Printed circuit board and manufacturing method for same-layer local multi-copper-thickness circuit pattern of same-layer local multi-copper-thickness circuit pattern thereof

Abstract

According to the printed circuit board and the manufacturing method for the same-layer local multiple-copper-thickness circuit pattern of the printed circuit board, the same-layer high-frequency signal circuit on the printed circuit board is patterned step by step, and the multiple-copper-thickness circuit is accurately constructed in the same circuit layer in combination with the two-time pattern electroplating process and the voltage conversion process. Specifically, a layer of surface copper foil is additionally covered on the surface of the copper foil of the copper-clad substrate to form a voltage-transferring substrate, the surface copper foil is used as a connecting layer between a first circuit layer and a second circuit layer, and two surfaces of the surface copper foil are independently electroplated twice, so that the copper thickness distribution of different circuit areas is accurately controlled, and the voltage-transferring effect is improved. And finally, a plurality of signal circuit patterns with coexisting copper thicknesses are constructed in the surface copper layer on the inner-layer voltage conversion substrate, so that the fineness and reliability of the signal circuit are ensured to meet the high-frequency signal transmission requirement, the layout flexibility of the signal circuit on the printed circuit board is improved, the impedance matching of the signal circuit is ensured, and the signal loss is reduced at the same time.

Description

Technical Field

[0001] The present invention relates to the field of printed circuit board manufacturing, and more particularly to a method for manufacturing circuit patterns with multiple copper thicknesses in the same layer of a printed circuit board and a printed circuit board. Background Art

[0002] With the continuous development of the printed circuit board (PCB) industry, the requirements for signal transmission quality on PCBs are gradually increasing in high-end application scenarios such as 5G communications, artificial intelligence servers, and autonomous driving radar. The application requirements of high-frequency, high-speed signal transmission and high power density integration have also placed higher demands on the design and manufacturing of PCBs. While demanding increased signal transmission rates and power density, PCBs are also required to develop towards extreme miniaturization, which places higher demands on the refinement and reliability of PCB signal lines. The transmission quality of high-speed signals requires highly refined signal lines on PCBs. The use of relatively thin copper lines to achieve fine line widths, optimize impedance control and signal integrity, and maintain uniform thickness and smooth surface of the signal lines to reduce skin effect losses during high-frequency signal transmission, signal scattering, and phase distortion. Traditional PCB manufacturing processes often employ a simplified design logic of uniform copper thickness across a single layer of the circuit board. However, in the design of high-frequency signal PCBs, using the same copper thickness for both signal transmission and reception leads to significant signal loss interference, restricting the transmission and reception of high-frequency signals on the PCB. Specifically, copper thickness directly affects the DC resistance of the circuit. Transmission lines typically need to carry higher currents, so thicker copper layers are required to reduce Joule heating and generate lower conductor resistance to minimize signal loss. Reception lines, on the other hand, have a higher tolerance for line resistance, so thin copper layers can meet this requirement. Identifying the copper thickness for both lines can lead to overheating of the transmission line or cost redundancy for the reception line. Furthermore, using the same copper thickness for both transmission and reception lines limits designers' ability to adjust line width and thickness combinations to meet impedance requirements within a limited space. This restricts layout flexibility on high-frequency PCBs, hindering optimization of transmission efficiency and reception sensitivity, and preventing differentiated configuration of signal line performance within the same circuit layer. Therefore, the copper thickness of the transmission and receiving lines of high-frequency signal lines needs to be independently optimized according to specific application scenarios, such as frequency, current, and impedance requirements, to ensure impedance matching, reduce signal loss, avoid reflections, and take into account thermal reliability and manufacturing costs.

[0003] In order to break through the limitation of copper thickness uniformity on a single circuit layer on a printed circuit board, different copper thickness circuit areas corresponding to various performance requirements are established in the same circuit layer on the printed circuit board. In the existing technical system, the following processing methods can be attempted: 1. After the thick copper signal circuit is produced as a whole, the local copper thickness on the signal circuit is adjusted by physical cutting methods such as mechanical controlled depth milling. However, the mechanical stress of the tool will cause micro cracks on the surface of the copper foil, and the surface roughness will deteriorate sharply, which cannot meet the flatness requirements of high-frequency signal circuits; 2. Using selective electroplating technology, the copper thickness is increased by superimposing an electroplated layer on the local area of ​​the signal circuit. This technical solution requires repeated pattern masking, development and etching. The process is complicated, and each deviation in mask alignment will form jagged burrs on the edge of the copper layer, seriously affecting the integrity of the high-frequency signal. Therefore, it is necessary to develop a production method that does not affect the production precision of the signal circuit on the printed circuit board and can establish circuit patterns of various copper thicknesses in the local area of ​​a single circuit layer on the printed circuit board. Summary of the Invention

[0004] The present invention aims to overcome at least one of the above-mentioned defects of the prior art and provides a method for manufacturing circuit patterns of multiple copper thicknesses on the same layer of a printed circuit board and a printed circuit board. By optimizing the circuit manufacturing process of the printed circuit board, the high-frequency signal circuits on a single circuit layer are patterned step by step and combined with the conversion process, differentiated configuration of local copper thickness is achieved within the single-layer circuit on the printed circuit board, thereby improving the layout flexibility on the printed circuit board, ensuring impedance matching, and reducing signal loss.

[0005] The technical solution adopted by the present invention is first to provide a method for producing circuit patterns with multiple copper thicknesses on the same layer of a printed circuit board, comprising the following steps: S1. Pretreatment: Covering the copper layer of the copper-clad substrate with an additional layer of surface copper foil to prepare a transfer substrate, and performing a pretreatment on the surface of the surface copper foil; S2. Primary circuit production: affixing a mask material to the surface of the surface copper foil, forming a first circuit pattern on the surface of the surface copper foil through a single exposure and development process, and simultaneously producing an alignment structure thereon; thickening the first circuit pattern through a single electroplating process to form a first circuit layer; after removing the mask material through a single stripping process, performing a browning treatment on the first circuit layer and the surface of the surface copper foil; S3, lamination: covering the first circuit pattern with a prepreg and a functional layer and laminating them, so that the surface copper foil, the first circuit pattern, the prepreg and the functional layer are laminated to form an inner layer transfer substrate; S4, separating and leveling: separating and leveling the copper-clad substrate and the inner-layer transfer substrate from the surface copper foil, and performing secondary pretreatment on the surface copper foil of the inner-layer transfer substrate after separation; S5. Secondary Circuit Fabrication: Based on the alignment structure, drilling and positioning are performed, a mask material is applied to the flattened surface of the surface copper foil, and a second circuit pattern is formed on the surface of the inner surface copper foil through a secondary exposure and development process; the second circuit pattern is thickened through a secondary electroplating process to form a second circuit layer; and the mask material is removed through a secondary stripping process. S1. Pretreatment: An additional layer of surface copper foil is applied to the surface of the copper-clad substrate to prepare a transfer substrate, and the surface of the surface copper foil is pretreated once. S2. Primary circuit production: affixing a mask material to the surface of the surface copper foil, forming a first circuit pattern on the surface of the surface copper foil through a single exposure and development process, and simultaneously producing an alignment structure thereon; thickening the first circuit pattern through a single electroplating process to form a first circuit layer; after removing the mask material through a single stripping process, performing a browning treatment on the first circuit layer and the surface of the surface copper foil; S3, lamination: covering the first circuit layer with a prepreg and a functional layer and laminating them, so that the surface copper foil, the first circuit layer, the prepreg and the functional layer are laminated to form an inner layer transfer substrate; S4, separating and leveling: separating and leveling the copper-clad substrate and the inner-layer transfer substrate from the surface copper foil, and performing secondary pretreatment on the surface copper foil of the inner-layer transfer substrate after separation; S5. Secondary circuit fabrication: Based on the alignment structure, drilling and positioning are performed, a mask material is applied to the flattened surface of the surface copper foil, and a second circuit pattern is formed on the surface of the inner surface copper foil through a secondary exposure and development process; the second circuit pattern is thickened through a secondary electroplating process to form a second circuit layer; and the mask material is removed through a secondary stripping process. S6. Flash etching: The surface copper foil of the inner layer transfer substrate is removed by flash etching to form a printed circuit board with circuit patterns of various copper thicknesses on the same layer of the surface.

[0006] In this technical solution, by patterning the high-frequency signal circuit on a single circuit layer on a printed circuit board in steps and combining a two-step pattern electroplating process with a transfer process, the precise construction of multiple copper thickness circuits is achieved within the same circuit. Specifically, by covering an additional layer of surface copper foil on the circuit substrate to form a transfer substrate, the surface copper foil covers the surface of the circuit substrate, and the surface exposed by the surface copper foil can be used as the production basis of the first circuit layer. After the production is completed, the inner layer transfer substrate is formed by covering the semi-cured sheet and other functional layers on the first circuit layer and hot pressing. Since the surface roughness of the primary circuit layer and the surface copper foil is increased by browning in the single circuit production process, the interlayer bonding strength between the primary circuit layer and the surface copper foil and the semi-cured sheet is enhanced, and the surface copper foil and the circuit substrate are not bonded, the bonded functional layer, semi-cured sheet, first circuit layer and surface copper foil can be easily separated from the circuit substrate, so that the surface copper foil exposes another flat surface, and the other flat surface exposed by the flattened surface copper foil is used as the production basis of the second circuit layer, thereby achieving the fine production of the second circuit layer. That is, by using the surface copper foil as the connecting layer between the first circuit layer and the second circuit layer, two independent electroplating processes are performed on the two surfaces of the surface copper foil respectively, the copper thickness distribution of different circuit areas is precisely controlled, and the redundant copper foil is selectively removed through the final flash etching process to reshape the circuit layer on the printed circuit board, and finally a signal circuit pattern with multiple copper thicknesses coexisting is constructed in the surface copper layer on the inner layer transfer substrate; wherein, the two circuit patterns are both made based on the flat surface of the surface copper foil, and the alignment structure of the second circuit pattern is made synchronously based on the first circuit pattern production, avoiding the alignment error when the two circuit patterns are made, ensuring the overall production accuracy of the signal circuit pattern produced in steps, while ensuring the fineness and reliability of the signal line to meet the requirements of high-frequency signal transmission, and solving the limitation of the copper thickness uniformity of single-layer line production in the traditional printed circuit board production process, improving the flexibility of the signal line layout on the printed circuit board, ensuring its impedance matching, and reducing signal loss.

[0007] Furthermore, in step S5, there is an overlapping area between the second circuit pattern and the adjacent first circuit pattern; and the length of the overlapping area is not less than 15 μm.

[0008] In this technical solution, by setting an overlapping coverage area of ​​not less than 15μm between the second circuit pattern and the adjacent first circuit pattern, a continuous conductive path is formed between the two, achieving a gradient transition and structural interlocking between circuits with different copper thicknesses, and avoiding impedance steps and signal reflections between circuits with different copper thicknesses; at the same time, the physical constraint of the overlapping length ensures the uniform deposition of copper ions in the junction area during the electroplating process, preventing current density concentration and local overheating caused by thickness mutations, thereby enhancing the mechanical bonding strength and thermal stability between the copper layers formed by the two circuit production while maintaining signal integrity, thereby optimizing the mechanical reliability and high-frequency electrical performance of the high-frequency circuit on the printed circuit board, and avoiding signal reflections and mechanical failures that are prone to occur at the interface in the multiple electroplating process.

[0009] Preferably, in step S1, the thickness of the surface copper foil is 1-3 μm. In this technical solution, by using ultra-thin copper foil as the initial conductive layer, the necessary electroplating base function is retained for the subsequent primary circuit fabrication, transfer process, and secondary circuit fabrication process. The ultra-thin nature of the copper foil also significantly reduces the risk of over-etching the first circuit pattern during the subsequent flash etching process. At the same time, the ultra-thin copper foil has a high surface flatness, which provides good surface conditions for the attachment of high-resolution masks, facilitating the high-precision fabrication of signal circuits in the two circuit fabrication processes. Due to the introduction of the transfer process in the two circuit production processes, the ultra-thin copper layer uses a semi-cured sheet to combine with other functional layers during the lamination process. Its low thickness characteristic can reduce the stress concentration between layers and reduce the risk of delamination caused by the mismatch of thermal expansion coefficients between layers. At the same time, due to the small original thickness of the surface copper foil, the oxide anchoring layer formed after the browning treatment of the primary circuit and the surface copper foil can be deeply embedded in the resin formed by the melting and curing of the semi-cured sheet, thereby enhancing the interlayer bonding of the inner-layer transfer substrate, which is conducive to de-boarding on the other side of the surface copper foil without damaging the inner-layer transfer substrate, thereby improving the reliability of establishing a same-layer multi-copper thickness structure on the surface of the inner-layer transfer substrate.

[0010] Preferably, in step S2, the copper thickness of the first circuit layer is 3-35 μm.

[0011] Preferably, in step S5, the copper thickness of the second circuit layer is 3-35 μm.

[0012] In this technical solution, by limiting the copper thickness of both the first and second circuit layers to a range of 3-35 μm, the resulting circuit layers meet the transmission requirements of high-frequency signal lines and are suitable for the production of fine circuits. However, the copper thickness of the circuit layer comprising the first and second circuit layers is not excessively large, thereby affecting the overall electrical performance of the circuit layer. This balances power density, signal integrity, and process stability within the limited thickness of a single layer on a printed circuit board. Preferably, the overall copper thickness of the circuit layer comprising the first and second circuit layers is no greater than 35 μm.

[0013] Furthermore, in the step S1 and the step S4, the micro-etching process is turned off during the primary pre-treatment and the secondary pre-treatment; The primary pretreatment and the secondary pretreatment process include deoxidation treatment and plasma cleaning process on the surface of the surface copper foil.

[0014] In this technical solution, by disabling the micro-etching process in the pre-treatment of steps S1 and S4, that is, not using traditional chemical etching methods to clean and roughen the surface of the copper foil, the structural integrity of the ultra-thin copper foil is protected and the compatibility with subsequent processes is optimized. In steps S1 and S4, when the exposed surface of the surface copper foil is pre-treated, a combination of deoxidation treatment and plasma cleaning is used instead. This ensures that the surface of the copper foil is clean and has a certain roughness suitable for the subsequent pattern transfer process, while avoiding the establishment of excessive surface roughness on the copper foil surface, which affects the mechanical and electrical properties of the ultra-thin copper foil, thereby optimizing the surface state and process compatibility of the ultra-thin copper foil. Specifically, the deoxidation treatment selectively removes copper surface oxides through a weakly acidic solution without damaging the substrate, thereby ensuring the original thickness and conductive properties of the ultra-thin copper layer; plasma cleaning further activates the surface and removes organic residues by physical bombardment, while avoiding the risk of chemical corrosion, forming a nano-scale rough structure to enhance the adhesion of subsequent mask materials and reduce edge peeling or development defects during the pattern transfer process; thereby avoiding excessive thinning of the ultra-thin copper foil by micro-etching and avoiding etching through the surface copper foil, and achieving a synergistic improvement in the cleanliness, bonding strength and mask accuracy of the copper surface through a composite surface treatment method, laying the foundation for the precise forming of fine circuits and uniform deposition of electroplating layers in the two-way circuit pattern production process, while maintaining the mechanical integrity of the copper foil as a transfer carrier to ensure the reliability of the transfer process.

[0015] Furthermore, in the step S2 and the step S5, the mask material is a laser direct imaging photosensitive dry film; During the primary circuit production and the secondary circuit production process, the film lamination temperature is 100-140° C., the film lamination pressure is 0.3-0.7 MPa, the film lamination speed is 2.0-2.5 m / min, and the exposure energy is 55-75 mj.

[0016] In this technical solution, during the circuit pattern transfer process in the primary and secondary circuit production processes, the bonding strength between the dry film and the micro-roughened surface of the surface copper foil is improved by using a laser direct imaging photosensitive dry film. At the same time, by limiting the lamination parameters of the laser direct imaging photosensitive dry film (temperature 100-140°C, pressure 0.3-0.7MPa, speed 2.0-2.5m / min) and exposure energy (55-75mJ), the precise and effective adhesion of the dry film to the surface copper foil is ensured, achieving high-fidelity transfer of high-resolution circuit patterns on the surface of ultra-thin copper foil. Specifically, precise lamination temperature and pressure match the dry film's thermoplastic properties with the copper foil's mechanical endurance limits, preventing deformation of the ultra-thin copper layer under pressure while ensuring bubble-free lamination of the dry film to the smooth surface of the ultra-thin copper foil. The optimized exposure energy window balances the polymerization efficiency of the photosensitive material with linewidth control accuracy, resulting in clearer and sharper edges for the developed circuit pattern. During the secondary circuit fabrication process, combined with a pre-set alignment structure, the use of a laser direct-write maskless exposure mode further eliminates traditional film alignment errors, ensuring the fabrication accuracy of high-frequency signal circuits.

[0017] Preferably, in step S2, after the browning treatment, the surface roughness of the surface copper foil and the surface of the first circuit layer is 0.5-1.0 μm. By precisely controlling the roughness of the surface copper foil and the surface of the first circuit layer after the browning treatment, a synergistic optimization of the pressing bonding strength and high-frequency performance is achieved. Specifically, by establishing a moderate roughness on the surface copper foil and the surface of the first circuit layer, the semi-cured sheet can fully penetrate the gap between the copper layers during the pressing process, enhancing the mechanical interlocking effect and avoiding the risk of delamination of the inner layer of the transferred substrate. At the same time, an effective balance is established between the improved adhesion brought about by the increase in surface area of ​​the copper foil during the browning process and the loss of high-frequency transmission of the circuit due to the skin effect of the copper layer surface.

[0018] Furthermore, in step S5, X-ray is used to capture the alignment structure, and laser drilling is performed at the capture site to form positioning holes, and the secondary circuit manufacturing process is performed based on the alignment of the positioning holes.

[0019] In this technical solution, the spatial alignment accuracy of the secondary circuit and primary circuit graphics is significantly improved by introducing the collaborative process of X-ray grabbing alignment structure and laser drilling positioning holes. Specifically, the prefabricated alignment structure in the inner layer transfer substrate is accurately captured by X-ray penetrating imaging technology, and precise positioning holes are punched through the corresponding positions on the inner layer transfer substrate by laser, and used as the physical reference point for the production of secondary circuit graphics, eliminating the cumulative error caused by thermal expansion of the substrate or accumulation of mechanical stress, improving the accuracy and reliability of secondary circuit production, and also ensuring the accurate alignment and connection between the primary circuit layer and the secondary circuit layer.

[0020] Another object of the present invention is to provide a printed circuit board, which is manufactured using the manufacturing method provided in the present technical solution; the printed circuit board includes at least one conversion circuit layer, and the conversion circuit layer includes at least two circuit layers with different copper thicknesses, namely a first circuit layer and a second circuit layer, and the copper thickness of the conversion circuit layer is 3-35μm.

[0021] This technical solution provides a printed circuit board (PCB) including a voltage conversion circuit layer. By integrating two differentiated copper thickness structures, a first circuit layer and a second circuit layer, within a single circuit layer, signal lines with different copper thicknesses can be locally established within the same circuit layer on the PCB based on usage requirements. This ensures impedance matching while increasing the flexibility of signal line layout within the same circuit layer, further reducing signal loss on the PCB and saving circuit conductor costs, making it more suitable for the manufacture and production of high-frequency PCBs. Furthermore, the use of a heterogeneous structure within a single circuit layer not only enables functional partitioning of signal lines, thereby reducing the number of design layers on the PCB, but also reduces the thickness of the interlayer dielectric, thereby reducing the parasitic capacitance and delay of the signal transmission path. Furthermore, to ensure the manufacturing quality and transmission performance of the signal lines on the high-frequency PCB, the total copper thickness of the first and second circuit layers in the voltage conversion circuit layer is limited to no more than 35 μm, thereby controlling the overall conductor cross-sectional area of ​​the signal lines and optimizing the skin effect and impedance matching on the high-frequency signal lines.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. By patterning the high-frequency signal circuits on a single circuit layer on a printed circuit board in steps and combining two pattern electroplating processes with a transfer process, the precise construction of multiple copper thickness circuits is achieved within the same circuit. Specifically, a transfer substrate is formed by covering the circuit substrate with an additional layer of surface copper foil. The surface copper foil covers the surface of the circuit substrate. The exposed surface of the surface copper foil can be used as the basis for the production of the first circuit layer. After the production is completed, the first circuit layer is covered with a prepreg and other functional layers and hot-pressed to form an inner layer transfer substrate. Subsequently, the bonded functional layer, prepreg, first circuit layer and surface copper foil are separated from the circuit substrate, exposing another flat surface of the surface copper foil. The other flat surface exposed by the flattened surface copper foil is used as the basis for the production of the second circuit layer, achieving the fine production of the second circuit layer. That is, by using the surface copper foil as the connecting layer between the first circuit layer and the second circuit layer, two independent electroplating processes are performed on the two surfaces of the surface copper foil respectively, the copper thickness distribution of different circuit areas is precisely controlled, and the redundant copper foil is selectively removed through the final flash etching process to reshape the circuit layer on the printed circuit board, and finally a signal circuit pattern with multiple copper thicknesses coexisting is constructed in the surface copper layer on the inner layer transfer substrate; wherein, the two circuit patterns are both made based on the flat surface of the surface copper foil, and the alignment structure of the second circuit pattern is made synchronously based on the first circuit pattern production, avoiding the alignment error when the two circuit patterns are made, ensuring the overall production accuracy of the signal circuit pattern produced in steps, while ensuring the fineness and reliability of the signal line to meet the requirements of high-frequency signal transmission, and solving the limitation of the copper thickness uniformity of single-layer line production in the traditional printed circuit board production process, improving the flexibility of the signal line layout on the printed circuit board, ensuring its impedance matching, and reducing signal loss.

[0023] 2. A printed circuit board (PCB) including a voltage conversion circuit layer is provided. By integrating two differentiated copper thickness structures, a first circuit layer and a second circuit layer, within a single circuit layer, signal lines with different copper thicknesses can be locally established within the same circuit layer on the PCB based on usage requirements. This ensures impedance matching while increasing the flexibility of signal line layout within the same circuit layer, further reducing signal loss on the PCB, saving circuit conductor costs, and making it more suitable for the manufacture and production of high-frequency PCBs. Furthermore, the use of a circuit structure combining multiple local thicknesses within a single circuit layer not only enables functional zoning of signal lines, thereby reducing the number of design layers on the PCB, but also reduces the thickness of the interlayer dielectric, thereby reducing parasitic capacitance and delay in the signal transmission path. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention provides a flow chart of a method for producing a single-layer, localized, and multiple-copper-thickness circuit pattern on a printed circuit board.

[0025] Figure 2 This is a structural schematic diagram of the transfer pressing process in the method for preparing a single-layer local multi-copper thickness circuit pattern of a printed circuit board provided in Example 2 of the present invention, including the pressing and board separation processes.

[0026] Figure 3 This is a schematic diagram of the partial structure of a printed circuit board provided by the present invention, which includes at least one voltage conversion circuit layer.

[0027] Figure 4 This is a partial schematic diagram of the manufacturing process of a printed circuit board including at least one voltage conversion circuit layer provided by the present invention. DETAILED DESCRIPTION

[0028] The accompanying drawings are for illustrative purposes only and are not to be construed as limiting the present invention. To better illustrate the following embodiments, some components in the accompanying drawings may be omitted, enlarged, or reduced in size, and do not represent actual product dimensions. Those skilled in the art will appreciate that some well-known structures and their descriptions may be omitted from the accompanying drawings.

[0029] Example 1 like Figure 1 As shown, this embodiment provides a method for producing a circuit pattern with multiple copper thicknesses on the same layer of a printed circuit board, comprising the following steps: S1. Pretreatment: Covering the copper layer of the copper-clad substrate with an additional layer of surface copper foil to prepare a transfer substrate, and performing a pretreatment on the surface of the surface copper foil; S2. Primary circuit production: affixing a mask material to the surface of the surface copper foil, forming a first circuit pattern on the surface of the surface copper foil through a single exposure and development process, and simultaneously producing an alignment structure thereon; thickening the first circuit pattern through a single electroplating process to form a first circuit layer; after removing the mask material through a single stripping process, performing a browning treatment on the first circuit layer and the surface of the surface copper foil; S3, lamination: covering the first circuit layer with a prepreg and a functional layer and laminating them, so that the surface copper foil, the first circuit layer, the prepreg and the functional layer are laminated to form an inner layer transfer substrate; S4, separating and leveling: separating and leveling the copper-clad substrate and the inner-layer transfer substrate from the surface copper foil, and performing secondary pretreatment on the surface copper foil of the inner-layer transfer substrate after separation; S5. Secondary circuit fabrication: Based on the alignment structure, drilling and positioning are performed, a mask material is applied to the flattened surface of the surface copper foil, and a second circuit pattern is formed on the surface of the inner surface copper foil through a secondary exposure and development process; the second circuit pattern is thickened through a secondary electroplating process to form a second circuit layer; and the mask material is removed through a secondary stripping process. S6. Flash etching: The surface copper foil of the inner layer transfer substrate is removed by flash etching to form a printed circuit board with circuit patterns of various copper thicknesses on the same layer of the surface.

[0030] Specifically, a transfer substrate is formed by additionally covering a layer of surface copper foil on the circuit substrate, and the surface copper foil covers the surface of the circuit substrate. The surface exposed by the surface copper foil can be used as the basis for making the first circuit layer. After the production is completed, the inner-layer transfer substrate is formed by covering the semi-cured sheet and other functional layers on the first circuit layer and hot pressing them. Since in the primary circuit production process, the surface roughness of the primary circuit layer and the surface copper foil is increased by browning treatment, the interlayer bonding force between the primary circuit layer and the surface copper foil and the semi-cured sheet is enhanced, and the surface copper foil and the circuit substrate are not bonded, the bonded functional layer, semi-cured sheet, first circuit layer and surface copper foil can be easily separated from the circuit substrate, so that the surface copper foil exposes another flat surface, and the other flat surface exposed by the flattened surface copper foil is used as the basis for making the second circuit layer, thereby realizing the fine production of the second circuit layer. That is, by using the surface copper foil as the connecting layer between the first circuit layer and the second circuit layer, two independent electroplating operations are performed on the two surfaces of the surface copper foil respectively, so as to accurately control the copper thickness distribution in different circuit areas, and selectively remove the redundant copper foil through the final flash etching process to reshape the circuit layer on the printed circuit board. Finally, a signal circuit pattern with multiple copper thicknesses coexisting is constructed in the surface copper layer on the inner layer transfer substrate, which improves the flexibility of the signal circuit layout on the printed circuit board, ensures its impedance matching, and reduces signal loss.

[0031] Furthermore, in step S5, an overlapping region exists between the second circuit pattern and the adjacent first circuit pattern; the length of the overlapping region is no less than 15 μm. By providing an overlapping region of no less than 15 μm between the second circuit pattern and the adjacent first circuit pattern, a continuous conductive path is formed between the two, achieving a gradient transition and structural interlocking between circuits of different copper thicknesses, avoiding impedance steps and signal reflections between circuits of different copper thicknesses. Furthermore, while maintaining signal integrity, the mechanical bond strength and thermal stability between the copper layers formed by the two circuit fabrications are enhanced.

[0032] Preferably, in step S1, the thickness of the surface copper foil is 1-3 μm. By using ultra-thin copper foil as the initial conductive layer, the necessary electroplating base function is retained for subsequent primary circuit fabrication, transfer process, and secondary circuit fabrication. Its ultra-thin nature also significantly reduces the risk of over-etching the surface of the first circuit pattern during the subsequent flash etching process. Furthermore, the ultra-thin copper foil has a high surface flatness, providing excellent surface conditions for attaching high-resolution masks, facilitating high-precision fabrication of signal circuits in both circuit fabrication processes. Due to the introduction of the transfer process in the two circuit production processes, the ultra-thin copper layer uses a semi-cured sheet to combine with other functional layers during the lamination process. Its low thickness characteristic can reduce the stress concentration between layers and reduce the risk of delamination caused by the mismatch of thermal expansion coefficients between layers. At the same time, due to the small original thickness of the surface copper foil, the oxide anchoring layer formed after the browning treatment of the primary circuit and the surface copper foil can be deeply embedded in the resin formed by the melting and curing of the semi-cured sheet, thereby enhancing the interlayer bonding of the inner-layer transfer substrate, which is conducive to de-boarding on the other side of the surface copper foil without damaging the inner-layer transfer substrate, thereby improving the reliability of establishing a same-layer multi-copper thickness structure on the surface of the inner-layer transfer substrate.

[0033] Preferably, in step S2, the copper thickness of the first circuit layer is 3-35 μm; and in step S5, the copper thickness of the second circuit layer is 3-35 μm. This ensures that both circuit layers are suitable for the production of fine circuits without excessively increasing the overall copper thickness of the circuit layer comprising the first and second circuit layers. This balances power density, signal integrity, and process stability within the limited thickness of a single layer on the printed circuit board. Preferably, the overall copper thickness of the circuit layer comprising the first and second circuit layers is no greater than 35 μm.

[0034] Furthermore, in the step S1 and the step S4, the micro-etching process is turned off during the primary pre-treatment and the secondary pre-treatment; The primary pretreatment and the secondary pretreatment process include deoxidation treatment and plasma cleaning process on the surface of the surface copper foil.

[0035] Specifically, by not using traditional chemical etching to clean and roughen the surface of the copper foil, a combination of deoxidation treatment and plasma cleaning is adopted. This not only ensures that the surface of the copper foil is clean and has a certain roughness suitable for the subsequent pattern transfer process, but also avoids the establishment of excessive surface roughness on the copper foil surface, which affects the mechanical and electrical properties of the ultra-thin copper foil, thereby optimizing the surface state and process compatibility of the ultra-thin copper foil.

[0036] Furthermore, in the step S2 and the step S5, the mask material is a laser direct imaging photosensitive dry film; During the primary circuit production and the secondary circuit production process, the film lamination temperature is 100-140° C., the film lamination pressure is 0.3-0.7 MPa, the film lamination speed is 2.0-2.5 m / min, and the exposure energy is 55-75 mj.

[0037] Specifically, during the circuit pattern transfer process during the primary and secondary circuit production processes, the use of laser direct imaging photosensitive dry film improves the bonding strength between the dry film and the micro-roughened surface of the surface copper foil. At the same time, by limiting the lamination parameters of the laser direct imaging photosensitive dry film to temperature 100-140°C, pressure 0.3-0.7MPa, speed 2.0-2.5m / min and exposure energy 55-75mJ, the accurate and effective adhesion of the dry film to the surface copper foil is ensured, achieving high-fidelity transfer of high-resolution circuit patterns on the surface of ultra-thin copper foil.

[0038] Preferably, in step S2, after the browning treatment, the surface roughness of the surface copper foil and the first circuit layer is 0.5-1.0 μm. Specifically, by establishing a moderate roughness on the surface copper foil and the first circuit layer, the prepreg can fully penetrate the gaps between the copper layers during the transfer and lamination process, enhancing the mechanical interlocking effect and avoiding the risk of delamination of the inner layer transfer substrate. At the same time, an effective balance is established between the increased surface area of ​​the copper foil caused by the browning process, which improves adhesion, and the skin effect of the copper layer surface, which reduces high-frequency transmission losses of the circuit.

[0039] Furthermore, in step S5, X-ray is used to capture the alignment structure, and laser drilling is performed at the capture site to form positioning holes, and the secondary circuit manufacturing process is performed based on the alignment of the positioning holes.

[0040] Specifically, X-ray penetrating imaging technology is used to accurately capture the prefabricated alignment structure in the inner-layer transfer substrate, and precise positioning holes are punched at the corresponding positions on the inner-layer transfer substrate through laser. These holes are used as physical reference points for the production of secondary circuit graphics, eliminating the cumulative errors caused by thermal expansion of the substrate or accumulation of mechanical stress, improving the accuracy and reliability of secondary circuit production, and also ensuring accurate alignment and connection between the primary and secondary circuit layers.

[0041] Example 2 like Figure 1-Figure 3 As shown, this embodiment provides a method for producing a plurality of copper thickness circuit patterns on the same layer of a printed circuit board. This embodiment differs from Example 1 in that the copper-clad substrate used in this embodiment is a double-sided copper-clad substrate. The double-sided copper-clad substrate includes a carrier core and 18μm copper foil laminated on both sides. The inner layer transfer substrate is produced on both surfaces of the double-sided copper-clad substrate. Specifically, the following steps are included: S1. Pretreatment: Cover the copper layer on both sides of the double-sided copper-clad substrate with a layer of 3μm surface copper foil to prepare a transfer substrate; and perform a pretreatment on the exposed surfaces of the surface copper foil on both sides; S2. Primary circuit fabrication: affixing a mask material to the surfaces of the double-sided copper foils, forming a first circuit pattern on the surfaces of the double-sided copper foils through a single exposure and development process, and simultaneously fabricating an alignment structure thereon; thickening the first circuit pattern through a single electroplating process to form a first circuit layer; after removing the mask material through a single stripping process, performing a browning treatment on the first circuit layer and the surface of the copper foils; S3, Lamination: Cover the first circuit layer on both sides with prepreg and functional layer (Core) and press them together, so that the surface copper foil, first circuit layer, prepreg and functional layer (Core) on both sides are pressed together to form the inner layer transfer substrate; S4. Separation and Leveling: Separate the double-sided copper-clad substrate and the inner-layer transfer substrate from the surface copper foil to form a separated double-sided copper-clad substrate and two inner-layer transfer substrates. Level the inner-layer transfer substrate and perform secondary pretreatment on the exposed surface copper foil of the separated inner-layer transfer substrate. S5. Secondary circuit fabrication: Based on the alignment structure, drilling and positioning are performed, a mask material is applied to the flattened surface of the surface copper foil, and a second circuit pattern is formed on the surface of the inner surface copper foil through a secondary exposure and development process; the second circuit pattern is thickened through a secondary electroplating process to form a second circuit layer; and the mask material is removed through a secondary stripping process. S6. Flash etching: removing the surface copper foil of the inner layer transfer substrate through a flash etching process, and simultaneously forming two printed circuit boards with circuit patterns of various copper thicknesses on the same surface.

[0042] Example 3 like Figure 3-Figure 4 As shown, this embodiment provides a printed circuit board, which is manufactured using the manufacturing method provided in Example 1 or Example 2; the printed circuit board includes at least one conversion circuit layer, and the conversion circuit layer includes at least two circuit layers with different copper thicknesses, namely a first circuit layer and a second circuit layer, and the copper thickness of the conversion circuit layer is 3-35μm.

[0043] Specifically, by integrating two differentiated copper thickness structures, the first and second circuit layers, within a single circuit layer, signal lines with different copper thicknesses can be locally established within the same circuit layer on a printed circuit board based on usage requirements. This ensures impedance matching while increasing the flexibility of signal line layout within the same circuit layer, further reducing signal loss on the printed circuit board and saving circuit conductor costs, making it more suitable for the manufacture and production of high-frequency printed circuit boards. Furthermore, the use of a heterogeneous structure within a single circuit layer not only enables functional partitioning of signal lines, thereby reducing the number of design layers on the printed circuit board, but also reduces the thickness of the interlayer dielectric, reducing the parasitic capacitance and delay of the signal transmission path, providing an integrated carrier for high-density, high-frequency circuits that combines power carrying, low-loss transmission, and space compression. Preferably, to ensure the manufacturing quality and transmission performance of signal lines on high-frequency printed circuit boards, the total copper thickness of the first and second circuit layers in the converter circuit layer is limited to no more than 35 μm, thereby controlling the overall conductor cross-sectional area of ​​the signal lines and optimizing the skin effect and impedance matching on the high-frequency signal lines.

[0044] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the technical solutions of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for producing circuit patterns with multiple copper thicknesses on the same layer of a printed circuit board, characterized in that: The following steps are involved: S1. Pretreatment: Covering the copper layer of the copper-clad substrate with an additional layer of surface copper foil to prepare a transfer substrate, and performing a pretreatment on the surface of the surface copper foil; S2. Primary circuit production: affixing a mask material to the surface of the surface copper foil, forming a first circuit pattern on the surface of the surface copper foil through a single exposure and development process, and simultaneously producing an alignment structure thereon; thickening the first circuit pattern through a single electroplating process to form a first circuit layer; after removing the mask material through a single stripping process, performing a browning treatment on the first circuit layer and the surface of the surface copper foil; S3, lamination: covering the first circuit layer with a prepreg and a functional layer and laminating them, so that the surface copper foil, the first circuit layer, the prepreg and the functional layer are laminated to form an inner layer transfer substrate; S4, separating and leveling: separating and leveling the copper-clad substrate and the inner-layer transfer substrate from the surface copper foil, and performing secondary pretreatment on the surface copper foil of the inner-layer transfer substrate after separation; S5. Secondary circuit production: Based on the alignment structure, drilling and positioning are performed, a mask material is attached to the flattened surface of the surface copper foil, and a second circuit pattern is formed on the surface of the inner surface copper foil through a secondary exposure and development process; Thickening the second circuit pattern by a secondary electroplating process to form a second circuit layer; and removing the mask material by a secondary stripping process; S6. Flash etching: The surface copper foil of the inner layer transfer substrate is removed by flash etching to form a printed circuit board with circuit patterns of various copper thicknesses on the same layer of the surface.

2. The production method according to claim 1, characterized in that In step S5, there is an overlapping area between the second circuit pattern and the adjacent first circuit pattern; The length of the overlapping area is not less than 15 μm.

3. The production method according to claim 1, characterized in that In the step S1, the thickness of the surface copper foil is 1-3 μm.

4. The production method according to claim 1, characterized in that In the step S2, the copper thickness of the first circuit layer is 3-35 μm.

5. The production method according to claim 1, characterized in that: In the step S5, the copper thickness of the second circuit layer is 3-35 μm.

6. The production method according to any one of claims 1 to 5, characterized in that: In the step S1 and the step S4, the micro-etching process is turned off during the primary pre-treatment and the secondary pre-treatment; The primary pre-treatment and the secondary pre-treatment process include deoxidation treatment and plasma cleaning process on the surface of the surface copper foil.

7. The production method according to any one of claims 1 to 5, characterized in that: In the step S2 and the step S5, the mask material is a laser direct imaging photosensitive dry film; During the primary circuit production and the secondary circuit production process, the film lamination temperature is 100-140° C., the film lamination pressure is 0.3-0.7 MPa, the film lamination speed is 2.0-2.5 m / min, and the exposure energy is 55-75 mj.

8. The production method according to any one of claims 1 to 5, characterized in that: In the step S2, after the browning treatment, the surface roughness of the surface copper foil and the surface of the first circuit layer is 0.5-1.0 μm.

9. The production method according to any one of claims 1 to 5, characterized in that: In step S5, the alignment structure is captured by X-ray, and laser drilling is performed at the captured location to form positioning holes. The secondary circuit manufacturing process is performed based on the alignment of the positioning holes.

10. A printed circuit board, characterized in that: The printed circuit board is manufactured using the manufacturing method described in any one of claims 1 to 9; the printed circuit board includes at least one voltage conversion circuit layer, and the voltage conversion circuit layer includes at least two circuit layers with different copper thicknesses, namely a first circuit layer and a second circuit layer, and the copper thickness of the voltage conversion circuit layer is 3-35 μm.

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