A transfer method of a micro light emitting diode chip

Abstract

The present application relates to a kind of transfer methods of micro light emitting diode chip, comprising: S1, provide a chip module and a receiving substrate;Micro light emitting diode chip is arranged on the first substrate of chip module, first magnetic structure is arranged on the light-emitting surface of the chip, the chip is inverted;Receiving substrate includes second substrate and second magnetic structure;S2, the side of the chip module provided with the chip is arranged opposite to receiving substrate, wherein there is mutual attraction between first magnetic structure and corresponding second magnetic structure;S3, the chip is separated from the first substrate, and the first magnetic structure is fixed on the receiving substrate from the side of the chip;S4, the chip on the receiving substrate is aligned and bonded with target substrate and removes receiving substrate.The transfer method of the present application has the advantage that the bonding effect between micro light emitting diode inverted chip and target substrate can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of micro light-emitting diodes, and in particular to a method for transferring micro light-emitting diode chips. Background Technology

[0002] Micro LEDs are ultra-small light-emitting diodes with side lengths ranging from 10 micrometers to 100 micrometers, which can be used to fabricate display modules with higher resolution.

[0003] Currently, in the fabrication process of display modules, it is typically necessary to first peel the micro-LED chips from their growth substrate and then transfer them to a target substrate with control circuitry according to a specific arrangement. During this process, because the arrangement of the chips on the growth substrate usually differs from their arrangement on the target substrate, it is often necessary to first arrange the chips on a temporary substrate as needed before transferring them to the target substrate. For flip chips, in order to ensure successful bonding of their electrode surfaces to the target substrate, the arranged chips also need to be transferred from the temporary substrate to a receiving substrate, and then from the receiving substrate to the target substrate. In other words, the chips need to be transferred sequentially to a temporary substrate and a receiving substrate before finally being transferred to the target substrate.

[0004] Although existing chip transfer methods can pre-arrange chip spacing and different types of chips, in practice, for micro LEDs using flip-chip technology, poor bonding can easily occur on the target substrate, leading to problems such as poor display performance of the display module. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a method for transferring a micro light-emitting diode chip, which has advantages such as improving the bonding effect between the flip-chip and the target substrate.

[0006] A method for transferring a miniature light-emitting diode chip includes the following steps:

[0007] S1. A chip module and a receiving substrate are provided; wherein, the chip module includes a first substrate, a micro light-emitting diode chip and a first magnetic structure, the micro light-emitting diode chip is fixed to the front side of the first substrate by its electrode surface and its light-emitting surface is away from the first substrate, the first magnetic structure is disposed on the light-emitting surface of the micro light-emitting diode chip, and the micro light-emitting diode chip is flip-chip; the receiving substrate includes a second substrate and a second magnetic structure disposed on the second substrate;

[0008] S2. The side of the chip module with the micro light-emitting diode chip is positioned opposite to the receiving substrate, wherein there is a mutual attraction between the first magnetic structure and the corresponding second magnetic structure.

[0009] S3. Separate the micro LED chip from the first substrate, and fix the side of the first magnetic structure away from the micro LED chip to the receiving substrate, wherein the orthographic projection of the first magnetic structure and the corresponding second magnetic structure on the second substrate at least partially overlaps.

[0010] S4. The micro LED chip on the receiving substrate is aligned with the target substrate and then removed from the receiving substrate.

[0011] The micro-LED chip transfer method of the present invention, by setting a first magnetic structure and a second magnetic structure with mutual attraction on the surface of the micro-LED chip and on the second substrate respectively, allows the micro-LED chip to be pulled by the attraction during the transfer from the first substrate to the receiving substrate, thereby accurately transferring it to the target position and ensuring that it is fixed on the receiving substrate in a specified orientation. This ensures that the micro-LED chip can be accurately transferred to the target substrate according to its arrangement on the first substrate, thereby effectively improving the bonding effect between the micro-LED chip and the target substrate.

[0012] Furthermore, the chip module includes multiple micro LED chips, and each micro LED chip has a first magnetic structure disposed on its light-emitting surface; the arrangement of the second magnetic structure on the second substrate corresponds one-to-one with the arrangement of the micro LED chips on the first substrate.

[0013] Furthermore, the receiving substrate also includes an adhesive layer disposed on one side surface of the second substrate. In step S2, the chip module faces the side of the receiving substrate with the adhesive layer. In step S3, the first magnetic structure is fixed to the adhesive layer. The adhesive layer can serve as a buffer layer between the micro-LED chip and the second substrate, and assists in fixing the micro-LED chip to the receiving substrate.

[0014] Furthermore, the second magnetic structure and the adhesive layer are respectively disposed on opposite sides of the second substrate. This design, where the second magnetic structure and the adhesive layer are disposed on different sides of the second substrate, not only makes the bond between the adhesive layer and the second substrate more stable, but also makes the surface of the adhesive layer smoother.

[0015] Furthermore, the first substrate is provided with a viscous thermally decomposable material or a thermally desiccant material at least at the location where it is connected to the micro LED chip. Meanwhile, in step S3, the micro LED chip is separated from the first substrate by heating.

[0016] Furthermore, the first substrate is provided with a photodegrading or photoadhesive material at least at the location where it is connected to the micro LED chip. Meanwhile, in step S3, the micro LED chip is separated from the first substrate by light irradiation.

[0017] Furthermore, the first magnetic structure is prepared using a magnetic material that undergoes thermal decomposition or volatilization upon heating. Simultaneously, the bonding process in step S4 is thermo-press bonding. This thermo-press bonding process allows for the decomposition or volatilization of the first magnetic structure disposed on the light-emitting surface of the chip while simultaneously achieving bonding between the micro-LED chip and the target substrate, effectively avoiding any impact of the first magnetic structure on the chip's light extraction efficiency.

[0018] Furthermore, the material of the first magnetic structure includes polyacrylonitrile or polyaminobenzoquinone.

[0019] Furthermore, the area of ​​the contact surface of the first magnetic structure that contacts the micro-LED chip is larger than the area of ​​its surface away from the micro-LED chip. This configuration allows the first magnetic structure to have a smaller contact surface with the receiving substrate, making it easier to remove the receiving substrate in step S4.

[0020] Furthermore, in step S3, the orthographic projections of the first magnetic structure and the corresponding second magnetic structure on the second substrate completely overlap.

[0021] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the chip module structure described in step S1 of the embodiment;

[0023] Figure 2 This is a schematic diagram of the structure of the receiving substrate described in step S1 of the embodiment;

[0024] Figure 3 This is a schematic diagram of the chip transfer process described in step S2 of the embodiment;

[0025] Figure 4 This is a schematic diagram of the chip transfer process described in step S3 of the embodiment;

[0026] Figure 5This is a schematic diagram of the chip transfer process described in step S4 of the embodiment. Detailed Implementation

[0027] To address the problem of poor chip bonding on the target substrate in existing flip-chip micro-light-emitting diodes, this invention analyzes the chip transfer process and finds that the poor bonding mainly stems from chip misalignment or flipping during the transfer from the temporary substrate to the receiving substrate. Specifically, in existing technologies, the temporary substrate is typically made of a material that decomposes or debonds upon exposure to light or heat. The chip is then detached from the temporary substrate and transferred to the receiving substrate using optical scanning (such as laser scanning) or heating. During this process, the chip mainly detaches from the temporary substrate and falls onto the receiving substrate under the influence of gravity and the gas generated when the temporary substrate decomposes upon exposure to light or heat. However, due to the small mass of the micro-LED chip, the gravitational force it experiences during drop is relatively small. The chip's trajectory is easily affected by forces generated when the temporary substrate decomposes upon exposure to light or heat, as well as other external forces, causing it to fall onto the receiving substrate rather than vertically. This results in the micro-LED chip shifting or tipping over on the receiving substrate. Therefore, in this invention, a first magnetic structure and a second magnetic structure that attract each other are respectively provided on the surface of the micro-LED chip and on the receiving substrate. During the transfer process, when the micro-LED chip detaches from the temporary substrate, in addition to being subjected to gravity and the gas force generated when the temporary substrate decomposes upon exposure to light or heat, it is also attracted by the second magnetic structure on the receiving substrate. This pulls and attracts the chip to a designated position on the receiving substrate, thus avoiding the positional shift or tipping problems that occur during the transfer of the micro-LED chip in existing methods.

[0028] To better illustrate the inventive concept of this invention, a specific implementation method for transferring a miniature light-emitting diode chip is provided below, which mainly includes the following steps:

[0029] Step S1: Provide a chip module and a receiving substrate.

[0030] Please see Figure 1 This is a schematic diagram of the structure of the chip module, which includes a first substrate 11, a plurality of micro light-emitting diode chips 12 disposed on the front side of the first substrate 11, and a first magnetic structure 13 disposed on the surface of each micro light-emitting diode chip 12.

[0031] The first substrate 11 can be made of materials such as polydimethylsiloxane (PDMS), polyester fiber, or PET. The first substrate 11 has at least one adhesive material on its front side that decomposes or debonds upon heating or under light irradiation. Furthermore, the first substrate 11 has at least one adhesive material on its front side at the location where it connects to the micro-LED chip, which also decomposes or debonds upon heating or under light irradiation. This decomposing or debonding material can be a thermally decomposable or volatile polymer such as polyacrylonitrile or polyaminobenzoquinone.

[0032] The micro LED chip 12 has a flip-chip structure, comprising opposing electrode surfaces and a light-emitting surface, and is fixed to the front side of the first substrate 11 by an electrode surface array. Specifically, the micro LED chip 12 can be a monochrome chip or a multicolor chip, and the micro LED chip 12 can be peeled off from its growth substrate and transferred to the first substrate 11, or it can be disposed on the first substrate 11 after multiple transfers and arrangements.

[0033] The first magnetic structure 13 is disposed on the light-emitting surface of each micro LED chip 12 in the chip module. The reason for disposing the first magnetic structure 13 on the surface of the micro LED chip 12 is that the spacing between the micro LED chips 12 in the chip module is very small, usually only a few micrometers. It is very inconvenient to place the first magnetic structure 13 between two micro LED chips 12, while it is easier to operate and implement to place the first magnetic structure 13 on the surface of the micro LED chip 12.

[0034] Furthermore, the first magnetic structure 13 can be made of magnetic polymer materials, such as polyacrylonitrile, polyaminobenzoquinone, and other magnetic materials that are thermally decomposable or volatilized after heating, and can be deposited on the light-emitting surface of the chip by methods such as dispensing or spin coating. The reason why the first magnetic structure 13 is made of a thermally decomposable or volatilized material is that, in the subsequent chip bonding steps, among the bonding methods that can directly remove the first magnetic structure 13 while bonding the chip to the target substrate, thermal bonding is the most effective.

[0035] Please see Figure 2 This is a schematic diagram of the structure of the receiving substrate, which includes a second substrate 21 and a second magnetic structure 22 and an adhesive layer 23 disposed on the surface of the second substrate.

[0036] In this configuration, based on the arrangement of the micro-LED chips 12 on the first substrate 11, the second substrate 21 has alignment marks at corresponding positions and plans the target transfer positions for each micro-LED chip 12. According to the target transfer positions, the second magnetic structure 22 is disposed on one side surface of the second substrate 21. Furthermore, the second magnetic structure 22 can be made of magnetic polymer materials, such as polyacrylonitrile, polyaminobenzoquinone, or other thermally decomposable or volatile magnetic materials after heating, and is prepared on the surface of the second substrate 21 by methods such as dispensing or spin coating. Moreover, the shape of the second magnetic structure 22 is not limited and can be trapezoidal or other shapes. In addition, to ensure mutual magnetic attraction between the second magnetic structure 22 and the corresponding first magnetic structure 13, one of the corresponding second magnetic structure 22 and the first magnetic structure 13 is a positive electrode and the other is a negative electrode.

[0037] The adhesive layer 23 is a transparent adhesive layer with adhesive properties. It can be an acrylic film, a polydimethylsiloxane (PDMS) film, etc., and can be prepared on the surface of the second substrate 21 by spin coating. The thickness of the adhesive layer 23 is 15-20 μm.

[0038] Furthermore, the adhesive layer 23 can be disposed on the same side or opposite side of the second substrate 21 as the second magnetic structure 22, as long as the adhesive layer 23 supporting the substrate and the front side of the first substrate 11 are facing each other, the first magnetic structure 13 and the second magnetic structure 22 attract each other. When the adhesive layer 23 and the second magnetic structure 22 are disposed on the same side of the second substrate 21, the adhesive layer 23 covers the second magnetic structure 22. Preferably, the adhesive layer 23 and the second magnetic structure 22 are disposed on opposite sides of the second substrate 21, so that the adhesive layer 23 can be completely adhered to the surface of the second substrate 21, and its adhesion effect and surface flatness are not affected by the second magnetic structure 22.

[0039] It should be understood that the adhesive layer 23 mainly serves as a buffer and an auxiliary fixation for the micro LED chip 12 in the receiving substrate. In some other embodiments, the receiving substrate may not include the adhesive layer.

[0040] Step S2, align the chip module with the receiving substrate.

[0041] Please see Figure 3 This is a schematic diagram of the micro LED chip transfer process described in step S2.

[0042] Specifically, the side of the chip module with the micro LED chip 12 is aligned with the side of the receiving substrate with the adhesive layer 23, and each micro LED chip 12 in the chip module is aligned with its target transfer position on the receiving substrate. Thus, after alignment, the orthogonal projections of the micro LED chip 12, the first magnetic structure 13, and the second magnetic structure 22 on the second substrate 21 completely overlap or at least partially overlap. Consequently, the first magnetic structure 13 will be attracted by the corresponding second magnetic structure 22.

[0043] Step S3: The micro LED chip is detached from the first substrate 11 and transferred to the receiving substrate.

[0044] Please see Figure 4 This is a schematic diagram of the micro LED chip transfer process described in step S3.

[0045] Specifically, in this step, depending on the material of the first substrate 11, heating or light scanning (e.g., laser scanning) can be used to de-adhere or decompose the first substrate 11, thereby causing the micro light-emitting diode chip 12 fixed thereon to detach from the first substrate 11 and fall onto the adhesive layer 23 of the receiving substrate along with the first magnetic structure 13.

[0046] In this step, since each micro LED chip 12 in the chip module is positioned directly opposite its target transfer position on the receiving substrate, and the light-emitting surface of the micro LED chip 12 and the target transfer position on the receiving substrate are respectively provided with a first magnetic structure 13 and a second magnetic structure 22 that attract each other, when the micro LED chip 12 detaches from the first substrate 11, in addition to being subjected to gravity and stress caused by the unbonding or decomposition of the first substrate 11, it will also be subjected to the attraction of the second magnetic structure 22 on the first magnetic structure 13. Thus, during the transfer to the receiving substrate, it can be accurately pulled to the target transfer position under the action of the attraction, and the first magnetic structure 13 provided on its light-emitting surface will be firmly adsorbed and adhered to the adhesive layer 23, thereby preventing the displacement or overturning phenomenon that occurs during the chip drop transfer process in the prior art.

[0047] Furthermore, since the first magnetic structure 13 and the second magnetic structure 22 are very small in size, and each first magnetic structure 13 corresponds to a second magnetic structure 22 below it, during the transfer of the micro LED chip 12 in step S3, the first magnetic structure 13 and the second magnetic structure 22 are minimally affected by the adjacent first magnetic structures and second magnetic structures, or even almost unaffected by them.

[0048] Step S4: Bond the micro LED chip to the target substrate and remove the receiving substrate.

[0049] Please see Figure 5 This is a schematic diagram of the chip transfer process described in step S4.

[0050] In this process, based on the arrangement of the micro-LED chips 12 on the receiving substrate, the target substrate 3 is provided with alignment marks, connection lines, pads, and solder (not shown in the figure). Specifically, the side of the receiving substrate with the micro-LED chips 12 is first aligned with the side of the target substrate 3 with the pads and solder. The alignment between the micro-LED chips 12 and the pads is completed according to the alignment marks on the surface of the receiving substrate and the surface of the target substrate 3. Then, the electrodes of the micro-LED chips 12 are eutectic bonded to the pads of the target substrate 3 by means of high-temperature hot pressing, etc. In some cases, the bonding process can also utilize intermolecular forces such as van der Waals forces, intramolecular forces, or even atomic forces.

[0051] Because eutectic bonding creates a more stable connection between the micro LED chip 12 and the target substrate 3 than between the micro LED chip 12 and the receiving substrate, the receiving substrate can be removed from the bonded display module after the micro LED chip 12 is bonded. Furthermore, the receiving substrate can be reused in the transfer process of the next batch of chips, thus saving materials and reducing costs.

[0052] Of course, in this step, the first magnetic material 13 is a material that can be thermally decomposed or volatilized after heating. Therefore, under high temperature, the first magnetic material 13 is removed due to the thermal decomposition of its own material or volatilization after heating.

[0053] In other embodiments, as a preferred option for the above solution, the contact area between the first magnetic structure 13 and the adhesive layer 23 of the substrate can be minimized, that is, the area of ​​the first magnetic structure 13 on the side away from the light-emitting surface of the micro LED chip can be reduced. For example, in this embodiment, the area of ​​the first magnetic structure 13 on the side away from the light-emitting surface of the micro LED chip is smaller than the area on the side closer to the light-emitting surface of the micro LED chip, and specifically it can be a trapezoidal cross-section platform, thereby ensuring a stable connection between the first magnetic structure 13 and the light-emitting surface of the micro LED chip 12 while also having a smaller contact area with the adhesive layer 23, so that the substrate can be more easily separated from the micro LED chip 12 in step S4.

[0054] In other embodiments, as a further preferred option of the above scheme, a photodegradable or photodegradable material is used as the material of the first substrate 11, and a thermally degradable or thermally volatilizable polymeric magnetic material is selected as the material of the first magnetic structure 13. Corresponding to this combination, in step S3 of the above scheme, the micro-LED chip 12 can be peeled off from the first substrate 11 by optical scanning (e.g., laser scanning), while ensuring that the laser does not affect the first magnetic structure 13; and in step S4, while the chip is bonded by high-temperature hot pressing, the first magnetic structure 13 will also decompose or volatilize at high temperature. This makes it easier to separate the receiving substrate from the micro-LED chip 12, and also avoids the problem of the residual first magnetic structure 13 obstructing the light emission of the chip 12.

[0055] It should be understood that in some other embodiments, the first magnetic structure 13 may also be made of a magnetic material that will not decompose or volatilize when heated. After the bonding of the micro LED chip 12 is completed in step S4, it will remain on the light-emitting surface of the micro LED chip 12. In subsequent processes, the first magnetic structure 13 may be further removed by grinding or etching according to the light emission requirements of the display module.

[0056] The micro LED chip transfer method of the present invention provides a first magnetic structure and a second magnetic structure with mutual attraction on the light-emitting surface of the micro LED chip and the receiving substrate, respectively. When the micro LED chip is transferred from the first substrate to the receiving substrate, it is subjected to the traction force from the second magnetic structure. This allows the micro LED chip to be accurately positioned at the target transfer position on the receiving substrate, ensuring that its light-emitting surface faces the adhesive layer of the receiving substrate. This effectively prevents the chip from shifting or flipping during the transfer process, thus affecting the bonding effect between the micro LED chip and the target substrate and consequently the display effect of the display module.

[0057] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for transferring a miniature light-emitting diode chip, comprising the following steps: S1. Provide a chip module and a receiving substrate; wherein... The chip module includes a first substrate, a micro LED chip, and a first magnetic structure. The micro LED chip is fixed to the front side of the first substrate by its electrode surface, and its light-emitting surface is away from the first substrate. The first magnetic structure is disposed on the light-emitting surface of the micro LED chip. The micro LED chip is flip-chip. The receiving substrate includes a second substrate, a second magnetic structure disposed on the second substrate, and an adhesive layer. The second magnetic structure and the adhesive layer are respectively disposed on opposite sides of the second substrate. S2. The side of the chip module with the micro light-emitting diode chip is arranged opposite to the side of the substrate with the adhesive layer, wherein there is a mutual attraction between the first magnetic structure and the corresponding second magnetic structure. S3. Separate the micro LED chip from the first substrate, and fix the side of the first magnetic structure away from the micro LED chip to the adhesive layer of the receiving substrate, and the orthographic projection of the first magnetic structure and the corresponding second magnetic structure on the second substrate at least partially overlaps. S4. The micro LED chip on the receiving substrate is aligned with the target substrate and then removed from the receiving substrate.

2. The transfer method according to claim 1, characterized in that, The chip module includes multiple micro LED chips, and each micro LED chip has a first magnetic structure disposed on its light-emitting surface; the arrangement of the second magnetic structure on the second substrate corresponds one-to-one with the arrangement of the micro LED chips on the first substrate.

3. The transfer method according to claim 1, characterized in that, The first substrate has a viscous, thermally decomposable material or a thermally desiccant material at least at the location where it is connected to the micro LED chip. Meanwhile, in step S3, the micro LED chip is separated from the first substrate by heating.

4. The transfer method according to claim 1, characterized in that, The first substrate has a photodegradable or photodegradable material at least at the location where it is connected to the micro LED chip. Meanwhile, in step S3, the micro LED chip is separated from the first substrate by light irradiation.

5. The transfer method according to claim 4, characterized in that, The first magnetic structure is prepared using magnetic materials that undergo thermal decomposition or volatilization after heating. Meanwhile, the bonding process in step S4 is hot-press bonding.

6. The transfer method according to claim 5, characterized in that: The material of the first magnetic structure includes polyacrylonitrile or polyaminobenzoquinone.

7. The transfer method according to any one of claims 1-6, characterized in that, The area of ​​the contact surface of the first magnetic structure that contacts the micro LED chip is greater than the area of ​​its surface that is far away from the micro LED chip.

8. The transfer method according to any one of claims 1-6, characterized in that: In step S3, the orthographic projections of the first magnetic structure and the corresponding second magnetic structure on the second substrate completely overlap.

9. The transfer method according to claim 7, characterized in that: In step S3, the orthographic projections of the first magnetic structure and the corresponding second magnetic structure on the second substrate completely overlap.

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