JPH04118873A - Anisortopic conductive circuit base material - Google Patents

Abstract

PURPOSE:To obtain a high adhesive strength even in a high temperature and a high humidity, to reduce the rise of conductive resistance, and to improve the durability, by composing the adhesive in two layers by using different resins at the glass base side and at the polyimide base side. CONSTITUTION:The adhesive is composed of two layers, by using an epoxy resin 3 at a glass base 1 side, while using a polyester resin 4 at the polyimide base 2 side. By such a constitution, the glass base 1 is adhered with the epoxy resin 3 while the polyimide base 2 is adhered with the polyester resin 4 rigidly respectively. And since the epoxy resin 3 and the polyester resin 4 are adhered in a good affinity at their interface, the glass base 1 and the polyimide base 2 are adhered rigidly. In such a way, the electrode 5 at the glass base 1 side, and the electrode 5 at the polyimide base 2 side are connected electrically through conductive particles 6.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an anisotropically conductive method in which a glass substrate on which an electric circuit is formed and a polyimide substrate are electrically connected with an anisotropically conductive adhesive. Regarding circuit base materials.

[Conventional technology]

Printed wiring boards and IC boards used in consumer electronic equipment such as televisions, audio equipment, and cameras, or industrial electronic equipment such as computers, communication equipment, and automobiles, include:
Inorganic substrates such as glass and polymer substrates such as polyimide are used.

The electric circuits formed on the glass substrate and the polyimide substrate are electrically connected via their respective electrodes.

With the recent trend toward smaller and thinner electronic components, electronic circuits are becoming increasingly denser, and conventional soldering and connector connections are no longer compatible with the above-mentioned board connections. As a result, anisotropic conductive adhesives have come to be used.

Anisotropic conductive adhesive is an adhesive in which conductive particles are dispersed between opposing electrodes, electrically connecting the electrodes, simultaneously insulating adjacent electrodes, and adhesively fixing the opposing electrodes. The adhesive components of such adhesives include thermosetting resins such as epoxy resins, acrylic ester resins, melamine resins, urea resins, and phenolic resins;
Resins that can be cured by electromagnetic wave irradiation with ultraviolet rays, electron beams, etc., such as acrylic esters of polyhydric alcohols, polyester acrylates, and unsaturated esters of polyhydric carboxylic acids, are known.

[Problem to be solved by the invention]

However, with circuit substrates in which a glass substrate on which an electric circuit is formed and a polyimide substrate are electrically connected using a conventional anisotropic conductive adhesive, although the initial connection performance is good, the durability is limited. The connection was unreliable. This is because under high temperature or high humidity conditions, the physical adhesive strength of conventional anisotropic conductive adhesives decreases and the adhesive components swell, resulting in an increase in connection resistance. .

Generally, when adhering specific materials industrially, the most suitable adhesive is selected from among a large number of adhesives that can be bonded, based on adhesive strength and the like.

However, since the anisotropic conductive adhesive is made by dispersing conductive fine particles in the adhesive component, the properties of the interface between the substrate surface and the adhesive during bonding are theoretically extremely complex.

On the other hand, with respect to adhesives, there is no established method to independently measure only the bonding force at the interface during adhesion, so it is difficult to find the best adhesive for connecting the glass substrate and polyimide substrate. It is almost impossible to select theoretically.

In view of the above problems, the present inventors have conducted numerous experiments and research on anisotropic conductive adhesives for electrically connecting glass substrates and polyimide substrates, and have found that they can withstand high temperatures and high humidity. The present invention has been completed by discovering an anisotropically conductive adhesive that has strong adhesive strength, little increase in conduction resistance, and excellent durability.

[Means to solve the problem]

The present invention provides an anisotropically conductive circuit substrate in which a glass substrate on which an electric circuit is formed and a polyimide substrate are electrically connected with an anisotropically conductive adhesive, in which the adhesive is made of epoxy resin on the glass substrate side. , relates to an anisotropically conductive circuit substrate characterized in that the polyimide substrate side is composed of two layers of polyester resin.

The anisotropically conductive circuit substrate according to the present invention will be specifically explained below.

In the present invention, an anisotropically conductive circuit substrate refers to a substrate in which two substrates on which an electric circuit is formed are electrically connected with an anisotropically conductive adhesive, and the glass substrate is a glass plate. A substrate having ITO or the like placed as an electrode on its surface is used, while a polyimide substrate having copper metal or the like placed as an electrode on the surface of a polyimide film is used.

In the anisotropically conductive circuit substrate according to the present invention, the adhesive is composed of two layers, with the glass substrate side using an epoxy resin and the polyimide substrate side using a polyester resin as an adhesive component.

With this configuration, the glass substrate is firmly adhered to the epoxy resin, and the polyimide substrate is firmly adhered to the polyester resin, and the epoxy resin and polyester resin are bonded with good compatibility at these interfaces.
The glass substrate and polyimide substrate are firmly bonded. In this way, the electrode on the glass substrate side and the electrode on the polyimide substrate side are electrically connected by the conductive particles.

Generally, two-component epoxy resins are used, which are made by combining a diglycidyl ether type of bisphenol A as the main ingredient and various polyamines, polyamides, acid anhydrides, polymercaptans, polysulfides, etc. as curing agents. use Epoxy resins come in liquid and powder forms, and there are also liquid chamber types.

Polyester resins include hot melt type, solution type,
Both thermoplastic and thermosetting types can be used.

Conductive particles dispersed in an insulating adhesive component are typically
Known materials such as metals such as nickel, gold, and silver used in anisotropically conductive adhesives, alloys thereof, oxides such as tin oxide, and carbon may be used. In particular, the conductive particles described in Japanese Patent Application No. 1-177997 are suitable.

These conductive particles may be dispersed in both resins or in either one of the resins before the substrate bonding operation, but when exposed to long-term conditions under high temperature and high humidity, From the viewpoint of physical adhesive strength, those dispersed in an epoxy resin are preferred.

Typically, 0.2 to 40% by weight of conductive particles are dispersed in the adhesive.

The shape of the adhesive before bonding the substrates is tape-like, which is convenient for bonding operations, but paste-like may also be used.

The drawing schematically shows a circuit substrate in which an electrode on the glass substrate side and an electrode on the polyimide substrate are electrically connected by conductive particles via an adhesive consisting of an epoxy resin layer and a polyester resin layer. This is shown in a cross-sectional view.

〔Example〕

A mixture of 487 g of ethyl alcohol and 389 g of water was kept at 35° C. while stirring, and 71.7 g of ammonia gas was dissolved in the mixture. 17.4 g of 28% ethyl silicate was added to this mixed solution, and stirring was continued for 2 hours to obtain a cloudy white liquid in which seed particles equivalent to 0.5% by weight were dispersed in 5 tar.

Immediately, 3.3 g of an aqueous solution in which 0.03 g of NaOH was dissolved was added to this cloudy liquid to obtain a heel sol in which seed particles were dispersed in a water-alcohol dispersion.

97 g of the obtained heel sol was kept at 35°C with stirring, and a mixture of 455 g of ethyl alcohol and 886 g of water and 570 g of 28% ethyl silicate were simultaneously added gradually over 19 hours while controlling the pH to 11.5 with ammonia gas. Added. After adding the entire amount, add NaO to the solution.
Add 103 g of an aqueous solution in which 1 g of H is dissolved, and heat this at 70°C.
The dispersion was heated to 2 hours and maintained for 2 hours to obtain a dispersion.

This dispersion was treated with ammonia gas in the same manner as above.
Ethyl alcohol, water and ethyl silicate were added while controlling H at 11.5, and after adding an aqueous NaOH solution, heating was repeated to obtain powder particles (G1) with an average particle size of 7 μm. These powder particles have an average particle diameter of 7 μm ± 10%,
It was 96% by weight.

On the other hand, 29.2 g of silver nitrate was dissolved in a solution prepared by diluting 281 fl of a 24% by weight ammonia aqueous solution with 800 g of water. 20 g of powder particles (Gl) were added to 600 g of water under stirring, and the ammoniacal silver nitrate aqueous solution was further added to sufficiently disperse the mixture. While stirring this mixed solution, a solution prepared by diluting 32.8 g of 30% formalin with 180 g of water was dropped, and the surfaces of the powder particles were silver-plated. Next, after filtration and washing, the particles were dried at 90° C. to obtain conductive particles (G2).

The obtained conductive particles have a specific gravity of 3.12, a plating film thickness of 400 mm, and a specific resistance of 3 x 10-! Ω・l
Met.

90 g of this conductive particle (G2) and methyl methacrylate resin powder (manufactured by Soken Chemical, trade name MP-1000, particle size 0.
4 μm, softening temperature 170° C.), and the resin was adsorbed onto the surface of the conductive particles (G2).

Next, the conductive particles on which the resin was adsorbed were placed in a ball mill and mixed, and the surfaces of the conductive particles were coated with the resin to obtain insulating thermoplastic resin-coated conductive particles (G3).

The average particle diameter of the insulating thermoplastic resin-coated conductive particles (G3) is 7.7 μm, and the thickness of the insulating thermoplastic resin coating layer is 0.3 μm, which is relative to the diameter of the conductive particles (G2). It was 4.2%.

This conductive particle (G3) was used as a conductive particle in the following examples.

A thermosetting resin (Toyobo Co., Ltd.) containing 10 parts by weight of conductive particles (G3) and an epoxy resin and acroyl monomer (Toyobo Co., Ltd.)
An anisotropically conductive adhesive (Bl) was prepared by dispersing the adhesive in 90 parts by weight (manufactured by KW45GA).

Further, an anisotropic conductive adhesive (B2) was prepared in which 10 parts by weight of conductive particles (G3) were dispersed in 90 parts by weight of a polyester resin (Vylon 500, manufactured by Toyobo Co., Ltd.).

(Manufacture of anisotropically conductive tape) Using an anisotropically conductive adhesive (B1) using a screen printing machine, a 50 μm thick polyethylene terephthalate resin (P
ET) film was printed through a 150 mesh screen, and this film was dried in a dryer at 100° C. for 10 minutes to obtain an anisotropic conductive tape (T1) coated with an adhesive (Bl) layer.

Next, the adhesive (B1) of this anisotropic conductive tape (TI)
An anisotropic conductive adhesive (B2) was screen printed on the layer, and the film was dried in a dryer at 120°C for 15 minutes to coat the adhesive (Bl) layer and the adhesive (B2) layer. An anisotropic conductive tape (T2) was obtained.

(Production of anisotropic conductive circuit substrate) An anisotropic conductive tape (T2) is placed on a polyimide film on which copper electrodes are installed with a distance of 30 μm between the electrodes so that the adhesive (B2) layer is in contact with the electrodes. After transferring the adhesive layer by pressing with a heat sealer at 150° C. for 10 seconds under a load of 20 kg/a/G, the PET film is peeled off.

Next, transparent electrodes provided on the surface of the glass substrate with a distance of 30 μm between the electrodes were set on the adhesive layer.
An anisotropically conductive circuit substrate (C1) electrically connected was produced by heat-pressing at 0 kg/cdG and 180°C.

1111 On the adhesive (Bl) layer of the anisotropic conductive tape (Tl) prepared in Example 1, a polyester resin adhesive containing no conductive particles was printed through a 120 mesh screen, and this tape was dried. It was dried in the machine at 120° C. for 15 minutes to obtain an anisotropic conductive tape (T3) coated with an adhesive (Bl) layer and a polyester resin adhesive layer.

Anisotropically conductive circuit substrate (C2) was electrically connected using this anisotropically conductive tape (T3) in the same manner as in Example 1.
) was produced.

and 111 [Anisotropically conductive circuit board electrically connected in the same manner as in Example 1 using the anisotropically conductive tape (T1) coated with only the adhesive (Bl) layer prepared in Example 1. Material (C
3) was produced.

Using a screen printer, the adhesive (B2) prepared in Example 1 was printed through a 150 mesh screen onto a 50 μm thick PET film, and the film was placed in a dryer at 120°C for 15 minutes. Once dry, glue (B2)
Anisotropic conductive tape coated with only one layer (T4)
I got it.

Anisotropically conductive circuit substrate (C4) was electrically connected using this anisotropically conductive tape (T4) in the same manner as in Example 1.
) was produced.

The following evaluation test was conducted on the anisotropically conductive circuit substrates C1, C2, C3, and C4 obtained in Example 1.2 and Comparative Example 1.2. The results are shown in Table 1.

(1) Vertical conductivity Measure the electrical resistance between the transparent electrode on the glass substrate side and the copper electrode on the film substrate side of 10 lines of the electrical circuit, and determine the percentage showing a resistance value of 50Ω or less (vertical conductivity) and the average resistance value. Ta.

(2) Adhesive strength A glass substrate was fixed to a chip pool, a part of the adhesive part was peeled off, it was fixed to a spring scale, the spring scale was pulled until the adhesive part was completely peeled off, and the strength (g) at that time was measured.

(3) Durability The anisotropic conductive circuit substrate was placed in a constant temperature and humidity chamber maintained at a temperature of 60°C and a relative humidity of 90%, and after being left for 500 hours, the above-mentioned vertical conductivity and adhesive strength were measured. .

From Table 1, it can be seen that the circuit base material (C3) connected by an adhesive layer made of only epoxy resin has weak adhesive strength, and the circuit base material (C4) connected by an adhesive layer made only of polyester resin
It can be seen that the vertical conduction resistance value increases and the vertical conductivity rate also decreases under high temperature and high pressure.

On the other hand, it is clear that the anisotropically conductive circuit substrate according to the present invention has excellent adhesive strength and durability.

In addition, we also measured the insulation rate between adjacent electrodes.
Both circuits were good.

〔Effect of the invention〕

The anisotropically conductive circuit substrate according to the present invention is composed of two layers: an epoxy resin on the glass substrate side and a polyester resin on the polyimide substrate side. It has high adhesive strength even under high temperature and high humidity conditions, and has excellent durability because there is little increase in conduction resistance when electrically connecting them.

[Brief explanation of drawings]

The drawing is a cross-sectional view schematically showing a circuit substrate in which an electrode on the glass substrate side and an electrode on the polyimide substrate are connected by an anisotropic conductive adhesive. Patent Applicant Catalysts & Chemicals Co., Ltd. Agent Patent Attorney Ishi 1) Masahisa

Claims (1)

[Claims] In an anisotropically conductive circuit substrate in which a glass substrate on which an electric circuit is formed and a polyimide substrate are electrically connected with an anisotropically conductive adhesive, the adhesive is epoxy resin on the glass substrate side and epoxy resin on the polyimide substrate side. An anisotropically conductive circuit substrate comprising two layers of polyester resin.