JPH0565348A - Anisotropically conductive film - Google Patents

Abstract

PURPOSE:To provide the subject film capable of bonding minute connecting terminals at a high reliability by incorporating a specified amt. of conductive particles having specified particle diameters into an insulting adhesive. CONSTITUTION:The objective film is produced by incorporating conductive particles (e.g. an atomized solder powder) having particle diameters in the range of 3-15mum and a mean particle diameter of 5-10mum into an insulating adhesive (e.g. one obtd. by reacting a mixture of a polyvinyl acetate resin and gamma-aminopropyltriethoxysilane with a bisphenol A epoxy resin) in an amt. of the particles of 1-20vol% based on the solid resin content of the adhesive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be used for electrical connection between minute circuits, more specifically for connection between an LCD (liquid crystal display) and a flexible circuit board, and micro joining between a semiconductor IC and an IC mounting circuit board. The present invention relates to an anisotropic conductive film that can be manufactured.

[0002]

2. Description of the Related Art With the recent miniaturization and thinning of electronic devices, the necessity of connecting minute circuits to each other, connecting minute parts to minute circuits, etc. has been dramatically increasing. Anisotropic conductive adhesives and films are beginning to be used. (For example, JP-A-59-120436, 60-191228,
61-274394, 61-287974, 62-244142, 63-153534, 63
-305591, 64-47084, 64-81878, JP-A-1-46549
, 1-251787, etc.)

According to this method, an adhesive or film containing a predetermined amount of conductive particles is sandwiched between the circuits to be connected, and thermocompression bonding is performed at a predetermined temperature, pressure and time to establish electrical connection between the circuits. At the same time, the insulation is secured between adjacent circuits.

Conventionally, this anisotropic conductive adhesive or anisotropic conductive film is roughly classified into a thermoplastic type having a thermoplastic resin as an adhesive component and a thermosetting type having a thermosetting resin as an adhesive component. Panel driver IC and LC
Adoption is rapidly advancing in applications such as connecting D substrates, and connecting a large number of minute circuit terminals together.

Recently, with the colorization and size increase of LCD panels, instead of the thermoplastic type, the adoption of a thermosetting type anisotropic conductive film centering on an epoxy resin, which is more reliable, is increasing. ..

Regarding workability, the adherend (LCD panel,
There is an upper limit for the heating temperature based on the heat resistance of the substrate, etc., and there is a strong demand for improving work efficiency such as shortening the cycle time.
Usually, it must be cured at about 150 to 200 ° C. for about 30 seconds or less. At the same time, under normal use conditions, storage stability at room temperature for 3 months or more (up to 6 months) is required, and after connection, it must be excellent in reliability such as moisture resistance.

Further, in the connection between the circuits by the anisotropic conductive film, recently, the demand for 10 to 20 terminals per 1 mm, that is, the connection of the pitch of 0.1 to 0.05 mm has been increased. This is due to the increase in the number of connection circuits that accompanies the high definition, multicolor and large size of the liquid crystal panel display.

As described above, the conventional anisotropic conductive film (for example, JP-A-60-
115678, 61-195178, JP-A-1-185380, 1-185381,
1-261478, 2-288019, etc.) and most of the commercially available products have a large conductive particle diameter and short-circuit adjacent connection terminals.

Further, as in the conventional case, there is a strong demand for a highly reliable thermosetting anisotropic conductive film having fast curing, long life, repairability, moisture resistance and low distortion.

[0010]

DISCLOSURE OF THE INVENTION The present invention has a thickness of 0.1 to 0.05 mm, which cannot be obtained by the conventional anisotropic conductive film.
Provided is an anisotropic conductive film capable of reliably connecting connection terminals having a pitch or less.

[0011]

DISCLOSURE OF THE INVENTION The present invention relates to an anisotropic conductive film containing 1 to 20% by volume of conductive particles with respect to the resin solid content in an insulating adhesive, and the particle size of the conductive particles. Is 3 to 15 μm and the average particle diameter is 5 to 10 μm.

Examples of the conductive particles include metals such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver and gold, metal oxides, alloys such as solder, carbon, graphite, glass and ceramics. , Conductive particles obtained by coating a core material such as plastic with a metal by a method such as plating. From the viewpoint of reliability, gold, nickel, solder alloy, indium alloy and the like are preferable.

These conductive particles are classified by air flow classification, wet classification,
It is possible to use those that have been subjected to precise classification by a sieving method or the like to have a uniform particle size distribution, or those in which a metal thin film has been formed by plating, surface modification, etc. on plastic that has grown to a uniform particle size by dispersion polymerization or the like. is there.

If the diameter of the conductive particles exceeds 15 μm, a short circuit may occur between adjacent circuits, and if it is 3 μm or less, reliability deteriorates.

The content of the conductive particles is preferably 1 to 20% by volume with respect to the solid content in the adhesive. If it is less than 1% by volume, stable conduction reliability cannot be obtained, and if it exceeds 20% by volume, the insulation reliability between adjacent circuits is deteriorated.

The average particle diameter of the present invention is 5 to 10 μm, and the average particle diameter is measured by a laser analysis method (Microtrack).

As the adhesive component used in the present invention, a highly reliable epoxy thermosetting or epoxy acrylate photocurable adhesive or the like is preferably used.

As described above, an anisotropic conductive film is prepared using the resin material and the conductive particles that have been selected and prepared.
Further, various surfactants, antifoaming agents and stabilizers may be appropriately added in order to improve the stability / compatibility of the resin solution and the dispersibility of the conductive particles.

The anisotropic conductive film is produced by the following method. That is, these resin solutions are uniformly mixed at a predetermined blending ratio, conductive particles which have been surface-treated in advance are weighed therein, and sufficiently stirred and mixed until uniformly dispersed in the resin solution. Then, additives and the like are added and adjusted with a solvent to prepare a resin solution for anisotropic conductive film having a solid content of 20 to 30%.

This resin solution is cast and dried on a polyester film or a Teflon film which has been subjected to a mold release treatment to obtain an anisotropic conductive film having a thickness after drying of 20 to 50 μm.

[0021]

The present invention will be described in detail below with reference to examples. In addition, a part represents a weight part.

Example 1 Degree of acetylation of 3 mol% or less, Degree of acetalization of 75 mol%
50% solution of bisphenol A type epoxy resin (epoxy equivalent 900 g / eq) in a mixture of 250 parts of 20% solution obtained by dissolving polyvinyl acetal resin in toluene in 1 part and 1 part of γ-aminopropyltriethoxysilane in toluene 50 parts, 80 parts of a bisphenol A type epoxy resin (epoxy equivalent 200 g / eq) and 30 parts of a microencapsulated imidazole derivative are rapidly stirred and mixed, and as conductive particles, the average particle size is 8 μm and the maximum particle size is 14 μm. Solder atomized powder with a minimum particle size of 3 μm was added to the resin solid content in an amount of 5% by volume and uniformly dispersed, and then toluene was added and dried on a FEP (tetrafluoroethylene-6-fluorinated propylene copolymer) film. Thickness is 20μ
It was cast and dried so that the thickness became m, to obtain the anisotropic conductive film.

Example 2 Benzoguanamine was electrolessly plated with nickel and gold in the same resin varnish as in Example 1 and the particle size was 5 ± 0.2 μm.
5% by volume of the conductive particles were dispersed in the resin solid content, and the particles were cast and dried so that the thickness after drying was 20 μm as in Example 1 to obtain an anisotropic conductive film.

Example 3 100 parts of bisphenol A diglycidyl methacrylate oligomer (so-called epoxy methacrylate type) as a photocurable adhesive, 1 part of benzyl diketal as a photoinitiator, and 0.003 part of benzoquinone as a sensitizer were roll-kneaded. Stir and mix with a machine, and indium / lead alloy atomized powder having the same particle size as in Example 1 is added to the resin solid content,
3% by volume is uniformly dispersed and cast on FEP to a thickness of 20μ
The anisotropic conductive film was obtained so as to have a thickness of m.

Comparative Example 1 An average particle size of 13 μ was put into the same resin varnish as in Example 1.
m, a maximum particle size of 32 μm, and a minimum particle size of 2 μm, 5% by volume of the solder atomized powder was added to the resin solid content and uniformly dispersed to obtain the anisotropic conductive film in the same manner as in Example 1.

Comparative Example 2 The same resin varnish as in Example 1 was filled with an average particle diameter of 1 μm.
A solder atomized powder having a maximum particle size of 3 μm and a minimum particle size of 0.5 μm was added to the resin solid content in an amount of 5% by volume and uniformly dispersed to obtain the anisotropic conductive film in the same manner as in Example 1.

Comparative Example 3 In the same resin varnish as in Example 1, the same solder atomized powder as conductive particles was added in an amount of 0.5% by volume based on the resin solid content and uniformly dispersed. I got a film.

Comparative Example 4 In the same resin varnish as in Example 1, 50% by volume of the same solder atomized powder as conductive particles was added to the resin solid content and uniformly dispersed, and the anisotropic conductive film was similarly obtained. Obtained.

The adherends of the test pieces used in the above Examples and Comparative Examples were copper foil 18 μm, nickel 5 μm and gold 0.5 μm.
Flexible circuit board (Pitch 0.1
mm, 200 terminals, pitch 0.05 mm, 20 terminals
0) and an ITO glass having a surface resistance of 15Ω were used.

In the test of short circuit between terminals, the resistance value between adjacent terminals was measured by pressure bonding to the back surface of the ITO glass (that is, the glass surface without the ITO film).

As a reliability test, -30 ° C./30 minutes →
The connection resistance between the adjacent terminals was measured after 300 cycles of the temperature cycle test with 25 ° C./5 minutes → 80 ° C./30 minutes → 25 ° C./5 minutes as one cycle. The above results are shown in Table 1.

[0032]

[Table 1]

[0033]

According to the present invention, it is possible to obtain an anisotropic conductive film capable of reliably connecting a connection terminal having a pitch of 0.1 to 0.05 mm or less, which is not obtained by the conventional anisotropic conductive film. , By using it to connect the input terminals of the liquid crystal panel display, higher definition, multicolor,
It is possible to deal with larger size.

Claims (1)

[Claims] 1. A resin solid content of 1 in an insulating adhesive.
An anisotropic conductive film containing conductive particles in an amount of ˜20% by volume, wherein the conductive particles have a particle size of 3 to 15 μm and an average particle size of 5 to 10 μm.