Silica gel for packaging high-voltage power device as well as preparation method and application of silica gel

Abstract

The invention relates to the technical field of organic silicon pouring sealants, in particular to silica gel for packaging a high-voltage power device and a preparation method and application thereof.The silica gel is prepared from, by weight, 100 parts of vinyl phenyl silicone oil, 0.01-0.5 part of an inhibitor, 0.7-2 parts of methyl silicone oil with a hydrogen-containing side chain, 0.1-9 parts of methyl silicone oil with a hydrogen-containing terminal and 0.1-1 part of a catalyst, one of a coupling agent and MQ hydrogen-containing silicon resin is selected from the following components in parts by weight: 0.1-9 parts of the coupling agent and 0.1-5 parts of the MQ hydrogen-containing silicon resin; the viscosity of the vinyl phenyl silicone oil is 500-2000 mPa.s, and the content of phenyl is 1-30%. The invention further discloses a preparation method of the silica gel for packaging the high-voltage power device. The silica gel for packaging the high-voltage power device has the characteristics of strong adhesion, high voltage resistance and the like, has good processability and usability, and can meet the requirement of the high-voltage power device on long-term working stability of a packaging material.

Description

Technical Field

[0001] This invention relates to the field of silicone potting compound technology, specifically to a silicone gel for packaging high-voltage power devices, its preparation method, and its application. Background Technology

[0002] As high-voltage power devices evolve towards higher voltage and higher power density, their packaging reliability faces severe challenges. The packaging insulation characteristics of power devices are closely related to the properties of their packaging insulation materials. The adhesion between the packaging material and the device interior is crucial. Good adhesion ensures a tight bond between the material and the chip, substrate, and housing, effectively conducting stress, dissipating heat, and preventing the intrusion of moisture or contaminants. Insufficient adhesion can lead to delamination or cracking at the interface under thermomechanical stress, resulting in local electric field distortion, deteriorated heat dissipation, and potentially fatal failures such as partial discharge and thermal breakdown, severely shortening device lifespan. Therefore, improving the interfacial adhesion between the material and the chip, substrate, and housing is of great significance for ensuring the stable operation of high-voltage devices under extreme conditions and preventing system collapse due to packaging failure.

[0003] High-molecular-weight organic polymers are commonly used in device encapsulation. Compared to traditional encapsulation materials such as epoxy resins and polyurethane elastomers, silicone gels exhibit superior heat resistance, weather resistance, and electrical insulation properties, making them an indispensable insulating material in high-voltage, high-power power electronic packaging. However, currently, commercially available silicone gels mostly use general-purpose methyl vinyl silicone oils, whose molecular side chains are primarily composed of inert methyl groups. This results in weak interaction with inorganic interfaces such as chips and ceramic substrates, leading to insufficient intrinsic adhesion and a tendency to create gaps with the substrate. To improve the adhesion of silicone gel materials, the industry commonly employs the addition of synthetic small-molecule adhesion promoters. These promoters typically participate in cross-linking reactions during curing and are introduced into the network structure of the silicone gel to improve interfacial bonding. However, small-molecule adhesion promoters have limited compatibility with the silicone gel matrix, easily agglomerating or migrating within the system, resulting in poor adhesion uniformity and an inability to form stable interfacial bonds, thus affecting the reliability of device encapsulation. Summary of the Invention

[0004] To address the technical problems of insufficient adhesion and stability of silicone gels, this invention provides a silicone gel for high-voltage power device packaging, its preparation method, and its applications. The core technical feature of this invention is that, unlike traditional modification methods that rely solely on adding coupling agents and other auxiliary reagents, this invention fundamentally improves the overall performance of the silicone gel by adjusting its intrinsic molecular structure. The silicone gel prepared in this way not only possesses significantly enhanced adhesion strength but also exhibits excellent high-voltage breakdown resistance and thermal stability, while also maintaining good processability. This effectively meets the stringent requirements of high-voltage power devices for long-term stable operation of packaging materials under harsh operating conditions.

[0005] The technical solution of this invention is as follows: In a first aspect, the present invention provides a silicone gel for packaging high-voltage power devices, the silicone gel comprising the following raw materials in parts by weight: 100 parts of vinylphenyl silicone oil, 0.01-0.5 parts of inhibitor, 0.7-2 parts of side-chain hydrogen-containing methyl silicone oil, 0.1-9 parts of terminal hydrogen-containing methyl silicone oil, 0.1-1 parts of catalyst, and one of coupling agent or MQ hydrogen-containing silicone resin, wherein the coupling agent is 0.1-9 parts and the MQ hydrogen-containing silicone resin is 0.1-5 parts; the vinylphenyl silicone oil has a viscosity of 500-2000 mPa·s and a phenyl content of 1-30%.

[0006] Vinylphenyl silicone oil is selected as the base polymer, and phenyl groups are directly embedded into the polysiloxane backbone in the form of side chains. The large volume and rigid structure of phenyl groups not only enhance the rigidity of the molecular chain and improve the heat resistance of the material, but also, due to their rich π-electron cloud, generate strong van der Waals forces and dipole interactions with the encapsulation interface, thereby significantly enhancing the interfacial affinity at the molecular level. Furthermore, the applicant discovered that controlling the phenyl content is crucial. When the phenyl content is too high (>30%), it may form continuous π-π stacked channels, which can become leakage current paths and severely degrade the insulation performance of the material. Therefore, this invention strictly controls the phenyl content to be less than 30%.

[0007] In addition, the main role of MQ hydrogen-containing silicone resin in the system is to regulate the density of the cross-linking network. The hardness of silicone gel is determined by the density of its three-dimensional network. MQ hydrogen-containing silicone resin has a relatively small molecular weight and a highly branched structure. When its vinyl content is not properly matched with the hydrogen-containing silicone oil in the system, it may destroy the original regular cross-linking, resulting in a decrease in effective cross-linking density and thus making the macroscopic appearance softer.

[0008] Furthermore, the inhibitor is one of 1-ethynyl-1-cyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, 2-methyl-3-butyn-2-ol, and methylvinylcyclotetrasiloxane, preferably 1-ethynyl-1-cyclohexanol. The selected inhibitor exhibits good compatibility with the silica gel and can effectively regulate the crosslinking reaction rate of the silica gel, preventing excessively rapid reactions, while not affecting the synergistic effect of other components in the system, thus improving the performance stability of the final product.

[0009] Furthermore, the coupling agent is one or more of vinyltrimethoxysilane A-171, methacryloxypropyltrimethoxysilane KH-570, γ-glycidyl etheroxypropyltrimethoxysilane KH-560, and aminopropyltriethoxysilane KH-550, with vinyltrimethoxysilane A-171 being preferred. The coupling agent, known as a "molecular bridge," can connect two materials with completely different properties. The coupling agent molecule contains two different active groups: the siloxane end hydrolyzes to generate silanol, which undergoes a condensation reaction with the hydroxyl groups on the substrate surface to form a covalent bond; the organic end contains functional groups such as vinyl and epoxy groups, which react with the polymer chains in the silicone gel. Adding a coupling agent can significantly reduce the surface tension of the resin, making it easier for the silicone gel to spread on the substrate surface and penetrate into the micropores, thereby increasing physical adsorption. Furthermore, during the curing process, the coupling agent forms a thin film at the interface, effectively absorbing and alleviating interfacial stress caused by thermal shrinkage, preventing the adhesive from detaching due to stress concentration.

[0010] Furthermore, the catalyst is a platinum catalyst with a platinum content of 2000-5000 ppm. Platinum catalysts have high activity and high catalytic efficiency, can suppress side reactions that occur during the reaction process, are relatively environmentally friendly, and produce silica gel with good stability after catalysis.

[0011] Secondly, the present invention provides a method for preparing silicon gel for packaging high-voltage power devices, comprising the following steps: S1. Add vinyl phenyl silicone oil to a container, add the inhibitor, and stir well; S2. Add side-chain hydrogen-containing methyl silicone oil and terminal hydrogen-containing methyl silicone oil sequentially to the mixture obtained in step S1, and stir until homogeneous; S3. Add one of the coupling agent or MQ hydrogen-containing silicone resin to the mixture obtained in step S2, and stir until uniform. S4. Add the catalyst to the mixture obtained in step S3 and stir until homogeneous; S5. Perform vacuum degassing on the raw material obtained in step S4; S6. The raw material after vacuum degassing is heated and cross-linked to obtain the silicone gel for packaging high-voltage power devices.

[0012] Furthermore, in step S5, the vacuum degree used for vacuum degassing is -100kPa; the vacuum pumping time is 30-40min.

[0013] By employing a high vacuum of -100kPa and a sufficient evacuation time of 30-40 minutes, trace amounts of dissolved and entrained air in the adhesive, as well as small air bubbles generated during mixing, can be completely removed, ensuring that the cured material is free of air bubbles. This is crucial for the packaging of high-voltage power devices, because any tiny air bubble can become the starting point of partial discharge under a high electric field, leading to insulation failure.

[0014] Furthermore, in step S6, the curing temperature is 100-120℃ and the curing time is 1.5h-2.5h.

[0015] Furthermore, after the silicone gel for packaging the high-voltage power device is cured, the adhesion strength is above 0.1 MPa when tested according to standard GB / T 13936-2014.

[0016] Thirdly, the present invention provides an application of silicone gel for high-voltage power device packaging in the packaging of high-voltage power devices.

[0017] The beneficial effects of this invention are as follows: (1) This invention uses vinylphenyl silicone oil as a matrix. By introducing phenyl into the silicone gel, a low content of phenyl is introduced into the side chain of the silicone gel at the intrinsic structural level to improve adhesion. When vinylphenyl silicone oil is crosslinked with side-chain hydrogen-containing methyl silicone oil and terminal hydrogen-containing methyl silicone oil, a more uniform and dense three-dimensional network structure can be constructed. Not only is the mechanical property stable, but the distribution of phenyl at the interface is also more uniform and consistent, avoiding the migration, precipitation or agglomeration problems caused by poor compatibility of small molecule adhesion promoters. Furthermore, by introducing coupling agents or MQ hydrogen-containing silicone resin to synergistically regulate the network structure, the adhesion strength of the prepared silicone gel can stably reach above 0.1 MPa, and the hardness is moderate.

[0018] (2) The high-voltage power device packaging silicone gel of the present invention ensures the three-dimensional structure and high electric field resistance required for device packaging, and the phenyl content is below 30%, which can effectively prevent the insulation performance from being reduced due to high phenyl content. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the method steps of the present invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0022] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this invention are all commercially available, and their specific specifications and sources are as follows: Hydrogen-terminated methyl silicone oil: viscosity 800~1000mPa·s, hydrogen-terminated content (mass fraction) 0.03% and 0.07% respectively, purchased from Shandong Dayi Chemical Co., Ltd.

[0023] Side-chain hydrogen-containing methyl silicone oil: viscosity is 800~1000mPa·s, side hydrogen content (mass fraction) includes specifications such as 0.01%, 0.05%, 0.08%, 0.1%, 0.18%, 0.3%, 0.35%, and 0.5%, purchased from Shandong Dayi Chemical Co., Ltd.

[0024] Platinum catalyst: Platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex (Karstedt catalyst) is used, wherein the platinum metal content is 2000-5000 ppm.

[0025] MQ hydrogen-containing silicone resin: purchased from Shandong Dayi Chemical Co., Ltd.

[0026] 1-Ethynyl-1-cyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, 2-methyl-3-butyn-2-ol: commercially available.

[0027] Coupling agents A-171, KH-570, KH-560, and KH-550: Commercially available.

[0028] It should be noted that the method for preparing vinyl phenyl silicone oil used in this invention is described in detail in the applicant's prior invention patent CN119219923A.

[0029] Example 1 A silicone gel for packaging high-voltage power devices, the silicone gel comprising the following raw materials in parts by weight: 100 parts vinylphenyl silicone oil, 0.01 parts 1-ethynyl-1-cyclohexanol, 0.7 parts side-chain hydrogen-containing methyl silicone oil, 4.9 parts terminal hydrogen-containing methyl silicone oil, 0.1 parts platinum catalyst, and 0.1 parts coupling agent A-171.

[0030] The vinyl phenyl silicone oil has a viscosity of 1000 mPa·s and a phenyl content of 10%.

[0031] A method for preparing the above-mentioned high-voltage power device packaging silicone gel includes the following steps: S1. Add 100 parts of vinylphenyl silicone oil to a container, add 0.01 parts of 1-ethynyl-1-cyclohexanol, put it in a mixer and stir for 2 minutes at a speed of 800 r / min until it is uniform. S2. Add 0.7 parts of side-chain hydrogen-containing methyl silicone oil with a mass fraction of 0.5% to the mixture obtained in step S1, and then add 4.9 parts of terminal hydrogen-containing methyl silicone oil with a mass fraction of 0.07%. Place the mixture in a mixer and stir for 2 minutes at a speed of 800 r / min until it is uniform. S3. Add 0.1 parts of coupling agent A-171 to the mixture obtained in step S2, put it in a mixer and stir for 2 minutes at a speed of 800 r / min until it is uniform. S4. Add 0.1 parts of platinum catalyst to the mixture obtained in step S3, and then put it into a mixer and stir for 3 minutes at a speed of 900 r / min until it is uniform. S5. The raw material obtained in step S4 is subjected to vacuum degassing treatment with a vacuum degree of -100kPa and a vacuum pumping time of 30min.

[0032] S6. The raw material after vacuum degassing is heated and cross-linked to cure. The curing temperature is 100℃ and the curing time is 2.5h to obtain the silicone gel for high voltage power device packaging.

[0033] Example 2 The composition and preparation method of the high-voltage power device packaging silicone gel described in this embodiment are the same as those in Example 1. The difference is that 0.1 parts of coupling agent A-171 added to the mixed system obtained in step S2 are replaced with 0.1 parts of MQ hydrogen-containing silicone resin.

[0034] Example 3 The composition and preparation method of the silicon gel for packaging high-voltage power devices described in this embodiment are the same as those in Example 1. The difference is that 0.5 parts of platinum catalyst are added in step S2.

[0035] Example 4 The composition and preparation method of the high-voltage power device packaging silicone gel described in this embodiment are the same as those in Embodiment 1. The difference is that in step S2, there are 0.9 parts of hydrogen-containing methyl silicone oil in the side chain and 5.0 parts of hydrogen-containing methyl silicone oil in the end.

[0036] Example 5 The composition and preparation method of the high-voltage power device packaging silicone gel described in this embodiment are the same as those in Embodiment 1. The difference is that in step S2, there are 2 parts of hydrogen-containing methyl silicone oil in the side chain and 9 parts of hydrogen-containing methyl silicone oil in the end.

[0037] Comparative Example 1 The composition and preparation method of the silicon gel for packaging high-voltage power devices described in Comparative Example 1 are the same as those in Example 1, except that 0.1 parts of coupling agent A-171 are not added to the mixed system obtained in step S2.

[0038] Comparative Example 2 The composition and preparation method of the high-voltage power device packaging silicone gel described in Comparative Example 2 are the same as those in Example 1, except that the phenyl content of the vinylphenyl silicone oil is 20%.

[0039] Comparative Example 3 The composition and preparation method of the high-voltage power device packaging silicone gel described in Comparative Example 3 are the same as those in Example 1, except that the phenyl content of the vinylphenyl silicone oil is 30%.

[0040] Comparative Example 4 The composition and preparation method of the high-voltage power device packaging silicone gel described in Comparative Example 4 are the same as those in Example 1, except that 100 parts of vinyl phenyl silicone oil are replaced with methyl vinyl silicone oil.

[0041] Comparative Example 5 Comparative Example 5 is the German Wacker 915HT commercial silicone gel.

[0042] Comparative Example 6 Comparative Example 6 is the Dow 3-4170 commercial silicone gel from the United States.

[0043] Performance testing: The high-voltage power device packaging silicone gels obtained in Examples 1-5 and Comparative Examples 1-6 were subjected to performance testing, which included the following: Test 1: Adhesion strength was tested according to standard GB / T 13936-2014.

[0044] Test 2: Hardness was tested according to GB / T 39693.4-2025 standard.

[0045] The performance test results are shown in Table 1: Table 1 Performance Test Results

[0046] As shown in Table 1, the adhesion strength of the silicone gels prepared in Examples 1-5 of this invention is significantly higher than 0.16 MPa, reaching a maximum of 0.2105 MPa (Example 5). Compared with the commercial products of Comparative Examples 5 and 6, the adhesion performance is improved by 5-10 times. This demonstrates that by adjusting the intrinsic molecular structure, introducing phenyl units, and optimizing the hydrogen-containing crosslinking network, the problem of weak adhesion of traditional silicone gels can be effectively solved.

[0047] Comparing the data from Example 1 and Example 2, it can be seen that after adding MQ hydrogen-containing silicone resin, the adhesion strength increased from 0.1664 MPa to 0.1825 MPa, while the hardness decreased from 12.5 gf to 11.2 gf. This indicates that the MQ resin with a specific structure not only plays a role in increasing adhesion due to steric hindrance in the system, but also achieves material softening by changing the topology of the crosslinked network.

[0048] The data in Table 1 for Examples 1, 4, and 5 show that as the ratio of side chains to end-hydrogen-containing methyl silicone oil is optimized, the hardness of the material gradually decreases, demonstrating good flexibility. Particularly noteworthy is Example 5, which maintains extremely low hardness (9.2 gf) while still possessing excellent adhesion strength (0.2105 MPa), achieving an effective synergy between flexibility and high adhesion. This effectively overcomes the problem of significantly increased material hardness caused by increased phenyl content in Comparative Examples 2 and 3 (e.g., the hardness of Comparative Example 3 reaches 20.4 gf), ensuring its ideal deformation range required in the packaging of high-voltage power devices.

[0049] By comparing the data from Examples 1, 4, and 5, it can be observed that with the optimization of the ratio of side chains to end-hydrogen-containing methyl silicone oil, the material as a whole exhibits a gradual softening trend. In particular, Example 5, while maintaining extremely low hardness (9.2 gf), still possesses excellent adhesion strength, achieving a synergistic improvement in mechanical properties and effectively solving the problem of a significant increase in hardness caused by increasing the phenyl content in Comparative Examples 2 and 3.

[0050] The adhesion strength of Comparative Example 1 (without coupling agent) decreased significantly, which fully demonstrates the key role of chemical bonding in the interface layer; while the data of Comparative Example 4 (without phenyl structure) shows that it is difficult to achieve the adhesion strength requirements of high voltage devices by relying solely on the methyl silicone oil system.

[0051] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A silicone gel for packaging high-voltage power devices, characterized in that, The silicone gel comprises the following raw materials in parts by weight: 100 parts vinylphenyl silicone oil, 0.01-0.5 parts inhibitor, 0.7-2 parts side-chain hydrogen-containing methyl silicone oil, 0.1-9 parts terminal hydrogen-containing methyl silicone oil, 0.1-1 parts catalyst, and one of coupling agent or MQ hydrogen-containing silicone resin, wherein the coupling agent is 0.1-9 parts and the MQ hydrogen-containing silicone resin is 0.1-5 parts; The vinylphenyl silicone oil has a viscosity of 500-2000 mPa·s and a phenyl content of 1-30%.

2. The silicon gel for packaging high-voltage power devices as described in claim 1, characterized in that, The inhibitor is one of 1-ethynyl-1-cyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, 2-methyl-3-butyn-2-ol, and methylvinylcyclotetrasiloxane.

3. The silicon gel for packaging high-voltage power devices as described in claim 1, characterized in that, The coupling agent is one or more of vinyltrimethoxysilane A-171, methacryloyloxypropyltrimethoxysilane KH-570, γ-glycidyl etheroxypropyltrimethoxysilane KH-560, and aminopropyltriethoxysilane KH-550.

4. The silicon gel for packaging high-voltage power devices as described in claim 1, characterized in that, The catalyst is a platinum catalyst with a platinum content of 2000-5000 ppm.

5. A method for preparing a silicon gel for packaging high-voltage power devices as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Add vinyl phenyl silicone oil to a container, add the inhibitor, and stir well; S2. Add side-chain hydrogen-containing methyl silicone oil and terminal hydrogen-containing methyl silicone oil sequentially to the mixture obtained in step S1, and stir until homogeneous; S3. Add one of the coupling agent or MQ hydrogen-containing silicone resin to the mixture obtained in step S2, and stir until uniform. S4. Add the catalyst to the mixture obtained in step S3 and stir until homogeneous; S5. Perform vacuum degassing treatment on the raw material obtained in step S4; S6. The raw material after vacuum degassing is heated and cross-linked to obtain the silicone gel for packaging high-voltage power devices.

6. The method for preparing silicon gel for high-voltage power device packaging as described in claim 5, characterized in that, In step S5, the vacuum degassing process uses a vacuum degree of -100 kPa and a vacuum pumping time of 30-40 min.

7. The method for preparing silicon gel for high-voltage power device packaging as described in claim 5, characterized in that, In step S6, the curing temperature is 100-120℃ and the curing time is 1.5h-2.5h.

8. The method for preparing the silicon gel for packaging high-voltage power devices as described in claim 5, characterized in that, After the silicone gel used for packaging the high-voltage power device is cured, the adhesion strength is above 0.1 MPa when tested according to standard GB / T 13936-2014.

9. The application of a high-voltage power device packaging silicone gel as described in any one of claims 1-4 in the packaging of high-voltage power devices.

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