Epoxy resin based on a five-membered heterocyclic structure of thiadiazole, and preparation method and application thereof
By introducing thiadiazole five-membered heterocyclic and alicyclic structures into epoxy resin, the problem of insufficient dielectric properties of epoxy resin is solved, the dielectric constant and dielectric loss are reduced, the dielectric properties and glass transition temperature of the material are improved, and the preparation process is simple and easy to mass-produce.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHUHAI HONGCHANG ELECTRONICS MATERIAL
- Filing Date
- 2026-03-23
- Publication Date
- 2026-05-29
AI Technical Summary
The dielectric properties of existing epoxy resins are insufficient, especially at high frequencies where the dielectric constant and dielectric loss are relatively large. There is a lack of technical solutions that introduce a thiadiazole five-membered heterocyclic structure.
By introducing epoxy resins with thiadiazole five-membered heterocyclic and alicyclic structures, and combining them with alicyclic epoxy resins, curing agents, curing accelerators, and toughening agents, epoxy resins with thiadiazole five-membered heterocyclic structures are prepared, thereby reducing dielectric constant and dielectric loss.
Significant reductions in dielectric constant and dielectric loss were achieved, dielectric properties were improved, and the glass transition temperature of the material increased with increasing thiadiazole content. The preparation process is simple and easy to mass-produce.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of new materials technology, specifically to epoxy resins based on thiadiazole five-membered heterocyclic structures, their preparation methods, and applications. Background Technology
[0002] Epoxy resins are a general term for a class of high molecular weight polymers containing two or more epoxy groups in their molecules. They exhibit excellent mechanical properties, adhesive properties, thermal stability, corrosion resistance, and processability, and are commonly used as the matrix for coatings, potting compounds, adhesives, or thermal protection materials, finding wide application in electronics, aerospace, and biomedicine. However, the polar groups in epoxy resin molecules result in relatively high dielectric constants and dielectric losses. Currently, there are two main methods to reduce dielectric constants and dielectric losses: introducing hollow structures to reduce the number of polarized molecules per unit volume, or embedding low-polarity chemical bonds into the epoxy resin structure, ultimately improving dielectric properties.
[0003] For example, some researchers, in the process of preparing high-frequency, low-dielectric-loss benzocyclobutene resin, obtained copolymers by polymerizing olefin compounds with benzocyclobutene. The hydrocarbon structure of benzocyclobutene suppressed the polarization of polar groups, significantly improving dielectric properties. Results showed that at 10 GHz, its dielectric constant and dielectric loss were 2.35-2.60 and 0.0004-0.0007, respectively. Other researchers, in the preparation of a benzocyclobutene-based resin composition, reacted polybutadiene with a benzocyclobutene monomer with a specific structure, ultimately producing copper-clad laminates with high dielectric loss at 10 GHz. k and D f The dielectric constants were below 3.52 and 0.0013, respectively. Some researchers have also introduced two types of POSS into epoxy resins, using POSS as nanofillers to improve dielectric properties through increased porosity and the low polarity of the nanoparticles themselves. Tests showed that when the POSS addition amount was 5 wt%, at 2 MHz, the dielectric constants of the epoxy resins modified with the two POSSes were 2.87 and 2.99, respectively, compared to the dielectric constant of pure epoxy resin (D...). k The figures were 3.41, representing decreases of 15.8% and 12.3% respectively.
[0004] There is currently no technical solution to improve the dielectric properties of materials by introducing a thiadiazole five-membered heterocyclic structure. Summary of the Invention
[0005] To address the aforementioned problems, this invention provides an epoxy resin based on a thiadiazole five-membered heterocyclic structure. This epoxy resin contains a thiadiazole five-membered heterocyclic structure and an alicyclic structure. The prepreg prepared based on this epoxy resin has a low dielectric constant and dielectric loss, effectively improving dielectric performance.
[0006] This invention provides an epoxy resin based on a thiadiazole five-membered heterocyclic structure, wherein the epoxy resin contains a thiadiazole five-membered heterocyclic structure and an alicyclic structure; The raw materials for preparing the epoxy resin include: alicyclic epoxy resin, curing agent, curing accelerator, and toughening agent; the mass ratio of the alicyclic epoxy resin, curing agent, curing accelerator, and toughening agent is 100:(20-35):(1-3):(1-5).
[0007] This epoxy resin possesses a five-membered heterocyclic structure of thiadiazole and an alicyclic structure of epoxy resin. Both molecular structures are sterically hindered groups with large volumes, which can effectively reduce the dielectric constant and dielectric loss, thereby solving the defect of insufficient dielectric properties in conventional epoxy resin materials. The reason for this may be due to the low molar polarizability and high molar volume of the alicyclic structure, which reduces the number of polarized molecules within the monomer volume. With the increase of thiadiazole content, at 10 GHz, the dielectric constant of the prepreg prepared based on the above epoxy resin first increases and then decreases, while the dielectric loss generally shows a decreasing trend. The lowest dielectric constant and dielectric loss can reach 2.87 and 0.01994, respectively.
[0008] In one embodiment, the alicyclic epoxy resin comprises at least one of bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate, 3,4-epoxycyclohexylcarbamate, or 3,4-epoxycyclohexylmethyl methacrylate. The curing agent comprises at least one of 2-amino-5-mercapto-1,3,4-thiadiazole, 5-amino-1,2,3-thiadiazole, 2-amino-5-methyl-1,3,4-thiadiazole, or 1,2,4-thiadiazole-3-amine.
[0009] In one embodiment, the curing accelerator includes at least one of catechol, resorcinol, or 2,4,6-tris(dimethylaminomethyl)phenol; The toughening agent includes polyurethane.
[0010] The present invention also provides a method for preparing the epoxy resin, comprising the following steps: dissolving an alicyclic epoxy resin and a toughening agent in an organic solvent to obtain a first solution; mixing a curing agent, a curing accelerator, and an organic solvent to obtain a second solution; mixing the first solution and the second solution, stirring to form a homogeneous solution, and performing programmed temperature rise to obtain an epoxy resin based on a thiadiazole five-membered heterocyclic structure.
[0011] In one embodiment, the programmed temperature increase is: 120℃ / 2 h, 150℃ / 2 h, 180℃ / 2 h.
[0012] In one embodiment, the organic solvent includes at least one of N,N-dimethylformamide or N,N-dimethylacetamide.
[0013] In one embodiment, the ratio of the total amount of organic solvent to the amount of alicyclic epoxy resin is 4-5 mL:1 g.
[0014] The present invention also provides a semi-cured sheet comprising a reinforcing material and the epoxy resin.
[0015] In one embodiment, the reinforcing material comprises glass fiber cloth.
[0016] The present invention also provides a method for preparing the prepreg, comprising the following steps: taking the raw materials for preparing the epoxy resin, dissolving the alicyclic epoxy resin and toughening agent in an organic solvent to obtain a first solution; mixing the curing agent, curing accelerator and organic solvent to obtain a second solution; mixing the first solution and the second solution, stirring to form a homogeneous solution, immersing the reinforcing material, performing programmed temperature rise, and drying overnight to obtain a prepreg.
[0017] In one embodiment, the temperature program in the preparation method of the prepreg is: 120℃ / 2 h, 150℃ / 2 h, 180℃ / 2 h.
[0018] In one embodiment, the overnight drying temperature is 140-150°C.
[0019] The present invention also provides the application of the epoxy resin or the prepreg in circuit boards.
[0020] Compared with the prior art, the present invention has the following beneficial effects: This invention relates to an epoxy resin based on a thiadiazole five-membered heterocyclic structure, its preparation method, and its application. This epoxy resin possesses both a thiadiazole five-membered heterocyclic structure and an alicyclic structure, which effectively improves the dielectric properties of the material. The semi-cured sheets prepared based on this epoxy resin can achieve dielectric constants and dielectric losses as low as 2.87 and 0.01994, respectively. Furthermore, the glass transition temperature Tg of the material is also low. g At 62~76 ℃, as the thiadiazole content increases, T g The temperature rises, reaching a maximum of 75.8 °C. This invention is prepared by reacting a nitrogen-containing five-membered heterocyclic compound with a specific alicyclic epoxy resin. The preparation process is simple, easy to mass-produce, and the chemical properties are stable. Attached Figure Description
[0021] Figure 1 The reaction equation for the epoxy resin based on the thiadiazole five-membered heterocyclic structure of the present invention is shown below.
[0022] Figure 2The infrared spectrum of 2-amino-5-mercapto-1,3,4-thiadiazole.
[0023] Figure 3 The images show the infrared spectra of the cured products from Examples 1-5.
[0024] Figure 4 The images shown are DSC diagrams of the cured products from Examples 1-5. Detailed Implementation
[0025] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.
[0026] 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 description of the 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.
[0027] Unless otherwise specified, all reagents, materials, and equipment used in this embodiment are commercially available; unless otherwise specified, all test methods are conventional test methods in this field.
[0028] The reaction equation for the epoxy resin based on the thiadiazole five-membered heterocyclic structure of this invention is as follows: Figure 1 As shown in the reaction formula, when the alicyclic epoxy resin is bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate and the curing agent is 2-amino-5-mercapto-1,3,4-thiadiazole, the theoretical mass ratio of alicyclic epoxy resin to curing agent is 100:35. However, when the inventors reacted 1 g of bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate and 0.35 g of 2-amino-5-mercapto-1,3,4-thiadiazole (other raw materials and reaction conditions were the same as in Example 1), they found that the resulting film was very brittle and could not be formed or characterized. If the curing agent was further increased, the product would become more viscous and could not be formed. Therefore, the inventors set five gradients (Examples 1-5, as shown below) with a mass ratio lower than the above theoretical ratio to reduce the brittleness of the film and enable the product to have both a thiadiazole five-membered heterocyclic ring and an alicyclic structure while also forming a stable film.
[0029] Example 1 Weigh 1 g of bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate (alicyclic epoxy resin) and 0.05 g of polyurethane (toughening agent) into thumb bottle A and dissolve them in 2 mL of N,N-dimethylformamide (organic solvent). Add 0.2 g of 2-amino-5-mercapto-1,3,4-thiadiazole (curing agent), 0.03 g of catechol (curing accelerator), and 2 mL of N,N-dimethylformamide (organic solvent) into thumb bottle B. After they are completely dissolved, pour the solution from thumb bottle A into thumb bottle B and stir thoroughly to form a homogeneous solution.
[0030] In this embodiment, the mass ratio of alicyclic epoxy resin, curing agent, curing accelerator, and toughening agent is 1:0.2:0.03:0.05 = 100:20:3:5, and the ratio of the total amount of organic solvent to the amount of alicyclic epoxy resin is 4 mL:1 g.
[0031] The obtained solution was poured into a polytetrafluoroethylene mold, and fiberglass cloth was impregnated in it. Curing was then performed on a heated platform using a programmed temperature rise schedule: 120℃ / 2 h, 150℃ / 2 h, 180℃ / 2 h. Finally, it was placed in a forced-air drying oven and dried overnight at 150℃ to remove any remaining solvent, resulting in a semi-cured sheet, labeled SZ-1.
[0032] Example 2 Weigh 1 g of bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate (alicyclic epoxy resin) and 0.05 g of polyurethane (toughening agent) into thumb bottle A and dissolve them in 2 mL of N,N-dimethylformamide (organic solvent). Add 0.222 g of 2-amino-5-mercapto-1,3,4-thiadiazole (curing agent), 0.03 g of catechol (curing accelerator), and 2 mL of N,N-dimethylformamide (organic solvent) into thumb bottle B. After they are completely dissolved, pour the solution from thumb bottle A into thumb bottle B and stir thoroughly to form a homogeneous solution.
[0033] In this embodiment, the mass ratio of alicyclic epoxy resin, curing agent, curing accelerator, and toughening agent is 1:0.222:0.03:0.05 = 100:22.2:3:5; the ratio of the total amount of organic solvent to the amount of alicyclic epoxy resin is 4 mL:1 g.
[0034] The obtained solution was poured into a polytetrafluoroethylene mold, and fiberglass cloth was impregnated in it. Curing was then performed on a heated platform using a programmed temperature rise schedule: 120℃ / 2 h, 150℃ / 2 h, 180℃ / 2 h. Finally, it was placed in a forced-air drying oven and dried overnight at 150℃ to remove any remaining solvent, resulting in a semi-cured sheet, labeled SZ-2.
[0035] Example 3 Weigh 1 g of bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate (alicyclic epoxy resin) and 0.05 g of polyurethane (toughening agent) into thumb bottle A and dissolve them in 2 mL of N,N-dimethylformamide (organic solvent). Add 0.250 g of 2-amino-5-mercapto-1,3,4-thiadiazole (curing agent), 0.03 g of catechol (curing accelerator), and 2 mL of N,N-dimethylformamide (organic solvent) into thumb bottle B. After they are completely dissolved, pour the solution from thumb bottle A into thumb bottle B and stir thoroughly to form a homogeneous solution.
[0036] In this embodiment, the mass ratio of alicyclic epoxy resin, curing agent, curing accelerator, and toughening agent is 1:0.25:0.03:0.05 = 100:25:3:5; the ratio of the total amount of organic solvent to the amount of alicyclic epoxy resin is 4 mL:1 g.
[0037] The obtained solution was poured into a polytetrafluoroethylene mold, and fiberglass cloth was impregnated in it. Curing was then performed on a heated platform using a programmed temperature rise schedule: 120℃ / 2 h, 150℃ / 2 h, 180℃ / 2 h. Finally, it was placed in a forced-air drying oven and dried overnight at 150℃ to remove any remaining solvent, resulting in a semi-cured sheet, labeled SZ-3.
[0038] Example 4 Weigh 1 g of bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate (alicyclic epoxy resin) and 0.05 g of polyurethane (toughening agent) into thumb bottle A and dissolve them in 2 mL of N,N-dimethylformamide (organic solvent). Add 0.286 g of 2-amino-5-mercapto-1,3,4-thiadiazole (curing agent), 0.03 g of catechol (curing accelerator), and 2 mL of N,N-dimethylformamide (organic solvent) into thumb bottle B. After they are completely dissolved, pour the solution from thumb bottle A into thumb bottle B and stir thoroughly to form a homogeneous solution.
[0039] In this embodiment, the mass ratio of alicyclic epoxy resin, curing agent, curing accelerator, and toughening agent is 1:0.286:0.03:0.05 = 100:28.6:3:5; the ratio of the total amount of organic solvent to the amount of alicyclic epoxy resin is 4 mL:1 g.
[0040] The obtained solution was poured into a polytetrafluoroethylene mold, and fiberglass cloth was impregnated in it. Curing was then performed on a heated platform using a programmed temperature rise schedule: 120℃ / 2 h, 150℃ / 2 h, 180℃ / 2 h. Finally, it was placed in a forced-air drying oven and dried overnight at 150℃ to remove any remaining solvent, resulting in a semi-cured sheet, labeled SZ-4.
[0041] Example 5 Weigh 1 g of bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate (alicyclic epoxy resin) and 0.05 g of polyurethane (toughening agent) into thumb bottle A and dissolve them in 2 mL of N,N-dimethylformamide (organic solvent). Add 0.333 g of 2-amino-5-mercapto-1,3,4-thiadiazole (curing agent), 0.03 g of catechol (curing accelerator), and 2 mL of N,N-dimethylformamide (organic solvent) into thumb bottle B. After they are completely dissolved, pour the solution from thumb bottle A into thumb bottle B and stir thoroughly to form a homogeneous solution.
[0042] In this embodiment, the mass ratio of alicyclic epoxy resin, curing agent, curing accelerator, and toughening agent is 1:0.333:0.03:0.05 = 100:33.3:3:5; the ratio of the total amount of organic solvent to the amount of alicyclic epoxy resin is 4 mL:1 g.
[0043] The obtained solution was poured into a polytetrafluoroethylene mold, and fiberglass cloth was impregnated in it. Curing was then performed on a heated platform using a programmed temperature rise schedule: 120℃ / 2 h, 150℃ / 2 h, 180℃ / 2 h. Finally, it was placed in a forced-air drying oven and dried overnight at 150℃ to remove any remaining solvent, resulting in a semi-cured sheet, labeled SZ-5.
[0044] Comparative Example 1 Comparative Example 1 is a blank control without the addition of toughening agent and curing agent.
[0045] Weigh 1 g of bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate from thumb bottle A, and weigh 0.03 g of catechol from thumb bottle B. Dissolve both in 2 mL of N,N-dimethylformamide and stir thoroughly to form a homogeneous solution. The remaining operations are the same as in Example 1, to obtain a semi-cured sheet, labeled SZ-0.
[0046] Experimental Example 1. Infrared spectroscopy was performed on 2-amino-5-mercapto-1,3,4-thiadiazole and the epoxy resin cured products of each example. The results are as follows: Figure 2 , Figure 3 As shown; DSC thermal analysis was performed on the epoxy resin cured products of each embodiment, and the results are as follows. Figure 4 As shown.
[0047] Figure 2 The results are from the infrared spectral analysis of 2-amino-5-mercapto-1,3,4-thiadiazole. Figure 3 The infrared spectral detection results of the epoxy resin cured products in each embodiment are provided by... Figure 3 It can be seen that the products prepared in each embodiment all have five-membered heterocyclic structures and alicyclic structures, as detailed below: (1) The characteristic vibrations of the five-membered heterocycle (1,3,4-thiadiazole ring) are all reflected in the spectrum: N–H stretching vibration (3341cm) -1 3249cm -1 3125cm -1 ): 3341cm -1 and 3249cm -1 The sharp double peaks are a typical signal of primary amines (–NH2), indicating the presence of an amino group on the thiadiazole ring. (3125 cm⁻¹) -1 The peaks may be attributed to the stretching vibrations of N–H in heterocycles (such as thionone structures). C=N stretching vibration (1632cm) -1 1554cm -1 1475cm -1 ): 1632cm -1 Primarily corresponds to the vibration of the C=N double bond in heterocyclic rings, superimposed with the –NH2 bending vibration; 1554 cm⁻¹ -1 and 1475cm -1 This belongs to the ring skeleton vibration (C–N / C=N coupling); N–N stretching vibration (1059 cm) -1 ): The vibration of the N–N bond in the thiadiazole ring, although coupled with skeletal vibration, is still diagnostic; C–S–C stretching vibration (753cm) -1 The C–S bond vibrations of sulfur atoms within the ring further support the heterocyclic structure.
[0048] (2) The infrared spectrum of the product showed characteristic peaks of alicyclic epoxy resin fragments, indicating that the alicyclic structure had been introduced through the reaction: O–H stretching vibration (3445cm) -1The broad peak indicates the formation of hydroxyl groups (–OH), which may originate from the ring-opening reaction of alicyclic epoxy resins. C–H stretching vibration (2935cm) -1 ): Vibrations of saturated C–H bonds (such as the methylene –CH2– in alicyclic or aliphatic chains) are typical signals of alicyclic structures; C=O stretching vibration (1729cm) -1 ): The ester group C=O vibration belongs to alicyclic epoxy resins, and is superimposed with the C=N vibration of the thiadiazole ring; C–O–C stretching vibration (1243cm) -1 1169cm -1 The asymmetric and symmetric stretching vibrations of C–O–C in the ester group further confirm the connection of alicyclic segments.
[0049] (3) Supporting evidence of successful reaction in each embodiment: The primary amine disappears: the raw material is at 3100–3400 cm⁻¹ -1 The primary amine bimodal phase at the NH2 ions significantly weakens or disappears in the product, indicating that –NH2 participates in the reaction. S–H peak missing: raw material at 2500–2600 cm⁻¹ -1 The absence of a distinct S–H peak indicates that the thiol group exists in the form of thionone (–NH–C=S), which is consistent with the stability characteristics of heterocycles.
[0050] 2. Dielectric properties of the prepregs prepared in Examples 1-5 and Comparative Example 1 were tested, namely dielectric constant and dielectric loss: According to the IPC-TM-650 test standard, the dielectric constant and dielectric loss of a square prepreg with a side length of 40 mm were tested at a frequency of 10 GHz using a split cylindrical resonator.
[0051] The results are shown in Table 1.
[0052] Table 1 Dielectric performance test results
[0053] The results show that at 10 GHz, the dielectric constant of the material first increases and then decreases, while the dielectric loss generally shows a decreasing trend. The dielectric constant D of the prepreg is... k Between 2.87 and 3.24, the dielectric loss D f The range is 0.01994 to 0.02536.
[0054] 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.
[0055] 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. An epoxy resin based on a five-membered heterocyclic structure of thiadiazole, characterized by, This epoxy resin contains a thiadiazole five-membered heterocyclic structure and an alicyclic structure; The raw materials for preparing the epoxy resin include: alicyclic epoxy resin, curing agent, curing accelerator, and toughening agent; the mass ratio of the alicyclic epoxy resin, curing agent, curing accelerator, and toughening agent is 100:(20-35):(1-3):(1-5).
2. The epoxy resin according to claim 1, characterized in that, The alicyclic epoxy resin includes at least one of bis(7-oxabicyclo[4.1.0]3-heptylmethyl) adipate, 3,4-epoxycyclohexylcarboxylate, or 3,4-epoxycyclohexylmethyl methacrylate. The curing agent comprises at least one of 2-amino-5-mercapto-1,3,4-thiadiazole, 5-amino-1,2,3-thiadiazole, 2-amino-5-methyl-1,3,4-thiadiazole, or 1,2,4-thiadiazole-3-amine.
3. The preparation method according to claim 1, characterized in that, The curing accelerator includes at least one of catechol, resorcinol, or 2,4,6-tris(dimethylaminomethyl)phenol; The toughening agent includes polyurethane.
4. Process for the preparation of the epoxy resin according to any one of claims 1 to 3, characterized in that, Includes the following steps: Alicyclic epoxy resin and toughening agent are dissolved in an organic solvent to obtain a first solution; curing agent, curing accelerator and organic solvent are mixed to obtain a second solution; the first solution and the second solution are mixed and stirred to form a homogeneous solution, and then subjected to programmed temperature rise to obtain an epoxy resin based on a thiadiazole five-membered heterocyclic structure.
5. The preparation method according to claim 4, characterized in that, The programmed temperature increase is: 120℃ / 2 h, 150℃ / 2 h, 180℃ / 2 h.
6. The preparation method according to claim 4, characterized in that, The organic solvent includes at least one of N,N-dimethylformamide or N,N-dimethylacetamide.
7. A prepreg, characterized by, It includes reinforcing materials and the epoxy resin according to any one of claims 1-3.
8. The prepreg according to claim 7, characterized in that, The reinforcing material includes fiberglass cloth.
9. The method for preparing the prepreg according to any one of claims 7-8, characterized in that, The process includes the following steps: taking the raw material for preparing the epoxy resin as described in any one of claims 1-3, dissolving the alicyclic epoxy resin and toughening agent in an organic solvent to obtain a first solution; mixing the curing agent, curing accelerator, and organic solvent to obtain a second solution; mixing the first solution and the second solution, stirring to form a homogeneous solution, immersing the reinforcing material in the solution, performing programmed temperature rise, and drying overnight to obtain a semi-cured sheet.
10. The use of the epoxy resin according to any one of claims 1-3 or the prepreg according to any one of claims 7-8 in a circuit board.