Circuit board processing method and circuit board

Abstract

The application provides a circuit board processing method and a circuit board. The processing method comprises the following steps: performing first drilling on the circuit board to form a plurality of through holes; obtaining horizontal position information of a target through hole in the plurality of through holes; measuring a position of a target signal layer corresponding to the target through hole in a vertical direction according to the horizontal position information of the target through hole, and obtaining vertical position information of the target signal layer, the target signal layer being exposed on a hole wall of the through hole; and performing second drilling on the target through hole of the circuit board according to the vertical position information of the target signal layer to form a back drilling hole, and ensuring that a residual stub length after the second drilling is within a preset range. The method can effectively avoid problems such as circuit damage and excessive residual stub length caused by position deviation, can strictly control the residual stub length after back drilling within the preset range, and significantly reduces the interference of the residual stub on high-frequency signals.

Description

Technical Field

[0001] This application belongs to the field of circuit board back drilling technology, and particularly relates to a circuit board processing method and a circuit board. Background Technology

[0002] In the current era of rapid development in the electronic information industry, the precision of the manufacturing process of printed circuit boards (PCBs), as the core carrier for signal transmission and electrical connection of electronic products, has an increasingly significant impact on the performance of terminal equipment.

[0003] The circuit board has multiple alternating dielectric and signal layers. The signal layers contain traces that connect to the metal layers on the walls of vias via the target signal layer, enabling signal transmission between different signal layers. Typically, back-drilling is used to create back-drilled holes on the circuit board to remove excess metal from the vias. The unused, suspended metal portions that are not completely drilled out—the redundant conductive portions—form the "Studying the Unwanted Barrel" (STUB). This STUB is located between the bottom of the back-drilled hole and the target signal layer.

[0004] In the field of CNC machining, circuit boards, as the core carriers for signal transmission and command execution, need to bear the rapid transmission of high-frequency signals. Their machining accuracy directly determines the equipment's response speed, operational stability, and anti-interference capability. Among these processes, back-drilling, as a key step in optimizing high-frequency signal paths and reducing signal interference from residual piling, has particularly stringent precision requirements.

[0005] However, with current circuit board processing methods, it is difficult to control the depth of back drilling, which can easily lead to damage to the circuit or excessive length of residual posts, making it difficult to meet the extremely high requirements for signal integrity in the CNC field. Summary of the Invention

[0006] The purpose of this application is to provide a circuit board processing method and a circuit board, which aims to solve the technical problem that the use of current related circuit board processing methods can easily lead to circuit damage or excessive residual length.

[0007] To achieve the above objectives, the technical solution adopted in this application is as follows:

[0008] Firstly, a circuit board processing method is provided, comprising:

[0009] The circuit board is drilled for the first time to create multiple through holes;

[0010] Obtain the horizontal position information of the target through hole among the plurality of through holes;

[0011] Based on the horizontal position information of the target through hole, the vertical position of the target signal layer corresponding to the target through hole is measured, and the vertical position information of the target signal layer is obtained. The target signal layer is exposed on the hole wall of the through hole.

[0012] Based on the vertical position information of the target signal layer, a second drilling is performed at the target through-hole position on the circuit board to form a back drill hole, and the length of the residual pile after the second drilling is within a preset range.

[0013] One possible aspect of the first aspect is that, prior to the first drilling of the circuit board, the process further includes:

[0014] Obtain the horizontal position information of each signal layer within the circuit board;

[0015] The location of the first borehole is determined based on the horizontal position information of each signal layer.

[0016] One possible scenario of the first aspect is that obtaining the horizontal position information of each signal layer within the circuit board includes:

[0017] The signal layer was identified through non-destructive measurement.

[0018] Measure the horizontal position information of each signal layer.

[0019] One possible aspect of the first aspect is that, before performing a second drilling at the location of the through hole on the circuit board, the process further includes:

[0020] Obtain the horizontal position information of the target signal layer in the horizontal direction;

[0021] The target position of the second borehole is compensated and corrected based on the horizontal position information of the target signal layer.

[0022] One possible scenario for the first aspect is that, after the initial drilling of the circuit board, the process further includes:

[0023] Obtain the interlayer dielectric thickness information of the circuit board.

[0024] One possible aspect of the first aspect is that obtaining the interlayer dielectric thickness information of the circuit board includes:

[0025] A predetermined frequency AC signal is applied to the drill bit in advance;

[0026] The circuit board forms a loop between the drilling platforms;

[0027] The vertical position information of each signal layer is determined by the amplitude of the electrical signal in the circuit.

[0028] The thickness of the interlayer medium is determined based on the vertical position information of each of the signal layers;

[0029] The depth of the back drill hole is determined based on the thickness of the interlayer medium.

[0030] One possible scenario of the first aspect is that obtaining the vertical position information of the target signal layer in the vertical direction includes:

[0031] The vertical position information of the target signal layer is obtained by optical measurement methods or non-destructive measurement methods.

[0032] One possible scenario in the first aspect is that obtaining the vertical position information of the target signal layer through optical measurement methods includes:

[0033] The incident light beam is projected onto the wall of the through hole, and the projection angle of the incident light beam is obtained;

[0034] The projection angle of the incident light is changed so that the projection position of the incident light on the hole wall of the through hole moves along the vertical direction, and the reflected light reflected by the hole wall of the through hole is emitted towards the light intensity measuring instrument.

[0035] The light intensity meter receives the reflected light rays reflected from the hole wall through the through hole, and generates a light intensity signal based on the reflected light rays.

[0036] The vertical position information of the target signal layer is obtained based on the change in the light intensity signal and the projection angle of the incident light.

[0037] One possible scenario in the first aspect is that obtaining the vertical position information of the target signal layer through optical measurement methods includes:

[0038] The incident light is projected at an angle toward the via, allowing it to pass through the dielectric layer of the circuit board and illuminate the target signal layer.

[0039] The interferometer receives the reflected light rays after they pass through the target signal layer and obtains the interference information formed by the interference of the reflected light rays with the reference light rays.

[0040] Based on the interference information and the tilt angle information of the incident light, the vertical position information of the target signal layer is obtained.

[0041] One possible aspect of the first part is that, after the back-drilled hole is formed, the following is also included:

[0042] Obtain the depth value of the back drill hole, and / or,

[0043] Obtain the length value of the residual pile in the back drill hole, and / or,

[0044] Obtain the deviation between the central axis of the back drill hole and the central axis of the through hole.

[0045] One possible aspect of the first part is that, after the back-drilled hole is formed, the following is also included:

[0046] The center coordinates of the target through hole are obtained by aligning a CCD camera with the target through hole.

[0047] The CCD camera is aligned with the back drill hole to obtain the center coordinates of the back drill hole;

[0048] The hole position deviation value of the back drill hole is determined based on the center coordinates of the target through hole and the center coordinates of the back drill hole.

[0049] One possible aspect of the first part is that, after the back-drilled hole is formed, the following is also included:

[0050] The polychromatic light rays are sequentially split and focused before being directed toward the back drill hole;

[0051] Acquire the first spectral information of the first reflected light reflected from the bottom surface of the back drill hole and the second spectral information of the second reflected light reflected from the target signal layer;

[0052] The depth of the back borehole is obtained based on the first spectral information; or, the length of the residual pile in the back borehole is obtained based on the first spectral information and the second spectral information.

[0053] One possible aspect of the first part is that, after the back-drilled hole is formed, the following is also included:

[0054] Project the incident light toward the back drill hole;

[0055] The first interference image formed by the incident light rays is acquired by a surface scanning camera;

[0056] Based on the first interference image, determine the first distance value from the area scanning camera to the plate surface where the hole of the back drill hole is located;

[0057] The area scanning camera is controlled to move by a second distance value, and a second interference image formed by the incident light rays is acquired through the area scanning camera;

[0058] Based on the second interference image, determine the third distance value from the area scanning camera to the bottom surface of the back drill hole;

[0059] The depth of the back drill hole is obtained based on the first distance value, the second distance value, and the third distance value.

[0060] One possible scenario for the first aspect is that, after the first drilling of the circuit board, the process further includes:

[0061] A metal layer is formed on the wall of the through hole.

[0062] One possible scenario of the first aspect is that, before the first drilling of the circuit board, the method further includes: correcting the drill tape data of the first drilling by reading the first data in the first tag, wherein the first tag is generated on the circuit board, and the first data includes the measurement data of the target signal layer before the first drilling and the processing data of the previous process.

[0063] After obtaining the vertical position information of the target signal layer, the method further includes: generating a second tag on the circuit board, the second tag storing second data, the second data including the measurement data of the through hole and the target signal layer after the first drilling;

[0064] Before the second drilling is performed, the method further includes: correcting the drill string data of the second drilling by reading the second data in the second tag;

[0065] After the second drilling is performed, the method further includes: generating a third tag on the circuit board, the third tag storing third data, the third data including residual stake related data and residual copper data of the hole wall, and correcting the first data according to the third data.

[0066] Secondly, a circuit board is provided, which is manufactured by the circuit board processing method described in the above embodiments.

[0067] The technical advantages of this application compared to existing technologies are as follows: This circuit board processing method addresses the stringent requirements for back-drilling accuracy in high-frequency signal transmission of circuit boards in the CNC field. By first forming multiple through holes and determining the horizontal position of the target through holes, and then accurately measuring the vertical position of the exposed target signal layer on the hole wall based on this, a second back-drilling is performed based on this position, achieving precise control over the back-drilling depth. This process effectively avoids problems such as circuit damage and excessive residual length caused by positional deviations, strictly controlling the residual length after back-drilling within a preset range, significantly reducing the interference of residual length on high-frequency signals, ensuring signal integrity, thereby improving the response speed, operational stability, and anti-interference capability of CNC equipment, and meeting the extremely high requirements for circuit board processing accuracy in the CNC field. Attached Figure Description

[0068] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0069] Figure 1 This is a cross-sectional view of the circuit board provided in an embodiment of this application;

[0070] Figure 2 This is a perspective view of the circuit board provided in the embodiment of this application;

[0071] Figure 3 This is a flowchart of the circuit board processing method provided in the embodiments of this application;

[0072] Figures 4 to 8 These are flowcharts of different embodiments of the circuit board processing method provided in this application for obtaining the vertical position information of the target signal layer in the vertical direction;

[0073] Figure 9 This is a flowchart illustrating the deviation between the center axis of the back drill hole and the center axis of the through hole in the circuit board processing method provided in this application.

[0074] Figure 10 This is a flowchart of obtaining the residual stake length value in the circuit board processing method provided in this application;

[0075] Figure 11 This is a flowchart of the circuit board processing method provided in this application for obtaining the back drill hole depth value and the residual pile length value;

[0076] Figure 12 This is a flowchart of obtaining the back drill hole depth value in the circuit board processing method provided in this application;

[0077] Figure 13 yes Figure 12 The flowchart in which incident light is projected toward the back borehole;

[0078] Figure 14 This is a flowchart of obtaining the back drill hole depth value in the circuit board processing method provided in this application;

[0079] Figure 15 This is a flowchart illustrating the process of obtaining multiple back-drill hole depth values ​​in the circuit board processing method provided in this application;

[0080] Figure 16 This is a flowchart of the entire data management process in the circuit board processing method provided in this application.

[0081] Explanation of reference numerals in the attached figures:

[0082] 100. Circuit board; 10a. First board surface; 10b. Second board surface; 11. Dielectric layer; 12. Signal layer; 121. Target signal layer; 101. Target via; 102. Metal through-hole; 103. Back drill hole; 1031. Bottom surface; 13. Metal layer. Detailed Implementation

[0083] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0084] In the description of this application, it should be understood that the terms "length", "width", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application 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, and therefore should not be construed as a limitation of this application.

[0085] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0086] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," 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 components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0087] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments.

[0088] In the current era of rapid development in the electronic information industry, printed circuit boards (PCBs), as the core carrier for signal transmission and electrical connection of electronic products, have an increasingly significant impact on the performance of terminal equipment due to their manufacturing process precision.

[0089] The circuit board has multiple alternating dielectric and signal layers. The signal layers contain traces that electrically connect to the metal layers on the walls of vias by surrounding the target signal layer, thus enabling signal transmission between different signal layers. Typically, back-drilling is used to create back-drilled holes on the circuit board to remove excess metal from the vias. The non-functional, suspended metal portions that are not completely drilled out—i.e., redundant conductive portions—form a stump (Studying the Unwanted Barrel, STUB). This stump is located between the bottom of the back-drilled hole and the target signal layer.

[0090] In the field of CNC machining, circuit boards, as the core carriers for signal transmission and command execution, must bear the rapid transmission of high-frequency signals. Their machining accuracy directly determines the equipment's response speed, operational stability, and anti-interference capabilities. Among these, back-drilling, as a crucial step in optimizing high-frequency signal paths and reducing signal interference from stubs (residual metal segments inside holes), has particularly stringent accuracy requirements. However, in current back-drilling processes, due to factors such as multilayer circuit board lamination errors and pre-drilling offsets, the actual horizontal position of the target signal layer deviates from the design coordinates. Furthermore, its vertical interlayer position is prone to fluctuations due to uneven dielectric layer thickness.

[0091] However, during the interlayer lamination process, the target signal layer may be affected by pressure and deviate from its original design position. Similarly, during through-hole machining, the position of the through-hole may also deviate from its original design position due to drill vibration. Furthermore, both the interlayer lamination and through-hole machining processes can lead to unevenness on the circuit board surface at the through-hole location, causing changes in the circuit board thickness and resulting in the target signal layer's vertical position deviating from its original design. Therefore, using current circuit board manufacturing methods, controlling the position and depth of back-drilled holes is difficult, easily leading to problems such as excessive or insufficient back-drilling depth, or misalignment between the back-drilled hole and the target signal layer. Excessive back-drilling depth can cause circuit damage, while insufficient back-drilling depth can result in excessively long residual studs. Back-drilling hole misalignment can lead to residual metal segments within the through-hole. Both of these problems can cause impedance abrupt changes, signal reflection, and crosstalk in high-frequency signal transmission, making it difficult to meet the extremely high signal integrity requirements of the CNC field.

[0092] Based on this, this application provides a circuit board processing method that can precisely control the processing position and depth of back drill holes, avoiding problems such as excessive or insufficient back drill hole depth or positional deviation, thereby improving the accuracy and reliability of circuit board processing.

[0093] Please refer to Figure 1 and Figure 2The circuit board 100 includes multiple dielectric layers 11 and multiple signal layers 12, which are arranged alternately in sequence. That is, a signal layer 12 is disposed between two adjacent dielectric layers 11, or a dielectric layer 11 is disposed between two adjacent signal layers 12. The signal layers 12 are made of a conductive metallic material, while the dielectric layers 11 are made of an insulating material, such as fiberglass resin. In this embodiment, the signal layer 12 includes at least one copper foil. Since there are multiple signal layers 12 in the circuit board 100, each signal layer 12 may contain multiple copper foils. For easy differentiation, the copper foil to be processed can be named the target copper foil, and correspondingly, the signal layer 12 formed after the target copper foil is pierced by a via is named the target signal layer 121.

[0094] In the following embodiments, the circuit board 100 is defined as being placed horizontally, that is, the plane on which the circuit board 100 is located is a horizontal plane, and the thickness direction of the circuit board 100 is always vertical. The circuit board 100 has a first plate surface 10a and a second plate surface 10b that are opposite to each other in the vertical direction.

[0095] Please see Figures 1 to 3 In this embodiment of the application, the processing method of the circuit board 100 includes:

[0096] S1. Drill holes in the circuit board 100 for the first time to form multiple through holes.

[0097] Based on the initial drill tape information, the corresponding positions of multiple through holes in the drill tape information are determined. These corresponding positions can be the corresponding positions of all through holes on the circuit board 100, or they can be the corresponding positions of some through holes; there is no limitation here. A drill bit is used to perform the first drilling in the vertical direction on the circuit board 100 to form multiple through holes corresponding to the drill tape information. Each through hole penetrates both the first board surface 10a and the second board surface 10b.

[0098] S2. Obtain the horizontal position information of the target through hole 101 among multiple through holes.

[0099] The target through-hole 101 is the through-hole among multiple through-holes that will be drilled a second time. A three-dimensional coordinate system is established based on the position of the circuit board 100. The two vertical directions on the horizontal plane where the circuit board 100 is located are defined as the X-axis and Y-axis, and the vertical direction is defined as the Z-axis. The horizontal position information of the target through-hole 101 includes the coordinate data of the through-hole in the horizontal direction, such as the X-axis coordinates and Y-axis coordinates of the center or wall position of the through-hole. Due to the shaking of the drill bit or the circuit board 100 during the first drilling process, the actual horizontal position of the target through-hole 101 may deviate from the horizontal position in the drill strip information. Obtaining the horizontal position information of the target through-hole 101 can provide a precise horizontal positioning reference for the subsequent detection of the target signal layer 121. S3. Based on the horizontal position information of the target through-hole 101, the vertical position of the target signal layer 121 corresponding to the target through-hole 101 is measured, and the vertical position information of the target signal layer 121 is obtained. The target signal layer 121 is exposed on the wall of the through-hole.

[0100] The detection equipment can correct the position of the preset design detection area based on the measured horizontal position information of the target through hole 101, and obtain the position information of the actual detection area that matches the actual horizontal coordinates of the target through hole 101, ensuring that the detection direction of the detection equipment (such as incident light and probe light) can be accurately aligned with the detection area where the target through hole 101 is located. Since the target through hole 101 penetrates the target signal layer 121, the target signal layer 121 can be exposed on the hole wall.

[0101] It should be noted that, considering the second drilling may involve a change of workstation or the flipping of circuit board 100, to avoid positional deviations caused by movement or flipping affecting the detection accuracy, the acquisition of vertical position information must be completed before the circuit board 100 is moved or flipped. This timing arrangement can preserve the accuracy of horizontal position calibration to the greatest extent and reduce the interference of mechanical operation on the detection alignment.

[0102] The vertical position information of the target signal layer 121 includes the coordinate data of the target signal layer 121 in the vertical direction, such as the Z-axis coordinate of the midpoint of the target signal layer 121 in the vertical direction in three-dimensional space, the Z-axis coordinate of the inner ring surface of the target signal layer 121 or at least one surface in the vertical direction in three-dimensional space, etc.

[0103] After forming the via and measuring the vertical position of the target signal layer 121, the via can be metallized, that is, a metal layer 13 is formed on the wall of the via. The metal layer 13 forms a cylindrical structure and can surround the metal through-hole 102. The metal layer 13 is in contact with the target signal layer 121 exposed on the wall of the via to achieve vertical conductivity of the target signal layer 121 in the circuit board 100.

[0104] S4. Based on the vertical position information of the target signal layer 121, a second drilling is performed on the through hole position of the circuit board 100 to form a back drill hole 103, and the length of the residual pile after the second drilling is within a preset range.

[0105] Based on the vertical position information of the target signal layer 121, the vertical movement distance of the drill bit or the Z-axis coordinate of the moving endpoint is obtained. Then, using a drill bit with an outer diameter larger than the diameter of the through hole, the drill bit moves vertically from the first board surface 10a side of the circuit board 100 towards the second board surface 10b side to perform a second drilling at the through hole position of the circuit board 100, forming a back drill hole 103. The final stop position of the drill bit does not reach the target signal layer 121, so that the back drill hole 103 and the target signal layer 121 are vertically spaced apart. Before the second drilling, the circuit board 100 is drilled a second time, so that the opening of the back drill hole 103 is located on the first board surface 10a. In other embodiments, the drill bit can also move from the second board surface 10b side of the circuit board 100 towards the first board surface 10a side to form the back drill hole 103. In this case, the opening of the back drill hole 103 is located on the second board surface 10b. This is not a limitation; the specific processing position can be selected according to processing requirements. The position of the drill bit before the first drilling and the orientation of the drill bit relative to the circuit board 100 before the second drilling can be the same or different; there is no restriction here.

[0106] The diameter of the back-drilled hole 103 is larger than that of the through hole. This allows the drill bit to remove a portion of the metal layer 13 during the second drilling, reducing the vertical length of the residual pile. Upon completion of the second drilling, a stepped structure is formed between the back-drilled hole 103 and the through hole; the platform of this stepped structure is the bottom surface 1031 of the back-drilled hole 103. The distance between the back-drilled hole 103 and the target signal layer 121 is the distance between the bottom surface 1031 of the back-drilled hole 103 and the surface of the target signal layer 121 facing the back-drilled hole 103, which is also the length of the residual pile. The length of the residual pile is within a preset range, which can be selected as 50µm-250µm.

[0107] After the second drilling, the process includes filling the back-drilled holes 103 and metal through-holes 102 with insulating material, such as insulating resin, to eliminate the influence of air or potential conductive impurities in the holes on the performance of the circuit board 100. Then, the insulating material protruding from the surface of the circuit board 100 is removed, for example, by grinding or scraping the first board surface 10a and the second board surface 10b flat, to eliminate unevenness caused by overflow or uneven shrinkage of the insulating material during the filling process, and to avoid defects such as printed pattern deformation and poor pad contact caused by local protrusions or depressions. Of course, the insulating material may only fill the back-drilled holes 103 or only fill the metal through-holes 102, or it may partially fill the back-drilled holes 103 and / or partially fill the metal through-holes 102; there are no limitations here.

[0108] This circuit board 100 processing method addresses the stringent requirements for back-drilling accuracy in high-frequency signal transmission within CNC circuit boards 100. By first forming multiple through-holes and determining the horizontal position of the target through-hole 101, the spatial alignment accuracy during vertical position detection of the target signal layer 121 is ensured. This provides a reliable data foundation for subsequent back-drilling depth control based on vertical position information, avoiding detection failures caused by horizontal deviations. Then, by measuring the vertical position of the exposed target signal layer 121 on the through-hole wall, a second back-drilling is performed based on this vertical position, achieving precise control of the back-drilled hole 103 depth. This process effectively avoids problems such as circuit damage and excessive residual length caused by positional deviations, strictly controlling the residual length after back-drilling within a preset range. This significantly reduces interference from residual length to high-frequency signals, ensuring signal integrity and thereby improving the response speed, operational stability, and anti-interference capability of CNC equipment, meeting the extremely high processing accuracy requirements of the CNC field for circuit board 100.

[0109] Understandably, before the first drilling of circuit board 100, the following steps are also included:

[0110] S01. Obtain the horizontal position information of each signal layer 12 within the circuit board 100.

[0111] The horizontal position information of each signal layer 12 includes the coordinate data of each signal layer 12 in the horizontal direction, such as the X-axis coordinates and Y-axis coordinates of the center of the design punch area of ​​the signal layer 12 or the boundary of the signal layer 12.

[0112] S02. Determine the location of the first borehole based on the horizontal position information of each signal layer 12.

[0113] The first drilling location must be within the boundary of the target signal layer 121 in the vertical direction to ensure that the target through-hole 101 passes through the middle of the target signal layer 121 and can be circumferentially closed around the target through-hole 101. Before drilling the first hole, the drill strip information of the first hole will be corrected according to the location of the first hole, and the horizontal position of the drill bit will be adjusted accordingly to avoid drilling off-center.

[0114] Before the first drilling, the horizontal position information of each signal layer 12 is obtained, and the position of the first drilling is determined accordingly. This can accurately compensate for the horizontal offset of the signal layer 12 position caused by interlayer lamination. By correcting the horizontal position of the drill bit, it is ensured that the target through hole 101 passes through the middle of the target signal layer 121, so that the formed signal layer 12 is circumferentially closed and accurately positioned. This avoids the target signal layer 121 from being broken or poorly connected due to the offset of the target through hole 101, laying the foundation for accurate positioning in the subsequent back drilling process. This effectively improves the reliability and processing accuracy of the conductive connection of the circuit board 100 and reduces the scrap rate caused by position deviation.

[0115] The acquisition of the horizontal position information of each signal layer 12 within the circuit board 100 includes:

[0116] S011. Identify each signal layer through non-destructive measurement 12;

[0117] S012, Measure the horizontal position information of each signal layer 12.

[0118] Non-destructive measurement methods include, but are not limited to, X-ray CT scanning, optical coherence tomography, ultrasonic microscopy, eddy current array detection, microwave detection, and terahertz time-domain spectroscopy, which will be introduced below.

[0119] X-ray CT scans include:

[0120] First, the circuit board 100 is fixed on the stage of the X-ray CT equipment. Then, the CT equipment is started to emit X-rays to the circuit board 100. When the X-ray beam penetrates the multi-layer structure of the circuit board 100, the detector can capture the difference in attenuation signal in different areas due to the significant difference in the attenuation coefficient between the target copper foil (metal material) and the dielectric layer 11 (insulating material), forming a two-dimensional tomographic image containing the contours of each signal layer 12.

[0121] Subsequently, the CT equipment drives the circuit board 100 to rotate or translate via a precision mechanical transmission system, acquiring a series of continuous two-dimensional tomographic images at different angles and positions. Then, using CT reconstruction algorithms (such as filtered back projection), these two-dimensional images are fused and reconstructed into a three-dimensional model of the circuit board 100. Each signal layer 12 is presented in the model as a high-contrast metal density region, clearly distinguishable from the surrounding dielectric layer 11.

[0122] Finally, the 3D model is processed using image analysis software: in the horizontal plane, the edge contours of each signal layer 12 are identified, and parameters such as its center coordinates and contour coordinates are extracted to obtain the horizontal position information of each signal layer 12.

[0123] Ultrasonic microscopy uses high-frequency ultrasound (typically above 10MHz) to scan the circuit board 100. By analyzing the acoustic impedance differences between different signal layers 12 (metal layer 13 and insulating layer), a high-resolution image of the interlayer structure is generated. It can accurately identify the vertical position, thickness, and relative relationship of the signal layer 12 to the via, and is particularly suitable for detecting the connection status between the signal layer 12 and the via wall.

[0124] Optical coherence tomography (OCT) is based on the principle of light interference to perform micron-level resolution tomographic imaging of the internal structure of circuit board 100. For the surface and near-surface signal layer 12, it can clearly show the exposed boundary of the via wall, and the detection speed is fast and radiation-free, making it suitable for fine position measurement of high-frequency signal layer 12.

[0125] Eddy current array detection uses a multi-channel eddy current probe to generate an alternating magnetic field around the via. The signal layer 12 (made of metal) will be induced with eddy currents, and the changes in these eddy currents will be captured by the probe. By analyzing the phase and amplitude of the eddy current signal, the vertical position of the signal layer 12 on the via wall and the interlayer distance can be located, making it particularly suitable for detecting the boundary of the conductive signal layer 12.

[0126] Microwave detection utilizes the reflection and transmission characteristics of microwaves in different media (the metal and insulating substrate of signal layer 12) to determine the spatial location of signal layer 12 by analyzing the echo signal. It has a certain detection capability for signal layers 12 that are deeply buried in multilayer circuit boards 100, and the equipment cost is relatively low, making it suitable for batch testing scenarios.

[0127] Terahertz time-domain spectroscopy technology utilizes terahertz waves, which have strong penetrating power through non-metallic materials (such as the substrate of circuit board 100) but produce strong reflections at the metallic signal layer 12. By analyzing the reflected signals of terahertz pulses, the depth and boundary of the signal layer 12 can be precisely located, making it particularly suitable for detecting subtle positional deviations in the high-frequency signal layer 12.

[0128] The aforementioned non-destructive measurement method obtains the horizontal position information of each signal layer 12, enabling non-contact penetration of the circuit board 100. Leveraging the significant difference between the metal and dielectric layers 11, the contours of each signal layer 12 are clearly identified, allowing for precise extraction of their positional parameters. This method avoids damage to the circuit board 100 structure, effectively preventing potential issues associated with traditional testing methods. Furthermore, it overcomes the obstruction limitations imposed by the multi-layered structure of the circuit board 100 on the observation of the internal signal layers 12, significantly improving the measurement accuracy and reliability of horizontal position information. This provides high-quality data support for accurate positioning during the subsequent first drilling process, helping to reduce back-drilling defects caused by positional deviations. It should be noted that the effects of the non-destructive measurement method used in subsequent embodiments are the same as those used during the detection of each signal layer 12, and will not be elaborated upon in subsequent embodiments.

[0129] Understandably, after the first drilling of the circuit board 100, the following steps are also included:

[0130] S11. Obtain the interlayer dielectric thickness information of the circuit board 100.

[0131] In the structure of the multilayer circuit board 100, the interlayer dielectric thickness refers to the distance between different signal layers 12 of the circuit board 100, i.e., the thickness of the dielectric layer 11. The interlayer dielectric thickness determines the relative position of the signal layers 12 in the thickness direction (vertical direction) of the circuit board 100. During the manufacturing process of the circuit board 100, due to deviations during the lamination process, it is necessary to measure the actual interlayer dielectric thickness. This interlayer dielectric thickness information can be fed back to the lamination process as a basis for adjusting the process parameters of the lamination process.

[0132] The acquisition of interlayer dielectric thickness information of circuit board 100 includes:

[0133] S111, Identify the signal layer 12 and / or dielectric layer 11 through non-destructive measurement;

[0134] S112. Measure the thickness of the interlayer medium of each signal layer 12 to obtain the interlayer medium thickness information.

[0135] The non-destructive measurement method, taking X-ray CT scanning as an example, includes first constructing a three-dimensional model of the circuit board 100. The method for constructing the three-dimensional model of the circuit board 100 is similar to the method for constructing the three-dimensional model of the circuit board 100 when obtaining the horizontal position information of the target copper foil, and will not be described in detail here.

[0136] Then, the three-dimensional model is processed by image analysis software: in the vertical direction, the signal layer 12 is identified and the spacing between two adjacent signal layers 12 is extracted, or the two opposing surfaces of the dielectric layer 11 in the vertical direction are identified and the spacing between the two surfaces is extracted, thereby obtaining the interlayer dielectric thickness information of the circuit board 100.

[0137] As an alternative implementation, the interlayer dielectric thickness information of the circuit board 100 can be obtained by current-based measurement or capacitance-based measurement. Specifically, obtaining the interlayer dielectric thickness information of the circuit board 100 includes:

[0138] S121. Apply an AC signal of a predetermined frequency to the drill bit in advance.

[0139] Both capacitive and current-based measurements require applying a specific frequency AC signal to the drill bit used for drilling. This signal serves as a detection source, providing the basis for subsequent identification of the signal layer 12 location through changes in the electrical signal: in capacitive measurements, the AC signal is used to excite the capacitor's charging and discharging process; in current-based measurements, the AC signal provides the potential difference for generating the loop current.

[0140] S122, A circuit is formed between the drilling platforms via the circuit board 100.

[0141] Capacitive measurement: The drilling platform of the circuit board 100 is grounded, and the upper and lower surfaces of the circuit board 100 are signal layers 12. A capacitive structure is formed between the drill bit and the drilling platform due to the signal layer 12 and the dielectric layer 11. The AC signal forms a capacitive circuit through the drill bit, the circuit board 100, and the drilling platform.

[0142] Current measurement: The ground terminal of the drilling machine control board is connected to each signal layer 12. When the drill bit contacts a certain signal layer 12, a conductive loop is formed through the drill bit, signal layer 12, and ground terminal of the control board, and the current signal can be transmitted along the loop.

[0143] S123. Determine the vertical position information of each signal layer 12 by the amplitude of the electrical signal in the circuit.

[0144] Capacitive measurement: When the drill bit contacts the first signal layer 12, a capacitor charging circuit is formed. The receiving circuit detects a sudden change in the charging voltage amplitude (from zero to one) and records the drill bit feed depth at this time, which is the vertical position of the first signal layer 12. When the drill bit continues to feed and passes through the dielectric layer 11 to contact the next signal layer 12, the voltage amplitude changes again. This process is repeated to determine the position of each signal layer 12.

[0145] Current measurement: When the drill bit contacts a certain signal layer 12, the circuit is turned on, and the receiving circuit detects the current signal amplitude from zero to one. The depth at this time is recorded as the position of the signal layer 12. After the drill bit penetrates the signal layer 12, the circuit is turned off, the current signal amplitude disappears, and the boundary of the signal layer 12 is further verified.

[0146] S124. Determine the thickness of the interlayer medium based on the vertical position information of each of the signal layers 12.

[0147] Based on the obtained vertical position coordinates of two adjacent signal layers 12 (e.g., the depth of the first layer is s1 and the depth of the second layer is s2), the thickness of the dielectric layer 11 between the two signal layers 12 can be obtained by calculating the difference between them (s2-s1). This process directly correlates the position of the signal layer 12 with the change of electrical signal, avoiding the indirect errors of traditional measurements.

[0148] S125. Determine the depth of the back drill hole 103 based on the thickness of the interlayer medium.

[0149] The thickness of the interlayer medium reflects the spacing and distribution of the signal layers 12. Combined with the vertical position of the target signal layer 121 (such as the depth of the signal layer 12 to be retained), the depth that the back-drilled hole 103 needs to reach (such as the preset distance from the surface to the top of the target signal layer 121) can be accurately calculated to ensure that the length of the residual pile after back-drilling is within the preset range.

[0150] By using capacitive or current-based electrical signal measurement methods, the vertical position of each signal layer 12 can be directly identified by utilizing the electrical characteristics of the drill bit and the signal layer 12. The interlayer dielectric thickness can be obtained synchronously without additional detection equipment, simplifying the measurement process and reducing costs. The abrupt change characteristics of the electrical signal amplitude ensure high accuracy in identifying the position of the signal layer 12 and reduce errors in the calculation of interlayer thickness. The back-drilling depth is determined based on the measured interlayer thickness, which can be specifically adapted to the actual structure of the circuit board 100, effectively avoiding problems such as excessively long residual piles or drilling through the signal layer 12, improving the reliability of the back-drilling process, and is especially suitable for the stringent accuracy requirements of high-frequency signal transmission in the CNC field for the circuit board 100.

[0151] It should be noted that this interlayer dielectric thickness can also be used to obtain the vertical position information of the signal layer 12 in the vertical direction in subsequent steps. Specifically, during the fabrication of the circuit board 100, by measuring the interlayer dielectric thickness and combining it with the information of the layer where the signal layer 12 is located in the circuit board 100 design file, the depth range of the signal layer 12 in the vertical direction can be accurately calculated. For example, assuming that the circuit board 100 has three conductive layers, and by measuring and finding that the interlayer dielectric thickness between the first and second layers is h1, and the interlayer dielectric thickness between the second and third layers is h2, if the signal layer 12 is located in the second conductive layer, it can be preliminarily determined that the depth of the signal layer 12 from the upper surface of the circuit board 100 is around h1.

[0152] The depth of the back-drilled hole 103 is the distance from the surface of the circuit board 100 to a specific location on the signal layer 12 (usually the starting position of the metal layer that needs to be preserved). After determining the exact location of the signal layer 12, the required depth of the back-drilled hole 103 can be calculated based on information such as the interlayer dielectric thickness. For example, if the distance from the upper surface of the circuit board 100 to the top of the signal layer 12 is h1, then to maintain a certain preset distance d between the bottom of the back-drilled hole 103 and the top of the signal layer 12, the depth of the back-drilled hole 103 is D = h1 - d.

[0153] In this way, if the measured thickness of the interlayer medium is deviated, causing the actual position of the signal layer 12 to differ from the expected position, the depth setting of the back drill hole 103 can be corrected in time to ensure the accuracy of the back drilling process and avoid problems such as the back drill hole 103 being too deep and damaging the target signal layer 121, or too shallow and causing the residual pile to be too long, thus ensuring the electrical performance of the circuit board 100.

[0154] In addition, the thickness of the interlayer medium directly determines the process parameters that the drill bit needs to overcome, such as the hardness and thickness distribution of the medium. For example, if the thickness of an interlayer medium is abnormally large (exceeding the design value), it may mean that there are air bubbles or uneven thickness in the medium layer 11 in that area, and the drill bit speed and feed pressure need to be adjusted to avoid drill breakage; if the thickness of the interlayer medium is too small, the drilling depth needs to be controlled to prevent drilling through the underlying copper foil.

[0155] The acquisition of the horizontal position information of the target signal layer 121 includes:

[0156] S3011, Identify the target signal layer 121 through non-destructive measurement;

[0157] S3012, Measure the horizontal position information of the target signal layer 121.

[0158] The non-destructive measurement method, taking X-ray CT scanning as an example, includes first constructing a three-dimensional model of the circuit board 100. The method for constructing the three-dimensional model of the circuit board 100 is similar to the method for constructing the three-dimensional model of the circuit board 100 when obtaining the horizontal position information of the target copper foil, and will not be described in detail here.

[0159] Then, the three-dimensional model is processed by image analysis software: in the horizontal plane, the edge contour of the target signal layer 121 is identified, and its center coordinates, radius, inner ring surface coordinates, outer contour coordinates and other parameters are extracted to obtain the horizontal position information of the target signal layer 121.

[0160] As an alternative embodiment, the step of obtaining the horizontal position information of the target signal layer 121 within the circuit board 100 includes:

[0161] S3021. Acquire image information of the target through hole 101, and measure the horizontal position information of the target through hole 101 based on the image information.

[0162] The formed target via 101 is photographed using a high-precision image acquisition device such as a CCD camera to obtain clear image information containing the target via 101. Because the target via 101 has undergone metallization, its hole wall forms a conductive metal layer 13, which will appear as a distinct metal perforation 102 in the image, clearly distinguishable from the surrounding dielectric layer 11. By processing the acquired image using image analysis technology, the horizontal position parameters of the target via 101 can be accurately measured, including the X-axis and Y-axis coordinates of the center of the target via 101, the boundary coordinates of the metal perforation 102 contour, etc., thereby determining the horizontal position information of the target via 101.

[0163] S3022. Obtain the horizontal position information of the target signal layer 121 based on the horizontal position information of the target through hole 101.

[0164] In the design and fabrication of circuit board 100, the target signal layer 121 and the target via 101 have a strict coaxial relationship, that is, their central axes coincide. Based on this structural characteristic, the horizontal position of the target via 101 is consistent with the horizontal position of the target signal layer 121. Therefore, the horizontal position information of the target via 101 measured in S3021 can be directly equated with the horizontal position information of the target signal layer 121, without the need for separate positioning of the signal layer 12.

[0165] This method acquires the horizontal position information of the target via 101 by acquiring an image of the via 101, and derives the horizontal position of the signal layer 12 by utilizing the coaxiality between the signal layer 12 and the target via 101. This achieves precise positioning without the need for complex internal detection equipment, simplifying the measurement process. Using image acquisition technologies such as CCD cameras, the metallization features of the target via 101 can be quickly captured, ensuring the measurement accuracy of the horizontal position parameters and effectively compensating for positional deviations during processing. Furthermore, this method directly derives the position based on the structural correlation between the two, avoiding direct detection of the signal layer 12, reducing operational difficulty and cost, providing reliable data support for precise alignment in subsequent drilling processes, and improving the overall accuracy and efficiency of circuit board 100 processing.

[0166] It is understandable that before drilling a second hole at the target through-hole 101 location on the circuit board 100, the following steps are also included:

[0167] S401. Obtain the horizontal position information of the target signal layer 121 in the horizontal direction.

[0168] Because the processing position was changed or the circuit board 100 was flipped before the second drilling process, the location of the target through-hole 101 deviated from the drill strip information in the second drilling process. Therefore, it is necessary to re-acquire the horizontal position information of the target signal layer 121 to achieve accurate positioning of the second drilling location. The horizontal position information of the target signal layer 121 can be obtained by re-measurement or calculated based on design deviation values ​​or empirical deviation values. There are no restrictions here, as long as the horizontal position information of the target signal layer 121 used in this step is within the allowable error range.

[0169] S402. Based on the horizontal position information of the target signal layer 121, the target position of the second borehole is compensated and corrected.

[0170] The drill strip information can be modified based on the horizontal position information of the target signal layer 121. The drill bit can then perform a second drilling based on the corrected drill strip information, so that the formed back drill hole 103 is coaxial or nearly coaxial with the target through hole 101.

[0171] Before the second drilling, the horizontal position information of the target signal layer 121 is obtained, and the target position of the second drilling is compensated and corrected accordingly. This can accurately offset the positional deviation that may occur after the first drilling, ensuring that the back drill hole 103 and the target signal layer 121 are accurately aligned in the vertical direction. This avoids the metal layer 13 remaining in the target through hole 101 during back drilling due to horizontal misalignment, further improving the positional accuracy of back drilling, ensuring the reliability of the through hole electrical connection and the high-frequency signal transmission performance, and reducing the risk of circuit failure caused by alignment deviation.

[0172] The method for obtaining the horizontal position information of the target signal layer 121 within the circuit board 100 is the same as the method for obtaining the horizontal position information of the target signal layer 121 before obtaining the vertical position information of the target signal layer 121 in the vertical direction. Both methods can be X-ray CT scanning or image acquisition of the target through hole 101, which will not be elaborated here.

[0173] Please combine Figure 4 Obtain the vertical position information of the target signal layer 121 in the vertical direction, including:

[0174] The vertical position information of the target signal layer 121 is obtained by optical measurement methods or non-destructive measurement methods.

[0175] By using optical measurement or non-destructive measurement methods to obtain the vertical position information of the target signal layer 121, the depth coordinates of the target signal layer 121 can be accurately captured without damaging the structure of the circuit board 100. This avoids the risk of damage to the signal layer 121 that may be caused by contact measurement, and can adapt to the detection requirements of signal layers 121 with different materials and different burial depths. It provides reliable data support for the precise control of the depth of the subsequent back drill hole 103, effectively ensures the compliance of the residual pile length, and improves the stability and processing yield of the high-frequency signal transmission of the circuit board 100.

[0176] Among them, taking X-ray CT scanning as an example of non-destructive measurement methods, the vertical position information of the target signal layer 121 obtained by X-ray CT scanning includes:

[0177] S311. Identify target signal layer 121 through X-ray CT scan;

[0178] S312. Measure the vertical position information of the target signal layer 121.

[0179] Specifically, a three-dimensional model of the circuit board 100 is first constructed. The method for constructing the three-dimensional model of the circuit board 100 is similar to the method for constructing the three-dimensional model of the circuit board 100 when obtaining the horizontal position information of the target copper foil, and will not be described in detail here.

[0180] Then, the three-dimensional model is processed by image analysis software: in the vertical direction, the start and end positions of the two surfaces of the target signal layer 121 in the Z-axis direction are determined by layer-cutting analysis, the thickness of the target signal layer 121 is calculated, and combined with the three-dimensional coordinate system transformation, the vertical position information of the target signal layer 121 is finally obtained.

[0181] When both the vertical and horizontal position information of the target signal layer 121 are acquired using X-ray CT scanning, the two pieces of information can be acquired simultaneously or in separate time periods; no restriction is imposed here.

[0182] Optical measurement can be implemented in various ways, and the following examples illustrate this.

[0183] As a first implementation method, please refer to Figure 5 The vertical position information of the target signal layer 121 in the vertical direction obtained by optical measurement methods includes:

[0184] S321. Project the incident light beam onto the wall of the target through hole 101 and obtain the projection angle of the incident light beam.

[0185] A light source can be placed on one side of the first surface 10a of the circuit board 100, and incident light is projected at an angle towards the first aperture so that the incident light can be projected onto the wall of the target through-hole 101. Simultaneously, the initial projection angle of the incident light, such as the angle between the incident light and the vertical direction, is recorded. This angled incident design ensures effective reflection of the light from the aperture wall, providing a basis for subsequent detection. Accurate recording of the projection angle is a key parameter for subsequent calculation of the vertical position. Specifically, the initial projection angle of the incident light must ensure that the reflected light from the wall of the target through-hole 101 can at least partially exit through the second aperture.

[0186] S322. Change the projection angle of the incident light so that the projection position of the incident light on the hole wall of the target through hole 101 moves in the vertical direction, and the reflected light reflected by the hole wall of the target through hole 101 is emitted towards the light intensity measuring instrument.

[0187] The light source is driven to rotate by a rotating component, thereby changing the projection direction of the incident light and causing the position of the incident light projected onto the wall of the target through-hole 101 to move vertically. Since the target signal layer 121 is made of metal and the other areas of the hole wall are made of dielectric layer 11, the movement of the light projection position will cover areas of different materials. At the same time, the reflection of light by the hole wall of the target through-hole 101 must meet a specific path to ensure that the reflected light reflected by the hole wall of the target through-hole 101 can exit from the second aperture and be projected toward the light intensity measuring instrument. During this process, the rotation angle of the incident light can be recorded synchronously by an angular displacement sensor to generate angle information.

[0188] S323. The light intensity meter receives the reflected light reflected from the hole wall of the target through hole 101 and generates a light intensity signal based on the reflected light.

[0189] A light intensity meter receives light reflected from the second aperture and converts the light signal into a quantifiable light intensity signal. When light is projected onto the dielectric layer 11, the reflected light intensity is weak; when it is projected onto the target signal layer 121 (metal), the light intensity signal is significantly enhanced due to the high reflectivity of the metal. An angular displacement sensor measures the rotation angle of the light in real time, providing data support for subsequent calculation of the vertical position of the target signal layer 121 based on the angle.

[0190] S324. Based on the changes in light intensity signal and the projection angle of incident light, obtain the vertical position information of the target signal layer 121.

[0191] When the light intensity signal changes from weak to strong and shows a significant peak, it indicates that the light has been projected onto the target signal layer 121. Combining parameters such as the projection angle of the light and the diameter of the target via 101, and using geometric optics principles (such as trigonometric relationships), the position of the projection point of the incident light on the wall of the target via 101 in the direction of the depth of the target via 101 can be calculated, that is, the vertical distance of the target signal layer 121 relative to the surface (or reference surface) of the circuit board 100, thereby determining the vertical position information of the target signal layer 121.

[0192] This first method achieves vertical scanning of the target through-hole 101 wall by changing the projection angle of the incident light. Utilizing the difference in reflectivity between the target signal layer 121 and the dielectric layer 11, the target signal layer 121 is accurately located by changes in light intensity signal, without needing to contact the target through-hole 101 wall, thus avoiding damage to the wall. The vertical position can be directly derived using angle information and geometric calculations. The operation process does not require complex mechanical moving components, resulting in high detection efficiency and strong stability. It can provide reliable data for secondary drilling depth control, effectively reducing processing defects caused by depth deviation, and is suitable for scenarios with high requirements for detection speed and non-contact.

[0193] As a second implementation method, please refer to Figure 6 The vertical position information of the target signal layer 121 in the vertical direction is obtained through optical measurement methods, including:

[0194] S331, Move the reflector vertically within the target through-hole 101 and obtain the displacement of the reflector.

[0195] The reflector can be a reflecting prism, and it has a reflecting surface that reflects light. When the reflector moves vertically within the target through-hole 101, the reflecting surface tilts towards the light source. In this embodiment, the reflecting surface can form a 45° angle with the horizontal plane. The reflector displacement can be obtained through a position sensor or based on the driving force of the driving mechanism that moves the reflector; this is not limited here. The reflector displacement can be obtained in real time or under set conditions; this is not limited here either.

[0196] S332, Project the incident light toward the reflector.

[0197] The incident light generated by the light source is projected vertically toward the target through-hole 101. The incident light may first pass through a cylindrical objective lens to shape the point ray into a line ray before entering the target through-hole 101. In other embodiments, the incident light may also be at a certain angle to the vertical direction, as long as it can be projected onto the reflector.

[0198] S333, The incident light is reflected to the wall of the target through hole 101 by the reflector, and the reflected light reflected back from the wall of the target through hole 101 is emitted towards the light intensity measuring instrument.

[0199] The reflector reflects the incident light to the hole wall of the target through hole 101 through the inclined reflective surface. The hole wall of the target through hole 101 reflects part of the incident light to form a reflected light. The reflected light can be projected onto the reflective surface and, after being reflected by the reflective surface, exits the target through hole 101 and is directed towards the light intensity measuring instrument.

[0200] S334. Receive the reflected light through a light intensity measuring instrument and generate a light intensity signal based on the reflected light.

[0201] Since the target signal layer 121 is made of metal and the dielectric layer 11 is made of insulating material, the light intensity reflected by the target signal layer 121 is much higher than that of the dielectric layer 11. Therefore, when the reflected light is projected onto the target signal layer 121, the light intensity meter will detect a significant light intensity peak; while when projected onto the dielectric layer 11, the light intensity signal remains low and stable. This characteristic of the light intensity signal becomes the direct basis for determining whether the reflected light has irradiated the target signal layer 121.

[0202] S335. Based on the changes in light intensity signal and the displacement of the reflector, obtain the vertical position information of the target signal layer 121.

[0203] Since the light intensity signal measured by the light intensity meter reaches its maximum value when the reflector reflects the reflected light to the target signal layer 121, it can be determined that the projection position of the reflected light at this time is the location of the target signal layer 121. Because the incident light is incident vertically and the reflecting surface is at a 45° angle to the horizontal plane, the vertical position of the reflector when the light intensity signal measured by the light intensity meter reaches its maximum value is the vertical position of the target signal layer 121. The initial position of the reflector can be the first surface 10a of the circuit board 100, which can be set as a reference surface. The reflector moves from the reference surface along the axis of the target through-hole 101 towards the second surface 10b. If the light intensity signal measured by the light intensity meter reaches its maximum value when the reflector moves a distance L within the target through-hole 101, then the distance of the target signal layer 121 from the reference surface is also L.

[0204] The second method utilizes the synergy between the vertical movement of the reflector and light reflection. By taking advantage of the reflectivity difference between the metal target signal layer 121 and the dielectric layer 11, the vertical position of the target signal layer 121 is accurately located through the peak value of the light intensity signal. This method has the advantage of non-contact measurement, avoiding damage to the wall of the target through-hole 101. At the same time, the direct correlation between the reflector displacement and the light intensity signal can quickly convert the detection result into the Z-axis coordinate of the target signal layer 121. The method is simple to operate and has a rapid response. The use of linear light also improves the detection stability in complex hole wall environments, providing high-precision vertical position data for the drilling depth control of the second drilling, effectively reducing the problems of line damage or excessively long residual piles caused by depth deviation.

[0205] In other embodiments, if the incident light is not incident vertically, or the reflecting surface is not tilted at 45°, the projection position information of the reflected light on the hole wall of the target through hole 101 can be obtained based on the incident angle of the incident light, the tilt angle of the reflecting surface, and the displacement of the reflector. This projection position is the specific position of the target signal layer 121 in the vertical direction.

[0206] As a third implementation method, please refer to Figure 7 The method of obtaining the vertical position information of the target signal layer 121 in the vertical direction through optical measurement methods includes:

[0207] S341. The probe assembly is attached to the wall of the target through hole 101 and moved vertically to obtain the displacement of the probe assembly.

[0208] The probe assembly is electrically connected to the power supply to form a circuit, providing a basis for subsequent electrical signal detection. The displacement of the probe assembly can be measured by a displacement measuring device, such as a grating ruler or encoder. The displacement measuring device can record the distance the probe assembly moves in real time. This displacement will serve as a key parameter for calculating the vertical position of the target signal layer 121, and its measurement accuracy directly affects the accuracy of the final position information.

[0209] S342. Obtain the electrical signal of the probe assembly during its movement through the electrical signal measurement component.

[0210] The electrical signal measurement component can monitor changes in electrical signals on the probe component. These electrical signals include at least one of inductance, current, voltage, capacitance, and resistance signals. Since the target signal layer 121 is made of metal (conductive), while other areas of the target via 101 are made of dielectric layer 11 (with extremely poor insulation or conductivity), the difference in conductivity between the two layers causes significant changes in the electrical signals when the probe moves from dielectric layer 11 to the target signal layer 121. For example, the inductance signal may increase, or the resistance signal may drop sharply. These changes will be accurately captured by the electrical signal measurement component.

[0211] S343. Determine the vertical position information of the target signal layer 121 by the change of electrical signal and the displacement of the probe assembly.

[0212] Using the first surface 10a of the circuit board 100 as a reference (i.e., the displacement starting point), the controller synchronously receives the displacement of the probe assembly and the signal data from the electrical signal measurement assembly. When the electrical signal undergoes a sudden change (such as a sudden increase in inductance or a sudden decrease in resistance), it indicates that the probe assembly has contacted the conductive target signal layer 121. At this time, the movement distance recorded by the displacement measuring device is the vertical distance of the target signal layer 121 relative to the reference surface. Through this correspondence, the specific position of the target signal layer 121 in the thickness direction of the circuit board 100 can be directly determined.

[0213] This third method, through direct electrical contact between the probe assembly and the target signal layer 121, utilizes the difference in conductivity between the metal and the dielectric layer 11 to sensitively capture sudden changes in electrical signals to locate the target signal layer 121. It features rapid response and accurate identification. Combined with the real-time recording of the movement distance by the displacement measuring device, it can directly correlate changes in electrical signals with vertical position without the need for complex signal conversion algorithms. It is easy to operate and has strong anti-interference capabilities, providing reliable vertical position data for second-stage drilling depth control. It effectively avoids problems such as line damage or excessively long residual piles caused by depth deviations, and is especially suitable for mass production scenarios with high requirements for detection efficiency and stability.

[0214] As a fourth implementation method, please refer to Figure 8 The vertical position information of the target signal layer 121 in the vertical direction is obtained through optical measurement methods, including:

[0215] S351, the incident light is tilted and projected toward the target via 101, so that the incident light can pass through the dielectric layer 11 and irradiate the target signal layer 121;

[0216] An incident light beam is projected at a certain angle toward the target via 101. Because the dielectric layer 11 is permeable to this incident light beam, the light can pass through the dielectric layer 11 and reach the target signal layer 121. The target signal layer 121 has a first surface parallel to the first surface 10a of the circuit board 100 and an opposing second surface in the vertical direction. The incident light beam can be projected from the first surface 10a side of the circuit board 100 onto the first surface of the target signal layer 121. Because the target signal layer 121 is made of metal and has a high reflectivity, it reflects the incident light beam, forming a reflected light beam. This reflected light beam can exit the circuit board 100, providing a signal source for subsequent interferometric detection.

[0217] S352. The reflected light rays reflected by the target signal layer 121 are received by the interferometer, and the interference information formed by the interference of the reflected light rays and the reference light rays is obtained.

[0218] The interferometer contains a reference ray (such as a ray from the same source that has passed through a fixed optical path). After receiving the reflected ray from the target signal layer 121, the reflected ray and the reference ray interfere with each other within the interferometer, forming alternating bright and dark interference fringes. The interferometer acquires interference information by collecting these interference fringes. The interference information may include the distribution characteristics of the interference fringes, the displacement of the interference fringes, the contrast of the interference fringes, and the position of the zero-order fringe.

[0219] S353. Based on the interference information and the tilt angle information of the incident light, the vertical position information of the target signal layer 121 is obtained.

[0220] The optical path of the reflected light can be derived from the interference information, that is, the total path of the incident light from the light source to the first surface of the target signal layer 121 and back to the interferometer. Combined with the tilt angle information of the incident light and the vertical direction, and using trigonometric function relationships (such as the projection of the optical path in the vertical direction and the cosine relationship of the tilt angle), the vertical distance of the first surface of the target signal layer 121 relative to the reference plane of the circuit board 100 (such as the first board surface 10a) can be calculated, and then the vertical position information of the target signal layer 121 can be determined.

[0221] This fourth method utilizes the principle of light interference to accurately obtain the optical path of the reflected light through interference information. Combined with the incident tilt angle, it calculates the vertical position of the target signal layer 121, achieving extremely high measurement accuracy. This meets the stringent requirements of high-density circuit boards 100 for positioning the target signal layer 121. The incident light penetrates the dielectric layer 11 and acts directly on the target signal layer 121 without contacting or scanning the hole wall, avoiding mechanical interference and hole wall damage. The detection process is also stable and reliable. Furthermore, the interference technology is highly sensitive to changes in optical path, capturing even minute differences in the vertical position of the target signal layer 121. This provides ultra-precise data support for second-drill depth control, effectively reducing processing defects caused by depth errors. It is suitable for precision manufacturing scenarios of high-end high-frequency circuit boards 100.

[0222] Please refer to the previous document. Figures 1 to 3 After forming the back drill hole 103, the method further includes step S5, which includes:

[0223] Obtain the depth value of back drill hole 103, and / or,

[0224] Obtain the length value of the residual pile within the back drill hole 103, and / or,

[0225] Obtain the deviation between the central axis of the back drill hole 103 and the central axis of the target through hole 101.

[0226] In other words, after the back borehole 103 is formed, at least one of the following values ​​is obtained: the depth of the back borehole 103, the length of the remaining pile, and the deviation of the central axis.

[0227] The acquisition of the depth value of the back borehole 103 can verify whether the actual drilling depth meets the design requirements, and avoid damage to the target signal layer 121 due to insufficient depth leading to excessively long residual piles or excessive depth. The measurement of the residual pile length value can directly determine whether it is within the preset range, ensuring that the high-frequency signal transmission is not interfered with by the residual piles and guaranteeing signal integrity. The deviation value of the center axis between the back borehole 103 and the through hole is used to evaluate the position alignment accuracy of the two drilling operations, preventing metal residue on the hole wall or damage to the circuit due to horizontal offset, and avoiding affecting the reliability of electrical connection.

[0228] These parameters are not only important criteria for judging whether the circuit board 100 is qualified, but also provide data support for subsequent process optimization. By analyzing the causes of deviations (such as equipment accuracy, positioning errors, etc.), drilling parameters or equipment calibration can be adjusted in a targeted manner to continuously improve the stability of the back drilling process and ultimately meet the stringent requirements of the CNC field for the high-frequency signal transmission performance and structural reliability of the circuit board 100.

[0229] It should be noted that the order in which the depth, residual pile length, and center axis deviation of the back borehole 103 are obtained is not important. In some embodiments, only one or two values ​​may be obtained, and this is not a limitation here.

[0230] There are several methods to obtain the depth and residual pile length of back borehole 103, and the following examples illustrate them.

[0231] As one embodiment for obtaining the deviation value between the central axis of the back drill hole 103 and the central axis of the target through hole 101, please refer to... Figure 9 After forming the back drill hole 103, the process also includes:

[0232] S511. Align the CCD camera with the target through hole 101 and obtain the center coordinates of the target through hole 101.

[0233] Utilizing the high-precision imaging capabilities of a CCD camera, the lens is aimed at the target through-hole 101 formed by the first drilling, and a clear image of the target through-hole 101 is captured. Through image recognition algorithms (such as edge detection, circle center fitting, etc.), the contour features of the hole wall of the target through-hole 101 are analyzed, and the center coordinates of the target through-hole 101 on the horizontal plane are accurately calculated (usually represented by the left side of the X-axis and the Y-axis coordinates), which serve as the position reference.

[0234] S512. Use a CCD camera to align with the back drill hole 103 and obtain the center coordinates of the back drill hole 103.

[0235] Using the same CCD camera, the lens was adjusted to align with the back drill hole 103 formed by the second drilling, and an image of the back drill hole 103 was captured. Similarly, image analysis technology was used to extract the edge information of the hole wall of the back drill hole 103, and the center coordinates of the back drill hole 103 were fitted and calculated as parameters for the actual processing position.

[0236] S513. Determine the hole position deviation value of the back drill hole 103 based on the center coordinates of the target through hole 101 and the center coordinates of the back drill hole 103.

[0237] The center coordinates of the target through hole 101 are compared with the center coordinates of the back drill hole 103. The deviation between the two in the horizontal direction (including the deviation in the X-axis direction, the deviation in the Y-axis direction, and the total offset distance) is obtained by calculating the coordinate difference (such as the Euclidean distance formula). This deviation is the hole position deviation value of the back drill hole 103.

[0238] This solution uses a CCD camera to accurately acquire the center coordinates of the target through hole 101 and the back-drilled hole 103 and calculate the hole position deviation value. It can intuitively quantify the horizontal alignment accuracy of the two drilling operations, providing objective data for evaluating the quality of back-drilling. The deviation value can be used as a basis for process optimization, helping to trace the cause of position deviation (such as equipment accuracy, positioning error, etc.), and then adjust drilling parameters to reduce subsequent processing deviations. At the same time, the non-contact optical measurement method avoids damage to the circuit board 100, ensuring the safety and accuracy of the detection process, and ultimately improving the stability of the back-drilling process of the circuit board 100 and ensuring the reliability of high-frequency signal transmission.

[0239] One method for obtaining the residual pile length value is described in conjunction with... Figure 10 After forming the back drill hole 103, the process also includes:

[0240] S521, Project the incident light toward the back drill hole 103;

[0241] The incident light beam enters the back-drilled hole 103 vertically and undergoes a first reflection upon contacting the bottom surface 1031 of the back-drilled hole 103, forming the first reflected light. Simultaneously, due to the permeability of the dielectric layer 11, some light can pass through the dielectric layer 11 and continue to illuminate the target signal layer 121, where it undergoes a second reflection, forming the second reflected light. Both the first and second reflected light can exit towards the photosensitive element.

[0242] S522, Obtain the optical path difference between the first reflected light reflected by the bottom surface 1031 of the back drill hole 103 and the second reflected light reflected by the target signal layer 121.

[0243] The photosensitive element can receive the first reflected light and the second reflected light, convert the optical signal into an electrical signal, and obtain the optical path difference between the first reflected light and the second reflected light based on the electrical signal.

[0244] S533. The length of the residual pile in the back drill hole 103 is obtained based on the optical path difference and the refractive index of the dielectric layer 11 in the circuit board 100.

[0245] The refractive index n of the dielectric layer 11 is related to the material of the dielectric layer 11 and can be set according to the material of the dielectric layer 11. In the embodiments of this application, the residual pile length of the back drill hole 103 to be tested can be determined by the formula ΔL / n based on the optical path difference and the refractive index of the dielectric layer 11.

[0246] Determining the residual pile length of the back borehole 103 to be tested based on the optical path difference and the refractive index of the medium layer 11 may include: determining the thickness value corresponding to each position on the surface of the medium layer 11 based on the optical path difference and the refractive index of the medium layer 11; and determining the residual pile length of the back borehole 103 to be tested based on the thickness value corresponding to each position on the surface of the medium layer 11.

[0247] In the embodiments of this application, the incident light from the back drill hole 103 under test is reflected by the surface of the dielectric layer 11 of the back drill hole 103 to form a first reflected light, and the incident light passing through the dielectric layer 11 is reflected by the signal layer 12 of the back drill hole 103 to form a second reflected light. By obtaining the optical path difference between the first and second reflected lights, the residual pile length of the back drill hole 103 under test is determined based on the optical path difference and the refractive index of the dielectric layer 11. On the one hand, the residual pile length can be obtained without damaging the circuit board 100 and without the need for optical fiber insertion. On the other hand, the residual pile length can be determined based on two reflected beams of light reflecting the same incident light from different layers of the back drill hole 103 under test, eliminating the process of switching the light source or adjusting the light band for different layers and improving the detection efficiency.

[0248] Furthermore, this application supports testing the back-drilled hole 103 to be tested after the back-drilling process is completed. Compared with the method of calculating the residual length based on the parameters before the back-drilled hole 103 is formed, the accuracy of the results will not be affected by processes such as exposure and development of outer layer circuits, etching of outer layer circuits, removal of dry film, resin plugging of holes, and on / off of board electrical test signals during the back-drilling process, which can easily cause changes in the thickness of the circuit board 100 and the height shift of the signal layer 12. Therefore, the reliability of the test can be improved.

[0249] S525. Obtain the length values ​​of the residual pile at each position in the circumferential direction of the back drill hole 103, and determine the classification result of the back drill hole 103.

[0250] Because the surface of the medium layer 11 of the back-drilled hole 103 is inclined after back drilling, the depth varies at different positions along the horizontal direction (perpendicular to the depth direction) of the back-drilled hole 103. The aforementioned first reflected light is the light reflected from the surface of the medium layer 11. The optical path difference and corresponding thickness value corresponding to the first reflected light reflected from different positions on the surface of the medium layer 11 may be different. In order to accurately determine the residual pile length of the back-drilled hole 103, it is necessary to analyze the thickness value corresponding to each position on the surface of the medium layer 11. For each position on the surface of the medium layer 11, based on the optical path difference corresponding to the first reflected light reflected at that position and the refractive index of the medium layer 11, the thickness value of the medium layer 11 along the depth direction at that position can be determined by the formula ΔL / n, i.e., the thickness value corresponding to that position. In some embodiments, the lowest thickness value corresponding to all positions can be used as the residual pile length of the back-drilled hole 103.

[0251] Using the center of the back-drilled hole 103 as the center, determine the minimum thickness value at each position in multiple central angle directions; and use the minimum thickness value in each central angle direction as the residual pile length in the corresponding central angle direction.

[0252] In some embodiments of this application, after obtaining the length of the residual pile in each central angle direction, the method for detecting the length of the residual pile may further include: determining the classification result of the back borehole 103 to be tested based on the length of the residual pile in each central angle direction.

[0253] Specifically, if the length of the residual pile in each central angle direction is greater than the first length threshold, the back-drilled hole 103 to be tested is classified as a back-drilled hole 103 with excessively long residual piles, indicating insufficient back-drilling depth. If the length of the residual pile in each central angle direction is less than the second length threshold, the back-drilled hole 103 to be tested is classified as a back-drilled hole 103 with damaged lines, indicating excessive back-drilling depth. If there is a residual pile length difference greater than the difference threshold among the residual pile length differences between different central angle directions, the back-drilled hole 103 to be tested is classified as a back-drilled hole 103 with residual copper in the hole, indicating that copper remains in the hole due to reasons such as center offset during back-drilling. If the length of the residual pile in each central angle direction is less than or equal to the first length threshold and greater than or equal to the second length threshold, the back-drilled hole 103 to be tested is classified as a correct back-drilled hole 103.

[0254] As one implementation method for obtaining the depth value of back-drilled hole 103 and the length value of the remaining pile, please refer to... Figure 11 After forming the back drill hole 103, the process also includes:

[0255] S531, so that the polychromatic light rays pass through the beam splitter and focused in sequence and are directed toward the back drill hole 103.

[0256] In this embodiment of the application, a polychromatic light source can be turned on to generate polychromatic light containing multiple wavelength components according to preset parameters (such as light intensity, spectral range, etc.).

[0257] In this embodiment, the distance between the optical lens module and the circuit board 100 can be precisely adjusted using corresponding driving components. The purpose of this adjustment is to enable the optical lens module to accurately capture the light signal reflected from the back drill hole 103, ensuring that the light propagation path and focusing effect are optimal, thereby improving the accuracy of detection.

[0258] S532, Obtain the first spectral information of the first reflected light reflected by the bottom surface 1031 of the back drill hole 103 and the second spectral information of the second reflected light reflected by the target signal layer 121;

[0259] After being split by the beam splitter in the optical lens module, the polychromatic light forms a first reflected light and a second reflected light. The first reflected light is the reflected light of the dielectric layer 11 in the back drill hole 103, and the second reflected light is the reflected light of the target signal layer 121 in the back drill hole 103.

[0260] In this embodiment, during optical measurement, when light is incident on the back drill hole 103, it is reflected in the dielectric layer 11 and the signal layer 12. The first and second reflected lights correspond to reflected light at different locations (dielectric layer 11 and signal layer 12), respectively. Since the speed of light propagation in the medium is related to the refractive index of the medium, and the length of the remaining pile causes the optical path of the two reflected lights to be different, the optical path difference can be calculated by analyzing their spectral information, and thus the length of the remaining pile can be obtained. The spectrometer can detect the spectral information of the first and second reflected lights, and the spectrum contains parameters such as the wavelength and intensity of the light. Light of different wavelengths has different propagation characteristics in the optical system.

[0261] S533. Obtain the depth value of the back drill hole 103 based on the first spectral information; or, obtain the length value of the residual pile in the back drill hole 103 based on the first spectral information and the second spectral information; or, control the polychromatic light to move radially along the back drill hole 103, so as to obtain the length value of the residual pile at different positions in the circumferential direction of the target through hole 101 based on the first spectral information and the second spectral information at each position.

[0262] Spectral analysis techniques, such as Fourier transform, can be used to extract optical path-related information from the spectral data. Specific wavelengths can correspond to different depths, and after obtaining the first spectral information, the depth of the back drill hole 103 can be calculated based on the wavelength.

[0263] Because the two reflected beams have different optical path lengths, their spectra exhibit phase differences. By analyzing the manifestation of this phase difference at different wavelengths, the optical path difference can be calculated. For example, for light of a specific wavelength, there is a definite relationship between its phase change and the optical path difference. By measuring the phase changes at multiple wavelengths, the optical path difference can be accurately calculated. The known formula for calculating the optical path difference is: Optical path difference = 2 × n × L (where n is the refractive index of the dielectric layer 11, L is the length of the remaining pile, and multiplying by 2 is due to the round-trip propagation of light). After calculating the optical path difference, combined with the known refractive index n of the dielectric layer 11, the length of the remaining pile in the back-drilled hole 103 can be calculated.

[0264] The measuring device for the circuit board 100 provided in this embodiment does not need to directly contact the back drill hole 103, thus avoiding potential damage to the back drill hole 103 due to contact. It is also suitable for some difficult-to-access or precision circuit board 100 testing scenarios.

[0265] In the step of obtaining the residual pile length values ​​at different positions around the target through hole 101, the optical lens module or the circuit board 100 can be moved to achieve relative movement between the two along the surface of the circuit board 100. During the movement, the step size and direction of the movement need to be precisely controlled to ensure that all back-drilled holes 103 positions on the circuit board 100 that need to be detected are covered. At each detection position, following the previous method, polychromatic light is generated using a polychromatic light source. After processing by the optical lens module, the residual pile length at each detection position around the back-drilled hole 103 is determined based on the first and second spectral information after spectral dispersion. According to the distribution of the residual pile length values, it can be seen whether the length values ​​of the residual piles are uniform around the back-drilled hole 103. If the difference between the maximum and minimum length values ​​exceeds the design error, it indicates that the horizontal position of the back-drilled hole 103 has shifted significantly.

[0266] As one implementation method for obtaining the depth value of the back drill hole 103, please refer to... Figure 12 After forming the back drill hole 103, the process also includes:

[0267] S541, Project the incident light toward the back drill hole 103.

[0268] When a user needs to detect the depth of the back drill hole 103 of the printed circuit board 100, the position of the surface scanning camera is first recorded as the initial acquisition position, and incident light rays with a preset light angle are emitted by the light source to the first board surface 10a of the circuit board 100 where the hole of the back drill hole 103 is located.

[0269] S542. Acquire the first interference image formed by the incident light rays using a surface scanning camera.

[0270] An interference image formed by the reflected light from the first plate surface 10a is acquired to obtain a first interference image, which is then sent to a processing device. The processing device receives the first interference information returned by the surface scanning camera.

[0271] S543. Based on the first interference image, determine the first distance value from the surface scanning camera to the plate surface where the hole of the back drill hole 103 is located.

[0272] After the processing device acquires the first interference image of the back drill hole 103 through the area scanning camera, it can determine the first distance from the area scanning camera to the top surface of the back drill hole 103 based on the first interference image.

[0273] The processing device can calculate the corresponding fringe height based on the parallel fringes of the first interference image and determine the fringe height as the first distance.

[0274] S544: Control the area scanning camera to move to the second distance value, and acquire the second interference image formed by the incident light rays through the area scanning camera.

[0275] After determining the first distance value from the surface scanning camera to the top surface of the back drill hole 103 based on the first interference image, the processing device can send a movement command carrying a second distance value to the surface scanning camera. The surface scanning camera receives and responds to the movement command, moving the second distance value from the initial acquisition position toward the circuit board 100. The processing device records the position of the surface scanning camera after movement as the current acquisition position. An incident light ray with a preset exit angle is emitted to the back drill hole 103, and the interference image formed by the reflected light of the high incident light ray is acquired to obtain a second interference image, which is then sent to the processing device. The processing device receives the second interference image returned by the surface scanning camera. Since the current acquisition position is closer to the bottom surface 1031 of the back drill hole 103 than the initial acquisition position, the incident light ray emitted from the current acquisition position is more likely to illuminate the bottom surface 1031 of the back drill hole 103. Based on the current acquisition position, the acquired second interference image is closer to the true interference image formed by the bottom surface 1031 of the back drill hole 103. Therefore, the second interference image is the interference image formed by the bottom surface 1031 of the back drill hole 103.

[0276] S545. Based on the second interference image, determine the third distance value from the surface scanning camera to the bottom surface 1031 of the back drill hole 103.

[0277] In this embodiment of the application, after the processing device controls the surface scanning camera to move a second distance value to obtain a second interference image of the back drill hole 103, a third distance value from the surface scanning camera to the bottom surface 1031 of the back drill hole 103 can be determined based on the second interference image.

[0278] Specifically, after the processing device controls the area scanning camera to move by a second distance value to acquire a second interference image of the back drill hole 103, it can determine the first pixel position corresponding to the current acquisition position of the area scanning camera and the second pixel position corresponding to the bottom surface 1031 in the second interference image, and calculate the third distance value based on the first pixel position and the second pixel position. Calculating the third distance value based on the current acquisition position and the pixel position corresponding to the bottom surface 1031 in the second interference image helps improve the accuracy of the third distance value calculation.

[0279] The processing device can draw a ray in any direction from the center of the concentric annular interference fringes corresponding to the second interference image. The intersection of the ray with the outer circle is the first pixel position, and the intersection of the ray with the inner circle is the second pixel position.

[0280] In some implementations, the first pixel position may include a preset number of first sub-pixel positions, and the second pixel position may include a preset number of second sub-pixel positions.

[0281] The processing device can divide the second interference image into a preset number of sector images, and determine a first sub-pixel position corresponding to the current acquisition position and a second sub-pixel position corresponding to the bottom surface 1031 in each sector image, thereby obtaining a preset number of first sub-pixel positions and a preset number of second sub-pixel positions. Based on a first sub-pixel position and a second sub-pixel position corresponding to each sector image, a corresponding sub-distance value is calculated to obtain a preset number of sub-distance values. The average value of the preset number of sub-distance values ​​is determined as a third distance value. Determining the third distance value based on the average distance value calculated from multiple pixel positions is beneficial to further improve the accuracy of the third distance value.

[0282] S546. Based on the first distance value, the second distance value, and the third distance value, the depth value of the back drill hole 103 is obtained.

[0283] After the processing device determines the third distance value from the surface scanning camera to the bottom surface 1031 of the back drill hole 103 based on the second interference image, it can determine the depth of the back drill hole 103 based on the first distance value, the second distance value, and the third distance value. This realizes the detection of the depth of the back drill hole 103 based on the interference image of the back drill hole 103 acquired by the surface scanning camera. This can avoid the damage to the printed circuit board 100 with the back drill hole 103 caused by metallographic slicing, and it is also beneficial to improve the detection efficiency of the depth detection of the back drill hole 103.

[0284] Specifically, after the processing device determines the third distance value from the surface scanning camera to the bottom surface 1031 of the back drill hole 103 based on the second interference image, it can calculate the sum of the second distance value and the third distance value to obtain the distance sum, and calculate the difference between the distance sum and the first distance value. This difference is the depth value of the back drill hole 103.

[0285] The solution provided in this embodiment acquires a first interference image of the back-drilled hole 103 using a surface scanning camera. Based on the first interference image, a first distance is determined from the surface scanning camera to the top surface of the back-drilled hole 103. The surface scanning camera is then moved a second distance to acquire a second interference image of the back-drilled hole 103. Based on the second interference image, a third distance is determined from the surface scanning camera to the bottom surface 1031 of the back-drilled hole 103. Finally, based on the first, second, and third distances, the depth of the back-drilled hole 103 is determined. This achieves depth detection of the back-drilled hole 103 based on the interference image acquired by the surface scanning camera. The non-contact detection method avoids damage to the printed circuit board 100 with the back-drilled hole 103 caused by metallographic slicing. By utilizing the fringe characteristics of the interference image and the method of multi-position acquisition and multi-pixel average calculation, the accuracy of distance measurement is improved, thereby enhancing the depth detection accuracy of the back-drilled hole 103. Meanwhile, it requires no complex mechanical structure, has an efficient operation process, and can quickly provide feedback on whether the back drilling depth meets the standard, providing timely basis for process adjustment and effectively ensuring the quality of back drilling. It is suitable for efficient quality inspection scenarios in mass production.

[0286] As an alternative implementation method, please refer to Figure 13 Projecting the incident light toward the back drill hole 103 also includes:

[0287] S5411. Determine the hole position angle of back drill hole 103.

[0288] In this embodiment, when a user needs to detect the depth of the back drill hole 103 of the printed circuit board 100, a detection command can be sent to the processing device. The processing device receives and responds to the detection command and can determine the hole position angle of the back drill hole 103.

[0289] The hole position angle of the back drill hole 103 can be used to characterize the ratio of the hole radius of the back drill hole 103 to the depth of the back drill hole 103.

[0290] The processing equipment can obtain the thickness of the printed circuit board 100 with the back drill hole 103, and determine the hole position angle based on the hole radius of the back drill hole 103 and the thickness of the circuit board 100. The hole position angle is calculated based on the thickness of the circuit board 100 and the hole radius of the back drill hole 103, which helps to improve the accuracy of the calculation of the hole position angle of the back drill hole 103.

[0291] The processing device can generate upload prompt information and receive the thickness of the circuit board 100 and the radius of the back drill hole 103 uploaded by the user according to the upload prompt information.

[0292] The upload prompt message can be used to prompt the user to upload the circuit board thickness 100 and hole radius to the processing device. The upload prompt message can be at least one of the following: text prompt message, sound prompt message, or light prompt message, etc., without limitation.

[0293] In one application scenario, the thickness of the printed circuit board 100 can be D, and the radius of the back-drilled hole 103 of the printed circuit board 100 can be r. The hole position angle θ can be calculated according to the following formula based on the thickness D of the circuit board 100 and the hole radius r:

[0294] θ = arctan(r / D).

[0295] S5412. Configure the preset output angle of the face scan camera according to the aperture angle.

[0296] In this embodiment, after the processing device determines the hole position angle of the back drill hole 103, it can configure a preset light emission angle for the face scan camera according to the hole position angle. When the emission angle of the face scan camera is too large, the emitted light cannot illuminate the bottom surface 1031 of the back drill hole 103. Therefore, a smaller emission angle can be configured for the face scan camera according to the hole position angle to improve the success rate of the emitted light illuminating the bottom surface 1031 of the back drill hole 103, which is beneficial to improving the acquisition accuracy of the second interference image.

[0297] The maximum light output angle can be calculated based on the aperture angle, and the preset light output angle can be determined to be less than the maximum light output angle.

[0298] In one application scenario, the preset output angle of the area scanning camera can be θ0. The maximum output angle θ1 of the area scanning camera can be calculated according to the aperture angle θ.

[0299] θ1=2θ=2arctan(r / D).

[0300] The preset exit angle θ0 of the area scan camera can be configured to be less than the maximum exit angle θ1.

[0301] As one implementation method for obtaining the depth value of the back drill hole 103, please refer to... Figure 14 After forming the back drill hole 103, the process also includes:

[0302] S551, Project the incident light toward the back drill hole 103.

[0303] The light emitted from the light source is split into a reference ray and an incident ray by a beam splitter. The incident ray is projected toward the back-drilled hole 103. The incident ray can be reflected at the bottom surface 1031 of the back-drilled hole 103 to form a third reflected ray, and can also be reflected on the surface of the circuit board 100 to form a fourth reflected ray.

[0304] S552. Obtain the third interference information of the third reflected light reflected by the bottom surface 1031 of the back drill hole 103 and the fourth interference information of the fourth reflected light reflected by the target signal layer 121.

[0305] The third and fourth reflected beams can return to the optical assembly and interfere with the reference beam obtained from the beam splitting. The photosensitive component can collect the interference signal formed by the interference, and can obtain the third interference information between the third reflected beam and the reference beam, and the fourth interference information between the fourth reflected beam and the reference beam.

[0306] S553. Based on the third interference information and the fourth interference information, the depth value of the back drill hole 103 is obtained.

[0307] Based on the third interference information, the vertical position information of the bottom surface 1031 of the back drill hole 103 can be obtained. Based on the fourth interference information, the vertical position information of the board surface of the circuit board 100 can be obtained. Based on the vertical position information of the bottom surface 1031 of the back drill hole 103 and the vertical position information of the board surface of the circuit board 100, the depth difference between the bottom surface 1031 of the back drill hole 103 and the board surface of the circuit board 100 can be obtained. This depth difference is the hole depth of the back drill hole 103.

[0308] This method splits the incident light into a reference ray and an incident ray. The third reflected light reflected from the bottom surface 1031 of the back-drilled hole 103 and the fourth reflected light reflected from the surface of the circuit board 100 interfere with the reference ray, respectively. The vertical positions of these two rays are accurately obtained using the third and fourth interference information, allowing for the calculation of the depth of the back-drilled hole 103. This non-contact measurement based on the principle of optical interference avoids damage to the hole structure caused by mechanical contact. Furthermore, the high sensitivity of the interference information to positional changes enables micron-level measurement accuracy, ensuring the accuracy of the back-drilled hole 103 depth detection. This provides reliable data for determining whether the back-drilling is too deep or too shallow, helping to optimize back-drilling process parameters and improve the processing quality of the circuit board 100.

[0309] A plurality of back-drilled holes 103 are formed on the circuit board 100. The processing method of the circuit board 100 also includes obtaining the depth values ​​of the plurality of back-drilled holes 103. As one embodiment of obtaining the depth values ​​of the plurality of back-drilled holes 103, please refer to... Figure 15 After forming the back drill hole 103, the process also includes:

[0310] S561: Obtain the focal depth of the measuring instrument.

[0311] The measuring instrument obtains the actual depth of the back-drilled hole 103 by emitting light into the circuit board 100 and the back-drilled hole 103 and receiving the reflected light. The measuring instrument has a defined depth of focus, also known as focal depth, which refers to the distance that the focal point (focal plane) is allowed to move along the optical axis of the lens while maintaining a relatively clear image. In other words, once the focal point position is determined, a clear image can be obtained within the depth of focus range.

[0312] S562: Divide the depth measurement range into multiple intervals based on the focal depth.

[0313] Specifically, multiple depth measurement intervals are divided based on the focal depth, with the interval distance between each interval being less than or equal to the focal depth. This ensures that when the focal point of the measuring instrument is within a depth measurement interval, accurate measurement of the back-drilled hole 103 within that interval is possible. The theoretical hole depth of each back-drilled hole 103 is then assigned to a specific depth measurement interval.

[0314] By dividing the circuit board 100 into measurement areas, the measuring instrument is prevented from repeatedly measuring the depth of the back drilled holes 103, thus improving the measurement efficiency of the back drilled holes 103. Furthermore, the measuring instrument can systematically measure the depth of the back drilled holes 103 in each measurement area of ​​the circuit board 100, ensuring that each back drilled hole 103 can be detected.

[0315] S563: Adjust the height of the measuring instrument so that the focus of the measuring instrument is located in different depth measurement ranges.

[0316] When the focus of the measuring instrument moves to any depth measurement interval, each measurement area in the circuit board 100 needs to be moved sequentially to the vertical direction of the measuring instrument. This ensures that all back-drilled holes 103 in the entire circuit board 100 whose theoretical hole depth falls within that depth measurement interval can be measured, and that the depth measurement accuracy of each back-drilled hole 103 is guaranteed. Simultaneously, the number of vertical movements of the measuring instrument is equal to the number of depth measurement intervals, which significantly reduces the number of vertical movements and the resulting shaking. This protects the optical components within the measuring instrument and improves its testing stability and long-term service life. Furthermore, when the focus of the measuring instrument's initial position is located in the first depth measurement interval, the number of vertical movements is one less than the number of depth measurement intervals, further reducing the number of vertical movements.

[0317] S564. The depth of multiple back-drilled holes 103 of different depths in the circuit board 100 is measured using a measuring instrument.

[0318] Specifically, the first distance D1 between the hole and the first surface 10a of the circuit board 100 is measured by a measuring instrument, and the second distance D2 between the hole and the bottom surface 1031 of the back drill hole 103 is measured by a measuring instrument. Then, the depth value of the back drill hole 103 is obtained by the difference between the first distance D1 and the second distance D2.

[0319] The depth detection method in this embodiment divides the depth measurement interval according to the focal depth of the measuring instrument and adjusts the height of the measuring instrument in sequence so that the focal point of the measuring instrument is located in different depth measurement intervals in sequence. This allows for accurate measurement of the actual hole depth of the back drilled hole 103 in different depth measurement intervals in sequence. This ensures that not only can the actual hole depth of each back drilled hole 103 in the circuit board 100 be measured by the same measuring instrument, but also that each back drilled hole 103 is measured within the focal depth range of the measuring instrument, thus guaranteeing the depth measurement accuracy of each back drilled hole 103.

[0320] Please combine Figure 16 During the processing of circuit board 100, a full-process data management system can be built, including the following steps:

[0321] P1. Before drilling the circuit board 100 for the first time, the method further includes: correcting the drill tape data of the first drilling by reading the first data in the first tag. The first tag is generated on the circuit board 100. The first data includes the measurement data of the target signal layer 121 before the first drilling and the processing data of the previous process.

[0322] After the lamination process, the circuit board 100 generates a first tag containing first data (which can be formed by Quick Response Code (QR) coding). The first data includes measurement data of the target signal layer 121 before the first drilling (such as interlayer alignment data obtained through X-ray inspection technology) and processing data from previous processes (such as the lamination process). Before the first drilling, the first tag is scanned and the first data is uploaded to the cloud to compensate the Gerber file, generate suitable first drilling tape data, correct the drill bit path and parameters, and ensure that the first drilling can accurately align with the target signal layer 121, reducing positional errors caused by lamination deviations.

[0323] P2. After obtaining the vertical position information of the target signal layer 121, the method further includes: generating a second tag on the circuit board 100. The second tag stores second data, which includes the measurement data of the target through hole 101 and the target signal layer 121 after the first drilling.

[0324] After the first drilling creates a through-hole, the horizontal position information of the target through-hole 101, the vertical position information of the target signal layer 121, and the thickness data of the interlayer dielectric are measured and obtained. These data together constitute the second data. At this time, a new QR code is generated on the circuit board 100 as a second tag, and the second data is stored in it, realizing the unique binding of these key data to the circuit board 100. Simultaneously, the second data is uploaded to the cloud, providing accurate basis for the generation of drill tape in the subsequent second drilling, and laying the foundation for data traceability and process connection.

[0325] P3. Before the second drilling, the drill strip data for the second drilling is corrected by reading the second data in the second tag.

[0326] Before the second drilling, the second data in the second tag is read by scanning the code. The cloud uses this data to compensate the Gerber file again and generate the drill strip data for the second drilling. This drill strip data can be used to adjust the back drilling depth and position to ensure that the back drilling hole 103 accurately controls the length of the residual pile, avoids damage to the target signal layer 121, and achieves high-precision processing of the second drilling.

[0327] P4. After the second drilling, the process also includes: generating a third tag on the circuit board 100, the third tag storing third data, the third data including residual stake data and residual copper data of the hole wall, and correcting the first data based on the third data.

[0328] After the second drilling to form the back drill hole 103, the back drill hole 103 undergoes quality inspection. Data related to the residual stud, such as its length and shape, as well as data related to the residual copper area and distribution on the hole wall, are collected. This data constitutes the third data. Subsequently, a new QR code is generated on the circuit board 100 as a third tag, and the third data is stored within it, achieving a unique binding with the circuit board 100 and being uploaded to the cloud. Based on the comparison and analysis between the third data and the first data, if problems such as excessive residual stud length or excessive residual copper on the hole wall are found, the measurement data of the target signal layer 121 before the first drilling and the processing data of previous processes are traced back to identify the source of the deviation and correct the first data. For example, if the excessive residual stud length is due to errors in interlayer alignment data, the interlayer alignment data in the first data is corrected, providing a more accurate initial data basis for the processing of subsequent circuit boards 100 of the same batch or type.

[0329] Furthermore, this third data can be fed back to the Laser Direct Imaging (LDI) process, allowing for the identification of issues such as residual copper distribution on via walls and deviations in the position of residual spikes. This traces back to the exposure accuracy of the circuit pattern in the LDI process (e.g., linewidth deviation, pattern alignment error). By analyzing the correlation between the third data and LDI process parameters, the laser exposure focal length, path, or pattern compensation value of LDI can be adjusted to optimize the edge alignment accuracy between the signal layer 12 circuits and the via ring. This reduces the abnormality of residual copper or residual spikes on the via walls caused by circuit pattern offset from the source, further improving the accuracy of the circuit board 100 pattern transfer and strengthening the collaborative optimization capability of the entire process.

[0330] This end-to-end data management solution uses QR codes to accurately bind and trace processing and measurement data throughout the entire process. It utilizes cloud-based data compensation to generate drill tape, ensuring that the parameters of the two drilling operations dynamically match the actual state of the circuit board 100, significantly improving processing accuracy. Key data is fed back to the lamination and LDI processes, forming a closed-loop control system that can continuously optimize process parameters and reduce systematic errors. At the same time, the quality measurement data after back drilling (residual studs, residual copper on the hole wall, etc.) is linked with the end-to-end data, providing a basis for quality analysis and process improvement, effectively improving the processing yield and performance stability of the circuit board 100, and meeting the stringent requirements of CNC field for high-frequency signal transmission.

[0331] This application embodiment also provides a circuit board 100, which can be manufactured by the above processing method. The circuit board 100 possesses multi-dimensional performance advantages: First, relying on the precise positioning and compensation mechanism of two drilling operations (such as measuring the vertical position of the target signal layer 121 based on the horizontal position of the target through hole 101 and correcting the back drilling parameters), the alignment accuracy between the back drill hole 103 and the through hole is extremely high, and the residual length is strictly controlled within the preset range, effectively reducing interference and loss in high-frequency signal transmission and ensuring signal integrity; Second, by combining non-destructive measurement, optical inspection, and other methods to accurately control the position of the signal layer 12, the thickness of the interlayer dielectric, and the quality of the back drilling, the interlayer structural stability and electrical connection reliability of the circuit board 100 are significantly improved, reducing the risk of defects such as circuit damage and residual copper on the hole wall; Third, full-process data management (labeled traceability and data reverse correction) ensures that the parameters of each process are dynamically matched with the actual state, resulting in strong process consistency and high product yield; Fourth, it is adapted to the stringent requirements of CNC field for equipment response speed and anti-interference capability, exhibiting excellent operational stability in high-frequency signal rapid transmission scenarios and possessing broad industrial application value.

[0332] The above descriptions are merely several specific embodiments of this application, and only specifically describe the technical principles of this application. These descriptions are only for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this interpretation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, as well as other specific embodiments of this application that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of this application.

Claims

1. A circuit board processing method, characterized in that, include: The circuit board is drilled for the first time to create multiple through holes; Obtain the horizontal position information of the target through hole among the plurality of through holes; Based on the horizontal position information of the target through hole, the vertical position of the target signal layer corresponding to the target through hole is measured, and the vertical position information of the target signal layer is obtained. The target signal layer is exposed on the hole wall of the through hole. Based on the vertical position information of the target signal layer, a second drilling is performed at the target through hole position on the circuit board to form a back drill hole, and the length of the residual pile after the second drilling is within a preset range. The vertical position information of the target signal layer includes the coordinate data of the target signal layer in the vertical direction, and the diameter of the back drill hole is larger than the diameter of the through hole. Before the first drilling of the circuit board, the method further includes: correcting the drill tape data of the first drilling by reading the first data in the first tag. The first tag is generated on the circuit board, and the first data includes the measurement data of the target signal layer before the first drilling and the processing data of the previous process. After obtaining the vertical position information of the target signal layer, the method further includes: generating a second tag on the circuit board, the second tag storing second data, the second data including the measurement data of the through hole and the target signal layer after the first drilling; Before the second drilling is performed, the method further includes: correcting the drill string data of the second drilling by reading the second data in the second tag; After the second drilling is performed, the method further includes: generating a third tag on the circuit board, the third tag storing third data, the third data including residual stake related data and residual copper data of the hole wall, and correcting the first data according to the third data.

2. The circuit board processing method as described in claim 1, characterized in that, Before the first drilling of the circuit board, the process also includes: Obtain the horizontal position information of each signal layer within the circuit board; The location of the first borehole is determined based on the horizontal position information of each signal layer.

3. The circuit board processing method as described in claim 2, characterized in that, The step of obtaining the horizontal position information of each signal layer within the circuit board includes: The signal layer was identified through non-destructive measurement. Measure the horizontal position information of each signal layer.

4. The circuit board processing method as described in claim 1, characterized in that, Before drilling the through-hole at the location of the circuit board for the second time, the method further includes: Obtain the horizontal position information of the target signal layer in the horizontal direction; The target position of the second borehole is compensated and corrected based on the horizontal position information of the target signal layer.

5. The circuit board processing method as described in claim 1, characterized in that, After the first drilling of the circuit board, the process also includes: Obtain the interlayer dielectric thickness information of the circuit board.

6. The circuit board processing method as described in claim 5, characterized in that, Obtaining the interlayer dielectric thickness information of the circuit board includes: A predetermined frequency AC signal is applied to the drill bit in advance; The circuit board forms a loop between the drilling platforms; The vertical position information of each signal layer is determined by the amplitude of the electrical signal in the circuit. The thickness of the interlayer medium is determined based on the vertical position information of each of the signal layers; The depth of the back drill hole is determined based on the thickness of the interlayer medium.

7. The circuit board processing method as described in claim 1, characterized in that, The step of obtaining the vertical position information of the target signal layer in the vertical direction includes: The vertical position information of the target signal layer is obtained by optical measurement methods or non-destructive measurement methods.

8. The circuit board processing method as described in claim 7, characterized in that, The process of obtaining the vertical position information of the target signal layer through optical measurement methods includes: The incident light beam is projected onto the wall of the through hole, and the projection angle of the incident light beam is obtained; The projection angle of the incident light is changed so that the projection position of the incident light on the hole wall of the through hole moves along the vertical direction, and the reflected light reflected by the hole wall of the through hole is emitted towards the light intensity measuring instrument. The light intensity meter receives the reflected light rays reflected from the hole wall through the through hole, and generates a light intensity signal based on the reflected light rays. The vertical position information of the target signal layer is obtained based on the change in the light intensity signal and the projection angle of the incident light.

9. The circuit board processing method as described in claim 7, characterized in that, The process of obtaining the vertical position information of the target signal layer through optical measurement methods includes: The incident light is projected at an angle toward the via, allowing it to pass through the dielectric layer of the circuit board and illuminate the target signal layer. The interferometer receives the reflected light rays after they pass through the target signal layer and obtains the interference information formed by the interference of the reflected light rays with the reference light rays. Based on the interference information and the tilt angle information of the incident light, the vertical position information of the target signal layer is obtained.

10. The circuit board processing method as described in claim 1, characterized in that, After forming the back drill hole, the method further includes: Obtain the depth value of the back drill hole, and / or, Obtain the length value of the residual pile in the back drill hole, and / or, Obtain the deviation between the central axis of the back drill hole and the central axis of the through hole.

11. The circuit board processing method as described in claim 1, characterized in that, After forming the back drill hole, the method further includes: The center coordinates of the target through hole are obtained by aligning a CCD camera with the target through hole. The CCD camera is aligned with the back drill hole to obtain the center coordinates of the back drill hole; The hole position deviation value of the back drill hole is determined based on the center coordinates of the target through hole and the center coordinates of the back drill hole.

12. The circuit board processing method as described in claim 1, characterized in that, After forming the back drill hole, the method further includes: The polychromatic light rays are sequentially split and focused before being directed toward the back drill hole; Acquire the first spectral information of the first reflected light reflected from the bottom surface of the back drill hole and the second spectral information of the second reflected light reflected from the target signal layer; The depth of the back borehole is obtained based on the first spectral information; or, the length of the residual pile in the back borehole is obtained based on the first spectral information and the second spectral information.

13. The circuit board processing method as described in claim 1, characterized in that, After forming the back drill hole, the method further includes: Project the incident light toward the back drill hole; The first interference image formed by the incident light rays is acquired by a surface scanning camera; Based on the first interference image, determine the first distance value from the area scanning camera to the plate surface where the hole of the back drill hole is located; The area scanning camera is controlled to move by a second distance value, and a second interference image formed by the incident light rays is acquired through the area scanning camera; Based on the second interference image, determine the third distance value from the area scanning camera to the bottom surface of the back drill hole; The depth of the back drill hole is obtained based on the first distance value, the second distance value, and the third distance value.

14. The circuit board processing method as described in claim 1, characterized in that, After the first drilling of the circuit board, the process also includes: A metal layer is formed on the wall of the through hole.

15. A circuit board, characterized in that, Manufactured by the circuit board processing method as described in any one of claims 1 to 14.

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