Circuit board back drilling hole nondestructive testing method and system

Abstract

The invention relates to a circuit board back drilling hole nondestructive testing method and system, and belongs to the technical field of multi-layer circuit board manufacturing. Comprising the following steps: acquiring position information and depth data of each back drilling hole in a circuit board to be detected; scanning the position of the back drilling hole according to the position information, and constructing a three-dimensional scanning image; wherein the three-dimensional scanning image comprises an XZ plane image; according to the XZ plane image, taking the bottom of the copper column reserved on the circuit board to be detected as a reference layer, and calculating the height of the copper column; measuring the thickness of the circuit board to be measured, and calculating the drilling depth of the back drilling hole according to the thickness and the height of the copper column; the drilling depth is compared with the depth data, and whether the height of the copper column is within a preset range or not is judged; when the drilling depth exceeds a preset range, judging that the drilling depth is abnormal; and when the drilling depth is within a preset range, determining that the drilling depth is normal. According to the invention, nondestructive and complete detection of the back drilling hole is realized, and the drilling depth and the drilling quality of the back drilling hole on the corresponding detected circuit board can be fed back.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-layer printed circuit board manufacturing, and in particular to a method and system for non-destructive detection of back-drilled holes on a printed circuit board. Background Art

[0002] In the production of multi-layer printed circuit boards, the back-drilling process is widely used to improve signal integrity and reduce interference in high-speed signal transmission. The main purpose of back-drilling is to remove the redundant copper pillars in the vias to avoid problems such as signal reflection, scattering, and delay caused by these copper pillars, thereby improving the quality of signal transmission.

[0003] However, after the production of back-drilled holes is completed, there are many limitations in the inspection methods of the holes. On the one hand, slice inspection is one of the commonly used detection means, but it can only inspect individual holes, and the sliced product will be damaged, resulting in the scrapping of the entire printed circuit board. On the other hand, although appearance inspection equipment and electrical inspection can detect some holes, they cannot accurately feedback the depth and drilling quality of the back-drilled holes. In addition, electrical testing can only cover some holes and cannot completely detect all the back-drilled holes on the printed circuit board, which easily leads to defective products flowing to the client. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the inability to perform non-destructive detection, complete detection, and the inability to feedback the depth and drilling quality of back-drilled holes in the prior art.

[0005] In a first aspect, to solve the above technical problem, the present invention provides a method for non-destructive detection of back-drilled holes on a printed circuit board, including:

[0006] S1. Obtain the position information and depth data of each back-drilled hole on the printed circuit board to be tested;

[0007] S2. Scan the positions of the back-drilled holes according to the position information and construct a two-dimensional scan image; wherein the two-dimensional scan image includes an XZ plane image;

[0008] S3. According to the XZ plane image, and taking the bottom of the copper pillar reserved on the printed circuit board to be tested as a reference layer, calculate the height of the copper pillar;

[0009] S4. Measure the thickness of the printed circuit board to be tested, and calculate the drilling depth of the back-drilled hole according to the thickness and the height of the copper pillar;

[0010] S5. Compare the drilling depth with the depth data to determine whether the height of the copper pillar is within a preset range; when the drilling depth exceeds the preset range, it is determined to be abnormal; when the drilling depth is within the preset range, it is determined to be normal.

[0011] In an embodiment of the present invention, in step S3, the steps of calculating the height of the copper pillar are as follows:

[0012] Obtain the gray values of pixels at different positions of the XZ plane image, and the expression of the gray value is:

[0013]

[0014] where (x, y) is the position coordinate of the pixel, Ig(x, y) is the final gray value of the pixel, I(x, y) is the gray value of the XZ plane image at (x, y), and P is a set threshold;

[0015] Form a copper pillar combination with the pixels corresponding to the final gray value of 1, and measure the first Z-axis coordinate value and the second Z-axis coordinate value of the copper pillar combination in the XZ plane view;

[0016] Calculate the height of the copper pillar according to the first Z-axis coordinate value and the second Z-axis coordinate value; the calculation formula is:

[0017] h 1 = Max(G 1 (x, y)) - Min(G 1 (x, y));

[0018] h 2 = Max(G 2 (x, y)) - Min(G 2 (x, y));

[0019] H = (h 1 , h 2 );

[0020] where h 1 and h 2 are the first height and the second height of the copper pillar respectively, H is the height of the copper pillar, and the height of the copper pillar is the set of the first height and the second height; G 1 (x, y) and G 2 (x, y) are the first Z-axis coordinate value and the second Z-axis coordinate value of the pixel corresponding to the final gray value of 1 respectively; Max(·) represents taking the maximum value, and Min(·) represents taking the minimum value.

[0021] In an embodiment of the present invention, in step S4, the calculation formula for calculating the drilling depth according to the thickness and the height of the copper pillar is:

[0022] K = T - H;

[0023] where K is the drilling depth, T is the thickness of the circuit board to be measured, and H is the height of the copper pillar.

[0024] In one embodiment of the present invention, the method for scanning the position of each back drill hole in S2 is as follows: Use an X-ray emitting device to rotate around the back drill hole for one week and emit X-rays to obtain a plurality of consecutive sampled pictures.

[0025] In one embodiment of the present invention, after comparing the drill hole depth with the depth data in S5, the drill hole depth is converted into a predefined format for output.

[0026] In one embodiment of the present invention, the predefined format includes the X coordinate value, Y coordinate value of the back drill hole, and the drill hole depth.

[0027] In a second aspect, to solve the above technical problems, the present invention provides a non-destructive detection system for back drill holes of a circuit board, including:

[0028] An information acquisition module, configured to acquire the position information and depth data of each back drill hole on the circuit board to be measured;

[0029] An image construction module, configured to scan the position of the back drill hole according to the position information and construct a two-dimensional scanned image; wherein the two-dimensional scanned image includes an XZ plane image;

[0030] A calculation module, configured to calculate the height of the copper pillar according to the XZ plane image and taking the bottom of the copper pillar retained on the circuit board to be measured as a reference layer; measure the thickness of the circuit board to be measured, and calculate the drill hole depth of the back drill hole according to the thickness and the copper pillar height;

[0031] A detection module, configured to compare the drill hole depth with the depth data to determine whether the height of the copper pillar is within a preset range; when the drill hole depth exceeds the preset range, it is determined as abnormal; when the drill hole depth is within the preset range, it is determined as normal.

[0032] In one embodiment of the present invention, the image construction module includes an X-ray emitting device and a receiver; the X-ray emitting device rotates around the back drill hole for one week and emits X-rays; the receiver captures the image after the X-rays pass through the back drill hole and generates a plurality of consecutive sampled pictures.

[0033] In one embodiment of the present invention, it further includes a storage module, configured to convert the drill hole depth into a predefined format and store it.

[0034] In a third aspect, to solve the above technical problems, the present invention provides an electronic device, including the non-destructive detection system for back drill holes of a circuit board as described above.

[0035] The above technical solutions of the present invention have the following beneficial effects compared with the prior art:

[0036] (1) The present invention discloses a method and system for nondestructive testing of back-drilled holes in a circuit board, which utilizes position information to scan the back-drilled holes and construct a two-dimensional scanned image including an XZ plane image. This step not only makes the internal structure of the back-drilled hole clearly visible, but also facilitates in-depth analysis and subsequent processing. On the basis of obtaining the XZ plane image, the present invention uses the bottom of the copper pillar retained on the circuit board as the reference layer to accurately calculate the height of the retained copper pillar. This step involves the precise measurement of the thickness of the circuit board, and the calculation of the drilling depth of the back-drilled hole is combined with the copper pillar height data. This comprehensive calculation method significantly improves the accuracy of the measurement and provides a solid data foundation for quality assessment.

[0037] (2) The present invention compares and analyzes the calculated drilling depth with the preset depth standard to determine whether the copper pillar height falls within the preset tolerance range. When the drilling depth exceeds the preset range, the system marks it as abnormal; conversely, when the drilling depth meets the preset standard, it is judged to be normal. This design can not only comprehensively detect the depth and drilling integrity of all back-drilled holes on the circuit board, but also realize true non-destructive testing.

[0038] (3) The present invention can provide specific back-drilling drilling depth data, which has important reference value for controlling the drilling depth in subsequent processes and helps to achieve precise control and quality improvement in the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0040] Figure 1 This is a flow chart of a circuit board back drilling nondestructive testing method in a preferred embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of an X-ray emitting device rotating around a back-drilled hole in a preferred embodiment of the present invention;

[0042] Figure 3 A receiver in a preferred embodiment of the present invention obtains a plurality of continuous sampling images;

[0043] Figure 4 It is an XY plane view in a preferred embodiment of the present invention;

[0044] Figure 5 It is an XZ plane view in a preferred embodiment of the present invention;

[0045] Figure 6 It is a YZ plane view in a preferred embodiment of the present invention;

[0046] Figure 7 This is a partially enlarged view of the XZ plane view in the preferred embodiment of the present invention;

[0047] Figure 8 This is a partial grayscale image in the XZ plane view of the preferred embodiment of the present invention. Detailed implementation manners

[0048] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the specific embodiments cited are not intended to limit the present invention.

[0049] Embodiment 1

[0050] Referring to Figure 1 As shown, the present invention provides a method for non-destructive detection of back-drilled holes on a circuit board, including but not limited to the following steps:

[0051] S1. Obtain the position information and depth data of each back-drilled hole on the circuit board to be tested;

[0052] S2. Scan the positions of the back-drilled holes according to the position information and construct a two-dimensional scanned image; wherein the two-dimensional scanned image includes an XZ plane image;

[0053] S3. According to the XZ plane image, and taking the bottom of the copper pillar retained on the circuit board to be tested as a reference layer, calculate the height of the copper pillar;

[0054] S4. Measure the thickness of the circuit board to be tested, and calculate the drilling depth of the back-drilled hole according to the thickness and the height of the copper pillar;

[0055] S5. Compare the drilling depth with the depth data to determine whether the height of the copper pillar is within a preset range; when the drilling depth exceeds the preset range, it is determined as abnormal; when the drilling depth is within the preset range, it is determined as normal.

[0056] An embodiment of the present invention provides a method for non-destructive detection of back-drilled holes on a circuit board. By the system, the position information and depth data of each back-drilled hole on the circuit board to be tested are obtained, ensuring the accuracy of measurement. According to these position information, the back-drilled holes are scanned, and a two-dimensional scanned image including an XZ plane image is constructed, making the internal structure of the back-drilled holes visible for subsequent analysis and processing. After obtaining the XZ plane image, taking the bottom of the copper pillar retained on the circuit board to be tested as the reference layer, the height of the copper pillar is calculated. This step calculates the drilling depth of the back-drilled hole by accurately measuring the thickness of the circuit board to be tested and combining with the height of the copper pillar. Such a calculation method not only improves the measurement accuracy but also provides reliable data support for subsequent quality judgment. Finally, the calculated drilling depth is compared with the preset depth data to determine whether the height of the copper pillar is within the preset range. If the drilling depth exceeds the preset range, it is determined as abnormal; if the drilling depth is within the preset range, it is determined as normal. Such a design can detect the depth and drilling integrity of all back-drilled holes on the board and completely achieve non-destructive detection. In addition, the drilling depth of the back-drilled holes of the corresponding circuit board to be detected can be fed back to provide data for the control of the drilling depth in the next process.

[0057] Specifically, for step S1, a data file containing the position and depth information of all back-drilled holes on the circuit board to be tested is obtained to ensure the unified format and complete information of the data file for subsequent processing. The specific information of each back-drilled hole is extracted from the data file. For example, for a certain back-drilled hole n defined in the data file, its definition format is:

[0058] X385986Y253562T3G83K2.0549M31;

[0059] Among them, the back-drilled hole coordinate X n = 385.986 mm, Y n = 253.562 mm, and the drilling depth K n = 2.0549 mm.

[0060] Specifically, for step S2, the specific steps for scanning the position of each back-drilled hole are:

[0061] First, place the test board in the working area of the measuring device, and then the moving mechanism of the device moves to the above given coordinate points X n , Y n . As shown in Figure 2 , at this position, use the X-ray emission device to rotate around this coordinate point and emit X-rays. During this process, the rays penetrate the circuit board and form an image on the receiver, thereby capturing a series of continuous sampling pictures. As shown in Figure 3 , marked as F0 , F 1 , …, F n .

[0062] Secondly, using computer reconstruction software, these sampled images are processed and reconstructed into two-dimensional images in three different directions: the top (XY plane) image, the front (XZ plane) image, and the side (YZ plane) image, as shown in Figure 4 、 Figure 5 and Figure 6 respectively. These images can provide a detailed view of the internal structure of the circuit board, making the detection process more intuitive and accurate. Among them, the top (XY plane) and side (YZ plane) images can be used in image analysis.

[0063] Specifically, for step S3, according to the sampled image, as shown in Figure 5 , the bottom of the copper pillar retained on the circuit board to be tested is used as the reference layer. Here, the meaning of the copper pillar retained on the circuit board to be tested is as follows: in the production of a multi-layer circuit board (the structure of a multi-layer circuit board is an integrated, multi-layer circuit board), for example, in the production of an eight-layer board, usually a drilling is carried out first, and then a copper plating treatment is carried out to form copper pillars penetrating from the first layer to the eighth layer to achieve a direct connection between the first layer and the eighth layer. However, in actual applications, if only the first layer needs to be connected to the sixth layer, and there is no circuit connection between the seventh layer and the eighth layer, then the redundant copper plating part (i.e., the copper pillars from the seventh layer to the eighth layer) will be drilled out. Because in high-frequency and high-speed circuit design, such redundant copper pillars will cause problems such as reflection, scattering, and delay during signal transmission, thus affecting signal integrity. Therefore, it is necessary to drill out the redundant copper pillars from the back side of the circuit board. The holes left after drilling the copper pillars are called back-drilled holes, and the copper pillars that are not removed are called retained copper pillars.

[0064] In the front view (XZ plane), as shown in the partial magnification Figure 7 , measure the first height h 1 and the second height h 2 . The first height and the second height are respectively the distances from the bottom to the top of the opposite sides of the copper pillar. According to the first height h 1 and the second height h 2 , the height H of the copper pillar is obtained as H = (h 1 , h 2 ), where (h 1 , h 2 ) represents the set of the first height h 1 and the second height h 2 . Since the image under X-ray projection is grayscale, there are differences in grayscale values between the copper-containing area of the hole, the surrounding substrate, and the copper-free area inside the hole, as shown in Figure 8As shown. Therefore, the height information of the copper pillar can be extracted by analyzing the gray values at different positions. The specific steps are as follows:

[0065] First, for the set threshold P, for any pixel coordinate (x, y), the gray value of the pixel where it is located is expressed as:

[0066]

[0067] where (x, y) is the position coordinate of the pixel point, Ig(x, y) is the final gray value of the pixel, I(x, y) is the gray value of the XZ plane image at (x, y), and P is the set threshold.

[0068] Secondly, the pixel points corresponding to the final gray value of 1, that is, the areas identified as copper pillars, are combined into a copper pillar combination according to their x and y coordinates. In the XZ plane view, the first Z-axis coordinate value and the second Z-axis coordinate value of the copper pillar combination are measured.

[0069] Finally, according to the measured first Z-axis coordinate value and the second Z-axis coordinate value, the height of the copper pillar is calculated. The calculation formula is:

[0070] h 1 =Max(G 1 (x,y))-Min(G 1 (x,y));

[0071] h 2 =Max(G 2 (x,y))-Min(G 2 (x,y));

[0072] H=(h 1 ,h 2 );

[0073] where h 1 and h 2 are the first height and the second height of the copper pillar respectively, H is the height of the copper pillar, G 1 (x,y) and G 2 (x,y) are the first Z-axis coordinate value and the second Z-axis coordinate value of the pixel points corresponding to the final gray value of 1 respectively; Max(·) represents taking the maximum value, and Min(·) represents taking the minimum value.

[0074] Through the above steps, the height of the copper pillar can be accurately calculated, providing important data support for subsequent quality control and process improvement. This method not only improves the measurement accuracy but also makes the detection process more intuitive and efficient. In addition, it should be noted that in the method of calculating the copper pillar height, in addition to using image grayscale calculation, other image processing methods and algorithms can also be used to achieve the extraction and calculation of the copper pillar height. These methods can use image processing technology to analyze the image of the copper pillar, thereby accurately calculating its height.

[0075] Specifically, for step S4, first measure the thickness of the circuit board to be measured, denoted as T. The methods for thickness measurement can include X-ray fluorescence method, electroplating coating method, laser scanning method, etc. Then, set the upper limit standard Shigh and lower limit standard Slow of the copper pillar to be retained in the corresponding holes as required. Among them, the upper limit standard Shigh generally should not exceed the maximum height allowed by the design to avoid affecting the reliability and heat dissipation performance of the package; the lower limit standard Slow needs to ensure that the copper pillar height is sufficient to meet the requirements of electrical connection and mechanical support. Determine whether it is within the allowable range by comparing whether the copper pillar height H falls between Shigh and Slow, that is, by judging the formula Shigh < H < Slow. If the value of the copper pillar height H exceeds this range, an exception prompt is thrown to facilitate timely corrective measures. Further, according to the copper pillar height H obtained in step S3, calculate the drilling depth K, and the specific calculation formula is:

[0076] K = T - H.

[0077] Specifically, for step S5, compare the obtained drilling depth with the depth data to determine whether the copper pillar height meets the set boundaries. In addition, since H is a set of h 1 , h 2 , so the output of K will also include two parts k 1 and k 2 . Convert the drilling depth into a predefined format for output. For example, for a certain back drill n, its drilling depth is output in the predefined format as:

[0078] X385986Y253562T3G83k1***k2***M31.

[0079] Here, k 1 and k 2 represent the drilling depth values at two different positions respectively, and * represents the delimiter, which can be omitted in actual applications. The predefined format includes the X coordinate value, Y coordinate value of the back drill, and the calculated drilling depth.

[0080] In this embodiment, the drilling depth K value is not only used for analyzing the drilling results during the optimization process, but can also be further compared with the K set in the drilling data file n for subsequent comparison as an important reference value for the subsequent drilling operation. In this way, the accuracy and consistency of the drilling process can be ensured, thereby improving the overall production quality and efficiency.

[0081] Embodiment 2

[0082] Based on the same inventive concept, this embodiment provides a non-destructive detection system for back drilling of printed circuit boards. The principle of solving problems is similar to that of the non-destructive detection method for back drilling of printed circuit boards provided in Embodiment 1, and the repeated parts will not be described again.

[0083] This embodiment provides a non-destructive detection system for back drilling of printed circuit boards, including:

[0084] An information acquisition module for acquiring the position information and depth data of each back drill hole on the printed circuit board to be measured;

[0085] An image construction module for scanning the positions of the back drill holes according to the position information and constructing a two-dimensional scanned image; wherein the two-dimensional scanned image includes an XZ plane image;

[0086] A calculation module for calculating the copper pillar height according to the XZ plane image and taking the bottom of the copper pillar reserved on the printed circuit board to be measured as a reference layer; measuring the thickness of the printed circuit board to be measured, and calculating the drilling depth of the back drill hole according to the thickness and the copper pillar height;

[0087] A detection module for comparing the drilling depth with the depth data to determine whether the copper pillar height is within a preset range; when the drilling depth exceeds the preset range, it is determined to be abnormal; when the drilling depth is within the preset range, it is determined to be normal.

[0088] Specifically, referring to Figure 2 , the image construction module includes an X-ray emitting device and a receiver. The X-ray emitting device rotates around the back drill hole for one week and emits X-rays; the receiver captures the image after the X-rays pass through the back drill hole and generates a plurality of consecutive sampled pictures, which can be referred to Figure 3 .

[0089] Specifically, the detection system provided in this embodiment further includes a storage module, which is designed to convert the acquired drilling depth data into a predefined standardized format. This formatting process not only ensures the consistency and readability of the data but also facilitates subsequent data processing and analysis. The storage module securely stores the converted data in the system for future querying, comparison, and record-keeping purposes. The storage module has efficient data management capabilities, can handle a large amount of drilling depth information, and supports fast retrieval and access. It also includes data backup and recovery functions to prevent data loss and ensure long-term data integrity and reliability.

[0090] Embodiment III

[0091] This embodiment provides an electronic device, including a non-destructive detection system for back drilling of a circuit board provided in Embodiment II.

[0092] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0093] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0094] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0095] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operation steps are executed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions for implementing the process Figure 1 one process or a plurality of processes and / or blocks Figure 1 steps for the functions specified in one block or a plurality of blocks.

[0096] Obviously, the above embodiments are only examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A circuit board back drilling nondestructive testing method, characterized in that: include: S1, obtaining the position information and depth data of each back-drilled hole on the circuit board to be tested; S2, scanning the position of the back-drilled hole according to the position information, and constructing a two-dimensional scan image; wherein the two-dimensional scan image includes an XZ plane image; S3, calculating the height of the copper pillar according to the XZ plane image and taking the bottom of the copper pillar retained on the circuit board to be tested as a reference layer; S4, measuring the thickness of the circuit board to be tested, and calculating the drilling depth of the back drilling hole according to the thickness and the height of the copper pillar; S5. Compare the drilling depth with the depth data to determine whether the copper pillar height is within a preset range; when the drilling depth exceeds the preset range, it is determined to be abnormal; when the drilling depth is within the preset range, it is determined to be normal.

2. A circuit board back drilling nondestructive testing method according to claim 1, characterized in that: The step of calculating the height of the copper pillar in S3 is as follows: The grayscale values ​​of pixels at different positions of the XZ plane image are obtained, and the grayscale values ​​are expressed as follows: Where (x, y) is the position coordinate of the pixel, Ig(x, y) is the final grayscale value of the pixel, I(x, y) is the grayscale value of the XZ plane image at (x, y), and P is the set threshold; The pixel points corresponding to the final grayscale value of 1 are combined into a copper column combination, and the first Z-axis coordinate value and the second Z-axis coordinate value of the copper column combination are measured in the XZ plane view; The copper column height is calculated according to the first Z-axis coordinate value and the second Z-axis coordinate value; wherein the calculation formula is: h1=Max(G1(x,y))-Min(G1(x,y)); h2=Max(G2(x,y))-Min(G2(x,y)); H=(h1,h2); Among them, h1 and h2 are the first height and the second height of the copper column respectively, H is the height of the copper column, and the copper column height is the set of the first height and the second height; G1(x, y) and G2(x, y) are the first Z-axis coordinate value and the second Z-axis coordinate value of the pixel point corresponding to the final grayscale value of 1 respectively; Max(·) means taking the maximum value, and Min(·) means taking the minimum value.

3. A circuit board back drilling nondestructive testing method according to claim 1, characterized in that: In S4, the calculation formula for calculating the drilling depth according to the thickness and the height of the copper pillar is: K = TH; Wherein, K is the drilling depth, T is the thickness of the circuit board to be tested, and H is the height of the copper column.

4. A circuit board back drilling nondestructive testing method according to claim 1, characterized in that: The method of scanning the position of each back-drilled hole in S2 is: using an X-ray emitting device to rotate around the back-drilled hole for one circle and emit X-rays to obtain a plurality of continuous sampling images.

5. A circuit board back drilling nondestructive testing method according to claim 1, characterized in that: In S5, after comparing the drilling depth with the depth data, the drilling depth is converted into a predefined format and outputted.

6. A circuit board back drilling nondestructive testing method according to claim 5, characterized in that: The predetermined format includes an X coordinate value, a Y coordinate value, and a drilling depth of the back-drilled hole.

7. A circuit board back drilling nondestructive testing system, characterized in that: include: An information acquisition module is used to obtain the position information and depth data of each back-drilled hole on the circuit board to be tested; An image construction module, configured to scan the position of the back-drilled hole according to the position information and construct a two-dimensional scanned image; wherein the two-dimensional scanned image includes an XZ plane image; A calculation module, used for calculating the height of the copper pillar according to the XZ plane image and taking the bottom of the copper pillar retained on the circuit board to be tested as a reference layer; Measuring the thickness of the circuit board to be tested, and calculating the drilling depth of the back drilling hole according to the thickness and the height of the copper pillar; The detection module is used to compare the drilling depth with the depth data to determine whether the copper column height is within a preset range; when the drilling depth exceeds the preset range, it is determined to be abnormal; when the drilling depth is within the preset range, it is determined to be normal.

8. A circuit board back drilling nondestructive testing system according to claim 7, characterized in that: The image construction module includes an X-ray emitting device and a receiver; the X-ray emitting device rotates around the back-drilled hole for one circle and emits X-rays; the receiver captures the image after the X-rays pass through the back-drilled hole and generates a plurality of continuous sampling pictures.

9. A circuit board back drilling nondestructive testing system according to claim 7, characterized in that: The method further comprises a storage module for converting the drilling depth into a predefined format and storing the format.

10. An electronic device, characterized in that: A circuit board back drilling nondestructive testing system comprising any one of claims 7 to 9.

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