A manufacturing method of a PCB side wall thick copper bottom thin copper metalization trapezoidal blind groove

Abstract

A method for manufacturing a trapezoidal blind trench with thick copper sidewalls and thin copper bottom on a PCB includes the following steps: Step 1: Providing a board with several spaced copper layers; Step 2: Grooving, creating a groove downwards from the top copper layer; Step 3: Plating copper, forming a plating copper layer on the outer surface of the top copper layer, the sidewalls of the groove, and the bottom surface; Step 4: Applying a dry film, applying a film layer on the outside of the plating copper layer; Step 5: Exposure; Step 6: Development, removing the film layer outside the exposure area to form a bump in the exposure area; Step 7: Electroplating copper on the outer surface of the top copper layer and the gap area to form an electroplated layer; Step 8: Film removal, forming a blind trench in the middle of the electroplated layer; Step 9: Micro-etching. This invention, through grooving, film application, exposure, and development, forms a film bump in the middle of the groove, controls the distance between the dry film edge and the trench edge, and utilizes the principle of filling holes to achieve thicker copper plating, which is far superior to traditional methods.

Description

Technical Field

[0001] This invention relates to the field of circuit board technology, and in particular to a method for manufacturing a trapezoidal blind slot with thick copper sidewalls and thin copper bottom on a PCB. Background Technology

[0002] Blind slots are localized areas on a printed circuit board (PCB) with varying heights, created through lamination, milling, or other methods. The main functions of blind slots are: first, to provide input and output ports for electrical signals between internal layers; second, to serve as cavities and carriers for mounting and attaching components such as chips, capacitors, and resistors; and third, to act as interconnecting channels for microwave components, allowing for cascading via gold wires or gold ribbons.

[0003] Currently, the common practice for metallized blind vias on PCBs involves slotting, followed by copper plating and then thickening the plating. However, this method typically results in a uniform copper thickness for the metallized blind vias, making it difficult to create the special blind via structure with thin copper at the bottom and thick copper on the sidewalls. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for manufacturing a trapezoidal blind slot with thick copper sidewalls and thin copper bottom on a PCB, addressing the shortcomings of existing technologies.

[0005] A method for fabricating a trapezoidal blind slot with thick copper sidewalls and thin copper bottom on a PCB includes the following steps:

[0006] Step 1: Provide a board with several spaced copper layers on it;

[0007] Step 2: Grooving. A groove is cut downwards from the top copper layer. The groove is trapezoidal and has a structure that is larger on the outside and smaller on the inside. The bottom end of the groove extends to the top surface of the second copper layer.

[0008] Step 3: Plating copper, forming a plating copper layer on the outer surface of the top copper layer, the sidewalls of the groove, and the bottom surface;

[0009] Step 4: Press dry film. Press a film layer on the outside of the copper plating layer. This film layer covers the groove and the top copper layer.

[0010] Step 5: Exposure. An exposure area is provided on the film layer, and the exposure area is located in the center of the groove.

[0011] Step 6, Development; Remove the film layer outside the exposure area to form a bump in the exposure area. There is a gap between the bump and the sidewall of the groove; the gap ranges from 60 to 125 μm.

[0012] Step 7: Electroplating; Electroplating copper on the outer surface of the top copper layer and the gap area to form an electroplated layer, wherein the electroplated layer is located on the outside of the copper plating layer;

[0013] Step 8: Remove the film; remove the bumps in the middle of the film layer to expose the electroplated layer and form a blind groove in the middle of the electroplated layer.

[0014] Step 9: Micro-etching. Micro-etch the outer surface of the electroplated layer and etch away the electroplated layer at the bottom of the blind trench 31 to expose the top copper layer.

[0015] Furthermore, the membrane layer fills the groove, and the top surface of the membrane layer is flush with the groove.

[0016] Furthermore, the electroplated layer fills the gap area, and the electroplated layer forms a concave arc-shaped configuration around the protrusion.

[0017] Furthermore, the copper layer is provided in four layers, wherein the distance between the top copper layer and the second copper layer is greater than the distance between other adjacent copper layers.

[0018] Furthermore, steps three and four also include an electroplating step to form an electroplated layer on the outside of the copper plating layer.

[0019] Furthermore, the board includes an effective area and a process waste edge disposed on the periphery of the effective area. A copper layer structure is disposed on both outer surfaces of the process waste edge. The copper layer structure includes a plurality of spaced copper protrusions, and the copper protrusions on both sides of the board are staggered.

[0020] Furthermore, the copper protrusions are evenly distributed on the process waste edge, and the shape of the copper protrusions is one of circular, rhomboid, or cross-shaped.

[0021] In summary, this invention forms film bumps in the center of the groove through a process of grooving, lamination, exposure, and development. By controlling the distance between the dry film edge and the groove edge, and utilizing the principle of filling holes, thick copper plating is achieved. This method can plate sidewall copper to a thickness of approximately 100-120 μm, which is significantly thicker than traditional methods. This invention is highly practical and has significant potential for widespread application. Attached Figure Description

[0022] Figure 1 This is a schematic flowchart of a method for manufacturing a trapezoidal blind slot with thick copper sidewalls and thin copper bottom in PCB metallization according to the present invention.

[0023] Figures 2 to 4 Three schematic diagrams showing the effective area of ​​a sheet metal part and the waste edges from the manufacturing process;

[0024] Figure 5 This is a schematic diagram of a partial cross-sectional structure of the waste edge from the process. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] like Figure 1 As shown, the present invention provides a method for manufacturing a trapezoidal blind slot with thick copper on the sidewall and thin copper on the bottom of a PCB. It is used to manufacture a PCB blind slot with thin copper on the bottom and thick copper on the sides. The blind slot has a structure that is wider on the outside and narrower on the inside.

[0027] The method for manufacturing a trapezoidal blind slot with thick copper sidewalls and thin copper bottom on a PCB specifically includes the following steps:

[0028] Step 1: Provide a board, the board including a substrate 1, a copper layer 10 disposed on the top surface of the substrate 1, and at least one copper layer 10 disposed on the bottom surface. In this embodiment, three copper layers 10 are disposed at intervals on the bottom surface of the substrate 1, wherein there is a large gap between the top copper layer 10 and the second copper layer 10.

[0029] Step 2: Grooving. A groove 11 is cut downwards from the top copper layer 10. The groove 11 is trapezoidal and has a structure that is larger on the outside and smaller on the inside. The bottom end of the groove 11 extends to the top surface of the second copper layer 10.

[0030] Step 3: Plating copper, forming a plating copper layer 12 on the outer surface of the top copper layer 10 and the sidewalls and bottom surface of the groove 11.

[0031] Furthermore, when the board is an ultra-thin board, the board includes an effective area 14 and a process waste edge 15 disposed on the outer periphery of the effective area 14. A copper layer structure is disposed on both outer surfaces of the process waste edge 15. The copper layer structure includes a plurality of spaced copper protrusions 151. In this embodiment, the shape of the copper protrusions 151 can be circular, rhomboid, or cross-shaped (e.g., Figures 2 to 4 (As shown); the copper protrusions of this structural shape have better venting effect than other shapes, and are less prone to problems such as bubbles and delamination during subsequent copper plating. In addition, the copper protrusions 151 on the two outer surfaces of the board are staggered (as shown). Figure 5 As shown in the figure, this makes the overall layout and support strength of the board more uniform, avoiding board deformation caused by some parts having strong support and others having weak support during the copper plating process.

[0032] Step 4: Press dry film. Press film layer 20 on the outside of copper plating layer 12. This film layer 20 covers the groove 11 and the top copper layer 10. In addition, if the bottom copper layer needs to have a certain thickness, another layer of copper can be plated to the required thickness before pressing dry film.

[0033] Step 5: Exposure. An exposure area 21 is provided on the film layer 20, which is located at the center of the groove 11. More specifically, the exposure area 21 is a blind groove preset position.

[0034] Step six, development; remove the film layer 20 outside the exposure area, forming a bump 22 in the exposure area 21. This bump 22 has a gap with the sidewall of the groove 11. After development, the gap between the edge of the tank and the copper plating area of ​​the dry film needs to be controlled within a certain range. This range directly affects whether subsequent electroplating can be performed and whether the gap can be fully filled by the dry film. In this embodiment, this certain range refers to a width of 60-125 μm. If the gap is too large, there will be a large depression between the dry film and the tank wall during electroplating, making it impossible to achieve the effect of forming thick copper on the sidewall after film removal. If the gap is too narrow, electroplating is prone to producing voids, i.e., voids exist in the thick copper on the sidewall. Simultaneously, because the bottom of the dry film is too close to the tank wall, the adhesion at this location will be too weak, easily causing bottom plating penetration.

[0035] Step 7: Electroplating; Electroplating copper between the top copper layer and the gap area, and fully filling the gap area to form an electroplated layer 30, which is disposed on the outside of the copper plating layer 12. In addition, the electroplated layer 30 is provided with a concave arc-shaped surface around the bump 22.

[0036] Step 8: Remove the film; remove the middle film layer bumps 22 to expose the electroplated layer 30, and form a blind groove 31 in the middle of the electroplated layer 30.

[0037] Step 9: Micro-etching. Micro-etch the outer surface of the electroplated layer 30 to make the edges of the tank smoother. At the same time, the micro-etching solution allows the tank to naturally form a thick copper blind tank with a wider top and a slightly narrower bottom. In addition, the electroplated layer 30 at the bottom of the blind tank 31 is etched away to form a thin copper layer. Understandably, when a certain thickness of the bottom copper layer is required, micro-etching can also be performed down to the immersion copper layer or electroplated layer.

[0038] In summary, this invention forms film bumps in the center of the groove through a process of grooving, lamination, exposure, and development. By controlling the distance between the dry film edge and the groove edge, and utilizing the principle of filling holes, thick copper plating is achieved. This method can plate sidewall copper to a thickness of approximately 100-120 μm, which is significantly thicker than traditional methods. This invention is highly practical and has significant potential for widespread application.

[0039] The above-described embodiments are merely one implementation of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for manufacturing a trapezoidal blind slot with thick copper sidewalls and thin copper bottom on a PCB, characterized in that, Includes the following steps: Step 1: Provide a board with a plurality of spaced copper layers on it; wherein, there are four copper layers, and the distance between the top copper layer and the second copper layer is greater than the distance between other adjacent copper layers. Step 2: Grooving. A groove is cut downwards from the top copper layer. The groove is trapezoidal and has a structure that is larger on the outside and smaller on the inside. The bottom end of the groove extends to the top surface of the second copper layer. Step 3: Plating copper, forming a plating copper layer on the outer surface of the top copper layer, the sidewalls of the groove, and the bottom surface; Step 4: Press dry film. Press a film layer on the outside of the copper plating layer. The film layer covers the groove and the top copper layer. The film layer fills the groove and the top surface of the film layer is flush. Step 5: Exposure. An exposure area is provided on the film layer, and the exposure area is located in the center of the groove. Step 6, Development; Remove the film layer outside the exposure area to form a bump in the exposure area. There is a gap between the bump and the sidewall of the groove. The gap distance of the gap ranges from 60 to 125 μm. Step 7: Electroplating; Electroplating copper on the outer surface of the top copper layer and the gap area to form an electroplating layer, the electroplating layer being disposed on the outside of the copper plating layer; the electroplating layer filling the gap area, and the electroplating layer forming a concave arc-shaped arrangement around the bump; Step 8: Remove the film; remove the bumps in the middle of the film layer to expose the electroplated layer and form a blind groove in the middle of the electroplated layer. Step 9: Micro-etching. Micro-etch the outer surface of the electroplated layer and etch away the electroplated layer at the bottom of the blind trench to expose the second copper layer.

2. The method for manufacturing a trapezoidal blind slot with thick copper sidewalls and thin copper bottom as described in claim 1, characterized in that: Steps three and four also include an electroplating step to form an electroplated layer on the outside of the copper plating layer.

3. The method for manufacturing a trapezoidal blind slot with thick copper sidewalls and thin copper bottom as described in claim 1, characterized in that: The board includes an effective area and a process waste edge disposed around the perimeter of the effective area. A copper layer structure is disposed on both outer surfaces of the process waste edge. The copper layer structure includes a plurality of spaced copper protrusions, and the copper protrusions on both sides of the board are staggered.

4. The method for manufacturing a trapezoidal blind slot with thick copper sidewalls and thin copper bottom as described in claim 3, characterized in that: The copper protrusions are evenly distributed on the process waste edge, and the shape of the copper protrusions is one of the following: circular, rhomboid, or cross-shaped.

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