Film clamping prevention method for isolated circuit of PCB (Printed Circuit Board) and PCB

Abstract

The invention relates to a PCB isolated circuit film clamping prevention method and a PCB, and the method comprises the following steps: S1, a substrate is covered with a first dry film, the first dry film is provided with a first window corresponding to an isolated circuit region, and the periphery of the first dry film corresponding to the isolated circuit region is provided with an auxiliary window; s2, electroplating the substrate, forming a first composite metal layer on the surface of the substrate corresponding to the first window, and forming an auxiliary composite metal layer on the surface of the substrate corresponding to the auxiliary window; s3, performing film stripping and first etching on the substrate, and forming an outer-layer circuit on the surface of the substrate; s4, covering the substrate with a second dry film, wherein the second dry film is provided with a second window corresponding to the auxiliary composite metal layer; and S5, removing the auxiliary composite metal layer through second etching. According to the method, the thickness of the copper layer can be homogenized during electroplating, poor film clamping is avoided, and meanwhile the subsequent etching residual risk caused by the too thick local plating layer is eliminated.

Description

Technical Field

[0001] The present invention relates to the field of printed circuit boards, and more particularly, to a method for preventing film clamping of isolated circuits on a PCB and a PCB. Background Art

[0002] Due to performance requirements on the circuit board, isolated circuits are designed, that is, circuit patterns independent of the main circuit area. During graphic electroplating of isolated circuits, the current at the position of the isolated circuit is greater than that in the large copper surface area, resulting in a copper thickness of the isolated circuit greater than that of other areas. When the thickness of the electroplated copper is greater than the thickness of the anti-plating dry film, it causes poor film clamping, which will cause the copper between the lines not to be etched away in the subsequent etching process, resulting in short-circuit scrapping. Currently, the solution in the industry is to use a thicker dry film. However, the resolution of such a thick dry film is insufficient and cannot be used for the production of PCB boards with fine line widths or fine line pitches. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preventing film clamping of isolated circuits on a PCB and a PCB, which can achieve the uniformization of the deposition thickness of the copper layer during electroplating, avoid poor film clamping, and eliminate the risk of subsequent etching residues caused by local over-thick plating.

[0004] A method for preventing film clamping of isolated circuits on a PCB, which is used to manufacture a PCB with an isolated circuit area, includes the following steps: S1. Cover a first dry film on the substrate. The first dry film is provided with a first window corresponding to the isolated circuit area and auxiliary windows corresponding to the periphery of the isolated circuit area; S2. Electroplate the substrate to form a first composite metal layer on the surface of the substrate corresponding to the first window, and simultaneously form an auxiliary composite metal layer on the surface of the substrate corresponding to the auxiliary window; S3. Perform the first film stripping and the first etching on the substrate to form an outer layer circuit on the surface of the substrate; S4. Cover a second dry film on the substrate. The second dry film is provided with a second window corresponding to the auxiliary composite metal layer; S5. Remove the auxiliary composite metal layer through the second etching.

[0005] In the above technical solution, through a two-stage masking and etching process, an auxiliary composite metal layer is formed around the isolated circuit, effectively balancing the electroplating current distribution and reducing the risk of copper thickness accumulation at the isolated circuit. The secondary etching is used to accurately remove the auxiliary structure, which can not only prevent the short-circuit problem caused by the residue of the first etching, but also avoid the line film clamping defect caused by insufficient dry film thickness in the traditional process.

[0006] Further, the auxiliary window includes a plurality of window units, and the plurality of window units are arranged along the outer periphery of the isolated circuit area.

[0007] In the above technical solution, the arrangement of multiple window units makes the peripheral current in the isolated circuit area more uniform, further preventing abnormal plating thickness caused by local current concentration.

[0008] Furthermore, there is a spacing between each of the window units and the isolated circuit area.

[0009] In the above technical solution, setting the safety spacing between the window unit and the circuit not only ensures the electric field regulation effect of the auxiliary composite metal layer, but also avoids the risk of metal residue between the auxiliary composite metal layer and the main circuit, improving the tolerance capacity of the etching process window.

[0010] Furthermore, the window unit is formed into a rectangle or a circle.

[0011] In the above technical solution, the window units with regular geometric shapes can enhance the process controllability. The circular design can also reduce the electric field distortion at the sharp corners, while the rectangle is conducive to high-density layout, improving the design flexibility.

[0012] Furthermore, after the step S3, applying a plating resist oil to the first composite metal layer is also included.

[0013] In the above technical solution, the plating resist oil coating forms a physical isolation barrier before the secondary patterning, preventing the formed circuit from being chemically eroded or accidentally electroplated in the subsequent processes, ensuring the integrity of the circuit pattern. At the same time, the plating resist oil can reduce the height difference between the composite metal layer and the substrate surface, enabling the second dry film to cover the substrate surface well.

[0014] Furthermore, after the step S5, performing a second stripping on the second dry film is also included.

[0015] In the above technical solution, the second stripping operation can remove the second dry film, facilitating subsequent processing.

[0016] Furthermore, both the first composite metal layer and the auxiliary composite metal layer include a copper layer and a tin layer.

[0017] The present invention also provides a PCB manufactured by using the method for preventing film clamping of isolated circuits of a PCB as described above.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: By opening auxiliary windows around the isolated circuit area corresponding to the first dry film, during the electroplating process, an auxiliary composite metal layer is formed around the isolated circuit area. This auxiliary composite metal layer effectively balances the current intensity distribution between conductor areas during the electroplating process, thereby significantly reducing the current density in the isolated circuit area, achieving uniform deposition thickness of the copper layer during electroplating, avoiding film clamping defects, and eliminating the subsequent etching residue risk caused by excessive local plating thickness. After completing the outer layer pattern, the auxiliary composite metal layer is removed by the second etching in this technical solution, which not only preserves the integrity of the functional circuit but also removes the auxiliary structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic flowchart of a method for preventing film clamping in isolated circuits of a PCB according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some but not all of the embodiments of the present application.

[0021] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the present application claimed, but merely represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0022] Please refer to Figure 1 , in a preferred embodiment, a method for preventing film clamping in isolated circuits of a PCB according to the present invention, which is used to manufacture a PCB with an isolated circuit area, includes the following steps: S1. Cover a first dry film on the substrate. The first dry film is provided with a first window corresponding to the isolated circuit area and an auxiliary window corresponding to the periphery of the isolated circuit area.

[0023] In this step, the substrate is a semi-finished printed circuit board after pretreatment, where the pretreatment includes pressing, drilling, copper deposition, and panel electroplating. The first dry film can be an existing anti-plating dry film, which covers the surface of the substrate and is provided with windows corresponding to the circuit pattern. In this embodiment, the first dry film is provided with a first window corresponding to the isolated circuit area and an auxiliary window corresponding to the periphery of the isolated circuit area.

[0024] S2. Electroplate the substrate to form a first composite metal layer on the surface of the substrate corresponding to the first window, and simultaneously form an auxiliary composite metal layer on the surface of the substrate corresponding to the auxiliary window.

[0025] In this step, both the first composite metal layer and the auxiliary composite metal layer include a copper layer and a tin layer, and the copper layer is located between the tin layer and the substrate surface. The specific electroplating method can adopt the existing conventional electroplating, which will not be elaborated in this application.

[0026] S3. Perform the first stripping and the first etching on the substrate to form an outer layer circuit on the surface of the substrate.

[0027] In this step, the stripping is to remove the first dry film, and the excess copper layer not covering the tin layer is removed by the first etching. After the first etching, it also includes removing the tin layer on the surface of the copper layer, so as to form an outer layer circuit on the surface of the substrate.

[0028] S4. Cover a second dry film on the substrate, and the second dry film is provided with a second window corresponding to the auxiliary composite metal layer.

[0029] In this step, the second dry film can adopt the existing anti-etch dry film, which covers the surface of the substrate and is provided with a second window corresponding to the auxiliary composite metal layer.

[0030] S5. Remove the auxiliary composite metal layer by the second etching.

[0031] It can be seen from the above technical solutions that through the two-stage masking and etching process, an auxiliary composite metal layer is formed around the isolated circuit, effectively balancing the electroplating current distribution and reducing the risk of copper thickness accumulation at the isolated circuit. The secondary etching is used to accurately remove the auxiliary structure, which can not only prevent the short-circuit problem caused by the residue of the first etching, but also avoid the line clamping film defect caused by the insufficient dry film thickness in the traditional process.

[0032] In this embodiment, the auxiliary window includes a plurality of window units, and the plurality of window units are arranged along the outer periphery of the isolated circuit area. The arrangement of multiple window units makes the current around the isolated circuit area more uniform, further preventing the abnormal coating thickness caused by local current concentration.

[0033] In this embodiment, there is a spacing between each window unit and the isolated circuit area. Setting the safety spacing between the window unit and the circuit can not only ensure the electric field regulation effect of the auxiliary composite metal layer, but also avoid the risk of metal residue between the auxiliary composite metal layer and the main circuit, improving the tolerance ability of the etching process window.

[0034] In this embodiment, the window unit is formed into a rectangle or a circle. The window unit with a regular geometric shape can enhance the process controllability. The circular design can also reduce the electric field distortion at the sharp corners, while the rectangle is conducive to high-density layout and improves the design flexibility.

[0035] In this embodiment, after step S3, it further includes coating a plating resist on the first composite metal layer. The plating resist coating forms a physical isolation barrier before the second patterning, preventing the formed circuit from being chemically eroded or accidentally electroplated in subsequent processes, ensuring the integrity of the circuit pattern. At the same time, the plating resist can reduce the height difference between the composite metal layer and the substrate surface, enabling the second dry film to cover the substrate surface well.

[0036] In this embodiment, after step S5, it further includes performing a second stripping on the second dry film. The second stripping operation can remove the second dry film, facilitating subsequent processing.

[0037] The present invention also provides a PCB manufactured by using the PCB isolated circuit anti-clamping film method as described above.

[0038] The present invention opens auxiliary windows corresponding to the first dry film around the isolated circuit area, so that during the electroplating process, an auxiliary composite metal layer is formed around the isolated circuit area. The auxiliary composite metal layer effectively balances the current intensity distribution between conductor areas during the electroplating process, thereby significantly reducing the current density in the isolated circuit area, achieving the uniformization of the copper layer deposition thickness during electroplating, avoiding poor clamping film, and at the same time eliminating the risk of subsequent etching residues caused by excessive local plating thickness. After the outer layer pattern is completed, this technical solution removes the auxiliary composite metal layer through the second etching, which not only retains the integrity of the functional circuit but also removes the auxiliary structure.

[0039] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more, unless otherwise specifically defined.

[0040] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preventing the clamping of isolated circuits on a PCB, which is used to manufacture a PCB with an isolated circuit area, and is characterized in that, It includes the following steps: S1. Cover a first dry film on the substrate. The first dry film is provided with a first window corresponding to the isolated circuit area and auxiliary windows corresponding to the periphery of the isolated circuit area; S2. Electroplate the substrate to form a first composite metal layer on the surface of the substrate corresponding to the first window, and simultaneously form an auxiliary composite metal layer on the surface of the substrate corresponding to the auxiliary windows; S3. Perform the first film stripping and the first etching on the substrate to form an outer layer circuit on the surface of the substrate; S4. Cover a second dry film on the substrate. The second dry film is provided with a second window corresponding to the auxiliary composite metal layer; S5. Remove the auxiliary composite metal layer through the second etching.

2. The PCB isolated line anti-pinch film method according to claim 1, wherein The auxiliary windows include a plurality of window units, and the plurality of window units are arranged along the outer periphery of the isolated circuit area.

3. The PCB isolated line anti-pinch film method according to claim 2, wherein There is a spacing between each window unit and the isolated circuit area.

4. The PCB isolated line anti-pinch film method according to claim 2, characterized in that, The window unit is formed into a rectangle or a circle.

5. The PCB isolated line anti-pinch film method according to claim 1, wherein After the step S3, it further includes coating a plating resist on the first composite metal layer.

6. The PCB isolated line anti-pinch film method according to claim 1, characterized in that, After the step S5, it further includes performing the second film stripping on the second dry film.

7. The method for preventing clamping of isolated circuits on a PCB according to claim 1, characterized in that, Both the first composite metal layer and the auxiliary composite metal layer include a copper layer and a tin layer.

8. A PCB, characterized in that, It is made by using the PCB isolated circuit anti-clamping film method according to any one of claims 1 to 8.

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