Halogen-free low dielectric resin composition for copper clad laminate and copper clad laminate

Abstract

This application relates to the field of copper clad laminates (CCLs), specifically disclosing a halogen-free low-dielectric resin composition for CCLs and a CCL made therefrom. The halogen-free low-dielectric resin composition for CCLs comprises the following raw materials in parts by weight: 50-70 parts of multifunctional epoxy resin, 10-20 parts of polyurethane-modified epoxy resin, 5-10 parts of terminal epoxy-based silicone oil, 12-25 parts of curing agent, 0.2-1 part of curing accelerator, 15-20 parts of flame retardant, and 15-30 parts of 4-aminomethylbenzoic acid-grafted alumina. The halogen-free low-dielectric resin composition for CCLs of this application and the CCL made therefrom have the advantages of good heat resistance and low dielectric loss.

Description

Technical Field

[0001] This application relates to the field of copper clad laminates, and more specifically, to a halogen-free low-dielectric resin composition for copper clad laminates and copper clad laminates. Background Technology

[0002] With the rapid development of electronic technology, higher frequency and higher speed signal transmission, as well as dynamic bending reliability are required for flexible printed circuit boards (FPCs). Flexible copper-clad laminate (CCL) is a thin, flexible composite material made by laminating copper foil onto an insulating base film. It is the core substrate of flexible printed circuit boards and is the second largest category of CCL after rigid CCL. Flexible CCL requires the base resin to have excellent dielectric properties (low Dk, low Df), high heat resistance, and halogen-free flame retardancy. It must also simultaneously meet the requirements of excellent flexibility (high flexural life), low moisture absorption, excellent dimensional stability, and high adhesion strength to the copper foil.

[0003] Currently, the main matrix resins for copper clad laminates include traditional polyimide systems, polyester systems, and epoxy / acrylate systems. Among them, polyimide systems have excellent heat resistance and mechanical properties, but are generally more expensive and have unstable dielectric constants; polyester systems have lower costs and better flexibility, but poorer heat resistance and limited application range; epoxy / acrylate systems generally have higher dielectric losses, insufficient heat resistance, and poor chemical resistance.

[0004] In view of this, this application proposes a halogen-free low-dielectric resin composition for copper-clad laminates with excellent heat resistance and low dielectric loss. Summary of the Invention

[0005] In order to obtain a resin composition for copper clad laminates with high heat resistance and low dielectric loss, this application provides a halogen-free low dielectric resin composition for copper clad laminates and a copper clad laminate.

[0006] In a first aspect, this application provides a halogen-free low-dielectric resin composition for copper-clad laminates, employing the following technical solution:

[0007] A halogen-free low-dielectric resin composition for copper-clad laminates comprises the following raw materials in parts by weight:

[0008] The mixture contains 50-70 parts of multifunctional epoxy resin, 10-20 parts of polyurethane modified epoxy resin, 5-10 parts of terminal epoxy silicone oil, 12-25 parts of curing agent, 0.2-1 parts of curing accelerator, 15-20 parts of flame retardant, and 15-30 parts of modified alumina.

[0009] Preferably, the multifunctional epoxy resin is selected from one or more of phenolic epoxy resin, bisphenol A epoxy resin, phenolic epoxy resin, o-cresol phenolic epoxy resin, and tetraphenol ethane tetraglycidyl ether.

[0010] Preferably, the modified alumina is obtained by surface treatment of alumina with γ-glycidoxypropyltrimethoxysilane followed by grafting 4-aminomethylbenzoic acid onto the surface.

[0011] Preferably, the alumina is subjected to acid washing and activation treatment before treatment with γ-glycidoxypropyltrimethoxysilane.

[0012] Preferably, the surface-grafted 4-aminomethylbenzoic acid comprises:

[0013] 4-Aminomethylbenzoic acid was dissolved in a reaction solvent, and alumina surface-treated with γ-glycidoxypropyltrimethoxysilane was added. The reaction was carried out at 40-60℃. After the reaction was completed, the alumina was centrifuged, washed, and dried to obtain 4-aminomethylbenzoic acid-grafted alumina, which was used as modified alumina.

[0014] Preferably, the mass ratio of the protected alumina to the 4-aminomethylbenzoic acid is 100:5-10.

[0015] Preferably, the modified alumina is obtained by grafting and oxidizing with 4-aminomethylbenzoic acid, followed by reaction with alicyclic anhydride;

[0016] The alicyclic anhydride is selected from one of hexahydrophthalic anhydride and methylhexahydrophthalic anhydride;

[0017] The mass ratio of the alumina, the 4-aminomethylbenzoic acid and the alicyclic anhydride is 100:5-10:5-12.

[0018] Preferably, the curing agent is selected from one or more of 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, dicyandiamide, m-phenylenediamine, diethylenetriamine, and diphenylmethanediamine.

[0019] Preferably, the curing accelerator is an imidazole accelerator, selected from one or more of 2-methylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, and 2-undecylimidazole.

[0020] Preferably, the flame retardant is a phosphorus-containing flame retardant.

[0021] Preferably, the halogen-free low-dielectric resin composition further includes an organic solvent selected from one or more of acetone, methyl ethyl ketone, and dimethylformamide.

[0022] Preferably, the solid content of the halogen-free low-dielectric resin composition for copper clad laminate is 40wt%-70wt%.

[0023] Secondly, this application provides a copper-clad laminate, which adopts the following technical solution:

[0024] A copper-clad laminate prepared using the above-mentioned halogen-free low-dielectric resin composition for copper clad laminates comprises: a polyimide insulating film, a layer of the halogen-free resin composition coated on the surface of the polyimide insulating film, and copper foil laminated on the halogen-free resin composition coating.

[0025] Preferably, the method for preparing the copper-clad laminate includes the following steps:

[0026] The halogen-free resin composition layer is coated onto the surface of a polyimide insulating film and heat-treated at 80-100°C for 4-6 minutes to form a partially cured halogen-free resin composition layer on the surface of the insulating film. The layer is then laminated with copper foil at 80-100°C and cured at 140-160°C to obtain a copper-clad laminate.

[0027] Preferably, the polyimide insulating film has a thickness of 10-75 μm; the copper foil is rolled copper foil or electrolytic copper foil with a thickness of 9-35 μm; and the halogen-free resin composition layer has a thickness of 10-25 μm.

[0028] In summary, this application has the following beneficial effects:

[0029] The present invention provides a halogen-free low-dielectric resin composition, which uses polyurethane modified epoxy resin and multifunctional epoxy resin together to improve the toughness and overall mechanical strength of the composite material. The addition of terminal epoxy silicone oil improves the dielectric properties and thermal oxidation stability. The homogeneous mixing of the components and good compatibility achieve a highly efficient synergy of heat resistance, flexibility, dielectric properties and interfacial compatibility.

[0030] In this application, the dielectric properties and heat resistance of the resin composition are improved by adding modified alumina. The modification treatment with 4-aminomethylbenzoic acid significantly improves the interfacial bonding and compatibility between alumina and the resin matrix, effectively alleviates the problem of increased brittleness caused by the addition of rigid fillers, and stabilizes the dielectric properties, which is beneficial to reducing dielectric loss. Alumina can play a certain physical barrier role, delaying the release of thermal decomposition products and heat conduction, improving the heat resistance of the resin composition and improving the flame retardancy to a certain extent. The benzene ring structure of 4-aminomethylbenzoic acid is conducive to char formation and synergistically improves the flame retardant efficiency with phosphorus-containing flame retardants.

[0031] This application further optimizes the heat resistance and dielectric properties of the composition by co-modifying it with 4-aminomethylbenzoic acid-grafted alumina and alicyclic anhydride. Detailed Implementation

[0032] To further aid in understanding the technical solution of this invention, several specific implementation examples are provided below to describe the technical solution of this invention in more detail. All of these described embodiments are only some embodiments of this invention, and not all of them.

[0033] The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments; and the reaction apparatus, monomer compounds, etc. involved in the following embodiments are all commercially available. It should be understood that the following description is only illustrative of the invention by way of example and is not intended to limit the scope of the invention. The scope of protection of the invention is determined by the appended claims. Furthermore, those skilled in the art will understand that modifications can be made to the technical solutions of the invention without departing from the spirit and purpose of the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0034] 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 the subject matter pertains. Before a detailed description of the invention, the following definitions are provided to better understand it.

[0035] In cases where numerical ranges are provided, such as concentration ranges, percentage ranges, or ratio ranges, it should be understood that, unless the context explicitly specifies otherwise, all intermediate values ​​between the upper and lower limits of the range, up to one-tenth of the lower limit unit, and any other values ​​or intermediate values ​​within the range are included in the subject matter. The upper and lower limits of these smaller ranges may be independently included in the smaller ranges, and such embodiments are also included in the subject matter, limited by any specific excluded limit values ​​within the range. Where the range includes one or two limit values, the range excluding any one or both of those included limit values ​​is also included in the subject matter.

[0036] In the context of this invention, many embodiments use the expressions "comprising," "including," or "basically / mainly composed of." The expressions "comprising," "including," or "basically / mainly composed of" are generally understood as open-ended expressions, indicating that they include not only the elements, components, parts, or method steps specifically listed after the expression, but also other elements, components, parts, or method steps. However, in this document, the expressions "comprising," "including," or "basically / mainly composed of" can also be understood as closed-ended expressions in certain cases, indicating that they only include the elements, components, parts, or method steps specifically listed after the expression, and do not include any other elements, components, parts, or method steps. In this case, the expression is equivalent to the expression "composed of."

[0037] To better understand this teaching and without limiting its scope, all figures and other numerical values ​​used in the specification and claims to express quantities, percentages, or proportions should, in all cases, be understood to be modified by the term "about." Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​that may vary depending on the desired properties sought. At a minimum, each numerical parameter should be interpreted based at least on the reported significant figures and by applying common rounding techniques.

[0038] In the context of the invention, ordinal numbers such as “first,” “second,” “third,” or “(1),” “(2),” “(3)” are used to describe the invention. It should be understood that the purpose of using ordinal numbers is only to distinguish the different components, structures, elements, steps, etc. involved in the description of the invention, and is not intended to limit the order or hierarchy of these different components, structures, elements, steps, etc., unless explicitly stated in the context.

[0039] In order to obtain a resin composition for copper clad laminates with good heat resistance and low dielectric loss, this application provides a halogen-free low dielectric resin composition for copper clad laminates and a copper clad laminate.

[0040] In a first aspect, the present invention provides a halogen-free low-dielectric resin composition for copper-clad laminates, the halogen-free low-dielectric resin composition for copper-clad laminates comprising the following raw materials in parts by weight: 50-70 parts of multifunctional epoxy resin, 10-20 parts of polyurethane modified epoxy resin, 5-10 parts of terminal epoxy silicone oil, 12-25 parts of curing agent, 0.2-1 parts of curing accelerator, 15-20 parts of flame retardant, and 15-30 parts of modified alumina.

[0041] To address the shortcomings of traditional copper-clad laminate resin compositions in terms of heat resistance, flexibility, and dielectric properties, this application combines polyurethane-modified epoxy resin, terminal epoxy-based silicone oil, and multifunctional epoxy resin. The multifunctional epoxy resin exhibits high crosslinking density and high mechanical properties, serving as the skeletal structure of the resin composition and providing excellent rigidity, mechanical strength, and reactivity. The multifunctional epoxy resin can be selected from one or more of phenolic epoxy resins, bisphenol A epoxy resins, phenolic epoxy resins, o-cresol phenolic epoxy resins, and tetraphenol ethane tetraglycidyl ether, preferably bisphenol A epoxy resins or phenolic epoxy resins, and more preferably bisphenol A epoxy resins. In one specific embodiment, the bisphenol A epoxy resin can be commercially available E51 type epoxy resin (NPEL-128) with an epoxy equivalent of 180-190 (g / eq).

[0042] Polyurethane-modified epoxy resins can increase the flexibility and compatibility of resin compositions. By introducing a microscopic phase-separated structure, polyurethane-modified epoxy resins significantly improve the toughness, impact resistance, and flexural strength of the resin composition. In one specific embodiment, the polyurethane-modified epoxy resin can be commercially available CVC HyPox UA10, CVC HyPox UA 11, or NPER-133L.

[0043] Organosilicon resins possess low dielectric loss, high-temperature stability, and a certain degree of flexibility. The Si-O bonds in organosilicon resins can significantly reduce the dielectric constant and improve heat resistance, thus slowing down the deterioration of properties after long-term thermal aging and ensuring stable electrical performance. Terminal epoxy-based silicone oils can participate in the curing process of epoxy resins as reactive toughening resins. Their siloxane segments can be anchored in the epoxy crosslinking network, participating in the construction of the resin crosslinking network, improving dielectric properties while effectively enhancing the toughness of the crosslinking system, and ensuring the homogeneity and stability of the resin system. In a specific embodiment, the terminal epoxy-based silicone oil can be selected from the IOTA 105 series.

[0044] The inventors used polyurethane-modified epoxy resin, terminal epoxy-based silicone oil, and multifunctional epoxy resin as film-forming resins. They stably embedded organosilicon segments and polyurethane segments in the epoxy crosslinking network, forming a more reasonable segment distribution, which synergistically improved flexibility, while also bringing heat resistance and improved dielectric properties.

[0045] In a preferred embodiment, this application employs a curing agent and a curing accelerator in synergy to adjust the curing efficiency and effect. The curing agent is selected from one or more of 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, dicyandiamide, m-phenylenediamine, diethylenetriamine, and diphenylmethanediamine. The curing accelerator is an imidazole accelerator, selected from one or more of 2-methylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, and 2-undecylimidazole.

[0046] In a preferred embodiment, the flame retardant is a phosphorus-containing flame retardant. The phosphorus-containing flame retardant may be selected from DOPO-ITA ([(6-oxo-(6H)-dibenzo-(c,e)(1,2)-oxophosphine-hexane-6-one)methyl]-succinic acid), DPO-HQ (2,5-dihydroxyphenyl(diphenyl)phosphine oxide), or commercially available products SPB-100, Exolit OP-935, and Exolit OP-930. The phosphorus-containing flame retardant is an environmentally friendly, highly efficient halogen-free flame retardant with good thermal stability and high compatibility with the resin matrix of this application. It can impart highly efficient flame retardant properties to the resin composition while having minimal impact on dielectric properties.

[0047] This application further reduces the coefficient of thermal expansion, improves heat resistance, and adjusts the dielectric constant by adding modified fillers.

[0048] In a preferred embodiment, the modified filler is 4-aminomethylbenzoic acid-grafted alumina, specifically obtained by surface-treating alumina with γ-glycidyl etheroxypropyltrimethoxysilane followed by grafting 4-aminomethylbenzoic acid onto its surface. Using alumina as the inorganic filler matrix provides performance support to the resin composition, helping to reduce the dielectric constant and dielectric loss. Furthermore, alumina acts as a physical barrier, delaying the release of thermal decomposition products and heat conduction, thus improving the heat resistance of the resin composition and, to some extent, enhancing its flame retardancy.

[0049] In a preferred embodiment, the alumina is acid-washed and activated before treatment with γ-glycidoxypropyltrimethoxysilane. Specifically, the acid-washing and activation step may include: immersing the alumina in a 0.5-1 mol / L acid solution, with a solid-liquid ratio of 1 g:20-50 ml, and stirring at 40-80°C for 2-4 hours; the acid solution may be hydrochloric acid or nitric acid. The acid-washing step enriches the alumina surface with active hydroxyl groups, which is beneficial for improving the surface treatment efficiency and effect of γ-glycidoxypropyltrimethoxysilane.

[0050] In a preferred embodiment, the alumina particle size is 0.1-2 μm, and the alumina can be solid alumina, porous alumina, or through-pore alumina. In a more preferred embodiment, the alumina is porous alumina with a porosity of 20-50%.

[0051] In a preferred embodiment, the surface treatment step of γ-glycidoxypropyltrimethoxysilane may include: dispersing γ-glycidoxypropyltrimethoxysilane in an aqueous ethanol solution, wherein the volume ratio of ethanol to water in the aqueous ethanol solution is (90:10)-(95:5), adjusting the pH value to 4-6, adding alumina or acid-washed activated alumina, treating at 40-60°C for 0.5-4 hours, washing and drying after the reaction, to obtain alumina with γ-glycidoxypropyltrimethoxysilane surface modification.

[0052] Surface treatment of alumina with γ-glycidoxypropyltrimethoxysilane improves the interfacial compatibility between alumina and the resin matrix, reduces interfacial polarization caused by poor compatibility and numerous interfacial defects, and helps reduce dielectric loss. It can also act as a bridging agent in reaction with 4-aminomethylbenzoic acid, enabling 4-aminomethylbenzoic acid to effectively graft and modify alumina. The surface modification of alumina by the γ-glycidoxypropyltrimethoxysilane-4-aminomethylbenzoic acid organic long-chain molecule can, to some extent, compensate for the decrease in toughness caused by the addition of rigid inorganic alumina. The organic long-chain molecule can transfer and disperse stress, reducing interfacial separation caused by stress concentration.

[0053] The silanol group generated after hydrolysis of γ-glycidoxypropyltrimethoxysilane can react with the surface of alumina to achieve surface modification of alumina. Its epoxy group can undergo a nucleophilic addition ring-opening reaction with the amino group of 4-aminomethylbenzoic acid to achieve grafting of 4-aminomethylbenzoic acid.

[0054] In a preferred embodiment, the surface grafting of 4-aminomethylbenzoic acid comprises: dissolving 4-aminomethylbenzoic acid in a reaction solvent (e.g., acetone, N,N-dimethylformamide), adding alumina surface-treated with γ-glycidoxypropyltrimethoxysilane and triethylamine catalyst, and reacting at 70-90°C; after the reaction is completed, centrifuging, washing, and drying are performed to obtain 4-aminomethylbenzoic acid-grafted alumina. The mass ratio of alumina to 4-aminomethylbenzoic acid is 100:5-10. 4-Aminomethylbenzoic acid is grafted onto the alumina surface via a reaction between its amino group and γ-glycidoxypropyltrimethoxysilane molecules. Its unreacted carboxyl groups can participate in the curing process of the epoxy resin matrix, allowing the modified alumina to bond into the resin crosslinking network, which facilitates the grafting and rational distribution of the modified alumina within the crosslinking network. The rigid embedding of 4-aminomethylbenzoic acid molecules compensates for the insufficient mechanical properties of the flexible segments in the crosslinking network, further improving heat resistance. The matching of the silicon-oxygen bonds embedded on the alumina surface and the long silicon-oxygen segments of the epoxy-based silicone oil embedded in the crosslinking network provides detailed control and improvement over interface defects, further optimizing polarization and reducing dielectric loss. Therefore, the modified alumina grafted with γ-glycidoxypropyltrimethoxysilane-4-aminomethylbenzoic acid and the three main resins of this application, in combination, form superior heat resistance and dielectric properties. Grafting modified alumina also helps reduce internal stress caused by differences in thermal expansion coefficients at high temperatures, improving the heat resistance of the resin composition; in addition, the low polarity benzene ring structure of 4-aminomethylbenzoic acid further improves dielectric properties; at the same time, 4-aminomethylbenzoic acid-grafted alumina can synergistically improve flame retardant efficiency with phosphorus-containing flame retardants.

[0055] After 4-aminomethylbenzoic acid reacts with γ-glycidoxypropyltrimethoxysilane on the surface of alumina, the surface grafted compound molecule (-O-CH2-CH(OH)-CH2-NH-C6H4-COOH) has terminal carboxyl groups and secondary hydroxyl groups. The terminal carboxyl groups can participate in the esterification and crosslinking reaction of epoxy resin, while the highly polar secondary hydroxyl groups have low thermal stability and a certain impact on dielectric loss. In order to further improve the high temperature resistance and dielectric properties of the resin system, alicyclic anhydrides are used to further modify the 4-aminomethylbenzoic acid grafted alumina.

[0056] In a preferred embodiment, the modified alumina is obtained by grafting and oxidizing with 4-aminomethylbenzoic acid, followed by reaction with an alicyclic anhydride; the alicyclic anhydride is selected from hexahydrophthalic anhydride and methylhexahydrophthalic anhydride; the mass ratio of the alumina, the 4-aminomethylbenzoic acid, and the alicyclic anhydride is 100:5-10:5-12. Alicyclic anhydrides (such as hexahydrophthalic anhydride and methylhexahydrophthalic anhydride) are common epoxy resin anhydride curing agents. The anhydride ring of the alicyclic anhydride undergoes a ring-opening esterification reaction with the secondary hydroxyl group of the 4-aminomethylbenzoic acid-grafted alumina, and the alicyclic structure is grafted onto the branch chain of 4-aminomethylbenzoic acid-γ-glycidoxypropyltrimethoxysilane to obtain alicyclic anhydride-modified 4-aminomethylbenzoic acid-grafted alumina. Alicyclic anhydride molecules possess a certain degree of rigidity, low polarity, and good thermal stability and dielectric properties, which helps improve high-temperature resistance and further reduce dielectric loss. After the reaction, the anhydride undergoes ring-opening, generating free carboxyl groups, increasing the carboxyl group density and active bonding sites on the alumina surface, enhancing the chemical bonding between alumina and the resin system, and improving interfacial bonding strength and crosslinking density. Co-modification with alicyclic anhydrides and 4-aminomethylbenzoic acid further anchors the alumina in the system through the modification of different carboxyl groups on the chains, embedding a rationally distributed benzene ring and alicyclic ring. The benzene ring structure complements the rigidity of the flexible polyurethane chains in the crosslinking network, and together with the epoxy-based silicone oil chains, improves the heat resistance of the composition. The alicyclic structure offers better dielectric properties and can coordinate the rigidity of the benzene rings in the epoxy resin with the flexibility of the silicone and polyurethane chains, resulting in a composition with both good dielectric and mechanical properties. Therefore, co-modification of alumina with 4-aminomethylbenzoic acid and alicyclic anhydrides can further optimize the heat resistance and dielectric properties of the composition.

[0057] In a preferred embodiment, the modification method of alicyclic anhydride-modified 4-aminomethylbenzoic acid grafted alumina is as follows:

[0058] 4-Aminomethylbenzoic acid-grafted alumina was dispersed in xylene, and alicyclic anhydride and triethylamine catalyst were added. The mixture was heated to 110-140℃ under nitrogen atmosphere, refluxed to remove water, and reacted for 3-6 hours. After cooling and filtration, the mixture was washed 3-5 times with ethanol and dried under vacuum at 80-100℃ to obtain alicyclic anhydride-modified 4-aminomethylbenzoic acid-grafted alumina.

[0059] In a preferred embodiment, the halogen-free low-dielectric resin composition further includes an organic solvent selected from one or more of cyclohexanone, acetone, methyl ethyl ketone, and dimethylformamide. The solid content and viscosity of the resin composition can be adjusted by adding an appropriate amount of organic solvent; preferably, the solid content of the halogen-free low-dielectric resin composition for copper clad laminates is 40wt%-70wt%.

[0060] In a second aspect, the present invention provides a copper-clad laminate comprising a polyimide insulating film, a halogen-free resin composition layer coated on the surface of the polyimide insulating film, and copper foil laminated on the halogen-free resin composition coating.

[0061] In a preferred embodiment, the method for preparing the copper-clad laminate includes the following steps:

[0062] The halogen-free resin composition layer is coated onto the surface of a polyimide insulating film and heat-treated at 80-100°C for 4-6 minutes to form a partially cured halogen-free resin composition layer on the surface of the insulating film. The layer is then rolled and laminated with copper foil at 80-100°C and cured at 14-160°C to obtain a copper-clad laminate.

[0063] In a preferred embodiment, the polyimide insulating film has a thickness of 10-75 μm; the copper foil is a rolled copper foil or an electrolytic copper foil with a thickness of 9-35 μm; and the halogen-free resin composition layer has a thickness of 10-25 μm.

[0064] Example

[0065] Specifications of the materials and reagents used in the specific embodiments:

[0066] Bisphenol A type epoxy resin: Nan Ya NPEL-128; polyurethane modified epoxy resin: CVC HyPox UA10; terminal epoxy silicone oil: IOTA 105-1; terminal hydroxyl silicone oil: IOTA 2110; phosphorus-containing flame retardant: Exolit OP-935; alumina: TWA1, with an average particle size of approximately 1.0 μm; γ-glycidoxypropyltrimethoxysilane: KH-560. The materials and reagents used in this invention are obtained through conventional commercial means.

[0067] Example 1

[0068] This embodiment provides a copper-clad laminate, the preparation method of which is as follows:

[0069] 1. Modification of alumina fillers

[0070] 1.1 Immerse 50 parts of alumina powder in a 1 mol / L nitric acid solution with a solid-liquid ratio of 1 g: 40 ml, stir at 45 °C for 2 h, wash with water three times, and then vacuum dry to obtain activated alumina.

[0071] 1.2 Add KH560 to an ethanol-water solution (ethanol-water volume ratio of 95:5) to prepare a coupling agent solution with a mass percentage of 5%, and add acetic acid to adjust the pH value to 4.5; immerse activated alumina in the coupling agent solution with a solid-liquid ratio of 1g:20ml, sonicate at 60℃ for 1h, and vacuum dry to obtain coupling modified alumina.

[0072] 1.3 The coupling-modified alumina was dispersed in N,N-dimethylformamide, and 2.5 parts by mass of 4-aminomethylbenzoic acid and 0.1 parts by mass of triethylamine were added. The mixture was stirred at 80°C for 4 hours. After the reaction was completed, the mixture was centrifuged and washed three times with N,N-dimethylformamide and ethanol, respectively. The mixture was then dried under vacuum to obtain 4-aminomethylbenzoic acid-grafted alumina.

[0073] 2. Copper Clad Laminate

[0074] The halogen-free low-dielectric resin composition comprises 60 parts by weight of bisphenol A type epoxy resin, 12 parts by weight of polyurethane modified epoxy resin, 8 parts by weight of terminal epoxy silicone oil, 14 parts by weight of m-phenylenediamine, 0.6 parts by weight of 2-phenylimidazolium, 18 parts by weight of phosphorus-containing flame retardant, and 22 parts by weight of 4-aminomethylbenzoic acid grafted alumina obtained in step 1.

[0075] The above raw materials were dispersed evenly with cyclohexanone, and the solid content was adjusted to 70% to obtain a liquid resin composition.

[0076] A liquid resin composition was coated onto the surface of a 75 μm polyimide insulating film with a coating thickness of 25 μm. The organic solvent was removed by baking at 150 °C, and a partially cured composition layer was formed on the surface of the insulating film.

[0077] The copper-clad laminate is obtained by roll-pressing with 35μm electrolytic copper foil at 100℃ and curing at 170℃.

[0078] Example 2

[0079] The only difference between this embodiment and Example 1 is that the mass fractions of each raw material in the halogen-free low-dielectric resin composition are different.

[0080] 1. Modification of alumina fillers

[0081] 1.1 Immerse 50 parts of alumina powder in a 1 mol / L nitric acid solution with a solid-liquid ratio of 1 g: 40 ml, stir at 45 °C for 2 h, wash with water three times, and then vacuum dry to obtain activated alumina.

[0082] 1.2 Add KH560 to an ethanol-water solution (ethanol-water volume ratio of 95:5) to prepare a coupling agent solution with a mass percentage of 5%, and add acetic acid to adjust the pH value to 4.5; immerse activated alumina in the coupling agent solution with a solid-liquid ratio of 1g:20ml, sonicate at 60℃ for 1h, and vacuum dry to obtain coupling modified alumina.

[0083] 1.3 The coupling-modified alumina was dispersed in N,N-dimethylformamide, and 2.5 parts by mass of 4-aminomethylbenzoic acid and 0.1 parts by mass of triethylamine were added. The mixture was stirred at 80°C for 4 hours. After the reaction was completed, the mixture was centrifuged and washed three times with N,N-dimethylformamide and ethanol, respectively. The mixture was then dried under vacuum to obtain 4-aminomethylbenzoic acid-grafted alumina.

[0084] 2. Copper Clad Laminate

[0085] The halogen-free low-dielectric resin composition comprises 65 parts by weight of bisphenol A type epoxy resin, 10 parts by weight of polyurethane modified epoxy resin, 10 parts by weight of terminal epoxy silicone oil, 14 parts by weight of m-phenylenediamine, 0.6 parts by weight of 2-phenylimidazolium, 18 parts by weight of phosphorus-containing flame retardant, and 16 parts by weight of 4-aminomethylbenzoic acid grafted alumina obtained in step 1.

[0086] The above raw materials were dispersed evenly with cyclohexanone, and the solid content was adjusted to 70% to obtain a liquid halogen-free low dielectric resin composition.

[0087] A liquid resin composition was coated onto the surface of a 75 μm polyimide insulating film with a coating thickness of 25 μm. The film was then baked at 150 °C to remove the organic solvent, resulting in a partially cured composition layer on the surface of the insulating film.

[0088] The copper-clad laminate is obtained by roll-pressing with 35μm electrolytic copper foil at 100℃ and curing at 170℃.

[0089] Example 3

[0090] The only difference between this embodiment and Example 1 is the ratio of alumina to 4-aminomethylbenzoic acid.

[0091] 1. Modification of alumina fillers

[0092] 1.1 Immerse 50 parts of alumina powder in a 1 mol / L nitric acid solution with a solid-liquid ratio of 1 g: 40 ml, stir at 45 °C for 2 h, wash with water three times, and then vacuum dry to obtain activated alumina.

[0093] 1.2 Add KH560 to an ethanol-water solution (ethanol-water volume ratio of 95:5) to prepare a coupling agent solution with a mass percentage of 5%, and add acetic acid to adjust the pH value to 4.5; immerse activated alumina in the coupling agent solution with a solid-liquid ratio of 1g:20ml, sonicate at 60℃ for 1h, and vacuum dry to obtain coupling modified alumina.

[0094] 1.3 The coupling-modified alumina was dispersed in N,N-dimethylformamide, and 4 parts by mass of 4-aminomethylbenzoic acid and 0.1 parts by mass of triethylamine were added. The mixture was stirred at 80°C for 4 hours. After the reaction was completed, the mixture was centrifuged and washed three times with N,N-dimethylformamide and ethanol, respectively. The mixture was then dried under vacuum to obtain 4-aminomethylbenzoic acid-grafted alumina.

[0095] 2. Copper Clad Laminate

[0096] The halogen-free low-dielectric resin composition comprises 60 parts by weight of bisphenol A type epoxy resin, 12 parts by weight of polyurethane modified epoxy resin, 8 parts by weight of terminal epoxy silicone oil, 14 parts by weight of m-phenylenediamine, 0.6 parts by weight of 2-phenylimidazolium, 18 parts by weight of phosphorus-containing flame retardant, and 22 parts by weight of 4-aminomethylbenzoic acid grafted alumina obtained in step 1.

[0097] The above raw materials were dispersed evenly with cyclohexanone, and the solid content was adjusted to 70% to obtain a liquid resin composition.

[0098] A liquid resin composition was coated onto the surface of a 75 μm polyimide insulating film with a coating thickness of 25 μm. The film was then baked at 150 °C to remove the organic solvent, resulting in a partially cured composition layer on the surface of the insulating film.

[0099] The copper-clad laminate is obtained by roll-pressing with 35μm electrolytic copper foil at 100℃ and curing at 170℃.

[0100] Example 4

[0101] The only difference between this embodiment and Example 1 is that hexahydrophthalic anhydride and 4-aminomethylbenzoic acid grafted alumina are added and mixed.

[0102] 1. Modification of alumina fillers

[0103] 1.1 Immerse 50 parts of alumina powder in a 1 mol / L nitric acid solution with a solid-liquid ratio of 1 g: 40 ml, stir at 45 °C for 2 h, wash with water three times, and then vacuum dry to obtain activated alumina.

[0104] 1.2 Add KH560 to an ethanol-water solution (ethanol-water volume ratio of 95:5) to prepare a coupling agent solution with a mass percentage of 5%, and add acetic acid to adjust the pH value to 4.5; immerse activated alumina in the coupling agent solution with a solid-liquid ratio of 1g:20ml, sonicate at 60℃ for 1h, and vacuum dry to obtain coupling modified alumina.

[0105] 1.3 The coupling-modified alumina was dispersed in N,N-dimethylformamide, and 2.5 parts by mass of 4-aminomethylbenzoic acid and 0.1 parts by mass of triethylamine were added. The mixture was stirred at 80°C for 4 hours. After the reaction was completed, the mixture was centrifuged and washed three times with N,N-dimethylformamide and ethanol, respectively. The mixture was then dried under vacuum to obtain 4-aminomethylbenzoic acid-grafted alumina.

[0106] 1.4 Modified alumina was obtained by thoroughly mixing 4-aminomethylbenzoic acid-grafted alumina and 2.5 parts by mass of hexahydrophthalic anhydride at high speed.

[0107] 2. Copper Clad Laminate

[0108] The halogen-free low-dielectric resin composition comprises 60 parts by weight of bisphenol A type epoxy resin, 12 parts by weight of polyurethane modified epoxy resin, 8 parts by weight of terminal epoxy silicone oil, 14 parts by weight of m-phenylenediamine, 0.6 parts by weight of 2-phenylimidazolium, 18 parts by weight of phosphorus-containing flame retardant, and 22 parts by weight of modified alumina obtained in step 1; the above raw materials are dispersed evenly with cyclohexanone, and the solid content is adjusted to 70% to obtain a liquid resin composition.

[0109] A liquid resin composition was coated onto the surface of a 75 μm polyimide insulating film with a coating thickness of 25 μm. The film was then baked at 150 °C to remove the organic solvent, resulting in a partially cured composition layer on the surface of the insulating film.

[0110] The copper-clad laminate is obtained by roll-pressing with 35μm electrolytic copper foil at 100℃ and curing at 170℃.

[0111] Example 5

[0112] The only difference between this embodiment and Example 1 is that hexahydrophthalic anhydride is used to modify 4-aminomethylbenzoic acid grafted onto alumina.

[0113] 1. Modification of alumina fillers

[0114] 1.1 Immerse 50 parts of alumina powder in a 1 mol / L nitric acid solution with a solid-liquid ratio of 1 g: 40 ml, stir at 45 °C for 2 h, wash with water three times, and then vacuum dry to obtain activated alumina.

[0115] 1.2 Add KH560 to an ethanol-water solution (ethanol-water volume ratio of 95:5) to prepare a coupling agent solution with a mass percentage of 5%, and add acetic acid to adjust the pH value to 4.5; immerse activated alumina in the coupling agent solution with a solid-liquid ratio of 1g:20ml, sonicate at 60℃ for 1h, and vacuum dry to obtain coupling modified alumina.

[0116] 1.3 The coupling-modified alumina was dispersed in N,N-dimethylformamide, and 2.5 parts by mass of 4-aminomethylbenzoic acid and 0.1 parts by mass of triethylamine were added. The mixture was stirred at 80°C for 4 hours. After the reaction was completed, the mixture was centrifuged and washed three times with N,N-dimethylformamide and ethanol, respectively. The mixture was then dried under vacuum to obtain 4-aminomethylbenzoic acid-grafted alumina.

[0117] 1.4 4-Aminomethylbenzoic acid-grafted alumina was dispersed in xylene, and 2.5 parts by mass of hexahydrophthalic anhydride and 0.2 parts by mass of p-toluenesulfonic acid were added. Nitrogen gas was introduced to replace the air, and the temperature was raised to 120°C under nitrogen conditions. The reaction was carried out for 5 hours, cooled, filtered, washed with ethanol, dried under vacuum at 85°C, and ground and dispersed to obtain hexahydrophthalic anhydride-modified 4-aminomethylbenzoic acid-grafted alumina.

[0118] 2. Copper Clad Laminate

[0119] The halogen-free low-dielectric resin composition comprises 60 parts by weight of bisphenol A type epoxy resin, 12 parts by weight of polyurethane modified epoxy resin, 8 parts by weight of terminal epoxy silicone oil, 14 parts by weight of m-phenylenediamine, 0.6 parts by weight of 2-phenylimidazolium, 18 parts by weight of phosphorus-containing flame retardant, and 22 parts by weight of hexahydrophthalic anhydride-modified 4-aminomethylbenzoic acid-grafted alumina obtained in step 1; the above raw materials are dispersed evenly with cyclohexanone, and the solid content is adjusted to 70% to obtain a liquid resin composition.

[0120] A liquid resin composition was coated onto the surface of a 75 μm polyimide insulating film with a coating thickness of 25 μm. The organic solvent was removed by baking at 150 °C, and a partially cured composition layer was formed on the surface of the insulating film.

[0121] The copper-clad laminate is obtained by roll-pressing with 35μm electrolytic copper foil at 100℃ and curing at 170℃.

[0122] Example 6

[0123] The only difference between this embodiment and Example 1 is that methyl hexahydrophthalic anhydride is used to modify 4-aminomethylbenzoic acid grafted onto alumina.

[0124] 1. Modification of alumina fillers

[0125] 1.1 Immerse 50 parts of alumina powder in a 1 mol / L nitric acid solution with a solid-liquid ratio of 1 g: 40 ml, stir at 45 °C for 2 h, wash with water three times, and then vacuum dry to obtain activated alumina.

[0126] 1.2 Add KH560 to an ethanol-water solution (ethanol-water volume ratio of 95:5) to prepare a coupling agent solution with a mass percentage of 5%, and add acetic acid to adjust the pH value to 4.5; immerse activated alumina in the coupling agent solution with a solid-liquid ratio of 1g:20ml, sonicate at 60℃ for 1h, and vacuum dry to obtain coupling modified alumina.

[0127] 1.3 The coupling-modified alumina was dispersed in N,N-dimethylformamide, and 2.5 parts by mass of 4-aminomethylbenzoic acid and 0.1 parts by mass of triethylamine were added. The mixture was stirred at 80°C for 4 hours. After the reaction was completed, the mixture was centrifuged and washed three times with N,N-dimethylformamide and ethanol, respectively. The mixture was then dried under vacuum to obtain 4-aminomethylbenzoic acid-grafted alumina.

[0128] 1.4 4-Aminomethylbenzoic acid-grafted alumina was dispersed in xylene, and 3 parts by mass of methylhexahydrophthalic anhydride and 0.2 parts by mass of p-toluenesulfonic acid were added. Nitrogen gas was introduced to replace the air, and the mixture was heated to 120°C under nitrogen conditions and reacted for 5 hours. After cooling, the mixture was filtered, washed with ethanol, dried under vacuum at 85°C, and ground and dispersed to obtain methylhexahydrophthalic anhydride-modified 4-aminomethylbenzoic acid-grafted alumina.

[0129] 2. Copper Clad Laminate

[0130] The halogen-free low-dielectric resin composition comprises 60 parts by weight of bisphenol A type epoxy resin, 12 parts by weight of polyurethane modified epoxy resin, 8 parts by weight of terminal epoxy silicone oil, 14 parts by weight of m-phenylenediamine, 0.6 parts by weight of 2-phenylimidazolium, 18 parts by weight of phosphorus-containing flame retardant, and 22 parts by weight of methylhexahydrophthalic anhydride modified 4-aminomethylbenzoic acid grafted alumina obtained in step 1.

[0131] The above raw materials were dispersed evenly with cyclohexanone, and the solid content was adjusted to 70% to obtain a liquid resin composition.

[0132] A liquid resin composition was coated onto the surface of a 75 μm polyimide insulating film with a coating thickness of 25 μm. The film was then baked at 150 °C to remove the organic solvent, resulting in a partially cured composition layer on the surface of the insulating film.

[0133] The copper-clad laminate is obtained by roll-pressing with 35μm electrolytic copper foil at 100℃ and curing at 170℃.

[0134] Example 7

[0135] The only difference between this embodiment and Example 1 is that phthalic anhydride is used to modify 4-aminomethylbenzoic acid grafted onto alumina.

[0136] 1. Modification of alumina fillers

[0137] 1.1 Immerse 50 parts of alumina powder in a 1 mol / L nitric acid solution with a solid-liquid ratio of 1 g: 40 ml, stir at 45 °C for 2 h, wash with water three times, and then vacuum dry to obtain activated alumina.

[0138] 1.2 Add KH560 to an ethanol-water solution (ethanol-water volume ratio of 95:5) to prepare a coupling agent solution with a mass percentage of 5%, and add acetic acid to adjust the pH value to 4.5; immerse activated alumina in the coupling agent solution with a solid-liquid ratio of 1g:20ml, sonicate at 60℃ for 1h, and vacuum dry to obtain coupling modified alumina.

[0139] 1.3 The coupling-modified alumina was dispersed in N,N-dimethylformamide, and 2.5 parts by mass of 4-aminomethylbenzoic acid and 0.1 parts by mass of triethylamine were added. The mixture was stirred at 80°C for 4 hours. After the reaction was completed, the mixture was centrifuged and washed three times with N,N-dimethylformamide and ethanol, respectively. The mixture was then dried under vacuum to obtain 4-aminomethylbenzoic acid-grafted alumina.

[0140] 1.4 4-Aminomethylbenzoic acid-grafted alumina was dispersed in xylene, and 2.5 parts by mass of phthalic anhydride and 0.2 parts by mass of p-toluenesulfonic acid were added. Nitrogen gas was introduced to replace the air, and the temperature was raised to 120°C under nitrogen conditions. The reaction was carried out for 5 hours, cooled, filtered, washed with ethanol, dried under vacuum at 85°C, and ground and dispersed to obtain phthalic anhydride-modified 4-aminomethylbenzoic acid-grafted alumina.

[0141] 2. Copper Clad Laminate

[0142] The halogen-free low-dielectric resin composition comprises 60 parts by weight of bisphenol A type epoxy resin, 12 parts by weight of polyurethane modified epoxy resin, 8 parts by weight of terminal epoxy silicone oil, 14 parts by weight of m-phenylenediamine, 0.6 parts by weight of 2-phenylimidazolium, 18 parts by weight of phosphorus-containing flame retardant, and 22 parts by weight of hexahydrophthalic anhydride-modified 4-aminomethylbenzoic acid-grafted alumina obtained in step 1; the above raw materials are dispersed evenly with cyclohexanone, and the solid content is adjusted to 70% to obtain a liquid resin composition.

[0143] A liquid resin composition was coated onto the surface of a 75 μm polyimide insulating film with a coating thickness of 25 μm. The organic solvent was removed by baking at 150 °C, and a partially cured composition layer was formed on the surface of the insulating film.

[0144] The copper-clad laminate is obtained by roll-pressing with 35μm electrolytic copper foil at 100℃ and curing at 170℃.

[0145] Example 8

[0146] The only difference between this embodiment and Example 1 is that adipic anhydride is used to modify 4-aminomethylbenzoic acid grafted onto alumina.

[0147] 1. Modification of alumina fillers

[0148] 1.1 Immerse 50 parts of alumina powder in a 1 mol / L nitric acid solution with a solid-liquid ratio of 1 g: 40 ml, stir at 45 °C for 2 h, wash with water three times, and then vacuum dry to obtain activated alumina.

[0149] 1.2 Add KH560 to an ethanol-water solution (ethanol-water volume ratio of 95:5) to prepare a coupling agent solution with a mass percentage of 5%, and add acetic acid to adjust the pH value to 4.5; immerse activated alumina in the coupling agent solution with a solid-liquid ratio of 1g:20ml, sonicate at 60℃ for 1h, and vacuum dry to obtain coupling modified alumina.

[0150] 1.3 The coupling-modified alumina was dispersed in N,N-dimethylformamide, and 2.5 parts by mass of 4-aminomethylbenzoic acid and 0.1 parts by mass of triethylamine were added. The mixture was stirred at 80°C for 4 hours. After the reaction was completed, the mixture was centrifuged and washed three times with N,N-dimethylformamide and ethanol, respectively. The mixture was then dried under vacuum to obtain 4-aminomethylbenzoic acid-grafted alumina.

[0151] 1.4 4-Aminomethylbenzoic acid-grafted alumina was dispersed in xylene, and 2.5 parts by mass of adipic anhydride and 0.2 parts by mass of p-toluenesulfonic acid were added. Nitrogen gas was introduced to replace the air, and the temperature was raised to 120°C under nitrogen conditions. The reaction was carried out for 5 hours, cooled, filtered, washed with ethanol, dried under vacuum at 85°C, and ground and dispersed to obtain adipic anhydride-modified 4-aminomethylbenzoic acid-grafted alumina.

[0152] 2. Copper Clad Laminate

[0153] The halogen-free low-dielectric resin composition comprises 60 parts by weight of bisphenol A type epoxy resin, 12 parts by weight of polyurethane modified epoxy resin, 8 parts by weight of terminal epoxy silicone oil, 14 parts by weight of m-phenylenediamine, 0.6 parts by weight of 2-phenylimidazolium, 18 parts by weight of phosphorus-containing flame retardant, and 22 parts by weight of hexahydrophthalic anhydride-modified 4-aminomethylbenzoic acid-grafted alumina obtained in step 1; the above raw materials are dispersed evenly with cyclohexanone, and the solid content is adjusted to 70% to obtain a liquid resin composition.

[0154] A liquid resin composition was coated onto the surface of a 75 μm polyimide insulating film with a coating thickness of 25 μm. The organic solvent was removed by baking at 150 °C, and a partially cured composition layer was formed on the surface of the insulating film.

[0155] The copper-clad laminate is obtained by roll-pressing with 35μm electrolytic copper foil at 100℃ and curing at 170℃.

[0156] Example 9

[0157] The only difference between this embodiment and Example 4 is that hexahydrophthalic anhydride is used to modify the coupled alumina.

[0158] 1. Modification of alumina fillers

[0159] 1.1 Immerse 50 parts of alumina powder in a 1 mol / L nitric acid solution with a solid-liquid ratio of 1 g: 40 ml, stir at 45 °C for 2 h, wash with water three times, and then vacuum dry to obtain activated alumina.

[0160] 1.2 Add KH560 to an ethanol-water solution (ethanol-water volume ratio of 95:5) to prepare a coupling agent solution with a mass percentage of 5%, and add acetic acid to adjust the pH value to 4.5; immerse activated alumina in the coupling agent solution with a solid-liquid ratio of 1g:20ml, sonicate at 60℃ for 1h, and vacuum dry to obtain coupling modified alumina.

[0161] 1.3 The coupling-modified alumina was dispersed in xylene, and 2.5 parts by mass of hexahydrophthalic anhydride and 0.2 parts by mass of triethylamine were added. Nitrogen gas was introduced to replace the air, and the temperature was raised to 120°C under nitrogen conditions. The reaction was carried out for 3 hours, cooled, filtered, washed with ethanol, dried under vacuum at 85°C, and ground and dispersed to obtain hexahydrophthalic anhydride-modified alumina.

[0162] 2. Copper Clad Laminate

[0163] The halogen-free low-dielectric resin composition comprises 60 parts by weight of bisphenol A type epoxy resin, 12 parts by weight of polyurethane modified epoxy resin, 8 parts by weight of terminal epoxy silicone oil, 14 parts by weight of m-phenylenediamine, 0.6 parts by weight of 2-phenylimidazolium, 18 parts by weight of phosphorus-containing flame retardant, and 22 parts by weight of hexahydrophthalic anhydride modified alumina obtained in step 1; the above raw materials are dispersed evenly with cyclohexanone, and the solid content is adjusted to 70% to obtain a liquid resin composition.

[0164] A liquid resin composition was coated onto the surface of a 75 μm polyimide insulating film with a coating thickness of 25 μm. The organic solvent was removed by baking at 150 °C, and a partially cured composition layer was formed on the surface of the insulating film.

[0165] The copper-clad laminate is obtained by roll-pressing with 35μm electrolytic copper foil at 100℃ and curing at 170℃. Comparative Example

[0166] Comparative Example 1

[0167] The difference between this comparative example and Example 1 is that the copper-clad laminate is prepared using a different method. Specifically, it is prepared using the following method:

[0168] The halogen-free low-dielectric resin composition comprises 60 parts by weight of bisphenol A type epoxy resin, 12 parts by weight of polyurethane modified epoxy resin, 8 parts by weight of terminal epoxy silicone oil, 14 parts by weight of m-phenylenediamine, 0.6 parts by weight of 2-phenylimidazolium, and 18 parts by weight of phosphorus-containing flame retardant.

[0169] The above raw materials were dispersed evenly with cyclohexanone, and the solid content was adjusted to 70% to obtain a liquid resin composition.

[0170] A liquid resin composition was coated onto the surface of a 75 μm polyimide insulating film with a coating thickness of 25 μm. The film was then baked at 150 °C to remove the organic solvent, resulting in a partially cured composition layer on the surface of the insulating film.

[0171] The copper-clad laminate is obtained by roll-pressing with 35μm electrolytic copper foil at 100℃ and curing at 170℃.

[0172] Comparative Example 2

[0173] The difference between this comparative example and Example 1 is that the copper-clad laminate is prepared using a different method. Specifically, it is prepared using the following method:

[0174] 1. Modification of alumina fillers

[0175] 1.1 Immerse 50 parts of alumina powder in a 1 mol / L nitric acid solution with a solid-liquid ratio of 1 g: 40 ml, stir at 45 °C for 2 h, wash with water three times, and then vacuum dry to obtain activated alumina.

[0176] 1.2 Add KH560 to an ethanol-water solution (ethanol-water volume ratio of 95:5) to prepare a coupling agent solution with a mass percentage of 5%, and add acetic acid to adjust the pH value to 4.5; immerse activated alumina in the coupling agent solution with a solid-liquid ratio of 1g:20ml, sonicate at 60℃ for 1h, and vacuum dry to obtain coupling modified alumina.

[0177] 1.3 The coupling-modified alumina was dispersed in N,N-dimethylformamide, and 2.5 parts by mass of 4-aminomethylbenzoic acid and 0.1 parts by mass of triethylamine were added. The mixture was stirred at 80°C for 4 hours. After the reaction was completed, the mixture was centrifuged and washed three times with N,N-dimethylformamide and ethanol, respectively. The mixture was then dried under vacuum to obtain 4-aminomethylbenzoic acid-grafted alumina.

[0178] 2. Copper Clad Laminate

[0179] The halogen-free low-dielectric resin composition comprises 60 parts by weight of bisphenol A type epoxy resin, 20 parts by weight of polyurethane modified epoxy resin, 14 parts by weight of m-phenylenediamine, 0.6 parts by weight of 2-phenylimidazolium, 18 parts by weight of phosphorus-containing flame retardant, and 22 parts by weight of 4-aminomethylbenzoic acid grafted alumina obtained in step 1. The above raw materials are dispersed evenly with cyclohexanone, and the solid content is adjusted to 70% to obtain a liquid resin composition.

[0180] A liquid resin composition was coated onto the surface of a 75 μm polyimide insulating film with a coating thickness of 25 μm. The film was then baked at 150 °C to remove the organic solvent, resulting in a partially cured composition layer on the surface of the insulating film.

[0181] The copper-clad laminate is obtained by roll-pressing with 35μm electrolytic copper foil at 100℃ and curing at 170℃.

[0182] Comparative Example 3

[0183] The difference between this comparative example and Example 1 is that the copper-clad laminate is prepared using a different method. Specifically, it is prepared using the following method:

[0184] 1. Modification of alumina fillers

[0185] 1.1 Immerse 50 parts of alumina powder in a 1 mol / L nitric acid solution with a solid-liquid ratio of 1 g: 40 ml, stir at 45 °C for 2 h, wash with water three times, and then vacuum dry to obtain activated alumina.

[0186] 1.2 Add KH560 to an ethanol-water solution (ethanol-water volume ratio of 95:5) to prepare a coupling agent solution with a mass percentage of 5%, and add acetic acid to adjust the pH value to 4.5; immerse activated alumina in the coupling agent solution with a solid-liquid ratio of 1g:20ml, sonicate at 60℃ for 1h, and vacuum dry to obtain coupling modified alumina.

[0187] 1.3 The coupling-modified alumina was dispersed in N,N-dimethylformamide, and 2.5 parts by mass of 4-aminomethylbenzoic acid and 0.1 parts by mass of triethylamine were added. The mixture was stirred at 80°C for 4 hours. After the reaction was completed, the mixture was centrifuged and washed three times with N,N-dimethylformamide and ethanol, respectively. The mixture was then dried under vacuum to obtain 4-aminomethylbenzoic acid-grafted alumina.

[0188] 2. Copper Clad Laminate

[0189] The halogen-free low-dielectric resin composition comprises 60 parts by weight of bisphenol A type epoxy resin, 12 parts by weight of polyurethane modified epoxy resin, 8 parts by weight of hydroxyl-terminated silicone oil, 14 parts by weight of m-phenylenediamine, 0.6 parts by weight of 2-phenylimidazolium, 18 parts by weight of phosphorus-containing flame retardant, and 22 parts by weight of 4-aminomethylbenzoic acid-grafted alumina obtained in step 1. The above raw materials are dispersed evenly with cyclohexanone, and the solid content is adjusted to 70% to obtain a liquid resin composition.

[0190] A liquid resin composition was coated onto the surface of a 75 μm polyimide insulating film with a coating thickness of 25 μm. The film was then baked at 150 °C to remove the organic solvent, resulting in a partially cured composition layer on the surface of the insulating film.

[0191] The copper-clad laminate is obtained by roll-pressing with 35μm electrolytic copper foil at 100℃ and curing at 170℃.

[0192] Comparative Example 4

[0193] The difference between this comparative example and Example 1 is that the copper-clad laminate is prepared using a different method. Specifically, it is prepared using the following method:

[0194] 1. Modification of alumina fillers

[0195] 1.1 Immerse 50 parts of alumina powder in a 1 mol / L nitric acid solution with a solid-liquid ratio of 1 g: 40 ml, stir at 45 °C for 2 h, wash with water three times, and then vacuum dry to obtain activated alumina.

[0196] 1.2 Add KH560 to an ethanol-water solution (ethanol-water volume ratio of 95:5) to prepare a coupling agent solution with a mass percentage of 5%, and add acetic acid to adjust the pH value to 4.5; immerse activated alumina in the coupling agent solution with a solid-liquid ratio of 1g:20ml, sonicate at 60℃ for 1h, and vacuum dry to obtain coupling modified alumina.

[0197] 2. Copper Clad Laminate

[0198] The halogen-free low-dielectric resin composition comprises 60 parts by weight of bisphenol A type epoxy resin, 12 parts by weight of polyurethane modified epoxy resin, 8 parts by weight of terminal epoxy silicone oil, 14 parts by weight of m-phenylenediamine, 0.6 parts by weight of 2-phenylimidazolium, 18 parts by weight of phosphorus-containing flame retardant, and 22 parts by weight of coupling modified alumina obtained in step 1; the above raw materials are dispersed evenly with cyclohexanone, and the solid content is adjusted to 70% to obtain a liquid resin composition.

[0199] A liquid resin composition was coated onto the surface of a 75 μm polyimide insulating film with a coating thickness of 25 μm. The film was then baked at 150 °C to remove the organic solvent, resulting in a partially cured composition layer on the surface of the insulating film.

[0200] The copper-clad laminate is obtained by roll-pressing with 35μm electrolytic copper foil at 100℃ and curing at 170℃.

[0201] Performance testing

[0202] The copper-clad laminates prepared in the above embodiments and comparative examples were subjected to performance tests, and the test methods are as follows:

[0203] Limiting immersion soldering temperature: Cut the obtained flexible copper-clad laminate into samples with a size of 50mm×50mm, and after dehumidification, immerse them in molten solder at 288℃, 320℃ and 360℃ for 60 seconds respectively. Observe whether there is delamination and bubbling. The highest temperature that passes is the limiting immersion soldering temperature.

[0204] Flame retardancy: After etching the metal layer, the sample was cut into 125mm×15mm size, placed at 23±2℃ and 50±5% humidity for 48h, then treated in a 70℃ oven for 12h, and tested according to UL94 vertical burning method after cooling to room temperature.

[0205] Flexural strength: The obtained flexible copper-clad laminate was cut into samples with a size of 150mm×50mm and tested according to JIS C-6471;

[0206] Dielectric properties: The obtained flexible copper-clad laminate was cut into samples with a size of 50mm×50mm, and placed at a temperature of 23±2℃ and a humidity of 50±5% for 48h. The samples were then tested according to the IPC-TM-650 2.5.5 method.

[0207] Ion migration resistance: A specific pattern of test circuitry is etched onto the copper-clad laminate. Under dual 85 conditions, a 100V DC voltage is applied to the sample electrodes for 1000 hours. If a short circuit occurs within 1000 hours, the test fails; otherwise, it passes.

[0208] Dendritic crystals: Observe whether there are "dendritic growths" in ion-resistant samples.

[0209] The test results are summarized in Tables 1 and 2.

[0210]

[0211] Table 2

[0212]

[0213] As can be seen from Example 1, Comparative Examples 2-4 and Table 1, the copper-clad laminate prepared according to the resin formulation disclosed in this application has excellent heat resistance, flame retardancy, folding resistance and ion migration resistance, and also has excellent dielectric properties.

[0214] As can be seen from Examples 1, Comparative Examples 1 and 4 and Tables 1 and 2, the addition of 4-aminomethylbenzoic acid-grafted alumina can improve the overall performance of copper clad laminates and reduce the dielectric constant. As can be seen from Examples 1 and 4-8 and Table 1, further modification and branching of 4-aminomethylbenzoic acid-grafted alumina with alicyclic anhydrides can further reduce dielectric loss and improve dielectric properties. However, grafting with phenyl anhydride and adipic anhydride results in some performance loss. This may be because phenyl anhydride itself has low reactivity with 4-aminomethylbenzoic acid-grafted alumina, excessive steric hindrance, which affects the wetting and encapsulation of alumina by the resin system. Furthermore, the reaction forms a highly polar benzene ring-ester structure, which leads to a loss of dielectric properties. In addition, the diphenyl structure of the grafted compound on the alumina surface causes excessive rigidity, which reduces flexibility. After reacting with 4-aminomethylbenzoic acid-grafted alumina, oxalic anhydride forms a straight-chain structure with good branch flexibility, which is beneficial to improving the folding resistance of the system. However, its heat resistance is poor, and its effect on improving dielectric properties is lower than that of alicyclic anhydrides.

[0215] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A halogen-free low-dielectric resin composition for copper-clad laminates, characterized in that, The following raw materials are included in parts by weight: 50-70 parts of multifunctional epoxy resin 10-20 parts of polyurethane-modified epoxy resin 5-10 parts of epoxy-terminated silicone oil 12-25 parts of curing agent Curing accelerator 0.2-1 part, 15-20 parts flame retardant 15-30 parts of modified alumina, wherein the modified alumina is obtained by surface treatment of alumina with γ-glycidoxypropyltrimethoxysilane followed by grafting 4-aminomethylbenzoic acid onto the surface.

2. The halogen-free low-dielectric resin composition for copper-clad laminates according to claim 1, characterized in that, Alumina is subjected to acid washing and activation treatment before treatment with γ-glycidoxypropyltrimethoxysilane.

3. The halogen-free low-dielectric resin composition for copper-clad laminates according to claim 1, characterized in that, The surface grafting of 4-aminomethylbenzoic acid comprises: dissolving 4-aminomethylbenzoic acid in a reaction solvent, adding alumina surface-treated with γ-glycidoxypropyltrimethoxysilane, and reacting at 40-60°C; after the reaction is completed, centrifuging, washing, and drying are performed to obtain 4-aminomethylbenzoic acid-grafted alumina, which is used as modified alumina.

4. The halogen-free low-dielectric resin composition for copper-clad laminates according to claim 3, characterized in that, The mass ratio of the alumina to the 4-aminomethylbenzoic acid is 100:5-10.

5. The halogen-free low-dielectric resin composition for copper-clad laminates according to any one of claims 1-3, characterized in that, The modified alumina is obtained by grafting and oxidizing with 4-aminomethylbenzoic acid, followed by reaction with alicyclic anhydride; The alicyclic anhydride is selected from one of hexahydrophthalic anhydride and methylhexahydrophthalic anhydride; The mass ratio of the alumina, the 4-aminomethylbenzoic acid and the alicyclic anhydride is 100:5-10:5-12.

6. The halogen-free low-dielectric resin composition for copper-clad laminates according to claim 1, characterized in that, The curing agent is selected from one or more of 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, dicyandiamide, m-phenylenediamine, diethylenetriamine, and diphenylmethanediamine; the curing accelerator is an imidazole accelerator.

7. The halogen-free low-dielectric resin composition for copper-clad laminates according to claim 1, characterized in that, The halogen-free low-dielectric resin composition further includes an organic solvent, which is selected from one or more of acetone, methyl ethyl ketone, and dimethylformamide; The solid content of the halogen-free low-dielectric resin composition is 40wt%-70wt%.

8. A copper-clad laminate prepared using the halogen-free low-dielectric resin composition for copper-clad laminates according to any one of claims 1-7, characterized in that, The copper-clad laminate includes: a polyimide insulating film, a halogen-free resin composition layer formed by coating the surface of the polyimide insulating film with a halogen-free low-dielectric resin composition for the copper-clad laminate, and a copper foil pressed onto the halogen-free resin composition layer.

9. The copper-clad laminate according to claim 8, characterized in that, The polyimide insulating film has a thickness of 10-75 μm; the copper foil is rolled copper foil or electrolytic copper foil with a thickness of 9-35 μm; and the halogen-free resin composition layer has a thickness of 10-25 μm.

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