A polysiloxane-polyurethane copolymer thermal interface material and a preparation method and application thereof

Abstract

This invention discloses a polysiloxane-polyurethane copolymer thermal interface material, its preparation method, and its applications. The preparation method includes the following steps: dissolving a polyether-type polyol polymer, an isocyanate compound, and a bifunctionalized polysiloxane polymer in an ester solvent, carrying out a polymerization reaction under the action of a catalyst, adding filler and mixing to obtain the polysiloxane-polyurethane copolymer thermal interface material. This invention, from a molecular design perspective, introduces multiple hydrogen bonds into the molecular chain of the polysiloxane-polyurethane copolymer thermal interface material through precise stepwise addition polymerization of polyether-type polyurethane and bifunctionalized polysiloxane. Utilizing the strong interaction and dynamic reversibility of hydrogen bonds, a breakthrough in material adhesion performance is achieved at the molecular level.

Description

Technical Field

[0001] This invention relates to the field of thermal interface materials technology, specifically to a polysiloxane-polyurethane copolymer thermal interface material, its preparation method, and its application. Background Technology

[0002] As integrated circuit devices rapidly develop towards higher integration and higher power density, they continuously generate a large amount of heat during operation. If this heat cannot be dissipated in a timely and efficient manner through the thermal management system, it will directly reduce the operational stability of the device and significantly shorten its lifespan. Thermal interface materials (TIMs), as the core medium for heat transfer in the thermal management system, fill the micro-gaps between heat-generating devices and heat-dissipating components. They can effectively eliminate the high thermal resistance caused by interfacial air gaps, enabling rapid heat conduction. Their thermal conductivity and interfacial adhesion properties directly determine the overall efficiency and long-term reliability of the thermal management system. Organosilicon materials, due to their excellent high-temperature resistance, low glass transition temperature, good flexibility, and compatibility with various substrates, have become the mainstream matrix materials for preparing thermal interface materials. Among them, hydroxyl-terminated polydimethylsiloxane is one of the most widely used organosilicon matrices.

[0003] However, silicone-based thermal interface materials have inherent technical defects: the silicone molecular chain contains a large number of nonpolar siloxane segments, and its low surface energy characteristics result in weak interfacial adhesion between silicone-based materials and heat dissipation substrates such as metals and ceramics. The interfacial adhesion strength of conventional silicone-based thermal interface materials is usually less than 1 MPa, and the adhesion energy is less than 200 J / m. 2 During the long-term operation of integrated circuit devices, weak interfacial adhesion can easily lead to problems such as interfacial peeling and delamination between the thermal interface material and the substrate, resulting in a sharp increase in interfacial thermal resistance, disruption of the heat transfer path, and ultimately device heat dissipation failure. This defect severely limits the application of silicone-based thermal interface materials in the thermal management of high-end integrated circuits.

[0004] To improve the adhesive properties of silicone-based thermal interface materials, current research focuses on polymer network structure optimization, filler synergistic modification, metamaterial structure design, and molecular architecture regulation. By controlling the branching and crosslinking degree of polydimethylsiloxane (PDMS) and optimizing the dispersion of aluminum fillers, the adhesive strength of the thermal interface material was increased to 3.30 ± 0.26 MPa, and the adhesive energy reached 913.2 ± 152.71 J / m. 2This study confirmed the regulatory role of polymer network structure and filler dispersion on adhesive performance; it also demonstrated that by designing metamaterial adhesives with nonlinear cutting architectures, the adhesive strength was increased by 60 times through crack back propagation mechanism; furthermore, research on polydimethylsiloxane bottle brush elastomers showed that the chemical structure and length of side chains can precisely control the interfacial energy release rate of the material, providing theoretical support for the molecular design of organosilicon copolymers; the particle size distribution and dispersion state of fillers were also shown to affect the coverage of the polymer matrix on the substrate and the formation of interfacial defects, and uniformly dispersed fillers can improve the long-term adhesive stability of materials under high-temperature aging environments.

[0005] While existing modification techniques have improved the adhesion performance of silicone-based thermal interface materials to some extent, they still fall short of meeting the comprehensive performance requirements of thermal interface materials in the integrated circuit field, exhibiting significant technical shortcomings: First, some modification schemes sacrifice adhesion energy for increased adhesion strength, or increase adhesion energy while decreasing adhesion strength, failing to achieve synergistic optimization of high adhesion strength and high adhesion energy simultaneously. Second, some modification schemes employ complex polymerization processes or metamaterial structure designs, resulting in cumbersome preparation processes, difficult process control, and high production costs, making them unsuitable for the miniaturization and large-scale assembly and production requirements of integrated circuit devices. Third, the improved adhesion performance of some modified materials relies on the addition of specific fillers or additives, which can easily lead to damage to other key properties such as material flexibility and thermal conductivity, failing to achieve a balance in the comprehensive performance of thermal interface materials. Therefore, there is an urgent need to develop a thermal interface material with a simple preparation process, controllable cost, and the ability to simultaneously achieve high adhesion strength and high adhesion energy. Summary of the Invention

[0006] The purpose of this invention is to solve the above-mentioned technical problems and provide a polysiloxane-polyurethane copolymer thermal interface material, its preparation method, and its application. This invention, from a molecular design perspective, introduces multiple hydrogen bonds into the synthesized polysiloxane-polyurethane copolymer thermal interface material, thereby endowing the material with excellent adhesive properties.

[0007] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0008] The first aspect of this invention provides a method for preparing a polysiloxane-polyurethane copolymer thermal interface material, comprising the following steps:

[0009] A polyether-type polyol polymer, an isocyanate compound, and a bifunctionalized polysiloxane polymer are dissolved in an ester solvent and polymerized under the action of a catalyst to obtain a polysiloxane-polyurethane copolymer solution. The polysiloxane-polyurethane copolymer solution is mixed with a filler to obtain the polysiloxane-polyurethane copolymer thermal interface material. The bifunctionalized polysiloxane polymer is a polysiloxane polymer with olefin, hydroxyl, carboxyl, epoxy, or amino groups at both ends. The mass ratio of polysiloxane-polyurethane copolymer to filler in the polysiloxane-polyurethane copolymer solution is (15-25):(75-85).

[0010] This invention, starting from the core perspective of molecular design, constructs and introduces multiple hydrogen bond interaction sites into the copolymer molecular chain through precise stepwise addition polymerization of polyether polyurethane and bifunctionalized polysiloxane. Utilizing the dynamic reversibility and strong interaction of hydrogen bonds, it endows the material with excellent interfacial adhesion properties at the molecular level, while simultaneously considering the flexibility and high-temperature resistance of polysiloxane and the adhesion and compatibility of polyurethane, achieving synergistic optimization of adhesion performance and substrate compatibility. Furthermore, the preparation process of this invention is simple, can be carried out in an air atmosphere without the need for inert gas protection, and the raw materials are readily available, making it suitable for large-scale production. Compared with existing complex modification processes, it has significant process and cost advantages.

[0011] Furthermore, the polyether-type polyol polymer is selected from one or more of polytetrahydrofuran, polypropylene oxide polyol, polyethylene oxide polyol, and ethylene oxide-propylene oxide copolyether.

[0012] Furthermore, the isocyanate compound is selected from one or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethane diisocyanate.

[0013] Furthermore, the dual-functionalized polysiloxane polymer is selected from one or more of dual-vinyl polydimethylsiloxane, dual-hydroxyl polydimethylsiloxane, dual-aminopropyl polydimethylsiloxane, dual-carboxypropyl polydimethylsiloxane, and dual-epoxypropylpolydimethylsiloxane.

[0014] Further, in step (1), the mass ratio of the polyether-type polyol polymer, the isocyanate compound and the difunctionalized polysiloxane polymer is 1:(0.02-20):(0.055-10), preferably 1:(0.02-1):(0.055-1).

[0015] Further, in step (1), the ester solvent is selected from one or more of ethyl acetate, butyl acetate and propylene glycol methyl ether acetate.

[0016] Further, in step (1), the catalyst is selected from one or more of dibutyltin dilaurate, stannous isooctanoate and zinc isooctanoate.

[0017] Furthermore, the mass ratio of the polyether-type polyol polymer to the ester solvent is 1:(1-20).

[0018] In a specific embodiment, the ratio of the polyether-type polyol polymer to the ester solvent is 1 g : 1-10 mL.

[0019] Further, in step (1), the mass ratio of the polyether-type polyol polymer to the catalyst is 1:(0.001-0.4).

[0020] Furthermore, the polymerization reaction is carried out at a temperature of 40-80 °C for a time of 1-5 h.

[0021] Furthermore, the content of polysiloxane-polyurethane copolymer in the polysiloxane-polyurethane copolymer solution is 45-55 wt%.

[0022] Furthermore, the filler is selected from one or more of alumina, aluminum powder, graphene, and hexagonal boron nitride.

[0023] Preferably, the mass ratio of polysiloxane-polyurethane copolymer to filler in the polysiloxane-polyurethane copolymer solution is (15-20):(80-85).

[0024] Furthermore, the mixing conditions are: vacuum degree ≤ -0.1 MPa, rotation speed 200-1800 r / min, and time 5-20 min.

[0025] In a specific embodiment, a method for preparing a polysiloxane-polyurethane copolymer thermal interface material includes the following steps:

[0026] (1) In an air atmosphere, using ester solvents as the reaction medium, a polyether-type polyol polymer, an isocyanate compound and a double-terminated polysiloxane polymer are mixed and polymerized. At the same time, a trace amount of catalyst is used to regulate the reaction rate and crosslinking network density to obtain a polysiloxane-polyurethane copolymer solution.

[0027] (2) The obtained polysiloxane-polyurethane copolymer solution is mixed with filler to obtain polysiloxane-polyurethane copolymer thermal interface material.

[0028] The second aspect of the present invention provides a polysiloxane-polyurethane copolymer thermal interface material prepared by the preparation method described in the first aspect.

[0029] The polysiloxane-polyurethane copolymer thermal interface material provided by this invention is a block copolymer formed by stepwise addition polymerization of polyurethane and polysiloxane segments. The molecular chain contains a large number of multiple hydrogen bonds composed of NH…O=C, OH…O=C, NH…N, etc. The dynamic reversibility of these hydrogen bonds allows the material to quickly form interfacial interactions upon interface contact, significantly improving interfacial adhesion strength and bonding energy. Simultaneously, the flexible characteristics of the polysiloxane segments give the material good interfacial compatibility with various heat dissipation substrates (such as metals and ceramics), avoiding interfacial delamination caused by mismatched coefficients of thermal expansion. The uniform dispersion of the filler provides excellent thermal conductivity, making it a thermal interface material that combines high adhesion, high thermal conductivity, and good flexibility.

[0030] The third aspect of this invention provides the application of the polysiloxane-polyurethane copolymer thermal interface material described in the first aspect in the preparation of electronic packaging adhesives.

[0031] The above-described technical solution of the present invention has the following beneficial effects:

[0032] This invention, from a molecular design perspective, introduces multiple hydrogen bonds into the molecular chain of the polysiloxane-polyurethane copolymer thermal interface material through precise stepwise addition polymerization of polyether-type polyurethane and bifunctionalized polysiloxane. Utilizing the strong interaction and dynamic reversibility of these hydrogen bonds, along with the synergistic effect of the filler and copolymer matrix, a breakthrough in material adhesion performance is achieved at the molecular level, resulting in high adhesive strength (up to 2.78 MPa) and high adhesive energy (up to 2297.40 J / m). 2 Thermal interface materials can be applied in the field of electronic packaging adhesives. Attached Figure Description

[0033] Figure 1 The image shows the infrared spectrum of the polysiloxane-polyurethane copolymer prepared in Example 1. Detailed Implementation

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0036] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0037] The polytetrahydrofuran (Mn=2000 g / mol) used in the following examples was purchased from Shanghai E-En Chemical Technology Co., Ltd.; isophorone diisocyanate with a molecular weight of 222.3 g / mol was purchased from Sinopharm Chemical Reagent Co., Ltd.; dibutyltin dilaurate was purchased from Sinopharm Chemical Reagent Co., Ltd.; ethyl acetate was purchased from Shanghai Titan Technology Co., Ltd.; hydroxyl-terminated polydimethylsiloxane (Mn=550 g / mol) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; and spherical alumina with a particle size of 6 μm was purchased from Ya'an Baitu High-Tech Materials Co., Ltd.

[0038] Example 1

[0039] A method for preparing a polysiloxane-polyurethane copolymer thermal interface material includes the following steps:

[0040] (1) Under an air atmosphere, 5 g of polytetrahydrofuran, 1.11 g of isophorone diisocyanate, 2.75 g of hydroxyl-terminated polydimethylsiloxane, 0.02 g of dibutyltin dilaurate, and 10 mL of ethyl acetate were added to a reaction vessel, mixed thoroughly, and reacted at 60 °C for 3 h to obtain a polysiloxane-polyurethane copolymer solution, wherein the content of the polysiloxane-polyurethane copolymer was 51 wt%. The polysiloxane-polyurethane copolymer was denoted as PT-OH, and its infrared spectrum characterization diagram is shown below. Figure 1 As shown, 2270 cm can be clearly seen. -1 The complete disappearance of the -NCO characteristic absorption peak at the point indicates the successful synthesis of the polysiloxane-polyurethane copolymer.

[0041] (2) Take 5.5 g of the PT-OH solution obtained in step (1) and add 11.22 g of alumina filler. The mass ratio of PT-OH to alumina filler is 20:80. Stir and mix evenly for 10 min under vacuum degree ≤ -0.1 MPa and rotation speed 1000 r / min to obtain polysiloxane-polyurethane copolymer thermal interface material.

[0042] Example 2

[0043] A method for preparing a polysiloxane-polyurethane copolymer thermal interface material includes the following steps:

[0044] Take 5.5 g of the PT-OH solution prepared in Example 1, add 15.89 g of alumina filler, the mass ratio of PT-OH to alumina filler is 15:85, stir and mix evenly under vacuum degree ≤ -0.1 MPa and rotation speed 1000 r / min to obtain polysiloxane-polyurethane copolymer thermal interface material.

[0045] Comparative Example 1

[0046] A method for preparing a polysiloxane-polyurethane copolymer solution includes the following steps:

[0047] Under an air atmosphere, 5 g of polytetrahydrofuran, 1.11 g of isophorone diisocyanate, 2.75 g of hydroxyl-terminated polydimethylsiloxane, 0.02 g of dibutyltin dilaurate, and 10 mL of ethyl acetate were added to a reaction vessel, mixed thoroughly, and reacted at 60 °C for 3 h to obtain a polysiloxane-polyurethane copolymer solution, wherein the content of polysiloxane-polyurethane copolymer was 51 wt%.

[0048] Comparative Example 2

[0049] A method for preparing a polysiloxane-polyurethane copolymer thermal interface material includes the following steps:

[0050] Take 5.5 g of the PT-OH solution prepared in Example 1, add 18.77 g of alumina filler, the mass ratio of PT-OH to alumina filler is 13:87, stir and mix evenly under vacuum degree ≤ -0.1 MPa and rotation speed 1000 r / min to obtain polysiloxane-polyurethane copolymer thermal interface material.

[0051] Comparative Example 3

[0052] A method for preparing a liquid organosilicon thermal interface material includes the following steps:

[0053] Prepolymer A and B components from commercial Dow Corning 184 were mixed at a mass ratio of 10:1 and reacted under normal pressure and temperature conditions by stirring at 8000 rpm for 5 min to obtain a liquid organosilicon thermal interface material.

[0054] Comparative Example 4

[0055] A method for preparing a liquid epoxy resin thermal interface material includes the following steps:

[0056] Commercial bisphenol A type CYD-128 and NN dimethyl benzylamine were mixed at a mass ratio of 10:1, and 0.5% methyl hexahydrophthalic anhydride was added. The mixture was stirred at 8000 rpm for 5 min under normal pressure and temperature to obtain liquid epoxy resin thermal interface material.

[0057] Test Example 1

[0058] The adhesive strength and adhesive energy of the polysiloxane-polyurethane copolymer thermal interface materials prepared in Examples 1-2, the polysiloxane-polyurethane copolymer solution prepared in Comparative Example 1, the polysiloxane-polyurethane copolymer thermal interface material prepared in Comparative Example 2, the liquid silicone thermal interface material prepared in Comparative Example 3, and the liquid epoxy resin thermal interface material prepared in Comparative Example 4 were tested using a ZQ-970 series testing machine. The specific testing methods are as follows:

[0059] (1) Take polysiloxane-polyurethane copolymer thermal interface material / polysiloxane-polyurethane copolymer solution and spin coat it evenly between two 46 nm thick aluminum sheets at a speed of 400 rpm. First, cure it at 80 ℃ for 12 h, and then cure it at 120 ℃ for 12 h. Control the thickness of the thermal interface material to be 400 μm to obtain the test sample of aluminum / polysiloxane-polyurethane copolymer thermal interface material / aluminum or aluminum / polysiloxane-polyurethane copolymer / aluminum.

[0060] (2) Take liquid silicone thermal interface material and spin coat it evenly between two 46 nm thick aluminum sheets at a speed of 400 rpm. First, cure it at 125 ℃ for 1 h, and then cure it at 145 ℃ for 3 h. Control the thickness of the thermal interface material to be 400 μm to obtain the aluminum / silicone thermal interface material / aluminum test sample.

[0061] (3) Take liquid epoxy resin thermal interface material and spin coat it evenly between two 46 nm thick aluminum sheets at a speed of 400 rpm. First cure at 125 ℃ for 1 h, then cure at 145 ℃ for 3 h. Control the thickness of the thermal interface material to be 400 μm to obtain the aluminum / epoxy resin thermal interface material / aluminum test sample.

[0062] (4) Under the conditions of 25 ℃ and 10 mm / min, the above aluminum sheet test specimens with thermal interface material were subjected to tensile test. The load force and displacement data during the tensile process were recorded in real time. The peak value of the load force was used as the bonding strength of the thermal interface material. The load force was integrated with respect to the displacement, and the result was used as the bonding energy of the thermal interface material.

[0063] The test results are shown in Table 1.

[0064] Table 1. Test results of adhesive strength and adhesive energy of thermal interface materials

[0065]

[0066] As shown in Table 1, the adhesive strength and adhesive energy of the polysiloxane-polyurethane copolymer thermal interface material prepared in this invention vary significantly under different filler contents. Example 2 exhibits the best overall adhesive performance, with an adhesive strength of 2775.98 ± 162.43 kPa and an adhesive energy of 2297.40 ± 61.59 J / m. 2 Both core adhesion indicators are significantly superior to those of other embodiments and comparative examples, demonstrating excellent mechanical adhesion performance and interfacial resistance to damage. The adhesive strength of Example 1 (1535.79 ± 280.82 KPa) is comparable to that of Comparative Example 4 (1591.00 ± 169.00 KPa), but its adhesive energy reaches 1703.35 ± 413.36 J / m. 2 This is compared to Example 4 (532.00 ± 40.00 J / m). 2 The bonding energy of the polysiloxane-polyurethane copolymer prepared in Comparative Example 1 is more than three times that of conventional epoxy resin-based materials, fully demonstrating the superior interfacial toughness and fatigue resistance of the material of this invention compared to conventional epoxy resin-based materials. 2 Example 2 showed better adhesion than Comparative Examples 3 and 4, but with a significant decrease in bond strength. Furthermore, Comparative Example 2 demonstrated a sharp decline in adhesive performance as the filler content continued to increase. In summary, the polysiloxane-polyurethane copolymer thermal interface materials prepared in the various embodiments of this invention generally exhibited better adhesive performance than the comparative examples, and Example 2 simultaneously possessed both high bond strength and excellent interfacial toughness.

[0067] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art should understand that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a polysiloxane-polyurethane copolymer thermal interface material, characterized in that, Includes the following steps: A polyether-type polyol polymer, an isocyanate compound, and a bifunctionalized polysiloxane polymer are dissolved in an ester solvent and polymerized under the action of a catalyst to obtain a polysiloxane-polyurethane copolymer solution. The polysiloxane-polyurethane copolymer solution is mixed with a filler to obtain the polysiloxane-polyurethane copolymer thermal interface material. The bifunctionalized polysiloxane polymer is a polysiloxane polymer with olefin, hydroxyl, carboxyl, epoxy, or amino groups at both ends. The mass ratio of polysiloxane-polyurethane copolymer to filler in the polysiloxane-polyurethane copolymer solution is (15-25):(75-85).

2. The preparation method according to claim 1, characterized in that, The polyether-type polyol polymer is selected from one or more of polytetrahydrofuran, polypropylene oxide polyol, polyethylene oxide polyol, and ethylene oxide-propylene oxide copolyether; the isocyanate compound is selected from one or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and dicyclohexylmethane diisocyanate; the dual-functionalized polysiloxane polymer is selected from one or more of dual-vinyl polydimethylsiloxane, dual-hydroxyl polydimethylsiloxane, dual-aminopropyl polydimethylsiloxane, dual-carboxypropyl polydimethylsiloxane, and dual-propoxypropyl polydimethylsiloxane.

3. The preparation method according to claim 1 or 2, characterized in that, The mass ratio of the polyether-type polyol polymer, isocyanate compound, and di-functionalized polysiloxane polymer is 1:(0.02-20):(0.055-10).

4. The preparation method according to claim 1, characterized in that, The ester solvent is selected from one or more of ethyl acetate, butyl acetate, and propylene glycol methyl ether acetate; the catalyst is selected from one or more of dibutyltin dilaurate, stannous isooctanoate, and zinc isooctanoate.

5. The preparation method according to claim 1 or 4, characterized in that, The mass ratio of the polyether polyol polymer to the ester solvent is 1:(1-20); the mass ratio of the polyether polyol polymer to the catalyst is 1:(0.001-0.4).

6. The preparation method according to claim 1, characterized in that, The polymerization reaction is carried out at a temperature of 40-80 °C for 1-5 h.

7. The preparation method according to claim 1, characterized in that, The polysiloxane-polyurethane copolymer solution contains 45-55 wt% polysiloxane-polyurethane copolymer.

8. The preparation method according to claim 1, characterized in that, The filler is selected from one or more of alumina, aluminum powder, graphene and hexagonal boron nitride; the mixing conditions are: vacuum degree ≤ -0.1 MPa, rotation speed 200-1800 r / min, and time 5-20 min.

9. A polysiloxane-polyurethane copolymer thermal interface material prepared by the preparation method according to any one of claims 1-8.

10. The application of the polysiloxane-polyurethane copolymer thermal interface material of claim 9 in the preparation of electronic packaging adhesives.

Images