A positioning and welding tool for a reverse insertion power device in a PCBA

Abstract

The application discloses a positioning and welding tool for reverse insertion type power devices in a PCBA (Printed Circuit Board Assembly), which belongs to the technical field of circuit board welding and comprises a supporting frame, a bottom plate and a pressing plate. The bottom plate is arranged on the base of the supporting frame, the pressing plate is arranged above the bottom plate in parallel and is connected with the supporting frame through a lifting mechanism, and the upper surface of the bottom plate is provided with a plurality of supporting blocks for positioning and carrying the PCBA board. When the PCBA board is placed on the supporting blocks with the A surface facing upwards, the distance between the B surface of the PCBA board and the upper surface of the bottom plate is the same as the distance between the B surface of the PCBA board and the back surface of the radiator after the PCBA board is actually assembled into the electric control box. The pressing plate can press and fix the PCBA board on the supporting blocks under the action of the lifting mechanism. The positioning and welding tool is used for positioning and clamping the PCBA board, the stress condition of the PCBA board installed in the electric control box can be simulated, the radiating surfaces of all the power devices are controlled on the same plane, the relative position relationship between the power devices and the PCBA board is ensured, and thus the welding precision of the power devices is improved.

Description

Technical Field

[0001] This invention relates to the field of circuit board welding technology, and in particular to a positioning welding fixture for reverse-insertion power devices in PCBA. Background Technology

[0002] Currently, there are two insertion methods for power devices on PCBAs, which are related to the PCB design. One method is that all devices are on side A of the PCB, which is called normal insertion; the other method is that only a few power devices are on side B, with their pins on side A, opposite to the other devices, which is called reverse insertion. Figure 1 As shown. Reverse insertion allows the heatsink to be suspended outside the entire control box, providing more ample assembly space. Currently, there is a process issue with soldering reverse-inserted power devices on PCBA boards: after the multiple pins of the power device are inserted into the pads on the PCBA board, they must be soldered. The key is that the plastic casing of the power device must be on a single plane; that is, each power device must be in very close contact with the contact surface of the heatsink. Otherwise, insufficient heat dissipation will lead to heat accumulation and cause the power device to burn out. Currently, there are two methods for soldering: soldering before and after.

[0003] 1. Pre-soldering: This is a common industry practice. A support bracket holds all power devices in place, ensuring they are on the same plane. The power devices are soldered before the PCBA board is assembled into the control box (the bracket slightly lifts the devices to ensure proper soldering). However, this method is highly inaccurate due to the manufacturing process of the plastic bracket, which causes deformation. After soldering and installation into the control box, the fit between the power device and the back of the heatsink remains inaccurate, showing significant differences in the X, Y, and Z directions. Simply tightening the bracket with screws can damage the device leads, cause the plastic casing to warp, or create gaps between the device and the heatsink. Warping and gaps severely impact heat dissipation. Furthermore, the bracket is fixed to the board after soldering, which is costly, as one bracket is needed for every board, making it impractical.

[0004] 2. Post-soldering: This involves first installing the PCBA board into the control box and screwing it in, then soldering. This is considered the most ideal method, as it eliminates the need for a support bracket and allows for precise soldering of power device pin positions. It also ensures a better fit between the top of the power device and the back of the heatsink, resulting in improved heat dissipation. However, post-soldering presents several problems. Since the PCBA board is already installed in the control box, the operation is inconvenient. Furthermore, with the heatsink fixed in place, the front of the power device is flush with the back of the heatsink, making the A-side of the PCBA board invisible. This prevents operators from inspecting the soldering quality from the A-side (both sides need to be checked). Additionally, unsoldered power devices may fall out during PCBA board relocation. Moreover, once the PCBA board is in the control box, it's difficult to perform conformal coating on the assembly line. Therefore, this method is inefficient for mass production. Summary of the Invention

[0005] To overcome the aforementioned shortcomings in the soldering of reverse-insertion power devices in existing PCBA boards, the technical problem to be solved by this invention is to provide a positioning and soldering fixture for reverse-insertion power devices in PCBA boards that can improve soldering accuracy and efficiency.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A positioning and welding fixture for reverse-insertion power devices in a PCBA is provided. This fixture is suitable for welding power devices between the B-side of the PCBA board and a heatsink. The PCBA board has a first mounting hole and a second mounting hole, and is fixed to a control box by screws passing through the first mounting hole. The power device has a third mounting hole aligned with the second mounting hole, and the heatsink has a fourth mounting hole aligned with the second mounting hole. The power device and the heatsink are connected together by screws passing through the third and fourth mounting holes. The positioning and welding fixture includes a support frame, a base plate, and a pressure plate. The base plate is mounted on the base of the support frame, and the pressure plate is positioned parallel above the base plate and connected to the support frame via a lifting mechanism. The upper surface of the base plate has multiple support blocks for positioning and supporting the PCBA board. When the PCBA board is placed on the support blocks with its A-side facing up, the distance from the B-side of the PCBA board to the upper surface of the base plate is the same as the distance from the B-side of the PCBA board to the back of the heatsink after it is actually assembled into the control box. The pressure plate can press and fix the PCBA board onto the support blocks under the action of the lifting mechanism.

[0008] Furthermore, the support block of the base is provided with a plurality of first positioning holes aligned with the first mounting holes on the PCBA board, and the bottom of the pressure plate is provided with a plurality of first positioning posts. The lower end of the first positioning post is provided with a shoulder. When the pressure plate presses the PCBA board, the lower end of the first positioning post can be inserted into the first positioning hole after passing through the first mounting hole of the PCBA board, and the PCBA board is pressed onto the support block by the shoulder.

[0009] Furthermore, the bottom of the pressure plate is provided with a plurality of second positioning posts, which are aligned with the second mounting holes on the PCBA board. The lower end of the second positioning post is provided with a second-stage pressure head, and the end of the second-stage pressure head is provided with a stepped surface. When the pressure plate presses the PCBA board, the end of the second-stage pressure head can be inserted into the third mounting hole of the power device after passing through the second mounting hole of the PCBA board, and the stepped surface is pressed tightly against the A side of the PCBA board.

[0010] Furthermore, the bottom of the pressure plate is provided with multiple third positioning posts. The second positioning posts are aligned with the second assembly holes on the PCBA board. The lower end of the third positioning posts is detachably equipped with a second-stage pressure head or a third-stage pressure head. The end of the second-stage pressure head is provided with a stepped surface. When the pressure plate presses the PCBA board, the end of the second-stage pressure head can pass through the second assembly hole of the PCBA board and then be embedded in the third assembly hole of the power device, and the stepped surface is pressed tightly against the A side of the PCBA board. The end of the third-stage pressure head is provided with two stepped surfaces. The bottom plate is provided with a second positioning hole. When the pressure plate presses the PCBA board, the end of the third-stage pressure head can pass through the second assembly hole of the PCBA board and the third assembly hole of the power device in sequence and then be embedded in the second positioning hole, and the two stepped surfaces are pressed tightly against the top surface of the power device and the A side of the PCBA board, respectively.

[0011] Furthermore, for power devices on the PCBA board that do not directly contact the back of the heat sink, a placeholder block is provided on the upper surface of the base plate at a position corresponding to its position. The upper and lower sides of the placeholder block are adapted to the bottom surface of the power device and the back of the heat sink, respectively. When the pressure plate presses the PCBA board, the placeholder block is pressed and filled between the power device and the heat sink.

[0012] Furthermore, the base plate and pressure plate include various interchangeable models with different structures, and the models of the two correspond one-to-one. The parts of the base plate and pressure plate where no power devices are installed have a hollow structure.

[0013] Furthermore, the base of the support frame is provided with a portal-shaped limiting frame, and the base plate is slidably disposed within the portal-shaped limiting frame.

[0014] Furthermore, the support frame has vertical guide rods on both sides, the pressure plate is slidably mounted on the guide rods, and the lifting mechanism is a hand-push pressure rod, a pneumatic pressure rod, a hydraulic pressure rod or an electric push rod. Its fixed part is located on the top of the support frame, and its lifting end is detachably connected to the pressure plate and can drive the pressure plate to slide up and down along the guide rod.

[0015] The beneficial effects of this invention are as follows: By using this positioning welding fixture to position and clamp the PCBA board, the stress situation of the PCBA board installed in the electrical control box can be simulated, and the heat dissipation surfaces of all power devices are controlled on the same plane, ensuring the relative positional relationship between the power devices and the PCBA board, thereby improving the welding accuracy of the power devices. After welding, it is also convenient to perform welding quality inspection, conformal coating and other external operations on the PCBA board, which can avoid the problem of substandard positional matching between the heat sink and the power devices, and improve the welding and assembly quality of the PCBA board. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the PCBA board installed in the electrical control box;

[0017] Figure 2 This is a schematic diagram of the structure of the present invention.

[0018] The diagram is labeled as follows: 1-PCBA board, 2-power device, 3-heat sink, 4-support frame, 5-base plate, 6-pressure plate, 7-lifting mechanism, 11-first assembly hole, 12-second assembly hole, 21-third assembly hole, 31-fourth assembly hole, 41-base, 42-gate-shaped limit frame, 43-guide rod, 51-support block, 52-first positioning hole, 53-second positioning hole, 54-placeholder block, 61-first positioning post, 62-second positioning post, 63-third positioning post, 64-second-stage pressure head, 65-third-stage pressure head. Detailed Implementation

[0019] The invention will be further described below with reference to the accompanying drawings.

[0020] It should be noted that if this invention uses directional terms such as up, down, left, right, front, and back, these are for describing the relative positions of components and are not specific references to the absolute positions of related components or the relationships between them. They are only used to explain the relative positional relationships and movements of components in a specific posture. If the specific posture changes, the directional indication will also change accordingly. If this invention uses terms related to quantity such as "many," "multiple," or "several," these specifically refer to two or more.

[0021] The present invention provides a positioning and soldering fixture for reverse-insertion power devices in PCBAs, suitable for soldering power devices 2 between the B side of PCBA board 1 and the heat sink 3. Its assembly structure is as follows: Figure 1 As shown, the PCBA board 1 has a first mounting hole 11 and a second mounting hole 12, and is fixed to the electrical control box by screws passing through the first mounting hole 11. The power device 2 has a third mounting hole 21 aligned with the second mounting hole 12, and the heat sink 3 has a fourth mounting hole 31 aligned with the second mounting hole 12. The second mounting hole 12 is a through hole with a large diameter, allowing screws to pass through. The third mounting hole 21 and the fourth mounting hole 31 are both threaded holes. The power device 2 and the heat sink 3 are connected together by screws passing through the third mounting hole 21 and the fourth mounting hole 31. The edge of the heat sink 3 is supported by some edges of the electrical control box, and is not simply suspended from the power device 2 by screws.

[0022] To ensure that all power devices 2 soldered onto PCBA board 1 are tightly attached to the back of heat sink 3, this invention provides a positioning soldering fixture, such as... Figure 2 As shown, the assembly includes a support frame 4, a base plate 5, and a pressure plate 6. The base plate 5 is mounted on the base 41 of the support frame 4. The pressure plate 6 is positioned parallel to the base plate 5 and connected to the support frame 4 via a lifting mechanism 7. The upper surface of the base plate 5 is provided with multiple support blocks 51 for positioning and supporting the PCBA board 1. Before soldering, the power device 2 is inserted backwards onto the PCBA board 1, and then placed with its A side facing up on the support block 51. The height of the support block 51 is such that the distance from the B side of the PCBA board 1 to the upper surface of the base plate 5 is the same as the distance from the B side of the PCBA board 1 to the back of the heat sink 3 after it is assembled into the control box. Finally, the pressure plate 6 is pushed downwards by the lifting mechanism 7 to press and fix the PCBA board 1 onto the support block 51. When PCBA board 1 is pressed, the power device 2 located on side B of PCBA board 1 will be in close contact with the upper surface of the base plate 5, thus simulating the first stress state of the back of the heat sink 3 and the power device 2 being in contact. When soldering is performed at this time, it can be ensured that all power devices 2 are necessarily on the same plane, and the fit can be guaranteed when they are assembled with the actual heat sink 3 in the future.

[0023] While the above structure ensures that all power devices 2 are on the same plane, the lifting mechanism 7 simply presses down on surface A of the PCBA board 1. This force condition is not entirely consistent with the actual force condition of the PCBA after being assembled and clamped in the control box, which may lead to soldering errors. Therefore, a further solution is to have multiple first positioning holes 52 on the support block 51 of the base 41, aligned with the first mounting holes 11 on the PCBA board 1, and multiple first positioning posts 61 at the bottom of the pressure plate 6. The lower end of each first positioning post 61 has a shoulder. When the pressure plate 6 presses the PCBA board 1, the lower end of the first positioning post 61 can pass through the first mounting holes 11 of the PCBA board 1 and embed into the first positioning holes 52, pressing the PCBA board 1 onto the support block 51 through the shoulder. This can realistically simulate the clamping force condition of the PCBA board 1 being assembled in the control box, allowing for more precise pin soldering under this force condition.

[0024] When determining the soldering position of the power device 2, in addition to considering its distance from the PCBA board 1, it is also necessary to consider whether the third mounting hole 21 on it is aligned with the second mounting hole 12 on the PCBA board 1, so that the screws can pass through the second mounting hole 12 when assembling the heat sink 3. Therefore, a further solution is that the bottom of the pressure plate 6 is provided with a plurality of second positioning posts 62, the second positioning posts 62 are aligned with the second mounting holes 12 on the PCBA board 1, and the lower end of the second positioning post 62 is provided with a second-stage pressure head 64, which can be integrally formed with the second positioning post 62, and has a stepped surface at its end. The second-stage pressure head 64 consists of two sections. The diameter of the lower section is smaller than the diameter of the second mounting hole 12 and is comparable to the diameter of the third mounting hole 21. The outer diameter of the upper section is larger than the diameter of the second mounting hole 12. Thus, when the pressure plate 6 presses the PCBA board 1, the end of the second-stage pressure head 64 can be inserted into the third mounting hole 21 of the power device 2 after passing through the second mounting hole 12 of the PCBA board 1, and the stepped surface is pressed and fitted against the A side of the PCBA board 1. This enables the Z-axis positioning of all power devices 2 on the PCBA board 1 and improves their welding accuracy.

[0025] Because the PCBA contains various types of power devices 2, such as rectifier bridges and IGBTs, which generally have fewer pins, their spatial positioning capability in the XY direction (i.e., planar direction) is relatively poor when the pins of these devices are inserted into the solder pads and holes of the PCB for soldering. In contrast, frequency converter IPM modules have a considerable number of pins, resulting in more uniform positioning in the XY direction. Therefore, to achieve better positioning for different power devices 2, the preferred embodiment of this invention is: the bottom of the pressure plate 6 is provided with multiple third positioning posts 63, the second positioning posts 62 are aligned with the second mounting holes 12 on the PCBA board 1, and the lower end of each third positioning post 63 is detachably equipped with a second-stage pressure head 64 or a third-stage pressure head 65. The end of the second-stage pressure head 64 has a stepped surface, allowing the end of the second-stage pressure head 64 to pass through the second mounting hole 12 of the PCBA board 1 when the pressure plate 6 presses against the PCBA board 1. The third mounting hole 21 of the power device 2 is inserted into hole 12, and the stepped surface is pressed tightly against the A-side of the PCBA board 1. The end of the three-stage pressure head 65 has two stepped surfaces, and the base plate 5 has a second positioning hole 53. When the pressure plate presses the PCBA board 1, the end of the three-stage pressure head 65 can pass through the second mounting hole 12 of the PCBA board 1 and the third mounting hole 21 of the power device 2 in sequence and then be inserted into the second positioning hole 53. The two stepped surfaces are pressed tightly against the top surface of the power device 2 and the A-side of the PCBA board 1, respectively. The second-stage pressure head 64 is the same as the above scheme. The three-stage pressure head 65 has a three-section structure. The second positioning hole 53 is designed according to the positional relationship between the heat sink 3 and the power device 2 in the actual assembly structure. During the pressing process, the three-stage pressure head 65 is inserted between the power device 2 and the second positioning hole 53, so that the third mounting holes 21 of all power devices 2 are aligned with the fourth mounting holes 31 on the heat sink 3, thereby improving the positioning of the power device 2 in the XY direction and further improving the welding accuracy. In practical applications, the choice between using a second-order pressure head 64 or a third-order pressure head 65 can be determined based on the type of power device 2 that needs to be soldered, i.e., the number of pins.

[0026] Furthermore, for some special power devices 2 or heat sinks 3, such as power device 2 whose heat dissipation surface is not flat (e.g., it may have ceramic pads), or the back of heat sink 3 being irregularly shaped and not flat, the positioning of power device 2 cannot be achieved directly by pressing the PCBA board 1. To address this, the present invention provides a solution where, for power devices 2 on the PCBA board 1 that do not directly contact the back of the heat sink 3, a placeholder block 54 is provided on the upper surface of the base plate 5 at a location corresponding to its position. The upper and lower surfaces of the placeholder block 54 are adapted to the bottom surface of the power device 2 and the back of the heat sink 3, respectively. When the pressure plate 6 presses the PCBA board 1, the placeholder block 54 is pressed and filled between the power device 2 and the heat sink 3, thereby satisfying the positioning requirements of the power device 2 and the PCBA board 1.

[0027] To broaden the applicability of this invention, the base plate 5 and pressure plate 6 are available in various interchangeable models with different structures, and the models of the two correspond one-to-one. To save costs, hollow structures are provided in the parts of the base plate 5 and pressure plate 6 where the power device 2 is not installed.

[0028] To facilitate the replacement of the base plate 5 and ensure its installation accuracy, a portal frame 42 is provided on the base 41 of the support frame 4, and the base plate 5 is slidably disposed within the portal frame 42. The portal frame 42 refers to a structure with baffles only on the left and right sides and the back of the base 41, and an open front. When the base plate 5 needs to be replaced, it can be pulled out from the front like a drawer, and then the new base plate 5 can be pushed back in along the same path.

[0029] Regarding the lifting mechanism of the pressure plate 6, to improve its lifting stability, the preferred embodiment provided by this invention is that vertical guide rods 43 are provided on both sides of the support frame 4, and the pressure plate 6 is slidably mounted on the guide rods 43. The lifting mechanism 7 can take various forms, such as a hand-push pressure rod, a pneumatic rod, a hydraulic rod, or an electric push rod. The hand-push pressure rod can achieve the locking function during pressing using a locking mechanism such as a cam, while pneumatic rods, hydraulic rods, and electric push rods directly utilize existing equipment with locking functions. The fixed part of the lifting mechanism 7 is located on the top of the support frame 4, and its lifting end is detachably connected to the pressure plate 6, facilitating the replacement of different models of pressure plates 6.

Claims

1. A positioning and welding fixture for reverse-insertion power devices in a PCBA, suitable for welding power devices (2) between the B side of a PCBA board (1) and a heat sink (3), wherein the PCBA board (1) has a first mounting hole (11) and a second mounting hole (12), and is fixed in an electrical control box by screws passing through the first mounting hole (11), wherein the power device (2) has a third mounting hole (21) aligned with the second mounting hole (12), and the heat sink (3) has a fourth mounting hole (31) aligned with the second mounting hole (12), wherein the power device (2) and the heat sink (3) are connected together by screws passing through the third mounting hole (21) and the fourth mounting hole (31), characterized in that: The positioning welding fixture includes a support frame (4), a base plate (5) and a pressure plate (6). The base plate (5) is set on the base (41) of the support frame (4). The pressure plate (6) is set parallel above the base plate (5) and connected to the support frame (4) through a lifting mechanism (7). The upper surface of the base plate (5) is provided with multiple support blocks (51) for positioning and supporting the PCBA board (1). When the PCBA board (1) is placed on the support block (51) with its A side facing up, the distance between the B side of the PCBA board (1) and the upper surface of the base plate (5) is the same as the distance between the B side of the PCBA board (1) and the back of the heat sink (3) after the PCBA board (1) is assembled into the electrical control box. The pressure plate (6) presses and fixes the PCBA board (1) on the support block (51) under the action of the lifting mechanism (7). The base (41) has a support block (51) with a plurality of first positioning holes (52) aligned with the first assembly holes (11) on the PCBA board (1). The bottom of the pressure plate (6) has a plurality of first positioning posts (61). The lower end of the first positioning post (61) has a shoulder. When the pressure plate (6) presses the PCBA board (1), the lower end of the first positioning post (61) passes through the first assembly hole (11) of the PCBA board (1) and is embedded in the first positioning hole (52), and the PCBA board (1) is pressed onto the support block (51) by the shoulder. The bottom of the pressure plate (6) is provided with a plurality of second positioning posts (62). The second positioning posts (62) are aligned with the second assembly holes (12) on the PCBA board (1). The lower end of the second positioning posts (62) is provided with a second-stage pressure head (64). The end of the second-stage pressure head (64) is provided with a stepped surface. When the pressure plate (6) presses the PCBA board (1), the end of the second-stage pressure head (64) passes through the second assembly hole (12) of the PCBA board (1) and is embedded in the third assembly hole (21) of the power device (2). The stepped surface is pressed and adhered to the A side of the PCBA board (1). The bottom of the pressure plate (6) is provided with a plurality of third positioning posts (63). The second positioning posts (62) are aligned with the second assembly holes (12) on the PCBA board (1). The lower end of the third positioning posts (63) is detachably equipped with a second-stage pressure head (64) or a third-stage pressure head (65). The end of the second-stage pressure head (64) is provided with a stepped surface. When the pressure plate (6) presses the PCBA board (1), the end of the second-stage pressure head (64) passes through the second assembly hole (12) of the PCBA board (1) and then embeds into the third assembly hole (2) of the power device (2). 1) In the process, the stepped surface is pressed and adhered to the A surface of the PCBA board (1); the end of the three-stage pressure head (65) is provided with two stepped surfaces, and the bottom plate (5) is provided with a second positioning hole (53). When the pressure plate presses the PCBA board (1), the end of the three-stage pressure head (65) is inserted into the second positioning hole (53) after passing through the second assembly hole (12) of the PCBA board (1) and the third assembly hole (21) of the power device (2) in sequence, and the two stepped surfaces are pressed and adhered to the top surface of the power device (2) and the A surface of the PCBA board (1) respectively.

2. The positioning and soldering fixture for reverse-insertion power devices in PCBA as described in claim 1, characterized in that: For power devices (2) on PCBA board (1) that do not directly contact the back of heat sink (3), a placeholder block (54) is provided on the upper surface of the base plate (5) at a position corresponding to its position. The upper and lower sides of the placeholder block (54) are adapted to the bottom surface of the power device (2) and the back of the heat sink (3), respectively. When the pressure plate (6) presses the PCBA board (1), the placeholder block (54) is pressed and filled between the power device (2) and the heat sink (3).

3. A positioning and soldering fixture for reverse-insertion power devices in PCBA as described in claim 1 or 2, characterized in that: The base plate (5) and pressure plate (6) include various models with different structures that can be replaced, and the models of the two correspond one to one. The parts of the base plate (5) and pressure plate (6) where no power device (2) is installed have a hollow structure.

4. The positioning and soldering fixture for reverse-insertion power devices in PCBA as described in claim 3, characterized in that: The base (41) of the support frame (4) is provided with a gate-shaped limiting frame (42), and the bottom plate (5) is slidably disposed within the gate-shaped limiting frame (42).

5. The positioning and soldering fixture for reverse-insertion power devices in PCBA as described in claim 3, characterized in that: The support frame (4) has vertical guide rods (43) on both sides. The pressure plate (6) is slidably mounted on the guide rods (43). The lifting mechanism (7) is a hand-push pressure rod, a pneumatic pressure rod, a hydraulic rod or an electric push rod. Its fixed part is located on the top of the support frame (4). Its lifting end is detachably connected to the pressure plate (6) and drives the pressure plate (6) to slide up and down along the guide rods (43).

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