Method for improving copper thickness uniformity of blind hole plate and reducing blind hole recess and PCB

Abstract

The invention discloses a method for improving the copper thickness uniformity of a blind hole plate and reducing blind hole recesses and a PCB in the field of printed circuit board manufacturing, and the method comprises the steps: firstly carrying out the inner-layer pattern manufacturing of a copper-clad substrate, and respectively pressing the inner-layer copper-clad plate except an outer layer into a first N plate and a second N plate; and then drilling, degumming, electroplating, back drilling, resin hole plugging, pattern manufacturing and other surface treatment processes are sequentially carried out on the two N plates. The processed first N plate and the processed second N plate are directly pressed on the outer-layer copper-clad substrate, so that the resin hole plugging area is covered by the outer-layer copper foil after pressing; and performing subsequent processes on the outer layer to form a complete multi-layer blind hole plate. By optimizing the layering mode and the outer layer processing flow, the outer layer is prevented from being electroplated for multiple times, the copper thickness uniformity is remarkably improved, blind hole resin sinking caused by glue removal in a traditional technology is effectively eliminated, and the flatness and electrical property consistency of the blind hole structure are improved.

Description

Technical Field

[0001] This invention relates to a method and PCB board for improving the uniformity of copper thickness in blind via boards and reducing blind via depressions, belonging to the field of printed circuit board manufacturing. Background Technology

[0002] In the PCB manufacturing process, blind via boards, as an important structural form used in high-speed communication equipment, server motherboards, and high-end computing platforms, have their processing precision and reliability directly affecting the electrical performance of the products. For example... Figure 1 As shown, existing multilayer blind via boards are usually produced using an N+N lamination structure. This involves laminating several inner copper-clad laminates to form two intermediate layer stacked structures, which are then laminated onto an outer copper-clad substrate to form a complete multilayer circuit board. To ensure electrical connection between the N board and the outer layer, several processes are often required on the N board after the first lamination, including drilling, desmearing, electroplating, back drilling, resin plugging, and pattern making. After the second lamination, the outer layer continues to undergo multiple electroplating and processing processes.

[0003] However, the existing process has several shortcomings. First, since electroplating is required in both the N-board processing stage and the outer layer processing stage, and the outer layer often undergoes multiple electroplating processes before the final pattern is made, the copper thickness of the outer layer is difficult to control, easily resulting in problems such as excessive or uneven copper thickness. Second, in the existing process, the N-board often needs to undergo a desmearing process directly after resin plugging. Since the resin plugging layer is not covered by the outer copper foil, it is easily eroded during the desmearing process, producing depressions that are difficult to fill by electroplating. These depressions can typically reach 25 micrometers or even deeper, thus negatively impacting electrical performance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and solve the problems in the existing processing technology of multilayer blind hole boards. Because the outer layer needs to undergo electroplating and pattern processing again after the second lamination, the outer copper surface actually undergoes multiple rounds of electroplating operations in the entire manufacturing process, which makes it difficult to control the copper thickness of the outer layer uniformly. This can easily lead to problems such as excessive copper thickness, uneven copper thickness distribution, difficulty in outer layer etching, and deviations in line width and line spacing.

[0005] To solve the above-mentioned technical problems, the present invention is implemented using the following technical solution: In a first aspect, a method for improving the copper thickness uniformity of blind via boards and reducing blind via depressions is provided, comprising the following steps: Patterning is performed on the copper-clad substrate; The copper-clad substrate with the pattern fabricated is laminated, the lamination process including: laminating the copper-clad boards except for the outer layer into a first N-plate and a second N-plate respectively; wherein, the copper-clad substrate is configured to have 20 layers; The first N-plate and the second N-plate are respectively subjected to surface treatment and graphic fabrication processes; The first N-board and the second N-board after processing are directly laminated onto the outer copper-clad substrate. Subsequent processing steps are performed on the outer copper-clad substrate.

[0006] Furthermore, the first N-plate includes: layers 2 to 10; The second N-plate includes: layers 11 to 19; The outer layer includes layer 1 and layer 20.

[0007] Furthermore, the surface treatment process includes drilling, adhesive removal, electroplating, back drilling, and resin plugging. The subsequent processing steps include: laser drilling of blind holes, through-hole drilling, adhesive removal, electroplating, back drilling, resin plugging, cap electroplating, graphic creation, solder resist, molding, electrical testing and inspection, and packaging.

[0008] Furthermore, the depth of the laser-drilled blind hole is set to: layer 1 to layer 2 or layer 1 to layer 3.

[0009] Furthermore, the drilling depth of the through hole is set to: layer 1 to layer 20.

[0010] Furthermore, during the process of directly laminating the first N-plate and the second N-plate onto the outer copper-clad substrate, the resin layer at the blind hole is in direct contact with the copper foil on the outer contact surface.

[0011] Furthermore, the copper layers of the first N-plate and the second N-plate are directly connected to the copper foil on the outer contact surface.

[0012] Secondly, a PCB board is provided, which is prepared by the method described in the second aspect for improving the uniformity of copper thickness in blind vias and reducing blind via depressions.

[0013] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention optimizes the layering and processing flow of blind via boards, allowing the first N-board and the second N-board to be directly laminated to the outer copper-clad substrate after resin plugging and pattern fabrication. This avoids the outer layer undergoing multiple electroplating processes throughout the manufacturing process, effectively reducing the cumulative increase in outer copper thickness and local differences, making the etching process more stable, and resulting in more uniform outer layer linewidth and spacing, more accurate impedance control, and significantly improving the processing consistency and signal transmission performance of the outer layer circuitry. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the existing N+N pressing method for multilayer blind hole plates; Figure 2 This is a schematic diagram of the method for improving the copper thickness uniformity of blind vias and reducing blind via depressions provided in this application. Figure 3 This is a schematic diagram of the graphic fabrication process in the method for improving the copper thickness uniformity of blind via boards and reducing blind via depressions provided in this application. Figure 4 This is a schematic diagram of the lamination process of the first N plate and the second N plate in the method for improving the copper thickness uniformity of blind vias and reducing blind via depressions provided in this application. Figure 5 This is a flowchart of the etching process of the first N plate and the second N plate in the method for improving the copper thickness uniformity of blind vias and reducing blind via depressions provided in this application. Figure 6 This is a schematic diagram of the structure after the first N plate and the second N plate are pressed together in the method for improving the copper thickness uniformity of blind hole plates and reducing blind hole depressions provided in this application. Detailed Implementation

[0015] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments and specific features in the embodiments are detailed descriptions of the technical solution of the present application, rather than limitations thereof. In the absence of conflict, the embodiments and technical features in the embodiments can be combined with each other.

[0016] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0017] In one specific embodiment, a method for improving the copper thickness uniformity of blind via boards and reducing blind via depressions is provided, the specific process of which is as follows: Taking a 20-layer thick blind hole plate as the target, firstly, as Figure 3 As shown, conventional inner layer patterning is performed on the copper-clad substrate, and inner layer circuits are formed on the copper-clad substrate through lamination, exposure and development, etching and stripping steps.

[0018] After the graphic is completed, the copper-clad board, excluding the outer layer, will be laminated for the first time; in this embodiment, as... Figure 2 and Figure 3 As shown, layers 2 to 10 are laminated to form the first N-plate, and layers 11 to 19 are laminated to form the second N-plate. The layered structure remains a two-layer lamination structure, consistent with the traditional N+N process, i.e., 10+10. However, by changing the layer distribution of the N-plate, the problem of uneven copper thickness caused by repeated electroplating of the outer layer is avoided from the structure.

[0019] like Figure 5As shown, after forming the first N-board and the second N-board, surface treatment is performed on both N-boards. In this embodiment, the surface treatment includes conventional processes such as drilling, adhesive removal, electroplating, back drilling, and resin plugging. Drilling forms the required through-hole structure, adhesive removal exposes the glass fiber in the hole walls, electroplating metallizes the hole walls and thickens the copper surface, back drilling removes excess conductive segments to improve signal performance, and resin plugging fills the holes, thus providing a flat surface for subsequent lamination. Then, interlayer circuitry is fabricated on the two N-boards to give layers 2-10 and layers 11-19 the final pattern structure.

[0020] like Figure 6 As shown, after the above processing is completed, the first N board and the second N board are directly laminated onto the outer copper-clad substrate, so that the first layer is formed outside the first N board and the 20th layer is formed outside the second N board. Specifically, the resin plugging layer near the outer side of the first N board is in direct contact with the copper foil of the outer first layer, and the resin plugging layer near the outer side of the second N board is in direct contact with the copper foil of the 20th layer. This ensures that the resin plugging area is completely covered under the copper foil after lamination, thereby avoiding direct erosion of the resin by the subsequent adhesive removal process and reducing the risk of depressions of more than 25 micrometers at the blind hole position.

[0021] Since the outer copper foil does not undergo multiple electroplating processes in the N-plate stage, this structure ensures that the outer layer maintains a copper thickness close to the baseline during subsequent pattern making, reducing etching difficulty and maintaining line width and spacing consistency.

[0022] After the second lamination is completed, the outer layer process is performed on the 20-layer board. In this embodiment, laser drilling is preferably used to form blind holes, the depth of which covers layers 1 to 2, or layers 1 to 3. After the blind holes are processed, through holes are formed by mechanical drilling, penetrating layers 1 to 20. Then, adhesive removal, electroplating, and back drilling are performed to ensure that both the blind holes and through holes are metal-connected.

[0023] Resin plugging is then used to fill the holes, followed by cap plating to seal the openings, ensuring a smooth and continuous copper surface for subsequent outer layer circuitry fabrication. Afterwards, the final patterns for layers 1 and 20 are created through lamination, exposure, and etching. Solder masking, characterization, molding, electrical testing, and packaging processes then continue, completing the entire manufacturing process of the multilayer PCB.

[0024] In this embodiment, a PCB board is also provided, which is prepared by the method mentioned above for improving the uniformity of copper thickness in blind vias and reducing blind via depressions.

[0025] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for improving the uniformity of copper thickness in blind via boards and reducing blind via depressions, characterized in that, Includes the following steps: Patterning is performed on the copper-clad substrate; The copper-clad substrate with the pattern fabricated is laminated, the lamination process including: laminating the copper-clad boards except for the outer layer into a first N-plate and a second N-plate respectively; wherein, the copper-clad substrate is configured to have 20 layers; The first N-plate and the second N-plate are respectively subjected to surface treatment and graphic fabrication processes; The first N-board and the second N-board after processing are directly laminated onto the outer copper-clad substrate. Subsequent processing steps are performed on the outer copper-clad substrate.

2. The method for improving the uniformity of copper thickness and reducing blind via depressions according to claim 1, characterized in that, The first N-plate includes: layers 2 to 10; The second N-plate includes: layers 11 to 19; The outer layer includes layer 1 and layer 20.

3. The method for improving the uniformity of copper thickness and reducing blind via depressions according to claim 1, characterized in that, The surface treatment process includes drilling, adhesive removal, electroplating, back drilling, and resin plugging. The subsequent processing steps include: laser drilling of blind holes, through-hole drilling, adhesive removal, electroplating, back drilling, resin plugging, cap electroplating, graphic creation, solder resist, molding, electrical testing and inspection, and packaging.

4. The method for improving the uniformity of copper thickness and reducing blind hole depressions according to claim 3, characterized in that, The depth of the laser-drilled blind hole is set to either layer 1 to layer 2 or layer 1 to layer 3.

5. The method for improving the uniformity of copper thickness and reducing blind via depressions according to claim 3, characterized in that, The drilling depth of the through holes is set to: layer 1 to layer 20.

6. The method for improving the copper thickness uniformity of blind vias and reducing blind via depressions according to claim 3, characterized in that, During the process of directly laminating the first N-plate and the second N-plate onto the outer copper-clad substrate, the resin layer at the blind hole is in direct contact with the copper foil on the outer contact surface.

7. The method for improving the copper thickness uniformity of blind vias and reducing blind via depressions according to claim 1, characterized in that, The copper layers of the first N-plate and the second N-plate are directly connected to the copper foil on the outer contact surface.

8. A PCB board, characterized in that, It is prepared by the method described in any one of claims 1-7 for improving the uniformity of copper thickness in blind vias and reducing blind via depressions.

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