Polymer-based heat-conducting composite material based on synergistic enhancement of modified boron nitride and liquid metal and preparation method of polymer-based heat-conducting composite material

Abstract

The invention belongs to the technical field of heat-conducting interface materials, and discloses a polymer-based heat-conducting composite material based on synergistic enhancement of modified boron nitride and liquid metal, and a preparation method and application thereof. The polymer-based heat-conducting composite material is mainly composed of an organic matrix, modified hexagonal boron nitride and liquid metal. The preparation method comprises the following steps: firstly, coating polydopamine on the surface of hexagonal boron nitride, and loading metal nanoparticles in situ; then blending and grinding with liquid metal to construct a solid-liquid hybrid filler; and finally, adding the mixture into an organic matrix for defoaming, curing and forming. A sheet-liquid-sheet heat conduction bridging network is constructed through interface chemical modification, the interface thermal resistance and the system compression modulus are greatly reduced, meanwhile, the liquid metal is effectively locked through the interface anchoring effect, leakage of the liquid metal is prevented, and wide application prospects are achieved in the fields of electronic packaging and high-power device thermal management.

Description

Technical Field

[0001] This invention belongs to the field of thermally conductive interface materials technology, and relates to a polymer-based thermally conductive composite material based on the synergistic reinforcement of modified boron nitride and liquid metal, and its preparation method. Background Technology

[0002] With the rapid development of 5G communication, artificial intelligence computing, and high-performance chip technology, electronic components are evolving towards miniaturization, high integration, and high power density. This leads to an exponential increase in the local heat flux density generated by electronic devices during operation. If heat cannot be dissipated effectively and in a timely manner, it will severely shorten the lifespan of electronic components and cause system failure. Therefore, coating or inserting thermally conductive interface materials between heat sources and heat sinks to fill air gaps between microscopic rough interfaces and reduce contact thermal resistance has become an indispensable key aspect of thermal management engineering.

[0003] Currently, polymers (such as silicone rubber, polyurethane, and epoxy resin) are widely used in industry as flexible matrices for thermally conductive interface materials. However, the intrinsic thermal conductivity of polymer matrices is extremely low (typically between 0.1 and 0.3 W / m·K), which cannot meet the requirements for efficient heat dissipation. The most common solution in existing technologies is to fill the polymer matrix with a large amount of highly thermally conductive inorganic rigid particles (such as hexagonal boron nitride (h-BN), alumina, and aluminum nitride). Hexagonal boron nitride (h-BN) is considered an ideal thermally conductive filler due to its excellent thermal conductivity and excellent electrical insulation. However, to achieve a practically valuable thermal conductivity in the composite material, it is usually necessary to add a very high volume fraction of rigid filler. This "high-filling" strategy inevitably disrupts the physical balance of the material: excessive rigid layers cause the viscosity of the uncured slurry of the composite material to increase dramatically, completely losing its processing fluidity; the hardness and compressive modulus of the cured material surge, losing the flexibility and deformation capability that TIMs should have, and cannot conform to the microstructure of the heat dissipation interface during actual bonding, instead introducing extremely high interfacial contact thermal resistance, which seriously restricts the actual heat dissipation efficiency.

[0004] To address the challenges of high modulus and processing associated with rigid fillers, the introduction of room-temperature liquid metals as synergistic reinforcing soft fillers has become a research hotspot in recent years. Liquid metals combine the extreme flexibility and deformability of liquid fluids with the ultra-high intrinsic thermal conductivity of metallic materials. Theoretically, introducing fluid liquid metals into a thermally conductive framework primarily composed of rigid boron nitride creates a "solid-liquid hybrid" dual-continuous filling network. The liquid metals can act as "thermally conductive liquid bridges," perfectly filling the microscopic voids formed by the stacked rigid boron nitride layers. This not only constructs low-thermal-resistance phonon transport channels but also acts as a liquid lubricant, alleviating frictional jamming between rigid particles, thereby endowing the composite material with extremely low compressive modulus and excellent interfacial conformation.

[0005] However, in existing practical preparation and applications, this "solid-liquid synergy" technology faces insurmountable thermodynamic and kinetic bottlenecks, exhibiting the following significant drawbacks: (1) Severe phase separation and extremely high interfacial thermal resistance.

[0006] (2) Frequent liquid metal leakage and short circuit risks.

[0007] (3) Severe corrosion of the metal heat dissipation substrate.

[0008] Therefore, the present invention aims to develop a thermally conductive composite material with high thermal conductivity, low modulus and extremely high long-term service reliability. Summary of the Invention

[0009] To address the shortcomings of existing technologies, a thermally conductive composite material with high thermal conductivity, low compressive modulus, and no risk of liquid metal leakage is provided.

[0010] The technical solution of the present invention: A polymer-based thermally conductive composite material based on the synergistic reinforcement of modified boron nitride and liquid metal comprises the following components by mass fraction: Organic matrix (e.g., PDMS): 40–60 wt% Modified hexagonal boron nitride: 20–40 wt% Liquid metal (LM): 20–40 wt% The modified hexagonal boron nitride is a hexagonal boron nitride with a surface coated with polydopamine and in-situ grown metal nanoparticles.

[0011] The polymer matrix is ​​one or a mixture of two or more of the following: polydimethylsiloxane (PDMS), room temperature vulcanizing silicone rubber, epoxy resin, polyurethane, and acrylic resin.

[0012] The liquid metal is a gallium-based alloy that is liquid at room temperature, preferably a gallium-indium alloy (EGaIn) or a gallium-indium-tin alloy (Galinstan).

[0013] The metal nanoparticles on the surface of the modified hexagonal boron nitride undergo an alloying reaction with the liquid metal at the solid-liquid interface, forming an intermetallic compound interface layer. Cu or Ag metal particles are preferred. The liquid metal occupies the gaps between the modified hexagonal boron nitride particles, forming a continuous "plate-liquid-plate" network structure. The organic matrix externally encapsulates this continuous "plate-liquid-plate" network structure of liquid metal and boron nitride.

[0014] A method for preparing a polymer-based thermally conductive composite material based on the synergistic reinforcement of modified boron nitride and liquid metal, comprising the following steps: (1) First, a layer of polydopamine is coated on the surface of hexagonal boron nitride. Chemical plating is carried out at a ratio of 1-3g of hexagonal boron nitride to 1L of plating solution. The water bath temperature is 20-40℃, the rotation speed is 200-600rpm, and the time is 12-24h. (The plating solution formula is 2.5mM-10mM of dopamine hydrochloride and 8mM-30mM of tris(hydroxymethyl)aminomethane). After the reaction is completed, the filtered powder is dried in a drying oven.

[0015] (2) Subsequently, the polydopamine-coated hexagonal boron nitride was subjected to chemical plating with loaded metal nanoparticles. The chemical plating was carried out at a ratio of 1-3g of polydopamine-coated hexagonal boron nitride to 1L of plating solution. The water bath temperature was 20-40℃, the rotation speed was 200-600rpm, and the time was 4-6h. The plating solution formula consisted of 5mM-20mM soluble metal salt, 5-40mM DMAB, 0.1M-0.2M boric acid, and 0.1M-0.2M polyvinylpyrrolidone. After the reaction was completed, the filtered powder was vacuum dried in a drying oven to finally obtain modified hexagonal boron nitride. (3) Modified hexagonal boron nitride and liquid metal are mechanically ground and mixed at a mass ratio of 0.5-2 to make the liquid metal and the loaded metal nanoparticles undergo an alloying reaction. (4) Add the above mixture to the organic matrix at a mass ratio of 0.5-2 with the organic groups and stir at a stirring rate of 1000-3000 rpm for 0.5-2 h. After vacuum degassing, apply 3-10 MPa pressure at 60-80℃ for hot pressing and curing for 1-4 h to obtain the thermally conductive interface material for heating and curing.

[0016] The pH value of the plating solution in step (1) should be 8.5.

[0017] The soluble metal salt in step (2) is selected from copper chloride, silver nitrate, etc.

[0018] In step (3), an auxiliary solvent is added during the mechanical mixing and grinding process. The auxiliary solvent is selected from anhydrous ethanol or n-hexane. After grinding, the auxiliary solvent is evaporated and removed.

[0019] Application of the aforementioned polymer-based thermally conductive composite material in electronic packaging thermal interface materials.

[0020] The beneficial effects of this invention are: (1) Extremely low interfacial thermal resistance: The alloying reaction between metal particles and LM drives the spontaneous spread of LM to form a continuous heat conduction network of “plate-liquid-plate”.

[0021] (2) Leakage prevention and high reliability: The interface chemical anchoring effect firmly locks in the liquid metal, completely solving the problems of oil leakage and copper substrate corrosion.

[0022] (3) Excellent processing and flexibility: LM replaces some rigid fillers, which significantly reduces the compressive modulus of the material. Attached Figure Description

[0023] Figure 1 This is a microscopic morphology diagram of the thermally conductive packing material in Example 1.

[0024] Figure 2 This is a cross-sectional morphology diagram of the thermally conductive interface material in Example 2.

[0025] Figure 3 This is a cross-sectional morphology diagram of the thermally conductive interface material in Example 3.

[0026] Figure 4 This is a microscopic morphology diagram of the thermally conductive filler in Example 4.

[0027] Figure 5 This is a cross-sectional morphology diagram of the thermally conductive interface material in Comparative Example 1.

[0028] Figure 6 This is a cross-sectional morphology diagram of the thermally conductive interface material in Comparative Example 2.

[0029] Figure 7 The thermal conductivity data are for Examples 1, 2, Comparative Examples 1 and 2.

[0030] Figure 8 The stress-strain curves are for Examples 1, 2, Comparative Examples 1 and 2. Detailed Implementation

[0031] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0032] Example 1 (1) 2g of hexagonal boron nitride was dispersed in Tris-HCl buffer (2g / L), dopamine hydrochloride was added and stirred for 12h, and after washing and drying, BN-PDA was obtained; then BN-PDA was chemically plated with copper (plating solution formula: CuCl2: 5mM; DMAB: 10mM), and after reacting for 4h, it was washed and dried to obtain BN-PDA-Cu powder.

[0033] (2) Weigh 20g of BN-PDA-Cu powder and 20g of gallium indium alloy (EGaIn) and place them in a grinder. Add an appropriate amount of anhydrous ethanol to assist grinding for 15 minutes. After the ethanol evaporates, a uniform gray composite powder is obtained.

[0034] (3) The above composite powder was added to 40g of PDMS (A glue: B glue = 10: 1), mixed evenly, and then subjected to intermittent vacuum degassing. Subsequently, it was injected into a mold and hot-pressed and cured at 80℃ with a pressure of 5 MPa for 2 hours to obtain a thermally conductive interface material.

[0035] Example 2 The preparation steps are the same as in Example 1, except that: in step 2, the amount of gallium-indium alloy added is 40g, BN-PDA-Cu is 20g, and in step 3, PDMS is 40g. This improves thermal conductivity and mechanical properties.

[0036] Example 3 The preparation steps are the same as in Example 1, except that: in step 2, the amount of gallium-indium alloy added is 20g, BN-PDA-Cu is 20g, and in step 3, PDMS is 60g. This results in a reduction in the basic corrosion of the copper substrate.

[0037] Example 4 Similar to Example 1, the electroless copper plating solution was supplemented with 0.1M boric acid as a stabilizer and 0.1M polyvinylpyrrolidone as a dispersant. This resulted in more uniform Cu particles on the boron nitride surface.

[0038] Comparative Example 1 20g of untreated raw hexagonal boron nitride was weighed and mixed with 20g of gallium indium alloy (EGaIn) and ground. The mixture was then added to 40g of PDMS and cured under the same conditions as in Example 1. Compared with Example 1, the results show that the thermal conductivity and mechanical properties of the polymer thermally conductive composite material are improved after the modified hexagonal boron nitride is mixed with liquid metal.

[0039] Comparative Example 2 20g of BN-PDA powder and 20g of gallium-indium alloy were weighed and ground, then added to 40g of PDMS and cured under the same conditions as in Example 1. Compared with Comparative Example 1 and Example 1, the influence of polydopamine on the surface of boron nitride on the properties of the polymer thermally conductive composite material was eliminated.

[0040] In summary, modified hexagonal boron nitride undergoes an alloying reaction with liquid metal at the solid-liquid interface, forming an intermetallic compound interface layer. The liquid metal occupies the gaps between the modified hexagonal boron nitride particles, forming a continuous "plate-liquid-plate" network structure. Thermal conductivity and stress-strain curves show that the modified boron nitride exhibits improved thermal conductivity, enhanced mechanical properties, and increased elongation at break compared to the polymer thermally conductive composite material made from unmodified boron nitride and liquid metal. Furthermore, the surface coating of boron nitride with polydopamine alone does not significantly improve performance compared to unmodified boron nitride, indicating that the metal nanoparticles on the surface of the modified hexagonal boron nitride play a crucial role.

Claims

1. A polymer-based thermally conductive composite material based on the synergistic reinforcement of modified boron nitride and liquid metal, characterized in that, This polymer-based thermally conductive composite material comprises the following components by mass fraction: Organic matrix: 40–60 wt% Modified hexagonal boron nitride: 20–40 wt% Liquid metal: 20–40 wt%.

2. The polymer-based thermally conductive composite material according to claim 1, characterized in that, The modified hexagonal boron nitride is a hexagonal boron nitride with polydopamine and in-situ grown metal nanoparticles coated on its surface, wherein the metal nanoparticles are metal Cu nanoparticles or metal Ag nanoparticles. The organic matrix is ​​one or a mixture of two or more of the following: polydimethylsiloxane, room temperature vulcanizing silicone rubber, epoxy resin, polyurethane, and acrylic resin. The liquid metal is a gallium-based alloy that is liquid at room temperature, preferably a gallium-indium alloy or a gallium-indium-tin alloy.

3. The polymer-based thermally conductive composite material according to claim 1, characterized in that, The metal nanoparticles on the surface of the modified hexagonal boron nitride undergo an alloying reaction with the liquid metal at the solid-liquid interface to form an intermetallic compound interface layer. The liquid metal occupies the gaps between the modified hexagonal boron nitride to form a continuous plate-liquid-plate network structure. The organic matrix encapsulates the continuous plate-liquid-plate network structure formed by the liquid metal and the modified hexagonal boron nitride.

4. A method for preparing a polymer-based thermally conductive composite material based on the synergistic reinforcement of modified boron nitride and liquid metal, characterized in that, The steps are as follows: (1) Coating a layer of polydopamine on the surface of hexagonal boron nitride: Add hexagonal boron nitride to the chemical plating solution for chemical plating. The chemical plating conditions are as follows: water bath temperature 20-40℃, rotation speed 200-600rpm, time 12-24h; after the chemical plating is completed, dry the filtered powder. (2) For hexagonal boron nitride loaded with polydopamine: hexagonal boron nitride coated with polydopamine was added to the chemical plating solution for chemical plating. The chemical plating conditions were as follows: water bath temperature 20-40℃, rotation speed 200-600rpm, time 4-6h; after chemical plating, the filtered powder was vacuum dried to obtain modified hexagonal boron nitride. (3) Modified hexagonal boron nitride and liquid metal are mechanically ground and mixed at a mass ratio of 0.5-2 to make the liquid metal and the metal nanoparticles on the surface of modified hexagonal boron nitride undergo an alloying reaction. (4) The mixture obtained in step (3) is mixed and stirred with the organic matrix at a mass ratio of 0.5-2. The stirring speed is 1000-3000 rpm and the stirring time is 0.5-2 h. After vacuum degassing, the mixture is hot-pressed and cured at 60-80℃ with a pressure of 3-10 MPa for 1-4 h to obtain the thermally conductive interface material. The polymer-based thermally conductive composite material is obtained by heating and curing.

5. The preparation method according to claim 4, characterized in that, In step (1), The concentration of hexagonal boron nitride in the electroless plating solution is 1-3 g / L; The chemical plating solution is formulated with 2.5mM-10mM dopamine hydrochloride and 8mM-30mM tris(hydroxymethyl)aminomethane.

6. The preparation method according to claim 4, characterized in that, In step (2), The concentration of hexagonal boron nitride coated with polydopamine in the electroless plating solution is 1-3 g / L; The chemical plating solution formulation consists of 5 mM-20 mM soluble metal salt, 5-40 mM DMAB, 0.1 M-0.2 M boric acid, and 0.1 M-0.2 M polyvinylpyrrolidone. The soluble metal salts are copper chloride or silver nitrate.

7. The preparation method according to claim 4, characterized in that, In step (3), In step (3), an auxiliary solvent is added during the mechanical grinding and mixing process. The auxiliary solvent is anhydrous ethanol or n-hexane. After the mechanical grinding and mixing is completed, the auxiliary solvent is evaporated and removed.

8. Application of a polymer-based thermally conductive composite material based on the synergistic reinforcement of modified boron nitride and liquid metal in electronic packaging thermal interface materials.

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