Printing screen assembly for semiconductor packaging

Abstract

The utility model discloses a printing screen assembly for semiconductor packaging, which comprises a screen body, the screen body is provided with meshes, and the screen body comprises a first area for correspondingly preparing solder balls with large solder paste amount and a second area for preparing solder balls with small solder paste amount. The thickness of the screen body a for independently preparing the solder balls with the large solder paste amount is X1 and the mesh sectional area is S1, the thickness of the screen body b for independently preparing the solder balls with the small solder paste amount is X2 and the mesh sectional area is S2, the thickness X of the screen body is equal to X1 + k (X2-X1) / 2, the mesh sectional area corresponding to the first area is larger than S1, the mesh sectional area corresponding to the second area is smaller than S2, and the thickness of the screen body b is equal to X1 + k (X2-X1) / 2. And the minimum width of the meshes corresponding to the second region is smaller than the width of the corresponding bonding pad. By controlling the thickness of the screen plate body and cooperating with hole shrinkage and hole expansion of the meshes in different areas of the screen plate body, the thickened screen plate body can meet the tin amount requirements of elements with two thicknesses and types, so that tin balls with different solder paste amounts are formed on a substrate through one-time printing, and the production efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tin ball printing, and in particular to a printing screen assembly for semiconductor packaging. BACKGROUND

[0002] With the rapid development of the electronic industry, the integration capability of electronic products is constantly improving, the function is increasingly powerful and the size is increasingly miniaturized, and 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 the tin paste through a printing screen plate to fall on the surface of the solder pad of the substrate to complete the ball mounting. However, the tin content of the tin balls prepared by single ball mounting is the same, which cannot meet the soldering tin content requirements of components with different heights. CONTENT OF THE UTILITY MODEL

[0003] In order to be able to single ball mounting to meet the soldering tin content requirements of components with two different heights, the present application provides a printing screen assembly for semiconductor packaging.

[0004] The printing screen assembly for semiconductor packaging provided by the present application adopts the following technical scheme:

[0005] The printing screen assembly for semiconductor packaging comprises a screen body, wherein the screen body is provided with screen holes, the screen body comprises a first area for preparing large tin paste content tin balls and a second area for preparing small tin paste content tin balls, the thickness of the screen body a for separately preparing large tin paste content tin balls is X1, the cross-sectional area of the screen hole is S1, the thickness of the screen body b for separately preparing small tin paste content tin balls is X2, the cross-sectional area of the screen hole is S2, the thickness of the screen body is X=X1+k(X2-X1) / 2, the cross-sectional area of the screen hole corresponding to the first area is greater than S1, the cross-sectional area of the screen hole corresponding to the second area is less than S2, and the minimum width of the screen hole corresponding to the second area is less than the width of the corresponding solder pad.

[0006] By adopting the above technical scheme, the thickness of the screen body is controlled, the screen holes in different areas of the screen body are shrunk and expanded, one thickened screen body can meet the tin content requirements of components with two thicknesses and types, thereby different tin paste content tin balls are formed on the substrate by one-time printing, and the production efficiency is improved.

[0007] Preferably, when the aspect ratio of the corresponding solder pad is greater than or equal to 2.5, two screen holes correspond to each solder pad, and the two screen hole units are located at the two ends of the corresponding solder pad; when the aspect ratio of the corresponding solder pad is less than 2.5, one screen hole corresponds to each solder pad.

[0008] By adopting the technical scheme, two mesh holes are arranged at two ends of the pad to replace one large mesh hole directly corresponding to one pad, thereby reducing the amount of solder paste required for stable connection with the pad. The mesh holes are arranged at the two ends of the pad, which can better ensure the strength and stability of the connection without changing the number and size of the mesh holes. Meanwhile, the probability of contact and fusion with adjacent solder balls due to excessive overflow of the solder paste is reduced. In addition, the gap between the two mesh holes provides a space allowance for the flow of the solder paste during printing.

[0009] Preferably, when one component corresponds to two pads with an aspect ratio greater than or equal to 2.5, four mesh holes corresponding to the two pads form a mesh hole group, and the center point of the two pads as a whole is defined as point N, and the four mesh holes are all outwardly offset relative to point N.

[0010] By adopting the technical scheme, the spacing between the four mesh holes corresponding to the same component is as large as possible, thereby compensating for the overflow of the solder paste due to the warping of the substrate to be printed during ball planting, reducing the probability of contact and fusion between adjacent solder balls, and causing short circuit.

[0011] Preferably, the sum of the cross-sectional areas of the two mesh holes corresponding to the same pad is 1 / 3 to 2 / 3 of the cross-sectional area of the corresponding pad.

[0012] By adopting the technical scheme, it is ensured that the solder paste has sufficient connection area with the pad, so that the solder paste can more stably connect the component to the pad.

[0013] Preferably, when one component corresponds to two pads with an aspect ratio less than 2.5, two mesh holes corresponding to the two pads form a mesh hole group, and the two mesh holes are symmetrically arranged and are both outwardly offset relative to the center line.

[0014] By adopting the technical scheme, the spacing between the two mesh holes corresponding to the same component is as large as possible, thereby compensating for the overflow of the solder paste due to the warping of the substrate to be printed during ball planting, reducing the probability of contact and fusion between adjacent solder balls, and causing short circuit.

[0015] Preferably, the mesh hole comprises a rectangular portion and an isosceles trapezoidal portion, the long side of the isosceles trapezoidal portion is connected with the rectangular portion, and the short side of the isosceles trapezoidal portion is located at one end of the isosceles trapezoidal portion close to the center line.

[0016] By adopting the technical scheme, the amount of solder paste discharged at the short side end of the isosceles trapezoidal portion is less than the amount of solder paste discharged at the long side end of the isosceles trapezoidal portion, thereby reducing the probability of contact and fusion between the solder piles formed by the two mesh holes in the same group.

[0017] Preferably, the width of the rectangular portion is greater than the width of the corresponding pad, and the short side of the isosceles trapezoidal portion is less than the width of the corresponding pad.

[0018] By adopting the technical scheme, the contact area of the solder ball and the pad is increased as much as possible under the condition that the adjacent solder balls do not contact and fuse, so that the solder ball can more stably mount the component on the pad.

[0019] Preferably, the ratio of the mesh hole sectional area to the mesh hole inner wall area is between 0.5 and 2.

[0020] By adopting the technical scheme, the situation that the solder paste is difficult to descend due to the excessive resistance of the mesh hole inner wall is prevented.

[0021] Preferably, the coefficient k is greater than 1.2 and less than 1.9.

[0022] In summary, the present application has at least one of the following beneficial technical effects: by printing the solder paste once through a mesh plate body, solder balls meeting the soldering requirements of components of two thicknesses and types can be formed, and the production efficiency is improved; by setting the shape of the mesh hole, reducing the area of the mesh hole, and offsetting the position of the mesh hole, the probability of short circuit caused by the fusion contact between adjacent solder balls is reduced as much as possible under the premise that the size of the printed solder ball meets the structural strength and connection strength; by the shape, area, and relationship between the dimensions of the solder paste, the solder paste can be smoothly discharged from the mesh hole to form a solder ball meeting the conditions during printing. In addition, while ensuring the above effects, when the length-width ratio of the pad is large, by setting the distance between the two mesh holes, a gap is formed between the two mesh holes to provide overflow space for the solder paste during printing in the warping condition, and on the basis of reducing the amount of solder paste, the possibility of overflow and short circuit caused by the flow of solder paste is further reduced. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a partial structure schematic diagram of a substrate in the embodiment of the present application;

[0024] Figure 2 is a partial structure schematic diagram of the embodiment of the present application;

[0025] Figure 3 is a corresponding relationship schematic diagram of a mesh hole group of four in one group and a pad in the embodiment of the present application;

[0026] Figure 4 is a corresponding relationship schematic diagram of a mesh hole group of two in one group and a pad in the embodiment of the present application.

[0027] Mark 1, mesh plate body; 11, first area; 12, second area; 2, mesh hole; 21, rectangular part; 22, isosceles trapezoidal part; 3, substrate; 4, pad. DETAILED DESCRIPTION

[0028] The present application will be further described in detail below with reference to the accompanying drawings.

[0029] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be described clearly and completely in combination with the drawings in the embodiments of the utility model below. Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by the person skilled in the art without creative labor belong to the protection scope of the utility model.

[0030] In order to deepen the understanding of the utility model scheme, the technical problem needs to be described in detail in combination with related technologies, and the specific content is as follows:

[0031] Generally, single-time solder paste printing can only form several solder balls with the same or similar amount of solder paste on the pads 4 of the substrate 3. Since the tin climbing height requirement after component welding is all greater than 50% of the component thickness, the solder paste amount required by the solder balls corresponding to different height components is different, that is, the higher the component, the greater the required solder paste amount. At this time, if two components with large height difference need to be mounted on a substrate 3, two kinds of solder balls with different solder paste amounts need to be printed on the pads 4 of the substrate 3. Assuming that the solder ball with large solder paste amount is solder ball A, and the solder ball with small solder paste amount is solder ball B.

[0032] When preparing, the inventor takes the screen plate body b corresponding to the preparation of the solder ball B, first performs one-time solder paste printing on the substrate 3 provided with the pads 4 to form the solder ball B. Then, the screen plate body a corresponding to the preparation of the solder ball A is taken, the screen plate body a is provided with an avoidance groove for covering B at the position corresponding to the solder ball B, the screen plate body a is covered on the substrate 3, and one-time solder paste printing is performed again on the substrate 3 provided with the pads 4 to form the solder ball A, thereby completing the preparation. However, this method needs two-time printing, the production efficiency is low, and it is also necessary to separately set the avoidance hole on the screen plate body a, so that the process steps are more and the operation is inconvenient.

[0033] In order to alleviate the above problems, the utility model provides a kind of printing screen plate assembly for semiconductor packaging, as follows: Figures 1 to 4 The embodiments of the present application are described in detail.

[0034] As Figure 1 And Figure 2 As shown in the present embodiment, the present embodiment includes screen plate body 1, screen plate body 1 is provided with mesh 2, screen plate body 1 includes the first area 11 corresponding to the preparation of solder ball A and the second area 12 for preparing solder ball B. The minimum width of the mesh 2 corresponding to the second area 12 is less than the width of the corresponding pad 4.

[0035] The thickness of the screen plate body a is X1, the cross-sectional area of the mesh hole 2 is S1, the thickness of the screen plate body b is X2, and the cross-sectional area of the mesh hole 2 is S2. The thickness of the screen plate body 1 is X=X1+k(X2-X1) / 2, and the coefficient k is greater than 1.2 and less than 1.9. The cross-sectional area of the mesh hole 2 corresponding to the first area 11 is greater than S1, and the cross-sectional area of the mesh hole 2 corresponding to the second area 12 is less than S2. The ratio of the cross-sectional area of the mesh hole 2 to the inner wall area of the mesh hole 2 is between 0.5 and 2.

[0036] The thickness of the screen plate body 1 is set between the thickness of the screen plate body a and the screen plate body b, and preferably close to the thickness of the screen plate body a. The first area 11 on the screen plate body 1 is expanded, and the second area 12 is contracted. After a single printing, the amount of solder paste transferred to the solder ball on the pad 4 of the substrate 3 through the mesh hole 2 of the first area 11 and the amount of solder paste transferred to the solder ball on the pad 4 of the substrate 3 through the mesh hole 2 of the second area 12 are significantly different, which can meet the mounting tin amount of two components with large height difference, thereby simplifying the production process and improving the production efficiency.

[0037] As shown in Figure 3 When the corresponding pad 4 aspect ratio is greater than or equal to 2.5, each pad 4 corresponds to two mesh holes 2, and the two mesh hole 2 units are respectively located at both ends of the corresponding pad 4. The corresponding four mesh holes 2 form a mesh hole group, and the center point of the two pads 4 corresponding to the mesh hole group is set as N point, and the four mesh holes 2 are all outwardly offset relative to the N point. The sum of the cross-sectional areas of the two mesh holes 2 corresponding to the same pad 4 is 1 / 3~2 / 3 of the cross-sectional area of the corresponding pad 4.

[0038] The two mesh holes 2 corresponding to the two ends of the pad 4 are used instead of a whole large mesh hole 2 directly corresponding to a pad 4, thereby reducing the amount of solder paste required for stable connection with the pad 4. At the same time, the mesh hole 2 is outwardly shifted relative to the N point, thereby reducing the probability of contact and fusion of adjacent solder balls due to excessive solder paste. Prevent the short circuit of the pad 4 caused by the contact of adjacent solder balls.

[0039] As shown in Figure 4 When the corresponding pad 4 aspect ratio is less than 2.5, each pad 4 corresponds to one mesh hole 2. The corresponding two mesh holes 2 form a mesh hole group, and the two mesh holes 2 are symmetrically arranged and are both outwardly offset relative to the center line. The mesh hole 2 includes a rectangular portion 21 and an isosceles trapezoidal portion 22, the long side of the isosceles trapezoidal portion 22 is connected with the rectangular portion 21, and the short side of the isosceles trapezoidal portion 22 is located at one end of the isosceles trapezoidal portion 22 close to the center line. The width of the rectangular portion 21 is greater than the width of the corresponding pad 4, and the short side of the isosceles trapezoidal portion 22 is less than the width of the corresponding pad 4.

[0040] The amount of tin paste dropped at the short side end of the isosceles trapezoidal part 22 is less than the amount of tin paste dropped at the long side end of the isosceles trapezoidal part 22, thereby reducing the probability of contact fusion between the tin piles formed by the two mesh holes 2 in the same group. At the same time, while ensuring that adjacent tin balls do not contact and fuse, the contact area of the tin ball with the pad 4 is as large as possible, so that the tin ball can more stably mount the component on the pad 4.

[0041] The embodiments of the present specific implementation are the preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Therefore, any equivalent changes made in the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A printing screen plate assembly for semiconductor packaging, comprising a screen plate body (1) having screen holes (2) formed therein, characterized in that: The screen plate body (1) includes a first area (11) corresponding to preparation of large tin paste amount tin balls and a second area (12) corresponding to preparation of small tin paste amount tin balls, the thickness of the screen plate body a for separately preparing large tin paste amount tin balls is X1, the cross-sectional area of the screen hole (2) is S1, the thickness of the screen plate body b for separately preparing small tin paste amount tin balls is X2, the cross-sectional area of the screen hole (2) is S2, the thickness X of the screen plate body (1) is X1+k(X2-X1) / 2, the coefficient k is greater than 0 and less than 2, the cross-sectional area of the screen hole (2) corresponding to the first area (11) is greater than S1, the cross-sectional area of the screen hole (2) corresponding to the second area (12) is less than S2, and the minimum width of the screen hole (2) corresponding to the second area (12) is less than the width of the corresponding pad (4).

2. A printing screen assembly for semiconductor encapsulation according to claim 1, wherein: When the aspect ratio of the corresponding pad (4) is greater than or equal to 2.5, each pad (4) corresponds to two screen holes (2), and the two screen hole (2) units are located at the two ends of the corresponding pad (4); when the aspect ratio of the corresponding pad (4) is less than 2.5, each pad (4) corresponds to one screen hole (2).

3. A printing screen assembly for semiconductor encapsulation according to claim 2, wherein: When one element corresponds to two pads (4) with an aspect ratio greater than or equal to 2.5, the corresponding four screen holes (2) form a screen hole group, and the center point of the two pads (4) as a whole is N point, and the four screen holes (2) are all outwardly offset relative to the N point.

4. A printing screen assembly for semiconductor encapsulation according to claim 3, wherein: The sum of the cross-sectional areas of the two screen holes (2) corresponding to the same pad (4) is 1 / 3-2 / 3 of the cross-sectional area of the corresponding pad (4).

5. A printing screen assembly for semiconductor encapsulation according to claim 2, wherein: When one element corresponds to two pads (4) with an aspect ratio less than 2.5, the corresponding two screen holes (2) form a screen hole group, and the two screen holes (2) are symmetrically arranged and are both outwardly offset relative to the center line.

6. A printing screen assembly for semiconductor encapsulation according to claim 5, wherein: The screen hole (2) includes a rectangular portion (21) and an isosceles trapezoidal portion (22), the long side of the isosceles trapezoidal portion (22) is connected with the rectangular portion (21), and the short side of the isosceles trapezoidal portion (22) is located at one end of the isosceles trapezoidal portion (22) close to the center line.

7. A printing screen assembly for semiconductor encapsulation according to claim 6, wherein: The width of the rectangular portion (21) is greater than the width of the corresponding pad (4), and the short side of the isosceles trapezoidal portion (22) is less than the width of the corresponding pad (4).

8. A printing screen assembly for semiconductor encapsulation according to claim 1, wherein: The ratio of the cross-sectional area of the screen hole (2) to the area of the inner side wall of the screen hole (2) is between 0.5-2.

9. The printing screen assembly for semiconductor packaging of claim 1, wherein: The coefficient k is greater than 1.2 and less than 1.9.

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