JP2014195113A - Light-reflective anisotropic conductive adhesive, and light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-reflective anisotropic conductive adhesive capable of obtaining high conductive reliability by maintaining light-emission efficiency of a light-emitting element and preventing occurrence of cracks, and to provide a light-emitting device.SOLUTION: A light-reflective anisotropic conductive adhesive contains: a thermosetting resin composition; conductive particles; and light-reflective needle-shaped insulating particles 10. The light-reflective needle-shaped insulating particles 10 are at least one kind of inorganic particles selected from a group consisting of titanium oxide, zinc oxide, and titanate.

Description

  The present invention relates to a light-reflective anisotropic conductive adhesive used for anisotropically conductive connection of a light-emitting element to a wiring board, and a light-emitting element using the light-reflective anisotropic conductive adhesive. The present invention relates to a light emitting device that is mounted on.

  Conventionally, a light emitting device using a light emitting element such as a light emitting diode (LED) element has been widely used. 3 to 5 show structural examples of an old type light emitting device. In the manufacture of the light emitting device shown in FIG. 3, the LED element 33 is bonded to the substrate 31 with a die bond adhesive 32, and the p electrode 34 and the n electrode 35 on the upper surface of the LED element 33 are bonded to the substrate 31 with a gold (Au) wire 37. Wire bonding is performed by silver plating 36. Thereby, the LED element 33 and the board | substrate 31 are electrically joined. Normally, the light emitting device seals the entire LED element 33 with a resin such as a transparent mold resin (not shown), but the connection of the gold wire 37 depends on the difference in linear expansion coefficient between the resin and the LED element 33 and the gold wire 37. Separation may occur in the portion, or an electrical connection failure may occur due to the disconnection of the gold wire 37.

  In general, such a light emitting device is required to maintain the light emission efficiency (light extraction efficiency) by suppressing the reduction of the reflectance of the light emitted from the LED element. In the light emitting device shown in FIG. 3, gold electrodes are usually used as the p electrode 34 and the n electrode 35 of the LED element 33. However, of the light emitted from the LED element 33, the gold electrode or the gold wire absorbs light having a wavelength of 400 to 500 nm emitted to the upper surface side, and the die bond adhesive 32 absorbs the light emitted downward. Such light absorption reduces the light emission efficiency (light extraction efficiency) of the LED element 33. Furthermore, since the bonding process using the die-bonding adhesive 32 is based on oven curing, there is a problem that it takes time to manufacture.

  In the light emitting device shown in FIG. 4, a conductive paste 37 typified by a silver paste is used. By this conductive paste 37, the p electrode 34 and the n electrode 35 on the lower surface of the LED element 33 and the silver plated portion 36 on the substrate 31. Are electrically connected. However, since the conductive paste 37 has a weak adhesive force, reinforcement with the sealing resin 38 is required. In addition, light may be diffused or absorbed inside the conductive paste 37, thereby reducing the light emission efficiency of the LED element 33.

  Therefore, for example, an LED element and a substrate are connected and fixed and electrically joined by curing an anisotropic conductive adhesive (ACP) or an anisotropic conductive adhesive film (ACF). For example, Patent Document 1 describes a method of flip-chip mounting an LED element. Further, for example, in the light emitting device shown in FIG. 5, the p-electrode 34 and the n-electrode 35 on the lower surface of the LED element 33 and the substrate 31 are electrically bonded by flip chip mounting using a commercially available anisotropic conductive adhesive 39. It is a thing. In this flip chip mounting technique, bumps 40 are formed on the p electrode 34 and the n electrode 35, respectively.

  In the technique of Patent Document 1, a light reflection layer is provided on the LED element by a metal vapor deposition layer or the like so as to be insulated from the p electrode and the n electrode. Thereby, the reduction | decrease of the reflectance of the light radiate | emitted from the LED element is suppressed, and luminous efficiency is maintained. However, the technique of Patent Document 1 has a problem that the number of manufacturing steps of the light emitting device is increased and an increase in cost is inevitable. On the other hand, although the light-emitting device shown in FIG. 5 does not have a light reflecting layer, Au or Ni used as conductive particles dispersed in the binder of ACP exhibits brown or dark brown, and the imidazole that the binder usually contains The ACP binder exhibits an overall brown color due to the system latent curing agent exhibiting a brown color, thereby absorbing light. As a result, the light emission efficiency of the LED element 33 decreases.

JP-A-11-168235

  By the way, the ACP uses an epoxy resin as a binder resin, but the ACP using the epoxy resin increases the conduction resistance and peels off the joint surface due to an internal stress based on a difference in thermal expansion coefficient with the connection substrate accompanying a temperature change. , Cracks and the like were generated. For this reason, reliability such as resistance to reflow of lead-free solder, resistance to thermal shock, and resistance to corrosion phenomenon of vapor deposition wiring when used and stored in a high temperature and high humidity atmosphere may be lowered.

  The present invention has been proposed in view of such a conventional situation, and a light emitting element such as an LED element is flip-chip mounted on a wiring board using an anisotropic conductive adhesive, resulting in a manufacturing cost. In a light-emitting device that maintains the light-emitting efficiency of a light-emitting element without providing such a light reflection layer on the LED element, the object is to prevent the occurrence of cracks in the anisotropic conductive adhesive and to obtain high conduction reliability It is.

  The present inventor has found that the occurrence of cracks can be prevented by making the light-reflective insulating particles added to the anisotropic conductive adhesive into a needle-like shape.

  That is, the present invention relates to a light-reflective anisotropic conductive adhesive used for anisotropically conductively connecting a light-emitting element to a wiring board, comprising a thermosetting resin, conductive particles, and light-reflective needle-like insulation. It is characterized by containing particles.

  In addition, the present invention is characterized in that the light emitting element is mounted on the wiring board by a flip chip method through such a light reflective anisotropic conductive adhesive.

  According to the light-reflective anisotropic conductive adhesive and the light-emitting device of the present invention, the light-reflective anisotropic conductive adhesive in the light-reflective anisotropic conductive adhesive can be obtained by adding light-reflective needle-like insulating particles to the anisotropic conductive adhesive. Generation of cracks can be prevented and high conduction reliability can be obtained.

It is sectional drawing of a light reflective electroconductive particle. It is sectional drawing of the light-emitting device in this Embodiment. It is sectional drawing of the conventional light-emitting device. It is sectional drawing of the conventional light-emitting device. It is sectional drawing of the conventional light-emitting device.

  Hereinafter, an example of a specific embodiment of the light-reflective anisotropic conductive adhesive to which the present invention is applied (hereinafter referred to as “this embodiment”) will be described with reference to the drawings. The light-reflective anisotropic conductive adhesive in the present embodiment is an adhesive used for anisotropically connecting an LED element, which is a light-emitting element, to a wiring board, and includes a thermosetting resin composition, It contains conductive particles and light reflective acicular insulating particles.

  As will be described later, the light-reflective acicular insulating particles are characterized by having an acicular shape having an aspect ratio within a predetermined range. When the thermosetting resin composition contains spherical particles, cracks are generated from the interface between the spherical particles and the thermosetting resin composition due to internal stress of the thermosetting resin composition when the stretchability decreases with temperature change. There is a case. Thus, when a crack arises in a light-reflective anisotropic conductive adhesive, conduction | electrical_connection reliability will be impaired. For this reason, the light-reflective anisotropic conductive adhesive needs to have excellent toughness.

  In the light-reflective anisotropic conductive adhesive in the present embodiment, needle-shaped light-reflective insulating particles having an aspect ratio in a predetermined range are added to the thermosetting resin composition. In the thermosetting resin composition, the acicular light-reflective insulating particles arranged in random directions propagate and absorb the internal stress of the thermosetting resin composition accompanying the temperature change in the acicular crystal. Thus, since it is possible to suppress the internal stress from being transmitted to the thermosetting resin, the toughness of the thermosetting resin composition can be increased. Thereby, the light-reflective anisotropic conductive adhesive exhibits excellent toughness, and can suppress generation of cracks and peeling of the adhesive surface even when the thermosetting resin composition expands and contracts due to temperature change. .

  In the light emitting device that emits visible light, the light-reflecting needle-like insulating particles are made of a white needle-like inorganic compound and reflect the light incident on the light-reflective anisotropic conductive adhesive to the outside. When the light-reflective needle-like insulating particles themselves exhibit white color, the wavelength dependence of the reflection characteristics with respect to visible light can be reduced, and visible light can be efficiently reflected.

  As described above, the light-reflective anisotropic conductive adhesive in the present embodiment is a particle composed of an inorganic compound that exhibits white color and has an acicular shape with an aspect ratio in a predetermined range (hereinafter referred to as “white acicular inorganic material”). In order to maintain the luminous efficiency of the light-emitting element by suppressing the reduction of the reflectance with respect to the light emitted from the light-emitting element, and to prevent cracks and the like and obtain high conduction reliability. Can do.

  Examples of the white acicular inorganic particles include acicular shapes such as titanate whiskers such as zinc oxide whisker, titanium oxide whisker, and potassium titanate whisker, aluminum borate whisker, and wollastonite (kaolin silicate acicular crystals). Mention may be made of inorganic compounds. Whisker is a crystal grown in a needle shape by a special manufacturing method, and since there is no disorder in the crystal structure, it has an advantage that it is rich in elasticity and hardly deforms. Since these inorganic compounds exhibit white color in a light emitting device that emits visible light, the wavelength dependency of the reflection characteristics with respect to visible light is small and the visible light is easily reflected. Among them, the zinc oxide whisker has a high whiteness and is a catalyst for photodegradation even when photocuring of the cured product of the thermosetting resin composition in the cured anisotropic conductive adhesive is concerned. It is particularly preferable because it has no property.

  When the white acicular inorganic particles are composed of a single acicular crystal (single acicular crystal), the fiber diameter (short-direction particle diameter) is preferably 5 μm or less. In addition, the aspect ratio of the white needle-like inorganic particles made of single needle crystals is preferably greater than 10 and less than 35, and particularly preferably greater than 10 and less than 20. When the aspect ratio of the white needle-like inorganic particles is larger than 10, the internal stress of the thermosetting resin can be sufficiently propagated and absorbed. Further, when the aspect ratio of the white needle-like inorganic particles is less than 35, the needle-like crystals are less likely to be broken and can be uniformly dispersed in the thermosetting resin. Connection is not hindered. When this aspect ratio is less than 20, the dispersibility in the thermosetting resin can be further improved.

  Since the toughness of the thermosetting resin composition can be increased by adding white needle-like inorganic particles having an aspect ratio of more than 10 and less than 35 to the thermosetting resin composition, the light reflecting anisotropy Even if the conductive adhesive expands and contracts, it is possible to suppress the peeling or cracking of the adhesive surface.

  In addition, as the white needle-like inorganic particles, instead of such a single needle-like crystal, for example, a shape formed by combining the center and apex of the tetrahedron, such as Tetrapod (registered trademark), etc. A crystal having a plurality of needle-like shapes (double needle-like crystals) may be used. The white needle-like inorganic particles of double needle crystals are superior in that they have a higher thermal conductivity than the white needle-like inorganic particles of single needle crystals, but they have a bulkier crystal structure than single needle crystals. It is necessary to be careful not to damage the substrate or the joined part of the element by the needle-like part during thermocompression bonding.

  The acicular white inorganic particles may be treated with a silane coupling agent, for example. Dispersibility in the thermosetting resin composition can be improved by treating the acicular white inorganic particles with the silane coupling agent. For this reason, the acicular white inorganic particle processed with the silane coupling agent can be mixed in the thermosetting resin composition uniformly in a short time.

The white needle-like inorganic particles have a refractive index (JIS K7142) that is preferably greater than the refractive index of the cured product of the thermosetting resin composition (JIS K7142), and more preferably at least about 0.02. preferable. This is because if the difference in refractive index is small, the reflection efficiency at the interface between them decreases. That is, as white needle-like inorganic particles, even if they are light-reflective and insulating inorganic particles, their refractive index is less than the refractive index of the thermosetting resin composition used, such as SiO _2. Is not applicable.

  If the blending amount of the white needle-like inorganic particles in the light-reflective anisotropic conductive adhesive is too small, sufficient light reflection cannot be realized. On the other hand, if the amount is too large, the adhesiveness of the thermosetting resin is insufficient. Therefore, it is preferable that it is 1-50 volume% (Vol%) with respect to a thermosetting resin composition, and it is especially preferable that it is 5-25 volume%.

  Since the light-reflective anisotropic conductive adhesive in the present embodiment contains such white needle-like inorganic particles and covers most of the conductive particles, the conductive particles exhibit a color such as brown. Even in this case, the whiteness of the thermosetting resin composition is realized. Because of the whiteness of such a thermosetting resin composition, the wavelength dependency of the reflection characteristic with respect to visible light is reduced and the visible light is easily reflected. While suppressing the fall of the reflectance of the emitted light, the light which a LED element light-emits toward the lower surface side can also be utilized efficiently. As a result, the light emission efficiency (light extraction efficiency) of the LED element can be improved.

  And the light-reflective anisotropic conductive adhesive in this Embodiment of the thermosetting resin composition accompanying a temperature change is because the shape of the white inorganic particle as a light-reflective insulating particle is needle shape. It is possible to prevent the internal stress from being transmitted to the thermosetting resin by propagating and absorbing the internal stress in the needle crystal. In addition, when the particle shape is spherical, the internal stress of the thermosetting resin composition is less likely to be propagated and absorbed in the particles than the needle-shaped particles.

  Since the light-reflective anisotropic conductive adhesive thus suppresses the internal stress from being transmitted to the thermosetting resin, the toughness of the thermosetting resin composition can be increased. Thereby, the light-reflective anisotropic conductive adhesive exhibits excellent toughness, and can suppress generation of cracks and peeling of the adhesive surface even when the thermosetting resin composition expands and contracts due to temperature change. .

The light-reflective anisotropic conductive adhesive in the present embodiment is a particle made of a spherical inorganic compound exhibiting white as light-reflective insulating particles (hereinafter referred to as “white spherical inorganic particles”). White needle-like inorganic particles may be added to the thermosetting resin composition containing the. The white spherical inorganic particles are preferably made of the same material as the white needle-shaped inorganic particles described above, and those having a refractive index equal to or lower than the refractive index of the thermosetting resin composition used are applied, such as SiO _2. Can not.

  By adding white spherical inorganic particles together with the white needle-like inorganic particles, the thermosetting resin composition can be further whitened and the light extraction efficiency of the LED element can be further improved. Also in this case, the toughness of the thermosetting resin can be increased. Here, it is preferable that the addition amount (Vol%) of the white needle-like inorganic particles be equal to or more than the addition amount (Vol%) of the white spherical inorganic particles.

  If the white spherical inorganic particles are too small, the reflectance will be low, and if they are too large, the connection with anisotropic conductive particles tends to be hindered. Therefore, the size is preferably 0.02 to 20 μm, 0 More preferably, it is 2 to 1 μm.

  The white spherical inorganic particles, like the white needle-like inorganic particles, preferably have a refractive index (JIS K7142) larger than the refractive index (JIS K7142) of the cured product of the thermosetting resin composition. More preferably, it is about 02 larger.

  As the spherical light-reflective insulating particles, resin-coated metal particles obtained by coating the surface of the spherical metal particles with a transparent insulating resin may be used instead of such white spherical inorganic particles. Examples of the metal particles include nickel, silver, and aluminum.

  The size of the resin-coated metal particles is preferably 0.1 to 30 μm, more preferably 0.2 to 10 μm. In addition, the magnitude | size of the resin coating metal particle has shown the magnitude | size including insulation coating.

  Various insulating resins can be used as the resin in such resin-coated metal particles. From the viewpoint of functional strength and transparency, a cured product of an acrylic resin can be preferably used. Preferable examples include resins obtained by radical copolymerization of methyl methacrylate and 2-hydroxyethyl methacrylate in the presence of a radical initiator such as an organic peroxide such as benzoyl peroxide. In this case, it is more preferable that it is crosslinked with an isocyanate-based crosslinking agent such as 2,4-tolylene diisocyanate.

  Moreover, as a metal particle, it is preferable to introduce | transduce (gamma) -glycidoxy group, a vinyl group, etc. to the metal surface previously with a silane coupling agent.

  Such resin-coated metal particles, for example, are charged with metal particles and a silane coupling agent in a solvent such as toluene and stirred at room temperature for about 1 hour, and then, a radical monomer, a radical polymerization initiator, and as necessary. It can be produced by adding a crosslinking agent and stirring the mixture while heating to the radical polymerization initiation temperature.

  In the light-reflective anisotropic conductive adhesive, the light-reflective anisotropic conductive adhesive can exhibit excellent toughness even when white spherical inorganic particles are added together with white needle-like inorganic particles. By being able to do, even if it expands and contracts by a temperature change, it can suppress that peeling of an adhesive surface and a crack generate | occur | produce.

  As the conductive particles contained in the light-reflective anisotropic conductive adhesive in the present embodiment, particles of a metal material used in conventional conductive particles for anisotropic conductive connection can be used. . That is, examples of the metal material for the conductive particles include gold, nickel, copper, silver, solder, palladium, aluminum, alloys thereof, multilayered products thereof (for example, nickel plating / gold flash plating products), and the like. it can.

  In addition, since the electroconductive particle which uses gold | metal | money, nickel, or copper as a metal material exhibits brown, it can enjoy the effect of this invention rather than another metal material. That is, as described above, in the thermosetting resin composition, since the white needle-like inorganic particles cover most of the conductive particles, the thermosetting resin composition exhibits a brown color due to the conductive particles. And the entire thermosetting resin composition exhibits high whiteness.

  Moreover, you may make it use the metal covering resin particle which coat | covered the resin particle with the metal material as electroconductive particle. Examples of such resin particles include styrene resin particles, benzoguanamine resin particles, and nylon resin particles. As a method of coating the resin particles with a metal material, a conventionally known method can be employed, and for example, an electroless plating method, an electrolytic plating method, or the like can be used. Moreover, the layer thickness of the metal material to coat | cover should just be the thickness which can ensure favorable connection reliability, and although it is based also on the particle size of a resin particle and the kind of metal, it is 0.1-3 micrometers normally.

  In addition, if the particle size of the resin particles is too small, poor conduction occurs, and if it is too large, there is a tendency for short between patterns to occur. preferable. In this case, the shape of the resin particles is preferably a spherical shape, but may be a flake shape or a rugby ball shape.

  The metal-coated resin particles have a spherical shape, and if the particle size is too large, the connection reliability is lowered, so that 1 to 20 μm is preferable, and 3 to 10 μm is more preferable.

  The conductive particles contained in the light-reflective anisotropic conductive adhesive in the present embodiment are light-reflective conductive with light reflectivity as shown in the cross-sectional views of FIGS. 1A and 1B, for example. It is also possible to use particles.

The light-reflective conductive particle 10 shown in FIG. 1A includes a core particle 1 coated with a metal material, and titanium oxide (TiO ₂ ) particles, zinc oxide (ZnO) particles, or aluminum oxide (Al ₂ O ₃ ) on the surface thereof. And a light reflecting layer 3 formed of at least one kind of inorganic particles 2 selected from the particles. The light reflecting layer 3 formed from such inorganic particles exhibits a color in a range from white to gray. For this reason, as described above, the wavelength dependency of the reflection characteristic with respect to visible light is small and the visible light is easily reflected, so that the luminous efficiency of the LED element can be further improved.

  In addition, when there is a concern about photodegradation of the cured product of the thermosetting resin composition of the cured anisotropic conductive adhesive among the titanium oxide particles, the zinc oxide particles or the aluminum oxide particles, as described above, Zinc oxide which is not catalytic to photodegradation and has a high refractive index can be preferably used.

  The core particle 1 is used for anisotropic conductive connection, and its surface is made of a metal foreign material. Examples of the core particle 1 include an embodiment in which the core particle 1 itself is a metal material, or an embodiment in which the surface of the resin particle is coated with a metal material.

  If the layer thickness of the light reflecting layer 3 formed from the inorganic particles 2 is too small with respect to the particle size of the core particle 1 from the viewpoint of the relative size with respect to the particle size of the core particle 1, the reflectance decreases. If it is too large, poor conduction will occur. For this reason, the layer thickness of the light reflecting layer 3 is preferably 0.5 to 50%, and more preferably 1 to 25%.

  Further, in the light-reflective conductive particles 10, if the particle size of the inorganic particles 2 constituting the light-reflecting layer 3 is too small, the light reflection phenomenon hardly occurs, and if it is too large, the formation of the light-reflecting layer tends to be difficult. There is. For this reason, the particle size of the inorganic particles 2 is preferably 0.02 to 4 μm, particularly preferably 0.1 to 1 μm and 0.2 to 0.5 μm. In this case, from the viewpoint of the wavelength of the light to be reflected, the particle size of the inorganic particles 2 is set so that the light to be reflected (that is, the light emitted from the light emitting element) is not transmitted. It is preferable that it is 50% or more. In this case, examples of the shape of the inorganic particles 2 include an amorphous shape, a spherical shape, a scaly shape, and a needle shape. Among these, a spherical shape is preferable from the viewpoint of the light diffusion effect, and a scaly shape is preferable from the viewpoint of the total reflection effect. .

  The light-reflective conductive particles 10 are manufactured by a known film formation technique (so-called mechanofusion method) in which a film made of small particles is formed on the surface of large particle diameter particles by physically colliding large and small powders. be able to. In this case, the inorganic particles 2 are fixed so as to bite into the metal material on the surface of the core particle 1, and on the other hand, the inorganic particles monolayers constitute the light reflecting layer 3 because the inorganic particles are hardly fused and fixed together. Therefore, in the case of FIG. 1A, the layer thickness of the light reflecting layer 3 is considered to be equal to or slightly thinner than the particle size of the inorganic particles 2.

  The light-reflective conductive particle 20 shown in FIG. 1B contains a thermoplastic resin 4 in which the light-reflective layer 3 functions as an adhesive, and the inorganic particles 2 are fixed to each other by the thermoplastic resin 4. It differs from the light-reflective conductive particle 10 of FIG. 1A in that it is formed (for example, two layers or three layers). By containing such a thermoplastic resin 4, the mechanical strength of the light reflecting layer 3 is improved, and the inorganic particles are hardly peeled off.

  As the thermoplastic resin 4, a halogen-free thermoplastic resin can be preferably used for the purpose of low environmental load. For example, polyolefins such as polyethylene and polypropylene, polystyrene, acrylic resins, and the like can be preferably used.

  Such light-reflective conductive particles 20 can also be manufactured by a mechanical fusion method. If the particle size of the thermoplastic resin 4 applied to the mechanical fusion method is too small, the adhesion function is lowered, and if it is too large, it is difficult to adhere to the core particles, so 0.02 to 4 μm is preferable, and 0.1 to 1 μm is preferable. More preferred. Further, if the blending amount of the thermoplastic resin 4 is too small, the adhesive function is deteriorated, and if it is too large, aggregates of particles are formed. 500 mass parts is preferable and 4-25 mass parts is more preferable.

  As the thermosetting resin contained in the light-reflective anisotropic conductive adhesive in the present embodiment, it is preferable to use a transparent and colorless resin as much as possible. This is because the light reflecting efficiency of the light-reflective conductive particles in the anisotropic conductive adhesive is reflected without lowering the incident light without changing the light color of the incident light. Here, colorless and transparent means that the cured product of the anisotropic conductive adhesive has a light transmittance of 1 cm (JIS K7105) with respect to visible light having a wavelength of 380 to 780 nm (JIS K7105) of 80% or more, preferably 90% or more. Means that

  In the light-reflective anisotropic conductive adhesive, if the blending amount of the conductive particles such as the light-reflective conductive particles with respect to 100 parts by mass of the thermosetting resin composition is too small, conduction failure occurs. Since there exists a tendency for a short circuit to arise, 1-100 mass parts is preferable and 10-50 mass parts is more preferable.

  The light-reflective anisotropic conductive adhesive in the present embodiment has a reflectance (JIS K7105) with respect to light having a wavelength of 450 nm of more than 9% by adding white needle-like inorganic particles to the thermosetting resin composition. High value. The reflection characteristics of the light-reflective anisotropic conductive adhesive in the present embodiment include various other factors such as the reflection characteristics and blending amount of the light-reflective conductive particles, the blending composition of the thermosetting resin composition, and the like. By adjusting appropriately, the reflectance (JIS K7105) for light with a wavelength of 450 nm is realized to be 30% or more. Usually, if the amount of light-reflective conductive particles having good reflection characteristics is increased, the reflectance tends to increase.

  Further, the reflection characteristics of the light-reflective anisotropic conductive adhesive can be evaluated from the viewpoint of refractive index. That is, when the reflectance of the cured product is larger than the refractive index of the cured product of the thermosetting resin composition excluding the conductive particles and the light-reflective insulating particles, the light-reflective insulating particles and the heat surrounding them are heated. This is because the amount of light reflection at the interface between the curable resin composition and the cured product increases. Specifically, the difference obtained by subtracting the refractive index (JIS K7142) of the cured product of the thermosetting resin composition from the refractive index (JIS K7142) of the light-reflective insulating particles is preferably 0.02 or more, more preferably. Is desirably 0.2 or more. In general, the refractive index of the thermosetting resin composition mainly composed of epoxy resin is about 1.5.

  As a thermosetting resin composition, what is used in the conventional anisotropic conductive adhesive and anisotropic conductive film can be utilized. Generally, such a thermosetting resin composition is obtained by blending an insulating binder resin with a curing agent. The insulating binder resin is preferably an epoxy resin mainly composed of an alicyclic epoxy compound, a heterocyclic epoxy compound, a hydrogenated epoxy compound, or the like.

  Preferred examples of the alicyclic epoxy compound include those having two or more epoxy groups in the molecule. These may be liquid or solid. Specific examples include glycidyl hexahydrobisphenol A, 3,4-epoxycyclohexenylmethyl-3 ', 4'-epoxycyclohexene carboxylate, and the like. Among these, glycidyl hexavidrobisphenol A, 3,4-epoxycyclohexenylmethyl-3 ′, 4 is preferred because it can ensure light transmission suitable for mounting LED elements on the cured product and is excellent in rapid curing. '-Epoxycyclohexenecarboxylate can be preferably used.

  Examples of the heterocyclic epoxy compound include an epoxy compound having a triazine ring, and 1,3,5-tris (2,3-epoxypropyl) -1,3,5-triazine-2,4 is particularly preferable. 6- (1H, 3H, 5H) -trione can be mentioned.

  As the water-added epoxy compound, hydrogenated products of the above-described alicyclic epoxy compounds and heterocyclic epoxy compounds, and other known hydrogenated epoxy resins can be used.

  Although an alicyclic epoxy compound, a heterocyclic epoxy compound, and a hydrogenated epoxy compound may be used independently, 2 or more types can be used together. In addition to these epoxy compounds, other epoxy compounds may be used in combination as long as the effects of the present invention are not impaired. For example, bisphenol A, bisphenol F, bisphenol S, tetramethylbisphenol A, diarylbisphenol A, hydroquinone, catechol, resorcin, cresol, tetrabromobisphenol A, trihydroxybiphenyl, benzophenone, bisresorcinol, bisphenol hexafluoroacetone, tetramethylbisphenol G, glycidyl ether obtained by reacting polychlorophenol and epichlorohydrin such as A, tetramethylbisphenol F, tris (hydroxyphenyl) methane, bixylenol, phenol novolak, cresol novolak, etc .; glycerin, neopentyl glycol, ethylene glycol, propylene glycol , Hexylene glycol, polyethylene glycol, polyp Polyglycidyl ether obtained by reacting an aliphatic polyhydric alcohol such as pyrene glycol with epichlorohydrin; a glycidyl ether obtained by reacting a hydroxycarboxylic acid such as p-oxybenzoic acid or β-oxynaphthoic acid with epichlorohydrin Esters: polyglycidyl esters obtained from polycarboxylic acids such as phthalic acid, methylphthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, endomethylenetetrahydrophthalic acid, endomethylenehexahydrophthalic acid, trimet acid, polymerized fatty acid Glycidylaminoglycidyl ether obtained from aminophenol, aminoalkylphenol; glycidylaminoglycidyl ester obtained from aminobenzoic acid; aniline, toluidine, tribromourea Glycidylamine obtained from nilin, xylylenediamine, diaminocyclohexane, bisaminomethylcyclohexane, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, and the like; and known epoxy resins such as epoxidized polyolefin .

  Examples of the curing agent include acid anhydrides, imidazole compounds, and dicyan. Among these, acid anhydrides that are difficult to discolor the cured product, particularly alicyclic acid anhydride-based curing agents, can be preferably used. Specifically, methylhexahydrophthalic anhydride etc. can be mentioned preferably.

  In the thermosetting resin composition, when using an alicyclic epoxy compound and an alicyclic acid anhydride-based curing agent, the respective amounts used are uncured if there is too little alicyclic acid anhydride-based curing agent. The epoxy compound increases, and if it is too much, the corrosion of the adherend material tends to be accelerated due to the influence of the excess curing agent. Therefore, the alicyclic acid anhydride-based curing is performed on 100 parts by mass of the alicyclic epoxy compound. The agent is preferably used in a proportion of 80 to 120 parts by mass, more preferably 95 to 105 parts by mass.

  The light-reflective anisotropic conductive adhesive in the present embodiment is manufactured by uniformly mixing a thermosetting resin composition, conductive particles, and white needle-like inorganic particles that are light-reflective insulating particles. can do. When a light-reflective anisotropic conductive film is used, a thermosetting resin composition, conductive particles, and white needle-like inorganic particles that are light-reflective insulating particles are dispersed and mixed together with a solvent such as toluene. Then, it may be applied to the peeled PET film so as to have a desired thickness and dried at a temperature of about 80 ° C.

  Next, a light-emitting device in which a light-emitting element is mounted on a wiring board using the light-reflective anisotropic conductive adhesive in this embodiment will be described with reference to FIG. A light-emitting device 200 shown in FIG. 2 includes a connection terminal 22 on a substrate 21 and a connection bump 26 formed on each of an n-electrode 24 and a p-electrode 25 of an LED element 23 as a light-emitting element. This is a light emitting device in which the above-described light-reflective anisotropic conductive adhesive is applied and the substrate 21 and the LED element 23 are flip-chip mounted. Here, the light-reflective anisotropic conductive adhesive cured product 100 is formed by dispersing the light-reflective insulating particles 10 in the cured product 11 of the thermosetting resin composition. In addition, you may seal with transparent mold resin so that the whole LED element 23 may be covered as needed.

  In the light emitting device 200 configured as described above, the LED element 23 reflects light in the cured product 100 of the light-reflective anisotropic conductive adhesive from light emitted toward the substrate 21 side. Reflected by the conductive insulating particles 10 and emitted from the upper surface of the LED element 23. Accordingly, it is possible to prevent a decrease in luminous efficiency.

  The configuration of the light emitting device 200 other than the light-reflective anisotropic conductive adhesive (LED element 23, bump 26, substrate 21, connection terminal 22, etc.) can be the same as the configuration of the conventional light emitting device. The light emitting device 200 can be manufactured using a conventional anisotropic conductive connection technique except that the light-reflective anisotropic conductive adhesive in the present embodiment is used. In addition, as a light emitting element, the well-known light emitting element other than the LED element 23 can be applied in the range which does not impair the effect of the present invention.

  Hereinafter, specific examples of the present invention will be described. The scope of the present invention is not limited to any of the following examples.

<Example 1>
(Production of anisotropic conductive adhesive)
Thermosetting resin composition comprising white needle-like inorganic particles and conductive particles (particle size 5 μm) whose surface of a spherical resin is gold-plated, and an epoxy curing adhesive (adhesive binder mainly composed of CEL2021P-MeHHPA) It mixed with the thing and produced the anisotropic conductive adhesive. The amount of white needle-like inorganic particles added was 12.0% by volume with respect to the thermosetting resin composition. As the white needle-like inorganic particles, titanium dioxide (TiO ₂ ) whiskers having a long direction particle size of 1.7 μm and a short direction particle size of 0.13 μm (aspect ratio of 13.1) were used. Moreover, the addition amount of electroconductive particle was 10 mass% with respect to the thermosetting resin composition.

(Evaluation of light reflectance)
The produced anisotropic conductive adhesive was applied on a white plate so as to have a thickness of 100 μm, and was cured by heating at 200 ° C. for 1 minute. About the obtained hardened | cured material, the total reflectance (specular reflection and diffuse reflection) with respect to the light of wavelength 450nm which used barium sulfate as a standard was measured using the spectrophotometer (Shimadzu Corporation UV3100).

(Production of LED mounting sample)
Using a bump holder (FB700, Kaijo Co., Ltd.) on a glass epoxy substrate having Ni / Au (5.0 μm thickness / 0.3 μm thickness) plated wiring on 100 μm pitch copper wiring, 15 μm high gold (Au) Bumps were formed. Flip a blue LED (Vf = 3.2V (If = 20 mA)) element at 200 ° C. for 20 seconds and 1 kg / chip on this epoxy substrate with gold bumps using a light-reflective anisotropic conductive adhesive. Chip mounting was performed to obtain a test LED module.

(Evaluation of total luminous flux)
About the obtained LED module for a test, the total luminous flux amount was measured using the total luminous flux measurement system (integral sphere) (LE-2100, manufactured by Otsuka Electronics Co., Ltd.) (measurement condition If = 20 mA (constant current control)). .

(Evaluation of conduction reliability and occurrence of cracks)
The conduction reliability and the presence or absence of cracks were evaluated by a thermal cycle test (TCT). Place the test LED module in the TCT, and (a) -40 ° C for 30 minutes ← → 100 ° C for 30 minutes, 1000 cycles, (b) -55 ° C, 30 minutes ← → 125 ° C, 30 minutes, 1000 cycles It was. That is, (a) exposure to an atmosphere of −40 ° C. and 100 ° C. for 30 minutes each, 1000 cycles of a cooling cycle with this as one cycle, and (b) exposure to an atmosphere of −55 ° C. and 125 ° C. for 30 minutes each, 1000 cycles of the cooling / heating cycle with this as one cycle were performed.

  For the evaluation of the conduction reliability, the Vf value at If = 20 mA was measured for the test LED module taken out from the TCT after 1000 cycles of the TCT. When the amount of increase in the Vf value from the initial Vf value is within 5%, it is judged that the conduction reliability is good, and the result is “◯”, and the amount of increase in the Vf value from the initial Vf value is 5% or more. In some cases, it was judged that the conduction reliability was not good, and “x” was given.

  For the evaluation of the presence or absence of cracks, after 1000 cycles of TCT, the test LED module taken out from the TCT was observed from the upper surface of the blue LED element with a metal microscope, and the presence or absence of cracks was observed. The case where no occurrence of cracks was observed in the light-reflective anisotropic conductive adhesive was evaluated as “◯”, and the case where generation of cracks was observed in the light-reflective anisotropic conductive adhesive was determined as “x”.

<Example 2>
Example 1 except that zinc oxide (ZnO) whiskers (Panatetra WZ-05F1, manufactured by Amtec) having a long particle size of 50 μm and a short particle size of 3 μm (aspect ratio of 16.7) were used as white needle-shaped inorganic particles. The same process was performed.

<Example 3>
Example 1 except that potassium titanate whiskers (Tismo series, manufactured by Otsuka Chemical Co., Ltd.) having a long-direction particle size of 20 μm and a short-direction particle size of 0.6 μm (aspect ratio of 33.3) were used as white needle-like inorganic particles. The same process was performed.

<Example 4>
As white needle-like inorganic particles, the surface of zinc oxide (ZnO) whisker (Panatetra WZ-05F1, Amtec) having a long particle size of 50 μm and a short particle size of 3 μm (aspect ratio of 16.7) is treated with a silane coupling agent. The same treatment as in Example 1 was performed, except that what was used was used.

<Example 5>
As white needle-like inorganic particles, zinc oxide (ZnO) whiskers (Panatetra WZ-05F1, manufactured by Amtec) having a long particle size of 50 μm, a short particle size of 3 μm, and an aspect ratio of 16.7 are used as thermosetting resin compositions. In addition to the addition of 9.0% by volume, zinc oxide (ZnO) white spherical inorganic particles (type I, manufactured by Sakai Chemical Co., Ltd.) having a particle size of 0.6 μm (aspect ratio of 1.0) are thermosetting. The same treatment as in Example 1 was performed, except that the resin composition was added at a ratio of 3.0% by volume.

<Comparative Example 1>
The same treatment as in Example 1 was performed except that the anisotropic conductive adhesive did not contain white needle-like inorganic particles.

<Comparative example 2>
Instead of the white needle-like inorganic particles of Example 1, white spherical inorganic particles of titanium oxide having a particle size of 0.9 μm (aspect ratio: 1.0) were in a ratio of 12.0% by volume with respect to the thermosetting resin composition. The same treatment as in Example 1 was carried out except that it was added in step 1.

<Comparative Example 3>
In place of the white needle-like inorganic particles of Example 1, 0.6 μm (aspect ratio: 1.0) zinc oxide white spherical inorganic particles were added at a ratio of 12.0 vol% with respect to the thermosetting resin composition. Except that, the same processing as in Example 1 was performed.

  Table 1 shows the results of Examples 1 to 5 and Comparative Examples 1 to 3.

As can be seen from the results of Example 1 shown in [Table 1], TiO ₂ (titanium dioxide) having an aspect ratio of 13.1 as white needle-like inorganic particles is 12.0 volumes with respect to the thermosetting resin composition. The reflectance at a wavelength of 450 nm of the cured product of the light-reflective anisotropic conductive adhesive added in% was 55%. Moreover, the total luminous flux of the LED mounting sample using this light-reflective anisotropic conductive adhesive was 350 (mlm). Both the reflectance and the light extraction efficiency from the LED were slightly lower than those of Comparative Example 2 using spherical TiO ₂ (white spherical inorganic particles). However, no cracks were generated after 1000 cycles of TCT (−40 to 100 ° C.) and 1000 cycles of TCT (−55 to 125 ° C.), and the crack resistance was improved.

  As can be seen from the results of Example 2, light in which ZnO (zinc oxide) having an aspect ratio of 16.7 was added as acicular white inorganic particles at a ratio of 12.0% by volume with respect to the thermosetting resin composition. The reflectance at a wavelength of 450 nm of the cured product of the reflective anisotropic conductive adhesive was 35%. Moreover, the total luminous flux of the LED mounting sample using this light-reflective anisotropic conductive adhesive was 300 (mlm). Both the reflectance and the light extraction efficiency from the LED were slightly lower than those of Comparative Example 3 using spherical ZnO (white spherical inorganic particles). However, no cracks were generated after 1000 cycles of TCT (−40 to 100 ° C.) and 1000 cycles of TCT (−55 to 125 ° C.), and the crack resistance was improved.

  As can be seen from the results of Example 3, light reflectivity obtained by adding potassium titanate having an aspect ratio of 33.3 as white needle-like inorganic particles in a proportion of 12.0% by volume with respect to the thermosetting resin composition. The reflectance of the cured anisotropic conductive adhesive at a wavelength of 450 nm was 30%. Moreover, the total luminous flux of the LED mounting sample using this light-reflective anisotropic conductive adhesive was 250 (mlm). Both the reflectance and the light extraction efficiency from the blue LED were slightly lower than those of Comparative Example 3 using granular ZnO (white spherical inorganic particles). However, no cracks were generated after 1000 cycles of TCT (−40 to 100 ° C.) and 1000 cycles of TCT (−55 to 125 ° C.), and the crack resistance was improved.

  As can be seen from the results of Example 4, light-reflective anisotropic in which ZnO having an aspect ratio of 16.7 was added as white needle-like inorganic particles at a ratio of 12.0% by volume with respect to the thermosetting resin composition. The reflectance of the cured product of the conductive conductive adhesive at a wavelength of 450 nm was 35%. Moreover, the total luminous flux of the LED mounting sample using this light-reflective anisotropic conductive adhesive was 300 (mlm). Both the reflectance and the light extraction efficiency from the LED were slightly lower than those of Comparative Example 3 using granular ZnO (white spherical inorganic particles). However, no cracks were generated after 1000 cycles of TCT (−40 to 100 ° C.) and 1000 cycles of TCT (−55 to 125 ° C.), and the crack resistance was improved.

  As can be seen from the results of Example 5, zinc oxide (ZnO) having an aspect ratio of 16.7 as white needle-like inorganic particles was added at a rate of 9.0% by volume with respect to the thermosetting resin composition. The reflectance at a wavelength of 450 nm of a cured product of a light-reflective anisotropic conductive adhesive obtained by adding spherical ZnO (white spherical inorganic particles) at a ratio of 3.0% by volume to the thermosetting resin composition is 40%. Moreover, the total luminous flux of the LED mounting sample using this light-reflective anisotropic conductive adhesive was 250 (mlm). Both the reflectance and the light extraction efficiency from the LED were slightly lower than those of Comparative Example 3 in which spherical zinc oxide (ZnO) was used as the white spherical inorganic particles. However, no cracks were generated after 1000 cycles of TCT (−40 to 100 ° C.) and 1000 cycles of TCT (−55 to 125 ° C.), and the crack resistance was improved.

  As can be seen from the result of Comparative Example 1, the wavelength of the cured product of the anisotropic conductive adhesive in which 10% by mass of the conductive particles were added to the thermosetting resin composition without adding the needle-shaped white inorganic particles was 450 nm. The reflectance at 8 was 8%. The total luminous flux of the LED mounting sample using this anisotropic conductive adhesive was 200 (mlm). Since the light with a wavelength of 450 nm emitted from the blue LED is absorbed by gold (Au), the reflectance with respect to this light is lowered, and thereby the emission efficiency (light extraction efficiency) of the blue LED is lowered. No cracks occurred after 1000 cycles of TCT (−40 to 100 ° C.) and 1000 cycles of TCT (−55 to 125 ° C.).

As can be seen from the results of Comparative Example 2, the wavelength of the light-reflective anisotropic conductive adhesive obtained by adding 12.0% by volume of white spherical inorganic particles of titanium dioxide (TiO ₂ ) to the thermosetting resin composition is 450 nm. The reflectance at was 62%. The total luminous flux of the LED mounting sample using this light-reflective anisotropic conductive adhesive was 390 (mlm). However, cracks did not occur after 1000 cycles of TCT (−40 to 100 ° C.), but cracks occurred after 1000 cycles of TCT (−55 to 125 ° C.).

  As can be seen from the results of Comparative Example 3, the light-reflective anisotropic conductive adhesive obtained by adding 12.0% by volume of white spherical inorganic particles of zinc oxide (ZnO) to the thermosetting resin composition at a wavelength of 450 nm. The reflectance of was 40%. The total luminous flux of the LED mounting sample using this light-reflective anisotropic conductive adhesive was 350 (mlm). Although cracks did not occur after 1000 cycles of TCT (−40 to 100 ° C.), cracks occurred after 1000 cycles of TCT (−55 to 125 ° C.).

  In the anisotropic conductive adhesives of Examples 1 to 5 and Comparative Examples 1 to 3, in the initial stage, after 1000 cycles of TCT (−40 to 100 ° C.) and after 1000 cycles of TCT (−55 to 125 ° C.) It has been found that it has high resistance to such temperature changes and exhibits excellent conduction reliability.

  As can be seen from the above results, in Examples 1 to 5 using the light-reflective anisotropic conductive adhesive in which the white needle-like inorganic particles are added to the thermosetting resin composition, the light emitted from the LED element is reduced. It was possible to suppress the decrease in reflectivity and improve the light emission efficiency (light extraction efficiency) of the LED element. Moreover, the light-reflective anisotropic conductive adhesive in Examples 1-5 has confirmed the high crack resistance also after TCT. This is presumably because the toughness of the thermosetting resin composition could be increased by the white needle-like inorganic particles having a needle-like shape. Moreover, it turned out that the light-reflective anisotropic conductive adhesive of Examples 1-5 has high tolerance with respect to a temperature change, and exhibits the outstanding conduction | electrical_connection reliability.

  21 substrate, 22 connection terminal, 23 LED element, 24 n electrode, 25 p electrode, 26 bump, 200 light emitting device

That is, the present invention is a light-reflective anisotropic conductive adhesive used for anisotropically conductively connecting a light-emitting element to a wiring board, and includes a thermosetting resin, conductive particles , and a light-reflective needle shape. It contains titanate whiskers as insulating particles.

Claims (10)

  A light-reflective anisotropic conductive adhesive used for anisotropic conductive connection of a light-emitting element to a wiring board, comprising a thermosetting resin, conductive particles, and light-reflective needle-like insulating particles A light-reflective anisotropic conductive adhesive characterized.   The light-reflective anisotropy according to claim 1, wherein the light-reflective acicular insulating particles are at least one kind of inorganic particles selected from the group consisting of titanium oxide, zinc oxide and titanate. Conductive adhesive.   The light-reflective anisotropic conductive adhesive according to claim 1, wherein the light-reflective needle-like insulating particles are obtained by treating the surface of zinc oxide with a silane agent.   4. The light-reflective anisotropic conductive adhesive according to claim 1, wherein an aspect ratio of the light-reflective needle-like insulating particles is greater than 10 and less than 35. 5.   The light-reflective anisotropic conductive adhesive according to any one of claims 1 to 3, wherein an aspect ratio of the light-reflective needle-like particles is greater than 10 and less than 20.   The amount of the light-reflective needle-like particles in the thermosetting resin composition is 1 to 50% by volume with respect to the thermosetting resin composition. The light-reflective anisotropic conductive adhesive according to item 1.   The light-reflective anisotropic conductive adhesive according to any one of claims 1 to 6, further comprising light-reflective spherical insulating particles.   8. The light-reflective anisotropic conductive adhesive according to claim 7, wherein the light-reflective needle-like insulating particles are contained in a volume amount equal to or greater than the volume amount of the light-reflective spherical insulating particles. Agent.   A light-emitting device, wherein the light-emitting element is mounted on the wiring board by a flip chip method through the light-reflective anisotropic conductive adhesive according to any one of claims 1 to 8.   The light emitting device according to claim 9, wherein the light emitting element is a light emitting diode.

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