Micro-component structure and method for manufacturing the same, and method for transferring LED chip

Abstract

The application relates to a micro component structure and a preparation method thereof and a transfer method of an LED chip, wherein the micro component structure comprises a substrate, a plurality of stacked glue layer structures arranged at a first surface of the substrate in a spaced manner and a plurality of LED chips arranged on the plurality of stacked glue layer structures correspondingly, the LED chip has two lead electrodes towards the surface of the stacked glue layer structure; the stacked glue layer structure comprises a photolysis glue layer and a pyrolysis glue layer arranged in a laminated mode, the photolysis glue layer is in contact with the first surface, the pyrolysis glue layer is located between the two lead electrodes, and the thickness of the pyrolysis glue layer is greater than the height of the lead electrodes. When the LED chip on the micro component structure is transferred through laser, the laser energy required for dissociating the photolysis glue layer in the stacked glue layer structure is low, so that the damage to the chip in the transfer process is small, and the existence of the pyrolysis glue layer can further slow down the damage of the laser to the chip, and the transfer yield of the chip is improved.

Description

Technical Field

[0001] This application relates to the field of display technology, and more particularly to a micro-element structure and its fabrication method, and a method for transferring LED chips. Background Technology

[0002] Currently, micro light-emitting diode (micro LED) display panels, as a new generation of display technology, have advantages such as higher brightness, better luminous efficiency, and lower power consumption, making micro LED display panels widely used.

[0003] In the fabrication of micro LED display panels, mass transfer technology is required to transfer three-color LED chips from their respective growth substrates to a display backplane. Stamp transfer is one of the mainstream mass transfer technologies, and its general process is as follows: 1) Multiple LED chips on the growth substrate are bonded to a temporary substrate with an adhesive layer, and then the growth substrate is peeled off, transferring the chips to the temporary substrate; 2) The LED chips are then pressed together using a transfer substrate, and the temporary substrate is peeled off by laser action on the adhesive layer, transferring the chips to the transfer substrate; 3) Finally, the LED chips on the transfer substrate are transferred to the display backplane. However, during step 2), the laser often acts on the chips (especially their two electrodes), causing some damage and reducing the chip transfer yield. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this application is to provide a micro-component structure and its fabrication method, as well as an LED chip transfer method, in order to solve the problems of large laser damage to the chip and low chip transfer yield during the chip transfer process.

[0005] A first aspect of this application provides a micro-element structure, comprising: a substrate; a plurality of stacked adhesive layer structures spaced apart on a first surface of the substrate; a plurality of LED chips correspondingly disposed on the plurality of stacked adhesive layer structures; each LED chip having two lead electrodes on the surface facing the stacked adhesive layer structures; the stacked adhesive layer structures include a photodegradable adhesive layer and a thermally degradable adhesive layer stacked together, wherein the photodegradable adhesive layer is in contact with the first surface; the thermally degradable adhesive layer is located between the two lead electrodes, and the thickness of the thermally degradable adhesive layer is greater than the height of the lead electrodes.

[0006] In this application, by setting a stacked adhesive layer structure spaced apart on the substrate between the substrate of the micro-element structure and the LED chip, when the LED chip on the micro-element structure needs to be transferred to the transfer substrate, the laser energy required to dissociate the photodegradable adhesive layer in the stacked adhesive layer structure connected to the LED chip is low, resulting in less damage to the LED chip. Furthermore, since a pyrolytic adhesive layer is also provided between the LED chip and the photodegradable adhesive layer and inserted between the two lead electrodes of the chip, and its thickness is greater than the height of the chip lead electrodes, when the photodegradable adhesive layer is dissociated by laser, the pyrolytic adhesive layer can block the laser from irradiating the LED chip to a certain extent, further reducing the damage of the laser to the LED chip, thereby significantly improving the chip transfer yield.

[0007] Optionally, the melting temperature of the pyrolytic adhesive layer is lower than that of the photolytic adhesive layer, and the difference between the melting temperatures of the pyrolytic adhesive layer and the photolytic adhesive layer is greater than 20°C. Thus, during the fabrication of this micro-element structure, when the pyrolytic adhesive layer is melted to embed the pyrolytic adhesive layer between the two electrodes of the LED chip, the photolytic adhesive material corresponding to the photolytic adhesive layer can maintain its configuration well.

[0008] Optionally, the thickness of the thermally degradable adhesive layer is greater than the thickness of the photodegradable adhesive layer. This allows the photodegradable adhesive layer to be subsequently degraded using a low-energy laser, while the thermally degradable adhesive layer can prevent laser damage to the LED chip during the photodegradation process.

[0009] Optionally, the width of the photolytic adhesive layer is greater than or equal to the width of the thermally degradable adhesive layer. Such a photolytic adhesive layer is easier to prepare, and it can better support the thermally degradable adhesive layer and the LED chip.

[0010] A second aspect of this application provides a method for fabricating a micro-element structure, comprising:

[0011] Photolytic adhesive and pyrolytic adhesive are sequentially stacked on the first surface of the substrate;

[0012] A growth substrate on which multiple LED chips are grown is thermally bonded to the substrate, so that the LED chips are embedded in the pyrolytic adhesive material, and the two lead electrodes of the LED chips face the photolytic adhesive material.

[0013] Peel off the growth substrate;

[0014] The pyrolytic adhesive between two adjacent LED chips is removed, and the remaining pyrolytic adhesive and the photolytic adhesive are etched to form a stacked adhesive layer structure between the substrate and the LED chip; wherein the stacked adhesive layer structure includes a photolytic adhesive layer and a pyrolytic adhesive layer, and the photolytic adhesive layer is spaced apart on the first surface; the pyrolytic adhesive layer is located between two lead electrodes of the LED chip, and the thickness of the pyrolytic adhesive layer is greater than the height of the lead electrodes.

[0015] The fabrication method of the aforementioned micro-component structure is simple, convenient, and highly controllable. The stacked adhesive layer structure formed on the resulting micro-component structure effectively solves the problem of laser damage to the LED chip during the transfer process. Furthermore, the high dimensional uniformity of the multiple stacked adhesive layer structures formed through two-step etching facilitates subsequent batch debonding of the photoresist layers in multiple stacked adhesive layer structures, avoiding the problem of some chips being easily damaged due to inconsistent debonding times.

[0016] Optionally, the method for removing the pyrolytic adhesive material between two adjacent LED chips includes: wet etching or dry etching; wherein the wet etching uses at least one of acetone and N-methylpyrrolidone as the etching solution; and the dry etching uses an etching gas including oxygen. Thus, with the aid of the LED chip mask, both wet and dry etching can achieve perpendicular etching of the pyrolytic adhesive material along its surface away from the photolytic adhesive material.

[0017] Optionally, the etching of the remaining pyrolytic adhesive material and the photolytic adhesive material is a dry etching process, which includes first etching with oxygen for 10-20 minutes, followed by etching with a fluorine-containing gas for 5-8 minutes. This specific dry etching process offers high controllability, easily forming a finely structured stacked adhesive layer, and the resulting stacked adhesive layer structure has high dimensional uniformity, minimizing the risk of damage to the LED chip.

[0018] A third aspect of this application provides a method for transferring an LED chip, comprising:

[0019] A micro-element structure as described in the first aspect of this application is provided, a transfer substrate is attached to the side of the micro-element structure where the LED chip is disposed, and the photodegradable adhesive layer is irradiated with a laser to transfer the LED chip and the thermal degradable adhesive layer to the transfer substrate;

[0020] The LED chip on the transfer substrate is transferred to the display backplane.

[0021] The aforementioned LED chip transfer method, when transferring the LED chip from a micro-component structure with a special stacked adhesive layer to a transfer substrate, allows for the use of lower laser energy to dissociate the photolytic adhesive layer attached to the chip and effectively blocks laser irradiation onto the LED chip. This significantly reduces laser damage to the chip during transfer and improves the transfer yield. Furthermore, when the LED chip on the transfer substrate is transferred to the display backplane, the pyrolytic adhesive layer attached to the chip can further enhance the bonding force between the LED chip and the display backplane after thermal melting and cooling.

[0022] Optionally, transferring the LED chip from the transfer substrate to the display backplane includes: placing the side of the transfer substrate with the LED chip facing the side of the display backplane with multiple pad groups; thermally bonding the leads to electrically connect the leads to the corresponding pad groups; after cooling, filling the space between the leads and the pad groups with the pyrolytic adhesive layer; and then peeling off the transfer substrate. This improves the adhesion between the LED chip and the display backplane.

[0023] The fourth aspect of this application provides a display device, including a display backplane and a plurality of LED chips, wherein the plurality of LED chips are transferred to the display backplane by the transfer method described in the third aspect of this application. Attached Figure Description

[0024] Figures 1 to 6 This illustrates a common process for mass-transferring LED chips to the display backplane.

[0025] Figures 7 to 13 This is a flowchart illustrating the fabrication process of a micro-element structure provided in one embodiment of this application.

[0026] Figures 14 to 18 This is a schematic diagram of the process flow of an LED chip transfer method provided in an embodiment of this application.

[0027] Explanation of reference numerals in the attached figures: 10-growth substrate, 20-LED chip, 21-lead electrode, 30-temporary substrate, 40-transfer substrate, 50-display backplane, 51-pad group, 300-substrate, 300a-first surface, 31-photolytic adhesive, 32-pyrolytic adhesive, 31'-photolytic adhesive layer, 32'-pyrolytic adhesive layer. Detailed Implementation

[0028] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0030] Generally, when the LED chip 20 is transferred to the display back panel 100, the red LED chip, blue LED chip and green LED chip are transferred respectively. The following explanation uses one type of LED chip 20 as an example. The other two types of LED chips are handled in the same way and will not be repeated in this application.

[0031] Figures 1 to 6 This illustrates a common process for mass-transferring LED chips to a display backplane. The specific process includes the following steps S11, S12, and S13.

[0032] Step S11: As Figure 1 As shown, a growth substrate 10 is provided, on which LED chips 20 are grown. Then, the side of the growth substrate 10 with the LED chips 20 is bonded to the side of a temporary substrate 30 with an adhesive layer (typically photoresist), thus bonding the LED chips 20 to the temporary substrate 30 (e.g., ...). Figure 2 (As shown). Next, the growth substrate 10 on the LED chip 20 is peeled off. This allows the LED chip 20 to be transferred onto the temporary substrate 30, as shown. Figure 3 As shown.

[0033] Step S12: Use the transfer substrate 40 to press the LED chip on the temporary substrate 30 together, and focus the laser onto the photoresist where the LED chip 20 to be picked up is attached (e.g., Figure 4 As shown, the photoresist under the corresponding LED chip is dissociated to selectively transfer the LED chip 20 onto the transfer substrate 40. Figure 5 The transfer substrate 40 is shown selectively picking up LED chips 20 from temporary substrate 30.

[0034] Step S13: Transfer the LED chip 20 on the transfer substrate 40 to the display backplane 50. (Reference) Figure 6 , Figure 6 This diagram shows a successful transfer of the LED chip 20 onto the display backplate 50.

[0035] From the above Figure 3 It can be seen that the photopolymer adhesive layer on the temporary substrate 30 generally covers the entire surface of the temporary substrate 30. When like Figure 4When the photopolymer adhesive layer is irradiated by a laser to pick up the LED chip 20, the laser energy required to dissociate the photopolymer adhesive layer corresponding to the LED chip 20 is generally high, and the laser will inevitably hit the lead electrode 21 of the LED chip 20, which may damage the LED chip 20, causing its electrical abnormality, and naturally reducing the transfer yield of the LED chip 20.

[0036] Therefore, this application aims to provide a solution that can solve the above-mentioned technical problems, the details of which will be described in subsequent embodiments.

[0037] refer to Figures 7 to 13 , Figure 13 This is a schematic diagram of the micro-component structure used in the LED chip transfer method provided in an embodiment of this application. Figures 7 to 13 This is a flowchart illustrating the fabrication process of a micro-element structure according to an embodiment of this application. The fabrication method of the micro-element structure includes the following steps S110-S150.

[0038] S110: Provides substrate 300, see [link / reference] Figure 7 Photolytic adhesive 31 and pyrolytic adhesive 32 are sequentially prepared on the first surface 300a of substrate 300.

[0039] The substrate 300 has two surfaces arranged opposite to each other, where the first surface 300a refers to the surface on which the photolytic adhesive 31 and the pyrolytic adhesive 32 are to be applied. For example... Figure 7 As shown, the photolytic adhesive 31 is continuously distributed on the first surface 300a of the substrate 300, and can completely cover the first surface 300a of the substrate 300. Correspondingly, the pyrolytic adhesive 32 can also be continuously distributed on the photolytic adhesive 31, and can completely cover the surface of the photolytic adhesive 31 away from the substrate 300. The photolytic adhesive 31 can degrade due to viscosity reduction under laser irradiation of a preset wavelength, and the pyrolytic adhesive can regain its tackiness after cooling. The pyrolytic adhesive 32 can degrade due to viscosity reduction when heated to a preset temperature. The pyrolytic adhesive 32 does not react with the laser.

[0040] Photolytic adhesive 31 and pyrolytic adhesive 32 can be prepared by coating methods, specifically, they can be independently selected from spin coating, brush coating, spray coating, etc. After coating the photolytic adhesive 31, it needs to be cured before coating the pyrolytic adhesive 32 on top and curing it. Optionally, the thickness of the photolytic adhesive 31 can be in the range of 2μm-3μm. A suitable thickness of photolytic adhesive 31 can provide good support for the LED chip in the subsequent process (e.g., ...). Figure 13 In addition, it facilitates subsequent degumming using a low-energy laser.

[0041] In this embodiment, the melting temperature of the pyrolytic adhesive 32 is lower than that of the photolytic adhesive 31. This ensures that when the substrate 100 is subsequently connected to the growth substrate on which the LED chip is grown using the pyrolytic adhesive 32, the photolytic adhesive 31 maintains its morphology. In some embodiments, the difference in melting temperature between the pyrolytic adhesive 32 and the photolytic adhesive 31 can be greater than or equal to 20°C. In this case, the difference in melting temperature between the two adhesives is suitable, allowing the photolytic adhesive 31 to maintain its configuration well when the pyrolytic adhesive 32 melts.

[0042] S120: As Figure 8 As shown, the growth substrate 10 on which multiple LED chips 20 are grown is thermally bonded to the substrate 300, so that the LED chips 20 are embedded in the thermally degradable adhesive 32, and the two lead electrodes 21 of the LED chips 20 face the thermally degradable adhesive 31 (e.g., ...). Figure 9 (as shown), and then peel off the growth substrate 10 (as shown). Figure 10 As shown), the result is as follows: Figure 11 The structure shown.

[0043] In step S120, during thermal bonding, the side of the growth substrate 10 with the LED chip 20 can be bonded to the side of the substrate 300 with the pyrolytic adhesive 32 using a bonding device. Under heat and pressure, the LED chip 20 is embedded in the pyrolytic adhesive 32. The thermal bonding temperature should be greater than or equal to the melting temperature of the pyrolytic adhesive 32, so that the pyrolytic adhesive 32 can be melted by heat, achieving the connection between the growth substrate 10 and the photolytic adhesive 31. Of course, the thermal bonding temperature should be lower than the melting temperature of the photolytic adhesive 31 to prevent the photolytic adhesive 31 from melting and deforming during thermal bonding.

[0044] In order to embed the LED chip 20 into the pyrolytic adhesive 32, the thickness of the pyrolytic adhesive 32 should be greater than or equal to the height of the LED chip 20. In some embodiments, the surface of the pyrolytic adhesive 32 facing away from the photolytic adhesive 31 can be flush with the surface of the LED chip 20 facing away from the photolytic adhesive 31.

[0045] Generally, multiple LED chips 20 are arranged in an array on the growth substrate 10, with a gap between any two adjacent LED chips 20. Each LED chip 20 generally has two electrodes 21, typically a positive electrode and a negative electrode, for subsequent connection to positive and negative pads on the display backplane. The growth substrate 10 is typically gallium-containing sapphire. The removal of the growth substrate 10 can be performed using laser lift-off (LLO) technology. Optionally, after removal, residual gallium metal on the LED chips 20 is cleaned with diluted hydrochloric acid.

[0046] S130: Remove the pyrolytic adhesive 32 between two adjacent LED chips 20 to obtain the following... Figure 12 The structure shown is then etched onto the remaining pyrolytic adhesive 32 and photolytic adhesive 31 to form a stacked adhesive layer structure between the substrate 300 and each LED chip 20, resulting in the structure shown. Figure 13 The micro-component structure shown is as follows. The stacked adhesive layer structure includes a photodegradable adhesive layer 31' and a thermally degradable adhesive layer 32', with the photodegradable adhesive layer 31' being spaced apart from each other on the first surface of the substrate 300; the thermally degradable adhesive layer 32' is located between the two lead electrodes 21 of the LED chip 20, and the thickness of the thermally degradable adhesive layer 32' is greater than the height of the lead electrodes 21.

[0047] In step S130, the method for removing the pyrolytic adhesive 32 between two adjacent LED chips 20 can include wet etching or dry etching. Specifically, the wet etching can use acetone, N-methylpyrrolidone (NMP), or a combination of acetone and NMP as the etching solution. The etching solution can be coated onto... Figure 11 With the pyrolytic adhesive 32 facing away from the photolytic adhesive 31, the inverted LED chip 20 can act as a mask for wet etching. This eliminates the need for an additional mask, enabling selective etching of the pyrolytic adhesive 32 between adjacent LED chips 20. Specifically, etching is performed perpendicular to the surface of the pyrolytic adhesive 32 facing away from the photolytic adhesive 31 (referred to as perpendicular etching), or along the thickness direction of the pyrolytic adhesive 32. Optionally, after wet etching, rinsing with ethanol or water is recommended. Figure 12 The structure shown is designed to prevent residual etching solution from affecting the next etching step.

[0048] The dry etching process uses an etching gas to vertically etch the pyrolytic adhesive 32 located between two adjacent LED chips 20. The inverted LED chip 20 can still serve as a mask for dry etching, eliminating the need for an additional mask. The etching gas can be directed towards the... Figure 11 The pyrolytic adhesive 32 faces away from the surface of the photolytic adhesive 31 and is introduced into the gas. The etching gas can be oxygen (O2).

[0049] In step S130, the etching of the remaining pyrolytic adhesive 32 and photolytic adhesive 31 is dry etching. Dry etching offers higher controllability than wet etching, makes it easier to form finer microstructures, is less likely to damage the LED chip, and results in a highly uniform size of the resulting stacked adhesive layer structure. In some embodiments, this dry etching includes first etching with oxygen for 10-20 minutes, followed by etching with a fluorine-containing gas for 5-8 minutes. The fluorine-containing gas can be at least one of CF4 and SF6, for example, CF4, SF6, or a mixture of CF4 and SF6. Because the etching rate of fluorine-containing gas is generally higher than that of oxygen, the etching time using fluorine-containing gas is shorter than that using oxygen, ensuring a product with a higher degree of matching to the desired microstructure. Optionally, the flow rate ratio of oxygen to fluorine-containing gas can be (5-40):1, for example, 10:1, 15:1, 20:1, 25:1, 30:1, or 40:1. Understandably, during the etching process in step S130, the temperature of the chamber where the substrate is located is lower than the melting temperature of the pyrolytic adhesive 32, so that the pyrolytic adhesive 32 and the photolytic adhesive 31 do not melt during the etching process, and the desired microstructure is obtained after etching.

[0050] Figure 13 The illustrated micro-component structure includes a substrate 300, multiple stacked adhesive layer structures, and multiple LED chips 20. The multiple stacked adhesive layer structures are spaced apart on a first surface 300a of the substrate 300. The LED chips 20 are located on the stacked adhesive layer structures, with each LED chip 20 corresponding to one of the stacked adhesive layer structures. Each LED chip 20 has two lead-out electrodes 21 on its surface facing the stacked adhesive layer structure. Each stacked adhesive layer structure includes a photodegradable adhesive layer 31' and a thermally degradable adhesive layer 32', stacked together. The photodegradable adhesive layer 31' is in contact with the first surface 300a. The thermally degradable adhesive layer 32' is located between the two lead-out electrodes 21 of the LED chip 20, and its thickness is greater than the height of the lead-out electrodes 21. Here, "one-to-one correspondence" means that each stacked adhesive layer structure is connected to one LED chip 20, and the number of stacked adhesive layer structures is the same as the number of LED chips 20.

[0051] Depend on Figure 13 It is known that the photoresist layer 31' is not continuously distributed on the first surface 300a, but rather spaced out, and its number is consistent with the number of LED chips 20. Compared with a substrate whose entire surface is covered with a photoresist layer, the total coverage of the photoresist layer 31' on the substrate 300 in this application is low. Figure 13 When the LED chip on the micro-component structure shown is transferred to the transfer substrate (see...) Figure 14The laser energy required to dissociate the photodegradable adhesive layer 31' in the stacked adhesive layer structure connected to the LED chip 20 is relatively low, resulting in less damage to the LED chip 20. In addition, since a thermally degradable adhesive layer 32' is also provided between the LED chip 20 and the photodegradable adhesive layer 31', and its thickness is greater than the height of the chip lead electrodes 21, when the photodegradable adhesive layer 31' is dissociated by laser, the thermally degradable adhesive layer 32' can block the laser from irradiating the LED chip 20, further reducing the damage of the laser to the LED chip 20, thereby significantly improving the chip transfer yield.

[0052] In this embodiment, the thickness of the thermally desorbable adhesive layer 32' is greater than the thickness of the photodesorbable adhesive layer 31'. This allows the photodesorbable adhesive layer 31' to be subsequently desorbed using a low-energy laser, and during the desorption process, the thermally desorbable adhesive layer 32' blocks the laser from irradiating the LED chip 20. In some embodiments, the thickness of the photodesorbable adhesive layer 31' is in the range of 2μm-3μm, for example, 2.2μm, 2.5μm, or 2.8μm. In this case, the photodesorbable adhesive layer 31' provides good support for the thermally desorbable adhesive layer 32' and the LED chip 20, and facilitates subsequent desorption. In some embodiments, the thickness of the thermally desorbable adhesive layer 32' is in the range of 4μm-6μm, for example, 4.5μm, 5μm, or 5.5μm.

[0053] It is understood that, since the pyrolytic adhesive layer 32' is located between the two lead electrodes 21 of the LED chip 20, the width d2 of the pyrolytic adhesive layer 32' should be less than or equal to the spacing between the two lead electrodes 21 of the LED chip 20. In some embodiments, the width d2 of the pyrolytic adhesive layer 32' can be in the range of 2μm-6μm, for example, 2.5μm, 3μm, 4μm, or 5μm. In some embodiments of this application, the width d1 of the photolytic adhesive layer 31' is greater than or equal to the width d2 of the pyrolytic adhesive layer 32'. Figure 13 The diagram shows d1 > d2. In other words, the projection of the photoresist layer 31' onto the substrate 300 covers the projection of the thermal resist layer 32' onto the substrate 300. This helps the photoresist layer 31' to better support the thermal resist layer 32' and the LED chip 20, and such a photoresist layer 31' is easier to achieve through the above-mentioned etching process. The width d1 of the photoresist layer 31' can be in the range of 4μm-9μm. Furthermore, the width d1 of the photoresist layer 31' can also be less than or equal to the spacing between the two lead electrodes 21 of the LED chip 20. This reduces laser irradiation onto the chip electrodes during laser separation of the photoresist layer 31'. Optionally, the spacing between two adjacent photoresist layers 31' is 30-40μm. In this case, the total coverage of the photoresist layer 31' on the substrate 300 is low, facilitating subsequent laser separation.

[0054] Of course, in some other embodiments of this application, the width d1 of the photodegradable layer 31' may be smaller than the width d2 of the thermal degradable layer 32'. In this case, when the photodegradable layer 31' is subsequently subjected to laser degradation, the thermal degradable layer 32' with a larger width thereon can effectively block the laser from irradiating onto the LED chip 20, thereby greatly reducing the damage to the LED chip 20 caused by the laser.

[0055] The fabrication method for the aforementioned micro-component structure provided in this application is simple, convenient, and highly controllable. The stacked adhesive layer structure formed on the resulting micro-component structure effectively solves the problem of laser damage to the LED chip during the transfer process. Furthermore, the high uniformity of the multiple stacked adhesive layer structures formed by the two-step etching in step S130 means that the dimensional differences of the stacked adhesive layer structures connected to each chip are small. This facilitates the subsequent batch debonding of the photodebonding adhesive layer 31' in multiple stacked adhesive layer structures using the same laser energy, and the debonding time is similar, avoiding the problem of some chips being easily damaged due to inconsistent debonding times.

[0056] This application also provides a method for transferring LED chips (also known as a mass transfer method), including the following steps S140 and S150.

[0057] S140: Provide the micro-component structure as described above in this application (e.g., Figure 13 (as shown) and a transfer substrate 40 are provided, see also Figure 14 The transfer substrate 40 is attached to the side of the microstructure in which the LED chip 20 is located, and the photopolymer layer 31' is irradiated with a laser to transfer the LED chip 20 and the thermally polymerizable adhesive layer 32' to the transfer substrate 40 (e.g., ...). Figure 15 (As shown).

[0058] The transfer of LED chips 20 in step S140 can be performed by transferring all LED chips 20 from the micro-component structure to the transfer substrate 40, or by selectively transferring a portion of the LED chips 20 to the transfer substrate 40 (also known as selective chip pickup). During the transfer of LED chips 20, the laser is focused onto the photodegradable adhesive layer 31' in the stacked adhesive layer structure connected to the LED chips to be picked up (which can be all chips or a portion of the chips) on the micro-component structure. The photodegradable adhesive layer 31' is irradiated with the laser to reduce its adhesion and desorb, thus separating the LED chips 20 from the substrate 300, thereby transferring the LED chips 20 to the transfer substrate 40. Since the adhesion of the thermally degradable adhesive layer 32' hardly changes during the degradation of the photodegradable adhesive layer 31', the thermally degradable adhesive layer 32' connected to the LED chips 20 is also transferred to the transfer substrate 50 accordingly.

[0059] It is understood that when selectively picking up LED chips 20 on the micro-element structure, to ensure that LED chips 20 that do not need to be picked up are not carried away by the transfer substrate 40, the transfer substrate 40 should have a certain adhesive force with the LED chips 20, and this adhesive force should be less than the adhesive force between the substrate 300 of the micro-element structure and the photopolymer layer 31'. In some embodiments of this application, the transfer substrate 40 that is bonded to the micro-element structure may have an adhesive layer, which can be used to selectively bond the LED chips 20 to the transfer substrate 40. In other embodiments of this application, the material of the transfer substrate 40 may be one or more of polydimethylsiloxane (PDMS), polyurethane (PUA), ethylene-vinyl acetate copolymer (EVA), polymethyl methacrylate (PMMA), etc. In this case, the transfer substrate 40 has a certain degree of adhesion, so it is not necessary to provide an adhesive layer on the transfer substrate 40, and it meets the above-mentioned adhesive force characteristics. Generally, PDMS is the most common material for the transfer substrate 40.

[0060] S150: Transfer the LED chip 20 on the transfer substrate 40 to the display backplate 50.

[0061] In some implementations, step S150 specifically includes:

[0062] S151: As Figure 16 As shown, the side of the transfer substrate 40 with the LED chip 20 is placed opposite the side of the display backplate 50 with multiple pad groups 51. Through thermal bonding, the lead-out electrodes 21 of the LED chip 20 are electrically connected to the corresponding pad groups 51. After cooling, the space between the lead-out electrodes 21 and the pad groups 51 is filled with a thermally dissolving adhesive layer 32'. Figure 17 As shown;

[0063] S152: Peel off the transfer substrate 40 to obtain the following... Figure 18 The product shown.

[0064] In step S151, when the transfer substrate 40 and the display backplate 50 are placed facing each other, the transfer substrate 40 can be suspended above the display backplate 50, so that the multiple LED chips 20 correspond one-to-one with the multiple pad groups 51 on the display backplate 50. The display backplate 50 can be a thin-film transistor (TFT) circuit board. The display backplate 50 has two opposing surfaces, one of which has multiple pad groups 51. Since these pad groups 51 are used for subsequent electrical connections with the two lead electrodes 21 (i.e., the positive lead electrode and the negative lead electrode) of the LED chip 20, each pad group 51 includes two pads, which can be called a positive pad and a negative pad. In the aforementioned facing placement, each LED chip 20's positive lead electrode corresponds to one positive pad, and its negative lead electrode corresponds to one negative pad.

[0065] During thermal bonding in S151, it can be performed by applying pressure and heating to the transfer substrate 40 and the display backplate 50. When thermal bonding is completed, the lead electrode 21 of the LED chip 20 and the pad group 51 of the display backplate 50 are fixedly connected, and the electrical connection stability between the two is guaranteed. This can also be described as the LED chip 20 completing a large-scale welding process.

[0066] In some embodiments, pressure can be applied to the surface of the transfer substrate 40 opposite to the LED chip 20 (e.g., pressure can be applied to the surface of the transfer substrate 40 away from the LED chip 20). Figure 17 As shown, the transfer substrate 40 is bonded to the display backplate 50, and the display backplate 50 is heated or the bonded structure is placed in a heated environment. Since the transfer substrate 40 can be made of a soft material such as PDMS, it has a certain deformability, preventing damage to the LED chip 20 when pressure is applied. Furthermore, since the thickness of the pyrolytic adhesive layer 32' is greater than the height of the chip electrode, the pyrolytic adhesive layer 32' can also be inserted between a pair of pads on the display backplate 50, and it can melt upon heating, filling the space between the lead electrode 21 and the pad group 51 after cooling, further strengthening the bonding force between the LED chip 20 and the display backplate 50, without the need for additional adhesive material to be coated on the display backplate 50 to strengthen its bond with the chip, as in some existing technologies. Similarly, the thermal bonding temperature in step S151 should be greater than or equal to the melting temperature of the pyrolytic adhesive layer 32'.

[0067] Of course, in other embodiments of this application, pressure can be applied simultaneously to the surface of the transfer substrate 40 away from the LED chip 20 and the surface of the display backplate 50 where the pad group 51 is not provided, so that the two are bonded together, and the structure after the two are bonded together is placed in a heating environment.

[0068] In some embodiments of this application, the removal of the transfer substrate 40 in step S152 can be performed mechanically. This is mainly because the bonding force between the LED chip 20 and the display backplate 50 is stronger than the adhesive force between the transfer substrate 40 and the LED chip 20. This method of removing the transfer substrate 40 is simpler. Of course, if, as shown in step S140 above, the transfer substrate 40 has an adhesive layer, then the removal of the transfer substrate 40 can be achieved by de-adhesiveizing the adhesive layer between the transfer substrate 40 and the LED chip 20.

[0069] As described above, the LED chip transfer method provided in this application embodiment, by utilizing a micro-element structure with a special stacked adhesive layer structure, allows for the removal of the photodegradable adhesive layer 31' bonded to the chip using a low-energy laser when transferring the LED chip 20 from the micro-element structure to the transfer substrate 40. Furthermore, the thermally degradable adhesive layer 32' can block laser irradiation onto the LED chip 20, thereby significantly reducing damage to the chip during laser transfer and significantly improving the chip transfer yield. In addition, when the LED chip 20 on the transfer substrate 40 is transferred again to the display backplane 50, the thermally degradable adhesive layer 32' can effectively fill the gaps between the chip's lead electrodes and the pads on the display backplane after thermal melting and cooling, further improving the bonding force between the LED chip 20 and the display backplane 50. Therefore, the LED chip transfer method provided in this application embodiment is simple in process, convenient in operation, has a high LED chip transfer yield, and exhibits strong adhesion between the LED chip and the display backplane.

[0070] Based on the LED chip transfer method provided in any of the above embodiments, refer to Figure 18 This application also provides a display device, which specifically includes a display back panel 50 and a plurality of LED chips 20, wherein the LED chips 20 are transferred onto the display back panel 50 using the transfer method provided in any of the above embodiments. This display device can be an LED display panel, as well as devices such as televisions, computers, and industrial computers using the LED display panel.

[0071] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A micro-component structure, characterized in that, include: Substrate, the substrate having a first surface; A plurality of stacked adhesive layers spaced apart on the first surface; Multiple LED chips are correspondingly disposed on multiple stacked adhesive layer structures, and each LED chip has two lead-out electrodes on the surface facing the stacked adhesive layer structure; The stacked adhesive layer structure includes a photodegradable adhesive layer and a thermally degradable adhesive layer stacked together. The photodegradable adhesive layer is in contact with the first surface, and the thermally degradable adhesive layer is located between the two lead-out electrodes. The thickness of the thermally degradable adhesive layer is greater than the height of the lead-out electrodes.

2. The micro-component structure according to claim 1, characterized in that, The melting temperature of the pyrolytic adhesive layer is lower than that of the photolytic adhesive layer, and the difference between the melting temperatures of the pyrolytic adhesive layer and the photolytic adhesive layer is greater than 20°C.

3. The micro-component structure according to claim 1, characterized in that, The thickness of the pyrolytic adhesive layer is greater than the thickness of the photolytic adhesive layer.

4. The micro-component structure according to any one of claims 1 to 3, characterized in that, The width of the photolytic adhesive layer is greater than or equal to the width of the pyrolytic adhesive layer.

5. The micro-component structure according to claim 1, characterized in that, The width of the photolytic adhesive layer is in the range of 4μm-9μm; the width of the pyrolytic adhesive layer is in the range of 2μm-6μm.

6. A method for fabricating a micro-component structure, characterized in that, include: Photolytic adhesive and pyrolytic adhesive are sequentially stacked on the first surface of the substrate; A growth substrate on which multiple LED chips are grown is thermally bonded to the substrate, so that the LED chips are embedded in the pyrolytic adhesive material, and the two lead electrodes of the LED chips face the photolytic adhesive material. Peel off the growth substrate; Remove the pyrolytic adhesive between two adjacent LED chips, and etch the remaining pyrolytic adhesive and the photolytic adhesive to form a stacked adhesive layer structure between the substrate and each LED chip; The stacked adhesive layer structure includes a photolytic adhesive layer and a thermally lytic adhesive layer, and the photolytic adhesive layer is spaced apart on the first surface; The pyrolytic adhesive layer is located between the two lead-out electrodes of the LED chip, and the thickness of the pyrolytic adhesive layer is greater than the height of the lead-out electrodes.

7. The preparation method according to claim 6, characterized in that, The method for removing the pyrolytic adhesive between two adjacent LED chips includes: wet etching or dry etching; wherein, the wet etching uses at least one of acetone or N-methylpyrrolidone as the etching solution; and the dry etching uses an etching gas including oxygen.

8. The preparation method according to any one of claims 6 or 7, characterized in that, The etching of the remaining pyrolytic adhesive and the photolytic adhesive is a dry etching process, which includes first etching with oxygen for 10-20 minutes, and then etching with fluorine-containing gas for 5-8 minutes.

9. A method for transferring an LED chip, characterized in that, include: A micro-element structure according to any one of claims 1-5 is provided, wherein a transfer substrate is attached to the side of the micro-element structure on which the LED chip is disposed, and the photodegradable adhesive layer is irradiated with a laser to transfer the LED chip and the photodegradable adhesive layer to the transfer substrate; The LED chip on the transfer substrate is transferred to the display backplane.

10. The transfer method according to claim 9, characterized in that, The step of transferring the LED chip on the transfer substrate to the display backplane includes: The side of the transfer substrate with the LED chip is placed opposite the side of the display backplate with multiple pad groups. The lead electrode is electrically connected to the corresponding pad group through thermal bonding. After cooling, the space between the lead electrode and the pad group is filled with the pyrolytic adhesive layer. The transfer substrate is peeled off.

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