Circuit board high-precision positioning welding processing device and process thereof

Abstract

The application discloses a high-precision positioning and welding processing device for a circuit board and a process thereof, and belongs to the technical field of circuit board welding processing. The device comprises a positioning and welding table, a welding assembly, a processing table, a positioning assembly and a plurality of ejectors arranged in an array. Each ejector can be independently jacked up and stopped after contacting the bottom of the circuit board to form a contoured supporting surface that is adapted to the actual bottom profile of the circuit board. A gas channel is arranged in the ejector, and a gas acting port is arranged at the top of the ejector. During preheating, the positive pressure gas shares the contact load and reduces friction, and cooperates with the flexible sleeve and the magnetorheological fluid to absorb the thermal expansion displacement of the circuit board. During welding, the corresponding ejector is excited and solidified according to the position of the welding spot and is switched to a negative pressure adsorption state to form a local rigid support area that moves with the welding spot, and the remaining ejectors remain flexible support. The device takes into account the profile compensation of the circuit board, the preheating stress release and the local rigid positioning of the welding spot, reduces the pressure on the device, the sinking of the board body and the thermal warping, and improves the welding positioning precision and quality.

Description

Technical Field

[0001] This invention relates to the field of circuit board welding and positioning technology, specifically to a high-precision positioning and welding processing device and process for circuit boards. Background Technology

[0002] Circuit board soldering is the process of connecting the pins, electrodes, or terminals of electronic components to pads on a circuit board using a soldering mechanism. For double-sided circuit boards, when soldering the second side, the first side is usually already assembled with components. Therefore, the circuit board needs to be positioned with the first side facing down and the second side facing up. Since the components on the first side have different dimensions and mounting heights, the downward-facing side of the circuit board has an uneven profile. Therefore, it is necessary to provide stable support for the circuit board while avoiding the components on the first side to reduce deformation during preheating and soldering.

[0003] Existing circuit board soldering fixtures typically have fixed support columns installed according to the board shape and the distribution of components on the first side of the circuit board. These fixed support columns abut against the exposed area or predetermined support area of ​​the circuit board. The position and height of the fixed support columns remain unchanged after the fixture is completed, providing continuous rigid support to the circuit board during preheating and soldering. For circuit boards that are prone to warping during soldering, pressure strips or clamping components can also be installed above the circuit board to limit vertical displacement.

[0004] However, the aforementioned fixed support structure still suffers from the problem of its support configuration not being compatible with the actual contours of the circuit board and the processing stage. Specifically, different circuit boards have varying component height tolerances, solder layer thicknesses, and initial warpage states, making it difficult for the fixed support pillars to reliably contact all support positions simultaneously. During the preheating stage, the in-plane friction constraints generated by the fixed support structure hinder the circuit board from releasing thermal expansion displacement. In the soldering stage, the current solder joint area requires high support stiffness, while other high-temperature areas still need to maintain lower constraints to release thermal stress. The support height and stiffness of existing support structures are usually not adjustable according to the actual bottom contours of the circuit board, solder joint positions, and processing stages, which can easily lead to local support failure, component or solder joint pressure, accumulation of thermal stress on the board, and sinking or warping of the solder joint area, thereby affecting the soldering positioning accuracy and soldering quality of the circuit board. Summary of the Invention

[0005] The purpose of this invention is to provide a high-precision positioning and welding processing device and process for circuit boards, so as to solve the problems in the prior art where the circuit board support structure cannot dynamically adjust the support state according to the actual bottom contour of the circuit board, the processing stage and the current solder joint position, resulting in unstable circuit board support, limited thermal expansion and easy deformation of the solder joint area.

[0006] The technical problem to be solved by the present invention can be achieved through the following technical solution: a high-precision positioning and welding processing device for circuit boards, comprising: a positioning welding table, on which a preheating mechanism is installed; a welding assembly, on which the welding assembly is installed; a processing table, on which the processing table is installed, and on which multiple positioning assemblies are installed; a positioning assembly, which is used to place the circuit board, and within which a driving assembly and multiple ejector pins are installed; wherein, the preheating mechanism is used to preheat the circuit board, the welding assembly is used to weld the circuit board; and the driving assembly is used to drive the multiple ejector pins to move, thereby supporting the circuit board during the preheating and welding processes.

[0007] Preferably, the welding assembly includes a welding frame mounted on the top of a positioning welding table, a first moving mechanism mounted on the welding frame, a second moving mechanism mounted on the output end of the first moving mechanism, and a welding mechanism mounted on the output end of the second moving mechanism.

[0008] Preferably, the drive assembly includes a lower release air chamber mounted on the processing table, a gas connection block is installed inside the lower release air chamber, and an upper lifting air chamber and a welding support block are sequentially installed at the top of the lower release air chamber.

[0009] Preferably, the ejector pin includes a telescopic tube, one end of which is connected to a gas connection block, and the other end of which is equipped with a lifting tube. The telescopic tube is slidably connected to the lower gas release chamber, and one end of the lifting tube is equipped with a convex spherical plate.

[0010] Preferably, a gas lifter is installed in the upper lifting chamber, and multiple evenly distributed lifting holes are opened in the upper lifting chamber. A lifting boss is installed on the outer wall of the lifting pipe and located in the lifting hole, and the lifting boss is slidably connected to the lifting hole.

[0011] Preferably, a flexible sleeve is embedded in the lifting tube, and a regulating fluid is disposed inside the flexible sleeve.

[0012] Preferably, the conditioning fluid is made of magnetorheological fluid.

[0013] Preferably, a plurality of limiting frames are installed inside the welding support block, and a plurality of pins pass through the corresponding limiting frames. An excitation component for generating a controllable magnetic field is installed on the inner wall of the limiting frame, and the frame material of the limiting frame is magnetic shielding material. A support frame is installed on the top of the welding support block.

[0014] Preferably, the welding mechanism is equipped with a position sensor, which is used to identify the limiting frame corresponding to the weld point currently being aligned by the welding mechanism.

[0015] A high-precision positioning and welding process for circuit boards includes the following steps: S1: Place the circuit board to be soldered on the support frame, with the soldering side of the circuit board facing the soldering component; S2: Gas is supplied into the upward lifting chamber through the gas lifter. The gas is used to apply a lifting force to the lifting boss of each ejector pin, causing multiple ejector pins to rise until the convex spherical plate at the top of each ejector pin contacts the corresponding position on the downward side of the circuit board and reaches force balance, so as to form a conformal support surface that matches the contour of the downward side of the circuit board. S3: When the circuit board is preheated, the excitation component is de-energized, which reduces the flow resistance of the magnetorheological fluid in the flexible sleeve. Positive pressure gas is supplied to the axial air passage of the ejector pin through the gas connection block in the lower release air chamber. The positive pressure gas is discharged through the air outlet structure of the convex spherical disk to share the normal load between the convex spherical disk and the circuit board, so that the ejector pin can move axially and shift laterally with the thermal deformation of the circuit board. S4: The welding mechanism is driven to move to the welding position by the first and second moving mechanisms, and the real-time welding position corresponding to the welding mechanism is obtained by the position sensor. The control system determines the corresponding ejector pin according to the real-time welding position. S5: Control the excitation component corresponding to the determined ejector pin to be energized, so that the magnetorheological fluid in the corresponding flexible sleeve increases the flow resistance under the action of the magnetic field, thereby improving the axial movement resistance and lateral offset resistance of the ejector pin; at the same time, stop supplying positive pressure gas to the determined ejector pin, and switch the axial air passage of the ejector pin from positive pressure to negative pressure through the gas connection block, so that the corresponding ejector pin generates a negative pressure holding effect on the downward side of the circuit board, thereby forming a local rigid support area at the real-time welding position; S6: Welding is performed on the real-time welding position by the welding mechanism. When the welding mechanism moves to the next welding position, the negative pressure holding effect of the ejector pin corresponding to the previous welding position is released and the corresponding excitation component is de-energized. At the same time, the ejector pin corresponding to the next welding position is energized and negative pressure held, so that the local rigid support area moves with the movement of the welding mechanism. S7: Repeat steps S4 to S6 until all soldering positions on the circuit board are completed. Then, control the power off of each excitation component to release the negative pressure holding effect and cause multiple ejector pins to descend and reset.

[0016] Compared with the prior art, the beneficial effects of this application are as follows: 1. This invention arranges multiple independently movable ejector pins in an array below the circuit board, and applies a predetermined lifting force to each ejector pin using an upper lifting air chamber. This ensures that the ejector pins reach force balance after contacting the substrate surface or the outer surface of the device on the downward side of the circuit board. Therefore, the support height of each ejector pin is no longer predetermined by the fixture according to a single nominal size, but is formed according to the actual contour of the downward side of the circuit board, thus creating a conformal support surface. This structure can compensate for device height tolerances, solder layer thickness differences, and initial warpage of the circuit board, reducing the possibility of damage to devices or solder joints due to excessive support height and contact failure due to insufficient support height. Furthermore, the densely distributed ejector pins can increase the support density in the middle of the circuit board and the gap area between devices.

[0017] 2. This invention supplies positive pressure gas to the bottom of the circuit board through the gas channel inside the ejector pin and the gas action port on the convex spherical plate. The normal support force generated by the gas shares part of the normal load borne by the solid contact between the convex spherical plate and the circuit board, thereby reducing the maximum static friction force at the support position. This allows the circuit board to generate controlled micro-slip with a small in-plane force during the preheating process. At the same time, when the excitation component is de-energized, the magnetorheological fluid in the flexible sleeve is in a low viscosity state, and the lifting tube can generate lateral displacement and axial follow-up within a limited range to absorb the thermal expansion displacement that has not yet been released through low-friction micro-slip. Therefore, this solution can reduce the rigidity restriction on the in-plane thermal expansion and thickness direction thermal deformation of the circuit board while maintaining vertical conformal support, and reduce the accumulation of thermal stress and the change in the position of the board caused by sudden stick-slip.

[0018] 3. Based on the current position of the welding mechanism, this invention selectively energizes the excitation components corresponding to the current weld point projection area or adjacent areas, thereby increasing the yield stress and apparent viscosity of the corresponding magnetorheological fluid. This increases the axial movement resistance and lateral offset resistance of the corresponding ejector pin, forming a local high-rigidity support area that moves with the weld point. Simultaneously, a negative pressure suction effect is formed through the gas port of the corresponding ejector pin to suppress the sinking, bulging, and warping of the current weld point area. The remaining areas that still need to release thermal stress maintain a flexible, low-friction support state. This allows the high-rigidity support requirements of the weld point area and the low-constraint expansion requirements of the non-welding area to be met at different positions and at different times. Furthermore, it eliminates the need for a pressure strip spanning the board surface above the circuit board, which helps reduce welding space interference and improve welding positioning accuracy and welding quality. Attached Figure Description

[0019] Figure 1 A three-dimensional structural diagram of the circuit board positioning and welding device provided by the present invention; Figure 2 A three-dimensional structural diagram of the welding assembly provided by the present invention; Figure 3 This is a three-dimensional structural diagram of the processing table provided by the present invention; Figure 4 A three-dimensional structural diagram of the positioning component provided by the present invention; Figure 5 This is a schematic diagram of the three-dimensional structure of the ejector pin provided by the present invention; Figure 6 A three-dimensional structural diagram of the welding support block provided by the present invention; Figure 7 This is a schematic diagram of the three-dimensional structure of the ejector pin provided by the present invention; Figure 8 This is a schematic diagram of the three-dimensional structure of the circuit board provided by the present invention.

[0020] Explanation of reference numerals in the attached figures: 1. Positioning welding table; 2. Welding assembly; 3. Processing table; 4. Positioning assembly; 5. Ejector pin; 21. Welding frame; 22. First moving mechanism; 23. Second moving mechanism; 24. Welding mechanism; 41. Lower release chamber; 42. Upper lifting chamber; 43. Welding support block; 44. Support frame; 45. Circuit board; 51. Telescopic tube; 52. Lifting tube; 53. Flexible sleeve; 54. Convex spherical plate. Detailed Implementation

[0021] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0022] Example 1 When soldering the second side of a double-sided circuit board, the components on the first side have already been assembled, so it can only be placed downwards. Therefore, the support method under the board becomes the key to determining the soldering accuracy.

[0023] Existing technologies typically involve customizing a fixture with fixed support columns according to the board type. However, the fixed support columns present two unavoidable technical problems: First, the support position is limited. The middle of the circuit board 45 is furthest from the frame and collapses the most after being heated and stressed. It should be the key support area, but this area happens to be the most densely populated part of the first side. The fixed support columns can only avoid the placement of components, and the position that needs support the most cannot be placed.

[0024] Secondly, the support height is uncertain. The components on the first side have height tolerances, the solder layer thickness is uneven, and the superimposed board is warped, causing the actual outline height of the circuit board on the 45-degree downward side to vary from piece to piece. The fixed support column can only be processed according to a single nominal height. If the height is too large, it will damage the components on the first side and their solder joints. If the height is too small, it will not be able to contact the board surface and will lose its supporting function.

[0025] This problem cannot be solved by improving the machining accuracy of the support column, because the uncertainty comes from the contour of the circuit board 45 itself, rather than the manufacturing error of the support column.

[0026] like Figures 1 to 5 In this embodiment, a high-precision positioning and welding processing device for circuit boards is disclosed. The device includes a positioning welding table 1, a welding component 2 and a processing table 3. The processing table 3 is installed on the positioning welding table 1, and the welding component 2 is installed on the positioning welding table 1 and located above the processing table 3. The positioning welding table 1 is also equipped with a preheating mechanism for preheating the circuit board 45 as a whole.

[0027] The processing table 3 is equipped with multiple positioning components 4. Each positioning component 4 is used to place a circuit board 45. The positioning component 4 is equipped with a driving component and multiple ejector pins 5. The driving component is used to drive the multiple ejector pins 5 to support the circuit board 45 during the preheating and soldering process.

[0028] Specifically, the drive assembly includes a lower release air chamber 41 mounted on the processing table 3. A gas connection block is installed inside the lower release air chamber 41. An upper lifting air chamber 42 and a welding support block 43 are installed sequentially from bottom to top on the top of the lower release air chamber 41. A support frame 44 is installed on the top of the welding support block 43. A gas lifter is installed inside the upper lifting air chamber 42, and multiple evenly distributed lifting holes are opened inside the upper lifting air chamber 42. Multiple limiting frames are provided inside the welding support block 43.

[0029] The ejector pin 5 includes a telescopic tube 51 and a lifting tube 52. The lower end of the telescopic tube 51 is connected to the gas connecting block in the lower release chamber 41 and is slidably connected to the lower release chamber 41. The upper end of the telescopic tube 51 is connected to the lifting tube 52. The lifting tube 52 passes through the lifting hole of the upper lifting chamber 42 and the corresponding limiting frame in the welding support block 43 from bottom to top. A convex spherical plate 54 is installed at the top of the lifting tube 52.

[0030] A lifting boss is arranged around the outer wall of the lifting tube 52. The lifting boss is located inside the lifting hole and is slidably connected to the lifting hole. This sliding fit transmits the lifting force and provides axial guidance for the lifting tube 52. Multiple ejector pins 5 are arranged in an array on the welding support block 43 at a preset interval. Multiple convex spherical disks 54 at their upper ends together form a support surface for supporting the circuit board 45.

[0031] Based on the above structure, the working principle of its adaptive support is as follows: After the circuit board 45 is placed into the support frame 44 with the first side facing down and completes the coarse positioning and contact, the upper lifting air chamber 42 is connected to multiple lifting holes respectively, and the same set air pressure is formed in each lifting hole.

[0032] Since each lifting hole is supplied with air independently and there is no mechanical linkage between each lifting tube 52, each ejector pin 5 moves upward independently under its own thrust, while its telescopic tube 51 slides upward synchronously relative to the lower release air chamber 41, maintaining air passage connection while compensating for stroke; each ejector pin 5 can move upward independently and stop independently according to the bottom contour of its corresponding position, regardless of the current stroke position of the ejector pin 5.

[0033] During the upward movement, once the convex spherical disk 54 comes into contact with the bottom surface of the circuit board 45 or the outer surface of the first device, it will cause the circuit board 45 that was previously coarsely positioned to move upward. After the contact reaction force and the lifting thrust are balanced, the ejector pin 5 will stop on the spot. The ejector pins 5 that have not yet come into contact continue to move upward until all the ejector pins 5 reach their respective equilibrium positions.

[0034] Since the stopping condition is whether or not there is contact rather than the preset stroke, the final stopping height of each ejector pin 5 is equal to the actual height of the bottom surface of the circuit board 45 at its corresponding position. As a result, multiple convex spherical disks 54 automatically form a conformal support surface that fits the actual bottom contour of the circuit board 45.

[0035] It should be emphasized that the core improvement of this embodiment is that the height of the support surface is changed from being preset by the fixture to being passively determined by the circuit board 45 itself during the clamping process. Multiple ejector pins 5 move independently with constant thrust and automatically stop when they make contact, so that the height of the support point becomes a direct reproduction of the true outline of the circuit board 45. This solves the two opposite failure modes at the same time: the fixed support column being too high and damaging the device, and the fixed support column being too low and causing contact failure.

[0036] Meanwhile, due to the small cross-section and dense arrangement of the ejector pins 5, a large number of points can be placed in the gaps between components, and the dense area in the middle can also be fully supported, which solves the problem that the fixed support column cannot be placed in the critical area due to avoiding components; its essence is to replace the rigid support surface formed in one step according to the nominal size with a passive adaptive support surface that stops with constant force, so that the support scheme no longer depends on the pre-measurement and input of the bottom contour of each circuit board 45.

[0037] It should be noted that the spacing between the ejector pins 5 is preferably one to two times less than the minimum gap between adjacent devices on the first surface, and the outer diameter of the lifting tube 52 and the convex spherical disk 54 is preferably less than half of the minimum gap, so that at least one ejector pin 5 can fall between any two adjacent devices.

[0038] The radius of the spherical surface of the convex spherical disk 54 should be greater than the spacing of the ejector pins 5 so that when the circuit board 45 is partially tilted, the contact point still falls within the effective area of ​​the spherical surface. The available stroke of the ejector pins 5 should be greater than the height of the highest device on the first side and leave a margin to ensure that the ejector pins 5 facing the high device can also stop normally without exhausting their stroke.

[0039] It should be noted that the sliding fit between the lifting boss and the lifting hole also serves as a guide, constraining the axial direction of the lifting tube 52; the limiting frame inside the welded support block 43 serves only as an upper guide for the lifting tube 52 in this embodiment, and the excitation element on its inner wall is not energized at this stage.

[0040] In addition, the lifting air pressure should be set according to the upper limit of the contact force so that the contact force of a single ejector pin 5 acting on the first surface device is lower than the allowable value of the device and its solder joints, so as to ensure that even if a ejector pin 5 happens to be directly in front of the device body, only a limited amount of light contact will be formed without causing damage.

[0041] In this embodiment, the air supply pressure of the upper lifting air chamber 42 is set to be adjustable so as to adjust the single needle contact force for circuit boards 45 with different board thicknesses and different device strengths; the gas lifter can adopt a zoned air supply structure, with the pressure of each zone set independently, so as to configure the support force according to the regional differences on the same circuit board 45.

[0042] The spherical portion of the convex spherical disk 54 can be made of a material that is resistant to high temperatures and has a hardness lower than that of the solder and the device housing, or a high-temperature resistant elastic coating can be provided on the spherical surface to further reduce contact stress.

[0043] Before the circuit board 45 is inserted, the upper lifting air chamber 42 is depressurized first, so that all the ejector pins 5 fall back to the lowest position under their own weight, leaving a clear space for the material to be loaded and avoiding the impact of the material falling directly acting on the top of the ejector pins 5; after the circuit board 45 is in place, the pressure is increased and lifted, which can effectively prevent dynamic load impact damage to the first-side components.

[0044] Example 2 It is understood that in Embodiment 1, multiple ejector pins 5 form a conformal support surface that matches the bottom contour of the circuit board 45 through independent lifting and stopping. When each ejector pin 5 supports the circuit board 45, there is a normal contact force between its convex spherical disk 54 and the bottom surface of the circuit board 45. This normal contact force gives the contact position the corresponding maximum static friction force.

[0045] During the preheating process, the preheating mechanism heats the circuit board 45 as a whole. The circuit board 45 will thermally expand along its own surface direction and may locally arch or deflect in the thickness direction. Since multiple convex spherical disks 54 are densely distributed under the circuit board 45, the friction at each contact point will jointly form a distributed resistance to the thermal expansion of the surface.

[0046] When the tangential driving force generated by local thermal expansion is insufficient to overcome the maximum static friction at the corresponding contact position, the circuit board 45 is constrained at that position and accumulates thermal stress; when the tangential driving force exceeds the maximum static friction, the circuit board 45 may experience sudden micro-slippage, thereby causing discontinuous stress release and changes in the position of the board.

[0047] Therefore, the preheating stage needs to reduce the frictional constraints at each support position while retaining the conformal support relationship formed in Embodiment 1, and provide flexible clearance space for the in-plane thermal expansion of the circuit board 45 when the residual friction is still insufficient to be released through stable sliding.

[0048] like Figures 4 to 8 In this embodiment, the stress relief structure of the high-precision positioning and welding processing device for circuit boards during the preheating stage is further disclosed. The connection relationship of the positioning component 4, the lower release air chamber 41, the upper lifting air chamber 42, the welding support block 43, the support frame 44, and the multiple ejector pins 5 remains unchanged. That is, the lower release air chamber 41 is installed on the processing table 3, and a gas connection block is installed in the lower release air chamber 41. The upper lifting air chamber 42 and the welding support block 43 are installed sequentially from bottom to top on the top of the lower release air chamber 41, and the support frame 44 is installed on the top of the welding support block 43. The lower end of the telescopic tube 51 of each ejector pin 5 is connected to the gas connection block and is slidably connected to the lower release air chamber 41. The lifting tube 52 passes through the lifting hole and the limiting frame and is equipped with a convex spherical plate 54 at its top. The lifting boss is slidably connected to the lifting hole.

[0049] Based on this, the telescopic tube 51 and the lifting tube 52 are provided with interconnected gas channels, and the lower end of the telescopic tube 51 is connected to the gas connecting block in the lower release gas chamber 41; the convex spherical disk 54 is provided with an air outlet structure that is connected to the gas channel inside the lifting tube 52.

[0050] The venting structure includes multiple micro vent holes distributed around the spherical contact area of ​​the convex spherical disk 54, or includes an annular venting groove surrounding the spherical contact area, to prevent the venting structure from being completely sealed when the convex spherical disk 54 comes into contact with the circuit board 45.

[0051] A flexible sleeve 53 is embedded in the lifting tube 52. The flexible sleeve 53 is filled with a regulating fluid, and the regulating fluid is made of magnetorheological fluid. The flexible sleeve 53 is located inside the corresponding limiting frame and corresponds to the excitation component installed on the inner wall of the limiting frame.

[0052] The working principle of preheating and stress release of circuit board 45 is as follows: After circuit board 45 completes the adaptive support as described in Embodiment 1, the upper lifting air chamber 42 maintains the set pressure that keeps each pin 5 in contact with circuit board 45, the excitation components in all limit frames are kept de-energized, and the magnetorheological fluid in flexible sleeve 53 is in a low-viscosity flow state under zero magnetic field.

[0053] The preheating mechanism heats the circuit board 45 according to the set heating rate. Before or after the preheating starts, the lower release chamber 41 supplies gas with a set pressure to each telescopic tube 51 through the gas connection block. The gas passes through the telescopic tube 51, the lifting tube 52 and the gas outlet structure on the convex spherical plate 54 in sequence, and is discharged outward from the contact area between the convex spherical plate 54 and the bottom surface of the circuit board 45.

[0054] The gas discharged from the vent structure creates a local positive pressure between the convex spherical disk 54 and the circuit board 45. This positive pressure exerts an upward normal force on the circuit board 45, thereby sharing part of the normal load that was originally borne by the solid contact between the convex spherical disk 54 and the circuit board 45.

[0055] After the normal load borne by the solid contact is reduced, the maximum static friction force between the convex spherical disk 54 and the circuit board 45 is reduced accordingly. The gas supply pressure of the lower release chamber 41 is controlled within the preset unloading range, so that the normal lifting force generated by the gas is less than the critical lifting force that causes the circuit board 45 and the convex spherical disk 54 to continue to separate.

[0056] Thus, the gas is mainly used to reduce the normal load borne by the solid contact, rather than replacing the conformal support formed by the multiple pins 5 on the circuit board 45; the convex spherical disk 54 maintains contact with the circuit board 45, or maintains a micro-gap state that can quickly restore contact with the local undulations of the circuit board 45, and the overall support position and vertical positioning relationship formed in Embodiment 1 are preserved.

[0057] When the in-plane tangential driving force generated by the thermal expansion of the circuit board 45 is greater than the maximum static friction force after the gas is unloaded, the circuit board 45 can slide continuously or in segments relative to the corresponding convex spherical disk 54. Since the sliding can occur at a low friction threshold, the circuit board 45 does not need to accumulate a large in-plane thermal stress, thus reducing the position jump caused when static friction is suddenly overcome.

[0058] When the residual friction force after gas unloading is still greater than the in-plane tangential driving force at a certain support position due to surface roughness, local load difference, or gas supply pressure difference, the circuit board 45 can drive the upper section of the corresponding lifting tube 52 to produce a slight offset in the same direction through the convex spherical disk 54. At this time, the flexible sleeve 53 undergoes elastic deformation, the magnetorheological fluid in the flexible sleeve 53 flows in a zero magnetic field state, and the lifting tube 52 undergoes a slight elastic bending within the range allowed by the lifting hole and the limiting frame.

[0059] Therefore, the circuit board 45 can release part of the thermal expansion displacement through the flexible clearance of the upper section of the ejector pin 5 without having to immediately overcome static friction.

[0060] As thermal expansion displacement continues to increase, the circuit board 45 can release in-plane displacement through two methods: low-friction micro-slip between the convex spherical disk 54 and the circuit board 45, and flexible offset of the upper section of the ejector pin 5. Gas unloading is used to reduce the friction threshold that needs to be overcome to cause relative sliding, and the elastic deformation of the flexible sleeve 53, low-viscosity magnetorheological fluid and lifting tube 52 is used to absorb the residual displacement that has not yet been released through relative sliding, thereby preventing the circuit board 45 from forming large stress accumulation and sudden stick-slip during the preheating process.

[0061] When the circuit board 45 experiences localized upward or downward arching, the compressibility of the gas in the upper lifting chamber 42 and the sliding fit of the telescopic tube 51 relative to the lower release chamber 41 enable the corresponding ejector pin 5 to move axially within a set range: when the circuit board 45 experiences localized upward arching, the corresponding ejector pin 5 can move upward appropriately or reduce the contact load; when the circuit board 45 experiences localized downward fall, the corresponding ejector pin 5 can re-follow the board surface under the action of the upper lifting chamber 42, thereby reducing the rigid restriction on the thermal deformation of the circuit board 45 in the thickness direction while maintaining vertical support.

[0062] It should be emphasized that the core improvement of this embodiment lies in the following: without changing the conformal support state formed in Embodiment 1, the gas discharged from the convex spherical disk 54 shares part of the normal load, reducing the solid contact pressure and maximum static friction at each support position, enabling the circuit board 45 to generate controlled micro-slip under relatively small thermal stress; when residual friction still restricts local thermal expansion, the elastic offset of the flexible sleeve 53 in a flexible state, the low-viscosity magnetorheological fluid, and the lifting tube 52 jointly absorb the residual in-plane displacement. This forms a two-stage stress release mechanism with gas unloading and friction reduction as the main method and flexible clearance of the ejector pin as a supplement.

[0063] It should be noted that the gas supply pressure of the lower release chamber 41 should be set according to the initial contact force of the ejector pin 5, the local stiffness of the circuit board 45, the gas outlet area of ​​the convex spherical disk 54, and the gas leakage gap; the normal support force generated by the gas should be less than the initial contact force at the corresponding position, and the minimum solid contact load that meets the stable support requirements of the circuit board 45 should be reserved.

[0064] If necessary, a pressure regulating valve, a flow regulating valve, and a pressure sensor can be installed on the air supply line of the lower air release chamber 41, and the air supply pressure can be adjusted in a closed loop according to the displacement detection results of the circuit board 45.

[0065] In this embodiment, the flexible sleeve 53 is not used to actively drive the lateral movement of the lifting tube 52, but rather to provide the lifting tube 52 with a passive clearance within a set range when the circuit board 45 undergoes lateral thermal expansion. The lateral offset of the lifting tube 52 is determined by the material elasticity of the flexible sleeve 53, the zero magnetic field viscosity of the magnetorheological fluid, the radial gap between the lifting boss and the lifting hole, the fitting gap between the flexible sleeve 53 and the limiting frame, and the bending stiffness of the lifting tube 52. The above parameters should ensure that the ejector pin 5 maintains stable guidance in the vertical direction, while avoiding excessive lateral stiffness that would restrict the thermal expansion of the circuit board 45 again.

[0066] In this embodiment, the lower gas release chamber 41 can adopt an overall gas supply or a zoned gas supply structure. When a zoned gas supply structure is adopted, the gas supply pressure of different areas can be adjusted according to the self-weight of each area of ​​the circuit board 45, the distribution of components, the number of pin contacts and the preheating temperature, so that the solid contact load of each area is kept within a similar range.

[0067] The gas supplied is preferably clean, dry air or inert gas, and can be preheated to a temperature close to that of the circuit board 45 before entering the lower release chamber 41, so as to reduce the local temperature difference caused by the airflow.

[0068] The preheating mechanism can be a heating plate, an infrared radiation mechanism, or a hot air mechanism, and preheats the circuit board 45 by means of low-speed heating, segmented heating and uniform temperature maintenance; after preheating, the control system enters the soldering stage according to the temperature and size stability of the circuit board 45.

[0069] When entering the welding stage, the ejector pin 5 corresponding to the current weld point can be switched from the gas supply state to the gas extraction state described in Example 3. Other ejector pins 5 that do not participate in the rigid support of the current weld point will continue to maintain low-pressure gas supply or switch to natural pressure relief state according to the temperature and stress release needs of the corresponding area, thereby avoiding the sudden application of overall friction constraint to the non-welded area of ​​the circuit board 45 after the welding starts.

[0070] Example 3 It is understandable that in Example 2, all the ejector pins 5 are in a flexible state throughout the preheating stage, which is extremely beneficial for stress release. However, once the formal welding stage begins, this state is no longer applicable in both time and space.

[0071] Regarding the solder joint being soldered, the soldering mechanism 24 moves point by point on the circuit board 45. There must be sufficient support rigidity directly below the current solder joint in order to withstand the force generated by the laser impact or the pressure of the soldering iron tip and hot press head. If the support is still a flexible state composed of an elastic air cushion and a low viscosity conditioning liquid, the solder joint area will sink locally under the soldering pressure, resulting in laser defocusing, insufficient depth of the soldering iron tip, lead floating, and poor soldering.

[0072] Meanwhile, the heat input during welding will cause the weld joint neighborhood to bulge and warp upwards, which cannot be suppressed by simply supporting it upwards. The existing technology can only add a pressure bar above the circuit board 45 to press it down. However, the pressure bar not only occupies the welding operation space and is easy to damage the installed components outside the first side, but also reintroduces lateral friction constraints to the circuit board 45, causing the stress resistance problem that was eliminated in Embodiment 2 to reappear.

[0073] In the unsoldered areas, while a solder joint is being soldered, most of the rest of the circuit board 45 remains at a high temperature and continues to expand. These areas need to remain flexible to continue releasing stress.

[0074] This creates a dual requirement: at the same time, the local area where the weld point is located requires high stiffness and downward support, while the vast other area requires low constraint and free expansion. No support structure with uniform stiffness throughout the entire field and that does not change over time can simultaneously meet both requirements.

[0075] like Figures 5 to 8 In this embodiment, structurally, the welding assembly 2 includes a welding frame 21 mounted on the top of the positioning welding table 1. A first moving mechanism 22 is mounted on the welding frame 21. A second moving mechanism 23 is mounted on the output end of the first moving mechanism 22. A welding mechanism 24 is mounted on the output end of the second moving mechanism 23. A position sensor is mounted on the welding mechanism 24. The position sensor is used to identify the limiting frame corresponding to the weld point currently aligned by the welding mechanism 24.

[0076] The multiple limiting frames within the welding support block 43 are arranged in an array and correspond one-to-one with the ejector pins 5. Each limiting frame has an excitation component installed on its inner wall to generate a controllable magnetic field. The frame material of the limiting frame is magnetic shielding material, and the excitation component on the inner wall of each limiting frame is independently connected to the control system.

[0077] The lower release chamber 41 is configured to switch between supplying and evacuating air for each ejector pin 5 according to a region; the telescopic tube 51 and the lifting tube 52 of the ejector pin 5 are provided with interconnected axial air passages, which extend upward to the spherical surface of the convex spherical disk 54 and form an adsorption port.

[0078] The working principle of the movable rigid support area moving synchronously with the welding point is as follows: The relative position between the position sensor and the welding head of the welding mechanism 24 is pre-calibrated. When the first moving mechanism 22 and the second moving mechanism 23 drive the welding mechanism 24 to move point by point, the position sensor outputs the planar coordinates of the current welding point in real time. The control system calculates the limit frame number corresponding to the welding point directly below it and energizes the excitation component of the limit frame only.

[0079] After the excitation component is energized, a magnetic field is established in the cell. The magnetic field passes through the flexible sleeve 53 and acts on the magnetorheological fluid inside it, causing the magnetic particles in the magnetorheological fluid to form chains along the magnetic field lines. The yield stress increases sharply within milliseconds and transforms into a solid-like state, thereby clamping and securing the lifting tube 52 between the inner walls of the limiting frame. The lateral degree of freedom and vertical sliding of the pin 5 are eliminated at the same time, forming a rigid support column directly opposite the welding point.

[0080] At the same time, the lower release chamber 41 switches from supplying air to evacuating air from the ejector pin 5. The negative pressure is transmitted through the axial air passage in the telescopic tube 51 and the lifting tube 52 to the suction port of the convex spherical disk 54, forming a downward suction force on the bottom surface of the circuit board 45, which counteracts the upward bulging and warping tendency caused by the welding heat input.

[0081] Since the frame of each limiting frame is made of magnetic shielding material, the magnetic field of the energized grid does not leak to the adjacent grid. Except for this grid, the regulating liquid of all the other pins 5 is still in a state of zero magnetic field and low viscosity. The remaining high temperature area of ​​the circuit board 45 continues to maintain the flexible support and free release of thermal expansion as described in Example 2.

[0082] When the welding head moves to the next welding point, the control system de-energizes the previous limit frame and energizes the new limit frame, and the rigid support area moves accordingly. Since the solidification and desolvation of the magnetorheological fluid are both in the millisecond range and are directly controlled by power on and off, its switching speed is much higher than the time interval of the welding head moving point by point. The rigid support area always arrives before or synchronously with the welding head.

[0083] It should be emphasized that the core improvement of this embodiment is that the set of strong constraints that would hinder stress release, namely the high-rigidity support and downward pull, are applied only in space to a single limiting frame directly below the current weld point, and only in time to the period during which the weld point is welded, while the rest of the positions and the rest of the time remain flexible.

[0084] Therefore, the mutually exclusive requirements of high stiffness and low constraint under a unified support structure are allocated to different locations and at different times to be met separately, without the need to compromise between the two.

[0085] Meanwhile, the function of pressing the circuit board 45 downward is achieved by the suction adsorption of the lower release air chamber 41 under the board, which replaces the pressure strip set on the upper part of the board in the prior art. This makes the upper surface of the circuit board 45 completely clear, eliminating the risk of damaging the components and no longer introducing new lateral friction constraints to the circuit board 45. The three defects that originally restrained each other, namely solder joint sinking, board bulging and stress resistance, are thus eliminated at the same time.

[0086] It should be noted that the position sensor can be a grating ruler, encoder or vision sensor. The coordinates output by the sensor are converted by a pre-calibrated offset and mapped to the row and column numbers of the limit frame array. The control system can trigger the excitation component of the target limit frame to be energized in advance during the stroke of the welding head from the previous welding point to the current welding point, so that the solidification process of the magnetorheological fluid overlaps with the movement process of the welding head in time, thus not occupying the welding cycle.

[0087] The frame material of the limit frame can be a high-permeability magnetic shielding material such as permalloy. The excitation component can be an electromagnetic coil wound on the inner wall of the limit frame. In order to avoid the residual magnetism after the excitation component is de-energized, which would prevent the magnetorheological fluid from completely returning to a low viscosity state, the control system can apply a reverse demagnetizing pulse when the power is off, so as to ensure that the pin 5 of the grid quickly returns to a flexible state and re-participates in stress release.

[0088] In addition, the fit clearance between the lifting tube 52 and the inner wall of the limiting frame should match the wall thickness of the flexible sleeve 53. If the clearance is too large, it will reduce the clamping stiffness after curing, and if the clearance is too small, it will generate unnecessary viscous resistance in the flexible state.

[0089] In this embodiment, the control system can also illuminate one or more surrounding limit frames simultaneously with the current limit frame, based on the heat load around the weld point and the local stiffness of the plate. This allows multiple ejector pins 5 to solidify and combine into a larger rigid support area, thus more effectively suppressing the sagging of the weld point's vicinity. Thanks to the compartmentalized isolation of the magnetic shielding frame, the rigid support area can be arbitrarily spliced ​​and added or removed in units of the limit frames, and the area outside its range remains unaffected and continues to release stress. This allows for adjustment of the support stiffness and stress release capability to a suitable level for different plate types. When two adjacent weld points are located in the corresponding area of ​​the same limit frame, that compartment can be continuously energized and welding can be completed continuously, reducing the number of switching operations.

[0090] After all solder joints are welded, the control system de-energizes and demagnetizes all excitation components. The lower release chamber 41 is switched from evacuation to supply, allowing the circuit board 45 to remain in a low-constraint state and retract freely during the cooling and shrinkage phase, thus avoiding residual stress in the solder joints due to obstructed shrinkage. Subsequently, the upper lifting chamber 42 is depressurized, and all ejector pins 5 fall back to their lowest position under their own weight. The circuit board 45 is lifted out by the support frame 44 and unloaded. The device is then reset to enter the next processing cycle.

[0091] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed application.

Claims

1. A high-precision positioning and welding processing device for circuit boards, characterized in that, include: Positioning welding table (1), on which a preheating mechanism is installed; Welding assembly (2), which is mounted on positioning welding table (1); The processing table (3) is installed on the positioning welding table (1), and multiple positioning components (4) are installed on the processing table (3). Positioning component (4), the positioning component (4) is used to place circuit board (45), and the positioning component (4) is equipped with a drive component and a plurality of ejector pins (5). The drive component includes a lower release air chamber (41) installed on the processing table (3). A gas connection block is installed in the lower release air chamber (41). An upper lifting air chamber (42) and a welding support block (43) are installed in sequence at the top of the lower release air chamber (41). The preheating mechanism is used to preheat the circuit board (45), the welding assembly (2) is used to weld the circuit board (45), and the driving assembly is used to drive multiple ejector pins (5) to support the circuit board (45) during the preheating and welding process.

2. The high-precision positioning and welding processing device for circuit boards as described in claim 1, characterized in that, The welding assembly (2) includes a welding frame (21) mounted on the top of the positioning welding table (1), a first moving mechanism (22) is mounted on the welding frame (21), a second moving mechanism (23) is mounted on the output end of the first moving mechanism (22), and a welding mechanism (24) is mounted on the output end of the second moving mechanism (23).

3. The high-precision positioning and welding processing device for circuit boards as described in claim 1, characterized in that, The ejector pin (5) includes a telescopic tube (51), one end of which is connected to a gas connection block, and the other end of which is equipped with a lifting tube (52). The telescopic tube (51) is slidably connected to the lower release chamber (41), and one end of the lifting tube (52) is equipped with a convex spherical plate (54).

4. The high-precision positioning and welding processing device for circuit boards as described in claim 3, characterized in that, A gas lifter is installed in the upper lifting chamber (42), and multiple evenly distributed lifting holes are opened in the upper lifting chamber (42). A lifting boss is installed on the outer wall of the lifting pipe (52) and located in the lifting hole. The lifting boss is slidably connected to the lifting hole.

5. The high-precision positioning and welding processing device for circuit boards as described in claim 4, characterized in that, A flexible sleeve (53) is embedded in the lifting tube (52), and a regulating fluid is provided inside the flexible sleeve (53).

6. The high-precision positioning and welding processing device for circuit boards as described in claim 5, characterized in that, The conditioning fluid is made of magnetorheological fluid.

7. The high-precision positioning and welding processing device for circuit boards as described in claim 1, characterized in that, Multiple limiting frames are installed inside the welding support block (43), and multiple pins (5) pass through the corresponding limiting frames respectively. An excitation component for generating a controllable magnetic field is installed on the inner wall of the limiting frame, and the frame material of the limiting frame is magnetic shielding material. A support frame (44) is installed on the top of the welding support block (43).

8. The high-precision positioning and welding processing device for circuit boards as described in claim 2, characterized in that, A position sensor is installed on the welding mechanism (24), which is used to identify the limiting frame directly below the welding point that the welding mechanism (24) is aligned with in real time.

9. A high-precision positioning and welding process for circuit boards, characterized in that, Including a high-precision positioning and welding processing apparatus for circuit boards as described in any one of claims 1 to 8, wherein the high-precision positioning and welding processing technology for circuit boards Includes the following steps: S1: Place the circuit board (45) to be soldered on the support frame (44) so ​​that the soldering surface of the circuit board (45) faces the soldering assembly (2). S2: Gas is supplied into the upward lifting chamber (42) by the gas lifter, and the gas is used to apply lifting force to the lifting boss of each ejector pin (5), so that multiple ejector pins (5) rise until the convex spherical disk (54) at the top of each ejector pin (5) contacts the corresponding position on the downward side of the circuit board (45) and reaches force balance, so as to form a conformal support surface that matches the contour of the downward side of the circuit board (45); S3: When the circuit board (45) is preheated, the excitation component is de-energized, which reduces the flow resistance of the magnetorheological fluid in the flexible sleeve (53) and supplies positive pressure gas to the axial air passage of the ejector pin (5) through the gas connection block in the lower release air chamber (41). The positive pressure gas is discharged through the air outlet structure of the convex spherical disk (54) to share the normal load between the convex spherical disk (54) and the circuit board (45), so that the ejector pin (5) can move axially and shift laterally with the thermal deformation of the circuit board (45). S4: The welding mechanism (24) is driven to move to the welding position by the first moving mechanism (22) and the second moving mechanism (23), and the real-time welding position corresponding to the welding mechanism (24) is obtained by the position sensor. The control system determines the corresponding ejector pin (5) according to the real-time welding position. S5: Control the excitation component corresponding to the determined ejector pin (5) to be energized, so that the magnetorheological fluid in the corresponding flexible sleeve (53) increases the flow resistance under the action of the magnetic field, so as to improve the axial movement resistance and lateral offset resistance of the ejector pin (5); at the same time, stop supplying positive pressure gas to the determined ejector pin (5), and switch the axial air passage of the ejector pin (5) from positive pressure to negative pressure through the gas connection block, so that the corresponding ejector pin (5) generates negative pressure suction on the downward side of the circuit board (45), thereby forming a local rigid support area at the real-time welding position; S6: Welding is performed on the real-time welding position by the welding mechanism (24), and when the welding mechanism (24) moves to the next welding position, the negative pressure holding effect of the ejector pin (5) corresponding to the previous welding position is released and the corresponding excitation component is de-energized. At the same time, the ejector pin (5) corresponding to the next welding position is energized and held under negative pressure, so that the local rigid support area moves with the movement of the welding mechanism (24). S7: Repeat steps S4 to S6 until all soldering positions on the circuit board (45) are completed. Then, control the power off of each excitation component, release the negative pressure holding effect, and lower and reset multiple pins (5).

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