JP3006944B2 - Anisotropic conductive thermal adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive heat adhesive used for connecting two electrode substrates and the like so as to be electrically conductive only in the thickness direction.

[0002]

2. Description of the Related Art When electrically connecting two electrode substrates, for example, a liquid crystal panel and a drive circuit substrate, a film-like or paste-like anisotropic conductive heat adhesive is used.

[0003] That is, a film-like anisotropic conductive thermal adhesive is sandwiched between both electrode substrates, or a paste-like anisotropic conductive thermal adhesive is applied to the surface of the electrode substrate, and this is heated and heated. Pressure to heat melt or thermally cure the thermal adhesive,
Thus, the liquid crystal panel and the drive circuit board are connected so as to be electrically conductive only in the thickness direction.

[0004] This type of anisotropic conductive heat adhesive mainly has good bonding reliability (there is no conduction failure due to a decrease in adhesive strength even when used in a severe environment after bonding).
And good joining workability (easy to store, handle and apply the adhesive, and have a wide temperature range for thermal bonding).

Furthermore, in order to improve product efficiency, repairability (when the connection electrode is misaligned after bonding, the adhesive is melted by reheating to peel off the electrode substrate, and can be reused by washing with a solvent) Is also desired.

Conventionally, as an anisotropic conductive thermal adhesive, a thermoplastic resin such as a thermoplastic polyester resin, a thermosetting resin such as a thermosetting epoxy resin, or a resin using both of them is used as a binder resin. Anisotropic conductive adhesives in which an appropriate amount of conductive fine powder is dispersed in this binder resin to form a film or a paste are known (for example, JP-A-60-120772 and JP-A-60-120772). 62-260877).

[0007]

However, an anisotropic conductive thermal adhesive using a thermoplastic resin has good connection workability and repairability, but has poor connection reliability. On the other hand, anisotropic conductive thermal adhesive using thermosetting resin has good connection reliability,
Poor connection workability and repairability. In addition, an anisotropic conductive thermal adhesive using both resins has good connection workability and connection reliability, but has poor repairability. As described above, the conventional anisotropic conductive heat adhesive has advantages and disadvantages.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide an anisotropic conductive heat adhesive having good joining workability, joining reliability and repairability. It is in.

[0009]

In order to achieve the above object, an anisotropic conductive heat adhesive of the present invention has a hydroxyl group.
Using a binder resin comprising a metal complex salt capable of reacting with the carboxyl groups of the resin and a thermoplastic polyester resin having a thermoplastic polyester resin and not a thermoplastic polyester resin and a carboxyl group of a carboxyl group, a suitable amount of conductive fine powder to Are dispersed.

The thermoplastic polyester resin having a carboxyl group used in the present invention includes a saturated dicarboxylic acid such as terephthalic acid, adipic acid and sebacic acid and a saturated divalent acid such as ethylene glycol, propylene glycol and 1,4-butanediol. A polycondensation reaction with an alcohol is carried out by a conventional method, and a carboxyl group is introduced into a molecular terminal or a molecular chain using an acid anhydride such as trimellitic anhydride, phthalic anhydride, and succinic anhydride. Obtainable.

[0011] A specific method for producing such a resin is widely known. Such resins are commercially available. The resin having an acid value of generally 5 to 40 is generally used. Such a thermoplastic polyester resin has good adhesion to various materials such as metal, and also has good heat resistance and water resistance, and is excellent as a binder resin.

The above-mentioned thermoplastic polyester resin having a carboxyl group is added to the thermoplastic polyester resin having a hydroxyl group.
And mix it with resin . In this case, the carboxyl group
Use of thermoplastic polyester resin with
Adhesion is further improved as compared to the case where Has a hydroxyl group
The thermoplastic polyester resin is generally blended in a range of 80% by weight or less.

[0013] In the present invention, a thermosetting resin having a hydroxyl group is used.
A metal complex salt capable of reacting with a carboxyl group of the resin is mixed with a plastic polyester resin and a thermoplastic polyester resin having a carboxyl group, and this is used as a binder resin.

As the metal complex salts, iron, cobalt, zinc,
An acetylacetonate complex salt of a metal such as nickel and aluminum, an 8-oxyquinoline complex salt and the like are used. These metal complex salts are preferable because of their good reactivity with the carboxyl group of the resin and solubility in a solvent. These metal complex salts are generally used in an amount of 0.5 to 3 mol, preferably 1.5 to 3 mol, per 1 mol of the carboxyl group of the thermoplastic polyester resin.
About 2.5 mol is blended.

Further, conductive fine powder is blended with the binder resin and uniformly dispersed. As conductive fine powder, metal powder such as gold, silver, nickel, copper, alloy powder such as aluminum / magnesium alloy, aluminum / nickel alloy, metal plating powder such as gold-plated nickel, etc. Tin oxide,
Metal oxides such as indium oxide, carbon black, and the like are used. These conductive fine powders generally have a size of 50 μm or less.

Such a conductive fine powder is generally used in an amount of 3 to 70% by weight based on 100 parts by weight of the binder resin.
An appropriate amount is blended within the range. If the compounding amount is too small, conduction will not occur not only in the lateral direction but also in the thickness direction. Conversely, if the blending amount is too large, conduction occurs not only in the thickness direction but also in the lateral direction, making it impossible to obtain anisotropy and lowering the adhesive strength.

The anisotropic conductive thermal adhesive of the present invention is generally formed into a paste or film by the following method. The paste-like anisotropic conductive thermal adhesive is prepared by dissolving the above-mentioned thermoplastic polyester resin and the metal complex salt in a suitable solvent such as tetrahydrofuran, methyl ethyl ketone, acetone, chloroform, carbitol acetate, etc. to form a binder resin solution. This is mixed with an appropriate amount of conductive fine powder and uniformly dispersed to form a paste. In this case, known thixotropic agents, dispersion stabilizers, defoaming agents and the like used in this type of adhesive are added as needed.

The film-like anisotropic conductive thermal adhesive is prepared by applying the above-mentioned paste-like anisotropic conductive thermal adhesive to one surface of a release sheet and drying the same to remove the solvent. Formed on top of the film. In this case, the thickness of the adhesive is generally 20 to 150 μm.

In order to electrically connect two electrode substrates using the film-like anisotropically conductive adhesive thus obtained, the film-like anisotropically conductive adhesive is applied to the two electrodes. Substrate, for example, a flexible printed circuit board (FP)
C) and a printed winding board (PWB), sandwiched between an electrode substrate such as a liquid crystal panel and a drive circuit board,
This is heated and pressurized to thermally melt the thermal adhesive.

When a paste-like anisotropic conductive thermal adhesive is used, the paste-like anisotropic conductive thermal adhesive is applied to the surface of one of the electrode substrates by screen printing or the like and dried. The other electrode substrate is placed on this, and is heated and pressurized to thermally melt the thermal adhesive.

The heating and pressurizing conditions vary depending on the molecular weight of the thermoplastic polyester resin to be used, the metal complex salt mixed therein, and the like.
It is hot pressed at 0 kg / cm ² for several seconds to several minutes. In this way, the two electrode substrates are connected by the film-like or paste-like anisotropic conductive thermal adhesive so as to be electrically conductive only in the thickness direction.

[0022]

According to the anisotropic conductive adhesive of the present invention, the carboxyl group of the resin reacts with the metal complex to cause ionic cross-linking between the resin molecules by metal ions, thereby improving heat resistance. When the ionic cross-linking is performed, the ionic bonds between the molecules of the resin are broken by reheating, and the resin is melted and easily flows. At this time,
Thermoplastic polyester having a hydroxyl group as an indole resin
Thermoplastic polyester with terresin and carboxyl group
Has a carboxyl group when used in combination with
When using a thermoplastic polyester resin alone
In addition, adhesion to adherends such as electrode substrates is further improved.
As well as reheating the adhesive to adhere
It can be easily peeled off from the body.

[0023]

EXAMPLES Examples and comparative examples of the present invention will be described below. Example 1 A thermoplastic polyester resin having a carboxyl group (average molecular weight: 15,000 to 20,000, acid value: 6 to 8 KOH m
g / g) (Byron RV-296: manufactured by Toyobo) 100
Parts by weight were dissolved in 100 parts by weight of a carbitol acetate solvent to prepare a polyester resin solution.

Also, 100 parts by weight of aluminum acetylacetonate was dissolved in 2.6 parts by weight of a carbitol acetate solvent to prepare a metal acetate solution. Gold-plated nickel powder (average particle size 20 μm) was used as the conductive fine particles.
m) was prepared.

80 parts by weight of the polyester resin solution, 20 parts by weight of the metal acetate solution, and 5 parts by weight of the conductive fine particles are mixed well to form a paste-like anisotropic conductive heat bond in which the conductive fine particles are uniformly dispersed. A preparation was made.

This paste-like anisotropic conductive thermal adhesive is applied to one side of a release sheet made of polyester treated with a release agent and dried with a hot air drier at about 100 ° C. An electrically conductive thermal adhesive was prepared.

This film-like anisotropic conductive heat-adhesive with a release sheet is cut into a strip having a width of 5 mm, placed on an electrode (wiring) surface of a flexible printed circuit board (FPC), and temporarily fixed with a hand sealer. After that, the release sheet is removed, and a print winding board (PWB) is placed on it.
The electrode (wiring) surfaces of the above were placed together, and this was thermocompression-bonded with a heat sealer at a temperature of about 150 ° C. under a pressure of about 30 kg / cm ² for about 10 seconds to bond the FPC and PWB and bond the test piece. Created.

In this case, the bonding temperature is 140 to 16
This was possible over a wide range of 0 ° C. Further, even after the film-like anisotropic conductive heat adhesive is left at room temperature for one month,
Adhesion was possible at 0 to 160 ° C.

With respect to this test piece, the adhesive force and the connection resistance were measured by the following methods immediately after bonding and after an environmental test (leaving for 500 hours in an environment of a temperature of 80 ° C. and a relative humidity of 95%). Further, the test pieces were evaluated for repairability. Table 1 shows the results. In the first embodiment, 1
The repairability when heated to 60 ° C depends on the adherend FP
The C electrode substrate may be peeled and damaged , which is slightly inferior to those of the other examples. However, if the heating temperature is slightly increased, there is no problem in repairability. However, if the heating temperature is slightly increased,
The FPC electrode substrate or PWB electrode plate as the body is slightly deformed
You.

(1) Measurement of Adhesive Strength The PWB was fixed so that the joint length of the test piece was 1 cm, and the peel strength was measured by pulling the FPC at a speed of 50 mm / min in the 90 ° direction. .

(2) Measurement of connection resistance At the joint of the test pieces, the electrodes (wirings) opposed to the FPC and the PWB were contacted with a stylus to measure the resistance value.

(3) Evaluation of Repairability The test piece was heated in a hot air drier at 160 ° C., and immediately after being taken out, the FPC and the PWB were peeled off.

Example 2 In Example 1, 100 parts by weight of the thermoplastic polyester resin having a carboxyl group was replaced by a thermoplastic polyester resin having a carboxyl group (molecular weight: 15,000).
20,000, acid value 6-8 KOH mg / g) (byron RV-296: manufactured by Toyobo Co., Ltd.), 50 parts by weight, and a thermoplastic polyester resin having a hydroxyl group (molecular weight: about 20,000)
(Stafix P-LC: manufactured by Fuji Photo Film Co., Ltd.) 5
A mixed resin with 0 parts by weight was used.

Otherwise, the procedure was the same as in Example 1. Table 1 shows the results. Example 3 In Example 1, 100 parts by weight of the thermoplastic polyester resin having a carboxyl group was replaced by a thermoplastic polyester resin having a carboxyl group (molecular weight: 15,000).
20,000, acid value 6-8 KOH mg / g) (Byron RV-296: manufactured by Toyobo Co., Ltd.), 20 parts by weight, and a thermoplastic polyester resin having a hydroxyl group (molecular weight: about 20,000)
(Stafix P-LC: manufactured by Fuji Photo Film Co., Ltd.) 8
A mixed resin with 0 parts by weight was used.

Otherwise, the procedure was the same as in Example 1. Table 1 shows the results. Example 4 In Example 1, a thermoplastic polyester resin having a carboxyl group (molecular weight: 15,000) was used instead of 100 parts by weight of the thermoplastic polyester resin having a carboxyl group.
20,000, acid value 6-8 KOH mg / g) (Viron RV-296: manufactured by Toyobo Co., Ltd.), 10 parts by weight, and a thermoplastic polyester resin having a hydroxyl group (molecular weight: about 20,000)
(Stafix P-LC: manufactured by Fuji Photo Film Co., Ltd.) 9
A mixed resin with 0 parts by weight was used.

Otherwise, the procedure was the same as in Example 1. Table 1 shows the results. Example 5 In Example 3, 100 parts by weight of aluminum acetylacetonate was used instead of 100 parts by weight of aluminum acetylacetonate, and 2.6 parts by weight of a chloroform solvent was used instead of 2.6 parts by weight of a carbitol acetate solvent. Was used.

Otherwise, the procedure was the same as in Example 3. Table 1 shows the results. Example 6 Paste-like anisotropic conductive thermal adhesive 10 prepared in Example 1
0 parts by weight of thixotropic agent (Dispalon @ 690
0-20X: 7.5 parts by weight of Kusumoto Kasei Co., Ltd., 0.5 parts by weight of a dispersion stabilizer for conductive particles (TSL-8350: manufactured by Toray Silicone Co., Ltd.), and an antifoaming agent (care @ 20: Seiko Advance Co., Ltd.) 1.0 parts by weight) were uniformly mixed to prepare a screen-printable paste-like anisotropic conductive heat adhesive (ink).

This paste-like anisotropic conductive thermal adhesive (ink) is screen-printed on the electrode (wiring) surface of a flexible printed circuit board (FPC), dried, and then placed on a printed winding board (PWB) electrode. (Wiring), and heat-pressed with a heat sealer at a temperature of about 150 ° C. under a pressure of about 30 kg / cm ² for about 10 seconds.
A test piece was prepared by bonding PC and PWB. Other than that, it carried out similarly to Example 1. Table 2 shows the results.

In this case, the bonding temperature is 140 to 1
This was possible over a wide range of 60 ° C. Further, the paste-like anisotropic conductive thermal adhesive could be bonded at 140 to 160 ° C. even after being left at room temperature for one month.

Example 7 The paste-like anisotropic conductive heat adhesive 10 prepared in Example 1 was used.
Instead of 0 parts by weight, 100 parts by weight of the paste-like anisotropic conductive thermal adhesive prepared in Example 2 was used.

Otherwise, the procedure was the same as in Example 6. Table 2 shows the results. Example 8 Paste-like anisotropic conductive thermal adhesive 10 prepared in Example 1
Instead of 0 parts by weight, 100 parts by weight of the paste-like anisotropic conductive thermal adhesive prepared in Example 3 was used.

Otherwise, the procedure was the same as in Example 6. Table 2 shows the results. Example 9 Paste-like anisotropic conductive thermal adhesive 10 prepared in Example 1
Instead of 0 parts by weight, 100 parts by weight of the paste-like anisotropic conductive thermal adhesive prepared in Example 4 was used.

Otherwise, the procedure was the same as in Example 6. Table 2 shows the results. Example 10 Paste-like anisotropic conductive thermal adhesive 10 prepared in Example 1
Instead of 0 parts by weight, 100 parts by weight of the paste-like anisotropic conductive thermal adhesive prepared in Example 5 was used.

Otherwise, the procedure was the same as in Example 6. Table 2 shows the results. Comparative Example 1 In Example 1, instead of 100 parts by weight of the thermoplastic polyester resin having a carboxyl group, a thermoplastic polyester resin having a hydroxyl group (molecular weight: about 20,000) (Stafix P-LC: manufactured by Fuji Photo Film Co., Ltd.) 100
Parts by weight were used. Also, no metal acetate solution was used.

Otherwise, the procedure was the same as in Example 1. Table 1 shows the results. Comparative Example 2 A commercially available thermosetting film-like anisotropic conductive adhesive (CP3
131: manufactured by Sony Chemical Co., Ltd.) using a heat sealer at a temperature of about 165 ° C. and a pressure of about 20 kg / cm ² for about 6 hours.
The test piece was prepared by thermocompression bonding for 0 second to bond the FPC and the PWB. Other than that, it carried out similarly to Example 1. Table 1 shows the results.

In this case, if the bonding temperature is too low, the bonding is not performed, and if the bonding temperature is too high, deformation occurs, and good bonding cannot be achieved unless the temperature is in a relatively narrow range of 160 to 170 ° C. When the film-like anisotropic conductive thermal adhesive is left at room temperature for one month, the curing proceeds to 160-170.
Could not be bonded at ℃.

Comparative Example 3 Paste Anisotropic Conductive Thermal Adhesive 1 Prepared in Example 1
Instead of 00 parts by weight, 100 parts by weight of the paste-like anisotropic conductive thermal adhesive prepared in Comparative Example 1 was used.

Other than that, it carried out similarly to Example 6. Table 2 shows the results. It should be noted that the first and sixth embodiments were used.
Are, together with Comparative Examples 1 to 3, different from the scope of the present invention.
One side conductive thermal adhesive.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

As described above, the anisotropic conductive adhesive of the present invention comprises a thermoplastic polyester resin having a hydroxyl group, a thermoplastic polyester resin having a carboxyl group, and a metal complex salt capable of reacting with the carboxyl group of the resin. The conductive fine powder is dispersed in a binder resin consisting of, and the property of the thermoplastic resin is maintained as it is before bonding. Therefore, the anisotropic conductive thermal adhesive using such a binder resin has the same joining workability as that using a conventional thermoplastic resin.

Further, such an anisotropic conductive thermal adhesive is
The carboxyl group of the resin reacts with the metal complex to cause ionic cross-linking by metal ions between the molecules of the resin, thereby improving heat resistance. In addition, a thermoplastic polyester resin having a hydroxyl group
Thermoplastic polyester resin with fat and carboxyl group
Can be used in combination with
Compared to using plastic polyester resin alone
The adhesion to adherends such as electrode substrates.
Up. Therefore, adhesive strength comparable to that using a conventional thermosetting resin is obtained, and good bonding reliability is obtained.

Moreover, the anisotropic conductive thermal adhesive after bonding is as follows:
When heated, the ionic bonds between the resin molecules are broken and the resin melts and flows. Therefore, the adherend adhered by reheating can be peeled off, washed with a solvent and reused,
It has good repairability similar to that using a conventional thermoplastic resin.

As described above, the anisotropic conductive thermal adhesive of the present invention has good bonding workability, bonding reliability, and repairability, and electrically conducts two electrode substrates only in the thickness direction. Excellent as a thermal adhesive for connecting.

Claims (1)

(57) [Claims] 1. A thermoplastic polyester resin having a hydroxyl group.
An anisotropic conductive heat adhesive characterized in that conductive fine powder is dispersed in a binder resin comprising a thermoplastic polyester resin having a fat and a carboxyl group and a metal complex salt capable of reacting with the carboxyl group of the resin. .