PCB back drilling depth compensation method based on measured board thickness

Abstract

The application discloses a PCB back drilling depth compensation method based on actually measured plate thickness and belongs to the technical field of PCB back drilling processes, and comprises the following steps: step 1, reading drilling tape data, step 2, visual positioning, step 3, coordinate conversion, step 4, laser thickness measurement, step 5, data matching, step 6, depth compensation, and step 7, outputting drilling tape data. Through the hole position level depth compensation based on the actually measured plate thickness, the real plate thickness of each hole position of the PCB can be accurately matched, not only the differentiated drilling control is realized by relying on a unified formula, but also links such as plate thickness data filtering and coordinate dynamic correction are included, so that the compensation result more accurately reflects actual processing requirements of each hole position and provides more scientific parameter basis for back drilling processing.

Description

Technical Field

[0001] This invention relates to the field of PCB back-drilling technology, and more specifically, to a PCB back-drilling depth compensation method based on measured board thickness. Background Technology

[0002] As PCBs evolve towards higher density, higher layer count, and higher speed signals, the impact of through-hole residue on signal integrity and impedance continuity is becoming increasingly prominent. To reduce the impact of through-hole residue on high-speed signals, the industry generally adopts back-drilling technology. This involves drilling along the axis of the through-hole from the back of the PCB after plating to remove excess copper residue. Back-drilling requires high precision in controlling the drilling depth. Drilling too deep may damage effective circuit layers or inner layer structures, while drilling too shallow will leave excessively long residue, affecting product performance. Therefore, a new back-drilling method is needed.

[0003] In the prior art, document CN117320289A discloses a "depth compensation method for back drill holes on PCB boards", which includes the following steps: S1: Obtain a PCB integrated board, and divide the PCB integrated board into a PCB unit area and a surface area; S2: Form a first origin position and a second origin position on the surface area, and form back drill holes at the first origin position and the second origin position, and obtain a first depth parameter and a second depth parameter accordingly; S3: Obtain a standard depth parameter, and obtain a compensation value by combining the first depth parameter and the second depth parameter, and obtain an actual depth parameter based on the compensation value; S4: Form a target back drill hole in the PCB unit area using the actual depth parameter as the processing depth.

[0004] The document CN112770508B discloses "A method for improving the drilling depth accuracy of PCB back drilling," which includes: each PCB board has a QR code, and each QR code has a unique code; identifying the QR code on the PCB board, measuring the PCB board thickness, and feeding the measured PCB board thickness data back to the storage unit; classifying the PCB board type according to the theoretical back drilling depth based on the obtained PCB board thickness data; calculating the compensation value for different types of PCB boards and generating back drilling production parameters for different types of products; and automatically retrieving the back drilling production parameters stored in the database corresponding to the QR code for back drilling production.

[0005] In summary, while existing technologies can improve back-drilling accuracy to some extent by classifying and compensating for the overall board thickness through laser scanning or by obtaining depth compensation values ​​using test holes in non-product areas, most existing technologies only perform classification compensation after detecting the overall board thickness or rely on test holes in non-processing areas to calculate compensation parameters. They cannot individually detect the actual board thickness for each back-drill hole and achieve differentiated depth adjustment at the hole position level. Furthermore, they do not uniformly calibrate multiple coordinate systems, which can easily lead to positioning deviations. They also lack data noise reduction and depth boundary verification mechanisms. When dealing with PCBs with uneven thickness distribution, back-drilling overcutting or excessive residual stubs are still likely to occur, making it difficult to guarantee processing consistency. Summary of the Invention

[0006] This invention provides a PCB back-drilling depth compensation method based on measured board thickness, which can solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a PCB back-drilling depth compensation method based on measured board thickness, comprising:

[0008] S1. Read the drill tape file corresponding to the PCB back drill and extract the hole coordinates, machining tool information and preset process parameters of all back drill holes in the file.

[0009] S2. Use two-dimensional vision equipment to acquire PCB board images, identify board reference marks, and establish the mapping relationship between the drill tape coordinate system and the equipment mechanical coordinate system;

[0010] S3. Perform joint calibration of the drill string coordinate system, mechanical coordinate system, two-dimensional vision coordinate system, and three-dimensional laser coordinate system, and uniformly transform all back-drilled hole position coordinates to the three-dimensional laser measurement coordinate system;

[0011] S4. The scanning operation is completed along the preset trajectory by the line laser measurement components arranged in opposite directions to collect the original plate thickness data of each back drill hole.

[0012] S5. Perform noise reduction and outlier removal on the original plate thickness data, and then associate and match the processed effective plate thickness data with the corresponding back drill hole positions.

[0013] S6. Following the method of processing each hole one by one, and combining the measured plate thickness with the preset process parameters, calculate the compensated drilling depth for each back drill hole.

[0014] S7. Generate a new version of the drill tape file based on the drill depth parameters after compensation for each hole position, and send the new version of the drill tape file to the back drilling machine to control the drilling machine to complete the PCB back drilling process.

[0015] Furthermore, in step S1, the back drill tape file in the industry's common format is read and the preset process parameters extracted include the theoretical PCB thickness, theoretical drilling depth, and drilling auxiliary process parameters. At the same time, a one-to-one correspondence between the hole position coordinates, tool information, and various process parameters is established based on the back drill hole number.

[0016] Furthermore, in step S2, an area array industrial camera is used in conjunction with a ring fill light to complete the image acquisition of the PCB board surface. The identified board reference marks include optical positioning points, process positioning holes, and board edge reference contours. The association and binding between the drill tape coordinate system and the equipment mechanical coordinate system are realized through image pixel conversion.

[0017] Furthermore, in step S3, a standard calibration plate is used to complete the joint static calibration of the coordinate system, and the coordinate transformation matrix is ​​obtained. Based on the transformation matrix, the coordinates of all back-drilled holes are transformed step by step, and finally all hole coordinates are uniformly incorporated into the three-dimensional laser measurement coordinate system.

[0018] Furthermore, in step S4, the line laser measurement components are arranged on the upper and lower sides of the PCB support platform and are in a vertically opposite state. The line laser adopts a straight structure and the laser line is parallel to the PCB board surface. The scanning trajectory is planned according to the distribution area of ​​the back drill holes, and the original board thickness related data of multiple points are collected simultaneously in a single scan.

[0019] Furthermore, in step S5, the original board thickness data is denoised using a sliding mean filter. Invalid and abnormal data are filtered out by combining the PCB board thickness tolerance range. Then, the processed valid board thickness data is bound one by one with the corresponding back drill hole number and coordinates.

[0020] Furthermore, in step S6, each back-drilled hole is used as an independent calculation unit. The measured plate thickness data of each hole position and the preset process parameters are retrieved sequentially to carry out the calculation. After the calculation is completed, the process interval boundary is checked for the compensation drilling depth.

[0021] Furthermore, in step S7, the new drill tape file retains the original file format, only replacing the drilling depth parameters of each back drill hole, while preserving the original process information such as hole position coordinates, tool type, and machining speed. The new drill tape file is then transmitted to the back drill machine via Ethernet.

[0022] The beneficial effects of the PCB back-drilling depth compensation method based on measured board thickness of this invention are as follows: By compensating the hole position depth based on the measured board thickness, the actual board thickness of each hole position on the PCB can be accurately matched. It not only relies on a unified formula to achieve differentiated drilling control, but also incorporates board thickness data filtering, dynamic coordinate correction and other links, so that the compensation results more accurately reflect the actual processing requirements of each hole position, and provide a more scientific parameter basis for back-drilling processing. In addition, through multi-coordinate system joint calibration and closed-loop correction, the thickness measurement data and drilling point position are accurately bound, breaking the accuracy bottleneck of traditional processes, enabling real-time synchronization of data in each link, improving the consistency and stability of back-drilling processing, and improving the accuracy of depth control and long-term operational reliability. At the same time, through safety threshold protection, the risk of over-cutting and under-cutting is effectively avoided, significantly improving production efficiency and significantly improving PCB processing yield and mass production capacity. Attached Figure Description

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific implementation methods.

[0024] Figure 1 This is a schematic diagram of the method flow for a PCB back-drilling depth compensation method based on measured board thickness according to the present invention. Detailed Implementation

[0025] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Example:

[0027] like Figure 1 As shown, a technical solution is provided: a PCB back-drilling depth compensation method based on measured board thickness, comprising:

[0028] Step 1: Read the drill strip data

[0029] Read the drill tape file corresponding to the PCB back drill, and extract the hole coordinates, machining tool information and preset process parameters of all back drill holes in the file;

[0030] Specifically, it is compatible with reading back drill tape files in the industry's common format. The extracted preset process parameters include the theoretical PCB thickness, theoretical drilling depth, and drilling auxiliary process parameters. At the same time, it establishes a one-to-one correspondence between hole position coordinates, tool information, and various process parameters based on the back drill hole number.

[0031] The system has a built-in multi-format universal parsing engine that can recognize and parse mainstream industry formats such as Gerber drill tape and standard CNC drilling file formats. The parsing process splits the data stream segment by segment according to the inherent data structure of the file, accurately distinguishes the basic instruction segment, hole position coordinate segment, tool configuration segment and process parameter segment in the file, and specifically performs targeted data capture for the points marked as back drill attributes in the file, extracting the basic information such as the plane coordinate value and the matching machining tool number corresponding to each back drill hole.

[0032] The association between the back drill hole number and various parameters is constructed by using the unique hole position number provided in the drill tape file as the main search index, traversing all the parsed back drill hole data entries one by one, dividing a dedicated data storage unit for each independent hole position, and then, according to the field classification rules, sequentially entering the hole position coordinates, tool information, theoretical PCB board thickness, theoretical drilling depth, and drilling auxiliary process parameters into the corresponding storage unit, strictly realizing a one-to-one binding between a single hole position number and the complete set of supporting process data;

[0033] In addition, by performing a pre-compliance verification operation on the captured raw drill data, it is first determined whether the hole position coordinate values ​​fall within the effective processing area of ​​the PCB board, and then the core process parameters such as theoretical board thickness and theoretical drilling depth are checked to see if they meet the product's preset processing specifications. Random data caused by file corruption or abnormal transmission and empty point data without actual processing significance are eliminated. At the same time, the same back drill hole coordinates that are repeatedly marked in the file are merged and marked to intercept invalid and abnormal information from the data source into the subsequent process.

[0034] Finally, the complete back-drilled hole dataset, after parsing, association binding, and pre-verification, is linearly cached and saved strictly according to the original hole position arrangement order in the drill tape file. A status command indicating that the data reading is complete is generated synchronously, and a ready signal is sent to the subsequent two-dimensional visual positioning and multi-coordinate system joint transformation processes. This ensures that the entire set of original data is complete and orderly, and also ensures that the execution timing of each process is matched and the data flow is smooth, providing a reliable data foundation for subsequent hole-by-hole plate thickness measurement and hole-by-hole compensation depth calculation.

[0035] Step 2, Visual Positioning

[0036] Two-dimensional vision equipment is used to acquire images of the PCB board surface, identify the board reference marks, and establish the mapping relationship between the drill tape coordinate system and the equipment mechanical coordinate system;

[0037] Specifically, an area array industrial camera is used in conjunction with a ring fill light to acquire images of the PCB board surface. The identified board reference marks include optical positioning points, process positioning holes, and board edge reference contours. The association and binding between the drill tape coordinate system and the equipment mechanical coordinate system are achieved through image pixel conversion.

[0038] First, place the PCB stably and fix it on the equipment platform. Then, adjust the focusing position, exposure time, image gain and other imaging parameters of the area array industrial camera in sequence. Simultaneously adjust the brightness, illumination angle and light output range of the ring fill light to make the light evenly cover the entire PCB board area and avoid adverse effects such as copper foil reflection, substrate color difference and ambient stray light. After the imaging state is stable, control the camera to complete a one-time full-area image acquisition to obtain a clear, distortion-free and detailed original PCB board image.

[0039] Then, the acquired raw images are preprocessed by grayscale conversion, edge extraction, and random noise filtering. Then, the contour feature matching algorithm is used to search the entire image domain. The target marks are identified one by one according to the priority of optical positioning points, process positioning holes, and board edge reference contours. At the same time, the pixel coordinates, contour size, and morphological features of each reference mark are extracted. The algorithm automatically distinguishes and filters out interference false features such as board surface scratches, ink stains, and small debris to ensure that all identified reference marks are real and valid.

[0040] Next, the camera calibration parameters and pixel equivalent data stored in the device are called. Multiple identified valid reference markers are used as reference groups. The image pixel coordinates corresponding to each reference are converted into physical coordinates in the device's mechanical coordinate system one by one. The coordinate offset value, rotation compensation amount and proportional conversion coefficient are calculated through multiple sets of coordinate samples to build an accurate conversion model between the image pixel position and the device's physical position.

[0041] Finally, based on the completed conversion model, all back-drill hole and drill strip coordinates obtained in step 1 are batch converted to the equipment's mechanical coordinate system. This completes the global association and binding between the drill strip coordinate system and the mechanical coordinate system. The correspondence between the two coordinate systems and the converted hole position coordinate data are temporarily cached, and a ready signal is sent to the next coordinate conversion process to ensure smooth process connection and complete data flow.

[0042] Step 3, Coordinate Transformation

[0043] The drill string coordinate system, mechanical coordinate system, two-dimensional vision coordinate system, and three-dimensional laser coordinate system are jointly calibrated, and all back-drilled hole position coordinates are uniformly transformed to the three-dimensional laser measurement coordinate system.

[0044] Specifically, a standard calibration plate is used to complete the joint static calibration of the coordinate system, and the coordinate transformation matrix is ​​obtained. Based on the transformation matrix, the coordinates of all back-drilled holes are transformed step by step, and finally all hole coordinates are uniformly incorporated into the three-dimensional laser measurement coordinate system.

[0045] First, the high-precision standard calibration board is stably and accurately fixed in the standard processing area of ​​the PCB carrier platform, ensuring that the surface of the calibration board is absolutely parallel to the subsequent PCB placement plane. The equipment is then started to sequentially control the two-dimensional vision device and the three-dimensional laser measurement components that shoot from both above and below to perform full-domain image acquisition and laser scanning on the calibration board. The original coordinate values ​​of the array of standard feature points on the calibration board in the mechanical coordinate system, the two-dimensional vision coordinate system, and the three-dimensional laser coordinate system are completely picked up. At the same time, the theoretical coordinate data of the corresponding feature points in the drill belt coordinate system are retrieved. The data are then summarized to form a complete set of coordinate samples of feature points from the same source in four coordinate systems, providing a real and sufficient data source for the calculation of the coordinate transformation matrix.

[0046] Then, based on the collected sets of coordinate samples of multiple source feature points, matrix fitting operations are performed to solve the multi-level coordinate transformation matrices from the drill belt coordinate system to the machine coordinate system, from the machine coordinate system to the two-dimensional vision coordinate system, and from the two-dimensional vision coordinate system to the three-dimensional laser measurement coordinate system step by step. After the operation is completed, the accuracy of each set of transformation matrices is checked one by one. The coordinate deviation values ​​after the feature point conversion are compared. Only the valid transformation matrices with coordinate deviations within the allowable range of the process are retained and stored locally. Matrix results with abnormal calculations or conversion errors are discarded to ensure the accuracy of coordinate conversion from the source.

[0047] Finally, the stored effective coordinate transformation matrices at all levels are invoked, and the coordinates of all back drill holes that have been transformed from the drill line coordinate system to the mechanical coordinate system in step 2 are continuously converted in batches according to the preset step-by-step transformation order. This ensures that the coordinates of each back drill hole are ultimately uniformly incorporated into the three-dimensional laser measurement coordinate system. After the coordinate transformation is completed, the new coordinates are re-associated and bound with the corresponding back drill hole number and process parameters and cached. At the same time, an execution signal is sent to the subsequent laser thickness measurement process to ensure that the laser scanning position and the actual position of the back drill hole are accurately matched.

[0048] Step 4: Laser thickness measurement

[0049] The scanning operation is completed along a preset trajectory by the line laser measurement components arranged in an up-and-down pattern, and the original plate thickness data of each back drill hole is collected.

[0050] Specifically, the line laser measurement components are arranged on the upper and lower sides of the PCB carrier platform in a vertically opposite manner. The line laser adopts a straight line structure and the laser line is parallel to the PCB board surface. The scanning trajectory is planned according to the distribution area of ​​the back drill holes, and the original board thickness data of multiple points are collected simultaneously in a single scan.

[0051] First, the position calibration and spacing locking of the upper and lower sets of linear laser measurement components are completed in advance, so that the upper laser emitting unit and the lower laser receiving unit are vertically aligned with each other, and the overall optical path is strictly perpendicular to the plane of the PCB support platform. At the same time, the output plane of the linear laser is adjusted to be completely parallel to the PCB board surface. The laser irradiation range is checked one by one to ensure that the laser line can completely cover all back drill holes in the effective processing area of ​​the PCB, avoiding measurement deviations caused by optical path tilting and component misalignment.

[0052] The scanning trajectory planning is based on the three-dimensional laser coordinate system coordinates of all back drilled holes converted in step 3. First, the dense hole area, sparse hole area and blank area are automatically divided according to the hole position density. Short-stroke reciprocating scanning trajectory is generated for dense hole area, long-stroke linear scanning trajectory is generated for sparse hole area, and blank area without back drilled hole is skipped without planning scanning path, so that the scanning trajectory completely matches the actual hole position distribution, which not only eliminates scanning blind spots, but also reduces invalid movement.

[0053] Then, the drive support mechanism drives the PCB board or laser assembly to move at a constant speed along the preset trajectory. The linear laser continuously scans the PCB board surface, and simultaneously captures the upper and lower surface distance signals of all measurement points within the optical path range during a single scan. According to the correspondence between the measurement points and the back drill hole coordinates, the original distance measurement data of each back drill hole is extracted one by one, and the synchronous acquisition of original board thickness related data at multiple points is completed.

[0054] Finally, based on the fixed center distance between the upper and lower laser components and the collected distance values ​​of the upper and lower surfaces, the original plate thickness value of each back drill hole position is calculated in real time. The original plate thickness data is temporarily bound and stored with the corresponding back drill hole number and coordinates. After the entire board scanning and acquisition work is completed, a run-ready instruction is sent to the subsequent data matching process to ensure that the measurement data is transferred to the next processing stage in a complete and orderly manner.

[0055] Step 5: Data Matching

[0056] The original plate thickness data is denoised and outlier data is removed. Then the processed effective plate thickness data is associated and matched with the corresponding back drill hole positions.

[0057] Specifically, the original board thickness data is denoised using a sliding mean filter, invalid and abnormal data is filtered out by combining the PCB board thickness tolerance range, and then the processed valid board thickness data is bound one by one with the corresponding back drill hole number and coordinates.

[0058] First, a fixed-length data sliding window is set according to the measurement accuracy requirements of this PCB product. All the original board thickness data collected in step 4 are traversed point by point according to the arrangement order of the back drill holes. The board thickness values ​​of the current measurement point and the adjacent measurement points in the window are summed and the average value is calculated. The calculated average value is used to replace the original single-point board thickness value. The noise reduction processing of the whole set of data is completed by sliding the window one by one, thereby eliminating random measurement noise caused by instantaneous fluctuations of laser signal, tiny dust on PCB surface, and slight unevenness of board surface, and ensuring the stability of single set of board thickness data.

[0059] Then, the factory-preset upper and lower limits of the thickness tolerance of the PCB board are retrieved, and the board thickness data after sliding mean filtering is compared one by one. Data that exceeds the tolerance range or deviates significantly from the normal board thickness range is judged as invalid abnormal data and marked and collected separately. At the same time, data within the tolerance range is filtered as valid board thickness data, and erroneous data caused by measurement errors or local damage to the board are removed from the data source.

[0060] In addition, referring to the back drill hole numbering and sorting rules used uniformly throughout steps 1 to 4, all the selected valid board thickness data are rearranged in order, and the total number of valid data is checked in sync with the actual total number of back drill holes on the PCB. If there are problems such as missing data or duplicate data, an early warning is issued and the laser thickness measurement process is re-executed to ensure that the valid board thickness data sequence and the back drill hole position sequence are completely aligned in the arrangement order.

[0061] Finally, using the unique back drill hole number as the association index, the sorted valid plate thickness data and the corresponding back drill hole coordinates are paired and bound one by one. At the same time, the theoretical plate thickness, theoretical drilling depth and other process parameters stored in the pre-stored data position are associated to generate a complete association dataset with one-to-one correspondence and cache it locally. After all data binding work is completed, a ready signal is sent to the subsequent depth compensation calculation process to provide an accurate and complete data source for calculating the compensation drilling depth hole by hole.

[0062] Step 6, Depth Compensation

[0063] By processing each hole individually, and combining the measured plate thickness with the preset process parameters, the compensated drilling depth for each back drill hole is calculated.

[0064] Specifically, each back-drilled hole is used as an independent calculation unit. The actual plate thickness data of each hole position is retrieved in sequence and the preset process parameters are used to carry out the calculation. After the calculation is completed, the process interval boundary is checked for the compensated drilling depth.

[0065] The complete associated dataset generated in step 5 is traversed line by line according to the order of the back drill hole numbers. Taking a single back drill hole as an independent calculation unit, the measured board thickness, theoretical PCB board thickness, and theoretical drilling depth corresponding to the current hole position are retrieved in sequence, and calculated using the following formula:

[0066]

[0067] In the formula, The actual drilling depth after compensation. This represents the measured plate thickness corresponding to the hole position. For theoretical plate thickness, To calculate the theoretical drilling depth, the corresponding parameters are substituted individually for each back drill hole to complete the numerical calculation, and the compensated drilling depth values ​​for all holes are obtained in sequence. Throughout the process, the calculation of each hole is independent of each other and is not affected by the data of adjacent holes.

[0068] The process interval boundary verification work involves importing the back drilling process specifications corresponding to the current batch of PCBs in advance, determining the maximum and minimum allowable back drilling depth as fixed verification thresholds, and comparing each calculated compensation drilling depth with the upper and lower thresholds. If the compensation depth is within the threshold range, it is judged as a qualified processing parameter. If the compensation depth is greater than the upper threshold, it is marked as an abnormal hole position with the risk of overcutting of inner layer circuits. If the compensation depth is less than the lower threshold, it is marked as an abnormal hole position with excessive through hole residual stakes. At the same time, the number, coordinates, and corresponding calculated values ​​of all abnormal holes are registered and stored one by one.

[0069] Finally, all qualified compensation drilling depth parameters are re-integrated and rearranged with the corresponding back drill hole number, original hole position coordinates, tool information and other original process data. A standardized parameter list is generated in strict accordance with the hole position sorting rules of the original drill strip file and local caching is completed. At the same time, all abnormal hole position information is summarized to form an independent abnormal ledger. The execution ready signal is sent to the next process in a synchronous manner, providing a complete and reliable parameter data source for the compilation and distribution of the new version of the drill strip file.

[0070] Step 7: Output drill strip data

[0071] A new version of the drill tape file is generated based on the drilling depth parameters after compensation for each hole position, and the new version of the drill tape file is sent to the back drilling machine to control the drilling machine to complete the PCB back drilling process;

[0072] Specifically, the new drill tape file retains the original file format, only replacing the drilling depth parameters of each back drill hole, while preserving the original process information such as hole coordinates, tool type, and machining speed. The new drill tape file is then transmitted to the back drill rig via Ethernet.

[0073] First, retrieve the standardized parameter list and abnormal hole position ledger completed in step 6. Strictly follow the coding specifications, data arrangement format, and instruction syntax of the original drill tape file to replicate the overall file framework. Iterate through each back-drilling hole record in the original drill tape line by line, accurately locate the dedicated data field of drilling depth in each record, and replace the original theoretical drilling depth value with only the compensated actual drilling depth. Completely retain all original process fields such as hole position coordinates, tool type, machining speed, feed rate, and drilling sequence to ensure that the structure and instruction logic of the new version of the drill tape file are completely compatible with the original version without making any changes to the parsing program of the back-drilling machine.

[0074] After the new version of the drill strip file is compiled, the system automatically performs file self-checking, verifying the file format, data integrity, and hole position parameter correspondence segment by segment. For abnormal hole positions recorded in the ledger, the original theoretical drilling depth is restored and implicitly marked inside the file. At the same time, a stable Ethernet communication channel is established, and the new version of the drill strip file is packaged and transmitted using a data verification algorithm. The data transmission status is monitored throughout the process. If problems such as packet loss, disconnection, or file corruption occur, the file is automatically retransmitted until the complete drill strip file is successfully stored in the designated storage directory of the back drilling rig.

[0075] Finally, the back-drilling machine reads and parses the received new version of the drill tape file. According to the differentiated drilling depth parameters corresponding to each back-drill hole in the file, it completes the back-drilling processing of the entire board in sequence. During the processing, the machine provides real-time feedback on the running status to the main control terminal. After all the back-drill holes of a single PCB are processed, the drilling machine automatically generates a processing log. The system associates and archives this processing log with the previous board thickness measurement, depth calculation, parameter verification and other full-process data to form a complete production data archive. The entire processing procedure is officially completed, and the equipment enters standby mode, waiting for the next PCB board to start the processing process.

[0076] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A PCB back-drilling depth compensation method based on measured board thickness, characterized in that: S1. Read the drill tape file corresponding to the PCB back drill and extract the hole coordinates, machining tool information and preset process parameters of all back drill holes in the file. S2. Use two-dimensional vision equipment to acquire PCB board images, identify board reference marks, and establish the mapping relationship between the drill tape coordinate system and the equipment mechanical coordinate system; S3. Perform joint calibration of the drill string coordinate system, mechanical coordinate system, two-dimensional vision coordinate system, and three-dimensional laser coordinate system, and uniformly transform all back-drilled hole position coordinates to the three-dimensional laser measurement coordinate system; S4. The scanning operation is completed along the preset trajectory by the line laser measurement components arranged in opposite directions to collect the original plate thickness data of each back drill hole. S5. Perform noise reduction and outlier removal on the original plate thickness data, and then associate and match the processed effective plate thickness data with the corresponding back drill hole positions. S6. Following the method of processing each hole one by one, and combining the measured plate thickness with the preset process parameters, calculate the compensated drilling depth for each back drill hole. S7. Generate a new version of the drill tape file based on the drill depth parameters after compensation for each hole position, and send the new version of the drill tape file to the back drilling machine to control the drilling machine to complete the PCB back drilling process.

2. The PCB back-drilling depth compensation method based on measured board thickness according to claim 1, characterized in that: In step S1, the back drill tape file in the industry's common format is read and the preset process parameters extracted include the theoretical PCB thickness, theoretical drilling depth and drilling auxiliary process parameters. At the same time, a one-to-one correspondence between the hole position coordinates, tool information and various process parameters is established according to the back drill hole number.

3. The PCB back-drilling depth compensation method based on measured board thickness according to claim 1, characterized in that: In step S2, an area array industrial camera is used in conjunction with a ring fill light to complete the image acquisition of the PCB board surface. The identified board reference marks include optical positioning points, process positioning holes, and board edge reference contours. The association and binding between the drill tape coordinate system and the equipment mechanical coordinate system are realized through image pixel conversion.

4. The PCB back-drilling depth compensation method based on measured board thickness according to claim 1, characterized in that: In step S3, the joint static calibration of the coordinate system is completed using a standard calibration plate, and the coordinate transformation matrix is ​​obtained. Based on the transformation matrix, the coordinates of all back-drilled holes are transformed step by step, and finally all hole coordinates are uniformly incorporated into the three-dimensional laser measurement coordinate system.

5. The PCB back-drilling depth compensation method based on measured board thickness according to claim 1, characterized in that: In step S4, the line laser measurement components are arranged on the upper and lower sides of the PCB support platform and are in a vertically opposite state. The line laser adopts a straight structure and the laser line is parallel to the PCB board surface. The scanning trajectory is planned according to the distribution area of ​​the back drill holes, and the original board thickness related data of multiple points are collected simultaneously in a single scan.

6. The PCB back-drilling depth compensation method based on measured board thickness according to claim 1, characterized in that: In step S5, the original board thickness data is denoised using a sliding mean filter. Invalid and abnormal data are filtered out in combination with the PCB board thickness tolerance range. Then, the processed valid board thickness data is bound one by one with the corresponding back drill hole number and coordinates.

7. The PCB back-drilling depth compensation method based on measured board thickness according to claim 1, characterized in that: In step S6, each back-drilled hole is used as an independent calculation unit. The measured plate thickness data of each hole position and the preset process parameters are retrieved in sequence to carry out the calculation. After the calculation is completed, the process interval boundary is checked for the compensation drilling depth.

8. The PCB back-drilling depth compensation method based on measured board thickness according to claim 1, characterized in that: In step S7, the new drill tape file retains the original file format, only replacing the drilling depth parameters of each back drill hole, while preserving the original process information such as hole position coordinates, tool type, and machining speed. The new drill tape file is then transmitted to the back drill machine via Ethernet.

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