A steel mesh structure suitable for a reflow soldering process of a pin-through-hole

Abstract

This utility model discloses a stencil structure suitable for through-hole reflow soldering of pins, including a first stencil, a second stencil, and a stencil mounting plate. The first stencil has a first stencil plate that adheres to the top surface of the PCB board. The first stencil has pin holes for solder paste to pass through. The size of the pin holes on the first stencil plate is half the diameter of the pins on the top surface of the PCB board, and the position of the pin holes on the first stencil plate is directly opposite the position of the pins on the top surface of the PCB board. The second stencil has a second stencil plate that adheres to the bottom surface of the PCB board. The size of the pin holes on the second stencil plate is equal to the diameter of the pins on the bottom surface of the PCB board, and the position of the pin holes on the second stencil plate is shifted outward by half the hole diameter from the position of the pins on the bottom surface of the PCB board. Using the stencil described in this utility model ensures the solder penetration rate of the pins and improves subsequent soldering efficiency.

Description

Technical Field

[0001] This utility model belongs to the field of printing technology for electronic products, and specifically relates to a steel mesh structure suitable for reflow soldering process of pin through holes. Background Technology

[0002] For products with a traditional PCB thickness of ≥2.5mm and a pin pitch of 1.27mm, pin soldering requires manual soldering, which is characterized by low solder penetration, inconsistent solder penetration, large amount of manual work, and high cost. Utility Model Content

[0003] The technical problem to be solved by this utility model is to provide a steel mesh structure that is reasonably designed, improves the solder penetration rate, and is suitable for the reflow soldering process of pin through holes, in order to address the shortcomings of the existing technology.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A stencil structure suitable for pin-through-hole reflow soldering process is characterized in that the structure includes a first stencil, a second stencil, and a stencil mounting plate. The first stencil has a first stencil plate that is attached to the top surface of a PCB board. The first stencil plate has pin holes for solder paste to pass through. The size of the pin holes on the first stencil plate is half the diameter of the pins on the top surface of the PCB board, and the position of the pin holes on the first stencil plate is directly opposite the position of the pins on the top surface of the PCB board. The second stencil has a second stencil plate that is attached to the bottom surface of the PCB board. The size of the pin holes on the second stencil plate is equal to the diameter of the pins on the bottom surface of the PCB board, and the position of the pin holes on the second stencil plate is shifted outward by half the hole diameter along the pin position on the bottom surface of the PCB board.

[0005] The technical problem to be solved by this utility model can also be achieved through the following technical solution: the steel mesh mounting plate is provided with a plate frame, a ring of positioning steps is provided on the inner wall of the plate frame, a positioning frame of the steel mesh body is provided on the top surface of the positioning steps, a ring of ventilation grooves is provided on the bottom surface of the positioning steps, and an air filling and emptying hole communicating with the ventilation grooves is provided on the plate frame, and an air filling and emptying valve is installed at the air filling and emptying hole.

[0006] The technical problem to be solved by this utility model can also be achieved through the following technical solution: the positioning frame is provided with positioning frames arranged along three sides of the plate frame, the positioning frame is provided with an entrance and exit of the steel mesh body on one side, the positioning frame and the frame are provided with a sliding groove communicating with the entrance and exit, and the entrance and exit are symmetrically provided with opposing baffles on both sides.

[0007] The technical problem to be solved by this utility model can also be achieved through the following technical solution: the outer wall of the ventilation groove is provided with a sealing strip that cooperates with the steel mesh body for sealing.

[0008] The technical problem to be solved by this utility model can also be achieved through the following technical solution: the inflation / deflation port is provided with two holes.

[0009] Compared with existing technologies, this invention features a hole on the first stencil with a diameter equal to half the pin diameter on the top surface of the PCB board, positioned directly opposite the pin location on the top surface of the PCB board, thus securing the pin within the pin hole. A hole equal in diameter to the pin diameter on the second stencil, with this hole shifted outward by half its diameter, secures the solder ball, improving subsequent soldering efficiency. Furthermore, by setting positioning steps, venting grooves, and inflation / deflation holes on the stencil mounting plate, the stencil body can be quickly disassembled or installed using inflation or deflation. A positioning bracket further accelerates the installation of the stencil body. This stencil structure is applicable to products with a pin center-to-center spacing of 1.27mm ± 0.10mm and a PCB thickness ≥ 2.5mm. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the openings in the first steel mesh. Figure 2 This is a schematic diagram of the openings in the second steel mesh; Figure 3 This is a front view of the steel mesh mounting plate. Figure 4 for Figure 3 Top view; Figure 5 for Figure 3 The left view.

[0011] In the diagram: 1-plate frame, 2-positioning frame, 3-ventilation groove, 4-inflation / de-inflation hole, 5-positioning step. Detailed Implementation

[0012] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0013] In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0014] Reference Figure 1-5A stencil structure suitable for pin-through-hole reflow soldering process is disclosed. The structure includes a first stencil, a second stencil, and a stencil mounting plate. The first stencil has a first stencil plate that is attached to the top surface of a PCB board. The first stencil has pin holes for solder paste to pass through. The size of the pin holes on the first stencil plate is half the diameter of the pins on the top surface of the PCB board, and the position of the pin holes on the first stencil plate is directly opposite the position of the pins on the top surface of the PCB board. The second stencil has a second stencil plate that is attached to the bottom surface of the PCB board. The size of the pin holes on the second stencil plate is equal to the diameter of the pins on the bottom surface of the PCB board, and the position of the pin holes on the second stencil plate is shifted outward by half the hole diameter along the pin position on the bottom surface of the PCB board.

[0015] By creating a hole on the first steel plate with a diameter equal to half the pin diameter on the PCB board bob surface, and aligning the hole with the pin position on the PCB board top surface, it is easier to securely fix the pins when mounting them on the PCB board bob surface.

[0016] By creating pin holes on the second steel plate with the same diameter as the pins on the PCB board's bob surface, and then shifting these pin holes outward by half a hole diameter along the pin position on the PCB board's bob surface, the solder paste will not completely cover the pin holes on the PCB board's bob surface when the solder balls are attached to it. During reflow soldering in the reflow oven, both the solder balls and solder paste melt to a flowing state. The pre-reserved half-diameter hole helps to expel gas from the pin holes as the melted solder balls and solder paste flow into them, ensuring a solder penetration rate of >=75% within the pin holes and guaranteeing that the soldering meets the process requirements.

[0017] The steel mesh mounting plate has a frame 1, and a ring of positioning steps 5 is provided on the inner wall of the frame 1. The top surface of the positioning steps 5 is provided with a positioning frame 2 for the steel mesh body, and the bottom surface of the positioning steps is provided with a ring of ventilation grooves 3. The frame 1 has inflation / deflation holes 4 that communicate with the ventilation grooves. An inflation / deflation valve is installed at the inflation / deflation holes 4, and there are two inflation / deflation holes 4.

[0018] The positioning frame 2 is provided with positioning frames along three sides of the plate frame. The positioning frame has an entrance and exit of the steel mesh body on one side. There is a sliding groove between the positioning frame and the frame that communicates with the entrance and exit. There are baffles symmetrically arranged on both sides of the entrance and exit.

[0019] The outer wall of the ventilation groove 3 is provided with a sealing strip that cooperates with the steel mesh body for sealing.

[0020] The working process of the steel mesh structure described in this utility model is as follows: First, silkscreen printing is performed on the top side of the PCB board. The first stencil is inserted into the stencil mounting plate along the positioning frame and secured by inserting and removing air nozzles. The entire stencil structure is then placed into a screen printing machine. The top surface of the PCB board is conveyed to the bottom of the stencil structure via a conveyor and positioned. A layer of solder paste is then applied to the surface of the stencil. The solder paste is then passed through the squeegee of the screen printing machine, flowing along the pin holes on the top surface to the solder joints on the top surface of the PCB board. Second, silkscreen printing is performed on the Bot side of the PCB board. The second stencil is inserted into the stencil mounting plate along the positioning frame and fixed by inserting and removing the air nozzle. Then, the entire stencil structure is placed into the screen printing machine, and the PCB board Bot side is conveyed to the bottom of the stencil structure through the conveying device and positioned. A layer of solder paste is applied to the surface of the stencil. The solder paste is then dripped through the squeegee of the screen printing machine along the pin holes on the Bot side to the solder joints on the PCB board Bot side.

[0021] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A steel mesh structure suitable for reflow welding process of pin through-holes, characterized in that, The structure includes a first stencil, a second stencil, and a stencil mounting plate. The first stencil has a first stencil plate that is attached to the top surface of the PCB board. The first stencil plate has pin holes for solder paste to pass through. The size of the pin holes on the first stencil plate is half the diameter of the pins on the top surface of the PCB board, and the position of the pin holes on the first stencil plate is directly opposite the position of the pins on the top surface of the PCB board. The second stencil has a second stencil plate that is attached to the bottom surface of the PCB board. The size of the pin holes on the second stencil plate is equal to the diameter of the pins on the bottom surface of the PCB board, and the position of the pin holes on the second stencil plate is shifted outward by half the hole diameter along the pin position on the bottom surface of the PCB board.

2. A steel mesh structure suitable for reflow welding process of pin through holes according to claim 1, characterized in that, The steel mesh mounting plate has a frame, and a positioning step is provided on the inner wall of the frame. The positioning frame of the steel mesh body is provided on the top surface of the positioning step. A ventilation groove is provided on the bottom surface of the positioning step. The frame has an air inlet / outlet hole that communicates with the ventilation groove. An air inlet / outlet valve is installed at the air inlet / outlet hole.

3. A steel mesh structure suitable for reflow welding process of pin through holes according to claim 2, characterized in that, The positioning frame is provided with positioning frames along three sides of the plate frame. The positioning frame has an entrance and exit of the steel mesh body on one side. There is a sliding groove between the positioning frame and the frame that communicates with the entrance and exit. There are baffles symmetrically arranged on both sides of the entrance and exit.

4. A steel mesh structure suitable for reflow welding process of pin through holes according to claim 2, characterized in that, The outer wall of the ventilation groove is provided with a sealing strip that cooperates with the steel mesh body for sealing.

5. A steel mesh structure suitable for reflow welding process of pin through holes according to claim 2, characterized in that, The inflation / deflation port is provided in two places.

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