LED chip, preparation method thereof and display device

Abstract

The invention provides an LED chip, a preparation method thereof and a display device. The LED chip comprises a light emitting layer; the insulating layer at least partially covers the bottom surface and the first side surface of the light-emitting layer; the first bonding pad electrode comprises a first electrode part and a second electrode part which are connected with each other, the first electrode part is fixed on the surface of the insulating layer covering the bottom surface and is electrically connected with one of the P electrode and the N electrode in the light-emitting layer through a first extension electrode, and the second electrode part is fixed on the surface of the insulating layer covering the first side surface. By adding the second electrode part on the first side surface of the light-emitting layer, the area of the first electrode part on the bottom surface of the light-emitting layer can be reduced on the premise that the area of the bonding pad electrodes is not reduced, so that the distance between the two bonding pad electrodes on the bottom surface can be increased, the phenomenon of bridging can be reduced, the proportion of top damage can be reduced, and the huge transfer yield can be improved; and the chip miniaturization difficulty is greatly reduced.

Description

Technical Field

[0001] The present application belongs to the field of chip manufacturing technology, and more specifically, to an LED chip, a preparation method thereof, and a display device. Background Art

[0002] In recent years, with the maturity of display technology, Mini LED chips and Micro LED chips have developed rapidly, and products such as SMD (Surface-Mounted Device) and COB (Chip on Board) have emerged in an endless stream. COB products have even entered the consumer market (ToC end). As the display pixel pitch (Pitch, referred to as P) has gradually narrowed from P0.9 and P0.78 to P0.6 or even smaller, the use of Mini / Micro LED chips in the same area has increased exponentially. This trend has put forward higher requirements for chip miniaturization and chip transfer yield.

[0003] The existing flip chip structure faces many challenges in dealing with chip miniaturization. Figure 1 In the existing Mini / Micro LED chip structure, first, the two pad electrodes 5 are located on the bottom surface of the light-emitting layer 1. If the size between the two pad electrodes 5 of the Mini / Micro LED chip is reduced, the luminous efficiency will be significantly reduced. Secondly, taking a 27-inch display box as an example, when the pixel pitch is reduced from P0.9 to P0.625, the number of sub-pixels surges from 691.2K to 1555.2K, showing a geometric growth. This growth will lead to the aggravation of the defects of the P&P (Pick&Place) process, resulting in an increase in the proportion of chip welding bridges and top injuries, which will greatly reduce the chip yield and increase the maintenance cost. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide an LED chip, a preparation method thereof and a display device, so as to solve the technical problem in the prior art that the miniaturization of chips leads to an increase in the proportion of LED chips and top damage, resulting in a significant decrease in chip yield.

[0005] To achieve the above objectives, the technical solution adopted in this application is: in the first aspect, an LED chip is provided, comprising:

[0006] Luminescent layer;

[0007] an insulating layer, at least partially covering a bottom surface and a first side surface of the light-emitting layer, wherein the bottom surface is opposite to the light-emitting surface along a thickness direction of the light-emitting layer, and the bottom surface is adjacent to the first side surface;

[0008] At least two pad electrodes, the at least two pad electrodes include a first pad electrode, the first pad electrode includes a first electrode portion and a second electrode portion connected to each other, the first electrode portion is fixed to the surface of the insulating layer covering the bottom surface, and the first electrode portion is electrically connected to one of the P electrode and the N electrode in the light-emitting layer through a first extended electrode, and the second electrode portion is fixed to the surface of the insulating layer covering the first side surface.

[0009] In an optional implementation of the first aspect, the at least two pad electrodes further include a second pad electrode, the second pad electrode includes a third electrode portion and a fourth electrode portion connected to each other, the insulating layer further at least partially covers a second side surface of the light-emitting layer, and the second side surface is adjacent to the bottom surface;

[0010] The third electrode portion is fixed on the surface of the insulating layer covering the bottom surface, and the third electrode portion is electrically connected to the other of the P electrode and the N electrode in the light-emitting layer through a second extended electrode. The fourth electrode portion is fixed on the surface of the insulating layer covering the second side surface.

[0011] In an optional implementation of the first aspect, the first side surface and the second side surface are arranged opposite to each other.

[0012] In an optional implementation of the first aspect, the LED chip is a Mini LED chip or a Micro LED chip.

[0013] In a second aspect, a method for preparing an LED chip is provided, comprising the following steps:

[0014] providing a light emitting layer;

[0015] forming a first extension electrode on a surface of one of the P electrode and the N electrode located on the bottom surface of the light emitting layer;

[0016] An insulating layer is formed on at least a portion of the bottom surface and the first side surface of the light-emitting layer; the bottom surface is opposite to the light-emitting surface along the thickness direction of the light-emitting layer, and the bottom surface is adjacent to the first side surface;

[0017] A first pad electrode is formed on the surface of the first extended electrode and a portion of the surface of the insulating layer. The first pad electrode includes a first electrode portion and a second electrode portion connected to each other. The first electrode portion is fixed on the surface of the first extended electrode and the surface of the insulating layer covering the bottom surface, and the second electrode portion is fixed on the surface of the insulating layer covering the first side surface.

[0018] In an optional implementation of the second aspect, the method further includes:

[0019] forming a second extension electrode on a surface of the other of the P electrode and the N electrode;

[0020] An insulating layer is formed on at least a portion of the second side surface of the light-emitting layer; the bottom surface is adjacent to the second side surface;

[0021] A second pad electrode is formed on the surface of the second extended electrode and a portion of the surface of the insulating layer, and the second pad electrode includes a third electrode portion and a fourth electrode portion connected to each other, the third electrode portion is fixed on the surface of the second extended electrode and the surface of the insulating layer covering the bottom surface, and the fourth electrode portion is fixed on the surface of the insulating layer covering the second side surface.

[0022] In an optional implementation of the second aspect, the LED chip includes: a red LED chip, a blue LED chip and a green LED chip;

[0023] The method further comprises:

[0024] The thickness of the insulating layer formed on the bottom surface of the light emitting layer of the blue LED chip and the green LED chip is greater than the thickness of the insulating layer formed on the bottom surface of the light emitting layer of the red LED chip.

[0025] In a third aspect, a display device is provided, comprising:

[0026] A substrate is provided with receiving portions arranged in an array;

[0027] An LED solder pad is fixed on the accommodating portion; the LED solder pad comprises a first soldering surface arranged opposite to the surface in the thickness direction of the substrate, and a second soldering surface extending in the thickness direction of the substrate; the first soldering surface is adjacent to the second soldering surface;

[0028] An LED chip, wherein the LED chip is an LED chip as described in any one of the first aspects, or an LED chip prepared by the LED chip preparation method as described in any one of the second aspects; the first welding surface is connected to the first electrode portion, and the second welding surface is connected to the second electrode portion.

[0029] In an optional embodiment of the third aspect, the LED chips on the substrate include a red LED chip, a blue LED chip, and a green LED chip, the thickness of the insulating layer covering the bottom surface of the blue LED chip and the insulating layer covering the bottom surface of the green LED chip are greater than the thickness of the insulating layer covering the bottom surface of the red LED chip, and the thickness of the red LED chip, the blue LED chip, and the green LED chip are the same.

[0030] In an optional embodiment of the third aspect, the thickness of the insulating layer covering the bottom surface in the blue LED chip is the same as the thickness of the insulating layer covering the bottom surface in the green LED chip, and is greater than 7 μm than the thickness of the insulating layer covering the bottom surface in the red LED chip.

[0031] In a fourth aspect, a display device is provided, comprising:

[0032] A substrate, on the first surface of which a receiving unit arranged in an array is provided, wherein the receiving unit includes a first receiving portion, a second receiving portion and a third receiving portion; the first receiving portion has a first receiving surface extending along the first surface, the second receiving portion has a second receiving surface extending along the first surface, and the third receiving portion has a third receiving surface extending along the first surface; and the distance between the first receiving surface and the first surface is greater than any one of the distance between the second receiving surface and the first surface and the distance between the third receiving surface and the first surface;

[0033] An LED soldering pad is fixed on the first accommodating portion, the second accommodating portion and the third accommodating portion; the LED soldering pad comprises a first soldering surface arranged opposite to the first surface, and a second soldering surface extending along the thickness direction of the substrate; the first soldering surface is adjacent to the second soldering surface;

[0034] The LED chip comprises a red LED chip, a green LED chip and a blue LED chip, wherein the red LED chip, the green LED chip and the blue LED chip are the LED chips described in any one of the first aspects, or LED chips prepared by the LED chip preparation method described in any one of the second aspects; the first electrode portion of the red LED chip is connected to the first welding surface of the LED pad fixed on the first accommodating portion, and the second electrode portion of the red LED chip is connected to the second welding surface of the LED pad fixed on the first accommodating portion; the first electrode portion of the green LED chip is connected to the first welding surface of the LED pad fixed on the second accommodating portion, and the second electrode portion of the green LED chip is connected to the second welding surface of the LED pad fixed on the second accommodating portion; the first electrode portion of the blue LED chip is connected to the first welding surface of the LED pad fixed on the third accommodating portion, and the second electrode portion of the blue LED chip is connected to the second welding surface of the LED pad fixed on the third accommodating portion.

[0035] The beneficial effect of this embodiment is that by adding a second electrode portion on the first side of the light-emitting layer, the area of ​​the first electrode portion on the bottom surface of the light-emitting layer can be reduced without reducing the area of ​​the pad electrode, thereby increasing the distance between the two pad electrodes on the bottom surface. This can not only reduce the phenomenon of overseas connection, reduce the proportion of top damage, improve chip resistance, and improve the mass transfer yield, but also greatly reduce the difficulty of chip miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0037] Figure 1 It is a structural schematic diagram of an LED chip in the prior art;

[0038] Figure 2 A cross-sectional view of an LED chip provided in one embodiment of the present application;

[0039] Figure 3 A cross-sectional view of an LED chip provided in another embodiment of the present application;

[0040] Figure 4 The overall flow chart of the LED chip preparation method provided in the embodiment of the present application;

[0041] Figure 5 A cross-sectional view of an epitaxial wafer provided in an embodiment of the present application;

[0042] Figure 6 A cross-sectional view of an epitaxial wafer after exposure, development, and etching provided in an embodiment of the present application;

[0043] Figure 7 A cross-sectional view after evaporation of a P electrode and an N electrode provided in an embodiment of the present application;

[0044] Figure 8 A cross-sectional view of a first extended electrode and a second extended electrode after evaporation according to an embodiment of the present application

[0045] Fig. 9 A cross-sectional view after the insulation layer is evaporated according to an embodiment of the present application;

[0046] Fig.10 A cross-sectional view of a first pad electrode and a second pad electrode after evaporation provided in an embodiment of the present application;

[0047] Fig.11A cross-sectional view of a LED chip after being split provided in an embodiment of the present application;

[0048] Fig.12 A cross-sectional view of an LED pad provided in an embodiment of the present application;

[0049] Fig.13 A schematic diagram of the structure of an LED soldering pad provided in an embodiment of the present application;

[0050] Fig.14 This is a schematic diagram of the structure after welding the LED chip and LED pad provided in an embodiment of the present application.

[0051] Among them, the reference numerals in the figure are:

[0052] 1-light-emitting layer, 11-N-type semiconductor layer, 12-multi-quantum well layer, 13-P-type semiconductor layer, 14-ITO layer, 15-DBR layer, 16-P electrode, 17-N electrode, 18-bottom surface, 19-first side surface, 110-second side surface, 111-light-emitting surface along the thickness direction of the light-emitting layer, 2-insulating layer, 3-first extended electrode, 4-second extended electrode, 5-pad electrode, 51-first pad electrode, 511-first electrode portion, 512-second electrode portion, 52-second pad electrode, 521-third electrode portion, 522-fourth electrode portion, 53-third pad electrode, 6-substrate, 7-LED pad, 71-first welding surface, 72-second welding surface, 73-PCB ink, 74-third welding surface, 75-fourth welding surface, 8-epitaxial wafer, 81-first receiving groove, 82-second receiving groove. DETAILED DESCRIPTION

[0053] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0054] In the description of the embodiments of the present application, the term "plurality" refers to more than two (including two).

[0055] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0056] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0057] It should be understood that in the embodiments of the present application, "electrical connection" can be understood as physical contact and electrical conduction between components; it can also be understood as a form in which different components in a circuit structure are connected through physical lines such as printed circuit board (PCB) copper foil or wires that can transmit electrical signals.

[0058] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", and "circumferential" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0059] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0060] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0061] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments in any suitable manner.

[0062] See also Figure 2 , an LED chip provided in an embodiment of the present application is now described, the LED chip comprising: a light-emitting layer 1; an insulating layer 2, at least partially covering a bottom surface 18 and a first side surface 19 of the light-emitting layer 1, the bottom surface 18 being opposite to a light-emitting surface 111 along a thickness direction of the light-emitting layer, and the bottom surface 18 being adjacent to the first side surface 19; at least two pad electrodes 5, the at least two pad electrodes 5 comprising a first pad electrode 51, the first pad electrode 51 comprising a first electrode portion 511 and a second electrode portion 512 connected to each other, the first electrode portion 511 being fixed on a surface of the insulating layer 2 covering the bottom surface 18, and the first electrode portion 511 being electrically connected to a P electrode 16 in the light-emitting layer 1 through a first extension electrode 3, and the second electrode portion 512 being fixed on a surface of the insulating layer 2 covering the first side surface 19.

[0063] Optionally, the light-emitting layer 1 is a very thin rectangular parallelepiped structure, which has six faces, namely, the top face, the bottom face 18 and four side faces, wherein the top face is the light-emitting face along the thickness direction of the light-emitting layer 1, and the first side face 19 can be any of the four side faces. The LED chip prepared based on the light-emitting layer 1 has five light-emitting faces, namely, the top face and four side faces.

[0064] The pad electrode 5 can be a gold electrode or a tin electrode. By energizing the pad electrode 5 , the light-emitting layer 1 can emit light to achieve the lighting function.

[0065] Specifically, one end surface of the first extended electrode 3 contacts the P electrode 16 located on the bottom surface 18 of the light-emitting layer 1, and the other end surface of the first extended electrode 3 contacts a partial first electrode portion 511 of the first pad electrode 51, thereby realizing electrical connection between the first electrode portion 511 and the P electrode 16 in the light-emitting layer 1 through the first extended electrode 3.

[0066] By providing the insulating layer 2 on at least a portion of the bottom surface 18 and the first side surface 19 of the light-emitting layer 1, the pad electrode 5 can be isolated from the light-emitting layer 1, thereby preventing the light-emitting layer 1 other than the first extension electrode 3 from being electrically connected to the first pad electrode 51. Optionally, the insulating layer 2 is made of silicon dioxide (SiO 2 ) material.

[0067] It is easy to understand that the extension height of the insulating layer 2 on the first side surface 19 must be greater than or equal to the extension height of the second electrode portion 512 , that is, it is necessary to ensure that the area facing the second electrode portion 512 is covered by the insulating layer 2 .

[0068] By adding a second electrode portion 512 to the first side surface 19 of the light-emitting layer 1, the present embodiment can reduce the area of ​​the first electrode portion 511 of the bottom surface 18 of the light-emitting layer 1 without reducing the area of ​​the pad electrode 5, thereby increasing the distance between the two pad electrodes 5 on the bottom surface 18. This can not only reduce the phenomenon of cross-linking, reduce the proportion of top damage, improve chip resistance, and improve the mass transfer yield, but also greatly reduce the difficulty of chip miniaturization.

[0069] Specifically, the overall size of the LED chip can be reduced by reducing the spacing between the pad electrodes 5 on the bottom surface 18 .

[0070] In addition, although the area of ​​the first electrode portion 511 of the bottom surface 18 of the light-emitting layer 1 is reduced in this embodiment, the total electrode area will not be reduced, and the light-emitting efficiency will not be reduced because the second electrode portion 512 is added to the first side surface 19 of the light-emitting layer 1. In this embodiment, the total area of ​​the pad electrode 5 can also be made larger, thereby increasing the light-emitting efficiency to a certain extent.

[0071] As an optional implementation, see Figure 2 At least two pad electrodes 5 further include a third pad electrode 53. The third pad electrode 53 is fixed on the surface of the insulating layer 2 covering the bottom surface 18, and the third pad electrode 53 is electrically connected to the N electrode 17 of the light emitting layer 1 through the second extension electrode 4.

[0072] It is easy to understand that the first pad electrode 51 and the third pad electrode 53 can also be set upside down, that is, the first electrode portion 511 of the first pad electrode 51 is electrically connected to the N electrode 17, and the third pad electrode 53 is electrically connected to the P electrode 16 (not shown in the figure).

[0073] As another optional implementation, see Figure 3 , at least two pad electrodes 5 further include a second pad electrode 52, the second pad electrode 52 includes a third electrode portion 521 and a fourth electrode portion 522 connected to each other, the insulating layer 2 also at least partially covers the second side surface 110 of the light-emitting layer 1, and the second side surface 110 is adjacent to the bottom surface 18. The third electrode portion is fixed to the surface of the insulating layer 2 covering the bottom surface 18, and the third electrode portion 521 is electrically connected to the N electrode 17 in the light-emitting layer 1 through the second extension electrode 4, and the fourth electrode portion 522 is fixed to the surface of the insulating layer 2 covering the second side surface 110.

[0074] Specifically, one end surface of the second extended electrode 4 contacts the N electrode 17 located on the bottom surface 18 of the light-emitting layer 1, and the other end surface of the second extended electrode 4 contacts part of the first electrode portion of the second pad electrode 52, thereby realizing electrical connection between the third electrode portion 521 and the N electrode 17 in the light-emitting layer 1 through the second extended electrode 4.

[0075] In this embodiment, the second electrode portion 512 is disposed on the first side surface 19 and the fourth electrode portion 522 is disposed on the second side surface 110, thereby reducing the area of ​​the first electrode portion 511 and the area of ​​the third electrode portion 521. Figure 2 In the embodiment shown, this embodiment can further reduce the distance between the first electrode portion 511 and the third electrode portion 521 , and by reducing the distance between the P electrode 16 and the N electrode 17 , the overall size of the LED chip is more compact.

[0076] Figure 3 The first side surface 19 and the second side surface 110 are arranged opposite to each other, and the first pad electrode 51 and the second pad electrode 52 can be a symmetrical structure, wherein the first side surface 19 is close to the P electrode 16 and the second side surface 110 is close to the N electrode 17 .

[0077] By symmetrically arranging the first pad electrode 51 and the second pad electrode 52, the current can be distributed more evenly in the light-emitting layer 1, reducing the risk of current concentration in a specific area, thereby improving the light efficiency and service life of the LED. The symmetrical structure may be easier to achieve during the manufacturing process, which can improve production efficiency and yield.

[0078] In some other optional embodiments, the first side surface 19 and the second side surface 110 may be arranged adjacent to each other (not shown in the figure), and the first pad electrode 51 and the second pad electrode 52 are asymmetrical structures. In this embodiment, the overall size of the LED chip can also be made more compact.

[0079] Figure 2 and Figure 3 The LED chip structures shown all include two pad electrodes 5. In other embodiments, in order to increase the area of ​​the pad electrodes 5, more pad electrodes 5 may be added. For example, at least two pad electrodes include four pad electrodes 5, namely, a first pad electrode 51, a second pad electrode 52, a fourth pad electrode and a fifth pad electrode (not shown in the figure), and at least a portion of the third side and the fourth side of the light-emitting layer are covered with an insulating layer, wherein the fourth pad electrode is fixed on the surface of the insulating layer covering the third side, and the fourth pad electrode is electrically connected to the first pad electrode; the fifth pad electrode is fixed on the surface of the insulating layer covering the fourth side, and the fourth pad electrode is electrically connected to the second pad electrode.

[0080] Exemplarily, the light emitting layer 1 in this embodiment includes a P-electrode 16, an N-electrode 17, and an N-type semiconductor layer 11, a multi-quantum well layer 12, a P-type semiconductor layer 13, an ITO layer 14, and a DBR layer 15 stacked in sequence. The P-electrode 16 extends from the P-type semiconductor layer 13 to the surface of the DBR layer 15 away from the ITO layer 14, and the N-electrode 17 extends from the N-type semiconductor layer 11 to the surface of the DBR layer 15 away from the ITO layer 14.

[0081] The N-type semiconductor layer 11 is the source of electrons (negative charge carriers) in the LED chip. It is usually composed of a semiconductor material (such as GaN) doped with donor impurities (such as silicon or germanium). When the LED is working, electrons are injected from the N-type semiconductor layer 11 into the active region (light-emitting layer 1) and recombine with holes to generate photons. The light-emitting surface 111 along the thickness direction of the light-emitting layer is the side of the N-type semiconductor layer 11 away from the multi-quantum well layer 12.

[0082] The multi-quantum well layer 12 is composed of multiple thin semiconductor layers alternately. Its function is to provide a light emission area where electrons and holes recombine to generate photons. The design of the quantum well can change the wavelength of the emitted light by changing the doping elements, thereby achieving light emission of different colors.

[0083] The P-type semiconductor layer 13 is the source of holes (positive charge carriers) in the LED chip. It is usually composed of semiconductor materials (such as GaN) doped with acceptor impurities (such as magnesium). When the LED is working, holes are injected from the P-type semiconductor layer 13 into the active region and recombine with electrons to generate photons.

[0084] The ITO layer 14 (indium tin oxide layer) is a transparent conductive layer that has good conductivity and light transmittance, and can evenly distribute current while allowing light to pass through. The ITO layer 14 plays the role of current expansion and light transmission in the LED chip.

[0085] The DBR layer 15 (distributed Bragg reflector) is a reflective structure formed by alternating multiple layers of materials with different refractive indices, which can selectively reflect light of a specific wavelength. In the LED chip, the DBR layer 15 is used to reflect light of a specific wavelength and propagate it toward the light-emitting surface, thereby improving the luminous efficiency.

[0086] The insulating layer 2 can be made of materials such as silicon dioxide or silicon nitride. By covering the outer surface of the epitaxial layer with the insulating layer 2, the electrode and the epitaxial layer can be effectively isolated to prevent current leakage.

[0087] As an optional implementation, the LED chip further includes a substrate 6, and the substrate 6 is in surface contact with the light-emitting surface of the light-emitting layer 1 along the thickness direction of the light-emitting layer 1. That is, the LED chip in this embodiment may include a substrate 6 or may be a structure without a substrate 6. The substrate 6 may be made of sapphire or silicon carbide with high thermal conductivity.

[0088] Optionally, the LED chip in the embodiment of the present application can be a flip chip, and the LED chip is a Mini LED chip or a Micro LED chip. Mini LED chip is an LED chip with a size between traditional LED and Micro LED, and its size is usually between tens to hundreds of microns. Micro LED chip is an LED chip with a smaller size, and its size is usually between a few microns and tens of microns. Due to its smaller size, Micro LED can achieve higher resolution, lower power consumption and better color performance.

[0089] See also Figures 4 to 11 The present application also provides a method for preparing an LED chip, comprising the following steps:

[0090] S1: exposing, developing, and etching the epitaxial wafer 8 to form a plurality of first receiving grooves 81 and a plurality of second receiving grooves 82 ; wherein the first receiving grooves 81 are etched to the P-type semiconductor layer 13 , and the second receiving grooves 82 are etched to the N-type semiconductor layer 11 .

[0091] See also Figure 5 and Figure 6 The epitaxial wafer 8 includes a substrate 6 and an epitaxial layer. Exemplarily, the epitaxial layer includes an N-type semiconductor layer 11, a multi-quantum well layer 12, a P-type semiconductor layer 13, an ITO layer 14 and a DBR layer 15 stacked in sequence, wherein the N-type semiconductor layer 11 is stacked on the substrate 6.

[0092] S2: vapor-depositing a P-type conduction electrode in the first receiving groove 81 and vapor-depositing an N-type conduction electrode in the second receiving groove 82 to obtain a light-emitting layer 1; wherein a gap exists between the outer wall of the N-type conduction electrode and the inner wall of the second receiving groove 82.

[0093] Optional, see Figure 7 , one end surface of the N-type conduction electrode and the P-type conduction electrode is flush with the end surface of the DBR layer 15. After completing S2, the light-emitting layer 1 can be obtained. Optionally, the light-emitting layer 1 that is the same as or different from that in this embodiment can also be obtained by other methods.

[0094] S3: vapor-depositing a first extension electrode 3 on one end surface of the P-type conduction electrode, and vapor-depositing a second extension electrode 4 on one end surface of the N-type conduction electrode.

[0095] The first extension electrode 3 and the second extension electrode 4 can be evaporated at the same time or sequentially, which is not limited in this embodiment.

[0096] See also Figure 8 , the thickness of the first extended electrode 3 is consistent with the thickness of the second extended electrode 4.

[0097] S4 : vapor-depositing the insulating layer 2 on at least a portion of the bottom surface 18 and the side surfaces of the light-emitting layer 1 .

[0098] See also Fig. 9 The insulating layer 2 closes the gap between the outer wall of the N-type conduction electrode and the inner wall of the second receiving groove 82, and the surface of the DBR layer 15 away from the insulating layer 2 is flush with the surface of the first extension electrode 3 away from the P electrode 16 and the surface of the second extension electrode 4 away from the N electrode 17.

[0099] Optionally, the insulating layer 2 is made of silicon dioxide (SiO2).

[0100] S5: The first pad electrode 51 is evaporated on the surface of part of the insulating layer 2 and the surface of the first extended electrode 3, and the second pad electrode 52 is evaporated on the surface of part of the insulating layer 2 and the surface of the second extended electrode 4, to obtain an array-type LED chip unit; the first pad electrode 51 includes a first electrode portion 511 and a second electrode portion 512 connected to each other, the first electrode portion 511 is fixed on the surface of the first extended electrode 3 and the surface of the insulating layer 2 covering the bottom surface, and the second electrode portion 512 is fixed on the surface of the insulating layer 2 covering the first side surface 19. The second pad electrode 52 includes a third electrode portion 521 and a fourth electrode portion 522 connected to each other, the third electrode portion 521 is fixed on the surface of the second extended electrode 4 and the surface of the insulating layer 2 covering the bottom surface 18, and the fourth electrode portion 522 is fixed on the surface of the insulating layer 2 covering the second side surface 110.

[0101] It is worth noting that the first pad electrode 51 and the second pad electrode 52 can be evaporated at the same time or sequentially, which is not limited in this embodiment.

[0102] See also Fig.10 The first pad electrode 51 is connected to the first extension electrode 3, the second pad electrode 52 is connected to the second extension electrode 4, and the first pad electrode 51 and the second pad electrode 52 are symmetrically arranged to provide a guarantee for the stable transmission of the electrical signal.

[0103] In another embodiment, the second pad electrode 52 in S5 may be replaced by a third pad electrode 53 , wherein the third pad electrode 53 is fixed on the surface of the insulating layer 2 covering the bottom surface 18 of the light-emitting layer 1 , and the third pad electrode 53 is in contact with the second extension electrode 4 .

[0104] S6: performing a splitting process on the array-type LED chip unit obtained in S5 to obtain a plurality of independent LED chips.

[0105] See also Fig.11 After splitting, multiple independent LED chips are formed.

[0106] S7: The LED chips are cleaned and tested after being split.

[0107] As an optional implementation, after step S5, step S51 is performed, in which the substrate 6 in the array LED chip unit is peeled off, and then steps S6 and S7 are performed to obtain an LED chip without substrate 6.

[0108] The LED chip preparation method of this embodiment can prepare a MiniLED chip or a micro LED chip with high density, high brightness and high reliability. Of course, LED chips of larger size can also be prepared.

[0109] The inventors found that in the existing flip-chip, the thickness of the light-emitting layer 1 of the green LED chip and the light-emitting layer 1 of the blue LED chip is about 7 μm thinner than the thickness of the light-emitting layer 1 of the red LED chip, which causes the screen to have a reddish color at a wide viewing angle. Therefore, in this embodiment, when preparing the red LED chip, the thickness of the insulating layer 2 covering the bottom surface 18 of the light-emitting layer 1 is 3 μm; when preparing the green and blue LED chips, the thickness of the insulating layer 2 covering the bottom surface 18 of the light-emitting layer 1 is adjusted to 10 μm, so that the thickness of the light-emitting layer 1 of the three colors of LED chips is consistent, weakening the color deviation problem at a wide viewing angle and improving the consistency of the display screen at a wide viewing angle.

[0110] See also Figure 12 to Figure 14 The present application also provides a display device, comprising: a substrate, provided with an array-arranged accommodating portion; an LED pad 7, fixed on the accommodating portion; the LED pad 7 comprises a first welding surface 71 arranged opposite to a surface in a thickness direction of the substrate, and a second welding surface 72 extending along the thickness direction of the substrate; the first welding surface 71 is adjacent to the second welding surface 72; and the LED chip in any of the above embodiments or the LED chip prepared by the above LED chip preparation method, the first welding surface 71 is connected to the first electrode portion, and the second welding surface 72 is connected to the second electrode portion.

[0111] Each LED chip is a sub-pixel, and a pixel consists of three sub-pixels, corresponding to the red LED chip, green LED chip, and blue LED chip. Multiple rows and columns of pixels are arranged on the substrate to form a display panel. By controlling the brightness of each sub-pixel, different colors can be combined to display images.

[0112] After the existing flip chip is miniaturized, the spacing between the LED chip arrays on the substrate (PCB GAP) can be reduced simultaneously. However, the yield will drop drastically for every 5μm reduction in the PCB GAP, and the manufacturing cost will also increase significantly. The reasons for this phenomenon include: after the chip is miniaturized, the accuracy requirements for installing the LED chip on the substrate are higher, and the chip offset and poor rotation phenomena will increase, resulting in a drastic drop in yield.

[0113] The present embodiment can meet the bonding requirements of smaller chips by designing the LED pad 7, and can effectively avoid welding deviation and rotation caused by chip miniaturization, thereby improving the bonding yield.

[0114] The substrate is provided with PCB ink 73, which has high thermal conductivity and good insulation, and can reduce the occurrence of short circuit or leakage when the LED chip is soldered to the substrate. The LED pad 7 can be made of copper.

[0115] Optionally, the LED soldering pad 7 also includes a third welding surface 74 arranged opposite to the surface in the thickness direction of the substrate, and a fourth welding surface 75 extending along the thickness direction of the substrate; the third welding surface 74 is adjacent to the fourth welding surface 75; the third welding surface 74 is connected to the third electrode portion 521, and the third welding surface 74 is connected to the fourth electrode portion 522.

[0116] Optionally, the third welding surface 74 and the fourth welding surface 75 are symmetrically arranged with respect to the first welding surface 71 and the second welding surface 72 .

[0117] Specifically, the LED chips on the substrate include red LED chips, blue LED chips, and green LED chips. Fig.13 , Fig.13 There are three LED pads 7, which can be connected to the pad electrodes 5 of the red, green and blue LED chips respectively.

[0118] As an optional embodiment, the thickness of the insulating layer 2 covering the bottom surface 18 in the blue light LED chip and the insulating layer 2 covering the bottom surface 18 in the green light LED chip is greater than the thickness of the insulating layer 2 covering the bottom surface 18 in the red light LED chip, and the thicknesses of the red light LED chip, the blue light LED chip and the green light LED chip are the same.

[0119] This embodiment can effectively solve the color shift problem under a wide viewing angle and improve the overall display effect of the display screen by keeping the thickness of the light-emitting layer 1 of the blue and green LED chips consistent with that of the red LED chip.

[0120] Specifically, the thickness of the insulating layer 2 covering the bottom surface 18 in the blue LED chip is the same as that in the green LED chip, and is greater than 7 μm in thickness of the insulating layer 2 covering the bottom surface 18 in the red LED chip.

[0121] In an optional embodiment, a display device is provided, comprising:

[0122] A substrate is provided with an array-arranged accommodating unit on the first surface, the accommodating unit includes a first accommodating portion, a second accommodating portion and a third accommodating portion; the first accommodating portion has a first accommodating surface extending along the first surface, the second accommodating portion has a second accommodating surface extending along the first surface, and the third accommodating portion has a third accommodating surface extending along the first surface; the distance between the first accommodating surface and the first surface is greater than any one of the distance between the second accommodating surface and the first surface and the distance between the third accommodating surface and the first surface.

[0123] The LED pad 7 is fixed on the first accommodating portion, the second accommodating portion and the third accommodating portion; the LED pad includes a first welding surface 71 arranged opposite to the first surface, and a second welding surface 72 extending along the thickness direction of the substrate; the first welding surface 71 is adjacent to the second welding surface 72.

[0124] The LED chip comprises a red LED chip, a green LED chip and a blue LED chip; the first electrode portion 511 of the red LED chip is connected to the first welding surface 71 of the LED solder pad 7 fixed on the first accommodating portion, and the second electrode portion 512 of the red LED chip is connected to the second welding surface 72 of the LED solder pad 7 fixed on the first accommodating portion; the first electrode portion 511 of the green LED chip is connected to the first welding surface 71 of the LED solder pad 7 fixed on the second accommodating portion, and the second electrode portion 512 of the green LED chip is connected to the second welding surface 72 of the LED solder pad fixed on the second accommodating portion; the first electrode portion 511 of the blue LED chip is connected to the first welding surface 71 of the LED solder pad 7 fixed on the third accommodating portion, and the second electrode portion 512 of the blue LED chip is connected to the second welding surface 72 of the LED solder pad 7 fixed on the third accommodating portion.

[0125] Specifically, the first surface of the substrate is a surface for soldering the LED pads, which may be referred to as a soldering surface or a component surface.

[0126] Since the thickness of the light-emitting layer 1 of the red LED chip in the existing flip chip is about 7μm thicker than that of the light-emitting layer 1 of the green LED chip and the light-emitting layer 1 of the blue LED chip, this causes the screen to be reddish at a large viewing angle. In order to overcome this problem, the first accommodation portion corresponding to the red LED chip is designed as a sinking groove structure in this embodiment. Optionally, the sinking depth of the first accommodation surface can be 7μm, while the second accommodation surface and the third accommodation surface are flush with the first surface; or the first accommodation surface, the second accommodation surface and the third accommodation surface are all sunken, but the sinking depth of the first accommodation surface is 7μm deeper than the sinking depth of the second accommodation surface and the third accommodation surface, so that the light-emitting surface 111 of the red LED chip along the direction of the light-emitting layer thickness and the light-emitting surface 111 of the blue LED chip along the direction of the light-emitting layer thickness and the light-emitting surface 111 of the green LED chip along the direction of the light-emitting layer thickness remain on the same plane.

[0127] This design can, on the one hand, reduce the reddishness of the screen at large viewing angles to a certain extent, and on the other hand, increase the contact area between the substrate and the LED pad 7 .

[0128] It is worth noting that the above 7μm is only an example. If it is found by measurement that the thickness of the light-emitting layer 1 of the red LED chip is about 5μm thicker than the thickness of the light-emitting layer 1 of the green LED chip and the thickness of the light-emitting layer 1 of the blue LED chip, then the above 7μm needs to be adjusted to 5μm accordingly.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. An LED chip, characterized in that: include: Luminescent layer; an insulating layer, at least partially covering a bottom surface and a first side surface of the light-emitting layer, wherein the bottom surface is opposite to the light-emitting surface along a thickness direction of the light-emitting layer, and the bottom surface is adjacent to the first side surface; At least two pad electrodes, the at least two pad electrodes include a first pad electrode, the first pad electrode includes a first electrode portion and a second electrode portion connected to each other, the first electrode portion is fixed to the surface of the insulating layer covering the bottom surface, and the first electrode portion is electrically connected to one of the P electrode and the N electrode in the light-emitting layer through a first extended electrode, and the second electrode portion is fixed to the surface of the insulating layer covering the first side surface.

2. The LED chip according to claim 1, characterized in that: The at least two pad electrodes further include a second pad electrode, the second pad electrode includes a third electrode portion and a fourth electrode portion connected to each other, the insulating layer further at least partially covers a second side surface of the light emitting layer, and the second side surface is adjacent to the bottom surface; The third electrode portion is fixed on the surface of the insulating layer covering the bottom surface, and the third electrode portion is electrically connected to the other of the P electrode and the N electrode in the light-emitting layer through a second extended electrode. The fourth electrode portion is fixed on the surface of the insulating layer covering the second side surface.

3. The LED chip according to claim 2, characterized in that: The first side surface and the second side surface are arranged opposite to each other.

4. The LED chip according to any one of claims 1 to 3, characterized in that: The LED chip is a Mini LED chip or a Micro LED chip.

5. A method for preparing an LED chip, characterized in that: The steps include: providing a light emitting layer; forming a first extension electrode on a surface of one of the P electrode and the N electrode located on the bottom surface of the light emitting layer; An insulating layer is formed on at least a portion of the bottom surface and the first side surface of the light-emitting layer; the bottom surface is opposite to the light-emitting surface along the thickness direction of the light-emitting layer, and the bottom surface is adjacent to the first side surface; A first pad electrode is formed on the surface of the first extended electrode and a portion of the surface of the insulating layer. The first pad electrode includes a first electrode portion and a second electrode portion connected to each other. The first electrode portion is fixed on the surface of the first extended electrode and the surface of the insulating layer covering the bottom surface, and the second electrode portion is fixed on the surface of the insulating layer covering the first side surface.

6. The method for preparing an LED chip according to claim 5, characterized in that: The method further comprises: forming a second extension electrode on a surface of the other of the P electrode and the N electrode; An insulating layer is formed on at least a portion of the second side surface of the light-emitting layer; the bottom surface is adjacent to the second side surface; A second pad electrode is formed on the surface of the second extended electrode and a portion of the surface of the insulating layer, and the second pad electrode includes a third electrode portion and a fourth electrode portion connected to each other, the third electrode portion is fixed on the surface of the second extended electrode and the surface of the insulating layer covering the bottom surface, and the fourth electrode portion is fixed on the surface of the insulating layer covering the second side surface.

7. The method for preparing an LED chip according to claim 5, wherein: The LED chips include: a red LED chip, a blue LED chip and a green LED chip; The method further comprises: The thickness of the insulating layer formed on the bottom surface of the light emitting layer of the blue LED chip and the green LED chip is greater than the thickness of the insulating layer formed on the bottom surface of the light emitting layer of the red LED chip.

8. A display device, characterized in that: include: A substrate is provided with receiving portions arranged in an array; An LED solder pad is fixed on the accommodating portion; the LED solder pad comprises a first soldering surface arranged opposite to the surface in the thickness direction of the substrate, and a second soldering surface extending in the thickness direction of the substrate; the first soldering surface is adjacent to the second soldering surface; An LED chip, wherein the LED chip is an LED chip as described in any one of claims 1-5, or an LED chip prepared by the LED chip preparation method as described in any one of claims 6-8; the first welding surface is connected to the first electrode portion, and the second welding surface is connected to the second electrode portion.

9. The display device according to claim 8, wherein: The LED chips on the substrate include a red LED chip, a blue LED chip, and a green LED chip. The thickness of the insulating layer covering the bottom surface of the blue LED chip and the insulating layer covering the bottom surface of the green LED chip are greater than the thickness of the insulating layer covering the bottom surface of the red LED chip, and the thickness of the red LED chip, the blue LED chip, and the green LED chip are the same.

10. The display device according to claim 9, characterized in that The thickness of the insulating layer covering the bottom surface of the blue LED chip is the same as the thickness of the insulating layer covering the bottom surface of the green LED chip, and is greater than 7 μm in thickness of the insulating layer covering the bottom surface of the red LED chip.

11. A display device, characterized in that: include: A substrate, on the first surface of which a receiving unit arranged in an array is provided, wherein the receiving unit includes a first receiving portion, a second receiving portion and a third receiving portion; the first receiving portion has a first receiving surface extending along the first surface, the second receiving portion has a second receiving surface extending along the first surface, and the third receiving portion has a third receiving surface extending along the first surface; and the distance between the first receiving surface and the first surface is greater than any one of the distance between the second receiving surface and the first surface and the distance between the third receiving surface and the first surface; An LED soldering pad is fixed on the first accommodating portion, the second accommodating portion and the third accommodating portion; the LED soldering pad comprises a first soldering surface arranged opposite to the first surface, and a second soldering surface extending along the thickness direction of the substrate; the first soldering surface is adjacent to the second soldering surface; LED chips, including red LED chips, green LED chips and blue LED chips, wherein the red LED chips, the green LED chips and the blue LED chips are LED chips as described in any one of claims 1 to 5, or LED chips prepared by the LED chip preparation method as described in any one of claims 6 to 8; the first electrode portion of the red LED chip is connected to the first welding surface of the LED pad fixed on the first accommodating portion, and the second electrode portion of the red LED chip is connected to the second welding surface of the LED pad fixed on the first accommodating portion; the first electrode portion of the green LED chip is connected to the first welding surface of the LED pad fixed on the second accommodating portion, and the second electrode portion of the green LED chip is connected to the second welding surface of the LED pad fixed on the second accommodating portion; the first electrode portion of the blue LED chip is connected to the first welding surface of the LED pad fixed on the third accommodating portion, and the second electrode portion of the blue LED chip is connected to the second welding surface of the LED pad fixed on the third accommodating portion.

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