JPH0793053B2 - Polyimide film molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is a highly heat-resistant, anisotropically conductive polyimide film-shaped molding having conductivity only in the thickness direction through conductive particles exposed on the front and back of a molded product. Regarding things.

[Conventional technology]

The polyimide film is useful as a high heat resistant material for electronics, and is widely used as a circuit board material and an insulating material. On the other hand, an anisotropically conductive film-shaped molded product is used as a circuit connecting material as represented by, for example, JP-A-51-21192. The resin flows at the time of pressure heating, whereby the conductive particles inside the molded product are exposed and electrical continuity between the circuits is achieved. Therefore, the heat resistance of the molded product is necessarily limited. Also, in the case of a material that exhibits excellent properties only after a complete curing process such as a polyimide molded product, the fluidity of the molded product is lost, and the connection method (method of anisotropic conductivity) as described above is Cannot be adopted.

For the same purpose, for example, JP-A-53-53796 and JP-A-53-5396
-33390, JP-A-54-57680, JP-A-53-14
There is also known a material capable of connecting both circuits by mixing conductive particles into an elastic matrix and inserting it between a sheet-shaped molded article and a connection circuit without a pressurizing operation as in 7991 publication. However, this molded product had a drawback that it was thick and bulky. Further, since the molding thickness is large, it is necessary to use conductive particles having a large particle diameter, and as a result, the resolution of the connection is low, which is not suitable for connecting fine circuits.

[Problems to be solved by the invention]

An object of the present invention is to provide a polyimide film-like molded product having excellent heat resistance and having anisotropic conductivity, which is useful for connecting fine circuits.

[Means for solving problems]

The present invention is characterized in that, in a polyimide film-shaped molded product containing conductive particles, the conductive particles are exposed on the surface of the film-shaped molded product so as to have conductivity only in the thickness direction through the conductive particles.

As the polyimide used for producing the polyimide film-shaped molded product of the present invention, those having a repeating unit represented by the general formula [I] are preferably used.

Here, R ₁ represents a tetravalent aromatic group, and R ₂ represents a divalent aromatic group or an aliphatic group. [I] is specifically a tetracarboxylic dianhydride containing R ₁ such as pyromellitic dianhydride or 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride;
Obtained as a reaction product with a diamine containing R ₂ such as 4′-diaminodiphenyl ether and paraphenylenediamine.

Further, polyimide is obtained by converting a polyamic acid having a repeating unit represented by the following general formula [II], which is a precursor of polyimide, into a polyimide by dehydration ring-closing imide conversion.

In the present invention, preferably the above [I] or [II]
A polymer having a repeating unit of is dissolved in a material solvent,
The conductive particles are mixed, but if necessary, additives such as a lubricant, an antioxidant, a colorant, and a conductivity-imparting agent can be added. Further, the conductive particles may be added to the monomer mixture before polymerization and then contained in the polyimide film-shaped molded product. Further, other heat resistant resins, for example, resins such as polyether sulfone, polysulfone, polyarylate, polyphenylene sulfide, and polyetherimide can be mixed.

Examples of the organic solvent include N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylformamide, N, N-diethylacetamide, N-methyl-
2-pyrrolidone, p-chlorophenol, m-chlorophenol, p-cresol, m-cresol, dimethyl sulfone, tetramethyl sulfone, dimethyl sulfoxide, and the like, which are commonly known, are used alone or in admixture of two or more. To use. Further, it can be used in combination with a non-solvent such as benzene, toluene, xylene, dioxane, cyclohexane and acetone.

The conductive particles of the present invention, the most commonly used metal particles, as examples of these metal particles, Fe, Ni, Cr, C
There are o, Al, Sb, Mo, Cu, Ag, Pt, Au, etc., and these may be used alone or as an alloy or oxide, and it is also possible to use two or more kinds of them in combination. Also, in the metal particles,
The thing which provided the said metal layer on the surface of glass or synthetic resin is also applicable.

The content of these conductive metal particles is preferably 0.1 to 10% by volume of the polyimide film-shaped molded product, and shows good anisotropic conductivity. When the conductive particles are less than 0.1% by volume, the number of conducting points is small, and when it exceeds 10% by volume, the insulating property in the surface direction of the molded product is impaired and anisotropic conductivity may not be maintained. The size of the conductive particles is particularly important and refers to the substantial size of the conductive particles present in the film-shaped molded product, and the conductive particles may be independent or aggregated. It doesn't matter. The thickness of the film-shaped molded product is not particularly limited, but 0.005 mm to 0.1 mm
Is appropriate. If it is thinner than 0.005 mm, it will be difficult to handle and it will be difficult to manufacture due to wrinkles. On the other hand, if the thickness is more than 0.1 mm, the particles used will become large and the resolution will decrease, making it unsuitable for connecting minute circuits.

For the film formation of the polyimide composition in which the conductive particles are mixed, the usual method for forming a polyimide film can be applied as it is. Industrially, for example, there is a method in which a polyimide composition is cast on a metal belt to a uniform thickness, the solvent is dried, the film is peeled from the substrate, and then the film is cured and heat-treated in a high temperature atmosphere. Generally, the solvent can be dried at 80 to 150 ° C and the heat treatment for curing can be performed at 200 to 450 ° C.

The polyimide film-shaped molded product containing conductive particles is in an uncured state (before curing heat treatment) or after curing heat treatment,
The polyimide composition on the surface of the molded product is removed, the conductive particles are exposed on the surface of the molded product, and the conductive particles have conductivity only in the thickness direction through the conductive particles.

As a method of exposing the conductive particles on the surface of the molded product as described above, it is preferable to etch the molded product. In the polyimide film-shaped molded product obtained by the above method, some conductive particles are exposed on the surface of the molded product before etching, but the surface of many conductive particles is covered with a thin film of the polyimide composition. Therefore, it is extremely preferable to remove this film by etching or the like.

For the etching, the means usually used for polyimide compositions can be used as it is. Commonly known etching solutions include tetramethyl ammonium hydroxide, hydrazine hydrate, potassium hydroxide aqueous solution, sodium hydroxide aqueous solution and the like. In addition to these wet etching methods, a dry method such as oxygen plasma etching or oxygen sputter etching can be used. The thickness of the composition to be removed by etching is not particularly limited, but is usually 0.1.
.About.1 .mu.m is sufficient, and the etching treatment time required for this is 10 to 300 seconds.

Further, when an insulating oxide film is formed on the surface of the conductive particles due to the influence of the curing heat treatment at a high temperature, it is preferable to perform a treatment such as washing with a dilute acid.

When the anisotropic conductive polyimide film-like molded product of the present invention is used as a connecting material for a circuit, for example, the molded product of the present invention is inserted between the circuits to be connected, and then both circuits are pressed and held. Alternatively, the object can be achieved by a method of injecting the liquid adhesive into the space between the circuits in a pressed state and then curing and fixing. Further, the polyimide film-shaped molded product of the present invention can be applied not only to the above-mentioned circuit connecting material but also to a switch member, a multilayer circuit member and the like.

〔Example〕

Hereinafter, the present invention will be described based on examples, but the present invention is not limited thereto.

Example 4,4'-diaminodiphenyl ether 17.0 in a 300 ml four-necked flask equipped with a thermometer, stirrer and calcium chloride tube.
g, 1.62 g of para-phenylenediamine and 229.1 g of N, N-dimethylformamide are added and dissolved by stirring. Add this solution to 10
21.8 g of pyromellitic dianhydride was gradually added while keeping the temperature around ℃, and then stirred for 3 hours to give a reduced viscosity of 2.34 dl / g (solvent N, N-dimethylformamide, concentration 0.1 g / dl, concentration 25
C.) was obtained. The solid content concentration of this varnish is 15%. The surface of the varnish was plated with Au particles having an average particle size of 8 μm by Au plating.
The mixture was mixed by volume% and sufficiently stirred, then cast on a glass plate and dried at 90 ° C. to obtain a conductive particle-containing polyimide acid film having a thickness of 10 μm. Then, this film was fixed to an iron frame and kept in a dryer at 250 ° C. for 5 minutes under tension to be imidized. Furthermore, this film is treated with KOH aqueous solution (KOH
It was dipped in 1.0N ethyl alcohol / water = 80/20) for about 5 seconds, washed with water and dried to obtain an etching-treated film having a thickness of 8 μm. The conduction resistance of the film before and after etching in this step was measured by the method shown in FIG. In FIG. 1, 1 is a polyimide film-shaped molded product, 2 is a copper foil having a thickness of 35 μm, and 3 is 0.5 × at the tip.
The probe was a gold-plated probe (probe A) having a size of 0.5 mm, and this probe was lightly pressed against 1 to measure the conduction resistance R in the film thickness direction. Further, the probe was formed into the shape shown in FIG. 2 and the resistance in the film surface direction was measured to obtain a measure of insulation resolution. In the probe (probe B) 4 in FIG. 2, the gold-plated terminal 5 is 0.5 × 3 mm, 6 is an insulating layer, and a polyester film is overlaid.
It is set to 0.1 mm and fixed with an adhesive. The measurement point is 1
The sample was set to 100 points. The results for the film before and after etching were as follows.

[Effects of the Invention] The anisotropic conductive film-like molded product made of the highly heat-resistant polyimide composition of the present invention is capable of conducting minute dots and has excellent insulation resolution in the plane direction.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a method for measuring the resistance in the thickness direction of a film-shaped molded product, and FIG. 2 shows a method for measuring the resistance in the surface direction of the film-shaped molded product to judge the insulation resolution. FIG. Explanation of symbols 1 ... Sample, 2 ... Copper foil 3 ... Probe (A), 4 ... Probe (B) 5 ... Terminal, 6 ... Insulating layer

Claims (1)

[Claims] 1. A polyamic acid varnish containing conductive particles is imidized to form a polyimide film-shaped molded product, and at least one surface of the molded product is wet-etched with an alkaline etching agent to obtain a surface of the film-shaped molded product. A conductive film is exposed to the inside of the polyimide film, and the conductive film is made to have conductivity only in the thickness direction through the conductive film.