SMT steel net and SMT steel net cooperation to realize multi-type component welding method

Abstract

The application discloses a kind of SMT steel net and SMT steel net cooperation realizes multiple types of component welding method, the steel net is realized by being set with jack hole corresponding shielding part on net body tin paste printing is avoided on jack hole, tin paste waste is avoided and is set on net body for adjusting the step part of SMT steel net local thickness, realizes step printing, reduces the production cost of pair of time also promotes the qualified rate, and the jack hole gap between jack hole and welding terminal and connecting piece can satisfy the soldering of welding terminal, soldering can penetrate from jack hole to the other side of PCB circuit board body, ensure that the terminal welding of the back side of PCB circuit board body is free from the phenomenon such as incomplete welding, virtual welding and build-up welding, and the like, and then through SMT steel net cooperation realizes multiple types of component welding method ensures that welding terminal and connecting piece are welded in the process of reflow soldering, and the subsequent separate welding process is omitted, so that the terminals on the PCB circuit board body can be effectively welded, and adverse conditions such as circuit board deformation are avoided.

Description

Technical Field

[0001] This invention relates to the field of printed circuit boards, and more specifically to an SMT stencil and a method for soldering multiple types of components using an SMT stencil. Background Technology

[0002] With the rapid development of the electronics industry, reflow soldering equipment has been widely used in the manufacturing sector. To increase output and reduce costs, various types of circuit boards also use reflow soldering equipment to replace manual soldering. However, products printed and reflow soldered using conventional methods cannot meet the soldering requirements of various types of components due to process limitations. This results in one or more types of components on the finished circuit board not being effectively soldered, leading to defects such as insufficient or excessive solder during printing. Finished products that have undergone reflow soldering exhibit issues such as cold solder joints, solder buildup, solder balls, and solder creep.

[0003] A circuit board often contains various types of components and terminals. The installation methods and soldering conditions of each type of component and terminal are quite different. Therefore, when soldering circuit boards in a conventional way, it is impossible to meet the soldering conditions of various types of components and terminals at the same time, which inevitably leads to soldering defects of components and terminals in the finished circuit board.

[0004] For circuit boards with various types of electronic components and terminals, using ordinary stencils to print solder paste has many disadvantages. First, regarding the characteristics of electronic components and terminals, electronic components have a small amount of solder paste printed on the pads, and then the pick-and-place machine places the electronic components onto the pads and completes the soldering through reflow soldering. However, terminals have a larger amount of solder paste printed on the pads. It is necessary not only to meet the soldering requirements on the side where the terminal is inserted, but also to ensure that there are no defects such as missing solder, cold solder joints, or solder creep on the back side of the terminal. This places higher requirements on the characteristics of the solder paste, the thickness of the solder paste, and the area of ​​the solder paste.

[0005] In summary, for circuit boards with various types of electronic components and terminals, there are problems such as inconvenient soldering operations, high production costs, and low pass rates. Summary of the Invention

[0006] The purpose of this invention is to provide an SMT stencil and a method for soldering multiple types of components using the SMT stencil. The stencil features shielding portions corresponding to the sockets to prevent solder paste waste during printing. Stepped portions on the stencil allow for adjustable local thickness printing, reducing production costs and improving yield. Furthermore, the gap between the sockets and the soldering terminals and connectors ensures that solder can penetrate from the sockets to the other side of the PCB, preventing defects such as missed soldering, cold solder joints, and solder build-up on the reverse side of the PCB. The SMT stencil method also enables simultaneous soldering of terminals and connectors during reflow soldering, eliminating the need for separate subsequent soldering processes and ensuring effective soldering of terminals on the PCB, preventing PCB deformation and other defects.

[0007] To achieve the above-mentioned technical objectives, the present invention is implemented through the following technical solution:

[0008] An SMT stencil, comprising:

[0009] The PCB circuit board body has a socket for fixing soldering terminals or connecting pieces. The socket and the pin of the soldering terminal or connecting piece are interference-fitted, and a socket gap is left between the socket and the soldering terminal or connecting piece.

[0010] The mesh body is attached to the PCB circuit board body at the bottom. The mesh body is provided with a shielding part corresponding to the center of the socket. The mesh body is also provided with a stepped part for increasing or decreasing the amount of solder paste printed locally.

[0011] As a further technical solution of the SMT stencil, the cross-section of the pin is a non-circular cross-section, so that the gap between the socket and the soldering terminal contains open space, so that the solder paste can pass through the gap between the socket and the pin and smoothly penetrate to the reverse side of the PCB circuit board body during soldering.

[0012] As a further technical solution of the SMT stencil, the diagonal length of the pin's cross-section is greater than the diameter of the socket, so that the socket and the pin have an interference fit, ensuring that the soldering terminals and connecting pieces are fixed before soldering. During soldering, it is prevented that the soldering terminals and connecting pieces will not change position due to the flow of solder paste when the solder paste melts in the reflow soldering machine, which would cause soldering failure. In addition, the diameter of the socket is smaller than the diameter of the soldering terminals and connecting pieces, which also ensures that the soldering terminals and connecting pieces are firmly fixed and achieve mechanical positioning.

[0013] As a further technical solution for the SMT stencil, when the pads are small but the required amount of solder paste is large, simply increasing the size of the holes can increase the amount of solder paste, but when the solder paste melts, the pull force of the solder as it converges towards the center is insufficient, resulting in weak adhesion to the PCB circuit board body. This fails to effectively gather the solder at the edges, leading to solder balls. To avoid this situation, the stencil also includes a first stencil and a second stencil. The second stencil is attached to the bottom of the first stencil, and a hollow portion is provided on the second stencil to form a convex step with the first stencil. The holes with small pads and a large amount of solder paste required are set on the convex step, and the amount of solder paste can be adjusted by adjusting the hollow height of the hollow portion.

[0014] As a further technical solution for the SMT stencil, when the amount of solder paste required for soldering on the PCB circuit board body is small, but the stencil body is thick and the stencil holes are already very small, the finished product still often experiences issues such as solder clogging and misalignment of surface mount components. Therefore, with a fixed number of holes, the amount of solder paste can be adjusted by reducing the local thickness of the stencil body. Thus, a concave step is formed by extending the plane corresponding to the hollow portion on the first stencil body towards the lower surface of the second stencil body. Setting the holes requiring less solder paste in the concave step can reduce the amount of solder paste required during printing.

[0015] As a further technical solution of the SMT stencil, the outer periphery of the socket is provided with solder pads. The PCB circuit board body also includes electronic components such as LED beads and resistors. The solder pads include a first solder pad and a second solder pad. The first solder pad is provided on the outer periphery of the socket, and the second solder pad is provided on the outer periphery of the electronic components. This allows the soldering of terminals and electronic components to be completed simultaneously during the reflow soldering process of the mounted PCB circuit board, eliminating the need for subsequent separate soldering processes and improving soldering quality.

[0016] As a further technical solution for the SMT stencil, since the center hole of the soldering terminal socket on the PCB circuit board body cannot have solder paste, the center part of the socket needs to be blocked on the solder paste hole on the stencil. Therefore, the shielding part includes a protective pad and a solder paste hole. The solder paste hole corresponds to the first pad and the second pad. The protective pad is connected to the outer circle of the solder paste hole. The protective pad is aligned with the center of the socket. This avoids solder paste waste and also prevents excessive solder from flowing to the reverse side of the PCB circuit board body during soldering, which would cause solder crawling on the reverse side terminals.

[0017] As a further technical solution for the SMT stencil, in order to further avoid solder paste adhering to the center hole of the socket, the diameter of the socket is less than or equal to the outer diameter of the protective pad.

[0018] As a further technical solution of the SMT stencil, the depth of the solder paste hole corresponding to the first pad is greater than the depth of the solder paste hole corresponding to the second pad, so that the molten solder paste can better penetrate to the reverse side of the PCB circuit board body during soldering, fill the gap between the pins and holes on the reverse side, and make the soldering on the reverse side saturated.

[0019] A method for soldering multiple types of components using SMT stencils includes the following steps:

[0020] S1. Using any one of the above technical solutions, solder paste is evenly distributed on the pads on one side of the front of the PCB circuit board body using the SMT stencil;

[0021] S2. Insert the welding terminal and connecting piece into the socket;

[0022] S3. Attach LED beads, resistors and other electronic components to the second pad;

[0023] S4. Reflow soldering.

[0024] As can be seen from the above technical solution, the SMT stencil and the method for soldering multiple types of components provided in this application achieve this by setting a shielding part on the stencil body corresponding to the socket to avoid solder paste waste by printing solder paste on the socket and setting a stepped part on the stencil body to adjust the local thickness of the SMT stencil to achieve stepped printing, which reduces production costs and improves the yield rate. Moreover, the socket gap between the socket and the soldering terminal and the connecting piece can meet the requirement that the solder of the soldering terminal can penetrate from the socket to the other side of the PCB circuit board body, ensuring that there are no defects such as missing solder, cold solder and solder accumulating on the reverse side of the PCB circuit board body. Furthermore, the method for soldering multiple types of components by using the SMT stencil ensures that the soldering of the soldering terminal and the connecting piece is achieved during the reflow soldering process, omitting the subsequent separate soldering process, so that the terminals on the PCB circuit board body can be effectively soldered, avoiding defects such as circuit board deformation. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0026] Figure 1 A schematic diagram of the steel mesh structure provided in the embodiments of this application;

[0027] Figure 2This is a schematic diagram of a PCB circuit board provided in an embodiment of this application;

[0028] Figure 3 This is a schematic diagram illustrating the mating of pins and sockets of PCB circuit board terminals or inserts provided in the embodiments of this application;

[0029] Figure 4 for Figure 1 A partial sectional view of AA (designed using a thickened steel mesh in the tin-plated section);

[0030] Figure 5 for Figure 1 A partial sectional view of another embodiment of AA (designed using a method of thinning the stencil in areas with less tin);

[0031] Figure 6 This is a schematic diagram of the PCB circuit board structure provided in the embodiments of this application;

[0032] Figure 7 The relevant settings and temperature profiles of the reflow soldering machine in the embodiments of this application are shown.

[0033] The attached diagram shows the markings and corresponding component names:

[0034] 1-Mesh body, 2-Solder paste hole, 3-Protective pad, 4-PCB circuit board body, 5-Hole, 6-First pad, 7-Second pad, 8-Pin, 9-Hole gap, 10-Connecting piece, 11-Soldering terminal, 12-First mesh body, 13-Second mesh body. Detailed Implementation

[0035] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the embodiments of this application.

[0036] In the description of the embodiments of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "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 the embodiments of this application 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 the embodiments of this application. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a replaceable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0038] Example 1

[0039] This embodiment 1 provides an SMT stencil, such as Figures 1-6As shown, the circuit includes a PCB body 4 and a mesh 1. The PCB body 4 includes solder terminals 11, connecting pieces 10, and electronic components such as LED beads and resistors. The PCB body 4 has insertion holes 5 for fixing the solder terminals 11 or connecting pieces 10. First solder pads 6 are provided on its outer periphery, and second solder pads 7 are provided on the outer periphery of the LED beads and resistors. This allows the solder terminals and electronic components to be soldered simultaneously during the reflow soldering process of the mounted PCB, eliminating the need for subsequent separate soldering processes and improving soldering quality. Furthermore, the socket 5 is fixed to the pin 8 of the solder terminal 11 or connecting piece 10 through an interference fit. In this embodiment, the diagonal length of the cross-section of the pin 8 is greater than the diameter of the socket 5, achieving an interference fit between the socket 5 and the pin 8. This ensures that the solder terminal and connecting piece are fixed before soldering, preventing positional changes due to solder paste flow during soldering and thus avoiding soldering failure. Additionally, the diameter of the socket 5 is smaller than the diameters of the solder terminal 11 and connecting piece 10, further ensuring a tighter connection between the solder terminal 11 and connecting piece 10. The current mechanical positioning; and the cross-section of the aforementioned pin 8 is a non-circular cross-section, so that a gap 9 is formed between the socket 5, the soldering terminal 11, and the connecting piece 10. During soldering, the solder paste can pass through the gap between the socket 5 and the pin 8 and smoothly penetrate to the reverse side of the PCB circuit board body. It should be noted that there are also solder pads on the back of the PCB circuit board body 4, because when the solder paste melts, it will gather towards the center like water droplets and adhere to the pin 8 of the soldering terminal 11. Due to the influence of gravity, some of the solder will flow downwards, thus realizing the solder paste from the PCB circuit board body. The front side of 4 penetrates the back side, and since there are also pads on the back side of the PCB circuit board body 4, both sides will be well soldered after the soldering is completed. Of course, in order to allow the molten solder paste to better penetrate the back side of the PCB circuit board body and fill the gap between the pins and holes on the back side, so that the soldering on the back side becomes saturated, the depth of the solder paste hole 2 corresponding to the first pad 6 is greater than the depth of the solder paste hole 2 corresponding to the second pad 7, so that the thickness of the solder paste on the pad at the position of the hole 5 on the PCB circuit board body 4 is thicker than that on the pad of components without holes (such as resistors, LSD beads, etc.).

[0040] The mesh body 1 includes a first mesh body 12 and a second mesh body 13. The second mesh body 13 is attached to the lower part of the first mesh body 12, and the lower part of the second mesh body 13 is attached to the PCB circuit board body 4. The mesh body 1 is also provided with a shielding part corresponding to the socket 5. In this embodiment, the shielding part includes a protective pad 3 and a solder paste hole 2. The solder paste hole 2 corresponds to the first pad 6 and the second pad 7. The protective pad 3 is connected to the outer circle of the solder paste hole 2 and aligned with the center of the socket 5. This avoids solder paste waste and also prevents excessive solder from flowing to the reverse side of the PCB circuit board body 4 during soldering, which would cause solder crawling on the reverse side terminals. To further prevent solder paste from adhering to the center hole of the socket 5, the diameter of the socket 5 is less than or equal to the outer diameter of the protective pad 3. The mesh body 1 is also provided with a stepped part for adjusting the local thickness of the SMT stencil. In this embodiment, there are two forms of the stepped part, see [link to relevant documentation]. Figure 4 When the solder pads are small but the required amount of solder paste is large, simply increasing the size of the holes can increase the amount of solder paste, but the solder's pulling force when melting is insufficient as it converges towards the center. This results in weak adhesion to the PCB board and ineffective gathering of solder at the edges, leading to solder balls. To avoid this, a second mesh 13 is attached below the first mesh 12. A hollow portion on the second mesh 13 forms a convex step with the first mesh 12. The small-pad, high-solder-paste-required insertion hole 5 is positioned on this convex step. The amount of solder paste can be adjusted by changing the height of the hollow portion. See also... Figure 5 When the amount of solder paste required for soldering on the PCB circuit board body 4 is small, but the mesh 1 is relatively thick, and the through holes 5 on the mesh 1 are already very small, the finished product still often experiences phenomena such as solder bulging and misalignment of surface mount components. Therefore, with a fixed number of holes, the amount of solder paste can be adjusted by reducing the local thickness of the mesh 1. Thus, a concave step is formed by extending the plane corresponding to the hollow part on the first mesh 12 to the lower surface of the second mesh 13. By setting the through holes that require less solder paste on the above-mentioned concave step, the amount of solder paste required during printing can be reduced.

[0041] Example 2

[0042] Based on the SMT stencil provided in Embodiment 1, Embodiment 2 provides a method for soldering multiple types of components using an SMT stencil, including the following steps:

[0043] S1. Using the SMT stencil described in Example 1, solder paste is evenly distributed on the pads on one side of the front of the PCB circuit board body 4;

[0044] S2. Insert the welding terminal 11 and the connecting piece 10 into the socket 5;

[0045] S3. Attach LED beads, resistors and other electronic components to the second pad 7;

[0046] S4. Reflow Soldering: Based on the size of the gap 9 between the pins 8 of the connector plate 10 and the solder terminals 11 on the PCB board body 4, and the fluidity of the solder paste during melting, the relevant operating parameters of the reflow soldering machine are set. In this embodiment, a 1.6mm thick PCB board is used as an example. The relevant settings of the reflow soldering machine and the temperature curve during operation are as follows: Figure 7 As shown.

[0047] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An SMT stencil, characterized in that, include: The PCB circuit board body (4) is provided with a socket (5) for fixing the soldering terminal (11) or the connecting piece (10). The socket (5) is interference-fitted with the pin (8) of the soldering terminal (11) or the connecting piece (10), and a socket gap (9) is left between the socket (5) and the soldering terminal (11) or the connecting piece (10). Mesh body (1), the mesh body (1) is attached to the PCB circuit board body (4) below, the mesh body (1) is provided with a shielding part corresponding to the center of the socket (5), and the mesh body (1) is provided with a stepped part for increasing or decreasing the amount of solder paste printed locally; The stepped portion includes convex steps and concave steps. The mesh body (1) includes a first mesh body (12) and a second mesh body (13). The second mesh body (13) is attached to the lower part of the first mesh body (12). A hollow part is provided on the second mesh body (13) to form the convex steps with the first mesh body (12). A plane on the first mesh body (12) corresponding to the hollow part of the second mesh body (13) extends to the lower surface of the second mesh body (13) to form the concave steps. The outer periphery of the socket (5) is provided with a first pad (6) and a second pad (7), and the outer periphery of the shielding part is provided with solder paste holes (2) corresponding to the first pad (6) and the second pad (7) respectively. The solder paste holes (2) are adapted to the socket gap (9) so that the printed solder paste can penetrate to the reverse side of the PCB circuit board body (4) through the socket gap (9) after melting.

2. The SMT stencil according to claim 1, characterized in that, The cross-section of the pin (8) is a non-circular cross-section.

3. The SMT stencil according to claim 2, characterized in that, The diagonal length of the cross section of the pin (8) is greater than the diameter of the socket (5).

4. The SMT stencil according to claim 1, characterized in that, The socket (5) is provided with a pad on its outer periphery. The PCB circuit board body (4) also includes electronic components. The first pad (6) is provided on the outer periphery of the socket (5), and the second pad (7) is provided on the outer periphery of the electronic components.

5. An SMT stencil according to claim 1, characterized in that, The shielding part also includes a protective disk (3), which is connected to the outer circle of the solder paste hole (2) and is aligned with the center of the socket (5).

6. The SMT stencil according to claim 5, characterized in that, The diameter of the jack (5) is less than or equal to the outer diameter of the protective disc (3).

7. An SMT stencil according to claim 5, characterized in that, The depth of the solder paste hole (2) corresponding to the first pad (6) is greater than the depth of the solder paste hole (2) corresponding to the second pad (7).

8. A method for soldering multiple types of components using an SMT stencil, characterized in that, Includes the following steps: S1. Using the SMT stencil as described in claim 6 or 7, solder paste is evenly distributed on the pads on one side of the front of the PCB circuit board body (4); S2. Insert the welding terminal (11) and the connecting piece (10) into the socket (5); S3. Attach the electronic components to the second pad (7); S4. Reflow soldering.

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