TWI788313B - Anisotropic conductive adhesive - Google Patents

Abstract

The present invention provides an anisotropic conductive adhesive with excellent heat resistance and light resistance. The above-mentioned anisotropic conductive adhesive connects the light-emitting element to the electrode of the wiring pattern of the substrate, and contains an inorganic adhesive and conductive particles. Since the adhesive components are inorganic materials, excellent heat resistance and light resistance can be obtained. In particular, even when an ultraviolet LED that emits ultraviolet light with 2 to 3 times the intensity of light energy of a blue LED is installed, excellent heat resistance and light resistance can be obtained.

Description

Anisotropic Conductive Adhesive

The invention relates to an anisotropic conductive adhesive for installing LED (Light Emitting Diode, light emitting diode). This application claims priority based on Japanese Patent Application No. Japanese Patent Application No. 2016-231826 filed in Japan on November 29, 2016, and this application is incorporated in this application by reference.

Conventionally, wire bonding is known as a method of mounting LED chip components on a circuit board. However, in wire bonding, the wires may be disconnected, resulting in poor electrical connection. Moreover, the versatility of the wire-bonded substrate is low, and it is difficult to achieve miniaturization or flexibility. As a method to solve the problem of wire bonding, Patent Documents 1 and 2 propose a method of flip-chip mounting LEDs using an anisotropic conductive film in which conductive particles are dispersed in an epoxy-based adhesive and formed into a film. . [Prior Art Document] [Patent Document] [Patent Document 1] Japanese Patent Laid-Open No. 2010-24301 [Patent Document 2] Japanese Patent Laid-Open No. 2012-186322

[Problem to be Solved by the Invention] In the conventional anisotropic conductive adhesive for flip-chip mounting, when a large current is passed to increase the illuminance of the LED, the bonding strength is reduced due to the heat of the large current, and the LED peels off. . In addition, when using the conventional anisotropic conductive adhesive to install ultraviolet LEDs, there is light energy that is 2 to 3 times stronger than that of blue LEDs, resulting in reduced adhesive strength, and the LEDs do not light up. The present invention solves the above-mentioned problems in the prior art, and provides an anisotropic conductive adhesive having excellent heat resistance and light resistance. [Technical means to solve the problem] The inventors of the present invention conducted diligent research and found that excellent heat resistance and light resistance can be obtained by using an inorganic material as the adhesive component (binder) of the anisotropic conductive adhesive sex. That is, the anisotropic conductive adhesive of the present invention is characterized in that it connects a light-emitting element to an electrode of a wiring pattern on a substrate, and contains an inorganic binder and conductive particles. In addition, the light-emitting device of the present invention is characterized in that it includes a substrate having a wiring pattern, an anisotropic conductive film formed on an electrode of the wiring pattern, and a light-emitting element mounted on the anisotropic conductive film. Atropic conductive film is a cured product of anisotropic conductive adhesive containing inorganic binder and conductive particles. In addition, the method for manufacturing a light-emitting device of the present invention is characterized in that an anisotropic conductive adhesive containing an inorganic binder and conductive particles is coated on an electrode of a wiring pattern of a substrate, and light is emitted through the above-mentioned anisotropic conductive adhesive. Components are heated and crimped. [Effects of the Invention] According to the present invention, since the adhesive component is an inorganic material, excellent heat resistance and light resistance can be obtained.

於如比較例1般使用含有胺系硬化劑之液狀異向性導電接著劑之情形時，由胺硬化系-環氧樹脂之極性導致吸水性較高，故而LED安裝樣品A於高溫高濕連續亮燈試驗中晶片剪切強度降低，LED安裝樣品B於高溫高濕連續亮燈試驗中順向電壓大幅度地變化。 又，於如比較例2般使用陽離子硬化ACF之情形時，LED安裝樣品A於高溫高濕連續亮燈試驗中藍色LED剝落，LED安裝樣品B於TCT試驗中於300小時變得不亮燈，於高溫高濕連續亮燈試驗中於130小時變得不亮燈。 又，於如比較例3般使用矽樹脂ACF之情形時，因矽樹脂較柔軟，故而LED安裝樣品A無法獲得較高之晶片剪切強度，LED安裝樣品B於TCT試驗中於200小時變得不亮燈，於高溫高濕連續亮燈試驗中於200小時變得不亮燈。 另一方面，於如實施例1～4般使用含有水玻璃之無機ACF之情形時，LED安裝樣品A即便於高溫高濕連續亮燈試驗中晶片剪切強度亦不降低，LED安裝樣品B即便於TCT試驗、及高溫高濕連續亮燈試驗中順向電壓之變化亦較小。即，可知藉由使用含有水玻璃之無機ACF，可獲得優異之耐熱性及耐光能性。Hereinafter, embodiments of the present invention will be described in detail in the following order with reference to the drawings. 1. Anisotropic conductive adhesive 2. Light-emitting device 3. Examples <1. Anisotropic conductive adhesive> The anisotropic conductive adhesive of this embodiment connects the light-emitting element to the electrode of the wiring pattern of the substrate, and Contains inorganic binder and conductive particles. When the adhesive component is an inorganic material, excellent heat resistance and light resistance can be obtained. [Inorganic binder] As the main component of the inorganic binder, it is preferably at least one selected from the group consisting of alkali metal silicate, phosphate, and _silica sol.・Alkali metal silicate represented by nSiO ₂ (M is any one of Na, K, and Li, and n is the molar ratio). The metal M of the alkali metal silicate generally follows the order of Na>K>Li and has good adhesion. Therefore, the main component of the inorganic binder is preferably sodium silicate (water glass). As the sodium silicate, it is preferable to use sodium silicate No. 1 to No. 3 based on JIS K1408, and among them, it is preferable to use sodium silicate No. 3 from the viewpoint of adhesive force. In addition, the inorganic adhesive can also contain the following compounds as hardeners in order to improve the adhesion: oxides and hydroxides of any of Zn, Mg, and C, silicides of any of Na, K, and Ca, and silicon Fluoride, phosphate of any of Al and Zn, borate of any of Ca, Ba, and Mg. [Conductive Particles] The conductive particles are preferably at least one selected from the group consisting of solder particles, metal particles, and resin core conductive particles in which metal is coated on resin particles. Among them, it is preferable to use solder particles, and it is preferable to use solder particles and resin core particles in combination. The average particle diameter of the conductive particles is preferably not less than 1 μm and not more than 30 μm, more preferably not less than 5 μm and not more than 25 μm. The compounding quantity of an electroconductive particle is preferably 3-120 mass parts with respect to 100 mass parts of inorganic binders, More preferably, it is 10-80 mass parts. As solder particles, for example, Sn-Pb system, Pb-Sn-Sb system, Sn-Sb system, Sn-Pb-Bi system, Bi-Sn system specified in JIS Z 3282-1999 according to electrode materials and connection conditions, etc. , Sn-Cu-based, Sn-Pb-Cu-based, Sn-In-based, Sn-Ag-based, Sn-Pb-Ag-based, Pb-Ag-based, etc. are appropriately selected and used. Also, the shape of the solder particles can be appropriately selected from granular, scaly, and the like. In addition, solder particles may be coated with an insulating layer in order to increase anisotropy. Also, the melting point of the solder is preferably from 100 to 250°C, more preferably from 150 to 200°C. Furthermore, solder particles can form an alloy with a terminal (electrode) even at a mounting temperature below the melting point of the solder particles due to a sufficient load at the time of crimping. It is preferable that the compounding quantity of a solder particle is 20-120 mass parts. If the blending amount of solder particles is too small, excellent heat dissipation properties cannot be obtained, and if the blending amount is too large, the anisotropy will be damaged, and excellent connection reliability cannot be obtained. When solder particles and resin-core conductive particles are used together, the average particle size of the solder particles is preferably larger than that of the resin-core conductive particles, and the average particle size of the solder particles is preferably 120-800% of the average particle size of the resin-core conductive particles. More preferably, it is 200 to 500%. Since the average particle size of the solder particles is larger than that of the resin core conductive particles, a sufficient load can be applied to the solder particles during crimping, and an alloy can be formed with the terminal (electrode) even at a mounting temperature below the melting point of the solder particles. As the metal particles, for example, various metals such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver, gold, or alloys thereof can be used. As the resin particle of the resin core conductive particle, for example, epoxy resin, phenol resin, acrylic resin, acrylonitrile-styrene (AS) resin, benzoguanamine resin, divinylbenzene resin, styrene resin can be used. wait. Also, as the metal to coat the resin particles, for example, various metals such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver, gold, or alloys thereof can be used. In addition, the anisotropic conductive adhesive of this embodiment may further contain an inorganic filler for the purpose of adjusting viscosity or linear expansion. Examples of the inorganic filler include silica, alumina, titanium oxide, aluminum nitride, calcium carbonate, and magnesium oxide. The average particle diameter of the inorganic filler is preferably 10 nm to 10 μm, and the blending amount of the inorganic filler is preferably 1 to 100 parts by mass relative to 100 parts by mass of the inorganic binder. In addition, the anisotropic conductive adhesive may contain white inorganic particles such as TiO ₂ , BN, ZnO, Al ₂ O ₃ , etc. in order to reflect light emitted from LEDs and obtain higher light extraction efficiency. The average particle diameter of the white inorganic particles is preferably at least 1/2 of the wavelength of the reflected light. According to such an anisotropic conductive adhesive, since the adhesive component is an inorganic material, excellent heat resistance and light resistance can be obtained. In particular, even when an ultraviolet LED that emits ultraviolet light with 2 to 3 times the intensity of light energy of a blue LED is installed, excellent heat resistance and light resistance can be obtained. <2. Light-emitting device> The light-emitting device of this embodiment includes a substrate having a wiring pattern, an anisotropic conductive film formed on an electrode of the wiring pattern, and a light-emitting element mounted on the anisotropic conductive film, and the anisotropic The conductive film is a cured product of an anisotropic conductive adhesive containing the above-mentioned inorganic binder and conductive particles. Thereby, excellent heat resistance and light resistance can be obtained. In addition, the manufacturing method of the light-emitting device of this embodiment is to apply an anisotropic conductive adhesive containing an inorganic binder and conductive particles on the electrodes of the wiring pattern of the substrate, and heat and press the light-emitting element through the anisotropic conductive adhesive. catch. FIG. 1 is a cross-sectional view showing an example of a light emitting device. The light-emitting element has, for example, a first conductivity type _cladding layer 11 including n-GaN, an active layer 12 including an _{InxAlyGa1 -xyN} layer, and a second conductivity type cladding layer 113 including p-GaN, for example. , with a so-called double heterostructure. In addition, a first conductivity type electrode 11 a formed on a part of the first conductivity type coating layer 11 via a passivation layer 14 and a second conductivity type electrode 13 a formed on a part of the second conductivity type coating layer 13 are provided. When a voltage is applied between the first conductivity type electrode 11a and the second conductivity type electrode 13a, carriers are concentrated in the active layer 12 and recombined to generate light emission. The light emitting element is not particularly limited, and may be an ultraviolet LED emitting ultraviolet light with a light emitting wavelength of about 200-300 nm, or a blue LED emitting blue light with a light emitting wavelength of about 460 nm. According to the calculation based on the light energy formula (E=hc/λ), the light energy of the blue LED is 2.8 eV, the light energy of the ultraviolet LED is 4.1-6.2 eV, and the ultraviolet LED has 2 to 3 times the intensity of the blue LED. Light energy, in this embodiment, since the adhesive component of the anisotropic conductive adhesive is an inorganic material, even in the case of using ultraviolet LEDs, it is possible to suppress the decrease in adhesive strength and obtain excellent heat resistance and light resistance sex. The substrate has a circuit pattern 22 for the first conductivity type and a circuit pattern 23 for the second conductivity type on the base material 21, and has electrodes at positions corresponding to the first conductivity type electrode 11a and the second conductivity type electrode 13a of the light emitting element, respectively. The substrate is preferably a transparent substrate. When the substrate 21 is a light-transmitting substrate, the substrate 31 is preferably a transparent substrate such as glass or PET (polyethylene terephthalate, polyethylene terephthalate). The conductive circuit pattern 23 and its electrodes are preferably ITO (Indium-Tin-Oxide, indium tin oxide), IZO (Indium-Zinc-Oxide, indium zinc oxide), ZnO (Zinc-Oxide, zinc oxide), IGZO (Indium-Gallium-Zinc-Oxide, indium gallium zinc oxide) and other transparent conductive films. Since the substrate is a light-transmitting substrate, the substrate side can be used as a display surface (light emitting surface). The anisotropic conductive film 30 is obtained by hardening the above-mentioned anisotropic conductive adhesive. By trapping conductive particles 31 between the terminals (electrodes 11a, 13a) of the light-emitting element and the terminals (electrodes) of the substrate, the light-emitting element and the terminal (electrode) are connected together. The substrate is electrically connected. According to such a light-emitting device, since the adhesive component of the anisotropic conductive adhesive is an inorganic material, excellent heat resistance and light resistance can be obtained. In particular, even when an ultraviolet LED that emits ultraviolet light with 2 to 3 times the intensity of light energy of a blue LED is installed, excellent heat resistance and light resistance can be obtained. <3. Examples> [Example] Hereinafter, examples of the present invention will be described. In this embodiment, various anisotropic conductive adhesives are produced. Then, a blue LED chip was mounted on the substrate using an anisotropic conductive adhesive to prepare an LED mounting sample A, and the chip shear strength was measured at the initial stage and after the high-temperature, high-humidity continuous lighting test, and the heat resistance was evaluated. In addition, using an anisotropic conductive adhesive to mount ultraviolet LED chips on the substrate to make LED mounting sample B, measure the forward direction at the initial stage, after the TCT (Temperature Cycling Test, temperature cycle test) test, and after the high-temperature and high-humidity continuous lighting test. Voltage and evaluate heat resistance and light resistance. Furthermore, the present invention is not limited to these examples. [Production of Mounted LED Samples] Fig. 2 is a diagram for explaining the steps of manufacturing LED mounted samples. As shown in Fig. 2, LED mounting samples were produced. A ceramic substrate 41 formed with metal wiring is arranged on a stage, and an anisotropic conductive adhesive 40 is coated on the ceramic substrate 41 by a stamping method. Then, mount the LED chip 42 on the anisotropic conductive adhesive 40 with a load of 60 g, and use the thermocompression bonding machine 43 to heat the head and the stage to perform thermocompression bonding mounting to obtain the LED mounting sample A or LED Install sample B. [Measurement of Wafer Shear Strength] A blue LED (350 mA rating, 45 mm square size, 460 nm wavelength) was used as the LED chip 42 to prepare an LED mounting sample A. Fig. 3 is a cross-sectional view showing the outline of a wafer shear strength test. As shown in Figure 3, using a wafer shear strength tester, under the conditions of a tool 50 with a shear rate of 20 μm/sec and a temperature of 25°C, the initial stage of each LED mounting sample A and after the high-temperature, high-humidity continuous lighting test were measured. wafer shear strength. The high temperature and high humidity continuous lighting test is continuous lighting under the conditions of temperature 85°C-humidity 90%-500 hours. [Measurement of Forward Voltage] A blue LED (Nitride Semiconductor, NS355C-2SAA, rated at 20 mA, forward voltage of 3.61 V, wavelength of 355 nm) was used as the LED chip 42 to prepare an LED mounting sample B. Measure the forward voltage of each LED mounting sample B at the initial stage, after the TCT test, and after the high temperature and high humidity continuous lighting test. In the TCT test, the LED mounting sample B was exposed to environments of -40°C and 100°C for 30 minutes each, and the heating and cooling cycle was performed 1000 times as one cycle. High temperature and high humidity continuous lighting test is continuous lighting under the conditions of temperature 85°C-humidity 90%-1000 hours, 20 mA. A change of 0.1 V or more from the initial forward voltage of the LED was evaluated as NG. <Example 1> As shown in Table 1, 100 parts by mass of water glass (sodium silicate No. 3 listed in JIS K1408) and solder particles (particle size 10-25 μm, melting point 180°C, Senju Metal Industrial Co., Ltd.) 60 parts by mass were stirred with a planetary mixer at 2000 rpm/2 min to prepare an anisotropic conductive adhesive. Mount the LED chip on the ceramic substrate through the anisotropic conductive adhesive, heat the head to 150°C, heat the stage to 50°C, and set the mounting temperature (maximum temperature) at 100°C for 60 seconds LED mounting samples A and B were obtained by thermocompression bonding. Table 1 shows the chip shear strength of the LED mounting sample A at the initial stage and after the high temperature and high humidity continuous lighting test, and the forward voltage of the LED mounting sample B at the initial stage, after the TCT test, and after the high temperature and high humidity continuous lighting test The measurement results. <Example 2> As shown in Table 1, weigh and add 100 parts by mass of water glass (sodium silicate No. 3 listed in JIS K1408), and resin core conductive particles (average particle size 5 μm, nickel-plated, resin core Particles (Nippon Chemical Co., Ltd. EH Core)) 10 parts by mass were stirred by a planetary mixer at 2000 rpm/2 min to prepare an anisotropic conductive adhesive. Except for this, LED mounting samples A and B were produced in the same manner as in Example 1. <Example 3> As shown in Table 1, weigh and add 100 parts by mass of water glass (sodium silicate No. 3 listed in JIS K1408), solder particles (particle size 10-25 μm, melting point 180°C, Senju Metal Industry Co., Ltd. 30 parts by mass of the company) and 5 parts by mass of resin core conductive particles (average particle size 5 μm, nickel-plated, resin core particles (Nippon Kagaku EH Core)) were stirred at 2000 rpm/2 min by a planetary mixer And make anisotropic conductive adhesive. Except for this, LED mounting samples A and B were produced in the same manner as in Example 1. <Example 4> As shown in Table 1, weigh and add 100 parts by mass of water glass (sodium silicate No. 3 listed in JIS K1408), solder particles (particle size 10-25 μm, melting point 180°C, Senju Metal Industry Co., Ltd. 60 parts by mass manufactured by the company) and 7 parts by mass of silicon dioxide particles (Aerosil RX300 manufactured by Aerosil Corporation of Japan) were stirred by a planetary mixer at 2000 rpm/2 min to produce anisotropy Conductive adhesive. Except for this, LED mounting samples A and B were produced in the same manner as in Example 1. <Comparative Example 1> As shown in Table 1, a liquid anisotropic conductive adhesive (BP series, resin: epoxy resin, particles: Ni particles) manufactured by Dexerials Co., Ltd. containing an amine-based hardener was used as the anisotropic conductive adhesive. Adhesive. Mount the LED chip on the ceramic substrate through the anisotropic conductive adhesive, heat the head to 200°C, heat the stage to 50°C, and set the mounting temperature (maximum temperature) at 150°C for 30 seconds LED mounting samples A and B were obtained by thermocompression bonding. <Comparative Example 2> As shown in Table 1, cation-curing ACF (Anisotropic Conductive Film, anisotropic conductive film) manufactured by Dexerials Co., Ltd. (resin: epoxy resin, particles: nickel-coated resin particles, particle size: 3 μm, Thickness: 6 μm, resin density: 60 Kpcs/mm ² ) as an anisotropic conductive adhesive. Mount the LED chip on the ceramic substrate through the anisotropic conductive adhesive, heat the head to 250°C, heat the stage to 70°C, and set the mounting temperature (maximum temperature) at 180°C for 30 seconds LED mounting samples A and B were obtained by thermocompression bonding. <Comparative Example 3> As shown in Table 1, 100 parts by mass of silicone resin (KER2500 manufactured by Shin-Etsu Chemical Co., Ltd.) and 60 parts by mass of solder particles (particle size 10 to 25 μm, melting point 180°C, manufactured by Senju Metal Industry Co., Ltd.) were weighed and added. parts by mass, stirred by a planetary mixer at 2000 rpm/2 min to make an anisotropic conductive adhesive. Mount the LED chip on the ceramic substrate through the anisotropic conductive adhesive, heat the head to 290°C, heat the stage to 60°C, and set the mounting temperature (maximum temperature) at 200°C for 60 seconds LED mounting samples A and B were obtained by thermocompression bonding. [Table 1]

In the case of using a liquid anisotropic conductive adhesive containing an amine-based hardener as in Comparative Example 1, the polarity of the amine-hardened epoxy resin leads to high water absorption, so LED mounting sample A is exposed to high temperature and high humidity. The wafer shear strength decreased in the continuous lighting test, and the forward voltage of the LED mounted sample B changed significantly in the high-temperature and high-humidity continuous lighting test. Also, when using cation-curing ACF as in Comparative Example 2, the blue LED peeled off in the LED-mounted sample A in the high-temperature, high-humidity continuous lighting test, and the LED-mounted sample B did not light up after 300 hours in the TCT test. , In the high-temperature and high-humidity continuous lighting test, the light did not turn on after 130 hours. Also, when the silicone resin ACF is used as in Comparative Example 3, since the silicone resin is soft, the LED mounting sample A cannot obtain a high chip shear strength, and the LED mounting sample B becomes weaker in 200 hours in the TCT test The lamp does not light up, and the lamp does not light up after 200 hours in the high-temperature, high-humidity continuous lighting test. On the other hand, when inorganic ACF containing water glass was used as in Examples 1 to 4, the chip shear strength of the LED mounted sample A did not decrease even in the high-temperature, high-humidity continuous lighting test, and the LED mounted sample B even In the TCT test and the high temperature and high humidity continuous lighting test, the change of the forward voltage is also small. That is, it was found that excellent heat resistance and light resistance can be obtained by using inorganic ACF containing water glass.

11‧‧‧first conductivity type coating layer 11a‧‧‧first conductivity type electrode 12‧‧‧active layer 13‧‧‧second conductivity type coating layer 13a‧‧‧second conductivity type electrode 14‧‧‧ Passivation layer 21‧‧‧substrate 22‧‧‧circuit pattern for the first conductivity type 23‧‧‧circuit pattern for the second conductivity type 30‧‧‧anisotropic conductive film 31‧‧‧conductive particles 40‧‧‧ Anisotropic conductive adhesive 41‧‧‧ceramic substrate 42‧‧‧LED chip 43‧‧‧thermocompression bonding machine 50‧‧‧tool

FIG. 1 is a cross-sectional view showing an example of a light emitting device. Fig. 2 is a diagram for explaining the manufacturing steps of LED mounted samples. Fig. 3 is a cross-sectional view showing the outline of a wafer shear strength test.

11‧‧‧The first conductivity type cladding layer

11a‧‧‧First conductivity type electrode

12‧‧‧active layer

13‧‧‧Second conductivity type cladding layer

13a‧‧‧Second conductivity type electrode

14‧‧‧passivation layer

21‧‧‧Substrate

22‧‧‧Circuit pattern for the first conductivity type

23‧‧‧Circuit pattern for the second conductivity type

30‧‧‧Anisotropic conductive film

31‧‧‧Conductive particles

Claims (8)

An anisotropic conductive adhesive, which connects light-emitting elements to the electrodes of the wiring pattern of the substrate, and contains an inorganic binder and conductive particles including solder particles with a melting point of 150-200°C. The above-mentioned inorganic binder is based on Sodium silicate No. 3 of JIS K1408 is used as the main component. The anisotropic conductive adhesive according to claim 1, wherein the conductive particles are at least one selected from the group consisting of solder particles, metal particles, and resin core conductive particles coated with metal on resin particles. The anisotropic conductive adhesive according to claim 1, wherein the compounding amount of the above-mentioned conductive particles is 3-120 parts by mass relative to 100 parts by mass of the above-mentioned inorganic binder. The anisotropic conductive adhesive according to claim 2, wherein the compounding amount of the above-mentioned conductive particles is 3 to 120 parts by mass relative to 100 parts by mass of the above-mentioned inorganic binder. The anisotropic conductive adhesive according to any one of claims 1 to 4, wherein the light-emitting element emits ultraviolet rays. The anisotropic conductive adhesive according to any one of claims 1 to 4, which further contains inorganic particles. A light emitting device comprising: a substrate having a wiring pattern; an anisotropic conductive film formed on electrodes of the wiring pattern; and a light emitting element mounted on the anisotropic conductive film; and the anisotropic The conductive film is a cured product of an anisotropic conductive adhesive containing an inorganic binder and conductive particles. The above-mentioned conductive particles include solder particles with a melting point of 150~200°C. The above-mentioned inorganic binder is made of sodium silicate No. 3 according to JIS K1408. main ingredient. A method for manufacturing a light-emitting device, which comprises coating an anisotropic conductive adhesive containing an inorganic binder and conductive particles on the electrodes of a wiring pattern on a substrate, and thermally bonding a light-emitting element through the above-mentioned anisotropic conductive adhesive. The conductive particles include solder particles with a melting point of 150-200° C., and the above-mentioned inorganic binder uses sodium silicate No. 3 according to JIS K1408 as a main component.

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