Method for realizing PCB interlayer alignment precision judgment and target spot thereof

Abstract

The invention provides a method for judging the interlayer alignment precision of a PCB (Printed Circuit Board) and a target spot thereof, and particularly, a circular target spot and an annular target spot which are concentrically nested are respectively used at the same position of two adjacent layers of PCBs, so that the interlayer alignment precision information between the two adjacent layers of PCBs can be quickly judged in a visual identification mode, and the accuracy of the interlayer alignment precision of the two adjacent layers of PCBs is improved. And whether the laminated two adjacent layers of PCBs are within the allowable error range of the layer deviation and whether the layer deviation adjustment is needed are accurately judged, so that the manufacturing process of judging the layer deviation information layer by layer in the PCB laminating process is simplified. According to the method, the target point system arranged on the multi-layer PCB is optimized, so that the position combination of the target points which are pressed for multiple times can quickly reflect the interlayer alignment condition in the current pressing state, and therefore, before the total pressing manufacturing of the multi-layer PCB, the inner-layer board which is staggered in the interlayer can be quickly identified and directionally replaced; the production yield of the multi-layer PCB is improved, the production efficiency of the multi-layer PCB is improved, the cost is saved, and the method is more suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the field of printed circuit board manufacturing, and more specifically, to a method for realizing PCB layer inter-layer alignment accuracy judgment and a target thereof. Background Art

[0002] In the production process of PCB (Printed Circuit Board), especially in the lamination process of multilayer boards, the interlayer alignment accuracy is very important. The circuit pattern of each layer needs to be accurately aligned to ensure the normal function of the entire circuit board. If the alignment is inaccurate, it may cause electrical problems such as signal interference, short circuit or open circuit, affecting the quality of the final product. In actual production, circuit board manufacturers usually use X-ACT (i.e. X-Axis Alignment Control Tool) to measure the interlayer alignment of the manufactured multilayer boards to prevent the occurrence of interlayer internal errors in the PCB and affect the reliability of the PCB. Interlayer internal errors refer to the failure of the inner layer board to accurately align with other layers during the lamination process of the multilayer PCB, resulting in the deviation of the inner layer circuit pattern. The measurement principle of X-CAT to identify interlayer internal errors is mainly to use high-precision laser or visual system to detect the position error between each layer of the PCB and the reference point, so as to judge the alignment accuracy between different layers, thereby identifying the multilayer boards with internal errors and scrapping them, and improving the yield rate of the product. However, in the actual production process, the multi-layer boards after lamination have to be scrapped after the internal errors between layers are identified, which greatly increases the cost of PCB production. If the internal errors between layers of the inner layer boards can be identified in time during the lamination process and the inner layer boards with internal errors can be replaced in a targeted manner, it is possible to save costs and ensure the production accuracy of multi-layer PCBs.

[0003] However, in the actual production process, to identify the risk of internal misalignment of the inner layer board in a timely manner, it is only possible to continuously monitor the interlayer alignment through X-ACT or other precision detection tools. That is, during the lamination process of multi-layer PCBs, after each lamination, it is necessary to use X-ACT or other precision alignment instruments to measure the interlayer alignment. The marking points of each layer are scanned through X-ACT and compared with the position of the alignment reference to find out whether there is a misalignment phenomenon. When X-ACT detects that the alignment error of a certain inner layer board exceeds the set tolerance range, the system will mark this layer and report the specific error type and its position; based on the error information, the operator can judge which specific layer board has been misaligned and determine the direction and magnitude of the misalignment; then, after discovering the misaligned layer, the operator can correct it by repositioning or re-laminating. If the misalignment cannot be corrected, the inner layer board can be replaced before the total lamination. The replaced inner layer board should be placed directionally according to the misalignment direction to ensure that the new layer board can be correctly aligned; after replacing or repairing the inner layer board, it is necessary to perform lamination again and at the same time perform X-ACT interlayer alignment inspection to ensure that the alignment between each layer is restored correctly. Although this method can accurately identify the internal misalignment between layers during the lamination process of multi-layer PCBs and replace the misaligned inner layer board in a timely manner, it requires multiple alignment inspections, the process is complex, and it affects the production efficiency of multi-layer PCBs. Therefore, it is necessary to explore a simple and fast method for judging the interlayer alignment accuracy that is applicable to mass production and can quickly identify the internal misalignment between layers before the total lamination of multi-layer PCBs. Summary of the Invention

[0004] The present invention aims to overcome at least one defect of the above-mentioned prior art, and provides a method for realizing the judgment of the interlayer alignment accuracy of PCBs and its target points. By optimizing the target point system set on multi-layer PCBs, the position combination between the target points of multiple laminations can quickly reflect the interlayer alignment situation under the current lamination state, so as to quickly identify the inner layer board with internal misalignment between layers and perform directional replacement before the total lamination of multi-layer PCBs.

[0005] The technical solution adopted by the present invention is first to provide a target point for realizing the judgment of the interlayer alignment accuracy of PCBs, which is used to realize the judgment of the positioning accuracy between the first PCB and the second PCB during the lamination process. The target point includes: A circular target point set on the first PCB, the radius of the circular target point is r1, and outside the circular target point is a circular boundary with an outer radius of R1; and, An annular target point set on the second PCB, the inner radius of the annular target point is r2, and the outer radius is R2; The circular target point corresponds to the annular target point, r1 < r2, R2 < R1, and (r2 - r1) < (R1 - R2).

[0006] In this technical solution, by setting circular targets and annular targets that are concentrically nested at the same position on adjacent two layers of PCBs, the interlayer alignment accuracy between adjacent two layers of PCBs can be quickly judged by visual recognition. Specifically, a circular target with a radius of r1 is set on the first PCB, and a circular boundary with a radius of R1 is concentrically arranged outside the circular target, so that the difference range of the interlayer alignment accuracy of the target recognition on the first PCB is defined by the radius of the circular target and the radius difference of the circular boundary; at the same time, the annular target set on the second PCB defines the difference range of the interlayer alignment accuracy of the target recognition on the second PCB through the inner radius r2 and the outer radius R2 of the annular target; then by setting the first PCB and the second PCB to be concentrically stacked, r1 < r2, R2 < R1, and (r2 - r1) < (R1 - R2), thus defining the splitting points of the two layer deviation accuracy values, namely (r2 - r1) and (R1 - R2). Further, through visual recognition methods, such as laser scanning and human eye judgment, the position information of the edge of the circular target and the inner edge of the annular target and the position information of the circular boundary and the outer edge of the annular target when adjacent two PCBs are stacked can be conveniently and quickly recognized, and by comprehensively comparing the above two position information, the layer deviation range between the two PCBs can be accurately judged, and it can be accurately judged whether the adjacent two layers of PCBs being pressed are within the allowable error range of layer deviation and whether layer deviation adjustment is required, simplifying the manufacturing process of judging the layer deviation information layer by layer during the PCB pressing process. Specifically, the process of judging the interlayer alignment accuracy of adjacent two layers of PCBs by adopting this technical solution is as follows: when the edge of the circular target and the inner edge of the annular target and the circular boundary and the outer edge of the annular target are not tangent, the interlayer alignment deviation between the first PCB and the second PCB is less than (r2 - r1); when the edge of the circular target and the inner edge of the annular target are tangent / intersecting, but the circular boundary and the outer edge of the annular target are not tangent, the interlayer alignment deviation amount between the first PCB and the second PCB is between (r2 - r1) and (R1 - R2); when the edge of the circular target and the inner edge of the annular target intersect, but the circular boundary and the outer edge of the annular target are tangent / intersecting, the interlayer alignment deviation amount between the first PCB and the second PCB is not less than (R1 - R2). By setting the splitting points of the two layer deviation accuracy values, three ranges for judging the interlayer alignment deviation amount between adjacent two PCB boards are defined, and these three alignment deviation amount ranges can respectively correspond to three states of the allowable layer deviation error range without adjustment, the allowable layer deviation error range that can be adjusted, and the state beyond the allowable layer deviation error range between the adjacent first PCB and the second PCB, so as to conveniently and quickly recognize the interlayer alignment accuracy between adjacent two PCBs and judge the adjustment requirements of their manufacturing states, improving the judgment speed while ensuring the layer deviation judgment accuracy, improving the production efficiency of multi-layer PCBs, improving the production yield of multi-layer PCBs and saving costs at the same time, and being more suitable for large-scale production situations.

[0007] Preferably, in order to ensure the inter-layer alignment accuracy of each layer of the multi-layer PCB, while reducing the setting area of ​​the target point, improving the board surface utilization and ensuring the precision and reliability of the overall production of the multi-layer PCB, the r2-r1 is set between 2-8 mil, the R1-R2 is set between 6-10 mil, and the (R1-R2)-(r2-r1) is set between 1-5 mil.

[0008] Furthermore, when the laminated PCB includes multiple layers, the first PCB and the second PCB are alternately arranged, and there is at least one middle layer PCB between the uppermost PCB and the lowermost PCB. The laminated multi-layer PCB is also provided with a target point for subsequent lamination, and the middle layer PCB is provided with a hollow area at a position corresponding to the target point for subsequent lamination, and the area of ​​the hollow area is larger than the area of ​​the circular target point or the annular target point.

[0009] In the present technical solution, the multi-layer PCB can also be manufactured by continuous pressing. In the overall structural setting of the multi-layer PCB, a first PCB with a circular target and a second PCB with an annular target are alternately arranged, so that in each pressing process of the continuous pressing, the inter-layer alignment state of the PCB after each pressing can be quickly identified by the positions of the circular target and the annular target. Furthermore, during continuous lamination, the PCB formed by one lamination will be used as an intermediate layer as a whole and will be stacked on top of other PCBs that have not been laminated, and will be laminated for a second time. Since the PCB lamination process will cause the board surface on the PCB to expand and shrink, the target points on the laminated PCB used to identify the interlayer alignment accuracy will be relatively displaced as the board surface expands and shrinks. In order to ensure the interlayer alignment recognition accuracy of each lamination during the continuous lamination process, it is set so that the circular target points and annular target points for determining the interlayer alignment accuracy are not reused in each lamination. Specifically, it is set so that the PCBs that form the multi-layer PCB are all provided with target points for determining the interlayer alignment accuracy, and each time the circular target points and annular target points for determining the interlayer alignment accuracy are set on the PCB that has not been laminated during the current lamination, when the lamination is performed The PCB that has undergone one pressing is used as an intermediate layer and is provided with a hollow area at the position of the target point set on the corresponding PCB that has not been pressed for subsequent pressing to judge the interlayer alignment accuracy. On the intermediate layer, the copper surface on the PCB is removed at the hollow area, and the area of ​​the hollow area is larger than the area of ​​the circular target point or the annular target point, so that the circular target point and the annular target point set on the PCB that has not been pressed in the current pressing can be directly observed by X-ray through the corresponding position of the intermediate layer, so as to accurately judge the overall interlayer internal error of the PCB formed during this pressing, avoid the influence of the PCB expansion and contraction caused by continuous pressing on the judgment of the overall interlayer internal error in the multi-layer PCB, and further improve the accuracy and convenience of identifying and judging the interlayer alignment accuracy during the continuous pressing of the multi-layer PCB.

[0010] Furthermore, it also includes: an expansion and contraction target point, wherein the expansion and contraction target point includes: A first window disposed on the first PCB, a first reference target point and a first judgment target point disposed in the first window, wherein the first reference target point and the first judgment target point are staggered with each other and are not on the same X-axis or Y-axis coordinate; and, A second window disposed on the second PCB, a second reference target point and a second judgment target point disposed in the second window, wherein the second reference target point and the second judgment target point are staggered with each other and are not on the same X-axis or Y-axis coordinate; The first window opening position corresponds to the second window opening position, The first reference target point corresponds to the second reference target point. The first judgment target point and the second judgment target point are in the same X-axis or Y-axis direction, and are staggered in the Y-axis or X-axis direction.

[0011] In this technical solution, in order to ensure the inter-layer alignment accuracy of the multi-layer PCB and ensure the validity of the circular target and annular target board data used to judge the inter-layer alignment accuracy, expansion and contraction targets are also synchronously set on the first PCB and the second PCB. Specifically, by setting windows on the first PCB and the second PCB, and setting mutually staggered reference targets and judgment targets in the windows, and the reference targets and the judgment targets are not on the same X-axis or Y-axis coordinates, it is convenient to simultaneously reflect the expansion and contraction characteristics in the X-axis or Y-axis direction on the PCB; at the same time, the window removes the copper surface of a part of the area around the expansion and contraction target to facilitate the identification of the reference targets and the judgment targets; then, by setting the first window and the second window positions respectively set on the first PCB and the second PCB to correspond, while the first reference target and the second reference target positions correspond, the first judgment target and the second judgment target are in the same X-axis or Y-axis direction, and staggered in the Y-axis or X-axis direction, by combining the alignment of the reference target and the position information of the judgment target, the expansion and contraction occurring on the pressed PCB is accurately identified, thereby ensuring the validity of the circular target and the annular target used to judge the inter-layer alignment accuracy and the PCB board surface data thereof, and further improving the accuracy of the inter-layer alignment accuracy judgment in the PCB.

[0012] Furthermore, in order to more accurately reflect the expansion and contraction characteristics of the PCB in the X-axis or Y-axis direction during lamination, the expansion and contraction target points are arranged to include two groups of X-axis expansion and contraction target points and Y-axis expansion and contraction target points, and in order to ensure the independence of the circular target points and annular target points for judging the inter-layer alignment accuracy and the expansion and contraction target points during production and use, the distance between any group of expansion and contraction target points and the circular boundary is arranged to be not less than 100 mil, the first reference target point, the first judgment target point, the second reference target point and the second judgment target point are circular, the diameters of the first reference target point and the second reference target point are equal, the diameters of the first judgment target point and the second judgment target point are equal, and in order to facilitate the distinction between the targets, the diameters of the first judgment target point and the second judgment target point are arranged to be larger than the diameters of the first reference target point and the second reference target point.

[0013] Preferably, in the continuous pressing of multi-layer PCBs, there is also a situation where at least three layers of PCBs are pressed simultaneously, that is, at least one third PCB is arranged between the first PCB and the second PCB. In order to ensure the alignment accuracy between the layers of PCBs in the continuous pressing on the multi-layer PCBs, to facilitate the identification of the interlayer alignment accuracy of the layers of PCBs in the continuous pressing, and to ensure the validity of the circular target points and annular target points used for judging the interlayer alignment accuracy and the PCB board surface data, the third PCB is also provided with interlayer expansion and contraction target points. Further, the interlayer expansion and contraction target includes: a third window arranged on a third PCB, a third reference target and a third judgment target arranged in the third window, the third reference target and the third judgment target are staggered with each other and are not on the same X-axis or Y-axis coordinate; specifically, the third window corresponds to the first window and the second window position, the third reference target corresponds to the first reference target and the second reference target position, the third judgment target is in the same X-axis or Y-axis direction as the first judgment target and the second judgment target, and is staggered with the first judgment target and the second judgment target in the Y-axis or X-axis direction; by combining the alignment of the reference targets set on the multi-layer PCB and the position information of the judgment targets, the expansion and contraction occurring on the pressed PCB is accurately identified, thereby ensuring the validity of the circular targets and annular targets used for judging the interlayer alignment accuracy and the PCB surface data thereof, and further improving the accuracy of the interlayer alignment accuracy judgment in the multi-layer PCB.

[0014] The technical solution also provides a method for determining the inter-layer alignment accuracy of PCBs, which is used to determine the positioning accuracy between two or more PCB layers during the lamination process. In a pressing process, the specific steps are as follows: S11. Etching a target as described in any one of claims 1 to 6 on the PCB to be pressed, wherein the circular target and the annular target are alternately arranged on adjacent PCBs; S12. Pre-positioning the PCB to be pressed; S13. Observe the target point by X-ray machine to determine whether the alignment between the PCBs to be pressed meets the accuracy requirements; S14. If the precision requirement is met, pressing is performed; if the precision requirement is not met, returning to step S12 and re-pre-positioning is performed.

[0015] In the present technical solution, the process of using the present technical solution to quickly judge the positioning accuracy between two or more PCB layers is as follows: concentric circular target points and annular target points are alternately set on two adjacent PCB layers on the PCB to be pressed, and after the PCB to be pressed is pre-positioned, the circular target points and annular target points superimposed on the PCB are observed by an X-ray machine to judge whether the alignment between the PCBs to be pressed meets the accuracy requirements; specifically, when the edge of the circular target point is not tangent to the inner edge of the annular target point and the circular boundary is not tangent to the outer edge of the annular target point, the inter-layer alignment accuracy between the two adjacent PCB layers is within the allowable range of layer deviation error, and the pressing procedure can be entered without adjustment; when the edge of the circular target point is tangent / intersecting with the inner edge of the annular target point, but ... not tangent to the inner edge of the annular target point, and the circular boundary is not tangent to the outer edge of the annular target point. When the outer edges of the target points are not tangent, although the interlayer alignment accuracy between the two adjacent PCB layers is within the allowable range of layer deviation error, it can be adjusted by means of layer deviation correction to improve the interlayer alignment accuracy of the PCB and improve the pressing alignment accuracy; when the edge of the circular target point intersects with the inner edge of the annular target point, but the circular boundary is tangent / intersects with the outer edge of the annular target point, the interlayer alignment accuracy between the two adjacent PCB layers exceeds the allowable range of layer deviation error, and the PCB needs to be replaced, and the pre-positioning program and the interlayer alignment accuracy judgment program are re-performed, thereby improving the interlayer alignment accuracy of the pressed PCB, improving the pressing alignment accuracy, thereby improving the production yield of multi-layer PCBs, while improving the efficiency of multi-layer PCB production and manufacturing, saving costs, and being more suitable for large-scale production situations.

[0016] Furthermore, in the multiple lamination production process of the multi-layer PCB, in order to ensure the inter-layer alignment recognition accuracy of each lamination during the lamination process, the multi-layer PCBs to be laminated are divided into n groups, each group of PCBs is first laminated into an n-layer core board according to steps S11-S14, and then the n-layer core boards are laminated multiple times once or successively, and each lamination is performed with independent target points between the PCBs or between the core boards; Alternatively, in the multiple pressing processes, the multi-layer PCBs to be pressed are divided into n groups, and the n-1 group of PCBs are first pressed into an n-1 core board according to steps S11-S14, and then the n-1 core board is pressed with the remaining PCBs after multiple pressing once or successively, and each pressing is performed with independent target points between the PCBs or between the core boards or between the core board and the PCBs; In the above-mentioned core board pressing process, when the PCB pressed by the core board includes three layers or more, in the process of steps S11-S14, the first PCB and the second PCB are alternately arranged, and there is at least one middle layer PCB between the uppermost PCB and the lowermost PCB. In step S11, the middle layer PCB also includes etching the hollow area at the position of the target point of subsequent pressing; the copper surface on the PCB is removed at the hollow area, and the area of ​​the hollow area is larger than the area of ​​the circular target point or the annular target point, so that the circular target point and the annular target point set on the PCB that has not been pressed in the current pressing can be directly observed by X-ray through the site corresponding to the hollow area of ​​the middle layer, thereby avoiding the influence of the PCB expansion and contraction caused by continuous pressing on the judgment of the overall interlayer internal error in the multi-layer PCB, and further improving the accuracy and convenience of identifying and judging the interlayer alignment accuracy during the continuous pressing of the multi-layer PCB.

[0017] Furthermore, when the core board is laminated in multiple layers at one time, the following steps are also included: S15. On the top PCB and the bottom PCB of the core board, corresponding to the position of the hollow area of ​​the middle layer PCB, the target point for pressing the core board is etched, and the circular target point and the annular target point are respectively located on the front and back sides of the core board and are concentrically arranged; S16. Pre-positioning the core plate to be pressed; S17. Observe the target point by X-ray machine to determine whether the alignment between the core plates to be pressed meets the accuracy requirements; S18. If the precision requirement is met, pressing is performed; if the precision requirement is not met, returning to step S16 to perform pre-positioning again.

[0018] Furthermore, when the core board is laminated in layers one by one, the hollow area of ​​the PCB in the middle layer includes more than two, and a core board is used as a base board, and the core boards are laminated one by one on the base board to form a new base board, which specifically includes the following steps: S25. On the topmost PCB and the bottommost PCB of the base plate and the core plate to be pressed together, select the position of the hollow area of ​​the PCB of the middle layer, etch out the target point for pressing the base plate and the core plate, the circular target point and the annular target point are respectively located on the front and back sides of the base plate and the core plate, and are concentrically arranged. By realigning the PCB after the expansion and contraction conditions are stabilized after one pressing, and etching out the target points on the front and back surfaces, the interlayer alignment accuracy of the PCB after one pressing in the subsequent pressing process is guaranteed, and the overall reliability of the multi-layer PCB is improved; and at the same time, on the PCB where the base plate and the core plate are bonded to each other, the corresponding hollow area is etched corresponding to the position of the hollow area of ​​the PCB of the remaining middle layer, so that X-rays can pass through the superimposed PCB layers and accurately identify the target point information used to judge the interlayer alignment accuracy during the pressing; S26. Pre-positioning the base plate and core plate to be pressed; S27. Observe the target point by X-ray machine to determine whether the alignment between the base plate and the core plate to be pressed meets the accuracy requirements; S28. If the accuracy requirement is met, the new base plate is pressed together. If the accuracy requirement is not met, the process returns to step S26 and the pre-positioning is performed again. S29. Repeat steps S25-28 until all core panels are pressed together.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. By setting two adjacent layers of PCB at the same position and using concentrically nested circular targets and annular targets respectively, the inter-layer alignment accuracy between the two adjacent layers of PCB can be quickly determined by visual recognition. Specifically, a circular target with a radius of r1 is arranged on the first PCB, and a circular boundary with a radius of R1 is concentrically arranged outside the circular target, so that the radius difference of the circular target and the radius difference of the circular boundary define the difference range of the alignment accuracy between the target identification layers on the first PCB; at the same time, the annular target arranged on the second PCB defines the difference range of the alignment accuracy between the target identification layers on the second PCB through the inner radius r2 and the outer radius R2 of the annular target; through visual recognition methods, such as laser scanning and human eye judgment, the position information of the edge of the circular target and the inner edge of the annular target and the position information of the circular boundary and the outer edge of the annular target when two adjacent PCBs are stacked can be easily and quickly identified, and the layer deviation range between the two PCBs can be accurately determined by comprehensively comparing the above two position information, and it can be accurately determined whether the two adjacent layers of PCBs pressed together are within the allowable error range of the layer deviation and whether the layer deviation adjustment is required, thereby simplifying the manufacturing process of judging the layer deviation information layer by layer during the PCB pressing process.

[0020] 2. By setting the first PCB and the second PCB to be concentrically stacked, and setting the inner and outer diameter dimensions of the circular target and the annular target thereon as: r1 < r2, R2 < R1, (r2 - r1) < (R1 - R2), the splitting points of the upper layer deviation precision value of the adjacent two PCBs to be laminated are defined, that is, (r2 - r1) and (R1 - R2). Specifically, when the edge of the circular target is not tangent to the inner edge of the annular target and the circular boundary is not tangent to the outer edge of the annular target, the interlayer alignment deviation between the first PCB and the second PCB is less than (r2 - r1); when the edge of the circular target is tangent to / intersects with the inner edge of the annular target, but the circular boundary is not tangent to the outer edge of the annular target, the amount of interlayer alignment deviation between the first PCB and the second PCB is between (r2 - r1) and (R1 - R2); when the edge of the circular target intersects with the inner edge of the annular target, but the circular boundary is tangent to / intersects with the outer edge of the annular target, the amount of interlayer alignment deviation between the first PCB and the second PCB is not less than (R1 - R2). By setting the splitting points of the two layer deviation precision values, three ranges for judging the interlayer alignment deviation amount between two adjacent PCBs are defined. These three alignment deviation amount ranges can respectively correspond to three states within the allowable range of layer deviation error that does not require adjustment, within the allowable range of layer deviation error that can be adjusted, and beyond the allowable range of layer deviation error between the adjacent first PCB and the second PCB. Thus, it is convenient and fast to identify the interlayer alignment precision between two adjacent PCBs and judge the adjustment requirements of their manufacturing states, improving the judgment speed while ensuring the layer deviation judgment precision, simplifying the production process of multi-layer PCBs, improving the production yield of multi-layer PCBs while increasing the production efficiency of multi-layer PCBs and saving costs, and being more suitable for large-scale production scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 FIG. is a schematic structural diagram of the circular target and the expansion and contraction target on the first PCB provided by the present invention.

[0022] Figure 2 FIG. is a schematic structural diagram of the annular target and the expansion and contraction target on the second PCB provided by the present invention.

[0023] Figure 3 FIG. is a schematic structural diagram of the target and the expansion and contraction target obtained by X-ray scanning after the first PCB and the second PCB provided by the present invention are laminated.

[0024] Figure 4 FIG. is a schematic structural diagram of the specific application of the target for realizing the interlayer alignment precision judgment of the PCB in the first lamination process of the multi-layer PCB manufacturing process provided by the present invention.

[0025] Figure 5Schematic diagram of the specific application of the target point for realizing the interlayer alignment accuracy judgment of the PCB in the secondary lamination process of the multi-layer PCB manufacturing process.

[0026] Figure 6 Schematic diagram of the specific application of the target point for realizing the interlayer alignment accuracy judgment of the PCB in the tertiary lamination process of the multi-layer PCB manufacturing process.

[0027] Description of the drawings: Circular target point 100, first window 110, first reference target point 120, first judgment target point 130, annular target point 200, second window 210, second reference target point 220, second judgment target point 230, hollow area 300. Detailed implementation manners

[0028] The drawings of the present invention are only for illustrative purposes and should not be construed as a limitation of the present invention. To better illustrate the following embodiments, some components in the drawings may be omitted, enlarged or reduced, and do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0029] Embodiment 1 As Figure 1-Figure 3 shown, this embodiment provides a target point for realizing the interlayer alignment accuracy judgment of the PCB, which is used to realize the judgment of the positioning accuracy between the first PCB and the second PCB during the lamination process. The target point includes: A circular target point 100 provided on the first PCB, the radius of the circular target point 100 is r1, and outside the circular target point 100 is a circular boundary with an outer radius of R1; and, An annular target point 200 provided on the second PCB, the inner radius of the annular target point 200 is r2, and the outer radius is R2; The circular target point 100 corresponds to the annular target point 200 in position, r1 < r2, R2 < R1, and (r2 - r1) < (R1 - R2).

[0030] Specifically, a circular target 100 with a radius of r1 is provided on the first PCB, and a circular boundary with a radius of R1 is concentrically arranged outside the circular target 100, thereby defining the difference range of the interlayer alignment accuracy of the target recognition layer on the first PCB by the radius difference between the circular target 100 and the circular boundary; at the same time, the annular target 200 provided on the second PCB defines the difference range of the interlayer alignment accuracy of the target recognition layer on the second PCB through the inner radius r2 and the outer radius R2 of the annular target 200; and the first PCB and the second PCB are stacked correspondingly, r1 < r2, R2 < R1, and (r2 - r1) < (R1 - R2). Further, through visual recognition methods, that is, X-ray scanning and human eye judgment, the position information of the edge of the circular target 100 and the inner edge of the annular target 200 and the position information of the circular boundary and the outer edge of the annular target 200 can be conveniently and quickly recognized when two adjacent PCBs are stacked, thereby defining the splitting points of the two layer offset precision values, that is, (r2 - r1) and (R1 - R2). By comprehensively comparing the above two position information, the layer offset range between the two PCBs can be accurately judged, and it can be accurately judged whether the adjacent two layers of PCBs being pressed are within the allowable error range of layer offset and whether layer offset adjustment is required, simplifying the manufacturing process of judging the layer offset information layer by layer during the PCB pressing process.

[0031] Specifically, the process of using the target provided in this embodiment to judge the interlayer alignment accuracy of two adjacent layers of PCBs is as follows: when the edge of the circular target 100 and the inner edge of the annular target 200 and the circular boundary and the outer edge of the annular target 200 are not tangent, the interlayer alignment deviation between the first PCB and the second PCB is less than (r2 - r1); when the edge of the circular target 100 is tangent to / intersects with the inner edge of the annular target 200, but the circular boundary and the outer edge of the annular target 200 are not tangent, the interlayer alignment deviation amount between the first PCB and the second PCB is between (r2 - r1) and (R1 - R2); when the edge of the circular target 100 intersects with the inner edge of the annular target 200, but the circular boundary and the outer edge of the annular target 200 are tangent to / intersect with each other, the interlayer alignment deviation amount between the first PCB and the second PCB is not less than (R1 - R2). Thus, the interlayer alignment deviation range between two adjacent PCBs can be conveniently and quickly recognized to judge whether layer offset correction is required, improving the judgment speed while ensuring the layer offset judgment accuracy, improving the production efficiency of multi-layer PCBs, improving the production yield of multi-layer PCBs, saving costs at the same time, and being more suitable for large-scale production scenarios.

[0032] Preferably, in order to ensure the inter-layer alignment accuracy of each layer of the multi-layer PCB, while reducing the setting area of ​​the target point, improving the board surface utilization and ensuring the precision and reliability of the overall production of the multi-layer PCB, r2-r1 is set between 2-8 mil, R1-R2 is between 6-10 mil, and (R1-R2)-(r2-r1) is between 1-5 mil.

[0033] Furthermore, when the laminated PCB includes multiple layers, and the multi-layer PCB can also be manufactured by continuous lamination, the first PCB and the second PCB are alternately arranged, so that in each lamination process of the continuous lamination, the interlayer alignment state of the PCB after each lamination can be quickly identified by the positions of the circular target point 100 and the annular target point 200; further, in the process of lamination more than once in the continuous lamination, there is at least one intermediate layer of PCB between the topmost PCB and the bottommost PCB. In order to ensure the interlayer alignment recognition accuracy of each lamination in the continuous lamination process, it is set so that the circular target point 100 and the annular target point 200 for judging the interlayer alignment accuracy are not repeated in each lamination. The multi-layer PCB after lamination is further provided with a target point for subsequent lamination, and the middle layer PCB is provided with a hollow area 300 at a position corresponding to the target point for subsequent lamination, and the copper surface on the PCB is removed at the hollow area 300. The area of ​​the hollow area 300 is larger than the area of ​​the circular target point 100 or the annular target point 200, so that the circular target point 100 and the annular target point 200 set on the PCB that has not been laminarized in the current lamination can be directly observed by X-ray through the corresponding position of the middle layer, thereby avoiding the influence of the expansion and contraction of the PCB caused by continuous lamination on the judgment of the overall interlayer internal misalignment in the multi-layer PCB, and further improving the accuracy and convenience of identifying and judging the interlayer alignment accuracy during the continuous lamination of the multi-layer PCB.

[0034] Furthermore, in order to ensure the inter-layer alignment accuracy of the multi-layer PCB and ensure the validity of the board surface data of the circular target 100 and the annular target 200 used to judge the inter-layer alignment accuracy, expansion and contraction targets are also synchronously set on the first PCB and the second PCB; Specifically, the expansion and contraction target includes: a first window 110 disposed on the first PCB, a first reference target 120 and a first judgment target 130 disposed in the first window 110, the first reference target 120 and the first judgment target 130 are staggered from each other and are not on the same X-axis or Y-axis coordinate; and, A second window 210 disposed on the second PCB, a second reference target point 220 and a second judgment target point 230 disposed in the second window 210, the second reference target point 220 and the second judgment target point 230 are staggered with each other and are not on the same X-axis or Y-axis coordinate; The first window 110 and the second window 210 are located in corresponding positions. The first reference target point 120 corresponds to the second reference target point 220. The first determination target point 130 and the second determination target point 230 are in the same X-axis or Y-axis direction, and are staggered in the Y-axis or X-axis direction.

[0035] Furthermore, in order to more accurately reflect the expansion and contraction characteristics of the PCB in the X-axis or Y-axis direction during lamination, the expansion and contraction targets are set to include two groups of X-axis expansion and contraction targets and Y-axis expansion and contraction targets, and in order to ensure the independence of the circular target 100 and the annular target 200 for judging the inter-layer alignment accuracy and the expansion and contraction targets during production and use, the distance between any group of expansion and contraction targets and the circular boundary is set to be no less than 100 mil, the first reference target 120, the first judgment target 130, the second reference target 220 and the second judgment target 230 are circular, the diameters of the first reference target 120 and the second reference target 220 are equal, the diameters of the first judgment target 130 and the second judgment target 230 are equal, and in order to facilitate the distinction between the targets, the diameters of the first judgment target 130 and the second judgment target 230 are set to be larger than the diameters of the first reference target 120 and the second reference target 220.

[0036] Preferably, in the continuous pressing of multi-layer PCBs, there is also a situation where at least three layers of PCBs are pressed simultaneously, that is, at least one third PCB is arranged between the first PCB and the second PCB. In order to ensure the alignment accuracy between the layers of PCBs in the continuous pressing of the multi-layer PCBs, to facilitate the identification of the interlayer alignment accuracy of the layers of PCBs in the continuous pressing, and to ensure the validity of the circular target points 100 and the annular target points 200 used to judge the interlayer alignment accuracy and the PCB surface data, the third PCB is also provided with interlayer expansion and contraction target points. Further, the interlayer expansion and contraction target includes: a third window set on the third PCB, a third reference target set in the third window, and a third judgment target, the third reference target and the third judgment target are staggered and are not on the same X-axis or Y-axis coordinates; specifically, the third window corresponds to the first window 110 and the second window 210, the third reference target corresponds to the first reference target 120 and the second reference target 220, the third judgment target is in the same X-axis or Y-axis direction as the first judgment target 130 and the second judgment target 230, and is staggered with the first judgment target 130 and the second judgment target 230 in the Y-axis or X-axis direction; by combining the alignment of the reference targets set on the multi-layer PCB and the position information of the judgment targets, the expansion and contraction occurring on the pressed PCB is accurately identified, thereby ensuring the validity of the circular targets 100 and the annular targets 200 used to judge the interlayer alignment accuracy and the PCB surface data thereof, and further improving the accuracy of the interlayer alignment accuracy judgment in the multi-layer PCB.

[0037] Example 2 like Figure 1-Figure 3As shown, this embodiment provides a method for determining the inter-layer alignment accuracy of a PCB, which is used to determine the positioning accuracy between two or more PCB layers during the lamination process. In a pressing process, the specific steps are as follows: S11. Etching a target as claimed in any one of claims 1 to 6 on the PCB to be pressed, the circular target 100 and the annular target 200 are alternately arranged on adjacent PCBs; S12. Pre-positioning the PCB to be pressed; S13. Observe the target point through an X-ray machine to determine whether the alignment between the PCBs to be pressed meets the accuracy requirements; S14. If the precision requirement is met, pressing is performed; if the precision requirement is not met, returning to step S12 and re-pre-positioning is performed.

[0038] like Figure 4 As shown, in the multi-layer PCB manufacturing process, first, a pressing process for each sub-board is included, and concentric circular target points 100 and annular target points 200 are alternately set on two adjacent layers of the inner layer board on the PCB to be pressed. After the PCB to be pressed is pre-positioned, the circular target points 100 and annular target points 200 overlapped and set on the PCB are observed by an X-ray machine to determine whether the alignment between the PCBs to be pressed meets the accuracy requirements; preferably, the circular annular target points 200 are used on the PCB surface set as the multi-layer PCB, so as to facilitate the combined use of the targets for judging the inter-layer alignment accuracy. Specifically, when the edge of the circular target 100 is not tangent to the inner edge of the annular target 200 and the circular boundary is not tangent to the outer edge of the annular target 200, the interlayer alignment accuracy between the two adjacent layers of PCB is within the allowable range of layer deviation error, and the pressing procedure can be entered without adjustment; when the edge of the circular target 100 is tangent / intersecting with the inner edge of the annular target 200, but the circular boundary is not tangent to the outer edge of the annular target 200, although the interlayer alignment accuracy between the two adjacent layers of PCB is within the allowable range of layer deviation error, it can be adjusted by means of layer deviation correction to improve the interlayer alignment accuracy of the PCB. Improve the pressing alignment accuracy; when the edge of the circular target 100 intersects with the inner edge of the annular target 200, but the circular boundary is tangent to / intersects with the outer edge of the annular target 200, the interlayer alignment accuracy between the two adjacent layers of the PCB exceeds the allowable range of the layer deviation error, and the PCB needs to be replaced, and the pre-positioning program and the interlayer alignment accuracy judgment program are re-performed, thereby improving the interlayer alignment accuracy of the pressed PCB, improving the pressing alignment accuracy, thereby improving the production yield of the multi-layer PCB, and at the same time improving the efficiency of the production of the multi-layer PCB, saving costs, and being more suitable for large-scale production situations.

[0039] Furthermore, in the multiple lamination production process of the multi-layer PCB, in order to ensure the inter-layer alignment recognition accuracy of each lamination during the lamination process, the multi-layer PCBs to be laminated are divided into n groups, each group of PCBs is first laminated into an n-layer core board according to steps S11-S14, and then the n-layer core boards are laminated multiple times once or successively, and each lamination is performed with independent target points between the PCBs or between the core boards; Alternatively, in the multiple pressing processes, the multi-layer PCBs to be pressed are divided into n groups, and the n-1 group of PCBs are first pressed into an n-1 core board according to steps S11-S14, and then the n-1 core board is pressed with the remaining PCBs after multiple pressing once or successively, and each pressing is performed with independent target points between the PCBs or between the core boards or between the core board and the PCBs; In the above-mentioned core board pressing process, when the PCB pressed by the core board includes three layers or more, in the process of steps S11-S14, the first PCB and the second PCB are alternately arranged, and there is at least one middle layer PCB between the uppermost PCB and the lowermost PCB. In step S11, the middle layer PCB also includes etching a hollow area 300 at the position of the target point to be subsequently pressed; the copper surface on the PCB is removed at the hollow area 300, and the area of ​​the hollow area 300 is larger than the area of ​​the circular target point 100 or the annular target point 200, so that the circular target points 100 and the annular target points 200 arranged on the surfaces of both sides of the PCB can be directly observed by X-ray through the sites corresponding to the middle layer hollow area 300, thereby avoiding the influence of the PCB expansion and contraction caused by continuous pressing on the judgment of the overall interlayer internal misalignment in the multi-layer PCB, thereby ensuring the alignment accuracy between the PCB layers in the secondary pressing process, and improving the accuracy and convenience of identifying and judging the interlayer alignment accuracy during the continuous pressing of the multi-layer PCB.

[0040] Furthermore, when the core board is laminated in multiple layers at one time, the following steps are also included: S15. On the topmost PCB and the bottommost PCB of the core board, corresponding to the position of the hollow area 300 of the middle layer of the PCB, the target point of the core board pressing is etched, and the circular target point 100 and the annular target point 200 are respectively located on the front and back sides of the core board and are concentrically arranged; S16. Pre-positioning the core plate to be pressed; S17. Observe the target point through an X-ray machine to determine whether the alignment between the core plates to be pressed meets the accuracy requirements; S18. If the precision requirement is met, pressing is performed; if the precision requirement is not met, returning to step S16 to perform pre-positioning again.

[0041] like Figure 5As shown, the multilayer PCB includes two lamination processes, and the interlayer alignment of each lamination process is performed by using two sets of target points arranged in parallel on the PCB. Specifically, in the first lamination process, each layer of the PCB is provided with a circular target point 100 or annular target point 200. Preferably, the PCB set on the surface of the multilayer PCB uses the annular target point 200, which is convenient for the combined use of the target points for judging the interlayer alignment accuracy. In the second lamination process, the core board formed by the first lamination is in the setting area of ​​the second lamination target point, and the middle layer is a hollow layer. After the core board formed after the first lamination is cooled and the expansion and contraction coefficient is fixed, the core board surface is developed and etched to form a circular target point 100 or annular target point 200 for judging the interlayer alignment accuracy in the second lamination. Similarly, preferably, the PCB set on the surface of the multilayer PCB uses the annular target point 200. . Furthermore, when the core board is laminated in layers one by one, the hollow area 300 of the middle layer PCB includes more than two. A core board is used as a base board, and the core boards are laminated one by one on the base board to form a new base board, which specifically includes the following steps: S25. On the topmost PCB and the bottommost PCB of the base plate and the core plate to be pressed together, select a position of the hollow area 300 of the middle layer PCB, etch out the target point of the base plate and the core plate pressed together, wherein the circular target point 100 and the annular target point 200 are respectively located on the front and back sides of the base plate and the core plate, and are concentrically arranged; and at the same time, on the PCB where the base plate and the core plate are bonded to each other, corresponding to the position of the hollow area 300 of the remaining middle layer PCB, etch out the corresponding hollow area 300; S26. Pre-positioning the base plate and core plate to be pressed; S27. Observe the target point through an X-ray machine to determine whether the alignment between the base plate and the core plate to be pressed meets the accuracy requirements; S28. If the accuracy requirement is met, the new base plate is pressed together. If the accuracy requirement is not met, the process returns to step S26 and the pre-positioning is performed again. S29. Repeat steps S25-28 until all core panels are pressed together.

[0042] like Figure 6As shown in the figure, the multi-layer PCB includes three lamination processes, and the inter-layer alignment of each lamination process is performed by using three groups of target points arranged in parallel on the PCB. Specifically, in the first lamination process, each layer of the PCB is provided with a circular target point 100 or an annular target point 200. Preferably, the annular target point 200 is used on the PCB surface of the multi-layer PCB to facilitate the combined use of the target points for judging the accuracy of inter-layer alignment. In the second lamination process, the core board formed by the first lamination is in the setting area of ​​the second lamination target point, and the middle layer is a hollow layer. After the core board formed after the first lamination is cooled and the expansion and contraction coefficient is fixed, the hollow layer is formed on the surface of the core board. The circular target 100 or the circular target 200 for judging the inter-layer alignment accuracy in the secondary lamination is formed by surface development and etching. It is also preferred that the circular target 200 is used on the PCB set as the surface of a multi-layer PCB. In the three-layer lamination process, the core board formed by the secondary lamination is in the setting area of ​​the three-layer lamination target, and the middle layer is a hollow layer. After the core board formed after the secondary lamination is cooled and the expansion and contraction coefficient is fixed, the circular target 100 or the circular target 200 for judging the inter-layer alignment accuracy in the three-layer lamination is formed by development and etching on the surface of the core board. It is also preferred that the circular target 200 is used on the PCB set as the surface of a multi-layer PCB.

[0043] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the claims of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A target for determining the inter-layer alignment accuracy of a PCB, used to determine the positioning accuracy between a first PCB and a second PCB during the lamination process, characterized in that: The target points include: A circular target point disposed on the first PCB, the radius of the circular target point being r1, and outside the circular target point being a circular boundary with an outer radius of R1; and, An annular target point disposed on the second PCB, the inner radius of the annular target point being r2 and the outer radius being R2; The circular target point corresponds to the annular target point in position, r1 < r2, R2 < R1, and (r2 - r1) < (R1 - R2).

2. The target point for determining the inter-layer alignment accuracy of a PCB according to claim 1, characterized in that: r2 - r1 is between 2 - 8 mil, R1 - R2 is between 6 - 10 mil, and (R1 - R2) - (r2 - r1) is between 1 - 5 mil.

3. The target for realizing the inter-layer alignment accuracy judgment of PCB according to any one of claims 1-2, characterized in that: When the pressed PCB includes multiple layers, the first PCB and the second PCB are alternately arranged, and there is at least one intermediate layer PCB between the top - most PCB and the bottom - most PCB. The pressed multi - layer PCB is also provided with target points for subsequent pressing. The intermediate layer PCB is provided with a hollowed - out area at the position corresponding to the target points for subsequent pressing, and the area of the hollowed - out area is larger than the area of the circular target point or the annular target point.

4. The target point for determining the inter-layer alignment accuracy of a PCB according to claim 1, characterized in that: It also includes: Expansion and contraction target points, and the expansion and contraction target points include: A first opening disposed on the first PCB, a first reference target point and a first judgment target point disposed within the first opening. The first reference target point and the first judgment target point are staggered from each other and are not on the same X - axis or Y - axis coordinates; And, A second opening disposed on the second PCB, a second reference target point and a second judgment target point disposed within the second opening. The second reference target point and the second judgment target point are staggered from each other and are not on the same X - axis or Y - axis coordinates; The first opening corresponds to the second opening in position, The first reference target point corresponds to the second reference target point in position, The first judgment target point and the second judgment target point are in the same X - axis or Y - axis direction and are staggered in the Y - axis or X - axis direction.

5. The target point for determining the inter-layer alignment accuracy of a PCB according to claim 4 is characterized in that: The expansion and contraction target points include two groups of X - axis expansion and contraction target points and Y - axis expansion and contraction target points. The distance between any group of expansion and contraction target points and the circular boundary is not less than 100 mil. The first reference target point, the first judgment target point, the second reference target point and the second judgment target point are circular. The diameters of the first reference target point and the second reference target point are equal, the diameters of the first judgment target point and the second judgment target point are equal, and the diameters of the first judgment target point and the second judgment target point are larger than the diameters of the first reference target point and the second reference target point.

6. The target for realizing the inter-layer alignment accuracy judgment of PCB according to any one of claims 4 or 5, characterized in that: It also includes at least one third PCB disposed between the first PCB and the second PCB. The third PCB is provided with inter - layer expansion and contraction target points, and the inter - layer expansion and contraction target points include: A third opening disposed on the third PCB, a third reference target point and a third judgment target point disposed within the third opening. The third reference target point and the third judgment target point are staggered from each other and are not on the same X - axis or Y - axis coordinates; The third opening corresponds to the first opening and the second opening in position, The third reference target point corresponds to the first reference target point and the second reference target point in position, The third judgment target point and the first judgment target point and the second judgment target point are in the same X - axis or Y - axis direction and are staggered from the first judgment target point and the second judgment target point in the Y - axis or X - axis direction.

7. A method for determining the inter-layer alignment accuracy of a PCB, which is used to determine the positioning accuracy between two or more PCB layers during the lamination process, and is characterized in that: In a pressing process, the specific steps are as follows: S11. Etching a target as described in any one of claims 1 to 6 on the PCB to be pressed, wherein the circular target and the annular target are alternately arranged on adjacent PCBs; S12. Pre-positioning the PCB to be pressed; S13. Observe the target point by X-ray machine to determine whether the alignment between the PCBs to be pressed meets the accuracy requirements; S14. If the precision requirement is met, pressing is performed; if the precision requirement is not met, returning to step S12 and re-pre-positioning is performed.

8. The method for determining the inter-layer alignment accuracy of a PCB according to claim 7, characterized in that: In the multiple pressing process, the multi-layer PCBs to be pressed are divided into n groups, each group of PCBs is first pressed into an n-layer core board according to steps S11-S14, and then the n-layer core boards are pressed multiple times once or successively, and each pressing has independent target points between the PCBs or between the core boards; or, In the multiple pressing process, the multi-layer PCBs to be pressed are divided into n groups, and the n-1 group of PCBs are first pressed into n-1 core boards according to steps S11-S14, and then the n-1 core boards are pressed with the remaining PCBs after multiple layers are pressed once or successively, and each time the pressing is performed, an independent target point is set between the PCBs or the core boards or between the core board and the PCBs; In the above-mentioned core board pressing process, when the PCB pressed by the core board includes three layers or more, in the process of steps S11-S14, the first PCB and the second PCB are alternately arranged, and there is at least one middle layer PCB between the topmost PCB and the bottommost PCB. In step S11, the middle layer PCB also includes etching the hollow area at the position of the target point of subsequent pressing.

9. The method for determining the inter-layer alignment accuracy of a PCB according to claim 8, characterized in that: When the core board is laminated in multiple layers at one time, the following steps are also included: S15. On the top PCB and the bottom PCB of the core board, corresponding to the position of the hollow area of ​​the middle layer PCB, the target point for pressing the core board is etched, and the circular target point and the annular target point are respectively located on the front and back sides of the core board and are concentrically arranged; S16. Pre-positioning the core plate to be pressed; S17. Observe the target point by X-ray machine to determine whether the alignment between the core plates to be pressed meets the accuracy requirements; S18. If the precision requirement is met, pressing is performed; if the precision requirement is not met, returning to step S16 to perform pre-positioning again.

10. The method for determining the inter-layer alignment accuracy of a PCB according to claim 8, characterized in that: When the core board is laminated in layers one by one, the hollow area of ​​the PCB in the middle layer includes more than two, a core board is used as a base board, and the core boards are laminated one by one on the base board to form a new base board, which specifically includes the following steps: S25. On the topmost PCB and the bottommost PCB of the base plate and the core plate to be pressed together, select a position of a hollow area of ​​the middle layer PCB, etch out the target point of the base plate and the core plate pressed together, wherein the circular target point and the annular target point are respectively located on the front and back sides of the base plate and the core plate, and are concentrically arranged; and at the same time, on the PCB where the base plate and the core plate are bonded to each other, the position of the hollow area of ​​the remaining middle layer PCB is etched out correspondingly; S26. Pre-positioning the base plate and core plate to be pressed; S27. Observe the target point by X-ray machine to determine whether the alignment between the base plate and the core plate to be pressed meets the accuracy requirements; S28. If the accuracy requirement is met, the new base plate is pressed together. If the accuracy requirement is not met, the process returns to step S26 and the pre-positioning is performed again. S29. Repeat steps S25-28 until all core panels are pressed together.

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