A type of SMT stencil

Abstract

This utility model belongs to the field of SMT solder paste printing technology and discloses an SMT stencil, including a detachable frame, a stencil sheet, and a high-load-bearing tension connection structure. The detachable frame is a rectangular metal frame spliced ​​from four sets of side strips, which achieve rigid connection and convenient disassembly through fixing wedges and bolts. The stencil sheet is a thin layer of stainless steel with solder paste printing ports corresponding to the PCB board. The high-load-bearing tension connection structure includes a substrate and a cover plate. The tension-reinforcing pillars of the substrate pass through the movable holes of the stencil sheet and engage with the cover plate, forming a composite connection with tension adhesive. This can convert vertical loads into horizontal tension, preventing the tension adhesive from tearing. This design improves load-bearing capacity, extends service life, and facilitates stencil sheet replacement, enhancing practicality and maintenance convenience.

Description

Technical Field

[0001] This utility model relates to the field of SMT solder paste printing technology, specifically to an SMT stencil. Background Technology

[0002] In the field of SMT (Surface Mount Technology) electronics manufacturing, the stencil is a core tool for solder paste printing, and its performance directly affects the soldering quality and production efficiency of PCBs (Printed Circuit Boards). Existing SMT stencils mainly consist of two parts: the frame and the stencil sheet. The stencil sheet is typically processed using high-precision etching or laser cutting techniques, with solder paste printing openings on its surface corresponding to the PCB pads. Through the action of the squeegee on the printer, solder paste is precisely applied to the PCB according to a preset pattern, providing a foundation for subsequent component placement and soldering.

[0003] However, the existing stencil design has gradually revealed significant flaws in its long-term use, especially the connection method between the stencil sheet and the frame, which has become a key bottleneck affecting its stability and service life. Currently, the industry-standard connection method involves using a special tension adhesive to bond the stencil sheet to the middle of the frame. This tension adhesive requires a certain preload during stencil sheet installation to maintain continuous tension, ensuring the stencil sheet remains flat during printing and guaranteeing solder paste printing accuracy.

[0004] However, this bonding method relying on tension adhesive has significant limitations: First, the mechanical properties of tension adhesive are limited by material characteristics, resulting in weak load-bearing capacity, especially when dealing with vertical loads. In actual production, the steel mesh inevitably experiences vertical pressure from the scraper, pushing force from the PCB board, and mechanical impact during cleaning. These vertical loads can cause the tension adhesive to be in a state of stress concentration for a long time, leading to problems such as tearing. Second, the adhesive strength of tension adhesive gradually decreases with temperature changes, usage time, and environmental humidity. When the adhesive strength is insufficient, the connection between the steel mesh and the frame will loosen or even detach completely, rendering the steel mesh unusable. Utility Model Content

[0005] To address the shortcomings of existing technologies, this utility model provides an SMT stencil to solve the problems mentioned in the background section, such as the tension adhesive being prone to tearing and detachment under high loads.

[0006] To achieve the above-mentioned objectives, this utility model provides the following technical solution: an SMT stencil, comprising: A detachable frame, wherein the detachable frame is a metal frame structure adapted to a solder paste printer, and the detachable frame includes four sets of side strips; A steel mesh sheet, wherein the steel mesh sheet is a thin layer of stainless steel sheet, and the steel mesh sheet is provided with solder paste printing ports; A high-load tension connection structure is provided, which is located at the inner ring of the detachable mesh frame, and the steel mesh is fixed inside the detachable mesh frame by the high-load tension connection structure.

[0007] Preferably, a fixing wedge is provided at each of the four corners of the detachable mesh frame, a first wedge groove is provided at one end of the edge strip, a second wedge groove is provided at the other end of the edge strip, the four sets of edge strips are spliced ​​together end to end, and the first wedge groove and the second wedge groove are spliced ​​together to form a wedge groove, and the fixing wedge is engaged in the wedge groove formed by the first wedge groove and the second wedge groove.

[0008] Preferably, the fixing wedge and the edge strip are provided with multiple sets of fixing screw holes, and the fixing wedge is fixedly connected to the edge strip by bolts.

[0009] Preferably, the solder paste printing port is composed of multiple sets of stencil openings, and the upper and lower cross-sectional areas of the stencil openings are not equal.

[0010] Preferably, the high-load tension connection structure includes a substrate and a cover plate, with the substrate placed below the steel mesh and the cover plate placed above the steel mesh.

[0011] Preferably, the substrate is provided with multiple sets of tension strengthening columns, the cover plate is provided with strengthening column snap-fit ​​holes corresponding to the tension strengthening columns, and the steel mesh is provided with movable fitting holes corresponding to the tension strengthening columns. The tension strengthening columns pass through the movable fitting holes and snap-fit ​​with the strengthening column snap-fit ​​holes.

[0012] Preferably, the diameter of the movable fitting hole is larger than the diameter of the tension-strengthening column.

[0013] Preferably, a substrate groove is provided inside the detachable mesh frame, the edge of the substrate is engaged in the substrate groove, and a cover plate groove corresponding to the cover plate is provided above the substrate groove, the edge of the cover plate is engaged in the cover plate groove.

[0014] Compared with the prior art, this utility model provides an SMT stencil with the following advantages: This SMT stencil features a detachable frame, stencil panels, and a high-load-bearing tension connection structure. It converts large vertical loads into horizontal tension. Compared to conventional methods using tension adhesive, the high-load-bearing tension connection structure offers superior mechanical properties while maintaining elasticity, ensuring uninterrupted use of the stencil. It prevents tearing and detachment of the tension adhesive, significantly extending its lifespan. Furthermore, the frame can be disassembled for easy replacement and installation of the stencil panels, making it convenient and highly practical. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of this utility model; Figure 2 This is a schematic diagram of the edge strip and fixing wedge structure of this utility model; Figure 3 This is a schematic diagram of the high-load tension connection structure of this utility model; Figure 4 This is a schematic diagram of the high-load tension connection structure of this utility model.

[0016] In the diagram: 1. Detachable mesh frame; 2. Edge strip; 3. Steel mesh sheet; 4. Solder paste printing port; 5. High load-bearing tension connection structure; 6. Substrate; 7. Cover plate; 8. Fixing wedge; 9. First wedge groove; 10. Second wedge groove; 11. Fixing screw hole; 12. Steel mesh opening; 13. Tension reinforcing column; 14. Reinforcing column snap-fit ​​hole; 15. Movable fitting hole; 16. Substrate groove; 17. Cover plate groove. Detailed Implementation

[0017] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0018] Please see Figure 1-4 This utility model provides a technical solution: An SMT stencil, comprising: The detachable frame 1 is a metal frame structure adapted to the solder paste printer. The detachable frame 1 includes four sets of side strips 2. The length of each pair of the four sets of side strips 2 is equal. The four sets of side strips 2 are spliced ​​together to form a rectangle. The specific size is not limited and depends on the existing solder paste printer.

[0019] The stencil 3 is a thin stainless steel sheet with solder paste printing ports 4. The specific form and processing technology of the stencil 3 are not limited, and those commonly used by technicians in the field are applicable. The solder paste printing ports 4 correspond to the PCB board to be processed, so that the solder paste can be printed on the PCB board according to the pattern of the solder paste printing ports 4.

[0020] A high-load-bearing tension connection structure 5 is installed at the inner ring of the detachable mesh frame 1. The steel mesh sheet 3 is fixed inside the detachable mesh frame 1 through the high-load-bearing tension connection structure 5. Tension adhesive is still required at the connection point. The high-load-bearing tension connection structure 5, as a skeleton, can significantly increase the load-bearing capacity and prevent the tension adhesive from tearing.

[0021] Furthermore, a fixing wedge 8 is provided at each of the four corners of the detachable mesh frame 1, a first wedge groove 9 is provided at one end of the edge strip 2, and a second wedge groove 10 is provided at the other end of the edge strip 2. The four sets of edge strips 2 are spliced ​​together end to end, and the first wedge groove 9 and the second wedge groove 10 are spliced ​​together to form a wedge groove. The fixing wedge 8 is engaged in the wedge groove formed by the first wedge groove 9 and the second wedge groove 10.

[0022] Furthermore, multiple sets of fixing screw holes 11 are provided on the fixing wedge 8 and the edge strip 2. The fixing wedge 8 is fixedly connected to the edge strip 2 by bolts. After the bolts are removed, the fixing wedge 8 can be pulled out along the wedge groove. After removing the fixing wedge 8, it is easy to disassemble the detachable mesh frame 1, which facilitates the reuse of the detachable mesh frame 1. At the same time, it is also easier to reassemble it with the steel mesh sheet 3.

[0023] Furthermore, the solder paste printing port 4 is composed of multiple sets of stencil openings 12, and the upper and lower cross-sectional areas of the stencil openings 12 are not equal. There are two situations where the cross-sectional areas are not equal: the side with the larger opening is closer to the solder paste, so that the amount of solder paste printed is slightly more, which is convenient for subsequent soldering operations; the side with the larger opening is closer to the PCB board, so that the solder paste is easier to release, which is suitable for situations with fine spacing and can prevent solder paste from sticking.

[0024] Furthermore, the high-load tension connection structure 5 includes a substrate 6 and a cover plate 7, with the substrate 6 placed below the steel mesh 3 and the cover plate 7 placed above the steel mesh 3.

[0025] Furthermore, the substrate 6 is provided with multiple sets of tension strengthening columns 13, the cover plate 7 is provided with strengthening column snap-fit ​​holes 14 corresponding to the tension strengthening columns 13, and the steel mesh 3 is provided with movable fitting holes 15 corresponding to the tension strengthening columns 13. The tension strengthening columns 13 pass through the movable fitting holes 15 and snap-fit ​​with the strengthening column snap-fit ​​holes 14.

[0026] Furthermore, the diameter of the movable fitting hole 15 is larger than the diameter of the tension reinforcing column 13. The entire steel mesh 3 can be horizontally displaced relative to the base plate 6 and the cover plate 7, that is, the tension reinforcing column 13 can be slightly offset in the movable fitting hole 15. If subjected to a large load, it can convert the vertical pressure into horizontal tension, which can avoid the phenomenon of tension adhesive tearing and delamination due to excessive load, and can greatly extend the service life and reduce the number of maintenance operations.

[0027] Furthermore, a substrate groove 16 is provided inside the detachable mesh frame 1, and the edge of the substrate 6 is engaged in the substrate groove 16. A cover plate groove 17 corresponding to the cover plate 7 is provided above the substrate groove 16, and the edge of the cover plate 7 is engaged in the cover plate groove 17.

[0028] Structural Description: Detachable frame 1: A rectangular metal frame structure adapted to solder paste printer, composed of four sets of side strips 2 spliced ​​together, used to install and fix steel mesh 3 and other components; Edge strip 2: A component of the detachable wire mesh frame 1, with two strips of equal length and a first wedge groove 9 and a second wedge groove 10 at each end, for splicing into a frame; Steel mesh 3: A thin stainless steel sheet with solder paste printing openings 4. It is fixed in the detachable frame 1 by a high-load tension connection structure 5 and is used for solder paste printing. Solder paste printing port 4: Set on the stencil 3, it consists of multiple sets of stencil openings 12, corresponding to the PCB board to be processed, so that the solder paste is printed on the PCB board according to the preset pattern. High load tension connection structure 5: includes base plate 6 and cover plate 7, set in the inner ring of detachable mesh frame 1, used to fix steel mesh 3 in the mesh frame, can transfer load to avoid damage to tension adhesive; Substrate 6: Placed below the steel mesh 3, with its edges snapped into the substrate groove 16, and has tension reinforcing columns 13 on it, which cooperate with the cover plate 7 to fix the steel mesh 3 and transfer the load; Cover plate 7: Placed above the steel mesh 3, with its edge snapped into the cover plate groove 17, and has reinforcing post snapping holes 14 on it, which are snapped into the tension reinforcing posts 13 of the base plate 6 to fix the steel mesh 3. Fixed wedges 8: set at the four corners of the detachable mesh frame 1, snapped into the wedge groove formed by the first wedge groove 9 and the second wedge groove 10, and fixed to the edge strip 2 by bolts to enhance the stability of the frame connection; First wedge groove 9: Located at one end of edge strip 2, it is spliced ​​with the second wedge groove 10 of another set of edge strip 2 to form a wedge groove, which is used to accommodate the fixing wedge 8 to realize the connection of edge strip 2; Second wedge groove 10: Located at the other end of the edge strip 2, it is spliced ​​with the first wedge groove 9 of another set of edge strips 2 to form a wedge groove, which is used to accommodate the fixing wedge 8 to realize the connection of the edge strip 2; Fixed screw hole 11: It is provided on the fixed wedge 8 and the edge strip 2, so that the bolt can pass through to fix the two, making the edge strip 2 more firmly spliced ​​and easy to disassemble; Stencil opening 12: forms the structure of solder paste printing opening 4. The cross-sectional areas on the upper and lower sides are different, which can optimize the amount of solder paste printed or avoid sticking according to the needs. Tension-strengthening column 13: It is set on the base plate 6, passes through the movable hole 15 of the steel mesh 3 and is engaged with the strengthening column snap-fit ​​hole 14 of the cover plate 7, which helps to fix the steel mesh 3 and participates in load transfer. Reinforcing column snap-fit ​​hole 14: It is provided on the cover plate 7, and corresponds to and snaps into the tension reinforcing column 13 of the base plate 6, so as to realize the connection between the base plate 6, the steel mesh 3 and the cover plate 7. Movable aperture 15: Located on the steel mesh 3, corresponding to the tension reinforcing column 13 and with a larger diameter, it provides horizontal displacement space for the steel mesh 3, facilitating load conversion; Substrate slot 16: It is formed inside the detachable mesh frame 1 and is used to snap the edge of the substrate 6 to realize the positioning and installation of the substrate 6 within the mesh frame; Cover plate groove 17: It is formed above the substrate groove 16 and corresponds to the cover plate 7. It is used to snap the edge of the cover plate 7 to realize the positioning and installation of the cover plate 7 within the mesh frame.

[0029] Working principle: The detachable frame 1 is formed by splicing four sets of side strips 2 to create a rectangular frame suitable for solder paste printing machines. The first wedge groove 9 and the second wedge groove 10 at both ends of the side strip 2 are spliced ​​to form a complete wedge groove. After the fixing wedge 8 is embedded, it is rigidly connected by bolts passing through the fixing screw holes 11, ensuring that the frame does not loosen or deform during the printing operation. This assembly method not only ensures the structural strength of the frame, but also provides a basis for subsequent disassembly and replacement of the steel mesh 3. When maintenance is required, the side strip 2 can be separated by unscrewing the bolts and pulling out the fixing wedge 8, which greatly reduces the difficulty of reusing the frame.

[0030] The steel mesh 3 is secured by the combined action of the high-load tension connection structure 5 and tension adhesive. The edge of the substrate 6 is inserted into the substrate groove 16 of the detachable mesh frame 1, and the cover plate 7 is correspondingly embedded in the upper cover plate groove 17, with the steel mesh 3 clamped between the two. The tension reinforcing post 13 on the substrate 6 passes through the movable fitting hole 15 of the steel mesh 3 and forms a snap-fit ​​with the reinforcing post snap-fit ​​hole 14 of the cover plate 7. At this time, tension adhesive is applied at the connection point to give the steel mesh 3 initial pretension. The design of the movable fitting hole 15 having a larger diameter than the tension reinforcing post 13 provides horizontal displacement space for the steel mesh 3, while the rigid frame formed by the substrate 6 and the cover plate 7 replaces the single load-bearing role of the traditional tension adhesive, forming a composite connection structure of frame support + tension adhesive assistance.

[0031] In solder paste printing, the high-load tension connection structure 5 plays a crucial role when the squeegee applies vertical pressure or the PCB board exerts a pushing force. When a vertical load is applied to the stencil 3, the stencil 3 undergoes a slight horizontal offset along the tension reinforcing column 13 through the movable fitting hole 15 (the horizontal offset is very small and will not affect solder paste printing), transforming the originally localized vertical force into a horizontal tension along the plane of the stencil 3. This force conversion mechanism significantly reduces the vertical stress borne by the tension adhesive, preventing it from tearing or delaminating due to stress concentration. At the same time, the rigid clamping of the substrate 6 and the cover plate 7 ensures that the stencil 3 remains flat under the horizontal tension, and the solder paste printing port 4 can be accurately aligned with the PCB board pads, ensuring that the solder paste is applied according to the preset pattern.

[0032] The stencil openings 12 with varying cross-sectional areas on the stencil sheet 3 can optimize the solder paste printing effect according to welding requirements: when the opening is larger on the side adjacent to the solder paste, the amount of solder paste printed in a single pass can be increased to meet the welding requirements of large solder joints; when the opening is larger on the side adjacent to the PCB board, it facilitates the release of solder paste, which is suitable for situations with fine spacing and can prevent solder paste from sticking together.

[0033] When the steel mesh 3 needs to be replaced due to wear or perforation deformation, the cover plate 7 and base plate 6 can be removed after disassembling the fixing wedge 8 to separate the edge strip 2. After replacing with a new steel mesh 3, it can be re-clamped and fixed, and tension adhesive can be added, significantly improving maintenance efficiency. This design retains the function of tension adhesive in providing initial tension, while improving load-bearing capacity through a rigid frame structure, achieving simultaneous optimization of printing accuracy, service life, and maintenance convenience.

[0034] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An SMT (Surface Mount Technology) stencil, characterized in that, include: Detachable frame (1), the detachable frame (1) is a metal frame structure adapted to solder paste printing machine, the detachable frame (1) includes four sets of side strips (2). Steel mesh (3), the steel mesh (3) is a thin layer of stainless steel sheet, and the steel mesh (3) is provided with solder paste printing port (4). A high load tension connection structure (5) is provided at the inner ring of the detachable mesh frame (1), and the steel mesh (3) is fixed inside the detachable mesh frame (1) by the high load tension connection structure (5).

2. The SMT stencil according to claim 1, characterized in that, The four corners of the detachable mesh frame (1) are provided with fixed wedges (8), one end of the edge strip (2) is provided with a first wedge groove (9), and the other end of the edge strip (2) is provided with a second wedge groove (10). The four sets of edge strips (2) are spliced ​​together end to end, and the first wedge groove (9) and the second wedge groove (10) are spliced ​​together to form a wedge groove. The fixed wedges (8) are engaged in the wedge groove formed by the first wedge groove (9) and the second wedge groove (10).

3. The SMT stencil according to claim 2, characterized in that, The fixed wedge (8) and the side strip (2) are provided with multiple sets of fixing screw holes (11), and the fixed wedge (8) is fixedly connected to the side strip (2) by bolts.

4. The SMT stencil according to claim 1, characterized in that, The solder paste printing port (4) is composed of multiple sets of stencil openings (12), and the cross-sectional areas of the upper and lower sides of the stencil openings (12) are not equal.

5. The SMT stencil according to claim 2, characterized in that, The high load tension connection structure (5) includes a substrate (6) and a cover plate (7), with the substrate (6) placed below the steel mesh (3) and the cover plate (7) placed above the steel mesh (3).

6. The SMT stencil according to claim 5, characterized in that, The substrate (6) is provided with multiple sets of tension reinforcing columns (13), the cover plate (7) is provided with reinforcing column snap-fit ​​holes (14) corresponding to the tension reinforcing columns (13), the steel mesh (3) is provided with movable fitting holes (15) corresponding to the tension reinforcing columns (13), and the tension reinforcing columns (13) pass through the movable fitting holes (15) and snap-fit ​​with the reinforcing column snap-fit ​​holes (14).

7. The SMT stencil according to claim 6, characterized in that, The diameter of the movable fitting hole (15) is larger than the diameter of the tension reinforcing column (13).

8. The SMT stencil according to claim 7, characterized in that, The detachable mesh frame (1) has a substrate groove (16) inside, and the edge of the substrate (6) is engaged in the substrate groove (16). Above the substrate groove (16) is a cover plate groove (17) corresponding to the cover plate (7), and the edge of the cover plate (7) is engaged in the cover plate groove (17).

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