Cooling assembly

Abstract

The disclosure relates to a cooling assembly (100) for cooling an electronic circuit (120). The cooling assembly comprises: a carrier (140); an electronic circuit (120) mounted on the carrier; a heat sink (110) mounted on the carrier above the electronic circuit; and a relaxation gap (132) arranged between the electronic circuit and the heat sink. The relaxation gap is formed to reduce an impact of a mechanical tension on the electronic circuit, which results from mounting the heat sink on the carrier. The cooling assembly comprises a liquid thermal interface material (130) arranged in the relaxation gap. The liquid thermal interface material is formed to provide a thermal dissipation interface between the electronic circuit and the heat sink. The cooling assembly comprises a sealing (131) surrounding the liquid thermal interface material and preventing the liquid thermal interface material from exiting the relaxation gap. The heat sink comprises an accumulating cavity (111) configured to accumulate part of the liquid thermal interface material to release pressure of the liquid thermal interface material onto the electronic circuit.

Description

[0001] COOLING ASSEMBLY

[0002] TECHNICAL FIELD

[0003] The disclosure relates to the field of thermal coupling and thermal interface materials. In particular, the disclosure relates to a cooling assembly for cooling an electronic circuit. More particularly, the disclosure relates to techniques for thermal coupling of chip and heat sink by liquid metal and magnetic field.

[0004] BACKGROUND

[0005] Low thermal resistance of TIM (Thermal interface material) significantly increases cooling performance of heat sink (HS). Liquid metal (LM) due to its high thermal conductivity can be a good solution for TIM. Unfortunately, many specific problems arise when using LM, such as degradation of thermal performance and possibility of mechanical damage of the chip by HS. Because compressible sealing material (S M) hasn’t any or weak adhesion to the surface without compression force, the sealing will be insecure. Mechanical impact transfer will result in mechanical damage of the chip due to c mi pression force applied directly from HS to the chip surface. A further disadvantage is the non-safe interaction between chip brittle material with HS under high pressure. Currently available sink mounting system provides a transfer of both heat and mechanical impacts between the and the HS. Such approach leads to the mechanical stress transfer from the heavy HS to the c lip which may result in cracking due to warpage under operating temperatures. Another risk is re ated to degrading of SM and leaking out of LM, which can lead to short circuit of the electronic on the PCB (Printed circuit board). Since, used SM is a polymer, degrading under op erature is inevitable. Degrading of polymer leads to reduction of mechanical properties, loosing of elasticity and cracking.

[0006] SUMMARY

[0007] This disclosure provides a solution for a novel heat transfer system to minimize mechanical interaction between the die and the heat s nk.

[0008] The present disclosure solves the problem of risk of chip damage due to direct mechanical contact between chip surface and heat sink and •ovides a solution for an effective heat transfer. At the same time the new solution helps to i e sealing reliability by making it resistible to degrading of polymers. The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

[0009] Aspects of the present disclosure provide a cooling assembly, comprising PCB, chip (or electronic circuit, respectively), frame, magnetic liquid, liquid TIM (L-TIM), magnetic frame, accumulating cavity and heat sink and mounting means, e.g., screws. Main issues of the presented solution are shown in the following:

[0010] The heat sink can, for example, be fixed to the PCB by (any) screwed or other mechanical connection that a gap between heat sink bottom surface and chip surface (on PCB) exists, and this gap is high enough (for example 350±50 um) to avoid direct contact of heat sink and chip.

[0011] To achieve low thermal resistance and low strength contact between chip and heat sink, the high conductive liquid TIM can be placed between heat sink and chip, and liquid TIM can be located at least on the chip surface.

[0012] To avoid losses of liquid TIM from the gap, the Magnetic Liquid can be placed around liquid TIM and between frame and Magnetic Frame, installed in the heat sink; due to magnetic forces from MF, the ML doesn’t move from Magnetic Frame and can seal the liquid TIM from outside space.

[0013] To avoid increasing pressure of liquid TIM, the accumulating cavities can be arranged inside heat sink in such a way, that exceeding amount of liquid TIM can be released to that cavities.

[0014] Composition of liquid TIM may consist of the following exemplary range of alloyed elements: 100-0.1 wt.% Ga, 51-0.1 wt.% In, 13-0.1 wt.% Sn, 33-0.1 wt.% Bi, 5-0.1 wt.% Ag based alloys.

[0015] Composition of Magnetic Liquid may consist, for example, of magnetic particles of about 0.1-20 um size (e.g., iron, iron oxide, iron-neodymium-boron, sendust (Fe-Si-Al) etc.) and viscous water- free liquid (e.g., polydimethylsiloxane, polydimethylsiloxane with polytetrafluoroethylene additives), applied volume of ML according to the case should be equal to about 0.52cc, for example.

[0016] An exemplary copper protection coating can be made of PVD or CVD disordered carbon coating tens of micrometers thickness, for example. The solution presented in this disclosure can be used in any electronic device, where the thermal coupling between chip and heat sink is necessary such as computers, routers, servers, radio remote units, vehicles etc.

[0017] The technology described in this disclosure can be applied to any chip including containing equipment, high performance computing workstations, server blades, personal computers, vehicles etc.

[0018] In order to describe the disclosure in detail, the following terms and notations will be used.

[0019] ML Magnetic liquid

[0020] MF Magnetic frame

[0021] LM Liquid metal

[0022] TIM Thermal interface material

[0023] L-TIM Liquid metal thermal interface material

[0024] HS Heat sink

[0025] PCB Printed Circuit Board wt.% Weight percent

[0026] SM Sealing material

[0027] CVD Chemical vapor deposition

[0028] PVD Physical vapor deposition

[0029] Galinstan alloy of 68.5 wt.% Gallium, 21.5 wt.% Indium and 13 wt.% Stanum, which is liquid in room temperature conditions.

[0030] According to a first aspect, the disclosure relates to a cooling assembly for cooling an electronic circuit, the cooling assembly comprising: a carrier; an electronic circuit mounted on the carrier; a heat sink mounted on the carrier above the electronic circuit; and a relaxation gap arranged between the electronic circuit and the heat sink, the relaxation gap being formed to reduce an impact of a mechanical tension on the electronic circuit, the mechanical tension resulting from mounting the heat sink on the carrier; a liquid thermal interface material arranged in the relaxation gap, the liquid thermal interface material being formed to provide a thermal dissipation interface between the electronic circuit and the heat sink; and a sealing surrounding the liquid thermal interface material and preventing the liquid thermal interface material from exiting the relaxation gap; wherein the heat sink comprises an accumulating cavity configured to accumulate part of the liquid thermal interface material to release pressure of the liquid thermal interface material onto the electronic circuit.

[0031] By using a relaxation gap between the electronic circuit and the heat sink, compression force for mounting the heat sink to the carrier is kept away from the electronic circuit surface, thus reducing the risk of mechanical damage of the electronic circuit.

[0032] When using a liquid TIM material, heat dissipation from electronic circuit to heat sink can be improved.

[0033] In an exemplary implementation of the cooling assembly, the cooling assembly comprises a mechanical attachment for mounting the heat sink on the carrier, the mechanical attachment being configured to mount the heat sink at a distance greater than a thickness of the electronic circuit above the carrier, such that the relaxation gap is formed between the electronic circuit and the heat sink.

[0034] By such mechanical attachment, the gap can precisely be formed.

[0035] In an exemplary implementation of the cooling assembly, the mechanical attachment comprises: One or more screw portions for screwing with the carrier and the heat sink, respectively; and a spacer for maintaining the distance between the heat sink and the carrier.

[0036] Such a mechanical attachment can be easily provided.

[0037] In an exemplary implementation of the cooling assembly, the liquid thermal interface material completely covers a surface of the electronic circuit facing the relaxation gap.

[0038] This results in efficient heat transfer by utilizing the whole surface of the electronic circuit.

[0039] In an exemplary implementation of the cooling assembly, the liquid thermal interface material completely fills the relaxation gap within the sealing.

[0040] This results in efficient heat transfer since air is displaced by the liquid thermal interface material which has better heat transfer characteristics than air. In an exemplary implementation of the cooling assembly, the accumulating cavity comprises an opening, the opening being arranged at a surface of the heat sink facing the liquid thermal interface material.

[0041] By the opening the liquid thermal interface material can escape from the gap without exerting pressure on the electronic circuit.

[0042] In an exemplary implementation of the cooling assembly, the accumulating cavity comprises a gas reservoir chamber and one or more channels connecting the gas reservoir chamber to the liquid thermal interface material.

[0043] By such feature, the liquid thermal interface material can accumulate in the gas reservoir chamber and / or the channels, thereby avoiding or releasing pressure on the electronic circuit.

[0044] The accumulating cavity with gas reservoir chambers hence avoids pressure rise of liquid TIM. It can neutralize pressure change due to thermal expansion, vibration, movement of components or atmospheric pressure change.

[0045] Since liquid metal may be incompressible liquid, compensation of pressure change can be organized using gas reservoirs. When liquid traps in the reservoir, gas changes own volume easily and keeps pressure in the range of 0.1-10.0 psi, for example.

[0046] In an exemplary implementation of the cooling assembly, the sealing is composed of magnetic liquid material.

[0047] This results in accurate positioning of the magnetic liquid material due to magnetic interaction with magnetic counterpart, e.g., magnetic frame.

[0048] In an exemplary implementation of the cooling assembly, the magnetic liquid material comprises magnetic particles of a size between 0.1 and 20 pm and a viscous water-free liquid.

[0049] Such magnetic particles can efficiently absorb magnetic forces and enable accurate positioning of the magnetic liquid material. In an exemplary implementation of the cooling assembly, the magnetic particles comprise one or more of iron, iron oxide, iron-neodymium-boron, sendust (Fe-Si-Al); and / or the water-free liquid comprises polydimethylsiloxane and / or polydimethylsiloxane with polytetrafluoroethylene additives.

[0050] Small size of magnetic particles helps to achieve its uniform distribution in the relaxation gap, which allows to get uniform barrier function ML and keep L-TIM inside the relaxation gap. Polydimethylsiloxane is non-hygroscopic, that means ambient humidity isn’t affecting on its properties. It is stable at temperatures far above reliability test, -5O...+23O°C.

[0051] In an exemplary implementation of the cooling assembly, the heat sink comprises a magnetic frame arranged at a surface of the heat sink facing the relaxation gap, the magnetic frame being configured to attract the magnetic liquid material of the sealing in order to seal the liquid thermal interface material within the relaxation gap.

[0052] Such magnetic frame allows accurate positioning of magnetic liquid on the magnetic frame due to magnetic interaction between magnetic frame and magnetic particles inside magnetic liquid. It allows avoiding losses of liquid TIM from the gap, because of barrier function of the magnetic liquid. Due to magnetic forces from magnetic frame, the magnetic liquid doesn’t move from magnetic frame and seals the liquid TIM from outside space.

[0053] In an exemplary implementation of the cooling assembly, the magnetic frame is arranged within a groove of the heat sink surrounding a projection area of the electronic circuit at the heat sink.

[0054] By such arrangement, the magnetic frame can be efficiently fixed in the heat sink.

[0055] In an exemplary implementation of the cooling assembly, the liquid thermal interface material is composed of a liquid metal alloy.

[0056] Using a liquid metal alloy allows to improve heat transfer.

[0057] In an exemplary implementation of the cooling assembly, the liquid metal alloy is composed of one or more of the following alloyed elements: Ga within a range of 100 to 0.1 weight percent, In within a range of 51 to 0.1 weight percent, Sn within a range of 13 to 0.1 weight percent, Bi within a range of 33 to 0.1 weight percent, Ag within a range of 5 to 0.1 weight percent. Variation of chemical content of L-TIM allows to reduce melting point and keep L-TIM liquid during subzero temperature. Doping by high thermal conductivity elements helps to reduce thermal resistance of thermos-coupling.

[0058] In an exemplary implementation of the cooling assembly, the cooling assembly comprises: a frame framing the electronic circuit; wherein the sealing is attached onto the frame.

[0059] The frame can protect the electronic circuit against environmental influences. The frame further allows to attach the sealing onto the frame and thus to protect the electronic circuit.

[0060] In an exemplary implementation of the cooling assembly, the liquid thermal interface material covers a surface of the electronic circuit facing the relaxation gap and at least partially covers a surface of the frame facing the relaxation gap.

[0061] This allows cover the full surface of the electronic circuit by the liquid thermal interface material, thereby improving heat transfer.

[0062] In an exemplary implementation of the cooling assembly, a surface of the heat sink facing the liquid thermal interface material is coated with an anti-corrosion material to protect the heat sink from reactions with the liquid thermal interface material.

[0063] Coating protects against alloying liquid TIM and copper heat sink together, which can lead to reduction of liquid TIM in thermo-coupling and changing of chemical content. Change of chemical content can lead to liquid TIM properties change.

[0064] According to a second aspect, the disclosure relates to a method for producing a cooling assembly for cooling an electronic circuit, the method comprising: providing a carrier; mounting an electronic circuit on the carrier; mounting a heat sink mounted on the carrier above the electronic circuit; and arranging a relaxation gap between the electronic circuit and the heat sink, wherein the relaxation gap is formed to reduce an impact of a mechanical tension on the electronic circuit, the mechanical tension resulting from mounting the heat sink on the carrier; arranging a liquid thermal interface material in the relaxation gap, the liquid thermal interface material being formed to provide a thermal dissipation interface between the electronic circuit and the heat sink; and providing a sealing surrounding the liquid thermal interface material and preventing the liquid thermal interface material from exiting the relaxation gap; wherein the heat sink comprises an accumulating cavity which is formed to accumulate part of the liquid thermal interface material to release pressure of the liquid thermal interface material onto the electronic circuit.

[0065] Such method allows safe production of a cooling assembly as described above with respect to the first aspect. By using a relaxation gap between the electronic circuit and the heat sink, compression force for mounting the heat sink to the carrier is kept away from the electronic circuit surface, thus reducing the risk of mechanical damage of the electronic circuit. When using a liquid TIM material, heat dissipation from electronic circuit to heat sink can be improved.

[0066] BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Further embodiments of the disclosure will be described with respect to the following figures, in which:

[0068] Figure 1 shows a schematic diagram illustrating the architecture of an exemplary cooling assembly 100 according to the disclosure;

[0069] Figure 2 shows a schematic diagram illustrating an exemplary system architecture 200 using the cooling assembly 100 shown in Figure 1; and

[0070] Figure 3 shows a schematic diagram illustrating an exemplary system architecture 300 using the cooling assembly 100 shown in Figure 1.

[0071] DETAILED DESCRIPTION OF EMBODIMENTS

[0072] In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, and in which is shown by way of illustration specific aspects in which the disclosure may be practiced. It is understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the disclosure is defined by the appended claims.

[0073] It is understood that comments made in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if a specific method step is described, a corresponding device may include a unit to perform the described method step, even if such unit is not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary aspects described herein may be combined with each other, unless specifically noted otherwise. Figure 1 shows a schematic diagram illustrating the architecture of an exemplary cooling assembly 100 for cooling an electronic circuit 120 according to the disclosure.

[0074] The cooling assembly 100 comprises: a carrier 140, e.g., a PCB; an electronic circuit 120 mounted on the carrier 140; a heat sink 110 mounted on the carrier 140 above the electronic circuit 120; and a relaxation gap 132 arranged between the electronic circuit 120 and the heat sink 110.

[0075] The relaxation gap 132 is formed to reduce an impact of a mechanical tension on the electronic circuit 120 which mechanical tension results from mounting the heat sink 110 on the carrier 140.

[0076] The cooling assembly 100 comprises: a liquid thermal interface material (L-TIM) 130 arranged in the relaxation gap 132. The liquid thermal interface material 130 is formed to provide a thermal dissipation interface between the electronic circuit 120 and the heat sink 110.

[0077] The cooling assembly 100 comprises: a sealing 131 surrounding the liquid thermal interface material 130 and preventing the liquid thermal interface material 130 from exiting the relaxation gap 132.

[0078] The heat sink 110 comprises an accumulating cavity 111 configured to accumulate part of the liquid thermal interface material 130 to release pressure of the liquid thermal interface material 130 onto the electronic circuit 120.

[0079] The cooling assembly 100 may comprise a mechanical attachment 150 for mounting the heat sink 110 on the carrier 140. The mechanical attachment may be configured to mount the heat sink at a distance greater than a thickness of the electronic circuit 120 above the carrier 140, such that the relaxation gap 132 is formed between the electronic circuit 120 and the heat sink 110. The mechanical attachment 150 may comprise one or more screw portions for screwing with the carrier 140 and the heat sink 110, respectively; and a spacer for maintaining the distance between the heat sink 110 and the carrier 140.

[0080] The accumulating cavity 111 may comprise an opening 113 which is arranged at a surface 114 of the heat sink 110 facing the liquid thermal interface material 130.

[0081] The accumulating cavity 111 may comprise a gas reservoir chamber I l la and one or more channels 111b connecting the gas reservoir chamber 11 la to the liquid thermal interface material 130. In Figure 1, an exemplary number of two accumulating cavities 111 are shown where each accumulating cavity 111 has a gas reservoir chamber I l la and one channel 11 lb to connect the chamber I l la to the liquid TIM 130. Any number of accumulating cavities with any number of chambers I l la and channels 111b can be implemented. Each chamber I l la may have its associated channel 111b or some chambers I l la may have more than one channel 111b. The channel 111b can run in vertical direction as shown in Figure 1 or it can run diagonally from the opening 113 to the cavity 111, for example. The chamber 111b may be partially filled with the L- TIM 130 as shown in Figure 1, for example.

[0082] The sealing 131 can be at least partially composed of magnetic liquid (ML) material 131, for example, as shown in Figure 1.

[0083] The magnetic liquid material may, for example, comprise magnetic particles of a size between 0.1 and 20 pm and a viscous water-free liquid.

[0084] The magnetic particles may, for example, comprise one or more of iron, iron oxide, iron- neodymium-boron, sendust (Fe-Si-Al). The water-free liquid may, for example, comprise polydimethylsiloxane and / or polydimethylsiloxane with polytetrafluoroethylene additives.

[0085] The heat sink 110 may comprise a magnetic frame (MF) 112 arranged at a surface 114 of the heat sink 110 facing the relaxation gap 132 (and thus the L-TIM 130). This magnetic frame 112 may be configured to attract the magnetic liquid material of the sealing 131 in order to seal the liquid thermal interface material 130 within the relaxation gap 132.

[0086] The magnetic frame 112 may, for example, be arranged within a groove 115 of the heat sink 110 surrounding a projection area of the electronic circuit 120 at the heat sink 110 as shown in Figure 1.

[0087] The liquid thermal interface material 130 may, for example, be composed of a liquid metal alloy.

[0088] Such a liquid metal alloy may be, for example, composed of one or more of the following alloyed elements: Ga within a range of 100 to 0.1 weight percent, In within a range of 51 to 0.1 weight percent, Sn within a range of 13 to 0.1 weight percent, Bi within a range of 33 to 0.1 weight percent, Ag within a range of 5 to 0.1 weight percent. The cooling assembly 100 may comprise a frame 121 framing the electronic circuit 120 as shown in Figure 1. The sealing 131, i.e., the magnetic liquid (ML) material, can be attached onto the frame 121. In this configuration, the sealing can be provided by both, the frame 121 and the ML material attached onto the frame 121. The side of the ML 131 which is opposite to the L-TIM 130 can be aligned with an external side of the frame 121 as shown in Figure 1. The ML 131 can be aligned with its both sides which correspond to the two sides of the groove 115 to the respective two sides of the MF 112 as shown in Figure 1.

[0089] The liquid thermal interface material 130 may cover a surface 122 of the electronic circuit 120 facing the relaxation gap 132 and at least partially cover a surface 123 of the frame 121 facing the relaxation gap 132.

[0090] A surface 116 of the heat sink 110 facing the liquid thermal interface material 130 may be coated with an anti-corrosion material to protect the heat sink 110 from reactions with the liquid thermal interface material 130. It understands that also other surfaces of the heat sink 110 may be covered by such anti-corrosion material, in particular inner surfaces forming the cavity 111 and surfaces forming the groove 115 for accommodating the MF 115.

[0091] In the following an exemplary embodiment of the cooling assembly 100 is described.

[0092] The cooling assembly according to this embodiment comprises a chip 120 on PCB 140, HS 110, L-TIM 130, ML 131, MF 112 installed in HS 110, cavities 111 in HS 110 with channels 11 lb to the area of L-TIM 130 application, protection coating on HS 110, screws (or other mechanical mounting 150) for rigid HS fixing under chip surface, with gap 132 equal 350 + / - 50um, for example.

[0093] PCB 140 has installation spots around the chip 120. PCB rack is used for rigid positioning of HS 110 under chip surface. Unthreaded height of PCB rack is equal to sum of heights of chip 120 and gap 132 for L-TIM 130. Area in a shape of square frame is made of mold around the chip 120 to protect PCB components of short circuit. Width of mold frame 121 around the chip 120 is equal or more than magnetic frame 112 width.

[0094] HS 110 has channels 111b which are connected to the air-filled (or gas-filled) cavities 111. Air (or gas) is nearly under atmospheric pressure. MF 112 is installed in the HS 110 around the chip projection area. Groove 115 for MF 112 installation is placed around the chip area. Depth of groove 115 is 4mm, for example, width 1mm, for example. Channels 111b and cavities 111 inner surfaces are coated in disordered carbon coating. Channels 111b connect area of L-TIM 130 positioning and lead away from the perpendicular direction, away from the heat flow direction, and connect with cavities (i.e., chambers 11 la of the cavities 111).

[0095] During assembling channel 111b and part of cavity 111 are filled in L-TIM 130. Air (or gas), which was initially in the cavity 111 is compressed by L-TIM 130. In one exemplary implementation, 3 channels can be used for 1 cavity. In one exemplary implementation, overall volume of 3 channels 111b and one cavity 111 can be equal to 0.75 cm3. Cavities 111 are placed away from heat flow to minimize thermal resistance. In this exemplary implementation, surface area being in a contact with L-TIM 130 is 3136mm2.

[0096] MF 112 can be made of single body magnet or combined by several magnets with appropriate length. In one exemplary implementation, magnetization of permanent magnet of MF 112 can be 1.2Tesla, for example. Surface of the magnet can be nickel plated, for example. In one exemplary implementation, surface area of the MF 112 exposed to the deposition of ML 131 can be equal to 228mm2.

[0097] ML 131 may consist of two components: viscous water- free liquid and magnetic particles. In one exemplary implementation, ML 131 can be prepared in proportion of 20% of viscous liquid and 80% of magnetic particles. According to the size and geometry of current embodiment, a volume of applied ML is 0.52cc. ML 131 can be applied uniformly on the whole exposed surface of MF 112.

[0098] L-TIM 130 may consist of alloyed metal elements being in liquid state. Amount of applied L-TIM 130 can be equal to 1.4 cc, in order to properly fill in gap of 350 + / -50um.

[0099] Mold can be applied around the chip 120 and creates one surface with it. Mold can contact chip side without spaces and emptiness.

[0100] L-TIM 130 can be applied on the chip surface, ML 131 can be applied on the MF 112. HS 110 with applied ML 131 can be turned over and be assembled. Since thermo-coupling is installed, during operating temperatures, it allows to achieve pressure on the chip surface below 10 psi and thermal resistance below 0.13 °C cm2 / W in one exemplary implementation. In the above-described exemplary embodiment of the cooling assembly 100, MF 112 is installed in the HS 110. MF 112 is arranged around the chip area. ML 131 is uniformly placed at least on the surface of the magnet with tolerance of about ±30%. ML 131 is placed around L-TIM 130 and between frame 121 and MF 112, installed in the HS 110.

[0101] This results in accurate positioning of ML 131 on the MF 112 due to magnetic interaction between MF 112 and magnetic particles inside ML 131. Losses of L-TIM 130 from the gap 132 can be avoided, because of barrier function of the ML 131. Due to magnetic forces from MF 112, the ML 131 does not move from MF 112 and seal the L-TIM 130 from outside space.

[0102] Further, accumulating cavity 111 is arranged inside HS 110 in such a way, that exceeding amount of L-TIM 130 can be released to that cavity 111 (for example when gap 132 decreases during drop test or at thermal expansions). In case of contraction L-TIM 130 is released from the cavities 111 to the gap 132 between chip 120 and HS 110.

[0103] This can avoid pressure rise of L-TIM 130. Pressure change can be neutralized due to thermal expansion, and atmospheric pressure change.

[0104] Composition of L-TIM 130 may consist of following exemplary range of alloyed elements: 100- 0.1 wt.% Ga, 51-0.1 wt.% In, 13-0.1 wt.% Sn, 33-0.1 wt.% Bi, 5-0.1 wt.% Ag based alloys. Variation of chemical content of L-TIM 130 allows to reduce melting point and keep L-TIM 130 liquid during subzero temperature. Doping by high thermal conductivity elements helps to reduce thermal resistance of thermo-coupling. Variation of chemical content of L-TIM allows to reduce melting point and keep L-TIM liquid during subzero temperature. Doping by high thermal conductivity elements helps to reduce thermal resistance of thermo-coupling.

[0105] Composition of ML 131 may consist of magnetic particles 0.1-20 um size (iron, iron oxide, iron- neodymium-boron, sendust (Fe-Si-Al) etc.) and viscous water-free liquid (polydimethylsiloxane, polydimethylsiloxane with polytetrafluoroethylene additives), for example. Small size of magnetic particles helps to achieve its uniform distribution in the gap 132, which allows to get uniform barrier function ML 131 and keep L-TIM 130 inside the gap 132. Polydimethylsiloxane is non- hygroscopic, that means ambient humidity isn’t affecting on its properties. It is stable at temperatures far above reliability test, -5O...+23O°C. Figure 2 shows a schematic diagram illustrating an exemplary system architecture 200 using the cooling assembly 100 shown in Figure 1.

[0106] The cooling assembly 100 as described above with respect to Figure 1 can be applied in a system 200 as shown in Figure 2 using thermo-coupling for air cooling of the electronic circuit 120 (or chip). In such a system 200, an air flow 212 is led by the heat sink 110 for cooling the heat sink 110 and thus the cooling assembly 100.

[0107] A fan 211 can be used for generating the air flow 212 from an ambient 210.

[0108] Figure 3 shows a schematic diagram illustrating an exemplary system architecture 300 using the cooling assembly 100 shown in Figure 1.

[0109] The cooling assembly 100 as described above with respect to Figure 1 can be applied in a system 300 as shown in Figure 3 using thermo-coupling for liquid cooling of the electronic circuit 120 (or chip). In such a system 300, a liquid flow 312, e.g., in a cooling channel, is led by the heat sink 110 for liquid cooling the heat sink 110 and thus the cooling assembly 100.

[0110] The liquid flow 312 can be cooled in a heat exchanger 301 that is connected to an air circulation comprising a fan 211 for generating an air flow 212 from an ambient 210 for cooling the liquid flow 312 in the heat exchanger 301.

[0111] The disclosure also relates to a method for producing a cooling assembly 100, e.g., as described above with respect to Figures 1 to 3, for cooling an electronic circuit 120.

[0112] Such a method comprises: providing a carrier 140; mounting an electronic circuit 120 on the carrier 140; mounting a heat sink 110 on the carrier 140 above the electronic circuit 120; and arranging a relaxation gap 132 between the electronic circuit 120 and the heat sink 110, wherein the relaxation gap 132 is formed to reduce an impact of a mechanical tension on the electronic circuit, the mechanical tension resulting from mounting the heat sink on the carrier.

[0113] The method further comprises: arranging a liquid thermal interface material 130 in the relaxation gap 132, the liquid thermal interface material being formed to provide a thermal dissipation interface between the electronic circuit 120 and the heat sink 110; and providing a sealing 131 surrounding the liquid thermal interface material 130 and preventing the liquid thermal interface material from exiting the relaxation gap 132; wherein the heat sink comprises an accumulating cavity 111 which is formed to accumulate part of the liquid thermal interface material 130 to release pressure of the liquid thermal interface material 130 onto the electronic circuit 120.

[0114] While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms "include", "have", "with", or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprise". Also, the terms "exemplary", "for example" and "e.g." are merely meant as an example, rather than the best or optimal. The terms “coupled” and “connected”, along with derivatives may have been used. It should be understood that these terms may have been used to indicate that two elements cooperate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other.

[0115] Although specific aspects have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein.

[0116] Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

[0117] Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the disclosure beyond those described herein. While the disclosure has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the disclosure. It is therefore to be understood that within the scope of the appended claims and their equivalents, the disclosure may be practiced otherwise than as specifically described herein.

Claims

CLAIMS:

1. A cooling assembly (100) for cooling an electronic circuit (120), the cooling assembly (100) comprising: a carrier (140); an electronic circuit (120) mounted on the carrier (140); a heat sink (110) mounted on the carrier (140) above the electronic circuit (120); and a relaxation gap (132) arranged between the electronic circuit (120) and the heat sink (110), the relaxation gap (132) being formed to reduce an impact of a mechanical tension on the electronic circuit (120), the mechanical tension resulting from mounting the heat sink (110) on the carrier (140); a liquid thermal interface material (130) arranged in the relaxation gap (132), the liquid thermal interface material (130) being formed to provide a thermal dissipation interface between the electronic circuit (120) and the heat sink (110); and a sealing (131) surrounding the liquid thermal interface material (130) and preventing the liquid thermal interface material (130) from exiting the relaxation gap (132); wherein the heat sink (110) comprises an accumulating cavity (111) configured to accumulate part of the liquid thermal interface material (130) to release pressure of the liquid thermal interface material (130) onto the electronic circuit (120).

2. The cooling assembly (100) of claim 1, wherein the accumulating cavity (111) comprises an opening, the opening being arranged at a surface of the heat sink (110) facing the liquid thermal interface material (130).

3. The cooling assembly (100) of claim 1 or 2, wherein the accumulating cavity (111) comprises a gas reservoir chamber and one or more channels connecting the gas reservoir chamber to the liquid thermal interface material (130).

4. The cooling assembly (100) of any of the preceding claims, wherein the sealing (131) is composed of magnetic liquid material.

5. The cooling assembly (100) of claim 4, wherein the magnetic liquid material comprises magnetic particles of a size between 0.1 and 20 pm and a viscous water-free liquid.

6. The cooling assembly (100) of claim 5, wherein the magnetic particles comprise one or more of iron, iron oxide, iron- neodymium-boron, sendust (Fe-Si-Al); and / orwherein the water-free liquid comprises polydimethylsiloxane and / or polydimethylsiloxane with polytetrafluoroethylene additives.

7. The cooling assembly (100) of any of claims 4 to 6, wherein the heat sink (110) comprises a magnetic frame (112) arranged at a surface of the heat sink (110) facing the relaxation gap (132), the magnetic frame (112) being configured to attract the magnetic liquid material of the sealing (131) in order to seal the liquid thermal interface material (130) within the relaxation gap (132).

8. The cooling assembly (100) of claim 7, wherein the magnetic frame (112) is arranged within a groove of the heat sink (110) surrounding a projection area of the electronic circuit (120) at the heat sink (110).

9. The cooling assembly (100) of any of the preceding claims, wherein the liquid thermal interface material (130) is composed of a liquid metal alloy.

10. The cooling assembly (100) of claim 9, wherein the liquid metal alloy is composed of one or more of the following alloyed elements:Ga within a range of 100 to 0.1 weight percent,In within a range of 51 to 0.1 weight percent,Sn within a range of 13 to 0.1 weight percent,Bi within a range of 33 to 0.1 weight percent,Ag within a range of 5 to 0.1 weight percent.

11. The cooling assembly (100) of any of the preceding claims, comprising: a frame (121) framing the electronic circuit (120); wherein the sealing (131) is attached onto the frame (121).

12. The cooling assembly (100) of claim 11, wherein the liquid thermal interface material (130) covers a surface of the electronic circuit (120) facing the relaxation gap (132) and at least partially covers a surface of the frame (121) facing the relaxation gap (132).

13. The cooling assembly (100) of any of the preceding claims, wherein a surface of the heat sink (110) facing the liquid thermal interface material (130) is coated with an anti-corrosion material to protect the heat sink (110) from reactions with the liquid thermal interface material (130).

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