TW201805388A - Anisotropic conductive adhesive and light emitting device - Google Patents

Abstract

To provide a technique of an anisotropic conductive adhesive which enables flip chip mounting of a light emitting element such as an LED chip having fine-pitch wiring and is capable of imparting high optical characteristics, high heat dissipation and high connection reliability to a light-emitting device such as an LED module. There is provided an anisotropic conductive adhesive 2 which comprises conductive particles 1 in which an insulation film is formed on the surface of metal particles and light-reflective insulation particles 4 in a binder material 3. The metal particles contain a soft metal and the insulation film is formed on the surface of metal particles by a sputtering method while applying vibration in an oxygen-containing atmosphere.

Description

Anisotropic conductive adhesive and light emitting device

The present invention relates to an anisotropic conductive adhesive, and more particularly to a technology for anisotropic conductive adhesive for mounting a semiconductor element such as an LED (light emitting diode) on a wiring substrate.

In recent years, light-emitting elements using LEDs are receiving attention.

For such a light-emitting element, flip-chip mounting in which an LED chip is directly mounted on a wiring substrate is performed for miniaturization and the like.

Conventionally, as a method for mounting an LED chip on a wiring substrate on a wiring substrate, a method using wire bonding, a method using metal eutectic bonding typified by Au-Sn solder, and a method using an anisotropic conductive adhesive are known. .

However, in the above-mentioned conventional techniques, there are various problems.

First, in the method using wire bonding, in the normal case, the periphery of the LED chip is sealed with resin. However, due to the difference in linear expansion coefficient between the resin and the bonding wire, peeling or bonding of the connecting portion of the bonding wire occurs The disconnection of the wire may cause poor electrical connection.

In addition, because gold is used as a material for the electrode, light having a wavelength of, for example, 400 to 500 nm is absorbed, and therefore, light emission efficiency is reduced.

Furthermore, in the case of this method, since the wafer bonding agent is hardened using an oven, the hardening time is long and it is difficult to improve the production efficiency.

Furthermore, in order to dissipate the heat generated by the light-emitting portion to the substrate side, heat is dissipated through a wafer base portion made of, for example, sapphire. Therefore, the heat radiation distance is increased according to the thickness of the wafer base portion, and therefore, the heat dissipation characteristics are improved. Will fall.

On the other hand, in the method using metal eutectic bonding using solder or the like, the linear expansion coefficient of the LED chip and the substrate are different, and therefore, there may be cases where electrical connection failure occurs due to cracks in the connection portion due to stress concentration. .

Moreover, in this method, in order to remove the oxide film of the surface metal, it is necessary to apply a flux, but there may be a case where the LED chip has a positional shift due to a small viscosity of the flux, resulting in poor electrical connection.

Furthermore, in this method, a cleaning process of a flux is required, and therefore, production takes time, and there may be cases where corrosion of the substrate occurs due to insufficient cleaning of the flux.

On the other hand, in the method using the anisotropic conductive adhesive, the color of the conductive particles in the anisotropic conductive adhesive is brown, so the color of the insulating adhesive resin also becomes brown, which is anisotropic conductive. Then, light is absorbed in the agent, resulting in a decrease in luminous efficiency.

In addition, the conventional anisotropic conductive adhesive using epoxy resin as a base resin is a material that is easily deteriorated by heat or light generated by the LED chip. Therefore, if a reflow test and a thermal shock test corresponding to a lead-free solder are performed, (TCT), high temperature, high humidity test and other reliability tests, due to the decrease in bonding strength, etc., due to internal stress caused by the difference in thermal expansion coefficient of the connection substrate Problems arise in that the on-resistance increases or the joint surface peels. This problem becomes an obstacle especially when flip chip mounting of narrow pitch wiring is performed.

Furthermore, an epoxy resin with a small thermal conductivity is interposed between the electrode of the LED chip and the electrode of the wiring substrate. Therefore, there is also a problem that the heat radiation characteristic of the heat generated by the LED chip to the wiring substrate is reduced.

In particular, it is well known that the light emitting layer of an LED chip generates a lot of heat in addition to light. If the temperature (junction temperature) of the light emitting layer becomes 100 ° C or higher, the light emitting efficiency will decrease and the life of the LED chip will be shortened (for example, refer to Patent Documents) 4).

[Prior technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2005-120375

[Patent Document 2] Japanese Unexamined Patent Publication No. 5-152464

[Patent Document 3] Japanese Patent Laid-Open No. 2003-26768

[Patent Document 4] Japanese Patent Laid-Open No. 2009-206422

The present invention was made in consideration of such a conventional technical problem, and an object thereof is to provide flip-chip mounting of light emitting elements such as LED chips with narrow pitch wiring, and to provide high optical characteristics to light emitting devices such as LED modules. Anisotropic conductive adhesive technology with higher heat dissipation and higher connection reliability.

The present invention completed in order to achieve the above-mentioned object is an anisotropic conductive adhesive, which is composed of conductive particles and light-reflective insulating particles in which an insulating film is formed on the surface of metal particles in a bonding material, and the metal particles include For a soft metal, the insulating film is formed on the surface of the metal particles by a sputtering method while applying vibration in an environment containing oxygen.

In the present invention, it is also effective when the soft metal of the metal particles is a solder alloy.

In the present invention, it is also effective when the film thickness T (nm) of the insulating film of the conductive particles is within a range of 2 nm <T <500 nm.

In this invention, it is effective also when the insulating film of the said electroconductive particle is a metal oxide containing at least 1 sort (s) of any one of a silicon oxide, an alumina, a titanium oxide, and a niobium oxide.

In the present invention, it is also effective when the average particle diameter D (μm) of the metal particles of the conductive particles is 1 μm ≦ D ≦ 20 μm.

In the present invention, it is also effective when the particle diameter of the light-reflective insulating particles is 2% or more and less than 20% of the particle diameter of the conductive particles.

On the other hand, the present invention is a light-emitting device including a wiring substrate having a pair of connection electrodes and a light-emitting element having a connection electrode corresponding to each of the pair of connection electrodes of the wiring substrate. Any one of the anisotropic conductive adhesives is bonded to the wiring substrate, and the connection electrode of the light-emitting element is electrically connected to the corresponding connection electrode of the wiring substrate via the conductive particles of the anisotropic conductive adhesive. connection.

In the present invention, an insulating film is formed on the surface of the conductive particles such as soft metal particles made of a solder alloy, and when mounting is performed by heating and pressing, the insulating film The electrode is connected to press the conductive particles and crushed. At the same time, the insulating film formed on the surface of the metal particles is broken to expose non-oxidized components such as solder, thereby connecting the opposite electrode to the metal particles. Metal eutectic bonds were formed between them.

On the other hand, the conductive particles existing between adjacent connection electrodes (for example, the anode electrode and the cathode electrode of the LED chip) other than the conductive portion where no pressure is applied can be used even when the conductive particles are in contact with each other. The presence of an insulating film maintains insulation.

As a result, according to the present invention, it is possible to mount, for example, a light-emitting element flip-chip with a connection electrode having a narrow pitch wiring on a wiring substrate with high connection reliability, and it is possible to efficiently generate heat generated from the light-emitting portion of the light-emitting element. Ground is dissipated to the wiring board side.

In particular, in the present invention, as the metal particles of the conductive particles, a soft metal made of, for example, a solder alloy is used. Therefore, the area of the connection portion between the conductive particles and the connection electrode can be increased. Improved connection reliability and heat dissipation characteristics.

Furthermore, in the present invention, since the light-reflective insulating particles are contained in the adhesive material of the anisotropic conductive adhesive, the light generated from the light-emitting portion of the light-emitting element can be efficiently reflected, thereby improving the light-emitting efficiency. In particular, in the case of using a wiring substrate having a gold-plated connection electrode that is generally implemented with high corrosion resistance, if the connection is made by gold-tin (Au-Sn) metal eutectic bonding, the self-emitting element is released. The emitted light is absorbed by the gold plating, and the luminous flux is reduced. In contrast, according to the present invention, a higher luminous flux can be obtained by performing light reflection using the light-reflective insulating particles in the anisotropic conductive adhesive.

As described above, according to the present invention, it is possible to provide a light-emitting element that can achieve miniaturization of a light-emitting element that can be used for flip-chip mounting of light-emitting elements with narrow pitch wiring, and has high optical characteristics and high heat dissipation. And higher connection reliability.

1‧‧‧ conductive particles

2‧‧‧Anisotropic conductive adhesive

3‧‧‧ Adhesive

4‧‧‧ light reflective insulating particles

5‧‧‧light-emitting device

10‧‧‧ metal particles

11‧‧‧ surface

12‧‧‧ insulating film

40‧‧‧Light-emitting element

50‧‧‧wiring board

FIG. 1 is a cross-sectional view schematically showing the structure of a conductive particle used in the present invention.

FIG. 2 is a view showing an example of a method for forming an insulating film of the conductive particles.

FIG. 3 is a cross-sectional view schematically showing the structure of the anisotropic conductive adhesive of the present invention.

Fig. 4 is a cross-sectional view showing the structure of an embodiment of a light-emitting device according to the present invention.

5 (a) to (c) are diagrams showing examples of manufacturing steps of the light emitting device of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[1. Conductive particles]

For example, as shown in FIG. 1, the conductive particles 1 used in the present invention are formed by forming an insulating film 12 on the surface 11 of the metal particles 10.

The average particle diameter of the conductive particles 1 can be appropriately determined according to the average particle diameter D of the metal particles 10 and the film thickness T of the insulating film 12 described below. The shape of the conductive particles 1 is not particularly limited, and can be appropriately determined according to the application.

The metal particles 10 include soft metals, so-called soft metals. The metal particles 10 may also include unavoidable impurities that are not intentionally mixed in the manufacturing steps. Examples of the soft metal that can be applied to the conductive particles 1 include a solder alloy and the like.

Conventionally, in order to mount electronic components (connected members) on a substrate such as an electronic circuit, a large amount of solder (lead-containing solder) as an alloy of lead (Pb) and tin (Sn) has been used. However, lead It is harmful to the human body, and there is concern about the adverse impact on the natural environment as a waste. Therefore, the development and popularization of lead-free solder that does not contain lead is currently being promoted.

Therefore, as described above, in the conductive particles 1 used in the present invention, lead-free solder can be favorably used from the viewpoint of safety to the human body and the environment.

The lead-free solder that can be applied to the conductive particles 1 is not particularly limited as long as it can be melted at approximately 150 ° C to 220 ° C and ensure high connection reliability as the anisotropic conductive adhesive described below. However, in the case where the conductive particles 1 are applied to an anisotropic conductive adhesive, a lead-free solder having a melting temperature lower than 150 ° C is added with In (indium) or Bi (bismuth) to reduce the melting point. Addition may cause weak mechanical strength as solder and poor connection reliability. On the other hand, if the melting temperature of the lead-free solder exceeds 220 ° C, there is a risk that the substrate, the connected member, or the like may be thermally damaged or deteriorated, which is not preferable. Therefore, for the conductive particles 1, it is preferable to use lead-free solder having a melting temperature of approximately 150 ° C to 220 ° C.

Examples of such lead-free solders include SnAgCu based Sn, Ag (silver), Cu (copper), SnZnBi based Sn, Zn (zinc), Bi, SnCu based Sn, Cu, Sn, Cu Sn, Ag, In, Bi, AgAg, Bi, SnZnAl, Sn, Zn, Al (Al), SnAgBi, Sn, Ag, Bi, etc. The composition ratio of the types of metals contained in the lead-free solder is not particularly limited, and can be appropriately adjusted according to the application.

In addition, in terms of being applicable to fine-pitch wiring having a narrow interval between electrodes, the average particle diameter D (μm) of the metal particles 10 is preferably within a range of 1 μm ≦ D ≦ 20 μm.

If the average particle diameter D of the metal particles 10 is less than 1 μm, in the case of an anisotropic conductive adhesive, a large number of conductive particles 1 are required to connect the substrate to the member to be connected, resulting in an increase in operation cost or There may be problems such as a decrease in applicability. In this case, the substrate The gap between the connection terminals of the member to be connected is also necessarily reduced. Therefore, the amount of the following bonding material 3 existing around the conductive particles 1 is also reduced, which may reduce the connection reliability.

On the other hand, if the average particle diameter D of the metal particles 10 exceeds 20 μm, it cannot be applied to fine-pitch wiring and the like, which is not preferable. Therefore, the average particle diameter D of the metal particles 10 is preferably within a range of 1 μm ≦ D ≦ 20 μm.

The shape of the metal particles 10 is not particularly limited, and can be appropriately determined depending on the application.

The insulating film 12 is made of a metal oxide, and the insulating film 12 may also contain unavoidable impurities that are not intentionally mixed in the manufacturing steps.

The metal oxide that can be applied to the conductive particles 1 used in the present invention is not particularly limited as long as the metal oxide can be formed on the surface 11 of the metal particles 10 and the insulating property of the conductive particles 1 can be ensured, and examples thereof include oxidation. Silicon, aluminum oxide, titanium oxide, niobium oxide, etc. The insulating film 12 may include at least one or more of any of the above metal oxides.

In addition, the metal oxide may include one having a different valence number or one having a different crystal structure. For example, regarding silicon oxide (SiO _x (1 ≦ x ≦ 2)), there are silicon oxide (SiO), silicon dioxide (SiO ₂ ), and the like. As for alumina (AlO _x (0.5 ≦ x ≦ 1.5)), there are alumina (III) (Al ₂ O ₃ ), alumina (II) (AlO), and alumina (I) (Al ₂ O). In the alumina (III), there are crystal structures such as α-alumina (steel type) and γ-alumina (spinel type). Further, as for titanium oxide (TiO _x (1 ≦ x ≦ 2)), there are titanium dioxide (IV) (TiO ₂ ), titanium oxide (II) (TiO), and the like. Among titanium dioxide (IV), there are anatase type, Rutile type, brookite type and other crystalline structures. Furthermore, as for niobium oxide (NbO _x (X is a number other than 2)), there are also niobium (II) oxide (NbO) and niobium (V) oxide (Nb ₂ O ₅ ).

When the insulating film 12 can be easily peeled from the surface 11 of the conductive particles 1 when the substrate is connected to the connected member, the film thickness T (nm) of the insulating film 12 is preferably in a range of 2 nm <T <500 nm. It is more preferably within a range of 5 nm ≦ T ≦ 480 nm, and particularly preferably within a range of 5 nm ≦ T ≦ 200 nm. If the film thickness T of the insulating film 12 is 2 nm or less, it is not preferable to prevent a short circuit between adjacent electrodes when the substrate and the member to be connected are connected. On the other hand, if the film thickness T of the insulating film 12 is 500 nm or more, the connection resistance value at the time of connection between the substrate and the member to be connected becomes high, which is not preferable. Therefore, the film thickness T of the insulating film 12 is preferably in a range of 2 nm <T <500 nm, more preferably in a range of 5 nm ≦ T ≦ 480 nm, and particularly preferably in a range of 5 nm ≦ T ≦ 200 nm.

[2. Manufacturing method of conductive particles]

The conductive particles 1 used in the present invention are those in which an insulating film 12 is formed on the surface 11 of the metal particles 10 shown in FIG. 1 by the following method, for example.

In the case of the present invention, as long as the deformation of the metal particles 10 can be suppressed and the insulating film 12 is formed on the surface 11 of the metal particles 10, the formation method is not particularly limited. For example, the PVD method (PVD, physical vapor) can be applied. deposition, physical vapor deposition). Examples of the PVD method include a sputtering method, a pulsed laser deposition (PLD) method, an ion plating method, an ion beam deposition method (IBD), and the like. Among them, the sputtering method can be favorably used in that the conductive particles 1 can be easily produced and the productivity is high and the film forming property is also good.

Hereinafter, as a method of forming the insulating film 12 on the surface 11 of the metal particles 10, a case where a sputtering method is applied is described as an example. Here, for example, an insulating film 12 may be formed on the surface 11 of the metal particles 10 using a sputtering device 30 including a vibration device 20 as shown in FIG. 2.

The sputtering apparatus 30 includes a vacuum tank 30 a, and a sputtering target 32 mounted on the cathode electrode 31 is disposed above the vacuum tank 30 a. A vacuum evacuation device 30b and a gas introduction device (not shown) are connected to the vacuum tank 30a, and the following gases can be introduced through these devices while evacuating the inside of the vacuum tank 30a.

The sputtering target 32 is composed of the following materials, and the material is composed of a metal type necessary for the formation of the insulating film 12. Examples of the metal type include silicon (Si), aluminum (Al), and titanium ( Ti), niobium (Nb), and the like.

In this embodiment, inert gas such as argon (Ar) or nitrogen (N ₂ ) and oxygen (O ₂ ) are introduced into the vacuum tank 30 a as the gas (sputtering gas) necessary for the formation of the insulating film 12. .

A vibrating device 20 is provided in the vacuum tank 30a. A container 21 is arranged below the sputtering target 32, and metal particles 10 are arranged inside the container 21 (on the substantially flat bottom surface 22). A vibrator 23 composed of, for example, an electromagnetic coil type or an ultrasonic horn is disposed below the container 21 in the vacuum tank 30a. The vibration device 20 is configured so that the metal particles 10 can be continuously vibrated by applying vibration to the container 21 by the vibrator 23.

When a film-forming treatment is performed on the particle surface by a sputtering method, a metal or resin vibration auxiliary material (vibration amplification means) is generally used. However, in this embodiment, as described above, since a soft metal is used as the metal particles 10, there is a possibility that deformation or deterioration may occur due to the collision between the metal particles 10 and the vibration auxiliary material.

Therefore, in order to prevent such a problem, it is preferable to form the insulating film 12 on the surface 11 of the metal particles 10 without using a vibration auxiliary material. However, if it is a vibration auxiliary material that has taken measures to prevent the metal particles 10 from causing a bad situation, its use is not limited.

Next, the details of the method of forming the insulating film 12 on the surface 11 of the metal particles 10 using the sputtering apparatus 30 will be described.

First, a specific sputtering target 32 is arranged in the vacuum tank 30a, and a specific amount of metal particles 10 are put into the container 21 of the vibration device 20 shown in FIG. 2, and the vacuum chamber 30a is evacuated by the vacuum exhaust device 30b. Exhaust and make it a vacuum environment. In the case of the present invention, it is preferable to adjust the arrival pressure V [Pa] before the sputtering process to 9 × 10 ^-5 Pa <V <2 × 10 ^-2 Pa, and it is particularly preferable to adjust it to 2 × 10 ^-4 Pa ≦ V ≦ 9 × 10 ^-3 Pa, but it is not particularly limited.

That is, if the film formation is performed under a state where the reaching pressure V is 9 × 10 ^-5 Pa or less, the impurities (mainly moisture) in the vacuum tank 30 a are reduced, the adhesion of the insulating film 12 is increased, and the film density is increased. The insulation film 12 does not peel off from the surface 11 of the metal particles 10 due to the pressing force when the substrate is connected to the connected member. Therefore, the connection resistance value may increase due to the remaining insulation film 12.

On the other hand, if the film is formed under a state where the reaching pressure V is 2 × 10 ^-2 Pa or more, the influence of impurities in the vacuum chamber 30 a reduces the adhesion of the insulating film 12 or the film density, and the conductivity cannot be maintained. Since the particle 1 has an insulating property, there is a possibility that a short circuit between electrodes cannot be prevented from occurring.

Therefore, from the viewpoint of obtaining an insulating film 12 having appropriate adhesion or film density, it is preferable to adjust the reaching pressure V [Pa] before the sputtering process to 9 × 10 ^-5 Pa <V <2 × 10 ^-2 Pa, and more preferably adjusted to 2 × 10 ^-4 Pa ≦ V ≦ 9 × 10 ^-3 Pa.

Then, the container 21 is continuously vibrated while the vibrator 23 generates vibration with a specific amplitude and number of vibrations, and a specific sputtering gas is introduced into the vacuum tank 30a. At this time, the flow rate of the sputtering gas is adjusted so that a specific pressure is maintained in the vacuum tank 30a.

Here, as shown in FIG. 2, the vibration applied to the container 21 by using the vibrator 23 is generally the vibration in the vertical direction. However, in addition to the vibration component in the vertical direction, a vibration having a horizontal vibration component may be applied in addition to the vibration component in the vertical direction. For lateral vibration. The amplitude of the vibrator 23 may be adjusted to, for example, ± (0.5 to 10) [mm]. Furthermore, the number of vibrations of the vibrator 23 may be adjusted to, for example, 15 Hz to 65 Hz, or may be changed within a range of a set frequency.

In addition, by applying a specific voltage to the sputtering target 32, the sputtering particles reach the metal particles 10, thereby forming an insulating film 12 having a specific film thickness on the surface 11 of the metal particles 10 to obtain the target conductivity. Particles 1.

According to the method of the present embodiment described above, while the vibration is applied in an environment containing oxygen, the insulating film 12 is formed on the surface 11 of the metal particles 10 containing soft metal by a sputtering method. Therefore, the insulating film 12 can be suppressed. The metal particles 10 are deformed during the formation, and the insulation between the electrodes can be ensured when the substrate is connected to the connected member, and high connection reliability can be maintained.

[3. Anisotropic conductive adhesive]

As shown in FIG. 3, the anisotropic conductive adhesive 2 of the present invention is obtained by containing the above-mentioned conductive particles 1 and light-reflective insulating particles 4 in a dispersed state in a bonding material 3.

In the case of the present invention, the form of the anisotropic conductive adhesive 2 may be film-like or paste-like, and may be appropriately determined according to the application.

As the bonding material 3 used in the present invention, a known thermosetting resin can be used. Examples of such thermosetting resins include epoxy resin, phenol resin, melamine resin, urea resin (urea resin), unsaturated polyester resin, alkyd resin, polyurethane resin, thermosetting polyimide, Acrylic resin, etc. In the present invention, at least one The above thermosetting resin is used as the bonding material 3. The type of the thermosetting resin used as the adhesive 3 is not particularly limited, and resins other than the above resins may be used depending on the application.

It is preferable that a hardening agent that reacts with the bonding material 3 is blended in the bonding material 3. The type of the hardener is not particularly limited, and for example, an isocyanate, an acid anhydride, an amino resin, or the like can be used.

In the adhesive material 3, in order to promote the curing reaction between the adhesive material 3 and the hardener, an appropriate coupling agent, a catalyst, a hardening accelerator, and other components corresponding to the application may be used in combination.

In the case where the form of the anisotropic conductive adhesive 2 is a paste (anisotropic conductive paste), in order to improve the coating property, the viscosity and the like may be adjusted using a solvent. The type of the anisotropic conductive paste is not particularly limited, and ester-based, ketone-based, alcohol-based, hydrocarbon-based, ether-based and the like can be used, and these can be used singly or in combination of two or more.

In the anisotropic conductive paste, a leveling material, a defoaming material, a dispersing material, etc. may be added as needed.

In the case of the present invention, the blending amount of the conductive particles 1 in the anisotropic conductive adhesive 2 is not particularly limited. From the viewpoint of ensuring good conduction reliability and insulation reliability, it is preferably relative to The 100% by volume adhesive material 3 contains the conductive particles 1 in an amount of 2% by volume or more and 40% by volume or less.

The light-reflective insulating particles 4 used in the present invention are used to reflect the light incident on the anisotropic conductive adhesive 2 to the outside.

Furthermore, particles having light reflectivity include particles made of metal, particles made of metal coated with resin, particles of metal oxides, metal nitrides, and metal sulfides that are gray to white under natural light. And other inorganic particles, particles formed by coating the resin core particles with inorganic particles, and particles having irregularities on the surface regardless of the material of the particles. However, at Among these particles, since the insulating property is required to be exhibited, the light-reflective insulating particles 4 usable in the present invention do not include particles made of metal. Moreover, among metal oxide particles, those having conductivity such as ITO cannot be used. Moreover, even if it is an inorganic particle which exhibits light reflectivity and insulation, the refractive index which is lower than the refractive index of the thermosetting resin composition used cannot be used.

Therefore, as a preferable specific example of such a light-reflective insulating particle 4, a material selected from the group consisting of titanium oxide (TiO ₂ ), boron nitride (BN), zinc oxide (ZnO), silicon oxide (SiO ₂ ), and aluminum oxide can be cited. (Al ₂ O ₃ ) at least one kind of inorganic particles in the group. Among them, TiO _{2 is} preferably used in terms of ensuring a high refractive index.

The shape of the light-reflective insulating particles 4 may be spherical, scaly, irregular, acicular, or the like. In consideration of light reflection efficiency, the shape is preferably spherical or scaly.

In the case of the present invention, the particle size of the light-reflective insulating particles 4 is not particularly limited, but it is preferably 2% or more and less than 20% of the particle size of the conductive particles 1. In addition, the particle size mentioned here refers to the use of D50 (in the particle size distribution of the powder, the number of particles larger than a certain particle size or mass accounts for the total number of particles or 50% of the particle size) .

When the particle size of the light-reflective insulating particles 4 with respect to the particle size of the conductive particles 1 is 20% or more, the light-reflective insulating particles 4 are embedded at the interface between the opposing electrode and the conductive particles 1. If it is less than 2%, the light generated in the light-emitting element cannot be efficiently reflected.

Specifically, the particle diameter of the light-reflective insulating particles 4 is preferably 0.02 μm or more and 20 μm or less, and more preferably 0.2 μm or more and 1 μm or less.

The refractive index (JIS K7142) of the light-reflective insulating particles 4 composed of inorganic particles is preferably higher than the refractive index of the cured product of the thermosetting resin composition as the bonding material 3. (JIS K7142) large, more preferably at least about 0.02. The reason is: if the refractive index difference is small, Then, the light reflection efficiency at the interface between the light-reflective insulating particles 4 and the bonding material 3 decreases.

[4. Manufacturing method of anisotropic conductive adhesive]

When the anisotropic conductive adhesive 2 of the present invention is produced, the conductive particles 1 and the light-reflective insulating particles 4 are not particularly limited as long as they can be dispersed in the bonding material 3, and a known dispersion method can be applied.

When manufacturing a film-shaped anisotropic conductive adhesive (anisotropic conductive film), a mixture obtained by dispersing conductive particles 1 and light-reflective insulating particles 4 in an adhesive 3 is molded into a film. The obtained anisotropic conductive paste is obtained by adjusting the viscosity and the like of the mixture obtained in the same manner as the anisotropic conductive film using a solvent.

[5. Light-emitting device and manufacturing method thereof]

Fig. 4 is a cross-sectional view showing the structure of an embodiment of a light-emitting device according to the present invention.

As shown in FIG. 4, the light-emitting device 5 of this embodiment is composed of, for example, a wiring board 50 made of ceramic and a light-emitting element 40 mounted on the wiring board 50.

In the case of this embodiment, the first and second connection electrodes 51 and 52 are formed on the wiring board 50 into a specific pattern shape as a pair of connection electrodes by, for example, nickel plating / gold plating.

For example, adjacent end portions of the first and second connection electrodes 51 and 52 are provided with convex-shaped terminal portions 51b and 52b made of, for example, columnar bumps.

On the other hand, as the light emitting element 40, for example, an LED wafer that emits visible light having a peak wavelength of 400 nm to 500 nm is used.

In particular, the present invention can favorably use blue LEDs having a peak wavelength around 450 nm.

The light-emitting element 40 has a main body portion 40 a formed in, for example, a rectangular parallelepiped shape, and first and second connection electrodes 41 and 42 serving as an anode electrode and a cathode electrode are provided on one surface. The first and second connection electrodes 41 and 42 are formed of, for example, a gold-tin alloy.

Here, when the terminal portions 51b and 52b of the first and second connection electrodes 51 and 52 of the wiring board 50 and the first and second connection electrodes 41 and 42 of the light emitting element 40 are arranged to face each other, each The size and shape of each of the connecting portions are set in the manner in which the connecting portions face each other.

The light-emitting element 40 is adhered to the wiring substrate 50 with the anisotropic conductive adhesive 2 hardened and containing the conductive particles 1 and the light-reflective insulating particles 4.

Here, the first and second connection electrodes 41 and 42 of the light-emitting element 40 correspond to the first and second connection electrodes 51 and 52 of the wiring substrate 50 via the conductive particles 1 of the anisotropic conductive adhesive 2 described above. (Terminal portions 51b, 52b) are electrically connected.

That is, the first connection electrode 41 of the light-emitting element 40 is electrically connected to the terminal portion 51b of the first connection electrode 51 of the wiring substrate 50 through the contact of the conductive particles 1, and the second connection electrode 42 of the light-emitting element 40 is borrowed. The conductive particles 1 are in electrical contact with the terminal portion 52 b of the second connection electrode 52 of the wiring board 50 by the contact.

On the other hand, the first connection electrode 51 of the wiring substrate 50 and the first connection electrode 41 of the light emitting element 40 and the second connection electrode 52 of the wiring substrate 50 and the second connection electrode 42 of the light emitting element 40 are bonded by anisotropic conduction. The insulating bonding material 3 in the agent 2 is insulated from each other.

5 (a) to (c) are diagrams showing examples of manufacturing steps of the light emitting device of the present invention.

First, as shown in FIG. 5 (a), a wiring substrate 50 having first and second connection electrodes 51 and 52 and a first and second connection electrodes 51 and 52 corresponding to the wiring substrate 50 are prepared, respectively. The light-emitting element 40 of the first and second connection electrodes 41 and 42.

Then, in a state where the terminal portions 51 b and 52 b of the first and second connection electrodes 51 and 52 of the wiring substrate 50 and the first and second connection electrodes 41 and 42 of the light-emitting element 40 are arranged in opposite directions, The non-hardened paste-shaped anisotropic conductive adhesive 2 a is disposed so as to cover the terminal portions 51 b and 52 b of the first and second connection electrodes 51 and 52 of the wiring substrate 50.

In addition, when the uncured anisotropic conductive adhesive 2a is a film, for example, the uncured anisotropic conductive adhesive 2a is attached to the wiring board 50 by, for example, an attaching device (not shown). The first and second connection electrodes 51 and 52 are provided at specific positions on the side surfaces.

Then, as shown in FIG. 5 (b), after the light-emitting element 40 is placed on the non-hardened anisotropic conductive adhesive 2a and aligned, the light-emitting side of the light-emitting element 40 is heated by a thermal head (not shown). The surface, that is, the surface 40b opposite to the side on which the first and second connection electrodes 41 and 42 are provided is pressurized and heated at a specific pressure and temperature.

Thereby, the bonding material 3a of the non-hardened anisotropic conductive adhesive 2a is hardened. As shown in FIG. 5 (c), the light-emitting element 40 is subsequently fixed to the hardened anisotropic conductive adhesive 2 by the bonding force of the hardened anisotropic conductive adhesive 2. On the wiring board 50.

In this thermocompression bonding step, the plurality of conductive particles 1 are respectively connected to the terminal portions 51b and 52b of the first and second connection electrodes 51 and 52 of the wiring substrate 50 and the first and second connection electrodes of the light emitting element 40. 41 and 42 are contacted and pressurized. As a result, the first connection electrode 41 of the light emitting element 40 is connected to the first connection electrode 51 of the wiring substrate 50, and the second connection electrode 42 of the light emitting element 40 is connected to the second connection of the wiring substrate 50. The electrodes 52 are electrically connected.

On the other hand, the first connection electrode 51 of the wiring substrate 50 and the first connection electrode 41 of the light emitting element 40 and the second connection electrode 52 of the wiring substrate 50 and the second connection of the light emitting element 40 The connection electrodes 42 are insulated from each other by the bonding material 3 in the anisotropic conductive adhesive 2.

Then, the target light emitting device 5 is obtained according to the above steps.

In the embodiment described above, in the conductive particles 1, an insulating film 12 is formed on the surface 11 of the soft metal particles 10 made of a solder alloy. When the insulating film 12 is mounted by heating or pressure, The conductive particles 1 are pressed and crushed by the first and second connection electrodes 41 and 42 of the light-emitting element 40 and the first and second connection electrodes 51 and 52 of the wiring substrate 50, and the conductive particles 1 are simultaneously crushed. The insulating film 12 formed on the surface 11 of the metal particles 10 is cracked to expose non-oxidized components such as solder. As a result, the first and second connection electrodes 41 and 42 of the light emitting element 40 and the first and second connection electrodes 50 of the wiring substrate 50 are exposed. 2 The connection electrodes 51 and 52 and the metal particles 10 form a metal eutectic bond, respectively.

On the other hand, there are adjacent connection electrodes other than the conducting portion where no pressure is applied, that is, the first and second connection electrodes 41 and 42 of the light emitting element 40 and the first and second connection electrodes 51 and 52 of the wiring substrate 50. Even when the conductive particles 1 are in contact with each other, the conductive particles 1 can maintain the insulating property by the presence of the insulating film 12 formed on the surface 11 of the metal particles 10.

As a result, according to this embodiment, the light-emitting element 40 having connection electrodes with narrow-pitch wiring can be flip-chip mounted on the wiring substrate 50 with high connection reliability, and the light-emitting portion of the light-emitting element 40 can be mounted. The generated heat is efficiently radiated to the wiring substrate 50 side.

That is, in this embodiment, since a soft metal made of, for example, a solder alloy is used as the metal particles 10 of the conductive particles 1, the first and second connection electrodes 41 of the conductive particles 1 and the light-emitting element 40 can be increased. , 42 and the area of the connection portions of the first and second connection electrodes 51 and 52 of the wiring substrate 50, whereby connection reliability and heat dissipation characteristics can be improved.

Furthermore, in this embodiment, since the light-reflective insulating particles 4 are contained in the bonding material 3 of the anisotropic conductive adhesive 2, the light generated by the light-emitting portion of the light-emitting element 40 can be efficiently reflected and the light-emitting efficiency can be improved. Promotion. In particular, in the case of using a wiring substrate having a gold-plated connection electrode that is generally implemented with high corrosion resistance, if the connection is made by gold-tin (Au-Sn) metal eutectic bonding, the self-emitting element is released On the other hand, according to the present embodiment, light emitted is absorbed by gold plating and the luminous flux is decreased. According to this embodiment, a high luminous flux can be obtained by reflecting light with the light-reflective insulating particles 4 in the anisotropic conductive adhesive 2.

As described above, according to the present embodiment, it is possible to provide a light-emitting device 5 which can realize miniaturization of the light-emitting element 40 which can be used for flip-chip mounting of the light-emitting element 40 with narrow pitch wiring, and has high optical characteristics, Higher heat dissipation and higher connection reliability.

The present invention is not limited to the above-mentioned embodiment, and various changes can be made.

For example, the light-emitting device 5 shown in FIGS. 4 and 5 (a) to (c) is a person who simplifies and schematically shows the shape or size of the light-emitting device 5. The shape, size, and The number and the like can be appropriately changed.

In addition, as the wiring substrate 50, in addition to the substrate made of ceramics described above, for example, a printed wiring substrate, a glass substrate for an LCD, a flexible printed substrate, and the like can be mentioned.

Furthermore, the anisotropic conductive adhesive 2 of the present invention is not limited to light-emitting elements such as LED wafers, and can be used for various electrical components.

However, the anisotropic conductive adhesive 2 of the present invention is particularly effective when applied to electrical parts that emit light and generate heat like the LED chip described above.

[Example]

Hereinafter, the present invention will be specifically described with reference to examples and comparative examples. The invention is not limited to the following examples.

<Preparation of Adhesive Composition>

50 parts by weight of epoxy resin (CEL2021P manufactured by Daicel Chemical Industry Co., Ltd.), 50 parts by weight of methyl hexahydrophthalic anhydride (MH-700 manufactured by Nippon Rika Chemical Co., Ltd.), and a hardening accelerator (four 1 part by weight of 2E4MZ manufactured by National Chemical Co., Ltd. to prepare an adhesive composition.

<Production of conductive particles>

[Example Particle 1]

A metal oxide film is formed on the surface of the solder alloy particles by using a sputtering device (a sputtering device 30 in FIG. 2) having a vibration device. The solder alloy particles are lead-free solder particles (M705 manufactured by Senju Metal Industry Co., Ltd.) composed of Sn-3.0Ag-0.5Cu (wt%) with an average particle diameter of 5 μm, and a sputtering target (Sputtering target 32 in FIG. 2) The system uses a silicon (Si) target.

Specifically, in a sputtering apparatus, a stainless steel container (container 21 in FIG. 2) having an opening diameter of Φ 12 cm is set on a vibration table, and 50 g of solder alloy particles are placed in the stainless steel container. After being sealed, a rotary pump and a cryogenic pump Operate and evacuate until the pressure inside the vacuum tank becomes 2 × 10 ^-4 Pa.

Next, in the vibration device 20, argon as a gas was introduced at a specific flow rate while a continuous flow was applied to the stainless steel container while generating a vibration with an amplitude of ± 2 mm and a vibration number of 30 Hz, while maintaining the pressure in the vacuum tank at 2 Pa. The gas (Ar) is 90% and the oxygen (O ₂ ) is 10%, and the exhaust speed is adjusted.

Furthermore, a direct current power of 300 W was applied to the silicon target, and an insulating film made of silicon oxide (SiO _x ) with a thickness of 50 nm was formed on the surface of the solder alloy particles by sputtering to obtain Example Particle 1.

[Example Particle 2]

The pressure inside the vacuum tank before film formation was set to 3 × 10 ^-4 Pa, and an insulating film made of silicon oxide (SiO _x ) with a thickness of 5 nm was formed on the surface of the solder alloy particles. Example particle 1 was prepared under the same conditions as Example particle 2.

[Example Particle 3]

The pressure inside the vacuum chamber before film formation was set to 5 × 10 ^-4 Pa, and an insulating film made of silicon oxide (SiO _x ) with a thickness of 200 nm was formed on the surface of the solder alloy particles. Example particle 1 was prepared under the same conditions as Example particle 3.

[Example Particle 4]

The pressure inside the vacuum tank before film formation was set to 4 × 10 ^-4 Pa, and the oxygen partial pressure was set to 5%. A sputtering target made of aluminum (Al) was used to form the surface of the solder alloy particles. Except that the insulating film made of alumina (AlO _x ) having a thickness of 50 nm was the same as that of the example particle 1, the example particle 4 was prepared under the same conditions as the example particle 1.

[Example Particle 5]

The pressure inside the vacuum tank before film formation was set to 4 × 10 ^-4 Pa, the oxygen partial pressure was set to 40%, and a titanium alloy (Ti) was used as a sputtering target to form the surface of the solder alloy particles. the insulating film of 50nm of titanium oxide (TiO _x) composed of the same thickness of the particles in Example 1 embodiment, except that, in under the same conditions of Example 1 particles prepared in Example 5 particles embodiment.

[Example Particle 6]

The pressure inside the vacuum chamber before film formation was set to 4 × 10 ^-4 Pa, and the oxygen partial pressure was set to 20%. A niobium (Nb) composed of niobium (Nb) was used as a sputtering target to form the surface of the solder alloy particles. Except that the insulating film made of niobium oxide (NbO _x ) having the same thickness as that of the example particle 1 was 50 nm, the example particle 6 was prepared under the same conditions as the example particle 1.

[Comparative Example Particle 1]

As the comparative example particle 1, the conductive particle which uses the same solder alloy particle as Example particle 1 and did not form the insulating film on the surface of this solder alloy particle is used.

[Comparative Example Particle 2]

The pressure inside the vacuum chamber before film formation was set to 4 × 10 ^-4 Pa, and an insulating film made of silicon oxide (SiO _x ) with a thickness of 2 nm was formed on the surface of the solder alloy particles. Comparative Example Particle 2 was prepared under the same conditions as Example Particle 1.

[Comparative Example Particle 3]

The pressure inside the vacuum chamber before film formation was set to 4 × 10 ^-4 Pa, and an insulating film made of silicon oxide (SiO _x ) with a thickness of 500 nm was formed on the surface of the solder alloy particles. Comparative Example Particle 3 was prepared under the same conditions as Example Particle 1.

[Comparative Example Particle 4]

Conductive particles having a thickness of 50 nm and an insulating film made of silicon oxide (SiO _x ) on the surfaces of the solder alloy particles under the same conditions as those of the example particles 1 were used as comparative example particles 4.

<Production of anisotropic conductive adhesive>

5% by weight of the above-mentioned particles of Examples 1 to 6 and Comparative Examples of particles 1 to 4 and 10% by weight of the above-mentioned adhesive composition were respectively made of titanium oxide (TiO ₂ ) Anisotropic conductive adhesives of Examples 1 to 6 and Comparative Examples 1 to 4 were obtained from the white particles (except for Comparative Example 4).

<Evaluation>

(1) Measurement of reflectance

The anisotropic conductive adhesives of Examples 1 to 6 and Comparative Examples 1 to 4 were coated on a smooth white plate so that the thickness after drying became 100 μm, and were cured by heating at 200 ° C for 1 minute to prepare Samples for reflectance measurement.

A spectrophotometer (CM-3600A manufactured by Konica Minolta) was used to measure the reflectance of each sample at a wavelength of 450 nm at a blue wavelength. The results are shown in Table 1.

(2) Manufacturing of LED modules

The anisotropic conductive adhesives of Examples 1 to 6 and Comparative Examples 1 to 4 were applied to two types of wiring boards made of ceramics for LED mounting.

Here, nickel plating / gold plating = 5.0 μm / 0.3 μm was performed with an interval between electrodes of the first wiring substrate being 70 μm.

On the other hand, nickel plating / gold plating = 5.0 μm / 0.3 μm was performed at an interval between electrodes of the second wiring substrate of 30 μm.

On the above wiring board, align and mount a blue LED chip (wafer size: 1mm × 1mm, forward voltage Vf = 3.1V (forward current If = 350mA)), at a temperature of 150 ℃ -5 minutes ~ 260 ℃- The LED modules of Examples 1 to 6 and Comparative Examples 1 to 4 were fabricated by heating and crimping with a pressure of 1 kg per wafer for 10 seconds.

The connection electrodes of the LED chips used in the examples and comparative examples were formed to have a thickness of 3 μm by gold / tin plating.

(3) Total luminous flux measurement of LED module

Using an integrating sphere-type total luminous flux measurement system (LE-2100 manufactured by Otsuka Electronics Co., Ltd.), under conditions of constant current control of If = 350mA, the LEDs of Examples 1 to 6 and Comparative Examples 1 to 4 were used. The total luminous flux of the module (when the first wiring board is used) is measured. The results are shown in Table 1.

(4) Determination of thermal resistance

Regarding the LED modules of the above-mentioned Examples 1 to 6 and Comparative Examples 1 to 4 (when the first wiring substrate is used), a static thermal resistance measuring device (T3STAR manufactured by Mentor Graphics) was used for the LED modules. The thermal resistance of the electrical connection is measured.

In this case, the measurement conditions are set to If = 350mA and Im = 1mA, and the thermal resistance value at the time of lighting for 0.1 second is read. The results are shown in Table 1.

(5) Continuity and insulation reliability

The LED modules of Examples 1 to 6 and Comparative Examples 1 to 4 were placed in an oven in an environment with a temperature of 85 ° C and a relative humidity of 85% RH, and lit under the condition of constant current control of If = 350mA for 1000 hours. After the hour test, it was removed from the oven.

(Evaluation of conduction reliability)

Before and after the environmental test described above, the LED modules of Examples 1 to 6 and Comparative Examples 1 to 4 were used to measure the Vf value of If = 350mA on samples using the first wiring substrate (inter-electrode space: 70 μm), and conducted. Evaluation of reliability.

In this case, the average value of Vf is set to 3.1V, and the case where the Vf value is within 0.05V higher than the average value is evaluated as "○", and the Vf value is higher than the average value by more than A "△" was evaluated for a case of 0.05 V and less than 0.1 V, and a case where the Vf value was higher than the average value by more than 0.1 V was evaluated as "×". The results are shown in Table 1.

(Evaluation of insulation reliability)

Before and after the above environmental test, a sample of the LED module of Examples 1 to 6 and Comparative Examples 1 to 4 using a second wiring substrate (inter-electrode interval: 30 μm) was measured to apply a reverse direction of 5 V. The leakage current value Ir at the time of the voltage is evaluated for insulation reliability.

In this case, a case where the leakage current value Ir is 1 μA or more is evaluated as NG (unusable). The results are shown in Table 1.

(6) Evaluation results

<Example 1>

As can be seen from Table 1, it was confirmed that Example 1 containing Example 50 containing an insulating film made of silicon oxide (SiO _x ) with a thickness of 50 nm was formed on the surface of the solder alloy particles, and titanium oxide (TiO ₂ In the LED module of the anisotropic conductive adhesive of Example 1 (reflectivity at 450nm = 62%) composed of light-reflective insulating particles, the total luminous flux is 7.0 (lm), and the use does not include light reflection Compared with the conventional anisotropic conductive adhesive (for example, Comparative Example 4: Reflectance = 8%) of an insulating insulating particle, the LED module (total luminous flux = 3.3 (lm)) has improved optical characteristics.

In addition, it was confirmed that the thermal resistance value of the electrical connection portion of the LED module was 13.2 (° C / W), which had high heat dissipation characteristics.

Furthermore, the initial conduction reliability and initial insulation reliability of the LED module are good. After conducting the lighting test (If = 350mA) under the environment of 85 ° C and 85% RH, stable conduction reliability and insulation reliability are also obtained. Sex.

<Example 2>

As can be seen from Table 1, it was confirmed that Example 2 containing an insulating film composed of silicon oxide (SiO _x ) having a thickness of 5 nm was formed on the surface of the solder alloy particles, and titanium oxide (TiO ₂ In the LED module of the anisotropic conductive adhesive of Example 2 (reflectivity at 450nm = 65%) composed of the light-reflective insulating particles, the total luminous flux was 7.3 (lm), which was the same as that in Comparative Example 4 described above. Compared with LED modules with anisotropic conductive adhesives, the optical characteristics are improved.

In addition, it was confirmed that the thermal resistance value of the electrical connection portion of the LED module was 12.5 (° C / W), which had high heat dissipation characteristics.

Furthermore, the initial conduction reliability and initial insulation reliability of the LED module are good. After conducting the lighting test (If = 350mA) under the environment of 85 ° C and 85% RH, stable conduction reliability and insulation reliability are also obtained. Sex.

<Example 3>

As can be seen from Table 1, it was confirmed that Example 3 containing an insulating film composed of silicon oxide (SiO _x ) having a thickness of 200 nm was formed on the surface of the solder alloy particles, and titanium oxide (TiO ₂ In the LED module of the anisotropic conductive adhesive of Example 3 (reflectivity at 450 nm = 57%) composed of the light-reflective insulating particles, the total luminous flux is 6.5 (lm), which is the same as that used in Comparative Example 4 above. Compared with LED modules with anisotropic conductive adhesives, the optical characteristics are improved.

In addition, it was confirmed that the thermal resistance value of the electrical connection portion of the LED module was 13.6 (° C / W), which had high heat dissipation characteristics.

Furthermore, the initial conduction reliability and initial insulation reliability of the LED module are good. After conducting the lighting test (If = 350mA) under the environment of 85 ° C and 85% RH, stable conduction reliability and insulation reliability are also obtained. Sex.

<Example 4>

As can be seen from Table 1, it was confirmed that the particles of Example 4 containing an insulating film made of alumina (AlO _x ) with a thickness of 50 nm on the surface of the solder alloy particles were confirmed to be made of titanium oxide (TiO ₂ ) with a particle diameter of 0.25 μm. In the LED module of the anisotropic conductive adhesive of Example 4 (reflectivity at 450 nm = 60%) of the light-reflecting insulating particles formed, the total luminous flux was 6.9 (lm), which is different from that in the above-mentioned Comparative Example 4. Compared with LED modules with directional conductive adhesive, the optical characteristics are improved.

In addition, it was confirmed that the thermal resistance value of the electrical connection portion of the LED module was 13.3 (C / W), which had high heat dissipation characteristics.

Furthermore, the initial conduction reliability and initial insulation reliability of the LED module are good. After conducting the lighting test (If = 350mA) under the environment of 85 ° C and 85% RH, stable conduction reliability and insulation reliability are also obtained. Sex.

<Example 5>

As can be seen from Table 1, it was confirmed that Example 5 containing an insulating film composed of titanium oxide (TiO _x ) having a thickness of 50 nm was formed on the surface of the solder alloy particles, and titanium oxide (TiO ₂ ) having a particle diameter of 0.25 μm was used. In the LED module of the anisotropic conductive adhesive of Example 5 (reflectivity at 450 nm = 64%) of the formed light-reflective insulating particles, the total luminous flux was 7.2 (lm), which was the same as that in Comparative Example 4 above. Compared with LED modules with anisotropic conductive adhesives, the optical characteristics are improved.

In addition, it was confirmed that the thermal resistance value of the electrical connection portion of the LED module was 13.1 (° C / W), which had high heat dissipation characteristics.

Furthermore, the initial conduction reliability and initial insulation reliability of the LED module are good. After conducting the lighting test (If = 350mA) under the environment of 85 ° C and 85% RH, stable conduction reliability and insulation reliability are also obtained. Sex.

<Example 6>

As can be seen from Table 1, it was confirmed that Example 6 containing Example 50 containing an insulating film made of niobium oxide (NbO _x ) with a thickness of 50 nm and a titanium oxide (TiO ₂ ) having a particle diameter of 0.25 μm were formed on the surface of the solder alloy particles. The anisotropic conductive adhesive of Example 6 composed of the light-reflective insulating particles (in an LED module with a reflectance of 450 nm = 61%, the total luminous flux is 6.9 (lm), which is different from the above-mentioned Comparative Example 4 Compared with LED modules used for directional conductive adhesives, the optical characteristics are improved.

In addition, it was confirmed that the thermal resistance value of the electrical connection portion of the LED module was 13.0 (° C / W), which had high heat dissipation characteristics.

Furthermore, the initial conduction reliability and initial insulation reliability of the LED module are good. After conducting the lighting test (If = 350mA) under the environment of 85 ° C and 85% RH, stable conduction reliability and insulation reliability are also obtained. Sex.

<Comparative example 1>

From Table 1, it can be seen that the difference between Comparative Example 1 using Comparative Example 1 containing Comparative Example Particle 1 in which an insulating film is not formed on the surface of the solder alloy particle and light-reflecting insulating particles made of titanium oxide (TiO ₂ ) having a particle diameter of 0.25 μm is used. In an LED module with anisotropic conductive adhesive (reflectivity at 450nm = 67%), the optical characteristics are good and the heat dissipation characteristics are good, but for the sample using the second wiring substrate (30 μm) with a small gap between the electrodes, The leakage current value is 1 μA or more, and becomes NG (unusable).

<Comparative example 2>

As can be seen from Table 1, Comparative Example Particles 2 containing a very thin insulating film made of silicon oxide (SiO _x ) having a thickness of 2 nm on the surface of the solder alloy particles were used, and titanium oxide ( TiO ₂ ) The LED module of the anisotropic conductive adhesive of Comparative Example 2 (reflectivity at 450 nm = 66%) composed of light-reflective insulating particles made of TiO ₂ ) has good optical characteristics and high heat dissipation characteristics. A sample having a second wiring substrate (30 μm) with a small gap between the electrodes had a leakage current value of 1 μA or more and became NG (unusable).

<Comparative example 3>

As can be seen from Table 1, Comparative Example Particle 3 containing an insulating film made of silicon oxide (SiO _x ) with a very thick thickness of 500 nm was formed on the surface of the solder alloy particle, and titanium oxide (particle size 0.25 μm) was used. TiO ₂ ) The LED module of the anisotropic conductive adhesive of Comparative Example 3 (reflectivity at 450 nm = 55%) composed of the light-reflective insulating particles made of TiO ₂ ) has good optical characteristics, but the electrical connection of the LED module Part of the thermal resistance value was 20.0 (° C / W). As a result, compared with Examples 1 to 6, the heat dissipation characteristics were poor.

In addition, the initial conduction reliability of an LED module using a first wiring substrate with a distance between electrodes of 70 μm and a second wiring substrate with a distance between electrodes of 30 μm is 0.05V higher than the average value of Vf. Furthermore, regarding the environment at 85 ° C and 85% RH The continuity after 1000 hours of the lighting test performed was 0.1V higher than the average value of Vf.

The reason is considered to be that a very thick insulating film with a thickness of 500 nm formed on the surface of the solder particles prevents conduction.

As described above, according to the present invention, it can be confirmed that by including anisotropic conductive adhesive on the surface of the particles, solder particles and light-reflective insulating particles having an insulating film formed thereon, it is possible to obtain an LED chip coating capable of performing narrow-pitch wiring. It is an anisotropic conductive adhesive that can be mounted on a crystal and can give LED modules higher optical characteristics, higher heat dissipation, and higher connection reliability.

1‧‧‧ conductive particles

10‧‧‧ metal particles

11‧‧‧ surface

12‧‧‧ insulating film

D‧‧‧ average particle size of metal particles

T‧‧‧ film thickness

Claims (7)

An anisotropic conductive adhesive, which is composed of conductive particles and light-reflective insulating particles in which an insulating film is formed on the surface of metal particles in a bonding material, the metal particles include a soft metal, and the insulating film includes In the environment of oxygen, a surface is formed on the surface of the metal particles by sputtering while a vibration is applied. For example, the anisotropic conductive adhesive according to item 1 of the application, wherein the soft metal of the metal particles is a solder alloy. For example, the anisotropic conductive adhesive of item 1 or 2 of the patent application range, wherein the film thickness T (nm) of the insulating film of the conductive particles is in the range of 2nm <T <500nm. For example, the anisotropic conductive adhesive according to item 1 or 2 of the scope of patent application, wherein the insulating film of the conductive particles is a metal oxide containing at least one of silicon oxide, aluminum oxide, titanium oxide, and niobium oxide. Thing. For example, the anisotropic conductive adhesive according to item 1 or 2 of the patent application range, wherein the average particle diameter D (μm) of the metal particles of the conductive particles is 1 μm ≦ D ≦ 20 μm. For example, the anisotropic conductive adhesive according to item 1 or 2 of the patent application range, wherein the particle size of the light-reflective insulating particles is 2% or more and less than 20% of the particle size of the conductive particles. A light emitting device includes a wiring substrate having a pair of connection electrodes and a light emitting element having a connection electrode corresponding to each of the pair of connection electrodes of the wiring substrate. The light emitting element is provided with an anisotropic conductive adhesive. Then on the wiring substrate, and the connection electrodes of the light-emitting element are electrically connected to the corresponding connection electrodes of the wiring substrate via the conductive particles of the anisotropic conductive adhesive, and The anisotropic conductive adhesive in the bonding material contains conductive particles and light-reflective insulating particles having an insulating film formed on the surface of the metal particles. The metal particles include soft metals, and the insulating film is in an environment containing oxygen. Those which are formed on the surface of the metal particles by sputtering while applying vibration.