PCB inner layer circuit determination method, device and equipment based on TDR measurement

Abstract

The application relates to a PCB inner layer line determination method, device and equipment based on TDR measurement, and specifically includes the following steps: establishing a TDR waveform database of standard differential lines; performing TDR measurement on differential lines in a to-be-measured PCB inner layer line, and obtaining a measured reflection waveform; comparing the measured reflection waveform with TDR waveforms in the TDR waveform database, identifying impedance mutation points and extracting measured characteristic parameters; and positioning a defect physical position according to the time delay of the measured reflection waveform, and determining a defect type in combination with the characteristic parameters. The application can realize non-destructive detection of the PCB, reduce detection procedures and detection costs, accurately position a defect position, and the defect position error is less than or equal to 1 mm; meanwhile, a plurality of processing defects such as scratches and uneven etching can be identified, and the application has a guiding effect on process improvement.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, specifically to a method, apparatus, and equipment for determining PCB inner layer circuits based on TDR measurement. Background Technology

[0002] Immersed in the design and manufacturing of high-speed printed circuit boards (PCBs), differential signal lines are widely used due to their excellent anti-interference capabilities. The impedance consistency of differential lines is crucial to signal integrity, and its value is mainly determined by physical parameters such as line width (W), line spacing (S), and dielectric layer thickness (H).

[0003] However, during the PCB inner layer processing, process fluctuations such as mechanical scratching, uneven etching, or lamination misalignment can cause abrupt changes in the W, S, or H impedances in localized areas. Such defects can lead to a sudden drop in local impedance (e.g., a drop to 30Ω), far below the design target value (typically 90Ω or 100Ω). These impedance anomalies significantly degrade high-speed signal quality, causing signal reflection, increased jitter, and even communication failure.

[0004] Currently, the electrical performance testing methods relied upon by the industry (such as impedance testers) can only detect impedance anomalies along the entire line, but they have two major drawbacks: (1) The physical location of the defect cannot be accurately located: the test results can only reflect the overall impedance deviation and cannot identify micron-level local abrupt change areas; (2) Unable to identify the type of defect: It is impossible to distinguish whether the root cause of the impedance abnormality is the change in line width, the offset of line spacing, the unevenness of dielectric thickness, or the coupling effect of multiple factors.

[0005] This contradiction of "detectable but not localizable or traceable" leads to a high degree of blindness in the rework process, often requiring destructive cross-section analysis based on engineers' experience. This is not only inefficient and costly but also prone to yield loss. Therefore, there is an urgent need for a new detection technology that can accurately locate defects and identify failure types to overcome the current quality control bottleneck in high-density PCB manufacturing. Summary of the Invention

[0006] In view of the above problems, embodiments of the present invention provide a method, apparatus and equipment for judging PCB inner layer circuits based on TDR measurement, which is used to solve the problems that the physical location of defects cannot be accurately located and the type of defects cannot be judged in the prior art PCB differential line inspection.

[0007] According to one aspect of the present invention, a method for determining the inner layer circuitry of a PCB based on TDR measurement is provided, the method comprising: Establish a TDR waveform database for standard difference lines; TDR measurement is performed on the differential lines in the inner layer circuit of the PCB under test to obtain the measured reflection waveform; The measured reflection waveform is compared with the TDR waveform in the TDR waveform database to identify impedance abrupt change points and extract measured characteristic parameters. The physical location of the defect is determined by the time delay of the measured reflected waveform, and the defect type is determined by combining the characteristic parameters.

[0008] In some optional embodiments, establishing the standard differential line TDR waveform database specifically includes: Construct a defect-free differential line reference model using electromagnetic field simulation software or measured standard samples; For each defect type and combination, TDR simulation / actual measurement is performed, the reflection coefficient waveform is recorded, and the defect characteristic parameters of the reflection coefficient waveform are extracted to establish a defect differential benchmark model. Based on the defect-free differential line reference model and the defect differential line reference model, a TDR waveform database is established to record defect types, defect characteristic parameters, and physical locations.

[0009] In some optional embodiments, the defect characteristic parameters include at least one or more of impedance abrupt change amplitude, waveform slope, pulse width, and oscillation mode.

[0010] In some optional embodiments, the step of performing TDR measurement on the differential lines in the inner layer circuitry of the PCB under test to obtain the measured reflection waveform specifically includes: Connect the differential probe of the TDR test instrument to the line under test of the PCB under test, and set the excitation parameters consistent with the TDR waveform database. The measured reflection waveform is obtained by scanning along the differential lines of the PCB, the impedance-delay curve of the current PCB is obtained, and the abnormal impedance abrupt change points in the impedance-delay curve are marked.

[0011] In some optional embodiments, the measured reflection waveform is compared with the TDR waveforms in the TDR waveform database to identify impedance abrupt changes and extract measured characteristic parameters, specifically including: The measured reflection waveform is time-domain aligned with the TDR standard waveform of the defect-free differential line reference model; Calculate the differential impedance deviation between the measured reflected waveform and the TDR standard waveform, and mark the time delay position where |ΔZ|>threshold; Extract one or more of the following parameters at the abrupt change point: impedance change amplitude, waveform slope, pulse width, and oscillation mode.

[0012] In some optional embodiments, the physical location of the defect is determined based on the time delay of the measured reflected waveform, and the defect type is determined in conjunction with characteristic parameters, specifically including: Calculate the physical location of the defect based on the time delay and the preset time delay calculation formula; The extracted measured feature parameters are matched with the TDR waveform database to obtain the defect type.

[0013] In some optional embodiments, the delay calculation formula is L=c·t·2Dk, where Dk is the dielectric constant of the PCB, c is the speed of light, and t is the delay.

[0014] In some optional embodiments, the extracted measured feature parameters are pattern matched with a database to obtain the defect type, specifically including: The defect type is identified by one or more of the measured characteristic parameters, including impedance change amplitude, waveform slope, pulse width, and oscillation mode; wherein the defect type includes at least scratch defects, etching unevenness, and lamination misalignment.

[0015] According to another aspect of the present invention, a PCB inner layer circuit determination device based on TDR measurement is provided, the device comprising: The TDR model building module is used to build a TDR waveform database for standard difference lines. The measured reflection waveform acquisition module is used to perform TDR measurements on the differential lines in the inner layer circuit of the PCB under test and acquire the measured reflection waveform. The feature comparison module is used to compare the measured reflection waveform with the TDR waveform in the TDR waveform database, identify impedance change points, and extract measured feature parameters. And a defect determination module, used to locate the physical location of the defect based on the time delay of the measured reflected waveform, and to determine the defect type in combination with characteristic parameters.

[0016] According to another aspect of the present invention, a PCB inner layer circuit determination device based on TDR measurement is provided, comprising: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other through the communication bus; The memory is used to store at least one executable instruction that causes the processor to perform operations such as the PCB inner layer circuit determination method based on TDR measurement described above.

[0017] The present invention provides a method, apparatus, and equipment for judging PCB inner layer circuits based on TDR measurement. The advantages of this invention are as follows: Specifically, the invention includes establishing a TDR waveform database of standard differential lines; performing TDR measurement on the differential lines in the inner layer circuits of the PCB under test to obtain measured reflected waveforms; comparing the measured reflected waveforms with the TDR waveforms in the TDR waveform database to identify impedance abrupt changes and extract measured characteristic parameters; locating the physical location of defects based on the time delay of the measured reflected waveforms, and determining the defect type based on the characteristic parameters. This invention achieves non-destructive testing of PCBs, reducing testing steps and costs, and accurately locating defects with a defect location error ≤1mm. Furthermore, it can identify various processing defects, such as scratches and uneven etching, providing guidance for process improvement.

[0018] The above description is merely an overview of the technical solutions of the embodiments of the present invention. In order to better understand the technical means of the embodiments of the present invention and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0019] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A flowchart illustrating the PCB inner layer circuit determination method based on TDR measurement according to Embodiment 1 of the present invention is shown. Figure 2 A flowchart illustrating step 110 of Embodiment 1 provided by the present invention is shown; Figure 3 A flowchart illustrating step 120 of Embodiment 1 provided by the present invention is shown; Figure 4 A flowchart illustrating step 130 of Embodiment 1 provided by the present invention is shown; Figure 5 This diagram shows a schematic of the PCB inner layer circuit determination device based on TDR measurement according to Embodiment 2 of the present invention. Figure 6 The diagram shows a schematic of the PCB inner layer circuit determination device based on TDR measurement according to Embodiment 3 of the present invention. Detailed Implementation

[0020] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0021] Example 1, Figure 1 This invention illustrates an embodiment of a PCB inner layer trace determination method based on TDR measurement, addressing the problems of inaccurate physical location and defect type identification in existing PCB differential line inspection techniques. The method includes: 110. Establish a TDR waveform database for the standard differential line; In step 110, establishing the TDR waveform database for the standard differential line specifically includes: constructing a defect-free differential line reference model using electromagnetic field simulation software or measured standard samples; performing TDR simulation / measurement for each defect type and combination, recording the reflection coefficient waveform, and extracting the defect characteristic parameters of the reflection coefficient waveform to establish a defect differential reference model; based on the defect-free differential line reference model and the defect differential line reference model, establishing a TDR waveform database that records the defect type, defect characteristic parameters, and physical location. The defect characteristic parameters include at least one or more of the following: impedance change amplitude, waveform slope, pulse width, and oscillation mode.

[0022] 120. Perform TDR measurement on the differential lines in the inner layer circuit of the PCB under test to obtain the measured reflection waveform. In step 120, performing TDR measurement on the differential lines in the inner layer circuit of the PCB under test to obtain the measured reflection waveform specifically includes: connecting the differential probe of the TDR test instrument to the line under test of the PCB under test, and setting the excitation parameters consistent with the TDR waveform database; scanning along the differential lines of the PCB to obtain the measured reflection waveform, obtaining the impedance-time delay curve of the current PCB, and marking the abnormal impedance abrupt change points in the impedance-time delay curve.

[0023] 130. Compare the measured reflected waveform with the TDR waveform in the TDR waveform database to identify impedance abrupt change points and extract measured characteristic parameters. Specifically, in step 130, comparing the measured reflected waveform with the TDR waveform in the TDR waveform database to identify impedance abrupt change points and extract measured characteristic parameters includes: aligning the measured reflected waveform with the TDR standard waveform of the defect-free differential line reference model in the time domain; calculating the differential impedance deviation between the measured reflected waveform and the TDR standard waveform, and marking the time delay position where |ΔZ|>threshold; and extracting one or more parameters from impedance abrupt change amplitude, waveform slope, pulse width, and oscillation mode at the abrupt change point.

[0024] 140. Locate the physical location of the defect based on the time delay of the measured reflected waveform, and determine the defect type by combining the characteristic parameters. In step 140, locating the physical location of the defect based on the time delay of the measured reflected waveform and determining the defect type by combining the characteristic parameters specifically includes: calculating the physical location of the defect based on the time delay and a preset time delay calculation formula; and performing pattern matching between the extracted measured characteristic parameters and the TDR waveform database to obtain the defect type.

[0025] Through steps 110-140, this invention specifically includes establishing a TDR waveform database for standard differential lines; performing TDR measurements on the differential lines in the inner layer circuitry of the PCB under test to obtain measured reflected waveforms; comparing the measured reflected waveforms with the TDR waveforms in the TDR waveform database to identify impedance abrupt change points and extract measured characteristic parameters; locating the physical location of defects based on the time delay of the measured reflected waveforms, and determining the defect type in conjunction with the characteristic parameters. This invention achieves non-destructive testing of PCBs, reducing testing steps and costs, while accurately locating defects with a defect location error ≤1mm; simultaneously, it can identify various processing defects, such as scratches and uneven etching, providing guidance for process improvement.

[0026] In step 110, see Figure 2 The establishment of the standard differential line TDR waveform database in this invention specifically includes: 210. Construct a defect-free differential line reference model using electromagnetic field simulation software or measured standard samples; 220. Perform TDR simulation / actual measurement for each defect type and combination, record the reflection coefficient waveform, extract the defect characteristic parameters of the reflection coefficient waveform, and establish a defect differential benchmark model; the defect characteristic parameters include at least one or more of the following: impedance change amplitude, waveform slope, pulse width, and oscillation mode.

[0027] 230. Based on the defect-free differential line reference model and the defect differential line reference model, establish a TDR waveform database that records defect types, defect characteristic parameters, and physical locations.

[0028] In steps 210-230, the electromagnetic field simulation software can be such as HFSS or CST. A defect-free differential line reference model is constructed using the electromagnetic field simulation software or measured standard samples, where W / S / H conform to the design values. When constructing the TDR waveform database, typical process defects are artificially introduced into the model: scratching defects, resulting in a narrowing of the local linewidth (W); uneven etching, causing random fluctuations in linewidth (W) or line spacing (S); and lamination offset, resulting in a reduction in the local dielectric thickness (H). TDR simulation / measurement is performed for each defect type and combination, recording the reflection coefficient waveform (horizontal axis is time delay τ, vertical axis is impedance Z). Key waveform characteristic parameters are extracted: impedance abrupt change amplitude ΔZ, such as a sudden drop of 30Ω; waveform slope dZ / dτ, reflecting the steepness of the abrupt change; pulse width, reflecting the spatial scale of the defect; and oscillation mode, where lamination defects easily induce multi-peak oscillations. A mapping table of <defect type, characteristic parameters, physical location> is established, which constitutes the TDR waveform database. In a specific example, the TDR waveform database can be shown in Table 1.

[0029]

[0030] Table 1 In step 120, see Figure 3 TDR measurement is performed on the differential lines in the inner layer circuitry of the PCB under test to obtain the measured reflection waveform, specifically including: 310. Connect the differential probe of the TDR test instrument to the line under test of the PCB under test, and set the excitation parameters consistent with the TDR waveform database. 320. Scan along the differential lines of the PCB to obtain the measured reflection waveform, obtain the impedance-delay curve of the current PCB, and mark the abnormal impedance abrupt change points in the impedance-delay curve.

[0031] In steps 310-320, a high-resolution TDR instrument is used, with the bandwidth set to ≥20GHz. The line under test is connected through a differential probe. Excitation parameters, such as pulse rise time and amplitude, are set to be consistent with the TDR waveform database to ensure waveform comparability. The measured reflection waveform is obtained by scanning along the differential line, and the impedance-time delay curve is recorded. The focus is on capturing abnormal impedance abrupt changes in the waveform, such as a sudden drop in Z value of more than 30%.

[0032] In step 130, see Figure 4 The measured reflection waveform is compared with the TDR waveforms in the TDR waveform database to identify impedance abrupt changes and extract measured characteristic parameters, specifically including: 410. Align the measured reflection waveform with the TDR standard waveform of the defect-free differential line reference model in the time domain. 420. Calculate the differential impedance deviation between the measured reflected waveform and the TDR standard waveform, and mark the time delay position where |ΔZ|>threshold; 430. Extract one or more measured characteristic parameters from impedance change amplitude, waveform slope, pulse width, and oscillation mode at the change point.

[0033] In steps 410-430, the measured waveform is time-domain aligned with a defect-free standard waveform of the same structure, specifically with the line starting point as τ=0; the differential impedance deviation between the measured waveform and the standard waveform is calculated, and the time delay position of |ΔZ|>threshold (e.g., 10Ω) is marked; at the abrupt change point, measured characteristic parameters such as ΔZ, dZ / dτ, pulse width, and oscillation frequency are extracted. The measured characteristic parameters can be consistent with the feature dimensions of the TDR waveform database.

[0034] In step 140, the physical location of the defect is determined based on the time delay of the measured reflected waveform, and the defect type is determined in conjunction with characteristic parameters, specifically including: The physical location of the defect is calculated based on the time delay and the preset time delay calculation formula; where the time delay calculation formula is L=c·t·2Dk, where Dk is the dielectric constant of the PCB, c is the speed of light, and t is the time delay.

[0035] The extracted measured feature parameters are pattern matched with a TDR waveform database to obtain the defect type. Specifically, this involves identifying the defect type through one or more of the measured feature parameters, including impedance abrupt change amplitude, waveform slope, pulse width, and oscillation mode. The defect type includes at least scratch defects, etching inhomogeneities, and lamination misalignment.

[0036] In this embodiment, the defect location is calculated based on the time delay τ using the time delay calculation formula. The positioning accuracy depends on the TDR rise time; for example, a 10ps rise time corresponds to ±1mm spatial resolution. The extracted feature parameter vector is pattern matched with the TDR waveform database: if [ΔZ=-32Ω, dZ / dτ=6Ω / ps, pulse width=8ps] → matches "scratching defect"; if [ΔZ=-28Ω, dZ / dτ=1.5Ω / ps, multi-peak oscillation] → matches "lamination offset". Furthermore, the discrimination accuracy can be improved by using a machine learning classifier such as SVM on the mixed features. In a specific example... Example 2: Figure 5 This invention illustrates an embodiment of a PCB inner layer circuit determination device based on TDR measurement. The PCB inner layer circuit determination device based on TDR measurement can detect the differential lines of the PCB by executing the method of Embodiment 1. Specifically, the PCB inner layer circuit determination device 500 based on TDR measurement includes a TDR model establishment module 510, a measured reflection waveform acquisition module 520, a feature comparison module 530, and a defect determination module 540. The TDR model establishment module is used to execute step 110 in Example 1, specifically including: constructing a defect-free differential line reference model using electromagnetic field simulation software or measured standard samples; performing TDR simulation / measurement for each defect type and combination, recording the reflection coefficient waveform, and extracting the defect characteristic parameters of the reflection coefficient waveform to establish a defect differential reference model; and establishing a TDR waveform database recording defect type, defect characteristic parameters, and physical location based on the defect-free differential line reference model and the defect differential line reference model. The defect characteristic parameters include at least one or more of the following: impedance change amplitude, waveform slope, pulse width, and oscillation mode.

[0037] The measured reflection waveform acquisition module is used to execute step 120 in Embodiment 1, specifically including: performing TDR measurement on the differential lines in the inner layer circuit of the PCB under test to acquire the measured reflection waveform, specifically including: connecting the differential probe of the TDR test instrument to the line under test of the PCB under test, and setting excitation parameters consistent with the TDR waveform database; scanning along the differential lines of the PCB to acquire the measured reflection waveform, acquiring the impedance-time delay curve of the current PCB, and marking abnormal impedance abrupt change points in the impedance-time delay curve.

[0038] The feature comparison module is used to perform step 130 in Example 1, specifically including: comparing the measured reflected waveform with the TDR waveform in the TDR waveform database, identifying impedance abrupt change points and extracting measured feature parameters, specifically including: aligning the measured reflected waveform with the TDR standard waveform of the defect-free differential line reference model in the time domain; calculating the differential impedance deviation between the measured reflected waveform and the TDR standard waveform, marking the time delay position of |ΔZ|>threshold; and extracting one or more parameters from impedance abrupt change amplitude, waveform slope, pulse width and oscillation mode at the abrupt change point.

[0039] The defect determination module is used to execute step 140 in embodiment 1, specifically including: locating the physical location of the defect based on the time delay of the measured reflected waveform, and determining the defect type by combining the feature parameters, specifically including: calculating the physical location of the defect based on the time delay and the preset time delay calculation formula; and performing pattern matching between the extracted measured feature parameters and the TDR waveform database to obtain the defect type.

[0040] Example 3: Figure 6 The diagram shows a schematic representation of an embodiment of the PCB inner layer circuit determination device based on TDR measurement according to the present invention. The specific embodiments of the present invention do not limit the specific implementation of the PCB inner layer circuit determination device based on TDR measurement.

[0041] like Figure 6 As shown, the 3D printing device may include: a processor 602, a communications interface 604, a memory 606, and a communications bus 608.

[0042] The processor 602, communication interface 604, and memory 606 communicate with each other via communication bus 608. Communication interface 604 is used to communicate with other network elements, such as clients or other servers. Processor 602 executes program 610, specifically performing the relevant steps in the fiber path compensation method embodiments described above.

[0043] Specifically, program 610 may include program code, which includes computer-executable instructions.

[0044] Processor 602 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present invention. The substructure-based container structure simulation equipment includes one or more processors, which may be processors of the same type, such as one or more CPUs; or processors of different types, such as one or more CPUs and one or more ASICs.

[0045] Memory 606 is used to store program 610. Memory 606 may include high-speed RAM memory, and may also include non-volatile memory, such as at least one disk storage device.

[0046] Specifically, program 610 can be called by processor 602 to cause the PCB inner layer circuit determination device based on TDR measurement to perform steps 110-140 of embodiment 1.

[0047] In addition, it includes an automated judgment system: integrating TDR equipment, data acquisition module and the aforementioned PCB inner layer circuit judgment equipment based on TDR measurement, to realize one-click defect detection and report generation.

[0048] When there are local physical defects in the differential circuitry of the inner layer of a PCB, such as reduced trace spacing, variations in trace width, or uneven dielectric thickness, its characteristic impedance will change due to abrupt changes in geometry. This impedance change will manifest as a "sudden impedance peak" at a specific location in the TDR reflection waveform. For example, reduced trace spacing will cause a sharp drop in impedance, while insufficient etching may cause a stepped fluctuation in impedance.

[0049] By analyzing key waveform features such as abrupt change amplitude, rising slope, and duration, the physical properties of the defect can be preliminarily determined. For example, abrupt changes caused by scratches usually present as steep rising edges, while uneven etching may manifest as multiple small fluctuations.

[0050] By setting preset process thresholds, such as an impedance drop range of 10-30Ω, the system can automatically trigger an alarm and generate a test report to guide the production end to quickly rework.

[0051] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. Similarly, for the sake of brevity and to aid in understanding one or more aspects of the invention, in the description of exemplary embodiments of the invention above, various features of the embodiments are sometimes grouped together in a single embodiment, figure, or description thereof. The claims, which follow the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0052] Those skilled in the art will understand that the modules in the device of the embodiment can be adaptively changed and placed in one or more devices different from that embodiment. Modules, units, or components in the embodiment can be combined into a single module, unit, or component, and further, they can be divided into multiple sub-modules, sub-units, or sub-components, except that at least some of such features and / or processes or units are mutually exclusive.

[0053] It should be noted that the above embodiments are illustrative of the invention and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several systems, several of these systems may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names. The steps in the above embodiments, unless otherwise specified, should not be construed as limiting the order of execution.

Claims

1. A method for determining the inner layer circuitry of a PCB based on TDR measurement, characterized in that, The method includes: Establish a TDR waveform database for standard difference lines; TDR measurement is performed on the differential lines in the inner layer circuit of the PCB under test to obtain the measured reflection waveform; The measured reflection waveform is compared with the TDR waveform in the TDR waveform database to identify impedance abrupt change points and extract measured characteristic parameters. The physical location of the defect is determined by the time delay of the measured reflected waveform, and the defect type is determined by combining the characteristic parameters. Specifically, establishing the standard differential line TDR waveform database includes: Construct a defect-free differential line reference model using electromagnetic field simulation software or measured standard samples; For each defect type and combination, TDR simulation / actual measurement is performed, the reflection coefficient waveform is recorded, and the defect characteristic parameters of the reflection coefficient waveform are extracted to establish a defect differential benchmark model. Based on the defect-free differential line reference model and the defect differential line reference model, a TDR waveform database is established to record defect types, defect characteristic parameters, and physical locations. The measured feature parameters extracted from the measured waveform are pattern matched with the TDR waveform database to obtain the defect type, wherein the defect type includes at least scratch defects, etching inhomogeneity, and lamination misalignment.

2. The PCB inner layer circuit determination method based on TDR measurement according to claim 1, characterized in that, The defect characteristic parameters include at least one or more of the following: impedance abrupt change amplitude, waveform slope, pulse width, and oscillation mode.

3. The PCB inner layer circuit determination method based on TDR measurement according to claim 1, characterized in that, The step of performing TDR measurement on the differential lines in the inner layer circuit of the PCB under test to obtain the measured reflection waveform specifically includes: Connect the differential probe of the TDR test instrument to the line under test of the PCB under test, and set the excitation parameters consistent with the TDR waveform database. The measured reflection waveform is obtained by scanning along the differential lines of the PCB, the impedance-delay curve of the current PCB is obtained, and the abnormal impedance abrupt change points in the impedance-delay curve are marked.

4. The PCB inner layer circuit determination method based on TDR measurement according to claim 1, characterized in that, The measured reflection waveform is compared with the TDR waveforms in the TDR waveform database to identify impedance abrupt changes and extract measured characteristic parameters, specifically including: The measured reflection waveform is time-domain aligned with the TDR standard waveform of the defect-free differential line reference model; Calculate the differential impedance deviation between the measured reflected waveform and the TDR standard waveform, and mark the time delay position where |ΔZ|>threshold; Extract one or more of the following parameters at the abrupt change point: impedance change amplitude, waveform slope, pulse width, and oscillation mode.

5. The PCB inner layer circuit determination method based on TDR measurement according to claim 1, characterized in that, The physical location of the defect is determined based on the time delay of the measured reflected waveform, and the defect type is determined in conjunction with characteristic parameters, specifically including: Calculate the physical location of the defect based on the time delay and the preset time delay calculation formula; The extracted measured feature parameters are matched with the TDR waveform database to obtain the defect type.

6. The PCB inner layer circuit determination method based on TDR measurement according to claim 5, characterized in that, The time delay calculation formula is L=c·t·2Dk, where Dk is the dielectric constant of the PCB, c is the speed of light, and t is the time delay.

7. The PCB inner layer circuit determination method based on TDR measurement according to claim 5, characterized in that, The extracted measured feature parameters are matched with the database to obtain the defect type, specifically including: The defect type can be identified by measuring one or more of the impedance change amplitude, waveform slope, pulse width, and oscillation mode among the measured characteristic parameters.

8. A PCB inner layer circuit determination device based on TDR measurement, characterized in that, The device includes: The TDR model building module is used to build a TDR waveform database for standard difference lines. The measured reflection waveform acquisition module is used to perform TDR measurements on the differential lines in the inner layer circuit of the PCB under test and acquire the measured reflection waveform. The feature comparison module is used to compare the measured reflection waveform with the TDR waveform in the TDR waveform database, identify impedance change points, and extract measured feature parameters. And a defect determination module, used to locate the physical location of the defect based on the time delay of the measured reflected waveform, and to determine the defect type in combination with characteristic parameters.

9. A PCB inner layer circuit identification device based on TDR measurement, characterized in that, include: The processor, memory, communication interface, and communication bus are provided, wherein the processor, memory, and communication interface communicate with each other via the communication bus. The memory is used to store at least one executable instruction that causes the processor to perform the operation of the PCB inner layer circuit determination method based on TDR measurement as described in any one of claims 1-7.

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