Heat dissipation structure

Abstract

The invention discloses a heat dissipation structure, and relates to the technical field of chip heat dissipation, the heat dissipation structure comprises a memory alloy liquid absorption core and a net structure made of memory alloy wires, meshes of the net structure are liquid absorption holes used for circulation of a cooling medium, the memory alloy liquid absorption core is attached to the surface of a chip, and after a preset temperature is reached, the wire diameter of the memory alloy wires is increased. When the heat dissipation structure provided by the invention is used, after the local hot spot temperature of the chip reaches the preset temperature, the wire diameter of the memory alloy wire of the memory alloy liquid absorption core of the net-shaped structure attached to the local part of the chip is increased to form a deformation area, the permeability of the deformation area is enhanced through the increased wire diameter, the flowing resistance of a cooling medium flowing to the deformation area is reduced, and the heat dissipation efficiency is improved. Therefore, more cooling media flow towards the deformation area, the phase-change heat transfer performance of the area is improved, the evaporation drying phenomenon of the local hot spot position is delayed due to the rapid supplement effect of the fluid, self-adaptive temperature regulation and control of the whole chip are achieved, and the working performance of the chip is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of chip heat dissipation, and in particular to a heat dissipation structure. Background Art

[0002] Phase change cooling is an efficient cooling solution. Structures such as heat spreaders based on the phase change cooling principle are widely used in the field of chip cooling due to their good temperature uniformity and high equivalent thermal conductivity. The traditional chip cooling method is to bond the heat spreader to the heat spreader through a thermal interface material layer. After the chip heat is transferred to the evaporation end of the heat spreader, the heat is transferred to the condensation end through the working fluid circulation process inside the heat spreader, and then the heat is dissipated through an external water-cooled or air-cooled radiator.

[0003] However, the working conditions of electronic chips are becoming more and more complicated, and overheating of local heating junctions occurs frequently. The position of the heating zone is also constantly adjusted with the changes in chip functions. Because the uniform temperature characteristics of the temperature equalizer are mainly reflected in the uniform effect of the condensation surface, this dynamic working condition heating form cannot be effectively solved. When local hot spots appear on the chip end, that is, the evaporation surface, the temperature equalizer is prone to local evaporation, and the internal working fluid cannot effectively participate in the phase change cycle. The local heat of the chip cannot be taken away, which further leads to local overheating of the chip and affects the chip service life.

[0004] Therefore, how to achieve adaptive heat dissipation for different parts of a chip is a technical problem that those skilled in the art currently need to solve. Summary of the invention

[0005] The object of the present invention is to provide a heat dissipation structure for realizing adaptive heat dissipation of different parts of a chip.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A heat dissipation structure, comprising:

[0008] The memory alloy liquid absorbent core is a mesh structure made of memory alloy wire. The mesh holes of the mesh structure are liquid absorbent holes for the circulation of cooling medium. The memory alloy liquid absorbent core is in contact with the surface of the chip, and after reaching a preset temperature, the wire diameter of the memory alloy wire increases.

[0009] Optionally, in the above heat dissipation structure, the memory alloy wire is a two-way memory alloy.

[0010] Optionally, in the above heat dissipation structure, the memory alloy wire is a nickel-titanium-based memory alloy, a copper-based memory alloy or an iron-based memory alloy.

[0011] Optionally, in the above heat dissipation structure, the mesh number of the mesh structure ranges from 100 mesh to 200 mesh, and / or; the diameter of the liquid suction hole ranges from 75um to 150um.

[0012] Optionally, in the above heat dissipation structure, the initial wire diameter of the memory alloy wire is in the range of 75um to 150um, and / or; when the preset temperature is 60°C to 95°C, the wire diameter of the memory alloy wire increases.

[0013] Optionally, the above heat dissipation structure further includes a packaging shell, which includes a medium accommodating cavity for accommodating the cooling medium, and the packaging shell is provided with a fixing hole connected to the medium accommodating cavity, and the side of the memory alloy wick facing away from the chip is sealed in the fixing hole.

[0014] Optionally, in the above heat dissipation structure, the medium accommodating cavity is provided with a plurality of support columns distributed at intervals, and each of the support columns extends along a height direction of the packaging shell.

[0015] Optionally, in the above heat dissipation structure, metal powder is arranged on the inner wall surface of the medium accommodating cavity and the outer surface of the support column, and the mesh size of the metal powder ranges from 120 mesh to 200 mesh.

[0016] Optionally, in the above heat dissipation structure, the packaging shell is provided with a liquid filling hole communicating with the medium accommodating cavity, so that the cooling medium can be filled into the medium accommodating cavity through the liquid filling hole.

[0017] Optionally, the heat dissipation structure further comprises a substrate, the chip is fixed on the substrate by flip-chip welding, and an underfill for protecting solder balls is applied between the chip and the substrate.

[0018] When the heat dissipation structure provided by the present invention is used, during the operation of the chip, after the local hot spot temperature of the chip reaches a preset temperature, the wire diameter of the memory alloy wire of the memory alloy liquid absorbing core with a mesh structure that fits the local part of the chip increases to form a deformation zone, and the increased wire diameter enhances the permeability of the deformation zone and reduces the flow resistance of the cooling medium to the deformation zone, thereby allowing more cooling medium to flow to the deformation zone, thereby improving the phase change heat dissipation performance of the region, and due to the rapid replenishment effect of the fluid, the occurrence of the local hot spot position evaporation phenomenon is delayed, so that when the chip has multiple local heating junctions, the memory alloy wire mesh structure of the memory alloy liquid absorbing core will be deformed accordingly to increase the permeability of multiple local places, so that more liquid refluxes to the heating junction with high heat flux density, and the phase change heat dissipation is more sufficient, while the heating junction with low heat flux density refluxes less liquid, and the phase change heat dissipation is weaker, thereby realizing adaptive temperature control of the entire chip and accurate and efficient heat dissipation of the chip under variable working conditions, thereby improving the working performance of the chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0020] Figure 1 It is a structural schematic diagram of the heat dissipation structure disclosed in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the initial state of the memory alloy wire in the liquid wick disclosed in the embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the memory alloy wire in the liquid wick disclosed in an embodiment of the present invention with an increased wire diameter.

[0023] Reference numerals:

[0024] 100 is a memory alloy liquid wick, and 110 is a memory alloy wire;

[0025] 200 for chips;

[0026] 300 is a packaging shell; 310 is a medium accommodating cavity, 320 is a supporting column, and 330 is a liquid filling hole;

[0027] 400 is a substrate;

[0028] 500 for welding balls;

[0029] 600 is the bottom filler;

[0030] 700 is metal powder. DETAILED DESCRIPTION

[0031] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0033] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The meaning of "several" is one or more, unless otherwise clearly and specifically defined.

[0034] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0035] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] The core of the present invention is to provide a heat dissipation structure for realizing adaptive heat dissipation of different parts of a chip.

[0037] like Figure 1 , Figure 2 and Figure 3As shown, an embodiment of the present invention discloses a heat dissipation structure including a memory alloy wick 100, wherein the memory alloy wick 100 is a mesh structure made of memory alloy wires 110, the mesh holes of the mesh structure are wicking holes, and the cooling medium penetrates and circulates through the wicking holes, the memory alloy wick 100 is in contact with the surface of the chip 200, the material of the memory alloy wire 110 is a memory alloy, and when the temperature of the external environment reaches a preset temperature, the wire diameter of the memory alloy wire 110 will increase. For example, as the chip 200 continues to work and run, the local temperature of the chip 200 continues to rise and reaches the preset temperature, the wire diameter of the memory alloy wire 110 that fits the local area with the memory alloy wick 100 increases to form a deformation area. At this time, the aperture of the wicking holes in the deformation area becomes smaller, and the porosity of the mesh memory alloy wick 100 becomes smaller, but the effective capillary radius and the capillary force of the deformation area remain unchanged, and the final permeability becomes larger, thereby reducing the flow resistance to the deformation area, causing a non-uniform flow, so that the cooling medium flows more to the deformation area, thereby improving the phase change heat transfer performance of the area, and due to the rapid replenishment effect of the fluid, the lateral reflux ability of the liquid to the position with smaller porosity, that is, the deformation area, is enhanced, prompting more cooling medium to flow back to the deformation area, delaying the occurrence of evaporation at the local hot spot position, and improving The maximum heating power of the chip 200, therefore, when the chip 200 has multiple local heating junctions, the mesh structure of the memory alloy wire 110 of the memory alloy wick 100 will be deformed accordingly to increase the permeability of multiple local locations, so that more liquid will flow back to the heating junction with high heat flux density, and the phase change heat transfer will be more complete, while the heating junction with low heat flux density will flow back less liquid and the phase change heat transfer will be weaker. After the temperature of the chip 200 drops, the memory alloy wire 110 returns to its initial state again, and the permeability of the entire memory alloy wick 100 remains the same to avoid the long-term accumulation of cooling medium and affect the uniformity of the entire heat dissipation cooling of the chip 200, meet the heat dissipation requirements of the chip 200 under variable working conditions, realize the adaptive temperature control of the entire chip 200, and the precise and efficient heat dissipation of the chip 200 under variable working conditions.

[0038] In a specific embodiment, the calculation formulas for the permeability K and the porosity ε are as follows:

[0039]

[0040] In the formula, d w is the wire diameter of the memory alloy wire 110, and N is the number of meshes of the memory alloy liquid wick 100;

[0041] The N of the memory alloy liquid absorbent core 100 is set to 1500, and the initial wire diameter d of the memory alloy wire 110 is w is 100um, and when the temperature reaches the preset temperature, the memory alloy wire 110 expands due to heat, and the initial wire diameter d of the memory alloy wire 110w It becomes 200um. Then, according to the calculation formula of permeability K and porosity ε, the initial wire diameter d of the memory alloy wire 110 can be calculated. w When the diameter is 100um, the values ​​of permeability K and porosity ε are as follows:

[0042]

[0043]

[0044] Memory alloy wire 110 heated wire diameter d w When it increases to 200um, the values ​​of permeability K and porosity ε are as follows:

[0045]

[0046] The capillary pressure ΔP of the memory alloy liquid wick 100 is c It can be expressed as:

[0047]

[0048] In the formula, σ is the surface tension of the liquid working fluid, which is the physical property parameter of the liquid itself, and r eff is the effective capillary radius of the wick

[0049] Memory alloy liquid wick 100r eff It can be expressed as

[0050]

[0051] where d p is the mesh aperture of the memory alloy liquid wick 100, d w is the initial wire diameter of the memory alloy wire 110 .

[0052] When the memory alloy wire 110 is deformed by heat, d w becomes larger, making d p decreases, the average value of the two remains unchanged, that is, r eff unchanged, so ΔP c The capillary force remains unchanged.

[0053] It can be seen from the above that after reaching the preset temperature, the wire diameter of the memory alloy wire 110 in the memory alloy wick 100 increases, the porosity of the mesh memory alloy wick 100 decreases, and the permeability increases.

[0054] At the same time, the memory alloy wire 110 is a two-way memory alloy, and the memory alloy wire 110 has a low-temperature phase state and a high-temperature phase state, that is, after the ambient temperature continues to rise and reaches a preset temperature, the memory alloy wire 110 presents a high-temperature phase state, and the diameter of the memory alloy wire 110 increases. After the temperature drops, the memory alloy wire 110 returns to the low-temperature phase state, and the wire diameter of the memory alloy wire 110 returns to the initial value. At this time, the aperture and permeability of the liquid absorption holes at various locations of the memory alloy liquid absorption core 100 are all the same, and the cooling medium is evenly spread throughout the entire memory alloy liquid absorption core 100, thereby ensuring that the cooling medium infiltrates the entire surface of the chip 200.

[0055] In addition, the memory alloy wire 110 can be made of materials such as nickel-titanium-based memory alloy, copper-based memory alloy or iron-based memory alloy, or technicians in this field can choose other materials for the memory alloy wire 110 according to actual needs, which will not be listed one by one in this article. Moreover, when making the memory alloy liquid-absorbing core 100, vacuum melting or arc melting can be used to make the blank of the memory alloy wire 110, and then chemical surface treatment is performed to remove impurities and improve the surface quality. After that, the shape memory alloy is subjected to thermal deformation training. First, the alloy is cooled to a low-temperature phase state, and then stress is applied to the alloy blank at this temperature to form a 10% to 30% reduction deformation ratio in the transverse direction and a slight elongation in the longitudinal direction. Then the external stress is removed and heated. When the temperature reaches the phase transition point, the alloy becomes larger and returns to its original size. After completing the training process after multiple thermal mechanical trainings, the memory alloy is wire-cut and wire-drawn to make the memory alloy wire 110, and the memory alloy wire 110 is woven into a mesh structure by a weaving machine to form a memory alloy liquid-absorbing core 100 of the memory alloy.

[0056] In a specific embodiment, the mesh number of the memory alloy absorbent core 100 with a mesh structure ranges from 100 mesh to 200 mesh, such as 100 mesh, 130 mesh, 160 mesh or 200 mesh. The mesh number of the memory alloy absorbent core 100 affects the initial capillary force and permeability. If the mesh number is less than the range, the initial capillary force will be weakened, and if the mesh number is greater than the range, the permeability will be weakened. These may affect the capillary performance of the memory alloy absorbent core 100 and reduce the heat dissipation effect on the chip 200. The diameter range of the absorbent hole in the corresponding mesh structure is 75um to 150um, which can be set to 75um, 85um, 100um or 150um, so that the memory alloy absorbent core 100 has a good permeability when reaching a high temperature phase state or a low temperature phase state, so that the cooling medium has good fluidity in the memory alloy absorbent core 100, and ensures good heat dissipation and cooling ability for the chip 200.

[0057] In another specific embodiment, the initial wire diameter of the memory alloy wire 110 ranges from 75um to 150um, and can be set to 75um, 90um, 120um or 150um, so that the memory alloy wick 100 has a stronger structure and is not easily damaged during repeated deformation processes. At the same time, the memory alloy wire 110 undergoes a high-temperature phase state, that is, the wire diameter of the memory alloy wire 110 increases, and the preset temperature setting range for deformation is 60°C to 95°C. If the set temperature is lower than this range, the chip 200 may still be in a good operating state, and there is no need for the memory alloy wire 110 to undergo a high-temperature phase state. The increase in wire diameter improves the local permeability. If the set high-temperature phase change temperature is higher than this range, before the wire diameter of the memory alloy wire 110 increases and the permeability is adjusted, high temperature may have occurred locally in the chip 200, resulting in the problem of evaporation of local hot spots, affecting the normal working performance of the chip 200 and the service life of the chip 200.

[0058] like Figure 1 As shown, the heat dissipation structure provided in this embodiment also includes a package shell 300, and the package shell 300 has a medium accommodating cavity 310. The cooling medium used to dissipate heat from the chip 200 is stored in the medium accommodating cavity 310, and the package shell 300 is provided with a fixing hole. When the package shell 300 is installed, the side of the memory alloy wick 100 facing away from the chip 200 is covered on the fixing hole, so that the package shell 300 and the memory alloy wick 100 are installed and fixed, and the cooling medium in the medium accommodating cavity 310 is ensured to infiltrate the entire memory alloy wick 100. In a specific embodiment, the package shell 300 can be made of C1020 oxygen-free copper, 6063 aluminum alloy, or aluminum silicon carbide, so that the package shell 300 has good thermal conductivity and is easy to process and manufacture, and the expansion coefficient of the package shell 300 is as close as possible to the expansion coefficient of the semiconductor material.

[0059] Furthermore, a plurality of support columns 320 are provided in the medium containing cavity 310, each support column 320 extends in the height direction of the packaging shell 300, and each support column 320 is distributed at intervals in the medium containing cavity 310, wherein both ends of a part of the support columns 320 are respectively connected to the upper and lower inner walls of the medium containing cavity 310, and one end of the support column 320 located in the fixing hole is connected to the inner wall of the medium containing cavity 310, and the other end is abutted against the memory alloy wick 100. In a specific embodiment, the number of support columns 320 ranges from 5 to 50, and the diameter of the support columns 320 ranges from 1 to 2 mm, so that the packaging shell 300 is supported and protected by the support columns 320, thereby enhancing the structural strength of the packaging shell 300.

[0060] like Figure 1As shown, metal powder 700 is evenly distributed on the inner wall surface of the medium containing cavity 310 and the outer surface of the support column 320, and the mesh number of the metal powder 700 ranges from 120 mesh to 200 mesh. The arranged metal powder 700 enhances the reflux efficiency of the cooling medium, promotes the flow of the cooling medium in the medium containing cavity 310, and then improves the heat dissipation and cooling efficiency of the cooling medium in the medium containing cavity 310, thereby further improving the working performance of the chip 200.

[0061] like Figure 1 As shown, the package shell 300 is provided with a liquid filling hole 330, which is connected to the medium accommodating chamber 310, so that the cooling medium is transported to the medium accommodating chamber 310 through the liquid filling hole 330, and the size range of the liquid filling hole 330 can be set between 1mm and 3mm. In a specific embodiment, the cooling medium should have the characteristics of a low boiling point, a large specific heat capacity, a large latent heat of phase change, etc., and needs to be compatible with semiconductor materials, package shell materials and memory alloy materials, and can be deionized water, ethanol, acetone, FC-72 electronic fluoride liquid or ethylene glycol. Specifically, when the package shell 300 is C1020 oxygen-free copper, 4J29 Kovar alloy, and the memory alloy wire 110 is a nickel-titanium-based material, deionized water can be injected as the cooling medium. When the package shell 300 is C1020 oxygen-free copper, aluminum silicon carbide, 4J29 Kovar alloy, 6063 aluminum alloy, and the memory alloy wire 110 is made of nickel-titanium-based or copper-based materials, acetone can be injected as a cooling medium. When the package shell 300 is C1020 oxygen-free copper, 4J29 Kovar alloy, and the memory alloy wire 110 is made of nickel-titanium-based materials, ethanol can be injected as a cooling medium. When the package shell 300 is C1020 oxygen-free copper, 4J29 Kovar alloy, and the memory alloy wire 110 is made of nickel-titanium-based, copper-based, or iron-based materials, FC-72 can be injected as a cooling medium. When the package shell 300 is C1020 oxygen-free copper, 4J29 Kovar alloy, and the memory alloy wire 110 is made of nickel-titanium-based materials, ethylene glycol can be injected as a cooling medium. At the same time, the filling ratio of the injected cooling medium is between 20% and 70%. After the injection is completed, the medium containing cavity 310 is evacuated to a vacuum degree of about 5 Pa by a vacuum pump, and then the liquid filling hole 330 of the packaging shell 300 is sealed with a vacuum adhesive.

[0062] In another specific embodiment, the heat dissipation structure provided in this embodiment also includes a substrate 400, and the chip 200 is fixed on the substrate 400 by flip-chip welding to have a smaller package size, a higher connection density, and better thermal management and reliability, etc., thereby improving the operating performance of the entire structure, and an underfill 600 is coated on the chip 200 and the substrate 400, and the underfill 600 is used to isolate the welding balls 500 from the outside world, thereby protecting the welding balls 500 and enhancing the reliability of the connection between the chip 200 and the substrate 400.

[0063] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0064] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A heat dissipation structure, characterized in that: include: The memory alloy liquid absorbent core is a mesh structure made of memory alloy wire. The mesh holes of the mesh structure are liquid absorbent holes for the circulation of cooling medium. The memory alloy liquid absorbent core is in contact with the surface of the chip, and after reaching a preset temperature, the wire diameter of the memory alloy wire increases.

2. The heat dissipation structure according to claim 1, characterized in that: The memory alloy wire is a two-way memory alloy.

3. The heat dissipation structure according to claim 1, characterized in that: The memory alloy wire is a nickel-titanium based memory alloy, a copper based memory alloy or an iron based memory alloy.

4. The heat dissipation structure according to claim 1, characterized in that: The mesh number of the reticular structure ranges from 100 to 200 meshes, and / or the diameter of the liquid absorption hole ranges from 75um to 150um.

5. The heat dissipation structure according to claim 1, characterized in that: The initial wire diameter of the memory alloy wire is in the range of 75um to 150um, and / or; when the preset temperature is 60°C to 95°C, the wire diameter of the memory alloy wire increases.

6. The heat dissipation structure according to claim 1, characterized in that: It also includes a packaging shell, which includes a medium accommodating cavity for accommodating the cooling medium, and the packaging shell is provided with a fixing hole connected to the medium accommodating cavity, and the side of the memory alloy wick facing away from the chip is covered with the fixing hole.

7. The heat dissipation structure according to claim 6, characterized in that: The medium containing cavity is provided with a plurality of support columns distributed at intervals, and each of the support columns extends along the height direction of the packaging shell.

8. The heat dissipation structure according to claim 7, characterized in that: Metal powder is arranged on the inner wall surface of the medium accommodating cavity and the outer surface of the supporting column, and the mesh number of the metal powder ranges from 120 meshes to 200 meshes.

9. The heat dissipation structure according to claim 6, characterized in that: The packaging shell is provided with a liquid filling hole communicating with the medium accommodating cavity, so as to fill the cooling medium into the medium accommodating cavity through the liquid filling hole.

10. The heat dissipation structure according to any one of claims 1 to 9, characterized in that: It also includes a substrate, the chip is fixed on the substrate by flip-chip welding, and an underfill for protecting welding balls is coated between the chip and the substrate.

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