A resin adhesive, a prepreg, a metal foil-coated laminate, and a printed circuit board.

Abstract

This invention provides a resin adhesive, a prepreg, a metal foil laminate, and a printed circuit board. The resin adhesive comprises the following components: a multifunctional phenolic epoxy resin, a bifunctional epoxy resin, a low-polarity curing agent, modified silicone oil, and a low-polarity solvent. The bifunctional epoxy resin has a number-average molecular weight ≥900. The resin adhesive of this invention has good leveling properties, resulting in a smooth prepreg prepared from it, and the copper foil laminate and printed circuit board manufactured from it exhibit better stability and heat resistance.

Description

Technical Field

[0001] This invention belongs to the field of laminate technology and relates to a resin adhesive, prepreg, metal foil-coated laminate and printed circuit board. Background Technology

[0002] With increasing demands for faster information transmission speeds and more diverse functions, electronic circuit boards in consumer electronics are trending towards smaller, thinner, and higher-density designs. The bonding sheets, copper-clad laminates, and copper foils used are becoming increasingly thinner, leading to a lower tolerance for quality issues during production. Even minor localized anomalies in the boards can become unacceptable defects for downstream customers. However, ultra-thin copper foil and fiberglass cloth are inherently challenging to process in prepreg and CCL (Cellular Circuit Board) fabrication. Even localized inhomogeneities in the resin composition can cause defects to manifest. The trend towards higher density has given rise to a series of complex and relatively fragile interconnect systems, such as multiple laminations, blind vias, and buried vias. Excessive internal stress in high-density interconnect circuit boards can cause interconnect failures when the board is heated or subjected to other stress release mechanisms, leading to electronic product malfunctions.

[0003] CN101792574A discloses an epoxy resin composite material modified with an epoxy-terminated silicone oil pre-reactant, its preparation method, and its application. The epoxy resin composite material is composed of 0.1–100 parts of an epoxy-terminated silicone oil pre-reactant, 100 parts of epoxy resin, 0–50 parts of silica, and 5–70 parts of a curing agent. The structural formula of the epoxy-terminated silicone oil pre-reactant is shown in formula (1). Because the epoxy-terminated silicone oil pre-reactant contains functional groups that can react with epoxy resin, it increases the polarity of the epoxy resin and improves its compatibility, thereby better modifying the epoxy resin. This results in a more uniform distribution of the epoxy-terminated silicone oil in the epoxy resin, a smaller phase region size, and increased toughness and thermal stability. The resulting epoxy resin composite material has a wide range of applications and can be used as a high-performance material such as coatings, structural adhesives, and electronic packaging materials. The excessively high proportion of end-capped epoxy silicone oil in this invention results in insufficient bonding strength between the resin composition and materials such as copper foil, posing a reliability risk to its application in electronic circuit boards. Furthermore, the epoxy resin used in this invention is primarily a bisphenol-type epoxy resin, which has a low Tg (heat resistance) generally below 170°C, indicating insufficient heat resistance.

[0004] Therefore, in this field, there is a desire to develop a material that can have better heat resistance. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a resin adhesive, a prepreg, a metal foil laminate, and a printed circuit board.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] On one hand, the present invention provides a resin adhesive comprising the following components: a polyfunctional phenolic epoxy resin, a bifunctional epoxy resin, a low-polarity curing agent, a modified silicone oil, and a low-polarity solvent, wherein the bifunctional epoxy resin has a number-average molecular weight ≥900.

[0008] Phenolic epoxy resins and high-molecular-weight bifunctional epoxy resins exhibit poor solubility in low-polarity solvents and are prone to phase separation when combined with low-polarity curing agents, leading to problems such as phase separation precipitation. While highly polar amide solvents can increase the solubility and compatibility of epoxy resins, their boiling points are generally high and they are difficult to completely remove, negatively impacting the dielectric properties of the substrate. The molecular structure of high-heat-resistant epoxy resins and low-polarity curing agent compositions contains a large number of aromatic structures, resulting in highly rigid molecular chains. Therefore, excessive local stress in the cured resins of this type leads to excessive localized stress on the copper foil during the pressing of thin copper foil and prepreg, causing localized pitting indentations on the copper foil surface during hot pressing of the copper-clad laminate, damaging the oxide layer. Simultaneously, excessive localized stress in the cured resins also causes warping and deformation of the prepreg and copper-clad laminate in high-density interconnect applications with thin media, resulting in poor expansion and contraction and insufficient reliability.

[0009] In this invention, a combination of multifunctional phenolic epoxy resin, high molecular weight bifunctional epoxy resin, low polarity curing agent, modified silicone oil, and low polarity solvent is used. The modified silicone oil has bifunctional groups that can react with the epoxy resin system and relatively soft molecular chains. The use of trace components unexpectedly improves compatibility and reduces the stress of the cured product, and no significant reduction is observed in the Tg and Td of the board, thus solving the above-mentioned problems.

[0010] This invention introduces trace amounts of modified silicone oil molecular chains into the epoxy resin curing system, which unexpectedly reduces the poor leveling problem during prepreg processing, reduces resin stress during CCL lamination, reduces the process sensitivity of the board processing, and improves product quality.

[0011] In this invention, the multifunctional phenolic epoxy resin is a phenolic epoxy resin with three or more functionalities.

[0012] In this invention, the multifunctional phenolic epoxy resin is an epoxy resin obtained by epoxidation of phenolic resin.

[0013] Preferably, the multifunctional phenolic epoxy resin includes any one or a combination of at least two of the following: phenolic epoxy resin, bisphenol A phenolic epoxy resin, o-cresol phenolic epoxy resin, dicyclopentadiene phenolic epoxy resin, or biphenyl phenolic epoxy resin.

[0014] In this invention, the bifunctional epoxy resin is a compound having two epoxy groups. Preferably, the high molecular weight bifunctional epoxy resin includes any one or a combination of at least two of the following: bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenolic epoxy resin, or copolymers formed from bisphenol type epoxy resin and at least one of isocyanate, bisphenol A, or bisphenol F.

[0015] In this invention, the number average molecular weight of the bifunctional epoxy resin is ≥900, such as 900, 1000, 1200, 1500, 1800, 2000, 2500, 3000, 4000, 5000, etc., and more preferably ≥1600.

[0016] In the resin solution of the present invention, the content of the bifunctional epoxy resin is 5%-60% of the weight of the polyfunctional phenolic epoxy resin, for example 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60%, preferably 20%-55%.

[0017] Multifunctional phenolic epoxy resins possess high heat resistance (Tg) and good heat resistance, which is beneficial for better stability at high temperatures and reduces the deformation and stress increase of electronic circuit boards due to heat. Bifunctional epoxy resins have relatively weaker cured heat resistance, but they help increase the toughness of multifunctional epoxy resins. That is, when the proportion of bifunctional epoxy resin is too high, the heat resistance will decrease; however, when the proportion of bifunctional epoxy resin is insufficient, the toughness of the cured product will be low, and the cured product will be brittle.

[0018] Preferably, the low-polarity curing agent is a non-amine epoxy curing agent.

[0019] Preferably, the low-polarity curing agent includes any one or a combination of at least two of the following: linear phenolic resin, phosphorus-containing phenolic resin, nitrogen-containing phenolic resin, benzoxazine resin, reactive ester resin, acid anhydride curing agent, or imidazole compound.

[0020] Preferably, the anhydride curing agent is a copolymer of maleic anhydride and styrene.

[0021] Preferably, the amount of low-polarity curing agent in the resin solution is 75%-300% of the total weight of the epoxy resin, for example 75%, 80%, 90%, 100%, 130%, 150%, 180%, 200%, 230%, 250%, 280% or 300%, more preferably 80%-200%, and more preferably 100%-160%.

[0022] The amount of curing agent used is generally to form a cross-linking network with epoxy resin. Too little curing agent will lead to insufficient curing, but too much curing agent will also lead to insufficient curing. Insufficient curing will reduce the heat resistance and toughness of the cured product.

[0023] Phenolic epoxy resins have weaker compatibility compared to bifunctional epoxy resins, exhibiting poor compatibility in solvents and components with low polarity. Even when stable and uniform in the adhesive solution, localized phase separation during solvent removal during drying can lead to poor smoothness. To address this issue, this invention utilizes modified silicone oil. Modified silicone oil participates in the resin system's reaction, adjusting the flexibility of the cured molecular chains, thereby enabling faster stress release during the curing process. This results in smoother prepreg and board surfaces and less processing stress damage. The modified silicone oil used in this invention is present in very low amounts, has minimal impact on crosslinking density, and has no negative effect on the heat resistance of the cured product.

[0024] Preferably, the modified silicone oil has two end functional groups and has the following structure:

[0025]

[0026] Where n is an integer greater than 1, such as 1, 2, 3, 4, 5, 6, 8, 10, 11, 16, 19,

[0027] 20, 30, 50, etc., preferably integers between 8 and 18;

[0028] G is a functional group containing the following structure:

[0029] -NH2、

[0030] Preferably, the modified silicone oil accounts for 0.001%-2% of the total weight of the resin solution, for example, 0.001%, 0.005%, 0.008%, 0.01%, 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8% or 2%, more preferably 0.003%-1%, and more preferably 0.005-0.5%.

[0031] In this invention, the purpose of modifying silicone oil is to improve the poor compatibility between multifunctional phenolic epoxy resin and low polarity curing agent. However, silicone oil without end functional groups is a free component in the resin composition, which is prone to migration and precipitation problems, which is not conducive to the bonding of prepreg.

[0032] The functional groups of the modified silicone oil end groups can improve the compatibility between silicone oil and resin, reduce the migration problem of silicone oil, and promote the cross-linking reaction between silicone oil and epoxy resin system. This allows the silicone oil molecular chains to be introduced into the cross-linking network of epoxy resin, increasing the flexibility of the network and thus reducing stress.

[0033] Preferably, the low-polarity solvent includes any one or a combination of at least two of acetone, methyl ethyl ketone, cyclohexane, isobutanol, isopropanol, toluene, xylene, benzene, propylene glycol methyl ether, ethylene glycol dimethyl ether, propylene glycol methyl ether acetate, ethyl acetate, n-butanol, or cyclohexanone.

[0034] Preferably, the amount of the low-polarity solvent is 20%-100% of the total weight of other components in the resin solution, for example 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100%, preferably 33%-66%.

[0035] Preferably, the resin solution further includes inorganic fillers.

[0036] Preferably, the inorganic filler includes any one or a combination of at least two of the following: silica, aluminum hydroxide, boehmite, talc, calcined kaolin, talc, alumina, barium sulfate, magnesium hydroxide, glass fiber rod, diatomaceous earth, calcium carbonate, or zinc molybdate.

[0037] Preferably, the amount of inorganic filler is 10%-300% of the total weight of epoxy resin, for example 10%, 30%, 50%, 60%, 75%, 80%, 90%, 100%, 130%, 150%, 180%, 200%, 230%, 250%, 280% or 300%, preferably 50%-200%, and more preferably 70%-150%.

[0038] Preferably, the resin solution further includes any one or a combination of at least two of the following: a silane coupling agent, a dispersant, or a toughening agent.

[0039] On the other hand, the present invention provides a prepreg obtained by impregnating a reinforcing material with a resin solution as described above, and drying to remove the solvent.

[0040] Preferably, the reinforcing material includes any one or a combination of at least two of the following: fiber paper, glass fiber nonwoven fabric, glass fiber cloth, or organic fiber cloth.

[0041] On the other hand, the present invention provides a metal foil laminate, the metal foil laminate comprising at least one prepreg as described above and metal foils covering both sides of the laminated prepreg.

[0042] On the other hand, the present invention provides a printed circuit board comprising at least one of the prepreg as described above or the metal foil laminate as described above.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The resin solution of the present invention has good leveling properties, which makes the prepreg prepared therefrom have smoothness, and the copper-clad laminate and printed circuit board made therefrom have better stability and heat resistance. Detailed Implementation

[0045] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0046] Example 1

[0047] 100 parts of dicyclopentadiene-type phenolic epoxy resin (DIC, trade name: HP-7200H), 28 parts of bisphenol A type epoxy resin (Guodu Chemical, KD214C, Mn 1800), 20 parts of styrene-maleic anhydride copolymer (Sartoma, SMA EF40) as an acid anhydride curing agent, 80 parts of phosphorus-containing phenolic resin (Olin, XZ92741), 2 parts of imidazole compound (Shikoku Chemical, 2E4MZ), 0.5 parts of diepoxy-terminated modified silicone oil (Shin-Etsu, KF-105), 80 parts of aluminum hydroxide (Albemarle, OL-104LEO), 80 parts of aluminum hydroxide (Lianrui New Materials, DS-1032), and 70 parts of methyl ethyl ketone were mixed. The mixture was stirred until homogeneous to obtain a uniformly dispersed resin solution. The resin solution was impregnated onto E-type glass fiber cloth (Taishan Glass Fiber, E1078) and dried at 155℃ for 8 minutes to remove the solvent, resulting in a prepreg with a resin content of 69%.

[0048] A 12μm copper foil was applied to each side of four overlapping prepreg sheets, and the sheets were hot-pressed at 200℃ and 3.0MPa for 90 minutes to obtain a double-sided copper foil laminate.

[0049] Example 2

[0050] 100 parts of dicyclopentadiene-type phenolic epoxy resin (DIC, trade name: HP-7200H), 55 parts of bisphenol A type epoxy resin (Changchun Resin, BE470EL, Mn is 982), and 40 parts of acid anhydride curing agent styrene-maleic anhydride copolymer (Sardoma, SMA) were mixed. The following components were mixed: EF40, 35 parts benzoxazine resin (Changchun Resin, BF3500), 100 parts reactive ester curing agent (DIC, HPC-8000-65T), 220 parts phosphorus-containing phenolic resin (Olin, XZ92741, 60% solid content), 0.2 parts imidazole compound (Shikoku Kasei, 2E4MZ), 1 part dialicyclic epoxy-terminated modified silicone oil (Shin-Etsu, X-22-169AS), 40 parts aluminum hydroxide (Albemarle, OL-104LEO), 30 parts silica (Lianrui New Materials, DQ1028L), and 75 parts methyl ethyl ketone. The mixture was stirred until homogeneous, resulting in a uniformly dispersed resin solution. This resin solution was impregnated onto E-type glass fiber cloth (Taishan Glass Fiber, E1078) and dried at 155℃ for 5 minutes to remove the solvent, yielding a prepreg with a resin content of approximately 69%.

[0051] A 12μm copper foil was applied to each side of four overlapping prepreg sheets, and the sheets were hot-pressed at 200℃ and 3.0MPa for 90 minutes to obtain a double-sided copper foil laminate.

[0052] Example 3

[0053] 100 parts of bisphenol A type phenolic epoxy resin (Changchun Resin, BNE210), 55 parts of bisphenol A type epoxy resin (Changchun Resin, BE470EL, Mn 982), 40 parts of acid anhydride curing agent styrene-maleic anhydride copolymer (Sartoma, SMA EF40), and 35 parts of benzoxazine resin (Changchun Resin, BF350) were mixed. 0 The following mixture was prepared: 100 parts of reactive ester curing agent (DIC, HPC-8000-65T), 220 parts of phosphorus-containing phenolic resin (Olin, XZ92741, 60% solid content), 0.2 parts of imidazole compound (Shikoku Kasei, 2E4MZ), 0.5 parts of bisphenol-terminated modified silicone oil (Shin-Etsu, KF2201), 50 parts of aluminum hydroxide (Albemarle, OL-104LEO), 300 parts of composite silica powder (Lianrui New Materials, DS1032A), and 380 parts of methyl ethyl ketone. The mixture was stirred until homogeneous, resulting in a uniformly dispersed resin solution. This resin solution was then impregnated onto E-type glass fiber cloth (Taishan Glass Fiber, E1078) and dried at 155℃ for 3.5 min to remove the solvent, yielding a prepreg with a resin content of approximately 70%.

[0054] A 12μm copper foil was applied to each side of four overlapping prepreg sheets, and the sheets were hot-pressed at 200℃ and 3.0MPa for 90 minutes to obtain a double-sided copper foil laminate.

[0055] Comparative Example 1

[0056] The only difference between this comparative example and Example 1 is that the resin solution does not contain modified silicone oil.

[0057] Comparative Example 2

[0058] The only difference between this comparative example and Example 1 is that 0.1 parts of the bisepoxy-terminated silicone oil in the resin solution of Example 1 were replaced with silicone oil (Shin-Etsu, KF640) that is modified without terminal active groups.

[0059] Comparative Example 3

[0060] The only difference between this comparative example and Example 1 is that the resin solution does not contain dicyclopentadiene-type phenolic epoxy resin, and the amount of bisphenol A-type epoxy resin used is 128 parts.

[0061] Comparative Example 4

[0062] The only difference between this comparative example and Example 1 is that the resin solution does not contain bisphenol A type epoxy resin, and the amount of dicyclopentadiene type phenolic epoxy resin used is 128 parts.

[0063] Comparative Example 5

[0064] The only difference between this comparative example and Example 1 is that the styrene-maleic anhydride copolymer, an anhydride curing agent in the resin solution of Example 1, is replaced with a highly polar curing agent (2 parts dicyandiamide and 5 parts diaminodiphenyl sulfone).

[0065] Comparative Example 6

[0066] The only difference between this comparative example and Example 1 is that the bisphenol A type epoxy resin in the resin solution of Example 1 is replaced with a low molecular weight bisphenol A epoxy resin (Hongchang Electronics, GELR128E, Mn approximately 380).

[0067] Performance tests were conducted on the double-sided copper-clad laminates of the embodiments and comparative examples. The test methods are as follows:

[0068] (1) Prepreg appearance: refers to the surface morphology of the prepreg after the solvent is dried.

[0069] (2) Copper surface bright spots: refers to the number of copper surface bright spots per square foot on the surface of the double-sided copper foil laminate. Bright spots are point-like defects on the copper surface that have more obvious reflective brightness than the overall surface.

[0070] (3) Glass transition temperature (Tg): The sample was tested using a differential calorimeter (DSC) at a heating rate of 20 / min in an N2 environment.

[0071] (4) Thermal decomposition temperature (Td): refers to the temperature at which a copper-free plate sample decomposes and loses 5% of its weight when heated. Thermogravimetric analysis (TGA) is used to test this temperature, with a heating rate of 10℃ / min.

[0072] (5) Peel strength (PS): refers to the tensile force required to peel copper foil per millimeter from copper-clad laminate at room temperature.

[0073] (6) Thermal stress of the plate: The copper plate sample, 50×50mm, was floated in a tin bath at 288°C, and the time of delamination or copper foil blistering was recorded.

[0074] The test results are shown in Table 1.

[0075] Table 1

[0076]

[0077] The results show that the prepregs in the examples have a smooth and even surface, but the prepregs in Comparative Examples 1, 4, and 5 all exhibit defects such as resin shrinkage, unevenness due to bubbles, or orange peel texture. The copper surface of the plate samples in the examples is relatively intact, without any bright spots. Although the prepreg in Comparative Example 2 has a smooth surface, the number of bright spots on the copper surface is relatively large, and the peel strength is low, indicating insufficient heat resistance. The copper surfaces of the other comparative examples all have noticeable bright spots, with Comparative Example 5, which uses a polar curing agent, showing the most obvious bright spots. Comparative Example 3 uses only bifunctional epoxy, resulting in poor heat resistance and a low Tg. Comparative Example 4 does not use bifunctional epoxy resin, and the prepreg surface shows bubbles, with poor thermal stress heat resistance time. Comparative Example 6 uses low molecular weight bisphenol A epoxy resin, causing a significant reduction in thermal stress heat resistance time and making it prone to delamination and cracking.

[0078] The applicant declares that the above embodiments illustrate the resin adhesive, prepreg, metal foil laminate, and printed circuit board of the present invention, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A resin adhesive, characterized in that, The resin adhesive comprises the following components: multifunctional phenolic epoxy resin, bifunctional epoxy resin, low-polarity curing agent, modified silicone oil, and low-polarity solvent. The number-average molecular weight of the bifunctional epoxy resin is ≥900. The modified silicone oil has two end functional groups and has the following structure: Where n is an integer greater than 1, and each region of G is independently selected from the functional groups of the following structures: -NH2 2. The resin adhesive according to claim 1, characterized in that, The multifunctional phenolic epoxy resin includes any one or a combination of at least two of the following: phenolic epoxy resin, bisphenol A phenolic epoxy resin, o-cresol phenolic epoxy resin, dicyclopentadiene phenolic epoxy resin, or biphenyl phenolic epoxy resin.

3. The resin adhesive according to claim 1, characterized in that, The bifunctional epoxy resin includes any one or a combination of at least two of the following: bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenolic epoxy resin, or copolymers formed from bisphenol type epoxy resin and at least one of isocyanate, bisphenol A, or bisphenol F.

4. The resin adhesive according to claim 1, characterized in that, The number-average molecular weight of the bifunctional epoxy resin is ≥1600.

5. The resin adhesive according to claim 1, characterized in that, The content of the bifunctional epoxy resin is 5%-60% of the weight of the polyfunctional phenolic epoxy resin.

6. The resin adhesive according to claim 5, characterized in that, The content of the bifunctional epoxy resin is 20%-55% of the weight of the polyfunctional phenolic epoxy resin.

7. The resin adhesive according to claim 1, characterized in that, The low-polarity curing agent is a non-amine epoxy curing agent.

8. The resin adhesive according to claim 1, characterized in that, The low-polarity curing agent includes any one or a combination of at least two of the following: linear phenolic resin, phosphorus-containing phenolic resin, nitrogen-containing phenolic resin, benzoxazine resin, reactive ester resin, acid anhydride curing agent, or imidazole compound.

9. The resin adhesive according to claim 8, characterized in that, The anhydride curing agent is a copolymer of maleic anhydride and styrene.

10. The resin adhesive according to claim 1, characterized in that, The amount of low-polarity curing agent in the resin solution is 75%-300% of the total weight of the epoxy resin.

11. The resin adhesive according to claim 10, characterized in that, The amount of low-polarity curing agent in the resin solution is 80%-200% of the total weight of the epoxy resin.

12. The resin adhesive according to claim 11, characterized in that, The amount of low-polarity curing agent in the resin solution is 100%-160% of the total weight of the epoxy resin.

13. The resin adhesive according to claim 1, characterized in that, The modified silicone oil is used in an amount of 0.001%-2% of the total weight of the resin solution.

14. The resin adhesive according to claim 13, characterized in that, The modified silicone oil is used in an amount of 0.003%-1% of the total weight of the resin solution.

15. The resin adhesive according to claim 14, characterized in that, The modified silicone oil is used in an amount of 0.005-0.5% of the total weight of the resin solution.

16. The resin adhesive according to claim 1, characterized in that, The low-polarity solvent includes any one or a combination of at least two of the following: acetone, methyl ethyl ketone, cyclohexane, isobutanol, isopropanol, toluene, xylene, benzene, propylene glycol methyl ether, ethylene glycol dimethyl ether, propylene glycol methyl ether acetate, ethyl acetate, n-butanol, or cyclohexanone.

17. The resin adhesive according to claim 1, characterized in that, The amount of the low-polarity solvent used is 20%-100% of the total weight of other components in the resin solution.

18. The resin adhesive according to claim 17, characterized in that, The amount of the low-polarity solvent is 33%-66% of the total weight of other components in the resin solution.

19. The resin adhesive according to claim 1, characterized in that, The resin solution also includes inorganic fillers.

20. The resin adhesive according to claim 19, characterized in that, The inorganic filler includes any one or a combination of at least two of the following: silicon dioxide, aluminum hydroxide, boehmite, talc, calcined kaolin, talc, aluminum oxide, barium sulfate, magnesium hydroxide, glass fiber rod, diatomaceous earth, calcium carbonate, or zinc molybdate.

21. The resin adhesive according to claim 19, characterized in that, The amount of inorganic filler used is 10%-300% of the total weight of epoxy resin.

22. The resin adhesive according to claim 21, characterized in that, The amount of inorganic filler used is 50%-200% of the total weight of epoxy resin.

23. The resin adhesive according to claim 22, characterized in that, The amount of inorganic filler used is 70%-150% of the total weight of epoxy resin.

24. The resin adhesive according to claim 1, characterized in that, The resin solution also includes any one or a combination of at least two of the following: silane coupling agent, dispersant, or toughening agent.

25. A prepreg, characterized in that, The prepreg is obtained by impregnating the reinforcing material with the resin solution as described in any one of claims 1-24, and then drying to remove the solvent.

26. A metal foil-coated laminate, characterized in that, The metal foil laminate includes at least one prepreg as described in claim 25 and metal foils covering both sides of the laminated prepreg.

27. A printed circuit board, characterized in that, The printed circuit board includes at least one of the prepreg as described in claim 25 or the metal foil laminate as described in claim 26.

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