JPH06232548A - Electric circuit connecting member - Google Patents

Abstract

PURPOSE:To obtain an electric circuit connecting member wherein a conductive pattern and a base film are excellent in adhesion to each other and a joint is hardly disconnected by a method wherein a coating layer is formed on the base film, and an electric circuit pattern of conductive paste is formed thereon. CONSTITUTION:It is important that a base film which is flexible and possessed of an electrical insulating property is used, and the base film is, for instance, above 10<8>OMEGA.cm in resistance, and it is preferable that the base film is over 10<10>OMEGA.cm in resistance. It is important that polymer contained in a coating layer formed on the base film and conductive paste is possessed of a functional group in a molecule. The above functional group is, for instance, an isocyanate group. It is necessary that polymer or compound possessed of a reactive group which combines with the above functional group is contained in the conductive paste. The above reactive group is such as a nitrile group, a mercapto group, a carboxyl group, or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat seal connector between electric circuits, and more particularly to a liquid crystal display (LC).
D), electroluminescence (EL), plasma display (PDP), light emitting diode (LED), connection between a display panel such as an electrochromic display (ECD) and a hard printed wiring board (PCB) or a flexible printed circuit board (FPC), Or PCB and P
The present invention relates to an electric circuit connecting member used for connecting CB, FPC and FPC, PCB and FPC and the like.

[0002]

2. Description of the Related Art A conventional electrical circuit connecting member is one in which a conductive pattern is directly formed on a base film with a conductive paste, and an anisotropic conductive adhesive member is provided on the electrical connection portion thereon.

[0003]

However, in order to obtain good conductivity in the above-mentioned conductive paste, the conductive filler must be mixed in a considerably large ratio with respect to the resin binder. Therefore, when a force in the peeling direction is applied to the connection portion, the conductive pattern is peeled off from the base film with a slight force, and there is an unavoidable inconvenience of disconnection at this portion resulting in poor conduction.

The present invention solves the above-mentioned conventional problems. In particular, the adhesion between the conductive pattern of the conductive paste and the base film is good, and the connection is extremely free from disconnection even if external force is applied. An object is to provide a stable electric circuit connecting member.

[0005]

Means for Solving the Problems The present invention has variously studied a method for improving the adhesion between a conductive pattern and a base film, and in particular, a method for obtaining good adhesion without adversely affecting the conductivity of the conductive pattern. The present invention has been completed.

That is, the gist of the present invention is the constituent features described in each of the claims.

Since the flexible base film used for the electric circuit connecting member of the present invention is used as a base for the anisotropic conductive connection of electricity, it is important that it has an electric insulating property, for example, 10 ⁸ A material having a volume resistivity of Ω · cm or more, preferably 10 ¹⁰ Ω · cm or more is used.

Examples of such a material having electrical insulation and flexibility include synthetic resins such as polyimide, polyester, polycarbonate, polyphenylene sulfide, ethylene-vinyl acetate copolymer, and polymethylmethacrylate. These may be a single resin film, a blended resin film, or a laminated film. Among these materials, the polyester film is preferable in consideration of temperature changeability, dimensional stability against external force, adhesion to the conductive pattern ink and adhesive, and the like. The thickness of the base film is 3 to 100 μm, preferably 5 to 50 μm in consideration of its flexibility and heat conductivity.
More preferably, it is 10 to 30 μm.

It is important that the polymer contained in the coating layer provided on the base film used for forming the electric circuit connecting member of the present invention and in the conductive paste contains a functional group in the molecule. . Examples of such functional groups include unsaturated hydrocarbon groups such as vinyl groups, fluorinated carbon groups, halogen groups, halogenated sulfur oxide groups, carboxyl groups, organic acid anhydride groups, ester groups, hydroxyl groups, methylol groups, and sulfurized groups. Examples thereof include a hydrogen group, a cyano group, an isocyanate group, an amino group, an epoxy group and a silanol group. These functional groups may be present in the linear chain of the polymer, or may be present in the side chains or as terminal groups.

Examples of the polymer having a skeleton having these functional groups include vinyl chloride resins, vinyl acetate resins, vinyl chloride-vinyl acetate copolymers, styrene resins, acrylic resins, polyesters, polyurethanes,
Polybutadiene, polyvinyl alcohol, polyvinyl butyral, polycarbonate, polyamide, polyimide, epoxy resin, alkyd resin, phenol resin,
Examples thereof include unsaturated polyester, isoprene rubber, butadiene rubber, butyl rubber, styrene-butadiene rubber, and butadiene acrylonitrile rubber.

When the coating layer according to the first aspect of the present invention described in claim 1 is used, it is preferable to select the same type in consideration of the adhesion to the base film. If polyethylene terephthalate, which is one of the polyester resins, is used, the coat layer is preferably a polyester resin as a main component and a blend of a polymer having the above functional group,
Alternatively, it is desirable that the skeleton is a polyester as a polymer having a functional group.

In the conductive paste in the first invention or in the coat layer in the second invention described in claim 2, a reactivity capable of reacting with the functional group in the polymer and binding. It is necessary to include a polymer or compound having a group. Such reactive groups include, for example, nitrile group, mercapto group, carboxyl group, epoxy group, amino group, hydroxyl group, halogen group, ester group, isocyanate group, methylol group, sulfone group, chlorosulfone group, nitrile group and A diazo group etc. are illustrated. These reactive groups may be bonded to the linear chain of the polymer, or may be bonded to the terminal or side chain, and those having these reactive groups are not only polymers but also low molecular weight compounds. It may be.

Among these combinations of functional groups and reactive groups, the pot life during work is long, the reaction in the drying step during the formation of the conductive pattern is possible, and the flexibility after reaction / bonding is good. Considering this, it is most preferable to combine an isocyanate group as one functional group and a group having active hydrogen such as a carboxy group, a hydroxyl group, a methylol group, an amino group and a silanol group as the other reactive group.

In these coat layers and conductive paste,
In any case, additives such as a curing accelerator such as a catalyst, a leveling agent, a dispersion stabilizer, a defoaming agent, a thixotropic agent, a metal deactivator, and a heat resistance improving filler may be appropriately added as necessary. it can.

The molar concentration of these functional groups and reactive groups with respect to the volume in the coating layer and the conductive paste is such that the reaction is established on each surface, and the remains of unreacted groups adversely affect the change with time. Since it is possible that the concentration is equal, it is desirable that the concentration is too low, and if the concentration is too low, the probability that the reactive group reacts with the functional group will decrease, which will not lead to improvement in adhesion, and conversely if the concentration is too high, flexibility will be increased. Causing a decline,
When the functional group or reactive group has self-crosslinking property, the pot life becomes short, so the concentration is usually 0.01 to 10 m.
A range of ol / liter is adopted. The preferred concentration is 0.1 to 5 mol / liter.

As a method for forming the coat layer on the surface of the base film, a conventionally known method can be applied, and the polymer-containing component to be the solution-coated coat layer is
For example, a uniform coating layer can be formed by a printing method such as screen printing or gravure printing, a coating method such as roll coating, bar coating, knife coating, spray coating or spin coating, or a dipping method.

Since the chemical bond based on the reaction with the functional group or reactive group contained in the conductive paste is mainly performed on the surface of the coat layer, the thickness of the coat layer is not particularly limited, but it is too thin. It is not preferable because defects such as pinholes are likely to occur. Further, if it is too thick, problems such as loss of material, lengthening of drying process, loss of flexibility and occurrence of unevenness are likely to occur, which is industrially disadvantageous. Usually, the thickness of the coat layer is preferably about 0.3 to 50 μm, preferably 1.0 to 20 μm.

Further, it is desirable to make the surface of the coat layer rough in order to improve the adhesiveness by the physical anchor effect and to substantially increase the reaction area by increasing the bonding area, but if it is too rough, Since it hinders the formation of a fine conductive pattern, it is usually desirable that the average roughness is 1/10 or less of the desired conductive pattern interval, and about 1/3 or less is practically more preferable.

The formation of the conductive pattern with the conductive paste can be carried out by a known method such as screen printing or gravure printing. As the anisotropic conductive adhesive member, an anisotropic conductive adhesive in which conductive particles are dispersed in an insulating adhesive is used, or in the conductive pattern, so that a part thereof protrudes to the conductive pattern surface. An example is one in which conductive particles are arranged and an insulating adhesive layer is provided thereon. The formation of these anisotropically conductive adhesives is achieved by a printing method, a coating method or the like.

As a method of disposing the conductive particles in the conductive pattern, a method of previously dispersing the conductive particles in a conductive paste or printing a conductive pattern and sprinkling the conductive particles before drying the conductive pattern Examples include a method of drying the pattern and fixing conductive particles on the conductive pattern to remove excess conductive particles.

The insulating adhesive may be a thermoplastic resin or a thermosetting resin as long as it exhibits adhesiveness when heated, or may be a blend of these. Thermoplastic resins have the characteristic that they can be bonded at a relatively low temperature in a short time and have a long pot life, and that thermosetting resins have large adhesive strength and excellent heat resistance. . These are appropriately selected depending on the purpose of use, target and desired performance.

As the thermoplastic resin, polyamide type, polyester type, ionomer type, EVA, EA
Examples include polyolefin resins such as A, EMA, EEA, various synthetic rubber resins, and modified products and composites thereof. Examples of the thermosetting resin include combinations of epoxy resin-based, urethane-based, acrylic-based, silicone-based, chloroprene-based, nitrile-based synthetic rubbers and a curing agent or a vulcanizing agent. A control agent, a deterioration preventing agent, a heat resistance additive, a thermal conductivity improver, a tackifier, a softening agent, a coloring agent and the like can be appropriately added to and mixed with the adhesive.

Examples of the solvent for dissolving these resins include ester solvents such as methyl acetate, ethyl acetate, isopropyl acetate, isobutyl acetate, butyl acetate and amyl acetate, methyl ethyl ketone, methyl isobutyl ketone and methyl isoamyl ketone. , Methyl amyl ketone, ethyl amyl ketone, isobutyl ketone, methoxymethylpentanone, cyclohexanone, ketone solvents such as diacetone alcohol, methyl cellosolve acetate,
Ethyl acetate cellosolve, butyl cellosolve acetate, methoxybutyl acetate, methyl carbitol acetate, ethyl carbitol acetate, ether ester solvents such as dibutyl carbitol acetate, trichloroethane, chlorinated hydrocarbon solvents such as trichloroethylene, n-butyl ether, Ether solvents such as diisoamyl ether, n-butyl phenyl ether, propylene oxide and furfural, alcohol solvents such as isopropyl alcohol, isobutyl alcohol, amyl alcohol and cyclohexanol, benzene, toluene, xylene,
Hydrocarbon-based solvents such as isopropylbenzene, petroleum spirit, and petroleum naphtha are mentioned.

As the conductive particles for imparting anisotropic conductivity. Metal particles of gold, silver, copper, nickel, palladium, stainless steel, brass, solder, etc., ceramic particles of tungsten carbide, silica carbide, etc., carbon particles, and plastic particles having their surfaces coated with metal are used. These particle sizes are determined in consideration of the connection stability and reliability, the allowable limit of peel strength, etc. in consideration of the coating thickness of the insulating adhesive, the connection pitch of the conductive lines, etc. Of 5 to 150 μm is used. Further, this shape is not particularly limited, and a spherical shape, a needle shape, a scale shape, a plate shape, a dendritic shape, a dice shape, a protruding spherical shape, an indefinite shape or a combination of these is used, and the like. The optimum one is selected in consideration of stability and reliability.

When this is used by dispersing it in an insulating adhesive, if the blending amount of the conductive particles is too small, the particles do not exist in the shape of the electrode terminals to be connected, resulting in disconnection and high resistance. If the amount is too large, the anisotropic conductivity will be stochastically connected in the plane direction and the anisotropic conductivity will be impaired. Therefore, the conductive particles are usually used in the range of 0.1 to 30 parts by volume per 100 parts by volume of the adhesive resin component. However, the preferred range amount is 1 to
15 parts by volume.

When the conductive particles are fixed on the conductive pattern, in order to obtain a stable connection, the number of particles is 20 or more, preferably 50 or more per 1 mm ² of the conductive pattern of the connecting portion. However,
As described above, when particles having a large particle size are mixed in the conductive paste, there is a problem in printability during formation of the conductive line, which is not preferable. It is necessary to appropriately determine the number of particles in consideration of both printability.

[0027]

As described above, in the present invention, the polymer having the functional group contained in the coat layer on the base film and the conductive paste in the molecule, and the reactive group capable of reacting with the functional group to be bonded. The adhesive strength between the conductive pattern and the base film is increased by the chemical bond between the polymer or the compound having, which may cause a handling or inspection process after connecting the electric circuit, or a drop or vibration after the product becomes a product. A force in the peeling direction is applied to the connection portion, and even if a slight peeling occurs, the conductive pattern is held on the base film, and the effect of preventing disconnection is provided.

[0028]

Examples Example 1 (1) Preparation of coating agent 100 parts by weight of unsaturated polyester having 1 mol / liter unsaturated hydrocarbon group in the molecular chain and 0.5 mol / liter of methylol group at the end were contained. 20 parts by weight of polytetramethylene ether glycol were dissolved in a mixed solvent of toluene: methyl ethyl ketone of 8: 2 to prepare a 30% by weight coating agent solution.

(2) Production of conductive paste 100 parts by weight of modified saturated polyester having 0.5 mol / liter of methylol groups at the end and an average particle size of 0.2 μm
1,000 parts by weight of scaly silver powder of carbitol 4
After dissolving and dispersing in 100 parts by weight, 12 parts by weight of a linear organic compound having an isocyanate group of 3.1 mol / liter as an end was added and stirred to prepare a uniform conductive paste.

(3) Manufacture of electrical circuit connecting member One side of a 25 μm-thick PET polyethylene terephthalate base film is coated with the coating agent prepared in the above (1) using a knife coater and dried to a thickness of 5 μm.
Was formed. On top of this, the conductor width of 0.
A conductive pattern with a pitch of 15 mm and a pitch of 0.3 mm is formed, and the solvent is removed by drying in an infrared (IR) furnace at 140 ° C. for 3 minutes to dry, and a straight chain having an isocyanate group of the modified saturated polyester in the conductive paste as a terminal is formed. Crosslinking with an organic compound and binding reaction between the residual isocyanate group and the coat layer were performed.

On top of this, anisotropic thermal conductivity was obtained by dispersing 5 parts by volume of dice-shaped carbon conductive particles having an average particle size of 25 μm in 100 parts by volume of the adhesive resin component in a polyester thermal adhesive. The conductive adhesive was screen-printed to a thickness of 25 μm to form an anisotropic conductive adhesive layer as an anisotropic conductive adhesive member. This was sized so that the number of patterns was 240 and the length in the longitudinal direction of the pattern was 35 mm to obtain an electric circuit connecting member of the present invention.

Evaluation Using the electric circuit connecting member manufactured in Example 1, a PCB with an LCD and a driver IC having a connecting electrode pitch of 0.3 mm was mounted at a temperature of 140 ° C. and a pressure of 30 kg / cm ² .
It was confirmed that the display was normal at the initial stage after heat sealing for 0 seconds and connection. This electrical circuit connecting member is LC
Fix it almost horizontally with the D connection side down,
gf) was suspended almost vertically. Then, the LCD side was vibrated for 1 minute at an amplitude of 10 mm and a frequency of 5 times / second, and the display state of the LCD was confirmed.
All of the 10 vehicles investigated displayed normally.

[0033]

As is apparent from the above-described embodiments, the one in which an electric circuit is connected by using the electric circuit connecting member of the present invention is used in various usage environments such as subsequent steps, dropping after product shipment, and vibration. Even if a force in the peeling direction is applied to the connection portion, no wire breakage occurs. Therefore, the product yield is high and it is not necessary to pay special attention to the work. Therefore, work efficiency is improved and productivity is improved.

Claims (3)

[Claims] 1. A coating layer containing a polymer having a functional group in its molecule is provided on a flexible base film, and a coating layer is reacted with the functional group of the polymer to form a chemical bond. An electric circuit pattern is formed by a conductive paste containing a polymer or a compound having a reactive group capable of forming an electric circuit pattern, and an anisotropic conductive adhesive member is provided at a connection portion of the electric circuit pattern with another electric circuit. Circuit connection member. 2. An electric circuit pattern made of a conductive paste containing a polymer having a functional group in a molecule on a flexible base film, which reacts with the functional group of the polymer to form a chemical bond. Formed through a coat layer containing a polymer or compound having a reactive group capable of,
An electric circuit connecting member, wherein an anisotropic conductive adhesive member is provided at a connection portion of the electric circuit pattern with another electric circuit. 3. The electric circuit connecting member according to claim 1, wherein the functional group is an isocyanate group, and the reactive group is a group having active hydrogen.