JPH05159622A - Anisotropic conductive thermal adhesive - Google Patents

Abstract

PURPOSE:To obtain the anisotropic conductive thermal adhesive having the excellent bonding workability, bonding reliability and repairing property (to heat a body to be bonded again after the adhesion for removal and use the body to be bonded again). CONSTITUTION:The resin solution, which consists of thermoplastic polyester resin including a carboxyl group at 50 parts by weight and thermoplastic polyester resin including a hydroxyl group at 50 parts by weight and carbitol acetate solvent at 100 parts by weight, is prepared. The metallic complex salt solution, which consists of aluminium acetylacetonate as the metallic complex salt at 100 parts by weight and calbitol acetate solvent at 2.6 parts by weight, is prepared. Gold plate nickel powder as the conductive fine particles at 5 parts by weight is mixed with the described resin solution at 80 parts by weight and the metallic complex salt solution at 20 parts by weight, and is dispersed evenly to obtain the target paste-type anisotropic conductive thermal adhesive. This paste-type anisotropic conductive thermal adhesive is applied to one surface of separation sheet, and is dried to obtain the objective film-shape anisotropic conductive thermal adhesive with the separation sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive thermal adhesive used for connecting two electrode substrates or 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-shaped or paste-shaped anisotropic conductive thermal adhesive is used.

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

The anisotropic conductive thermal adhesive of this type mainly has good bonding reliability (even if it is used in a severe environment after bonding, conduction failure does not occur due to a decrease in adhesive strength).
And good bonding workability (the adhesive is easy to store, handle and apply, and the temperature range of thermal bonding is wide).

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

Conventionally, as the 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 in which both are used as a binder resin. An anisotropic conductive thermal adhesive is known, which is formed into a film or paste by dispersing an appropriate amount of conductive fine powder in this binder resin (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 poor connection reliability. On the other hand, an anisotropic conductive thermal adhesive using a thermosetting resin has good connection reliability,
Connection workability and repairability are poor. Further, the anisotropic conductive thermal adhesive that uses both resins together has good connection workability and connection reliability, but poor repairability. As described above, the conventional anisotropic conductive thermal adhesive has advantages and disadvantages.

The present invention solves the above problems, and an object of the present invention is to provide an anisotropic conductive thermal adhesive having good bonding workability, bonding reliability and repairability. It is in.

[0009]

In order to achieve the above object, the anisotropic conductive thermal adhesive of the present invention comprises a thermoplastic polyester resin containing a thermoplastic polyester resin having a carboxyl group and a carboxyl group of the resin. A binder resin composed of a reactive metal complex salt is used, and an appropriate amount of conductive fine powder is dispersed therein.

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

A specific method for producing such a resin is widely known. Also, such resins are commercially available. The acid value of the resin is generally 5 to 40. Such a thermoplastic polyester resin has excellent adhesiveness to various materials such as metals, 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 can be used by blending a thermoplastic polyester resin having no carboxyl group, for example, a normal thermoplastic polyester resin having a hydroxyl group. In this case, the adhesiveness is further improved. The usual thermoplastic polyester resin is generally blended in the range of 80% by weight or less.

In the present invention, a thermoplastic polyester resin containing a thermoplastic polyester resin having a carboxyl group is mixed with a metal complex salt capable of reacting with the carboxyl group of the resin, and this is used as a binder resin.

As the metal complex salt, iron, cobalt, zinc,
Acetylacetonate complex salts of metals such as nickel and aluminum, 8-oxyquinoline complex salts and the like are used. These metal complex salts are preferable because they have good reactivity with the carboxyl group of the resin and solubility in a solvent. These metal complex salts are generally 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 this binder resin and uniformly dispersed. As the conductive fine powder, metal powder of gold, silver, nickel, copper, etc., alloy powder of aluminum / magnesium alloy, aluminum / nickel alloy, etc., metal plating powder of gold-plated nickel etc., metal plated plastic peas, Tin oxide,
A metal oxide such as indium oxide, carbon black or the like is used. As the conductive fine powder, those having a size of 50 μm or less are generally used.

Such conductive fine powder is generally 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 blending amount is too small, electrical connection will not occur not only in the lateral direction but also in the thickness direction. On the other hand, if the blending amount is too large, conduction is caused not only in the thickness direction but also in the lateral direction, anisotropy cannot be obtained, and the adhesive force is also reduced.

The anisotropically 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 thermoplastic polyester resin and metal complex salt in an appropriate solvent such as tetrahydrofuran, methyl ethyl ketone, acetone, chloroform, carbitol acetate to form a binder resin solution. An appropriate amount of conductive fine powder is mixed with this 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 in appropriate amounts, if necessary.

Further, the film-shaped anisotropic conductive thermal adhesive is obtained by applying the above-mentioned paste-shaped anisotropic conductive thermal adhesive on one surface of the release sheet and drying it to remove the solvent. It is formed into a film on the top. 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-shaped anisotropic conductive thermal adhesive thus obtained, this film-shaped anisotropic conductive thermal adhesive is used to connect two electrode substrates. Substrate, for example, flexible printed circuit board (FP
C) and the print winding board (PWB), sandwiched between the liquid crystal panel and the electrode substrate such as the drive circuit board,
This is heated and pressed to heat-melt the thermal adhesive.

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

The heating and pressurizing conditions vary depending on the molecular weight of the thermoplastic polyester resin used, the metal complex salt to be blended with the thermoplastic polyester resin, 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 a film-shaped or paste-shaped anisotropic conductive thermal adhesive so as to be electrically conductive only in the thickness direction.

[0022]

In the anisotropically conductive thermal adhesive of the present invention, the carboxyl group of the resin reacts with the metal complex salt to cause ionic cross-linking due to metal ions between the molecules of the resin, and the heat resistance is improved. Further, this ionic crosslink is melted by breaking the ionic bond between the molecules of the resin when reheated, and easily flows.

[0023]

EXAMPLES Examples and comparative examples of the present invention will be shown below. Example 1 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 Co., Ltd.) 100
A polyester resin solution was prepared by dissolving 100 parts by weight of carbitol acetate solvent.

Further, 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. In addition, as conductive fine particles, gold-plated nickel powder (average particle size 20 μm
m) 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 well mixed to form a paste-like anisotropic conductive thermal adhesive in which the conductive fine particles are uniformly dispersed. The agent was created.

This paste-like anisotropic conductive thermal adhesive is applied to one side of a release sheet treated with a release agent made of polyester and dried by a hot air dryer at about 100 ° C. to form a film-like anisotropic sheet with a release sheet. A one-way conductive thermal adhesive was prepared.

This film-shaped anisotropic conductive thermal adhesive with a release sheet is cut into a strip of 5 mm width, placed on the electrode (wiring) surface of a flexible printed circuit board (FPC), and temporarily fixed with a hand sealer. After removing the release sheet, print winding board (PWB) on it
Put the electrode (wiring) surface together and heat-press this with a heat sealer for about 10 seconds at a temperature of about 150 ° C and a pressure of about 30 kg / cm ² , and bond the FPC and PWB to a test piece. Created.

In this case, the bonding temperature is 140 to 16
It was possible in a wide range of 0 ° C. In addition, even after leaving this film-like anisotropic conductive thermal adhesive at room temperature for 1 month,
It was possible to bond at 0 to 160 ° C.

With respect to this test piece, the adhesive force and the connection resistance were measured by the following method immediately after the adhesion and after the environmental test (left for 500 hours in an environment of a temperature of 80 ° C. and a relative humidity of 95%). In addition, the test pieces were evaluated for repairability. The results are shown in Table 1. In the first embodiment, 1
The repairability when heated to 60 ° C. is slightly inferior to that of the other examples, but there is no problem with the repairability if the heating temperature is raised a little.

(1) Measurement of Adhesive Strength The PWB is fixed so that the length of the joint portion of the test piece is 1 cm, and the FPC is pulled in the direction of 90 degrees at a speed of 50 mm / min to measure the peel strength. ..

(2) Measurement of connection resistance At the joint portion of the test piece, the resistance value was measured by touching the opposing electrodes (wiring) of the FPC and PWB.

(3) Evaluation of Repairability The test piece was heated in a hot-air dryer at 160 ° C., and immediately after taking out the test piece, the FPC and PWB were peeled off, and the damage condition of both was observed and evaluated.

Example 2 In Example 1, 100 parts by weight of the thermoplastic polyester resin having a carboxyl group was replaced with a thermoplastic polyester resin having a carboxyl group (molecular weight: 15,000).
˜20,000, acid value 6 to 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: Fuji Photo Film Co., Ltd.) 5
A mixed resin with 0 parts by weight was used.

Otherwise, the same procedure as in Example 1 was carried out. The results are shown in Table 1. Example 3 In Example 1, 100 parts by weight of the thermoplastic polyester resin having a carboxyl group was replaced with a thermoplastic polyester resin having a carboxyl group (molecular weight: 15,000).
˜20,000, acid value 6 to 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: Fuji Photo Film Co., Ltd.) 8
A mixed resin with 0 parts by weight was used.

Otherwise, the same procedure as in Example 1 was carried out. The results are shown in Table 1. Example 4 In Example 1, 100 parts by weight of the thermoplastic polyester resin having a carboxyl group was replaced with a thermoplastic polyester resin having a carboxyl group (molecular weight: 15,000).
To 20000, acid value 6 to 8 KOH mg / g) (Byron RV-296: manufactured by Toyobo Co., Ltd.) and 10 parts by weight of a thermoplastic polyester resin having a hydroxyl group (molecular weight about 20,000).
(STAFIX P-LC: Fuji Photo Film Co., Ltd.) 9
A mixed resin with 0 parts by weight was used.

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

Otherwise, the same procedure as in Example 3 was carried out. The results are shown in Table 1. Example 6 A paste-like anisotropic conductive thermal adhesive 10 prepared in Example 1
0 parts by weight of thixotropic agent (Disparlon # 690
0-20X: Kusumoto Kasei Co., Ltd.) 7.5 parts by weight, conductive particle dispersion stabilizer (TSL-8350: Toray Silicone Co., Ltd.) 0.5 part by weight, and defoaming agent (care # 20: Seiko Advance Co., Ltd.) 1.0 part by weight was uniformly mixed to prepare a screen-printable paste-like anisotropic conductive thermal adhesive (ink).

This paste-like anisotropic conductive thermal adhesive (ink) is screen-printed on the electrode (wiring) surface of the flexible printed circuit board (FPC), dried, and then the electrode of the print winding board (PWB). Place the (wiring) together and thermocompress with a heat sealer at a temperature of about 150 ° C and 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 was performed like Example 1. The results are shown in Table 2.

In this case, the bonding temperature is 140 to 1
It was possible in a wide range of 60 ° C. Further, even after the paste-like anisotropic conductive thermal adhesive was left at room temperature for 1 month, it was possible to bond at 140 to 160 ° C.

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

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

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

Otherwise, the same procedure as in Example 6 was carried out. The results are shown in Table 2. Example 10 Paste-like anisotropically 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 same procedure as in Example 6 was carried out. The results are shown in Table 2. Comparative Example 1 In Example 1, 100 parts by weight of the thermoplastic polyester resin having a carboxyl group was replaced with 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. In addition, no metal salt solution was used.

Otherwise, the same procedure as in Example 1 was carried out. The results are shown in Table 1. Comparative Example 2 Commercially available thermosetting film-like anisotropic conductive adhesive (CP3
131: manufactured by Sony Chemicals Co., Ltd.) with a heat sealer at a temperature of about 165 ° C. and a pressure of about 20 kg / cm ² for about 6
Thermocompression bonding was performed for 0 seconds, and FPC and PWB were bonded to each other to prepare a test piece. Other than that was performed like Example 1. The results are shown in Table 1.

In this case, if the bonding temperature is too low, the bonding does not occur, and if it is too high, the bonding temperature is deformed, and good bonding cannot be achieved unless the temperature is in a relatively narrow range of 160 to 170 ° C. In addition, the film-shaped anisotropic conductive thermal adhesive left at room temperature for 1 month was cured to 160 to 170.
Could not bond at ℃.

Comparative Example 3 , Paste-like 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.

Otherwise, the same procedure as in Example 6 was carried out. The results are shown in Table 2.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

As described above, the anisotropic conductive thermal adhesive of the present invention comprises a thermoplastic polyester resin containing 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 the binder resin, and the properties of the thermoplastic resin are maintained as they are before the bonding. Therefore, the anisotropic conductive thermal adhesive using such a binder resin has a good bonding workability similar to that using a conventional thermoplastic resin.

Further, such an anisotropic conductive thermal adhesive is
The carboxyl group of the resin and the metal complex salt react with each other to cause ionic cross-linking by metal ions between the molecules of the resin, thereby improving heat resistance. Therefore, an adhesive force comparable to that using a conventional thermosetting resin can be obtained, and good bonding reliability can be obtained.

Moreover, the anisotropic conductive thermal adhesive after adhesion is
When heated, the ionic bonds between the molecules of the resin are broken and the resin melts and flows. Therefore, the adherend adhered by reheating can be peeled off, this can be washed with a solvent and reused,
It has good repairability as well as the one using 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 connects two electrode substrates or the like only in the thickness direction. It is excellent as a thermal adhesive for making connections.

Claims (1)

[Claims] 1. A conductive resin powder is dispersed in a binder resin composed of a thermoplastic polyester resin containing a thermoplastic polyester resin having a carboxyl group and a metal complex salt capable of reacting with the carboxyl group of the resin. Anisotropically conductive thermal adhesive.