JP2921740B2 - Conductive particles for anisotropic conductive adhesive and anisotropic conductive adhesive using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to conductive particles for anisotropic conductive adhesives and to anisotropic conductive adhesives using the same.

[0002]

2. Description of the Related Art In recent years, with the trend toward miniaturization and high performance of electronic equipment, the area of terminals to be connected and the terminal pitch have become extremely small. For this reason, anisotropic conductive adhesives capable of connecting between such terminals have been widely used. For example, when manufacturing a liquid crystal panel, indium-tin-oxide (IT) formed on a glass substrate is used.
An anisotropic conductive adhesive is used to establish a connection between a transparent electrode such as O) and a copper terminal formed on TAB.

[0003] As such anisotropic conductive adhesive, a one-part thermosetting type in which conductive particles are dispersed in an insulating adhesive component basically comprising an epoxy resin and a curing agent is mainly used. I have. In this case, the conductive particles generally include conductive particles obtained by coating a homogeneous insulating particle made of an insulating resin such as polystyrene or polydivinylbenzene with a plating layer of a conductive material such as gold or copper by an electroless plating method or the like. in use.

When a liquid crystal panel is manufactured using an anisotropic conductive adhesive using such conductive particles, as shown in FIG. 3, a flat press table 31 and a glass substrate 32 are attached. The TAB 33 is placed so that the ITO electrode 32a of the glass substrate 32 and the electrode 33a of the TAB 33 face each other, and they are flattened via an anisotropic conductive adhesive layer 34 containing conductive particles 36 and having a predetermined thickness. Press head 35
Thermocompression bonding is performed.

[0005]

However, when thermocompression bonding is performed in the same manner as in FIG. 3 using insulating resin such as benzoguanamine which is relatively hard and hard to deform as the insulating particles constituting the conductive particles, FIG. As shown in FIG. 4, when the pressing accuracy of the press head 35 is not sufficient and the thermocompression bonding operation is performed in a slightly inclined state, the conductive particles 36a in the anisotropic conductive adhesive layer 34 are not sufficiently crushed. However, the conductive particles 36b are not pressed, and as a result, there is a problem that the initial resistance value is increased. Further, even if the hit accuracy of the press head 35 is good, as shown in FIG.
When the electrode 33 has the bumps 37a to 37c as its electrodes, and the thickness accuracy of the bumps 37a to 37c is not good and non-uniform, the conductive particles 36a can be sufficiently filled as in the case of FIG. As a result, the conductive particles 36b are not pressed, so that there is a problem that the initial resistance value is increased.

On the other hand, when a relatively soft and easily deformable insulating resin such as an acrylic resin or a urethane resin is used as the insulating particles constituting the conductive particles, as shown in FIG. When the height of the bumps 37a to 37c of the TAB 33 is insufficient, as shown in FIG. 7, the conductive particles 36a and 36b in the anisotropic conductive adhesive layer 34 are sufficient. The initial conductivity is relatively good because it is crushed, but excessively crushing causes the insulating adhesive component 34x to be removed from the original bonding area, and the layer thickness of the anisotropic conductive adhesive layer 34 to be reduced. There is a problem that the adhesive strength is reduced. Further, when thermal stress is applied, the conductive particles undergo plastic deformation during thermocompression bonding, so that there is a problem that the resistance value after aging increases.

For this reason, it is conceivable to produce conductive particles from an insulating resin having an intermediate softness and a degree of deformation. In this case, however, an insulating resin that is hard and hard to deform and an insulating resin that is soft and easily deformable are used. The disadvantage cannot be compensated for while maintaining the advantages of both resins, and they exhibit intermediate properties between the two, resulting in a problem that the initial conductivity becomes insufficient and the conduction reliability after aging becomes insufficient. .

As described above, the requirement that the conductive particles for the anisotropic conductive adhesive should not be excessively crushed during the thermocompression bonding, and the accuracy of the press head contact and the height accuracy of the TAB bump during the thermocompression bonding. The requirement of sufficient crushing so as to obtain stable conduction even when insufficient is mutually contradictory. Conventionally, a conductive material for an anisotropic conductive adhesive which satisfies these conflicting requirements at the same time. No particles were present.

The present invention is intended to solve the above-mentioned technical problems of the prior art, and provides conductive particles for an anisotropic conductive adhesive which simultaneously satisfy the above two contradictory requirements. An object of the present invention is to provide an isotropic conductive adhesive.

[0010]

Means for Solving the Problems The present inventors coated an inner core that is relatively hard and hard to deform with an outer layer that is relatively soft and easily deformable as insulating particles constituting conductive particles for an anisotropic conductive adhesive. It has been found that the above object can be achieved by using a multilayer structure, and the present invention has been completed.

That is, the present invention relates to a conductive particle for an anisotropic conductive adhesive comprising insulating particles and a conductive material covering the same, wherein the insulating particles comprise at least an inner core and an outer layer covering the inner core. And the outer layer is softer than the inner core,
Compressive strength of inner core of insulating particles at 10% compressive displacement
Is 15 kgf / mm ² or more, and the compressive strength of the outer layer is 5
kgf / mm ² or less, the diameter of the inner core is 1 μm or more, the thickness of the outer layer is 0.5 μm or more, and the diameter of the insulating particles is 2 to 20 μm. Provide conductive particles for use.

Hereinafter, the conductive particles for anisotropic conductive adhesive of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a conductive particle for an anisotropic conductive adhesive according to a preferred embodiment of the present invention. The conductive particles 10
Has a structure in which insulating particles 3 composed of an inner core 1 and an outer layer 2 covering the inner core 1 are covered with a conductive material layer 4. Here, the outer layer 2 is formed of a material softer than the inner core 1. In the conductive particle 10 having such a structure, as shown in FIG. 2A, the inner core 1 is not excessively crushed during thermocompression bonding, but the outer layer 2 is sufficiently crushed. Therefore, as shown in FIG. 2B, even when the contact accuracy of the press head 35 is insufficient, the outer layer 2 can be sufficiently collapsed to ensure good conduction. Moreover, since the inner core 1 is not excessively crushed, a sufficient adhesive force can be secured without excessively reducing the thickness of the adhesive layer. Further, even under the temperature condition at the time of thermocompression bonding in which the outer layer 2 undergoes large plastic deformation, as long as the inner core 1 can maintain its shape, thermocompression bonding can be performed. be able to.

In the present invention, as an index of the softness between the inner core 1 and the outer layer 2, the compressive strength at the time of 10% compressive displacement can be preferably used. The reason is 10%
This is because the compressive strength at the time of compressive displacement becomes a substitute characteristic for measuring hardness in a region of elastic deformation regardless of the type of resin.

When the inner core 1 and the outer layer 2 are compared from the viewpoint of compressive strength, the compressive strength of the inner core 1 is set to be higher than the compressive strength of the outer layer 2. Specifically, the compressive strength of the inner core 1 of the insulating particles 3 at the time of a 10% compressive displacement is preferably 10 kgf / mm, since if the compressive strength is too low, the compressive strength is too high.
² or more, more preferably 15 kgf / mm ² or more.
The compressive strength of the outer layer 2, does not sufficiently crushed when too high thermocompression bonding, preferably less than 10 kgf / mm ^2, more preferably from 5 kgf / mm ² or less. In this case, if the difference in compressive strength between the inner core 1 and the outer layer 2 is too small, the effect of the present invention tends not to be sufficiently obtained.
Preferably, the pressure is at least 4 kgf / mm ² .

In the present invention, 10% of the conductive particles
The data at room temperature may be applied to the compressive strength at the time of compressive displacement.

On the other hand, if the diameter of the inner core 1 is too small, for example, it tends to penetrate into irregularities between the TAB and the glass substrate and the conduction becomes unstable, so that the diameter is preferably 1 μm or more. . On the other hand, if the layer thickness of the outer layer 2 is too small, the layer will not be sufficiently collapsed when the contact accuracy of the press head is insufficient and the conduction tends to be unstable, so that it is preferably 0.5 μm or more. . In this case, if the diameter of the insulating particles is too small, conduction becomes unstable, and if the diameter is too large, a short circuit tends to occur between terminals during connection. Therefore, the diameter of the inner core 1 and the layer thickness of the outer layer 2 are: The diameter of the insulating particles 3 is set to be in the range of 2 to 20 μm.

As the material of the inner core 1 and the outer layer 2 described above, various insulating synthetic resins, for example, polystyrene,
Polydivinylbenzene, benzoguanamine resin, melamine resin, acryl-styrene resin, urethane resin and the like can be appropriately selected and used.

The compressive strength of these synthetic resins at a 10% compressive displacement can be adjusted by appropriately adjusting the type of resin used, the degree of polymerization, and the like.

In the present invention, as the conductive material layer 4 covering the insulating particles 3, a layer conventionally used for conductive particles for an anisotropic conductive adhesive can be applied. For example, an electroless gold plating layer, an electroless copper / nickel plating layer, or the like can be applied. Further, the layer thickness and the like can be appropriately determined.

The conductive particle 10 of the embodiment shown in FIG. 1 is an example in which the insulating particle 3 uses an insulating particle 3 having a two-layer structure composed of an inner core 1 and an outer layer 2 covering the inner core. The conductive particles for an anisotropic conductive adhesive of the present invention are not limited to those using the insulating particles 3 having a two-layer structure, but also include embodiments in which the outer layer surrounding the inner core uses two or more insulating particles.

The conductive particles for the anisotropic conductive adhesive of the present invention can be produced by a conventional method. For example, the conductive particles in FIG. Co., Ltd.) and a conductive material layer formed on the outer layer by an electroless plating method.

When an anisotropic conductive adhesive is produced using the conductive particles of the present invention, the conductive particles of the present invention are used in an amount of 1 to 23 parts by weight, preferably 3 to 100 parts by weight of the insulating adhesive component.
To 15 parts by weight. Here, the adhesive component may have the same configuration as the adhesive component used in the conventionally known anisotropic conductive adhesive. For example, basically, a polymerizable component such as a solid or liquid epoxy resin may be used. And an insulating adhesive component comprising a curing component such as an imidazole-based curing agent or a modified amine-based curing agent.

Such an anisotropic conductive adhesive can be produced by a conventional method. The conductive particles of the present invention are added to an insulating adhesive component, and if necessary, a dispersing aid and a thermoplastic elastomer are added. It can be manufactured by blending a film-forming component such as, or an adhesive component such as an aliphatic petroleum resin, and uniformly dispersing them.

The anisotropic conductive adhesive can be used in the same manner as the conventional anisotropic conductive adhesive. As a particularly preferred use mode,
An anisotropic conductive adhesive sheet prepared by applying an anisotropic conductive adhesive to which an adhesive component has been added to a PET film or the like that has been subjected to a release treatment with a silicone-based release agent or the like and forming a film can be given. .

[0026]

In the conductive particles for anisotropic conductive adhesive of the present invention, the structure of the insulating particles constituting the conductive particles is obtained by covering the inner core, which is relatively hard and hard to deform, with the outer layer, which is relatively soft and easily deformable. I have. Therefore, the inner core does not collapse excessively during thermocompression bonding, but the outer layer collapses sufficiently. Therefore,
Even when the contact accuracy of the press head and the accuracy of the bump height of the TAB are insufficient, the outer layer can be sufficiently collapsed to ensure good conduction. Moreover, since the inner core is not excessively crushed, a sufficient adhesive force can be secured without excessively reducing the thickness of the adhesive layer.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments.

Examples 1 to 14 and Comparative Examples 1 to 3 Using a material having a compressive strength at 10% compressive displacement shown in Table 1 and a combination and size shown in Table 2, a hybridization device (manufactured by Nara Machine Co., Ltd.) ) To form an insulative particle, form an electroless nickel plating layer having a thickness of about 0.1 μm on the outer layer, and further form an electroless nickel plating layer having a thickness of about 500 μm on the nickel layer.
By forming a thick electroless gold plating layer, conductive particles A to M for an anisotropic conductive adhesive were produced. Here, the conductive particles A to J are the conductive particles for the anisotropic conductive adhesive of the present invention, and the conductive particles KM are conductive particles for comparison without an outer layer formed.

The compression data at 10% compression displacement of each resin in Table 1 was obtained using a micro compression tester (MCTM-200, manufactured by Shimadzu Corporation) using a test load of 3.00 (gf) and a load speed constant of 2 (0.135 gf / sec), displacement scale 5.00 (μm), and indenter 50 (μmφ).

[0030]

[Table 1] Compressive strength Resin name Manufacturer Main component (kgf / mm ² ) Ephostar GPH Nippon Kagaku Kogyo Co., Ltd. Pensoamine / Melamine 18.1 Microbar SP20525 Sekisui Fine Chemical Co., Ltd. 4.60 Microval SP210 Sekisui Fine Chemical Co., Ltd. Sekisui Fine Chemical Co., Ltd. 23.9 10% cross-linked polystyrene Co., Ltd. Sanno polystyrene 4.37 15% cross-linked polystyrene Co., Ltd. Sanno polystyrene 9.23

[0031]

[Table 2] An inner core layer insulating particle diameter conductive particle material diameter ([mu] m) material thickness (μm) (μm) A epo star GPH 4.0 Mikuroha ° Lumpur SP20525 0.5 5.0 B Epo Star GPH 3.0 Mikuroha ° Lumpur SP20525 5.0 10 .3 C Eposter GPH 2.0 Microjar SP20525 8.0 18.0 D Eposter GPH 4.0 Microjar SP20525 0.3 4.6 E Estar GPH 4.0 10% crosslinked polystyrene 5.0 14.0 F Estar GPH 4.0 15% crosslinked polystyrene 4.0 12.0 G micropoly SP210 5.0 15% crosslinked polystyrene 2.0 9.0 H micropoly SP20525 4.0 10% crosslinked polystyrene 1.0 6.0 I Epostar GPH 0.8 MICROVAL SP20525 0.3 1.4 J EHOSTAR GPH 10.0 MICROVAL SP20525 6.0 22.0 K EHOSTAR GPH .6 - - 4.6 L Mikuroha ° Lumpur SP210 5.0 - - 5.0 M 10% crosslinking port polystyrene 8.0 - - 8.0

Separately, 40 parts by weight of a phenoxy resin (YP50, manufactured by Toto Kasei), 30 parts by weight of a liquid epoxy resin (EP828, manufactured by Yuka Shell) and 30 parts by weight of a latent curing agent (HX3941HP) (Manufactured by Asahi Kasei Corporation) was adjusted to a solid content of 70% with toluene to prepare a binder for an anisotropic conductive adhesive.

To 100 parts by weight of the binder, 5 parts by weight of the conductive particles shown in Table 3 (Examples 1 to 14) and Table 4 (Comparative Examples 1 to 3) were added and uniformly mixed to obtain anisotropic conductive adhesive. An agent was manufactured. However, in Examples 11 to 14, 0.5 parts by weight, 10 parts by weight, 20 parts by weight, and 25 parts by weight of the conductive particles B were respectively added.

[0034] The obtained anisotropic conductive adhesive is peeled PET.
First, an anisotropic conductive adhesive sheet is prepared by coating the film to a dry thickness of 25 μm on a film, and the anisotropic conductive adhesive layer is formed on the glass substrate on which the ITO solid electrode is formed using the sheet. Was stuck.

Next, 70 μm of TAB was added to the adhesive layer.
Pitch terminals (25 μm thick Cu / Sn plating) are superimposed, and they are heated at a temperature of 160 ° C. and a pressure of 30 kg / cm.
^The connection was made by thermocompression bonding at ² for 15 seconds. At this time, micro jacks are placed at the bottom of the press table at each vertex of a square with a side of 15 cm, and the height of the micro jacks is shifted 1 mm left and right with respect to the plane of the press head, and the contact accuracy of the press head Decreased.

(Evaluation) Regarding the conduction reliability of the connection portion of the substrate bonded with the anisotropic conductive adhesive and the insulation resistance between two adjacent terminals, after thermal compression bonding (initial) and after aging (85 ° C./85), respectively. % RH / 1000 hours) and evaluated according to the following evaluation criteria. The results are shown in Table 3 (Examples 1 to 14) and Table 4 (Comparative Examples 1 to 3).

Evaluation standard of conduction reliability of connection part (1) After thermocompression bonding (initial) Rank resistance value ○: less than 10Ω △: 10 to 20Ω ×: 20Ω or more (2) After aging Rank state ○: initial Less than 2 times of Δ: 2 to 3 times of initial ×: 3 times or more of initial Insulation resistance between two adjacent terminals (1) Rank resistance common in both cases after thermocompression bonding (initial) and after (2) aging Value ○: 1 × 10 ⁸ Ω or more △: 1 × 10 ⁶ Ω to 1 × 10 ⁸ Ω ×: Less than 1 × 10 ⁶ Ω

[0038]

[Table 3] Example 1 2 3 4 5 6 7 8 9 9 10 11 12 13 14 Conductive particles ABCDFGHIJBBBB (Evaluation) Conduction reliability (1) Initial ○ ○ ○ ○ ○ ○ ○ ○ ○ △ ○ ○ ○ ○ ○ (2) After the attack ○ ○ ○ ○ ○ ○ ○ ○ △ △ ○ △ ○ ○ ○ Insulation resistance (1) Initial ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ (2) After ○ ○ ○ ○ ○ ○ ○ ○ ○ △ ○ ○ ○ △

[0039]

[Table 4]

From the results shown in Table 3, the conductive particles A to J of the present invention were obtained.
The anisotropic conductive adhesives of Examples 1 to 14 using No. were not evaluated as “x” for conduction reliability and insulation resistance, and had no practical problem.

The reason why the evaluation of conduction reliability after aging in Example 4 is “Δ” is considered to be because the thickness of the outer layer of the conductive particles D used is as thin as 0.3 μm. In this connection, conductive particles A having an outer layer thickness of 0.5 μm
The evaluation of Example 1 using “実 施” is “○”. Therefore, it is understood that the preferable thickness of the outer layer is about 0.5 μm or more.

The reason why the evaluation of conduction reliability after aging in Example 8 is "△" is considered that the compressive strength at the time of 10% compression displacement of the inner core is as low as 4.60 kgf / mm ² . In this connection, the evaluation of Examples 1-4 using conductive particles A-D having a compressive strength of 18.1 kgf / mm < ² > at 10% compressive displacement of the inner core is "O". Accordingly, it can be seen that the compressive strength of the inner core at the time of the preferable 10% compressive displacement is about 10 kgf / mm ² or more, which is an almost intermediate value between the ^two .

The reason why the evaluation of conduction reliability after aging in Example 9 is “△” is considered that the thickness of the outer layer of the conductive particles I used in the same manner as in Example 4 is as thin as 0.3 μm. The reason why the evaluation of the initial conduction reliability is “△” is considered that the diameter of the inner core is as small as 0.8 μm. In this connection, the evaluation of Example 3 using conductive particles C having an inner core diameter of 2 μm is “○”. Therefore,
The preferred diameter of the inner core is 1 μm, which is an intermediate value between the two.
It turns out that it is more than about.

The reason why the evaluation of the insulation resistance after aging in Example 10 is “Δ” is considered to be because the insulating particles of the conductive particles J used were as large as 22 μm. In this connection, the evaluation of Example 3 using the conductive particles C having an insulating particle diameter of 18 μm is “「 ”. Therefore, it is understood that it is preferable that the diameter of the insulating particles is set to about 20 μm or less, which is an intermediate value between the two.

The reason why the evaluation of the conductive reliability after aging in Example 11 is “△” is considered that the amount of the conductive particles B used was as small as 0.5 part by weight with respect to 100 parts by weight of the binder. . Therefore, it is understood that the amount of the conductive particles is preferably set to 1 weight or more.

The reason why the evaluation of the insulation resistance after aging in Example 14 is “Δ” is considered to be because the amount of the conductive particles B used was as large as 25 parts by weight with respect to 100 parts by weight of the binder. Therefore, it is understood that the compounding amount of the conductive particles is preferably set to about 23 weight or less.

On the other hand, in Comparative Examples 1 and 2, since the used insulating particles of the conductive particles K and L did not have a two-layer structure and consisted only of a relatively hard inner core, the press accuracy was poor. Under sufficient conditions, both the initial and after aging conduction reliability were insufficient. Comparative Example 3
In the above, the insulating particles of the conductive particles M used did not have a two-layer structure and consisted only of a relatively soft inner core, so that the conduction reliability after aging was insufficient.

[0048]

The conductive particles for the anisotropic conductive adhesive of the present invention do not excessively crush during thermocompression bonding, but are sufficient to obtain stable conduction even when the hitting accuracy of the press head is insufficient. Can be crushed. Therefore, the anisotropic conductive adhesive using the conductive particles of the present invention can realize high conduction reliability between connected terminals and can realize high insulation resistance between adjacent terminals that are not connected.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of the conductive particles for an anisotropic conductive adhesive of the present invention.

FIG. 2 is an explanatory view (FIG. 2 (a)) of a state in which the conductive particles for anisotropic conductive adhesive of the present invention are crushed during thermocompression bonding, and FIG. It is explanatory drawing (the same figure (b)).

FIG. 3 shows a glass substrate and a TA using an anisotropic conductive adhesive.
FIG. 4 is an explanatory diagram in the case of connecting B.

FIG. 4 shows a glass substrate and TA when press accuracy is insufficient.
FIG. 6 is an explanatory diagram of a connection state with B.

FIG. 5 is an explanatory diagram of a connection state between the glass substrate and the TAB when the accuracy of the bump height of the TAB is insufficient.

FIG. 6 shows a glass substrate and TA when press accuracy is insufficient.
FIG. 6 is an explanatory diagram of a connection state with B.

FIG. 7 is an explanatory diagram of a connection state between the glass substrate and the TAB when the bump height accuracy of the TAB is insufficient.

[Explanation of symbols]

 Reference Signs List 1 inner core 2 outer layer 3 insulating particle 4 conductive material layer 10 conductive particle 31 press table 32 glass substrate 33 TAB 34 anisotropic conductive adhesive layer 35 press head 36a, 36b conductive particle 37a, 37b bump

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Suga 12-3 Satsuki-cho, Kanuma City, Tochigi Prefecture Sony Chemical Corporation (56) References JP-A-7-50104 (JP, A) JP-A-6-203640 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C09J 9/02 H01B 1/00 H01L 21/60

Claims (2)

(57) [Claims] 1. A conductive particle for an anisotropic conductive adhesive comprising insulating particles and a conductive material covering the same, wherein the insulating particles comprise at least an inner core and an outer layer covering the inner core, and the outer layer is Softer than inner core, 10% compression displacement
The compressive strength of the inner core of the insulating particles is 15 kgf /
and mm ² or more, the compressive strength of the outer layer is 5kgf / mm ² or more
Below, the diameter of the inner core is 1 μm or more, the thickness of the outer layer is 0.5 μm or more, and the diameter of the insulating particles is 2 to 20 μm.
Conductive particles for an anisotropic conductive adhesive, characterized in that: 2. An anisotropic conductive adhesive containing 1 to 23 parts by weight of the conductive particles according to claim 1 based on 100 parts by weight of an insulating adhesive component.