ of the housing) to the side wall.

[0414] The profile of the extruded material that is used to form the side wall (e.g. the extruded section) may be chosen to accommodate one or more of: an EMI, weather, or other seal on the top surface of the extruded material, bolt holes, or a surface for stud welding, thick enough walls to provide structural rigidity and ability to attach mounting hardware and / or a mounting surface for inputs / outputs.

[0415] The side wall may comprise one or more sections for mounting weld studs or drilling and tapping holes. The profile may be shaped to provide structural rigidity and to accommodate inputs / output hardware.

[0416] The side wall may comprise one or more of: a wall mount bracket, an O-ring seal, a mount plate, and bolt holes. These structures provide means for attaching wall and / or pole mounting hardware to the frame of the housing.

[0417] Typically, the frame is designed to be structurally rigid while not compromising weather and EMI sealing. The mounting hardware may then be bolted to the frame using the mount plate to provide a bolting surface, and to integrate an EMI / weather seal so as not to compromise sealing. Typically, the mount plate has a groove to accommodate the O-ring and / or an EMI gasket.

[0418] Typically, the frame accommodates and / or comprises an EMI / weather seal. To accommodate this seal, the extruded material that forms the side wall of the frame may be extruded so as to comprise a recess for accommodating the seal.

[0419] Such shaping of the extruded material can leave corners where the frame folds meet as the side wall is folded. Therefore, in some embodiments, the recess may be machined into the surface of the frame afterthe side wall of the frame has been bent and welded together. Such a method of forming the recess offers additionally flexibility in the groove path and dimensions of the groove.

[0420] The EMI shield and the base sheet 904 (e.g. the side wall of the frame) may be manufactured as a single component. Equally, these components may be joined together to provide a high dimensional tolerance part onto which sheet metal finned sections can be bolted. Local tolerance at the cooling pad and the adjacent bolt holes / end stops can provide precise alignment from the pad to the component to be cooled. The inherent flexibility of the (thin) finned parts enables the heat sink finned sections to be pushed / pulled to the correct position to provide optimal heat transfer through the inflated chambers of the housing (e.g. the inflated chambers of the thermal section).

[0421] Typically, the (rigid) EMI shield 920 provides a precise location onto which the (flexible) base sheet 904 can be attached. This base sheet can then be manipulated (e.g. pushed / pulled) to obtain a desirable location of the base sheet relative to the EMI shield so that this combination of components provides optimal transfer of heat from the components to be cooled or, for example, precise location of other hardware relative to the PCB assembly. The flexible base sheet can be locally deformed (e.g. near the fin cut-outs) in order to ensure that each component of the board 912 is optimally located adjacent a corresponding inflated chamber 910 of the base sheet.

[0422] Alternatives and modifications

[0423] It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

[0424] For example, while the background and the detailed description have considered the context of m-MIMOs and componentry that may be used with RANs, more generally the heat sink disclosed herein may be used in any context or with any componentry.

[0425] For example, the heat sink may be modified to include sides and a lid so as to provide a clamshell for cooling (any) outdoor products. Equally, the heat sink may be mounted to a server blade so as to provide a system for cooling a server card. In another example, the heat sink may be mounted to the fuselage of a plane so as to cool electrical componentry of the plane (in such a use case there is typically a high-speed airflow over the fins of the heat sink, therefore the fins may be made of a stiff material to prevent deformation of the fins in this high-speed airflow).

[0426] While the detailed description has primarily focused on a thermal spreader that is formed using a roll bonding process, it will be appreciated that other methods of forming the plate and the inflated chambers are possible. For example, a laser welding process may be used to join two sheets with chambers between these two sheets then being inflated.

[0427] While the detailed description has considered the thermal spreader and the filling rig being used to form a plate for a heat sink, it will be appreciated that the thermal spreader may more generally be used in various situations in which it is desirable to provide a plate with inflated chambers. For example, the plate with inflated chambers may be used to form the air frame of a drone. Such a plate may still comprise heat transfer structures located adjacent electronic componentry of the drone so as to provide both structural support and also to transfer heat away from this electrical componentry. Similarly, the plate with inflated chambers may be used to form the structural and thermal aspects of high power LED luminaires. Similarly, the plate with inflated chambers may be used to cool battery packs of electric vehicles.

[0428] In some embodiments, the inflated chambers comprise one or more fluid transfer chambers that are arranged to provide a channel for moving a fluid (e.g. a liquid and / or a coolant) around the thermal spreader 230. The fluid transfer chambers may be arranged to transfer the fluid into and / or out of the thermal spreader so as to move heated fluid out of the thermal spreader and to introduce cooler fluid into the thermal spreader. The coolant transfer chambers may use an inflation point (e.g. the inflation point 324) in order to move the fluid into and / or out of the thermal spreader. This precludes the need to provide a separate inflation point. The fluid transfer chambers provide a mechanism for removing heat from the thermal spreader and more specifically may be used to provide a fluid cooling loop in the thermal spreader.

[0429] Reference numerals appearing in the claims are by way of illustration only and shall have no limiting effect on the scope of the claims.

Claims

Claims1 . A filling rig for filling a chamber located on a plate, the filling rig comprising: a connector, the connector comprising: a sealing component for sealing the filling rig to the plate at a location of a filling hole on the plate; a fill tube for injecting a working fluid into the chamber via the filling hole; a hole-forming tool for forming the filling hole in the plate following the sealing of the filling rig to the plate; a pump connected to the connector, the pump being arranged to extract air from the chamber so as to provide a low pressure in the chamber; a working fluid reservoir, the reservoir being connected to the fill tube so as to be able to provide working fluid to the chamber via the fill tube; and a sealing mechanism for sealing the hole using a cold weld prior to the releasing of the sealing component from the plate.

2. The filling rig of claim 1 , wherein the pump is arranged to extract air from the chamber via the fille tube.

3. The filling rig of any preceding claim, wherein the hole-forming tool comprises a punch.

4. The filling rig of any preceding claim, wherein the sealing mechanism is arranged to seal the pressure hole while the chamber is at a low pressure.

5. The filling rig of any preceding claim, comprising a connector chamber located at a first end of the fill chamber, preferably wherein the connector chamber comprises one or more of: a widened portion, a cutout, and a recess of the fill chamber.

6. The filling rig of any preceding claim, comprising a seal die and a seal punch that are arranged to interact in order to deform material around a filling hole located between the seal die and the seal punch so as to seal the filling hole, preferably wherein the connector comprises the seal die.

7. The filling rig of any preceding claim, wherein the working fluid reservoir is connected to the connector via a fill chamber, preferably wherein the reservoir is connected to the fill chamber via a valve, preferably a precision valve.

8. The filling rig of any preceding claim, comprising: a sensor for determining a volume of fluid in the fill chamber; and / or a sensor for determining a volume of fluid in the working fluid reservoir.

9. The filling rig of any preceding claim, comprising a working fluid hopper that is arranged to provide working fluid to the reservoir, preferably wherein the hopper is connected to the reservoir via a valve.

10. The filling rig of any preceding claim, wherein the pump is arranged to provide a vacuum or a near vacuum in the chamber, preferably wherein the pump is arranged to provide a pressure of no more than 10-4mBar, no more than 10-5mBar, and / or no more than 10-6mBar.

11. The filling rig of any preceding claim, wherein the pump is arranged to provide a low pressure between the sealing component and the plate so as to seal the sealing component to the plate.

12. The filling rig of any preceding claim, comprising a sensor for monitoring a degassing process in the reservoir, preferably a sensor for detecting quantities of bubbles in the reservoir.

13. The filling rig of any preceding claim, comprising a temperature loop for altering a temperature of one or more components of the filling rig and / or for altering a temperature of one or more fluids within the one or more components, preferably for altering a relative temperature between two of the components of the filling rig and / or for altering a relative temperature of two or more fluids within the two or more components.

14. The filling rig of claim 13, comprising one or more of: a high temperature loop for increasing the temperature of a component of the filling rig; and a low temperature loop for decreasing the temperature of a component of the filling rig.

15. The filling rig of any preceding claim, comprising one or more liquid jackets located around one or more of: the connector; the reservoir; and the fill chamber.

16. The filling rig of any preceding claim, comprising a controller, preferably a proportional integral derivative controller, for controlling the temperature loop.

17. The filling rig of any preceding claim, wherein the sealing component comprises an O-ring and / or a suction cup.

18. The filling rig of any preceding claim, comprising a degassing mechanism for degassing a working fluid in the working fluid reservoir.

19. The filling rig of any preceding claim, wherein the pump is arranged to extract air from the chamber via the fill tube.

20. A method of operating the filling rig of any preceding claim.21 . A method of operating a filling rig so as to transfer a working fluid to a chamber of a plate, the method comprising: sealing a connector to the plate via a sealing component such that a fill tube of the connector is located adjacent a filling hole of the plate; creating a low pressure in the chamber, preferably using a pump of the filling rig, more preferably wherein the pump is connected to the chamber via the fill tube; and injecting a working fluid into the chamber via the fill tube.

22. The method of claim 20 or 21 , comprising sealing the connector to the plate by creating an area of low pressure between the sealing component and the plate, preferably creating the area of low pressure by using the pump.

23. The method of any of claims 20 to 22, comprising forming the filling hole, preferably using a punch.

24. The method of any of claims 20 to 23, comprising pressurising the chamber prior to the forming of the filling hole.

25. The method of any of claims 20 to 24, comprising transferring working fluid from a working fluid hopperto a working fluid reservoir.

26. The method of any of claims 20 to 25, comprising degassing the working fluid in the working fluid reservoir, preferably degassing the working fluid by: reducing a pressure in the working fluid reservoir such that the working fluid starts to boil; sealing the working fluid reservoir to enable gases to collect at the top of the reservoir; and removing the gases from the working fluid reservoir; preferably, wherein said degassing steps are repeated, preferably wherein said degassing steps are performed at least three times.

27. The method of any of claims 20 to 26, comprising: transferring the working fluid from the working fluid reservoir to a fill chamber, preferably comprising heating the working fluid reservoir relative to the fill chamber so as to create a pressure gradient between the working fluid reservoir and the fill chamber; and / or transferring the working fluid from the fill chamber to the chamber of the plate, preferably comprising heating the fill chamber so as to create a pressure gradient between the fill chamber and the chamber of the plate.

28. The method of any of claims 20 to 27, comprising sealing the filling hole, preferably sealing the filling hole while the chamber of the thermal spreader remains at a low pressure.

29. The method of any of claims 20 to 28, comprising: locating a seal die on a first side of the plate adjacent the filling hole, preferably wherein the seal die is a part of the connector; locating a seal punch on a second side of the plate; and moving the seal punch relative to the seal die so as to deform the plate in the region of the filling hole so as to seal the filling hole.

30. The method of any of claims 20 to 29, comprising forming a chamber in the plate using the seal die and the seal punch, preferably by dividing a first chamber into a plurality of sub-chambers using the seal die and the seal punch.31 . A thermal spreader for a heat sink, the heat sink being arranged to be located adjacent to components so as to cool the components, the thermal spreader comprising one or more inflated chambers, wherein one or more of the inflated chambers comprises a heat transfer structure, wherein the heat transfer structure is arranged to provide a thermal connection between a plurality of components with similar operating temperatures.

32. The thermal spreader of claim 31 , wherein: the heat transfer structures are an integral part of the thermal spreader; and / or the thermal spreader comprises thermosyphons and / or heat pipes that are integral to the thermal spreader.

33. The thermal spreader of claim 31 or 32, being formed by a roll bonding process and / or a laser welding process.

34. The thermal spreader of any of claims 31 to 33, wherein the heat transfer structures comprise inflated chambers, preferably wherein:the inflated chambers comprise a working fluid, preferably a fluid that promotes heat transfer and / or a fluid with a heat capacity of at least 4,000 J / kgK and / or the inflated chambers comprise wicks; and / or each of the inflated chambers comprises a flattened outer surface; and / or the thermal spreader comprises a plurality of inflated chambers of different heights and / or thicknesses; and / or the inflated chambers comprise additional elements, preferably one or more of: a wick, and a mesh; and / or the inflated chambers comprise one or more looped heat pipes.

35. The thermal spreader of any of claims 31 to 34, wherein the thermal spreader is formed of a plurality of sheets and / or layers (e.g. two or more sheets), preferably a plurality of sheets of different composition and / or material, preferably wherein: one or more sheets of the thermal spreader comprises paint arranged to separate adjacent layers during a roll bonding process; and / or each layer is separated by a thermal interface material (TIM).

36. The thermal spreader of any of claims 31 to 35, wherein an inner sheet of the thermal spreader comprises one or more holes, wherein each hole connects: a first inflated chamber located between the inner sheet and the first outer sheet; and a second inflated chamber located between the inner sheet and the second outer sheet.

37. The thermal spreader of any of claims 31 to 36, wherein the thermal spreader comprises a first, outer, sheet, a second, inner, sheet, and a third, outer, sheet, wherein the second, inner, sheet is located between the first and third outer sheets, preferably wherein the second, inner, sheet is formed of a stiffer material than the first and third outer sheets.

38. A thermal spreader for a heat sink, wherein: the thermal spreader comprises one or more structural components arranged to provide structural rigidity to the thermal spreader, preferably wherein the structural components comprise the heat transfer components; and / or one or more of the inflated chambers contain a fluid, preferably one or more of: a pressurised gas, a non-compressible liquid, and a solid.

39. The thermal spreader of any of claims 31 to 38, wherein the thermal spreader comprises a first heat transfer structure and a second heat transfer structure; preferably wherein: the first heat transfer structure overlaps the second heat transfer structure; and / or a first inflated chamber of the first heat transfer structure overlaps a second inflated chamber of the second heat transfer structure, wherein, at the point of overlap, the first inflated chamber is formed between the first, outer, sheet and the second, inner, sheet and the second inflated chamber is formed between the third, outer, sheet and the second, inner, sheet.

40. The thermal spreader of any of claims 31 to 39, comprising a stiffening structure arranged around at least a portion of the perimeter of the thermal spreader, preferably wherein the stiffening structure comprises a structural inflated chamber.41 . The thermal spreader of any of claims 31 to 40, comprising one or more walls that extend perpendicular to a base of the thermal spreader, preferably comprising one or more structural inflated chambers on anexterior face of a wall, more preferably wherein one or more of said structural inflated chambers are connected, via a hole on the inner plate, to one or more structural inflated chambers on the base of the interior face of thermal spreader.

42. The thermal spreader of any of claims 31 to 41 , comprising one or more insulating components for thermally isolating components with differing operating temperatures.

43. The thermal spreader of any of claims 31 to 42, comprising a trunk and one or more branches that extend from the trunk, the branches comprising the heat transfer components.

44. The thermal spreader of any of claims 31 to 43, being formed using a constructal theory design.

45. A heat sink comprising the thermal spreader of any of claims 31 to 44.

46. The heat sink of claim 45, comprising a housing, preferably wherein the housing is arranged to provide electromagnetic interference (EMI) protection and / or weather protection.

47. The heat sink of claim 45 or 46, comprising one or more heat dissipation structures, preferably one or more fins, preferably wherein: the heat dissipation structures comprise a trunk and one or more branches that extend from the trunk; and / or the heat dissipation structures comprise extruded heat dissipation structures; and / or the heat dissipation structures are formed from a folded sheet of material, preferably a folded sheet of metal, preferably wherein the folded sheet comprises holes; and / or the heat dissipation structures each comprise a trunk that extends away from the heat sink and one or more branches that extend from the trunk; and / or the heat dissipation structures are formed using a constructal theory design.

48. The heat sink of any of claims 45 to 47, wherein: a first heat transfer component of the thermal spreader is arranged to transfer heat to a first surface of the heat sink, the first surface being adjacent a first heat dissipation structure; and second heat transfer component of the thermal spreader is arranged to transfer heat to a second surface of the heat sink, the second surface being adjacent a first heat dissipation structure; preferably, wherein the first surface and the second surface are thermally isolated surfaces.

49. A telecoms device comprising the heat sink of any of claims 45 to 48, preferably wherein the telecoms device comprises a massive multiple-input, multiple-output antenna (m-MIMO).

50. A radio access network comprising one or more telecoms devices according to claim 49.51 . A method of manufacturing the thermal spreader of any of claims 31 to 44.

52. A method of manufacturing a thermal spreader for a heat sink, the method comprising: providing a first sheet and a second sheet; applying a paint to a surface of the first sheet; locating the first sheet adjacent the second sheet with the painted surface of the first sheet being in contact with the second sheet;feeding the first sheet and the second sheet into a rolling machine to bond the first sheet and the second sheet so as to form a thermal spreader; and inflating the thermal spreader so as to form inflated chambers between the first sheet and the second sheet at the locations of the paint.

53. The method of claim 51 or 52, comprising: inflating the thermal spreader so as to provide a plurality of connected inflated chambers; and separating the plurality of chambers so as to form multiple separate chambers; preferably, wherein separating the plurality of chambers comprises deforming the thermal spreader so as to seal one or more channels connecting the inflated chambers.

54. The method of claim 51 or 53, comprising locating a stop near the thermal spreader prior to the inflation of the thermal spreader so as to form inflated chambers that have flatted surfaces, preferably, wherein a subset of the plurality of chambers have different heights.

55. The method of any of claims 51 to 54, comprising annealing the thermal spreader.

56. The method of any of claims 51 to 55, further comprising providing a working fluid to the inflated chambers, preferably: wherein providing the working fluid comprises creating a vacuum in the inflated chambers so as to pull the working fluid into the inflated chambers; and / or wherein the method comprises sealing the inflated chambers; and / or wherein the method comprises providing wicks in the inflated chambers.

57. The method of any of claims 51 to 56, wherein the inflated chambers comprise one or more of: heat transfer structures, thermosyphons, and heat pipes.

58. The method of any of claims 51 to 57, wherein: a set (e.g. a first set) of the inflated chambers comprises heat transfer structures; and / or a set (e.g. a second set) of the inflated chambers comprises structural chambers, preferably wherein: the structural chambers contain a pressurised fluid (e.g. gas) and / or a reinforcement structure; and / or the method comprises injecting a pressurised fluid into the structural chambers; and / or a set (e.g. a third set) of the inflated chambers forms a channel for moving fluid (e.g. a liquid and / or a coolant) around the thermal spreader, preferably wherein the channel is connected to an edge of the thermal spreader so as to enable the transfer of fluid into and / or out of the set of inflated chambers that forms a channel for moving fluid around the thermal spreader.

59. The method of any of claims 51 to 58, comprising: providing a third sheet; locating the third sheet adjacent the second sheet with the painted surface of the third sheet being in contact with the second sheet; feeding the first sheet, the second sheet, and the third sheet into a rolling machine to bond the first sheet, the second sheet, and the third sheet so as to form the thermal spreader; and inflating the thermal spreader so as to form inflated chambers between the first sheet and the second sheet and between the second sheet and the third sheet at the locations of the paint.

60. The method of any of claims 51 to 59, comprises providing holes in the second sheet prior to the bonding of the first sheet, the second sheet, and the third sheet, preferably comprising drilling holes in the thirdsheet; preferably, wherein the holes are arranged so as to provide connections between inflated chambers located between the first sheet and the second sheet and inflated chambers located between the second sheet and the third sheet.

61. The method of any of claims 51 to 60, comprising providing additional elements on one or more of the sheets prior to the bonding of the sheets; preferably, wherein: the additional elements comprise a wick and / or a mesh structure; and / or the sheets are combined so that the additional elements are located between the first sheet and the second sheet and / or between the second and the third sheet.

62. The method of any of claims 51 to 61 , comprising manipulating the thermal spreader so as to form walls on the thermal spreader, preferably deep drawing, cutting, and / or welding the thermal spreader to form the walls.

63. The method of any of claims 51 to 62, comprising one or more of: adding strengthening structures to the thermal spreader, preferably strengthening embossments and / or ribs; adding a working fluid to the inflated chambers; adding a fluid that encourages the transfer of heat to a set of inflated chambers that comprise heat transfer structures; and adding a pressurised fluid to a set of inflated chambers that comprise structural chambers.

64. The method of any of claims 51 to 63, comprising providing the working fluid to the inflated chambers using the filling rig of any of claims 1 to 19 and / or using the method of any of claims 20 to 30.

65. A method of manufacturing the heat sink of any of claims 45 to 47.

66. A method of manufacturing a heat sink, the method comprising: locating thermal dissipation structures so as to receive heat from a thermal spreader; and combining the thermal dissipation structures with the thermal spreader.

67. The method of claim 65 or 66, wherein: the heat sink comprises the aforesaid thermal spreader; and / or the thermal spreader of the heat sink is manufactured using the aforesaid method; and / or the method comprises: providing a housing; locating thermal dissipation structures adjacent the housing; locating the thermal spreader inside the housing; and applying pressure to the sides of the housing so as to combine the housing, the thermal dissipation structures, and the thermal spreader; and / or the method comprises applying a thermal interface material to an inner surface of the heat dissipation structures prior to the locating of the thermal dissipation structures adjacent the housing; and / or the method comprises applying a thermal interface material to the thermal spreader prior to the locating of the thermal spreader in the housing; and / or the method comprises affixing heat transfer structures, preferably heat pipes, to the thermal spreader; and / or the method comprises applying a thermal interface material to the heat transfer structures prior tothe affixing of the heat transfer structures to the thermal spreader; and / or the method comprises inserting attachment structures through the layers of the heat sink so as to secure together the layers of the heat sink; and / or the method comprises injecting a working fluid into the chambers.

68. The method of any of claims 65 to 67, comprising providing a housing for the heat sink, wherein: the housing comprises one or more attachment options for mounting electronics within the housing; and / or the housing comprises one or more clearance structure for enabling the use of the heat sink with components of various sizes; the housing comprises one or more selective welds and / or selective cuts for controlling the flow of heat through the heat sink; and / or the housing comprises one or more thermally segregated zones, preferably wherein the thermally segregated zones are formed by providing areas of selective thinning and / or wherein the thermally segregated zones comprise their own cooling fins; and / or a side wall of the housing comprises one or more sections for mounting weld studs and / or drilling or tapping holes; and / or a side wall of the frame comprises a recess for accommodating a sealing component.

9. The method of any of claims 65 to 68, comprising forming a side wall of a housing of the heat sink by: extruding a section of material; cutting notches into the extruded section; bending the cut section; and securing the ends of the bent section in order to form a continuous side wall, preferably wherein: securing the ends comprises welding the ends; and / or the cuts are formed so as to not fully penetrate the extruded profile of the section.

Images