Die Bonding Method for LED Chip and LED Panel

Abstract

An embodiment of the present application discloses a die bonding method for an LED chip and an LED panel. The die bonding method includes: S10, placing an array substrate including a plurality of pads in a first cavity; S20, coating an adhesive on the pads, the adhesive including glue and conductive particles dispersed in the glue; S30, placing the LED chip on the pads coated with the adhesive; S40, compressing the adhesive so that the conductive particles are electrically connected in the thickness direction of the array substrate; S50, curing the adhesive. The die bonding method for the LED chip provided by the embodiment of the present invention realizes die bonding of the LED chip by dispersing conductive particles in glue to replace the solder paste in the prior art. On the one hand, the high-temperature process of solder paste reflow soldering can be avoided, the high-temperature resistance requirements for the materials selected for the LED chip and the array substrate can be reduced, and the influence of the thermal stress remaining in the high-temperature process can be reduced. On the other hand, different glue materials can be selected according to different application requirements, and the material selection is diversified, and the flexible application degree of the process is high.

Description

Technical Field

[0001] The present invention relates to the field of display technologies, and particularly to a method for fixing an LED chip and an LED panel. Background Art

[0002] Mini / Mirco LED (Mini / Mirco Light-Emitting Diode) displays have attracted increasing attention due to their advantages in aspects such as contrast ratio, lifespan, and energy consumption. Currently, after an LED chip is transferred onto an array substrate, the chip is mainly fixed on the substrate by means of solder paste reflow soldering. The reflow soldering temperature is usually higher than 200°C. The high-temperature treatment poses more stringent requirements on the heat resistance of the materials of the device and the array substrate. At the same time, the influence of thermal stress at high temperatures may lead to poor reliability of the device bonding.

[0003] Therefore, the existing die bonding process for LED chips needs to be improved. Summary of the Invention

[0004] Embodiments of the present invention provide a method for fixing an LED chip and an LED panel to solve the technical problem that the existing method for fixing an LED chip involves a high-temperature process of a solder paste reflow bar, resulting in high requirements for the high-temperature resistance performance of the LED chip and the array substrate.

[0005] To solve the above problems, the technical solutions provided by the present invention are as follows:

[0006] Embodiments of the present invention provide a method for fixing an LED chip, including:

[0007] S10, placing an array substrate including a plurality of pads in a first cavity;

[0008] S20, coating an adhesive on the pads, where the adhesive includes glue and conductive particles dispersed in the glue;

[0009] S30, placing the LED chip on the pads coated with the adhesive;

[0010] S40, compressing the adhesive so that the conductive particles are electrically connected in the thickness direction of the array substrate;

[0011] S50, curing the adhesive.

[0012] In some embodiments of the present invention, the S40 includes:

[0013] S401, placing a transition substrate on the LED chip;

[0014] S402, evacuate the first cavity, and press down the transition substrate until a sealed second cavity is formed between the transition substrate and the array substrate;

[0015] S403, introduce gas into the first cavity, and under the action of the internal and external pressure difference in the second cavity, the conductive particles are uniformly compressed.

[0016] In some embodiments of the present invention, the transition substrate includes a substrate body for contacting the LED chip and a sealing ring located on four sides of the substrate body. In S402:

[0017] Press down the substrate body until the substrate body, the sealing ring and the array substrate together form the second cavity, wherein the LED chip and the adhesive are located in the second cavity.

[0018] In some embodiments of the present invention, at least one air hole that can be opened or closed is provided on the substrate body. After S50, the die bonding method further includes:

[0019] Open the air hole and remove the transition substrate.

[0020] In some embodiments of the present invention, the compression rate of the conductive particles is 15% - 30%.

[0021] In some embodiments of the present invention, after the conductive particles are compressed, the conductive particles on the side of the adhesive close to the pad contact the pad, and the conductive particles on the side of the adhesive away from the pad contact the LED chip.

[0022] In some embodiments of the present invention, the curing temperature of the adhesive is 80°C - 120°C.

[0023] In some embodiments of the present invention, the way to cure the adhesive includes at least one of thermal curing and light curing.

[0024] In some embodiments of the present invention, the mass ratio between the conductive particles and the glue is 1% - 3%.

[0025] The embodiments of the present invention also provide an LED panel prepared by using the die bonding method of the LED chip in any of the above embodiments. The LED panel includes:

[0026] An array substrate, including a plurality of pads;

[0027] An adhesive layer, disposed on the pads. The adhesive layer includes glue and conductive particles dispersed in the glue;

[0028] An LED chip, bonded and connected to the pads through the adhesive layer.

[0029] The beneficial effects of the present invention are as follows: An embodiment of the present invention provides a method for fixing an LED chip and an LED panel. The method for fixing the chip includes: S10, placing an array substrate including a plurality of pads in a first cavity; S20, coating an adhesive on the pads, the adhesive including glue and conductive particles dispersed in the glue; S30, placing the LED chip on the pads coated with the adhesive; S40, compressing the adhesive so that the conductive particles are electrically connected in the thickness direction of the array substrate; S50, curing the adhesive. The method for fixing an LED chip provided by the embodiment of the present invention realizes the fixing of the LED chip by dispersing conductive particles in glue to replace the solder paste in the prior art. On the one hand, it can avoid the high-temperature process of solder paste reflow soldering, reduce the high-temperature resistance requirements for the materials selected for the LED chip and the array substrate, and reduce the influence of the thermal stress remaining in the high-temperature process. On the other hand, different glue materials can be selected according to different application requirements, with a wide variety of material selections and high flexibility in the application of the process. Description of the Drawings

[0030] Figure 1 It is a schematic structural diagram of the LED panel provided by the embodiment of the present invention;

[0031] Figure 2 It is a schematic flow chart of the steps of the method for fixing an LED chip provided by the embodiment of the present invention;

[0032] Figure 3 It is a schematic structural diagram of the chip fixing device when evacuating the first cavity provided by the embodiment of the present invention;

[0033] Figure 4 It is a schematic structural diagram of the sealed second cavity provided by the embodiment of the present invention;

[0034] Figure 5 It is a schematic structural diagram of the chip fixing device when introducing gas into the first cavity provided by the embodiment of the present invention;

[0035] Figure 6 It is a schematic structural diagram of releasing the sealed state between the transition substrate and the array substrate provided by the embodiment of the present invention.

[0036] Figure 7 It is a schematic structural diagram of the LED display panel after removing the transition substrate provided by the embodiment of the present invention. Detailed Embodiments

[0037] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0038] In the description of the present application, it should be understood that the orientation or positional relationship indicated by terms such as "thickness", "upper", "lower", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features.

[0039] As Figure 1 shown, an embodiment of the present invention provides an LED panel 100, and the LED panel includes an array substrate 10 and an LED chip 20. The array substrate 10 includes a pixel driving circuit (not shown in the figure) for driving the LED chip 20 to emit light. The array substrate 10 further includes a pad 11, and the pad 11 is electrically connected to the pixel driving circuit. The LED chip 20 is connected to the pad 11 by bonding to achieve electrical connection with the pixel driving circuit.

[0040] Specifically, the LED panel 100 further includes an adhesive layer 30, the adhesive layer 30 is disposed on the pad 11, and the LED chip 20 is bonded to the pad 11 through the adhesive layer 30. The LED chip 20 can be any one of a Mini LED chip and a Micro LED chip. The LED panel can be an LED backlight panel or an LED display panel. When the LED panel 100 is an LED backlight panel, the LED chip 20 can provide a backlight source for a liquid crystal display panel, a quantum dot display panel, etc.; when the LED panel 100 is an LED display panel, the LED chip 20 can directly serve as a light-emitting unit for light-emitting display.

[0041] The adhesive layer 30 is cured by an adhesive. The adhesive includes glue and conductive particles dispersed in the glue. The shape of the conductive particles includes spherical, and the conductive particles can be selected from gold-plated particles. The glue has bonding properties, and the glue includes but is limited to at least one of epoxy resin, acrylic resin and other materials. Since the adhesive still needs to be cured, the adhesive also includes a curing agent, and the curing temperature of the adhesive is 80°C to 120°C, and the curing temperature includes but is not limited to 80°C, 90°C or 95°C. Within this curing temperature range, the solid crystal process of the LED chip will not damage the array substrate and the LED chip. Compared with the 200°C solid crystal process required for solder paste reflow, the embodiment of the present invention can reduce the temperature resistance requirements for the materials of the LED chip and the array substrate, and can avoid the high temperature process of solder paste reflow, thereby reducing the residual stress influence of the high temperature process.

[0042] The selection of the glue and the curing agent can be adjusted according to the temperature, humidity, illumination, heat dissipation and other conditions when the LED panel is working. The conductive particles include but are not limited to spherical conductive particles. For example, the conductive particles can be gold balls, the conductive particles include a gold-nickel plating layer and a resin, and the glue is a liquid glue, and the glue includes epoxy resin or acrylic resin.

[0043] The conductive particles have uniform particle sizes, certain compressibility and good dispersibility. The mixing ratio of the conductive particles is adjusted according to the particle size and density of the conductive particles. After the adhesive is compressed and cured, the conductive particles are conductive in the thickness direction but not in the horizontal direction. The mass ratio between the conductive particles and the glue is 1% to 3%. Specifically, they can be mixed in a ratio of 100 grams of glue to 1 to 3 grams of gold balls. The conductive particles and the glue can be mixed evenly by rotating and stirring. The particle size of the conductive particles can be selected according to the thickness of the cured adhesive layer and the compression performance of the conductive particles.

[0044] See also Figure 2 and Figure 3 The embodiment of the present invention further provides a method for bonding LED chips, comprising: S10, placing an array substrate 10 including a plurality of pads in a first cavity 200 (the pads are not Figure 3 ); S20, applying an adhesive 30' on the pad, wherein the adhesive 30' includes glue and conductive particles dispersed in the glue; S30, placing the LED chip 20 on the pad coated with the adhesive 30'; S40, compressing the adhesive 30' so that the conductive particles are conductive in the thickness direction of the array substrate 10; S50, curing the adhesive 30'.

[0045] The die bonding method of the LED chip provided by the embodiment of the present invention mixes conductive particles with glue, coats them on the pads of the array substrate, and realizes the electrical connection between the LED chip and the array substrate by compressing the conductive particles, and cures the glue to bond and fix the LED chip, which can avoid the high-temperature die bonding process of solder paste reflow soldering in the prior art, reduce the requirement for the materials used in the LED chip and the array substrate to be heat-resistant, and at the same time can also reduce the influence of residual stress in the high-temperature process.

[0046] Specifically, in the step S20, an adhesive is prepared by mixing conductive particles and glue in a mixing ratio of 100:3 by mass, and is coated on the pads of the array substrate 10 by means of screen printing or dispensing.

[0047] After transferring the LED chip 20 to the array substrate 10, it should be noted that premature curing of the adhesive must be avoided during the transfer. For example, when selecting the laser transfer method, light energy is involved and will irradiate the glue. If there is a photocuring reaction in the glue or the curing agent in the glue, when selecting the laser energy, the light source of the corresponding wavelength should be avoided. For example, if the glue is a UV-curable glue, the light source on the device can be selected as a red light source. If the glue is a heat-curable glue, attention should be paid to controlling the heat generation of the devices on the equipment to avoid heat transfer to the adhesive and premature curing.

[0048] Please refer to Figure 4 and Figure 5 , when compressing the adhesive 30', the internal and external pressure difference of the die bonding equipment can be used to uniformly extrude the adhesive, so as to achieve the effect that the conductive particles are in contact with the pads of both the LED chip 20 and the array substrate 10 after compression. In the embodiment of the present invention, the die bonding equipment for the LED chip involved in the die bonding process of the LED chip includes a first cavity 200, and the die bonding process of the LED chip is carried out in the first cavity 200. The equipment also includes a transition substrate 40, and the transition substrate 40 includes a substrate body 41 and sealing rings 42 located on the four sides of the substrate body 41.

[0049] In the step S40, the process of compressing the adhesive 30' includes: S401, placing a transition substrate 40 on the LED chip 20, as Figure 3 shown; S402, evacuating the first cavity 200 and pressing down the transition substrate 40 until the transition substrate 40 and the array substrate 10 form a closed second cavity 400; S403, introducing air into the first cavity 200, and under the action of the internal and external pressure difference in the second cavity 400, the conductive particles are uniformly compressed, as Figure 5As shown. After the conductive particles are compressed, the conductive particles on the side of the adhesive 30' close to the pad 11 are in contact with the pad 11, and the conductive particles on the side of the adhesive 30' away from the pad 11 are in contact with the LED chip 20, so as to achieve the purpose of electrically connecting the LED chip 20 and the array substrate 10.

[0050] In an embodiment of the present invention, the compression ratio of the conductive particles is 15% to 30%. In other words, the ratio of the thickness of the conductive particles after compression to the thickness before compression is 70% to 85%, that is, the ratio of the thickness of the adhesive layer formed by the adhesive to the thickness of the adhesive coated on the pad is 70% to 85%.

[0051] Specifically, the downward movement of the transition substrate 40 can be controlled by mechanical pressure. When the gas environment in the first cavity 200 reaches a certain negative pressure, the substrate body 41 is pressed down until the substrate body 41, the sealing ring 42 and the array substrate 10 together form the closed second cavity 400. Since the first cavity 200 has been evacuated before pressing down the transition substrate 40, when the second cavity 400 forms a closed environment, the gas environment inside it is a vacuum environment. Since the application of mechanical pressure is mainly to make the transition substrate 40 move downward and will not completely compress the conductive particles below, the conductive particles still need to be further compressed to achieve the purpose of electrically connecting the LED chip 20 and the array substrate 10.

[0052] As Figure 5 shown, after the closed second cavity 400 is formed, since the gas environments inside and outside the second cavity 400 are both the same vacuum environment and there is no pressure difference, the conductive particles in the second cavity 400 will not be compressed. Therefore, after the closed second cavity 400 is formed, gas can be introduced into the first cavity 200. At this time, the second cavity 400 is a sealed vacuum environment, so there will be a pressure difference between the inside and outside environments of the second cavity 400. Under the action of the pressure difference between the inside and outside of the second cavity 400, the substrate body 41 will be subjected to a uniform gas pressure in the thickness direction, thereby uniformly squeezing the conductive particles and conducting the LED chip 20 and the array substrate 10. The gas introduced includes but is not limited to nitrogen, other inert gases or the atmosphere.

[0053] The magnitude of the vacuum degree mentioned above can be determined according to the compression condition of the conductive particles verified by different vacuum degree tests, but it is necessary to ensure that the compressed conductive particles can simultaneously contact the pads of the LED chip and the array substrate, that is, to ensure that the compressed conductive particles are conductive in the thickness direction of the array substrate 10.

[0054] Furthermore, as Figure 4As shown, the substrate body 41 is provided with at least one openable or closed air hole 401. Specifically, a cover body adapted to the air hole 401 can be provided on the substrate body 41, and the cover body covers the air hole 401 or opens the air hole 401 according to actual needs.

[0055] The position and number of the air holes 401 can be optimized according to actual application conditions. The purpose of providing the air holes 401 is to release the sealing state between the transition substrate 40 and the array substrate 10 after the adhesive is cured, so as to facilitate safe removal of the transition substrate 40 .

[0056] It is understandable that before the conductive particles are compressed, the pores 401 are in a blocked state so that the formed second cavity 400 is in a closed vacuum environment. After the conductive particles are compressed, the entirety formed by the pressed transition substrate 40 and the array substrate 10 is light-cured or heat-cured according to the characteristics of the glue. After the curing is completed, the pores 401 are opened so that the gas environment inside and outside the second cavity 400 is consistent. Finally, the transition substrate 40 is removed, and the LED chip bonding process is completed to obtain an LED panel. Figure 6 and Figure 7 shown.

[0057] The LED chip solid crystal method provided by the embodiment of the present invention and the LED panel prepared by the method achieve the LED chip solid crystal by dispersing conductive particles in glue to replace the solder paste in the prior art. On the one hand, it can avoid the high temperature process of solder paste reflow soldering, reduce the high temperature resistance requirements for the materials selected for LED chips and array substrates, and reduce the impact of thermal stress residual from the high temperature process. On the other hand, different glue materials can be selected according to different application requirements, which has diversity in material selection and a high degree of flexible application of the process.

[0058] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0059] The above is a detailed introduction to a LED chip bonding method provided in an embodiment of the present invention and an LED panel prepared by the bonding method. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the technical solutions and core ideas of the present invention. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for die - bonding an LED chip, characterized in that, it includes: S10, placing an array substrate including a plurality of pads in a first cavity; S20, coating an adhesive on the pads, the adhesive including glue and conductive particles dispersed in the glue; S30, placing the LED chip on the pads coated with the adhesive; S40, compressing the adhesive so that the conductive particles are electrically connected in the thickness direction of the array substrate; S50, curing the adhesive; wherein, the S40 includes: S401, placing a transition substrate on the LED chip, the transition substrate including a substrate body for contacting the LED chip and sealing rings located on four sides of the substrate body; S402, evacuating the first cavity and pressing down the substrate body until the substrate body, the sealing rings and the array substrate form a sealed second cavity, and the LED chip and the adhesive are located in the second cavity; S403, introducing gas into the first cavity, and under the action of the internal - external pressure difference in the second cavity, the conductive particles are uniformly compressed.

2. The method for die - bonding an LED chip according to claim 1, characterized in that, at least one openable or closable air hole is provided on the substrate body, and after the S50, the die - bonding method further includes: opening the air hole and removing the transition substrate.

3. The method for die - bonding an LED chip according to claim 1, characterized in that, the compression ratio of the conductive particles is 15% - 30%.

4. The method for die - bonding an LED chip according to claim 3, characterized in that, after the conductive particles are compressed, the conductive particles on the side of the adhesive close to the pads contact the pads, and the conductive particles on the side of the adhesive away from the pads contact the LED chip.

5. The method for die - bonding an LED chip according to claim 1, characterized in that, the curing temperature of the adhesive is 80°C - 120°C.

6. The method for die - bonding an LED chip according to claim 5, characterized in that, the way of curing the adhesive includes at least one of thermal curing and light curing.

7. The method for die - bonding an LED chip according to claim 1, characterized in that, the mass ratio between the conductive particles and the glue is 1% - 3%.

8. An LED panel, characterized in that, the LED panel is prepared by using the method for die - bonding an LED chip according to any one of claims 1 - 7, and the LED panel includes: an array substrate including a plurality of pads; an adhesive layer provided on the pads, the adhesive layer including glue and conductive particles dispersed in the glue; an LED chip bonded and connected to the pads through the adhesive layer.

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