Mini LED mass transfer process method

Abstract

The invention relates to the technical field of semiconductors, and discloses a Mini LED mass transfer process method, which comprises the steps of pasting a transfer film on a transfer plate, removing a transfer film area except chips based on the arrangement positions of the chips on the transfer plate, and arranging the chips on the transfer plate; arranging a transfer plate above the PCB substrate so as to align the position of the chip with the position of the PCB bonding pad; the transfer plate is pressed down to enable the chip and the bonding pad of the PCB substrate to be aligned and then to be pressed and welded; and the transfer plate is lifted up to separate the transfer film from the chip, and transfer is completed. According to the invention, the problem of low yield of Mini LED giant conversion is solved, the first pass yield of giant conversion is improved, the first pass yield is improved from 95% to 99%, the production efficiency is improved by more than 30%, and the production cost is reduced by more than 20%; the problem of light color inconsistency caused by chip deviation is solved, and the light color consistency of each angle of the display screen is improved; and the quality reliability problem caused by pseudo soldering and overvoltage is solved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a process method for mass transfer of Mini LEDs. Background Art

[0002] Mini LED display has the characteristics of high efficiency, low power consumption, high stability, long life and low cost. It is an important choice for the current mainstream display technology and has the potential to replace existing technologies in many fields. Compared with OLED, Mini LED is not inferior in terms of contrast and color, and has important advantages such as low cost, flexible specifications and long life. It adapts to the development needs of the two major optoelectronic sectors of panel / LED industry chain and will be widely used in the display field. In the prior art, the mass transfer method is to hit the chip from the raw material carrier film to the highest point, and then suck the chip with a suction nozzle and send it to the pre-arranged carrier plate. The stability during the transfer process determines the actual operational feasibility of the production capacity. However, during the conventional mass transfer downward pressure action, the transfer plate presses the LED chip downward to contact the PCB board. In this process, the transfer film is squeezed and deformed. In the actual process, due to the difference in LED chip thickness and the poor flatness of the PCB substrate, there is often uneven diffusion of the transfer film at different LED chips, resulting in insufficient compensation of the chip and the PCB substrate. At present, the transfer yield of MiniLED direct display products cannot reach 100%, and there will be a certain proportion of bad pixels, which reduces the yield of the entire line and increases the product cost.

[0003] Therefore, there is a need in the prior art to improve the process method for mass transfer of Mini LEDs. Summary of the invention

[0004] In view of this, the purpose of an embodiment of the present invention is to propose a process method for mass transfer of Mini LEDs, which not only solves the chip tilting and deviation caused by unbalanced stress of the transfer film, but also solves the risks of cold solder joints and overvoltage during pressing, greatly improves the yield and reduces production costs.

[0005] Based on the above purpose, an embodiment of the present invention provides a process method for mass transfer of Mini LEDs, including: A transfer film is attached to a transfer plate, and based on the arrangement position of the chip on the transfer plate, the transfer film area outside the chip is removed, and the chip is arranged on the transfer plate; Placing the transfer plate above the PCB substrate to align the chip with the PCB pad position; Press down the transfer plate to align the chip with the pads of the PCB substrate and then press and weld them; Lift the transfer plate to separate the transfer film from the chip to complete the transfer.

[0006] In some embodiments, the area outside the chip on the transfer film is removed by laser cutting.

[0007] In some embodiments, removing the area outside the chip on the transfer film by laser cutting includes: The position of the transfer film to be removed is calibrated by a laser positioning device, the laser parameters are adjusted according to the material properties and thickness of the transfer film, and the calibrated position is irradiated with laser to remove the transfer film.

[0008] In some embodiments, the calibration position is spaced 10-50 μm from the chip boundary.

[0009] In some embodiments, a film cutter is used to remove the area outside the chip on the transfer film.

[0010] In some embodiments, the compression welding is performed by means of laser welding.

[0011] In some embodiments, the step of laser welding includes: S1 Alignment and fixation: Use a positioning system or fixture to accurately align the LED chip with the pad of the PCB substrate, and apply force to fix it; S2 Laser welding: Start the laser welding machine, focus the laser beam on the pad, and use the laser energy to melt the solder and penetrate between the LED chip and the PCB substrate for welding; S3 welding quality inspection: after welding, the welding quality is inspected to ensure that there are no cold or false welding problems at the solder joints.

[0012] In some embodiments, the chip is arranged on the transfer plate in a spike arrangement.

[0013] In some embodiments, the transfer plate is a quartz glass substrate or a silicate glass substrate.

[0014] In some embodiments, the transfer film is a UV film or a blue film.

[0015] The present invention has at least the following beneficial technical effects: After the transfer film is attached to the transfer plate, the method of this aspect performs laser removal on the area outside the chip on the transfer film, which can be before or after the crystallization, so that the following problems can be solved: 1. The stress in the transfer film is released; 2. When the giant turn is pressed down, the transfer film material under the chip will diffuse outward evenly, solving the chip offset problem; 3. When the giant turn is pressed down, the transfer film material under the chip will diffuse more easily to the groove area, making the downward pressure compensation greater and solving the overpressure problem; 4. By appropriately increasing the transfer film thickness, the compensation stroke is further increased to solve the problem of cold soldering. The method of the present invention can solve the problem of low yield of MiniLED giant turn, improve the pass rate of giant turn, and the pass rate is increased from 95% to 99%, the production efficiency is increased by more than 30%, and the production cost is reduced by more than 20%; solve the problem of inconsistent light color caused by chip deviation, and improve the consistency of light color at all angles of the display screen; solve the quality reliability problem caused by cold soldering and overpressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying creative work.

[0017] Figure 1 Schematic diagram of stress distribution of conventional giant rotation pressing diagram in the prior art; Figure 2 A flow chart of a first embodiment of a process method for mass transfer of Mini LEDs provided by the present invention; Figure 3 A flow chart of a first embodiment of a process method for mass transfer of Mini LEDs provided by the present invention; Figure 4 A schematic diagram of an embodiment of the giant rotation pressing provided by the present invention; Figure 5 A schematic diagram of an embodiment of the giant rotation compression stress distribution provided by the present invention.

[0018] Description of reference numerals: 1. Transfer plate; 2. Transfer film; 3. Chip; 3.1. Chip electrode; 4. PCB substrate; 4.1. Solder pad. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field of the present invention; the terms used in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. For example, the directions or positions indicated by the terms "length", "width", "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the directions or positions shown in the drawings, which are only for the convenience of description and should not be understood as limitations on the present technical solution.

[0021] The terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions; the terms "first", "second", etc. in the specification and claims of the present invention or the above-mentioned drawings are used to distinguish different objects rather than to describe a specific order. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0022] In the specification and claims of the present invention and the above-mentioned drawings, when an element is referred to as being "fixed to" or "mounted on" or "disposed on" or "connected to" another element, it may be directly or indirectly located on the other element. For example, when an element is referred to as being "connected to" another element, it may be directly or indirectly connected to the other element.

[0023] In addition, reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0024] The conventional Mini LED giant transfer process includes: sticking the transfer film on the transfer glass; arranging the LED chip on the transfer film through spike crystals; placing the transfer plate above the PCB and aligning the chip with the PCB pads; pressing down the transfer plate to make the LED chip basically contact the PCB; using laser welding to basically weld the LED chip to the PCB; lifting the transfer plate to separate the transfer film from the LED chip to complete the transfer; and inspecting the post-transfer process.

[0025] When the giant turns and presses down, the LED chip will squeeze the transfer film under the chip. If the thickness of the LED chip is completely consistent, the PCB substrate is completely flat, and the thickness of the transfer film and the internal stress are completely uniform, the transfer success rate and yield rate can be guaranteed. However, this is impossible in reality. Due to the inconsistent thickness of the LED chip, the flatness of the PCB substrate, the uniformity of the transfer film thickness and the internal stress, there are problems such as Figure 1 As shown in the figure, the transfer film 2 is a film with uniform thickness that is tightly attached to the transfer plate, the chip 3 connected below has different thicknesses, and there are multiple pads on the PCB substrate 4. When the giant turns and presses down, the thicker LED chip 3 and the transfer film 2 in the convex area of ​​the PCB substrate 4 will be squeezed more, and the transfer film 2 will spread around the chip 3. However, the space for diffusion is limited and it will not be squeezed to a certain extent. However, the thin thickness of some chips 3 and the concave area of ​​the PCB substrate 4 have not been compensated in place, resulting in uneven stress at various places where the transfer film 2 contacts the chip 3, such as Figure 1 The stress distribution on the left and right sides of the transfer film 2 above the chip 3 is uneven, and the downward pressure at different locations is inconsistent, which leads to poor connection between the chip and the PCB board.

[0026] The transfer film is a flexible material that plays the role of bonding and binding the chip. The conventional method of increasing the thickness of the transfer film solves the problem of pressure compensation to a certain extent, but it adds a new problem, that is, chip offset. Due to the uneven stress distribution in the film, the chip transfer film will also offset in different directions when squeezed, such as Figure 1 Therefore, the present invention provides a process method for mass transfer of Mini LEDs to solve the existing problems, such as Figure 2-3 The flowchart of an embodiment of a process method for mass transfer is shown, comprising the following steps: S1 attaches the transfer film 2 to the transfer plate 1, removes the transfer film 2 area outside the chip based on the arrangement position of the chip 3 on the transfer plate 1, and arranges the chip 3 on the transfer plate 1; S2: placing the transfer plate above the PCB substrate 4 to align the chip with the PCB pad 4.1; S3 presses down the transfer plate to align the chip 3 with the pad 4.1 of the PCB substrate 4 and then presses and welds them together; S4 lifts the transfer plate 1 to separate the transfer film 2 from the chip 3, and the transfer is completed.

[0027] Further, the area outside the chip on the transfer film is removed by laser cutting. In some embodiments, removing the area outside the chip on the transfer film by laser cutting includes: calibrating the position of the transfer film to be removed by a laser positioning device, adjusting laser parameters according to the material properties and thickness of the transfer film, and irradiating the calibrated position with laser to remove the transfer film.

[0028] Laser removal of part of the transfer film specifically includes the following steps: 1. Laser positioning and focusing: First, the laser positioning device is used to determine the specific location where the transfer film needs to be removed. The laser beam is focused at the target location to form a sufficiently small and concentrated laser spot.

[0029] 2. Laser parameter adjustment: According to the material properties and thickness of the transfer film, the laser power, pulse width and frequency and other parameters are adjusted. The adjustment of these parameters is crucial to ensure the effective removal of the transfer film.

[0030] 3. Laser irradiation: Irradiation is performed at the focused laser spot, and the laser beam interacts with the surface of the transfer film; the laser energy locally heats the transfer film to its melting point or vaporization point.

[0031] 4. Material stripping: Due to the thermal effect generated by laser irradiation, the transfer film melts or vaporizes at a local location. By controlling the time and intensity of laser irradiation, partial removal of the transfer film can be achieved.

[0032] 5. Peeling precision control: The precision and accuracy of the transfer film removal can be ensured by the sophisticated laser control system, which is crucial for the precise placement and positioning of subsequent LED chips or other micro components.

[0033] The beneficial effects of laser cutting to remove areas other than the chip on the transfer film include: High precision: Laser removal technology can achieve high-precision transfer film removal, ensuring the precise placement of LED chips or other micro components. High efficiency: The laser removal process is fast and efficient, which can significantly reduce production time and costs. At the same time, laser technology can also achieve automated operations to further improve production efficiency. No damage: By precisely controlling laser parameters and irradiation time, it can be ensured that the removal process does not damage the LED chip or other micro components, which helps to maintain the integrity and performance stability of the product. And environmental protection and energy saving: Laser removal technology is an environmentally friendly removal method that does not produce harmful waste and gas emissions. At the same time, laser equipment has low energy consumption during operation, which helps to reduce production costs and reduce energy consumption.

[0034] In some embodiments, the calibration position is spaced 10-50 μm from the chip boundary, and the setting of this spacing helps to reduce the possible deviation of the laser beam during operation, thereby ensuring the accuracy and consistency of the transfer film removal.

[0035] Furthermore, a film cutter can also be used to remove areas outside the chip on the transfer film. The film cutter uses advanced laser or mechanical cutting technology to accurately control the cutting path to ensure that only areas outside the chip are removed without causing any damage to the chip itself. This precision greatly improves production efficiency and product quality. Modern film cutters usually have automated operation functions, which can automatically identify and locate the chip position, and perform fast and accurate cutting. This not only reduces manual intervention, but also improves production efficiency. However, compared to laser cutting, film cutters may be insufficient in cutting accuracy, especially for application scenarios that require high-precision cutting. In addition, the material adaptability of film cutting is limited. Although the film cutter has a wide range of applicability, it may not achieve the desired effect when processing certain special materials or films that require extremely high cutting accuracy.

[0036] Furthermore, if Figure 4 As shown, the left figure is a schematic diagram of the pressing process, and the right figure is a schematic diagram after pressing. Press welding is performed by laser welding, and the chip electrode 3.1 is aligned with the pad 4.1 of the PCB substrate 4 and then pressed and welded. In some embodiments, the steps of laser welding include: S1 Alignment and fixation: Use a positioning system or fixture to accurately align the LED chip with the pad of the PCB substrate, and apply force to fix it; S2 Laser welding: Start the laser welding machine, focus the laser beam on the pad, and use the laser energy to melt the solder and penetrate between the LED chip and the PCB substrate for welding; S3 welding quality inspection: after welding, the welding quality is inspected to ensure that there are no cold or false welding problems at the solder joints.

[0037] In addition, it can further include cleaning and curing steps. If necessary, the LED chip and PCB substrate after welding are cleaned to remove the residues generated during the welding process. If conductive adhesive welding and other solders that need to be cured are used, the welded LED chip and PCB substrate are placed in a thermal cycle oven for constant temperature curing to improve the reliability and stability of welding.

[0038] Furthermore, the chip is arranged on the transfer plate in a needle-like arrangement. That is, the needle-like transfer technology accurately places the LED chip at a predetermined position on the transfer film by moving the ejector pin. This technology can achieve high-speed and high-precision chip arrangement. Specifically, using automated equipment, the Mini LED chips are placed one by one or in batches on the transfer film in a needle-like manner to form a predetermined chip array.

[0039] Furthermore, the transfer plate can be a quartz glass substrate or a silicate glass substrate, wherein the quartz glass substrate is characterized in that quartz glass has extremely high purity and high temperature resistance, and can withstand process operations in a high temperature environment without deformation or deterioration. In addition, quartz glass also has good light transmittance and chemical stability. The characteristics of the silicate glass substrate are that it has the advantages of low cost, good light transmittance, and easy processing. However, compared with quartz glass, silicate glass may be slightly inferior in terms of high temperature resistance and chemical stability, and those skilled in the art can choose to use it according to actual needs.

[0040] Furthermore, the transfer film is a UV film or a blue film. The UV film can not only fix the chip, but also provide a certain degree of protection during the processing to prevent the chip from being physically damaged or contaminated. Compared with the UV film, the cost of the blue film is usually lower, and the viscosity of the blue film is relatively stable and is not easily affected by external factors (such as temperature) and changes significantly.

[0041] like Figure 5 FIG. 1 is a schematic diagram of an embodiment of the giant rotation compression stress distribution provided by the present invention. Figure 1 As shown in the figure, the problems of the prior art can be seen. The transfer film improved by the method of the present invention is set as multiple independent areas, the internal stress of the corresponding transfer film on each chip is released, and the transfer film material under the chip will diffuse outward evenly when the chip is pressed down by a huge rotation, solving the chip offset problem. The transfer film material under the chip will diffuse more easily to the groove area when the chip is pressed down by a huge rotation, which is suitable for chips of different thicknesses to be pressed down by a huge rotation at the same time without interfering with each other, solving the overpressure problem; by appropriately increasing the transfer film thickness, the compensation stroke is further increased to solve the problem of cold soldering.

[0042] The present invention is further explained below in conjunction with specific embodiments. It should be noted that the order of the transfer film removal step and the chip arrangement step on the transfer plate of the present invention is not limited.

[0043] Example 1 like Figure 2 The flowchart of the first embodiment of the process method for mass transfer of Mini LEDs provided by the present invention includes the following steps: 1. Stick the transfer film on the transfer glass; 2. Arrange the LED chips on the transfer film through the thorn crystal; 3. Remove the chip area through laser processing to form a groove 4. Place the transfer plate above the PCB base and align the chip with the PCB pad position; 5. Press down the transfer plate to make the LED chip basically contact with the PCB; use laser welding to basically weld the LED chip and PCB; 6. Lift the transfer plate to separate the transfer film from the LED chip to complete the transfer.

[0044] Example 2 like Figure 3 The flowchart of the first embodiment of the process method for mass transfer of Mini LEDs provided by the present invention includes the following steps: 1. Stick the transfer film on the transfer glass; 2. Remove the chip area through laser processing to form a groove 3. Arrange the LED chips on the transfer film through the thorn crystal; 4. Place the transfer plate above the PCB base and align the chip with the PCB pad position; 5. Press down the transfer plate to make the LED chip basically contact with the PCB; use laser welding to basically weld the LED chip and PCB; 6. Lift the transfer plate to separate the transfer film from the LED chip to complete the transfer.

[0045] The above are exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications may be made without departing from the scope disclosed in the embodiments of the present invention as defined in the claims. The functions, steps and / or actions of the method claims according to the disclosed embodiments described herein do not need to be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless explicitly limited to the singular.

[0046] It should be understood that, as used herein, the singular forms "a", "an" are intended to include the plural forms as well, unless the context clearly supports an exception. It should also be understood that, as used herein, "and / or" refers to any and all possible combinations including one or more of the associated listed items.

[0047] The serial numbers of the embodiments disclosed in the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0048] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the above embodiments of the present invention, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A process method for mass transfer of Mini LEDs, characterized in that: include: Affixing a transfer film to a transfer plate, removing the transfer film area outside the chip based on the arrangement position of the chip on the transfer plate, and arranging the chip on the transfer plate; The transfer plate is arranged above the PCB substrate to align the chip with the PCB pad position; Pressing down the transfer plate to align the chip with the pad of the PCB substrate and then press-welding them; The transfer plate is lifted to separate the transfer film from the chip, thereby completing the transfer.

2. The process method for mass transfer of Mini LEDs according to claim 1, wherein: The area outside the chip on the transfer film is removed by laser cutting.

3. The process method for mass transfer of Mini LEDs according to claim 2, wherein: Removing the area other than the chip on the transfer film by laser cutting includes: The position of the transfer film to be removed is calibrated by a laser positioning device, the laser parameters are adjusted according to the material properties and thickness of the transfer film, and the calibrated position is irradiated with laser to remove the transfer film.

4. The process for mass transfer of Mini LEDs according to claim 3, wherein: The calibration position is spaced 10-50 μm from the chip boundary.

5. The process for mass transfer of Mini LEDs according to claim 1, wherein: The area other than the chip on the transfer film was removed using a film cutter.

6. The process for mass transfer of Mini LEDs according to claim 1, wherein: Press-fit welding is performed by means of laser welding.

7. The process for mass transfer of Mini LEDs according to claim 6, wherein: The steps of laser welding include: S1: Aligning and fixing: using a positioning system or a fixture to accurately align the LED chip with the pad of the PCB substrate, and applying force to fix them; S2 laser welding: start the laser welding machine, focus the laser beam on the pad, melt the solder through the laser energy and penetrate into the space between the LED chip and the PCB substrate for welding; S3 welding quality inspection: after welding, the welding quality is inspected to ensure that there are no cold or false welding problems at the solder joints.

8. The process for mass transfer of Mini LEDs according to claim 1, wherein: The chips are arranged on the transfer plate in a spike arrangement manner.

9. The process for mass transfer of Mini LEDs according to claim 1, wherein: The transfer plate is a quartz glass substrate or a silicate glass substrate.

10. The process method for mass transfer of Mini LEDs according to claim 1, wherein: The transfer film is a UV film or a blue film.

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