JPH04242010A - Anisotropic conductive agent for connection - Google Patents

Abstract

PURPOSE:To stabilize conductive resistance of an anisotropic conductive agent for conductively bonding opposing connection circuits. CONSTITUTION:An anisotropic conductive agent incorporates conductive particles, where the surface of a high polymer particle having an epoxy group is covered with a metal plating film, a potential epoxy hardener (imidazole hardener) crosslinked with the high polymer particle, and a binder of a bisphenol A type epoxy resin. An epoxy group of the high polymer particle included in the conductive particle is chemically connected to an epoxy group of an epoxy resin via the hardener at the time of bonding under pressure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive agent for connection for conductively bonding opposing connection circuits.

0002

[Prior Art] Connecting terminals are arranged facing each other at a fine pitch, such as when connecting an integrated circuit to a wiring board, connecting a display device such as a liquid crystal display to a wiring board, or connecting an electric circuit to a lead. A connection method using an anisotropic conductive agent has been proposed as a connection method in this case. This is particularly suitable for connection of fine circuits, which are becoming increasingly dense and precise. In this connection method, an adhesive resin film (so-called anisotropic conductive material) in which conductive particles are dispersed is placed between opposing connection circuits, and conduction is established between the connection circuits by applying pressure or heating. This provides insulation between matching circuits and adhesively fixes opposing connected circuits.

Conventionally, such anisotropic conductive agents include (
I) An anisotropic conductive agent made by dispersing conductive particles, for example cross-linked polystyrene particles whose surfaces are plated with metal, for example Ni and Au, in a styrene-butadiene rubber binder; Anisotropic conductive agent (see Japanese Patent Publication No. 2-829), (II
I) Anisotropic conductive agents formed by dispersing solder particles in an epoxy thermosetting binder are known.

0004

[Problems to be Solved by the Invention] However, in the above-mentioned anisotropic conductive agent (I), the styrene-butadiene binder has a thermal expansion coefficient of 1.4 x 10-4, and the conductive particles have a thermal expansion coefficient of 1.4 x 10-4. 7.0 x 10-5, it has the disadvantage that when connecting opposing connection circuits (i.e. terminals), the conduction resistance tends to change due to thermal shock such as thermal shock due to the difference in coefficient of thermal expansion. Ta. That is, as shown in FIG. 3, when the terminal 3 of the liquid crystal display main body 2 and the terminal 5 of the flexible wiring board 4 are connected via the anisotropic conductive material 1 (see FIG. 3A), high and low temperatures are periodically changed. When repeated thermal shocks are applied, the binder 6 has a larger thermal expansion than the conductive particles 7 at high temperatures, so the contact between the conductive particles 7 and the terminals 3 and 5 comes off (see Figure 3B), resulting in a large conduction resistance. Become.

[0005] Furthermore, the above-mentioned anisotropic conductive agent (II) is
During crimping, the metal plating layer of the conductive particles cracks and the polystyrene particles inside and the binder adhere, but this is only a simple adhesion between the polystyrene particles and the binder.
Aging at high temperatures reduces the cohesive force of the binder, and the difference in thermal expansion coefficient causes an increase in conduction resistance. Furthermore, in the above-mentioned anisotropic conductive agent (III), since the binder has a thermal expansion coefficient of 5.2 x 10-5 and the solder particles have a thermal expansion coefficient of 2.5 x 10-5, (I) Similar to the anisotropic conductive agent, conduction resistance tends to increase due to thermal shock, etc.

In view of the above points, the present invention provides an anisotropic conductive agent that can improve the reliability of conduction.

[0007]

[Means for Solving the Problems] The present invention provides an anisotropic conductive agent for connection which can be interposed in a thin layer between opposing connection circuits and pressurized between the connection circuits to obtain continuity and adhesion between the connection circuits. In , an anisotropic conductive agent 15, conductive particles 13 formed by coating the surface of a polymer particle 11 having a functional group with a conductive metal thin film 12, a curing agent crosslinking with the polymer particle 11, and an insulating The organic adhesive 14 is made up of:

[0008]

[Operation] In the present invention, when the anisotropic conductive agent 15 is interposed between opposing connection circuits and pressurized, the conductive particles 1
The conductive metal thin film 12 of No. 3 is cracked, and the polymer particles 1 inside
1 is exposed, the functional group on the surface of the polymer particle 11 and the functional group of the insulating organic adhesive 14 react via the curing agent in the insulating organic adhesive 14, and the polymer of the conductive particle 13 reacts with the functional group of the insulating organic adhesive 14. Particles 11 and insulating organic adhesive 14 are chemically bonded.

[0009] Therefore, whether the expansion and contraction of the conductive particles 13 and the expansion and contraction of the insulating organic adhesive 14 are equal to each other.
Alternatively, in order to firmly bond the two, conductive particles 1
The expansion and contraction of No. 3 is suppressed, and stable conduction resistance can be obtained even after subsequent thermal shock tests such as thermal shock.

0010

[Example] In the present invention, as shown in FIG. 1, for example, hydroxyl group (-OH), carboxyl group (-COOH),
The surface of the polymer particle 11 having a functional group such as an amino group (-NH3), an epoxy group (Chem.
Conductive particles 13 coated with a metal plating film such as layer plating)
The conductive particles 13 are dispersed in a binder (insulating organic adhesive) 14 containing a curing agent that reacts with each of the corresponding functional groups described above to form a target anisotropic conductive agent 15.

[Chemical formula 1]

The conductive particles 13 of the anisotropic conductive agent 15 are used, for example, between opposing connection circuits as shown in FIG. The polymer particles 11 are formed in a press-deformed shape such that a portion of the polymer particles 11 is exposed from the conductive metal thin film 12 and comes into contact with the binder 14. The polymer particles 11 having a functional group on their surface may be formed of a polymer having a functional group, or may be formed by adding a functional group to the surface of the polymer particle 11.

As the binder 14, for example, a thermosetting resin, an ultraviolet curable resin, an electron beam curable resin, or the like, which starts a reaction during pressing, is used. As the curing agent, one that reacts with both the binder 14 and the functional groups of the conductive particles 13 is used.

[0013] In the anisotropic conductive agent 15 having such a structure, the conductive particles come into planar contact with each other or with the circuit portion by applying pressure or heating and pressurization during connection, thereby forming a conductive state. Ru. At this time, when the conductive metal thin film 12 of the conductive particles 13 is cracked by pressure and some of the internal polymer particles 11 are exposed, the functional groups of the polymer particles 11 and the functional groups of the binder 14 are Reaction occurs via the curing agent, and the polymer particles 11 and the binder 14 are chemically bonded and integrated. This conductive particle 13 and binder 1
4, the expansion and contraction of the conductive particles 13 is suppressed, and the stability of conduction resistance is improved even when subjected to thermal shock such as thermal shock. Therefore, sufficient durability can be obtained even when applied to a vehicle-mounted liquid crystal display device, for example.

Next, a specific example will be shown. [Comparative example 1]
Ingredients
styrene butadiene rubber
50 parts by weight Terpene phenol (adhesive agent) 50
Part by weight Conductive particles A

5 parts by weight However, conductive particles A are crosslinked porstyrene particles whose surfaces are plated with Ni and Au and have an average particle size of 8 μm.
m metal plated particles. The above components are blended to create an anisotropic conductive agent. In this anisotropic conductive agent, the thermal expansion coefficient of the conductive particles A is 7 x 10-5, and the thermal expansion coefficient of the binder is 1.4 x.
It is 10-4.

[Comparative Example 2]
Ingredients
Bisphenol A type epoxy resin (solid) 50 parts by weight Bisphenol A type epoxy resin (liquid) 50 parts by weight
latent epoxy hardener
40 parts by weight
Conductive particles B
30 parts by weight However, the conductive particles B are solder particles with an average particle size of 10 μm. The above components are blended to create an anisotropic conductive agent. In this anisotropic conductive agent, the thermal expansion coefficient of conductive particles B is 2.5×10−
5. The coefficient of thermal expansion of the binder is 5.2 x 10-5.

[Example 1]
Ingredients
Bisphenol A type epoxy resin (solid) 50 parts by weight Bisphenol A type epoxy resin (liquid) 50 parts by weight
latent epoxy hardener
40 parts by weight
Conductive particles C
5 parts by weight However, the conductive particles C are metal-plated particles having an average particle size of 7 μm, which are obtained by plating Ni and Au on the surfaces of polymer particles having epoxy groups added to the surfaces of polystyrene particles. The above components are blended to create an anisotropic conductive agent. In this anisotropic conductive agent,
The thermal expansion coefficient of the conductive particles C is 6.8 x 10-5, and the thermal expansion coefficient of the binder is 5.2 x 10-5.

[Example 2]
Ingredients
Bisphenol A type epoxy resin (solid) 50 parts by weight Bisphenol A type epoxy resin (liquid) 50 parts by weight
latent epoxy hardener
40 parts by weight
Toluene diisocyanate (curing agent)
0.5 parts by weight Conductive particles D
5 parts by weight However, the conductive particles D are polymer particles with a hydroxyl group (-OH) added to the surface of the polystyrene particles, and the surfaces of the particles are plated with Ni and Au, and the average particle size is 7 μm.
m metal plated particles. Toluene diisocyanate reacts with the hydroxyl group (-OH) of the conductive particles D and the hydroxyl group (-OH) of the binder. Bisphenol A
The type of epoxy resin has a hydroxyl group (-OH). The above components are blended to create an anisotropic conductive agent. In this anisotropic conductive agent, the thermal expansion coefficient of conductive particles D is 6.8×
10-5, the coefficient of thermal expansion of the binder is 5.2×10-
It is 5.

[Comparative Example 3]
Ingredients
Bisphenol A type epoxy resin (solid) 50 parts by weight Bisphenol A type epoxy resin (liquid) 50 parts by weight
latent epoxy hardener
40 parts by weight
Conductive particles D
An anisotropic conductive agent is prepared by blending 5 parts by weight of the above components. In this anisotropic conductive agent, the thermal expansion coefficient of the conductive particles is 6.8×10-5,
The coefficient of thermal expansion of the binder is 5.2 x 10-5.

[Comparative Example 4]
Ingredients
Bisphenol A type epoxy resin (solid) 50 parts by weight Bisphenol A type epoxy resin (liquid) 50 parts by weight
latent epoxy hardener
40 parts by weight
Conductive particles A
An anisotropic conductive agent is prepared by blending 5 parts by weight of the above components. In this anisotropic conductive agent, the thermal expansion coefficient of the conductive particles is 7.0×10-5,
The coefficient of thermal expansion of the binder is 5.2 x 10-5.

[0020] The above Examples 1 and 2, Comparative Examples 1, 2, 3,
Table 1 shows the results of the initial conduction resistance and the conduction resistance after thermal shock when opposing circuit parts were bonded using each of the anisotropic conductive agents No. 4.

[0021]

[Table 1] Thermal shocks are -40℃ (30 minutes) and +12℃.
This is a thermal shock test in which a temperature change of 0°C (30 minutes) is applied for 200 cycles.

According to Table 1, in Comparative Example 1, a thermoplastic binder is used as the binder, and the coefficient of thermal expansion is large, and since the conductive particles and the binder are only in contact with each other, the increase in conduction resistance after thermal shock is large. . In Comparative Example 2, since a thermosetting binder is used, the increase in conduction resistance after thermal shock is not so large. In comparison, the conduction resistance increases.

On the other hand, in Example 1, a thermosetting binder is used, and when pressurized, the epoxy groups of the binder and the epoxy groups of the polymer particles exposed from the metal plating layer of the conductive particles form a latent epoxy curing agent. (That is, an imidazole-based curing agent) causes chemical bonding, so there is little change in conduction resistance after thermal shock, and stable conduction resistance can be obtained. Chemical reaction formula 2 shows the chemical reaction formula of Example 1.

[0024]

[Chemical formula 2] In this way, the epoxy groups of the binder and the epoxy groups of the conductive particles react through the imidazole curing agent, and the binder and the conductive particles are integrated, causing expansion and contraction of the conductive particles and the binding of the conductive particles. Will the expansion and contraction of
Alternatively, the expansion and contraction of the conductive particles can be suppressed because they are firmly bonded to each other.

In addition, in Example 2, the hydroxyl group (-OH) of the epoxy resin as the binder and the hydroxyl group (-OH) of the conductive particles
-OH) are chemically bonded via toluene diisocyanate (curing agent), similarly stable conduction resistance can be obtained. Chemical reaction formula 3 shows the chemical reaction formula of Example 2.

[0026]

[Chemical formula 3] In this way, a reaction occurs in which toluene diisocyanate connects the hydroxyl groups of the epoxy resin and the hydroxyl groups of the conductive particles, and as in Example 1, the expansion and contraction of the conductive particles becomes equivalent to the expansion and contraction of the binder. or because they are firmly bonded to each other, expansion and contraction of the conductive particles can be suppressed.

Comparative Example 3 is a comparison with Example 2. In Comparative Example 3, since toluene diisocyanate was not included in the blending system, the conduction resistance was slightly increased compared to Example 2. Comparative Example 4 is a comparison with Example 1. This comparative example 4
Since the polymer particles, which are the core of the conductive particles, do not have functional groups, the conduction resistance increases significantly.

As described above, in Examples 1 and 2, the conduction resistance does not change much even after the thermal shock;
It is stable, and therefore the reliability of the conduction resistance can be improved.

[0029]

[Effects of the Invention] According to the anisotropic conductive agent of the present invention, the stability of conduction resistance against thermal shock such as thermal shock is improved compared to the conventional one, and reliability as an anisotropic conductive agent is improved. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an anisotropic conductive agent for connection according to the present invention.

FIG. 2 is a configuration diagram at the time of adhesion according to the present invention.

FIG. 3 is an explanatory diagram of a conventional anisotropic conductive agent for connection.

[Explanation of symbols]

3, 5 Terminal 11 Polymer particles 12 Conductive metal thin film 13 Conductive particles 14 Insulating organic adhesive 15 Anisotropic conductive agent for connection

Claims (1)

[Claims] 1. An anisotropic conductive agent for connection, which is interposed in a thin layer between opposing connection circuits and presses the connection circuits to obtain continuity and adhesion between the connection circuits, comprising:
The anisotropic conductive agent comprises conductive particles formed by coating the surface of polymer particles having a functional group with a conductive metal thin film, a curing agent that crosslinks with the polymer particles, and an insulating organic adhesive. An anisotropic conductive agent for connection, characterized by comprising: