JP5033332B2 - Anisotropic conductive adhesive, anisotropic conductive adhesive film, and electrode connection method - Google Patents

Description

  The present invention relates to an anisotropic conductive adhesive, an anisotropic conductive adhesive film used for electrical connection between a display device and a circuit board, and an electrode connection method using the same, for example.

Conventionally, for example, anisotropic conductive adhesive films have been used as means for electrically connecting a liquid crystal display device and an integrated circuit substrate or the like.
This anisotropic conductive adhesive film is used to connect connection terminals such as flexible printed circuit boards (FPC) and IC chips to ITO (Indium Tin Oxide) electrode terminals formed on the glass substrate of LCD panels. As described above, it is used when various terminals are bonded and electrically connected, and is a film in which conductive particles are dispersed in an insulating adhesive resin.

  In order to perform bonding and electrical connection between terminals using this anisotropic conductive adhesive film, an anisotropic conductive adhesive film is interposed between the connection terminal and the electrode terminal, heated and pressed by a thermocompression bonding head. And crimp.

  By the way, when the electrode material is made of a metal such as aluminum, an oxide film is likely to be formed on the surface, so conventionally, using metal particles as the conductive particles of the anisotropic conductive adhesive film, breaking through the oxide film, The stable conduction is ensured. However, the connection member that is bonded and electrically connected by the above-described crimping may loosen based on the spread of the interval between the electrodes with the passage of time after the crimping, and when metal particles are used as the conductive particles Since there is no elasticity, there is a problem that it is not possible to follow the loosening and to ensure a stable conduction.

  Therefore, in recent years, as the conductive particles capable of following the looseness of the connection portion, particles obtained by plating particles having high elasticity such as resin particles are also used. However, this particle has a problem that due to its softness, it cannot break through the oxide film formed on the electrode surface, resulting in high conduction resistance.

  On the other hand, as conductive particles having both the hardness of the metal particles and the elasticity of the resin particles, the surface of the resin particles is subjected to electroless plating to form a metal thin film, and the processing temperature is set when the electroless plating is performed. There has also been proposed a conductive particle in which protrusions are provided on the surface of the metal thin film by changing the thickness (see Patent Document 1).

Further, among conductive particles, metal particles can be connected to an electrode by dispersing them as an aggregate of particles in addition to being dispersed as a single particle in an insulating adhesive (Patent Document 2). To 4). However, this agglomerate is designed to be intentionally broken by pressure during pressure bonding, and as a result, an effect more than that obtained by dispersing single metal particles cannot be obtained.
JP 2000-195339 A JP 60-218706 A Japanese Patent Laid-Open No. 3-126783 JP-A-6-136332

  The present invention has been made in order to solve the above-described problems of the prior art, and an anisotropic conductivity capable of maintaining high connection reliability over a long period of time in connection of an electrode on which an oxide film is easily formed. It is an object of the present invention to provide an adhesive, an anisotropic conductive adhesive film, and an electrode connection method using the same.

The invention according to claim 1 made to achieve the above object is configured as an aggregate in which spherical metal fine particles are aggregated in an insulating adhesive component, and voids are formed between the metal fine particles. An anisotropic conductive adhesive in which conductive particles are blended and dispersed, wherein the conductive particles have an average particle diameter of 10 μm or less and a tap density of 2.0 g / cm ³ or more. This is a conductive adhesive.
The invention according to claim 2 is the anisotropic conductive adhesive according to claim 1, wherein the conductive particles have a tap density of 3.0 g / cm ³ or less.
Invention of Claim 3 is an anisotropic conductive adhesive in which electroconductive particle is mix | blended in 1-40 volume% in the invention of any one of Claim 1 or 2 .
Invention 請 Motomeko 4 aspect of the present invention, in any one of claims 1 to 3, wherein the surface of the conductive particles, an anisotropic conductive adhesive having irregularities based on metal particles of agglomerated spherical It is.
A fifth aspect of the present invention is the anisotropic conductive adhesive according to any one of the first to fourth aspects, wherein the conductive particles have an average particle diameter of 4 μm or less.
The invention according to claim 6 is an anisotropic conductive adhesive film formed by forming the anisotropic conductive adhesive according to any one of claims 1 to 5 into a film shape.
According to a seventh aspect of the present invention, the anisotropic conductive adhesive according to any one of the first to fifth aspects, or the sixth aspect of the present invention is provided between a plurality of mutually facing connecting members having connection electrodes. The anisotropic conductive adhesive film is disposed between the electrodes, and heated and pressed to bond the connecting members together and electrically connect the electrodes to each other. .

  In the case of this invention, since it has a void | hole between the metal microparticles which comprise electroconductive particle, it is easy to deform | transform compared with the electroconductive particle which consists of a metal simple substance, and its elasticity is large. In particular, the conductive particles having a specific tap density can be positioned between the electrodes without breaking the conductive particles.

  As a result, according to the present invention, even when the connection portion is loosened due to the spread between the electrodes with the passage of time, it is possible to follow the looseness and ensure conduction between the electrodes.

  Further, in the case of the present invention, since there are hard protrusions made of metal fine particles on the surface portion of the conductive particles, even if an insulating oxide film is formed on the surface of the connection electrode The oxide film is pierced and brought into contact with the connection electrode, whereby a low conduction resistance with the connection electrode can be ensured.

  According to the present invention, high connection reliability can be maintained over a long period of time in the connection of an electrode on which an oxide film is easily formed.

Hereinafter, preferred embodiments of the anisotropic conductive adhesive and the electrode connecting method using the same according to the present invention will be described with reference to the drawings.
The present invention can be applied to any paste-like or film-like anisotropic conductive adhesive.

1A and 1B are schematic views showing an embodiment of an anisotropic conductive adhesive according to the present invention, and FIG. 1A is a configuration diagram showing an anisotropic conductive adhesive film, FIG. (B) is a figure which expands and shows the electrically-conductive particle of this Embodiment.
As shown in FIG. 1, the anisotropic conductive adhesive film 1 of the present invention has conductive particles 3 dispersed in a film-like insulating adhesive resin 2.

  In the case of the present invention, the insulating adhesive resin 2 is not particularly limited, but from the viewpoint of securing desirable conduction reliability, a composition containing an epoxy resin, a phenoxy resin, and a curing agent, or ( A composition containing a (meth) acrylic monomer and an initiator can be suitably used.

  As shown in FIG. 1B, in the case of the present embodiment, the conductive particles 3 are formed as an aggregate in which spherical metal fine particles 4 are aggregated. The surface of the conductive particles 3 has a large number of irregularities due to the agglomerated metal fine particles 4.

  In addition, many gaps, here, holes 5 exist inside the conductive particles 3. The holes 5 provide a space where the conductive particles 3 are deformed as a whole when a compressive load is applied to the conductive particles 3 from the outside.

  In the present invention, the porosity of the conductive particles 3 is not particularly limited, but is preferably 20 to 80% from the viewpoint of ensuring desired elasticity of the conductive particles 3. In addition, More preferably, it is 30 to 70%, More preferably, it is 40 to 60%.

Further, the tap density of the conductive particles 3 is not particularly limited, but is 2.0 or more from the viewpoint of maintaining long-term elasticity without destroying the form of the aggregate of conductive particles. It is preferably 2.0 to 3.0 g / cm ³ .

  Here, the tap density is a density measured when a certain vibration (tapping) is applied in order to increase the packing density of the powder material, and conductive particles having a desired tapping density are obtained depending on the degree of the applied vibration. be able to.

Although it does not specifically limit as the metal microparticle 4 used for this invention, From a viewpoint of ensuring desired hardness, it is preferable to use the microparticles | fine-particles which consist of nickel.
Furthermore, the particle diameter of the conductive particles 3 can be determined by various conditions such as the total thickness of the anisotropic conductive adhesive film, the electrode height, the pitch between the electrodes, and the expected spread between the electrodes. In consideration of variation, the average particle size is preferably 10 μm or less, and more preferably 4 μm or less.

Moreover, the compounding quantity of the electroconductive particle 3 is although it does not specifically limit, From a viewpoint of ensuring connection reliability and the insulation between adjacent particle | grains, it is preferable that it is 1-40 volume%.
The electroconductive particle 3 of this Embodiment can be manufactured by the method described in Unexamined-Japanese-Patent No. 2005-2395, for example.
Hereinafter, the manufacturing method of the electroconductive particle 3 at the time of using nickel microparticles as the metal microparticle 4 is demonstrated in detail.

  In the case of the present invention, the nickel fine particles can be produced using a commercially available porous spherical nickel compound. In this case, although not particularly limited, it is preferable to use a nickel compound that can be decomposed at a heat treatment temperature to be described later and obtain nickel oxide containing impurities within an acceptable range in terms of its characteristics. Nickel compounds such as nickel oxide, nickel carbonate, basic nickel carbonate and nickel nitrate can be suitably used.

  Among these, from the viewpoint of obtaining a porous microstructure, it is more preferable to use at least one selected from nickel hydroxide, nickel carbonate, or basic nickel carbonate. Further, nickel hydroxide and / or basic nickel carbonate are particularly preferable from the viewpoint of making the effect of forming fine pores by dehydration and decarboxylation in the heating process more remarkable.

  The spherical nickel compound is, for example, an aqueous solution containing various nickels such as nickel hydroxide and nickel nitrate, and at least one selected from a caustic alkaline aqueous solution, an alkaline carbonate aqueous solution, or an aqueous ammonium solution, Spherical particles having a predetermined average particle size and particle size distribution can be prepared by reacting under conditions that optimize the liquid temperature, pH, stirring, and the like.

In producing the nickel fine particles used in the present invention, first, the spherical nickel compound is heat-treated in two stages at a predetermined temperature in a neutral or oxidizing atmosphere.
Of the two-stage heat treatment, the temperature of the first-stage heat treatment is preferably 300 to 500 ° C. The reason is that if the temperature is lower than 300 ° C., the reaction of the spherical nickel compound is decomposed to produce nickel oxide powder becomes insufficient. On the other hand, if the temperature exceeds 500 ° C., the spherical nickel compound is rapidly pyrolyzed. This is because the spherical outer structure and the inner fine structure are broken.

  The temperature of the second stage heat treatment is preferably 800 to 1300 ° C. The reason is that if the temperature is lower than 800 ° C., a strong spherical outer structure cannot be formed, whereas if it exceeds 1300 ° C., a porous nickel oxide powder having a high specific surface area cannot be obtained. In addition, More preferably, it is 800-900 degreeC.

  Here, the temperature and the treatment time of the heat treatment in the first stage and the second stage are such that the characteristics of the spherical nickel compound can be controlled from the viewpoint of enabling control of characteristics such as the average particle diameter, particle size distribution, and specific surface area of the obtained nickel oxide powder. Select according to type and heat treatment equipment. Further, the temperature rising pattern of the heat treatment from the first stage to the second stage is not particularly limited, but may be performed continuously or once cooled.

The atmosphere for the heat treatment is preferably a neutral or oxidizing atmosphere. This is because metallic nickel is generated in a reducing atmosphere.
As a heating apparatus used in the heat treatment, for example, a muffle furnace, a pot furnace, a tubular furnace, a rolling furnace adjusted to a neutral or oxidizing atmosphere can be used.

  By this heat treatment, the spherical nickel compound is thermally decomposed, and the nickel oxide powder having a strong outer shape having a porous microstructure having characteristics such as a desired average particle size and particle size distribution and specific surface area is obtained with high yield. Obtained at a rate. The structure of the nickel oxide powder is maintained after the subsequent hydrogen reduction treatment.

Next, this nickel oxide powder is heated in a hydrogen atmosphere and subjected to hydrogen reduction treatment to produce spherical nickel fine particles.
Although the heating temperature in this process is not specifically limited, It is preferable to set it as 350-700 degreeC. The reason is that when the temperature is lower than 350 ° C., unreduced nickel oxide powder remains and the oxygen concentration of the nickel fine particles increases. On the other hand, when the temperature exceeds 700 ° C., coarse particles are formed by aggregation of the generated nickel fine particles. Is formed. In addition, More preferably, it is 450-650 degreeC.

Here, depending on the properties of the nickel oxide powder obtained after the above heat treatment and the reducing device used, by selecting a predetermined temperature and treatment time within the range of the heating temperature during the hydrogen reduction treatment, the average particle size, particle size Properties such as distribution and specific surface area can be controlled.
Moreover, as a reducing apparatus used for the hydrogen reduction treatment, for example, a muffle furnace, a pot furnace, a tubular furnace, a rolling furnace or the like adjusted to a hydrogen atmosphere with a predetermined concentration can be used.

  The nickel fine particles obtained by the above production method are spherical nickel powders having a porous fine structure, and can be produced by controlling properties such as average particle size, particle size distribution, and specific surface area to be desired values.

  In the above production method, the nickel oxide powder obtained after the heat treatment is finely pulverized prior to the hydrogen reduction treatment if necessary. Thereby, the particle diameter of the obtained nickel fine particles can be controlled. In the fine pulverization treatment, various commercially available pulverizers such as a ball mill, a bead mill, an attritor mill, a jet mill, and a stamp mill can be used.

  In order to create the anisotropic conductive adhesive film 1 according to the present embodiment using the conductive particles 3 obtained by the above manufacturing method, first, an appropriate solution is dissolved in a solution in which the insulating adhesive resin 2 is dissolved. Conductive particles 3 dispersed in a solvent are added to obtain a paste-like mixture. Next, the paste-like mixture is coated on a release film such as a polyester film and dried to obtain the anisotropic conductive adhesive film 1.

Next, an electrode connecting method using the anisotropic conductive adhesive according to the present invention will be described.
2 (a) to 2 (c) are schematic views showing a process of electrical connection using the anisotropic conductive adhesive according to the present invention, and FIG. 2 (a) is before heating and pressurization. FIG. 2B is a configuration diagram showing a state after heating and pressurization, and FIG. 2C is an enlarged view showing a connection portion of FIG. 2B. It is.

  In order to electrically connect the connection electrodes 8 and 9 using the anisotropic conductive adhesive film 1 according to the present embodiment, first, as shown in FIG. The anisotropic conductive adhesive film 1 is disposed between the connection electrode 8 of the connection member 6 and the connection electrode 9 of the circuit board (connection member) 7.

Then, as shown in FIG. 2 (b), the IC chip 6 is pressed against the circuit board 7 with the anisotropic conductive adhesive film 1 sandwiched between them using a thermocompression bonding head (not shown).
Thereby, the two connection electrodes 8 and 9 facing each other are electrically connected via the conductive particles 3 and the IC chip 6 and the circuit board 7 are bonded.

  In the anisotropic conductive adhesive film 1 of this Embodiment demonstrated above, since it has the void | hole 5 between the metal microparticles 4 which comprise the electroconductive particle 3, compared with the electroconductive particle which consists of a metal simple substance. It is easy to deform and has great elasticity.

  As a result, according to the present embodiment, even if the connection portion between the connection electrodes 8 and 9 is loosened over time, the elasticity of the conductive particles 3 follows the looseness. The continuity between the connection electrodes 8 and 9 can be ensured.

  Furthermore, in the case of the present embodiment, since there are hard protrusions made of metal fine particles 4 on the surface portion of the conductive particles 3, as shown in FIG. 2 (c), the surfaces of the connection electrodes 8, 9 Even in the case where the insulating oxide film 10 is formed thereon, the oxide film 10 is pierced to come into contact with the connection electrodes 8 and 9, thereby reducing the low conduction resistance between the connection electrodes 8 and 9. Can be secured.

  Examples of the present invention will be described below in detail together with comparative examples.

<Example 1>
As an insulating adhesive resin, 30 parts by weight of a phenoxy resin (YP50 manufactured by Toto Kasei Co., Ltd.), 45 parts by weight of a liquid epoxy resin (EP828 manufactured by Japan Epoxy Resin Co., Ltd.), 25 parts by weight of an imidazole curing agent (HK3941HP manufactured by Asahi Kasei Co., Ltd.), conductive particles 10 parts by weight (manufactured by Sumitomo Metal Mining Co., Ltd., average particle size 4 μm) 10 parts by weight (tap density 1.0 g / cm ³ ) was dissolved and mixed with a mixer using 100 parts by weight of toluene as a solvent to obtain a paste.

  And the paste mentioned above was apply | coated on PET film which performed the peeling process, it heated for 4 minutes with the electric oven set to 65 degreeC, and the sample of the anisotropic conductive adhesive film whose dry film thickness is 20 micrometers was created.

<Examples 2 to 5>
An anisotropic conductive adhesive film using the same material and method as in Example 1 except that the tap density of the conductive particles was changed to 1.5, 2.0, 2.5 and 3.0 g / cm ^3. A sample was created.

<Comparative Example 1>
Anisotropic conduction is performed using the same materials and methods as in Example 1 except that the conductive particles are nickel-gold plated particles (manufactured by Nippon Chemical Industry Co., Ltd., average particle size: 4 μm). An adhesive film sample was prepared.

<Comparative Example 2>
A sample was prepared by the same method as in Example 1 except that conventionally used nickel metal particles (manufactured by Nippon Chemical Industry Co., Ltd., average particle size 4 μm) were used.

<Evaluation>
The connection members were pressure-bonded using the samples of Examples 1 to 5 and Comparative Examples 1 and 2, and the conduction reliability was evaluated.

In this case, as one connecting member, an electrode pattern in which a nickel / gold plating is applied to a copper foil having a thickness of 15 μm on a substrate made of polyimide having a thickness of 75 μm (trade name Upilex-S manufactured by Ube Industries) TCP formed with a pitch of 50 μm was used.
As the other connecting member, TEG (Test Element Group) is used, in which an aluminum electrode with a thickness of 0.5 μm is vapor-deposited on a glass plate with a thickness of 0.7 mm and a surface insulation resistance of 1 × 10 ¹⁵ Ω or more. It was.

  The crimping conditions are a temperature of 170 ° C., a pressure of 2 MPa, and a time of 20 seconds. A TCP and a glass substrate are crimped and connected with a connection width of 1 mm using the above-described sample, and the temperature is 85 ° C. and the relative humidity is 85%. Aging was performed for 125 hours, 250 hours, and 500 hours, and a continuity test between the electrodes was performed. The results are shown in Table 1.

  In this case, the conduction reliability is determined by measuring the resistance increase as less than 3Ω, evaluating a good case considered almost unchanged as “◯”, and then measuring the resistance increase between 3 and 5Ω. The case where there was no problem in practical use was evaluated as “Δ”, and the case where the increase in resistance was measured to exceed 5Ω and it was determined that there was an apparent increase in resistance was evaluated as “bad”.

<Evaluation results>
About Example 1, it turns out that it is controlled by the resistance rise of 3-5 (ohm) over 500 hours after aging immediately after thermocompression bonding (initial stage), and it turns out that the electrical connection between electrodes is stable for a long period of time. This is because the conductive particles of Example 1 can break through the insulating oxide film formed on the aluminum electrode surface of the circuit board with the nickel fine particles located on the outer surface, and further spread between the electrodes over time. It shows that it is possible to follow the looseness of the connecting part based on.
Moreover, in Examples 2-5, high conduction | electrical_connection is possible immediately after thermocompression bonding, and it turns out that there is almost no resistance rise over 500 hours of Examples 3-5.

  On the other hand, in Comparative Example 1, a resistance increase of 5Ω or more is observed after aging for 250 hours. This is because the resin particles plated with nickel-gold as the conductive particles have a shallow degree of breakage of the insulating oxide film formed on the surface of the aluminum electrode of the circuit board. As a result, the resin particles are made elastic. It can also be seen that it is not possible to follow the looseness of the connecting portion based on the spread between the electrodes.

  In Comparative Example 2, almost no increase in resistance is observed from just after thermocompression bonding to after aging for 125 hours, but after aging for 250 hours, a resistance increase of 5Ω is observed. This shows that although the metal particles have sufficiently penetrated the insulating oxide film, they hardly follow once the film has spread in the thickness direction or the connection portion has loosened once.

(A) (b): It is the schematic which shows embodiment of the anisotropically conductive adhesive which concerns on this invention. (A)-(c): It is the schematic which shows the process of making an electrical connection using the anisotropic conductive adhesive which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anisotropic conductive adhesive film 2 Insulating adhesive resin 3 Conductive particle 4 Metal fine particle 5 Hole 6 IC chip (connection member)
7 Circuit board (connection member)
8 Connecting electrode 9 Connecting electrode 10 Oxide coating

Claims (7)

An anisotropic conductive adhesive comprising an insulating adhesive component, which is configured as an aggregate in which spherical metal fine particles are aggregated, and in which conductive particles having pores are blended and dispersed between the metal fine particles Because
An anisotropic conductive adhesive, wherein the conductive particles have an average particle diameter of 10 μm or less and a tap density of 2.0 g / cm ³ or more. The anisotropic conductive adhesive according to claim 1, wherein the conductive particles have a tap density of 3.0 g / cm ³ or less.   The anisotropic conductive adhesive according to claim 1, wherein the conductive particles are blended in a range of 1 to 40% by volume. The anisotropic conductive adhesive according to any one of claims 1 to 3 , wherein the surface of the conductive particles has irregularities based on aggregated spherical metal fine particles. The conductive particles, anisotropic conductive adhesive according to any one of claims 1 to 4 having an average particle diameter of not more than 4 [mu] m. An anisotropic conductive adhesive film formed by forming the anisotropic conductive adhesive according to any one of claims 1 to 5 into a film shape. The anisotropic conductive adhesive according to any one of claims 1 to 5 or the anisotropic conductive adhesive film according to claim 6 between a plurality of mutually facing connection members having electrodes for connection. An electrode connection method comprising a step of adhering the connection members and electrically connecting them by arranging the electrodes between the electrodes and performing heating and pressurization.

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