High thermal conductive WCu sheet and preparation method and application thereof

Abstract

The present application relates to the field of metal heat dissipation material manufacturing, especially relates to the field of B22F3 / 00, and more particularly relates to a high-thermal-conductivity WCu sheet and a preparation method and application thereof. The present application uses high-purity tungsten powder and graphene copper as the main preparation raw material of the WCu sheet, and combines specific process steps, including dry mixing, wet mixing, drying, pressing, sintering and rolling, so that a WCu sheet with high thermal conductivity can be prepared. The WCu sheet has high compactness and low thickness of the finished material, and is especially suitable for application in the fields of heat sink materials and electronic packaging materials.

Description

Technical Field

[0001] This invention relates to the field of metal heat dissipation material manufacturing, particularly to the field of B22F3 / 00, and more specifically to a high thermal conductivity WCu sheet, its preparation method, and its application. Background Technology

[0002] With the rapid development of communications and integrated circuits, more and more electronic devices have emerged. High-power electronic devices, in particular, have high heat flux densities and compact internal components. During long-term operation, they generate a large amount of heat. If this heat cannot be dissipated in time, it will lead to decreased efficiency of the electronic chips, thermal failures, short circuits, and even fire hazards. Therefore, high-performance heat dissipation materials are increasingly widely used in electronic devices, and the requirements for their thickness, density, airtightness, and thermal conductivity are becoming increasingly stringent. WCu (tungsten copper) composite materials have excellent thermal and electrical conductivity. They are mainly composed of a high-melting-point, high-hardness, low-expansion tungsten component and a highly conductive and thermally conductive copper component. The thermal conductivity and coefficient of thermal expansion of WCu composite materials can be adjusted by changing the ratio of tungsten to copper. Currently, they are widely used as heat dissipation materials, possessing a coefficient of thermal expansion that matches that of silicon, gallium arsenide, and ceramic materials. Therefore, the development of high-performance WCu materials with different compositions, thicknesses, and densities is crucial. Currently, traditional production processes for tungsten copper sheets or plates mostly employ compression molding or cold isostatic pressing. The resulting green billet dimensions are limited by the mold size, and a thickness greater than 3mm is considered too thick, requiring further processing such as CNC (computer-controlled precision machining) or multi-wire cutting to produce thinner billets. This process limits the shape and size of the products, incurs high costs for custom molds, has extremely low material utilization, results in large thickness tolerances in the billets, and exhibits defects such as component segregation. Subsequent rolling plastic deformation processing can increase material density, achieving the required thickness, size, and precision for tungsten copper sheets. However, excessive rolling deformation in thick billets can easily lead to cracks, reducing yield and complicating the process, which is lengthy and complex. Furthermore, its thermal conductivity and safety in use can also be affected.

[0003] The prior art CN115870503A discloses a fine equiaxed tungsten-copper sheet, whose main preparation process includes: (1) tungsten-nickel powder mixing; (2) cold isostatic pressing; (3) high-temperature pre-sintering; (4) melting and infiltration; (5) grinding; (6) multi-wire cutting; (7) annealing; (8) double-sided grinding; (9) polishing. However, the actual production of this tungsten-copper sheet technology has revealed the following problems: (1) Although cold isostatic pressing replaces the traditional molding process, the forming size and thickness are still limited by the mold and equipment, and the cost is relatively high. (1) The yield is low and the density of the green blank is less than 65%. Direct sintering is difficult to meet the density requirements of 85 tungsten copper and 90 tungsten copper. (2) High-temperature pre-burning of tungsten skeleton and then copper infiltration process can easily cause closed-pore defects in tungsten skeleton, resulting in micropores and other non-dense defects in tungsten copper composition. (3) Thin sheets are achieved by multi-wire cutting process, which has low cutting efficiency and poor surface quality and precision. More post-processing steps are required to make up for it: such as grinding and polishing. Further processing is needed to meet the surface quality requirements, which ultimately leads to low material utilization and production efficiency. The prior art CN101450381B discloses a process for preparing tungsten copper heat sinks and electronic packaging materials, which mainly includes: A, powder preparation; B, adding inducing agents and mixing; C, molding; D, isostatic pressing; E, pre-sintering; F, liquid copper impregnation; G, double-sided grinding. The resulting materials are uniform and the production efficiency of bulk products is high. However, this process cannot achieve low-cost and high-efficiency production of tungsten copper sheets, especially those with a thickness of less than 2 mm, and it is difficult to meet the density requirements of tungsten copper products with low copper content, such as 85 tungsten copper and 90 tungsten copper. Summary of the Invention

[0004] In summary, it is particularly necessary to study a low-cost and high-efficiency method for preparing tungsten-copper thin-film heat sink materials with high thermal conductivity and high density. To address this technical problem, the first aspect of this invention provides a method for preparing high thermal conductivity WCu, comprising at least the following steps:

[0005] S1. Material selection: Select tungsten powder and graphene copper powder for later use;

[0006] S2. Dry mixing: Place tungsten powder or tungsten powder and graphene copper powder in a powder mixer for dry mixing.

[0007] S3, Wet mixing: Dilute the binder with water in a certain proportion and set aside; mix the material obtained in step S2 with 5-20 wt% of the diluted binder and then perform wet mixing by water bath heating;

[0008] S4. Drying: Dry the material obtained in step S3, then sieve it and granulate it.

[0009] S5. Pressing: Press the material obtained in step S4 to obtain a raw blank;

[0010] S6. Sintering: The green blank obtained in step S5 is sintered in a reducing gas atmosphere and then cooled.

[0011] S7. Rolling: Roll the material obtained in step S6 to obtain high thermal conductivity WCu thin sheets.

[0012] Preferably, in step S1, the purity of the tungsten powder is not less than 99.95%, the graphene copper powder is in the form of a graphene copper powder film, the thickness of the graphene copper powder film is 3-20 nm, and the graphene copper powder film has a regular hexagonal structure.

[0013] Preferably, the mass ratio of tungsten powder to graphene copper powder is (50-99):(1-50); as an implementable example, the mass ratio of tungsten powder to graphene copper powder may include one of 1:1, 55:45, 7:3, 4:1, 85:15 or 98:2.

[0014] Graphene is the thinnest material known to date. A single layer of graphene is only one carbon atom thick. This thickness of graphene possesses many properties that other materials do not have, such as ultra-high strength and excellent thermal conductivity, which can theoretically reach up to 5300 W / m·K. In addition, its excellent lubricity, oxidation resistance, hydrophobicity, and thermal conductivity have promoted the application of graphene in the field of heat dissipation materials. During the research and development process, the inventors discovered that by combining graphene copper powder with a thickness of 3-20 nm and tungsten powder with a purity of over 99.95%, WCu sheets with high thermal conductivity can be obtained. According to market product specifications, the mass ratio of tungsten powder to graphene copper powder is (50-99):(1-50). Through the technology and process of this invention, the density, thickness, and tolerance of WCu sheets can be stably and controllably produced. The thickness of each component of the tungsten copper sheet can reach less than 1.1 mm. Furthermore, due to the high thermal conductivity of graphene and its growth on the surface of copper powder, there are no interface defects between the graphene copper and copper phases, which can further improve the thermal conductivity of copper. Therefore, the tungsten copper material prepared from this graphene copper has higher thermal conductivity.

[0015] Preferably, the raw materials for preparing the adhesive in step S3 include, by mass percentage: waterborne polyurethane: 20-50% by mass, dispersant: 0.1-3% by mass, coupling agent: 0.1-1% by mass, wetting agent: 0.1-3% by mass, nano tungsten powder: 1-5% by mass, defoamer: 0.1-1% by mass, and the remainder being deionized water; the preparation method of the adhesive is as follows: (1) the above materials are stirred and dispersed according to the ratio to obtain a transparent and uniform adhesive liquid; (2) the prepared adhesive is diluted with deionized water at a mass ratio of 1:50 and set aside; (3) nano tungsten powder is added to the diluted adhesive in batches and subjected to strong stirring and nano-dispersion; (4) the strong stirring is planetary stirring with a stirring speed of 800-1200 rpm / min;

[0016] The inventors have discovered that when the binder prepared using the aforementioned specific components is applied in this preparation process, it offers advantages such as low addition amount, high forming force, no need for a separate degreasing process, energy saving and environmental protection, and a sintering residual carbon rate of less than 0.008%. It can effectively bond tungsten powder and graphene copper powder, resulting in higher product stability. Furthermore, this invention utilizes a combination of dry mixing, wet mixing, and pressing molding steps to further improve the compositional uniformity and density of the WCu billet. After material selection, dry mixing and premixing using a double-cone mixer initially improves the dispersion uniformity of the raw materials. Then, wet mixing and granulation under the action of the binder further improves the flowability of the mixed material, resulting in higher dispersion uniformity of each component and high bonding strength. This prevents loosening, uneven component distribution, and rolling cracking during pressing, sintering, and rolling, leading to thinner WCu sheets with higher density and superior heat dissipation performance.

[0017] Preferably, the drying temperature in step S4 is 80-120°C and the drying time is 1-3 hours. As an implementable example, the drying time may include one of 80°C, 90°C, 100°C, 110°C or 120°C; the drying time may include one of 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0018] Preferably, the mesh size of the sieve is at least one of 20 to 200 mesh. As an implementable example, the mesh size of the sieve includes at least one of 20, 50, 80, 100, 120, 150, 180, and 200 mesh. More preferably, the mesh size of the sieve may include 50 and 120 mesh.

[0019] During the actual research and development process, the inventors discovered that only materials with particle sizes in the range of 50 and 120 mesh have more suitable flowability and are more compatible with the pressing and molding process of the present invention. While ensuring the molding of tungsten-copper blanks, the density of the blanks can reach 60-65%, the thickness is less than 2 mm, the thickness tolerance is less than 0.1 mm, and continuous roll-to-roll production is possible. Through practical experience, the inventors have discovered that when the particle size of the material sieved in step S4 is less than 120 mesh, the specific surface area is relatively large due to the small particle size, resulting in poor flowability. Therefore, it is not conducive to the forming of the blank during the pressing process, and it is easy to cause defects such as local micropores, which is not conducive to improving the thermal conductivity of the thermally conductive material. If the particle size of the sieved material is greater than 50 mesh, although it can improve the flowability of the material to a certain extent, the particle size is too large and cannot form the optimal powder packing density, resulting in a low density of the formed blank, which cannot meet the density requirements of tungsten copper sheets with low copper specifications. Only by sieving the material with a mesh size between 50 and 120 mesh can the 50-90 tungsten copper sheets be prepared more effectively and stably.

[0020] Preferably, in step S5, the pressing is performed using a pressing machine, the thickness of which is not higher than 2mm, and the pressing pressure is 100-150KN.

[0021] Preferably, in step S6, sintering is performed on a ceramic plate; the ceramic plate is an alumina ceramic plate, the reducing gas includes hydrogen, the sintering temperature is 1200-1500℃, the boat pushing speed during the sintering process is 2-5 mm / min, and the cooling temperature is 20-40℃.

[0022] More preferably, the hydrogen gas is hydrogen gas obtained by decomposing ammonia gas.

[0023] Preferably, in step S7, the total deformation of rolling is 5-20%, the deformation per pass is 1-5%, and the number of rolling passes is 1-20.

[0024] This invention, through the specific process steps mentioned above, including dry mixing, wet mixing, drying, pressing, sintering, and rolling, effectively reduces the thickness of WCu sheets while ensuring high density and thermal conductivity, solving many technical problems associated with traditional cold isostatic pressing or molding processes for sheet preparation. If subsequent post-processing steps such as cutting are required to meet the sheet quality requirements, not only will the product size be limited by the mold, the process be lengthy, and material utilization be low, but it will also lead to low production efficiency, surface cracking, and reduced yield. Furthermore, this invention uses graphene copper powder and high-purity tungsten powder as raw materials for WCu sheet preparation, resulting in higher thermal conductivity compared to commercially available tungsten-copper alloy heat dissipation sheets. Simultaneously, due to the excellent thermal conductivity and oxidation resistance of graphene, the service life and stability of the WCu sheets can be significantly improved.

[0025] A second aspect of the present invention provides a WCu sheet, which is prepared by the above-described WCu sheet preparation method.

[0026] The third aspect of this invention provides an application of WCu thin films, mainly in the fields of heat sink materials and electronic packaging materials.

[0027] Beneficial effects

[0028] (1) The present invention uses high-purity tungsten powder and graphene copper powder as the main raw materials for preparing WCu thin sheets, which can improve the thermal conductivity and density of tungsten copper thin sheets.

[0029] (2) The binder used in this invention has the advantages of low addition amount, high molding capacity, no need for separate degreasing process and energy saving and environmental protection, and the sintering residual carbon rate is less than 0.008%, which can also improve the stability and reliability of WCu green blank molding.

[0030] (3) The present invention employs special process steps including: dry mixing, granulation (wet mixing, drying), pressing, sintering, and rolling. The green blank can be thinned during the pressing stage, breaking through the thickness limitations of traditional molding processes. At the same time, the green blank achieves higher density, with a density of over 60%.

[0031] (4) The sintered material of the present invention has higher density, and can achieve higher density without rolling products with large deformation. At the same time, the process route is shorter, the sintering temperature is lower, the raw material utilization rate is higher, and energy and cost can be saved.

[0032] (5) In the granulation step of this invention, the use of a sieve with a specific mesh size can effectively improve the flowability of the material, increase the molding strength and density of the WCu blank, and help to further reduce the thickness of the blank to below 2mm. From the source of the blank, the process flow of tungsten copper sheet is shortened, the material utilization rate is improved, and the production cost is reduced. Attached Figure Description

[0033] Figure 1 This is a SEM image of graphene in the graphene copper in Example 1.

[0034] Figure 2 This is a SEM image of the graphene copper in Example 1.

[0035] Figure 3 This is a SEM image of the tungsten powder in Example 1.

[0036] Figure 4 The image shows the Raman spectrum of the graphene copper in Example 1.

[0037] Figure 5 This is a SEM image of the WCu thin film prepared in Example 1.

[0038] Figure 6 This is a SEM image of the WCu thin film prepared in Example 2.

[0039] Figure 7 SEM image of the WCu thin film prepared in Comparative Example 1 Detailed Implementation

[0040] Example 1

[0041] The first aspect of this embodiment provides a method for preparing a high thermal conductivity WCu thin film, specifically including the following steps:

[0042] S1. Material selection: Select tungsten powder and graphene copper powder with a purity of 99.95%. The graphene copper powder film thickness is 3-20nm, and the graphene structure is a regular hexagonal structure.

[0043] S2. Dry mixing: Tungsten powder and graphene copper powder are placed in a double cone mixer at a mass ratio of 4:1 for dry mixing.

[0044] S3. Wet Mixing: The material obtained in step S2 is mixed with 10wt% diluted binder and wet-mixed in a water bath at 100°C for 1 hour. The raw materials for the binder are as follows by mass fraction: waterborne polyurethane: 50wt%, brand name UW-1527DF, manufacturer: UBE Corporation; dispersant: 0.5wt%, the dispersant is sodium dodecylbenzenesulfonate; coupling agent: 0.1wt%, the coupling agent is KH-560; wetting agent: 0.3wt%, the wetting agent is TEGO-270; nano tungsten powder: 3wt%, the nano tungsten powder has a size of 50nm; defoamer: 0.2wt%. The defoamer mentioned is BYK-011; the remainder is deionized water; the preparation method of the adhesive is as follows: (1) waterborne polyurethane, dispersant, coupling agent, wetting agent, defoamer, and deionized water are mixed and stirred and dispersed according to the ratio to obtain a transparent and uniform adhesive liquid; (2) the prepared transparent and uniform adhesive liquid is diluted with deionized water at a mass ratio of 1:50 and set aside; (3) nano-tungsten powder is added to the diluted adhesive in 3 batches and subjected to strong stirring and nano-dispersion. The strong stirring speed is 1500 rpm / min; (4) the strong stirring is changed to planetary stirring, the stirring speed is 800 rpm / min, and the stirring time is 2h to obtain the adhesive.

[0045] S4. Drying: Dry the material obtained in step S3 at a temperature of 100℃ for 1 hour. Then, first sieve it through a 50-mesh sieve, and then sieve it through a 120-mesh sieve to obtain material with a mesh size of 50-120 mesh. Then dry it for 4 hours.

[0046] S5. Pressing: The material obtained in step S4 is pressed into shape using a press. The pressing size is 135*90*1.5mm, and the pressing pressure is 120KN to obtain a tungsten copper blank.

[0047] S6. Sintering: The green body obtained in step S5 is placed on an alumina ceramic plate for sintering. The sintering atmosphere is hydrogen obtained from ammonia decomposition, the sintering temperature is 1465℃, the boat pushing speed is 2.8mm / min, and then it is naturally cooled to room temperature before the sintered material is taken out.

[0048] S7. Rolling: The material obtained in step S6 is rolled with a total deformation of 10.5%, of which the deformation per pass is 2.1%. The material is rolled 5 times to obtain a high thermal conductivity WCu sheet.

[0049] The tungsten powder is a commercially available product; the graphene copper powder was purchased from Suzhou Shengguang Materials Co., Ltd.

[0050] The SEM image of graphene in graphene copper in this embodiment is as follows: Figure 1 As shown.

[0051] The SEM image of graphene copper in this embodiment is as follows: Figure 2 As shown.

[0052] The SEM image of the tungsten powder in this embodiment is as follows: Figure 3 As shown.

[0053] The Raman spectrum of graphene copper in this embodiment is as follows: Figure 4 As shown.

[0054] The SEM image of the WCu thin film prepared in this embodiment is shown below. Figure 5 As shown.

[0055] The second aspect of this embodiment provides a high thermal conductivity WCu sheet prepared by the above-described high thermal conductivity WCu sheet preparation method.

[0056] The third aspect of this embodiment provides an application of high thermal conductivity WCu thin film, mainly used in the fields of heat sink materials and electronic packaging materials.

[0057] Example 2

[0058] The first aspect of this embodiment provides a method for preparing a high thermal conductivity WCu thin film, specifically including the following steps:

[0059] S1. Material selection: Select tungsten powder and graphene copper powder with a purity of 99.95%. The graphene copper powder film thickness is 3-20nm, and the graphene structure is a regular hexagonal structure.

[0060] S2. Dry mixing: Tungsten powder and graphene copper powder are placed in a double cone mixer at a mass ratio of 98:2 for dry mixing.

[0061] S3. Wet Mixing: The material obtained in step S2 is mixed with 10wt% diluted binder and wet-mixed in a water bath at 100°C for 1 hour. The raw materials for the binder are as follows by mass fraction: waterborne polyurethane: 50wt%, brand name UW-1527DF, manufacturer: UBE Corporation; dispersant: 0.5wt%, the dispersant is sodium dodecylbenzenesulfonate; coupling agent: 0.1wt%, the coupling agent is KH-560; wetting agent: 0.3wt%, the wetting agent is TEGO-270; nano tungsten powder: 3wt%, the nano tungsten powder has a size of 50nm; defoamer: 0.2wt%. The defoamer mentioned is BYK-011; the remainder is deionized water; the preparation method of the adhesive is as follows: (1) waterborne polyurethane, dispersant, coupling agent, wetting agent, defoamer, and deionized water are mixed and stirred and dispersed according to the ratio to obtain a transparent and uniform adhesive liquid; (2) the prepared transparent and uniform adhesive liquid is diluted with deionized water at a mass ratio of 1:50 and set aside; (3) nano-tungsten powder is added to the diluted adhesive in 3 batches and subjected to strong stirring and nano-dispersion. The strong stirring speed is 1500 rpm / min; (4) the strong stirring is changed to planetary stirring, the stirring speed is 800 rpm / min, and the stirring time is 2h to obtain the adhesive.

[0062] S4. Drying: Dry the material obtained in step S3, then sieve it through a 50-mesh sieve and then through a 120-mesh sieve to sieve out the material with a mesh size of 50-120 mesh, and then dry it for 4 hours.

[0063] S5. Pressing: Press the material obtained in step S4 using a press machine. The pressing size is 135*90*0.9mm, and the pressing pressure is 120KN to obtain a raw blank.

[0064] S6. Sintering: Place the green blank obtained in step S5 on an alumina ceramic plate, cut the graphene Cu foil to the above-mentioned planar size, weigh 10% of the weight of the green blank Cu foil, fix it on the green blank and sinter it. The sintering atmosphere is hydrogen gas obtained from ammonia decomposition, the sintering temperature is 1495℃, the boat pushing speed is 2.8mm / min, and then it is cooled.

[0065] S7. Rolling: The material obtained in step S6 is rolled with a total deformation of 18%, of which the deformation per pass is 2%, and a total of 9 rolling passes are performed to obtain high thermal conductivity WCu thin sheets.

[0066] The tungsten powder is a commercially available product; the graphene copper powder and graphene copper foil were purchased from Suzhou Shengguang Materials Co., Ltd.

[0067] The SEM image of the WCu thin film prepared in this embodiment is shown below. Figure 6 As shown.

[0068] The second aspect of this embodiment provides a high thermal conductivity WCu sheet prepared by the above-described high thermal conductivity WCu sheet preparation method.

[0069] The third aspect of this embodiment provides an application of high thermal conductivity WCu thin film, mainly used in the fields of heat sink materials and electronic packaging materials.

[0070] Example 3

[0071] The first aspect of this embodiment provides a method for preparing a high thermal conductivity WCu thin film, specifically including the following steps:

[0072] S1. Material selection: Select tungsten powder and graphene copper powder with a purity of 99.95%. The graphene film thickness in the graphene copper powder is 3-20nm, and the graphene structure is a regular hexagonal structure.

[0073] S2. Dry mixing: Tungsten powder and graphene copper powder are placed in a double cone mixer at a mass ratio of 55:45 and dry mixed.

[0074] S3. The material obtained in step S2 is mixed with 10wt% diluted binder and wet-mixed in a water bath at 100°C for 1 hour. The raw materials for preparing the binder are as follows by mass fraction: waterborne polyurethane: 50wt%, waterborne polyurethane brand is UW-1527DF, manufacturer is UBE Corporation; dispersant: 0.5wt%, the dispersant is sodium dodecylbenzenesulfonate; coupling agent: 0.1wt%, the coupling agent is KH-560; wetting agent: 0.3wt%, the wetting agent is TEGO-270; nano tungsten powder: 3wt%, the nano tungsten powder has a size of 50nm; defoamer: 0.2wt%. The defoamer is BYK-141; the remainder is deionized water; the preparation method of the adhesive is as follows: (1) waterborne polyurethane, dispersant, coupling agent, wetting agent, defoamer, and deionized water are mixed and stirred and dispersed according to the ratio to obtain a transparent and uniform adhesive liquid; (2) the prepared transparent and uniform adhesive liquid is diluted with deionized water at a mass ratio of 1:50 and set aside; (3) nano-tungsten powder is added to the diluted adhesive in 3 batches and subjected to strong stirring and nano-dispersion. The strong stirring speed is 1500 rpm / min; (4) the strong stirring is changed to planetary stirring, the stirring speed is 800 rpm / min, and the stirring time is 2h to obtain the adhesive.

[0075] S4. Drying: Dry the material obtained in step S3, then sieve it through a 50-mesh sieve and then through a 120-mesh sieve to sieve out the material with a mesh size of 50-120 mesh, and then dry it for 6 hours.

[0076] S5. Pressing: Press the material obtained in step S4 using a press machine. The pressing size is 135*90*1.8mm, and the pressing pressure is 150KN to obtain a green blank.

[0077] S6. Sintering: The green body obtained in step S5 is placed on an alumina ceramic plate for sintering. The sintering atmosphere is hydrogen gas obtained from ammonia decomposition. The sintering temperature is 1250℃ and the boat pushing speed is 5.0 mm / min. Then it is cooled.

[0078] S7. Rolling: The material obtained in step S6 is rolled with a total deformation of 5%, of which the deformation per pass is 1%, and a total of 5 rolling passes are performed to obtain high thermal conductivity WCu thin sheets.

[0079] The tungsten powder is a commercially available product; the graphene copper powder was purchased from Suzhou Shengguang Materials Co., Ltd.

[0080] The second aspect of this embodiment provides a high thermal conductivity WCu sheet prepared by the above-described high thermal conductivity WCu sheet preparation method.

[0081] The third aspect of this embodiment provides an application of high thermal conductivity WCu thin film, mainly used in the fields of heat sink materials and electronic packaging materials.

[0082] Comparative Example 1

[0083] The first aspect of this comparative example provides a method for preparing a high thermal conductivity WCu thin film, specifically including the following steps:

[0084] S1. Material selection: Select tungsten powder with a purity of 99.95% and electrolytic copper powder with a purity of 99.95% for later use;

[0085] S2. Dry mixing: Tungsten powder and electrolytic copper powder are placed in a double cone mixer at a mass ratio of 98:2 for dry mixing.

[0086] S3. Wet Mixing: The material obtained in step S2 is mixed with 10wt% diluted binder and wet-mixed in a water bath at 100°C for 1 hour. The raw materials for the binder are as follows by mass fraction: waterborne polyurethane: 50wt%, brand name UW-1527DF, manufacturer: UBE Corporation; dispersant: 0.5wt%, the dispersant is sodium dodecylbenzenesulfonate; coupling agent: 0.1wt%, the coupling agent is KH-560; wetting agent: 0.3wt%, the wetting agent is TEGO-270; nano tungsten powder: 3wt%, the nano tungsten powder has a size of 50nm; defoamer: 0.2wt%. The defoamer mentioned is BYK-141; the remainder is deionized water; the preparation method of the adhesive is as follows: (1) waterborne polyurethane, dispersant, coupling agent, wetting agent, defoamer, and deionized water are mixed and stirred and dispersed according to the ratio to obtain a transparent and uniform adhesive liquid; (2) the prepared transparent and uniform adhesive liquid is diluted with deionized water at a mass ratio of 1:50 and set aside; (3) nano tungsten powder is added to the diluted adhesive in 3 batches and subjected to strong stirring and nano-dispersion. The strong stirring speed is 1500 rpm / min; (4) the strong stirring is changed to planetary stirring, the stirring speed is 800 RPM / min, and the stirring time is 2h to obtain the adhesive.

[0087] S4. Drying: Dry the material obtained in step S3, then sieve it through a 50-mesh sieve and then through a 120-mesh sieve to sieve out the material with a mesh size of 50-120 mesh, and then dry it for 4 hours.

[0088] S5. Pressing: Press the material obtained in step S4 using a press machine. The pressing size is 135*90*0.9mm, and the pressing pressure is 120KN to obtain a raw blank.

[0089] S6. Sintering: Place the green blank obtained in step S5 on an alumina ceramic plate, cut the Cu foil to the above-mentioned planar size, weigh 10wt% of the Cu foil of the green blank, fix it on the green blank and sinter it. The sintering atmosphere is hydrogen obtained from the decomposition of ammonia, the sintering temperature is 1495℃, the boat pushing speed is 2.8mm / min, and then it is cooled.

[0090] S7. Rolling: The material obtained in step S6 is rolled with a total deformation of 18%, of which the deformation per pass is 2%, and a total of 9 rolling passes are performed to obtain high thermal conductivity WCu thin sheets.

[0091] The tungsten powder and electrolytic copper powder mentioned are commercially available products.

[0092] The SEM image of the WCu thin film prepared in this example is shown below. Figure 7 As shown.

[0093] The second aspect of this embodiment provides a high thermal conductivity WCu sheet prepared by the above-described high thermal conductivity WCu sheet preparation method.

[0094] The third aspect of this embodiment provides an application of high thermal conductivity WCu thin film, mainly used in the fields of heat sink materials and electronic packaging materials.

[0095] Performance testing

[0096] Test subjects: WCu thin films prepared in Examples 1-3 and Comparative Example 1

[0097] Test Item 1: Thickness of high thermal conductivity WCu sheet. Test method (or national standard): digital micrometer method. Record the experimental results in Table 1.

[0098] Test Item 2: Density of high thermal conductivity WCu thin sheets. The test method (or national standard) is Archimedes' displacement method. The experimental results are recorded in Table 1.

[0099] Test Item 3: Thermal conductivity of high thermal conductivity WCu thin sheets. The test method (or national standard) is as follows: laser flare method for determining thermal diffusivity, differential scanning calorimetry method for determining specific heat capacity, and the thermal conductivity is calculated using the formula: thermal conductivity = thermal diffusivity * specific heat capacity * density. The experimental results are recorded in Table 1.

[0100] Table 1

[0101] Example 1 0.9 99.2 210 Example 2 0.4 98.8 168 Example 3 1.2 99.8 288.34 Comparative Example 1 0.4 98.7 142

Claims

1. A method for preparing a high thermal conductivity WCu thin sheet, characterized in that, At least the following steps are included: S1. Material selection: Select tungsten powder and graphene copper powder for later use; S2, Dry mixing: Tungsten powder and graphene copper powder are placed in a powder mixer for dry mixing; S3. Wet mixing: Dilute the adhesive with water according to a certain ratio and set aside; The material obtained in step S2 is mixed with 5-20 wt% diluted binder and then subjected to wet mixing and granulation in a water bath. S4. Drying: Dry the material obtained in step S3, and then sieve it through a screen. S5. Pressing: Press the material obtained in step S4 to obtain a raw blank; S6. Sintering: The green blank obtained in step S5 is sintered in a reducing gas atmosphere and then cooled. S7. Rolling: Roll the material obtained in step S6 to obtain high thermal conductivity WCu sheet. In step S1, the purity of the tungsten powder is not less than 99.95%, the graphene copper powder is in the form of a graphene copper powder film with a thickness of 3~20nm, and the graphene structure is a regular hexagonal structure; the mass ratio of tungsten powder to graphene copper powder is (50-90):(10-50). The raw materials for preparing the adhesive in step S3 include, by mass percentage: waterborne polyurethane: 20-50% by mass, dispersant: 0.1-3% by mass, coupling agent: 0.1-1% by mass, wetting agent: 0.1-3% by mass, nano tungsten powder: 1-5% by mass, defoamer: 0.1-1% by mass, and the remainder being deionized water; The adhesive is prepared by: (1) Stir and disperse the above materials according to the proportion to obtain a transparent and uniform adhesive liquid; (2) Dilute the prepared adhesive with deionized water at a mass ratio of 1:50 and set aside; (3) Add nano-tungsten powder to the diluted binder in batches, and perform strong stirring and nano-dispersion to obtain the product; wherein the strong stirring is planetary stirring with a stirring speed of 800~1200 rpm. In step S5, the thickness of the pressed green blank is 0.5-2.0 mm, the pressing pressure is 100-150 kN, and the density is 50-65%. The mesh size of the sieve includes 50 and 120 mesh; In step S6, the reducing gas includes hydrogen, the sintering temperature is 1200~1500℃, the boat pushing speed during the sintering process is 2~5mm / min, and the cooling temperature is 20~40℃. In step S7, the total deformation during rolling is 5-20%, the deformation per pass is 1-5%, and the number of rolling passes is 1-20. The graphene copper powder mentioned is graphene copper powder grown on the surface of copper powder.

2. The method for preparing high thermal conductivity WCu thin films according to claim 1, characterized in that, In step S3, the water bath heating temperature is 80~100℃, and the water bath heating time is 0.5~2h.

3. A high thermal conductivity WCu sheet prepared by the method according to any one of claims 1-2, having a thickness of 0.2-1.1 mm and a density greater than 98.6%.

4. An application of the high thermal conductivity WCu thin sheet according to claim 3, characterized in that, The high thermal conductivity WCu sheet is used in the fields of heat sink materials and electronic packaging materials.

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