JPH06181074A - Thermally adhesive flexible connecting member - Google Patents

Abstract

PURPOSE:To provide a thermally adhesive flexible connecting member by which disconnection and leakage are not caused and which can be manufactured easily and can be used for connection between electric circuits. CONSTITUTION:In a thermally adhesive flexible connecting member 1, a wiring pattern is formed at least on one surface of a base material 2 composed of an insulating flexible high polymer material by means of electrically conductive paste. An insulating thermal adhesive layer 4 formed by blending and dispersing insulating particles is arranged at least in a part of this wiring pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-bonding flexible connecting member, particularly between electric circuits, for example, LCD (liquid crystal display), EL (electro luminescence), LED.
(Light emitting diode), ECD (Electrochromic display), PDP (Plasma display)
Connection of display panel such as PCB and PCB (rigid printed wiring board) or FPC (flexible printed circuit board), PCB
And PCB, FPC and PCB, and FPC and FPC.

[0002]

2. Description of the Related Art Conventionally, various types of heat-bonding flexible connecting members have been known, which are, for example, (a) FIG. 3 (a) and enlarged sectional view of FIG. 3 (b). As shown in FIG. 1, a wiring pattern 13 is formed on the electrically insulating base material (hereinafter simply referred to as the base material) 12 by a conductive paste.
After forming and drying, a method is known in which an insulating thermal adhesive 15 in which conductive particles 14 are uniformly dispersed is applied to a portion in contact with a wiring pattern for heat seal connection.

Regarding this, (b) as shown in FIG. 3 (c) which is an enlarged sectional view, conductive fine powder 23 contributing to the formation of an electric circuit and heat seal connection are formed on the base material 22. Conductive particles that sometimes contribute to electrical connection between wiring patterns
A wiring pattern 25 is formed by a conductive paste or ink containing 24 and dried, and then at least the heat-sealed connection portion is coated with an insulating heat-adhesive adhesive 26 containing no conductive particles. Are known.

Further, as shown in FIG. 3 (d) which is an enlarged sectional view of this, conductive fine powder is formed on the substrate 32.
The wiring pattern 34 of the first layer is formed from a conductive paste containing 33, dried, and then the second layer wiring is formed by using a conductive paste containing conductive fine powder 35 and conductive particles 36 thereon. It is also known that the pattern 37 is formed by overlapping, dried, and then coated with an insulating heat-adhesive adhesive 38 containing no conductive particles.

[0005]

However, in this known method, in the case of (a), if the conductive particles dispersed and mixed in the insulating adhesive have a poor dispersion, a high density area is generated. In the electrical insulation between the wiring patterns can not be maintained, especially when this wiring pattern is fine, only a few particles are in the agglomerate and leak occurs,
Further, when heat-sealed, there is a disadvantage that conductive particles are often arranged between the wiring patterns due to the flow of the heat-seal adhesive to cause a leak.

Further, in the above-mentioned (b), the wiring pattern is usually formed by the screen printing method.
Since the conductive particles 24 may clog the screen printing plate, in order to avoid this, the mesh number of the screen printing plate may be reduced to increase the opening or the particle size of the conductive particles 24 may be reduced. However, in the former case, the screen printing plate of 200 mesh or more necessary for printing the fine pattern cannot be used, so the fine wiring pattern is limited, and in the latter case, the grain pattern is limited. Since the diameter is smaller than the print thickness of the fine pattern, the conductive particles are embedded in the fine pattern, and there is a disadvantage that the stability of the connection is weakened.

Further, in the above (c), the wiring pattern has two layers, and the function of the wiring pattern is achieved by the first layer. The conductive fine powder 36 in the second layer can be projected from the wiring pattern 37, but in this case, the wiring patterns 34 and 37 of the first layer and the second layer are easily displaced, so There is a disadvantage that it is difficult to form a simple wiring pattern.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a heat-bonding flexible connecting member which solves the above-mentioned disadvantages of the known ones, which is a substrate made of an insulating flexible polymer material. A wiring pattern is formed on at least one surface of the conductive paste by an electrically conductive paste, and an insulating thermal adhesive layer formed by mixing and dispersing insulating particles is provided on at least a part of the wiring pattern. is there.

That is, the present inventor has conducted various studies to develop a heat-bonding flexible connecting member which does not cause leakage and can be easily manufactured, and therefore has a fine wiring pattern with high accuracy. After forming a wiring pattern by a known method on the above, by providing an insulating heat-adhesive adhesive layer in which insulating particles are mixed and dispersed on the wiring pattern, the insulating particles are present in the wiring pattern during heat sealing. We found that the wiring pattern around the insulating particles rises up and the insulating thermal adhesive is eliminated, and the wiring pattern and the connecting electrodes of the circuit board to be connected come into direct contact with each other to obtain conduction. The present invention has been completed by conducting research on various materials used here and combinations thereof. This will be described in more detail below.

[0010]

The present invention relates to a heat-bonding flexible connecting member, in which a wiring pattern is formed on at least one side of a substrate with a conductive paste, and insulating particles are mixed and dispersed in at least a part of the wiring pattern. The above-mentioned insulating heat-adhesive adhesive layer is provided, but this one has the advantage that connections between electric circuits can be surely made and no leak occurs.

The heat-adhesive flexible connecting member of the present invention has a wiring pattern formed on at least one surface of a base material, and an insulating heat-adhesive adhesive layer in which insulating particles are mixed and dispersed is provided on the wiring pattern. The base material is made of an insulating and flexible polymer material.

Therefore, examples of the base material include those made of polyimide, polyester, polycarbonate, polyphenylene sulfide, liquid crystal polymer, etc., but since the connecting member of the present invention is used for electrical connection, It is necessary that the material has an electrical insulating property with a volume resistivity of 10 ⁸ Ωcm or more, preferably 10 ¹⁰ Ωcm or more. Therefore, it has excellent heat resistance and dimensional stability against external force of temperature change. Polyesters are preferred. The thickness of the base material is 5 to 50 μm, preferably 10 to 30 μm from the viewpoint of flexibility.

A wiring pattern is formed on at least one surface of the base material with a conductive paste. The conductive paste is composed of an organic binder, a solvent, conductive fine powder and other additives. To be taken. As the organic binder, vinyl chloride resin, vinyl acetate resin, copolymers thereof, acrylic resin, thermoplastic polyester, thermoplastic polyurethane, polybutadiene, polyimide resin, epoxy resin, alkyd resin,
Phenol resin and the like are exemplified, but if necessary, a curing agent such as isocyanates, amines and acid anhydrides may be added thereto.

The solvent used here is an ester-based solvent,
Ketone type, ether ester type, chlorine type, ether type,
It may be either an alcohol type or a hydrocarbon type, which includes methyl acetate, ethyl acetate, isopropyl acetate, isobutyl acetate, 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, butyl cellosolve acetate, methoxybutyl acetate, methyl carbitol acetate, 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,
Examples include isopropylbenzene, petroleum spirit, petroleum naphtha, etc., but generally ester-based, ketone-based,
It is preferable to use an ether ester type, and these are not particularly limited, but this conductive paste has a viscosity of 50 to 1.0
It should be used in a range where 00 poise and thixotropy are adjusted to 2-15.

Further, the conductive fine powder used here has a particle size of 0.01 to 10 μm, such as granular, scale-like, plate-like,
Dendritic, dice-shaped silver, silver-plated copper, copper, gold, nickel, palladium, and alloys thereof, resin powder plated with one or more of these metals, carbon such as furnace black, channel black, etc. One or two or more of black and graphite powder are exemplified, and these are 10 to 90 with respect to the above organic binder.
It may be mixed and dispersed by weight%.

The conductive paste used in the present invention can be obtained by mixing a predetermined amount of the above-mentioned organic binder, solvent and conductive fine powder. If necessary, a curing accelerator and leveling may be added. Agent, dispersion stabilizer,
You may add additives, such as a defoaming agent, a thixotropic agent, and a metal deactivator. In addition, in order to form a wiring pattern using the conductive paste thus produced, it may be printed by a screen printing method, a gravure printing method, or the like.
The thickness of the wiring pattern should be 5 to obtain good electrical connection.
Since it is desirable that the thickness is at least μm, screen printing is preferable in order to obtain this thickness.

The heat-adhesive flexible connecting member of the present invention can be obtained by applying an insulating heat-adhesive containing dispersed insulating particles on the wiring pattern thus prepared. The insulating heat-adhesive to be used is a thermoplastic resin, a thermosetting resin, or a blend thereof in which insulating particles are dispersed and blended. Examples of the thermoplastic resin include polyamide-based, polyester-based, ionomer-based, polyolefin-based resins such as EVA, EAA, EMA, and EEA, various synthetic rubber-based resins, and modified products and composites thereof. Examples of the resin include epoxy resin-based, urethane-based, acrylic-based, silicone-based, chloroprene-based, nitrile-based, and other synthetic rubbers, or a mixture thereof. Agent, control agent, deterioration inhibitor, heat resistance additive,
A thermal conductivity improver, a tackifier, a softening agent, a coloring agent and the like may be added as appropriate.

This thermoplastic resin is characterized in that it can be bonded at a relatively low temperature in a short time and has a long pot life. Thermosetting resin has a large adhesive strength and excellent heat resistance. Therefore, these may be appropriately selected according to the purpose and range of use. In addition, it is preferable that these are dissolved in a preliminarily solvent at the time of coating, and the same solvent as that used at the time of preparing the conductive paste can be exemplified as this solvent.

Next, the insulating particles dispersedly blended therein are embedded in the wiring pattern at the time of heat-sealing and swell the wiring pattern around the particles. Even if this exists between the wiring patterns, leakage does not occur. In order to make it more than 10 ⁸ Ω · cm, preferably
It is necessary to have an electrical insulation property of 10 ¹⁰ Ωcm or more, and this is because the compressive strength at the heat seal temperature is 0.5 kgf / cm ² in order to be embedded in the wiring pattern during heat seal. As described above, it is preferably 2 kgf / cm ² or more.

Further, if the particle diameter of the insulating particles is too large with respect to the thickness of the wiring pattern, the particles will get caught in the wiring pattern, and even if the wiring pattern in the surrounding area rises, the size of the circuit board to be connected will rise. since there is a possibility that contact between the connection electrode and the wiring pattern is not made, this is less than the thickness of the wiring pattern, preferably the thickness of the wiring pattern ^_3/4
It is recommended to set the following, but if this is too small for the thickness of the wiring pattern, the rise of the wiring pattern during heat sealing will be small and stable electrical connection will be difficult to obtain, so this is 3 μm or more, preferably 5 μm. the upper limit is less than the thickness of the wiring pattern above, preferably be of the _^3/4 or less of the thickness of the wiring pattern.

The insulating particles are acrylic resin, polycarbonate resin, polyester resin, vinyl chloride resin, polyimide resin, polyamide resin, epoxy resin, phenol resin, resin particles such as liquid crystal polymer, glass particles,
It may be made of ceramic particles or the like. This shape is not particularly limited, it is spherical, needle-like, scale-like, plate-like, resin-like, dice-like, protuberant spherical,
The shape may be an irregular shape or the like, but a spherical shape or a shape close to a spherical shape is preferable in terms of easiness of embedding into the wiring pattern and suppression of increase in resistance value due to tension of particles after embedding.

The insulating thermal adhesive used in the present invention is a printing method such as a screen printing method, a gravure printing method, a kiss coating method, a bar coating method, a knife coating method, or a dipping method on the wiring pattern. The heat-bondable flexible connecting member of the present invention is obtained by forming a coating layer by a method such as a method.

However, in this case, if the amount of the insulating particles added is too small, it is difficult to obtain a stable resistance value, and if it is too large, the adhesiveness of the adhesive may be impaired. 40 pieces / mm ² or more, preferably 100
Guide which the pieces / mm ² or more, often area ratio is set to be _^1/2 or less, the thickness of the adhesive layer when it is too thick adhesive when heat-sealing is intended not fully exclude If the conductivity cannot be obtained, and if it is too thin, the holding force of the connection structure tends to be small and reliability is lacking.
It is desirable that the thickness is 30 μm, preferably 5 to 20 μm.

The heat-bondable flexible connecting member of the present invention thus produced is as shown in FIG. FIG. 1 (a) is a plan view of a heat-adhesive flexible connecting member 1 of the present invention in which a wiring pattern is formed on a base material, and FIG. 1 (b) is an enlarged sectional view thereof. First of all,
As shown in (a), the wiring pattern 3 is formed on the substrate 2 made of an insulating flexible polymer substance with a conductive paste. The wiring pattern 3 contains the conductive fine particles 4 as shown in FIG. 1B, but the heat-adhesive flexible connecting member 1 of the present invention is shown in FIG. 1A. It is made by applying an insulating heat-adhesive adhesive 6 containing insulating particles 5 to an object.

The conditions for heat sealing when connecting between electric circuits using the heat adhesive flexible connecting member of the present invention are that the viscosity of the insulating heat adhesive adhesive used for this is At a temperature of 5 × 10 ⁶ poise or less, preferably 5 × 10 ⁵ poise or less, and 5 kgf / cm ² or more, preferably 10 kgf /
It is preferable to keep the pressure at cm ² or more for 3 seconds or more. According to this, as shown in the enlarged cross-sectional view of FIG. 2, the insulating particles 6 are embedded in the wiring pattern 3 and the wiring pattern around it is As shown in FIG. 9A, the insulating heat-adhesive adhesive 5 in this portion is lifted up in an annular shape to be removed. The agent layer 5 has an advantage that the connection is retained and a good connection structure can be obtained.

[0026]

EXAMPLES Next, examples and comparative examples of the present invention will be described. Example A conductive film consisting of 100 parts by weight of a urethane-based binder, 800 parts by weight of scaly silver powder having an average particle size of 0.3 μm, 200 parts by weight of carbitol acetate, and 2 parts by weight of a silicone-based leveling agent on one surface of a 25 μm-thick polyester film. Sex paste
A 400 mesh screen plate was used to print with a pitch of 0.3 mm and a conductor width of 0.15 mm and dried to form a wiring pattern. The thickness of this wiring pattern was 12 μm.

Next, a spherical phenol resin having an average particle size of 8 μm and a compressive strength of 4.0 kgf / mm ² was applied on the wiring pattern in a polyester adhesive having a viscosity of 3 × 10 ⁵ poise at 130 ° C. When the dispersed adhesive layer was formed by screen printing using a 120-mesh screen plate, the thickness of this adhesive layer was 15 μm, and the particle dispersion density was 150 particles / mm ² , so this Was sized so that the number of wiring patterns was 240 and the length in the length direction of the wiring patterns was 25 mm, to prepare the heat-bonding flexible connecting member of the present invention, and 500 pieces of the same were manufactured by the same method.

Next, using 200 of these connecting members, 0.3
An LCD having a connecting electrode at a mm pitch and a PCB having a driver IC mounted thereon were heat-sealed at 130 ° C. for 30 seconds at 30 kgf / cm ² , and all 200 were normally connected. The yield of 500 connecting members was 98.6% and the defective rate was extremely low.

Comparative Example 1 Insulating particles dispersed in an insulating thermal adhesive have an average particle size of
We prepared 500 heat-bonding flexible connecting members in the same manner as in the example except that they used 20 μm amorphous nickel particles (which are, of course, electrically conductive). The yield was 63.3%, and when this 200 pieces were heat-sealed, 34 of these pieces had display defects due to leaks because nickel particles moved with the flow of the adhesive. .

Comparative Example 2 100 parts by weight of amorphous nickel particles having an average particle size of 20 μm were further added to the conductive particles in the conductive paste of Example, and no insulating particles were added to the insulating thermal adhesive. Other than that, when 500 thermo-adhesive flexible connecting members were made by the same method as in the example, this product had a large number of disconnection of the wiring pattern due to the significant clogging of the nickel particles on the screen mesh. It was 0 when all of the 240 wiring parts were conducting.

[0031]

INDUSTRIAL APPLICABILITY The present invention relates to a heat-bonding flexible connecting member, in which a wiring pattern is formed on one surface of an insulating flexible substrate with a conductive paste, and insulating particles are formed on the wiring pattern. Insulating heat-adhesive adhesive layer having dispersed therein is provided, but this connecting member can be easily manufactured without causing disconnection and leakage, and also prevents leakage caused by heat sealing. Therefore, the labor required for repair can be reduced, and this has the advantage that stable electrical continuity can be obtained because the wiring pattern and the connecting electrodes of the circuit board to be connected are in direct contact with this connecting member. is there.

[Brief description of drawings]

1A and 1B show a heat-bonding flexible connecting member of the present invention, in which FIG. 1A is a plan view thereof and FIG. 1B is an enlarged sectional view thereof.

FIG. 2 is an enlarged cross-sectional view of a connection structure using the heat-bondable flexible connection member of the present invention.

3A and 3B show a conventionally known heat-bonding flexible connecting member, in which FIG. 3A is a plan view thereof, and FIG.
(C), (d) is an expanded sectional view of other known examples.

[Explanation of reference numerals] 1 , 11 , 21 , 31 ... Thermal adhesive flexible connecting member 2, 12,
22, 32 …… Base material, 3, 13, 25, 34, 37 …… Wiring pattern, 4, 33, 35 …… Conductive fine powder 5, 15, 26, 38 ……
Insulating thermal adhesive, 6 ... Insulating particles, 7
...... Connected circuit board, 8 ...... Connection electrode, 9 ...
… Swells, 14, 24, 36… Conductive particles.

Claims (1)

[Claims] 1. A wiring pattern is formed of a conductive paste on at least one surface of a base material made of an insulating flexible polymer material, and insulating particles are mixed and dispersed in at least a part of the wiring pattern. A heat-adhesive flexible connection member comprising an insulating heat-adhesive layer.