A PCB board and a preparation method thereof

Abstract

The present invention relates to the technical field of circuit boards, and it relates to a PCB board and a preparation method thereof. A groove is formed on a dielectric layer by laser etching, and then a magnetic composite material is filled into the groove. Finally, the magnetic composite material is cured on the dielectric layer to form a shielding wall; a copper foil is attached to the surface of a substrate, a photoresist is coated on the surface of the copper foil, and a signal path pattern is transferred onto the photoresist through ultraviolet light exposure and development. The copper foil is etched using a ferric chloride solution, and only the copper foil in the signal path part is retained to form a conductive layer; a magnetic thin film layer is deposited on the surface of the conductive layer by magnetron sputtering technology. After stacking each layer of materials in the order of magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer, it is pressed and formed into multiple layers. A via hole is formed between the conductive layers on the multiple layers by a drilling machine, and chemical copper plating and electroplating copper treatment are performed on the via hole. The present invention realizes the effective suppression of interlayer signal interference in a GHz-level high-speed signal environment.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit boards, and more specifically, it relates to a PCB board and a method for preparing the same. Background Art

[0002] With the increasing complexity of electronic device functions and performance improvement, printed circuit boards (PCBs) play an increasingly important role in high-density design and high-speed signal transmission. However, the problem of interlayer signal interference in multi-layer PCBs has become a key bottleneck restricting the improvement of their performance.

[0003] As the signal frequency gradually increases to the GHz level, the crosstalk and coupling phenomena between high-speed signal paths become non-negligible. The transmission of high-speed signals will be affected by electromagnetic interference from adjacent layers, resulting in jitter, increased bit error rate, and even eye diagram closure, seriously affecting signal integrity.

[0004] CN117677081B proposes a method of embedding resistors in the gold finger area, which optimizes the transmission quality of high-speed signals by improving the impedance continuity of the local area. However, this method is only limited to the impedance control of the gold finger area and lacks a comprehensive solution to the overall high-speed signal interference problem in multi-layer PCBs.

[0005] CN118175726B proposes a buried groove structure in a PCB. By setting initial buried grooves on the dielectric layer and the core board, and using the intermediate laminated structure formed by lamination to hold the target oil body in the buried grooves, the function of storing and supplying the target oil body inside the PCB is realized. By setting insulating blind holes in the intermediate laminated structure and connecting them to the buried grooves, the quantitative extraction of the oil body is realized, optimizing the oil supply effect of the signal detection module and reducing the interference of the external container on signal detection.

[0006] The ability of this technology to suppress interlayer interference in high-speed signal paths is difficult to meet the requirements of GHz-level signal transmission. Summary of the Invention

[0007] For this reason, the present invention provides a PCB board and a method for preparing the same, which sets a shielding wall made of magnetic composite material in the dielectric layer to effectively suppress interlayer signal interference in a GHz-level high-speed signal environment.

[0008] To achieve the above object, the present invention provides a PCB board and a method for preparing the same,

[0009] The PCB board has a multi-layer structure and is used for loading electronic components. The PCB board includes a substrate layer, a conductive layer, a dielectric layer, and a magnetic thin film layer. The PCB board is prepared by the following method:

[0010] Step S1: A groove is formed on the dielectric layer by laser etching, then the magnetic composite material is filled into the groove, and finally the magnetic composite material is cured on the dielectric layer to form a shielding wall;

[0011] Step S2: A copper foil is attached to the surface of the substrate, a photoresist is coated on the surface of the copper foil, and the signal path pattern is transferred to the photoresist through ultraviolet light exposure and development. The copper foil is etched using a ferric chloride solution, and only the copper foil in the signal path part is retained to form a conductive layer;

[0012] Step S3: A magnetic thin film layer is deposited on the surface of the conductive layer by magnetron sputtering technology, and then an antioxidant coating is formed on the surface of the magnetic thin film layer by chemical vapor deposition process;

[0013] Step S4: After stacking each layer of materials in the order of magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer, they are pressed and formed into a multi-layer;

[0014] Step S5: Vias are formed between the conductive layers on the multi-layer by a drilling machine, and chemical copper plating and electroplating copper treatment are performed on the vias.

[0015] Furthermore: In step S1, the cross-section of the groove is trapezoidal, the upper width of the groove is 50 µm, the lower width is 30 µm, and the ratio of the depth to the thickness of the dielectric layer is 0.8 - 0.9.

[0016] Furthermore: In step S1, the magnetic composite material, by weight, specifically consists of: 40 - 50 parts of nickel-zinc ferrite particles; 15 - 25 parts of cobalt-based alloy particles; 25 - 35 parts of modified epoxy resin; 3 - 7 parts of liquid crystal polymer; 1 - 3 parts of nano graphene; 2 - 5 parts of silane coupling agent, 3 parts of boron nitride particles; 2 parts of phosphate ester flame retardant; 0.8 part of fluorine-containing surfactant.

[0017] Furthermore: The specific steps of step S1 are as follows:

[0018] S11: The surface of the dielectric layer is subjected to plasma cleaning to remove surface contaminants, and then a groove is etched on the surface of the dielectric layer by an ultraviolet laser etching device. The material is removed layer by layer using the multiple scanning method, and the etched groove surface is subjected to plasma spraying treatment to fill the existing micropores;

[0019] S12: The glue solution prepared from the magnetic composite material is sprayed into the groove using a microspraying machine. The viscosity of the glue solution is controlled at 1000 - 2000 cps, the spraying pressure is 0.1 - 0.2 MPa, and the groove is filled by multiple coverages during the spraying process;

[0020] After spraying is completed, use a vacuum chamber device to degas the filled dielectric layer. Control the negative pressure at -0.7 MPa for 10 minutes, and control the ambient temperature to 40 - 45 °C to accelerate the discharge of bubbles;

[0021] S13. Use a microsprayer to inject the magnetic composite adhesive into the groove again, and supplement the groove until it is completely filled. During the spraying process, control the nozzle pressure at 0.1 - 0.15 MPa and the flow rate at 0.05 mL / s;

[0022] S14. Place the dielectric layer in a curing device. The curing process is as follows:

[0023] The first temperature control stage: Raise the temperature to 55 - 65 °C and maintain it for 8 - 12 minutes to initially harden the material surface and reduce the material fluidity.

[0024] The second temperature control stage: Raise the temperature from 55 - 65 °C to 85 - 95 °C, slowly increase the temperature at a rate of 4 - 6 °C per minute, and maintain it for 15 - 25 minutes to release the internal stress of the material and enhance the stability of the internal structure.

[0025] The third temperature control stage: Further raise the temperature to 125 - 135 °C, slowly increase it at a rate of 1 - 3 °C per minute, and maintain it for 35 - 45 minutes to complete the crosslinking and curing of the filling material.

[0026] The cooling stage: After curing is completed, gradually reduce the temperature to room temperature of 20 - 30 °C at a cooling rate of 1 - 3 °C per minute to avoid thermal stress caused by rapid cooling.

[0027] Furthermore: The curing process of S14 is as follows:

[0028] The first temperature control stage: Place the dielectric layer filled with the magnetic composite material in the curing device, raise the temperature to 60 °C, and maintain it for 10 minutes to initially harden the material surface and reduce the material fluidity;

[0029] The second temperature control stage: Raise the temperature from 60 °C to 90 °C, slowly increase the temperature at a rate of 5 °C per minute, and maintain it for 20 minutes to release the internal stress of the material and enhance the stability of the internal structure;

[0030] The third temperature control stage: Further raise the temperature to 130 °C, slowly increase it at a rate of 2 °C per minute, and maintain it for 40 minutes to complete the crosslinking and curing of the filling material;

[0031] The cooling stage: After curing is completed, gradually reduce the temperature to room temperature of 25 °C at a cooling rate of 1 °C per minute to avoid thermal stress caused by rapid cooling.

[0032] Furthermore: The specific steps of step S3 are as follows:

[0033] S31. During the magnetron sputtering process, a cobalt-iron alloy target is used, the vacuum degree is controlled at -0.8 to -1.0 MPa, the sputtering power is 200 - 400 W, high-purity argon gas is introduced, and the gas flow rate is 10 - 20 sccm, obtaining a magnetic thin film layer with a thickness of 1 - 3 µm;

[0034] S32. An antioxidant coating is formed on the surface of the magnetic thin film layer by chemical vapor deposition. The coating thickness is 50 - 100 nm, the reaction pressure is 10 - 50 Pa, the substrate temperature is 150 - 250 °C, and the reaction time is 10 - 20 minutes;

[0035] S33. An oxygen-free copper wire microcoil with a wire diameter of 10 - 20 µm is arranged below the magnetic thin film layer. The embedding depth of the coil is 20 - 50 µm, and it is fixed by filling with epoxy resin. The curing conditions are 80 - 100 °C and the time is 30 minutes.

[0036] Furthermore: The preparation process of the magnetic composite material:

[0037] Surface modification of magnetic particles: Put 45 parts of nickel-zinc ferrite particles and 20 parts of cobalt-based alloy particles into a container.

[0038] Prepare a silane coupling agent solution. Weigh 3 parts of silane coupling agent according to the formula ratio and dissolve it in absolute ethanol to control its concentration at 3% (mass fraction, w / w).

[0039] Add 3% silane coupling agent ethanol solution to the container, stir evenly, soak for 30 minutes, take out the soaked particles, and place them in an oven to dry at 80 - 100 °C for 1 hour;

[0040] First-stage mixing: Add the surface-modified particles and 30 parts of modified epoxy resin to the mixing equipment and stir at a speed of 200 rpm for 15 minutes under vacuum conditions;

[0041] Second-stage mixing: Add 5 parts of liquid crystal polymer, 3 parts of boron nitride particles, and 2 parts of phosphate flame retardant to the stirred material, increase the rotation speed to 500 - 1000 rpm, and stir for 20 minutes;

[0042] High-speed shear dispersion: Add 2 parts of nano-graphene and use a high-speed disperser for dispersion treatment. The shear rate is 2000 - 3000 rpm, and the dispersion time is 5 minutes to ensure that the particles are evenly distributed in the matrix;

[0043] Vacuum degassing: Place the mixed material in a vacuum degassing equipment, control the vacuum degree at -0.8 to -0.9 MPa. During the degassing process, apply a dynamic vibration of 20 - 50 Hz for 10 - 15 minutes to remove the bubbles in the material;

[0044] Viscosity adjustment: Test the viscosity of the mixed material to ensure it is controlled within 1000 - 2000 cps. Add 0.8 parts of fluorosurfactant to further improve the fluidity of the material and enhance the filling performance.

[0045] If the viscosity of the material exceeds the range, add 1% - 3% of the modified epoxy diluent based on the total weight and stir evenly.

[0046] Filtration: Filter the mixed material through a 200 - mesh filter screen to remove large - particle impurities present.

[0047] Furthermore: Specifically in S12, after each spraying to form a glue - liquid layer with a depth of 1 / 5 of the groove, perform a degassing treatment on the filled dielectric layer with a negative pressure of - 0.7 MPa for 10 minutes, and control the ambient temperature at 40 - 45 °C.

[0048] Furthermore: Before filling the groove on the surface of the dielectric layer in step S1, attach a polyimide masking film with a thickness of 10 - 20 µm on the outer surface of the dielectric layer, expose the groove area through laser etching, and remove the masking film after filling.

[0049] Comparing with the deficiencies of the prior art, the beneficial effects of the present invention are as follows:

[0050] By using the shielding wall prepared and formed with magnetic composite materials and its curing process, the shielding effectiveness can be effectively improved in the PCB board, and it has significant advantages in the high - frequency band (1 MHz - 10 GHz). BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic structural diagram of the PCB board of the present invention;

[0052] Figure 2 It is a process flow chart of the present invention;

[0053] Figure 3 It is a schematic diagram of the cooperation steps of the dielectric layer and the masking film of the present invention;

[0054] Figure 4 It is a relationship curve graph of the porosity and signal loss of the present invention.

[0055] Magnetic thin - film layer 1, conductive layer 2, dielectric layer 3, substrate layer 4, groove 30, masking film 5. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0056] In order to make the objectives and advantages of the present invention clearer and more understandable, the present invention will be further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0057] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and do not limit the protection scope of the present invention.

[0058] It should be noted that in the description of the present invention, the terms indicating directions or positional relationships such as "upper", "lower", "left", "right", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings. This is only for convenience of description and does not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0059] In addition, it should also be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installation", "connection", "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0060] After stacking each layer of materials in the order of magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer, it is pressed and formed into multiple layers;

[0061] Reference Figure 1 For the PCB board provided by the embodiment of the present invention, specifically including: the PCB board has a multi-layer structure and is used to load electronic components. The PCB board includes a substrate layer, a conductive layer, a dielectric layer, and a magnetic thin film layer, wherein there are two conductive layers, and the dielectric layer is arranged between the two conductive layers. The uppermost layer of the PCB board is the magnetic thin film layer, the lowermost layer is the substrate layer, and the two conductive layers are respectively placed below the magnetic thin film layer and above the substrate layer.

[0062] Reference Figures 2 - 3 The method for preparing the PCB board provided by the embodiment of the present invention:

[0063] Step 1: Perform plasma cleaning on the surface of the dielectric layer 3 to remove surface contaminants, and then etch a groove 30 on the surface of the dielectric layer 3 through an ultraviolet laser etching device. The cross-section of the groove 30 is trapezoidal, the upper width of the groove is 50 µm, the lower width is 30 µm, and the ratio of the depth to the thickness of the dielectric layer is 0.8 - 0.9.

[0064] Adopt the multi-scan method to remove materials layer by layer, and perform plasma spraying treatment on the surface of the etched groove 30 to fill the existing micropores.

[0065] To achieve the injection of glue into the grooves of the dielectric layer, first, a layer of polyimide masking film 5 (with a thickness of 10 - 20 µm) is coated on the surface of the dielectric layer, and the groove 30 area is precisely cut and exposed through laser etching; the edge of the masking film 5 needs to be aligned with the groove boundary to ensure complete coverage of the area outside the groove 30.

[0066] Use a high-precision microspraying machine from Nordson EFD, combined with a three-axis motion platform. The spraying parameters are set as follows: pressure: 0.1 MPa (initial spraying) to 0.15 MPa (supplementary spraying); flow rate: 0.05 - 0.1 mL / s to control the amount of glue; distance: the distance between the nozzle and the groove surface is 5 - 10 mm, and the glue made of magnetic composite material is sprayed into the groove.

[0067] The viscosity of the glue is controlled at 1000 - 2000 cps, the spraying pressure is 0.1 - 0.2 MPa, and the groove is filled through multiple thin-layer coverings during the spraying process. After each spraying, the thickness of the glue is controlled at 1 / 5 of the groove depth. After each layer of spraying is completed, a vacuum chamber device is used to degas the filled dielectric layer. The negative pressure is controlled at -0.7 MPa for 10 minutes, and the ambient temperature is controlled at 40 - 45 °C to accelerate the discharge of air bubbles.

[0068] Supplementary spraying and removal of the masking film: Use the microspraying machine again to inject the magnetic composite material glue into the groove. During the spraying process, control the nozzle pressure at 0.1 - 0.15 MPa and the flow rate at 0.05 mL / s. After the groove is filled completely, remove the masking film, and use plasma to clean the surface of the dielectric layer to ensure no glue residue on the outer surface. Before removing the polyimide masking film, detect the flatness of the surface of the magnetic composite material glue in the filled groove, and control the flatness error within ±5%. This can be achieved by scanning one or more laser lines on the glue surface through a laser profiler, capturing the deformation of the light reflection through a camera to calculate the surface height distribution, comparing the measured glue surface height data with the ideal plane, calculating the deviation value of each point, and using software to convert the measurement results into a color distribution map or a height distribution map, so as to quickly locate which areas are higher or lower than the set tolerance.

[0069] After finding areas that are locally too high or too low, corresponding correction strategies can be taken: for locally too low areas, use the microspraying machine to add a small amount of glue to this part; if it is locally too high, gently remove or level the excess glue with a micro spatula or a special adsorption mechanism.

[0070] Place the dielectric layer in a curing device (this is a UVLED curing machine) so that the magnetic composite material in the groove 30 cures to form a shielding wall. An example of this curing process is:

[0071] The first temperature control stage: Place the dielectric layer filled with magnetic composite material in the curing device, raise the temperature to 60 °C, and maintain it for 10 minutes to preliminarily harden the material surface and reduce the material fluidity;

[0072] The second temperature control stage: Raise the temperature from 60 °C to 90 °C, slowly increase the temperature at a rate of 5 °C / minute, and maintain it for 20 minutes to release the internal stress of the material and enhance the stability of the internal structure;

[0073] The third temperature control stage: Further raise the temperature to 130 °C, slowly increase it at a rate of 2 °C / minute, and maintain it for 40 minutes to complete the crosslinking and curing of the filling material;

[0074] The cooling stage: After the curing is completed, gradually reduce the temperature to room temperature of 25 °C at a cooling rate of 2 °C / minute to avoid thermal stress caused by rapid cooling.

[0075] Place the dielectric layer in the curing device (this is a UVLED curing machine). The curing process example two is as follows:

[0076] The first temperature control stage: Raise the temperature to 55 °C and maintain it for 8 minutes to preliminarily harden the material surface and reduce the material fluidity,

[0077] The second temperature control stage: Raise the temperature from 55 °C to 85 °C, slowly increase the temperature at a rate of 4 °C / minute, and maintain it for 15 minutes to release the internal stress of the material and enhance the stability of the internal structure,

[0078] The third temperature control stage: Further raise the temperature to 125 °C, slowly increase it at a rate of 1 °C / minute, and maintain it for 35 minutes to complete the crosslinking and curing of the filling material,

[0079] The cooling stage: After the curing is completed, gradually reduce the temperature to room temperature of 20 °C at a cooling rate of 1 °C / minute to avoid thermal stress caused by rapid cooling.

[0080] Place the dielectric layer in the curing device (this is a UVLED curing machine). The curing process example three is as follows:

[0081] The first temperature control stage: Raise the temperature to 65 °C and maintain it for 12 minutes to preliminarily harden the material surface and reduce the material fluidity,

[0082] The second temperature control stage: Raise the temperature from 65 °C to 95 °C, slowly increase the temperature at a rate of 6 °C / minute, and maintain it for 25 minutes to release the internal stress of the material and enhance the stability of the internal structure,

[0083] The third temperature control stage: Further raise the temperature to 135 °C, slowly increase it at a rate of 3 °C / minute, and maintain it for 45 minutes to complete the crosslinking and curing of the filling material,

[0084] Cooling stage: After curing is completed, the temperature is gradually reduced to room temperature of 30°C at a cooling rate of 3°C per minute to avoid thermal stress caused by rapid cooling. Finally, the purpose of fabricating a shielding wall on the dielectric layer is achieved. The functions of the shielding wall are: reducing interlayer crosstalk, suppressing electromagnetic interference (EMI), and enhancing signal integrity.

[0085] Among them, crosstalk refers to the interference of a signal on one signal path to an adjacent signal path, resulting in signal distortion or error codes.

[0086] The shielding wall forms a physical isolation between different signal layers, blocks or weakens the coupling of electromagnetic waves, significantly reduces the crosstalk phenomenon, and ensures the independence and stability of each signal path.

[0087] Among them, electromagnetic interference (EMI) refers to the electromagnetic wave interference from external or internal sources, which affects the transmission of sensitive signals on the PCB.

[0088] The shielding wall utilizes the electromagnetic shielding characteristics of high-permeability materials to absorb or reflect unwanted electromagnetic waves, reduce their impact on internal signals, and improve the electromagnetic compatibility of the PCB.

[0089] Among them, signal integrity refers to the ability of a signal to maintain its original waveform and characteristics during transmission.

[0090] By isolating different signal layers, the shielding wall helps to maintain the clarity and stability of the signal, avoid signal distortion or distortion caused by interference, and thus ensure the accurate transmission of high-speed signals.

[0091] Step 2: Bond a copper foil with a thickness of 18 - 35 µm to the surface of the substrate to form the basis of the conductive layer. Coat a photoresist with a thickness of 30 µm on the surface of the copper foil. Transfer the signal path pattern to the photoresist through ultraviolet light exposure and development. The exposure energy is 300 mJ / cm². Etch the copper foil using ferric chloride solution. The etching temperature is 55°C and the time is 90 seconds. Only the copper foil in the signal path part is retained to form the conductive layer; perform micro-etching on the surface of the conductive layer to make its roughness reach 1 - 3 µm.

[0092] Step 3: Deposit a magnetic thin film layer on the surface of the conductive layer by magnetron sputtering technology. Specifically, a cobalt-iron alloy target is used during magnetron sputtering. The vacuum degree is controlled at -0.8 to -1.0 MPa, the sputtering power is 200 - 400 W, high-purity argon gas is introduced, and the gas flow rate is 10 - 20 sccm, obtaining a magnetic thin film layer with a thickness of 1 - 3 µm.

[0093] Form an antioxidant coating on the surface of the magnetic thin film layer by chemical vapor deposition process. The coating thickness is 50 - 100 nm, the reaction pressure is 10 - 50 Pa, the substrate temperature is 150 - 250°C, and the reaction time is 10 - 20 minutes;

[0094] An oxygen-free copper wire microcoil with a wire diameter of 10 - 20 µm can be arranged below the magnetic thin film layer. The embedding depth of the coil is 20 - 50 µm, and it is fixed by filling with epoxy resin. The curing conditions are 80 - 100 °C and the time is 30 minutes.

[0095] Step Four: Stack the layers of materials in the order of magnetic thin film layer 1 - conductive layer 21 - dielectric layer 3 - conductive layer 22 - substrate layer 4, and then press and mold them into multiple layers.

[0096] Step Five: Form vias between the conductive layers on the multi-layer by a drilling machine, and perform electroless copper plating and electroplating copper treatment on the vias.

[0097] The specific components of the magnetic composite material by weight are: 40 - 50 parts of nickel-zinc ferrite particles; 15 - 25 parts of cobalt-based alloy particles; 25 - 35 parts of modified epoxy resin; 3 - 7 parts of liquid crystal polymer; 1 - 3 parts of nano-graphene; 2 - 5 parts of silane coupling agent, 3 parts of boron nitride particles; 2 parts of phosphate flame retardant; 0.8 part of fluorine-containing surfactant.

[0098] Example One of the preparation process of the magnetic composite material is as follows:

[0099] Surface modification of magnetic particles: Place 45 parts of nickel-zinc ferrite particles and 20 parts of cobalt-based alloy particles in a container.

[0100] Prepare the silane coupling agent solution: Weigh 3 parts of silane coupling agent according to the formula ratio, dissolve it in absolute ethanol, and control its concentration at 3% (mass fraction, w / w).

[0101] Add 3% of the silane coupling agent ethanol solution to the container, stir evenly, soak for 30 minutes, take out the soaked particles, and place them in an oven to dry at 80 - 100 °C for 1 hour.

[0102] First-stage mixing: Add the surface-modified magnetic particles and 30 parts of modified epoxy resin to a mixing device, and stir at a speed of 200 rpm for 15 minutes under vacuum conditions.

[0103] Second-stage mixing: Add 5 parts of liquid crystal polymer, 3 parts of boron nitride particles, and 2 parts of phosphate flame retardant to the stirred material, increase the rotation speed to 500 - 1000 rpm, and stir for 20 minutes.

[0104] High-speed shear dispersion: Add 2 parts of nano-graphene, and use a high-speed disperser for dispersion treatment. The shear rate is 2000 - 3000 rpm, and the dispersion time is 5 minutes to ensure uniform distribution of the particles and avoid particle agglomeration.

[0105] Vacuum degassing: Place the mixed materials in a vacuum degassing device, control the vacuum degree at -0.8 to -0.9 MPa. During the degassing process, apply dynamic vibration at 20 - 50 Hz for 10 - 15 minutes to remove the air bubbles in the materials and improve the material density and uniformity.

[0106] Viscosity adjustment: Test the viscosity of the mixed materials to ensure it is controlled within 1000 - 2000 cps. Add 0.8 parts of fluorosurfactant to further improve the fluidity of the materials and enhance the filling performance.

[0107] If the material viscosity exceeds the range, add 1% - 3% of the modified epoxy diluent based on the total weight and stir evenly.

[0108] Filtration: Filter the mixed materials through a 200 - mesh filter screen to remove the existing large - particle impurities.

[0109] Example two of the preparation process of the magnetic composite material is as follows:

[0110] Surface modification of magnetic particles: Place 40 parts of nickel - zinc ferrite particles and 15 parts of cobalt - based alloy particles in a container.

[0111] Prepare the silane coupling agent solution: Weigh 2 parts of silane coupling agent according to the formula ratio, dissolve it in anhydrous ethanol, and control its concentration at 3% (mass fraction, w / w);

[0112] Add 3% of the silane coupling agent ethanol solution to the container, stir evenly, soak for 30 minutes, take out the soaked particles, and place them in an oven to dry at 80 - 100 °C for 1 hour.

[0113] First - stage mixing: Add the surface - modified magnetic particles and 25 parts of modified epoxy resin to a mixing device, and stir at a speed of 200 rpm for 15 minutes under vacuum conditions.

[0114] Second - stage mixing: Add 3 parts of liquid crystal polymer, 3 parts of boron nitride particles, and 2 parts of phosphate - based flame retardant to the stirred materials, increase the rotation speed to 500 - 1000 rpm, and stir for 20 minutes.

[0115] High - speed shear dispersion: Add 2 parts of nano - graphene, and use a high - speed disperser for dispersion treatment. The shear rate is 2000 - 3000 rpm, and the dispersion time is 5 minutes to ensure that the particles are evenly distributed in the matrix.

[0116] Vacuum degassing: Place the mixed materials in a vacuum degassing device, control the vacuum degree at -0.8 to -0.9 MPa. During the degassing process, apply dynamic vibration at 20 - 50 Hz for 10 - 15 minutes to remove the air bubbles in the materials.

[0117] Viscosity adjustment: Test the viscosity of the mixed material to ensure it is controlled within 1000 - 2000 cps. Add 0.8 parts of fluorosurfactant to further improve the fluidity of the material and enhance the filling performance.

[0118] If the material viscosity exceeds the range, add 1% - 3% of the total weight of modified epoxy diluent and stir evenly.

[0119] Filtration: Filter the mixed material through a 200 - mesh filter screen to remove large - particle impurities present.

[0120] Example three of the preparation process of magnetic composite materials is as follows:

[0121] Surface modification of magnetic particles: Place 50 parts of nickel - zinc ferrite particles and 25 parts of cobalt - based alloy particles in a container;

[0122] Prepare silane coupling agent solution: Weigh 2 parts of silane coupling agent according to the formula ratio and dissolve it in absolute ethanol to control its concentration at 3% (mass fraction, w / w);

[0123] Add 3% of the silane coupling agent ethanol solution to the container, stir evenly, soak for 30 minutes, take out the soaked particles, and place them in an oven to dry for 1 hour at 80 - 100 °C.

[0124] First - stage mixing: Add the surface - modified magnetic particles and 35 parts of modified epoxy resin to the mixing equipment and stir at a speed of 200 rpm for 15 minutes under vacuum conditions.

[0125] Second - stage mixing: Add 7 parts of liquid - crystal polymer, 3 parts of boron nitride particles, and 2 parts of phosphate - based flame retardant to the stirred material, increase the speed to 500 - 1000 rpm, and stir for 20 minutes.

[0126] High - speed shear dispersion: Add 2 parts of nano - graphene and use a high - speed disperser for dispersion treatment. The shear rate is 2000 - 3000 rpm and the dispersion time is 5 minutes to ensure that the particles are evenly distributed in the matrix.

[0127] Vacuum degassing: Place the mixed material in a vacuum degassing equipment, control the vacuum degree at - 0.8 to - 0.9 MPa. During the degassing process, apply a dynamic vibration of 20 - 50 Hz for 10 - 15 minutes to remove air bubbles in the material.

[0128] Viscosity adjustment: Test the viscosity of the mixed material to ensure it is controlled within 1000 - 2000 cps. Add 0.8 parts of fluorosurfactant to further improve the fluidity of the material and enhance the filling performance.

[0129] If the material viscosity exceeds the range, add 1% - 3% of the total weight of modified epoxy diluent and stir evenly.

[0130] Filtration: Filter the mixed materials through a 200-mesh filter screen to remove the existing large particle impurities.

[0131] Example 1:

[0132] Spray the magnetic composite material glue obtained in the first example of the preparation process of the magnetic composite material onto the dielectric layer through a high-precision micro sprayer of Nordson EFD. The specific process is as described above. After supplementing the grooves until they are completely filled, remove the masking film, and clean the surface of the dielectric layer with plasma to ensure that there is no glue residue on the outer surface. Finally, place the dielectric layer in a curing device (this is a UVLED curing machine) and use the first implementation method of the curing process to obtain a dielectric layer with a shielding wall. Then combine the dielectric layer with the conductive layer and the magnetic thin film layer obtained in Step 2 and Step 3, and stack them in the following order according to Step 4: magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer, and then press and form them into multiple layers. Finally, obtain a multi-layer PCB board after Step 5, named Sample 1.

[0133] Example 2:

[0134] Spray the magnetic composite material glue obtained in the first example of the preparation process of the magnetic composite material onto the dielectric layer through a high-precision micro sprayer of Nordson EFD. The specific process is as described above. After supplementing the grooves until they are completely filled, remove the masking film, and clean the surface of the dielectric layer with plasma to ensure that there is no glue residue on the outer surface. Finally, place the dielectric layer in a curing device (this is a UVLED curing machine) and use the second implementation method of the curing process to obtain a dielectric layer with a shielding wall. Then combine the dielectric layer with the conductive layer and the magnetic thin film layer obtained in Step 2 and Step 3, and stack them in the following order according to Step 4: magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer, and then press and form them into multiple layers. Finally, obtain a multi-layer PCB board after Step 5, named Sample 2.

[0135] Example 3:

[0136] Spray the magnetic composite material glue obtained in the first example of the preparation process of the magnetic composite material onto the dielectric layer through a high-precision micro sprayer of Nordson EFD. The specific process is as described above. After supplementing the grooves until they are completely filled, remove the masking film, and clean the surface of the dielectric layer with plasma to ensure that there is no glue residue on the outer surface. Finally, place the dielectric layer in a curing device (this is a UVLED curing machine) and use the third implementation method of the curing process to obtain a dielectric layer with a shielding wall. Then combine the dielectric layer with the conductive layer and the magnetic thin film layer obtained in Step 2 and Step 3, and stack them in the following order according to Step 4: magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer, and then press and form them into multiple layers. Finally, obtain a multi-layer PCB board after Step 5, named Sample 3.

[0137] Example 4:

[0138] The magnetic composite material adhesive solution obtained in Preparation Process Example 2 of the magnetic composite material was sprayed on the dielectric layer by a high-precision micro sprayer of Nordson EFD. The specific process was as described above. After supplementing the grooves until they were completely filled, the masking film was removed, and the surface of the dielectric layer was cleaned with plasma to ensure that there was no residual adhesive solution on the outer surface. Finally, the dielectric layer was placed in a curing device (this was a UV LED curing machine) and the dielectric layer with a shielding wall was obtained by using the implementation method of Example 1 in the curing process. Then, the dielectric layer was combined with the conductive layer and the magnetic thin film layer obtained in Step 2 and Step 3. In the manner of Step 4: magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer, they were stacked and then compression molded into multiple layers. Finally, a multilayer PCB board named Sample 4 was obtained after Step 5.

[0139] Example 5:

[0140] The magnetic composite material adhesive solution obtained in Preparation Process Example 2 of the magnetic composite material was sprayed on the dielectric layer by a high-precision micro sprayer of Nordson EFD. The specific process was as described above. After supplementing the grooves until they were completely filled, the masking film was removed, and the surface of the dielectric layer was cleaned with plasma to ensure that there was no residual adhesive solution on the outer surface. Finally, the dielectric layer was placed in a curing device (this was a UV LED curing machine) and the dielectric layer with a shielding wall was obtained by using the implementation method of Example 2 in the curing process. Then, the dielectric layer was combined with the conductive layer and the magnetic thin film layer obtained in Step 2 and Step 3. In the manner of Step 4: magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer, they were stacked and then compression molded into multiple layers. Finally, a multilayer PCB board named Sample 5 was obtained after Step 5.

[0141] Example 6:

[0142] The magnetic composite material adhesive solution obtained in Preparation Process Example 2 of the magnetic composite material was sprayed on the dielectric layer by a high-precision micro sprayer of Nordson EFD. The specific process was as described above. After supplementing the grooves until they were completely filled, the masking film was removed, and the surface of the dielectric layer was cleaned with plasma to ensure that there was no residual adhesive solution on the outer surface. Finally, the dielectric layer was placed in a curing device (this was a UV LED curing machine) and the dielectric layer with a shielding wall was obtained by using the implementation method of Example 3 in the curing process. Then, the dielectric layer was combined with the conductive layer and the magnetic thin film layer obtained in Step 2 and Step 3. In the manner of Step 4: magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer, they were stacked and then compression molded into multiple layers. Finally, a multilayer PCB board named Sample 6 was obtained after Step 5.

[0143] Example 7:

[0144] The magnetic composite material glue obtained in Example 3 of the preparation process of the magnetic composite material is sprayed on the dielectric layer through a high-precision microspraying machine of Nordson EFD. The specific process is as described above. After the grooves are supplemented until completely filled, the masking film is removed, and the surface of the dielectric layer is cleaned with plasma to ensure that there is no glue residue on the outer surface. Finally, the dielectric layer is placed in a curing device (this is a UVLED curing machine) and the dielectric layer with a shielding wall is obtained by using the implementation method of Example 1 of the curing process. Then, the dielectric layer is combined with the conductive layer and the magnetic thin film layer obtained in Step 2 and Step 3. In the manner of Step 4: magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer, they are stacked and then pressed into a multi-layer. Finally, a multi-layer PCB board, named Sample Seven, is obtained after Step 5.

[0145] Example Eight:

[0146] The magnetic composite material glue obtained in Example 3 of the preparation process of the magnetic composite material is sprayed on the dielectric layer through a high-precision microspraying machine of Nordson EFD. The specific process is as described above. After the grooves are supplemented until completely filled, the masking film is removed, and the surface of the dielectric layer is cleaned with plasma to ensure that there is no glue residue on the outer surface. Finally, the dielectric layer is placed in a curing device (this is a UVLED curing machine) and the dielectric layer with a shielding wall is obtained by using the implementation method of Example 2 of the curing process. Then, the dielectric layer is combined with the conductive layer and the magnetic thin film layer obtained in Step 2 and Step 3. In the manner of Step 4: magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer, they are stacked and then pressed into a multi-layer. Finally, a multi-layer PCB board, named Sample Eight, is obtained after Step 5.

[0147] Example Nine:

[0148] The magnetic composite material glue obtained in Example 3 of the preparation process of the magnetic composite material is sprayed on the dielectric layer through a high-precision microspraying machine of Nordson EFD. The specific process is as described above. After the grooves are supplemented until completely filled, the masking film is removed, and the surface of the dielectric layer is cleaned with plasma to ensure that there is no glue residue on the outer surface. Finally, the dielectric layer is placed in a curing device (this is a UVLED curing machine) and the dielectric layer with a shielding wall is obtained by using the implementation method of Example 3 of the curing process. Then, the dielectric layer is combined with the conductive layer and the magnetic thin film layer obtained in Step 2 and Step 3. In the manner of Step 4: magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer, they are stacked and then pressed into a multi-layer. Finally, a multi-layer PCB board, named Sample Nine, is obtained after Step 5.

[0149] Shielding Effectiveness Test: The shielding effectiveness of the test samples in the frequency band from 1 MHz to 10 GHz is tested in dB to verify the performance of the samples in signal shielding.

[0150] Thermal conductivity test: Measure the thermal conductivity of the sample (unit: W / m·K) using a laser thermal conductivity meter, and simultaneously conduct a thermal cycle stability test.

[0151] Chemical stability test: Place the sample in acidic (pH = 3) and alkaline (pH = 10) environments, and analyze the retention rates of shielding effectiveness and mechanical properties.

[0152] Signal integrity test: Measure signal loss and crosstalk in high-speed signal transmission scenarios to verify the applicability of the sample in electronic devices.

[0153] Comparison data table 1 obtained by detecting Sample 1, Sample 2, Sample 3, Sample 4, Sample 5, Sample 6, Sample 7, Sample 8, and Sample 9:

[0154]

[0155] Comparative Example 1: Spray the magnetic composite material glue obtained in the preparation process example 1 of the magnetic composite material onto the dielectric layer through a high-precision micro sprayer of Nordson EFD. The specific steps are sprayed into the grooves of the dielectric layer by the specific spraying method in Sample 1, and then the dielectric layer is sent to a curing device (this is a UVLED curing machine) for curing. When curing, set the constant temperature curing temperature to 120°C and keep it for 60 minutes to complete crosslinking curing. After curing, cool the sample to room temperature (20 - 30°C) in a natural cooling manner. Finally, obtain the dielectric layer. Combine this dielectric layer with the conductive layer and magnetic thin film layer obtained in Step 2 and Step 3, stack them in the manner of Step 4: magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer, and then press and form them into multiple layers. Finally, obtain a multi-layer PCB board through Step 5, named Sample 10.

[0156] Comparative Example 2: Spray the magnetic composite material glue obtained in the preparation process example 1 of the magnetic composite material onto the dielectric layer through a high-precision micro sprayer of Nordson EFD. The specific steps are sprayed into the grooves of the dielectric layer by the specific spraying method in Sample 1, and then the dielectric layer is sent to a curing device (this is a UVLED curing machine) for curing. Set the initial temperature to 40°C and continuously raise the temperature to 130°C at a rate of 3°C per minute. After reaching the target temperature, keep it at a constant temperature for 40 minutes to complete crosslinking curing. After curing, cool the temperature to room temperature (20 - 30°C) at a rate of 1°C per minute. Finally, obtain the dielectric layer. Combine this dielectric layer with the conductive layer and magnetic thin film layer obtained in Step 2 and Step 3, stack them in the manner of Step 4: magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer, and then press and form them into multiple layers. Finally, obtain a multi-layer PCB board through Step 5, named Sample 11.

[0157] Data comparison table 2 based on Sample 10, Sample 11 and Sample 1:

[0158]

[0159] According to Table 1, Table 2 and Figure 4 the relationship curve between porosity and signal loss in

[0160] The following analysis is carried out from the perspective of the finally obtained different samples (Sample 1 to Sample 9), focusing on their performance in key indicators such as shielding effectiveness, thermal conductivity, porosity, thermal stability, chemical stability and signal loss, and exploring the relationship between these performance indicators and the material formulations and process conditions adopted respectively.

[0161] Sample 1 (Formulation Example 1 + Curing Process Example 1):

[0162] Shielding effectiveness is 20 dB, thermal conductivity is 8 W / m·K, porosity is <0.3%, thermal stability is 95%, chemical stability (acid / alkali retention rate) is 92 / 94, and signal loss is 0.15 dB.

[0163] Generally speaking, Sample 1 performs excellently in all indicators: it has a relatively high shielding effectiveness, outstanding thermal conductivity, extremely low porosity, good thermal stability and chemical stability, and relatively low signal loss. This sample can be used as a benchmark for optimizing the process and formulation.

[0164] Sample 2 (Formulation Example 1 + Curing Process Example 2):

[0165] Shielding effectiveness is 17 dB, thermal conductivity is 7 W / m·K, porosity is 0.6%, thermal stability is 88%, chemical stability is 87 / 89, and signal loss is 0.20 dB.

[0166] Compared with Sample 1, the shielding effectiveness and thermal conductivity of Sample 2 are slightly reduced, the porosity increases, and the thermal stability and chemical stability are also slightly inferior, resulting in an increase in signal loss. This result shows that changing the curing process parameters will affect the density and internal structure of the material, thus affecting the overall performance.

[0167] Sample 3 (Formulation Example 1 + Curing Process Example 3):

[0168] Shielding effectiveness is 18 dB, thermal conductivity is 7.5 W / m·K, porosity is 0.4%, thermal stability is 91%, chemical stability is 89 / 90, and signal loss is 0.18 dB.

[0169] Although Sample 3 is slightly lower than Sample 1, its overall performance is still at a relatively high level, indicating that the change in curing conditions has an obvious impact on the release of internal stress and porosity control of the material. The performance of this sample in each indicator is relatively balanced.

[0170] Sample 4 (Formulation Example 2 + Curing Process Example 1):

[0171] Shielding effectiveness of 16 dB, thermal conductivity of 6.8 W / m·K, porosity of 0.7%, thermal stability of 85%, chemical stability of 84 / 86, signal loss of 0.25 dB.

[0172] Compared with the sample using formulation example 1, the indicators of sample four are generally lower than those of sample one, indicating that changes in the formulation (such as reducing the proportion of magnetic particles or adjusting the content of liquid crystal polymer) will affect the density and performance of the material. Under the same curing process, formulation adjustment is an important factor leading to performance changes.

[0173] Sample five (formulation example 2 + curing process example 2):

[0174] Shielding effectiveness of 15 dB, thermal conductivity of 6.6 W / m·K, porosity of 0.8%, thermal stability of 83%, chemical stability of 82 / 84, signal loss of 0.27 dB.

[0175] Compared with sample four, it further decreases. It can be seen that on the basis of a "weaker" formulation, if the curing process control is not as fine as in example 1 and example 3, it will lead to an increase in porosity, a decrease in thermal stability and chemical stability, and ultimately a significant increase in signal loss.

[0176] Sample six (formulation example 2 + curing process example 3):

[0177] Shielding effectiveness of 17 dB, thermal conductivity of 7.2 W / m·K, porosity of 0.5%, thermal stability of 89%, chemical stability of 86 / 88, signal loss of 0.19 dB.

[0178] When sample six is compared with samples two and five, the improvement of the curing process (example 3) can significantly make up for the deficiencies of the formulation, so that the performance has a significant recovery compared with samples four and five. Thus, precise curing conditions help to reduce porosity and improve the overall performance of the material.

[0179] Sample seven (formulation example 3 + curing process example 1):

[0180] Shielding effectiveness of 19 dB, thermal conductivity of 7.8 W / m·K, porosity <0.4%, thermal stability of 93%, chemical stability of 90 / 92, signal loss of 0.16 dB.

[0181] Compared with sample one, sample seven also shows excellent overall performance, indicating that formulation example 3 with a high content of magnetic particles and an appropriate additive ratio can achieve high performance close to or slightly inferior to that of sample one after a suitable curing process (example 1), and has good development potential.

[0182] Sample eight (formulation example 3 + curing process example 2):

[0183] Shielding effectiveness: 18 dB, Thermal conductivity: 7.4 W / m·K, Porosity: 0.5%, Thermal stability: 92%, Chemical stability: 89 / 91, Signal loss: 0.17 dB.

[0184] It is slightly inferior compared to Sample Seven, but still at a relatively good level. This shows that under a high-performance formulation (Example Three), even if the curing conditions are relatively less stringent than those in Example One, good performance can still be maintained.

[0185] Sample Nine (Formulation Example Three + Curing Process Example Three):

[0186] Shielding effectiveness: 19.5 dB, Thermal conductivity: 7.9 W / m·K, Porosity: <0.4%, Thermal stability: 94%, Chemical stability: 91 / 93, Signal loss: 0.16 dB.

[0187] The performance of Sample Nine is similar to or slightly better than that of Sample One and Sample Seven. The shielding effectiveness is close to 20 dB, the porosity is less than 0.4%, and the signal loss is only 0.16 dB. This indicates that when a high-performance formulation (Example Three) is combined with a refined curing process (Example Three), the best comprehensive performance can be achieved. This sample is representative, demonstrating that the optimal matching of material formulation and process conditions can result in the best performance.

[0188] Different formulations (Example One, Example Two, Example Three) and different curing processes (Example One, Example Two, Example Three) jointly determine the comprehensive performance of the final samples. A high proportion of magnetic particles, high-quality surface modification, and appropriate additive ratios can bring better shielding and thermal conductivity performance as well as lower porosity.

[0189] Among all the samples, the lower the porosity (<0.4%), the lower the signal loss, and the higher the shielding effectiveness and stability. This shows that by optimizing the spraying process, vacuum degassing, and curing conditions, bubbles and internal defects can be effectively reduced, achieving better dielectric uniformity and electromagnetic shielding performance.

[0190] Under the same formulation, different strategies for the heating-up, holding, and cooling-down stages of curing directly affect the release of internal stress and curing uniformity. Progressive heating and cooling and sufficient holding time can improve thermal, chemical stability, and electrical performance, reduce internal stress, and thus optimize signal integrity and shielding effect.

[0191] Excellent solutions such as Sample One, Sample Seven, and Sample Nine provide feasible references for practical applications. In actual production, appropriate formulations and curing schemes can be selected according to the operating frequency band of the equipment, thermal management requirements, and environmental tolerance requirements to obtain the best performance.

[0192] By analyzing at the sample level, the interaction relationship among the material formula, process parameters, and final performance was clarified. Optimizing the component ratio and microstructure control of the magnetic composite material, combined with refined curing processes and spraying conditions, high-performance multilayer PCB products with high shielding efficiency, low signal loss, high reliability, and excellent environmental adaptability can be prepared.

[0193] The main difference between Comparative Example 1 (Sample 10) and Comparative Example 2 (Sample 11) lies in the control method of the curing conditions: the former uses a relatively simplified constant-temperature curing and natural cooling, while the latter uses a progressive heating and cooling control.

[0194] Comparison with Sample 1, Sample 7, and Sample 9:

[0195] Samples 1, 7, and 9 represent highly optimized formulations and curing processes. They adopt a multi-stage heating and heat preservation strategy, which can achieve surface curing, internal stress release, and deep cross-linking in different temperature ranges respectively. This meticulous temperature control process helps to significantly reduce the porosity and internal stress, thereby improving the shielding efficiency, thermal conductivity, and signal integrity.

[0196] In contrast, Sample 10 (single constant-temperature curing) lacks the pre-hardening and stress release links in stages, with more internal stress residues and less satisfactory porosity control than expected, resulting in inferior performance compared to the optimized samples. Although Sample 11 has a certain heating and cooling control, it is still only a single progressive curve rather than a multi-stage fine-tuning, and it is still inferior to the optimal solution in terms of stress release and porosity control.

[0197] Comparison with Sample 2 and Sample 5:

[0198] Samples 2 and 5 also adopt relatively simple curing conditions, and their performance is generally inferior to the most optimized samples (such as Samples 1, 7, and 9). As comparative (i.e., reference) solutions, Samples 10 and 11 have similar problems in terms of process fineness to Samples 2 and 5: they fail to precisely control the curing speed and stress release in each temperature section, resulting in relatively mediocre overall performance. This is not the best choice for high-speed PCBs with high requirements for shielding efficiency, thermal conductivity, and low signal loss.

[0199] The correlation between porosity and signal loss:

[0200] From the previous analysis, it can be seen that porosity is one of the key influencing factors. Using a single constant temperature (Sample 10) or only one linear heating and cooling curve (Sample 11) for curing is difficult to effectively expel the tiny air bubbles in the material like multi-stage fine curing, resulting in a relatively high porosity. This will directly lead to an increase in the inhomogeneity of the dielectric layer, causing an increase in signal transmission loss and a decrease in shielding efficiency.

[0201] Stress release and structural uniformity:

[0202] The curing conditions of Sample Ten and Sample Eleven are not as precise in stress relaxation as those of the aforementioned optimal samples (such as Sample One and Sample Nine). The strategy of multi-stage control (such as pre-hardening at low temperature first, then gradually increasing the temperature at medium temperature for stress release, finally curing completely at high temperature, and cooling slowly) is crucial for improving the structural uniformity and stability of the material. These refined measures are not reflected in the comparative examples, so their performance is inferior to that of the optimized examples in terms of porosity, thermal stability, shielding effectiveness, and signal loss.

[0203] The above are only the embodiments of the present invention and are not intended to limit the present invention. Any ordinary changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a PCB board, characterized in that, It includes the following steps: Step S1: Form a groove on the dielectric layer by laser etching, then fill the groove with a magnetic composite material, and finally cure the magnetic composite material on the dielectric layer to form a shielding wall; Step S2: Bond a copper foil on the surface of the substrate, coat a photoresist on the surface of the copper foil, transfer the signal path pattern to the photoresist through ultraviolet light exposure and development, and etch the copper foil with a ferric chloride solution to retain only the copper foil in the signal path part to form a conductive layer; Step S3: Deposit a magnetic thin film layer on the surface of the conductive layer by magnetron sputtering technology, and then form an antioxidant coating on the surface of the magnetic thin film layer by chemical vapor deposition process; Step S4: Stack the layers of materials in the order of magnetic thin film layer - conductive layer - dielectric layer - conductive layer - substrate layer and then press and mold them into multiple layers; Step S5: Form vias between the conductive layers on the multiple layers by a drilling machine, and perform electroless copper plating and electroplating copper treatment on the vias, In step S1, before filling the groove on the surface of the dielectric layer, a polyimide masking film with a thickness of 10 - 20 µm is attached to the outer surface of the dielectric layer, and the groove area is exposed by laser etching. After filling is completed, the masking film is removed.

2. A method for preparing a PCB board according to claim 1, wherein, In step S1, the cross-section of the groove is trapezoidal, the upper width of the groove is 50 µm, the lower width is 30 µm, and the ratio of the depth to the thickness of the dielectric layer is 0.8 - 0.

9.

3. A method for preparing a PCB board according to claim 2, wherein In step S1, the magnetic composite material is calculated by weight, and the specific components are: 40 - 50 parts of nickel-zinc ferrite particles; 15 - 25 parts of cobalt-based alloy particles; 25 - 35 parts of modified epoxy resin; 3 - 7 parts of liquid crystal polymer; 1 - 3 parts of nano-graphene; 2 - 5 parts of silane coupling agent, 3 parts of boron nitride particles; 2 parts of phosphate flame retardant; 0.8 part of fluorinated surfactant.

4. A method for preparing a PCB board according to claim 3, wherein The specific steps of step S1 are as follows: S11: Perform plasma cleaning on the surface of the dielectric layer to remove surface contaminants, then etch a groove on the surface of the dielectric layer by an ultraviolet laser etching device, adopt the multi-scan method to remove materials layer by layer, and perform plasma spraying treatment on the etched groove surface to fill the existing micropores; S12: Use a micro-spraying machine to spray the glue solution prepared from the magnetic composite material into the groove, the viscosity of the glue solution is controlled at 1000 - 2000 cps, the spraying pressure is 0.1 - 0.2 MPa, and the groove is filled by multiple thin layer coverings during the spraying process; After spraying is completed, use a vacuum chamber device to perform degassing treatment on the filled dielectric layer, the negative pressure is controlled at -0.7 MPa, the time is 10 minutes, and the ambient temperature is controlled at 40 - 45 °C to accelerate the discharge of air bubbles; S13: Use the micro-spraying machine again to inject the magnetic composite material glue solution into the groove to supplement the groove until it is completely filled. During the spraying process, control the nozzle pressure at 0.1 - 0.15 MPa and the flow rate at 0.05 mL / s; S14: Place the dielectric layer in a curing device for curing treatment, and the curing process is: The first temperature control stage: Raise the temperature to 55 - 65 °C and keep it for 8 - 12 minutes to initially harden the material surface and reduce the material fluidity, Second temperature control stage: Raise the temperature from 55 - 65°C to 85 - 95°C, slowly increase the temperature at a rate of 4 - 6°C per minute, and maintain for 15 - 25 minutes to release the internal stress of the material and enhance the stability of the internal structure. Third temperature control stage: Further raise the temperature to 125 - 135°C, slowly increase the temperature at a rate of 1 - 3°C per minute, and maintain for 35 - 45 minutes to complete the cross - linking and curing of the filling material. Cooling stage: After the curing is completed, gradually reduce the temperature to room temperature of 20 - 30°C at a cooling rate of 1 - 3°C per minute to avoid thermal stress caused by rapid cooling.

5. A method for preparing a PCB board according to claim 4, characterized in that, The curing process of S14 is as follows: First temperature control stage: Place the dielectric layer filled with magnetic composite material in the curing device, raise the temperature to 60°C, and maintain for 10 minutes to preliminarily harden the material surface and reduce the material fluidity. Second temperature control stage: Raise the temperature from 60°C to 90°C, slowly increase the temperature at a rate of 5°C per minute, and maintain for 20 minutes to release the internal stress of the material. Third temperature control stage: Further raise the temperature to 130°C, slowly increase the temperature at a rate of 2°C per minute, and maintain for 40 minutes to complete the cross - linking and curing of the filling material. Cooling stage: After the curing is completed, gradually reduce the temperature to room temperature of 25°C at a cooling rate of 1°C per minute to avoid thermal stress caused by rapid cooling.

6. A method for preparing a PCB board according to claim 1, characterized in that, The specific steps of step S3 are as follows: S31. During the magnetron sputtering process, a cobalt - iron alloy target is used, the vacuum degree is controlled at - 0.8 to - 1.0 MPa, the sputtering power is 200 - 400 W, high - purity argon gas is introduced, and the gas flow rate is 10 - 20 sccm to obtain a magnetic thin film layer with a thickness of 1 - 3 µm. S32. Form an antioxidant coating on the surface of the magnetic thin film layer through chemical vapor deposition process, the coating thickness is 50 - 100 nm, the reaction pressure is 10 - 50 Pa, the substrate temperature is 150 - 250°C, and the reaction time is 10 - 20 minutes. S33. Arrange an oxygen - free copper wire micro - coil with a wire diameter of 10 - 20 µm under the magnetic thin film layer, the coil embedding depth is 20 - 50 µm, and it is fixed by filling with epoxy resin, and the curing conditions are 80 - 100°C and the time is 30 minutes.

7. A method for preparing a PCB board according to claim 3, characterized in that, The preparation process of the magnetic composite material: Surface modification of magnetic particles: Place 45 parts of nickel - zinc ferrite particles and 20 parts of cobalt - based alloy particles in a container. Prepare a silane coupling agent solution, weigh 3 parts of silane coupling agent according to the formula ratio, dissolve it in absolute ethanol, and control its concentration at 3%. Add 3% silane coupling agent ethanol solution to the container, stir evenly, the treatment time is 30 minutes, take out the treated particles, place them in an oven, and dry them at 80 - 100°C for 1 hour. First - stage mixing: Add the surface - modified particles and 30 parts of modified epoxy resin to the mixing equipment, and stir at a speed of 200 rpm for 15 minutes under vacuum conditions. Second - stage mixing: Add 5 parts of liquid crystal polymer, 3 parts of boron nitride particles and 2 parts of phosphate - based flame retardant to the stirred material, increase the rotation speed to 500 - 1000 rpm, and stir for 20 minutes. High-speed shear dispersion: Add 2 parts of nano-graphene and disperse it using a high-speed disperser. The shear rate is 2000 - 3000 rpm, and the dispersion time is 5 minutes to ensure that the particles are evenly distributed in the matrix; Vacuum degassing: Place the mixed material in a vacuum degassing device, control the vacuum degree at -0.8 to -0.9 MPa. During the degassing process, apply dynamic vibration at 20 - 50 Hz for 10 - 15 minutes to remove the bubbles in the material; Viscosity adjustment: Test the viscosity of the mixed material to ensure it is controlled within 1000 - 2000 cps. Add 0.8 parts of fluorinated surfactant to further improve the fluidity of the material and enhance the filling performance. If the viscosity of the material exceeds the range, add 1% - 3% of the total weight of the modified epoxy diluent and stir evenly; Filtration: Filter the mixed material through a 200-mesh filter screen to remove the existing large particle impurities.

8. A method for preparing a PCB board according to claim 4, wherein, Specifically in S12, after each spraying to form a glue layer with a depth of 1 / 5 of the groove, perform a degassing treatment on the filled dielectric layer with a negative pressure of -0.7 MPa for 10 minutes, and control the ambient temperature at 40 - 45 °C.

9. A PCB board, characterized in that, It is made by using the preparation method of the PCB board according to any one of claims 1 to 8.

Images