Printing screen plate suitable for large-size substrate
By optimizing the mesh structure and overflow reduction sheet design of the large-size substrate printing screen, the problems of solder paste overflow and short circuit were solved, and the effective connection between solder balls and pads and high-quality forming were achieved.
Patent Information
- Application Number
- CN202520031861.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-07
- Publication Date
- 2025-12-23
- Estimated Expiration
- 2035-01-07
AI Technical Summary
During the manufacturing process of electronic products, when solder paste is dropped from the stencil onto the pads, adjacent solder balls are prone to fusion contact, which can lead to short circuits. This is especially true in miniaturized electronic products, where the small spacing between solder balls and substrate warping can cause solder paste to overflow, increasing the probability of short circuits.
Design a stencil suitable for large-size substrates. The mesh group is a centrally symmetrical pattern with rounded corners. Anti-overflow sheet is set. The mesh spacing and area are optimized to ensure smooth solder paste feeding and complete correspondence between solder balls and pads, reducing solder ball fusion contact.
By optimizing the mesh structure, the probability of solder ball fusion contact is reduced, short circuits are prevented, and the solder ball is fully connected to the pad, thereby improving the forming quality and connection reliability of the solder ball.
Smart Images
Figure CN223714280U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of substrate printing, and particularly relates to a printing screen plate suitable for large-size substrates. BACKGROUND
[0002] With the rapid development of the electronic industry, the integration capability of electronic products is continuously improved, the functions are increasingly powerful, and the size is increasingly miniaturized. Chip ball mounting is an important link in the processing of electronic products. The tin paste ball mounting method is one of the ball mounting technologies, which mainly prints and falls tin paste on the surface of the solder pad of the substrate through a printing screen plate to complete ball mounting. However, if the volume of the component to be mounted is small or the distance between the components is small, the distance between the tin balls to be prepared is small, and the distance between the printing holes on the printing screen plate is also small. At this time, when the tin paste is dropped from the printing screen plate to the solder pad to be printed, the adjacent tin balls are prone to fusion contact, resulting in short circuit. CONTENT
[0003] In order to reduce the probability of short circuit, the present application provides a printing screen plate suitable for large-size substrates.
[0004] The present application provides a printing screen plate suitable for large-size substrates, which adopts the following technical scheme:
[0005] The printing screen plate suitable for large-size substrates comprises a screen plate body, wherein a plurality of screen holes are arranged on the screen plate body, and each four screen holes form a screen hole group. The screen hole group corresponds to a component to be mounted, and the center point of the four solder pads corresponding to the four screen holes is point N, and the center point of a single solder pad is point O. The center point of the screen hole is located on the extension line of points N and O.
[0006] By adopting the above technical scheme, the distance between the four screen holes corresponding to the same component is as large as possible, so as to compensate for the tin paste overflow caused by the warping of the substrate to be printed during ball mounting, reduce the probability of fusion contact between adjacent tin balls, and cause short circuit.
[0007] Preferably, the projection of the screen hole in the vertical direction is completely located in the corresponding solder pad.
[0008] By adopting the above technical scheme, the formed tin ball can be as completely as possible in the corresponding solder pad, so as to prevent the tin paste from being completely offset due to the warping of the substrate to be printed during ball mounting, and make the tin ball unable to be connected with the solder pad.
[0009] Preferably, the screen hole is a central symmetric pattern.
[0010] By adopting the technical scheme, the speed of the solder paste flowing and overflowing downward from all directions is as same as possible, and the different resistances of each side when the solder paste is discharged are reduced, so that the same tin ball is not high at different positions. On the other hand, the central symmetry pattern is helpful for the design and processing of the pattern, and the error amount and the possibility of error in the design and processing are reduced
[0011] Preferably, the mesh hole is a similar pattern corresponding to the pad.
[0012] By adopting the technical scheme, the tin ball formed can be connected with the pad as completely as possible, and the deviation amount between the tin paste and the expected pad pattern after flowing due to warping can be reduced.
[0013] Preferably, the four corners of the mesh hole are round.
[0014] By adopting the technical scheme, the round corner setting can reduce the side wall area of the mesh hole, so that the solder paste flows more smoothly and forms a tin ball.
[0015] Preferably, the four side inner walls of the mesh hole are provided with overflow reduction sheets, and the two top corners of the overflow reduction sheet towards the center of the mesh hole are round.
[0016] By adopting the technical scheme, the width of the middle section of the mesh hole is reduced by the overflow reduction sheet. When the doctor blade coats the solder paste, the overflow reduction sheet reduces the excessive dispersion of the solder paste in the middle section caused by the pushing force of the solder paste on one side to the solder paste in the middle section when the solder paste passes through the mesh hole, and prevents the bridging between adjacent solder balls after printing.
[0017] Preferably, the distance between the two symmetrical overflow reduction sheets on the mesh hole is 1 / 2-4 / 5 of the width of the pad.
[0018] By adopting the technical scheme, if the overflow reduction sheet is too wide, the side area will be larger, which will cause the side area of the mesh hole to be larger, and after exceeding a certain value, it will affect the discharge of the solder paste; if the overflow reduction sheet is too narrow, the limitation of the solder paste dispersion is limited. The distance between the overflow reduction sheets ensures that the solder paste can be discharged smoothly, and also ensures that the solder paste will not be dispersed to the adjacent solder ball bridge.
[0019] Preferably, the area of the mesh hole is 0.2-0.5 of the area of the corresponding pad.
[0020] By adopting the technical scheme, in the case of ensuring that the tin ball formed by discharging through the mesh hole will not be bridged with other tin balls, the mesh hole is as large as possible, so that the discharge is more smooth, and the tin ball formed by the ball planting is larger, which is better for subsequent connection with other components.
[0021] Preferably, the center point of the mesh hole is S, and OS is 1 / 15-1 / 5 of ON.
[0022] By adopting the technical scheme, the tin balls formed by the mesh can not be bridged with other tin balls, offset is reduced, and the connection area of the tin ball and the pad is as large as possible.
[0023] In conclusion, the present application has at least one of the following beneficial technical effects: by moving the hole, reducing the hole, and setting the overflow sheet to form a special-shaped mesh, the adjacent tin balls formed by printing are not bridged, and the short circuit caused by the fusion contact of the adjacent tin balls is reduced. Meanwhile, the mesh is as large as possible under the condition that the solder paste can be smoothly discharged and the adjacent tin balls formed by the solder paste are not bridged, so that the tin ball with the largest connection area and the pad is prepared. BRIEF DESCRIPTION OF DRAWINGS
[0024] Fig. 1 is a structural schematic diagram of a mesh in embodiment 1 of the present application;
[0025] Fig. 2 is a structural schematic diagram of a mesh group of embodiment 1 of the present application projected onto the corresponding pad.
[0026] Marked as follows: 1, mesh body; 2, mesh; 3, pad; 4, substrate; 5, overflow sheet. DETAILED DESCRIPTION
[0027] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.
[0028] In order to deepen the understanding of the scheme of the present application, the technical problem needs to be described in detail in combination with related technologies, and the specific content is as follows:
[0029] The function of tin paste printing is to print the tin paste on the pad on the substrate to prepare for the welding of components. Specifically, the printing mesh plate is abutted on the substrate, so that the mesh hole corresponds to the pad to be planted, then the tin paste is fed to the printing mesh plate, the excess tin paste is scraped off by the scraper, and the required tin paste is transferred to the pad on the substrate through the mesh hole of the printing mesh plate, thereby completing the printing process of the tin paste.
[0030] In a conventional case, the smaller the component to be mounted, the denser the pad distribution and the smaller the area. Due to the warping of the substrate, when the doctor blade prints the solder paste, excess solder paste will seep into the gap between the substrate and the printing screen plate, forming solder paste overflow. This causes the solder paste under adjacent screen holes to appear to be in contact, resulting in substrate short circuit.
[0031] To alleviate the above problems, the utility model provides a printing screen plate suitable for large size substrate, below combining Figs. 1-2 The embodiments of the present application are described in detail.
[0032] As Fig. 1 and Fig. 2 shown, the present embodiment includes a screen plate body 1, the screen plate body 1 is equipped with screen hole 2, each screen hole 2 corresponds to a pad 3 on the substrate 4. Screen hole 2 is the similar figure of pad 3, and screen hole 2 is the central symmetric figure. When printing the solder paste, the projection of screen hole 2 along the vertical direction falls in its corresponding pad 3 completely. Every four screen holes 2 form a screen hole group. Each screen hole group corresponds to a component to be mounted. The center point of the four pads 3 corresponding to the screen hole group is N point, the center point of single pad 3 is O, and the center point of single screen hole 2 is S. S is located on the extension line of NO.
[0033] By moving S relative to O to the direction away from N, the outward shift of adjacent screen holes 2 is realized, thereby expanding the distance between the same group of adjacent screen holes 2, reserving space for subsequent solder paste overflow, reducing the probability of fusion contact between adjacent solder balls, leading to substrate 4 short circuit. Specifically, OS is 1 / 15~1 / 5 of ON.
[0034] Further, screen hole 2 is rectangular or square, and the four corners of screen hole 2 are all rounded. The inner wall of the four sides of screen hole 2 is all equipped with overflow reduction sheet 5, and the two top corners of the end of overflow reduction sheet 5 towards the center of screen hole 2 are rounded. The distance between the two symmetrical overflow reduction sheets 5 on screen hole 2 is 1 / 2~4 / 5 of the width of pad 3. The length of overflow reduction sheet 5 is 1 / 3~2 / 3 of the length of the side wall of screen hole 2.
[0035] The width of the middle section of the mesh 2 is reduced by the overflow-reducing piece 5. When the squeegee is used to apply the solder paste, the overflow-reducing piece 5 reduces the excessive dispersion of the solder paste in the middle section of the mesh 2 due to the pushing force of the solder paste on one side on the solder paste in the middle section, and prevents the bridging between the adjacent solder balls after printing. The top corner of the overflow-reducing piece 5 and the four corners of the mesh 2 are arranged to reduce the area of the side wall of the mesh 2, so that the solder paste can be smoothly discharged to form a solder ball. The area of the side wall of the mesh 2 and the overflow-reducing piece 5 is set to be the area of the side wall of the mesh 2, and the area of the hole type formed by the side wall of the mesh 2 and the overflow-reducing piece 5 is set to be the area of the mesh 2. The length of the overflow-reducing piece 5 and the distance between the two symmetric overflow-reducing pieces 5 limit the size of the area of the side wall of the mesh 2 and ensure the size of the area of the mesh 2, thereby preventing the solder paste from being discharged due to the area of the side wall of the mesh 2 being much larger than the area of the mesh 2.
[0036] The area of the mesh 2 is 0.2-0.5 times the area of the corresponding pad 3. This data setting can maximize the area of the mesh 2 while ensuring that the solder ball formed by the mesh 2 will not be bridged with other solder balls, thereby making the discharge more smooth and also making the solder ball formed by the ball placement larger and better for subsequent connection with other components.
[0037] The embodiments of the specific embodiments are the preferred embodiments of the present application, and are not limited to the protection scope of the present application. Therefore, any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.
Claims
1. A printing screen suitable for large-size substrates, comprising a screen body (1), wherein the screen body (1) is provided with mesh openings (2), characterized in that: Every four mesh holes (2) form a mesh group, and the mesh group corresponds to a component to be mounted. Let the center point of the four pads (3) corresponding to the four mesh holes (2) be point N, and the center point of a single pad (3) be O. The center point of the mesh hole (2) is located on the extension line of NO.
2. A printing screen suitable for large-size substrates according to claim 1, characterized in that: The projection of the mesh (2) along the vertical direction is completely located in its corresponding pad (3).
3. A printing screen suitable for large-size substrates according to claim 2, characterized in that: The mesh (2) is a centrally symmetrical shape.
4. A printing screen suitable for large-size substrates according to claim 3, characterized in that: The mesh (2) is a similar pattern to the corresponding pad (3).
5. A printing screen suitable for large-size substrates according to claim 4, characterized in that: The four corners of the mesh (2) are all rounded.
6. A printing screen suitable for large-size substrates according to claim 4, characterized in that: The inner walls of the four sides of the mesh (2) are provided with anti-overflow plates (5), and the two top corners of the anti-overflow plates (5) facing the center of the mesh (2) are rounded.
7. A printing screen suitable for large-size substrates according to claim 6, characterized in that: The distance between the two symmetrical anti-overflow tabs (5) on the mesh (2) is 1 / 2 to 4 / 5 of the width of the pad (3).
8. A printing screen suitable for large-size substrates according to claim 2, characterized in that: The area of the mesh (2) is 0.2 to 0.5 times the area of its corresponding pad (3).
9. A printing screen suitable for large-size substrates according to claim 2, characterized in that: Let S be the center point of the mesh (2), and OS be 1 / 15 to 1 / 5 of ON.