Preparation method of high-thermal-conductivity low-dielectric-constant thermal conductive gasket and product thereof

Abstract

The application relates to the technical field of C09K5 / 08, in particular to a preparation method and product of a high-thermal-conductivity low-dielectric-constant thermal conductive gasket, which comprises the following steps: S1. uniformly stirring thermal conductive fillers and an adhesive to obtain a thixotropic paste, and extruding the thixotropic paste to obtain a sheet; S2. placing the sheet into a muffle furnace to perform high-temperature sintering, so as to obtain a thermal conductive framework; S3. spraying a reinforcing agent on the upper surface of the thermal conductive framework, and then stacking the thermal conductive framework, so as to obtain a multilayer thermal conductive framework; and S4. heating the multilayer thermal conductive framework to obtain a thermal conductive block, and then cutting the thermal conductive block to obtain the high-thermal-conductivity low-dielectric-constant thermal conductive gasket. The preparation method can further improve the thermal conductivity of the thermal conductive gasket, reduce the dielectric constant, and prolong the service life of the thermal conductive gasket.

Description

Technical Field

[0001] This invention relates to the field of C09K5 / 08 technology, specifically to a method for preparing a thermally conductive pad with high thermal conductivity and low dielectric constant, and the product thereof. Background Technology

[0002] Thermal pads are widely used in electronic components. There are two main types of high thermal conductivity materials available on the market: isotropic thermal pads made primarily of aluminum nitride or diamond, achieving a thermal conductivity of 8-15 W / mK; and anisotropic thermal pads made primarily of carbon fiber using directional technology, achieving a thermal conductivity of 15-40 W / mK. While both types of high thermal conductivity materials offer the advantage of high thermal conductivity, they also have corresponding disadvantages. Isotropic thermal pads made primarily of aluminum nitride or diamond have a high dielectric constant, typically greater than 6.0 when the applied current frequency is 1 MHz. Anisotropic thermal pads made primarily of carbon fiber using directional technology have poor electrical properties, with a dielectric strength generally below 1 KV / mm, posing a risk of electrical breakdown to the chip during use.

[0003] Chinese patent application number CN201611090517.X provides a low-density, high-strength thermally conductive silicone pad, which uses thermally conductive powder and organosilicon polymer, but does not effectively improve the thermal conductivity of the pad.

[0004] Therefore, providing a thermally conductive pad with high thermal conductivity and low dielectric constant is the main technical problem that needs to be solved. Summary of the Invention

[0005] To address the above problems, the first aspect of this invention provides a method for preparing a thermally conductive pad with high thermal conductivity and low dielectric constant, comprising the following steps:

[0006] S1. Stir the thermally conductive filler and adhesive evenly to obtain a thixotropic paste, and then extrude it to obtain a sheet;

[0007] S2. Place the sheet material into a muffle furnace for high-temperature sintering to obtain a heat-conducting skeleton;

[0008] S3. After spraying a reinforcing agent onto the upper surface of the thermal conductive skeleton, the thermal conductive skeleton is then stacked to obtain a multi-layer thermal conductive skeleton.

[0009] S4. After heating the multi-layer thermally conductive skeleton, a thermally conductive block is obtained. After slitting, a thermally conductive pad with high thermal conductivity and low dielectric constant is obtained.

[0010] Preferably, the particle size of the thermally conductive filler in S1 is 0.5-200 μm.

[0011] Preferably, the thermally conductive filler in S1 is selected from one or more of boron nitride, silicon dioxide, and aluminum oxide.

[0012] Furthermore, the thermally conductive filler in S1 includes boron nitride, silicon dioxide, and aluminum oxide.

[0013] Preferably, the mass ratio of boron nitride, silicon dioxide, and aluminum oxide is (5-10):(2-4):1.

[0014] Furthermore, the mass ratio of boron nitride, silicon dioxide, and aluminum oxide is (6-9):(2-4):1.

[0015] Furthermore, the boron nitride in S1 is plate-shaped hexagonal boron nitride with a particle size of 10-200 μm.

[0016] Furthermore, the boron nitride in S1 is plate-shaped hexagonal boron nitride with a particle size of 80-200 μm.

[0017] Furthermore, the particle size of the silica in S1 is 0.2-120 μm.

[0018] Furthermore, the alumina in S1 has an α-alumina crystal form and a particle size of 0.2-120 μm.

[0019] Preferably, the thickness of the sheet in S1 is less than 1 mm.

[0020] Preferably, the width of the sheet in S1 is 80-120mm and the length is 350-450mm.

[0021] Furthermore, the sheet in S1 has a width of 100mm and a length of 400mm.

[0022] Preferably, the viscosity of the adhesive in S1 at 25°C is 500-2000 mPa·s.

[0023] Preferably, the adhesive in S1 is selected from one of polybutene, polyacrylic acid, and polyurethane.

[0024] Preferably, the polybutene is polybutadiene.

[0025] Preferably, the adhesive further comprises a coupling agent.

[0026] Preferably, the adhesive in S1 comprises 90-95% polybutadiene and 5-10% coupling agent by mass percentage.

[0027] Furthermore, the amount of adhesive used in S1 accounts for 10-30% of the total mass of the thermally conductive filler and adhesive.

[0028] Furthermore, the amount of thermally conductive filler in S1 accounts for 70-90% of the total mass of thermally conductive filler and adhesive.

[0029] The coupling agent is selected from one or more of 3-aminopropyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, aluminate, and phthalate.

[0030] Preferably, the coupling agent is γ-methacryloyloxypropyltrimethoxysilane.

[0031] Preferably, the CAS number of the γ-methacryloyloxypropyltrimethoxysilane is 2530-85-0.

[0032] To improve the thixotropic properties of the resulting paste and facilitate its processing into sheets, the inventors creatively discovered during experiments that a thixotropic paste could be obtained by mixing a binder with a viscosity of 500-2000 mPa·s, particularly polybutadiene with a viscosity of 500-2000 mPa·s, with boron nitride, silica, and alumina of specific particle sizes. When the viscosity of the binder is too low, the polybutadiene molecular chains are short, and the gaps between the molecular chains are relatively large. While this can encapsulate boron nitride, silica, and alumina, it cannot form a thixotropic paste after mixing. When the viscosity of the binder is too high, the polybutadiene molecular chains are long, and the molecular chains entangle with each other, failing to effectively and uniformly disperse the sheet-like boron nitride, silica, and alumina, thus preventing the formation of a thixotropic paste.

[0033] Preferably, after obtaining the sheet in step S1, the sheet is placed on a heat-resistant cast iron plate with thermally conductive powder on its surface.

[0034] Preferably, after obtaining the sheet in step S1, the sheet is placed on a heat-resistant cast iron plate with a layer of thermally conductive powder on its surface.

[0035] Preferably, the thermally conductive powder is selected from one or more of boron nitride, aluminum oxide, and silicon dioxide.

[0036] Preferably, the thermally conductive powder is boron nitride.

[0037] Preferably, the boron nitride has a particle size of 0.5-10 μm.

[0038] Furthermore, the boron nitride has a particle size of 0.5-5 μm.

[0039] Preferably, in step S2, the heat-resistant cast iron plate and sheet are transferred to a muffle furnace for high-temperature sintering to obtain a heat-conducting skeleton.

[0040] Preferably, the temperature for high-temperature sintering in the muffle furnace is 600-1000℃.

[0041] To obtain a complete thermally conductive skeleton and achieve easy separation between the thermally conductive skeleton and the heat-resistant cast iron plate, the inventors creatively discovered in experiments that placing the sheet material onto a heat-resistant cast iron plate with a layer of thermally conductive powder on its surface, specifically using boron nitride with a specific particle size as the thermally conductive powder to isolate the sheet material and the heat-resistant cast iron plate, and then transferring the heat-resistant cast iron plate and sheet material to a muffle furnace for high-temperature sintering to obtain a complete thermally conductive skeleton, can achieve easy separation between the thermally conductive skeleton and the heat-resistant cast iron plate. The possible reason is that the binder is sintered away during the high-temperature sintering process, resulting in a skeleton formed by thermally conductive filler, and the thermally conductive powder can conduct heat during the high-temperature sintering process and will not be sintered away.

[0042] Preferably, the thickness of the reinforcing agent sprayed on the upper surface of the thermally conductive skeleton in S3 is 80-120 μm.

[0043] Preferably, in step S3, after the thermally conductive skeleton is placed into the container, a reinforcing agent is sprayed onto the upper surface of the thermally conductive skeleton to obtain a multi-layer thermally conductive skeleton, and the container maintains a vacuum degree of 0.01-0.5 MPa.

[0044] Preferably, the uppermost layer of the multilayer thermally conductive skeleton in S3 is subjected to a pressure of 0.1-1 MPa and held at that pressure for 20-50 minutes.

[0045] Preferably, the reinforcing agent is a polysiloxane.

[0046] Furthermore, the viscosity of the polysiloxane at 25°C is 20-100 mPa·s.

[0047] Furthermore, the raw materials for preparing the polysiloxane, by mass percentage, include 50-60% vinyl silicone oil, 15-20% end-hydrogen silicone oil, and 15-25% side-hydrogen silicone oil.

[0048] The method for preparing the polysiloxane includes the following steps: mixing vinyl silicone oil, end-hydrogen silicone oil, and side-hydrogen silicone oil to obtain polysiloxane.

[0049] Furthermore, the raw material for preparing the polysiloxane is a combination of vinyl silicone oil and hydrogen-terminated silicone oil.

[0050] Furthermore, the hydrogen-containing silicone oil was purchased from Shandong Dayi Chemical Co., Ltd., and its viscosity at 25°C was 60 mPa·s.

[0051] Furthermore, the vinyl silicone oil is an end-vinyl silicone oil, which is purchased from Shanghai Jingri New Material Technology Co., Ltd., and has a viscosity of 60 mPa·s at 25°C.

[0052] Furthermore, the hydrogen content in the side-containing silicone oil is 0.8% by mass, the viscosity at 25°C is 60 mPa·s, and the manufacturer is Shin-Etsu Silicone International Trading (Shanghai) Co., Ltd.

[0053] In order to enable the reinforcing agent to impregnate and fill the gaps in the thermally conductive skeleton and improve the toughness of the thermally conductive pad, the inventors creatively discovered in experiments that by placing the thermally conductive skeleton in a container and then spraying the reinforcing agent on the upper surface of the thermally conductive skeleton to obtain a multi-layer thermally conductive skeleton, and then maintaining the container at a vacuum degree of 0.01-0.5MPa, and applying a pressure of 0.1-1MPa to the top layer of the multi-layer thermally conductive skeleton for 20-50 minutes, the wetting speed of polysiloxane in the thermally conductive skeleton can be increased, ensuring that the polysiloxane can impregnate and fill the gaps in the thermally conductive skeleton and improve the toughness of the thermally conductive pad.

[0054] Preferably, in step S4, the multi-layer thermally conductive skeleton is placed in an oven at 105-130°C and heated for 20-40 minutes to obtain the thermally conductive block.

[0055] To further improve the thermal conductivity, reduce the dielectric constant, and extend the service life of thermal pads, the inventors creatively discovered in experiments that by vacuum pressurizing a multi-layer thermally conductive skeleton and then heating it in an oven at 105-130℃ for 20-40 minutes, a thermally conductive pad with high thermal conductivity and low dielectric constant can be obtained. The likely reason is that vacuum pressurizing followed by heating allows the polysiloxane to form a three-dimensional network structure with the multi-layer thermally conductive skeleton, improving the toughness of the thermal pad and preventing breakage under external impact and compression. This also results in high thermal conductivity, low dielectric constant, and low dielectric strength.

[0056] A second aspect of the present invention provides a thermally conductive pad with high thermal conductivity and low dielectric constant, which is prepared according to the above-described preparation method.

[0057] Beneficial effects

[0058] 1. The preparation method provided by this invention can improve the thixotropic properties of the obtained paste, which is beneficial for molding into sheets.

[0059] 2. The preparation method provided by this invention can obtain a complete heat-conducting skeleton and make it easy to separate the heat-conducting skeleton from the heat-resistant cast iron plate.

[0060] 3. The preparation method provided by the present invention enables the reinforcing agent to impregnate and fill the gaps in the thermally conductive skeleton, thereby improving the toughness of the thermally conductive pad.

[0061] 4. The preparation method provided by this invention can further improve the thermal conductivity of the thermal pad, reduce the dielectric constant, and increase the service life of the thermal pad. Detailed Implementation

[0062] Example 1

[0063] The first aspect of this embodiment provides a method for preparing a thermally conductive pad with high thermal conductivity and low dielectric constant, comprising the following steps:

[0064] S1. Stir the thermally conductive filler and adhesive evenly to obtain a thixotropic paste, and then extrude it to obtain a sheet;

[0065] S2. Place the sheet onto a heat-resistant cast iron plate with a layer of thermally conductive powder on its surface;

[0066] S3. Transfer the heat-resistant cast iron plate and sheet to a muffle furnace for high-temperature sintering to obtain a heat-conducting skeleton;

[0067] S4. Place the thermally conductive skeleton in a container, spray a reinforcing agent on the upper surface of the thermally conductive skeleton, and then stack the thermally conductive skeleton to obtain a multi-layer thermally conductive skeleton.

[0068] S5. After heating the multi-layer thermally conductive skeleton, a thermally conductive block is obtained. After slitting, a thermally conductive pad with high thermal conductivity and low dielectric constant is obtained.

[0069] The amount of adhesive used in S1 accounts for 20% of the total mass of the thermally conductive filler and adhesive.

[0070] The thermally conductive filler in S1 accounts for 80% of the total mass of the thermally conductive filler and adhesive.

[0071] The thermally conductive filler in S1 comprises boron nitride, silicon dioxide, and aluminum oxide, and the mass ratio of boron nitride, silicon dioxide, and aluminum oxide is 8:3:1.

[0072] The boron nitride in S1 is plate-shaped hexagonal boron nitride with a particle size of 150 μm.

[0073] The silica in S1 has a particle size of 20 μm.

[0074] The alumina has an α-alumina crystal form and a particle size of 1 μm.

[0075] The thickness of the sheet in S1 is 0.8 mm.

[0076] The sheet in S1 has a width of 100mm and a length of 400mm.

[0077] The adhesive in S1 has a viscosity of 1000 mPa·s at 25°C.

[0078] The adhesive in S1 comprises, by weight percentage, 95% polybutadiene and 5% coupling agent.

[0079] The coupling agent is γ-methacryloyloxypropyltrimethoxysilane.

[0080] The CAS number of the γ-methacryloyloxypropyltrimethoxysilane is 2530-85-0.

[0081] The thermally conductive powder in S2 is boron nitride.

[0082] The boron nitride in S2 has a particle size of 3 μm.

[0083] The temperature for high-temperature sintering in the muffle furnace is 800°C.

[0084] The thickness of the reinforcing agent sprayed on the upper surface of the thermally conductive skeleton in S4 is 100 μm.

[0085] After obtaining the multi-layer thermally conductive skeleton in S4, the container maintains a vacuum of 0.1 MPa.

[0086] The top layer of the multi-layer thermally conductive skeleton in S4 is subjected to a pressure of 0.3 MPa and held at that pressure for 30 minutes.

[0087] The reinforcing agent is polysiloxane.

[0088] The raw materials for preparing the polysiloxane, by mass percentage, include 55% vinyl silicone oil, 20% end-hydrogen silicone oil, and 25% side-hydrogen silicone oil.

[0089] The method for preparing the polysiloxane includes the following steps: mixing vinyl silicone oil, end-hydrogen silicone oil, and side-hydrogen silicone oil to obtain polysiloxane.

[0090] In step S5, the multi-layer thermally conductive skeleton is placed in an oven at 120°C and heated for 30 minutes to obtain a thermally conductive block.

[0091] The hydrogen-containing silicone oil was purchased from Shandong Dayi Chemical Co., Ltd., and its viscosity at 25°C was 60 mPa·s.

[0092] The vinyl silicone oil is an end-vinyl silicone oil, which was purchased from Shanghai Jingri New Material Technology Co., Ltd., and has a viscosity of 60 mPa·s at 25°C.

[0093] The hydrogen-containing silicone oil has a hydrogen content of 0.8% by mass and a viscosity of 60 mPa·s at 25°C. It was purchased from Shin-Etsu Silicone International Trading (Shanghai) Co., Ltd.

[0094] The second aspect of this embodiment provides a thermally conductive pad with high thermal conductivity and low dielectric constant, which is prepared according to the above-described preparation method.

[0095] Example 2

[0096] The first aspect of this embodiment provides a method for preparing a thermally conductive pad with high thermal conductivity and low dielectric constant, comprising the following steps:

[0097] S1. Stir the thermally conductive filler and adhesive evenly to obtain a thixotropic paste, and then extrude it to obtain a sheet;

[0098] S2. Place the sheet onto a heat-resistant cast iron plate with a layer of thermally conductive powder on its surface.

[0099] S3. Transfer the heat-resistant cast iron plate and sheet to a muffle furnace for high-temperature sintering to obtain a heat-conducting skeleton;

[0100] S4. Place the thermally conductive skeleton in a container, spray a reinforcing agent on the upper surface of the thermally conductive skeleton, and then stack the thermally conductive skeleton to obtain a multi-layer thermally conductive skeleton.

[0101] S5. After heating the multi-layer thermally conductive skeleton, a thermally conductive block is obtained. After slitting, a thermally conductive pad with high thermal conductivity and low dielectric constant is obtained.

[0102] The amount of adhesive used in S1 accounts for 20% of the total mass of the thermally conductive filler and adhesive.

[0103] The thermally conductive filler in S1 accounts for 80% of the total mass of the thermally conductive filler and adhesive.

[0104] The thermally conductive filler in S1 comprises boron nitride, silicon dioxide, and aluminum oxide, and the mass ratio of boron nitride, silicon dioxide, and aluminum oxide is 6:2:1.

[0105] The boron nitride in S1 is plate-shaped hexagonal boron nitride with a particle size of 200 μm.

[0106] The silica in S1 has a particle size of 15 μm.

[0107] The alumina has an α-alumina crystal form and a particle size of 1 μm.

[0108] The thickness of the sheet in S1 is 0.9 mm.

[0109] The sheet in S1 has a width of 100mm and a length of 400mm.

[0110] The adhesive in S1 has a viscosity of 2000 mPa·s at 25°C.

[0111] The adhesive in S1 comprises, by weight percentage, 95% polybutadiene and 5% coupling agent.

[0112] The coupling agent is γ-methacryloyloxypropyltrimethoxysilane.

[0113] The CAS number of the γ-methacryloyloxypropyltrimethoxysilane is 2530-85-0.

[0114] The thermally conductive powder in S2 is boron nitride.

[0115] The boron nitride in S2 has a particle size of 2 μm.

[0116] The temperature for high-temperature sintering in the muffle furnace is 900℃.

[0117] The thickness of the reinforcing agent sprayed on the upper surface of the thermally conductive skeleton in S4 is 120 μm.

[0118] After obtaining the multi-layer thermally conductive skeleton in S4, the container maintains a vacuum of 0.3 MPa.

[0119] The top layer of the multi-layer thermally conductive skeleton in S4 is subjected to a pressure of 0.5 MPa and held at that pressure for 30 minutes.

[0120] The reinforcing agent is polysiloxane.

[0121] The raw materials for preparing the polysiloxane, by mass percentage, include 55% vinyl silicone oil, 20% end-hydrogen silicone oil, and 25% side-hydrogen silicone oil.

[0122] The method for preparing the polysiloxane includes the following steps: mixing vinyl silicone oil, end-hydrogen silicone oil, and side-hydrogen silicone oil to obtain polysiloxane.

[0123] In step S4, the multi-layer thermally conductive skeleton is placed in an oven at 130°C and heated for 20 minutes to obtain a thermally conductive block.

[0124] The hydrogen-containing silicone oil was purchased from Shandong Dayi Chemical Co., Ltd., and its viscosity at 25°C was 60 mPa·s.

[0125] The vinyl silicone oil is an end-vinyl silicone oil, which was purchased from Shanghai Jingri New Material Technology Co., Ltd., and has a viscosity of 60 mPa·s at 25°C.

[0126] The hydrogen-containing silicone oil has a hydrogen content of 0.8% by mass and a viscosity of 60 mPa·s at 25°C. It was purchased from Shin-Etsu Silicone International Trading (Shanghai) Co., Ltd.

[0127] The second aspect of this embodiment provides a thermally conductive pad with high thermal conductivity and low dielectric constant, which is prepared according to the above-described preparation method.

[0128] Example 3

[0129] The first aspect of this embodiment provides a method for preparing a thermally conductive pad with high thermal conductivity and low dielectric constant, comprising the following steps:

[0130] S1. Stir the thermally conductive filler and adhesive evenly to obtain a thixotropic paste, and then extrude it to obtain a sheet;

[0131] S2. Place the sheet onto a heat-resistant cast iron plate with a layer of thermally conductive powder on its surface;

[0132] S3. Transfer the heat-resistant cast iron plate and sheet to a muffle furnace for high-temperature sintering to obtain a heat-conducting skeleton;

[0133] S4. Place the thermally conductive skeleton in a container, spray a reinforcing agent on the upper surface of the thermally conductive skeleton, and then stack the thermally conductive skeleton to obtain a multi-layer thermally conductive skeleton.

[0134] S5. After heating the multi-layer thermally conductive skeleton, a thermally conductive block is obtained. After slitting, a thermally conductive pad with high thermal conductivity and low dielectric constant is obtained.

[0135] The amount of adhesive used in S1 accounts for 20% of the total mass of the thermally conductive filler and adhesive.

[0136] The thermally conductive filler in S1 accounts for 80% of the total mass of the thermally conductive filler and adhesive.

[0137] The thermally conductive filler in S1 comprises boron nitride, silicon dioxide, and aluminum oxide, and the mass ratio of boron nitride, silicon dioxide, and aluminum oxide is 9:4:1.

[0138] The boron nitride in S1 is plate-shaped hexagonal boron nitride with a particle size of 100 μm.

[0139] The silica in S1 has a particle size of 10 μm.

[0140] The alumina has an α-alumina crystal form and a particle size of 0.5 μm.

[0141] The thickness of the sheet in S1 is 0.7 mm.

[0142] The sheet in S1 has a width of 100mm and a length of 400mm.

[0143] The adhesive in S1 has a viscosity of 500 mPa·s at 25°C.

[0144] The adhesive in S1 comprises, by weight percentage, 95% polybutadiene and 5% coupling agent.

[0145] The coupling agent is γ-methacryloyloxypropyltrimethoxysilane.

[0146] The CAS number of the γ-methacryloyloxypropyltrimethoxysilane is 2530-85-0.

[0147] The thermally conductive powder in S2 is boron nitride.

[0148] The boron nitride in S2 has a particle size of 3 μm.

[0149] The temperature for high-temperature sintering in the muffle furnace is 650°C.

[0150] The thickness of the reinforcing agent sprayed on the upper surface of the thermally conductive skeleton in S4 is 80 μm.

[0151] After obtaining the multi-layer thermally conductive skeleton in S4, the container maintains a vacuum of 0.1 MPa.

[0152] The top layer of the multi-layer thermally conductive skeleton in S4 is subjected to a pressure of 0.3 MPa and held at that pressure for 30 minutes.

[0153] The reinforcing agent is polysiloxane.

[0154] The raw materials for preparing the polysiloxane, by mass percentage, include 55% vinyl silicone oil, 20% end-hydrogen silicone oil, and 25% side-hydrogen silicone oil.

[0155] The method for preparing the polysiloxane includes the following steps: mixing vinyl silicone oil, end-hydrogen silicone oil, and side-hydrogen silicone oil to obtain polysiloxane.

[0156] In step S4, the multi-layer thermally conductive skeleton is placed in an oven at 120°C and heated for 30 minutes to obtain a thermally conductive block.

[0157] The hydrogen-containing silicone oil was purchased from Shandong Dayi Chemical Co., Ltd., and its viscosity at 25°C was 60 mPa·s.

[0158] The vinyl silicone oil is an end-vinyl silicone oil, which was purchased from Shanghai Jingri New Material Technology Co., Ltd., and has a viscosity of 60 mPa·s at 25°C.

[0159] The hydrogen-containing silicone oil has a hydrogen content of 0.8% by mass and a viscosity of 60 mPa·s at 25°C. It was purchased from Shin-Etsu Silicone International Trading (Shanghai) Co., Ltd.

[0160] The second aspect of this embodiment provides a thermally conductive pad with high thermal conductivity and low dielectric constant, which is prepared according to the above-described preparation method.

[0161] Example 4

[0162] The first aspect of this embodiment provides a method for preparing a thermally conductive pad with high thermal conductivity and low dielectric constant, comprising the following steps:

[0163] S1. Stir the thermally conductive filler and adhesive evenly to obtain a thixotropic paste, and then extrude it to obtain a sheet;

[0164] S2. Place the sheet onto a heat-resistant cast iron plate with a layer of thermally conductive powder on its surface;

[0165] S3. Transfer the heat-resistant cast iron plate and sheet to a muffle furnace for high-temperature sintering to obtain a heat-conducting skeleton;

[0166] S4. Place the thermally conductive skeleton in a container, spray a reinforcing agent on the upper surface of the thermally conductive skeleton, and then stack the thermally conductive skeleton to obtain a multi-layer thermally conductive skeleton.

[0167] S5. After heating the multi-layer thermally conductive skeleton, a thermally conductive block is obtained. After slitting, a thermally conductive pad with high thermal conductivity and low dielectric constant is obtained.

[0168] The amount of adhesive used in S1 accounts for 20% of the total mass of the thermally conductive filler and adhesive.

[0169] The thermally conductive filler in S1 accounts for 80% of the total mass of the thermally conductive filler and adhesive.

[0170] The thermally conductive filler in S1 comprises boron nitride, silicon dioxide, and aluminum oxide, and the mass ratio of boron nitride, silicon dioxide, and aluminum oxide is 8:3:1.

[0171] The boron nitride in S1 is plate-shaped hexagonal boron nitride with a particle size of 150 μm.

[0172] The silica in S1 has a particle size of 20 μm.

[0173] The alumina has an α-alumina crystal form and a particle size of 1 μm.

[0174] The thickness of the sheet in S1 is 0.8 mm.

[0175] The sheet in S1 has a width of 100mm and a length of 400mm.

[0176] The adhesive in S1 has a viscosity of 1000 mPa·s at 25°C.

[0177] The adhesive in S1 comprises, by weight percentage, 95% polybutadiene and 5% coupling agent.

[0178] The coupling agent is γ-methacryloyloxypropyltrimethoxysilane.

[0179] The CAS number of the γ-methacryloyloxypropyltrimethoxysilane is 2530-85-0.

[0180] The thermally conductive powder in S2 is boron nitride.

[0181] The boron nitride in S2 has a particle size of 3 μm.

[0182] The temperature for high-temperature sintering in the muffle furnace is 800°C.

[0183] The thickness of the reinforcing agent sprayed on the upper surface of the thermally conductive skeleton in S4 is 100 μm.

[0184] The reinforcing agent is polysiloxane.

[0185] The raw materials for preparing the polysiloxane, by mass percentage, include 75% vinyl silicone oil, 10% end-hydrogen silicone oil, and 15% side-hydrogen silicone oil.

[0186] The method for preparing the polysiloxane includes the following steps: mixing vinyl silicone oil, end-hydrogen silicone oil, and side-hydrogen silicone oil to obtain polysiloxane.

[0187] In step S5, the multi-layer thermally conductive skeleton is placed in an oven at 120°C and heated for 30 minutes to obtain a thermally conductive block.

[0188] The hydrogen-containing silicone oil was purchased from Shandong Dayi Chemical Co., Ltd., and its viscosity at 25°C was 60 mPa·s.

[0189] The vinyl silicone oil is an end-vinyl silicone oil, which was purchased from Shanghai Jingri New Material Technology Co., Ltd., and has a viscosity of 60 mPa·s at 25°C.

[0190] The hydrogen-containing silicone oil has a hydrogen content of 0.8% by mass and a viscosity of 60 mPa·s at 25°C. It was purchased from Shin-Etsu Silicone International Trading (Shanghai) Co., Ltd.

[0191] The second aspect of this embodiment provides a thermally conductive pad with high thermal conductivity and low dielectric constant, which is prepared according to the above-described preparation method.

[0192] Example 5

[0193] The first aspect of this embodiment provides a method for preparing a thermally conductive pad with high thermal conductivity and low dielectric constant, comprising the following steps:

[0194] S1. Stir the thermally conductive filler and reinforcing agent evenly to obtain a paste, and then extrude it in one step to obtain a sheet;

[0195] S2. After heating the profile in an oven at 120°C for 30 minutes, a thermally conductive block is obtained. After slitting, a thermally conductive pad with high thermal conductivity and low dielectric constant is obtained.

[0196] The thermally conductive filler in S1 comprises boron nitride, silicon dioxide, and aluminum oxide, and the mass ratio of boron nitride, silicon dioxide, and aluminum oxide is 8:3:1.

[0197] The boron nitride in S1 is plate-shaped hexagonal boron nitride with a particle size of 150 μm.

[0198] The silica in S1 has a particle size of 20 μm.

[0199] The alumina has an α-alumina crystal form and a particle size of 1 μm.

[0200] The thickness of the sheet in S1 is 0.8 mm.

[0201] The sheet in S1 has a width of 100mm and a length of 400mm.

[0202] The reinforcing agent is polysiloxane.

[0203] The raw materials for preparing the polysiloxane, by mass percentage, include 75% vinyl silicone oil, 10% end-hydrogen silicone oil, and 15% side-hydrogen silicone oil.

[0204] The method for preparing the polysiloxane includes the following steps: mixing vinyl silicone oil, end-hydrogen silicone oil, and side-hydrogen silicone oil to obtain polysiloxane.

[0205] The hydrogen-containing silicone oil was purchased from Shandong Dayi Chemical Co., Ltd., and its viscosity at 25°C was 60 mPa·s.

[0206] The vinyl silicone oil is an end-vinyl silicone oil, which was purchased from Shanghai Jingri New Material Technology Co., Ltd., and has a viscosity of 60 mPa·s at 25°C.

[0207] The hydrogen-containing silicone oil has a hydrogen content of 0.8% by mass and a viscosity of 60 mPa·s at 25°C. It was purchased from Shin-Etsu Silicone International Trading (Shanghai) Co., Ltd.

[0208] The second aspect of this embodiment provides a thermally conductive pad with high thermal conductivity and low dielectric constant, which is prepared according to the above-described preparation method.

[0209] Performance testing

[0210] The thermally conductive blocks prepared in Examples 1-5 were cut into thermally conductive pads with a thickness of 1 mm, a width of 90 mm, and a length of 100 mm. The thermally conductive pads obtained in Example 5 were also cut into thermally conductive pads with a thickness of 1 mm, a width of 90 mm, and a length of 100 mm. Ten thermally conductive pads obtained in Examples 1-5 were taken and tested using a thermal conductivity tester and a dielectric constant tester along the length direction. The maximum and minimum values ​​of the thermal conductivity, dielectric constant, and dielectric strength were removed, and the average value was recorded. The test results are shown in Table 1.

[0211] Table 1

[0212] Example Thermal conductivity (W / mK) Dielectric constant Dielectric strength (kV / mm) Example 1 11.1 2.0 5.8 Example 2 9.8 2.2 5.2 Example 3 9.7 2.4 4.7 Example 4 4.6 1.9 4.0 Example 5 2.6 2.0 5.5

Claims

1. A method for preparing a thermally conductive pad with high thermal conductivity and low dielectric constant, characterized in that, Includes the following steps: S1. Stir the thermally conductive filler and adhesive evenly to obtain a thixotropic paste, and then extrude it to obtain a sheet. Place the sheet on a heat-resistant cast iron plate with thermally conductive powder on its surface. S2. Transfer the heat-resistant cast iron plate and sheet to a muffle furnace for high-temperature sintering to obtain a heat-conducting skeleton; S3. After spraying a reinforcing agent onto the upper surface of the thermal conductive skeleton, the thermal conductive skeleton is then stacked to obtain a multi-layer thermal conductive skeleton. S4. After heating the multi-layer thermally conductive skeleton, a thermally conductive block is obtained. After being cut, a thermally conductive pad with high thermal conductivity and low dielectric constant is obtained. The particle size of the thermally conductive filler in S1 is 0.5-200 μm; The thermally conductive filler comprises boron nitride, silicon dioxide, and aluminum oxide; the mass ratio of boron nitride, silicon dioxide, and aluminum oxide is (5-10):(2-4):1; The reinforcing agent is polysiloxane.

2. The method for preparing the high thermal conductivity and low dielectric constant thermal pad as described in claim 1, characterized in that, The adhesive in S1 has a viscosity of 500-2000 mPa·s at 25°C.

3. The method for preparing a high thermal conductivity, low dielectric constant thermally conductive pad as described in any one of claims 1-2, characterized in that, The thickness of the reinforcing agent sprayed on the upper surface of the thermally conductive skeleton in S3 is 80-120 μm.

4. The method for preparing the high thermal conductivity and low dielectric constant thermal pad as described in claim 1, characterized in that, In step S3, after the thermally conductive skeleton is placed in the container, a reinforcing agent is sprayed onto the upper surface of the thermally conductive skeleton to obtain a multi-layer thermally conductive skeleton. The container is then kept at a vacuum level of 0.01-0.5 MPa.

5. The method for preparing the high thermal conductivity and low dielectric constant thermal pad as described in claim 4, characterized in that, The uppermost layer of the multi-layer thermally conductive skeleton in S3 is subjected to a pressure of 0.1-1 MPa.

6. A thermally conductive pad with high thermal conductivity and low dielectric constant, characterized in that, The high thermal conductivity and low dielectric constant thermal pad is prepared using the preparation method of any one of claims 1-5.