LED package module and manufacturing method thereof

Abstract

The application discloses an LED packaging module and a manufacturing method thereof. The LED packaging module uses a second surface of a conductive sheet layer to reflect light and enhance light utilization of LED chips. Meanwhile, the conductive sheet layer can improve heat dissipation, and the conductive sheet layer is patterned to realize isolation of two electrodes of the LED chip. In addition, the conductive sheet layer has an upward bending part at a first interval position, so as to prevent solder from flowing to a position of a heterogeneous electrode, and further ensure reliability of bonding.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of light emitting diode (LED) packaging display, in particular to an LED packaging module and a manufacturing method thereof. BACKGROUND

[0002] In the Chip-Scale Package (CSP) of the LED chip, the welding layer is less due to the small electrode area during actual welding, and the pulling force may not be enough. At the same time, due to the flow of the welding layer, there may be a risk of short circuit between the positive and negative electrodes. SUMMARY

[0003] In order to solve the above problems, the present application provides an LED packaging module with good welding reliability and short circuit prevention risk avoidance, which uses a conductive sheet layer to improve the flexibility of electrical interconnection, and forms a first protruding part by the first interval of the conductive sheet layer to prevent short circuit, as follows:

[0004] The embodiment of the present application provides an LED packaging module, comprising: a circuit board comprising an insulating substrate and a conductive sheet layer adhered to the insulating substrate, the circuit board comprising a plurality of arrayed sub-regions; each sub-region comprising a middle region and an edge region surrounding the middle region, the conductive sheet layer comprising a warped edge portion in the edge region and a planar portion in the middle region, the warped edge portion being warped in a direction away from the insulating substrate compared to the planar portion; in each sub-region, the conductive sheet layer comprises a first conductive sheet and a second conductive sheet arranged at an insulating interval, the first conductive sheet and the second conductive sheet having a first interval therebetween; the first conductive sheet and the second conductive sheet on both sides of the first interval have a curved portion warped in a direction away from the insulating substrate; a plurality of LED chips are arranged one by one on the planar portions of 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 part of the curved portion is located directly below the LED chip; a sealing layer is arranged on the circuit board and seals the LED chip.

[0005] The beneficial effects of the above embodiment are as follows: (1) the second surface of the conductive sheet layer is used to reflect light, enhancing the light utilization rate of the LED chip light emission. (2) The conductive sheet layer of the present application can improve heat dissipation, and the patterned conductive sheet layer realizes the isolation of the two electrodes of the LED chip, and at the first interval position, the conductive sheet layer also has an upward curved portion to prevent the solder from flowing to the position of the dissimilar electrode, further ensuring the reliability of the bonding.

[0006] Further, the application also discloses a manufacturing method of the LED packaging module, which comprises the following steps: (1) prefabricating a circuit board, wherein the circuit board comprises an insulating substrate and a conductive sheet layer adhered to the insulating substrate, the circuit board comprises a plurality of array-arranged sub-regions; each sub-region comprises a middle region and an edge region surrounding the middle region, the conductive sheet layer comprises a warped edge part in the edge region and a planar part in the middle region, the warped edge part is warped in a direction away from the insulating substrate compared with the planar part; in each sub-region, the conductive sheet layer comprises first and second conductive sheets which are arranged in an insulating manner, and the first and second conductive sheets have a first interval therebetween; the first and second conductive sheets on both sides of the first interval have first bending parts which are warped in a direction away from the insulating substrate; (2) welding a plurality of LED chips one by one on the planar parts of the plurality of sub-regions; the LED chips cross the first interval and are electrically connected to the first and second conductive sheets respectively, and at least a part of the first bending parts is located directly below the LED chips; (3) forming a sealing layer, wherein the sealing layer is arranged on the circuit board and seals the LED chips.

[0007] The application utilizes a mold to heat-press form the light-reflecting (warped edge part) and electrically isolating (bending part) structures, and combines the thermoplasticity of the upper insulating substrate, so that the method is simple, low in cost and high in reliability. BRIEF DESCRIPTION OF DRAWINGS

[0008] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0009] Figure 1 It is a top view of the circuit board of the present application;

[0010] Figure 2 It is a sectional view along the A1A2 line of Figure 1

[0011] Figure 3 It is a sectional view along the B1B2 line of Figure 1

[0012] Figures 4-7 It is a flowchart of preparing the circuit board of the present application;

[0013] Figure 8 It is a top view of the LED packaging module of the present application;

[0014] ​​Figure 9 FIG. 1 is a sectional view of an LED packaging module according to an embodiment of the present application;

[0015] Figures 10-12 FIG. 2 is a flowchart illustrating a process of manufacturing the LED packaging module according to an embodiment of the present application;

[0016] Figure 13 FIG. 3 is a plan view of a display device according to an embodiment of the present application.

[0017] Explanation of Reference Numerals:

[0018] 10: insulating substrate; 11: base layer; 12: adhesive layer; 121: first protrusion; 122: second protrusion; 20: conductive sheet layer; 21: first conductive sheet; 22: second conductive sheet; 23: first curved portion; 24: second curved portion; 201: first interval; 202: second interval; 30: LED chip; 31: first electrode; 32: second electrode; 40: conductive via; 50: sealing layer; 60: driving circuit board; 70: bonding portion; 80: temporary carrier; 90: mold. DETAILED DESCRIPTION

[0019] The embodiments of the present application will be described in detail with reference to the drawings and examples, so that the implementation process of how the present application applies technical means to solve technical problems and achieves corresponding technical effects can be fully understood and implemented. The embodiments of the present application and each feature in the examples can be combined with each other without conflict, and the formed technical solutions are all within the protection scope of the present application. In the drawings, the size and relative size of layers and regions may be exaggerated for clarity. The same reference numerals represent the same elements throughout.

[0020] It should be understood that although the terms "first", "second", "third" and the like can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part without departing from the teachings of the present application.

[0021] It will be understood that the spatially relative terms "above", "upper", "below", "lower", and the like, as used herein, can be used for ease of description to describe the elements as they are oriented in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientations depicted in the figures. For example, if a device described is turned over, then a downwardly facing surface, which was previously facing upward, would then face upward. Thus, the example term "below" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative terms used herein interpreted accordingly.

[0022] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0023] Embodiments of the present application are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the present application. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, embodiments of the present application should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. Embodiments of the present application are described herein with reference to plan

[0024] For a thorough understanding of the present application, reference should be made to the following detailed description, in conjunction with the accompanying drawings, in which:

[0025] With particular reference to Figure 1 , Figure 2 and Figure 3 , in order to ensure the reliability of the welding of LED chips and to provide the utilization rate of the light emitted by the LED chips, the present application designs a circuit board, which at least comprises an insulating substrate 10 and a conductive sheet layer 20 attached to the insulating substrate 10, wherein the conductive sheet layer 20 can be fixed to the insulating substrate 10 by an adhesive method. The insulating substrate 10 can be a polymeric plate with a total thickness of 100-500 microns, which is mainly a waterproof and insulating organic polymer material. Preferably, with reference to Figure 2The insulating substrate 10 comprises a two-layer structure, sequentially a base layer 11 and an adhesive layer 12, wherein the adhesive layer 12 is arranged between the base layer 11 and the conductive sheet layer 20. The material of the base layer 11 can be a supporting material such as PI, EVA, POE, etc., and the thickness thereof is between 80-400 microns; the material of the adhesive layer 12 is a thermoplastic material, for example, a low-crosslinking-degree EVA material, a thermoplastic epoxy resin, etc., and the thickness thereof is between 50-120 microns (excluding the positions with the first and second protruding portions), the thermoplastic material has viscosity after heating and can be used to adhere the conductive sheet layer.

[0026] The adhesive layer 12 and the base layer 11 can be pre-adhered, and the two can form the above-mentioned insulating substrate 10 through a hot-pressing process. In particular, the insulating substrate 10 can be patterned through a mechanical or etching method, and has a certain flexibility, so that the finally prepared LED packaging module has a certain flexibility and can be bent.

[0027] As shown in Figure 1 The thickness of the conductive sheet layer 20 is a small metal sheet, for example, between 100-300 microns, and specifically can be 100 microns, 150 microns, 200 microns, 250 microns, or 300 microns. The conductive sheet layer 20 is formed by mechanical die casting or laser, etc., to have the first and second conductive sheets 21 and 22 which are isolated, wherein the first conductive sheet 21 can be connected to one of the positive or negative poles of the LED chip, and the second conductive sheet 22 can be connected to the other of the positive or negative poles 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 side) is greater than that of the side of the conductive sheet layer 20 facing away from the insulating substrate 10 (hereinafter referred to as the back side), that is, the roughness of the top side of the conductive sheet layer 20 is less than that of the back side, so that the top side reflects light better, increases the light utilization rate of the LED chip, and at the same time, the roughness of the back side is larger, which can ensure the adhesion with the adhesive layer 12 and prevent peeling problems. In particular, the side of the conductive sheet layer 20 away from the insulating substrate 10 can be polished.

[0028] The conductive sheet layer 20 on the circuit board is divided into a plurality of sub-regions (which can also be called packaging units, as shown in Figure 1 The plurality of square regions are divided by the boundary lines and the intermediate dashed lines), and each sub-region is used to arrange at least one LED chip. As shown in Figure 2 and Figure 3, the first conductive sheet 21 and the second conductive sheet 22 in each sub-region have a first interval 201 and a second interval 202, wherein the width between the first intervals 201 is smaller than the width between the second intervals 202. Firstly, the narrower first intervals 201 can match the smaller electrode interval of the LED chip, facilitating the welding; secondly, the larger second intervals 202 can easily ensure that the adhesive layer 12 is embedded in the interval part of the conductive sheet layer 20, preventing the conductive sheet layer 202 from peeling off from the insulating substrate 10; thirdly, the larger second intervals 202 can prevent too much adhesive layer material from covering the top surface of the conductive sheet layer 20 when the circuit board is prepared, thereby reducing the reflection effect of the top surface; finally, the smaller first intervals 201 can ensure that the adhesive layer material can effectively form the first protruding part 121 when the circuit board is prepared, thereby ensuring the electrical isolation of the positive and negative electrodes of the LED chip during welding.

[0029] Further, referring to Figure 2 and Figure 3 , each sub-region includes a middle region and an edge region surrounding the middle region, the conductive sheet layer 20 is in a warped part of the edge region and in a planar part of the middle region, the warped part is warped in a direction away from the insulating substrate compared to the planar part; in 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 part 23 warped 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 part 24 warped in a direction away from the insulating substrate 10. The height of the first curved part 23 and the second curved part 24 is substantially the same.

[0030] Referring to Figure 2 , the adhesive layer 12 between the first intervals 201 is upwardly protruding to form a first protruding part 121, the cross section of the first protruding part 121 is arched, and the top end of the first protruding part 121 is higher than the top surface of the conductive sheet layer 20, thereby ensuring the electrical isolation of the positive and negative electrodes of the LED chip during welding. Specifically, the top end of the first protruding part 121 is higher than the highest position of the first curved part 23, generally needs to be higher than 100 microns.

[0031] Referring to Figure 3 , the adhesive layer 12 between the second intervals 202 is upwardly protruding to form a second protruding part 122, the cross section of the second protruding part 122 is also arched, and the top end of the second protruding part 122 is lower than the top end of the first protruding part 121, thereby ensuring the adhesion while preventing the second protruding part 122 from flowing to the top surface of the conductive sheet layer 20 to cause the reflectivity to decrease. Further, the top end of the second protruding part 122 can be lower than the highest position of the second curved part 24. The first protruding part 121 and the second protruding part 122 are integrally formed with the adhesive layer 12 without a boundary line.

[0032] Referring to 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 accommodating the protruding portion, wherein the minimum spacing portion between the protruding portion of the first conductive sheet 21 and the recessed portion of the second conductive sheet 22 constitutes the first spacing 201, so as to facilitate the differentiation of the positive and negative conductive sheets and facilitate positioning, and the LED chip is arranged at the position. The second spacing 202 can be formed in the area outside the protruding portion and the recessed portion.

[0033] The preparation process of the circuit board can refer to Figures 4-7 . First, the conductive sheet layer 20 is laid on the temporary carrier 80 with rigidity, referring to Figure 4 ; then, the conductive sheet layer portion of the isolation part is removed by stamping process to form a patterned conductive sheet layer 20, so as to form the first conductive sheet 21 and the second conductive sheet 22 separated by the first spacing 201 and the second spacing 202, referring to Figure 5 ; then, the conductive sheet layer 20 is taken off from the temporary carrier 80 and transferred to the insulating substrate 10, and the insulating substrate 10 is stacked with the conductive sheet layer 20, specifically, the adhesive layer 12 is attached with the conductive sheet layer 20, and the base layer 11 is arranged on the other side of the adhesive layer 12. Before that, 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 improve the reflectivity; finally, the adhesive layer 12 is heated to soften, and the insulating substrate 10 is used as a support and hot-pressed by a mold 90. The stamping surface topography of the mold 90 is consistent with the top surface topography of the conductive sheet layer to be formed, which has a protrusion to form the edge lifting portion and the first curved portion 23, the second curved portion 24, etc. in the first conductive sheet 21 and the second conductive sheet 22, respectively, referring to Figure 6 ; finally, the mold 90 is removed to obtain the circuit board structure, referring to Figure 7 .

[0034] The application also provides an LED packaging module formed based on the above-mentioned circuit board, referring to Figure 8 and Figure 9 , the single LED chip 30 spans the first spacing 201, and its positive and negative electrodes are respectively connected to the first conductive sheet 21 and the second conductive sheet 22, for example, by solder ball welding. In order to prevent short circuit caused by melting of solder balls during welding, at least a part of the first protruding portion 121 is arranged directly below the LED chip 30 and separates the positive and negative electrodes of the LED chip 30. Of course, multiple LED chips 30 can be arranged in each sub-region, and the multiple LED chips 30 in each sub-region are in parallel structure.

[0035] wherein at least a part of the first curved portion 23 is located directly below the LED chip 30, referring toFigure 9 In this way, when the two different electrodes of the LED chip 30 are joined to the first and second conductive pads 21 and 22 by solder balls, even if the solder balls melt, the material of the solder balls can be prevented from flowing to cause short circuit, and the first protruding part 121 can also prevent the hot melt of the solder balls from flowing.

[0036] Further, the planar part of the conductive pad layer 20 is used to join the LED chip 30, and the flange part surrounds the planar part, so that the flange part forms a reflective cup shape for reflecting the light emitted by the LED chip, ensuring the efficiency of the light emission. Moreover, the roughness of the surface (top surface) of the conductive pad layer 20 on the side facing the LED chip 30 is less than the roughness of the surface (back surface) on the side facing away from the LED chip 30, so that the top surface has a high light reflection efficiency.

[0037] In the LED chip, the first electrode and the second electrode are arranged on the same surface of the LED chip, and the distance between the first electrode and the second electrode is s, and the width of the first interval is d, and s and d satisfy 0.6d≤s≤1.5d, so as to ensure the reliability of the electrical interconnection of the LED chip and prevent short circuit during joining.

[0038] Further, a sealing layer 50 can also be arranged on the circuit board, and the sealing layer 50 seals the plurality of 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. The sealing layer 50 can be distributed with fluorescent powder material to achieve light conversion.

[0039] Further, the insulating substrate 10 also has a conductive via 40, which is connected to the conductive pad layer 20 and has the other end exposed from the side of the insulating substrate 10 away from the conductive pad layer. The conductive via 40 is made of metal such as copper or aluminum, and is formed by electroplating or other processes. An interconnection part 70 is arranged at the exposed position of the conductive via 40, which is used to interconnect other components and can be a solder ball or a copper pillar.

[0040] The specific preparation process is described in Figures 10-12 First, the LED chip 30 is welded to the circuit board by a joining material such as a solder ball, wherein the LED chip 30 is arranged across the first interval 201 and the first protruding part 121, the first protruding part 121 separates the positive and negative electrodes, and at least part of the first curved part 23 is arranged directly below the LED chip 30 to separate the two solder balls (or welding parts), as shown in Figure 10 The positive and negative electrodes of the LED chip 30 are respectively welded to the first and second conductive pads 21 and 22 by solder balls. Next, referring to Figure 11 A sealing layer 50 is formed on the circuit board by hot pressing or injection molding to cover the LED chip 30, and the sealing layer 50 wraps the plurality of LED chips 30. Finally, referring toFigure 12 With the support of the sealing layer 50, a through hole is formed in the insulating substrate 10 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 respectively. One end of the conductive through hole 40 is connected to the conductive sheet layer 20, and the other end is exposed from the side of the insulating substrate 10 away from the conductive sheet layer 20. Further, a bonding part 70 can be bonded to the position where the conductive through hole 40 is exposed from the insulating substrate 10 for interconnecting other components.

[0041] Further, referring to Figure 13 The application also provides a display device, which comprises the above LED packaging module and a driving circuit board 60 to which the LED packaging module is bonded. The driving circuit board 60 is connected to the LED chip 30 through the conductive through hole 40 and the bonding part 70, i.e. the driving circuit board 60 is bonded to the circuit board to achieve electrical connection.

[0042] The beneficial effects of the above embodiments are as follows: (1) The second surface of the conductive sheet layer is used to reflect light, enhancing the light utilization rate of the LED chip. (2) The conductive sheet layer of the application can improve heat dissipation, and the patterned conductive sheet layer can achieve isolation of the two electrodes of the LED chip. In addition, the conductive sheet layer has an upward bending part at the first interval position, which prevents the solder from flowing to the position of the dissimilar electrode, further ensuring the reliability of the bonding.

[0043] The above is only a specific embodiment of the application, but the protection scope of the application is not limited thereto. Any changes or replacements within the technical scope disclosed in the application can be easily thought of by those skilled in the art, which should be covered within the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection 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; 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.

2. 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.

3. The LED packaging module according to claim 1, 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.

4. 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.

5. 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.

6. 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.

7. 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, the sealing layer being disposed on the circuit board and sealing the LED chip; 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 to 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 is performed on the insulating substrate as a support, so that the protrusions of the mold form the warped edge portion and the first bent portion in the first conductive sheet and the second conductive sheet respectively; (3) removing the mold.

8. The method for manufacturing an LED packaging module according to claim 7, 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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