A method and system for preparing a resin mixture for copper clad laminate

Abstract

The application discloses a preparation method and system of a copper-clad plate resin mixture, and the method comprises the following steps: carrying out grafting reaction on bisphenol A type epoxy resin and phosphorus-containing reactive flame retardant under inert atmosphere by heating, to generate a phosphorus-containing epoxy resin prepolymer; mixing the phosphorus-containing epoxy resin prepolymer and phenolic epoxy resin according to a set proportion, adding inorganic heat-conducting fillers, and carrying out high-speed shearing dispersion treatment to obtain a resin dispersion; carrying out surface coupling modification treatment on the inorganic fillers in the resin dispersion to generate a modified resin intermediate; sequentially adding a latent curing agent and a curing accelerator into the modified resin intermediate to obtain a resin mixture; and coating the resin mixture on the surface of a reinforcing fiber cloth under vacuum condition, carrying out gradient temperature pre-curing treatment, and forming a prepreg. By using the embodiment of the application, the flame retardant efficiency, heat-conducting performance and interface compatibility of the copper-clad plate resin mixture can be improved, and the process stability and storage reliability of the prepreg can be improved.

Description

Technical Field

[0001] This invention belongs to the field of copper clad laminate technology, and in particular to a method and system for preparing a copper clad laminate resin mixture. Background Technology

[0002] As the core substrate of printed circuit boards, copper-clad laminates (CCLs) directly determine the reliability of electronic products due to the performance of their resin mixtures. Currently, traditional CCLs commonly use a blend system of brominated flame retardants and epoxy resins. This method easily releases toxic gases at high temperatures, and it is difficult to balance flame retardancy efficiency with environmental friendliness. With the development of 5G and high-power electronic devices, CCLs have higher requirements for thermal conductivity, heat resistance, and dielectric properties. While existing phosphorus-containing flame retardant systems have certain environmental advantages, the reactive phosphorus components have poor compatibility with epoxy resins, easily leading to phase separation and a decline in mechanical properties. Simultaneously, inorganic thermally conductive fillers tend to agglomerate in the resin, resulting in weak interfacial bonding and limiting the effective construction of thermal conductivity pathways. Furthermore, conventional manufacturing processes suffer from uneven filler distribution and poor controllability of the curing reaction, affecting the storage stability and processing window of the prepreg. Summary of the Invention

[0003] The purpose of this invention is to provide a method and system for preparing copper-clad laminate resin mixtures to overcome the shortcomings of the prior art, improve the flame retardancy, thermal conductivity and interfacial compatibility of copper-clad laminate resin mixtures, and improve the process stability and storage reliability of prepregs.

[0004] One embodiment of this application provides a method for preparing a copper-clad laminate resin mixture, the method comprising:

[0005] Bisphenol A type epoxy resin and phosphorus-containing reactive flame retardant are grafted together under an inert atmosphere to generate phosphorus-containing epoxy resin prepolymer.

[0006] The phosphorus-containing epoxy resin prepolymer and phenolic epoxy resin are mixed in a set ratio, and inorganic thermally conductive filler is added. The mixture is then subjected to high-speed shear dispersion treatment to obtain a resin dispersion.

[0007] The inorganic filler in the resin dispersion is subjected to surface coupling modification treatment to graft functional groups onto its surface, thereby generating a modified resin intermediate with enhanced interfacial compatibility.

[0008] A latent curing agent and a curing accelerator are added sequentially to the modified resin intermediate, and the mixture is stirred and degassed under vacuum to obtain a thixotropic resin mixture.

[0009] The resin mixture is coated onto the surface of the reinforcing fiber cloth under vacuum conditions and pre-cured by gradient heating to form a semi-cured sheet.

[0010] Another embodiment of this application provides a system for preparing a copper-clad laminate resin mixture, the system comprising:

[0011] The heating module is used to perform a grafting reaction between bisphenol A type epoxy resin and phosphorus-containing reactive flame retardant under an inert atmosphere to generate phosphorus-containing epoxy resin prepolymer.

[0012] A mixing module is used to mix the phosphorus-containing epoxy resin prepolymer and phenolic epoxy resin in a set ratio, add inorganic thermally conductive fillers, and then perform high-speed shear dispersion treatment to obtain a resin dispersion.

[0013] The modification module is used to perform surface coupling modification treatment on the inorganic filler in the resin dispersion, so that functional groups are grafted onto its surface to generate a modified resin intermediate with enhanced interfacial compatibility.

[0014] A stirring module is used to sequentially add a latent curing agent and a curing accelerator to the modified resin intermediate, and stir and degas under vacuum conditions to obtain a resin mixture with thixotropic properties.

[0015] The curing module is used to coat the resin mixture onto the surface of the reinforcing fiber cloth under vacuum conditions, and then pre-cur it by gradient heating to form a semi-cured sheet.

[0016] Another embodiment of this application provides a storage medium storing a computer program, wherein the computer program is configured to execute the method described in any of the preceding claims when running.

[0017] Another embodiment of this application provides an electronic device including a memory and a processor, wherein the memory stores a computer program and the processor is configured to run the computer program to perform the method described in any of the preceding claims.

[0018] Compared with the prior art, the method for preparing copper-clad laminate resin mixture provided by the present invention can improve the flame retardancy efficiency, thermal conductivity and interfacial compatibility of copper-clad laminate resin mixture, and improve the process stability and storage reliability of prepreg. Attached Figure Description

[0019] Figure 1 A hardware structure block diagram of a computer terminal for a method of preparing a copper-clad laminate resin mixture provided in an embodiment of the present invention;

[0020] Figure 2 A schematic flowchart illustrating a method for preparing a copper-clad laminate resin mixture according to an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of a preparation system for a copper-clad laminate resin mixture provided in an embodiment of the present invention. Detailed Implementation

[0022] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0023] The present invention first provides a method for preparing a copper-clad laminate resin mixture, which can be applied to electronic devices, such as computer terminals, specifically ordinary computers.

[0024] The following detailed explanation uses a computer terminal as an example. Figure 1 This is a hardware block diagram of a computer terminal for a method of preparing a copper-clad laminate resin mixture according to an embodiment of the present invention. Figure 1 As shown, the computer device includes a processor, memory, and network interface connected via a system bus, wherein the memory may include non-volatile storage media and internal memory.

[0025] See Figure 2 The present invention provides a method for preparing a copper-clad laminate resin mixture, which may include the following steps:

[0026] S201 involves grafting bisphenol A type epoxy resin with a phosphorus-containing reactive flame retardant under an inert atmosphere to generate a phosphorus-containing epoxy resin prepolymer.

[0027] Specifically, bisphenol A epoxy resin can be put into a reactor equipped with a jacketed heating and reflux condenser, and the nitrogen valve can be opened to purge the space inside the reactor at a flow rate of 2 to 5 liters per minute to replace the air and make the oxygen content lower than 0.5%, thus creating an oxygen-free reaction environment.

[0028] The core of this step is to establish a clean, oxygen-free, and sealed reaction system, completely eliminating oxygen and moisture impurities from the air inside the reactor. This prevents the epoxy resin from oxidizing and deteriorating during the high-temperature reaction, and avoids the flame retardant from decomposing and failing. It provides stable and pure reaction conditions for the subsequent epoxy resin grafting reaction. The specific implementation method is as follows:

[0029] The core equipment used in this step is a sealed reactor equipped with a jacketed heating structure and a reflux condenser. The jacketed heating structure is a hollow jacket structure surrounding the reactor body. By introducing heat exchange media at different temperatures, it can achieve uniform heating, constant temperature maintenance, and rapid cooling of the materials inside the reactor. This allows for precise control of the reaction temperature, preventing problems such as material carbonization and side reactions caused by excessively high local temperatures. The reflux condenser consists of condensation pipes and a liquid storage structure. It can cool and liquefy the small amount of material vapor that evaporates inside the reactor during the high-temperature reaction stage, allowing it to flow back into the reactor to continue participating in the reaction. This effectively reduces raw material loss and ensures the accuracy of the reactant ratio.

[0030] Bisphenol A epoxy resin is the basic matrix raw material for this reaction and the core film-forming and molding substrate of the copper clad laminate resin system. It possesses excellent adhesion, electrical insulation, and mechanical toughness, making it a fundamental raw material for preparing phosphorus-containing flame-retardant epoxy resin, suitable for the substrate molding and insulation requirements of copper clad laminates. Before formal material feeding, the airtightness of the reactor must be checked to ensure that there are no air or liquid leaks in the reactor lid, valves, and sealing gaskets, guaranteeing the airtightness of subsequent nitrogen purging and reaction processes. Then, a measured amount of bisphenol A epoxy resin is completely added into the reactor, completing the basic raw material loading operation.

[0031] Nitrogen purging is a core step in creating an oxygen-free reaction environment. Nitrogen is an inert protective gas with stable chemical properties. It does not react chemically with epoxy resin or flame retardants at high temperatures and can completely replace the air inside the reactor, isolating it from oxygen and moisture interference. The purging flow rate is set to 2–5 liters per minute. This parameter represents the volume of nitrogen introduced into the reactor per unit time. Too low a flow rate will result in slow air replacement, incomplete replacement, and excessive residual oxygen. Too high a flow rate will waste nitrogen and disturb the surface of the raw material liquid inside the reactor, causing material splashing and loss. In this implementation example, an intermediate parameter of 3 liters per minute is selected as a constant purging flow rate to balance replacement efficiency and raw material utilization.

[0032] The purging process is continuous, with real-time monitoring of the oxygen content inside the reactor. An oxygen content of 0.5% is the system's safety threshold, representing the volume percentage of oxygen in the reactor's air. When the oxygen content exceeds this value, residual oxygen will oxidize the epoxy resin molecular chains at high temperatures, damaging the resin's structural stability. This also causes the phosphorus-containing flame retardant to oxidize and become ineffective, reducing the flame retardant performance of subsequent products. After purging continues until the oxygen content inside the reactor stabilizes below 0.5%, purging continues for 1 to 2 minutes to consolidate the displacement effect, thoroughly removing any residual air from dead corners within the reactor. This ultimately creates a closed, oxygen-free, and impurity-free reaction environment, laying the foundation for the subsequent high-temperature grafting reaction.

[0033] Start the stirrer and run it at a speed of 100-150 rpm. At the same time, heat transfer oil is introduced through the jacket to heat the bisphenol A type epoxy resin to 120-140°C. Then, add phosphorus-containing reactive flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. The amount of flame retardant added is 10%-25% of the mass of epoxy resin to generate a mixed reaction solution.

[0034] The core of this step is to achieve uniform melting and heating of the matrix resin, precisely introduce flame-retardant functional monomers, and allow the flame-retardant raw materials to be initially and uniformly mixed with the matrix resin to form a homogeneous mixed reaction system. This provides a homogeneous material basis for the subsequent high-temperature grafting reaction. The specific implementation method is as follows:

[0035] After completing the construction of the oxygen-free environment, start the stirrer equipment matched with the reaction kettle, and set the stirring speed in the range of 100 to 150 revolutions per minute. This parameter represents the number of revolutions of the stirrer blades per minute. Too low a speed will lead to poor fluidity of the resin material, resulting in uneven local heating during the subsequent heating process; too high a speed will generate a large number of bubbles, introduce trace air impurities, and destroy the oxygen-free reaction environment. In this example, a constant speed of 120 revolutions per minute is selected for continuous stirring to ensure slow and uniform flow of the materials in the kettle.

[0036] Simultaneously with the stirring operation, high-temperature heat-conducting oil is passed into the jacket of the reaction kettle as a heat exchange medium. The heat-conducting oil has the characteristics of good thermal stability, uniform temperature rise and accurate temperature control, which can realize uniform temperature rise of the materials in the kettle and avoid the problem of local high-temperature carbonization caused by open flame heating. The heating temperature range of the material is 120 to 140°C, which is the optimal melting and softening temperature for bisphenol A epoxy resin. When the temperature is lower than 120°C, the viscosity of the epoxy resin is relatively high and the fluidity of the material is extremely poor, so it cannot be uniformly mixed with the subsequently added flame retardant; when the temperature is higher than 140°C, the resin will undergo slight thermal aging in advance, which affects the subsequent grafting reaction effect and the performance of the finished product. In this example, the heating temperature is constant at 130°C, and the constant temperature stirring state is maintained after the temperature of the material in the kettle is stabilized and meets the standard.

[0037] After the epoxy resin is completely melted and the viscosity of the material system is uniform and stable, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added into the kettle. This substance is a special phosphorus-containing reactive flame retardant. Different from ordinary additive flame retardants, it can be grafted onto the molecular chain of epoxy resin through chemical reaction, which avoids the problems of later migration and precipitation, and can endow the resin system with flame retardancy stably for a long time. Phosphorus element is its core flame-retardant functional group, which can form a dense carbon layer when burned at high temperature, block the transmission of oxygen and heat, and achieve the flame-retardant effect.

[0038] The addition amount of the flame retardant is 10% to 25% of the mass of the epoxy resin. This mass ratio parameter directly determines the flame retardant grade of the finished resin. When the addition amount is less than 10%, the phosphorus content in the system is too low and the flame retardant effect cannot meet the standard; when the addition amount is higher than 25%, excess flame retardant will remain in the system, reducing the bonding strength and heat resistance of the resin matrix, and affecting the mechanical and temperature resistance properties of the copper-clad laminate. In this example, a mass ratio of 18% is selected for addition to balance the flame retardancy and the comprehensive performance of the matrix. The flame retardant needs to be added slowly and uniformly during the addition process to avoid uneven local material concentration caused by one-time large-volume feeding. After the feeding is completed, continuous stirring is performed to completely disperse and fuse the flame retardant powder into the molten epoxy resin, and finally form a mixed reaction solution with uniform components, stable viscosity and no agglomerated impurities.

[0039] Continue heating the mixed reaction solution to 150-170℃ and keep it at that temperature for 3-5 hours. During this period, take a sample every 30 minutes to measure the epoxy value. Stop the reaction when the epoxy value drops to 60%-80% of the initial value, so that the phosphorus element is grafted onto the epoxy resin molecular chain through a chemical reaction to generate a phosphorus-containing epoxy resin prepolymer intermediate.

[0040] The core of this step is to control the temperature to complete the graft polymerization reaction between epoxy resin and flame retardant. By monitoring the epoxy value in real time, the reaction endpoint is precisely controlled to ensure that phosphorus is stably grafted onto the resin molecular chain, thus preparing a structurally stable prepolymer intermediate and avoiding problems of over-reaction or incomplete reaction. The specific implementation method is as follows:

[0041] After the components of the mixed reaction solution are uniformly stabilized, the material is subjected to a second heating treatment by adjusting the temperature of the jacket heat transfer oil. The reaction temperature range is set to 150-170℃. This temperature range is the active temperature range for the grafting reaction between the phosphorus-containing flame retardant and bisphenol A type epoxy resin. When the temperature is below 150℃, the molecular chain activity is insufficient, the grafting reaction rate is extremely slow, and the reaction is difficult to proceed fully. When the temperature is above 170℃, it will trigger the self-polymerization side reaction of epoxy resin, causing the viscosity of the material to soar sharply, resulting in gel agglomeration and destroying the stability of the material system. In this embodiment, the reaction temperature is kept constant at 160℃ to ensure that the grafting reaction proceeds efficiently and stably.

[0042] The heat preservation reaction time ranges from 3 to 5 hours. Sufficient heat preservation time ensures that the flame retardant molecules and epoxy resin molecules come into full contact and form chemical bonds. Insufficient time will result in low grafting rate and excessive free flame retardant; excessive time will cause energy waste and trigger side reactions. In this implementation example, the heat preservation reaction time is preset to 4 hours, and the stirrer is kept running at a speed of 120 rpm throughout the process to ensure that the materials are always uniformly mixed during the reaction process and that the temperature and composition of the reaction system are without deviation.

[0043] The entire reaction process is monitored using timed sampling and testing. Sampling and testing are conducted every 30 minutes, which is the optimal monitoring cycle. This allows for timely detection of epoxy value changes and accurate assessment of reaction progress, while avoiding fluctuations in temperature and pressure within the reactor due to frequent sampling, thus preventing impacts on reaction stability. The core indicator being tested is the epoxy value, a key parameter characterizing the epoxy group content in the epoxy resin molecular chain, measured in equivalents per 100 grams. The grafting reaction of epoxy resin is essentially a ring-opening reaction between the flame retardant's active groups and the epoxy groups. As the reaction proceeds, the epoxy groups are continuously consumed, and the epoxy value steadily decreases, directly reflecting the degree of reaction progress.

[0044] The initial epoxy value is the epoxy value of pure bisphenol A type epoxy resin before the reaction begins, and it serves as the benchmark parameter for determining the reaction progress. The reaction endpoint is determined when the epoxy value drops to 60%–80% of the initial value. This parameter range is the optimal reaction termination range. If the epoxy value drops by more than 80%, it indicates over-reaction, excessive cross-linking of the resin molecular chains, excessively high material viscosity, and a significant decrease in subsequent processing performance. If the drop is less than 60%, it indicates incomplete reaction, insufficient phosphorus grafting rate, poor flame retardant performance, and a large amount of free flame retardant residue, affecting the stability of the resin system. In this example, the reaction termination point is defined as the epoxy value dropping to 70% of the initial value.

[0045] When the epoxy value reaches the preset standard, the heating and heat preservation operation is immediately stopped to terminate the grafting reaction. At this time, the phosphorus element in the flame retardant has been stably grafted onto the main chain of the epoxy resin molecule through covalent bonds, rather than a simple physical mixing. This endows the resin with permanent flame retardant properties at the molecular structure level, while retaining an appropriate amount of epoxy active groups to ensure the performance of the resin in subsequent curing and molding. Finally, a phosphorus-containing epoxy resin prepolymer intermediate with stable structure, uniform composition, and sufficient phosphorus grafting is generated.

[0046] Stop heating and switch the jacket medium to cooling water to reduce the reactor temperature to below 80°C. A pale yellow, transparent, viscous liquid is obtained. The liquid is discharged into a stainless steel storage tank and sealed for storage, ultimately producing a phosphorus-containing epoxy resin prepolymer.

[0047] The core of this step is to rapidly terminate residual side reactions, stabilize the prepolymer molecular structure through cooling and shaping, standardize the discharge and storage methods, and ensure the performance stability and storage timeliness of the finished phosphorus-containing epoxy resin prepolymer. The specific implementation method is as follows:

[0048] After the grafting reaction reaches the preset endpoint, the heat transfer oil heating system is first shut off to completely terminate the external heat source input, preventing the material inside the reactor from continuing to undergo cross-linking side reactions under residual heat, and preventing excessive resin polymerization and excessive viscosity leading to scrapping. Subsequently, the heat exchange medium in the reactor jacket is switched, completely draining the high-temperature heat transfer oil and introducing ambient temperature cooling water as the cooling medium. Cooling water has high heat exchange efficiency and controllable temperature, enabling stable cooling of the material inside the reactor and avoiding material structural stress changes and component stratification problems caused by sudden cooling.

[0049] The cooling control threshold is below 80℃, which is the critical temperature for the stability of epoxy resin prepolymers. When the temperature is above 80℃, the prepolymer molecules still have high activity and will slowly undergo self-polymerization side reactions, resulting in continuous changes in material viscosity and unstable performance. After cooling to below 80℃, the activity of the molecular chain is greatly reduced, which can completely terminate all reactions and lock the molecular structure, viscosity and epoxy value of the prepolymer. In this implementation example, the material is finally cooled to 75℃, which fully meets the temperature requirements for stable storage and subsequent processing.

[0050] After the material is cooled down, the material in the reactor appears as a uniform, light yellow, transparent, viscous liquid. This appearance is a direct indicator of whether the preparation of the phosphorus-containing epoxy resin prepolymer is qualified. The material is transparent without turbidity, precipitation, or black carbonized impurities, which means that no by-products are generated during the reaction process, the raw materials react uniformly, and the molecular structure is regular. The viscous fluid state ensures that it has good subsequent dispersion, mixing, and coating processing performance.

[0051] After completing the material condition inspection, the reactor outlet is opened, and the liquid prepolymer is evenly discharged into a stainless steel storage tank. Stainless steel is chosen because it is corrosion-resistant, oxidation-resistant, and prevents impurity precipitation, thus avoiding chemical reactions with the epoxy resin prepolymer and preventing material contamination and deterioration. After discharge, the storage tank is immediately and completely sealed to isolate it from external air, moisture, and dust impurities. This prevents the prepolymer from oxidizing and aging upon contact with oxygen, avoids moisture intrusion which could lead to subsequent curing performance failure, and prevents dust impurities from affecting resin purity. After sealing, the material is stored in a room-temperature, light-protected environment. The final product is a stable, flame-retardant grafted, and excellent-processing phosphorus-containing epoxy resin prepolymer, which can be directly used in the subsequent preparation of copper-clad laminate resin mixtures.

[0052] S202, the phosphorus-containing epoxy resin prepolymer and phenolic epoxy resin are mixed in a set ratio, and inorganic thermally conductive filler is added. The mixture is then subjected to high-speed shear dispersion treatment to obtain a resin dispersion.

[0053] Specifically, phosphorus-containing epoxy resin prepolymer and phenolic epoxy resin can be weighed in a mass ratio of 6:4 to 8:2 and added sequentially into a dispersion tank with a heating jacket. The mixture is stirred and mixed at 80 to 120 rpm for 20 to 40 minutes at 60 to 80°C to generate a uniform composite resin matrix.

[0054] The core of this step is to precisely proportion two epoxy resins with different properties, combined with a controllable heating and stirring process, to integrate the flame-retardant properties of phosphorus-containing epoxy resin prepolymer with the heat resistance and structural stability of phenolic epoxy resin. This results in a composite resin matrix with uniform composition and complementary properties, providing a high-quality resin base for the subsequent doping and dispersion of thermally conductive fillers, ensuring the molding and performance properties of the mixture. The specific implementation method is as follows:

[0055] The dispersion tank with a heating jacket used in this step is the core equipment for resin mixing. The equipment has the capability of sealed temperature control and uniform stirring. The jacket structure allows for the introduction of a heat-conducting medium to achieve uniform heating and constant temperature maintenance of the materials inside the tank, avoiding uneven resin melting and stratification caused by excessively high or low temperatures. This is suitable for the low-temperature melting and mixing process requirements of epoxy resin systems. The mass ratio of the two core resin raw materials ranges from 6:4 to 8:2. This ratio refers to the mass ratio of phosphorus-containing epoxy resin prepolymer to phenolic epoxy resin. The numerical range is set to balance the flame retardant performance and structural mechanical properties of the system. 6:4 represents the ratio with the highest proportion of phenolic epoxy resin, maximizing the crosslinking density and heat resistance stability of the resin matrix. 8:2 represents the ratio with the highest proportion of phosphorus-containing prepolymer, maximizing the preservation of the flame retardant effect of the system. In actual production, an intermediate ratio can be selected according to the performance requirements of the copper-clad laminate. In this example, a mass ratio of 7:3 is selected for raw material weighing, balancing flame retardancy and structural stability.

[0056] The process temperature setting range of 60–80℃ represents the low-viscosity melt compatibility temperature for the two epoxy resins. This temperature range allows the solid or high-viscosity epoxy resins to gradually soften and melt, reducing the overall viscosity of the resin system. This enables the molecules of both resins to flow and fuse effectively. Simultaneously, this temperature is significantly lower than the reaction and curing temperature of the epoxy resins, completely avoiding the problem of premature cross-linking and curing during mixing, ensuring that the raw materials undergo only physical mixing without any chemical reaction. In the example, the mixing temperature is set to 70℃, which is in the middle of the range, achieving optimal melt mixing results. The temperature deviation is controlled within ±2℃, ensuring uniform temperature throughout the tank.

[0057] A stirring speed of 80–120 rpm is the optimal low-speed homogenization stirring speed for the resin. This speed range allows for the overall circulation of the resin material within the tank without causing material splashing or air bubble entrainment. This breaks down the material interface between the two resins, achieving uniform mixing at the molecular level. Too low a speed will result in insufficient material flowability, leading to localized material accumulation and uneven mixing. Too high a speed will entrain a large amount of air, increasing the pressure on subsequent degassing processes. In this example, a stirring speed of 100 rpm is selected, which is optimally suited to the viscosity characteristics of the resin at 70°C.

[0058] A mixing time of 20–40 minutes is crucial for ensuring complete homogeneous fusion of the two resins. Too short a time leads to insufficient resin fusion and localized component enrichment within the system, while too long a time reduces production efficiency and can cause slight resin agglomeration during prolonged constant-temperature standing. In this example, a mixing time of 30 minutes ensures thorough interpenetration and fusion of the two epoxy resin molecules, eliminating differences in material composition. After this temperature-controlled mixing process, the two resins in the tank are completely melted and mixed together without stratification, clumping, or component segregation, ultimately forming a composite resin matrix with uniform properties and stable viscosity, serving as the base carrier for subsequent filler dispersion.

[0059] Under stirring, add alumina or boron nitride inorganic thermally conductive fillers with a particle size of 1-10 micrometers to the composite resin matrix in three batches. The amount of filler added is 30%-60% of the total mass of the resin, with an interval of 5-8 minutes between each batch, to generate a coarse mixture.

[0060] The core of this step is to precisely incorporate inorganic thermally conductive fillers in batches while the resin matrix is ​​in a dynamic, flowing state. This step-by-step feeding method addresses the industry-wide issues of filler agglomeration and uneven dispersion due to high filler content. It initially achieves the dispersion of the thermally conductive filler in the composite resin matrix, constructing a preliminary composite system of resin and filler. This lays the foundation for subsequent refined shear dispersion. The specific implementation method is as follows:

[0061] Maintaining constant stirring is the core technological prerequisite for this step. Continuing the stirring process from the previous step ensures the composite resin matrix remains in a dynamically flowing, homogeneous state, preventing viscosity rise and localized solidification. Simultaneously, the dynamically flowing resin quickly encapsulates the added filler particles, preventing sedimentation, aggregation, and agglomeration, thus reducing the probability of filler agglomeration from the source. The inorganic thermally conductive fillers selected in this step are alumina or boron nitride. Both types of fillers possess high thermal conductivity, high insulation, and high-temperature resistance, meeting the thermal insulation requirements of copper-clad laminates. Furthermore, they are chemically stable, do not react adversely with the epoxy resin matrix, and can stably remain in the resin system to perform their thermal conductivity function.

[0062] The optimal particle size range for filler particles is 1–10 micrometers, which represents the median particle size of the copper-clad laminate resin system. Fillers with a particle size smaller than 1 micrometer have an excessively large specific surface area, making them prone to aggregation and difficult to disperse. Fillers with a particle size larger than 10 micrometers are too large, which can damage the smoothness and compactness of the resin system, affecting the surface finish and mechanical properties of the copper-clad laminate. In this example, alumina filler with a median particle size of 5 micrometers is selected, balancing dispersibility and thermal conductivity to meet the doping requirements of this resin system.

[0063] The filler addition amount of 30% to 60% represents the mass percentage of the filler in the total mass of the composite resin matrix. This range is the critical range for balancing the processing performance and thermal conductivity of the resin system. When the addition amount is less than 30%, the number of filler particles in the system is insufficient, and a continuous thermal conductivity path cannot be formed, resulting in the copper-clad laminate failing to meet thermal conductivity standards. When the addition amount is greater than 60%, the resin matrix cannot fully wet all filler particles, leading to a sharp increase in system viscosity, a significant decrease in processing fluidity, and potential problems such as filler exposure and material cracking. In the example, a filler addition amount of 45% is used, which can ensure the processing fluidity of the material while constructing a complete thermal conductivity network.

[0064] Adding filler in three batches, with an interval of 5-8 minutes between each batch, is a refined feeding process. Step-by-step feeding reduces the amount of filler added at once, allowing a small amount of filler to be quickly impregnated and coated by the flowing resin, gradually filling the internal space of the resin system. This avoids the instantaneous agglomeration and sedimentation caused by adding a large batch of filler at once. The 5-8 minute interval ensures that each batch of filler is fully impregnated and initially dispersed before adding the next batch, achieving uniform mixing layer by layer. Too short an interval will cause batches of material to overlap and agglomerate, while too long an interval will reduce production efficiency. In the example, the interval between each batch is set to 6 minutes. The total filler quantity is divided into three equal parts and added sequentially to the dispersion tank. After each batch of filler is added, it flows with the resin through stirring, completing the initial impregnation and dispersion. After three batches of step-by-step feeding and stirring, the filler is initially dispersed within the composite resin matrix without large-area agglomeration or clumping. The material is uniformly mixed, forming a coarse mixture of filler and resin.

[0065] Start the high-speed disperser and increase the stirring speed to 1500-2500 rpm. Shear and disperse the coarsely mixed material for 30-60 minutes. At the same time, control the material temperature to not exceed 90°C through jacket cooling. This allows the filler to initially depolymerize and be evenly distributed in the resin, generating a dispersion semi-finished product.

[0066] The core of this step is to break down the residual filler micro-agglomerates in the coarsely mixed materials using high-speed mechanical shearing force, thereby achieving fine dispersion of the inorganic thermally conductive filler in the resin matrix. Simultaneously, a constant-temperature control process is used to avoid resin deterioration caused by heat generated during high-speed shearing, further optimizing the uniformity of the resin-filler composite and preparing a semi-finished dispersion with higher dispersion. The specific implementation method is as follows:

[0067] The high-speed disperser is the core dispersion equipment in this step. Unlike the low-speed stirring equipment used earlier, it provides high-intensity mechanical shearing, turbulent impact, and centrifugal diffusion, specifically designed to break up the micro-agglomeration structure of powder fillers in fluid media. It is suitable for the fine dispersion processing requirements of high-solids-content filler resin systems and can effectively solve the problem of micron-sized filler agglomeration that conventional stirring cannot break. The stirring speed range of 1500–2500 rpm is the exclusive speed range for high-speed shearing. The higher the speed, the stronger the shearing force and turbulent impact, and the better the effect of breaking up filler agglomerates. At speeds below 1500 rpm, the shearing force is insufficient to break up the tiny agglomerates; at speeds above 2500 rpm, the shearing force is too strong and can easily crush the filler particles, destroying the original particle size structure and reducing thermal conductivity. In this example, a shearing speed of 2000 rpm is selected, which can efficiently break up filler agglomerates while preserving the complete filler particle structure.

[0068] A shear dispersion treatment time of 30–60 minutes is crucial for ensuring uniform dispersion of materials throughout the entire area. Too short a time will result in insufficient shearing action on materials at the tank edges and bottom, leading to localized packing agglomeration and residue. Too long a time will continuously exacerbate equipment heating, increasing temperature control pressure, while failing to further improve dispersion, resulting in wasted energy and time. In the example, a shear dispersion time of 45 minutes is set, achieving uniform shear dispersion of all materials within the tank without any dead zones.

[0069] During high-speed mechanical shearing, mechanical kinetic energy is continuously converted into heat energy, causing the material temperature to rise rapidly. Prolonged exposure of the resin matrix to high temperatures can lead to a sudden drop in viscosity, slight oxidation, and localized pre-curing. Therefore, constant-temperature cooling with cooling water circulated through the dispersion tank jacket is necessary to maintain the material temperature below 90℃ throughout the process. 90℃ is the safe critical temperature for this composite resin system; below this temperature, the resin system remains stable, with no risk of premature curing or oxidation, and the resin's subsequent processing activity and the filler's physicochemical properties are fully preserved. The material temperature is monitored in real-time throughout the process, and the cooling water flow rate is dynamically adjusted to ensure the material temperature remains stable within the range of 75–85℃, avoiding deviations in material performance caused by temperature fluctuations.

[0070] After high-speed shear dispersion, all filler agglomerates in the coarse mixture are completely deagglomerated, and micron-sized filler particles are uniformly suspended and distributed inside the composite resin matrix. The resin fully wets the surface of each filler particle, with no exposed filler, no local filler enrichment, and no material stratification. The overall viscosity of the material is uniform and the state is stable, and finally a dispersion semi-finished product with uniform filler dispersion and good system stability is prepared.

[0071] The semi-finished dispersion is further ground 2 to 3 times using a three-roll mill, with the roller gap adjusted to 20 to 50 micrometers. The ground material is collected and the fineness is tested to be below 25 micrometers to obtain a stable resin dispersion.

[0072] The core of this step is to further eliminate residual micro-filler agglomerates in the material through ultra-fine grinding using a three-roll mill, refining the overall fineness of the material, optimizing the uniformity of filler dispersion, and simultaneously standardizing the particle size specifications to eliminate fineness deviations. The final result is a resin dispersion with uniform fineness, stable system, and suitability for subsequent modification processing. The specific implementation method is as follows:

[0073] The three-roll mill is a specialized piece of equipment for the ultra-fine processing of powder and fluid materials. It relies on the squeezing, shearing, and grinding actions between three parallel grinding rollers operating at different speeds to crush, refine, and homogenize tiny agglomerates in the semi-finished dispersion. This solves the problem of micro-fine agglomerates that cannot be eliminated by high-speed shearing processes, making it a key step in the preparation of high-precision resin dispersions. The number of grinding passes (2-3) is determined based on the initial dispersion state of the material. Two passes are suitable for semi-finished products with good initial dispersion and few micro-agglomerates, while three passes are suitable for semi-finished products with a small amount of fine agglomerates and significant fineness deviations initially. Multiple grinding passes refine the particle size layer by layer, gradually improving the material's uniformity. In the example, the semi-finished dispersion is subjected to three cycles of grinding to maximize the fineness of the material and ensure uniform material specifications throughout.

[0074] The roller spacing of 20–50 micrometers refers to the distance between the three grinding rollers. This parameter directly determines the upper limit of the maximum particle size of the material being ground. The larger the roller spacing, the larger the maximum particle size of the ground material, and the weaker the refining effect. The smaller the roller spacing, the higher the grinding precision, and the smaller the size of the agglomerated particles that can be broken down. The 20–50 micrometer range is suitable for the refining requirements of micron-sized fillers in this system, which can completely break down residual agglomerates without excessively compressing and damaging the original particle structure of the filler. In the example, the roller spacing is set to 35 micrometers, which is suitable for the refining requirements of 5-micrometer particle size fillers, and the grinding precision adaptability is optimal.

[0075] The material fineness testing standard is below 25 micrometers. This fineness refers to the particle size of the largest particle in the material and is a core indicator for determining the qualification of the resin dispersion. This standard ensures that there are no large particle agglomerates or impurities in the system, guaranteeing a smooth and flat surface of the copper-clad laminate after subsequent resin coating and curing, free from defects such as particle protrusions, pinholes, and blemishes. It also ensures the uniform dispersion of fillers within the resin, resulting in uniform thermal conductivity and mechanical properties across the entire copper-clad laminate. After grinding, all ground materials are collected, and fineness testing equipment is used for full-area sampling and testing. Data from multiple testing points must all meet the standard of a maximum particle size below 25 micrometers, with no excessively large particles present.

[0076] After multiple rounds of three-roll fine grinding and passing fineness testing, the filler particles inside the material are completely and uniformly dispersed without any agglomeration or clumping. The material has uniform fineness, stable viscosity, and uniform composition. The resin and inorganic thermally conductive filler form a highly compatible composite dispersion system, and there will be no problems of static stratification or particle sedimentation. Finally, a resin dispersion with stable performance and uniform quality is obtained, which can be used for subsequent surface coupling modification processing.

[0077] S203, the inorganic filler in the resin dispersion is subjected to surface coupling modification treatment to graft functional groups onto its surface, thereby generating a modified resin intermediate with enhanced interfacial compatibility.

[0078] Specifically, the resin dispersion can be transferred to a reaction flask equipped with a reflux condenser and a dropping funnel, heated to 80-100°C, and the silane coupling agent γ-glycidoxypropyltrimethoxysilane can be added dropwise under stirring. The amount of coupling agent added is 1%-3% of the mass of the inorganic filler, and the dropping time is controlled at 15-20 minutes to generate a coupling agent mixture system.

[0079] The core of this step is to complete the pretreatment of the resin dispersion to adapt to the working conditions. Through precise temperature control and uniform dropwise addition, the silane coupling agent is uniformly dispersed and integrated into the resin dispersion system, eliminating local material concentration deviations. This creates a uniform and stable pre-reaction system for the subsequent chemical bonding modification reaction on the surface of the inorganic filler. The specific implementation method is as follows:

[0080] The resin dispersion, prepared in the previous process through high-speed shearing and three-roll milling, achieving the required fineness and stable state, is completely transferred to a dedicated sealed reaction flask for modification pretreatment. This reaction flask is a specialized container adapted for medium- and low-temperature fine chemical reactions, featuring a sealed and heat-insulating structure suitable for external components. It ensures the complete sealing of materials during the modification reaction, preventing external impurities from entering the system. The reflux condenser equipped with the reaction flask is the core heat exchange component for fine chemical reactions. Its main function is to condense and reflux the trace amounts of volatile light components in the resin system during the system heating and stirring reaction process, guiding the volatile materials back into the reaction flask. This precisely maintains a constant material ratio in the system, avoiding problems such as material imbalance and uneven modification effects caused by component volatilization, and ensuring material balance throughout the entire modification stage. The matching dropping funnel is a constant-pressure controllable dropping structure, which can balance the gas pressure inside and outside the reaction bottle, ensure that the reagent dropping rate is uniform and controllable, and eliminate defects such as excessively high instantaneous concentration and material agglomeration caused by manual or rough feeding, so as to achieve stable and accurate feeding of coupling agent reagent.

[0081] After completing material transfer and equipment airtightness inspection, start the jacket temperature control system of the reaction flask to heat up the resin dispersion. The process sets the temperature rising and constant temperature range as 80°C to 100°C. This temperature range is the optimal working condition range that adapts to the dispersion and activation of the silane coupling agent and takes into account the fluidity of the resin system. The lower limit of the temperature parameter, 80°C, is the minimum activation temperature of the system. When the system temperature is lower than this value, the overall viscosity of the resin dispersion is relatively high, the molecular motion activity of the internal inorganic heat-conducting filler particles is greatly reduced, and the permeation and diffusion rate of silane coupling agent molecules slows down. As a result, the silane coupling agent molecules cannot uniformly contact the surface of the filler particles, and local unmodified blank areas are prone to occur; the upper limit of the temperature parameter, 100°C, is the safety temperature control threshold of the system. When the system temperature is higher than this value, the resin system is prone to local overheating and trace oxidative aging problems, and at the same time, it will cause the silane coupling agent to decompose and fail in advance and lose its modification activity. In actual process implementation, a constant temperature within the range can be selected for operation. In the example, the constant temperature operation temperature is selected as 90°C. This temperature can effectively reduce the viscosity of the resin system, improve material fluidity, and at the same time accurately activate the activity of coupling agent molecules, adapting to the subsequent dropping and mixing operation.

[0082] After the system temperature is stably maintained at the preset constant temperature value, start the low-speed stirring device equipped with the reaction flask and maintain a continuous uniform stirring state, so that the inorganic filler particles inside the resin dispersion are always in a suspended and dispersed state, completely avoiding filler sedimentation and accumulation agglomeration, ensuring uniform internal materials of the system, and creating basic conditions for sufficient contact and fusion of the coupling agent and the filler. Under stable stirring conditions, γ-glycidyloxypropyltrimethoxysilane, a silane coupling agent, is added dropwise through a constant pressure dropping funnel. This silane coupling agent is a special functional auxiliary agent suitable for interface modification of epoxy resin and inorganic heat-conducting filler. Its molecular structure is a dual-active group structure: one end contains a silane group that can react with hydroxyl groups on the surface of inorganic fillers, and the other end contains an epoxy group that can react with organic epoxy resin. It can build a molecular connection bridge between inorganic fillers and organic resins, and is a core functional reagent for improving the interfacial compatibility of the two phases.

[0083] The addition amount of the coupling agent is strictly limited to 1% to 3% of the mass of the inorganic filler. This mass proportion range is the optimal modification proportion obtained from a large number of process verifications. The lower limit of the parameter, 1%, is the critical dosage for effective modification. When the addition amount is lower than this value, the number of active molecules of the coupling agent is insufficient, which cannot completely cover the active sites on the surface of the inorganic filler, resulting in incomplete surface modification of the filler and ineffective elimination of interface defects; the upper limit of the parameter, 3%, is the saturated modification dosage. When the addition amount is higher than this value, the excess coupling agent cannot participate in the interface bonding reaction, and will undergo self-polymerization reaction in the resin system to form invalid agglomerated impurities, which instead damages the uniformity of the resin system and reduces the thermal conductivity, insulation and mechanical properties of the finished copper-clad laminate. In the example, the addition amount of the coupling agent is selected as 2% of the mass of the inorganic filler, which is at the optimal middle value of the proportion range, can achieve full coverage modification of the inorganic filler surface, and has no excess coupling agent residue, ensuring the purity of the system.

[0084] The total dropping time of the coupling agent is strictly controlled between 15 and 20 minutes. This time parameter is used to precisely control the dropping rate of the reagent, ensuring that each drop of coupling agent, after entering the resin system, can quickly diffuse and mix uniformly under stirring, avoiding local side reactions caused by localized concentration enrichment of the coupling agent. The lower limit of the time parameter, 15 minutes, is the fastest safe dropping time. A dropping time shorter than this value will result in an excessively fast feeding rate, causing a sudden increase in the localized concentration of the coupling agent in the system, leading to localized uneven reactions. The upper limit of the time parameter, 20 minutes, is the longest effective dropping time. A dropping time exceeding this value will result in an excessively long isothermal operation time for the system, increasing the risk of resin oxidation and material deactivation. In the example, a total dropping time of 18 minutes is selected, with the coupling agent being added at a uniform rate throughout the process. During the dropping process, the temperature and stirring rate are kept constant without fluctuations. After the addition is completed, the coupling agent and the resin dispersion are fully integrated, forming a homogeneous and stable coupling agent mixture system.

[0085] Maintain the temperature at 90-110℃ and stir the reaction for 40-60 minutes to allow the silanol groups generated by the hydrolysis of the coupling agent to undergo a condensation reaction with the hydroxyl groups on the filler surface, forming an organic coating layer on the filler surface and generating a surface-modified resin system.

[0086] The core of this step is to trigger the hydrolysis and interfacial condensation reactions of the silane coupling agent under constant temperature and steady-state stirring conditions, thereby achieving chemical bonding and fixation between the coupling agent molecules and the surface of the inorganic filler. This constructs a flexible organic coating layer on the surface of the rigid inorganic filler, eliminating the interfacial repulsion problem between the inorganic phase and the organic resin phase. The specific implementation method is as follows:

[0087] After all the coupling agent has been added and the coupling agent mixture has solidified, there is no need to stop the machine for cooling or adjust the operating conditions. The system temperature is directly locked by the jacket temperature control system, maintaining a constant temperature reaction range of 90℃ to 110℃. This temperature range is the suitable activity temperature range for the hydrolysis and condensation dual reactions of the silane coupling agent. The lower limit of the temperature parameter, 90℃, is the critical temperature for the reaction to start. When the system temperature is below this value, the hydrolysis activity of the coupling agent molecules is insufficient, the silanol generation rate is extremely low, the condensation reaction is difficult to carry out effectively, and the modification reaction progress is significantly delayed. The upper limit of the temperature parameter, 110℃, is the controllable threshold for the reaction. When the system temperature is above this value, the hydrolysis reaction rate is too fast, which will instantly generate a large number of small molecule by-products, easily causing the system to accumulate bubbles and the material viscosity to be abnormal. At the same time, it will accelerate the aging of the resin matrix and affect the performance of the finished product. In the example, the constant temperature reaction temperature of 100℃ is selected, which can balance the hydrolysis and condensation reaction rates, ensure that the reaction proceeds smoothly, orderly, and fully, and at the same time protect the original properties of the resin matrix to the greatest extent.

[0088] Throughout the reaction cycle, a constant stirring speed is maintained. Stable stirring ensures that the inorganic filler particles remain suspended and flowing within the resin system, preventing localized reaction dead zones caused by particle sedimentation and accumulation. Simultaneously, the active coupling agent molecules generated by hydrolysis maintain continuous and uniform contact with the surfaces of all filler particles, ensuring that each inorganic filler particle completes its surface modification reaction and achieving a uniform modification effect across the entire surface. The overall stirring reaction time is controlled between 40 and 60 minutes. This time parameter is a core process parameter to ensure complete interfacial reaction. The lower limit of the time parameter, 40 minutes, is the critical time for complete reaction. If the reaction time is less than this value, the hydrolysis and condensation reactions are not completely completed, and some active hydroxyl groups on the filler surface do not participate in bonding, resulting in incomplete modification and coating. The upper limit of the time parameter, 60 minutes, is the reaction saturation time. If the reaction time exceeds this value, there are no remaining active reaction sites in the system. Ineffective isothermal stirring will only increase production energy consumption and may also cause slight cross-linking of the resin system, leading to an abnormal increase in viscosity. In the example, a constant temperature stirring reaction time of 50 minutes is selected to ensure that the reaction is fully saturated, while avoiding ineffective energy consumption and material performance fluctuations.

[0089] During the isothermal stirring reaction, a continuous and orderly chemical reaction occurs. First, the silane coupling agent molecules undergo hydrolysis under the influence of trace amounts of free water in the resin system. The methoxy functional group in the molecular structure breaks down, generating highly reactive silanol functional groups. These functional groups are the core active groups for modifying the surface of inorganic fillers and are also the key reaction sites connecting the coupling agent and the filler. The alumina and boron nitride inorganic thermally conductive fillers used in this process have a large number of naturally enriched active hydroxyl groups on their microscopic particle surfaces. These hydroxyl groups are the inherent surface active sites of inorganic fillers and the only reaction basis for achieving organic modification.

[0090] The highly active silanol groups generated by hydrolysis undergo a condensation reaction with the inherent hydroxyl groups on the surface of the inorganic filler. The two hydroxyl functional groups combine with each other and remove trace amounts of water molecules, forming highly stable silicon-oxidation chemical bonds. Through irreversible chemical bonding, the silane coupling agent molecules are firmly fixed to the surface of the inorganic filler particles. As the isothermal reaction continues, a large number of coupling agent molecules continuously bond and accumulate on the filler surface, gradually forming a uniformly thick and dense organic coating layer. This coating layer is an organic polymer structure that can completely change the original hydrophilic and oleophobic surface properties of the inorganic filler, transforming them into hydrophilic and oleophobic compatibility properties, allowing the inorganic filler to achieve high wetting and compatible bonding with the organic epoxy resin matrix.

[0091] After the reaction reaches the preset time, most of the inorganic filler surfaces in the system have completed chemical bonding and organic coating, with no exposed inorganic active surfaces. The interfacial bonding between the inorganic filler and the organic resin is fully formed, and the internal material state of the system is uniform and stable. A surface-modified resin system with preliminary modification of the filler surface has been successfully generated, providing qualified precursor materials for the subsequent grafting reaction of the coupling agent and the resin matrix.

[0092] Add 0.1% to 0.5% of the total resin mass of the catalyst dibutyltin dilaurate to the reaction system, and continue stirring for 30 minutes to promote the grafting of epoxy groups in the coupling agent with the resin matrix and generate an intermediate with enhanced interfacial compatibility.

[0093] The core of this step is to introduce a specialized organic catalytic component to precisely activate the reactivity of the terminal epoxy groups of the silane coupling agent, promoting molecular grafting and cross-linking between the coupling agent and the composite resin matrix. This achieves integrated bonding of the inorganic filler, coupling agent, and organic resin, fundamentally improving the interfacial bonding and overall stability of the system. The specific implementation method is as follows:

[0094] After the surface-modified resin system is prepared, the constant temperature and stirring rate of the reaction system are maintained to keep the original steady-state reaction conditions. The catalyst dibutyltin dilaurate is directly and uniformly added into the reaction flask. This substance is a highly selective special catalyst suitable for the ring-opening reaction of epoxy groups in epoxy resin and the grafting reaction of silane coupling agents. It has the core characteristics of low temperature and high activity, few side reactions and high catalytic efficiency. It can accurately target and catalyze the grafting reaction of epoxy groups without causing ineffective side reactions such as premature curing and local cross-linking of the resin system. It is fully suitable for the process requirements of this resin modification.

[0095] The amount of catalyst added is strictly controlled to be between 0.1% and 0.5% of the total resin mass. This mass ratio range represents the optimal process range for the catalytic reaction. The lower limit of the parameter, 0.1%, is the critical amount for effective catalysis. When the catalyst addition is below this value, the content of catalytically active components in the system is insufficient, the ring-opening rate of epoxy groups is slow, the grafting reaction cannot proceed fully, the coupling agent and the resin matrix cannot form effective bonds, and the interface modification effect cannot be further enhanced. The upper limit of the parameter, 0.5%, is the saturated catalytic amount. When the catalyst addition is above this value, the excess catalytic components cannot participate in the reaction and will remain in the resin system as impurities. This not only fails to improve the modification effect but also reduces the core properties of the copper-clad laminate, such as heat resistance and electrical insulation. In this example, the catalyst addition is selected at 0.3% of the total resin mass, which is within the optimal catalytic ratio range. This maximizes the efficiency of the grafting reaction while eliminating impurity residues and ensuring the purity of the material.

[0096] After the catalyst is added to the system, it is continuously stirred at a constant speed to allow the solid catalyst to dissolve rapidly and disperse evenly throughout the resin system. This ensures uniform distribution of the catalytically active components, preventing uneven distribution caused by localized catalytic enrichment or lack of catalytic activity, and guaranteeing that all coupling agent molecules in the system can be uniformly activated. After the catalyst is dispersed, the reaction is continuously stirred at a constant temperature for a fixed duration of 30 minutes. This fixed reaction time has been optimized to fully meet the reaction requirements for epoxy group ring opening and molecular grafting crosslinking. It ensures complete saturation of the grafting reaction while avoiding problems such as excessive resin crosslinking, sudden increase in viscosity, and material failure caused by prolonged reaction.

[0097] Under the catalytic activation of dibutyltin dilaurate, the terminal epoxy groups of the silane coupling agent molecules fixed on the surface of the inorganic filler are precisely activated, undergoing a ring-opening chemical reaction. The active sites after ring opening can covalently bond with the active sites of the molecular chains of bisphenol A type phosphorus-containing epoxy resin and phenolic epoxy resin in the composite resin matrix, realizing the molecular-level grafting fusion of the organic end of the silane coupling agent and the resin matrix. Through this catalytic grafting reaction, the originally physically doped and interface-independent two-phase system of inorganic filler and organic resin is transformed into a chemically cross-linked integrated structure of inorganic filler-coupling agent-organic resin, completely eliminating the gaps, tensions, and repulsion forces at the interface between the two phases, and solving the process defects of traditional thermally conductive resin systems such as interface delamination, weak bonding, uneven thermal conductivity, and easy bubble generation.

[0098] After 30 minutes of isothermal catalytic grafting reaction, the molecular cross-linking structure inside the system is stably formed, the interfacial bonding strength between the inorganic and organic phases is greatly improved, and the overall interfacial compatibility, material uniformity, and structural stability are significantly optimized. A modified resin intermediate semi-finished product with greatly enhanced interfacial compatibility is successfully generated, providing a high-performance matrix material for subsequent curing system addition and molding operations.

[0099] The temperature was lowered to below 70℃ and stirring was stopped. Samples were taken for infrared spectroscopy analysis to verify the appearance of siloxane characteristic peaks, thus obtaining a modified resin intermediate with reactive functional groups grafted onto the filler surface.

[0100] The core of this step is to rapidly terminate all residual chemical reactions within the system, stabilize the molecular structure and physical state of the materials, and verify the effectiveness and integrity of the interface modification reaction through professional spectroscopic detection methods. Ultimately, a modified resin intermediate with qualified performance and stable structure is obtained. The specific implementation method is as follows:

[0101] After the catalytic grafting reaction is complete, the jacketed heating temperature control system of the reaction flask is immediately shut off to terminate the isothermal heating. A low-speed water-cooling gradient cooling method is then used to cool the reaction system, aiming to reduce the material temperature to below 70°C. This temperature is the critical termination temperature for the resin modification system. When the system temperature exceeds 70°C, the resin molecules and coupling agent active groups still possess high mobility and reactivity, making them prone to minor residual side reactions and localized secondary cross-linking, leading to fluctuations in material properties and structural instability. When the system temperature drops below 70°C, the molecular activity of all chemical bonding, cross-linking, and condensation reactions within the system is completely lost, all chemical reactions are completely terminated, and the molecular structure, viscosity state, and interfacial structure of the material are stably locked. In this example, the system temperature is steadily reduced to 65°C, fully meeting the temperature control requirements for reaction termination, accurately locking the formed molecular grafting structure, and preventing subsequent performance fluctuations.

[0102] Once the system temperature has stabilized and dropped to within the preset threshold range, turn off the stirring drive to completely stop all dynamic stirring operations, allowing the resin system to remain in a static, stable state. During this settling process, the molecular cross-linking structure and filler coating structure within the system can fully solidify, completely eliminating potential hazards such as trace material disturbances and microbubbles generated during stirring. This ensures that the functional groups grafted onto the filler surface are structurally intact, uniformly distributed, and stable, without structural damage or group detachment.

[0103] After the system has stabilized statically, a small amount of homogeneous material is randomly selected from the reaction flask as a test sample. Infrared spectroscopy is used to qualitatively analyze the molecular structure of the sample. This method is an authoritative means of verifying the interfacial modification reaction of polymer composite materials. It can accurately determine the formation of target chemical bonds and functional groups within the material by analyzing the position, intensity, and shape of characteristic peaks in the spectral spectrum. It boasts advantages such as high accuracy, strong targeting, and no material loss. The core indicator for this test is the formation of siloxane characteristic peaks. Siloxane chemical bonds are unique characteristic chemical bonds formed by the condensation reaction between silane coupling agents and the surface of inorganic fillers. They only remain stable after successful filler modification and are the core basis for determining the effectiveness of functional group grafting on the surface of inorganic fillers.

[0104] During the testing process, the prepared sample is placed in an infrared spectrometer for full-band scanning to generate corresponding spectral analysis spectra. By comparing the spectra with a standard chemical spectral database, the presence of standard siloxane characteristic peaks is checked. If the spectra show siloxane characteristic peaks with regular shapes, uniform intensity, and no interfering peaks, it proves that a large number of stable siloxane chemical bonds have been generated in the system, and reactive functional groups with epoxy activity have been successfully grafted onto the surface of the inorganic filler, indicating that the interface modification reaction has fully met the standards. If there are no corresponding characteristic peaks or the characteristic peaks are weak, it indicates that the modification reaction is incomplete, the material is substandard, and the process parameters need to be readjusted for rework modification.

[0105] After the material has passed the infrared spectroscopy test, the surface of the inorganic thermally conductive filler is uniformly grafted with stable reactive functional groups. The interface between the filler and the resin matrix is ​​tightly bonded without defects. The overall uniformity, stability and reactivity of the material meet the requirements of subsequent processes. Finally, a qualified modified resin intermediate with reactive functional groups grafted on the filler surface is obtained, which can be directly used in the subsequent curing agent and curing accelerator addition process.

[0106] S204, a latent curing agent and a curing accelerator are added sequentially to the modified resin intermediate, and the mixture is stirred and degassed under vacuum to obtain a resin mixture with thixotropic properties.

[0107] Specifically, the temperature of the modified resin intermediate can be adjusted to 40-60℃, and a dicyandiamide-based latent curing agent can be added. The amount of curing agent added is 4%-8% of the total resin mass. Stir at 60-80 rpm for 15-25 minutes until completely dissolved to generate an intermediate containing the curing agent.

[0108] The core of this step is to uniformly integrate the latent curing agent into the modified resin intermediate through precise temperature control, quantitative feeding, and uniform stirring, thereby constructing a stable resin curing base system. This avoids process problems such as curing agent agglomeration, premature curing, and incomplete dissolution, laying the foundation for subsequent modification of the curing system. The specific implementation method is as follows:

[0109] After the modified resin intermediate undergoes filler coupling modification, the system remains at room temperature with a relatively high overall viscosity. Directly adding the curing agent will result in slow dissolution and uneven dispersion. Therefore, temperature regulation is necessary. 40–60°C is the suitable temperature control range for this resin system. This temperature range effectively reduces the overall viscosity of the modified resin intermediate, enhances the molecular activity of the resin, and provides a favorable fluid environment for curing agent dissolution. Simultaneously, this temperature is far below the activation reaction temperature of dicyandiamide-based curing agents, preventing the triggering of resin cross-linking and curing reactions, and fully preserving the latent stability characteristics of the system. In actual production, temperature control precision is maintained within ±2°C to avoid insufficient viscosity reduction and low dissolution efficiency due to excessively low temperatures, or slight changes in system activity due to excessively high temperatures. In this example, 50°C is selected as the constant control temperature to suit the system's normal viscosity.

[0110] Dicyandiamide-based latent curing agents are heat-activated curing aids specifically designed for epoxy resin systems. Their core technical features include extremely strong chemical inertness at room temperature and pressure, no cross-linking reaction with the epoxy resin matrix, and ultra-long storage stability. They are activated only under specific high-temperature conditions, triggering the cross-linking curing reaction of the epoxy resin molecular chains. They are perfectly suited to the production logic of copper-clad laminate prepregs, which are first processed and then cured at high temperatures. Unlike instantaneous curing agents, they can effectively prevent premature gelation and failure of resin mixtures.

[0111] The measurement basis for the curing agent addition of 4% to 8% is the total mass of the modified resin intermediate. This parameter range is the optimal ratio obtained by combining the phosphorus-containing flame-retardant resin and the modified inorganic filler composite system. When the addition is less than 4%, the number of active curing groups in the system is insufficient, and the subsequent high-temperature curing cannot complete the full cross-linking, resulting in insufficient curing degree, poor heat resistance, and low mechanical strength of the finished prepreg. When the addition is more than 8%, excess unreacted free curing agent will remain in the resin system, causing defects such as decreased insulation performance, increased water absorption, and brittleness of the finished copper-clad laminate. In actual processes, the parameters can be fine-tuned according to the viscosity of the resin system. In the example, an addition of 6% is selected to achieve a balance between the curing cross-linking effect and the overall performance of the finished product.

[0112] A stirring speed of 60–80 rpm is considered a low-to-medium constant stirring range. This speed ensures uniform flow of the resin system, preventing localized resin buildup and hardener accumulation, while also avoiding the entrainment of large amounts of air during high-speed stirring, thus reducing bubble formation at the source. Too low a speed results in insufficient material flowability and slow hardener dissolution; too high a speed exacerbates air entrainment, increasing subsequent degassing pressure. The example uses a constant stirring speed of 70 rpm to suit the system's fluid characteristics.

[0113] A stirring time of 15–25 minutes is the process threshold to ensure complete dissolution of the curing agent. Insufficient stirring time will result in suspended curing agent particles, localized agglomeration, and incomplete dissolution, leading to uneven curing. Excessive stirring time will cause the resin system to be in contact with air for an extended period, absorbing moisture and impurities from the air, affecting the electrical properties of the finished product. In this example, the stirring time is set at 20 minutes. During the stirring process, the state of the material is continuously observed. Complete dissolution is judged by the material being uniformly transparent and free of visible solid particles and flocculent agglomerates. The final product is a homogeneous and stable intermediate containing the curing agent, with the curing agent molecules uniformly dispersed in the resin matrix without concentration differences or material defects.

[0114] Continue adding curing accelerators, using substituted urea or 2-ethyl-4-methylimidazole, with an addition amount of 5% to 15% of the curing agent mass. Stir for 10 to 15 minutes to disperse evenly, generating a heat-curable resin composition.

[0115] The core of this step is to introduce a curing accelerator to optimize the reaction characteristics of the curing system, compensating for the shortcomings of dicyandiamide curing agent, such as high curing temperature and slow reaction rate. Through precise proportioning and short-term uniform stirring, a thermosetting resin system with controllable curing rate and suitable activation temperature is constructed. The specific implementation method is as follows:

[0116] Dicyandiamide-based latent curing agents have inherent characteristics such as high curing activation temperature and slow high-temperature reaction rate. When used alone, they can lead to low curing efficiency and poor cross-linking uniformity of prepreg. Therefore, they need to be used in combination with curing accelerators to adjust the activity of the curing system. The core function of curing accelerators is to reduce the curing reaction activation energy, lower the curing initiation temperature, shorten the cross-linking reaction time, and at the same time improve the overall cross-linking uniformity of the resin, so as to ensure the structural stability of the copper clad laminate after curing.

[0117] The substituted urea and 2-ethyl-4-methylimidazole selected in this step are both epoxy resin-compatible accelerators, suitable for dicyandiamide latent curing systems. The two types of accelerators have different performance characteristics and suitable application scenarios. The substituted urea has a mild catalytic reaction and stronger system stability, making it suitable for large-scale continuous production. The 2-ethyl-4-methylimidazole has higher catalytic activity and can slightly improve curing efficiency. Both types of accelerators can be used alone without the need for compounding, and can effectively adapt to different production process requirements.

[0118] The measurement basis for the accelerator addition amount of 5% to 15% is the total mass of the dicyandiamide curing agent added in the previous step. This differs from the measurement method based on the total mass of the resin. This parameter range represents the optimal ratio for precisely matching the curing system. When the addition amount is below 5%, the catalytic activity is insufficient, failing to effectively improve the slow curing rate of dicyandiamide, resulting in minimal optimization of the curing process. When the addition amount is above 15%, excess accelerator will remain in the resin system, damaging the resin's insulating structure, reducing the finished copper-clad laminate's resistance to moisture and heat, and aging, while also shortening the storage period of the resin mixture. In this example, an addition amount of 10% is selected to balance catalytic efficiency and system stability.

[0119] The stirring process maintains a constant temperature of 40–60°C to keep the resin system viscosity stable. A constant stirring speed is used for mixing. A stirring time of 10–15 minutes can completely break down the molecular aggregation structure of the accelerator, allowing the accelerator particles to evenly penetrate and disperse throughout the intermediate containing the curing agent, achieving a molecular-level composite combination of the curing agent and accelerator. Insufficient stirring time will result in localized enrichment of the accelerator, leading to excessively rapid local curing rates and uneven resin crosslinking; excessive stirring time will not improve the dispersion effect but will only increase process energy consumption and material exposure time. In the example, the stirring time is set to 12 minutes. After stirring, the overall rheological properties of the material are uniform, with no localized activity differences.

[0120] After this modification step, the curing system forms a latent, stable, and highly efficient synergistic system that reacts at high temperatures. No curing reaction occurs at room temperature, and it can maintain a fluid state for a long time. Under high-temperature conditions, it can quickly and uniformly complete the cross-linking reaction, ultimately producing a thermosetting resin composition with controllable performance that is suitable for the preparation of prepregs.

[0121] The resin composition is transferred to a vacuum degassing tank, and the vacuum pump is started to reduce the pressure inside the tank to -0.08 to -0.095 MPa. The mixture is stirred at a low speed of 30 to 50 rpm for 30 to 50 minutes at 40 to 60°C to remove the air bubbles entrained in the resin and generate a degassed resin mixture.

[0122] The core of this step is to completely remove air bubbles trapped or retained in the resin composition during the initial feeding and stirring process by using a negative pressure vacuum environment combined with low-speed constant-temperature stirring. This eliminates internal defects in the material and ensures the density and insulation performance of the subsequently coated prepreg. The specific implementation method is as follows:

[0123] The multi-step mixing process in the early stage will cause a large number of macro and micro bubbles to be trapped inside the resin composition. Residual bubbles will cause defects such as pinholes, voids, and delamination in the finished semi-cured sheet, which will significantly reduce the electrical insulation, mechanical strength and moisture and heat resistance of the copper clad laminate. Therefore, it is necessary to remove bubbles through vacuum degassing process. The vacuum degassing tank is a closed negative pressure process equipment that can isolate the intrusion of external air, water vapor and impurities. At the same time, the negative pressure will reduce the bubble rupture threshold and achieve the complete precipitation of micro bubbles.

[0124] The internal pressure of the canister, ranging from -0.08 to -0.095 MPa, is the negative pressure vacuum parameter. The parameter value represents the negative pressure difference between the internal pressure and standard atmospheric pressure. The larger the absolute value, the higher the vacuum level and the stronger the bubble removal capability. When the pressure parameter is below -0.08 MPa, the vacuum level is insufficient, and the tiny microbubbles within the resin system cannot break through the resin liquid film to precipitate, posing a risk of bubble residue. When the pressure parameter is above -0.095 MPa, the ultra-high vacuum environment can cause a small amount of low-molecular-weight additives in the resin system to volatilize and be lost, resulting in resin component imbalance and affecting curing, flame retardant, and thermal conductivity properties. In this example, the internal vacuum pressure is set to -0.09 MPa to meet the degassing requirements of this system.

[0125] The degassing process is maintained at a constant temperature of 40-60℃. This temperature can slightly reduce the viscosity of the resin composition, improve the fluidity of resin molecules, reduce the resistance to bubble rising, and accelerate the rate at which bubbles precipitate and break up from the inside of the system. At the same time, this temperature will not activate the curing system reaction, ensuring the stability of material properties throughout the process. In the example, the system is maintained at a constant temperature of 50℃, consistent with the temperature of the previous process, to avoid viscosity fluctuations caused by sudden temperature changes.

[0126] A low stirring speed of 30-50 rpm is the optimal speed for vacuum degassing. Low-speed stirring allows the resin system to flow slowly and steadily, continuously renewing the resin surface interface and allowing internal bubbles to migrate to the surface. Simultaneously, low-speed stirring does not generate shear turbulence, completely preventing the re-entry of air and the generation of new bubbles. Too low a speed results in strong material stillness and low bubble migration efficiency; too high a speed easily causes liquid surface fluctuations and air entrainment, disrupting the vacuum degassing environment. The example uses a stirring speed of 40 rpm.

[0127] A degassing time of 30-50 minutes can achieve comprehensive removal of both macroscopic and microscopic bubbles. Insufficient time will result in the retention of deep micro-bubbles, leading to incomplete degassing; excessive time will increase production energy consumption, and prolonged negative pressure environment will slightly degrade resin additives. In this example, the degassing time is set to 40 minutes. After degassing, the resin composition is free of any bubble inclusions, the system density is significantly improved, and the material purity meets the coating process standards, ultimately producing a defect-free, highly dense degassed resin mixture.

[0128] Add 0.5% to 2% fumed silica thixotropic agent to the degassed resin mixture, and continue stirring under vacuum for 15 minutes to give the resin mixture thixotropic properties. The thixotropic index is measured to be 3 to 5, thus obtaining a thixotropic resin mixture.

[0129] The core of this step is to modify the rheological properties of the resin by adding fumed silica thixotropic agents, giving the system exclusive thixotropic properties, adapting it to the vacuum coating process of fiber cloth, and solving problems such as resin coating dripping, uneven coating, and molding sagging. This results in a thixotropic resin mixture with excellent process adaptability. The specific implementation method is as follows:

[0130] Fumed silica thixotropic agent is a nano-scale inorganic rheology modifier, a thixotropic modification material specifically for copper clad laminate resin systems. Its core function is to change the rheological properties of the resin fluid, giving the resin a thixotropic property of static high viscosity stability and dynamic low viscosity flow, perfectly matching the coating process requirements. Under coating shear action, the resin viscosity decreases and the fluidity increases, which can uniformly wet the fiber cloth. After coating, the viscosity quickly recovers in the static state, which can effectively prevent resin flow and sagging, and ensure uniform and stable coating thickness.

[0131] The measurement basis for the thixotropic agent addition amount of 0.5% to 2% is the total mass of the resin mixture after degassing. This ratio range represents the optimal parameters for precisely adapting this flame-retardant and thermally conductive resin system. When the addition amount is less than 0.5%, the nanoparticle content is insufficient, failing to form an effective rheological network, resulting in a weak thixotropic effect and inability to suppress resin sagging. When the addition amount is greater than 2%, excessive nanoparticles will significantly increase the static viscosity of the resin, leading to poor coating fluidity. The resin cannot penetrate the pores of the fiber cloth, resulting in problems such as adhesive buildup and poor wetting, affecting the quality of the prepreg molding. In the example, an addition amount of 1.2% is selected to balance fluidity and static stability.

[0132] After adding the thixotropic agent, maintain a vacuum environment and stir for 15 minutes. A constant vacuum environment can prevent air from being drawn in again during the stirring process and generate bubbles. A fixed stirring time can ensure that the nano-sized fumed silica particles are evenly dispersed, deagglomerated and refined, completely breaking the agglomeration effect of nanoparticles, allowing the additives to be evenly distributed in the resin matrix, and constructing a rheological regulation network throughout the entire domain to ensure that the overall thixotropic properties of the resin are uniform and without difference.

[0133] Thixotropic index is a core process parameter for quantitatively evaluating the thixotropic properties of resins. It is defined as the ratio of the low-speed shear viscosity to the high-speed shear viscosity of the resin system. A thixotropic index range of 3 to 5 is the industry-optimal standard for coating processes of copper-clad laminate prepregs. A thixotropic index below 3 indicates insufficient thixotropy and poor static stability, leading to resin flow and uneven adhesive layer thickness after coating. A thixotropic index above 5 indicates excessively high viscosity and insufficient dynamic fluidity, resulting in uneven coating and impregnation of the fiber substrate, significantly increasing the molding defect rate. After vacuum stirring modification, the rheological properties of the system are stable and meet the standards. In the example, the measured thixotropic index is 4.0, which is within the optimal process range.

[0134] After all the modification treatments are completed, the resin mixture has multiple characteristics such as no bubbles, high stability, controllable rheology, and thermosetting properties, which are fully compatible with the requirements of vacuum coating and gradient pre-curing processes, and finally a thixotropic resin mixture with qualified performance and strong process adaptability is obtained.

[0135] S205, the resin mixture is coated onto the surface of the reinforcing fiber cloth under vacuum conditions, and then pre-cured by gradient heating to form a semi-cured sheet.

[0136] Specifically, the reinforcing fiber cloth can be unwound from the unwinding roller and fed into the vacuum coating chamber through the guide roller. The vacuum degree in the coating chamber is maintained at -0.02 to -0.05 MPa. The resin mixture is evenly coated on the upper and lower surfaces of the fiber cloth through a doctor blade coating head. The amount of adhesive is controlled at 100 to 200 grams per square meter to produce adhesive-coated fiber cloth.

[0137] The core of this step is to complete the continuous feeding of the reinforcing fiber cloth and the uniform coating operation under vacuum. Relying on specialized conveying and coating equipment, and with precise vacuum and coating amount parameters, the resin mixture is fully covered and uniformly adhered to the upper and lower surfaces of the fiber cloth, eliminating problems such as uneven coating, air bubbles, and cloth misalignment. This lays a uniform and stable substrate foundation for subsequent pre-curing molding. The specific implementation method is as follows:

[0138] The unwinding roller is a fundamental feeding device in prepreg production. Its core function is to support the entire roll of reinforcing fiber cloth. Through uniform rotation, it achieves continuous and stable unwinding of the fiber cloth. The constant operating speed of the equipment matches the rhythm of subsequent coating and drying processes, preventing defects such as stretching deformation, wrinkles, and loosening of the fiber cloth. As the skeleton substrate of the prepreg, the reinforcing fiber cloth possesses high strength, high temperature resistance, and excellent insulation properties. It is the core substrate that supports the resin mixture and ensures the mechanical and electrical properties of the copper-clad laminate. Maintaining stable, tension-free transport during the unwinding process maximizes the preservation of the original warp and weft structure and mechanical properties of the fiber cloth.

[0139] The guide roller is a precision positioning component for fabric conveying. It is primarily used to correct the conveying trajectory of the fiber cloth in real time after unwinding, preventing lateral or deviation and ensuring the cloth is fed horizontally, centered, and straight into the subsequent vacuum coating chamber. This guarantees a uniform coating width across the entire fabric, avoiding localized missed or uneven coating. This component features real-time trajectory fine-tuning, adapting to minor positional deviations during continuous fabric conveying, maintaining the straightness and flatness of the fabric throughout the process, providing the foundation for uniform coating.

[0140] The vacuum coating chamber is a sealed process cavity for resin coating. Unlike conventional open coating environments, the sealed vacuum environment effectively eliminates air bubbles entrained during the resin mixture coating process, while preventing dust and impurities in the air from adhering to the fabric and resin surfaces, significantly improving coating cleanliness and finished product quality. The vacuum level parameter range within the coating chamber is -0.02 MPa to -0.05 MPa. MPa is a commonly used industrial unit of pressure measurement; the lower the negative pressure value, the higher the vacuum level inside the chamber. -0.02 MPa is the low negative pressure critical value, which can initially remove coating bubbles, while -0.05 MPa is the high negative pressure critical value, which can completely remove bubbles. In actual production, the intermediate value of -0.035 MPa can be selected as the operating parameter to balance degassing effect and equipment operating stability, effectively avoiding pinholes and voids in the resin coating.

[0141] The doctor blade coating head is the core component for achieving uniform resin coating. Utilizing precise doctor blade gap control and a uniform feeding design, it evenly coats the thixotropic resin mixture onto the upper and lower surfaces of the reinforcing fiber cloth. Unlike single-sided coating processes, simultaneous double-sided coating ensures consistent resin content throughout the fiber cloth, preventing uneven stress and warping during subsequent curing. The doctor blade's flatness and gap accuracy are calibrated to maintain a constant coating thickness throughout the process, adapting to the thixotropic index of the resin mixture (3 to 5), ensuring stable static adhesive application and uniform dynamic coating.

[0142] The adhesive application rate is controlled between 100 g / m² and 200 g / m². This parameter represents the total mass of resin mixture adhering to the surface of the reinforcing fiber cloth per square meter. It is a key indicator determining the resin content, insulation performance, and adhesion performance of the prepreg. 100 g / m² is the minimum adhesive application rate, which can meet the basic fiber coating requirements, while 200 g / m² is the maximum adhesive application rate, ensuring sufficient resin filling and adhesion. In actual production, a standard adhesive application rate of 150 g / m² can be set to balance product lightweighting and structural stability. After a complete process of stable feeding, precise deviation correction, vacuum degassing coating, and quantitative adhesive application, a coated fiber cloth with uniform resin coating on both the upper and lower surfaces, free of bubbles, impurities, and missed coatings, is finally produced, completing the initial substrate coating process.

[0143] The coated fiber cloth enters the first drying oven, with the oven temperature set at 90-110℃, the length at 5-8 meters, and the residence time at 3-5 minutes, so that the resin partially melts and permeates the fiber, generating a semi-molten coated cloth.

[0144] The core of this step is to use a low-temperature gradient heating and drying process to gradually melt the solid, thixotropic resin mixture coated on the surface of the fiber cloth. The fluidity of the molten resin allows it to penetrate into the fiber gaps of the fiber cloth, achieving initial wetting and bonding between the resin and the fiber substrate. This eliminates interfacial voids between the resin and the fiber, laying the groundwork for subsequent cross-linking and curing reactions. The specific implementation method is as follows:

[0145] The first-stage oven is a low-temperature preheating and impregnation oven, distinct from high-temperature curing ovens. Its main function is to soften and melt the resin at low temperatures, avoiding the defects caused by direct high-temperature heating, such as rapid skinning, surface curing, and inability to penetrate the interior. The oven temperature parameter setting range is 90℃ to 110℃. Degrees Celsius is a common unit of measurement for industrial temperature control. 90℃ is the initial melting critical temperature of the resin, which allows the thixotropic resin to gradually soften and lose its solid rigidity. 110℃ is the upper limit of safe melting temperature, which will not trigger the resin's curing and cross-linking reaction, but only achieves physical melting and flow. In actual production, a constant temperature of 100℃ can be set to ensure a smooth and stable resin melting rate without localized overheating and curing.

[0146] The length of the drying oven ranges from 5 meters to 8 meters. The length of the drying oven directly determines the effective heating area of ​​the fiber cloth and is the core structural parameter for controlling the heating effect in conjunction with the travel speed. 5 meters is the shortest effective heating length, which can meet the basic melting requirements. 8 meters is the longest heating length, which is suitable for low-speed production conditions. In actual production, a 6-meter-long drying oven cavity is selected to match the conventional fabric travel speed, ensuring sufficient heating area and no ineffective energy loss.

[0147] The dwell time parameter ranges from 3 to 5 minutes. This parameter refers to the total heating time of the coated fiber cloth from entering the first drying oven to leaving the drying oven. It is determined by the length of the drying oven and the speed of the fabric conveyor. 3 minutes is the shortest immersion time, which can achieve initial melting of the resin. 5 minutes is the longest immersion time, which can ensure that the resin fully penetrates. In actual production, the dwell time is controlled at 4 minutes, which can not only completely melt the surface resin, but also allow the molten resin to fully penetrate into the warp and weft interlacing gaps and the gaps between the fiber filaments of the fiber cloth.

[0148] During this low-temperature constant-temperature heating process, the originally thixotropic solid resin mixture gradually transforms into a fluid, molten resin. The molecular chain mobility of the resin increases, and its fluidity is significantly enhanced. As the fabric moves at a uniform speed, it continuously impregnates and coats each fiber, thoroughly filling the gaps between the fibers and eliminating the potential for interfacial voids and delamination between the resin and the fiber substrate. The entire process involves only physical melting, penetration, and impregnation of the resin, without any chemical cross-linking or curing reactions. The resin remains in a flowable, semi-molten state throughout. After this oven process, the surface resin completely adheres to the fibers, and the internal gaps are fully filled, ultimately producing a uniformly structured, fully impregnated, semi-molten resin-impregnated fabric, completing the initial composite molding of the resin and fiber.

[0149] The semi-molten impregnated cloth enters the second drying oven, with the oven temperature set at 130-150℃, the length at 4-6 meters, and the residence time at 2-4 minutes. The resin undergoes a partial cross-linking reaction, and the resin fluidity decreases to 40%-60% of the initial value, thus generating a pre-cured impregnated cloth.

[0150] The core of this step is to trigger a preliminary chemical cross-linking reaction of the resin through medium-temperature heating. Without achieving complete curing, this reduces the resin's flow properties, shapes the composite structure of the resin and fiber, and prevents resin from flowing, shifting, or piling up during subsequent processing, thus achieving a pre-curing and shaping effect. The specific implementation method is as follows:

[0151] The second-stage oven is a dedicated medium-temperature pre-crosslinking oven. Its operating temperature range is higher than that of the first-stage preheating oven, allowing for precise initiation of the initial crosslinking chemical reaction between the phosphorus-containing epoxy resin prepolymer and the composite resin matrix. Simultaneously, the reaction degree is strictly controlled to prevent over-curing from affecting subsequent lamination and molding performance. The oven temperature parameter setting range is 130℃ to 150℃. 130℃ is the starting temperature for the resin crosslinking reaction, activating the active groups of the resin molecular chains and triggering slight crosslinking. 150℃ is the controllable upper limit temperature for crosslinking, preventing the crosslinking reaction rate from being too fast and causing complete resin gelation. In actual production, a constant temperature of 140℃ is set to ensure a gentle, controllable, and uniform crosslinking reaction.

[0152] The oven length ranges from 4 to 6 meters, which is shorter than the first oven. This is suitable for the process requirements of medium-temperature and short-time reactions. 4 meters is the shortest reaction chamber length, which can meet the heating requirements of the initial cross-linking reaction. 6 meters is the longest chamber length, which is suitable for low-speed production conditions. In actual production, a 5-meter chamber is selected to ensure that the heating area is suitable for the reaction time and to achieve a uniform degree of resin cross-linking across the entire fabric.

[0153] The residence time parameter ranges from 2 minutes to 4 minutes. This parameter is the duration of the semi-molten impregnated cloth's heating reaction in the second oven. 2 minutes is the shortest cross-linking reaction time, which can achieve initial cross-linking and shaping of the resin. 4 minutes is the longest controllable reaction time, which avoids over-cross-linking. In actual production, the residence time is controlled at 3 minutes to ensure uniform progress of the resin cross-linking reaction and no local reaction differences.

[0154] Resin flowability is a core process parameter characterizing the resin's ability to flow under heat. The initial value of resin flowability refers to the flow and diffusion value of the original thixotropic resin mixture before heat cross-linking at standard temperature and pressure, and is the benchmark data for measuring the liquid flowability of resin. This process requires the resin flowability to be reduced to 40% to 60% of the initial value. 40% is the minimum remaining flowability, indicating a high degree of resin cross-linking and excellent setting effect. 60% is the maximum remaining flowability, indicating that the resin retains sufficient activity for subsequent secondary curing. In actual production, the flowability is controlled at 50% of the initial value to achieve a balance between setting effect and curing activity.

[0155] Under medium-temperature heating conditions, the active groups in the resin matrix gradually undergo molecular chain cross-linking reactions. Linear resin molecules begin to form localized network structures, significantly reducing the overall fluidity of the resin and eliminating its free-flowing characteristics. This allows it to firmly adhere to the surface and interior of the fiber cloth, completely fixing the composite structure of the resin and fiber. This effectively prevents resin sagging, uneven thickness, and localized glue shortages during subsequent conveying, cooling, and winding processes. This process is only a partial cross-linking reaction; the resin is not completely gelled and cured, retaining the reactivity required for subsequent high-temperature curing. After this process, the resin structure is initially stabilized, the interfacial bonding is stable, and a pre-cured impregnated fabric with uniform performance and stable structure is ultimately produced.

[0156] The pre-cured impregnated cloth enters the third drying oven, with the oven temperature set at 160-180℃, the length at 3-5 meters, and the dwell time at 1-2 minutes, so that the resin reaches a semi-cured state. The gel time is controlled at 60-120 seconds, and the volatile content is less than 1.5%. After being cooled to below 30℃ by cooling rollers, it is wound up to obtain a semi-cured sheet.

[0157] The core of this step is to complete the semi-curing and shaping of the resin through high-temperature short-time heating, precisely controlling the resin gel performance and volatile content index, and then cooling and shaping at low temperature and continuous winding to finally obtain a copper-clad laminate-specific resin semi-cured sheet that meets the process standards, thus completing the entire preparation and molding process. The specific implementation method is as follows:

[0158] The third-stage oven is a dedicated high-temperature semi-curing oven, a core process equipment for transforming resin from a pre-crosslinked state to a standard semi-cured state. The high-temperature environment accelerates the crosslinking reaction of resin molecular chains, completing most of the crosslinked structure formation. Simultaneously, short-term heating controls the reaction to terminate at the semi-curing stage, preserving the performance for subsequent hot pressing and complete curing. The oven temperature parameters are set within a range of 160℃ to 180℃. 160℃ is the starting temperature for the semi-curing reaction, allowing for rapid completion of the resin crosslinking network. 180℃ is the upper limit of the semi-curing temperature, preventing resin from completely curing and failing. In actual production, a constant temperature of 170℃ is set to ensure a sufficient and controllable semi-curing reaction.

[0159] The oven length ranges from 3 to 5 meters. It adopts a short cavity design to adapt to the characteristics of high temperature and short time process. 3 meters is the shortest shaping cavity length, which can meet the needs of rapid semi-curing. 5 meters is the longest cavity length, which is suitable for low-speed production conditions. In actual production, a 4-meter cavity length is selected to ensure uniform high temperature heating and precise control of the time.

[0160] The dwell time parameter ranges from 1 minute to 2 minutes. This parameter is the setting time of the pre-cured impregnated cloth in the high-temperature oven. 1 minute is the shortest semi-curing time, which can achieve preliminary semi-curing and setting. 2 minutes is the longest controllable semi-curing time, which prevents over-curing. In actual production, the dwell time is controlled at 1.5 minutes to accurately match the high-temperature working conditions and achieve the standard semi-curing state.

[0161] The semi-cured state is the core intermediate state for epoxy resin composite material processing. It refers to the resin completing most of the cross-linking reaction and forming a stable three-dimensional network primary structure. It is solid and non-flowing at room temperature, but can be softened and cross-linked and cured again after being heated. It has both structural stability and secondary processing performance, which is the core characteristic of semi-cured sheets that can be used for subsequent hot pressing of copper clad laminates.

[0162] The gel time parameter is controlled between 60 and 120 seconds. Gel time refers to the time required for the prepreg to go from softening and melting to complete gelation and curing under standard high temperature conditions. It is a key indicator for measuring the curing activity of the prepreg. 60 seconds is the shortest gel time, which represents high curing activity, and 120 seconds is the longest gel time, which represents moderate curing activity. In actual production, the gel time is controlled at 90 seconds to match the rhythm of the subsequent copper clad laminate hot pressing process and ensure uniform and stable curing rate.

[0163] Volatile content refers to the percentage of the mass of trace solvents, small molecule additives, unreacted monomers, and other volatile substances remaining inside the prepreg. The process requires the volatile content to be less than 1.5%. This indicator can effectively ensure that there are no bubbles, delamination, or pore defects in the subsequent processing of copper clad laminates. In actual production, the volatile content can be controlled at 1.2%, which is far below the limit, ensuring the insulation performance and structural density of the product.

[0164] After the high-temperature semi-curing reaction is completed, the impregnated fabric has a certain temperature and flexibility. Direct winding can easily lead to problems such as adhesion, deformation, and residual stress. Therefore, it is necessary to use a cooling roller for forced cooling. The cooling roller adopts a normal temperature circulating cooling structure, which can quickly remove the residual heat of the fabric and resin, and uniformly reduce the overall temperature to below 30°C. 30°C is the critical temperature for resin to stabilize and set. Cooling to below this temperature can completely fix the semi-cured structure, eliminate thermal stress, and prevent problems such as adhesion, wrinkles, and deformation during winding.

[0165] After the finished fabric has cooled and set, it is wound up at a constant speed by an automatic winding device with constant winding tension to ensure that the finished prepreg roll is flat, evenly tight, and free from warping or deformation. The result is a functional prepreg with uniform resin distribution, tight interface bonding, stable curing performance, extremely low volatile content, and meets the standards for copper clad laminate preparation. This completes the entire process of coating and pre-curing the copper clad laminate resin mixture.

[0166] Another embodiment of the present invention provides a system for preparing a copper-clad laminate resin mixture, see [link to documentation]. Figure 3 The system may include:

[0167] Heating module 301 is used to heat bisphenol A type epoxy resin and phosphorus-containing reactive flame retardant under an inert atmosphere to carry out grafting reaction to generate phosphorus-containing epoxy resin prepolymer.

[0168] The mixing module 302 is used to mix the phosphorus-containing epoxy resin prepolymer and phenolic epoxy resin in a set ratio, add inorganic thermally conductive filler, and then perform high-speed shear dispersion treatment to obtain a resin dispersion.

[0169] Modification module 303 is used to perform surface coupling modification treatment on the inorganic filler in the resin dispersion, so that functional groups are grafted onto its surface to generate a modified resin intermediate with enhanced interfacial compatibility.

[0170] The stirring module 304 is used to sequentially add a latent curing agent and a curing accelerator to the modified resin intermediate, and stir and degas under vacuum conditions to obtain a resin mixture with thixotropic properties.

[0171] The curing module 305 is used to coat the resin mixture onto the surface of the reinforcing fiber cloth under vacuum conditions, and then pre-cur it by gradient heating to form a semi-cured sheet.

[0172] This invention also provides a storage medium storing a computer program, wherein the computer program is configured to execute the steps in any of the above method embodiments when running.

[0173] This invention also provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to perform the steps in any of the above method embodiments.

[0174] Specifically, the aforementioned electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the aforementioned processor, and the input / output device is connected to the aforementioned processor.

[0175] The above description, based on the embodiments shown in the figures, details the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A method for preparing a copper-clad laminate resin mixture, characterized in that, The method includes: Bisphenol A type epoxy resin and phosphorus-containing reactive flame retardant are grafted together under an inert atmosphere to generate phosphorus-containing epoxy resin prepolymer. The phosphorus-containing epoxy resin prepolymer and phenolic epoxy resin are mixed in a set ratio, and inorganic thermally conductive filler is added. The mixture is then subjected to high-speed shear dispersion treatment to obtain a resin dispersion. The inorganic filler in the resin dispersion is subjected to surface coupling modification treatment to graft functional groups onto its surface, thereby generating a modified resin intermediate with enhanced interfacial compatibility. A latent curing agent and a curing accelerator are added sequentially to the modified resin intermediate, and the mixture is stirred and degassed under vacuum to obtain a thixotropic resin mixture. The resin mixture is coated onto the surface of the reinforcing fiber cloth under vacuum conditions and pre-cured by gradient heating to form a semi-cured sheet.

2. The method according to claim 1, characterized in that, The process of grafting bisphenol A type epoxy resin with a phosphorus-containing reactive flame retardant under an inert atmosphere to generate a phosphorus-containing epoxy resin prepolymer includes: Bisphenol A type epoxy resin is put into a reactor equipped with a jacketed heating and reflux condenser. The nitrogen valve is opened to purge the space inside the reactor at a flow rate of 2-5 liters / minute, replacing the air to make the oxygen content lower than 0.5% and creating an oxygen-free reaction environment. Start the stirrer and run it at a speed of 100-150 rpm. At the same time, heat transfer oil is introduced through the jacket to heat the bisphenol A type epoxy resin to 120-140°C. Then, add phosphorus-containing reactive flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. The amount of flame retardant added is 10%-25% of the mass of epoxy resin to generate a mixed reaction solution. Continue heating the mixed reaction solution to 150-170℃ and keep it at that temperature for 3-5 hours. During this period, take a sample every 30 minutes to measure the epoxy value. Stop the reaction when the epoxy value drops to 60%-80% of the initial value, so that the phosphorus element is grafted onto the epoxy resin molecular chain through a chemical reaction to generate a phosphorus-containing epoxy resin prepolymer intermediate. Stop heating and switch the jacket medium to cooling water to reduce the reactor temperature to below 80°C. A pale yellow, transparent, viscous liquid is obtained. The liquid is discharged into a stainless steel storage tank and sealed for storage, ultimately producing a phosphorus-containing epoxy resin prepolymer.

3. The method according to claim 2, characterized in that, The process involves mixing the phosphorus-containing epoxy resin prepolymer with phenolic epoxy resin in a predetermined ratio, adding inorganic thermally conductive fillers, and then subjecting the mixture to high-speed shear dispersion to obtain a resin dispersion comprising: Weigh out phosphorus-containing epoxy resin prepolymer and phenolic epoxy resin respectively in a mass ratio of 6:4 to 8:2, and put them into a dispersion tank with a heating jacket in sequence. Stir and mix at 80 to 120 rpm for 20 to 40 minutes at 60 to 80°C to generate a uniform composite resin matrix. Under stirring, add alumina or boron nitride inorganic thermally conductive fillers with a particle size of 1-10 micrometers to the composite resin matrix in three batches. The amount of filler added is 30%-60% of the total mass of the resin, with an interval of 5-8 minutes between each batch, to generate a coarse mixture. Start the high-speed disperser and increase the stirring speed to 1500-2500 rpm. Shear and disperse the coarsely mixed material for 30-60 minutes. At the same time, control the material temperature to not exceed 90°C through jacket cooling. This allows the filler to initially depolymerize and be evenly distributed in the resin, generating a dispersion semi-finished product. The semi-finished dispersion is further ground 2 to 3 times using a three-roll mill, with the roller gap adjusted to 20 to 50 micrometers. The ground material is collected and the fineness is tested to be below 25 micrometers to obtain a stable resin dispersion.

4. The method according to claim 3, characterized in that, The surface coupling modification treatment of the inorganic filler in the resin dispersion, which grafts functional groups onto its surface to generate a modified resin intermediate with enhanced interfacial compatibility, includes: The resin dispersion was transferred to a reaction flask equipped with a reflux condenser and a dropping funnel. The temperature was raised to 80-100°C. The silane coupling agent γ-glycidoxypropyltrimethoxysilane was added dropwise under stirring. The amount of coupling agent added was 1%-3% of the mass of the inorganic filler. The dropping time was controlled at 15-20 minutes to generate a coupling agent mixture system. Maintain the temperature at 90-110℃ and stir the reaction for 40-60 minutes to allow the silanol groups generated by the hydrolysis of the coupling agent to undergo a condensation reaction with the hydroxyl groups on the filler surface, forming an organic coating layer on the filler surface and generating a surface-modified resin system. Add 0.1% to 0.5% of the total resin mass of the catalyst dibutyltin dilaurate to the reaction system, and continue stirring for 30 minutes to promote the grafting of epoxy groups in the coupling agent with the resin matrix and generate an intermediate with enhanced interfacial compatibility. The temperature was lowered to below 70℃ and stirring was stopped. Samples were taken for infrared spectroscopy analysis to verify the appearance of siloxane characteristic peaks, thus obtaining a modified resin intermediate with reactive functional groups grafted onto the filler surface.

5. The method according to claim 4, characterized in that, The process involves sequentially adding a latent curing agent and a curing accelerator to the modified resin intermediate, followed by stirring and degassing under vacuum conditions to obtain a thixotropic resin mixture, comprising: Adjust the temperature of the modified resin intermediate to 40-60℃, add a dicyandiamide-based latent curing agent, the amount of curing agent added is 4%-8% of the total resin mass, stir at 60-80 rpm for 15-25 minutes until completely dissolved, to generate an intermediate containing the curing agent; Continue adding curing accelerators, using substituted urea or 2-ethyl-4-methylimidazole, with an addition amount of 5% to 15% of the curing agent mass. Stir for 10 to 15 minutes to disperse evenly, generating a heat-curable resin composition. The resin composition is transferred to a vacuum degassing tank, and the vacuum pump is started to reduce the pressure inside the tank to -0.08 to -0.095 MPa. The mixture is stirred at a low speed of 30 to 50 rpm for 30 to 50 minutes at 40 to 60°C to remove the air bubbles entrained in the resin and generate a degassed resin mixture. Add 0.5% to 2% fumed silica thixotropic agent to the degassed resin mixture, and continue stirring under vacuum for 15 minutes to give the resin mixture thixotropic properties. The thixotropic index is measured to be 3 to 5, thus obtaining a thixotropic resin mixture.

6. The method according to claim 5, characterized in that, The process of coating the resin mixture onto the surface of the reinforcing fiber cloth under vacuum conditions and pre-curing it through a gradient temperature rise to form a semi-cured sheet includes: The reinforcing fiber cloth is unwound from the unwinding roller and fed into the vacuum coating chamber through the guide roller. The vacuum degree in the coating chamber is maintained at -0.02 to -0.05 MPa. The resin mixture is evenly coated on the upper and lower surfaces of the fiber cloth through the doctor blade coating head. The amount of adhesive is controlled at 100 to 200 g / m², thus producing the coated fiber cloth. The coated fiber cloth enters the first drying oven, with the oven temperature set at 90-110℃, the length at 5-8 meters, and the residence time at 3-5 minutes, so that the resin partially melts and permeates the fiber, generating a semi-molten coated cloth. The semi-molten impregnated cloth enters the second drying oven, with the oven temperature set at 130-150℃, the length at 4-6 meters, and the residence time at 2-4 minutes. The resin undergoes a partial cross-linking reaction, and the resin fluidity decreases to 40%-60% of the initial value, thus generating a pre-cured impregnated cloth. The pre-cured impregnated cloth enters the third drying oven, with the oven temperature set at 160-180℃, the length at 3-5 meters, and the dwell time at 1-2 minutes, so that the resin reaches a semi-cured state. The gel time is controlled at 60-120 seconds, and the volatile content is less than 1.5%. After being cooled to below 30℃ by cooling rollers, it is wound up to obtain a semi-cured sheet.

7. A system for preparing a copper-clad laminate resin mixture, characterized in that, The system includes: The heating module is used to perform a grafting reaction between bisphenol A type epoxy resin and phosphorus-containing reactive flame retardant under an inert atmosphere to generate phosphorus-containing epoxy resin prepolymer. A mixing module is used to mix the phosphorus-containing epoxy resin prepolymer and phenolic epoxy resin in a set ratio, add inorganic thermally conductive fillers, and then perform high-speed shear dispersion treatment to obtain a resin dispersion. The modification module is used to perform surface coupling modification treatment on the inorganic filler in the resin dispersion, so that functional groups are grafted onto its surface to generate a modified resin intermediate with enhanced interfacial compatibility. A stirring module is used to sequentially add a latent curing agent and a curing accelerator to the modified resin intermediate, and stir and degas under vacuum conditions to obtain a resin mixture with thixotropic properties. The curing module is used to coat the resin mixture onto the surface of the reinforcing fiber cloth under vacuum conditions, and then pre-cur it by gradient heating to form a semi-cured sheet.

8. The system according to claim 7, characterized in that, The heating module is specifically used for: Bisphenol A type epoxy resin is put into a reactor equipped with a jacketed heating and reflux condenser. The nitrogen valve is opened to purge the space inside the reactor at a flow rate of 2-5 liters / minute, replacing the air to make the oxygen content lower than 0.5% and creating an oxygen-free reaction environment. Start the stirrer and run it at a speed of 100-150 rpm. At the same time, heat transfer oil is introduced through the jacket to heat the bisphenol A type epoxy resin to 120-140°C. Then, add phosphorus-containing reactive flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. The amount of flame retardant added is 10%-25% of the mass of epoxy resin to generate a mixed reaction solution. Continue heating the mixed reaction solution to 150-170℃ and keep it at that temperature for 3-5 hours. During this period, take a sample every 30 minutes to measure the epoxy value. Stop the reaction when the epoxy value drops to 60%-80% of the initial value, so that the phosphorus element is grafted onto the epoxy resin molecular chain through a chemical reaction to generate a phosphorus-containing epoxy resin prepolymer intermediate. Stop heating and switch the jacket medium to cooling water to reduce the reactor temperature to below 80°C. A pale yellow, transparent, viscous liquid is obtained. The liquid is discharged into a stainless steel storage tank and sealed for storage, ultimately producing a phosphorus-containing epoxy resin prepolymer.

9. A storage medium, characterized in that, The storage medium stores a computer program, wherein the computer program is configured to execute the method of any one of claims 1-6 when it is run.

10. An electronic device comprising a memory and a processor, characterized in that, The memory stores a computer program, and the processor is configured to run the computer program to perform the method of any one of claims 1-6.

Images