JPH0685336B2 - Thermocompression bonding member and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermocompression-bonding connecting member, and more particularly to a liquid crystal display (LCD), an electroluminescence (EL), an emitting diode (LED), an electrochromic display (ECD), a display such as a plasma display. The present invention relates to a thermocompression-bonding connecting member used for connecting between a connection terminal and a circuit board on which a driving part thereof is mounted, or a board of various electric circuits, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a display device such as an LCD, EL, LED, ECD, or plasma display is connected to a hard printed wiring board (PCB) or a flexible printed circuit board (FPC), or between a PCB or an FPC. Thermocompression-bondable connecting members are used. As the thermocompression-bonding connecting member, as shown in FIG. 3, a desired pattern 13 is formed on the insulating flexible base material 11 with a conductive paste, and the conductive fine particles 12 are insulating-bonded thereon. It is known that an anisotropic conductive adhesive layer formed by being dispersed in the agent 14 is provided.

However, in recent years, miniaturization of electric and electronic equipment,
With the refinement, the pitch of connecting terminals required for thermo-compression bonding connecting members has been reduced to 0.3 mm and 0.2 mm order. Therefore, the conductive fine particles as described above were dispersed in the insulating adhesive. In the type, since the patterns are easily short-circuited by the conductive fine particles, the conductive paste 18 in which the conductive fine particles 17 are dispersed and mixed on the insulating flexible base material 16 is used as shown in FIG. Form the desired pattern,
It is proposed that an insulating adhesive layer 19 is provided on top of this.

In the conventional thermocompression-bonding connecting members shown in FIGS. 3 and 4, the insulating flexible base material 11,
In order to reliably and electrically connect the pattern made of the conductive pastes 13 and 18 provided in 16 and the connection terminals 15 and 20 made of ITO or the like, conductive fine particles different from the conductivity-imparting agent in the conductive paste are used. The presence of 12 and 17 is indispensable, and as the conductive fine particles, fine particles of precious metals such as Au, Ag and Pt, metal particles such as Ni, Al and Fe, or the surfaces thereof are plated with precious metals. Materials, high hardness carbon black, graphite powder, carbon fiber, etc. are used.

[0005]

However, the conductive fine particles used here are the deformation of the insulating flexible base material, the conductive paste and the insulating adhesive layer due to heating and pressure during thermocompression bonding, It cannot easily follow the amount of flow change, and moves microscopically under the residual stress of the insulating flexible base material, conductive paste and insulating adhesive layer under various environments after connection. Since it partially causes conduction failure and high resistance, it has seriously affected the reliability of electrical connection.

Therefore, there is proposed a conductive fine particle having a low hardness insulating plastic elastic body as a core and a precious metal plating on the surface thereof. At that time, a minute crack is generated on the surface due to the hardness difference between the noble metal and the insulating plastic elastic body, and the surface of the insulating plastic elastic body on which the electrolyte and ions are attached is exposed during plating, and the electrolyte and ions cause Then, there is a problem that electrolytic corrosion occurs, and there is a problem that the manufacturing cost is increased because the precious metal is used.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a thermocompression-bonding connecting member and a method for producing the same, which solves the above disadvantages and problems. The method is characterized in that a desired pattern is formed by a conductive paste mixed with fine insulating fine particles, and an insulating adhesive layer is provided at least on the connection terminal portion of the pattern. The particle size (r) is expressed by the formula (1/3) t ≦ r on at least one surface of the flexible substrate.
≦ L (where t is the thickness of the pattern, and L is the length of one side of the screen opening), a conductive paste mixed with porous insulating fine particles is formed into a desired pattern by screen printing. It is characterized by doing.

That is, the present inventor has conducted various studies to develop a thermocompression-bonding connecting member capable of solving the disadvantages and drawbacks of the conventionally known ones, and as a result, in the electrical connecting structure between various connecting terminals and the pattern, the conductive If you mix porous insulating fine particles with the paste and project the coating of the conductive paste that covers the porous insulating fine particles so that the connecting terminals are in direct contact with each other and connected, a more reliable electrical conduction is achieved. The present invention has been completed by researching the types of materials such as porous insulating fine particles used here and the constitutions by these materials. This will be described in more detail below.

[0009]

The present invention relates to a thermocompression-bonding connecting member, in which a desired pattern is formed on at least one surface of an insulating flexible base material by a conductive paste mixed with porous insulating fine particles. It is characterized in that an insulating adhesive layer is provided on the connection terminal portion of the pattern, but according to this, there is no fear of a short circuit between the connection terminals, and since porous insulating fine particles are used. There is an advantage that the connection terminals of various display bodies and various electric circuit boards can be connected with high reliability without fear of electrolytic corrosion.

In the thermocompression-bonding connecting member of the present invention, a pattern is formed by a conductive paste in which porous insulating fine particles are mixed with an insulating flexible base material, and an insulating adhesive layer is formed on the connecting terminal portion of this pattern. It is provided. The insulating flexible substrate used here is not particularly limited, and examples thereof include polyimide, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate,
Polycarbonate, polyphenylene sulfide, poly-1,4-cyclohexanedimethylene terephthalate,
The thickness selected from polyarylate, liquid crystal polymer, etc.
A polymer film having a heat resistance of 10 to 50 μm may be used.

The conductive paste used here has an organic binder made of a resin composition such as an insulating thermoplastic resin or thermosetting resin.
It is preferably made of a thermosetting resin so that it can withstand heating and pressurization at the time of connection, and if necessary, a curing accelerator, a leveling agent, a dispersion stabilizer, a defoaming agent, a rocking agent. A modifier or the like may be added. In addition, a conductivity-imparting agent is added to the resin composition as the organic binder in order to make it conductive, but the outer diameter is 0.1 to 1
0 micron spherical, granular, scale-like, plate-like, dendritic, dice-like, sponge-like Ag, Ag-plated Cu, Au, N
i, Pd, one of these alloys, resin powder plated with these, carbon black such as furnace black and channel black, and one or two of graphite powder.
More than one kind may be used, and the addition amount of this product to 100 parts by weight of the resin composition may be 10 to 950 parts by weight.

In the present invention, the porous insulating fine particles are added to the conductive paste. The shape of the porous insulating fine particles is spherical, granular, scale-like, dendritic, plate-like, or dice-like. , Spongy, etc.,
In order to obtain a more stable electrical connection in the pressed state, it is preferable that the conductive pattern has a dendritic or sponge-like shape so as to make contact with the connection terminal facing it at multiple points.

Further, the porous insulating fine particles prevent the porous insulating fine particles from breaking through the coating of the conductive paste at the time of forming the conductive pattern and at the time of thermocompression bonding, and the porous surface has an organic binder component in the conductive paste. In order to be able to physically adsorb and thereby obtain very high adhesion, it is necessary for the surface to be porous. Therefore, it is more preferable that the difference between the SP value of the surface and that of the organic binder in the conductive paste is 2 or more, preferably 1 or less. The binding force and the similarity are obtained, the wettability between the porous insulating fine particles and the organic binder is improved, and high adhesion can be obtained.

However, as the porous insulating fine particles, those which are easily dissolved in the organic solvent in the conductive paste cannot be used, and those which easily absorb the organic solvent and cause expansion are also not preferable. Should not be one that melts easily during thermocompression bonding at 80 to 200 ° C, so a resin with a melting point of 80 ° C or higher, preferably 120 ° C or higher,
It is often made from plastic, rubber, etc., and therefore it is made of polystyrene, polyimide, polyacrylic, polyester, polyurethane, polyamide, phenol, epoxy, polyolefin, polyvinyl, etc. Resins or copolymers thereof, and elastomer resins thereof, synthetic rubbers such as isoprene-based and butadiene-based rubbers, natural rubbers, etc. may be used, which include solvent resistance, elastic modulus, molding Polyamide resins, such as nylon, aramid, and polyimide, are particularly preferable in terms of properties, oil absorption, adhesion, and the like. The shape and elasticity of this resin and rubber can be controlled,
It also provides the advantage that the surface can be made porous and the SP value of the surface can be adjusted.

The conductive paste in which the porous insulating fine particles are dispersed and mixed is then applied onto the surface of the above-mentioned insulating flexible base material to form a conductive pattern.
Screen printing is optimal for forming the conductive pattern in order to obtain a thickness enough to bury the porous insulating fine particles in one printing. However, in order to maintain a stable connected state of the porous insulating fine particles embedded and fixed in the conductive pattern formed by this, the number of particles is more than 20 per 1 mm ² of the connection terminal portion of the conductive pattern. If it is too small, the presence of particles will be reduced when it is thermocompression bonded, and the absence of particles will occur. In particular, when the pitch is low, a stable connection state cannot be achieved, and the number of particles is extremely large. And when it is screen-printed with it causes plate clogging by particles, or the volume resistivity of the conductive paste decreases and stable resistance value cannot be obtained, so this is the number of particles is 20 or more, preferably 50 From the above viewpoint, the number of blending parts of the porous insulating fine particles dispersed and blended in the conductive paste is 5 to 500.
It is preferable that the capacity part is 5 to 100 parts by volume.

The application of the conductive paste to the insulating flexible substrate is usually carried out by screen printing. The screen material used for this screen printing has a wire diameter of 10 mm.
-40μm stainless steel and other iron alloys are plain woven or twill woven, or electroformed plates formed in a grid pattern by nickel plating etc. are stretched on a rigid frame, but a precise pattern is formed. In order to do so, it is necessary to make the wire material thin so that the openings of the mask material such as acrylic resin are not blocked by the wire material or the intersections of the wire materials, and the mesh thickness (Ts) is inevitably thin, but the passage of the conductive paste From the point of sex Ts
The ratio of the opening ratio (φ) to the diameter is preferably 0.8 or more, more preferably 1.5 or more. For that purpose, the strength of the wire rod should be increased without decreasing the strength of the gauze or plate, and the wire diameter should be reduced. Is required, φ is 35% or more, preferably 60
It is better to set it to% or more.

For this screen printing, 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 is used as another screen material. In this case, when printing at a low pitch, it is necessary to use a material whose strength is not easily deformed by squeegeeing during printing from the viewpoint of dimensional stability, and sufficient care must be taken in printing.

Regarding the particle diameter of the porous insulating fine particles, when the above-mentioned conductive paste is applied to the insulating flexible substrate by screen printing, the porous paste dispersed and blended with the conductive paste is used. Particle size of insulating particles (r)
Is determined by the relationship between the line width (Tc) and thickness (t) of the pattern and the length (L) of one side of the grid-like openings of the printing plate. If r is too small with respect to t, the protrusion Since it is difficult to form and the connection is less stable,
(1/3) t, preferably r ≧ t, and r
Is larger than Tc and L, it becomes difficult to form a pattern physically, and a plate jam occurs during printing. Therefore, r <Tc, r <L, and preferably r <(1/2) Tc. Well, therefore, this r needs to be (1/3) t ≦ r ≦ L.

However, the thickness (t) of this conductive pattern is usually about 5 to 30 μm, and the length (L) of one side of the grid-like openings of the printing plate varies depending on the screen mesh, but is 0.4 mm pitch or less. When forming a fine conductive pattern, a plate with a size of 250 mesh or more and up to about 500 mesh is often used. Since L at this time is about 25 to 70 μm, the particle size (r) of the porous insulating fine particles is Is 5
It may be appropriately selected from the range of 70 μm, preferably 20 to 50 μm.

Further, regarding the porous insulating fine particles, it is necessary to determine the variation coefficient of the particle size distribution in order to obtain the screen printability and the stable connection state when continuously printed, but this variation coefficient is 80%. If it is larger, large particles that do not pass through the mesh will remain on the plate during screen printing, resulting in clogging of the plate and an electrically connected conductive pattern cannot be obtained, or after thermocompression bonding when used as a thermocompression bonding connecting member. Since the heights of the protruding portions of the conductive patterns are different and the connection state may be sparse, and a stable connection may not be obtained, this variation coefficient is required to be 80% or less.

In the thermocompression-bonding connecting member of the present invention, a pattern is formed with a conductive paste prepared by dispersing and mixing the above-mentioned porous insulating fine particles in the above-mentioned insulating flexible base material,
It is formed by providing an insulating adhesive layer on the connection terminal portion of this pattern, but this insulating adhesive is not particularly limited, as long as it exhibits adhesiveness by heating, thermoplastic, It may be either thermosetting, but thermoplastics can be bonded at relatively low temperature for a short period of time, have a long pot life, and thermosettings have high adhesive strength and excellent heat resistance. Therefore, these may be appropriately selected according to the purpose of use.

This insulating adhesive includes ethylene-vinyl acetate copolymer, carboxyl-modified ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, ethylene-
Ethyl acrylate copolymer, ethylene-isobutyl acrylate copolymer, polyamide, polyester, polymethyl methacrylate, polyvinyl ether, polyvinyl butyral, polyurethane, styrene-butylene-styrene (SBS) copolymer, carboxyl modified SBS copolymer, styrene -Isoprene-styrene (SIS) copolymer, styrene-ethylene-butylene-styrene (S
EBS) copolymer, maleic acid modified SEBS copolymer,
1 selected from polybutadiene rubber, chloroprene rubber (CR), carboxyl modified CR, styrene-butadiene rubber, isobutylene-isoprene copolymer, acrylonitrile-butadiene rubber (NBR), carboxyl modified NBR, epoxy resin, silicone rubber (SR), etc.
It may be obtained by one kind or a combination of two or more kinds.

Incidentally, rosin, a rosin derivative, a terpene resin, a terpene-
One or more of phenol copolymers, petroleum resins, coumarone-indene resins, styrene resins, isoprene resins, alkylphenol resins, phenol resins and the like, and reactive auxiliaries, phenol resins as crosslinking agents, polyols, Isocyanates, melamine resins, urea resins, urotropins, amines, acid anhydrides, peroxides,
Metal oxides, organic acid metal salts such as chromium trifluoroacetate salts, alkoxides such as titanium, zirconia and aluminum, organometallic compounds such as dibutyltin oxide,
It is optional to add a photoinitiator such as 2,2-diethoxyacetophenone and benzyl, a sensitizer such as amines, phosphorus compounds and chlorine compounds, and a curing agent and a vulcanizing agent. A control agent, an anti-degradation agent, a heat resistance additive, a thermal conductivity improver, a softening agent, a coloring agent, various coupling agents, a metal deactivator and the like may be appropriately added.

The insulating adhesive is prepared as a solution and formed on the connection terminal by an appropriate method such as screen printing. The solvent used here is an ester-based, ketone-based or ether ester-based solvent. , Chlorine-based, ether-based, alcohol-based, hydrocarbon-based, such as methyl acetate, ethyl acetate, isopropyl acetate, isobutyl acetate,
Butyl acetate, amyl acetate, methyl ethyl ketone, methyl isoamyl ketone, methyl amyl ketone, ethyl amyl ketone, isobutyl ketone, methoxymethylpentanone, cyclohexanone, diacetone alcohol, methyl cellosolve acetate, ethyl cellosolve acetate, butyl cetosolve acetate, methoxybutyl acetate, acetic acid Methyl carbitol, ethyl carbitol acetate, dibutyl carbitol acetate, trichloroethane, trichloroethylene, n-butyl ether, diisoamyl ether, n-butyl phenyl ether, propylene oxide, furfural, isopropyl alcohol, isobutyl alcohol, amyl alcohol, cyclohexanol, benzene , Toluene, xylene, isopropylbenzene, petroleum spirit, petroleum naphtha, etc. Is, this is an ester, ketones, such as those of the ester type are frequently used.

The thermocompression-bonding connecting member of the present invention is manufactured by the above-mentioned method. The thermocompression-bonding connecting member of the present invention thus produced has a porous insulating property in the conductive paste forming the pattern. Fine particles are dispersed and mixed, and they are embedded and fixed in the paste to form a protruding portion on the pattern.Therefore, when the connection is heated and pressed, the protruding portion of the conductive paste is opposed to the connecting terminal. Although electrical contact is made by direct contact, this thermo-compression bonding connecting member makes electrical connection by direct contact between the connecting terminals, so there is no risk of short-circuiting between the connecting terminals, and the porous insulating property Since fine particles are used, no electrolytic corrosion occurs, and since the insulating adhesive layer firmly holds the adhesive structure between the connection terminals, the reliability of electrical continuity in various environments is improved. Advantage that can be achieved is given.

The thermocompression-bonding connecting member of the present invention is constructed as described above, and the connecting terminal portion is dispersed and blended in the conductive paste 3 forming a pattern on the base material 1 as shown in FIG. Due to the porous insulating fine particles 2 thus formed,
A projecting portion (projecting coating film of the conductive paste 3) is formed on the pattern, and the insulating adhesive layer 4 is provided thereon. By heating and pressurizing this at the time of connection, as shown in FIG.
Is to make an electrical connection by breaking through the insulating adhesive layer 4 and making direct contact with the opposing connection terminal 5.

Therefore, as shown in FIG. 2B, the connection terminals (the conductive paste 3 and the ITO connection terminal 5) are brought into direct contact with each other for electrical connection, so that there is no possibility of a short circuit between the connection terminals. Moreover, since the insulating porous insulating fine particles 2 are used, there is no possibility of causing electrolytic corrosion. Furthermore, since the porous insulating fine particles 2 are porous, they are well wetted with the conductive paste 3, and the conductive paste 3 does not break through during pattern formation and during heating and pressurization. ), (C), the porous insulating fine particles 2 are deformed in a pressed state due to their elasticity, and the repulsive force keeps the contact pressure of the connecting terminals 5 facing each other, and is stable in various environments. And the reliability of the electrical connection is improved.

[0028]

EXAMPLES Next, examples and comparative examples of the present invention will be described. Examples 1 to 4 and Comparative Examples 1 to 2 (Preparation of conductive paste) As organic binder, molecular weight 20,000 to 25,000, hydroxyl value 6.0 KOH mg / g, acid value 1.0 KO
Using a mixture of saturated copolyester resin with H mg / g and solubility parameter of 9.2 and blocked isocyanate obtained by blocking biuret trimer of hexamethylene diisocyanate with methyl ethyl ketoxime, 100 parts by weight of scaly particles as conductive particles were used. Diameter 1-3 μm Ag
870 parts by weight of powder, 5 parts by weight of each of an organic polymer type leveling agent and silica as a thixotropic agent were added, and these were dissolved in 200 parts by weight of ethyl carbitol acetate.

Then, the compressive strength at 10% deformation is 3.0k.
The following 4 types of porous nylon resin elastic fine particles (average particle size of about 30 μm, gf / mm ² ;
Particle size distribution variation coefficient 7%, spongy, [Example 1] Porous nylon resin elastic fine particles (average particle size of about 5 μm,
Particle size distribution variation coefficient 4%, spongy, [Example 2] Porous nylon resin elastic fine particles (average particle size of about 80 μm,
Particle size distribution variation coefficient 8%, spongy, [Example 3] Porous nylon resin elastic fine particles (average particle size of about 30 μm,
Four kinds of conductive pastes A to D were prepared by adding 45 parts by volume of the particle size distribution variation coefficient of 120%, sponge-like) and [Example 4] as porous insulating fine particles.

Further, regarding this, the compression strength at 10% deformation is 3.4 kgf / mm ² , the average particle size is about 30 μm, the particle size distribution variation coefficient is 7%, and spherical non-porous acrylic resin elastic fine particles. [Comparative Example 1] The compressive strength at 10% deformation is 16.3 kgf / mm ² , and the average particle size is about 30 μm.
Then, two kinds of conductive pastes E and F were prepared by adding 45 volume parts of spherical Au-plated Ni particles having a particle size distribution variation coefficient of 8% [Comparative Example 2].

(Preparation of Insulating Adhesive Solution) 100 parts by weight of carboxyl-modified NBR, 40 parts by weight of alkylphenol tackifier, phenol resin as deterioration inhibitor, titanium oxide and amine silane coupling as heat resistant additive 1 part by weight of each agent was added, and this was dissolved in a mixed solvent of petroleum naphtha: butyl carbitol = 1: 1 to obtain 35% by weight.
An insulating adhesive solution was prepared.

(Production of thermocompression-bonding connecting member) Next, the thickness
On the insulating flexible base material made of a 25 μm PEN film, the conductive pastes A to F obtained above were screen wire diameter 16 μm, gauze thickness 35 μm, opening side length (l) 63 μm, opening ratio A pattern of 0.3 mm pitch is formed using either the 65% reinforced stainless screen plate or the stainless-nickel foil laminated screen plate,
The insulating adhesive prepared above is applied to the entire surface using a bar coater so that the thickness after removal of the solvent will be 20 μm, dried to form an insulating adhesive layer, and cut into desired dimensions. Then, a thermocompression bonding connection member was prepared.

Then, the thermocompression-bonding connecting member thus obtained was connected to a connecting terminal of a transparent conductive oxide film substrate (ITO) having an area resistivity of 30Ω under the conditions of 140 ° C., 30 kg / cm ² , and 12 seconds. Thermocompression bonding and thermal shock test (85 ° C, 30 minutes-
After 30 ℃, 30 minutes), change the resistance value between both connecting terminals and 60 ℃, 95% R
When the relationship between the time left in the H environment and the change in the resistance value between both connection terminals was examined, the results shown in Tables 1 and 2 were obtained. In the conductive paste E, the mixed insulating fine particles did not wet well, and this penetrated the conductive paste during pattern formation or after thermocompression bonding.

[0034]

[Table 1]

[Table 2]

[0035]

The present invention relates to a thermocompression-bonding connecting member and a method for producing the same, which, as described above, has a conductive material obtained by mixing porous insulating fine particles on at least one side of an insulating flexible substrate. Pattern is formed by a conductive paste, and an insulating adhesive layer is provided on at least a connecting terminal portion of the pattern, and a thermocompression-bonding connecting member, and at least one surface of an insulating flexible base material. , The particle diameter (r) is expressed by the formula (1/3) t ≦ r ≦ L (where t is the thickness of the pattern, and L is the length of one side of the screen opening). The present invention is directed to a method for manufacturing a thermocompression-bonding connecting member, which is characterized in that a conductive pattern in which is mixed is formed into a desired pattern by screen printing.

However, when the thermocompression-bonding connecting member of the present invention is used, there is no fear of short-circuiting even in connection terminals of fine electric and electronic circuits, and the porous insulating fine particles are contained in the conductive paste. Is dispersed and mixed, and is embedded and fixed in the paste, so that the protruding part can be reliably connected to the opposing connecting terminal by heating and pressurizing operation, and the reliability of electrical conduction can be improved. Since no noble metal is used as the conductive particles, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a thermocompression-bonding connecting member of the present invention.

2A is a connection explanatory view of a thermocompression-bonding connection member of the present invention and a pattern ITO, FIG. 2B is a longitudinal sectional view taken along line XX thereof, and FIG. 2C is a line YY thereof. It is a longitudinal cross-sectional view along.

FIG. 3 is a vertical sectional view of a conventionally known thermocompression-bonding connecting member.

FIG. 4 is a vertical cross-sectional view of another conventionally known thermocompression-bonding connecting member.

[Explanation of symbols]

1, 11, 16 ... Insulating flexible base material, 2 ... Porous insulating fine particles, 3, 13, 18 ... Conductive paste, 4, 19 ... Insulating adhesive layer, 5 ... ITO connection terminal, 12, 17 ... Conductive fine particles.

Claims (4)

[Claims] 1. A desired pattern is formed on at least one surface of an insulating flexible substrate with a conductive paste mixed with porous insulating fine particles, and an insulating adhesive layer is provided at least on the connection terminal portion of the pattern. A thermocompression-bonding connecting member characterized by being provided. 2. The thermocompression bonding connecting member according to claim 1, wherein the porous insulating fine particles are made of a polyamide resin. 3. The thermocompression-bonding connecting member according to claim 1, wherein the coefficient of variation of the particle size distribution of the porous insulating fine particles is within 80%. 4. The particle size (r) of the formula (1/3) t ≦ r ≦ L on at least one surface of the insulating flexible substrate (where t is the thickness of the pattern, and L is the opening of the screen). 2. The method for producing a thermocompression-bondable connecting member according to claim 1, wherein the conductive paste mixed with the porous insulating fine particles having a length of one side is formed into a desired pattern by screen printing.