HK1139785B - Method for connecting electronic part and jointed structure - Google Patents

Description

Method for connecting electronic components and bonded body

Technical Field

The present invention relates to a method for connecting electronic components, and more particularly to a method for connecting electronic components using an anisotropic conductive adhesive and a bonded body.

Background

Conventionally, anisotropic conductive adhesives in which conductive particles are dispersed in an adhesive have been used for connection of electronic components.

However, in recent years, with the narrowing of the pitch of terminals of electronic products, conductive particles are aggregated between adjacent terminals when electronic components are connected, and short circuits (short) occur between the terminals.

In particular, when a device (TAB) having a semiconductor Chip connected to a carrier Tape or a device (COF) having a semiconductor Chip connected to a film carrier is connected to a terminal at an edge portion of an LCD panel (liquid crystal panel), a pressure bonding tool is displaced to press and bond a corner portion (edge portion) of the LCD panel, and conductive particles are intercepted at the edge portion to cause aggregation of the particles, thereby causing a problem of short circuit between adjacent terminals.

As a technique for reducing short-circuiting caused by aggregation of such conductive particles, there have been proposed the use of particles having an insulating coating applied to the surface of the conductive particles, the reduction of the particle diameter of the conductive particles, the reduction of the density of the conductive particles, and the like.

Particles coated with an insulating film have the following problems: when the coagulation occurs, a short circuit occurs only by applying an external stress that breaks the insulating film.

Further, simply reducing the particle diameter of the conductive particles is not preferable because not only the short circuit due to aggregation of the particles cannot be completely solved, but also the characteristics (restoring force and the like) of the conductive particles themselves are lowered.

Further, the method of reducing the particle density to suppress the particle aggregation has a problem that the particle trapping between the terminals is insufficient to cause conduction failure.

Further, anisotropic conductive adhesives in which insulating particles are added together with conductive particles in order to completely prevent short circuits caused by aggregation of the particles are known (see patent documents 1 to 5).

However, when the particle diameter of the insulating particles is large, the insulating particles are held before the conductive particles are held between the terminals of the electronic component. Here, when the insulating particles are sandwiched first, the conductive particles cannot contact the terminals, or even if the conductive particles contact the terminals, the pressing force applied to the conductive particles is reduced, so that the deformation amount is reduced, and a problem of poor conduction between the terminals is caused.

After the electronic component is connected, the number of captured conductive particles is checked to confirm the reliability of the connection. When the conductive particles are held between the terminals, a minute protrusion is generated on the back surface of the terminal due to a repulsive force generated when the conductive particles are deformed. Therefore, the number of conductive particles held between the terminals can be obtained by observing the back surface of the terminals on the front surface of the glass substrate from the back surface side of the glass substrate of the LCD panel with a differential microscope (differential interferometer) and counting the number of the fine bumps.

However, when the insulating particles are sandwiched between the terminals, the same fine protrusions as when the conductive particles are sandwiched between the terminals also occur. Here, since the minute projection due to the insulating particles sandwiched between the terminals and the minute projection due to the conductive particles sandwiched between the terminals cannot be distinguished, the number of trapped conductive particles cannot be accurately measured.

Further, in order to increase the contact area between the conductive particles and the terminals, when the conductive particles are deformed by pressing, the probability that the insulating particles are sandwiched between the terminals becomes high, and thus such a problem is particularly serious.

In addition, since the insulating particles are generally made of resin particles, the insulating particles easily absorb a solvent in the anisotropic conductive adhesive during or after the production of the anisotropic conductive adhesive. When the insulating particles absorb the solvent, they swell and have a large particle diameter, and therefore, the problems of poor conduction between terminals and measurement of the number of trapped particles become more serious.

When the insulating particles absorb the solvent, the solvent is released from the insulating particles when the anisotropic conductive adhesive is heated, and the solvent evaporates, thereby generating air bubbles (voids) in the anisotropic conductive adhesive.

If the voids occur, the connection strength of the electronic component is lowered, and the electronic component floats (separates) from the anisotropic conductive adhesive when left for a long time, and conduction failure occurs.

Patent document 1: japanese laid-open patent application No. 2001-85083

Patent document 2: japanese patent laid-open No. 2005-347273

Patent document 3: japanese patent laid-open publication No. 2002-

Patent document 4: japanese patent laid-open publication No. 2003-165825

Patent document 5: japanese laid-open patent publication No. 8-113654

Disclosure of Invention

The present invention is to solve the above problems and to achieve the following object:

that is, an object of the present invention is to provide a method of connecting an electronic component and a joined body, which can accurately measure the number of captured conductive particles and have high conduction reliability after connection.

(1) A method of connecting electronic components, comprising: a mixing step of mixing a dispersion solvent, a binder resin dissolved in the dispersion solvent, conductive particles, and insulating particles having a smaller particle size than the conductive particles to produce an anisotropic conductive adhesive; and a thermal extrusion step of opposing substrate-side terminals of a substrate and component-side terminals of an electronic component with the anisotropic conductive adhesive interposed therebetween, applying heat and a pressing force to the substrate and the electronic component, and sandwiching the conductive particles between the substrate-side terminals and the component-side terminals to deform the conductive particles, wherein the pressing force in the thermal extrusion step is smaller than both a breaking pressing force for breaking the conductive particles and a deforming pressing force for making the particle diameter of the conductive particles the same as the particle diameter of the insulating particles.

(2) The method for connecting electronic components according to (1), wherein the total volume of the insulating particles is 0.2 times or more and 2 times or less the total volume of the conductive particles.

(3) The method for connecting electronic components according to any one of (1) to (2), wherein the insulating particles are insulating particles that do not swell due to contact with the dispersion solvent.

(4) The method for connecting electronic components according to any one of (1) to (3), wherein the insulating particles are organic-inorganic hybrid particles in which a functional monomer is bonded to the surface of an inorganic particle, and the binder resin contains a polymerization resin capable of polymerizing with the functional monomer in the organic-inorganic hybrid particles.

(5) The method for connecting electronic components according to any one of (1) to (3), wherein the insulating particles are organic-inorganic hybrid particles in which an inorganic material is bonded to the surface of organic particles.

(6) The method for connecting electronic components according to any one of (1) to (3), wherein the insulating particles are an inorganic resin chemically bonded to at least one inorganic material skeleton in an organic polymer skeleton.

(7) An anisotropic conductive joined body, characterized by using the connection method of an electronic component according to any one of (1) to (6).

According to the present invention, the existing problems can be solved, and the above object can be achieved. That is, according to the present invention, it is possible to provide a method of connecting an electronic component and a joined body, which can accurately measure the number of captured conductive particles and have high conduction reliability after connection.

In the present invention, the relationship between the fracture particle diameter of the conductive particles when the conductive particles are fractured, the particle diameter of the conductive particles, and the pressing force is previously determined by a preliminary test before the electronic component is connected to the substrate.

The state in which the conductive particles are destroyed means a state in which the conductive particles lose recovery characteristics that cannot be restored even when the pressing force is released, and for example, when the conductive particles are metal-coated resin particles in which a metal coating is formed on the surface of the resin particles, this means a state in which the resin particles themselves are destroyed.

The composition, mixing ratio, film thickness, area of planar shape, and particle diameter (before deformation) of conductive particles added to the anisotropic conductive adhesive used for connecting the substrate and the electronic component are known in advance.

In the preliminary test, first, a test piece having the same thickness and the same area and made of the same anisotropic conductive adhesive as the anisotropic conductive adhesive used for connecting the substrate and the electronic component is sandwiched between two test boards having flat surfaces, and is pressed at the same temperature as the temperature at the time of connecting the substrate and the electronic component, and the relationship between the pressing force and the particle diameter of the conductive particles is previously solved by the distance between the pressing force and the test boards.

Then, the conductive particles added to the anisotropic conductive adhesive are pressed and deformed, and the fracture particle diameter of the conductive particles is obtained in advance.

Further, by obtaining the particle size of the insulating particles in advance, it is possible to know which of the particle size of the insulating particles and the fracture particle size of the conductive particles is larger, and further, it is possible to determine which of the fracture pressing force at which the conductive particles are fractured and the deformation pressing force described later is an upper limit value so that the conductive particles can be deformed to be larger than the insulating particles without fracturing the conductive particles, and the number of trapped conductive particles can be accurately measured.

When the insulating particles expand due to contact with the dispersion solvent during or after production of the anisotropic conductive adhesive, the expansion particle diameter of the insulating particles during expansion is determined in advance, and a pressing force for bringing the conductive particles to the same value as the expansion particle diameter is set as a deforming pressing force.

According to the present invention, the insulating particles do not swell and are not larger than the conductive particles. Further, the conductive particles are not smaller than the insulating particles even if they are pressed. Therefore, the particle diameter of the conductive particles is not less than the particle diameter of the insulating particles, and the insulating particles do not interfere with the connection of the conductive particles, so that the on-resistance is low. Further, since the substrate-side terminal has a minute projection only in a portion where the conductive particles are sandwiched, the number of trapped conductive particles can be accurately counted. Further, since the conductive particles are not broken, the conduction reliability is high. Since the insulating particles do not absorb the dispersion solvent, voids do not occur even when the anisotropic conductive adhesive is heated.

Drawings

Fig. 1 is a cross-sectional view of an anisotropic conductive adhesive;

fig. 2A is a sectional view of a process of connecting a first electronic component;

fig. 2B is a sectional view of a process of connecting a second electronic component;

FIG. 3 is a front view of a schematic representation of a bond;

fig. 4 is a cross-sectional view illustrating the inspection process after connection.

Detailed Description

(connection method of electronic Components)

The method for connecting electronic components of the present invention includes at least a mixing step and a hot-pressing step, and further includes other steps appropriately selected as necessary.

< mixing step >

The mixing step is a step of mixing a dispersion solvent, a binder resin dissolved in the dispersion solvent, conductive particles, insulating particles having a particle diameter smaller than that of the conductive particles, and other components appropriately selected as necessary to prepare an anisotropic conductive adhesive.

Dispersing solvent-

The dispersion solvent is not particularly limited and may be appropriately selected according to the purpose. The dispersion solvent is not limited to a mixed solvent of ethyl acetate and toluene, and for example, an organic solvent such as Methyl Ethyl Ketone (MEK), toluene, propylene glycol monomethyl ether acetate (PGMAC), and ethyl acetate may be used. The organic-inorganic hybrid particles and the silicone resin particles described later are not dissolved nor expanded in these organic solvents.

Binder resin-

The binder resin is not particularly limited as long as it is soluble in the dispersion solvent, and may be appropriately selected according to the purpose. The binder resin includes either one or both of a thermosetting resin and a thermoplastic resin. The thermosetting resin is polymerized by heating to harden the binder, the thermoplastic resin exhibits adhesive properties by heating, and the binder is solidified by being cooled after the heating is completed.

-thermosetting resin — -, thermosetting resin —

The thermosetting resin is not particularly limited, and may be appropriately selected according to the purpose, and for example, the following resins may be used: an anionic hardening epoxy resin using an epoxy resin and a microencapsulated amine-based curing agent as a curing agent, a cationic hardening epoxy resin using an onium salt or a sulfonium salt as a curing agent, a radical hardening resin using an organic peroxide as a curing agent, and the like.

-thermoplastic resin —

The thermoplastic resin is not particularly limited, and may be appropriately selected according to the purpose, and for example, phenoxy resin, urethane resin, polyester resin, or the like can be used.

Conductive particles-

The conductive particles are not particularly limited and may be appropriately selected according to the purpose, and examples thereof include conductive particles obtained by plating nickel or gold on the surface of organic resin spherical fine particles formed of a monomer or copolymer of benzoguanamine, styrene, divinylbenzene, an acrylic compound, and a methacrylic compound, or conductive particles obtained by plating the surface of inorganic particles such as nickel fine particles with gold.

The deformation amount of the conductive particles is not particularly limited, and it is preferable to set the deformation amount (the amount of decrease in particle diameter) of the conductive particles to 20% or more from the viewpoint of the conductive reliability.

When the conductive particles are metal-coated resin particles, the amount of deformation at the time of fracture is generally 60%, and the fracture particle diameter is 0.4 times the particle diameter before the deformation.

The conductive particles preferably have a particle size accuracy with a CV value of 20% or less, preferably 10% or less. The CV value is a value obtained by dividing the standard deviation by the particle diameter.

Insulating particles-

The insulating particles are not particularly limited as long as the particle diameter thereof is smaller than the particle diameter of the conductive particles, and may be appropriately selected according to the purpose, and examples thereof include organic-inorganic hybrid particles such as silicone resin particles. The insulating particles are not dissolved in the dispersion solvent, and do not absorb the dispersion solvent and swell, so that the particle diameter of the insulating particles does not change, and the particle diameter is maintained to be smaller than the particle diameter of the conductive particles.

Since the insulating particles do not absorb the dispersion solvent, voids do not occur in the binder during heating. The substrate and the electronic component are mechanically firmly connected by the cured adhesive.

The content range of the insulating particles is preferably more than 0.05 times and less than 2.5 times of the total volume of the conductive particles, and more preferably 0.2 to 2 times of the total volume of the conductive particles.

In the case where the conductive particles are metal-coated resin particles, there is a large difference in specific gravity between the ceramic particles and the conductive particles, and therefore, there is a possibility that the insulating particles may cause a problem in dispersibility in the anisotropic conductive adhesive.

The insulating particles preferably have a particle size accuracy with a CV value of 20% or less, preferably 10% or less. The CV value is a value obtained by dividing the standard deviation by the particle diameter.

-organic-inorganic hybrid particles —

The organic-inorganic hybrid particles are not particularly limited, and may be appropriately selected according to the purpose, for example:

1. organic-inorganic hybrid particles in which a constituent material of an inorganic material is bonded to a functional monomer on the surface of an inorganic particle

2. Organic-inorganic hybrid particles in which organic particle-constituting material is bonded to inorganic material on the surface of organic particles

3. Organic-inorganic hybrid particles composed of an inorganic-containing resin in which at least one inorganic material is chemically bonded to an organic polymer skeleton in advance, and the like.

The inorganic particles used in the organic-inorganic hybrid material particles are not particularly limited, and may be appropriately selected according to the purpose, and examples thereof include silica particles, calcium carbonate particles, and the like.

The functional monomer is not particularly limited and may be appropriately selected according to the purpose, and examples thereof include a vinyl monomer, an acrylic monomer, a methacrylic monomer, an epoxy monomer, a propylene oxide monomer, and an isocyanate monomer. The kind of the functional monomer bonded to one inorganic particle may be one kind, or two or more kinds.

The organic-inorganic hybrid particles in which the organic compound is exposed on the surface may swell depending on the type of the hybrid solvent. However, since the organic compound is only a few molecules deposited on the surface of the organic-inorganic hybrid particles and the thickness of the organic compound layer is negligibly smaller than the particle diameter of the entire organic-inorganic hybrid particles (for example, 2 μm or more and 4 μm or less), the swelling ratio does not exceed 30% even if the particles swell in the mixed solvent.

The organic-inorganic hybrid particles in which the functional monomer is exposed on the surface have higher affinity with the binder resin than the inorganic particles in which only the inorganic material is exposed, and therefore have excellent dispersibility in the anisotropic conductive binder.

If the binder resin contains a resin polymerizable with the functional group of the functional monomer, the resin is polymerized with the functional monomer at the time of main pressure bonding, and the mechanical strength of the cured anisotropic conductive adhesive is further improved.

Examples of the resin polymerizable with the acrylic monomer and the methacrylic monomer include acrylic resins and the like, examples of the resin polymerizable with the ethylene monomer, the epoxy monomer, and the propylene oxide monomer include epoxy resins and the like, and examples of the resin polymerizable with the isocyanate monomer include urethane resins.

In the organic-inorganic hybrid particles, the phrase "organic-inorganic hybrid particles in which a constituent material of organic particles and an inorganic material are bonded to the surface of organic particles" refers to organic-inorganic hybrid particles in which an inorganic compound such as polysiloxane is bonded to the surface of organic fine particles (resin particles), and examples thereof include "soliostar 15". The "soliostar 15" polymerizes an acrylic polymer having a siloxane skeleton, thereby bonding an inorganic compound (silicon) on the surface of the acrylic resin particle.

In the organic-inorganic hybrid particles, the "organic-inorganic hybrid particles composed of an inorganic resin having at least one inorganic material chemically bonded to an organic polymer skeleton in advance" means organic-inorganic hybrid particles obtained by polymerizing at least one compound having a polysiloxane skeleton to an organic polymer skeleton, and examples thereof include silicone resin particles.

The polysiloxane skeleton of the silicone resin particles has an acrylic acid structure of the following chemical formula (1) as a repeating unit.

[ solution 1]

..

The silicone resin has an organic substituent such as an alkyl group or a phenyl group bonded to a part or all of the acrylic structure of the polysiloxane skeleton.

The organic-inorganic hybrid particles have good chemical resistance, swelling resistance, and heat resistance, and have a low thermal expansion ratio, and the particle diameter does not become larger than that of the conductive particles even when heated. In particular, since the silicone resin particles are less expensive than other organic-inorganic hybrid particles, the production cost of the anisotropic conductive adhesive can be reduced by using the silicone resin particles as the insulating particles.

The insulating particles are not limited to the organic-inorganic hybrid particles, and resin particles may be used as long as they do not swell in the dispersion solvent in the anisotropic conductive adhesive.

The resin particles are not particularly limited as long as they do not dissolve in the dispersion solvent and swell, and may be appropriately selected according to the purpose. The organic polymer skeleton of the resin particles is not particularly limited in terms of molecular weight, composition, structure, presence or absence of functional groups, and the like, and examples thereof include polymers of acrylic monomers, methacrylic monomers, acrylonitrile, benzoguanamine, and formaldehyde condensates of melamine.

Other ingredients-

In addition to the thermosetting resin and the thermoplastic resin, various additives such as a curing agent, silane, a filler, and a colorant may be added to the solid component of the anisotropic conductive adhesive.

< Hot extrusion Process >

The thermal extrusion step is a step of deforming the conductive particles by opposing substrate-side terminals of a substrate and component-side terminals of an electronic component with the anisotropic conductive adhesive interposed therebetween, applying heat and a pressing force to the substrate and the electronic component, and sandwiching the conductive particles between the substrate-side terminals and the component-side terminals.

A substrate

The substrate is not particularly limited and may be appropriately selected according to the purpose, and for example, a transparent plate of an LCD (liquid crystal display) may be mentioned.

-electronic components-

The electronic component is not particularly limited, and may be appropriately selected according to the purpose, and examples thereof include a film-like device (COF, TAB device) in which a semiconductor chip is mounted on a film-like substrate.

< other Process >

The other steps are not particularly limited and may be appropriately selected according to the purpose.

Hereinafter, an example of a process for producing the anisotropic conductive adhesive used in the present invention will be described with reference to the drawings.

Fig. 1 is a schematic cross-sectional view of an anisotropic conductive adhesive 10. The anisotropic conductive adhesive 10 has a colloidal adhesive 11 in which an adhesive resin is dissolved in a dispersion solvent, and conductive particles 15 and insulating particles 12 dispersed in the adhesive 11, respectively, and is entirely colloidal.

The isotropic adhesive 10 may be used in a gel form as it is, or may be used after being made into a thin film.

To describe an example of the thinning, a gel-like anisotropic conductive adhesive 10 containing a mixed solvent (dispersion solvent) is applied to the surface of a release film by a coating method such as doctor blade coating to form a coating layer having a predetermined thickness, and then the coating layer is heated to remove the excessive mixed solvent, thereby obtaining a film-like anisotropic conductive adhesive (adhesive film).

If the insulating particles 12 absorb the mixed solvent and swell, the particle diameter thereof increases. When the particle diameter of the insulating particles 12 is increased, a rib is generated at the time of coating, and when the particle diameter exceeds the film thickness of a coating layer to be formed, a bonding thin film having a uniform film thickness cannot be obtained.

Since the insulating particles 12 do not swell in the dispersion solvent and no rib is generated at the time of coating, the thickness of the adhesive film is uniform.

Next, a method of using the anisotropic conductive adhesive 10 will be described.

The conductive particles 15 contained in the anisotropic conductive adhesive 10 are particles whose surfaces are exposed to a conductive material and which can be deformed by pressing.

For example, the conductive particles 15 are metal-coated resin particles in which a metal coating 17 is formed on the surface of a resin particle 16, or metal particles, and the metal-coated resin particles are elastically deformed by pressing and the metal particles are plastically deformed by pressing.

The relationship between the fracture particle diameter of the conductive particles 15, the pressing force when the conductive particles 15 are deformed to fracture, and the particle diameter of the conductive particles 15 is obtained by a preliminary test.

The particle size of the insulating particles 12 is known, and the particle size of the insulating particles 12 and the particle size of the conductive particles 15 at break are compared. When the particle diameter of the insulating particles 12 does not reach the fracture particle diameter of the conductive particles 15, the extrusion force (fracture extrusion force) at which the particle diameter of the conductive particles 15 reaches the fracture particle diameter is obtained from the relationship between the extrusion force and the particle diameter of the conductive particles 15, and the fracture extrusion force is set as the upper limit value of the extrusion force in the hot extrusion step.

When the particle diameter of the insulating particles 12 is equal to or larger than the fracture particle diameter, the pressing force (deforming pressing force) at which the particle diameter of the conductive particles 15 is equal to the particle diameter of the insulating particles 12 is obtained from the relationship between the pressing force and the particle diameter of the conductive particles 15, and the deforming pressing force is set as the upper limit value of the pressing force in the hot pressing step.

Within a range not exceeding the set upper limit, the pressing force capable of deforming the conductive particles 15 is set.

Further, an example of a process of connecting the substrate and the electronic component based on the set pressing force will be described.

Fig. 2A shows a substrate 20. The substrate 20 has a plate-like substrate body 21 and substrate-side terminals 25 arranged on the surface of the substrate body 21. The substrate terminals 25 are exposed at the edge portion of the surface of the substrate body 21, and the adhesive 10 in a gel form is applied to the edge portion of the surface, or the adhesive 10 in a film form is attached, and the exposed portions of the substrate terminals 25 are covered (temporarily attached) with the adhesive 10.

Fig. 2B shows an electronic component 30 such as a COF device or a TAB device. The electronic component 30 includes an elongated component body 31 and component-side terminals 35 disposed on the surface of the component body 31, and the component-side terminals 35 are exposed at the end of the surface of the component body 31.

After the substrate 20 and the electronic component 30 are overlapped (temporarily fixed) so that the anisotropic conductive adhesive 10 is sandwiched between the substrate-side terminals 25 and the component-side terminals 35 and opposed to each other, either one or both of the substrate 20 and the electronic component 30 (here, the electronic component 30) are pressed by the press 40 directly or through the buffer 43.

Here, the crimper 40 is provided with a heating device, not shown, and presses the electronic component 30 while heating the electronic component, and when a predetermined pressing force is applied to the electronic component 30 and the substrate 20, the adhesive 11 softened by heating is pushed out from between the substrate-side terminals 25 and the component-side terminals 35, and the conductive particles 15 are sandwiched between the substrate-side terminals 25 and the component-side terminals 35 and pressed and deformed, and therefore, the substrate-side terminals 25 and the component-side terminals 35 are electrically connected by the conductive particles 15.

Fig. 4 shows bonded body 1 in which electronic component 30 is electrically and mechanically connected to substrate 20, and inspection of the number of captured conductive particles 15 is performed on bonded body 1.

The substrate body 21 is formed of a transparent substrate such as a glass substrate or a plastic substrate.

Fig. 4 shows an observation device 45 having a microscope (for example, a differential interference microscope, a phase difference microscope, or the like), and the observation device 45 is used to observe the rear surface 47 of the substrate-side terminal 25 from the side surface of the substrate body 21 opposite to the side where the substrate-side terminal 25 is arranged, and count the number of minute bumps generated on the rear surface 47.

As described above, since the pressing force does not exceed the breaking pressing force and the deforming pressing force of the conductive particles 15, the conductive particles 15 are not broken, the particle diameter of the conductive particles 15 does not become smaller than the particle diameter of the insulating particles 12, and the distance between the substrate-side terminal 25 and the component-side terminal 35 is not smaller than the particle diameter of the insulating particles 12.

Since the insulating particles 12 are not pressed by the substrate-side terminals 25 and the component-side terminals 35, and only the conductive particles 15 are pressed and deformed to form fine protrusions, the number of the fine protrusions matches the number of the conductive particles 15 pressed by the substrate-side terminals 25 and the component-side terminals 35. Therefore, the number of trapped conductive particles 15 can be accurately determined.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

< Process for producing adhesive film >

A phenoxy resin as a thermoplastic resin was dissolved in a toluene/ethyl acetate 1/1 (weight ratio) dispersion solvent to obtain a 30 wt% phenoxy resin dissolved product.

Next, a curing agent, an epoxy resin as a thermosetting resin, a coupling agent, insulating particles, and conductive particles were added to the dissolved product in the amounts shown in table 1 below with respect to the amount of the phenoxy resin, and the solid content (the total amount of the phenoxy resin, the curing agent, the epoxy resin, the coupling agent, the insulating particles, and the conductive particles) was adjusted with toluene so as to be40 wt%, thereby obtaining six kinds of adhesive material dissolved products.

A dissolved adhesive material was applied to the surface of a release film having a thickness of 50 μm, and the release film was left in an oven at 90 ℃ for three minutes to evaporate the solvent, thereby obtaining adhesive films (film-form anisotropic conductive adhesives) of examples 1 to 4 and comparative examples 1 and 2 having a thickness of 18 μm.

[ Table 1]

Table 1: composition of Anisotropic conductive solid component (parts by weight)

(insulating particles and conductive particles are in volume ratio)

The amounts of the curing agent, the epoxy resin, the phenoxy resin, and the coupling agent are given as weight ratios, and the amounts of the insulating particles and the conductive particles are given as volume percentages in the binder (solid component) excluding the mixed solvent.

In table 1, the trade name [ HX3941] is a microcapsule-type amine epoxy hardener manufactured by asahi chemical corporation, the trade name [ EP828] is a bisphenol a-type liquid epoxy resin manufactured by japan epoxy resin corporation, the trade name [ YP50] is a bisphenol a-type phenoxy resin manufactured by toyoto chemical corporation, and the trade name [ KBE403] is an epoxy silane coupling agent manufactured by shin-Etsu chemical industry corporation.

The conductive particles 15 are metal-coated resin particles (average particle diameter 4 μm) having a Ni/Au plating film formed on the surface of acrylic resin particles, and are manufactured by water-immersion chemical industry (ltd.) under the trade name of "AUL 704".

In the insulating particles 12, silicone resin particles manufactured by Momentive Performance Materials Japan were designated by the trade name [ Tospearl107] and the trade name [ Tospearl140], respectively, the particle diameter (average particle diameter) of [ Tospearl107] was 0.7 μm, and the particle diameter (average particle diameter) of [ Tospearl140] was 4.0. mu.m. Further, the trade name of the catalyst is [ soliostar15] which is an organic-inorganic hybrid particle (a silicon-propylene composite compound) manufactured by Japan catalyst corporation, and the particle diameter (average particle diameter) thereof is 1.5. mu.m. None of the three kinds of insulating particles 12 swells or dissolves in the dispersion solvent.

< assembling Process >

As the substrate 20 for evaluation test, an aluminum wiring glass substrate (surface resistance 10. omega./□, glass thickness 0.7mm) having an aluminum terminal formed on the surface of the glass substrate was used, and a COF device having a Sn-plated copper terminal formed on the surface of a base film having a thickness of 38 μm was prepared as an electronic component.

In addition, the pitch between the aluminum wiring glass substrate and the terminal of the COF device was 38 μm, L (terminal width)/S (distance between terminals) was 23 μm/15 μm, and the top width of the terminal of the COF device was 15 μm, respectively.

The adhesive films of examples 1 to 4 and comparative examples 1 and 2, which were cut to a width of 1.5mm, were temporarily bonded to the aluminum wiring glass substrate by pressing the adhesive films with a tool width of 2.0mm at 80 ℃ under 1MPa for 2 seconds via a buffer material made of a polytetrafluoroethylene film ("Teflon" is a registered trademark) having a thickness of 70 μm.

Next, temporary fixing was performed on the COF apparatus at 80 ℃ for 0.5MPa and 0.5 second by the same crimper as used for temporary bonding.

Finally, hot pressing was performed at 190 ℃ for 10 seconds at 3MPa using a crimper 40 having a tool width of 1.5mm and a cushioning material 43 made of silicone rubber having a thickness of 200 μm, and a final crimp was performed, thereby obtaining bonded bodies of examples 1 to 4 and comparative examples 1 and 2. As shown in fig. 2B, the conductive particles 15 are intentionally aggregated by performing main pressure bonding with the pressure bonding machine 40 being displaced by 0.3mm from the edge of the aluminum wiring glass substrate (substrate 20).

< incidence of short-circuiting and on-resistance >

FIG. 3 is a schematic front view of the bonded body, and as shown in FIG. 3, a voltage of 30V was applied between terminals (component-side terminals 35) of the COF device to measure the insulation resistance, and the measured insulation resistance was set to 1.0X 10^-6The short circuit is assumed to occur below Ω, and the "short circuit occurrence rate" (initial stage) is obtained. In fig. 3, the insulation resistance is measured by an insulation resistance measuring device 39.

In a state where the parts-side terminals 35 were electrically connected to each other, each bonded body was left under high-temperature and high-humidity conditions of 85 ℃ and 85% humidity for 500 hours, and then "short-circuit occurrence rate" was checked again. And, for the bonded body after being left under the high temperature and high humidity condition, "on resistance" between the terminal of the aluminum wiring glass substrate and the terminal of the COF device thereof was solved.

< Capture judgment >

The aluminum terminal back surfaces of the bonded bodies of examples 1 to 4 and comparative examples 1 and 2 were observed by a differential interferometer (differential microscope), and the number of minute protrusions (indentations) was counted.

Next, the COF device was peeled off from the aluminum wiring glass substrate, and the number of conductive particles actually remaining on the surface of the aluminum terminal was counted. When the number of indentations was equal to the number of remaining conductive particles, the test was judged as "good", and when the number of conductive particles was less than the number of indentations, the test was judged as "poor".

Table 2 shows the results of "short-circuit occurrence rate", "on-resistance", and "capture determination".

[ Table 2]

Table 2: measurement results

(measurement N is 200)

As is clear from table 2 above, in comparative example 1 in which no insulating particles were added to the adhesive film, aggregation of the conductive particles occurred at the edge portion of the aluminum wiring glass substrate, and short-circuiting occurred between the adjacent terminals.

Under the above-described main pressure bonding conditions, the bonded bodies of comparative examples 1 and 2 and examples 1 to 4 were not broken and deformed by 10% to 60%, and the particle diameter of the conductive particles was not equal to or smaller than that of the insulating particles in examples 1 to 4.

In contrast, in comparative example 2, the particle size of the conductive particles did not reach the particle size of the insulating particles, and the insulating particles were pressed together with the conductive particles and deformed, so that an error occurred in the capture determination, and further, a pressing force was applied to the insulating particles, so that the amount of breakage of the conductive particles was small, and the on-resistance was high.

Examples 1 to 4 have lower on-resistance than comparative example 2, and the results of the trapping determination were also correct.

In examples 2 and 4, the types of the insulating particles were different, but the results of "on resistance", "short-circuit occurrence rate", and "capture number determination" were not changed regardless of the types. Therefore, if the particle diameter of the deformed conductive particles is equal to or larger than the particle diameter of the insulating particles, a bonded body having high conduction reliability can be obtained regardless of the kind of the insulating particles.

Example 1 has a low occurrence rate of short circuit compared to comparative example 1, but the occurrence rate of short circuit is higher than that of the other examples. In example 1, the content (total volume) of the insulating particles was very small and was only 0.05 times the content (total volume) of the conductive particles, and therefore, in order to more reliably prevent the occurrence of short circuits, the content of the insulating particles was required to be more than 0.05 times (volume ratio) the content of the conductive particles.

Further, although example 3 obtained excellent results in terms of both the short-circuit occurrence rate and the number of traps, the on-resistance was higher than that of the other examples.

In example 3, since the content (total volume) of the insulating particles was too large and 2.5 times the content (total volume) of the conductive particles, the exclusivity of the adhesive 11 between the aluminum terminal and the copper terminal was poor, the on-resistance was increased, and the conduction failure was caused. Therefore, in order to prevent conduction failure, it is necessary to control the insulating particles to be less than 2.5 times (volume ratio) of the conductive particles.

In the above description, although the case where the electronic component 30 is temporarily fixed after the anisotropic conductive adhesive 10 is temporarily attached to the substrate 20 has been described, the present invention is not limited to this, and the anisotropic conductive adhesive 10 may be temporarily attached to the electronic component 30, or may be temporarily attached to both the electronic component 30 and the substrate 20. Further, the main pressure bonding may be performed by the same pressure bonding machine as the pressure bonding machine used when temporarily fixing the electronic component 30.

The connection method of the present invention is not limited to the connection between the substrate and the electronic component, and can be used for connection between various electronic components such as a semiconductor chip, a resistive element, a flexible wiring board, and a rigid wiring board.

Therefore, when the particle diameter of the insulating particles 12 is less than 0.4 times the particle diameter of the conductive particles 15 before deformation, the particle diameter of the insulating particles 12 does not reach the fracture particle diameter, and therefore the fracture extrusion force may be set to the upper limit value of the extrusion force in the hot extrusion step.

The particle diameter of the insulating particles 12 is preferably 10% or more of the particle diameter of the conductive particles 15 before deformation. If the concentration is less than 10%, the effect of preventing short-circuiting is insufficient when the conductive particles 15 are aggregated.

If particles that do not swell or dissolve in the dispersion solvent are used as the insulating particles 12, the particle diameter of the insulating particles 12 does not increase, and even if the use conditions such as the mixing ratio of the anisotropic conductive adhesive 10 and the heating temperature slightly deviate from the preliminary test, the particle diameter of the conductive particles 15 does not become smaller than the particle diameter of the insulating particles 12 when the particles are pressed with a pressing force close to the deforming pressing force.

In the present invention, the "insulating particles that do not swell in a dispersion solvent" refers to insulating particles having a particle diameter da of 1.3 times or less (a swelling ratio of 30% or less) than a particle diameter db before immersion in a dispersion solvent, the particle diameter da being obtained when the insulating particles are immersed in the same dispersion solvent as the dispersion solvent used for the anisotropic conductive adhesive for 30 minutes.

Claims (4)

1. A method for producing an anisotropic conductive joined body, comprising:

a mixing step of mixing a dispersion solvent, a binder resin dissolved in the dispersion solvent, conductive particles, and insulating particles having a smaller particle size than the conductive particles to produce an anisotropic conductive adhesive;

a thermal extrusion step of opposing substrate-side terminals of a substrate and component-side terminals of an electronic component with the anisotropic conductive adhesive interposed therebetween, applying heat and a pressing force to the substrate and the electronic component, and sandwiching the conductive particles between the substrate-side terminals and the component-side terminals to deform the conductive particles,

the pressing force in the hot pressing step is smaller than both a breaking pressing force for breaking the conductive particles and a deforming pressing force for making the particle diameter of the conductive particles the same as the particle diameter of the insulating particles,

the conductive particles are formed by plating the surface of the resin fine particles,

the insulating particles are organic-inorganic hybrid particles in which a functional monomer is bonded to the surface of an inorganic particle, and the binder resin includes a polymer resin capable of polymerizing with the functional monomer in the organic-inorganic hybrid particles.

2. The method of producing an anisotropic conductive assembly according to claim 1, wherein the total volume of the insulating particles is 0.2 to 2 times the total volume of the conductive particles.

3. The method of producing an anisotropic conductive assembly according to claim 1, wherein the insulating particles are insulating particles that do not swell when in contact with the dispersion solvent.

4. An anisotropic conductive joined body produced by the method for producing an anisotropic conductive joined body according to claim 1.