JP2017171868A - Anisotropic conductive adhesive and light-emitting device - Google Patents

Abstract

An object of the present invention is to enable the flip-chip mounting of light emitting elements such as LED chips with narrow pitch wiring, and to impart high optical characteristics, high heat dissipation and high connection reliability to light emitting devices such as LED modules. The technology of conductive conductive adhesive is provided. The present invention provides an anisotropic conductive adhesive 2 containing conductive particles 1 in which an insulating film is formed on the surface of metal particles and light-reflective insulating particles 4 in a binder material 3. . The metal particles include a soft metal, and the insulating film is formed on the surface of the metal particles by a sputtering method while applying vibration in an atmosphere containing oxygen. [Selection] Figure 3

Description

  The present invention relates to an anisotropic conductive adhesive, and more particularly to a technique of an anisotropic conductive adhesive used for flip chip mounting of a semiconductor element such as an LED (light emitting diode) on a wiring board.

In recent years, light-emitting elements using LEDs have attracted attention.
As such a light emitting element, flip chip mounting in which an LED chip is directly mounted on a wiring board is performed for miniaturization and the like.

  Conventionally, as a method of flip-chip mounting an LED chip on a wiring board, a method by wire bonding, a method by metal eutectic bonding represented by Au-Sn solder, and a method by anisotropic conductive adhesive are known. .

However, the above-described prior art has various problems.
First, in the method by wire bonding, the periphery of the LED chip is usually sealed with a resin, but due to the difference in the linear expansion coefficient between the resin and the bonding wire, the bonding wire is peeled off or the bonding wire is disconnected. An electrical connection failure may occur.

Further, by using gold as the material of the electrode, for example, light having a wavelength of 400 to 500 nm is absorbed, so that the light emission efficiency is lowered.
Furthermore, in the case of this method, since the die bond adhesive is cured using an oven, the curing time is long and it is difficult to improve the production efficiency.

  Furthermore, since the heat generated in the light emitting part is radiated to the substrate side through the chip base part made of, for example, sapphire, the heat radiation distance is increased by the thickness of the chip base part. Will fall.

  On the other hand, in a method using metal eutectic bonding using solder or the like, since the linear expansion coefficient of the LED chip and the substrate are different, an electrical connection failure may occur due to a crack in the connection portion due to stress concentration.

In this method, it is necessary to apply a flux in order to remove the oxide film on the surface metal. However, due to the low viscosity of the flux, the position of the LED chip is displaced, resulting in poor electrical connection. May occur.
Furthermore, since this method requires a flux cleaning process, production takes time and the substrate may be corroded due to insufficient flux cleaning.

  On the other hand, in the method using the anisotropic conductive adhesive, since the color of the conductive particles in the anisotropic conductive adhesive is brown, the color of the insulating adhesive resin is also brown. As the light is absorbed in, the luminous efficiency is lowered.

  In addition, conventional anisotropic conductive adhesives based on epoxy resins are materials that are easily deteriorated by heat and light generated from LED chips, so reflow tests and thermal shock tests for lead-free solder ( When reliability tests such as TCT) and high-temperature high-humidity tests are performed, there is a problem that due to the internal stress based on the difference in thermal expansion coefficient of the connection substrate due to a decrease in adhesive strength, etc., the conduction resistance increases and the joint surface peels off is there. This problem is particularly hindered when Philip chip mounting of narrow pitch wiring is performed.

Furthermore, since an epoxy resin having a small thermal conductivity is interposed between the electrode of the LED chip and the electrode of the wiring board, there is a problem that heat radiation characteristics of the heat generated from the LED chip to the wiring board are deteriorated.
In particular, the light-emitting layer of the LED chip generates a lot of heat in addition to light, but if the temperature of the light-emitting layer (junction temperature) is 100 ° C. or higher, the light-emitting efficiency is lowered and the life of the LED chip is shortened. Generally known (see, for example, Patent Document 4).

JP 2005-120375 A JP-A-5-152464 JP 2003-26768 A JP 2009-206422 A

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to enable flip-chip mounting of light-emitting elements such as LED chips with narrow pitch wiring and LED modules. It is an object of the present invention to provide a technique of an anisotropic conductive adhesive capable of imparting high optical characteristics, high heat dissipation, and high connection reliability to a light-emitting device.

The present invention made to achieve the above object is an anisotropic conductive adhesive comprising conductive particles in which an insulating film is formed on the surface of metal particles and light-reflective insulating particles in a binder material. The metal particles include a soft metal, and the insulating film is an anisotropic conductive adhesive formed on the surface of the metal particles by sputtering while applying vibration in an oxygen-containing atmosphere. is there.
In the present invention, the soft metal of the metal particles is also effective when it is a solder alloy.
In the present invention, the film thickness T (nm) of the insulating film of the conductive particles is also effective when it is in the range of 2 nm <T <500 nm.
In the present invention, the insulating film of the conductive particles is also effective when it is a metal oxide containing at least one of silicon oxide, aluminum oxide, titanium oxide, and niobium oxide.
In the present invention, the average particle diameter D (μm) of the metal particles of the conductive particles is also effective when 1 μm ≦ D ≦ 20 μm.
In the present invention, it is also effective when 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.
On the other hand, the present invention includes a wiring board having a pair of connection electrodes, and a light emitting element having a connection electrode corresponding to each of the connection electrodes to be a pair of the wiring boards, and any one of the above anisotropic conductive adhesives The light emitting element is bonded onto the wiring board by an agent, and the connection electrode of the light emitting element is electrically connected to the corresponding connection electrode of the wiring board through the conductive particles of the anisotropic conductive adhesive. Connected light emitting devices.

  In the present invention, an insulating film is formed on the surface of conductive metal particles, for example, soft metal particles made of a solder alloy, and when mounting is performed by heat and pressure, the conductive particles are pressed by the opposing connection electrodes. At the same time, the insulating film formed on the surface of the metal particles is broken and not oxidized, for example, the solder component is exposed, and thereby the metal eutectic bonding between the opposing connection electrode and the metal particles, respectively. It is formed.

  On the other hand, the conductive particles existing between the 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 are not even when the conductive particles are in contact with each other. Insulation can be maintained due to the presence of.

  As a result, according to the present invention, for example, a light emitting element having connection electrodes with narrow pitch wiring can be flip-chip mounted on a wiring board with high connection reliability, and heat generated in the light emitting portion of the light emitting element can be efficiently generated. Heat can be radiated to the wiring board side.

  In particular, in the present invention, since the metal particles of the conductive particles include a soft metal made of, for example, a solder alloy, the area of the connection portion between the conductive particles and the connection electrode can be increased. Thus, connection reliability and heat dissipation characteristics can be improved.

  Furthermore, in the present invention, since the light-reflective insulating particles are contained in the binder material of the anisotropic conductive adhesive, the light generated in the light emitting portion of the light emitting element is efficiently reflected to improve the light emission efficiency. be able to. In particular, when a wiring substrate having a connection electrode plated with gold having high corrosion resistance is generally used, light emitted from the light emitting element is gold in connection by metal-tin (Au—Sn) metal eutectic bonding. Whereas the amount of luminous flux is reduced by being absorbed by plating, according to the present invention, a high luminous flux can be obtained by reflection of light by the light-reflective insulating particles in the anisotropic conductive adhesive.

  As described above, according to the present invention, it is possible to reduce the size of a light-emitting element that can be adopted by flip-chip mounting of a light-emitting element with a narrow pitch wiring, as well as high optical characteristics, high heat dissipation, and high connection reliability. The light emitting element which has can be provided.

It is sectional drawing which shows typically the structure of the electroconductive particle used for this invention. It is a figure which shows the example of the formation method of the insulating film of the electroconductive particle. It is sectional drawing which shows typically the structure of the anisotropic conductive adhesive which concerns on this invention. It is sectional drawing which shows the structure of embodiment of the light-emitting device which concerns on this invention. (A)-(c): It is a figure which shows the example of the manufacturing process of the light-emitting device of this 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 particle 1 used in the present invention is formed by forming an insulating film 12 on the surface 11 of a metal particle 10.

  The average particle diameter of the conductive particles 1 is appropriately determined according to the average particle diameter D of the metal particles 10 described later and the film thickness T of the insulating film 12, and the shape of the conductive particles 1 is particularly limited. However, it can be determined appropriately according to the application.

  The metal particles 10 include a soft metal, so-called soft metal, and the metal particles 10 may include inevitable impurities that are unintentionally mixed during the manufacturing process. Examples of the soft metal that can be applied to the conductive particles 1 include a solder alloy.

Conventionally, in order to mount electronic components (members to be connected) on a substrate such as an electronic circuit, solder (lead-containing solder) that is an alloy of lead (Pb) and tin (Sn) has been used in large quantities. However, since lead is harmful to the human body and there are concerns about adverse effects on the natural environment as waste, development and popularization of lead-free solder (lead-free solder) that does not contain lead is currently underway.
For this reason, as above-mentioned in the electroconductive particle 1, a lead-free solder can be utilized suitably from a viewpoint of the safety | security to a human body or an environment.

  The lead-free solder that can be applied to the conductive particles 1 is not particularly limited as long as it melts at approximately 150 ° C. to 220 ° C. and can secure high connection reliability as an anisotropic conductive adhesive described later. Absent. However, when the conductive particles 1 are applied to an anisotropic conductive adhesive, the lead-free solder having a melting temperature lower than 150 ° C. has a melting point lowered by adding In (indium) or Bi (bismuth). Addition of such a metal may have poor mechanical strength as a 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 of thermal destruction or deterioration of the substrate or the connected member, which is not preferable. Therefore, for the conductive particles 1, it is preferable to use lead-free solder having a melting temperature of about 150 ° C to 220 ° C.

  Examples of such lead-free solder include SnAgCu series containing Sn, Ag (silver) and Cu (copper), SnZnBi series containing Sn, Zn (zinc) and Bi, SnCu series containing Sn and Cu, Sn and Ag. SnAgInBi system including In, Bi, SnZnAl system including Sn, Zn, and Al (aluminum), SnAgBi system including Sn, Ag, and Bi. The composition ratio of the metal species contained in the lead-free solder is not particularly limited and can be appropriately adjusted according to the application.

The average particle diameter D (μm) of the metal particles 10 is preferably in the range of 1 μm ≦ D ≦ 20 μm because it can be applied to a fine pitch wiring having a narrow space between electrodes.
When the average particle diameter D of the metal particles 10 is less than 1 μm, a large amount of the conductive particles 1 are required to connect the substrate and the connected member when applied to the anisotropic conductive adhesive, and the operation cost is increased. There is a possibility that problems such as an increase in coating property and a decrease in coating property may occur. In such a case, since the gap between the connection terminals of the substrate and the connected member is inevitably small, the amount of a binder material 3 to be described around the conductive particles 1 is reduced, and the connection reliability is reduced. There is a risk of lowering.

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

Moreover, it does not specifically limit about the shape of the metal particle 10, It can determine suitably according to a use.
The insulating film 12 is made of a metal oxide, and the insulating film 12 may contain inevitable impurities that are unintentionally mixed during the manufacturing process.

  The metal oxide applicable to the conductive particle 1 used in the present invention is not particularly limited as long as it can be formed on the surface 11 of the metal particle 10 and the insulating property of the conductive particle 1 can be secured. , Silicon oxide, aluminum oxide, titanium oxide, niobium oxide and the like. The insulating film 12 only needs to contain at least one of the metal oxides described above.

Moreover, about the said metal oxide, the thing of a different valence and the thing of a different crystal structure may be contained. For example, silicon oxide (SiOx (1 ≦ x ≦ 2)) includes silicon monoxide (SiO) and silicon dioxide (SiO ₂ ). Moreover, in aluminum oxide (AlO _x (0.5 ≦ x ≦ 1.5)), aluminum oxide (III) (Al ₂ O ₃ ), aluminum oxide (II) (AlO), aluminum oxide (I) (Al ₂ O) and the like, and aluminum (III) oxide has crystal structures such as α-alumina (corundum type) and γ-alumina (spinel type). Further, in titanium oxide (TiO _x (1 ≦ x ≦ 2)), there are titanium dioxide (IV) (TiO ₂ ), titanium oxide (II) (TiO), etc. In titanium dioxide (IV), anatase type, There are crystal structures such as rutile type and brookite type. Further, niobium oxide (NbO _x (x is a number other than 2)) includes niobium oxide (II) (NbO) and niobium oxide (V) (Nb ₂ O ₅ ).

  The film thickness T (nm) of the insulating film 12 is 2 nm <T <because the insulating film 12 can be easily separated from the surface 11 of the conductive particles 1 when the substrate and the connected member are connected. It is preferably in the range of 500 nm, more preferably in the range of 5 nm ≦ T ≦ 480 nm, and particularly preferably in the range of 5 nm ≦ T ≦ 200 nm. If the thickness T of the insulating film 12 is 2 nm or less, it is not preferable because a short circuit between adjacent electrodes cannot be prevented when the substrate and the connected member are connected. On the other hand, when the 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 connected member becomes high, which is not preferable. Therefore, the thickness T of the insulating film 12 is preferably in the range of 2 nm <T <500 nm, more preferably in the range of 5 nm ≦ T ≦ 480 nm, and particularly in the range of 5 nm ≦ T ≦ 200 nm. Preferably there is.

[2. Method for producing conductive particles]
The conductive particle 1 used in the present invention is one in which an insulating film 12 is formed on the surface 11 of the metal particle 10 shown in FIG.

  In the present invention, the formation method is not particularly limited as long as the deformation of the metal particle 10 can be suppressed and the insulating film 12 can be formed on the surface 11 of the metal particle 10. For example, the PVD method (PVD: physical vapor deposition) ) Etc. can be applied. Examples of the PVD method include a sputtering method, a pulsed laser deposition method (PLD), an ion plating method, an ion beam deposition method (IBD), and the like. Among these, the sputtering method is suitably used because it can be easily produced, has high productivity, and has good film formability.

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

  The sputtering apparatus 30 includes a vacuum chamber 30a, and a sputtering target 32 attached to the anode electrode 31 is disposed above the inside of the vacuum chamber 30a. A vacuum evacuation device 30b and a gas introduction device (not shown) are connected to the vacuum chamber 30a, and a gas described later can be introduced while the inside of the vacuum chamber 30a is evacuated by these devices.

  The sputtering target 32 is made of a material made of a metal species necessary for forming the insulating film 12, and examples of the metal species include silicon (Si), aluminum (Al), titanium (Ti), niobium (Nb), and the like. Can be mentioned.

In the present embodiment, an inert gas such as argon (Ar) gas or nitrogen (N ₂ ) gas and oxygen (O ₂ ) gas are used as the gas (sputtering gas) necessary for forming the insulating film 12. It introduce | transduces in the vacuum chamber 30a.

  The vibration device 20 is installed in the vacuum chamber 30a. A container 21 is disposed below the sputtering target 32, and the metal particles 10 are placed inside the container 21 (on the substantially planar bottom surface 22). It is arranged. In addition, below the container 21 in the vacuum chamber 30a, a vibrator 23 made of, for example, an electromagnetic coil type or an ultrasonic horn is disposed. The vibration device 20 is configured to continuously vibrate the metal particles 10 by applying vibration to the container 21 by the vibrator 23.

  In the case where a film formation process is performed on the particle surface by a sputtering method, it is common to use a vibration auxiliary material (vibration amplification means) made of metal or resin. However, in the present embodiment, since a soft metal is used as the metal particle 10 as described above, there is a possibility that deformation or deterioration due to collision between the metal particle 10 and the vibration assisting material may occur.

  Therefore, in order to prevent the occurrence of such a problem, it is preferable to form the insulating film 12 on the surface 11 of the metal particle 10 without using a vibration assisting material. However, as long as the vibration assisting material has taken measures to prevent problems with the metal particles 10, its use is not hindered.

Next, details of a method of forming the insulating film 12 on the surface 11 of the metal particle 10 using the sputtering apparatus 30 described above will be described.
First, a predetermined sputtering target 32 is placed in the vacuum chamber 30a, a predetermined amount of metal particles 10 is put into the container 21 of the vibration device 20 shown in FIG. 2, and the inside of the vacuum chamber 30a is evacuated by the vacuum exhaust device 30b. Evacuate to a vacuum atmosphere. In the present invention, although not particularly limited, it is preferable to adjust the ultimate pressure V [Pa] before the sputtering treatment to 9 × 10 ⁻⁵ Pa <V <2 × 10 ⁻² Pa, particularly 2 It is more preferable to adjust to × 10 ⁻⁴ Pa ≦ V ≦ 9 × 10 ⁻³ Pa.

That is, when film formation is performed in a state where the ultimate pressure V is 9 × 10 ⁻⁵ Pa or less, impurities (mainly moisture) in the vacuum chamber 30a are reduced, adhesion of the insulating film 12 is increased, and film density is increased. The insulating film 12 is not peeled off from the surface 11 of the metal particle 10 by the pressing force when the substrate and the member to be connected are connected, and the connection resistance value may be increased due to the remaining insulating film 12.

On the other hand, when film formation is performed in a state where the ultimate pressure V is 2 × 10 ⁻² Pa or more, the adhesion and film density of the insulating film 12 are reduced due to the influence of impurities in the vacuum chamber 30a, and the conductive particles 1 Since insulation is not maintained, there is a possibility that occurrence of a short circuit between the electrodes cannot be suppressed.

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

  Next, vibration is generated with a predetermined amplitude and frequency by the vibrator 23, and a predetermined sputtering gas is introduced into the vacuum chamber 30a while continuously vibrating the container 21. At that time, the flow rate of the sputtering gas is adjusted so that the inside of the vacuum chamber 30a is maintained at a predetermined pressure.

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

  Then, by applying a predetermined voltage to the sputtering target 32, the sputtered particles reach the metal particles 10, whereby an insulating film 12 having a predetermined film thickness is formed on the surface 11 of the metal particles 10, and the intended conductivity Particles 1 are obtained.

  According to the method of the present embodiment described above, the insulating film 12 is formed on the surface 11 of the metal particle 10 containing a soft metal by sputtering while applying vibration in an atmosphere containing oxygen. It is possible to suppress the deformation of the metal particles 10 at the time of forming, and to ensure insulation between the electrodes when connecting the substrate and the member to be connected, thereby maintaining high connection reliability.

[3. Anisotropic conductive adhesive]
As shown in FIG. 3, the anisotropic conductive adhesive 2 of the present invention comprises a binder material 3 containing the above-described conductive particles 1 and light-reflective insulating particles 4 dispersed therein. It is.
In the case of the present invention, the form of the anisotropic conductive adhesive 2 may be a film or a paste, and can be appropriately determined according to the application.

  As the binder material 3 used in the present invention, a known thermosetting resin can be used. Examples of such thermosetting resins include epoxy resins, phenol resins, melamine resins, urea resins (urea resins), unsaturated polyester resins, alkyd resins, polyurethane resins, thermosetting polyimides, acrylic resins, and the like. . In the present invention, at least one kind of the thermosetting resin can be used as the binder material 3. The kind of thermosetting resin used as the binder material 3 is not particularly limited, and it is possible to use a resin other than the above depending on the application.

The binder material 3 is preferably blended with a curing agent that reacts with the binder material 3. Although the kind of hardening | curing agent is not specifically limited, For example, what consists of isocyanate, an acid anhydride, an amino resin, etc. can be used.
In order to accelerate the curing reaction between the binder material 3 and the curing agent, the binder material 3 may be used in combination with a suitable coupling agent, a catalyst, an accelerator, and other components according to other uses.

  When the anisotropic conductive adhesive 2 is in the form of a paste (anisotropic conductive paste), the viscosity or the like may be adjusted using a solvent in order to improve the coating property. In such an anisotropic conductive paste, the type of solvent is not particularly limited, and ester-type, ketone-type, alcohol-type, hydrocarbon-type, ether-type, and the like can be used. The above can be mixed and used.

In the anisotropic conductive paste, a leveling material, an antifoaming material, a dispersing material, etc. may be added as necessary.
In the present invention, the blending amount of the conductive particles 1 in the anisotropic conductive adhesive 2 is not particularly limited, but from the viewpoint of ensuring good conduction reliability and insulation reliability, the binder material 3 The conductive particles 1 are preferably contained in an amount of 2% by volume to 40% by volume with respect to 100% by volume.

The light-reflective insulating particles 4 used in the present invention are for reflecting light incident on the anisotropic conductive adhesive 2 to the outside.
The light-reflective particles include inorganic particles such as metal particles, metal particles coated with resin, and metal oxides, metal nitrides, and metal sulfides that are gray to white under natural light. In addition, particles having resin core particles coated with inorganic particles, and particles having irregularities on the surface thereof are included, regardless of the material of the particles. However, among these particles, the light-reflective insulating particles 4 that can be used in the present invention do not include particles made of metal because they are required to exhibit insulating properties. Moreover, among metal oxide particles, those having conductivity such as ITO cannot be used. Moreover, even if it is an inorganic particle which shows light reflectivity and insulation, what is lower than the refractive index of the thermosetting resin composition which the refractive index uses cannot be used.

Preferable specific examples of such light-reflective insulating particles 4 include titanium oxide (TiO ₂ ), boron nitride (BN), zinc oxide (ZnO), silicon oxide (SiO ₂ ), and aluminum oxide (Al ₂ O ₃ ). And at least one inorganic particle selected from the group consisting of: Among these, TiO ₂ is preferably used from the viewpoint of a high refractive index.

The shape of the light-reflective insulating particles 4 may be spherical, scaly, indeterminate, acicular, etc., but considering the light reflection efficiency, spherical and scaly are preferable.
In the present invention, the particle size of the light-reflective insulating particles 4 is not particularly limited, but is preferably 2% or more and less than 20% of the particle size of the conductive particles 1. In addition, the particle size here means that by D50 (the particle size when the number or mass larger than a certain particle size occupies 50% of the total powder in the particle size distribution of the powder).

When the particle size of the light-reflective insulating particle 4 with respect to the particle size of the conductive particle 1 is 20% or more, the light-reflective insulating particle 4 bites into the interface between the opposing connection electrode and the conductive particle 1 to dissipate heat. If it is less than 2%, the light generated in the light emitting element cannot be efficiently reflected.
Specifically, the particle size of the light-reflective insulating particles 4 is preferably 0.02 μm to 20 μm, more preferably 0.2 μm to 1 μm.

  The refractive index (JIS K7142) of the light-reflective insulating particles 4 made of inorganic particles is preferably larger than the refractive index (JIS K7142) of the cured product of the thermosetting resin composition that is the binder material 3. More preferably, it is about 02 larger. This is because if the difference in refractive index is small, the light reflection efficiency at the interface between them decreases.

[4. Method for producing anisotropic conductive adhesive]
When the anisotropic conductive adhesive 2 of the present invention is manufactured, there is no particular limitation as long as the conductive particles 1 and the light-reflective insulating particles 4 can be dispersed in the binder material 3, and a known dispersion method is applied. be able to.

  When producing a film-like anisotropic conductive adhesive (anisotropic conductive film), a mixture of conductive particles 1 and light-reflective insulating particles 4 dispersed in a binder material 3 is molded into a film shape. The anisotropic conductive paste is obtained by adjusting the viscosity and the like using a solvent for the mixture obtained in the same manner as the anisotropic conductive film.

[5. Light emitting device and manufacturing method thereof]
FIG. 4 is a cross-sectional view showing the configuration of the embodiment of the light emitting device according to the present invention.
As shown in FIG. 4, the light emitting device 5 according to the present embodiment is configured by mounting a wiring substrate 50 made of, for example, ceramics, and a light emitting element 40 mounted on the wiring substrate 50.

In the case of the present embodiment, first and second connection electrodes 51 and 52 are formed in a predetermined pattern shape on the wiring board 50 as a pair of connection electrodes by, for example, nickel / gold plating.
For example, convex terminal portions 51b and 52b made of stud bumps, for example, are provided at adjacent ends of the first and second connection electrodes 51 and 52, respectively.

On the other hand, as the light emitting element 40, for example, an LED chip that emits visible light having a peak wavelength of 400 nm to 500 nm is used.
In particular, the present invention can suitably use a blue LED having a peak wavelength in the vicinity of 450 nm.

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

  Here, 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. In addition, the size and the shape are set so that the connection portions face each other.

The light emitting element 40 is bonded onto the wiring substrate 50 by the cured anisotropic conductive adhesive 2 containing the conductive particles 1 and the light-reflective insulating particles 4 described above.
Here, the first and second connection electrodes 41 and 42 of the light emitting element 40 correspond to the corresponding first and second connections of the wiring board 50 through the conductive particles 1 of the anisotropic conductive adhesive 2 described above. The electrodes 51 and 52 (terminal portions 51b and 52b) are electrically connected to each other.

  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 board 50 by the contact of the conductive particles 1, and the first connection electrode 41 of the light emitting element 40 is also connected. The two connection electrodes 42 are electrically connected to the terminal portions 52 b of the second connection electrodes 52 of the wiring substrate 50 by the contact of the conductive particles 1.

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

5A to 5C are diagrams showing an example of a manufacturing process of the light emitting device of the present invention.
First, as shown in FIG. 5A, the wiring board 50 having the first and second connection electrodes 51 and 52 and the first and second connection electrodes 51 and 52 of the wiring board 50 respectively. A light emitting element 40 having first and second connection electrodes 41 and 42 is prepared.

  And the state which has arrange | positioned the terminal parts 51b and 52b of the 1st and 2nd connection electrodes 51 and 52 of the wiring board 50, and the 1st and 2nd connection electrodes 41 and 42 of the light emitting element 40 in the opposing direction. Thus, for example, an uncured pasty anisotropic conductive adhesive 2a is disposed so as to cover the terminal portions 51b and 52b of the first and second connection electrodes 51 and 52 of the wiring board 50.

  For example, when the uncured anisotropic conductive adhesive 2a is in the form of a film, the uncured anisotropic conductive adhesive 2a is removed from the first and second wiring boards 50 by a pasting device (not shown), for example. Affixed to a predetermined position on the surface on which the two connection electrodes 51 and 52 are provided.

  Then, as shown in FIG. 5B, after the light emitting element 40 is placed on the uncured anisotropic conductive adhesive 2a and aligned, the surface on the light emitting side of the light emitting element 40 by a thermocompression bonding head (not shown). 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 predetermined pressure and temperature.

  Thereby, the binder material 3a of the uncured anisotropic conductive adhesive 2a is cured, and the light emitting element 40 is connected to the wiring board by the adhesive force of the cured anisotropic conductive adhesive 2 as shown in FIG. Adhesive fixing on 50.

  In this thermocompression bonding step, a plurality of terminal portions 51b and 52b of the first and second connection electrodes 51 and 52 of the wiring board 50 and a plurality of first and second connection electrodes 41 and 42 of the light emitting element 40 are provided. The conductive particles 1 are in contact with each other and pressed, and as a result, the first connection electrode 41 of the light emitting element 40, the first connection electrode 51 of the wiring substrate 50, and the second connection electrode 42 of the light emitting element 40. And the second connection electrode 52 of the wiring board 50 are electrically connected to each other.

On the other hand, the first connection electrode 51 of the wiring board 50 and the first connection electrode 41 of the light emitting element 40, and the second connection electrode 52 of the wiring board 50 and the second connection electrode 42 of the light emitting element 40 are Then, they are insulated from each other by the binder material 3 in the anisotropic conductive adhesive 2.
And the target light-emitting device 5 is obtained according to the above process.

  In the present embodiment described above, in the conductive particle 1, the insulating film 12 is formed on the surface 11 of the soft metal particle 10 made of a solder alloy, and when the mounting is performed by heating and pressing, the light emitting element The conductive particles 1 are pressed and crushed by the first and second connection electrodes 41 and 42 of 40 and the first and second connection electrodes 51 and 52 of the wiring substrate 50, and at the same time, the metal of the conductive particles 1 The insulating film 12 formed on the surface 11 of the particle 10 is not broken and oxidized, for example, a solder component is exposed, whereby the first and second connection electrodes 41 and 42 of the light emitting element 40 and the first of the wiring substrate 50 are exposed. In addition, metal eutectic bonding is formed between the second connection electrodes 51 and 52 and the metal particles 10, respectively.

  On the other hand, adjacent connection electrodes other than the conductive part to which 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 board 50 are used. Even when the conductive particles 1 are in contact with each other, the conductive particles 1 existing between them can be kept insulative due to the presence of the insulating film 12.

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

  In particular, in the present embodiment, the soft particles made of, for example, a solder alloy are used as the metal particles 10 of the conductive particles 1, so that the conductive particles 1 and the first and second connection electrodes of the light emitting element 40 are used. 41 and 42 and the area of the connection part of the 1st and 2nd connection electrodes 51 and 52 of the wiring board 50 can be enlarged, and, thereby, connection reliability and a thermal radiation characteristic can be improved.

  Furthermore, in the present embodiment, since the light-reflective insulating particles 4 are contained in the binder material 3 of the anisotropic conductive adhesive 2, the light generated in the light emitting portion of the light emitting element 40 is efficiently reflected. The luminous efficiency can be improved. In particular, when a wiring substrate having a connection electrode plated with gold having high corrosion resistance is generally used, light emitted from the light emitting element is gold in connection by metal-tin (Au—Sn) metal eutectic bonding. Whereas the amount of light flux is reduced by being absorbed by plating, according to the present embodiment, a high light flux amount can be obtained by reflection of light by the light-reflective insulating particles 4 in the anisotropic conductive adhesive 2. .

  As described above, according to the present embodiment, it is possible to reduce the size of the light emitting element 40 that can be adopted by flip chip mounting of the light emitting element 40 with a narrow pitch wiring, as well as high optical characteristics and high heat dissipation. The light emitting device 5 having high connection reliability can be provided.

The present invention is not limited to the above-described embodiment, and various changes can be made.
For example, the light-emitting device 5 shown in FIG. 4 and FIGS. 5A to 5C is schematically shown by simplifying the shape and size thereof, and the shape and size of the wiring substrate and the connection electrodes of the light-emitting elements. The size and number can be changed as appropriate.

Examples of the wiring board 50 include a printed wiring board, a glass substrate for LCD, and a flexible printed board in addition to the above-described ceramic substrate.
Furthermore, the anisotropic conductive adhesive 2 of this invention is not restricted to light emitting elements, such as a LED chip, It can be used for various electrical components.
However, the anisotropic conductive adhesive 2 of the present invention is particularly effective when applied to an electrical component that generates heat simultaneously with light emission, such as the LED chip described above.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to a following example.

<Preparation of adhesive composition>
50 parts by weight of epoxy resin (CEL2021P manufactured by Daicel Chemical Industries, Ltd.), 50 parts by weight of methylhexahydrophthalic anhydride (MH-700 manufactured by Shin Nippon Chemical Co., Ltd.) as a curing agent, and 1 accelerator (2E4MZ manufactured by Shikoku Chemical Co., Ltd.) 1 An adhesive composition was prepared using parts by weight.

<Creation of conductive particles>
[Example particle 1]
A metal oxide film was formed on the surface of the solder alloy particles using a sputtering device (sputtering device 30 in FIG. 2) equipped with a vibration device. As the solder alloy particles, lead-free solder particles (M705 manufactured by Senju Metal Industry Co., Ltd.) having a Sn-3.0Ag-0.5Cu (wt%) composition with an average particle diameter of 5 μm are used, and a sputtering target (sputtering target 32 in FIG. 2) For this, a silicon (Si) target was used.

Specifically, in a sputtering apparatus, a stainless steel container (container 21 in FIG. 2) having an opening diameter of φ12 cm is placed on a vibration table, 50 g of solder alloy particles are placed in the stainless steel container, and after sealing, a rotary pump and a cryopump. Was evacuated until the pressure inside the vacuum chamber reached 2 × 10 ⁻⁴ Pa.

Next, in the vibration device 2, vibrations with an amplitude of ± 2 mm and a vibration frequency of 30 Hz are generated, and argon (Ar) 90% and oxygen (O ₂ ) 10% are used as gases while continuously applying vibration to the stainless steel container. The pumping speed was adjusted by introducing at a predetermined flow rate so that the pressure in the vacuum chamber was maintained at 2 Pa.

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

[Example particle 2]
Example particle 1 except that the pressure inside the vacuum chamber before film formation was set to 3 × 10 ⁻⁴ Pa and an insulating film made of silicon oxide (SiO _x ) having a thickness of 5 nm was formed on the surface of the solder alloy particles. Example particles 2 were prepared under the same conditions as in Example 1.

[Example particle 3]
Example particle 1 except that 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 ) having a thickness of 200 nm was formed on the surface of the solder alloy particles. Example particles 3 were prepared under the same conditions as in Example 1.

[Example particle 4]
The pressure inside the vacuum chamber 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 on the surface of the solder alloy particles. Example particle 4 was prepared under the same conditions as Example particle 1 except that an insulating film made of aluminum oxide (AlO _x ) having the same thickness as that of particle 1 and having a thickness of 50 nm was formed.

[Example particle 5]
The pressure inside the vacuum chamber before film formation was set to 4 × 10 ⁻⁴ Pa and the oxygen partial pressure was set to 40%, and a sputtering target made of titanium (Ti) was used on the surface of the solder alloy particles. Example particle 5 was prepared under the same conditions as Example particle 1 except that an insulating film made of titanium oxide (TiO _x ) having the same thickness as that of particle 1 and having a thickness of 50 nm was formed.

[Example particle 6]
The pressure inside the vacuum chamber before film formation was set to 4 × 10 ⁻⁴ Pa, the oxygen partial pressure was set to 20%, and a sputtering target made of niobium (Nb) was used on the surface of the solder alloy particles. Example particle 6 was prepared under the same conditions as Example particle 1 except that an insulating film made of niobium oxide (NbO _x ) having the same thickness as that of particle 1 and having a thickness of 50 nm was formed.

[Comparative Example Particle 1]
The same solder alloy particles as those of Example Particle 1 were used, and conductive particles that did not form an insulating film on the surface of the solder alloy particles were used as Comparative Example Particle 1.

[Comparative Example Particle 2]
Example particle 1 except that 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 ) having 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 in Example 1.

[Comparative Example Particle 3]
Example particle 1 except that 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 ) having 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 in Example 1.

[Comparative Example Particle 4]
Conductive particles in which an insulating film made of silicon oxide (SiO _x ) having a thickness of 50 nm was formed on the surface of the solder alloy particles under the same conditions as in Example particles 1 were used as Comparative Example particles 4.

<Creation of anisotropic conductive adhesive>
The above-mentioned adhesive composition is composed of 5% by weight of the above-described Example Particles 1 to 6 and Comparative Example Particles 1 to 4 and titanium oxide (TiO ₂ ) having a particle size of 0.25 μm as light-reflective insulating particles. The white particles were mixed in an amount of 10% by weight (excluding Comparative Example 4) to obtain anisotropic conductive adhesives of Examples 1 to 6 and Comparative Examples 1 to 4.

<Evaluation>
(1) Reflectance measurement The anisotropic conductive adhesives of Examples 1 to 6 and Comparative Examples 1 to 4 were applied on a smooth white plate so that the thickness after drying was 100 μm, and the temperature was 1 at 200 ° C. A sample for reflectance measurement was prepared by heating and curing for minutes.
About each sample, the reflectance in wavelength 450nm which is a blue wavelength was measured using the spectrocolorimeter (Konica Minolta company make CM-3600A). The results are shown in Table 1.

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

Here, the space between the electrodes of the first wiring board is 70 μm, and nickel / gold plating = 5.0 μm / 0.3 μm is applied.
On the other hand, the space between the electrodes of the second wiring board is 30 μm, and nickel / gold plating = 5.0 μm / 0.3 μm is applied.

A blue LED chip (chip size: 1 mm × 1 mm, forward voltage Vf = 3.1 V (forward current If = 350 mA)) is aligned and mounted on the wiring board described above, and the temperature is 150 ° C.-5 minutes to 260 ° C.-10. Second, thermocompression bonding was performed at a pressure of 1 kg per chip, and LED modules of Examples 1 to 6 and Comparative Examples 1 to 4 were produced.
The connection electrodes of the LED chips used in the examples and comparative examples are formed with a thickness of 3 μm by gold / tin plating.

(3) Measurement of total luminous flux of LED module Examples 1 to 6 and comparison were performed under the condition of constant current control of If = 350 mA using an integral total spherical luminous flux measurement system (LE-2100 manufactured by Otsuka Electronics Co., Ltd.). The total luminous flux of the LED modules of Examples 1 to 4 (using the first wiring board) was measured. The results are shown in Table 1.

(4) Thermal resistance measurement For the LED modules (using the first wiring board) of Examples 1 to 6 and Comparative Examples 1 to 4 described above, a static transient thermal resistance measurement device (Mentor Graphics, Inc.) T3STAR) was used to measure the thermal resistance value of the electrical connection portion of the LED module.
In this case, the measurement conditions were If = 350 mA and Im = 1 mA, and the thermal resistance value when lit for 0.1 second was read. The results are shown in Table 1.

(5) Conduction reliability and insulation reliability The LED modules of Examples 1 to 6 and Comparative Examples 1 to 4 described above are placed in an oven in an environment with a temperature of 85 ° C. and a relative humidity of 85% RH, and If = 350 mA. It was lit under the condition of constant current control and removed from the oven after 1000 hours test.

(Evaluation of conduction reliability)
Before and after the environmental test, the Vf value at If = 350 mA was measured for the sample using the first wiring board (inter-electrode space: 70 μm) among the LED modules of Examples 1 to 6 and Comparative Examples 1 to 4. The conduction reliability was evaluated.

  In this case, the average value of Vf is 3.1 V, and the case where the Vf value is within 0.05 V compared to this average value is “◯”, the height is higher than 0.05 V and within 0.1 V The case of “Δ” was evaluated as “Δ”, and the case of being higher than 0.1 was evaluated as “×”. The results are shown in Table 1.

(Evaluation of insulation reliability)
Before and after the environmental test, when a reverse voltage of 5 V was applied to a sample using the second wiring board (interelectrode space: 30 μm) among the LED modules of Examples 1 to 6 and Comparative Examples 1 to 4. The leakage current value Ir was measured, and the insulation reliability was evaluated.
In this case, the case where the leakage current value Ir was 1 μA or more was evaluated as NG (unusable). The results are shown in Table 1.

(6) Evaluation results <Example 1>
As is apparent from Table 1, Example Particle 1 in which an insulating film made of silicon oxide (SiO _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 size of 0.25 μm. In the LED module using the anisotropic conductive adhesive of Example 1 (reflectance at 450 nm = 62%) containing the light-reflective insulating particles made of the total luminous flux is 7.0 (lm), Optical characteristics compared to LED modules (total light flux = 3.3 (lm)) using a conventional anisotropic conductive adhesive that does not contain light-reflective insulating particles (for example, Comparative Example 4: reflectivity = 8%) Was confirmed to improve.

Moreover, the thermal resistance value of the electrical connection part of this LED module was 13.2 (° C./W), and it was confirmed that it had high heat dissipation characteristics.
Furthermore, this LED module has good initial conduction reliability and initial insulation reliability, and stable conduction reliability and insulation reliability even after a lighting test (If = 350 mA) in an environment of 85 ° C. and 85% RH. was gotten.

<Example 2>
As is apparent from Table 1, Example Particle 1 in which an insulating film made 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 ) having a particle size of 0.25 μm. In the LED module using the anisotropic conductive adhesive of Example 2 containing the light-reflective insulating particles consisting of (reflectance at 450 nm = 65%), the total luminous flux is 7.3 (lm), It was confirmed that the optical characteristics were improved as compared with the LED module using the anisotropic conductive adhesive of Comparative Example 4 above.

Moreover, the thermal resistance value of the electrical connection part of this LED module was 12.5 (° C./W), and it was confirmed that it had high heat dissipation characteristics.
Furthermore, this LED module has good initial conduction reliability and initial insulation reliability, and stable conduction reliability and insulation reliability even after a lighting test (If = 350 mA) in an environment of 85 ° C. and 85% RH. was gotten.

<Example 3>
As is apparent from Table 1, Example Particle 3 in which an insulating film made of silicon oxide (SiO _x ) having a thickness of 200 nm is formed on the surface of the solder alloy particle, and Titanium oxide (TiO ₂ ) having a particle size of 0.25 μm. In the LED module using the anisotropic conductive adhesive of Example 3 (reflectance at 450 nm = 57%) containing the light-reflective insulating particles consisting of: Total luminous flux is 6.5 (lm), It was confirmed that the optical characteristics were improved as compared with the LED module using the anisotropic conductive adhesive of Comparative Example 4 above.

Moreover, the thermal resistance value of the electrical connection part of this LED module was 13.6 (° C./W), and it was confirmed that it had high heat dissipation characteristics.
Furthermore, this LED module has good initial conduction reliability and initial insulation reliability, and stable conduction reliability and insulation reliability even after a lighting test (If = 350 mA) in an environment of 85 ° C. and 85% RH. was gotten.

<Example 4>
As is apparent from Table 1, from Example Particle 4 in which an insulating film made of aluminum oxide (AlO _x ) having a thickness of 50 nm is formed on the surface of the solder alloy particle, and Titanium oxide (TiO ₂ ) having a particle size of 0.25 μm. In the LED module using the anisotropic conductive adhesive of Example 4 (reflectance at 450 nm = 60%) containing the light-reflective insulating particles, the total luminous flux is 6.9 (lm), It was confirmed that the optical characteristics were improved as compared with the LED module using the anisotropic conductive adhesive of Comparative Example 4.

Moreover, the thermal resistance value of the electrical connection part of this LED module is 13.3 (degreeC / W), and it confirmed that it had a high heat dissipation characteristic.
Furthermore, this LED module has good initial conduction reliability and initial insulation reliability, and stable conduction reliability and insulation reliability even after a lighting test (If = 350 mA) in an environment of 85 ° C. and 85% RH. was gotten.

<Example 5>
As apparent from Table 1, from Example Particle 5 in which an insulating film made of titanium oxide (TiO _x ) having a thickness of 50 nm is formed on the surface of the solder alloy particles, and Titanium oxide (TiO ₂ ) having a particle size of 0.25 μm. In the LED module using the anisotropic conductive adhesive of Example 5 containing the light-reflective insulating particles (reflectance at 450 nm = 64%), the total luminous flux is 7.2 (lm), It was confirmed that the optical characteristics were improved as compared with the LED module using the anisotropic conductive adhesive of Comparative Example 4.

Moreover, the thermal resistance value of the electrical connection part of this LED module was 13.1 (° C./W), and it was confirmed that it had high heat dissipation characteristics.
Furthermore, this LED module has good initial conduction reliability and initial insulation reliability, and stable conduction reliability and insulation reliability even after a lighting test (If = 350 mA) in an environment of 85 ° C. and 85% RH. was gotten.

<Example 6>
As apparent from Table 1, from Example Particle 6 in which an insulating film made of niobium oxide (NbO _x ) having a thickness of 50 nm is formed on the surface of the solder alloy particle, and Titanium oxide (TiO ₂ ) having a particle size of 0.25 μm. In the LED module using the anisotropic conductive adhesive of Example 6 (reflectance at 450 nm = 61%) containing the light-reflective insulating particles, the total luminous flux is 6.9 (lm), It was confirmed that the optical characteristics were improved as compared with the LED module using the anisotropic conductive adhesive of Comparative Example 4.

Moreover, the thermal resistance value of the electrical connection part of this LED module was 13.0 (° C./W), and it was confirmed that it had high heat dissipation characteristics.
Furthermore, this LED module has good initial conduction reliability and initial insulation reliability, and stable conduction reliability and insulation reliability even after a lighting test (If = 350 mA) in an environment of 85 ° C. and 85% RH. was gotten.

<Comparative Example 1>
As is apparent from Table 1, Comparative Example Particle 1 in which an insulating film is not formed on the surface of the solder alloy particles and Comparative Example 1 containing light-reflective insulating particles made of titanium oxide (TiO ₂ ) having a particle size of 0.25 μm. The LED module using the anisotropic conductive adhesive (reflectance at 450 nm = 67%) had good optical characteristics and high heat dissipation characteristics, but the space between the electrodes was small (30 μm). The leakage current value of the sample using the wiring board was 1 μA or more, which was NG (unusable).

<Comparative example 2>
As is apparent from Table 1, Comparative Example Particle 2 in which an insulating film made of a very thin silicon oxide (SiO _x ) having a thickness of 2 nm is formed on the surface of the solder alloy particle, and a titanium oxide having a particle size of 0.25 μm ( The LED module using the anisotropic conductive adhesive of Comparative Example 2 containing light-reflective insulating particles made of TiO ₂ ) (reflectance at 450 nm = 66%) has good optical characteristics and high heat dissipation characteristics. However, the leak current value of the sample using the second wiring board with a small inter-electrode space (30 μm) was 1 μA or more, and it was NG (unusable).

<Comparative Example 3>
As is apparent from Table 1, Comparative Example Particle 3 in which an insulating film made of a very thick silicon oxide (SiO _x ) having a thickness of 500 nm is formed on the surface of the solder alloy particle, and a titanium oxide having a particle size of 0.25 μm ( In the LED module using the anisotropic conductive adhesive of Comparative Example 2 (reflectance at 450 nm = 55%) containing light-reflective insulating particles made of TiO ₂ ), the optical characteristics were good, but the LED module The thermal resistance value of the electrical connection portion was 20.0 (° C./W), and the heat dissipation characteristics were inferior to those of Examples 1 to 6.

In addition, the initial conduction reliability of the LED module using the first wiring board with the space between the electrodes of 70 μm and the second wiring board with the space between the electrodes of 30 μm is 0.05 V higher than the average value of Vf. Furthermore, the continuity after 1000 hours in the lighting test under the environment of 85 ° C. and 85% RH was 0.1 V higher than the average value of Vf.
The reason for this is considered to be that a very thick insulating film having a thickness of 500 nm formed on the surface of the solder particles hinders conduction.

  As described above, according to the present invention, the anisotropic conductive adhesive contains solder particles having an insulating film formed on the particle surface and light-reflective insulating particles, thereby enabling LED chips with narrow pitch wiring. As a result, it was possible to demonstrate that an anisotropic conductive adhesive capable of imparting high optical characteristics, high heat dissipation, and high connection reliability to the LED module can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Conductive particle 2 ... Anisotropic conductive adhesive 3 ... Binder material 4 ... Light reflective insulating particle 5 ... Light-emitting device 10 ... Metal particle 11 ... Surface 12 ... Insulating film 40 ... Light emitting element 50 ... Wiring board

Claims (7)

In the binder material, an anisotropic conductive adhesive containing conductive particles in which an insulating film is formed on the surface of metal particles, and light-reflective insulating particles,
The metal particles include a soft metal,
The anisotropic conductive adhesive, wherein the insulating film is formed on the surface of the metal particles by sputtering while applying vibration in an atmosphere containing oxygen.   The anisotropic conductive adhesive according to claim 1, wherein the soft metal of the metal particles is a solder alloy.   The anisotropic conductive adhesive according to claim 1, wherein a thickness T (nm) of the insulating film of the conductive particles is in a range of 2 nm <T <500 nm.   The anisotropy according to any one of claims 1 to 3, 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. Conductive adhesive.   5. The anisotropic conductive adhesive according to claim 1, wherein an average particle diameter D (μm) of the metal particles of the conductive particles is 1 μm ≦ D ≦ 20 μm.   The anisotropic conductive adhesive according to any one of claims 1 to 5, wherein a particle diameter of the light-reflective insulating particles is 2% or more and less than 20% of a particle diameter of the conductive particles. A wiring board having a pair of connection electrodes;
A light emitting element having connection electrodes corresponding to the connection electrodes to be paired with the wiring board,
The light emitting element is bonded onto the wiring board by the anisotropic conductive adhesive according to any one of claims 1 to 6, and the connection electrode of the light emitting element is connected to the anisotropic conductive adhesive. A light emitting device that is electrically connected to the corresponding connection electrode of the wiring board via the conductive particles.

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