KR20230165655A - Display module including micro light emitting diodes - Google Patents

Abstract

A display module is disclosed. The display module includes a substrate provided with a plurality of light-emitting diodes, a plurality of electrode pads to which electrodes of the plurality of light-emitting diodes are connected, and an adhesive layer for fixing the plurality of light-emitting diodes to the substrate. The adhesive layer includes a non-conductive polymer resin, It may include a flux agent mixed in a non-conductive polymer resin and a plurality of conductive particles dispersed in the non-conductive polymer resin and connecting the electrodes of the plurality of light emitting diodes and the plurality of electrode pads.

Description

Display module including micro light emitting diodes {DISPLAY MODULE INCLUDING MICRO LIGHT EMITTING DIODES}

This disclosure relates to a display module including micro light emitting diodes.

The display panel includes a substrate with a plurality of thin film transistors (TFTs) and a plurality of light emitting diodes mounted on the substrate.

Many of the light emitting diodes may be inorganic light emitting diodes that emit light on their own. Multiple light emitting diodes operate on a pixel or sub-pixel basis to express various colors. The operation of each pixel or subpixel is controlled by multiple TFTs. Each light emitting diode emits a different color, such as red, green, and blue.

According to an embodiment of the present disclosure, a display module having reliable bonding strength between an electrode of a micro light emitting diode and an electrode pad of a substrate can be provided.

According to an embodiment of the present disclosure, it may include a plurality of light emitting diodes, a substrate, and an adhesive layer. The substrate may be provided with a plurality of electrode pads to which electrodes of the plurality of light emitting diodes are connected. The adhesive layer may fix the plurality of light emitting diodes to the substrate.

The adhesive layer may include a non-conductive polymer resin, a flux agent mixed with the non-conductive polymer resin, and a plurality of conductive particles. The plurality of conductive particles may be dispersed within the non-conductive polymer resin. The plurality of conductive particles may electrically and physically connect the electrodes of the plurality of light emitting diodes and the plurality of electrode pads.

The flux agent may be made of a material that improves the wetting properties of the plurality of conductive particles.

The plurality of conductive particles may include a plurality of first conductive particles and a plurality of second conductive particles. The second plurality of conductive particles may have higher wettability than the first plurality of conductive particles.

1 is a block diagram showing a display device according to an embodiment of the present disclosure.
Figure 2 is a plan view showing a display module according to an embodiment of the present disclosure.
FIG. 3 is a diagram schematically showing a cross section of a pixel provided in a display module according to an embodiment of the present disclosure.
FIG. 4 is a diagram illustrating an example of aligning a relay substrate on which micro LEDs are arranged with respect to a substrate before transferring it to the substrate.
Figure 5 is a diagram showing an example of transferring micro LEDs arranged on a relay substrate to a substrate using a laser transfer method.
Figure 6 is a diagram showing an example of heat-compressing a micro LED transferred to a substrate using a pressing member.
FIG. 7 is a diagram schematically showing a cross section of a pixel provided in a display module according to an embodiment of the present disclosure.
FIG. 8 is a diagram schematically showing a cross section of a pixel provided in a display module according to an embodiment of the present disclosure.
FIG. 9 is a diagram schematically showing a cross section of a pixel provided in a display module according to an embodiment of the present disclosure.
FIG. 10 is a diagram schematically showing a cross section of a pixel provided in a display module according to an embodiment of the present disclosure.
FIG. 11 is a diagram schematically showing a cross section of a pixel provided in a display module according to an embodiment of the present disclosure.
Figure 12 is a diagram showing an example of heat-compressing a micro LED transferred to a substrate using a pressing member.
FIG. 13 is a diagram illustrating an example in which first conductive particles and second conductive particles dispersed in an adhesive layer are gathered between an electrode of a micro LED and an electrode pad of a substrate to form solder.

Hereinafter, various embodiments will be described in more detail with reference to the attached drawings. The embodiments described herein may be modified in various ways. Specific embodiments may be depicted in the drawings and described in detail in the detailed description. However, the specific embodiments disclosed in the attached drawings are only intended to facilitate understanding of the various embodiments. Accordingly, the technical idea is not limited to the specific embodiments disclosed in the attached drawings, and should be understood to include all equivalents or substitutes included in the spirit and technical scope of the present disclosure.

In the present disclosure, terms including ordinal numbers, such as first, second, etc., may be used to describe various components, but these components are not limited by the above-described terms. The above-mentioned terms are used only for the purpose of distinguishing one component from another.

In the present disclosure, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof. When a component is said to be "connected" or "connected" to another component, it is understood that it may be directly connected to or connected to the other component, but that other components may exist in between. It should be. On the other hand, when it is mentioned that a component is “directly connected” or “directly connected” to another component, it should be understood that there are no other components in between.

In the present disclosure, the expression 'same' means not only complete matching but also including a degree of difference taking into account the processing error range.

In addition, when describing the present disclosure, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present disclosure, the detailed description thereof is abbreviated or omitted.

According to an embodiment of the present disclosure, a display module may include a plurality of light emitting diodes for displaying images. The display module may include a flat display panel or a curved display panel.

According to an embodiment of the present disclosure, the light emitting diode included in the display module may be an inorganic light emitting diode with a size of 100 μm or less. For example, the inorganic light emitting diode may be a micro LED or mini LED, but is not limited thereto. Inorganic light emitting diodes have higher brightness, luminous efficiency, and longer lifespan than organic light emitting diodes (hereinafter referred to as 'OLED'). An inorganic light-emitting diode may be a semiconductor chip that can emit light on its own when power is supplied. Inorganic light-emitting diodes have fast response speed, low power, and high brightness. If the inorganic light emitting diode is a micro LED, the efficiency of converting electricity into photons may be higher compared to LCD or OLED. For example, micro LEDs can have higher “brightness per watt” compared to LCD or OLED displays. Accordingly, micro LED can produce the same brightness with about half the energy compared to LED or OLED that exceeds 100㎛. Micro LED is capable of realizing high resolution, excellent color, contrast, and brightness, so it can accurately express a wide range of colors and produce a clear screen even outdoors, which is brighter than indoors. Micro LED is resistant to burn-in and generates less heat, ensuring a long lifespan without deformation.

According to an embodiment of the present disclosure, the light emitting diode may be in the form of a flip chip in which an anode and a cathode electrode are disposed on opposite sides of the light emitting surface.

According to an embodiment of the present disclosure, a TFT (Thin Film Transistor) layer with a TFT (Thin Film Transistor) circuit may be disposed on the first side of the substrate (eg, the front surface of the substrate). The substrate may have a power supply circuit that supplies power to the TFT circuit, a data drive driver, a gate drive driver, and a timing controller that controls each drive driver disposed on the second side (e.g., the rear surface of the substrate). there is. The substrate may have multiple pixels arranged on the TFT layer. Each pixel can be driven by a TFT circuit.

According to one embodiment of the present disclosure, the TFT formed on the TFT layer may be a low-temperature polycrystalline silicon (LTPS) TFT, a low-temperature polycrystalline oxide (LTPO) TFT, or an oxide TFT.

According to an embodiment of the present disclosure, the substrate is a glass substrate, a synthetic resin series having flexibility (e.g., polyimide (PI), polyethylene terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), It may be a PC (polycarbonate, etc.) substrate, or a ceramic substrate.

According to an embodiment of the present disclosure, the TFT layer of the substrate may be formed integrally with the first side of the substrate, or may be manufactured in the form of a separate film and attached to the first side of the substrate.

According to one embodiment of the present disclosure, the first surface of the substrate may be divided into an active area and an inactive area. The active area may be an area occupied by the TFT layer among the entire area of the first side of the substrate. The inactive area may be an area excluding the active area among the entire area of the first side of the substrate.

According to an embodiment of the present disclosure, the edge area of the substrate may be the outermost area of the substrate. For example, the edge area of the substrate may include an area corresponding to a side surface of the substrate, a partial area of the first surface of the substrate adjacent to the side surface, and a partial area of the second surface of the substrate. A plurality of side wirings may be disposed in the edge area of the substrate to electrically connect the TFT circuit on the first side of the substrate and the driving circuit on the second side of the substrate.

According to one embodiment of the present disclosure, the substrate may be formed in a quadrangle type. For example, the substrate may be formed as a rectangle or square.

According to an embodiment of the present disclosure, the TFT provided on the substrate includes, for example, LTPS TFT (Low-temperature polycrystalline silicon TFT), oxide TFT, Si TFT (poly silicon, a-silicon), organic TFT, graphene TFT, etc. It can also be implemented as: TFT can also be applied by making only a P-type (or N-type) MOSFET in the Si wafer CMOS process.

According to an embodiment of the present disclosure, the substrate included in the display module may omit the TFT layer on which the TFT circuit is formed. In this case, multiple micro IC chips that function as TFT circuits may be mounted on the first side of the substrate. In this case, a plurality of micro ICs may be electrically connected to a plurality of light emitting diodes arranged on the first side of the substrate through wiring.

According to an embodiment of the present disclosure, the pixel driving method of the display module may be an active matrix (AM) driving method or a passive matrix (PM) driving method.

According to an embodiment of the present disclosure, the display module can be installed and applied to wearable devices, portable devices, handheld devices, and electronic products or battlefields that require various displays.

According to an embodiment of the present disclosure, a plurality of display modules are connected in a grid arrangement to display a monitor for a personal computer, a high-resolution television, signage (or digital signage), an electronic display, etc. A display device can be formed.

According to one embodiment of the present disclosure, one pixel may include multiple light emitting diodes. In this case, one light emitting diode may be a subpixel. In the present disclosure, one 'light emitting diode', one 'micro LED', and one 'subpixel' can be used interchangeably with the same meaning.

Below, with reference to the attached drawings, an embodiment of the present disclosure will be described in detail so that those skilled in the art can easily implement it. However, one embodiment of the present disclosure may be implemented in various different forms, and is not limited to the one embodiment of the present disclosure described here. In order to clearly describe an embodiment of the present disclosure in the drawings, parts that are not related to the description of the present disclosure are omitted, and similar parts are given similar reference numerals throughout the specification.

Hereinafter, a display module and a display device including the same according to an embodiment of the present disclosure will be described with reference to the drawings.

1 is a block diagram showing a display device according to an embodiment of the present disclosure.

Referring to FIG. 1, a display device 1 according to an embodiment of the present disclosure may include a display module 3 and a processor 5.

The display module 3 according to an embodiment of the present disclosure can display various images. Here, video is a concept that includes still images and/or moving images. The display module 3 can display various images such as broadcast content, multimedia content, etc. Additionally, the display module 3 may display a user interface and icons.

The display module 3 may include a display panel 10 and a display driver integrated circuit (IC) 7 for controlling the display panel 10.

The display driver IC 7 may include an interface module 7a, a memory 7b (eg, buffer memory), an image processing module 7c, or a mapping module 7d. The display driver IC 7, for example, transmits image information including image data or an image control signal corresponding to a command for controlling the image data to another device of the display device 1 through the interface module 7a. Can be received from components. For example, image information may be received from the processor 5 (e.g., a main processor (e.g., an application processor) or an auxiliary processor (e.g., a graphics processing unit) that operates independently of the functions of the main processor.

The display driver IC 7 may store at least some of the received image information in the memory 7b, for example, on a frame basis. For example, the image processing module 7c pre-processes or post-processes at least a portion of the image data (e.g., adjusts resolution, brightness, or size) based on the characteristics of the image data or the characteristics of the display panel 10. can be performed. The mapping module 7d may generate a voltage value or current value corresponding to the image data pre- or post-processed through the image processing module 7c. According to one embodiment, the generation of a voltage value or a current value is based on, for example, the properties of the pixels of the display panel 10 (e.g., an array of pixels (RGB stripe structure or RGB pentile structure), or the size of each subpixel). ) can be performed based at least in part on At least some pixels of the display panel 10 are, for example, driven based at least in part on the voltage value or current value to display visual information (e.g., text, image, or icon) corresponding to the image data on the display panel ( 10) can be displayed.

The display driver IC 7 may transmit a driving signal (eg, a driver driving signal, a gate driving signal, etc.) to the display based on the image information received from the processor 5.

The display driver IC 7 can display an image based on the image signal received from the processor 5. As an example, the display driver IC 7 generates a driving signal for a plurality of subpixels based on an image signal received from the processor 5 and displays an image by controlling the emission of the plurality of subpixels based on the driving signal. can do.

The display module 3 may further include a touch circuit (not shown). The touch circuit may include a touch sensor and a touch sensor IC for controlling the touch sensor. The touch sensor IC may control the touch sensor, for example, to detect a touch input or hovering input for a designated location on the display panel 10. For example, the touch sensor IC can detect a touch input or a hovering input by measuring a change in a signal (eg, voltage, light amount, resistance, or charge amount) for a specified location on the display panel 10. The touch sensor IC may provide information (e.g., location, area, pressure, or time) regarding the detected touch input or hovering input to the processor 5. According to one embodiment, at least a portion of the touch circuit (e.g., touch sensor IC) is part of the display driver IC 7, or the display panel 10, or another component disposed outside the display module 3 ( e.g. co-processor).

The processor 5 is a digital signal processor (DSP), microprocessor, graphics processing unit (GPU), artificial intelligence (AI) processor, neural processing unit (NPU), and TCON that processes digital image signals. (time controller), but is not limited to this, and may be implemented as a central processing unit (CPU), micro controller unit (MCU), micro processing unit (MPU), controller, or application. It may include one or more of an application processor (AP), a communication processor (CP), or an ARM processor, or may be defined by these terms. In addition, the processor 5 has a built-in processing algorithm. It may be implemented as a system on chip (SoC) or large scale integration (LSI), or as an application specific integrated circuit (ASIC) or field programmable gate array (FPGA).

The processor 5 can control hardware or software components connected to the processor 5 by running an operating system or application program, and can perform various data processing and calculations. Additionally, the processor 5 may load and process commands or data received from at least one of the other components into volatile memory and store various data in non-volatile memory.

Figure 2 is a plan view showing a display module according to an embodiment of the present disclosure. FIG. 3 is a diagram schematically showing a cross section of a pixel provided in a display module according to an embodiment of the present disclosure.

Referring to FIG. 2, the display module 3 may include a substrate 50 and a plurality of pixels 100 provided on the first surface of the substrate 50.

The substrate 50 may have a thin film transistor (TFT) circuit electrically connected to the plurality of pixels 100 on the first side.

Each of the plurality of pixels 100 may include at least three subpixels. The subpixel may be a micro LED, an inorganic light emitting diode. Hereinafter, for convenience, the subpixel is referred to as micro LED. Here, micro LED can be defined as an LED with a size of 100㎛ or less. The “size” may be the diameter in a given direction on the plane of a normally mounted micro LED. In one example, the given direction may be horizontal or vertical, and in another example, the given direction may be the direction having the largest diameter in a plane.

Referring to FIG. 3, the pixel 100 includes a first micro LED 110 that emits light in a red wavelength band, a second micro LED 120 that emits light in a green wavelength band, and a blue wavelength band. It may include a third micro LED 130.

In the pixel 100, a first micro LED 110, a second micro LED 120, and a third micro LED 130 may be disposed in a pixel area defined on the substrate 50. A plurality of TFTs for driving the first to third micro LEDs 110, 120, and 130 may be disposed in areas of the pixel area that are not occupied by the first to third micro LEDs 110, 120, and 130.

The first to third micro LEDs 110, 120, and 130 may be arranged in a row at regular intervals, but are not limited to this. For example, the first to third micro LEDs 110, 120, and 130 may be arranged in an L shape or in a pentile RGBG manner. The Pentile RGBG method is a method of arranging the number of red, green, and blue subpixels in a ratio of 1:1:2 (RGBG), using the cognitive characteristic of humans to identify green better than blue. The Pentile RGBG method can increase yield and lower unit costs. The Pentile RGBG method can achieve high resolution on a small screen.

The light emission characteristics of the first micro LED 110 may be the same as those of the second and third micro LEDs 120 and 130. The light emitted from the first micro LED 110 may have the same color as the light emitted from the second and third micro LEDs 120 and 130. In one example, the first to third micro LEDs 110, 120, and 130 may all emit blue light, green light, or red light. Accordingly, monochromatic light of red, green, or blue may be emitted from the pixel 100, or light mixed with red, green, or blue may be emitted.

The display module 3 may be a touch screen combined with a touch sensor, a flexible display, a rollable display, and/or a three-dimensional display.

The TFT provided on the substrate 50 includes amorphous silicon (a-Si) TFT, low temperature polycrystalline silicon (LTPS) TFT, low temperature polycrystalline oxide (LTPO) TFT, hybrid oxide and polycrystalline silicon (HOP) TFT, and liquid crystalline polymer (LCP). ) It may be TFT, or OTFT (organic TFT).

Referring to FIG. 3, a plurality of electrode pads 51 and 52 may be arranged in pairs at intervals on the first surface 50a of the substrate 50. The plurality of electrode pads 51 and 52 may be electrically connected to the first to third micro LEDs 110, 120, and 130, respectively.

For example, a pair of electrodes 111 and 112 provided on the first micro LED 110 may be connected to a pair of electrode pads 51 and 52 of the substrate 50. The pair of electrodes 111 and 112 may be respectively electrically and physically connected to the pair of electrode pads 51 and 52 of the substrate 50 by solder 30 .

Solder 30 may be tin (Sn) or indium (In). Solder 30 is made of tin (Sn), silver (Ag), indium (In), copper (Cu), nickel (Ni), gold (Au), bismuth (Bi), aluminum (Al), zinc (Zn), and gallium (Ga).

The first surface 50a of the substrate 50 may be covered with an adhesive layer 70 . In this case, the adhesive layer 70 may cover the solder 30 and the plurality of electrode pads 51 and 52.

A pair of electrodes of the second micro LED 120 and the third micro LED 130 may be electrically and physically connected to a corresponding pair of electrode pads of the substrate 50 by solder 30.

The first micro LED 110 may be in the form of a flip chip. For example, the first micro LED 110 may have a pair of electrodes 111 and 112 disposed on the opposite side 110b of the light emitting side 110a. The second micro LED 120 and the third micro LED 130 may have a flip chip form that is substantially the same as the first micro LED 110. In this case, the first to third micro LEDs 110, 120, and 130 may all have the same size, but are not limited thereto. For example, at least one of the first to third micro LEDs 110, 120, and 130 may have a different size from the others.

The substrate 50 may be provided with electrode pads 51 and 52 to which the electrodes of the first to third micro LEDs 110, 120, and 130 are electrically connected, respectively.

The electrode pads 51 and 52 of the substrate 50 may each be electrically connected to the TFT circuit of the TFT layer through via hole wiring.

The electrode pads 51 and 52 of the substrate 50 may be electrically connected to the electrodes 111 and 112 of the first micro LED 110, respectively. The electrode pads 51 and 52 of the substrate 50 are, for example, titanium/aluminum/titanium (Mo/Ti/Mo) alloy, molybdenum/aluminum/molybdenum (Mo/Al/Mo) alloy, nickel/gold (Ni) /Au) alloy, may be made of indium (In), nickel (Ni), or copper (Cu).

The electrodes 111 and 112 of the first micro LED 110, which are electrically connected to the electrode paddles 51 and 52 of the substrate 50 by solder 30, are made of nickel/gold (Ni/Au) alloy, titanium/ It may be made of gold (Ti/Au) alloy, copper (Cu), copper/nickel (Cu/Ni) alloy, or tin/silver (Sn/Ag) alloy.

The first surface 50a of the substrate 50 may be covered by the adhesive member 70. The adhesive layer 70 may be laminated on the first surface 50a of the substrate 50 before the first to third micro LEDs 110, 120, and 130 are transferred to the substrate 50. In this case, the adhesive layer 70 may cover the plurality of electrode pads 51 and 52 arranged on the first surface 50a of the substrate 10.

The adhesive layer 70 may include a non-conductive polymer resin and a flux agent. The adhesive layer 70 may be molded into a film shape.

The non-conductive polymer resin may be an insulating polymer resin having thermosetting properties or UV (ultraviolet) curing properties.

The non-conductive polymer resin may include, for example, an epoxy-based curable resin composition or an acrylic-based curable resin composition.

The epoxy-based thermosetting resin composition may include, for example, a compound or resin having two or more epoxy groups in the molecule, an epoxy curing agent, a film forming component, etc. A compound or resin having two or more epoxy groups in the molecule may be in a liquid or solid state.

For example, compounds or resins having two or more epoxy groups in the molecule include bifunctional epoxy resins such as bisphenol A-type epoxy resin and bisphenol F-type epoxy resin, and novolak-type epoxy resins such as phenol novolak-type epoxy resin and cresol novolak-type epoxy resin. It may be a resin, etc.

As an epoxy curing agent, for example, an amine-based curing agent, an imidazole-based curing agent, an acid anhydride-based curing agent, a sulfonium cationic curing agent, etc. may be used.

As a film forming component, for example, an epoxy compound, a phenoxy resin compatible with an epoxy resin, an acrylic resin, etc. can be used.

The acrylic thermosetting resin composition may include, for example, a (meth)acrylate monomer, a film-forming resin, an inorganic filler such as silica, a silane coupling agent, a radical polymerization initiator, etc. As (meth)acrylate monomers, monofunctional (meth)acrylate monomers, polyfunctional (meth)acrylate monomers, or modified monofunctional monomers obtained by introducing epoxy groups, urethane groups, amino groups, ethylene oxide groups, propylene oxide groups, etc. into these monomers. Alternatively, polyfunctional (meth)acrylate monomers may be used. Additionally, (meth)acrylate monomers and other monomers capable of radical copolymerization, such as (meth)acrylic acid, vinyl acetate, styrene, and vinyl chloride, may be used in combination.

Resins for film formation of the acrylic thermosetting resin composition include phenoxy resin, polyvinyl acetal resin, polyvinyl butyral resin, alkylated cellulose resin, polyester resin, acrylic resin, styrene resin, urethane resin, and polyethylene terephthalate resin. there is.

Examples of radical polymerization initiators include organic peroxides such as benzoyl peroxide, dicumyl peroxide, and dibutyl peroxide, and azobis-based compounds such as azobisisobutyronitrile and azobisvaleronitrile.

The acrylic thermosetting resin composition may further contain, if necessary, a stress reliever such as butadiene rubber, a solvent such as ethyl acetate, a colorant, an antioxidant, an anti-aging agent, etc.

The flux agent may be made of a material that improves the wetting property of the solder 30 and prevents oxidation of the solder 30.

The flux agent may be, for example, an anhydride capable of generating a Lewis acid, or a thermal acid generator (TAG) that decomposes upon heating to generate an acid. The anhydrate may be selected to contain an acyl group. The thermal acid generator may be a sulfite-based compound. The flux agent is not limited to these and may be an inorganic flux such as zinc chloride-based or zinc chloride-ammonia chloride-based. The flux agent may be a rosin-based flux such as activated rosin or inert rosin. The flux agent may be a water-soluble flux such as salts, acids, or amines. The flux agent may be an organic flux such as glutamic acid hydrochloride or ethylenediamine stearic acid hydrochloride.

FIG. 4 is a diagram illustrating an example of aligning a relay substrate on which micro LEDs are arranged with respect to a substrate before transferring it to the substrate.

Referring to FIG. 4, solder 30 may be formed on each of the plurality of electrode pads 51 and 52 of the substrate 50.

The adhesive layer 70 may be in the form of a film and may be attached to the first surface 50a of the substrate 50 by lamination. The adhesive layer 70 may have a thickness of approximately 1㎛ to 10㎛. The adhesive layer 70 may cover the electrode pads 51 and 52 and the solder 30 on the first surface 50a of the substrate 50.

The relay substrate 80 on which the first to third micro LEDs 110, 120, and 130 are arranged is such that the first to third micro LEDs 110, 120, and 130 are respectively transferred to preset positions on the substrate 50. It can be aligned with respect to the substrate 50 so that it can be aligned. In this case, the substrate 50 serves as a target onto which the first to third micro LEDs 110, 120, and 130 are transferred, so it may be referred to as a target substrate.

The light-emitting surfaces of the first to third micro LEDs 110, 120, and 130 may be temporarily attached to the bottom of the relay substrate 80, respectively. In this case, an adhesive to which the first to third micro LEDs 110, 120, and 130 can be temporarily attached may be applied to the bottom of the relay substrate 80, or a thin film with an adhesive component may be formed.

Figure 5 is a diagram showing an example of transferring micro LEDs arranged on a relay substrate to a substrate using a laser transfer method.

Referring to FIG. 5 , the laser beam LB is irradiated with the first micro LED 110 while the relay substrate 80 aligned with the substrate 50 is brought into close contact with the substrate 50 .

As the first micro LED 110 is heated by the laser beam LB, the adhesive or thin film containing an adhesive component formed on the bottom of the relay substrate 80 may be melted by being heated by the laser beam LB. In this case, the first micro LED 110 may be separated from the bottom of the relay substrate 80.

Like the first micro LED 110, the second and third micro LEDs 120 and 130 may be separated from the bottom of the relay substrate 80 by the laser beam LB.

The first to third micro LEDs 110, 120, and 130 may be transferred to the substrate 50 by a laser transfer method, but the present invention is not limited thereto. For example, the first to third micro LEDs 110, 120, and 130 are transferred to the wafer or relay by a pick and place transfer method, a stamping transfer method, a rollable transfer method, or a fluid self-assembly transfer method. It may be transferred from the substrate 80 to the substrate 50.

Figure 6 is a diagram showing an example of thermal compression bonding of a micro LED transferred to a substrate using a pressing member.

Referring to FIG. 6 , the pressing member 90 may pressurize the first to third micro LEDs 110, 120, and 130 separated from the relay substrate 80. In this case, high temperature heat may be applied to the substrate 50 and the first to third micro LEDs 110, 120, and 130.

When the first to third micro LEDs 110, 120, and 130 are heat-compressed in this way, the electrodes located between the electrodes of the first to third micro LEDs 110, 120, and 130 and the electrode pads of the substrate 50 Solder 30 may melt. In this case, the electrodes of the first to third micro LEDs 110, 120, and 130 and the electrode pads of the substrate 50 are metal bonded by solder 30, so that physical and electrical connection can be made to each other. there is.

Additionally, the adhesive layer 70 may undergo phase decomposition between the non-conductive polymer resin and the flux agent due to the heat applied to the substrate 50. In this case, the flux agent can improve the wettability of the electrodes of the first to third micro LEDs 110, 120, and 130. Accordingly, the solder 30 can be melted during thermocompression bonding and smoothly fused to the electrodes of the first to third micro LEDs 110, 120, and 130 and the electrode pads of the substrate 50.

The adhesive layer 70 may be melted by heat applied to the substrate 50 and may have fluidity. The adhesive layer 70 that has fluidity can flow between the electrodes of the first to third micro LEDs 110, 120, and 130, and can flow between the electrode pads of the substrate 50. Between the electrodes of the first to third micro LEDs 110, 120, and 130 and between the electrode pads of the substrate 50 can be filled without gaps by the adhesive layer 70.

After the above-described thermocompression bonding, the adhesive layer 70 may be hardened when cooled to room temperature or below room temperature. Accordingly, the first to third micro LEDs 110, 120, and 130 can be firmly fixed to the substrate 50 by the hardened adhesive layer 70.

FIG. 7 is a diagram schematically showing a cross section of a pixel provided in a display module according to an embodiment of the present disclosure.

The display module 100a according to an embodiment of the present disclosure shown in FIG. 7 has substantially the same components as the display module 100 according to an embodiment of the present disclosure shown in FIG. 3 except for the adhesive layer 70a. can do.

Referring to FIG. 7 , the adhesive layer 70a may include a non-conductive polymer resin, a flux, and a pigment or dye having a black-based color. The adhesive layer 70a may be molded into a film shape.

The adhesive layer 70a can prevent light reflection by absorbing external light irradiated to the display module, and can minimize color mixing of lights of different colors emitted from micro LEDs placed adjacent to each other. Accordingly, the adhesive layer 70a can improve the contrast ratio of the display module.

In FIG. 7, the unexplained symbol 30 is solder, 51 and 52 are electrode pads, and 111 and 112 are electrodes.

FIG. 8 is a diagram schematically showing a cross section of a pixel provided in a display module according to an embodiment of the present disclosure.

The display module 100b according to an embodiment of the present disclosure shown in FIG. 8 has substantially the same components as the display module 100 according to an embodiment of the present disclosure shown in FIG. 3 except for the adhesive layer 170. can do.

Referring to FIG. 8, the adhesive layer 170 may include a non-conductive polymer resin 171 containing a flux agent, and a plurality of conductive particles 173. The adhesive layer 170 may be molded into a film shape.

The plurality of conductive particles 173 may be generally evenly distributed within the adhesive layer 170.

Among the plurality of conductive particles 173, the conductive particles 173 around the solder 30 are melted during thermal compression bonding and are melted together with the solder 30 to the electrodes of the first to third micro LEDs 110, 120, and 130. and the corresponding electrode pads of the substrate 50 may be electrically connected.

In this case, the plurality of conductive particles 173 can increase the electrical contact area between the electrodes of the first to third micro LEDs 110, 120, and 130 and the corresponding electrode pads of the substrate 50, thereby increasing the bonding yield. can be improved.

The plurality of conductive particles 173 may have various sizes, for example, about 10 nm to 1 μm, depending on the gap size of the junction and the height of the micro LED. Here, the gap size of the junction is the gap between the electrodes of the first to third micro LEDs 110, 120, and 130 and the corresponding electrode pads of the substrate 50, or the gap size between the first to third micro LEDs 110, 120, and 130. , 120, 130) and the corresponding solder 30.

The plurality of conductive particles 173 prevent or minimize short circuits between a pair of adjacent electrodes 51 and 52 and/or short circuits between a pair of electrodes 111 and 112 of the adjacent first micro LED 110. An amount equivalent to about 0.1% to 5% of the total amount of the adhesive layer 170 may be included in the adhesive layer 170.

The plurality of conductive particles 173 are at least one of tin (Sn), indium (In), copper (Cu), silver (Ag), nickel (Ni), chromium (Cr), gold (Au), and platinum (Pt). may include.

The conductive particles 173 may be in the shape of a ball. In this case, the conductive particles 173 may be coated with a conductive film on the core and the outer periphery of the core. The core may be an elastic polymer resin. The conductive film may include gold (Au), copper (Cu), or tin (Sn).

In FIG. 8, unexplained symbols 51 and 52 are electrode pads, and 111 and 112 are electrodes.

FIG. 9 is a diagram schematically showing a cross section of a pixel provided in a display module according to an embodiment of the present disclosure.

The display module 100c according to an embodiment of the present disclosure shown in FIG. 9 has substantially the same components as the display module 100b according to an embodiment of the present disclosure shown in FIG. 8 except for the adhesive layer 170a. can do.

Referring to FIG. 9 , the adhesive layer 170a may include a non-conductive polymer resin 171a containing a flux agent, a plurality of conductive particles 173a, and a pigment or dye having a black-based color. The adhesive layer 170a may be molded into a film shape.

Other than the pigment or dye having a black-based color, the remaining components of the adhesive layer 170a may be substantially the same as the adhesive layer 170 shown in FIG. 8.

The adhesive layer 170a can prevent light reflection by absorbing external light irradiated to the display module and minimize color mixing of light of different colors emitted from micro LEDs placed adjacent to each other. Accordingly, the adhesive layer 170a can improve the contrast ratio of the display module.

In FIG. 9, unexplained symbol 30 is solder, 51 and 52 are electrode pads, and 111 and 112 are electrodes.

FIG. 10 is a diagram schematically showing a cross section of a pixel provided in a display module according to an embodiment of the present disclosure.

The display module 100d according to an embodiment of the present disclosure shown in FIG. 10 has substantially the same components as the display module 100b according to an embodiment of the present disclosure shown in FIG. 8 except for the adhesive layer 270. can do.

Referring to FIG. 10, the adhesive layer 270 may include a non-conductive polymer resin paste 271 mixed with a flux agent, and a plurality of conductive particles 273 dispersed in the non-conductive polymer resin paste 271.

The adhesive layer 270 may be formed in the form of paste. After the solder 30 is formed on the electrodes of the substrate 50, the adhesive layer 270 is formed to a predetermined thickness on the first surface 50a of the substrate 50 to cover the solder 30 and the electrodes of the substrate 50. It can be applied.

The plurality of conductive particles 273 may be configured substantially the same as the plurality of conductive particles 173 in FIG. 8 .

In FIG. 10, unexplained numerals 51 and 52 are electrode pads, and 111 and 112 are electrodes.

FIG. 11 is a diagram schematically showing a cross section of a pixel provided in a display module according to an embodiment of the present disclosure. Figure 12 is a diagram showing an example of heat-compressing a micro LED transferred to a substrate using a pressing member. FIG. 13 is a diagram illustrating an example in which first conductive particles and second conductive particles dispersed in an adhesive layer are gathered between an electrode of a micro LED and an electrode pad of a substrate to form solder.

Most of the configurations of the display module 100e according to an embodiment of the present disclosure shown in FIG. 11 are similar to the display module 100b according to an embodiment of the present disclosure shown in FIG. 8, and there are differences in some configurations. There may be.

Hereinafter, in describing the display module according to an embodiment of the present disclosure shown in FIG. 11, a configuration different from the display module according to the embodiment of the present disclosure shown in FIG. 8 will be described.

Referring to FIG. 11 , the adhesive layer 370 may include a non-conductive polymer resin 371, a flux agent, and a plurality of conductive particles 373.

The adhesive layer 370 may be in the form of a film. In this case, the adhesive layer 370 may be attached to the first surface 50a of the substrate 50 using a lamination method.

The adhesive layer 370 is not limited to a film form and may be formed, for example, in a paste form. In this case, the adhesive layer 370 may be applied to the first surface 50a of the substrate 50 to a predetermined thickness.

The non-conductive polymer resin 371 may be mixed with a flux agent. The non-conductive polymer resin 371 may contain a pigment or dye having a black-based color along with a flux agent.

A plurality of conductive particles 373 may be evenly distributed within the non-conductive polymer resin 371. The plurality of conductive particles 373 may include first conductive particles 373a and second conductive particles 373b.

The first conductive particle 373a may be an alloy containing at least one of tin (Sn), silver (Ag), copper (Cu), bismuth (Bi), and cobalt (Co).

The second conductive particles 373b are formed on the substrate so that the first conductive particles 373a can be well wetted with the electrodes of the substrate 50 and/or the electrodes of the first to third micro LEDs 110, 120, and 130. 50) and/or may be made of a material that is substantially the same as or similar to the electrodes of the first to third micro LEDs 110, 120, and 130. The second conductive particles 373b may be made of, for example, gold (Au), copper (Cu), or silver (Ag).

The plurality of first and second conductive particles 373a and 373b may have various sizes, for example, about 10 nm to 1 μm, depending on the gap size of the junction and the height of the micro LED.

The plurality of conductive particles 373 move to the electrodes of the substrate 50 and/or the electrodes of the first to third micro LEDs 110, 120, and 130 within the non-conductive polymer resin 371 during thermocompression bonding. By self-assembly attached to the electrodes of the substrate 50 and/or the electrodes of the first to third micro LEDs 110, 120, and 130, the first to third micro LEDs 110 , 120, 130) and the corresponding electrode pads of the substrate 50 may be electrically connected to each other.

Referring to FIG. 12, during thermocompression bonding, the first micro LED 110 transferred to the substrate 50 is pressed by the pressing member 90. In this case, high temperature heat may be applied to the substrate 50.

The non-conductive polymer resin 371 becomes fluid as its viscosity decreases due to high-temperature heat. Accordingly, the plurality of first and second conductive particles 373a and 373b can move toward the electrode pads of the surrounding substrate 50 and the electrodes of the first to third micro LEDs 110, 120, and 130. there is.

While the plurality of first and second conductive particles 373a and 373b have high wettability to the electrode pads of the substrate 50 and the electrodes of the first to third micro LEDs 110, 120, and 130, the substrate ( The wettability may be low for other parts of 50). Accordingly, between the plurality of first and second conductive particles 373a and 373b and the electrode pads of the substrate 50 and between the plurality of first and second conductive particles 373a and 373b and the first to third micro LEDs An attractive force may act between the electrodes (110, 120, and 130), respectively.

The plurality of first and second conductive particles 373a and 373b may adhere to the electrode pads of the substrate 50 and the electrodes of the first to third micro LEDs 110, 120, and 130. The plurality of first and second conductive particles 373a and 373b gradually increase in volume to fill the space between the electrode pads of the substrate 50 and the electrodes of the first to third micro LEDs 110, 120, and 130. You can.

A plurality of first and second conductive particles 373a and 373b between the electrode pads of the substrate 50 and the electrodes of the first to third micro LEDs 110, 120, and 130 are melted by high temperature heat. You can.

In this case, a plurality of first conductive particles 373b are formed of a material similar to the electrode pads of the substrate 50 and the electrodes of the first to third micro LEDs 110, 120, and 130. The particles 373a can be more smoothly fused to the electrode pads of the substrate 50 and the electrodes of the first to third micro LEDs 110, 120, and 130.

Referring to FIG. 13, the electrodes of the first to third micro LEDs 110, 120, and 130 are stably electrically connected to the electrode pads of the substrate 50 and are robust by solder formed by aggregating a plurality of conductive particles 373. A physical connection can be established.

In addition, the non-conductive polymer resin 371 of the adhesive layer 370 can more firmly support the physical connection between the electrodes of the first to third micro LEDs 110, 120, and 130 and the electrode pads of the substrate 50. You can.

In the above, preferred embodiments of the present disclosure have been shown and described, but the present disclosure is not limited to the specific embodiments described above, and may be used in the technical field pertaining to the present disclosure without departing from the gist of the present disclosure as claimed in the claims. Of course, various modifications can be made by those with the knowledge, and these modifications should not be understood individually from the technical ideas or perspectives of the present disclosure.

3: Display module
50: substrate
51, 52: electrode pads on the substrate
70, 70a, 170, 170a, 270, 370: Adhesive layer
171, 171a, 271, 371: Non-conductive polymer resin
173, 173a, 273, 373a, 373b: conductive particles
110, 120, 130: first to third micro LEDs
111, 112: Electrodes of the first micro LED

Claims (10)

Multiple light emitting diodes;
a substrate provided with a plurality of electrode pads to which electrodes of the plurality of light emitting diodes are connected; and
It includes an adhesive layer that secures the plurality of light emitting diodes to the substrate,
The adhesive layer is,
Non-conductive polymer resin;
A flux agent mixed with the non-conductive polymer resin;
A display module comprising: a plurality of conductive particles dispersed in the non-conductive polymer resin and connecting the electrodes of the plurality of light emitting diodes and the plurality of electrode pads. According to paragraph 1,
The flux agent is a display module made of a material that improves wetting properties of the plurality of conductive particles. According to claim 1 or 2,
The plurality of conductive particles are,
a plurality of first conductive particles; and
A display module comprising: a plurality of second conductive particles having higher wettability than the plurality of first conductive particles. According to paragraph 3,
A display module wherein the plurality of first conductive particles are an alloy containing at least one of tin (Sn), silver (Ag), copper (Cu), bismuth (Bi), and cobalt (Co). According to paragraph 3,
The display module wherein the plurality of second conductive particles are made of the same material as the material of the electrodes of the plurality of light emitting diodes or the material of the plurality of electrodes of the substrate. According to clause 5,
The second conductive particle 373b is a display module made of any one of gold (Au), copper (Cu), and silver (Ag). According to paragraph 1,
A display module in which the plurality of conductive particles have a size of 10nm to 1㎛. According to paragraph 1,
The adhesive layer further includes a pigment or dye having a black-based color. According to paragraph 1,
A display module in which the adhesive layer is in the form of a film. According to paragraph 1,
A display module in which the adhesive layer is in the form of paste.

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