A method and system for aligning and exposing a multi-layer flexible circuit board

Abstract

The application provides a kind of alignment exposure method and manufacturing system of multilayer flexible circuit board, and the alignment exposure method includes the board surface of multilayer flexible circuit board after pressing is divided into multiple independent exposure areas, three-dimensional deformation curvature data of each exposure area is collected, inflation parameter and the target offset amount in it are collected; each target is allocated dynamic weight, the two blind hole targets and two through hole targets with the highest dynamic weight are selected as alignment reference combination; according to three-dimensional deformation curvature and alignment reference combination, dynamic scaling and / or rotation correction are carried out on exposure pattern; each exposure area is exposed in turn, and the outer layer circuit image matched with the inner layer circuit pattern is obtained. By using the alignment exposure method of the application, the alignment accuracy under the pressing deformation scene of multilayer flexible circuit board can be significantly improved, the adjacent outer layer circuit image edge error is not more than 15 μm, the overall alignment accuracy is not more than ± 25 μm, and it is compatible with the existing LDI laser direct imaging equipment, and has wide industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of flexible circuit board manufacturing technology, and particularly relates to a method and system for alignment exposure of multilayer flexible circuit boards. Background Technology

[0002] In the lamination process of flexible printed circuit boards (FPCs), uneven distribution of inner layer circuit patterns, differences in the thermal expansion coefficients of different substrates and adhesive sheets, uneven pressure and temperature distribution during lamination, inconsistent adhesive flow, and different states of edge constraint and central region release can lead to significant upward bulging and expansion deformation in the central region of the board. This type of non-uniform deformation is commonly referred to in the industry as "bulging deformation." This deformation is characterized by large expansion at the center, small expansion at the edges, and an overall arc-shaped bulge. It causes regional dimensional elongation and positional shift in the X and Y directions of the board surface, with the deformation degree in the central region being significantly higher than that in the edge regions, resulting in non-linear dimensional errors that cannot be eliminated through global alignment.

[0003] Traditional exposure processes use a global reference hole or a single mark point for overall alignment, which can only correct for overall rotation and translation, but cannot compensate for regional nonlinear deformation. When large-area deformation occurs, it is easy to have problems such as edge alignment but center misalignment, or center alignment but edge misalignment, directly leading to alignment failure. At the same time, the structural depth and stress state of the through-hole targets and blind-hole targets inside the FPC are different, and their offset patterns are inconsistent during compression deformation, resulting in misalignment of through-hole and blind-hole targets. Existing technologies mostly use a single type of hole position as the alignment reference, which cannot take into account the alignment accuracy of both types. This causes the alignment deviation between the outer layer circuit and the inner layer through-hole target to exceed the standard, resulting in defects such as short circuits, open circuits, and hole position misalignment, making it difficult to improve the yield. Summary of the Invention

[0004] In view of the problems existing in the prior art, the main objective of the present invention is to provide a method and manufacturing system for alignment exposure of multilayer flexible circuit boards, in order to address one or more of the problems mentioned above.

[0005] The objective of this invention is achieved through the following technical solution: This invention provides a method for alignment exposure of a multilayer flexible circuit board, comprising the following steps: A multilayer flexible circuit board that has undergone a lamination process is provided, wherein multiple target groups are formed on the board surface, the target groups including multiple blind hole targets and multiple through hole targets distributed in different areas of the board surface; The surface of the multilayer flexible circuit board is divided into multiple independent exposure areas, and three-dimensional deformation curve data, expansion parameters, and offset of blind hole targets and through hole targets in each exposure area are collected. Based on the obtained offset of blind hole targets and through hole targets, dynamic weights are assigned to the blind hole targets and through hole targets in each of the exposure areas, and the two blind hole targets and two through hole targets with the highest dynamic weights in each exposure area are selected as their alignment reference combination. Based on the three-dimensional deformation curve data of each exposure area, the alignment reference combination and the expansion parameters, the preset exposure pattern is dynamically scaled and / or rotated and / or radially compressed to generate a corrected exposure pattern. Each of the exposure areas is exposed sequentially according to the corrected exposure pattern to obtain an outer layer circuit image that aligns with the inner layer circuit pattern of the flexible circuit board.

[0006] As a further description of the previous solution, in the step of "dividing the surface of the multilayer flexible circuit board into multiple independent exposure areas, collecting the three-dimensional deformation data of each exposure area, and the offset of the blind hole target and the offset of the through hole target located in its area", The surface of the multilayer flexible circuit board is divided into multiple independent exposure areas according to the size of the multilayer flexible circuit board and the preset deformation distribution rules; Each of the exposure areas was scanned separately using a three-dimensional scanning device to collect its three-dimensional deformation data; A GIS graphic image system is used to perform image recognition on each of the exposure areas to obtain their dilation parameters; An AOI / X-ray inspection device is used to determine the actual position coordinates of the blind hole target and the through hole target in each of the exposure areas, and compare them with the preset coordinates to obtain the offset of the blind hole target and the through hole target.

[0007] As a further description of the previous solution, the step "assigning dynamic weights to the blind hole targets and through hole targets located in each of the exposure areas based on the obtained offsets of the blind hole targets and through hole targets" specifically includes: Set an offset qualification threshold ; When the offset of any of the blind hole targets or through hole targets is greater than the offset qualification threshold When this happens, the weight of the blind hole target or through hole target is reset to 0; When the offset of any of the blind hole targets or through hole targets is less than or equal to the offset qualification threshold When the weight is calculated, it is done using the following formula: Blind hole target weight ; Through-hole target weight ; in, This represents the offset of the blind hole target. This represents the offset of the through-hole target. , All are regional strategy coefficients.

[0008] As a further description of the previous solution, when the exposure area is located in the center region of the plate surface, =1.2, =0.8; When the exposure area is located at the edge of the plate surface =0.8, =1.2.

[0009] As a further description of the previous solution, before the step of “selecting the two blind hole targets and two through hole targets with the highest dynamic weights in each exposure area as its alignment reference combination”, two sets of alignment parameters are independently calculated based on the blind hole targets and through hole targets in the current exposure area, and the consistency of the two sets of alignment parameters is compared. If the comparison deviation exceeds the preset value, the dynamic weight allocation is adjusted or the blind hole targets and / or through hole targets are re-selected.

[0010] As a further description of the previous solution, in the step "based on the three-dimensional deformation curve data of each exposure area, the alignment reference combination, and the dilation parameters, the preset exposure pattern is dynamically scaled and / or rotated and / or radially compressed to generate a corrected exposure pattern", The scaling ratio for dynamically scaling the preset exposure graphic ranges from ±0.5% to ±2%. The rotation angle range for the preset exposure pattern is ±0.01° to ±0.1°.

[0011] As a further description of the previous solution, in the step of "based on the three-dimensional deformation curve data of each exposure area, the alignment reference combination and the dilation parameter, the preset exposure pattern is dynamically scaled and / or rotated and / or radially compressed to generate a corrected exposure pattern", radial compression compensation is performed on the center of the exposure area according to the dilation parameter.

[0012] As a further description of the previous solution, in the step of "exposing each of the exposure areas sequentially according to the corrected exposure pattern to obtain an outer layer circuit image that aligns with the inner layer circuit pattern of the flexible circuit board", the edge-to-edge error of adjacent outer layer circuit images is no greater than 15μm.

[0013] This invention also provides a multilayer flexible circuit board manufacturing system, which exposes the multilayer flexible circuit board using the alignment exposure method described above, including: A partitioning module is used to divide the multilayer flexible circuit board into multiple exposure areas; The data acquisition module is used to acquire the three-dimensional deformation curve data, expansion parameters, and offset of blind hole targets and through hole targets in each exposure area. The weight evaluation and screening module is used to assign dynamic weights to blind hole targets and through hole targets in each exposure area according to the obtained offset of blind hole targets and through hole targets, and select the two blind hole targets and two through hole targets with the highest dynamic weights in each exposure area as their alignment reference combination. The cross-validation module is used to independently calculate two sets of alignment parameters based on blind hole targets and through hole targets in the same exposure area, and compare the consistency of the two sets of alignment parameters. If the comparison deviation exceeds the preset value, the dynamic weight allocation is adjusted or the blind hole targets and / or through hole targets are re-screened. The graphic correction module is used to perform partitioned dynamic scaling and / or rotation and / or radial compression compensation on the preset exposure graphic based on the three-dimensional deformation curve data of each exposure area, the alignment reference combination and the expansion parameter, so as to generate the corrected exposure graphic. An exposure control module is used to control the exposure light source to sequentially expose each exposure area according to the corrected exposure pattern in order to obtain an outer layer circuit image that aligns with the inner layer circuit pattern of the flexible circuit board, and to monitor the edge-fitting error of adjacent outer layer circuit images.

[0014] By employing the above technical solutions, the outstanding effects of this invention are as follows: The alignment exposure method for multilayer flexible circuit boards provided by this invention effectively overcomes the alignment deviation problem caused by non-uniform deformation after lamination of multilayer flexible circuit boards and inconsistent through-hole and blind hole target offset through the synergistic effect of zoned exposure, target dynamic weight allocation and deformation compensation, and significantly improves the interlayer alignment accuracy. Attached Figure Description

[0015] Figure 1 This is a structural view of the multilayer flexible circuit board before exposure pattern correction, using the alignment exposure method of the multilayer flexible circuit board in this embodiment of the invention. Figure 2 This is a structural view of the exposed pattern after correction using the alignment exposure method of the multilayer flexible circuit board in this embodiment of the invention.

[0016] Explanation of icon numbers: 1. Positioning reference hole; 2. Inner layer circuit pattern; 3. Outer layer circuit image. Detailed Implementation

[0017] 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.

[0018] In the description of this invention, it should be noted that the terms "upper," "middle," "lower," "inner," "outer," "front," "rear," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The embodiments of this invention will now be described according to its overall structure.

[0019] Please see Figures 1 to 2 Specifically, this invention discloses a method and manufacturing system for aligning and exposing multilayer flexible circuit boards. The disclosed method for aligning and exposing multilayer flexible circuit boards includes the following steps: A multilayer flexible circuit board that has undergone a lamination process is provided, wherein multiple target groups are formed on the board surface, the target groups including multiple blind hole targets and multiple through hole targets distributed in different areas of the board surface; The surface of the multilayer flexible circuit board is divided into multiple independent exposure areas, and three-dimensional deformation curve data, expansion parameters, and offset of blind hole targets and through hole targets in each exposure area are collected. Based on the obtained offset of blind hole targets and through hole targets, dynamic weights are assigned to the blind hole targets and through hole targets in each of the exposure areas, and the two blind hole targets and two through hole targets with the highest dynamic weights in each exposure area are selected as their alignment reference combination. Based on the three-dimensional deformation curve data of each exposure area, the alignment reference combination and the expansion parameters, the preset exposure pattern is dynamically scaled and / or rotated and / or radially compressed to generate a corrected exposure pattern. Each of the exposure areas is exposed sequentially according to the corrected exposure pattern to obtain an outer layer circuit image 3 that aligns with the inner layer circuit pattern 2 of the flexible circuit board.

[0020] Using the above method, the surface of the multilayer flexible circuit board after the lamination process is first divided into multiple independent exposure areas. Then, the three-dimensional deformation curvature data, expansion parameters, and offset of the blind and through-hole targets of each exposure area are collected to provide a precise data basis for independent correction of each exposure area. Based on this, dynamic weights are assigned to the blind and through-hole targets in each exposure area according to the offset of each target, and the two blind and two through-hole targets with the highest weights are selected as the alignment reference combination for that exposure area, realizing adaptive optimization of the alignment reference. Furthermore, by combining the three-dimensional deformation curvature data, alignment reference combination, and expansion parameters of each exposure area, the preset exposure pattern is dynamically scaled, rotated, and radially compressed to make the corrected exposure pattern highly matched with the actual deformation of the physical board (including the central "bulge", local stretching, and rotation). Finally, each exposure area is exposed sequentially according to the corrected exposure pattern to obtain the outer layer circuit image 3 that is precisely aligned with the inner layer circuit pattern 2. Through the synergistic effect of the above-mentioned partitioned exposure, target dynamic weight allocation and deformation compensation, the alignment deviation problem caused by non-uniform deformation after pressing and inconsistent target offset of through-holes is effectively overcome, and the interlayer alignment accuracy is significantly improved.

[0021] One embodiment includes the following steps: First, a six-layer flexible circuit board with a lamination process is provided. After lamination, due to differences in the thermal expansion coefficients of the layers and uneven adhesive flow, a "bulging" deformation occurs in the central area of ​​the board ("→" represents the direction of the bulging deformation after lamination). The expansion rate in the central area reaches 0.15%, while the deformation in the edge area is smaller. The surface of the board is pre-formed with positioning reference holes 1 (used only to identify the front and back of the board and its orientation) and multiple target groups through photolithography. The target groups include multiple blind hole targets and multiple through hole targets distributed in different areas of the board surface (e.g., the four corners and the center), which are used for subsequent alignment identification.

[0022] Next, based on the board size and a preset deformation distribution rule (e.g., larger deformation in the middle area and smaller deformation in the two side edge areas), the surface of the multilayer flexible circuit board is divided into three independent exposure areas: the left area, the middle area, and the right area (of course, in other embodiments, it can also be divided into six independent exposure areas: the upper left area, the upper middle area, the upper right area, the lower left area, the lower middle area, and the lower right area). The middle area corresponds to the middle region of the board surface, and the left and right areas correspond to the two side edge areas of the board surface. A three-dimensional scanning device is used to scan each exposure area to collect its three-dimensional deformation data; a GIS image system is used to perform image recognition on each exposure area to obtain its expansion parameters; an AOI / X-ray inspection device is used to determine the actual position coordinates of the blind hole targets and through-hole targets in each exposure area, and these coordinates are compared with preset coordinates to obtain the offset of the blind hole targets and through-hole targets.

[0023] The specific collection results are as follows: Left zone: Average offset of blind hole target ≈10μm, average offset of through-hole target It has a diameter of approximately 5 μm, an expansion rate of approximately 0.02%, and a relatively small three-dimensional deformation curvature.

[0024] Middle zone: Average offset of blind hole target ≈8μm, average offset of through-hole target The diameter is approximately 12 μm, the expansion rate is about 0.15%, and the three-dimensional deformation curvature shows a clear radial bulge at the center.

[0025] Right zone: Average offset of blind hole target ≈9μm, average offset of through-hole target ≈6μm, expansion rate of about 0.03%, three-dimensional deformation curvature.

[0026] Then, for each exposure area, dynamic weights are assigned to each target based on the obtained offsets of blind hole targets and through hole targets, and the two blind hole targets and two through hole targets with the highest dynamic weights are selected as the alignment reference combination in each exposure area.

[0027] The specific allocation method is as follows: Set the offset qualification threshold =25μm. When the offset of any blind hole target or through hole target is greater than 25μm, the target weight is reset to 0 (in this embodiment, all target offsets are less than 5μm, so they are all included in the calculation); when the measured offset For sizes ≤25μm, the weights are calculated using the following formula: Blind hole target weight ; Through-hole target weight ; in, This represents the offset of the blind hole target. This represents the offset of the through-hole target. , All are regional strategy coefficients.

[0028] More specifically, the regional strategy coefficient , The location of the exposure area on the board surface is determined, specifically: when the exposure area is located in the central area (middle area) of the board surface, =1.2, =0.8 (blind hole target preferred); when the exposure area is located in the edge region of the plate surface (left and right areas), =0.8, =1.2 (through-hole target preferred).

[0029] For a blind hole target in the middle zone ( =8μm) and a through-hole target ( The weight calculation for (12μm) is as follows: Blind hole target weight =0.5×(1-8 / 25)×1.2=0.408 Through-hole target weight =0.5×(1-12 / 25)×0.8=0.208 After calculating the weights of all targets within the region, they were sorted from highest to lowest weight. The two blind hole targets with the highest weights (0.408 and 0.402 respectively) and the two through hole targets (0.208 and 0.205 respectively) were selected as the alignment reference combination for the central region. Since the weight of blind holes is significantly higher than that of through holes, blind holes are used as the primary alignment reference.

[0030] For a blind hole target in the left region ( =10μm) and a through-hole target ( The weight calculation for (5μm) is as follows: Blind hole target weight =0.5×(1-10 / 25)×0.8=0.24 Through-hole target weight =0.5×(1-5 / 25)×1.2=0.48 The weight of the through-hole target in this region is significantly higher than that of the blind-hole target. Therefore, the alignment reference is based on the through-hole target. The results for the right region are similar, and no further examples will be provided here.

[0031] In addition, cross-identification verification is performed before selecting the alignment reference combination to ensure the consistency of the alignment parameters calculated for the blind hole target group and the through hole target group, and to eliminate interference from abnormal targets. More specifically, taking the central area as an example, this exposure area contains 4 blind hole targets (numbered blind hole 1, blind hole 2, blind hole 3, and blind hole 4) and 4 through hole targets (numbered through hole 1, through hole 2, through hole 3, and through hole 4), and the blind holes and the corresponding numbered through holes are almost overlapping in position (i.e., blind hole 1 and through hole 1 are close in position, and so on). First, calculate two sets of alignment parameters independently based on the blind hole group and the through hole group respectively: Calculate one set of alignment parameters (translation amount) based on the blind hole group (blind hole 1, blind hole 2, blind hole 3, blind hole 4). , Rotation angle ); and another set of alignment parameters (translation amount) calculated based on the through-hole group (through-hole 1, through-hole 2, through-hole 3, through-hole 4). , Rotation angle );in, , The translational amount of the alignment reference in the X and Y directions, calculated based on the blind hole group; , The translational amount of the alignment reference in the X and Y directions, calculated based on the through-hole group; , These are the rotation angles of the alignment references calculated based on the blind hole group and the through hole group, respectively.

[0032] To verify the reliability of the two sets of benchmarks, two different target-grabbing combinations were designed for comparative testing. The reliability of each set of targets was determined by exposure, AOI scanning after etching, and visual inspection of the misalignment. Option 1: Select blind vias 1 and 3, and vias 2 and 4 as a composite target combination (i.e., 2 blind vias + 2 vias). Using this combination, calculate the alignment reference. After exposure and etching, inspect the misalignment between the outer layer circuit image 3 (which includes the outer layer via target and blind via target) and the inner layer circuit pattern 2 (which includes the inner layer vias, blind vias, and copper pads) using AOI scanning and visual inspection. Option 2: Select blind vias 2 and 4, and through vias 1 and 3 as a composite target combination. After exposure and etching, check the misalignment.

[0033] The detection results of the two methods were then compared: If neither scheme shows significant misalignment (i.e., alignment deviation ≤ preset threshold), it indicates that the blind hole group and the through hole group are in good agreement, and both sets of benchmarks are reliable. Scheme 1 (or the result of dynamic weight allocation) can be directly used as the alignment benchmark.

[0034] If Scheme 1 is significantly off-target while Scheme 2 is normal, it indicates that there are abnormal targets (such as excessive offset or local deformation interference) in the blind holes 1, blind holes 3 or through holes 2 and through holes 4 selected in Scheme 1. In this case, the dynamic weight allocation should be adjusted (reduce the weight of abnormal targets) or the targets should be re-screened, and the combination of Scheme 2 should be given priority.

[0035] If both methods result in misalignment, the original data of the exposed area needs to be re-examined, or the target screening range needs to be expanded.

[0036] It should be understood that in actual mass production, it is unnecessary to perform exposure tests for both schemes every time. Instead, a deviation model between the alignment parameters of the blind via group and the through via group is established in advance through a small number of tests. Specifically, the calculation... and The difference and The difference and The difference: If all deviations are less than the preset threshold (e.g., translation deviation does not exceed 2μm, angle deviation does not exceed 0.005°), then the two sets of benchmarks are considered consistent, and the optimal combination selected after dynamic weight allocation is directly used for exposure; if any deviation exceeds the preset threshold, an adjustment mechanism is triggered: for example, temporarily increasing the exposure value. or The weight of a certain type of target can be increased, or blind and / or through-hole targets can be re-screened (e.g., the target with the lowest weight is removed and then recalculated) until the two sets of parameters are consistent.

[0037] Through the above cross-identification verification, abnormal targets caused by local deformation or detection errors can be effectively eliminated, ensuring the reliability and consistency of the alignment reference.

[0038] Subsequently, based on the three-dimensional deformation curve data of each exposure area, the alignment reference combination, and the dilation parameters, the preset exposure pattern is dynamically scaled and / or rotated and / or radially compressed to generate a corrected exposure pattern: For the central area: Due to a 0.15% radial expansion and a small rotational offset, the preset exposure pattern (i.e., the designed exposure pattern) corresponding to the central area undergoes radial compression compensation (based on the expansion parameters, the center of the exposure area is radially compressed by 0.8%) to counteract the central bulge caused by the "bulge" deformation. It is also dynamically scaled (compressed by 1.2%; of course, in other embodiments, the dynamic scaling ratio can be other values ​​within the range of ±0.5% to ±2%, depending on actual needs). Simultaneously, rotation correction is applied (rotation angle of 0.08°; of course, in other embodiments, the rotation angle can be other values ​​within the range of ±0.01° to ±0.1°, depending on actual needs). The generated corrected pattern highly matches the actual deformation of the central area.

[0039] For the left region (edge ​​region): the deformation is small, and only a small scaling correction (scaling ratio of about 0.5%) and a small rotation (0.01°) are made based on its expansion rate (0.02%) and offset data, without radial compression compensation; For the right area (edge ​​area), similar to the left area, make minor adjustments (scaling ratio of approximately 0.5%, rotation of approximately 0.01°).

[0040] Finally, using an LDI laser direct imaging device, each exposure area was sequentially exposed according to the corrected exposure pattern. The exposure order was: left area → middle area → right area. Each exposure area was independently aligned and exposed. During the exposure process, the edge-to-edge error of adjacent outer layer circuit images 3 was monitored in real time. The measurement results were: the edge-to-edge error between the left and middle areas was 12μm, and the edge-to-edge error between the middle and right areas was 10μm, both not exceeding 15μm.

[0041] After exposure, subsequent processes such as development and etching are performed on the board to obtain the outer layer circuit pattern that is precisely aligned with the inner layer circuit pattern 2. AOI optical inspection shows that the overall alignment accuracy reaches ±23μm (better than the target value of ±25μm), and the maximum edge error between adjacent outer layer circuit images 3 is 12μm, with no defects such as short circuits, open circuits, or via misalignment. Compared with the traditional global alignment method (alignment accuracy of approximately ±40μm), this embodiment improves the alignment accuracy by more than 40%.

[0042] In summary, this embodiment first divides the surface of the multilayer flexible circuit board into a central region (middle zone) and an edge region (left and right zones). Then, it collects the three-dimensional deformation curvature data, expansion parameters, and through-hole / blind-hole target offsets for each zone, achieving "zone-by-zone detection" to avoid interference from overall deformation data on local correction. Through dynamic weight allocation, the central zone prioritizes blind-hole targets (blind-hole targets have better following properties with board deformation), while the edge zone prioritizes through-hole targets (through-hole targets have higher stability in areas with small deformation), achieving adaptive optimal target selection. Cross-identification verification ensures that the alignment parameters calculated for the blind-hole group and the through-hole group are consistent, eliminating interference from abnormal targets. Combining the three-dimensional deformation curvature, expansion parameters, and alignment references of each zone, the preset exposure pattern is subjected to zone scaling, rotation, and radial compression compensation to ensure that the pattern highly matches the actual deformation of the physical board. Finally, sequential exposure yields a high-precision aligned outer layer circuit image 3, with adjacent edge errors and overall alignment accuracy meeting design requirements. This method significantly improves the alignment accuracy in scenarios involving deformation of the "big belly" after compression.

[0043] Specifically, this embodiment also provides a multilayer flexible circuit board manufacturing system, which uses the alignment exposure method for multilayer flexible circuit boards described above to expose the multilayer flexible circuit board, including: A partitioning module is used to divide the multilayer flexible circuit board into multiple exposure areas; The data acquisition module is used to acquire the three-dimensional deformation curve data, expansion parameters, and offset of blind hole targets and through hole targets in each exposure area. The weight evaluation and screening module is used to assign dynamic weights to blind hole targets and through hole targets in each exposure area according to the obtained offset of blind hole targets and through hole targets, and select the two blind hole targets and two through hole targets with the highest dynamic weights in each exposure area as their alignment reference combination. The cross-validation module is used to independently calculate two sets of alignment parameters based on blind hole targets and through hole targets in the same exposure area, and compare the consistency of the two sets of alignment parameters. If the comparison deviation exceeds the preset value, the dynamic weight allocation is adjusted or the blind hole targets and / or through hole targets are re-screened. The graphic correction module is used to perform partitioned dynamic scaling and / or rotation and / or radial compression compensation on the preset exposure graphic based on the three-dimensional deformation curve data of each exposure area, the alignment reference combination and the expansion parameter, so as to generate the corrected exposure graphic. An exposure control module is used to control the exposure light source to sequentially expose each exposure area according to the corrected exposure pattern in order to obtain an outer layer circuit image 3 that aligns with the inner layer circuit pattern 2 of the flexible circuit board, and to monitor the edge error of adjacent outer layer circuit images 3.

[0044] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any changes, 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 method for alignment exposure of a multilayer flexible circuit board, characterized in that, Includes the following steps: A multilayer flexible circuit board that has undergone a lamination process is provided, wherein multiple target groups are formed on the board surface, the target groups including multiple blind hole targets and multiple through hole targets distributed in different areas of the board surface; The surface of the multilayer flexible circuit board is divided into multiple independent exposure areas, and three-dimensional deformation curve data, expansion parameters, and offset of blind hole targets and through hole targets in each exposure area are collected. Based on the obtained offset of blind hole targets and through hole targets, dynamic weights are assigned to the blind hole targets and through hole targets in each of the exposure areas, and the two blind hole targets and two through hole targets with the highest dynamic weights in each exposure area are selected as their alignment reference combination. Based on the three-dimensional deformation curve data of each exposure area, the alignment reference combination and the expansion parameters, the preset exposure pattern is dynamically scaled and / or rotated and / or radially compressed to generate a corrected exposure pattern. Each of the exposure areas is exposed sequentially according to the corrected exposure pattern to obtain an outer layer circuit image that aligns with the inner layer circuit pattern of the flexible circuit board.

2. The alignment exposure method for a multilayer flexible circuit board according to claim 1, characterized in that, In the step of "dividing the surface of the multilayer flexible circuit board into multiple independent exposure areas, collecting three-dimensional deformation data of each exposure area, and the offset of blind hole targets and through hole targets located within that area", The surface of the multilayer flexible circuit board is divided into multiple independent exposure areas according to the size of the multilayer flexible circuit board and the preset deformation distribution rules; Each of the exposure areas was scanned separately using a three-dimensional scanning device to collect its three-dimensional deformation data; A GIS graphic image system is used to perform image recognition on each of the exposure areas to obtain their dilation parameters; An AOI / X-ray inspection device is used to determine the actual position coordinates of the blind hole target and the through hole target in each of the exposure areas, and compare them with the preset coordinates to obtain the offset of the blind hole target and the through hole target.

3. The alignment exposure method for a multilayer flexible circuit board according to claim 1, characterized in that, The step "Assigning dynamic weights to the blind hole targets and through hole targets located in each of the exposure areas based on the obtained offsets of the blind hole targets and through hole targets" specifically includes: Set an offset qualification threshold ; When the offset of any of the blind hole targets or through hole targets is greater than the offset qualification threshold When this happens, the weight of the blind hole target or through hole target is reset to 0; When the offset of any of the blind hole targets or through hole targets is less than or equal to the offset qualification threshold When the weight is calculated, it is done using the following formula: Blind hole target weight ; Through-hole target weight ; in, This represents the offset of the blind hole target. This represents the offset of the through-hole target. , All are regional strategy coefficients.

4. The alignment exposure method for a multilayer flexible circuit board according to claim 3, characterized in that, When the exposure area is located in the center region of the plate surface =1.2, =0.8; When the exposure area is located at the edge of the plate surface =0.8, =1.

2.

5. The alignment exposure method for a multilayer flexible circuit board according to claim 1, characterized in that, Before the step of "selecting the two blind hole targets and two through hole targets with the highest dynamic weights in each exposure area as its alignment reference combination", two sets of alignment parameters are independently calculated based on the blind hole targets and through hole targets in the current exposure area, and the consistency of the two sets of alignment parameters is compared. If the comparison deviation exceeds the preset value, the dynamic weight allocation is adjusted or the blind hole targets and / or through hole targets are re-screened.

6. The alignment exposure method for a multilayer flexible circuit board according to claim 1, characterized in that, In the step "based on the three-dimensional deformation curve data of each exposure area, the alignment reference combination, and the dilation parameters, the preset exposure pattern is dynamically scaled and / or rotated and / or radially compressed to generate a corrected exposure pattern", The scaling ratio for dynamically scaling the preset exposure graphic ranges from ±0.5% to ±2%. The rotation angle range for the preset exposure pattern is ±0.01° to ±0.1°.

7. The alignment exposure method for a multilayer flexible circuit board according to claim 1, characterized in that, In the step "based on the three-dimensional deformation curve data of each exposure area, the alignment reference combination and the dilation parameter, the preset exposure pattern is dynamically scaled and / or rotated and / or radially compressed to generate a corrected exposure pattern", radial compression compensation is performed on the center of the exposure area according to the dilation parameter.

8. The alignment exposure method for a multilayer flexible circuit board according to claim 1, characterized in that, In the step of "exposing each of the exposure areas sequentially according to the corrected exposure pattern to obtain an outer layer circuit image that aligns with the inner layer circuit pattern of the flexible circuit board", the edge-to-edge error of adjacent outer layer circuit images is no greater than 15μm.

9. A multilayer flexible circuit board manufacturing system, characterized in that, Expose a multilayer flexible circuit board using the alignment exposure method for any one of claims 1 to 8, comprising: A partitioning module is used to divide the multilayer flexible circuit board into multiple exposure areas; The data acquisition module is used to acquire the three-dimensional deformation curve data, expansion parameters, and offset of blind hole targets and through hole targets in each exposure area. The weight evaluation and screening module is used to assign dynamic weights to blind hole targets and through hole targets in each exposure area according to the obtained offset of blind hole targets and through hole targets, and select the two blind hole targets and two through hole targets with the highest dynamic weights in each exposure area as their alignment reference combination. The cross-validation module is used to independently calculate two sets of alignment parameters based on blind hole targets and through hole targets in the same exposure area, and compare the consistency of the two sets of alignment parameters. If the comparison deviation exceeds the preset value, the dynamic weight allocation is adjusted or the blind hole targets and / or through hole targets are re-screened. The graphic correction module is used to perform partitioned dynamic scaling and / or rotation and / or radial compression compensation on the preset exposure graphic based on the three-dimensional deformation curve data of each exposure area, the alignment reference combination and the expansion parameter, so as to generate the corrected exposure graphic. An exposure control module is used to control the exposure light source to sequentially expose each exposure area according to the corrected exposure pattern in order to obtain an outer layer circuit image that aligns with the inner layer circuit pattern of the flexible circuit board, and to monitor the edge-fitting error of adjacent outer layer circuit images.

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