A thermally conductive insulating sheet and a method for preparing the same

Abstract

The present application relates to the field of thermally conductive insulating materials, and discloses a thermally conductive insulating sheet and a preparation method thereof. A thermally conductive insulating sheet comprises an insulating layer and a thermally conductive layer, wherein the insulating layer is a polyimide film, and the thermally conductive layer is cured by curing a thermally conductive adhesive made from the following raw materials in parts by weight: 10-20 parts of methylphenyl vinyl silicone rubber, 40-50 parts of vinyl silicone oil, 15-20 parts of methyl hydrogenated silicone oil, 35-45 parts of thermally conductive filler, 4-8 parts of tackifier, 1-2 parts of dimethyl silicone oil and 0.5-1 parts of catalyst; the thermally conductive filler is made of aluminum oxide, boron nitride, a coupling agent and a cross-linking agent; the cross-linking agent is composed of pentaerythritol triallyl ether, trimethylallyl isocyanate and tetramethyl divinyl disilazane; the preparation method is as follows: the raw materials are evenly mixed, the thermally conductive adhesive is prepared and coated on the surface of the insulating layer, and vulcanized. The preparation process of the present application is simple, and the thermally conductive insulating sheet prepared has good thermal conductivity and insulation, good lamination stability, and no damage or residual adhesive when torn off.

Description

Technical Field

[0001] The present application relates to the field of thermally conductive insulating materials, and more specifically, to a thermally conductive insulating sheet and a preparation method thereof. Background Art

[0002] Thermally conductive insulation sheet is a material with dual functions of thermal conductivity and insulation. It can effectively conduct heat and prevent current leakage. It can work stably in high temperature environment and has certain flexibility and durability. It is usually used in new energy vehicle battery heat dissipation, electronic equipment or household radiators such as PTC water heaters and so on.

[0003] Conventional thermally conductive insulating sheets generally use polyimide film as a substrate, and a thermally conductive material is coated or cast on the polyimide film. The thermally conductive material is generally composed of silicone, thermally conductive fillers and other additives, and has a certain self-adhesiveness, which is suitable for product assembly; however, the adhesion of the thermally conductive insulating sheet is relatively low. In order to improve the assembly stability, additional adhesive backing is required. However, the adhesive backing easily reduces the thermal conductivity of the thermally conductive insulating sheet. After adding the adhesive backing, it is difficult to tear off during later maintenance or when the accessories need to be recycled. Therefore, the performance of the thermally conductive insulating sheet is reduced. Summary of the invention

[0004] In order to solve the problem that conventional thermally conductive insulating sheets cannot have both adhesiveness, thermal conductivity and insulation properties, the present application provides a thermally conductive insulating sheet and a preparation method thereof.

[0005] In a first aspect, the present application provides a thermally conductive insulating sheet, which adopts the following technical solution:

[0006] A heat-conducting insulating sheet comprises an insulating layer and a heat-conducting layer, wherein the insulating layer is a polyimide film, and the heat-conducting layer is prepared by curing a heat-conducting adhesive, wherein the heat-conducting adhesive is prepared from the following raw materials in parts by weight:

[0007] Methylphenyl vinyl silicone rubber 10-20 parts

[0008] 40-50 parts of vinyl silicone oil

[0009] 15-20 parts of methyl hydrogen silicone oil

[0010] Thermally conductive filler 35-45 parts

[0011] 4-8 parts of tackifier

[0012] 1-2 parts dimethyl silicone oil

[0013] Catalyst 0.5-1 part;

[0014] The thermal conductive filler is made of aluminum oxide, boron nitride, a coupling agent and a cross-linking agent;

[0015] The crosslinking agent consists of pentaerythritol triallyl ether, trimethylallyl isocyanate and tetramethyldivinyldisilazane.

[0016] By adopting the above technical scheme, a polyimide film is used as an insulating layer, which has good insulation and mechanical property reinforcement effects. A thermal conductive adhesive is coated on the polyimide film. The thermal conductive adhesive of the present application uses a compound of methylphenyl vinyl silicone rubber and vinyl silicone oil as the main body of vinyl silicone. Under the action of a catalyst, a hydrosilylation reaction is carried out with hydrogen-containing silicone oil. Methylphenyl vinyl silicone rubber introduces phenyl groups in the side chain, and compounding with vinyl silicone oil can better improve the thermal properties of the thermal conductive adhesive. The thermal conductive filler can be dispersed in the silicone system to improve the thermal conductivity and mechanical properties of the thermal conductive adhesive. The present application uses aluminum oxide, boron nitride, a coupling agent and a cross-linking agent to prepare the thermal conductive filler. The aluminum oxide and boron nitride are subjected to a coupling agent and a cross-linking agent. Modification is carried out by using pentaerythritol triallyl ether, trimethylallyl isocyanate and tetramethyl divinyl disilazane as a crosslinking agent, which can produce a good synergistic effect with the coupling agent, improve the dispersion uniformity of aluminum oxide and boron nitride, and further crosslink with the silicone system, thereby improving the thermal conductivity and insulation of the thermally conductive insulating sheet. Dimethyl silicone oil can improve the viscosity and surface tension of the silicone system, thereby improving the processing stability of the silicone system. The thermally conductive insulating sheet prepared in this way has good bonding stability and thermal conductivity, and can maintain good insulation under high voltage. It is used in product assembly and has good bonding stability, heat dissipation and insulation, and there is no damage or residual glue when it is torn off. It can be used in new energy vehicle batteries, electronic equipment or household radiators such as PTC water heaters, etc.

[0017] Preferably, the weight ratio of the pentaerythritol triallyl ether, the trimethylallyl isocyanate and the tetramethyldivinyldisilazane is (1-2):(0.5-1):1.

[0018] By adopting the above technical scheme, pentaerythritol triallyl ether, trimethylallyl isocyanate and tetramethyldivinyldisilazane in an optimal dosage ratio are used as cross-linking agents. The three have a good synergistic effect and can be cross-linked with hydrogen-containing silicone oil to give the silicone system soft segments and a three-dimensional network interwoven structure, thereby making aluminum oxide and boron nitride evenly dispersed in the interwoven structure, thereby improving the thermal conductivity of the obtained thermally conductive insulating sheet, and being able to maintain good insulation under high voltage. At the same time, the interwoven structure gives the thermally conductive adhesive stable cohesion and adhesion. While the fitting is stable, it is not easy to be damaged when torn off and it is not easy to have residual adhesive.

[0019] Preferably, the coupling agent is composed of polydimethyldiallylammonium chloride and γ-aminopropyltriethoxysilane in a weight ratio of 1:(1-3).

[0020] By adopting the above technical scheme, polydimethyldiallylammonium chloride is a cationic polymer with strong adsorption, which can form an adsorption film on the surface of alumina and boron nitride, and has a synergistic effect on the modification of alumina and boron nitride. It can cooperate with γ-aminopropyltriethoxysilane to further improve the compatibility and dispersion uniformity of the cross-linking agent with alumina and boron nitride, thereby improving the thermal conductivity of the prepared thermal conductive adhesive, maintaining good insulation under high voltage, and improving the bonding stability.

[0021] Preferably, the thermally conductive filler is made from the following raw materials in parts by weight:

[0022] Alumina 50-60 parts

[0023] Boron nitride 20-30 parts

[0024] 4-6 parts of coupling agent

[0025] Crosslinking agent 10-15 parts.

[0026] Preferably, the thermally conductive filler is prepared by the following steps:

[0027] A1. Add 50-60 parts of aluminum oxide and 20-30 parts of boron nitride to 60-80 parts of 50-85wt% ethanol aqueous solution, heat to 55-65°C, add 4-6 parts of coupling agent, stir for 1-2h, filter, and dry to obtain a pretreated filler;

[0028] A2. Add 10-15 parts of a cross-linking agent to the pretreated filler, raise the temperature to 70-90°C, and knead for 30-60 minutes to obtain a thermally conductive filler.

[0029] By adopting the above technical scheme, a coupling agent is used to carry out surface treatment on aluminum oxide and boron nitride in an ethanol aqueous solution of a relatively optimal concentration to improve the dispersion performance of aluminum oxide and boron nitride, and then a cross-linking agent is added to the obtained pretreated filler. The cross-linking agent is interwoven and dispersed in the cross-linking agent system, thereby enhancing the bonding force between the pretreated fillers and improving the compatibility between the pretreated fillers and the silica gel system. The thermally conductive filler obtained in this way has good dispersion and cross-linking properties in the thermally conductive adhesive, and can improve the thermal conductivity, insulation and bonding stability of the obtained thermally conductive insulating sheet.

[0030] Preferably, the particle size of the aluminum oxide is 70-100 nm, and the particle size of the boron nitride is 20-50 nm.

[0031] By adopting the above technical scheme, coarse-grained aluminum oxide and fine-grained boron nitride are stably matched, so that the boron nitride is stably dispersed in the gaps of the aluminum oxide, the mutual contact area in the silicone system is increased, and the filling density is increased. The thermally conductive insulating sheet obtained in this way has good thermal conductivity and can maintain good insulation under high voltage. At the same time, the cohesive force is not easily lost during the bonding and tearing process, so that the thermally conductive insulating sheet has good bonding stability and is easy to tear without being damaged or producing thermal conductive adhesive residue.

[0032] Preferably, the tackifier is composed of polyethylene glycol monoallyl ether and γ-methacryloxypropyltrimethoxysilane in a weight ratio of (1-2):(0.5-1).

[0033] By adopting the above technical scheme, polyethylene glycol monoallyl ether and γ-methacryloxypropyltrimethoxysilane in an optimal weight ratio have a good synergistic effect, can be further cross-linked with hydrogen-containing silicone oil, and improve the cross-linking performance of the thermal conductive adhesive, thereby improving the bonding performance of the thermal conductive adhesive, and at the same time can produce a good synergistic effect with the thermal conductive filler, improve the dispersion performance of the thermal conductive filler in the silicone system, and thereby improve the thermal conductivity and insulation of the prepared thermal conductive insulating adhesive.

[0034] Preferably, the catalyst is a platinum catalyst.

[0035] By adopting the above technical solution, the platinum catalyst can promote the cross-linking reaction of each component, increase the curing speed and cross-linking density of the thermal conductive adhesive, and significantly improve the efficiency and quality of the thermal conductive adhesive curing.

[0036] In a second aspect, the present application provides a method for preparing a thermally conductive insulating sheet, using the following technical solution:

[0037] A method for preparing a thermally conductive insulating sheet comprises the following steps:

[0038] S1. Preparation of thermal conductive adhesive: Mix methylphenyl vinyl silicone rubber, vinyl silicone oil, dimethyl silicone oil and thermal conductive filler evenly, then add tackifier, hydrogen-containing silicone oil and catalyst and mix evenly to prepare thermal conductive adhesive;

[0039] S2, coating the thermal conductive adhesive on the surface of the insulating layer, heat preservation and vulcanization, and obtaining a thermal conductive insulating sheet.

[0040] By adopting the above technical scheme, the thermally conductive adhesive is first prepared, and then coated on the surface of the insulating layer. The thermal insulation treatment can make the thermally conductive adhesive evenly flow on the surface of the insulating layer and achieve preliminary shaping. Then, vulcanization is performed to solidify the thermally conductive adhesive, thereby obtaining a thermally conductive insulating sheet with good adhesion stability, thermal conductivity and insulation.

[0041] Preferably, the coating amount of the thermal conductive adhesive in step S2 is 40-50 g / m 2 , the vulcanization temperature is 100-120°C.

[0042] By adopting the above technical solution, the optimal coating amount and vulcanization temperature can make the thermal conductive adhesive solidify on the surface of the insulating layer to form a thermal conductive layer with uniform thickness, thereby improving the performance stability of the prepared thermal conductive insulating sheet.

[0043] In summary, this application has the following beneficial effects:

[0044] 1. The thermally conductive insulating sheet of the present application uses a polyimide film as a thermally conductive layer and a thermally conductive adhesive as a thermally conductive layer. The thermally conductive adhesive is made of methylphenyl vinyl silicone rubber, vinyl silicone oil, methyl hydrogen silicone oil, thermally conductive filler, tackifier, dimethyl silicone oil and catalyst. Pentaerythritol triallyl ether, trimethylallyl isocyanate and tetramethyl divinyl disilazane are used as cross-linking agents, and the thermally conductive filler is prepared with aluminum oxide, boron nitride and coupling agent. The prepared thermally conductive insulating sheet has good bonding stability and thermal conductivity, can maintain good insulation under high voltage, is used in product assembly, has good lamination stability and heat dissipation, and is tearable without damage or residual adhesive. It can be used in new energy vehicle batteries, electronic equipment or household radiators such as PTC water heaters, etc.

[0045] 2. Using polydimethyldiallylammonium chloride and γ-aminopropyltriethoxysilane in a better dosage ratio as coupling agents, alumina and boron nitride are modified to further improve the compatibility and dispersion uniformity of the cross-linking agent with alumina and boron nitride, thereby improving the thermal conductivity and insulation of the prepared thermal conductive adhesive, while improving the bonding stability.

[0046] 3. Using polyethylene glycol monoallyl ether and γ-methacryloxypropyltrimethoxysilane in a preferred weight ratio as thickeners has a good synergistic effect, can further cross-link with hydrogen-containing silicone oil, improve the cross-linking performance of the thermal conductive adhesive, and then improve the bonding performance of the thermal conductive adhesive. At the same time, it can produce a good synergistic effect with the thermal conductive filler, improve the dispersion performance of the thermal conductive filler in the silicone system, and then improve the thermal conductivity and insulation of the obtained thermal conductive insulating adhesive.

[0047] 3. The preparation method of the present application, by coating a thermally conductive adhesive on the surface of an insulating film and performing heat preservation vulcanization, the obtained thermally conductive insulating sheet has good adhesion stability, thermal conductivity and insulation. DETAILED DESCRIPTION

[0048] The present application is further described in detail below with reference to the embodiments.

[0049] The following are the sources and specifications of some raw materials of this application. The raw materials used in the preparation examples and embodiments of this application can be obtained from the market, including but not limited to the raw materials of the following models and manufacturers. Raw materials with equivalent performance can be used:

[0050] 1. Methylphenyl vinyl silicone rubber: molecular weight 600,000, phenyl content 15%, vinyl content 0.23%;

[0051] 2. Vinyl silicone oil: molecular weight 2000-5000, vinyl content 1-1.3%;

[0052] 3. Methyl hydrogen silicone oil: hydrogen content 1.4-1.6%, viscosity 20-60mm 2 / s;

[0053] 4. Alumina: spherical alumina, particle size 70-100nm, purity 99.99%;

[0054] 5. Boron nitride: particle size 20-50nm, purity 99.9%;

[0055] 6. Pentaerythritol triallyl ether: CAS No. 1471-17-6, content 99%;

[0056] 7. Trimethylallyl isocyanate: CAS No. 6291-95-8, content 99%;

[0057] 8. Tetramethyldivinyldisilazane: CAS No. 7691-02-3, content 98%;

[0058] 9. Polydimethyldiallylammonium chloride: CAS No. 26062-79-3, content 40%;

[0059] 10. Polyethylene glycol monoallyl ether: CAS No. 27274-31-3, APEG-500;

[0060] 11. Platinum catalyst: platinum content 1000-2000ppm;

[0061] 12. Dimethyl silicone oil: Dow Corning, PMX-200, viscosity 1000-2000cP / 25℃.

[0062] Preparation example of thermal conductive filler

[0063] Preparation Example 1

[0064] Preparation Example 1 discloses a thermally conductive filler, which is prepared by the following steps:

[0065] A1. Add 5 kg of aluminum oxide and 3 kg of boron nitride to 6 kg of 50 wt% ethanol aqueous solution, heat to 55° C., add 0.4 kg of γ-aminopropyltriethoxysilane as a coupling agent, stir for 1 hour, filter, and dry to obtain a pretreated filler;

[0066] A2. Add 1 kg of a crosslinking agent (composed of pentaerythritol triallyl ether, trimethylallyl isocyanate and tetramethyldivinyldisilazane in a weight ratio of 3:1:0.5) to the pretreated filler, raise the temperature to 70° C., and knead for 60 minutes to obtain a thermally conductive filler.

[0067] Preparation Example 2-3

[0068] The difference between Preparation Example 2-3 and Preparation Example 1 is that the amount of raw materials used and the preparation conditions are different, see Table 1 below for details.

[0069] Table 1 Raw material dosage and preparation conditions of Preparation Examples 1-3

[0070]

[0071]

[0072] Preparation Example 4

[0073] The difference between Preparation Example 4 and Preparation Example 1 is that the ratio of specific types of cross-linking agents is different, the usage ratio of pentaerythritol triallyl ether, trimethylallyl isocyanate and tetramethyldivinyldisilazane in Preparation Example 4 is 1:1:1, and the others are the same as Preparation Example 1.

[0074] Preparation Example 5

[0075] The difference between Preparation Example 5 and Preparation Example 1 is that the ratio of specific types of cross-linking agents is different. The usage ratio of pentaerythritol triallyl ether, trimethylallyl isocyanate and tetramethyldivinyldisilazane in Preparation Example 4 is 2:0.5:1, and the others are the same as Preparation Example 1.

[0076] Preparation Example 6

[0077] The difference between Preparation Example 6 and Preparation Example 5 is that the specific type of coupling agent is different. The coupling agent in Preparation Example 6 is composed of polydimethyldiallylammonium chloride and γ-aminopropyltriethoxysilane. The amount of polydimethyldiallylammonium chloride is 0.2kg, and the amount of γ-aminopropyltriethoxysilane is 0.2kg. The rest is the same as Preparation Example 5.

[0078] Preparation Example 7

[0079] The difference between Preparation Example 7 and Preparation Example 5 is that the amount of polydimethyldiallylammonium chloride used is 0.1 kg, the amount of γ-aminopropyltriethoxysilane used is 0.3 kg, and the rest is the same as Preparation Example 5.

[0080] Preparation Comparative Example 1

[0081] The difference between Preparation Comparative Example 1 and Preparation Example 1 is that an equal amount of trimethylallyl isocyanate in the cross-linking agent is replaced with pentaerythritol triallyl ether, and the rest is the same as Preparation Comparative Example 1.

[0082] Preparation Comparative Example 2

[0083] The difference between Preparation Comparative Example 2 and Preparation Example 1 is that an equal amount of tetramethyldivinyldisilazane is replaced by vinyltrimethoxysilane, and the rest is the same as Preparation Example 1.

[0084] Preparation Comparative Example 3

[0085] The difference between Preparation Comparative Example 3 and Preparation Example 1 is that an equal amount of pentaerythritol triallyl ether is replaced by allyl glycidyl ether, and the rest is the same as Preparation Example 1.

[0086] Preparation Example Comparative Example 4

[0087] The difference between Preparation Example 4 and Preparation Example 1 is that the coupling agent is replaced by an equal amount of a cross-linking agent, and the cross-linking agent is added according to the specific type and proportion of Preparation Example 1, and the rest is the same as Preparation Example 1.

[0088] Example

[0089] Example 1

[0090] Example 1 discloses a thermally conductive insulating sheet, including an insulating layer and a thermally conductive layer, the insulating layer is a polyimide film, the thickness of the polyimide film is 0.025-0.05 mm, and the thermal conductivity is 0.4-0.8 W / (m·K). The thermal conductivity of the polyimide film in this embodiment is 0.8 W / (m·K), the thickness is 0.038 mm, and the thermally conductive layer is made by curing a thermally conductive adhesive.

[0091] The preparation method of the thermally conductive insulating sheet is as follows:

[0092] S1. Preparation of thermal conductive adhesive: 1 kg of methylphenyl vinyl silicone rubber, 5 kg of vinyl silicone oil, 0.1 kg of dimethyl silicone oil and 3.5 kg of the thermal conductive filler prepared in Preparation Example 1 were mixed evenly, and then 0.8 kg of γ-methacryloxypropyltrimethoxysilane as a tackifier, 1.5 kg of hydrogen-containing silicone oil and 0.05 kg of platinum catalyst were added and mixed evenly to prepare a thermal conductive adhesive;

[0093] S2, the prepared thermal conductive adhesive is 2The coating amount is applied on the surface of the insulating layer, kept warm at 45°C for 20 minutes, and then vulcanized at 100°C for 15 minutes to obtain a thermally conductive insulating sheet.

[0094] Example 2-3

[0095] The difference between Example 2-3 and Example 1 is that the component dosage of the thermal conductive adhesive is different, and the preparation process parameters of the thermal conductive insulating sheet are different, see Table 2 below for details.

[0096] Table 2 Preparation parameters of Examples 1-3

[0097]

[0098]

[0099] Embodiment 4-7

[0100] The difference between Examples 4-7 and Example 1 is that the sources of the thermal conductive fillers are different, see Table 3 below for details.

[0101] Table 3 Sources of thermal conductive fillers in Examples 4-7

[0102] Example Source of thermal conductive filler Example 4 Preparation Example 4 Example 5 Preparation Example 5 Example 6 Preparation Example 6 Example 7 Preparation Example 7

[0103] Example 8

[0104] The difference between Example 8 and Example 6 is that the specific type and dosage ratio of the thickener are different. The thickener in Example 11 is composed of polyethylene glycol monoallyl ether and γ-methacryloxypropyltrimethoxysilane, the dosage of polyethylene glycol monoallyl ether is 0.4 kg, the dosage of γ-methacryloxypropyltrimethoxysilane is 0.4 kg, and the rest is the same as Example 6.

[0105] Example 9

[0106] The difference between Example 9 and Example 6 is that the tackifier consists of polyethylene glycol monoallyl ether and γ-methacryloxypropyltrimethoxysilane, the amount of polyethylene glycol monoallyl ether used is 0.64 kg, the amount of γ-methacryloxypropyltrimethoxysilane used is 0.16 kg, and the rest is the same as Example 6.

[0107] Comparative Example

[0108] Comparative Examples 1-4

[0109] The difference between Comparative Examples 1-4 and Example 1 is that the sources of the thermal conductive fillers are different, see Table 4 below for details.

[0110] Table 4 Sources of thermal conductive fillers of Comparative Examples 1-4

[0111] Comparative Example Source of thermal conductive filler Comparative Example 1 Preparation Comparative Example 1 Comparative Example 2 Preparation Comparative Example 2 Comparative Example 3 Preparation Comparative Example 3 Comparative Example 4 Preparation Comparative Example 4

[0112] Performance Testing The following performance tests were conducted on the thermally conductive insulating sheets prepared in Examples 1-9 and Comparative Examples 1-4:

[0113] 1. Thermal conductivity test:

[0114] Refer to the test method of ASTM D5470 to test the thermal conductivity (unit: W / (m·K)) of the thermally conductive insulation sheet, and test and record the test results;

[0115] 2. Insulation test:

[0116] According to the test method of ASTM D257, the test voltage is 1KV, and the volume resistance (unit: Ω·cm) of the thermal conductive insulation sheet is tested and the test results are recorded;

[0117] 3. Adhesion performance test:

[0118] Refer to the test method of ASTM-D3330 to test the peel strength (unit: MPa) of the thermally conductive insulation sheet and record the test results. After peeling, observe whether there is residual glue on the surface and whether the surface of the thermal conductive layer is damaged, and record the test results.

[0119] The following are the performance test data of the thermally conductive insulating sheets of Examples 1-9 and Comparative Examples 1-4, see Table 5 below for details.

[0120] Table 5 Performance test data of thermally conductive insulating sheets of Examples 1-9 and Comparative Examples 1-4

[0121]

[0122]

[0123] Combining Examples 1-3 and Examples 4-7, Comparative Examples 1-4 and Table 5, it can be concluded that the thermally conductive insulating sheet made using the thermally conductive filler made of aluminum oxide, boron nitride, a coupling agent and a cross-linking agent of the present application has good thermal conductivity, can maintain good insulation under high voltage, and also has good bonding stability, has no residual glue when torn off, and is not easy to be damaged.

[0124] Specifically, compared with Example 1, Examples 5-6 optimize the usage ratio of pentaerythritol triallyl ether, trimethylallyl isocyanate and tetramethyl divinyl disilazane in the cross-linking agent, and the thermal conductivity of the obtained thermally conductive insulating sheet is increased by 0.05 W / (m·K), and the volume resistivity is increased by 0.14×10 15Ω·cm, and the glass peel strength is also improved by 0.4MPa; in Comparative Example 1, trimethylallyl isocyanate is replaced by pentaerythritol triallyl ether in an equal amount, tetramethyl divinyl disilazane is replaced by vinyl trimethoxysilane in an equal amount in Comparative Example 2, and pentaerythritol triallyl ether is replaced by allyl glycidyl ether in an equal amount in Comparative Example 3. It can be seen from the above data table that compared with Example 1, the thermal conductivity and system resistance of the thermally conductive insulating sheet of Comparative Examples 1-3 are significantly reduced, and the peel strength is also significantly reduced. When the thermal conductive layer of the thermally conductive insulating sheet is peeled off, the thermal conductivity coefficient of the thermally conductive insulating sheet is significantly reduced. It is now damaged, thus it can be known that the compound use of pentaerythritol triallyl ether, trimethylallyl isocyanate and tetramethyldivinyldisilazane in a better dosage ratio can significantly improve the dispersibility and cross-linking performance of the thermally conductive filler in the silica gel system, thereby improving the comprehensive performance of the thermally conductive insulating sheet obtained; while in Comparative Example 4, the coupling agent is replaced by a cross-linking agent, and the performance of the thermally conductive insulating sheet obtained is also reduced, indicating that the coupling agent of the present application can improve the dispersion uniformity of the cross-linking agent and alumina and boron nitride, and in the absence of the compatibility effect of the coupling agent, the performance of the thermally conductive filler obtained is also reduced.

[0125] Compared with Example 5, Examples 6-7 further optimized the type and proportion of the coupling agent in the thermally conductive filler, and the thermal conductivity of the thermally conductive insulating sheet obtained was increased by 0.04 W / (m·K), and the volume resistivity was increased by 0.08×10 15 Ω·cm, and the peel strength increased by 0.3MPa.

[0126] Furthermore, in combination with Examples 8-9, compared with Example 6, the ratio of the tackifier is further optimized, and the thermal conductivity, insulation and bonding stability of the prepared thermally conductive insulating sheet are improved.

[0127] In summary, the thermally conductive insulating sheet of the present application has good thermal conductivity, insulation and bonding stability, and can be selected according to the thermal conductive layer of different thicknesses and the insulating layer of different thicknesses and thermal conductivity, the thermal conductivity can reach 2.0-7.0W / (m·K), and the volume resistivity can reach 10 15 Ω·cm.

[0128] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A thermally conductive insulating sheet, characterized in that: It includes an insulating layer and a heat-conducting layer, wherein the insulating layer is a polyimide film, and the heat-conducting layer is made by curing a heat-conducting adhesive, wherein the heat-conducting adhesive is made of the following raw materials in parts by weight: Methylphenyl vinyl silicone rubber 10-20 parts 40-50 parts of vinyl silicone oil 15-20 parts of methyl hydrogen silicone oil Thermally conductive filler 35-45 parts 4-8 parts of tackifier 1-2 parts dimethyl silicone oil Catalyst 0.5-1 part; The thermal conductive filler is made of aluminum oxide, boron nitride, a coupling agent and a cross-linking agent; The crosslinking agent consists of pentaerythritol triallyl ether, trimethylallyl isocyanate and tetramethyldivinyldisilazane.

2. A thermally conductive insulating sheet according to claim 1, characterized in that: The weight ratio of the pentaerythritol triallyl ether, the trimethylallyl isocyanate and the tetramethyldivinyldisilazane is (1-2): (0.5-1):

1.

3. The thermally conductive insulating sheet according to claim 1, characterized in that: The coupling agent is composed of polydimethyldiallylammonium chloride and gamma-aminopropyltriethoxysilane in a weight ratio of 1:(1-3).

4. A thermally conductive insulating sheet according to any one of claims 1 to 3, characterized in that: The thermally conductive filler is prepared from the following raw materials in parts by weight: Alumina 50-60 parts Boron nitride 20-30 parts Coupling agent 4-6 parts Cross-linking agent 10-15 parts.

5. A thermally conductive insulating sheet according to claim 4, characterized in that: The thermally conductive filler is prepared by the following steps: A1. Add 50-60 parts of aluminum oxide and 20-30 parts of boron nitride to 60-80 parts of 50-85wt% ethanol aqueous solution, heat to 55-65°C, add 4-6 parts of coupling agent, stir for 1-2h, filter, and dry to obtain a pretreated filler; A2. Add 10-15 parts of a cross-linking agent to the pretreated filler, raise the temperature to 70-90°C, and knead for 30-60 minutes to obtain a thermally conductive filler.

6. The thermally conductive insulating sheet according to claim 1, characterized in that: The particle size of the aluminum oxide is 70-100 nm, and the particle size of the boron nitride is 20-50 nm.

7. The thermally conductive insulating sheet according to claim 1, characterized in that: The tackifier is composed of polyethylene glycol monoallyl ether and gamma-methacryloxypropyl trimethoxysilane in a weight ratio of (1-2):(0.5-1).

8. The thermally conductive insulating sheet according to claim 1, characterized in that: The catalyst is a platinum catalyst.

9. A method for preparing a thermally conductive insulating sheet according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Preparation of thermal conductive adhesive: methylphenyl vinyl silicone rubber, vinyl silicone oil, dimethyl silicone oil and thermal conductive filler are mixed evenly, and then a tackifier, methyl hydrogen silicone oil and a catalyst are added and mixed evenly to prepare a thermal conductive adhesive; S2, coating the thermal conductive adhesive on the surface of the insulating layer, heat preservation and vulcanization, and obtaining a thermal conductive insulating sheet.

10. A method for preparing a thermally conductive insulating sheet as claimed in claim 9, characterized in that: The coating amount of the thermal conductive adhesive in step S2 is 40-50 g / m 2 , the vulcanization temperature is 100-120°C.

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