JP2011176013A - Printed circuit board and metal foil plating lamination plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed circuit board with superior folding endurance. <P>SOLUTION: The printed circuit board 100 includes: a core substrate 30 where a fiber base material is embedded in a first resin; a pair of second resin layers 10 arranged to hold the core substrate 30 between them; and a conductor 7 arranged on at least one of a surface 100a opposed to the core substrate 30 in the resin layer 10 or the interface of the resin layer and the core substrate. In the printed circuit board 100, the thickness of the fiber base material is ≤40 μm, and a tension elastic modulus in the cured object of the first resin at a temperature of 25°C is larger than that in the second resin layers 10 at a temperature of 25°C and also ≤3.0 GPa. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a printed wiring board and a metal foil-clad laminate.

  With the spread of information terminal electronic devices, electronic devices are becoming smaller and thinner. Under such circumstances, there is an increasing demand for higher density and thinner printed wiring boards mounted in electronic devices. In addition, as represented by mobile phones, the high-functionality of electronic devices has led to high reliability in the connection of various high-performance modules such as cameras and printed wiring boards mounted at high density. It has been demanded.

  On the other hand, the mounting number of electronic components has also increased rapidly, and in order to mount many electronic components in a limited space, not only conventional rigid printed wiring boards but also soft printed wiring boards that can be bent freely are used. It has been. As a material for such a foldable printed wiring board, a thermoplastic resin film centered on polyimide is employed.

  However, since a thermoplastic resin film such as polyimide has low adhesion to a metal foil for forming a conductor, it is necessary to laminate a resin layer having a physical property value different from that of polyimide on the thermoplastic resin film. For this reason, there exists a problem that manufacturing cost will rise. There is also a problem that shape stability and dimensional stability are not sufficient.

  In order to solve such problems, various methods have been proposed. For example, in order to improve the dimensional stability of a resin film, resin short fibers are blended into the resin (see, for example, Patent Document 1), and resin layers having different thermal expansion coefficients are formed for the purpose of reducing warpage and twisting. (For example, refer to Patent Documents 2 and 3), forming a resin layer having a low coefficient of thermal expansion near the metal foil for the purpose of reducing the coefficient of thermal expansion (for example, refer to Patent Document 4), and the like. In particular, a printed wiring board material that can be arbitrarily bent and has excellent dimensional stability has been proposed (see Patent Document 5).

JP 49-25499 A JP-A-1-245586 JP-A-8-250860 JP-A-5-347461 JP 2006-66894 A

  However, in the case of a printed wiring board in which short glass fibers are blended as in Patent Document 1, although the amount of dimensional change can be reduced compared to a resin-only printed wiring board, the variation in dimensional change locally increases. When providing fine wiring, sufficient connection stability cannot be obtained. Moreover, since the flexible printed circuit boards like patent documents 2-4 are all comprised only with the resin layer and cannot fully reduce hygroscopicity and a coefficient of thermal expansion, they contain glass cloth and glass nonwoven fabric. Compared to a printed wiring board, the dimensional stability after etching a metal foil or after circuit processing is not sufficient. Patent Document 5 discloses a printed circuit that has excellent dimensional stability and can be arbitrarily bent by setting the tensile elastic modulus at 25 ° C. of a substrate made of an insulating resin layer containing a fiber base material to 0.5 GPa or more and 10 GPa or less. Achieve the board.

  However, the demand for higher mounting density has become stricter, and a higher level of bendability than the level achieved in Patent Document 5 has been required.

  This invention is made | formed in view of the said situation, and aims at providing the metal foil tension laminated board which can form the printed wiring board provided with the more excellent folding resistance, and the said printed wiring board.

In order to achieve the above object, in the first invention of the present invention, a core substrate in which a fiber base material is embedded in a first resin, and a pair of second resin layers provided so as to sandwich the core substrate, A printed wiring board comprising a conductor provided on a surface opposite to the core substrate side of the resin layer or on at least one of an interface between the resin layer and the core substrate,
The fiber base has a thickness of 40 μm or less,
Provided is a printed wiring board in which the cured elastic product of the first resin has a tensile elastic modulus at 25 ° C. which is larger than the tensile elastic modulus at 25 ° C. of the second resin layer and is 3.0 GPa or less.

  In such a printed wiring board, the tensile elastic modulus of the cured product of the first resin contained in the core substrate is 3.0 GPa or less at 25 ° C., and the tensile elastic modulus of the resin layer provided so as to sandwich the core substrate. Is bigger than. In this way, by placing a resin cured product having a large tensile elastic modulus in the vicinity of the fiber base material and arranging a resin layer having a small tensile elastic modulus on the outer side (site close to the surface) where the largest tensile stress is generated during bending, Generation | occurrence | production of a crack is suppressed and a softness | flexibility and bending resistance can be improved. Moreover, since the printed wiring board of the present invention has a fiber base material, it has excellent dimensional stability, and since a fiber base material having a thickness of 40 μm or less is used, it is sufficiently excellent in flexibility. ing. Since such a printed wiring board can be bent and mounted in a housing, it can be stored at a high density. The core substrate and the second resin layer in the metal foil-clad laminate and the printed wiring board according to the present invention are in a cured state (including a partially cured state).

  In the printed wiring board of the present invention, it is preferable that the core substrate has an internal resin layer (first resin layer) made of the first resin on the side in contact with the resin layer. Thereby, it can be set as the printed wiring board which is further excellent in a softness | flexibility.

  In the printed wiring board of the present invention, it is preferable that at least one of the core substrate and the second resin layer contains a resin having a glycidyl group. Thereby, heat resistance can be improved.

  In the printed wiring board of the present invention, it is preferable that at least one of the core substrate and the second resin layer contains a resin having an amide group. Thereby, heat resistance can be improved.

  In the printed wiring board of the present invention, it is preferable that at least one of the core substrate and the second resin layer contains one or both of an acrylic resin and a polyamideimide resin. Thereby, flexibility and heat resistance can be improved.

  In the printed wiring board of the present invention, it is preferable that at least one of the core substrate and the second resin layer contains a polyamideimide resin containing a siloxane bond. Thereby, flexibility and heat resistance can be further improved.

  The printed wiring board of the present invention preferably has a conductor thickness of 0.01 to 30 μm. Thereby, while having the outstanding connection reliability, peeling of a conductor is suppressed at the time of bending, and folding resistance can be improved further.

  The second invention of the present invention is a core substrate in which a fiber base material is embedded in a first resin, a pair of second resin layers provided so as to sandwich the core substrate, and the core of the resin layer A metal foil-clad laminate comprising a metal foil provided on a surface opposite to the substrate side or on at least one of the interface between the resin layer and the core substrate, and the thickness of the fiber substrate is 40 μm or less And providing a metal foil-clad laminate having a tensile elastic modulus at 25 ° C. of the cured product of the first resin that is larger than the tensile elastic modulus at 25 ° C. of the second resin layer and 3.0 GPa or less. .

  In such a metal foil-clad laminate, the tensile elastic modulus of the cured product of the first resin contained in the core substrate is 3.0 GPa or less at 25 ° C., and the second resin is provided so as to sandwich the core substrate. It is greater than the tensile modulus of the layer. As described above, by arranging a resin having a large tensile elastic modulus in the vicinity of the fiber base material and providing a resin layer having a relatively small tensile elastic modulus on the outside where the largest tensile stress is generated during bending, the generation of cracks is suppressed. , Flexibility and folding resistance can be improved. In addition, the metal foil-clad laminate of the present invention has a fiber base material and is excellent in dimensional stability, and since a fiber base material having a thickness of 40 μm or less is used, it is sufficiently flexible. Are better. If such a metal foil-clad laminate is used, a printed wiring board that can be stored in the housing at a high density can be easily produced.

  In the metal foil-clad laminate of the present invention, the core substrate preferably has an internal resin layer (first resin layer) made of the first resin on the side in contact with the second resin layer. This makes it possible to easily produce a printed wiring board with further flexibility.

  In the metal foil-clad laminate of the present invention, it is preferable that at least one of the core substrate and the second resin layer contains a resin having a glycidyl group. Thereby, heat resistance can be improved.

  In the metal foil-clad laminate of the present invention, it is preferable that at least one of the core substrate and the second resin layer contains a resin having an amide group. Thereby, heat resistance can be improved.

  In the metal foil-clad laminate of the present invention, it is preferable that at least one of the core substrate and the second resin layer contains one or both of an acrylic resin and a polyamideimide resin. Thereby, flexibility and heat resistance can be improved.

  In the metal foil-clad laminate of the present invention, it is preferable that at least one of the core substrate and the second resin layer contains a polyamideimide resin containing a siloxane bond. Thereby, flexibility and heat resistance can be further improved.

  Moreover, it is preferable that the thickness of a metal layer is 0.01-30 micrometers in the metal foil tension laminated board of this invention. When a printed wiring board in which a wiring pattern is formed from such a metal layer is bent, the wiring pattern is difficult to peel off, so that the folding resistance can be further improved. Moreover, it can be set as the printed wiring board which has sufficient connection reliability.

  ADVANTAGE OF THE INVENTION According to this invention, the metal foil tension laminated board which can form the printed wiring board provided with the more excellent folding resistance and the said printed wiring board easily can be provided.

It is a fragmentary sectional view of the printed wiring board concerning one suitable embodiment of the present invention. It is a fragmentary sectional view of the printed wiring board concerning another suitable embodiment of the present invention. 1 is a partial cross-sectional view of a metal foil-clad laminate according to a preferred embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and duplicate descriptions are omitted.

FIG. 1 is a partial cross-sectional view of a printed wiring board according to a preferred embodiment of the present invention. A printed wiring board 100 shown in FIG. 1 is a multilayer printed wiring board having a multilayer structure, and includes a core substrate 30 containing a fiber base material and a first cured resin, and the core substrate 30 sandwiching the core substrate 30 therebetween. A pair of resin layers 10 each made of a second cured resin and a conductor 7 provided on the surface of the resin layer 10 opposite to the core substrate 30 side.

  The core substrate 30 is a pair of internal resins provided on the fiber substrate layer 3 containing the fiber substrate and the cured resin, and on the opposing surfaces of the fiber substrate layer 3 with the fiber substrate layer 3 interposed therebetween. Layer 5. It is preferable that the resin cured products contained in the fiber base layer 3 and the internal resin layer 5 are the same. That is, the internal resin layer 5 is preferably made of a first cured resin.

  The fiber base material contained in the resin base material layer 3 is not particularly limited as long as it is used when producing a metal foil-clad laminate or a multilayer printed wiring board. For example, a woven fabric or a non-woven fabric is used. Can do. Examples of the fiber base material include glass, alumina, boron, silica alumina glass, silica glass, tyrano, silicon carbide, silicon nitride, zirconia, and other inorganic fibers, and aramid, polyether ketone, polyether imide, polyether sulfone. And organic fibers such as carbon and cellulose, and mixed papers thereof. Among these, a glass nonwoven fabric and a glass fiber woven fabric are preferable, and a glass fiber woven fabric is more preferable from the viewpoint of achieving both excellent dimensional stability and folding resistance at a higher level.

  In addition, although the fiber base material has an unevenness | corrugation on the surface normally, thickness B of the fiber base material (fiber base material layer 3) in this embodiment is a metal foil tension laminated board, for example with an electron microscope or a metal microscope. It can be measured by observing the cross section. If it is before producing a metal foil-clad laminate, the thickness of the composite resin layer can also be confirmed with a micrometer. The maximum thickness in a printed wiring board or metal foil-clad laminate. In this embodiment, the thickness B of the resin base material is 40 μm or less. The thickness B is preferably 1 to 30 μm, and more preferably 10 to 20 μm, from the viewpoint of achieving both the excellent folding resistance and dimensional stability of the printed wiring board 100 at a higher level. The thickness of each layer of the metal foil-clad laminate or the printed wiring board 100 can be measured by observing the cross section of the printed wiring board 100 with an optical microscope.

  The resin cured product (first resin cured product) contained in the fiber base layer 3 and the internal resin layer (first resin layer) 5 is preferably a thermosetting resin cured product, such as an epoxy resin or a polyimide. Examples thereof include resins, polyamideimide resins, triazine resins, phenol resins, melamine resins, polyester resins, cyanate ester resins, and modified systems of these resins. These resins may be used alone or in combination of two or more.

  Examples of the epoxy resin contained in the fiber base layer 3 and the inner resin layer (first resin layer) 5 include polyhydric phenols such as bisphenol A, novolac type phenol resins, and orthocresol novolac type phenol resins, or 1,4-butane. Polyglycidyl ester, amine, amide or heterocyclic nitrogen obtained by reacting polyglycidyl ether, phthalic acid, hexahydrophthalic acid or other polybasic acid such as diol with epichlorohydrin and epichlorohydrin Examples thereof include N-glycidyl derivatives of base-containing compounds and alicyclic epoxy resins.

  As for the above-mentioned resin cured material, it is more preferable to contain resin which has a glycidyl group. Moreover, the resin cured product contained in the fiber base material layer 3 and the internal resin layer (first resin layer) 5 more preferably contains a polyamideimide resin or an acrylic resin from the viewpoint of improving flexibility and heat resistance. preferable. More preferably, the polyamideimide resin has a siloxane bond. Thereby, flexibility and heat resistance can be further improved.

  The tensile elastic modulus (hereinafter referred to as “tensile elastic modulus E1”) of the cured resin and the internal resin layer (first resin layer) 5 included in the fiber base layer 3 is 3.0 GPa or less, and It is preferably 01 to 3.0 GPa, more preferably 0.01 to 2.0 GPa. When the tensile elastic modulus E1 exceeds 3.0 GPa, it cannot be a printed wiring board having excellent folding resistance. On the other hand, when the tensile modulus E1 is less than 0.01 GPa, the handleability and workability of the printed wiring board tend to be impaired.

  In addition, the tensile elastic modulus in this specification is based on the mechanical property standard (4.2 of JPCA-BU01-1998) in the build-up wiring board standard of the Japan Printed Circuit Industry Association. Can be measured.

  On the printed wiring board 100, an internal resin layer (first resin layer) 5 made of a cured resin having a tensile elastic modulus larger than that of the resin layer 10 is formed between the fiber base layer 3 and the resin layer 10. Has been. That is, the tensile elastic modulus of the internal resin layer (first resin layer) 5 is higher than the tensile elastic modulus of the resin layer 10. By having such a structure, the tensile stress generated at the time of bending is dispersed in the resin layer 10, the internal resin layer (first resin layer) 5 and the fiber base layer 3, so that the folding resistance can be further improved. it can.

  The thickness of the internal resin layer (first resin layer) 5 is preferably 0.1 to 20 μm, and more preferably 1 to 10 μm. A printed wiring board provided with an internal resin layer (first resin layer) 5 having a thickness of 1 to 10 μm has more excellent folding resistance. If the thickness of the internal resin layer (first resin layer) 5 exceeds 10 μm, the printed circuit board tends to be difficult to bend. In addition, from the viewpoint of further improving the folding resistance and flexibility of the printed wiring board 100, the thickness of the pair of internal resin layers (first resin layers) 5 provided with the fiber base layer 3 interposed therebetween is the same. It is preferable. The internal resin layer (first resin layer) 5 is formed, for example, by allowing the curable resin composition to protrude from the fiber base material when the fiber base material such as glass cloth is impregnated with the curable resin composition. can do.

  The resin layer 10 is preferably made of a cured resin. Examples of the cured resin contained in the resin layer 10 include those similar to the cured resin contained in the fiber base layer 3 and the internal resin layer (first resin layer) 5 described above.

  The tensile elastic modulus (hereinafter referred to as “tensile elastic modulus E2”) of the resin layer 10 is smaller than the tensile elastic modulus E1, preferably 0.1 to 2.5 GPa, and preferably 0.2 to 1.5 GPa. It is more preferable. When the tensile modulus E2 exceeds 2.5 GPa, sufficiently excellent flexibility tends to be impaired. On the other hand, when the tensile elastic modulus E2 is less than 0.1 GPa, the shape stability tends to be impaired. The tensile elastic modulus E1 and the tensile elastic modulus E2 can be adjusted by changing the components of the resin cured product and the weight average molecular weight of the resin.

  In addition, it is preferable that the tensile elasticity modulus E1 and the tensile elasticity modulus E2 satisfy | fill following formula (1). The printed wiring board having the core substrate 30 and the resin layer 10 satisfying the relationship of the following formula (1) can achieve both folding resistance and dimensional stability at a higher level.

  0.1 ≦ E1-E2 ≦ 1.5 (1)

The thickness _{d 10} of the resin layer 10 is preferably 5 to 30 [mu] m, and more preferably 10 to 20 [mu] m. Printed circuit board to which the thickness _{d 10} is provided with the resin layer 10 is 5~30μm has more excellent folding endurance. When the thickness d ₁₀ of the resin layer 10 is more than 30 [mu] m, there is a tendency that the printed wiring board is hardly bent.
The thickness of the resin layer is measured, for example, by observing a cross section of the printed wiring board with an electron microscope or a metal microscope.

From the viewpoint of improving the folding endurance and flexibility of the printed circuit board 100 further, the thickness d ₁₀ of the pair of the resin layer 10 provided to sandwich the core substrate 30 are preferably the same. The total thickness (C + 2d ₁₀ ) of the core substrate 30 and the pair of resin layers 10 is preferably 120 μm or less. When the thickness exceeds 120 μm, sufficiently excellent flexibility tends to be impaired. In addition, the thickness of each material which comprises the printed wiring board 100 is not specifically limited.

  The conductor 7 is a wiring pattern, for example, obtained by etching a copper foil. The thickness A of the conductor 7 is preferably 0.01 to 30 μm, and more preferably 0.01 to 20 μm. If the thickness A of the conductor 7 exceeds 30 μm, the conductor 7 tends to be peeled off when bent. On the other hand, when the thickness A of the conductor 7 is less than 0.01 μm, the electrical connection stability of the obtained printed wiring board tends to be impaired.

  FIG. 2 is a partial cross-sectional view of a printed wiring board according to another preferred embodiment of the present invention. The printed wiring board 200 includes a pair of second resin layers 10 provided so as to sandwich the core substrate 30, and a conductor 9 provided on a surface of the second resin layer 10 opposite to the core substrate 30 side. . A conductor 7 is provided between the second resin layer 10 and the inner resin layer (first resin layer) 5 of the core substrate.

  A printed wiring board 200 which is such a multilayer printed wiring board is formed by pulling a core substrate 30 including a fiber base material layer 3 having a predetermined thickness and a cured resin having a tensile elastic modulus E1 and sandwiching the core substrate 30 therebetween. It has a laminated structure in which a resin layer 10 made of a cured resin having a tensile modulus of elasticity E2 smaller than the modulus of elasticity E1 is laminated. For this reason, it has both sufficiently excellent folding resistance and sufficiently excellent dimensional stability. Further, since the conductor 7 and the conductor 9 are arranged at different positions in the thickness direction, it is possible to provide wiring with higher density.

  FIG. 3 is a partial cross-sectional view of a metal foil-clad laminate according to a preferred embodiment of the present invention. The metal foil-clad laminate 300 of this embodiment includes a core substrate 30 including a fiber base layer 3 and a pair of internal resin layers (first resin layers) 5 provided so as to sandwich the fiber base layer, and the core A pair of second resin layers 10 is provided so as to further sandwich the substrate 30, and a pair of metal layers 12 provided on the surfaces 100 a and 100 b on the opposite side of the second resin layer 10 from the core substrate 30 side are provided. Further prepare.

  A wiring pattern can be formed by applying a known method such as photolithography to the metal layer 12 constituting the outermost layer of the metal foil-clad laminate 300. This makes it possible to produce a multilayer printed wiring board that is sufficiently excellent in folding resistance and dimensional stability. As the metal layer 12, metal foils, such as copper foil and aluminum foil, can be used, and copper foil is preferable among these.

  The thickness D of the metal layer 12 is preferably 0.01 to 30 μm, and more preferably 0.01 to 20 μm. When the thickness D of the metal layer 12 exceeds 30 μm, the wiring pattern formed from the metal layer 12 tends to peel off when bent. On the other hand, when the thickness D of the metal layer 12 is less than 0.01 μm, the electrical connection stability of the obtained printed wiring board tends to be impaired.

  Next, a method for manufacturing the printed wiring boards 100 and 200 and the metal foil-clad laminate 300 according to a preferred embodiment of the present invention will be described below with reference to FIGS. First, a fiber base material and a curable resin composition are prepared. Commercially available glass fibers can be used as the fiber base material.

  As the curable resin composition, a resin composition varnish obtained by mixing a resin component with a solvent can be suitably used. As the resin component, epoxy resin, polyimide resin, polyamideimide resin, triazine resin, phenol resin, melamine resin, polyester resin, cyanate ester resin, modified resins of these resins, and the like can be used. . When a polyamideimide resin is used, it is better from the viewpoint of bendability to use a polyamideimide resin containing a siloxane bond. These resins may be used alone or in combination of two or more. However, when combining 2 or more types, adhesion of resin layers can be made favorable by using a common resin system.

  As the solvent, alcohols, ethers, ketones, amides, aromatic hydrocarbons, esters, nitriles, and the like can be used. These may be used individually by 1 type, and may be used as a mixed solvent which combined 2 or more types.

  As the resin component, an acrylic resin may be contained. As the acrylic resin, it is possible to use an acrylic acid monomer, a methacrylic acid monomer, acrylonitrile, an acrylic monomer having a glycidyl group alone, or a copolymer obtained by copolymerizing a plurality thereof. The molecular weight of the acrylic resin is not particularly limited, but those having a weight average molecular weight in terms of standard polystyrene of 300,000 to 1,000,000, preferably 400,000 to 800,000 can be used.

  The curable resin composition may contain a curing agent, an accelerator, a flame retardant, a flow regulator, a coupling agent, and the like. A well-known thing can be used for a hardening | curing agent. For example, when using an epoxy resin, dicyandiamide, diaminodiphenylmethane, diaminodiphenylsulfone, phthalic anhydride, pyromellitic anhydride, polyfunctional phenols such as phenol novolac and cresol novolac, and the like can be used.

  The accelerator is used for the purpose of accelerating the reaction between the resin and the curing agent, and the type and blending amount are not particularly limited. As the accelerator, for example, an imidazole compound, an organic phosphorus compound, a tertiary amine, a quaternary ammonium salt, or the like can be used. A hardening | curing agent and a promoter may be used individually by 1 type, respectively, or may be used in combination of 2 or more type.

  Next, a curable resin composition (resin composition varnish) is applied to the fiber substrate to prepare a resin-impregnated substrate. There is no restriction | limiting in particular in application | coating conditions, For example, it can apply | coat using a commercially available coating apparatus. In addition, the thickness of the core substrate 30 (the thickness of the internal resin layer 5) can be adjusted by performing multiple coatings as necessary.

  It is preferable to perform drying by heating at a temperature above which the solvent can be volatilized after application and before molding. In this case, it is preferable that 80% by mass or more is volatilized with respect to the total amount of the solvent used in the resin composition varnish by heating to a temperature at which the solvent used for preparing the resin composition varnish can be volatilized. From this point of view, the temperature during drying is preferably 80 to 180 ° C. Moreover, it is preferable that the resin composition varnish impregnation amount with respect to a fiber base material is 30-80 mass% of resin solid content with respect to the resin solid content and the total amount of a fiber base material.

  A prepreg can be obtained by heating and pressurizing the resin-impregnated substrate after heat drying. The conditions for heating and pressurizing the resin-impregnated substrate are preferably a molding temperature of 80 to 250 ° C., a molding pressure of 0.5 to 8.0 MPa, a molding temperature of 130 to 230 ° C., and a molding pressure of 1.5 to More preferably, it is 5.0 MPa. By this heating and pressurization, the curable resin composition impregnated in the fiber substrate can be brought into a semi-cured (B stage) state.

  The thickness of the prepreg is preferably about 0.1 to 10 μm thicker than the thickness of the fiber base material. That is, it is preferable to form the internal resin layer 5 having a total thickness of 0.1 to 10 μm on both main surfaces of the fiber base layer.

  The tensile modulus of the cured prepreg is preferably 4.7 GPa or less. Thereby, a printed wiring board having excellent folding resistance can be obtained.

  Apart from this prepreg, a resin-attached metal foil in which a resin composition layer is formed on the surface of the metal foil is produced. For example, a commercially available copper foil can be used as the metal foil. The kind in particular of copper foil is not restrict | limited, For example, what has a thickness of 0.01-30 micrometers can be used.

  A resin-coated metal foil can be formed by applying a resin composition varnish containing a curable resin composition and a solvent on the copper foil and drying at a temperature at which the solvent can be volatilized. That is, the resin layer in the metal foil with resin is in a B stage state. In addition, the thing similar to what is apply | coated to the above-mentioned fiber base material can be used for the resin composition varnish used in this case. However, since the resin composition varnish used here is cured to form the resin layer 10 to be described later, the tensile elastic modulus after curing needs to be smaller than the cured resin contained in the core substrate 30. .

  The thickness of the resin layer of the metal foil with resin is preferably 5 to 100 μm, and more preferably 10 to 80 μm.

  Next, with the prepreg sandwiched between them, the resin composition layer side of the metal foil with resin is directed to the prepreg, the metal foil with resin is laminated on both surfaces of the prepreg, respectively, and heated and pressed, 3 can be obtained. The conditions for heating and pressurization at this time are not particularly limited, but are preferably 150 to 280 ° C. and 0.5 to 20 MPa, more preferably 170 to 250 ° C. and 1 to 8 MPa.

  Next, a printed wiring board 100 in which a wiring pattern (conductor 7) is formed on 100a and 100b as shown in FIG. The wiring pattern can be formed by a normal method such as a photolithography method.

  Separately from the printed wiring board 100, metal foils are stacked on both sides of the prepreg, heated and pressed, and then a wiring pattern 7 is formed by a normal method such as a photolithography method. By heating and pressurizing the resin composition layer side toward the surface on which the wiring pattern 7 is formed, and forming the wiring pattern 9 on the outermost metal foil by a normal method such as photolithography. A printed wiring board 200 as shown in FIG. 2 can be obtained.

  The pressing conditions at this time are preferably a temperature of 150 to 280 ° C. and a pressure of 0.5 to 20 MPa, and more preferably a temperature of 170 to 250 ° C. and a pressure of 1 to 8 MPa.

  The conductors 7 and 9 can be electrically connected, for example, by providing a through hole in the resin layer 10 and forming a conductor therewith by plating or the like.

  The printed wiring boards 100 and 200 described above are sufficiently excellent in folding resistance and dimensional stability, and are mounted with a predetermined circuit component (not shown) and folded and stored in a predetermined space such as a housing. Can do. This enables high-density mounting.

  In addition, a pair of copper foils with resin are laminated on both sides so that the printed wiring board 200 is sandwiched with the resin composition layer side facing the printed wiring board 200, for example, a temperature of 150 to 280 ° C., a pressure of 0. By pressing at 5 to 20 MPa, a resin layer and a metal foil are further laminated to form a metal foil-clad laminate, and then a conductor can be formed by a known method such as photolithography.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. Further, a plurality of resin layers having a tensile elastic modulus between the tensile elastic modulus of the internal resin layer 5 and the tensile elastic modulus of the resin layer 10 may be provided between the internal resin layer 5 and the resin layer 10. In that case, it is preferable that the resin layers are arranged so that the tensile elastic modulus gradually decreases from the inner resin layer 5 toward the outside.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

  First, thermosetting resin varnishes 1 to 7 were prepared according to formulation examples 1 to 7 described below.

(Formulation example 1)
44 parts by mass of biphenyl novolac type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., trade name: NC-3000H) and 11 parts by mass of aminotriazine novolac epoxy resin (manufactured by Dainippon Ink & Chemicals, Inc., trade name: LA-3018) And 0.2 parts by mass of 2-phenylimidazole (manufactured by JSR Corporation, trade name: G-809L) and 30 parts by weight of acrylic rubber (manufactured by Nagase ChemteX Corporation, trade name: HM6-IM50) After dissolving in isobutyl ketone and stirring for about 3 hours until the resin component became uniform, it was allowed to stand at room temperature for 24 hours for defoaming to prepare a thermosetting resin varnish 1 having a resin solid content of 30% by mass. .

(Formulation example 2)
37 parts by mass of biphenyl novolac type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., trade name: NC-3000H) and 9 parts by mass of aminotriazine novolac epoxy resin (manufactured by Dainippon Ink & Chemicals, Inc., trade name: LA-3018) And 0.2 parts by mass of 2-phenylimidazole (manufactured by JSR Corporation, trade name: G-809L) and 40 parts by weight of acrylic rubber (manufactured by Nagase ChemteX Corporation, trade name: HM6-IM50) After dissolving in isobutyl ketone and stirring for about 3 hours until the resin component became uniform, it was allowed to stand at room temperature for 24 hours for defoaming to prepare a thermosetting resin varnish 2 having a resin solid content of 30% by mass. .

(Formulation example 3)
33 parts by mass of biphenyl novolac type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., trade name: NC-3000H) and 8 parts by mass of aminotriazine novolac epoxy resin (manufactured by Dainippon Ink & Chemicals, Inc., trade name: LA-3018) And 0.2 parts by mass of 2-phenylimidazole (manufactured by JSR Corporation, trade name: G-809L) and 45 parts by weight of acrylic rubber (manufactured by Nagase ChemteX Corporation, trade name: HM6-IM50) After dissolving in isobutyl ketone and stirring for about 3 hours until the resin component became uniform, it was allowed to stand at room temperature for 24 hours for defoaming to prepare a thermosetting resin varnish 3 having a resin solid content of 30% by mass. .

(Formulation example 4)
Polyamideimide resin (manufactured by Hitachi Chemical Coated Sand Co., Ltd., trade name: CSD40) 24.87 kg (resin solid content: 28.1% by mass) and epoxy resin (trade name: EPPN502H, manufactured by Nippon Kayaku Co., Ltd.) 2 0.0 kg of methyl ethyl ketone solution (resin solid content: 50% by mass), 3.0 kg of HP4032D (trade name, manufactured by Nippon Kayaku Co., Ltd.) and 1.0 kg of methyl ethyl ketone of NC 3000H (trade name, manufactured by Nippon Kayaku Co., Ltd.) A solution (solid content of resin: 50% by mass) and 8.0 g of 1-cyanoethyl-2-ethyl-1-methylimidazole were combined, and 1.0 kg of OP930 (manufactured by Clariant, trade name) and HP360 (Showa) Denko Co., Ltd., trade name) 1.5 kg was added, and after stirring for about 3 hours until the resin component became uniform, it was 24:00 for defoaming The resin solid content of 30% by weight of the resin composition varnish 4 was prepared to stand at room temperature.

(Formulation example 5)
Polyamideimide resin (manufactured by Hitachi Chemical Co., Ltd., trade name: KS9003) 23.18 kg (resin solid content: 30.2 mass%) and epoxy resin (manufactured by Nippon Kayaku Co., Ltd., trade name: EPPN502H) 2.0 kg Of methyl ethyl ketone solution (resin solid content: 50% by mass), 3.0 kg of HP4032D (trade name, manufactured by Nippon Kayaku Co., Ltd.), and 1.0 kg of methyl ethyl ketone solution (trade name: manufactured by Nippon Kayaku Co., Ltd., trade name) Resin solid content: 50% by mass) and 1-cyanoethyl-2-ethyl-1-methylimidazole 8.0 g, OP930 (manufactured by Clariant, trade name) 1.0 kg, HP360 (Showa Denko Co., Ltd.) (Product name, product name) 1.5 kg was added and stirred for about 3 hours until the resin component became uniform, then left at room temperature for 24 hours for defoaming The resin composition varnish 5 of the resin solid content of 40 mass% was prepared Te.

(Formulation example 6)
Polyamideimide resin (manufactured by Hitachi Chemical Co., Ltd., trade name: KS9900B) 22.44 kg (resin solid content: 31.2% by mass) and epoxy resin (manufactured by Nippon Kayaku Co., Ltd., trade name: EPPN502H) 2.0 kg Of methyl ethyl ketone solution (resin solid content: 50% by mass), 3.0 kg of HP4032D (trade name, manufactured by Nippon Kayaku Co., Ltd.), and 1.0 kg of methyl ethyl ketone solution (trade name: manufactured by Nippon Kayaku Co., Ltd., trade name) Resin solid content 50 mass%) and 1-cyanoethyl-2-ethyl-1-methylimidazole 8.0 g, OP930 (manufactured by Clariant, trade name) 1.0 kg, HP360 (Showa Denko KK) (Product name) 1.5 kg was added and stirred for about 3 hours until the resin component became uniform, then left at room temperature for 24 hours for defoaming Resin solid content of 40 wt% of the resin composition varnish 6 was prepared Te.

(Formulation example 7)
Brominated bisphenol A type epoxy resin (manufactured by JER Co., Ltd., trade name: Epicoat 5046, epoxy equivalent: 475), 100 parts by mass, dicyandiamide 4 parts by mass, and imidazole (manufactured by Shikoku Kasei Co., Ltd., trade name: 2E4MZ) 0.5 parts by mass was dissolved in propylene glycol monomethyl ether and stirred for about 3 hours until the resin component became uniform, and then allowed to stand at room temperature for 24 hours for defoaming to have a resin solid content of 70% by mass. A thermosetting resin varnish 7 was prepared.

[Measurement of tensile modulus]
The tensile elastic modulus of the cured product of the thermosetting resin varnishes 1 to 7 is based on the mechanical property standard (JPCA-BU01-1998 4.2) in the build-up wiring board standard of the Japan Printed Circuit Industry Association. The measurement was performed according to the following procedure. First, the thermosetting resin varnishes 1 to 7 are applied on a copper foil having a thickness of 18 μm by a horizontal coating machine so that the thickness of the resin composition layer after drying becomes 50 μm, and the temperature is 100 to 140 ° C. Resin was dried by staying in a drying furnace for 5 minutes to produce a resin-coated copper foil. On the resin composition layer of each copper foil with resin, a copper foil having a roughened surface (manufactured by Nippon Electrolytic Co., Ltd., HLA18, thickness 18 μm) is overlaid so that the roughened surface is in contact with the resin composition layer. Then, pressing was performed at 170 ° C. for 90 minutes under 4.0 MPa pressing conditions to produce a double-sided copper-clad laminate. The copper foil on the outer side of each double-sided copper clad laminate was completely removed by double-side etching. Then, it cut | disconnected to the size of 80 mm x 10 mm, and obtained the test piece for a tensile elasticity modulus measurement.

  Using an autograph (manufactured by Shimadzu Corporation, model number: AG-100C), the tensile elastic modulus of each test piece prepared as described above was measured. The measurement was performed at 25 ° C., a measurement length of 60 mm, and a tensile speed of 5 mm / min. A stress-strain curve was created based on the measurement results, and the tensile elastic modulus was determined from the initial inclination of the measurement. The measurement results were as shown in Tables 1 to 3.

Example 1
<Preparation of prepreg>
The thermosetting resin varnish 1 is applied to a glass cloth WEX-1027 (manufactured by Asahi Schavel Co., Ltd., trade name, thickness 19 μm) with a vertical coating machine so that the thickness of the prepreg is 20 μm, and 120 to 150 ° C. And baked for 20 minutes to prepare a prepreg.

<Preparation of copper foil with resin>
A thermosetting resin varnish 2 is applied with a horizontal coating machine on a copper foil having a thickness of 18 μm (trade name: HLA18, manufactured by Nippon Electrolytic Co., Ltd.), and the residence time is 5 minutes in a drying furnace at 100 to 140 ° C. Then, the resin-coated copper foil having a thickness of 15 μm and 50 μm was prepared.

<Production of evaluation substrate>
A copper foil with a resin having a resin thickness of 15 μm was bonded to both sides of the prepreg so that the prepreg was sandwiched, and the resin composition layer side was in contact with the prepreg, and pressed at 170 ° C. for 90 minutes at a pressure of 4.0 MPa. Thus, a double-sided copper foil-clad laminate was produced.

  Next, the copper foil on one side (main surface) of the double-sided copper foil-clad laminate was etched to produce a conductive pattern circuit having a line width of 75 μm and a space between lines of 75 μm. The copper foil on the other side was completely removed by etching the entire surface. 3. A pair of resin-attached copper foils having a resin thickness of 50 μm are bonded to the laminate thus obtained so that the resin composition layer side is in contact with the laminate, and 170 ° C. for 90 minutes. Pressing was performed under 0 MPa pressing conditions, and the outer layer copper foil was entirely removed by etching to obtain an evaluation substrate. When the thickness of the evaluation substrate and the thickness of each layer were observed with an optical microscope, they were as shown in Table 1.

(Example 2)
An evaluation substrate was prepared in the same manner as in Example 1 except that the thermosetting resin varnish 3 was used in place of the thermosetting resin varnish 2 as the thermosetting resin varnish for producing the resin-coated copper foil. .

(Examples 3 and 4)
In the preparation of the prepreg, an evaluation substrate was prepared in the same manner as in Example 2 except that the thermosetting resin varnish 1 was applied with a vertical coater so that the thickness of the prepreg was 30 μm and 40 μm, respectively.

(Examples 5 to 8)
As a thermosetting resin varnish shown in Table 1 instead of the thermosetting resin varnish 1 as a thermosetting resin varnish for producing a prepreg, as a thermosetting resin varnish for producing a copper foil with resin, An evaluation substrate was prepared in the same manner as in Example 1 except that the thermosetting resin varnish shown in Table 1 was used instead of the curable resin varnish 2.

(Comparative Example 1)
<Preparation of prepreg>
The thermosetting resin varnish 1 is applied to a glass cloth (manufactured by Asahi Schwer, Co., Ltd., trade name: WEX-1027, thickness 19 μm) with a vertical coating machine so that the thickness of the prepreg is 50 μm. A prepreg was prepared by heating and drying at 150 ° C. for 20 minutes.

<Preparation of copper foil with resin>
The thermosetting resin varnish 1 is applied on a copper foil having a thickness of 18 μm (trade name: HLA18, manufactured by Nippon Electrolytic Co., Ltd.) with a horizontal coating machine, and the residence time is 5 minutes in a drying furnace at 100 to 140 ° C. Was heated and dried to produce a resin-coated copper foil having a resin composition layer thickness of 50 μm.

<Production of evaluation substrate>
A copper foil having a thickness of 18 μm (trade name: HLA18, manufactured by Nippon Electrolytic Co., Ltd.) was stacked on both sides of the prepreg so as to sandwich the prepreg, and both sides were pressed at 170 ° C. for 90 minutes under 4.0 MPa pressing conditions. A copper foil-clad laminate was produced.

  Next, the copper foil on one side of the double-sided copper foil-clad laminate was etched to produce a conductive pattern circuit with a line width of 75 μm and a space between lines of 75 μm. The copper foil on the other side was completely removed by etching the entire surface. The laminated plate thus obtained was bonded with a pair of resin-coated copper foils having a resin thickness of 50 μm prepared as described above so that the resin composition layer side was in contact with the laminated plate, 170 ° C., The substrate was pressed for 90 minutes under a 4.0 MPa pressing condition, and the outer layer copper foil was entirely removed by etching to obtain an evaluation substrate. When the thickness of the evaluation substrate and the thickness of each layer were observed with an optical microscope, they were as shown in Table 2.

(Comparative Examples 2 and 3)
As a thermosetting resin varnish shown in Table 2 instead of the thermosetting resin varnish 1 as a thermosetting resin varnish for producing a prepreg, as a thermosetting resin varnish for producing a copper foil with resin, An evaluation substrate was produced in the same manner as in Comparative Example 1 except that the thermosetting resin varnish shown in Table 2 was used instead of the curable resin varnish 1.

(Comparative Example 4)
As a thermosetting resin varnish shown in Table 2 instead of the thermosetting resin varnish 1 as a thermosetting resin varnish for producing a prepreg, as a thermosetting resin varnish for producing a copper foil with resin, An evaluation substrate was prepared in the same manner as in Example 1 except that the thermosetting resin varnish shown in Table 2 was used instead of the curable resin varnish 2.

(Comparative Examples 5 and 6)
As the thermosetting resin varnish for producing the prepreg, the thermosetting resin varnish shown in Table 2 or 3 is used instead of the thermosetting resin varnish 1, and the thermosetting resin varnish for producing the resin-coated copper foil. As described above, an evaluation substrate was prepared in the same manner as in Comparative Example 1 except that the thermosetting resin varnish shown in Table 2 or 3 was used instead of the thermosetting resin varnish 1.

(Comparative Examples 7-9)
As the thermosetting resin varnish shown in Table 3 instead of the thermosetting resin varnish 1 as the thermosetting resin varnish for producing the prepreg, as the thermosetting resin varnish for producing the copper foil with resin, An evaluation substrate was prepared in the same manner as in Example 1 except that the thermosetting resin varnish shown in Table 3 was used instead of the curable resin varnish 2.

(Comparative Example 10)
In the production of the evaluation substrate, instead of a copper foil having a thickness of 18 μm (trade name: HLA18, manufactured by Nippon Electrolytic Co., Ltd.), a copper foil having a thickness of 35 μm (product name: HLA35, manufactured by Nippon Electrolytic Co., Ltd.) An evaluation substrate was produced in the same manner as in Comparative Example 1 except that it was overlaid.

(Comparative Example 11)
<Preparation of prepreg>
The thermosetting resin varnish 2 is applied to a glass cloth WEX-1080 (manufactured by Asahi Schavel Co., Ltd., trade name, thickness 45 μm) with a vertical coating machine so that the thickness of the prepreg is 45 μm, and 120 to 150 ° C. For 20 minutes to prepare a prepreg.

<Production of copper foil with resin and evaluation substrate>
A resin-coated copper foil and an evaluation board were produced in the same manner as in Example 2 except that the prepreg was used.

[Evaluation of tensile modulus of cured prepreg]
The tensile modulus (25 ° C.) of the cured prepreg produced in each Example and Comparative Example was measured in the same manner as the method for measuring the tensile modulus of the cured product of the thermosetting resin varnishes 1 to 7 described above. The measurement results were as shown in Tables 1 to 3.

[Evaluation of folding resistance]
The folding resistance of the evaluation boards prepared in Examples 1 to 8 and Comparative Examples 1 to 11 was tested in accordance with the copper-clad laminate testing method for flexible printed wiring boards (JIS C6471 (1995)). Evaluation was performed using a machine (manufactured by Toyo Seiki Seisakusho, trade name: 2121011-00). The test was performed under the conditions of a weight of 500 g, a bending angle of 135 degrees, and a speed of 175 cpm (cycles per minutes) with respect to a bending radius of 0.38 mm, and the number of bendings until the conductor circuit pattern was disconnected was measured (measurement number: 5). Times). In all measurements, those that could be bent 20 times or more were considered good. The measurement results were as shown in Tables 1-3.

  As shown in Tables 1 to 3, the thickness of the glass cloth is 40 μm or less, the tensile elastic modulus of the cured resin contained in the fiber base layer is 3.0 GPa or less, and the tensile elastic modulus of the resin layer disposed outside. It was confirmed that Examples 1-8 higher than that were excellent in folding resistance and could be bent at least 20 times. In Comparative Examples 2 and 8 and Comparative Example 11, the number of folding times of 30 may be achieved, but the wire may be disconnected after about 10 times, and it cannot be determined that the variation is large and the bending resistance is excellent.

DESCRIPTION OF SYMBOLS 3 ... Fiber base material layer, 5 ... Internal resin layer (1st resin layer), 7, 9 ... Conductor, 10 ... Resin layer (2nd resin layer), 12 ... Metal layer, 30 ... Core substrate, 30a, 30b, 100a, 100b ... surface (main surface), 100, 200 ... printed wiring board, 300 ... metal foil-clad laminate.

Claims (14)

A core substrate in which a fiber base material is embedded in a first resin, a pair of second resin layers provided so as to sandwich the core substrate, and a surface of the resin layer opposite to the core substrate side Or a printed wiring board comprising a conductor provided on at least one of the interface between the resin layer and the core substrate,
The fiber base has a thickness of 40 μm or less,
A printed wiring board in which a tensile elastic modulus at 25 ° C. of the cured product of the first resin is larger than a tensile elastic modulus at 25 ° C. of the second resin layer and is 3.0 GPa or less.   The printed wiring board according to claim 1, wherein the core substrate has an internal resin layer (first resin layer) made of the first resin on a surface side in contact with the second resin layer.   The printed wiring board according to claim 1, wherein at least one of the core substrate and the second resin layer contains a resin having a glycidyl group.   The printed wiring board according to any one of claims 1 to 3, wherein at least one of the core substrate and the second resin layer contains a resin having an amide group.   The printed wiring board according to any one of claims 1 to 4, wherein at least one of the core substrate and the second resin layer contains one or both of an acrylic resin and a polyamideimide resin.   The printed wiring board according to any one of claims 1 to 5, wherein at least one of the core substrate and the second resin layer contains a polyamideimide resin containing a siloxane bond.   The printed wiring board according to claim 1, wherein the conductor has a thickness of 0.01 to 30 μm. A core substrate in which a fiber base material is embedded in a first resin, a pair of second resin layers provided so as to sandwich the core substrate, and a surface of the resin layer opposite to the core substrate side Or a metal foil-clad laminate comprising a metal foil provided on at least one of the interface between the resin layer and the core substrate,
The fiber base has a thickness of 40 μm or less,
A metal foil-clad laminate in which the cured product of the first resin has a tensile elastic modulus at 25 ° C. that is greater than the tensile elastic modulus at 25 ° C. of the second resin layer and is 3.0 GPa or less.   The metal foil-clad laminate according to claim 8, wherein the core substrate has an internal resin layer (first resin layer) made of the first resin on a surface side in contact with the second resin layer.   The metal foil-clad laminate according to claim 8 or 9, wherein at least one of the core substrate and the second resin layer contains a resin selected from a resin having a glycidyl group, a resin having an amide group, and an acrylic resin. .   The metal foil-clad laminate according to any one of claims 8 to 10, wherein at least one of the core substrate and the second resin layer contains a resin having an amide group.   The metal foil-clad laminate according to any one of claims 8 to 11, wherein at least one of the core substrate and the second resin layer contains one or both of an acrylic resin and a polyamideimide resin.   The metal foil-clad laminate according to any one of claims 8 to 12, wherein at least one of the core substrate and the second resin layer contains a polyamide-imide resin containing a siloxane bond.   The metal foil-clad laminate according to any one of claims 8 to 13, wherein the metal foil has a thickness of 0.01 to 30 µm.

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