Intelligent double-platform LDI system and alternate exposure method

Abstract

The invention provides an intelligent double-platform LDI system and an alternate exposure method, and belongs to the field of intelligent laser processing, the intelligent double-platform LDI system comprises an exposure station, a material table A, a material table B, an alignment module and a peripheral module for controlling temperature, humidity and pressure; the material platform A and the material platform B are arranged on the two sides of the exposure station and alternately feed and discharge materials; the two alignment modules are arranged above the material tables on the corresponding sides in a crossing mode and used for front positioning of materials to be machined, and a rear positioning module is further arranged at the exposure station and used for positioning the materials to be machined before and after machining. According to the application, front and back double-station alternate exposure is adopted, so that the production efficiency is high, the dovetail type air floating platform design ensures long-stroke high-precision angle swing precision control, the active focusing adjustment scheme improves the exposure precision, and the application is convenient to popularize and apply in the fields of IC support plates, soft plates, HDI plates, multi-layer plates, ceramic substrates, alloy plates and the like.

Description

Technical Field

[0001] The invention belongs to the field of laser processing, and in particular relates to an intelligent dual-platform LDI system and an alternating exposure method. Background Art

[0002] Laser Direct Imaging (LDI) is a device that uses laser beams to accurately project circuit patterns onto photosensitive materials to form high-precision circuit board patterns. It is mainly used in the field of circuit board manufacturing, especially in the exposure process of PCB (Printed Circuit Board) technology.

[0003] When facing IC substrates, it is found that the one-way or single-channel exposure efficiency is low, and for plates with slight height differences, or for the exposure processing of different layers of the same plate, the traditional focusing method has low accuracy and slow response speed. Therefore, it is urgent to develop an exposure machine that works alternately in both directions. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, an object of the present invention is to provide an intelligent dual-platform LDI system and an alternating exposure method, which can solve the above-mentioned problems.

[0005] An intelligent dual-platform LDI system comprises an exposure station, a material table A, a material table B, an alignment module and a peripheral module for controlling temperature, humidity and pressure; the material table A and the material table B are arranged on both sides of the exposure station for alternate loading and unloading of materials; two alignment modules are arranged across the material tables on the corresponding sides for front positioning of materials to be processed, and a rear positioning module is also provided at the exposure station for front and rear positioning of materials to be processed.

[0006] Furthermore, the exposure station includes a laser array processing module, an active focusing module, an exposure transverse shift module and a rear positioning module; the laser array processing module includes a laser source, an exposure frame and an exposure lens array, and the exposure lens array is supported by the exposure frame; the active focusing module is arranged below the exposure lens array, and provides active focus to the exposure lens array as the surface undulation of the product to be processed changes; the exposure transverse shift module drives the entire laser array processing module to move laterally; the rear positioning module is arranged at one end side of the exposure lens array, and is used for positioning the product before exposure.

[0007] Furthermore, the material platforms A and B have the same material platform structure and share a carrier line, and the material platforms include a material platform driver, an air flotation guide assembly, a material platform frame, a carrier module and a plate carrier module; the material platform frame is connected to the dovetail protrusion at the top of the carrier line through the floating port of the air flotation guide assembly, and the material platform driver is arranged between the carrier line and the material platform frame, and the bottom of the height-adjustable carrier module is fixedly connected to the top of the material platform frame, and a plate carrier module with a vacuum suction plate is arranged on the top of the carrier module.

[0008] Furthermore, the alignment module includes an alignment gantry, an alignment transverse shift drive module, a front alignment adapter plate, a front alignment camera lens assembly and a front alignment light source, the front alignment camera lens assembly and the front alignment light source are connected to the movable end of the alignment transverse shift drive module through the front alignment adapter plate, and the alignment transverse shift drive module is horizontally arranged on the crossbeam of the alignment gantry.

[0009] Furthermore, the intelligent dual-platform LDI system also includes an exposure calibration module, which includes a calibration frame, a calibration camera array, a calibration cover and a calibration adapter; the calibration camera array is arranged on the calibration frame with its emission direction facing upward and is buckled through the calibration cover; calibration holes are opened on the upper plate surface of the calibration cover, the number of which is equal to the number of calibration cameras and the positions match; a calibration adapter is also provided on the calibration frame, and the entire exposure calibration module is connected to the carrier module of the A material stage and the B material stage through the calibration adapter.

[0010] Furthermore, a front-end material station and a rear-end material station are provided before and after the processing flow line in which the A material table, the exposure station, and the B material table are arranged in a straight line; wherein the front-end material station includes a front-end loading mechanism, a front-end cleaning mechanism, a front-end conveying mechanism, a loading robot, a unloading robot, and a unloading and receiving mechanism; the rear-end material station includes a material receiving flap mechanism and a rear-end transfer module.

[0011] The present invention also provides an alternating exposure method, which is implemented based on the aforementioned intelligent dual-platform LDI system, and includes the following steps: S1, loading is completed on material stage A, and material stage B is waiting for loading; S2, material stage A starts to align, and material stage B is loading; S3, material stage A has completed alignment and is ready for exposure, and material stage B is loading; S4, material stage A has completed exposure, and material stage B is waiting for alignment; S5, material stage A returns to zero, and material stage B starts to align; S6, material stage A has completed returning to zero and is ready for loading, and material stage B has completed alignment and is ready for exposure; S7, material stage A is loading, and material stage B has completed exposure; S8, material stage A starts to align, and material stage B returns to zero; S9, material stage A has completed alignment, and material stage B has completed returning to zero and is ready for loading.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: the system adopts front and rear double-station alternating exposure, with high production efficiency; the dovetail air floating platform design ensures long-stroke and high-precision angular swing accuracy control; the active focus adjustment scheme improves exposure accuracy, and is convenient for promotion and application in the fields of IC substrates, soft boards, HDI boards, multi-layer boards, ceramic substrates, alloy boards, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 and Figure 2 Schematic diagrams of different viewing angles of the intelligent dual-platform LDI system of the present invention; Figure 3 is a schematic diagram of the exposure station; Figure 4 It is a schematic diagram of the A material station and the B material station; Figure 5 is a schematic diagram of the alignment module; Figure 6 This is a schematic diagram of the exposure calibration module; Figure 7 is a schematic diagram of another embodiment of the intelligent dual-platform LDI system; Figure 8 Schematic diagram of the process of the alternating exposure method.

[0014] In the figure, 100, exposure station; 110, laser array processing module; 111, laser source; 112, exposure frame; 113, exposure lens array; 114, DMD image acquisition component; 120, active focusing module; 130, exposure lateral shift module; 140, rear positioning module; 200, material platform A; 300, material platform B; 231, platform line; 232, material platform driver; 233, air floating guide assembly; 234, material platform frame; 235, platform module; 236, carrier module; 237, material platform buffer stop mechanism; 238, platform height adjustment mechanism; 400, alignment module; 410, alignment gantry; 420, alignment transverse shift drive module; 430, front alignment adapter plate; 440, front alignment camera lens assembly; 450, front alignment light source; 460, alignment slide rail balance module; 470, alignment transverse shift stop assembly; 480, front alignment displacement sensor; 500, exposure calibration module; 510, calibration frame; 520, calibration camera array; 530, calibration cover; 531, calibration hole; 540, calibration adapter; 600, temperature control module; 700, water cooling machine; 800, dryer; 900, gas tank; 1000, blower; 1100, platform chassis; 1200, front end feeding mechanism; 1300, front cleaning mechanism; 1400, front end conveying mechanism; 1500, loading robot; 1600, unloading robot; 1700, material unloading and receiving mechanism; 1800, material receiving flap mechanism; 1900, rear end transfer and transmission module; 1910, rear end transmission roller mechanism; 1920, transfer material box. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] It should be understood that the "system", "device", "mechanism", "component", "module" and / or "module" used in this specification is a method for distinguishing different components, elements, parts, parts or assemblies at different levels. However, if other words can achieve the same purpose, the words can be replaced by other expressions.

[0017] Flowcharts are used in this specification to illustrate the operations performed by the system according to the embodiments of this specification. It should be understood that the preceding or following operations are not necessarily performed precisely in order. Instead, the steps may be processed in reverse order or simultaneously. At the same time, other operations may also be added to these processes, or one or more operations may be removed from these processes.

[0018] Intelligent dual-platform LDI system Intelligent dual-platform LDI system, see Figure 1-Figure 7 , including an exposure station 100, an A material table 200, a B material table 300, an alignment module 400, an exposure calibration module 500 and a peripheral module for controlling temperature, humidity and pressure; the A material table 200 and the B material table 300 are arranged on both sides of the exposure station 100, and load and unload materials alternately; two alignment modules 400 are arranged across the material tables on the corresponding sides, and are used for front positioning of the materials to be processed. The exposure station 100 is also provided with a rear positioning module 140, which is used for front and back positioning of the materials to be processed.

[0019] Among them, see Figure 3 The exposure station 100 includes a laser array processing module 110, an active focusing module 120, an exposure transverse shift module 130 and a rear positioning module 140; the laser array processing module 110 includes a laser source 111, an exposure frame 112 and an exposure lens array 113, and the exposure lens array 113 is supported by the exposure frame 112; the active focusing module 120 is arranged below the exposure lens array 113, and provides active focus to the exposure lens array 113 as the surface undulation of the product to be processed changes; the exposure transverse shift module 130 drives the entire laser array processing module 110 to move laterally; the rear positioning module 140 is arranged at one end of the exposure lens array 113, and is used for positioning the product before exposure.

[0020] The laser source 111 of the laser array processing module 110 adopts high-power ultraviolet / near-ultraviolet laser coupling technology, and the exposure lens array 113 adopts a high-precision mixed-band imaging lens design.

[0021] Furthermore, a DMD image acquisition component 114 is provided at each exposure lens of the exposure lens array 113 for image acquisition during the processing.

[0022] The active focusing module 120 may include two front and rear laser displacement sensors, a focusing processor and an optical wedge. The focusing processor adopts a vector diagram position compensation algorithm. Based on the real-time product surface height signal of the working laser displacement sensor, it corrects the exposure position accuracy uncertainty caused by the motion accuracy error through an algorithm to reduce hardware costs.

[0023] Among them, see Figure 4 The material platforms A 200 and B 300 have the same material platform structure and share a platform line 231. The material platforms include a material platform driver 232, an air floating guide assembly 233, a material platform frame 234, a platform module 235 and a carrier module 236; the material platform frame 234 is connected to the dovetail protrusion at the top of the platform line 231 through the floating port of the air floating guide assembly 233, the material platform driver 232 is arranged between the platform line 231 and the material platform frame 234, the bottom of the height-adjustable platform module 235 is fixedly connected to the top of the material platform frame 234, and a carrier module 236 with a vacuum suction plate is arranged on the top of the platform module 235.

[0024] A driving groove is provided in the middle of the dovetail-shaped convex top of the carrier line 231 for installing the material platform driver 232.

[0025] The air flotation guide assembly 233 includes a rigid air flotation block vertically arranged on the top of the material rack 234 and flexible air flotation blocks obliquely arranged on both sides of the material rack 234 .

[0026] The air flotation rod of the rigid air flotation block is a rigid rod, so that the bottom surface of the top plate of the material stand 234 is vertically air-floated and guided relative to the top surface of the carrier line 231; the air flotation rod of the flexible air flotation block is a combination of a rigid rod and a spring, or is itself a single elastic rod, so that the inner inclined surface of the inclined plate of the material stand 234 is obliquely and vertically air-floated and guided relative to the raised side inclined surface of the carrier line 231.

[0027] Furthermore, the material platform also includes a material platform buffer stop mechanism 237 at both ends and in the middle, and the platform module 235 adopts a platform height adjustment mechanism 238 composed of a screw drive and oblique and vertical slider assemblies.

[0028] Among them, see Figure 5The alignment module 400 includes an alignment gantry 410, an alignment transverse shift drive module 420, a front alignment adapter plate 430, a front alignment camera lens assembly 440 and a front alignment light source 450. The front alignment camera lens assembly 440 and the front alignment light source 450 are connected to the movable end of the alignment transverse shift drive module 420 via the front alignment adapter plate 430. The alignment transverse shift drive module 420 is horizontally arranged on the crossbeam of the alignment gantry 410.

[0029] Furthermore, an alignment slide rail balancing module 460 and an alignment transverse stop assembly 470 are also provided on the alignment gantry 410 .

[0030] Furthermore, a front alignment displacement sensor 480 is disposed on the front alignment adapter plate 430 .

[0031] For the exposure calibration module 500, see Figure 6 The exposure calibration module 500 includes a calibration frame 510, a calibration camera array 520, a calibration cover 530 and a calibration adapter 540; the calibration camera array 520 is arranged on the calibration frame 510 with an emission direction facing upward, and is buckled through the calibration cover 530; calibration holes 531 equal in number to the calibration cameras and matching in position are opened on the upper plate surface of the calibration cover 530; a calibration adapter 540 is also provided on the calibration frame 510, and the entire exposure calibration module 500 is connected to the carrier module 236 of the A material stage 200 and the B material stage 300 through the calibration adapter 540.

[0032] Furthermore, a digital display is provided on the calibration frame 510 , and a digital display hole is correspondingly opened on the calibration cover 530 .

[0033] Among them, see Figure 1 and Figure 2 The peripheral modules include a temperature control module 600, a water cooler 700, a dryer 800, a gas storage tank 900 and a blower 1000, which are used to control the exposure station 100 to be in a constant temperature, constant humidity and constant pressure working environment.

[0034] The bottoms of the exposure station 100 , the A material table 200 , the B material table 300 and the alignment module 400 are arranged on a platform chassis 1100 .

[0035] For further information, see Figure 7 A front-end material station and a rear-end material station are provided before and after the processing flow line in which the A material table 200, the exposure station 100, and the B material table 300 are arranged in a straight line; wherein the front-end material station includes a front-end loading mechanism 1200, a front-end cleaning mechanism 1300, a front-end conveying mechanism 1400, a loading robot 1500, a unloading robot 1600, and a unloading and receiving mechanism 1700; the rear-end material station includes a material receiving flap mechanism 1800 and a rear-end transfer and transmission module 1900.

[0036] Among them, a front-end transverse lifting and transferring line and a front-station longitudinal lifting and transferring line can also be set at the front-end material station, and correspondingly, a rear-end transverse lifting and transferring line and a rear-station longitudinal lifting and transferring line can also be set at the rear-end material station.

[0037] Furthermore, a clapper assembly may be provided at the front feeding mechanism 1200. The front cleaning mechanism 1300 may use a dust collector, such as a plasma air knife, etc. The front conveying mechanism 1400 may use multiple rollers, which may be actively driven electric cylinder rollers, etc.

[0038] The loading robot 1500 uses a six-axis robot arm, and the unloading robot 1600 uses a four-axis robot arm to achieve the handling function. Of course, a six-axis robot arm can also be used.

[0039] The material unloading and receiving mechanism 1700 uses a multi-layer material box, which can be fixed, and the unloading robot 1600 unloads the material layer by layer or the rear station at the rear station moves vertically and lifts the loading line to adsorb and lift the material. The multi-layer material box can also be cyclically stacked, and the empty box and full box can be automatically lifted and loaded.

[0040] The material receiving flap mechanism 1800 can be a conventional 180° flap mechanism. Furthermore, a rear station cleaning mechanism can be provided at the rear end transfer and transmission module 1900 downstream of the material receiving flap mechanism 1800.

[0041] The rear-end transfer and transmission module 1900 can be an integrated type or a split type. Referring to the attached drawings, the rear-end transfer and transmission module 1900 uses multiple sets of rear-end transmission roller mechanisms 1910, and a transfer material box 1920 is set at the end of the rear-end transmission roller mechanism 1910 near the rear station. The rear station longitudinal lifting and transporting line lifts and moves the materials at the rear-end transmission roller mechanism 1910 to the transfer material box 1920 for temporary storage, and the other side of the product to be exposed is transported from the transfer material box 1920 to the rear station corresponding to the B material table 300.

[0042] The intelligent dual-platform LDI system adopts a multi-coordinate system fusion calibration algorithm. By taking the standard film as the reference coordinate system, the alignment coordinate system, exposure coordinate system, calibration coordinate system, and world coordinate system are aligned to the reference coordinate system to achieve the fusion and unification of multiple coordinate systems. The system adopts a three-fixed bridge gantry air-floating mechanical structure, which can adjust the workpiece height to match the products to be exposed with different thicknesses.

[0043] Alternating exposure method An alternating exposure method, see Figure 8 The method is implemented based on the aforementioned intelligent dual-platform LDI system, and the method includes the following steps (executed repeatedly in a loop).

[0044] S1. Loading on material table A is completed, and material table B is waiting for loading.

[0045] S2. Material table A starts to align, and material table B is loading.

[0046] S3. The A material table is aligned and ready for exposure, and the B material table is loading.

[0047] S4. The exposure of stage A is completed (indicated by odd-numbered stripes), and stage B is waiting for alignment.

[0048] S5, the A stage returns to zero (the last strip of the even-numbered strips is exposed), and the B stage begins to align.

[0049] S6. The A stage has completed zero return and is ready for loading, and the B stage has completed alignment and is ready for exposure.

[0050] S7. Loading is in progress on stage A, and exposure of stage B is completed (indicated by odd-numbered stripes).

[0051] S8, the A stage starts to align, and the B stage returns to zero (the last strip of the even-numbered strips is exposed).

[0052] S9. The A material table is aligned, the B material table returns to zero and is ready for loading.

[0053] Computer readable storage medium The present invention also provides a computer-readable storage medium on which computer instructions are stored, and when the computer instructions are executed, the steps of the above method are executed. The method is described in detail in the above part and will not be described here.

[0054] Those skilled in the art will appreciate that all or part of the steps in the various methods of the above embodiments can be completed by instructing the relevant hardware through a program, and the program can be stored in a computer-readable storage medium, and the computer-readable medium includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be a computer-readable instruction, a data structure, a module of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, read-only compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include temporary computer-readable media (transitory media), such as modulated data signals and carriers.

[0055] terminal The present invention also provides a terminal, including a memory and a processor, wherein the memory stores data provider information and computer instructions that can be run on the processor, and the processor executes the steps of the above method when running the computer instructions. The method is described in detail in the above section and will not be described here.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An intelligent dual-platform LDI system, characterized by: The invention comprises an exposure station (100), a material table A (200), a material table B (300), an alignment module (400) and a peripheral module for controlling temperature, humidity and pressure; the material table A (200) and the material table B (300) are arranged on both sides of the exposure station (100) to alternately load and unload materials; two alignment modules (400) are arranged across the material tables on the corresponding sides and are used for front positioning of the material to be processed; the exposure station (100) is also provided with a rear positioning module (140) for front and rear positioning of the material to be processed.

2. The intelligent dual-platform LDI system according to claim 1, characterized in that: The exposure station (100) comprises a laser array processing module (110), an active focusing module (120), an exposure lateral shift module (130) and a rear positioning module (140); the laser array processing module (110) comprises a laser source (111), an exposure frame (112) and an exposure lens array (113), wherein the exposure lens array (113) is supported by the exposure frame (112); the active focusing module (120) is arranged below the exposure lens array (113) and provides active focusing to the exposure lens array (113) as the surface of the product to be processed changes; the exposure lateral shift module (130) drives the entire laser array processing module (110) to move laterally; and the rear positioning module (140) is arranged at one end of the exposure lens array (113) and is used for positioning the product before exposure.

3. The intelligent dual-platform LDI system according to claim 1, characterized in that: The material platforms A (200) and B (300) have the same material platform structure and share a platform line (231). The material platforms include a material platform driver (232), an air-floating guide assembly (233), a material platform frame (234), a platform module (235) and a carrier module (236); the material platform frame (234) is connected to a dovetail-shaped protrusion at the top of the platform line (231) through a floating port of the air-floating guide assembly (233); the material platform driver (232) is arranged between the platform line (231) and the material platform frame (234); the bottom of the height-adjustable platform module (235) is fixedly connected to the top of the material platform frame (234); and a carrier module (236) provided with a vacuum suction plate is arranged on the top of the platform module (235).

4. The intelligent dual-platform LDI system according to claim 3, characterized in that: A driving groove is provided in the middle of the dovetail-shaped convex top of the carrier line (231) for mounting the material platform driver (232).

5. The intelligent dual-platform LDI system according to claim 3, characterized in that: The air flotation guide assembly (233) comprises a rigid air flotation block vertically arranged on the top of the material stand (234) and flexible air flotation blocks obliquely arranged on both sides of the material stand (234).

6. The intelligent dual-platform LDI system according to claim 1, characterized in that: The alignment module (400) comprises an alignment gantry (410), an alignment transverse shift drive module (420), a front alignment adapter plate (430), a front alignment camera lens assembly (440) and a front alignment light source (450); the front alignment camera lens assembly (440) and the front alignment light source (450) are connected to the movable end of the alignment transverse shift drive module (420) via the front alignment adapter plate (430); and the alignment transverse shift drive module (420) is horizontally arranged on a crossbeam of the alignment gantry (410).

7. The intelligent dual-platform LDI system according to claim 3, characterized in that: The intelligent dual-platform LDI system further comprises an exposure calibration module (500), the exposure calibration module (500) comprising a calibration frame (510), a calibration camera array (520), a calibration cover (530) and a calibration adapter (540); the calibration camera array (520) is arranged on the calibration frame (510) with its emission direction facing upward, and is buckled via the calibration cover (530); Calibration holes (531) are provided on the upper plate surface of the calibration cover (530), the number of which is equal to that of the calibration cameras and the positions of which match those of the calibration cameras; a calibration adapter (540) is also provided on the calibration frame (510), and the entire exposure calibration module (500) is connected to the carrier modules (236) of the A material stage (200) and the B material stage (300) via the calibration adapter (540).

8. The intelligent dual-platform LDI system according to claim 1, characterized in that: The peripheral module comprises a temperature control module (600), a water cooler (700), a dryer (800), a gas storage tank (900) and a blower (1000), and is used to control the exposure station (100) to maintain a constant temperature, constant humidity and constant pressure working environment.

9. The intelligent dual-platform LDI system according to claim 1, characterized in that: The bottoms of the exposure station (100), the A material table (200), the B material table (300) and the alignment module (400) are arranged on a platform chassis (1100).

10. The intelligent dual-platform LDI system according to claim 8 or 9, characterized in that: A front-end material station and a rear-end material station are provided before and after the processing flow line in which the A material table (200), the exposure station (100), and the B material table (300) are arranged in a straight line; wherein the front-end material station includes a front-end loading mechanism (1200), a front-end cleaning mechanism (1300), a front-end conveying mechanism (1400), a loading robot (1500), a unloading robot (1600), and a unloading and receiving mechanism (1700); and the rear-end material station includes a material receiving flap mechanism (1800) and a rear-end transfer and transmission module (1900).

11. An alternating exposure method, characterized in that: The method is implemented based on the intelligent dual-platform LDI system according to any one of claims 1 to 10, and the method comprises: S1, loading is completed on the A material table, and the B material table is waiting for loading; S2, material table A starts to align, material table B is loading; S3, A material table is aligned and ready for exposure, B material table is loading; S4, the exposure of the A material stage is completed, and the B material stage is waiting for alignment; S5, material table A returns to zero, and material table B starts to align; S6, the A stage has completed zero return and is ready for loading, and the B stage has completed alignment and is ready for exposure; S7, loading is in progress on stage A, and exposure of stage B is completed; S8, material table A starts to align, and material table B returns to zero; S9. The A material table is aligned, the B material table returns to zero and is ready for loading.

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