Control method for preventing deviation of two drill holes of PCB (Printed Circuit Board)

Abstract

The invention discloses a control method for preventing deviation of two drill holes of a PCB, and relates to the technical field of PCB processing, and the method comprises the steps: obtaining hole center coordinates, hole diameter size, edge reflection state and hole wall contour information after first drilling, and recording the information in a unified coordinate system; dividing the printed circuit board into a plurality of identification areas, comparing the hole center coordinates in each identification area with design reference coordinates, identifying the areas with consistent offset directions and offset exceeding a preset offset threshold value, and determining an area correction displacement value; and according to the edge reflection state and the hole wall contour information, identifying the hole site with the abnormal hole wall, and marking the hole site as the hole site which cannot be used for path adjustment. According to the method, data such as the hole center coordinate, the hole wall reflection state, the hole wall contour feature and the hole diameter after first-time drilling are comprehensively collected, data integration is conducted under the unified coordinate system, and the adjusting basis of second-time drilling is more comprehensive and reliable.

Description

Technical Field

[0001] This invention relates to the field of PCB processing technology, specifically to a control method for preventing misalignment of two drill holes in a PCB. Background Technology

[0002] In the manufacturing process of printed circuit boards, the drilling process is usually divided into two parts: the first drilling and the second drilling. The first drilling is used to establish the processing reference, while the second drilling requires adjusting the drilling path based on the actual position data of the first drilling to ensure that the final hole position is consistent with the design reference. In the existing printed circuit board drilling process, the second drilling positioning is generally based on single-hole measurement and single-hole compensation. The path correction of the corresponding hole position is based on the measurement results of a single hole position. Although this method can correct the offset of a single hole position, its adjustment capability is still limited when dealing with the overall offset of local areas, abnormal hole wall features, and measurement differences between drilling of different structural types. With the widespread application of multilayer printed circuit boards and high-density interconnect structures, the hole wall characteristics after the first drilling are more complex, and the hole center offset trend in local areas is more diverse. In this context, different drilling areas may show a consistent offset in the overall direction, or the measurement values ​​may show regional differences due to differences in material stacking structures. At the same time, some hole walls may become abnormal due to thermal effects, material stress release, or local melting, making some hole positions unsuitable as a basis for path adjustment. Furthermore, different structural types may exhibit different structural response characteristics during measurement, and their center position acquisition methods and error distribution patterns also differ, making it difficult to meet the requirements of high-precision drilling compensation by adopting a uniform measurement method for all holes; therefore, this invention proposes a control method for preventing the misalignment of two drill holes in PCBs. Summary of the Invention

[0003] The purpose of this invention is to provide a control method for preventing misalignment of two drill holes in a PCB, so as to solve the problems mentioned in the background art.

[0004] This invention can be achieved through the following technical solution: a control method for preventing misalignment of two drill holes on a PCB, comprising the following steps: Step 1: Obtain the center coordinates, diameter, edge reflection status, and borehole wall contour information after the first drilling, and record them in a unified coordinate system; Step 2: Divide the printed circuit board into multiple recognition areas, compare the center coordinates of the holes in each recognition area with the design reference coordinates, identify areas with the same offset direction and offset exceeding the preset offset threshold, and determine the area correction displacement value. Step 3: Based on the edge reflection status and hole wall contour information, identify hole locations with abnormal hole walls and mark them as hole locations that cannot be used for path adjustment; Step 4: Based on the borehole diameter, depth, and borehole layer structure information, determine the borehole structure type, and use the center measurement processing method corresponding to the structure type to obtain the borehole center position; Step 5: Based on the regional correction displacement value, the hole center position that can be used for path adjustment, and the measurement and processing results corresponding to the structure type, determine the path adjustment amount for the second drilling; Step 6: Verify the path adjustment amount. If the verification is successful, perform the second drilling. If the verification fails, correct the path and then perform the second drilling.

[0005] A further technical improvement of the present invention is that step one includes: For each borehole, the center coordinates, diameter, edge reflection status, and borehole wall profile information are measured at least twice. Repeated measurements refer to the continuous acquisition of independent data using the same measuring equipment under the same measuring conditions; For each parameter, multiple sets of measurement results are compared for error. When the deviation between any two sets of measurement values ​​of a parameter exceeds the preset absolute error tolerance of the parameter, the parameter is marked as an abnormal parameter. For abnormal parameters, the arithmetic mean of other normal measurements is used as the final valid value. For parameters not marked as abnormal, the original measurement value is used directly. All valid measurement results are recorded in a unified coordinate system for subsequent analysis and adjustment of the borehole path.

[0006] A further technical improvement of the present invention lies in: the method for dividing the identified region in step two includes: Obtain the center coordinates of all holes on the printed circuit board, and construct a spatial adjacency network containing the connectivity of adjacent holes based on the spatial adjacency relationship between the center coordinates. Based on the spatial adjacency network, the changes in hole spacing, hole group density, and hierarchical changes in the corresponding region of the plate structure are calculated. By assigning preset weights to the three normalized changes and performing weighted summation, spatial distribution continuity evaluation parameters for quantitatively characterizing the continuity state of the regional structure are generated. The spatial distribution continuity evaluation parameters are compared with the preset area identification judgment conditions. When the spatial distance change, density change or structural hierarchy change reaches the judgment conditions, it is determined that the boundary of the area has changed and the area is identified as the identification area. The identified regions will be used as the identification regions for subsequent drilling position offset trend identification and drilling path displacement compensation processing.

[0007] A further technical improvement of the present invention is that the preset region identification and determination conditions include: z1. Does the change in spatial distance between the coordinates of adjacent borehole centers exceed the distance change threshold? z2. Does the local borehole density change rate exceed the density abrupt change threshold? z3. Does the number of layers in the plate structure corresponding to the target area undergo a step-like abrupt change? When at least two of z1, z2, and z3 are satisfied simultaneously, it is determined that the boundary of the region has changed, and the region is identified as the recognition region accordingly.

[0008] A further technical improvement of the present invention lies in: a method for determining the regional correction displacement value of the identified region, comprising: Within each identified area, obtain the center coordinates of all boreholes that can be used for path adjustment, and calculate the offset vector of the center coordinates of each borehole relative to the corresponding design reference coordinates. The offset vectors are compared for directional consistency based on their directional characteristics. When the angle difference between multiple offset vectors is within the preset directional tolerance range, the set of offset vectors is determined as the set of offset vectors with consistent offset directions. The offset vectors in the set of offset vectors with the same offset direction are weighted according to the measurement reliability factor of each borehole position, and the weighted offset vectors are averaged to obtain the regional correction displacement value of the identified area.

[0009] A further technical improvement of the present invention is that step three, identifying the location of abnormal hole walls, includes: a1. Based on the preset threshold for judging abnormal edge reflection intensity, analyze the distribution of edge reflection intensity in the circumferential direction for each borehole; When the edge of any borehole has a continuous region whose reflection intensity is lower than the edge reflection intensity abnormality judgment threshold, and the distribution range of the continuous region in the angular dimension exceeds the preset angular judgment range, the borehole is judged to have edge reflection abnormality characteristics. a2. Based on the preset threshold for determining the integrity of the borehole wall contour structure, perform multi-layer depth slicing along the axial direction for each borehole and extract the borehole wall contour information of each slice layer. When there is a geometric difference between the contour boundaries of adjacent slices that is greater than the threshold for determining the integrity of the borehole wall contour structure, or when there is a lack of continuity in the spatial connection relationship, the borehole is determined to have abnormal borehole wall structure characteristics. For boreholes that meet any of the above-mentioned abnormal judgment conditions a1 and a2, the boreholes are marked as boreholes that cannot be used for borehole path displacement compensation processing and are removed from the subsequent borehole path displacement compensation processing. For the remaining borehole locations that are not marked as abnormal, record the corresponding borehole center coordinates and the measurement processing results output under the measurement method used for the corresponding structural type.

[0010] A further technical improvement of the present invention lies in: the method for obtaining the center position of the drilled hole in step four includes: Collect the borehole diameter, borehole depth parameters, and plate structure information of the corresponding borehole area for each borehole. The plate structure information includes the number of plates traversed by the borehole and their material composition. Based on the ratio of hole diameter to hole depth, the threshold ratio of hole depth to plate thickness, and the number of layers penetrated by the drill, the drill structure type is determined to be one of through hole, blind hole, or stepped hole. Based on the structural type determined by the borehole, select and execute the corresponding center measurement processing method, including: Through hole: The center position of the hole is obtained by circumferential edge fitting; Blind holes: The center of the hole is determined by projecting the center of the bottom surface of the hole. Stepped holes: The hole centers of each layer are extracted and weighted averaged based on the layer weights to obtain the final hole center position coordinates.

[0011] A further technical improvement of the present invention lies in: the method for obtaining the path adjustment amount of the second drilling in step five includes: Within each identified region, based on the region-corrected displacement value of that region, the center position of all boreholes within that region that can be used for path adjustment is initially corrected at the region level to obtain the initially corrected center coordinates. Based on the measurement processing results output under the measurement method corresponding to the structure type of each borehole position, the center offset related to the structure features is extracted from the initially corrected borehole center coordinates. The structure type correction weight is set according to the sensitivity requirements of different structure types, and the center offset is corrected by structure type weighting. The preliminary displacement correction results at the regional level are combined and superimposed with the weighted correction results based on the structure type to form the path adjustment amount for each borehole location.

[0012] A further technical improvement of the present invention is that step six, before performing the second drilling, includes: Obtain the path adjustment amount for each borehole position; Based on the path adjustment amount and the motion control parameters of the drilling device, a set of path execution trajectory parameters corresponding to each drilling position is generated. Based on the set of path execution trajectory parameters, the validity of the path execution trajectory is verified according to preset path adjustment validity judgment conditions. The path adjustment validity judgment conditions include: Adjust whether the path is within the operating space of the drilling equipment: Adjust whether the trajectory smoothness of the path during continuous motion meets the preset rate of change threshold: Are there any risks of spatial interference or intersection conflicts between the various borehole paths? When all drilling paths meet the criteria for determining the validity of path adjustment, a second drilling operation is performed. If any drilling path fails to meet the validity criteria for path adjustment, the path adjustment amount for that path is corrected, the path execution trajectory parameter set is updated, and the validity of the path execution trajectory is repeatedly verified until all paths pass verification before the second drilling is performed.

[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention comprehensively collects data such as the borehole center coordinates, borehole wall reflection state, borehole wall contour features, and borehole diameter after the first drilling, and integrates the data under a unified coordinate system, making the adjustment basis for the second drilling more comprehensive and reliable. Compared with the method of compensation based on single-hole measurement values, by eliminating abnormal borehole positions, the propagation of compensation deviation caused by abnormal holes can be avoided, thereby effectively improving the stability and accuracy of subsequent path adjustment data. Furthermore, this invention employs a method of region identification and region correction displacement value calculation, combined with the direction consistency judgment of the borehole offset vector, so that when there is a local area overall offset, it can correctly identify and generate a region-level correction amount. At the same time, it further combines the real measurement response characteristics of boreholes of different structural types, calculates the center offset amount through the measurement processing method corresponding to the structural type, and performs weighted correction based on structural sensitivity, so that the path adjustment amount can take into account both regional trends and local structural differences, significantly improving the matching degree and adaptability of the second borehole compensation.

[0014] On the other hand, this invention verifies the effectiveness of the adjusted path before performing the second drilling, including judging the path's operability, trajectory smoothness, and the risk of interference between paths. This ensures that the path is not only theoretically feasible but also remains stable under the actual equipment movement constraints. Furthermore, if the path fails the verification, the path adjustment amount can be dynamically optimized through cyclic correction. This ensures that the final second drilling path meets the processing equipment requirements and effectively improves the drilling quality and overall manufacturing consistency of printed circuit boards. Attached Figure Description

[0015] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0016] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0017] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0018] Please see Figure 1 As shown, this invention provides a method for controlling the misalignment of two drill holes on a PCB, comprising the following steps: Step 1: Obtain the center coordinates, diameter, edge reflection status, and borehole wall contour information after the first drilling, and record them in a unified coordinate system; For each borehole, the center coordinates, diameter, edge reflection status, and borehole wall profile information are measured at least twice. Repeated measurements refer to the continuous acquisition of independent data using the same measuring equipment under the same measuring conditions; For each parameter, multiple sets of measurement results are compared for error. When the deviation between any two sets of measurement values ​​of a parameter exceeds the preset absolute error tolerance of the parameter, the parameter is marked as an abnormal parameter. For abnormal parameters, the arithmetic mean of other normal measurements is used as the final valid value. For parameters not marked as abnormal, the original measurement value is used directly. All valid measurement results are recorded in a unified coordinate system for subsequent analysis and adjustment of the borehole path.

[0019] Specifically, after the first drilling is completed, the printed circuit board is fixed on the measuring fixture, and a high-precision laser rangefinder is used to sequentially perform a complete initial measurement of the center coordinates, diameter, edge reflection status, and wall contour information of all drilled holes. Without changing the equipment, measurement angle, or light source conditions, at least one repeat measurement is immediately performed to ensure that the requirement of repeated measurement—that is, continuously acquiring independent data using the same measuring equipment under the same measurement conditions—is met. For example, if the initial measured diameter of a hole is 0.212 mm, the results of repeated measurements should fluctuate within its physical tolerance range to ensure sampling stability.

[0020] Secondly, after obtaining multiple measurement data for each borehole, the error of multiple sets of measurement results for each parameter is compared, and a targeted tolerance control strategy is introduced. That is, when the deviation between any two sets of measurement values ​​for a parameter exceeds the preset absolute error tolerance for that parameter, the parameter is marked as an abnormal parameter. For example, if the absolute error tolerance for the borehole diameter is set to ±0.005mm, and a borehole is recorded as 0.211mm and 0.218mm in two measurements respectively, then because the deviation is 0.007mm, it exceeds the tolerance range, and the borehole diameter needs to be marked as an abnormal parameter without affecting the validity of the borehole center coordinates, edge reflection state, and borehole wall contour information.

[0021] For outlier parameters, the arithmetic mean of other normal measurements is used as the final valid value to avoid the risk of overall data invalidation. For parameters not marked as outliers, the original measurement value is used directly as the final result. For example, if the hole wall profile measurement results in three measurement cycles are: shape continuity scores of 92%, 91%, and 92%, all within the tolerance, then the parameter is not corrected and the original value is retained; however, if the reflectivity of the edge reflection state is 0.89, 0.75, and 0.90, with 0.75 being significantly lower, then after removing the outlier, the average of the other two sets of results, 0.895, is set as the final valid value.

[0022] Finally, after verifying the validity of all parameters, the obtained hole center coordinates, hole diameter, edge reflection status, and hole wall contour information are recorded in a unified coordinate system and used for subsequent drilling path analysis and adjustment. This coordinate system is constructed based on the fixed edge reference of the printed circuit board to ensure the consistency of all hole position information in spatial distribution and avoid position drift caused by measurement correction process.

[0023] Step 2: Divide the printed circuit board into multiple recognition areas, compare the center coordinates of the holes in each recognition area with the design reference coordinates, identify areas with the same offset direction and offset exceeding the preset offset threshold, and determine the area correction displacement value. Methods for dividing the identification region include: Obtain the center coordinates of all holes on the printed circuit board, and construct a spatial adjacency network containing the connectivity of adjacent holes based on the spatial adjacency relationship between the center coordinates. Based on the spatial adjacency network, the changes in hole spacing, hole group density, and hierarchical changes in the corresponding region of the plate structure are calculated. By assigning preset weights to the three normalized changes and performing weighted summation, spatial distribution continuity evaluation parameters for quantitatively characterizing the continuity state of the regional structure are generated. The spatial distribution continuity evaluation parameters are compared with the preset area identification judgment conditions. When the spatial distance change, density change or structural hierarchy change reaches the judgment conditions, it is determined that the boundary of the area has changed and the area is identified as the identification area. The identified regions will be used as the identification regions for subsequent drilling position offset trend identification and drilling path displacement compensation processing.

[0024] The preset region identification criteria include: z1. Does the change in spatial distance between the coordinates of adjacent borehole centers exceed the distance change threshold? z2. Does the local borehole density change rate exceed the density abrupt change threshold? z3. Does the number of layers in the plate structure corresponding to the target area undergo a step-like abrupt change? When at least two of z1, z2, and z3 are satisfied simultaneously, it is determined that the boundary of the region has changed, and the region is identified as the recognition region accordingly.

[0025] Specifically, the steps in this embodiment include: First, the coordinates of the center holes of all drill holes on the printed circuit board are obtained, and all drill hole center coordinate data are uniformly converted into the global two-dimensional coordinate system of the printed circuit board. To construct a spatial adjacency network structure between drill holes, Delaunay triangulation is used to process the entire set of drill hole center coordinates, generating a set of spatial connection edges. Each spatial connection edge connects two geometrically nearest neighbor drill hole centers, forming a spatial adjacency network structure that includes the spatial connectivity relationships of drill hole centers. In this structure, all drill hole centers connected by spatial connection edges are considered to have a spatial adjacency relationship.

[0026] Subsequently, based on the spatial adjacency network structure, three indices reflecting the continuity of the local structure are calculated sequentially, including: Hole spacing variation: This indicator is obtained by calculating the difference between the actual spatial distance between the centers of each pair of spatially adjacent boreholes and the theoretical hole spacing in the corresponding design drawings to obtain the spatial deviation of a single pair of borehole centers; furthermore, in each area to be evaluated, the standard deviation of all deviation values ​​is calculated, and the standard deviation value is used as the hole spacing variation of that area.

[0027] Drill hole density variation: The surface of the printed circuit board is divided into several sliding analysis window units, and the number of drill holes is counted in each analysis window. Then, the difference in drill hole density between adjacent analysis windows is calculated and divided by the spatial distance between the center points of the analysis windows to obtain the local drill hole density variation rate, which reflects the degree of uniformity change of the drill hole distribution in this area.

[0028] The change in the layer structure of the printed circuit board: Based on the layer number information of each drill hole recorded in the design file, the layer differences between spatially adjacent drill holes are compared one by one, and the maximum value of the layer number difference in each region is counted to measure the change in the material stacking structure in the region.

[0029] Subsequently, the changes in borehole spacing, borehole density, and printed circuit board layer structure were normalized and weighted by setting weighting coefficients to form spatial distribution continuity evaluation parameters for the region, which were used to initially quantify the structural continuity status of the region.

[0030] Furthermore, the determination of structural continuity will be combined with preset region identification criteria, specifically including the following three items: z1. Does the change in spatial distance between the coordinates of adjacent borehole centers exceed the distance change threshold? The distance variation threshold is the maximum allowable value of the standard deviation. If the actual standard deviation exceeds this value, the area is considered to have hole spacing disturbance.

[0031] z2. Does the local borehole density change rate exceed the density abrupt change threshold? The density mutation threshold is the maximum allowable value of the density change rate. This value is derived from the density gradient boundary actually measured during the production process and is used to identify structural discontinuities caused by arrangement differences. If the density change rate exceeds this threshold, it is considered that there is a distribution mutation in the local area.

[0032] z3. Does the number of layers in the plate structure corresponding to the target area undergo a step-like abrupt change? Step-by-step abrupt changes are used to identify whether there are abrupt changes in the number of layers in the board structure traversed by a drill hole at the regional scale. Specifically, the layer structure information of each drill hole (including the number of copper foils penetrated, the number of dielectric layers, etc.) is obtained from the design documents, and the layer difference between the centers of spatially adjacent drill holes is compared one by one. In each candidate region, the proportion of all hole pairs with a layer difference greater than or equal to 2 layers is counted. If this proportion exceeds 20% of the number of hole pairs in the region, a step-by-step abrupt change is identified in that region. This judgment is based on boundary statistics of common skip-layer structures in multilayer board designs and can effectively reflect the risk of abrupt changes in the stacked structure of the board within a region.

[0033] Preferably, when at least two of z1, z2, and z3 are satisfied simultaneously, it is determined that there is a structural continuity break in the current analysis region, thereby marking the boundary of the region as changed, and delineating the region as the identification region accordingly.

[0034] The method for determining the regional correction displacement value of the identified region includes: Within each identified area, obtain the center coordinates of all boreholes that can be used for path adjustment, and calculate the offset vector of the center coordinates of each borehole relative to the corresponding design reference coordinates. The offset vectors are compared for directional consistency based on their directional characteristics. When the angle difference between multiple offset vectors is within the preset directional tolerance range, the set of offset vectors is determined as the set of offset vectors with consistent offset directions. The offset vectors in the set of offset vectors with the same offset direction are weighted according to the measurement reliability factor of each borehole position, and the weighted offset vectors are averaged to obtain the regional correction displacement value of the identified area.

[0035] Specifically, within each defined identification area, all drill holes that are not marked as abnormal and can be used for path adjustment are extracted, and their center coordinates are obtained after measurement processing. Simultaneously, the design reference coordinates corresponding to these drill holes are extracted from the printed circuit board design file. Based on the difference between the center coordinates and the design reference coordinates, the offset vector for each drill hole is calculated.

[0036] Subsequently, the directional characteristics of the offset vectors are analyzed. By calculating the angle between any two sets of offset vectors, the consistency of the offset direction within the identification region is determined. If the difference in the angle between all offset vectors is less than a preset directional tolerance threshold, such as no more than fifteen degrees, it is considered that there is a set of offset vectors with consistent offset directions within the region.

[0037] For a set of offset vectors with the same offset direction, the offset vectors are weighted according to the measurement reliability factor of each borehole position.

[0038] After the weighted processing is completed, a vector average operation is performed on all weighted offset vectors in the set to finally obtain the region correction displacement value of the identified region.

[0039] In this embodiment, the measurement reliability factor is set using a weighted scoring method. The measurement results of each borehole position are evaluated and scored from the following four dimensions: borehole diameter stability factor, structure type matching factor, edge reflection integrity factor, and contour continuity factor.

[0040] Among them, the aperture stability factor is calculated based on the relative error between the actual borehole diameter and the standard borehole diameter, and the smaller the error, the higher the score; the structure type matching factor gives a score based on the degree of matching between the identified borehole structure type and the standard structure type, and sets a structural credibility weight for through holes, blind holes and buried holes respectively; the edge reflection integrity factor is derived based on the continuity of the distribution of circumferential edge reflection intensity, and the highest score is given if there is no low reflection interval; the contour continuity factor is scored by calculating the contour overlap or boundary matching degree of the borehole wall in multi-layer slices, and the higher the boundary continuity, the higher the score.

[0041] Finally, the four factor scores are weighted and combined to form a comprehensive measurement reliability factor, which is used for the weighted average processing of the offset vector to ensure that the final obtained regional correction displacement value has higher data reliability and path adjustment accuracy.

[0042] Step 3: Based on the edge reflection status and hole wall contour information, identify hole locations with abnormal hole walls and mark them as hole locations that cannot be used for path adjustment; The steps for identifying borehole locations with abnormal borehole walls include: a1. Based on the preset threshold for judging abnormal edge reflection intensity, analyze the distribution of edge reflection intensity in the circumferential direction for each borehole; When the edge of any borehole has a continuous region whose reflection intensity is lower than the edge reflection intensity abnormality judgment threshold, and the distribution range of the continuous region in the angular dimension exceeds the preset angular judgment range, the borehole is judged to have edge reflection abnormality characteristics. Specifically, edge reflection intensity distribution data for each borehole in the circumferential direction is acquired. Edge reflection intensity is the intensity of reflected light signal obtained after a 360° full-angle scan of the borehole edge using a high-resolution optical imaging device. The resulting reflection intensity sequence is converted into an angle-intensity function in polar coordinates, and the signal is smoothed using a sliding window averaging method. Continuous low-reflection areas are then identified using threshold judgment.

[0043] The threshold for judging abnormal edge reflection intensity is a boundary value set in advance based on the statistical characteristics of normal borehole reflection, preferably the critical value determined by subtracting two standard deviations from the mean reflection intensity.

[0044] If, in the reflection curve of a borehole, there is a range of angles that are continuously below the judgment threshold, and the span of this continuous low-reflection area in terms of angle is greater than the edge reflection angle judgment range, for example, exceeding the set 30 degrees (which can be set as a threshold parameter instead of a fixed value), then the borehole is judged to have abnormal edge reflection characteristics.

[0045] a2. Based on the preset threshold for determining the integrity of the borehole wall contour structure, perform multi-layer depth slicing along the axial direction for each borehole and extract the borehole wall contour information of each slice layer. When there is a geometric difference between the contour boundaries of adjacent slices that is greater than the threshold for determining the integrity of the borehole wall contour structure, or when there is a lack of continuity in the spatial connection relationship, the borehole is determined to have abnormal borehole wall structure characteristics. Specifically, for each borehole, multi-layer axial slice images are obtained along the borehole depth direction to extract the borehole wall contour boundary at each depth level.

[0046] Contour extraction employs the Canny edge detection algorithm based on edge gradients, and the extracted contours undergo standardized curvature fitting to unify them under a circular reference model.

[0047] Subsequently, the contour structure difference value between adjacent slices is calculated, preferably using Hausdorff distance or maximum boundary offset as the difference index.

[0048] If the difference in the contour structure between two layers is greater than the threshold for determining the integrity of the borehole wall contour structure, or if a situation is found in the curvature continuity test where a closed loop is not formed or a boundary fracture is found between the two layers, then the borehole is determined to have abnormal borehole wall structure characteristics.

[0049] For boreholes that meet any of the above-mentioned abnormal judgment conditions a1 and a2, the boreholes are marked as boreholes that cannot be used for borehole path displacement compensation processing and are removed from the subsequent borehole path displacement compensation processing. For the remaining borehole locations that are not marked as abnormal, record the corresponding borehole center coordinates and the measurement processing results output under the measurement method used for the corresponding structural type.

[0050] Finally, for borehole locations not marked as abnormal, their corresponding borehole center coordinates are recorded. Based on the structural type of the borehole location (e.g., through hole, blind hole, stepped hole), a preset measurement processing method is invoked to obtain the measurement processing results required for path correction, including but not limited to the average borehole center coordinates, radial offset, and reconstructed coordinates of the structural geometric center. These measurement processing results will serve as the basic data input for subsequent path compensation calculations.

[0051] Step 4: Based on the borehole diameter, depth, and borehole layer structure information, determine the borehole structure type, and use the center measurement processing method corresponding to the structure type to obtain the borehole center position; Methods for obtaining the center position of a drilled hole include: Collect the borehole diameter, borehole depth parameters, and plate structure information of the corresponding borehole area for each borehole. The plate structure information includes the number of plates traversed by the borehole and their material composition. Based on the ratio of hole diameter to hole depth, the threshold ratio of hole depth to plate thickness, and the number of layers penetrated by the drill, the drill structure type is determined to be one of through hole, blind hole, or stepped hole. Based on the structural type determined by the borehole, select and execute the corresponding center measurement processing method, including: Through hole: The center position of the hole is obtained by circumferential edge fitting; Blind holes: The center of the hole is determined by projecting the center of the bottom surface of the hole. Stepped holes: The hole centers of each layer are extracted and weighted averaged based on the layer weights to obtain the final hole center position coordinates.

[0052] Specifically, the borehole diameter, depth parameters, and plate structure information of the area where the borehole is located are collected for each borehole. The borehole diameter can be measured by circumferential averaging using a high-precision imager, and the depth parameter can be obtained by a laser displacement sensor to measure the vertical depth of the borehole from the top surface to the bottom reflecting surface.

[0053] The information on the plate structure comes from the thickness, material type and position order of each plate layer as recorded in the design documents; for example, in a specific drill hole, the diameter is measured to be 0.2 mm and the depth is 0.35 mm. The corresponding design documents show that the drill hole passes through three layers of copper foil and two layers of substrate.

[0054] Based on parameters such as the ratio of hole diameter to hole depth, the ratio of hole depth to total plate thickness, and the number of layers penetrated by the drill, the structural type of each drill hole is determined. If the hole depth is greater than the hole diameter and penetrates all plate layers, it is determined to be a through hole. If the hole depth is less than the plate thickness and only penetrates part of the plate layer without being completely through, it is determined to be a blind hole. If the hole depth varies across multiple layers and the hole diameter is different in different layers, it is determined to be a stepped hole.

[0055] In the example drilling above, the hole depth is equivalent to the total plate thickness and the entire layer is penetrated, so its structural type is determined to be a through hole.

[0056] Based on the determined structure type, select the center measurement processing method suitable for that structure type; For through holes, the circumferential edge point fitting method is used. The edge reflection points on the circumference of the hole are used as input to perform elliptical least squares fitting to obtain the coordinates of the hole center. For blind holes, the hole center extraction method is adopted, which obtains the hole center position by calculating the centroid of the gray-scale distribution of the bottom cross-section image; For stepped holes, the center coordinates of each structural segment are extracted, and a weighted average is calculated based on the proportion of each structural segment in the total hole depth as the final center position.

[0057] Finally, the hole center position coordinates output by the measurement processing method determined according to the structure type are uniformly converted to the global two-dimensional coordinate system of the printed circuit board and stored together with the drilling structure type to provide structural matching data support for subsequent path adjustment and offset compensation.

[0058] Step 5: Based on the regional correction displacement value, the hole center position that can be used for path adjustment, and the measurement and processing results corresponding to the structure type, determine the path adjustment amount for the second drilling; The method for obtaining the path adjustment amount for the second borehole includes: Within each identified region, based on the region-corrected displacement value of that region, the center position of all boreholes within that region that can be used for path adjustment is initially corrected at the region level to obtain the initially corrected center coordinates. Based on the measurement processing results output under the measurement method corresponding to the structure type of each borehole position, the center offset related to the structure features is extracted from the initially corrected borehole center coordinates. The structure type correction weight is set according to the sensitivity requirements of different structure types, and the center offset is corrected by structure type weighting. The preliminary displacement correction results at the regional level are combined and superimposed with the weighted correction results based on the structure type to form the path adjustment amount for each borehole location.

[0059] In this embodiment, to achieve more adaptive path adjustment control during the second drilling process, firstly, within each identification area, the center coordinates of all borehole positions marked as usable for path adjustment are acquired; then, based on the area correction displacement value of the identification area, the original center coordinates of all the aforementioned borehole positions within that area are uniformly corrected. Specifically, the following method is used: The center coordinates of each borehole are vector-superimposed according to the displacement vectors in the regional corrected displacement values ​​to obtain the corresponding preliminary corrected center coordinates. This operation is used to achieve overall path offset compensation at the regional scale.

[0060] Based on the preliminarily corrected center coordinates of the borehole, the measurement processing results output by the measurement method corresponding to the structural type of each borehole position are further introduced.

[0061] The measurement and processing results contain multiple parameters that reflect the geometric characteristics of the hole, such as eccentricity, centroid offset, and tilt angle distribution.

[0062] By extracting features from the above parameters, a center offset is extracted to reflect the degree of center deviation under the structural features, and this offset is used as the basis for subsequent structural sensitivity compensation calculations.

[0063] Considering the different tolerances of different borehole structure types to center offset errors, a structure type correction weight is preset according to the sensitivity requirements of various structure types. The structure type correction weight can be set based on empirical statistics or the structure complexity level.

[0064] For example, higher correction weights can be set for borehole types with blind hole structures, stepped hole structures, and multi-layer heterogeneous structures; while relatively lower correction weights can be set for borehole types with through holes and single-layer structures.

[0065] The center offset is multiplied by the corresponding structure type correction weight to obtain the structure type weighted correction result, which is used as the refined path compensation amount under the structure dimension.

[0066] Finally, the displacement vector between the weighted correction result of the above structure type and the initially corrected hole center coordinates is superimposed to obtain the final path adjustment amount of the borehole position.

[0067] The path adjustment takes into account both regional error trends and structural accuracy requirements, and serves as the core parameter input for the second borehole path planning and displacement compensation process, in order to improve the overall borehole accuracy and structural matching.

[0068] Step 6: Verify the path adjustment amount. If the verification is successful, perform the second drilling. If the verification fails, correct the path and then perform the second drilling.

[0069] Before performing the second drilling, the following is included: Obtain the path adjustment amount for each borehole location; this path adjustment amount is a borehole displacement compensation parameter obtained after integrating the regional correction displacement value and the structure type weighted correction result, which is used to indicate the amount of spatial correction required relative to the initial borehole path.

[0070] Based on the path adjustment amount and the motion control parameters of the drilling device, a set of path execution trajectory parameters corresponding to each drilling position is generated; the trajectory parameter set includes, but is not limited to, the motion displacement sequence of the drilling head in three-dimensional coordinate space, the velocity change curve, the feed direction change law, and the point coordinate set of the path trajectory.

[0071] Based on the set of path execution trajectory parameters, the validity of the path execution trajectory is verified according to preset path adjustment validity judgment conditions. The path adjustment validity judgment conditions include: Adjust whether the path is within the operating space of the drilling equipment: Specifically, the effective operating space is the enclosed space range determined by the mechanical structure dimensions of the drilling equipment, the range of motion of the worktable, and the maximum reach of the processing head. In practical applications, the coordinates of the borehole center after the path adjustment is applied are used to determine the boundary. If the coordinates do not meet the geometric boundary conditions of the operating space (e.g., not within the maximum stroke range), the current path is considered to be outside the operable range of the equipment and does not meet the judgment condition.

[0072] Adjust whether the trajectory smoothness of the path during continuous motion meets the preset rate of change threshold: Specifically, trajectory smoothness is quantified by calculating the rate of change of angle or acceleration per unit length of the path segment. When the rate of continuous change of trajectory angle caused by path adjustment exceeds a preset rate of change threshold (e.g., excessive angle change per unit time, requiring the machining head to drastically change direction), the path is considered to have abrupt change characteristics and does not meet the trajectory smoothness requirements. The trajectory rate of change threshold is set based on parameters such as the motion response characteristics of the drilling equipment and the maximum permissible angular acceleration.

[0073] Are there any risks of spatial interference or intersection conflicts between the various borehole paths? Specifically, based on the spatial trajectory parameters of all drilling paths, the minimum distance between paths is compared pairwise. If the shortest spatial distance between two paths is less than the set path interval threshold, or if the trajectory envelopes overlap, a spatial conflict risk is identified. The path interval threshold is set based on the equipment's machining accuracy, safety clearance, and minimum trajectory interference limits.

[0074] When all drilling paths meet the criteria for determining the validity of path adjustment, a second drilling operation is performed. If any drilling path fails to meet the validity criteria for path adjustment, the path adjustment amount for that path is corrected, the path execution trajectory parameter set is updated, and the validity of the path execution trajectory is repeatedly verified until all paths pass verification before the second drilling is performed. Specifically, for paths that do not meet the conditions, the judgment dimension to which the non-compliance item belongs is determined, and the key parameters that cause the path failure are further analyzed (such as excessive concentration of offset direction, abnormal amplification of structure type correction coefficient, excessive superposition of correction displacement, etc.). Based on this, the path adjustment amount of the current path is modified at the parameter level.

[0075] The correction process may include: adjusting the direction or magnitude of the regional correction displacement value, correcting the structural type weighting coefficient, constraining the upper limit of the magnitude of the composite result of the offset vector, or applying a path change rate suppression coefficient to improve the continuity and smoothness of the trajectory.

[0076] After the path adjustment is corrected, the trajectory parameter set for the borehole path is updated with the corrected parameters, and the validity of the updated trajectory is verified again. If there are still paths that do not meet the path validity conditions, the loop of path correction and re-verification continues. This process will continue to iterate until all borehole paths pass the path adjustment validity verification.

[0077] Once all paths have been verified, the second drilling process can be triggered to ensure that the drilling path is operable, has a smooth trajectory, and is free from interference, thereby guaranteeing the quality and accuracy control of subsequent drilling.

[0078] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters and thresholds in the formulas are set by those skilled in the art according to the actual situation.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A control method for preventing misalignment of two drill holes in a PCB, characterized in that, include: Step 1: Obtain the center coordinates, diameter, edge reflection status, and borehole wall contour information after the first drilling, and record them in a unified coordinate system; Step 2: Divide the printed circuit board into multiple recognition areas, compare the center coordinates of the holes in each recognition area with the design reference coordinates, identify areas with the same offset direction and offset exceeding the preset offset threshold, and determine the area correction displacement value. Step 3: Based on the edge reflection status and hole wall contour information, identify hole locations with abnormal hole walls and mark them as hole locations that cannot be used for path adjustment; Step 4: Based on the borehole diameter, depth, and borehole layer structure information, determine the borehole structure type, and use the center measurement processing method corresponding to the structure type to obtain the borehole center position; Step 5: Based on the regional correction displacement value, the hole center position that can be used for path adjustment, and the measurement and processing results corresponding to the structure type, determine the path adjustment amount for the second drilling; Step 6: Verify the path adjustment amount. If the verification is successful, perform the second drilling. If the verification fails, correct the path and then perform the second drilling.

2. The control method for preventing misalignment of two drill holes in a PCB according to claim 1, characterized in that, Step one includes: For each borehole, the center coordinates, diameter, edge reflection status, and borehole wall profile information are measured at least twice. For each parameter, multiple sets of measurement results are compared for error. When the deviation between any two sets of measurement values ​​of a parameter exceeds the preset absolute error tolerance of the parameter, the parameter is marked as an abnormal parameter. For abnormal parameters, the arithmetic mean of other normal measurements is used as the final valid value. For parameters not marked as abnormal, the original measurement value is used directly, and all valid measurement results are recorded in a unified coordinate system.

3. The control method for preventing misalignment of two drill holes in a PCB according to claim 1, characterized in that, The method for dividing the identification region in step two includes: Obtain the center coordinates of all holes on the printed circuit board, and construct a spatial adjacency network containing the connectivity of adjacent holes based on the spatial adjacency relationship between the center coordinates. Based on the spatial adjacency network, the changes in hole spacing, hole group density, and hierarchical changes in the corresponding region of the plate structure are calculated. By assigning preset weights to the three normalized changes and performing weighted summation, spatial distribution continuity evaluation parameters for quantitatively characterizing the continuity state of the regional structure are generated. The spatial distribution continuity evaluation parameters are compared with the preset area identification judgment conditions. When the spatial distance change, density change or structural hierarchy change reaches the judgment conditions, it is determined that the boundary of the area has changed and the area is identified as the identification area. The identified regions will be used as the identification regions for subsequent drilling position offset trend identification and drilling path displacement compensation processing.

4. The control method for preventing misalignment of two drill holes in a PCB according to claim 3, characterized in that, The preset region identification criteria include: z1. Does the change in spatial distance between the coordinates of adjacent borehole centers exceed the distance change threshold? z2. Does the local borehole density change rate exceed the density abrupt change threshold? z3. Does the number of layers in the plate structure corresponding to the target area undergo a step-like abrupt change? When at least two of z1, z2, and z3 are satisfied simultaneously, it is determined that the boundary of the region has changed, and the region is identified as the recognition region accordingly.

5. The control method for preventing misalignment of two drill holes in a PCB according to claim 4, characterized in that, The method for determining the regional correction displacement value of the identified region includes: Within each identified area, obtain the center coordinates of all boreholes that can be used for path adjustment, and calculate the offset vector of the center coordinates of each borehole relative to the corresponding design reference coordinates. The offset vectors are compared for directional consistency based on their directional characteristics. When the angle differences between multiple offset vectors are all within the preset directional tolerance range, the set of offset vectors is determined as the set of offset vectors with consistent offset directions. The offset vectors in the set of offset vectors with the same offset direction are weighted according to the measurement reliability factor of each borehole position, and the weighted offset vectors are averaged to obtain the regional correction displacement value of the identified area.

6. The control method for preventing misalignment of two drill holes in a PCB according to claim 1, characterized in that, Step three, identifying the locations of boreholes with abnormal borehole walls, includes: a1. Based on the preset threshold for judging abnormal edge reflection intensity, analyze the distribution of edge reflection intensity in the circumferential direction for each borehole; When the edge of any borehole has a continuous region whose reflection intensity is lower than the edge reflection intensity abnormality judgment threshold, and the distribution range of the continuous region in the angular dimension exceeds the preset angular judgment range, the borehole is judged to have edge reflection abnormality characteristics. a2. Based on the preset threshold for determining the integrity of the borehole wall contour structure, perform multi-layer depth slicing along the axial direction for each borehole and extract the borehole wall contour information of each slice layer. When there is a geometric difference between the contour boundaries of adjacent slices that is greater than the threshold for determining the integrity of the borehole wall contour structure, or when there is a lack of continuity in the spatial connection relationship, the borehole is determined to have abnormal features of the borehole wall structure. For boreholes that meet any of the above-mentioned abnormal judgment conditions a1 and a2, the boreholes are marked as boreholes that cannot be used for borehole path displacement compensation processing and are removed from the subsequent borehole path displacement compensation processing. For the remaining borehole locations that are not marked as abnormal, record the corresponding borehole center coordinates and the measurement processing results output under the measurement method used for the corresponding structure type.

7. The control method for preventing misalignment of two drill holes in a PCB according to claim 1, characterized in that, The method for obtaining the center position of the drilled hole in step four includes: Collect the borehole diameter, borehole depth parameters, and plate structure information of the corresponding borehole area for each borehole. The plate structure information includes the number of plates traversed by the borehole and their material composition. Based on the ratio of hole diameter to hole depth, the threshold ratio of hole depth to plate thickness, and the number of layers penetrated by the drill, the drill structure type is determined to be one of through hole, blind hole, or stepped hole. Based on the structural type determined by the borehole, select and execute the corresponding center measurement processing method, including: Through hole: The center position of the hole is obtained by circumferential edge fitting; Blind holes: The center of the hole is determined by projecting the center of the bottom surface of the hole. Stepped holes: The hole centers of each layer are extracted and weighted averaged based on the layer weights to obtain the final hole center position coordinates.

8. The control method for preventing misalignment of two drill holes in a PCB according to claim 1, characterized in that, The method for obtaining the path adjustment amount for the second drilling in step five includes: Within each identified region, based on the region-corrected displacement value of that region, the center position of all boreholes within that region that can be used for path adjustment is initially corrected at the region level to obtain the initially corrected center coordinates. Based on the measurement processing results output under the measurement method corresponding to the structure type of each borehole position, the center offset related to the structure features is extracted from the initially corrected borehole center coordinates. The structure type correction weight is set according to the sensitivity requirements of different structure types, and the center offset is corrected by structure type weighting. The preliminary displacement correction results at the regional level are combined and superimposed with the weighted correction results based on the structure type to form the path adjustment amount for each borehole location.

9. The control method for preventing misalignment of two drill holes in a PCB according to claim 1, characterized in that, Step six, performed before the second drilling operation, includes: Obtain the path adjustment amount for each borehole position; Based on the path adjustment amount and the motion control parameters of the drilling device, a set of path execution trajectory parameters corresponding to each drilling position is generated. Based on the path execution trajectory parameter set, the path execution trajectory is validated according to the preset path adjustment validity judgment conditions. The path adjustment validity judgment conditions include: whether the adjustment path is within the operable space of the drilling equipment, whether the trajectory smoothness of the adjustment path in the continuous movement process meets the preset change rate threshold, and whether there is a risk of spatial interference or cross conflict between the drilling paths. When all drilling paths meet the criteria for determining the validity of path adjustment, a second drilling operation is performed. If any drilling path fails to meet the validity criteria for path adjustment, the path adjustment amount for that path is corrected, the path execution trajectory parameter set is updated, and the validity of the path execution trajectory is repeatedly verified until all paths pass verification before the second drilling is performed.

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