A method for manufacturing a PCB by etching copper reduction for cancelling hole filling plating

Abstract

The application relates to the technical field of PCB manufacturing, and discloses a PCB manufacturing method adopting etching copper reduction for cancelling hole filling electroplating, which comprises the following steps: selecting a substrate with a thick copper layer, determining a copper reduction position through film pasting, exposure and development, etching a copper layer PAD, and reserving a substrate copper layer with a preset thickness under the copper layer PAD; using RCC material to press the substrate after etching, and filling the recessed area formed by the copper layer PAD with resin; removing the copper foil and the excess resin on the surface through grinding to expose the copper layer PAD; performing non-hole filling electroplating to thicken the surface copper layer, realizing interlayer conduction; peeling off the substrate, forming a double-sided circuit pattern through inner layer etching, and obtaining a double-sided PCB. The purpose of the PCB manufacturing method adopting etching copper reduction for cancelling hole filling electroplating is to solve the problems of complicated drilling and hole filling electroplating process flow, high manufacturing cost, long production cycle, and defects such as hole copper defects and resin plug hole defects in the prior art.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, specifically to a PCB manufacturing method that eliminates the need for through-hole plating and uses etching to reduce copper content. Background Technology

[0002] Currently, the mainstream method for achieving interlayer conductivity in the PCB industry is to first create the inner layer circuit pattern, then drill through-holes on the substrate using mechanical drilling, and finally deposit copper layers inside the holes using a via-filling electroplating process to form a conductive structure. This traditional process is a technology that has gradually matured with the development of multilayer and high-density PCBs. The drilling process uses a precision drill bit to create vertical through-holes at predetermined locations, while the via-filling electroplating process plating copper layers on the hole walls and inside the holes to achieve interlayer electrical connections. This process involves multiple steps, including drilling equipment positioning, drill bit selection and replacement, hole position inspection, desmearing, and in-hole electroplating, requiring specialized drilling machines, via-filling electroplating equipment, and corresponding testing equipment.

[0003] However, traditional drilling and via-filling electroplating processes suffer from cumbersome procedures and high manufacturing costs. Specifically, the drilling process consumes a large number of drill bits and tools, resulting in high maintenance costs for drilling equipment and affecting drilling accuracy due to mechanical wear. The via-filling electroplating process requires specialized electroplating tanks and complex electroplating solution formulations, making it difficult to control the uniformity of copper layer deposition within the holes, which can easily lead to defects such as poor copper deposits and inadequate resin plugging. The overall process chain is long, requiring multiple steps including drilling, desmearing, via-filling electroplating, and resin plugging, resulting in long production cycles and significant challenges in quality control. Consequently, PCB manufacturing costs remain high, and production efficiency is difficult to improve. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of cumbersome drilling and filling electroplating processes, high manufacturing costs, long production cycles, and defects such as poor copper filling and poor resin plugging in the existing technology. The invention proposes a PCB manufacturing method that eliminates filling electroplating and uses etching to reduce copper.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A PCB manufacturing method that eliminates the need for in-hole plating and uses etching to reduce copper content includes the following steps: S1. Select a substrate with a thick copper layer, determine the copper reduction position by film application, exposure and development, and etch out the copper layer PAD. A substrate copper layer of a preset thickness is retained under the copper layer PAD. S2. The etched substrate is laminated using RCC material, and the recessed area formed by the copper layer PAD is filled with resin. S3. Remove the copper foil and excess resin from the surface by grinding to expose the copper layer PAD; S4. Perform non-hole-filling electroplating to thicken the surface copper layer to achieve interlayer conductivity;

[0006] S5. Peel off the substrate and form double-sided circuit patterns through inner layer etching to obtain a double-sided PCB board.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, in S1, the exposure process uses an LDI exposure machine for direct imaging. After dry film lamination, the etched protective pattern is formed through exposure and development. Subsequently, during the etching operation, the etching amount is increased to control the degree of lateral etching, so that the copper layer PAD presents a regular three-dimensional columnar structure. After etching, the copper layer PAD is automatically inspected by an AOI inspection machine and manually inspected by a VRS manual inspection machine to confirm that the positional accuracy, shape regularity, and etching depth of the copper layer PAD meet the design requirements.

[0009] Furthermore, in S1, the etching operation achieves precision control by adjusting etching parameters in multiple dimensions. These etching parameters include etching solution concentration ratio, etching solution temperature, nozzle spray pressure, etching line running speed, and board placement method. Through the coordinated adjustment of these parameters, the etching depth of the copper layer PADs at various positions on the substrate is made uniform, and the sidewall straightness meets the requirements for subsequent lamination, ensuring that the cylindrical shape of the copper layer PADs remains consistent throughout the entire board.

[0010] Furthermore, in S2, the RCC material is a copper foil composite material with a resin layer. Before lamination, hand-riveting holes need to be punched for positioning, and manual stacking and riveting operations are carried out. The operator aligns and rivets the RCC material with the etched substrate using standardized stacking techniques. By optimizing the number of riveting points, the distribution of riveting positions, and the riveting force, the alignment accuracy between layers is controlled. At the same time, the lamination program parameters, including the lamination temperature curve, lamination pressure, holding time, and heating and cooling rates, are adjusted so that the resin in the RCC material can fully flow and fill the recessed area formed by the copper layer PAD during the hot pressing process. This avoids defects such as resin leakage, insufficient resin filling, and surface depressions after lamination, ensuring the flatness of the board surface and the density of resin filling after lamination.

[0011] Furthermore, in S3, the grinding operation adopts a multi-stage grinding process. The first stage is coarse grinding to remove the copper foil layer of RCC material on the surface, and the second stage is fine grinding to remove excess resin until the copper layer PAD surface is completely exposed. Before grinding, a 3D measuring instrument is used to scan and measure the flatness of the entire board surface after lamination. The pressure distribution of the grinding head and the grinding time of the grinding equipment are adjusted according to the measurement data. During the grinding process, a CMI device is used to monitor the board thickness and thickness uniformity online. After grinding, a 3D measuring instrument is used again to check the flatness of the board surface, and an optical microscope or AOI device is used to check whether the copper layer PAD is completely exposed and whether there is no resin residue on the surface, to ensure the contact conductivity of the subsequent electroplating process.

[0012] Furthermore, in step S4, a non-filling electroplating process is used to thicken the surface copper layer of the ground board. By controlling electroplating parameters such as electroplating current density, electroplating solution temperature, electroplating time, and electroplating solution concentration, the electroplated copper layer is uniformly deposited on the exposed copper layer PAD surface and other areas of the board surface. The thickness of the surface copper layer after electroplating meets the design requirements. The copper layer PAD and the electroplated surface copper layer form a metallurgical bond to achieve interlayer electrical connection. During the electroplating process, the uniformity of the coating thickness distribution and the flatness of the coating are ensured by Hull cell test and electroplating uniformity test.

[0013] Furthermore, in S5, the substrate peeling adopts the ETS etching and tin stripping process, which selectively dissolves the substrate material or the bonding layer between the substrate and the copper layer PAD through a chemical solution. After the substrate is completely peeled off, a double-sided structure is obtained. Then, the two sides are respectively subjected to film application, exposure and development to form a circuit pattern protective layer. The copper layer in the non-circuit area is removed by the inner layer pattern etching process, revealing the final designed double-sided circuit pattern, forming a double-sided PCB board with interlayer conductive structure.

[0014] Furthermore, when the method is applied to the fabrication of multilayer PCBs, a layer-by-layer stacking method is adopted. After the first layer forms the first set of interlayer conductive structures according to steps S1 to S4, the semi-finished product is used as a new substrate to repeat steps S1 to S4 to form the second set of interlayer conductive structures. This process is repeated to complete the layer-by-layer construction and interlayer conductivity of the multilayer circuits. After all interlayer conductive structures are fabricated, the substrate is peeled off and the outer layer circuits on both sides are etched to obtain a multilayer PCB with multiple inner layer circuits and multiple sets of interlayer conductive structures.

[0015] Furthermore, in S1, the initial thickness of the substrate copper layer is 35 μm to 105 μm, and the thickness of the substrate copper layer retained after etching is 10 μm to 50 μm. The etching depth of the copper layer PAD is determined to be 25 μm to 70 μm according to the interlayer conductivity design requirements. The diameter or side length of the copper layer PAD is set according to the electrical performance requirements. The etching sidewall angle is controlled within the range of 75 degrees to 90 degrees. The setting of the above-mentioned dimensional parameters takes into account the integrity of resin filling and the controllability of the polishing process during subsequent RCC lamination.

[0016] Furthermore, the method forms a copper layer PAD as an interlayer conductive structure through etching and copper reduction in step S1, replacing the mechanical drilling and hole-filling electroplating processes in the traditional process. The copper layer PAD is formed by etching rather than drilling, and the resin filling is completed by RCC lamination rather than hole-filling electroplating. The interlayer conductivity is achieved by thickening the copper layer on the surface of the copper layer PAD through non-hole-filling electroplating in step S4. The entire process does not involve drilling equipment, drilling tools, hole-filling electroplating tanks, or corresponding hole position inspection equipment.

[0017] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: This invention utilizes mature film-coating exposure, development, and etching technologies to form copper-layer PADs, eliminating the need for drill bits and avoiding the high investment and maintenance costs of drilling equipment. Etching accuracy is unaffected by mechanical wear, resulting in higher positional accuracy and shape consistency. The use of RCC material lamination allows resin to flow naturally, filling the recessed areas formed by the copper-layer PADs. This eliminates the need for specialized through-hole plating tanks and complex plating solution formulations, avoiding the challenge of controlling the uniformity of copper deposition within the holes and eliminating defects such as poor copper deposition and resin plugging. After grinding to expose the copper-layer PADs, non-through-hole plating is then performed. The thick copper layer enables reliable interlayer conductivity. The entire process eliminates multiple steps such as drilling, desmearing, via-filling electroplating, and resin plugging, shortening the process chain, significantly reducing the production cycle, and reducing quality control points, making yield easier to control. In addition, the etching, RCC lamination, grinding, and non-via-filling electroplating processes used in this invention are all mature processes in the PCB industry. The equipment is highly versatile and does not require additional dedicated drilling machines and via-filling electroplating equipment, which greatly reduces manufacturing costs and significantly improves production efficiency, providing a more economical and efficient solution for interlayer conductivity in PCB manufacturing. Attached Figure Description

[0018] Figure 1 This is a flowchart of the present invention; Figure 2 This is a schematic diagram of the substrate structure with thick copper foil used in the cutting process of this invention; Figure 3 This is a schematic diagram showing the exposure position of the film in this invention; Figure 4 This is a schematic diagram of the present invention after etching; Figure 5 This is a schematic diagram of the present invention after pressing; Figure 6 This is a schematic diagram of the material after grinding according to the present invention; Figure 7 This is a schematic diagram of the non-filling electroplating process of the present invention; Figure 8 This is a schematic diagram of the connection structure between the resin and the copper layer of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention discloses a PCB manufacturing method that eliminates the need for through-hole plating and reduces copper content through etching, comprising the following steps: S1. Select a substrate with a thick copper layer, determine the copper reduction position by film application, exposure and development, and etch out the copper layer PAD. A substrate copper layer of a preset thickness is retained under the copper layer PAD.

[0021] like Figure 1 As shown, the blanking process uses a substrate with a thick copper layer. The initial thickness of the copper layer on the substrate selected in S1 is 35 μm to 105 μm. Different thicknesses of copper foil substrates can be selected according to product design requirements. The thicker copper layer provides sufficient copper layer thickness guarantee for subsequent etching and copper reduction. Figure 2 As shown, in the film coating and exposure process, the exposure stage uses an LDI exposure machine for direct imaging. First, a dry film is coated on the substrate surface. The LDI exposure machine directly images the dry film with a laser, eliminating the need to make film. The direct imaging method reduces alignment errors. After the dry film is coated, it is exposed and developed to form an etched protective pattern. After development, the dry film in the unexposed areas is dissolved and removed by the developer, exposing the copper layer area to be etched. The dry film in the exposed areas is cured to form a protective layer.

[0022] like Figure 3As shown, in the etching operation, precision control is achieved by adjusting etching parameters in multiple dimensions. These parameters include the etching solution concentration ratio, etching solution temperature, nozzle spray pressure, etching line running speed, and board placement method. The etching solution concentration is typically copper chloride solution or alkaline etching solution, ranging from 150 g / L to 250 g / L. The etching solution temperature is controlled between 45°C and 55°C. The nozzle spray pressure is set between 0.15 MPa and 0.25 MPa. The etching line running speed is adjusted to 1.5 m / min according to the required etching depth. Up to 3.0 m / min, the board placement method can be selected as horizontal or vertical to adapt to different pattern distributions. During the etching operation, the etching amount is increased to control the degree of side etching, so that the copper layer PAD presents a regular three-dimensional columnar structure. By extending the etching time or increasing the activity of the etching solution, the etching amount is increased, so that the ratio of side etching depth to vertical etching depth is reasonable. Through the coordinated adjustment of the above parameters, the etching depth of the copper layer PAD at all positions on the substrate is uniform, and the sidewall straightness meets the requirements of subsequent lamination, ensuring that the columnar shape of the copper layer PAD remains consistent throughout the entire board. The thickness of the retained substrate copper layer after etching ranges from 10 μm to 50 μm. The etching depth of the copper layer PAD is determined to be 25 μm to 70 μm according to the interlayer conductivity design requirements. The retained substrate copper layer serves as a support layer to prevent resin leakage during subsequent lamination. The diameter or side length of the copper layer PAD is set according to electrical performance requirements. The etching sidewall angle is controlled within the range of 75 degrees to 90 degrees. A near-vertical sidewall angle is beneficial for resin filling and subsequent electroplating connection. After etching, the copper layer PADs undergo automatic optical inspection by an AOI inspection machine and manual inspection by a VRS manual inspection machine to confirm that the positional accuracy, shape regularity, and etching depth meet the design requirements. The AOI inspection machine scans and detects the positional offset and shape integrity of all copper layer PADs on the board, while the VRS manual inspection machine is used by operators to verify the quality of copper layer PADs in key positions on the display screen. This dual inspection ensures the etching quality.

[0023] S2. The etched substrate is laminated using RCC material, and the recessed area formed by the copper layer PAD is filled with resin.

[0024] like Figure 4As shown, RCC material is a copper foil composite material with a resin layer. This material is composed of a copper foil layer and an epoxy resin layer. The resin layer thickness is usually 20 μm to 80 μm, and the appropriate thickness of RCC material can be selected according to the etching depth of the copper layer PAD. Before lamination, hand-riveting holes need to be punched for positioning, and manual stacking and riveting operations are performed. Positioning hand-riveting holes are punched at the four corners or edges of the substrate and RCC material. The hole diameter is usually 3 mm to 5 mm. The operator aligns and rivets the RCC material with the etched substrate using standardized stacking techniques. During stacking, it is necessary to ensure that the RCC material is flat and wrinkle-free, and that the resin surface and the etched surface are tightly adhered. The alignment accuracy between layers is controlled by optimizing the number of riveting points, the distribution of riveting positions, and the riveting force. The number of riveting points is determined according to the board size, and usually 2 to 4 riveting points are set on each side. The riveting position is selected in non-critical circuit areas, and the riveting force is moderate to avoid material deformation. After the lamination and riveting are completed, the plates are fed into the press. The pressing parameters are adjusted, including the pressing temperature profile, pressing pressure, holding time, and heating / cooling rates. The pressing temperature profile is divided into preheating, heating, curing, and cooling sections. The preheating temperature is set to 100℃ to 130℃ and held for 15 to 25 minutes. The heating rate is controlled at 2℃ / min to 4℃ / min. The curing temperature reaches 170℃ to 185℃ and is held for 60 to 90 minutes. The pressing pressure is set to 15 kgf / cm to 25 kgf / cm. The cooling section lowers the temperature... The heating rate is controlled at 3℃ / min to 5℃ / min, so that the resin in the RCC material can fully flow and fill the recessed area formed by the copper layer PAD during the hot pressing process. The viscosity of the resin decreases under heating and pressurization conditions, causing it to flow from the resin layer of the RCC material to the recessed area of ​​the copper layer PAD and fill it. This avoids defects such as resin leakage, incomplete resin filling, and surface depressions after pressing, ensuring the flatness of the board surface and the density of resin filling after pressing. The flatness deviation of the board surface after pressing is controlled within 30 μm, and the resin filling rate reaches more than 95%.

[0025] S3. Remove the copper foil and excess resin from the surface by grinding to expose the copper layer PAD.

[0026] like Figure 5As shown, the grinding operation employs a multi-stage grinding process. The first stage, coarse grinding, removes the copper foil layer of the RCC material on the surface. The second stage, fine grinding, removes excess resin until the copper layer PAD surface is completely exposed. Coarse grinding uses larger-grit abrasive paper or grinding wheels (80-120 mesh) at a speed of 800-1200 rpm, removing approximately 12-35 μm of copper foil layer. Fine grinding uses fine-grit abrasive materials (180-320 mesh) at a reduced speed of 400-600 rpm, gradually removing excess resin until the copper layer PAD is exposed. Before grinding, a 3D measuring instrument is used to scan and measure the flatness of the entire board surface after lamination. The 3D measuring instrument uses laser or optical methods to scan the board surface morphology, obtaining height distribution data at various locations across the board, identifying protruding and recessed areas. Based on the measurement data, the grinding head pressure distribution and grinding time of the grinding equipment are adjusted. For protruding areas, the grinding head pressure is increased or the grinding time is extended, while for flat areas, conventional grinding parameters are maintained, achieving differentiated grinding control. During the grinding process, a CMI (Content Management Instrument) is used to monitor the board thickness and thickness uniformity online. The CMI measures the board thickness in real time using a capacitance or eddy current sensor, with a monitoring frequency of 5 to 10 measurements per second. When the board thickness approaches the target thickness, the grinding speed is automatically reduced or grinding is stopped, and the thickness uniformity deviation is controlled within 10 μm. After grinding, a 3D measuring instrument is used again to check the flatness of the board surface, and an optical microscope or AOI (Automated Optical Inspection) device is used to check whether the copper layer PAD is fully exposed and whether there is any resin residue on the surface. The magnification of the optical microscope is set to 50x to 200x to observe whether there is any residual resin film on the surface of the copper layer PAD. The AOI device determines the exposure by comparing the difference in optical reflectance between the copper layer PAD area and the surrounding area, ensuring the contact conductivity of subsequent electroplating processes.

[0027] S4. Perform non-filling electroplating to thicken the surface copper layer and achieve interlayer conductivity.

[0028] like Figure 6As shown, a non-fill-through-hole electroplating process is used to thicken the surface copper layer of the polished board. Unlike traditional fill-through-hole electroplating, non-fill-through-hole electroplating eliminates the need for copper deposition inside the holes; instead, planar electroplating is performed only on the exposed copper PAD surface and other copper areas of the board. Electroplating parameters such as current density, solution temperature, plating time, and solution concentration are controlled. The current density is set to 2A / dm² to 4A / dm², as a higher current density accelerates the deposition rate but must prevent a rough coating. The solution temperature is controlled between 22℃ and 28℃, as excessively high or low temperatures affect the coating quality. The plating time is calculated based on the target coating thickness and is typically 40 to 90 minutes. The plating solution uses a copper sulfate solution with a concentration of 180g / L to 220g / L and a sulfuric acid concentration of 50g / L to 70g / L, with a brightener added. The plating performance is optimized with leveling agents to ensure uniform deposition of the electroplated copper layer on the exposed copper PAD surface and other areas of the board. The thickness of the surface copper layer after electroplating meets the design requirements, typically 20 μm to 40 μm. The copper PAD and the electroplated surface copper layer form a metallurgical bond to achieve interlayer electrical connection. The electroplated copper atoms and the copper atoms on the copper PAD surface form a continuous lattice structure, resulting in high bonding strength and low resistance. During the electroplating process, Hull cell tests and electroplating uniformity tests are used to ensure the uniformity of the plating thickness distribution and the flatness of the plating layer. The Hull cell test is conducted before actual electroplating, using small-sized test pieces electroplated at different current densities to observe the appearance and thickness distribution of the plating layer and optimize the electroplating parameters. The electroplating uniformity test is conducted after electroplating, measuring the plating thickness at different locations on the board surface and calculating the thickness deviation, with the uniformity deviation controlled within 15%.

[0029] S5. Peel off the substrate and form double-sided circuit patterns through inner layer etching to obtain a double-sided PCB board.

[0030] like Figure 7As shown, the substrate is removed using the ETS etching and tin stripping process. ETS stands for Etchant Tin Stripping. It selectively dissolves the substrate material or the bonding layer between the substrate and the copper layer PAD using a chemical solution. The stripping solution is usually an alkaline solution or a special stripping agent. The soaking time is 20 to 40 minutes and the soaking temperature is 40°C to 60°C. During the stripping process, the chemical solution penetrates to the interface between the substrate and the copper layer PAD, dissolving the remaining thin copper layer of the substrate or the bonding interface. After the substrate is completely stripped, a double-sided structure is obtained. At this time, the product presents a symmetrical structure with copper layers on both sides, and the middle is a copper layer PAD and an interlayer conductive structure formed by filling resin. Subsequently, a protective layer for the circuit pattern is formed by applying a film to both sides and exposing and developing it. Dry film is then applied to both sides, and exposure and development are performed according to the designed circuit pattern. After exposure, the dry film in the circuit area is cured to protect the underlying copper layer. The dry film in the non-circuit area is removed after development to expose the copper layer. The copper layer in the non-circuit area is removed by an inner layer pattern etching process. The board is then fed into the etching line, where the etching solution etches away the copper layer that is not protected by the dry film, revealing the final double-sided circuit pattern and forming a double-sided PCB board with interlayer conductivity. After etching, the dry film protective layer is removed to obtain a finished double-sided PCB with fine circuit pattern and reliable interlayer conductivity.

[0031] In another embodiment, when the method is applied to the fabrication of a multilayer PCB, a layer-by-layer stacking method is adopted. After the first layer forms the first set of interlayer conductive structures according to steps S1 to S4, the semi-finished product is used as a new substrate to repeat steps S1 to S4 to form the second set of interlayer conductive structures, and so on to complete the layer-by-layer construction and interlayer conductivity of the multilayer circuit. Specifically, steps S1 to S4 are first completed on the first substrate to obtain the first layer semi-finished product. The surface of the semi-finished product has formed the first set of copper PADs, which are thickened by electroplating to achieve conductivity. The semi-finished product is used as the substrate of the second layer, and on its surface... The second copper layer PAD is formed by film lamination, exposure, development, and etching. Then, RCC material is laminated, ground, and electroplated to form the second interlayer conductive structure. By stacking layers in this way, four-layer, six-layer, or even more-layer PCB structures can be achieved. After all interlayer conductive structures are made, the substrate is peeled off and the outer layer circuits on both sides are etched to obtain a multilayer PCB board with multiple inner layer circuits and multiple interlayer conductive structures. During the fabrication of the multilayer board, the positions of the copper layer PADs between each layer must be precisely aligned. The accuracy of interlayer conductivity is ensured by using an optical positioning system or X-ray perspective positioning.

[0032] The method described herein forms a copper layer PAD as an interlayer conductive structure through etching in step S1, replacing the mechanical drilling and via-filling electroplating processes in traditional processes. Traditional processes require drilling equipment to drill vertical holes in the substrate, followed by via-filling electroplating to deposit a copper layer inside the holes. In this method, the copper layer PAD is formed by etching rather than drilling, and resin filling is achieved through RCC lamination rather than via-filling electroplating. The copper layer PAD formed by etching has high positional accuracy and controllable shape, while the resin filling through RCC lamination has good density. Interlayer conductivity is achieved by thickening the copper layer on the surface of the copper layer PAD through non-via-filling electroplating in step S4. The entire process does not involve drilling equipment, drilling tools, via-filling electroplating tanks, or corresponding hole position inspection equipment, simplifying equipment configuration, reducing equipment investment and maintenance costs, shortening the process flow, and improving production efficiency.

[0033] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, including an element by a statement does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A PCB manufacturing method that eliminates the need for through-hole plating and uses etching to reduce copper content, characterized in that... Includes the following steps: S1. Select a substrate with a thick copper layer, determine the copper reduction position by film application, exposure and development, and etch out the copper layer PAD. A substrate copper layer of a preset thickness is retained under the copper layer PAD. S2. The etched substrate is laminated using RCC material, and the recessed area formed by the copper layer PAD is filled with resin. S3. Remove the copper foil and excess resin from the surface by grinding to expose the copper layer PAD; S4. Perform non-hole-filling electroplating to thicken the surface copper layer to achieve interlayer conductivity; S5. Peel off the substrate and form double-sided circuit patterns through inner layer etching to obtain a double-sided PCB board.

2. The PCB manufacturing method according to claim 1, which eliminates the need for through-hole plating and uses etching to reduce copper content, is characterized in that... In step S1, the exposure process uses an LDI exposure machine for direct imaging. After dry film lamination, the copper layer PAD is exposed and developed to form an etched protective pattern. Subsequently, the etching amount is increased during the etching operation to control the degree of lateral etching, so that the copper layer PAD presents a regular three-dimensional columnar structure. After etching, the copper layer PAD is automatically inspected by an AOI inspection machine and manually inspected by a VRS manual inspection machine to confirm that the positional accuracy, shape regularity and etching depth of the copper layer PAD meet the design requirements.

3. The PCB manufacturing method according to claim 1, which eliminates the need for through-hole plating and uses etching to reduce copper content, is characterized in that... In S1, the etching operation achieves precision control by adjusting etching parameters in multiple dimensions. These etching parameters include etching solution concentration ratio, etching solution temperature, nozzle spray pressure, etching line running speed, and board placement method. Through the coordinated adjustment of these parameters, the etching depth of the copper layer PADs at various positions on the substrate is made uniform, and the straightness of the sidewalls meets the requirements for subsequent lamination, ensuring that the cylindrical shape of the copper layer PADs remains consistent throughout the entire board.

4. The PCB manufacturing method according to claim 1, which eliminates the need for through-hole plating and uses etching to reduce copper content, is characterized in that... In S2, the RCC material is a copper foil composite material with a resin layer. Before lamination, hand-riveting holes need to be punched for positioning, and manual stacking and riveting operations are carried out. The operator aligns and rivets the RCC material with the etched substrate using standardized stacking techniques. By optimizing the number of riveting points, the distribution of riveting positions, and the riveting force, the alignment accuracy between layers is controlled. At the same time, the lamination program parameters, including the lamination temperature curve, lamination pressure, holding time, and heating and cooling rates, are adjusted to ensure that the resin in the RCC material flows and fills the recessed area formed by the copper layer PAD during the hot pressing process. This avoids defects such as resin leakage, insufficient resin filling, and surface depressions after lamination, ensuring the flatness of the board surface and the density of resin filling after lamination.

5. A PCB manufacturing method that eliminates the need for through-hole plating and reduces copper content through etching, as described in claim 1, is characterized in that... In step S3, the grinding operation adopts a multi-stage grinding process. The first stage is coarse grinding to remove the copper foil layer of RCC material on the surface. The second stage is fine grinding to remove excess resin until the copper layer PAD surface is completely exposed. Before grinding, a 3D measuring instrument is used to scan and measure the flatness of the entire board surface after lamination. The pressure distribution of the grinding head and the grinding time of the grinding equipment are adjusted according to the measurement data. During the grinding process, a CMI device is used to monitor the board thickness and thickness uniformity online. After grinding, a 3D measuring instrument is used again to check the flatness of the board surface, and an optical microscope or AOI device is used to check whether the copper layer PAD is completely exposed and whether there is no resin residue on the surface, to ensure the contact conductivity of the subsequent electroplating process.

6. A PCB manufacturing method that eliminates the need for through-hole plating and reduces copper content through etching, as described in claim 1, is characterized in that... In step S4, a non-filling-hole electroplating process is used to thicken the surface copper layer of the ground board. By controlling electroplating parameters such as electroplating current density, electroplating solution temperature, electroplating time, and electroplating solution concentration, the electroplated copper layer is uniformly deposited on the exposed copper layer PAD surface and other areas of the board surface. The thickness of the surface copper layer after electroplating meets the design requirements. The copper layer PAD and the electroplated surface copper layer form a metallurgical bond to achieve interlayer electrical connection. During the electroplating process, the uniformity of the coating thickness distribution and the flatness of the coating are ensured by Hull cell test and electroplating uniformity test.

7. A PCB manufacturing method that eliminates the need for through-hole plating and reduces copper content through etching, as described in claim 1, is characterized in that... In step S5, the substrate peeling adopts the ETS etching and tin stripping process, which selectively dissolves the substrate material or the bonding layer between the substrate and the copper layer PAD through a chemical solution. After the substrate is completely peeled off, a double-sided structure is obtained. Then, the two sides are respectively subjected to film application, exposure and development to form a circuit pattern protective layer. The copper layer in the non-circuit area is removed by the inner layer pattern etching process, revealing the final designed double-sided circuit pattern, forming a double-sided PCB board with interlayer conductive structure.

8. A PCB manufacturing method that eliminates the need for through-hole plating and reduces copper content through etching, as described in claim 1, is characterized in that... When the method is applied to the fabrication of multilayer PCBs, a layer-by-layer stacking method is adopted. After the first layer forms the first set of interlayer conductive structures according to steps S1 to S4, the semi-finished product is used as a new substrate to repeat steps S1 to S4 to form the second set of interlayer conductive structures. This process is repeated to complete the construction of multilayer circuits and interlayer conductivity. After all interlayer conductive structures are fabricated, the substrate is peeled off and the outer layer circuits on both sides are etched to obtain a multilayer PCB with multiple inner layer circuits and multiple sets of interlayer conductive structures.

9. A PCB manufacturing method that eliminates the need for through-hole plating and reduces copper content through etching, as described in claim 1, is characterized in that... The initial thickness of the substrate copper layer selected in S1 is 35 μm to 105 μm, and the thickness of the substrate copper layer retained after etching is 10 μm to 50 μm. The etching depth of the copper layer PAD is determined to be 25 μm to 70 μm according to the interlayer conductivity design requirements. The diameter or side length of the copper layer PAD is set according to the electrical performance requirements. The etching sidewall angle is controlled within the range of 75 degrees to 90 degrees. The setting of the above-mentioned dimensional parameters takes into account the integrity of resin filling and the controllability of the polishing process during subsequent RCC lamination.

10. A PCB manufacturing method that eliminates the need for through-hole plating and reduces copper content through etching, as described in claim 1, is characterized in that... The method forms a copper layer PAD as an interlayer conductive structure through etching and copper reduction in step S1, replacing the mechanical drilling and hole-filling electroplating processes in the traditional process. The copper layer PAD is formed by etching rather than drilling, and the resin filling is completed by RCC lamination rather than hole-filling electroplating. The interlayer conductivity is achieved by thickening the copper layer on the surface of the copper layer PAD through non-hole-filling electroplating in step S4. The entire process does not involve drilling equipment, drilling tools, hole-filling electroplating tanks, or corresponding hole position inspection equipment.

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