JPH06103788B2 - Flexible printed wiring board - Google Patents

Description

TECHNICAL FIELD The present invention relates to a flexible printed wiring board having excellent flexibility and heat resistance.

(Prior Art) In recent years, the electronics field has been remarkably developed, and electronic devices such as communication consumer products are becoming smaller, lighter, and higher in density, and requirements for these performances are becoming more and more advanced. There is.

In response to such demands, the flexible printed wiring board has flexibility, so that it can be mounted in a narrow space with a three-dimensional high density, and can withstand repeated bending, and wiring to electronic equipment,
Its applications are expanding as composite parts with cable and connector functions.

A substrate for flexible printed wiring is generally a polyimide or polyester resin film used as an insulating base material, and a base is obtained by laminating and integrating these substrates and a metal foil such as a copper foil or an aluminum foil with an adhesive. ,
Circuits are formed on this and mounted on many devices such as cameras, calculators, and computers. This flexible printed wiring board is required to have good properties such as heat resistance, chemical resistance, flexibility, and electrical insulation as well as adhesiveness between the metal foil and the film. Furthermore, recently, it has been increasingly used as a part of a printer, a floppy disk drive, a hard disk drive, etc., in a movable part, and accordingly, the above-mentioned characteristics are satisfied and especially the flexibility is required.

Conventionally, as an adhesive that should meet these requirements, NBR
Various adhesives have been proposed, such as epoxy resin, butyral resin, nylon / epoxy, NBR / phenol, and carboxyl group-containing NBR / epoxy. However, these adhesives have merits and demerits, and none of them have the above characteristics sufficiently.

(Object of the Invention) An object of the present invention is to provide a substrate for flexible printed wiring, which has been made in order to satisfy the above characteristics and is particularly excellent in flexibility and heat resistance.

(Structure of the invention) As a result of intensive studies to satisfy the above characteristics, the present inventors have found that a low temperature plasma-treated insulating film has a polyester resin, a heat resistant epoxy resin, a general-purpose epoxy resin, an acid anhydride as a curing agent, and an aromatic compound. The present inventors have found that the flexible printed wiring substrate satisfies the above characteristics by laminating and integrating metal foils via an adhesive composed of diamine and imidazole, and is particularly excellent in flexibility and heat resistance, resulting in the present invention. .

The present invention will be described in detail below.

Examples of the insulating film used in the present invention include a polyimide film, a polyparabanic acid film, a polyester film, a polyethersulfone film, a polyetheretherketone film, and the like, and a polyimide film is particularly preferable. As the metal foil, electrolytic copper foil, rolled copper foil, aluminum foil, dangsten foil and the like are used.

The present invention is laminated and integrated using the above-mentioned insulating film and metal foil and the above-mentioned adhesive. This insulating film is subjected to low-temperature plasma treatment with an inorganic gas in advance to improve the adhesion between the film and the adhesive. It is necessary to improve.

As the method of this low-temperature plasma treatment, the insulating film is put in a low-temperature plasma treatment apparatus capable of reducing the pressure, and the inside of the apparatus is kept in an atmosphere of inorganic gas at a pressure of 0.001-10 torr, preferably 0.01-1 torr, 0.1 to 10k between electrodes
A low-temperature plasma of inorganic gas is generated by applying a direct current or an alternating current of around V to cause glow discharge, and the surface is continuously plasma-treated while sequentially moving the insulating film, but the plasma treatment time is approximately 0.1 to 100 seconds. It is good to As the inorganic gas, helium, neon, an inert gas such as argon, and oxygen, nitrogen, carbon monoxide, carbon dioxide, ammonia, air, etc. are used.
These are not limited to one type, and a mixture of two or more types may be optionally used.

Next, the adhesive used in the present invention is polyester resin 100
Parts by weight, 10 to 60 parts by weight of epoxy resin having 3 or more epoxy groups in the molecule, 50 to 200 parts by weight of epoxy resin having 2 epoxy groups in the molecule, acid anhydride 3 to 3 as a curing agent
The essential components are 0 parts by weight, 1 to 10 parts by weight of the aromatic diamine, and 0.1 to 5 parts by weight of the imidazole compound.

Examples of polyester resins include those synthesized from the following polyols and acid components. As the polyol, ethylene glycol, diethylene glycol,
Examples include triethylene glycol, propylene grill coal, neopentyl glycol, trimethylolpropane, and trimethylolpropane ethylene oxide adduct. Examples of the acid component include terephthalic acid, isophthalic acid, adipic acid, trimellitic acid, pyromellitic acid and their acid anhydrides.

The polyester resin suitable for the present invention has a molecular weight of 10,000 to 3
It is preferable that 0000 or less is less than OH group or --COOH group.

As the epoxy resin, it is essential to use two or more kinds of epoxy resins having two epoxy groups and three or more epoxy groups in one molecule. There are bisphenol A type, ether type, ether ester type, etc. as having two epoxy groups in one molecule, and commercially available products are Epicoat 828, 871, 1001, 517 (produced by Yuka Shell Epoxy Co.,
Product name), Sumiepoxy ELA115, 127 (Sumitomo Chemical Co.,
Trade names) and the like can be mentioned, and those having a long straight chain are particularly preferable, which increases the degree of freedom between binding molecules and improves flexibility. If the amount of these epoxy resins is too large, the heat resistance will decrease, and if they are too small, flexibility will be lost. Further, those having three or more epoxy groups in one molecule include novolac type and glycidylamine type, and commercially available products are Epicoat 154, 6
04 (produced by Yuka Shell Epoxy Co., Ltd.), Sumiepoxy
ESCN-195XL, ELM120 (trade name, manufactured by Sumitomo Chemical Co., Ltd.) and the like are included, which increase the crosslink density and improve solvent resistance and heat resistance. If the amount of these epoxy resins is too large, the adhesiveness and flexibility are lost, and if the amount is too small, the heat resistance deteriorates.

Next, monofunctional type and polyfunctional type are used as the acid anhydride serving as the curing agent. The former is methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, etc. and the reaction of C ₅ , C ₁₀ dienes with maleic anhydride, the latter is trimellitic anhydride, Examples include pyromellitic dianhydride, benzophenone tetracarboxylic acid and the like. Among these, monofunctional acid anhydrides obtained by the reaction of C ₁₀ diene and maleic anhydride are particularly preferable, and have excellent hygroscopic pot life and moisture resistance, heat resistance, and electrical characteristics of a cured product. If the amount of these acid anhydrides is too large, unreacted acid will remain, resulting in poor electrical properties, and if too small, the heat resistance will be poor.

Imidazole has the general formula (Wherein R ¹ and R ² represent a hydrogen atom or an alkyl group, and R ³ represents a hydrogen atom or an alkyl derivative), 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4methyl There are imidazoles, 2-heptadecyl imidazoles, and their derivatives. Imidazole also acts as a curing accelerator for acid anhydride and the like as the epoxy resin cures. If the amount is too large, the electrical properties and the like deteriorate, and if it is too small, the heat resistance and the like deteriorate.

As the aromatic diamine, diaminodiphenylmethane,
Diaminodiphenyl sulfone or the like is used. These are for sufficiently crosslinking the unreacted polyester resin and the unreacted epoxy resin, which improves heat resistance.

As a method for manufacturing a flexible printed wiring board,
Use a reverse roll coater, comma coater, etc. to apply the adhesive composition dissolved in a solvent to a polyimide film or metal foil in a dry state so as to have a thickness of 25 ± 15 μm, and then dry at 80 to 140 ° C for 2 to 20 minutes. To evaporate the solvent and leave the adhesive in a semi-cured state. Overlap metal foil (or polyimide film) such as copper foil, aluminum foil, etc. on the adhesive surface of this polyimide film (or metal foil) with adhesive, heat press bond with a roll laminator, and perform after-cure if necessary. Thus, a flexible printed wiring board can be obtained. The crimping condition is a temperature of 140 ± 40
℃, linear pressure 1 ~ 50kg / cm ² , speed 0.5 ~ 10m / min range is good, after-cure is preferably carried out in two stages. In this case, the first stage is temperature 80 ± 20 ℃, time 0.5 ~
The second step may be carried out for 5 hours at a temperature of 160 ± 40 ° C. for 1 to 10 hours.

Next, the present invention will be specifically described with reference to examples.

All parts and percentages in the examples are by weight.

(Reference example: low temperature plasma treatment of insulating film) A 25 cm square 25 μm thick Kapton film (Dupont polyimide film product name) was placed in a low temperature plasma treatment apparatus, oxygen was introduced at a vacuum degree of 0.2 torr, and 110 kHz, 1.5 kv An AC voltage was applied to the electrodes to cause glow discharge, and low temperature plasma treatment was performed for 20 seconds. The Kapton film was placed on the lower electrodes of the upper and lower counter electrodes, and the distance between the electrodes was 10 cm. This was a low temperature plasma A treatment. Similarly, low-temperature plasma treatment was performed using 0.2 torr pressure of argon and a mixed gas of argon and oxygen. These were designated as low temperature plasma B treatment and low temperature plasma C treatment, respectively.

Example 1 500 parts by weight of 20% solution of Vylon 300 (trade name of polyester resin manufactured by Toyobo Co., Ltd.) in methyl ethyl ketone, 50% methyl ethyl ketone solution of Epicoat 154 (trade name of novolac epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd.) 50
Part, 50% methyl ethyl ketone solution of Epicoat 828 (trade name of bisphenol A type epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd.), 5 parts of trialkyltetrahydrophthalic anhydride, 5 parts of diaminodiphenylmethane, 2E4MZ-CN (manufactured by Shikoku Fine Chemicals, 1 part of imidazole (trade name) was weighed and charged, and sufficiently dissolved by stirring to prepare an adhesive solution.

Apply this to Kapton film (described above) that has been treated with low-temperature plasma A so that the thickness after drying will be about 20 μm.
Drying was performed at 10 ° C for 10 minutes and 110 ° C for 2 minutes. A rolled copper foil (made by Nippon Mining Co., Ltd.) with a thickness of 35 μm is laminated on this, and 140
° C., a linear pressure 5 kg / cm ^2, and pressed together by a roll laminator at a speed of 2m / min. Then in an oven at a temperature of 80 ° C for 2 hours, a temperature of 120 ° C for 1 hour, and a temperature of 170 ° C for 3 hours.
After heating for an hour, after-cure was performed. The characteristics of the flexible printed wiring board thus obtained are shown in the table. In the treatment column of Table-1, C-24 / 20/60 is the temperature
To leave for 24 hours in an atmosphere of 20 ° C and 60% humidity, C-
240/150 should be left in an atmosphere of 150 ° C for 240 hours, C-96 / 20/60 should be left in an atmosphere of 20 ° C and 60% humidity for 96 hours, and E-240 / 150 should be In an atmosphere at a temperature of 150 ° C
Indicates that it is left for 240 hours.

Example 2 Byron 295 (manufactured by Toyobo Co., Ltd., trade name of polyester resin)
500 parts of a 20% solution prepared by dissolving
50 parts of 195XL (Sumitomo Chemical Co., Ltd., novolac type epoxy resin trade name) 50% methyl ethyl ketone solution, Epicoat 87
100 parts of 50% methylethylketone solution of 1 (Okaka Shell Epoxy Co., Ltd., fatty acid polyepoxy resin trade name), 5 parts of methyltetrahydrophthalic anhydride, 2E4ME-CN (above) 2
Parts, 5 parts of diaminodiphenyl sulfone, respectively,
It was charged, sufficiently stirred and dissolved, and the adhesive was adjusted. From this, a substrate for flexible printed wiring was manufactured according to the procedure shown in Example 1. The physical properties are shown in Table 1.

Example 3 Byron 300 (manufactured by Toyobo Co., Ltd., trade name of polyester resin)
Of 20% solution of dioxane in 500 parts, Epikote 604
35 parts of 50% dioxane solution of diglycidylamine epoxy resin (trade name, manufactured by Yuka Shell Epoxy Co., Ltd.), Epicoat
517 (trade name of epoxy resin, manufactured by Yuka Shell Epoxy Co., Ltd.)
160% 50% dioxane solution, 10 parts Epicure YH307 (Okaka Ciel Evoxy, acid anhydride trade name), 2E4MZ (Shikoku Fine Chemicals, imidazole trade name) 4 parts,
Weigh 5 parts of diaminodiphenylmethane,
It was sufficiently stirred and dissolved to prepare an adhesive. From this, a substrate for flexible printed wiring was manufactured according to the procedure shown in Example 1. The physical properties are shown in Table 1.

Comparative Example 1 Flexible printed wiring was carried out under the same conditions as in Example 1 except that 5 parts of trialkyltetrahydrophthalic anhydride, 1 part of 2E4MZ-CN (supra) and 15 parts of diaminodiphenylmethane were used instead of 5 parts of diaminodiphenylmethane. A substrate for manufacturing was manufactured. The physical properties are shown in Table 1.

Comparative Example 2 A flexible printed wiring board was manufactured under the same conditions as in Example 1 except that diaminodiphenylmethane was not used. The physical properties are shown in Table 1.

Comparative Example 3 A flexible printed wiring board was manufactured under the same conditions as in Example 2, except that 500 parts of the 20% methyl ethyl ketone solution of Byron 295 (supra) was replaced with 1000 parts.
The physical properties are shown in Table 1.

Comparative Example 4 In Example 3, 35 parts of 50% dioxane solution of Epikote 604 (supra) and 160 parts of 50% dioxane solution of Epikote 517 (supra) were added to 320 parts of 50% dioxane solution of Epikote 517 (supra). A flexible printed wiring board was manufactured under the same conditions except that the substrate was replaced. Regarding physical properties,
The results are shown in Table-1.

Examples 4 and 5 The flexible printed wiring board was manufactured under the same conditions as in Example 1 except that Kapton treated with low temperature plasma B and Kapton treated with low temperature plasma C were used instead of Kapton treated with low temperature plasma A. The properties of Examples 4 and 5 are shown in Table 1.

Comparative Example 5 A substrate for flexible printed wiring was manufactured under the same conditions as in Example 1, except that untreated Kapton was used instead of Kapton treated with the low temperature plasma A. The characteristics are shown in Table-1.

Claims (1)

[Claims] 1. A substrate for flexible printed wiring, which is obtained by laminating and integrating a metal foil with an insulating film subjected to low-temperature plasma treatment via an adhesive having the following composition a) Polyester resin 100 parts by weight b) 3 or more in a molecule Epoxy resin having an epoxy group of 10 to 60 parts by weight c) Epoxy resin having two epoxy groups in a molecule 50 to 200 parts by weight D) Acid anhydride 3 to 30 parts by weight e) Aromatic diamine 1 to 10 parts by weight Parts and f) 0.1 to 5 parts by weight of imidazole compound