A visual detection method for micro-hole deviation of high-density interconnection circuit board

Abstract

The application discloses a kind of high-density interconnection circuit board micro-hole offset visual detection methods, specifically related to circuit board visual detection technical field, for solving the problem of existing high-density interconnection circuit board micro-hole visual detection, when micro-hole offset is close to the boundary of allowable offset, and the aperture or target pad local boundary is missing due to factors such as reflection, sidewall imaging, it is difficult to distinguish between real geometric offset and apparent offset caused by boundary imaging missing, leading to micro-hole offset defect determination uncertainty. By forming the aperture center feasible region, target pad center feasible region and offset feasible region based on the unified circumferential reference, determine the dominant uncertain boundary slot when judging boundary crossing, and use complementary review lighting to form stationary boundary evidence to redefine the center feasible region and update the offset feasible region, so as to distinguish between real geometric offset and apparent offset caused by local boundary imaging missing, reduce micro-hole offset defect misjudgment and determination uncertainty.

Description

Technical Field

[0001] This invention relates to the field of circuit board visual inspection technology, specifically a visual inspection method for microvia misalignment on high-density interconnect circuit boards. Background Technology

[0002] As the line density of high-density interconnect circuit boards continues to increase, the size of microvias is gradually decreasing. The relative position between the microvia opening and the target pad has become a crucial factor affecting the quality of interlayer interconnects. Existing microvia offset detection typically involves acquiring images of the microvia area using an industrial camera, extracting the aperture boundary and the target pad boundary visible through the aperture from the image, calculating the relative offset between them based on the identified center position, and comparing the calculation result with a preset allowable offset range to determine if the microvia has an offset defect. For cases where both the aperture and the target pad boundary are stably and completely visible, the above method can directly perform offset detection.

[0003] However, in actual visual inspection, the reflection states of incident light by the micro-hole walls, metal surfaces, and target pads are not consistent. Some circumferential areas are easily affected by factors such as local reflection, sidewall occlusion, brightness saturation, or lighting direction, causing local missing, discontinuous, or unstable position display at the aperture or target pad boundaries. Existing detection methods typically perform center fitting or position calculation based on the boundaries that can be identified in a single acquired image. When some boundary evidence is missing, different boundary values ​​may correspond to different aperture centers or target pad centers, thus causing variations in the obtained offset results. Especially when the actual offset is close to the allowable offset boundary, the positional uncertainty caused by missing boundary imaging may result in the detection result being both within and outside the allowable range.

[0004] Therefore, the main problem in the existing technology is that when the microvia offset is near the allowable offset boundary and the local aperture boundary or target pad boundary cannot be stably presented, it is difficult to determine whether the current offset result is caused by the real geometric offset between the microvia and the target pad or by the apparent position change caused by the lack of local boundary imaging based solely on the detection image under a single illumination condition. This can easily lead to uncertainty in the microvia offset defect judgment result and affect the reliability of the visual detection result under the critical offset state. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a visual inspection method for microvia misalignment in high-density interconnect circuit boards, thereby solving the problems mentioned in the background section.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a visual inspection method for microvia misalignment in high-density interconnect circuit boards, comprising:

[0007] Step 1: Obtain the initial microvia detection image, divide the orifice boundary slots and target pad boundary slots according to the circumferential reference, and mark the effective boundary slots and the boundary slots to be confirmed according to the edge continuity;

[0008] Step 2: Utilize the effective boundary slots to form the feasible region at the center of the orifice, the feasible region at the center of the target pad, and the feasible region of offset. Determine the boundary crossing status based on the overlap relationship between the feasible region of offset and the allowed offset region.

[0009] Step 3: When the offset feasible region crosses the boundary of the allowable offset region, determine the crossing direction of the judgment boundary, calculate the feasible region shrinkage of the boundary slot to be confirmed, and take the first slot in the sorting as the dominant uncertain boundary slot;

[0010] Step 4: Determine the complementary verification illumination conditions based on the circumferential position of the dominant uncertain boundary slot, keep the imaging position fixed, and acquire verification images sequentially;

[0011] Step 5: Locally register the initial micropore detection image and the verification image, form residency boundary evidence based on the geometric position relationship of the candidate boundary, and redefine the corresponding center feasible region;

[0012] Step 6: Update the offset feasible region based on the redefined central feasible region and determine the micropore offset defect status. The dominant uncertain boundary slot that forms the evidence of the dwelling boundary and obtains a non-empty redefined central feasible region is determined as the confirmed boundary slot. Write it and the complementary verification lighting conditions into the subsequent micropore priority acquisition record.

[0013] Furthermore, step one includes:

[0014] The design hole position is converted to the initial detection image coordinates of the microhole after the plate surface positioning mark is used as the fixed origin. The positive horizontal direction of the plate manufacturing coordinate is used as the circumferential starting direction, and the circumferential reference is established according to the locked rotation direction.

[0015] The same set of radial dividing lines is used to divide the orifice boundary slots and the target pad boundary slots;

[0016] Adjacent actual edge points whose circumferential spacing does not exceed the connection interval are grouped into the same actual edge segment. Valid boundary slots and unconfirmed boundary slots are marked according to coverage, maximum gap length, and location dispersion.

[0017] Furthermore, step two includes:

[0018] Set the orifice center candidate position and the target pad center candidate position according to the same center candidate position grid, and form the orifice center feasible region and the target pad center feasible region according to the actual edge points and boundary allowable zone of the effective boundary slot;

[0019] The offset feasible region is formed by combining candidate positions based on the offset diameter of the orifice center relative to the target pad center;

[0020] Two candidate offset positions whose horizontal and vertical coordinate differences do not exceed the arrangement interval and do not overlap with each other are considered adjacent positions, thus forming a continuous position group;

[0021] When a continuous set of positions contains candidate offset positions that are strictly within or outside the allowed offset domain, the boundary crossing state is determined.

[0022] Furthermore, step three includes:

[0023] In a continuous set of positions that simultaneously contains candidate offset positions inside and outside the allowed offset domain, the straight-line distances between the inner and outer candidate offset positions are compared, and the position combination with the smallest distance is selected from all comparison results.

[0024] When candidates are in parallel, a unique combination is determined by ascending order of the horizontal and vertical coordinates of the internal candidate offset position and the horizontal and vertical coordinates of the external candidate offset position. The direction from the internal candidate offset position to the external candidate offset position is the decision boundary crossing direction.

[0025] Establish a direction axis that passes through the zero offset position and is parallel to the direction, and use the distance between the maximum and minimum projected positions of the offset feasible region on the direction axis as the original range length.

[0026] Furthermore, step three also includes:

[0027] Within the radial range of the edge of each boundary slot to be confirmed, possible boundary positions are formed;

[0028] Each of these is used as a new boundary constraint. Candidate center positions are selected from the corresponding original feasible center regions and combined with candidate positions from another feasible center region to form candidate offset positions.

[0029] Project the candidate offset position onto the direction axis to determine the length of the retention range, use the maximum value as the conservative retention range length, and calculate the feasible region shrinkage.

[0030] Sort by feasible domain shrinkage in descending order and slot order in ascending order. When slot orders are the same, slots at the orifice boundary are given priority to determine the dominant uncertain boundary slots.

[0031] Furthermore, step four includes:

[0032] The circumferential position is determined by the middle direction of the dominant uncertain boundary slot coverage angle range;

[0033] Select the first lighting zone with the smallest angle difference between the central lighting direction and the circumferential position, and take the opposite direction of its central lighting direction as the complementary target direction. Select the second lighting zone with the smallest angle difference between the central lighting direction and the complementary target direction from the remaining zones.

[0034] When the minimum angle difference is the same, the lighting zone that is ranked later is selected according to the rotation direction used when establishing the circumferential reference;

[0035] Complementary verification illumination conditions are formed by using the first and second illumination conditions corresponding to the two zones, and verification images are acquired sequentially at fixed imaging positions.

[0036] Furthermore, step five includes:

[0037] Using the initial micropore detection image as a coordinate reference, from the effective boundary slots outside the dominant uncertain boundary slots and in both the initial micropore detection image and all verification images, the slot interval is determined by the angle between the slots in the middle direction not exceeding half a circumference. The two slots with the largest interval are selected as the reference positions. When they are side by side, the combination is determined according to the slot order.

[0038] Local registration is completed by determining the rotation angle and translation amount based on the location reference point;

[0039] Within the dominant uncertain boundary slot, candidate combinations are established, and the geometric position preservation relationship is determined when the effective common circumferential coverage length and geometric position change are satisfied.

[0040] Furthermore, step five also includes:

[0041] Candidate combinations that form geometric position preservation relationships are sorted in descending order of effective common circumferential coverage length, ascending order of geometric position change, and circumferential starting position, and the first one is taken as the corresponding candidate boundary group.

[0042] The locations where candidate boundary points are present in all the images participating in the comparison within their common circumferential coverage area are taken as valid comparison locations. The stationary location interval is formed by the innermost to the outermost candidate boundary location of each location, and this constitutes the stationary boundary evidence.

[0043] Only the central candidate locations that share a common location with each stationing location interval and the corresponding allowable boundary location range are retained, forming a redefined corresponding central feasible region.

[0044] Furthermore, step six includes:

[0045] When both the corresponding center feasible region and the other center feasible region are not empty, the candidate positions are combined according to the offset diameter of the orifice center relative to the target pad center to form the updated offset feasible region.

[0046] If the boundary of the allowed offset domain belongs to this domain, it is judged as no offset defect detected when all candidate offset positions belong to the allowed offset domain; if all candidate offset positions do not belong to the allowed offset domain, it is judged as an offset defect detected; the rest are judged as pending verification.

[0047] The dominant uncertain boundary slots that form evidence of the residency boundary and are redefined as non-empty central feasible regions are identified as confirmed boundary slots, and the confirmed boundary slots and the actual complementary verification lighting conditions are written into the subsequent micro-hole priority acquisition records.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1. By dividing the microvia aperture boundary and the target pad boundary into boundary slots according to a unified circumferential reference, feasible regions for the aperture center, feasible regions for the target pad center, and feasible regions for offset are formed based on the effective boundary slots. When the feasible region for offset crosses the boundary of the allowable offset region, the dominant uncertain boundary slot is determined. For this slot, a verification image is obtained using complementary verification lighting conditions. Based on the geometric position retention relationship of the candidate boundary under different lighting conditions, residency boundary evidence is formed. The feasible region for the center is further redefined and the feasible region for offset is updated. This achieves the effect of distinguishing between the actual geometric offset and the apparent offset caused by the lack of boundary evidence when the microvia offset is close to the allowable boundary and the local boundary cannot be stably presented due to reflection, sidewall imaging, or local optical defects. This reduces the uncertainty caused by a single lighting image in the determination of microvia offset defects.

[0050] 2. By comparing the feasible region shrinkage of each unconfirmed boundary slot with the feasible region of the offset according to the direction of the boundary crossing, the unconfirmed boundary slot with the first place in the feasible region shrinkage ranking is identified as the dominant uncertain boundary slot. Then, complementary verification lighting conditions are formed according to the circumferential position of the slot. This achieves the effect of concentrating the verification collection on the local boundary area that has a greater impact on the current micropore offset determination, avoiding indiscriminate repeated collection of all uncertain boundaries, and enabling the boundary evidence obtained by the verification to directly affect the shrinkage of the current offset determination range.

[0051] 3. By writing the boundary slots confirmed by the boundary evidence and the corresponding verification lighting conditions into the priority acquisition record of subsequent microholes, and limiting this record to only affect the acquisition priority order of existing verification lighting conditions for subsequent microholes that meet the applicable conditions, without changing the design hole position mapping position, circumferential reference, center feasible domain formation rules and allowable offset domain, the goal is to achieve the effect of continuously accumulating the correspondence between the same type of boundary slots and effective verification lighting conditions while maintaining the stability of the microhole offset detection reference and defect judgment boundary, so that subsequent microholes of the same type can preferentially use existing effective verification conditions to complete the boundary evidence supplementation. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the overall process for visual inspection of micro-hole displacement;

[0053] Figure 2 This is a schematic diagram of the initial detection image formation and anomaly acquisition and processing for micropores.

[0054] Figure 3 This is a schematic diagram of the circumferential slot division and edge continuity marking;

[0055] Figure 4 A schematic diagram showing the formation of the central feasible region and the offset feasible region;

[0056] Figure 5 A schematic diagram is created to determine the boundary crossing status and direction;

[0057] Figure 6 A schematic diagram illustrating the shrinkage of the feasible region and the determination of the dominant uncertain boundary slot.

[0058] Figure 7 A schematic diagram illustrating the determination of complementary verification lighting conditions and the acquisition of formal verification images;

[0059] Figure 8 This is a schematic diagram for verifying local registration and validity of images;

[0060] Figure 9 A schematic diagram illustrating the relationship between candidate boundary combinations and geometric position preservation.

[0061] Figure 10 Schematic diagram for the formation of evidence at the stationed boundary and the redefinition of the central feasible region;

[0062] Figure 11 This is a schematic diagram of the updated feasible region of offset and the determination of the micropore offset defect status;

[0063] Figure 12 A schematic diagram illustrating the formation and sorting of confirmed boundary slots and priority acquisition records;

[0064] Figure 13 This is a schematic diagram for subsequent micro-hole priority acquisition and recording recall and rollback closed loop. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0066] Example: Combined with Appendix Figures 1-13This embodiment provides a visual inspection method for microvia misalignment on high-density interconnect circuit boards, including:

[0067] Step 1: Obtain the initial microvia inspection image, divide the aperture boundary slots and target pad boundary slots according to the circumferential reference, and mark the effective boundary slots and the boundary slots to be confirmed based on the edge continuity. The specific implementation is as follows:

[0068] After the high-density interconnect circuit board enters the micro-hole visual inspection station, the inspection control unit moves the micro-hole to be inspected to the imaging area according to the current board identification and the design hole position record. While the board is kept fixed, the industrial imaging device is triggered to acquire the original image of the area where the current micro-hole is located.

[0069] The design hole position record is derived from the manufacturing design file corresponding to the current board. The design hole position of the current microhole is converted to the current image coordinates by the board surface positioning mark and serves as the fixed origin for dividing the circumferential position in this step. The position obtained later based on the hole edge is not used to replace this origin.

[0070] After the industrial imaging device completes the acquisition, it first checks whether the original image completely covers the detection area centered on the fixed origin, capable of accommodating the complete aperture and the edge of the target pad presented through the aperture. At the same time, it checks the changes in the board position and the image clarity during exposure. The image clarity is judged according to the clarity check area and clarity threshold locked by the current imaging parameter version. When all clarity check positions in the aperture detection area fail to reach the clarity threshold, it is recorded as a whole area out of focus. Only when the coverage area meets the preset detection area, the changes in the board position do not exceed the position tolerance range specified by the current imaging parameter version, and there is no whole area out of focus, is the original image registered as the initial micro-hole detection image.

[0071] Original images that do not meet the aforementioned conditions will only retain acquisition traces and will not be used for boundary slot division. They will be reacquired within the number of reacquisitions allowed at the current workstation. If a qualified image is not formed after reaching the number of reacquisitions, the current microhole will be registered as a state pending inspection. Initial microhole detection images will not be generated by supplementing adjacent microhole images, historical images at the same location, or design graphics.

[0072] After the initial microvia detection image is formed, the translational and angular deviations of the entire image relative to the fixed coordinates of the detection station are corrected based on the actual position of the board positioning mark in the image. This correction only changes the coordinate assignment of the entire image and does not change the existing relative geometric position between the aperture and the target pad. Subsequently, isolated pixels are checked according to the fixed neighborhood range and minimum number of similar adjacent pixels locked by the current imaging parameter version. Only when the number of similar adjacent pixels in the fixed neighborhood of a certain bright or dark pixel is lower than the minimum number of similar adjacent pixels is it removed as a separate bright spot or a separate dark spot. Pixels that have formed continuous edge directions must not be deleted, and edges must not be added to positions where there is no pixel information in the original image.

[0073] After the sorting is completed, a circumferential reference is established with the fixed origin after the design hole position is mapped to the current image. The horizontal positive direction of the board manufacturing coordinate is taken as the circumferential starting direction, and the circumferential position is divided in sequence according to the locked rotation direction. All microholes in the same batch adopt the same starting direction and rotation direction. When the board is loaded in a different direction, the manufacturing coordinate direction is restored first according to the board surface positioning mark, and then the circumferential division is performed.

[0074] Both the orifice boundary slot and the target pad boundary slot are divided using the fixed origin, the circumferential starting direction, the rotation direction, and the same set of radial dividing lines. The radial range of the orifice edge is pre-locked based on the design orifice diameter, corresponding manufacturing acceptance tolerance, edge position measurement tolerance, and the maximum allowable deviation range of the orifice center as specified in the current product inspection rules in the manufacturing design documents. The radial range of the target pad edge is pre-locked in each circumferential direction based on the target pad design shape, corresponding manufacturing acceptance tolerance, edge position measurement tolerance, and the maximum allowable deviation range of the target pad center in the manufacturing design documents. For each circumferential inspection position, the position where the radial line extending from the fixed origin along the circumferential direction intersects with the design edge contour corresponding to the current boundary type is determined as the design edge radial position corresponding to that circumferential position. Image areas falling between two adjacent radial dividing lines and located within the radial range of the orifice edge form the corresponding orifice boundary slot, and image areas falling between the same set of radial dividing lines and located within the radial range of the target pad edge presented through the orifice form the corresponding target pad boundary slot, thereby ensuring that the same slot sequence always corresponds to the same circumferential direction.

[0075] Edge points located on the radial dividing line are uniformly assigned to the slots reached after rotation, and are not recorded repeatedly in adjacent slots.

[0076] For each via boundary slot and target pad boundary slot, the detection control unit starts from the starting circumferential position of the slot and sequentially sets circumferential inspection positions along the locking rotation direction according to the pre-locked circumferential inspection position spacing of the current edge judgment rule. It then checks the brightness changes of adjacent pixels radially along each circumferential inspection position. If the distance between the ending circumferential position of the slot and the previous inspection position is less than one circumferential inspection position spacing, no additional inspection position is set. When there are consecutive bright-dark transitions in the same direction radially, the number of consecutive positions reaches the minimum number of consecutive positions locked by the current edge judgment rule, and the brightness change amplitude reaches the corresponding threshold, the corresponding position is registered as the actual edge point of the slot. Single positional abrupt changes, repeated changes in the bright-dark transition direction between adjacent inspection positions, or bright-dark boundaries located within a continuous saturation region are not registered as actual edge points.

[0077] The actual edge points in the same slot are arranged sequentially according to their circumferential positions. When the circumferential position interval between adjacent actual edge points does not exceed the connection interval specified by the current edge continuity rule, they are included in the same actual edge segment. When the connection interval is exceeded, the current actual edge segment is terminated and the next actual edge segment begins. Missing interval positions in the original image are only recorded as empty and no virtual edge points are generated.

[0078] Edge continuity is determined by the actual coverage of the actual edge segments within the slot's circumferential range, the maximum gap length, and the dispersion of the actual edge points. First, the circumferential coverage intervals of each actual edge segment are unioned, and the coverage is determined by the ratio of the total coverage length of this union to the inspectable circumferential length of the current slot. The maximum gap length is the maximum length among the consecutive gap intervals within the inspectable circumferential range of the current slot that are not covered by the aforementioned union. The gap intervals include uncovered intervals located at the slot's start or end boundaries. For each circumferential inspection position with actual edge points, if there is only one actual edge point, the radial position of that actual edge point is taken as the edge position of the current circumferential inspection position. If there are two or more actual edge points, the midpoint between the radial positions of the innermost and outermost actual edge points is taken as the edge position of the current circumferential inspection position. For two adjacent circumferential inspection positions within the same actual edge segment, the radial variation between the actual edge positions and the radial variation between the corresponding design edge radial positions are obtained. The absolute value of the difference between the two is taken as the local position variation difference of the adjacent positions. The maximum local position variation difference among all actual edge segments of the current slot is taken as the position dispersion degree of the slot. Actual edge segments containing only one circumferential inspection position do not have their position dispersion degree increased separately. When there are no actual edge points in the current slot, or when all actual edge segments in the current slot contain only one circumferential inspection position, the position dispersion degree is recorded as 0. Slots without actual edge points cannot be marked as valid boundary slots due to coverage conditions. Thus, the actual edge points at different circumferential positions are compared after uniformly eliminating the radial variation caused by the design contour itself according to their corresponding design edge radial positions.

[0079] The three indicators are compared with the coverage threshold, gap threshold and location dispersion threshold pre-locked in the current edge continuity rules. Only when the coverage reaches the coverage threshold, the maximum gap length does not exceed the gap threshold, and the location dispersion does not exceed the location dispersion threshold, is the slot marked as a valid boundary slot. If any one of the conditions is not met, the slot is marked as a boundary slot to be confirmed.

[0080] Since only images that completely cover the specified detection area can form the initial microvia detection image, each aperture boundary slot and target pad boundary slot entering the slot marking stage are within the effective field of view, and ultimately only one of the valid boundary slots or the boundary slots to be confirmed can be marked. There is no simultaneous marking state, and the marking in this round is not changed in reverse according to the subsequent detection results.

[0081] When localized highlighting causes consecutive pixels in a certain slot to reach the saturation value specified in the imaging parameter version, the area inside the saturated region is not considered as an actual edge. When there are multiple actual edge segments in the same slot, they are still judged uniformly according to the aforementioned coverage, maximum gap length and position dispersion, without setting additional manual selection rules.

[0082] After completing the arrangement of all slots, write the current microvia boundary record in the slot order according to the circumferential reference. Record at least the associated board identifier, microvia identifier, microvia initial detection image identifier, the slot to which the slot belongs or the target pad boundary slot, slot order, actual edge point position, actual edge segment range, edge continuity, and three comparison results, as well as the mark of the effective boundary slot or the boundary slot to be confirmed.

[0083] The recording sequence is fixed as follows: first, lock the initial micropore detection image; then, lock the slot division result; then, write the actual edge points and actual edge segments; finally, form the slot marker. Each subsequent record can only reference the previous record and must not overwrite the previous record.

[0084] The same board identifier, micro-hole identifier, and initial micro-hole detection image identifier constitute the unique record ownership for the current step. Duplicate submissions with the same ownership will not generate slot records again. Slots in the same image are written in the locked circumferential order, and duplicate slots in the same order must not be written.

[0085] Imaging parameters, circumferential division rules, edge determination rules, and edge continuity rules are all locked in version before the start of the current batch detection. Rule adjustments during batch detection generate new versions, which only apply to the newly formed initial micropore detection image and do not cover the current micropore boundary record that has already been completed. The original image, initial micropore detection image, rule version, actual edge record, and slot mark are kept correlated and traced.

[0086] The records generated in this step serve only as evidence for the quality inspection of micro-holes on the circuit board. They do not directly modify the drilling equipment or processing parameters, and access to the records is limited to the scope authorized for the current inspection task.

[0087] The valid boundary slots and the boundary slots to be confirmed, together with the corresponding actual edge records, are handed over to the next step for reading in the locking order. The next step shall not change the slot markings on its own without obtaining new records of the current step.

[0088] Preferably, in a set of online detection conditions, the image spatial resolution can be set to 1 pixel corresponding to 1 micrometer to 3 micrometers, the specified detection area can cover the outer side of the designed aperture by no less than 0.5 times the radial margin of the designed aperture, the allowable range of plate position change can be set to 2 pixels, the number of re-acquisitions can be set to 2 times, the interval between adjacent re-acquisitions can be set to 100 milliseconds, the circumferential reference can be divided into 16 slots, each slot covering 22.5 degrees, and a valid boundary slot is marked when the continuous actual edge coverage reaches 60%, the maximum gap length does not exceed 5 pixels, and the position dispersion does not exceed 3 pixels; for example, if 13 of the 16 aperture boundary slots of the current microhole simultaneously meet the above 3 conditions, then the 13 slots are marked as valid boundary slots, and the remaining 3 slots are marked as boundary slots to be confirmed.

[0089] On-site spot checks can be conducted by randomly selecting no less than 100 microholes from each batch of tested boards. The slot division position and slot marking are then checked against the saved initial microhole test images. If the slot assignment consistency rate reaches 99% or more and there are no duplicate markings for the same slot, the current rule version is maintained; otherwise, the rule version is suspended from being used for new batches.

[0090] As an alternative implementation method, the number of circumferential slots can be adjusted according to the microvia design aperture and image spatial resolution. As long as the same detection rule version still uses a fixed origin, a unified circumferential reference and the same set of radial boundary lines, so that the slots at the aperture boundary correspond one-to-one with the slots at the target pad boundary, and continues to mark the unique valid boundary slots and the boundary slots to be confirmed according to the coverage of the actual edge segments, the maximum gap length and the degree of positional dispersion, it can be implemented in the same way.

[0091] Step 2: Utilize the effective boundary slots to form the feasible region at the orifice center, the feasible region at the target pad center, and the feasible region for offset. Determine the boundary crossing state based on the overlap between the feasible region for offset and the allowed offset region. Specifically, the implementation is as follows:

[0092] After the effective boundary slots and corresponding actual edge records of the current microvias are locked, the detection control unit reads all effective orifice boundary slots and all effective target pad boundary slots corresponding to the same board identifier, the same microvia identifier, and the same initial detection image identifier of the microvia. At the same time, it reads the locked orifice allowable geometric size range, target pad allowable geometric size range, center candidate position arrangement spacing, orifice center candidate position search range, and target pad center candidate position search range in the current product detection rule version.

[0093] The allowable geometric dimensions of both the orifice and the target pad are derived from the nominal dimensions specified in the current board manufacturing design document, combined with the corresponding manufacturing acceptance tolerances, and uniformly converted to the physical length units corresponding to the current microvia initial inspection image. The spacing between candidate center positions is a fixed interval between two adjacent candidate center positions in the horizontal or vertical direction of the image coordinates. The candidate position grid uses a fixed origin as the grid reference, and the horizontal and vertical directions of the grid are consistent with the horizontal and vertical directions of the board manufacturing coordinates, respectively, and remain unchanged during the formation of the feasible domain of the same microvia. The search range for the orifice center candidate position is centered on the position of the designed orifice mapped to the current microvia initial inspection image, and the search range for the target pad center candidate position is centered on the position of the target pad design center mapped to the current microvia initial inspection image in the manufacturing design document. When the designed orifice and the target pad design center coincide, they share a fixed origin as the center of the search range. The boundaries of the search range for each candidate center position are determined by the corresponding maximum allowable position deviation range pre-specified by the current product inspection rules, and are not temporarily expanded based on the current actual edge position.

[0094] The above parameters are locked in version before the current micropore begins to form the central feasible region. The boundary slot to be confirmed is not included in the limitation of this step, and the missing edges in the boundary slot to be confirmed are not supplemented according to the design graphics, historical images and adjacent micropore records.

[0095] The detection and control unit first defines the feasible region of the orifice center using the effective orifice boundary slots. Within the orifice center candidate position search range, the orifice center candidate positions are arranged sequentially according to the locked center candidate position arrangement spacing. For each orifice center candidate position, the actual edge points in all effective orifice boundary slots are read one by one.

[0096] For circular orifices, with the current candidate center position as a reference, the actual radial distance from the candidate center position to each actual edge point is determined. The minimum allowable radius limited by the allowable geometric size range of the orifice is reduced by the edge position measurement tolerance locked by the current edge position measurement tolerance version, and the maximum allowable radius is added to the edge position measurement tolerance. Together, they constitute the orifice boundary tolerance zone corresponding to the candidate center position. All slots of the same micro-hole adopt the same edge position measurement tolerance, and no individual adjustment is made for a single slot.

[0097] The current candidate position of the orifice center is retained only when all the actual edge points in the valid orifice boundary slots are within the corresponding orifice boundary allowable zone; any candidate position is excluded if any actual edge point exceeds the orifice boundary allowable zone.

[0098] All retained candidate positions of the orifice center are directly used to form the feasible region of the orifice center according to the original image coordinates. The feasible region of the orifice center is recorded in this step using the set of retained candidate positions, without expanding the set by circumscribed contour, fitted curve and automatic point filling. Therefore, when adding effective boundary constraints in the future, only positions that do not meet the conditions can be excluded from the original retained candidate positions, and no new candidate positions that did not meet the previous constraints can be added.

[0099] If there are no candidate locations that can simultaneously satisfy all valid orifice boundary slots, then the feasible region of the orifice center will not be formed. The current micro-orifice will stop the subsequent formation process of this step and enter the detection and verification state. At the same time, the record of the valid boundary slots that caused all candidate locations to be excluded and the corresponding rule version will be retained. The allowable geometric size range of the orifice, the measurement tolerance of the edge position, and the search range of the candidate location of the orifice center will not be automatically widened.

[0100] After the feasible region of the orifice center is formed, within the search range of the target pad center candidate positions, the target pad center candidate positions are arranged sequentially according to the same coordinate origin, the same coordinate direction, the same physical length unit, the same center candidate position arrangement spacing, and the same center candidate position grid, and the feasible region of the target pad center is defined by the effective target pad boundary slot.

[0101] For circular target pads, the minimum allowable radius defined by the geometric size range of the target pad minus the locked edge position measurement tolerance, plus the maximum allowable radius plus the edge position measurement tolerance, together form the target pad boundary tolerance zone. The actual radial distance from each candidate position of the target pad center to all valid actual edge points of the target pad is checked one by one. Only candidate positions where all actual edge points fall within the target pad boundary tolerance zone are retained. All retained positions directly constitute the feasible region of the target pad center.

[0102] If there are no candidate positions that satisfy the boundary slots of all valid target pads, the subsequent formation process will stop and the process will be switched to the inspection and verification state if the feasible region of the orifice center fails to be formed. The allowable geometric size range of the target pad, the edge position measurement tolerance, and the search range of the candidate position of the target pad center will not be automatically widened. The design center, historical inspection center, and adjacent target pad center will not be used to replace the current feasible region of the target pad center.

[0103] After the feasible regions for the orifice center and the feasible regions for the target pad center are formed, the feasible region for offset is formed accordingly. Specifically, according to the positive lateral and longitudinal directions already locked in the board manufacturing coordinates, each candidate position of the orifice center in the feasible region for the orifice center is combined with each candidate position of the target pad center in the feasible region for the target pad center. The corresponding candidate offset position is determined by the difference in lateral and longitudinal positions of the candidate position of the orifice center relative to the candidate position of the target pad center. The offset direction is always recorded according to the direction of "orifice center relative to target pad center". It is not allowed to exchange reference objects in the same inspection record.

[0104] All candidate offset positions obtained by combination are directly formed into the offset feasible region after deduplication of the same coordinate position. When the same candidate offset position is repeatedly formed by combination of multiple center positions, only one position record is retained, without increasing the weight or changing its position attribute in the offset feasible region.

[0105] Then, the allowed offset domains locked in the current product inspection rule version are read. The offset positions are recorded using relative displacement coordinates. The zero offset position corresponding to the center of the hole and the center of the target pad is in the same position is used as the origin of the offset coordinates. The positive directions of the horizontal and vertical directions follow the corresponding positive directions of the board manufacturing coordinates. The allowed offset domains are established using the same zero offset position, the same coordinate direction, and the same physical length unit. Their shape and range are directly derived from the current product micro-hole alignment acceptance requirements. The boundary of the allowed offset domain belongs to the allowed offset domain itself. Candidate offset positions located on this boundary are recorded according to the allowable range, not according to the out-of-limit position.

[0106] The detection and control unit determines the boundary crossing state based on the overlap between the feasible offset domain and the allowable offset domain. First, it establishes the adjacency relationship between candidate offset positions within the feasible offset domain according to the spacing of the center candidate positions. When the difference between two candidate offset positions in both the horizontal and vertical coordinates does not exceed one spacing of the center candidate positions, and their coordinates are not completely the same, they are recorded as adjacent candidate offset positions. Candidate offset positions that can be connected one by one through consecutive adjacent candidate offset positions are grouped into the same continuous position group.

[0107] The current micropore formation determination boundary crossing state is determined only when there are both candidate offset positions strictly located inside the allowable offset domain and candidate offset positions strictly located outside the allowable offset domain within the same continuous position group.

[0108] When the entire feasible offset region is located within the allowable offset region, the entire feasible offset region is located outside the allowable offset region, the only candidate offset positions located at the boundary of the allowable offset region and one side thereof, or the internal candidate offset positions and the external candidate offset positions are located in a continuous group of unconnected positions, it is uncertain whether the state is a boundary crossing state.

[0109] For current micropores that have not yet formed a boundary crossing state, they will not proceed to the subsequent determination and verification of the dominant uncertain boundary slot. When all candidate offset positions in the feasible offset region belong to the allowable offset region, the micropore offset defect status is directly recorded as "no detected offset defect." When none of the candidate offset positions belong to the allowable offset region, the micropore offset defect status is directly recorded as "detected offset defect." Other cases where a boundary crossing state has not yet formed and there are candidate offset positions belonging to both the allowable and non-allowable offset regions are registered as "to be checked." Only current micropores that have formed a boundary crossing state proceed to step three.

[0110] The current steps are executed in a fixed order: forming the feasible region at the center of the orifice, forming the feasible region at the center of the target pad, forming the offset feasible region, and confirming the overlapping relationship. The next record can only reference the previous locked record. It is not allowed to delete the effective boundary slot or modify the spacing of the center candidate position to change the already formed feasible region.

[0111] The record should be associated with at least the board identifier, microvia identifier, initial microvia detection image identifier, effective boundary slot record identifier, orifice allowable geometry range version, target pad allowable geometry range version, edge position measurement tolerance version, center candidate position arrangement spacing, orifice center candidate position search range, target pad center candidate position search range, orifice center feasible region, target pad center feasible region, offset feasible region, allowable offset region version, and judgment boundary crossing status. Duplicate submissions with the same board identifier, microvia identifier, initial microvia detection image identifier, and rule version will not form new feasible region records. The new version will only apply to newly started detection records and will not overwrite currently locked results.

[0112] The resulting offset feasible region and the determination of the boundary crossing status are recorded and locked in this step and then handed over to the next step for reading. The next step must not modify the effective boundary slot, the two center feasible regions, and the version of the allowed offset region used in this step.

[0113] Preferably, in a set of online microvia detection conditions, the orifice design diameter can be set to 100 micrometers, the orifice allowable radius range can be set to 48 micrometers to 52 micrometers, the target pad allowable radius range can be set to 108 micrometers to 112 micrometers, the edge position measurement tolerance can be set to 1 micrometer, the center candidate position arrangement spacing can be set to 1 micrometer, and the allowable offset domain can be set to a closed area centered on the zero offset position with an allowable offset distance not exceeding 50 micrometers; in the offset feasible domain formed after being limited by the effective boundary slot, when there is an internal candidate offset position with an offset distance of 47 micrometers and an external candidate offset position with an offset distance of 54 micrometers in the same continuous position group, the judgment boundary crossing state is determined.

[0114] As an alternative implementation, for target pads with fixed non-circular design contours, the target pad design contour can be extended to both sides of the contour according to manufacturing acceptance tolerances and edge position measurement tolerances to form a target pad boundary allowable zone, while keeping the target pad design direction consistent with the board manufacturing coordinate direction. Then, the candidate center position of the target pad is selected according to whether the actual edge points of all valid target pads are located within the target pad boundary allowable zone, while the formation caliber of the remaining center feasible region, offset feasible region and determination boundary crossing state remains unchanged.

[0115] Step 3: When the offset feasible region crosses the boundary of the allowable offset region, determine the crossing direction of the judgment boundary, calculate the feasible region shrinkage of the boundary slot to be confirmed, and take the first slot in the sorting as the dominant uncertain boundary slot. The specific implementation is as follows:

[0116] After the current microvia has formed a boundary crossing state, the detection control unit reads the corresponding offset feasible region, allowable offset region, aperture center feasible region, target pad center feasible region and all boundary slot records to be confirmed for the microvia, and determines the boundary crossing direction based on the boundary crossing state.

[0117] This step only organizes consecutive position groups that simultaneously have candidate offset positions strictly located inside and strictly located outside the allowed offset domain. For each consecutive position group, the shortest straight-line distance between each internal candidate offset position and each external candidate offset position in the same consecutive position group under the same horizontal and vertical coordinates is compared. From all the comparison results, the internal and external candidate offset positions with the smallest distance are selected, and the direction from the internal candidate offset position to the external candidate offset position is determined as the decision boundary crossing direction.

[0118] When multiple sets of the same minimum distance exist, first arrange the internal candidate offset positions in ascending order of horizontal coordinates and vertical coordinates, and then arrange the external candidate offset positions in ascending order of horizontal coordinates and vertical coordinates. Take the first set of sorted positions to determine the decision boundary crossing direction. When different consecutive position groups all have the aforementioned position combinations, continue to determine a unique set of positions in the position combinations formed by all consecutive position groups according to the same minimum distance and coordinate sorting rules, so that the same feasible region and allowable offset region can only obtain one decision boundary crossing direction.

[0119] After determining the boundary crossing direction, a direction axis is established that passes through the zero offset position and is parallel to that direction. The boundary crossing direction is defined as the positive direction of the direction axis. All candidate offset positions in the current feasible offset region are vertically projected onto this direction axis. The corresponding directed projection positions are recorded according to the relationship between each projection position and the zero offset position on the direction axis. The physical distance between the maximum and minimum projection positions among all directed projection positions is taken as the original range length of the current feasible offset region along the boundary crossing direction. When the current feasible offset region contains only one candidate offset position, the original range length is recorded as 0. All subsequent feasible region shrinkage amounts are determined using the same direction axis and do not change direction due to different boundary slots to be confirmed.

[0120] Then, following the slot order locked in the previous step, the feasible domain shrinkage of each unconfirmed boundary slot is calculated one by one.

[0121] For the orifice boundary slot, a fixed origin is used as the location point grid reference, and the horizontal and vertical directions of the board manufacturing coordinates are used as the grid directions. Within the radial range of the orifice edge pre-locked for the boundary slot to be confirmed, location points are set according to the spacing of the candidate center positions. Each location point is checked one by one to see if it can form a geometric relationship with at least one candidate orifice center position in the current feasible region of the orifice center that satisfies the allowable geometric size range of the orifice and the measurement tolerance of the edge position. If it satisfies the relationship, the location point is retained as a possible boundary position for the current boundary slot to be confirmed; otherwise, it is excluded. For the target pad boundary slot, the same location point grid reference and grid direction are used to set location points within the radial range of the corresponding target pad edge. The possible boundary positions are screened according to the current feasible region of the target pad center, the allowable geometric size range of the target pad, and the measurement tolerance of the edge position.

[0122] When the hole and target pad are circular, the geometric relationship is confirmed by whether the actual distance from the center candidate position to the corresponding position falls within the range formed by the minimum allowable radius minus the edge position measurement tolerance to the maximum allowable radius plus the edge position measurement tolerance; a position is reserved as a possible boundary position as long as there is at least one center candidate position that meets this condition.

[0123] For target pads with fixed non-circular design contours, the target pad design contours, after being extended according to manufacturing acceptance tolerances and edge position measurement tolerances, are translated to the candidate center positions of each target pad. Whether a position point in the current boundary slot to be confirmed falls into the extended contour area corresponding to at least one candidate center position of the target pad is used to determine whether the position point is retained as a possible boundary position.

[0124] When the same location point is repeatedly supported by multiple candidate center locations, only one location record is retained, and its subsequent comparison weight is not changed as the number of times it is supported increases.

[0125] For each possible boundary location, temporarily treat this location as a new boundary constraint for the corresponding boundary slot to be confirmed, and re-select the corresponding candidate center location according to the same criteria used when forming the feasible center region in the previous step; when it belongs to the orifice boundary slot, retain the orifice center candidate location that simultaneously satisfies all the original valid orifice boundary slots and the constraint of the possible boundary location from the original feasible center region, and the original feasible center region of the target pad remains unchanged; when it belongs to the target pad boundary slot, retain the target pad center candidate location that simultaneously satisfies all the original valid target pad boundary slots and the constraint of the possible boundary location from the original feasible center region of the target pad, and the original feasible center region of the orifice remains unchanged, and no new candidate center locations outside the original feasible center region are allowed.

[0126] Based on the candidate positions of the orifice center and the target pad center after screening, candidate offset positions are recombined according to the offset direction and aperture of "orifice center relative to target pad center" locked in the previous step. Duplicate candidate offset positions are removed and projected onto the determined direction axis. The physical distance between the maximum and minimum projected positions after all candidate offset positions are projected according to the same direction axis and the same positive aperture is taken as the retention range length when the possible boundary position is valid. The retention range length is recorded as 0 when only 1 candidate offset position is retained, and the retention range length is also recorded as 0 when no candidate offset position is retained.

[0127] After performing the aforementioned screening on all possible boundary positions of the same boundary slot to be confirmed, the longest retention range length is taken as the conservative retention range length of the boundary slot to be confirmed. The non-negative length obtained by subtracting the conservative retention range length from the original range length of the current feasible region along the boundary crossing direction is determined as the feasible region shrinkage amount of the boundary slot to be confirmed.

[0128] The maximum retention range length is used as the comparison criterion, so that each boundary slot to be confirmed is uniformly compared according to the case that has the weakest constraint on the current offset feasible region among its possible boundary positions, thus avoiding the expansion of the feasible region shrinkage of the slot due to the pre-selection of a boundary position with a stronger constraint.

[0129] When no possible boundary position is formed in the unconfirmed boundary slot, its feasible domain shrinkage is recorded as 0, and the scattered actual edges in the unconfirmed boundary slot that have not yet reached the effective boundary slot condition are not used to replace the possible boundary position.

[0130] All unconfirmed boundary slots use the same decision boundary crossing direction, the same direction axis, the same center candidate position arrangement spacing, and the same edge position measurement tolerance version. Among them, the orifice boundary slots uniformly use the currently locked orifice allowable geometry range version, and the target pad boundary slots uniformly use the currently locked target pad allowable geometry range version. During the calculation, the corresponding diameter must not be changed for a single unconfirmed boundary slot.

[0131] After completing the shrinkage of all feasible regions, arrange all the boundary slots to be confirmed in descending order of the shrinkage amount of the feasible region. When the shrinkage amounts of the feasible regions are the same, arrange them from front to back according to the slot order under the circumferential reference. When the same slot order has both the hole boundary slot and the target pad boundary slot, arrange the hole boundary slot before the target pad boundary slot, thus forming a unique sorting result.

[0132] The first unconfirmed boundary slot in the sorting is identified as the dominant uncertain boundary slot. The current step does not change the original unconfirmed boundary slot marker of this slot, nor does it write the possible boundary positions temporarily used during the calculation of the feasible region shrinkage into the actual edge record.

[0133] The generated record associates the board identifier, microvia identifier, offset feasible region record identifier, allowed offset region version, decision boundary crossing direction, direction axis, unconfirmed boundary slot identifier, set of possible boundary positions corresponding to each unconfirmed boundary slot, conservative retention range length, feasible region shrinkage, sorting order, and dominant uncertain boundary slot identifier. It also associates the hole center feasible region version, target pad center feasible region version, hole allowable geometry range version, target pad allowable geometry range version, and edge position measurement tolerance version referenced in this round. When the same microvia is repeatedly executed under the same preceding record and the same rule version, the locked result is used, and different sorting records are not generated repeatedly.

[0134] If there are no unconfirmed boundary slots in the current microwell, no dominant uncertain boundary slot will be formed and the process will switch to the detection pending verification state. The remaining microwells will continue to be detected in the current batch.

[0135] Once the dominant uncertain boundary slots and the direction of boundary crossing are recorded and locked, they are handed over to the next step for reading. The next step must not modify the feasible domain shrinkage and sorting results already formed in this step.

[0136] Preferably, in a set of online detection conditions, the original range length of the current offset feasible domain along the direction of the decision boundary crossing can be set to 18 micrometers. The maximum retained range length formed by each possible boundary position corresponding to the first aperture to be confirmed boundary slot is 7 micrometers, and its feasible domain shrinkage is 11 micrometers. The maximum retained range length corresponding to the second target pad to be confirmed boundary slot is 10 micrometers, and its feasible domain shrinkage is 8 micrometers. The feasible domain shrinkage of the remaining to be confirmed boundary slots does not exceed 6 micrometers. Then, the aperture to be confirmed boundary slot with a feasible domain shrinkage of 11 micrometers is ranked first and determined as the dominant uncertain boundary slot.

[0137] As an alternative implementation, the spacing between the location points in the area covered by the boundary slot to be confirmed can be set to a fixed spacing smaller than the spacing between the central candidate locations. However, all the boundary slots to be confirmed still use the same fixed origin as the location point grid reference, adopt the same grid direction and uniform location point spacing, and continue to form the feasible domain shrinkage amount according to the difference between the conservatively retained range length and the original range length. This can be implemented in the same way.

[0138] Step 4: Determine the complementary verification illumination conditions based on the circumferential position of the dominant uncertain boundary slot, keep the imaging position fixed, and acquire verification images sequentially. The specific implementation is as follows:

[0139] The detection and control unit reads the dominant uncertain boundary slot record that has been locked in the previous stage, and reads the fixed origin, circumferential starting direction, rotation direction and the starting and ending radial boundary positions of the slot used in the record. The circumferential position is determined by the middle direction of the angle interval covered by the dominant uncertain boundary slot along the locked rotation direction from the starting radial boundary position to the ending radial boundary position. When the slot crosses the circumferential starting position, the ending radial boundary position is continuously expanded along the locked rotation direction before determining the middle direction. The middle position is not directly calculated according to the smaller angle value, so that the same dominant uncertain boundary slot forms a unique circumferential position under the same circumferential reference.

[0140] The complementary nucleus lighting conditions are then determined based on the circumferential position of the dominant uncertain boundary slot.

[0141] When using a ring-shaped zoned lighting device, the center lighting direction of each lighting zone is recorded before the equipment is put into testing. All center lighting directions are represented by the same fixed origin, circumferential starting direction and rotation direction as the circumferential reference. The lighting zone with the smallest angle difference between the center lighting direction and the circumferential position of the dominant uncertain boundary slot is selected as the first lighting zone. If there are two lighting zones with the same minimum angle difference, the lighting zone reached after locking the rotation direction is selected.

[0142] The center illumination direction of the first illumination zone is rotated 180 degrees circumferentially to form a complementary target direction. Then, the illumination zone with the smallest angle difference between the center illumination direction and the complementary target direction is selected from the remaining illumination zones as the second illumination zone. If the same minimum angle difference occurs, the illumination zone reached after the locked rotation direction is still selected. The first and second illumination zones must be different illumination zones. If the existing lighting device cannot form two different illumination zones, the current round will not continue to collect verification images and the current micro-hole will be switched to the detection pending verification state.

[0143] The first illumination condition corresponding to the first illumination zone and the second illumination condition corresponding to the second illumination zone together form complementary verification illumination conditions. Each illumination condition locks at least the illumination zone, the central illumination direction, the illumination brightness, and the illumination stabilization time. The two illumination conditions for the same current micro-hole adopt the illumination brightness predetermined in the current verification imaging parameter version. When the same product inspection rule version specifies that the two illumination directions use the same brightness level, the camera exposure time, imaging gain, focal plane position, and imaging magnification remain unchanged, so that the acquisition conditions actively changed between the two verification images are limited to the illumination direction.

[0144] For products for which the current product testing rules have pre-defined two lighting directions with different brightness levels, the two lighting conditions shall be read from the pre-locked lighting brightness of this version, and the subsequent lighting conditions in this round shall not be temporarily changed based on the currently obtained verification images.

[0145] After the complementary verification illumination conditions are formed, the imaging position is kept fixed. The fixed imaging position is defined as the period from the start of this step at the current micro-hole until all formal verification images are acquired. The planar position and board orientation of the circuit board relative to the industrial imaging device, the optical axis position of the industrial imaging device, the working distance, the focal plane position, and the imaging magnification are all kept within the corresponding allowable range locked in the current imaging parameter version.

[0146] During on-site verification, the position record of the positioning platform carrying the circuit board is read before each formal acquisition, and the current position of the board is checked against the board surface positioning mark used in the initial micro-hole detection image. If a position coding device is set, the position record of the corresponding motion mechanism of the industrial imaging device is read at the same time. Only when the change of the current board surface position relative to the beginning of this step, the change of the board surface direction, and the change of the position of the industrial imaging device do not exceed the corresponding allowable range locked by the current imaging parameter version, is the imaging position confirmed to be fixed.

[0147] If a positional change exceeds the permissible range under different lighting conditions, all officially verified images obtained in this round will be disqualified from this round, and the images before and after the positional change will not be submitted to the next stage together; once the current microaperture is restored to meet the imaging position fixation conditions, complete acquisition will restart from the first lighting condition.

[0148] After the imaging position is confirmed, the lighting conditions are switched sequentially according to the order of complementary verification lighting condition locking. First, the directional lighting zone that does not belong to the first lighting condition is closed, and then the first lighting zone is enabled. When the lighting status feedback signal is set, the industrial imaging device is triggered to acquire the first verification image after the actual lighting brightness enters the lock tolerance range corresponding to the target lighting brightness and is continuously maintained until the lock stabilization time is reached. When the lighting status feedback signal is not set, the fixed stabilization time determined by the equipment calibration stage and written into the current verification imaging parameter version is waited before the acquisition is triggered.

[0149] After the first verification image is acquired, the first illumination zone is turned off, the second illumination zone is turned on, and the second verification image is acquired using the same stable verification caliber.

[0150] The image acquired under each lighting condition must completely cover the detection area corresponding to the initial micro-hole detection image. The current imaging position must still be within the locked allowable range, and there must be no area of ​​complete defocus, complete saturation, or complete underexposure in the area corresponding to the dominant uncertain boundary slot. Complete defocus is determined according to the sharpness check position and sharpness threshold locked in the current verification imaging parameter version. When all sharpness check positions in the area corresponding to the dominant uncertain boundary slot fail to reach the sharpness threshold, it is determined to be complete defocus. Complete saturation is determined by whether the proportion of pixels in the area corresponding to the dominant uncertain boundary slot that reach or exceed the locked pixel brightness upper limit reaches the total number of collectable pixels in that area and meets the saturation pixel ratio threshold locked in the current verification imaging parameter version. Complete underexposure is determined by whether the proportion of pixels that are lower than or equal to the locked pixel brightness lower limit reaches the corresponding underexposure pixel ratio threshold in the total number of collectable pixels in that area. The first image that meets the above conditions is registered as the official verification image for that lighting condition; images that do not meet any of the conditions are only retained as acquisition records and do not proceed to the next stage.

[0151] If no formal verification image is obtained under the same lighting conditions, the image is re-acquired under the same lighting conditions according to the allowed number of acquisitions specified in the current version of the verification imaging parameters, without changing the lighting direction, to replace the image missing under the previous lighting conditions; if no formal verification image is obtained after reaching the allowed number of acquisitions, the current micro-orifice is put into the detection pending verification state.

[0152] Once a formal verification image has been obtained under the first illumination condition, the first formal verification image can continue to be used during the re-acquisition under the second illumination condition, as long as the imaging position remains within the locked allowable range. If the imaging position exceeds the allowable range, both illumination conditions will be re-acquired from the first illumination condition.

[0153] After both lighting conditions generate formal verification images, they are associated and saved in a fixed order according to the first and second lighting conditions. Each verification image is associated with at least the board identifier, micro-hole identifier, dominant uncertain boundary slot identifier, circumferential position of the dominant uncertain boundary slot, complementary verification lighting condition version, lighting condition sequence, lighting zone, central lighting direction, lighting brightness, camera exposure parameters, imaging position record, and acquisition time. The same board identifier, micro-hole identifier, dominant uncertain boundary slot identifier, and complementary verification lighting condition version correspond to the same round of verification acquisition. Only one formal verification image is retained for the same lighting condition sequence. Qualified images obtained repeatedly are only used for acquisition record keeping and do not replace the locked formal verification images.

[0154] This step does not confirm the boundary positions in the verification image, does not merge images obtained under different lighting conditions, and does not reverse the dominant uncertain boundary slots and complementary verification lighting conditions based on the content of the verification image. The two completed formal verification images, along with the corresponding complementary verification lighting conditions, are handed over to the next step for reading in the locked order.

[0155] Preferably, in a set of online detection conditions, the annular partition lighting device can be uniformly set with 16 lighting partitions along the circumference. When the angle difference between the circumferential position of the dominant uncertain boundary slot and the center lighting direction of the 5th lighting partition is less than the angle difference between it and the center lighting directions of other lighting partitions, the 5th lighting partition is determined as the 1st lighting partition, and its complementary target directions are 180 degrees apart, corresponding to the 13th lighting partition being determined as the 2nd lighting partition. The lighting brightness of both lighting partitions can be set to 60% of the rated brightness, the camera exposure time can be set to 1 millisecond, the lighting stabilization time can be set to 20 milliseconds, the allowable range of plate plane position change can be set to 2 micrometers, the allowable range of plate surface direction change can be set to 0.02 degrees, the allowable range of industrial imaging device working distance change can be set to 5 micrometers, and each lighting condition allows for 2 acquisitions. Under the condition that the imaging position continuously meets the above allowable ranges, the verification image corresponding to the 5th lighting partition and the verification image corresponding to the 13th lighting partition are obtained sequentially.

[0156] As an alternative implementation, a directional lighting device capable of changing the lighting orientation around the optical axis of the industrial imaging device can be used. The first lighting direction is set to a pre-calibrated executable lighting direction with the smallest angular difference from the circumferential position of the dominant uncertain boundary slot. The second lighting direction is set to another pre-calibrated executable lighting direction with the smallest angular difference from the complementary target direction obtained by rotating the first lighting direction by 180 degrees. By maintaining the imaging position fixed and the acquisition sequence of the first lighting condition preceding the second lighting condition, the same formation process can be implemented.

[0157] Step 5: Locally register the initial micropore detection image and the verification image, form residency boundary evidence based on the geometric positional relationship of the candidate boundaries, and redefine the corresponding feasible region. The specific implementation is as follows:

[0158] After the detection control unit obtains the initial detection image of the micropore corresponding to the current micropore and all formal verification images formed under the complementary verification illumination conditions of this round, it uses the initial detection image of the micropore as a fixed coordinate reference to perform local registration on each verification image.

[0159] Local registration only eliminates the overall planar position deviation and overall orientation deviation that may still exist under the condition of keeping the imaging position fixed, without changing the local dimensions and relative geometric relationships between the orifice, the target pad and its boundary.

[0160] The location reference is determined from the region outside the dominant uncertain boundary slot, which has been previously marked as a valid boundary slot. For each valid boundary slot that can be used as a location reference, the actual edge segment with the largest circumferential continuous length in the initial micro-hole detection image is selected as the location reference segment for that slot. When there are actual edge segments with the same continuous length, the actual edge segment with the first circumferential position along the locking rotation direction is selected. In each verification image, actual edge segments are formed within the same boundary type and the same slot according to the isolated pixel criterion, actual edge point formation rule, and actual edge segment formation rule locked in step one. When there are multiple actual edge segments, the actual edge segment with the largest overlapping length with the location reference segment in the initial micro-hole detection image is selected as the corresponding edge segment. When the overlapping lengths are the same, the actual edge segment with the larger circumferential continuous length is selected. When they are still the same, the actual edge segment with the first circumferential position along the locking rotation direction is selected. No missing edges in the verification image are filled in.

[0161] Local registration is only performed when there are valid boundary slots with corresponding edge segments in both the initial micropore detection image and all formal verification images. The smaller circumferential angle between the middle directions of each available slot is no more than 180 degrees, which is used as the slot interval. The two slots with the largest slot interval are selected as the reference positions. When the slot intervals are the same, the two slots are compared in the slot order and the combination with the first slot is selected.

[0162] If there are fewer than two available reference locations, the evidence of the remaining boundary will not be determined. The current image and the record of missing references will be retained, and the current microwell will be transferred to the detection pending verification state.

[0163] For each reference segment, first determine the midpoint of its circumferential coverage area. Then, select the actual edge point with the smallest circumferential distance from the midpoint from the actual edge segment as the position reference point. If two actual edge points have the same minimum distance, select the actual edge point reached first along the locking rotation direction. Arrange the two reference positions according to the slot order, using the position reference point with the earlier slot order as the starting point and the position reference point with the later slot order as the ending point. This forms initial references with the same start and end correspondence in the initial micropore detection image and the current verification image, respectively. The direction and verification reference direction are determined as follows: Following the same manufacturing coordinate direction for the same board, the verification reference direction is rotated to the required angle consistent with the initial reference direction, with an absolute rotation angle not exceeding 180 degrees. This is defined as the overall rotation angle. When the absolute values ​​of two representable angles are both 180 degrees, the rotation direction is determined according to the locked rotation direction. Using the reference point corresponding to the first slot in the sequence as the rotation reference, the rotation angle conversion is completed. Then, the lateral and longitudinal position differences between this reference point and the corresponding reference point in the initial micro-hole detection image are obtained, and the overall translation amount is determined accordingly. Local registration does not rewrite the original pixel values ​​of the verification image. It only converts the pixel positions and edge coordinates in the verification image to the unified coordinate aperture of the initial micro-hole detection image according to the overall translation amount and overall rotation angle. Only translation and rotation angle correction maintaining the board surface direction are allowed; mirror reflection, local stretching, and non-uniform scaling are not permitted.

[0164] After the conversion is completed, the corresponding position differences of all available position reference points in the unified coordinate system are checked, and the largest corresponding position difference is taken as the registration remaining position difference of the current verification image. Only when the registration remaining position differences of all formal verification images do not exceed the registration tolerance range locked by the current local registration parameter version will the subsequent candidate boundary comparison begin. If any formal verification image exceeds the registration tolerance range, the uncertain boundary evidence in this round will be retained, and the current micro-hole will be transferred to the detection pending verification state.

[0165] After each image is locally registered, candidate boundaries are determined within the range of the dominant uncertain boundary slot according to the formation aperture of the actual edge points and actual edge segments mentioned above. When it belongs to the aperture boundary slot, only the actual edge segments whose actual edge points all fall within the radial range of the aperture edge pre-locked in step one are retained as aperture candidate boundaries. When it belongs to the target pad boundary slot, only the actual edge segments whose actual edge points all fall within the radial range of the corresponding target pad edge are retained as target pad candidate boundaries. Manual judgment is not used to replace this assignment rule.

[0166] Candidate boundaries in each formal verification image are used to establish candidate combinations according to their circumferential positions. Each candidate combination must contain one candidate boundary from each formal verification image. Only when each candidate boundary has a common circumferential coverage area within the dominant uncertain boundary slot, and the common circumferential coverage length reaches the dwell coverage threshold locked by the current dwell determination parameter version, will the candidate combination continue to participate in the geometric position preservation relationship judgment.

[0167] For a common circumferential coverage area, starting from the initial circumferential position of the common circumferential coverage area, comparison positions are sequentially set along the locked rotation direction according to the locked position comparison interval, and the radial direction pointing from the fixed origin to the corresponding circumferential direction of each comparison position is used as the unified position comparison direction. For each image participating in the comparison, within a circumferential range of 0.5 position comparison intervals before and after each comparison position, the candidate boundary actual edge point with the smallest circumferential distance is selected as the edge position of that comparison position. When there are the same minimum distance, the actual edge point reached first along the locked rotation direction is selected. If no actual edge point exists in any formal verification image within this range, the comparison position is not included in the common circumferential coverage. After all comparison positions are filtered, circumferential coverage areas with a length not exceeding 1 position comparison interval are formed with the retained valid comparison positions as the center. Each circumferential coverage area is then bounded within the original common circumferential coverage area, and their union is calculated. The total length of this union is used to redetermine the effective common circumferential coverage length of the current candidate combination. Only when the effective common circumferential coverage length reaches the dwell coverage threshold is the geometric position change calculated. If the dwell coverage threshold is not reached, the current candidate combination does not form a geometric position preservation relationship. For candidate combinations that reach the dwell coverage threshold, the distance between the outermost and innermost edges of all participating comparison positions in each retained comparison position is taken as the position difference of that comparison position. Then, the largest position difference among all comparison positions is taken as the geometric position change of that candidate combination. Only when the geometric position change does not exceed the allowable range for geometric position preservation is the candidate combination determined to have a geometric position preservation relationship. The common circumferential coverage length used for subsequent candidate combination ranking is uniformly adopted as the effective common circumferential coverage length.

[0168] In this round of complementary verification lighting conditions, both formal verification images corresponding to the first and second lighting conditions must have candidate boundaries participating in the same candidate combination. When the initial micro-hole detection image has one candidate boundary within the same circumferential range, that candidate boundary is used as an additional candidate boundary. When there are more than two candidate boundaries, the candidate boundary with the largest overlap length in the common circumferential coverage area of ​​the current candidate combination of the two formal verification images is selected first. If the overlap lengths are the same, the candidate boundary with the larger continuous circumferential length is selected. If they are still the same, the candidate boundary with the earlier starting circumferential position along the locking rotation direction is selected. The uniquely selected candidate boundary is used as an additional candidate boundary and included in the determination of the position difference, geometric position change, and subsequent dwell position interval of the corresponding comparison position. When there are no continuous candidate boundaries in the initial micro-hole detection image within this range, the geometric position preservation relationship is determined only by the two formal verification images.

[0169] When multiple candidate combinations satisfy the conditions, they are first arranged in descending order of effective common circumferential coverage length, then in ascending order of geometric position change. If they are still the same, they are arranged in ascending order of the starting circumferential position of the common circumferential coverage interval. If they are still the same, they are arranged in ascending order of the starting circumferential position of the candidate boundary of the first lighting condition and the candidate boundary of the second lighting condition. The candidate combination ranked first is taken as the unique corresponding candidate boundary group.

[0170] Based on the corresponding candidate boundary group, the stationary boundary evidence is determined. Within the common circumferential coverage area, each valid comparison position is recorded item by item along the same position comparison interval. The closed position interval formed by the innermost and outermost positions of all candidate boundary actual positions of the participating comparison images under each comparison position is taken as the stationary position interval of the comparison position. All valid comparison positions and their corresponding stationary position intervals together constitute the stationary boundary evidence. Therefore, the stationary boundary evidence does not use a single edge line in any single image to replace it, but preserves the boundary position range supported by different lighting conditions.

[0171] Candidate boundaries do not constitute evidence of a dwelling boundary if they appear only in a single formal verification image, if the effective common circumferential coverage length is below the dwelling coverage threshold, or if the geometric position change exceeds the allowable range for geometric position maintenance.

[0172] After the evidence of the dwelling boundary is formed, the corresponding center feasible region is redefined accordingly. When the dominant uncertain boundary slot belongs to the orifice boundary slot, the orifice center candidate position is checked one by one from the original orifice center feasible region. When it belongs to the target pad boundary slot, the target pad center candidate position is checked only from the original target pad center feasible region.

[0173] For each comparison position in the boundary evidence, the permissible boundary position range that the candidate center position can be established in the current circumferential direction is determined based on the current candidate center position, the corresponding permissible geometric dimension range, and the edge position measurement tolerance. For circular apertures or circular target pads, a radial inspection line extending from a fixed origin along the circumferential direction of each comparison position is established. With the current candidate center position as the center, the area between the minimum permissible radius minus the edge position measurement tolerance and the maximum permissible radius plus the edge position measurement tolerance is taken as the boundary allowable area corresponding to the current candidate center position. All position intervals formed by the intersection of this radial inspection line and the boundary allowable area are collectively taken as the permissible boundary position range of the comparison position; if there is no intersection position, the current candidate center position does not meet the limitation at this comparison position. For target pads with a fixed non-circular design profile, the target pad design profile expanded according to the manufacturing acceptance tolerance and the edge position measurement tolerance is translated to the current candidate center position of the target pad, and then the permissible boundary position range is determined by the intersection position of the profile allowable area and the current radial inspection line. A candidate center position is retained only if the evidence of the stationed boundary has a common position with the range of the allowed boundary position, and all comparison positions meet this condition. If no comparison position has a common position, the candidate center position is excluded.

[0174] The re-restriction only allows the deletion of candidate center positions that do not meet the residency boundary evidence requirements from the original corresponding center feasible region. It does not add positions outside the original center feasible region, does not change the center feasible region of another object, and does not change the existing restriction relationship formed by the preceding valid boundary slots.

[0175] When no evidence of a dwelling boundary is formed, the corresponding feasible region of the center remains the original locking result of this round. The current micro-hole is transferred to the detection pending verification state and does not enter step six. The edge of the single verification image is not shrunk. When there are no candidate center positions after re-limitation, the local registration record, the corresponding candidate boundary group and the evidence of a dwelling boundary are retained. The current micro-hole is transferred to the detection pending verification state. The existing threshold is not relaxed to restore the candidate center position.

[0176] The record generated in the current step is associated with at least the initial micropore detection image identifier, the formal verification image identifier, the reference position, the local registration result, the registration remaining position difference, the dominant uncertain boundary slot identifier, the candidate boundary, the corresponding candidate boundary group, the common circumferential coverage area, the effective common circumferential coverage length, the geometric position change, the residency boundary evidence, and the corresponding center feasible region after re-definition. When the same set of images and the same rule version are executed repeatedly, the already locked results are used.

[0177] Preferably, the position comparison interval can be set to 1 micrometer, the allowable range of registration remaining position difference can be set to 2 micrometers, the dwell coverage threshold can be set to 70% of the detectable circumferential length of the dominant uncertain boundary slot, and the allowable range of geometric position retention can be set to 3 micrometers; when the common circumferential coverage ratio of the candidate boundary in the two formal verification images is 80% and the maximum position difference formed by each comparison position is 1.5 micrometers, the evidence of dwell boundary is determined, and the original corresponding center feasible region is re-selected according to the dwell position interval corresponding to each comparison position.

[0178] As an alternative implementation, two or more dispersed location references can be added to jointly complete the local registration, but the initial micro-hole detection image must still be used as a fixed coordinate reference. Only overall translation and overall rotation correction are allowed, and the dwelling boundary evidence is determined according to the same common circumferential coverage, unified radial position comparison and dwelling position interval formation rules.

[0179] Step Six: Update the offset feasible region based on the redefined central feasible region and determine the micropore offset defect status. The dominant uncertain boundary slot that forms evidence of the dwelling boundary and obtains a non-empty redefined central feasible region is identified as the confirmed boundary slot. This slot, along with the complementary verification lighting conditions, is written into the subsequent micropore priority acquisition record. The specific implementation is as follows:

[0180] After the current microvia forms a non-empty, redefined center feasible region, the detection control unit reads the redefined center feasible region and another center feasible region that retains the previous locking result, and updates the offset feasible region according to the offset direction diameter of the previously fixed "orifice center relative to the target pad center".

[0181] When the feasible region of the orifice center is redefined, each of the retained orifice center candidate positions is combined with each of the target pad center candidate positions in the current feasible region of the target pad center; when the feasible region of the target pad center is redefined, each of the orifice center candidate positions in the current feasible region of the orifice center is combined with each of the retained target pad center candidate positions, and the lateral position difference and longitudinal position difference of the orifice center candidate position relative to the target pad center candidate position are recorded respectively.

[0182] The offset position is recorded using relative displacement coordinates. The zero offset position corresponding to the center of the hole and the center of the target pad being in the same position is taken as the origin of the offset coordinates. The positive direction of the coordinates and the physical length unit follow the locking diameter of the previous offset feasible region. The design hole mapping position used for circumferential division is not taken as the origin of the offset coordinates.

[0183] All candidate offset positions obtained by combination are deduplicated according to the horizontal position difference and the vertical position difference. When the same offset position is formed repeatedly, only one copy is retained. The candidate offset positions after deduplication directly form the updated offset feasible region. New offset positions are not automatically added between adjacent candidate offset positions, nor are central candidate positions that have been excluded from the corresponding central feasible region by the evidence of the stationed boundary re-introduction.

[0184] If the corresponding feasible region after the previous step is empty, the current micropore remains in the state of being detected and checked, and does not proceed to this step; if both the corresponding feasible region after the previous step and the other feasible region are not empty, at least one candidate offset position is formed.

[0185] After the updated feasible offset region is formed, the same version of the allowed offset region used in the current micropore pre-judgment is read. The zero offset position, coordinate direction, physical length unit and boundary belonging diameter of the allowed offset region remain unchanged, and the boundary of the allowed offset region belongs to the allowed offset region.

[0186] The detection and control unit checks each candidate offset position in the updated feasible offset domain to see if it belongs to the allowed offset domain, and determines the micropore offset defect status based on the assignment results of all candidate offset positions: when all candidate offset positions belong to the allowed offset domain, the micropore offset defect status is determined to be an undetected offset defect; when none of the candidate offset positions belong to the allowed offset domain, the micropore offset defect status is determined to be a detected offset defect; when there are both candidate offset positions belonging to the allowed offset domain and candidate offset positions not belonging to the allowed offset domain, the micropore offset defect status is determined to be pending verification.

[0187] Candidate offset positions located on the boundary of the allowed offset domain are recorded according to their belonging to the allowed offset domain. Therefore, the aforementioned three states are mutually exclusive and cover all cases when the updated feasible offset domain is not empty.

[0188] Once the updated feasible offset domain and the corresponding micropore offset defect state are formed, they are locked. Candidate offset positions are not added or deleted in reverse according to the obtained state, nor is the allowed offset domain used in this round changed.

[0189] For the dominant uncertain boundary slot that has been formed in the previous step and obtained a non-empty redefined central feasible region based on the boundary evidence, it is identified as the confirmed boundary slot. The establishment of the confirmed boundary slot does not require that the redefined central feasible region must further reduce the number of candidate positions compared with the original central feasible region. As long as the boundary evidence has been formed in accordance with the aforementioned geometric position preservation rules and a non-empty redefined central feasible region can be obtained based on the boundary evidence, the confirmation of the current boundary slot is completed.

[0190] This confirmed status is saved as a new record formed in this round of review, and does not cover the original record of the unconfirmed boundary slot formed in the initial micropore detection image stage.

[0191] The detection and control unit reads the boundary type, slot order, circumferential position, and complementary verification lighting conditions actually used when forming the evidence of the stationary boundary corresponding to the confirmed boundary slot, and writes the confirmed boundary slot and verification lighting conditions into the priority acquisition record of subsequent micropores.

[0192] Subsequent microvias are defined as microvias that have not yet started acquiring initial microvia inspection images after the priority acquisition record is locked, and that have the same product inspection rule version, the same microvia design type, the same board manufacturing coordinate direction, and the same imaging illumination configuration as the current microvia that formed the record. The microvia design type is jointly identified by the designed aperture, the target pad design shape, and the target pad design size. The imaging illumination configuration is jointly identified by the type of illumination device, the set of executable illumination directions, the number of illumination zones, and the fixed imaging parameters of the camera. Microvias that have started or have completed acquiring initial microvia inspection images when the record is locked will not be retroactively applied to this record.

[0193] Priority is given to collecting records based on the product inspection rule version, micropore design type, board manufacturing coordinate direction, imaging lighting configuration, boundary type, and slot sequence to determine applicable items. For each applicable item, the record includes the confirmed circumferential position of the boundary slot, the version of the verification lighting conditions, the first lighting condition, the second lighting condition, the micropore identifier that forms the record, the identifier of the remaining boundary evidence record, and the time of initial confirmation.

[0194] When the same applicable item forms the exact same verification lighting conditions again, only the confirmation count of the corresponding relationship is increased and the original first confirmation time is retained, and a new competing record is not created repeatedly; when the same applicable item forms different verification lighting conditions, the confirmation count of each verification lighting condition is retained. The verification lighting conditions with more confirmation counts are ranked first. If the confirmation counts are the same, they are ranked first according to the earlier first confirmation time. If they are still the same, they are ranked in ascending order according to the incremental version number of the verification lighting conditions. The version number is uniquely incremented in chronological order when the version is generated, thus forming a unique priority order.

[0195] When acquiring subsequent microvia records, the acquisition priority is determined only if the subsequent microvia forms a dominant uncertain boundary slot with the same applicable items as the record, and the verification lighting conditions in the record still satisfy the complementary relationship determined in step four based on the circumferential position of the slot. If the verification lighting conditions in the record do not satisfy the mapping rules in step four, the complementary verification lighting conditions are re-determined according to the current locking rules in step four. Priority acquisition records must not modify the design hole mapping position, circumferential reference, allowable geometry range of the hole opening, allowable geometry range of the target pad, center feasible region formation rules, or allowable offset region of subsequent microvias.

[0196] Slots that have not formed residency boundary evidence, whose residency boundary evidence has failed to form a non-empty redefined central feasible region, or whose corresponding complementary verification lighting conditions have not been actually collected, shall not be included in the valid priority collection record.

[0197] The updated offset feasible region, micropore offset defect status, confirmed boundary slot and priority acquisition record formed in the current step are all associated with the corresponding previous center feasible region version, residence boundary evidence and verification lighting condition version and saved. When the same previous record and the same rule version are executed repeatedly, the locked results are used.

[0198] Preferably, in a set of online detection conditions, the updated feasible offset region formed after the re-definition of the dwelling boundary evidence can be composed of several candidate offset positions. When all candidate offset positions fall within the allowable offset region with an allowable offset distance of no more than 50 micrometers, it is determined that the offset defect is not detected. When all candidate offset positions are outside the allowable offset region, it is determined that the offset defect is detected. When the candidate offset positions are simultaneously distributed inside and outside the allowable offset region, the micropore offset defect status is determined to be pending verification. For the same applicable item that has been written into the priority acquisition record, subsequent micropores that have actually called the first-ranked review lighting conditions and completed the review after it takes effect can be continuously checked to ultimately form the dwelling boundary. The number of micropores in the same boundary slot is used as the consistency number. The total number of applicable micropores that have been verified and confirmed under the first-ranked lighting condition is used as the statistical total. When the cumulative number of applicable micropores reaches 100, the proportion of the consistency number to the statistical total is calculated. When the proportion reaches 99%, the current priority order is maintained. When it is below 99%, the lighting condition is no longer ranked first, but the historical record is retained. The ranking first is re-determined according to the number of confirmations of the remaining valid lighting conditions and the established tie-breaking rules. When the total number of micropores is less than 100 at the end of the current batch, all applicable micropores in the batch are counted. The statistical results are only used as the basis for the validity of the record of the same version in the next batch.

[0199] As an alternative implementation method, independent priority acquisition records can be established for different micro-hole design types. As long as the updated offset feasible region is still re-formed by the redefined central feasible region according to the same relative displacement aperture, the micro-hole offset defect status is still uniquely determined according to the belonging relationship of all candidate offset positions to the allowable offset region, and the priority acquisition record only changes the acquisition priority order of subsequent micro-holes under the existing verification lighting conditions without modifying the design position and defect judgment boundary, it can be implemented in the same way.

[0200] In the operating scenario shown in this embodiment: online visual inspection of microvia offset is performed on a batch of high-density interconnect circuit boards. The board of the current inspected board is identified as PCB-A01, and the current microvia is identified as VIA-0237. The microvia is designed with a diameter of 100 micrometers. The target pad is a circular pad with an allowable radius range of 108 micrometers to 112 micrometers. The edge position measurement tolerance is 1 micrometer. The allowable offset domain is set as a closed area centered on the zero offset position with an allowable offset distance of no more than 50 micrometers.

[0201] After the board enters the micro-hole vision inspection station, the inspection control unit moves the VIA-0237 to the imaging area of ​​the industrial imaging device according to the design hole position record and board surface positioning mark in the manufacturing design document. After the positioning platform stops moving, the original image is acquired.

[0202] During this acquisition process, the position of the board did not change by more than 2 pixels. The image completely covered the hole opening and the edge of the target pad presented through the hole opening. There was no area of ​​defocus in the hole opening detection area. Therefore, this original image was registered as the initial micro-hole detection image corresponding to VIA-0237.

[0203] The detection control unit corrects the translational and angular deviations of the entire image according to the positioning marks on the board surface. It takes the designed hole mapping position as the fixed origin and the positive horizontal direction of the board manufacturing coordinate as the circumferential starting direction. The hole boundary and the target pad boundary are divided into 16 circumferential boundary slots, each slot covering 22.5 degrees. The circumferential inspection position is set item by item in each slot according to the pre-locked circumferential inspection position spacing, and the bright-dark conversion is checked along the corresponding radial direction.

[0204] After processing the actual edge points and actual edge segments, 13 out of the 16 hole boundary slots had an actual edge coverage of over 60%, a maximum gap length of no more than 5 pixels, and a positional dispersion of no more than 3 pixels. These slots were marked as valid boundary slots. The remaining 3 hole boundary slots were marked as unconfirmed boundary slots due to insufficient actual edge coverage caused by local reflections. Among the target pad boundary slots, 15 were marked as valid boundary slots, and another 1 was marked as unconfirmed boundary slot due to a lack of illumination on the local edge presented by the hole.

[0205] Subsequently, the detection and control unit reads all valid orifice boundary slots and valid target pad boundary slots. Within the corresponding center candidate position search range, the center candidate positions are arranged at a spacing of 1 micrometer to form the orifice center candidate position and the target pad center candidate position. Based on the orifice allowable radius of 48 to 52 micrometers, the target pad allowable radius of 108 to 112 micrometers, and the 1 micrometer edge position measurement tolerance, the candidate positions that cannot simultaneously satisfy all valid boundary slots are eliminated one by one, thus forming the orifice center feasible region and the target pad center feasible region respectively.

[0206] The detection and control unit combines candidate positions from the two center feasible regions one by one and removes duplicate positions according to the fixed offset direction of the orifice center relative to the target pad center to form the offset feasible region.

[0207] There is a continuous set of positions in the feasible region of the offset, where the candidate offset position with an offset distance of 47 micrometers is located inside the allowed offset region, and the candidate offset position with an offset distance of 54 micrometers is located outside the allowed offset region. Therefore, the current micropore formation determination boundary crossing state is determined, indicating that the existence of an offset defect in VIA-0237 cannot be uniquely confirmed based solely on the current valid boundary evidence.

[0208] The detection and control unit further compares the distance between the internal candidate offset position and the external candidate offset position in the continuous position group, determines the unique decision boundary crossing direction according to the predefined minimum distance and coordinate sorting rules, and establishes a direction axis that passes through the zero offset position and is parallel to that direction.

[0209] The original range length of the current offset feasible region formed along this direction axis is 18 micrometers.

[0210] Subsequently, possible boundary positions were set for the aforementioned four boundary slots to be confirmed, and each possible boundary position was assumed to be valid. The corresponding center feasible region was then re-screened, and the range that the offset feasible region could retain along the same directional axis was observed.

[0211] Among them, the maximum retention range length formed by the fifth orifice boundary slot in all possible boundary positions is 7 micrometers, corresponding to a feasible domain shrinkage of 11 micrometers; the maximum retention range length formed by the boundary slot to be confirmed for a certain target pad is 10 micrometers, corresponding to a feasible domain shrinkage of 8 micrometers; the feasible domain shrinkage of the other two boundary slots to be confirmed is less than 6 micrometers.

[0212] After arranging the feasible region shrinkage from largest to smallest, the fifth orifice boundary slot was determined as the dominant uncertain boundary slot.

[0213] The detection and control unit reads the 16 lighting zones of the annular partition lighting device according to the circumferential position of the slot. The angle difference between the center lighting direction of the 5th lighting zone and the circumferential position of the slot is the smallest. Therefore, the 5th lighting zone is determined as the 1st lighting zone, and the 13th lighting zone, which is 180 degrees away from it, is determined as the 2nd lighting zone. The two form the current complementary verification lighting conditions.

[0214] Keep the circuit board plane position, board orientation, working distance of the industrial imaging device, focal plane position and imaging magnification within the locked allowable range. First, illuminate with 60% of the rated brightness of the 5th illumination zone, stabilize for 20 milliseconds, and then obtain the first formal verification image with an exposure time of 1 millisecond. Then, turn off the 5th illumination zone and turn on the 13th illumination zone to obtain the second formal verification image under the same illumination brightness and exposure conditions.

[0215] Both images completely cover the detection area. There are no areas of defocusing, saturation, or underexposure in the dominant uncertain boundary slots. Furthermore, the change in the planar position of the board during the acquisition period did not exceed 2 micrometers, the change in the board surface direction did not exceed 0.02 degrees, and the change in the working distance of the industrial imaging device did not exceed 5 micrometers. Therefore, both images are registered as official review images.

[0216] The detection control unit uses the initial micro-hole detection image as a fixed coordinate reference. It selects the two available slots with the largest circumferential spacing from the effective boundary slots other than the dominant uncertain boundary slot as reference positions. It obtains two position reference points according to the locked reference point formation rules and completes the overall rotation and translation correction of the two formal verification images based on the correspondence between the two position reference points.

[0217] After correction, the remaining positional difference between the two formal verification images did not exceed 2 micrometers, and they entered the candidate boundary comparison stage.

[0218] In the fifth aperture boundary slot, both the verification images of the fifth illumination zone and the thirteenth illumination zone form candidate boundaries. The effective common circumferential coverage length of the two candidate boundaries reaches 80% of the detectable circumferential length of the slot, exceeding the 70% dwell coverage threshold. After comparing each item at a position comparison interval of 1 micrometer, the maximum position difference among the effective comparison positions is 1.5 micrometers, which is within the allowable range of geometric position preservation of less than 3 micrometers. Therefore, it is determined that the candidate boundaries under the two illumination conditions form a geometric position preservation relationship.

[0219] Record the dwell position interval formed by the innermost and outermost positions of the candidate boundaries of the two formal review images at each effective comparison position. The dwell boundary evidence of the fifth orifice boundary slot is formed by all effective comparison positions and the corresponding dwell position intervals.

[0220] The detection control unit then uses the evidence of the dwelling boundary to re-examine each candidate position of the orifice center in the original feasible region of the orifice center, and retains only the candidate positions of the orifice center that can make the allowable boundary position range and the dwelling position interval have the same position in all comparison positions, thereby obtaining the redefined feasible region of the orifice center, while the original feasible region of the target pad center remains unchanged.

[0221] After recombining the redefined feasible region of the orifice center and the original feasible region of the target pad center, all candidate offset positions in the updated offset feasible region are concentrated in the range of 46 to 49 micrometers from the zero offset position, and all are located inside the allowable offset region. Therefore, the micro-hole offset defect status of VIA-0237 is determined to be an undetected offset defect.

[0222] The results indicate that the missing boundary of the fifth aperture boundary slot in the initial micro-aperture detection image is mainly caused by insufficient optical visibility under the current illumination direction, while the evidence of the dwelling boundary obtained under complementary verification illumination can exclude candidate positions in the original offset feasible region that exceed the allowable offset region.

[0223] Since the fifth orifice boundary slot has formed evidence of the resident boundary and a non-empty redefined feasible region of the orifice center has been obtained, the slot is registered as a confirmed boundary slot, and its slot sequence, circumferential position, and the verification lighting conditions corresponding to the fifth and thirteenth lighting zones are written into the priority collection record corresponding to the current product inspection rule version.

[0224] Subsequently, in subsequent microholes that have the same microhole design type, the same board manufacturing coordinate direction, and the same imaging illumination configuration, and have not yet started acquiring initial microhole detection images after the priority acquisition record is locked, if the same fifth aperture boundary slot is formed again as the dominant uncertain boundary slot, the detection control unit will prioritize reading the fifth and thirteenth illumination zones in the record as existing complementary verification illumination conditions to perform verification acquisition. However, it will still independently determine the microhole offset defect status according to the candidate boundary, dwelling boundary evidence, and updated offset feasible domain that the current microhole actually forms. It will not directly use the detection results of VIA-0237, nor will it modify the design aperture mapping position, circumferential reference, or allowable offset domain of subsequent microholes. In this way, the complete and continuous operation process of the current microhole from initial visual inspection, boundary uncertainty identification, dominant uncertain boundary positioning, complementary verification acquisition, dwelling boundary confirmation to final microhole offset defect status determination and subsequent acquisition experience recording is completed.

[0225] The calculations involved in the embodiments are all dimensionless numerical calculations, and the preset parameters and thresholds in the calculations are set by those skilled in the art according to the actual situation.

[0226] It should be noted that this invention can be deployed on the device itself to realize embedded applications, or it can run on a PC or other terminal with a user interface, thereby meeting various hardware environments and usage requirements.

[0227] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wireless or wired transmission; wired transmission methods include optical fiber, twisted pair, coaxial cable, etc.; wireless transmission includes infrared, microwave, etc. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center containing one or more sets of available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium. A semiconductor medium can be a solid-state drive.

[0228] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and modules described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0229] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or modules may be electrical, mechanical, or other forms.

[0230] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules; they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0231] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0232] If the aforementioned functions are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0233] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0234] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A visual inspection method for microvia misalignment on a high-density interconnect circuit board, characterized in that, include: Step 1: Obtain the initial microvia inspection image, divide the orifice boundary slots and target pad boundary slots according to the circumferential reference, and mark the effective boundary slots and the boundary slots to be confirmed according to the edge continuity; Step 2: Utilize the effective boundary slots to form the feasible region at the center of the orifice, the feasible region at the center of the target pad, and the feasible region of offset. Determine the boundary crossing status based on the overlap relationship between the feasible region of offset and the allowed offset region. Step 3: When the offset feasible region crosses the boundary of the allowable offset region, determine the crossing direction of the judgment boundary, calculate the feasible region shrinkage of the boundary slot to be confirmed, and take the first slot in the sorting as the dominant uncertain boundary slot; Step 4: Determine the complementary verification illumination conditions based on the circumferential position of the dominant uncertain boundary slot, keep the imaging position fixed, and acquire verification images sequentially; Step 5: Locally register the initial micropore detection image and the verification image, form residency boundary evidence based on the geometric position relationship of the candidate boundary, and redefine the corresponding center feasible region; Step 6: Update the offset feasible region based on the redefined central feasible region and determine the micropore offset defect status. The dominant uncertain boundary slot that forms the evidence of the dwelling boundary and obtains a non-empty redefined central feasible region is determined as the confirmed boundary slot. Write it and the complementary verification lighting conditions into the subsequent micropore priority acquisition record.

2. The visual inspection method for microvia misalignment on a high-density interconnect circuit board according to claim 1, characterized in that, Step one includes: The design hole position is converted to the initial detection image coordinates of the microhole after the plate surface positioning mark is used as the fixed origin. The positive horizontal direction of the plate manufacturing coordinate is used as the circumferential starting direction, and the circumferential reference is established according to the locked rotation direction. The same set of radial dividing lines is used to divide the orifice boundary slots and the target pad boundary slots; Adjacent actual edge points whose circumferential spacing does not exceed the connection interval are grouped into the same actual edge segment. Valid boundary slots and unconfirmed boundary slots are marked according to coverage, maximum gap length, and location dispersion.

3. The visual inspection method for microvia misalignment on a high-density interconnect circuit board according to claim 1, characterized in that, Step two includes: Set the orifice center candidate position and the target pad center candidate position according to the same center candidate position grid, and form the orifice center feasible region and the target pad center feasible region according to the actual edge points and boundary allowable zone of the effective boundary slot; The offset feasible region is formed by combining candidate positions based on the offset diameter of the orifice center relative to the target pad center; Two candidate offset positions whose horizontal and vertical coordinate differences do not exceed the arrangement interval and do not overlap with each other are considered adjacent positions, thus forming a continuous position group; When a continuous set of positions contains candidate offset positions that are strictly within or outside the allowed offset domain, the boundary crossing state is determined.

4. The visual inspection method for microvia misalignment on a high-density interconnect circuit board according to claim 1, characterized in that, Step three includes: In a continuous set of positions that simultaneously contains candidate offset positions inside and outside the allowed offset domain, the straight-line distances between the inner and outer candidate offset positions are compared, and the position combination with the smallest distance is selected from all comparison results. When candidates are in parallel, a unique combination is determined by ascending order of the horizontal and vertical coordinates of the internal candidate offset position and the horizontal and vertical coordinates of the external candidate offset position. The direction from the internal candidate offset position to the external candidate offset position is the decision boundary crossing direction. Establish a direction axis that passes through the zero offset position and is parallel to the direction, and use the distance between the maximum and minimum projected positions of the offset feasible region on the direction axis as the original range length.

5. The visual inspection method for microvia misalignment on a high-density interconnect circuit board according to claim 4, characterized in that, Step three also includes: Within the radial range of the edge of each boundary slot to be confirmed, possible boundary positions are formed; Each of these is used as a new boundary constraint. Candidate center positions are selected from the corresponding original feasible center regions and combined with candidate positions from another feasible center region to form candidate offset positions. Project the candidate offset position onto the direction axis to determine the length of the retention range, use the maximum value as the conservative retention range length, and calculate the feasible region shrinkage. Sort by feasible domain shrinkage in descending order and slot order in ascending order. When slot orders are the same, slots at the orifice boundary are given priority to determine the dominant uncertain boundary slots.

6. The visual inspection method for microvia misalignment on a high-density interconnect circuit board according to claim 1, characterized in that, Step four includes: The circumferential position is determined by the middle direction of the dominant uncertain boundary slot coverage angle range; Select the first lighting zone with the smallest angle difference between the central lighting direction and the circumferential position, and take the opposite direction of its central lighting direction as the complementary target direction. Select the second lighting zone with the smallest angle difference between the central lighting direction and the complementary target direction from the remaining zones. When the minimum angle difference is the same, the lighting zone that is ranked later is selected according to the rotation direction used when establishing the circumferential reference; Complementary verification illumination conditions are formed by using the first and second illumination conditions corresponding to the two zones, and verification images are acquired sequentially at fixed imaging positions.

7. The visual inspection method for microvia misalignment on a high-density interconnect circuit board according to claim 1, characterized in that, Step five includes: Using the initial micropore detection image as a coordinate reference, from the effective boundary slots outside the dominant uncertain boundary slots and in both the initial micropore detection image and all verification images, the slot interval is determined by the angle between the slots in the middle direction not exceeding half a circumference. The two slots with the largest interval are selected as the reference positions. When they are side by side, the combination is determined according to the slot order. Local registration is completed by determining the rotation angle and translation amount based on the location reference point; Within the dominant uncertain boundary slot, candidate combinations are established, and the geometric position preservation relationship is determined when the effective common circumferential coverage length and geometric position change are satisfied.

8. The visual inspection method for microvia misalignment on a high-density interconnect circuit board according to claim 7, characterized in that, Step five also includes: Candidate combinations that form geometric position preservation relationships are sorted in descending order of effective common circumferential coverage length, ascending order of geometric position change, and circumferential starting position, and the first one is taken as the corresponding candidate boundary group. The locations where candidate boundary points are present in all the images participating in the comparison within their common circumferential coverage area are taken as valid comparison locations. The stationary location interval is formed by the innermost to the outermost candidate boundary location of each location, and this constitutes the stationary boundary evidence. Only the central candidate locations that share a common location with each stationing location interval and the corresponding allowable boundary location range are retained, forming a redefined corresponding central feasible region.

9. The visual inspection method for microvia misalignment on a high-density interconnect circuit board according to claim 1, characterized in that, Step six includes: When both the corresponding center feasible region and the other center feasible region are not empty, the candidate positions are combined according to the offset diameter of the orifice center relative to the target pad center to form the updated offset feasible region. If the boundary of the allowed offset domain belongs to this domain, it is judged as no offset defect detected when all candidate offset positions belong to the allowed offset domain; if all candidate offset positions do not belong to the allowed offset domain, it is judged as an offset defect detected; the rest are judged as pending verification. The dominant uncertain boundary slots that form evidence of the residency boundary and are redefined as non-empty central feasible regions are identified as confirmed boundary slots, and the confirmed boundary slots and the actual complementary verification lighting conditions are written into the subsequent micro-hole priority acquisition records.

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