Low-loss resin composition, prepreg and copper-clad substrate

Abstract

This invention discloses a low-loss resin composition, comprising, by weight, the following main components: 10-90 parts of acenaphthene-p-vinylbiphenyl copolymer, 10-70 parts of crosslinking agent, 20-60 parts of elastomer, 0.1-3 parts of initiator, and 10-90 parts of filler. The acenaphthene-p-vinylbiphenyl copolymer is obtained by prepolymerizing acenaphthene and divinylbiphenyl, resulting in less residual acenaphthene monomer, which is less likely to volatilize in the resin system. This maintains good reactivity while preventing excessively rapid curing and polymerization. The resulting cured product exhibits high crosslinking density, good heat resistance, and a wide processing window, facilitating subsequent production and processing. Furthermore, the high symmetry and rigidity of the acenaphthene structure, along with the absence of oxygen, sulfur, and nitrogen, contribute to the resin composition's excellent dielectric and thermal properties, low coefficient of thermal expansion, and the elastomer serving as the crosslinking and curing matrix material, providing characteristics such as low dielectric constant, low dielectric loss, and low water absorption.

Description

Technical Field

[0001] This invention relates to the field of copper foil substrates, and in particular to a low-loss resin composition, a prepreg, and a copper-clad laminate. Background Technology

[0002] High-frequency, high-speed copper-clad laminates are mainly used in AI servers, high-speed network equipment, the communications industry, and high-performance computing. With the widespread adoption of AI across various industries, the demand for computing power will grow exponentially, leading to a rapid increase in the demand for AI servers. This rapid growth in AI servers will drive up the demand for high-speed resins, resulting in a significant market increase for resins suitable for high-speed copper-clad laminates in the future.

[0003] For high-frequency, high-speed circuit copper-clad laminates with a Low Loss rating or higher (substrate Df≤0.008), there are two main resin composition process routes: one is a process route based on thermoplastic resin systems represented by PTFE; the other is a process route based on thermosetting resin systems represented by hydrocarbon resins or modified polyphenylene ether resins. In the second process route based on thermosetting resin systems, the mainstream route currently uses "PPO as the main component + crosslinking agent [the crosslinking agent can be bismaleimide resin, triallyl triisocyanate (TAIC), elastomer, etc.]". Meanwhile, the resin composition design technology for high-frequency, high-speed copper-clad laminates has continued to advance in recent years, becoming more diversified. Process routes using modified maleimide (bi- or multi-functional type) as the main resin and processes using special epoxy resins (dicyclopentadiene type, diphenyl ether type, etc.) + benzoxazine resins have emerged, achieving very low loss ratings. Among them, Chinese patent CN117416106A discloses a novel polymer resin for high-frequency, high-speed copper-clad laminates. This resin is prepared from acenaphthene monomer. Using acenaphthene as a raw material, heating and adding an initiator, a polyacenaphthene resin is obtained through reaction. A prepreg is prepared by impregnating glass cloth with this resin. The copper-clad laminate made from this prepreg exhibits excellent dielectric properties and has a lower dielectric constant compared to copper-clad laminates made with polyphenylene ether resin. However, the resin adhesive used for impregnation in this patent does not contain fillers, and the glass transition temperature and coefficient of thermal expansion are not studied; only the influence of the resin on the dielectric properties of the copper-clad laminate is mentioned. In addition, Chinese patent CN112368311A discloses a resin composition containing acenaphthene compounds. This resin composition can maintain low dielectric properties well after water absorption treatment, but acenaphthene is added in monomer form, which is easily volatile and will affect subsequent processing. Therefore, it is necessary to propose a new solution to obtain a low-loss resin composition with excellent dielectric properties, high heat resistance, and a low coefficient of thermal expansion. Summary of the Invention

[0004] In view of this, the present invention addresses the deficiencies of the prior art, and its main objective is to provide a low-loss resin composition, prepreg, and copper-clad laminate, which have extremely low dielectric constant and dielectric loss, as well as high heat resistance and low coefficient of thermal expansion.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A low-loss resin composition, by weight, comprises the following main components: 10-90 parts of acenaphthene-p-vinylbiphenyl copolymer, 10-70 parts of crosslinking agent, 20-60 parts of elastomer, 0.1-3 parts of initiator, and 10-90 parts of filler; wherein the structural formula of the acenaphthene-p-vinylbiphenyl copolymer is:

[0007]

[0008] ; where m and n are the number of repeating units and are both positive integers.

[0009] As a preferred embodiment, the preparation process of the acenaphthene-p-vinylbiphenyl copolymer is as follows:

[0010] 1000g of acenaphthene, 210g of p-divinylbiphenyl, and 1200mL of toluene were added to a 3000mL four-necked round-bottom flask equipped with a stirrer, condenser, thermometer, and nitrogen protection while stirring. After the acenaphthene and p-divinylbiphenyl were completely dissolved, the mixture was heated to 70°C. After the solution in the flask stabilized at 70°C for 30 minutes, a 10% BPO toluene solution initiator was added dropwise using a peristaltic pump. The flow rate of the peristaltic pump was set so that 200g of the 10% BPO toluene solution was added dropwise over 6 hours. The reaction was maintained at 70°C for another 2 hours to complete the polymerization reaction and obtain the acenaphthene-p-divinylbiphenyl copolymer.

[0011] As a preferred embodiment, the crosslinking agent is one or a combination of at least two of the following: 1,2-bis(vinylphenyl)ethane, divinylbenzyl ether, divinylbenzene, divinylnaphthalene, divinylbiphenyl, tert-butylstyrene, triallyl isocyanurate, triallyl cyanurate, 1,2,4-trivinylcyclohexane, diallyl bisphenol A, styrene, butadiene, decadiene, octadiene, vinylcarbazole, and acrylate.

[0012] As a preferred embodiment, the crosslinking agent is 1,2-bis(vinylphenyl)ethane. 1,2-bis(p-vinylphenyl)ethane contains multiple unsaturated double bonds, which can chemically react with the functional groups in the resin molecules to form covalent bonds, thereby transforming linear or slightly branched macromolecules into a three-dimensional network structure and improving the thermal stability, mechanical strength and chemical stability of the material.

[0013] As a preferred embodiment, the elastomer has a 1,2-vinyl structure and a styrene structure, wherein the 1,2-vinyl structure comprises 20%-90% of the elastomer's mass, and the styrene structure comprises 10%-30% of the elastomer's mass.

[0014] As a preferred embodiment, the initiator is one or a combination of at least two of the following: dicumyl peroxide, tert-butyl peroxide, 2,5-di(2-ethylhexanoylperoxy)-2,5-dimethylhexane, di-(tert-butylperoxyisopropyl)benzene, (2,4-dichlorobenzoyl peroxide), 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, tert-butyl peroxide-2-ethylhexyl carbonate, 2,5-dimethyl-2,5-bis(tert-butylperoxy)-3-hexyne, butyl 4,4-di(tert-butylperoxy)valerate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 3,3,5,7,7-pentamethyl-1,2,4-trioxane, di-tert-butylperoxide, or tert-butylperoxyisopropylbenzene.

[0015] As a preferred embodiment, the filler is one or a combination of at least two of the following: crystalline silica, fused silica, spherical silica, hollow silica, glass powder, hollow glass microspheres, aluminum nitride, boron nitride, silicon carbide, silicon aluminum carbide, polytetrafluoroethylene powder, polyphenylene sulfide, polyetherimide, polyphenylene ether, and polyethersulfone powder.

[0016] A semi-cured sheet is prepared by impregnating glass cloth in an adhesive solution formed from the aforementioned low-loss resin composition, and then baking it in an oven at 80-150°C for 1-20 minutes.

[0017] A copper-clad laminate is prepared by taking the aforementioned prepreg, covering each of the top and bottom surfaces with a copper foil, placing it in a vacuum hot press, gradually raising the temperature to 220°C, and then holding it under heat and pressure for 80 minutes to cure it.

[0018] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, as can be seen from the above technical solution:

[0019] By first prepolymerizing acenaphthene and divinylbiphenyl to obtain a acenaphthene-p-vinylbiphenyl copolymer with a certain molecular weight, the acenaphthene monomer residue is low and difficult to volatilize in the resin system. While maintaining good reactivity, it also prevents the resin system from curing too quickly and causing explosive polymerization. The subsequent cured product has high crosslinking density, good heat resistance, and a wide processing window, which facilitates subsequent production and processing. In addition, the acenaphthene structure has high symmetry and rigidity and does not contain elements such as oxygen, sulfur, and nitrogen, which makes the resin composition have excellent dielectric and thermal properties, low coefficient of thermal expansion, and elastomer as its crosslinking and curing matrix material, which can provide low dielectric constant, low dielectric loss and low water absorption, further improving the performance of the resin composition. The prepreg and copper-clad laminate made from the resin composition have extremely low dielectric constant and dielectric loss, high heat resistance and low coefficient of expansion.

[0020] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to specific embodiments. Detailed Implementation

[0021] This invention discloses a low-loss resin composition, comprising, by weight, the following main components: 10-90 parts of acenaphthene-p-vinylbiphenyl copolymer, 10-70 parts of crosslinking agent, 20-60 parts of elastomer, 0.1-3 parts of initiator, and 10-90 parts of filler; wherein the structural formula of the acenaphthene-p-vinylbiphenyl copolymer is:

[0022]

[0023] ; where m and n are the number of repeating units and are both positive integers.

[0024] The preparation process of the acenaphthene-p-vinylbiphenyl copolymer is as follows:

[0025] 1000g of acenaphthene, 210g of p-divinylbiphenyl, and 1200mL of toluene were added to a 3000mL four-necked round-bottom flask equipped with a stirrer, condenser, thermometer, and nitrogen protection while stirring. After the acenaphthene and p-divinylbiphenyl were completely dissolved, the mixture was heated to 70°C. After the solution in the flask stabilized at 70°C for 30 minutes, a 10% BPO toluene solution initiator was added dropwise using a peristaltic pump. The flow rate of the peristaltic pump was set so that 200g of the 10% BPO toluene solution was added dropwise over 6 hours. The reaction was maintained at 70°C for another 2 hours to complete the polymerization reaction, resulting in an acenaphthene-p-divinylbiphenyl copolymer with a certain viscosity. The reaction process is shown below.

[0026]

[0027] The crosslinking agent is one or a combination of at least two of the following: 1,2-bis(vinylphenyl)ethane, divinylbenzyl ether, divinylbenzene, divinylnaphthalene, divinylbiphenyl, tert-butylstyrene, triallyl isocyanurate, triallyl cyanurate, 1,2,4-trivinylcyclohexane, diallyl bisphenol A, styrene, butadiene, decanadiene, octadiene, vinylcarbazole, and acrylate. Preferably, 1,2-bis(vinylphenyl)ethane can be used as the crosslinking agent. 1,2-bis(p-vinylphenyl) contains multiple unsaturated double bonds, which can chemically react with the functional groups in the resin molecule to form covalent bonds, thereby transforming linear or slightly branched macromolecules into a three-dimensional network structure, improving the thermal stability, mechanical strength, and chemical stability of the material.

[0028] Furthermore, the elastomer refers to a polymer with viscoelasticity that imparts toughness to electronic materials, resulting in electronic materials with better toughness and a lower dielectric constant. The elastomer also has unsaturated functional groups, allowing it to undergo cross-linking reactions with other components possessing unsaturated functional groups. The elastomer has a 1,2-vinyl structure and a styrene structure, with the 1,2-vinyl structure comprising 20%-90% of the elastomer's mass and the styrene structure comprising 10%-30% of the elastomer's mass. Specifically, examples of elastomers include, but are not limited to, polybutadiene, polyisoprene, and olefin copolymers such as styrene. The aforementioned elastomers can be used individually or in any combination; this document uses polybutadiene.

[0029] The initiator is one or a combination of at least two of the following: dicumyl peroxide, tert-butyl peroxide, 2,5-di(2-ethylhexanoylperoxy)-2,5-dimethylhexane, di-(tert-butylperoxyisopropyl)benzene, (2,4-dichlorobenzoyl peroxide), 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, tert-butyl peroxide-2-ethylhexyl carbonate, 2,5-dimethyl-2,5-bis(tert-butylperoxy)-3-hexyne, butyl 4,4-di(tert-butylperoxy)valerate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 3,3,5,7,7-pentamethyl-1,2,4-trioxane, di-tert-butylperoxide, or tert-butylperoxyisopropylbenzene.

[0030] All fillers are low-dielectric fillers, including inorganic and organic fillers. The inorganic fillers are one or a combination of at least two of the following: crystalline silica, fused silica, spherical silica, hollow silica, glass powder, hollow glass microspheres, aluminum nitride, boron nitride, silicon carbide, and silicon aluminum carbide. The organic fillers are one or a combination of at least two of the following: polytetrafluoroethylene powder, polyphenylene sulfide, polyetherimide, polyphenylene ether, and polyethersulfone powder. The combination of species; in addition, the present invention does not limit the shape and particle size of the inorganic filler, and the particle size commonly used is 0.01-50μm, such as 0.01μm, 0.05μm, 0.08μm, 0.1μm, 0.2μm, 0.5μm, 1μm, 3μm, 5μm, 8μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm or 50μm, etc.

[0031] The present invention also discloses a semi-cured sheet, which is prepared by impregnating glass cloth in an adhesive solution formed by the aforementioned low-loss resin composition and then baking it in an oven at 80-150°C for 1-20 minutes.

[0032] The present invention also discloses a copper-clad laminate, wherein the aforementioned prepreg is covered with a copper foil on each of the top and bottom surfaces, placed in a vacuum hot press, and gradually heated to 220°C, and then kept at the temperature and pressure for 80 minutes to cure and obtain the copper-clad laminate.

[0033] The raw materials used in the following examples and comparative examples are shown in Table 1.

[0034]

[0035] The component ratios of the embodiments and comparative examples in Table 1 are shown in Table 2.

[0036]

[0037] Table 2

[0038] Performance tests were conducted on the above embodiments and comparative examples, and the test methods are as follows:

[0039] Measurement of dielectric constant (Dk) and dielectric loss factor (Df)

[0040] According to the IPC TM 650 2.5.5.13 specification, the dielectric constant (Dk) and dielectric loss factor (Df) of the multilayer board are measured and calculated at an operating frequency of 10 GHz.

[0041] Glass transition temperature (Tg) test

[0042] The copper-clad laminate used for evaluation was etched to remove the copper foil on both sides, resulting in an unclad board. The glass transition temperature (Tg) of the unclad board was measured. Specifically, the Tg of the unclad board was determined using a dynamic mechanical analysis (DMA) instrument (model DMA850) manufactured by TA Instruments. The test conditions were as follows: a bending module was used at a frequency of 10 Hz, and the heating rate was 3 °C / min, with dynamic viscoelasticity measurements performed during the temperature rise from room temperature to 280 °C. Tg is the temperature at which tanδ reaches its maximum value in the obtained viscoelastic curve.

[0043] expansion coefficient α1

[0044] According to IPC-TM-650 2.4.24c, the copper foil on both sides of the copper-clad substrate used for evaluation was etched away to obtain an unclad board. The glass transition temperature (Tg) of the unclad board was then measured. Specifically, a TMA450 instrument manufactured by TA Instruments was used. Thermomechanical analyzer Thermomechanical analysis (TMA) was used to determine the coefficient of thermal expansion α1 of the unclad plate. The test conditions were as follows: a compression module was used, with a heating rate of 10 °C / min, from room temperature to 280 °C. α1 is the slope of the curve before the glass transition temperature.

[0045] Thermal stratification time

[0046] Tested according to IPC-TM-650 2.4.9 specification. A TMA450 model manufactured by TA Instruments was used. Thermomechanical analyzer Thermomechanical analysis (TMA) was used to determine the Tg of the unclad plate. The test conditions were as follows: a compression module was used, the heating rate was 10℃ / min, the temperature was increased from room temperature to 288℃, and held for 60 min. A significant abrupt change in the curve indicated delamination, and the time was recorded.

[0047] The test results are shown in Table 3.

[0048]

[0049] Table 3

[0050] Analysis of the above data, as shown in Examples 1-6, reveals that the resin composition of the present invention exhibits a high glass transition temperature, a low coefficient of thermal expansion, extremely low dielectric constant and dielectric loss, and good heat resistance. It is also evident that the higher the content of acenaphthene-p-vinylbiphenyl copolymer, the higher the glass transition temperature and the lower the coefficient of thermal expansion. Specifically, compared to Comparative Example 1, Example 3, Example 4, and Example 5, under the same conditions, the resin composition using acenaphthene-p-vinylbiphenyl copolymer as the main component exhibits superior glass transition temperature, dielectric properties, coefficient of thermal expansion, and heat resistance compared to resin compositions using polyacenaphthene resin or acenaphthene as the main component. Furthermore, compared to Examples 1 and 2, and Comparative Examples 1 and 2, different mass fractions of 1,2-vinyl elastomers were used. Example 1 used an elastomer with a 1,2-vinyl content of... The mass fraction of 2-vinyl is 80%, and the mass fraction of 1,2-vinyl in the elastomer of Example 2 is 70%. However, there is no significant difference in performance between Example 1 and Example 2. It can be seen that within a certain range, the mass fraction of 1,2-vinyl in the elastomer will not have a significant impact on the resin system. In comparison with Example 5, the crosslinking agent ratio of Example 5 is increased and the elastomer ratio is decreased. Its Tg is significantly improved compared with the other two examples, and the coefficient of expansion is reduced. It can be seen that increasing the crosslinking agent ratio can effectively improve the Tg of the resin composition and reduce the coefficient of expansion of the resin composition. On the other hand, comparing Comparative Example 1 and Comparative Example 3, the elastomer ratio in Comparative Example 3 is increased, and the Tg and coefficient of expansion are significantly reduced, but the dielectric properties and heat resistance are improved.

[0051] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A low-loss resin composition, characterized in that: By weight, it comprises the following main components: 10-90 parts of acenaphthene-p-vinylbiphenyl copolymer, 10-70 parts of crosslinking agent, 20-60 parts of elastomer, 0.1-3 parts of initiator, and 10-90 parts of filler; wherein, the structural formula of the acenaphthene-p-vinylbiphenyl copolymer is: Wherein, m and n are the number of repeating units and are both positive integers; wherein, the crosslinking agent is one of 1,2-bis(vinylphenyl)ethane, divinylbenzyl ether, divinylbenzene, divinylnaphthalene, and divinylbiphenyl; the elastomer has a 1,2-vinyl structure and a styrene structure, and the mass of the 1,2-vinyl group is 20%-90% of the elastomer mass, and the mass of the styrene group is 10%-30% of the elastomer mass.

2. The low-loss resin composition according to claim 1, characterized in that: The preparation process of the acenaphthene-p-vinylbiphenyl copolymer is as follows: 1000g of acenaphthene, 210g of p-divinylbiphenyl, and 1200mL of toluene were added to a 3000mL four-necked round-bottom flask equipped with a stirrer, condenser, thermometer, and nitrogen protection while stirring. After the acenaphthene and p-divinylbiphenyl were completely dissolved, the mixture was heated to 70°C. After the solution in the flask stabilized at 70°C for 30 minutes, a 10% BPO toluene solution initiator was added dropwise using a peristaltic pump. The flow rate of the peristaltic pump was set so that 200g of the 10% BPO toluene solution was added dropwise over 6 hours. The mixture was then kept at 70°C for another 2 hours to complete the polymerization reaction and obtain the acenaphthene-p-divinylbiphenyl copolymer.

3. The low-loss resin composition according to claim 1, characterized in that: The crosslinking agent is 1,2-bis(vinylphenyl)ethane.

4. The low-loss resin composition according to claim 1, characterized in that: The initiator is one or a combination of at least two of the following: dicumyl peroxide, tert-butyl peroxide, 2,5-di(2-ethylhexanoylperoxy)-2,5-dimethylhexane, di-(tert-butylperoxyisopropyl)benzene, (2,4-dichlorobenzoyl peroxide), 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, tert-butyl peroxide-2-ethylhexyl carbonate, 2,5-dimethyl-2,5-bis(tert-butylperoxy)-3-hexyne, butyl 4,4-di(tert-butylperoxy)valerate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 3,3,5,7,7-pentamethyl-1,2,4-trioxane, di-tert-butylperoxide, or tert-butylperoxyisopropylbenzene.

5. The low-loss resin composition according to claim 1, characterized in that: The filler is one or a combination of at least two of the following: crystalline silica, fused silica, spherical silica, hollow silica, glass powder, hollow glass microspheres, aluminum nitride, boron nitride, silicon carbide, and aluminum silicon carbide.

6. A semi-cured sheet, characterized in that: The glass cloth is impregnated in a liquid formed by the low-loss resin composition of any one of claims 1-5, and then baked in an oven at 80-150°C for 1-20 minutes to obtain the product.

7. A copper-clad laminate, characterized in that: Take the semi-cured sheet as described in claim 6, cover each of the top and bottom surfaces with a copper foil, place it in a vacuum hot press, gradually raise the temperature to 220°C, and then keep it at the temperature and pressure for 80 minutes to cure and obtain a copper foil-coated substrate.

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