A micro LED chip and control substrate eutectic structure and preparation method thereof

Abstract

The present invention discloses a micro LED chip and a control substrate eutectic structure and a preparation method thereof. The structure is obtained by welding a micro LED chip (1) and a control substrate (2) together simultaneously by using a laser. The micro LED chip (1) comprises a chip substrate (14) and a plurality of LED chips (11) fixed on the chip substrate (14). The plurality of LED chips (11) have a common first negative electrode (12), and the plurality of LED chips (11) respectively have an independent first positive electrode (13). The control substrate (2) is located below the micro LED chip (1) and comprises a control substrate body. (21) and a plurality of second positive electrodes (22) and a second negative electrode (23) located on the control substrate body (21); wherein the longitudinal thickness of the first negative electrode (12) is equal to the longitudinal thickness of the first positive electrode (13); the longitudinal thickness of the second negative electrode (23) is equal to the sum of the longitudinal thickness of the second positive electrode (22) and the longitudinal thickness of the LED chip (11), and this thickness allows the welding to be completed with the same heating time during eutectic welding, thereby solving the problem that during laser eutectic welding, the first positive electrode (13) has melted, while the first negative electrode (12) is too thick and has not melted.

Description

Technical Field

[0001] The patent of this invention belongs to the field of micro LED technology, and specifically relates to a eutectic structure of a micro LED chip and a control substrate and a preparation method thereof. Background Art

[0002] MicroLED technology is a miniature matrix technology for LEDs, which refers to a high-density micrometer-level LED array integrated on a chip. It is widely used in display screens, visible light communications, smart portable devices and other fields. It has the advantages of stable performance and long life, and also continues the advantages of LED such as low power consumption, fast response speed and strong contrast. It also inherits the advantages of LED such as low power consumption, color saturation, fast response speed and strong contrast. The brightness of MicroLED is 30 times higher than that of OLED, and the energy consumption is about 10% of LCD and 50% of OLED.

[0003] MicroLED will have great application prospects in the future, but the current problem of MicroLED manufacturing cost has seriously affected its commercialization process. The main reason is that the bottleneck of mass transfer technology still needs to be broken through. The traditional mass transfer is single transfer and single eutectic welding. Single transfer seriously limits the mass production process of MicroLED. Due to the higher resolution of MicroLED, a small MicroLED display contains a large number of LED chips. For example, a 0.39-inch MicroLED display contains about 2.4 million LED chips. If the single transfer method is used, it is particularly time-consuming and labor-intensive and difficult to implement. Single eutectic welding will greatly reduce the product qualification rate. The reason is that single eutectic welding is to transfer an LED chip and heat the control substrate to weld it to the control substrate. After the next LED chip is transferred, the control substrate will be heated as a whole to weld the second LED chip to the control substrate. When the control substrate is heated as a whole, the welding point of the first LED chip will melt. The problem of secondary melting occurs multiple times, which damages the LED chip and seriously affects the product qualification rate.

[0004] More specifically, in the prior art, the eutectic heating method on the circuit board side is to place LEDs one by one on the control substrate. Each time they are placed, they will be heated repeatedly. Repeated heating will damage the eutectic LED grains and make it difficult to achieve mass transfer of LEDs. The present invention uses laser eutectic welding. Eutectic laser welding is a eutectic method that aligns and welds the entire LED array on the control substrate once and then removes the sapphire substrate. The present invention aligns and mounts a micro LED chip with multiple LED chips and a control substrate together; the laser eutectic welding system is used to heat the welding points and complete the welding. It can effectively prevent the secondary melting of the eutectic welding points of a single MicroLED transfer and cause damage to the MicroLED.

[0005] However, since the N pole (positive pole) is located at the top of the LED light-emitting layer, its initial position is one LED light-emitting layer thicker than the P pole (negative pole). Therefore, if the N pole and the P pole of the micro LED chip are to be at the same height, the thickness of the P pole must be one LED light-emitting layer thicker than the N pole ( Figure 2 ), which will result in the N pole being melted during laser eutectic welding, while the P pole is too thick and has not yet melted. In order to ensure that the P pole is melted, the heating time will be too long, which may cause damage to the LED chip.

[0006] In order to solve this problem, the present invention is proposed. Summary of the invention

[0007] First, the present invention proposes to use laser heating to complete the eutectic welding and mounting of MicroLED and control substrate. Furthermore, the present invention adjusts the thickness of the positive (N pole) and negative (P pole) welding points on the micro LED chip and the control substrate, and the present invention proposes a eutectic structure of the micro LED chip and the control substrate, that is, the LED electrode metal film layer is the heating surface. In order to ensure that the P pole and N pole of the micro LED chip are heated evenly and the heating time is consistent, the P pole and N pole film layers of the LED electrode metal film layer are the same thickness; the control substrate electrode metal film layer is a passive heating surface. Because the P pole of the micro LED chip is different from the N pole by the thickness of the LED light-emitting layer, the N pole of the control substrate electrode metal layer is thicker than the P pole by the same thickness of the LED. It not only ensures that the alignment and bonding points of the two are on the same horizontal plane, but also ensures that the P pole and N pole thickness of the micro LED chip are the same.

[0008] In summary, the objectives of the present invention are: 1. When the LED and the control substrate are eutectic, the metal film layer at the eutectic point is heated evenly and the heating time is consistent. 2. The eutectic metal film layer structure of the micro LED and the control substrate is prepared to meet the requirements of laser eutectic.

[0009] The first aspect of the present invention provides a micro LED chip and control substrate eutectic structure, which is obtained by welding a plurality of LED chips in a micro LED chip 1 and a control substrate 2 together simultaneously by using a laser; the micro LED chip 1 includes a control substrate 2 and a micro LED chip 1 having a plurality of LED chips;

[0010] The micro LED chip 1 includes a chip substrate 14 and a plurality of LED chips 11 fixed on the chip substrate 14; the plurality of LED chips 11 have a common first negative electrode 12, and the plurality of LED chips 11 respectively have an independent first positive electrode 13;

[0011] The control substrate 2 is located below the micro LED chip 1, and includes a control substrate body 21 and a plurality of second positive electrodes 22 and a second negative electrode 23 located on the control substrate body 21;

[0012] The longitudinal thickness of the first negative electrode 12 is equal to the longitudinal thickness of the first positive electrode 13 ; the longitudinal thickness of the second negative electrode 23 is equal to the sum of the longitudinal thickness of the second positive electrode 22 and the longitudinal thickness of the LED chip 11 .

[0013] LED chips are also known as LED lamp beads, which are essentially LED light emitting diodes. The longitudinal thickness of the LED chip described in the present invention is not just the thickness of an LED lamp bead, but the thickness of the entire LED light emitting layer.

[0014] Preferably, the second negative electrode 23 includes a first titanium or chromium layer 24, a second nickel layer 25, a third gold-tin layer 26, a fourth titanium or nickel or chromium layer 27, and a fifth gold-tin layer 28, which are arranged in sequence starting from one side of the control substrate body 21, totaling five layers.

[0015] Preferably, the sum of the longitudinal thicknesses of the fourth titanium or nickel or chromium layer 27 and the fifth gold-tin layer 28 is equal to the longitudinal thickness of the LED chip 11; the sum of the longitudinal thicknesses of the first titanium or chromium layer 24, the second nickel layer 25 and the third gold-tin layer 26 is equal to the longitudinal thickness of the second positive electrode 22.

[0016] Preferably, the first negative electrode 12 includes a first titanium or chromium layer 24 , a second nickel layer 25 , and a third gold-tin layer 26 which are arranged in sequence starting from one side of the chip substrate 14 .

[0017] Preferably, the first positive electrode 13 includes a first titanium or chromium layer 24 , a second nickel layer 25 , and a third gold-tin layer 26 which are arranged in sequence starting from one side of the chip substrate 14 .

[0018] Preferably, the second positive electrode 22 includes a first titanium or chromium layer 24 , a second nickel layer 25 , and a third gold-tin layer 26 which are sequentially arranged starting from one side of the control substrate body 21 .

[0019] Preferably, the number of the second positive electrodes 22 is equal to the number of the first positive electrodes 13 .

[0020] Preferably, the positions of the first positive electrode 13 and the second positive electrode 22 correspond to each other, and the accuracy deviation is less than 0.7 μm.

[0021] Preferably, the first negative electrode 12 and the second negative electrode 23 are both one and planar, and a plurality of the LED chips 11 are electrically connected to the control substrate 2 in a common cathode manner.

[0022] A second aspect of the present invention provides a method for preparing a eutectic structure of a micro LED chip and a control substrate, comprising the following steps:

[0023] 1) coating an electrode photoresist on the micro LED chip 1;

[0024] 2) coating the first positive electrode 13 and the first negative electrode 12 on the micro LED chip 1; the longitudinal thickness of the first negative electrode 12 is equal to the longitudinal thickness of the first positive electrode 13;

[0025] 3) removing the electrode photoresist on the micro LED chip 1;

[0026] 4) coating an electrode photoresist on the control substrate 2;

[0027] 5) Plating the second positive electrode 22 and the first portion of the second negative electrode 23 on the control substrate 2; the longitudinal thickness of the first portion of the second negative electrode 23 is equal to the longitudinal thickness of the second positive electrode 22;

[0028] 6) removing the electrode photoresist on the control substrate 2;

[0029] 7) coating a titanium, nickel or chromium layer 27 on the first portion of the second negative electrode 23;

[0030] 8) coating an electrode photoresist on the control substrate 2;

[0031] 9) Plating a second portion of the second negative electrode 23 on the control substrate 2; the sum of the longitudinal thickness of the titanium or nickel or chromium layer 27 and the longitudinal thickness of the second portion of the second negative electrode 23 is equal to the longitudinal thickness of the LED chip 11;

[0032] 10) The micro LED chip 1 and the control substrate 2 are aligned and mounted together; a laser eutectic welding system is used to heat the welding points and complete the welding.

[0033] The electrode photoresist is a photosensitive glue, which is coated on. The method of removing the electrode photoresist is to soak it in liquid medicine and then wash it off with clean water.

[0034] In the present method, the first part of the second negative electrode 23 is the first titanium or chromium layer 24, the second nickel layer 25, and the third gold-tin layer 26 arranged in sequence; the second part of the second negative electrode 23 is the fifth gold-tin layer 28. The longitudinal thickness of these two parts and the middle titanium or nickel or chromium layer 27 together constitute the second negative electrode 23. The essential purpose of controlling the thickness of the second negative electrode 23 in the present invention is that after the micro LED chip 1 and the control substrate 2 are aligned and mounted, both the first negative electrode 12 and the second negative electrode 23, and both the first positive electrode 13 and the second positive electrode 22 are just in contact, and under the premise that the longitudinal thickness of the first positive electrode 13 and the first negative electrode 12 are equal.

[0035] Preferably, the laser eutectic welding device used in the present invention can refer to the patent application already applied by the present applicant, with application number: 2021106926206, entitled: A laser eutectic welding device and method for a micro LED chip and a control substrate. Similarly, all descriptions of the laser eutectic welding device in the patent are also applicable to the present application.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The present invention proposes to use laser heating to complete the eutectic welding and mounting of MicroLED and control substrate. Laser eutectic welding is to melt the electrode metal film layer on the LED and the control substrate by the energy of laser irradiation, so that the LED electrode metal film layer and the electrode metal film layer on the control substrate are welded together. The laser eutectic is irradiated from the sapphire side of the LED. The LED light-emitting layer (GaN layer) is a transparent layer. The laser can pass through the LED light-emitting layer and directly irradiate the heating layer titanium (Ti) layer and nickel (Ni) layer plated on the reflective layer, wherein titanium can be replaced by chromium Cr. The laser irradiates the heating layer to heat the titanium and nickel to melt the upper layer of gold tin (AuSn) to achieve welding. This eutectic method can realize the mass transfer of LEDs and the modular transfer eutectic welding of MicroLEDs, avoiding the secondary melting of the single transfer eutectic welding points of a single MicroLED, which causes damage to the MicroLED.

[0038] 2. The present invention proposes a eutectic structure of a micro LED chip and a control substrate, that is, the LED electrode metal film layer is a heating surface. To ensure that the P pole and N pole of the micro LED chip are heated evenly and the heating time is consistent, the P pole and N pole film thickness of the LED electrode metal film layer are the same; the control substrate electrode metal film layer is a passive heating surface. Because the P pole of the micro LED chip is thicker than the N pole by the thickness of the LED light-emitting layer, the N pole of the control substrate electrode metal layer is thicker than the P pole by the same thickness of the LED. This ensures that the alignment and bonding of the two are on the same horizontal plane, and that the P pole and N pole thickness of the micro LED chip are the same ( Figure 2 ). This solves the problem that during laser eutectic welding, the N pole has melted, but the P pole is too thick and has not melted.

[0039] 3. The present invention transfers the eutectic welding speed in the form of MicroLED modular array, which is fast and effectively improves the eutectic speed.

[0040] 4. The laser heats and melts the MicroLED and the metal electrode (InSn) that controls the basic surface, and finally combines the two together without adding other solder. This reduces the solder adding process and saves production costs.

[0041] 5. The laser beam shaping system shapes the laser beam into a plane beam with uniform energy density distribution, and cooperates with the focusing mirror to make the laser spot size irradiated on the eutectic welding platform match the size of the eutectic welding chip. When the size of the eutectic welding chip changes, the laser beam size will also be changed and adjusted accordingly.

[0042] 6. The present invention electrically connects the plurality of LED chips 11 to the control substrate 2 in a common cathode manner.

[0043] 7. The eutectic process of the present invention does not need to remove the sapphire backing plate of the MicroLED, and is directly adsorbed by the quartz negative pressure adsorption device to allow the equipment to complete the eutectic welding work. In the prior art, the sapphire backing plate chip substrate is usually removed first, and then the LED chips are moved one by one to the control substrate in an upright manner. The present invention does not need to remove the sapphire backing plate of the MicroLED, and is directly adsorbed by the quartz negative pressure adsorption device and flipped on the control substrate, and then the equipment completes the eutectic welding work, which effectively improves the transfer and eutectic speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic diagram of the eutectic structure of the micro LED chip and the control substrate when eutectic formation is not possible;

[0045] Figure 2 A schematic diagram of the primary eutectic structure of a micro LED chip and a control substrate;

[0046] Figure 3This is a schematic diagram of the eutectic structure of the micro LED chip and the control substrate of the present invention;

[0047] Figure 4 for Figure 3 Schematic diagram of the laser eutectic welding device for eutectic welding of micro LED chips and control substrate;

[0048] Figure 5 This is a schematic diagram of the structure of the micro LED chip of the present invention;

[0049] Figure 6 This is a schematic diagram of the control substrate structure of the present invention;

[0050] Figure 7 This is a schematic diagram of the structure of the micro LED chip and the control substrate when they are aligned and bonded together;

[0051] Figure 1 In the circuit, the thickness of the eutectic metal layer on the LED and the control circuit is the same, so the LED N pole cannot contact the control substrate N pole and eutectic cannot be achieved.

[0052] Figure 2 In the eutectic metal coating of the LED, the N-pole and P-pole coatings are different, so that they can contact with the metal coating of the control substrate below to achieve laser heating eutectic. However, because the laser is irradiated from above the LED, the heating time is different due to the different thickness of the P-pole and N-pole film layers of the LED eutectic metal layer, which will cause the P-pole to overheat.

[0053] Figure 3 In the process, the thickness of the LED eutectic metal layer is the same, the N-pole coating thickness of the control substrate eutectic metal layer is thicker than the P-pole coating thickness by the thickness of the LED structure layer, and the P-pole and N-pole of the eutectic metal layer of the LED and the control substrate are just in contact. Since the laser irradiates from the bottom of the LED and the LED metal layer is the same, the heating time is consistent, and perfect eutectic welding can be achieved.

[0054] The names of the accompanying drawings are: 1-micro LED chip, 11-LED wafer, 12-first negative electrode, 13-first positive electrode, 14-chip substrate, 2-control substrate, 21-control substrate body, 22-second positive electrode, 23-second negative electrode, 24-first titanium or chromium layer, 25-second nickel layer, 26-third gold-tin layer, 27-fourth titanium or nickel or chromium layer, 28-fifth gold-tin layer, 3-laser eutectic welding system. DETAILED DESCRIPTION

[0055] The present invention is further described in detail below in conjunction with embodiments.

[0056] Those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or the product specifications are used. If the manufacturer of the materials or equipment used is not specified, they are all conventional products that can be purchased.

[0057] Those skilled in the art will appreciate that, unless expressly stated otherwise, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" to another element, it may be directly connected to the other element, or there may be intermediate elements. In addition, the "connection" used herein may include wireless connections.

[0058] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two. The terms "inside", "upper", "lower", etc., indicating positions or state relationships, are based on the positions or state relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operate in a specific position, and therefore cannot be understood as limiting the present invention.

[0059] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "provided with" 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. For ordinary technicians in this field, the specific meanings of the above terms in the present invention will be understood according to specific circumstances.

[0060] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0061] Example 1

[0062] This embodiment is Figure 1The micro LED chip and the control substrate have a eutectic structure, in which the thickness of the eutectic metal layer on the LED and the control circuit are the same, so that the LED N pole cannot contact the control substrate N pole and eutectic cannot be achieved.

[0063] Example 2

[0064] This embodiment is Figure 2 The micro LED chip and control substrate have a eutectic structure, in which the N-pole and P-pole coatings in the eutectic metal coating of the LED are different, so that they can contact with the metal coating of the control substrate below to achieve laser heating eutectic. However, because the laser is irradiated from above the LED, the heating time is different due to the different thickness of the P-pole and N-pole film layers of the LED eutectic metal layer, which will cause overheating of the P-pole.

[0065] Example 3

[0066] This embodiment is Figure 3 The micro LED chip and the control substrate have a eutectic structure, in which the LED eutectic metal layer has the same thickness, and the N-pole coating of the control substrate eutectic metal layer is thicker than the P-pole coating by the thickness of the LED structure layer. The P-pole and N-pole of the eutectic metal layer of the LED and the control substrate are just in contact. Since the laser is irradiated from the bottom of the LED, the LED metal layers are the same and the heating time is consistent, which can achieve perfect eutectic welding.

[0067] The preparation method is a preparation method of a eutectic structure of a micro LED chip and a control substrate, comprising the following steps:

[0068] Coating an electrode photoresist on the micro LED chip 1;

[0069] The first positive electrode 13 and the first negative electrode 12 are plated on the micro LED chip 1; the longitudinal thickness of the first negative electrode 12 is equal to the longitudinal thickness of the first positive electrode 13;

[0070] Removing the electrode photoresist on the micro LED chip 1;

[0071] Coating an electrode photoresist on the control substrate 2;

[0072] The second positive electrode 22 and the first portion of the second negative electrode 23 are plated on the control substrate 2; the longitudinal thickness of the first portion of the second negative electrode 23 is equal to the longitudinal thickness of the second positive electrode 22;

[0073] Removing the electrode photoresist on the control substrate 2;

[0074] A titanium, nickel or chromium layer 27 is coated on the first portion of the second negative electrode 23;

[0075] Coating an electrode photoresist on the control substrate 2;

[0076] A second portion of the second negative electrode 23 is plated on the control substrate 2; the longitudinal thickness of the second portion of the second negative electrode 23 is equal to the longitudinal thickness of the LED chip 11;

[0077] The micro LED chip 1 and the control substrate 2 are aligned and mounted together; the laser eutectic welding system 3 is used to heat the welding points and complete the welding.

Claims

1. A micro LED chip and a control substrate eutectic structure, characterized in that: The micro LED chip (1) and the control substrate (2) are obtained by welding them together simultaneously using a laser; the micro LED chip (1) comprises a control substrate (2) and a micro LED chip (1) having a plurality of LED wafers; The micro LED chip (1) comprises a chip substrate (14) and a plurality of LED chips (11) fixed on the chip substrate (14); the plurality of LED chips (11) have a common first negative electrode (12), and the plurality of LED chips (11) respectively have an independent first positive electrode (13); The control substrate (2) is located below the micro LED chip (1), and comprises a control substrate body (21) and a plurality of second positive electrodes (22) and a second negative electrode (23) located on the control substrate body (21); The longitudinal thickness of the first negative electrode (12) is equal to the longitudinal thickness of the first positive electrode (13); the longitudinal thickness of the second negative electrode (23) is equal to the sum of the longitudinal thickness of the second positive electrode (22) and the longitudinal thickness of the LED chip (11); The first positive electrode (13) comprises a first titanium or chromium layer (24), a second nickel layer (25), and a third gold-tin layer (26) which are arranged in sequence starting from one side of the chip substrate (14); The first negative electrode (12) comprises a first titanium or chromium layer (24), a second nickel layer (25), and a third gold-tin layer (26) which are arranged in sequence starting from one side of the chip substrate (14).

2. The micro LED chip and control substrate eutectic structure according to claim 1, characterized in that: The second negative electrode (23) comprises a first titanium or chromium layer (24), a second nickel layer (25), a third gold-tin layer (26), a fourth titanium or nickel or chromium layer (27), and a fifth gold-tin layer (28), which are arranged in sequence starting from one side of the control substrate body (21), for a total of five layers.

3. The micro LED chip and control substrate eutectic structure according to claim 2, characterized in that: The sum of the longitudinal thicknesses of the fourth titanium or nickel or chromium layer (27) and the fifth gold-tin layer (28) is equal to the longitudinal thickness of the LED chip (11); the sum of the longitudinal thicknesses of the first titanium or chromium layer (24), the second nickel layer (25) and the third gold-tin layer (26) is equal to the longitudinal thickness of the second positive electrode (22).

4. The micro LED chip and control substrate eutectic structure according to claim 1, characterized in that: The second positive electrode (22) comprises a first titanium or chromium layer (24), a second nickel layer (25), and a third gold-tin layer (26) which are arranged in sequence starting from one side of the control substrate body (21).

5. The micro LED chip and control substrate eutectic structure according to claim 1, characterized in that: The number of the second positive electrodes (22) is equal to the number of the first positive electrodes (13).

6. The micro LED chip and control substrate eutectic structure according to claim 1, characterized in that: The positions of the first positive electrode (13) and the second positive electrode (22) correspond to each other, and the accuracy deviation is less than 0.7 μm.

7. The micro LED chip and control substrate eutectic structure according to claim 1, characterized in that: The first negative electrode (12) and the second negative electrode (23) are both one and planar, and a plurality of LED chips (11) are electrically connected to the control substrate (2) in a common cathode manner.

8. A method for preparing the eutectic structure of the micro LED chip and the control substrate according to claim 2, characterized in that: The preparation method comprises the following steps: (1) coating an electrode photoresist on the micro LED chip (1); (2) coating the first positive electrode (13) and the first negative electrode (12) on the micro LED chip (1); the longitudinal thickness of the first negative electrode (12) is equal to the longitudinal thickness of the first positive electrode (13); (3) removing the electrode photoresist on the micro LED chip (1); (4) coating an electrode photoresist on the control substrate (2); (5) The second positive electrode (22) and the first portion of the second negative electrode (23) are plated on the control substrate (2); the longitudinal thickness of the first portion of the second negative electrode (23) is equal to the longitudinal thickness of the second positive electrode (22); (6) removing the electrode photoresist on the control substrate (2); (7) coating the fourth titanium, nickel or chromium layer (27) on the first portion of the second negative electrode (23); (8) coating an electrode photoresist on the control substrate (2); (9) a second portion of the second negative electrode (23) is plated on the control substrate (2); the sum of the longitudinal thickness of the fourth titanium or nickel or chromium layer (27) and the longitudinal thickness of the second portion of the second negative electrode (23) is equal to the longitudinal thickness of the LED chip (11); (10) The micro LED chip (1) and the control substrate (2) are aligned and mounted together; and a laser eutectic welding system is used to heat the welding points and complete the welding.

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