A thermally conductive epoxy film and its preparation method

Abstract

This invention relates to a thermally conductive epoxy film and its preparation method. The thermally conductive epoxy film comprises the following components: 10-12 parts epoxy resin, 5-12 parts curing agent, 0.015-0.11 parts accelerator, 28-80 parts inorganic filler, 0.1-0.5 parts pigment, 0.4-1 part coupling agent, and 0.3-1.2 parts toughening agent; the inorganic filler is silica powder, including silica powder with a particle size of 2 μm, 0.5 μm, and 4 μm. The preparation method includes step S1, mixing; and step S2, coating. Step S3, surface drying; Step S4, lamination. The advantage lies in the combination of epoxy resin, phenolic curing agent, imidazole accelerator, silica powder, pigment, coupling agent, and toughening agent. It is prepared through mixing, stirring, degassing, coating, solvent removal, and lamination steps, which improves the production efficiency of epoxy film, reduces the maximum baking temperature of coating oven, broadens the technical indicators of epoxy film, prolongs room temperature storage stability, improves thermal conductivity, improves dimensional stability during use, enhances the bonding force with copper materials, and improves the performance of the product.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin film preparation technology, and in particular to a thermally conductive epoxy film and its preparation method. Background Technology

[0002] In modern electronic packaging technology, epoxy films are widely used in the packaging of various electronic components due to their excellent adhesion, electrical properties, and chemical stability. However, with the development of electronic devices towards miniaturization, high integration, and high frequency, higher requirements are placed on the performance of epoxy films, such as good adhesion, low coefficient of thermal expansion, and high glass transition temperature. During the use of epoxy films, the defoaming effect and the overflow rate of the adhesive layer are also important factors affecting the success rate of molding.

[0003] However, in the existing epoxy film preparation process, the solvent evaporation rate is slow, and high-boiling-point solvents have good film-forming effect, but the oven temperature required for solvent removal is high and the coating production efficiency is low. During the hot pressing process of epoxy film, the defoaming effect is poor, and the glue layer overflow rate is large after lamination, resulting in insufficient thickness and uneven film surface, which affects the performance of the film after curing. As a result, it is necessary to raise the temperature from low temperature to high temperature for additional defoaming, which affects the production efficiency of the application end.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention discloses a thermally conductive epoxy film and its preparation method.

[0006] The technical solution adopted in this invention is as follows:

[0007] A thermally conductive epoxy film comprising, by weight:

[0008] The composition includes 10-12 parts epoxy resin, 5-12 parts curing agent, 0.015-0.11 parts accelerator, 28-80 parts inorganic filler, 0.1-0.5 parts pigment, 0.4-1 part coupling agent, and 0.3-1.2 parts toughening agent; the inorganic filler is silicon micro powder, which includes silicon micro powder with a particle size of 2 μm, silicon micro powder with a particle size of 0.5 μm, and silicon micro powder with a particle size of 4 μm.

[0009] Furthermore, the proportion of the 2µm silicon micropowder in the inorganic filler ranges from 5% to 30%, the proportion of the 0.5µm silicon micropowder in the inorganic filler ranges from 15% to 18.75%, and the proportion of the 4µm silicon micropowder in the inorganic filler ranges from 60% to 75%.

[0010] Furthermore, the epoxy resin includes phenolic epoxy resin, biphenyl-type epoxy resin, naphthol-type epoxy resin, dicyclopentadiene-type epoxy resin, and combinations thereof.

[0011] Furthermore, the curing agent includes a phenolic curing agent.

[0012] Furthermore, the accelerator includes imidazole accelerators.

[0013] Furthermore, the toughening agent includes a core-shell toughening agent.

[0014] Furthermore, the coupling agent includes a silane coupling agent.

[0015] Furthermore, the pigment includes carbon black.

[0016] A method for preparing a thermally conductive epoxy film includes the following steps:

[0017] Step S1, Mixing: Place epoxy resin, curing agent, solvent, and toughening agent into a mixer and stir until the resin is fully dissolved and mixed evenly to obtain a resin mixture; place inorganic filler, pigment, coupling agent, and toughening agent into a mixer and stir until the mixture is fully mixed to obtain modified pigments and fillers; add the modified pigments and fillers into the resin mixture, stir, and then disperse by three-roll milling; then add accelerator, and the mixture is vacuum degassed to finally obtain a resin composition;

[0018] Step S2: Coat the resin composition onto the base film;

[0019] Step S3, surface drying: the base film undergoes stepwise solvent removal and is heated in three stages to obtain an epoxy resin film.

[0020] Step S4: Composite the epoxy resin film and the protective film together, and finally roll them up.

[0021] Furthermore, in step S1, the epoxy resin, curing agent, solvent, and toughening agent are mixed at a stirring speed of 300 rpm-500 rpm for 30 min; the inorganic filler, pigment, coupling agent, and toughening agent are mixed at a stirring temperature of 120℃ for 1 h and a stirring speed of 800 rpm-1000 rpm; the modified pigment, filler, and resin mixture is mixed at a stirring speed of 600 rpm-800 rpm for 60 min; the three-roll mill dispersion has a feed gap of 50 μm and a discharge gap of 30 μm; the vacuum degassing speed is 400 rpm-600 rpm for 6 min-8 min.

[0022] Furthermore, in step S3, the first step temperature range is 40–60°C, the second step temperature range is 80–95°C, and the third step temperature range is 70–80°C.

[0023] Furthermore, in step S4, the composite temperature range is 80–110°C.

[0024] The beneficial effects of this invention are as follows:

[0025] 1. The epoxy film is prepared by mixing, stirring, degassing, coating, solvent removal, and compounding raw materials such as epoxy resin, phenolic curing agent, imidazole accelerator, silica powder, pigment, coupling agent, and toughening agent. Different particle size filler combinations are introduced to improve the thermal conductivity of the epoxy film, reduce the coefficient of thermal expansion, and improve its dimensional stability. The film has good stability, adhesion and surface roughness. After the film is applied, the film surface is flat, the glue overflow rate is small, and the film surface has a matte finish, which is beneficial for copper plating and copper cladding.

[0026] 2. 2µm silica powder is used as a filler, in combination with 0.5µm and 4µm fillers, to improve the surface roughness of the epoxy film after film formation, improve coating and baking efficiency, and make the solvent evaporation rate of the film fast during the preparation process, meeting the production needs of large-width films and greatly improving production efficiency.

[0027] 3. Optimize the process window and widen the residual solvent tolerance of the finished product. Ensure that all components are fully dissolved, that fillers are evenly packed and filled to different depths in the resin, and reduce the impact of residual solvent in the film on surface dryness.

[0028] 4. Baking the film with a high-boiling-point solvent at a relatively low temperature reduces the degree of semi-curing reaction, which helps to extend the gel time of the film. This not only keeps the film in a soft state but also extends the room temperature storage stability of the film.

[0029] 5. Hot pressing is performed within the appropriate temperature window for the adhesive film, resulting in good air venting, low adhesive flow, and low overflow rate, which is beneficial for the flatness of the film surface. The film surface has a matte finish, which is conducive to copper plating and copper cladding, improves the adhesion to metals / non-metals, and enhances the performance of the product.

[0030] 6. 2µm silica powder is used as a filler, which is combined with 0.5µm and 4µm fillers to fill the heat conduction channels and improve the thermal conductivity of the cured film. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the appearance after baking at 150°C for 30 minutes to show the natural fit of Example 1.

[0032] Figure 2 This is a schematic diagram of the appearance after baking at 150°C for 30 minutes to show the natural fit of Example 2.

[0033] Figure 3This is a schematic diagram of the appearance after baking at 150°C for 30 minutes to show the natural fit of Example 3.

[0034] Figure 4 This is a schematic diagram showing the appearance after baking at 150℃ for 30 minutes to ensure a natural fit, as shown in Comparative Example 1.

[0035] Figure 5 This is a schematic diagram showing the appearance of the product after baking at 150℃ for 30 minutes to ensure a natural fit, as shown in Comparative Example 2.

[0036] Figure 6 This is a schematic diagram showing the appearance of Comparative Example 3 after baking at 150℃ for 30 minutes to ensure natural adhesion.

[0037] Figure 7 This is a schematic diagram of the steps involved in making a thermally conductive epoxy film. Detailed Implementation

[0038] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0039] Example 1:

[0040] A thermally conductive epoxy film comprises 12 parts of phenolic epoxy resin, 6 parts of phenolic curing agent, 0.05 parts of imidazole accelerator, 80 parts of silica powder (using a combination of 20 parts with particle size of 2 μm, 12 parts with particle size of 0.5 μm, and 48 parts with particle size of 4 μm), 0.3 parts of pigment, 1 part of coupling agent, 0.5 parts of toughening agent, and 15 parts of butyl acetate.

[0041] The coupling agent is a silane coupling agent, the toughening agent is a core-shell toughening agent, and the pigment is carbon black.

[0042] Its preparation method, such as Figure 7 As shown, it includes the following steps:

[0043] Step S1, Mixing: Place the phenolic epoxy resin, phenolic curing agent, solvent, and toughening agent into a mixer, set the speed to 500 rpm, and the mixing time to 30 minutes to ensure the resin is fully dissolved and uniformly mixed. Mix the inorganic filler, pigment, coupling agent, and toughening agent uniformly using a planetary mixer, and modify by stirring at 120℃ for 1 hour. Using mechanical stirring, add the modified pigment and filler mixture to the resin curing agent mixture, adjust the speed to 800 rpm, and the mixing time to 60 minutes to ensure the silica powder is uniformly dispersed in the mixture. Perform three-roll milling dispersion with feed gaps of 50 μm and discharge gaps of 30 μm, and then with feed gaps of 30 μm and discharge gaps of 10 μm. Finally, add the accelerator and degas the mixture under vacuum for 8 minutes to remove air bubbles.

[0044] Step S2: Coat the resin composition onto the base film, controlling the dry adhesive thickness to be 130 μm.

[0045] Step S3, surface drying: The base film is baked at a stepped temperature, using a three-stage heating method to remove the solvent. First, it is heated at 40°C, then at 80°C, and finally at 70°C. The heating time is controlled at 10.5 minutes to form the epoxy resin film.

[0046] Step S4: Composite the epoxy resin film and the protective film at a temperature of 80℃ and a pressure of 2MPa, then rewind.

[0047] Example 2:

[0048] A thermally conductive epoxy film comprises 12 parts of phenolic epoxy resin, 6 parts of phenolic curing agent, 0.05 parts of imidazole accelerator, 80 parts of silica powder (using a combination of 2µm (10 parts) and 0.5µm (14 parts) and 4µm (56 parts) particle sizes), 0.3 parts of pigment, 1 part of coupling agent, 0.5 parts of toughening agent, and 15 parts of butyl acetate.

[0049] The coupling agent is a silane coupling agent, the toughening agent is a core-shell toughening agent, and the pigment is carbon black.

[0050] Its preparation method includes the following steps:

[0051] Step S1, Mixing: Place the phenolic epoxy resin, phenolic curing agent, solvent, and toughening agent into a mixer, set the speed to 500 rpm, and the mixing time to 30 minutes to ensure the resin is fully dissolved and uniformly mixed. Mix the inorganic filler, pigment, coupling agent, and toughening agent uniformly using a planetary mixer, and modify by stirring at 120℃ for 1 hour. Using mechanical stirring, add the modified pigment and filler mixture to the resin curing agent mixture, adjust the speed to 800 rpm, and the mixing time to 60 minutes to ensure the silica powder is uniformly dispersed in the mixture. Perform three-roll milling dispersion with feed gaps of 50 μm and discharge gaps of 30 μm, and then with feed gaps of 30 μm and discharge gaps of 10 μm. Finally, add the accelerator and degas the mixture under vacuum for 8 minutes to remove air bubbles.

[0052] Step S2: Coat the resin composition onto the base film, controlling the dry adhesive thickness to be 130 μm.

[0053] Step S3, surface drying: The base film is heated in a stepped manner, using a three-stage heating method to remove the solvent. First, it is heated at 50°C, then at 90°C, and finally at 70°C. The heating time is controlled at 14 minutes to form an epoxy resin film.

[0054] Step S4: Composite the epoxy resin film and the protective film at a temperature of 80℃ and a pressure of 2MPa, then rewind.

[0055] Example 3:

[0056] A thermally conductive epoxy film comprises 12 parts of phenolic epoxy resin, 6 parts of phenolic curing agent, 0.05 parts of imidazole accelerator, 80 parts of silica powder (5 parts with a particle size of 2 μm, 15 parts with a particle size of 0.5 μm, and 60 parts with a particle size of 4 μm), 0.3 parts of pigment, 1 part of coupling agent, 0.5 parts of toughening agent, and 15 parts of butyl acetate.

[0057] The coupling agent is a silane coupling agent, the toughening agent is a core-shell toughening agent, and the pigment is carbon black.

[0058] Its preparation method includes the following steps:

[0059] Step S1, Mixing: Place the phenolic epoxy resin, phenolic curing agent, solvent, and toughening agent into a mixer, set the speed to 500 rpm, and the mixing time to 30 minutes to ensure the resin is fully dissolved and uniformly mixed. Mix the inorganic filler, pigment, coupling agent, and toughening agent uniformly using a planetary mixer, and modify by stirring at 120℃ for 1 hour. Using mechanical stirring, add the modified pigment and filler mixture to the resin curing agent mixture, adjust the speed to 800 rpm, and the mixing time to 60 minutes to ensure the silica powder is uniformly dispersed in the mixture. Perform three-roll milling dispersion with feed gaps of 50 μm and discharge gaps of 30 μm, and then with feed gaps of 30 μm and discharge gaps of 10 μm. Finally, add the accelerator and degas the mixture under vacuum for 8 minutes to remove air bubbles.

[0060] Step S2: Coat the resin composition onto the base film, controlling the dry adhesive thickness to be 130 μm.

[0061] Step S3, surface drying: The base film is heated in a stepped manner, using a three-stage heating method to remove the solvent. First, it is heated at 60°C, then at 95°C, and finally at 80°C. The heating time is controlled at 17.5 minutes to form an epoxy resin film.

[0062] Step S4: Composite the epoxy resin film and the protective film at a temperature of 80℃ and a pressure of 2MPa, then rewind.

[0063] Example 4:

[0064] The difference from Example 1 is that the epoxy resin used is a biphenyl type epoxy resin.

[0065] The performance of the prepared product is similar to that of the product obtained in Example 1.

[0066] Example 5:

[0067] The difference from Example 1 is that the epoxy resin used is a naphthol-type epoxy resin.

[0068] The performance of the prepared product is similar to that of the product obtained in Example 1.

[0069] Example 6:

[0070] The difference from Example 1 is that the epoxy resin used is a dicyclopentadiene type epoxy resin.

[0071] The performance of the prepared product is similar to that of the product obtained in Example 1.

[0072] Example 7:

[0073] The difference from Example 1 is that it uses a combination of two or more of the following epoxy resins: phenolic epoxy resin, biphenyl epoxy resin, naphthol epoxy resin, and dicyclopentadiene epoxy resin.

[0074] The performance of the prepared product is similar to that of the product obtained in Example 1.

[0075] Comparative Example 1:

[0076] Raw materials include 12 parts phenolic epoxy resin, 6 parts phenolic curing agent, 0.05 parts imidazole accelerator, 80 parts silica powder (0.5um (53 parts) and 4um (27 parts) are used together), 0.3 parts pigment, 1 part coupling agent, 0.5 parts toughening agent, and 15 parts butyl acetate.

[0077] The degassed mixture was coated and baked using a coating machine to remove the solvent. The coating was first heated to 60°C, then to 95°C, and finally to 80°C, with a baking time of 17.5 minutes and a dry adhesive thickness of 130 μm to obtain an epoxy film. The resulting epoxy film was then hot-pressed at 80°C and 2 MPa.

[0078] Comparative Example 2:

[0079] Raw materials include 12 parts phenolic epoxy resin, 6 parts phenolic curing agent, 0.05 parts imidazole accelerator, 80 parts silica powder (0.5um (53 parts) and 4um (27 parts) are used together), 0.3 parts pigment, 1 part coupling agent, 0.5 parts toughening agent, and 15 parts butyl acetate.

[0080] The degassed mixture was coated and baked to remove the solvent using a coating machine. The coating was first heated at 60°C, then at 95°C, and finally at 80°C. The baking time was controlled at 21 minutes, and the dry adhesive thickness was controlled at 130 μm to obtain an epoxy film. The obtained epoxy film was then hot-pressed at 80°C and 2 MPa.

[0081] Comparative Example 3:

[0082] Raw materials include: 12 parts phenolic epoxy resin, 6 parts phenolic curing agent, 0.05 parts imidazole accelerator, 80 parts silica powder (0.5µm (53 parts) and 4µm (27 parts) used together), 0.3 parts pigment, 1 part coupling agent, 0.5 parts toughening agent, and 15 parts butyl acetate.

[0083] The degassed mixture was coated and baked to remove the solvent using a coating machine. The coating was first heated at 60°C, then at 95°C, and finally at 80°C for 23 minutes. The dry adhesive thickness was controlled at 130 μm to obtain an epoxy film. The obtained epoxy film was then hot-pressed at 80°C and 2 MPa.

[0084] Adhesive film performance testing:

[0085] Equal amounts of the adhesive film were taken from Examples 1-3 and Comparative Examples 1-3 respectively for comprehensive performance testing.

[0086] The test results are shown in Table 1.

[0087]

[0088] Table 1

[0089] Analysis of experimental results:

[0090] Example 1: The membrane material has good surface drying properties; low solvent residue; matte surface gloss; good adhesion performance with no air bubbles on the surface; good stability after 20 days of storage at room temperature; gel time of 230s; thermal conductivity of 1.2w / mk; and viscosity of 600pa·s at high temperature.

[0091] Example 2: The membrane material has good surface drying properties; low solvent residue; matte surface gloss; good adhesion performance with no air bubbles on the surface; good stability after 14 days of storage at room temperature; gel time of 200s; thermal conductivity of 0.9w / mk; and viscosity of 350pa·s at high temperature.

[0092] Example 3: The membrane material has good surface drying properties; low solvent residue; matte surface gloss; good adhesion performance with no air bubbles on the surface; good stability after 12 days of storage at room temperature; gel time of 180s; thermal conductivity of 0.8w / mk; and viscosity of 280pa·s at high temperature.

[0093] Comparative Example 1: Unlike Example 1, the silicon micropowder formulation was different, and the baking temperature was higher and the baking time was longer. Compared with the film material of Example 1, the film material of Comparative Example 1 had a higher solvent content, could not be easily demolded, had decreased room temperature storage stability, and showed reduced surface quality and thermal conductivity after natural curing.

[0094] Comparative Example 2: The difference from Example 1 is the different silicon powder composition, baking temperature and time window, and the baking time is further extended based on Comparative Example 1. The surface quality of the film material in Comparative Example 2 is not as good as that in Example 1, but the solvent residue can be reduced by baking at a higher temperature and for a longer time. The surface quality after natural film curing is better than that in Comparative Example 1, but at the same time, the room temperature storage stability is affected.

[0095] Comparative Example 3: The difference from Example 1 is the different silicon powder composition, baking temperature and time window, and the baking time is further extended based on Comparative Example 2. The surface quality of the film material in Comparative Example 3 is not as good as that in Example 1, but the solvent residue is further reduced by baking at a higher temperature and for a longer time, and the surface quality of the film material is better than that in Comparative Example 2. At the same time, room temperature storage stability is sacrificed to a greater extent, and the storage time is further reduced.

[0096] In summary, from the perspective of the macroscopic properties of the membrane material, the combination of raw materials such as epoxy resin, phenolic curing agent, imidazole accelerator, silica powder, pigments, coupling agents, and toughening agents with fillers of different particle sizes achieves the goal of improving frictional stability, adhesion performance, and surface roughness. The introduction of fillers with particle sizes of 2µm, 0.5µm, and 4µm results in a rapid solvent evaporation rate during the membrane preparation process, and also fills in the thermal conductivity channels, improving the thermal conductivity of the cured membrane. A suitable baking process window ensures that the components are fully dissolved and the fillers are uniformly stacked, reducing the impact of solvent residue on the surface dryness of the membrane.

[0097] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0098] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A thermally conductive epoxy film, characterized in that, Including components counted by weight: 10-12 parts epoxy resin, 5-12 parts curing agent, 0.015-0.11 parts accelerator, 28-80 parts inorganic filler, 0.1-0.5 parts pigment, 0.4-1 part coupling agent, and 0.3-1.2 parts toughening agent; The inorganic filler is silicon micro powder, which includes silicon micro powder with a particle size of 2 μm, silicon micro powder with a particle size of 0.5 μm, and silicon micro powder with a particle size of 4 μm. The proportion of 2µm silicon micropowder in the inorganic filler ranges from 5% to 30%, the proportion of 0.5µm silicon micropowder in the inorganic filler ranges from 15% to 18.75%, and the proportion of 4µm silicon micropowder in the inorganic filler ranges from 60% to 75%; all silicon micropowder constitutes 100% of the total. The epoxy resin is phenolic epoxy resin, biphenyl type epoxy resin, naphthol type epoxy resin, dicyclopentadiene type epoxy resin, or a combination thereof; The curing agent is a phenolic curing agent; The accelerator is an imidazole accelerator; The toughening agent is a core-shell toughening agent; The coupling agent is a silane coupling agent; The method for preparing a thermally conductive epoxy film includes the following steps: Step S1, Mixing: Place epoxy resin, curing agent, solvent, and toughening agent into a mixer and stir until the resin is fully dissolved and mixed evenly to obtain a resin mixture; place inorganic filler, pigment, coupling agent, and toughening agent into a mixer and stir until the mixture is fully mixed to obtain modified pigments and fillers; add the modified pigments and fillers into the resin mixture, stir, and then disperse by three-roll milling; then add accelerator, and the mixture is vacuum degassed to finally obtain a resin composition; Step S2: Coat the resin composition onto the base film; Step S3, surface drying: the base film is subjected to step heating to remove the solvent. The epoxy resin film is obtained by a three-stage heating method. Step S4: Composite the epoxy resin film and the protective film together, and finally roll them up.

2. The thermally conductive epoxy film according to claim 1, characterized in that: The pigments include carbon black.

3. The thermally conductive epoxy film according to claim 1, characterized in that: In step S1, the epoxy resin, curing agent, solvent, and toughening agent are mixed at a stirring speed of 300 rpm-500 rpm for 30 min; the inorganic filler, pigment, coupling agent, and toughening agent are mixed at a stirring temperature of 120℃ for 1 h and a stirring speed of 800 rpm-1000 rpm; the modified pigment, filler, and resin mixture is mixed at a stirring speed of 600 rpm-800 rpm for 60 min; the three-roll mill dispersion has a feed gap of 50 μm and a discharge gap of 30 μm; the vacuum degassing speed is 400 rpm-600 rpm for 6 min-8 min. In step S3, the first step temperature range is 40~60℃, the second step temperature range is 80~95℃, and the third step temperature range is 70~80℃. In step S4, the lamination temperature range is 80~110℃. In step S2, the coating thickness is 1.0~1.2 times the thickness of the adhesive film after surface drying.

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