A substrate packaging method

Abstract

The present application relates to a kind of substrate packaging methods, wherein substrate packaging method includes providing substrate, the substrate has opposite first face and second face, select welding area on substrate, the first face of the welding area is used for chip welding;The substrate is baked;Provide upper steel plate, the second face of the upper steel plate has protruding first pressing surface, the first pressing surface of the upper steel plate is pressed to the first face of the welding area, so that the first face of the welding area forms the concave portion recessed to the second face;After the substrate is exposed, developed, after substrate manufacturing back-end process, then the chip is welded on the concave portion of the welding area.The present application can be pressed out concave portion by being baked to the substrate, so that it is more consistent with chip in the welding of chip, improve the success rate of welding.

Description

Technical Field

[0001] This invention relates to a semiconductor packaging method, and more particularly to a substrate packaging method. Background Technology

[0002] The description in this section provides only background information related to the disclosure of this invention and does not constitute prior art.

[0003] In the substrate packaging process, after the substrate is fabricated, the soldering areas of the substrate are typically soldered to the chip. However, due to differences in material thermal expansion and internal stress release, the bare chip often has a concave profile at its center, causing the solder balls on the bottom of the chip to fail to contact the substrate, especially the solder balls on the sides of the chip, where gaps exist between them and the substrate. Similarly, during actual processing, the substrate itself may also have protrusions in the opposite direction to the chip, further increasing the gaps on the sides, preventing the solder balls from contacting the substrate surface, leading to soldering failure.

[0004] It should be noted that the above description of the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of the present invention and facilitating understanding by those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because they have been described in the background section of this invention. Summary of the Invention

[0005] The purpose of this invention is to provide a substrate packaging method that can press concave portions into the substrate after baking, so that it fits the chip better during soldering, thereby improving the success rate of soldering.

[0006] To achieve the above objectives, the present invention discloses a substrate packaging method, which includes the following steps:

[0007] A substrate is provided having opposing first and second surfaces, and a soldering area is selected on the substrate, wherein the first surface of the soldering area is used for chip soldering.

[0008] The substrate is baked;

[0009] An upper steel plate is provided, the second surface of which has a raised first pressing surface. The first pressing surface of the upper steel plate is pressed against the first surface of the welding area, so that the first surface of the welding area forms a concave portion that is recessed into the second surface. At the same time, a lower steel plate is provided, the first surface of which has an inwardly concave second pressing surface. The second pressing surface of the lower steel plate is pressed against the second surface of the welding area, so that the second surface of the welding area forms a convex portion that is raised away from the first surface.

[0010] After the substrate is exposed and developed, the substrate fabrication process is carried out, and then the chip is soldered onto the concave portion of the soldering area.

[0011] The first pressing surface includes a first segment, a second segment, and a third segment that are connected together. The first and third segments are inclined surfaces, and the second segment is a plane. The second pressing surface includes a fourth segment, a fifth segment, and a sixth segment that are connected together. The fourth and sixth segments are inclined surfaces, and the fifth segment is a plane.

[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 and third segments of the first pressing surface are set as arc-shaped inclined surfaces, and the first and third segments of the first pressing surface naturally and smoothly transition to the corresponding edge of the second segment; the fourth and sixth segments of the second pressing surface are set as arc-shaped inclined surfaces, and the fourth and sixth segments of the second pressing surface naturally and smoothly transition to the corresponding edge of the fifth segment.

[0014] As a further description of the above technical solution, before the step of "baking the substrate", the method further includes the steps of pre-treatment of the substrate with green paint and application of green paint.

[0015] 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 dry film, the pressing pressure is 1.5-2.0 MPa; when the green paint type is wet film, the pressing pressure is 0.8-1.5 MPa.

[0016] As a further description of the above technical solution, in the step of "selecting a welding area on the substrate, wherein the first side of the welding area is used for chip welding", the horizontal projection of the welding area at least covers the entire horizontal projection of the chip.

[0017] By employing the above technical solutions, the beneficial effects of the present invention are as follows:

[0018] The substrate packaging method of the present invention can improve the success rate of soldering by pressing concave portions into the substrate after baking, making it fit better with the chip during soldering. Specifically, in order to avoid separation of the substrate from the chip on both sides during subsequent soldering, the corresponding areas of the substrate can be pre-pressed to make them concave portions that fit better with the solder balls on the bottom surface of the chip. This avoids the problem of non-fitting caused by the reverse curvature of the original chip or substrate, and improves the yield of soldering.

[0019] To further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are for reference and illustration only and are not intended to limit the present invention. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the pressing of the upper and lower steel plates in a substrate packaging method provided in the embodiments of this specification;

[0022] Figure 2 This is a schematic diagram of the green paint pretreatment for a substrate packaging method provided in the embodiments of this specification;

[0023] Figure 3 This is a schematic diagram of green paint coating and baking for a substrate packaging method provided in the embodiments of this specification;

[0024] Figure 4 This is a schematic diagram of the pressing of a substrate packaging method provided in the embodiments of this specification;

[0025] Figure 5 This is a schematic diagram of the exposure and development of a substrate packaging method provided in the embodiments of this specification;

[0026] Figure 6 This is a comparative schematic diagram provided in the embodiments of this specification;

[0027] In the picture:

[0028] 1. Substrate; 11. Soldering area; 12. Concave portion; 13. Convex portion;

[0029] 2. Upper steel plate; 21. First section; 22. Second section; 23. Third section;

[0030] 3. Lower steel plate; 31. Fourth section; 32. Fifth section; 33. Sixth section;

[0031] 4. Chip. Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0033] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various 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. Furthermore, the accompanying drawings of the present invention are for simple illustrative purposes only and are not depictions of actual dimensions; this is stated in advance. The following embodiments will further describe the relevant technical content of the present invention in detail, but the disclosed content is not intended to limit the scope of protection of the present invention.

[0034] It should be understood that while terms such as "first," "second," and "third" may be used in this document 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. Furthermore, the term "or" as used herein should, as appropriate, include any combination of one or more of the related listed items.

[0035] Please see Figure 1-5 This embodiment provides a substrate packaging method, wherein the substrate packaging method includes:

[0036] A substrate 1 is provided, the substrate 1 having a first side and a second side opposite to each other, and a soldering area 11 is selected on the substrate 1, the first side of the soldering area 11 being used for soldering the chip 4.

[0037] The substrate 1 is baked;

[0038] An upper steel plate 2 is provided, the second side of which has a raised first pressing surface. The first pressing surface of the upper steel plate 2 is pressed 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 recessed into the second surface.

[0039] After the substrate 1 is exposed and developed, the substrate 1 fabrication process is carried out, and then the chip 4 is soldered onto the concave portion 12 of the soldering area.

[0040] Specifically, the processing steps of the specific substrate 1 can be found in [reference needed]. Figure 2-5Among them, in Figure 2 In the process, the substrate undergoes a pretreatment for green paint, cleaning the substrate surface to remove oil, dust, and impurities, ensuring that subsequent green paint and other materials can adhere firmly and improving the yield of subsequent processes; Figure 3 In the process of applying green paint, a layer of green insulating protective paint is coated on the surface of substrate 1. This can be in the form of a dry film or a wet film. The paint serves to protect the circuitry, prevent oxidation, provide insulation, and prepare for subsequent pattern development. Then, the green paint on substrate 1 is initially heated and baked to allow it to partially cure. Figure 4 For details on the pressing step of substrate 1, please refer to [link / reference needed]. Figure 1 The welding area 11 of the substrate 1 can be pressed by an upper steel plate 2 with a raised 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 deforms, ultimately forming a concave portion that matches the shape of the first pressing surface; Figure 5 In order to perform normal exposure and development operations on the substrate 1 after pressing and deformation, the purpose is to irradiate the green paint pattern area on the substrate with ultraviolet light, so that the green paint in the irradiated area hardens, and the unexposed soft green paint is washed away with developer to form clear pad openings and protective area patterns.

[0041] The aforementioned soldering area 11 is actually the C4 area, which is an array of metal pads on the packaging substrate 1 that are precisely aligned with the C4 solder balls (flip-chip interconnect solder joints) of the chip 4.

[0042] In fact, in the above steps, after development and before soldering chip 4, the substrate fabrication process also includes Post+UVCure (post-processing + ultraviolet curing) process. The purpose is to use ultraviolet curing to completely cross-link and shape the photosensitive material film, and to eliminate residual stress and enhance film stability through post-processing heating and curing. Then, it also includes Router (cutting) to process the substrate 1 into the finished shape, remove excess areas of the border, and cut out the required size outline. Then, it also includes U-ball (solder ball mounting), which involves mounting solder balls in the corresponding soldering area 11 of the substrate 1. Finally, after the soldering is completed, the substrate 1 and other components need to be cleaned.

[0043] Based on the above steps of the present invention, by pressing a concave portion 12 into the substrate 1 after baking, it can better fit the chip 4 during soldering, thereby improving the soldering success rate. Specifically, to avoid separation between the sides of the substrate 1 and the chip 4 during subsequent soldering, the corresponding area of ​​the substrate 1 can be pre-pressed to make it a concave portion 12 that fits better with the solder balls on the bottom surface of the chip 4. This avoids the problem of non-fitting caused by the original reverse curvature of the chip 4 or the substrate 1, thus improving the soldering yield. It is also worth noting that the pressing method using the upper steel plate 2 in the present invention can be achieved with just one mold, resulting in a simple process and stable physical shaping.

[0044] In another embodiment, please refer to Figure 1 In the step of "providing an upper steel plate 2, the second surface of which has a raised 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 recessed into the second surface", a lower steel plate 3 is simultaneously provided. The first surface of the lower steel plate 3 has an inwardly 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 raised away from the first surface. Where only the upper steel plate 2 is used to press the substrate 1, and the substrate 1 is still flat at the bottom, it may be difficult to achieve proper adhesion to the upper steel plate 2. Therefore, by using a lower steel plate 3 at the bottom, the deformation of the substrate 1 can be more easily controlled, and by supporting its bottom, the substrate 1 is subjected to vertical force, making it easier to bend.

[0045] Based on the above embodiments, the first pressing surface and the second pressing surface have the same dimensions, and the concave portion and the convex portion have the same dimensions. Therefore, since the dimensions of the upper and lower steel plates are matched, the deformation of the substrate 1 can be stabilized, and the fit between the deformed substrate 1 and the upper and lower steel plates is better.

[0046] Furthermore, the first pressing surface includes a first segment 21, a second segment 22, and a third segment 23 connected together, wherein the first segment 21 and the third segment 23 are inclined surfaces, and the second segment 22 is a plane; the second pressing surface includes a fourth segment 31, a fifth segment 32, and a sixth segment 33 connected together, wherein the fourth segment 31 and the sixth segment 33 are inclined surfaces, and the fifth segment 32 is a plane. In other words, the steel plate used to press the substrate 1 in this application is composed of three segments, with a flat bottom and inclined sides, forming a convex structure with inclined transitions on both sides, which facilitates the mold production of the upper steel plate 2 and the lower steel plate 3.

[0047] It is worth noting that, based on the aforementioned second section surface 22 being planar and fifth section surface 32 being planar, its planar configuration is not only more conducive to the production of steel plate molds, but also in the welding process, such as Figure 1 As shown, due to the better planar fit, there is a stress that is guided from both sides to the middle when pressed. In the substrate 1 where the second section 22 is flat and the fifth section 32 is flat, especially when the middle section is arc-shaped, the stress is dispersed to both sides, which is not conducive to the bonding of the solder balls during soldering.

[0048] Furthermore, the first segment 21 and the third segment 23 mentioned above are naturally smooth transitioning arc-shaped slopes, and the fourth segment 31 and the sixth segment 33 are naturally smooth transitioning arc-shaped slopes. Therefore, the arc shape can better guide the stress of the solder ball towards the center position. 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 arc shape, when in contact with the solder ball, a component force converging towards the center can be generated.

[0049] Based on the above-mentioned 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, the force applied between 1-1.2MPa. Through the above method, it is possible to ensure that the pressing meets the requirements and control it within 1.2MPa to avoid unexpected situations such as material rigidity fracture due to excessive force.

[0050] 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 dry film, the pressing pressure is 1.5-2.0 MPa. In the dry film scenario, high pressure is beneficial to solve the bonding and filling problems; when the green paint type is wet film, the pressing pressure is 0.8-1.5 MPa. In the wet film scenario, low pressure helps to control the flowability and thickness uniformity.

[0051] In the above embodiments, the horizontal projection of the soldering area 11 at least covers the entire horizontal projection of the chip 4, which avoids the possibility of solder balls coming out at the edge and has a certain amount of redundancy.

[0052] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention specification and drawings are included in the scope of the patent application of the present invention.

[0053] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0054] Although this application has been described by way of examples, those skilled in the art will know that this application has many modifications and variations without departing from the spirit of this application, and it is intended that the appended embodiments include these modifications and variations without departing from this application.

Claims

1. A substrate packaging method, characterized in that, The substrate packaging method includes the following steps: A substrate is provided having opposing first and second surfaces, and a soldering area is selected on the substrate, wherein the first surface of the soldering area is used for chip soldering. The substrate is baked; An upper steel plate is provided, the second surface of which has a raised first pressing surface. The first pressing surface of the upper steel plate is pressed against the first surface of the welding area, so that the first surface of the welding area forms a concave portion that is recessed into the second surface. At the same time, a lower steel plate is provided, the first surface of which has an inwardly concave second pressing surface. The second pressing surface of the lower steel plate is pressed against the second surface of the welding area, so that the second surface of the welding area forms a convex portion that is raised away from the first surface. After the substrate is exposed and developed, the substrate fabrication process is carried out, and then the chip is soldered onto the concave portion of the soldering area. The first pressing surface includes a first segment, a second segment, and a third segment that are connected together. The first and third segments are inclined surfaces, and the second segment is a plane. The second pressing surface includes a fourth segment, a fifth segment, and a sixth segment that are connected together. The fourth and sixth segments are inclined surfaces, and the fifth segment is a plane.

2. The substrate packaging method according to claim 1, characterized in that: The first pressing surface and the second pressing surface have the same dimensions, and the concave portion and the convex portion have the same dimensions.

3. The substrate packaging method according to claim 1, characterized in that: The first and third segments of the first pressing surface are set as curved slopes, and the first and third segments of the first pressing surface naturally and smoothly transition to the corresponding edges of the second segment; the fourth and sixth segments of the second pressing surface are set as curved slopes, and the fourth and sixth segments of the second pressing surface naturally and smoothly transition to the corresponding edges of the fifth segment.

4. The substrate packaging method according to claim 1, characterized in that: Before the step of "baking the substrate", the method further includes the steps of pretreatment of the substrate with green paint and application of green paint.

5. The substrate packaging method according to claim 4, characterized in that: 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 dry film, the pressing pressure is 1.5-2.0 MPa; when the green paint type is wet film, the pressing pressure is 0.8-1.5 MPa.

6. The substrate packaging method according to claim 1, characterized in that: In the step "selecting a soldering area on the substrate, the first side of the soldering area being used for chip soldering", the horizontal projection of the soldering area at least covers the entire horizontal projection of the chip.

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