Substrate packaging method

Abstract

The invention relates to a substrate packaging method which comprises the steps that a substrate is provided, the substrate is provided with a first face and a second face which are opposite to each other, a welding area is selected on the substrate, and the first face of the welding area is used for chip welding; the substrate is baked; an upper steel plate is provided, the second face of the upper steel plate is provided with a protruding first pressing face, the first pressing face of the upper steel plate is used for pressing the first face of the welding area, and a concave part which is concave towards the second face is formed on the first face of the welding area; and after exposing and developing the substrate, carrying out a back-end process of manufacturing the substrate, and then welding the chip on the concave part of the welding area. According to the invention, the concave part can be pressed on the substrate after baking, so that the concave part is more attached to the chip during welding of the substrate and the chip, and the success rate of welding is improved.

Description

Technical Field

[0001] The present invention relates to a semiconductor packaging method, and in particular to a substrate packaging method. Background Art

[0002] The description in this section merely provides background information related to the present disclosure and may not constitute prior art.

[0003] During the substrate packaging process, after the substrate is fabricated, the chip is soldered to its soldering area. However, due to differences in thermal expansion and internal stress release within the chip itself, the bare chip often sags in the center, forming a concave profile. This prevents the solder balls at the bottom of the chip from contacting the substrate, especially at the sides of the chip, where gaps form between the solder balls and the substrate. Similarly, during processing, the substrate itself may bulge in the opposite direction of the chip, further increasing these gaps and preventing the solder balls from contacting the substrate surface, leading to solder failure.

[0004] It should be noted that the above technical background is merely provided to provide a clear and complete description of the technical solutions of the present invention and to facilitate understanding by those skilled in the art. Simply because these solutions are described in the technical background section of the present invention, it should not be assumed that the above technical solutions are well known to those skilled in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a substrate packaging method, which can press a concave portion on the substrate after baking, so that it can fit the chip better during welding and improve the success rate of welding.

[0006] In order to achieve the above object, the present invention discloses the following substrate packaging method, which includes the following steps:

[0007] Providing a substrate having a first surface and a second surface opposite to each other, selecting a welding area on the substrate, wherein the first surface of the welding area is used for chip welding;

[0008] baking the substrate;

[0009] Providing an upper steel plate, wherein the second surface of the upper steel plate has a convex first pressing surface, and pressing the first pressing surface of the upper steel plate against the first surface of the welding area so that the first surface of the welding area forms a concave portion concave toward the second surface;

[0010] After the substrate is exposed and developed, the back-end process of substrate production is carried out, and then the chip is welded on the concave portion of the welding area.

[0011] As a further description of the above technical solution, in the step of "providing an upper steel plate, the second surface of the upper steel plate having a convex first pressing surface, and pressing the first pressing surface of the upper steel plate against the first surface of the welding area so that the first surface of the welding area forms a concave portion concave toward the second surface", a lower steel plate is simultaneously provided, the first surface of the lower steel plate having an inwardly concave second pressing surface, and pressing the second pressing surface of the lower steel plate against the second surface of the welding area so that the second surface of the welding area forms a convex portion convex away from the first surface.

[0012] As a further description of the above technical solution, the first pressing surface and the second pressing surface have the same size, and the concave portion and the convex portion have the same size.

[0013] As a further description of the above technical solution, the first pressing surface includes a first section, a second section, and a third section arranged in a continuous manner, the first section and the third section are inclined surfaces, and the second section is a plane; the second pressing surface includes a fourth section, a fifth section, and a sixth section arranged in a continuous manner, the fourth section and the sixth section are inclined surfaces, and the fifth section is a plane.

[0014] As a further description of the above technical solution, the first section and the third section of the first pressing surface are set as arc-shaped inclined surfaces, and the first section and the third section of the first pressing surface are naturally and smoothly transitioned to the edges corresponding to the second section; the fourth section and the sixth section of the second pressing surface are set as arc-shaped inclined surfaces, and the fourth section and the sixth section of the second pressing surface are naturally and smoothly transitioned to the edges corresponding to the fifth section.

[0015] As a further description of the above technical solution, before the step of "baking the substrate", the steps of green paint pre-treatment and green paint coating on the substrate are also included.

[0016] As a further description of the above technical solution, in the step of "pressing the first pressing surface of the upper steel plate against the first surface of the welding area", when the green paint type is a dry film, the pressing pressure is 1.5-2.0 MPa; when the green paint type is a wet film, the pressing pressure is 0.8-1.5 MPa.

[0017] As a further description of the above technical solution, in the step of "selecting a welding area on the substrate, wherein the first surface of the welding area is used for chip welding", the horizontal projection of the welding area at least covers the horizontal projection of all the chips.

[0018] By means of the above technical solution, the beneficial effects of the present invention are as follows:

[0019] The substrate packaging method of the present invention can create a concave portion on the substrate after baking, allowing it to better fit the chip during soldering, thereby improving the success rate of soldering. Specifically, to prevent separation between the two sides of the substrate and the chip during subsequent soldering, the corresponding areas of the substrate can be pre-pressed to form a concave portion that better fits the solder balls on the bottom surface of the chip. This avoids the problem of misalignment caused by the reverse curvature of the original chip or substrate, and improves the soldering yield rate.

[0020] To further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are only for reference and illustration and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0022] Figure 1 This is a schematic diagram of pressing the upper steel plate and the lower steel plate of a substrate packaging method provided in an embodiment of this specification;

[0023] Figure 2 This is a schematic diagram of green paint pre-treatment of a substrate packaging method provided in an embodiment of this specification;

[0024] Figure 3 This is a schematic diagram of green paint coating and baking of a substrate packaging method provided in an embodiment of this specification;

[0025] Figure 4 This is a schematic diagram of a pressing method for a substrate packaging method provided in an embodiment of this specification;

[0026] Figure 5 This is a schematic diagram of exposure and development of a substrate packaging method provided by an embodiment of this specification;

[0027] Figure 6 This is a comparative example provided in the embodiments of this specification;

[0028] In the picture:

[0029] 1. Substrate; 11. Welding area; 12. Concave portion; 13. Concave portion;

[0030] 2. Upper steel plate; 21. First section; 22. Second section; 23. Third section;

[0031] 3. Lower steel plate; 31. Fourth section surface; 32. Fifth section surface; 33. Sixth section surface;

[0032] 4. Chip. DETAILED DESCRIPTION

[0033] To help those skilled in the art better understand the technical solutions in this specification, the following will provide a clear and complete description of the technical solutions in the embodiments of this specification, in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of this specification, not all of them. All other embodiments derived by those skilled in the art based on the embodiments in this specification without creative effort shall fall within the scope of protection of this specification.

[0034] The following is an explanation of the embodiments of the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. In addition, the drawings of the present invention are only simple schematic illustrations and are not depicted according to actual dimensions. It is stated in advance. The following embodiments will further explain the relevant technical contents of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention.

[0035] It should be understood that although terms such as "first," "second," and "third" may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are primarily used to distinguish one component from another, or one signal from another. In addition, the term "or" as used herein may include any one or more combinations of the associated listed items, as appropriate.

[0036] See Figure 1-5 , is a substrate packaging method of this embodiment, wherein the substrate packaging method includes:

[0037] A substrate 1 is provided, wherein the substrate 1 has a first surface and a second surface opposite to each other, and a welding area 11 is selected on the substrate 1, wherein the first surface of the welding area 11 is used for welding the chip 4;

[0038] Baking the substrate 1;

[0039] Providing an upper steel plate 2, wherein the second surface of the upper steel plate 2 has a convex first pressing surface, and pressing the first pressing surface of the upper steel plate 2 against the first surface of the welding area 11, so that the first surface of the welding area 11 forms a concave portion 12 that is concave toward the second surface;

[0040] After the substrate 1 is exposed and developed, the back-end process of manufacturing the substrate 1 is carried out, and then the chip 4 is welded to the concave portion 12 of the welding area.

[0041] Specifically, the processing steps of the specific substrate 1 can be found in Figure 2-5 ; Among them, Figure 2 In the process, the substrate is pre-treated with green paint to clean the surface of the substrate and remove oil, dust and impurities to ensure that the green paint and other materials in the next step can adhere firmly and improve the yield rate of subsequent processes; Figure 3 In the process of green paint coating, a layer of green insulating protective paint is applied on the surface of the substrate 1. The green paint can be in the form of dry film or wet film to protect the circuit, prevent oxidation, and insulate, and to prepare for subsequent pattern development. The green paint on the substrate 1 is then preliminarily heated by heating and baking the substrate 1 to allow the green paint to be preliminarily solidified. Figure 4 For the steps of pressing the substrate 1, please refer to Figure 1 , the welding area 11 of the substrate 1 can be pressed by means of the upper steel plate 2 with a convex surface. The material strength of the upper steel plate 2 is greater than that of the substrate 1. Under pressure, the area where the welding area 11 of the substrate 1 contacts the first pressing surface of the upper steel plate 2 is deformed, and finally a concave portion matching the shape of the first pressing surface is formed; Figure 5 In order to perform normal exposure and development operations on the substrate 1 after compression deformation, the purpose is to irradiate ultraviolet light to the green paint pattern area on the substrate, so that the green paint in the irradiated area is hardened, and the unexposed soft green paint is washed away with a developer to form a clear pad opening and protection area pattern.

[0042] The aforementioned welding area 11 is actually specifically the C4 area, which is a metal pad array on the package substrate 1 that is precisely aligned with the C4 solder balls (flip chip interconnection solder joints) of the chip 4 .

[0043] In fact, in the above steps, after development and before welding the chip 4, the back-end process of the substrate production also includes the Post+UVCure (post-processing + ultraviolet curing) process, the purpose of which is to make the film of the photosensitive material completely cross-linked and fixed through ultraviolet curing, and to eliminate residual stress through post-processing heating and curing to enhance the stability of the film layer; then, it also includes Router (cutting), processing the substrate 1 into the finished shape, removing the excess area of ​​the frame, and cutting out the required size contour, and then also includes U-ball (solder ball placement), which is to place solder balls on the corresponding welding areas 11 of the substrate 1. Finally, after the welding is completed, the substrate 1 and the like need to be cleaned.

[0044] Based on the above steps of the present invention, a concave portion 12 can be pressed out of the substrate 1 after baking, so that it can better fit the chip 4 during welding with the chip 4, thereby improving the success rate of welding. Specifically, in order to avoid the separation of the two sides of the substrate 1 from the chip 4 during subsequent welding, the corresponding area of ​​the substrate 1 can be pre-pressed starting from the substrate 1, so that it becomes a concave portion 12 that is more in line with the bottom solder ball of the chip 4, thereby avoiding the problem of non-fitting caused by the reverse curvature of the original chip 4 or the substrate 1, and improving the yield rate of welding. At the same time, it is worth noting that the method of pressing with the help of the upper steel plate 2 in the present invention can be achieved with a set of molds, the process is simple, and the physical shaping is stable.

[0045] In another embodiment, see Figure 1 In the step of "providing an upper steel plate 2, wherein the second surface of the upper steel plate 2 has a convex first pressing surface, and pressing the first pressing surface of the upper steel plate 2 against the first surface of the welding area 11 so that the first surface of the welding area 11 forms a concave portion 12 that is concave toward the second surface", a lower steel plate 3 is simultaneously provided, wherein the first surface of the lower steel plate 3 has a concave second pressing surface, and pressing the second pressing surface of the lower steel plate 3 against the second surface of the welding area 11 so that the second surface of the welding area 11 forms a convex portion 13 that is convex away from the first surface. In the case where only the upper steel plate 2 is present to press the substrate 1, it may be difficult to achieve adhesion to the upper steel plate 2 when the bottom of the substrate 1 is still flat. Therefore, with the provision of a lower steel plate 3 at the bottom, the deformation of the substrate 1 can be easily controlled, and the bottom is supported so that the substrate 1 is subjected to forces from top to bottom, making it easier to bend.

[0046] Based on the above embodiment, the first pressing surface and the second pressing surface have the same size, and the concave portion and the convex portion have the same size. Therefore, since the sizes of the upper and lower steel plates match each other, the deformation of the base plate 1 can be made more stable, and the fit between the deformed base plate 1 and the upper and lower steel plates can be improved.

[0047] Furthermore, the first pressing surface includes a first section 21, a second section 22, and a third section 23, which are connected to each other. The first section 21 and the third section 23 are inclined surfaces, and the second section 22 is a plane. The second pressing surface includes a fourth section 31, a fifth section 32, and a sixth section 33, which are connected to each other. The fourth section 31 and the sixth section 33 are inclined surfaces, and the fifth section 32 is a plane. In other words, the steel plate used to press the substrate 1 in this application is a three-section structure, with a flat bottom section and inclined sides, forming a convex structure with inclined transitions on both sides, which is more convenient for the production of molds for the upper steel plate 2 and the lower steel plate 3.

[0048] It is worth noting that, based on the second section surface 22 being a plane and the fifth section surface 32 being a plane, the plane configuration is not only more conducive to the production of steel plate molds, but also more convenient in the welding process, such as Figure 1 As shown, due to the better flat fit, there is a stress directed from both sides to the middle when pressing. In the substrate 1 without the second section 22 being a plane and the fifth section 32 being a plane, especially when the middle section is curved, the stress is dispersed to both sides, which is not conducive to the fit of the solder balls during welding.

[0049] Furthermore, the first and third sections 21, 23 are naturally smoothly transitioned curved slopes, and the fourth and sixth sections 31, 33 are also naturally smoothly transitioned curved slopes. Therefore, the curved shape can better guide the solder ball stress toward the center. In fact, in this embodiment, the height of the concave portion 12 and the convex portion 13 is much lower than the width of their soldering area 11. Therefore, based on the curved shape, when the solder ball is attached, a component of force is generated that converges toward the center.

[0050] Based on the above-mentioned applied pressure, a preset pressing pressure can be set for each specific dry film. On the basis of the preset pressing pressure, a redundant pressure range based on the preset pressing pressure can be set. For example, when the preset pressing pressure to be pressed is 1MPa, a 20% redundant pressure range can be set, that is, a force applied between 1-1.2MPa. Through the above method, it is possible to ensure that the pressing meets the requirements in an extremely precise manner by controlling it within 1.2MPa to avoid unexpected situations caused by excessive force and rigid fracture of the material.

[0051] In another embodiment, in the step of "pressing the first pressing surface of the upper steel plate 2 against the first surface of the welding area 11", when the green paint type is a dry film, the pressing pressure is 1.5-2.0 MPa. In the dry film scenario, high pressure is beneficial to solving the fitting and filling problems; when the green paint type is a wet film, the pressing pressure is 0.8-1.5 MPa. In the wet film scenario, low pressure helps to control fluidity and thickness uniformity.

[0052] In the above embodiment, the horizontal projection of the soldering area 11 at least covers the horizontal projection of the entire chip 4 , which prevents the possibility of solder balls at the edge positions falling out and has a certain redundancy.

[0053] The contents disclosed above are only preferred feasible embodiments of the present invention and do not limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made using the contents of the description and drawings of the present invention are included in the scope of the patent application of the present invention.

[0054] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0055] Although the present application has been described through embodiments, those skilled in the art will appreciate that there are many modifications and variations to the present application without departing from the spirit of the present application. It is intended that the appended embodiments include these modifications and variations without departing from the present application.

Claims

1. A substrate packaging method, characterized in that: The substrate packaging method comprises the following steps: Providing a substrate having a first surface and a second surface opposite to each other, selecting a welding area on the substrate, wherein the first surface of the welding area is used for chip welding; baking the substrate; Providing an upper steel plate, wherein the second surface of the upper steel plate has a convex first pressing surface, and pressing the first pressing surface of the upper steel plate against the first surface of the welding area so that the first surface of the welding area forms a concave portion concave toward the second surface; After the substrate is exposed and developed, the back-end process of substrate production is carried out, and then the chip is welded on the concave portion of the welding area.

2. The substrate packaging method according to claim 1, wherein: In the step of "providing an upper steel plate, wherein the second surface of the upper steel plate has a convex first pressing surface, and pressing the first pressing surface of the upper steel plate against the first surface of the welding area so that the first surface of the welding area forms a concave portion concave toward the second surface", a lower steel plate is simultaneously provided, wherein the first surface of the lower steel plate has a concave second pressing surface, and pressing the second pressing surface of the lower steel plate against the second surface of the welding area so that the second surface of the welding area forms a convex portion convex away from the first surface.

3. The substrate packaging method according to claim 2, wherein: The first pressing surface and the second pressing surface have the same size, and the concave portion and the convex portion have the same size.

4. The substrate packaging method according to claim 3, wherein: The first pressing surface includes a first section surface, a second section surface, and a third section surface that are connected to each other, the first section surface and the third section surface are inclined surfaces, and the second section surface is a plane; the second pressing surface includes a fourth section surface, a fifth section surface, and a sixth section surface that are connected to each other, the fourth section surface and the sixth section surface are inclined surfaces, and the fifth section surface is a plane.

5. The substrate packaging method according to claim 4, wherein: The first section and the third section of the first pressing surface are set as arc-shaped inclined surfaces, and the first section and the third section of the first pressing surface are naturally and smoothly transitioned to the edges corresponding to the second section; the fourth section and the sixth section of the second pressing surface are set as arc-shaped inclined surfaces, and the fourth section and the sixth section of the second pressing surface are naturally and smoothly transitioned to the edges corresponding to the fifth section.

6. The substrate packaging method according to claim 1, wherein: Before the step of "baking the substrate", the steps of pre-treating the substrate with green paint and coating the substrate with green paint are also included.

7. The substrate packaging method according to claim 6, wherein: In the step of "pressing the first pressing surface of the upper steel plate against the first surface of the welding area", when the green paint type is a dry film, the pressing pressure is 1.5-2.0 MPa; when the green paint type is a wet film, the pressing pressure is 0.8-1.5 MPa.

8. The substrate packaging method according to claim 1, wherein: In the step of "selecting a welding area on the substrate, wherein the first surface of the welding area is used for chip welding", the horizontal projection of the welding area at least covers the horizontal projection of all the chips.

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