Micro LED panel packaging structure and packaging adhesive

Abstract

The application relates to a Micro LED panel packaging structure and packaging glue, which comprises a light-emitting chip, a sapphire packaging layer and a glue layer, the sapphire packaging layer is coated on the light-emitting chip, the glue layer is coated on the sapphire packaging layer, diffusion powder is arranged at the contact surface of the glue layer and the sapphire packaging layer, the diffusion powder comprises milky white powder with a foggy surface and transparent powder with a smooth surface. The application uses compounded diffusion powder, which can comprehensively improve the brightness and light scattering effect. When light is emitted and meets the diffusion powder, reflection occurs, the light is scattered, the problem of inconsistent light caused by phase separation is improved, the refractive index of the diffusion powder is larger than that of the base glue, the diffusion powder is arranged at the contact surface of the glue layer and the sapphire packaging layer, part of the diffusion powder is in contact with the sapphire packaging layer, the total reflection angle of light at the contact surface of the diffusion powder and the sapphire packaging layer is larger than that at the contact surface of the base glue and the sapphire packaging layer, more light can be refracted and emitted, and the brightness is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of LED packaging, and in particular relates to a Micro LED panel packaging structure and packaging glue. BACKGROUND

[0002] In recent years, MIP (Mini / Micro LED in Package) packaging technology has attracted attention. Compared with COB (Chip on Board) packaging, MIP packaging does not need to go through high-cost repair and directly test and sort, which reduces the difficulty of point testing and sorting and also reduces the repair cost. LED display is developing towards miniaturization, and with continuous miniaturization, the brightness problem needs to be solved. The light consistency problem caused by miniaturization has always been an industry problem.

[0003] As shown in Figure 1 , n1 is the refractive index inside the lamp bead, n2 is the refractive index outside the lamp bead, θ1 is the incident angle, θ2 is the exit angle, and according to the refraction law , it can be known that The smaller the incident angle is, the less light enters from the inside of the lamp bead to the outside of the lamp bead, and the lower the brightness is.

[0004] COB packaging adopts transferring a light-emitting chip to a substrate, and then molding a layer of glue on the surface. The refractive index of the glue is generally between 1.3 and 1.7.

[0005] MIP packaging adopts integrating multiple light-emitting chips together to make a lamp bead, and then transferring the lamp bead to a substrate and molding a layer of glue on the surface. Due to the process difficulty, the packaging layer of the Micro lamp bead on the market does not use glue, but sapphire, as shown in Figure 2 , the refractive index of which is 1.7-1.8, which is higher than that of glue. In theory, the same light-emitting chip, the same packaging structure and the same external environment, because the refractive index of sapphire is larger, more light is totally reflected, and the brightness is lower when sapphire is used.

[0006] In addition, as shown in Figure 6 , there is sometimes a small air layer 5 between the outer glue layer and the sapphire in the MIP packaging process, which changes the light path and the light transmittance, resulting in a screen with a dot. SUMMARY

[0007] The Micro LED panel packaging structure and packaging glue provided by the embodiments of the present application solve the problem of low brightness of the lamp bead in MIP packaging in the related art.

[0008] In a first aspect, a Micro LED panel packaging structure is provided, which comprises:

[0009] a light emitting chip;

[0010] a sapphire encapsulation layer covering the light emitting chip;

[0011] a glue layer covering the sapphire encapsulation layer, the glue layer being provided with diffusion powder for dispersing light at a contact surface of the glue layer and the sapphire encapsulation layer, the diffusion powder including milky white powder with a foggy surface and transparent powder with a smooth surface.

[0012] In some embodiments, the transparent powder with a smooth surface is amorphous powder, and the milky white powder with a foggy surface is spherical powder.

[0013] The milky white powder with a foggy surface is processed from the transparent powder with a smooth surface by an alternating current high frequency plasma melting method, a gas combustion flame method or a high temperature melting spraying method.

[0014] In some embodiments, the transparent powder with a smooth surface includes silicon dioxide.

[0015] In some embodiments, in the diffusion powder, the mass ratio of the milky white powder with a foggy surface and the transparent powder with a smooth surface is 1: (0.1-10).

[0016] In some embodiments, the diffusion powder is dispersed in the glue layer.

[0017] In some embodiments, the glue layer is solidified from an encapsulation glue, and the encapsulation glue includes, in terms of mass fraction:

[0018] 30%-60% diffusion powder, 15%-45% epoxy resin, 15%-20% acid anhydride curing agent and 5%-10% additive.

[0019] In some embodiments, the epoxy resin includes alicyclic epoxy resin.

[0020] And / or, the acid anhydride curing agent includes one or more of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride.

[0021] And / or, the additive includes one or more of toughening agent and adhesion promoter.

[0022] And / or, the encapsulation glue further includes 0.01%-5% coupling agent.

[0023] In some embodiments, the thickness of the sapphire encapsulation layer is 30-80 μm.

[0024] In a second aspect, an encapsulation glue is provided, which includes, in terms of mass fraction:

[0025] Diffusion powder 30%~60%, epoxy resin 15%~45%, acid anhydride curing agent 15%~20%, auxiliary agent 5%~10%;

[0026] The diffusion powder comprises milky white powder with a misty surface and transparent powder with a smooth surface.

[0027] In some embodiments, the epoxy resin comprises alicyclic epoxy resin.

[0028] The acid anhydride curing agent comprises one or more of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride.

[0029] The auxiliary agent comprises one or more of toughening agent and adhesion promoter.

[0030] The encapsulation adhesive further comprises 0.01%~5% coupling agent.

[0031] The technical scheme provided in the application has the following beneficial effects:

[0032] In the application, the diffusion powder is compounded, that is, the milky white powder with a misty surface and the transparent powder with a smooth surface are uniformly mixed. If the milky white powder with a misty surface is used alone, the brightness will be too low, and if the transparent powder with a smooth surface is used alone, it is difficult to play a good role in dispersing light. Therefore, the use of compounded powder can comprehensively improve the brightness and the effect of dispersing light, so that when light encounters the diffusion powder, reflection occurs, playing a role in dispersing light, and improving the problem of inconsistent light caused by phase separation.

[0033] For the base glue of the glue layer, the refractive index of the diffusion powder is greater than the refractive index of the base glue. The diffusion powder is arranged at the contact surface of the glue layer and the sapphire encapsulation layer, so that part of the diffusion powder is in contact with the sapphire encapsulation layer. According to the law of refraction, the total reflection angle of light at the contact surface of the diffusion powder and the sapphire encapsulation layer is greater than the total reflection angle of light at the contact surface of the base glue and the sapphire encapsulation layer, so that more light can be refracted and emitted, and the brightness is improved. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical scheme in the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0035] Figure 1 The diagram is a refraction diagram;

[0036] Figure 2 The diagram is a schematic diagram of MIP encapsulation using sapphire;

[0037] Figure 3 Fig. 3 is a schematic diagram of light emission of a light emitting chip in a normal case;

[0038] Figure 4 Fig. 4 is a schematic diagram of light emission of a micro-sized lamp bead on the market;

[0039] Figure 5 Fig. 5 is a schematic diagram of a light emitting angle of a micro-sized lamp bead;

[0040] Figure 6 Fig. 6 is a schematic diagram of an air layer in a MIP packaging process;

[0041] Figure 7 Fig. 7 is a schematic diagram of a Micro LED panel packaging structure provided by an embodiment of the present application;

[0042] Figure 8 Fig. 8 is a schematic diagram of a sapphire packaging layer after thinning according to an embodiment of the present application.

[0043] In the figure: 1, a light emitting chip; 2, a sapphire packaging layer; 3, a glue layer; 4, diffusion powder; 5, an air layer. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0045] Referring to Figure 7 The embodiment of the present application provides a Micro LED panel packaging structure, which includes a light emitting chip 1, a sapphire packaging layer 2 and a glue layer 3. The sapphire is used to package the light emitting chip 1, and the sapphire is coated on the light emitting chip 1 to form the sapphire packaging layer 2. Then, the packaging glue is coated on the sapphire packaging layer 2, and after solidification, the glue layer 3 coated on the sapphire packaging layer 2 is formed. The glue layer 3 is provided with diffusion powder 4 for dispersing light at the contact surface of the glue layer 3 and the sapphire packaging layer 2. The diffusion powder 4 includes milky white powder with a foggy surface and transparent powder with a smooth surface.

[0046] In the present application, the diffusion powder 4 is a compound, that is, a mixture of the milky white powder with a misty surface and the transparent powder with a smooth surface. If the milky white powder with a misty surface is used alone, the brightness will be too low, and if the transparent powder with a smooth surface is used alone, it will be difficult to play a good role in dispersing light. Therefore, the compound powder can comprehensively improve the brightness and the effect of dispersing light, so that when the light encounters the diffusion powder, reflection occurs, playing a role in dispersing light and improving the problem of inconsistent light caused by phase separation.

[0047] In addition, for the base glue of the glue layer 3, the refractive index of the diffusion powder is greater than that of the base glue. The diffusion powder 4 is arranged at the contact surface of the glue layer 3 and the sapphire packaging layer 2, so that part of the diffusion powder 4 is in contact with the sapphire packaging layer 2. According to the law of refraction, the total reflection angle of light at the contact surface of the diffusion powder 4 and the sapphire packaging layer 2 is greater than that at the contact surface of the base glue and the sapphire packaging layer 2, so that more light can be refracted and emitted, thereby improving the brightness.

[0048] In the present application, the transparent powder with a smooth surface is an amorphous powder, and the milky white powder with a misty surface is a spherical powder.

[0049] Both the above-mentioned powders can be directly purchased as finished products.

[0050] Alternatively, the transparent powder with a smooth surface can be treated to obtain the milky white powder with a misty surface. For example, the milky white powder with a misty surface is obtained by treating the transparent powder with a smooth surface by an alternating high-frequency plasma melting method, a gas combustion flame method, or a high-temperature melting spraying method.

[0051] It can be understood that the above-mentioned alternating high-frequency plasma melting method, gas combustion flame method, or high-temperature melting spraying method is a common treatment means, which will not be described here.

[0052] It can be understood that the transparent powder with a smooth surface can be selected from silica or other powders with the same or similar properties to achieve the effect of dispersing light.

[0053] Since the treated diffusion powder is the milky white powder with a misty surface, if the proportion is too high, the brightness will be low, and if the proportion is too low, it will be difficult to play a good role in dispersing light. After a large number of test tests, the proportion of the two is optimized. Specifically, in the diffusion powder 4, the mass ratio of the milky white powder with a misty surface and the transparent powder with a smooth surface is 1: (0.1-10).

[0054] Preferably, the mass ratio of the milky white powder with a misty surface and the transparent powder with a smooth surface is 1: (1-5).

[0055] For example, the mass ratio of the milky white powder with a foggy surface and the transparent powder with a smooth surface is 1:1, 1:2, 1:3, 1:4, 1:5, or any value between any two of the above ratios, which is not limited in the embodiments of the present disclosure.

[0056] In the present application, the diffusion powder 4 can be located between the adhesive layer 3 and the sapphire packaging layer 2.

[0057] In order to simplify the manufacturing process and reduce the manufacturing difficulty, the diffusion powder 4 is dispersed in the adhesive layer 3, that is, the diffusion powder 4 is dispersed and mixed in the base adhesive of the adhesive layer 3 to form a packaging adhesive, and then coated and solidified to obtain the adhesive layer 3. The diffusion powder 4 dispersed on the wall surface in contact with the sapphire packaging layer 2 in the adhesive layer 3 can contact the sapphire packaging layer 2.

[0058] Further, the adhesive layer 3 is formed by solidifying the packaging adhesive, and the packaging adhesive includes, in terms of mass fraction, 30% to 60% of diffusion powder, 15% to 45% of epoxy resin, 15% to 20% of acid anhydride curing agent, and 5% to 10% of auxiliary agent.

[0059] It can be understood that the adhesive layer 3 includes the base adhesive and the diffusion powder, and the base adhesive is composed of the remaining components after removing the diffusion powder from the adhesive layer 3, that is, the base adhesive includes the epoxy resin, the acid anhydride curing agent, and the auxiliary agent.

[0060] The epoxy resin can use alicyclic epoxy resin.

[0061] The acid anhydride curing agent includes one or more of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride.

[0062] The auxiliary agent includes one or more of a toughening agent and an adhesion promoter, and both the toughening agent and the adhesion promoter can select commonly used substances.

[0063] In order to solve the problem of pitting, the packaging adhesive provided by the present application further includes 0.01% to 5% of a coupling agent.

[0064] Appropriately increasing the proportion of the coupling agent can make the adhesive layer 3 and the sapphire packaging layer 2 fully infiltrate, reduce the probability of the presence of the air layer 5, thereby increasing the light emission and avoiding the occurrence of pitting.

[0065] The coupling agent is preferably a silane coupling agent, such as propyltrimethoxysilane.

[0066] Since the refractive index of the coupling agent is smaller than the refractive index of the base adhesive of the adhesive layer 3, the refractive index of the coupling agent is generally 1.4 to 1.5. If the coupling agent is too little, the above infiltration effect may not be significant, and if the coupling agent is too much, the light emission without the base adhesive is more under the same conditions, and the brightness will be lower. In addition, too much coupling agent will cause the viscosity of the glue to be too high, which cannot be used normally.

[0067] After a large number of test experiments, the amount of coupling agent is optimized in the present application, which can be selected from 0.01% to 5%, taking into account the infiltration effect and improving brightness.

[0068] For example, the mass fraction of the coupling agent is 0.01%, 0.05%, 0.%, 0.2%, 0.4%, 0.5%, 0.6%, 1%, 2%, 3%, 4%, 5%, or any value between any two of the foregoing, which is not limited in the embodiments of the present disclosure.

[0069] Preferably, the mass fraction of the coupling agent is 0.5% to 1.5%.

[0070] As shown in Figure 3 , under normal circumstances, the light-emitting chip emits light in a fan-shaped structure, and the light is uniformly distributed. The structure size of the micro-size lamp bead on the market is generally as shown in Figure 4 , which is five-face light emission. The light emitted from the upper surface and the four sides is superimposed, resulting in M-shaped light emission. As shown in Figure 4 , the packaging layer is sapphire, and its refractive index is 1.7-1.8. In the air, the total reflection angle is about 34.5° according to the refraction law. The red light chip and the blue light chip are located away from the center of the lamp bead, and the red light chip is located on one side of the upper surface. The red light emission angle is 31°, and the blue light emission angle is 34.5°. When viewed from the left side of Figure 4 , the color is blue, and for the same reason, the blue light chip is located on one side of the upper surface. The blue light emission angle is 31°, and the red light emission angle is 34.5°. When viewed from the right side of Figure 4 , the color is red, as shown in Figure 5 , which is the general light-emitting angle of the micro-size lamp bead. This results in color temperature fluctuations when viewed from different directions, and the blue phase or red phase deviates, resulting in poor light emission consistency.

[0071] The applicant has conducted a large number of experimental studies on the reasons for the above-mentioned blue phase or red phase deviation, which further leads to poor light emission consistency. Many factors are analyzed, including refractive index, air temperature, light-emitting chip temperature, packaging layer temperature, etc. Finally, it is found that the thickness of sapphire affects the blue phase or red phase deviation. The reason why the commercially available lamp bead structure deviates from the blue phase or red phase and leads to poor light emission consistency is mainly that the thickness of the sapphire reaches 100 μm.

[0072] Based on this discovery, in order to ensure the light emission consistency of large viewing angle and improve the brightness, the present application provides a solution, specifically, as shown in Figure 4 and Figure 8 , the thickness of the sapphire packaging layer 2 is thinned, so that the R / G / B chips are located on the upper surface of the lamp bead, and total reflection occurs on the left and right sides, ensuring the light emission consistency of large viewing angle and improving the brightness.

[0073] After a large number of test experiments, the thickness of the sapphire packaging layer 2 is preferably selected to be 30-80 μm.

[0074] For example, the thickness of the sapphire packaging layer 2 is 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, or any value between any two of the foregoing, and the embodiments of the present disclosure do not limit this.

[0075] Preferably, the thickness of the sapphire packaging layer 2 is 40-70 μm, such as Figure 8 In particular, the thickness of the sapphire packaging layer 2 is 60 μm.

[0076] In addition, the applicant has also found through a large number of researches that, when the diffusion powder 4 is provided, a coupling agent is used, and the thickness of the sapphire packaging layer 2 is thinned, the color temperature change of the Micro LED panel packaging structure is ≤1000k, and the luminance is increased by 10%-30% at a large viewing angle of 175°C.

[0077] The application also provides an encapsulation glue which can be applied to the MIP packaging process to solidify a glue layer on the sapphire, and according to the mass fraction, it comprises: 30%-60% of diffusion powder, 15%-45% of epoxy resin, 15%-20% of acid anhydride curing agent, and 5%-10% of auxiliary agent; wherein the diffusion powder comprises milky white powder with a misty surface and transparent powder with a smooth surface.

[0078] In order to improve the wetting effect and avoid the presence of an air layer between the sapphire and the glue layer, the encapsulation glue further comprises 0.01%-5% of a coupling agent.

[0079] In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise specifically defined and limited, the terms "mounting", "connection", and "connection" should be broadly understood, for example, they can be fixedly connected, or detachably connected, or integrally connected; they can be mechanically connected, or electrically connected; they can be directly connected, or indirectly connected through an intermediate medium, and they can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0080] It should be noted that, in the present application, the relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another, without necessarily requiring or implying any actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0081] The foregoing is merely illustrative of the principles of the application and various modifications can be made by those skilled in the art without departing from the spirit and scope of the application. The above embodiments are illustrative, and not restrictive, of the scope of the application.

Claims

1. A Micro LED panel MIP encapsulation structure, characterized in that, It comprises: a light emitting chip (1); a sapphire encapsulation layer (2) covering the light emitting chip (1); a glue layer (3) covering the sapphire encapsulation layer (2), the glue layer (3) being provided with diffusion powder (4) for dispersing light at the contact surface of the glue layer (3) and the sapphire encapsulation layer (2), the diffusion powder (4) comprising milky white powder with a foggy surface and transparent powder with a smooth surface, the transparent powder with a smooth surface being amorphous powder, and the milky white powder with a foggy surface being spherical powder; the mass ratio of the milky white powder with a foggy surface and the transparent powder with a smooth surface in the diffusion powder (4) being 1: (1-5); the thickness of the sapphire encapsulation layer (2) being 30-80 μm; the glue layer (3) being formed by curing encapsulation glue, and the encapsulation glue comprising, in terms of mass fraction, diffusion powder 30%-60%, epoxy resin 15%-45%, acid anhydride curing agent 15%-20%, auxiliary agent 5%-10%, and coupling agent 0.01%-5%.

2. The Micro LED panel MIP encapsulation structure of claim 1, wherein: the milky white powder with a foggy surface is processed from the transparent powder with a smooth surface by an alternating high-frequency plasma melting method, a gas combustion flame method, or a high-temperature melting spraying method.

3. The Micro LED panel MIP encapsulation structure of claim 1, wherein: the transparent powder with a smooth surface comprises silicon dioxide.

4. The Micro LED panel MIP encapsulation structure of claim 1, wherein: the diffusion powder (4) is dispersed in the glue layer (3).

5. The Micro LED panel MIP encapsulation structure of claim 1, wherein: the epoxy resin comprises an alicyclic epoxy resin; and / or, the acid anhydride curing agent comprises one or more of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride; and / or, the auxiliary agent comprises one or more of a toughening agent and an adhesion promoter.

Images