LED chip, display panel and manufacturing method thereof

Abstract

The present application discloses an LED chip, a display panel, and a method for manufacturing the same. The LED chip includes a chip body and at least one electrode located on one side of the chip body; wherein the electrode includes a first metal portion and a second metal portion, wherein the first end face of the first metal portion is fixedly connected to the chip body, the second metal portion covers at least a portion of the outer surface of the first metal portion, and the melting point of the first metal portion is higher than the melting point of the second metal portion. When bonding the LED chip to the driver backplane, the electrode is aligned with the soldering pad of the driver backplane, and then heated to a temperature at which the second metal portion melts and the first metal portion does not melt. After the second metal portion cools and solidifies, the first metal portion is fixedly connected to the soldering pad to achieve bonding between the LED chip and the driver backplane. Therefore, the present application can reduce the difficulty of alignment when aligning the electrode and the soldering pad, and can reduce the stress between the LED chip and the driver backplane during bonding, thereby improving the transfer yield of transferring a large number of LED chips to the driver backplane.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to an LED chip, a display panel, and a method for manufacturing the same. Background Art

[0002] Micro LED displays are miniaturized LED arrays. This is achieved by thinning, miniaturizing, and arraying LED chips, then transferring them en masse to a driver backplane. This results in a Micro LED display with nanometer-level spacing between the LED chips. Compared to displays like LCDs and OLEDs, Micro LED displays offer higher brightness and efficiency, faster response times, longer lifespans, and a wider operating range. They are considered the ultimate display, with applications in consumer products such as televisions, augmented and virtual reality (AR / VR), automotive displays, wearable devices, and smartphones.

[0003] However, the technology for mass-transferring LED chips currently faces considerable technical challenges. In existing technologies, the LED chip array is usually arranged on a temporary transfer substrate first, and then the LED chips are transferred to the driver backplane by applying pressure or irradiating lasers. However, the transfer yield is relatively low. Summary of the Invention

[0004] The main technical problem solved by the present application is to provide an LED chip, a display panel and a preparation method thereof, which can improve the transfer yield of transferring a large number of LED chips to a driving backplane.

[0005] To solve the above technical problems, a technical solution adopted in this application is to provide an LED chip, comprising:

[0006] A chip body, and at least one electrode located on one side of the chip body;

[0007] The electrode includes a first metal part and a second metal part, the first end face of the first metal part is fixedly connected to the chip body, the second metal part covers at least part of the outer surface of the first metal part, and the melting point of the first metal part is higher than the melting point of the second metal part.

[0008] The first metal part includes a second end surface arranged opposite to the first end surface, and the second metal part covers the second end surface.

[0009] In which, the electrode includes multiple groups of the first metal parts and the second metal parts; and in the direction away from the chip body, multiple groups of the first metal parts and the second metal parts are stacked in sequence; in which, the second metal part is farthest from the chip body, and the first metal part is closest to the chip body, and the first metal part closest to the chip body is fixedly connected to the chip body.

[0010] The second metal portion further covers at least a portion of a sidewall of the first metal portion.

[0011] wherein the roughness of the sidewall of the first metal portion is smaller than the roughness of the second end surface;

[0012] Preferably, the second end surface is provided with a rough structure.

[0013] Wherein, the LED chip further includes: a protective layer covering at least a portion of the outer surface of the electrode.

[0014] To solve the above technical problems, another technical solution adopted in this application is to provide a display panel, comprising:

[0015] A driving backplane, comprising a bearing surface, wherein the bearing surface is provided with a plurality of bearing areas, and each bearing area is provided with at least one solder pad;

[0016] A plurality of LED chips, one of the LED chips is fixedly arranged on one of the supporting areas, and the LED chip includes a chip body and at least one electrode located on one side of the chip body, the electrode is electrically connected to the soldering pad; the electrode includes a first metal part and a second metal part, the first end face of the first metal part is fixedly connected to the chip body, the melting points of the first metal part and the soldering pad are higher than the melting point of the second metal part; wherein the second metal part continuously covers a portion of the outer surface of the first metal part away from the first end face, and at least a portion of the outer surface of the soldering pad, and a portion of the outer surface of the first metal part close to the first end face is not covered by the second metal part.

[0017] The display panel further includes a plurality of insulating spacers located on the carrying surface, and the insulating spacers are arranged around the pads and the corresponding electrodes.

[0018] Wherein, the height of the insulating spacer is less than or equal to the height of the first metal part.

[0019] To solve the above technical problems, another technical solution adopted in this application is to provide a method for preparing a display panel, comprising:

[0020] Provide a plurality of LED chips according to the above technical solution, and a driving backplane, wherein the driving backplane includes a bearing surface, the bearing surface is provided with a plurality of bearing areas, and each bearing area is provided with at least one solder pad;

[0021] Arrange one of the LED chips corresponding to one of the supporting areas on the supporting surface, and align and contact the electrodes with the pads;

[0022] heating the electrode position to a temperature higher than a melting point of the second metal portion and lower than a melting point of the first metal portion and the pad;

[0023] The melted second metal portion is cooled and solidified, so that the second metal portion continuously covers a portion of the outer surface of the first metal portion away from the first end surface and at least a portion of the outer surface of the pad.

[0024] The present application provides the following beneficial effects: The LED chip provided herein includes a chip body and at least one electrode located on one side of the chip body; wherein the electrode includes a first metal portion and a second metal portion, wherein a first end surface of the first metal portion is fixedly connected to the chip body, and the second metal portion covers at least a portion of the outer surface of the first metal portion, and the melting point of the first metal portion is higher than that of the second metal portion. When bonding the LED chip to the driver backplane, the electrode is aligned with the soldering pad of the driver backplane, then heated to a temperature at which the second metal portion melts but the first metal portion does not melt. After the second metal portion cools and solidifies, the first metal portion is fixedly connected to the soldering pad, thereby achieving bonding between the LED chip and the driver backplane. In this process, the soldering pad has a relatively large area, which can reduce the difficulty of alignment when aligning the electrode and the soldering pad. Moreover, bonding is achieved by heating and cooling and solidifying, rather than using pressure to bind, which can reduce stress between the LED chip and the driver backplane during bonding, thereby improving the transfer yield of large-scale LED chip transfer to the driver backplane. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without inventive efforts. Among them:

[0026] Figure 1 This is a schematic structural diagram of an embodiment of the LED chip of the present application;

[0027] Figure 2 for Figure 1 A schematic diagram of the structure of the LED chip from another perspective;

[0028] Figure 3 This is a schematic structural diagram of another embodiment of the LED chip of the present application;

[0029] Figure 4 This is a schematic structural diagram of another embodiment of the LED chip of the present application;

[0030] Figure 5 This is a schematic structural diagram of another embodiment of the LED chip of the present application;

[0031] Figure 6 This is a schematic flow chart of an embodiment of a method for manufacturing a display panel of the present application;

[0032] Figure 7 for Figure 6 A structural diagram of an implementation method of step S12;

[0033] Figure 8 for Figure 6 A structural diagram of an implementation method of step S14;

[0034] Figure 9 This is a schematic structural diagram of another embodiment of the display panel of the present application;

[0035] Figure 10 for Figure 9 Schematic diagram of the overhead structure of the local area. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0037] See also Figure 1 , Figure 1 This is a schematic diagram of the structure of an embodiment of the LED chip of the present application. The LED chip includes a chip body 11 and at least one electrode 12 located on one side of the chip body 11. In this embodiment, the LED chip includes two electrodes 12 located on the same side of the chip body 11, such as Figure 1 In other embodiments, the electrodes of the LED chip may also be arranged on different sides.

[0038] The electrode 12 includes a first metal portion 121 and a second metal portion 122. The first end surface (not shown) of the first metal portion 121 is fixedly connected to the chip body 11, and the second metal portion 122 covers at least part of the outer surface of the first metal portion 121. The outer surfaces of the first metal portion 121 other than the first end surface can be covered by the second metal portion 122. Figure 1 The second metal portion 122 is schematically shown covering the sidewall of the first metal portion 121 .

[0039] The melting point of the first metal portion 121 is higher than that of the second metal portion 122. For example, the first metal portion is made of gold, and the second metal portion is made of indium.

[0040] When preparing the LED chip, the chip body 11 and the first metal portion 121 may be prepared according to the conventional method, and then the second metal portion 122 may be formed on the sidewall of the first metal portion 121 using a lift-off process.

[0041] See also Figure 2 , Figure 2 for Figure 1 In the structural diagram of the LED chip from another perspective, it can be seen that the second metal portion 122 covers the sidewalls of the first metal portion 121. The cross-section of the first metal portion 121 is circular, and the cross-section of the second metal portion 122 is annular. In other embodiments, the first metal portion 121 and the second metal portion 122 can also be configured as other shapes, and this application is not limited to this.

[0042] The LED chip also includes a protective layer 13 that covers at least a portion of the outer surface of electrode 12. Protective layer 13 protects electrode 12 before bonding the LED chip to the driver backplane, reducing its oxidation rate. During bonding, protective layer 13 can be removed to allow electrode 12 to achieve ohmic contact with the driver backplane's pad.

[0043] When bonding the LED chip to the driver backplane in this embodiment, align the electrode 12 with the pad of the driver backplane, and then heat it to a temperature at which the second metal part 122 melts and the first metal part 121 does not melt. Since the second metal part 122 covers the outer surface of the first metal part 121, the molten second metal part 122 can flow from the outer surface of the first metal part 121 to the surface of the pad in contact with the electrode 12. After the second metal part 122 cools and solidifies, the first metal part 121 can be fixedly connected to the pad to achieve bonding between the LED chip and the driver backplane. In this process, the area of ​​the pad is relatively large, which can reduce the difficulty of alignment when aligning the electrode and the pad. In addition, bonding is achieved by heating and cooling and solidifying, without the need for pressure bonding. This can reduce the stress on the LED chip and the driver backplane during bonding, thereby improving the transfer yield of large-scale transfer of LED chips to the driver backplane.

[0044] In one embodiment, see Figure 3 , Figure 3 This is a schematic diagram of the structure of another embodiment of the LED chip of the present application. Similar to the above embodiment, this LED chip includes a chip body 21 and two electrodes 22 located on the same side of the chip body 21. The electrode 22 includes a first metal portion 221 and a second metal portion 222. The first end surface (not shown) of the first metal portion 221 is fixedly connected to the chip body 21, and the melting point of the first metal portion 221 is higher than that of the second metal portion 222.

[0045] The first metal portion 221 includes a second end surface (not shown) disposed opposite to the first end surface. In this embodiment, the second metal portion 222 covers the second end surface.

[0046] When bonding the LED chip to the driver backplane in this embodiment, after the electrode 22 is aligned with the soldering pad, the second metal part 222 is heated to melt. There is no need to wait for the molten second metal part 222 to flow. After it cools and solidifies, the LED chip and the driver backplane can be bonded. This can improve the transfer yield of large quantities of LED chips to the driver backplane and improve process efficiency.

[0047] In one embodiment, see Figure 4 , Figure 4 This is a schematic structural diagram of another embodiment of the LED chip of the present application. Similar to the above embodiment, the LED chip includes a chip body 31 and two electrodes 32 located on the same side of the chip body 31. Among them, the electrode 32 includes multiple groups of first metal parts 321 and second metal parts 322. In the direction away from the chip body 31, the multiple groups of first metal parts 321 and second metal parts 322 are stacked in sequence. Among them, the second metal part 322 is farthest from the chip body 31, and the first metal part 321 is closest to the chip body 31. The first metal part 321 closest to the chip body 31 is fixedly connected to the chip body 31. Moreover, the melting point of the first metal part 321 is higher than the melting point of the second metal part 322.

[0048] When bonding the LED chip to the driver backplane in this embodiment, after the electrode 32 is aligned with the soldering pad, the second metal part 322 is heated to melt, and the second metal part 322 located between the first metal parts 321 partially flows to the surface of the soldering pad under natural extrusion, and the remaining part connects the adjacent first metal parts 321. After the molten second metal part 222 flowing to the surface of the soldering pad and the second metal part 222 located between the first metal part 321 and the soldering pad are cooled and solidified, the first metal part 321 is connected to the soldering pad to achieve bonding of the LED chip to the driver backplane, which can improve the transfer yield of transferring a large number of LED chips to the driver backplane and improve the structural stability after bonding.

[0049] In one embodiment, see Figure 5 , Figure 5 This is a schematic diagram of the structure of another embodiment of the LED chip of the present application. Similar to the above embodiment, this LED chip includes a chip body 41 and two electrodes 42 located on the same side of the chip body 41. The electrode 42 includes a first metal portion 421 and a second metal portion 422. The second metal portion 422 covers the second end surface and at least a portion of the side wall of the first metal portion 421. Figure 5The second metal portion 422 is schematically shown to continuously cover the second end surface and all sidewalls of the first metal portion 421 , and the melting point of the first metal portion 421 is higher than that of the second metal portion 422 .

[0050] The roughness of the sidewall of the first metal part 421 is less than that of the second end surface. Preferably, the second end surface is provided with a rough structure, such as saw teeth, depressions, etc., and the second metal part 422 covering the second end surface fills these saw teeth and depressions.

[0051] When bonding the LED chip to the driver backplane in this embodiment, after aligning the electrode 42 with the pad, heating is performed to melt the second metal portion 422. The second metal portion 422 covering the sidewall of the first metal portion 421 naturally flows onto the surface of the pad. The second metal portion 422 covering the second end surface is essentially retained between the second end surface and the pad due to the presence of the rough structure. This prevents the molten second metal portion 422 from spreading further and causing electrical conduction between adjacent pads or electrodes. Furthermore, this embodiment can improve the transfer yield of large quantities of LED chips to the driver backplane and enhance the structural stability after bonding.

[0052] In other embodiments, in order to control the speed at which the molten second metal part flows to the surface of the pad so that it does not spread too quickly, the side wall of the first metal part 421 can also be set as a slope, that is, the second end face is smaller than the first end, and the slope angle can be 45 degrees, 60 degrees, etc., which can be set according to actual needs.

[0053] It is understandable that the above Figure 3-Figure 5 In each of the illustrated embodiments, the LED chip may further include a protective layer to protect the electrodes. When the LED chip needs to be bonded to the driving backplane, the protective layer is removed.

[0054] In addition, this application also provides a method for preparing a display panel, see Figure 6 , Figure 6 1 is a flow chart of an embodiment of a method for manufacturing a display panel of the present application. The method includes the following steps.

[0055] Step S11: providing a plurality of LED chips and a driving backplane.

[0056] The driving backplane includes a bearing surface, the bearing surface is provided with a plurality of bearing areas, and each bearing area is provided with at least one soldering pad.

[0057] The LED chip is the LED chip described in any of the above embodiments. The specific structure of the LED chip can be found in the above embodiments and will not be described again here.

[0058] In step S12 , one LED chip is placed on the carrying surface corresponding to one carrying area, and the electrodes are aligned with and in contact with the pads.

[0059] Please refer to the following for details: Figure 7 , Figure 7 for Figure 6 A structural diagram of an embodiment of step S12 in FIG. Figure 1 Taking the LED chip in FIG as an example, the protective layer 13 is first removed, and then one LED chip is placed on the carrying surface corresponding to one carrying area, and the electrode 12 is aligned with and in contact with the pad. Figure 7 The middle drive backplane is labeled 500, the bearing area is labeled A, and the pad is labeled 51. Figure 7 Two bearing areas A are schematically drawn in FIG.

[0060] Specifically, multiple LED chips 100 are arrayed on a temporary transfer substrate, which is then placed on one side of the driver backplane 500, with the electrodes 12 aligned with the pads 51. A laser is then used to illuminate the interface between the LED chips and the temporary transfer substrate through the temporary transfer substrate, causing the LED chips to fall off and fall onto the supporting surface, bringing the electrodes 12 into contact with the pads 51.

[0061] In step S13 , the electrode position is heated to a temperature higher than the melting point of the second metal portion and lower than the melting points of the first metal portion and the pad.

[0062] Please continue reading Figure 7 Then, the electrode 12 is heated to a temperature higher than the melting point of the second metal portion 122 and lower than the melting points of the first metal portion 121 and the pad 51 , so that the second metal portion 122 is in a molten state.

[0063] Step S14 , waiting for the molten second metal portion to cool and solidify, so that the second metal portion continuously covers a portion of the outer surface of the first metal portion away from the first end face and at least a portion of the outer surface of the pad.

[0064] Please combine Figure 7 See Figure 8 , Figure 8 for Figure 6 A structural schematic diagram of an embodiment of step S14 shows that after heating, the second metal part 122 is in a molten state and flows naturally to the surface of the pad 51, and wraps around the end of the first metal part 121 close to the pad 51. After waiting for the second metal part 122 to cool and solidify, the second metal part 122 continuously covers the portion of the outer surface of the first metal part 121 away from the first end face, and at least a portion of the outer surface of the pad 51, and fixes the first metal part 121 and the pad 51 to be fixedly connected, thereby realizing the bonding of the LED chip and the driving backplane 500, and obtaining a display panel including multiple LED chips.

[0065] In the preparation method provided in this embodiment, the area of ​​the solder pad relative to the electrode is larger, which reduces the difficulty of alignment between the two, and the bonding is achieved by heating and cooling solidification, which can reduce the stress on the LED chip and the driver backplane during bonding, thereby improving the transfer yield of transferring a large number of LED chips to the driver backplane.

[0066] In addition, this application also provides a display panel, please continue to refer to Figure 8 , Figure 8 It is also a structural diagram of an embodiment of a display panel of the present application, which includes a driving backplane 500 and a plurality of LED chips 100 .

[0067] The driving backplane 500 includes a bearing surface (not shown), which is provided with a plurality of bearing areas A. Each bearing area A is provided with at least one solder pad 51. Figure 8 FIG. 5 schematically illustrates a case where there are two pads 51 in a bearing area A. FIG.

[0068] An LED chip 100 is fixedly mounted on a supporting area A. The LED chip includes a chip body 11 and at least one electrode 12 located on one side of the chip body 11. The electrode 12 is electrically connected to the solder pad 51. The electrode 12 includes a first metal portion 121 and a second metal portion 122. The first end surface of the first metal portion 121 is fixedly connected to the chip body 11. The melting points of the first metal portion 121 and the solder pad 51 are higher than the melting point of the second metal portion 122. The second metal portion 122 continuously covers the portion of the outer surface of the first metal portion 121 away from the first end surface and at least a portion of the outer surface of the solder pad 51. The portion of the outer surface of the first metal portion 121 near the first end surface is not covered by the second metal portion 122.

[0069] It can be seen from the above preparation method that before the electrode 12 is electrically connected to the pad 51, the second metal part 122 covers at least part of the outer surface of the first metal part 121; when the electrode 12 is electrically connected to the pad 51, the second metal part 122 is heated to a molten state, flows to the surface of the pad 51, and after cooling and solidifying, the second metal part 122 covers part of the outer surface of the first metal part 121 away from the first end face, exposing part of the outer surface of the first metal part 121 close to the first end face.

[0070] Before the electrode 12 of the LED chip 100 is electrically connected to the pad 51, its structure can be as described in any of the above-mentioned embodiments of the LED chip, for example, Figure 1-Figure 5 This embodiment has the beneficial effects of any of the above embodiments, which will not be described in detail here.

[0071] In one embodiment, see Figure 9 , Figure 9This is a schematic diagram of the structure of another embodiment of the display panel of the present application. Figure 8 As shown in the display panel, in this embodiment, the display panel further includes a plurality of insulating spacers 700 located on the supporting surface, and the insulating spacers 700 are arranged around the pads 51 and the corresponding electrodes 12 .

[0072] Please combine Figure 9 See Figure 10 , Figure 10 for Figure 9 The top view of the partial region in the figure shows the insulating spacer 700, which can be made of an organic or inorganic insulating material. This material prevents the molten second metal portion 122 from flowing onto the surface of adjacent pads, thus preventing display abnormalities caused by short circuits between adjacent pads. The present application does not limit the shape or number of insulating spacers 700. Their preparation is performed before bonding the driver backplane 500 to the LED chip 100.

[0073] The height of the insulating spacer 700 is less than or equal to the height of the first metal portion 121 , thereby avoiding affecting the bonding process between the driving backplane 500 and the LED chip 100 and improving the structural stability of the display panel.

[0074] The above description is only an implementation method of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. An LED chip, characterized in that: include: A chip body, and at least one electrode located on one side of the chip body; In which, the electrode includes a first metal part and a second metal part, the first end face of the first metal part is fixedly connected to the chip body, the second metal part covers at least part of the outer surface of the first metal part, and the melting point of the first metal part is higher than the melting point of the second metal part; the first metal part includes a second end face arranged opposite to the first end face, the second metal part covers the second end face, and the second metal part also covers at least part of the side wall of the first metal part; the roughness of the side wall of the first metal part is less than the roughness of the second end face.

2. The LED chip according to claim 1, wherein: The electrode includes multiple groups of the first metal parts and the second metal parts; and in the direction away from the chip body, the multiple groups of the first metal parts and the second metal parts are stacked in sequence; wherein, the second metal part is farthest from the chip body, and the first metal part is closest to the chip body, and the first metal part closest to the chip body is fixedly connected to the chip body.

3. The LED chip according to claim 1, wherein: The second end surface is provided with a rough structure.

4. The LED chip according to claim 1, wherein Also includes: A protective layer covers at least a portion of the outer surface of the electrode.

5. A display panel, characterized in that: include: A driving backplane, comprising a bearing surface, wherein the bearing surface is provided with a plurality of bearing areas, and each bearing area is provided with at least one solder pad; A plurality of LED chips, one of the LED chips is fixedly arranged on one of the supporting areas, and the LED chip includes a chip body and at least one electrode located on one side of the chip body, the electrode is electrically connected to the soldering pad; the electrode includes a first metal part and a second metal part, the first end face of the first metal part is fixedly connected to the chip body, the melting points of the first metal part and the soldering pad are higher than the melting point of the second metal part; wherein the second metal part continuously covers a portion of the outer surface of the first metal part away from the first end face, and at least a portion of the outer surface of the soldering pad, and a portion of the outer surface of the first metal part close to the first end face is not covered by the second metal part; the first metal part includes a second end face arranged opposite to the first end face, the second metal part covers the second end face, and the second metal part also covers at least a portion of the side wall of the first metal part; the roughness of the side wall of the first metal part is less than the roughness of the second end face.

6. The display panel according to claim 5, wherein: The display panel further includes a plurality of insulating spacers located on the carrying surface, and the insulating spacers are arranged around the pads and the corresponding electrodes.

7. The display panel according to claim 6, wherein: A height of the insulating spacer is less than or equal to a height of the first metal portion.

8. A method for preparing a display panel, characterized in that: include: A plurality of LED chips according to any one of claims 1 to 3 and a driving backplane are provided, wherein the driving backplane comprises a bearing surface, the bearing surface is provided with a plurality of bearing areas, and each bearing area is provided with at least one solder pad; Arrange one of the LED chips corresponding to one of the supporting areas on the supporting surface, and align and contact the electrodes with the pads; heating the electrode position to a temperature higher than a melting point of the second metal portion and lower than a melting point of the first metal portion and the pad; The melted second metal portion is cooled and solidified, so that the second metal portion continuously covers a portion of the outer surface of the first metal portion away from the first end surface and at least a portion of the outer surface of the pad.

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