Circuit substrate, LED module and display device, and method for manufacturing LED module and method for manufacturing display device

Abstract

The purpose of the present invention is to form a stable connection structure with a back plate as a flip chip type LED. The LED module includes a first electrode and a second electrode arranged on a substrate, an LED chip arranged on the first electrode and the second electrode, a first bump between the LED chip and the first electrode, and a second bump between the LED chip and the second electrode. The LED chip has a cathode electrode opposite to the first electrode, an anode electrode opposite to the second electrode, and a step difference between the cathode electrode and the anode electrode. The distance between the first electrode and the cathode electrode is greater than the distance between the second electrode and the anode electrode, and the first bump is arranged in a manner to fill the step difference.

Description

Technical Field

[0001] The present invention relates to an LED module in which light emitting diodes (LEDs) are arranged, a display device in which LEDs are mounted in pixels, and a circuit board before LEDs are mounted. Background Art

[0002] A micro-LED display is known in which tiny light-emitting diodes called micro-LEDs are installed in pixels arranged in a matrix. The micro-LED display has a structure in which micro-LEDs that have been solidified from a wafer or the like are installed on a substrate on which a circuit called a backplane is formed. Micro-LEDs are tiny chips, so the ratio of the cross-sectional area to the area of ​​the plan view becomes large. As a result, micro-LEDs have such a problem that the influence of non-radiative recombination occurring on the side wall of the active layer can no longer be ignored, and the luminous efficiency is reduced.

[0003] In order to improve the light extraction efficiency, a flip-chip type micro-LED having a structure for extracting light through a transparent sapphire substrate is known (for example, see Patent Document 1). Regarding the flip-chip type micro-LED, a structure in which a passivation film is provided on the side wall of the active layer to prevent non-radiative recombination is disclosed (for example, see Patent Document 2).

[0004] In a flip-chip LED, the heights of the cathode electrode and the anode electrode are different. According to the micro-LEDs disclosed in Patent Documents 1 and 2, the thickness of the bumps on the cathode electrode side is larger than that of the bumps on the anode electrode side. In contrast, as an electrode structure of a flip-chip LED, an electrode structure is disclosed in which a groove is formed to penetrate the p-type semiconductor layer and the active layer to reach the n-type semiconductor layer and is made into a planar type (for example, see Patent Document 3). In addition, as an electrode structure of a micro-LED, a structure is disclosed in which the cathode electrode is formed by crossing the step difference between the n-type semiconductor layer and the p-type semiconductor layer, and the connection portion with the bump is set on the p-type semiconductor layer (see Patent Document 4).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: U.S. Patent No. 10446714

[0008] Patent Document 2: U.S. Patent Publication No. 2020 / 0161499

[0009] Patent Document 3: Chinese Patent Publication No. 111063779

[0010] Patent Document 4: Japanese Patent Application Publication No. 2020-088383

[0011] Since the height of the cathode electrode and the anode electrode of the tiny LEDs called micro LEDs and mini LEDs are different, it is necessary to work on the shape of the bumps or the shape of the cathode electrode when performing flip-chip mounting. However, making the bumps separately for cathode and anode is the main reason for the complexity of the manufacturing process and the increase in manufacturing costs. On the other hand, in a planar electrode structure or a structure in which the cathode electrode is led out on a p-type semiconductor layer, a short circuit between the electrodes becomes a problem. That is, since the chip size of the LED is small, the electrode spacing between the cathode electrode and the anode electrode becomes narrower. If the solder that forms the bumps flows during the mounting process, a short circuit between the cathode electrode and the anode electrode becomes a problem. Summary of the invention

[0012] In view of such a problem, an object of one embodiment of the present invention is to provide a micro LED module that is a flip-chip type LED and can form a stable connection structure, a display device in which pixels are formed by micro LEDs, and a method for manufacturing the same.

[0013] An LED module according to an embodiment of the present invention includes a first electrode and a second electrode provided on a substrate, an LED chip disposed on the first electrode and the second electrode, a first bump between the LED chip and the first electrode, and a second bump between the LED chip and the second electrode. The LED chip has a cathode electrode opposed to the first electrode, an anode electrode opposed to the second electrode, and a step portion between the cathode electrode and the anode electrode. The distance between the first electrode and the cathode electrode is greater than the distance between the second electrode and the anode electrode, and the first bump is provided in a manner that fills the step portion.

[0014] A display device according to one embodiment of the present invention includes a first electrode and a second electrode provided in a pixel, at least one LED chip disposed on the first electrode and the second electrode, a first bump between at least one LED chip and the first electrode, and a second bump between at least one LED chip and the second electrode. At least one LED chip has a cathode electrode opposed to the first electrode, an anode electrode opposed to the second electrode, and a step portion between the cathode electrode and the anode electrode. The distance between the first electrode and the cathode electrode is greater than the distance between the second electrode and the anode electrode, and the first bump is provided in a manner that fills the step portion.

[0015] A method for manufacturing an LED module according to an embodiment of the present invention includes: forming a first bump on a first electrode on a substrate, forming a second bump on a second electrode, arranging an LED chip on the first bump and the second bump, heating the first bump and the second bump, and electrically connecting the LED chip to the first electrode and the second electrode. The LED chip has a step portion on a surface facing the first bump and the second bump, and the first bump is formed in a manner that fills the step portion.

[0016] A method for manufacturing a display device according to an embodiment of the present invention includes: forming a first bump on a first electrode provided in a pixel, forming a second bump on a second electrode, arranging an LED chip on the first bump and the second bump, heating the first bump and the second bump, and electrically connecting the LED chip to the first electrode and the second electrode. The LED chip has a step portion on a surface facing the first bump and the second bump, and the first bump is formed in a manner that fills the step portion.

[0017] A circuit board according to an embodiment of the present invention comprises a first electrode for connecting to a cathode electrode of an LED, a second electrode for connecting to an anode electrode of the LED, a first bump formed on the first electrode, and a second bump formed on the second electrode. The first bump has a first spherical body and a second spherical body on the first electrode, the first spherical body and the second spherical body have different sizes, and the first bump has a shape formed by merging the first spherical body and the second spherical body. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1A A plan view showing an LED module according to an embodiment of the present invention.

[0019] Figure 1B A cross-sectional view showing an LED module according to an embodiment of the present invention, showing Figure 1A The corresponding structure between A1 and A2 is shown.

[0020] Figure 2A A plan view showing a bump of an LED module according to an embodiment of the present invention.

[0021] Figure 2B A cross-sectional view showing a bump of an LED module according to an embodiment of the present invention.

[0022] Figure 3A A plan view showing a bump of an LED module according to an embodiment of the present invention.

[0023] Figure 3B A cross-sectional view showing a bump of an LED module according to an embodiment of the present invention.

[0024] Figure 4A The cross-sectional structure of a bump of an LED module according to one embodiment of the present invention is shown.

[0025] Figure 4B The cross-sectional structure of a bump of an LED module according to one embodiment of the present invention is shown.

[0026] Figure 4C The cross-sectional structure of a bump of an LED module according to one embodiment of the present invention is shown.

[0027] Figure 5AA method for manufacturing an LED module according to an embodiment of the present invention is shown, and the method shows a stage of forming a first electrode, a second electrode, an insulating film, and a base metal film on a substrate.

[0028] Figure 5B A method for manufacturing an LED module according to an embodiment of the present invention is shown, and the method shows a stage in which a first resist mask is formed on a base metal film.

[0029] Figure 5C A method for manufacturing an LED module according to an embodiment of the present invention is shown, showing a stage in which a first bump layer and a second bump layer are formed.

[0030] Fig. 6A A method for manufacturing an LED module according to an embodiment of the present invention is shown, and the method shows a stage in which a second resist mask is formed on a substrate.

[0031] Figure 6B The method for manufacturing an LED module according to one embodiment of the present invention is shown, and the stage in which the second resist mask is removed after the third bump layer is formed is shown.

[0032] Figure 6C A method for manufacturing an LED module according to an embodiment of the present invention is shown, showing a stage in which a first bump is provided on a first electrode and a second bump is provided on a second electrode.

[0033] Fig. 7A A method for manufacturing an LED module according to an embodiment of the present invention is shown, and the method shows a stage of mounting an LED chip on a substrate.

[0034] Figure 7B A method for manufacturing an LED module according to an embodiment of the present invention is shown, showing a stage in which the first bumps and the second bumps are bonded to the cathode electrode and the anode electrode of the LED chip.

[0035] Fig. 8A A method for manufacturing an LED module according to an embodiment of the present invention shows a step of forming a first bump layer on a first electrode via a base metal film and forming a second bump layer on a second electrode.

[0036] Figure 8B The method for manufacturing an LED module according to one embodiment of the present invention is shown, and the step of performing a heat treatment to reflow the first bump layer and the second bump layer is shown.

[0037] Figure 8C A method for manufacturing an LED module according to an embodiment of the present invention is shown, and the method shows a stage in which a fourth resist mask is formed on a substrate.

[0038] Fig.9AA method for manufacturing an LED module according to an embodiment of the present invention is shown, showing a stage in which a fourth bump layer is formed.

[0039] Fig. 9B The method for manufacturing an LED module according to one embodiment of the present invention is shown, and the method shows a stage in which the fourth resist mask is removed.

[0040] Fig. 9C A method for manufacturing an LED module according to an embodiment of the present invention is shown, and the stage in which the fourth bump layer is reflowed by heat treatment is shown.

[0041] Fig. 10A A method for manufacturing an LED module according to an embodiment of the present invention is shown, and the method includes a step of providing a first electrode, a second electrode, an insulating film, and a base metal film on a substrate.

[0042] Fig. 10B A method for manufacturing an LED module according to an embodiment of the present invention is shown, and the method shows a stage in which a first resist mask is formed on a base metal film.

[0043] Fig. 10C A method for manufacturing an LED module according to an embodiment of the present invention is shown, showing a stage in which a first bump layer and a second bump layer are formed.

[0044] Fig.11A A method for manufacturing an LED module according to an embodiment of the present invention is shown, and the method shows a stage in which a second resist mask is formed on a substrate.

[0045] Fig. 11B A method for manufacturing an LED module according to an embodiment of the present invention is shown, showing a stage in which a third bump layer is formed.

[0046] Fig. 11C A method for manufacturing an LED module according to an embodiment of the present invention is shown, and the method shows a stage in which the second resist mask is removed and the base metal film is etched.

[0047] Fig.12 It is a diagram showing the structure of a display device according to one embodiment of the present invention.

[0048] Fig.13 It is a diagram showing a cross-sectional structure of a pixel of a display device according to one embodiment of the present invention.

[0049] Fig.14A An example of the arrangement of the LED chip, the first electrode, and the second electrode in a pixel of a display device according to an embodiment of the present invention is shown.

[0050] Fig. 14BAn example of the arrangement of the LED chip, the first electrode, and the second electrode in a pixel of a display device according to an embodiment of the present invention is shown.

[0051] Description of Reference Numerals

[0052] 100 LED module, 102 LED chip, 104 step difference portion, 106 cathode electrode, 108 anode electrode, 110 first bump, 112 second bump, 114 passivation film, 115 opening portion, 116 first electrode, 118 second electrode, 120 substrate, 122 step difference portion, 124 insulating film, 125 opening portion, 126 base metal film, 128 first resist mask, 129 1st opening, 130 2nd opening, 132 1st bump layer, 134 2nd bump layer, 136 3rd bump layer, 138 2nd resist mask, 139 3rd opening, 140 4th resist mask, 141 4th opening, 142 4th bump layer, 144 1st insulating layer, 146 2nd insulating layer, 148 3rd insulating layer, 150 4th insulating layer, 152 n-type semiconductor layer,

[0053] 154 active layer, 156 p-type semiconductor layer, 158 contact hole, 200 display device, 202 display unit, 204 pixel, 206 scanning signal line, 208 data signal line, 210 input terminal unit, 212 flexible printed wiring substrate, 214 driver IC DETAILED DESCRIPTION

[0054] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms, and is not limited and explained by the contents of the following embodiments. In order to make the description clearer, the accompanying drawings schematically represent the width, thickness, shape, etc. of each part compared with the actual form, but this is only an example and does not limit the interpretation of the present invention. In addition, in this specification and each figure, for the same elements as those described in the previous figures, the same mark is attached (or a, b, etc. are attached after the number) and the detailed description is appropriately omitted. Furthermore, the words "1st" and "2nd" attached to each element are convenient identifiers used to distinguish each element, and have no further meaning unless otherwise specified.

[0055] In this specification, when a component or region is above (or below) other components or regions, unless otherwise specified, it includes not only the case where it is immediately above (or immediately below) other components or regions, but also the case where it is above (or below) other components or regions, that is, it also includes the case where other components are included between the above (or below) other components or regions. In addition, in the following description, unless otherwise specified, in the cross-sectional view, the direction in which the first electrode pattern and the second electrode pattern are set on the substrate is set as "up", "above", "upper surface" or "upper surface side", and the opposite direction is set as "down", "below", "lower surface" or "lower surface side".

[0056] In one embodiment of the present invention, micro LED refers to a chip size of several micrometers or more and 100 μm or less, and mini LED refers to a chip size of 100 μm or more. In one embodiment of the present invention, LEDs of any size can be used, and can be appropriately differentiated for use according to the purpose and form of the light-emitting device.

[0057] 1. LED module structure

[0058] The structure of an LED module according to one embodiment of the present invention will be described. Hereinafter, the structure of bumps for electrically connecting an LED chip to a pad provided on a substrate will be mainly described.

[0059] (1) LED chip mounting structure

[0060] Figure 1A and Figure 1B The structure of an LED module 100 according to one embodiment of the present invention is shown. Figure 1A FIG. 1 is a plan view showing the LED module 100 mounted on the substrate 120 . Figure 1B express Figure 1A The cross-sectional view between A1 and A2 is shown.

[0061] The LED chip 102 is a two-terminal component having a cathode electrode 106 and an anode electrode 108, and is flip-chip mounted on a substrate 120 via a first bump 110 and a second bump 112. On the substrate 120, a first electrode 116 and a second electrode 118 are provided corresponding to the cathode electrode 106 and the anode electrode 108 of the LED chip 102. The first bump 110 is provided corresponding to the cathode electrode 106 of the LED chip 102, and the second bump 112 is provided corresponding to the anode electrode 108.

[0062] Figure 1BAlthough not shown in detail, the LED chip 102 has a structure in which an n-type semiconductor layer, an active layer, and a p-type semiconductor layer are stacked. A passivation film 114 may be provided on the side of the LED chip 102 to prevent surface recombination. The passivation film 114 is also formed on the cathode electrode 106 and the anode electrode 108. Therefore, in the passivation film 114, a first opening 115a for exposing the cathode electrode 106 and a second opening 115b for exposing the anode electrode 108 are formed. The first bump 110 and the cathode electrode 106 are connected through the first opening 115a, and the second bump 112 and the anode electrode 108 are connected through the second opening 115b.

[0063] like Figure 1B As shown in FIG. 1 , the heights of the cathode electrode 106 and the anode electrode 108 of the LED chip 102 are different. Since the cathode electrode 106 is provided in a region where a part of the semiconductor layer (p-type semiconductor layer, active layer) is removed, a step portion 104 is formed between the cathode electrode 106 and the anode electrode 108. When the LED chip 102 is mounted, the interval between the first electrode 116 and the cathode electrode 106 becomes larger than the interval between the second electrode 118 and the anode electrode 108.

[0064] In order to make the area of ​​the light-emitting region (the area of ​​the active layer) as large as possible, the area of ​​the region where the cathode electrode 106 is formed is made as small as possible. On the other hand, it can be considered that in order to form a stable mounting structure for the LED chip 102 on the substrate 120, it is preferred to make the first bump 110 on the cathode side and the second bump 112 on the anode side as large as possible.

[0065] Therefore, the LED module 100 of this embodiment is as follows Figure 1A and Figure 1B The structure shown in the figure is that the first bump 110 on the cathode side is arranged to exceed the step portion 104 of the LED chip 102 and fill the step portion 104. Therefore, the LED chip 102 is arranged so that the height of the first bump 110 and the second bump 112 are the same height. In addition, the LED chip 102 can be formed so that the width of the first bump 110 is larger than that of the second bump 112. The first bump 110 has such a shape that the LED chip 102 can be stably connected. That is, the first bump 110 has a shape that fills the step portion 104, so that the LED chip 102 can be mounted horizontally. In other words, by making the first bump 110 have a region with different thicknesses so that the width of the first bump 110 can be expanded, the LED chip 102 can be kept in a horizontal state and mounted on the substrate 120 in a stable state. Furthermore, by providing the first bumps 110 over a wide area so as to fill the step portion 104 , the LED chip 102 can be mounted on the substrate in a stable state.

[0066] Furthermore, in order to form bumps of different thicknesses by filling the step portion 104 of the LED chip 102, it is necessary to create regions of different thicknesses within one bump. However, forming bumps of different thicknesses separately or cutting off a portion of the bump is inappropriate because the number of steps increases and the processing becomes difficult. Therefore, in this embodiment, a solder having a low melting point is used to form the bumps, and such a problem is eliminated by utilizing its characteristics. That is, by utilizing the low melting point and softness of the solder and by working on its initial shape, the first bump 110 is made as Figure 1B As shown, the step portion 104 is filled to form a shape including a region with different thicknesses.

[0067] (2) Structure of bumps

[0068] Figure 2A and Figure 2B The initial structures (shapes before the LED chip 102 is mounted) of the first bumps 110 and the second bumps 112 of the present embodiment are shown. Figure 2A A plan view showing the initial structures of the first bump 110 and the second bump 112 formed on the first electrode 116 and the second electrode 118, respectively. Figure 2B Representation and Figure 2A The cross-sectional structure corresponding to B1-B2 is shown.

[0069] like Figure 2A and Figure 2B As shown, the first bump 110 is formed on the first electrode 116, and the second bump 112 is formed on the second electrode. The second bump 112 has a spherical surface, while the first bump 110 has a shape formed by fusing two spherical (or hemispherical) bodies of different sizes. In other words, the first bump 110 has a spherical surface and has a shape including a region of thickness d1 and a region of thickness d2. The thickness d1 has a value greater than the thickness d2 (d1>d2).

[0070] Regarding the first bump 110, the region of thickness d1 corresponds to the lower side region of the step portion 104, and the region of thickness d2 corresponds to the higher side region of the step portion 104 with respect to the LED chip 102. Therefore, regarding the first bump 110, the region of thickness d2 is formed on the closer side to the first bump 110, and the region of thickness d1 is formed on the farther side from the first bump 110. In addition, the thickness d0 of the second bump 112 is smaller than d1, and may be equal to d2.

[0071] The first bump 110 and the second bump 112 are heated and flow when the LED chip 102 is mounted, thereby Figure 2A and Figure 2B The shape changes as shown Figure 1B By adopting Figure 2A The first bump 110 having an initial structure of a shape formed by fusing hemispherical bodies as shown in FIG. 1 can form a bump such as the step difference portion 104 across the LED chip 102, and can form a bump including regions with different thicknesses. That is, by making the initial structure of the first bump 110 include regions with different thicknesses, such as Figure 1B As shown in FIG. 1 , the first bump 110 can be provided in a shape that has a region with different thicknesses, fills the step portion 104 , and expands toward the anode electrode 108 .

[0072] Figure 3A and Figure 3B Another form of the initial structure of the first bump 110 and the second bump 112 is shown. Figure 3A A plan view showing the initial structures of the first bump 110 and the second bump 112 formed on the first electrode 116 and the second electrode 118, respectively. Figure 3B Representation and Figure 3A The corresponding cross-sectional structure between C1 and C2 is shown.

[0073] Figure 3A and Figure 3B The structure of the first bump 110 is a structure in which bumps of different sizes are stacked in such a manner that the first bump 110 includes regions of different thicknesses. That is, the first bump 110 matches the step portion 104 of the LED chip 102, and has a shape in which a plurality of structures having spherical surfaces are partially stacked in such a manner that the portion on the cathode electrode 106 side can be buried. In other words, the first bump 110 has an initial structure in which a second structure having a spherical surface is protrudingly arranged on the first structure having a spherical surface. The first bump 110 includes a region of thickness d1 and a region of thickness d2 that is smaller than thickness d1. Here, the region of thickness d1 is arranged at a position far from the second bump 112, and the region of thickness d2 is arranged at a position close to the second bump 112.

[0074] By having Figure 3A and Figure 3B The first bump 110 and the second bump 112 of the initial structure as shown in FIG. 1 can also form bumps such as the step difference portion 104 across the LED chip 102, and can form bumps including regions with different thicknesses. That is, by making the initial structure of the first bump 110 include regions with different thicknesses, such as Figure 1B As shown, the first bump 110 can be provided in a shape in which the first bump 110 has a region with a different thickness, fills the step portion 104 and expands toward the anode electrode 108 side.

[0075] Figure 4AThe first bump 110 has a stepped shape, and the second bump 112 does not have a stepped shape. The stepped shape of the first bump 110 has a shape corresponding to the stepped portion 104 of the LED chip 102. The first bump 110 has a region with a thickness of d1 and a region with a thickness of d2 (d1>d2), and the difference in film thickness (d1-d2) has a size corresponding to the height of the stepped portion 104. That is, the first bump 110 has an initial structure in which the high side of the step is arranged at a position far from the second bump 112, and the low side of the step is arranged at a position close to the second bump 112.

[0076] The thickness d0 of the first bump 110 is the same as the thickness d2 of the first bump. By using the first bump 110 and the second bump 112 having such initial shapes, Figure 1B The LED chip 102 is mounted on the substrate 120 as shown.

[0077] Figure 4B The first bump 110 has an inclined upper surface. The first bump 110 has a shape in which the thickness decreases continuously from d1 to d2 from the outer end toward the inner end in a cross-sectional view. The thickness d2 of the first bump 110 is the same as the thickness d0 of the second bump 112. According to the shape of the first bump 110, a region where the film thickness increases from d2 to d1 is included, so that the step portion 104 of the LED chip 102 can be buried by the increase in its volume. Figure 4B The initial structure of the first bump 110 and the second bump 112 shown in the figure can also be set to be heated when the LED chip 102 is mounted to promote the flow. Figure 1B The shapes of the first bump 110 and the second bump 112 are as shown.

[0078] Figure 4C The structure in which the first electrode 116 is provided with a step portion 122 is shown. The first bump 110 is provided so as to overlap with the step portion 122 of the first electrode 116 and fill the step portion 122. The first electrode 116 has a region with a film thickness of t1 and a region with a film thickness of t2 (t1>t2) which is smaller than the film thickness of the region, and has a step portion 122 formed by the difference in the film thickness. Such a step portion 122 of the first electrode 116 is provided at a position that meshes with the step portion 104 of the LED chip 102 mounted thereon. The first bump 110 is raised by an amount increased by the step portion 122 of the first electrode 116, and a structure equivalent to that in which the film thickness is substantially locally increased can be obtained. Such a step portion 122 of the first electrode 116 can be formed by stacking conductive films. By using a conductive film having Figure 4CThe first bump 110 having the initial shape shown can also be formed as a bump that straddles the step portion 104 of the LED chip 102, and can be formed as a bump that includes a region with different thicknesses.

[0079] 2. Manufacturing method of LED module

[0080] A method for manufacturing the LED module 100 according to one embodiment of the present invention will be described below, with the description focusing on the steps of forming the first bump 110 on the first electrode 116 and the second bump 112 on the second electrode 118 .

[0081] (1) First method for manufacturing bumps

[0082] Reference Figure 5A to Figure 5C and Figure 6A to Figure 6C , indicating the manufacturing Figure 2A and Figure 2B The process of manufacturing the first bump 110 and the second bump 112 is shown (first manufacturing method).

[0083] Figure 5A The figure shows a stage where the first electrode 116, the second electrode 118, the insulating film 124, and the base metal film 126 are provided on the substrate 120. The first electrode 116 and the second electrode 118 are formed of a metal film such as aluminum (Al). The insulating film 124 is formed of a silicon oxide film, a silicon nitride film, or the like. Openings 125a and 125b are formed in the insulating film 124 to expose the upper surfaces of the first electrode 116 and the second electrode 118. The base metal film 126 is provided on the insulating film 124 and is formed to contact the first electrode 116 and the second electrode 118 in the openings 125a and 125b. The base metal film 126 is formed of a metal material such as titanium (Ti), nickel (Ni), and nickel palladium (NiPd). For example, the base metal film 126 can be formed by stacking a titanium (Ti) film and a nickel palladium (NiPd) film.

[0084] Figure 5B The figure shows a state where the first resist mask 128 is formed on the base metal film 126. The first resist mask 128 has a thickness of, for example, about 20 to 70 μm and is formed by a so-called thick film resist. The first resist mask 128 forms a first opening 129 corresponding to the first electrode 116 and forms a second opening 130 corresponding to the second electrode 118. The second opening 130 is formed so that the center position overlaps with the center of the second electrode 118. The center position of the first opening 129 deviates from the center of the first electrode 116 and is formed at a position deviated from the second electrode 118 as shown in the figure.

[0085] Figure 5CIndicates the stage of forming the first bump layer 132 and the second bump layer 134. The first bump layer 132 and the second bump layer 134 are formed of a low melting point metal material having a melting point of less than 300°C, preferably less than 250°C. For example, the first bump layer 132 and the second bump layer 134 are formed of solder. As solder materials, tin (Sn), tin alloys (SnPb alloy, SnCu alloy, SnBi alloy, SnAg alloy, etc.), indium tin alloy (InSn), etc. are used. Such a first bump layer 132 and the second bump layer 134 formed of a low melting point metal material are manufactured, for example, by solder plating. After the first bump layer 132 and the second bump layer 134 are formed, the first resist mask 128 is removed.

[0086] Fig. 6A 1 shows a stage where the second resist mask 138 is formed on the substrate 120. The second resist mask 138 is formed by using a thick film resist similarly to the first resist mask 128, and covers the first bump layer 132 and the second bump layer 134. The second resist mask 138 has a third opening 139, and the third opening 139 is formed in a region on the first electrode 116 where the first bump layer 132 is not formed.

[0087] exist Fig. 6A In the state shown, the third bump layer 136 is formed. The third bump layer 136 is made of the same low melting point metal material as the first bump layer 132 and the second bump layer 134 and is manufactured by the same manufacturing method.

[0088] Figure 6B The second resist mask 138 is removed after forming the third bump layer 136. The third bump layer 136 is formed adjacent to the first bump layer 132 on the first electrode 116. The third bump layer 136 has a shape larger in thickness and width than the first bump layer 132.

[0089] right Figure 6B The first bump layer 132, the second bump layer 134, and the third bump layer 136 in the state shown are subjected to a heat treatment for reflow. The first bump layer 132 and the third bump layer 136 are flowed and integrated by the heat treatment. Furthermore, the first bump layer 132 and the second bump layer 134 are changed in shape to have a spherical surface, thereby forming the first bump 110. In addition, the second bump layer 134 is changed in shape by reflow to have a spherical surface, thereby forming the second bump 112. Due to the difference in film thickness between the first bump layer 132 and the third bump layer 136, the first bump 110 is formed as shown in FIG. Figure 2A As described above, it is formed to include a region with a thickness of d1 and a region with a thickness of d2.

[0090] Then, the base metal film 126 is etched using the first bump 110 and the second bump 112 as a mask. Figure 6C As shown, an initial structure in which the first bump 110 is provided on the first electrode 116 and the second bump 112 is provided on the second electrode 118 can be formed.

[0091] Fig. 7A 102 is a stage where the LED chip 102 is mounted on the substrate 120. The LED chip 102 is arranged on the first bump 110 and the second bump 112 with the cathode electrode 106 and the anode electrode 108 facing the substrate 120. In this state, a heating treatment is performed to a temperature above the melting point of the solder material forming the first bump 110 and the second bump 112. This heating treatment is performed, for example, by irradiation with a laser. Figure 7B As shown, the first bump 110 and the second bump 112 can be bonded to the cathode electrode 106 and the anode electrode 108 of the LED chip 102 .

[0092] When the bump formed by solder is connected to the LED chip, if a void is formed in the bump, poor connection (broken wire) may occur. Solder is used for the connection of electronic circuits, and it is known that broken wires are produced by creep rupture. If there are voids in the bump formed by the solder material, the stress acts and the voids grow, and creep rupture is prone to occur. However, as in the first bump 110 shown in the present embodiment, by pre-forming a shape with different thicknesses corresponding to the step difference portion 104 of the LED chip 102, it is possible to prevent the occurrence of voids during the bonding caused by the heat treatment, and suppress the occurrence of creep rupture.

[0093] according to Figure 5A to Figure 5C as well as Figure 6A to Figure 6C The bump manufacturing method shown in the figure can make the first bump 110 and the second bump 112 have different shapes through two steps of manufacturing a resist mask, two steps of forming solder, and a subsequent reflow step, so that the first bump 110 can be formed into a shape formed by fusing two spherical (or hemispherical) bodies of different sizes. According to the shape of the first bump 110, a stable connection structure can be formed without being affected by the step difference of the LED chip 102.

[0094] (2) Second method for manufacturing bumps

[0095] Reference Figure 8A to Figure 8C as well as Figures 9A to 9C , indicating the manufacturing Figure 3A and Figure 3B The process of manufacturing the first bump 110 and the second bump 112 is shown (second manufacturing method).

[0096] Fig. 8AThe figure shows a state where the first bump layer 132 is formed on the first electrode 116 and the second bump layer 134 is formed on the second electrode 118 via the base metal film 126. The first bump layer 132 and the second bump layer 134 have different thicknesses. The first bump layer 132 is preferably formed thicker than the second bump layer 134. The first bump layer 132 and the second bump layer 134 having different thicknesses can be manufactured by a single solder plating process. The method for manufacturing the bump layer by solder plating is the same as the method described in the first manufacturing method.

[0097] Figure 8B 13 shows a stage where the first bump layer 132 and the second bump layer 134 are reflowed by heat treatment. The first bump layer 132 and the second bump layer 134 are formed into spherical surfaces by reflowing. The first bump layer 132 is formed with a thickness d2, and the second bump layer 134 is formed with a thickness d0. The first bump layer 132 is formed larger than the second bump layer 134 (d2>d0).

[0098] Figure 8C 1 shows a stage where the fourth resist mask 140 is formed on the substrate 120. The fourth resist mask 140 is provided to cover the reflowed first bump layer 132 and the second bump layer 134, and has a fourth opening 141 that exposes a portion of the upper end side of the first bump layer 132.

[0099] Fig.9A 1 shows a stage of forming the fourth bump layer 142. The fourth bump layer 142 is formed so as to fill the fourth opening 141 of the fourth resist mask 140. The fourth bump layer 142 can be manufactured using the same low melting point metal material as the first bump layer 132 by the same manufacturing method.

[0100] Fig. 9B FIG. 1 shows a stage where the fourth resist mask 140 has been removed. By removing the fourth resist mask 140, a structure in which the fourth bump layer 142 is provided protrudingly on the first bump layer 132 is formed.

[0101] Fig. 9C The fourth bump layer 142 is shown in a state where it is reflowed by heat treatment. Through the reflow process, the fourth bump layer 142 having a spherical surface is formed on the upper part of the first bump layer 132. Through such a process, a protruding shape is formed. Figure 3A The first bump 110 and the second bump 112 are shaped as shown. The first bump 110 has a structure including a region with a large film thickness d1 and a region with a film thickness d2 smaller than the film thickness d1. The base metal film 126 is etched using the first bump 110 and the second bump 112 as masks.

[0102] according to Figure 8A to Figure 8C and Figures 9A to 9CThe bump manufacturing method shown in the figure can make the first bump 110 and the second bump 112 have different shapes through three steps of manufacturing a resist mask, three steps of forming a solder layer, and two subsequent steps of reflow, so that the first bump 110 can be formed into a shape formed by fusing two spherical (or hemispherical) bodies of different sizes. With such a shape of the first bump 110, a stable connection structure can be formed without being affected by the step difference of the LED chip 102.

[0103] (3) Third method for manufacturing bumps

[0104] Reference Figures 10A to 10C and Figures 11A to 11C , indicating the manufacturing Figure 4A A method (third manufacturing method) for manufacturing the first bump 110 and the second bump 112 is shown. Hereinafter, descriptions overlapping with those of the first manufacturing method will be appropriately omitted.

[0105] Fig. 10A 1 shows a stage where the first electrode 116, the second electrode 118, the insulating film 124, and the base metal film 126 are provided on the substrate 120. The structure of the first electrode 116, the second electrode 118, the insulating film 124, and the base metal film 126 is similar to the structure of the reference Figure 5A Same as described.

[0106] Fig. 10B The first resist mask 128 is formed on the base metal film 126. The first resist mask 128 has a first opening 129 and a second opening 130 of a size that exposes the upper surface of the region where the base metal film 126 overlaps with the first electrode 116 and the second electrode 118.

[0107] Fig. 10C 1 shows the stage of forming the first bump layer 132 and the second bump layer 134. The first bump layer 132 and the second bump layer 134 are formed of a low melting point metal material having a melting point of 300° C. or less, preferably 250° C. or less. After the first bump layer 132 and the second bump layer 134 are formed, the first resist mask 128 is removed.

[0108] Fig.11A FIG. 1 shows a stage where the second resist mask 138 is formed on the substrate 120. The second resist mask 138 is formed to cover a portion of the first bump layer 132 and the second bump layer 134. The second resist mask 138 has a third opening 139 that exposes a portion of the upper surface of the first bump layer 132.

[0109] Fig. 11B1 shows a stage of forming the third bump layer 136. The third bump layer 136 is formed to fill the third opening 139 of the second resist mask 138. The third bump layer 136 is made of the same low melting point metal material as the first bump layer 132 and the second bump layer 134 by the same manufacturing method.

[0110] Fig. 11C 1 shows a state after the second resist mask 138 is removed and the base metal film 126 is etched. The first bump 110 has a shape including a region with a step-like step difference and a different film thickness. Figure 2B The cross-sectional view shows a stepped shape, with a region of thickness d1 and a region of thickness d2 (d1>d2). On the other hand, the second bump 112 is formed with a constant thickness d0. The thickness d0 is the same as the thickness d2 of the first bump 110 (d0=d2).

[0111] according to Figures 10A to 10C as well as Figures 11A to 11C The bump manufacturing method shown can make the shapes of the first bump 110 and the second bump 112 different by two steps of manufacturing a resist mask and two steps of forming solder, and can manufacture the first bump 110 including at least two regions with different film thicknesses. With such a shape of the first bump 110, a stable connection structure can be formed without being affected by the step difference of the LED chip 102.

[0112] In this section, the first manufacturing method, the second manufacturing method, and the third manufacturing method related to bumps require at least two resist mask manufacturing processes and at least two solder film manufacturing processes, but these processes can be carried out on a large-area substrate and can uniformly process a wide range of areas. For example, the bump manufacturing process shown in this section can be applied to the pixel area of ​​a micro LED display.

[0113] 3. Display device

[0114] The structure of a display device according to one embodiment of the present invention is shown. The display device according to this embodiment has a structure in which an LED chip is provided in a pixel. Figure 1A and Figure 1B That is, the display device shown in this embodiment has a structure in which the LED chip is mounted in the same structure as the mounting structure of the LED module shown in FIG.

[0115] Fig.12The structure of the display device 200 of the present embodiment is shown. The display device 200 has a display unit 202 on a substrate 120 in which a plurality of pixels 204 are arranged in a matrix. An LED chip 102 is mounted in the pixel 204. In each pixel, an LED chip 102 having a different wavelength of emitted light can be appropriately mounted. For example, the plurality of pixels 204 may include a pixel in which an LED chip emitting red light is mounted, a pixel in which an LED chip emitting green light is mounted, and a pixel in which an LED chip emitting blue light is appropriately mounted. In addition, as a color filter display device, an LED chip emitting white light can be mounted in each pixel, or, as a quantum dot display device, an LED chip emitting blue light or ultraviolet light can be mounted in each pixel.

[0116] The display unit 202 is provided with scanning signal lines 206 for inputting scanning signals to the pixels 204 and data signal lines 208 for inputting image signals. The scanning signal lines 206 and the data signal lines 208 are arranged to cross each other. An input terminal portion 210a of the scanning signal line 206 and an input terminal portion 210b of the data signal line 208 are provided at the periphery of the substrate 120. The input terminal portions 210a and 210b are connected to a flexible printed wiring substrate 212. A driver IC 214 may be mounted on the flexible printed wiring substrate 212.

[0117] Fig.13 An example of a cross-sectional structure of the pixel 204 is shown. The structure of the pixel 204 is as follows: a first insulating layer 144, a second insulating layer 146, a third insulating layer 148, and a fourth insulating layer 150 are stacked, a scanning signal line 206 is provided between the first insulating layer 144 and the second insulating layer 146, and a data signal line 208 is provided between the second insulating layer 146 and the third insulating layer 148.

[0118] The first electrode 116 and the second electrode 118 are provided on the third insulating layer 148. The first electrode 116 is also electrically connected to the scanning signal line 206 through the second insulating layer 146 and the first contact hole 158a penetrating the second insulating layer 146, and the second electrode 118 is electrically connected to the data signal line 208 through the second contact hole 158b penetrating the third insulating layer 148. The fourth insulating layer 150 is provided on the upper layer side of the first electrode 116 and the second electrode 118. The first electrode 116 and the second electrode 118 are exposed through the opening formed in the fourth insulating layer 150 at the position where the first bump 110 and the second bump 112 are provided.

[0119] The LED chip 102 includes an n-type semiconductor layer 152, an active layer 154, and a p-type semiconductor layer 156, which are formed of a semiconductor material such as gallium nitride. In the LED chip 102, the cathode electrode 106 is provided in a region where the p-type semiconductor layer 156 and the active layer 154 are removed, and the anode electrode 108 is provided on the p-type semiconductor layer 156.

[0120] The LED chip 102 is disposed on the first electrode 116 and the second electrode 118. The cathode electrode 106 of the LED chip 102 is electrically connected to the first electrode 116 via the first bump 110, and the anode is electrically connected to the second electrode 118 via the second bump 112. A base metal film 126 may be provided between the first bump 110 and the first electrode 116 and between the second bump 112 and the second electrode 118.

[0121] like Fig.13 As shown, by filling the step portion 104 with the first bump 110 having regions with different thicknesses, the LED chip 102 can be mounted horizontally on the first electrode 116 and the second electrode 118. In addition, the contact area between the cathode electrode 106 and the first bump 110 can be increased, and a stable mounting structure can be formed. That is, since the first bump 110 has regions with different thicknesses, the step of the LED chip 102 can be filled, the contact area with the first electrode 116 can be ensured, and the LED chip 102 can be held horizontally.

[0122] Here, regarding the first bump 110 and the second bump 112, as an initial structure before mounting the LED chip 102, it is possible to apply Figure 2A and Figure 2B , Figure 3A and Figure 3B as well as Figure 4A and Figure 4B In addition, as the first electrode 116, it is possible to apply Figure 4C In addition, as a method for manufacturing the first bump 110 and the second bump 112, it is possible to apply Figure 5A to Figure 5C , Figure 6A to Figure 6C as well as Figure 7A to Figure 7B The manufacturing method shown, Figure 8A to Figure 8C as well as Figures 9A to 9C The manufacturing method shown, Figures 10A to 10C as well as Figures 11A to 11C The manufacturing method shown is used to manufacture a display device.

[0123] in addition, Fig.13 Although an example of a passive matrix display device 200 is shown, the present embodiment is not limited thereto, and light emission of each pixel can also be applied to an active matrix display device in which light emission is controlled by a pixel circuit using transistors.

[0124] Fig.14A and Fig. 14B An example of the arrangement of the LED chip 102 , the first electrode 116 , and the second electrode 118 in the pixel 204 is shown. Fig.14A The example in which the first LED chip 102a, the second LED chip 102b, and the third LED chip 102c are arranged in the pixel 204 is shown. These LED chips radiate light of different wavelength bands. For example, the first LED chip 102a radiates light of a wavelength band corresponding to red, the second LED chip 102b radiates light of a wavelength band corresponding to green, and the third LED chip 102c radiates light of a wavelength band corresponding to blue. When such LED chips 102 are mounted on the pixel 204, the first electrode 116 connected to the cathode electrode 106 (106a, 106b, 106c) can be shared, and the second electrode 118 (118a, 118b, 118c) connected to the anode electrode 108 (108a, 108b, 108c) is provided corresponding to each LED chip 102. The first bumps 110a, 110b, 110c and the second bumps 112a, 112b, 112c are provided for each LED chip 102. According to such a structure of the pixel 204, the shape of the electrode can be simplified, and by providing the first electrode 116 over a wide area, the mounting position of the LED chip 102 can have redundancy, thereby improving the manufacturing yield.

[0125] Fig. 14B The example in which the preliminary second electrode 118 is provided in the pixel 204 is shown. The preliminary second electrode 118d is provided adjacent to the first electrode 116. The second electrode 118d can be used for repairing when a problem occurs in the LED chip in the pixel 204. For example, the LED chip 102d for repair can be mounted on the first electrode 116 and the second electrode 118d. In addition, the second electrode 118 can also be provided on both sides in a manner of sandwiching the first electrode 116.

[0126] Fig.13 , Fig.14A and Fig. 14B The structure of the pixel 204 shown can be applied to a display device equipped with a mini LED chip or a micro LED chip. As an LED chip, even when a bare chip with a cathode and an anode having different heights is used, the connection stability can be ensured by using the bumps (the first bump 110 and the second bump 112) shown in this embodiment, thereby improving reliability.

[0127] According to the pixel structure of the display device described as one embodiment of the present invention, a pixel structure obtained by appropriately changing the design and implementing it by a person skilled in the art also belongs to the technical scope of the present invention as long as it includes the gist of the present invention.

[0128] In the scope of the concept of the present invention, those skilled in the art can think of various variations and modifications, and these variations and modifications also belong to the technical scope of the present invention. For example, in one embodiment of the present invention described above, the scope after the addition, deletion, and modification, and the scope after the addition, omission, and modification of processes by those skilled in the art also belong to the technical scope of the present invention as long as they do not deviate from the main purpose of the present invention.

[0129] Furthermore, it is naturally understood that the effects brought about by the aspects described in one embodiment of the present invention are brought about by the present invention if they are clear from the description of this specification and can be appropriately imagined by a person skilled in the art.

Claims

1. A method for manufacturing an LED module, characterized in that: Including the following processes: forming a first bump on the first electrode on the substrate, and forming a second bump on the second electrode on the substrate; Arrange LED chips on the first bump and the second bump; and heating the first bump and the second bump to electrically connect the LED chip to the first electrode and the second electrode; The LED chip has a step portion on a surface facing the first bump and the second bump, and the first bump is formed by filling the step portion. The formation of the first bump and the second bump includes the following steps: forming a first bump layer on the first electrode and forming a second bump layer on the second electrode; as well as Further, forming a third bump layer on the first electrode at a position on the opposite side of the first bump layer to the second bump layer; The third bump layer is formed thicker than the first bump layer.

2. A method for manufacturing an LED module, characterized in that: Including the following processes: forming a first bump on the first electrode on the substrate, and forming a second bump on the second electrode on the substrate; Arrange LED chips on the first bump and the second bump; and heating the first bump and the second bump to electrically connect the LED chip to the first electrode and the second electrode; The LED chip has a step portion on a surface facing the first bump and the second bump, and the first bump is formed by filling the step portion. The formation of the first bump and the second bump includes the following steps: forming a first bump layer on the first electrode and forming a second bump layer on the second electrode; and A third bump layer is formed on the first bump layer at a position opposite to the second bump layer side of the first bump layer.

3. The method for manufacturing an LED module according to claim 2, wherein: After forming the first bump layer and the second bump layer, performing a first heat treatment to reflow the first bump and the second bump; After the second bump layer is formed, a second heat treatment is performed to reflow the third bump layer.

4. A method for manufacturing an LED module, characterized in that: Including the following processes: forming a first bump on the first electrode on the substrate, and forming a second bump on the second electrode on the substrate; Arrange LED chips on the first bump and the second bump; and heating the first bump and the second bump to electrically connect the LED chip to the first electrode and the second electrode; The LED chip has a step portion on a surface facing the first bump and the second bump, and the first bump is formed by filling the step portion. The formation of the first bump and the second bump includes the following steps: forming a first bump layer on the first electrode and forming a second bump layer on the second electrode; as well as forming a third bump layer in a partial area on the first bump layer; The third bump layer is formed so as to be offset to the side opposite to the second bump layer side.

5. A method for manufacturing an LED module, characterized in that: Including the following processes: forming a first bump on the first electrode on the substrate, and forming a second bump on the second electrode on the substrate; Arrange LED chips on the first bump and the second bump; and heating the first bump and the second bump to electrically connect the LED chip to the first electrode and the second electrode; The LED chip has a step portion on a surface facing the first bump and the second bump, and the first bump is formed by filling the step portion. The formation of the first bump and the second bump includes: forming a first bump layer on the first electrode and forming a second bump layer on the second electrode; The first bump layer is formed to have a tapered upper surface, and the second bump layer is formed to have a flat upper surface.

6. A method for manufacturing a display device, characterized in that: Including the following processes: Forming a first bump on a first electrode disposed in a pixel, and forming a second bump on a second electrode disposed in the pixel; Arrange LED chips on the first bump and the second bump; and heating the first bump and the second bump to electrically connect the LED chip to the first electrode and the second electrode; The LED chip has a step portion on a surface facing the first bump and the second bump, and the first bump is formed in a manner of filling the step portion. The formation of the first bump and the second bump includes the following steps: forming a first bump layer on the first electrode and forming a second bump layer on the second electrode; as well as Further, forming a third bump layer on the first electrode at a position on the opposite side of the first bump layer to the second bump layer; The third bump layer is formed thicker than the first bump layer.

7. The method for manufacturing a display device according to claim 6, wherein: After forming the first bump layer and the second bump layer, performing a first heat treatment to reflow the first bump and the second bump; After the second bump layer is formed, a second heat treatment is performed to reflow the third bump layer.

8. The method for manufacturing a display device according to claim 6, wherein: The formation of the first bump and the second bump includes the following steps: forming a first bump layer on the first electrode and forming a second bump layer on the second electrode; as well as forming a third bump layer in a partial area on the first bump layer; The third bump layer is formed so as to be offset to the side opposite to the second bump layer side.

9. A method for manufacturing a display device, characterized in that: Including the following processes: Forming a first bump on a first electrode disposed in a pixel, and forming a second bump on a second electrode disposed in the pixel; Arrange LED chips on the first bump and the second bump; and heating the first bump and the second bump to electrically connect the LED chip to the first electrode and the second electrode; The LED chip has a step portion on a surface facing the first bump and the second bump, and the first bump is formed in a manner of filling the step portion. The formation of the first bump and the second bump includes the following steps: forming a first bump layer on the first electrode and forming a second bump layer on the second electrode; and A third bump layer is formed on the first bump layer at a position opposite to the second bump layer side of the first bump layer.

10. A method for manufacturing a display device, characterized in that: Including the following processes: Forming a first bump on a first electrode disposed in a pixel, and forming a second bump on a second electrode disposed in the pixel; Arrange LED chips on the first bump and the second bump; and heating the first bump and the second bump to electrically connect the LED chip to the first electrode and the second electrode; The LED chip has a step portion on a surface facing the first bump and the second bump, and the first bump is formed in a manner of filling the step portion. The formation of the first bump and the second bump includes the following steps: forming a first bump layer on the first electrode and forming a second bump layer on the second electrode; The first bump layer is formed to have a tapered upper surface, and the second bump layer is formed to have a flat upper surface.

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