A longitudinally stretchable through-type metal-based thermal interface material and its preparation method

Abstract

This invention relates to the field of thermal management materials technology for electronic devices, and in particular to a longitudinally stretchable through-metal-based thermal interface material and its preparation method. The invention prepares the longitudinally stretchable through-metal-based thermal interface material through steps including polyurethane sponge pretreatment, catalytic activation, pre-compression electroless copper plating, electroless silver plating for anti-oxidation treatment, and elastomer potting. The longitudinally stretchable through-metal-based thermal interface material prepared by this invention exhibits high thermal conductivity, high through-conductivity, and high longitudinal strain tensile capacity. The entire preparation process of this invention is completed in a low-temperature liquid phase, possessing the potential for low-cost, large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of thermal management materials for electronic devices, and in particular to a longitudinally stretchable through-type metal-based thermal interface material and its preparation method. Background Technology

[0002] With the rapid development of microelectronics and artificial intelligence technologies, the thermal management of high-power chips faces unprecedented challenges. Thermal interface materials (TIMs), as a key bridge connecting the heat source (chip) and the heat sink, primarily function to fill the microscopic gaps at the interface, enabling efficient heat conduction and preventing device overheating failure.

[0003] Currently, polymer-based composite thermal interface materials are the most common on the market. These materials incorporate highly thermally conductive metal or ceramic particles into a polymer matrix (such as epoxy resin), allowing heat conduction through the contact between the fillers. To overcome the thermal conductivity bottleneck caused by polymer barriers between filler particles, researchers have proposed another approach: vertically penetrating thermal interface materials. This approach vertically embeds highly thermally conductive carbon fiber arrays or upright metal nanowire arrays into the polymer matrix, forming a direct heat conduction channel connecting the heat source and the heat sink. Furthermore, to address the issue of the inability to stretch such vertically rigid arrays, some studies have employed grazing angle deposition technology to grow extremely thin copper nanospring arrays on a substrate, aiming to provide a degree of flexible buffering.

[0004] However, the aforementioned existing technologies have significant limitations in practical applications: In traditional polymer-based composite thermal interface materials, the thermally conductive particles are isolated from each other by an insulating and low-thermal-conductivity polymer matrix, resulting in huge microscopic interfacial thermal resistance between the particles, which obstructs the heat conduction path, and the thermal conductivity is usually below 5 W / (m·K); Although the scheme using vertically upright carbon fiber or metal nanowire arrays significantly improves the longitudinal thermal conductivity, its thermally conductive skeleton is rigid and does not have longitudinal tensile capacity. When large-size chips undergo significant warping deformation due to thermal expansion and contraction under high-temperature operation, the chip edges will exert huge longitudinal tensile stress on the thermal interface material, which will directly cause the rigid vertical array to physically break or detach at the interface, completely destroying the heat conduction path; While the scheme using grazing angle deposition technology to prepare nanospring arrays endows the material with a certain degree of deformability, this process requires expensive and precise vacuum deposition equipment, resulting in extremely low production efficiency, and the prepared spring arrays are only on the micrometer scale, with extremely limited buffering capacity in actual packaging, making it difficult to promote large-scale industrial application.

[0005] Therefore, developing a longitudinally stretchable through-type metal-based thermal interface material that combines high longitudinal thermal conductivity, high longitudinal strain tensile capacity, low cost, and mass production capability is of great practical significance for achieving large-area industrial application. Summary of the Invention

[0006] The purpose of this invention is to provide a longitudinally stretchable through-type metal-based thermal interface material and its preparation method. The longitudinally stretchable through-type metal-based thermal interface material prepared by the method of this invention has high through-type thermal conductivity and high longitudinal strain tensile capacity.

[0007] To achieve the above objectives, the present invention provides a method for preparing a longitudinally stretchable through-type metal-based thermal interface material, comprising the following steps: Polyurethane foam sponge is immersed in an alkaline solution and hydrolyzed to obtain modified polyurethane foam sponge. The modified polyurethane foam was placed in an ethanol solution of silver salt and reduced in situ to obtain an activated polyurethane foam. The activated polyurethane foam sponge is pre-compressed and then chemically plated with copper to obtain copper-plated polyurethane foam sponge. The copper-plated polyurethane foam sponge is chemically plated with silver to obtain silver-plated polyurethane foam sponge. A liquid elastic matrix is ​​poured into the silver-plated polyurethane foam and then hot-pressed to cure, resulting in a longitudinally stretchable through-type metal-based thermal interface material.

[0008] In this invention, the alkaline solution is preferably a sodium hydroxide solution; the mass concentration of the sodium hydroxide solution is preferably 10% to 30%. As a specific embodiment of this invention, the mass concentration of the sodium hydroxide solution can be 10% or 30%.

[0009] In this invention, the hydrolysis modification temperature is preferably 40~60℃, more preferably 60℃; the hydrolysis modification time is preferably 1~2h, more preferably 2h. This invention involves immersing a polyurethane foam sponge with a three-dimensional porous network structure in an alkaline solution for hydrolysis modification, causing the urethane bonds on the surface of the polyurethane foam sponge skeleton to break, generating abundant carboxylates and primary amino groups in situ, thereby greatly improving the surface hydrophilicity and surface energy.

[0010] In this invention, the concentration of silver ions in the ethanol solution of the silver salt is 0.5~1.5 mol / L, more preferably 1 mol / L; the silver salt preferably includes nitrate; the in-situ reduction is preferably carried out under light-protected conditions; the temperature of the in-situ reduction is preferably 20~50℃, more preferably 30℃; the time of the in-situ reduction is preferably 0.5~1.5 h, more preferably 1 h; the in-situ reduction is followed by rinsing and drying; this invention does not have special requirements for the rinsing and drying, and rinsing and drying methods well known to those skilled in the art can be used. The active groups generated by hydrolysis modification will coordinate and anchor with silver ions in the in-situ reduction reaction. Ethanol, as a mild reducing agent, reduces silver ions in-situ into nano-silver catalytic particles uniformly distributed on the surface of polyurethane foam without the need to introduce additional strong reducing agents.

[0011] In this invention, the compression ratio of the pre-compression is preferably 10% to 30%. As a specific embodiment of this invention, the compression ratio of the pre-compression can be 10% or 30%.

[0012] In this invention, the electroless copper plating is preferably carried out in a copper plating solution; the copper plating solution preferably includes copper sulfate, sodium hydroxide, disodium ethylenediaminetetraacetate, sodium tartrate, and formaldehyde solution; in the copper plating solution, the concentration of copper sulfate is preferably 13-16 g / L, the concentration of sodium hydroxide is preferably 13-16 g / L, the concentration of disodium ethylenediaminetetraacetate is preferably 15-25 g / L, the concentration of sodium tartrate is preferably 8-12 g / L, and the concentration of formaldehyde solution is preferably 30-40 g / L; the pH of the copper plating solution is preferably 12-13. As a specific embodiment of this invention, in the copper plating solution, the concentration of copper sulfate can be 14 g / L, the concentration of sodium hydroxide can be 14 g / L, the concentration of disodium ethylenediaminetetraacetate can be 20 g / L, the concentration of sodium tartrate can be 10 g / L, the concentration of formaldehyde solution can be 40 g / L, and the pH of the copper plating solution can be 12.

[0013] In this invention, the electroless copper plating is preferably performed under ultrasonic conditions; the ultrasonic power is preferably 100-500W; more preferably 300W; the electroless copper plating temperature is preferably 40-60℃, more preferably 50℃; and the electroless copper plating time is preferably 5-25 minutes. As a specific embodiment of this invention, the electroless copper plating time can be 15 minutes; the electroless copper plating process also includes washing and drying; this invention does not have special requirements for the washing and drying, and washing and drying methods well-known to those skilled in the art can be used. This invention applies a specific proportion of pre-compression deformation to activated polyurethane foam sponge, and performs ultrasonic electroless copper plating while maintaining the compressed state. The copper plating solution quickly and uniformly enters the polyurethane foam sponge skeleton, thereby causing a thick, continuous copper plating layer to conformally grow on the surface of the compressed, wrinkled polyurethane foam sponge skeleton, forming a three-dimensional continuous copper network.

[0014] In this invention, the electroless silver plating is preferably carried out in a silver plating solution; the silver plating solution preferably includes silver nitrate, sodium thiosulfate, sodium sulfite, potassium metabisulfite, and potassium iodide; in the silver plating solution, the concentration of silver nitrate is preferably 8-12 g / L, the concentration of sodium thiosulfate is preferably 120-160 g / L, the concentration of sodium sulfite is preferably 40-60 g / L, the concentration of potassium metabisulfite is preferably 20-40 g / L, and the concentration of potassium iodide is preferably 0.15-0.25 g / L; the pH of the silver plating solution is preferably 5-6. As a specific embodiment of this invention, in the silver plating solution, the concentration of silver nitrate can be 10 g / L, the concentration of sodium thiosulfate can be 150 g / L, the concentration of sodium sulfite can be 50 g / L, the concentration of potassium metabisulfite can be 30 g / L, the concentration of potassium iodide can be 0.2 g / L, and the pH of the silver plating solution can be 5. In this invention, the preferred temperature for electroless silver plating is 20-30°C; the electroless silver plating time is 5-10 minutes; as a specific embodiment of this invention, the electroless silver plating time can be 5 minutes or 10 minutes; the electroless silver plating process also includes washing and drying; this invention does not have special requirements for the washing and drying, and washing and drying methods well known to those skilled in the art can be used. This invention, through a short-time (5-10 minutes) electroless silver plating process, coats the outer surface of the copper plating layer with a dense silver protective layer, which can prevent the copper network from oxidizing.

[0015] In this invention, the liquid elastic matrix preferably comprises polydimethylsiloxane (PDMS) and a curing agent; the mass ratio of PDMS to curing agent is preferably 10:1. This invention does not have special requirements for the curing agent; any method known to those skilled in the art can be used. As a specific embodiment of this invention, the curing agent can be DC184 (purchased from Dow Corning). The process before filling preferably includes vacuum degassing of the liquid elastic matrix; this invention does not have special requirements for the vacuum degassing; any vacuum degassing method known to those skilled in the art can be used. The temperature for hot-press curing is preferably 75~90℃, more preferably 80℃; the time for hot-press curing is preferably 1.5~2 hours, more preferably 2 hours.

[0016] The present invention does not impose any particular restrictions on the source of the above-mentioned raw materials; conventional commercially available products known to those skilled in the art can be used.

[0017] The present invention also provides a longitudinally stretchable through-type metal-based thermal interface material prepared by the above preparation method.

[0018] This invention provides a method for preparing a longitudinally stretchable, through-type metal-based thermal interface material, comprising the following steps: immersing polyurethane foam in an alkaline solution for hydrolysis modification to obtain modified polyurethane foam; placing the modified polyurethane foam in an ethanol solution of silver salt for in-situ reduction to obtain activated polyurethane foam; pre-compressing the activated polyurethane foam and then chemically plating it with copper to obtain copper-plated polyurethane foam; chemically plating the copper-plated polyurethane foam with silver to obtain silver-plated polyurethane foam; and injecting a liquid elastic matrix into the silver-plated polyurethane foam and hot-pressing to cure it, thereby obtaining a longitudinally stretchable, through-type metal-based thermal interface material. This invention utilizes a fully interconnected three-dimensional polyurethane foam as a template for continuous chemical plating, eliminating the polymer thermal resistance barrier between particles in traditional composite materials, constructing a direct, high-speed heat flow channel, and achieving ultra-high longitudinal thermal conductivity (up to 20.64 W / m²). ).

[0019] This invention employs a pre-compression chemical plating technique, which allows a rigid metal layer to adhere to the shrinking skeleton during the growth period. When faced with longitudinal displacement caused by thermal stress, it can release the displacement like a stretched spring, thereby solving the problem of easy fracture and failure of rigid thermal interface materials and endowing the thermal interface material with excellent flexibility and ultra-large longitudinal tensile strength.

[0020] This invention involves depositing a metal coating on a three-dimensional polyurethane foam sponge under physical compression. After stress release and encapsulation with an elastomer, the metal skeleton is not only omnidirectionally connected in three-dimensional space but also pre-stores sufficient folds and bending allowances in the longitudinal direction. Under tension, the metal skeleton of this invention adapts to the tension through its own structural stretching and deformation, rather than relying on the lattice extension of the metal material itself. Example data shows that the longitudinally stretchable through-type metal-based thermal interface material prepared by this invention can achieve a fracture strain of approximately 600% for its silver-plated skeleton (silver-plated polyurethane foam sponge).

[0021] This invention constructs a core-shell structure on the surface of a copper layer through chemical silver plating, which endows the material with excellent oxidation resistance and reliability under complex working conditions. The entire process is completed in a low-temperature liquid phase, which has greater potential for large-scale industrial mass production compared to vapor phase deposition technology. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic flowchart of the preparation method of the longitudinally stretchable through-type metal-based thermal interface material provided in Example 1; Figure 2 An optical microscope image of the copper-plated polyurethane foam sponge prepared in Example 1; Figure 3 An optical microscope image of the silver-plated polyurethane foam sponge prepared in Example 1; Figure 4 The stress-strain curve of the silver-plated polyurethane foam sponge prepared in Example 1 is shown. Figure 5 The copper plating thickness diagrams are shown for the longitudinally stretchable through-type metal-based thermal interface materials prepared in Examples 1-4. Figure 6 The graph shows the relationship between fracture strain and electrical resistance of the longitudinally stretchable through-type metal-based thermal interface materials prepared in Examples 1-4 as a function of copper content. Figure 7 Infrared thermal images of PCA-TIM prepared in Example 1, CPFP prepared in Comparative Example 1, and PDMS prepared in Comparative Example 2 on a heating plate at 120°C. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0025] The copper plating solution used in this embodiment of the invention comprises the following components: copper sulfate, sodium hydroxide, disodium ethylenediaminetetraacetate, sodium tartrate, and formaldehyde solution. The concentrations are as follows: copper sulfate 14 g / L, sodium hydroxide 14 g / L, disodium ethylenediaminetetraacetate 20 g / L, sodium tartrate 10 g / L, and formaldehyde solution 40 g / L; the pH of the copper plating solution is 12.

[0026] The silver plating solution used in this embodiment of the invention consists of the following components: silver nitrate, sodium thiosulfate, sodium sulfite, potassium metabisulfite, and potassium iodide. The concentrations are as follows: silver nitrate 10 g / L, sodium thiosulfate 150 g / L, sodium sulfite 50 g / L, potassium metabisulfite 30 g / L, and potassium iodide 0.2 g / L; the pH of the silver plating solution is 5.

[0027] Example 1 This embodiment provides a method for preparing a longitudinally stretchable through-type metal-based thermal interface material, which consists of the following steps: The modified polyurethane foam was obtained by immersing polyurethane foam in a 10% NaOH aqueous solution and hydrolyzing it at 60°C for 2 hours. The modified polyurethane foam was placed in an ethanol solution of 1 mol / L AgNO3 (calculated as silver ions) and reduced in situ for 1 h at 30 °C under light-protected conditions. It was then rinsed with deionized water and dried to obtain activated polyurethane foam. The activated polyurethane foam sponge was placed in a chemical copper plating tank with mechanical clamps (the chemical copper plating tank was filled with copper plating solution). After pre-compression with a compression rate of 10% using mechanical clamps, it was ultrasonically chemically copper plating for 15 minutes at 50℃ and 300W. After removal, it was washed with deionized water and dried to obtain copper-plated polyurethane foam sponge. The copper-plated polyurethane foam sponge was immersed in silver plating solution, chemically silvered for 5 minutes at room temperature in the dark, then washed and dried to obtain silver-plated polyurethane foam sponge. Polydimethylsiloxane (PDMS) in a mass ratio of 10:1 was mixed with a curing agent (Dow Corning, model DC184), and after vacuum degassing, it was poured into silver-plated polyurethane foam. The mixture was then hot-pressed and cured at 80°C for 2 hours. After releasing the mechanical clamps, a longitudinally stretchable through-type metal-based thermal interface material, denoted as PCA-TIM, was obtained.

[0028] A flowchart illustrating the preparation method of the longitudinally stretchable through-type metal-based thermal interface material provided in this embodiment is shown below. Figure 1 .

[0029] Example 2 This embodiment provides a method for preparing a longitudinally stretchable through-type metal-based thermal interface material, which is basically the same as the steps in Embodiment 1, except that the chemical copper plating time is 5 minutes.

[0030] Example 3 This embodiment provides a method for preparing a longitudinally stretchable through-type metal-based thermal interface material, which is basically the same as the steps in Embodiment 1, except that the time for chemical copper plating is 10 minutes.

[0031] Example 4 This embodiment provides a method for preparing a longitudinally stretchable through-type metal-based thermal interface material, which is basically the same as the steps in Embodiment 1, except that the chemical copper plating time is 20 minutes.

[0032] Example 5 This embodiment provides a method for preparing a longitudinally stretchable through-type metal-based thermal interface material, which is basically the same as the steps in Embodiment 1, except that the chemical copper plating time is 25 minutes.

[0033] Example 6 This embodiment provides a method for preparing a longitudinally stretchable through-type metal-based thermal interface material, which consists of the following steps: The modified polyurethane foam was obtained by immersing polyurethane foam in a 10% NaOH aqueous solution and hydrolyzing it at 60°C for 2 hours. The modified polyurethane foam was placed in an ethanol solution of 1 mol / L AgNO3 (calculated as silver ions) and reduced in situ for 1 h at 30 °C under light-protected conditions. It was then rinsed with deionized water and dried to obtain activated polyurethane foam. The activated polyurethane foam sponge was placed in a chemical copper plating tank with mechanical clamps (the chemical copper plating tank was filled with copper plating solution). After pre-compression with a compression rate of 10% using mechanical clamps, it was ultrasonically chemically copper plating for 15 minutes at 50℃ and 300W. After removal, it was washed with deionized water and dried to obtain copper-plated polyurethane foam sponge. The copper-plated polyurethane foam sponge was immersed in silver plating solution, chemically silvered for 10 minutes at room temperature in the dark, then washed and dried to obtain silver-plated polyurethane foam sponge. PDMS and curing agent were mixed at a mass ratio of 10:1, and after vacuum degassing, the mixture was poured into silver-plated polyurethane foam. The mixture was then hot-pressed and cured at 80°C for 2 hours. The mechanical clamps were then released to obtain a longitudinally stretchable through-type metal-based thermal interface material.

[0034] Example 7 This embodiment provides a method for preparing a longitudinally stretchable through-type metal-based thermal interface material, which consists of the following steps: The modified polyurethane foam was obtained by immersing polyurethane foam in a 10% NaOH aqueous solution and hydrolyzing it at 60°C for 2 hours. The modified polyurethane foam was placed in an ethanol solution of 1 mol / L AgNO3 (calculated as silver ions) and reduced in situ for 1 h at 30 °C under light-protected conditions. It was then rinsed with deionized water and dried to obtain activated polyurethane foam. The activated polyurethane foam sponge was placed in a chemical copper plating tank with mechanical clamps (the chemical copper plating tank was filled with copper plating solution). After pre-compression at a compression rate of 30% using mechanical clamps, it was ultrasonically chemically copper plating for 15 minutes at 50℃ and 300W. After removal, it was washed with deionized water and dried to obtain copper-plated polyurethane foam sponge. The copper-plated polyurethane foam sponge was immersed in silver plating solution, chemically silvered for 5 minutes at room temperature in the dark, then washed and dried to obtain silver-plated polyurethane foam sponge. PDMS and curing agent were mixed at a mass ratio of 10:1, and after vacuum degassing, the mixture was poured into silver-plated polyurethane foam. The mixture was then hot-pressed and cured at 80°C for 2 hours. The mechanical clamps were then released to obtain a longitudinally stretchable through-type metal-based thermal interface material.

[0035] Example 8 This embodiment provides a method for preparing a longitudinally stretchable through-type metal-based thermal interface material, which consists of the following steps: The modified polyurethane foam was obtained by immersing polyurethane foam in a 30% NaOH aqueous solution and hydrolyzing it at 60°C for 2 hours. The modified polyurethane foam was placed in an ethanol solution of 1 mol / L AgNO3 (calculated as silver ions) and reduced in situ for 1 h at 30 °C under light-protected conditions. It was then rinsed with deionized water and dried to obtain activated polyurethane foam. The activated polyurethane foam sponge was placed in a chemical copper plating tank with mechanical clamps (the chemical copper plating tank was filled with copper plating solution). After pre-compression with a compression rate of 10% using mechanical clamps, it was ultrasonically chemically copper plating for 15 minutes at 50℃ and 300W. After removal, it was washed with deionized water and dried to obtain copper-plated polyurethane foam sponge. The copper-plated polyurethane foam sponge was immersed in silver plating solution, chemically silvered for 5 minutes at room temperature in the dark, then washed and dried to obtain silver-plated polyurethane foam sponge. PDMS and curing agent were mixed at a mass ratio of 10:1, and after vacuum degassing, the mixture was poured into silver-plated polyurethane foam. The mixture was then hot-pressed and cured at 80°C for 2 hours. The mechanical clamps were then released to obtain a longitudinally stretchable through-type metal-based thermal interface material.

[0036] Comparative Example 1 Commercially available spherical copper powder (Guangzhou Metallurgy) with a diameter of 1 micrometer was ground and mixed with PDMS and a curing agent (Dow Corning, model DC184). After vacuum degassing, the mixture was hot-pressed and cured at 80°C for 2 hours to obtain the comparative sample CPFP. The copper content in CPFP was similar to that in Example 1, approximately ~50 wt%.

[0037] Comparative Example 2 PDMS was mixed with curing agent (Dow Corning, model DC184) at a mass ratio of 10:1, and after vacuum degassing, it was hot-pressed and cured at 80°C for 2 h to obtain the comparative sample PDMS.

[0038] Characterization tests: The copper-plated polyurethane foam sponge prepared in Example 1 was characterized using an optical microscope, and the results are as follows: Figure 2 As shown. By Figure 2 As can be seen, the present invention enables a thick, continuous copper plating layer to conformally grow on the surface of a PU skeleton in a compressed and wrinkled state through ultrasonic chemical copper plating, forming a three-dimensional continuous copper network.

[0039] The silver-plated polyurethane foam sponge prepared in Example 1 was characterized using an optical microscope, and the results are as follows: Figure 3 As shown. By Figure 3 It is understood that the present invention successfully coats the outer surface of the copper plating layer of the copper-plated polyurethane foam sponge skeleton with a silver protective layer by chemical silver plating, which can prevent the copper plating layer from oxidizing.

[0040] The mechanical properties of the silver-plated polyurethane foam obtained in Example 1 were characterized using a tensile testing machine, and the results are as follows: Figure 4 As shown. By Figure 4 It is known that the silver-plated polyurethane foam sponge (silver-plated skeleton) of the present invention has excellent tensile properties, and its fracture strain can reach about 600%.

[0041] Performance testing: The longitudinally stretchable through-type metal-based thermal interface materials prepared in Examples 1-4 were subjected to tensile and electrical conductivity tests, and the results are as follows: Figure 5 and Figure 6 As shown. From Figure 5 and Figure 6It can be seen that the thickness and content of the copper plating layer can be controlled by adjusting the electroless copper plating time. The copper plating layer thicknesses (contents) obtained by copper plating times of 5 min (Example 2), 10 min (Example 3), 15 min (Example 1), and 20 min (Example 4) were 76 mm (14.41 wt%), 82 mm (27.76 wt%), 89 mm (49.00 wt%), and 93 mm (70.38 wt%), respectively. When the copper plating time was 5 min, the plating layer was relatively thin, with an elongation at break of 90.5% and a corresponding resistance of approximately 1.4 Ω. As the copper content continued to increase, the plating layer became thicker, while both the elongation at break and the resistance decreased. Therefore, it is necessary to adjust the appropriate plating thickness to balance the tensile properties and electrical conductivity of the material.

[0042] The PCA-TIM prepared in Example 1, the CPFP prepared in Comparative Example 1, and the PDMS prepared in Comparative Example 2 were scanned using a high-precision infrared thermal imager. The results are as follows: Figure 7 As shown. By Figure 7 As can be seen, PCA-TIM exhibits superior thermal conductivity compared to PDMS and CPFP. The thermal conductivity of PCA-TIM, measured using a laser thermal conductivity meter, is as high as 20.64 W / (m·K).

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a longitudinally stretchable through-type metal-based thermal interface material, characterized in that, Includes the following steps: Polyurethane foam sponge is immersed in an alkaline solution and hydrolyzed to obtain modified polyurethane foam sponge. The modified polyurethane foam was placed in an ethanol solution of silver salt and reduced in situ to obtain an activated polyurethane foam. The activated polyurethane foam was pre-compressed and then chemically plated with copper to obtain copper-plated polyurethane foam. The copper-plated polyurethane foam is chemically plated with silver to obtain silver-plated polyurethane foam. A liquid elastic matrix is ​​poured into the silver-plated polyurethane foam and then hot-pressed to cure, resulting in a longitudinally stretchable, through-type metal-based thermal interface material.

2. The method for preparing the longitudinally stretchable through-type metal-based thermal interface material according to claim 1, characterized in that, The alkaline solution is a sodium hydroxide solution; the mass concentration of the sodium hydroxide solution is 10%~30%.

3. The method for preparing the longitudinally stretchable through-type metal-based thermal interface material according to claim 1, characterized in that, The hydrolysis modification temperature is 40~60℃; the hydrolysis modification time is 1~2h.

4. The method for preparing the longitudinally stretchable through-type metal-based thermal interface material according to claim 1, characterized in that, In the ethanol solution of the silver salt, the concentration of silver ions is 0.5~1.5 mol / L, and the silver salt includes silver nitrate; The in-situ reduction is carried out under light-protected conditions; the temperature of the in-situ reduction is 20~50℃; and the time of the in-situ reduction is 0.5~1.5h.

5. The method for preparing the longitudinally stretchable through-type metal-based thermal interface material according to claim 1, characterized in that, The compression rate of the pre-compression is 10% to 30%.

6. The method for preparing the longitudinally stretchable through-type metal-based thermal interface material according to claim 1, characterized in that, The electroless copper plating is carried out in a copper plating solution; the copper plating solution includes copper sulfate, sodium hydroxide, disodium ethylenediaminetetraacetate, sodium tartrate, and formaldehyde solution; the pH of the copper plating solution is 12-13.

7. The method for preparing the longitudinally stretchable through-type metal-based thermal interface material according to claim 1, characterized in that, The electroless copper plating is performed under ultrasonic conditions; the power of the ultrasonic wave is 100~500W; the temperature of the electroless copper plating is 40~60℃; and the time of the electroless copper plating is 5~25min.

8. The method for preparing the longitudinally stretchable through-type metal-based thermal interface material according to claim 1, characterized in that, The electroless silver plating is carried out in a silver plating solution; the silver plating solution includes silver nitrate, sodium thiosulfate, sodium sulfite, potassium metabisulfite, and potassium iodide; the pH of the silver plating solution is 5-6; the temperature of the electroless silver plating is 20-30℃; and the electroless silver plating time is 5-10 min.

9. The method for preparing the longitudinally stretchable through-type metal-based thermal interface material according to claim 1, characterized in that, The liquid elastic matrix comprises polydimethylsiloxane and a curing agent; the mass ratio of polydimethylsiloxane to curing agent is 10:1; the hot-press curing temperature is 75~90℃; and the hot-press curing time is 1.5~2h.

10. A longitudinally stretchable through-type metal-based thermal interface material prepared by the preparation method according to any one of claims 1 to 9.

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