A method for manufacturing a PCB board with a stepped impedance stub

Abstract

The application discloses a kind of manufacturing method of PCB with step-shaped impedance stub, comprising: material preparation, tape sticking, cutting tape waste edge, PP slot milling, pressing, drilling, electroplating, depth control milling, tearing tape and other process steps.The manufacturing method of PCB with step-shaped impedance stub provided by the application selectively removes the waste area above the impedance line by combining the process of depth control milling and high-temperature tape protection, forming a step-shaped impedance stub structure, thereby greatly reducing the interference of the waste area on the impedance, improving the accuracy of impedance value determination, especially suitable for high-precision impedance control scenarios of high-end high-speed PCB, providing reliable protection for the integrity of high-frequency signal transmission.

Description

Technical Field

[0001] This invention relates to the field of PCB impedance bonding technology, specifically to a method for manufacturing a PCB board with stepped impedance bonding. Background Technology

[0002] In the impedance control design of high-end high-speed printed circuit boards (PCBs), impedance control is one of the core technical indicators to ensure signal transmission integrity. As a key structure for achieving precise impedance control, the design rationality and process reliability of the impedance connector directly determine the high-frequency signal transmission performance of the PCB. With the development of electronic devices towards higher speed, smaller size, and higher integration, the requirements for the impedance accuracy of PCBs are becoming increasingly stringent. Even small deviations in impedance values ​​can lead to signal reflection, attenuation, or crosstalk, thereby affecting the stability and efficiency of the entire electronic system.

[0003] In existing technologies, impedance bonding typically employs a full-layer lamination process, where the inner substrate containing the impedance lines is directly laminated with other functional layers using prepreg (PP) to form a single structure, without any specific isolation or avoidance structures above the impedance layer. However, this traditional full-layer lamination process for impedance bonding has significant drawbacks: the waste area above the impedance lines acts as an electromagnetic interference source, creating parasitic capacitance, inductance, and other non-ideal parameters between the waste area and the impedance lines. This interferes with the signal transmission path and electromagnetic field distribution, causing deviations between the actual impedance measurement and the design target, affecting the accurate determination of impedance characteristics. Especially in high-speed signal transmission scenarios, this interference can lead to a decrease in signal integrity, failing to meet the signal transmission quality requirements of high-end electronic devices. Summary of the Invention

[0004] To overcome the problem in existing impedance bonding technologies where full-layer lamination is used without creating steps, resulting in interference from waste material above the impedance lines and affecting impedance value determination, this invention provides a method for manufacturing a PCB board with stepped impedance bonding. By combining controlled-depth milling with high-temperature tape protection, the waste material area above the impedance lines is selectively removed to form a stepped impedance bonding structure, thereby greatly reducing the interference of waste material area on impedance and improving the accuracy of impedance value determination.

[0005] The technical solution of this invention is as follows: A method for manufacturing a PCB board with stepped impedance, comprising: Preparation: Prepare the upper sub-board and the lower impedance bonding sub-board. The impedance bonding area of ​​the lower impedance bonding sub-board is provided with impedance lines on the top surface. Applying tape: Apply high-temperature tape to the impedance bonding area, with the ends of all impedance wires exposed by the high-temperature tape and the rest covered by the high-temperature tape; Cutting the waste edges of the tape: The waste edges of the high-temperature tape are cut; PP milling groove: A groove is milled in the PP layer at the bottom of the upper sub-board corresponding to the area of ​​the high-temperature tape to form a tape receiving groove; Pressing: Press the upper sub-board after milling the grooves with the lower sub-board after applying adhesive tape to form a whole board; Drilling and electroplating: Drill through holes in the entire board and electroplat the through holes to make them conductive. Each through hole corresponds to the end of an impedance line. Controlled depth milling and tape removal: A mechanical controlled depth milling machine is used to remove the waste area corresponding to the high-temperature tape on the whole board and to remove the high-temperature tape, thereby obtaining a PCB board with stepped impedance.

[0006] According to the above-mentioned method for manufacturing a PCB board with stepped impedance, the distance between the cut high-temperature tape and the end of the impedance line is not less than 2mm.

[0007] According to the above-described method for manufacturing a PCB board with stepped impedance bonding, the width of the cut high-temperature tape is the same as the width of the impedance bonding area.

[0008] According to the above-described method for manufacturing a PCB board with stepped impedance, the thickness of the high-temperature tape is 60-80 μm.

[0009] According to the above-described method for manufacturing a PCB board with stepped impedance, the thickness of the high-temperature tape is the same as the depth of the tape receiving groove.

[0010] According to the above-mentioned method for manufacturing a PCB board with stepped impedance, the length and width of the tape receiving groove are both larger than the length and width of the cut high-temperature tape.

[0011] According to the above-mentioned method for manufacturing a PCB board with stepped impedance, the length and width of the tape receiving groove are both 3-8 mil larger than the length and width of the cut high-temperature tape.

[0012] According to the above-described method for manufacturing a PCB board with stepped impedance, the thickness of the waste area is the same as the thickness of the upper sub-board, and the length and width of the waste area are both greater than the length and width of the cut high-temperature tape.

[0013] According to the above-mentioned method for manufacturing a PCB board with stepped impedance, the length and width of the waste area are both 4-8 mil larger than the length and width of the cut high-temperature tape.

[0014] According to the above-mentioned method for manufacturing a PCB board with stepped impedance, in the step of cutting the waste edge of the adhesive tape, a CO2 laser drill is used to cut the waste edge of the high-temperature adhesive tape. The spot diameter of the CO2 laser drill is 4-8 mil, and the cutting spacing is 1-3 mil.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a method for manufacturing a PCB board with a stepped impedance bonding structure. Through processes such as material preparation, tape application, tape scrap trimming, PP milling, lamination, drilling, electroplating, controlled-depth milling, and tape removal, the waste area above the impedance line is selectively removed to form a stepped impedance bonding structure. This significantly reduces the interference of the waste area on the impedance and improves the accuracy of impedance value determination. It is particularly suitable for high-precision impedance control scenarios in high-end high-speed PCBs, providing a reliable guarantee for the integrity of high-frequency signal transmission. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart illustrating a method for manufacturing a PCB board with stepped impedance according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a PCB board with stepped impedance according to an embodiment of the present invention.

[0018] In the diagram, 1. Upper sub-board; 2. Impedance Kobon lower sub-board; 3. Impedance line; 4. Through hole. Detailed Implementation

[0019] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that similar reference numerals and letters in the following drawings indicate similar items; therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. It is also stated that the embodiments described below are for illustrative purposes only and are not intended to limit the invention.

[0020] It should be noted that the terms "comprising" and "having," and any variations thereof, in the specification and claims of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices. The terms "installed," "set up," "connected," "fixed," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements or the interaction between two elements, unless otherwise expressly defined. The orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the product is usually placed in during use, or the orientation or positional relationship that is commonly understood by those skilled in the art. It is only for the purpose of facilitating the description of this application and simplifying the description, and is not intended to 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, it should not be construed as a limitation of this application.

[0021] Please see Figure 1 , Figure 2 This embodiment provides a method for manufacturing a PCB board with stepped impedance, including: Material Preparation: Prepare the upper sub-board 1 and the lower sub-board 2 (impedance bonding area). Impedance lines 3 are installed on the top surface of the impedance bonding area of ​​the lower sub-board 2. Impedance lines 3 are a key structure ensuring signal transmission integrity; their placement clearly defines the areas requiring special protection and processing during subsequent processing, ensuring precise impedance control on the final PCB. The upper sub-board 1 and the lower sub-board 2 are the main components for subsequent processing and are both multilayer boards, meaning they have already undergone one lamination, providing the material basis for the overall PCB structure. The upper sub-board 1 and the lower sub-board 2 have the same length and width dimensions to ensure accurate alignment during lamination, avoiding lamination defects such as misalignment and gaps caused by dimensional differences, thus ensuring the overall structural stability and performance consistency of the PCB.

[0022] Applying adhesive tape: Apply high-temperature adhesive tape to the impedance bonding area, ensuring that the ends of all impedance lines 3 are exposed above the tape (i.e., not covered by the tape, but not explicitly stated). The high-temperature tape acts as an insulator, guaranteeing that the ends of the impedance lines 3 can be properly processed in subsequent drilling and electroplating processes. It also creates a vertical separation between the waste area and the impedance bonding area, preventing them from sticking together during subsequent lamination. This lays the foundation for the step-like structure. Furthermore, the high-temperature tape can withstand the high temperatures during lamination, hence its selection. The thickness of the high-temperature tape is 60-80μm, preferably 70μm. This thickness ensures effective isolation while accommodating the ease of operation in subsequent milling and controlled-depth milling processes, as well as the rationality of the final step-like structure. If the high-temperature tape is too thin, it may not effectively isolate the waste area; if it is too thick, it may increase the processing difficulty and cost, affecting the overall performance of the PCB board.

[0023] Cutting the waste edges of the high-temperature tape: A CO2 laser drill is used to cut the waste edges of the high-temperature tape. The CO2 laser drill has advantages such as high processing precision, high speed, and a small heat-affected zone, enabling precise cutting of the waste edges of the high-temperature tape. This ensures the flatness and smoothness of the cut edges, reducing defects such as burrs and flash generated during the cutting process, and preventing these defects from adversely affecting subsequent processes and PCB board performance. Specifically, the CO2 laser drill has a spot diameter of 4-8 mil and a cutting spacing of 1-3 mil. This spot diameter and cutting spacing setting accurately removes the waste edges of the high-temperature tape while avoiding excessive damage to the high-temperature tape surrounding the cutting area, ensuring the integrity and isolation performance of the high-temperature tape.

[0024] The width of the cut high-temperature tape is the same as the width of the impedance bonding area, ensuring that the high-temperature tape can completely cover the impedance bonding area, achieving comprehensive and effective isolation and preventing contact interference between the waste area and the impedance bonding area in the width direction. At the same time, the distance between the cut high-temperature tape and the end of the impedance line 3 is not less than 2mm. Since the through hole 4 penetrates all layers and corresponds to the end of the impedance line 3, and electroplating is required, maintaining a sufficient distance can prevent the electroplating solution from seeping under the high-temperature tape, avoiding delamination and making subsequent processes impossible.

[0025] PP milling: A milling groove is made in the PP layer at the bottom of the upper subboard 1, corresponding to the area of ​​the high-temperature tape, to form a tape receiving groove, providing a space for the high-temperature tape. The depth of the tape receiving groove is the same as the thickness of the high-temperature tape, ensuring the overall board surface remains flat after lamination. This avoids unevenness caused by unsuitable groove dimensions, guaranteeing PCB flatness and reducing subsequent depth milling errors due to unevenness. The length and width of the tape receiving groove are 3-8 mil larger than the cut high-temperature tape, providing buffer space for minor deformations of the high-temperature tape during lamination. This prevents wrinkling or cracking of the PP layer of the upper subboard 1 due to slight expansion of the high-temperature tape, enhancing the tightness of the interlayer bonding.

[0026] Lamination: The milled upper sub-board 1 and the tape-applied impedance bonding lower sub-board 2 are laminated together to form a complete board, achieving a stable connection between layers. During the lamination process, the high-temperature tape acts as an insulator, ensuring that the waste area and the impedance bonding area do not stick together, creating conditions for subsequent removal of the waste area, while ensuring the structural stability and signal transmission performance of the entire board.

[0027] Drilling and electroplating: Through-holes 4 are drilled vertically through the entire board, and the through-holes 4 are electroplated to ensure conductivity. Each through-hole 4 corresponds to the end of an impedance line 3. Through the electroplated through-holes 4, the impedance lines 3 of the inner layer can be connected to the top and / or bottom layers of the PCB board for impedance testing.

[0028] Controlled-depth milling and tape removal: A mechanical controlled-depth milling machine is used to remove the waste area corresponding to the high-temperature tape on the entire board, and the high-temperature tape is then torn off, resulting in a PCB board with stepped impedance bonding. The thickness of the waste area is the same as that of the upper sub-board 1, and the length and width of the waste area are both 4-8 mil larger than the length and width of the cut high-temperature tape. Removing the waste area corresponding to the high-temperature tape through controlled-depth milling effectively reduces the interference of the waste area on impedance and improves the accuracy of impedance value determination. Since the presence of high-temperature tape in the final product affects the actual effect of the stepped impedance bonding, removing the high-temperature tape further optimizes the structural performance of the stepped impedance bonding, enabling it to better play its role in reducing interference and ensuring signal transmission.

[0029] Since the thickness of the waste area is the same as that of the upper sub-board 1, a mechanical depth-controlled milling machine can precisely control the milling depth, ensuring that the waste area corresponding to the high-temperature tape is completely and accurately removed. This results in a distinct stepped structure between the impedance bonding area and the area after waste removal. The length and width of the waste area are both 4-8 mil larger than the length and width of the cut high-temperature tape, ensuring that the waste area corresponding to the high-temperature tape can be completely removed during the depth-controlled milling operation, avoiding residual waste due to dimensional deviations. At the same time, it prevents damage to the impedance bonding area or other critical structures due to excessive depth-controlled milling, ensuring the integrity and quality stability of the PCB board.

[0030] In summary, the manufacturing method of this invention selectively removes the waste area above the impedance line 3 through processes such as material preparation, tape application, tape scrap cutting, PP milling, pressing, drilling, electroplating, controlled depth milling, and tape removal, forming a stepped impedance bonding structure. This greatly reduces the interference of the waste area on the impedance and improves the accuracy of impedance value determination. It is especially suitable for high-precision impedance control scenarios in high-end high-speed PCBs, providing a reliable guarantee for the integrity of high-frequency signal transmission.

[0031] Furthermore, although the operations of the method of the present invention are described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0032] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

[0033] The present invention has been described above with reference to the accompanying drawings. Obviously, the implementation of the present invention is not limited to the above-described manner. Any improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A method for manufacturing a PCB board with stepped impedance, characterized in that, include: Preparation: Prepare the upper sub-board and the lower impedance bonding sub-board. The impedance bonding area of ​​the lower impedance bonding sub-board is provided with impedance lines on the top surface. Applying tape: Apply high-temperature tape to the impedance bonding area. The high-temperature tape is used to prevent the waste area above it from adhering to the impedance bonding area during the pressing process. The ends of all the impedance wires are exposed on the high-temperature tape, and the rest are covered by the high-temperature tape. Cutting the waste edges of the high-temperature tape: The waste edges of the high-temperature tape are cut using a CO2 laser drill. The spot diameter of the CO2 laser drill is 4-8 mil, and the cutting spacing is 1-3 mil. PP milling groove: A groove is milled in the PP layer at the bottom of the upper sub-board corresponding to the area of ​​the high-temperature tape to form a tape receiving groove. The depth of the tape receiving groove is the same as the thickness of the high-temperature tape, and the length and width of the tape receiving groove are both larger than the length and width of the cut high-temperature tape. Pressing: Press the upper sub-board after milling the grooves with the lower sub-board after applying adhesive tape to form a whole board; Drilling and electroplating: Drill through holes in the entire board and electroplat the through holes to make them conductive. Each through hole corresponds to the end of an impedance line to conduct the impedance line to the top and / or bottom layer of the entire board for impedance testing. Controlled-depth milling and tape removal: A mechanical controlled-depth milling machine is used to remove the waste area corresponding to the high-temperature tape above the entire board. The thickness of the waste area is the same as the thickness of the upper sub-board. The length and width of the waste area are both larger than the length and width of the cut high-temperature tape. The high-temperature tape is then removed to obtain a PCB board with stepped impedance.

2. The method for manufacturing a PCB board with stepped impedance according to claim 1, characterized in that, The distance between the cut high-temperature tape and the end of the impedance wire shall be no less than 2 mm.

3. The method for manufacturing a PCB board with stepped impedance according to claim 1, characterized in that, The width of the cut high-temperature tape is the same as the width of the impedance bonding area.

4. The method for manufacturing a PCB board with stepped impedance according to claim 1, characterized in that, The thickness of the high-temperature tape is 60-80μm.

5. The method for manufacturing a PCB board with stepped impedance according to claim 1, characterized in that, The length and width of the tape receiving groove are both 3-8 mil larger than the length and width of the cut high-temperature tape.

6. The method for manufacturing a PCB board with stepped impedance according to claim 1, characterized in that, The length and width of the waste area are both 4-8 mil larger than the length and width of the cut high-temperature tape.

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