Light-emitting device, backboard assembly and display panel

Abstract

The utility model discloses a light-emitting device, a backboard and a display panel, the light-emitting device for the display panel comprises a light-emitting element and a solder gradient layer, the light-emitting element comprises a light-emitting epitaxial layer and a pad layer formed on the light-emitting epitaxial layer, the solder gradient layer is arranged on the pad layer of the light-emitting element, and the solder gradient layer is arranged on the pad layer of the light-emitting element in the direction away from the pad layer. The melting point of the solder gradient layer is gradually reduced. In the process of welding the light-emitting device to the back plate, due to the fact that a plurality of melting point areas or metal layers with different melting points exist in the solder gradient layer, in the process of one-time welding and repairable welding, the temperature of one-time welding is controlled to be larger than the temperature of repairable welding, the influence of repairable welding on welding spots formed during one-time welding can be avoided, and the welding quality of the light-emitting device is improved. And the welding yield during welding is effectively controlled.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor device packaging, and in particular to a light-emitting device, a backplane assembly and a display panel. Background Art

[0002] When packaging semiconductor devices, the chip needs to be placed on a backplane and conductively connected to it. When the chip and the backplane are conductively connected, solder generally needs to be deposited on the chip or the backplane, and after the specific solder is melted, a metallurgical joint is formed to weld the chip and the backplane.

[0003] In the prior art, a solder with a fixed melting point is usually deposited on the chip or backplane. Since the melting point of the solder is fixed, the range of suitable welding temperature is generally narrow. However, chips and other components may be used in different products of different customers. For different application scenarios, due to the differences in temperature resistance or other characteristics of other components in customer products, there are differences in the expected welding temperature of chips and other components. Therefore, improving the usability of chips and other components is crucial to improving the user experience. How to improve the applicability of chips and other components has also become a technical problem that technicians in this field need to solve urgently.

[0004] In addition, in Micro LED display devices, the welding temperature when welding the chip to the backplane is generally fixed. However, the chip generally needs to be welded twice. After one welding, the chip needs to be inspected and then a second repair welding is performed. However, since the welding temperature during welding is fixed, the second repair welding will affect the already welded solder joints. For example, the already formed solder joints need to be re-melted, which affects the reliability of welding.

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a light-emitting device, a backplane assembly and a display panel to increase the application scope of components such as chips and improve the reliability of welding. Utility Model Content

[0006] In order to achieve the above-mentioned object and other related objects, the present application provides a light-emitting device, including:

[0007] A light-emitting element, the light-emitting element comprising a light-emitting epitaxial layer and a pad layer formed on the light-emitting epitaxial layer; the light-emitting element further comprising an electrode structure disposed between the light-emitting epitaxial layer and the pad layer and a bonding layer disposed between the electrode structure and the pad layer;

[0008] The solder gradient layer is arranged on the pad layer of the light emitting element, and the melting point of the solder gradient layer gradually decreases in the direction away from the pad layer.

[0009] Optionally, the solder gradient layer is a single-layer structure, the single-layer structure includes at least two metal materials, and in a direction away from the pad layer, the content of each metal material in the single-layer structure is different.

[0010] Optionally, the solder graded layer includes indium and tin, and the content of indium metal in the solder graded layer gradually increases in a direction away from the pad layer.

[0011] Optionally, in the direction away from the pad layer, the solder gradient layer includes a first melting point zone, a second melting point zone and a third melting point zone in sequence, the melting point range of the first melting point zone is between 180°C and 230°C, the melting point range of the second melting point zone is between 120°C and 180°C, and the melting point range of the third melting point zone is between 100°C and 120°C.

[0012] Optionally, the indium content of the first melting point region is between 0% and 25%, the indium content of the second melting point region is between 25% and 60%, and the indium content of the third melting point region is between 60% and 70%.

[0013] Optionally, the distance between the surface of the solder gradient layer away from the light-emitting element and the surface of the electrode structure facing away from the solder layer is the thickness of the solder gradient layer; the ratio of the thickness of the solder gradient layer to the area of ​​the orthographic projection of the solder gradient layer on the light-emitting element is 0.001 to 0.1.

[0014] Optionally, the distance between the surface of the solder gradient layer away from the light-emitting element and the surface of the electrode structure facing away from the solder layer is the thickness of the solder gradient layer; the ratio of the thickness of the solder gradient layer to the maximum width of the orthographic projection of the solder gradient layer on the light-emitting element is 0.01 to 0.3.

[0015] Optionally, an area of ​​an orthographic projection of the bonding layer on the light-emitting epitaxial layer is larger than an area of ​​an orthographic projection of the solder gradient layer on the light-emitting epitaxial layer.

[0016] Optionally, the area of ​​the orthographic projection of the bonding layer on the light-emitting epitaxial layer is 1.15 to 2.5 times the area of ​​the orthographic projection of the solder gradient layer on the light-emitting epitaxial layer; and / or, the bonding layer extends toward the side close to the solder gradient layer to the side of the solder gradient layer.

[0017] Optionally, an orthographic projection area of ​​the bonding layer on the light-emitting epitaxial layer is larger than an orthographic projection area of ​​the electrode structure on the light-emitting epitaxial layer.

[0018] Optionally, the orthographic projection area of ​​the bonding layer on the light-emitting epitaxial layer is 1.15 to 2.5 times the orthographic projection area of ​​the electrode structure on the light-emitting epitaxial layer; and / or the bonding layer extends toward a side close to the electrode structure to a side surface of the electrode structure.

[0019] The present application also provides a backplane assembly, comprising:

[0020] A back plate having pads for soldering light-emitting elements;

[0021] The solder gradient layer is arranged on the solder pad of the back plate, and the melting point of the solder gradient layer gradually decreases in the direction away from the solder pad;

[0022] A connecting electrode is located at a side of the pad away from the solder gradient layer;

[0023] The bonding layer is located between the connecting electrode and the pad.

[0024] Optionally, the solder gradient layer is a single-layer structure, the single-layer structure includes at least two metal materials, and in a direction away from the pad, the content of each metal material in the single-layer structure is different.

[0025] Optionally, the solder graded layer includes indium and tin, and the content of indium metal in the solder graded layer gradually increases in a direction away from the solder pad.

[0026] Optionally, in the direction away from the pad, the solder gradient layer includes a first melting point zone, a second melting point zone and a third melting point zone in sequence, the melting point range of the first melting point zone is between 180°C and 230°C, the melting point range of the second melting point zone is between 120°C and 180°C, and the melting point range of the third melting point zone is between 100°C and 120°C.

[0027] Optionally, the indium content of the first melting point region is between 0% and 25%, the indium content of the second melting point region is between 25% and 60%, and the indium content of the third melting point region is between 60% and 70%.

[0028] Optionally, the distance between the surface of the solder gradient layer away from the pad and the surface of the connecting electrode away from the pad is the thickness of the solder gradient layer; the ratio of the thickness of the solder gradient layer to the orthographic projection area of ​​the solder gradient layer on the back panel is 0.001 to 0.1.

[0029] Optionally, the distance between the surface of the solder gradient layer away from the pad and the surface of the connecting electrode away from the pad is the thickness of the solder gradient layer; the ratio of the thickness of the solder gradient layer to the maximum width of the orthographic projection of the solder gradient layer on the back panel surface is 0.01 to 0.3.

[0030] Optionally, the backplane further comprises a substrate, the pad is arranged on the surface of the substrate, and the orthographic projection area of ​​the bonding layer on the substrate is larger than the orthographic projection area of ​​the solder gradient layer on the substrate.

[0031] Optionally, the orthographic projection area of ​​the bonding layer on the substrate is 1.15 to 2.5 times the orthographic projection area of ​​the solder gradient layer on the substrate; and / or, the bonding layer extends toward a side close to the solder gradient layer to a side of the solder gradient layer.

[0032] Optionally, the backplane further comprises a substrate, the connecting electrode is arranged on the substrate, and an orthographic projection area of ​​the bonding layer on the substrate is larger than an orthographic projection area of ​​the electrode on the substrate.

[0033] Optionally, the pad layer is arranged on the connecting electrode, and the back panel also includes an adhesive layer arranged between the pad and the connecting electrode, and the orthographic projection area of ​​the adhesive layer on the substrate is 1.15 to 2.5 times the orthographic projection area of ​​the electrode on the substrate; and / or, the adhesive layer extends toward the side close to the connecting electrode to the side of the connecting electrode.

[0034] The present application also provides a display panel, comprising:

[0035] Back panel;

[0036] The light emitting device fixed on the back plate is any one of the light emitting elements mentioned above, and the light emitting device is soldered on the back plate through the solder gradient layer on the solder pad layer.

[0037] The present application also provides a display panel, comprising:

[0038] A backplane assembly according to any of the above;

[0039] The light emitting element is soldered on the back panel assembly through the solder gradient layer.

[0040] Compared with the prior art, the light emitting device, backplane assembly and display panel described in this application have at least the following features:

[0041] Beneficial effects:

[0042] The solder pad layer of the light emitting device described in the present application is provided with a solder gradient layer, wherein the melting point of the solder gradient layer gradually decreases in the direction away from the solder pad layer. In the process of soldering the light emitting device to the backplane, since there are multiple melting point areas or metal layers with different melting points in the solder gradient layer, in the process of primary welding and repair welding, the primary welding temperature is controlled to be higher than the temperature during repair welding, which can avoid the repair welding from affecting the solder joints formed during the primary welding, and effectively control the welding yield during welding.

[0043] In the backplane assembly described in the present application, a solder gradient layer is provided on the pad of the backplane, wherein the melting point of the solder gradient layer gradually decreases in the direction away from the pad. In the process of soldering the light-emitting element to the backplane assembly, since the solder gradient layer in the backplane assembly includes a plurality of melting point zones or metal layers with different melting points, during one soldering, a lower soldering temperature is used to melt the solder far away from the backplane and with a relatively low melting point, and most of the solder close to the backplane with a higher melting point does not melt. The light-emitting element is inspected, and if a defective light-emitting element is found, the chip is easier to remove after one soldering.

[0044] In addition, the light emitting device and backplane in the present application can also be applied to products with different welding temperatures, and have wider applicability. The welding method and display panel described in the present application include the above light emitting device or backplane assembly, and can also achieve the above technical effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1a This is a schematic structural diagram of a light-emitting device described in one embodiment of Embodiment 1 of the present application;

[0046] Figure 1b This is a schematic structural diagram of a light-emitting device described in another embodiment of Embodiment 1 of the present application;

[0047] Figure 2a This is a schematic structural diagram of a light-emitting device described in another embodiment of Embodiment 1 of the present application;

[0048] Figure 2b This is a schematic structural diagram of a light-emitting device described in another embodiment of Embodiment 1 of the present application;

[0049] Figure 2c This is a schematic structural diagram of a light-emitting device described in another embodiment of Embodiment 1 of the present application;

[0050] Figure 2d This is a schematic structural diagram of a light-emitting device described in another embodiment of Embodiment 1 of the present application;

[0051] Figure 2e This is a schematic structural diagram of a light-emitting device described in another embodiment of Embodiment 1 of the present application;

[0052] Figure 2f This is a schematic structural diagram of a light-emitting device described in another embodiment of Embodiment 1 of the present application;

[0053] Figure 3a This is a schematic structural diagram of a backplane assembly described in one embodiment of Embodiment 2 of the present application;

[0054] Figure 3bThis is a schematic structural diagram of a backplane assembly described in another embodiment of Embodiment 2 of the present application;

[0055] Figure 4a This is a schematic structural diagram of the backplane assembly described in another embodiment of Example 2 of the present application.

[0056] Figure 4b This is a schematic structural diagram of the backplane assembly described in another embodiment of Example 2 of the present application.

[0057] Figure 4c This is a schematic structural diagram of the backplane assembly described in another embodiment of Example 2 of the present application.

[0058] Figure 4d This is a schematic structural diagram of the backplane assembly described in another embodiment of Example 2 of the present application.

[0059] Figure 5 This is a schematic diagram of the structure in which the light emitting device in Example 1 is transferred to the top of the backplane;

[0060] Figure 6 This is a schematic diagram of the structure of welding the light emitting device to the back plate in Example 1 of the present application;

[0061] Figure 7 This is a structural schematic diagram of transferring the light-emitting device to the top of the backplane assembly in Example 2 of the present application;

[0062] Figure 8 This is a schematic diagram of the structure of welding the light emitting device to the backplane assembly in Example 2 of the present application;

[0063] Fig. 9 This is a schematic diagram of the structure of the display panel described in Example 3 of the present application;

[0064] Fig.10 This is a schematic diagram of the structure of the display panel described in Example 4 of the present application.

[0065] Description of reference numerals:

[0066] 100: solder gradient layer; 110: first melting point zone; 120: second melting point zone: 130: third melting point zone; 101: first metal layer; 102: second metal layer; 103: third metal layer; 2: light-emitting device; 20: light-emitting element; 200: LED chip substrate; 201: first bonding layer; 202: pad layer; 203: light-emitting epitaxial layer; 204: electrode structure; 3: backplane assembly; 300: backplane; 301: second bonding layer; 302: primary welding pad; 303: substrate; 304: connecting electrode. DETAILED DESCRIPTION

[0067] The following specific embodiments illustrate the implementation of the present application, and those familiar with the technology can easily understand other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0068] It should be noted that the diagrams provided in the embodiments of the present application are only schematic illustrations of the basic concept of the present application. Although the diagrams only show the components related to the present application rather than the number, shape and size of the components in the actual implementation, the form, quantity and proportion of each component can be changed at will during the actual implementation, and the component layout form may also be more complex. The structures, proportions, sizes, etc. illustrated in the drawings of the specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the restrictive conditions that can be implemented in the present application, so they have no technical substantive significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed in the present application without affecting the effects and purposes that can be achieved by the present application.

[0069] Based on the background technology and the problems existing in the prior art, the present application provides a light-emitting device, a backplane assembly, a display panel and a light-emitting device welding method, and a solder gradient layer is set on the light-emitting device or the backplane assembly. The solder gradient layer includes multiple gradient melting points to set different welding temperatures for different welding processes, thereby improving the repairability of the LED chip.

[0070] Example 1

[0071] The present embodiment provides a light-emitting device 2 for a display panel, the light-emitting device 2 comprising a light-emitting element 20 and a solder gradient layer 100 disposed on the light-emitting element 20, the light-emitting element 20 comprising a light-emitting epitaxial layer 203 and a pad layer 202 formed on the light-emitting epitaxial layer 203. The solder gradient layer 100 is disposed on the pad layer 202 of the light-emitting element 20, and the melting point of the solder gradient layer 100 gradually decreases in a direction away from the pad layer 202.

[0072] Among them, the pad layer 202 formed on the light-emitting epitaxial layer 203 can be understood as being formed on one side of the light-emitting epitaxial layer 203, but this embodiment does not limit the pad layer 202 to be directly set on the surface of the light-emitting epitaxial layer 203, and other necessary structural layers can also be arranged between the pad layer 202 and the light-emitting epitaxial layer 203.

[0073] For example, in the light emitting device 2, the light emitting element 20 may be an LED chip. It should be noted that the light emitting device 2 including the light emitting element 20 and the solder gradient layer 100 may still be regarded as an improved LED chip. For the convenience of description, in this embodiment, the LED chip is the light emitting element 20 unless otherwise specified. Figure 1a The LED chip (ie, the light emitting element 20) includes an LED chip substrate 200 and a light emitting epitaxial layer 203 formed on the surface of the LED chip substrate 200 (see Figure 2a or Figure 2b ). Optionally, the light-emitting epitaxial layer 203 includes a first semiconductor layer, an active layer, and a second semiconductor layer of opposite conductivity type to the first semiconductor layer, which are sequentially formed on the surface of the LED chip substrate 200, and the active layer is the light-emitting layer of the light-emitting element. The first semiconductor layer can be an N-type semiconductor layer, and the second semiconductor layer can be a P-type semiconductor layer. Of course, it is also possible for the first semiconductor layer to be a P-type semiconductor layer and the second semiconductor layer to be an N-type semiconductor layer. Optionally, the above-mentioned first semiconductor layer can be an N-type GaN layer, the active layer can be a quantum well layer, and the second semiconductor layer can be a P-type GaN layer. The light-emitting element 20 can be a vertical LED chip or a flip-chip LED chip.

[0074] In this embodiment, refer to Figure 2a An electrode structure 204 is formed on the other surface of the LED chip substrate 200 (the side facing away from the light-emitting epitaxial layer 203) (refer to Figure 2a ). Or refer to Figure 2b In some embodiments, the electrode structure 204 can be arranged on the same side surface of the LED chip substrate 200 as the light-emitting epitaxial layer 203, that is, the electrode structure 204 is arranged on the side of the light-emitting epitaxial layer 203 facing away from the LED chip substrate 200. A soldering pad layer 202 is formed on the surface of the electrode structure 204. It can be understood that the light-emitting element 20 also includes an electrode structure 204 arranged between the light-emitting epitaxial layer 203 and the soldering pad layer 202. The electrode structure 204 is the N electrode (negative electrode) or P electrode (positive electrode) of the LED chip. The N electrode is connected to the N-type semiconductor layer of the light-emitting epitaxial layer 203, and the P electrode is connected to the P-type semiconductor layer of the light-emitting epitaxial layer 203. It can be understood that when the light-emitting element 20 is a flip-chip LED chip, there are usually two electrode structures 204 (not shown in the figure) on the same side of the LED chip substrate 200, corresponding to the N electrode and the P electrode respectively, and a soldering pad layer 202 is formed on the surface of each electrode structure 204. Refer to Figure 5, the pad layer 202 is used to solder the LED chip (light emitting element 20) to the back plate 300. Optionally, an adhesive layer is formed between the electrode structure 204 on the surface of the LED chip substrate 200 and the pad layer 202. In this embodiment, the adhesive layer in the light emitting device 2 is referred to as the first adhesive layer 201, which is used to fix the pad layer 202 and the electrode structure 204.

[0075] Reference Figure 1a or Figure 1b The solder gradient layer 100 is formed on the pad layer 202 of the light emitting element 20, and the melting point of the solder gradient layer 100 gradually decreases in a direction away from the pad layer 202. Figure 1a and Figure 1b In the orientation shown, the solder graded layer 100 is disposed below the pad layer 202 , and the melting point of the solder graded layer 100 gradually decreases in a top-down direction.

[0076] In one embodiment, referring to Figure 1a , the solder gradient layer 100 includes a single-layer structure formed by at least two metal materials, and the content of each metal material in the single-layer structure is different from that in the direction away from the pad layer 202. Specifically, in the present embodiment, the solder gradient layer 100 includes tin and indium. The solder gradient layer 100 includes a first melting point region 110, a second melting point region 120 and a third melting point region 130 in the direction away from the pad layer 202. The melting point range of the first melting point region 110 is between 180°C and 230°C, the melting point range of the second melting point region 120 is between 120°C and 180°C, and the melting point of the third melting point region 130 is between 100°C and 120°C. Among them, the indium content of the first melting point region 110 is between 0% and 25%, the indium content of the second melting point region 120 is between 25% and 60%, and the indium content of the third melting point region 130 is 60% to 70%. The solder gradient layer 100 can be gradually formed by evaporating on the pad layer of the light-emitting element by multi-source evaporation. For example, during the evaporation process, the tin-indium ratio is controlled to be Sn:In=8:1, Sn:In=7:1, Sn:In=6:1, Sn:In=5:1, Sn:In=4:1, Sn:In=3:1, Sn:In=2:1, Sn:In=1:1, and after evaporating the same thickness at the same indium-tin ratio, the indium-tin ratio is adjusted once until the solder gradient layer 100 is formed.

[0077] In another embodiment, referring to Figure 1bThe solder gradient layer 100 is a multi-layer structure, which includes a plurality of metal layers stacked in sequence, and each metal layer has a different melting point. Each metal layer can be formed by mixing at least two metals, or by a single metal, and the metals contained in each metal layer can be the same or different. It should be noted that in this embodiment, as long as the melting point of each metal layer is different and the melting point of the metal layer gradually decreases in the direction away from the pad layer 202, there is no restriction on the material composition of each metal layer. Specifically, refer to Figure 1b The solder gradient layer 100 includes a first metal layer 101, a second metal layer 102 and a third metal layer 103 in the direction away from the pad layer 202, and each metal layer is formed by multi-source evaporation. The melting point of the first metal layer 101 ranges from 180°C to 230°C, the melting point of the second metal layer 102 ranges from 120°C to 180°C, and the melting point of the third metal layer 103 is 100°C to 120°C. The first metal layer 101 can be made of tin metal, the second metal layer 102 can be made of indium metal, and the third metal layer 103 is made of indium and tin metal.

[0078] In some embodiments, reference Figure 2a or Figure 2b , the distance h1 between the surface of the solder gradient layer 100 away from the light emitting element 20 and the surface of the electrode structure 204 facing away from the pad layer 202 is the thickness of the solder gradient layer 100. The orthographic projection area of ​​the solder gradient layer 100 on the light emitting element 20 is S1, and the ratio of the thickness of the solder gradient layer 100 to the orthographic projection area of ​​the solder gradient layer 100 on the light emitting element 20 is 0.001 to 0.1, that is, h1 / S1=0.001 to 0.1. In some specific embodiments, h1 / S1 is preferably 0.002 to 0.028. More specifically, for example, when the light-emitting element 20 corresponds to an LED chip of model 3458, h1 / S1 is 0.0037, when the light-emitting element 20 corresponds to an LED chip of model 1525, h1 / S1 is 0.028, and when the light-emitting element 20 corresponds to an LED chip of model 1730, h1 / S1 is 0.0192. By setting the ratio of the thickness to the area of ​​the solder gradient layer 100 to the above ratio, the welding of the light-emitting device 2 to a back panel 300 can be more stable, the electrical connectivity between the light-emitting device 2 and the back panel 300 can be better, and the resistance can be lower.

[0079] In some embodiments, the orthographic projection shape of the solder gradient layer 100 on the light emitting element 20 is a rectangle, and the lengths of the two perpendicular sides of the rectangle are W1 and W2 respectively. The orthographic projection area S1 of the aforementioned solder gradient layer 100 on the light emitting element 20 is equal to the product of W1 and W2. For example, if W1 is greater than W2, the thickness of the solder gradient layer 100 can also be determined with reference to the side length W1. For example, the ratio of the thickness h1 of the solder gradient layer 100 to the side length W1 is in the range of 0.01 to 0.3. Of course, the orthographic projection shape of the solder gradient layer 100 on the light emitting element 20 can also be other shapes such as a circle, an ellipse, an irregular shape, etc., and the thickness of the solder gradient layer 100 can be determined with reference to the maximum width Wmax of the orthographic projection of the solder gradient layer 100 on the light emitting element 20. The ratio of the thickness h1 of the solder gradient layer 100 to the maximum width Wmax of the orthographic projection of the solder gradient layer 100 on the light emitting element 20 is in the range of 0.01 to 0.3. In some specific embodiments, h1 / Wmax is preferably 0.06 to 0.2. More specifically, for example, when the light-emitting element 20 corresponds to an LED chip of model 3458, h1 / Wmax is 0.067, when the light-emitting element 20 corresponds to an LED chip of model 1525, h1 / Wmax is 0.18, and when the light-emitting element 20 corresponds to an LED chip of model 1730, h1 / Wmax is 0.15. By setting the ratio of the thickness to the area of ​​the solder gradient layer 100 to the above ratio, when a light-emitting element is soldered to the above-mentioned backplane assembly 3, the soldering can be more stable, the electrical connectivity between the light-emitting element and the backplane assembly 3 can be better, and the resistance can be lower. In some embodiments, the area of ​​the orthographic projection of the first bonding layer 201 on the light-emitting epitaxial layer 203 is denoted as S2, and the area of ​​the orthographic projection of the solder gradient layer 100 on the light-emitting epitaxial layer 203 is denoted as S3. Figure 2a and Figure 2b , area S2 can also be understood as the positive projection area of ​​the first bonding layer 201 on the LED chip substrate 200, and area S3 can also be understood as the positive projection area of ​​the solder gradient layer 100 on the LED chip substrate 200. In some embodiments, area S2 is different from area S3. Specifically, refer to Figure 2c , area S2 is greater than area S3, more specifically, area S2 is 1.15 to 2.5 times of area S3. That is, in some embodiments, the area of ​​the orthographic projection of the first bonding layer 201 on the light-emitting epitaxial layer 203 is 1.15 to 2.5 times of the orthographic projection area of ​​the solder gradient layer 100 on the light-emitting epitaxial layer 203. This can prevent the solder gradient layer 100 from overflowing when it is melted during welding, provide a larger welding area, and achieve a better soldering effect. Figure 2dIn some embodiments, the first bonding layer 201 also extends toward the side close to the solder gradient layer 100 to the side of the solder gradient layer 100. It can be understood that the first bonding layer 201 forms a groove structure, and the solder gradient layer 100 is arranged in the groove structure to better prevent the overflow problem of the solder gradient layer 100.

[0080] In some embodiments, the area of ​​the positive projection of the electrode structure 204 on the light-emitting epitaxial layer 203 is recorded as area S4. Figure 2a and Figure 2b Area S4 can also be understood as the positive projection area of ​​the electrode structure 204 on the LED chip substrate 200. In some embodiments, area S4 is different from area S2. Figure 2f Specifically, the area S2 is greater than the area S4, and more specifically, the area S2 is 1.15 to 2.5 times the area S4, that is, the positive projection area of ​​the first bonding layer 201 on the light-emitting epitaxial layer 203 is 1.15 to 2.5 times the positive projection area of ​​the electrode structure 204 on the light-emitting epitaxial layer 203. The first bonding layer 201 can effectively isolate the electrode structure 204 from the solder gradient layer 100. Figure 2f As shown, area S2 can be set larger than area S3 and larger than area S4 at the same time, but this embodiment does not limit the size relationship between area S3 and area S4. Figure 2e As shown, in some embodiments, the first adhesive layer 201 further extends toward one side of the electrode structure 204 to the side of the electrode structure 204 .

[0081] The above-mentioned light emitting device 2 is used for welding, and the welding method is as follows:

[0082] S101: providing a light emitting device 2;

[0083] Reference Figures 1a to 2f or Figure 5 , a light-emitting device 2 is provided. The light-emitting device 2 can be any one of the light-emitting devices 2 mentioned in the above embodiments. The light-emitting device 2 includes a light-emitting element 20 and the aforementioned solder gradient layer 100. The light-emitting element 20 is an LED chip, and the structure of the LED chip is the same as the structure of the above LED chip, which will not be described in detail here. The solder gradient layer 100 is arranged on the pad layer 202 of the light-emitting element 20, and the melting point of the solder gradient layer 100 gradually decreases in the direction away from the pad layer 202. The structure of the solder gradient layer 100 can be the solder gradient layer 100 in any of the above embodiments, which will not be described in detail here. And, in this embodiment, with Figure 1a The light emitting device 2 shown is used as an example for description.

[0084] S102: providing a back plate;

[0085] Reference Figure 5A back plate 300 is provided, and a surface of the back plate 300 is provided with soldering pads for soldering the light-emitting device 2, and the soldering pads include a primary soldering pad 302 for soldering the light-emitting device 2, and a repair soldering pad (not shown in the figure) for soldering the light-emitting element for repair, and the repair soldering pad is arranged one by one with the primary soldering pad 302.

[0086] Optionally, a second adhesive layer 301 is further provided between the primary welding pad 302 and the back plate 300 to fix the primary welding pad 302 to the electrode layer on the back plate 300 .

[0087] S103: transferring the light emitting device to the primary soldering pad, and heating the solder graded layer at a first soldering temperature to solder the light emitting device to the primary soldering pad;

[0088] Reference Figure 5 , transfer the chip (i.e., the light emitting device 2) to the primary soldering pad 302, melt the solder gradient layer 100 on the light emitting device 2 at a first soldering temperature, and solder the chip (i.e., the light emitting device 2) to the primary soldering pad 302 of the back plate 300, completing the primary soldering. In this embodiment, the first soldering temperature is controlled to be in the range of 120°C to 230°C. For example, the first soldering temperature may be 150°C, 180°C, and 200°C.

[0089] S104: transferring the light-emitting device to the repair pad corresponding to the light-emitting device that cannot be normally lit, and heating the solder gradient layer at a second soldering temperature to solder the light-emitting device to the repair pad;

[0090] Reference Figure 5 or Figure 6 When testing a chip that has been soldered once, if it is found that the chip cannot light up normally, the second soldering temperature can be used to heat the solder gradient layer 100 on the chip to solder the chip (that is, the light-emitting device 2) to the repair pad. In this process, it is necessary to control the first soldering temperature and the second soldering temperature to be within the melting point range of the solder gradient layer 100. And during soldering, the second soldering temperature is controlled to be lower than the first soldering temperature to prevent the second soldering temperature from affecting the solder joints generated during the first soldering, so as to affect the reliability of the solder joints. In this embodiment, the second soldering temperature ranges from 120°C to 180°C. For example, the second soldering temperature can be 120°C, 150°C and 180°C.

[0091] A solder gradient layer 100 is formed on the pad layer 202 of the light-emitting device 2 in the present embodiment. In the process of soldering the light-emitting device 2 to the back panel 300, since there are multiple melting point zones or metal layers with different melting points in the solder gradient layer 100, during the primary welding and repair welding processes, the primary welding temperature is controlled to be higher than the temperature during the repair welding, which can avoid the repair welding from affecting the solder joints formed during the primary welding and effectively control the welding yield during welding.

[0092] Example 2

[0093] The present embodiment provides a backplane assembly 3 for soldering light-emitting elements, which includes a backplane 300 and a solder gradient layer 100 disposed on the solder pad of the backplane 300. The solder gradient layer 100 is disposed on the solder pad of the backplane 300, and the melting point of the solder gradient layer 100 gradually decreases in the direction away from the solder pad.

[0094] Among them, refer to Figure 3a or Figure 3b The back plate 300 (combined with the solder gradient layer 100 to form the back plate assembly 3) is used to carry the light emitting element to form a display panel. Specifically, the back plate 300 includes a substrate 303 (refer to Figure 4c or Figure 4d ) and a driving circuit layer (not shown in the figure) disposed on the substrate 303. Optionally, the driving circuit layer includes thin film transistors sequentially disposed on the substrate 303 and electrodes electrically connected to the thin film transistors. The thin film transistors include an active layer, a gate insulating layer, a gate, a source and a drain, etc. Optionally, the thin film transistors may be low temperature polysilicon (LTPS) thin film transistors or indium gallium zinc oxide (IGZO) thin film transistors.

[0095] A primary soldering pad 302 is disposed on the surface of the electrode layer of the back plate 300. The solder gradient layer 100 is formed on the surface of the primary soldering pad 302. Figure 4c or Figure 4dIn some embodiments, the electrode layer of the backplane 300 includes a connecting electrode 304 disposed on the substrate 303. The connecting electrode 304 is disposed on the side of the pad away from the solder gradient layer 100, that is, the connecting electrode 304 is located between the substrate 303 and the primary soldering pad 302. The number of connecting electrodes 304 is, for example, multiple. For example, corresponding to a soldering position of a light-emitting element, there may be two connecting electrodes 304 for soldering the two poles of the light-emitting element respectively. For a vertical LED chip, there may be only one connecting electrode 304 at one LED chip position. The number of corresponding primary soldering pads 302 corresponds to the number of connecting electrodes 304, and each connecting electrode 304 is provided with a primary soldering pad 302.

[0096] In one embodiment, referring to Figure 3a , the solder gradient layer 100 includes a single-layer structure formed by at least two metal materials, and the content of each metal material in the single-layer structure is different from that in the direction away from the primary soldering pad 302. Specifically, in the present embodiment, the solder gradient layer 100 includes tin and indium. The solder gradient layer 100 includes a first melting point region 110, a second melting point region 120 and a third melting point region 130 in the direction away from the primary soldering pad 302. The melting point range of the first melting point region 110 is between 180°C and 230°C, the melting point range of the second melting point region 120 is between 120°C and 180°C, and the melting point of the third melting point region 130 is between 100°C and 120°C. Among them, the indium content of the first melting point region 110 is between 0% and 25%, the indium content of the second melting point region 120 is between 25% and 60%, and the indium content of the third melting point region 130 is between 60% and 70%. The solder gradient layer 100 can be gradually formed by evaporating on the pad of the back plate 300 in a multi-source evaporation manner. For example, during the evaporation process, the tin-indium ratio is controlled to be Sn:In=8:1, Sn:In=7:1, Sn:In=6:1, Sn:In=5:1, Sn:In=4:1, Sn:In=3:1, Sn:In=2:1, Sn:In=1:1, and after evaporating the same thickness at the same indium-tin ratio, the indium-tin ratio is adjusted once until the solder gradient layer 100 is formed.

[0097] In another embodiment, referring to Figure 3b The solder gradient layer 100 is a multi-layer structure, which includes a plurality of metal layers stacked in sequence, and each metal layer has a different melting point. Each metal layer can be formed by mixing at least two metals, or by a single metal, and the metals contained in each metal layer can be the same or different. It should be noted that in this embodiment, as long as the melting points of each metal layer are different and the melting points of the metal layers gradually decrease in the direction away from the primary soldering pad 302, there is no restriction on the material composition of each metal layer. Specifically, refer to Figure 3bThe solder gradient layer 100 includes a first metal layer 101, a second metal layer 102 and a third metal layer 103 in the direction away from the primary soldering pad 302, and each metal layer is formed by multi-source evaporation. The melting point of the first metal layer 101 ranges from 180°C to 230°C, the melting point of the second metal layer 102 ranges from 120°C to 180°C, and the melting point of the third metal layer 103 is 100°C to 120°C. The first metal layer 101 can be made of tin metal, the second metal layer 102 can be made of indium metal, and the third metal layer 103 is made of indium and tin metal.

[0098] Reference Figure 4a , the distance h2 between the surface of the solder gradient layer 100 away from the pad and the surface of the connection electrode 304 away from the pad (primary solder pad 302) is the thickness of the solder gradient layer 100, and the positive projection area of ​​the solder gradient layer 100 on the back plate 300 can be recorded as area A1, and area A1 can also be understood as the positive projection area of ​​the solder gradient layer 100 on the substrate 303. In some embodiments, the ratio of the thickness h2 of the solder gradient layer 100 to the area A1 ranges from 0.001 to 0.1. In some specific embodiments, h2 / A1 is preferably 0.002 to 0.028. More specifically, for example, in the backplane assembly 3 for soldering an LED chip with model number 3458, h2 / A1 is 0.0037; for example, in the backplane assembly 3 for soldering an LED chip with model number 1525, h2 / A1 is 0.028; for example, in the backplane assembly 3 for soldering an LED chip with model number 1730, h2 / A1 is 0.0192. By setting the ratio of the thickness to the area of ​​the solder gradient layer 100 to the above ratio, the soldering between the light-emitting element and the backplane 300 can be made more firmly.

[0099] In some embodiments, the orthographic projection shape of the solder gradient layer 100 on the back plate 300 is a rectangle, and the lengths of the two perpendicular sides of the rectangle are L1 and L2 respectively. The orthographic projection area A1 of the aforementioned solder gradient layer 100 on the back plate 300 is equal to the product of L1 and L2. For example, if L1 is greater than L2, the thickness of the solder gradient layer 100 can also be determined with reference to the side length L1. For example, the ratio of the thickness h2 of the solder gradient layer 100 to the side length L1 is in the range of 0.01 to 0.3. Of course, the orthographic projection shape of the solder gradient layer 100 on the back plate 300 may also be other shapes such as a circle, an ellipse, an irregular shape, etc., then the thickness of the solder gradient layer 100 may be set with reference to the maximum width Lmax of the orthographic projection of the solder gradient layer 100 on the back plate 300, and the ratio of the thickness h2 of the solder gradient layer 100 to the maximum width Lmax of the orthographic projection of the solder gradient layer 100 on the back plate 300 is in the range of 0.01 to 0.3. In some specific embodiments, h2 / Lmax is preferably 0.06 to 0.2. More specifically, for example, in the back plate assembly 3 for soldering the LED chip of model 3458, h2 / Lmax is 0.067, in the back plate assembly 3 for soldering the LED chip of model 1525, h2 / Lmax is 0.18, and in the back plate assembly 3 for soldering the LED chip of model 1730, h2 / Lmax is 0.15.

[0100] In some embodiments, an adhesive layer is further provided between the connection electrode 304 and the pad. In this embodiment, the adhesive layer on the back plate 300 is recorded as the second adhesive layer 301. The area of ​​the orthographic projection of the second adhesive layer 301 on the substrate 303 is recorded as A2, and the area of ​​the orthographic projection of the solder gradient layer 100 on the substrate 303 is recorded as A3. In some embodiments, the area A2 is different from the area A3. Specifically, refer to Figure 4b , area A2 is greater than area A3, more specifically, area A2 is 1.15 to 2.5 times the area A3. That is, in some embodiments, the area of ​​the orthographic projection of the second bonding layer 301 on the substrate 303 is 1.15 to 2.5 times the area of ​​the orthographic projection of the solder gradient layer 100 on the substrate 303. It can prevent the overflow of the solder gradient layer 100 when it is welded and melted, provide a larger welding area, and achieve a better soldering effect. In some embodiments, the second bonding layer 301 also extends to the side of the solder gradient layer 100 toward the side close to the solder gradient layer 100, which can be understood as the second bonding layer 301 forming a groove structure, and the solder gradient layer 100 is arranged in the groove structure to better prevent the overflow problem of the solder gradient layer 100.

[0101] In some embodiments, the area of ​​the orthographic projection of the connecting electrode 304 on the substrate 303 is recorded as area A4. In some embodiments, area A4 is different from area A2. Figure 4dSpecifically, area A2 is greater than area A4, and more specifically, area A2 is 1.15 to 2.5 times of area A4, that is, the positive projection area of ​​the second bonding layer 301 on the substrate 303 is 1.15 to 2.5 times of the positive projection area of ​​the connecting electrode 304 on the substrate 303. The second bonding layer 301 can effectively isolate the connecting electrode 304 from the solder gradient layer 100. Figure 4d As shown, the second adhesive layer 301 also extends toward the side close to the connecting electrode 304 to the side of the connecting electrode 304 to achieve a better isolation effect.

[0102] The light emitting element is welded to the back plate assembly 3, and the welding method specifically includes the following steps:

[0103] S101: Provide a backplane assembly;

[0104] Reference Figures 3a to 4d or Figure 7 , a back plate 300 is provided, the structure of the back plate 300 is the same as the structure of the above-mentioned back plate 300, a solder gradient layer 100 is arranged on the pad of the back plate 300, so as to form a back plate assembly 3 with the back plate 300, and the melting point of the solder gradient layer 100 gradually decreases in the direction away from the pad. The specific arrangement of the solder gradient layer 100 can refer to the above description of embodiment 2, and will not be repeated here. In this embodiment, Figure 3b The backplane assembly 3 shown is taken as an example for explanation.

[0105] S102: providing a light emitting element;

[0106] A light-emitting element is provided, which may be an LED chip, and the LED chip includes an LED chip substrate 200 and a light-emitting structure (not shown in the figure) formed on the surface of the LED chip substrate 200. Optionally, the light-emitting structure includes a first semiconductor layer, an active layer, and a second semiconductor layer of opposite conductivity type to the first semiconductor layer, which are sequentially formed on the surface of the LED chip substrate 200, and the active layer is a light-emitting layer of the light-emitting element. The first semiconductor layer may be an N-type semiconductor layer, and the second semiconductor layer may be a P-type semiconductor layer. Of course, it is also possible that the first semiconductor layer is a P-type semiconductor layer and the second semiconductor layer is an N-type semiconductor layer. Optionally, the above-mentioned first semiconductor layer may be an N-type GaN layer, the active layer may be a quantum well layer, and the second semiconductor layer may be a P-type GaN layer.

[0107] In this embodiment, an electrode structure (not shown in the figure) is formed on the other surface of the LED chip substrate 200 , and a pad layer is formed on the surface of the electrode structure. The pad layer is used to solder the LED chip to the back plate 300 .

[0108] S103: melting the solder gradient layer at a first soldering temperature to solder the light emitting element to the back plate;

[0109] Reference Figure 7 Or 8, using the first welding temperature to melt the solder gradient layer 100 on the back plate 300 to weld the chip (ie, the light-emitting element) to the back plate 300 to complete a welding process. It should be noted that during a welding process, the first welding temperature needs to be controlled to be as small as possible to melt the solder at one end of the solder gradient layer 100 away from the back plate 300, the solder with a smaller melting point, and the solder in other areas does not melt. Optionally, the first welding temperature is between 120°C and 180°C, and the second welding temperature can be 120°C, 150°C and 180°C.

[0110] S104: Perform a lighting test on the light-emitting element soldered to the backplane. If the light-emitting element cannot light up normally, directly remove the light-emitting element.

[0111] Reference Figure 8 After one soldering, the chip (ie, the light emitting element) soldered to the back plate 300 is tested for lighting. If the light emitting element cannot light up normally, the chip is directly removed.

[0112] In the process of soldering the light emitting element to the back plate assembly 3 of this embodiment, since the solder gradient layer in the back plate assembly 3 includes multiple melting point zones or metal layers with different melting points, during one soldering, a lower soldering temperature is used to melt the solder far from the back plate 300 and with a relatively low melting point, and most of the solder with a high melting point close to the back plate 300 is not melted. The light emitting element is inspected, and if a defective light emitting element is found, the chip after one soldering can be easily removed, thereby improving the repair efficiency of the LED chip.

[0113] Example 3

[0114] This embodiment provides a display panel, referring to Fig. 9 The display panel includes a back panel 300 and a light-emitting device fixed on the back panel 300, wherein the light-emitting device is the light-emitting device 2 described in Example 1. In this embodiment, the light-emitting element in the light-emitting device 2 is an LED chip, and the light-emitting device 2 is soldered to the back panel 300 through the solder gradient layer 100 on the pad layer 202.

[0115] In the display panel in this embodiment, the light-emitting device 2 in Example 1, during the process of soldering the light-emitting device 2 to the back panel 300, since the solder gradient layer 100 in the light-emitting device 2 includes a plurality of melting point zones or metal layers with different melting points, during the primary welding and repair welding processes, the primary welding temperature is controlled to be greater than the temperature during the repair welding, which can avoid the repair welding from affecting the solder joints formed during the primary welding, effectively control the welding quality and yield during welding, and thus improve the yield and service life of the display panel.

[0116] Example 4

[0117] This embodiment also provides a display panel, referring to Fig.10 The display panel includes a backplane 300 and a light-emitting element fixed on the backplane 300, wherein the backplane 300 is the backplane 300 described in Example 2, and a solder gradient layer 100 is arranged on the pad of the backplane 300 to form the backplane assembly 3 described in Example 2, and the melting point of the solder gradient layer 100 gradually decreases in the direction away from the pad. The specific arrangement of the solder gradient layer 100 can refer to the description of the aforementioned Example 2, and will not be repeated here. The light-emitting element is soldered to the backplane 300 through the solder gradient layer 100 located on the pad layer of the backplane 300. In this embodiment, the light-emitting element is an LED chip.

[0118] In the display panel of this embodiment, in the process of soldering the light-emitting element to the backplane assembly 3 in the embodiment 2, since the solder gradient layer in the backplane assembly 3 includes multiple melting point zones or metal layers with different melting points, during one soldering, a lower soldering temperature is used to melt the solder far away from the backplane 300 and with a relatively low melting point, and most of the solder with a high melting point close to the backplane 300 is not melted. The light-emitting element is inspected, and if a defective light-emitting element is found, the chip after one soldering can be easily removed, thereby improving the repair efficiency of the LED chip.

[0119] The above embodiments are merely illustrative of the principles and effects of the present application and are not intended to limit the present application. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present application shall still be covered by the claims of the present application.

Claims

1. A light emitting device, characterized in that: include: A light-emitting element, the light-emitting element comprising a light-emitting epitaxial layer and a pad layer formed on the light-emitting epitaxial layer; the light-emitting element further comprising an electrode structure disposed between the light-emitting epitaxial layer and the pad layer and a bonding layer disposed between the electrode structure and the pad layer; The solder gradient layer is arranged on the pad layer of the light emitting element, and the melting point of the solder gradient layer gradually decreases in a direction away from the pad layer.

2. The light emitting device according to claim 1, characterized in that: In the direction away from the pad layer, the solder gradient layer includes a first melting point zone, a second melting point zone and a third melting point zone in sequence. The melting point range of the first melting point zone is between 180°C and 230°C, the melting point range of the second melting point zone is between 120°C and 180°C, and the melting point range of the third melting point zone is between 100°C and 120°C.

3. The light emitting device according to claim 1, characterized in that: The distance between the surface of the solder gradient layer away from the light-emitting element and the surface of the electrode structure facing away from the solder layer is the thickness of the solder gradient layer; the ratio of the thickness of the solder gradient layer to the area of ​​the positive projection of the solder gradient layer on the light-emitting element is 0.001 to 0.

1.

4. The light emitting device according to claim 1, characterized in that: The distance between the surface of the solder gradient layer away from the light-emitting element and the surface of the electrode structure facing away from the solder layer is the thickness of the solder gradient layer; the ratio of the thickness of the solder gradient layer to the maximum width of the positive projection of the solder gradient layer on the light-emitting element is 0.01 to 0.

3.

5. The light emitting device according to claim 1, characterized in that: An orthographic projection area of ​​the bonding layer on the light-emitting epitaxial layer is larger than an orthographic projection area of ​​the solder gradient layer on the light-emitting epitaxial layer.

6. The light emitting device according to claim 5, characterized in that The orthographic projection area of ​​the bonding layer on the light-emitting epitaxial layer is 1.15 to 2.5 times the orthographic projection area of ​​the solder gradient layer on the light-emitting epitaxial layer; And / or, the bonding layer extends toward a side close to the solder gradient layer to a side surface of the solder gradient layer.

7. The light emitting device according to claim 1, characterized in that: The orthographic projection area of ​​the bonding layer on the light-emitting epitaxial layer is larger than the orthographic projection area of ​​the electrode structure on the light-emitting epitaxial layer.

8. The light emitting device according to claim 7, characterized in that: The orthographic projection area of ​​the bonding layer on the light-emitting epitaxial layer is 1.15 to 2.5 times the orthographic projection area of ​​the electrode structure on the light-emitting epitaxial layer; and / or the bonding layer extends toward a side close to the electrode structure to a side surface of the electrode structure.

9. A backplane assembly, characterized in that: include: A back plate having pads for soldering light-emitting elements; A solder gradient layer is arranged on the pad of the back plate, and the melting point of the solder gradient layer gradually decreases in a direction away from the pad; A connecting electrode is located at a side of the pad away from the solder gradient layer; The bonding layer is located between the connecting electrode and the pad.

10. The back plate assembly according to claim 9, characterized in that: In the direction away from the pad, the solder gradient layer includes a first melting point zone, a second melting point zone and a third melting point zone in sequence. The melting point range of the first melting point zone is between 180°C and 230°C, the melting point range of the second melting point zone is between 120°C and 180°C, and the melting point range of the third melting point zone is between 100°C and 120°C.

11. The back plate assembly according to claim 9, characterized in that: The distance between the surface of the solder gradient layer away from the pad and the surface of the connecting electrode away from the pad is the thickness of the solder gradient layer; the ratio of the thickness of the solder gradient layer to the orthographic projection area of ​​the solder gradient layer on the backplane is 0.001 to 0.

1.

12. The back plate assembly according to claim 9, characterized in that: The distance between the surface of the solder gradient layer away from the pad and the surface of the connecting electrode away from the pad is the thickness of the solder gradient layer; the ratio of the thickness of the solder gradient layer to the maximum width of the orthographic projection of the solder gradient layer on the backplane surface is 0.01 to 0.

3.

13. The back plate assembly according to claim 9, characterized in that: The backplane also includes a substrate, the pad is arranged on the surface of the substrate, and the orthographic projection area of ​​the bonding layer on the substrate is larger than the orthographic projection area of ​​the solder gradient layer on the substrate.

14. The back plate assembly according to claim 13, characterized in that: The orthographic projection area of ​​the bonding layer on the substrate is 1.15 to 2.5 times the orthographic projection area of ​​the solder gradient layer on the substrate; And / or, the bonding layer extends toward a side close to the solder gradient layer to a side surface of the solder gradient layer.

15. The back plate assembly according to claim 9, characterized in that: The backplane further comprises a substrate, the connecting electrode is arranged on the substrate, and the orthographic projection area of ​​the bonding layer on the substrate is larger than the orthographic projection area of ​​the electrode on the substrate.

16. The back plate assembly according to claim 15, characterized in that: The orthographic projection area of ​​the bonding layer on the substrate is 1.15 to 2.5 times the orthographic projection area of ​​the electrode on the substrate; and / or the bonding layer extends toward a side close to the connecting electrode to a side surface of the connecting electrode.

17. A display panel, characterized in that: include: Back panel; A light emitting device fixed on the back plate, wherein the light emitting device is the light emitting device according to any one of claims 1 to 8, and the light emitting device is soldered to the back plate through a solder gradient layer on a solder pad layer.

18. A display panel, characterized in that: include: The back panel assembly according to any one of claims 9 to 16; The light emitting element is soldered onto the back panel assembly through the solder gradient layer.

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