A laser lift-off mass transfer system and method

Abstract

This invention discloses a mass transfer system and method for laser lift-off. The system includes a transfer device and a receiving device. The transfer device has LED chips awaiting transfer, forming an LED chip matrix along a first direction and a second direction. The receiving device includes a target substrate. A photoresist layer is formed on the target substrate, and corresponding grooves are pre-formed at the LED chip mounting positions on the photoresist layer. These grooves correspond to and match the LED chips, exposing bonding electrodes at the bottom. This invention's mass transfer system and method for laser lift-off utilizes a photoresist layer with corresponding grooves on the receiving device to position the falling LED chips, thus significantly improving the alignment accuracy of the LED chips during installation and enabling precise micro-operations.

Description

Technical Field

[0001] The present invention relates to the field of LED assembly technology, and in particular to an improved mass transfer system and method for Micro-LEDs. Background Art

[0002] Among existing technologies, Micro-LED technology is the latest development of television and display technology. As a new generation of display technology, Micro-LED has higher brightness, better luminous efficiency, and lower power consumption than the existing OLED technology. In May 2017, Apple has begun the development of a new generation of display technology. In February 2018, Samsung launched the Micro LED TV at CES 2018.

[0003] Micro-LED displays have advantages in stability, lifespan, and operating temperature. They also inherit the advantages of LEDs such as low power consumption, color saturation, fast response speed, and high contrast, and have great application prospects.

[0004] like Figure 1 The Micro-LED display backplane includes several pixel regions SPR (Sub-Pixel Rendering), each pixel region SPR includes red LED (R), blue LED (B), green LED (G) chips 100. In the display manufacturing process, the red, green and blue LED chips 100 need to be transferred from their respective growth substrates 101 (WAFER) to the display backplane 102 of the display. In some technical cases, white (W) LED chips may also need to be transferred and assembled.

[0005] As disclosed in U.S. Pat. No. 8,361,268B2, Figure 2A-2D As shown, when the first substrate 1 and the second substrate 7 are at a predetermined distance d (this predetermined distance is usually set very small according to actual technical needs), the laser Lh selectively irradiates the micro-device (Micro-LED) area on the first substrate 1, and the peeling layer 3 can be decomposed by laser irradiation, thereby peeling off the corresponding peeling layer 3, so that the corresponding micro-device (Micro-LED) 5 falls into the second substrate (target substrate) 7, and an adhesive layer 9 is provided on the second substrate 7 to stick the corresponding micro-device 5, thereby completing the transfer process of the Micro-LED.

[0006] However, if Figure 3 As shown, in the prior art, during the transfer process, when the micro-device (Micro-LED) falls into the target substrate 102 (i.e. Figure 2A-2D The second substrate 7 and Figure 1During the process of display backplane 102 in the display panel, the position of the micro-device (Micro-LED) may be offset, that is, the micro-device (Micro-LED) cannot be aligned with the corresponding position on the second substrate (target substrate). Figure 3 As shown, the first column shows several common offset situations from left to right. In the figure, LED1, LED2, LED3, LED4, and LED5 all have different offsets. The dotted line shows the position where the LED should be transferred, and the solid line shows the actual position where the LED is transferred. The offset from rotation to up, down, left, and right will cause faults on the circuit board and reduce the product yield. At the same time, due to the small size of the micro-LED device, it is difficult to achieve precise positioning during the transfer process in batches.

[0007] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0008] The purpose of the present invention is to provide a mass transfer system and method for laser lift-off, so as to realize a transfer system and method with more precise positioning, in order to solve the problem of position deviation in the transfer process during the batch processing of micro devices Micro-LED in the prior art.

[0009] The technical solution of the present invention is as follows:

[0010] A mass transfer system for laser lift-off, comprising a transfer device and a receiving device;

[0011] The transfer device is provided with LED chips waiting to be transferred, and the LED chips form an LED chip matrix along a first direction and a second direction;

[0012] The receiving device includes a target substrate;

[0013] A photoresist layer is arranged on the target substrate, and a corresponding groove is pre-arranged at a corresponding LED chip assembly position of the photoresist layer, the groove matches the LED chip, and a bonding electrode is exposed at the bottom.

[0014] The laser peeling mass transfer system, wherein the transfer device includes: a transparent carrier and an LED chip waiting to be transferred arranged at a corresponding position on the surface of the transparent carrier facing the receiving device; the LED chip is connected to the transparent carrier through a peeling layer.

[0015] In the mass transfer system of laser stripping, a boss is provided on a surface of the transparent carrier facing the receiving device, corresponding to the position of the LED chip and the stripping layer.

[0016] The mass transfer system of laser lift-off, wherein a functional layer is provided on a side of the transparent carrier away from the receiving device, the functional layer comprising a light-shielding particle region and a transparent region spaced apart in the first direction;

[0017] The positive projection position of the LED chip on the functional layer belongs to the position of the transparent area, the shading particle area is arranged between two adjacent columns of transparent areas, and a first electrode and a second electrode are arranged on both sides of the shading particle area close to the transparent area, which are used to power on to control the movement of the shading particles in the shielding area of ​​the shading particles.

[0018] In the mass transfer system of laser lift-off, the shielding area of ​​the light-shielding particles can be distributed in the entire light-shielding particle area or concentrated in the midline portion of the light-shielding particle area under power-on control.

[0019] In the laser lift-off mass transfer system, the lift-off layer is made of polyimide.

[0020] The mass transfer system of laser stripping, wherein the light-shielding particle material includes a combination of one or more of the following materials: Cu2+ copper ions, Fe2+ ferrous ions, Ni2+ nickel ions, Cr3+ chromium ions, Au3+ gold ions.

[0021] A mass transfer method for laser lift-off of the system includes the following steps:

[0022] A. Align the position of the LED chip on the transfer device with the groove on the receiving device;

[0023] B. controlling the entire light-shielding particle region to be light-shielded by energizing the first electrode and the second electrode;

[0024] C. Use laser to irradiate the peeling layer through the window between the light-shielding particle areas, so that the LED chip is separated from the transfer device and falls into the groove.

[0025] The mass transfer method of laser lift-off, wherein the following steps are further included after step C:

[0026] D. controlling the light-shielding particles to be concentrated at the center of the light-shielding particle area by re-energizing the first electrode and the second motor to expand the laser transmission area;

[0027] E. Use laser to penetrate the transparent carrier to irradiate and dissolve the photoresist layer.

[0028] The present invention provides a laser stripping mass transfer system and method, which uses a photoresist layer with corresponding grooves arranged on a receiving device to hold the fallen LED chip in place, thereby greatly improving the alignment accuracy of the LED chip during the installation process; at the same time, by controlling the moving position of the shading particles, the photoelectric operation during the installation of the micro-device Micro-LED reduces the mechanical working steps, thereby achieving the accuracy of the micro-operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the working principle of the micro-device transfer process in the prior art.

[0030] Figure 2A-2D It is a schematic diagram of an embodiment of the transfer process of the prior art.

[0031] Figure 3 Schematic diagram of micro-device positioning deviation during the transfer process of the prior art.

[0032] Figure 4 FIG. 1 is a schematic diagram of a preferred embodiment of the laser lift-off mass transfer system of the present invention.

[0033] Figure 5 FIG. 1 is a top view schematically showing an example of a functional layer of a mass transfer system for laser lift-off according to the present invention.

[0034] Figure 6 A schematic diagram of the working process of the mass transfer system for laser lift-off according to the present invention.

[0035] Figure 7 This is a second schematic diagram of the working process of the mass transfer system for laser lift-off according to the present invention.

[0036] Figure 8 Schematic diagram of the working process of the mass transfer system of laser lift-off according to the present invention.

[0037] Fig. 9 Shown is another example of a top view schematic diagram of the functional layer of the laser lift-off mass transfer system of the present invention. DETAILED DESCRIPTION

[0038] The preferred embodiments of the present invention are described in detail below.

[0039] The present invention provides a mass transfer system and method of laser lift-off, which is mainly aimed at the transfer process of micro-device Micro-LED. Since the size of the micro-device is very small and the number on the display screen is very large, faster processing is required to improve processing efficiency. The system and method of the present invention can quickly realize the transfer process by utilizing secondary irradiation and lift-off of laser without using washing liquid.

[0040] Specifically, in a preferred embodiment of the present invention, the laser lift-off mass transfer system is as follows: Figure 4 As shown, it includes a transfer device 210 and a receiving device 220. The transfer device 210 is provided with LED chips 230 waiting to be transferred. Specifically, they can be different LED chips of R, G, B and white light, etc., which are arranged on the lower side of the transfer device 210, that is, on the side corresponding to the receiving device. The LED chips 230 form an LED chip matrix along the first direction A and the second direction B, such as Figure 5 and Fig. 9 As for the directions of the arrows shown, it should be understood that the first direction A and the second direction B are relative and are not limited to the directions shown in the figure, and may also be swapped.

[0041] Opposite to the lower side of the transfer device 210 is a receiving device 220. In the improved embodiment of the present invention, the receiving device 220 is provided with a target substrate 221, on which a photoresist layer 222 is provided, and on which a pre-set groove 223 corresponding to the position where the LED chip is installed is provided. The groove 223 can be provided by a pre-processing technology, such as using a photolithography method, which will not be described in detail here. The shape and size of the groove 223 are completely matched with the corresponding LED chip to be assembled, and a corresponding bonding electrode 224 is provided at the bottom of the groove 223 to expose the corresponding bonding electrode.

[0042] On the transfer device 210, in a preferred embodiment, the present invention can also be provided with a transparent carrier 211, and LED chips 230 corresponding to the assembly positions are arranged on the lower side of the transparent carrier 211, specifically arranged in a matrix manner, preferably, the LED chips are connected to the transparent carrier through a peeling layer 212, and the peeling layer can be implemented but not limited to polyimide, and of course other adhesive materials can also be used, as long as the LED chip can be released by a predetermined technical means. The polyimide material can be rapidly evaporated by laser irradiation, thereby explosively peeling off the LED chip.

[0043] In a more preferred embodiment, the mass transfer system of laser lift-off of the present invention is provided with a boss 213 below the transparent carrier 211 of the transfer device 210, corresponding to the position of the LED chip 230 and the lift-off layer 212. Figure 4 As shown, the LED chip 230 can be extended from the lower side of the transparent carrier to the receiving device, which facilitates faster assembly of the LED chip.

[0044] In a further embodiment of the mass transfer system for laser lift-off of the present invention, a functional layer 214 is further provided on the upper side of the transfer device 210, such as Figure 4 As shown, the functional layer 214 is provided to form a plurality of light-shielding particle regions 216, and a corresponding light-transmitting window 215, i.e., a transparent region, is formed on the transparent carrier at the positions of the light-shielding particle regions corresponding to the orthographic projection of the LED chip and the stripping layer. The transparent region may be slightly larger than the orthographic projection size of the LED chip, and the window is actually formed by surrounding light-shielding particle regions 216. That is to say, light-shielding particle regions 216 are provided between adjacent LED chips and stripping layer positions, and a first electrode 217 and a second electrode 218 are provided at both ends of each light-shielding particle region 216, so that power-on control can be performed from above the transparent carrier 211 to control the movement of the light-shielding particles, thereby controlling the light-shielding degree of the light-shielding particle region, mainly controlling the light-shielding particles to be evenly distributed in the entire light-shielding particle region to completely shield the entire light-shielding particle region, or concentrating the light-shielding particles in the midline portion of the region, thereby reducing the area of ​​total light shielding to form a state of substantially total light transmission.

[0045] like Figure 5 and Figure 6 , Figure 7 As shown, the gap between adjacent shading particle areas 216 is the window 215 for transmitting the laser. At this time, if the entire shading particle area is evenly distributed and opaque through the power-on control mode of the first electrode 217 and the second electrode 218, the laser will enter the boss 213 through the window and irradiate the peeling layer 212, so that the corresponding LED chip can be peeled off and released (at this time, the LED chip on the transfer device needs to be aligned with the corresponding groove on the receiving device), so that the corresponding LED chip falls into the corresponding groove 223.

[0046] The shading particle materials used in the shading particle area are common in the prior art. Commonly used materials include but are not limited to Cu2+ copper ions, Fe2+ ferrous ions, Ni2+ nickel ions, Cr3+ chromium ions, and Au3+ gold ions. The bonding material of one or more of these particles can be any metal particles that have been ionized. At the same time, the control of the light transmittance of shading particles is also known in the prior art, so it will not be repeated here.

[0047] like Figure 5 and Fig. 9As shown, the setting of the shading particle area can be realized in a stripe or grid manner. If the shading particle area 216 cannot be covered, the gap between the shading particle areas 216 and not used as the window 215 can be kept in a light-transmitting state in advance to form a completely light-transmitting area 310; in other embodiments, the light-transmitting area 310 can also use the same coating material as the shading particle area 216, but it is noted that each electrode 217 or 218 may need to be reused, or set at multiple locations, and its circuit composition must be considered, and the processing and manufacturing process requirements are more complicated, such as Figure 5 and Fig. 9 The difference shown is that the embodiments of the light-shielding particle region 216 and the first electrode 217 and the second electrode 218 are arranged in different ways.

[0048] Figure 5 In the embodiment shown in , the light-shielding particle region 216 is arranged between any two adjacent windows 215, and the first electrode 217 and the second electrode 218 are arranged at the ends in sequence from top to bottom (second direction B) and from left to right (first direction A), so that a docking circuit can be arranged according to each window 215, and the first electrode 217 is arranged on the upper side and left side of each window 215, and the second electrode 218 is arranged on the lower side and right side, so that the light-shielding particle region 216 between adjacent windows 215 has positive and negative poles, so that the light-shielding degree can be switched between the state of full light-shielding and concentrated light-shielding to the center (i.e., basically no light-shielding) by powering on. A square transparent region 310 will be formed between the four adjacent windows 215.

[0049] Of course, the arrangement of the two electrodes is not limited to that of the present embodiment, and other convenient modifications may be made. For example, 217-218-217-218 may be arranged in sequence from the top in a clockwise direction around the window 215, and in another window adjacent to the window, 218-217-218-217 may be arranged in sequence from the top in a clockwise direction. In this way, different electrodes are arranged at both ends of a certain light-shielding particle area 216, thereby facilitating circuit control.

[0050] It can be understood that in a preferred embodiment of the present invention, the light-shielding particle area 216 can be set between two transparent areas in at least one direction (the first direction A, the second direction B or both directions at the same time), that is, the window 215, and a first electrode 217 and a second electrode 218 are set on both sides of the light-shielding particle area 216 close to the transparent area, which serve as positive and negative electrodes respectively, for electrically controlling the light-shielding particle area 216 to have a shielded area that is the entire area or concentrated in the center (basically not shielded at all).

[0051] and Fig. 9In another preferred embodiment shown in , the light shielding particle area 216 is arranged between any two adjacent columns of windows 215, and the first electrode 217 and the second electrode 218 are directly arranged in a strip shape on both sides of each column of windows 215, and a light-transmitting area 310 is arranged between two adjacent windows 215 in the same column. In this way, the first electrode 217 and the second electrode 218 are easier to conduct and connect due to their longer strip shape, and it is easier to set up external circuit connections. Figure 5 For the embodiment shown, the layout on the functional layer 214 is simpler, and the implementation is more in line with the simplified process requirements of actual processing. In a further embodiment, the light-transmitting area 310 can also be set to adopt a solution of a light-shielding particle area, but the first electrode 217 and the second electrode 218 need to be designed and arranged in advance so that the movement of the light-shielding particles in the area can also be controlled. For example, the first electrode and the second electrode are respectively provided with independent control electrodes for the area (the light-transmitting area 310 area in the figure), and for another example, the independent control electrode is arranged along the area as an independent electrode.

[0052] like Figures 6 to 8 As shown, in a preferred embodiment of the present invention, by controlling the power on of the first electrode 217 and the second electrode 218 (the control mode is known in the prior art), the light-shielding particles in each light-shielding particle area 216 can be controlled to change from shading in the entire coverage area to concentrating in the center of the area, thereby expanding the light-transmitting area of ​​the transparent carrier. At this time, the photoresist layer 222 on the entire target substrate 221 can be irradiated and dissolved by laser irradiation. Finally, only a tiny residual photoresist layer 225 is left on the target substrate 221, and this residual part does not affect the use of the entire display panel. Therefore, the mass transfer of the entire panel can be completed.

[0053] The present invention also provides a transfer method for the mass transfer system of the above preferred embodiment, which specifically includes the following steps: Figure 6 As shown, firstly, the position of the LED chip on the transfer device 210 is aligned with the corresponding groove on the receiving device 220; then, the first electrode 217 and the second electrode 218 are energized to control the overall uniform shading of each light-shielding particle area. At this time, the laser irradiates the transfer device from the front, and the peeling layer 212 can be irradiated through the window 215 between the light-shielding particle areas 216, so that the LED chip falls into the corresponding groove 223, as shown in FIG. Figure 7 shown.

[0054] By controlling the re-energization of the first electrode 217 and the second electrode 218, the movement of the light-shielding particles can be adjusted and controlled so that the light-shielding particles in each light-shielding particle region 216 are concentrated at the center position 219 of the light-shielding particle region. Figure 8 At this time, laser irradiation can be used to irradiate the photoresist layer 222 of the receiving device 220 through most of the transparent carrier. The laser beam can dissolve most of the photoresist layer, leaving only a tiny residual portion of the photoresist layer 229, thereby completing the mass transfer process of the micro device.

[0055] The mass transfer system and method of laser stripping described in the present invention, due to the use of a groove structure set on the receiving device, facilitates the accurate positioning of the LED chip on the receiving device to the assembly position, and utilizes the positioning effect of the groove, so that the position of the dropped LED chip on the target substrate is more accurate. In addition, the system and method described in the present invention utilizes the control of the moving position of the shading particles, and through the energization of the first electrode and the second electrode, the shading particle area switches between different shading modes concentrated in the overall and central positions, thereby realizing two irradiations of different areas by the laser beam, thereby achieving not only the stripping of the LED chip, but also the dissolution of the photoresist layer on the target substrate, without the need for additional cleaning of the photoresist layer, saving process time and improving work efficiency. The present invention makes the entire process simpler by secondary irradiation of the laser beam (expanding the irradiation area).

[0056] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A laser lift-off mass transfer system, characterized in that: including a transfer device and a receiving device; The transfer device is provided with LED chips to be transferred, and the LED chips form an LED chip matrix along a first direction and a second direction. A side of the transfer device away from the LED chips is provided with a plurality of light-shielding particle areas and a plurality of transparent areas, the light-shielding particle areas are arranged around the transparent areas, and the light-shielding particles in the light-shielding particle areas are arranged in different states under the action of electricity. The receiving device includes a target substrate; A photoresist layer is arranged on the target substrate, and a corresponding groove is pre-arranged at a corresponding LED chip assembly position of the photoresist layer, the groove matches the LED chip, and a bonding electrode is exposed at the bottom.

2. The laser lift-off mass transfer system according to claim 1, characterized in that: The transfer device comprises: a transparent carrier and an LED chip waiting to be transferred arranged at a corresponding position on a surface of the transparent carrier facing the receiving device; the LED chip is connected to the transparent carrier via a peeling layer.

3. The laser lift-off mass transfer system according to claim 2, characterized in that: A boss is arranged on a surface of one side of the transparent carrier facing the receiving device, corresponding to the position of the LED chip and the peeling layer.

4. The laser lift-off mass transfer system according to claim 2 or 3, characterized in that: A functional layer is arranged on a side of the transparent carrier away from the receiving device, the functional layer comprising a light-shielding particle region and a transparent region spaced apart in the first direction; The positive projection position of the LED chip on the functional layer belongs to the transparent area, the shading particle area is arranged between two adjacent columns of transparent areas, and a first electrode and a second electrode are arranged on both sides of the shading particle area close to the transparent area for powering on to control the movement of the shading particles in the shading particle area.

5. The laser lift-off mass transfer system according to claim 4, characterized in that: The light-shielding particles can be distributed in the entire light-shielding particle area or concentrated in the center line portion of the light-shielding particle area under power-on control.

6. The laser lift-off mass transfer system according to claim 5, characterized in that: The peeling layer is made of polyimide.

7. The laser lift-off mass transfer system according to claim 6, characterized in that: The light-shielding particle material includes one or more combinations of the following materials: Cu2+copper ions, Fe2+ferrous ions, Ni2+nickel ions, Cr3+chromium ions, and Au3+gold ions.

8. A method for mass transfer of laser lift-off according to claim 4 or 5, comprising the following steps: A. Align the position of the LED chip on the transfer device with the groove on the receiving device; B. controlling the entire light-shielding particle region to be light-shielded by energizing the first electrode and the second electrode; C. Use laser to irradiate the peeling layer through the window between the light-shielding particle areas, so that the LED chip is separated from the transfer device and falls into the groove.

9. The laser lift-off mass transfer method according to claim 8, characterized in that: After step C, the method further comprises the following steps: D. controlling the light-shielding particles to be concentrated at the center of the light-shielding particle area by re-energizing the first electrode and the second electrode to expand the laser transmission area; E. Use laser to penetrate the transparent carrier to irradiate and dissolve the photoresist layer.

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