Heat exchange member and method for manufacturing the same

Abstract

The present invention provides a heat exchange member having excellent heat dissipation and electrical properties, and a method for manufacturing the same. [Solution] The method for manufacturing a heat exchange member includes the following steps: A step of adding a carbon material consisting of carbon nanotubes, carbon nanofibers, graphene, or a mixture thereof to a solvent and performing a first ultrasonic irradiation treatment to produce a dispersion of the carbon material. A step of adding a metal oxide to the dispersion and further performing a second ultrasonic irradiation treatment to reduce the metal and produce nanoparticles of the metal in the dispersion, thereby supporting the metal nanoparticles on the carbon material. A step of using the dispersion of the carbon material supporting the metal nanoparticles as an electrolyte, performing an electroplating treatment with the substrate of the heat exchange member as the cathode and the metal as the anode, thereby forming a porous layer on the surface of the substrate of the heat exchange member in which a void-forming material consisting of the carbon material supporting the metal nanoparticles and the metal are mixed.

Description

Technical Field

[0001] The present invention relates to a heat exchange member used in a heat sink, a heat spreader, a heat transfer sheet, a heat exchanger, etc., and a method for manufacturing the same.

Background Art

[0002] In electronic devices (such as semiconductor elements) equipped with electronic devices, the amount of heat generated is increasing due to high integration and large current. If the heat dissipation of the electronic device becomes insufficient, malfunction may occur, or damage to joints and devices may occur. Therefore, in order to ensure the reliability and durability of electronic devices, a heat exchange member that promotes heat dissipation is often provided. The heat exchange member is, for example, a heat sink, a heat spreader, etc. provided on one side or both sides of a power module (semiconductor device) on which a power device (power semiconductor) is mounted. However, there are limitations in the heat dissipation and thermal conductivity of conventional heat exchange members, and in particular, in electronic devices with high heat generation, further improvement of heat dissipation characteristics is required.

[0003] From such a perspective, a technique has also been proposed to improve the heat dissipation characteristics by roughening the surface of a heat exchange member such as aluminum or copper by means of ending or other physical means. However, such means have limitations in the fineness of roughening, and it has been difficult to obtain excellent heat dissipation characteristics.

[0004] As a more precise roughening means, for example, as shown in Patent Document 1, a proposal has also been made to realize finer roughening by forming a layer of fine metal particles on the surface of a substrate such as aluminum or copper.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the invention described in Patent Document 1 involves coating an aggregate of adhesive nickel or nickel alloy fine particles with a particle size of 0.1 to 2 μm with an alloy layer consisting of nickel and phosphorus and / or sulfur to obtain a roughened metal foil. However, even if metal fine particles at the μm level are used, there are limits to the degree of roughening, and it was not possible to obtain a heat exchange member that is finer, has a larger surface area, and has superior heat dissipation characteristics.

[0007] In particular, manufacturing metal particles with uniform size at or below the μm level, such as nanoscale particles, and forming them as a uniform layer on the surface of heat exchange components such as aluminum and copper, has been technically extremely difficult.

[0008] This invention was proposed to solve the problems of the prior art described above. The object of this invention is to provide a heat exchange member having excellent heat dissipation and electrical properties, and a method for manufacturing the same. [Means for solving the problem]

[0009] To achieve the above objective, the heat exchange member of the present invention is characterized in that a porous layer is formed on the surface of a substrate, comprising a void-forming material comprising a carbon material consisting of carbon nanotubes, carbon nanofibers, graphene, or a mixture thereof, on which metal nanoparticles are supported, and a metal material made of the same material as the metal nanoparticles.

[0010] The heat exchange member of the present invention preferably has the following configuration. (1) The porous layer, which consists of the void-forming material and the metal material, is a plated layer formed on the surface of the substrate by electroplating. (2) The metal nanoparticles and the metal material are one of silver, gold, copper, platinum, or palladium. (3) The carbon material is a mixture of multiple materials selected from carbon nanotubes, carbon nanofibers, and graphene. (4) The base material has a heat dissipation fin or rib shape. (5) The base material is a metal foil.

[0011] The method for manufacturing the heat exchange member of the present invention comprises the following steps. (1) A step of adding a carbon material consisting of carbon nanotubes, carbon nanofibers, graphene, or a mixture thereof to a solvent and performing a first ultrasonic irradiation treatment to produce a dispersion of the carbon material. (2) A step of adding a metal oxide to the dispersion, and further performing a second ultrasonic irradiation treatment to reduce the metal and generate metal nanoparticles in the dispersion, and supporting the metal nanoparticles on the carbon material. (3) A step of electroplating using a dispersion of the carbon material on which the metal nanoparticles are supported as an electrolyte, with the substrate of the heat exchange member as the cathode and the metal as the anode, to form a porous layer on the surface of the substrate of the heat exchange member in which a void-forming material made of the carbon material on which the metal nanoparticles are supported and a metal material made of the same material as the metal nanoparticles are mixed.

[0012] In the method for manufacturing a heat exchange member of the present invention, it is preferable to adopt the following configuration. (1) The solvent of the dispersion is a mixture of one or more selected from water, ethanol, isopropanol, and ethylene glycol. (2) The step of supporting metal nanoparticles on the carbon material includes the step of adding metal ions to the dispersion. (3) The dispersion is obtained by adding a surfactant. (4) The dispersion is obtained by adding a reducing agent. (5) The metal nanoparticles and the metal material are one of silver, gold, copper, platinum, or palladium. (6) The carbon material is a mixture of multiple materials selected from carbon nanotubes, carbon nanofibers, and graphene. [Effects of the Invention]

[0013] According to the present invention, a heat exchange member having excellent heat dissipation characteristics and electrical characteristics can be obtained because a material for forming voids in which metal nanoparticles are supported on a carbon material and a porous layer in which a metal material of the same material as the metal nanoparticles is mixed are formed on the surface of the heat exchange member. Further, according to the manufacturing method of the present invention, by using ultrasonic cavitation to generate a material for forming voids in which metal nanoparticles are supported on a carbon material, it becomes possible to form a porous layer having the material for forming voids on the surface of a heat sink by electroplating. As a result, it becomes possible to impart excellent heat dissipation characteristics and electrical characteristics to the surface of the heat exchange member.

Brief Description of the Drawings

[0014] [Figure 1] Flowchart of an embodiment of the manufacturing method of the heat exchange member of the present invention. [Figure 2] Photograph showing a SEM image of the surface state of the heat exchange member in Example 1. [Figure 3] Graph showing heat transfer and heat dissipation characteristics in Example 1 compared with the prior art. [Figure 4] Thermography diagram showing heat dissipation characteristics in Example 1. [Figure 5] Photograph showing a SEM image obtained by a scanning electron microscope with an analysis function by forming the porous plating layer of Example 1 on an aluminum flat plate. [Figure 6] Graph showing the quantitative analysis results of the porous plating layer of Example 1. [Figure 7] Diagram of a map image corresponding to the quantitative analysis of the porous plating layer of Example 1. [Figure 8] Photograph showing a SEM image of the surface state of the heat exchange member in Example 2. [Figure 9] Thermography diagram showing heat dissipation characteristics in Example 2.

Mode for Carrying Out the Invention

[0015] The embodiments of the present invention will now be described in detail. The method for manufacturing the heat exchange member of this embodiment has the following steps, as shown in Figure 1.

[0016] 1.Dispersion process By adding the carbon material to an aqueous solution containing a suitable surfactant (S1, S2) and performing a first ultrasonic cavitation treatment (S3), a highly concentrated and stable dispersion state is obtained. 2. Decomposition of metal compounds or salts, generation of metal nanoparticles, and loading of metal nanoparticles. A metal compound or salt is added to the dispersion (S4), and a second ultrasonic treatment is performed (S5). The second ultrasonic cavitation reduces the metal compound or salt, generating metal ions. These metal ions are reduced by the reducing agent in the dispersion, forming metal nanoparticles. The generated metal nanoparticles are adsorbed onto the surface of the carbon material and uniformly supported (S6). 3. Electroplating process A heat sink substrate made of a metal at the anode and a material such as aluminum at the cathode is placed (S7), and a dispersion is used as the electrolyte. Metal ion water is added as needed (S8), and the mixture is stirred with ultrasound and a stirrer, and electroplating is performed in the same manner as conventional metal plating (S9). As a result, a plating film having a porous layer made of a carbon material supporting metal nanoparticles together with the metal is formed on the surface of the heat sink substrate.

[0017] The chemical reaction equation related to supporting metal nanoparticles is shown below, using silver oxide as the metal and a mixture of carbon nanotubes and graphene as the carbon material, as an example. (1) Reduction reaction of silver oxide Ag2O + reducing agent → ultrasonic treatment → 2Ag + oxidation product (2) Production and loading of silver nanoparticles Ag++e-→Ag(nanoparticles) (CNT / Graphene+Ag (nanoparticles) → CNT / Graphene-Ag (3) Process for supporting silver nanoparticles CNT / Graphene + Ag2O + Reducing agent → Ultrasonic treatment → CNT / Graphene - Ag + Oxidizing agent

[0018] The details of the materials, processes, etc., in each step of the present invention will be described individually below.

[0019] [Carbon materials] It is preferable to obtain a nanocarbon material powder by using carbon nanotube (multiwall carbon nanotube; MWNT, preferably with an average diameter of 1 to 100 nm and an average length of 1 to 10 μm) powder as the main material and mixing it with 1 to 30% (more preferably 10 to 20%) of carbon material pulverized to nano-order size (average particle size of 20 nm to 10 μm) by weight.

[0020] The carbon material mixed with the carbon nanotube powder is preferably one or more of graphene, carbon black, and activated carbon. Alternatively, carbon nanofibers, fullerenes, carbon nanohorns, carbon microcoils, diamond-like carbon, carbon nanocrystals, etc., may be used instead or in addition to these.

[0021] The nanocarbon material powder is not limited to carbon nanotubes and carbon materials mixed with them; carbon nanofibers, fullerenes, carbon nanohorns, carbon microcoils, diamond-like carbon, and carbon nanocrystals can also be used individually. Furthermore, it is possible to select and mix multiple types of these carbon materials. Using a mixture of multiple carbon materials with different average particle sizes reduces the tendency of the carbon materials to aggregate in the dispersion, allowing for uniform and high-concentration dispersion of the carbon materials.

[0022] This excellent dispersibility is thought to be achieved because nano-order sized carbon materials other than carbon nanotubes contained in the nanocarbon material powder are embedded and immobilized between the carbon nanotubes, preventing the carbon nanotubes from aggregating, and furthermore, the dispersion ability of the anionic or nonionic surfactant added to the solvent is enhanced by ultrasonic treatment.

[0023] [Metals and their compounds] Any metal that can generate metal nanoparticles and can be electroplated can be used in this invention. Silver, gold, platinum, and palladium are particularly preferred, and among these, silver, gold, and copper are especially preferred from the viewpoint of thermal conductivity and other factors. Furthermore, in order to generate metal nanoparticles by ultrasonic cavitation, it is necessary to add a metal compound or salt to the dispersion, but there are no particular limitations on the compound or salt. Representative metals and their compounds or salts are given below as examples.

[0024] 1.Silver (Ag) Silver oxide (Ag2O) can be used to synthesize silver nanoparticles. Other silver compounds and salts can also be used. Typical examples include silver nitrate (AgNO3), silver chloride (AgCl), silver acetate (AgC2H3O2), and silver fluoride (AgF). When using these compounds, the composition and preparation method of the dispersion may change. The following describes an overview of each compound and points to consider.

[0025] (1) Silver oxide (Ag2O) Solvent: Polar solvents such as water or ethanol are preferred. Since silver oxide is practically insoluble in water, it should be used in suspension form. Reducing agent: To produce silver nanoparticles from silver oxide, it is preferable to use a reducing agent. Hydrazine, sodium borohydride (NaBH4), and ascorbic acid can be used. NaBH4 is a strong reducing agent and tends to reduce particle size. It is also possible to control particle growth by using a milder reducing agent. Reaction temperature: The reaction temperature varies depending on the choice of reducing agent and solvent, but it is generally preferable to carry out the reaction at room temperature to around 60°C. Higher temperatures can promote particle growth. Reaction Monitoring: During the reaction, it is recommended to monitor the progress of the reaction using methods such as UV-Vis spectroscopy. Since silver nanoparticles have a characteristic absorption peak, the formation process can be observed in real time. Nanoparticle stabilization: The generated silver nanoparticles have a tendency to aggregate. Therefore, it is preferable to stabilize the particles using surfactants or polymers (e.g., PVP, PEG, etc.).

[0026] (2) Silver nitrate (AgNO3) Instructions for use: Due to its high water solubility, silver ions are reduced using a reducing agent to synthesize silver nanoparticles. Dispersion composition: Silver nanoparticles are generated by adding a reducing agent (e.g., glucose, hydrazine, sodium citrate) to a silver nitrate solution.

[0027] (3) Silver chloride (AgCl) Instructions for use: Due to its extremely low solubility, silver nanoparticles are synthesized by light irradiation or chemical reduction. Dispersion composition: It is preferable to use it as a suspension in a solvent such as water or ethanol, and reduction by light irradiation.

[0028] (4) Silver acetate (AgC2H3O2) Instructions for use: It has moderate solubility and is used in aqueous solutions together with a reducing agent. Dispersion composition: The product is dissolved in water or ethanol, and a reducing agent is added to carry out the synthesis. Ascorbic acid or sodium borate are preferred as reducing agents.

[0029] (5) Silver fluoride (AgF) Instructions for use: Due to its high water solubility and strong oxidizing properties, caution is required. Dispersion composition: A reducing agent is added to an aqueous solution of silver fluoride. Due to its strong oxidizing power, careful selection of the reducing agent is necessary. For example, reducing agents with mild reducing power, such as ascorbic acid (vitamin C) and glucose, are preferable because they allow for easier control of the size and shape of metal nanoparticles even with strong oxidizing agents like silver fluoride, and the reaction proceeds relatively gently. On the other hand, in the case of a strong reducing agent such as sodium borohydride (NaBH4), the nanoparticle size can be kept small and uniform by carefully adding a very small amount of NaBH4.

[0030] 2. Gold (Au) Chlorauric acid (HAuCl4) Instructions for use: Chloroauric acid is preferred for the synthesis of gold nanoparticles. Sodium borohydride or sodium citrate are preferred as reducing agents.

[0031] 3. Copper (Cu) Copper sulfate (CuSO4) Instructions for use: Copper nanoparticles are produced using copper sulfate together with a reducing agent. Hydrazine or ascorbic acid is preferred as the reducing agent.

[0032] 4. Palladium (Pd) Palladium chloride (PdCl2) Instructions for use: Palladium nanoparticles are produced from palladium chloride using a reducing agent. The reaction is preferable under acidic conditions.

[0033] 5. Platinum (Pt) Platinum chloride (H2PtCl6) Instructions for use: Synthesize platinum nanoparticles using a reducing agent. Sodium borohydride is preferred.

[0034] [Dispersion] Water can be used as the solvent for the dispersion, but ethanol, isopropanol, ethylene glycol, or mixtures of water and these can also be used as solvents. For example, it is preferable to use an aqueous solution containing 10-100% by weight of a lower alcohol, to which 0.01-10% by weight of anionic or nonionic surfactant has been added as the solvent. It is preferable to use one or more of the following lower alcohols: methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, ethylene glycol, diethylene glycol, propylene glycol, and glycerin.

[0035] [Metal nanoparticles] In the examples, silver nanoparticles mainly derived from silver oxide were used as the metal nanoparticles, but other metals such as those listed below can also be used. 1. Gold (Au): Similar methods are used for the synthesis of gold nanoparticles. For example, gold nanoparticles can be obtained by using a gold salt (such as H[AuCl4]) and combining it with a reducing agent and sonication. 2. Palladium (Pd): It is possible to produce palladium nanoparticles by using palladium salts and reducing them using ultrasonic cavitation. 3. Platinum (Pt): Platinum nanoparticles can also be synthesized using platinum compounds, combining ultrasonic cavitation with a reducing agent. 4. Copper (Cu): Copper nanoparticles can be synthesized using a similar method.

[0036] [Surfactants] As a surfactant, one can be used as appropriate depending on the metal nanoparticles to be generated. As an anionic or nonionic surfactant, it is preferable to use one or more of the following: sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, triethanolamine lauryl sulfate, and dodecyl itaconate.

[0037] In particular, it is preferable to use one or more surfactants that form micellar structures. Surfactants that form micellar structures have hydrophilic and hydrophobic parts due to their molecular structure, and form micelles (spherical structures with the hydrophilic part on the outside and the hydrophobic part on the inside) under specific conditions. For example, the following can be used. Sodium dodecyl sulfate (SDS) Sodium Alkylbenzene Sulfonate (SDBS) Cetyl trimethylammonium bromide (CTAB) Benzalkonium Chloride (BAC) Lecithin N-Alkyl Betaine Polyoxyethylene sorbitan ester (Polysorbate) Polyethylene glycol alkyl ether Polyoxyethylene(100) Stearyl Ether:

[0038] [Reducing agent] A reducing agent can also be added to the dispersion. In addition to the action of ultrasonic cavitation, the reducing agent reduces metal ions, further promoting the generation of metal nanoparticles. Various reducing agents can be used, including hydrogen, alcohol, polyphenols, and citric acid. The following are typical reducing agents and the types of metal nanoparticles suitable for each.

[0039] 1. Sodium citrate Usage example: gold (Au), silver (Ag) Features: Sodium citrate is suitable for the synthesis of gold nanoparticles. Gold ions (Au3+ It reduces ) to produce gold nanoparticles of a relatively stable size. In addition, citric acid acts as a stabilizer, adsorbing onto the surface of the nanoparticles to prevent aggregation.

[0040] 2. Ascorbic Acid Usage examples: Silver (Ag), Gold (Au), Copper (Cu) Features: Ascorbic acid can gently reduce silver and gold ions, making it easy to control particle size and shape.

[0041] 3. Hydrazine Examples of use: Silver (Ag), Copper (Cu), Palladium (Pd), Platinum (Pt) Features: Hydrazine is a very powerful reducing agent that rapidly reduces silver and copper ions to produce metal nanoparticles. The resulting particles tend to be small, and their high reducing power allows for rapid synthesis.

[0042] 4. Sodium borohydride (NaBH4) Examples of use: Silver (Ag), Gold (Au), Palladium (Pd) Features: NaBH4 is a powerful reducing agent that allows for the rapid synthesis of very small metal nanoparticles.

[0043] 5. Polyols (e.g., ethylene glycol) Examples of use: Silver (Ag), Gold (Au), Platinum (Pt) Features: Polyols (polyhydric alcohols) are used as reducing agents. Ethylene glycol and glycerin are typical examples, and in addition to reduction, they also have the effect of controlling the shape and size of particles. Reduction proceeds more easily at higher temperatures, so the generation of nanoparticles can be controlled by temperature control.

[0044] When selecting a reducing agent, the reaction rate, i.e., the strength of the reducing agent, affects the particle size and shape. Strong reducing agents promote rapid reduction and tend to produce smaller particles. Furthermore, since the reducing agent adsorbs onto the surface of nanoparticles, improving the stability of the generated nanoparticles, it is also effective to select reducing agents that perform both reduction and stabilization, such as sodium citrate or ascorbic acid. In addition, the selection of a reducing agent depends on the type of metal ion being reduced. For example, gold and silver are easily reduced even with relatively mild reducing agents, but metals such as palladium and platinum may require stronger reducing agents.

[0045] [Ultrasonic cavitation] Ultrasonic cavitation is a highly effective method for synthesizing metal nanoparticles. This method involves irradiating a liquid with ultrasound to induce cavitation (formation and collapse of small bubbles), and the resulting localized high-temperature and high-pressure environment helps to generate metal nanoparticles from metal salts and metal compounds. The dispersion of nanocarbon material obtained by ultrasonic cavitation according to the present invention has excellent dispersibility. Unlike nanocarbon material dispersions obtained by conventional techniques, which re-aggregate after several hours to several days, the dispersion maintains almost the same level of dispersibility as immediately after the dispersion treatment even after several days.

[0046] Ultrasonic cavitation involves placing a solution in an ultrasonic homogenizer or ultrasonic bath and irradiating it with ultrasound at an appropriate frequency (generally 20 kHz to 40 kHz). This ultrasound irradiation causes cavitation in the liquid, generating bubbles. The extreme localized temperature increase and pressure generated when these bubbles collapse reduce metal compounds or metal salts, forming metal nanoparticles.

[0047] For ultrasonic cavitation, ultrasonic homogenizers and ultrasonic baths can be used. Ultrasonic homogenizers are suitable for high-viscosity liquids and small sample volumes. They are particularly effective for reactions and processes requiring high energy. Ultrasonic baths are suitable for processing multiple samples or large volumes of liquid at once. When manufacturing large heat sinks, it is preferable to use an ultrasonic bath.

[0048] The output and frequency of ultrasonic homogenizers and ultrasonic baths used to generate metal nanoparticles depend heavily on the size and shape of the nanoparticles being produced, as well as the type of metal used. For example, the following output and frequency settings are selected depending on the size and shape of the heat sink being manufactured.

[0049] 1. Output (1) Low power output (50W~100W) This method is suitable for generating nanoparticles with very small sample sizes or under relatively mild conditions. For example, it is used when you want to generate very small nanoparticles or when the chemical reaction is sensitive to high temperatures or pressures. Generally, at low power levels, the particle size tends to be slightly larger and the shape tends to be more uniform. (2) Medium power output (100W~500W) This is a standard output range for many nanoparticle synthesis applications. It is suitable for generating metal nanoparticles and for processing multiple samples simultaneously. It yields results with uniform and easily controllable particle size. For example, it is suitable for synthesizing silver and gold nanoparticles. (3) High output (500W or more) It is used for large-scale processing (such as mass production) and handling of high-viscosity solutions. High-power cavitation triggers a strong reaction, making it effective for generating very fine nanoparticles and particles with special shapes (e.g., nanorods and nanowires).

[0050] 2. Frequency (kHz) (1) Low frequency (20kHz~30kHz): This method is suitable for applications requiring strong cavitation. Because it generates a stronger impact force, the resulting metal nanoparticles tend to have smaller particle sizes. (2) Medium frequency (30kHz~60kHz): This is the most suitable vibration frequency for generating the various metal nanoparticles of the present invention. It provides balanced cavitation and allows for relatively uniform control of particle size and shape. (3) High frequency (60 kHz or higher): This method is suitable when more delicate processing is required. It is used when cavitation is gentle and precise control of particle shape is desired. While particles tend to be slightly larger, the uniformity of shape is higher.

[0051] 3. Specific usage examples (1) Silver nanoparticles (Ag) Output: 100W~300W Frequency: 20kHz~30kHz Reason: Silver nanoparticles can be produced relatively easily, allowing for good results at standard power and low frequencies. (2) Gold nanoparticles (Au) Output: 100W~400W Frequency: 20kHz~40kHz Reason: When controlling the size and shape of gold nanoparticles is important, medium power and medium frequency are recommended. (3) Platinum nanoparticles (Pt) Output: 200W~500W Frequency: 20kHz~30kHz Reason: Because platinum is a solid metal, it requires relatively high power output and low vibration frequency.

[0052] [Metal ion solution] In the electroplating process (S8), the metal ion water added as needed is of the following types depending on the type of metal to be electroplated. Basically, it is preferable to use an aqueous solution of the metal compound or salt added in the metal compound or salt addition process (S4), but as an example, the following can be used. Silver ions: Silver nitrate (AgNO3) Gold ion: Chloroauric acid (HAuCl4) Copper ion: Copper(II) Sulfate, CuSO4·5H2O Platinum ion: Chloroplatinic acid (H2PtCl6) Palladium ion: Palladium(II) chloride (PdCl2)

[0053] [Other embodiments] The present invention is not limited to the embodiments described above, but also encompasses other embodiments such as the following. (1) In the above embodiment, a mixed layer of carbon material supporting metal nanoparticles and metal is formed on the surface of the heat sink by using an aluminum heat sink with a large number of heat dissipation fins as the base material. However, in addition to such heat sinks, the mixed layer can be formed on the surface of heat sinks of various shapes. For example, it is also possible to form the mixed layer directly on metal parts such as the surface of the case of electronic components such as CPUs.

[0054] (2) A sheet-like or film-like substrate can be used to form a mixed layer of carbon material and metal on its surface, with metal nanoparticles supported on the carbon material. Such heat exchange members can be used not only by being attached to the surface of electrical components to promote heat dissipation, but also by being placed between electronic components or between printed circuit boards and electronic components to improve heat dissipation and heat transfer from these components.

[0055] This type of metal foil manufacturing method is characterized by attaching aluminum foil to the negative electrode (cathode) instead of a fin-shaped heat sink substrate during the plating process. In this case, the sheet-shaped metal foil is unwound while connected to the negative electrode and continuously immersed in the plating tank while being wound up, thereby forming the mixed layer of the present invention on the surface of the long metal foil. A drying device may be provided downstream of the plating tank as needed.

[0056] (3) The mixed layer of the present invention can also be formed on the surface of the plastic by electroplating after performing pretreatment such as etching, seed layer formation, or chemical plating.

[0057] (4) The above-described embodiment applies the heat exchange member of the present invention to an air-cooled heat sink. However, the heat exchange member of the present invention is not limited to air-cooled systems and can also be applied to heat exchange devices using liquids such as water-cooled systems. In other words, according to the present invention, the surface area of ​​the heat exchange member is increased, which increases the contact area between the heat exchange member and the cooling liquid, improving the thermal conductivity between them and resulting in excellent heat exchange efficiency.

[0058] With the increasing demand for higher cooling performance in large-scale GPU systems such as those used in data sensors, water cooling methods, particularly immersion cooling and boiling cooling, are becoming increasingly common. Heat exchangers in these advanced water cooling systems need to be more efficient in heat transfer between the liquid coolant and heat-generating components, while maintaining robustness even under extreme thermal cycling and high-flow conditions. This requires new specifications that simultaneously elevate heat exchange efficiency, durability, and reliability to a high level. This invention satisfies these requirements simultaneously and will become a crucial component of next-generation high-performance cooling systems.

[0059] In particular, the strong bonding achieved by the electroplating process of the present invention offers the advantage that the coating remains undamaged even under the extreme thermal cycling and high flow rate conditions required in advanced liquid cooling systems. Thus, the properties of the heat exchanger component of the present invention are well in line with the demands of recent trends in the cooling industry, making it ideal for use in advanced cooling solutions for GPUs, data centers, and other large-scale systems. [Examples]

[0060] [First Embodiment] A first embodiment of the present invention, in which silver is used as the metal, is shown below. 1. Materials and equipment (1) Aluminum substrate (pure aluminum) (2) Silver anode (99.9999% pure silver) (3) Electrolyte • A mixture of carbon nanotubes and 50 wt% graphene Silver oxide (Ag2O) • Industrial alcohol (e.g., 2-propanol) • Surfactants • Silver ion solution (6 ppm to 30 ppm) (4) Ultrasonic treatment device (5) Stirrer (6) Power supply for electroplating

[0061] 2. Procedure (1) Preparation of dispersion: Carbon nanotubes and graphene are dispersed in an industrial alcohol solution containing a surfactant. • Use ultrasonic treatment to create a uniform dispersion. Silver oxide (Ag2O) is added to the dispersion, and sonication is performed again to reduce the Ag2O to silver nanoparticles (Ag). The resulting solution contains a heat exchanger / graphene on which silver nanoparticles are uniformly supported. (2) Preparation of electrolyte: Mix the dispersion with a silver ion solution (6 ppm to 30 ppm). • Use an ultrasonic device and a stirrer to thoroughly mix and disperse the contents.

[0062] 3. Setup of the electroplating equipment • The aluminum substrate is placed in the electroplating bath as the cathode. • Place the silver anode on the opposite side of the aluminum substrate. • Pour the prepared electrolyte into the electroplating bath.

[0063] 4. Electroplating process Connect the aluminum cathode and silver anode to the power supply. • Apply the appropriate voltage and current to start the electroplating process. • Monitor the process to ensure that the composite material is deposited uniformly onto the aluminum substrate.

[0064] 5. Post-processing: Once the electroplating process is complete, remove the aluminum substrate from the bath. • To remove residual electrolyte, the plated aluminum substrate is washed with distilled water. Dry at room temperature or using a low-temperature drying process.

[0065] The photograph in Figure 2 shows the appearance of the electrodeposited heat exchange component (CNT / Graphene-Ag composite) after pretreatment of the aluminum surface (pretreatment with surfactant (alkyltrimethylammonium) followed by washing with pure water) under the electrodeposition conditions of the example (electrical control conditions of electrode voltage 10-30V and current (1-3A)).

[0066] [Effects of the First Embodiment] The effects of the first embodiment having the above-described configuration are as follows.

[0067] (1) In the first embodiment, when silver oxide is added to the dispersion, the silver oxide is transformed into nanoscale particles within the dispersion. The ultrasonic treatment provides energy to homogenize the particles in the dispersion and prevents aggregation of the particles, so that the silver oxide effectively adheres to the surface of the heat exchanger.

[0068] (2) During ultrasonic treatment, silver oxide is reduced to form silver nanoparticles. In this process, the silver nanoparticles bond to the surface of the heat exchanger, forming a stable composite material.

[0069] (3) By using electroplating technology on the silver nanoparticle-supported heat exchanger, this particle-supported heat exchanger moves in response to an electric field and tends to accumulate particularly at the negative electrode (cathode). This is because the excellent conductivity of the silver nanoparticles and their interaction with the high surface area of ​​the heat exchanger allow the electric field to act effectively.

[0070] (4) The silver-supported heat exchanger material accumulates at the negative electrode, forming a new plating layer with a different structure from conventional plating layers. This new plating layer exhibits improved electrical and mechanical properties due to the presence of silver nanoparticles, such as increased conductivity of the plating layer, and increased strength and durability of the material.

[0071] (5) In the first embodiment, instead of using the silver-supported heat exchange member alone, silver is used in the positive electrode (anode), causing the silver in the positive electrode to dissolve into the electrolyte as silver ions, which accumulate on the substrate surface of the heat sink provided at the negative electrode, along with the silver-supported heat exchange member alone. As a result,

[0072] (6) CNTs supported with silver nanoparticles have a very high specific surface area (surface area per unit mass). When these are formed on a metal surface, a network structure of CNTs is formed, increasing the complexity of the surface irregularities at the nanoscale, and as a result, the total surface area of ​​the metal surface increases significantly.

[0073] (7) The silver nanoparticles themselves are very small, and the attachment of numerous nanoparticles to the surface of the CNTs can be expected to further increase the surface area. In particular, porous structures formed by CNTs can be created in the range from nanoscale to macroscale (hundreds of microns or more), and this has a significant effect on increasing the surface area.

[0074] (8) When CNTs are formed on a metal surface, the surface area increases. Heat dissipation generally improves with a larger surface area. In particular, CNTs supported with silver nanoparticles form a complex surface structure at the nanoscale, allowing heat to be efficiently released from the metal into the air.

[0075] (9) Since silver is a metal with very high thermal conductivity, the thermal conductivity of the entire metal surface is improved when silver nanoparticles are supported on CNTs. Furthermore, since CNTs themselves also have high thermal conductivity, the efficiency of heat dissipation from the metal is improved.

[0076] (10) On the substrate, not only are there CNTs supported with silver nanoparticles, but also silver metal itself exists as a mixed layer, which further improves thermal conductivity.

[0077] Figure 2 shows SEM images of the surface structure of a heat exchange member with the mixed layer of the first embodiment formed on an aluminum plate, observed at 2000x and 20000x magnification. As can be seen from these images, CNTs supporting silver nanoparticles appear on the surface of the heat exchange member, exhibiting a three-dimensional porous structure. In particular, the 20000x image shows the formation of a nanocomposite with a very unique shape composed of CNTs and graphene.

[0078] Figure 3 shows an example in which the heat dissipation effect was confirmed using the heat sink of the first embodiment formed as described above. The aluminum heat sink used in this example measures L61mm × W30 × H30mm, and its surface is finished with anodizing, consisting of an aluminum oxide (Al2O3) layer. This layer is very hard, corrosion-resistant, and electrically insulating, so it needs to be removed as a pretreatment before electroplating to prevent adhesion. Therefore, it was immersed in a solvent of hydrochloric acid (approximately 8-10%) and a surfactant (alkyltrimethylammonium salt), and the treatment time was controlled to avoid excessive etching.

[0079] The reaction equation for the reaction of hydrochloric acid with aluminum oxide (Al2O3) to form a soluble aluminum salt (aluminum chloride: AlCl3) is shown below. Reaction equation: Al2O3 + 6HCl → 2AlCl3 + 3H2O

[0080] After dissolving and removing the anodized film in this manner, the aluminum is washed with pure water before proceeding to the electrodeposition process. On the other hand, surfactants are used to promote the dissolution of the oxide layer on the aluminum surface, enhance the effect of hydrochloric acid, remove oil and contaminants from the surface, and improve the adhesion of the plating layer during electroplating, thereby obtaining a high-quality plating layer.

[0081] Figure 3 shows the results of measuring the temperature (measured at the side plate) of a conventional aluminum heatsink and a new heatsink with interface treatment using the electrodeposition technology described in this patent application, both on a heater (temperature-controlled heater plate: IKAC-MAGHS7) during temperature rise and fall at the same temperature. The vertical axis represents temperature, and the horizontal axis represents heating time and heat dissipation time. In Figure 3, the graph on the left for temperature rise shows the change in seconds, and the graph on the right for temperature fall shows the change in minutes. A temperature difference of approximately 10°C was observed during both temperature rise and fall, indicating a dramatic improvement in the temperature dissipation characteristics of the new heatsink compared to the conventional one.

[0082] Furthermore, the temperature distribution during the temperature decrease process was also observed using thermography. As a result, as shown in Figure 4, it was confirmed once again that the heat sink B of this embodiment, which has a mixed layer formed on the right, has a temperature difference of more than 10°C compared to the original aluminum heat sink A, as indicated by the data, and the temperature decrease was measured to be almost uniform throughout the entire heat sink B. On the other hand, in the original aluminum heat sink A on the left, it is immediately apparent that the temperature of the main body is higher in the center, and that heat radiation to the surrounding area is also large.

[0083] Next, to further investigate the composition of this porous plating layer composed of CNTs / graphene / Ag, the porous plating layer of this example was formed on an aluminum plate, and SEM image observation and analysis were performed using a scanning electron microscope with analytical capabilities (JEOL Ltd. JSM-6390(LA)). Figure 5 shows the SEM image at 20,000x magnification. Subsequently, quantitative analysis (ZAF method) was attempted on this sample using the electron microscope. [Measurement conditions] Acceleration voltage: 20.0kV Irradiation current: 1.00000nA Energy range: 0-20 keV The following was revealed by looking at the graph in Figure 6, which shows the results of the quantitative analysis.

[0084] (1) At low energy levels, Ag and C are displayed simultaneously. This is consistent with the fact that Ag nanoparticles are supported on the surface of CNTs or graphene, meaning that Ag is physically supported on the surface of graphene or carbon nanotubes, and it is thought that chemical bonds are formed as a result.

[0085] (2) Ag exists independently at a large point on the X-axis. The Ag peak is presumed to be observed at a specific energy (e.g., Ag Lα or Ag Kα). The presence of this peak suggests that Ag is present in a very small amount in a form specific to that location (e.g., metallic Ag nanoparticles).

[0086] Next, Figure 7 shows map images of the components C and Ag corresponding to the quantitative analysis of the porous plating layer formed on the aluminum plate. From this, it can be seen that the C component, CNT / graphene, is present almost uniformly throughout the material, and Ag is also present throughout, with locally precipitated Ag also present.

[0087] Images labeled BF are bright-field images taken with a scanning electron microscope (SEM). Bright-field images are contrast images obtained by direct transmission of electrons incident on a sample, and are used to visualize the shape and structural information of the sample surface (such as the arrangement, size, and shape of metal particles and other materials, as contrast is generated by differences in density and atomic number of the sample). From this figure, it can be seen that when bright areas are observed in the BF image, it is likely that they indicate areas of high density, i.e., areas where heavy elements (e.g., Ag) are present, which is in good agreement with the above result that Ag nanoparticles are supported over a wide area on the surface of CNTs or graphene, while there are also areas where metallic Ag is present locally.

[0088] [Second Example] In the second embodiment, copper is used as the metal nanoparticle instead of silver as in the first embodiment, as shown below. 1. Metal compounds or salts: Copper sulfate (CuSO4) 2. Solvent of the dispersion: 90 wt% water and 10 wt% ethylene glycol 3. Surfactant: Polyvinylpyrrolidone (PVP) 2wt% 4. Reducing agent: Sodium borohydride (NaBH4) 0.5 wt% 5. Copper ions added in the electroplating process: Aqueous solution of copper sulfate (CuSO4) 6. Carbon materials: A mixture of carbon nanotubes and 50 wt% graphene.

[0089] Using the materials described above, a void-forming material consisting of metal nanoparticles supported on the surface of a heat sink substrate and a porous layer containing a metal material identical to the metal nanoparticles were formed in the same manner as in the first embodiment. The heat dissipation and heat transfer characteristics of this heat exchange member were confirmed using the same method as in the case of the silver nanoparticles shown in Figure 3.

[0090] Figure 8 is an SEM image (20,000x magnification) of a porous plating layer formed on a copper plate. As can be seen from this SEM image, the presence of CNT / graphene nanocomposites can also be confirmed in Example 2.

[0091] Figure 9 shows the results of observing the heat dissipation characteristics by thermography after fixing the heat sink of Example 2 to the bottom surface of a wooden support and a copper plate to the top surface. In the experiment, the original copper plate and the copper plate with a porous plating layer, which were in close proximity, were uniformly heated simultaneously with a heater, and then the heater heating was stopped, and a snapshot of the thermography was taken as the temperature decreased. They were fixed in diagonally opposite positions to minimize mutual thermal interference as much as possible. As can be seen from these observation results, the contribution of the porous plating layer of Example 2 to the heat dissipation characteristics of the cooling characteristics was confirmed. [Explanation of Symbols]

[0092] S1…dispersion liquid S2…Carbon material addition S3...First ultrasonic treatment S4…Addition of metal compounds (or salts) S5...Second ultrasonic treatment S6...Supporting of metal nanoparticles S7... Set metal as the anode and substrate as the cathode. S8...Addition of metal ion water S9... Electroplating

Claims

1. A heat exchange member having a porous layer formed on the surface of a substrate, comprising a void-forming material comprising a carbon material consisting of carbon nanotubes, carbon nanofibers, graphene, or a mixture thereof, on which metal nanoparticles are supported, and a metal material made of the same material as the metal nanoparticles.

2. The heat exchange member according to claim 1, wherein the porous layer, comprising the void-forming material and the metal material, is a plated layer formed on the surface of the substrate by electroplating.

3. The heat exchange member according to claim 2, wherein the metal nanoparticles and the metal material are one of silver, gold, copper, platinum, and palladium.

4. The heat exchange member according to claim 2 or 3, wherein the carbon material is a mixture of a plurality of materials selected from carbon nanotubes, carbon nanofibers, and graphene.

5. The heat exchange member according to claim 3, wherein the base material has heat dissipation fins.

6. The heat exchange member according to claim 3, wherein the base material is a metal foil.

7. A carbon material consisting of carbon nanotubes, carbon nanofibers, graphene, or a mixture thereof is added to a solvent and subjected to a first ultrasonic irradiation treatment to produce a dispersion of the carbon material. The process involves adding a metal oxide to the dispersion, then performing a second ultrasonic irradiation treatment to reduce the metal and generate metal nanoparticles in the dispersion, and supporting the metal nanoparticles on the carbon material. A method for manufacturing a heat exchange member, characterized in that a dispersion of the carbon material on which the metal nanoparticles are supported is used as an electrolyte, an electroplating treatment is performed with the substrate of the heat exchange member as the cathode and the metal as the anode, and a void-forming material made of the carbon material on which the metal nanoparticles are supported and a porous layer in which a metal material of the same material as the metal nanoparticles are mixed are formed on the surface of the substrate of the heat exchange member.

8. The method for producing a heat exchange member according to claim 7, wherein the solvent of the dispersion is a mixture of one or more selected from water, ethanol, isopropanol, and ethylene glycol.

9. The method for manufacturing a heat exchange member according to claim 7, wherein the step of supporting metal nanoparticles on the carbon material includes a process of adding metal ions to a dispersion.

10. The method for manufacturing a heat exchange member according to claim 7, wherein the dispersion contains a surfactant.

11. The method for manufacturing a heat exchange member according to claim 7, wherein the dispersion contains a reducing agent.

12. A method for manufacturing a heat exchange member according to any one of claims 7 to 11, wherein the metal nanoparticles and the metal material are one of silver, gold, copper, platinum, and palladium.

13. The method for manufacturing a heat exchange member according to claim 12, wherein the carbon material is a mixture of a plurality of materials selected from carbon nanotubes, carbon nanofibers, and graphene.

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