LED packaging module and manufacturing method thereof

Abstract

According to the LED packaging module and the manufacturing method thereof disclosed by the invention, the LED packaging module realizes light reflection by utilizing the second surface of the conducting strip layer, so that the light utilization rate of emergent light of the LED chip is enhanced. Meanwhile, heat dissipation can be improved through the conducting strip layer, isolation of the two electrodes of the LED chip is achieved through patterning of the conducting strip layer, and the conducting strip layer is further provided with an upward bending part at the first interval position, so that soldering tin is prevented from flowing towards the opposite electrodes, and the joint reliability is further guaranteed.

Description

Technical Field

[0001] This invention relates to the field of light-emitting diode (LED) packaging and display, and more specifically to an LED packaging module and its manufacturing method. Background Technology

[0002] In LED chip-scale packaging (CSP), during actual soldering, due to the small electrode area and fewer solder layers, the pull force may be insufficient; at the same time, due to the flow of the solder layers, there may be a risk of short circuit between the positive and negative electrodes. Summary of the Invention

[0003] To address the aforementioned issues, this application provides an LED packaging module with improved welding reliability and the ability to mitigate short-circuit risks. It utilizes conductive layers to enhance the flexibility of electrical interconnections and forms a first protrusion through a first spacing within the conductive layers to prevent short circuits, as detailed below: This application provides an LED packaging module, comprising: a circuit board including an insulating substrate and a conductive sheet layer bonded to the insulating substrate; the circuit board including a plurality of sub-regions arranged in an array; each sub-region including a central region and an edge region surrounding the central region; the conductive sheet layer including a raised edge portion in the edge region and a planar portion in the central region, the raised edge portion being raised relative to the planar portion in a direction away from the insulating substrate; within each sub-region, the conductive sheet layer including a first conductive sheet and a second conductive sheet disposed at an insulating distance, the first conductive sheet and the second conductive sheet having a first gap between them; the first conductive sheet and the second conductive sheet on both sides of the first gap having curved portions raised in a direction away from the insulating substrate; a plurality of LED chips, correspondingly disposed on the planar portions of the plurality of sub-regions; the LED chips spanning the first gap and electrically connected to the first conductive sheet and the second conductive sheet respectively, and at least a portion of the curved portions being located directly below the LED chips; and a sealing layer disposed on the circuit board and sealing the LED chips.

[0004] The beneficial effects of the above embodiments are as follows: (1) The second surface of the conductive sheet layer is used to realize light reflection, thereby enhancing the light utilization rate of the LED chip. (2) The conductive sheet layer of this application can improve heat dissipation, and the patterning of the conductive sheet layer is used to realize the isolation of the two electrodes of the LED chip. In addition, at the first interval position, the conductive sheet layer also has an upward bending portion, thereby preventing solder from flowing to the opposite electrode position and further ensuring the reliability of the connection.

[0005] Furthermore, this application also discloses a method for manufacturing an LED packaging module, which includes the following steps: (1) prefabricating a circuit board, the circuit board including an insulating substrate and a conductive sheet layer bonded to the insulating substrate, the circuit board including a plurality of sub-regions arranged in an array; each sub-region including a central region and an edge region surrounding the central region, the conductive sheet layer including a raised edge portion in the edge region and a planar portion in the central region, the raised edge portion being raised in a direction away from the insulating substrate relative to the planar portion; in each sub-region, the conductive sheet layer including a first conductive sheet and a second conductive sheet disposed with an insulating gap, the first conductive sheet and the second conductive sheet having a first gap; the first conductive sheet and the second conductive sheet on both sides of the first gap having a first curved portion raised in a direction away from the insulating substrate; (2) soldering a plurality of LED chips one-to-one onto the planar portions of the plurality of sub-regions; the LED chips span the first gap and are electrically connected to the first conductive sheet and the second conductive sheet respectively, and at least a portion of the first curved portion is located directly below the LED chip; (3) forming a sealing layer, the sealing layer being disposed on the circuit board and sealing the LED chips.

[0006] This invention utilizes a mold to hot-press and form a reflective (curved edge) and electrically isolated (bent part) structure, while combining the thermoplasticity of the upper insulating substrate, resulting in a simple, low-cost, and highly reliable solution. Attached Figure Description

[0007] 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.

[0008] Figure 1 This is a top view of the circuit board of this application; Figure 2 For along Figure 1 A cross-sectional view of line A1A2; Figure 3 For along Figure 1 A cross-sectional view of line B1B2; Figure 4-7 A schematic diagram of the process for fabricating the circuit board of this application; Figure 8 This is a top view of the LED packaging module of this application; Figure 9 This is a cross-sectional view of the LED packaging module of this application; Figure 10-12A schematic diagram of the process for preparing the LED packaging module of this application; Figure 13 This is a top view of the display device of this application.

[0009] Explanation of reference numerals in the attached figures: 10. Insulating substrate; 11. Substrate layer; 12. Adhesive layer; 121. First protrusion; 122. Second protrusion; 20. Conductive sheet layer; 21. First conductive sheet; 22. Second conductive sheet; 23. First bent portion; 24. Second bent portion; 201. First spacer; 202. Second spacer; 30. LED chip; 31. First electrode; 32. Second electrode; 40. Conductive via; 50. Sealing layer; 60. Driver circuit board; 70. Joint; 80. Temporary carrier board; 90. Mold. Detailed Implementation

[0010] The following detailed description of the embodiments of this application, in conjunction with the accompanying drawings, will provide a thorough understanding of how this application uses technical means to solve technical problems and achieve corresponding technical effects, enabling its implementation. The embodiments of this application and the various features within them can be combined with each other without conflict, and the resulting technical solutions are all within the protection scope of this application. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. The same reference numerals denote the same elements throughout.

[0011] It should be understood that although the terms "first," "second," "third," etc., may be used to describe various elements, components, areas, layers, and / or parts, these elements, components, areas, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or part from another element, component, area, layer, or part. Therefore, without departing from the teachings of this application, the first element, component, area, layer, or part discussed below may be referred to as the second element, component, area, layer, or part.

[0012] It should be understood that spatial relation terms such as "above," "located above," "below," "located below," etc., are used herein for convenience of description to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, then the element or feature described as "below other elements" will be oriented "above" other elements or features. Therefore, the exemplary terms "below" and "below" can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or otherwise) and the spatial descriptive terms used herein will be interpreted accordingly.

[0013] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising” and / or “including,” when used in this specification, identify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0014] Embodiments of this application are described herein with reference to cross-sectional views illustrating ideal embodiments (and intermediate structures). Thus, variations in the shape shown can be anticipated due to, for example, fabrication techniques and / or tolerances. Therefore, embodiments of this application should not be limited to the specific shape of the region shown herein, but should include shape deviations due to, for example, fabrication processes.

[0015] To fully understand this application, detailed structures and steps will be presented in the following description to illustrate the technical solutions proposed in this application. Preferred embodiments of this application are described in detail below; however, in addition to these detailed descriptions, this application may have other implementation methods.

[0016] See details Figure 1 , Figure 2 and Figure 3 To ensure the reliability of LED chip soldering and improve the utilization rate of LED chip light output, this application designs a circuit board, which includes at least an insulating substrate 10 and a conductive sheet layer 20 attached to the insulating substrate 10. The conductive sheet layer 20 can be fixed to the insulating substrate 10 by adhesive bonding. The insulating substrate 10 can be a polymer board with a total thickness of 100-500 micrometers, primarily made of waterproof and insulating organic polymer material. Preferably, see [reference needed]. Figure 2 The insulating substrate 10 includes a two-layer structure, consisting of a substrate layer 11 and an adhesive layer 12, wherein the adhesive layer 12 is disposed between the substrate layer 11 and the conductive sheet layer 20. The substrate layer 11 can be made of a supporting material such as PI, EVA, or POE, with a thickness between 80 and 400 micrometers. The adhesive layer 12 is made of a thermoplastic material, such as low-crosslinked EVA or thermoplastic epoxy resin, with a thickness between 50 and 120 micrometers (excluding the positions with the first and second protrusions). The thermoplastic material becomes adhesive after heating, allowing it to bond the conductive sheet layer.

[0017] The adhesive layer 12 and the substrate layer 11 can be pre-bonded, and the two can be formed into the insulating substrate 10 by a hot pressing process. In particular, the insulating substrate 10 can be patterned by mechanical or etching methods, and it has a certain degree of flexibility, so that the final LED packaging module has a certain degree of flexibility and can be bent.

[0018] like Figure 1 As shown, the conductive sheet layer 20 is made of a relatively thin metal sheet, for example, between 100-300 micrometers, specifically 100 micrometers, 150 micrometers, 200 micrometers, 250 micrometers, and 300 micrometers. The conductive sheet layer 20 is formed by mechanical die casting or laser processing, etc., into a first conductive sheet 21 and a second conductive sheet 22 that are separated. The first conductive sheet 21 can be connected to either the positive or negative electrode of the LED chip, while the second conductive sheet 22 can be connected to the other of the positive or negative electrode of the LED chip. The reflectivity of the side of the conductive sheet layer 20 away from the insulating substrate 10 (hereinafter referred to as the top surface) is greater than that of the side facing away from the insulating substrate 10 (hereinafter referred to as the back surface). That is, the roughness of the top surface of the conductive sheet layer 20 is less than that of its back surface. This allows for better reflection on the top surface, increasing the light utilization rate of the LED chip. Simultaneously, the greater roughness of the back surface ensures adhesion to the adhesive layer 12, preventing peeling problems. In particular, the side of the conductive sheet 20 away from the insulating substrate 10 can be polished.

[0019] The conductive layer 20 on the circuit board is divided into multiple sub-regions (also called packaging units, such as...) Figure 1 The system comprises multiple square regions divided by boundary lines and a central dashed line, each sub-region used to house at least one LED chip. Each sub-region includes a first conductive sheet 21 and a second conductive sheet 22 separated by an isolation portion. (See also...) Figure 2 and Figure 3 Each sub-region has a first spacing 201 and a second spacing 202 between the first conductive sheet 21 and the second conductive sheet 22, wherein the width between the first spacings 201 is smaller than the width between the second spacings 202. Firstly, the narrower first spacing 201 can match the smaller spacing between the positive and negative electrodes of the LED chip, facilitating soldering. Secondly, the larger second spacing 202 can easily ensure that the adhesive layer 12 is embedded within the spacing of the conductive sheet layer 20, preventing the conductive sheet layer 202 from peeling off from the insulating substrate 10. Thirdly, the larger second spacing 202 can prevent excessive adhesive layer material from covering the top surface of the conductive sheet layer 20 during circuit board fabrication, thereby reducing the reflection effect of the top surface. Finally, the smaller first spacing 201 can ensure that the adhesive layer material can effectively form the first protrusion 121 during circuit board fabrication, ensuring electrical isolation during LED chip positive and negative electrode soldering.

[0020] Further, see Figure 2 and Figure 3 Each sub-region includes a central region and an edge region surrounding the central region. The conductive sheet layer 20 has a raised edge portion in the edge region and a flat portion in the central region, the raised edge portion being raised relative to the flat portion in a direction away from the insulating substrate. Within each sub-region, the first conductive sheet 21 and the second conductive sheet 22 on both sides of the first interval 201 have a first curved portion 23 that is raised in a direction away from the insulating substrate 10, and the first conductive sheet 21 and the second conductive sheet 22 on both sides of the second interval 202 have a second curved portion 24 that is raised in a direction away from the insulating substrate 10. The heights of the first curved portion 23 and the second curved portion 24 are approximately the same.

[0021] See Figure 2 The adhesive layer 12 between the first intervals 201 protrudes upward to form a first protrusion 121. The cross-section of the first protrusion 121 is arched, and the top of the first protrusion 121 is higher than the top surface of the conductive sheet layer 20, thereby ensuring electrical isolation during the soldering of the positive and negative electrodes of the LED chip. Specifically, the top of the first protrusion 121 is higher than the highest point of the first curved portion 23, generally by more than 100 micrometers.

[0022] See Figure 3 The adhesive layer 12 between the second intervals 202 protrudes upward to form a second protrusion 122. The cross-section of the second protrusion 122 is also arched, and the top of the second protrusion 122 is lower than the top of the first protrusion 121. This ensures adhesion while preventing the second protrusion 122 from flowing onto the top surface of the conductive sheet layer 20 and causing a decrease in reflectivity. Furthermore, the top of the second protrusion 122 can be lower than the highest position of the second curved portion 24. The first protrusion 121 and the second protrusion 122 are integrally formed with the adhesive layer 12 without a dividing line.

[0023] See Figure 1 The first conductive sheet 21 has a protruding portion facing the second conductive sheet 22, and the second conductive sheet 22 has a recessed portion to accommodate the protruding portion. The minimum distance between the protruding portion of the first conductive sheet 21 and the recessed portion of the second conductive sheet 22 constitutes the first interval 201, which facilitates the differentiation of positive and negative conductive sheets and allows for convenient positioning of the LED chip. The second interval 202 can be formed in the area outside the protruding and recessed portions.

[0024] The circuit board manufacturing process can be found in [reference needed]. Figure 4-7 First, a conductive sheet layer 20 is laid flat on a rigid temporary carrier plate 80, see [reference]. Figure 4Then, the conductive sheet portion of the isolation section is removed using a stamping process to form a patterned conductive sheet 20, thereby forming a first conductive sheet 21 and a second conductive sheet 22 separated by a first interval 201 and a second interval 202, see [reference]. Figure 5 Next, the conductive sheet layer 20 is removed from the temporary carrier plate 80 and transferred to the insulating substrate 10. The insulating substrate 10 and the conductive sheet layer 20 are stacked. Specifically, the adhesive layer 12 is bonded to the conductive sheet layer 20, and the substrate layer 11 is disposed on the other side of the adhesive layer 12. Before this, the top surface of the conductive sheet layer 20 can be polished to reduce the roughness of the top surface of the conductive sheet layer 20 and increase the reflectivity. Finally, the adhesive layer 12 is heated until it softens, and the insulating substrate 10 is used as a support and the die 90 is used for hot pressing. The stamping surface morphology of the die 90 is consistent with the top surface morphology of the conductive sheet layer to be formed. It has protrusions to form raised edges and first bent portions 23 and second bent portions 24 in the first conductive sheet 21 and the second conductive sheet 22, respectively. See [reference needed]. Figure 6 Finally, remove mold 90 to obtain the circuit board structure, see [link / reference]. Figure 7 .

[0025] This application also provides an LED packaging module based on the above-mentioned circuit board, see reference. Figure 8 and Figure 9 A single LED chip 30 spans the first interval 201, and its positive and negative terminals are respectively bonded to the first conductive sheet 21 and the second conductive sheet 22, for example, by soldering with solder balls. To prevent short circuits caused by solder ball melting during soldering, at least a portion of the first protrusion 121 is disposed directly below the LED chip 30 and separates the positive and negative terminals of the LED chip 30. Of course, multiple LED chips 30 can be disposed in each sub-region, and the multiple LED chips 30 in each sub-region are in a parallel structure.

[0026] In this configuration, at least a portion of the first curved portion 23 is located directly below the LED chip 30, see [reference needed]. Figure 9 In this way, when the two opposite electrodes of the LED chip 30 are joined to the first conductive sheet 21 and the second conductive sheet 22 with solder balls, the solder balls can prevent the material flow of the solder balls from causing a short circuit even when they are molten. At the same time, the first protrusion 121 can also prevent the hot melt flow of the solder balls.

[0027] Furthermore, the planar portion of the conductive sheet layer 20 is used to bond the LED chip 30, and the raised edge portion surrounds the planar portion so that the raised edge portion forms a reflective cup shape to reflect the light emitted by the LED chip, ensuring the light emission efficiency. In addition, the surface roughness of the conductive sheet layer 20 facing the LED chip 30 (top surface) is less than the surface roughness of the side facing away from the LED chip 30 (back surface), thereby improving the top surface reflectivity.

[0028] The LED chip includes a first electrode and a second electrode spaced apart on the same surface. Preferably, the distance between the first electrode and the second electrode is s, and the width of the first distance is d. s and d satisfy 0.6d≤s≤1.5d to ensure the reliability of the electrical interconnection of the LED chip and prevent short circuits during bonding.

[0029] Furthermore, a sealing layer 50 can be provided on the circuit board to seal the multiple LED chips 30 on the circuit board. The sealing layer 50 can be a thermoplastic material or a thermosetting material, such as epoxy resin or silicone. Phosphor material can be distributed within the sealing layer to achieve light conversion.

[0030] Furthermore, the insulating substrate 10 also has a conductive via 40, which is connected to the conductive sheet layer 20, and the other end of which is exposed from the side of the insulating substrate 10 away from the conductive sheet layer. The conductive via 40 is made of metals such as copper and aluminum, and is formed by processes such as electroplating. A joint portion 70 is provided at the exposed position of the conductive via 40, which is used to interconnect other components. It can be a solder ball or a copper pillar.

[0031] For the specific preparation process, please refer to Figure 10-12 First, the LED chip 30 is soldered onto the circuit board using bonding materials such as solder balls. The LED chip 30 spans the first gap 201 and the first protrusion 121, the first protrusion 121 separating the positive and negative electrodes. At least a portion of the first bent portion 23 is positioned directly below the LED chip 30 to isolate the two solder balls (or soldering portions). Figure 10 As shown, the positive and negative terminals of the LED chip 30 are soldered to the first conductive sheet 21 and the second conductive sheet 22 respectively using solder balls. Next, see... Figure 11 A sealing layer 50 is formed on the circuit board by hot pressing or injection molding, covering multiple LED chips 30. Finally, see... Figure 12 Supported by a sealing layer 50, a through-hole penetrating the thickness of the insulating substrate 10 is formed and filled with a conductive material to form a conductive through-hole 40. The conductive material can be copper, aluminum, or other materials. The conductive through-hole 40 is electrically connected to the first conductive sheet 21 and the second conductive sheet 22. One end of the conductive through-hole 40 is connected to the conductive sheet layer 20, and the other end protrudes from the side of the insulating substrate 10 away from the conductive sheet layer 20. Furthermore, a joint portion 70 can be joined at the location where the conductive through-hole 40 protrudes from the insulating substrate 10 for interconnecting other components.

[0032] Further, see Figure 13The present invention also provides a display device, which includes, in addition to the aforementioned LED packaging module, a driving circuit board 60 to which the LED packaging module is bonded. The driving circuit board 60 is connected to the internal LED chip 30 through conductive vias 40 and bonding portions 70, i.e., the driving circuit board 60 is bonded to the circuit board to achieve electrical connection.

[0033] The beneficial effects of the above embodiments are as follows: (1) The second surface of the conductive sheet layer is used to realize light reflection, thereby enhancing the light utilization rate of the LED chip. (2) The conductive sheet layer of this application can improve heat dissipation, and the patterning of the conductive sheet layer is used to realize the isolation of the two electrodes of the LED chip. In addition, at the first interval position, the conductive sheet layer also has an upward bending portion, thereby preventing solder from flowing to the opposite electrode position and further ensuring the reliability of the connection.

[0034] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An LED packaging module, comprising: A circuit board includes an insulating substrate and a conductive sheet layer bonded to the insulating substrate. The circuit board includes a plurality of sub-regions arranged in an array. Each sub-region includes a central region and an edge region surrounding the central region. The conductive sheet layer includes a raised edge portion in the edge region and a planar portion in the central region. The raised edge portion is raised relative to the planar portion in a direction away from the insulating substrate. Within each sub-region, the conductive sheet layer includes a first conductive sheet and a second conductive sheet that are insulatingly spaced apart, with a first gap between the first conductive sheet and the second conductive sheet. The first conductive sheet and the second conductive sheet on both sides of the first gap have a first curved portion that is raised in a direction away from the insulating substrate. Multiple LED chips are disposed one-to-one on the planar portions of the multiple sub-regions; the LED chips span the first interval and are electrically connected to the first conductive sheet and the second conductive sheet respectively, and at least a portion of the first curved portion is located directly below the LED chip; A sealing layer is disposed on the circuit board and seals the LED chip.

2. The LED packaging module according to claim 1, characterized in that, The insulating substrate includes a first protrusion, which is embedded in the first gap, and the highest position of the first protrusion is higher than the highest position of the first bend.

3. The LED packaging module according to claim 1, characterized in that, The first conductive sheet has a protruding portion, and the second conductive sheet has a recessed portion that accommodates the protruding portion. The minimum distance between the protruding portion and the recessed portion constitutes the first interval.

4. The LED packaging module according to claim 2, characterized in that, The insulating substrate includes a base layer and an adhesive layer on the base layer, wherein the first protrusion is integrally formed with the adhesive layer, and the adhesive layer is conformally formed with the conductive sheet layer.

5. The LED packaging module according to claim 1, characterized in that, The LED chip includes a first electrode and a second electrode spaced apart on the same surface, the distance between the first electrode and the second electrode being s, and the width of the first distance being d, wherein 0.6d≤s≤1.5d.

6. The LED packaging module according to claim 1, characterized in that, The height of the warped edge is greater than the height of the first curved portion.

7. The LED packaging module according to claim 1, characterized in that, The conductive sheet includes a first surface that adheres to an insulating substrate and a second surface that bonds to the LED chip, wherein the roughness of the second surface is less than that of the first surface.

8. A method for manufacturing an LED packaging module, comprising the following steps: (1) A prefabricated circuit board is formed, the circuit board including an insulating substrate and a conductive sheet layer bonded to the insulating substrate, the circuit board including a plurality of sub-regions arranged in an array; each sub-region including a central region and an edge region surrounding the central region, the conductive sheet layer having a raised edge portion in the edge region and a planar portion in the central region, the raised edge portion being raised relative to the planar portion in a direction away from the insulating substrate; within each sub-region, the conductive sheet layer includes a first conductive sheet and a second conductive sheet disposed with an insulating gap, the first conductive sheet and the second conductive sheet having a first gap; the first conductive sheet and the second conductive sheet on both sides of the first gap having a first curved portion raised in a direction away from the insulating substrate; (2) A plurality of LED chips are soldered one-to-one in the plurality of sub-regions; the LED chips span the first interval and are electrically connected to the first conductive sheet and the second conductive sheet respectively, and at least a portion of the first bent portion is located directly below the LED chip; (3) A sealing layer is formed, which is disposed on the circuit board and seals the LED chip.

9. The method for manufacturing an LED packaging module according to claim 8, characterized in that, The prefabrication of the circuit board specifically includes: (1) patterning the conductive sheet layer to form the first conductive sheet and the second conductive sheet, and transferring them onto an insulating substrate, the insulating substrate including a thermoplastic adhesive layer, the conductive sheet layer being disposed on the adhesive layer; (2) using a mold with protrusions, hot-pressing the insulating substrate as a support, so that the protrusions of the mold form the warped portion and the first bent portion in the first conductive sheet and the second conductive sheet respectively; (3) removing the mold.

10. The method for manufacturing an LED packaging module according to claim 8, characterized in that, The method also includes step (4): forming a through hole in the insulating substrate and filling it with conductive material to form a conductive through hole connecting the first conductive sheet and the second conductive sheet, wherein the conductive through hole is exposed from the side of the insulating substrate away from the conductive sheet layer.

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