An ultra-low electrical property resin composition, prepreg and copper clad plate thereof

Abstract

The present application relates to printed circuit board production technical field, specifically, it relates to a kind of ultra-low electrical resin composition and its prepreg and copper-clad plate, comprising the following components: biphenyl type multifunctional acid ester 0.1~3 parts by weight, biphenyl bismaleimide resin 10~15 parts by weight, crosslinking agent 70~85 parts by weight;The biphenyl type multifunctional acid ester is modified by being connected with the 4-vinylbenzoic acid end group with certain polarity at the both ends of 4-4'-dihydroxy biphenyl.Formation of thermoset material by self-crosslinking or reaction with other unsaturated crosslinking agent, biphenyl structure increases the density of molecular reactive site, so as to enhance the heat resistance and bonding properties of resin, as resin component, can make laminated board simultaneously have excellent dielectric properties, high peel strength and heat resistance.

Description

Technical Field

[0001] This invention relates to the field of high-frequency electronic communication materials, and more specifically, to an ultra-low electrical resin composition and its prepreg and copper-clad laminate. Background Technology

[0002] With the rapid development of fifth-generation mobile communication technology (5G) and the future Internet of Things (6G), the transmission frequency of printed circuit boards will become higher and higher. Low dielectric substrate materials suitable for high-frequency and high-speed information transmission have become the main development direction of printed circuit boards.

[0003] To reduce transmission loss in high-frequency bands and cope with high-temperature soldering and multilayer assembly in PCB manufacturing, copper-clad laminate (CCL) substrates are required to have increasingly lower dielectric constants and dielectric losses at high frequencies. However, the lower the dielectric constant and dielectric loss, the lower the polarity of the resin used in the CCL. Reduced polarity leads to a decrease in the adhesion between the substrate and the copper foil. When the CCL's Dissipation Factor (Df) (10 GHz) is below 0.0015, the adhesion between the substrate and the copper foil can no longer meet the processing requirements. Therefore, improving the adhesion between the ultra-low dielectric loss CCL substrate and the copper foil has become an urgent problem to be solved.

[0004] Based on this, the present invention discloses an ultra-low electrical resin composition, its prepreg and copper-clad laminate. Summary of the Invention

[0005] To address the problem mentioned in the background art that copper-clad laminate substrates have increasingly lower dielectric constants and dielectric losses at high frequencies, and that the adhesion between the substrate and copper foil can no longer meet the processability requirements, this invention provides an ultra-low electrical resin composition, its prepreg, and a copper-clad laminate to overcome the aforementioned defects.

[0006] To achieve the above-mentioned objectives, the present invention is implemented through the following technical solution:

[0007] An ultra-low electrical resin composition comprises the following components: 0.1 to 3 parts by weight of biphenyl polyfunctional ester, 10 to 15 parts by weight of biphenyl bismaleimide resin, and 70 to 85 parts by weight of crosslinking agent.

[0008] Preferably, the biphenyl-type polyfunctional ester I has the following structure:

[0009] .

[0010] Preferably, the crosslinking agent includes at least two of benzocyclobutene copolymer, styrene-butadiene copolymer, styrene-modified polyphenylene ether, triallyl triisocyanate, and P,P'-divinyl-1,2-diphenylethane, wherein the number-average molecular weight of the benzocyclobutene copolymer is 1000-5000 g / mol, and the number-average molecular weight of the styrene-butadiene copolymer is 2000-5000 g / mol.

[0011] Preferably, the crosslinking agent comprises 5-15 parts by weight of benzocyclobutene copolymer, 0-15 parts by weight of styrene-butadiene copolymer, 0-8 parts by weight of styrene-modified polyphenylene ether, 0-35 parts by weight of triallyl triisocyanate, and 20-62 parts by weight of P,P'-divinyl-1,2-diphenylethane.

[0012] Preferably, based on 100 parts by weight of the ultra-low electrical resin composition, the weight of the biphenyl-type polyfunctional ester, the biphenyl bismaleimide resin, and the crosslinking agent containing a biphenyl or benzocyclobutene structure accounts for 25-35% of the weight of the ultra-low electrical resin composition.

[0013] Preferably, the composition further comprises 1 to 10 parts by weight of flame retardant, 50 to 100 parts by weight of filler, 0.1 to 1 part by weight of accelerator, 0.1 to 1 part by weight of coupling agent, and 50 to 100 parts by weight of solvent.

[0014] Preferably, the flame retardant is one of ethylene phenoxyphosphazene compound, bis(3,5-dimethylphenyl)phosphine oxide, triphenylphosphine oxide, and p-xylylbis(diphenylphosphine oxide); the filler is spherical silica; the coupling agent is a vinyl silane coupling agent; the accelerator is a peroxide catalyst; and the solvent is at least one of toluene, xylene, butanone, and cyclohexanone.

[0015] Preferably, the biphenyl-type polyfunctional ester is prepared as follows: 46.5 g (0.25 mol) of 4,4'-dihydroxybiphenyl and 500 g of dichloromethane are added to a three-necked flask, followed by the addition of 60.6 g (0.6 mol) of triethylamine and 6.1 g of 4-dimethylaminopyridine as a catalyst. N2 gas is introduced, and 81 g of 4-vinylbenzoyl chloride is added dropwise under stirring in an ice bath. After the addition is complete, the ice is removed, and the reaction is carried out at room temperature for 2.5 h. After the reaction is completed, the filtrate is filtered, and the filtrate is washed with 20 ml of saturated sodium carbonate aqueous solution. After separation, the organic layer is washed several times with water, and the biphenyl-type polyfunctional ester is obtained by rotary evaporation.

[0016] Preferably, a prepreg comprises a reinforcing material and an ultra-low electrical resin composition, as described in any one of the above description, impregnated, dried, and attached to the reinforcing material.

[0017] Preferably, a copper-clad laminate comprises one or at least two sheets stacked from the prepregs described above.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. The biphenyl-type polyfunctional ester provided by the present invention can crosslink with itself or other unsaturated crosslinking agents to form thermosetting materials, thereby improving the crosslinking performance. It can form thermosetting materials through self-crosslinking or reaction with other unsaturated crosslinking agents. The biphenyl structure increases the density of molecular reactive sites, thereby enhancing the heat resistance and adhesion of the resin. When used as a resin component, it enables the laminate to simultaneously possess excellent dielectric properties, high peel strength and heat resistance.

[0020] 2. The thermosetting resin composition provided by the present invention has certain limitations in terms of dosage when there is a need for ultra-low dielectric properties. Adding too much will result in the electrical properties not meeting the requirements, while adding too little will not improve the adhesion. By precisely controlling the amount of resin, it is possible to avoid both excessive amount leading to a decrease in dielectric properties and insufficient amount affecting adhesion. The amount of unsaturated crosslinking agent can be freely adjusted to meet different electrical properties and adhesion requirements. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Therefore, the present invention provides an ultra-low electrical conductivity resin composition, a prepreg, and a copper-clad laminate thereof. An ultra-low electrical conductivity resin composition comprises the following components: 0.1-3 parts by weight of a biphenyl polyfunctional ester, 10-15 parts by weight of a biphenyl bismaleimide resin, and 70-85 parts by weight of a crosslinking agent.

[0023] All "parts by weight" in this invention are calculated based on solid content.

[0024] Preferably, the biphenyl-type polyfunctional ester I has the following structure:

[0025] .

[0026] This invention forms a modified biphenyl-type polyfunctional ester by attaching polar 4-vinylbenzoic acid end groups to both ends of a 4-4'-dihydroxybiphenyl compound. This modified biphenyl-type polyfunctional ester can crosslink with itself or other unsaturated crosslinking agents to form thermosetting materials, significantly improving the heat resistance of polyfunctional ester resins and further enhancing their adhesive properties. This modified polyfunctional ester, when combined with other unsaturated crosslinking resins, can serve as a resin component in thermosetting resin compositions, resulting in laminates that possess excellent dielectric properties, high peel strength, and heat resistance.

[0027] The thermosetting resin composition of this invention includes resin components, which include biphenyl polyfunctional esters, biphenyl bismaleimide, and other unsaturated crosslinking agents. Due to the presence of polar chains in their molecules, the amount of biphenyl polyfunctional esters and biphenyl bismaleimide is limited when ultra-low dielectric properties are required. Adding too much will result in insufficient electrical properties, while adding too little will not improve the adhesion. In the resin composition, the amount of other unsaturated crosslinking agents is unlimited and can be adjusted according to the electrical and adhesion requirements.

[0028] Specifically, the resin component of the present invention includes 0.1-3 PHR (e.g., 0.1 PHR, 0.3 PHR, 0.5 PHR, 0.8 PHR, 1 PHR, 1.5 PHR, 2 PHR, 2.5 PHR, 3 PHR, etc.) of biphenyl polyfunctional ester having the structure shown in Formula I, 10-15 PHR (e.g., 10 PHR, 12 PHR, 13 PHR, 15 PHR, etc.) of biphenyl bismaleimide resin, and 70-85 PHR (e.g., 70 PHR, 72 PHR, 75 PHR, 78 PHR, 80 PHR, 83 PHR, 85 PHR, etc.) of crosslinking agent (proportion range), that is, in the present invention, the resin component of the thermosetting resin composition includes 0. The resin composition contains 1-3 PHR biphenyl polyfunctional esters, 10-15 PHR biphenyl bismaleimide resin, and 70-85 PHR crosslinking agents. Within this range, it can maintain the low dielectric properties of other unsaturated crosslinking agents while significantly improving the adhesive properties of the resin composition. When the amount of biphenyl polyfunctional ester in the resin composition is greater than 3 PHR, the introduction of excessive polar ester groups will reduce the dielectric properties of the material. When the amount of biphenyl bismaleimide resin in the resin composition is greater than 15 PHR, the introduction of excessive polar bismaleimide groups will reduce the dielectric properties of the material. If the amount of biphenyl bismaleimide resin is less than 10 PHR, the introduced polar groups are too few, and the effect of effectively improving the peel strength of the material cannot be achieved.

[0029] As a preferred technical solution, the bismaleimide of the present invention is a biphenyl-type bismaleimide, whose own biphenyl structure can enhance its interaction with biphenyl-type polyfunctional esters and improve the peel strength of the material.

[0030] As a preferred technical solution, the crosslinking agent of the present invention includes at least two of the following: benzocyclobutene copolymer, styrene-butadiene copolymer, styrene-modified polyphenylene ether, triallyl triisocyanate, and P,P'-divinyl-1,2-diphenylethane, wherein the number-average molecular weight of the benzocyclobutene copolymer is 1000-5000 g / mol, and the number-average molecular weight of the styrene-butadiene copolymer is 2000-5000 g / mol. The crosslinking agent of the present invention contains a biphenyl or benzocyclobutene structure, which can be layered with biphenyl bismaleimide. When participating in the free radical polymerization reaction to form a three-dimensional network structure, the bonding strength between the cured product and the copper foil can be further improved under the bonding of the biphenyl-type polyfunctional ester.

[0031] Specifically, the crosslinking agent of the present invention comprises 5-15 parts by weight of benzocyclobutene copolymer, 0-15 parts by weight of styrene-butadiene copolymer, 0-8 parts by weight of styrene-modified polyphenylene ether, 0-35 parts by weight of triallyl triisocyanate, and 20-62 parts by weight of P,P'-divinyl-1,2-diphenylethane.

[0032] In this invention, the ultra-low charge resin composition comprises, by weight, 25-35% of the biphenyl-type polyfunctional ester, biphenyl bismaleimide resin, and crosslinking agent containing biphenyl or benzocyclobutene structures in 100 parts by weight of the ultra-low charge resin composition.

[0033] In this invention, when the proportion of biphenyl bismaleimide and crosslinking agent containing biphenyl or benzocyclobutene structure in the total resin is 25-35 PHR, the bonding strength between the substrate and the copper foil is significantly improved. When the proportion is less than 25 PHR, the bonding strength between the substrate and the copper foil is insufficient.

[0034] The composition also includes 1 to 10 parts by weight of flame retardant, 50 to 100 parts by weight of filler, 0.1 to 1 part by weight of accelerator, 0.1 to 1 part by weight of coupling agent, and 50 to 100 parts by weight of solvent.

[0035] Preferably, the flame retardant is one of ethylene phenoxyphosphazene compound (SPV100), bis(3,5-dimethylphenyl)phosphine oxide, triphenylphosphine oxide, and p-xylylbis(diphenylphosphine oxide) (XDPO); the filler is spherical silica; the coupling agent is a vinyl-type silane coupling agent; the accelerator is a peroxide catalyst, preferably chemically produced spherical silica with a particle size of 0.5-10 micrometers; the accelerator is a peroxide catalyst, such as di-tert-butyl peroxide or odorless DCP, which can lower the curing temperature of the composition and increase the degree of curing and crosslinking; the coupling agent is a vinyl-type silane coupling agent, which can act as a bridge between the filler and the resin matrix, increasing their bonding ability; the solvent is at least one of toluene, xylene, methyl ethyl ketone, and cyclohexanone.

[0036] A second aspect of the present invention provides a prepreg, wherein the above-mentioned ultra-low electrical resin composition is dissolved or dispersed in a solvent to obtain a composition solution, and the composition solution is transferred to a glue tank; then, a reinforcing material is completely immersed in the glue tank under the action of an impregnation roller, and the glue solution enters the interior of the reinforcing material to complete the impregnation process; then, the impregnated reinforcing material is pressed by adjusting the extrusion roller to make its glue content 65-80% (mass percentage), and baked at a temperature of 120-160°C for 3-6 minutes to obtain a prepreg; wherein the reinforcing material can be glass fiber cloth.

[0037] A third aspect of the present invention provides a copper-clad laminate, wherein one or at least two of the above-mentioned semi-cured sheets are stacked together, and copper foil is then covered on one or both sides of the stacked cured sheets, and then the copper-clad laminate is formed by pressing them together using a hot press.

[0038] The copper-clad laminate prepared by the above-mentioned ultra-low electrical resin composition has a glass transition temperature of 190-210℃, a 5% thermogravimetric temperature Td of 420-450℃, a dielectric constant of 3.2 (refer to IPC-TM-650) and a dielectric loss of 0.00131-0.00151 (refer to IPC-TM-650) when tested at 10GHz frequency. The flame retardancy rating is V0 according to the UL94 method, and the peel strength is 0.69-1.12 N / mm.

[0039] The following will further explain the resin composition, prepreg, and copper-clad laminate through the following operating steps.

[0040] All raw materials used in the examples and comparative examples were conventional commercially available raw materials, including:

[0041] (A) Polyfunctional ester copolymers 0.1–3 PHR;

[0042] A1 biphenyl polyfunctional ester (prepared in-house)

[0043] A2 pentaerythritol triacrylate (Sartoma SR454NS)

[0044] (B) Bismaleimide resin 10-15 PHR;

[0045] B1 biphenyl bismaleimide resin (Dongcai DFE-956)

[0046] B2 diphenylmethane bismaleimide (commercially available)

[0047] (C) Crosslinking agent 70-85 PHR;

[0048] C1 benzocyclobutene copolymer (GFH700)

[0049] C2 styrene-butadiene copolymer (trade name Ricon100)

[0050] C3 styrene-modified polyphenylene ether (Mitsubishi OPE-2ST)

[0051] C4 triallyl isocyanate (TAIC) (commercially available)

[0052] C5P,P'-Divinyl-1,2-diphenylethane (Keyi GU010)

[0053] (D): Flame retardant 1-10 PHR;

[0054] D1 Ethylenephenoxyphosphazene Compound (Otsuka SPV-100)

[0055] (E): Packing material 50-100 PHR;

[0056] E1 chemically produced spherical silica powder (Jinyi SE0047)

[0057] (F) Curing accelerator 0.1–1 PHR;

[0058] F1 Odorless DCP (Commercially Available)

[0059] (G) Coupling agent 0.1–1 PHR;

[0060] G1 contains vinyl silane coupling agent (commercially available).

[0061] (H) Solvent 50-100 pHR

[0062] Among them, biphenyl polyfunctional ester A1 was prepared in-house, and the preparation method is as follows:

[0063] 46.5 g (0.25 mol) of 4,4'-dihydroxybiphenyl and 500 g of dichloromethane were added to a three-necked flask, followed by 60.6 g (0.6 mol) of triethylamine and 6.1 g of 4-dimethylaminopyridine as a catalyst. N2 gas was bubbled through the flask, and 81 g of 4-vinylbenzoyl chloride was added dropwise with stirring in an ice bath. After the addition was complete, the ice was removed, and the reaction was carried out at room temperature for 2.5 h. After the reaction was completed, the mixture was filtered, and the filtrate was washed with 20 ml of saturated sodium carbonate aqueous solution. The organic layer was washed several times with water, and the biphenyl polyfunctional ester was obtained by rotary evaporation. Its specific structure is as follows:

[0064] .

[0065] The biphenyl-type polyfunctional esters prepared by the above method can crosslink with themselves or other unsaturated crosslinking agents to form thermosetting materials, which can significantly improve the heat resistance of polyfunctional ester resins and further enhance their adhesive properties. These modified polyfunctional esters, when combined with other unsaturated crosslinking resins, can serve as resin components in thermosetting resin compositions, resulting in laminates that possess excellent dielectric properties, high peel strength, and heat resistance.

[0066] The above-mentioned A~H resin materials are then dissolved or dispersed in a solvent to obtain a halogen-free high-frequency, high-speed, low-expansion coefficient resin composition liquid.

[0067] The adhesive composition is transferred to a glue tank, and then the reinforcing material L-Glass is completely immersed in the glue tank under the action of the glue dipping roller. In the glue tank, the adhesive enters the interior of the reinforcing material to complete the glue dipping process. Then, the glue-dipping reinforcing material is squeezed by adjusting the extrusion roller to make its glue content 65% to 80% (mass percentage), and baked at a temperature of 120 to 160°C for 2 to 6 minutes to obtain a semi-cured sheet.

[0068] Eight prepreg sheets were stacked with a 1oz copper foil on each side, and then pressed together in a vacuum laminator at 190°C for 120 minutes to obtain a copper-clad laminate. The properties of this copper-clad laminate were then evaluated.

[0069] The reinforcing material can be fiberglass cloth, which can be NE fiberglass cloth or quartz cloth, etc.

[0070] Example 1

[0071] Add 0.1 parts by weight of the prepared biphenyl polyfunctional ester copolymer, 15 parts by weight of biphenyl bismaleimide resin, 15 parts by weight of benzocyclobutene copolymer, 34 parts by weight of triallyl triisocyanate, 25.9 parts by weight of P,P'-divinyl-1,2-diphenylethane, and 10 parts by weight of ethylene phenoxyphosphazene compound to 70 parts of toluene solvent and stir until homogeneous. Then add 100 parts by weight of chemically produced spherical silica powder, 0.1 parts by weight of coupling agent, and 0.3 parts by weight of odorless DCP and continue stirring until homogeneous. Filter to obtain resin solution.

[0072] The above-mentioned adhesive solution was impregnated onto the reinforcing material L-Glass and baked in an oven at 120-160℃ for 2-6 minutes to obtain a semi-cured sheet. Eight semi-cured sheets were stacked with a 1OZ copper foil on each side and placed in a vacuum laminator for pressing. The lamination was maintained at 190℃ for 120 minutes to obtain a copper-clad laminate. The properties of the copper-clad laminate were then evaluated.

[0073] The measured glass transition temperature of the copper-clad laminate was 195℃, the peel strength was 1.08 N / mm, the XY axis CTE was 11.0 PPM (50~125℃) (refer to IPC-TM-650), the dielectric constant was 3.17 (refer to IPC-TM-650) and the dielectric loss was 0.00140 (refer to IPC-TM-650) when tested at 10 GHz, and the flame retardancy rating was V0 according to the UL94 method.

[0074] In Examples 2-11 and Comparative Examples 1-4, the components and contents of the resin compositions are shown in Tables 1 and 3, where the amount of each component is expressed in "parts by weight" of solid content. The preparation methods of the prepreg and copper-clad laminate are the same as in Example 1.

[0075] The test results of the prepregs and copper-clad laminates of Examples 1-11 and Comparative Examples 1-4 are shown in Tables 2 and 4.

[0076] Tables 1 to 4 show the experimental results of copper-clad laminates prepared from resin compositions with different mixing ratios.

[0077] Table 1: Formulation of the Composition (Part 1) (parts by weight)

[0078]

[0079] Table 2: Characteristic Evaluation

[0080]

[0081] Table 3: Formulation ratio of the composition (I) (parts by weight)

[0082]

[0083] Table 4: Feature Evaluation

[0084]

[0085] As can be seen from the comparison between Examples 1 and 2 and Comparative Examples 1 and 2, when using ordinary acrylates and adding the same amount, the biphenyl polyfunctional ester has a greater improvement in the adhesion between the substrate and the copper foil, which is 0.09 N / mm more than that of ordinary acrylates. Moreover, after the addition ratio is increased, ordinary acrylates will cause the copper clad laminate to explode during tin dipping, while the biphenyl polyfunctional ester does not reduce the moisture resistance of the copper clad laminate.

[0086] A comparison of Examples 3 and 4 with Comparative Examples 3 and 4 shows that when the weight percentages of biphenyl-type polyfunctional ester, biphenyl bismaleimide resin, and crosslinking agent containing biphenyl or benzocyclobutene structures account for 25-35% of the weight percentages of the ultra-low electrical resin composition (in the examples: A1+B1+C1+C3), the adhesion between the substrate and the copper foil is better. When the proportion exceeds this range, such as 20%, the adhesion significantly decreases. Therefore, the present invention achieves high peel strength while maintaining low dielectric properties and a low coefficient of thermal expansion by appropriately adjusting the ratio of biphenyl-type polyfunctional ester to biphenyl bismaleimide, biphenyl, or benzocyclobutene crosslinking agent.

[0087] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0088] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An ultra-low electrical resin composition, characterized in that, It includes the following components: 0.1 to 3 parts by weight of biphenyl polyfunctional ester, 10 to 15 parts by weight of biphenyl bismaleimide resin, and 70 to 85 parts by weight of crosslinking agent; The biphenyl-type polyfunctional ester has the following molecular structure: Equation I; The crosslinking agent comprises 5-15 parts by weight of benzocyclobutene copolymer, 0-15 parts by weight of styrene-butadiene copolymer, 0-8 parts by weight of styrene-modified polyphenylene ether, 0-35 parts by weight of triallyl triisocyanate, and 20-62 parts by weight of P,P'-divinyl-1,2-diphenylethane. The number average molecular weight of the benzocyclobutene copolymer is 1000-5000 g / mol, and the number average molecular weight of the styrene-butadiene copolymer is 2000-5000 g / mol. Based on 100 parts by weight of the ultra-low electrical resin composition, the biphenyl-type polyfunctional ester, the biphenyl bismaleimide resin, and the crosslinking agent containing a benzocyclobutene structure account for 25-35% of the weight of the ultra-low electrical resin composition.

2. The ultra-low electrical resin composition according to claim 1, characterized in that, The composition further includes 1 to 10 parts by weight of flame retardant, 50 to 100 parts by weight of filler, 0.1 to 1 part by weight of accelerator, 0.1 to 1 part by weight of coupling agent, and 50 to 100 parts by weight of solvent.

3. The ultra-low electrical resin composition according to claim 2, characterized in that, The flame retardant is one of ethylene phenoxyphosphazene compound, bis(3,5-dimethylphenyl)phosphine oxide, triphenylphosphine oxide, and p-xylylbis(diphenylphosphine oxide); the filler is spherical silica; the coupling agent is a vinyl-type silane coupling agent; the accelerator is a peroxide catalyst; and the solvent is at least one of toluene, xylene, butanone, and cyclohexanone.

4. The ultra-low electrical conductivity resin composition according to claim 1, characterized in that, The preparation of the biphenyl-type polyfunctional ester is as follows: 46.5 g of 4,4'-dihydroxybiphenyl and 500 g of dichloromethane were added to a three-necked flask, followed by the addition of 60.6 g of triethylamine and 6.1 g of 4-dimethylaminopyridine as a catalyst. N2 gas was introduced, and 81 g of 4-vinylbenzoyl chloride was added dropwise under stirring in an ice bath. After the addition was complete, the ice was removed, and the reaction was carried out at room temperature for 2.5 h. After the reaction was completed, the mixture was filtered, and the filtrate was washed with 20 ml of saturated sodium carbonate aqueous solution. After separation, the organic layer was washed several times with water. The biphenyl-type polyfunctional ester was then obtained by rotary evaporation.

5. A semi-cured sheet, characterized in that, The semi-cured sheet comprises a reinforcing material and an ultra-low electrical resin composition as described in any one of claims 1-4, which is impregnated, dried, and then attached to the reinforcing material.

6. A copper-clad laminate, characterized in that, The copper-clad laminate comprises one or at least two stacked prepreg sheets as described in claim 5.

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