Display panel and manufacturing method thereof

Abstract

The present invention relates to a display panel and a method for manufacturing the same. The display panel of the present invention comprises: a substrate provided with a plurality of grooves, solder pads arranged on the substrate within the grooves, a memory metal layer covering the sidewalls of the grooves, and an LED chip that is detachably inserted into the grooves and electrically connected to the solder pads; when the memory metal layer is in a state higher than the maximum operating temperature of the LED chip, the internal space of the grooves is expanded so that the electrodes of the LED chip are loosely matched with the grooves, and the electrodes can be inserted into or removed from the grooves; when the memory metal layer is in a state lower than or equal to the maximum operating temperature of the LED chip, the grooves are interference-fitted with the electrodes of the LED chip inserted therein, so that the electrodes are fixedly connected to the solder pads in the grooves. The display panel of the present invention has the advantages of close integration of the LED chip and the solder pads, convenient replacement of the LED chip, avoidance of damage to the substrate solder pads caused by chip insertion and removal, and simplicity and environmental protection.

Description

Technical Field

[0001] The present invention relates to the field of LED technology, and in particular to a display panel and a manufacturing method thereof. Background Art

[0002] Currently, in the production of Micro LED display panels, solder is usually used to fix the Micro LED chip to the substrate. First, the solder is set on the pad of the substrate, and then the electrode of the chip is aligned with the solder of the substrate. The solder is then heated to a molten state. After the aligned chip and solder are attached together, the solder is solidified by cooling, thereby achieving electrical connection between the chip and the substrate.

[0003] If a defective Micro LED chip exists, it must be transferred and replaced after it has been fixed to the substrate. Prior to transfer, the solder in a specific area of ​​the substrate must be heated and melted to separate the defective chip from the substrate for transfer. However, precisely heating the solder to only the area below a specific chip is difficult. During the heating process, the solder beneath the chips surrounding the chip to be transferred will also melt, causing these chips that do not need to be transferred to become loose or shifted on the substrate, resulting in poor electrical connection and ultimately affecting their luminous performance. Summary of the Invention

[0004] Based on this, an object of the present invention is to provide a display panel and a method for manufacturing the same.

[0005] The display panel of the present invention comprises: a substrate provided with a plurality of grooves, solder pads arranged on the substrate in the grooves, a memory metal layer covering the sidewalls of the grooves, and an LED chip detachably inserted into the grooves and electrically connected to the solder pads;

[0006] When the memory metal layer is at a temperature higher than the maximum operating temperature of the LED chip, the internal space of the groove is expanded so that the electrode of the LED chip fits into the groove gap and the electrode can be inserted into or removed from the groove;

[0007] When the memory metal layer is at a state lower than or equal to the maximum operating temperature of the LED chip, the groove and the electrode of the LED chip inserted therein are interference-fitted, so that the electrode is fixedly connected to the pad in the groove.

[0008] The display panel described in the present invention has the advantages of tight integration of LED chips and solder pads, convenient replacement of LED chips, avoidance of damage to substrate solder pads caused by chip insertion and removal, simplicity and environmental protection. During the chip replacement process, the remaining chips affected are not easily loosened from the substrate; the memory metal layer can be recycled, and there is no need to remove the original solder and reset the solder when replacing the chip.

[0009] Furthermore, the material of the memory metal layer is selected from any one or more alloys of Au-Cd, Ag-Cd, Cu-Zn, Cu-Zn-Sn, Cu-Sn, Cu-Zn-Ga, In-Ti, Au-Cu-Zn, Ni-Al, Fe-Pt, Ni-Ti, Ti-Ni-Pd, Ti-Nb, U-Nb and Fe-Mn-Si.

[0010] Furthermore, the substrate includes an insulating substrate and an elastic insulating layer disposed on the insulating substrate; the elastic insulating layer is provided with a plurality of grooves, with each pad disposed on the insulating substrate within a corresponding groove. The elastic insulating layer is elastic, ensuring that the memory metal does not loosen from the groove when deformed, thereby maintaining its electrical conductivity.

[0011] Furthermore, the elastic insulating layer is made of silicone or polydimethylsiloxane.

[0012] Furthermore, a memory metal layer is provided on the surface of the pad in the groove, thereby further strengthening the interference fit between the groove and the LED electrode.

[0013] Furthermore, a protective metal layer is provided on the memory metal layer on the surface of the pad in the groove. The protective metal layer can prevent the memory metal from being oxidized and affecting the conductivity, and at the same time has the function of protecting the metal and strengthening the bonding force between the memory metal and the pad.

[0014] Furthermore, the protective metal layer is Au, Mo or Ti.

[0015] Furthermore, the depth of the inner space of the groove is smaller than the length of the electrode of the LED chip, thereby ensuring that the LED chip electrode is in full contact with the solder pad at the bottom of the groove.

[0016] Furthermore, the shrinkage center of the memory metal layer located on the sidewall of the groove coincides with the center of the LED chip electrode, ensuring that the memory metal can be in close contact with the LED electrode or fully expand the internal space of the groove to facilitate the removal of the LED electrode.

[0017] Furthermore, the method for manufacturing the display panel includes: making grooves on a substrate provided with solder pads, with the bottom of each groove corresponding to a solder pad; preparing a memory metal layer on the sidewalls or the sidewalls and bottom of the grooves; inserting an LED chip into the grooves, wherein the electrodes of the LED chip are conductively connected to the solder pads.

[0018] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of a display panel according to embodiment 1 of the present invention;

[0020] Figure 2 This is a schematic diagram of the panel structure after a groove is made on a substrate provided with a solder pad;

[0021] Figure 3 is a schematic diagram of the panel structure after photoresist is coated on the elastic insulating layer;

[0022] Figure 4 Schematic diagram of the panel structure after preparing a memory metal layer on the photoresist;

[0023] Figure 5 This is a schematic diagram of the panel structure after removing the metal and photoresist except for the substrate pads and the openings of the elastic insulating layer;

[0024] Figure 6 A schematic diagram of the panel structure showing a protective metal layer formed on the memory metal layer at the bottom of the groove;

[0025] Figure 7 This is a schematic structural diagram of a display panel according to embodiment 2 of the present invention;

[0026] Figure 8 This is a diagram showing the working principle of the display panel of the present invention when the temperature is higher than the maximum working temperature of the LED chip.

[0027] Reference numerals: substrate 10 , insulating substrate 12 , elastic insulating layer 14 , pad 20 , memory metal layer 30 , protective metal layer 40 , LED chip 50 , photoresist 102 . DETAILED DESCRIPTION

[0028] In response to the existing technology that removes defective Micro LED chips from the panel and causes thermal impact on the surrounding chips, the present invention redesigns the structure of the display panel and sets a memory metal layer between the LED chip and the substrate to facilitate the removal of the LED chip.

[0029] Example 1

[0030] See also Figure 1 , which is a schematic structural diagram of a display panel according to Example 1 of the present invention. The display panel includes a substrate 10 , a pad 20 , a memory metal layer 30 , a protective metal layer 40 and an LED chip 50 .

[0031] The substrate 10 includes an insulating substrate 12 and an elastic insulating layer 14 covering the insulating substrate 12. The elastic insulating layer 14 is provided with an array of grooves. The solder pads 20 are disposed on the bottom surfaces of the grooves. The memory metal layer 30 covers the groove sidewalls and the solder pads 20. The protective metal layer 40 covers the bottom surface of the memory metal layer 30. The LED chip 50 is disposed on the protective metal layer 40 in the grooves.

[0032] Specifically, the elastic insulating layer 14 is made of silicone or polydimethylsiloxane (PDMS). The depth of the groove in the elastic insulating layer 14 is less than the length of the electrode of the LED chip 50 to ensure that the electrode of the LED chip 50 can effectively bond with the protective metal layer 40 in the groove.

[0033] In order to enable the memory metal layer 30 to produce appropriate deformation at different temperatures to facilitate the removal of the LED chip 50 and ensure the normal operation of the LED chip 50, special parameter design is required for the memory metal layer 30. Specifically, when the temperature is higher than the maximum operating temperature of the LED chip 50 (generally 60°C), the diameter of the groove formed by the memory metal layer 30 is larger than the diameter of the electrode of the LED chip 50; when the temperature is lower than or equal to the maximum operating temperature of the LED chip 50, the diameter of the groove formed by the memory metal layer 30 is smaller than the diameter of the electrode of the LED chip 50. The shrinkage center of the memory metal layer 30 located on the side wall of the groove coincides with the center of the electrode of the LED chip 50, so that the memory metal layer 30 can have an interference fit with the electrode of the LED chip 50 therein, stably wrapping and fixing the electrode of the LED chip 50. The material of the memory metal layer 30 is selected from one or more of Au-Cd, Ag-Cd, Cu-Zn, Cu-Zn-Sn, Cu-Sn, Cu-Zn-Ga, In-Ti, Au-Cu-Zn, Ni-Al, Fe-Pt, Ni-Ti, Ti-Ni-Pd, Ti-Nb, U-Nb and Fe-Mn-Si.

[0034] The protective metal layer 40 is made of one or more materials selected from Au, Mo, and Ti to prevent oxidation of the memory metal layer 30 .

[0035] The LED chip 50 is preferably a Mini-LED chip or a Micro-LED chip.

[0036] See also Figure 2-Figure 6 The steps of the display panel manufacturing method include:

[0037] S1 : An array of pads 20 is provided on the insulating substrate 12 .

[0038] S2: An elastic insulating layer 14 is formed on the insulating substrate 12 by spin coating, covering the solder pad 20. A groove is then etched at the location of the solder pad 20 by exposure, development, and etching, exposing the solder pad 20 within the groove. The opening width of the groove should be larger than the electrode size of the LED chip 50 to be inserted.

[0039] S3: Prepare a memory metal layer 30 on the sidewall and bottom of the groove; see Figure 3-5 , S3 specific steps include:

[0040] S21: Spin-coating a 1-2 μm thick photoresist 102 on the elastic insulating layer 14, and then performing exposure and development processes to expose the grooves on the elastic insulating layer 14;

[0041] S22: forming a memory metal layer 30 on the bottom surface and sidewalls of the groove and the surface of the photoresist by electron beam evaporation or magnetron sputtering process;

[0042] S23: Remove the metal and photoresist outside the opening of the pad 20 and the elastic insulating layer 14 through the gold stripping and adhesive stripping process. The groove opening width is larger than the electrode diameter of the chip to be inserted, and the groove depth should be smaller than the electrode length of the inserted chip.

[0043] S4: preparing a protective metal layer 40 on the bottom surface of the memory metal layer 30. The steps for preparing the protective metal layer 40 are the same as those for preparing the memory metal layer 30, and are not described in detail here.

[0044] S5: inserting the LED chip 50 into the groove, so that the electrode of the LED chip 50 is bonded to the protective metal layer 40 , and is conductively connected to the soldering pad 20 through the protective metal layer 40 and the memory metal layer 30 .

[0045] Before the memory metal layer 30 is formed by the above process, the memory metal needs to be trained, specifically:

[0046] Memory metal shrinkage: Lower the temperature below Mf (the martensitic transformation termination temperature of the memory metal) to transform the austenite metal in the memory metal into martensite, and apply external force to shrink the memory metal structure and reduce the groove size;

[0047] Memory metal expansion: When the memory metal is heated to Af (the reverse transformation termination temperature of the memory metal), the martensite in the memory metal gradually becomes austenite, causing its shape to reverse to its original shape and restore the groove size.

[0048] The above training needs to be repeated several times until the test shows that when the temperature is lower than the maximum operating temperature of the chip, the groove and the LED chip 50 electrode have an interference fit. When the temperature is higher than the maximum operating temperature of the chip, the memory metal layer 30 is deformed and the groove and the LED chip 50 electrode have a clearance fit. Specifically, the size of the memory metal layer 30 set at the bottom of the groove is reduced to a state where the chip can maintain a grip on the chip at room temperature. The specific size is about 90% of the chip electrode size.

[0049] Example 2

[0050] Specifically, see Figure 7, which is a schematic diagram of the structure of a display panel according to Example 2 of the present invention. The structure and manufacturing method of the display panel of this embodiment are basically the same as those of Example 1, with the following differences: In this embodiment, the protective metal layer 40 is not provided, and the memory metal layer 30 covers the sidewalls of the groove; and the LED chip 50 is provided on the solder pad 20 of the groove.

[0051] Accordingly, the difference between the manufacturing method of the display panel of this embodiment and embodiment 1 is: S3: preparing a memory metal layer 30 on the side wall of the groove; skipping step S4; S5: inserting the LED chip 50 into the groove so that the electrode of the LED chip 50 is bonded to the pad 20.

[0052] The working principle of the display panel of the present invention can be found in Figure 1 、 Figure 8 When the display panel of the present invention is working, the memory metal layer 30 covering the sidewalls of the groove tightly wraps the electrodes of the LED chip 50. The groove on the substrate 10 and the electrodes of the LED chip 50 are interference-fitted and not easily fall off. When a defective LED chip on the array needs to be replaced, the portion of the display panel where the chip needs to be replaced is heated (above 60°C). At this time, the groove opening expands, and the groove and the electrode gap of the LED chip are matched. The defective LED chip can be directly pulled out and a new LED chip can be inserted into the groove to complete the replacement. At this time, other LED chips located around the defective LED chip may be squeezed, but the elasticity of the elastic insulating layer 14 on the sidewalls of the groove can alleviate this squeezing. When the display panel cools to below 60°C, due to the two-way memory effect of the memory metal, the groove on the display panel that has expanded due to high temperature shrinks toward the center and restores its original shape. Since the center of the LED chip 50 coincides with the shrinkage center of the groove sidewall, the memory metal layer 30 can be interference-fitted with the LED chip 50 therein, stably wrapping and fixing the LED chip 50. During this process, the memory metal will not fall off during the deformation process due to the elastic insulating layer 14 having a certain elasticity. In some embodiments, the protective metal layer 40 covers the memory metal layer 30 to prevent the memory metal layer 30 from oxidizing and strengthen the bonding force between the memory metal layer 30 and the pad 20.

[0053] Compared with the existing technology, the present invention uses recyclable memory metal materials and cleverly uses the characteristics of memory metal to set a groove structure that can match the LED chip on the display panel. It overcomes the problem of loosening and shifting of other chips caused by traditional replacement of LED chips by heating solder, avoids damage to the substrate pad due to chip insertion and removal, and has the advantages of tight combination of LED chip and pad, convenient LED chip replacement, and environmental protection and durability.

[0054] The above-described embodiments merely represent several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, and the present invention is intended to encompass such modifications and variations.

Claims

1. A display panel, characterized in that: The invention comprises a substrate with a plurality of grooves, solder pads arranged on the substrate in the grooves, a memory metal layer covering the sidewalls of the grooves and the surfaces of the solder pads in the grooves, and an LED chip detachably inserted into the grooves and electrically connected to the solder pads; When the memory metal layer is at a temperature higher than the maximum operating temperature of the LED chip, the internal space of the groove is expanded so that the electrode of the LED chip fits into the groove gap and the electrode can be inserted into or removed from the groove; When the memory metal layer is at a temperature lower than or equal to the maximum operating temperature of the LED chip, the groove and the electrode of the LED chip inserted therein are interference-fitted, so that the electrode is fixedly connected to the pad in the groove; The substrate includes an insulating substrate and an elastic insulating layer provided on the insulating substrate; the elastic insulating layer is provided with a plurality of grooves, and each pad is correspondingly provided on the insulating substrate in a groove; The memory metal layer is located at a shrinkage center of the groove sidewall that coincides with the center of the LED chip electrode.

2. The display panel according to claim 1, wherein: The material of the memory metal layer is selected from any one or more alloys of Au-Cd, Ag-Cd, Cu-Zn, Cu-Zn-Sn, Cu-Sn, Cu-Zn-Ga, In-Ti, Au-Cu-Zn, Ni-Al, Fe-Pt, Ni-Ti, Ti-Ni-Pd, Ti-Nb, U-Nb and Fe-Mn-Si.

3. The display panel according to claim 1 or 2, wherein: The elastic insulating layer is made of silicone or polydimethylsiloxane.

4. The display panel according to claim 3, wherein: A protective metal layer is provided on the memory metal layer on the surface of the pad in the groove.

5. The display panel according to claim 4, wherein: The protective metal layer is Au, Mo or Ti.

6. The display panel according to claim 5, wherein: The depth of the inner space of the groove is smaller than the length of the electrode of the LED chip.

7. A method for manufacturing the display panel according to any one of claims 1 to 6, characterized in that: include: S1: An array of pads is provided on an insulating substrate; S2: A flexible insulating layer covering the pad is formed on the insulating substrate by spin coating, and then a groove is etched at the pad position by exposure, development and etching to expose the pad in the groove. The opening width of the groove should be larger than the electrode size of the LED chip to be inserted. S3: preparing a memory metal layer on the sidewall and bottom of the groove; S4: preparing a protective metal layer on the bottom surface of the memory metal layer; S5: Insert the LED chip into the groove, so that the electrode of the LED chip is bonded to the protective metal layer, and is conductively connected to the soldering pad through the protective metal layer and the memory metal layer.

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