Preparation method of copper-clad ceramic substrate with local plating layer

Abstract

The invention relates to a preparation method of a copper-clad ceramic substrate with a local coating, and the preparation method comprises the following steps: S1, carrying out the first pretreatment of the copper-clad ceramic substrate, and obtaining a substrate after the first treatment; s2, sequentially carrying out primary film pasting, primary exposure, primary development, etching and primary film stripping on the substrate subjected to the first treatment obtained in the step S1 to obtain a substrate subjected to circuit etching; s3, carrying out second pretreatment on the substrate after the circuit is etched in the step S2 to obtain a substrate after the second pretreatment; and S4, sequentially carrying out secondary film pasting, secondary exposure, secondary development, chemical plating and secondary film stripping on the substrate subjected to the second treatment obtained in the step S3 to obtain the copper-clad ceramic substrate with a local plating layer. According to the invention, precise alignment of the local plating copper-clad ceramic substrate can be realized, the tolerance of a chemical plating area is reduced, and the product precision is improved.

Description

Technical Field

[0001] This invention relates to the field of electronic materials technology, and specifically to a method for preparing a copper-clad ceramic substrate with a partial plating layer. Background Technology

[0002] As electronic devices evolve towards miniaturization and high performance, traditional circuit materials (such as FR4) are no longer sufficient to meet the high-performance requirements of new electronic components due to limitations in heat dissipation and high-frequency operation. Copper-clad ceramic substrates, with their excellent thermal conductivity and electrical properties, are an ideal choice for electronic components. In particular, locally plated copper-clad ceramic substrates, with customized plating in specific areas, can further optimize the integration, heat dissipation, and electrical performance of electronic components.

[0003] Currently, in the local coating manufacturing of copper-clad ceramic substrates, wet film printing is usually used to protect the non-coating areas. However, the existing wet film printing technology has many drawbacks: (1) ink overflow is easy to occur during the printing process, resulting in poor alignment accuracy, which makes it difficult to meet the strict requirements for coating position in the manufacturing of high-precision electronic components; (2) wet film printing has low efficiency and is difficult to adapt to the needs of large-scale production; (3) ink will remain in the water during the stripping process, generating a large number of suspended ink particles, which not only contaminates the stripping solution, but also increases the difficulty and cost of subsequent processing.

[0004] Therefore, providing a method for preparing copper-clad ceramic substrates that can guarantee local plating accuracy and improve local plating efficiency is a technical problem that needs to be solved. Summary of the Invention

[0005] To address the above problems, the present invention aims to provide a method for preparing a copper-clad ceramic substrate with a partial plating layer.

[0006] To achieve this objective, the present invention employs the following technical solution: This invention provides a method for preparing a copper-clad ceramic substrate with a partial plating layer, the method comprising the following steps: S1, The copper-clad ceramic substrate is subjected to a first pretreatment to obtain a first-treated substrate; S2, the first processed substrate obtained in step S1 is subjected to one film application, one exposure, one development, one etching and one film removal in sequence to obtain the substrate after etching the lines. S3, the substrate with the etched lines obtained in step S2 is subjected to a second pretreatment to obtain a second pretreated substrate; S4, the second processed substrate obtained in step S3 is subjected to secondary film application, secondary exposure, secondary development, chemical plating and secondary film removal in sequence to obtain a copper-clad ceramic substrate with partial coating.

[0007] The preparation method provided by this invention employs a combination of secondary lamination, secondary exposure, secondary development, electroless plating, and secondary stripping for localized coating. This enables precise alignment of the copper-clad ceramic substrate with localized coating, reduces tolerance in the electroless plating area, and improves product precision. Compared to traditional ink printing methods, this method saves time, increases production efficiency, avoids ink residue during the stripping process, reduces pollution, and simplifies post-processing.

[0008] Preferably, step S1, the first pretreatment, includes sequential cleaning and roughening.

[0009] In this invention, the copper-clad ceramic substrate is first cleaned through a first pretreatment to remove surface impurities. Then, roughening is performed to enhance the adhesion between the subsequent metal layer and the dry film. The roughening method can employ conventional methods in the art, such as SPS system-based roughening.

[0010] Preferably, the roughened surface roughness Ra is 0.4-0.9 μm, for example, it can be 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm or 0.9 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0011] In this invention, the roughened surface roughness Ra can be selected according to the type of copper-clad ceramic substrate. For example, when using an AMB copper-clad ceramic substrate, Ra is 0.4-0.7 μm, and when using a DBC copper-clad ceramic substrate, Ra is 0.7-0.9 μm.

[0012] Preferably, step S2, the first film application, includes: applying a first dry film to both sides of the first processed substrate.

[0013] Preferably, the first dry film comprises an acid-resistant photosensitive dry film.

[0014] In this invention, the acid-resistant etching photosensitive dry film can be a commonly used acid-resistant etching photosensitive dry film in the art, which is commercially available.

[0015] Preferably, the single exposure in step S2 is performed using a CCD exposure machine or an LDI exposure machine.

[0016] Preferably, the exposure energy of the CCD exposure machine in the single exposure is set to 7-8 divisions of the 21st energy bar.

[0017] Preferably, the exposure energy of the LDI exposure machine in the single exposure is set to 300-500mJ, for example, it can be 300mJ, 320mJ, 340mJ, 350mJ, 360mJ, 380mJ, 400mJ, 420mJ, 450mJ, 460mJ, 480mJ or 500mJ, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] Preferably, the developing solution used in step S2 for the first development contains sodium carbonate.

[0019] Preferably, the sodium carbonate concentration in the developing solution used in the first development is 8-12 g / L, for example, it can be 8 g / L, 9 g / L, 10 g / L, 11 g / L or 12 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the developing linear velocity for one development is 2.2-2.8 m / min, for example, it can be 2.2 m / min, 2.3 m / min, 2.4 m / min, 2.5 m / min, 2.6 m / min, 2.7 m / min or 2.8 m / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, the film removal solution used in step S2 for the first film removal contains sodium hydroxide.

[0022] Preferably, the mass concentration of sodium hydroxide in the stripping solution used for the first stripping is 3.5-7.3%, for example, it can be 3.5%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5%, 5.2%, 5.4%, 5.6%, 5.8%, 6%, 6.2%, 6.4%, 6.6%, 6.8%, 7%, 7.3%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the stripping speed in step S2 is 0.6-1.0 m / min, for example, it can be 0.6 m / min, 0.7 m / min, 0.8 m / min, 0.9 m / min or 1.0 m / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] In this invention, a copper-clad ceramic substrate undergoes a first-stage film application, with acid-resistant etching photosensitive dry films applied to both sides. Following this, a CCD or LDI exposure machine is used for a first-stage exposure to achieve high-precision circuit pattern transfer, allowing the dry film in the desired circuit areas to cross-link and solidify. A subsequent development stage dissolves and removes the dry film from the unexposed areas to be etched, clearly exposing the copper layer and preparing for subsequent etching. Next, the desired circuitry is precisely etched onto the copper layer. After etching, a water washing process removes residual etching solution and copper ions. Finally, a stripping stage removes all solidified dry film from the substrate surface, completing the initial fabrication of the circuit board.

[0025] Preferably, step S3, the second pretreatment, includes cleaning.

[0026] In this invention, a second pretreatment is used to remove surface impurities, preparing for subsequent secondary film application.

[0027] Preferably, the secondary film application in step S4 includes: applying a second dry film to both sides of the second processed substrate.

[0028] Preferably, the second dry film comprises an anti-electroplated photosensitive dry film.

[0029] In this invention, the anti-electroplated photosensitive dry film is a commonly used anti-electroplated photosensitive dry film in the art, which is commercially available.

[0030] Preferably, the secondary exposure is performed using an LDI exposure machine.

[0031] Preferably, the exposure energy of the LDI exposure machine in the secondary exposure is set to 700-850mJ, for example, it can be 700mJ, 720mJ, 740mJ, 760mJ, 780mJ, 800mJ, 820mJ, 840mJ or 850mJ, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] In this invention, by optimally controlling the exposure energy of the LDI exposure machine during secondary exposure, it is possible to further achieve the transfer of refined patterns, reduce regional errors, and thereby improve the plating accuracy.

[0033] In this invention, four-point positioning is used in the secondary exposure, which can further ensure that the positional offset and dimensional error of the product are within 50μm.

[0034] Preferably, the developing solution used in the secondary development contains sodium carbonate; Preferably, the sodium carbonate concentration in the developing solution used for the secondary development is 8-12 g / L, for example, it can be 8 g / L, 9 g / L, 10 g / L, 11 g / L or 12 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the developing linear velocity of the secondary developing process is 1.2-1.8 m / min, for example, it can be 1.2 m / min, 1.3 m / min, 1.4 m / min, 1.5 m / min, 1.6 m / min, 1.7 m / min or 1.8 m / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] In this invention, by optimizing the development linear speed of the secondary development, the accuracy of pattern transfer can be further improved, thereby improving the accuracy of the plating area.

[0037] Preferably, the plating temperature in step S4 is 25-35℃, for example, it can be 25℃, 26℃, 28℃, 30℃, 32℃, 34℃ or 35℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] Preferably, the plating time is 2-4 minutes, for example, 2 minutes, 2.5 minutes, 3 minutes, 3.5 minutes or 4 minutes, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] In this invention, the metal for local plating in the electroplating area can be selected as needed, including but not limited to silver, nickel, gold, etc., and the electroplating solution can be selected accordingly. For example, when localizing silver plating, a silver nitrate solution of 5-20 g / L can be selected.

[0040] Preferably, the stripping solution used in the secondary stripping process contains sodium hydroxide.

[0041] Preferably, the mass concentration of sodium hydroxide in the stripping solution used for the secondary stripping is 3.5-7.3%, for example, it can be 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7% or 7.3%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] In this invention, an anti-plating photosensitive dry film is applied to the surface of a copper-clad ceramic substrate via a secondary film application process, and areas that do not require electroplating are subjected to secondary exposure. During the secondary exposure, the exposure energy of the LDI exposure machine is controlled, and the areas requiring electroplating are kept unexposed (i.e., windowing treatment) to prevent plating from occurring in the unexposed areas. Subsequently, a secondary development process is performed to remove the dry film from the unexposed electroplating areas, exposing the surface of the ceramic substrate and forming a pattern for the areas to be plated. Electroplating is then performed to achieve a localized plating layer, and finally, a secondary film stripping process is used to remove all the cured dry film (i.e., the dry film from the exposed areas).

[0043] As a preferred embodiment of the present invention, the preparation method includes the following steps: S1, the copper-clad ceramic substrate is cleaned and then roughened to a surface roughness Ra of 0.4-0.9μm to obtain the first processed substrate; S2, the first processed substrate obtained in step S1 is coated with a first dry film on both sides. The first dry film is an acid-resistant etchable photosensitive dry film. Then, a CCD exposure machine or an LDI exposure machine is used for a single exposure. In the single exposure, the exposure energy of the CCD exposure machine is set to 7-8 grids of 21-level energy bars, and the exposure energy of the LDI exposure machine is set to 300-500mJ. Then, a developing solution with a sodium carbonate mass concentration of 8-12g / L is used for a single development at a developing line speed of 2.2-2.8m / min. Then, etching is performed. Next, a stripping solution with a sodium hydroxide mass concentration of 3.5-7.3% is used for a single stripping at a stripping line speed of 0.6-1.0m / min to obtain the substrate with etched lines. S3, clean the substrate with the etched lines obtained in step S2 to obtain the second processed substrate. S4, the second processed substrate obtained in step S3 is coated with a second dry film on both sides. The second dry film is an anti-electroplating photosensitive dry film. The second exposure is performed using an LDI exposure machine. The exposure energy of the LDI exposure machine is set to 700-850mJ. Then, a developing solution with a sodium carbonate mass concentration of 8-12g / L is used for secondary development at a linear speed of 1.2-1.8m / min. Then, chemical plating is performed at a temperature of 25-35℃ for 2-4min. After that, a stripping solution with a sodium hydroxide mass concentration of 3.5-7.3% is used for secondary stripping to obtain a copper-clad ceramic substrate with partial coating.

[0044] Compared with the prior art, the present invention has the following beneficial effects: The preparation method provided by this invention employs a combination of secondary lamination, secondary exposure, secondary development, electroless plating, and secondary stripping for localized coating. This enables precise alignment of the copper-clad ceramic substrate with localized coating, reduces tolerances in the electroless plating area, and lowers the error in the electroless plating area to below 28 μm, and under optimal conditions, to below 18 μm, thereby improving product precision. Compared to traditional ink printing methods, this method saves time, increases production efficiency, avoids ink residue during the stripping process, reduces pollution, and simplifies post-processing. Detailed Implementation

[0045] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0046] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0047] Example 1 This embodiment provides a method for preparing a copper-clad ceramic substrate with a partial plating layer, the method comprising the following steps: S1, the copper-clad ceramic substrate is cleaned to remove surface impurities, and then roughened to a surface roughness Ra of 0.6μm to obtain the first-processed substrate, which enhances the adhesion between the subsequent metal layer and the dry film. S2, the first processed substrate obtained in step S1 is coated with a first dry film on both sides. The first dry film is an acid-resistant photosensitive dry film with a thickness of 38μm. Then, a CCD exposure machine is used for a single exposure, in which the exposure energy of the CCD exposure machine is set to 7 grids of 21-level energy bars, thereby realizing the line exposure; Then, a developing solution with a sodium carbonate concentration of 10 g / L was used for the first development at a linear speed of 2.5 m / min to expose the area to be etched. Then, etching is performed to etch the copper onto the copper-clad ceramic substrate; Next, a stripping solution with a sodium hydroxide concentration of 5% was used for one stripping operation at a stripping speed of 0.8 m / min to obtain the substrate with etched lines, thus completing the initial fabrication of the circuit board. S3, clean the substrate after etching the lines obtained in step S2 to prepare for subsequent film application, and obtain the second processed substrate. S4, the second processed substrate obtained in step S3 is coated with a second dry film on both sides. The second dry film is an anti-electroplating photosensitive dry film with a thickness of 50μm. Then, an LDI exposure machine was used to perform a second exposure on the areas that did not require chemical plating. The exposure energy of the LDI exposure machine was set to 800mJ during the second exposure. Then, a secondary development was performed using a sodium carbonate developer with a mass concentration of 10 g / L to remove the dry film from the unexposed areas. The development linear speed was 1.5 m / min, forming the area to be plated. Then, silver nitrate of 10 g / L was used for electroplating at 30°C for 3 minutes to form a silver plating layer. Then, a stripping solution with a sodium hydroxide concentration of 5% was used for a second stripping process to remove the dry film in the exposed area, resulting in a copper-clad ceramic substrate with a localized coating.

[0048] Example 2 This embodiment provides a method for preparing a copper-clad ceramic substrate with a partial plating layer, the method comprising the following steps: S1, the copper-clad ceramic substrate is cleaned to remove surface impurities, and then roughened to a surface roughness Ra of 0.4μm to obtain the first-processed substrate, which enhances the adhesion between the subsequent metal layer and the dry film. S2, the first processed substrate obtained in step S1 is coated with a first dry film on both sides. The first dry film is an acid-resistant photosensitive dry film with a thickness of 38μm. Then, an LDI exposure machine is used for a single exposure, in which the exposure energy of the LDI exposure machine is set to 300mJ, thereby achieving the circuit exposure; Then, a developing solution with a sodium carbonate concentration of 8 g / L was used for the first development at a linear speed of 2.8 m / min to expose the area to be etched. Then, etching is performed to etch the copper onto the copper-clad ceramic substrate; Next, a stripping solution with a sodium hydroxide concentration of 7.3% was used for one stripping operation at a stripping speed of 0.6 m / min to obtain the substrate with etched lines, thus completing the initial fabrication of the circuit board. S3, clean the substrate after etching the lines obtained in step S2 to prepare for subsequent film application, and obtain the second processed substrate. S4, the second processed substrate obtained in step S3 is coated with a second dry film on both sides. The second dry film is an anti-electroplating photosensitive dry film with a thickness of 50μm. Then, an LDI exposure machine was used to perform a second exposure on the areas that did not require chemical plating. The exposure energy of the LDI exposure machine was set to 700mJ during the second exposure. Then, a secondary development was performed using a sodium carbonate developer with a mass concentration of 12 g / L to remove the dry film from the unexposed areas. The development linear speed was 1.2 m / min, forming the area to be plated. Then, using 10 g / L silver nitrate, a silver plating layer was formed by electroplating at 25°C for 2 minutes. Then, a stripping solution with a sodium hydroxide concentration of 3.5% was used for a second stripping process to remove the dry film in the exposed area, resulting in a copper-clad ceramic substrate with a localized coating.

[0049] Example 3 This embodiment provides a method for preparing a copper-clad ceramic substrate with a partial plating layer, the method comprising the following steps: S1, the copper-clad ceramic substrate is cleaned to remove surface impurities, and then roughened to a surface roughness Ra of 0.9μm to obtain the first-processed substrate, which enhances the adhesion between the subsequent metal layer and the dry film. S2, the first processed substrate obtained in step S1 is coated with a first dry film on both sides. The first dry film is an acid-resistant photosensitive dry film with a thickness of 38μm. Then, an LDI exposure machine is used for a single exposure, in which the exposure energy of the LDI exposure machine is set to 500mJ, thereby achieving line exposure; Then, a developing solution with a sodium carbonate concentration of 12 g / L was used for the first development at a linear speed of 2.2 m / min to expose the area to be etched. Then, etching is performed to etch the copper onto the copper-clad ceramic substrate; Next, a stripping solution with a sodium hydroxide concentration of 3.5% was used for one stripping operation at a stripping speed of 1.0 m / min to obtain the substrate with etched lines, thus completing the initial fabrication of the circuit board. S3, clean the substrate after etching the lines obtained in step S2 to prepare for subsequent film application, and obtain the second processed substrate. S4, the second processed substrate obtained in step S3 is coated with a second dry film on both sides. The second dry film is an anti-electroplating photosensitive dry film with a thickness of 50μm. Then, an LDI exposure machine was used to perform a second exposure on the areas that did not require chemical plating. The exposure energy of the LDI exposure machine was set to 850mJ during the second exposure. Then, a secondary development was performed using a sodium carbonate developer with a mass concentration of 8 g / L to remove the dry film from the unexposed areas. The development linear speed was 1.8 m / min, forming the area to be plated. Then, silver nitrate of 10 g / L was used for electroplating at 35°C for 4 minutes to form a silver plating layer. Then, a stripping solution with a sodium hydroxide concentration of 7.3% was used for a second stripping process to remove the dry film in the exposed area, resulting in a copper-clad ceramic substrate with a localized coating.

[0050] Example 4 This embodiment provides a method for preparing a copper-clad ceramic substrate with a partial coating. The only difference between this method and that of Embodiment 1 is that the exposure dose of the LDI exposure machine is set to 600mJ during the secondary exposure.

[0051] Example 5 This embodiment provides a method for preparing a copper-clad ceramic substrate with a partial coating. The only difference between this method and that of Embodiment 1 is that the exposure dose of the LDI exposure machine is set to 900mJ during the secondary exposure.

[0052] Example 6 This embodiment provides a method for preparing a copper-clad ceramic substrate with a partial coating. The only difference between this method and that of Example 1 is that the developing linear speed in the secondary exposure is 0.8 m / min.

[0053] Example 7 This embodiment provides a method for preparing a copper-clad ceramic substrate with a partial coating. The only difference between this method and that of Embodiment 1 is that the developing linear speed in the secondary exposure is 2.2 m / min.

[0054] Comparative Example 1 This comparative example provides a method for preparing a copper-clad ceramic substrate with a partial coating. The only difference from Example 1 is that in S4, the secondary film application is replaced with wet ink printing.

[0055] The plating error of the copper-clad ceramic substrates with partial plating obtained in the above embodiments and comparative examples was detected, and the results are shown in Table 1.

[0056] Table 1 As can be seen from the data in Table 1: (1) As can be seen from the data of Examples 1-7, under better conditions, the error of the electroplating area can be reduced to below 28 μm, and under better conditions, it can be reduced to below 18 μm.

[0057] (2) As can be seen from the comparison between Example 1 and Examples 4-7, the present invention can further improve the accuracy of the electroplating area and reduce the error by optimizing the exposure dose and development speed of the LDI exposure machine in the secondary exposure.

[0058] (3) By comparing Example 1 and Comparative Example 1, it can be seen that the present invention, by controlling the use of anti-electroplating photosensitive dry film, has higher precision than wet ink printing, and can improve the processing speed and reduce the difficulty of removing the film solution.

[0059] In summary, the present invention can achieve precise alignment of locally coated copper-clad ceramic substrates, reduce tolerance in the plating area, and improve product precision.

[0060] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a copper-clad ceramic substrate with a partial plating layer, characterized in that, The preparation method includes the following steps: S1, The copper-clad ceramic substrate is subjected to a first pretreatment to obtain a first-treated substrate; S2, the first processed substrate obtained in step S1 is subjected to one film application, one exposure, one development, one etching and one film removal in sequence to obtain the substrate after etching the lines. S3, the substrate with the etched lines obtained in step S2 is subjected to a second pretreatment to obtain a second pretreated substrate; S4, the second processed substrate obtained in step S3 is subjected to secondary film application, secondary exposure, secondary development, chemical plating and secondary film removal in sequence to obtain a copper-clad ceramic substrate with partial coating.

2. The preparation method according to claim 1, characterized in that, Step S1, the first preprocessing, includes sequential cleaning and roughening; Preferably, the roughened surface roughness Ra is 0.4-0.9 μm.

3. The preparation method according to claim 1 or 2, characterized in that, Step S2, the single film application, includes: applying a first dry film to both sides of the first processed substrate; Preferably, the first dry film comprises an acid-resistant photosensitive dry film.

4. The preparation method according to any one of claims 1-3, characterized in that, The single exposure described in step S2 uses a CCD exposure machine or an LDI exposure machine; Preferably, the exposure energy of the CCD exposure machine in the single exposure is set to 7-8 divisions of the 21st energy bar; Preferably, the exposure energy of the LDI exposure machine in the single exposure is set to 300-500mJ.

5. The preparation method according to any one of claims 1-4, characterized in that, The developing solution used in step S2 for the first development contains sodium carbonate; Preferably, the sodium carbonate concentration in the developing solution used in the first development is 8-12 g / L. Preferably, the linear velocity of the developing process in one development is 2.2-2.8 m / min.

6. The preparation method according to any one of claims 1-5, characterized in that, The stripping solution used in step S2 for the first stripping process contains sodium hydroxide; Preferably, the mass concentration of sodium hydroxide in the stripping solution used for the first stripping is 3.5-7.3%.

7. The preparation method according to any one of claims 1-6, characterized in that, The linear speed of film removal in step S2 is 0.6-1.0 m / min.

8. The preparation method according to any one of claims 1-7, characterized in that, Step S3, the second pretreatment, includes cleaning.

9. The preparation method according to any one of claims 1-8, characterized in that, Step S4, the secondary film application, includes: applying a second dry film to both sides of the second-treated substrate; Preferably, the second dry film comprises an anti-electroplating photosensitive dry film; Preferably, the secondary exposure is performed using an LDI exposure machine; Preferably, the exposure energy of the LDI exposure machine in the secondary exposure is set to 700-850 mJ; Preferably, the developing solution used in the secondary development contains sodium carbonate; Preferably, the sodium carbonate concentration in the developing solution used for the secondary development is 8-12 g / L. Preferably, the linear velocity of the secondary development is 1.2-1.8 m / min.

10. The preparation method according to any one of claims 1-9, characterized in that, The temperature for the electroplating in step S4 is 25-35℃; Preferably, the plating time is 2-4 minutes; Preferably, the stripping solution used in the secondary stripping process contains sodium hydroxide; Preferably, the mass concentration of sodium hydroxide in the stripping solution used for the secondary stripping is 3.5-7.3%.

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