JP2011109082A - Flexible double-sided copper-clad laminate, flexible circuit board, and multilayered circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible double-sided copper-clad laminate, a flexible circuit substrate, and a multilayered circuit substrate having high flexibility and resistivity against bending action, and high handleability on manufacturing and processing a wiring substrate. <P>SOLUTION: The flexible double-sided copper-clad laminate has a copper-foil layer at both sides of a polyimide insulating layer, a first copper-foil layer with its equivalent flexural rigidity of 0.003-0.2 N mm per a unit width at a thickness of 9-35 μm, and a second copper-foil layer with its equivalent flexural rigidity of 0.00001-less than 0.003 N mm per the unit width at the thickness of 3-12 μm. In the flexible double-sided copper-clad laminate, the first copper-foil layer has its equivalent flexural rigidity higher than that of the second copper-foil layer, the thickness of the polyimide insulating layer lies is 7-50 μm, and the tensile elastic modulus is 2-9 GPa at 25°C. The flexible circuit substrate has the wiring circuit utilizing the second copper-foil layer. The multilayered circuit substrate is formed by forming the flexible circuit substrate in the multilayered structure. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a flexible double-sided copper-clad laminate suitable as a substrate for use in an electronic device such as a mobile phone, a flexible circuit board obtained by processing the wiring, and a multilayer circuit board obtained by multilayering the flexible circuit board. Is.

  In recent years, electronic devices represented by mobile phones, notebook computers, digital cameras, game machines, and the like have been rapidly reduced in size, thickness, and weight. High-density, high-performance materials that can accommodate components are desired. As a material that meets this requirement, flexible circuit boards that are thin and can be folded into a narrow space and have high bending resistance are widely used. However, materials that are more flexible and easy to bend are required for flexible circuit boards that are used in movable parts such as folding cellular phones and sliding cellular phones, which require high density. In the conventional flexible circuit board, when the number of layers is increased or the bending radius is reduced, there is a problem that disconnection occurs after a long period of use, and a substrate having sufficient bending resistance is not necessarily obtained. Therefore, thinning of a flexible circuit board has been studied in order to realize further high bending resistance, and as one of the methods, research for thinning a polyimide insulating layer and a metal foil layer as materials has been conducted.

For example, in Japanese Patent No. 3356568 (Patent Document 1), a copper film having a thickness of 10 μm or less is formed on one or both sides of a polyimide film having a thickness of 10 μm or less made of a polyimide polymer having an initial tensile elastic modulus of 400 kg / mm ² or more. A flexible copper-clad laminate in which layers are directly formed has been proposed. However, although the flexible copper-clad laminate shown in Patent Document 1 has a certain degree of high bending resistance, a polyimide film is produced once in the production process of the flexible copper-clad laminate, and a copper layer is formed thereon. Therefore, it is necessary for the polyimide film to have an initial tensile elastic modulus of a certain level or more due to the problem of handling at the time of production, and there is a limit to the thinning of the polyimide layer.

  On the other hand, a method for producing a laminate for a flexible substrate by a so-called casting method in which a polyimide precursor resin is applied in a solution state to a metal foil such as a copper foil and heat-treated is also known. In order to maintain the handleability in the transporting process, a copper foil thickness of a certain level or more is required. In addition, as a method for producing a laminate for a flexible circuit board with a thin metal foil, a polyimide precursor resin is applied in a solution state to an ultrathin metal foil with a carrier comprising a carrier, a release layer and an ultrathin metal foil, Although heat treatment is disclosed in the pamphlet of WO 2006/106723 (Patent Document 2), an increase in the process of peeling the carrier and a manufacturing cost increase, and therefore, it is possible to provide a laminate for a flexible circuit board by a simple manufacturing method. desired.

  Furthermore, the thin laminated board for a flexible circuit board has a drawback that the handling property in the circuit processing process is also deteriorated, leading to a decrease in product yield in the processing process. In order to solve this problem, a method for manufacturing a flexible copper-clad laminate in which the copper foil on both sides is thinned by forming the laminate and then thinning the copper foil by etching is disclosed in JP-A-2-22896 (Patent Document 3). However, since this method is a method of reducing the copper foil thickness by etching the double-sided thin copper foil-clad flexible circuit board that has been once produced, the increase in the manufacturing process and the manufacturing cost are required. In addition to the increase, there is a concern about the problem of the processing of the etching solution required for etching, and therefore, it is desired to provide a laminate for a flexible circuit board that is simple and economical.

Japanese Patent No. 3356568 WO2006 / 106723 pamphlet JP-A-2-22896

  The present invention has been made in view of the above-described problems of the prior art, and has high bending resistance and bending resistance, high handling properties at the time of manufacturing a flexible double-sided copper-clad laminate, and subsequent flexibility. An object of the present invention is to provide a flexible double-sided copper-clad laminate having both high handling properties in the processing step of processing the double-sided copper-clad laminate into a wiring circuit.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained a first copper foil having a specific thickness and high rigidity on the copper foil on both sides of the polyimide insulating layer of the flexible double-sided copper-clad laminate. It has been found that the above-mentioned problems can be solved by using different copper foils so as to include a high-flexibility second copper foil layer having a specific thickness and a layer, and the present invention has been completed. .

  That is, according to the present invention, in a flexible double-sided copper clad laminate having copper foil layers on both sides of a polyimide insulating layer, the thickness is 9 μm or more and 35 μm or less, and the equivalent bending rigidity per unit width is 0.003 N · mm or more and 0. The first copper foil layer in the range of 2 N · mm or less, the thickness is 3 μm or more and 12 μm or less, and the equivalent bending rigidity per unit width is in the range of 0.00001 N · mm or more and less than 0.003 N · mm The equivalent bending rigidity of the first copper foil layer is higher than the equivalent bending rigidity of the second copper foil layer, and the thickness of the polyimide insulating layer is not less than 7 μm and not more than 50 μm A flexible double-sided copper-clad laminate having a tensile elastic modulus at 25 ° C. of 2 GPa or more and 9 GPa or less.

  Moreover, this invention is a flexible circuit board which forms a wiring circuit using the 2nd copper foil layer of the said flexible double-sided copper clad laminated board, and uses at least one part of a wiring circuit for a bending part. Furthermore, the present invention is a multilayer circuit board obtained by multilayering this flexible circuit board.

  According to the present invention, a substrate material having excellent handling properties in a manufacturing process of a flexible double-sided copper-clad laminate having a thin copper foil layer and a circuit processing step of wiring circuit processing of this flexible double-sided copper-clad laminate Can be provided. The obtained flexible double-sided copper-clad laminate has practical mechanical strength and is expected to have the high bending properties required for wiring boards. It is suitably used for electronic parts, HDD suspensions, etc. that require bending resistance and repeated bending resistance, such as bent portions around liquid crystals. In particular, a flexible circuit board obtained by etching and removing a copper foil layer on one side of a flexible double-sided copper-clad laminate has excellent folding resistance, and by using this as a multilayer circuit board, electronic devices can be further reduced in size and thickness. It is valid.

FIG. 1 (A) is a schematic side view showing a flexible double-sided copper clad laminate of the present invention, and FIG. 1 (B) shows a state of a flexible circuit board obtained by removing a part of the first copper foil layer. It is a schematic diagram which shows. 2A and 2B are schematic side views showing a state in which a bent portion is formed on the flexible circuit board. FIG. 3 is a schematic side view illustrating a multilayer circuit board using a flexible circuit board. FIG. 4 is a schematic side view showing an embodiment in which a shield layer is provided on a flexible circuit board.

Hereinafter, the present invention will be described in detail.
The flexible double-sided copper-clad laminate of the present invention (hereinafter sometimes simply referred to as “double-sided copper-clad laminate”) has copper foils on both sides of the polyimide insulating layer. Rolled copper foil and the like, and alloy copper foil containing 90% or more of copper is also included. Specifically, the copper foil provided on both sides of the polyimide insulating layer has different characteristics, and on one side of the polyimide insulating layer, the thickness is 9 μm or more and 35 μm or less, preferably 12 μm or more and 18 μm or less. A first copper foil layer having an equivalent bending rigidity per unit width of 0.003 N · mm to 0.2 N · mm, preferably 0.004 N · mm to 0.05 N · mm; On the opposite side of the foil layer, the thickness is 3 μm or more and 12 μm or less, preferably 6 μm or more and 12 μm or less, and the equivalent bending rigidity per unit width of the copper foil layer is 0.00001 N · mm or more and less than 0.003 N · mm, preferably Has a second copper foil layer in the range of 0.0002 N · mm to 0.002 N · mm. That is, the first copper foil layer has a higher equivalent bending rigidity than the second copper foil, and ensures handling at the time of manufacturing a flexible double-sided copper-clad laminate or processing a wiring circuit. On the other hand, the second copper foil layer has lower flexibility than the first copper foil layer and has flexibility, and ensures the bending resistance when the wiring circuit is formed. Specifically, the equivalent bending rigidity of the first copper foil layer is preferably 1.2 times or more higher than the equivalent bending rigidity of the second copper foil, and more preferably 2 times or more. Most preferably, it is in the range of 2 to 100 times.

  If the thickness of the first copper foil layer is less than 9μm and the equivalent bending stiffness per unit width of the copper foil layer is less than 0.003N · mm, the handling of the double-sided copper-clad laminate itself will be impaired and mass production will begin. On the other hand, if the thickness of the copper foil layer exceeds 35 μm and the equivalent bending rigidity per unit width of the copper foil layer exceeds 0.2 N · mm, the copper foil price becomes too expensive and economical. Disadvantageous. On the other hand, if the thickness of the second copper foil layer is less than 3 μm and the equivalent bending rigidity per unit width of the copper foil layer is less than 0.00001 N · mm, it is difficult to obtain the copper foil, It is not suitable for mass production because it impairs its own handling characteristics. Conversely, if the thickness of the copper foil layer exceeds 12μm and the equivalent bending rigidity per unit width of the copper foil layer is 0.003N · mm or more, it will be bent. It becomes a material with inferior properties. The equivalent bending rigidity per unit width of the copper foil layer represents the rigidity of the copper foil when bent in the rolling direction (MD direction) of the copper foil, and is a direction orthogonal to the rolling direction of the copper foil (TD). This shows the rigidity of the copper foil per 1 mm along (direction). Since the rolled copper foil is usually wound in a roll shape along the rolling direction, the MD direction and the TD direction of the copper foil roll wound in the roll shape can be immediately identified. Further, when the copper foil is an electrolytic copper foil, the MD direction cannot be regarded as the longitudinal direction of the copper foil wound around the roll.

  The copper foils forming the first copper foil layer and the second copper foil layer can be selected and used as those having the thickness and rigidity as described above, and as a specific example, commercially available Furukawa Electric industry F2-WS foil, UWZ foil, Nippon Electrolytic Co., Ltd. HLB foil, Mitsui Kinzoku Co., Ltd. DFF foil, Nikko Metal Co., Ltd. BHY foil, HA foil, etc. can be mentioned. In addition, even if these other products are used, including these commercially available products, as will be described later, by heat curing when forming the polyimide insulating layer, heat treatment applied in the thermocompression bonding process, etc. The equivalent bending rigidity of the copper foil may be in a predetermined range.

  The polyimide insulating layer in the flexible double-sided copper-clad laminate of the present invention has a thickness of 7 μm to 50 μm, preferably 12 μm to 25 μm, and a tensile elastic modulus at 25 ° C. of 2 GPa to 9 GPa, preferably 4 GPa to 8 GPa. It is necessary to be. If the thickness of the polyimide insulating layer is less than 7 μm or the tensile modulus is less than 2 GPa, it is difficult to manufacture the flexible copper clad laminate in the manufacturing process and the subsequent circuit processing process due to handling problems. On the other hand, if the thickness of the polyimide insulating layer exceeds 50 μm or exceeds 9 GPa, it may be difficult to develop sufficient bending resistance and the flexibility of the wiring board may be impaired.

  The polyimide insulating layer is preferably formed by a so-called casting method in which a polyimide precursor resin solution (also referred to as a polyamic acid solution) is directly applied on a copper foil and then dried and cured by heat treatment. The polyimide insulating layer may be formed of only a single layer or may be formed of a plurality of layers. When making a polyimide insulating layer into multiple layers, it can form by apply | coating another polyimide precursor resin sequentially on the polyimide precursor resin which consists of a different structural component. When the polyimide insulating layer is composed of a plurality of layers, the polyimide precursor resin having the same configuration may be used twice or more.

  The polyimide precursor resin solution can be produced by polymerizing a known diamine and acid anhydride in the presence of a solvent, and the resin viscosity to be polymerized should be in the range of 500 cps to 35,000 cps. Is preferred.

  Examples of the diamine used include 4,6-dimethyl-m-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 2,4-diaminomesitylene, 4,4′-methylenedi-o-toluidine, 4, 4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 2,4-toluenediamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2,2-bis [ 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-di Minodiphenyl ether, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, benzidine, 3,3'-diamino Biphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 4,4'-diamino-p-terphenyl, 3,3'-diamino-p-terphenyl, bis (p-aminocyclohexyl) methane, bis (p-β-amino-t-butylphenyl) ether, bis (p-β-methyl-δ-aminopentyl) benzene, p-bis (2-methyl-4-aminopentyl) ) Benzene, p-bis (1,1-dimethyl-5-aminopentyl) benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis (β-amino-t-butyl) toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylene Diamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3 , 7-diaminodibenzofuran, 1,5-diaminofluorene, dibenzo-p-dioxin-2,7-diamine, 4,4′-diaminobenzyl and the like.

  Examples of the acid anhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, and 2,2 ′, 3,3′-benzophenone tetracarboxylic acid dianhydride. Anhydride, 2,3,3 ', 4'-benzophenonetetracarboxylic dianhydride, naphthalene-1,2,5,6-tetracarboxylic dianhydride, naphthalene-1,2,4,5-tetracarboxylic Acid 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 acid Anhydride, 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-terphenyl Tetracarboxylic dianhydride, 2,2``, 3,3 ''-p-terphenyltetracarboxylic dianhydride, 2,3,3 '', 4 ''-p-terphenyltetracarboxylic dianhydride Anhydride, 2,2-bis (2,3-dicarboxyphenyl) -propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -propane dianhydride, bis (2,3-di Carboxyphenyl) ether dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3.4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) sulfone dianhydride Bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1- (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, perylene-2,3,8,9-tetracarboxylic dianhydride Perylene-3,4,9,10-tetracarboxylic dianhydride, perylene-4,5,10,11-tetracarboxylic dianhydride, perylene-5,6,11,12-tetracarboxylic dianhydride Phenanthrene-1,2,7,8-tetracarboxylic dianhydride, phenanthrene-1, 2,6,7-tetracarboxylic dianhydride, phenanthrene-1,2,9,10-tetracarboxylic dianhydride Anhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic Acid dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, etc. Can be mentioned.

  Each diamine and acid anhydride may be used alone or in combination of two or more. Examples of the solvent used for the polymerization include dimethylacetamide, N-methylpyrrolidinone, 2-butanone, diglyme, xylene and the like, and they can be used alone or in combination of two or more.

  Although there is no restriction | limiting in particular about the method of manufacturing the flexible double-sided copper clad laminated board of this invention, Preferably, the said polyimide insulating layer is formed on the highly rigid 1st copper foil layer, and cupric copper with high flexibility after that is preferable. It is good to obtain by laminating | stacking a foil layer on heating-pressing conditions. In forming the polyimide insulating layer, first, a highly rigid first copper foil layer is prepared, and at least one polyimide precursor resin solution is directly coated on the first copper foil, followed by drying and imide It is better to perform heat treatment to make it easier. As a coating method of the resin solution, a known method can be used as appropriate, and examples thereof include a roll coater, a die coater, and a bar coater. Moreover, as drying conditions of the polyimide precursor resin solution coated on the 1st copper foil layer, what is necessary is just the conditions which can remove the solvent in a resin solution, for example, it is preferable that it is a temperature of 150 degrees C or less. The heat treatment for imidization is preferably performed at a temperature of 120 ° C. or higher and 400 ° C. or lower for 5 minutes or longer.

  Thus, after obtaining the flexible one side copper clad laminated body by which the polyimide insulating layer was formed on the 1st copper foil layer, in this flexible one side copper clad laminated body, so that a 2nd copper foil may become an outer side further That is, it laminates | stacks so that a polyimide insulating layer and a 2nd copper foil layer may contact | connect. As a method of laminating, a publicly known method can be adopted as appropriate, for example, a normal hydro press, a vacuum type hydro press, an autoclave pressurizing vacuum press, a heating roll press, a double belt press, a continuous thermal laminator, etc. Can be used. In this case, the lamination temperature is preferably in the range of 300 ° C. or higher and 430 ° C. or lower, more preferably 350 ° C. or higher and 400 ° C. or lower, from the viewpoint of the adhesive strength between the copper foil and the polyimide.

  The obtained flexible double-sided copper-clad laminate can be formed into a flexible circuit board by patterning into a predetermined shape by etching. Usually, a flexible circuit board is protected by a coverlay film after the wiring circuit is processed. The method for the etching treatment is not particularly limited, and a known method can be used as appropriate. As a suitable method for such an etching process, for example, after a circuit pattern is formed on a copper foil using an alkali development type dry film, a portion of the conductor not protected by the dry film using an etching solution is used. A method of forming a wiring circuit by removing the film and then peeling the dry film can be mentioned.

  The flexible circuit board of the present invention is a wiring circuit component used in a bent or bent portion, and is used as a flexible circuit board in which the wiring circuit used in the bent or bent portion is provided substantially only on one side. be able to. Preferably, a wiring circuit can be formed using the second copper foil layer of the flexible double-sided copper-clad laminate, and at least a part of the wiring circuit can be used as a bent portion, more preferably at least a bent portion. The first copper foil layer at a position corresponding to is preferably used after being removed. That is, in the present invention, a flexible circuit board having excellent folding resistance such as repeated bending can be obtained by providing a wiring circuit used for a bent or bent portion substantially on only one side.

  FIG. 1 (A) shows a flexible double-sided copper clad laminate of the present invention, and FIG. 1 (B) is for removing a part of the first copper foil layer 1 to form a bent portion. It is a schematic diagram which shows the mode of this flexible circuit board. The first copper foil layer 1 to be removed varies depending on the type and application of the flexible circuit board, but the main part of the first copper foil layer (that is, 80% or more) is removed, as shown in FIG. It is preferable that the copper foil remains only in a portion not related to the bent portion without leaving a portion that functions as a wiring circuit.

  The flexible circuit board configured as described above is used in a form as shown in FIG. 2, for example. At this time, the wiring circuit formed by the second copper foil layer may be positioned outside as shown in FIG. 2 (A) when bent, as shown in FIG. 2 (B). As such, it may be located inside. Further, the bent portion 4 formed on the flexible circuit board is not only formed by folding in two or the like, but also includes any repeated operation selected from sliding bending, bending bending, hinge bending or sliding bending, for example. Even a bent portion can exhibit excellent bending resistance.

  FIG. 3 shows a multilayer circuit board obtained by multilayering the flexible circuit board. By making the flexible circuit board multilayer, the electronic device can be reduced in size and thickness. As shown in FIG. 3, a flexible circuit board having the form shown in FIG. 1 is prepared, and the surface processed into the wiring circuit is covered with an insulating layer 5 such as a coverlay film. Protect. The insulating layer 5 used here is not particularly limited, and examples thereof include a coverlay film in which an adhesive layer of an epoxy or acrylic resin is provided on one surface of a polyimide film. The thickness of the insulating layer 5 is not particularly limited, but is preferably 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 30 μm or less. As such an insulating layer 5, a commercially available coverlay film can be used. For example, CAE0525KA (manufactured by Arisawa), CAE0515KA (manufactured by Arisawa), CISV1215 (manufactured by Nikkan Kogyo), CA231 (manufactured by Shin-Etsu). ) And the like. And if the flexible circuit board by which the 1st copper foil layer 1 and the 2nd copper foil layer 3 were protected by the insulating layer 5 is piled up via the contact bonding layer 6 which consists of a well-known bonding sheet etc., a multilayer circuit board will be obtained. be able to.

  Further, the flexible circuit board may be provided with a film-like or paste-like shield layer 7 as shown in FIG. 4 in order to have a shielding effect as required. The material for forming the shield layer 7 is not particularly limited, but it is preferable to use a shield film or the like in order to reduce the repulsive force at the bent portion (bent portion). As described above, the flexible circuit board can be formed into a multilayer circuit board by fixing the part other than the bent portion with an adhesive layer or the like and multilayering it into two or more layers. Note that FIG. 3 is a laminate in which the bent portion has two layers, but it is possible to further increase the number of layers by stacking three layers and four layers.

  Hereinafter, based on an Example, this invention is demonstrated in detail. In addition, each characteristic evaluation in the following Example was performed with the following method.

[Measurement of tensile modulus]
The value of the tensile elastic modulus was measured in an environment of a temperature of 23 ° C. and a relative humidity of 50% using a strograph R-1 manufactured by Toyo Seiki Co., Ltd.

[Calculation of equivalent bending stiffness per unit width of double-sided copper-clad laminate]
As a method for evaluating the handling property of the material, the equivalent bending stiffness per 1 mm width (“equivalent bending stiffness / width”) along the TD direction of the copper foil forming the circuit in the flexible double-sided copper-clad laminate is as follows. Calculated. First, a polyimide insulating layer was formed independently under the same conditions as mentioned in each example, and the tensile elastic modulus (E _PI ) was measured. Similarly, the copper foil subjected to the same heat treatment as those mentioned in each example tensile elastic modulus in the MD direction (that of the copper foil used in the second copper foil layer and E _CA, it is referred to as E _CB of the copper foil used for the first copper foil layer) was measured. Then, the thickness of the polyimide insulating layers of the same conditions mentioned in Examples (t _PI), it thickness of the copper foil (copper foil used in the second copper foil layer and t _CA, the first copper foil layer therewith a to t _CB) of a copper foil was used, with the elastic modulus of the previously obtained from the following equation (1), was determined the equivalent flexural rigidity per 1mm width of the flexible double-sided copper-clad laminate.

[Calculation of equivalent bending stiffness per unit width of single-sided copper-clad laminate]
As a material evaluation that requires high bending resistance and bending resistance, per 1 mm width along the TD direction of the copper foil that forms a circuit in a single-sided copper foil-laminated flexible laminate from which the highly rigid first copper foil is removed. The equivalent bending stiffness (“equivalent bending stiffness / width”) was calculated from the following equation (2) in the same manner as in the previous equation (1).

[Calculation of equivalent bending stiffness per unit width of copper foil]
The equivalent bending rigidity per unit width of the copper foil indicates the rigidity of the material when the copper foil is bent in the MD direction, and the MD of the copper foil that has been subjected to the same heat treatment as that described in each example. The tensile modulus in the direction was measured. And the rigidity of the copper foil per 1 mm of TD direction of copper foil was computed from the following formula | equation (3) using the elasticity modulus calculated | required previously with the thickness of the copper foil of the same conditions quoted in each Example. .

[Handling judgment]
As an evaluation of the handling properties of flexible double-sided copper-clad laminates, the value of the equivalent bending stiffness / width obtained above is less than 0.05 N · mm, and x is judged, and 0.05 N · mm to 0.1 N · mm Evaluation was made in three stages with a value exceeding 0.1 N · mm as ◎.

[Determination of repulsive force]
As the repulsive force evaluation of the single-sided copper foil-laminated flexible laminate from which the high-stiffness copper foil used for the first copper foil layer was removed, the evaluation was made in the following three stages based on the value of equivalent bending rigidity / width.
0.00N ・ mm or more and 0.01N ・ mm or less
○ Judged 0.01N ・ mm or more and 0.05N ・ mm or less,
0.05 N · mm <was determined as x.

[Comprehensive judgment]
A case where both the handling property and the repulsive force were judged as “good” or “good” was regarded as a comprehensive judgment “総 合”, and a case where there was a “x” judgment in either one was designated as a comprehensive judgment “x”.

(Synthesis Example 1)
N, N-dimethylacetamide was placed in the reaction vessel, and 4,4′-diamino-2′-methoxybenzanilide (MABA) was dissolved in the reaction vessel with stirring. Next, pyromellitic anhydride (PMDA) and 4,4′-diaminodiphenyl ether (DAPE) were added. At this time, the total amount of monomers charged was 15 wt%, and the molar ratio of each diamine was charged so that MABA: DAPE was 60:40. Thereafter, stirring was continued for 3 hours to carry out a polymerization reaction to obtain a viscous polyimide precursor resin liquid a.

(Synthesis Example 2)
N, N-dimethylacetamide is placed in a reaction vessel, and 2,2'-bis [4- (4-aminophenoxy) phenyl] propane (BAPP) and 1,4-bis (4-aminophenoxy) benzene are added to this reaction vessel. (TPE-Q) was dissolved in the vessel with stirring. Next, PMDA was added. At this time, the total amount of monomers charged was 15 wt%, and the molar ratio of each diamine was charged so that BAPP: TPE-Q was 80:20. Thereafter, stirring was continued for 3 hours to conduct a polymerization reaction, thereby obtaining a viscous polyimide precursor resin liquid b.

[Example 1]
As a copper foil used for the first copper foil layer, a 12 μm-thick electrolytic copper foil (copper foil 1) having mechanical properties shown in Table 1 was prepared, and the polyimide precursor obtained in Synthesis Example 2 on this copper foil. The resin liquid b was applied so that the thickness after curing was 2 μm, dried at 130 ° C. for 5 minutes, and then the polyimide precursor resin liquid a obtained in Synthesis Example 1 was cured so that the thickness after curing was 8 μm. It was applied and dried at 130 ° C. for 5 minutes. Further, the polyimide precursor resin liquid b obtained in Synthesis Example 2 was applied so that the thickness after curing was 2 μm, and dried by heating at 130 ° C. to remove the solvent. This was passed through a heat treatment step in which the temperature was raised stepwise from 130 ° C. to 380 ° C. over 10 minutes to obtain a single-sided copper clad laminate having a polyimide resin layer (polyimide insulating layer) thickness of 12 μm. A 12 μm-thick rolled copper foil (copper foil 2) having the mechanical properties described in Table 1 as a second copper foil is layered on the polyimide resin layer of this single-sided copper-clad laminate, and the set temperature of the roll surface is 380 ° C., press The second copper foil layer was laminated by continuous thermocompression bonding with a linear pressure between rolls of 150 kN / cm and a passage time of 3 seconds, to obtain a double-sided copper-clad laminate according to Example 1. In addition, the physical-property value of each copper foil shown in Table 1 was calculated | required by heat-processing in the same conditions as an Example beforehand.

  As a result of calculating the equivalent bending rigidity per 1 mm width of the obtained double-sided copper-clad laminate, it was a result showing good handling properties as 0.0073 N · mm. Moreover, as a result of calculating the equivalent bending rigidity of the single-sided copper clad laminate from which the first copper foil layer was removed by etching, the result showed a low repulsion force of 0.010 N · mm. The results are shown in Table 2.

[Example 2]
A single-sided copper clad laminate was obtained in the same manner as in Example 1 except that the first copper foil layer was changed to an 18 μm thick electrolytic copper foil (copper foil 3) having mechanical properties shown in Table 1. Moreover, Example 1 except having changed the 2nd copper foil layer piled up on the polyimide resin layer of this single-sided copper clad laminated body to the 3 micrometers-thick electrolytic copper foil (copper foil 4) which has the mechanical physical property of Table 1. A double-sided copper-clad laminate was obtained by the same method.

  As a result of calculating the equivalent bending rigidity of the obtained double-sided copper-clad laminate, it was 0.082 N · mm, indicating good handling properties. Moreover, as a result of calculating the equivalent bending rigidity of the single-sided copper clad laminate from which the first copper foil layer was removed by etching, the result showed a low repulsion force of 0.004 N · mm. The results are shown in Table 2.

[Example 3]
As a 1st copper foil layer, the 18-micrometer-thick electrolytic copper foil (copper foil 3) which has the mechanical physical property of Table 1 was prepared, and the polyimide precursor resin liquid b obtained by the synthesis example 2 on this copper foil was used. After coating to a thickness of 2 μm after curing and drying at 130 ° C. for 5 minutes, the polyimide precursor resin liquid a obtained in Synthesis Example 1 was applied to a thickness of 21 μm after curing, and 130 It dried at 5 degreeC for 5 minutes, and also apply | coated the polyimide precursor resin liquid b obtained by the synthesis example 2 so that the thickness after hardening might be set to 2 micrometers, and it heat-dried at 130 degreeC, and removed the solvent. This was passed through a heat treatment step in which the temperature was raised stepwise from 130 ° C. to 380 ° C. over 10 minutes to obtain a single-sided copper clad laminate having a polyimide resin layer thickness of 25 μm. As the second copper foil layer to be laminated on the polyimide resin layer of this single-sided copper clad laminate, a 9 μm-thick rolled copper foil (copper foil 5) having the mechanical properties shown in Table 1 was used. A double-sided copper clad laminate was obtained by this method.

  As a result of calculating the equivalent bending rigidity of the obtained double-sided copper-clad laminate, the result was as good as 0.203 N · mm. Moreover, as a result of calculating the equivalent bending rigidity of the single-sided copper clad laminate from which the first copper foil layer was removed by etching, the result showed a low repulsive force of 0.029 N · mm. The results are shown in Table 2.

[Example 4]
A single-sided copper clad laminate was obtained in the same manner as in Example 3 except that a rolled copper foil (copper foil 6) having a thickness of 35 μm having mechanical properties shown in Table 1 was used as the first copper foil layer. The same method as in Example 1 was used by using a 6 μm thick electrolytic copper foil (copper foil 7) having the mechanical properties shown in Table 1 as the second copper foil layer for the polyimide resin layer of this single-sided copper clad laminate. A double-sided copper-clad laminate was obtained.

  As a result of calculating the equivalent bending rigidity of the obtained double-sided copper-clad laminate, it was 0.442 N · mm and a good handling property. Moreover, as a result of calculating the equivalent bending rigidity of the single-sided copper clad laminate from which the first copper foil layer was removed by etching, the result showed a low repulsion force of 0.031 N · mm. The results are shown in Table 2.

[Example 5]
A single-sided copper clad laminate was obtained in the same manner as in Example 1 except that a 9 μm-thick electrolytic copper foil (copper foil 8) having mechanical properties shown in Table 1 was used as the first copper foil layer. The same method as in Example 1 was used by using, as the second copper foil layer, a 9 μm-thick electrolytic copper foil (copper foil 9) having the mechanical properties shown in Table 1 for the polyimide resin layer of this single-sided copper clad laminate. A double-sided copper-clad laminate was obtained.

  As a result of calculating the equivalent bending rigidity of the obtained double-sided copper-clad laminate, it was 0.082 N · mm, indicating good handling properties. Moreover, as a result of calculating the equivalent bending rigidity of the single-sided copper clad laminate from which the first copper foil layer was removed by etching, the result showed a low repulsion force of 0.010 N · mm. The results are shown in Table 2.

[Comparative Example 1]
A single-sided copper clad laminate was obtained in the same manner as in Example 1 except that a rolled copper foil (copper foil 10) having a thickness of 6 μm having mechanical properties shown in Table 1 was used as the first copper foil layer. By using a 6 μm-thick rolled copper foil (copper foil 10) having mechanical properties described in Table 1 as the second copper foil layer in the polyimide resin layer of this single-sided copper-clad laminate, the same method as in Example 1 was used. A double-sided copper-clad laminate was obtained.

  As a result of calculating the equivalent bending rigidity of the single-sided copper-clad laminate in which the first copper foil layer of the obtained double-sided copper-clad laminate was removed by etching, the result showed a low repulsive force of 0.004 N · mm. As a result of calculating the equivalent bending rigidity of the double-sided copper-clad laminate, the result was as low as 0.013 N · mm. The results are shown in Table 2.

[Comparative Example 2]
A single-sided copper clad laminate was obtained in the same manner as in Example 1 except that a 9 μm-thick rolled copper foil (copper foil 11) having mechanical properties shown in Table 1 was used as the first copper foil layer. By using the 2 μm-thick rolled copper foil (copper foil 12) having the mechanical properties described in Table 1 as the second copper foil layer in the polyimide resin layer of this single-sided copper clad laminate, the same method as in Example 1 was used. A double-sided copper-clad laminate was obtained.

  As a result of calculating the equivalent bending rigidity of the single-sided copper-clad laminate obtained by etching away the first copper foil layer of the obtained double-sided copper-clad laminate, the result showed a low repulsion force of 0.002 N · mm. As a result of calculating the equivalent bending rigidity of the double-sided copper-clad laminate, the result was as low as 0.035 N · mm. The results are shown in Table 2.

[Comparative Example 3]
A single-sided copper clad laminate was obtained in the same manner as in Example 3 except that an 18 μm-thick electrolytic copper foil (copper foil 3) having mechanical properties shown in Table 1 was used as the first copper foil layer. In this single-sided copper clad laminate, an 18 μm-thick electrolytic copper foil (copper foil 13) having mechanical properties described in Table 1 was used as the second copper foil layer in the same manner as in Example 1. A double-sided copper-clad laminate was obtained.

  As a result of calculating the equivalent bending rigidity of the obtained double-sided copper-clad laminate, it was a result showing good handling properties of 0.787 N · mm, but the single-sided copper-clad laminate in which the first copper foil layer was removed by etching As a result of calculating the equivalent bending stiffness, the result showed a high repulsive force of 0.104 N · mm. The results are shown in Table 2.

1: first copper foil layer 2: polyimide insulating layer 3: second copper foil layer 4: bent portion 5: insulating layer 6: adhesive layer 7: shield layer

Claims (5)

In a flexible double-sided copper-clad laminate with copper foil layers on both sides of the polyimide insulation layer,
A first copper foil layer having a thickness of 9 μm or more and 35 μm or less and an equivalent bending rigidity per unit width of 0.003 N · mm or more and 0.2 N · mm or less;
A second copper foil layer having a thickness of 3 μm or more and 12 μm or less and an equivalent bending stiffness per unit width in the range of 0.00001 N · mm or more and less than 0.003 N · mm, The equivalent bending stiffness of the layer is higher than the equivalent bending stiffness of the second copper foil layer, and
A flexible double-sided copper-clad laminate, wherein the polyimide insulating layer has a thickness of 7 µm to 50 µm and a tensile elastic modulus at 25 ° C of 2 GPa to 9 GPa.   The flexible circuit board which forms a wiring circuit using the 2nd copper foil layer of the flexible double-sided copper clad laminated board of Claim 1, and uses at least one part of a wiring circuit for a bending part.   The flexible circuit board according to claim 2, wherein at least the first copper foil layer at a position corresponding to the bent portion is removed.   4. The flexible circuit board according to claim 2, wherein a bent portion having a repetitive operation selected from sliding bending, bending bending, hinge bending, or sliding bending is formed. 5.   A multilayer circuit board obtained by multilayering the flexible circuit board according to claim 2.

Images