A method for manufacturing a high-speed circuit board metal blind slot

Abstract

The application provides a manufacturing method of a high-speed circuit board metal blind groove, which comprises the following steps: laying copper sheets with a size of 0.2-0.4 mm larger than the size of the blind groove on one side of the blind groove area of a core board, designing the bottom copper sheet of the bottom of the blind groove in the mode of the core board, laminating all the core boards to form a multilayer PCB substrate, then controlling the depth in sections, milling the waste in the blind groove, and then performing copper deposition and electroplating to form a PCB substrate containing a blind groove, wherein the original copper sheet in the sidewall and the bottom of the blind groove can be directly contacted with the deposited copper in the blind groove in the subsequent copper deposition and electroplating process and is electroplated into an integral whole, so that the riveting effect is achieved, reliable reverse pulling force is provided during welding, the metal blind groove with high reliability, good heat resistance and multiple welding performance can be manufactured on the PCB, and the risk of copper sheet falling off of the blind groove is effectively reduced, and the product quality is improved.

Description

Technical Field

[0001] This invention relates to the field of circuit board technology, and more particularly to a method for manufacturing a metal blind slot on a high-speed circuit board. Background Technology

[0002] High-speed circuit boards are crucial components used in high-speed network communication servers, switches, and data centers, serving as vital carriers for data transmission in high-speed networks. Achieving high-speed network transmission requires the use of copper-clad laminate materials with low dielectric constants and copper foil with low roughness to reduce energy loss and latency during data transmission. The design of metal blind slots on high-speed circuit boards primarily addresses market demands for high integration in the assembly of chips, resistors, and other components, requiring the blind slot structure to withstand temperatures up to 260°C and multiple soldering operations.

[0003] The existing technical solution involves: first, prefabricating a core board and the circuit pattern within it. This core board requires copper removal treatment for the PCB blind slot locations. Multiple core boards are then stacked sequentially and further pressed to form a substrate structure containing the inner layer circuit pattern. A CNC milling machine then mills grooves of the pre-designed depth. Finally, the PCB board with the grooves undergoes a copper plating and electroplating process, allowing copper to be deposited on the grooves and holes together to form a metallized blind slot. While this existing solution can achieve blind slot metallization, the bottom and sidewalls of the blind slot are pure substrate areas. Directly performing the copper plating process results in poor adhesion between the deposited copper and the high-speed board substrate. When the blind slot area is too large, the copper covering the bottom and sidewalls of the blind slot is prone to peeling off during PCB soldering and heating, requiring improvement. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a method for manufacturing metal blind slots for high-speed circuit boards, thereby reducing the risk of copper foil peeling off the blind slots and improving product quality.

[0005] To solve the above technical problems, a method for manufacturing a metal blind slot on a high-speed circuit board provided by this invention is provided, comprising the following steps:

[0006] S1: Core board A is cut into the corresponding size according to the design. The corresponding circuit pattern is further etched. Copper pouring is required for the inner layer circuit and blind slot area. The copper pouring range of the blind slot area is enlarged by 0.2-0.4mm on each side of the required blind slot size.

[0007] S2: Core board B is cut into the corresponding size according to the design. After the circuit film is applied, it is exposed and etched. The bottom copper skin of the blind trench area needs to be made. Each side of the required blind trench size is enlarged by 0.4mm to make the bottom copper skin of the blind trench area.

[0008] S3: Core board C cutting, the copper-clad board is cut to the corresponding size according to the design, and after the circuit film is applied, exposed and etched, the inner circuit core board is made as required.

[0009] S4: Core board browning, core boards A, B and C are browned to improve the bonding force between the copper surface of the core board and the laminating resin;

[0010] S5: Pressing, the browned core board A, core board B and core board C are pre-stacked according to the design requirements, a prepreg is placed between the two core boards, and after being fixed with rivets, they are pressed into a multi-layer PCB substrate.

[0011] S6: Drilling holes in the PCB substrate to drill through holes for corresponding circuits and tool positioning holes for subsequent processes;

[0012] S7: Blind slot controlled depth milling. The blind slot of the required size is milled in the blind slot area of ​​the PCB substrate. Before implementation, it is necessary to slice and measure the height from the middle position of the bottom copper skin of the blind slot to the board surface after lamination. This height is used as the target depth H of controlled depth milling. Then, the segmented controlled depth method is used to process until the bottom copper skin of the complete blind slot is exposed.

[0013] S8: Plasma cleaning, which involves plasma cleaning the PCB substrate to remove drilling debris from blind trenches and drill holes, thereby increasing the bonding stability between inner layer copper and deposited copper.

[0014] S9: Immersion copper plating, a process of immersion copper plating and electroplating on PCB substrate, to achieve conductivity between layers and complete copper coverage inside the blind trench to achieve the effect of metal blind trench.

[0015] Preferably, in step S2, the thickness of the bottom copper foil in the blind slot region is 150 μm.

[0016] Preferably, in step S7, a 180° flat-bottomed milling cutter is used to mill the blind groove.

[0017] Preferably, the segmented depth control in step S7 includes the following steps: First, control the depth according to 2 / 3 of H; Second, measure the current remaining depth; Third, control the depth according to 2 / 3 of the current remaining depth; Fourth, repeat steps two and three until the bottom copper skin of the complete blind slot is exposed.

[0018] The beneficial effects of this invention are as follows: This invention provides a method for manufacturing a metal blind slot for a high-speed circuit board. A copper foil 0.2-0.4 mm larger than the blind slot size on each side is laid in the blind slot area of ​​the core board. The bottom copper foil of the blind slot is designed using a core board approach. All core boards are then stacked and pressed into a multi-layer PCB substrate. Subsequently, the depth is controlled in sections, and the waste material inside the blind slot is milled away. After copper plating, a PCB substrate containing the blind slot is formed. The original copper foil in the sidewalls and bottom of the blind slot can directly contact and be electroplated into a whole with the deposited copper in the blind slot during the subsequent copper plating process, achieving a riveting effect. This provides reliable reverse pull force during soldering, enabling the fabrication of highly reliable, heat-resistant, and reusable metal blind slots on the PCB. This effectively reduces the risk of copper foil detachment from the blind slot and improves product quality. Attached Figure Description

[0019] Figure 1 A schematic diagram illustrating the cutting process of core board A of the present invention is shown.

[0020] Figure 2 A schematic diagram illustrating the cutting process of the core board B of the present invention is shown.

[0021] Figure 3 A schematic diagram illustrating the cutting process of the core board C of the present invention is shown.

[0022] Figure 4 A schematic diagram illustrating the structure of the multilayer PCB substrate of the present invention is shown.

[0023] Figure 5 A schematic diagram illustrating the controlled depth milling process on a multilayer PCB substrate according to the present invention is shown.

[0024] Figure 6 A schematic diagram illustrating the process of fabricating blind slots on a multilayer PCB substrate according to the present invention is shown. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure.

[0026] Based on the embodiments described in this disclosure, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this disclosure.

[0027] refer to Figure 1-6 .

[0028] This invention provides a method for manufacturing a metal blind slot on a high-speed circuit board, comprising the following steps:

[0029] S1: Core board A is cut to the designed dimensions. The copper-clad laminate is then etched to create the corresponding circuit patterns. Copper pouring is required for the inner layer circuits and blind slot areas. The copper pouring range for the blind slot areas is defined by expanding each side of the required blind slot size by 0.2-0.4mm (see attached diagram). Figure 1 (as shown)

[0030] S2: Core board B cutting: The copper-clad laminate is cut to the corresponding dimensions according to the design. After circuit film application, exposure, and etching, the bottom copper layer of the blind slot area needs to be made. Each side of the required blind slot size is enlarged by 0.4mm to form the bottom copper layer of the blind slot area (as shown in the attached diagram). Figure 2 (as shown)

[0031] S3: Core board C blanking: The copper-clad laminate is cut to the corresponding dimensions according to the design. After circuit film application, exposure, and etching, the inner layer circuit core board is manufactured as required (as shown in the attached document). Figure 3 (as shown)

[0032] S4: Core board browning, core boards A, B and C are browned to improve the bonding force between the copper surface of the core board and the laminating resin;

[0033] S5: Lamination. The browned core boards A, B, and C are pre-stacked according to design requirements, with prepregs placed between two core boards. After securing with rivets, they are pressed into a multi-layer PCB substrate (see attached). Figure 4 (as shown)

[0034] S6: Drilling holes in the PCB substrate to drill through holes for corresponding circuits and tool positioning holes for subsequent processes;

[0035] S7: Blind Slot Deep Milling. This involves milling blind slots of the required dimensions into the blind slot area of ​​the PCB substrate. Before implementation, it is necessary to slice and measure the height from the center of the bottom copper layer of the blind slot to the board surface after lamination. This height is used as the target depth H for controlled milling. Then, a segmented depth control method is used until the complete bottom copper layer of the blind slot is exposed (as shown in the attached diagram). Figure 5 (as shown)

[0036] S8: Plasma cleaning, which involves plasma cleaning the PCB substrate to remove drilling debris from blind trenches and drill holes, thereby increasing the bonding stability between inner layer copper and deposited copper.

[0037] S9: Copper plating, a process of copper plating and electroplating on the PCB substrate, to achieve interlayer conductivity and complete copper coverage within the blind trench, thus achieving the effect of a metallic blind trench (see attached). Figure 6 (as shown in step three).

[0038] After copper plating, and subsequent processes such as circuitry, solder mask, and character printing, the PCB substrate will look like the attached image. Figure 6 As shown in step four.

[0039] The principle is as follows: a copper foil 0.2-0.4mm larger than the blind slot size on each side is laid in the blind slot area of ​​the core board, and the bottom copper foil of the blind slot is designed in the form of a core board. Then, all the core boards are stacked and pressed into a multi-layer PCB substrate. Subsequently, the depth is controlled in sections, and the waste inside the blind slot is milled away. After copper immersion plating, a PCB substrate containing the blind slot is made. In the subsequent copper immersion plating process, the original copper foil in the side wall and bottom of the blind slot can directly contact the deposited copper in the blind slot and be electroplated into a whole, achieving the riveting effect. It can provide reliable reverse pull force during welding. It can produce highly reliable, heat-resistant, and reusable metal blind slots on the PCB, effectively reducing the risk of copper foil falling off the blind slot and improving product quality.

[0040] Based on the above embodiments, in step S2, the thickness of the bottom copper foil in the blind slot area is 150µm. The thickness of the core board B can be selected according to the requirements of the PCB board's stack-up thickness. Limiting the copper foil thickness to 150µm can ensure the accuracy tolerance of controlled depth milling. At the same time, there is a sufficient copper foil layer at the bottom of the blind slot, which is directly bonded to the core board substrate to achieve the purpose of stable copper plating.

[0041] Based on the above embodiments, in step S7, a 180° flat-bottomed milling cutter is used to mill the blind groove to ensure the flatness of the bottom of the blind groove.

[0042] Based on the above embodiments, the segmented depth control in step S7 includes the following steps: First, control the depth according to 2 / 3 H; Second, measure the current remaining depth; Third, control the depth according to 2 / 3 of the current remaining depth; Fourth, repeat steps two and three until the bottom copper skin of the complete blind slot is exposed, which can ensure processing efficiency and the integrity of the bottom copper skin of the blind slot.

[0043] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for manufacturing a metal blind slot on a high-speed circuit board, characterized in that, It includes the following steps: S1: Core board A is cut into the corresponding size according to the design. The corresponding circuit pattern is further etched. Copper pouring is required for the inner layer circuit and blind slot area. The copper pouring range of the blind slot area is enlarged by 0.2-0.4mm on each side of the required blind slot size. S2: Core board B is cut into the corresponding size according to the design. After the circuit film is applied, it is exposed and etched. The bottom copper skin of the blind trench area needs to be made. Each side of the required blind trench size is enlarged by 0.4mm to make the bottom copper skin of the blind trench area. S3: Core board C cutting, the copper-clad board is cut to the corresponding size according to the design, and after the circuit film is applied, exposed and etched, the inner circuit core board is made as required. S4: Core board browning, core boards A, B and C are browned to improve the bonding force between the copper surface of the core board and the laminating resin; S5: Pressing, the browned core board A, core board B and core board C are pre-stacked according to the design requirements, a prepreg is placed between the two core boards, and after being fixed with rivets, they are pressed into a multi-layer PCB substrate. S6: Drilling holes in the PCB substrate to drill through holes for corresponding circuits and tool positioning holes for subsequent processes; S7: Blind slot controlled depth milling. The blind slot of the required size is milled in the blind slot area of ​​the PCB substrate. Before implementation, it is necessary to slice and measure the height from the middle position of the bottom copper skin of the blind slot to the board surface after lamination. This height is used as the target depth H of controlled depth milling. Then, the segmented controlled depth method is used to process until the bottom copper skin of the complete blind slot is exposed. S8: Plasma cleaning, which involves plasma cleaning the PCB substrate to remove drilling debris from blind trenches and drill holes, thereby increasing the bonding stability between inner layer copper and deposited copper. S9: Immersion copper plating, a process of immersion copper plating and electroplating on PCB substrate, to achieve conductivity between layers and complete copper coverage inside the blind trench to achieve the effect of metal blind trench.

2. The fabrication process of the high-speed circuit board metal blind slot according to claim 1, characterized in that, In step S2, the thickness of the bottom copper foil in the blind slot area is 150um.

3. The fabrication process of the high-speed circuit board metal blind slot according to claim 1, characterized in that, In step S7, a blind groove is milled using a 180° flat-bottomed milling cutter.

4. The fabrication process of the high-speed circuit board metal blind slot according to claim 1, characterized in that, The segmented depth control in step S7 includes the following steps: First, control the depth according to 2 / 3 H; Step 2: Measure the current remaining depth; Step 3: Control the depth according to 2 / 3 of the current remaining depth; Step 4: Repeat steps 2 and 3 until the bottom copper layer of the complete blind slot is exposed.

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