JPH01249880A - Anisotropically electrically conductive adhesive sheet - Google Patents

Abstract

PURPOSE:To provide the present sheet durable to such severe test conditions as cold heat cycling esp. under highly humid conditions, having such constitution that silane coupling agent-adsorbed electrically conductive particles are dispersed in a thermoplastic resin. CONSTITUTION:The objective sheet having such constitution that (A) such electrically conductive particles that (i) normally 0.01-5 (pref., 0.1-3) pts.wt. of a silane coupling agent such as 3-glycidoxypropyl trymethoxysilane or an alkoxysilane such as methylmethoxysilane is adsorbed on (ii) 100 pts.wt. of electrically conductive particles (e.g., Ni, iron, Cr, Co, Sb, Mo, copper, silver, platinum, gold) with at least its surface consisting of metal is dispersed in (B) a thermoplastic resin comprising styrene-butadiene-styrene block copolymer. This sheet can suitably be used for integrated circuits in the electronics industry and the circuit connections in various displays.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an anisotropic conductive adhesive sheet suitable for use in circuit connections of integrated circuits and various display devices in the electronic industry.

(Prior art) As a method of bonding two types of planar conductive adherends A%B to obtain conductivity (anisotropic conductivity) only in the thickness direction between 8 and 8,
For example, there is a method in which an anisotropically conductive adhesive sheet made of conductive particles such as nickel powder dispersed in a thermoplastic polymer sheet as an adhesive is sandwiched between adherends A%B and bonded under heat. This adhesive sheet becomes fluidized by heating and exhibits adhesive properties, and also exhibits conductivity anisotropically only in the thickness direction of the sheet due to the presence of conductive particles.

However, in recent years, the conductive circuit portion of the conductive adherend has become smaller due to the miniaturization of components used in the electronics industry.
There is a trend toward finer pitch (fine pitch), and the number of connections of circuits with three or more trees/fi is increasing.

(Problems to be Solved by the Invention) When a conventional anisotropically conductive adhesive sheet is used for the above-mentioned fine-pitch circuit connection, there are problems with durability such as heat resistance and mixing resistance.

For example, conductivity failures (opens) may occur in a short period of time only when repeated thermal cycle tests are conducted over a long period of time in highlands, or when used on flexible printed circuit boards (FPC) that are subject to large thermal deformation stress. There was room for improvement in length.

(Problem M to be solved by the invention) The present invention solves the above-mentioned conventional problems, and its purpose is to provide excellent durability, especially for severe tests such as repeated heating and cooling cycles at high temperatures. An object of the present invention is to provide an anisotropically conductive adhesive sheet that can withstand various conditions.

(Means for Solving the Problems) The anisotropically conductive adhesive sheet of the present invention has conductive particles in which a silane coupling agent or alkoxysilane is adsorbed to particles whose surfaces are at least made of metal, dispersed in a thermoplastic resin. As a result, the above objective is achieved from K.

Particles that are adsorbed by silane curing agents or alkoxysilanes include metal powders such as Niraglu, iron, chromium, cobalt, antimony, molybdenum, copper, silver, platinum, and gold, as well as metal coatings on resins, glass, etc. conductive powder can also be used.

The average particle size of the conductive particles is, for example, in the range of 1 to 50 pm, preferably in the range of FiS to 35 pm. If the distance is less than 1 km, it is necessary to incorporate a large amount of conductive particles to obtain the desired conductivity, which tends to reduce the adhesive strength of the adhesive sheet. If it exceeds 50 m, it is difficult to obtain smoothness on the surface of the adhesive sheet, resulting in gaps during adhesion, which causes a decrease in adhesive strength.

The conductive particles are preferably contained in an amount of α1 to 10% by volume based on the total solid content of the adhesive sheet. a, 1% by volume
If the value is less than K, the desired 1# conductivity can be obtained. 10% by volume
If it exceeds , the insulating properties of the adhesive sheet in the plane direction decrease, and therefore anisotropic conductivity cannot be obtained. Moreover, the adhesive strength of the adhesive sheet tends to decrease. Although the shape of the tetraelectric particles is not particularly limited, it is preferable that they are spherical.

When an adhesive sheet containing spherical conductive particles is fluidized by heating, the conductive particles come into almost point contact with the adhesive surface. Therefore, anisotropic conductivity can be obtained without reducing the adhesive strength of the adhesive sheet.

In contrast, the seven-lake-shaped conductive particles have a larger number of areas in surface contact with the adhesive surface. Therefore, the adhesive strength of the adhesive sheet tends to decrease, and there is a possibility that anisotropic conductivity may not be obtained. Thus, conductive particles with such a large aspect ratio are not preferred.

Silane coupling agents generally have in their molecules an organic functional group that has affinity (or reactivity) with organic materials and a hydrolyzable group that has affinity (or reactivity) with inorganic materials. It is widely known as having the function of chemically bonding organic and inorganic materials.

Specific examples of the silane coupling agent used in the present invention include 3-glycidoxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, N-
(2-aminoethyl)3-aminopropyltrimethoxysilane and the like.

In the present invention, new alkoxysilanes can be used together with or instead of the above-mentioned silane coupling agents, and specific examples thereof include methyltrimethoxysilane, octyltrimethoxysilane, phenyltrimethoxysilane, etc. be able to.

These silane coupling agents or alkoxysilanes generally contain α01 to 5 parts by weight, preferably α01 to 3 parts by weight, based on 100 parts by weight of conductive particles whose surfaces are made of metal.
Parts by weight are used.

This is because if the weight is less than 1 part αO1, deterioration of electrical resistance cannot be effectively prevented, and even if the weight exceeds 5 parts, the effectiveness of preventing deterioration will not increase.

Among the thermoplastic resins, those used for heat-sensitive quiz sheets include styrene-butadiene-styrene block Ut combination, styrene'-isoprene-styrene block copolymer, and styrene-ethylene-butylene-styrene block copolymer. (5EBS), synthetic rubber such as ethylene-vinyl acetate copolymer, polyethylene, ethylene-propylene copolymer, ethylene-acrylic acid ester copolymer, polyvinyl butyral, polyester, polyisobutylene, acid polypropylene, polyurethane, etc. can be mentioned. Also, those used for pressure-sensitive type sheets include acrylic ester rubber, natural rubber, silicone rubber, polychlorogrene, butadiene-styrene copolymer, polyvinyl acetate, ethylene-vinyl acetate copolymer, Examples include polyisobutyl and polyvinyl ether rubber.

These resins can be used alone or in combination of two or more.

Next, an example of a method for manufacturing the sheet of the present invention will be described. First, the silane coupling agent or alkoxysilane is diluted and dissolved in a volatile solvent such as toluene, and a predetermined amount of the conductive particles is poured into the solution, stirred thoroughly to disperse it, and then the solvent is volatilized. This allows the particles to be adsorbed onto the surface of the particles.

Next, the adsorption-treated conductive particles are added to a separately prepared solution or hot melt of the thermoplastic resin, and mixed by normal stirring to obtain a conductive adhesive composition.

This is applied using a percoater or the like onto a plastic film such as polyethylene terephthalate or a separator such as release paper, and then dried to obtain an anisotropically conductive adhesive sheet. When the adhesive sheet is used, only the adhesive portion is peeled off from the separator.

Note that modifiers such as tackifiers, antioxidants, pigments, and surfactants may be added to the anisotropically conductive adhesive sheet of the present invention as necessary.

(Example) Examples of the present invention will be described below.

Example L After diluting and dissolving 1 part by weight of Vc3-glycidoxyglopyltrimethoxycycne in 100 parts by weight of toluene, 100 parts by weight of nickel powder (average particle size 5 t m ) was added, and the mixture was heated at room temperature for 1 hour. Stirred.

Thereafter, the toluene was completely evaporated and removed by heating at 80° C. for 24 hours to obtain treated nickel powder. Another KSEB
S (weight average molecular weight approximately 70,000, styrene content 28% by weight) 100 parts by weight, Ta! 100 parts by weight of Ronindene resin (softening point: 130"C), 50 parts by weight of aliphatic petroleum resin (softening point (105°C)), and 1 part by weight of an antioxidant were dissolved in toluene in advance. Parts by weight of the treated nickel powder SO were dispersed in a stirrer (at this time, the nickel powder was calculated to be about 2% by volume of the total solids).

). Polyethylene terephthalate (polyethylene terephthalate) whose surface has been treated with silicone to release this dispersion! S! Film (separator)
It was coated on top using a bar coater. The coating material was adjusted so that the layer thickness after drying was 25 km. Heat this at 80℃ for 10
An adhesive sheet was obtained by drying for a minute.

This adhesive sheet was cut into 3fi width and electrode width 9゜pm% electrode spacing 90μm 1 electrode terminal number 140 wood FPC (base film is 75m thick polyimide [trade name Ubilex], electrode holder 35.8m thick After attaching the electrode end part Kgc (made of copper foil with 7-markings), the separator was separated by 11 minutes.

Then, ITO (Injikumu tin) was applied to the entire surface of the 1Alf surface.
Glass plate (50M x 5
0 ta X L 1 wx thickness, surface resistance 10-150
/d) and (Bl elemental crow (50 [X 50 was
X L 1n thickness) were stacked on each end. These were thermocompressed for 10 seconds at a temperature of 180° C. by applying a pressure of LOK9/cd (these are referred to as test pieces A and B).

For the test piece AK obtained in this way, the conduction resistance value between the electrode end part of the FPC and a point on the glass with ITO is measured, and for the fc test piece BK, the conduction resistance value between the electrode end part of the FPC and a point on the glass with ITO is
After measuring the insulation resistance value between
time/cycle) and tracked the changes in continuity and insulation resistance, as well as the incidence of continuity failures. These results are shown in Table 1.

Example λ The same procedure as in Example 1 was used except that adsorption-treated nickel obtained by using 3 g of 3-glycidoxyglopyltrimethoxysilane per 100 parts of nickel powder was used. It is shown in Table 1.

Example λ Table 1 shows the results obtained in the same manner as in Example 1 except that adsorption-treated nibuglu obtained by using 1 part by weight of methyltrimethoxysilane per 100 parts by weight of nickel powder was used.

Comparative Example Table 1 shows the results obtained by carrying out the same procedure as in Example 1 except that untreated nickel powder was used.

As is clear from the Examples and Comparative Examples in Table 1, the anisotropically conductive adhesive sheet of the present invention has stable conduction resistance even in the above tests, and the incidence of conduction defects is extremely low over a long period of time. The insulation resistance is also sufficiently high at over 101°Ω.
Moreover, the adhesion work is easy.

(Effects of the Invention) The anisotropically conductive adhesive sheet of the present invention exhibits excellent performance even in durability tests assuming harsh usage conditions, and therefore can last for a long time even when used for circuit connection of 7-inch bits. Accurate conduction (X-layer direction) and insulation (along-layer direction) can be obtained. Therefore, it can be effectively used for conductive bonding between a display gray material such as a liquid crystal display device and an FPC.

Claims (1)

[Claims] 1. An anisotropically conductive adhesive sheet comprising conductive particles having at least a metal surface adsorbed with a silane coupling agent or an alkoxysilane and dispersed in a thermoplastic resin.