Epoxy resin composition for packaging thin-film capacitor and preparation method of epoxy resin composition

Abstract

The invention belongs to the technical field of capacitors, and particularly relates to an epoxy resin composition for packaging a thin-film capacitor and a preparation method of the epoxy resin composition. The epoxy resin composition for packaging the thin film capacitor comprises a component A and a component B, the mass ratio of the component A to the component B is 1: (0.8-1); the component A is prepared from the following raw materials in parts by weight: 30 to 35 parts of epoxy resin, 1 to 5 parts of toughening agent, 10 to 20 parts of filler, 20 to 30 parts of flame retardant, 1 to 3 parts of flatting agent, 1 to 3 parts of flatting aid, 0.2 to 0.4 part of wear-resistant agent and 0.6 to 0.8 part of pigment; the component B comprises the following raw materials in parts by weight: 5-10 parts of a curing agent and 0.1-0.3 part of an accelerant. The composition has the advantages of excellent heat-conducting property, excellent cracking resistance, high toughness and mechanical strength.

Description

Technical Field

[0001] This invention belongs to the field of capacitor technology, specifically relating to an epoxy resin composition for encapsulating thin-film capacitors and its preparation method. Background Technology

[0002] With the rapid development of power electronics technology towards higher frequencies, greater integration, and higher power, film capacitors, as key passive components, play an irreplaceable role in fields such as electric drive systems for new energy vehicles, photovoltaic / wind power inverters, rail transit, and smart grids. Their core functions include efficient energy buffering, DC support, and noise filtering, and their operating environment often involves high voltage, high current, and frequent thermal cycling. Against this backdrop, encapsulation materials have evolved from simple physical protective layers to core factors determining the overall performance, reliability, and lifespan of capacitors. Epoxy resin, due to its excellent electrical insulation, good bonding strength, mature processability, and controllable cost, has become the mainstream material for film capacitor encapsulation. However, the inherent performance limitations of traditional epoxy resin systems are increasingly becoming a bottleneck restricting breakthroughs in high-end film capacitor technology.

[0003] The current technical challenge lies in the fact that thermal conductivity, toughness, and crack resistance are often mutually restrictive. While increasing thermal conductivity often involves the extensive use of inorganic fillers, this can lead to a surge in system viscosity, poor processability, and may compromise toughness and crack resistance due to filler agglomeration or weakened interfacial bonding. Conversely, simply toughening may sacrifice material stiffness, heat resistance, and thermal conductivity. Therefore, the forefront of research and innovation in this field focuses on how to overcome the "seesaw" effect between properties through sophisticated molecular structure design, surface functionalization of fillers, synergistic construction of multi-scale composite systems, and precise control of the curing process, achieving a unified balance between high thermal conductivity, high toughness, and strong crack resistance in epoxy resin encapsulation materials. Based on the above, this invention provides an epoxy resin encapsulation material that combines excellent thermal conductivity, superior crack resistance, and high toughness. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the first objective of the present invention is to provide an epoxy resin composition for encapsulating thin-film capacitors, which has excellent thermal conductivity, excellent crack resistance and high toughness.

[0005] The second objective of this invention is to provide a method for preparing an epoxy resin composition for encapsulating thin-film capacitors, which is simple to operate.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An epoxy resin composition for encapsulating thin-film capacitors includes component A and component B; the mass ratio of component A to component B is 1:(0.8-1). By weight, component A comprises the following raw materials: 30-35 parts epoxy resin, 1-5 parts toughening agent, 10-20 parts filler, 20-30 parts flame retardant, 1-3 parts leveling agent, 1-3 parts leveling aid, 0.2-0.4 parts abrasion resistant agent, and 0.6-0.8 parts pigment; By weight, component B comprises the following raw materials: 5-10 parts of curing agent and 0.1-0.3 parts of accelerator.

[0007] Furthermore, the preparation process of the toughening agent in component A is as follows: (1) After cleaning the carbon fiber, add it to the glutaric acid solution, heat and stir to react, then wash and dry to obtain activated carbon fiber; (2) Take the activated carbon fiber from step (1) and add it to a dimethyl sulfoxide solution of diammonium glycyrrhizate. Then add N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine, heat and react. After the reaction is completed, filter with ethanol and water in sequence, and dry to obtain the toughening agent.

[0008] Furthermore, in step (1), the mass ratio of carbon fiber to glutaric acid is 1:(10-12); the concentration of the glutaric acid solution is 15-20wt%; and the temperature of the heating and stirring reaction is 50-60℃, and the time is 1-3h.

[0009] Furthermore, in step (2), the mass ratio of activated carbon fiber, diammonium glycyrrhizate, N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 1:(1-5):(6-12):(1-2); the concentration of diammonium glycyrrhizate in dimethyl sulfoxide solution is 10-15wt%; the heating reaction temperature is 55-65℃, and the time is 5-8h.

[0010] Furthermore, the preparation process of the filler is as follows: Alumina was added to an aqueous ethanol solution, followed by the addition of silane coupling agent and polyvinyl alcohol microspheres. After stirring, the mixture was filtered, dried, and calcined to obtain the filler.

[0011] Furthermore, the mass ratio of the alumina, ethanol aqueous solution, silane coupling agent, and polyvinyl alcohol microspheres is 1:(9-12):(0.2-0.5):(0.5-1); the silane coupling agent is KH560.

[0012] Furthermore, the stirring temperature is 40-50℃ and the time is 1-2h; the calcination temperature is 300-350℃ and the time is 1-1.5h.

[0013] Furthermore, the flame retardant in component A is aluminum hydroxide; the leveling agent is leveling agent 503; the leveling aid is hydrogenated castor oil; the abrasion resistant agent is polyethylene wax; and the pigment is composed of iron oxide red 130, titanium dioxide, and ruby ​​red BK in a mass ratio of 1:1:0.27.

[0014] Furthermore, the curing agent in component B is phenolic resin 8012; the accelerator is composed of triphenylphosphine and dimethylimidazole in a mass ratio of 1:2.4.

[0015] The method for preparing the epoxy resin composition for encapsulating the above-mentioned thin-film capacitor includes the following steps: S1. According to the stated weight parts, the epoxy resin, leveling agent, leveling aid, abrasion resistant agent and pigment in component A are mixed evenly, and then toughening agent, filler and flame retardant are added. After mixing evenly, component A is obtained. S2. Mix the raw materials evenly according to the stated weight proportions to obtain component B; S3. Mix component A and component B evenly according to the stated mass ratio.

[0016] The beneficial technical effects of this invention are as follows: 1. The epoxy resin composition for encapsulating thin-film capacitors provided by the present invention has excellent thermal conductivity, excellent crack resistance, high toughness and mechanical strength.

[0017] 2. The addition of the toughening agent in this invention enhances the impact resistance and mechanical strength of the material. Specifically, carbon fibers are activated by glutaric acid treatment to introduce carboxyl groups, which then undergo esterification with the hydroxyl groups in diammonium glycyrrhizate molecules under the action of a catalyst, firmly grafting diammonium glycyrrhizate onto the carbon fiber surface. The diammonium glycyrrhizate molecules on the carbon fiber surface contain a large number of hydroxyl groups, which can undergo ring-opening reactions with the epoxy groups of epoxy resin, improving the interfacial compatibility between carbon fibers and epoxy resin. Diammonium glycyrrhizate is a flexible glycoside macromolecule, which forms a flexible transition layer on the carbon fiber surface after grafting. When the encapsulation material is subjected to external impact, the flexible long chains can absorb impact energy through curling deformation, alleviate interfacial stress concentration, effectively inhibit the formation and propagation of microcracks in the epoxy resin matrix, improve the impact resistance of the encapsulation material, and enhance its toughness.

[0018] 3. The addition of filler in this invention enhances the thermal conductivity, mechanical strength, and heat resistance of the material. Specifically, alumina is modified with a silane coupling agent and polyvinyl alcohol microspheres, followed by calcination. The polyvinyl alcohol microspheres undergo thermal decomposition and complete carbonization, leaving abundant pores, but without disrupting the chemical bonds formed by the silane coupling agent on the alumina surface. This yields a filler with an active silane layer and a porous structure. The silane coupling agent on the filler surface can form a strong covalent bond interface with the epoxy resin, improving the filler's dispersibility and interfacial bonding. The porous structure increases the contact area between the filler and the epoxy resin matrix, while simultaneously improving the heat resistance and thermal conductivity of the encapsulation material. Attached Figure Description

[0019] Figure 1 This is a SEM image of the toughening agent obtained in Example 1 of the present invention; Figure 2 This is a SEM image of the packing material obtained in Example 1 of the present invention. Detailed Implementation

[0020] The following is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all reagents or instruments used are conventional products obtained through commercial channels.

[0021] In component A of this invention, the flame retardant is aluminum hydroxide 1250 mesh; the leveling agent is leveling agent 503; the leveling aid is hydrogenated castor oil; the abrasion resistant agent is polyethylene wax; and the pigment is composed of iron oxide red 130, titanium dioxide, and ruby ​​red BK in a mass ratio of 1:1:0.27. In component B, the curing agent is phenolic resin 8012; the accelerator consists of triphenylphosphine and dimethylimidazole in a mass ratio of 1:2.4.

[0022] (I) Implementation Examples Example 1

[0023] This embodiment provides an epoxy resin composition for encapsulating thin-film capacitors, comprising component A and component B; the mass ratio of component A to component B is 1:0.9; By weight, component A comprises the following raw materials: 32 parts epoxy resin, 4 parts toughening agent, 16 parts filler, 23 parts flame retardant, 2 parts leveling agent, 2 parts leveling aid, 0.3 parts abrasion resistant agent, and 0.7 parts pigment; By weight, component B comprises the following raw materials: 8 parts curing agent and 0.2 parts accelerator.

[0024] The toughening agent is prepared as follows: (1) With a mass ratio of carbon fiber to glutaric acid of 1:11, the carbon fiber was washed and added to a glutaric acid solution with a concentration of 18wt%. The mixture was heated and stirred at 55°C for 2 hours. After the reaction was completed, the carbon fiber was washed and dried to obtain activated carbon fiber. (2) With the mass ratio of activated carbon fiber, diammonium glycyrrhizate, DCC, and DMAP being 1:4:7:1.5, the activated carbon fiber from step (1) was added to a 13wt% diammonium glycyrrhizate dimethyl sulfoxide solution, followed by the addition of N,N'-dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP). The reaction was carried out at 60°C for 7 hours. After the reaction was completed, the mixture was filtered through ethanol and water sequentially, and dried to obtain the toughening agent. The SEM image of the toughening agent is shown below. Figure 1 As shown.

[0025] The preparation process of the filler is as follows: Alumina, ethanol aqueous solution, silane coupling agent, and polyvinyl alcohol microspheres were mixed in a mass ratio of 1:10:0.4:0.7. Alumina was added to a 95wt% ethanol aqueous solution, followed by the addition of KH560 and polyvinyl alcohol microspheres. The mixture was stirred for 1 hour, filtered, dried at 150℃ for 1 hour, and then calcined at 320℃ for 1.2 hours to obtain the filler. The SEM image of the filler is shown below. Figure 2 As shown.

[0026] This embodiment also provides a method for preparing the above-mentioned epoxy resin composition for encapsulating thin-film capacitors, comprising the following steps: S1. According to the stated weight parts, the epoxy resin, leveling agent, leveling aid, abrasion resistant agent and pigment in component A are mixed evenly, and then toughening agent, filler and flame retardant are added. After mixing evenly, component A is obtained. S2. Mix the raw materials evenly according to the stated weight proportions to obtain component B; S3. Mix component A and component B evenly according to the stated mass ratio. Example 2

[0027] This embodiment provides an epoxy resin composition for encapsulating thin-film capacitors, comprising component A and component B; the mass ratio of component A to component B is 1:0.8; By weight, component A comprises the following raw materials: 30 parts epoxy resin, 1 part toughening agent, 10 parts filler, 20 parts flame retardant, 1 part leveling agent, 1 part leveling aid, 0.2 parts abrasion resistant agent, and 0.6 parts pigment. By weight, component B comprises the following raw materials: 5 parts curing agent and 0.1 parts accelerator.

[0028] The toughening agent is prepared as follows: (1) With a mass ratio of carbon fiber to glutaric acid of 1:10, the carbon fiber was washed and added to a glutaric acid solution with a concentration of 15wt%. The mixture was heated and stirred at 50°C for 3 hours. After the reaction was completed, the carbon fiber was washed and dried to obtain activated carbon fiber. (2) With the mass ratio of activated carbon fiber, diammonium glycyrrhizate, DCC and DMAP as 1:1:6:1, take the activated carbon fiber from step (1) and add it to a 10wt% diammonium glycyrrhizate dimethyl sulfoxide solution, then add DCC and DMAP, react at 55℃ for 8h, filter with ethanol and water in sequence after the reaction is completed, and dry to obtain the toughening agent.

[0029] The preparation process of the filler is as follows: The filler was prepared by adding alumina, ethanol aqueous solution, silane coupling agent and polyvinyl alcohol microspheres in a mass ratio of 1:9:0.2:0.5. Alumina was added to a 95wt% ethanol aqueous solution, KH560 and polyvinyl alcohol microspheres were added and stirred for 1 hour. After filtration, the mixture was dried at 150℃ for 1 hour and then calcined at 300℃ for 1.5 hours to obtain the filler.

[0030] This embodiment also provides a method for preparing the above-mentioned epoxy resin composition for encapsulating thin-film capacitors, comprising the following steps: S1. According to the stated weight parts, the epoxy resin, leveling agent, leveling aid, abrasion resistant agent and pigment in component A are mixed evenly, and then toughening agent, filler and flame retardant are added. After mixing evenly, component A is obtained. S2. Mix the raw materials evenly according to the stated weight proportions to obtain component B; S3. Mix component A and component B evenly according to the stated mass ratio. Example 3

[0031] This embodiment provides an epoxy resin composition for encapsulating thin-film capacitors, comprising component A and component B; the mass ratio of component A to component B is 1:1. By weight, component A comprises the following raw materials: 35 parts epoxy resin, 5 parts toughening agent, 20 parts filler, 30 parts flame retardant, 3 parts leveling agent, 3 parts leveling aid, 0.4 parts abrasion resistant agent, and 0.8 parts pigment; By weight, component B comprises the following raw materials: 10 parts curing agent and 0.3 parts accelerator.

[0032] The toughening agent is prepared as follows: (1) With a mass ratio of carbon fiber to glutaric acid of 1:12, the carbon fiber was washed and added to a glutaric acid solution with a concentration of 20wt%. The mixture was heated and stirred at 60°C for 1 hour. After the reaction was completed, the carbon fiber was washed and dried to obtain activated carbon fiber. (2) With the mass ratio of activated carbon fiber, diammonium glycyrrhizate, DCC and DMAP as 1:5:12:2, take the activated carbon fiber from step (1) and add it to a 15wt% diammonium glycyrrhizate dimethyl sulfoxide solution, then add DCC and DMAP, react at 65℃ for 5h, filter with ethanol and water in sequence after the reaction is completed, and dry to obtain the toughening agent.

[0033] The preparation process of the filler is as follows: The filler was prepared by adding alumina, ethanol aqueous solution, silane coupling agent and polyvinyl alcohol microspheres in a mass ratio of 1:12:0.5:1 to a 95wt% ethanol aqueous solution, then adding KH560 and polyvinyl alcohol microspheres and stirring for 1 hour. After filtration, the filler was dried at 150℃ for 1 hour and then calcined at 350℃ for 1 hour.

[0034] This embodiment also provides a method for preparing the above-mentioned epoxy resin composition for encapsulating thin-film capacitors, comprising the following steps: S1. According to the stated weight parts, the epoxy resin, leveling agent, leveling aid, abrasion resistant agent and pigment in component A are mixed evenly, and then toughening agent, filler and flame retardant are added. After mixing evenly, component A is obtained. S2. Mix the raw materials evenly according to the stated weight proportions to obtain component B; S3. Mix component A and component B evenly according to the stated mass ratio.

[0035] (ii) Comparative Example Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that activated carbon fiber is used instead of the toughening agent in component A, and the preparation method of activated carbon fiber is the same as in Example 1.

[0036] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that alumina is used instead of the filler in component A.

[0037] The epoxy resin compositions prepared in the embodiments and comparative examples of the present invention were cured at 85°C for 30 min and then cured at 105°C for 120 min before performance testing, as detailed in Table 1.

[0038] Table 1 As shown in Table 1, the material obtained in Comparative Example 1 has lower impact strength and poorer mechanical strength compared to Example 1. These results indicate that the addition of the toughening agent enhances the material's impact resistance and mechanical strength. Specifically, carbon fibers are activated by glutaric acid treatment, introducing carboxyl groups. Then, under the action of a catalyst, these carboxyl groups undergo an esterification reaction with the hydroxyl groups in diammonium glycyrrhizate molecules, firmly grafting diammonium glycyrrhizate onto the carbon fiber surface. The diammonium glycyrrhizate molecules on the carbon fiber surface contain a large number of hydroxyl groups, which can undergo ring-opening reactions with the epoxy groups of the epoxy resin, improving the interfacial compatibility between the carbon fiber and the epoxy resin. Diammonium glycyrrhizate is a flexible glycoside macromolecule; after grafting, it forms a flexible transition layer on the carbon fiber surface. When the encapsulation material is subjected to external impact, the flexible long chains can absorb impact energy through curling deformation, alleviating interfacial stress concentration, effectively inhibiting the formation and propagation of microcracks in the epoxy resin matrix, improving the impact resistance and toughness of the encapsulation material.

[0039] As shown in Table 1, compared to Example 1, the material obtained in Comparative Example 2 has a lower thermal conductivity and poorer mechanical strength and heat resistance. These results indicate that the addition of filler enhances the thermal conductivity, mechanical strength, and heat resistance of the material. Specifically, alumina was modified with a silane coupling agent and polyvinyl alcohol microspheres and then calcined. The polyvinyl alcohol microspheres underwent thermal decomposition and complete carbonization, leaving abundant pores, but without disrupting the chemical bonds formed by the silane coupling agent on the alumina surface. This resulted in a filler with an active silane layer and a porous structure. The silane coupling agent on the filler surface can form a strong covalent bond interface with the epoxy resin, improving the filler's dispersibility and interfacial bonding. The porous structure increases the contact area between the filler and the epoxy resin matrix, while simultaneously improving the heat resistance and thermal conductivity of the encapsulation material.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. An epoxy resin composition for encapsulating thin-film capacitors, characterized in that, It includes component A and component B; the mass ratio of component A to component B is 1:(0.8-1); By weight, component A comprises the following raw materials: 30-35 parts epoxy resin, 1-5 parts toughening agent, 10-20 parts filler, 20-30 parts flame retardant, 1-3 parts leveling agent, 1-3 parts leveling aid, 0.2-0.4 parts abrasion resistant agent, and 0.6-0.8 parts pigment; By weight, component B comprises the following raw materials: 5-10 parts of curing agent and 0.1-0.3 parts of accelerator.

2. The epoxy resin composition for encapsulating thin-film capacitors according to claim 1, characterized in that, The preparation process of the toughening agent in component A is as follows: (1) After cleaning the carbon fiber, add it to the glutaric acid solution, heat and stir to react, then wash and dry to obtain activated carbon fiber; (2) Take the activated carbon fiber from step (1) and add it to a dimethyl sulfoxide solution of diammonium glycyrrhizate. Then add N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine, heat and react. After the reaction is completed, filter with ethanol and water in sequence, and dry to obtain the toughening agent.

3. The epoxy resin composition for encapsulating thin-film capacitors according to claim 2, characterized in that, In step (1), the mass ratio of carbon fiber to glutaric acid is 1:(10-12); the concentration of the glutaric acid solution is 15-20wt%; the temperature of the heating and stirring reaction is 50-60℃, and the time is 1-3h.

4. The epoxy resin composition for encapsulating thin-film capacitors according to claim 2, characterized in that, In step (2), the mass ratio of activated carbon fiber, diammonium glycyrrhizate, N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 1:(1-5):(6-12):(1-2); the concentration of diammonium glycyrrhizate in dimethyl sulfoxide solution is 10-15wt%; the heating reaction temperature is 55-65℃ and the time is 5-8h.

5. The epoxy resin composition for encapsulating thin-film capacitors according to claim 1, characterized in that, The preparation process of the filler is as follows: Alumina was added to an aqueous ethanol solution, followed by the addition of silane coupling agent and polyvinyl alcohol microspheres. After stirring, the mixture was filtered, dried, and calcined to obtain the filler.

6. The epoxy resin composition for encapsulating a thin-film capacitor according to claim 5, characterized in that, The mass ratio of alumina, aqueous ethanol solution, silane coupling agent, and polyvinyl alcohol microspheres is 1:(9-12):(0.2-0.5):(0.5-1); the silane coupling agent is KH560.

7. The epoxy resin composition for encapsulating a thin-film capacitor according to claim 5, characterized in that, The stirring temperature is 40-50℃ and the time is 1-2h; the calcination temperature is 300-350℃ and the time is 1-1.5h.

8. The epoxy resin composition for encapsulating thin-film capacitors according to claim 1, characterized in that, The flame retardant in component A is aluminum hydroxide; the leveling agent is leveling agent 503; the leveling aid is hydrogenated castor oil; the abrasion resistant agent is polyethylene wax; and the pigment is composed of iron oxide red 130, titanium dioxide, and ruby ​​red BK in a mass ratio of 1:1:0.

27.

9. The epoxy resin composition for encapsulating a thin-film capacitor according to claim 1, characterized in that, The curing agent in component B is phenolic resin 8012; the accelerator is composed of triphenylphosphine and dimethylimidazole in a mass ratio of 1:2.

4.

10. A method for preparing an epoxy resin composition for encapsulating a thin-film capacitor according to any one of claims 1-9, characterized in that, Includes the following steps: S1. According to the stated weight parts, the epoxy resin, leveling agent, leveling aid, abrasion resistant agent and pigment in component A are mixed evenly, and then toughening agent, filler and flame retardant are added. After mixing evenly, component A is obtained. S2. Mix the raw materials evenly according to the stated weight proportions to obtain component B; S3. Mix component A and component B evenly according to the stated mass ratio.

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