A PCB fabrication method to improve circuit density
By using laser ablation and resist layer protection, the problem of increasing circuit density in existing PCB processes has been solved, enabling the production of high-density circuits on conventional equipment and reducing production difficulty and cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 珠海杰赛科技有限公司
- Filing Date
- 2024-06-14
- Publication Date
- 2026-06-30
AI Technical Summary
Existing PCB processes struggle to improve line width/spacing on conventional equipment. Side etching results in uneven line shapes, and etching pre-compensation increases costs and makes it difficult to produce high-density lines.
The method of laser ablation and resist protection is adopted. The copper layer is ablated by laser and then etched to avoid side etching. The dry film line width spacing is directly used as the line width spacing after etching, eliminating the need for etching pre-compensation. The resist layer is used to protect the sides of the circuit. The copper layer becomes thinner after etching, reducing the etching difficulty.
It enables a significant increase in line density on conventional equipment, allowing the production of PCBs with a line width of 35/35 micrometers. Substrate PCB manufacturers can produce PCBs with a line width of 25/25 micrometers or even 20/20 micrometers, reducing production difficulty and cost.
Smart Images
Figure CN118632445B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of PCB manufacturing technology, and in particular to a PCB manufacturing method that improves circuit density. Background Technology
[0002] As electronic products evolve towards portability, high integration, and high computing power, increasingly higher demands are being placed on the line density of PCBs (Printed Circuit Boards). The requirement is to increase line width / spacing from the original 75 / 75 micrometers to 50 / 50 micrometers, and even down to 30 / 30 micrometers or 25 / 25 micrometers at the substrate level. For most conventional PCB manufacturers, achieving 75 / 75 micrometers of line width / spacing capability is already the limit; further increases would raise equipment investment and production costs by an order of magnitude. How to improve line width / spacing capabilities based on existing PCB process equipment is currently the biggest demand and challenge in the PCB industry.
[0003] In existing technologies, when etching the copper layer, the etching solution will laterally etch the copper layer beneath the resist layer (tin layer), a process known in the PCB industry as side etching. Side etching results in narrower lines in the final product. Therefore, it is generally necessary to pre-compensate for the narrower lines, a process called etching pre-compensation. This involves widening the dry film lines during the engineering design, typically by at least 25 micrometers. When a copper layer linewidth / spacing of 75 / 75 micrometers is required after etching, the actual design is a linewidth of 100 micrometers and a spacing of 50 micrometers. Due to the 25-micrometer side etching, the resulting linewidth is 100-25=75 micrometers, and the spacing is 50+25=75 micrometers. The minimum linewidth / spacing capability of conventional dry film is 50 / 50 micrometers, and a dry film spacing of 50 micrometers is the limit. Therefore, the spacing of the etched lines must be no less than 75 micrometers.
[0004] Additionally, side etching can cause the etched circuit to take the shape of a trapezoid that is narrower at the top and wider at the bottom, with a width difference of 50 micrometers between the top and bottom. Since the actual line width is taken as the wider part at the bottom of the line during actual operation, if the bottom (widest part) of the line is less than 75 micrometers, the top of the line will be less than 25 micrometers. In extreme cases, the top may even be completely etched away and the anti-etching tin layer will fall off. Therefore, the line width (bottom width) after etching generally needs to be ≥75 micrometers. Summary of the Invention
[0005] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a PCB manufacturing method that can significantly increase the line density and improve the process level by utilizing conventional production equipment.
[0006] According to a first aspect of the present invention, a PCB manufacturing method for improving circuit density is provided, comprising the following steps: material cutting → external light imaging → pattern electroplating → film removal → resist layer fabrication → laser ablation → circuit etching → resist layer removal.
[0007] According to the PCB manufacturing method for improving circuit density of the present invention, in the material cutting step, a copper-clad laminate is cut into a suitable processing size. The copper-clad laminate is an epoxy resin board with a layer of copper foil on its surface.
[0008] According to the PCB manufacturing method for improving circuit density described in this invention, in the external light imaging step, a dry film is coated on the surface of the copper-clad laminate. The dry film is exposed to light by laser exposure, and the circuit pattern is transferred onto the dry film. Then, the unexposed dry film is removed by development and cleaning to form the desired circuit pattern.
[0009] According to the PCB manufacturing method for improving line density of the present invention, in the external light imaging step, no etching pre-compensation is performed on the line width spacing of the dry film, and the line width spacing formed by the dry film is the line width spacing after etching.
[0010] According to the PCB manufacturing method for improving line density of the present invention, in the pattern electroplating step, a layer of copper is plated onto the area not covered by the dry film by electroplating copper.
[0011] According to the PCB manufacturing method for improving circuit density described in this invention, in the film removal step, the dry film is dissolved and removed by the principle of sodium hydroxide solution or plasma etching.
[0012] According to the PCB manufacturing method for improving line density of the present invention, in the resist layer manufacturing step, a resist layer is formed on the entire copper surface by means of electroplating tin or electroplating nickel or coating an organic film.
[0013] According to the PCB manufacturing method for improving line density of the present invention, in the laser ablation step, a laser is used to ablate the resist layer at the bottom of the valley between the lines. The laser ablation needs to ablate the copper layer below the resist layer by more than 2 micrometers to ensure that the resist layer is completely removed. Etching compensation is reserved on both sides of the laser ablation, and the compensation value is 5 micrometers to 20 micrometers on one side.
[0014] According to the PCB manufacturing method for improving circuit density described in this invention, in the laser ablation step, the thickness of the copper layer above the ablated epoxy resin board is 1 micrometer to 5 micrometers.
[0015] According to the PCB manufacturing method for improving line density described in this invention, in the line etching step, the exposed copper after laser ablation is dissolved and removed by spraying an etching solution. The copper surface in the area not ablated by the laser is preserved due to the protection of the resist layer, and the sides of the lines are also protected from lateral etching due to the protection of the resist layer. In the resist removal step, the resist layer above the line layer is removed using a resist removal agent, leaving only the copper layer lines.
[0016] This invention offers at least the following advantages: A PCB manufacturing method for improving line density eliminates the need for etching pre-compensation of the dry film's linewidth spacing during the external light imaging step. The linewidth spacing formed by the dry film is the same as the linewidth spacing after etching; therefore, the linewidth limit of the dry film is the limit of the etched lines. During stripping, the absence of a tin layer that readily reacts with sodium hydroxide allows for extended processing time, ensuring thorough stripping and almost completely avoiding film trapping. Furthermore, the copper layer on the sides of the lines, due to the presence of a resist layer, completely avoids side etching issues. The thinner copper layer after laser ablation makes line etching easier and reduces etching difficulty. Therefore, conventional PCB manufacturers using this solution can produce PCBs with linewidths as low as 35 / 35 micrometers; while carrier PCB manufacturers using this solution will find it significantly easier to produce carrier boards with linewidths of 25 / 25 micrometers or even 20 / 20 micrometers.
[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description
[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments;
[0019] Figure 1 This is a process flow diagram of a preferred embodiment of the present invention;
[0020] Figure 2 This is a schematic diagram of the structure of the copper-clad laminate according to a preferred embodiment of the present invention;
[0021] Figure 3 This is a schematic diagram of the structure after external light imaging in a preferred embodiment of the present invention;
[0022] Figure 4 This is a schematic diagram of the structure after pattern electroplating in a preferred embodiment of the present invention;
[0023] Figure 5 This is a schematic diagram of the structure after film removal in a preferred embodiment of the present invention;
[0024] Figure 6 This is a schematic diagram of the structure after the anti-corrosion layer is fabricated according to a preferred embodiment of the present invention;
[0025] Figure 7This is a schematic diagram of the structure after line etching in a preferred embodiment of the present invention;
[0026] Figure 8 This is a schematic diagram of the structure after the anti-corrosion layer has been removed in a preferred embodiment of the present invention.
[0027] Figure label:
[0028] Epoxy resin board 10, copper foil layer 20, dry film 30, anti-corrosion layer 40. Detailed Implementation
[0029] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.
[0030] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.
[0031] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.
[0032] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.
[0033] Reference Figures 1 to 8 A PCB manufacturing method for increasing circuit density includes the following steps:
[0034] Material cutting → external light imaging → pattern electroplating → film removal → resist layer fabrication → laser ablation → circuit etching → resist layer removal.
[0035] It is understood that, in the embodiments of the present invention, the external light imaging step does not require etching pre-compensation for the linewidth spacing of the dry film 30. The linewidth spacing formed by the dry film is the same as the linewidth spacing after etching; therefore, the linewidth limit capability of the dry film is the limit capability of the etched circuit. During film removal, since there is no tin layer that easily reacts with sodium hydroxide, the processing time can be extended as much as possible, ensuring sufficient film removal and almost completely avoiding film trapping. As for the copper layer on the side of the circuit, because a resist layer 40 is made, the problem of side etching can be completely avoided. The copper foil layer 20 becomes thinner after laser ablation, making circuit etching easier and reducing etching difficulty. Therefore, it can significantly increase the circuit density of PCBs manufactured by conventional factories. Conventional PCB factories can produce PCBs with linewidth spacing as low as 35 / 35 micrometers using this solution; while when carrier PCB factories use this solution, the difficulty of producing carrier boards with linewidth spacing of 25 / 25 micrometers or even 20 / 20 micrometers will be significantly reduced.
[0036] Furthermore, in the cutting step, the copper-clad laminate is cut into suitable processing dimensions. The copper-clad laminate is an epoxy resin board 10 with a copper foil layer 20 on its surface.
[0037] Furthermore, in the external light imaging step, a dry film 30 is coated on the surface of the copper-clad board. The dry film 30 is exposed to light by laser exposure, and the circuit pattern is transferred onto the dry film 30. Then, the unexposed dry film 30 is removed by development and cleaning to form the desired circuit pattern.
[0038] Furthermore, in the external light imaging step, no etching pre-compensation is performed on the linewidth spacing of the dry film 30, and the linewidth spacing formed by the dry film 30 is the linewidth spacing after etching.
[0039] Understandably, the absence of etching compensation allows for a significant reduction in line spacing and line width, thereby increasing line density.
[0040] Furthermore, in the pattern electroplating step, a layer of copper is plated onto the uncovered areas of the dry film 30 by electroplating copper.
[0041] Furthermore, in the film removal step, the dry film 30 is dissolved and removed by means of sodium hydroxide solution or plasma etching.
[0042] It should be noted that, in the embodiments of the present invention, since there is no tin layer that easily reacts with sodium hydroxide, the stripping step can extend the processing time as much as possible, ensuring sufficient stripping and almost completely avoiding film trapping.
[0043] Furthermore, in the resist layer fabrication step, an resist layer 40 is formed on the entire copper surface by electroplating tin or nickel or coating with an organic film.
[0044] It is understandable that the resist layer 40 can protect the sidewalls of the copper layer of the circuit and prevent the copper layer of the circuit from being eroded.
[0045] It is worth noting that, in the embodiments of the present invention, the anti-corrosion layer 40 can be plated by electroplating or coated by coating.
[0046] Furthermore, in the laser ablation step, a laser is used to ablate the resist layer 40 at the bottom of the valley between the lines. The laser ablation needs to ablate the copper foil layer 20 below the resist layer 40 by more than 2 micrometers to ensure that the resist layer 40 is completely removed. Etching compensation is reserved on both sides of the laser ablation, with the compensation value being 5 micrometers to 20 micrometers on one side.
[0047] Understandably, the laser ablation step can remove the resist layer 40 above the copper foil layer 20 on the bottom surface of the circuit to be processed, thereby achieving the etching of the copper foil layer 20.
[0048] It should be noted that during the laser ablation step, the laser energy must not be too high to avoid completely penetrating the underlying copper layer and ablating the epoxy resin board 10.
[0049] It should be noted that precise alignment with the preset target on the PCB is required during the laser ablation process.
[0050] Furthermore, in the laser ablation step, the thickness of the copper foil layer 20 above the ablated epoxy resin plate 10 is 1 micrometer to 5 micrometers.
[0051] Understandably, when producing extremely fine line spacing, such as 20 / 20 micrometers, the laser energy can be adjusted appropriately in this step, so that the copper foil layer after ablation is reduced to only 1 to 5 micrometers. This makes line etching easier and significantly reduces the etching difficulty.
[0052] Furthermore, in the circuit etching step, the exposed copper after laser ablation is dissolved and removed by spraying with etching solution. The copper surface in the area not ablated by the laser is preserved due to the protection of the resist layer 40, and the sides of the circuit will also not be eroded due to the protection of the resist layer 40. In the resist removal step, the resist layer 40 above the circuit layer is removed using a resist removal agent, leaving only the copper circuit layer.
[0053] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.
Claims
1. A method of making a PCB with increased line density, characterized by, Includes the following steps: Material cutting → external light imaging → pattern electroplating → film removal → resist layer preparation → laser ablation → circuit etching → resist layer removal; In the laser ablation step, a laser is used to ablate the resist layer at the bottom of the valley between the lines. The laser ablation needs to ablate the copper layer below the resist layer by more than 2 micrometers to ensure that the resist layer is completely removed. Etching compensation is reserved on both sides of the laser ablation, with a compensation value of 5 micrometers to 20 micrometers on one side. In the laser ablation step, the thickness of the copper layer above the ablated epoxy resin board is 1 micrometer to 5 micrometers. In the external light imaging step, a dry film is coated on the surface of the copper-clad board. The dry film is exposed by laser exposure, and the circuit pattern is transferred onto the dry film. Then, the unexposed dry film is removed by development and cleaning to form the desired circuit pattern. In the external light imaging step, no etching pre-compensation is performed on the linewidth spacing of the dry film. The linewidth spacing formed by the dry film is the linewidth spacing after etching. In the pattern electroplating step, copper is electroplated onto the areas not covered by the dry film to form a layer of copper. In the stripping step, the dry film is dissolved and removed by the principle of sodium hydroxide solution or plasma etching. In the process of creating the resist layer, a resist layer is formed on the entire copper surface by means of electroplating tin or nickel or coating an organic film.
2. The method of claim 1, wherein, In the material cutting step, the copper-clad laminate is cut into appropriate processing dimensions. The copper-clad laminate is an epoxy resin board with a layer of copper foil on its surface.
3. The PCB manufacturing method for improving circuit density according to claim 1, characterized in that, In the circuit etching step, the exposed copper after laser ablation is dissolved and removed by spraying with etching solution. The copper surface in the area not ablated by the laser is preserved due to the protection of the resist layer, and the sides of the circuit will also not be etched due to the protection of the resist layer. In the resist removal step, the resist layer above the circuit layer is removed by using a resist removal agent, leaving only the copper circuit layer.