A low dielectric benzocyclobutene resin and a method for preparing the same

Abstract

The application belongs to the technical field of low dielectric resin preparation, and discloses a low dielectric benzocyclobutene resin and a preparation method thereof; the resin is a three-dimensional network structure obtained by ladder curing and crosslinking of a diene copolymer functionalized with a benzocyclobutene group; the corresponding functionalized copolymer is prepared by taking a polymer containing a diene structure and benzocyclobutene-based dimethyl silane as raw materials and through a silicon hydrogen addition reaction; the resin crosslinking network is uniform and dense, and no small molecule residues are left, and the resin has excellent dielectric properties, mechanical toughness and high temperature resistance. The resin can meet the application requirements of low dielectric materials for high frequency communication components and packaging of heat sensitive devices, the preparation process does not need to use expensive raw materials or complex equipment, is suitable for existing mature production lines, has obvious comprehensive application advantages, and has good industrialization popularization prospect.

Description

Technical Field

[0001] This invention belongs to the field of low dielectric resin preparation technology, and in particular to a low dielectric benzocyclobutene resin and its preparation method. Background Technology

[0002] With the rapid penetration of the digital economy, communication technology is at a critical juncture, transitioning from large-scale commercialization of 5G to forward-looking research and development of 6G. High frequency, broadband, and low latency are becoming the core evolutionary directions. High-frequency integrated circuits, as the core carrier of communication systems, are rapidly iterating towards high integration, high operating frequency, and low power consumption, placing stringent requirements on the dielectric properties, thermal stability, and process adaptability of packaging and substrate materials. In high-frequency signal transmission scenarios, the dielectric constant of the material directly affects the signal propagation speed, and dielectric loss determines the energy loss of signal transmission. Lower dielectric constants and dielectric losses can effectively reduce signal delay and attenuation. Simultaneously, materials need to be adaptable to mild curing conditions to meet the packaging requirements of heat-sensitive devices. Developing high-performance packaging materials suitable for high-frequency communication scenarios has become a core industry demand. Benzocyclobutene resin, due to its excellent thermal stability, low moisture absorption, and good mechanical properties, has been widely used in high-frequency communication and semiconductor packaging. However, traditional benzocyclobutene resin has a dielectric constant higher than 2.7 at a 10GHz testing frequency and a curing temperature reaching 300℃, which cannot meet the performance requirements of next-generation high-frequency substrates.

[0003] Existing modification schemes are mainly divided into two categories. The first category is modification by introducing fluorine-containing groups. Chinese patent application number CN202110168571.6 discloses a method for preparing fluorine-containing polyarylene ether low dielectric materials. By introducing fluorine atoms to reduce the degree of molecular electronic polarization and increase the free volume between molecules, the dielectric constant is reduced. This scheme does not require adjustment of the existing molding process and can be directly adapted to conventional substrate production lines. However, it does not solve the problems of high cost of fluorinated raw materials and complex synthesis process. Moreover, the introduction of fluorine groups can easily increase the brittleness of the material and cannot meet the bending resistance requirements of high-integration packaging.

[0004] The second category involves constructing porous structures for modification. Chinese patent application number CN201010226858.1 discloses a method for preparing low-dielectric insulating materials by controlling the foaming structure through interface engineering. It utilizes the difference in thermal properties between the nucleating agent and the matrix to induce the nucleation of interfacial bubbles, forming a uniform and dense foaming structure to reduce the dielectric constant. This method can be adapted to various polymer matrices and has a large range of dielectric constant control. However, it does not solve the problem of the decrease in mechanical strength of the material after foaming. At the same time, the porous structure is prone to accelerating the environmental aging rate and reducing the reliability of encapsulation. Moreover, the foaming process has high requirements for equipment precision, resulting in high preparation costs.

[0005] Current modification methods all suffer from the drawback of difficulty in balancing performance, cost, and process compatibility. There is an urgent need to develop new low-dielectric benzocyclobutene resin preparation methods to meet the performance requirements of advanced electronic packaging. Summary of the Invention

[0006] To address the shortcomings of existing low-dielectric benzocyclobutene resin modification schemes, such as high cost, performance imbalance, and excessively high curing temperature, this invention provides a low-dielectric benzocyclobutene resin and its preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A low-dielectric benzocyclobutene resin is disclosed. The resin is a three-dimensional network structure obtained by step-curing and crosslinking of a diene copolymer functionalized with benzocyclobutene groups. The diene copolymer functionalized with benzocyclobutene groups is prepared by hydrosilylation reaction of a polymer containing a diene structure and benzocyclobutene dimethylsilane as raw materials. The resin crosslinking network is uniform and dense, with no small molecule residues, and has excellent dielectric properties, mechanical toughness and high temperature resistance. It can meet the application requirements of low-dielectric materials for high-frequency communication components and heat-sensitive device packaging.

[0008] Preferably, the polymer containing a diene structure is an unsaturated polymer with double bonds in the main chain or side chain, including any one of polyisoprene, polychloroprene, polybutadiene, and butadiene-styrene copolymer. The polyisoprene includes cis-1,4-polyisoprene, 1,2-polyisoprene, and 3,4-polyisoprene. The polybutadiene includes cis-1,4-polybutadiene and trans-1,4-polybutadiene. The average molecular weight of the unsaturated polymer is 1000-100000. Diene polymers in this molecular weight range can react fully with benzocyclobutene units, avoiding dielectric degradation and mechanical property decline caused by small molecule residues.

[0009] Preferably, the structural formula of benzocyclobutenyldimethylsilane is shown in Formula I:

[0010] Among them, benzocyclobutenyldimethylsilane is composed of a benzocyclobutenyl group connected to a dimethylsilyl group, and a hydrogen atom and two methyl groups are attached to the silicon atom. The symmetrical structure with bifunctionality in the structural formula of benzocyclobutenyldimethylsilane can realize efficient hydrosilylation reaction with dienes, reduce the occurrence of side reactions such as random crosslinking, and improve the uniformity of the crosslinking network.

[0011] Preferably, a polymer containing a diene structure and benzocyclobutene dimethylsilane are used as reactants. After hydrosilylation reaction to obtain a diene copolymer functionalized with benzocyclobutene groups, the target resin is obtained by step-curing crosslinking. The resulting product has a uniform and dense crosslinking network with no small molecule residues. It also has excellent dielectric properties, mechanical toughness and mild curing conditions, which are suitable for the material requirements of the high-frequency packaging field.

[0012] Preferably, it includes the following steps: S1. Raw material pretreatment: Benzocyclobutenyl dimethylsilane and diene polymer are vacuum dried to remove water and oxygen, and the moisture content is controlled to be below 50 ppm to avoid side reactions caused by trace amounts of water and oxygen and improve product purity. S2. Atmosphere replacement: Vacuum the dry three-necked flask and circulate nitrogen gas 3-5 times to make the oxygen content of the reaction system lower than 10 ppm, so as to avoid the negative impact of oxygen inhibition on the addition reaction and ensure the stability of the reaction conversion rate. S3. Gradient feeding and dissolution: Under a nitrogen atmosphere, first add the diene polymer, inject some solvent, stir at low speed at 40-60℃ until completely dissolved, then add benzocyclobutenyl dimethylsilane, and continue stirring until a uniform and transparent solution is obtained, to avoid the formation of gelation byproducts caused by excessively high local material concentration. S4. Pre-reaction activation: Heat the solution to 70-90℃ and stir at a constant temperature for 30-60 min to complete the activation of double bonds and homogenization of the system. S5. Segmented heating polymerization: Heat to 100-110℃ at a rate of 2-5℃ / min, react at a constant temperature for 1-2 hours, continue to heat to 120℃, add catalyst, stir at a constant temperature for 4 hours, and achieve a stable and controllable reaction rate by gradient temperature control to avoid explosive polymerization. S6. Catalytic Termination: Add a catalyst terminator and stir for 15-30 minutes to deactivate the catalytic active center, quench the active center, and avoid performance fluctuations caused by post-crosslinking during product storage. S7. Primary filtration: The reaction solution is cooled to room temperature and filtered through a neutral alumina chromatography column to remove the catalyst and insoluble impurities, effectively removing residual metal catalysts and reducing dielectric loss. S8. Decolorization and refining: The filtrate is decolorized by activated carbon adsorption, stirred at 30-50℃ for 30 minutes, and then filtered twice to obtain a clear filtrate, removing colored impurities and improving the light transmittance and film uniformity of the product. S9. Gradient sedimentation purification: The filtrate is slowly added dropwise with a settling agent under stirring, and the process is carried out in sequence: first sedimentation, centrifugation, second sedimentation, centrifugation, third sedimentation, centrifugation. The crude product is collected, and unreacted monomers and oligomer by-products are removed step by step to improve the purity of the product. S10. Vacuum drying: The crude product is placed in a vacuum oven and dried at 50-70℃ for 12-24 hours to obtain a high-purity benzocyclobutene functionalized diene copolymer. Residual solvents and precipitants are removed to avoid bubble defects during the film formation process. S11. Solution preparation and film formation: Dissolve the polymer in a solvent to prepare a coating solution with a solid content of 10-30wt%. Filter the solution through a 0.22μm filter membrane to remove bubbles, ensuring that the coating solution is uniform and stable and that the film is free of particle defects. S12, Step Curing: The coating liquid is spin-coated or scraped into a wet film, and the temperature is increased according to the program to complete the curing. The maximum curing temperature is 250℃, and a low dielectric benzocyclobutene resin film is obtained.

[0013] Preferably, the solvent is mesitylene, whose boiling point matches the reaction temperature, reducing solvent evaporation during the reaction process, ensuring stable system concentration, and avoiding local gel formation; The structural formula of the high-purity benzocyclobutene-functionalized diene copolymer is shown in Formula II:

[0014] R is selected from any one of polyisoprene, polychloroprene, polybutadiene, and butadiene-styrene copolymer.

[0015] Preferably, the catalyst is a platinum catalyst with a concentration of 5-20 mg / mL. The platinum catalyst has moderate catalytic activity and can stably initiate the hydrosilylation reaction at a set temperature without the problem of uneven crosslinking caused by over-catalysis. The catalyst terminator is any one of dimethyl sulfoxide, triphenylphosphine, and pyridine. The terminator can quickly coordinate with the platinum active center for deactivation without residual impurities affecting the dielectric properties.

[0016] Preferably, methanol is used as the settling agent. The polarity difference between methanol and the reaction solvent is moderate, which can achieve selective sedimentation of the product and avoid the decrease in purity caused by co-precipitation of oligomers.

[0017] Preferably, the stirring speed in steps S3 to S5 is 300-600 r / min. This speed range can ensure that the system is mixed evenly and that no air bubbles are entrained, thus avoiding pore defects in the reaction process.

[0018] Preferably, the stepped curing process is as follows: heating from room temperature to 70-100℃ and holding for 30-45 minutes, then heating to 100-150℃ and holding for 30-45 minutes, then heating to 150-200℃ and holding for 30-45 minutes, and finally heating to 250℃ and holding for 1-1.5 hours. The total heating rate is 1-3℃ / min. This multi-stage gradient heating and curing process can achieve the simultaneous evaporation of solvent and crosslinking reaction. The resulting film has high density, uniform and stable dielectric and mechanical properties, and the highest curing temperature is lower than that of traditional benzocyclobutene resin, which is suitable for the encapsulation requirements of heat-sensitive devices.

[0019] The present invention has the following beneficial effects: This invention introduces a low-polarity rigid aliphatic cage structure into the benzocyclobutene molecular backbone, reducing the overall polarizability of the material without introducing fluorine-containing groups or constructing a porous structure. Simultaneously, it increases the intermolecular free volume, achieving low dielectric constant and low dielectric loss. This effectively solves the shortcomings of existing fluorine-containing modification schemes, such as high raw material costs, complex synthesis processes, and high material brittleness. It also avoids the problems of decreased mechanical strength, easy aging, and insufficient encapsulation reliability caused by porous structure modification schemes. Furthermore, it retains the excellent thermal stability and low hygroscopicity of benzocyclobutene resin itself, achieving a balance between dielectric properties and basic mechanical and weather resistance properties.

[0020] This invention effectively reduces the activation energy required for the ring-opening crosslinking of the resin by grafting low-activation-energy reactive groups onto the side of the benzocyclobutene molecule. This allows for curing and molding under milder conditions, effectively solving the defects of traditional benzocyclobutene resin, such as excessively high curing temperature and high energy consumption, which make it unsuitable for the packaging requirements of heat-sensitive devices. This expands the scope of the resin's applicable scenarios.

[0021] The preparation process of this invention is highly compatible with the existing industrial production process of benzocyclobutene resin. It can achieve large-scale mass production without the need for new special production equipment or adjustments to existing packaging and molding processes. It can be widely used in multiple electronic material fields such as high-frequency communication substrates, high-integration semiconductor packaging, and thermal device integration, and has good industry promotion value. Attached Figure Description

[0022] Figure 1 This invention proposes a general formula for the synthesis reaction of low dielectric benzocyclobutene resin; Figure 2 This is a bar chart comparing the tensile strength and maximum curing temperature of different samples proposed in this invention. Figure 3 This is a bar chart comparing the dielectric properties of different samples at 10 GHz proposed in this invention. Figure 4 This is a line graph showing the effect of the catalyst concentration proposed in this invention on the core performance of the product. Detailed Implementation

[0023] The following will refer to the appendices in the embodiments of the present invention. Figure 1-4 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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.

[0024] Example 1

[0025] Preparation of benzocyclobutenyldimethylsilane: A solution of 26.08 g of 4-bromobenzocyclobutene dissolved in 100 mL of tetrahydrofuran was added dropwise to a mixture of 5.13 g of magnesium shavings, 26.97 g of dimethylchlorosilane, and 100 mL of tetrahydrofuran. After stirring at room temperature for 15 h, the reaction mixture was filtered through diatomaceous earth. The filtrate was washed with water and concentrated under reduced pressure to obtain a pale yellow liquid. This liquid was purified by reduced-pressure distillation to obtain a colorless, oily benzocyclobutenyldimethylsilane with a yield of 88.5%. The reaction formula is shown in Formula III.

[0026] This reaction uses conventional bulk raw materials and does not require the introduction of fluorine-containing monomers, thus effectively controlling raw material costs. The reaction formula for synthesizing benzocyclobutenyldimethylsilane from bromobenzocyclobutene and dichlorosilane via a Grignard reaction involves placing 0.7g of benzocyclobutenyldimethylsilane and 2.1g of 1,2-polyisoprene separately in a vacuum drying oven at 50℃ for 6 hours to remove moisture and oxygen, controlling the moisture content to be below 50ppm. The selected 1,2-polyisoprene has a number average molecular weight of 50,000.

[0027] Install a condenser, thermometer, and constant-pressure dropping funnel on a dry three-necked flask. Evacuate the system and circulate high-purity nitrogen three times to ensure the oxygen content is below 10 ppm. Under nitrogen protection, first add 1,2-polyisoprene, then inject 40 mL of mesitylene solution. Stir at 45°C and 450 rpm until completely dissolved. Next, add benzocyclobutenyldimethylsilane and continue stirring until the solution is homogeneous and transparent.

[0028] The solution was heated to 80°C and stirred at this temperature for 45 min to complete the activation of the double bonds and homogenization of the system. The temperature was then increased to 105°C at a rate of 3°C / min and the reaction was carried out at this temperature for 1.5 h. The temperature was then further increased to 120°C, and 0.05 mL of a 10 mg / mL isopropanol chloroplatinate solution was added. The mixture was stirred at this temperature for 4 h to complete the hydrosilylation.

[0029] Add 0.1 mL of dimethyl sulfoxide and stir for 20 min to completely deactivate the catalytic active sites. Cool the reaction solution to room temperature and filter it through a neutral alumina chromatography column to remove the catalyst and insoluble impurities. Add 0.2 g of activated carbon to the filtrate, stir at 40 °C for 30 min to decolorize, and filter a second time to obtain a clear filtrate.

[0030] The filtrate was slowly added dropwise to methanol under stirring, and the mixture was subjected to three separate sedimentation and centrifugation operations to remove small molecules, unreacted monomers, and solvent residues. The crude product was collected and placed in a vacuum oven and dried at 60°C for 18 hours to obtain a high-purity benzocyclobutene-functionalized diene copolymer.

[0031] The polymer was dissolved in mesitylene to prepare a coating solution with a solid content of 20 wt%. After filtration through a 0.22 μm filter membrane, the solution was degassed under vacuum for 30 min. The coating solution was then applied as a wet film and cured according to a stepwise procedure: room temperature → 80℃ for 40 min → 120℃ for 40 min → 180℃ for 40 min → 250℃ for 1.2 h, with a heating rate of 2℃ / min. After natural cooling, a low-dielectric benzocyclobutene resin film was obtained.

[0032] Example 2

[0033] Preparation of benzocyclobutenyldimethylsilane raw materials: To a mixture of 5.13 g magnesium shavings, 26.97 g dichlorosilane, and 100 mL tetrahydrofuran, 26.08 g 4-bromobenzocyclobutene dissolved in 100 mL tetrahydrofuran was added dropwise. After stirring at room temperature for 15 h, the reaction mixture was filtered through diatomaceous earth. The filtrate was washed with water and concentrated under reduced pressure to obtain a light yellow liquid. After purification by reduced pressure distillation, a colorless oily benzocyclobutenyldimethylsilane was obtained with a yield of 88.5%.

[0034] 0.7 g of benzocyclobutenyl dimethylsilane and 2.7 g of cis-1,4-polybutadiene were placed in a vacuum drying oven and dried at 50°C for 6 h to remove water and oxygen, with the moisture content controlled to be below 50 ppm. The selected cis-1,4-polybutadiene had a number average molecular weight of 50,000.

[0035] Install a condenser, thermometer, and constant-pressure dropping funnel on a dry three-necked flask. Evacuate the system and circulate high-purity nitrogen four times to ensure the oxygen content is below 10 ppm. Under nitrogen protection, first add cis-1,4-polybutadiene, then inject 40 mL of trimethylbenzene solution. Stir at 50°C and 450 rpm until completely dissolved. Next, add benzocyclobutenyldimethylsilane and continue stirring until the solution is homogeneous and transparent.

[0036] The solution was heated to 90°C and stirred at this temperature for 30 min to activate the double bonds and homogenize the system. The temperature was then increased to 110°C at a rate of 5°C / min and held at this temperature for 1 h. The temperature was further increased to 120°C, and 0.05 mL of a 20 mg / mL isopropanol chloroplatinate solution was added. The mixture was stirred at this temperature for 4 h to complete the hydrosilylation. Finally, 0.1 mL of dimethyl sulfoxide was added and stirred for 30 min to completely deactivate the catalytic active sites.

[0037] The reaction solution was cooled to room temperature and filtered through a neutral alumina chromatography column to remove the catalyst and insoluble impurities. 0.2 g of activated carbon was added to the filtrate, and the mixture was stirred at 50°C for 30 min to decolorize. A second filtration was then performed to obtain a clear filtrate.

[0038] The filtrate was slowly added dropwise to methanol under stirring, and the mixture was subjected to three separate sedimentation and centrifugation operations to remove small molecules, unreacted monomers, and solvent residues. The crude product was collected and placed in a vacuum oven and dried at 70°C for 12 hours to obtain a high-purity benzocyclobutene-functionalized diene copolymer.

[0039] The polymer was dissolved in mesitylene to prepare a coating solution with a solid content of 25 wt%. After filtration through a 0.22 μm filter membrane, the solution was degassed under vacuum for 30 min. The coating solution was then applied as a wet film and cured according to a stepwise procedure: room temperature → 100℃ for 30 min → 150℃ for 30 min → 200℃ for 30 min → 250℃ for 1 h, with a heating rate of 3℃ / min. After natural cooling, a low-dielectric benzocyclobutene resin film was obtained.

[0040] Example 3

[0041] First, prepare the raw material for benzocyclobutenyl dimethylsilane: Add dropwise a solution of 26.08 g of 4-bromobenzocyclobutene dissolved in 100 mL of tetrahydrofuran to a mixture of 5.13 g of magnesium shavings, 26.97 g of dimethylchlorosilane, and 100 mL of tetrahydrofuran. After stirring at room temperature for 15 h, filter the reaction mixture through diatomaceous earth. Wash the filtrate with water and concentrate it under reduced pressure to obtain a light yellow liquid. Purify the liquid by reduced pressure distillation to obtain a colorless oily benzocyclobutenyl dimethylsilane with a yield of 88.5%.

[0042] 0.7g of benzocyclobutenyl dimethylsilane and 3.5g of butadiene-styrene copolymer were placed in a vacuum drying oven and dried at 50℃ for 6 hours to remove water and oxygen, with the moisture content controlled to be below 50ppm. The selected butadiene-styrene copolymer had a number average molecular weight of 50,000.

[0043] A condenser, thermometer, and constant-pressure dropping funnel were installed on a dry three-necked flask. The system was evacuated and purged with high-purity nitrogen five times to ensure the oxygen content was below 10 ppm. Under nitrogen protection, butadiene-styrene copolymer was added first, followed by 40 mL of mesitylene solution. The mixture was stirred at 60°C and 450 rpm until completely dissolved. Then, benzocyclobutenyl dimethylsilane was added, and stirring continued until the solution was homogeneous and transparent.

[0044] The solution was heated to 70°C and stirred at this temperature for 60 min to activate the double bonds and homogenize the system. The temperature was then increased to 100°C at a rate of 2°C / min and held at this temperature for 2 h. The temperature was further increased to 120°C, and 0.05 mL of a 10 mg / mL isopropanol chloroplatinate solution was added. The mixture was stirred at this temperature for 4 h to complete the hydrosilylation. Finally, 0.1 mL of dimethyl sulfoxide was added and stirred for 15 min to completely deactivate the catalytic active sites.

[0045] The reaction solution was cooled to room temperature and filtered through a neutral alumina chromatography column to remove the catalyst and insoluble impurities. 0.2 g of activated carbon was added to the filtrate, and the mixture was stirred at 30°C for 30 min to decolorize. A second filtration was performed to obtain a clear filtrate. Methanol was slowly added dropwise to the filtrate while stirring, and the mixture was subjected to three separate sedimentation and centrifugation operations to remove small molecules, unreacted monomers, and solvent residues. The crude product was collected and placed in a vacuum oven, where it was dried at 50°C for 24 h to obtain a high-purity benzocyclobutene-functionalized diene copolymer.

[0046] The polymer was dissolved in mesitylene to prepare a coating solution with a solid content of 15 wt%. After filtration through a 0.22 μm filter membrane, the solution was degassed under vacuum for 30 min. The coating solution was then applied as a wet film and cured according to a stepwise procedure: room temperature → 70℃ for 45 min → 100℃ for 45 min → 150℃ for 45 min → 250℃ for 1.5 h, with a heating rate of 1℃ / min. After natural cooling, a low-dielectric benzocyclobutene resin film was obtained.

[0047] Example 4

[0048] First, prepare the raw material for benzocyclobutenyl dimethylsilane: Add dropwise a solution of 26.08 g of 4-bromobenzocyclobutene dissolved in 100 mL of tetrahydrofuran to a mixture of 5.13 g of magnesium shavings, 26.97 g of dimethylchlorosilane, and 100 mL of tetrahydrofuran. After stirring at room temperature for 15 h, filter the reaction mixture through diatomaceous earth. Wash the filtrate with water and concentrate it under reduced pressure to obtain a light yellow liquid. Purify the liquid by reduced pressure distillation to obtain a colorless oily benzocyclobutenyl dimethylsilane with a yield of 88.5%.

[0049] 0.7 g of benzocyclobutenyl dimethylsilane and 2.1 g of 1,2-polyisoprene were placed in a vacuum drying oven and dried at 50 °C for 6 h to remove water and oxygen, with the moisture content controlled to be below 50 ppm. The selected 1,2-polyisoprene had a number average molecular weight of 100,000.

[0050] Install a condenser, thermometer, and constant-pressure dropping funnel on a dry three-necked flask. Evacuate the system and circulate high-purity nitrogen three times to ensure the oxygen content is below 10 ppm. Under nitrogen protection, first add 1,2-polyisoprene, then inject 40 mL of mesitylene solution. Stir at 40°C and 450 rpm until completely dissolved. Next, add benzocyclobutenyldimethylsilane and continue stirring until the solution is homogeneous and transparent.

[0051] The solution was heated to 70°C and stirred at this temperature for 60 min to activate the double bonds and homogenize the system. The temperature was then increased to 100°C at a rate of 2°C / min and held at this temperature for 2 h. The temperature was further increased to 120°C, and 0.05 mL of a 5 mg / mL isopropanol chloroplatinate solution was added. The mixture was stirred at this temperature for 4 h to complete the hydrosilylation. Finally, 0.1 mL of dimethyl sulfoxide was added, and the mixture was stirred for 20 min to completely deactivate the catalytic active sites.

[0052] The reaction solution was cooled to room temperature and filtered through a neutral alumina chromatography column to remove the catalyst and insoluble impurities. 0.2 g of activated carbon was added to the filtrate, and the mixture was stirred at 40°C for 30 min to decolorize. A second filtration was performed to obtain a clear filtrate. Methanol was slowly added dropwise to the filtrate while stirring, and the mixture was subjected to three separate sedimentation and centrifugation operations to remove small molecules, unreacted monomers, and solvent residues. The crude product was collected and placed in a vacuum oven, where it was dried at 60°C for 18 h to obtain a high-purity benzocyclobutene-functionalized diene copolymer.

[0053] The polymer was dissolved in mesitylene to prepare a coating solution with a solid content of 20 wt%. After filtration through a 0.22 μm filter membrane, the solution was degassed under vacuum for 30 min. The coating solution was then applied as a wet film and cured according to a stepwise procedure: room temperature → 80℃ for 40 min → 120℃ for 40 min → 180℃ for 40 min → 250℃ for 1.2 h, with a heating rate of 2℃ / min. After natural cooling, a low-dielectric benzocyclobutene resin film was obtained.

[0054] Comparative Example 1 Fluorinated benzocyclobutene monomers were used as raw materials to obtain fluorinated modified benzocyclobutene polymers through free radical polymerization. The polymers were then formulated into coating solutions and cured at 300℃ to prepare thin films.

[0055] Comparative Example 2 Ordinary benzocyclobutene resin was used as the matrix, and an interfacial nucleating agent was added. Foamed benzocyclobutene resin was obtained through a high-pressure foaming process. After being prepared into a film, it was cured at 300℃ to compare the inherent defect of low mechanical strength of foamed modified benzocyclobutene resin.

[0056] Performance test data table Table 1 Comparison of Core Process Parameters

[0057] This table summarizes the core process parameters of all samples. Examples 1-4 all adopted a non-fluorinated, non-foaming synthesis route, with a maximum curing temperature of 250℃, lower than the 300℃ curing temperature of traditional benzocyclobutene resin. All raw materials used were readily available industrial raw materials, requiring no special monomers or foaming equipment, and were compatible with existing benzocyclobutene production lines. Comparative Example 1 used a fluorinated modification route, requiring the use of special fluorinated monomers, while Comparative Example 2 used a foaming modification route, requiring additional high-precision foaming equipment.

[0058] Table 2 Comparison of Core Performance Test Results

[0059] This table summarizes the core performance test results of all samples. The glass transition temperature (Tg) was measured using differential scanning calorimetry (DSC) at a heating rate of 10℃ / min; the 5% thermogravimetric temperature (Td) was measured using thermogravimetric analysis (TGA) under a nitrogen atmosphere at a heating rate of 10℃ / min. The dielectric constants of Examples 1-4 at 10GHz are all below 2.6, the dielectric losses are all below 0.001, the glass transition temperatures are all above 300℃, and the 5% thermogravimetric temperatures are all above 400℃. These performance characteristics are comparable to the dielectric properties of the two existing modification schemes, while exhibiting better thermal stability than the comparative examples, thus meeting the performance requirements of high-frequency communication and high-temperature packaging scenarios. The tensile strength of Examples 1-4 is higher than that of Comparative Examples 1 and 2, effectively solving the defects of high material brittleness caused by fluorine modification and low mechanical strength caused by foaming modification. The highest curing temperature of Examples 1-4 is 250℃, which is much lower than the 300℃ curing temperature of existing modification schemes, and can be adapted to the encapsulation requirements of heat-sensitive devices, solving the defect of excessively high curing temperature of traditional benzocyclobutene resin.

[0060] refer to Figure 2 This figure can intuitively show the core performance differences between the present invention and existing modification schemes. The tensile strength of all embodiments is higher than that of the two comparative examples, verifying that the present invention solves the defects of high brittleness of fluorinated modified materials and low mechanical strength of foamed modified materials. The maximum curing temperature of the embodiments is 50°C lower than that of the existing schemes, which is suitable for the encapsulation requirements of heat-sensitive devices. The embodiments with different diene types, molecular weights and catalyst concentrations have stable performance, which proves that the process of the present invention has strong adaptability.

[0061] refer to Figure 3This figure visually demonstrates the high-frequency dielectric properties of all samples. The dielectric constants of the four embodiments of this invention are all below 2.6, and the dielectric losses are all below 0.001, which are at the same level as the dielectric properties of existing fluorinated and foamed modification schemes, meeting the performance requirements of low dielectric materials for 5G / 6G high-frequency communication and advanced packaging scenarios. At the same time, this solution does not require the use of expensive fluorinated monomers or complex foaming equipment, and optimizes the mechanical properties and curing process while maintaining the same dielectric properties, resulting in significant comprehensive application advantages.

[0062] refer to Figure 4 This figure illustrates the performance stability of the present invention under different catalyst dosages. Within the catalyst concentration range of 5-20 mg / mL, the tensile strength of the product remains above 71 MPa, and the dielectric constant remains below 2.6, with no significant performance fluctuations. This confirms that the catalytic process window of the present invention is wide, and qualified products can be obtained without strictly controlling the catalyst concentration within a very small range. This reduces the difficulty of process control in industrial production and is suitable for production scenarios with different capacity and cost requirements.

[0063] 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. A low-dielectric benzocyclobutene resin, characterized in that, The resin is a three-dimensional network structure obtained by step-curing and crosslinking of a diene copolymer functionalized with benzocyclobutene groups. The benzocyclobutene-functionalized diene copolymer is prepared by hydrosilylation reaction of a polymer containing a diene structure and benzocyclobutene dimethylsilane as raw materials.

2. The low-dielectric benzocyclobutene resin according to claim 1, characterized in that, The polymer containing a diene structure is an unsaturated polymer with double bonds in the main chain or side chain, including any one of polyisoprene, polychloroprene, polybutadiene, and butadiene-styrene copolymer; the polyisoprene includes cis-1,4-polyisoprene, 1,2-polyisoprene, and 3,4-polyisoprene; the polybutadiene includes cis-1,4-polybutadiene and trans-1,4-polybutadiene; the average molecular weight of the unsaturated polymer is 1,000-100,000.

3. The low-dielectric benzocyclobutene resin according to claim 1, characterized in that, The structural formula of the benzocyclobutenyldimethylsilane is shown in Formula I: The benzocyclobutenyl dimethylsilane is composed of a benzocyclobutenyl group connected to a dimethylsilyl group, and the silicon atom is further connected to a hydrogen atom and two methyl groups.

4. A method for preparing a low-dielectric benzocyclobutene resin, used to prepare the low-dielectric benzocyclobutene resin as described in any one of claims 1 to 3, characterized in that, A benzocyclobutene-functionalized diene copolymer was prepared by hydrosilylation reaction of a polymer containing a diene structure and benzocyclobutene dimethylsilane as reactants, followed by stepwise curing and crosslinking to obtain the target resin.

5. The method for preparing a low-dielectric benzocyclobutene resin according to claim 4, characterized in that, Includes the following steps: S1. Raw material pretreatment: Benzocyclobutenyldimethylsilane and diene polymer are vacuum dried to remove water and oxygen, and the moisture content is controlled to be less than 50 ppm. S2. Atmosphere replacement: Vacuum the dry three-necked flask and circulate nitrogen gas 3-5 times. S3, Gradient feeding and dissolution: Under a nitrogen atmosphere, first add the diene polymer, inject some solvent, stir at low speed at 40-60℃ until completely dissolved, then add benzocyclobutenyldimethylsilane, and continue stirring until a homogeneous and transparent solution is obtained. S4. Pre-reaction activation: Heat the solution to 70-90℃ and stir at a constant temperature for 30-60 min to complete the activation of double bonds and homogenization of the system. S5. Segmented heating polymerization: Heat to 100-110℃ at a rate of 2-5℃ / min, react at a constant temperature for 1-2 hours, continue heating to 120℃, add catalyst, and stir at a constant temperature for 4 hours. S6. Catalytic Termination: Add catalyst terminator and stir for 15-30 min to deactivate the catalytic active center; S7. Primary filtration: After the reaction solution is cooled to room temperature, it is filtered through a neutral alumina chromatography column to remove the catalyst and insoluble impurities. S8. Decolorization and purification: The filtrate is decolorized by activated carbon adsorption, stirred at 30-50℃ for 30 minutes, and then filtered twice to obtain a clear filtrate. S9. Gradient sedimentation purification: The filtrate is slowly added dropwise with a settling agent under stirring, and the process is repeated in sequence: first sedimentation, centrifugation, second sedimentation, centrifugation, third sedimentation, centrifugation, and crude product is collected. S10. Vacuum drying: The crude product is placed in a vacuum oven and dried at 50-70℃ for 12-24 hours to obtain a high-purity benzocyclobutene functionalized diene copolymer. S11, Solution preparation and film formation: Dissolve the polymer in a solvent to prepare a coating solution with a solid content of 10-30wt%, and filter it through a 0.22μm filter membrane to remove bubbles; S12, Step Curing: The coating liquid is spin-coated or scraped into a wet film, and the temperature is increased according to the program to complete the curing. The maximum curing temperature is 250℃, and a low dielectric benzocyclobutene resin film is obtained.

6. The method for preparing low-dielectric benzocyclobutene resin according to claim 5, characterized in that, The solvent is mesitylene; The structural formula of the high-purity benzocyclobutene-functionalized diene copolymer is shown in Formula II: R is selected from any one of polyisoprene, polychloroprene, polybutadiene, and butadiene-styrene copolymer.

7. The method for preparing low-dielectric benzocyclobutene resin according to claim 5, characterized in that, The catalyst is a platinum catalyst with a concentration of 5-20 mg / mL; the catalyst terminator is any one of dimethyl sulfoxide, triphenylphosphine, and pyridine.

8. The preparation method according to claim 5, characterized in that, The settling agent is methanol.

9. The method for preparing low-dielectric benzocyclobutene resin according to claim 5, characterized in that, The stirring speed in steps S3 to S5 is 300-600 r / min.

10. The method for preparing low-dielectric benzocyclobutene resin according to claim 5, characterized in that, The step curing procedure is as follows: heat from room temperature to 70-100℃ and hold for 30-45 minutes, continue to heat to 100-150℃ and hold for 30-45 minutes, then heat to 150-200℃ and hold for 30-45 minutes, and finally heat to 250℃ and hold for 1-1.5 hours. The heating rate throughout the process is 1-3℃ / min.

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