JP2001028280A - Circuit connection member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit connection member for mutually connecting a soft substrates such as a plastic liquid crystal or film liquid crystal, and a soft substrate such as a flexible board. SOLUTION: This circuit connection member connects electrodes of substrates, each having a wiring pattern formed on a base material with a pencil hardness of 3B-5H. The circuit connection member is composed of an organic binder and electroconductive particles, each having a compressibility range of 40-80% per load (gf) and a recovery of 1-20%. By using the circuit connection member, a connection method which does not damage the substrates, and is high in connection reliability can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit connecting member used for connecting an electronic component to a circuit board.

[0002]

2. Description of the Related Art Conventionally, circuit connecting members have been used to connect electronic components such as a liquid crystal display panel and an integrated circuit board to a circuit board. The circuit connecting member is capable of connecting a wiring board having a wiring pattern formed on a surface thereof,
The circuit connection members are interposed between the substrates to be connected, and the wiring patterns of the two substrates are connected to face each other.

The above-mentioned circuit connecting member is made by dispersing an appropriate amount of conductive particles in an insulating binder, and is directly applied on a substrate to be connected or processed into a film shape to form a circuit connecting member. Intervened. Then, they are connected by heat compression bonding or the like, and after connection, they have conductivity in the thickness direction and can provide insulation in the plane direction, and are sometimes referred to as anisotropic conductive adhesives. .

A circuit connecting member is disclosed, for example, in Japanese Patent Laid-Open No. 58-23 / 1983.
No. 174, the metal particles such as tin, lead, silver, gold, copper, aluminum, etc. are mixed with an adhesive organic material which flows under heat and pressure and formed into a film or a sheet. And use it.

Japanese Patent Application Laid-Open Nos. Sho 62-165886 and Sho 62-177082 disclose a method in which a metal thin film is coated on an inorganic fine particle such as glass or ceramic or an organic polymer particle such as an organic resin instead of the above-mentioned metal. Proposals have been made for the use of conductive particles.

[0006]

These conventional circuit connecting members can be used stably for connection of a hard one such as a glass substrate or an epoxy glass substrate. Also, when connecting a hard substrate such as a glass substrate or an epoxy substrate to a film-like substrate such as a flexible substrate, it can be used as a conventional circuit connecting member by adjusting the pressure and temperature of the pressure bonding. However, it was not possible to connect substrates having low hardness, such as connecting flexible substrates.

Further, in recent years, for the purpose of weight reduction and crack prevention, development of a liquid crystal panel of a liquid crystal display from a conventional glass substrate to a plastic substrate or a film substrate has been advanced. When connection is made to the liquid crystal panel substrate made of these plastic base materials or film base materials by heating and pressure bonding using the above-described conventional circuit connection member, conductive particles contained in the circuit connection member are formed on the substrate. In such a case, the electrodes may be buried in the electrodes such as wiring patterns or the liquid crystal panel substrate itself, causing a phenomenon of destruction of the electrode portions, and there is a problem that good connection reliability cannot be ensured.

In particular, a plastic substrate or a film substrate is easily softened during thermocompression bonding and easily deformed according to the shape of the conductive particles. As a result, the electrode portion is liable to be broken, for example, a hole is formed through the wiring pattern printed on the base material, or the wiring pattern around the deformed portion is peeled off.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a circuit capable of obtaining extremely good connection reliability without causing deformation or destruction of a wiring pattern on a soft substrate. It is intended to provide a connecting member.

That is, the present invention has a pencil hardness of 3B to 5H.
In the circuit connecting member for connecting the electrodes of the substrate having the wiring pattern formed on the base material thereof, the circuit connecting member has an organic binder and one conductive particle, and the compression ratio at a load of 1 gf is in the range of 40 to 80%; And the restoration rate is 1-20%
And a circuit connecting member made of conductive particles.

Further, the conductive particles are made of a plastic material as a core, and the core is coated with a metal or a metal oxide.
It is more preferable that the conductive particles have a point at which a sudden change occurs in the weight-displacement amount correlation of the conductive particles at a weight value of 1.5 gf.

The organic binder which can be used in the circuit connecting member of the present invention is not limited to a specific one, but may be a thermosetting resin, a thermoplastic resin, a photo-curable resin, an electron beam-curable resin. For example, a known resin can be used.
For example, epoxy resin, phenol resin, silicone resin, urethane resin, acrylic resin, polyimide resin, phenoxy resin, polyvinyl butyral resin, SBR, S
BS, SEBS, SIS, NBR, polyether sulfane resin, polyether terephthalate resin, polyphenylene sulfide resin, polyamide resin, polyether oxide resin, polyacetal resin, polystyrene resin, polyethylene resin, polyisobutylene resin, alkylphenol resin, styrene butadiene resin , Polycarbonate resin, polyester resin, acrylic rubber, melamine resin, and modified resins thereof. In addition, resins, rubbers, elastomers, and the like having a polar functional group such as a hydroxyl group, a carboxyl group, a glycidyl group, a vinyl group, an amino group, and the like can be given.

In the case of a curable resin, a known curing agent can be added so as to be cured by various methods such as heat curing and light curing. Also, in the organic binder,
Coupling agents, dispersants, leveling materials, antioxidants,
An antifoaming material, a lubricant, an antistatic agent, an ion adsorbent, a pigment, a filler, a plasticizer, an additive, a solvent and the like can be added as required.

The conductive particles added to the circuit connecting member of the present invention have a compression ratio (displacement / particle size before deformation) at a weight of 1 gf of one conductive particle in the range of 40 to 80%, and are restored. Those having a ratio of 1 to 20% can be used. However, the compression ratio was measured using a Shimadzu Micro Compression Tester to measure the amount of displacement when one of the conductive particles dispersed on a glass plate with a plane indenter diameter of 50 μm was compressed and deformed at 1 gf. It is measured and compared with the particle size before compression. At this time, if the compression ratio is less than 40%, even if the pressure at the time of thermocompression bonding is as low as 1 to 2 MPa, the plastic substrate or the film substrate may be damaged, and sufficient reliability cannot be obtained.

When the compression ratio of the conductive particles exceeds 80%, the conductive particles are significantly deformed during the temporary compression, and the organic binder is not sufficiently extruded during the final compression after the temporary compression, or the conductive particles may not be crushed. There is a high possibility that a clearance is generated at the contact surface between the electrodes and the conductivity becomes unstable.

The restoration rate needs to be 1 to 20%. If the restoration rate is 1% or less, there is a high possibility that a clearance is generated at the contact surface between the crushed conductive particles and the electrode and the conductivity becomes unstable, and if the restoration rate is 20% or more, the plastic substrate Or the electrode portion of the film base material may be compressed to cause damage, thereby reducing connection reliability.

The substrates used in the present invention have a surface hardness of 3B to 5H, and examples thereof include polyimide, polyethersulfone, and polycarbonate. Further, if the hardness of the substrate falls within the hardness range, several coating layers can be formed on the surface of a plastic or a film. As the kind of the coating material, a known material such as a silane-based or UV-curable polyfunctional acrylic can be used, and the thickness and the number of coating layers can be arbitrarily adjusted. Providing a coating layer on the surface, especially when used in a liquid crystal display panel, can prevent aesthetic contamination such as surface scratches and dirt that has entered the scratches, and also prevent the incorporation of moisture due to display. It is effective because it can.

The wiring pattern formed on the base material may be a wiring pattern formed by etching or screen printing a copper foil, a conductive paste, ITO, or the like.

Further, the conductive particles of the present invention include those obtained by using a plastic material as a core and coating the core with a metal or metal oxide. The conductive particles of the present invention have a weight of one conductive particle of 0.1 to 1.5 at room temperature.
It is more preferable that the weight value of gf has a point at which a sudden change occurs in the weight-displacement amount correlation of the conductive particles.

Japanese Patent Application Laid-Open No. 9-14 / 1999
As described in 3441, there is no particular limitation as long as it does not cause changes such as breakage, melting, flow, decomposition, and carbonization within the temperature, pressure, and time applied when connecting the circuit. For example, acrylic resins such as PMMA derivatives, polystyrene resins, metal oxides, carbon, graphite, glass, ceramics, and the like can be used. In addition, as a conductive metal for coating it, nickel, iron, copper, aluminum, solder, palladium, tin, lead, chromium, cobalt, silver, gold, and the like are mentioned, and as a coating method, electroless plating is used. It is formed by plating such as electrolytic plating or vapor deposition by sputtering. Examples of the metal oxide include tin oxide and indium oxide, and one or more of these can be used.

The circuit connecting member according to the present invention is prepared as follows. An appropriate amount of the conductive particles, the organic binder, and the curing agent are mixed. At this time, dilution with a solvent can be performed if necessary. In the mixing, stirring is performed using a generally known stirring device until the components are uniformly dispersed or dissolved to obtain a circuit connecting member.

The liquid circuit connecting member can be applied directly to terminals and electrodes on a substrate to be connected by a dispenser, screen printing, or the like. At this time, the monomer and the solvent can be dried if necessary, and a thin film can be directly formed on a substrate and used. When a film-like circuit connecting member is obtained, it can be applied on a PET film using a bar coater or the like, and dried at 40 to 100 ° C. as necessary. At this time, the film-like circuit connecting member is 5 to 1
Adjust to a thickness of about 00 μm, adjust to the required width, slit and use.

Conventional connection conditions include a temperature of 160 to 2
00 ° C and a pressure of 2 to 5 MPa were required. But,
When a soft substrate such as a film substrate or a plastic substrate is used, distortion due to temperature occurs, which may cause connection instability. Also, if the pressure is too high, it may damage the substrate,
This can cause the destruction of the ITO electrode formed on the substrate. Therefore, a circuit connecting member that can be connected at low temperature and low pressure is required. On the other hand, the circuit connecting member of the present invention exhibits excellent characteristics with sufficient connection reliability even at a low temperature and a low pressure, since the conductive particles have appropriate deformability and hardness.

According to the present invention, when connecting a flexible substrate such as a film substrate or a plastic substrate, the behavior of the hardness of the conductive particles contained in the circuit connecting member is quantified, and as a result, it has been conventionally used. It has been found that connection can be made at a low pressure without damaging the substrate, as compared with a thermosetting circuit connection member. From this, PES and P
It is also possible to convert a relatively inexpensive base material such as C or PET into a substrate.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram (cross-sectional view) showing the configuration of the conductive particles according to the present invention. As shown in FIG.
The conductive particles 1 of the present invention include a plastic core 2 and a conductive coating 3 formed on the surface of the core 2.

The conductive particles 1 dispersed in the circuit connecting member of the present invention are characterized by a compression ratio and a restoration ratio when a compression load of 1 gf is applied thereto.

[Method of Measuring Compressibility] Using a compression tester manufactured by Shimadzu Corporation, one conductive particle was compressed, and the amount of compression displacement and the compression ratio when 1 gf was loaded were detected.

The load speed was 0.15 gf / sec, and the weight for the origin was 0.01 gf.

FIG. 2 shows the state of the conductive particles before the compression load is applied and the state when the compression load of 1 gf is applied. When the particle diameter before applying compression load is X ₀ and the amount of compression displacement in the compression direction is X ₁ , the compression ratio = (X ₁
/ X ₀ ) × 100 (%).

[Method of Measuring Restoration Ratio] In the same manner as the method of measuring the compression ratio, one conductive particle is compressed using a compression tester manufactured by Shimadzu Corporation. During compression, the compression load is gradually increased at a constant load speed, and the compression displacement at this time is detected. After the compression weight reaches the reversal weight, de-weighting is performed at the same constant load speed,
The relationship between the weight and the compression displacement up to the weight value for the origin described later is measured.

FIG. 3 shows the conductive particles before the compression load is applied.
Child weight, then apply compression weight to inversion weight value (1gf)
The state of the conductive particles at the time of
It shows a state when the compression load is reduced. compression
X is the particle size before applying weight. ₀And pressurize to the reversal weight.
X is the amount of compressive displacement when compressive weight is applied.₁And origin weight
The amount of compression displacement when the compression load is reduced to the value₂When
, The restoration amount of the conductive particles (μm) = X₁-X₂,
And the ratio of the restoration amount to the original particle diameter is expressed as a percentage.
When the expressed value is defined as the restoration rate, the restoration rate (%) = (X
₁-X₂) / X ₀Is required.

The measurement conditions at this time are as follows.
0 gf, the load speed was 0.15 gf / sec, and the weight for the origin was 0.01 gf.

The conductive particles 1 dispersed in the circuit connecting member of the present invention have a weight of one conductive particle at room temperature of 0.3.
More preferably, the conductive particles have a point at which the conductive particles are crushed at a weight value of 1 to 1.5 gf and a sudden displacement occurs in the weight-compression displacement correlation.

FIG. 4 shows a weight-compression displacement diagram A of the conductive particles 1 dispersed in the circuit connecting member of the present invention, and a weight-compression displacement diagram B or C of the existing conductive particles. FIG.

The existing conductive particles of the load-compression displacement diagram B shown in FIG. 4 have an increase in the amount of compression displacement in proportion to the increase in the compression load. The amount of compressive displacement is large, indicating that the conductive particles are a soft elastic body.

The conductive particles in the load-compression displacement diagram C are small elastic members, ie, hard elastic bodies, until the compression load reaches a load of about 2 gf. This indicates that the particles are crushed, that is, broken, and the amount of compressive displacement increases rapidly.

On the other hand, the conductive particles dispersed in the circuit connecting member of the present invention shown in the load-compression displacement diagram A are soft elastic bodies when the compression load is small, but are 0.1 to 1.5.
At the weighted value of gf, the conductive particles are crushed and have a point where a sudden displacement occurs in the weight-compression displacement correlation.

【Example】

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

[Preparation of Sample] An insulating binder having the following compounding ratio was prepared. In addition, all the addition amounts are represented by parts by weight. Binder composition: bisphenol A type epoxy resin EP
100 parts of -828 (manufactured by Yuka Shell Epoxy), 100 parts of high molecular weight epoxy resin Epicoat 1010 (manufactured by Yuka Shell Epoxy), and the surface of a reaction product of an imidazole compound and an epoxy compound as a curing agent, which was subjected to isocyanate treatment. Masterbatch type curing agent Novacur HX3772 (made by Asahi Kasei Corporation) 50 dispersed in epoxy resin
The parts were kneaded to obtain an insulating binder.

With respect to 100 parts by weight of the binder, Table 1
4 parts by weight of the conductive particles described in 1) above, toluene was added thereto so that the solid content became 65%, and the mixed coating solution was dried on a release PET film to a dry film thickness of 25 μm using a bar coater. A film was prepared as follows. Circuit connection members obtained by slit-cutting this film into a width of 2 mm were used as samples of the following examples and comparative examples.

The conductive particles used as samples of the examples and comparative examples are shown in Table 1 below.

[0042]

[Table 1]

Next, using the above-mentioned sample, a film substrate and a TCP (tape carrier package) were pressure-bonded by the following method. This TCP has a thickness of 75
An electrode having a pitch of 70 μm formed of a 18 μm thick tin-plated copper foil on a μm polyimide substrate was used. As a film substrate, a 100 μm thick P
An ITO electrode formed on one surface of C (polycarbonate) having a pencil hardness of B to 2H was used.

[Crimping Method] Temperature 150 ° C., Pressure 2MP
a, Pressure bonding was performed under the conditions of 20 seconds.

[Connectivity and Reliability Test] With respect to the test pieces connected by the above-described method, the resistance value between adjacent electrodes was measured. Regarding connection reliability, the test piece after measurement was aged at a temperature of 85 ° C. and a relative humidity of 85% for 500 hours, and then the resistance value between adjacent electrodes was measured. Table 2 summarizes the reliability test results. In addition, as a judgment at that time, a circle within two times the initial connection resistance value is indicated by a circle.

[Observation of Film After Compression] At the same time, in order to confirm the influence of the conductive particles on the substrate, the compression portion of the film substrate was observed with a scanning electron microscope. If the film and the ITO electrode film on the film substrate have no problem, then ○ indicates that there is no problem, and x indicates that the conductive particles are embedded in the film substrate and that the film substrate or ITO electrode can be damaged or damaged such as cracks. did.

Table 2 shows the test results.

[0048]

[Table 2]

From the above results, the circuit connecting members obtained by dispersing the conductive particles of Examples 1 and 2 have good connectivity and connection reliability.

The reliability results can be explained with reference to FIGS.

In the figure, 11a and 11b are base materials,
Reference numerals a and 12b denote electrodes formed on a substrate. 14
Is an organic binder, and 13 is conductive particles. Example 1
The conductive particles are connected at an ideal recovery rate without damaging the film substrate or the ITO electrode formed on the substrate as shown in FIG.

As shown in FIG. 6, the conductive particles of Comparative Example 4 are very elastic and do not damage the film substrate or the ITO electrode formed on the substrate. Clearance occurs on the connection surface of the electrode,
The reliability of vertical conduction cannot be obtained.

The conductive particles of Comparative Examples 1 to 3 are shown in FIG.
Indicated by

The conductive particles of Comparative Example 1 exhibit elasticity with an ideal compressibility, but have a high restoration rate, and can be said to be harder than Examples 1 and 2. For this reason, the connection reliability is uneasy because it sinks into the film substrate or the ITO electrode formed on the substrate.

The conductive particles of Comparative Examples 2 and 3 have a low compression ratio and are hard, so that they damage the film substrate and the ITO electrodes formed on the substrate similarly to Comparative Example 1, and are concerned about the connection reliability. For the reasons described above, it is possible to provide a highly reliable circuit connecting member without damaging a film substrate or an ITO electrode formed on a substrate by using the conductive particles of Examples 1 and 2. I found that I can do it.

[0056]

As described above, by using the circuit connecting member of the present invention, it is possible to obtain a connection method having high connection reliability without damaging the substrates.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a conductive particle of the present invention.

FIG. 2 is an explanatory diagram of a method of measuring a compression ratio.

FIG. 3 is an explanatory diagram of a method of measuring a restoration rate.

FIG. 4 is a load-compression displacement diagram of a conductive particle.

FIG. 5 is a diagram illustrating a connection state of the first and second embodiments.

FIG. 6 is a diagram showing a connection state of Comparative Example 4;

FIG. 7 is a diagram showing connection states of Comparative Examples 1 to 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductive particle 2 Nucleus 3 Conductive film 11a, 11b Base material 12a, 12b Electrode 13 Conductive particle 14 Organic binder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01B 1/22 H01B 1/22 DF Term (Reference) 4J004 AA05 AA07 AA08 AA10 AA11 AA12 AA13 AA14 AA15 AA16 AA18 AA19 AB04 CA06 CC02 FA05 4J040 DB032 DF052 EC061 HA026 HA036 HA066 HA136 HA346 HA366 HC24 JA09 JB02 JB07 JB08 JB10 KA03 KA07 KA16 KA32 LA09 NA20 5G301 DA02 DA42 DA60 DD03

Claims (4)

[Claims] In a circuit connecting member for connecting electrodes of a substrate having a wiring pattern formed on a base material having a pencil hardness of 3B to 5H, the circuit connecting member is formed by compressing an organic binder and one conductive particle under a load of 1 gf. A circuit connecting member comprising conductive particles having a ratio in the range of 40 to 80% and a restoration ratio of 1 to 20%. 2. The conductive particles are made of a plastic material as a nucleus, and the nucleus is coated with a metal or metal oxide. Further, the weight of one conductive particle is 0.1-1. 5
2. The circuit connection member according to claim 1, wherein the circuit connection member has a point where a sudden change occurs in the weight-displacement amount correlation of the conductive particles at the weight value of gf. 3. The circuit connecting member according to claim 1, wherein one of the substrates having a wiring pattern formed on a substrate having a pencil hardness of 3B to 5H is a substrate used for a plastic liquid crystal or a film liquid crystal. 4. The circuit connecting member according to claim 1, wherein the substrate having a wiring pattern formed on a substrate having a pencil hardness of 3B to 5H is a substrate obtained by surface-coating polyethersulfone or polycarbonate.