A method for manufacturing a thick copper circuit board with exposed blind holes

Abstract

This application discloses a method for manufacturing a thick copper circuit board with exposed blind vias, specifically relating to the field of printed circuit board technology. The equipment includes: pre-pressing and merging inner core boards in groups and using ultrasonic testing to check the bonding degree; dynamically manufacturing outer core boards and blind vias based on measured expansion and contraction coefficients; covering blind vias with dry film and using a horizontal resin plugging process; performing stepped manual polishing to control the amount of copper removed; using adhesive-free PP material for lamination under optimized temperature and pressure; and finally completing the electroplating and etching of the outer layer circuit patterns. This invention effectively solves the problems of interlayer alignment deviation, blind via residue, and uneven surface finish through dynamic expansion and contraction compensation, layered lamination, and precision surface treatment. It achieves high-reliability manufacturing of thick copper circuit boards with blind via depths reaching 50% of the board thickness and copper thickness uniformity within ±5%. Simultaneously, by utilizing a specially formulated adhesive-free PP material, it achieves adhesive-free lamination, effectively avoiding poor conductivity caused by adhesive residue in subsequent processes.

Description

Technical Field

[0001] This application relates to the field of printed circuit board technology, and more specifically, to a method for manufacturing a thick copper circuit board with exposed blind vias. Background Technology

[0002] As electronic devices develop towards miniaturization and high performance, the demand for multilayer blind via circuit boards is increasing. Blind via technology can achieve high-density interconnection between layers, but traditional blind via manufacturing methods have problems such as copper leakage, no copper in the hole, and glue residue, which affect the reliability and performance of the circuit board.

[0003] However, existing blind via thick copper circuit board manufacturing technologies have several shortcomings: First, due to the significant cumulative effect of thermal stress during multilayer board lamination, the core boards of each layer experience non-uniform expansion and contraction due to differences in material properties and thermal history, leading to increased interlayer alignment deviations. This problem is particularly prominent in high-end HDI boards, where conventional static compensation methods are difficult to effectively control cumulative errors, resulting in excessive board deformation and affecting blind via alignment accuracy and circuit integrity. Second, during resin plugging, gaps in the substrate of thick copper areas are prone to forming voids due to residual adhesive or insufficient filling. This not only reduces the mechanical reliability of the circuit board but also leads to corrosion risks caused by residual electroplating solution. Traditional vertical filling processes are prone to surface depressions or protrusions due to difficulties in controlling resin flowability, severely affecting surface flatness and lamination quality. Third, traditional lamination processes use conventional PP materials, which are prone to adhesive overflow and residue in blind vias under high temperature and pressure, leading to poor conductivity or even open circuits during electroplating. At the same time, due to the significant difference between the thermal expansion coefficient of the adhesive and that of copper, delamination is prone to occur during long-term reliability testing.

[0004] Therefore, a method for manufacturing thick copper circuit boards with exposed blind vias is proposed to address the above problems. Summary of the Invention

[0005] The purpose of this application is to provide a method for manufacturing a thick copper circuit board with exposed blind vias.

[0006] The method for manufacturing an exposed blind via thick copper circuit board provided in this application adopts the following technical solution: A method for manufacturing a thick copper circuit board with exposed blind vias includes the following steps: S1. Fabrication of inner core board assembly: The L3-L10 core boards are fabricated and pressed according to the predetermined dynamic expansion and contraction coefficients. The first pressing adopts an expansion and contraction compensation coefficient of +18 in the X direction and +24 in the Y direction. S1.5 Divide the core board of L3-L10 into two groups, L3-L6 and L7-L10, and pre-press them separately. After pre-pressing, use ultrasonic testing to check the interlayer bonding degree. After passing the test, press them together as a whole. S2, Outer Core Board Preparation: Based on the measured expansion and contraction coefficient after S1 lamination, L11-L12 core boards are fabricated and blind hole drilling is completed; S3, Blind via processing of the outermost layer: Based on the measured expansion and contraction coefficients of the L3-L12 layers after overall lamination, blind vias are fabricated in the L1-L2 layers; S4, Residual Resin Hole Plug: After the L3-L12 layer circuit is fabricated, dry film is used to cover the blind hole openings, and a horizontal resin plugging machine is used to fill the gaps in the outer substrate of the thick copper area. S5. Precision surface treatment: Manually polish the plugged hole area, controlling the amount of copper removed to be within the range of 5-8μm. S6, Adhesive-free lamination: Using adhesive-free PP material, lamination is carried out at 190-205℃ and 350-400psi for 25-35 minutes. S7. Outer layer circuit fabrication: Outer layer circuit patterns are fabricated on the surface of the laminated board. The copper thickness of the circuit is made up to the design requirements through electroplating. Then, etching is performed to precisely remove excess copper foil and form a clear outer layer circuit structure.

[0007] Preferably, the method for determining the dynamic expansion and contraction coefficient solves the problem of interlayer deviation accumulation caused by traditional static compensation. The method includes: after completing N layers of lamination and N≥2, the actual deformation of the plate is measured by laser scanning, and the subsequent lamination compensation coefficient is generated iteratively.

[0008] By adopting the above technical solution, this application can dynamically adjust the subsequent lamination parameters according to the actual deformation of the plate, effectively control the cumulative effect of thermal stress caused by multi-layer lamination, and significantly reduce the misalignment between layers.

[0009] Preferably, in order to precisely control the size of the dry film coverage, the thickness of the dry film in step S4 is 15-25 μm, and the coverage area extends 0.3-0.5 mm beyond the edge of the blind hole.

[0010] Preferably, in order to ensure the compactness of the resin filling, the process parameters of the horizontal resin plugging machine include: resin viscosity 800-1200cps, filling pressure 0.4-0.6MPa, and standing curing for 30±5 minutes after filling.

[0011] By adopting the above technical solution, the resin can fully penetrate the gaps in the thick copper substrate, effectively avoiding the voids, surface depressions or protrusions that are easily generated by the traditional vertical filling process. At the same time, static curing ensures that the resin and the substrate form a stable bond, significantly improving the mechanical reliability and surface flatness of the circuit board.

[0012] Preferably, in order to achieve high-precision polishing of the plugging area, the manual polishing in step S5 is carried out with graded sandpaper, using P800→P1500→P3000 grit sandpaper in sequence for stepped polishing.

[0013] By adopting the above technical solution, the surface roughness of the plugging area can be gradually refined. While controlling the amount of copper removal, it can effectively eliminate the small protrusions or depressions after resin filling, ensuring that the surface flatness reaches within ±3μm. This provides a uniform contact interface for subsequent glue-free lamination and significantly reduces the risk of lamination delamination caused by uneven surface.

[0014] Preferably, the non-adhesive PP material ensures both the flowability of the PP material and prevents adhesive overflow. The non-adhesive PP material comprises: 30-40wt% epoxy resin, 25-35wt% modified phenolic resin, and 10-15wt% nano-silica.

[0015] By adopting the above technical solution, sufficient fluidity can be maintained to fill the gaps between layers, and the thickening effect of nano-silica can effectively limit the overflow of colloid. At the same time, the synergistic curing reaction of epoxy resin and modified phenolic resin forms a dense cross-linked structure, avoiding the delamination phenomenon caused by the difference in thermal expansion coefficient of traditional PP materials, and significantly improving the reliability of the pressing process and the long-term stability of the product.

[0016] Preferably, the problem of deformation during blind hole processing in thin plates is solved, wherein the thickness of the L1-L2 layer is 0.125mm, and the depth of the blind hole is ≤50% of the plate thickness.

[0017] By adopting the above technical solution, while ensuring the mechanical load-bearing capacity of the blind hole, a suitable depth-to-width ratio is provided for resin filling.

[0018] Preferably, in order to improve the surface cleanliness of the plates and enhance the interlayer bonding force, plasma cleaning is performed before final pressing. The process parameters are: argon flow rate 50-80 sccm, power 300-500W, and processing time 90-120 seconds.

[0019] By adopting the above technical solution, organic pollutants, oxide layers and particles on the surface of the board can be effectively removed, significantly improving surface activity and cleanliness, providing a clean interface for the tight bonding of the non-adhesive PP material and the core board, thereby enhancing interlayer bonding and reducing pressing defects caused by surface contamination.

[0020] Preferably, in order to ensure the accuracy of temperature control at each stage of the pressing process, the pressing process is divided into a preheating stage, a pressurizing stage, and a heat preservation stage. The temperature of the preheating stage is 160-170℃, and the preheating time is 10 minutes; the temperature of the pressurizing stage is 190-205℃, and the pressurizing time is 15 minutes; the temperature of the heat preservation stage is 205℃, and the heat preservation time is 10 minutes.

[0021] By adopting the above technical solution, the temperature and time parameters at each stage work together to ensure the full flow and curing of the non-adhesive PP material, while avoiding material degradation or board deformation caused by excessive temperature or time, thus significantly improving the pressing quality and product reliability.

[0022] Preferably, in order to achieve high-precision control of the copper thickness of the circuit, the copper ion concentration is controlled at 25-35 g / L and the current density is set at 2.0-2.5 A / dm² in the electroplating process to ensure that the copper thickness uniformity of the circuit reaches within ±5%.

[0023] By adopting the above technical solution, the precise control of copper ion concentration and current density enables copper ions to be uniformly deposited on the circuit surface under the action of electric field, effectively avoiding the problem of uneven copper thickness caused by concentration or current fluctuations, ensuring that the copper thickness uniformity of the circuit reaches within ±5%, and meeting the performance requirements of high reliability thick copper circuit boards.

[0024] The technical effects and advantages of this application are as follows: 1. Compared with the existing technology, the manufacturing method of the exposed blind hole thick copper circuit board significantly reduces the interlayer alignment deviation through dynamic expansion and contraction coefficient iteration control, and improves the interlayer bonding accuracy by combining the layer lamination strategy. It effectively solves the problem of board deformation caused by thermal stress accumulation in traditional processes, so that the flatness error of the multilayer board after lamination is controlled within ±0.1mm. 2. Compared with the prior art, the manufacturing method of the exposed blind via thick copper circuit board adopts a dry film covering and horizontal resin plugging process to completely eliminate the risk of residual glue in blind vias. By precisely controlling the thickness and coverage of the dry film, and with the optimized combination of resin viscosity and filling pressure, the 100% filling rate of the substrate gap in the thick copper area is ensured. At the same time, the height of the copper foil protrusion on the surface after plugging is controlled within ±3μm, which significantly improves the flatness of the circuit board surface. 3. Compared with the existing technology, this method for manufacturing exposed blind hole thick copper circuit boards achieves copper removal control of ≤8μm through manual step-by-step precision grinding, ensuring the flatness of the hole wall. This process avoids the problems of copper surface scratches or excessive reduction that may be caused by mechanical grinding. Combined with the step-by-step polishing design of graded sandpaper, the curvature radius of the transition zone between the hole plugging area and the copper surface of the substrate is controlled within the range of 0.2-0.5mm, providing ideal surface contact conditions for subsequent glue-free lamination. 4. Compared with the existing technology, this method for manufacturing exposed blind via thick copper circuit boards utilizes a special formula of non-adhesive PP material to achieve non-overflow adhesive bonding under optimized parameters of 190-205℃, simultaneously solving the problems of delamination and adhesive residue in the holes, and effectively avoiding poor conductivity caused by adhesive residue in subsequent processes.

[0025] 5. Compared with the existing technology, this method for manufacturing exposed blind via thick copper circuit boards enhances the bonding force by combining plasma cleaning, ultimately enabling the blind via depth control of the thick copper circuit board to reach 50% of the board thickness and the uniformity of electroplated copper thickness to ±5%, thus meeting the miniaturization and high-performance manufacturing requirements of high-reliability exposed blind via thick copper circuit boards. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the process of this application. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] like Figure 1 The method for manufacturing a thick copper circuit board with exposed blind vias, as shown, includes the following steps: S1. Fabrication of inner core board assembly: The L3-L10 core boards are fabricated and pressed according to the predetermined dynamic expansion and contraction coefficients. The first pressing uses expansion and contraction compensation coefficients of +18 in the X direction and +24 in the Y direction. These coefficients are determined through preliminary material testing and process verification and can initially compensate for the thermal shrinkage deformation of the core board during the first pressing. During the pressing process, a high-precision hot press is used to control the temperature uniformity and ensure that the pressure distribution error between each core board layer does not exceed ±5psi, providing a stable basis for subsequent dynamic compensation. After pressing, the actual dimensions of the board are recorded through an online optical detection system and compared with the theoretical design values ​​to generate an initial deformation database.

[0029] S1.5 Divide the core board of L3-L10 into two groups, L3-L6 and L7-L10, and pre-press them separately. After pre-pressing, use ultrasonic flaw detection to test the interlayer bonding degree. After passing the test, press the whole board together to avoid interlayer bubbles and uneven expansion and contraction caused by pressing too many layers at one time. The interlayer bonding strength is improved. S2, Outer Core Board Preparation: Based on the measured expansion and contraction coefficient after S1 lamination, L11-L12 core boards are fabricated and blind hole drilling is completed. During the fabrication process, a high-precision CNC drilling machine is used for blind hole processing. By monitoring the drill bit wear in real time and automatically adjusting the feed speed, the diameter accuracy of the blind hole is ensured to be controlled within ±0.02mm. At the same time, a negative pressure dust collection device is used to remove debris in the hole in time to prevent the hole wall quality from deteriorating due to debris residue. After drilling is completed, a laser microscope is used to perform a full inspection of the blind holes and record key parameters such as hole diameter and hole position deviation to provide accurate data support for subsequent interlayer alignment. S3. Blind Hole Processing in the Secondary Outer Layer: Based on the measured expansion and contraction coefficients after the overall lamination of layers L3-L12, blind holes in layers L1-L2 are fabricated. During the blind hole processing stage, a dual calibration using a laser positioning system and a mechanical positioning device is employed to ensure precise alignment between the blind holes in layers L1-L2 and the inner layer circuitry, achieving an alignment accuracy within ±0.05mm. During processing, the spindle speed and feed pressure of the drilling machine are dynamically adjusted to adapt to the rigidity of the 0.125mm thin plate, preventing excessively large hole diameters or hole wall damage due to vibration. Simultaneously, online hole diameter detection is utilized. The instrument provides real-time data feedback. When the hole diameter is detected to be outside the ±0.03mm range, the system automatically triggers a compensation program to adjust the processing parameters until the hole diameter is qualified. After the blind hole is processed, an ultrasonic cleaner is used to remove residual metal debris and oil stains inside the hole. The cleaning fluid temperature is controlled at 50-60℃ and the cleaning time is set to 3 minutes to ensure that the cleanliness inside the hole meets the IPC-6012 standard level 3 requirements, providing an ideal hole wall condition for subsequent resin plugging. The resin plugging material can be replaced with other high-hardness filling materials according to the actual situation. S4. Residual Resin Through-hole Filling: After the L3-L12 layer circuitry is fabricated, dry film is used to cover the blind hole openings. A horizontal resin through-hole filling machine is used to fill the gaps in the substrate outside the thick copper area. Before the through-hole filling operation, the dry film is pre-baked at a temperature of 80-90℃ for 2-3 minutes to remove volatile components, enhance its adhesion to the board, and prevent the dry film from shifting or falling off during the filling process. During the filling, resin is extruded from the storage tank of the horizontal resin through-hole filling machine at a constant pressure and precisely injected into the blind holes through a precision guide tube. At the same time, the vision positioning system equipped with the through-hole filling machine monitors the resin filling status in real time. When the resin level is close to the top of the blind hole, the filling pressure is automatically reduced to 0.2-0.3MPa for slow filling to avoid resin overflow or air bubbles. After filling, the board is immediately transferred to the static curing area and left to stand at a constant temperature of 25℃ for 30±5 minutes to allow the resin to initially cure and form a stable filling structure. S5. Precision Surface Treatment: Manually grind the plugged hole area, controlling the copper removal amount within the range of 5-8μm. During grinding, operators must wear anti-static gloves and use a special grinding fixture to fix the board, ensuring uniform and stable grinding pressure. First, use P800 grit sandpaper for rough grinding to remove the protruding resin and copper foil on the surface of the plugged hole area. Move the sandpaper at a uniform speed along the length of the board, controlling the movement distance at 10-15cm per minute. After the surface protrusions are basically eliminated, switch to P1500 grit sandpaper for medium grinding. The surface roughness is refined in the next step. At this time, the grinding direction is changed to be perpendicular to the coarse grinding direction to eliminate the scratches left by the coarse grinding. During the intermediate grinding process, the surface condition needs to be observed with a microscope continuously. When the scratch depth is less than 3μm, the fine grinding stage is entered. Finally, P3000 grit sandpaper is used for fine grinding to control the radius of curvature of the transition zone between the plugged hole area and the copper surface of the substrate within the range of 0.2-0.5mm. After the fine grinding is completed, the surface of the board is wiped with a lint-free cloth dipped in special cleaning agent to remove residual grinding debris and oil stains to ensure that the surface cleanliness meets the requirements. S6. Adhesive-free lamination: Using adhesive-free PP material, lamination is performed at 190-205℃ and 350-400psi for 25-35 minutes. Before lamination, the adhesive-free PP material is cut to match the size of the board, ensuring that it covers the entire lamination area and the edges extend 2-3mm beyond the board boundary to prevent the PP material from shifting during lamination. During the lamination process, segmented temperature control is used. In the initial stage, the temperature is increased to 160℃ at a rate of 5℃ per minute and held for 5 minutes to allow the PP material to soften initially. Then, the temperature is increased to 190-205℃ at a rate of 3℃ per minute, while gradually increasing the pressure to 350-400psi to ensure that the PP material flows fully and fills the tiny gaps between the boards. During the heat preservation stage, the temperature and pressure are kept stable to allow the PP material to fully cure and form a stable interlayer bonding structure. After lamination, an online X-ray inspection system is used to check for bubbles or delamination between the layers to ensure that the lamination quality meets the standard requirements. S7. Outer Layer Circuit Fabrication: The outer layer circuit pattern is fabricated on the surface of the laminated board. Electroplating is used to achieve the designed copper thickness, followed by etching to precisely remove excess copper foil, forming a clear outer layer circuit structure. Before fabricating the outer layer circuit pattern, the surface of the laminated board is cleaned using a combination of chemical cleaning and mechanical brushing to remove the surface oxide layer and impurities, providing a good adhesion base for subsequent electroplating. During electroplating, the copper ion concentration is strictly controlled within the range of 25-35 g / L, and the current density is set at 2.0-2.5 A / dm². The temperature and pH value of the electroplating bath are monitored in real time to ensure the stability of the electroplating process, ensuring that the copper thickness uniformity of the circuit is within ±5%. During etching, a suitable etching solution is selected, and the etching speed and time are controlled to precisely remove excess copper foil, avoiding over-etching that could lead to thinner circuits or under-etching that could leave residual copper foil. After etching, optical inspection equipment is used to perform a full inspection of the circuit, recording key dimensions such as circuit width and spacing to ensure that the outer layer circuit structure meets the design requirements.

[0030] The method for determining the dynamic expansion and contraction coefficient includes: after completing N layers of lamination, and N≥2, measuring the actual deformation of the plate by laser scanning, and iteratively generating the subsequent lamination compensation coefficient.

[0031] In step S4, the thickness of the dry film is 15-25 μm, and the coverage area extends 0.3-0.5 mm beyond the edge of the blind hole, so that the dry film can effectively block resin overflow during the plugging process and prevent residual glue from entering the blind hole.

[0032] The process parameters of the horizontal resin plugging machine include: resin viscosity 800-1200cps, filling pressure 0.4-0.6MPa, and static curing for 30±5 minutes after filling. By precisely controlling these parameters, it is ensured that the resin can fully fill the gaps in the substrate, while avoiding resin overflow or insufficient filling due to excessive filling pressure. The static curing process after filling ensures the stability and reliability of the resin.

[0033] In step S5, manual polishing is performed using graded sandpaper, with P800 → P1500 → P3000 grit sandpaper used in sequence for stepped polishing. This stepped polishing method can gradually refine the surface roughness.

[0034] The non-adhesive PP material comprises 30-40wt% epoxy resin, 25-35wt% modified phenolic resin, and 10-15wt% nano-silica. This non-adhesive PP material ensures the fluidity of the material during high-temperature pressing, effectively filling the tiny gaps between the sheets. Through the synergistic effect of modified phenolic resin and nano-silica, a dense cross-linked structure is formed, preventing glue overflow during pressing. At the same time, the addition of nano-silica significantly improves the heat resistance and mechanical strength of the material, ensuring that the PP material can be stably cured at a pressing temperature of 190-205℃ without producing residual glue. This provides a reliable material basis for subsequent glue-free pressing processes. The non-adhesive PP can be replaced with other low-residue PP materials depending on the actual application.

[0035] The thickness of the L1-L2 layer board is 0.125mm, and the depth of the blind via is ≤50% of the board thickness. Controlling the depth of the blind via to within 50% of the board thickness can not only meet the electrical connection requirements of the circuit board design, but also effectively avoid the risk of deformation during the processing, and ensure the processing quality of the blind via and the flatness of the board.

[0036] Plasma cleaning is performed before final lamination. The process parameters are: argon flow rate 50-80 sccm, power 300-500W, and processing time 90-120 seconds. Plasma cleaning can effectively remove organic contaminants and microparticles from the surface of the boards, enhance the activity of the board surface, and thus improve the bonding force between the boards. This creates favorable conditions for the subsequent glue-free lamination process, ensuring tight interlayer bonding after lamination and reducing the probability of quality problems such as delamination.

[0037] The lamination process is divided into a preheating stage, a pressurizing stage, and a heat preservation stage. The preheating stage temperature is 160-170℃, and the preheating time is 10 minutes. The pressurizing stage temperature is 190-205℃, and the pressurizing time is 15 minutes. The heat preservation stage temperature is 205℃, and the heat preservation time is 10 minutes. By controlling the temperature and pressure in stages, the PP material is gradually softened and fully fills the gaps between the boards. At the same time, it avoids material deformation or bubble formation caused by sudden temperature rise. The temperature and pressure parameters of each stage have been verified and determined in the early process to ensure the stability and reliability of the lamination process. Finally, a uniform and dense interlayer bonding structure is formed, which effectively improves the mechanical strength and electrical performance of the circuit board.

[0038] In the electroplating process, the copper ion concentration is controlled at 25-35 g / L, and the current density is set at 2.0-2.5 A / dm² to ensure that the copper thickness uniformity of the circuit reaches within ±5%, avoiding the problem of uneven copper thickness caused by environmental fluctuations. At the same time, it meets the miniaturization and high-performance manufacturing requirements of high-reliability exposed blind via thick copper circuit boards.

[0039] The working process of this application is as follows: In the actual production process, the inner core board assembly is first manufactured according to step S1. The core boards of layers L3-L10 are manufactured and pressed according to the predetermined dynamic expansion and contraction coefficient. The core boards of layers L3-L10 are divided into two groups: layers L3-L6 and layers L7-L10. Pre-pressing operations are carried out separately. After the pre-pressing is completed, ultrasonic testing is used to detect the interlayer bonding degree. Only products that pass the test can enter the subsequent overall pressing process. The first pressing uses an expansion and contraction compensation coefficient of +18 in the X direction and +24 in the Y direction. After the first pressing is completed, step S2 is carried out. Based on the measured expansion and contraction coefficient obtained after pressing in step S1, L1 is manufactured. The core board of layers 1-L12 is completed and blind via drilling is finished. Then, in step S3, blind vias of layers L1-L2 are made based on the measured expansion and contraction coefficients after the overall lamination of layers L3-L12. After the blind vias are made, the process moves to step S4, which is a process to prevent residual adhesive from plugging the vias. After the circuitry of layers L3-L12 is completed, a dry film with a thickness of 15-25μm is used to cover the blind via openings, and the coverage area extends 0.3-0.5mm beyond the edge of the blind via. Then, a horizontal resin plugging machine is used to fill the gaps in the substrate outside the thick copper area under process parameters of resin viscosity of 800-1200cps and filling pressure of 0.4-0.6MPa. After filling, the vias are allowed to stand and cure for 30±5 minutes.

[0040] Following this, the S5 precision surface treatment step is performed, where the plugged area is manually polished using graded sandpaper, sequentially using P800→P1500→P3000 grit sandpaper for stepped polishing, controlling the copper removal amount within the range of 5-8μm. After completing the surface treatment, the S6 adhesive-free lamination step is performed, using a non-adhesive PP material containing 30-40wt% epoxy resin, 25-35wt% modified phenolic resin, and 10-15wt% nano-silica, at 190- Pressing is performed at 205℃ and 350-400psi for 25-35 minutes. Plasma cleaning is required before final pressing. The process parameters are argon flow rate of 50-80sccm, power of 300-500W, and processing time of 90-120 seconds. The pressing process is divided into a preheating stage at 160-170℃ for 10 minutes, a pressurization stage at 190-205℃ for 15 minutes, and a heat preservation stage at 205℃ for 10 minutes.

[0041] Finally, the S7 outer layer circuit fabrication step is performed. The outer layer circuit pattern is created on the surface of the laminated board. Through electroplating, the copper ion concentration is controlled at 25-35 g / L, and the current density is set at 2.0-2.5 A / dm² to ensure the copper thickness meets design requirements and the copper thickness uniformity is within ±5%. Etching is then performed to precisely remove excess copper foil, forming a clear outer layer circuit structure. Throughout the process, the dynamic expansion / contraction coefficient is determined by measuring the actual deformation of the board after every N layers (N≥2). This dynamic adjustment effectively solves the problem of interlayer deviation accumulation caused by traditional static compensation, greatly improving the accuracy and quality of multilayer board lamination. The resulting exposed blind via thick copper circuit board features high reliability, miniaturization, and high performance, meeting the stringent requirements of various fields for circuit boards.

Claims

1. A method for manufacturing a thick copper circuit board with exposed blind vias, characterized in that, Includes the following steps: S1. Fabrication of inner core board assembly: The L3-L10 core boards are fabricated and pressed according to the predetermined dynamic expansion and contraction coefficients. The first pressing adopts an expansion and contraction compensation coefficient of +18 in the X direction and +24 in the Y direction. S1.5 Divide the core board of L3-L10 into two groups, L3-L6 and L7-L10, and pre-press them separately. After pre-pressing, use ultrasonic testing to check the interlayer bonding degree. After passing the test, press them together as a whole. S2, Outer Core Board Preparation: Based on the measured expansion and contraction coefficient after S1 lamination, L11-L12 core boards are fabricated and blind hole drilling is completed; S3, Blind via processing of the outermost layer: Based on the measured expansion and contraction coefficients of the L3-L12 layers after overall lamination, blind vias are fabricated in the L1-L2 layers; S4, Residual Resin Hole Plug: After the L3-L12 layer circuit is fabricated, dry film is used to cover the blind hole openings, and a horizontal resin plugging machine is used to fill the gaps in the outer substrate of the thick copper area. S5. Precision surface treatment: Manually polish the plugged hole area, controlling the amount of copper removed to be within the range of 5-8μm. S6, Adhesive-free lamination: Using adhesive-free PP material, lamination is carried out at 190-205℃ and 350-400psi for 25-35 minutes. S7. Outer layer circuit fabrication: Outer layer circuit patterns are fabricated on the surface of the laminated board. The copper thickness of the circuit is made up to the design requirements through electroplating. Then, etching is performed to precisely remove excess copper foil and form a clear outer layer circuit structure.

2. The method for manufacturing a thick copper circuit board with exposed blind vias according to claim 1, characterized in that: The method for determining the dynamic expansion and contraction coefficient includes: after each N-layer lamination is completed, and N≥2, the actual deformation of the plate is measured by laser scanning, and the subsequent lamination compensation coefficient is iteratively generated.

3. The method for manufacturing a thick copper circuit board with exposed blind vias according to claim 1, characterized in that: The thickness of the dry film in step S4 is 15-25 μm, and the coverage area extends 0.3-0.5 mm beyond the edge of the blind hole.

4. The method for manufacturing a thick copper circuit board with exposed blind vias according to claim 1, characterized in that: The process parameters of the horizontal resin plugging machine include: resin viscosity 800-1200cps, filling pressure 0.4-0.6MPa, and static curing for 30±5 minutes after filling.

5. The method for manufacturing a thick copper circuit board with exposed blind vias according to claim 1, characterized in that: In step S5, manual polishing is performed using graded sandpaper, with P800 → P1500 → P3000 grit sandpaper used in sequence for stepped polishing.

6. The method for manufacturing a thick copper circuit board with exposed blind vias according to claim 1, characterized in that: The non-adhesive PP material comprises: 30-40wt% epoxy resin, 25-35wt% modified phenolic resin, and 10-15wt% nano-silica.

7. The method for manufacturing a thick copper circuit board with exposed blind vias according to claim 1, characterized in that: The thickness of the L1-L2 layer is 0.125mm, and the depth of the blind hole is ≤ 50% of the layer thickness.

8. The method for manufacturing a thick copper circuit board with exposed blind vias according to claim 1, characterized in that: Plasma cleaning is performed before final pressing. The process parameters are: argon flow rate 50-80 sccm, power 300-500W, and processing time 90-120 seconds.

9. The method for manufacturing a thick copper circuit board with exposed blind vias according to claim 1, characterized in that: The pressing process is divided into a preheating stage, a pressurizing stage and a heat preservation stage. The temperature of the preheating stage is 160-170℃ and the preheating time is 10 minutes. The pressurization stage temperature is 190-205℃, and the pressurization time is 15 minutes. The temperature during the heat preservation stage is 205℃, and the heat preservation time is 10 minutes.

10. A method for manufacturing a thick copper circuit board with exposed blind vias according to claim 1, characterized in that: In the electroplating process, the copper ion concentration is controlled at 25-35 g / L, and the current density is set at 2.0-2.5 A / dm² to ensure that the copper thickness uniformity of the circuit reaches within ±5%.

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