Patent Application
20220336423
The present disclosure relates to technology related to a display device, and more particularly to a method for manufacturing a display device using a micro-light emitting diode (micro-LED) and a substrate used in manufacturing the display device.
Recently, in the field of display technology, a display device having excellent characteristics in terms of thinness and flexibility has been developed. On the other hand, currently commercialized major displays are represented by a liquid crystal display (LCD) and organic light emitting diodes (OLED).
However, in the case of the LCD, the response time is not sufficiently short and it is difficult to implement a flexible display. In the case of the OLED, the lifespan of the OLED is short and the mass production yield thereof is not good.
A light emitting diode (LED) is a light emitting semiconductor device that is well known for converting electric current into light. Red LEDs using GaAsP compound semiconductors began to be commercialized in 1962, and have been used as light sources along with GaP:N-based green LEDs for image display on electronic devices including information and communication devices. Accordingly, one solution to the above-described issues may be to implement a display using the light emitting semiconductor device. The light emitting semiconductor device has various advantages, such as a long lifespan, low power consumption, excellent characteristics related to initial driving, and high resistance against vibration, compared to a filament-based light emitting device.
However, in order to implement a large-area high-resolution display device using semiconductor light emitting diodes (LEDs), a very large number of semiconductor LEDs should be accurately assembled with or transferred to a wiring substrate of the display device.
Accordingly, the present disclosure provides a method for manufacturing a display device in which semiconductor LEDs are transferred onto the wiring substrate with a minimum number of alignment errors, and a substrate used in manufacturing the display device.
An object of the present disclosure is to provide a method for manufacturing a display device having high reliability using semiconductor LEDs.
Another object of the present disclosure is to provide an assembly substrate and a wiring substrate capable of minimizing alignment errors during a transfer process in which semiconductor LEDs are transferred to manufacture a large-area display device.
Further, another object of the present disclosure is to solve various problems not mentioned herein. Those skilled in the art will appreciate the embodiments of the present disclosure through the description and drawings to be described later.
In accordance with an aspect of the present disclosure, a method for manufacturing a display device may include assembling a lighting semiconductor light emitting device (LED) into a first assembly groove of an assembly substrate; assembling an alignment semiconductor LED into a second assembly groove of the assembly substrate; transferring the semiconductor LEDs assembled into the assembly substrate from the assembly substrate to a transfer substrate; and transferring the semiconductor LEDs transferred onto the transfer substrate from the transfer substrate to a wiring substrate, wherein the assembling the lighting semiconductor LED and the alignment semiconductor LED into the assembly substrate includes performing self-assembling using an electric field and a magnetic field.
The lighting semiconductor LED and the alignment semiconductor LED may be semiconductor LEDs having a same structure formed by a same fabrication process.
The assembling the semiconductor LED into the first assembly groove or the second assembly groove may include introducing the semiconductor LEDs into a fluid chamber; disposing the assembly substrate at an upper surface of the fluid chamber; allowing the semiconductor LEDs floating in the fluid chamber to be in contact with the first assembly groove or the second assembly groove of the assembly substrate using an assembly device having a magnetic material; and assembling the semiconductor LEDs into the first assembly groove or the second assembly groove based on an electric field received through an assembly electrode formed in the assembly substrate.
The transfer substrate may include a plurality of protrusions formed not only at a position corresponding to the lighting semiconductor LED assembled into the assembly substrate, but also at a position corresponding to the alignment semiconductor LED. The transferring the semiconductor LEDs assembled into the assembly substrate from the transfer substrate to the transfer substrate may include overlapping the assembly substrate and the transfer substrate in a manner that the protrusions and the semiconductor LEDs overlap each other; allowing the overlapped semiconductor LEDs to contact the protrusions so that the semiconductor LEDs are fixed; and removing the assembly substrate.
The assembly substrate and the transfer substrate may be provided with alignment keys having the same uneven structure for alignment at positions where the assembly substrate and the transfer substrate are arranged to correspond to each other.
The transferring the semiconductor LEDs assembled into the assembly substrate may include overlapping the alignment keys formed at the positions where the assembly substrate and the transfer substrate are arranged to correspond to each other.
The transferring the semiconductor LEDs transferred onto the transfer substrate from the transfer substrate to the wiring substrate may include aligning the transfer substrate and the wiring substrate in manner that the semiconductor LEDs are disposed in a partial region corresponding to the semiconductor LEDs transferred onto the transfer substrate, from among an entire region of the wiring substrate; and fixing the semiconductor LEDs to a region corresponding to the semiconductor LEDs of the wiring substrate, and removing the transfer substrate.
The wiring substrate may be formed of light transmissive material, and the aligning of the transfer substrate and the wiring substrate may be performed using an image photographed by a camera disposed at a back surface of the wiring substrate.
The aligning of the transfer substrate and the wiring substrate may include overlapping a region corresponding to the semiconductor LEDs of the transfer substrate and a region corresponding to the semiconductor LEDs of the wiring substrate, using the image photographed by the camera.
The transfer substrate and the wiring substrate may be provided with alignment keys having a same uneven structure for alignment at positions where the transfer substrate and the wiring substrate are arranged to correspond to each other.
The aligning the transfer substrate and the wiring substrate may include a first alignment step in which the alignment keys formed at the positions corresponding to each other in the transfer substrate and the wiring substrate are disposed to overlap each other; and a second alignment step in which the alignment semiconductor LED transferred onto the transfer substrate is disposed to overlap an alignment mark of the wiring substrate formed at a position corresponding to the alignment semiconductor LED.
The method may further include: after transferring the semiconductor LED onto the wiring substrate, performing a wiring process in a manner that the lighting semiconductor LED is electrically connected to the wiring substrate.
The method may further include: applying a material having low light transmittance at an upper portion of the alignment semiconductor LED.
The assembly substrate may include a first assembly substrate assembled with the first semiconductor LED emitting first color light, when the display device is driven; and a second assembly substrate assembled with the second semiconductor LED emitting second color light different from the first color light.
In accordance with another aspect of the present disclosure, a display device may include a wiring substrate; and a plurality of semiconductor light emitting devices (LEDs) disposed in the wiring substrate, wherein the plurality of semiconductor LEDs include a lighting semiconductor LED and an alignment semiconductor LED. The lighting semiconductor LED and the alignment semiconductor LED may have the same shape and the same light emitting color, the lighting semiconductor LED may be electrically connected to a wiring electrode of the wiring substrate, and a blackout layer having low light transmittance may be disposed at an upper surface of the alignment semiconductor LED.
The number of the lighting semiconductor LEDs for each unit area within the wiring substrate is at least 100 times larger than the number of the alignment semiconductor LEDs for each unit area within the wiring substrate.
The wiring substrate may further include an alignment key having an uneven structure.
The semiconductor LED may be a micro-LED having a size of a micrometer (μm) unit.
As is apparent from the above description, the embodiments of the present disclosure can provide a new method for manufacturing a high-reliability display device using semiconductor LEDs.
Specifically, when the semiconductor LEDs are self-assembled with an assembly substrate using an electromagnetic field, an assembly groove assembled with the semiconductor LEDs for alignment may be formed in the assembly substrate. In this case, the alignment semiconductor LED assembled in the assembly groove may be used for alignment in a step of transferring the semiconductor LEDs to the final wiring substrate. Unlike the legacy alignment key, the alignment semiconductor LED is designed in a manner that alignment errors of the semiconductor LEDs can be reflected in the transfer process after assembly. As a result, the semiconductor LEDs are transferred to the wiring substrate based on the alignment semiconductor LED, thereby increasing transfer accuracy.
Further, according to another embodiment of the present disclosure, there are additional technical effects not mentioned here. Those skilled in the art can understand the present disclosure through the purposes of the specification and drawings.
Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts, and redundant description thereof will be omitted. As used herein, the suffixes “module” and “unit” are added or used interchangeably to facilitate preparation of this specification and are not intended to suggest distinct meanings or functions. In describing embodiments disclosed in this specification, relevant well-known technologies may not be described in detail in order not to obscure the subject matter of the embodiments disclosed in this specification. In addition, it should be noted that the accompanying drawings are only for easy understanding of the embodiments disclosed in the present specification, and should not be construed as limiting the technical spirit disclosed in the present specification.
Furthermore, although the drawings are separately described for simplicity, embodiments implemented by combining at least two or more drawings are also within the scope of the present disclosure.
In addition, when an element such as a layer, region or module is described as being “on” another element, it is to be understood that the element may be directly on the other element or there may be an intermediate element between them.
The display device described herein is a concept including all display devices that display information with a unit pixel or a set of unit pixels. Therefore, the display device may be applied not only to finished products but also to parts. For example, a panel corresponding to a part of a digital TV also independently corresponds to the display device in the present specification. The finished products include a mobile phone, a smartphone, a laptop, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation system, a slate PC, a tablet, an Ultrabook, a digital TV, a desktop computer, and the like.
However, it will be readily apparent to those skilled in the art that the configuration according to the embodiments described herein is applicable even to a new product that will be developed later as a display device.
In addition, the light emitting semiconductor device mentioned in this specification is a concept including an LED, a micro LED, and the like, and may be used interchangeably therewith.
As shown in
The flexible display may include, for example, a display that can be warped, bent, twisted, folded, or rolled by external force.
Furthermore, the flexible display may be, for example, a display manufactured on a thin and flexible substrate that can be warped, bent, folded, or rolled like paper while maintaining the display characteristics of a conventional flat panel display.
When the flexible display remains in an unbent state (e.g., a state having an infinite radius of curvature) (hereinafter referred to as a first state), the display area of the flexible display forms a flat surface. When the display in the first state is changed to a bent state (e.g., a state having a finite radius of curvature) (hereinafter referred to as a second state) by external force, the display area may be a curved surface. As shown in
The unit pixel of the flexible display may be implemented by a light emitting semiconductor device. In the present disclosure, a light emitting diode (LED) is exemplified as a type of the light emitting semiconductor device configured to convert electric current into light. The LED may be formed in a small size, and may thus serve as a unit pixel even in the second state.
Hereinafter, a flexible display implemented using the LED will be described in more detail with reference to the drawings.
As shown in
The display device 100 shown in
The substrate 110 may be a flexible substrate. For example, to implement a flexible display device, the substrate 110 may include glass or polyimide (PI). Any insulative and flexible material such as polyethylene naphthalate (PEN) or polyethylene terephthalate (PET) may be employed. In addition, the substrate 110 may be formed of either a transparent material or an opaque material.
The substrate 110 may be a wiring substrate on which the first electrode 120 is disposed. Thus, the first electrode 120 may be positioned on the substrate 110.
As shown in
The auxiliary electrode 170, which is an electrode that electrically connects the first electrode 120 and the light emitting semiconductor device 150, is positioned on the insulating layer 160, and is disposed to correspond to the position of the first electrode 120. For example, the auxiliary electrode 170 may have a dot shape and may be electrically connected to the first electrode 120 by an electrode hole 171 formed through the insulating layer 160. The electrode hole 171 may be formed by filling a via hole with a conductive material.
As shown in
The conductive adhesive layer 130 may be a layer having adhesiveness and conductivity. For this purpose, a material having conductivity and a material having adhesiveness may be mixed in the conductive adhesive layer 130. In addition, the conductive adhesive layer 130 may have ductility, thereby providing making the display device flexible.
As an example, the conductive adhesive layer 130 may be an anisotropic conductive film (ACF), an anisotropic conductive paste, a solution containing conductive particles, or the like. The conductive adhesive layer 130 may be configured as a layer that allows electrical interconnection in the direction of the Z-axis extending through the thickness, but is electrically insulative in the horizontal X-Y direction. Accordingly, the conductive adhesive layer 130 may be referred to as a Z-axis conductive layer (hereinafter, referred to simply as a “conductive adhesive layer”).
The ACF is a film in which an anisotropic conductive medium is mixed with an insulating base member. When the ACF is subjected to heat and pressure, only a specific portion thereof becomes conductive by the anisotropic conductive medium. Hereinafter, it will be described that heat and pressure are applied to the ACF. However, another method may be used to make the ACF partially conductive. The other method may be, for example, application of only one of the heat and pressure or UV curing.
In addition, the anisotropic conductive medium may be, for example, conductive balls or conductive particles. For example, the ACF may be a film in which conductive balls are mixed with an insulating base member. Thus, when heat and pressure are applied to the ACF, only a specific portion of the ACF is allowed to be conductive by the conductive balls. The ACF may contain a plurality of particles formed by coating the core of a conductive material with an insulating film made of a polymer material. In this case, as the insulating film is destroyed in a portion to which heat and pressure are applied, the portion is made to be conductive by the core. At this time, the cores may be deformed to form layers that contact each other in the thickness direction of the film. As a more specific example, heat and pressure are applied to the whole ACF, and an electrical connection in the Z-axis direction is partially formed by the height difference of a counterpart adhered by the ACF.
As another example, the ACF may contain a plurality of particles formed by coating an insulating core with a conductive material. In this case, as the conductive material is deformed (pressed) in a portion to which heat and pressure are applied, the portion is made to be conductive in the thickness direction of the film. As another example, the conductive material may be disposed through the insulating base member in the Z-axis direction to provide conductivity in the thickness direction of the film. In this case, the conductive material may have a pointed end.
The ACF may be a fixed array ACF in which conductive balls are inserted into one surface of the insulating base member. More specifically, the insulating base member may be formed of an adhesive material, and the conductive balls may be intensively disposed on the bottom portion of the insulating base member. Thus, when the base member is subjected to heat and pressure, it may be deformed together with the conductive balls, exhibiting conductivity in the vertical direction.
However, the present disclosure is not necessarily limited thereto, and the ACF may be formed by randomly mixing conductive balls in the insulating base member, or may be composed of a plurality of layers with conductive balls arranged on one of the layers (as a double—ACF).
The anisotropic conductive paste may be a combination of a paste and conductive balls, and may be a paste in which conductive balls are mixed with an insulating and adhesive base material. Also, the solution containing conductive particles may be a solution containing any conductive particles or nanoparticles.
Referring back to
After the conductive adhesive layer 130 is formed with the auxiliary electrode 170 and the second electrode 140 positioned on the insulating layer 160, the light emitting semiconductor device 150 is connected thereto in a flip-chip form by applying heat and pressure. Thereby, the light emitting semiconductor device 150 is electrically connected to the first electrode 120 and the second electrode 140.
Referring to
For example, the light emitting semiconductor device may include a p-type electrode 156, a p-type semiconductor layer 155 on which the p-type electrode 156 is formed, an active layer 154 formed on the p-type semiconductor layer 155, an n-type semiconductor layer 153 formed on the active layer 154, and an n-type electrode 152 disposed on the n-type semiconductor layer 153 and horizontally spaced apart from the p-type electrode 156. In this case, the p-type electrode 156 may be electrically connected to the auxiliary electrode 170, which is shown in
Referring back to
More specifically, the light emitting semiconductor device 150 may be press-fitted into the conductive adhesive layer 130 by heat and pressure. Thereby, only the portions of the light emitting semiconductor device 150 between the p-type electrode 156 and the auxiliary electrode 170 and between the n-type electrode 152 and the second electrode 140 may exhibit conductivity, and the other portions of the light emitting semiconductor device 150 do not exhibit conductivity as they are not press-fitted. In this way, the conductive adhesive layer 130 interconnects and electrically connects the light emitting semiconductor device 150 and the auxiliary electrode 170 and interconnects and electrically connects the light emitting semiconductor device 150 and the second electrode 140.
The plurality of light emitting semiconductor devices 150 may constitute a light emitting device array, and a phosphor conversion layer 180 may be formed on the light emitting device array.
The light emitting device array may include a plurality of light emitting semiconductor devices having different luminance values. Each light emitting semiconductor device 150 may constitute a unit pixel and may be electrically connected to the first electrode 120. For example, a plurality of first electrodes 120 may be provided, and the light emitting semiconductor devices may be arranged in, for example, several columns. The light emitting semiconductor devices in each column may be electrically connected to any one of the plurality of first electrodes.
In addition, since the light emitting semiconductor devices are connected in a flip-chip form, light emitting semiconductor devices grown on a transparent dielectric substrate may be used. The light emitting semiconductor devices may be, for example, nitride light emitting semiconductor devices. Since the light emitting semiconductor device 150 has excellent luminance, it may constitute an individual unit pixel even when it has a small size.
As shown in
In addition, when the base member of the ACF is black, the partition wall 190 may have reflectance and increase contrast even without a separate black insulator.
As another example, a reflective partition wall may be separately provided as the partition wall 190. In this case, the partition wall 190 may include a black or white insulator depending on the purpose of the display device. When a partition wall including a white insulator is used, reflectivity may be increased. When a partition wall including a black insulator is used, it may have reflectance and increase contrast.
The phosphor layer 180 may be positioned on the outer surface of the light emitting semiconductor device 150. For example, the light emitting semiconductor device 150 may be a blue light emitting semiconductor device that emits blue (B) light, and the phosphor conversion layer 180 may function to convert the blue (B) light into a color of a unit pixel. The phosphor conversion layer 180 may be a red phosphor 181 or a green phosphor 182 constituting an individual pixel.
That is, the red phosphor 181 capable of converting blue light into red (R) light may be laminated on a blue light emitting semiconductor device at a position of a unit pixel of red color, and the green phosphor 182 capable of converting blue light into green (G) light may be laminated on the blue light emitting semiconductor device at a position of a unit pixel of green color. Only the blue light emitting semiconductor device may be used alone in the portion constituting the unit pixel of blue color. In this case, unit pixels of red (R), green (G), and blue (B) may constitute one pixel. More specifically, a phosphor of one color may be laminated along each line of the first electrode 120. Accordingly, one line on the first electrode 120 may be an electrode for controlling one color. That is, red (R), green (G), and blue (B) may be sequentially disposed along the second electrode 140, thereby implementing a unit pixel.
However, embodiments of the present disclosure are not limited thereto. Unit pixels of red (R), green (G), and blue (B) may be implemented by combining the light emitting semiconductor device 150 and the quantum dot (QD) rather than using the phosphor.
Also, a black matrix 191 may be disposed between the phosphor conversion layers to improve contrast. That is, the black matrix 191 may improve contrast of light and darkness.
However, embodiments of the present disclosure are not limited thereto, and anther structure may be applied to implement blue, red, and green colors.
Referring to
In this case, each light emitting semiconductor device 150 may be a red, green, or blue light emitting semiconductor device to form a unit pixel (sub-pixel). For example, red, green, and blue light emitting semiconductor devices R, G, and B may be alternately disposed, and unit pixels of red, green, and blue may constitute one pixel by the red, green and blue light emitting semiconductor devices. Thereby, a full-color display may be implemented.
Referring to
Referring to
Referring back to this example, the light emitting semiconductor device is positioned on the conductive adhesive layer to constitute a unit pixel in the display device. Since the light emitting semiconductor device has excellent luminance, individual unit pixels may be configured despite even when the light emitting semiconductor device has a small size.
Regarding the size of such an individual light emitting semiconductor device, the length of each side of the device may be, for example, 80 μm or less, and the device may have a rectangular or square shape. When the light emitting semiconductor device has a rectangular shape, the size thereof may be less than or equal to 20 μm×80 μm.
In addition, even when a square light emitting semiconductor device having a side length of 10 μm is used as a unit pixel, sufficient brightness to form a display device may be obtained.
Therefore, for example, when the unit pixel is a rectangular pixel having one side of 600 μm and the other side of 300 μm, the distance between the semiconductor LEDs is relatively large.
Therefore, in this case, a flexible display device implementing high-quality images higher than HD quality or greater can be implemented.
It is assumed that
Also, as shown in
The step in which the semiconductor LEDs are assembled into the assembly substrate is performed by a self-assembly method using an electric field and a magnetic field, and as such a detailed description thereof will be given later.
In
According to the manufacturing method shown in
Specifically, the assembly substrate may include a red assembly substrate to assemble the red semiconductor LED, a green assembly substrate to assemble the green semiconductor LED, and a blue assembly substrate to assemble the blue semiconductor LED.
In addition, the manufacturing method may be broadly classified into a first step S610 for assembling the semiconductor LEDs in the template, a second step S610 for transferring the semiconductor LEDs onto the transfer substrate such as a stamp, and a third step S630 for transferring the semiconductor LEDs onto the wiring substrate capable of being driven by active matrix.
First, the step S610 of assembling the semiconductor LED into the assembly substrate may include assembling semiconductor LEDs emitting different colors of light into the corresponding assembly substrates, respectively. For example, a first semiconductor LED emitting first color light may be assembled into a first assembly substrate, and a second semiconductor LED emitting second color light different from the first color light may be assembled into a second assembly substrate.
Thereafter, the semiconductor LEDs respectively assembled into the assembly substrates may be transferred onto different transfer substrates (S620). That is, the first semiconductor LED assembled into the first assembly substrate may be transferred onto the first transfer substrate, and the second semiconductor LED assembled into the second assembly substrate may be transferred onto the second transfer substrate.
Referring to
Finally, the respective transfer substrates are compressed onto the wiring substrate, so that the red semiconductor LED, the green semiconductor LED, and the blue semiconductor LED are transferred onto the wiring substrate (S630).
In order to implement a large-area display device, the process of transferring the semiconductor LEDs from the transfer substrate to the wiring substrate may be performed multiple times. A tiling transfer action may be performed multiple times such that each of the transfer steps can be performed at a predetermined position of one wiring substrate.
In contrast, unlike the method shown in
For example, the step of transferring the semiconductor LEDs respectively assembled into three assembly substrates onto the wiring substrate may include transferring the semiconductor LEDs assembled into the assembly substrates onto only one transfer substrate (RGB integrated stamp); and transferring all three kinds of semiconductor LEDs onto the wiring substrate by compressing the transfer substrate with the wiring substrate.
In addition, only one kind of assembly substrate and only one kind of transfer substrate may also be used to transfer the semiconductor LEDs respectively corresponding to red, green and blue onto the wiring substrate. In this case, when self-assembly is performed, all semiconductor LEDs corresponding to red, green, and blue are assembled into one assembly substrate, and are collectively transferred onto the transfer substrate and the wiring substrate.
Meanwhile, the detailed steps included in each step shown in
Referring to
Thereafter, the assembly substrate 210 may be disposed on the chamber 230. According to one embodiment, the assembly substrate 210 may also be introduced into the chamber 230.
One pair of two electrodes 213 and 214 corresponding to the respective semiconductor LEDs 150 to be assembled may be formed in the assembly substrate 210. The electrodes 213 and 214 may be implemented as a transparent electrode such as indium tin oxide (ITO) or may also be formed of other general materials as needed. The electrodes 213 and 214 may generate an electric field upon receiving a voltage, and may be used as assembly electrodes capable of stably fixing the semiconductor LEDs 150 contacting the assembly grooves 211 and 212.
Specifically, an AC voltage may be applied to the electrodes 213 and 214, and each of the semiconductor LEDs 150 floating around the electrodes 213 and 214 may have a polarity by dielectric polarization. In addition, the dielectrically polarized semiconductor LED may be moved or fixed in a specific direction by a non-uniform electric field formed around the electrodes 213 and 214. This operation is referred to as dielectrophoresis. In the self-assembly process of the present disclosure, the semiconductor LEDs 150 can be stably fixed to the assembly grooves 211 and 212 using dielectrophoresis.
In addition, the assembly grooves may include a first assembly groove 211 for a lighting semiconductor LED and a second assembly groove 212 for a semiconductor LED for alignment (hereinafter referred to as an alignment semiconductor LED). The alignment assembly groove 212 is mainly used for alignment rather than for implementation of display pixels, so that the number of alignment assembly grooves 212 is less than the number of first assembly grooves. For example, when 100 first assembly grooves 211 are formed, one or more second assembly grooves 212 may be formed. However, in the process of transferring the semiconductor LEDs 150 assembled in the second assembly grooves 212 onto the final wiring substrate, a minimum number of second assembly grooves for enabling alignment should be provided. For example, three or more second assembly grooves 212 may be formed in the assembly substrate. Since one or two assembly grooves can define a point or a line region only, the one or two assembly grooves can be used for alignment by which a two-dimensional (2D) region can be specified through three or more assembly grooves.
Each of the second assembly grooves 212 may have a smaller diameter than each of the first assembly grooves 211. Generally, when the diameter of the assembly groove is small so that the assembly groove is similar in size to the semiconductor LED, a time required to assemble the semiconductor LED may increase. However, since the number of second assembly grooves 212 is much smaller than the number of first assembly grooves 211, the time required to assemble the semiconductor LED 150 into the second assembly groove 212 does not greatly affect the assembly time in which all the semiconductor LEDs are assembled into the assembly substrate 210.
For example, the spacing between the assembly electrodes 213 and 214 may be smaller than the width of the semiconductor LED or the diameter of each assembly groove 211 or 212, so that the assembly position of the semiconductor LEDs can be more precisely fixed using the electric field.
In addition, an insulation layer 215 may be formed over the assembly electrodes 213 and 214 to protect the electrodes 213 and 214 from the fluid 220 and to prevent leakage of current flowing through the assembly electrodes 213 and 214. For example, the insulation layer 215 may be formed of an inorganic insulator such as silica or alumina or an inorganic insulator as a monolayer or multilayer structure. In addition, the insulation layer 215 may have a minimum thickness to prevent damage to the assembly electrodes 213 and 214 when the semiconductor LEDs 150 are assembled, and may have a maximum thickness to stably assemble the semiconductor LEDs 150.
A barrier 216 may be formed over the insulation layer 215. A partial region of the barrier 216 may be disposed over the assembly electrodes 213 and 214, and the remaining regions other the partial region may be disposed over the assembly substrate 210.
For example, when the assembly substrate 210 is manufactured, some of the barrier formed over the entire upper portion of the insulation layer 215 may be removed, thereby forming the assembly grooves 211 and 212 where the semiconductor LEDs 150 are coupled to the assembly substrate 210.
As shown in
Meanwhile, the assembly groove 211 may have a shape and a size corresponding to the shape of the semiconductor LED to be assembled. As a result, it is possible to prevent other semiconductor LEDs from being assembled into the assembly groove 211 or to prevent a plurality of semiconductor LEDs from being assembled into the assembly groove 211.
In addition, the depth of the assembly groove 211 may be smaller than a vertical height of each semiconductor LED 150. Accordingly, the semiconductor LED may be formed to protrude from the spacing between the barriers 216, and may easily contact a protrusion of the transfer substrate in a transfer process after completion of the assembly process.
Also, as shown in
By the magnetic field generated by the assembly device 240, the semiconductor LEDs 150 in the chamber 150 may move toward the assembly device 240.
While the semiconductor LED 150 moves toward the assembly device 240, the semiconductor LED 150 may enter the assembly groove 211 and thus contact the assembly substrate 210.
The semiconductor LED 150 may be the same type of semiconductor LED manufactured by the same fabrication process. However, the semiconductor LED assembled into the first assembly groove 211 as shown in
The semiconductor LED 150 may serve as a horizontal semiconductor LED, as shown in
Further, the assembly groove 211 and/or the semiconductor LED 150 may be formed to include a pattern or a shape that enables the second conductive semiconductor layer 153 of the semiconductor LED 150 to be in contact with the assembly substrate 210.
On the other hand, due to an electric field generated by the assembly electrodes 213 and 214 of the assembly substrate 210, the semiconductor LED 150 contacting the assembly substrate 210 can be prevented from being separated by movement of the assembly device 240.
Therefore, according to the self-assembly method using the electromagnetic field shown in
As described above, according to the self-assembly method using the electromagnetic field, the semiconductor LEDs are dispersed in the fluid, and the assembly substrate may be disposed over the chamber filled with the fluid (S611).
In addition, the semiconductor LEDs may have the same structure formed by the same fabrication process, and the assembly substrate may include an assembly groove for the lighting semiconductor LED and an assembly groove for the alignment semiconductor LED.
The semiconductor LED may be a horizontal semiconductor LED, and may be formed in a circular shape having no directivity to shorten the time required to assemble the semiconductor LED into the assembly groove.
In the self-assembly method, the plurality of semiconductor LEDs is simultaneously assembled into the assembly substrate within the fluid, the lighting semiconductor LED and the alignment semiconductor LED may be simultaneously assembled into the assembly substrate without an additional process (S612). Since all semiconductor LEDs are assembled into the assembly groove previously formed in the assembly substrate, the assembly process can be completed (S613).
Referring to
The semiconductor LEDs assembled into the assembly substrate 210 can be broadly classified into the lighting semiconductor LED 1501 and the alignment semiconductor LED 1502. In addition, as shown in
Since the width (F) of the second assembly groove is smaller than the width (E) of the first assembly groove, the semiconductor LED can be used for more precise alignment purposes in the transfer step thereof in the future. For example, when the semiconductor LED has a horizontal length of 50 μm, the width of the first assembly groove assembled with the lighting semiconductor LED may be set to 55 μm, so that a spacing difference of about 5 μm or less between the lighting semiconductor LED and the alignment semiconductor LED may be considered efficient in terms of the assembly time. If the width of the assembly groove is almost the same as the horizontal length of the semiconductor LED, the semiconductor LED can be precisely assembled, but a long time will be consumed to assemble the semiconductor LED in consideration of a total number of semiconductor LEDs to be assembled.
However, the number of alignment semiconductor LEDs to be assembled is much smaller than the number of lighting semiconductor LEDs to be assembled, so that the entire assembly time of all semiconductor LEDs may be less affected by the assembly time of each semiconductor LED, and the second assembly groove may be formed to have the assembly groove of 51 μm to 53 μm, so that the second assembly groove can be used for more precise alignment purposes. That is, when using the semiconductor LED assembled into the first assembly groove, the position of the semiconductor LED may be changed within the range of 5 μm in the first assembly groove. In contrast, when using the other semiconductor LED assembled into the second assembly groove, the position of the semiconductor LED may be changed within the range of 1 μm to 3 μm in the second assembly groove. Thus, assuming that the semiconductor LED assembled into the second assembly groove while being more precisely controlled in position is utilized as an alignment index, precise transfer is also possible even in the final wiring substrate.
However, in the present disclosure, the second assembly groove is not necessarily smaller than the first assembly groove. The reason why the alignment assembly groove is separately formed is to predetermine a positional deviation of the semiconductor LEDs in a transfer process after completion of the self-assembly process, thereby minimizing the alignment error of the semiconductor LEDs disposed on the wiring substrate in response to the positional deviation. Therefore, the second assembly groove may be equal to or larger in size than the first assembly groove. For more precise transfer, it is more preferable that the second assembly groove be smaller in size than the first assembly groove.
The semiconductor LEDs formed in the assembly substrate 210 may include the lighting semiconductor LED 1501 and the alignment semiconductor LED 1502.
In addition, the protrusion 311 of the transfer substrate may have sufficient adhesive force required to transfer the semiconductor LEDs 1501 and 1502.
The protrusions 311 may be arranged at intervals of a predetermined distance corresponding to the spacing between the semiconductor LEDs 1501 and 1502 of the assembly substrate 210. In addition, the alignment process may be performed to accurately transfer the protrusions 311 and the semiconductor LEDs 1501 and 1502.
For example, in the alignment process, any one of the assembly substrate 210 and the transfer substrate 310 may horizontally move with respect to the other one, and may then vertically move with respect to the other one, so that the alignment process can be performed. Thereafter, it is determined whether the position of the protrusion 311 of the transfer substrate corresponding to the semiconductor LED overlaps with the position of the semiconductor LEDs 1501 and 1502 of the assembly substrate 210 by the camera sensor and the like. In this case, if the position of the protrusion 311 of the transfer substrate overlaps with the position of the semiconductor LEDs 1501 and 1502 of the assembly substrate 210, the semiconductor LEDs may be transferred in response to the protrusion 311, and the assembly substrate 210 may be removed.
In addition, the assembly substrate 210 and the transfer substrate 310 may include alignment keys for alignment at positions corresponding to each other. For example, the alignment keys may be formed into the respective substrates while having the same uneven structure. In this case, the alignment keys may be in contact with each other. However, the scope or spirit of the present disclosure is not limited thereto, and other alignment keys having various structures conceivable by those skilled in the art are also possible.
On the other hand, if the number of semiconductor LEDs to be assembled into the assembly substrate 210 is small, it is possible to determine whether the protrusion 311 of the transfer substrate 310 overlaps with each of the semiconductor LEDs of the assembly substrate 210 as described above, and the transfer process can be performed according to the result of such determination. However, if the number of semiconductor LEDs to be assembled into the assembly substrate 210 is extremely large, a long inspection time is consumed to recognize each of the semiconductor LEDs and the position of a protrusion corresponding to the semiconductor LED. Therefore, assuming that the alignment key for the assembly substrate and the other alignment key for the transfer substrate are formed, the presence or absence of overlapping between the two alignment keys is determined, so that the transfer process of the semiconductor LEDs can be performed according to the result of determination.
Referring to
The protrusion 311 may be a flexible film material such as polydimethylsiloxane (PDMS) having sufficient adhesive force to contact and transfer the semiconductor LED. In addition, the main material of the transfer substrate 310 supporting the protrusion 311 may include at least one of polyethylene terephthalate (PET), polycarboxylate ether (PCE), and glass.
The wiring substrate 110 may include an electrode unit for electrically connecting the lighting semiconductor LED 1501 to the wiring substrate 110.
On the other hand, the electrode unit is not formed at the position where the alignment semiconductor LED 1502 is transferred. The alignment semiconductor LED 1502 is transferred for precise alignment in the process of transferring from the transfer substrate 310 to the wiring substrate 110, so that the alignment semiconductor LED may not serve as a light emitting device (LED) after completion of the future wiring process.
In addition, an alignment mark corresponding to the alignment semiconductor LED may be formed over the wiring substrate 110 at the transfer position where the alignment semiconductor LED 1502 is transferred.
In addition, the wiring substrate 110 may include not only the above-described alignment mark 11, but also another alignment key having the same structure as the alignment key of the transfer substrate 310 at a position corresponding to the alignment key of the transfer substrate 310.
In addition, an adhesive layer for stably fixing the semiconductor LED 150 to the wiring substrate 110 may be formed in the wiring substrate 110. The adhesive layer may be, for example, an anisotropic conductive adhesive layer, and the semiconductor LED 150 can be wiring-processed while being transferred onto the substrate.
In addition, a reflective layer may be disposed at a position where the lighting semiconductor LED 1501 of the wiring substrate 110 will be transferred. The reflective layer may allow light emitted toward the wiring substrate 110 to be reflected when the lighting semiconductor LED 1501 is driven, resulting in an increase in external light extraction efficiency.
In addition, the arrangement spacing among the adhesive layer, the electrode unit, and the reflective layers should be identical to the arrangement spacing among the semiconductor LEDs disposed in the transfer substrate 310. Therefore, in order to accurately transfer the semiconductor LEDs from the transfer substrate 310 to the wiring substrate 110, the alignment process may be performed.
The alignment process may include photographing, by the camera, each of the transfer substrate having the semiconductor LED and the wiring substrate formed before the semiconductor LEDs are transferred. In this case, the photographing process may be performed only at a specified position where the semiconductor LEDs will be transferred at the wiring substrate.
For precise alignment, the wiring substrate 110 may be formed of light transmissive material. Thus, the step of performing alignment between the transfer substrate 310 and the wiring substrate 110 may be performed using the image photographed by the camera disposed at the rear surface of the wiring substrate not facing the transfer substrate 310.
Specifically, the camera installed at the rear surface of the wiring substrate 110 may photograph the semiconductor LED of the transfer substrate 310 and the front surface of the wiring substrate 110 where the semiconductor LED will be transferred. Thereafter, through the image photographed by the camera, the region corresponding to the semiconductor LEDs of the transfer substrate 310 may overlap the other region corresponding to the semiconductor LEDs of the wiring substrate 110, so that an accurate position to be used for such transfer can be determined or established.
On the other hand, if the number of semiconductor LEDs to be transferred onto the wiring substrate 110 is large, a long inspection time is consumed to mark the region corresponding to each of the semiconductor LEDs on the wiring substrate 10 and to determine whether the marked region overlaps with the semiconductor LED. Therefore, assuming that the alignment corresponding to the transfer substrate and the alignment key corresponding to the wiring substrate are formed, the transfer process of the semiconductor LED can be performed after confirming whether the alignment keys overlap each other.
However, the alignment key formed in the transfer substrate is highly likely to be deformed through multiple transfer processes. Since the transfer substrate is formed of a flexible material having adhesive force required to transfer the semiconductor LED, the transfer substrate may be stretched or deformed by repeated transfer processes.
Furthermore, the semiconductor LEDs to be transferred onto the transfer substrate may have a positional deviation before and after the transfer process is performed due to physical properties of the transfer substrate.
Meanwhile, the alignment key has already been formed in the transfer substrate, it is impossible for the positional deviation to be reflected into the transfer process. As a result, if the transfer process is performed based on the alignment key, an alignment error of the semiconductor LEDs may occur due to the positional deviation.
Therefore, assuming that the alignment key previously formed in the transfer substrate is used, the alignment error of the semiconductor LEDs may become serious in proportion to the increasing number of transfer processes.
As a result, the alignment step configured to use not only the above alignment key formed in the transfer substrate, but also an additional alignment mark capable of minimizing the alignment error of the semiconductor LEDs may be required.
The alignment semiconductor LED may be used as the alignment mark.
In the self-assembly process, the alignment semiconductor LED is assembled into the assembly substrate, is transferred onto the transfer substrate, and is finally transferred onto the wiring substrate.
In a situation where the transfer process is performed in the transfer substrate and the transfer process is performed on the wiring substrate, this transfer process is performed in the same manner as in the lighting semiconductor LED, even when the alignment error of the semiconductor LEDs is generated before and after the transfer process, the alignment error can be reflected to the transfer process without change. That is, assuming that the alignment semiconductor LED is used for alignment purposes, the influence of the alignment error likely to be generated in the process of transferring the semiconductor LEDs on the wiring substrate can be ignored.
Therefore, the step for performing alignment using the alignment semiconductor LED can be divided into the following steps. First, the first alignment step in which the alignment keys formed at the corresponding positions of the transfer substrate 310 and the wiring substrate 110 overlap each other can be performed. Furthermore, the second alignment step in which the alignment marks 111 formed in the regions corresponding to the alignment semiconductor LED 1502 formed in the transfer substrate 310 and the alignment semiconductor LED previously formed in the wiring substrate 110 overlap each other can be performed.
Through the first alignment step, an approximate transfer position where the semiconductor LED of the transfer substrate 310 will be transferred onto the wiring substrate 110 is confirmed. Through the second alignment step, the semiconductor LED of the transfer substrate 310 can be precisely transferred onto the wiring substrate 110.
On the other hand, in the process of manufacturing the display device using the transfer substrate 310 shown in
Referring to
As described above, the lighting semiconductor LED 1501 and the alignment semiconductor LED 1502 are the same semiconductor LEDs formed by the same fabrication process, but the role of the semiconductor LEDs to be used in future may be determined differently according to the assembly grooves of the assembly substrate 210.
As shown in
Referring to
The width of each of the protrusions 311 and 312 may be larger than that of each of the semiconductor LEDs so that the semiconductor LEDs can be stably bonded and transferred onto the substrate.
The semiconductor LEDs assembled into the assembly substrate of
However, the alignment key formed in the transfer substrate may be formed of a flexible material such as a material constituting the protrusions formed in the transfer substrate, so that the alignment key may be deformed by repeated execution of the transfer process.
Referring to
In addition, the alignment mark 111 may be formed at a position corresponding to the alignment semiconductor LED of the transfer substrate.
As described above, the process of transferring the semiconductor LEDs 1501 and 1502 onto the wiring substrate 110 is as follows.
First, the alignment key formed in the transfer substrate and the other alignment key formed in the wiring substrate may overlap each other so that the appropriate transfer position can be confirmed based on the result of overlapping between the two alignment keys.
The reason why the final position where the transfer process will be performed on the wiring substrate using the above-described alignment key is not determined is that the above alignment key has already been formed in the transfer substrate and thus positional deviation between the semiconductor LEDs cannot be reflected in the transfer process.
Here, the positional deviation may refer to a state in which the average position of the semiconductor LED array is changed before and after the transfer process due to physical properties (e.g., a stamp structure and a flexible material) of the transfer substrate. Therefore, when the transfer process is performed only using the alignment keys, the positional deviation is reflected in the transfer process without change so that the alignment error of the semiconductor LEDs may occur in the wiring substrate. In addition, as the transfer process is repeatedly performed, each of the alignment keys may be deformed so that the above alignment error may become serious.
Therefore, when the approximate transfer position where the semiconductor LEDs of the transfer substrate will be transferred is determined in the wiring substrate using the alignment key, the alignment semiconductor LED disposed in the transfer substrate and the alignment mark 111 formed in the wiring substrate may overlap each other so that the accurate transfer position can be determined.
The alignment semiconductor LED is formed by the same transfer process as in the peripheral semiconductor LEDs, and the average position change of the semiconductor LED array before and after the transfer process is reflected in the transfer process without change, so that the alignment error caused by the positional deviation generated before and after the transfer process may not occur.
As a result, when the alignment step is performed two times, the alignment semiconductor LED 1502 may be transferred onto the alignment mark 111 as shown in
In
In order to implement the large-area display device, the process of transferring the semiconductor LEDs from the transfer substrate to the wiring substrate may be performed multiple times.
For example, when using the wiring substrate 110 shown in
Each transfer process should be precisely adjusted in the wiring substrate 110. As shown in
In more detail, when the transfer substrate overlaps with the wiring substrate 110 to perform transfer of the semiconductor LEDs, overlapping or non-overlapping of the alignment keys 113 may be determined. If the alignment keys 113 overlap each other, the transfer position may be precisely adjusted in a manner that the alignment key 111 of the wiring substrate 110 overlaps with the alignment semiconductor LED of the transfer substrate and the lighting semiconductor LED and the lighting semiconductor LED are then transferred onto the wiring substrate 110.
In
In addition, the number of lighting semiconductor LEDs to be transferred by only one transfer may be much larger than the number of alignment semiconductor LEDs. For example, the number of lighting semiconductor LEDs for each unit area within the wiring substrate may be at least 100 times larger than the number of alignment semiconductor LEDs for each unit area within the wiring substrate.
Referring to
In contrast, as shown in
The blackout layer 183 may prevent light generated by the alignment semiconductor LED from leaking to the outside when the display device is driven. In more detail, although the alignment semiconductor LED is not electrically connected to the wiring substrate 110, first light generated by the peripheral lighting semiconductor LED 1501 may be transmitted to the lighting semiconductor LED, so that second light may be generated by the alignment semiconductor LED, so that the blackout layer 183 can prevent such light from being emitted to the outside.
The above description is merely illustrative of the technical spirit of the present disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the spirit and scope of the disclosure.
Therefore, the embodiments disclosed in the present disclosure are merely illustrative of the technical spirit of the present disclosure. The scope of the technical spirit of the present disclosure is not limited by these embodiments.
The scope of the present disclosure should be construed by the appended claims, and all technical ideas within the scope equivalent thereto should be construed as being within the scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2019-0095606 | Aug 2019 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2019/009862 | 8/7/2019 | WO |
