JP2018088498A - Anisotropic Conductive Adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anisotropic conductive adhesive which includes an excellent heat resistance and light resistance energy properties.SOLUTION: An anisotropic conductive adhesive that connects a light emission element onto an electrode of a wiring pattern of a substrate, includes: an inorganic binder; and a conductive particle. Since an adhesive component is an inorganic material, excellent heat resistance and light resistance energy properties can be obtained. Specifically, even when an ultraviolet light LED that emits an ultraviolet light of a light energy having two to three times stronger than a blue is mounted, the excellent heat resistance and the light resistance energy properties can be obtained.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an anisotropic conductive adhesive for mounting an LED (Light Emitting Diode).

  Conventionally, wire bonding is known as a method of mounting LED chip components on a circuit board. However, in the wire bond bonding, the wire is cut and an electrical connection failure may occur. Moreover, the wire bond bonding has low versatility of the substrate, and it is difficult to reduce the size and flexibility.

  As a technique for solving the problem of wire bond bonding, Patent Documents 1 and 2 disclose that an anisotropic conductive film in which conductive particles are dispersed in an epoxy adhesive and formed into a film is used, and an LED is flip-chip mounted. A method has been proposed.

JP 2010-24301 A JP 2012-186322 A

  In the conventional anisotropic conductive adhesive for flip chip mounting, when a large current is applied to increase the illuminance of the LED, the adhesive strength decreases due to the heat of the large current, and the LED may be peeled off. In addition, when an ultraviolet LED is mounted using a conventional anisotropic conductive adhesive, the adhesive strength decreases due to light energy twice to three times as strong as that of a blue LED, and the LED may not light up. .

  The present invention solves the above-described problems in the prior art, and provides an anisotropic conductive adhesive having excellent heat resistance and light energy resistance.

  As a result of intensive studies, the present inventors have found that excellent heat resistance and light energy resistance can be obtained by using an adhesive component (binder) of an anisotropic conductive adhesive as an inorganic material.

  That is, the anisotropic conductive adhesive according to the present invention is an anisotropic conductive adhesive for connecting a light emitting element on an electrode of a wiring pattern of a substrate, and contains an inorganic binder and conductive particles. And

  The light emitting device according to the present invention 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. The anisotropic conductive film is a cured product of an anisotropic conductive adhesive containing an inorganic binder and conductive particles.

  In the method for manufacturing a light emitting device according to the present invention, an anisotropic conductive adhesive containing an inorganic binder and conductive particles is applied on an electrode of a wiring pattern of a substrate, and the anisotropic conductive adhesive is applied. The light-emitting element is heat-pressed through.

  According to the present invention, since the adhesive component is an inorganic material, excellent heat resistance and light energy resistance can be obtained.

FIG. 1 is a cross-sectional view illustrating an example of a light emitting device. FIG. 2 is a diagram for explaining a manufacturing process of the LED mounting sample. FIG. 3 is a cross-sectional view showing an outline of the die shear strength test.

Hereinafter, embodiments of the present invention will be described in detail in the following order with reference to the drawings.
1. 1. Anisotropic conductive adhesive 2. Light emitting device Example

<1. Anisotropic conductive adhesive>
The anisotropic conductive adhesive according to the present embodiment is an anisotropic conductive adhesive for connecting a light emitting element on an electrode of a wiring pattern on a substrate, and contains an inorganic binder and conductive particles. When the adhesive component is an inorganic material, excellent heat resistance and light energy resistance can be obtained.

[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 silica sols. Among these, molecular formula M ₂ O · nSiO ₂ (M is Na, K , Li and n is a molar ratio.) It is preferable to use an alkali metal silicate represented by the following formula.

  The metal M of the alkali metal silicate generally has good adhesion in the order of Na> K> Li. For this reason, it is preferable that the main component of an inorganic binder is sodium silicate (water glass). As sodium silicate, sodium silicate Nos. 1 to 3 in accordance with JIS K1408 are preferably used, and sodium silicate No. 3 is preferably used from the viewpoint of adhesive strength.

  In addition, in order to improve the adhesive force, the inorganic binder is used as a curing agent such as any one of oxides, hydroxides, hydroxides, Na, K, and Ca of any one of Zn, Mg, and C. Any one kind of phosphate, Ca, Ba, Mg may be contained.

[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 resin particles are coated with metal. Among these, 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 1 μm or more and 30 μm or less, and more preferably 5 μm or more and 25 μm or less. The blending amount of the conductive particles is preferably 3 to 120 parts by mass and more preferably 10 to 80 parts by mass with respect to 100 parts by mass of the inorganic binder.

  Examples of the solder particles include Sn-Pb, Pb-Sn-Sb, Sn-Sb, Sn-Pb-Bi, Bi-Sn, and Sn-Cu based on JIS Z 3282-1999. , Sn—Pb—Cu, Sn—In, Sn—Ag, Sn—Pb—Ag, Pb—Ag, and the like can be appropriately selected according to the electrode material, connection conditions, and the like. Further, the shape of the solder particles can be appropriately selected from granular, flake shaped, and the like. The solder particles may be covered with an insulating layer in order to improve anisotropy. Moreover, it is preferable that melting | fusing point of solder is 100-250 degreeC, and it is more preferable that it is 150-200 degreeC. Note that the solder particles can form an alloy with the terminals (electrodes) even at a mounting temperature lower than the melting point of the solder particles by a sufficient load at the time of pressure bonding.

  The blending amount of the solder particles is preferably 20 to 120 parts by mass. If the blending amount of the solder particles is too small, excellent heat dissipation characteristics cannot be obtained, and if the blending amount is too large, 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 size larger than that of the resin core conductive particles, and the average particle size of the solder particles is 120, which is the average particle size of the resin core conductive particles. It is preferable that it is -800%, and it is more preferable that it is 200-500%. Because the average particle size of the solder particles is larger than that of the resin core conductive particles, a sufficient load is applied to the solder particles during crimping, and an alloy is formed between the terminals (electrodes) even at a mounting temperature below the melting point of the solder particles. Can do.

  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 particles of the resin core conductive particles, for example, epoxy resin, phenol resin, acrylic resin, acrylonitrile / styrene (AS) resin, benzoguanamine resin, divinylbenzene resin, styrene resin, and the like can be used. Moreover, as a metal which coat | covers a resin particle, various metals, such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver, gold | metal | money, or these alloys can be used, for example.

  Moreover, the anisotropic conductive adhesive according to the present embodiment may further contain an inorganic filler in order to adjust viscosity and linear expansion. Examples of the inorganic filler include silica, alumina, titanium oxide, aluminum nitride, calcium carbonate, and magnesium oxide. The average particle size 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 with respect 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, and Al ₂ O _{3 in} order to reflect light emitted from the LED and obtain high light extraction efficiency. The average particle size of the white inorganic particles is preferably at least 1/2 of the wavelength of light to be reflected.

  According to such an anisotropic conductive adhesive, excellent heat resistance and light energy resistance can be obtained because the adhesive component is an inorganic material. In particular, even when an ultraviolet LED that emits ultraviolet light having a light energy 2 to 3 times that of a blue LED is mounted, excellent heat resistance and light energy resistance can be obtained.

<2. Light emitting device>
The light emitting device according to the present 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. The anisotropic conductive film is a cured product of the anisotropic conductive adhesive containing the above-described inorganic binder and conductive particles. Thereby, the outstanding heat resistance and light energy resistance can be obtained.

  Further, in the method for manufacturing the light emitting device according to the present embodiment, an anisotropic conductive adhesive containing an inorganic binder and conductive particles is applied on the electrodes of the wiring pattern of the substrate, and the anisotropic conductive adhesive is applied. The light emitting element is thermocompression-bonded via the substrate.

FIG. 1 is a cross-sectional view illustrating an example of a light emitting device. The light emitting element includes a first conductivity type clad layer 11 made of, for example, n-GaN, an active layer 12 made of, for example, an In _x Al _y Ga _1-xy N layer, and a second conductivity type clad made of, for example, p-GaN. A layer 113 and a so-called double heterostructure. Further, a first conductivity type electrode 11 a formed on a part of the first conductivity type cladding layer 11 by the passivation layer 14 and a second conductivity type electrode 13 a formed on a part of the second conductivity type cladding layer 13 are provided. Prepare. When a voltage is applied between the first conductivity type electrode 11a and the second conductivity type electrode 13a, carriers are concentrated on the active layer 12, and light is emitted by recombination.

  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 by 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 to 6.2 eV, and the ultraviolet LED is a blue LED. However, in this embodiment, since the adhesive component of the anisotropic conductive adhesive is an inorganic material, the adhesive strength can be obtained even when an ultraviolet LED is used. Can be suppressed, and excellent heat resistance and light energy resistance can be obtained.

  The substrate includes a first conductivity type circuit pattern 22 and a second conductivity type circuit pattern 23 on a base material 21, and positions corresponding to the first conductivity type electrode 11a and the second conductivity type electrode 13a of the light emitting element. Each has an electrode.

  The substrate is preferably a translucent substrate. When the base material 21 is a translucent substrate, the base material 31 is preferably a transparent base material such as glass or PET (polyethylene terephthalate), and the first conductive type circuit pattern 22 and the second conductive type circuit pattern. 23, and its electrode is a transparent conductive film such as ITO (Indium-Tin-Oxide), IZO (Indium-Zinc-Oxide), ZnO (Zinc-Oxide), IGZO (Indium-Gallium-Zinc-Oxide) Is preferred. Since the substrate is a light-transmitting substrate, the substrate side can be a display surface (light emitting surface).

  The anisotropic conductive film 30 is obtained by curing the above-described anisotropic conductive adhesive, and the conductive particles 31 are captured between the terminals (electrodes 11a and 13a) of the light emitting element and the terminals (electrodes) of the substrate. As a result, the light emitting element and the substrate are electrically connected.

According to such a light emitting device, excellent heat resistance and light resistance can be obtained because the adhesive component of the anisotropic conductive adhesive is an inorganic material. In particular, even when an ultraviolet LED that emits ultraviolet light having a light energy 2 to 3 times that of a blue LED is mounted, excellent heat resistance and light energy resistance can be obtained.
<3. Example>

  Examples of the present invention will be described below. In this example, various anisotropic conductive adhesives were produced. Then, a blue LED chip was mounted on the substrate using an anisotropic conductive adhesive to produce an LED mounting sample A, and the heat resistance was evaluated by measuring the die shear strength after the initial and high-temperature and high-humidity continuous lighting tests. . In addition, an ultraviolet LED chip is mounted on a substrate using an anisotropic conductive adhesive to prepare an LED mounting sample B, and forward voltage after initial, TCT (Temperature Cycling Test) test and after high temperature and high humidity continuous lighting test Were measured for heat resistance and light energy resistance. The present invention is not limited to these examples.

[Production of LED mounting sample]
FIG. 2 is a diagram for explaining a manufacturing process of the LED mounting sample. As shown in FIG. 2, an LED mounting sample was produced. A ceramic substrate 41 on which metal wiring was formed was placed on a stage, and an anisotropic conductive adhesive 40 was applied on the ceramic substrate 41 by a stamping method. Then, the LED chip 42 is mounted on the anisotropic conductive adhesive 40 with a load of 60 g, and the head and the stage are heated by thermocompression bonding using the thermocompression bonder 43, and the LED mounting sample A or LED mounting is performed. Sample B was obtained.

[Die shear strength measurement]
An LED mounting sample A was produced using a blue LED (rated 350 mA, size 45 mm square, wavelength 460 nm) as the LED chip 42.

  FIG. 3 is a cross-sectional view showing an outline of the die shear strength test. As shown in FIG. 3, using a die shear tester, the die shear strength is measured at the initial stage of each LED mounting sample A and after the high temperature and high humidity continuous lighting test under the conditions of a shear rate of the tool 50 of 20 μm / sec and a temperature of 25 ° C. did. In the high-temperature and high-humidity continuous lighting test, lighting was continuously performed under conditions of a temperature of 85 ° C., a humidity of 90%, and 500 hours.

[Measurement of forward voltage]
An LED mounting sample B was prepared using a blue LED (Nitride Semiconductor, NS355C-2SAA, rated 20 mA, forward voltage 3.61 V, wavelength 355 nm) as the LED chip 42.

  The forward voltage after each LED mounting sample B, after the TCT test, and after the high temperature and high humidity continuous lighting test was measured. In the TCT test, the LED mounting sample B was exposed to an atmosphere of −40 ° C. and 100 ° C. for 30 minutes each, and 1000 cycles of a cooling / heating cycle were performed. In the high-temperature and high-humidity continuous lighting test, the lighting was continuously performed under the conditions of a temperature of 85 ° C., a humidity of 90% and 1000 hours, and 20 mA. What changed 0.1V or more from the initial forward voltage of LED was evaluated as NG.

<Example 1>
As shown in Table 1, 100 parts by mass of water glass (sodium silicate No. 3 shown in JIS K1408) 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.) are weighed. And stirred with a planetary stirrer at 2000 rpm / 2 min to prepare an anisotropic conductive adhesive. An LED chip is mounted on a ceramic substrate through this anisotropic conductive adhesive, the head is heated to 150 ° C., the stage is heated to 50 ° C., and the thermocompression bonding is performed at a mounting temperature (attained top temperature) of 100 ° C. for 60 seconds. After mounting, LED mounting samples A and B were obtained. Table 1 shows the die shear strength after the initial stage of the LED mounting sample A and after the high temperature and high humidity continuous lighting test, and the measurement results of the forward voltage after the initial stage, after the TCT test and after the high temperature and high humidity continuous lighting test of the LED mounting sample B.

<Example 2>
As shown in Table 1, 100 parts by mass of water glass (sodium silicate No. 3 shown in JIS K1408) and resin core conductive particles (average particle size 5 μm, nickel plating, resin core particles (EH Core manufactured by Nippon Kagaku Co., Ltd.)) 10 parts by mass was weighed and added, and stirred with a planetary stirrer at 2000 rpm / 2 min to produce an anisotropic conductive adhesive. Other than this, in the same manner as in Example 1, LED mounting samples A and B were produced.

<Example 3>
As shown in Table 1, 100 parts by mass of water glass (sodium silicate No. 3 shown in JIS K1408), 30 parts by mass of solder particles (particle size 10 to 25 μm, melting point 180 ° C., Senju Metal Industry Co., Ltd.), and resin core 5 parts by weight of conductive particles (average particle size 5 μm, nickel plating, resin core particles (EH core manufactured by Nippon Kagaku)) are weighed and added, and stirred with a planetary stirrer at 2000 rpm / 2 min, anisotropic conductive bonding An agent was prepared. Except 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 silicate No. 3 shown in JIS K1408), 60 parts by mass of solder particles (particle size 10 to 25 μm, melting point 180 ° C., Senju Metal Industry Co., Ltd.), and silica particles (Aerosil RX300 manufactured by Nippon Aerosil Co., Ltd.) 7 parts by weight were weighed and added, and stirred with a planetary stirrer at 2000 rpm / 2 min to prepare an anisotropic conductive adhesive. Except 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, as the anisotropic conductive adhesive, an amine-based curing agent-containing liquid anisotropic conductive adhesive (BP series, resin: epoxy resin, particle: Ni particle) manufactured by Dexialials was used. An LED chip is mounted on a ceramic substrate via this anisotropic conductive adhesive, the head is heated to 200 ° C., the stage is heated to 50 ° C., and thermocompression bonding is performed at a mounting temperature (attained top temperature) of 150 ° C. for 30 seconds. After mounting, LED mounting samples A and B were obtained.

<Comparative example 2>
As shown in Table 1, as an anisotropic conductive adhesive, a cation-cured ACF manufactured by Dexerials (resin: epoxy resin, particles: nickel-coated resin particles, particle size: 3 μm, thickness: 6 μm, resin density: 60 Kpcs / mm) ² ) was used. An LED chip is mounted on a ceramic substrate through this anisotropic conductive adhesive, the head is heated to 250 ° C., the stage is heated to 70 ° C., and the thermocompression bonding is performed at a mounting temperature (attained top temperature) of 180 ° C. for 30 seconds. After mounting, LED mounting samples A and B were obtained.

<Comparative Example 3>
As shown in Table 1, 100 parts by mass of silicon resin (KE 2500 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., Senju Metal Industry Co., Ltd.) were weighed and added. Stirring was performed at 2000 rpm / 2 min with a planetary stirrer to prepare an anisotropic conductive adhesive. An LED chip is mounted on a ceramic substrate via this anisotropic conductive adhesive, the head is heated to 290 ° C., the stage is heated to 60 ° C., and thermocompression bonding is performed at a mounting temperature (attained top temperature) of 200 ° C. for 60 seconds. After mounting, LED mounting samples A and B were obtained.

  When an amine-based curing agent-containing liquid anisotropic conductive adhesive is used as in Comparative Example 1, since the water absorption is high due to the polarity of the amine curing system-epoxy resin, the LED mounting sample A is a high-temperature, high-humidity continuous lighting test. , The die shear strength decreased, and the forward voltage of the LED mounting sample B greatly changed in the high-temperature and high-humidity continuous lighting test.

  In addition, when the cation-cured ACF is used as in Comparative Example 2, the blue LED peels off in the LED mounting sample A in the high temperature and high humidity continuous lighting test, and the LED mounting sample B does not light in 300 hours in the TCT test. Thus, in the high-temperature and high-humidity continuous lighting test, lighting was not performed in 130 hours.

  Further, when the silicon resin ACF is used as in Comparative Example 3, since the silicon resin is soft, the LED mounting sample A cannot obtain a high die shear strength, and the LED mounting sample B does not reach 200 hours in the TCT test. It turned on, and it turned off in 200 hours in the high temperature and high humidity continuous lighting test.

  On the other hand, when the inorganic ACF containing water glass is used as in Examples 1 to 4, the LED mounting sample A does not decrease the die shear strength even in the high-temperature and high-humidity continuous lighting test, and the LED mounting sample B is TCT. The change in forward voltage was also small in the test and the high-temperature and high-humidity continuous lighting test. That is, it was found that excellent heat resistance and light energy resistance can be obtained by using inorganic ACF containing water glass.

DESCRIPTION OF SYMBOLS 11 1st conductivity type clad layer, 11a 1st conductivity type electrode, 12 Active layer, 13 2nd conductivity type clad layer, 13a 2nd conductivity type electrode, 14 Passivation layer, 21 Base material, 22 Circuit pattern for 1st conductivity type , 23 Circuit pattern for second conductivity type, 30 anisotropic conductive film, 31 conductive particles, 40 anisotropic conductive adhesive, 41 ceramic substrate, 42 LED chip, 43 thermocompression bonder, 50 tool

Claims (9)

An anisotropic conductive adhesive for connecting a light emitting element on an electrode of a wiring pattern on a substrate,
An anisotropic conductive adhesive containing an inorganic binder and conductive particles. The inorganic binder is mainly composed of an alkali metal silicate represented by the molecular formula M ₂ O · nSiO ₂ (M is any one of Na, K, and Li, and n is a molar ratio). The anisotropic conductive adhesive according to claim 1.   The anisotropic conductive adhesive according to claim 1, wherein the inorganic binder is mainly composed of sodium silicate No. 3 based on JIS K1408.   4. The anisotropic material 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 in which resin particles are coated with metal. Conductive adhesive.   The anisotropic conductive adhesive according to any one of claims 1 to 4, wherein a blending amount of the conductive particles is 3 to 120 parts by mass with respect to 100 parts by mass of the inorganic binder.   The anisotropic conductive adhesive according to claim 1, wherein the light emitting element emits ultraviolet light.   The anisotropic conductive adhesive according to claim 1, further comprising inorganic particles. A substrate having a wiring pattern;
An anisotropic conductive film formed on the electrode of the wiring pattern;
A light emitting device mounted on the anisotropic conductive film,
The light emitting device in which the anisotropic conductive film is a cured product of an anisotropic conductive adhesive containing an inorganic binder and conductive particles. A method for manufacturing a light-emitting device, wherein an anisotropic conductive adhesive containing an inorganic binder and conductive particles is applied on an electrode of a wiring pattern on a substrate, and a light-emitting element is heated and pressure-bonded via the anisotropic conductive adhesive .

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