TW201834275A - Anisotropic conductive adhesive - Google Patents

Abstract

Provided is an anisotropic electrically-conductive adhesive agent that has excellent heat resistance and light energy resistance. An anisotropic electrically-conductive adhesive agent for connecting a light-emitting element on an electrode of a wiring pattern of a substrate, wherein said anisotropic electrically-conductive adhesive agent contains an inorganic binder and electrically conductive particles. Because the adhesive component is an inorganic material, it is possible to obtain excellent heat resistance and light energy resistance. Particularly, even when an ultraviolet LED that emits ultraviolet rays of light energy having an intensity 2-3 times that of a blue LED is mounted, it is possible to obtain excellent heat resistance and light energy resistance.

Description

Anisotropic conductive adhesive

The present invention relates to an anisotropic conductive adhesive for mounting an LED (Light Emitting Diode). The present application claims priority on the basis of Japanese Patent Application No. Hei. No. Hei.

Previously, as a method of mounting a wafer component of an LED on a circuit board, wire bonding was known. However, there is a case where the wire bonding is broken and the electrical connection is poor. Moreover, the versatility of the wire bonding substrate is low, and it is difficult to achieve miniaturization or flexibility. As a method for solving the problem of wire bonding, Patent Literatures 1 and 2 propose a method of flip chip mounting of an LED using an anisotropic conductive film in which conductive particles are dispersed in an epoxy-based adhesive and formed into a film shape. . [PRIOR ART DOCUMENT] [Patent Document 1] Japanese Patent Laid-Open Publication No. 2010-24301 (Patent Document 2) Japanese Patent Laid-Open Publication No. 2012-186322

[Problems to be Solved by the Invention] When a conventional anisotropic conductive adhesive for flip chip mounting has a large current flowing in order to increase the illuminance of the LED, there is a case where the bonding strength is lowered by the heat of a large current, and the LED is peeled off. . Further, when the ultraviolet LED is mounted using the conventional anisotropic conductive adhesive, there is a light energy of 2 to 3 times the intensity of the blue LED, which causes the subsequent strength to decrease and the LED to become unlit. The present invention has been made in view of the above problems in the prior art, and provides an anisotropic conductive adhesive having excellent heat resistance and light resistance. [Means for Solving the Problems] As a result of intensive studies, the inventors of the present invention have found that excellent heat resistance and light resistance can be obtained by using an adhesive component (adhesive) of an anisotropic conductive adhesive as an inorganic material. 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 of a substrate, and contains an inorganic binder and conductive particles. Further, the light-emitting device of the present invention includes a substrate having a wiring pattern, an anisotropic conductive film formed on the electrode of the wiring pattern, and a light-emitting element mounted on the anisotropic conductive film, and the difference The directional conductive film is a cured product of an anisotropic conductive adhesive containing an inorganic binder and conductive particles. Moreover, the method for producing a light-emitting device according to the present invention is characterized in that an anisotropic conductive adhesive containing an inorganic binder and conductive particles is applied onto an electrode of a wiring pattern of a substrate, and the light is emitted through the anisotropic conductive adhesive. The component is 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.

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. Example <1. Anisotropic conductive adhesive> The anisotropic conductive adhesive of the present embodiment connects the light-emitting element to the electrode of the wiring pattern of the substrate, and Contains inorganic binders and conductive particles. Excellent heat resistance and light resistance can be obtained by using an adhesive component as an inorganic material. [Inorganic binder] The main component of the inorganic binder is preferably at least one selected from the group consisting of alkali metal silicates, phosphates, and cerium sols. Among them, the molecular formula M ₂ O is preferably used.・The alkali metal silicate represented by nSiO ₂ (M is any one of Na, K, and Li, and n is a molar ratio). The metal M of the alkali metal niobate generally has a good adhesion in the order of Na>K>Li. Therefore, the main component of the inorganic binder is preferably sodium citrate (water glass). As sodium citrate, sodium citrate No. 1 to No. 3 according to JIS K1408 is preferably used. Among them, sodium citrate No. 3 is preferably used from the viewpoint of adhesion. Further, the inorganic binder may contain the following compounds as a curing agent for improving the adhesion: an oxide or a hydroxide of any one of Zn, Mg, and C, and a telluride or bismuth of any of Na, K, and Ca. Fluoride, a phosphate of any of Al, Zn, or a borate of any of Ca, Ba, and Mg. [Electrically 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 coated with a resin particle. Among them, solder particles are preferably used, and solder particles and resin core particles are preferably used in combination. The average particle diameter of the conductive particles is preferably 1 μm or more and 30 μm or less, more preferably 5 μm or more and 25 μm or less. The amount of the conductive particles is preferably from 3 to 120 parts by mass, more preferably from 10 to 80 parts by mass, per 100 parts by mass of the inorganic binder. The solder particles can be, for example, an Sn-Pb system, a Pb-Sn-Sb system, a Sn-Sb system, a Sn-Pb-Bi system, or a Bi-Sn system, which are defined in accordance with JIS Z 3282-1999, depending on the electrode material or the connection conditions. The Sn-Cu system, the Sn-Pb-Cu system, the Sn-In system, the Sn-Ag system, the Sn-Pb-Ag system, and the Pb-Ag system are appropriately selected and used. Further, the shape of the solder particles can be appropriately selected from granular or scaly shapes. Further, the solder particles may be coated with the insulating layer in order to improve the anisotropy. Further, the melting point of the solder is preferably from 100 to 250 ° C, more preferably from 150 to 200 ° C. Further, the solder particles can be alloyed with the terminal (electrode) even at a mounting temperature below the melting point of the solder particles by a sufficient load at the time of pressure bonding. The amount of the solder particles is preferably from 20 to 120 parts by mass. If the amount of the solder particles is too small, excellent heat dissipation characteristics cannot be obtained, and if the amount is too large, the anisotropy is impaired, and excellent connection reliability cannot be obtained. When the solder particles and the resin core conductive particles are used in combination, the solder particles preferably have an average particle diameter larger than the resin core conductive particles, and the average particle diameter of the solder particles is preferably 120 to 800% of the average particle diameter of the resin core conductive particles. More preferably 200 to 500%. When the average particle diameter of the solder particles is larger than the resin core conductive particles, the load can be sufficiently applied to the solder particles during the pressure bonding, and an alloy is formed between the terminals and the electrodes even at the 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 the like, or alloys thereof can be used. As the resin particles of the resin core conductive particles, for example, an epoxy resin, a phenol resin, an acrylic resin, an acrylonitrile-styrene (AS) resin, a benzoguanamine resin, a divinylbenzene resin, or a styrene resin can be used. Wait. Further, as the metal to be coated with the resin particles, for example, various metals such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver, gold, or the like, or alloys thereof can be used. Further, the anisotropic conductive adhesive of the present embodiment may further contain an inorganic filler in order to adjust the viscosity or the linear expansion. Examples of the inorganic filler include cerium oxide, aluminum oxide, titanium oxide, aluminum nitride, calcium carbonate, and magnesium oxide. The average particle diameter of the inorganic filler is preferably from 10 nm to 10 μm, and the amount of the inorganic filler is preferably from 1 to 100 parts by mass based on 100 parts by mass of the inorganic binder. Further, the anisotropic conductive adhesive may contain white inorganic particles of TiO ₂ , BN, ZnO, Al ₂ O ₃ or the like in order to reflect the light emitted from the LED and obtain high light extraction efficiency. The average particle diameter of the white inorganic particles is preferably 1/2 or more of the wavelength of the reflected light. According to such an anisotropic conductive adhesive, excellent heat resistance and light resistance can be obtained by using an adhesive component as an inorganic material. In particular, even when an ultraviolet LED emitting ultraviolet light having a light energy of 2 to 3 times the intensity of the blue LED is mounted, excellent heat resistance and light resistance can be obtained. <2. Light-emitting device> The light-emitting device of the present embodiment includes a substrate having a wiring pattern, an anisotropic conductive film formed on the electrode of the wiring pattern, and a light-emitting element mounted on the anisotropic conductive film, and anisotropy The conductive film is a cured product of an anisotropic conductive adhesive containing the above inorganic binder and conductive particles. Thereby, excellent heat resistance and light resistance can be obtained. Further, in the method of manufacturing a light-emitting device of the present embodiment, an anisotropic conductive adhesive containing an inorganic binder and conductive particles is applied to an electrode of a wiring pattern of a substrate, and the light-emitting element is heated by an anisotropic conductive adhesive. Pick up. Fig. 1 is a cross-sectional view showing an example of a light-emitting device. The light-emitting element includes, for example, a first conductive type cladding layer 11 including n-GaN, an active layer 12 including, for example, an In _x Al _y Ga _1-xy N layer, and a second conductive type cladding layer 113 including, for example, p-GaN. It has a so-called double heterostructure. Further, the first conductive type electrode 11a formed in one portion of the first conductive type cladding layer 11 by the passivation layer 14 and the second conductive type electrode 13a formed in a part of the second conductive type cladding layer 13 are provided. When a voltage is applied between the first conductive type electrode 11a and the second conductive type electrode 13a, the carriers are concentrated and recombined in the active layer 12, thereby generating light emission. The light-emitting element is not particularly limited, and may be an ultraviolet LED that emits ultraviolet light having an emission wavelength of about 200 to 300 nm, or a blue LED that emits blue light having an emission wavelength of about 460 nm. According to the calculation based on the light energy type (E=hc/λ), the light energy of the blue LED is 2.8 eV, the light energy of the ultraviolet LED is 4.1 to 6.2 eV, and the ultraviolet LED has the intensity of 2 to 3 times that of the blue LED. In the present embodiment, since the adhesive component of the anisotropic conductive adhesive is an inorganic material, even when an ultraviolet LED is used, the deterioration of the adhesive strength can be suppressed, and excellent heat resistance and light resistance can be obtained. Sex. The substrate is provided with the first conductive type circuit pattern 22 and the second conductive type circuit pattern 23 on the substrate 21, and has electrodes at positions corresponding to the first conductive type electrode 11a and the second conductive type electrode 13a of the light emitting element. The substrate is preferably a light transmissive substrate. In the case where the substrate 21 is a light-transmitting substrate, the substrate 31 is preferably a transparent substrate such as glass or PET (polyethylene terephthalate), and the first conductive type circuit pattern 22 and the second The conductive type circuit pattern 23 and the electrode thereof are preferably ITO (Indium-Tin-Oxide, indium tin oxide), IZO (Indium-Zinc-Oxide), ZnO (Zinc-Oxide, zinc oxide), IGZO. A transparent conductive film such as (Indium-Gallium-Zinc-Oxide, indium gallium zinc oxide). The substrate side is a light-transmitting substrate, and the substrate side can be set as a display surface (light-emitting surface). The anisotropic conductive film 30 is obtained by curing the anisotropic conductive adhesive, and the light-emitting element is obtained by trapping the conductive particles 31 between the terminals (electrodes 11a and 13a) of the light-emitting element and the terminals (electrodes) of the substrate. 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 emitting ultraviolet light having a light energy of 2 to 3 times the intensity of the blue LED is mounted, excellent heat resistance and light resistance can be obtained. <3. Examples> [Examples] Hereinafter, examples of the invention will be described. Various anisotropic conductive adhesives were prepared in this example. Then, a blue LED wafer was mounted on the substrate by using an anisotropic conductive adhesive to prepare an LED mounting sample A, and the wafer shear strength after the initial and high-temperature and high-humidity continuous lighting test was measured, and the heat resistance was evaluated. Moreover, an LED mounting sample B was produced by mounting an ultraviolet LED chip on a substrate using an anisotropic conductive adhesive, and the measurement was performed after the initial stage, the TCT (Temperature Cycling Test) test, and the high-temperature and high-humidity continuous lighting test. The voltage was evaluated for heat resistance and light resistance. Furthermore, the invention is not limited to the embodiments. [Production of LED Mounting Sample] FIG. 2 is a diagram for explaining a manufacturing procedure of an LED mounting sample. An LED mounting sample was fabricated as shown in FIG. The ceramic substrate 41 on which the metal wiring is formed is placed on the stage, and the anisotropic conductive adhesive 40 is applied onto the ceramic substrate 41 by a stamping method. Then, the LED wafer 42 is mounted on the anisotropic conductive adhesive 40 under a load of 60 g, and the head and the stage are heated by a thermocompression bonding machine 43, and the pressure is mounted by heating, and the LED mounting sample A or LED is obtained. Install sample B. [Measurement of Wafer Shear Strength] An LED mounting sample A was produced using a blue LED (350 mA nominal, 45 mm square, wavelength 460 nm) as the LED wafer 42. Fig. 3 is a cross-sectional view showing an outline of a wafer shear strength test. As shown in FIG. 3, the initial stage of each LED mounting sample A and the high-temperature and high-humidity continuous lighting test were measured using a wafer shear strength tester under the conditions of a shear rate of 20 μm/sec of the tool 50 and a temperature of 25 ° C. Wafer shear strength. The high temperature and high humidity continuous lighting test is continuously lit at a temperature of 85 ° C - humidity of 90% - 500 hours. [Measurement of Forward Voltage] An LED mounting sample B was produced using a blue LED (Nitride Semiconductor, NS355C-2SAA, rated 20 mA, forward voltage 3.61 V, wavelength 355 nm) as the LED wafer 42. The forward voltage after the initial stage of each LED mounting sample B, after the TCT test, and after the high temperature and high humidity continuous lighting test was measured. The TCT test was performed by exposing the LED mounting sample B to an environment of -40 ° C and 100 ° C for 30 minutes, and performing this as a one-cycle hot and cold cycle 1000 times. The high temperature and high humidity continuous lighting test is continuously lit at a temperature of 85 ° C - humidity of 90% - 1000 hours, 20 mA. It was evaluated as NG when it was changed by 0.1 V or more from the initial forward voltage of the LED. <Example 1> As shown in Table 1, 100 parts by mass of water glass (sodium citrate No. 3 shown in JIS K1408) and solder particles (particle diameter of 10 to 25 μm, melting point of 180 ° C, and living metal) were weighed and added. 60 parts by mass manufactured by Industrial Co., Ltd., and anisotropic conductive adhesive was produced by stirring at 2000 rpm / 2 min by a planetary mixer. The LED chip was mounted on a ceramic substrate via the anisotropic conductive adhesive, the head was heated to 150 ° C, and the stage was heated to 50 ° C at a mounting temperature (maximum limit temperature) of 100 ° C for 60 seconds. The LED mounting samples A and B were obtained by heating and crimp mounting. Table 1 shows the initial stage of the LED mounting sample A and the wafer shear strength after the high-temperature and high-humidity continuous lighting test, and the initial voltage of the LED mounting sample B, the TCT test, and the high-temperature and high-humidity continuous lighting test. The measurement result. <Example 2> As shown in Table 1, 100 parts by mass of water glass (sodium citrate No. 3 shown in JIS K1408) and resin core conductive particles (average particle diameter of 5 μm, nickel plating, resin core) were weighed and added. 10 parts by mass of particles (EH Core manufactured by Nippon Chemical Co., Ltd.) were produced 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, 100 parts by mass of water glass (sodium citrate No. 3 shown in JIS K1408) and solder particles (particle diameter of 10 to 25 μm, melting point of 180 ° C, and the living metal industry) were weighed and added. 5 parts by mass of resin core conductive particles (average particle size 5 μm, nickel plating, resin core particles (EH Core manufactured by Nippon Chemical Co., Ltd.)), 5 parts by mass, stirred by a planetary mixer at 2000 rpm / 2 min An anisotropic conductive adhesive is produced. 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, 100 parts by mass of water glass (sodium citrate No. 3 shown in JIS K1408) and solder particles (particle diameter of 10 to 25 μm, melting point of 180 ° C, and Kansei Metal Industry) were weighed and added. (manufactured by the company) 7 parts by mass of cerium oxide particles (Aerosil RX300 manufactured by Aerosil Co., Ltd.), and anisotropically produced by stirring at 2000 rpm / 2 min by a planetary mixer 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) containing an amine-based curing agent manufactured by Dexrils Co., Ltd. was used as an anisotropic conductive material. Follow-up agent. The LED chip was mounted on a ceramic substrate via the anisotropic conductive adhesive, the head was heated to 200 ° C, and the stage was heated to 50 ° C at a mounting temperature (maximum limit temperature) of 150 ° C for 30 seconds. The LED mounting samples A and B were obtained by heating and crimp mounting. <Comparative Example 2> As shown in Table 1, a cationically cured ACF (Anisotropic Conductive Film) manufactured by Dexrils Co., Ltd. (resin: epoxy resin, particles: nickel-coated resin particles, particle diameter: 3 μm, Thickness: 6 μm, resin density: 60 Kpcs/mm ² ) as an anisotropic conductive adhesive. The LED chip was mounted on a ceramic substrate via the anisotropic conductive adhesive, the head was heated to 250 ° C, the stage was heated to 70 ° C, and the mounting temperature (limit maximum temperature) was 180 ° C for 30 seconds. The LED mounting samples A and B were obtained by heating and crimp mounting. <Comparative Example 3> As shown in Table 1, 100 parts by mass of enamel resin (KER2500 manufactured by Shin-Etsu Chemical Co., Ltd.) and solder particles (particle diameter: 10 to 25 μm, melting point: 180 ° C, manufactured by Senju Metal Industry Co., Ltd.) were added. An aliquot of an anisotropic conductive adhesive was prepared by stirring at 2000 rpm / 2 min with a planetary mixer. The LED chip was mounted on a ceramic substrate via the anisotropic conductive adhesive, the head was heated to 290 ° C, and the stage was heated to 60 ° C at a mounting temperature (maximum limit temperature) of 200 ° C for 60 seconds. The LED mounting samples A and B were obtained by heating and crimp mounting. [Table 1] When a liquid anisotropic conductive adhesive containing an amine-based curing agent is used as in Comparative Example 1, the polarity of the amine-hardening-epoxy resin is high, so that the LED mounting sample A is high-temperature and high-humidity. In the continuous lighting test, the wafer shear strength was lowered, and the LED mounting sample B greatly changed in the forward voltage in the high-temperature and high-humidity continuous lighting test. Further, in the case where the cation-hardened ACF was used as in Comparative Example 2, the LED mounting sample A was peeled off in the high-temperature and high-humidity continuous lighting test, and the LED-mounted sample B became unlit at 300 hours in the TCT test. In the high temperature and high humidity continuous lighting test, it did not light up in 130 hours. Further, in the case where the enamel resin ACF was used as in Comparative Example 3, since the enamel resin was soft, the LED mounting sample A could not obtain a high wafer shear strength, and the LED mounting sample B became 200 hours in the TCT test. If it does not light up, it will not light up in 200 hours in the high temperature and high humidity continuous lighting test. On the other hand, when the inorganic ACF containing water glass was used as in Examples 1 to 4, the LED mounting sample A did not lower the wafer shear strength even in the high-temperature and high-humidity continuous lighting test, and the LED mounting sample B even The change in forward voltage was also small in the TCT test and in the high temperature and high humidity continuous lighting test. That is, it is understood that excellent heat resistance and light resistance can be obtained by using inorganic ACF containing water glass.

11‧‧‧1st conductive coating

11a‧‧‧1st conductive electrode

12‧‧‧Active layer

13‧‧‧2nd conductive coating

13a‧‧‧2nd conductive 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‧‧‧Electrical particles

40‧‧‧ Anisotropic conductive adhesive

41‧‧‧Ceramic substrate

42‧‧‧LED chip

43‧‧‧heated crimping machine

50‧‧‧ Tools

Fig. 1 is a cross-sectional view showing an example of a light-emitting device. Figure 2 is a diagram for explaining the steps of fabricating the LED mounting sample. Fig. 3 is a cross-sectional view showing an outline of a wafer shear strength test.

Claims (9)

An anisotropic conductive adhesive which connects a light-emitting element to an electrode of a wiring pattern of a substrate and contains an inorganic binder and conductive particles. The anisotropic conductive adhesive according to claim 1, wherein the inorganic binder is an alkali metal represented by a molecular formula of M ₂ O·nSiO ₂ (M is any one of Na, K, and Li, and n is a molar ratio). Citrate is the main component. The anisotropic conductive adhesive according to claim 1, wherein the inorganic binder is a main component of sodium citrate No. 3 according to JIS K1408. The anisotropic conductive adhesive according to any one of claims 1 to 3, wherein the conductive particles are selected from the group consisting of solder particles, metal particles, and resin core-coated conductive particles coated with metal on the resin particles. At least one. The anisotropic conductive adhesive according to any one of claims 1 to 3, wherein the amount of the conductive particles is from 3 to 120 parts by mass based on 100 parts by mass of the inorganic binder. The anisotropic conductive adhesive according to any one of claims 1 to 3, wherein the light-emitting element emits ultraviolet light. The anisotropic conductive adhesive according to any one of claims 1 to 3, which further contains inorganic particles. A light-emitting device comprising: 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 anisotropy The conductive film is a cured product of an anisotropic conductive adhesive containing an inorganic binder and conductive particles. A method of producing a light-emitting device, comprising applying an anisotropic conductive adhesive containing an inorganic binder and conductive particles to an electrode of a wiring pattern of a substrate, and heating and pressure-bonding the light-emitting element via the anisotropic conductive adhesive.