Low-loss resin composition containing active ester, prepreg, and copper-clad plate

Abstract

The application discloses a low-loss resin composition containing active ester, a prepreg and a copper-clad plate, and the resin composition contains the following main components in parts by weight: 30-70 parts of an epoxy resin, 30-70 parts of an epoxy curing agent, 0-3 parts of a curing accelerator, and 20-100 parts of a filler; wherein the epoxy curing agent is a tetraphenol fluorenyl active ester; the prepreg is prepared by immersing glass cloth in glue liquid formed by the low-loss resin composition, and then baking the glass cloth in an oven at 80-200 DEG C for 1-20 min; and the copper-clad plate is prepared from the prepreg, and the fluorine-containing tetrafunctional active ester is synthesized by esterification reaction of tetraphenol fluorene and pentafluorobenzoyl chloride, and the rigid fluorene ring structure is introduced, which is helpful to improve the thermal performance of the cured epoxy composite material; and the application effectively solves the problem of insufficient heat resistance of the resin composition used for preparing the copper-clad plate, and the amount of the filler is increased to meet the requirement of low polarity, the interface compatibility of the resin and the filler is poor, and the dielectric loss is further improved.

Description

Technical Field

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

[0002] With the rapid development of 5G communication technology and the electric vehicle industry, the demand for high-performance, high-density electronic devices and packaging materials is becoming increasingly urgent. Epoxy resin has attracted much attention due to its excellent performance characteristics and has become one of the important materials in the field of electronic packaging. Epoxy resin needs to undergo chemical cross-linking with a curing agent to form an insoluble and infusible three-dimensional network structure in order to exert its excellent properties. Commonly used curing agents include amines, phenols, and acid anhydrides. Among them, amine and phenolic curing agents contain active hydrogen, which reacts with epoxy groups to produce a large number of highly polar hydroxyl groups, increasing the water absorption and dielectric loss of the cured product. Acid anhydride curing agents do not produce additional hydroxyl groups after reacting with epoxy groups, but the curing conditions are harsh, and acid anhydrides themselves are highly susceptible to absorbing water and becoming free acids during storage, which affects the degree of curing and performance of the cured product, and also exhibits poor resistance to humid heat. Therefore, commonly used curing agents cannot meet the requirements of next-generation low-dielectric packaging materials.

[0003] In recent years, reactive ester curing agents have received unprecedented attention to better meet the requirements of high-frequency and high-speed electronic packaging materials, and related literature has been increasing year by year. Reactive esters are compounds containing two or more ester groups in their molecules. The ester groups of reactive esters have high reactivity and can react with epoxy groups under the action of accelerators to form a three-dimensional network structure. After the reaction, they do not produce strongly polar hydroxyl groups, but rather ester groups with low polarity and large volume. The resulting epoxy cured products have lower water absorption and dielectric loss, making them more suitable for high-frequency and high-speed electronic packaging materials.

[0004] While using reactive esters to cure epoxy resins in copper clad laminates (CCLs) can improve the dielectric properties and water absorption of traditional amine / phenolic curing systems, several technical defects still exist, affecting their application in high-end electronics. The main problems are as follows: 1. Insufficient heat resistance. This is mainly manifested in low crosslinking density. Reactive esters cure epoxy resins through transesterification, avoiding the formation of secondary hydroxyl groups, but the resulting aromatic ester bonds have large steric hindrance, leading to a lower crosslinking network density than amine-cured systems. This directly lowers the glass transition temperature, making CCLs prone to deformation under high-temperature reflow soldering or long-term heat loads. To improve heat resistance, alicyclic or aromatic fused-ring rigid structures are often introduced into the reactive esters. However, these structures have large molecular weights, which reduces the density of reactive ester groups and weakens the crosslinking effect. For example, although the reactive ester curing agent in patent CN107915830A improves dielectric properties, the Tg is still relatively low. 2. Difficulty in balancing dielectric properties. While reactive ester curing reduces hydrophilic hydroxyl groups, the rigid structure added to improve heat resistance may increase molecular polarity, partially offsetting the advantage of low dielectric constant, thus limiting the design for low polarity. Achieving low polarity often requires high filler content, but excessive filler can worsen interfacial compatibility with the resin, potentially leading to increased dielectric loss. III. Bottlenecks in Flame Retardant Technology. To meet environmental requirements, halogen-free flame retardants are necessary. However, additive phosphorus-based flame retardants have poor compatibility, are prone to migration, and can easily cause localized flame retardant failure; reactive phosphorus-based flame retardants increase resin polarity, raising the dielectric constant and water absorption rate. While phosphorus-nitrogen synergistic flame retardant systems can improve flame retardant efficiency, the strong hygroscopicity of nitrogen heterocycles may lead to a rebound in water absorption. Therefore, it is necessary to improve existing resin compositions used in the preparation of copper-clad laminates. Summary of the Invention

[0005] 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 containing active esters, a prepreg, and a copper-clad laminate. This invention can effectively solve the problems of insufficient heat resistance of existing resin compositions used to prepare copper-clad laminates, the need for increased filler content to meet low polarity requirements, the deterioration of interfacial compatibility between resin and filler, and the resulting increase in dielectric loss.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A low-loss resin composition containing an active ester, comprising, by weight, the following main components: 30-70 parts epoxy resin, 30-70 parts epoxy curing agent, and 0-3 parts curing accelerator; wherein the epoxy curing agent is a tetraphenol fluorene active ester.

[0008] As a preferred embodiment, it further includes 20-100 parts of filler.

[0009] As a preferred embodiment, the filler is silicon dioxide.

[0010] As a preferred embodiment, the epoxy resin is DCPD phenol epoxy resin or MDI-modified epoxy resin.

[0011] As a preferred embodiment, the curing accelerator is one of 4-dimethylaminopyridine, butyltriphenylphosphine bromide, and diethyltetramethylimidazole.

[0012] As a preferred embodiment, the epoxy curing agent has the following structure:

[0013]

[0014] As a preferred embodiment, the epoxy curing agent is prepared by the following steps:

[0015] (1) 500 g of 2,7-dihydroxy-9-fluorenone, 1330.50 g of phenol, 1500 g of ethyl acetate and 300 g of p-toluenesulfonic acid were added to a 5000 mL four-necked round-bottom flask equipped with a stirrer, condenser and thermometer. Under nitrogen protection, the mixture was heated and stirred until homogeneous. The reaction was carried out at a reflux temperature of 77 °C for 7 h. After the reaction solution cooled, it was washed with deionized water until neutral. The solvent and phenol were removed by vacuum distillation. After vacuum drying, crude tetraphenol fluorene was obtained. Then, the crude tetraphenol fluorene was dissolved in an ethanol / water mixed solvent, cooled and crystallized. After filtration, tetraphenol fluorene was obtained.

[0016] (2) Under nitrogen protection, 1000 ml of butanone solvent was added to a 3000 mL four-necked round-bottom flask equipped with a stirrer, condenser and thermometer. Then, 100 g of tetraphenol fluorene, 161.71 g of pentafluorobenzoyl chloride and 2 g of DMAP were added in sequence. After stirring until completely dissolved, the flow rate of the peristaltic pump was adjusted so that 120 g of 20% sodium hydroxide solution was added dropwise over 3 hours. The reaction was continued at room temperature for 12 hours to obtain a white precipitate. Then, it was washed with 5% hydrochloric acid solution until neutral, and then washed with deionized water. After filtration, recrystallization and purification, the white precipitate was dried under reduced pressure at 40 °C for 24 hours to obtain tetraphenol fluorene active ester.

[0017] 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 80-200°C for 1-20 minutes after impregnation.

[0018] A copper-clad laminate made from the aforementioned prepreg.

[0019] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, as can be seen from the above technical solution:

[0020] I. In this invention, a fluorinated tetrafunctional active ester is synthesized through the esterification reaction of tetraphenol fluorene and pentafluorobenzoyl chloride, introducing a rigid fluorene ring structure, which helps to improve the thermal properties of the cured epoxy composite material. Tetraphenol fluorene contains four phenolic hydroxyl groups and has high functionality. In the polymerization reaction, it can act as a crosslinking node to form a three-dimensional network structure with high crosslinking density. The tetrafunctional active ester synthesized based on tetraphenol fluorene has higher heat resistance and higher Tg after curing with epoxy with high crosslinking density.

[0021] 2. The tetraphenol fluorenyl active ester contains fluorine atoms. The high electronegativity of fluorine atoms significantly reduces molecular polarizability and reduces the dipole orientation of the cross-linked network under an electric field, so that Dk can be reduced to below 3.5. At the same time, the pentafluorine substitution on the benzene ring forms a dense electron cloud, which effectively shields external electric field interference and improves signal integrity. Moreover, after the fluorine atoms replace hydrogen atoms, the surface energy of the material is significantly reduced, and the water absorption rate can be controlled to below 0.3%. In a high humidity environment, water is difficult to penetrate the cross-linked network, maintaining dielectric stability.

[0022] Third, the bond energy of the CF bond is much higher than that of the CH and CO bonds, which can delay high-temperature thermal decomposition and increase the thermal weight loss initiation temperature. At the same time, the fluorine atom inhibits the high-temperature oxidation of the benzene ring, reduces the formation of carbonized conductive paths, and indirectly improves the resistance to leakage current tracking. Moreover, the CF bond is inert to acids, alkalis and organic solvents, making it suitable for copper plating processes on high-frequency and high-speed substrates, especially cyanide-free copper plating systems, which can reduce resin interface erosion.

[0023] Fourth, fluorine and phosphorus-based flame retardants form a PF synergistic flame retardant mechanism. If flame retardants need to be introduced into copper clad laminates, fluorine can effectively reduce the amount of flame retardant used, which can be reduced to 8%, thus avoiding the degradation of dielectric properties caused by excessive flame retardant.

[0024] 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

[0025] This invention discloses a low-loss resin composition containing an active ester, comprising, by weight, the following main components: 30-70 parts epoxy resin, 30-70 parts epoxy curing agent, 0-3 parts curing accelerator, and 20-100 parts filler; wherein the epoxy curing agent is a tetraphenol fluorene-based active ester; specifically, the structure of the epoxy curing agent is as follows:

[0026]

[0027] The epoxy curing agent is prepared through the following steps:

[0028] (1) 500 g of 2,7-dihydroxy-9-fluorenone, 1330.50 g of phenol, 1500 g of ethyl acetate and 300 g of p-toluenesulfonic acid were added to a 5000 mL four-necked round-bottom flask equipped with a stirrer, condenser and thermometer. Under nitrogen protection, the mixture was heated and stirred until homogeneous. The reaction was carried out at reflux temperature of 77 °C for 7 h. After the reaction solution cooled, it was washed with deionized water until neutral. The solvent and phenol were removed by vacuum distillation. After vacuum drying, crude tetraphenol fluorene was obtained. Then, the crude tetraphenol fluorene was dissolved in an ethanol / water mixed solvent, cooled and crystallized. After filtration, tetraphenol fluorene was obtained. The reaction route is as follows:

[0029]

[0030] (2) Under nitrogen protection, 1000 mL of butanone solvent was added to a 3000 mL four-necked round-bottom flask equipped with a stirrer, condenser, and thermometer. Then, 100 g of tetraphenol fluorene, 161.71 g of pentafluorobenzoyl chloride, and 2 g of DMAP were added sequentially. After stirring until completely dissolved, the flow rate of the peristaltic pump was adjusted so that 120 g of 20% sodium hydroxide solution was added dropwise over 3 hours. The reaction was continued at room temperature for 12 hours to obtain a white precipitate. Subsequently, the precipitate was washed with 5% hydrochloric acid solution until neutral, then washed with deionized water, filtered, recrystallized, and purified. The white precipitate was then dried under reduced pressure at 40 °C for 24 hours to obtain tetraphenol fluorene active ester. The reaction pathway is as follows:

[0031]

[0032] Furthermore, the epoxy resin is DCPD phenol epoxy resin or MDI modified epoxy resin; the curing accelerator is one of 4-dimethylaminopyridine, butyltriphenylphosphine bromide, and diethyltetramethylimidazole; and the filler is silica.

[0033] 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 baking it in an oven at 80-200°C for 1-20 minutes after impregnation.

[0034] In addition, the present invention discloses a copper-clad laminate made from the aforementioned prepreg.

[0035] The following description is based on several embodiments and comparative examples. The raw materials and codes used in the embodiments and comparative examples are shown in Table 1, and the specific composition is shown in Table 2.

[0036]

[0037] Table 1

[0038]

[0039]

[0040] Table 2

[0041] Performance tests were conducted on the above embodiments and comparative examples, and the test methods are as follows:

[0042] Glass transition temperature (Tg) test

[0043] 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 TA Instruments DMA850 dynamic mechanical analysis (DMA) instrument. The test conditions were as follows: a tensile module was used at a frequency of 10 Hz, a heating rate of 3 °C / min, and dynamic viscoelasticity was measured 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.

[0044] Dielectric constant (Dk) and dielectric loss factor (Df)

[0045] 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.

[0046] Peel strength (PS)

[0047] The peel strength of the metal capping layer was tested according to the "receiver state" experimental conditions in IPC-TM-650 2.4.8 method.

[0048] Thermal stratification time

[0049] Tested according to IPC-TM-650 2.4.9 specification. A TMA450 instrument manufactured by TA Instruments was used. Thermomechanical analyzer Thermomechanical analysis (TMA) was used to determine the thermal delamination time of the copper 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 300℃, and held for 130 min. A significant abrupt change in the curve was considered delamination, and the time was recorded.

[0050] PCT water absorption rate

[0051] The water absorption test was performed according to the method specified in IPC-TM-650 2.6.2.1. Three 50×50mm samples were dried in an oven at 105℃ for 2 hours, cooled, and weighed (accuracy 0.1mg). Then, they were kept in a pressure cooking device at 121℃, 100%RH, and 2atm for 3 hours. After being removed, the surface moisture was wiped off, and the samples were weighed within 10 minutes.

[0052] The test results are shown in Table 3.

[0053]

[0054]

[0055] Table 3

[0056] Analysis of the above data, as shown in Examples 1-5, reveals that the resin composition of the present invention has a high glass transition temperature, low dielectric constant and dielectric loss, high metal peel strength, good heat resistance, and low water absorption; wherein the glass transition temperature is above 200°C, the dielectric constant is below 3.90, the dielectric loss is below 0.0080, the peel strength is greater than 1.30 N / mm, the T300 is greater than 120 minutes, and the water absorption is below 0.30%.

[0057] Specifically, compared with Comparative Example 1, Example 2 with Comparative Example 4, and Example 5 with Comparative Example 5, the resin composition of the present invention exhibits a higher glass transition temperature, superior dielectric properties, higher metal peel strength, better heat resistance, and lower water absorption. Compared with Comparative Examples 2 and 3, the resin composition of Example 1 using tetraphenol fluorene active ester as the curing agent in the present invention shows significantly better dielectric properties, heat resistance, and hygroscopicity than the resin composition using non-active ester epoxy curing agent. Furthermore, compared with Example 1 and Example 2, and Comparative Examples 1 and 4, the resin compositions using different epoxy resins also exhibit lower dielectric constants and dielectric losses. Compared with Example 1 and Example 5, and Comparative Examples 1 and 5, the addition of filler increases the dielectric constant of the resin composition, but simultaneously decreases the dielectric loss. As can be seen from Examples 1, 2, and 3, the resin composition of the present invention exhibits better overall performance under different ratios of epoxy resin and curing agent, with Example 1 showing relatively better performance.

[0058] 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 containing an active ester, characterized in that: By weight, it comprises the following main components: 30-70 parts epoxy resin, 30-70 parts epoxy curing agent, and 0-3 parts curing accelerator; wherein, the epoxy curing agent is a tetraphenol fluorenyl active ester, and its structure is as follows: 。 2. The low-loss resin composition containing active ester according to claim 1, characterized in that: It further includes 20-100 parts of filler.

3. The low-loss resin composition containing active ester according to claim 2, characterized in that: The filler is silicon dioxide.

4. The low-loss resin composition containing active ester according to claim 1, characterized in that: The epoxy resin is DCPD phenol epoxy resin or MDI modified epoxy resin.

5. The low-loss resin composition containing active ester according to claim 1, characterized in that: The curing accelerator is one of 4-dimethylaminopyridine, butyltriphenylphosphine bromide, and diethyltetramethylimidazole.

6. The low-loss resin composition containing active ester according to claim 1, characterized in that: The epoxy curing agent is prepared by the following steps: (1) 500 g of 2,7-dihydroxy-9-fluorenone, 1330.50 g of phenol, 1500 g of ethyl acetate and 300 g of p-toluenesulfonic acid were added to a 5000 mL four-necked round-bottom flask equipped with a stirrer, condenser and thermometer. Under nitrogen protection, the mixture was heated and stirred until homogeneous. The reaction was carried out at a reflux temperature of 77 °C for 7 h. After the reaction solution cooled, it was washed with deionized water until neutral. The solvent and phenol were removed by vacuum distillation. After vacuum drying, crude tetraphenol fluorene was obtained. Then, the crude tetraphenol fluorene was dissolved in an ethanol / water mixed solvent, cooled and crystallized. After filtration, tetraphenol fluorene was obtained. (2) Under nitrogen protection, 1000 ml of butanone solvent was added to a 3000 mL four-necked round-bottom flask equipped with a stirrer, condenser and thermometer. Then, 100 g of tetraphenol fluorene, 161.71 g of pentafluorobenzoyl chloride and 2 g of DMAP were added in sequence. After stirring until completely dissolved, the flow rate of the peristaltic pump was adjusted so that 120 g of 20% sodium hydroxide solution was added dropwise over 3 hours. The reaction was continued at room temperature for 12 hours to obtain a white precipitate. Then, it was washed with 5% hydrochloric acid solution until neutral, and then washed with deionized water. After filtration, recrystallization and purification, the white precipitate was dried under reduced pressure at 40 °C for 24 hours to obtain tetraphenol fluorene active ester.

7. A semi-cured sheet, characterized in that: The glass cloth is impregnated in an adhesive solution formed by the low-loss resin composition according to any one of claims 1-6, and after impregnation, it is baked in an oven at 80-200°C for 1-20 minutes to obtain the product.

8. A copper-clad laminate, characterized in that: It is made from the prepreg as described in claim 7.

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