A gallium-based alloy and a smelting preparation process

Abstract

The embodiment of the application provides a gallium-based alloy and a smelting preparation process, and relates to the technical field of thermal interface material preparation. The smelting preparation process of the gallium-based alloy comprises the following steps: preparing raw materials according to the alloy composition of the gallium-based alloy, wherein the raw materials comprise gallium metal and tin metal; adding the raw materials into a smelting container, so that the raw materials form a mixed layer and a gallium layer from bottom to top in sequence, and the gallium layer completely covers the mixed layer; the mixed layer comprises all amounts of the tin metal and part of the amount of the gallium metal, and the gallium metal and the tin metal are mixed together in at least part of the area; the gallium layer comprises the remaining amount of the gallium metal; under the condition of inert gas protection or vacuum, the temperature is raised to a smelting temperature, and smelting treatment is carried out under continuous stirring. The smelting preparation process of the gallium-based alloy is rapid, and the alloy composition of the gallium-based alloy obtained by smelting is uniform and has low interface thermal resistance.

Description

Technical Field

[0001] This application relates to the field of thermal interface material preparation technology, and more specifically, to a gallium-based alloy and its melting and preparation process. Background Technology

[0002] As electronic devices evolve towards higher integration and higher power density, heat dissipation has become a critical challenge affecting product performance and reliability. If heat cannot be dissipated effectively, devices will overheat, leading to issues ranging from frequency throttling and malfunctions to outright damage. Thermal interface materials (TIMs) are crucial materials used to fill the gap between heat-generating components (such as chips) and heat sinks, eliminating air gaps and reducing contact thermal resistance. Ideal TIMs should possess high thermal conductivity, low thermal resistance, and long-term stability. Liquid metals, such as gallium-based alloys (e.g., Ga-In-Sn), exhibit thermal conductivity as high as 30–40 W / (m·K) and interfacial thermal resistance as low as 0.04 °C·cm. 2 With a strength below / W and excellent thermal stability and reusability, it is one of the high-performance thermal interface materials.

[0003] The existing smelting and preparation process of gallium-based alloys usually involves adding tin (Sn), indium (In), and gallium (Ga) sequentially into a crucible, followed by heating and stirring. This process is time-consuming, and the resulting gallium-based alloys have insufficient alloy composition uniformity and high interfacial thermal resistance, which limits the application of gallium-based alloys. Summary of the Invention

[0004] The purpose of this application is to provide a gallium-based alloy and a melting preparation process, which allows for rapid melting and produces a gallium-based alloy with uniform alloy composition and low interfacial thermal resistance.

[0005] In a first aspect, embodiments of this application provide a smelting and preparation process for a gallium-based alloy, which includes the following steps: Prepare raw materials according to the alloy composition of the gallium-based alloy, wherein the raw materials include gallium metal and tin metal; The raw material is added to a melting vessel, so that the raw material forms a mixing layer and a gallium material layer from bottom to top, and the gallium material layer completely covers the mixing layer. The mixing layer includes all the amount of the tin metal and a portion of the gallium metal, and at least a portion of the gallium metal and the tin metal are mixed together. The gallium material layer includes the remaining amount of the gallium metal. Under inert gas protection or vacuum conditions, the temperature is raised to the melting temperature and smelted under continuous stirring.

[0006] In the above technical solution, a specific layered covering structure is constructed in the melting container, consisting of a gallium-tin mixed layer at the bottom and a gallium material layer at the top, to achieve physical coating of tin metal. Throughout the melting process, an inert atmosphere or vacuum condition is used to reduce the oxygen content in the controlled environment, greatly inhibiting the formation of oxide films. In the initial stage of heating and melting, the gallium material layer in the upper layer has a lower melting point (approximately 29.76°C), and the molten gallium forms a liquid sealing layer, effectively isolating trace amounts of oxygen in the melting container, reducing the oxidation of gallium in the lower mixed layer, and greatly reducing the resistance to tin metal dissolution due to oxide films. Simultaneously, at least a portion of the gallium and tin metal in the mixed layer are mixed together, and the molten gallium in the mixed layer gradually wets the high-melting-point tin metal (approximately 232°C), achieving efficient solid-liquid interface contact, constructing a dissolution channel for tin metal, and promoting the rapid dissolution of tin metal in the liquid gallium for co-dissolution. This results in rapid melting and ultimately an alloy with uniform composition and low interfacial thermal resistance.

[0007] In one possible implementation, the raw material further includes indium metal, which is added to form at least one of the mixed layer, the gallium layer, and the separate indium layer.

[0008] In the above technical solution, when the alloy composition of the gallium-based alloy includes gallium, tin and indium, the addition position of indium metal can be flexibly adjusted to enable the melting system to adapt to the melting point differences of the ternary system of gallium, indium and tin, so that each element melts in stages and the uniformity of the complex alloy composition is improved.

[0009] In one possible implementation, the mass ratio of all the gallium metal to all the tin metal is 4 to 10:1; And / or, the mass of the gallium metal in the mixed layer is 1 / 3 to 1 / 2 of the total amount of gallium metal, and the mass of the gallium metal in the gallium material layer is 1 / 2 to 2 / 3 of the total amount of gallium metal.

[0010] In the above technical solution, the precise quantification of the overall ratio of gallium to tin enables the gallium-based alloy to possess fundamental properties such as a wide liquid temperature range and high thermal conductivity. Placing 1 / 3 to 1 / 2 of the gallium metal in the mixing layer is sufficient to allow the tin metal to be fully wetted and pre-encapsulated by the liquid gallium, providing a good contact interface for eutectic melting; while the remaining 2 / 3 to 1 / 2 of the gallium metal serves as a covering layer to form a sufficiently thick liquid sealing layer, enhancing the oxygen barrier protection effect in the early stages of melting.

[0011] In one possible implementation, the tin metal is tin particles with a particle size D50 of 1~10 mm and a purity ≥99.99%. And / or, the purity of the gallium metal is ≥99.99%.

[0012] In the above technical solution, by controlling the particle size of tin particles and increasing their contact surface area with liquid gallium, dissolution and diffusion can be accelerated during the melting process, shortening the melting time and reducing energy consumption. At the same time, strictly limiting the purity of raw materials reduces the introduction of defects such as oxide inclusions from the source, improves melting efficiency, and gives the obtained gallium-based alloy high purity and high uniformity physical properties.

[0013] In one possible implementation, the method for forming the mixed layer is to sequentially add the tin metal and the gallium metal to the melting vessel, and shake or stir to initially mix the tin metal and the gallium metal; And / or, the gallium layer is formed by adding the gallium metal over the mixed layer to cover the upper surface of the mixed layer.

[0014] In the above technical solution, after sequentially adding tin metal and a portion of gallium metal and then shaking or stirring, the liquid gallium formed by the gallium metal flows downwards, making it easier to fully wet the tin metal. This achieves uniform mixing of the two metal materials in the mixed layer and forms a uniform contact interface. When forming the gallium material layer, the gallium metal is added directly over the surface, which is convenient and ensures that the liquid gallium formed by the gallium material layer can completely and uniformly cover the mixed layer below.

[0015] In one possible implementation, the melting temperature is 100~220°C; The rate of continuous stirring is controlled to achieve a stirring state without generating vortices.

[0016] In the above technical solution, the set melting temperature is lower than the melting point of tin. However, under the action of liquid gallium, dissolution is achieved through efficient solid-liquid interface contact, avoiding energy waste and component oxidation caused by high temperatures. Different stirring methods and parameters are selected for different equipment and production requirements, enabling tin metal to dissolve quickly in liquid gallium while avoiding the formation of vortices that could entrain oxide films and gases, thus maintaining a uniform alloy composition and temperature field during the melting process.

[0017] In one possible implementation, the smelting process includes: first, continuously stirring for a first duration to melt all the raw materials, and then continuing to stir for a second duration; optionally, the first duration is 10 to 30 minutes, and the second duration is 10 to 60 minutes.

[0018] In the above technical solution, the smelting process is divided into two stages. First, the mixture is stirred for a first duration to dissolve all solid raw materials in liquid gallium, forming a macroscopically uniform alloy melt. After the raw materials are completely melted, the mixture is stirred for a second duration to further promote the diffusion of elements at the microscopic level through forced convection.

[0019] In one possible implementation, after the melting process is completed, a cooling process is also included, which includes: naturally cooling to room temperature under the protection of an inert gas; optionally, the cooling process also includes cooling to room temperature and then continuously stirring for 3 to 7 minutes.

[0020] In the above technical solution, the inert gas protection is extended to the cooling stage, effectively preventing oxidation of the high-temperature alloy liquid upon contact with air during cooling; and natural cooling is employed, resulting in a gradual cooling rate. Furthermore, continued stirring after cooling to room temperature reduces component enrichment and further improves the compositional uniformity of the gallium-based alloy.

[0021] In one possible implementation, after the melting process is completed, a filtration process is also included; optionally, the filtration process uses a pre-filter and a post-filter in sequence.

[0022] In the above technical solution, filtration is introduced after smelting to effectively remove oxide slag, incompletely dissolved impurities and particles that may exist in the alloy melt, as well as foreign matter introduced during the smelting process, thereby purifying the alloy melt and significantly improving the purity of the material.

[0023] Secondly, embodiments of this application provide a gallium-based alloy, which is prepared by the smelting and preparation process of the gallium-based alloy provided in the first aspect. The relative standard deviation of the gallium and tin content at the upper, middle and lower positions of the gallium-based alloy is ≤2%, and the interfacial thermal resistance of the gallium-based alloy is below 0.02℃·cm² / W.

[0024] In the above technical solution, the alloy has ultra-high uniformity, specifically manifested in extremely low relative standard deviation (RSD) of gallium and tin content in different parts (≤2%) and extremely low oxide content, achieving excellent thermophysical properties, that is, the interface thermal resistance is controlled at an extremely low level of less than 0.02℃·cm² / W. Detailed Implementation

[0025] The most common thermal interface materials on the market include the following: Thermal grease: It mainly uses silicone oil as the base and adds some thermally conductive fillers (such as Al2O3, ZnO, AlN, BN, etc.). The thermal conductivity is usually 1~5 W / (m·K), and the interfacial thermal resistance is about 0.1~0.8℃·cm. 2 Thermal grease is convenient to use and inexpensive; however, it is prone to drying out and aging during long-term use, leading to a significant decrease in performance.

[0026] Thermal pads: Flexible silicone-based composite materials with a thermal conductivity of 1~6 W / (m·K). When used, they usually require high pressure to effectively reduce contact thermal resistance, which limits their application in low-pressure packaging scenarios.

[0027] Phase change materials (PCMs): PCMs are solid at room temperature, but soften and fill the interface when heated. They have a thermal conductivity of approximately 2–8 W / (m·K) and an interfacial thermal resistance of approximately 0.2–0.5 °C·cm. 2 However, it requires a certain start-up temperature and is prone to performance degradation after multiple thermal cycles.

[0028] Liquid metals: Represented by gallium-based alloys (such as Ga-In-Sn), they have thermal conductivity as high as 30~40 W / (m·K) and interfacial thermal resistance as low as 0.04℃·cm. 2 With a strength below / W and excellent thermal stability and reusability, it is one of the best-performing thermal interface materials currently available.

[0029] Current smelting and preparation processes for liquid metals mainly involve adding tin (Sn), indium (In), and gallium (Ga) sequentially into a crucible, followed by heating and stirring. Although liquid metals possess excellent properties, current smelting and preparation processes have significant drawbacks, resulting in inhomogeneous alloy compositions, poor batch-to-batch stability, and high interfacial thermal resistance, thus limiting their applications.

[0030] The applicant discovered that tin has a high melting point of 232°C, and a dense oxide film (Ga2O3) easily forms on the surface of liquid gallium. This film has high chemical inertness and hinders atomic contact between liquid gallium and tin particles. During the melting process, this oxide film encapsulates the tin particles, preventing direct contact between tin and liquid gallium, resulting in slow tin dissolution or even prolonged insolubility, thus lengthy melting times. Furthermore, the oxide film formed on the surface of liquid gallium can be drawn into the melt during stirring, forming oxide inclusions that act as scattering centers for heat conduction, increasing interfacial thermal resistance.

[0031] Conventional melting methods focus on melting temperature and stirring intensity, assuming that sufficiently high temperatures and strong stirring will improve alloy composition uniformity. However, this approach often fails to achieve the desired results. The slow dissolution of high-melting-point tin, persistent oxide film interference, and microscopic compositional inhomogeneity during the melting process are the fundamental reasons for long melting times, resulting in alloys with uneven composition, poor batch stability, and high thermal resistance. These problems are interconnected, and optimizing the overall alloy performance cannot be achieved by simply solving one issue.

[0032] After extensive exploration, this application designs a liquid metal melting and preparation process. During feeding, tin and a portion of gallium are mixed at the bottom of the container, and the remaining gallium is used to cover the upper layer. The gallium in the upper layer forms a liquid sealing layer, which reduces the obstruction of tin dissolution caused by the oxide film. At the same time, the liquid gallium in the mixed layer wets the tin particles, establishing a highly efficient solid-liquid interface for tin dissolution. The melting is rapid, and the alloy properties are ultimately optimized.

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0034] The gallium-based alloys and their smelting and preparation processes according to embodiments of this application will be described in detail below.

[0035] This application provides a process for melting and preparing gallium-based alloys, which includes the following steps: Prepare raw materials according to the alloy composition of gallium-based alloys, including gallium metal and tin metal; Raw materials are added to a melting container, so that the raw materials form a mixed layer and a gallium material layer from bottom to top, and the gallium material layer completely covers the mixed layer. The mixed layer includes all the amount of tin metal and a portion of the amount of gallium metal, and at least a portion of the gallium metal and tin metal are mixed together. The gallium material layer includes the remaining amount of gallium metal. Under inert gas protection or vacuum conditions, the temperature is raised to the melting temperature and smelted under continuous stirring.

[0036] In this application, since tin has a melting point as high as 232°C, tin metal as a raw material is usually tin particles. For ease of understanding, tin particles will be used directly in the following description, but this does not exclude the possibility of using liquid tin as a raw material.

[0037] This application employs a layered coating technique, mixing tin and a portion of gallium at the bottom of a melting vessel, and then covering the upper layer with the remaining gallium. This step breaks away from the traditional approach of direct high-temperature mixing. Through a specific layered feeding sequence, the upper gallium layer forms a liquid sealing layer. The lower mixed layer uses liquid gallium as a solvent to wet high-melting-point tin particles at a lower temperature, achieving efficient solid-liquid interface contact and constructing a dissolution channel. Moreover, the gallium in the mixed layer can establish direct contact with the tin particles before an oxide film forms and rapidly begin to wet them. Once gallium and tin begin to dissolve, the subsequent oxide film can no longer block this established dissolution channel, resulting in rapid melting and ultimately obtaining an alloy with uniform composition and low interfacial thermal resistance.

[0038] In some alternative embodiments of this application, the raw materials also include indium metal, which is added to form at least one of a mixed layer, a gallium layer, and a separate indium layer.

[0039] In this application, indium metal as a raw material is usually indium particles. For ease of understanding, indium particles will be used directly in the following description, but this does not exclude the possibility of using liquid indium metal as a raw material.

[0040] The gallium-based alloy of this application can be a Ga-Sn system or a Ga-In-Sn system. For example, the alloy composition of the Ga-In-Sn system can be Ga... 68.5 In 21.5 Sn 10 Ga 75 In 15 Sn 10 wait.

[0041] When the alloy composition of a gallium-based alloy includes In, and the corresponding smelting raw materials also include indium particles, the smelting preparation process of this application embodiment further optimizes the smelting process of the multi-element alloy by flexibly adjusting the indium addition position. Specifically, indium particles can be added to the bottom mixing layer and blended with tin and gallium, or indium particles can be added to the upper gallium material layer, or a separate indium material layer can be formed. The layering position of the indium material layer is not limited. The melting point of indium (approximately 156.6°C) is higher than that of gallium and lower than that of tin. After gallium melts to form liquid gallium, the liquid gallium wets indium and tin, achieving stepwise melting.

[0042] In other embodiments, trace amounts of elements such as zinc, silver, and bismuth can be added as needed to adjust the melting point or wettability. By smelting according to the smelting preparation process of this application, a gallium-based alloy with excellent comprehensive performance can be obtained.

[0043] In some optional embodiments of this application, the mass ratio of all gallium metal to all tin metal is 4 to 10:1; exemplaryly, the mass ratio of all gallium metal to all tin metal is 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or any intermediate value between two ratios.

[0044] In some optional embodiments of this application, the mass of gallium metal in the mixed layer is 1 / 3 to 1 / 2 of the total amount of gallium metal, and the mass of gallium metal in the gallium material layer is 1 / 2 to 2 / 3 of the total amount of gallium metal; for example, the mixed layer contains 1 / 3 of the total amount of gallium metal, and the gallium material layer contains 2 / 3 of the total amount of gallium metal; or, the mixed layer contains 5 / 12 of the total amount of gallium metal, and the gallium material layer contains 7 / 12 of the total amount of gallium metal; or, the mixed layer and the gallium material layer each contain 1 / 2 of the total amount of gallium metal.

[0045] In this embodiment, the overall ratio of gallium to tin is precisely quantified to be 4~10:1, giving the gallium-based alloy fundamental properties such as a wide liquid temperature range and high thermal conductivity. Furthermore, the distribution ratio of gallium metal in the mixing layer and the gallium layer covering the mixing layer is clearly defined: placing 1 / 3 to 1 / 2 of the gallium metal in the mixing layer is sufficient to allow the tin particles to be fully wetted and pre-encapsulated by the liquid gallium, providing a good contact interface for eutectic melting; while the remaining 2 / 3 to 1 / 2 of the gallium metal serves as a covering layer to form a sufficiently thick liquid sealing layer, enhancing the oxygen barrier protection effect during the initial melting stage.

[0046] In some optional embodiments of this application, the particle size D50 of the tin particles is 1~10mm, optionally 3~5mm, and the purity is ≥99.99%; and / or, the purity of the gallium metal is ≥99.99%. Optionally, the particle size D50 of the tin particles is 1mm, 2mm, 3mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm or any intermediate value between two values.

[0047] In this embodiment, by controlling the particle size of tin particles, the contact surface area between them and liquid gallium is increased, which accelerates dissolution and diffusion during the melting process, shortens melting time, and reduces energy consumption. If the particle size is too small, the surface area is large, and theoretically dissolution is fast, but due to floating and being covered by the oxide film on the surface of liquid gallium, dissolution is actually slow; if the particle size is too large, the dissolution time is too long, affecting efficiency. At the same time, strictly limiting the impurity content reduces the introduction of defects such as oxide inclusions from the source, avoiding the formation of stress concentration points in the alloy or affecting its electrical and thermal conductivity.

[0048] In some optional embodiments of this application, the gallium metal is gallium particles with a particle size D50 of 1~10mm, which can be 3~5mm. The method for forming the mixed layer is to add tin particles and gallium particles to the melting container in sequence, shake or stir to initially mix the tin particles and gallium particles. The method for forming the gallium material layer is to add gallium particles on top of the mixed layer so that they cover the upper surface of the mixed layer.

[0049] In this embodiment, gallium metal raw materials are gallium particles. The layered covering structure constructed using the above method is simple to operate and highly effective. Tin particles and a portion of gallium particles are added sequentially, followed by shaking or stirring to initially mix them. Since the gallium particles are closer to the top than the tin particles, during melting and heating, the gallium particles melt into liquid gallium first and flow downwards, easily and fully wetting the tin particles. This achieves uniform mixing of the two metal raw materials in the mixed layer and forms a uniform contact interface. When forming the gallium layer, gallium particles are added in a covering manner, which is convenient and ensures that the liquid gallium formed by the melting of the gallium layer completely and uniformly covers the underlying mixed layer, forming a physical barrier without dead corners.

[0050] In other embodiments, the gallium metal raw material can also be liquid gallium, and a mixing layer and a feeding layer can be formed in a similar manner. The liquid gallium in the mixing layer is mixed with tin particles, and the liquid gallium wets the tin particles to achieve efficient contact at the solid-liquid interface. The liquid gallium in the mixing layer directly covers the upper surface of the mixing layer to form a liquid sealing layer.

[0051] In the actual smelting process, the smelting temperature is adjusted according to the specific alloy composition of the gallium-based alloy. In some optional embodiments of this application, the smelting temperature is 100~220℃, optionally 110~130℃. Exemplarily, the smelting temperature is 100℃, 110℃, 115℃, 120℃, 125℃, 130℃, 150℃, 170℃, 200℃, 220℃, or any intermediate value between the above two values. As one embodiment, the gallium-based alloy is a Ga-In-Sn system, specifically composed of gallium, indium, and tin, with trace amounts of bismuth, zinc, etc., added as needed; the corresponding smelting temperature is 110~130℃. As another embodiment, the specific alloy composition of the gallium-based alloy also includes trace amounts of silver; the corresponding smelting temperature is approximately 200℃.

[0052] This implementation achieves low-temperature, high-efficiency melting by controlling the melting temperature. The set melting temperature is below the melting point of tin. Once the target melting temperature is reached, liquid gallium encapsulates the tin particles, and atomic contact is achieved between the liquid metal and the wetted tin particles. The tin is dissolved by heat penetration.

[0053] In some optional embodiments of this application, the stirring rate is controlled to reach a stirring state without generating vortices. The specific stirring speed can be adjusted according to the stirring method and the amount of material fed. For example, magnetic stirring (the rotor can be a rotor composed of a PTFE-coated magnetic core) is used, with a stirring speed of 80~100 rpm; or, mechanical stirring paddle (the stirring paddle material can be 316L stainless steel or ceramic) is used, with a stirring speed of 150~200 rpm; or, ultrasonic-assisted stirring is used, with a power of 20~40 kHz, which has a good effect on destroying the oxide film.

[0054] This implementation provides various stirring methods and parameters, including magnetic stirring, mechanical stirring, and ultrasonic-assisted stirring, to meet different equipment and production requirements. These parameters provide sufficient shear force to achieve convection diffusion, accelerating the dissolution of tin particles in liquid gallium, while avoiding the formation of vortices that could entrain oxide films and gases, thus ensuring a high degree of uniformity in the composition and temperature field of the alloy liquid.

[0055] In one implementation, the melting vessel uses an open-type high-temperature resistant crucible made of alumina, quartz, or graphite. Inert gas protection is achieved through continuous purging with nitrogen or argon at a flow rate of 2-5 L / min. In another implementation, the melting vessel can also be a closed furnace (such as a vacuum tube furnace, vacuum induction melting furnace, or box-type atmosphere furnace). The inert gas protection is implemented as follows: a. Place the crucible containing the raw materials into the sealed furnace chamber, ensuring a tight seal.

[0056] b. Start the vacuum pump to evacuate the furnace (vacuum level recommended: 10). -2 ~10 -1 Pa), to completely remove air (especially oxygen and water vapor) from the furnace.

[0057] c. After the vacuum is completed, refill the furnace with high-purity inert gas (argon or nitrogen to atmospheric pressure or slightly positive pressure).

[0058] d. Optionally, the "vacuuming-recharging" cycle can be repeated 2 to 3 times to further reduce the residual oxygen content in the furnace.

[0059] e. Under a dynamically flowing inert atmosphere (maintaining a slight positive pressure and continuous low-flow ventilation) or a static protective atmosphere, perform melting, heating, heat preservation, and stirring according to the melting preparation process of this application.

[0060] Enclosed furnaces combined with a "vacuum-refill" method can more thoroughly remove oxygen, making them particularly suitable for alloy formulations that are extremely sensitive to oxygen content (such as those containing trace amounts of easily oxidized elements like magnesium and aluminum), and can minimize oxide film formation. For enclosed furnaces where real-time observation and manual stirring are inconvenient, long-handled tools or built-in magnetic / mechanical stirring systems must be used.

[0061] In some optional embodiments of this application, the smelting process includes: first, continuously stirring for a first duration to melt all raw materials (disappearing solid particles), and then continuing to stir for a second duration. In the actual smelting process, the stirring times for the first and second durations are adjusted according to the specific alloy composition of the gallium-based alloy. Optionally, the first duration is 10-30 minutes, and the second duration is 10-60 minutes. As one embodiment, the gallium-based alloy is a Ga-In-Sn system, specifically composed of gallium, indium, and tin, with trace amounts of bismuth, zinc, etc., added as needed. The first stirring duration is 10-20 minutes, and the second duration is 15-25 minutes.

[0062] This implementation divides the melting and stirring process into two stages. The first stage (continuous stirring for the first duration) is the melting-dissolution period, which aims to rapidly dissolve all solid raw materials in liquid gallium to form a macroscopically homogeneous alloy melt. The second stage (continuous stirring for the second duration) is the homogenization period, which aims to further promote the diffusion of elements at the microscale through forced convection.

[0063] In some optional embodiments of this application, after the melting process is completed, a cooling process is further included. The cooling process includes: stopping stirring and heating, and naturally cooling to room temperature under the protection of an inert gas. Optionally, the cooling process also includes cooling to room temperature and then continuing to stir for 3 to 7 minutes. The cooling process can also be to simply stop heating, cool to room temperature under the protection of an inert gas while continuing to stir, and then continue to stir for a period of time after cooling to room temperature.

[0064] In some optional embodiments of this application, after the melting process is completed, a filtration process is also included; optionally, the filtration process uses a pre-filter and a post-filter in sequence.

[0065] In this embodiment, a filtration process is introduced after melting to effectively remove any oxide slag, incompletely dissolved impurities or particles that may be present in the alloy melt, as well as foreign matter introduced during the melting process, thereby purifying the alloy melt and significantly improving the purity of the material. A graded purification system is formed by sequential filtration using pre- and post-filters. The pre-filter, with its coarse mesh, intercepts larger impurities, preventing clogging of the post-filter; the post-filter, with its fine mesh, captures tiny suspended particles, achieving deep purification. This step ensures that the final gallium-based alloy, especially when used in thermal interface materials or precision seals, has an extremely low defect rate, guaranteeing its reliability and performance consistency in thin-layer applications.

[0066] As one implementation method, the smelting and preparation process of gallium-based alloys specifically includes the following steps: (1) Raw material preparation: Accurately weigh high-purity (≥99.99%) gallium particles, indium particles, and tin particles according to the target alloy composition (e.g., Ga-In-Sn), and control the total mass to a certain scale, such as 100g~1000g.

[0067] Layered loading: Place the PTFE-coated magnetic stir bar at the bottom of a high-temperature resistant crucible (made of alumina, quartz, or graphite).

[0068] First, spread the high-melting-point tin particles evenly at the bottom of the crucible. Then, pour in some (1 / 3 to 1 / 2 of the total amount) gallium particles to cover the tin particles. You can gently shake or start stirring to promote the initial mixing of gallium and tin particles. Add all the indium particles to form an indium layer. Slowly add the remaining gallium particles to completely cover all the materials to form a gallium layer.

[0069] (2) Atmosphere protection: Inert protective gas (nitrogen or argon, flow rate 2~5L / min) is continuously introduced into the crucible to purge air and establish and maintain an inert atmosphere.

[0070] (3) Heating: Heat the crucible to the melting temperature and precisely control the temperature at 110~130℃. Although this temperature is far below the melting point of tin (232℃), it is sufficient to dissolve the tin particles.

[0071] Dissolution stage: Turn on the magnetic stirrer and set the speed to 80~100 rpm to avoid creating vortices; in this stage, the gallium particles melt into liquid gallium first, and the indium particles and tin particles gradually dissolve in the liquid gallium. Usually, after 10~20 minutes, the solid particles completely disappear.

[0072] Homogenization stage: After the solid particles are completely dissolved, continue stirring at a constant temperature for 15 to 25 minutes. Through forced convection, eliminate the micro-scale tin enrichment zone in the alloy melt, so that the composition tends to be completely homogeneous at the atomic level.

[0073] (4) Cooling: After stirring, turn off the heating and stirring, and cool to room temperature under continuous inert atmosphere protection to obtain alloy melt.

[0074] (5) Continue stirring for another 3 to 8 minutes to avoid segregation and ensure uniform composition.

[0075] (6) Filtration: The surface oxides are removed by using a pre-filter and a post-filter to obtain a gallium-based alloy.

[0076] This application also provides a gallium-based alloy, which is prepared by the smelting process of the gallium-based alloy provided in the first aspect. The relative standard deviation (RSD) of the gallium and tin content at the upper, middle and lower positions of the gallium-based alloy is ≤2%, and the interfacial thermal resistance of the gallium-based alloy is below 0.02℃·cm² / W.

[0077] The gallium-based alloy of this application is prepared according to a specific melting and preparation process. Through the aforementioned layered feeding and temperature- and time-controlled stirring process, ultra-high uniformity of the alloy is achieved. Specifically, the relative standard deviation (RSD) of gallium and tin content in the upper, middle, and lower parts of the alloy ingot is extremely low (≤2%), effectively solving the problem of compositional segregation caused by gravity. This excellent uniformity directly translates into superior thermophysical properties, namely, the interfacial thermal resistance is controlled at an extremely low level below 0.02℃·cm² / W. As a thermal interface material, this alloy can greatly reduce the contact thermal resistance between electronic devices and heat sinks, and has significant application advantages in fields with stringent requirements for heat transfer efficiency and reliability, such as high-power chip heat dissipation.

[0078] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0079] Example 1 This embodiment provides a gallium-based alloy whose alloy composition is Ga. 68.5 In 21.5 Sn 10 It is prepared according to the following process: (1) Gallium particles (D50=4mm, purity 99.99%), indium particles (D50=4mm, purity 99.99%), and tin particles (D50=4mm, purity 99.99%) were weighed according to the mass ratio of Ga 68.5%, In 21.5%, and Sn 10.0%, with a total mass of 1000g: 685g of gallium particles, 215g of indium particles, and 100g of tin particles; the gallium particles were divided into two parts: the first part of gallium particles was about 1 / 3 of the total gallium particles, 228g, and the second part of gallium particles was about 2 / 3 of the total gallium particles, 457g.

[0080] Place the PTFE stir bar at the bottom of the alumina crucible, then spread 100g of tin particles evenly at the bottom of the crucible, add the first portion of gallium particles (228g), and stir appropriately to initially mix the two; add 215g of indium particles; finally, slowly add the second portion of gallium particles (457g) to cover the entire surface.

[0081] (2) Connect the nitrogen tube to the nitrogen cylinder. Fix the outlet of the nitrogen tube 2cm above the crucible opening. Open the valve, adjust the flow rate to 3L / min, and purge continuously for 5 minutes. Then keep the flow rate constant and continue purging.

[0082] (3) Set the oil bath temperature of the crucible to 130°C and heat until the temperature inside the crucible stabilizes at 120±2°C (measured using a K-type thermocouple); turn on the magnetic stirrer at 90 rpm and observe every 5 minutes to record the time when the raw material particles completely disappear. In this embodiment, the raw material particles completely dissolve after about 14 minutes; after the raw material particles have completely dissolved, continue stirring for 20 minutes.

[0083] (4) Turn off heating and stirring, remove the crucible from the oil bath, being careful to avoid shaking, and allow it to cool naturally to room temperature (about 25°C) under nitrogen protection to obtain the alloy melt.

[0084] (5) After the alloy melt cools to room temperature, continue stirring for 5 minutes to avoid segregation.

[0085] (6) A gallium-based alloy was obtained by filtering using a 50μm nylon filter screen in the front and a 20μm Teflon sintered filter element in the back.

[0086] The alloy melt during the above smelting process and the final gallium-based alloy were tested respectively: Using a syringe, samples were taken from 1 cm below the surface of the alloy melt (corresponding to the upper layer), the middle of the surface (corresponding to the middle layer), and 1 cm from the bottom (corresponding to the lower layer). The composition of each of the three points at each location was analyzed by SEM-EDS, and the RSD of each element in the three layers was calculated.

[0087] Test the interfacial thermal resistance of the alloy melt according to ASTM D5470 (80°C, 35 psi), perform three tests, and calculate the average value.

[0088] The results show that the RSDs of Ga, In and Sn in the alloy melt obtained in step (3) are 0.49%, 0.72% and 0.73%, respectively, with a maximum RSD of 0.73%; the interfacial thermal resistance is 0.011℃·cm² / W.

[0089] The RSDs of Ga, In and Sn in the alloy melt obtained in step (4) are 0.16%, 0.51% and 0.44%, respectively, with a maximum RSD of 0.51%; the interfacial thermal resistance is 0.005℃·cm² / W.

[0090] The RSDs of Ga, In and Sn in the alloy melt obtained in step (5) are 0.15%, 0.49% and 0.42%, respectively, with a maximum RSD of 0.49%; the interfacial thermal resistance is 0.01℃·cm² / W.

[0091] The interfacial thermal resistance of the gallium-based alloy obtained in step (6) is close to that of the alloy melt obtained in step (4).

[0092] Example 2 This embodiment provides a gallium-based alloy whose alloy composition is Ga. 75 In 15 Sn 10 The difference between this preparation process and Example 1 is that in step (1), the raw materials are weighed according to the mass ratio of Ga 75.0%, In 15.0%, Sn 10.0%, and the total mass of the raw materials is still 1000g.

[0093] The results show that the RSDs of Ga, In and Sn in the alloy melt obtained in step (4) are 0.28%, 0.62% and 0.55%, respectively, with a maximum RSD of 0.62%; the interfacial thermal resistance is 0.013℃·cm² / W.

[0094] Example 3 This embodiment provides a gallium-based alloy. The difference between this preparation process and that of Embodiment 1 is that in step (3), the oil bath temperature is set to 140°C and the temperature inside the crucible is stabilized at 130±2°C. In this embodiment, the time for the raw material particles to completely dissolve is shortened to 10 minutes.

[0095] The results show that the RSDs of Ga, In and Sn in the alloy melt obtained in step (4) are 0.21%, 0.48% and 0.39%, respectively, with a maximum RSD of 0.48%; the interfacial thermal resistance is 0.009℃·cm² / W.

[0096] Example 4 This embodiment provides a gallium-based alloy. The difference between this preparation process and that of Embodiment 1 is that in step (3), the magnetic stirring speed is set to 100 rpm.

[0097] The results show that the RSDs of Ga, In and Sn obtained in step (4) are 0.19%, 0.55% and 0.46%, respectively, with a maximum RSD of 0.55%; the average interface thermal resistance is 0.011℃·cm² / W.

[0098] Example 5 This embodiment provides a gallium-based alloy. The difference between this preparation process and that of Embodiment 1 is that in step (3), after the raw material particles are completely dissolved, stirring is continued for 15 minutes.

[0099] The results show that the RSDs of Ga, In and Sn in the alloy melt obtained in step (4) are 0.32%, 0.78% and 0.65%, respectively, with a maximum RSD of 0.78%; the interfacial thermal resistance is 0.012℃·cm² / W.

[0100] Example 6 This embodiment provides a gallium-based alloy. The difference between this preparation process and that of Embodiment 1 is that in step (1), 100g of tin particles and 215g of indium particles are mixed evenly and then spread at the bottom of the crucible. Then, 228g of gallium particles are added and stirred evenly. Finally, 457g of gallium particles are slowly added to cover the entire surface.

[0101] In step (3), the raw material particles completely dissolve in about 16 minutes.

[0102] The results show that the RSDs of Ga, In and Sn in the alloy melt obtained in step (4) are 0.22%, 0.58% and 0.49%, respectively, with a maximum RSD of 0.58%; the interfacial thermal resistance is 0.016℃·cm² / W.

[0103] Example 7 This embodiment provides a gallium-based alloy. The difference between this preparation process and that of Embodiment 1 is that in step (1), the basic ratio is still 68.5% gallium (Ga), 21.5% indium (In), and 10.0% tin (Sn). Bismuth particles are added on this basis, with the amount added being 1% of the total mass. The bismuth particles are added to the crucible together with the indium particles.

[0104] In step (3), the raw material particles completely dissolve in about 16 minutes.

[0105] The results show that the RSD of Ga, In and Sn in the alloy melt obtained in step (4) is less than 0.8%, with a maximum RSD of 0.72%; the interfacial thermal resistance is 0.007℃·cm² / W.

[0106] Comparative Example 1 This comparative example provides a gallium-based alloy, the preparation process of which differs from that of Example 1 in that: In step (1), 100g of tin particles are evenly spread at the bottom of the crucible, and then 685g of gallium particles are slowly added; finally, 215g of indium particles are added, with a total raw material mass of 1000g.

[0107] In step (3), the raw material particles are completely dissolved in 30 minutes.

[0108] The results showed that the RSDs of Ga, In and Sn in the alloy melt obtained by step (3) of the comparative example were 0.51%, 1.36% and 1.39%, respectively, with a maximum RSD of 1.39%; the interfacial thermal resistance was 0.015℃·cm² / W.

[0109] The RSDs of Ga, In, and Sn in the alloy melt obtained in step (4) of the comparative example are 0.49%, 0.72%, and 0.73%, respectively, with a maximum RSD of 0.73%; the interfacial thermal resistance is 0.011℃·cm² / W.

[0110] In summary, the gallium-based alloy smelting and preparation process of the embodiments of this application is rapid, and the gallium-based alloy obtained by smelting has uniform alloy composition and low interfacial thermal resistance.

[0111] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A smelting and preparation process for a gallium-based alloy, characterized in that, It includes the following steps: Prepare raw materials according to the alloy composition of the gallium-based alloy, wherein the raw materials include gallium metal and tin metal; The raw material is added to a melting vessel, so that the raw material forms a mixing layer and a gallium material layer from bottom to top, and the gallium material layer completely covers the mixing layer. The mixing layer includes all the amount of the tin metal and a portion of the gallium metal, and at least a portion of the gallium metal and the tin metal are mixed together. The gallium material layer includes the remaining amount of the gallium metal. Under inert gas protection or vacuum conditions, the temperature is raised to the melting temperature and smelted under continuous stirring.

2. The smelting and preparation process of gallium-based alloys according to claim 1, characterized in that, The raw materials also include indium metal, which is added to form at least one of the mixed layer, the gallium layer, and the separate indium layer.

3. The smelting and preparation process of the gallium-based alloy according to claim 1, characterized in that, The mass ratio of all the gallium metal to all the tin metal is 4 to 10:1; And / or, the mass of the gallium metal in the mixed layer is 1 / 3 to 1 / 2 of the total amount of gallium metal, and the mass of the gallium metal in the gallium material layer is 1 / 2 to 2 / 3 of the total amount of gallium metal.

4. The smelting and preparation process of gallium-based alloys according to claim 1, characterized in that, The tin metal is in the form of tin particles, the particle size D50 of which is 1~10mm and the purity is ≥99.99%; And / or, the purity of the gallium metal is ≥99.99%.

5. The smelting and preparation process of gallium-based alloys according to claim 1, characterized in that, The method for forming the mixed layer is as follows: tin metal and gallium metal are added sequentially to the melting container, and the mixture is shaken or stirred to initially mix the tin metal and gallium metal; And / or, the gallium layer is formed by adding the gallium metal over the mixed layer to cover the upper surface of the mixed layer.

6. The smelting and preparation process of the gallium-based alloy according to claim 1, characterized in that, The melting temperature is 100~220℃; The rate of continuous stirring is controlled to achieve a stirring state without generating vortices.

7. The smelting and preparation process of gallium-based alloys according to claim 1, characterized in that, The smelting process includes: first, continuously stirring for a first duration to melt all the raw materials, and then continuing to stir for a second duration; optionally, the first duration is 10 to 30 minutes, and the second duration is 10 to 60 minutes.

8. The smelting and preparation process of gallium-based alloys according to claim 1, characterized in that, After the melting process is completed, a cooling process is also included, which includes: naturally cooling to room temperature under the protection of an inert gas; optionally, the cooling process also includes continuing to stir for 3 to 7 minutes after cooling to room temperature.

9. The smelting and preparation process of gallium-based alloys according to claim 1, characterized in that, After the smelting process is completed, a filtration process is also included; optionally, the filtration process uses a pre-filter and a post-filter in sequence.

10. A gallium-based alloy, characterized in that, It is prepared by the smelting process of gallium-based alloy as described in any one of claims 1 to 9, wherein the relative standard deviation of gallium and tin content at the upper, middle and lower positions of the gallium-based alloy is ≤2%, and the interfacial thermal resistance of the gallium-based alloy is below 0.02℃·cm² / W.