Manufacturing method of miniature full-color LED

Abstract

The invention provides a manufacturing method of a miniature full-color LED, and belongs to the technical field of LED display. The micro LED packaging technology solves the problems that an existing micro LED packaging technology is complex in technology, high in cost and incapable of achieving submillimeter pixel pitch packaging, and comprises the following steps that a flexible substrate is manufactured and divided into a plurality of micro substrate units, and a double-face copper-clad circuit is manufactured on each micro substrate unit to form a functional area and a bonding pad; the front face of the transparent glass carrier plate is coated with high-temperature-resistant UV dissociation glue in a spinning mode, then the flexible substrate is attached to the transparent glass carrier plate, and high-temperature curing is completed; the R / G / B color chips are fixedly placed on the flexible substrate through a mass transfer technology; spin-coating black resin ink on the surface of the flexible substrate on which the micro LED chip is fixed, and attaching the glass subjected to surface optical treatment to the spin-coated black resin ink; a laser process is adopted to complete cutting; a film reversing machine and a splitting machine are used for completing stripping of a single miniature LED finished product; the manufacturing method is applied to manufacturing of the miniature LED.

Description

Technical Field

[0001] The invention provides a method for manufacturing a miniature full-color LED, belonging to the technical field of LED display. Background Art

[0002] At present, traditional display LEDs use LED chips with a size of more than 100um. The chip structure includes a substrate, an epitaxial layer, and a current spreading layer structure. The overall thickness is generally greater than 80um. The size of the RGB three-color chip integrated into the package is greater than 0.6*0.6mm. When implementing sub-millimeter packaging, it cannot meet the size requirements of miniaturized packaging.

[0003] To solve the above problems, the Chinese patent with application number 202211384384.2 disclosed in the prior art proposes a method for realizing the packaging and manufacturing of micro LED display devices. By designing a new micro LED array display device structure, the electrode externalization photolithography process and the patch packaging process are combined to carry out the packaging integration of the micro LED array display device and the driver circuit board. On the one hand, by preparing the electrode externalization structure, the electrode area of ​​the pixel can be increased, making the patch bonding process easier to operate and more accurate, effectively simplifying the bonding steps; on the other hand, combined with the leak printing solder paste technology, the chip is bonded to the substrate, reducing the use of gold wire or alloy materials, and by adopting the chip high pixel density array production, the production efficiency is improved and the production cost is reduced.

[0004] However, the above technical solution mainly achieves the improvement of the manufacturing process of the flexible substrate, which mainly improves the electrodes on the circuit board of the micro-LED, leads the electrodes outward, and reduces the difficulty of connection; however, the manufacturing process of this technology still cannot reduce the size and thickness of the LED chip, and cannot realize display products with sub-millimeter pixel pitch. Summary of the invention

[0005] In order to solve the problems of complex process, high cost and inability to achieve sub-millimeter pixel pitch in the existing micro LED packaging process, the present invention proposes a method for manufacturing a micro full-color LED.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for manufacturing a miniature full-color LED, comprising the following steps: S1: Ultra-flexible substrate production: Use ultra-thin flexible material to produce a flexible substrate, and divide the flexible substrate into multiple micro-substrate units. Make double-sided copper-clad circuits on each micro-substrate unit, deposit a die-bonding pad functional area on the front of each micro-substrate unit, and lead out four square fan-out external lead pads on the back of each micro-substrate unit, and expose the die-bonding pad functional area and the square fan-out external lead pads. S2: Spin coating and laminating carrier: Select a transparent glass carrier, clean its surface, spin coat the front of the transparent glass carrier with UV dissociation glue that can withstand high temperatures, and then laminate the flexible substrate made in step S1 on the transparent glass carrier, and cure it at high temperature; S3: Mass transfer: First, print solder paste on the bonding pad functional area of ​​the flexible substrate through a printing process, and then use a mass transfer process to accurately align the R / G / B color chips of the micro LED chips on the pads of the bonding pad functional area on the front of the flexible substrate. Use a laser rapid welding process to heat the electrodes at both ends of the micro LED chip and the solder paste on the bonding pad functional area of ​​the flexible substrate, and quickly melt the solder paste to complete the welding of the micro LED chip and the flexible substrate; S4: Spin coating: Spin coating black resin ink on the surface of the flexible substrate where the micro LED chip is solidified, and then use a flat vacuum suction tool to bond the glass that has undergone surface optical treatment to the just-spin coated black resin ink, and then use high temperature curing after bonding; S5: Laser cutting: Use laser technology to cut the optical glass along each micro unit on the front of the flexible substrate using a hidden cutting process to cut the surface glass of each micro light-emitting unit; then use infrared laser to project the hidden cutting line of the surface optical glass to cut each layer of each micro substrate unit below the surface optical glass; S6: Film inversion and UV dissociation: Use a film inversion machine to invert the entire micro LED that has been cut onto the blue film, so that the optical glass surface is close to the blue film, and then use ultraviolet light to irradiate the transparent glass carrier to peel off the entire encapsulated micro LED from the transparent glass carrier; then transfer it to a splitting machine to complete the splitting of the upper surface glass and separate it into single micro LED finished products.

[0007] The method also includes step S7: point test and sorting: using point test and sorting equipment to perform probe electrical connection test and photoelectric parameter classification on the finished micro LED products.

[0008] Three standard alignment holes are set at the four corners of the flexible substrate in step S1, and alignment MARK points are set at the four corners of the transparent glass carrier in step S2. The alignment MARK points are consistent with the alignment holes of the flexible substrate to facilitate alignment.

[0009] In the step S1, a double-sided copper-clad circuit is manufactured on each micro substrate unit by exposure, development, and chemical deposition processes. Copper-filled vias are formed from the front to the back of the double-sided copper-clad circuit by perforation and copper filling. The positions of the copper-filled vias on the back of each micro substrate unit are formed into four square fan-out external lead pads at the four corners of the micro substrate unit by chemical plating.

[0010] In the step S1, the bonding pad functional area on each micro basic unit is formed by chemically plating 1-2 um of gold in the middle functional area by chemically immersing gold to form 6 bonding pad functional areas.

[0011] In the step S1, the die bonding pad functional area and the square fan-out external lead pad are exposed by printing black solder resist ink on the front and back sides of the flexible substrate respectively, and then exposing the die bonding pad functional area and the square fan-out external lead pad by exposure and development.

[0012] In the step S1, chemical plating leads are connected between each two micro substrate units, and a horizontal cutting line and a vertical cutting line are printed in the middle of each micro substrate unit.

[0013] The particle size of the solder paste used in step S3 is 2-11 um.

[0014] The thickness of the black resin ink spin-coated on the flexible substrate in step S4 is 5-10 um higher than the upper surface of the micro LED chip, and the thickness of the optical glass is 0.12-0.2 mm.

[0015] The optical glass used in step S4 is provided with cutting paths corresponding to the transverse cutting lines and the longitudinal cutting lines of the micro basic units, and hidden cutting lines are provided on the cutting paths.

[0016] The beneficial effects of the present invention compared to the prior art are as follows: the present invention realizes the packaging of micro display LEDs through the corresponding semiconductor process, and through this process, it will promote the micro display LEDs to move towards large-scale applications, push LED display from millimeter level to sub-millimeter level application, and drive LED display to penetrate into consumer display application scenarios such as large TVs, all-in-one conference machines, computer displays, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below in conjunction with the accompanying drawings: Figure 1-3 Schematic diagram of the front, back and top views of the flexible substrate after step S1.1 of the present invention is completed; Figure 4-6 Schematic diagram of the front, back and top views of the flexible substrate after step S1.2 of the present invention is completed; Figure 7 This is a schematic structural diagram of a transparent glass carrier plate used in the present invention; Figure 8-10 Schematic diagram of the front, back and top views of the flexible substrate after step S2 of the present invention is completed; Fig.11 This is a schematic diagram of the front structure of the flexible substrate after printing solder paste in step S3 of the present invention; Figure 12-13Schematic diagram of the front and top view of the flexible substrate after step S3 of the present invention is completed; Figure 14-15 It is a schematic diagram of the front view and top view of the structure of the flexible substrate after the black resin ink is spin-coated and then bonded to the optical glass in step S4 of the present invention; Figure 16-17 It is a schematic diagram of the front and back structures of the flexible substrate after the optical glass is divided into cutting lanes in step S5 of the present invention; Figure 18-19 This is a schematic diagram of the front and back structures of the flexible substrate after the entire micro LED is inverted onto the blue film in step S6 of the present invention; Figure 20-21 It is a schematic diagram of the front and back structures of the finished micro LED product of the present invention; In the figure: 1 is a flexible substrate, 2 is an alignment hole, 3 is a copper-clad circuit, 4 is a copper-filled through hole, 5 is a solid crystal Pad functional area, 6 is a square fan-out external lead pad, 7 is a chemical electroplating lead, 8 is a solder resist ink, 9 is a horizontal cutting line, 10 is a vertical cutting line, 11 is a polarity mark, 12 is a transparent glass carrier, 13 is an alignment MARK point, 14 is a UV dissociation glue, 15 is a solder paste, 16 is a micro LED chip, 17 is a black resin ink, 18 is an optical glass, 19 is a cutting path, 20 is a blue film, 21 is a micro substrate unit, and 22 is a micro LED finished product. DETAILED DESCRIPTION

[0018] like Figures 1 to 21 As shown, the method for manufacturing a micro full-color LED provided by the present invention includes the steps of manufacturing an ultra-thin flexible substrate, spin coating, laminating a carrier, macro-bonding, spin coating, laminating, laser cutting, electrical measurement and sorting, etc. Each step is described in detail below.

[0019] S1: Ultra-thin flexible substrate production: S1.1: If Figure 1-3 As shown, a flexible substrate 1 is made of PI or other plastic insulating ultra-thin flexible materials, and three standard alignment holes 2 are set at the four corners of the flexible substrate 1; each flexible substrate 1 is divided into a plurality of micro substrate units 21, and a double-sided copper-clad circuit 3 is made on each micro substrate unit by exposure, development, chemical deposition and other processes, and a copper plugging via 4 is formed by perforating and filling copper from the front to the back of the double-sided copper-clad circuit 3, and a 1-2 um gold is chemically plated on the middle functional area of ​​the front functional area of ​​the flexible substrate 1 by chemical gold deposition to form 6 solid crystal Pad functional areas 5, and four square fan-out external lead pads 6 are formed at the four corners of the four copper plugging vias 4 on the back by chemical plating, and chemical plating leads 7 are connected between each micro substrate unit to improve the efficiency of chemical plating; S1.2: If Figure 4-6As shown, the solder resist ink 8 is printed on the back of the flexible substrate 1, and then the square fan-out external lead pad 6 is exposed by exposure and development, and then the horizontal cutting line 9 and the vertical cutting line 10, as well as the polarity mark 11 are printed in the middle of the four square fan-out external lead pads 6 of each micro substrate unit 21; next, the black solder resist ink 8 is printed on the front of the flexible substrate 1 (the black solder resist layer is to increase the black proportion of the front, thereby improving the display contrast when lit), and then the middle 6 solid crystal pad functional areas 5 are exposed by exposure and development, which is convenient for the subsequent mass transfer solid crystal operation. Then, the horizontal cutting line 9 and the vertical cutting line 10 are brushed in the middle position of each micro substrate unit by printing.

[0020] S2: Spin coating and laminating substrate: Prepare a transparent glass substrate 12 with a thickness of about 2 mm, with three positions of alignment marks 13 at its four corners, which are located in the same position as the alignment holes 2 of the flexible substrate 1, so as to facilitate lamination and alignment. Figure 7 As shown; clean the surface of the transparent glass carrier 12, then spin-coat the high-temperature-resistant UV dissociation glue 14 on the front side, and then accurately attach the flexible substrate 1 made in the previous process to the transparent glass carrier 12 according to the position of the alignment hole 2, and cure it at a high temperature of 120°C; the purpose of attaching the glass substrate is to facilitate the subsequent process. After completing this step, the flexible substrate 1 is as shown Figure 8-10 shown.

[0021] S3: Mass transfer: First, solder paste 15 is printed on the die bonding pad functional area 5 of the flexible substrate 1 by a printing process, such as Fig.11 As shown, the solder paste 15 uses 7# solder balls with a particle size of 2~11um. Then, the micro R\G\B color LED chips are precisely aligned and fixed to the 6 pads of the die bonding Pad functional area 5 on the front of the flexible substrate 1 through a mass transfer process. The electrodes at both ends of the micro LED chip 16 and the solder paste 15 on the die bonding Pad functional area 5 of the flexible substrate 1 are heated through a laser rapid welding process, and the solder paste 15 is quickly melted to complete the welding of the micro LED chip 16 and the flexible substrate 1, as shown in FIG. Figure 12-13 shown.

[0022] S4: Spin coating: Spin coating the black resin ink 17 with good viscosity on the surface of the flexible substrate 1 where the micro LED chip 16 has been solidified. The thickness is controlled to be slightly higher than the upper surface of the micro LED chip 16 by about 5~10um. Then, the 0.12~0.2mm glass with surface optical treatment is bonded to the newly spin-coated black resin ink 17 using a flat vacuum suction tool. The bonding force is 3~5g. The bonding process needs to be even and slow to avoid bubbles. After bonding, it can be cured at 120℃ for 60 minutes. Figure 14-15 shown.

[0023] S5: Laser cutting: Use laser technology to perform alignment cutting along the horizontal cutting line 9 and the vertical cutting line 10 in the middle of each micro unit on the front of the flexible substrate 1, and use the hidden cutting process to cut the optical glass 18 on the surface glass of each micro light-emitting unit; then use infrared laser to project through the hidden cutting line of the surface optical glass to complete the cutting of each layer of each micro substrate unit below the surface optical glass 18, and accurately control its depth and feedback to achieve just complete cutting through the flexible substrate 1 and reach the UV dissociation glue 14 of the bonding layer between the transparent glass carrier 12 and the flexible substrate 1. Figure 16-17 shown.

[0024] S6: Inverted UV dissociation: Use an inverted film machine to invert the entire micro LED after cutting onto the blue film 20, that is, the optical glass 18 is closely attached to the blue film 20. Figure 18-19 As shown, the transparent glass carrier 12 is then irradiated with ultraviolet light to peel off the entire packaged micro LED from the transparent glass carrier 12; it is then transferred to a chipping machine to complete the chipping of the upper surface glass 18 and separate into single micro LED finished products 22, as shown in FIG. Figure 20-21 As shown, the four fan-out external lead pads of each micro LED product 22 face outwards, which is convenient for spot testing and sorting of the micro LED products.

[0025] S7: Point testing and sorting: Use point testing and sorting equipment to perform probe electrical connection testing and photoelectric parameter grading on the micro LED finished product 22.

[0026] The present invention miniaturizes the LED chip to 60um or less, uses laser lift-off technology to peel off the substrate, so that the thickness of the miniaturized chip is 5-8um, and then uses the semiconductor SIP system-level packaging process to achieve a minimum of 0.2*0.2mm when performing miniaturized system packaging, so that a tiny display device can be realized.

[0027] Regarding the specific structure of the present invention, it should be noted that the connection relationship between the various component modules adopted in the present invention is definite and feasible. Except for special instructions in the embodiments, the specific connection relationship can bring about corresponding technical effects, and solve the technical problems raised by the present invention without relying on the execution of corresponding software programs. The components, modules, models of specific components, the connection methods between each other, and the conventional use methods and expected technical effects brought about by the above-mentioned technical features, except for specific instructions, all belong to the disclosed contents in patents, journal articles, technical manuals, technical dictionaries, and textbooks that can be obtained by technical personnel in this field before the application date, or belong to the existing technologies such as conventional technologies and common knowledge in this field, and there is no need to elaborate, so that the technical solution provided in this case is clear, complete, and feasible, and the corresponding physical products can be reproduced or obtained according to the technical means.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for manufacturing a miniature full-color LED, characterized in that: The steps include: S1: Ultra-flexible substrate production: Use ultra-thin flexible material to produce a flexible substrate, and divide the flexible substrate into multiple micro-substrate units. Make double-sided copper-clad circuits on each micro-substrate unit, deposit a die-bonding pad functional area on the front of each micro-substrate unit, and lead out four square fan-out external lead pads on the back of each micro-substrate unit, and expose the die-bonding pad functional area and the square fan-out external lead pads. S2: Spin coating and laminating carrier: Select a transparent glass carrier, clean its surface, spin coat the front of the transparent glass carrier with UV dissociation glue that can withstand high temperatures, and then laminate the flexible substrate made in step S1 on the transparent glass carrier, and cure it at high temperature; S3: Mass transfer: First, print solder paste on the bonding pad functional area of ​​the flexible substrate through a printing process, and then use a mass transfer process to accurately align the R / G / B color chips of the micro LED chips on the pads of the bonding pad functional area on the front of the flexible substrate. Use a laser rapid welding process to heat the electrodes at both ends of the micro LED chip and the solder paste on the bonding pad functional area of ​​the flexible substrate, and quickly melt the solder paste to complete the welding of the micro LED chip and the flexible substrate; S4: Spin coating: Spin coating black resin ink on the surface of the flexible substrate where the micro LED chip is solidified, and then use a flat vacuum suction tool to bond the glass that has undergone surface optical treatment to the just-spin coated black resin ink, and then use high temperature curing after bonding; S5: Laser cutting: Use laser technology to cut the optical glass along each micro unit on the front of the flexible substrate using a hidden cutting process to cut the surface glass of each micro light-emitting unit; then use infrared laser to project the hidden cutting line of the surface optical glass to cut each layer of each micro substrate unit below the surface optical glass; S6: Film inversion and UV dissociation: Use a film inversion machine to invert the entire micro LED that has been cut onto the blue film, so that the optical glass surface is close to the blue film, and then use ultraviolet light to irradiate the transparent glass carrier to peel off the entire encapsulated micro LED from the transparent glass carrier; then transfer it to a splitting machine to complete the splitting of the upper surface glass and separate it into single micro LED finished products.

2. The method for manufacturing a miniature full-color LED according to claim 1, characterized in that: The method also includes step S7: point test and sorting: using point test and sorting equipment to perform probe electrical connection test and photoelectric parameter classification on the finished micro LED products.

3. The method for manufacturing a miniature full-color LED according to claim 2, characterized in that: Three standard alignment holes are set at the four corners of the flexible substrate in step S1, and alignment MARK points are set at the four corners of the transparent glass carrier in step S2. The alignment MARK points are consistent with the alignment holes of the flexible substrate to facilitate alignment.

4. The method for manufacturing a miniature full-color LED according to claim 3, characterized in that: In the step S1, a double-sided copper-clad circuit is manufactured on each micro substrate unit by exposure, development, and chemical deposition processes. Copper-filled vias are formed from the front to the back of the double-sided copper-clad circuit by perforation and copper filling. The positions of the copper-filled vias on the back of each micro substrate unit are formed into four square fan-out external lead pads at the four corners of the micro substrate unit by chemical plating.

5. The method for manufacturing a miniature full-color LED according to claim 4, characterized in that: In the step S1, the bonding pad functional area on each micro basic unit is formed by chemically plating 1-2 um of gold in the middle functional area by chemically immersing gold to form 6 bonding pad functional areas.

6. The method for manufacturing a miniature full-color LED according to claim 5, characterized in that: In the step S1, the die bonding pad functional area and the square fan-out external lead pad are exposed by printing black solder resist ink on the front and back sides of the flexible substrate respectively, and then exposing the die bonding pad functional area and the square fan-out external lead pad by exposure and development.

7. The method for manufacturing a miniature full-color LED according to claim 6, characterized in that: In the step S1, chemical plating leads are connected between each two of the micro substrate units, and a horizontal cutting line and a vertical cutting line are printed in the middle of each micro substrate unit.

8. The method for manufacturing a miniature full-color LED according to claim 7, characterized in that: The particle size of the solder paste used in step S3 is 2-11 um.

9. The method for manufacturing a miniature full-color LED according to claim 7, characterized in that: The thickness of the black resin ink spin-coated on the flexible substrate in step S4 is 5-10 um higher than the upper surface of the micro LED chip, and the thickness of the optical glass is 0.12-0.2 mm.

10. The method for manufacturing a miniature full-color LED according to claim 7, characterized in that: The optical glass used in step S4 is provided with cutting paths corresponding to the transverse cutting lines and the longitudinal cutting lines of the micro basic units, and hidden cutting lines are provided on the cutting paths.

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