JPH0869850A - Manufacture of thermocompression bonding connecting member - Google Patents

Abstract

PURPOSE: To improve adhesion between insulating particulates and conductive paste, and keep excellent electric connection by mixing the insulating particulates in the conductive paste after an electric conductivity imparting agent is stuck to surfaces of the insulating particulates, and forming a desired pattern on a surface of a connectable flexible base material. CONSTITUTION: A thermocompression bonding connecting member is composed of an insulating flexible base material 1, insulating particulates 2, an electric conductivity applying agent 2b, conductive paste 3 and an insulating adhesive layer 4. The manufacturing method is characterized in that after the electric conductivity applying agent 2b to be used in the conductive paste 3 is stuck to surfaces of the insulating particulates 2, the particulates 2 are dispersed and mixed in the paste 3, and a desired pattern is formed on a single surface or both surfaces of the base material 1, and the insulating adhesive layer 4 is arranged at least in a connecting terminal part. Resin powder by plating Ag, Cu, Au, Ni, Pd and the alloy having an outside diameter of 0.1 to 10μm, carbon black or the like can be used as the electric conductivity imparting agent 2b. The electric conductivity imparting agent 2b is dispersed and blended at a rate of 10 to 90wt.%, in an organic binder.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a liquid crystal display (LC
D), electroluminescence (EL), light-emitting diode (LED), electrochromic display (ECD), plasma display, etc. The connection terminals of the display body and the circuit board on which the drive part is mounted or the boards of various electric circuits are connected. The present invention relates to a thermocompression-bondable connecting member.

[0002]

2. Description of the Related Art Conventionally, thermocompression bonding members are LCDs,
It is used for connecting display devices such as EL, LED, ECD, and plasma displays to PCBs (hard printed wiring boards) and FPCs (flexible printed circuit boards), or between PCBs and FPCs. As shown in FIG. 2, the thermocompression-bonding connection member is formed by forming a desired pattern b on an insulating flexible base material a with a conductive paste, and forming conductive fine particles c on the insulating paste with an insulating adhesive. It is known that an anisotropic conductive adhesive layer formed by dispersing d is provided (Japanese Examined Patent Publication No. 55).
-38073, Japanese Patent Publication No. 58-56996, etc.) However, with the recent miniaturization and refinement of electrical and electronic equipment, the pitch of connection terminals required for thermocompression bonding members is in the 0.3 mm range.
It has been miniaturized to 2 mm level. In such a case, in the type in which the conductive fine particles c are dispersed in the insulating adhesive d, a short circuit easily occurs between the patterns b due to the conductive fine particles c.
It has been proposed that a desired pattern is formed on an insulating flexible base material with a conductive paste in which conductive fine particles are dispersed and mixed, and an insulating adhesive is provided on the conductive paste (Japanese Patent Publication No. 62-62- No. 500828, JP-A-62-154746, etc.). In each of the above-described conventional configurations, as shown in FIG. 3, the conductivity for electrically connecting the pattern b made of the conductive paste provided on the insulating flexible base material a and the connection terminal such as ITO. The presence of the conductive fine particles c separate from the conductivity imparting agent in the paste was essential. In the figure, d is an insulating adhesive layer. Conductive particles include Au, Ag, Pt
Noble metal fine particles such as Ni, Al, Fe and other fine metal particles,
Further, those having a core thereof and plated with a noble metal on the surface thereof, and those having high hardness such as carbon black, graphite powder, and carbon fiber are used.

However, such conductive fine particles cannot easily follow the deformation and flow variation of the insulating flexible base material, the conductive paste and the insulating adhesive layer due to heating and pressure during thermocompression bonding. Under various environments after connection, the conductive fine particles move microscopically under the residual stress of the insulating flexible base material, the conductive paste, and the insulating adhesive layer, causing partial conduction failure and high conductivity. There is a risk that resistance may be changed and seriously adversely affect the reliability of electrical continuity. Further, in order to avoid the above danger, conductive fine particles having a core of a low hardness insulating plastic elastic body and plated with a precious metal on the surface thereof have been proposed. Due to the hardness difference between the noble metal and the insulating plastic elastic body when pressure is applied, minute cracks are generated on the surface, and the elastic surface of the insulating plastic to which electrolytes and ions are attached is exposed during plating. There was also a risk of electric contact. Further, since the precious metal is used, the manufacturing cost is high and there is a problem in mass production.

[0004]

Therefore, in order to solve the above-mentioned conventional problems, the present inventor has developed conductive fine particles for performing the electrical connection between the connection terminal and the pattern, which has been indispensable until now. A thermocompression-bonding connecting member for connecting insulating particles by mixing insulating particles in the conductive paste, projecting a film of the conductive paste coating the insulating particles, and directly connecting the connection terminals to each other without using them separately. I proposed earlier. The present invention has solved all the above-mentioned conventional problems. That is, since the conductive fine particles are not used, no short circuit occurs between the patterns and no electrolytic corrosion occurs. Since no precious metal is used, it can be manufactured at low cost, and since the pattern directly connects the terminals, it has excellent reliability. However, according to the present invention, as the insulating fine particles, inorganic materials such as glass, talc, silica, ceramics, polymethylmethacrylate, polyamide, polystyrene, benzoguanamine, phenol, epoxy, aramid, acrylonitrile-butadiene rubber (NBR), chloroprene rubber are used. (CR) Silicon
Organic substances such as rubber (SR) are used. Among these, the adhesiveness of the conductive paste mixed with these to the organic binder or conductivity-imparting agent is poor, and the surface of the insulating fine particles is Some are not covered, it is difficult to select the material by judging compatibility with the conductive paste, and the elastic properties of the selected material may be different from the desired one. Inevitably, it is necessary to use insulating fine particles that are limited to the above.In addition, even in such carefully selected materials, due to the poor adhesion between the conductive paste and the insulating fine particles and the difference in elastic properties, the insulating properties The fine particles broke through the film of the conductive paste and the insulating fine particles fell off, resulting in problems such as not being able to obtain good electrical connection. The object of the present invention is to improve the adhesion between the insulating fine particles and the conductive paste, to enable the use of any material as the insulating fine particles, to arbitrarily select the elastic characteristics, and to make the insulating fine particles conductive when thermocompression bonding is performed. Provided is a method for producing a thermocompression-bonding connecting member capable of maintaining good electrical connection without breaking through a film of a conductive paste or dropping insulating fine particles.

[0005]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventor has found that if a conductivity-imparting agent contained in a conductive paste is attached to the surface of insulating fine particles in advance and mixed, It was found that the adhesion between the fine particles and the conductive paste was improved, the selectivity of the insulating fine particle material was lost, the selection range of the elastic characteristics was widened, and good electrical connection stability was obtained, and the present invention was achieved. did. That is, in the method for producing a thermocompression-bonding connecting member according to the present invention, after the conductivity-imparting agent used in the conductive paste is attached to the surface of the insulating fine particles, the insulating fine particles are dispersed and mixed in the conductive paste. Then, a desired pattern is formed on one surface or both surfaces of the insulating flexible base material, and the insulating adhesive is provided on at least the connection terminal portion thereof. In the present invention, “insulating” means that the volume resistivity exceeds 10 ⁶ Ω · cm, and “conductive” means that it is 10 ⁶ Ω · cm or less. FIG. 1 is a longitudinal sectional view showing an example of a thermocompression bonding member obtained by the manufacturing method of the present invention.
Reference numeral 1 is an insulating flexible base material, 2a is insulating fine particles, 2b is a conductivity imparting agent, 3 is a conductive paste, and 4 is an insulating adhesive layer.

The conductivity-imparting agents used in this conductive paste include Ag, A, such as spherical, granular, scale-like, plate-like, dendritic, dice-like, sponge-like particles having an outer diameter of 0.1 to 10 μm.
g Plating Cu, Cu, Au, Ni, Pd, and alloys thereof, resin powder plated with one or more of these, carbon black such as furnace black and channel black, and one or two of graphite powder The above may be selected appropriately, and they are dispersed and blended at a ratio of 10 to 90% by weight with respect to the organic binder described later. For the insulating organic binder in which the conductivity-imparting agent is dispersed, a resin composition such as a thermoflexible and thermosetting resin is used, but it has heat resistance, and particularly, it can withstand heating and pressure during connection. It is preferable to use a thermosetting resin in order to obtain the resin. Further, if necessary, a curing accelerator, a leveling agent, a dispersion stabilizer, an antifoaming agent, a thixotropic agent, etc. may be added thereto.

The shape of the insulating fine particles to be mixed with the conductive paste after the conductivity-imparting agent is adhered may be spherical, granular, scale-like, plate-like, dendritic, dice-like, sponge-like or the like. It is selected appropriately, but in order to obtain a more stable electrical connection in the pressed state, a shape in which the conductive pattern is in contact with the connecting terminal opposite thereto at multiple points, for example, a sponge shape, a dendritic shape, etc. Is more preferable. Further, the insulating fine particles cannot be used if they are easily dissolved in the organic solvent in the conductive paste, and those that easily absorb the organic solvent and cause expansion are also not preferable. Furthermore, it is desirable that the insulating fine particles have heat resistance that does not easily melt when thermocompression-bonded at 80 to 200 ° C. When this is used as a resin, the melting point is 80 ° C or higher, preferably 120 ° C. The above is better. Therefore, the insulating fine particles include, for example, polystyrene-based, polyimide-based, polyacrylic-based, polyester-based, polyurethane-based, polyamide-based, phenol-based, epoxy-based, polyolefin-based, polyvinyl-based resins, copolymers thereof, and the like. These elastomer resins, synthetic rubbers such as isoprene-based and butadiene-based rubbers, and the like, and the inorganic substances include glass, talc, silica, ceramics, and the like.

Examples of the method of attaching the conductivity-imparting agent to the surface of the insulating fine particles include a method using physical means such as pressure and impact force, a method using chemical means such as an organic binder, and the like. As the physical means, for example, a known stirrer such as a mixer or a mill is used, or a particle surface modification device (see JP-A-62-83029, etc.) is used,
It is possible to fix the mixture of the insulating fine particles and the conductivity-imparting agent by applying pressure and shear between the hard plates. As a chemical means, for example, an organic polymer compound such as a resin is dissolved or melted to coat the surface of the insulating fine particles, a conductivity-imparting agent is attached using this as a binder, and then the organic polymer compound is crosslinked and cured. Any method can be used. When using a mixer or a mill, for example, the insulating fine particles and the conductivity-imparting agent are put into a container such as a ball mill, and the mixture is stirred for several to several tens of hours. A conductivity-imparting agent is attached to the surface of the fine particles. Although this method has some weak adhesion, it can be used as a simple method. The particle surface modification device has been developed in recent years.
Although the device becomes a little complicated, it has an advantage that it has a strong adhesive force and can perform the adhesion treatment in a short time.

When an electrically conductive agent is adhered to the surface of the insulating fine particles by using an organic polymer substance such as resin as a binder, the binder component is mixed with the solvent in the electrically conductive paste when it is mixed with the electrically conductive paste later. Since it does not dissolve, it is preferable to use one that can be chemically hardened and cross-linked. For example, resins such as urethane, epoxy, polyester, polyethylene, amino, vinyl, acrylic, natural rubber, chloroprene, silicone, etc. Synthetic rubber can be used and the surface of the insulating fine particles may be coated with a conductivity-imparting agent, or the insulating particles may be added to a mixture of these and the conductivity-imparting agent in advance. You may make it adhere. When the insulating fine particles thus formed are dispersed and mixed in a conductive paste to form a conductive pattern, screen printing is used to obtain a thickness enough to bury the insulating fine particles in one printing. Optimum is that the insulating fine particles buried and fixed in the conductive pattern formed by this method have 20 or more particles per 1 mm ² of the connection terminal portion of the conductive pattern in order to obtain a stable connection state. It is preferable that the number is 50 or more. If the number of particles is less than 20, there are few particles when this is thermocompression bonded,
Alternatively, particles may not be present in the thermocompression bonded portion, and in the case of a low pitch, a stable connected state cannot be obtained. Also, if the number of particles is excessively large, when this is provided by screen printing, particles may cause plate clogging, or the volume resistivity of the conductive paste may decrease, and a stable resistance value may not be obtained. . Therefore, it is desirable that the number of parts of the insulating fine particles dispersed and mixed in the conductive paste is 5 to 90 parts by volume.

The screen material used for the screen printing is a plain weave or twill weave of an iron alloy such as stainless steel having a wire diameter of 10 to 40 μm, and an electroforming plate formed in a grid pattern by nickel plating or the like is stretched on a rigid frame. Generally used to form a fine pattern, the opening of the mask material such as acrylic, that is, the opening approximately equal to the shape of the desired pattern is made thin so that the wire or the intersection of the wire is not blocked. However, the thickness (Ts) is inevitably thin, but the thickness of the conductive paste is T.
The ratio of the aperture ratio (φ) to s is preferably 0.8 or more, more preferably 1.5 or more. For that purpose, it is necessary to increase the strength of the wire rod and reduce the wire diameter without reducing the strength of the gauze or plate. Therefore, φ is preferably 35% or more, and more preferably 60% or more. As another screen material, a screen called a metal mask in which a thin nickel foil or the like is electrolytically laminated on a metal mesh such as stainless steel and a pattern is formed by etching may be used, but when performing low-pitch printing. In terms of dimensional stability, it is necessary to use a material whose strength is not easily deformed by squeegeeing during printing, and printing requires great care.

The particle size (r) of the insulating fine particles dispersed and blended in the conductive paste to be screen-printed is the line width Tc and thickness (t) of the pattern, and the length of one side of the grid-like openings of the printing plate. S (l), and That is, if r is too small with respect to t, it becomes difficult to form the protrusion and the stability of the connection deteriorates. Therefore, r ≧ (1/3)
t, preferably r ≧ t, and when r is larger than Tc and l, it becomes physically difficult to form a pattern, and a plate jam occurs during printing. Therefore, r <Tc,
It is preferable that r <l, preferably r <(1/2) Tc. That is, it is necessary that (1/3) t ≦ r ≦ l. Generally, the thickness (t) of the conductive pattern is 5 to 30 μm
The length (1) of one side of the grid-like openings of the printing plate varies depending on the screen mesh. When forming a fine conductive pattern of 0.4 mm pitch or less, 250 mesh or more up to about 500 mesh. Is often used, and l at this time is about 25 μm to 70 μm,
The particle size (r) of the insulating fine particles is 5 to 70 μm, preferably 20
It is optimal to select appropriately from the range of up to 50 μm. Furthermore, the coefficient of variation of the particle size distribution of the insulating fine particles must be 80% or less in order to obtain a screen printability and a stable connection state during continuous printing. If the coefficient of variation exceeds 80%, particles with a size that does not pass through the mesh will remain on the plate during screen printing, causing plate clogging and the formation of an electrically connected conductive pattern, or thermocompression bonding connection members. In such a case, the height of the protruding portion of the conductive pattern after thermocompression bonding may be different, and the connection state may be sparse, so that stable connection may not be obtained.

It is necessary to provide an insulating adhesive layer in order to firmly fix a desired pattern formed on an insulating flexible base material using these conductive paste and insulating fine particles to the opposing connecting terminal. . The insulating adhesive layer may be either thermoflexible or thermosetting as long as it exhibits adhesiveness by heating, but thermoflexible ones are heated at a relatively low temperature for a short time. Since they adhere to each other and have a long pot life, and thermosetting ones have high adhesive strength and excellent heat resistance, these may be appropriately selected according to the purpose of use. The main component of this insulating adhesive is ethylene-vinyl acetate copolymer, carboxyl-modified ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-isobutyl acrylate copolymer. Coalesced, polyamide, polyester, polymethylmethacrylate, polyvinylether,
Polyvinyl butyral, polyurethane, styrene-butylene-styrene (SBS) copolymer, carboxyl-modified SBS copolymer, styrene-isoprene-styrene (S
IS) copolymer, styrene-ethylene-butylene-styrene (SEBS) copolymer, maleic acid-modified SEBS copolymer, polybutadiene rubber, chloroprene rubber (C
R), carboxyl-modified CR, styrene-butadiene rubber, isoptylene-isoprene copolymer, acrylonitrile-butadiene rubber (NBR), carboxyl-modified N
It is obtained by one kind or a combination of two or more kinds selected from BR, epoxy resin, silicone rubber (SR) and the like.

As the tackifier, rosin,
Rosin derivative, terpene resin, terpene-phenol copolymer, petroleum resin, coumarone-indene resin, styrene resin, isoprene resin, alkylphenol resin,
One kind or two or more kinds such as a phenol resin is appropriately added. Further, a reactive auxiliary agent, a phenol resin as a crosslinking agent, polyols, isocyanates, melamine resin,
Urea resin, urotropins, amines, acid anhydrides, peroxides, metal oxides, organic acid metal salts such as chromium trifluoroacetate, alkoxides of titanium, zirconia, aluminum, etc., organometallic compounds such as dibutyltin oxide, etc. ,
Photoinitiators such as 2.2-diethoxyacetophenone and benzine, sensitizers such as amines, phosphorus compounds and chlorine compounds, etc. may be appropriately selected and used as necessary. Further, a curing agent, a vulcanizing agent, a control agent, a deterioration preventing agent, a heat resistance additive, a thermal conductivity improver, a softening agent, a colorant, various coupling agents, a metal deactivator, etc. may be appropriately added to these. .

As a solvent for dissolving these, ester-based, ketone-based, ether ester-based, chlorine-based, ether-based, alcohol-based, hydrocarbon-based solvents such as methyl acetate, ethyl acetate, isopropyl acetate, isobutyl acetate are used. , Butyl acetate, amyl acetate, methyl ethyl ketone, methyl isobutyl ketone, methyl isoamyl ketone, methyl amyl ketone, ethyl amyl ketone, isobutyl ketone, methoxymethylpentanone, cyclohexanone, diacetone alcohol, methyl cellosolve acetate, ethyl cellosolve acetate, acetic acid Butyl cellosolve, methoxybutyl acetate, methyl carbitol acetate, ethyl carbitol acetate, dibutyl carbitol acetate, trichloroethane, trichloroethylene, n-butyl ether, diisoamyl ether, n-bu Ruphenyl ether, propylene oxide, furfural, isopropyl alcohol, isobutyl alcohol, amyl alcohol, cyclohexanol, benzene, toluene, xylene, isopropylbenzene, petroleum spirit, petroleum naphtha, etc., but ester-based, ketone-based, ether Ester type is often used.

Examples of the insulating flexible base material of the thermocompression bonding member to which the present invention is applied include polyimide, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polycarbonate, polyphenylene sulfide, poly-1,4-cyclohexane. A polymer film having a heat resistance of 10 to 50 μm selected from dimethylene terephthalate, polyarylate, liquid crystal polymer and the like is used, and insulating fine particles to which the conductivity-imparting agent is previously attached are dispersed and blended thereon. Conductive paste,
After forming a desired pattern by screen printing, the insulating adhesive is applied to at least the connecting terminal portion by a conventionally known method, that is, roll coating, bar coating, knife coating, spray coating,
It is provided using a method such as screen printing or gravure printing.

[0016]

According to the method for producing a thermocompression-bonding connecting member of the present invention, in order to attach the conductivity-imparting agent contained in the conductive paste to the surface of the insulating fine particles and mix it with the conductive paste, It has good dispersibility in the conductive paste, does not break through the film of the conductive paste by using any particles, has excellent adhesion, breaks through the conductive pattern film during thermocompression bonding, insulating fine particles A thermocompression-bondable connecting member that does not fall off can be obtained. As a result, the material selection range for the insulating fine particles is widened, and it is possible to select a material having higher reliability of electrical connection or a cheaper material.

[0017]

EXAMPLES Specific embodiments of the present invention will now be described with reference to examples. (1) Adhesion of Conductivity-Giving Agent to Various Insulating Fine Particles The following three types of insulating fine particles were used, and Ketjen Black EC (Lion Agzo Co., trade name) was used as a conductivity-imparting agent for surface modification. Equipment: Mixing with a high-prediction system NHS-0 (trade name, manufactured by Nara Machinery Co., Ltd.),
A conductivity-imparting agent was attached to the surface of the insulating fine particles. Sponge-like nylon resin fine particles with an average particle size of 40 μm, particle size distribution variation coefficient of 7%. Average particle size 40μm, particle size distribution variation coefficient 7%, spherical SB
R fine particles. Spherical acrylic resin fine particles with an average particle size of 40 μm, particle size distribution variation coefficient of 7%. (2) Preparation of various conductive pastes As an organic binder, molecular weight 20,000 to 25,000, hydroxyl value 6.0KOHmg / g, acid value 0.1KOHmg / g, solubility parameter
Using a mixture of blocked isocyanates obtained by blocking the saturated copolymerized polyester resin of 9.2 and the biuret trimer of hexamethylene diisocyanate with methyl ethyl ketoxime, Ketjen Black EC, graphite as a conductivity-imparting agent, a leveling agent and a dispersion stabilizer. After adding 1 part by weight each of a defoaming agent and a thixotropic agent and dissolving them in ethyl carbitol acetate, 45 parts by volume of each of the insulating fine particles prepared in (1) above was added to prepare 3 kinds of conductive pastes. did.

(3) Preparation of Insulating Adhesive Solution For each 100 parts by weight of carboxyl-modified NBR, 40 parts by weight of an alkylphenol tackifier, 1 part by weight of a deterioration inhibitor, a heat-resistant additive, and 1 part by weight of an amine silane coupling agent. Each part was added and dissolved in a mixed solvent of petroleum naphtha: butyl carbitol = 1: 1 to prepare a 35 wt% insulating adhesive solution. (4) Manufacture of thermocompression-bondable connecting member Next, various conductive pastes prepared in (2) above were coated on an insulating flexible substrate made of a PET film having a thickness of 25 μm with a screen wire diameter of 30 μm and a gauze. A 0.6 mm pitch pattern was formed using a stainless screen plate having a thickness of 60 μm, the length of one side of the opening (1) 71 μm, and an aperture ratio of 50%. Next, the insulating adhesive prepared in (3) above is applied to the entire surface by a bar coater so that the thickness after removing the solvent is 15 μm, and dried to form an insulating adhesive layer, A thermocompression-bonding connecting member was obtained by cutting into a desired size. The thermocompression-bonding connecting member thus obtained was connected to a transparent conductive oxide film substrate (ITO) connecting terminal having an area resistivity of 30Ω at 130 ° C., 20 kg / cm ² , 9
Thermal compression test under the condition of second, thermal shock test (85 ℃, 30 minutes and −30
The relationship between the standing time after the test piece was repeatedly performed at 30 ° C. for 30 minutes and the change in the resistance value between both connection terminals (unit: Ω) was measured, and the results are shown in Table 1.

[0019]

[Table 1]

[0020]

According to the method for manufacturing a thermocompression-bonding connecting member of the present invention, even if various insulating fine particles are used, the conductive paste film is not breached, so that the degree of freedom in selecting insulating fine particles is increased. It is cheaper and you can freely select one with high electrical connection reliability, there is no detachment of insulating fine particles during thermocompression bonding, and the protruding parts of the conductive paste can be securely connected to the opposing connection terminals The reliability of electrical continuity can be improved even under severe conditions such as outdoors, in a car, and underwater.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an example of a thermocompression bonding connecting member obtained by a manufacturing method of the present invention.

FIG. 2 is a vertical cross-sectional view showing an example of a thermocompression bonding connection member obtained by a conventional method.

FIG. 3 is a vertical cross-sectional view showing another example of the thermocompression-bonding connection member obtained by a conventional method.

[Explanation of symbols]

a, 1 ... Insulating flexible base material, c, 2a ...
Insulating fine particles, 2b ... Conductivity imparting agent,
3 ... Conductive paste, d, 4 ... Insulating adhesive layer, b ... Pattern.

Claims (1)

[Claims] 1. A conductive agent used in a conductive paste is adhered to the surface of insulating fine particles, and the insulating fine particles are mixed with the conductive paste to form one side of an insulating flexible substrate. A method for producing a thermocompression-bonding connecting member, which comprises forming a desired pattern on both surfaces and providing an insulating adhesive on at least the connecting terminal portion thereof.