Micro LED encapsulation structure containing color conversion layer

Abstract

The application relates to the technical field of semiconductor display, and discloses a MicroLED packaging structure containing a color conversion layer, which comprises a bottom layer and a plurality of LED crystals; the top of the bottom layer is provided with a packaging layer one; the inside of the packaging layer one is provided with a plurality of conductive blocks; the material of the conductive blocks is copper, which is used for providing current for the LED crystals; one side of the LED crystals is fixedly connected to the outside of the conductive blocks; the outside of the packaging layer one and the LED crystals is provided with a wrapping layer; the outside of the wrapping layer is provided with a contact layer; the outside of the wrapping layer and the contact layer is provided with a flat layer; and the outside of the flat layer is provided with a color conversion layer. The color conversion layer is efficiently excited by vertical blue light, so that the color conversion layer fully converts blue light into other color light, reduces light transmission loss, realizes the effect of higher brightness in the case of smaller size LED, greatly improves display performance, and provides strong support for the miniaturization and high performance of display products.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor display, in particular to a MicroLED packaging structure containing a color conversion layer. BACKGROUND

[0002] At present, with the rapid development of display technology, MicroLED has become a promising technology direction in the display field due to its high brightness, high contrast, low power consumption, long service life and many other advantages. As a key link to realize the display performance of MicroLED, the MicroLED packaging structure has always been the focus of research and development. Traditional MicroLED packaging structure meets the display requirements, but also faces the challenges of continuously improving performance and reducing cost. With the increasing demand of consumer market for light and thin, small and high resolution display products, the optimization of MicroLED packaging structure becomes particularly urgent.

[0003] The MicroLED packaging structure in the prior art is usually realized by using multiple materials and processes. For example, sapphire is used as a substrate for epitaxial growth of MicroLED chips, the chips are connected with conductive structures by metal welding and other methods, and different packaging layers and protection structures are used to ensure the normal work and stability of the chips. In terms of color realization, AlGaInP material is often used to realize red light display. The principle is based on the light emitting characteristics of semiconductor materials, and specific wavelength light is generated by the recombination of electrons and holes. At the same time, in order to ensure the propagation of light and display effect, structures such as light filters and light blocking blocks are also set to control the propagation path and color purity of light.

[0004] In practical application scenarios, as the size of MicroLED devices continues to decrease, the drawbacks of the prior art gradually appear. For example, in wearable devices such as smart watches, in order to achieve higher resolution and more compact appearance design, smaller size MicroLED devices need to be used. However, for traditional AlGaInP red light LEDs, the efficiency will decrease significantly as the device size decreases. This is because the internal quantum efficiency and carrier recombination efficiency of AlGaInP material will be affected at small size, resulting in reduced light emitting efficiency; in addition, when red light is realized by using blue light MicroLED plus red light quantum dots, new challenges are also faced. When the size of the blue light LED device is reduced, and the flip chip pad size is less than 10um, soldering or wiring becomes extremely difficult. For example, in high-definition display devices such as mobile phones, in order to improve the pixel density of the screen, smaller size blue light LEDs need to be used. However, due to the small size of the flip chip pad, the traditional soldering process cannot guarantee reliable electrical connection, and problems such as false soldering and short circuit are prone to occur, and the reduction of wiring space also increases the difficulty of circuit design, resulting in reduced production efficiency and increased cost. Therefore, the present application provides a MicroLED packaging structure containing a color conversion layer to solve the deficiencies in the prior art. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a MicroLED packaging structure containing a color conversion layer to solve the problem of reduced light efficiency caused by reduced device size in the prior art MicroLED packaging structure.

[0006] To achieve the above purpose, the present application is implemented by the following technical scheme: a MicroLED packaging structure containing a color conversion layer, comprising a bottom layer and a plurality of LED crystals, the top of the bottom layer is provided with a packaging layer one, the inside of the packaging layer one is provided with a plurality of conductive blocks, one side of the LED crystal is fixedly connected to the outside of the conductive block, the outside of the packaging layer one and the LED crystal is provided with a wrapping layer, the outside of the wrapping layer is provided with a contact layer, the outside of the wrapping layer and the contact layer is provided with a flat layer, the outside of the flat layer is provided with a color conversion layer, a plurality of light blocking blocks are installed in the inside of the color conversion layer, and one end of the light blocking block is attached to the outside of the flat layer, the light blocking block and the other end and the outside of the color conversion layer are provided with a packaging layer two, the outside of the packaging layer two is provided with a filter one and a filter two, the outside of the packaging layer two, the filter one and the filter two is provided with a packaging layer three;

[0007] The LED crystal is a composite material, comprising metal, ITO, p+-GaN, MQW, n+-GaN and u-GaN, the material of the cladding layer is one of SiO or SiN, or a laminated structure of both, the contact layer is used for ohmic contact, and the material of the contact layer is ITO, the light blocking block is black photoresist, used for absorbing and blocking light, and the materials of the encapsulation layer one, the encapsulation layer two and the encapsulation layer three are all silicon nitride, aluminum oxide or a composite material thereof, used for blocking the erosion of water vapor and oxygen to other structures.

[0008] Preferably, the material of the conductive block is copper, used for providing current to the LED crystal.

[0009] Preferably, the material of the flat layer is an organic matter, used for flatness and insulation.

[0010] Preferably, the colors of the filter one and the filter two are different, used for shielding the blue light that is not completely converted.

[0011] A MicroLED encapsulation method with a color conversion layer, applied to the MicroLED encapsulation structure with a color conversion layer, comprises the following steps:

[0012] S1, the MicroLED used is peeled off from sapphire through a laser peeling technology;

[0013] S2, the MicroLED is welded at the conductive block through AuSn eutectic welding, AuIn eutectic welding or ACF welding;

[0014] S4, the u-GaN and n+-GaN in the LED crystal are thinned, and wrapped with a PV cladding layer;

[0015] S5, a hole is dug outside the cladding layer, an ohmic contact is made with a contact layer, and then a flat layer is covered to protect the circuit structure;

[0016] S6, a light blocking block is arranged outside the flat layer to absorb and block light;

[0017] S7, a color conversion layer is placed outside the light blocking block, the color conversion layer is quantum dot material or fluorescent powder material, and then encapsulation layer two is used for encapsulation;

[0018] S8, filter one and filter two are arranged outside the encapsulation layer two to shield the blue light that is not completely converted, and then encapsulation layer three is used for covering, that is, the overall structure encapsulation operation is completed.

[0019] The application provides a MicroLED encapsulation structure with a color conversion layer.

[0020] 1、The present application is through the vertical blue light + color conversion structure scheme, in the whole packaging process, from laser stripping optimization substrate connection, to the multi-layer structure guarantee performance stability, each link synergistic cooperation, vertical blue light efficient color conversion structure, make the color conversion structure fully convert blue light into other color light, reduce the light transmission loss, realized in the case of smaller size LED to achieve higher brightness effect, greatly improve the display performance, for the display product miniaturization and high performance provide strong support.

[0021] 2、The present application uses color conversion structure to realize red light structure in display structure, abandon the traditional AlGaInP red light, quantum dot material characteristics make it show color in red light conversion, effectively improve the light efficiency, reduce the energy waste, at the same time, avoid using relatively complex and high cost AlGaInP material, significantly reduce the production cost, for display product in guarantee quality at the same time realize more competitive price, promote the development of display industry towards high efficiency, low cost direction. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is the whole structure schematic diagram of the present application.

[0023] Among them, 1, bottom layer; 2, packaging layer one; 3, conductive block; 4, LED crystal; 5, wrapping layer; 6, contact layer; 7, flat layer; 8, light blocking block; 9, color conversion layer; 10, packaging layer two; 11, filter one; 12, filter two; 13, packaging layer three. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the specification of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0025] Please refer to the drawings of the present application Figure 1The embodiment of the present application provides a MicroLED packaging structure containing a color conversion layer, which comprises a bottom layer 1 and a plurality of LED crystals 4, the top of the bottom layer 1 is provided with a packaging layer one 2, the inside of the packaging layer one 2 is provided with a plurality of conductive blocks 3, the MicroLED is welded at the conductive block 3 in a mode of AuSn eutectic welding, AuIn eutectic welding, ACF welding and the like, taking the AuSn eutectic welding as an example, gold-tin alloy (20% of tin) is in a liquid state at a temperature above 280 DEG C, when the temperature slowly decreases, eutectic reaction occurs, good connection is formed, thereby realizing the stable electrical connection of the MicroLED and the conductive block 3, one side of the LED crystal 4 is fixedly connected to the outside of the conductive block 3, the material of the conductive block 3 is copper, copper has good conductivity, can provide stable current input for the LED crystal 4, meets the working requirement of the LED crystal 4, the LED crystal 4 is a composite material, contains metal, ITO, p+-GaN, MQW, n+-GaN and u-GaN.After the welding is completed, the u-GaN and n+-GaN parts in the LED crystal 4 need to be thinned, and the wafer needs to be thinned. There are many benefits to thinning the wafer. The volume of the thinned chip is smaller, which can adapt to thinner packaging design, and has a shorter heat diffusion path and a higher surface area to volume ratio, which helps to transfer the heat generated by the chip during operation faster and more effectively. If the chip is too thick, heat will accumulate inside the chip during the transfer process, causing local overheating and affecting device performance. Then, the outside of the packaging layer 2 and the LED crystal 4 is provided with a wrapping layer 5, which is made of one of SiO or SiN, or a laminated structure of both. This layer mainly protects the LED crystal 4 from external environmental factors. The outside of the wrapping layer 5 is provided with a contact layer 6, which is used for ohmic contact outside the wrapping layer 5. The material of the contact layer 6 is ITO, which has good electrical conductivity and optical transparency, allowing for ohmic contact while minimizing the impact on light propagation, ensuring that the subsequent light can be smoothly emitted. The outside of the wrapping layer 5 and the contact layer 6 is provided with a flat layer 7, which is made of PI, OC or other materials, and has good insulation performance, which can effectively isolate the circuit and prevent short circuit and other problems. At the same time, it provides a flat foundation for the subsequent structure, which is used to protect the circuit structure. The outside of the flat layer 7 is provided with a color conversion layer 9, which is installed with a plurality of light blocking blocks 8, and one end of the light blocking block 8 is attached to the outside of the flat layer 7. The light blocking block 8 is black photoresist, which mainly absorbs and blocks light to prevent light crosstalk between different pixel units, thereby improving the contrast and color purity of the display, making the display clearer and more vivid. The other end of the light blocking block 8 and the outside of the color conversion layer 9 are provided with a packaging layer two 10, which is packaged with the packaging layer two 10. The material of the packaging layer two 10 is a composite material of silicon nitride and aluminum oxide, which has good chemical stability, corrosion resistance and light transmission, can block the erosion of water vapor and oxygen to the internal structure, further protect the internal LED crystal 4, contact layer 6 and other structures from external environmental damage, and prolong the service life of the entire packaging structure. The outside of the packaging layer two 10 is provided with a filter one 11 and a filter two 12, which have different colors. Its function is to shield the blue light that has not been completely converted, and through selective filtering of light, the final emitted light is more consistent with the display requirements in color and spectrum, optimizing the display effect. The outside of the packaging layer two 10, the filter one 11 and the filter two 12 is provided with a packaging layer three 13, which is finally covered with the packaging layer three 13. The material of the packaging layer three 13 is also a composite material of silicon nitride and aluminum oxide, which further strengthens the protection of the internal structure and blocks the interference of external adverse factors.At this point, the whole structure packaging operation is completed, and through the vertical blue light color conversion layer structure scheme, smaller LED can achieve higher brightness effect, which has significant advantages in the display field, and is expected to promote the development of related display products to higher performance.

[0026] Please refer to the attached Figure 1 The embodiment of the present application also provides a MicroLED packaging method with a color conversion layer, comprising the following steps:

[0027] S1, the MicroLED used is peeled off from the sapphire by laser peeling technology;

[0028] S2, the MicroLED is welded at the conductive block 3 by AuSn eutectic welding, AuIn eutectic welding or ACF welding;

[0029] S4, the u-GaN and n+-GaN parts in the LED crystal 4 are thinned, and the PV wrapping layer 5 is used for wrapping;

[0030] S5, the ohmic contact is made by the contact layer 6 outside the wrapping layer 5, and then the flat layer 7 is covered to protect the circuit structure;

[0031] S6, the light blocking block 8 is arranged outside the flat layer 7 to absorb and block light;

[0032] S7, the color conversion layer 9 made of quantum dot material or fluorescent powder material is placed outside the light blocking block 8, and then the second packaging layer 10 is used for packaging;

[0033] S8, the light filter 1 11 and the light filter 2 12 are arranged outside the second packaging layer 10 to shield the blue light which is not completely converted, and then the third packaging layer 13 is used for covering, that is, the whole structure packaging operation is completed.

[0034] Specifically, first, the MicroLED used is peeled off from the sapphire by laser peeling technology. Since the MicroLED chip based on GaN light emitting material often uses sapphire as the mainstream substrate for epitaxial growth, because the lattice mismatch degree of GaN and sapphire is low and the price of sapphire is low. However, the sapphire substrate has problems such as non-conductivity and poor heat conduction, which seriously affect the light emitting efficiency of the MicroLED device and are not conducive to its application in flexible display. Laser peeling technology uses short-wavelength laser whose photon energy is greater than the energy band gap of gallium nitride (GaN) and less than the band gap of sapphire and aluminum nitride (AlN). From the side of sapphire, the laser is irradiated. After the laser passes through the sapphire and AlN, it is absorbed by the surface GaN. The surface GaN undergoes thermal decomposition to generate nitrogen and metallic gallium. Nitrogen escapes, and the GaN epitaxial layer and sapphire substrate can be separated by mechanical force. This step lays the foundation for subsequent reasonable installation of MicroLED and optimization of its performance. Subsequently, the MicroLED is welded at the conductive block 3 by AuSn eutectic welding, AuIn eutectic welding, ACF welding and other methods. Eutectic reaction occurs to form a stable and reliable connection, achieving good electrical connection between the MicroLED and the conductive block 3, ensuring that the conductive block 3 can stably provide current for the MicroLED, and ensuring the power supply required for the normal operation of the LED crystal 4. Then, the u-GaN,The n+-GaN portion is thinned, resulting in a smaller chip size. This thinner chip has a shorter heat diffusion path and a higher surface area to volume ratio, facilitating faster and more efficient heat dissipation during chip operation. A PV encapsulation layer 5 then encapsulates the LED crystal 4, protecting it from external environmental factors. An ohmic contact layer 6 is then applied outside the encapsulation layer 5. This ohmic contact ensures smooth current transmission between the encapsulation layer 5 and subsequent structures. Simultaneously, its good optical transparency minimizes the impact on light propagation while achieving ohmic contact, ensuring successful light emission. The planarization layer 7 protects the circuit structure. The material of planarization layer 7 has excellent insulation properties, effectively isolating the circuit and preventing short circuits. A light-blocking block 8, made of black photoresist, is placed outside the planarization layer 7 to absorb and block light. Its main function is to prevent crosstalk between different pixel units. During display, if crosstalk occurs between different pixel units, it will lead to reduced contrast, decreased color purity, and a blurry image. The presence of the light-blocking block 8 effectively absorbs and blocks this crosstalk light, improving the contrast and color purity of the display, making the image clearer and the colors more vibrant, greatly enhancing the display effect. Next, encapsulation layer 2 (10) is used for encapsulation. Encapsulation layer 2 (10) is made of a silicon nitride and aluminum oxide composite material. This composite material has good chemical stability, corrosion resistance, and light transmittance. Encapsulation layer 2 (10) can block external adverse factors such as moisture and oxygen from corroding the internal structure, further protecting the internal LED crystal 4, contact layer 6, and other structures from environmental damage, thereby extending the lifespan of the entire encapsulation structure and ensuring its long-term stable operation. Filters 1 (11) and 2 (12) are placed outside encapsulation layer 2 (10) to shield any incompletely converted blue light. Finally, encapsulation layer 3 (13) is used for coverage. Encapsulation layer 3 (13) is also made of a silicon nitride and aluminum oxide composite material. By combining materials and further strengthening the protection of the internal structure to block interference from adverse external factors, the overall structural encapsulation is completed through the above series of operations. Ultimately, a vertical blue light + color conversion structure solution achieves higher brightness with a smaller LED. In this solution, the vertical blue light structure can more efficiently excite the color conversion layer 9, allowing the quantum dots to more fully convert blue light into other desired colors. Simultaneously, due to the optimized structural design, light loss during transmission is reduced, thus achieving higher brightness even with a smaller LED size. This has significant advantages in the display field and is expected to drive the development of related display products towards higher performance.

[0035] Working principle: first, the used MicroLED is peeled off from the sapphire by laser peeling technology, the MicroLED is welded at the conductive block 3 by AuSn eutectic welding, AuIn eutectic welding, ACF welding and other ways, then the u-GaN, n+-GaN part in LED crystal 4 is thinned, then the PV wrapping layer 5 is wrapped, the ohmic contact is made on the outside of the wrapping layer 5 by the contact layer 6, then the flat layer 7 is covered to protect the circuit structure, the light blocking block 8 is set outside the flat layer 7 to absorb and block light, then the encapsulation layer two 10 is used for encapsulation, the filter one 11 and the filter two 12 are set outside the encapsulation layer two 10 to shield the blue light which is not completely converted, then the encapsulation layer three 13 is used for covering, that is, the overall structure encapsulation operation is completed, through the vertical blue light + color conversion structure scheme, the smaller LED realizes the higher brightness effect.

[0036] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, the scope of the present application being defined by the appended claims and their equivalents.

Claims

1. A MicroLED encapsulation structure containing a color conversion layer, comprising a bottom layer (1) and a plurality of LED crystals (4), characterized in that, The top of the bottom layer (1) is provided with an encapsulation layer one (2), the inside of the encapsulation layer one (2) is provided with a plurality of conductive blocks (3), the material of the conductive block (3) is copper, which is used to provide current for the LED crystal (4), one side of the LED crystal (4) is fixedly connected to the outside of the conductive block (3), the outside of the encapsulation layer one (2) and the LED crystal (4) is provided with a wrapping layer (5), the outside of the wrapping layer (5) is provided with a contact layer (6), the outside of the wrapping layer (5) and the contact layer (6) is provided with a flat layer (7), the material of the flat layer (7) is organic matter, which is used for flatness and insulation, the outside of the flat layer (7) is provided with a color conversion layer (9), a plurality of light blocking blocks (8) are installed in the inside of the color conversion layer (9), and one end of the light blocking block (8) is attached to the outside of the flat layer (7), the light blocking block (8) and the other end and the outside of the color conversion layer (9) are provided with an encapsulation layer two (10), the outside of the encapsulation layer two (10) is provided with a filter one (11) and a filter two (12), the color of the filter one (11) and the filter two (12) is different, which is used to shield the blue light that is not completely converted, the outside of the encapsulation layer two (10), the filter one (11) and the filter two (12) is provided with an encapsulation layer three (13); The LED crystal (4) is a composite material, including metal, ITO, p+-GaN, MQW, n+-GaN and u-GaN, the material of the wrapping layer (5) is one of SiO or SiN, or a laminated structure of both, the contact layer (6) is used for ohmic contact, and the material of the contact layer (6) is ITO, the light blocking block (8) is black photoresist, which is used to absorb and block light, the materials of the encapsulation layer one (2), the encapsulation layer two (10) and the encapsulation layer three (13) are all silicon nitride, aluminum oxide or their composite materials, which are used to block the invasion of water vapor and oxygen to other structures.

2. The MicroLED encapsulation method with a color conversion layer is applied to the MicroLED encapsulation structure with a color conversion layer in claim 1, characterized in that, It includes the following steps: S1, the MicroLED used is peeled off from the sapphire by laser peeling technology; S2, the MicroLED is welded at the conductive block (3) by AuSn eutectic welding, AuIn eutectic welding or ACF welding; S4, the u-GaN and n+-GaN in the LED crystal (4) are thinned, and the PV wrapping layer (5) is used for wrapping; S5, the wrapping layer (5) is externally excavated to use the contact layer (6) for ohmic contact, and then the flat layer (7) is covered to protect the circuit structure; S6, the light blocking block (8) is arranged outside the flat layer (7) to absorb and block light; S7, the color conversion layer (9) is placed outside the light blocking block (8), the color conversion layer (9) is quantum dot material or fluorescent powder material, and then the encapsulation layer two (10) is used for encapsulation; S8, the filter one (11) and the filter two (12) are arranged outside the encapsulation layer two (10) to shield the blue light that is not completely converted, and then the encapsulation layer three (13) is used for covering, that is, the overall structure encapsulation operation is completed.

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