Mass transfer method of light emitting diode, light emitting device and display panel

Abstract

The invention provides a mass transfer method of a light-emitting diode, a light-emitting device and a display panel, and belongs to the technical field of photoelectron manufacturing. The mass transfer method comprises the steps that different pixel chips are transferred to a first adhesive layer of a first temporary substrate in a laser lift-off mode, and electrodes of the pixel chips are made to be away from the first adhesive layer; the pixel chip of the first temporary substrate is bonded to a second adhesive layer of a second temporary substrate, so that an electrode of the pixel chip is connected with the second adhesive layer, and the viscosity of the second adhesive layer is larger than that of the first adhesive layer; and the pixel chip of the second temporary substrate is bonded to a third adhesive layer of a circuit substrate, so that an electrode of the pixel chip is far away from the third adhesive layer, and the viscosity of the third adhesive layer is larger than that of the second adhesive layer. According to the invention, the number of laser irradiation times can be reduced, the influence of laser irradiation on the pixel chip is improved, and the mass transfer yield is improved.

Description

Technical Field

[0001] The present disclosure relates to the field of optoelectronic manufacturing technologies, and particularly to a method for mass transfer of light-emitting diodes, a light-emitting device, and a display panel. Background Art

[0002] In the new display field, Mini / Micro LEDs are recognized as the next-generation display technology, continuously expanding the application boundary of display screens. The light-emitting device of MIP (Micro LED in package) includes a plurality of pixel chips and a circuit substrate. The plurality of pixel chips are arranged at intervals on the circuit substrate and are bonded to the solder joints on the circuit substrate.

[0003] In related technologies, FCOC (Flip Chip On Carrier) is usually adopted for mass transfer of pixel chips. During the preparation of FCOC, first, a wafer on which a plurality of pixel chips are grown is bonded to a temporary substrate, and the pixel chips are peeled off from the substrate of the wafer using a laser, so that the electrodes of the pixel chips face the temporary substrate; then, the pixel chips on the temporary substrate are bonded to a carrier, so that the electrodes of the pixel chips are away from the carrier, so as to perform laser peeling on the FCOC subsequently to achieve mass transfer of the pixel chips.

[0004] However, during the preparation of FCOC, the pixel chips need to be transferred twice, and each peeling process of the pixel chips needs to be irradiated by a laser, and the laser irradiation will have a great impact on the electrical properties of the pixel chips, causing the pixel chips to leak electricity or generate defects, affecting the yield of mass transfer. Summary of the Invention

[0005] Embodiments of the present disclosure provide a method for mass transfer of light-emitting diodes, a light-emitting device, and a display panel, which can reduce the number of laser irradiations, improve the influence of laser irradiation on pixel chips, and improve the mass transfer yield. The technical solutions are as follows:

[0006] Embodiments of the present disclosure provide a method for mass transfer of light-emitting diodes. The mass transfer method includes: transferring different pixel chips to a first adhesive layer on a first temporary substrate by means of laser peeling, so that the electrodes of the pixel chips are away from the first adhesive layer; bonding the pixel chips on the first temporary substrate to a second adhesive layer on a second temporary substrate, so that the electrodes of the pixel chips are connected to the second adhesive layer, and the viscosity of the second adhesive layer is greater than that of the first adhesive layer; removing the first temporary substrate and the first adhesive layer, and bonding the pixel chips on the second temporary substrate to a third adhesive layer on a circuit substrate, so that the electrodes of the pixel chips are away from the third adhesive layer, and the viscosity of the third adhesive layer is greater than that of the second adhesive layer.

[0007] In another implementation manner of the embodiment of the present disclosure, the adhesiveness of the second adhesive layer is 2 to 3 times that of the first adhesive layer; the adhesiveness of the third adhesive layer is 6 to 10 times that of the first adhesive layer.

[0008] In another implementation manner of the embodiment of the present disclosure, the ratio of the adhesive to the curing agent in the first adhesive layer is 9:1 to 11:1, the ratio of the adhesive to the curing agent in the second adhesive layer is 13:1 to 15:1, and the third adhesive layer is a non-conductive adhesive layer.

[0009] In another implementation manner of the embodiment of the present disclosure, before transferring different pixel chips to the first adhesive layer of the first temporary substrate by means of laser lift-off, it further includes: bonding the wafer to the carrier plate so that the electrodes of the pixel chips of the wafer are connected to the photosensitive adhesive layer of the carrier plate; irradiating the wafer with laser so that the pixel chips are separated from the substrate of the wafer.

[0010] In another implementation manner of the embodiment of the present disclosure, transferring different pixel chips to the first adhesive layer of the first temporary substrate by means of laser lift-off includes: laser-decomposing the photosensitive adhesive layer on the carrier plate so that the pixel chips fall from the carrier plate onto the first adhesive layer of the first temporary substrate.

[0011] In another implementation manner of the embodiment of the present disclosure, laser-decomposing the photosensitive adhesive layer on the carrier plate includes: controlling the laser wavelength to be 248 nm, 266 nm or 355 nm, and irradiating the photosensitive adhesive layer with excimer laser or solid laser.

[0012] In another implementation manner of the embodiment of the present disclosure, after transferring different pixel chips to the first adhesive layer of the first temporary substrate by means of laser lift-off, it further includes: etching away the first adhesive layer between adjacent pixel chips; after bonding the pixel chips of the first temporary substrate to the second adhesive layer of the second temporary substrate, it further includes: etching away the second adhesive layer between adjacent pixel chips; after bonding the pixel chips of the second temporary substrate to the third adhesive layer of the circuit board, it further includes: etching away the third adhesive layer between adjacent pixel chips.

[0013] In another implementation manner of the embodiment of the present disclosure, after bonding the pixel chips of the second temporary substrate to the third adhesive layer of the circuit board, it further includes: forming a packaging adhesive on the surface of the circuit board to form a packaging adhesive layer that fills and wraps each pixel chip.

[0014] Embodiments of the present disclosure provide a light-emitting device, which includes: a circuit substrate, a plurality of pixel chips, and a packaging adhesive layer. The plurality of pixel chips are transferred onto the circuit substrate by the mass transfer method described above. The packaging adhesive layer is located on the surface of the circuit substrate and wraps each pixel chip.

[0015] Embodiments of the present disclosure provide a display panel, which includes a plurality of the light-emitting devices, a driving integrated circuit, and a circuit board as described above. The plurality of light-emitting devices and the driving integrated circuit are both located on the circuit board.

[0016] The beneficial effects brought by the technical solutions provided by the embodiments of the present disclosure at least include:

[0017] When transferring pixel chips by the mass transfer method provided by the embodiments of the present disclosure, first, different pixel chips are transferred onto the first adhesive layer of the first temporary substrate; then, the pixel chips on the first temporary substrate are bonded to the second adhesive layer of the second temporary substrate. Since the viscosity of the second adhesive layer is higher than that of the first adhesive layer, the pixel chips can be more easily peeled off from the first temporary substrate by using the second adhesive layer with higher viscosity and transferred onto the second temporary substrate; then, the pixel chips on the second temporary substrate are bonded to the third adhesive layer of the circuit substrate. Since the viscosity of the third adhesive layer is higher than that of the second adhesive layer, the pixel chips can be more easily peeled off from the second temporary substrate by using the third adhesive layer with higher viscosity and transferred onto the circuit substrate, achieving the purpose of transferring the pixel chips onto the circuit substrate.

[0018] Compared with the laser lift-off method in the related art, the embodiments of the present disclosure use the viscosity gradient to transfer pixel chips, without the need for additional laser lift-off. Reducing the number of laser irradiations can largely reduce the impact on the electrical properties of pixel chips, ultimately ensuring the yield of mass transfer. Moreover, by directly transferring pixel chips through the difference in adhesion force, without the need for a laser device for peeling, the transfer efficiency is higher. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present disclosure. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0020] Figure 1 is a flowchart of a mass transfer method for a light-emitting diode provided by an embodiment of the present disclosure;

[0021] Figure 2 is a flowchart of another mass transfer method for a light-emitting diode provided by an embodiment of the present disclosure;

[0022] Figure 3 is a transfer state diagram of a light-emitting device provided by an embodiment of the present disclosure;

[0023] Figure 4 is a transfer state diagram of a light-emitting device provided by an embodiment of the present disclosure;

[0024] Figure 5 is a transfer state diagram of a light-emitting device provided by an embodiment of the present disclosure;

[0025] Figure 6 is a transfer state diagram of a light-emitting device provided by an embodiment of the present disclosure;

[0026] Figure 7 is a top view of a light-emitting device provided by an embodiment of the present disclosure;

[0027] Figure 8 is a top view of a light-emitting device provided by an embodiment of the present disclosure.

[0028] The descriptions of the marks in the figure are as follows:

[0029] 11. First temporary substrate; 110. First adhesive layer;

[0030] 12. Second temporary substrate; 120. Second adhesive layer;

[0031] 13. Circuit substrate; 130. Third adhesive layer;

[0032] 14. Carrier plate; 140. Photosensitive adhesive layer;

[0033] A wafer;

[0034] 20. Pixel chip; 21. First pixel chip; 22. Second pixel chip; 23. Third pixel chip;

[0035] 31. First pad; 32. Second pad; 33. Third pad; 34. Fourth pad;

[0036] 41. First electrode; 42. Second electrode;

[0037] 50. Encapsulation adhesive layer. Detailed implementation manners

[0038] To make the objectives, technical solutions, and advantages of the present disclosure clearer, the following will further describe the embodiments of the present disclosure in detail with reference to the accompanying drawings.

[0039] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by a person of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," "third," and similar words used in the patent specification and claims of this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish between different components. Similarly, terms such as "a" or "an" do not indicate a quantitative limitation, but rather indicate the presence of at least one. Terms such as "include" or "comprise" mean that the elements or objects preceding "include" or "comprises" encompass the elements or objects listed after "include" or "comprises," and their equivalents, and do not exclude other elements or objects. Terms such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," "right," "top," and "bottom" are used only to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0040] In related technologies, mass transfer is used to transfer the Micro LED three-color pixel chip to a flexible substrate, which is then bonded with a highly viscous adhesive material to transfer the pixel chip in batches to the circuit substrate using the difference in viscosity, and then the unit packaging is performed.

[0041] There are two common methods for transferring pixel chips in large quantities onto substrates. The first is laser COW (Chip on Wafer) direct transfer, which uses laser irradiation to directly peel the pixel chip from the substrate. During the peeling process, the laser decomposes the epitaxial material, such as GaN, between the pixel chip and the substrate to achieve the purpose of transferring the three-color pixel chips separately through the air. This solution requires a lot of laser energy to decompose the GaN material, resulting in extremely unstable and inaccurate pixel chip placement, making it difficult to achieve mass production yield.

[0042] Secondly, FCOC is used for mass transfer of pixel chips. In the process of preparing FCOC, the wafer with multiple pixel chips is first bonded to a temporary substrate so that the pixel chips are peeled off from the substrate of the wafer and the electrodes of the pixel chips are facing the temporary substrate; then, the pixel chips on the temporary substrate are bonded to the carrier so that the electrodes of the pixel chips are away from the carrier, so that the FCOC can be laser peeled off later to achieve mass transfer of pixel chips. Although this solution does not require laser decomposition of the epitaxial material between the pixel chip and the substrate, it can allow the pixel chips to be stably arranged in corresponding positions on the substrate. However, in the process of preparing FCOC, the pixel chips need to be transferred twice, and each peeling process of the pixel chips requires laser irradiation, which will have a greater impact on the electrical properties of the pixel chips, causing the pixel chips to leak or produce defects, affecting the yield of mass transfer.

[0043] To this end, the embodiments of the present disclosure provide a method for mass transfer of light-emitting diodes. Figure 1 It is a flowchart of a method for mass transfer of light-emitting diodes provided by the embodiments of the present disclosure. As Figure 1 shown, the mass transfer method includes:

[0044] Step 101: Transfer different pixel chips 20 to the first adhesive layer 110 of the first temporary substrate 11 by means of laser lift-off, so that the electrodes of the pixel chips 20 are away from the first adhesive layer 110.

[0045] Step 102: Bond the pixel chips 20 of the first temporary substrate 11 to the second adhesive layer 120 of the second temporary substrate 12, so that the electrodes of the pixel chips 20 are connected to the second adhesive layer 120.

[0046] Among them, the viscosity of the second adhesive layer 120 is greater than that of the first adhesive layer 110.

[0047] Step 103: Remove the first temporary substrate 11 and the first adhesive layer 110, and bond the pixel chips 20 of the second temporary substrate 12 to the third adhesive layer 130 of the circuit board 13, so that the electrodes of the pixel chips 20 are away from the third adhesive layer 130.

[0048] Among them, the viscosity of the third adhesive layer 130 is greater than that of the second adhesive layer 120.

[0049] When the mass transfer method provided by the embodiments of the present disclosure transfers the pixel chips 20, first, transfer different pixel chips 20 to the first adhesive layer 110 of the first temporary substrate 11; then bond the pixel chips 20 of the first temporary substrate 11 to the second adhesive layer 120 of the second temporary substrate 12. Since the viscosity of the second adhesive layer 120 is higher than that of the first adhesive layer 110, the pixel chips 20 can be more easily peeled off from the first temporary substrate 11 by using the second adhesive layer 120 with higher viscosity and transferred to the second temporary substrate 12; then, bond the pixel chips 20 of the second temporary substrate 12 to the third adhesive layer 130 of the circuit board 13. Since the viscosity of the third adhesive layer 130 is higher than that of the second adhesive layer 120, the pixel chips 20 can be more easily peeled off from the second temporary substrate 12 by using the third adhesive layer 130 with higher viscosity and transferred to the circuit board 13, achieving the purpose of transferring the pixel chips 20 to the circuit board 13.

[0050] Compared with the laser lift-off method in the related art, the embodiments of the present disclosure use the viscosity gradient to transfer the pixel chips, eliminating the need for additional laser lift-off. Reducing the number of laser irradiations can significantly reduce the impact on the electrical properties of the pixel chips, ultimately ensuring the yield of mass transfer. Moreover, by directly transferring the pixel chips through the adhesive force difference without using a laser device for lift-off, the transfer efficiency is higher.

[0051] Figure 2 It is a flowchart of another method for mass transfer of light-emitting diodes provided by the embodiments of the present disclosure.

[0052] As Figure 2 shown, the mass transfer method includes:

[0053] Step 201: Bond the wafer 15 to the carrier 14 so that the electrodes of the pixel chips 20 on the wafer 15 are connected to the photosensitive adhesive layer 140 of the carrier 14.

[0054] Step 202: Irradiate the wafer 15 with a laser to separate the pixel chips 20 from the substrate of the wafer 15.

[0055] Figure 3 It is a transfer state diagram of a light-emitting device provided by the embodiments of the present disclosure. As Figure 3 shown, first bond the wafer 15 to the photosensitive adhesive layer 140 of the carrier 14 so that the photosensitive adhesive layer 140 is connected to the electrodes of the pixel chips 20 on the wafer 15; then, irradiate the wafer 15 with a laser to decompose the epitaxial material between the pixel chips 20 and the substrate, so as to peel the substrate from the pixel chips 20.

[0056] Compared with the related art, when peeling the pixel chips 20 and the substrate, since the pixel chips 20 are first fixed on the carrier 14 through the photosensitive adhesive layer 140, even if the laser decomposition of the epitaxial material is unstable, there will be no problem of inaccurate landing of the pixel chips 20 on the carrier 14, thus effectively improving the yield of mass transfer.

[0057] Exemplarily, the carrier 14 can be a sapphire substrate or a glass substrate.

[0058] In the embodiments of the present disclosure, steps 201 to 202 can prepare three carriers 14, and different colored pixel chips 20 are arranged on the three carriers 14 respectively.

[0059] Optionally, the different colored pixel chips 20 include a first pixel chip 21, a second pixel chip 22, and a third pixel chip 23, and the emission colors of the first pixel chip 21, the second pixel chip 22, and the third pixel chip 23 are all different.

[0060] In the embodiments of the present disclosure, the first pixel chip 21 may be a pixel chip that emits red light, the second pixel chip 22 may be a pixel chip that emits green light, and the third pixel chip 23 may be a pixel chip that emits blue light.

[0061] In the embodiments of the present disclosure, each pixel chip includes an epitaxial layer, a passivation layer, and an electrode. The epitaxial layer is located on the surface of the substrate. The epitaxial layer includes a p-type layer, a light-emitting layer, and an n-type layer that are stacked in sequence. The n-type layer has a groove exposing the p-type layer. The passivation layer is located on the surface and in the groove of the n-type layer, and the passivation layer has a through hole exposing the n-type layer and the groove.

[0062] Wherein, a first electrode 41 and a second electrode 42 are provided on the surface of the passivation layer. The first electrode 41 and the second electrode 42 are respectively connected to the n-type layer and the p-type layer through two through holes.

[0063] In the embodiments of the present disclosure, the plurality of pixel chips include a first pixel chip 21 that emits red light, a second pixel chip 22 that emits green light, and a third pixel chip 23 that emits blue light.

[0064] The difference between the first pixel chip 21, the second pixel chip 22, and the third pixel chip 23 lies in the different light-emitting colors of the epitaxial layers.

[0065] For the first pixel chip 21, the epitaxial layer is a red-light epitaxial layer. For the second pixel chip 22, the epitaxial layer is a green-light epitaxial layer. For the third pixel chip 23, the epitaxial layer is a blue-light epitaxial layer.

[0066] Wherein, the red-light epitaxial layer includes a first p-type layer, a first light-emitting layer, and a first n-type layer that are stacked in sequence.

[0067] In the red-light epitaxial layer, the first p-type layer includes a p-type AlInP layer.

[0068] Wherein, the first light-emitting layer includes alternately grown AlGaInP quantum well layers and AlGaInP quantum barrier layers. Among them, the Al content in the AlGaInP quantum well layers and the AlGaInP quantum barrier layers is different. The first light-emitting layer may include alternately stacked 3 to 8 periods of AlGaInP quantum well layers and AlGaInP quantum barrier layers.

[0069] Wherein, the first n-type layer includes an n-type AlGaInP current spreading layer.

[0070] In the embodiments of the present disclosure, the green-light epitaxial layer includes a second p-type layer, a second light-emitting layer, and a second n-type layer that are stacked in sequence.

[0071] In the green-light epitaxial layer, the second p-type layer includes a p-type GaN layer.

[0072] Among them, the second light-emitting layer includes alternately grown InGaN quantum well layers and GaN quantum barrier layers. The second light-emitting layer may include 3 to 8 periods of alternately stacked InGaN quantum well layers and GaN quantum barrier layers.

[0073] Among them, the second n-type layer includes an n-type GaN layer.

[0074] In the embodiment of the present disclosure, the blue light epitaxial layer includes a third p-type layer, a third light-emitting layer, and a third n-type layer stacked in sequence.

[0075] In the blue light epitaxial layer, the third p-type layer includes a p-type GaN layer.

[0076] Among them, the third light-emitting layer may include alternately grown InGaN quantum well layers and GaN quantum barrier layers. The third light-emitting layer may include 3 to 8 periods of alternately stacked InGaN quantum well layers and GaN quantum barrier layers.

[0077] Among them, the third n-type layer includes an n-type GaN layer.

[0078] Optionally, the thickness of the pixel chip is 2 μm to 10 μm.

[0079] Exemplarily, the thickness of the red light epitaxial layer is 5 μm, the thickness of the green light epitaxial layer is 8 μm, and the thickness of the blue light epitaxial layer is 6 μm.

[0080] Step 203: Transfer different pixel chips to the first adhesive layer 110 of the first temporary substrate 11 by means of laser lift-off, so that the electrodes of the pixel chips are away from the first adhesive layer 110.

[0081] In the embodiment of the present disclosure, three different color pixel chips can be transferred to the first temporary substrate 11 by means of laser lift-off. That is, the carrier plates 14 of the three pixel chips with different colors are irradiated with laser, so that the pixel chips of different colors can fall onto the corresponding positions of the first temporary substrate 11.

[0082] Specifically, it may include, as Figure 4 shown, the laser decomposes the photosensitive adhesive layer 140 on the carrier plate 14, so that the pixel chips fall from the carrier plate 14 onto the first adhesive layer 110 of the first temporary substrate 11. Figure 4 It is schematically shown that the laser decomposes the photosensitive adhesive layer 140, so that the first pixel chip 21 emitting red light can fall onto the corresponding position of the first temporary substrate 11.

[0083] In the above implementation manner, the laser separation of the photosensitive adhesive layer 140 is easier than the epitaxial material, so it is not necessary to use a large laser energy, which can make the landing point of the pixel chip more stable and accurate, and improve the yield of mass transfer.

[0084] Exemplarily, the photosensitive adhesive layer 140 can be an epoxy acrylate layer, a polyurethane acrylate layer, or a polyester acrylate layer.

[0085] Optionally, when laser decomposes the photosensitive adhesive layer 140, the laser wavelength is controlled to be 248 nm, 266 nm, or 355 nm, and the photosensitive adhesive layer 140 is irradiated with an excimer laser or a solid laser.

[0086] Among them, the excimer laser is a gas pulsed laser that generates short-wavelength laser in the ultraviolet band by exciting a mixed gas of inert gas and halogen gas, and has the characteristics of a cold light source and high-precision cutting ability.

[0087] Exemplarily, the wavelength of the excimer laser can be 248 nm. It is used for chip manufacturing in a lithography machine, and realizes nano-scale circuit patterns through high-precision exposure.

[0088] Among them, the solid laser uses a crystal, glass, or ceramic as the gain medium, and generates laser through the excitation of a pump source, and has the characteristics of high power, high stability, and wavelength tunability.

[0089] Exemplarily, the wavelength of the solid laser can be 266 nm or 355 nm.

[0090] Among them, when the wavelength of the solid laser is 266 nm, it is used for LED sapphire substrate peeling, decomposes the GaN layer through high absorption rate, and improves the luminous efficiency. When the wavelength of the solid laser is 266 nm, it is used for separating the polyimide layer in flexible OLED manufacturing, replacing the traditional excimer laser to reduce the maintenance cost.

[0091] After step 203, the mass transfer method may further include: etching and removing the first adhesive layer 110 between adjacent pixel chips.

[0092] Exemplarily, the residual adhesive in the channel between pixel chips can be removed by ICP etching, and at the same time, the adhesion between the pixel chips and the first temporary substrate 11 can be weakened, which is convenient for the next transfer.

[0093] Step 204: Bond the pixel chips on the first temporary substrate 11 to the second adhesive layer 120 on the second temporary substrate 12, so that the electrodes of the pixel chips are connected to the second adhesive layer 120.

[0094] As Figure 5 shown, the second adhesive layer 120 is first formed on the surface of the second temporary substrate 12. The second temporary substrate 12 presses on the pixel chips on the surface of the first temporary substrate 11 from above, so that the second adhesive layer 120 is connected to the electrodes of the pixel chips, and the first temporary substrate is removed.

[0095] Among them, the adhesiveness of the second adhesive layer 120 is greater than that of the first adhesive layer 110. By utilizing the stronger adhesiveness of the second adhesive layer 120, the pixel chip can be more easily adhered from the first temporary substrate 11, thereby avoiding the use of laser decomposition to peel the pixel chip from the adhesive layer and reducing the number of times the pixel chip is irradiated by the laser.

[0096] Exemplarily, the adhesiveness of the second adhesive layer 120 is 2 to 3 times that of the first adhesive layer 110. For example, the ratio of the adhesive to the curing agent in the first adhesive layer 110 is 9:1 to 11:1, and the ratio of the adhesive to the curing agent in the second adhesive layer 120 is 13:1 to 15:1. By controlling the ratio of the adhesive to the curing agent within the above range, the adhesiveness of the second adhesive layer 120 can be 2 to 3 times that of the first adhesive layer 110.

[0097] Exemplarily, the first adhesive layer 110 can be Dow Corning Sylgard 184 adhesive with a ratio of adhesive to curing agent of 10:1.

[0098] Exemplarily, the second adhesive layer 120 can be Dow Corning Sylgard 184 adhesive with a ratio of adhesive to curing agent of 14:1, or Dow Corning 109 adhesive.

[0099] After step 204, the mass transfer method may further include: etching and removing the second adhesive layer 120 between adjacent pixel chips.

[0100] Exemplarily, the ICP etching method can be used to remove the residual adhesive on the channels and electrode surfaces between the pixel chips. In addition to cleaning the substrate, this process can also weaken the adhesiveness between the pixel chips and the second temporary substrate 12, facilitating the next transfer.

[0101] Step 205: Bond the pixel chips on the second temporary substrate 12 to the third adhesive layer 130 on the circuit substrate 13, with the electrodes of the pixel chips away from the third adhesive layer 130.

[0102] As Figure 6 shown, a third adhesive layer 130 is first formed on the surface of the circuit substrate 13. The circuit substrate 13 covers the pixel chips on the surface of the second temporary substrate 12 from below, such that the third adhesive layer 130 is connected to the pixel chips, and the second temporary substrate is removed.

[0103] Among them, the adhesiveness of the third adhesive layer 130 is greater than that of the second adhesive layer 120. By utilizing the stronger adhesiveness of the third adhesive layer 130, the pixel chips can be more easily adhered from the second temporary substrate 12, thereby avoiding the use of laser decomposition to peel the pixel chips from the adhesive layer and reducing the number of times the pixel chips are irradiated by the laser.

[0104] Among them, before bonding, the third adhesive layer 130 is pre-semi-cured to control the viscosity of the third adhesive layer 130 to avoid excessive viscosity.

[0105] Exemplarily, the viscosity of the third adhesive layer 130 is 6 to 10 times that of the first adhesive layer 110. For example, the third adhesive layer 130 is a non-conductive adhesive layer. The viscosity of the non-conductive adhesive layer is 6 to 10 times that of Dow Corning Sylgard 184 adhesive with a viscosity of 10:1.

[0106] After step 205, the mass transfer method may further include: etching to remove the third adhesive layer 130 between adjacent pixel chips.

[0107] Exemplarily, the ICP etching method can be used to remove the residual adhesive on the surface of the channels and electrodes between the pixel chips, which can not only clean the substrate but also facilitate the subsequent formation of the encapsulation adhesive on the circuit board 13.

[0108] Step 206: Form an encapsulation adhesive on the surface of the circuit board 13 to form an encapsulation adhesive layer 50 that fills and wraps each pixel chip.

[0109] Specifically, it may include: coating the encapsulation adhesive on the surface of the circuit board 13, and after the encapsulation adhesive fills the gaps between the pixel chips, curing the encapsulation adhesive to obtain the encapsulation adhesive layer 50.

[0110] Optionally, the light absorption rate of the encapsulation adhesive layer 50 is greater than or equal to 0.8. Wrapping the pixel chips with the encapsulation adhesive layer 50 with a light absorption rate greater than or equal to 0.8 can block the lateral light emission of the pixel chips and improve the front light emission effect of the light-emitting device.

[0111] Exemplarily, the encapsulation adhesive layer 50 may be black. Black is more likely to absorb light to avoid more light emitting laterally from the pixel chips. Moreover, during the injection of the encapsulation adhesive, the black encapsulation adhesive is easier to observe, which is beneficial for technicians to accurately judge whether the encapsulation adhesive completely wraps each pixel chip.

[0112] Optionally, curing the encapsulation adhesive to obtain the encapsulation adhesive layer 50 may also include two implementation methods.

[0113] The first curing method is heat curing. Specifically, it may include: controlling the temperature to rise above 50°C to heat-cure the encapsulation adhesive; controlling the temperature to rise above 150°C and baking the encapsulation adhesive for 1 to 2 hours to obtain the encapsulation adhesive layer 50.

[0114] Among them, first controlling the temperature to rise above 50°C can accelerate the curing speed and achieve rapid curing of the encapsulation adhesive; then controlling the temperature to rise above 150°C and baking the encapsulation adhesive can make the encapsulation adhesive completely cured.

[0115] The second curing method is ultraviolet light curing, which may specifically include: irradiating the encapsulating adhesive with ultraviolet light for 1 minute to 10 minutes to obtain the encapsulating adhesive layer 50 .

[0116] The curing speed of the encapsulation adhesive by ultraviolet light irradiation is faster, which can improve the preparation efficiency of the encapsulation adhesive layer 50.

[0117] After step 206 , ISO etching may be performed to etch out the external dimensions of the light-emitting device, and multiple light-emitting devices may be obtained by laser scribing.

[0118] The embodiment of the present disclosure provides a light emitting device, which includes: a circuit substrate 13, a plurality of pixel chips and an encapsulation layer 50. The plurality of pixel chips are transferred onto the circuit substrate 13 using the mass transfer method of light emitting diodes as described above. Figure 7 This is a top view of a light-emitting device provided by an embodiment of the present disclosure. Figure 7 The diagram shows the state before the encapsulation adhesive layer 50 is formed on the circuit substrate 13 . Figure 8 This is a top view of a light-emitting device provided by an embodiment of the present disclosure. Figure 8 The diagram shows a state after a packaging adhesive layer 50 is formed on the circuit substrate 13 .

[0119] like Figure 7 、 8 As shown, the light-emitting device includes: a circuit substrate 13, a plurality of pixel chips and an encapsulation layer 50; the plurality of pixel chips are located on the surface of the circuit substrate 13, the encapsulation layer 50 is located on the surface of the circuit substrate 13, and wraps each pixel chip, and the surface of the encapsulation layer 50 away from the circuit substrate 13 is flush with the surface of the pixel chip away from the circuit substrate 13.

[0120] Alternatively, as Figure 7 、 8 As shown, the plurality of pixel chips include: a first pixel chip 21 , a second pixel chip 22 and a third pixel chip 23 , and the first pixel chip 21 , the second pixel chip 22 and the third pixel chip 23 all emit light of different colors.

[0121] Alternatively, as Figure 7 As shown, the light emitting device further includes a first pad 31, a second pad 32, a third pad 33 and a fourth pad 34. The first pad 31, the second pad 32, the third pad 33 and the fourth pad 34 are all located on the surface of the circuit substrate 13 and connected to the solder joints of the circuit substrate 13.

[0122] like Figure 7 As shown, the first electrode 41 of the first pixel chip 21 , the first electrode 41 of the second pixel chip 22 , and the first electrode 41 of the third pixel chip 23 are all connected to the first pad 31 .

[0123] In this way, the first pad 31 is connected to the first electrode 41 of each pixel chip, and the first pad 31 is used as a common pad, thereby avoiding setting a larger number of pads on the flat layer to reduce the size of the light-emitting device.

[0124] As Figure 7 shown, the second electrode 42 of the first pixel chip 21 is connected to the second pad 32, the second electrode 42 of the second pixel chip 22 is connected to the third pad 33, and the second electrode 42 of the third pad 33 is connected to the fourth pad 34.

[0125] In the embodiments of the present disclosure, a pad is provided separately for each pixel chip, and whether the pixel chip emits light can be controlled by controlling the energization of the pad corresponding to the pixel chip.

[0126] In the embodiments of the present disclosure, the plurality of pixel chips include a first pixel chip 21 that emits red light, a second pixel chip 22 that emits green light, and a third pixel chip 23 that emits blue light.

[0127] The difference between the first pixel chip 21, the second pixel chip 22, and the third pixel chip 23 lies in the different light-emitting colors of the epitaxial layers.

[0128] For the first pixel chip 21, the epitaxial layer is a red-light epitaxial layer. For the second pixel chip 22, the epitaxial layer is a green-light epitaxial layer. For the third pixel chip 23, the epitaxial layer is a blue-light epitaxial layer.

[0129] Among them, the red-light epitaxial layer includes a first p-type layer, a first light-emitting layer, and a first n-type layer stacked in sequence.

[0130] In the red-light epitaxial layer, the first p-type layer includes a p-type AlInP layer.

[0131] Among them, the first light-emitting layer includes alternately grown AlGaInP quantum well layers and AlGaInP quantum barrier layers, where the Al content in the AlGaInP quantum well layers and the AlGaInP quantum barrier layers is different. The first light-emitting layer may include 3 to 8 periods of alternately stacked AlGaInP quantum well layers and AlGaInP quantum barrier layers.

[0132] Among them, the first n-type layer includes an n-type AlGaInP current spreading layer.

[0133] In the embodiments of the present disclosure, the green-light epitaxial layer includes a second p-type layer, a second light-emitting layer, and a second n-type layer stacked in sequence.

[0134] In the green-light epitaxial layer, the second p-type layer includes a p-type GaN layer.

[0135] Among them, the second light-emitting layer includes alternately grown InGaN quantum well layers and GaN quantum barrier layers. The second light-emitting layer may include 3 to 8 periods of alternately stacked InGaN quantum well layers and GaN quantum barrier layers.

[0136] Among them, the second n-type layer includes an n-type GaN layer.

[0137] In an embodiment of the present disclosure, the blue light epitaxial layer includes a third p-type layer, a third light-emitting layer, and a third n-type layer stacked in sequence.

[0138] In the blue light epitaxial layer, the third p-type layer includes a p-type GaN layer.

[0139] Among them, the third light-emitting layer may include alternately grown InGaN quantum well layers and GaN quantum barrier layers. The third light-emitting layer may include 3 to 8 periods of alternately stacked InGaN quantum well layers and GaN quantum barrier layers.

[0140] Among them, the third n-type layer includes an n-type GaN layer.

[0141] Optionally, the thickness of the pixel chip is 2 μm to 10 μm.

[0142] Exemplarily, the thickness of the red light epitaxial layer is 5 μm, the thickness of the green light epitaxial layer is 8 μm, and the thickness of the blue light epitaxial layer is 6 μm.

[0143] Exemplarily, the substrate may be a sapphire substrate or a glass substrate.

[0144] Optionally, the passivation layer may be a silicon oxide layer. Among them, the thickness of the silicon oxide layer may be 3 μm to 30 μm.

[0145] Exemplarily, the thickness of the passivation layer may be 10 μm.

[0146] Optionally, the passivation layer may be a Distributed Bragg Reflection (DBR) layer. The DBR layer includes multiple periodically alternately stacked SiO2 layers and TiO2 layers. And the number of periods of the DBR layer may be between 20 and 50. For example, the number of periods of the DBR layer is 32.

[0147] Among them, the thickness of the SiO2 layer in the DBR layer may be 800 Å to 1200 Å, and the thickness of the TiO2 layer may be 500 Å to 900 Å.

[0148] In an embodiment of the present disclosure, the first electrode 41 of each pixel chip is connected to the n-type layer, and the second electrode 42 of each pixel chip is connected to the p-type layer. And the first electrode 41 is connected to the first pad 31, so the first pad 31 is the negative pad. Correspondingly, the second pad 32, the third pad 33, and the fourth pad 34 are all positive pads.

[0149] Embodiments of the present disclosure provide a display panel, which includes a plurality of light-emitting devices, a driving integrated circuit (IC for short), and a circuit board as described above. The plurality of light-emitting devices and the driving IC are both located on the circuit board.

[0150] Exemplarily, the plurality of light-emitting devices are arranged in an array on the circuit board.

[0151] Among them, the driving IC is electrically connected to the circuit board through driving traces on the circuit board, and the solder pads of the plurality of light-emitting devices are also electrically connected to the driving traces on the circuit board. In this way, the driving IC can control each light-emitting device through the driving traces.

[0152] The above is not any form of limitation to the present disclosure. Although the present disclosure has been disclosed as above through embodiments, it is not intended to limit the present disclosure. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the above-disclosed technical content without departing from the technical solution of the present disclosure. However, as long as it does not depart from the technical solution of the present disclosure, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present disclosure still fall within the scope of the technical solution of the present disclosure.

Claims

1. A method for massive transfer of light-emitting diodes, characterized in that, The mass transfer method includes: Transferring different pixel chips (20) onto the first adhesive layer (110) of the first temporary substrate (11) by means of laser lift-off, such that the electrodes of the pixel chips (20) are away from the first adhesive layer (110); Bonding the pixel chips (20) on the first temporary substrate (11) to the second adhesive layer (120) of the second temporary substrate (12), such that the electrodes of the pixel chips (20) are connected to the second adhesive layer (120), and the viscosity of the second adhesive layer (120) is greater than that of the first adhesive layer (110); Removing the first temporary substrate (11) and the first adhesive layer (110), and bonding the pixel chips (20) on the second temporary substrate (12) to the third adhesive layer (130) of the circuit board (13), such that the electrodes of the pixel chips (20) are away from the third adhesive layer (130), and the viscosity of the third adhesive layer (130) is greater than that of the second adhesive layer (120).

2. The massive transfer method according to claim 1, characterized in that The viscosity of the second adhesive layer (120) is 2 to 3 times that of the first adhesive layer (110); The viscosity of the third adhesive layer (130) is 6 to 10 times that of the first adhesive layer (110).

3. The massive transfer method according to claim 1, characterized in that The ratio of the adhesive to the curing agent in the first adhesive layer (110) is 9:1 to 11:1, the ratio of the adhesive to the curing agent in the second adhesive layer (120) is 13:1 to 15:1, and the third adhesive layer (130) is a non-conductive adhesive layer.

4. The mass transfer method according to any one of claims 1 to 3, characterized in that Before transferring different pixel chips (20) onto the first adhesive layer (110) of the first temporary substrate (11) by means of laser lift-off, it further includes: Bonding the wafer (15) to the carrier plate (14), such that the electrodes of the pixel chips (20) on the wafer (15) are connected to the photosensitive adhesive layer (140) of the carrier plate (14); Irradiating the wafer (15) with laser, such that the pixel chips (20) are separated from the substrate of the wafer (15).

5. The massive transfer method according to claim 4, wherein Transferring different pixel chips (20) onto the first adhesive layer (110) of the first temporary substrate (11) by means of laser lift-off includes: Laser decomposing the photosensitive adhesive layer (140) on the carrier plate (14), such that the pixel chips (20) fall from the carrier plate (14) onto the first adhesive layer (110) of the first temporary substrate (11).

6. The massive transfer method according to claim 5, wherein Laser decomposing the photosensitive adhesive layer (140) on the carrier plate (14) includes: Controlling the laser wavelength to be 248 nm, 266 nm or 355 nm, and irradiating the photosensitive adhesive layer (140) with excimer laser or solid laser.

7. The massive transfer method according to any one of claims 1 to 3, characterized in that, After transferring different pixel chips (20) onto the first adhesive layer (110) of the first temporary substrate (11) by means of laser lift-off, it further includes: Etching and removing the first adhesive layer (110) between adjacent pixel chips (20); After bonding the pixel chips (20) on the first temporary substrate (11) to the second adhesive layer (120) of the second temporary substrate (12), it further includes: Etching and removing the second adhesive layer (120) between adjacent pixel chips (20); After bonding the pixel chips (20) of the second temporary substrate (12) to the third adhesive layer (130) of the circuit substrate (13), it further includes: Etching and removing the third adhesive layer (130) between adjacent pixel chips (20).

8. The method for massive transfer according to any one of claims 1 to 3, characterized in that, After bonding the pixel chips (20) of the second temporary substrate (12) to the third adhesive layer (130) of the circuit substrate (13), it further includes: Forming a packaging adhesive on the surface of the circuit substrate (13) to form a packaging adhesive layer (50) that fills and wraps each pixel chip (20).

9. A light-emitting device, characterized in that, The light-emitting device includes: a circuit substrate (13), a plurality of pixel chips (20), and a packaging adhesive layer (50). The plurality of pixel chips (20) are transferred to the circuit substrate (13) by the mass transfer method according to any one of claims 1 to 8. The packaging adhesive layer (50) is located on the surface of the circuit substrate (13) and wraps each pixel chip (20).

10. A display panel, characterized in that, The display panel includes a plurality of light-emitting devices, a driving integrated circuit, and a circuit board according to claim 9. The plurality of light-emitting devices and the driving integrated circuit are both located on the circuit board.

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