A re-printing device for defective circuit board and process thereof

Abstract

The application relates to the field of circuit board printing, and discloses a re-printing device for circuit board defective products and a process thereof. The re-printing device for circuit board defective products comprises two fixing plates, the two fixing plates are respectively fixed on the top surface of a workbench, the top surface of a printing box is communicated with a fixed feeding pipe, the feeding pipe is provided with a first conveying pump, the inner bottom surface of the printing box is provided with a plurality of discharge holes, the inner parts of the plurality of discharge holes are respectively fixed with discharge pipes, and the plurality of discharge pipes are respectively provided with second conveying pumps. In the application, the cooperation of the first guide rail, the fixing frame, the first electric push rod, the printing box, the plurality of discharge pipes, the plurality of second conveying pumps, the second electric push rod, the placing table, the L-shaped frame and the printing plate facilitates the local printing of the circuit board defective products, avoids the traditional overall printing, reduces the waste of the tin paste, and lowers the production cost.

Description

Technical Field

[0001] This invention relates to the technical field of circuit board printing, specifically to a reprinting apparatus and process for defective circuit boards. Background Technology

[0002] Circuit boards are one of the key components in electronic devices, providing electrical connections and support for electronic components. With the continuous development of electronic product technology, the manufacturing precision and functional requirements of circuit boards are also constantly increasing. However, solder paste printing is one of the critical steps in the circuit board assembly process. Accurate solder paste printing is crucial to the electrical performance, connection quality, and long-term stability of the circuit board. However, in mass production, factors such as improper machine adjustment, material problems, or human error may lead to uneven solder paste distribution or insufficient solder paste, thus requiring reprinting of defective circuit boards.

[0003] Currently, when most defective circuit boards are reprinted using printing equipment, the entire board is usually reprinted with solder paste. This has the following disadvantages: it is not possible to print only a portion of the defective circuit board, which increases the waste of solder paste and thus increases production costs. Summary of the Invention

[0004] The purpose of this invention is to provide a reprinting apparatus and process for defective circuit boards, in order to solve the problem that the printing process cannot print on only a portion of the defective circuit board, which increases the waste of solder paste and thus increases production costs.

[0005] To achieve the above-mentioned objectives, the present invention employs the following technical solution: a reprinting device for defective circuit boards, comprising two fixing plates, each fixed to the top surface of a workbench, with fixing grooves formed on the inner sides of the two fixing plates. A PLC controller is fixed to the front side of the workbench. First guide rails are fixed inside the two fixing grooves, and the first guide rails are electrically connected to the PLC controller. A fixing frame is fixed between the sliders of the two first guide rails. A first electric push rod is fixed to the top surface of the fixing frame, and the first electric push rod is electrically connected to the PLC controller. A connecting frame is fixed to one end of the telescopic rod of the first electric push rod. A printing box is fixed to the bottom surface of the connecting frame, and the top surface of the printing box... A fixed feed pipe is connected, and a first conveying pump is provided on the feed pipe. The first conveying pump is electrically connected to a PLC controller. Several discharge holes are opened on the bottom surface of the printing box. Discharge pipes are fixed inside the discharge holes. Second conveying pumps are provided on the discharge pipes. The second conveying pumps are electrically connected to the PLC controller. A mounting groove is opened on the top surface of the worktable. A second electric push rod is fixed inside the mounting groove. The second electric push rod is electrically connected to the PLC controller. One end of the telescopic rod of the second electric push rod is fixed to a placement platform. Two L-shaped frames are movably arranged above the worktable. A printing plate is arranged between the two L-shaped frames. Several printing holes are opened on the top surface of the printing plate.

[0006] Preferably, an automatic optical inspection instrument is fixed on the right side of the workbench, the automatic optical inspection instrument is electrically connected to the PLC controller, a second guide rail is fixed on the inner side of the two fixed plates respectively, a movable plate is fixed between the sliders of the two second guide rails, a CCD camera is fixed on the bottom surface of the movable plate, and the CCD camera is electrically connected to the PLC controller.

[0007] Preferably, a scraper is detachably provided on the front side of the outer wall of the printing box.

[0008] Preferably, the outer wall of the printing box has a plurality of threaded grooves on the front side, and the scraper has a plurality of threaded holes on the front side. Bolts are threaded into the plurality of threaded holes, and the threaded ends of the plurality of bolts are threaded into the plurality of threaded grooves.

[0009] Preferably, the top surface of the placement platform is provided with a movable groove, and the left and right sides of the placement platform are respectively provided with movable holes. Two clamping plates are movably arranged inside the movable groove. The left and right sides of the placement platform are respectively fixed with third electric push rods, and one end of the telescopic rods of the two third electric push rods is fixedly connected to the outer side of the two clamping plates respectively.

[0010] Preferably, the inner sides of the two fixing plates are respectively provided with connecting grooves, and the interior of the two connecting grooves are respectively fixed with a fourth electric push rod. One end of the telescopic rod of the two fourth electric push rods is respectively fixedly connected to the outer side of the two L-shaped frames.

[0011] Preferably, a plurality of fifth electric push rods are fixed on the inner sides of the two L-shaped frames respectively.

[0012] Preferably, a measuring rod is fixed between the two fixing plates, and a scale is provided on the front side of the measuring rod. The top surfaces of the two L-shaped frames are respectively fixed with measuring plates.

[0013] The present invention also provides a reprinting process for defective circuit boards, comprising the following steps:

[0014] S1: The worker first connects the feed tube to the solder paste storage device (not shown in the figure), and injects an appropriate amount of solder paste into the printing box through the first delivery pump. Then, the worker activates the fourth electric push rod to make the L-shaped frame move left and right, adjusts the distance between the two L-shaped frames, and then places the printed circuit board on the two L-shaped frames. Then, the worker activates the fifth electric push rod so that one end of its telescopic rod contacts the top surface of the printed circuit board and presses and fixes the printed circuit board. Then, the worker places the defective circuit board on the top surface of the placement table.

[0015] S2: After the circuit board is placed, the staff will activate the second electric push rod to raise the placement platform and the circuit board until the circuit board is in contact with the bottom of the printed circuit board. The second guide rail will be activated to allow the slider to move back and forth, thereby moving the moving plate and CCD camera back and forth. When the CCD camera moves above the circuit board, it will automatically take a picture of the circuit board and transmit the data to the automatic optical inspection instrument.

[0016] S3: After the automatic optical inspection instrument receives the data, it uses image processing algorithms to quickly identify the location of missing solder paste on the circuit board and feeds back the location information of the defective area to the PLC controller. Based on this information, the PLC controller controls the first guide rail to make the fixing frame and printing box automatically move to the defective area.

[0017] S4: The PLC controller controls the first electric push rod to lower the connecting frame and the printing box to the top surface of the printed circuit board. Then, the second delivery pump on the discharge pipe corresponding to the missing solder paste position on the circuit board is started to squeeze the solder paste in the printing box into the printing hole of the printed circuit board through the discharge pipe, and squeeze the solder paste to the missing solder paste position on the circuit board.

[0018] S5: When the printing box moves, it can drive the scraper to move, which in turn can scrape the solder paste on the printing board and squeeze the solder paste onto the surface of the circuit board to complete the printing work on the circuit board.

[0019] Compared with existing technologies, a reprinting device for defective circuit boards that adopts the above technical solution has the following advantages:

[0020] 1. In use, the operator first connects the feed tube to the solder paste storage device (not shown in the figure), and injects an appropriate amount of solder paste into the printing box through the first delivery pump. Then, the operator places the defective circuit board on the top surface of the placement table, activates the second electric push rod to raise the placement table and the circuit board until the circuit board is in contact with the bottom surface of the printed circuit board. Then, the slider of the first guide rail is activated to move back and forth, thereby driving the fixing frame, connecting frame and printing box to move synchronously, so that the printing box moves above the position where the solder paste is missing on the circuit board. Then, the first electric push rod is activated to lower the connecting frame and the printing box to the top surface of the printed circuit board. Then, the second delivery pump on the discharge tube corresponding to the position where the solder paste is missing on the circuit board is activated to squeeze the solder paste in the printing box into the printing hole of the printed circuit board through the discharge tube, and squeeze the solder paste to the position where the solder paste is missing on the circuit board. By using the first guide rail, the fixed frame, the first electric push rod, the printing box, several discharge pipes, several second conveying pumps, the second electric push rod, the placement table, the L-shaped frame and the printing board in combination, it is easy to achieve local printing of defective circuit boards, avoid the traditional whole printing, reduce the waste of solder paste, and thus reduce production costs.

[0021] Second, during use, when the CCD camera moves above the circuit board, it automatically captures an image of the circuit board and transmits the data to the automatic optical inspection instrument. The automatic optical inspection instrument uses image processing algorithms to quickly identify the location of missing solder paste on the circuit board and feeds back the location information of the defective area to the PLC controller. Based on this information, the PLC controller controls the first guide rail to make the fixing frame and printing box automatically move to the defective area, realizing automatic printing and soldering of the defective area, improving the automation level of the printing process and reducing the complexity and error of manual operation;

[0022] Thirdly, during use, when the printing box moves, it can drive the squeegee to move as well, thereby scraping the solder paste on the printing board and squeezing the solder paste onto the surface of the circuit board to complete the printing process and achieve uniform application of solder paste. The use of threaded grooves and bolts facilitates the disassembly and assembly of the squeegee, making it easy for workers to clean or replace it. After the worker places the circuit board on the top surface of the placement table, activating the third electric push rod brings the two clamping plates closer together, clamping and fixing the circuit board to ensure its stability during the printing process and preventing a decrease in printing quality due to circuit board movement.

[0023] IV. During use, activating the fourth electric push rod allows the L-shaped frame to move left and right for adjustment, facilitating the worker to adjust the distance between the two L-shaped frames. This allows for the placement of printing plates of different sizes, improving the flexibility and practicality of the device. After the worker places the printing plate between the two L-shaped frames, activating the fifth electric push rod causes one end of its telescopic rod to contact the top surface of the printing plate, pressing and fixing the plate in place. This ensures the stability of the printing plate during the printing process and prevents a decrease in print quality due to plate movement. When adjusting the distance between the two L-shaped frames, the worker can accurately measure the distance by observing the movement of the measuring plate on the front side of the measuring rod and the scale readings on the ruler. This provides not only intuitive measurement data but also ensures the accuracy of the distance between the L-shaped frames. Attached Figure Description

[0024] Figure 1 This is a three-dimensional schematic diagram of an embodiment.

[0025] Figure 2 This is an exploded view of an embodiment.

[0026] Figure 3 This is an exploded view of the fixing frame and scraper in the embodiment.

[0027] Figure 4 This is a cross-sectional view of the printing box in the embodiment.

[0028] Figure 5 This is an exploded view of the placement platform and clamping plate in the embodiment.

[0029] Figure 6 This is an exploded view of the fixing plate and L-shaped frame in the embodiment.

[0030] Figure 7 Examples Figure 2 Enlarged diagram of point A in the middle.

[0031] In the diagram: 1. Fixed plate; 2. Workbench; 3. Fixed groove; 4. First guide rail; 5. Fixed frame; 6. First electric push rod; 7. Connecting frame; 8. Printing box; 9. Feeding pipe; 10. First conveying pump; 11. Discharge hole; 12. Discharge pipe; 13. Second conveying pump; 14. Mounting groove; 15. Second electric push rod; 16. Placement table; 17. L-shaped frame; 18. Printing plate; 19. Automatic optical inspection instrument; 20. Second guide rail; 21. Moving plate; 22. CCD camera; 23. Scraper; 24. Threaded groove; 25. Threaded hole; 26. Bolt; 27. Movable groove; 28. Movable hole; 29. ​​Clamping plate; 30. Third electric push rod; 31. Connecting groove; 32. Fourth electric push rod; 33. Fifth electric push rod; 34. Measuring rod; 35. Scale; 36. Measuring plate. Detailed Implementation

[0032] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0033] like Figures 1-7 As shown, a reprinting device for defective circuit boards includes two fixing plates 1, which are respectively fixed to the top surface of a workbench 2. Fixing grooves 3 are respectively formed on the inner sides of the two fixing plates 1. A PLC controller is fixed to the front side of the workbench 2. First guide rails 4 are respectively fixed inside the two fixing grooves 3 and are electrically connected to the PLC controller. A fixing frame 5 is fixed between the sliders of the two first guide rails 4. A first electric push rod 6 is fixed to the top surface of the fixing frame 5 and is electrically connected to the PLC controller. A connecting frame 7 is fixed to one end of the telescopic rod of the first electric push rod 6. A printing box 8 is fixed to the bottom surface of the connecting frame 7. The top surface of the printing box 8 is connected to a fixed feeding pipe 9, which is equipped with a first conveyor belt. Pump 10 is electrically connected to the PLC controller. The bottom surface of the printing box 8 has several discharge holes 11. Each discharge hole 11 has a discharge pipe 12 fixed inside. Each discharge pipe 12 has a second pump 13. The second pump 13 is electrically connected to the PLC controller. The top surface of the workbench 2 has a mounting groove 14. A second electric push rod 15 is fixed inside the mounting groove 14. The second electric push rod 15 is electrically connected to the PLC controller. One end of the telescopic rod of the second electric push rod 15 is fixed to a placement platform 16. Two L-shaped frames 17 are movably arranged above the workbench 2. A printing plate 18 is arranged between the two L-shaped frames 17. The top surface of the printing plate 18 has several printing holes.

[0034] In use, the operator first connects the feed pipe 9 to the solder paste storage device (not shown in the diagram), and injects an appropriate amount of solder paste into the printing box 8 through the first delivery pump 10. Then, the operator places the defective circuit board on the top surface of the placement platform 16, activates the second electric push rod 15 to raise the placement platform 16 and the circuit board until the circuit board is in contact with the bottom surface of the printed circuit board 18. Then, the slider of the first guide rail 4 is activated to move back and forth, thereby driving the fixing frame 5, the connecting frame 7 and the printing box 8 to move synchronously, so that the printing box 8 moves above the position where the solder paste is missing on the circuit board. Then, the first electric push rod 6 is activated to lower the connecting frame 7 and the printing box 8 to the top surface of the printed circuit board 18. Then, the second delivery pump 13 on the discharge pipe 12 corresponding to the position where the solder paste is missing on the circuit board is activated to squeeze the solder paste in the printing box 8 into the printing hole of the printed circuit board 18 through the discharge pipe 12, and squeeze the solder paste to the position where the solder paste is missing on the circuit board.

[0035] By using the first guide rail 4, the fixing frame 5, the first electric push rod 6, the printing box 8, several discharge pipes 12, several second conveying pumps 13, the second electric push rod 15, the placement table 16, the L-shaped frame 17 and the printing board 18 together, it is convenient to realize the local printing of defective circuit boards, avoid the traditional whole printing, reduce the waste of solder paste, and thus reduce production costs.

[0036] like Figure 1 , Figure 2 and Figures 5-7 As shown, an automatic optical inspection instrument 19 is fixed on the right side of the workbench 2. The automatic optical inspection instrument 19 is existing technology, and its model is Koh Young Zenith 2. The automatic optical inspection instrument 19 is electrically connected to the PLC controller. The inner sides of the two fixed plates 1 are respectively fixed with second guide rails 20. A movable plate 21 is fixed between the sliders of the two second guide rails 20. A CCD camera 22 is fixed on the bottom surface of the movable plate 21. The CCD camera 22 is existing technology, and its model is Teledyne DALSA Genie Nano. The CCD camera 22 is electrically connected to the PLC controller.

[0037] In use, after the operator places the circuit board on the top surface of the placement platform 16, the second guide rail 20 is activated to allow the slider to move back and forth, thereby driving the moving plate 21 and CCD camera 22 to move back and forth. When the CCD camera 22 moves above the circuit board, it automatically captures an image of the circuit board and transmits the data to the automatic optical inspection instrument 19. The automatic optical inspection instrument 19 uses image processing algorithms to quickly identify the location of missing solder paste on the circuit board and feeds back the location information of the defective area to the PLC controller. Based on this information, the PLC controller controls the first guide rail 4 to allow the fixing frame 5 and the printing box 8 to automatically move to the defective area. Then, it controls the first electric push rod 6 to move the printing box 8 downward, and at the same time controls the second electric push rod 15 to move the placement platform 16 and the circuit board upward, so that the circuit board is in contact with the printing plate 18. Then, it controls the second delivery pump 13 on the corresponding discharge pipe 12 to realize automatic printing and solder replenishment of the defective area, which improves the automation level of the printing process and reduces the complexity and error of manual operation.

[0038] like Figures 1-5As shown, a scraper 23 is detachably provided on the front side of the outer wall of the printing box 8. Several threaded grooves 24 are opened on the front side of the outer wall of the printing box 8. Several threaded holes 25 are opened on the front side of the scraper 23. Bolts 26 are threadedly connected to the several threaded holes 25 respectively. The threaded ends of the several bolts 26 are threadedly connected to the inside of the several threaded grooves 24 respectively. A movable groove 27 is opened on the top surface of the placement platform 16. Movable holes 28 are opened on the left and right sides of the placement platform 16 respectively. Two clamping plates 29 are movably arranged inside the movable groove 27. Third electric push rods 30 are fixed on the left and right sides of the placement platform 16 respectively. One end of the telescopic rod of the two third electric push rods 30 is fixedly connected to the outside of the two clamping plates 29 respectively.

[0039] During use, when the printing box 8 moves, it moves the squeegee 23, which in turn scrapes the solder paste on the printing plate 18, squeezing the solder paste onto the surface of the circuit board to complete the printing process and achieve uniform application of the solder paste. The use of the threaded groove 24 and the bolt 26 facilitates the disassembly and assembly of the squeegee 23, making it easy for workers to clean or replace it. After the worker places the circuit board on the top surface of the placement table 16, activating the third electric push rod 30 brings the two clamping plates 29 closer together, clamping and fixing the circuit board to ensure its stability during the printing process and preventing a decrease in printing quality due to circuit board movement.

[0040] like Figure 1 , Figure 2 , Figure 6 and Figure 7 As shown, the inner sides of the two fixed plates 1 are respectively provided with connecting grooves 31, and the inside of the two connecting grooves 31 are respectively fixed with fourth electric push rods 32. One end of the telescopic rod of the two fourth electric push rods 32 is respectively fixedly connected to the outside of the two L-shaped frames 17. Several fifth electric push rods 33 are respectively fixed on the inner sides of the two L-shaped frames 17. A measuring rod 34 is fixed between the two fixed plates 1. A scale 35 is provided on the front side of the measuring rod 34. A measuring plate 36 is respectively fixed on the top surface of the two L-shaped frames 17.

[0041] During use, activating the fourth electric push rod 32 allows the L-shaped frame 17 to move left and right for adjustment, facilitating the adjustment of the distance between the two L-shaped frames 17 and enabling the placement of printing plates 18 of different sizes, thus improving the flexibility and practicality of the device. After the printing plate 18 is placed between the two L-shaped frames 17, activating the fifth electric push rod 33 causes one end of its telescopic rod to contact the top surface of the printing plate 18, pressing and fixing it in place. This ensures the stability of the printing plate 18 during the printing process and prevents a decrease in printing quality due to movement of the printing plate 18. When adjusting the distance between the two L-shaped frames 17, the operator can accurately measure the distance by observing the movement of the measuring plate 36 in front of the measuring rod 34 and the scale value on the ruler 35. This provides not only intuitive measurement data but also ensures the accuracy of the distance between the L-shaped frames 17.

[0042] The present invention also provides a reprinting process for defective circuit boards, comprising the following steps:

[0043] S1: The worker first connects the feed pipe 9 to the solder paste storage device (not shown in the diagram), and injects an appropriate amount of solder paste into the printing box 8 through the first delivery pump 10. Then, the worker activates the fourth electric push rod 32 so that the L-shaped frame 17 can move left and right, adjusts the distance between the two L-shaped frames 17, and then places the printed circuit board 18 on the two L-shaped frames 17. Then, the worker activates the fifth electric push rod 33 so that one end of its telescopic rod contacts the top surface of the printed circuit board 18 and presses and fixes the printed circuit board 18. Then, the worker places the defective circuit board on the top surface of the placement table 16.

[0044] S2: After the circuit board is placed, the staff activates the second electric push rod 15 to raise the placement platform 16 and the circuit board until the circuit board is in contact with the bottom surface of the printed circuit board 18. The second guide rail 20 is activated to allow the slider to move back and forth, thereby driving the moving plate 21 and the CCD camera 22 to move back and forth. When the CCD camera 22 moves above the circuit board, it automatically takes a picture of the circuit board and transmits the data to the automatic optical inspection instrument 19.

[0045] S3: After the automatic optical inspection instrument 19 receives the data, it uses the image processing algorithm to quickly identify the location of missing solder paste on the circuit board and feeds back the location information of the defective area to the PLC controller. Based on this information, the PLC controller controls the first guide rail 4 to make the fixing frame 5 and the printing box 8 automatically move to the defective area.

[0046] S4: The PLC controller controls the first electric push rod 6 to lower the connecting frame 7 and the printing box 8 to the top surface of the printed circuit board 18. Then, the second delivery pump 13 on the discharge pipe 12 corresponding to the missing solder paste position on the circuit board is started to squeeze out the solder paste in the printing box 8 and enter the printing hole of the printed circuit board 18 through the discharge pipe 12, and squeeze the solder paste to the missing solder paste position on the circuit board.

[0047] S5: When the printing box 8 moves, it can drive the scraper 23 to move, thereby scraping the solder paste on the printing board 18 and squeezing the solder paste onto the surface of the circuit board to complete the printing work on the circuit board.

[0048] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A reprinting apparatus for defective circuit boards, comprising two fixing plates (1), the two fixing plates (1) being respectively fixed to the top surface of a workbench (2), characterized in that, The inner sides of the two fixed plates (1) are respectively provided with fixed grooves (3). A PLC controller is fixed on the front side of the workbench (2). The interior of the two fixed grooves (3) is respectively fixed with first guide rails (4). The first guide rails (4) are electrically connected to the PLC controller. A fixed frame (5) is fixed between the sliders of the two first guide rails (4). The top surface of the fixed frame (5) is fixed with a first electric push rod (6). The first electric push rod (6) is electrically connected to the PLC controller. One end of the telescopic rod of the first electric push rod (6) is fixed with a connecting frame (7). The bottom surface of the connecting frame (7) is fixed with a printing box (8). The top surface of the printing box (8) is connected to a fixed feeding pipe (9). A first conveying pump (10) is provided on the feeding pipe (9). The first conveying pump (10) is electrically connected to the PLC controller. Next, the bottom surface of the printing box (8) is provided with several discharge holes (11), and discharge pipes (12) are fixed inside the discharge holes (11). A second conveying pump (13) is provided on each of the discharge pipes (12). The second conveying pump (13) is electrically connected to the PLC controller. The top surface of the workbench (2) is provided with an installation groove (14). A second electric push rod (15) is fixed inside the installation groove (14). The second electric push rod (15) is electrically connected to the PLC controller. One end of the telescopic rod of the second electric push rod (15) is fixed with a placement platform (16). Two L-shaped frames (17) are movably arranged above the workbench (2). A printing plate (18) is provided between the two L-shaped frames (17). The top surface of the printing plate (18) is provided with several printing holes. An automatic optical inspection instrument (19) is fixed on the right side of the workbench (2). The automatic optical inspection instrument (19) is electrically connected to the PLC controller. The inner sides of the two fixed plates (1) are respectively fixed with second guide rails (20). A movable plate (21) is fixed between the sliders of the two second guide rails (20). A CCD camera (22) is fixed on the bottom surface of the movable plate (21). The CCD camera (22) is electrically connected to the PLC controller. The top surface of the placement platform (16) is provided with a movable groove (27). The left and right sides of the placement platform (16) are respectively provided with movable holes (28). Two clamping plates (29) are movably arranged inside the movable groove (27). The left and right sides of the placement platform (16) are respectively fixed with third electric push rods (30). One end of the telescopic rod of the two third electric push rods (30) is respectively fixedly connected to the outside of the two clamping plates (29). Several fifth electric push rods (33) are respectively fixed on the inside of the two L-shaped frames (17).

2. The reprinting apparatus for defective circuit boards according to claim 1, characterized in that: The printing box (8) is detachably equipped with a scraper (23) on the front side of its outer wall.

3. The reprinting apparatus for defective circuit boards according to claim 2, characterized in that: The printing box (8) has several threaded grooves (24) on the front side of its outer wall, and the scraper (23) has several threaded holes (25) on the front side. Bolts (26) are threaded into the several threaded holes (25), and the threaded ends of the several bolts (26) are threaded into the several threaded grooves (24).

4. The reprinting apparatus for defective circuit boards according to claim 2, characterized in that: The inner sides of the two fixed plates (1) are respectively provided with connecting grooves (31), and the inside of the two connecting grooves (31) are respectively fixed with fourth electric push rods (32). One end of the telescopic rods of the two fourth electric push rods (32) is respectively fixedly connected to the outside of the two L-shaped frames (17).

5. The reprinting apparatus for defective circuit boards according to claim 4, characterized in that: A measuring rod (34) is fixed between the two fixed plates (1), and a scale (35) is provided on the front side of the measuring rod (34). A measuring plate (36) is fixed on the top surface of the two L-shaped frames (17).

6. A reprinting process for defective circuit boards, based on the reprinting apparatus for defective circuit boards as described in claim 4, characterized in that, The steps include the following: S1: The staff first connects the feed pipe (9) to the solder paste storage device, and injects an appropriate amount of solder paste into the printing box (8) through the first delivery pump (10). Then the staff starts the fourth electric push rod (32) so that the L-shaped frame (17) can move left and right, adjust the distance between the two L-shaped frames (17), and then place the printing board (18) on the two L-shaped frames (17). Then the staff starts the fifth electric push rod (33) so that one end of its telescopic rod contacts the top surface of the printing board (18) and presses and fixes the printing board (18). Then the staff places the defective circuit board on the top surface of the placement table (16). S2: After the circuit board is placed, the staff will activate the second electric push rod (15) to raise the placement platform (16) and the circuit board until the circuit board is in contact with the bottom surface of the printed circuit board (18). The second guide rail (20) will be activated to allow the slider to move back and forth, thereby driving the moving plate (21) and CCD camera (22) to move back and forth. When the CCD camera (22) moves above the circuit board, it will automatically take a picture of the circuit board and transmit the data to the automatic optical inspection instrument (19). S3: When the automatic optical inspection instrument (19) receives the data, it uses the image processing algorithm to quickly identify the location of missing solder paste on the circuit board and feeds back the location information of the defective area to the PLC controller. Based on this information, the PLC controller controls the first guide rail (4) so ​​that the fixing frame (5) and the printing box (8) automatically move to the defective area. S4: The PLC controller controls the first electric push rod (6) to lower the connecting frame (7) and the printing box (8) to the top surface of the printed circuit board (18). Then, the second delivery pump (13) on the discharge pipe (12) corresponding to the missing solder paste position on the circuit board is started to squeeze out the solder paste in the printing box (8) and enter the printing hole of the printed circuit board (18) through the discharge pipe (12) to squeeze the solder paste to the missing solder paste position on the circuit board. S5: When the printing box (8) moves, it can drive the scraper (23) to move, thereby scraping the solder paste on the printing board (18) and squeezing the solder paste onto the surface of the circuit board to complete the printing work of the circuit board.

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