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WO2020211930A1 - A device for transferring heat between a first unit and a second unit - Google Patents

A device for transferring heat between a first unit and a second unit Download PDF

Info

Publication number
WO2020211930A1
WO2020211930A1 PCT/EP2019/059800 EP2019059800W WO2020211930A1 WO 2020211930 A1 WO2020211930 A1 WO 2020211930A1 EP 2019059800 W EP2019059800 W EP 2019059800W WO 2020211930 A1 WO2020211930 A1 WO 2020211930A1
Authority
WO
WIPO (PCT)
Prior art keywords
unit
biasing element
thermally conductive
members
conductive material
Prior art date
Application number
PCT/EP2019/059800
Other languages
French (fr)
Inventor
Fredrik Ohlsson
Original Assignee
Huawei Technologies Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Huawei Technologies Co., Ltd. filed Critical Huawei Technologies Co., Ltd.
Priority to PCT/EP2019/059800 priority Critical patent/WO2020211930A1/en
Publication of WO2020211930A1 publication Critical patent/WO2020211930A1/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/36—Selection of materials, or shaping, to facilitate cooling or heating, e.g. heatsinks
    • H01L23/373—Cooling facilitated by selection of materials for the device or materials for thermal expansion adaptation, e.g. carbon
    • H01L23/3737—Organic materials with or without a thermoconductive filler
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4266—Thermal aspects, temperature control or temperature monitoring
    • G02B6/4268—Cooling
    • G02B6/4269—Cooling with heat sinks or radiation fins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/36—Selection of materials, or shaping, to facilitate cooling or heating, e.g. heatsinks
    • H01L23/373—Cooling facilitated by selection of materials for the device or materials for thermal expansion adaptation, e.g. carbon
    • H01L23/3733—Cooling facilitated by selection of materials for the device or materials for thermal expansion adaptation, e.g. carbon having a heterogeneous or anisotropic structure, e.g. powder or fibres in a matrix, wire mesh, porous structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/36—Selection of materials, or shaping, to facilitate cooling or heating, e.g. heatsinks
    • H01L23/373—Cooling facilitated by selection of materials for the device or materials for thermal expansion adaptation, e.g. carbon
    • H01L23/3736—Metallic materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/42—Fillings or auxiliary members in containers or encapsulations selected or arranged to facilitate heating or cooling
    • H01L23/433—Auxiliary members in containers characterised by their shape, e.g. pistons
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K7/00—Constructional details common to different types of electric apparatus
    • H05K7/20—Modifications to facilitate cooling, ventilating, or heating
    • H05K7/2039—Modifications to facilitate cooling, ventilating, or heating characterised by the heat transfer by conduction from the heat generating element to a dissipating body
    • H05K7/20436—Inner thermal coupling elements in heat dissipating housings, e.g. protrusions or depressions integrally formed in the housing
    • H05K7/20445—Inner thermal coupling elements in heat dissipating housings, e.g. protrusions or depressions integrally formed in the housing the coupling element being an additional piece, e.g. thermal standoff
    • H05K7/20472—Sheet interfaces

Definitions

  • the invention relates to a device for transferring heat between a first unit and a second unit.
  • the invention also relates to an apparatus for cooling a thermally conductive first unit, the apparatus including a device of the above-mentioned sort.
  • the invention relates to a network access node for a wireless communication system, wherein the network access node comprises an apparatus of the above-mentioned sort.
  • the network access node may comprise a base station.
  • thermal cooling may be performed by transferring heat from the unit or competent, which is to be cooled, to the ambient or to another unit or component, such as an electrical active cooling device or a passive heat sink.
  • a passive heat sink does not require any electric power to transfer heat.
  • a heat sink may be seen as a passive heat exchanger configured to transfer heat generated by a component to another medium, such as air or any other fluid medium, for example liquid.
  • a heat sink can for example release received heat to the ambient via cooling fins of a fin structure. Between the unit or component to be cooled and the active cooling device or heat sink, there may be structures and thermally insulating air gaps which impair the heat transfer to the active cooling device or heat sink.
  • An object of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.
  • the above-mentioned and other objects are achieved with a device for transferring heat between a first unit and a second unit.
  • the device comprises a first member made of a thermally conductive material and a second member made of a thermally conductive material.
  • Each of the first and second members is at least partly resilient.
  • the first member is configured to abut against the first unit, and the second member is configured to abut against the second unit.
  • the first member and the second member are thermally coupled to one another.
  • the device comprises a biasing element made of a first material, the first material being different from the thermally conductive material of each of the first and second members.
  • the biasing element is located between the first member and the second member.
  • the biasing element is configured to urge, or force, the first member in a direction away from the second member.
  • An advantage of the device according to the first aspect is that the biasing element between the first member and the second member forces the thermally conductive first member and second member toward an expanded state and makes the thermally conductive material, for example a thermal interface material, of each of the first and second members properly fill the air gap or air gaps between the first and second unit.
  • the efficient air gap-filling character of the first and second members and the thermal coupling between the first and second members provide an efficient heat transfer from the first unit to the second unit and consequently an efficient cooling of the first unit.
  • Introduction of the biasing element between the first and second member solves the problem of impaired resilience of the conventional solid-state thermal interface materials in an efficient manner.
  • the biasing element may comprise an elastic element (e.g.
  • An advantage of the device according to the first aspect is that the heat transfer from the first unit to the second unit is improved. Consequently, an improved heat dissipation is provided.
  • the biasing element is configured to urge, or force, the second member in a direction away from the first member.
  • the first material is a thermally conductive material. Strong thermal coupling between the first and second member can thus be achieved, further improving the heat transfer from the first unit to the second unit.
  • the thermal conductivity of the first material is equal to or higher than the thermal conductivity of the thermally conductive material of each of the first and second members.
  • the thermally conductive material of each of the first and second members is a thermal interface material, TIM.
  • the thermal interface material in the embodiments of the present invention is related to a member, i.e. the first member or second member, it is to be understood that the thermal interface material is a solid-state thermal interface material.
  • a plurality of solid-state thermal interface materials per se is known to the person skilled in the art.
  • a solid-state thermal interface material may for example comprise a polymer, for example an elastomer, to which particles comprising or consisting of a metal or a metal alloy have been added.
  • An advantage with this implementation form is that the efficiency of the heat transfer from the first unit to the second unit is further improved.
  • the solid-state thermal interface material and the biasing element are merged or combined in a single component.
  • the first member has a first surface configured to contact the first unit, wherein the first surface is covered by a low-friction material layer.
  • the low-friction material layer comprises anyone from the group comprising: a polymer film and a metal foil.
  • the biasing element is sandwiched between the first member and the second member.
  • the device comprises a shell, wherein the shell comprises the first and second members, and wherein the biasing element is enclosed by the shell.
  • the first member is formed as a plate
  • the second member is formed as a plate
  • the biasing element is formed from a plate
  • the biasing element has an edge, and wherein the edge extends outside the first and second members.
  • the above mentioned and other objects are achieved with an apparatus for cooling a thermally conductive first unit, wherein the apparatus comprises a device according to any one of the appended claims 1 to 10, or according to any of the above- or below-mentioned embodiments/implementation forms of the device, wherein the apparatus comprises the second unit, which is a heat sink, and a compartment configured to receive and hold the first unit.
  • the apparatus comprises the second unit, which is a heat sink, and a compartment configured to receive and hold the first unit.
  • the compartment is configured to detachably secure the first unit.
  • first unit is easily removed from its position in the compartment for replacement or inspection.
  • the embodiments of the device according to the present invention are especially advantageous, i.e. for situations when a first unit is removed from its contact with the first member and subsequently a first unit is put back in the compartment and into contact with the first member.
  • the biasing element between the first member and the second member forces the thermally conductive first member and second member back towards an expanded state and makes the thermally conductive material of each of the first and second members properly fill the air gap between the first unit and the heat sink.
  • the compartment is configured to receive and hold the first unit, wherein the first unit is in the form of a transceiver module to which a signal cable is connectable.
  • the transceiver module is mechanically connectable to the signal cable.
  • the transceiver module may in turn be electrically connectable or connected to a printed circuit board, PCB.
  • the transceiver module may be an optical transceiver module and the signal cable may be an optical signal cable, for example an optical fibre cable.
  • an optical transceiver module When in use, an optical transceiver module produces a substantial amount of heat which should be dissipated or transferred away from the optical transceiver module, and also away from a printed circuit board located close to the transceiver module. The heat is produced when the optical transceiver module converts optical signals to electrical signals. The electrical signals are then transmitted to the printed circuit board.
  • the first unit is a transceiver module, for example an optical transceiver module
  • the embodiments of the apparatus according to the present invention are especially advantageous.
  • the apparatus comprises a metal housing, which houses the compartment, and a printed circuit board, to which the housing is attached, wherein the compartment has a first opening for receiving the first unit connectable to the printed circuit board, wherein the compartment has a second opening, and wherein the device is received and held in the second opening.
  • the embodiments of the device according to the present invention are especially advantageous.
  • an interface comprising a metal housing is often used for connecting a signal cable to a printed circuit board via a first unit, for example a transceiver module, held by a compartment in the housing.
  • the biasing element covers the second opening and is in contact with the housing, and wherein the first material comprises or consists of a metal or a metal alloy.
  • the first member is formed as a plate
  • the second member is formed as a plate
  • the biasing element is formed from a plate
  • the biasing element has an edge, and that the edge extends outside the first and second members.
  • a second opening in the compartment could increase the risk of electromagnetic interference, EMI, leakage from the first unit, for example the transceiver module, and from a connector electrically connecting the transceiver module to the printed circuit board.
  • the electromagnetic interference leakage could for example influence an antenna nearby.
  • a second opening in the compartment could increase the risk of interference caused by signals from an antenna nearby or from other electrical components.
  • an advantage with this implementation form since the biasing element is made of a first material comprising or consisting of a metal or a metal alloy and covers the second opening, is that electromagnetic interference shielding is provided. Thus, an improved heat transfer is provided between the first unit and the heat sink without an increased risk of electromagnetic interference leakage.
  • the apparatus comprises the first unit.
  • a network access node which may comprise a base station, for a wireless communication system, wherein the network access node comprises an apparatus according to any one of the appended claims 1 1 to 16, or according to any of the above- or below- mentioned embodiments of the apparatus.
  • Advantages of the network access node correspond to the advantages of the device and apparatus and their embodiments mentioned above or below.
  • the network access node may comprise a base station.
  • FIG. 1 is a schematic cross-section view of a device according to a first embodiment of the invention
  • Figs. 2a-2c illustrate the manufacturing of the biasing element of the device of Fig. 1 ;
  • FIG. 3 is a schematic perspective view of an alternative to the biasing element of
  • FIG. 4 is a schematic perspective view of another alternative to the biasing element of Figs. 1 -3;
  • FIG. 5 is a schematic perspective view of a further alternative to the biasing element of Figs. 1 -4;
  • FIG. 6 is a schematic exploded view of a device according to a second embodiment of the invention.
  • FIG. 7 is a schematic perspective view of the device according to a third embodiment of the invention.
  • Fig. 8 is a schematic exploded view of the device of Fig. 7;
  • FIG. 9 is a schematic cross-section view of the device of Figs. 7 and 8;
  • FIG. 10 is a schematic cross-section view of an apparatus according to
  • FIG. 1 1 is a schematic perspective view of the apparatus of Fig. 10;
  • Fig. 12 is an exploded view of the apparatus of Fig. 1 1 ;
  • FIG. 13 is a schematic view of the apparatus of Fig. 1 1 but with the second
  • Fig. 14 is an enlargement view of the apparatus of Fig. 13.
  • thermally conductive filling materials which provide and facilitate the heat transfer, may be placed between the unit to be cooled and the heat sink or the active cooling device.
  • the purpose of these thermally conductive filling materials is to fill the thermally insulting air gap or air gaps between the unit to be cooled and the heat sink or active cooling device.
  • a so-called thermal interface material, TIM may be used as a thermally conductive filling material.
  • Various compositions of the thermal interface material are possible.
  • a solid-state thermal interface material may for example comprise an elastomer to which particles comprising or consisting of a metal or a metal alloy have been added.
  • these thermal interface materials are resilient to a certain extent to be able to expand from a compressed state towards a non-compressed state in order to fill the air gaps between the unit to be cooled and the heat sink or active cooling device, and this improves the heat transfer therebetween.
  • the inventor of the present invention has identified drawbacks associated with conventional solid-state thermal interface materials used, for example between an electrical component and a heat sink or an active cooling device. For example, the solid-state thermal interface material when installed and compressed between a first unit and a second unit will set in a compressed state after some time and lose its resilient character completely or to some degree.
  • the solid-state thermal interface material may not properly expand and fill the air gaps between the first unit and the second unit.
  • thermally insulating air gaps or air pockets will be present between the solid-state thermal interface material and the first unit and/or between the solid-state thermal interface material and the second unit. Because of these air gaps or air pockets the heat transfer between the first unit and the second unit is impaired, and there will be a temperature increase regarding the first unit, which may result in a short life time for the first unit when it for example comprises an electrical component, such as a temperature-sensitive optical transceiver, and an increased risk of overheating of the first unit.
  • a device 102 for transferring or conducting heat between a first unit 104 (see Fig. 10) and a second unit 106 (see Fig. 10) is schematically illustrated.
  • the first and second unit 104, 106 are thermally conductive.
  • the device 102 includes a first member 108 made of a thermally conductive material and a second member 1 10 made of a thermally conductive material.
  • Each of the first and second members 108, 1 10 is at least partly resilient, for example at least resilient to a certain degree.
  • the thermally conductive material of the first and second members 108, 1 10 may be at least partly resilient.
  • the thermally conductive material of the first and second members 108, 1 10 may for example be a solid-state thermal interface material, TIM, comprising for example a composite material made of a polymer, for example an elastomer, with particles comprising or consisting of a metal or a metal alloy added to the polymer. Thus, said particles are mixed into the polymer.
  • the thermal conductivity of a solid-state thermal interface material may be up to 10 W/mK.
  • the first member 108 is configured to abut against the first unit 104
  • the second member 1 10 is configured to abut against the second unit 106.
  • the first member 108 and the second member 1 10 are thermally coupled to one another, for example through physical abutment or via additional thermally conductive material and/or via a biasing element 1 12.
  • the device 102 includes the biasing element 1 12.
  • thermal coupling is meant that there is a heat transfer between the first and second members 108, 1 10, or in other words, that there is a heat-conducting communication between the first and second members 108, 1 10.
  • the biasing element 1 12 which also may be called a resilient element or a spring element, is made of a first material, wherein the first material is different from the thermally conductive material of each of the first and second members 108, 1 10. As illustrated in Fig. 1 , the biasing element 1 12 is located between the first member 108 and the second member 1 10. The biasing element 1 12 is configured to force (or urge or bias) the first member 108 in a direction away from the second member 1 10 and/or force (or urge or bias) the second member 1 10 in a direction away from the first member 108.
  • the biasing element 1 12 is configured to push (or impel) the first member 108 in relation to the second member 1 10 in a direction away from the second member 1 10 and to push (or impel) the second member 1 10 in relation to the first member 108 in direction away from the first member 108.
  • the biasing element 1 12 may be formed from a plate 1 13 made of the first material which may be a thermally conductive material.
  • the first material of the biasing element 1 12 may be a thermally conductive material.
  • the first material of the biasing element 1 12 comprises or consists of a metal or a metal alloy.
  • the thermal conductivity of the first material of the biasing element 1 12 may be above 10 W/mK.
  • the plate 1 13 is provided with through-holes or grooves which form a plurality of tongues 1 1 1 . With reference to Fig. 2c and Fig. 1 , these tongues 1 1 1 are bent to provide a biasing or resilient character of the biasing element 1 12.
  • the device 102 comprises a shell 1 18 including the first and second members 108, 1 10, wherein the biasing element 1 12 is enclosed by the shell 1 18.
  • the shell 1 18 may be provided by over-moulding to completely enclose the biasing element 1 12 by means of the shell 1 18.
  • the first material of the two alternative biasing elements 1 12a, 1 12b may comprise or consist of a metal or a metal alloy.
  • the first material of the two alternative biasing elements 1 12a, 1 12b is a thermally conductive material.
  • the first member 108 of the device 102 has a first surface 1 14 configured to contact the first unit 104.
  • the first surface 1 14 is covered by a low-friction material layer 1 16.
  • a low-friction material is a material with a low coefficient of friction, COF.
  • the low- friction material layer 1 16 may comprise anyone from the group comprising: a polymer film and a metal foil.
  • the metal foil may be made of a metal or a metal alloy.
  • the polymer film may be made of one polymer, for example polyimide, or a mixture of polymers.
  • An advantage with low- friction material layer 1 16 is that the first unit 104 can be easily slid against the first surface 1 14 in a direction along the first surface 1 14 with a reduced risk of damaging the first member 108 and with reduced wear to the first member 108. Thus, the first unit 104 can be removed from its contact with the first member 108 or introduced into contact with the first member 108 in an efficient manner.
  • a device 202 according to a second embodiment of the invention for transferring or conducting heat between a first unit 104 and a second unit 106 is schematically illustrated.
  • the device 202 includes another alternative biasing element 212 located between the first and second members 208, 210 of the device 202.
  • the biasing element 212 of Figs. 5 and 6 has a grid shape.
  • the first material of the biasing element 212 of Figs. 5 and 6 may comprise silicone or other flexible material.
  • the cavities 215 of the grid- shaped biasing element 212 may be filed by the material of the first and second members 208, 210, or by an additional thermally conductive material which thermally couples the first member 208 to the second member 210.
  • the biasing element 212 of Figs. 5 and 6 may also be enclosed by a shell 208 which includes the first and second members 208, 210. Otherwise, the first and second members 208, 210 of the second embodiment of Figs. 5 and 6 may essentially correspond to the first and second members 108, 1 10 of the first embodiment of Fig. 1.
  • a device 302 for transferring or conducting heat between a first unit 104 (see Fig. 10) and a second unit 106 (see Fig. 10) is schematically illustrated.
  • the device 302 includes a first member 308 made of a thermally conductive material and a second member 310 made of a thermally conductive material.
  • the material of the first and second members 308, 310 of the device 302 of Figs. 7 to 9 may correspond to the material of the first and second members 108, 1 10 of the device 102 of Fig. 1 .
  • Each of the first and second members 308, 310 is at least partly resilient.
  • the thermally conductive material of the first and second members 308, 310 of the device 302 of Figs. 7 to 9 may be similar to the thermally conductive material of the first and second members 108, 1 10 of the device 102 of Fig. 1.
  • the first member 308 is configured to abut against the first unit 104
  • the second member 310 is configured to abut against the second unit 106.
  • the first member 308 and the second member 310 are thermally coupled to one another, for example through physical abutment or via additional thermally conductive material and/or via a biasing element 312 of the device 302.
  • the biasing element 312 is made of a first material, wherein the first material is different from the thermally conductive material of each of the first and second members 308, 310.
  • the basing element 312 of the device 302 of Figs. 7 to 9 may correspond to the biasing element 1 12 of the device 102 of Fig. 1 and is thus not disclosed in further detail.
  • the biasing element 312 is located between the first member 308 and the second member 310.
  • the biasing element 312 is configured to force (or urge or bias) the first member 308 in a direction away from the second member 310 and/or force (or urge or bias) the second member 310 in a direction away from the first member 308.
  • the first member 308 is formed as a plate
  • the second member 310 is formed as a plate
  • the biasing element 312 is formed from a plate.
  • the biasing element 312 has an edge 320.
  • the edge 320 extends outside the first and second members 308, 310.
  • the device 302 of Figs. 7-9 is especially suitable for an application further disclosed hereinbelow in connection with Figs. 10 to 14.
  • the biasing element 1 12, 1 12a-b, 212, 312 may be designed in different ways than those disclosed above.
  • the biasing element may be a mesh, a net, a spring wire etc. It is also possible to introduce a plurality of biasing elements, i.e. two or more biasing elements, for example separated from one another.
  • the thermal conductivity of the first material of the biasing element 1 12, 212, 312 may be equal to or higher than the thermal conductivity of the thermally conductive material of each of the first and second members 108, 1 10, 208, 210, 308, 310.
  • the biasing element 1 12, 312 of the device 102, 302 is sandwiched between the first member 108, 308 and the second member 1 10, 310.
  • the biasing element 312 is attached to the first member 308 and the second member 310, for example by an adhesive or simply by being sandwiched between the first member 308 and the second member 310 and/or integrated with the first and second members 308 310. This may also be the case for the biasing member 1 12 of the device 102 shown in Fig. 1 .
  • an apparatus 402 for cooling a thermally conductive first unit 104 according to a first embodiment of the invention is schematically illustrated.
  • the apparatus 402 may include a device 102, 202, 302 according to any one of the embodiments disclosed above. However, in Figs. 10 to 14, the apparatus 402 is illustrated with the device 302 according to the third embodiment of Figs. 7 to 9.
  • the apparatus 402 also includes the second unit 106 which is in the form of a heat sink 404 having cooling fins 405. Further, the apparatus 402 includes one or more compartments 406 configured to receive and hold a first unit 104. To the left in Fig. 10, the compartment 406 is illustrated without a first unit 104, and to the right in Fig.
  • the compartment 406 is illustrated with a first unit 104 received and held.
  • the compartment 406 is configured to detachably secure the first unit 104.
  • the compartment 406 is configured to receive and hold the first unit 104 which is in the form of a transceiver module 408 to which a signal cable is connectable.
  • Each compartment 406 may be housed in a metal housing 410.
  • the metal housing 410 may house a connector electrically connecting the first unit 104, for example the transceiver module 408, to a printed circuit board (PCB) 412 of the apparatus 402.
  • PCB printed circuit board
  • the apparatus 402 includes both the metal housing 410 and the printed circuit board 412.
  • the apparatus 402 may also include the first unit 104.
  • the metal housing 410 may be made of a material comprising or consisting of a metal or a metal alloy.
  • the illustrated apparatus 402 has two comportments 406 and two transceiver modules 408 received and held in the compartments 406.
  • the apparatus 402 may have fewer or more compartments 406.
  • the transceiver module 408 may be an optical transceiver module 408 to which an optical signal cable, for example an optical fibre cable, is connected.
  • the transceiver module 408 may also be configured to be connectable to an electrical signal cable.
  • the apparatus 402 is especially advantageous for applications including an optical transceiver module 408, since when converting optical signals from the optical signal cable to electrical signals for transmission to the printed circuit board 412, an optical transceiver module 408 generates a substantial amount of heat, which should be dissipated or transferred away from the optical transceiver module 408, to protect the optical transceiver module 408 from heat, since the optical transceiver module 408 is sensitive to high temperatures.
  • the reliability and life time of a transceiver module 408 is related to the module temperature. Typical allowed maximum temperatures for the optical transceiver module 408 is 75°C or 85°C.
  • the temperature of the optical transceiver module 408 can be reduced by 2- 5°C, but also by more, for example by 10-20°C, if a thermally insulating air gap or air pocket is avoided by the use of the device 302 and the apparatus 402.
  • the heat generated by the signal conversion of the optical transceiver module 408 may also be dissipated to protect the printed circuit board 412 from high temperatures, since the printed circuit board 412 is located close to the compartment 406 and the optical transceiver module 408.
  • the metal housing 410 of the apparatus 402 is attached to the printed circuit board 412 of the apparatus 402.
  • Each compartment 406 has a first opening 414 for receiving the first unit 104, which is connectable to the printed circuit board 412.
  • Each compartment 406 has a second opening 416.
  • the device 302 is received in and held in the second opening 416 and thus brought into physical and thermal contact with the first unit 104 held in the compartment 406.
  • the device 302 is also in physical and thermal contact with the heat sink 404.
  • the device 302 may be attached to the second unit 106, for example the heat sink 304, by suitable means, for example by way of an adhesive.
  • the biasing element 312 of the device 302 may be attached the metal housing 410.
  • the first member 308 of the device 302 abuts against the first unit 104, for example the transceiver module 408, and the second member 310 of the device 302 abuts against the second unit 106, for example the heat sink 404, and thereby a thermal coupling is provided between the first unit 104 and the device 302 and between the device 302 and the second unit 106, whereby a heat transfer between the first unit 104 and a second unit 106 is provided.
  • the heat transfer from the first unit 104 to the second unit 106 is improved. Consequently, an improved heat dissipation is provided.
  • the housing 410 of the apparatus 402 may be called a cage or a casing. Instead of two compartments as illustrated in Figs. 10 to 14, the apparatus 402 may include more compartments, for example four compartments.
  • the biasing element 312 covers the second opening 416 of the compartment 406. Thus, biasing element 312 is bigger than the second opening 416. As shown in Figs. 10 and 14, the biasing element 312 is in contact, i.e. physical and/or mechanical contact, with the housing 410.
  • the first material of the biasing element 312 comprises or consists of a metal or a metal alloy.
  • the biasing element 312 in this embodiment is made of an electrically conductive material, which is also the case for the metal housing 410, and advantageously completely covers the second opening 416, this embodiment provides improved electromagnetic interference (EMI) shielding compared to an example where a second opening in the metal housing is not covered by a biasing element or a metal plate.
  • the device 302 of Figs. 10 to 14 is still configured to transfer heat between the first unit 104 and the second unit 106, such that also an efficient heat dissipation is provided.
  • the compartment 406 may be described as a slot in the housing 410.
  • the housing 410 may be an SFP (small-factor form pluggable) or QSFP (quad small form-factor pluggable) housing.
  • the transceiver module 408 may be an SFP or QSFP module.
  • the signal cable which may be an optical fibre cable, may be connectable to an SFP or QSFP transceiver module. SFP and QSFP per se are known to the person skilled in the art and are thus not further described in this disclosure.
  • the embodiments of the present invention also include a network access node for a wireless communication system.
  • the network access node includes an apparatus 402 according to the embodiments disclosed above.
  • the network access node may comprise a base station, for example a base radio station.
  • the network access node may include one or more antennas.
  • the base station may have a housing which houses the antenna. Alternatively, the antenna is mounted outside the housing of the base station, for example with a distance to the housing of the base station.
  • the antenna may be connectable to the printed circuit board 412 via a suitable cable.

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  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Computer Hardware Design (AREA)
  • Power Engineering (AREA)
  • Optics & Photonics (AREA)
  • Thermal Sciences (AREA)
  • Cooling Or The Like Of Electrical Apparatus (AREA)

Abstract

The invention relates to a device (102; 202; 303) for transferring heat between a first unit (104), for example an optical transceiver module (408), and a second unit (106), for example a heat sink (404). The device (102; 202; 302) has a first member (108; 208; 308) made of a thermally conductive material and a second member (110; 210; 310) made of a thermally conductive material. Each of the first and second members (108, 110; 208, 210; 308, 310) is at least partly resilient. The first member (108; 208; 308) is configured to abut against the first unit (104), and the second member (110; 210; 310) is configured to abut against the second unit (106). The first member (108; 208) and the second member (110; 210; 310) are thermally coupled to one another for transferring heat therebetween: The device (102; 202; 302) includes a biasing element (112; 212; 312) made of a first material different from the thermally conductive material of each of the first and second members (108, 110; 208, 210; 308, 310). The biasing element (112; 212; 312) is located between the first member (108; 208) and the second member (110; 210; 310). The biasing element (112; 212; 312) is configured to force the first member (108; 208) in a direction away from the second member (110; 210; 310). An advantage of the device (102; 202; 302) is that the heat transfer from the optical transceiver module (408) to the heat sink (404) is improved. Consequently, an improved heat dissipation is provided. Furthermore, the invention also relates to an apparatus (402) including the device (102; 202; 302) and a network access node including the apparatus (402) for a wireless communication system.

Description

A DEVICE FOR TRANSFERRING HEAT BETWEEN A FIRST UNIT AND A SECOND UNIT
Technical Field
The invention relates to a device for transferring heat between a first unit and a second unit. The invention also relates to an apparatus for cooling a thermally conductive first unit, the apparatus including a device of the above-mentioned sort. Further, the invention relates to a network access node for a wireless communication system, wherein the network access node comprises an apparatus of the above-mentioned sort. The network access node may comprise a base station.
Background
In many areas, for example within the field of telecommunications, components, for example electrical components, may require thermal cooling. This may for example be the case for components in a network access node for a wireless communication system, for example including a base station. Thermal cooling may be performed by transferring heat from the unit or competent, which is to be cooled, to the ambient or to another unit or component, such as an electrical active cooling device or a passive heat sink. A passive heat sink does not require any electric power to transfer heat. In general, a heat sink may be seen as a passive heat exchanger configured to transfer heat generated by a component to another medium, such as air or any other fluid medium, for example liquid. A heat sink can for example release received heat to the ambient via cooling fins of a fin structure. Between the unit or component to be cooled and the active cooling device or heat sink, there may be structures and thermally insulating air gaps which impair the heat transfer to the active cooling device or heat sink.
Summary
An object of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.
According to a first aspect of the invention, the above-mentioned and other objects are achieved with a device for transferring heat between a first unit and a second unit. The device comprises a first member made of a thermally conductive material and a second member made of a thermally conductive material. Each of the first and second members is at least partly resilient. The first member is configured to abut against the first unit, and the second member is configured to abut against the second unit. The first member and the second member are thermally coupled to one another. The device comprises a biasing element made of a first material, the first material being different from the thermally conductive material of each of the first and second members. The biasing element is located between the first member and the second member. The biasing element is configured to urge, or force, the first member in a direction away from the second member.
An advantage of the device according to the first aspect is that the biasing element between the first member and the second member forces the thermally conductive first member and second member toward an expanded state and makes the thermally conductive material, for example a thermal interface material, of each of the first and second members properly fill the air gap or air gaps between the first and second unit. The efficient air gap-filling character of the first and second members and the thermal coupling between the first and second members provide an efficient heat transfer from the first unit to the second unit and consequently an efficient cooling of the first unit. Introduction of the biasing element between the first and second member solves the problem of impaired resilience of the conventional solid-state thermal interface materials in an efficient manner. The biasing element may comprise an elastic element (e.g. a spring) or a resilient element, and may therefore be referred to herein also as a spring element or resilient element. An advantage of the device according to the first aspect is that the heat transfer from the first unit to the second unit is improved. Consequently, an improved heat dissipation is provided.
In an implementation form of a device according to the first aspect, the biasing element is configured to urge, or force, the second member in a direction away from the first member.
In an implementation form of a device according to the first aspect, the first material is a thermally conductive material. Strong thermal coupling between the first and second member can thus be achieved, further improving the heat transfer from the first unit to the second unit.
In an implementation form of a device according to the first aspect, the thermal conductivity of the first material is equal to or higher than the thermal conductivity of the thermally conductive material of each of the first and second members. An advantage with this implementation form is that the biasing element supports the thermal coupling between the first and second member in an even better manner, and thus makes the heat transfer from the first unit to the second unit more efficient.
In an implementation form of a device according to the first aspect, the thermally conductive material of each of the first and second members is a thermal interface material, TIM. Since the thermal interface material in the embodiments of the present invention is related to a member, i.e. the first member or second member, it is to be understood that the thermal interface material is a solid-state thermal interface material. A plurality of solid-state thermal interface materials per se is known to the person skilled in the art. A solid-state thermal interface material may for example comprise a polymer, for example an elastomer, to which particles comprising or consisting of a metal or a metal alloy have been added. An advantage with this implementation form is that the efficiency of the heat transfer from the first unit to the second unit is further improved. In some implementation forms of a device according to the first aspect, the solid-state thermal interface material and the biasing element are merged or combined in a single component.
In an implementation form of a device according to the first aspect, the first member has a first surface configured to contact the first unit, wherein the first surface is covered by a low-friction material layer. An advantage with this implementation form is that the first unit can be removed from its contact with the first member or introduced or reintroduced into contact with the first member in an efficient manner. The first unit can be easily slid against the first surface in a direction along the first surface with a reduced risk of damaging the first member and with reduced wear to the first member. Thus, the first unit can be efficiently moved, for example pushed, into contact with the first member and/or efficiently moved away, for example pulled, from its contact with the first member with a reduced risk of damaging the first member. Thus, the heat transfer from the first unit to the second unit is made more efficient.
In an implementation form of a device according to the first aspect, the low-friction material layer comprises anyone from the group comprising: a polymer film and a metal foil. An advantage with this implementation form is that the first unit can be efficiently moved into contact with the first member or moved away from its contact with the first member with a reduced risk of damaging the first member and with reduced wear to the first member. Thus, the heat transfer from the first unit to the second unit is made more efficient.
In an implementation form of a device according to the first aspect, the biasing element is sandwiched between the first member and the second member. An advantage with this implementation form is that the biasing element is efficiently integrated and incorporated between and into the first and second members, whereby an efficient thermal coupling between the first and second member is attained. Thus, the heat transfer from the first unit to the second unit is further improved.
In an implementation form of a device according to the first aspect, the device comprises a shell, wherein the shell comprises the first and second members, and wherein the biasing element is enclosed by the shell. An advantage with this implementation form is that a single- piece device is provided in an efficient way, and the single-piece device may be given a smooth exterior, whereby the heat transfer from the first unit to the second unit is further improved.
In an implementation form of a device according to the first aspect, the first member is formed as a plate, wherein the second member is formed as a plate, wherein the biasing element is formed from a plate, wherein the biasing element has an edge, and wherein the edge extends outside the first and second members. An advantage with this implementation form is that the biasing member may be in lateral contact with a surrounding structure when installed while still ensuring an efficient heat transfer from the first unit to the second unit. Reasons for a lateral contact between the biasing member, for example when made of a first material comprising or consisting of a metal or a metal alloy, and a surrounding structure is disclosed in further detail hereinbelow.
According to a second aspect of the invention, the above mentioned and other objects are achieved with an apparatus for cooling a thermally conductive first unit, wherein the apparatus comprises a device according to any one of the appended claims 1 to 10, or according to any of the above- or below-mentioned embodiments/implementation forms of the device, wherein the apparatus comprises the second unit, which is a heat sink, and a compartment configured to receive and hold the first unit. An advantage of the apparatus according to the second aspect is that an improved heat transfer between a first unit held in the compartment and the second unit in the form of a heat sink is provided. Further advantages correspond to the advantages of the device and its embodiments mentioned above or below.
In an implementation form of an apparatus according to the second aspect, the compartment is configured to detachably secure the first unit. An advantage with this implementation form is that first unit is easily removed from its position in the compartment for replacement or inspection. For this application, the embodiments of the device according to the present invention are especially advantageous, i.e. for situations when a first unit is removed from its contact with the first member and subsequently a first unit is put back in the compartment and into contact with the first member. As disclose above, the biasing element between the first member and the second member forces the thermally conductive first member and second member back towards an expanded state and makes the thermally conductive material of each of the first and second members properly fill the air gap between the first unit and the heat sink.
In an implementation form of an apparatus according to the second aspect, the compartment is configured to receive and hold the first unit, wherein the first unit is in the form of a transceiver module to which a signal cable is connectable. The transceiver module is mechanically connectable to the signal cable. When the signal cable s connected to the transceiver module a signal connection is provided between the transceiver module and signal cable, i.e. a connection through which signal transmission is possible. The transceiver module may in turn be electrically connectable or connected to a printed circuit board, PCB. The transceiver module may be an optical transceiver module and the signal cable may be an optical signal cable, for example an optical fibre cable. When in use, an optical transceiver module produces a substantial amount of heat which should be dissipated or transferred away from the optical transceiver module, and also away from a printed circuit board located close to the transceiver module. The heat is produced when the optical transceiver module converts optical signals to electrical signals. The electrical signals are then transmitted to the printed circuit board. Thus, for applications where the first unit is a transceiver module, for example an optical transceiver module, the embodiments of the apparatus according to the present invention are especially advantageous.
In an implementation form of an apparatus according to the second aspect, the apparatus comprises a metal housing, which houses the compartment, and a printed circuit board, to which the housing is attached, wherein the compartment has a first opening for receiving the first unit connectable to the printed circuit board, wherein the compartment has a second opening, and wherein the device is received and held in the second opening. For this application, the embodiments of the device according to the present invention are especially advantageous. Conventionally, an interface comprising a metal housing is often used for connecting a signal cable to a printed circuit board via a first unit, for example a transceiver module, held by a compartment in the housing. By the second opening and embodiments of the device according to the present invention, an improved heat transfer is provided between the first unit and the heat sink for reasons mentioned above.
In an implementation form of an apparatus according to the second aspect, the biasing element covers the second opening and is in contact with the housing, and wherein the first material comprises or consists of a metal or a metal alloy. The feature of this implementation is advantageously combined with the features of the above-mentioned implementation defining that the first member is formed as a plate, that the second member is formed as a plate, that the biasing element is formed from a plate, that the biasing element has an edge, and that the edge extends outside the first and second members. A second opening in the compartment could increase the risk of electromagnetic interference, EMI, leakage from the first unit, for example the transceiver module, and from a connector electrically connecting the transceiver module to the printed circuit board. The electromagnetic interference leakage could for example influence an antenna nearby. Further, a second opening in the compartment could increase the risk of interference caused by signals from an antenna nearby or from other electrical components. However, an advantage with this implementation form, since the biasing element is made of a first material comprising or consisting of a metal or a metal alloy and covers the second opening, is that electromagnetic interference shielding is provided. Thus, an improved heat transfer is provided between the first unit and the heat sink without an increased risk of electromagnetic interference leakage.
In an implementation form of an apparatus according to the second aspect, the apparatus comprises the first unit.
According to a third aspect of the invention, the above mentioned and other objects are achieved with a network access node, which may comprise a base station, for a wireless communication system, wherein the network access node comprises an apparatus according to any one of the appended claims 1 1 to 16, or according to any of the above- or below- mentioned embodiments of the apparatus. Advantages of the network access node correspond to the advantages of the device and apparatus and their embodiments mentioned above or below. The network access node may comprise a base station.
Further applications and advantages of the embodiments of the invention will be apparent from the following detailed description.
Brief Description of the Drawings
The appended drawings are intended to clarify and explain different embodiments of the invention, in which:
- Fig. 1 is a schematic cross-section view of a device according to a first embodiment of the invention;
- Figs. 2a-2c illustrate the manufacturing of the biasing element of the device of Fig. 1 ;
- Fig. 3 is a schematic perspective view of an alternative to the biasing element of
Figs. 1 and 2;
- Fig. 4 is a schematic perspective view of another alternative to the biasing element of Figs. 1 -3;
- Fig. 5 is a schematic perspective view of a further alternative to the biasing element of Figs. 1 -4;
- Fig. 6 is a schematic exploded view of a device according to a second embodiment of the invention;
- Fig. 7 is a schematic perspective view of the device according to a third embodiment of the invention;
- Fig. 8 is a schematic exploded view of the device of Fig. 7;
- Fig. 9 is a schematic cross-section view of the device of Figs. 7 and 8;
- Fig. 10 is a schematic cross-section view of an apparatus according to
embodiments of the invention;
- Fig. 1 1 is a schematic perspective view of the apparatus of Fig. 10;
- Fig. 12 is an exploded view of the apparatus of Fig. 1 1 ;
- Fig. 13 is a schematic view of the apparatus of Fig. 1 1 but with the second
unit removed for illustrative purposes; and
Fig. 14 is an enlargement view of the apparatus of Fig. 13.
Detailed Description
Conventionally, in order to provide an efficient thermal transfer from a unit to be cooled, for example an electrical component, to the heat sink or the active cooling device, various thermally conductive filling materials, which provide and facilitate the heat transfer, may be placed between the unit to be cooled and the heat sink or the active cooling device. The purpose of these thermally conductive filling materials is to fill the thermally insulting air gap or air gaps between the unit to be cooled and the heat sink or active cooling device. In conventional solutions, a so-called thermal interface material, TIM, may be used as a thermally conductive filling material. Various compositions of the thermal interface material are possible. A solid-state thermal interface material may for example comprise an elastomer to which particles comprising or consisting of a metal or a metal alloy have been added. Conventionally, these thermal interface materials are resilient to a certain extent to be able to expand from a compressed state towards a non-compressed state in order to fill the air gaps between the unit to be cooled and the heat sink or active cooling device, and this improves the heat transfer therebetween. The inventor of the present invention has identified drawbacks associated with conventional solid-state thermal interface materials used, for example between an electrical component and a heat sink or an active cooling device. For example, the solid-state thermal interface material when installed and compressed between a first unit and a second unit will set in a compressed state after some time and lose its resilient character completely or to some degree. When the first unit is removed and replaced by another first unit or the same first unit is reintroduced after inspection, the solid-state thermal interface material may not properly expand and fill the air gaps between the first unit and the second unit. Thus, thermally insulating air gaps or air pockets will be present between the solid-state thermal interface material and the first unit and/or between the solid-state thermal interface material and the second unit. Because of these air gaps or air pockets the heat transfer between the first unit and the second unit is impaired, and there will be a temperature increase regarding the first unit, which may result in a short life time for the first unit when it for example comprises an electrical component, such as a temperature-sensitive optical transceiver, and an increased risk of overheating of the first unit.
With reference to Figs. 1 and 2a-2c, a device 102 according to a first embodiment of the invention for transferring or conducting heat between a first unit 104 (see Fig. 10) and a second unit 106 (see Fig. 10) is schematically illustrated. The first and second unit 104, 106 are thermally conductive. The device 102 includes a first member 108 made of a thermally conductive material and a second member 1 10 made of a thermally conductive material. Each of the first and second members 108, 1 10 is at least partly resilient, for example at least resilient to a certain degree. Thus, the thermally conductive material of the first and second members 108, 1 10 may be at least partly resilient. Each of the first and second members 108, 1 10 is resilient and/or flexible enough to fill out the gap or gaps between the first and second units 104, 106. The thermally conductive material of the first and second members 108, 1 10 may for example be a solid-state thermal interface material, TIM, comprising for example a composite material made of a polymer, for example an elastomer, with particles comprising or consisting of a metal or a metal alloy added to the polymer. Thus, said particles are mixed into the polymer. The thermal conductivity of a solid-state thermal interface material may be up to 10 W/mK. The first member 108 is configured to abut against the first unit 104, and the second member 1 10 is configured to abut against the second unit 106. The first member 108 and the second member 1 10 are thermally coupled to one another, for example through physical abutment or via additional thermally conductive material and/or via a biasing element 1 12. The device 102 includes the biasing element 1 12. By thermal coupling is meant that there is a heat transfer between the first and second members 108, 1 10, or in other words, that there is a heat-conducting communication between the first and second members 108, 1 10.
The biasing element 1 12, which also may be called a resilient element or a spring element, is made of a first material, wherein the first material is different from the thermally conductive material of each of the first and second members 108, 1 10. As illustrated in Fig. 1 , the biasing element 1 12 is located between the first member 108 and the second member 1 10. The biasing element 1 12 is configured to force (or urge or bias) the first member 108 in a direction away from the second member 1 10 and/or force (or urge or bias) the second member 1 10 in a direction away from the first member 108. In otherwords, the biasing element 1 12 is configured to push (or impel) the first member 108 in relation to the second member 1 10 in a direction away from the second member 1 10 and to push (or impel) the second member 1 10 in relation to the first member 108 in direction away from the first member 108. With reference to Figs. 2a-2c, the biasing element 1 12 may be formed from a plate 1 13 made of the first material which may be a thermally conductive material. Thus, the first material of the biasing element 1 12 may be a thermally conductive material. In the embodiment of Figs. 1 and 2a-2c, the first material of the biasing element 1 12 comprises or consists of a metal or a metal alloy. The thermal conductivity of the first material of the biasing element 1 12 may be above 10 W/mK. As illustrated in Fig. 2b, the plate 1 13 is provided with through-holes or grooves which form a plurality of tongues 1 1 1 . With reference to Fig. 2c and Fig. 1 , these tongues 1 1 1 are bent to provide a biasing or resilient character of the biasing element 1 12.
With reference to Fig. 1 , the device 102 comprises a shell 1 18 including the first and second members 108, 1 10, wherein the biasing element 1 12 is enclosed by the shell 1 18. The shell 1 18 may be provided by over-moulding to completely enclose the biasing element 1 12 by means of the shell 1 18.
With reference to Figs. 3 and 4, two alternative biasing elements 1 12a, 1 12b made of a first material are illustrated. The first material of the two alternative biasing elements 1 12a, 1 12b may comprise or consist of a metal or a metal alloy. Thus, the first material of the two alternative biasing elements 1 12a, 1 12b is a thermally conductive material.
With reference to Fig. 1 , the first member 108 of the device 102 has a first surface 1 14 configured to contact the first unit 104. The first surface 1 14 is covered by a low-friction material layer 1 16. A low-friction material is a material with a low coefficient of friction, COF. The low- friction material layer 1 16 may comprise anyone from the group comprising: a polymer film and a metal foil. The metal foil may be made of a metal or a metal alloy. The polymer film may be made of one polymer, for example polyimide, or a mixture of polymers. An advantage with low- friction material layer 1 16 is that the first unit 104 can be easily slid against the first surface 1 14 in a direction along the first surface 1 14 with a reduced risk of damaging the first member 108 and with reduced wear to the first member 108. Thus, the first unit 104 can be removed from its contact with the first member 108 or introduced into contact with the first member 108 in an efficient manner.
With reference to Figs. 5 and 6, a device 202 according to a second embodiment of the invention for transferring or conducting heat between a first unit 104 and a second unit 106 is schematically illustrated. The device 202 includes another alternative biasing element 212 located between the first and second members 208, 210 of the device 202. The biasing element 212 of Figs. 5 and 6 has a grid shape. The first material of the biasing element 212 of Figs. 5 and 6 may comprise silicone or other flexible material. The cavities 215 of the grid- shaped biasing element 212 may be filed by the material of the first and second members 208, 210, or by an additional thermally conductive material which thermally couples the first member 208 to the second member 210. The biasing element 212 of Figs. 5 and 6 may also be enclosed by a shell 208 which includes the first and second members 208, 210. Otherwise, the first and second members 208, 210 of the second embodiment of Figs. 5 and 6 may essentially correspond to the first and second members 108, 1 10 of the first embodiment of Fig. 1.
With reference to Figs. 7 to 9, a device 302 according to a third embodiment of the invention for transferring or conducting heat between a first unit 104 (see Fig. 10) and a second unit 106 (see Fig. 10) is schematically illustrated. The device 302 includes a first member 308 made of a thermally conductive material and a second member 310 made of a thermally conductive material. The material of the first and second members 308, 310 of the device 302 of Figs. 7 to 9 may correspond to the material of the first and second members 108, 1 10 of the device 102 of Fig. 1 . Each of the first and second members 308, 310 is at least partly resilient. The thermally conductive material of the first and second members 308, 310 of the device 302 of Figs. 7 to 9 may be similar to the thermally conductive material of the first and second members 108, 1 10 of the device 102 of Fig. 1. The first member 308 is configured to abut against the first unit 104, and the second member 310 is configured to abut against the second unit 106. The first member 308 and the second member 310 are thermally coupled to one another, for example through physical abutment or via additional thermally conductive material and/or via a biasing element 312 of the device 302.
With reference to Figs. 7 to 9, the biasing element 312 is made of a first material, wherein the first material is different from the thermally conductive material of each of the first and second members 308, 310. The basing element 312 of the device 302 of Figs. 7 to 9 may correspond to the biasing element 1 12 of the device 102 of Fig. 1 and is thus not disclosed in further detail. As illustrated in Figs. 7 and 9, the biasing element 312 is located between the first member 308 and the second member 310. The biasing element 312 is configured to force (or urge or bias) the first member 308 in a direction away from the second member 310 and/or force (or urge or bias) the second member 310 in a direction away from the first member 308. With reference to Fig. 8, the first member 308 is formed as a plate, the second member 310 is formed as a plate, and the biasing element 312 is formed from a plate. With reference to Figs. 7 and 9, the biasing element 312 has an edge 320. The edge 320 extends outside the first and second members 308, 310. The device 302 of Figs. 7-9 is especially suitable for an application further disclosed hereinbelow in connection with Figs. 10 to 14. It is to be understood that the biasing element 1 12, 1 12a-b, 212, 312 may be designed in different ways than those disclosed above. For example, the biasing element may be a mesh, a net, a spring wire etc. It is also possible to introduce a plurality of biasing elements, i.e. two or more biasing elements, for example separated from one another.
The thermal conductivity of the first material of the biasing element 1 12, 212, 312 may be equal to or higher than the thermal conductivity of the thermally conductive material of each of the first and second members 108, 1 10, 208, 210, 308, 310. With reference to Figs. 1 and 9, the biasing element 1 12, 312 of the device 102, 302 is sandwiched between the first member 108, 308 and the second member 1 10, 310. With reference to the device 302 of Figs. 7 to 9, the biasing element 312 is attached to the first member 308 and the second member 310, for example by an adhesive or simply by being sandwiched between the first member 308 and the second member 310 and/or integrated with the first and second members 308 310. This may also be the case for the biasing member 1 12 of the device 102 shown in Fig. 1 .
With reference to Figs. 10 to 14, an apparatus 402 for cooling a thermally conductive first unit 104 according to a first embodiment of the invention is schematically illustrated. The apparatus 402 may include a device 102, 202, 302 according to any one of the embodiments disclosed above. However, in Figs. 10 to 14, the apparatus 402 is illustrated with the device 302 according to the third embodiment of Figs. 7 to 9. The apparatus 402 also includes the second unit 106 which is in the form of a heat sink 404 having cooling fins 405. Further, the apparatus 402 includes one or more compartments 406 configured to receive and hold a first unit 104. To the left in Fig. 10, the compartment 406 is illustrated without a first unit 104, and to the right in Fig. 10, the compartment 406 is illustrated with a first unit 104 received and held. Advantageously, the compartment 406 is configured to detachably secure the first unit 104. Advantageously, the compartment 406 is configured to receive and hold the first unit 104 which is in the form of a transceiver module 408 to which a signal cable is connectable. Each compartment 406 may be housed in a metal housing 410. The metal housing 410 may house a connector electrically connecting the first unit 104, for example the transceiver module 408, to a printed circuit board (PCB) 412 of the apparatus 402. In the embodiments shown in Figs. 10 to 14, the apparatus 402 includes both the metal housing 410 and the printed circuit board 412. The apparatus 402 may also include the first unit 104. The metal housing 410 may be made of a material comprising or consisting of a metal or a metal alloy.
With reference to the embodiment of Figs. 1 1 to 14, the illustrated apparatus 402 has two comportments 406 and two transceiver modules 408 received and held in the compartments 406. However, the apparatus 402 may have fewer or more compartments 406. The transceiver module 408 may be an optical transceiver module 408 to which an optical signal cable, for example an optical fibre cable, is connected. However, the transceiver module 408 may also be configured to be connectable to an electrical signal cable. The apparatus 402 according to the embodiments of the present invention is especially advantageous for applications including an optical transceiver module 408, since when converting optical signals from the optical signal cable to electrical signals for transmission to the printed circuit board 412, an optical transceiver module 408 generates a substantial amount of heat, which should be dissipated or transferred away from the optical transceiver module 408, to protect the optical transceiver module 408 from heat, since the optical transceiver module 408 is sensitive to high temperatures. The reliability and life time of a transceiver module 408 is related to the module temperature. Typical allowed maximum temperatures for the optical transceiver module 408 is 75°C or 85°C. The temperature of the optical transceiver module 408 can be reduced by 2- 5°C, but also by more, for example by 10-20°C, if a thermally insulating air gap or air pocket is avoided by the use of the device 302 and the apparatus 402. The heat generated by the signal conversion of the optical transceiver module 408 may also be dissipated to protect the printed circuit board 412 from high temperatures, since the printed circuit board 412 is located close to the compartment 406 and the optical transceiver module 408.
With reference to Figs. 10-14, the metal housing 410 of the apparatus 402 is attached to the printed circuit board 412 of the apparatus 402. Each compartment 406 has a first opening 414 for receiving the first unit 104, which is connectable to the printed circuit board 412. Each compartment 406 has a second opening 416. The device 302 is received in and held in the second opening 416 and thus brought into physical and thermal contact with the first unit 104 held in the compartment 406. The device 302 is also in physical and thermal contact with the heat sink 404. The device 302 may be attached to the second unit 106, for example the heat sink 304, by suitable means, for example by way of an adhesive. Alternatively, or in addition, the biasing element 312 of the device 302 may be attached the metal housing 410. More specifically, to the right in Fig. 10, the first member 308 of the device 302 abuts against the first unit 104, for example the transceiver module 408, and the second member 310 of the device 302 abuts against the second unit 106, for example the heat sink 404, and thereby a thermal coupling is provided between the first unit 104 and the device 302 and between the device 302 and the second unit 106, whereby a heat transfer between the first unit 104 and a second unit 106 is provided. By means of embodiments of the device 102; 202; 302 and embodiments of the apparatus 402, the heat transfer from the first unit 104 to the second unit 106 is improved. Consequently, an improved heat dissipation is provided.
With reference to Figs. 10 to 14, the housing 410 of the apparatus 402 may be called a cage or a casing. Instead of two compartments as illustrated in Figs. 10 to 14, the apparatus 402 may include more compartments, for example four compartments. The biasing element 312 covers the second opening 416 of the compartment 406. Thus, biasing element 312 is bigger than the second opening 416. As shown in Figs. 10 and 14, the biasing element 312 is in contact, i.e. physical and/or mechanical contact, with the housing 410. The first material of the biasing element 312 comprises or consists of a metal or a metal alloy. Since the biasing element 312 in this embodiment is made of an electrically conductive material, which is also the case for the metal housing 410, and advantageously completely covers the second opening 416, this embodiment provides improved electromagnetic interference (EMI) shielding compared to an example where a second opening in the metal housing is not covered by a biasing element or a metal plate. However, the device 302 of Figs. 10 to 14 is still configured to transfer heat between the first unit 104 and the second unit 106, such that also an efficient heat dissipation is provided.
The compartment 406 may be described as a slot in the housing 410. The housing 410 may be an SFP (small-factor form pluggable) or QSFP (quad small form-factor pluggable) housing. The transceiver module 408 may be an SFP or QSFP module. The signal cable, which may be an optical fibre cable, may be connectable to an SFP or QSFP transceiver module. SFP and QSFP per se are known to the person skilled in the art and are thus not further described in this disclosure.
The embodiments of the present invention also include a network access node for a wireless communication system. The network access node includes an apparatus 402 according to the embodiments disclosed above. The network access node may comprise a base station, for example a base radio station. The network access node may include one or more antennas. The base station may have a housing which houses the antenna. Alternatively, the antenna is mounted outside the housing of the base station, for example with a distance to the housing of the base station. The antenna may be connectable to the printed circuit board 412 via a suitable cable.
The resilience discussed above may be called mechanical resilience. Thus, a resilient member may be called a mechanically resilient member. Finally, it should be understood that the invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

1 . A device (102; 202; 302) for transferring heat between a first unit (104) and a second unit (106), the device (102; 202; 302) comprising a first member (108; 208; 308) made of a thermally conductive material and a second member (1 10; 210; 310) made of a thermally conductive material, each of the first and second members (108, 1 10; 208, 210; 308, 310) being at least partly resilient, the first member (108; 208; 308) being configured to abut against the first unit (104), and the second member (1 10; 210; 310) being configured to abut against the second unit (106), wherein the first member (108; 208; 308) and the second member (1 10; 210; 310) are thermally coupled to one another, wherein the device (102; 202; 302) comprises a biasing element (1 12; 212; 312) made of a first material, the first material being different from the thermally conductive material of each of the first and second members (108, 1 10; 208, 210; 308, 310), wherein the biasing element (1 12; 212; 312) is located between the first member (108; 208; 308) and the second member (1 10; 210; 310), and wherein the biasing element (1 12; 212; 312) is configured to urge the first member (108; 208; 308) in a direction away from the second member (1 10; 210; 310).
2. A device (102; 202; 302) according to claim 1 , wherein the biasing element (1 12; 212) is configured to urge the second member (1 10; 210) in a direction away from the first member (108; 208).
3. A device (102; 202; 302) according to claim 1 or 2, wherein the first material is a thermally conductive material.
4. A device (102; 202; 302) according to claim 3, wherein the thermal conductivity of the first material is equal to or higher than the thermal conductivity of the thermally conductive material of each of the first and second members (108, 1 10; 208, 210).
5. A device (102; 202; 302) according to any one of the claims 1 to 4, wherein the thermally conductive material of each of the first and second members (108, 1 10; 208, 210) is a thermal interface material, TIM.
6. A device (102; 202; 302) according to any one of the claims 1 to 5, wherein the first member (108) has a first surface (1 14) configured to contact the first unit (104), and wherein the first surface (1 14) is covered by a low-friction material layer (1 16).
7. A device (102; 202; 302) according to claim 6, wherein the low-friction material layer (1 16) comprises anyone from the group comprising: a polymer film and a metal foil.
8. A device (102; 202; 302) according to any one of the claims 1 to 7, wherein the biasing element (1 12; 212) is sandwiched between the first member (108; 208) and the second member (1 10; 210).
9. A device (102; 202) according to any one of the claims 1 to 8, wherein the device (102) comprises a shell (1 18) comprising the first and second members (108, 1 10), and wherein the biasing element (1 12) is enclosed by the shell (1 18).
10. A device (302) according to any one of the claims 1 to 8, wherein the first member (308) is formed as a plate, wherein the second member (310) is formed as a plate, wherein the biasing element (312) is formed from a plate, wherein the biasing element (312) has an edge (320), and wherein the edge (320) extends outside the first and second members (308, 310).
1 1 . An apparatus (402) for cooling a thermally conductive first unit (104), wherein the apparatus (402) comprises a device (102; 202; 302) according to any one of the claims 1 to 10, and wherein the apparatus (402) comprises the second unit (106), which is a heat sink (404), and a compartment (406) configured to receive and hold the first unit (104).
12. An apparatus (402) according to claim 1 1 , wherein the compartment (406) is configured to detachably secure the first unit (104).
13. An apparatus (402) according to claim 1 1 or 12, wherein the compartment (406) is configured to receive and hold the first unit (104), the first unit (104) being in the form of a transceiver module (408) to which a signal cable is connectable.
14. An apparatus (402) according to any one of the claims 1 1 to 13, wherein the apparatus (402) comprises a metal housing (410), which houses the compartment (406), and a printed circuit board (412), to which the housing (410) is attached, wherein the compartment (406) has a first opening (414) for receiving the first unit (104) connectable to the printed circuit board (412), wherein the compartment (406) has a second opening (416), and wherein the device (102; 202; 302) is received and held in the second opening (416).
15. An apparatus (402) according to claim 14, wherein the biasing element (312) covers the second opening (416) and is in contact with the housing (410), and wherein the first material comprises or consists of a metal or a metal alloy. 16. An apparatus (402) according to any one of the claims 11 to 15, wherein the apparatus
(402) comprises the first unit (104).
17. A network access node for a wireless communication system, wherein the network access node comprises an apparatus (402) according to any one of the claims 11 to 16.
PCT/EP2019/059800 2019-04-16 2019-04-16 A device for transferring heat between a first unit and a second unit WO2020211930A1 (en)

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