Bottle brush type polydimethylsiloxane film, preparation method thereof, thermal interface material and application
By forming a vertical copper array on a bottle-brush type polydimethylsiloxane film, the thermal interface material solves the problems of viscosity increase and poor interface adhesion caused by high filler in the prior art, and achieves efficient thermal conduction and tight adhesion, which is suitable for heat dissipation of electronic devices.
Patent Information
- Application Number
- CN202610263456.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-05
- Publication Date
- 2026-05-15
AI Technical Summary
Existing thermal interface materials exhibit a sharp increase in viscosity, a decrease in flexibility and interfacial adhesion when the filler content is high, and the process is complex, making it difficult to achieve efficient heat conduction and tight adhesion.
A bottle-brush type polydimethylsiloxane membrane is used to form a vertically oriented copper array on it. Combined with laser drilling and electrodeposition processes, a thermal interface material is prepared. The branched structure is used to form a stable three-dimensional network to suppress molecular chain entanglement and small molecule migration, so as to achieve tight bonding under low pressure.
It significantly improves the axial thermal conductivity of thermal interface materials, reduces lateral interface scattering, lowers contact thermal resistance, and maintains the flexibility and processability of materials. The process is simple and easy to scale up for production.
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Figure CN122037578A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of thermal interface materials technology, and in particular to bottle brush type polydimethylsiloxane film, its preparation method, thermal interface materials, and applications. Background Technology
[0002] With advancements in technology, the miniaturization of electronic components has led to a rapid increase in the thermal density per unit area, placing higher demands on device thermal design. Thermal interface materials (TIMs) are widely used to dissipate excess heat from electronic components (such as CPUs, GPUs, and LED panels). TIMs are a key component of the thermal management system for electronic devices, used to fill the micro-gaps between heat-generating elements and heat dissipation structures, reducing contact thermal resistance and improving heat transfer efficiency. As electronic devices develop towards higher power and higher integration, even higher requirements are placed on the thermal conductivity, interface adhesion, and process applicability of TIMs.
[0003] Existing technologies commonly employ high thermal conductivity fillers to fill the polymer matrix to improve the thermal conductivity of thermally conductive materials (TIMs). When the filler content reaches the percolation threshold, a continuous thermally conductive network can be formed, significantly improving the material's thermal conductivity. However, this method has inherent limitations: firstly, high filler content leads to a sharp increase in system viscosity and deterioration of material processing performance; secondly, excessive filler can impair the material's flexibility and interfacial adhesion, resulting in significant contact thermal resistance in practical applications; most importantly, even when a thermally conductive network is formed, numerous filler-filler interfaces and filler-matrix interfaces exacerbate phonon scattering, limiting further improvements in thermal conductivity.
[0004] Furthermore, at the process level, high-filler-content systems typically require molding methods such as rolling or hot pressing, which can easily lead to the planar orientation of sheet-like or fibrous fillers, resulting in significant anisotropy in thermal conductivity. To obtain out-of-plane oriented filler distributions, current common processes include ice template methods, magnetic field orientation, and electric field orientation. However, these methods involve complex processes and are not conducive to scalable production. Summary of the Invention
[0005] In view of this, the purpose of the present invention is to provide a bottle brush type polydimethylsiloxane film, its preparation method, thermal interface material and application, which significantly improves axial thermal conductivity, reduces transverse interface scattering, and can achieve close adhesion with the heating interface under low pressure, thereby reducing contact thermal resistance.
[0006] The following is a summary of this disclosure to provide a basic understanding of some aspects. This summary is not intended to identify key or important elements, nor is it intended to limit the implementation or any aspects of the claims. Furthermore, this summary provides a simplified overview of some aspects that can be described in more detail in other parts of this disclosure.
[0007] The present invention solves the above-mentioned technical problems through the following technical means: In a first aspect, the present invention provides a bottle-brush type polydimethylsiloxane film, wherein the bottle-brush type polydimethylsiloxane film is formed by curing bottle-brush type polydimethylsiloxane, wherein the bottle-brush type polydimethylsiloxane has polymethylvinylsiloxane with double bonds in the side chain as the main chain, silanol-based single-terminated polydimethylsiloxane as the bottle-brush chain, and silanol-based double-terminated polydimethylsiloxane as the crosslinking chain, and the density of the bottle-brush chain is 10-70 mol.
[0008] In conjunction with the first aspect, in some embodiments, the raw materials for preparing the bottle-brush type polydimethylsiloxane membrane include: polymethylvinylsiloxane with double bonds in the side chains, silanol-based single-terminated polydimethylsiloxane, silanol-based double-terminated polydimethylsiloxane, nano-silica, and Karstedt catalyst; the amount of nano-silica used is 3-10 wt% of the total mass of the polymethylvinylsiloxane with double bonds in the side chains, silanol-based single-terminated polydimethylsiloxane, and silanol-based double-terminated polydimethylsiloxane; and / or, In the raw materials for preparing the bottle-brush type polydimethylsiloxane film, the molar ratio of vinyl to silane groups is (0.8–1.5):1; and / or, The platinum in the total amount of the Karstedt catalyst is 20 to 500 ppm by mass of polymethylvinylsiloxane with double bonds in the side chain.
[0009] In conjunction with the first aspect, in some embodiments, the molecular weight of the polymethylvinylsiloxane containing double bonds in its side chains is 5000–80000 g / mol; and / or, The molecular weight of the silanol-based single-terminated polydimethylsiloxane is 1000–8000 g / mol; and / or, The molecular weight of the silanol-based double-terminated polydimethylsiloxane is 3000–30000 g / mol; and / or, The particle size of the nano-silica is 3-50 nm.
[0010] In a second aspect, the present invention also provides a method for preparing the bottle-brush type polydimethylsiloxane film described in the first aspect, comprising the following steps: Polymethylvinylsiloxane with double bonds in the side chain, silane-hydrogen mono-terminated polydimethylsiloxane, and nano-silica are mixed, and then Karstedt catalyst and silane-hydrogen double-terminated polydimethylsiloxane are added and stirred to mix evenly. After degassing, a mixed slurry is obtained. The mixed slurry is coated and heated to 30-150℃ for 1-20 hours to cure, thus obtaining a bottle brush type polydimethylsiloxane film.
[0011] The bottle-brush type polydimethylsiloxane film of this invention, compared with linear polymers, has a main chain backbone and a large number of branched structures connected to the main chain, forming a unique spatial configuration. This molecular structure enables the bottle-brush type polydimethylsiloxane to maintain a high molecular weight while having a low viscosity, mainly due to the branched structure effectively suppressing the entanglement and orderly arrangement between molecular chains; at the same time, the branched structure forms a stable three-dimensional network through physical action without forming a chemical cross-linking network, effectively restricting the migration of small molecules. Applying the bottle-brush type polydimethylsiloxane film of this invention to the preparation of thermal interface materials can achieve good interfacial contact, obtain low contact thermal resistance, and the low adhesion before curing is conducive to the coating to form a thin film, and the formation of a thinner film is beneficial to reducing the bulk thermal resistance of the thermal interface material.
[0012] Thirdly, the present invention also provides a thermal interface material, comprising the bottle brush type polydimethylsiloxane film described in the first aspect, and a copper array vertically oriented on the bottle brush type polydimethylsiloxane film, wherein the diameter of each copper dot in the copper array is 0.2 to 0.5 mm, and the spacing between two adjacent copper dots is 0.5 to 1 mm.
[0013] Fourthly, the present invention also provides a method for preparing the thermal interface material described in the third aspect, comprising the following steps: Using a carbon dioxide laser, with a laser power of 0.55–11W and a scanning rate of 10–250 mm / s, a bottle brush type polydimethylsiloxane film is laser-drilled to form a vertically oriented array of holes on the bottle brush type polydimethylsiloxane film. The perforated bottle-brush type polydimethylsiloxane film was subjected to plasma cleaning treatment, and then magnetron sputtering was performed to sequentially form a titanium layer and a copper layer on the wall of each hole. Copper was deposited in each hole using a single-pulse deposition method, forming a copper array vertically oriented on a bottle-brush type polydimethylsiloxane film.
[0014] In conjunction with the fourth aspect, in some embodiments, the ratio of the aperture of the hole to the thickness of the bottle brush type polydimethylsiloxane film is 1:(0.3 to 1.5).
[0015] In conjunction with the fourth aspect, in some embodiments, the thickness of the titanium layer is 50–150 nm, and the thickness of the copper layer is 150–400 nm.
[0016] In conjunction with the fourth aspect, in some embodiments, the pulse current density of the single-pulse deposition method is 0.1–5 mA / mm². 2 The pulse period is 1-3 seconds, and the conduction time T m =0.5s, turn-off time T on =0.5~2.5s, deposition time is 2~5h.
[0017] The thermal interface material of the present invention forms a copper array by depositing a bottle-brush type polydimethylsiloxane film with good tear resistance. The copper array has several vertically oriented copper pillars, which significantly improves the axial thermal conductivity of the material and reduces lateral interface scattering.
[0018] Fifthly, the present invention also provides the application of the thermal interface material described in the third or fourth aspect in heat dissipation of electronic devices.
[0019] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages: (1) By forming a vertically oriented copper pillar array in a bottle brush type polydimethylsiloxane film with good tear resistance, the axial thermal conductivity of the thermal interface material is significantly improved and the transverse interface scattering is reduced. (2) The bottle brush type polydimethylsiloxane film of the present invention has controllable viscoelasticity, which can achieve close adhesion to the heating interface under low pressure and reduce contact thermal resistance; (3) The bottle brush type polydimethylsiloxane film prepared by the entanglement and interaction between nano-silica and bottle brush chains in the bottle brush type polymer has good flexibility, excellent viscoelasticity and high tensile breaking length. (4) The laser drilling and electrodeposition processes in the thermal interface preparation method of the present invention can be scaled up, avoiding high-pressure injection or complex external field orientation equipment. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of the molecular chain entanglement and cross-linking network of bottle-brush type polydimethylsiloxane. Detailed Implementation
[0021] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.
[0022] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.
[0023] The abbreviations used in this application are defined as follows: PDMS: Polydimethylsiloxane; PVMS: Polymethylvinylsiloxane with double bonds in the side chain; Single-PHMS: Hydrosilane-based single-terminated polydimethylsiloxane; Double-PHMS: Hydrosilane-based double-terminated polydimethylsiloxane; PTFE: Polytetrafluoroethylene.
[0024] Bottle brush polymers are grafted polymers, characterized by dense side chains attached to the main chain. The type and structure of both the main chain and the side chains affect the properties of the polymer, but the most prominent feature of bottle brush polymers is their relatively dense side chains. These side chains have a significant impact on the conformation and movement of the polymer, thereby affecting its properties.
[0025] like Figure 1 As shown, the bottle brush type polydimethylsiloxane film of this application is formed by curing bottle brush type polydimethylsiloxane. The bottle brush type polydimethylsiloxane uses polymethylvinylsiloxane with double bonds in the side chain as the main chain, silanol mono-terminated polydimethylsiloxane as the bottle brush chain, and silanol double-terminated polydimethylsiloxane as the crosslinking chain. The density of the bottle brush chain is 10-70 mol.
[0026] The bottle-brush type polydimethylsiloxane film using the above-described technical solution, compared with linear polymers, possesses a main chain backbone and numerous branched structures connected to the main chain, forming a unique spatial configuration. This molecular structure allows the bottle-brush type polydimethylsiloxane to maintain a high molecular weight while exhibiting low viscosity, primarily due to the branched structure effectively suppressing entanglement and orderly arrangement between molecular chains. Simultaneously, the branched structure forms a stable three-dimensional network through physical interaction without forming a chemical cross-linking network, effectively limiting the migration of small molecules. Applying the bottle-brush type polydimethylsiloxane film of this application to the preparation of thermal interface materials can achieve good interfacial contact, obtain low contact thermal resistance, and the low adhesion before curing facilitates the coating process into thin films. Forming thinner films further reduces the bulk thermal resistance of the thermal interface material.
[0027] In specific implementation, the raw materials for preparing the bottle-brush type polydimethylsiloxane film include: polymethylvinylsiloxane with double bonds in the side chain, silane-hydrogen mono-terminated polydimethylsiloxane, silane-hydrogen double-terminated polydimethylsiloxane, nano-silica, and Karstedt catalyst. The amount of nano-silica used is 3–10 wt%, preferably 6–9 wt%, of the total mass of the polymethylvinylsiloxane with double bonds in the side chain, silane-hydrogen mono-terminated polydimethylsiloxane, and silane-hydrogen double-terminated polydimethylsiloxane. The particle size of the nano-silica is 3–50 nm, preferably 10–30 nm. The addition of nano-silica is mainly for thickening, which facilitates the uniform coating of the bottle-brush type polydimethylsiloxane to form a thin film, and also helps to improve the tear resistance of the bottle-brush type polydimethylsiloxane film.
[0028] In specific implementations, the amounts of PVMS used with Single-PHMS and Double-PHMS are proportioned according to a vinyl to silane group molar ratio of (0.8–1.5):1, preferably (0.9–1.1):1. The platinum content in the total amount of Karstedt catalyst is 20–500 ppm of PVMS, preferably 50–150 ppm, for example, 20 ppm, 50 ppm, 100 ppm, 150 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, etc.
[0029] In specific implementations, the molecular weight of polymethylvinylsiloxane containing double bonds in the side chain is 5000-80000 g / mol, preferably 10000-50000 g / mol, for example 5000 g / mol, 10000 g / mol, 15000 g / mol, 20000 g / mol, 25000 g / mol, 30000 g / mol, 35000 g / mol, 40000 g / mol, 45000 g / mol, 50000 g / mol, 60000 g / mol, 80000 g / mol, etc. The molecular weight of the bottle brush chain silane-terminated monocapped polydimethylsiloxane is 1000–8000 g / mol, preferably 3000–6000 g / mol, for example 1000 g / mol, 2000 g / mol, 3000 g / mol, 4000 g / mol, 5000 g / mol, 6000 g / mol, 7000 g / mol, 8000 g / mol, etc. The density of the bottle brush chain is 10–70 mol%, preferably 50–70 mol%, for example 10 mol%, 20 mol%, 30 mol%, 40 mol%, 50 mol%, 60 mol%, 70 mol%, etc. The density of the bottle brush chain refers to the percentage of double bonds used to react with the bottle brush chain relative to the total vinyl group. The molecular weight of the cross-linked silane-hydrogen-based double-terminated polydimethylsiloxane is 3000–30000 g / mol, preferably 8000–15000 g / mol, for example 3000 g / mol, 5000 g / mol, 8000 g / mol, 10000 g / mol, 12000 g / mol, 15000 g / mol, etc.
[0030] The bottle-brush type polydimethylsiloxane film of this application has a thickness of 0.15–0.5 mm and can be used to prepare thermal interface materials. Specifically, the thermal interface material of this application includes a bottle-brush type polydimethylsiloxane film and a copper array vertically oriented on the bottle-brush type polydimethylsiloxane film. The diameter of each copper dot in the copper array is 0.2–0.5 mm, and the spacing between two adjacent copper dots is 0.5–1 mm.
[0031] The method for preparing the thermal interface material in this application includes the following steps: Using a carbon dioxide laser, with a laser power of 0.55–11W and a scanning rate of 10–250 mm / s, a bottle brush type polydimethylsiloxane film is laser-drilled to form a vertically oriented array of holes on the bottle brush type polydimethylsiloxane film. The perforated bottle-brush type polydimethylsiloxane film is subjected to plasma cleaning to remove impurities from the film surface and pores. Then, magnetron sputtering is performed to electrochemically treat the pore walls of each pore. Titanium and copper layers are sputtered sequentially on the pore walls of each pore. The titanium layer serves as an adhesion layer with a thickness of 50–150 nm, and the copper layer has a thickness of 150–400 nm. Copper is deposited in each hole using a single-pulse deposition method to form a copper array that is vertically oriented on a bottle-brush type polydimethylsiloxane film, thereby improving the thermal conductivity of the entire film.
[0032] In specific implementations, the laser power is preferably 0.55–5.5W, for example, 0.55W, 1.1W, 1.65W, 2.2W, 5.5W, etc. The scanning rate is 10–250 mm / s, preferably 100–250 mm / s, for example, 10 mm / s, 20 mm / s, 30 mm / s, 40 mm / s, 50 mm / s, 60 mm / s, 70 mm / s, 80 mm / s, 90 mm / s, 100 mm / s, 120 mm / s, 140 mm / s, 160 mm / s, 200 mm / s, 250 mm / s, etc. The ratio of the aperture size to the thickness of the bottle-brush type polydimethylsiloxane film is 1:(0.3–1.5), preferably 1:(0.5–1.5). The thickness of the titanium layer is 50–150 nm, and the thickness of the copper layer is 150–400 nm. The pulse current density of the single-pulse deposition method is 0.1–5 mA / mm. 2 Preferably, it is 0.1–2.5 mA / cm 2 For example, it can be 0.1 mA / cm 2 0.2mA / cm 2 0.3mA / cm 2 0.4mA / cm 2 0.5mA / cm 2 0.6mA / cm 2 0.7mA / cm 2 0.8mA / cm 2 0.9mA / cm 2 1mA / cm 2 1.5mA / cm 2 2mA / cm 2 2.5mA / cm 2 The pulse period is 1–3 seconds, and the conduction time T is [missing information]. m =0.5s, turn-off time T on =0.5~2.5s, with a preferred turn-off time of 1~2s. The deposition time is 2~5h, and the specific time is selected according to the current density in the actual implementation.
[0033] The following detailed description of the above-mentioned bottle brush type polydimethylsiloxane film and thermal interface material and their preparation method will be provided through specific embodiments: Example 1
[0034] The preparation method of the bottle brush type polydimethylsiloxane film in this embodiment is as follows: Weigh out 5g of PVMS (molecular weight 35000 g·mol⁻¹). -1 2.53g of single-PHMS (molecular weight 5000 g·mol⁻¹) -1 1.05g of Double-PHMS (molecular weight 10000g·mol⁻¹) -1 The catalyst used in this embodiment contains 0.85 g of nano-silica and 100 ppm of Karstedt catalyst with a total platinum content of PVMS. The molar ratio of vinyl to silane groups in this embodiment is 1:1, and the bottle brush chain density is 67 mol%.
[0035] In a planetary mixer, PVMS, single-PHMS and nano-silica were added and stirred at 1500 rpm for 2 min. Then, Karstedt catalyst and Double-PHMS were added and stirred at 1500 rpm for 2 min. After stirring at 2000 rpm for 2 min to remove bubbles, a mixed slurry was obtained. The mixed slurry was then coated onto a PTFE membrane and placed in an oven to be heated to 30°C for 20 h to obtain a bottle-brush type polydimethylsiloxane membrane with a thickness of 150 micrometers. Example 2
[0036] The preparation method of the bottle brush type polydimethylsiloxane film in this embodiment is as follows: Weigh out 5g of PVMS (molecular weight 35000 g·mol⁻¹). -1 ), 2.3g of single-PHMS (molecular weight 5000g·mol⁻¹) -1 1.26g of Double-PHMS (molecular weight 10000g·mol⁻¹) -1 The catalyst contained 0.80 g of nano-silica (representing 9.35% of the total mass of PVMS, single-PHMS, and double-PHMS) and 100 ppm of Karstedt catalyst with a total platinum content of PVMS. In this embodiment, the bottle brush chain density was 60 mol%.
[0037] In a planetary mixer, PVMS, single-PHMS and nano-silica were added and stirred at 1500 rpm for 2 min. Then, Karstedt catalyst and Double-PHMS were added and stirred at 1500 rpm for 2 min. After stirring at 2000 rpm for 2 min to remove bubbles, a mixed slurry was obtained. The mixed slurry was then coated onto a PTFE membrane and placed in an oven to be heated to 120℃ for 1 h to obtain a bottle-brush type polydimethylsiloxane membrane with a thickness of 150 micrometers. Example 3
[0038] The preparation method of the bottle brush type polydimethylsiloxane film in this embodiment is as follows: Weigh out 5g of PVMS (molecular weight 3000 g·mol⁻¹). -1 ), 1.9g of single-PHMS (molecular weight 5000g·mol⁻¹) -1 1.58g of Double-PHMS (molecular weight 10000g·mol⁻¹) -1 The sample contained 0.85 g of nano-silica and 100 ppm of Karstedt catalyst with a total platinum content of PVMS. In this embodiment, the bottle brush chain density was 50 mol%. In a planetary mixer, PVMS, single-PHMS and nano-silica were added and stirred at 1500 rpm for 2 min. Then, Karstedt catalyst and Double-PHMS were added and stirred at 1500 rpm for 2 min. After stirring at 2000 rpm for 2 min to remove bubbles, a mixed slurry was obtained. The mixed slurry was then coated onto a PTFE membrane and placed in an oven to be heated to 150℃ for 1 h to obtain a bottle-brush type polydimethylsiloxane membrane with a thickness of 150 micrometers. Example 4
[0039] The thermal interface material used in this embodiment is the bottle-brush type polydimethylsiloxane film prepared in Example 1. The preparation method of the thermal interface material in this embodiment is as follows: Using a carbon dioxide laser at a laser power of 5W and a scanning rate of 100mm / s, a bottle-brush type polydimethylsiloxane film was laser-drilled to form a vertically oriented array of holes on the film. In this embodiment, the diameter of the holes in the array is 200μm, and the spacing between the holes is 800μm. The drilled bottle-brush type polydimethylsiloxane film was then subjected to plasma cleaning for 2 minutes to remove impurities. Following this, it underwent magnetron sputtering conductivity treatment. A 100nm thick titanium layer was first sputtered onto the hole wall of each hole, followed by a 300nm thick copper layer. For the conductivity-treated bottle-brush type polydimethylsiloxane film, copper was deposited in each hole using a single-pulse deposition method at a current density of 0.2mA / mm². 2 The deposition time was 4 hours, the pulse period was 1 second, the turn-off time was 0.5 seconds, and the turn-on time was 0.5 seconds. Finally, a copper array was formed on the bottle brush type polydimethylsiloxane film with vertical orientation, which is the thermal interface material. Example 5
[0040] The thermal interface material used in this embodiment is the bottle-brush type polydimethylsiloxane film prepared in Example 2. The preparation method of the thermal interface material in this embodiment is as follows: Using a carbon dioxide laser at a power of 10W and a scanning rate of 100mm / s, a bottle-brush type polydimethylsiloxane film was laser-drilled to form a vertically oriented array of holes. In this embodiment, the diameter of the holes in the array was 200μm, and the spacing between the holes was 1000μm. The drilled bottle-brush type polydimethylsiloxane film was then subjected to plasma cleaning for 2 minutes to remove impurities. Following this, it underwent magnetron sputtering conductivity treatment. A 100nm thick titanium layer was first sputtered onto the hole wall of each hole, followed by a 300nm thick copper layer. For the conductivity-treated bottle-brush type polydimethylsiloxane film, copper was deposited in each hole using a single-pulse deposition method at a current density of 0.5mA / mm². 2 The deposition time was 5 hours, the pulse period was 1 second, the turn-off time was 0.5 seconds, and the turn-on time was 0.5 seconds. Finally, a copper array was formed that was vertically oriented on the bottle brush type polydimethylsiloxane film, which is the thermal interface material.
[0041] The heat dissipation performance of the thermal interface material in this embodiment was tested: an electric heating element was used as the heat source, and a copper sheet was used as the heat sink. A certain heating power was applied, and the temperature was recorded after reaching a steady state. The thermal interface material in this embodiment had a temperature 6.7°C lower than that under no-load conditions (without thermal interface material). Example 6
[0042] The thermal interface material used in this embodiment is the bottle-brush type polydimethylsiloxane film prepared in Example 3. The preparation method of the thermal interface material in this embodiment is as follows: Using a carbon dioxide laser at a power of 11W and a scanning rate of 100mm / s, a bottle-brush type polydimethylsiloxane film was laser-drilled to form a vertically oriented array of holes. In this embodiment, the diameter of the holes in the array was 500μm, and the spacing between the holes was 800μm. The drilled bottle-brush type polydimethylsiloxane film was then subjected to plasma cleaning for 2 minutes to remove impurities. Following this, it underwent magnetron sputtering conductivity treatment. A 100nm thick titanium layer was first sputtered onto the hole wall of each hole, followed by a 300nm thick copper layer. For the conductivity-treated bottle-brush type polydimethylsiloxane film, copper was deposited in each hole using a single-pulse deposition method at a current density of 0.2mA / mm². 2 The deposition time was 4 hours, the pulse period was 3 seconds, the turn-off time was 0.5 seconds, and the turn-on time was 2.5 seconds. Finally, a copper array was formed on the bottle brush type polydimethylsiloxane film with vertical orientation, which is the thermal interface material. Example 7
[0043] The thermal interface material used in this embodiment is the bottle-brush type polydimethylsiloxane film prepared in Example 3. The preparation method of the thermal interface material in this embodiment is as follows: Using a carbon dioxide laser at a laser power of 5W and a scanning rate of 100mm / s, a bottle-brush type polydimethylsiloxane film was laser-drilled to form a vertically oriented array of holes on the film. In this embodiment, the diameter of the holes in the array is 200μm, and the spacing between the holes is 800μm. The drilled bottle-brush type polydimethylsiloxane film was then subjected to plasma cleaning for 2 minutes to remove impurities. Following this, it underwent magnetron sputtering conductivity treatment. A 100nm thick titanium layer was first sputtered onto the hole wall of each hole, followed by a 300nm thick copper layer. For the conductivity-treated bottle-brush type polydimethylsiloxane film, copper was deposited in each hole using a single-pulse deposition method at a current density of 0.2mA / mm². 2 The deposition time was 5 hours, the pulse period was 3 seconds, the turn-off time was 0.5 seconds, and the turn-on time was 2.5 seconds. Finally, a copper array was formed on the bottle brush type polydimethylsiloxane film with vertical orientation, which is the thermal interface material.
[0044] The bottle-brush type polydimethylsiloxane films prepared in Examples 1-3 and the thermal interface materials prepared in Examples 4-7 were used as samples for performance testing as follows: (1) The standard for testing tensile modulus and elongation at break is ASTM D412. The bottle brush type polydimethylsiloxane film prepared in Examples 1-3 is used as the sample. The test steps are as follows: the PDMS sample film (without Cu composite) with a thickness of 2 mm is cut out and prepared into a dumbbell-shaped sample. Both ends are held by the clamps of the tensile testing machine and the tensile speed is 500 mm / min until the test breaks. The Young's modulus and elongation at break are obtained as shown in Table 1.
[0045] (2) The tear strength test standard is ASTM D624. The bottle brush type polydimethylsiloxane film prepared in Examples 1-3 is used as the sample. The test procedure is as follows: a universal testing machine is used to test the sample according to the ASTM D624 standard Type C (trouser tear method). The specific process is as follows: the PDMS sample film is cut into a standard trouser-shaped specimen and an initial cut is pre-made in the center; then, the specimen is symmetrically clamped on the testing machine fixture and stretched at a constant rate (e.g., 500 mm / min) until the specimen is completely torn; by recording and analyzing the force-displacement curve during the stretching process, the average value of its peak force is taken as the tear strength of the material (unit: kN / m), as shown in Table 1.
[0046] (3) The thermal resistance was tested using the steady-state thermal method, with ASTM D5470 as the standard. The thermal interface material prepared in Examples 4-7 was used as the sample. The test procedure was as follows: First, the sample was cut to the specified size and its thickness was accurately measured. Then, it was placed between the upper and lower heat flux meters of the thermal resistance tester. After applying a standard contact pressure (e.g., 10 psi), a stable temperature difference was set for the system to establish a one-dimensional steady-state heat flux. When the heat flux density and temperature readings remained stable, the data were recorded, and the total thermal resistance was calculated according to the formula R_total = ΔT / (Q / A), with the unit being K·cm²·W⁻¹. The final results are shown in Table 2.
[0047] (4) The out-of-plane thermal conductivity was tested using a laser thermal conductivity meter, and the vertical thermal diffusivity of the sample was measured using the laser thermal conductivity meter. α Differential scanning calorimetry for determining the specific heat capacity of materials c p Determination of density by weighing method ρ Based on the formula λ=α·c p · ρ The out-of-plane thermal conductivity of the thermal interface material sample was calculated, and the final results are shown in Table 2.
[0048] Table 1. Test results of mechanical properties of bottle-brush type polydimethylsiloxane film Performance indicators Example 1 (Bottle brush chain density 67%) Example 2 (Bottle brush chain density 60%) Example 3 (Bottle brush chain density 50%) Young's modulus (kPa) 75 80 85 Compression modulus (kPa) 360 370 375 Elongation at break (%) 450 420 440 Tear resistance (kN / m) 28～35 22～28 16～22 <![CDATA[Fatigue threshold, Γ0 (J / m²)]]> 950～1150 800～1000 650～850 Fracture energy (J / m²) 3000～3600 2500～3100 1800～2500 Lag ratio (%) 8.5～12 7～9 5～7 Table 2 Performance test results of thermal interface materials Sample source Hole diameter (μm) Hole spacing (μm) Effective thermal conductivity (W / m·K) Thermal resistance (K·cm² / W) Example 4 200 800 12.75 0.118 Example 5 200 1000 8.92 0.168 Example 6 500 800 46.66 0.032 Example 7 200 800 10.8 0.139 Table 1 shows that, in terms of mechanical properties, the PDMS membrane, as a polymer matrix, exhibits excellent flexibility, a Young's modulus of less than 100 kPa, an elongation at break of approximately 400%, and good tear resistance. Therefore, this PDMS membrane is an excellent TIM matrix.
[0049] Table 2 shows that the thermal interface material of this invention exhibits high thermal conductivity and low thermal resistance. Breaking away from the traditional approach of using ultra-high filler content in compounding to improve thermal conductivity, this invention only requires a small amount of highly oriented copper array to achieve high thermal conductivity, while maintaining the flexibility of the composite material. Therefore, the thermal interface material of this invention can be used for heat dissipation in electronic devices.
[0050] The foregoing description includes examples from this specification. Of course, for the purposes of describing this specification, it is impossible to describe every conceivable combination of components or methods; however, those skilled in the art will understand that many other combinations and arrangements are possible. Therefore, this specification is intended to cover all such changes, modifications, and variations that fall within the spirit and scope of the appended claims. Furthermore, with regard to the use of the term "comprising" in the detailed description or claims, the term is intended to be inclusive in a manner similar to the term "including," as interpreted when "comprising" is used as a transitional word in the claims.
[0051] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. 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 be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A bottle-brush type polydimethylsiloxane film, characterized in that, The bottle-brush type polydimethylsiloxane film is formed by curing bottle-brush type polydimethylsiloxane. The bottle-brush type polydimethylsiloxane uses polymethylvinylsiloxane with double bonds in the side chain as the main chain, silanol mono-terminated polydimethylsiloxane as the bottle-brush chain, and silanol double-terminated polydimethylsiloxane as the crosslinking chain. The density of the bottle-brush chain is 10-70 mol.
2. The bottle-brush type polydimethylsiloxane film according to claim 1, characterized in that, The raw materials for preparing the bottle-brush type polydimethylsiloxane membrane include: polymethylvinylsiloxane with double bonds in the side chain, silanol-based single-terminated polydimethylsiloxane, silanol-based double-terminated polydimethylsiloxane, nano-silica, and Karstedt catalyst; the amount of nano-silica used is 3-10 wt% of the total mass of the polymethylvinylsiloxane with double bonds in the side chain, silanol-based single-terminated polydimethylsiloxane, and silanol-based double-terminated polydimethylsiloxane; and / or, In the raw materials for preparing the bottle-brush type polydimethylsiloxane film, the molar ratio of vinyl to silane groups is (0.8–1.5):1; and / or, The platinum in the total amount of the Karstedt catalyst is 20 to 500 ppm by mass of polymethylvinylsiloxane with double bonds in the side chain.
3. The bottle-brush type polydimethylsiloxane film according to claim 2, characterized in that, The polymethylvinylsiloxane with double bonds in its side chains has a molecular weight of 5000–80000 g / mol; and / or, The molecular weight of the silanol-based single-terminated polydimethylsiloxane is 1000–8000 g / mol; and / or, The molecular weight of the silanol-based double-terminated polydimethylsiloxane is 3000–30000 g / mol; and / or, The particle size of the nano-silica is 3-50 nm.
4. The method for preparing the bottle-brush type polydimethylsiloxane film according to any one of claims 1-3, characterized in that, Includes the following steps: Polymethylvinylsiloxane with double bonds in the side chain, silane-hydrogen mono-terminated polydimethylsiloxane, and nano-silica are mixed, and then Karstedt catalyst and silane-hydrogen double-terminated polydimethylsiloxane are added and stirred to mix evenly. After degassing, a mixed slurry is obtained. The mixed slurry is coated and heated to 30-150℃ for 1-20 hours to cure, thus obtaining a bottle brush type polydimethylsiloxane film.
5. A thermal interface material, characterized in that, The invention includes a bottle brush type polydimethylsiloxane film as described in any one of claims 1-3, and a copper array vertically oriented on the bottle brush type polydimethylsiloxane film, wherein the diameter of each copper dot in the copper array is 0.2-0.5 mm, and the spacing between two adjacent copper dots is 0.5-1 mm.
6. The method for preparing the thermal interface material according to claim 5, characterized in that, Includes the following steps: Using a carbon dioxide laser, with a laser power of 0.55–11W and a scanning rate of 10–250 mm / s, a bottle brush type polydimethylsiloxane film is laser-drilled to form a vertically oriented array of holes on the bottle brush type polydimethylsiloxane film. The perforated bottle-brush type polydimethylsiloxane film was subjected to plasma cleaning treatment, and then magnetron sputtering was performed to sequentially form a titanium layer and a copper layer on the wall of each hole. Copper was deposited in each hole using a single-pulse deposition method, forming a copper array vertically oriented on a bottle-brush type polydimethylsiloxane film.
7. The method for preparing the thermal interface material according to claim 6, characterized in that, The ratio of the aperture diameter of the hole to the thickness of the bottle brush type polydimethylsiloxane film is 1:(0.3~1.5).
8. The method for preparing the thermal interface material according to claim 6, characterized in that, The thickness of the titanium layer is 50–150 nm, and the thickness of the copper layer is 150–400 nm.
9. The method for preparing the thermal interface material according to claim 6, characterized in that, The pulse current density of the single-pulse deposition method is 0.1–5 mA / mm. 2 The pulse period is 1-3 seconds, and the conduction time T m =0.5s, turn-off time T on =0.5~2.5s, deposition time is 2~5h.
10. The application of the thermal interface material according to any one of claims 5-9 in heat dissipation of electronic devices.