TWI384909B - Laminate for wiring substrate - Google Patents

Description

Laminate for wiring board

The present invention relates to a laminated body for a wiring board which can be used as a flexible printed circuit board or an HDD suspension device for a substrate for an electronic device such as a cellular phone.

In recent years, the high-performance or high-performance of electronic devices has progressed rapidly, and even with the use of electronic components used in electronic devices or substrates on which these components are mounted, the demand for higher-density high-performance users has changed. high. On the other hand, electronic devices tend to be lighter, smaller, and thinner, and the space for accommodating electronic components has become narrow. Further, in the flexible printed circuit board used for the movable portion such as the folding type mobile phone or the slide type mobile phone, the high density of the wiring and the high bending resistance of the flexible printed circuit board are similarly required. However, when the conventional flexible printed circuit board is multi-layered or has a small radius of curvature, there is a problem that disconnection occurs after a long period of use, and it is not necessarily obtained that the movable portion of the folding type mobile phone or the slide type mobile phone is sufficient. Resistance to bending.

[Patent Document 1] Japanese Patent Laid-Open Publication No. JP-A No. 2004-311740 (Patent Document No. JP-A-2004-311740) [Patent Document 3] Japanese Patent Laid-Open Publication No. 2005-209913 (Patent Document 4) Japanese Patent No. Japanese Patent Laid-Open No. Hei 6-29667

As a technique for the purpose of applying to a flexible printed circuit board, for example, a copper clad laminate having a thickness of 20 to 60 μm and a patent of Japanese Patent Laid-Open Publication No. 2002-84050, Japanese Patent No. 2002-84050 In the adhesive-type one-sided copper foil laminate having a thickness of 70 μm or less in JP-A-2004-311740, an adhesive-type single-sided copper plate having a thickness of 20 μm or less in Japanese Patent Laid-Open Publication No. 2005-209913 is disclosed. . However, since any of these copper foil laminates requires an adhesive, there is a problem that the base material or the conductor layer is limited, and when the conductor layer is thinned, there is a problem that the capacity is insufficient. In addition, due to the adhesive layer, there is also the problem of electrical reliability or unsuitability for component mounting at high temperatures.

Further, Japanese Patent No. 3356568 discloses a laminate in which the thickness of the polyimide layer is 10 μm or less and the thickness of the conductor layer is 10 μm or less. However, the operation of a polyimide layer of 10 μm or less in a process such as circuit processing is difficult, and when a land of the same shape is formed on both sides of the film, the film may be broken due to a shearing force. When the tray portion is detached, there is a problem that the so-called tray is detached. Further, the problem that the conductor of 10 μm or less has insufficient capacitance has a problem in that the conduction of the communication when the connection process by the anisotropic conductive film (ACF) is performed.

Further, in Japanese Laid-Open Patent Publication No. Hei 6-29667, a method of thinning a polyimide layer by laser melting, chemical etching, plasma etching or polishing is provided, but the surface of the thinned portion is provided. There is a problem of smoothness or mechanical strength, and there is a problem that it is difficult to obtain sufficient effects.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a laminate for a wiring board, which has practical circuit workability, secondary workability such as component mounting or ACF connection, electrical reliability, and sufficient capacitance of the circuit. And the wire breakage of the conductor circuit can be sufficiently prevented when the bending is repeated.

As a result of continuous research and development, the inventors of the present invention have found that the flexural resistance is improved so that the tensile modulus at 25 ° C is 5 GPa or less using a polyimide polyimide insulating layer. The practical mechanical strength and the bending resistance are both in the range of 10 to 15 μm, and the bending resistance is improved by using a highly flexible metal foil layer having a tensile modulus of 40 GPa or less at 25 ° C. By setting the thickness to a range of 7 to 15 μm, a laminate for a wiring board in which bending resistance, capacitance, and ACF bondability are obtained can be obtained, and the present invention has been completed.

That is, the present invention is a laminate for a wiring board, which has a tensile modulus of 5 GPa or less and a thickness of 10 to 15 μm on one side or both sides of the polyimide layer at 25 ° C, and has 25 ° C. A metal foil layer having a tensile modulus of 40 GPa or less and a thickness of 7 to 15 μm.

Since the laminated body for a wiring board of the present invention has practical circuit processing properties and has a capacitance of a circuit required for a wiring board and has high bending characteristics, it can be suitably used for a movable portion such as a folding type or a slide type mobile phone. Share.

Hereinafter, the present invention will be described in detail.

The laminate system for a wiring board of the present invention has a metal foil layer on one side or both sides of the polyimide layer. The polyimine insulating layer constituting the laminate for a wiring board can be dried or hardened by applying a polyimide resin precursor solution (also referred to as a polyamidite solution). The so-called casting method is formed by the so-called casting method in which the metal foil is formed by thermal lamination of the metal foil by coating the thermoplastic polyimide polyimide. A method of forming a conductive layer by sputtering after the surface of the polyimide film is formed by a sputtering method to form a conductor layer by electroplating. Among these, although it is most suitable to form by forming a polyimine precursor resin solution, and hardening and drying, it is not limited to this.

The polyimine precursor resin solution used in the above casting method can be produced by polymerizing a well-known diamine and an anhydride in the presence of a solvent.

The diamine to be used may, for example, be 4,6-dimethyl-m-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 2,4-diamino mesitylene, 4,4. '-Methylene-di-o-toluidine, 4,4'-methylenebis-2,6-dimethylaniline, 4,4'-methylene-2,6-diethylaniline, 2,4 -toluenediamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodi Phenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2,2-anthracene [4-(4-Aminophenoxy)phenyl]propane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'- Diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 1,3 - 贰(3-aminophenoxy)benzene, 1,3-anthracene (4-aminophenoxy)benzene, 1,4-anthracene (4-aminophenoxy)benzene, benzidine, 3, 3'-Diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 4,4'-diamino- Correct Triphenyl, 3,3'-diamino-para-triphenyl, anthracene (p-aminocyclohexyl)methane, anthracene (p-β-amino-t-butylphenyl) ether, hydrazine (p-beta) -methyl-δ-amino-pentyl)benzene, p-oxime (2-methyl-4-aminopentyl)benzene, p-oxime (1,1-dimethyl-5-aminopentyl) Benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-anthracene (β-amino-t-butyl)toluene, 2,4-diaminotoluene, m- Xylene-2,5-diamine, p-xylene-2,5-diamine, m-phenylenediamine, p-xylylenediamine, 2,6-diaminepyridine, 2, 5-diaminopyridine, 2,5-diamino-1,3,4- Diazole, hexahydropyrazine, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,7-diaminodiphenylfuran, 1,5-diaminopurine, two Benzoquinone-pair-two Alkane-2,7-diamine, 4,4'-diaminobenzene, and the like.

Further, examples of the anhydride include pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 2,2',3,3'-benzophenone tetracarboxylic acid. Acid dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, naphthalene-1,2,5,6-tetracarboxylic dianhydride, naphthalene-1,2,4,5- Tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, naphthalene-1,2,6,7-tetracarboxylic dianhydride, 4,8-dimethyl-1,2, 3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene- 2,3,6,7-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5, 8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 1,4,5,8-tetrachloronaphthalene-2,3, 6,7-tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3, 3',4'-biphenyltetracarboxylic dianhydride, 3,3",4,4"-p-terphenyltetracarboxylic dianhydride, 2,2",3,3"-p-terphenyl Tetracarboxylic dianhydride, 2,3,3",4"-p-terphenyltricarboxylic dianhydride, 2,2-indole (2,3-dicarboxyphenyl)propane dianhydride, 2,2-贰(3,4-two Carboxyphenyl)propane dianhydride, hydrazine (2,3-dicarboxyphenyl)ether dianhydride, hydrazine (2,3-dicarboxyphenyl)methane dianhydride, hydrazine (3,4-dicarboxyphenyl)methane Dihydride, bismuth (2,3-dicarboxyphenyl) sulfone dianhydride, ruthenium (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-anthracene (2,3-dicarboxyphenyl)ethane Dihydride, 1,1-anthracene (3,4-dicarboxyphenyl)ethane dianhydride, guanidine-2,3,8,9-tetracarboxylic dianhydride, 苝-3,4,9,10-four Carboxylic dianhydride, indole-4,5,10,11-tetracarboxylic dianhydride, indole-5,6,11,12 tetracarboxylic dianhydride, phenanthrene-1,2,7,8-tetracarboxylic acid Anhydride, phenanthrene-1,2,6,7-tetracarboxylic dianhydride, phenanthrene-1,2,9,10-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic acid Anhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic acid Anhydride, 4,4'-oxyphthalic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, and the like.

The diamine and the anhydride may be used in combination of only one type or two types or more. Further, in the case of a polyimide-imide insulating layer obtained by a polyimide precursor, a combination of these compounds is selected such that the tensile modulus of elasticity satisfies the above numerical value. When the polyimine insulating layer is formed of a plurality of polyimine layers, the above values may be satisfied as a whole.

Examples of the solvent system include dimethylacetamide, N-methylpyrrolidone, 2-butanone, diglyme, and xylene. These may be used alone or in combination of two or more.

The polyimine insulating layer is preferably formed by directly coating the metal foil in the state of a polyimide precursor. In this case, the viscosity of the polymer to be polymerized is preferably in the range of 500 cps to 35,000 cps. The polyimide layer may be formed of only a single layer, or may be formed of a plurality of layers. When the polyimine insulating layer is a plurality of layers, it can be formed by sequentially coating another polyimide polyimide precursor resin on a polyimide intermediate precursor resin composed of different constituent components. When the polyimine insulating layer is composed of three or more layers, the polyimide component precursor resin having the same composition may be used twice or more.

The laminate for a wiring board of the present invention can be produced by applying a polyimide film of a polyimide film to the metal foil as described above, or by laminating one or more layers of a polyimide film to a copper foil. The laminated body for a wiring board manufactured by this method can be used as a base layer for a single-sided wiring board having a metal foil on one side, or as a laminate for a double-sided wiring board having metal foil on both sides. Among these laminated bodies for wiring boards, those in which copper foil is used as a metal foil are referred to as single-sided copper-clad laminates and double-sided copper foil laminated sheets. After the base layer system for a double-sided wiring board is formed in a laminated body for a single-sided wiring board, the metal foil is pressed by hot pressing, and the two metal foil layers are pressed by a polyimide film. The method can be obtained.

In the laminate for a wiring board of the present invention, the tensile modulus of the polyimide film at 25 ° C must be 5 GPa or less, preferably 2.5 to 4.6 GPa. When the value of the tensile modulus of the polyimide layer exceeds 5 GPa, it is difficult to exhibit sufficient bending resistance. Further, the thickness of the polyimide layer of the polyimide must be in the range of 10 to 15 μm. When the thickness of the polyimide layer is less than 10 μm, wrinkles or breaks are likely to occur in the steps of circuit processing, etc., in addition to the difficulty of operation, when the same shape of the land is formed on both sides of the film, the film may be When the shearing force is broken, the tray portion is detached, and the problem that the tray portion is detached easily occurs. When the thickness exceeds 15 μm, the performance of sufficient bending resistance is difficult, or the flexibility of the wiring board is impaired. Further, when the polyimine insulating layer is composed of a plurality of layers of a polyimide layer, the tensile modulus and thickness are values of the entire polyimide layer.

In the present invention, the polyimide elastic layer must have a tensile modulus of 5 GPa or less, but the low elasticity is opposite to the low linear expansion coefficient necessary for the laminated board for printed wiring. For the coexistence of both, use 2'-methoxy-4,4'-diamino-N-benzamide, 2.2'-dimethyl-4,4'-diaminobiphenyl or 2 A monomer having a rigid structure such as 3,6,7-naphthalenetetracarboxylic dianhydride, and the hardening condition is optimized to control molecular alignment, and can be a low linear expansion coefficient. On the other hand, as appropriate, 3,3',4,4'-biphenyltetracarboxylic dianhydride or 4,4'-diaminodiphenyl ether soft monomer can be selected as the optimum amount. The copolymer reduces the modulus of elasticity.

The polyimine insulating layer has a thickness of 10 to 15 μm and is coated with a copper foil-coated polyimine precursor. The drying and hardening casting method is most suitable. This method is carried out in a solution state when the precursor is applied, and since it is applied at a thickness of 5 times to 20 times that of the actual use, the thickness can be controlled with high precision. This result makes it possible to precisely control the thickness necessary for practical use of the film polyimine. Although the thermoplastic polyimide may be applied to both sides of the polyimide film to press the copper foil, the polyimide which is the original material must be used in a very thin range of 5 to 9 μm.

The metal foil used in the present invention may be a conductive metal foil such as copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, zinc or an alloy of these metals, and preferably copper foil or copper containing 90%. The above alloy copper foil. The metal foil on the surface side of the polyimide layer is preferably an electrolytic copper foil having a surface roughness (Rz) of 3.5 μm or less, and more preferably 2.5 μm or less.

In the laminate for a wiring board of the present invention, the tensile modulus of the metal foil at 25 ° C must be 40 GPa or less, preferably 25 to 35 GPa. When the value of the tensile modulus exceeds 40 GPa, the flexibility of the metal foil is low, and it is difficult to exhibit sufficient bending resistance. Further, the thickness of the metal foil must be in the range of 7 to 15 μm. When the thickness of the metal foil is less than 7 μm, the circuit cross section cannot be sufficiently ensured and the capacity is insufficient. Further, when an anisotropic conductive film (ACF) is joined, the distance between the terminals to be connected is too long, which may cause problems in the communication. When it exceeds 15 μm, regardless of the modulus of elasticity of the metal foil, the stress generated in the metal foil increases, and it is difficult to exhibit sufficient bending resistance. Although a commercially available copper foil can be used as the metal foil having such a characteristic, generally, the commercially available copper foil is less than 10 μm. In this case, a copper foil satisfying the above tensile modulus is selected, and when the thickness of the copper foil is large The thickness of the copper foil may be a predetermined thickness by chemical etching or the like as necessary. Further, after the sputtering treatment of the above-mentioned polyimide film layer, the desired metal foil may be deposited by plating.

The laminated body for a wiring board of the present invention can be patterned by etching, and then the wiring circuit can be protected by a coverlay film to form a printed circuit board. The method of the etching treatment is not particularly limited, and a suitable conventional method can be used. In a suitable method for the etching treatment in this manner, for example, a circuit pattern is formed by using an alkali developing type dry film on a metal foil, and then a conductive film is removed from the conductor film of the unprotected portion of the dry film by an etching solution to form a wiring circuit, and then stripped. Dry film method.

The cover film to be used is not particularly limited, and for example, a cover film provided with an adhesive layer of an epoxy resin or an acrylic resin on one surface of the polyimide film is exemplified. The thickness of the cover film is not particularly limited and is preferably 5 to 50 μm, more preferably 10 to 30 μm. As such a cover film, a commercially available cover film can be used, and it is not particularly limited, and examples thereof include CVA0525KA (manufactured by Tosawa Co., Ltd.), CVA0515KA (manufactured by Toray Industries Co., Ltd.), CISV1225 (manufactured by NIKKAN Industrial Co., Ltd.), and CA231 (manufactured by Shin-Etsu Co., Ltd.). ).

[Examples]

The present invention is specifically described by the following examples, but the present invention is not limited by the scope of the examples.

The abbreviations used in the examples and the like are as follows.

BAPP: 2,2-贰[4-(4-Aminophenoxy)phenyl]propane PMDA: pyromellitic dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic acid Anhydride DAPE: 4,4'-diaminodiphenyl ether MABA: 2'-methoxy-4,4'-diamino-benzimidamide m-TB: 2.2'-dimethyl-4, 4'-Diaminobiphenyl NTCDA: 2,3,6,7-naphthalenetetracarboxylic dianhydride DMAc: N,N-dimethylacetamide

[Determination of Tensile Elasticity of Polyimine]

The copper foil portion of the laminate for the wiring board was etched and removed using an aqueous solution of ferric chloride to form a polyimide film, and a polyimide film having a width of 12.7 mm and a length of 170 mm was used using a tensile tester. A tensile test of 50 mm/min was carried out by applying a load of 10 kg to a distance of 100 mm between chucks.

[Measurement of tensile modulus of copper foil]

The polyimine portion of the laminate for the wiring board was etched and removed using a polyimine chemical etching solution TPE3000 manufactured by Toray Engineering to prepare a copper foil sample, and a copper foil having a width of 12.7 mm and a length of 170 mm was used using a tensile tester. A tensile test of 5 mm/min was performed by applying a load of 10 kg to a distance of 100 mm between chucks.

[Bending resistance test (IPC bending test)]

A circuit having a test piece width of 8 mm and a test piece length of 150 mm was used to form a circuit of L/S=100 μm/100 μm, and a CVK0525KA manufactured by Azawa Seisakusho Co., Ltd. was used as a cover material by press-pressing on the circuit. The cover material was laminated, and an acceleration test was performed using an IPC bending tester manufactured by Shin-Etsu Machinery Co., Ltd. under the conditions of a curvature r: 1.25 mm, a vibration stroke: 20 mm, and a vibration speed: 1500 times/min. In this test, the number of times the resistance of the sample was raised to 5% was determined.

Synthesis Example 1

After dissolving BAPP 40 mol (16421 g) in 102 kg of DMAc, PMDA 34 mol (7416 g) and BPDA 6 mol (1765 g) were gradually added to carry out a reaction to obtain a viscous polyamine solution.

Synthesis Example 2

After dissolving DAPE 20 mol (4005 g) and MABA 20 mol (5146 g) in 72 kg of DMAc, PMDA 40 molar (8725 g) was slowly added to carry out a reaction to obtain a viscous polyamine solution.

Synthesis Example 3

After dissolving DAPE 20 mol (4005 g) and m-TB 20 mol (4246 g) in 68 kg of DMAc, PMDA 40 molar (8725 g) was slowly added to carry out a reaction to obtain a viscous polyamine solution.

Synthesis Example 4

After dissolving DAPE 20 Moore (4005g) and m-TB 20 Moer (4246g) in 71kg of DMAc, slowly add PMDA 30 Moer (6544g) and BPDA 10 Moer (2942g) to obtain a viscous shape. Polylysine solution.

Synthesis Example 5

After dissolving DAPE 32 mol (6408 g) and m-TB 8 mol (1698 g) in 75 kg of DMAc, NTCDA 40 mol (1072 g) was slowly added to carry out a reaction to obtain a viscous polyamine solution.

Example 1

The polyaminic acid solution prepared in Synthesis Example 1 was applied onto F2-WS manufactured by Furukawa Circuit Foil Co., Ltd. having a thickness of 12 μm by using an applicator to have a film thickness after hardening of about 2 μm. After drying at 130 ° C for 1 minute, the polyamic acid solution prepared in Synthesis Example 2 was applied individually to a thickness of about 8 μm after curing, and dried at 130 ° C for 1 minute. Next, the polyamic acid solution prepared in Synthesis Example 1 was applied so as to have a film thickness after hardening of about 2 μm, and then at 130 ° C, 160 ° C, 200 ° C, 230 ° C, and 280 ° C, Each of 320 ° C and 360 ° C was subjected to a stepwise heat treatment for 2 to 12 minutes to obtain a laminate for a wiring board having a multilayer polyimide layer having a total thickness of 12 μm.

The tensile modulus of the polyimide obtained in the laminate for a wiring board was measured to be 4.5 GPa, and the tensile modulus of the copper foil was measured to be 30 GPa. Further, the number of times of IPC bending of the laminated body for wiring boards which were processed by the circuit was 1,200,000 times.

Comparative example 1

The polyamic acid solution prepared in Synthesis Example 2 was applied in the same manner as in Example 1 except that the film thickness after curing was applied to a thickness of about 21 μm so as to have a total thickness of 25 μm. The tensile modulus of the polyimide obtained in the laminate for a wiring board was measured to be 4.5 GPa, and the tensile modulus of the copper foil was measured to be 30 GPa. The number of times of IPC bending of the laminated body for wiring boards which were processed by the circuit was 19,000 times.

Example 2

The polyaminic acid solution prepared in Synthesis Example 1 was applied to HLB manufactured by Nippon Electrolysis Co., Ltd. having a thickness of 12 μm at a temperature of 130 ° C using a trickle dryer to a thickness of about 2 μm. After drying for 1 minute, the polyamic acid solution prepared in Synthesis Example 3 was applied individually to a thickness of about 8 μm after curing, and dried at 130 ° C for 1 minute. Next, the polyamic acid solution prepared in Synthesis Example 1 was applied so as to have a film thickness after hardening of about 2 μm, and then at 130 ° C, 160 ° C, 200 ° C, 230 ° C, and 280 ° C, 320. C and 360 ° C were each subjected to a stepwise heat treatment for 2 to 12 minutes to obtain a laminate for a wiring board having a multilayer polyimide layer having a total thickness of 12 μm.

The tensile modulus of the polyimide obtained in the laminate for a wiring board was measured to be 4.6 GPa, and the tensile modulus of the copper foil was measured to be 25 GPa. The number of times of IPC bending of the laminated body for wiring boards which were processed by the circuit was 1,500,000 times.

Comparative example 2

The same procedure as in Example 2 was carried out except that the polyamic acid solution prepared in Synthesis Example 4 was used instead of the polyamic acid solution prepared in Synthesis Example 3. Regarding the laminate for the wiring board produced, the tensile modulus of the polyimide was measured to be 7.5 GPa, and the tensile modulus of the copper foil was measured to be 25 GPa. The number of times of IPC bending of the laminated body for wiring boards which were processed by the circuit was 860,000 times.

Comparative example 3

The same procedure as in Example 2 was carried out except that the BHY foil manufactured by Nippon Mining Co., Ltd., having a thickness of 18 μm, was replaced by HLB manufactured by Nippon Electrolysis Co., Ltd. having a thickness of 12 μm. Regarding the laminate for the wiring board produced, the tensile modulus of the polyimide was measured to be 4.6 GPa, and the tensile modulus of the copper foil was measured to be 28 GPa. The number of times of IPC bending of the laminated body for wiring boards which were processed by the circuit was 660,000 times.

Comparative example 4

The same procedure as in Example 2 was carried out except that the SQ-VLP foil manufactured by Mitsui Mining Co., Ltd., having a thickness of 12 μm, was replaced by HLB manufactured by Nippon Electrolysis Co., Ltd. having a thickness of 12 μm. Regarding the laminate for the wiring board produced, the tensile modulus of the polyimide was measured to be 4.6 GPa, and the tensile modulus of the copper foil was measured to be 69 GPa. The number of times of IPC bending of the laminated body for wiring boards which were processed by the circuit was 150,000 times.

Example 3

The same procedure as in Example 1 was carried out except that the polyamic acid solution prepared in Synthesis Example 5 was used instead of the polyamic acid solution prepared in Synthesis Example 2. Regarding the laminate for the wiring board produced, the tensile modulus of the polyimide was measured to be 2.6 GPa, and the tensile modulus of the copper foil was measured to be 30 GPa. The number of times of IPC bending of the laminate for wiring circuit processing was determined to be 1,200,000 times.

Comparative Example 5

The same procedure as in Example 3 was carried out except that the polyamic acid solution prepared in Synthesis Example 5 was applied so as to have a film thickness of about 4 μm after hardening to a total thickness of 8 μm. With respect to the laminate for the wiring board produced, the tensile modulus of the polyimide was measured to be 2.6 GPa. Further, the tensile modulus of the copper foil was measured to be 30 GPa. The number of times of IPC bending of the laminated body for wiring boards which were processed by the circuit was 210,000 times.

The results are summarized in Table 1.

Claims (3)

A laminated body for a wiring board which is provided on one side or both sides of a polyimide elastic layer having a tensile modulus of 5 GPa or less and a thickness of 10 to 15 μm at 25 ° C, and is directly provided without passing through an adhesive layer. A metal foil layer having a tensile modulus of 40 GPa or less and a thickness of 7 to 15 μm at ° C. The laminate for a wiring board according to the first aspect of the invention, wherein the polyimide layer is coated on a metal foil, and the polyimide precursor resin is applied, dried, and cured in a solution state. The laminate for a wiring board according to the first or second aspect of the invention, wherein the laminate system for a wiring board is used for a wiring board of a deformed portion of a folding type or a sliding type mobile phone.