Method for detecting length of back-drilling stub, signal processing assembly and system

Abstract

The application is suitable for the field of optical measurement technology, and provides a back-drilling residual stub length detection method, a signal processing assembly and a system. The back-drilling residual stub length detection method comprises the following steps: obtaining an optical path difference between first reflected light and second reflected light, the first reflected light being reflected light of an incident light beam of a to-be-detected back-drilling hole reflected by a medium layer surface of the to-be-detected back-drilling hole, and the second reflected light being reflected light of the light beam of the incident light beam through the medium layer reflected by a signal layer of the to-be-detected back-drilling hole; and determining a residual stub length of the to-be-detected back-drilling hole according to the optical path difference and a refractive index of the medium layer. Embodiments of the application can reflect the same incident light beam by different layers of the to-be-detected back-drilling hole, determine the residual stub length based on the optical path difference between the two reflected light beams, and improve the detection efficiency.

Description

Technical Field

[0001] This application belongs to the field of optical measurement technology, and in particular relates to a method, signal processing component and system for detecting the length of back-drilled pile residue. Background Technology

[0002] With the widespread use of printed circuit boards (PCBs) in communication and computing devices, the precision of back-drilling directly affects signal transmission quality. In multilayer circuit boards, improper handling of redundant conductive portions formed by through-hole metallization can lead to signal reflection and interference. Therefore, controlling the back-drilling depth is crucial for controlling the length of the "stump" (Studying the Unwanted Barrel). The stump length refers to the non-functional, suspended conductor pillars (copper pillars) in the signal hole that are not completely drilled out after the back-drilling process; these are the redundant conductive portions. Over-drilling during back-drilling can damage internal connections, while insufficient back-drilling depth results in excessive stumps that compromise signal integrity.

[0003] In related technologies, the length of residual piles is often measured using cross-section analysis. This method requires vertically cutting the PCB at the location of the back drill hole to be tested, which damages the sample and is extremely inefficient, making it unsuitable for production applications. Fiber optic probing, on the other hand, easily damages the fiber, leading to increased testing costs and slower efficiency. Summary of the Invention

[0004] This application provides a method, signal processing component, and system for detecting the length of a back-drilled pile. The system can reflect the same incident light beam from different layers of the back-drilled hole under test, and determine the length of the pile based on the optical path difference between the two reflected beams, thereby improving detection efficiency.

[0005] The first aspect of this application provides a method for detecting the length of a back-drilled pile, comprising: obtaining the optical path difference between a first reflected light and a second reflected light, wherein the first reflected light is reflected by the surface of the medium layer of the back-drilled hole to be tested, and the second reflected light is reflected by the signal layer of the back-drilled hole to be tested, wherein the incident light passes through the medium layer and is reflected by the medium layer; and determining the length of the pile in the back-drilled hole to be tested based on the optical path difference and the refractive index of the medium layer.

[0006] In some embodiments of the first aspect, the incident beam of the back drill hole to be tested is obtained by a beam splitter splitting the outgoing beam of the light source, wherein the outgoing beam of the light source is split into a reference beam and the incident beam by the beam splitter; the step of obtaining the optical path difference between the first reflected light and the second reflected light includes: during the process of the beam splitter moving towards the back drill hole to be tested along the depth direction of the back drill hole, obtaining a first interference signal between the first reflected light and the reference beam and a second interference signal between the second reflected light and the reference beam; and determining the optical path difference based on the first interference signal and the second interference signal.

[0007] In some embodiments of the first aspect, determining the optical path difference based on the first interference signal and the second interference signal includes: determining a first position where the interference intensity between the first reflected light and the reference beam is strongest based on the first interference signal, and determining a first optical path of the first reflected light based on the first position; determining a first position where the interference intensity between the first reflected light and the reference beam is greater than a first preset threshold based on the first interference signal, and determining a first optical path of the first reflected light based on the first position; determining a second position where the interference intensity between the second reflected light and the reference beam is greater than a second preset threshold based on the second interference signal, and determining a second optical path of the second reflected light based on the second position; and obtaining the optical path difference by the difference between the first optical path and the second optical path.

[0008] In some embodiments of the first aspect, determining a first position where the intensity of interference light between the first reflected light and the reference beam is greater than a first preset threshold based on the first interference signal includes: determining a first intensity variation sequence of interference fringes between the first reflected light and the reference beam based on the first interference signal; converting the first intensity variation sequence into a frequency domain signal using a Fourier transform, and extracting the phase difference between the first reflected light and the reference beam from the frequency domain signal; calculating the optical path difference between the first reflected light and the reference beam based on the phase difference; and taking the position where the optical path difference between the first reflected light and the reference beam is less than or equal to the difference threshold as the first position.

[0009] In some embodiments of the first aspect, determining a second position where the intensity of the interference light between the second reflected light and the reference beam is greater than a second preset threshold based on the second interference signal includes: determining a second intensity variation sequence of interference fringes between the second reflected light and the reference beam based on the second interference signal; converting the second intensity variation sequence into a frequency domain signal using a Fourier transform, and extracting the phase difference between the second reflected light and the reference beam from the frequency domain signal; calculating the optical path difference between the second reflected light and the reference beam based on the phase difference; and taking the position where the optical path difference between the second reflected light and the reference beam is less than or equal to the difference threshold as the second position.

[0010] In some embodiments of the first aspect, determining the residual pile length of the back-drilled hole to be tested based on the optical path difference and the refractive index of the medium layer includes: determining the thickness value corresponding to each position on the surface of the medium layer based on the optical path difference and the refractive index of the medium layer; and determining the residual pile length of the back-drilled hole to be tested based on the thickness value corresponding to each position on the surface of the medium layer.

[0011] In some embodiments of the first aspect, determining the residual pile length of the back-drilled hole to be tested based on the thickness value corresponding to each position on the surface of the medium layer includes: determining the thickness value of the medium layer to the target layer on the stepped hole formed by the back-drilling, and determining the minimum thickness value of the medium layer to the target layer as the residual pile length.

[0012] In some embodiments of the first aspect, the method for detecting the length of the back-drilled residual pile further includes: determining the state classification result of the back-drilling process based on the length of the residual pile in the inner diameter direction of each plate surface of the stepped hole.

[0013] A second aspect of this application provides a device for detecting the length of a back-drilled pile, comprising: an optical path difference acquisition unit, used to acquire the optical path difference between a first reflected light and a second reflected light, wherein the first reflected light is reflected light from the surface of the dielectric layer of the back-drilled hole to be tested, and the second reflected light is reflected light from the signal layer of the back-drilled hole to be tested, wherein the incident light passes through the dielectric layer; and a pile length detection unit, used to determine the length of the pile in the back-drilled hole to be tested based on the optical path difference and the refractive index of the dielectric layer.

[0014] A third aspect of this application provides a signal processing component, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the above-described method for detecting the length of the back-drilled residual pile.

[0015] A fourth aspect of this application provides a system for detecting the length of a back-drilled hole residual pile, comprising: a light source; an optical device group including a beam splitter and a reference mirror; the beam splitter is used to split the emitted light beam from the light source into a reference beam and an incident beam from the back-drilled hole to be tested; the reference mirror is used to reflect the reference beam back to the beam splitter; the incident beam is reflected by the dielectric layer of the back-drilled hole to be tested to form a first reflected light, and the incident beam is reflected by the signal layer of the back-drilled hole to be tested after passing through the dielectric layer to form a second reflected light; a photosensitive component is used to collect an interference-formed optical signal, the interference-formed optical signal including an interference signal formed by the interference of the first reflected light with the reference beam through the beam splitter, and an interference signal formed by the interference of the second reflected light with the reference beam through the beam splitter; and a signal processing component is used to obtain the optical path difference between the first reflected light and the second reflected light using Fourier transform, and to determine the residual pile length of the back-drilled hole to be tested based on the optical path difference and the refractive index of the dielectric layer.

[0016] In some embodiments of the fourth aspect, the emitted light beam from the light source is either red light or infrared light.

[0017] A fifth aspect of this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the above-described method for detecting the length of back-drilled residual piles.

[0018] The sixth aspect of this application provides a computer program product that, when run, causes the aforementioned method for detecting the length of back-drilled residual piles to be executed.

[0019] In the embodiments of this application, the dielectric layer surface of the back drill hole to be tested reflects the incident light beam of the back drill hole to be tested to form a first reflected light, and the signal layer of the back drill hole to be tested reflects the incident light beam that has passed through the dielectric layer 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 to be tested is determined based on the optical path difference and the refractive index of the dielectric layer. On the one hand, the residual pile length can be obtained without damaging the PCB board and without the need for optical fiber insertion. On the other hand, the residual pile length can be determined based on two reflected beams that reflect the same incident light beam from different layers of the back drill hole to be tested, eliminating the process of switching the light source or adjusting the beam band for different layers and improving the detection efficiency. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a back-drilled residual pile length detection system provided in an embodiment of this application;

[0022] Figure 2 This is a schematic diagram of a back-drilled hole provided in an embodiment of this application;

[0023] Figure 3 This is a schematic diagram of the specific structure of the back-drilled residual pile length detection system provided in the embodiments of this application;

[0024] Figure 4 This is a schematic diagram illustrating the implementation process of a method for detecting the length of a back-drilled residual pile provided in an embodiment of this application;

[0025] Figure 5 This is a schematic diagram illustrating the principle of the method for detecting the length of back-drilled residual piles provided in the embodiments of this application;

[0026] Figure 6 This is a schematic diagram of the first point cloud image provided in an embodiment of this application;

[0027] Figure 7 This is a schematic diagram of the second point cloud image provided in an embodiment of this application;

[0028] Figure 8 This is a schematic diagram of the stepped hole provided in an embodiment of this application;

[0029] Figure 9 This is a schematic diagram of the state classification results of back drilling provided in the embodiments of this application;

[0030] Figure 10 This is a schematic diagram of the structure of a back-drilled residual pile length detection device provided in an embodiment of this application;

[0031] Figure 11 This is a schematic diagram of the structure of the signal processing component provided in the embodiments of this application. Detailed Implementation

[0032] 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. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are protected by this application.

[0033] With the widespread application of printed circuit boards (PCBs) in communication and computing equipment, the precision of back-drilling directly affects signal transmission quality. Improper handling of redundant conductive portions formed by through-hole metallization in multilayer PCBs can lead to signal reflection and interference, making back-drilling depth control crucial for controlling residual stake length. Residual stake length refers to the non-functional, suspended conductor pillars in the signal hole that are not completely drilled away after the back-drilling process—essentially redundant conductive portions. Over-drilling during back-drilling can damage internal connections, while insufficient back-drilling depth results in excessive residual stakes that compromise signal integrity. In related technologies, residual stake length is often analyzed using a slicing method. This method requires vertically cutting the PCB at the location of the back-drilled hole to be tested, which damages the sample and is extremely inefficient, making it unsuitable for production applications. Fiber optic probing, on the other hand, easily damages the fiber, leading to increased testing costs and reduced efficiency.

[0034] Based on this, this application provides a method for detecting the length of a back drilled hole remnant, which can obtain the length of the remnant without damaging the PCB board or requiring optical fiber insertion. Furthermore, it can determine the length of the remnant based on two reflected beams that reflect the same incident beam from different layers of the back drilled hole, eliminating the need for switching light sources or adjusting beam bands for different layers and improving detection efficiency.

[0035] To illustrate the technical solution of this application, specific embodiments are described below.

[0036] Please refer to Figure 1 , Figure 1 This application illustrates a system for detecting the length of back-drilled residual piles. The back-drilled residual pile length detection system 1 may include:

[0037] Light source 10;

[0038] Optical device group 20 includes a beam splitter 201 and a reference mirror 202; wherein, the beam splitter 201 is used to split the emitted beam from the light source 10 into a reference beam and an incident beam from the back drill hole to be tested; the reference mirror 202 is used to reflect the reference beam back to the beam splitter 201; the incident beam is reflected by the dielectric layer of the back drill hole to be tested to form a first reflected light, and the incident beam is reflected by the signal layer of the back drill hole to be tested after passing through the dielectric layer to form a second reflected light; and is collected by the photosensitive component;

[0039] The photosensitive component 30 is used to collect the light signal formed by interference. The light signal formed by interference includes the interference signal formed by the interference of the first reflected light with the reference beam through the beam splitter 201, and the interference signal formed by the interference of the second reflected light with the reference beam through the beam splitter 201.

[0040] The signal processing component 40 is used to process the signal output by the photosensitive component 30, such as performing the steps of the back-drilled residual pile length detection method provided in this application, to obtain the optical path difference between the first reflected light and the second reflected light using Fourier transform, and to determine the residual pile length of the back-drilled hole to be tested based on the optical path difference and the refractive index of the medium layer.

[0041] Figure 2 A schematic diagram of a back-drilled hole is shown. The dielectric layer and signal layer are arranged sequentially along the depth direction of the back-drilled hole. The signal layer is where the copper wires transmitting signals are located. The dielectric layer, also called the insulating layer, is an insulating material layer used to separate and support the copper wires of the signal layer. Residual piles are non-functional, suspended copper pillars that were not completely drilled out of the back-drilled hole.

[0042] To achieve the detection method of this application, the emitted light beam of the light source 10 is light that can be partially absorbed by the insulating material of the dielectric layer and reflected by the material of the signal layer (usually copper). In some embodiments of this application, the emitted light beam of the light source 10 is either red light or infrared light. The infrared light can specifically refer to near-infrared light. The specific wavelength of the emitted light beam can be in the range of [750nm, 1750nm], and the wavelength value can be determined according to the material of the dielectric layer.

[0043] Thus, when the incident light beam from the back-drilled hole to be tested is perpendicularly injected into the hole to be tested, the first reflection will occur when it first comes into contact with the surface of the dielectric layer. At the same time, part of the light beam passes through the dielectric layer and continues to shine down to the signal layer, where it will be reflected a second time. The two reflections form the first reflected light and the second reflected light, respectively.

[0044] In some embodiments of this application, please refer to Figure 3 The optical device group 20 may include a beam splitter 201, a reference mirror 202, and an object lens 203. The object lens 203 can be used to shape the beam emitted from the beam splitter 201 toward the back drill hole to be tested, so that the incident beam of the back drill hole to be tested is collimated.

[0045] Furthermore, the object lens 203 can be used to form a light spot of a preset size according to the focal length. The preset size may include, but is not limited to, 1mm × 1mm, 4mm × 4mm, and 10mm × 10mm, and the specific value can be set according to the requirements of detection accuracy and detection efficiency.

[0046] In some embodiments of this application, the optical device group 20 may further include one or more mirrors for changing the optical path.

[0047] In some embodiments of this application, the optical device group 20 may further include one or more lenses for beam collimation.

[0048] In some embodiments of this application, the photosensitive component 30 may include a pixel array and an integrated readout circuit. A reference beam is reflected back to the beam splitter 201 by the reference mirror 202, interfering with the reflected beams from the two back-drilled holes under test (i.e., the first reflected light and the second reflected light). The pixel array can be used to receive the interference signal and perform photoelectric conversion. The integrated readout circuit can be used to process and transmit the converted electrical signal so that the signal processing component 40 can perform signal processing.

[0049] In some embodiments of this application, the photosensitive component 30 and the signal processing component 40 may be integrated, for example, integrated on the same circuit board. In some embodiments of this application, the photosensitive component 30 and the signal processing component 40 may be non-integrated, for example, the signal processing component 40 may be a processor on a smart electronic device (such as a computer or smartphone), and the photosensitive component 30 may be a peripheral device of the smart electronic device.

[0050] In some embodiments of this application, the aforementioned back-drilled residual pile length detection system 1 may further include: a drive assembly for driving the beam splitter 201 in the optical device group 20 to move along the depth direction of the back-drilled hole to be measured. The object lens 203 may move synchronously with the beam splitter 201.

[0051] In some embodiments of this application, the moving speed and travel distance of the aforementioned driving component can be adjusted according to actual needs. The travel distance of the driving component may refer to the focal depth, which may include, but is not limited to, 1.4 mm, 0.7 mm, and 0.35 mm, in order to image the entire back borehole to be tested.

[0052] The following is combined with Figure 4 This application describes a method for detecting the length of back-drilled residual piles. This method can be applied to a back-drilled residual pile length detection system 1 and can be executed by a signal processing component 40. Specifically, the method may include steps S401 to S402.

[0053] Step S401: Obtain the optical path difference between the first reflected light and the second reflected light.

[0054] As mentioned above, the first reflected light is the reflected light from the dielectric layer surface of the back drill hole to be tested, which reflects the incident beam of the back drill hole to be tested. The second reflected light is the reflected light from the signal layer of the back drill hole to be tested, which reflects the incident beam after it passes through the dielectric layer.

[0055] In the embodiments of this application, after the aforementioned photosensitive element receives an optical signal and converts it into an electrical signal, the signal processing component 40 can obtain the optical path difference ΔL between the first reflected light and the second reflected light based on the electrical signal and using Fourier transform.

[0056] Step S402: Determine the length of the residual pile of the back borehole to be tested based on the optical path difference and the refractive index of the medium layer.

[0057] The refractive index n of the dielectric layer is related to the material of the dielectric layer and can be set according to the material of the dielectric layer. In the embodiments of this application, the residual pile length of the back borehole 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.

[0058] Figure 5 This diagram illustrates the principle of the method for detecting the length of a back-drilled pile as provided in this application. The incident beam from the back-drilled hole is reflected by the surface of the dielectric layer to form a first reflected beam, and the incident beam is reflected by the surface of the signal layer after passing through the dielectric layer to form a second reflected beam. The optical path difference between the two beams is the product of the geometric path difference between the two reflected beams and the refractive index of the dielectric layer. The geometric path difference between the two reflected beams reflects the length of the pile.

[0059] In the embodiments of this application, the dielectric layer surface of the back drill hole to be tested reflects the incident light beam of the back drill hole to be tested to form a first reflected light, and the signal layer of the back drill hole to be tested reflects the incident light beam that has passed through the dielectric layer 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 to be tested is determined according to the optical path difference and the refractive index of the dielectric layer. On the one hand, the residual pile length can be obtained without damaging the PCB board and without the need for optical fiber insertion. On the other hand, the residual pile length can be determined based on two reflected beams that reflect the same incident light beam from different layers of the back drill hole to be tested, eliminating the process of switching the light source 10 or adjusting the beam band for different layers, thus improving the detection efficiency.

[0060] Furthermore, this application supports testing the back-drilled hole 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 is formed, the accuracy of the results will not be affected by processes that easily cause changes in PCB board thickness and signal layer position height shifts during the back-drilling process, 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 switching of board electrical test signals. Therefore, it can improve the reliability of the test.

[0061] In some embodiments of this application, the incident beam of the back drilled hole to be tested is obtained by splitting the emitted beam of the light source 10 by the beam splitter 201. The emitted beam of the light source 10 is split into a reference beam and the incident beam of the back drilled hole to be tested by the beam splitter 201. The aforementioned acquisition of the optical path difference between the first reflected light and the second reflected light may include: acquiring a first interference signal between the first reflected light and the reference beam and a second interference signal between the second reflected light and the reference beam as the beam splitter 201 moves along the depth direction of the back drilled hole to be tested. The optical path difference is then determined based on the first interference signal and the second interference signal.

[0062] The first interference signal and the second interference signal can refer to the signals provided by the photosensitive element 30 to the signal processing element 40. Specifically, the driving element can drive the beam splitter 201 to move along the depth direction of the back drilled hole to be tested. During the movement of the beam splitter 201 towards the back drilled hole, the first reflected light reflected from the surface of the dielectric layer of the back drilled hole reaches the beam splitter 201, interferes with the reference beam, and forms interference light with ring interference fringes. The photosensitive element receives the interference light and performs photoelectric conversion, outputting the first interference signal to the signal processing element 40.

[0063] Similarly, the second reflected light from the back-drilled signal layer reaches the beam splitter 201, where it interferes with the reference beam, forming interference light with ring-shaped interference fringes. The photosensitive element receives the interference light and performs photoelectric conversion, outputting the second interference signal to the signal processing component 40.

[0064] At this time, the first interference signal and the second interference signal carry light intensity information, which can be used to determine the optical path difference between the first reflected light and the second reflected light.

[0065] Specifically, determining the optical path difference based on the first interference signal and the second interference signal may include: determining a first position where the intensity of the interference light between the first reflected light and the reference beam is greater than a first preset threshold based on the first interference signal, and determining a first optical path of the first reflected light based on the first position. Determining a second position where the intensity of the interference light between the second reflected light and the reference beam is greater than a second preset threshold based on the second interference signal, and determining a second optical path of the second reflected light based on the second position. The optical path difference is obtained by the difference between the first optical path and the second optical path.

[0066] The first and second preset thresholds can be set according to actual conditions, and they can be the same or different. The first and second preset thresholds can be used to extract locations with strong interference light intensity. The first location with the first preset threshold and the second location with interference light intensity greater than the second preset threshold can refer to the location on the surface of the dielectric layer and the location of the signal layer, respectively.

[0067] Specifically, determining a first position where the intensity of the interference light between the first reflected light and the reference beam is greater than a first preset threshold based on the first interference signal may include: determining a first intensity change sequence of interference fringes between the first reflected light and the reference beam based on the first interference signal; converting the first intensity change sequence into a frequency domain signal using Fourier transform, and extracting the phase difference between the first reflected light and the reference beam from the frequency domain signal; calculating the optical path difference between the first reflected light and the reference beam based on the phase difference; and taking the position where the optical path difference between the first reflected light and the reference beam is less than or equal to the difference threshold as the first position.

[0068] Specifically, the optical path difference between the first reflected light and the reference beam being less than or equal to the difference threshold can refer to the position where the optical path difference is 0. Since the optical path difference between the first reflected light and the reference beam is 0, this is one of the cases where the intensity of the interference fringe light is strongest. Therefore, the position where the optical path difference between the first reflected light and the reference beam is less than or equal to the difference threshold can be taken as the first position. When the optical path difference is 0, the optical path of the reference beam is equivalent to the optical path of the first reflected light, and the optical path of the reference beam can be obtained based on the structural situation. Therefore, based on the first position, the first optical path L1 of the first reflected light can be obtained, that is, the optical path of the first reflected light from the surface of the dielectric layer of the back-drilled hole to the beam splitter 201.

[0069] Similarly, determining a second position where the intensity of the interference light between the second reflected light and the reference beam is greater than a second preset threshold based on the second interference signal may include: determining a second intensity change sequence of the interference fringes between the second reflected light and the reference beam based on the second interference signal; converting the second intensity change sequence into a frequency domain signal using Fourier transform, and extracting the phase difference between the second reflected light and the reference beam from the frequency domain signal; calculating the optical path difference between the second reflected light and the reference beam based on the phase difference; and taking the position where the optical path difference between the second reflected light and the reference beam is less than or equal to the difference threshold as the second position.

[0070] Specifically, the optical path difference between the second reflected light and the reference beam being less than or equal to the difference threshold can be defined as the position where the optical path difference is 0. Since the optical path difference between the second reflected light and the reference beam is 0, this is one of the cases where the intensity of the interference fringe light is strongest at the second position. Therefore, the position where the optical path difference between the second reflected light and the reference beam is less than or equal to the difference threshold can be taken as the second position. When the optical path difference is 0, the optical path of the reference beam is equivalent to the optical path of the second reflected light. Therefore, based on the second position, the second optical path L2 of the second reflected light can be obtained, that is, the optical path of the second reflected light from the signal layer to the beam splitter 201.

[0071] At this point, by calculating the difference between the first optical path L1 and the second optical path L2, the optical path difference ΔL between the first and second reflected light can be obtained. Subsequently, based on the optical path difference ΔL between the first and second reflected light and the refractive index n of the medium layer, the length of the residual pile in the back borehole to be tested can be determined.

[0072] In other embodiments of this application, obtaining the optical path difference between the first reflected light and the second reflected light may further include: determining a first point cloud image of the dielectric layer surface based on a first interference signal, wherein the pixel value of each pixel in the first point cloud image represents the optical path of the first reflected light reflected from the corresponding position on the dielectric layer surface; determining a second point cloud image of the signal layer based on a second interference signal, wherein the pixel value of each pixel in the second point cloud image represents the optical path of the second reflected light reflected from each position on the signal layer; and determining the optical path difference between the first reflected light and the second reflected light based on the lowest pixel value in the first point cloud image and the lowest pixel value in the second point cloud image, and using this optical path difference as the length of the residual stake.

[0073] Example type, Figure 6 and Figure 7 The first point cloud image and the second point cloud image are shown respectively. Assuming that the lowest pixel value in the first point cloud image is -152 and the lowest pixel value in the second point cloud image is -496, the optical path difference ΔL = -152 - (-496) can be calculated. At this time, the optical path difference ΔL / n is the length of the residual stake.

[0074] In some embodiments of this application, determining the residual pile length of the back borehole to be tested based on the optical path difference and the refractive index of the medium layer may include: determining the thickness value corresponding to each position on the surface of the medium layer based on the optical path difference and the refractive index of the medium layer; and determining the residual pile length of the back borehole to be tested based on the thickness value corresponding to each position on the surface of the medium layer.

[0075] In some embodiments of this application, determining the residual pile length of the back-drilled hole to be tested based on the thickness value corresponding to each position on the surface of the medium layer may include: determining the thickness value of the medium layer to the target layer on the stepped hole based on the back-drilling process to form a stepped hole, and determining the minimum thickness value of the medium layer to the target layer as the residual pile length.

[0076] The target layer can refer to the back-drilling stop layer, which is the signal layer where the drill bit is positioned at its predetermined stop point during back-drilling. For details, please refer to [link / reference needed]. Figure 8Because the back-drilled hole becomes a stepped hole after back-drilling, the dielectric layer surface of the stepped hole is beveled. The depth varies at different positions along the inner diameter direction (perpendicular to the depth direction) of the back-drilled hole on the PCB surface. The inner diameter direction refers to the ray direction radiating outwards from the center of the back-drilled hole. The optical path difference and corresponding thickness values ​​of the first reflected light at different positions on the dielectric layer surface may differ. To accurately determine the residual pile length of the back-drilled hole, the thickness value of the dielectric layer to the target layer on the stepped hole can be determined, and the minimum thickness value between the dielectric layer and the target layer can be determined as the residual pile length to obtain an accurate residual pile length.

[0077] More specifically, for each location on the surface of each medium layer, the thickness of the medium layer along the depth direction at that location can be determined using the formula ΔL / n, based on the optical path difference corresponding to the first reflected light at that location and the refractive index of the medium layer. Then, the lowest thickness value corresponding to all locations is taken as the residual pile length of the back-drilled borehole to be measured.

[0078] Considering that the back drill hole is a hole-like structure, in some embodiments of this application, the residual pile length of the back drill hole to be tested is determined based on the thickness value corresponding to each position on the surface of the medium layer. This may include: determining the minimum thickness value in the inner diameter direction of each plate based on the thickness value corresponding to each position in the inner diameter direction of multiple plate surfaces; and taking the minimum thickness value in the inner diameter direction of each plate surface as the residual pile length in the corresponding inner diameter direction of the plate surface.

[0079] for example, Figure 8 The two inner diameter directions A and B shown can be used to determine the minimum thickness values ​​in these directions, thus obtaining the residual pile lengths in each direction. This allows for the calculation of residual pile lengths at different orientations of the back-drilled borehole. The multiple inner diameter directions can be set according to actual needs; for example, each 10° section in a horizontal plane perpendicular to the depth direction can be considered a single inner diameter direction.

[0080] In some embodiments of this application, the method for detecting the length of the back-drilled residual pile may further include: determining the state classification result of the back-drilling process based on the length of the residual pile in the inner diameter direction of each plate surface of the stepped hole. The state classification result of the back-drilling process characterizes the accuracy of the back-drilling depth and position when performing back-drilling processing on the back-drilled hole to be tested. The state classification result can be specifically determined based on the length of the residual pile in the inner diameter direction of each plate surface.

[0081] For details, please refer to Figure 9If the length of the residual piles in each inner diameter direction of the board surface is greater than the first length threshold, the back-drilling status classification result is "residual pile too long," indicating insufficient back-drilling depth. If the length of the residual piles in each inner diameter direction of the board surface is less than the second length threshold, for example, if the residual pile length is 0, the back-drilling status classification result is "damaged circuit," 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 inner diameter directions of the board surface, the back-drilling status classification result is "hole copper residue," indicating that some hole copper remains due to center offset or other reasons during back-drilling. If the length of the residual piles in each inner diameter direction of the board surface is less than or equal to the first length threshold and greater than or equal to the second length threshold, the back-drilling status classification result is determined to be "correct back-drilling."

[0082] The specific values ​​of the first length threshold, the second length threshold, and the difference threshold can all be set according to the actual situation.

[0083] It should be noted that, for the sake of simplicity, the aforementioned method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, because according to this application, some steps can be performed in other orders.

[0084] like Figure 10 The diagram shown is a structural schematic of a back-drilled pile length detection device 1000 provided in an embodiment of this application. The back-drilled pile length detection device 1000 is disposed on the signal processing component 40.

[0085] Specifically, the detection device 1000 for the length of the back-drilled residual pile may include:

[0086] The optical path difference acquisition unit 1001 is used to acquire the optical path difference between the first reflected light and the second reflected light. The first reflected light is the reflected light reflected by the surface of the dielectric layer of the back drill hole to be tested to the incident light beam of the back drill hole to be tested. The second reflected light is the reflected light reflected by the signal layer of the back drill hole to be tested to the light beam of the incident light beam passing through the dielectric layer.

[0087] The residual pile length detection unit 1002 is used to determine the residual pile length of the back drilled hole to be tested based on the optical path difference and the refractive index of the medium layer.

[0088] In some embodiments of this application, the incident beam of the back drill hole to be tested is obtained by splitting the emitted beam of the light source 10 by the beam splitter 201. The emitted beam of the light source 10 is split into the reference beam and the incident beam by the beam splitter 201. The optical path difference acquisition unit 1001 is specifically used to: acquire the first interference signal between the first reflected light and the reference beam and the second interference signal between the second reflected light and the reference beam during the process of the beam splitter 201 moving towards the back drill hole to be tested along the depth direction of the back drill hole; and determine the optical path difference based on the first interference signal and the second interference signal.

[0089] In some embodiments of this application, the optical path difference acquisition unit 1001 is specifically used to: determine a first position where the interference light intensity between the first reflected light and the reference beam is greater than a first preset threshold based on the first interference signal, and determine a first optical path of the first reflected light based on the first position; determine a second position where the interference light intensity between the second reflected light and the reference beam is greater than a second preset threshold based on the second interference signal, and determine a second optical path of the second reflected light based on the second position; and obtain the optical path difference through the difference between the first optical path and the second optical path.

[0090] In some embodiments of this application, the optical path difference acquisition unit 1001 is specifically used to: determine a first intensity change sequence of interference fringes between the first reflected light and the reference beam based on the first interference signal; convert the first intensity change sequence into a frequency domain signal using Fourier transform, and extract the phase difference between the first reflected light and the reference beam from the frequency domain signal; calculate the optical path difference between the first reflected light and the reference beam based on the phase difference; and take the position where the optical path difference between the first reflected light and the reference beam is less than or equal to a difference threshold as the first position.

[0091] In some embodiments of this application, the optical path difference acquisition unit 1001 is specifically used to: determine a second intensity change sequence of interference fringes between the second reflected light and the reference beam based on the second interference signal; convert the second intensity change sequence into a frequency domain signal using Fourier transform, and extract the phase difference between the second reflected light and the reference beam from the frequency domain signal; calculate the optical path difference between the second reflected light and the reference beam based on the phase difference; and take the position where the optical path difference between the second reflected light and the reference beam is less than or equal to a difference threshold as the second position.

[0092] In some embodiments of this application, the residual pile length detection unit 1002 is specifically used to: determine the thickness value corresponding to each position on the surface of the medium layer based on the optical path difference and the refractive index of the medium layer; and determine the residual pile length of the back drilled hole to be tested based on the thickness value corresponding to each position on the surface of the medium layer.

[0093] In some embodiments of this application, the residual pile length detection unit 1002 is specifically used to: determine the thickness value of the medium layer to the target layer on the stepped hole based on back drilling to form a stepped hole, and determine the minimum thickness value of the medium layer to the target layer as the residual pile length.

[0094] In some embodiments of this application, the back-drilling residual pile length detection device 1000 further includes a classification unit, specifically used to: determine the state classification result of the back-drilling process based on the residual pile length in the inner diameter direction of each plate surface of the stepped hole.

[0095] It should be noted that, for the sake of convenience and brevity, the specific working process of the aforementioned back-drilled residual pile length detection device 1000 can be found in the following reference: Figures 4 to 9 The corresponding process of the method will not be described in detail here.

[0096] like Figure 11 The diagram shown is a schematic of a signal processing component 40 provided in an embodiment of this application. Specifically, the signal processing component 40 may include: a processor 400, a memory 401, and a computer program 402 stored in the memory 401 and executable on the processor 400, such as a program for detecting the length of back-drilled pile residue. When the processor 400 executes the computer program 402, it implements the steps in the various back-drilled pile residue length detection method embodiments described above, for example... Figure 4 Steps S401 to S402 are shown. Alternatively, when the processor 400 executes the computer program 402, it implements the functions of each module / unit in the above-described device embodiments, for example... Figure 10 The functions of the optical path difference acquisition unit 1001 and the residual pile length detection unit 1002 are shown.

[0097] The computer program can be divided into one or more modules / units, which are stored in the memory 401 and executed by the processor 400 to complete this application. The one or more modules / units can be a series of computer program instruction segments capable of performing specific functions, which describe the execution process of the computer program in the signal processing component 40.

[0098] For example, the computer program can be divided into: an optical path difference acquisition unit and a residual pile length detection unit. The specific functions of each unit are as follows: the optical path difference acquisition unit is used to acquire the optical path difference between a first reflected light and a second reflected light, wherein the first reflected light is the reflected light from the surface of the dielectric layer of the back-drilled hole to which the incident light beam is reflected, and the second reflected light is the reflected light from the signal layer of the back-drilled hole to which the incident light beam passes through the dielectric layer; the residual pile length detection unit is used to determine the residual pile length of the back-drilled hole to which the incident light beam is located based on the optical path difference and the refractive index of the dielectric layer.

[0099] The signal processing component 40 may include, but is not limited to, a processor 400 and a memory 401. Those skilled in the art will understand that... Figure 11 This is merely an example of the signal processing component 40 and does not constitute a limitation on the signal processing component 40. It may include more or fewer components than shown, or combine certain components, or different components. For example, the signal processing component 40 may also include input / output devices, network access devices, buses, etc.

[0100] The processor 400 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), off-the-shelf programmable gate arrays or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0101] The memory 401 can be an internal storage unit of the signal processing component 40, such as a hard disk or memory of the signal processing component 40. The memory 401 can also be an external storage device of the signal processing component 40, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the signal processing component 40. Furthermore, the memory 401 can include both internal storage units and external storage devices of the signal processing component 40. The memory 401 is used to store the computer program and other programs and data required by the signal processing component 40. The memory 401 can also be used to temporarily store data that has been output or will be output.

[0102] It should be noted that, for the sake of convenience and brevity, the structure of the signal processing component 40 described above can also be referred to the specific description of the structure in the method embodiment, and will not be repeated here.

[0103] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0104] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0105] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for various specific applications, but such implementations should not be considered beyond the scope of this application.

[0106] In the embodiments provided in this application, it should be understood that the disclosed apparatus / signal processing component 40 and method can be implemented in other ways. For example, the apparatus / signal processing component 40 embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0107] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0108] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0109] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0110] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for detecting the length of a back-drilled residual pile, characterized in that, include: As the beam splitter moves towards the back drill hole along its depth direction, it acquires a first interference signal between the first reflected light and the reference beam, and a second interference signal between the second reflected light and the reference beam. The first reflected light is the reflected light from the dielectric layer surface of the back drill hole, which reflects the incident beam from the back drill hole. The second reflected light is the reflected light from the signal layer of the back drill hole, which reflects the incident beam through the dielectric layer. The incident beam is obtained by the beam splitter splitting the emitted beam from the light source into the reference beam and the incident beam. Based on the first interference signal and the second interference signal, the optical path difference between the first reflected light and the second reflected light is determined; The length of the residual pile in the back borehole to be tested is determined based on the optical path difference and the refractive index of the medium layer.

2. The method for detecting the length of back-drilled residual piles as described in claim 1, characterized in that, Determining the optical path difference based on the first interference signal and the second interference signal includes: Based on the first interference signal, a first position is determined where the intensity of the interference light between the first reflected light and the reference beam is greater than a first preset threshold, and a first optical path of the first reflected light is determined based on the first position. Based on the second interference signal, a second position is determined where the intensity of the interference light between the second reflected light and the reference beam is greater than a second preset threshold, and a second optical path of the second reflected light is determined based on the second position. The optical path difference is obtained by the difference between the first optical path and the second optical path.

3. The method for detecting the length of back-drilled residual piles as described in claim 2, characterized in that, Determining the first position where the intensity of the interference light between the first reflected light and the reference beam is greater than a first preset threshold based on the first interference signal includes: Based on the first interference signal, a first intensity variation sequence of interference fringes between the first reflected light and the reference beam is determined; Using Fourier transform, the first intensity change sequence is converted into a frequency domain signal, and the phase difference between the first reflected light and the reference beam is extracted from the frequency domain signal; Based on the phase difference, the optical path difference between the first reflected light and the reference beam is calculated; The position where the optical path difference between the first reflected light and the reference beam is less than or equal to the difference threshold is taken as the first position.

4. The method for detecting the length of back-drilled residual piles as described in any one of claims 1-3, characterized in that, The step of determining the residual pile length of the back-drilled hole to be tested based on the optical path difference and the refractive index of the medium layer includes: The thickness value corresponding to each position on the surface of the dielectric layer is determined based on the optical path difference and the refractive index of the dielectric layer. Based on the thickness values ​​at various locations on the surface of the medium layer, the residual pile length of the back-drilled hole to be tested is determined.

5. The method for detecting the length of back-drilled residual piles as described in claim 4, characterized in that, Determining the residual pile length of the back-drilled hole to be tested based on the thickness values ​​corresponding to various positions on the surface of the medium layer includes: Based on the back-drilling process to form a stepped hole, the thickness value of the medium layer to the target layer on the stepped hole is determined, and the minimum value of the thickness of the medium layer to the target layer is determined as the residual pile length.

6. The method for detecting the length of back-drilled residual piles as described in claim 5, characterized in that, The method for detecting the length of the back-drilled residual pile also includes: The state classification result of the back drilling is determined based on the residual pile length in the inner diameter direction of each plate surface of the stepped hole.

7. A signal processing component, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method for detecting the length of the back-drilled residual pile as described in any one of claims 1 to 6.

8. A system for detecting the length of back-drilled residual piles, characterized in that, include: light source; An optical device assembly includes a beam splitter and a reference mirror; the beam splitter is used to split the outgoing beam of the light source into a reference beam and an incoming beam of the back drill hole to be tested. The reference mirror is used to reflect the reference beam to the beam splitter; the incident beam is reflected by the dielectric layer of the back drill hole to be tested to form a first reflected beam, and the incident beam is reflected by the signal layer of the back drill hole to be tested after passing through the dielectric layer to form a second reflected beam. A photosensitive component is used to collect optical signals formed by interference, wherein the optical signals formed by interference include an interference optical signal formed by the interference of the first reflected light with the reference beam through the beam splitter, and an interference optical signal formed by the interference of the second reflected light with the reference beam through the beam splitter; A signal processing component is configured to acquire a first interference signal between the first reflected light and the reference beam and a second interference signal between the second reflected light and the reference beam during the process of the beam splitter moving towards the back borehole to be tested along the depth direction of the back borehole to be tested; determine the optical path difference between the first reflected light and the second reflected light based on the first interference signal and the second interference signal; and determine the residual pile length of the back borehole to be tested according to the optical path difference and the refractive index of the dielectric layer.

9. The detection system for the length of back-drilled residual piles as described in claim 8, characterized in that, The emitted light beam from the light source is either red light or infrared light.

Images