JPH1153942A - Anisotropic conductive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a pressurized connection of low pressure to act as a sufficient high-conductivity connection by constituting a composition of an organic binder and a specific rate of conductive metallic particles having a specified deformation rate. SOLUTION: A composition comprises an organic binder and 0.1 to 25 vol.% of conductive metallic particles ranging from 3 to 9 μm in diameter whose deformation rate per particle under 1 gf load is 8 to 60%. Preferably, the conductive metallic particles are crystalline particles within 80 to 5000 Å-sized crystal grains exist in the particles, and metallic powder composed of one or more kinds selected from among silver, copper and tin is suitable. Such metallic powder is desirable being prepared by combining atomized powder, electrolytically plated powder, non-electrolytically plated powder, chemically reduced powder, vapor deposited powder, mechanical alloying powder, CVD powder, and metallic powder is by heat treatment and the like. As the organic binder, epoxy resin, phenol resin, silicone resin, urethane resin, or the like is used. Preferably, the anisotropic conductive composition thus acquired is applied as coating to a base film for forming an anisotropic conductive film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an anisotropic conductive composition, and relates to a liquid crystal display, a plasma display, and an EL.
Panels such as displays, mobile phones, personal computers, televisions, monitors, car navigation systems, PCMCIA, IC cards, photodiodes and M
It can be used for LSI mounting on CMs, printed boards, and flexible boards.

[0002]

2. Description of the Related Art Many anisotropic conductive films have been disclosed. For example, JP-A-7-197001 and JP-A-4-242001 disclose anisotropic conductive films using conductive particles obtained by plating metal on a resin ball. Further, for example, JP-A-61-55809, JP-A-5-40402, JP-A-7-73740, JP-A-7-65028 and the like include nickel powder, solder powder, gold-plated nickel powder and the like. An anisotropic conductive film using metal powder is disclosed.

[0003]

In the case of using conductive particles obtained by plating a metal on a resin ball, the effect of reducing the thermal stress is exhibited, but the pressure is several hundreds at the time of pressure connection. Is not uniformly applied to a certain connection terminal, and depending on the terminal, excessive pressure may be applied to the conductive particles,
For this reason, the resin ball is broken in the terminal where the pressure is applied too much, and the connection cannot be stably obtained, and the environmental property is deteriorated.

In the case of nickel powder or gold-plated nickel powder, the powder is too hard to be easily deformed and a sufficient contact area cannot be obtained. Therefore, when used for connection to a glass substrate or the like, considerable pressure is required, and the glass substrate is often broken. Until now, 180 ° C or higher was required as a connection condition. However, in the recent flow of fine pitch connection, the problem of pitch deviation due to a difference in thermal expansion has become apparent, and lower temperature has been called for. I have. As for the pressure, the load cell has become too large at a pressure of 30 kg / cm ² or more, such as the conventional Ni powder, in the trend of increasing the size of the panel, and has reached its limit. Therefore, lower pressure is required.

[0005]

The present invention has been made to solve the above-mentioned problems, and comprises an organic binder and 0.2 to 25% by volume of conductive metal particles. The particles provide an anisotropic conductive composition characterized in that a deformation ratio (displacement amount / particle size before deformation) of 3 to 20 μ particles at a weight of 1 gf is 8 to 60%.

The conductive metal particles that can be used in the present invention are contained in an amount of 0.3 to 25% by volume based on the organic binder. If the amount is less than 0.2, the number of conductive particles contributing to connection is small. It is not possible to obtain a stable connection resistance. On the other hand, if it exceeds 25% by volume, the number of conductive metal particles is too large, and the insulation between adjacent electrodes is reduced. Preferably, it is 0.2 to 15% by volume.

The conductive metal particles used in the present invention are 3 to 9
For particles having a size of μ, the amount of displacement of the particles when crushed by applying a load of 1 gf / the particle size before deformation is 8 to 60%
It is characterized by being. The weight at this time was determined using a flat indenter 5 using a micro compression tester MCTM manufactured by Shimadzu Corporation.
The amount of deformation when one of the conductive metal particles dispersed on a glass plate is compressed and deformed at a speed of 0.79 g / s using a 0 micron diameter is determined by the deformation ratio of the particle diameter before compression, that is, by compression. The ratio of the amount of deformation of the obtained particle size / the particle size before compression is measured. At this time, if the deformation rate under a load of 1 gf is less than 8%, sufficient deformation of the conductive particles cannot be obtained even at a low pressure of 10 to ²⁰ kgf / cm ² , and the contact area with the electrode becomes insufficient.

Conversely, when the deformation ratio exceeds 60%,
Deformation of the conductive metal particles occurs at the time of temporary compression of the anisotropic conductive composition, and at the time of final compression after the temporary attachment, insufficient removal of the organic binder and instability of the connection surface with the electrode are likely to occur. Preferably, it is 9 to 40%, and more preferably, 12 to 40%.
~ 35%. The conductive metal particles used at this time relate to conductive particles in the range of 3 to 9 μ which most easily contribute to connection, but are preferably 3 to 8 μ, more preferably 4 to 8 μ. Most preferably, 4.5
These are values for ~ 7μ particles.

Preferably, the conductive metal particles also have a particle distribution. In other words, during pressure welding, there is variation in the degree of balance of the pressure welding head, and if there is a particle size distribution, even if the balance of the head deviates, the head can always be connected to the terminals. Thus, there is an advantage that the powder having a small particle diameter serves as a cushion for the head and suppresses the dispersion of the head. As the particle size distribution, it is preferable that 30% or more of particles having an average particle diameter of ± 2 μm exist. More preferably, the minimum particle size /
It is preferable that the maximum particle diameter ratio is 0.001 to 0.49. As used herein, the term “maximum particle diameter” refers to the minimum particle diameter when the integrated value is 3% and the maximum particle diameter when the integrated value is 97% in the volume integrated particle size distribution. The average particle diameter referred to here is a volume-integrated average particle diameter, and the measurement is performed by using a laser diffraction type measuring device RODOS SR type (SYMPATEC).
(HEROS & RODOS) was used.

The conductive metal particles used in the present invention are:
In order to secure sufficient conductivity, a metal powder (including an alloy) having at least one component selected from metallic silver, gold, copper, solder, tin, lead, and indium is preferable. In this case, atomized powder, electrolytic plating powder, electroless plating powder,
Chemical reduction powder, evaporation powder, mechanical alloying powder, CV
D powder and metal powder prepared by combining heat treatment and the like are preferable.

Further, the conductive metal powder may include a solid solution layer and an intermetallic compound layer. Since the conductive metal particles used in the present invention have deformability under a suitable pressing force, they can be appropriately deformed at the time of press-contact and have a sufficient contact area with the electrode. Therefore, there is an advantage that the glass substrate is not broken, and when a soft organic substrate or the like is used, problems such as deformation of the substrate caused by hard particles are reduced. In particular, in connection with a large panel, the load on the load cell can be reduced, and the displacement of press bonding and damage to the substrate can be reduced.

Further, in the case of the conductive metal particles used in the present invention, it is preferable that the conductive particles have crystal grain boundaries, that is, the particles are easily deformed along the grain boundaries when pressed. is there. The size of crystal grains is 80-50
It is preferably about 00 °. In addition, 80-300
0 ° and 100 to 2000 ° are more preferable. The size of the crystal grain is obtained by observing the cross section of the conductive metal particle with an electron microscope. The crystal grain size was determined from the relationship between the height of the crystal peak by X-ray diffraction and the half width of the maximum crystal peak.

When the angle is less than 80 °, the crystal grain boundaries are small and the deformability under pressure is poor. If it exceeds 5000 °, the grain boundaries are too large and the smoothness of the deformability is lost. As a method for preparing the conductive metal powder used in the present invention, for example, as described above, a predetermined amount of a metal component is mixed and dissolved at a high temperature (100 ° C. or more from the melting point). The molten metal is rapidly cooled and solidified while spraying helium, nitrogen, hydrogen, and argon gas into fine powder. If the rapid solidification is excessively performed, the growth of the crystal is suppressed. Therefore, it is necessary to select an appropriate rapid cooling rate. This is preferably controlled by the supply rate of the melt and the cooling gas, and furthermore, heat treatment is performed after rapid solidification. As preferable conditions of the rapid solidification used in the present invention, it is preferable that the cooling gas ejection speed is 0.05 to 10 weight ratio to the melt ejection speed. If the cooling is too much, the crystal diameter becomes too small. The cooling gas is
If the temperature is controlled at 150 ° C. or lower before collision with the melt, sufficient cooling capacity can be obtained.

Further, it is more preferable to perform heat treatment after rapid solidification. After solidifying the obtained conductive metal powder, in an inert gas atmosphere (for example, in nitrogen, helium, or argon)
It is necessary to gradually cool to 50 ° C. over 1 to 5 hours to grow crystals to some extent. For this reason, it is important that the inert gas warmed by heat exchange with the powder be enclosed in the system without purging the cooling gas with fresh inert gas immediately after solidification. At this time, the solidified powder is deposited in a collection container, and gradually cooled while storing heat to obtain conductive particles having uniform crystallinity. If the cooling is performed too quickly, the strain in the crystal remains, and when the connection is heated and compressed as an anisotropic conductive composition, smooth deformation cannot be obtained.

After the heat treatment, the surface of the conductive metal powder may be plated. As the plating, a combination of electroless plating and electrolytic plating can be used. As a plating component, gold, tin, solder, nickel, silver, and indium can be used. As the thickness of the plating layer,
It is preferably about 10 to 3000 °. Further, the conductive metal powder used in the present invention preferably contains a large amount of a component having low oxidizability on the particle surface. For example, gold, silver, and the like are preferable. When these components are present on the particle surface at a higher concentration than the average composition, migration properties and environmental resistance can be further improved. For example, a copper-silver alloy-based powder having a high silver concentration on the particle surface, a copper alloy powder having a high gold concentration, or the like is used.
The silver concentration or the gold concentration on the particle surface may be a value measured by a peak at which the highest intensity of each element is obtained by XPS (X-ray photoelectron spectroscopy). The charged concentration is preferably measured by completely dissolving the powder with an ICP (high frequency inductively coupled plasma analyzer).

The organic binder that can be used in the present invention contains at least one resin selected from thermosetting resins, thermoplastic resins, photocurable resins, and electron beam curable resins. These resins include, for example, epoxy resin, phenol resin, silicone resin, urethane resin, acrylic resin, polyimide resin, phenoxy resin, polyvinyl butyral resin, SBR, SBS, NB
R, polyether sulfone resin, polyether terephthalate resin, polyphenylene sulfide resin, polyamide resin, polyether oxide resin, polyacetal resin, polystyrene resin, polyethylene resin, polyisobutylene resin, alkylphenol resin, styrene butadiene resin, carboxyl-modified nitrile resin, polyphenylene Examples thereof include an ether resin, a polycarbonate resin, a polyether ketone resin, and the like, and modified resins thereof.
In particular, when adhesiveness to a substrate is required, it is preferable to include an epoxy resin. When an epoxy resin is used, phenoki resin, polyester resin, acrylic rubber, SBR, N
BR, silicone resin, polyvinyl butyral resin, urethane resin, polyacetal resin, melamine resin, polyamide resin, polyimide resin, SBS, cyanoacrylate, carboxyl group, hydroxyyl group, vinyl group,
It is preferable to mix and use rubbers and elastomers containing a functional group such as an amino group.

As the epoxy resin, bisphenol A
Type, bisphenol F type, bisphenol S type, novolak type, alicyclic, heterocyclic, alkyl polyphenol type, phenylglycidyl ether type, polyfunctional polyether type, brominated phenol novolak type, naphthalene type,
It is preferable to use an epoxy resin such as a modified bisphenol S type, a diglycidyl aniline type, a diglycidyl ortho toluidine type, a urethane modified type, a rubber modified type, a silicone modified type, and a chain modified type.

The anisotropic conductive composition of the present invention is characterized by containing 0.1 to 25% by volume of conductive particles with respect to an organic binder, preferably 0.2 to 15% by volume, more preferably 0.2 to 15% by volume. Is 0.2 to 10% by volume. If the amount is less than 0.1% by volume, the number of conductive particles contributing to the connection is insufficient, and the terminals vary. If it exceeds 25% by volume, a problem of current leakage between terminals occurs.

When an epoxy resin is used as the organic binder, it is preferable to use a latent curing agent as the curing agent. As the latent curing agent, boron compounds, hydrazide, tertiary amine, imidazole, dicyandiamide,
Preference is given to inorganic acids, carboxylic anhydrides, thiols, isocyanates, boron complexes and their derivatives. Among the latent curing agents, a microcapsule-type curing agent is preferable. The microcapsule-type curing agent is obtained by coating the surface of the curing agent with a thermoplastic resin or the like.The microcapsules are broken by the temperature and pressure during the connection work, and the curing agent is rapidly diffused into the organic binder and cured. Facilitate. Among the microcapsule-type latent curing agents, microcapsule-type imidazole derivative epoxy compounds are more preferable.

As the microcapsule type imidazole derivative epoxy compound, a product obtained by pulverizing a reaction product of the imidazole derivative and the epoxy compound into fine powder is further reacted with, for example, an isocyanate compound or the like, and encapsulated. It is a thing that raised the character. Examples of the imidazole derivative include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-
4-methylimidazole, 2-phenylimidazole, 2
-Phenyl-4 methyl imidazole, 1-benzyl-2
-Methylimidazole, 1-benzyl-2-ethylimidazole, 1-benzyl-2-ethyl-5-methylimidazole, 2-phenyl-4-methyl-5hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole and the like Is mentioned.

When these curing agents are used,
Examples of the epoxy compound include glycidyl ether type epoxy resins such as bisphenol A type, bisphenol F type, phenol novolac type, and bisphenol A bromide, diglycidyl dimer acid ester, diglycidyl phthalate ester, and naphthalene type. When these epoxy resins are used, the microcapsule-type curing agent can be used in an amount of 5 to 250 parts by weight based on 100 parts by weight of the epoxy resin. If the amount of the microcapsule type curing agent is less than 5 parts by weight, curing tends to be insufficient, and 2
If it exceeds 50 parts by weight, storage stability is insufficient.

The average particle diameter of the microcapsule type curing agent is preferably 1 to 10 μm. When the average particle size exceeds 10 μm, when the anisotropic conductive composition is formed into a film (referred to as an anisotropic conductive film), thickness unevenness of the coating film occurs. When applying the anisotropic conductive composition of the present invention, an appropriate solvent can be used as necessary. Solvents that do not damage the microcapsule curing agent are preferred. For example, MEK, toluene, benzene, xylene, methyl isobutyl ketone, ethyl acetate, butyl acetate, aromatic hydrocarbon, ether, ketone, ester and the like are preferable.

The anisotropic conductive composition of the present invention contains a known silane coupling agent, titanium coupling agent, aluminum coupling agent and the like in order to improve the dispersibility of the conductive particles and the moisture resistance after connection. Can be blended. When a coupling agent is used, it can be added up to 5 parts by weight based on 100 parts by weight of the conductive particles. Preferably,
It is preferable that the conductive particles are previously treated with a coupling agent.

The anisotropic conductive composition of the present invention is prepared as follows. An appropriate amount of conductive particles and an organic binder (dissolved in a solvent if necessary) and, if necessary, a curing agent are mixed. Mixing is performed using a known device such as a planetary mixer, a three-roller, a kneader, a defoamer, a stirrer with blades, and a ball mill. At this time, it is preferable to sufficiently disperse the conductive particles. The thus obtained anisotropic conductive composition has a viscosity of 1000 CPS to 200,000 CPS.
The degree is preferably, but not necessarily, within this range. The obtained anisotropic conductive composition can be applied as it is on electrodes or terminals on the connection substrate by a printing method such as dispenser or screen printing. Further, the film may be in the form of a film in which an anisotropic conductive composition is coated on a base film (referred to as an anisotropic conductive film). When coating on a base film, a known method such as a blade or a die coater can be used. When the applied anisotropic conductive film contains a solvent, it is preferable to dry it sufficiently. The drying temperature is preferably adjusted in the range from room temperature to 80 ° C. The thickness of the anisotropic conductive film is 5 to 500
It is about μ, and the width is not particularly limited. When an anisotropic conductive film is used for connection, it can be slit and used. For example, it is preferable that an anisotropic conductive film having a width of about 0.2 to 200 mm is drawn from a state of being wound on a reel and is attached to connection terminals of a substrate for use.

The anisotropic conductive composition of the present invention has not been applied to a large-sized panel because the conductive particles are so hard that the conductive particles are not easily deformed at the time of pressure welding and the conductive area is not sufficient. Deformability is good, like problems and resin particles,
There was no problem that the oxide film such as metal wiring could not be destroyed.
It has moderate hardness and can relieve the pressure well during the welding process.
It has an advantage that it has a sufficient contact area that can prevent the destruction of glass and the like, and that the oxide film on the metal wiring is scraped off at the time of plastic deformation to provide stable contact with the metal component of the wiring. Further, when the average particle diameter is 2 to 15 μ and the particle size distribution is provided, the buffering property of the pressure is good, and the buffering effect is obtained even when the pressure is uneven. Further, it is preferable that the difference between the maximum particle diameter and the minimum particle diameter is at least 1 μm because the gap between electrodes (displacement of pressure) can be successfully compensated.

The anisotropically conductive composition and the anisotropically conductive film of the present invention can be used for connection between terminals on a substrate and for connection between chip electrodes and substrate terminals. Connection substrates include liquid crystal displays (amorphous silicon, high-temperature polysilicon, low-temperature polysilicon), plasma displays, panels such as electroluminescence, printed boards, IC card boards, and build-up boards (insulating layers and conductive circuit layers alternately or alternately). A substrate provided with electrical wiring such as a low-temperature baking substrate can be used. As a connected substrate or a connected chip, a flexible or hard wiring substrate, a capacitor, a magnetic sensor, a resistor, an LSI chip, a coil,
LSI packages (QFP, DIP, SOP, BGA,
CSP etc.).

The material of the connection board or the board to be connected is not particularly limited. Examples of the material include polyimide, glass epoxy, photosensitive epoxy, paper phenol, polyester,
Glass, silicon, quartz, polyphenylene ether, polyetherimide, polyetherketone, polyethylene terephthalate, polyphenylene sulphone, alumina, alumina nitride, polyamide imide, tetrafluoroethylene, polyphenylene terephthalate, BT resin, and derivatives, single layers and laminates thereof Plate (build-up substrate), ceramic substrate and the like.

The conductor of the connection electrode (terminal) formed on the connection substrate or the substrate to be connected is not particularly limited, and examples thereof include ITO, IO, copper, silver, copper-silver alloy, silver palladium, and gold. , Platinum, nickel, aluminum, silver platinum, tin-lead solder, tin-silver solder, tin, chromium, indium alloy, and conductors plated with gold, tin, nickel, tin-lead, chrome, etc. Known conductors such as conductors may be used. The conductor can be formed by a known method. For example, for conductors, plating, evaporation, reflow, conductor paste,
It is manufactured by wire bonding and photolithography.

When the anisotropically conductive composition and the anisotropically conductive film of the present invention are repaired, a defective connection substrate (for example, TAB or the like) or a chip is mechanically peeled off and an anisotropic conductive film remaining on the substrate is repaired. A part of the conductive composition or the anisotropic conductive film is repeatedly peeled off using a solvent. The process is repeated until the anisotropic conductive composition or the anisotropic conductive film on the connection terminal is removed to some extent.

Conventionally, connection conditions are as follows:
In many cases, the temperature exceeds 180 ° C., and uneven connection occurs due to a difference in coefficient of thermal expansion. Pressure is also N
30kg / cm ² when using i powder as conductive powder
Since the above pressure is required, and the connection of large panels and the like, which is expected in the future, has come to exceed the limit of the load cell, an anisotropic conductive film that can cope with low pressure is required. On the other hand, the anisotropic conductive composition and the anisotropic conductive film of the present invention have moderate deformability,
It has excellent hardness that can be connected with a sufficiently high conductivity even at low pressure because it has the same hardness, and also has excellent connection reliability by sufficiently breaking the oxide film of the conductor having an oxide film. .

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the anisotropically conductive composition and anisotropically conductive film of the present invention are shown below, and the present invention will be described in more detail.

[0032]

EXAMPLES Table 1 shows conductive metal powders used in Examples and Comparative Examples. Further, the anisotropic conductive composition and the anisotropic conductive film in Table 2 are shown. The resin solid at room temperature was prepared by adding a solvent and adding a mixed solution of ethyl acetate and toluene.
The anisotropic conductive film was coated on a PET film as a base film. After coating, it was dried in a continuous furnace at 60 ° C. Table 3 shows the evaluation results of the anisotropic conductive composition and the film. Regarding the continuity, four-terminal resistance was measured, and a connection resistance value of 200 mOhm or less was evaluated as ○. 20
0 to 500 mOhm was rated as Δ, and exceeding the rating was rated as x.

Regarding the variation, when the connection resistance value was measured at 10 terminals and there was no value more than 3 times the average value of the connection resistance, it was evaluated as ○, and when there was a terminal exceeding 3 times as much as ×. For environmental properties, -55 to 125 ° C (30 minutes each)
The case where the resistance value exceeded 5 times in 1000 heat cycles was evaluated as X, the case where the resistance value was 2 to 5 times as Δ, and the case where the resistance value was less than 2 times as O. Regarding the insulating property, a symbol “○” indicates an insulation resistance of 10 ¹⁵ ohms or more between terminals, and a symbol “×” indicates an insulation resistance between terminals. Table 4 shows the anisotropic conductive compositions used in Comparative Examples. Table 5 shows an evaluation example of the comparative example.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

[Table 5]

[0039]

Industrial Applicability The anisotropic conductive composition of the present invention can be applied to a large-sized panel because the conductive particles are so hard that the conductive particles are not easily deformed at the time of pressure welding and the conductive area cannot be sufficiently obtained. There was no problem that did not exist, and there was no problem that the oxide film of metal wiring etc. could not be destroyed, as in the case of resin particles, but there was no problem. This has the advantage of having a sufficient contact area, preventing the oxide film on the metal wiring from being scraped off during plastic deformation, and having a stable contact with the metal component of the wiring. Furthermore, to include moderate crystal grains and grain boundaries, deformation proceeds well along the grain size even at low pressure during pressure welding,
There is little unevenness in pressure contact.

Claims (4)

[Claims] 1. An organic binder comprising 0.1 to 25% by volume of conductive metal particles, wherein the conductive metal particles are 3 to
An anisotropic conductive composition, wherein a deformation ratio (displacement amount / particle size before deformation) of one particle in a range of 9 μm with a weight of 1 gf is 8 to 60%. 2. The conductive metal particles are crystalline particles, and the size of the crystal grains present inside the conductive metal particles is 80 to 5
2. The anisotropically conductive composition according to claim 1, wherein said composition is 000 °. 3. The anisotropic conductive composition according to claim 1, wherein the conductive metal particles are a metal powder having at least one component selected from copper, silver, gold, and tin. Stuff. 4. An anisotropic conductive film comprising the anisotropic conductive composition according to claim 1.