JPH0130320B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a flexible printed circuit board. More specifically, the present invention relates to a flexible printed circuit board formed by bonding an aromatic polyimide film made of a reaction product of a biphenyltetracarboxylic acid component and an aromatic diamine with a metal foil using a specific adhesive composition. It is something. A flexible printed circuit board (flexible metal foil clad board), which is a structure in which a plastic film and a metal foil are bonded together directly or through an adhesive, is a board for configuring a flexible printed circuit. In recent years, it has been increasingly used for the purpose of simplifying and increasing the density of electronic circuits. Various materials have been used or proposed for the plastic film that is its constituent material, but among these, aromatic polyimide film has excellent mechanical, electrical, and chemical properties, and is particularly heat resistant. It is a preferred material for plastic films for flexible printed circuit boards because of its excellent properties such as hardness and dimensional stability. Since aromatic polyimide film has poor adhesion to metal foil, an adhesive is usually used to form a flexible metal foil laminate. However, the aromatic polyimide film made of the reaction product of a biphenyltetracarboxylic acid component and an aromatic diamine generally has low adhesion to adhesives, so the formed aromatic polyimide film and metal foil are There was a problem in that it was not possible to obtain a flexible metal foil clad plate with sufficient adhesive strength even if it was bonded using a common adhesive. Regarding adhesion between a heat-resistant film such as polyamideimide or polyimide and metal foil, the use of a resin composition containing an epoxy resin and a carboxyl group-containing diene rubber is proposed in Japanese Patent Publication No. 1158/1983. However, according to the inventor's study, the above resin composition is effective for adhering heat-resistant films such as ordinary polyamide-imide and polyimide to metal foil, but aromatic polyimide, especially adhesive It has been found that an aromatic polyimide film made of a reaction product of a low biphenyltetracarboxylic acid component and an aromatic diamine cannot exhibit satisfactory adhesion with metal foil. For this reason, the surface of the aromatic polyimide film, which is difficult to adhere to, as described above, must be chemically treated with a caustic soda aqueous solution, a chromic acid mixture, an aluminum hydroxide aqueous solution, etc., or physically treated, such as corona discharge or sanding. Many methods have been adopted to improve the adhesion between the aromatic polyimide film and the adhesive by performing surface treatments such as roughening. However, even with such surface treatments, it is difficult to sufficiently improve the adhesion, and on the other hand, these surface treatments require complicated operations, resulting in complication of the manufacturing process of flexible metal foil laminates. There is also a drawback that it leads to. Furthermore, when the above-mentioned surface treatment is applied, there is a problem in that the mechanical properties of the aromatic polyimide film deteriorate. The present inventor has conducted various studies in order to solve the above problems, and has found excellent adhesiveness even to the above-mentioned hard-to-adhesion aromatic polyimide film that has not been subjected to surface treatment such as roughening. The present invention has been achieved by discovering an adhesive composition that exhibits the following properties and also has excellent properties as a constituent material of a flexible metal foil clad board. That is, the present invention includes 100 parts by weight of a bisphenol A type epoxy resin, 80 to 200 parts by weight of a carboxyl group-containing acrylonitrile-butadiene copolymer,
15 to 30 parts by weight of aromatic primary diamine, and dithiocarbamates, thiurams, thioureas,
Then, an adhesive composition containing 0.1 to 10 parts by weight of a vulcanization accelerator selected from sulfur atom-containing morpholine derivatives is used to create an aromatic compound consisting of a reaction product of a biphenyltetracarboxylic acid component and an aromatic diamine. The present invention provides a flexible printed circuit board characterized by being made of a polyimide film and a metal foil bonded together. Next, the present invention will be explained in detail. The flexible printed circuit board of the present invention can be produced by bonding the above-mentioned hard-to-adhesive aromatic polyimide film and metal foil using a specific adhesive composition. Among the aromatic polyimide films made of the reaction product of biphenyltetracarboxylic acid component and aromatic diamine used in the present invention, aromatic polyimide film made of the reaction product of biphenyltetracarboxylic dianhydride and aromatic diamine Polyimide film is particularly preferable as a constituent material of the flexible printed circuit board of the present invention because it has excellent various chemical properties, mechanical properties, heat resistance, etc., and also has very high alkali resistance. Examples of the biphenyltetracarboxylic dianhydride which is one of the production raw materials for the above particularly preferred aromatic polyimide film include 3,3',4,4'-biphenyltetracarboxylic dianhydride;
Mention may be made of 3,3',4'-biphenyltetracarboxylic dianhydride. These compounds can be used alone or in combination of two or more. Examples of the aromatic diamine used as the other manufacturing raw material for this aromatic polyimide film include p-phenylene diamine, m-phenylene diamine, 4,
4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-thiodianiline, 4,4'-diaminodiphenyl sulfone, o-
Examples include tolidine, o-dianisidine, 2,4-diaminotoluene, and 2,5-diaminonaphthalene. Each of these compounds can be used alone or in combination of two or more. As a method for producing an aromatic polyimide film using the above-mentioned raw material compounds, each compound is mixed with N-methyl-2-pyrrolidone (NMP), N-methyl-2-pyrrolidone (NMP),
N,N'-dimethylformamide (DMF) or N,N'-dimethylacetamide (DMAc)
A method can be mentioned in which a polyamic acid is obtained by reacting in an organic polar solvent such as, and then dehydrated. Alternatively, each raw material compound may be converted into phenol, o-chlorophenol, p-chlorophenol, o-cresol, m-cresol, p-
-bromophenol or 3-chloro-6
- A method of directly forming a polyimide by heating in a phenolic solvent such as hydroxytoluene can be mentioned. The desired aromatic polyimide film can be produced by casting the above polyamic acid solution onto a glass plate and then heating and dehydrating it, or by casting the polyimide solution onto a glass plate and removing the solvent. It can be prepared by a method. The thickness of the aromatic polyimide film used in the present invention is usually in the range of 10 to 150μ, but
Any thickness can be used as required. The metal foil used in the present invention can be arbitrarily selected from those that have been conventionally used for flexible printed circuit boards or those that have been proposed for use. Copper foil is generally used, and electrolytic or rolled copper foil whose surface has been roughened is particularly preferred. However, metal foils made of other conductive metals such as aluminum foil, nickel foil, etc. can also be used. The metal foil typically used has a thickness of 10 to 100 μm. The adhesive composition used for manufacturing the flexible printed circuit board of the present invention includes 100 parts by weight of bisphenol A type epoxy resin as the first component, and a carboxyl group-containing acrylonitrile-butadiene copolymer as the second component. 80 to 200 parts by weight (preferably 100 to 170 parts by weight), and 15 to 200 parts by weight of aromatic primary diamine as the third component.
30 parts by weight (preferably 15 parts to 25 parts by weight),
And, as a fourth component, a vulcanization accelerator selected from dithiocarbamates, thiurams, thioureas, and sulfur atom-containing morpholine derivatives is added at a concentration of 0.1 to 10%.
This is a composition containing as a main component parts by weight. Examples of bisphenol A type epoxy resins as the first component include epoxy resins that are polyglycidyl ethers obtained from bisphenol A and epichlorohydrin, such as Epicote 827 and Epichlorohydrin.
Liquid epoxy resins such as 828 (trade name, manufactured by Yuka Ciel Epoxy Co., Ltd.) and Epicoat 1001,
1004, 1007 (product name, manufactured by Yuka Ciel Epoxy Co., Ltd.)
Examples include solid epoxy resins such as. These epoxy resins may be used alone or in combination, and other types of epoxy resins may be mixed in appropriate amounts as long as the properties of the above-mentioned epoxy resins are not impaired. It is possible. Various types of epoxy resins have been known so far, but in the adhesive composition used in the present invention, it is necessary to use the above-mentioned bisphenol A type epoxy resins.
If a polyglycidyl ether based on a cresol novolac type resin is used instead of a bisphenol A type epoxy resin, the high adhesiveness which is the object of the present invention cannot be obtained. Examples of the carboxyl group-containing acrylonitrile-butadiene copolymer as the second component include the solid copolymer Hiker 1072 (trade name, manufactured by Gutdrich Co., Ltd., USA) and the liquid copolymer Hiker
CTBN1300×8, CTBN1300×9, CTBN1300×13, CTBN
Examples include 1300×15 (trade name, manufactured by Gutsudoritsuchi Co., Ltd. in the United States). Among these, solid carboxyl group-containing acrylonitrile and butadiene are used because of the ease of preparing the adhesive composition solution and the ease of reaching the B-stage state (swollen and undissolved state). Preferably, polymers are used. These carboxyl group-containing acrylonitrile-butadiene copolymers may be used alone or in combination. Although there are many known nitrile rubbers that do not contain carboxyl groups (for example, Hiker 1042), in the present invention, in place of the carboxyl group-containing acrylonitrile-butadiene copolymer as the second component, carboxyl groups are used. If a nitrile rubber that does not contain nitrile rubber is used, undesirable results such as poor solvent resistance of the resulting adhesive layer will occur. This is because the carboxyl group-containing acrylonitrile-butadiene copolymer in the present invention reacts with the epoxy resin by curing and is integrated to form a three-dimensional structure, whereas the functional group that reacts with the epoxy group is This is presumed to be because the nitrile rubber that does not contain the adhesive layer does not undergo such three-dimensionalization, resulting in the rubber component existing almost independently in the adhesive layer even after curing. Examples of the aromatic primary diamine as the third component include 4,4'-diaminodiphenylsulfone, 4,
Examples include 4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, p-phenylenediamine, and m-diphenyldiamine. Various types of curing agents for epoxy resins have been known, but in the adhesive composition of the present invention, it is necessary to use aromatic primary diamines such as those described above. , acid anhydride, aliphatic polyamine, alicyclic polyamine, polyamide amine, etc., in place of the aromatic primary diamine, B of the adhesive composition. The disadvantage is that it is not easy to reach the stage states, and their B-stage states are relatively unstable. As an adhesive for bonding aromatic polyimide film and metal foil, even if the adhesive composition consists of three components from the first component to the third component as described above, under certain conditions It may also exhibit peel strength. However, there is a limit to the adhesive strength that can be achieved with an adhesive composition consisting only of these components, and it cannot be said to be practically satisfactory. For example, when electrolytic copper foil is used as a metal foil, the surface of the copper foil is roughened, so it has a relatively high peel resistance (peel resistance) for interfacial peeling of the copper foil/adhesive layer. ), but on the other hand,
Regarding the interfacial peeling of the aromatic polyimide film/adhesive layer with an untreated surface, a drawback arises in that its peeling resistance is significantly inferior to that of the copper foil/adhesive layer described above. . In contrast, by adding the vulcanization accelerator specifically selected in the present invention as the fourth component of the adhesive composition, a high degree of peeling resistance can be achieved without subjecting the polyimide film to surface treatment such as roughening. Strength is imparted for interfacial delamination of the polyimide film/adhesive layer. In the adhesive composition used in the present invention, the fourth component, the vulcanization accelerator, is selected from dithiocarbamates, thiurams, thioureas, and sulfur atom-containing morpholine derivatives. Examples of dithiocarbamates include piperidine pentamethylene dithiocarbamate, pipecoline pipecolyldithiocarbamate, and various metal salts of dithiocarbamic acid. Examples of thiurams include tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetramethylthiuram monosulfide, dipentamethylenethiuram tetrasulfide, and dipentamethylenethiuram disulfide. Examples include hexasulfide. Examples of thioureas include trimethylthiourea, diethylthiourea, dibutylthiourea, dilaurylthiourea, diorthotolylthiourea, and N,N'-diphenylthiourea. Examples of morpholine derivatives containing sulfur atoms include:
Mention may be made of 4,4'-dithiomorpholine. In the adhesive composition used in the present invention, the vulcanization accelerator as the fourth component can be used alone or as a mixture of two or more types. The adhesive composition of the present invention is usually used in the form of a solution dissolved in a solvent. Examples of solvents used for this purpose include acetone, ketones such as methyl ethyl ketone, cyclic ethers such as dioxane and tetrahydrofuran, aromatic hydrocarbons such as benzene and toluene, ethylene chloride, and trichloroethane. Mention may be made of chlorinated hydrocarbons. In the present invention, the bonding operation and bonding conditions for bonding the aromatic polyimide film and metal foil using the above adhesive composition are those conventionally used for flexible printed circuit boards. It is possible to arbitrarily select the conditions or the bonding operations and bonding conditions for which the use thereof has been proposed. Next, an example of a two-step operation suitable for manufacturing the flexible printed circuit board of the present invention will be given. (1) Dryness to the touch by applying the adhesive composition and removing the solvent The adhesive solution is applied to the aromatic polyimide film so that the adhesive layer has the desired thickness after pressure bonding. , 80-170℃, preferably
The solvent is removed by heating to 100 to 150[deg.] C., and the adhesive composition is brought into a B-stage state to prepare an aromatic polyimide film with an adhesive that is dry to the touch. (2) Adhesion to metal foil Layer the aromatic polyimide film with adhesive prepared above on metal foil at a temperature of 130 to 250°C.
Preferably, the temperature is 150-200°C and the pressure is 5-200°C.
A flexible printed circuit board is obtained by curing under the conditions of 100 Kg/cm ² , preferably 10 to 50 Kg/cm ² . As detailed above, the flexible printed circuit board of the present invention uses an aromatic polyimide film made of a reaction product of a biphenyltetracarboxylic acid component and an aromatic diamine as a plastic film, It is manufactured by adhering to metal foil using an adhesive composition in It also has excellent characteristics. Next, examples of the present invention and comparative examples will be shown.
These do not limit the invention. Example 1 Epicote 828 (trade name, Yuka Ciel Epoxy Co., Ltd.)
70 parts by weight of bisphenol A type polyglycidyl ether (manufactured by Bisphenol A), 100 parts by weight of Hiker 1072 (trade name, carboxyl group-containing acrylonitrile-butadiene copolymer, manufactured by Gutudrich Co., Ltd., USA), 4.
A composition consisting of 17.5 parts by weight of 4'-diaminodiphenylsulfone and 2 parts by weight of tetramethylthiuram disulfide was added to 900 parts by weight of a mixed solvent of methyl ethyl ketone and ethylene dichloride (1:4, volume ratio). , and sufficiently dissolved to prepare an adhesive solution. The above adhesive solution was adhered to a 25μ thick aromatic polyimide film prepared from 3,3',4,4'-biphenyltetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether. The adhesive layer was applied to a thickness of 30 μm and dried at 120° C. for 15 minutes until it was dry to the touch. Next, an electrolytic copper foil with a thickness of 35μ was layered on top of it, and the temperature was 170℃, 40Kg/cm ²
The copper clad board (printed circuit board) A was obtained by heating and pressing for 30 minutes. Example 2 Example 1 except that the same amount of trimethylthiourea was used instead of tetramethylthiuram disulfide.
An adhesive solution was prepared in the same manner as above, and copper clad board B was obtained in the same manner using this. Example 3 An adhesive solution was prepared in the same manner as in Example 1, except that the same amount of piperidine pentamethylene dithiocarbamate was used in place of tetramethylthiuram disulfide, and copper-clad plate C was prepared in the same manner using this adhesive solution. I got it. Example 4 The same amount of 4,4'-dithiomorpholine was used instead of tetramethylthiuram disulfide.
An adhesive solution was prepared in the same manner as in Example 1, and a copper clad board D was obtained in the same manner using this. Example 5 An adhesive solution was prepared in the same manner as in Example 1, except that the same amount of dipentamethylenethiuram hexasulfide was used in place of tetramethylthiuram disulfide, and copper was prepared in the same manner using this adhesive solution. Panel E was obtained. Example 6 Epicote 1004 (trade name, manufactured by Yuka Ciel Epoxy Co., Ltd., bisphenol A type polyglycidyl ether) was used as a bisphenol A type epoxy resin.
An adhesive solution was prepared in the same manner as in Example 1, except that 80 parts by weight was used, and a copper clad board F was obtained in the same manner using this. Example 7 An adhesive solution was prepared in the same manner as in Example 1, except that 15 parts by weight of 4,4'-diaminodiphenylmethane was used in place of 4,4'-diaminodiphenyl sulfone. A copper clad plate G was obtained in the same manner. Comparative Example 1 An adhesive solution was prepared in the same manner as in Example 1 except that tetramethylthiuram disulfide was not used, and a copper clad board H was obtained in the same manner using this adhesive solution. Comparative example 2 Araldite ECN1280 as epoxy resin
An adhesive solution was prepared in the same manner as in Example 1, except that 70 parts by weight of (trade name, manufactured by Ciba Geigy, cresol novolac type resin polyglycidyl ether) was used. Panel I
I got it. Comparative Example 3 An acrylonitrile-butadiene copolymer containing no carboxyl group was used as the nitrile rubber.
An adhesive solution was prepared in the same manner as in Example 1, except that 100 parts by weight was used, and a copper clad board J was obtained in the same manner using this. Comparative Example 4 An adhesive solution was prepared in the same manner as in Example 1, except that 4,4'-diaminodiphenyl sulfone was not used, and using this, a copper clad board K was obtained in the same manner as in Example 1. Ta. Comparative Example 5 An adhesive solution was prepared in the same manner as in Example 1, except that the same molar amount of hexamethylene diamine was used instead of 4,4'-diaminodiphenylsulfone,
Using this, a copper clad plate L was obtained in the same manner as in Example 1. Comparative Example 6 An adhesive solution was prepared in the same manner as in Example 1, except that the same molar amount of hexahydrophthalic anhydride was used instead of 4,4'diaminodiphenylsulfone,
Using this, a copper clad board M was obtained in the same manner as in Example 1. Comparative Example 7 An adhesive solution was prepared in the same manner as in Example 1, except that the same molar amount of benzoguanidine was used instead of tetramethylthiuram disulfide, and using this solution, copper cladding was prepared in the same manner as in Example 1. Plate N was obtained. [Evaluation results of various properties of printed circuit boards] Peel resistance, solvent resistance, alkali resistance,
And solder heat resistance was evaluated by the method described below. (1) Peel resistance In accordance with JIS C-6481, 180° peeling of a sample with a width of 10 mm was measured using an autograph at a tensile speed of 50 mm/min. Note that this peel strength is determined by the interface between the copper foil and the adhesive layer (Cu/A
) and the interface between the aromatic polyimide film and the adhesive layer (denoted as f/A). (2) Solvent resistance According to JIS C-6481, the sample was immersed in trichlene, acetone, and methylene dichloride, and left at room temperature for 15 minutes.
The condition was visually determined. (3) Alkali resistance In accordance with JIS C-6481, the sample was immersed in a 10% aqueous sodium hydroxide solution, boiled for 30 minutes or left at room temperature for 3 days, and its condition was visually determined. (4) Soldering heat resistance In accordance with JIS C-6481, the sample was immersed in a 30°C solder bath for 1 minute, and then the appearance of "blister" etc. was visually judged. The results obtained are shown in Table 1.

[Table] Note: Regarding solvent resistance, except for copper clad board J which showed corrosion due to solvent, no abnormalities were observed in other copper clad boards. Regarding alkali resistance, no abnormalities were observed for all copper clad plates. Regarding solder heat resistance, except for copper clad plates J and M which showed blistering, no abnormality was observed in the other copper clad plates.

Claims (1)

[Claims] 1 100 parts by weight of bisphenol A type epoxy resin,
80 to 200 parts by weight of a carboxyl group-containing acrylonitrile-butadiene copolymer, 15 to 30 parts by weight of aromatic primary diamine, and selected from dithiocarbamates, thiurams, thioureas, and sulfur atom-containing morpholine derivatives. Vulcanization accelerator
An aromatic polyimide film made of a reaction product of a biphenyltetracarboxylic acid component and an aromatic diamine is bonded to a metal foil using an adhesive composition containing 0.1 to 10 parts by weight as a main component. Flexible printed circuit board.