A PCB screen for transferring a precise dose of solder paste to a designated location on a PCB

Abstract

The utility model relates to PCB steel net technical field, and disclose a kind of PCB steel net for transferring accurate dose of tin paste to PCB designated position, including PCB steel net body, the four around sides of PCB steel net body are provided with first frame and second frame, the both ends of first frame are all set up first connecting thread hole, the both ends of second frame are all set up second connecting thread hole, the both ends of first frame are all connected with second frame by fastening bolt passing first connecting thread hole and second connecting thread hole, the inside middle part of first frame is set up and is inserted into recess, the utility model is set up by inserting into male tongue, inserting into recess, fastening bolt, first frame, second frame, first connecting thread hole and second connecting thread hole, utilize the mutual cooperation between them, to enhance the bending and deformation resistance of PCB steel net, keep long-term tension and flatness, prolong service life.

Description

Technical Field

[0001] This utility model relates to the field of PCB stencil technology, specifically a PCB stencil for transferring precise amounts of solder paste to designated locations on a PCB. Background Technology

[0002] Stencils, formerly known as wire mesh, are stainless steel molds used in SMT (Surface Mount Technology) processes to transfer precise amounts of solder paste to designated locations on a PCB. They are manufactured using three processes: laser cutting, chemical etching, and electroforming. Laser stencils, due to their direct fabrication from data files and an error margin of ≤±4μm, have become the mainstream method. These molds have evolved from early wire mesh designs to stainless steel and can be categorized into seven types based on their manufacturing process, including laser stencils and electropolished stencils. Electropolished stencils achieve smooth hole walls through electrochemical treatment, electroformed stencils allow for adjustable local thickness, and stepped stencils meet the thickness requirements of different areas within the same PCB.

[0003] Existing PCB stencils used to transfer precise amounts of solder paste to designated locations on the PCB have weak resistance to bending and deformation during use, making it unable to maintain long-term tension and flatness, thus shortening their service life. Secondly, during mold closing, the PCB stencil is prone to sagging and deformation under the pressure of the squeegee, resulting in thicker solder paste in the central area. In addition, operators cannot directly observe the markings on the PCB below for quick and intuitive preliminary alignment verification, making them completely dependent on machine vision systems. Therefore, there is an urgent need for a PCB stencil for transferring precise amounts of solder paste to designated locations on the PCB to solve the above technical problems. Utility Model Content

[0004] The purpose of this invention is to provide a PCB stencil for transferring precise amounts of solder paste to designated locations on a PCB, thereby solving the problems mentioned in the background art. These problems include weak resistance to bending and deformation, inability to maintain long-term tension and flatness, shortened service life, and the tendency for the PCB stencil to sag and deform under squeegee pressure during mold closing, resulting in thicker solder paste in the central area. Furthermore, operators cannot directly observe the markings on the PCB below for quick and intuitive initial alignment verification, leading to complete reliance on machine vision systems.

[0005] To achieve the above objectives, this utility model provides the following technical solution: A PCB stencil for transferring precise amounts of solder paste to designated locations on a PCB includes a PCB stencil body. A first frame and a second frame are arranged around the PCB stencil body. Each end of the first frame has a first threaded hole, and each end of the second frame has a second threaded hole. Both ends of the first frame are threadedly connected to the second frame via fastening bolts passing through the first and second threaded holes. An insertion groove is provided in the middle of the inner side of the first frame. A insertion tab is connected to one side of the PCB stencil body corresponding to the insertion groove. The PCB stencil body is inserted into the insertion groove of the first frame via the insertion tab. Unobstructed holes are provided on the PCB stencil body near the alignment points of key components on the PCB board. An elastic pad is provided on the non-pad area of ​​the PCB stencil body that contacts the PCB.

[0006] As a preferred technical solution of this utility model, the number of the plug-in protrusions is set to two, and the two plug-in protrusions are arranged symmetrically about the left and right axes about the PCB stencil.

[0007] As a preferred embodiment of this utility model, the number of the insertion grooves is set to two, and the two insertion grooves are arranged symmetrically about the first frame.

[0008] As a preferred embodiment of this utility model, the insertion tongue and the insertion groove are adapted to each other.

[0009] As a preferred embodiment of this utility model, the number of holes is set to four, and the four holes are arranged in pairs opposite each other about the PCB stencil.

[0010] As a preferred embodiment of this utility model, the number of elastic pads is set to six, with three on each side of the PCB stencil.

[0011] As a preferred embodiment of this invention, the elastic gasket is made of polyimide film.

[0012] As a preferred technical solution of this utility model, the connection between the elastic gasket and the PCB stencil is by adhesive bonding.

[0013] Compared with the prior art, the present invention has the following beneficial effects: This utility model enhances the PCB stencil's resistance to bending and deformation by setting up a plug-in tongue, a plug-in groove, a fastening bolt, a first frame, a second frame, a first connecting threaded hole, and a second connecting threaded hole, and by utilizing the interaction between them, it maintains long-term tension and flatness, and extends its service life.

[0014] This invention uses multiple elastic pads to ensure that these pads contact the PCB before the mesh area during mold closing, providing a small reverse support force to counteract the sagging deformation caused by the squeegee pressure and ensuring that the thickness of the solder paste printed in the central area is consistent with that in other areas.

[0015] This invention allows operators to directly observe the markings on the PCB below through multiple holes, enabling rapid and intuitive preliminary alignment verification and reducing complete reliance on machine vision systems. Attached Figure Description

[0016] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the overall structure of this utility model; Figure 2 This is a cross-sectional view of the overall structure of this utility model; Figure 3 This utility model Figure 2 Enlarged structural diagram at point A; Figure 4 This is a cross-sectional view of the second frame of this utility model; Figure 5 This is a cross-sectional structural diagram of the first frame of this utility model; Figure 6 This is a schematic diagram showing the connection relationship between the PCB stencil and the plug-in tongue of this utility model.

[0017] In the diagram: 1. PCB stencil; 2. First frame; 3. Second frame; 4. First connecting threaded hole; 5. Second connecting threaded hole; 6. Fastening bolt; 7. Insertion groove; 8. Elastic washer; 9. Hole; 10. Insertion tongue. Detailed Implementation

[0018] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the utility model. Furthermore, it should be noted that, for ease of description, only the parts relevant to the utility model are shown in the accompanying drawings. In the embodiments of the present utility model, the different types of cross-sectional lines are not labeled according to national standards, nor do they specify material requirements for the components; they are used to distinguish the cross-sectional views of the components in the drawings.

[0019] Please see Figure 1-6A PCB stencil for transferring precise amounts of solder paste to designated locations on a PCB includes a PCB stencil body 1. A first frame 2 and a second frame 3 are provided around the PCB stencil body 1. First threaded holes 4 are provided at both ends of the first frame 2, and second threaded holes 5 are provided at both ends of the second frame 3. Both ends of the first frame 2 are threadedly connected to the second frame 3 via fastening bolts 6 passing through the first threaded holes 4 and the second threaded holes 5. An insertion groove 7 is provided in the middle of the inner side of the first frame 2. An insertion tab 10 is connected to one side of the PCB stencil body 1 corresponding to the insertion groove 7. The PCB stencil body 1 is inserted into the insertion groove 7 of the first frame 2 through the insertion tab 10. The interaction between these elements enhances the PCB stencil's resistance to bending and deformation, maintains long-term tension and flatness, and extends its service life. Unobstructed holes 9 are provided on the PCB stencil body 1 near the alignment points of key components on the PCB. Elastic pads 8 are provided on the non-pad area of ​​the PCB stencil body 1 on the side in contact with the PCB.

[0020] The number of plug-in protrusions 10 is set to two, and the two plug-in protrusions 10 are arranged symmetrically about the left and right axes about the PCB stencil body 1.

[0021] The number of insertion grooves 7 is set to two, and the two insertion grooves 7 are arranged symmetrically about the first frame 2.

[0022] The tongue 10 and the groove 7 are compatible.

[0023] The number of holes 9 is set to four, and the four holes 9 are arranged in pairs opposite each other about the PCB stencil body 1. Setting multiple holes 9 allows the operator to directly observe the marking points on the PCB below through the holes 9, so as to achieve quick and intuitive preliminary alignment verification and reduce complete reliance on the machine vision system.

[0024] The number of elastic pads 8 is set to six, with three on each side of the PCB stencil 1. The multiple elastic pads 8 are set so that these pads contact the PCB before the mesh area when the mold is closed, providing a small reverse support force to counteract the sagging deformation caused by the squeegee pressure and ensure that the thickness of the solder paste printed in the central area is consistent with that in other areas.

[0025] Among them, the elastic gasket 8 is made of polyimide film.

[0026] The connection between the elastic gasket 8 and the PCB stencil 1 is achieved by adhesive bonding.

[0027] The working principle and usage process of this utility model: First, the first frame 2 and the second frame 3 are connected and locked by the fastening bolts 6 at the four corners to form a solid rectangular outer frame, which provides strong external support and tension for the entire steel mesh body. The PCB steel mesh body 1 is not simply laid flat or welded on the first frame 2 and the second frame 3, but is inserted into the insertion groove 7 on the inner side of the first frame through the insertion protrusion 10 on its side. When the fastening bolt 6 is tightened, the first frame 2 and the second frame 3 generate a strong clamping force. This clamping force is directly transmitted to the insertion tongue 10 through the side wall of the insertion groove 7, thereby applying a horizontal and uniform tension force to the PCB stencil body 1 itself. This tension force causes the thin sheet-like PCB stencil body 1 to be flattened like a drumhead, greatly enhancing its overall resistance to bending and deformation. Even under long-term squeegee pressure, it can maintain excellent flatness, thereby ensuring the uniformity of solder paste thickness and extending the service life of the stencil itself. After the operator or equipment has initially installed the stencil and PCB, they can directly observe the optical positioning points on the PCB board below through these holes 9 with the naked eye. By observing the overlap between the holes and the marking points, a preliminary and intuitive alignment check can be quickly performed. This greatly reduces the complete reliance on the machine vision system, improves the efficiency of machine setup, and can quickly determine whether the misalignment is caused by a problem with the stencil, the PCB, or the equipment, making it easier to troubleshoot. As the stencil moves downwards towards the PCB, these slightly raised elastic pads 8 contact the PCB surface before the areas with open pads. Before the squeegee begins to apply pressure, these pads are slightly compressed, generating a small, upward elastic reaction force. When the squeegee applies a large downward pressure, this pre-existing reverse support force can effectively counteract some of the force that causes the stencil to sag in the center, acting like a miniature jack to help the stencil remain horizontal. By preventing abnormal sagging in the central area, it ensures that the gap between the stencil and the PCB (i.e., the solder paste thickness) remains uniform across the entire board surface. Any content not described in detail in this specification is prior art known to those skilled in the art.

[0028] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the utility model involved in this application is not limited to the technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A PCB stencil for transferring a precise amount of solder paste to a designated location on a PCB, comprising a PCB stencil body (1), characterized in that: The PCB stencil (1) is provided with a first frame (2) and a second frame (3) on its four sides. The first frame (2) has a first connecting threaded hole (4) at both ends, and the second frame (3) has a second connecting threaded hole (5) at both ends. The first frame (2) is threaded to the second frame (3) by fastening bolts (6) passing through the first connecting threaded hole (4) and the second connecting threaded hole (5). The first frame (2) has an insertion groove (7) at the middle of its inner side. The PCB stencil (1) has an insertion tongue (10) connected to the insertion groove (7) on one side. The PCB stencil (1) is inserted into the insertion groove (7) of the first frame (2) through the insertion tongue (10). The PCB stencil (1) has unobstructed holes (9) near the alignment points of key components on the PCB board. The PCB stencil (1) has an elastic pad (8) on the side that contacts the PCB and is not a solder pad.

2. A PCB stencil for transferring a precise amount of solder paste to a designated location on a PCB according to claim 1, characterized in that: The number of the plug-in protrusions (10) is set to two, and the two plug-in protrusions (10) are arranged symmetrically about the left and right axes about the PCB stencil body (1).

3. A PCB stencil for transferring a precise amount of solder paste to a designated location on a PCB according to claim 1, characterized in that: The number of the insertion grooves (7) is set to two, and the two insertion grooves (7) are arranged symmetrically about the first frame (2) on the left and right sides.

4. A PCB stencil for transferring a precise amount of solder paste to a designated location on a PCB according to claim 1, characterized in that: The insertion tongue (10) and the insertion groove (7) are compatible with each other.

5. A PCB stencil for transferring a precise amount of solder paste to a designated location on a PCB according to claim 1, characterized in that: The number of holes (9) is set to four, and the four holes (9) are arranged in pairs opposite each other about the PCB stencil (1).

6. A PCB stencil for transferring a precise amount of solder paste to a designated location on a PCB according to claim 1, characterized in that: The number of elastic pads (8) is set to six, and three are set on each side of the PCB steel mesh (1).

7. A PCB stencil for transferring a precise amount of solder paste to a designated location on a PCB according to claim 1, characterized in that: The elastic pad (8) is made of polyimide film.

8. A PCB stencil for transferring a precise amount of solder paste to a designated location on a PCB according to claim 1, characterized in that: The connection between the elastic pad (8) and the PCB steel mesh (1) is achieved by adhesive bonding.

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