Transfer member for LED element and transfer method for LED element

Abstract

To simultaneously transfer, onto a circuit board, a plurality of LED elements formed on each of a plurality of LED wafers.SOLUTION: A transfer member for LED elements includes: a plurality of LED wafers, each wafer including a plurality of LED elements provided on a first side thereof; and a support plate to which the LED wafers are bonded via an adhesive layer on a second side opposite the first side. The adhesive layer has a plurality of openings having a shape corresponding to the shape of each LED wafer, each LED element, or an electrode of each LED element. The LED wafers are bonded to the support plate via the adhesive layer such that each LED wafer, each LED element or the electrode of each LED element overlaps with each opening.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a transfer member for an LED element and a method for transferring an LED element. [Background technology]

[0002] In recent years, micro LED (Light Emitting Diode) displays have been attracting attention as a new display technology. A micro LED display is a display device in which miniaturized LED elements are arranged in an array on the display surface as pixels. By individually controlling the light emission of the LED elements of each pixel, a micro LED display can display images with high contrast and high response speed.

[0003] In the manufacturing process of such micro LED displays, a method is being considered in which multiple LED elements are formed on a wafer suitable for crystal growth of compound semiconductors, and then the wafer is bonded to a circuit board to transfer the multiple LED elements to the circuit board at once.

[0004] For example, the following Patent Document 1 discloses a bonding device that bonds a substantially plate-shaped first member and a transparent substantially plate-shaped second member. The bonding device disclosed in Patent Document 1 bonds a transparent substantially plate-shaped wafer on which multiple LED elements are formed to a circuit board on which an adhesive is applied, thereby simultaneously fixing multiple LED elements onto the connection pattern of the circuit board. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-202252 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, with the bonding apparatus disclosed in the above Patent Document 1, it is difficult to simultaneously transfer a plurality of wafers onto a circuit board.

[0007] Therefore, in order to further reduce the manufacturing costs of micro LED displays, there has been a demand for simultaneously transferring multiple LED elements formed on multiple LED wafers onto a circuit board. [Means for solving the problem]

[0008] In order to solve the above problems, according to one aspect of the present invention, there is provided a transfer member for LED elements, comprising: a plurality of LED wafers each having a plurality of LED elements provided on a first surface; and a support plate to which the plurality of LED wafers are bonded via an adhesive layer on a second surface opposite the first surface, wherein the adhesive layer has a plurality of openings having shapes corresponding to the shapes of the plurality of LED wafers, the plurality of LED elements, or electrodes of the plurality of LED elements, and the plurality of LED wafers are bonded to the support plate via the adhesive layer such that the electrodes of the plurality of LED wafers, the plurality of LED elements, or the plurality of LED elements overlap with the plurality of openings.

[0009] In addition, in order to solve the above problem, according to another aspect of the present invention, there is provided a method for transferring LED elements, comprising the steps of: forming a plurality of LED elements on a first surface of a plurality of LED wafers; adhering the plurality of LED wafers to a support plate on a second surface opposite to the first surface via an adhesive layer having a plurality of openings shaped corresponding to the shapes of the plurality of LED wafers, the plurality of LED elements, or electrodes of the plurality of LED elements, so that the electrodes of the plurality of LED elements and the plurality of openings overlap; and facing a circuit board having a plurality of bumps at positions corresponding to the electrodes of the plurality of LED elements adhered to the support plate, to the support plate, and joining the electrodes of the plurality of LED elements to the plurality of bumps. Effect of the Invention

[0010] As described above, according to the present invention, a plurality of LED elements formed on a plurality of LED wafers can be transferred onto a circuit board simultaneously. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a schematic perspective view showing a configuration of a transfer member according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic plan view showing an example of the shape of an opening corresponding to the outer shape of an LED wafer. [Diagram 3] FIG. 2 is a schematic plan view showing an example of the shape of an opening corresponding to the outer shape of an LED element. [Figure 4] 1 is a schematic plan view showing an example of the shape of an opening corresponding to the outer shape of an electrode of an LED element. FIG. [Diagram 5] 4 is a schematic diagram showing a laser lift-off process for a transfer member having an adhesive layer with the openings shown in FIG. 3. FIG. [Figure 6] FIG. 2 is a flow chart showing a procedure for transferring an LED element according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configurations are designated by the same reference numerals, and duplicated explanations will be omitted.

[0013] <1. Transfer material> The configuration of a transfer member for an LED element according to one embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic perspective view showing the configuration of a transfer member 10 according to this embodiment.

[0014] 1, the transfer member 10 according to this embodiment includes a plurality of LED wafers 100, an adhesive layer 210, and a support plate 200. The plurality of LED wafers 100 are attached to the main surface of the support plate 200 via the adhesive layer 210. Therefore, the transfer member 10 can simultaneously transfer a plurality of LED elements 110 formed on each of the LED wafers 100 to the circuit board 300 by pressing the main surface of the support plate 200 to which the LED wafers 100 are attached, against the circuit board 300.

[0015] The circuit board 300 is a board provided with a drive circuit for individually driving each of the transferred LED elements 110 and a control circuit for controlling the drive of each of the LED elements 110. The circuit board 300 may be, for example, a glass board, a glass epoxy board, an epoxy board, a polyimide board, or a (meth)acrylic board, or may be a flexible board made of polyester or polyethersulfone. The circuit board 300 may be, for example, a pixel array board of a micro LED display device.

[0016] Bumps 310 having a convex shape such as a cone shape, a cylinder shape, or a tapered shape are provided on the surface of the circuit board 300 to which the LED elements 110 are transferred. At least the surface of the bumps 310 is made of metal, and the bumps 310 are connection terminals that electrically connect the driving circuit and the control circuit provided on the circuit board 300 to the electrodes of the LED elements 110. The bumps 310 may be made of, for example, a single metal or multiple metals, or may be made by coating the surface of a resin with a metal. For example, multiple bumps 310 may be provided per pixel in an arrangement corresponding to the pixel pitch of the micro LED display device.

[0017] The LED wafer 100 is a substrate on one of the main surfaces of which a plurality of LED elements 110 are formed in a matrix. Specifically, a pn junction is formed in the stacking direction by crystal growth of a compound semiconductor on one of the main surfaces of the LED wafer 100. The crystal-grown compound semiconductor layer is then patterned into a lattice shape, thereby forming the LED elements 110 in a matrix shape on one of the main surfaces of the LED wafer 100. Each of the patterned LED elements 110 has two electrodes formed thereon, each of which functions as a positive electrode or a negative electrode.

[0018] For example, the LED wafer 100 may be a transparent sapphire substrate having a disk or rectangle shape suitable for crystal growth of a compound semiconductor that constitutes the LED element 110. The compound semiconductor that constitutes the LED element 110 may be, for example, InGaN, GaN, AlGaN, or the like.

[0019] The support plate 200 is a rigid substrate having a main surface with an area larger than that of the LED wafer 100. Specifically, the support plate 200 is a substrate having a main surface with an area corresponding to the plurality of LED wafers 100, and the plurality of LED wafers 100 are bonded to the main surface of the support plate 200 via an adhesive layer 210. The support plate 200 can simultaneously transfer the plurality of LED elements 110 formed on each of the LED wafers 100 to the circuit board 300 by pressing the main surface to which the plurality of LED wafers 100 are bonded against the circuit board 300.

[0020] The support plate 200 may be, for example, a transparent glass substrate having a flat main surface. By attaching the LED wafer 100 to the flat main surface of the support plate 200, warping caused by the formation of the LED elements 110 can be corrected.

[0021] The adhesive layer 210 is made of a polyimide adhesive, an epoxy adhesive, or an acrylic adhesive, and bonds the support plate 200 and the LED wafer 100. The adhesive layer 210 is provided with a plurality of openings 211 that serve as references for alignment (i.e., alignment marks) when attaching the LED wafer 100 to the support plate 200.

[0022] Specifically, the adhesive layer 210 is provided with a plurality of openings 211 corresponding to the shape of the LED wafer 100 attached to the support plate 200, the LED elements 110 formed on the LED wafer 100, or the electrodes provided on the LED elements 110. For example, the adhesive layer 210 may be provided with a plurality of openings 211 having a shape corresponding to at least a part of the outer shape of the LED wafer 100, the LED elements 110, or the electrodes provided on the LED elements 110.

[0023] According to this, when attaching the LED wafer 100 to the support plate 200 via the adhesive layer 210, the worker can see the openings 211 of the adhesive layer 210 through the LED wafer 100. Therefore, the worker can attach the LED elements 110 to the support plate 200 with higher positional accuracy by aligning the LED wafer 100, the LED elements 110, or the electrodes provided on the LED elements 110 with the openings 211. Therefore, the transfer member 10 can transfer the LED elements 110 to the circuit board 300 with higher positional accuracy.

[0024] The LED wafers 100 are attached to the support plate 200 such that the pitch of the LED elements 110 is the same among the LED wafers 100. That is, the LED wafers 100 are attached to the main surface of the support plate 200 such that the LED elements 110 are arranged at a pitch corresponding to the arrangement pitch of the bumps 310 provided on the circuit board 300.

[0025] Furthermore, the adhesive layer 210 may be configured to include a dye, a pigment, a fluorescent material, or the like. This can improve the distinguishability due to the difference in color between the adhesive layer 210 and the opening 211 from which the adhesive layer 210 has been removed, thereby further improving the visibility of the opening 211.

[0026] The multiple openings 211 provided in the adhesive layer 210 may be formed, for example, by patterning a photosensitive polyimide adhesive constituting the adhesive layer 210 by photolithography. Since the photosensitive polyimide adhesive has negative photosensitive properties, the multiple openings 211 can be formed with higher positional accuracy in the adhesive layer 210 by removing the unexposed parts by photolithography by alkaline development.

[0027] 2 to 4, the shape of the openings 211 provided in the adhesive layer 210 will be described in more detail. As shown in Fig. 2 to 4, a plurality of LED elements 110 are arranged in a matrix on the LED wafer 100. Each of the arranged LED elements 110 is provided with two electrodes 111 corresponding to, for example, a positive electrode and a negative electrode.

[0028] Fig. 2 is a schematic plan view showing an example of the shape of the opening 211A corresponding to the outer shape of the LED wafer 100. As shown in Fig. 2, the adhesive layer 210 may be provided with, for example, four openings 211A at positions corresponding to the four corners of the rectangular outer shape of the LED wafer 100. According to the openings 211A shown in Fig. 2, a worker can attach the LED wafer 100 to a desired position on the support plate 200 by aligning the positions of the four corners of the LED wafer 100 with the corners of the four openings 211A.

[0029] FIG. 3 is a schematic plan view showing an example of the shape of the opening 211B corresponding to the outer shape of the LED element 110. As shown in FIG. 3, the adhesive layer 210 may be provided with the openings 211B at positions corresponding to the outer shapes of the LED elements 110 provided on the LED wafer 100, for example. According to the openings 211B shown in FIG. 3, the worker can bond the LED wafer 100 to a desired position on the support plate 200 by aligning the positions of the outer shapes of the LED elements 110 provided on the LED wafer 100 with the openings 211B. In particular, according to the openings 211B shown in FIG. 3, the worker can bond the electrodes 111 of the LED elements 110 and the bumps 310 of the circuit board 300 with higher accuracy when pressing the transfer member 10 against the circuit board 300.

[0030] FIG. 4 is a schematic plan view showing an example of the shape of the opening 211C corresponding to the outer shape of the electrode 111 of the LED element 110. As shown in FIG. 4, the adhesive layer 210 may be provided with the openings 211C at positions corresponding to the outer shapes of the two electrodes 111 provided on the LED element 110. According to the opening 211C shown in FIG. 4, a worker can attach the LED wafer 100 to a desired position on the support plate 200 by aligning the outer shapes of the two electrodes 111 of the LED element 110 with the positions of the openings 211C. In particular, according to the opening 211C shown in FIG. 4, a worker can bond the electrodes 111 of the LED element 110 and the bumps 310 of the circuit board 300 with even higher accuracy when pressing the transfer member 10 against the circuit board 300.

[0031] Furthermore, the opening 211B shown in Fig. 3 makes it easier to peel off the LED wafer 100 and the LED elements 110 (so-called laser lift-off), which is performed after the transfer member 10 is pressed against the circuit board 300. This point will be described with reference to Fig. 5. Fig. 5 is a schematic diagram showing a laser lift-off process for the transfer member 10 having the adhesive layer 210 with the opening 211B shown in Fig. 3 provided therein.

[0032] 5, the transfer member 10 first presses the main surface of the support plate 200 to which the LED wafer 100 is bonded against the circuit board 300, thereby simultaneously transferring the LED elements 110 formed on the LED wafer 100 to the circuit board 300. Next, a laser beam L is irradiated from a laser beam irradiation device 400 to the interface between the LED wafer 100 and the LED elements 110 from the main surface of the support plate 200 opposite to the main surface to which the LED wafer 100 is bonded, thereby performing laser lift-off of the LED elements 110. In the laser lift-off, the compound semiconductor near the interface between the LED elements 110 and the LED wafer 100 is vaporized by the irradiated laser beam L, and the LED elements 110 are peeled off from the LED wafer 100.

[0033] Here, the opening 211B provided in the adhesive layer 210 has a shape corresponding to the outer shape of the LED element 110. Therefore, the laser light L irradiated from the laser light irradiation device 400 can reach the interface between the LED element 110 and the LED wafer 100 through the opening 211B without being absorbed or scattered by the adhesive layer 210. Therefore, the transfer member 10 having the adhesive layer 210 provided with the opening 211B can irradiate the laser light L to the LED element 110 as it is in a state pressed against the circuit board 300, so that the laser lift-off of the LED element 110 can be performed more easily.

[0034] <2. Transfer method> Next, the flow of the method for transferring the LED element 110 will be described with reference to Fig. 6. Fig. 6 is a flow chart showing the flow of transferring the LED element 110. In the following, it is assumed that the opening 211 provided in the adhesive layer 210 is the opening 211B shown in Fig. 3 which corresponds to the outer shape of the LED element 110.

[0035] 6, first, a plurality of LED elements 110 are formed on an LED wafer 100 (S101). Specifically, after a pn junction of a compound semiconductor is formed on the LED wafer 100, patterning and electrode formation are performed to form a plurality of LED elements 110.

[0036] Next, the LED wafers 100 are bonded to the support plate 200 via the adhesive layer 210 having the openings 211B (S103). Specifically, first, the adhesive layer 210 having the openings 211B patterned thereon is formed on the support plate 200 using photolithography. Thereafter, the LED wafer 100 is bonded to the support plate 200 via the adhesive layer 210 by aligning the positions of the respective outer shapes of the LED elements 110 provided on the LED wafer 100 with the respective openings 211B of the adhesive layer 210. In this way, the transfer member 10 is formed.

[0037] Next, the LED wafer 100 on which the LED elements 110 are provided is opposed to the circuit board 300, and the transfer member 10 is pressed against the circuit board 300, thereby adhering the multiple LED elements 110 to the circuit board 300 (S105). Specifically, the main surface of the support plate 200 on which the LED wafer 100 is adhered is opposed to the main surface of the circuit board 300 on which the bumps 310 are provided, and the transfer member 10 is pressed against the circuit board 300. As a result, the electrodes 111 of the multiple LED elements 110 are joined to the bumps 310, respectively, and the multiple LED elements 110 are adhered to the circuit board 300 by the adhesive.

[0038] Thereafter, the laser light L is irradiated onto the interfaces between the LED wafer 100 and the LED elements 110 through the openings 211B of the adhesive layer 210 (S107). Specifically, the laser light L is irradiated onto the interfaces between the LED wafer 100 and the LED elements 110 through the supporting plate 200, the openings 211B of the adhesive layer 210, and the LED wafer 100 from the main surface of the supporting plate 200 opposite to the main surface to which the LED wafer 100 is bonded.

[0039] As a result, the compound semiconductor in the vicinity of the interface between the LED elements 110 and the LED wafer 100 is vaporized by the irradiated laser light L, and the LED elements 110 are peeled off from the LED wafer 100 (S109). Therefore, the transfer member 10 can peel off the LED wafer 100, the adhesive layer 210, and the support plate 200 from the circuit board 300 onto which the multiple LED elements 110 have been transferred.

[0040] According to the above-mentioned operation flow, the transfer member 10 can collectively transfer the LED elements 110 formed on the multiple LED wafers 100 to the circuit board 300. Therefore, the transfer member 10 can transfer the LED elements 110 to the circuit board 300, which is a pixel array board of a micro LED display device, with higher positional accuracy and at lower cost.

[0041] Although the preferred embodiment of the present invention has been described in detail above with reference to the accompanying drawings, the present invention is not limited to such an example. It is clear that a person having ordinary knowledge in the technical field to which the present invention pertains can conceive of various modified or altered examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present invention. [Explanation of symbols]

[0042] 10...transfer member, 100...LED wafer, 110...LED element, 111...electrode, 200...support plate, 210...adhesive layer, 211, 211A, 211B, 211C...openings, 300...circuit board, 310...bump, 400...laser light irradiation device, L...laser light

Claims

1. A plurality of LED wafers each having a plurality of LED elements provided on a first surface thereof; a support plate having a second surface opposite to the first surface to which the LED wafers are bonded via an adhesive layer; Equipped with the adhesive layer has a plurality of openings having shapes corresponding to the shapes of the LED wafers, the LED elements, or the electrodes of the LED elements; A transfer member for LED elements, wherein the plurality of LED wafers are adhered to the support plate via the adhesive layer so that the electrodes of the plurality of LED wafers, the plurality of LED elements, or the plurality of LED elements overlap with the plurality of openings.

2. the plurality of openings have shapes corresponding to the shapes of the plurality of LED elements, The transfer member for an LED element according to claim 1 , wherein the plurality of LED wafers are adhered to the support plate via the adhesive layer such that the plurality of openings and the plurality of LED elements overlap each other.

3. The transfer member for an LED element according to claim 1 , wherein the plurality of LED elements are arranged in a matrix on the first surface of the plurality of LED wafers.

4. The transfer member for an LED element according to claim 1 , wherein the adhesive layer includes a photosensitive adhesive.

5. A transfer member for an LED element as described in any one of claims 1 to 4, further comprising a circuit board having a plurality of bumps at positions corresponding to the electrodes of the plurality of LED elements adhered to the support plate, and facing the support plate to join the electrodes of the plurality of LED elements to the plurality of bumps.

6. forming a plurality of LED elements on a first surface of a plurality of LED wafers; a step of adhering the plurality of LED wafers to a support plate on a second surface opposite to the first surface via an adhesive layer having a plurality of openings having shapes corresponding to shapes of the plurality of LED wafers, the plurality of LED elements, or the electrodes of the plurality of LED elements, such that the plurality of openings overlap the plurality of LED wafers, the plurality of LED elements, or the electrodes of the plurality of LED elements; a step of placing a circuit board having a plurality of bumps at positions corresponding to the electrodes of the plurality of LED elements bonded to the support plate, facing the support plate, and bonding the electrodes of the plurality of LED elements to the plurality of bumps; A method for transferring an LED element, comprising:

7. the plurality of openings have shapes corresponding to the shapes of the plurality of LED elements, The method for transferring an LED element according to claim 6 , wherein the LED wafers are bonded to the support plate via the adhesive layer such that the openings and the LED elements overlap each other.

8. 8. The method for transferring an LED element according to claim 7, further comprising a step of peeling off the plurality of LED elements from the LED wafer by irradiating laser light from the second surface through the plurality of openings to interfaces between the plurality of LED elements and the LED wafer.

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