High-power PCB uniform temperature heat dissipation process based on high-thermal-conductivity composite medium layer

Abstract

The application relates to the technical field of printed circuit board processes, and discloses a high-power PCB uniform-temperature heat dissipation process based on a high-thermal-conductivity composite medium layer, which comprises the following steps: dissolving 2,2-bis(4-cyanophenyl)propane, bisphenol F type and low-molecular-weight liquid bisphenol A type epoxy resin in butanone, adding a rheological control agent, a modified composite filler and a catalyst to prepare a resin glue solution; immersing and coating the resin glue solution on glass fiber cloth and baking to prepare a B-stage semi-cured sheet; stacking the semi-cured sheet and a copper foil on both sides of a PCB inner-layer circuit core plate to form a laminated structure; placing the laminated structure in a vacuum hot press, heating, applying an initial positive pressure, melting the resin to fill holes, discharging the pressure to a low-pressure state to perform rearrangement treatment, restoring the molding pressure to complete crosslinking and curing, cooling and post-curing. The application is matched with a specific resin system and a pressure-discharging rearrangement operation, can eliminate the extrusion internal stress of the thermal-conductivity filler, induce the establishment of a three-dimensional thermal-conductivity network, and realize high thermal conductivity, no holes and low stress molding of the insulating medium layer.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board technology, specifically to a high-power PCB temperature homogenization and heat dissipation process based on a high thermal conductivity composite dielectric layer. Background Technology

[0002] With the increasing integration and power density of electronic components, high-power printed circuit boards face high heat loads during operation. The insulating dielectric layer inside the printed circuit board is the basic component for achieving electrical isolation between the inner circuit and the outer structure, and it is also a physical barrier layer for heat conduction to the outside. Conventional epoxy glass cloth laminates have low thermal conductivity and cannot meet the heat conduction and heat dissipation requirements of high-power devices.

[0003] To improve the thermal conductivity of the insulating dielectric layer, inorganic thermally conductive fillers such as alumina or boron nitride are incorporated into the resin matrix during the manufacturing process. The addition of a high proportion of inorganic thermally conductive powders will cause the overall viscosity of the resin system to increase, which will limit the rheological properties of the adhesive in the heated molten state. In the lamination process of the prepreg, the high viscosity resin with limited flowability cannot densely fill the resin plug and blind hole structure on the surface of the inner circuit core board, resulting in residual tiny air gaps and physical pores inside the board after lamination.

[0004] To address the issue of insufficient filling of pores by high-viscosity resin, the conventional approach is to continuously increase the molding pressure during the pressing process. Under this forced extrusion flow environment, the inorganic thermally conductive filler undergoes intense friction and collisions in the narrow pores and line gaps, accumulating mechanical internal stress within the matrix. When the resin matrix directly enters the cross-linking and curing stage under high pressure, the inorganic powder particles lose the space for repositioning and stress relaxation. The extrusion internal stress is directly sealed within the cross-linking network. The presence of residual stress can trigger microcracks within the dielectric layer and interlayer delamination defects, thereby compromising the structural stability and thermal reliability of the final printed circuit board. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a high-power PCB uniform temperature dissipation process based on a high thermal conductivity composite dielectric layer. This solves the problem that in the manufacturing of high thermal conductivity insulating dielectric layers for existing high-power printed circuit boards, the high amount of inorganic thermally conductive filler leads to a decrease in resin fluidity, making it difficult to simultaneously meet the requirements of dense resin filling of vias and release of internal extrusion stress, which in turn causes microcracks and interlayer delamination defects in the dielectric layer.

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

[0007] A high-power PCB heat dissipation process based on a high thermal conductivity composite dielectric layer includes the following steps:

[0008] 2,2-bis(4-cyanooxyphenyl)propane, bisphenol F epoxy resin and low molecular weight liquid bisphenol A epoxy resin were dissolved in methyl ethyl ketone solvent. Then, a rheology control agent and a modified composite filler containing spherical alumina and plate-like boron nitride were added for dispersion. Subsequently, zinc octanoate and 2-ethyl-4-methylimidazole were added and stirred to prepare a high thermal conductivity resin solution.

[0009] A high thermal conductivity resin solution was uniformly coated onto the surface of electronic grade glass fiber cloth, and the resin system was partially prepolymerized by baking to prepare a B-stage semi-cured sheet.

[0010] A B-stage prepreg and an outer copper foil are stacked on the top and bottom sides of the inner circuit core board of the PCB to form a stacked structure.

[0011] The laminated structure is placed in a vacuum hot press, heated and subjected to initial positive pressure, and maintained in an initial heat and pressure state to promote complete resin melting and filling of the resin pore structure.

[0012] When the resin plug is fully filled and the resin matrix is ​​not yet fully cross-linked and maintains its rearrangement flow capability, the pressure is released to a low pressure state below the initial positive pressure and maintained to perform pressure release and rearrangement treatment. Then, the pressure is restored to the molding pressure and the temperature is maintained to complete the deep cross-linking and curing of the resin matrix. After cooling, it is transferred to an oven for free state post-curing treatment.

[0013] By adopting the above technical solution, and by using a composite system of cyanate ester and epoxy resin, combined with a pressure relief and rearrangement process introduced in the resin molten state, an insulating dielectric layer with high thermal conductivity, few pores, and low residual stress is obtained.

[0014] The specific principles and reaction mechanisms are as follows:

[0015] During the initial heat preservation and pressure holding stage, the system is heated above its softening point and enters a low-viscosity liquid state. Under the initial positive pressure, the adhesive undergoes shear flow and fills the resin plug holes in the printed circuit board core. During this operation period, the resin system undergoes preliminary ring-opening and cross-linking reactions. The specific reaction steps are as follows:

[0016] Under the catalysis of zinc octanoate, the cyanate ester group in 2,2-bis(4-cyanooxyphenyl)propane undergoes a cyclotrimerization reaction to generate a highly cross-linked network containing a triazine ring structure.

[0017] 2-Ethyl-4-methylimidazol initiates ring-opening polymerization of the epoxy groups inside bisphenol F epoxy resin and low molecular weight liquid bisphenol A epoxy resin.

[0018] Unreacted cyanate monomers undergo copolymerization addition with epoxy groups to form oxazolidinone structures, which promotes chemical interlocking between the triazine ring network and the epoxy network.

[0019] When the resin plugs are fully filled and the resin matrix is ​​in a critical state close to the gel point, a decompression and rearrangement process is performed. Removing the positive pressure releases the rigid extrusion stress generated by the inorganic thermally conductive filler during forced flow. In a low-pressure, constant-temperature environment, the strong vertical compression is released, and the filler detaches from the agglomeration state. Driven by thermodynamic surface tension, it rearranges its position and forms a continuous thermally conductive permeation channel on the horizontal plane. Subsequently, the molding pressure is restored, and the rearranged inorganic powder structure is physically locked during the gelation of the three-dimensional polymer network, ultimately achieving low-stress molding of the high thermal conductivity medium layer.

[0020] Preferably, the high thermal conductivity resin adhesive is made from raw materials comprising the following parts by weight:

[0021] 2,2-Bis(4-cyanooxyphenyl)propane: 70.0 to 140.0 parts by weight;

[0022] Bisphenol F type epoxy resin: 30.0 to 80.0 parts by weight;

[0023] Low molecular weight liquid bisphenol A type epoxy resin: 18.0 to 38.5 parts by weight;

[0024] Butanone solvent: 300.0 to 450.0 parts by weight;

[0025] Rheology control agent: 40.0 to 85.0 parts by weight;

[0026] Modified composite filler: 700.0 to 800.0 parts by weight;

[0027] Zinc octanoate: 1.0 to 1.4 parts by weight;

[0028] 2-Ethyl-4-methylimidazole: 0.5 to 0.9 parts by weight.

[0029] By adopting the above technical solution, the basic material composition of the resin system is limited. 2,2-bis(4-cyanooxyphenyl)propane constitutes the polymer network backbone to provide heat resistance and low dielectric loss. Bisphenol F type epoxy resin compensates for the matrix fluidity under high filler loading. Low molecular weight liquid bisphenol A type epoxy resin with an epoxy equivalent of 180 to 195 g / eq and a viscosity of 11,000 to 15,000 mPa·s at 25°C is used to adjust the crosslinking density of the cured network. Zinc octoate is compounded with 2-ethyl-4-methylimidazole to make the latency of the resin system match the pressing temperature window.

[0030] Preferably, the rheology control agent is made from raw materials comprising the following parts by weight:

[0031] Bisphenol A: 91.3 to 136.9 parts by weight;

[0032] Polymer of 4,4'-(1-methylethylidene)bisphenol and (chloromethyl)ethylene oxide: 152.0 to 228.0 parts by weight;

[0033] Cyclohexanone: 360.0 to 540.0 parts by weight;

[0034] 2-Ethyl-4-methylimidazole: 0.15 to 0.35 parts by weight.

[0035] By adopting the above technical solution, the phenolic hydroxyl groups of bisphenol A and the epoxy groups of the polymer of 4,4'-(1-methylethylidene)bisphenol and (chloromethyl)ethylene oxide undergo a linear chain extension polymerization reaction under catalysis to generate high molecular weight phenoxy resin. The high molecular weight phenoxy resin is distributed in the cross-linking network, which improves the fracture toughness of the cured resin and increases the lower limit of the viscosity of the molten adhesive, preventing resin overflow in the early stage of pressing.

[0036] Preferably, the modified composite filler is made from raw materials comprising the following parts by weight:

[0037] 3-Glycidyl etheroxypropyltrimethoxysilane: 0.5 to 2.0 parts by weight;

[0038] Spherical alumina: 75.0 to 85.0 parts by weight;

[0039] Boron nitride: 15.0 to 25.0 parts by weight.

[0040] By adopting the above technical solution, the hydrolysis products of 3-glycidyl etheroxypropyltrimethoxysilane are coated on the surface of inorganic powder, the terminal epoxy groups are cross-linked with the matrix resin, the spherical alumina maintains the volumetric thermal conductivity and reduces the viscosity of the mixed system, and the lamellar structure of boron nitride is oriented in the horizontal direction during the decompression and rearrangement stage. Together, they establish an anisotropic thermal conductive network with high in-plane thermal conductivity.

[0041] Preferably, the steps for preparing the B-stage prepreg include:

[0042] The material is traction-speeded at 3.75 to 6.0 m / min through a continuous tunnel oven at 140 to 160°C, with the baking time controlled at 4.0 to 6.4 min.

[0043] By adopting the above technical solution and setting specific temperature and time parameters, the methyl ethyl ketone solvent is fully evaporated, while the resin molecules are partially prepolymerized to prevent free monomers from crystallizing at room temperature, thus maintaining the surface of the prepreg with a slightly viscous texture suitable for the lamination process.

[0044] Preferably, the resin content of the obtained B-stage semi-cured sheet is controlled to be 45.0% to 72.0%, and the gel time at 171°C is controlled to be 90s to 130s.

[0045] By adopting the above technical solution, the physicochemical state of the prepreg is quantified and clarified. The resin content here is the percentage of the total mass of the resin system, including inorganic thermally conductive fillers, to the total mass of the prepreg. The resin content within the specified range meets the requirements for wrapping the rolled copper foil circuit and filling the blind via structure. The specified gel time is obtained by taking the resin powder peeled off the surface of the prepreg and placing it on a 171°C constant temperature hot plate, starting from the time the resin melts, until the resin is picked up and broken, losing its fluidity. This parameter provides the reaction time for the resin melting and flow during the pressing stage.

[0046] Preferably, the steps for maintaining the initial heat preservation and pressure preservation state include:

[0047] Heating to 180 to 220°C in a vacuum environment at a heating rate of 1.5 to 3.0°C / min, while applying an initial positive pressure of 1.5 to 3.5 MPa, and maintaining a constant temperature and pressure state for 4.0 to 6.0 min after reaching the temperature.

[0048] By adopting the above technical solution, the solid semi-cured sheet can smoothly transition to a viscous flow state at a specific heating rate. Combined with the basic gel characteristics of 90s to 130s at 171℃, the latency of the resin is extended by a heating slope of 1.5 to 3.0℃ / min. This allows the resin system to evolve into a critical gel state that is not yet fully cross-linked and still retains its internal rearrangement flow capacity after reaching 180 to 220℃ and maintaining it for 4.0 to 6.0 min. During this pressing window, mechanical pressure provides static fluid pressure, forcing the high-viscosity resin to displace the gas in the core board pores, thus achieving a dense filling of the medium layer with fewer voids.

[0049] Preferably, the steps for depressurization and rearrangement include:

[0050] The initial positive pressure is depressurized to a low pressure of 0.1 to 0.8 MPa within 10.0 to 15.0 seconds, and then maintained at 180 to 220°C and the low pressure for 15.0 minutes.

[0051] By adopting the above technical solution, a sudden pressure drop is achieved in the initial gelation zone of the resin with rearrangement flow capability. The sudden pressure drop is intended to prevent the inorganic filler from undergoing lattice damage under high pressure, so that the powder can complete stress relaxation and reposition rearrangement in the matrix resin, and repair the rheological defects caused by high pressure shear.

[0052] Preferably, the steps for completing the deep cross-linking and curing of the resin matrix include:

[0053] Restore the molding pressure to 1.5 to 3.5 MPa and maintain a constant temperature of 180 to 220°C for 40.0 to 60.0 min.

[0054] By adopting the above technical solution, the external constraint conditions are reconstructed after the internal stress is fully released, so that the composite system completes the three-dimensional network cross-linking of triazine ring and oxazolidinone under specific pressure, fixes the spatial position of inorganic filler, and improves the mechanical properties of the board.

[0055] Preferably, the step of performing free-state post-curing treatment includes:

[0056] After cooling, the circuit board is transferred to an oven at 215 to 240°C for free curing for 90.0 to 150.0 minutes.

[0057] By adopting the above technical solution, the polymerization conversion rate of residual cyanate monomers is improved by utilizing a high-temperature environment, the thermal stress accumulated during the pressing and cooling process is alleviated, and the glass transition temperature and dimensional thermal expansion coefficient of the final printed circuit board are stabilized.

[0058] This invention provides a high-power PCB temperature homogenization and heat dissipation process based on a high thermal conductivity composite dielectric layer. It has the following beneficial effects:

[0059] 1. This invention combines initial heat preservation and pressure holding with pressure relief and rearrangement under low pressure during the pressing stage. Under the guidance of initial positive pressure, the adhesive liquid is induced to undergo shear flow to fill the resin plug holes of the printed circuit board core board. Subsequently, the positive pressure is removed to eliminate the extrusion stress accumulated by the thermally conductive filler in the forced flow. The pressure relief action, combined with the low-pressure constant temperature environment, causes the thermally conductive filler to detach from the agglomerate state and establish continuous thermally conductive permeation channels on the horizontal plane, thereby preparing an insulating dielectric layer with low porosity and low residual stress.

[0060] 2. This invention utilizes 2,2-bis(4-cyanooxyphenyl)propane with different types of epoxy resins and introduces a high molecular weight phenoxy resin copolymerized from bisphenol A and a polymer as a rheology control agent. During the crosslinking process, the cyanate ester groups are promoted to triazine ring structure to form a chemical interlock with the epoxy network. The formulated resin system meets the matrix flow requirements under high filler load conditions, increases the lower limit of the viscosity of the molten adhesive to prevent overflow in the early stage of pressing, and imparts heat resistance to the printed circuit board after molding.

[0061] 3. This invention uses a mixture of spherical alumina and boron nitride pretreated with 3-glycidyl etheroxypropyltrimethoxysilane as the thermally conductive powder. A coupling agent is used to coat the surface of the inorganic powder, which promotes the chemical cross-linking of the terminal epoxy groups with the matrix resin to enhance the interfacial bonding force. The spherical alumina is used to maintain the volumetric thermal conductivity and suppress the viscosity increase of the mixed system. The layered boron nitride is aligned horizontally in conjunction with the decompression and rearrangement process. The two powders work together to build a three-dimensional thermally conductive network inside the insulating dielectric layer. Attached Figure Description

[0062] Figure 1This is a step distribution diagram of the rheological dynamics of the resin system of the present invention;

[0063] Figure 2 This is a heat flow curve of the curing reaction of the prepolymer resin powder of the present invention;

[0064] Figure 3 The X-ray diffraction pattern of the high thermal conductivity composite dielectric layer of the present invention is shown below.

[0065] Figure 4 This is a comparison diagram of thermal conductivity anisotropy data between embodiments and comparative examples of the present invention;

[0066] Figure 5 This is a dynamic thermomechanical analysis loss factor curve of the composite dielectric layer of the present invention;

[0067] Figure 6 This is a graph showing the thermal weight loss of the composite dielectric layer of the present invention.

[0068] Figure 7 This is a distribution diagram showing the relationship between the local thickness of the composite dielectric layer and the single-point breakdown voltage of the present invention. Detailed Implementation

[0069] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0070] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0071] Bisphenol F type epoxy resin, CAS No. 37231-36-0, commercially available industrial grade, epoxy equivalent of 160 to 180 g / eq;

[0072] 2,2-Bis(4-cyanooxyphenyl)propane, CAS No. 1156-51-0, commercially available industrial grade;

[0073] Bisphenol A, CAS number 80-05-7, commercially available industrial grade;

[0074] Low molecular weight liquid bisphenol A type epoxy resin, namely a polymer of 4,4'-(1-methylethylidene)bisphenol and (chloromethyl)ethylene oxide, CAS number 25068-38-6, commercially available industrial grade, epoxy equivalent of 185 to 195 g / eq, viscosity at 25℃ of 11000-15000 mPa·s;

[0075] Zinc octoate, CAS number 557-09-5, commercially available industrial grade;

[0076] 2-Ethyl-4-methylimidazole, CAS No. 931-36-2, commercially available industrial grade;

[0077] Spherical alumina, CAS number 1344-28-1, commercially available industrial grade, crystal form is α phase, and the central value of particle size distribution D50 is set to 5 to 10 μm;

[0078] Boron nitride, CAS number 10043-11-5, commercially available industrial grade, specifically using hexagonal boron nitride with a two-dimensional layered microstructure and a particle size distribution center value D50 set to 1 to 3 μm;

[0079] 3-Glycidyl etheroxypropyltrimethoxysilane, CAS No. 2530-83-8, commercially available industrial grade, commonly known as KH-560;

[0080] Electronic grade fiberglass cloth, commercially available industrial grade, plain weave structure, specifications selected from 106, 1080, 2116, 3313 or 7628;

[0081] PCB inner layer circuit core board, commercially available semi-finished product, with FR-4 epoxy glass cloth copper-clad board containing 1.0oz to 3.0oz thick rolled copper foil circuitry and resin-filled via structure.

[0082] In this invention, the units of measurement for all materials and solvents are uniformly referred to as parts by weight.

[0083] Preparation Example 1:

[0084] This preparation example provides a method for preparing high molecular weight bisphenol A type phenoxy resin, including the following steps:

[0085] 91.3 parts by weight of bisphenol A, 152.0 parts by weight of the polymer of 4,4'-(1-methylethylidene)bisphenol and (chloromethyl)ethylene oxide, and 360.0 parts by weight of cyclohexanone were added to a reactor equipped with a condenser, and stirring was started and the temperature was raised until the substances were completely dissolved.

[0086] 0.15 parts by weight of 2-ethyl-4-methylimidazolium were added to the reactor, and the temperature was raised to 130°C under nitrogen protection to carry out linear chain extension polymerization for 4.0 h.

[0087] After the reaction is completed, the material is cooled and discharged, and finally a high molecular weight bisphenol A phenoxy resin solution with a weight average molecular weight of about 40,000 is obtained, hereinafter referred to as rheology control agent A.

[0088] Preparation Example 2:

[0089] This preparation example provides a method for preparing high molecular weight bisphenol A type phenoxy resin, including the following steps:

[0090] 114.1 parts by weight of bisphenol A, 190.0 parts by weight of the polymer of 4,4'-(1-methylethylidene)bisphenol and (chloromethyl)ethylene oxide, and 450.0 parts by weight of cyclohexanone were added to a reactor equipped with a condenser, and stirring was started and the temperature was raised until the substances were completely dissolved.

[0091] 0.25 parts by weight of 2-ethyl-4-methylimidazolium were added to the reactor, and the temperature was raised to 140°C under nitrogen protection to carry out linear chain extension polymerization for 6.0 h.

[0092] After the reaction is completed, the material is cooled and discharged, and finally a high molecular weight bisphenol A phenoxy resin solution with a weight average molecular weight of about 50,000 is obtained, hereinafter referred to as rheology control agent B.

[0093] Preparation Example 3:

[0094] This preparation example provides a method for preparing high molecular weight bisphenol A type phenoxy resin, including the following steps:

[0095] 136.9 parts by weight of bisphenol A, 228.0 parts by weight of the polymer of 4,4'-(1-methylethylidene)bisphenol and (chloromethyl)ethylene oxide, and 540.0 parts by weight of cyclohexanone were added to a reactor equipped with a condenser, and stirring was started and the temperature was raised until the substances were completely dissolved.

[0096] 0.35 parts by weight of 2-ethyl-4-methylimidazolium were added to the reactor, and the temperature was raised to 150°C under nitrogen protection to carry out linear chain extension polymerization for 8.0 h.

[0097] After the reaction is completed, the material is cooled and discharged, and finally a high molecular weight bisphenol A phenoxy resin solution with a weight average molecular weight of about 60,000 is obtained, hereinafter referred to as rheology control agent C.

[0098] Preparation Example 4:

[0099] This preparation example provides a surface coupling pretreatment method for dual-state composite fillers, including the following steps:

[0100] Add 0.5 parts by weight of 3-glycidyl etheroxypropyltrimethoxysilane to a mixture containing 4.5 parts by weight of anhydrous ethanol and 0.28 parts by weight of deionized water, stir and hydrolyze for 30.0 min to obtain the coupling agent hydrolysate for later use.

[0101] 85.0 parts by weight of spherical alumina and 15.0 parts by weight of boron nitride were put into a high-speed mixer and heated to 100°C at a stirring rate of 500 r / min. Then, the prepared coupling agent hydrolysate was added dropwise by spraying. The mixture was continuously mixed at 100°C and dry-modified for 1.2 h.

[0102] The mixed powder was removed and dried in a vacuum oven at 100°C for 1.5 hours to remove small molecule volatiles, and finally the surface-coupled pretreated bimodal composite filler was obtained, hereinafter referred to as modified composite filler A.

[0103] Preparation Example 5:

[0104] This preparation example provides a surface coupling pretreatment method for dual-state composite fillers, including the following steps:

[0105] 1.0 part by weight of 3-glycidyl etheroxypropyltrimethoxysilane was added to a mixture containing 9.5 parts by weight of anhydrous ethanol and 0.55 parts by weight of deionized water, stirred and hydrolyzed for 45.0 min to obtain the coupling agent hydrolysate for later use.

[0106] 80.0 parts by weight of spherical alumina and 20.0 parts by weight of boron nitride were put into a high-speed mixer and heated to 110°C at a stirring rate of 650 r / min. Then, the prepared coupling agent hydrolysate was added dropwise by spraying. The mixture was continuously mixed at 110°C and dry-modified for 1.6 h.

[0107] The mixed powder was removed and dried in a vacuum oven at 110°C for 2.5 hours to remove small molecule volatiles, and finally the surface-coupled pretreated bimodal composite filler was obtained, hereinafter referred to as modified composite filler B.

[0108] Preparation Example 6:

[0109] This preparation example provides a surface coupling pretreatment method for dual-state composite fillers, including the following steps:

[0110] 2.0 parts by weight of 3-glycidyl etheroxypropyltrimethoxysilane were added to a mixture containing 18.5 parts by weight of anhydrous ethanol and 1.15 parts by weight of deionized water, stirred and hydrolyzed for 60.0 min to obtain a coupling agent hydrolysate for later use.

[0111] 75.0 parts by weight of spherical alumina and 25.0 parts by weight of boron nitride were put into a high-speed mixer and heated to 120°C at a stirring rate of 800 r / min. Then, the prepared coupling agent hydrolysate was added dropwise by spraying. The mixture was continuously mixed at 120°C and dry-modified for 2.2 h.

[0112] The mixed powder was removed and dried in a vacuum oven at 120°C for 3.5 hours to remove small molecule volatiles, and finally the surface-coupled pretreated bimodal composite filler was obtained, hereinafter referred to as modified composite filler C.

[0113] Example 1:

[0114] This embodiment provides a high-power PCB temperature homogenization and heat dissipation process based on a high thermal conductivity composite dielectric layer, including the following steps:

[0115] 100.0 parts by weight of 2,2-bis(4-cyanooxyphenyl)propane, 60.0 parts by weight of bisphenol F epoxy resin, and 28.0 parts by weight of low molecular weight liquid bisphenol A epoxy resin were dissolved in 350.0 parts by weight of butanone solvent. The mixture was stirred and kept completely miscible. Then, 60.0 parts by weight of rheology control agent B and 750.0 parts by weight of modified composite filler B were added, and the mixture was dispersed at 1500 r / min for 45.0 min using a high-speed disperser. Subsequently, 1.2 parts by weight of zinc octanoate and 0.8 parts by weight of 2-ethyl-4-methylimidazole were added to the mixture, and the mixture was stirred for another 15.0 min to obtain a uniform high thermal conductivity resin solution.

[0116] A high thermal conductivity resin solution was uniformly coated onto the surface of 1080 specification electronic grade glass fiber cloth. The cloth was then passed through a continuous tunnel oven at 150℃ at a traction speed of 4.8 m / min. The baking time was controlled to be 5.0 min to evaporate the methyl ethyl ketone solvent and promote partial prepolymerization of the resin system. The resin content of the obtained B-stage prepreg was controlled to be 60.0% to 65.0%, and the gel time at 171℃ was 100 s to 120 s. The B-stage prepreg was finally obtained.

[0117] Prepare a PCB inner layer circuit core board with a 2.0oz thick rolled copper foil circuit on the surface and a resin plug structure. Stack a B-stage prepreg and an outer copper foil on the top and bottom sides of the PCB inner layer circuit core board to form a stacked structure.

[0118] The laminated structure was placed in a vacuum hot press and heated to 200°C at a heating rate of 2.0°C / min in a vacuum environment, while an initial positive pressure of 2.5MPa was applied. After reaching 200°C, the temperature and pressure were maintained at a constant level for 5.0min to promote complete melting of the resin and fill the resin pore structure. At this time, the resin system was in a critical gel state with high viscosity but not yet fully cross-linked and cured, and still retained the internal rearrangement flowability.

[0119] After the initial heat preservation and pressure holding stage, the initial positive pressure is released to 0.5 MPa within 10.0 seconds, and then maintained at 200℃ and 0.5 MPa for 15.0 minutes to release internal stress and induce resin horizontal rearrangement. Subsequently, the molding pressure is restored to 2.5 MPa and the temperature is maintained for 40.0 minutes to complete the deep cross-linking and curing of the resin matrix. Then, it is cooled to room temperature of 25.0℃ by natural cooling. Finally, the pressed circuit board is transferred to an oven at 230℃ for 120.0 minutes of free state post-curing treatment, thus completing the manufacturing of the high-power PCB.

[0120] Example 2:

[0121] This embodiment provides a high-power PCB temperature homogenization and heat dissipation process based on a high thermal conductivity composite dielectric layer, including the following steps:

[0122] 140.0 parts by weight of 2,2-bis(4-cyanooxyphenyl)propane, 80.0 parts by weight of bisphenol F epoxy resin, and 38.5 parts by weight of low molecular weight liquid bisphenol A epoxy resin were dissolved in 300.0 parts by weight of butanone solvent. The mixture was stirred and kept completely miscible. Then, 40.0 parts by weight of rheology control agent A and 700.0 parts by weight of modified composite filler A were added, and the mixture was dispersed at 1200 r / min for 35.0 min using a high-speed disperser. Subsequently, 1.0 parts by weight of zinc octanoate and 0.5 parts by weight of 2-ethyl-4-methylimidazole were added to the mixture, and the mixture was stirred for another 10.0 min to obtain a uniform high thermal conductivity resin solution.

[0123] A high thermal conductivity resin solution was uniformly coated onto the surface of 106-gauge electronic-grade glass fiber cloth. The cloth was then passed through a continuous tunnel oven at 140°C at a traction speed of 6.0 m / min. The baking time was controlled to be 4.0 min to evaporate the methyl ethyl ketone solvent and promote partial prepolymerization of the resin system. The resin content of the obtained B-stage prepreg was controlled to be 68.0% to 72.0%, and the gel time at 171°C was 110 s to 130 s. The B-stage prepreg was finally obtained.

[0124] Prepare a PCB inner layer circuit core board with a 1.0oz thick rolled copper foil circuit on the surface and a resin plug structure. Stack a B-stage prepreg and an outer copper foil on the top and bottom sides of the PCB inner layer circuit core board to form a stacked structure.

[0125] The laminated structure was placed in a vacuum hot press and heated to 180°C at a heating rate of 1.5°C / min in a vacuum environment, while an initial positive pressure of 1.5MPa was applied. After reaching 180°C, the temperature and pressure were maintained for 4.0 min to promote complete melting of the resin and fill the resin pore structure. At this time, the resin system was in a critical gel state with high viscosity but not yet fully cross-linked and cured, and still retained the internal rearrangement flowability.

[0126] After the initial heat preservation and pressure holding stage, the initial positive pressure is released to 0.1 MPa within 10.0 seconds, and then maintained at 180°C and 0.1 MPa for 15.0 minutes to release internal stress and induce horizontal rearrangement of the resin. Subsequently, the molding pressure is restored to 1.5 MPa and the temperature is maintained for 40.0 minutes to complete the deep cross-linking and curing of the resin matrix. Then, it is cooled to room temperature of 22.0°C by natural cooling. Finally, the pressed circuit board is transferred to an oven at 215°C for 90.0 minutes of free state post-curing treatment, thus completing the manufacturing of the high-power PCB.

[0127] Example 3:

[0128] This embodiment provides a high-power PCB temperature homogenization and heat dissipation process based on a high thermal conductivity composite dielectric layer, including the following steps:

[0129] 70.0 parts by weight of 2,2-bis(4-cyanooxyphenyl)propane, 30.0 parts by weight of bisphenol F epoxy resin, and 18.0 parts by weight of low molecular weight liquid bisphenol A epoxy resin were dissolved in 450.0 parts by weight of butanone solvent. The mixture was stirred and kept completely miscible. Then, 80.0 parts by weight of rheology control agent C and 800.0 parts by weight of modified composite filler C were added, and the mixture was dispersed at 1800 r / min for 55.0 min using a high-speed disperser. Subsequently, 1.4 parts by weight of zinc octanoate and 0.6 parts by weight of 2-ethyl-4-methylimidazole were added to the mixture, and the mixture was stirred for another 20.0 min to obtain a uniform high thermal conductivity resin solution.

[0130] A high thermal conductivity resin solution was uniformly coated onto the surface of 7628 specification electronic grade glass fiber cloth. The cloth was then passed through a continuous tunnel oven at 160℃ at a traction speed of 4.0 m / min. The baking time was controlled to be 6.0 min to evaporate the methyl ethyl ketone solvent and promote partial prepolymerization of the resin system. The resin content of the obtained B-stage prepreg was controlled to be 45.0% to 50.0%, and the gel time at 171℃ was 90 s to 110 s. The B-stage prepreg was finally obtained.

[0131] Prepare a PCB inner layer circuit core board with a 3.0oz thick rolled copper foil circuit on the surface and a resin plug structure. Stack a B-stage prepreg and an outer copper foil on the top and bottom sides of the PCB inner layer circuit core board to form a stacked structure.

[0132] The laminated structure was placed in a vacuum hot press and heated to 220°C at a heating rate of 3.0°C / min in a vacuum environment, while an initial positive pressure of 3.5MPa was applied. After reaching 220°C, the temperature and pressure were maintained at a constant level for 6.0min to promote complete melting of the resin and fill the resin pore structure. At this time, the resin system was in a critical gel state with high viscosity but not yet fully cross-linked and cured, and still retained the internal rearrangement flowability.

[0133] After the initial heat preservation and pressure holding stage, the initial positive pressure is released to 0.8 MPa within 15.0 seconds, and then maintained at 220°C and 0.8 MPa for 15.0 minutes to release internal stress and induce horizontal rearrangement of the resin. Subsequently, the molding pressure is restored to 3.5 MPa and the temperature is maintained at a constant level for 60.0 minutes to complete the deep cross-linking and curing of the resin matrix. Then, it is cooled to room temperature of 28.0°C by natural cooling. Finally, the pressed circuit board is transferred to an oven at 240°C for 150.0 minutes of free state post-curing treatment, thus completing the manufacturing of the high-power PCB.

[0134] Example 4:

[0135] This embodiment provides a high-power PCB temperature homogenization and heat dissipation process based on a high thermal conductivity composite dielectric layer, including the following steps:

[0136] 105.0 parts by weight of 2,2-bis(4-cyanooxyphenyl)propane, 50.0 parts by weight of bisphenol F epoxy resin, and 23.0 parts by weight of low molecular weight liquid bisphenol A epoxy resin were dissolved in 380.0 parts by weight of butanone solvent. The mixture was stirred and kept completely miscible. Then, 50.0 parts by weight of rheology control agent B and 770.0 parts by weight of modified composite filler C were added, and the mixture was dispersed at 1400 r / min for 40.0 min using a high-speed disperser. Subsequently, 1.3 parts by weight of zinc octanoate and 0.7 parts by weight of 2-ethyl-4-methylimidazole were added to the mixture, and the mixture was stirred for another 12.0 min to obtain a uniform high thermal conductivity resin solution.

[0137] High thermal conductivity resin liquid was uniformly coated onto the surface of 2116 specification electronic grade glass fiber cloth. It was then passed through a continuous tunnel oven at 145℃ at a traction speed of 5.0 m / min. The baking time was controlled to be 4.8 min to evaporate the methyl ethyl ketone solvent and promote partial prepolymerization of the resin system. The resin content of the obtained B-stage prepreg was controlled to be 52.0% to 56.0%, and the gel time at 171℃ was 105 s to 125 s. The B-stage prepreg was finally obtained.

[0138] Prepare a PCB inner layer circuit core board with 1.5oz thick rolled copper foil lines on the surface and resin plug structure. Stack a B-stage prepreg and an outer copper foil on the top and bottom sides of the PCB inner layer circuit core board to form a stacked structure.

[0139] The laminated structure was placed in a vacuum hot press and heated to 190°C at a heating rate of 2.5°C / min in a vacuum environment, while an initial positive pressure of 2.0MPa was applied. After reaching 190°C, the temperature and pressure were maintained at a constant level for 5.0min to promote complete melting of the resin and fill the resin pore structure. At this time, the resin system was in a critical gel state with high viscosity but not yet fully cross-linked and cured, and still retained the internal rearrangement flowability.

[0140] After the initial heat preservation and pressure holding stage, the initial positive pressure is released to 0.3 MPa within 10.0 seconds, and then maintained at 190°C and 0.3 MPa for 15.0 minutes to release internal stress and induce horizontal rearrangement of the resin. Subsequently, the molding pressure is restored to 2.0 MPa and the temperature is maintained for 45.0 minutes to complete the deep cross-linking and curing of the resin matrix. Then, it is cooled to room temperature of 24.0°C by natural cooling. Finally, the pressed circuit board is transferred to an oven at 220°C for 100.0 minutes of free state post-curing treatment, thus completing the manufacturing of the high-power PCB.

[0141] Example 5:

[0142] This embodiment provides a high-power PCB temperature homogenization and heat dissipation process based on a high thermal conductivity composite dielectric layer, including the following steps:

[0143] 110.0 parts by weight of 2,2-bis(4-cyanooxyphenyl)propane, 55.0 parts by weight of bisphenol F epoxy resin, and 33.0 parts by weight of low molecular weight liquid bisphenol A epoxy resin were dissolved in 320.0 parts by weight of butanone solvent. The mixture was stirred and kept completely miscible. Then, 85.0 parts by weight of rheology control agent B and 715.0 parts by weight of modified composite filler B were added, and the mixture was dispersed at 1600 r / min for 50.0 min using a high-speed disperser. Subsequently, 1.1 parts by weight of zinc octanoate and 0.9 parts by weight of 2-ethyl-4-methylimidazole were added to the mixture, and the mixture was stirred for another 18.0 min to obtain a uniform high thermal conductivity resin solution.

[0144] A high thermal conductivity resin solution was uniformly coated onto the surface of 3313 specification electronic grade glass fiber cloth. The cloth was then passed through a continuous tunnel oven at 155℃ at a traction speed of 3.75 m / min. The baking time was controlled to be 6.4 min to evaporate the methyl ethyl ketone solvent and promote partial prepolymerization of the resin system. The resin content of the obtained B-stage prepreg was controlled to be 55.0% to 58.0%, and the gel time at 171℃ was 95 s to 115 s. The B-stage prepreg was finally obtained.

[0145] Prepare a PCB inner layer circuit core board with a 2.5oz thick rolled copper foil circuit on the surface and a resin plug structure. Stack a B-stage prepreg and an outer copper foil on the top and bottom sides of the PCB inner layer circuit core board to form a stacked structure.

[0146] The laminated structure was placed in a vacuum hot press and heated to 210°C at a heating rate of 1.8°C / min in a vacuum environment, while an initial positive pressure of 3.0MPa was applied. After reaching 210°C, the temperature and pressure were maintained for 5.0min to promote complete melting of the resin and fill the resin pore structure. At this time, the resin system was in a critical gel state with high viscosity but not yet fully cross-linked and cured, and still retained the internal rearrangement flowability.

[0147] After the initial heat preservation and pressure holding stage, the initial positive pressure is released to 0.6 MPa within 15.0 seconds, and then maintained at 210°C and 0.6 MPa for 15.0 minutes to release internal stress and induce horizontal rearrangement of the resin. Subsequently, the molding pressure is restored to 3.0 MPa and the temperature is maintained for 55.0 minutes to complete the deep cross-linking and curing of the resin matrix. Then, it is cooled to room temperature of 26.0°C by natural cooling. Finally, the pressed circuit board is transferred to an oven at 235°C for 135.0 minutes of free state post-curing treatment, thus completing the manufacturing of the high-power PCB.

[0148] Comparative Example 1:

[0149] Compared with Example 1, the difference lies in the pressure control procedure during the pressing stage. In this comparative example, the constant pressure of 2.5 MPa is maintained throughout the heating and 200°C constant temperature for 60.0 min stages and the subsequent natural cooling to room temperature process. The pressure is not reduced to 0.5 MPa. All other aspects are the same.

[0150] Comparative Example 2:

[0151] Compared with Example 1, the difference lies in the resin formulation. In this comparative example, rheology control agent B was not added, but was replaced with 60.0 parts by weight of bisphenol F epoxy resin. All other aspects are the same.

[0152] Comparative Example 3:

[0153] Compared with Example 1, the difference is that the pressure application logic in the pressing stage adopts the traditional process of low pressure first and then high pressure. In this comparative example, only an initial pressure of 0.5MPa is applied in the heating stage. After reaching 200°C, the pressure is suddenly increased to 2.5MPa and maintained for 60.0min. Then, it is cooled to room temperature under pressure. The rest are the same.

[0154] Test Example 1:

[0155] The high thermal conductivity resin solutions prepared in Examples 1, 2, 5 and Comparative Example 2 were extracted. The high thermal conductivity resin solutions prepared in Examples 1, 2, 5 and Comparative Example 2 were placed in a vacuum drying oven and subjected to vacuum treatment at 50°C to evaporate and remove the methyl ethyl ketone solvent, and the desolventized resin colloidal matrix was obtained as a rheological test sample. At the same time, the B-stage semi-cured sheets of the corresponding batches of Examples 1, 2, 5 and Comparative Example 2 after baking in a continuous tunnel oven were extracted, and the prepolymerized resin powder on the surface of the B-stage semi-cured sheets was peeled off with a non-metallic scraper as a curing exothermic test sample.

[0156] The rheological properties of the resin colloidal matrix were tested using a rotational rheometer. A 25mm parallel plate test fixture was used, and the ambient temperature of the test chamber was kept constant at 100℃ to simulate the molten flow state of the resin colloidal matrix during the initial stage of high-temperature pressing. The flow scanning mode was activated, and the shear rate range was set to 0.01s. -1 up to 100s -1 Because the rheometer applies shear stress in a stepwise manner during actual measurements, it continuously records and collects the apparent viscosity data corresponding to each discrete shear rate point, and organizes the data to generate a rheological step distribution map. Shear rates of 0.05 s⁻¹ are then extracted. -1 And 50s -1 The apparent viscosity values ​​under the given conditions are used for performance comparison.

[0157] The heat flow characteristics of the prepolymer resin powder sample were scanned using a differential scanning calorimeter. 5 to 8 mg of prepolymer resin powder was weighed and placed in a standard aluminum crucible and sealed with a cap. The standard aluminum crucible containing the prepolymer resin powder was placed in the test furnace chamber, and high-purity nitrogen was introduced into the test furnace chamber as a protective gas. The heating program was set to heat from room temperature to 280°C at a heating rate of 10°C / min. The heat flow change trajectory during the test was continuously recorded by the differential scanning calorimeter. The peak temperature value of the exothermic peak of the curing reaction was extracted and the heat flow characteristics were presented in the form of integrated area.

[0158] The data obtained from the test is shown in the table below:

[0159] Table 1. Summary of Rheological Parameters and Thermodynamic Exothermic Characteristics of Resin Systems:

[0160]

[0161] According to Table 1 and Figure 1 and Figure 2 The data shows that at 0.05s -1 Under low shear conditions, the apparent viscosity values ​​of Examples 1, 2, and 5 reached 16543.2 Pa·s, 8932.7 Pa·s, and 27851.4 Pa·s, respectively; the shear rate increased to 50 s⁻¹. -1 At that time, the apparent viscosity of Examples 1, 2 and 5 decreased to 412.5 Pa·s, 325.6 Pa·s and 674.3 Pa·s, respectively. The apparent viscosity decreased with increasing shear rate, exhibiting pseudoplastic characteristics in non-Newtonian fluids.

[0162] During the depressurization stage of the lamination process, the edges of the laminate lose the external extrusion pressure difference, and the shear rate of the resin at the edges of the laminate decreases. The viscosity of the resin in the low-shear state increases, and it transforms into a gel-like semi-solid state. This physical flow-blocking boundary, based on pseudoplastic rheological characteristics, can be formed in the initial melting stage at 100°C and remains effective throughout the entire low-shear process window during the subsequent heating to high-temperature hot pressing. The gel-like semi-solid state constructs a physical boundary around the medium layer, which prevents the overflow of the high-filler-content resin that remains liquid inside.

[0163] Comparative Example 2 did not include any rheology control agent in the mixed system. The apparent viscosities of Comparative Example 2 under low shear and high shear conditions were 862.8 Pa·s and 158.4 Pa·s, respectively. Due to the high content of inorganic fillers in the system, Comparative Example 2 exhibited slight shear thinning. However, because no rheology control agent was added to construct a polymer entanglement network, Comparative Example 2 lacked strong viscosity rebound characteristics in the low shear region during processing. Its absolute viscosity was too low, and no physical barrier was established at the edge of the laminate to prevent material overflow.

[0164] Based on the exothermic peak temperature data, the curing exothermic peak temperatures of Examples 1, 2, and 5 were distributed in the range of 194.1℃ to 198.2℃, which is similar to the 196.5℃ recorded in Comparative Example 2. Introducing a rheology control agent into the resin system to change the mechanical rheological behavior of the resin system did not affect the thermodynamic process of the curing and crosslinking reaction within the resin system. The non-Newtonian fluid rheological characteristics and the curing and crosslinking reaction maintained an independent mechanism in the material system.

[0165] Test Example 2:

[0166] The circuit boards that were laminated and post-cured in Examples 1, 3, Comparative Example 1 and Comparative Example 3 were extracted. The outer copper foil on the surface of the circuit board was removed by chemical etching to expose the high thermal conductivity composite dielectric layer inside the circuit board after curing. The high thermal conductivity composite dielectric layer was cut into a specific size as a test sample.

[0167] The surface of the high thermal conductivity composite dielectric layer of the test sample was scanned using an X-ray diffractometer. A copper target Kα radiation source was configured, with the tube voltage set to 40 kV, the tube current set to 40 mA, the scanning angle 2θ range set to 10° to 60°, and the scanning rate set to 2° / min. The diffraction peak intensity of the basic plane, characterized by the horizontal arrangement of the two-dimensional sheet-like filler, located near 26.7°, and the diffraction peak intensity of the edge side section, characterized by the vertical arrangement of the two-dimensional sheet-like filler, located near 41.6°, were extracted. The ratio of the diffraction peak intensity of the basic plane to that of the edge side section was calculated as the horizontal orientation index.

[0168] The thermal conductivity of the test samples was tested using a laser flash thermal conductivity meter. The test samples were processed into circular pieces with a diameter of 12.7 mm for the vertical thermal conductivity test along the Z-axis and into circular pieces with a diameter of 25.4 mm for the horizontal thermal conductivity test along the XY plane. The horizontal thermal conductivity test along the XY plane was performed using a special fixture for in-plane thermal conductivity testing. The thermal conductivity was calculated by heating the center locally and measuring the radial thermal diffusivity at the edges. A graphite layer was sprayed onto the surface of the test sample to increase the light absorption rate. The sample was then irradiated with a pulsed laser at 25°C, and the temperature change of the back side of the test sample over time was recorded. The vertical thermal conductivity along the Z-axis and the horizontal thermal conductivity along the XY plane were then calculated.

[0169] In addition, to verify the uniform heat dissipation effect, the test samples of the examples and comparative examples were processed into substrates with a size of 50mm×50mm. A ceramic heating resistor with a power of 5W was attached to the center of the substrate. After heating for 30.0 minutes at room temperature to reach thermal equilibrium, an infrared thermal imager was used to scan the temperature field on the surface of the substrate, extract the highest temperature at the center of the heat source and the lowest temperature at the edge of the substrate, and calculate the difference between the two as the maximum temperature difference on the board surface.

[0170] The data obtained from the test is shown in the table below:

[0171] Table 2. Summary of Crystallographic Characteristics and Thermal Anisotropy Data of Resin Systems:

[0172]

[0173] According to Table 2 and Figure 3 and Figure 4 The data show that the basic plane diffraction peak intensities of Examples 1 and 3 are 8541.6au and 9128.4au, respectively; the edge side section diffraction peak intensities are 351.2au and 324.1au, respectively; the horizontal orientation indices are 24.32 and 28.16, respectively; the XY plane horizontal thermal conductivity of Examples 1 and 3 is 31.42 W / (m·K) and 38.65 W / (m·K), respectively; and the Z-axis vertical thermal conductivity is 4.25 W / (m·K) and 3.86 W / (m·K), respectively.

[0174] After the initial constant pressure stage of the pressing process, a pressure drop operation is performed on the high thermal conductivity composite medium layer. The compressed resin matrix inside the high thermal conductivity composite medium layer expands in volume, generating a horizontal flow from the center to the edge. The horizontal flow guides the two-dimensional sheet-like boron nitride filler to slide and rearrange in the XY plane. The base plane of the two-dimensional sheet-like boron nitride filler is parallel to the orientation of the XY plane, forming a thermally anisotropic structure. The horizontal thermal conductivity of the XY plane increases, which fully conducts and disperses the heat from the center of the heat source. The maximum temperature difference between the plate surfaces of Examples 1 and 3 is significantly reduced to 4.2℃ and 3.5℃, respectively, achieving excellent uniform temperature heat dissipation effect.

[0175] Comparative Example 1 was operated under constant pressure throughout the process, while Comparative Example 3 was operated under pressure during the heat preservation stage. The horizontal orientation indices of Comparative Example 1 and Comparative Example 3 were 2.84 and 2.47, respectively, and the horizontal thermal conductivity in the XY plane was 9.24 W / (m·K) and 8.86 W / (m·K), respectively. No pressure relief process was introduced during the curing stage of Comparative Example 1 and Comparative Example 3, and the resin matrix did not undergo volume expansion and horizontal flow. The two-dimensional lamellar boron nitride filler was randomly distributed in the high thermal conductivity composite medium layer and did not form a continuous heat conduction network in the horizontal direction of the XY plane, resulting in a large accumulation of heat at the central heat source. The maximum temperature difference between the boards of Comparative Example 1 and Comparative Example 3 was as high as 15.6℃ and 16.8℃, respectively, indicating poor heat dissipation capacity.

[0176] Test Example 3:

[0177] Extract the copper-clad laminates from Examples 1, 4, and Comparative Example 2 after lamination, and cut the copper-clad laminates into strip-shaped test samples with a width of 3.2 mm. Use a universal tensile testing machine to test the standard peel strength of the interface between the surface copper foil and the internal composite dielectric layer of the strip-shaped test sample. Set the tensile speed to 50.8 mm / min and the peel angle to 90°. Peel the surface copper foil continuously at room temperature and record the average force load of the universal tensile testing machine during the peeling process. Calculate the peel strength data by the ratio of the average force load to the width of the strip-shaped test sample.

[0178] The copper-clad laminates from Examples 1, 4, and Comparative Example 2 were extracted, and the outer copper foil on the surface of the copper-clad laminate was removed by chemical etching to obtain the cured composite dielectric layer. The composite dielectric layer was cut into standard strips with a length of 35 mm and a width of 10 mm. Thermomechanical properties were tested using a dynamic thermomechanical analyzer. A tensile test fixture was selected, the dynamic loading frequency was set to 1 Hz, and the heating program was set to heat from 50 °C to 300 °C at a heating rate of 5 °C / min. The storage modulus and loss factor of the composite dielectric layer as a function of temperature were tested and recorded to generate a dynamic thermomechanical analysis loss factor curve. The peak temperature of the loss factor curve was extracted as the glass transition temperature.

[0179] The composite dielectric layer after etching to remove the copper foil was extracted. A special slicing machine was used to cut the composite dielectric layer into small cube samples with a size not exceeding 2mm × 2mm. Thermogravimetric analysis was used to test the thermal weight loss of the cube samples. 10mg to 15mg cube samples were weighed and placed in an alumina standard crucible. High-purity nitrogen gas with a flow rate of 50mL / min was introduced into the test furnace to isolate oxygen. The heating program was set to continuously heat from 30℃ to 600℃ at a heating rate of 10℃ / min. The dynamic change data of the mass retention rate of the cube samples with temperature was recorded to generate a thermogravimetric curve. The temperature at which the mass retention rate dropped to 95% was taken as the 5% thermogravimetric temperature.

[0180] The data obtained from the test is shown in the table below:

[0181] Table 3. Summary of data on interfacial adhesion properties and heat resistance characteristics of resin systems:

[0182]

[0183] According to Table 3 and Figure 5 and Figure 6 The data shows that the peel strengths of Example 1 and Example 4 are 1.42 N / mm and 1.38 N / mm, respectively, while the peel strength of Comparative Example 2 is 0.64 N / mm. The resin formulation system of Comparative Example 2 did not contain rheology control agents. The resin matrix corresponding to Comparative Example 2 experienced outflow during the melting and viscosity reduction stage of the high-temperature pressing process, resulting in a lack of resin in the surface area of ​​the composite dielectric layer. The amount of residual resin on the surface layer did not establish a dense interfacial bonding network between the composite dielectric layer and the outer copper foil, causing a decrease in the interfacial peel strength of Comparative Example 2.

[0184] In Examples 1 and 4, a flow-blocking physical boundary is established around the perimeter of the composite dielectric layer to prevent the overflow and loss of liquid resin inside the composite dielectric layer, maintain the resin matrix retention ratio in the surface area, and ensure the mechanical adhesion performance of the interface between the outer copper foil and the composite dielectric layer.

[0185] Based on the glass transition temperature and 5% thermogravimetric temperature data, the glass transition temperatures of Examples 1, 4, and Comparative Example 2 range from 209.5℃ to 218.7℃, and the 5% thermogravimetric temperatures range from 421.9℃ to 431.2℃. Introducing high molecular weight bisphenol A phenoxy resin into the resin formulation system did not reduce the thermal stability of the matrix material. The terminal epoxy groups in the phenoxy resin and the cyanate ester groups form a synergistic crosslinking network, maintaining the resin crosslinking network density. While introducing physical rheological control characteristics, the overall heat resistance reliability and high-temperature structural stability of the composite dielectric layer material system are maintained.

[0186] Test Example 4:

[0187] Large-size copper-clad laminates were extracted from Examples 1, 2, 4, Comparative Example 1, and Comparative Example 3. The physical dimensions of the large-size copper-clad laminates were all 457mm × 610mm. To ensure consistency in the comparative tests, the number of pre-stressed sheets in stage B was adjusted before pressing the test boards in each example and comparative example to uniformly control the nominal thickness of the dielectric layer to 100μm. The outer copper foil on the surface of the large-size copper-clad laminate was removed by chemical etching to expose the solidified composite dielectric layer inside the large-size copper-clad laminate. The composite dielectric layer was divided into 25 rectangular test areas of the same size, consisting of 5 rows and 5 columns. Test points were set at the geometric center of each rectangular test area, and a total of 25 independent test points were obtained.

[0188] A high-precision digital thickness gauge was used to measure the thickness of the composite dielectric layer at 25 test points. The thickness value of each test point was recorded, the average value of the thickness values ​​of the 25 test points was calculated, the maximum and minimum values ​​of the thickness values ​​of the 25 test points were extracted, the difference between the maximum and minimum values ​​was calculated as the thickness range, and the thickness variance was calculated using the thickness values ​​of the 25 test points.

[0189] An AC withstand voltage tester was used to test the electrical breakdown voltage of 25 test points on the composite dielectric layer. A spherical electrode was selected, and the composite dielectric layer was placed flat between the spherical electrode and the lower plate electrode. The voltage rise rate was set to 0.5 kV / s, and AC voltage was continuously applied at room temperature. The voltage value of the composite dielectric layer at the moment of insulation breakdown at each test point was monitored and recorded. The average breakdown voltage of the 25 test points was calculated as the average breakdown voltage, and the lowest value among the 25 test point breakdown voltages was extracted as the minimum breakdown voltage.

[0190] The data obtained from the test is shown in the table below:

[0191] Table 4. Summary of Test Data on Thickness Uniformity and Breakdown Voltage of Large-Size Dielectric Layers:

[0192]

[0193] According to Table 4 and Figure 7 The data shows that the thickness range of Examples 1, 2, and 4 is between 3.75 μm and 4.86 μm, and the thickness variance is between 1.48 μm. 2 Up to 2.21μm 2 The average breakdown voltage ranges from 7.41 kV to 7.68 kV, with the lowest breakdown voltage remaining above 6.95 kV. The thickness ranges for Comparative Example 1 and Comparative Example 3 are 18.62 μm and 22.15 μm, respectively, with thickness variances of 24.36 μm. 2 With 29.81μm 2 The average breakdown voltages were 5.23kV and 4.86kV, respectively, and the minimum breakdown voltages dropped to 3.14kV and 2.67kV. In Examples 1, 2 and 4, flow-blocking physical boundaries were established around the periphery of the composite dielectric layer to prevent the overflow of liquid resin, reduce the resin loss deviation caused by the force difference between the central and peripheral regions, and maintain the consistency of the composite dielectric layer thickness under large area.

[0194] Comparative Examples 1 and 3 did not introduce a flow-blocking physical boundary, resulting in uneven loss of the resin matrix over a large area. This caused an increase in the thickness range and thickness variance, and the loss of thickness in some areas resulted in lower breakdown voltage test values. The uneven loss of the resin matrix caused disordered migration of the filler, forming micropores and structural defects in local thinner areas. Under the action of AC voltage, the micropores triggered partial discharge, causing low-voltage breakdown in local areas of Comparative Examples 1 and 3, resulting in a decrease in the average breakdown voltage. Examples 1, 2, and 4 maintained a uniform distribution of resin and filler, reduced the generation of weak insulation areas, and maintained the overall electrical insulation performance of the composite dielectric layer.

[0195] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to the equipment structure, process flow, step sequence, operating parameters, or working medium type in these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the core technical solutions disclosed above and their equivalent substitutions.

Claims

1. A high-power PCB temperature homogenization and heat dissipation process based on a high thermal conductivity composite dielectric layer, characterized in that, The process includes the following steps: 2,2-bis(4-cyanooxyphenyl)propane, bisphenol F epoxy resin and low molecular weight liquid bisphenol A epoxy resin were dissolved in methyl ethyl ketone solvent. Then, a rheology control agent and a modified composite filler containing spherical alumina and plate-like boron nitride were added for dispersion. Subsequently, zinc octanoate and 2-ethyl-4-methylimidazole were added and stirred to prepare a high thermal conductivity resin solution. The high thermal conductivity resin solution was uniformly coated onto the surface of electronic grade glass fiber cloth, and the resin system was partially prepolymerized by baking to prepare a B-stage semi-cured sheet. The B-stage prepreg and the outer copper foil are stacked on the upper and lower sides of the inner circuit core board of the PCB to form a stacked structure. The laminated structure is placed in a vacuum hot press, heated and subjected to initial positive pressure, and maintained in an initial heat and pressure state to promote complete melting of the resin and fill the resin pore structure. When the resin plug is fully filled and the resin matrix is ​​not yet fully cross-linked and maintains its rearrangement flow capability, the pressure is released to a low pressure state below the initial positive pressure and maintained to perform pressure release and rearrangement treatment. Then, the pressure is restored to the molding pressure and the temperature is maintained to complete the deep cross-linking and curing of the resin matrix. After cooling, it is transferred to an oven for free state post-curing treatment.

2. The high-power PCB uniform temperature dissipation process based on a high thermal conductivity composite dielectric layer according to claim 1, characterized in that, The high thermal conductivity resin adhesive is made from raw materials comprising the following parts by weight: 2,2-Bis(4-cyanooxyphenyl)propane: 70.0 to 140.0 parts by weight; Bisphenol F type epoxy resin: 30.0 to 80.0 parts by weight; Low molecular weight liquid bisphenol A type epoxy resin: 18.0 to 38.5 parts by weight; Butanone solvent: 300.0 to 450.0 parts by weight; Rheology control agent: 40.0 to 85.0 parts by weight; Modified composite filler: 700.0 to 800.0 parts by weight; Zinc octanoate: 1.0 to 1.4 parts by weight; 2-Ethyl-4-methylimidazole: 0.5 to 0.9 parts by weight.

3. The high-power PCB uniform temperature dissipation process based on a high thermal conductivity composite dielectric layer according to claim 1, characterized in that, The rheology control agent is made from raw materials comprising the following parts by weight: Bisphenol A: 91.3 to 136.9 parts by weight; Polymer of 4,4'-(1-methylethylidene)bisphenol and (chloromethyl)ethylene oxide: 152.0 to 228.0 parts by weight; Cyclohexanone: 360.0 to 540.0 parts by weight; 2-Ethyl-4-methylimidazole: 0.15 to 0.35 parts by weight.

4. The high-power PCB uniform temperature dissipation process based on a high thermal conductivity composite dielectric layer according to claim 1, characterized in that, The modified composite filler is made from raw materials comprising the following parts by weight: 3-Glycidyl etheroxypropyltrimethoxysilane: 0.5 to 2.0 parts by weight; Spherical alumina: 75.0 to 85.0 parts by weight; Boron nitride: 15.0 to 25.0 parts by weight.

5. The high-power PCB uniform temperature dissipation process based on a high thermal conductivity composite dielectric layer according to claim 1, characterized in that, The steps for preparing the B-stage semi-cured sheet include: The material is traction-speeded at 3.75 to 6.0 m / min through a continuous tunnel oven at 140 to 160°C, with the baking time controlled at 4.0 to 6.4 min.

6. The high-power PCB uniform temperature dissipation process based on a high thermal conductivity composite dielectric layer according to claim 1, characterized in that, The steps for preparing the B-stage semi-cured sheet include: The resin content of the obtained B-stage semi-cured sheet is controlled to be 45.0% to 72.0%, and the gel time at 171°C is controlled to be 90s to 130s.

7. The high-power PCB uniform temperature dissipation process based on a high thermal conductivity composite dielectric layer according to claim 1, characterized in that, The steps for maintaining the initial heat preservation and pressure preservation state include: Heating to 180 to 220°C in a vacuum environment at a heating rate of 1.5 to 3.0°C / min, while applying an initial positive pressure of 1.5 to 3.5 MPa, and maintaining a constant temperature and pressure state for 4.0 to 6.0 min after reaching the temperature.

8. The high-power PCB uniform temperature dissipation process based on a high thermal conductivity composite dielectric layer according to claim 1, characterized in that, The steps for depressurization and rearrangement include: The initial positive pressure is depressurized to a low pressure of 0.1 to 0.8 MPa within 10.0 to 15.0 seconds, and then maintained at 180 to 220°C and the low pressure for 15.0 minutes.

9. The high-power PCB uniform temperature dissipation process based on a high thermal conductivity composite dielectric layer according to claim 1, characterized in that, The step of completing the deep cross-linking and curing of the resin matrix includes: Restore the molding pressure to 1.5 to 3.5 MPa and maintain a constant temperature of 180 to 220°C for 40.0 to 60.0 min.

10. The high-power PCB uniform temperature dissipation process based on a high thermal conductivity composite dielectric layer according to claim 1, characterized in that, The steps of performing the free-state post-curing treatment include: After cooling, the circuit board is transferred to an oven at 215 to 240°C for free curing for 90.0 to 150.0 minutes.

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