JP2016194044A - Substrate, substrate for flexible printed wiring board, and method for manufacturing flexible printed wiring board and substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate and a substrate for a flexible printed wiring board having little temperature dependence of electric characteristics and excellent transmission characteristics.SOLUTION: The substrate in one embodiment of the present invention comprises a matrix and a reinforcing material included in the matrix, in which the matrix essentially comprises a fluorocarbon resin; and the substrate has, at -40°C or higher and 125°C or lower and at 10 GHz, a relative permittivity of 2.6 or less, a dielectric loss tangent of 0.004 or less, a variation width of the relative permittivity of 0.0001 or more and 0.08 or less, and a variation width of the dielectric loss tangent of 0.00001 or more and 0.002 or less. The substrate for a flexible printed wiring board in one embodiment of the present invention includes the above substrate and a conductive layer laminated on one surface side of the substrate. The reinforcing material is preferably glass cloth or resin cloth, and is preferably laminated in the middle in a thickness direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a substrate, a substrate for a flexible printed wiring board, a flexible printed wiring board, and a method for manufacturing the substrate.

  In recent years, the amount of information communication has been increasing, and in order to respond to this, communication in a high frequency region such as microwaves and millimeter waves has been actively performed in devices such as IC cards and mobile phone terminals.

  In a general printed wiring board, the transmission speed V and the transmission loss αd satisfy the following relations (Equation (1) and Equation (2)) with the relative dielectric constant εr, frequency f, and dielectric loss tangent tanδ of the substrate, respectively.

  That is, in order to increase the transmission speed V and reduce the transmission loss αd, it is desirable to reduce the relative dielectric constant εr of the substrate. For this reason, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene are used as substrate materials. It has been proposed to use a fluororesin such as a copolymer (ETFE) or poly (vinylidene fluoride) (PVdF) (see, for example, Japanese Patent Application Laid-Open Nos. 2001-7466 and 4296250).

JP 2001-7466 A Japanese Patent No. 4296250

  It can be said that the board | substrate using the said conventional fluororesin is a board | substrate which meets a request | requirement in the point which can be used for high frequency communication. However, in order to obtain stable electrical characteristics with a substrate, it is necessary to suppress variations in relative permittivity and dielectric loss tangent. However, the conventional substrate can sufficiently control relative permittivity and dielectric loss tangent. That's not true.

  Furthermore, in the communication in the high frequency region, there are an increasing number of usage examples and utilization examples outdoors such as an in-vehicle millimeter wave radar, an application using millimeter waves in portable devices such as portable information devices and portable communication terminals. For this reason, there is a demand for a substrate with less temperature dependence of electrical characteristics, but the conventional substrate using a fluororesin is not sufficient in this respect.

  The present invention has been made on the basis of the above-described circumstances, and has a substrate with low temperature dependency of electrical characteristics and excellent transmission characteristics, a substrate for flexible printed wiring boards, a flexible printed wiring board, and the like. An object of the present invention is to provide a method for manufacturing a simple substrate.

  A substrate according to one embodiment of the present invention made to solve the above-mentioned problem is a substrate containing a matrix and a reinforcing material contained in the matrix, the main component of the matrix being a fluororesin, The relative dielectric constant at 40 GHz to 125 ° C. and 10 GHz is 2.6 or less, the dielectric loss tangent is 0.004 or less, the change width of the relative dielectric constant is 0.0001 or more and 0.08 or less, and the change width of the dielectric loss tangent is 0.00. It is a substrate which is 00001 or more and 0.002 or less.

  A flexible printed wiring board substrate according to another aspect of the present invention made to solve the above-described problem is a flexible printed wiring comprising the substrate and a conductive layer laminated on one surface side of the substrate. It is a base material for board.

  The flexible printed wiring board which concerns on another one aspect | mode of this invention made | formed in order to solve the said subject is a flexible printed wiring board using the said base material for flexible printed wiring boards.

  Another method for manufacturing a substrate according to one aspect of the present invention, which has been made to solve the above problems, includes a step of superposing a resin film containing a fluororesin as a main component on both surfaces of a glass cloth or a resin cloth, And the step of thermocompression bonding the combined material while vacuum suction, and the resulting substrate has a relative dielectric constant of −40 ° C. or higher and 125 ° C. or lower and 10 GHz at 2.6 GHz or lower, a dielectric loss tangent of 0.004 or lower, and a relative dielectric constant. Is a variation of 0.0001 to 0.08, and the variation of the loss tangent is 0.00001 to 0.002.

  A method for producing a substrate according to another embodiment of the present invention, which has been made to solve the above-described problems, includes a step of impregnating a surface and inside of a glass cloth or a resin cloth with a composition containing a fluororesin as a main component, Heating the impregnated composition, and the resulting substrate has a dielectric constant of −40 ° C. or more and 125 ° C. or less and a dielectric constant at 10 GHz of 2.6 or less, a dielectric loss tangent of 0.004 or less, and a change in relative dielectric constant. This is a method for manufacturing a substrate having a width of 0.0001 or more and 0.08 or less, and a change in dielectric tangent of 0.00001 or more and 0.002 or less.

  The substrate, the substrate for flexible printed wiring, and the flexible printed wiring board of the present invention have less temperature dependence of electrical characteristics and excellent transmission characteristics. The substrate manufacturing method of the present invention can easily manufacture a substrate with less temperature dependence of electrical characteristics and excellent transmission characteristics.

It is typical sectional drawing which shows the board | substrate of one Embodiment of this invention. It is typical sectional drawing which shows the base material for flexible printed wiring boards of one Embodiment of this invention. It is a graph which shows the temperature dependence of the dielectric constant of Examples 1, 2 and Comparative Examples 1, 2. It is a graph which shows the temperature dependence of the dielectric loss tangent of Examples 1, 2 and Comparative Examples 1, 2.

[Description of Embodiment of the Present Invention]
A substrate according to one embodiment of the present invention includes a matrix and a reinforcing material included in the matrix, and the main component of the matrix is a fluororesin, and is at −40 ° C. or higher and 125 ° C. or lower and at 10 GHz. The relative dielectric constant is 2.6 or less, the dielectric loss tangent is 0.004 or less, the change width of the relative dielectric constant is 0.0001 or more and 0.08 or less, and the change width of the dielectric loss tangent is 0.00001 or more and 0.002 or less.

  Since the main component of the matrix of the substrate is a fluororesin, transmission loss when used in a high frequency region can be suppressed. Moreover, since the said board | substrate contains a reinforcing material in a matrix, intensity | strength and dimensional stability are securable. Further, since the substrate has a relative dielectric constant and a dielectric loss tangent at −40 ° C. or higher and 125 ° C. or lower and 10 GHz in the above range, the substrate has excellent transmission characteristics. In addition, since the substrate has a relative dielectric constant variation range and a dielectric loss tangent variation range of −40 ° C. or more and 125 ° C. or less and 10 GHz, the temperature dependence of electrical characteristics is small.

  Here, the “main component” is a component having the largest content, for example, a component having a content of 50% by mass or more, preferably 90% by mass or more. “Relative permittivity” and “dielectric loss tangent” are values in the thickness direction measured at a relative humidity of 50% by a cavity resonator perturbation method in accordance with JIS-C-2138 (2007), respectively. is there.

  The reinforcing material is preferably a glass cloth or a resin cloth, and is preferably laminated in the middle in the thickness direction. Thus, when the reinforcing material is a glass cloth or a resin cloth and is laminated in the middle in the thickness direction, the strength and dimensional stability can be further improved, and the occurrence of warpage in the substrate can be more effectively suppressed.

  The fluororesin preferably contains 50% by mass or more of tetrafluoroethylene-hexafluoropropylene copolymer (FEP) or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). When the substrate contains FEP or PFA as a matrix as a main component, the temperature dependency of the electrical characteristics can be reduced while obtaining better electrical characteristics. This is presumably because FEP and PFA have a small degree of crystallinity and further a small change in electrical characteristics accompanying a change in crystal structure.

  As content of the said reinforcing material, 1 volume% or more and 50 volume% or less are preferable. By making content of the said reinforcing material into the said range, the temperature dependence of an electrical property can be made less, without affecting the electrical property in the area | region where a reinforcing material is included by planar view. Here, the “content of the reinforcing material” means the content in a region where the reinforcing material is included in a plan view.

  The substrate preferably has a modified layer containing a siloxane bond and a hydrophilic functional group on one surface. By having the modified layer on one side in this way, the adhesion can be improved without performing a roughening treatment that inhibits suppression of transmission loss on the conductive layer laminated on one side, The peeling of the conductive layer can be further suppressed.

  The base material for flexible printed wiring boards which concerns on another aspect of this invention is equipped with the said board | substrate and the electrically conductive layer laminated | stacked on the one surface side of this board | substrate. Since the flexible printed wiring board base material includes the substrate, the temperature dependence of electrical characteristics is small and the transmission characteristics are excellent.

  The conductive layer is preferably a copper foil. Copper foil is excellent in conductivity and flexibility, and is advantageous in terms of cost. Better flexibility can be obtained while obtaining excellent transmission characteristics by using a copper foil as the conductive layer.

  The peel strength between the substrate and the conductive layer is preferably 10 N / cm or more. By setting the peeling strength to be equal to or higher than the lower limit, peeling of the conductive layer can be further suppressed. Here, the said peeling strength points out the peeling strength obtained by the test method based on "Adhesive-peeling adhesive strength test method-2 part: 180 degree peeling" of JIS-K-6854-2 (1999). .

The heat deformability of the flexible printed wiring board substrate is preferably 0.5% or less. By setting the heat deformability to the upper limit or less, the dimensional stability can be further improved, and the temperature dependence of the electrical characteristics can be further reduced. The heat deformability is measured by measuring the dimensional change rate of the copper foil before and after heating under the conditions of a temperature of 150 ° C. and a time of 30 minutes in accordance with “Dimensional stability” of JIS-C-6471 (1995). Is a value obtained by Here, the dimensional change rate is obtained from the following equation.
Dimensional change rate (%) = (absolute value of difference between distance between gauge points after heating and distance between gauge points before heating) / (distance between gauge points before heating) × 100

  The flexible printed wiring board which concerns on another aspect of this invention is a flexible printed wiring board using the said base material for flexible printed wiring boards. Since the flexible printed wiring board uses the base material for flexible printed wiring boards, the temperature dependence of electrical characteristics is small and the transmission characteristics are excellent.

  The substrate manufacturing method according to another aspect of the present invention includes a step of superposing a resin film containing a fluororesin as a main component on both surfaces of a glass cloth or a resin cloth, and thermocompression bonding the superposed material while vacuum suctioning. The substrate has a relative dielectric constant of 2.6 or lower, a dielectric loss tangent of 0.004 or lower, and a relative dielectric constant variation range of 0.0001 or higher and 0.08. Hereinafter, the change width of the dielectric loss tangent is 0.00001 or more and 0.002 or less.

  The substrate manufacturing method can easily manufacture a substrate having less temperature dependence of electrical characteristics and excellent transmission characteristics.

  It is preferable to start vacuum suction before the start of the thermocompression bonding. Thus, if vacuum suction is started before the thermocompression bonding is started, a substrate in which the glass cloth or the resin cloth and the resin film are more integrated can be obtained.

  The method for producing a substrate according to another aspect of the present invention includes a step of impregnating a glass cloth or a resin cloth with a composition containing a fluororesin as a main component on the surface and inside thereof, and a step of heating the impregnated composition. The relative permittivity of the obtained substrate at −40 ° C. to 125 ° C. and 10 GHz is 2.6 or less, the dielectric loss tangent is 0.004 or less, and the variation range of the relative permittivity is 0.0001 to 0.08, This is a method for manufacturing a substrate in which the variation width of the dielectric loss tangent is 0.00001 or more and 0.002 or less.

  The substrate manufacturing method can easily manufacture a substrate having less temperature dependence of electrical characteristics and excellent transmission characteristics.

[Details of the embodiment of the present invention]
Hereinafter, a substrate, a substrate for flexible printed wiring boards, a flexible printed wiring board, and a method for manufacturing a board according to the present invention will be described with reference to the drawings.

<Board>
A substrate 1 shown in FIG. 1 contains a matrix and a reinforcing material contained in the matrix, and the main component of the matrix is a fluororesin. Specifically, the substrate 1 includes a fluororesin layer 2, a reinforcing material layer 3 laminated in the middle of the thickness direction of the fluororesin layer 2, and a modified layer laminated on one surface of the fluororesin layer 2. 4.

[Fluororesin layer]
The fluororesin layer 2 is mainly composed of a fluororesin that is a main component of the matrix of the substrate 1. Here, the “fluororesin” refers to an organic group in which at least one hydrogen atom bonded to the carbon atom constituting the repeating unit of the polymer chain has a fluorine atom or a fluorine atom (hereinafter referred to as “fluorine atom-containing group”). )). The fluorine atom-containing group is a group in which at least one hydrogen atom in a linear or branched organic group is substituted with a fluorine atom, and examples thereof include a fluoroalkyl group, a fluoroalkoxy group, and a fluoropolyether group. .

  The “fluoroalkyl group” means an alkyl group in which at least one hydrogen atom is substituted with a fluorine atom, and examples thereof include a “perfluoroalkyl group”. Specific examples of the fluoroalkyl group include a group in which all hydrogen atoms of the alkyl group are substituted with fluorine atoms, and a group in which a hydrogen atom other than one hydrogen atom at the terminal of the alkyl group is substituted with fluorine atoms. It is done.

  The “fluoroalkoxy group” means an alkoxy group in which at least one hydrogen atom is substituted with a fluorine atom, and examples thereof include a “perfluoroalkoxy group”. Specific examples of the fluoroalkoxy group include a group in which all hydrogen atoms of the alkoxy group are substituted with fluorine atoms, and a group in which a hydrogen atom other than one hydrogen atom at the terminal of the alkoxy group is substituted with fluorine atoms. It is done.

  The “fluoropolyether group” is a monovalent group having an oxyalkylene unit as a repeating unit and having an alkyl group or a hydrogen atom at the terminal, and at least one of the alkylene oxide chain or the terminal alkyl group. A monovalent group in which a hydrogen atom is substituted with a fluorine atom. Examples of the fluoropolyether group include a “perfluoropolyether group” having a plurality of perfluoroalkylene oxide chains as repeating units.

  Examples of the fluororesin include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-ethylene copolymer. Polymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinyl fluoride (PVF), tetrafluoroethylene, hexafluoro Examples thereof include thermoplastic fluororesin (THV) and fluoroelastomer formed by three types of monomers such as propylene and vinylidene fluoride. Moreover, the mixture and copolymer containing these compounds can also be used as the said fluororesin.

  Among these, as the fluororesin, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) is preferable, and the fluororesin contains 50% by mass or more of these resins. It is preferable to contain. Since these fluororesins are materials having a relatively low relative dielectric constant and low temperature dependency, transmission loss can be further suppressed by using these fluororesins as the main component of the matrix.

  More specifically, PTFE has a specific crystal structure change at 19 ° C. and 30 ° C., a linear expansion coefficient and a specific gravity change, and electrical characteristics are also greatly changed (for example, “Fluorine Resin Handbook” (Nikkan Kogyo Shimbun, (Issued in 1990)). Furthermore, the crystallinity of PTFE is 60% or more and 85% or less, the crystallinity of PFA is 50% or more and 60% or less, and the crystallinity of FEP is 40% or more and 50% or less. Thus, the crystallinity of FEP and PFA is smaller than the crystallinity of PTFE. Therefore, PFA and FEP have a low degree of crystallinity, and even if a specific change in the crystal structure occurs, it is estimated that there is little influence on the change in electrical characteristics and the like. For this reason, compared with PTFE, PFA and FEP have a smaller fluctuation range of electrical characteristics due to temperature changes, and electrical characteristics are stable. That is, PFA and FEP have better temperature dependence of electrical characteristics than PTFE.

  The matrix may contain components (arbitrary components) other than the fluororesin. Examples of this optional component include resins other than the above-mentioned fluororesins, flame retardants, flame retardant aids, pigments, antioxidants, reflection imparting agents, masking agents, lubricants, processing stabilizers, plasticizers, foaming agents, and the like. . In this case, as an upper limit of content of the arbitrary component in the said matrix, 20 mass% is preferable and 10 mass% is more preferable.

  The fluororesin layer 2 may have a hollow structure. Since the dielectric constant can be further reduced by having a hollow structure, transmission loss can be more effectively suppressed.

  The upper limit of the relative dielectric constant of the portion 2a (matrix of the substrate 1) other than the reinforcing material of the fluororesin layer 2 is preferably 2.7, and more preferably 2.5. On the other hand, the lower limit of the relative dielectric constant is preferably 1.2, more preferably 1.4. When the relative dielectric constant exceeds the upper limit, the dielectric loss tangent becomes too large, and there is a possibility that the transmission loss cannot be sufficiently reduced, and a sufficient transmission rate may not be obtained. Further, when the relative dielectric constant is less than the lower limit, the circuit width may not be sufficiently reduced when the circuit is provided by etching the substrate 1 having the conductive layer laminated on one surface side, and the strength is low. May decrease.

The upper limit of the linear expansion coefficient of the portion 2a (matrix of the substrate 1) other than the reinforcing material of the fluororesin layer 2 is preferably 2 × 10 ⁻⁵ / ° C. On the other hand, the lower limit of the linear expansion coefficient is preferably 1.2 × 10 ⁻⁴ / ° C. When the said linear expansion coefficient exceeds the said upper limit, the fluororesin layer 2 produces a volume change by a temperature change, and there exists a possibility that generation | occurrence | production of curvature cannot be suppressed effectively. Moreover, when the said linear expansion coefficient is less than the said minimum, there exists a possibility of producing a problem in cost.

  The fluororesin layer 2 is divided into two upper and lower layers by the reinforcing material layer 3, and the pair of layers preferably have substantially the same thickness. If the thicknesses of the pair of layers are greatly different, the fluororesin layer 2 may be warped due to thermal expansion. Note that “substantially the same thickness” means that the ratio of the average thickness of the other layer to the average thickness of the one layer is 0.9 or more and 1.1 or less.

  The upper limit of the average thickness of each layer divided by the reinforcing material layer 3 of the fluororesin layer 2 is preferably 1 mm, more preferably 100 μm, and even more preferably 50 μm. On the other hand, the lower limit of the average thickness is preferably 0.5 μm, more preferably 1 μm, and even more preferably 10 μm. When the average thickness exceeds the upper limit, application to an electronic device that requires flexibility may be difficult. Further, when the average thickness is less than the lower limit, the dielectric loss tangent of the substrate 1 is increased, and there is a possibility that the transmission loss cannot be sufficiently reduced or a sufficient transmission speed cannot be obtained.

  In this specification, “average thickness” means the distance between the average line of the front-side interface and the average line of the back-side interface within the measurement length in the cross-section cut in the thickness direction of the object. Point to. Here, the “average line” is an imaginary straight line drawn along the interface, and the total area of the mountains (the total area above the imaginary straight line) divided by the interface and the imaginary straight line and the total of the valleys. It means a line having an equal area (total area below the virtual straight line).

(Reinforcement layer)
The reinforcing material layer 3 is a layer containing a film-like or cloth-like reinforcing material.

  The reinforcing material is not particularly limited as long as the coefficient of linear expansion is smaller than that of the portion 2a other than the reinforcing material of the fluororesin layer 2, but the insulating property and the heat resistance that does not melt and flow at the melting point of the fluororesin. Desirably, it has tensile strength equal to or better than that of fluororesin, and corrosion resistance. As such a reinforcing material, for example, a glass cloth in which glass is formed in a cloth shape, a fluororesin-containing glass cloth in which such a glass cloth is impregnated with a fluororesin, metal, ceramics, polytetrafluoroethylene, polyetheretherketone Resin cloth containing heat-resistant fibers formed of polyimide, aramid, etc., polytetrafluoroethylene, liquid crystal polymer, polyimide, polyamideimide, polybenzimidazole, polyetheretherketone, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl It can be composed of a heat-resistant film mainly composed of a vinyl ether copolymer, a thermosetting resin, a cross-linked resin, or the like. In addition, as said resin cloth and a heat resistant film, what has melting | fusing point (or heat deformation temperature) more than the temperature of the process of thermocompression bonding with the manufacturing method of the board | substrate mentioned later is preferable. As a weaving method of the resin cloth, a plain weave is preferable to make the fluororesin layer 2 thin, but a twill weave and a satin weave are preferable to make the fluororesin layer 2 bendable. In addition, a known weaving method can be applied.

  When the reinforcing material is the fluororesin-containing glass cloth, the fluororesin impregnated in the glass cloth may be a matrix of the substrate 1.

  Among these, as the reinforcing material, the glass cloth or the resin cloth is preferable from the viewpoint of further improving the strength and dimensional stability.

  The upper limit of the content of the reinforcing material in the substrate 1 is preferably 50% by volume, more preferably 40% by volume, and still more preferably 30% by volume with respect to the total volume of the substrate 1. On the other hand, as a minimum of the above-mentioned content, 1 volume% is preferred, 5 volume% is more preferred, and 10 volume% is still more preferred. When the content exceeds the upper limit, there is a possibility that electrical characteristics are deteriorated due to a temperature change. Moreover, when the said content is less than the said minimum, there exists a possibility of producing a fall of intensity | strength and a fall of dimensional stability by a temperature change.

The upper limit of the density of the glass fibers of the glass cloth is preferably ^{5g / m 3, 3g / m} 3 and more preferably. On the other hand, the lower limit of the density is preferably 1 g / ^{m 3,} more preferably 2 g / ^{m 3.}

  As an upper limit of the tensile strength of the glass fiber of the said glass cloth, 10 GPa is preferable and 5 GPa is more preferable. On the other hand, the lower limit of the tensile strength is preferably 1 GPa, more preferably 2 GPa.

  As an upper limit of the tensile elasticity modulus of the glass fiber of the said glass cloth, 200 GPa is preferable and 100 GPa is more preferable. On the other hand, the lower limit of the tensile modulus is preferably 10 GPa, more preferably 50 GPa.

  The upper limit of the maximum elongation of the glass fiber of the glass cloth is preferably 20%, and more preferably 10%. On the other hand, the lower limit of the maximum elongation is preferably 1%, more preferably 3%.

  As an upper limit of the softening point of the glass fiber of the said glass cloth, 1200 degreeC is preferable and 1000 degreeC is more preferable. On the other hand, as a minimum of the above-mentioned softening point, 700 ° C is preferred and 800 ° C is more preferred. The said softening point means the softening point measured by the ring and ball method prescribed | regulated to JIS-K-7234 (1986).

  The upper limit of the relative dielectric constant of the reinforcing material is preferably 10, more preferably 6, and even more preferably 5. On the other hand, the lower limit of the relative dielectric constant is preferably 1.2, more preferably 1.5, and still more preferably 1.8. When the relative dielectric constant exceeds the above upper limit, the dielectric loss tangent becomes large and there is a possibility that the transmission loss cannot be sufficiently reduced, and there is a possibility that a sufficient transmission speed cannot be obtained. Moreover, when the said dielectric constant is less than the said minimum, there exists a possibility that cost may become high.

The upper limit of the linear expansion coefficient of the reinforcing material is preferably 5 × 10 ⁻⁵ / ° C., and more preferably 4.7 × 10 ⁻⁵ / ° C. On the other hand, the lower limit of the linear expansion coefficient is preferably −1 × 10 ⁻⁴ / ° C., more preferably 0 / ° C. When the said linear expansion coefficient exceeds the said upper limit, there exists a possibility that generation | occurrence | production of the curvature by a temperature change cannot be suppressed effectively. Moreover, when the said linear expansion coefficient is less than the said minimum, there exists a possibility that cost may become high.

  The upper limit of the ratio of the linear expansion coefficient of the reinforcing material to the linear expansion coefficient of the portion 2a other than the reinforcing material of the fluororesin layer 2 is preferably 0.95 and more preferably 0.1. On the other hand, the lower limit of the ratio is preferably 0.001 and more preferably 0.002. When the ratio exceeds the above upper limit, the occurrence of warpage in the substrate 1 may not be effectively suppressed. Moreover, when the said ratio is less than the said minimum, there exists a possibility that the cost of a reinforcing material may become high.

  The upper limit of the average thickness of the reinforcing material layer 3 is preferably 50 μm, more preferably 40 μm, and still more preferably 35 μm. On the other hand, the lower limit of the average thickness is preferably 1 μm, more preferably 3 μm, and even more preferably 5 μm. When the average thickness exceeds the upper limit, sufficient flexibility may not be obtained. Moreover, when the said average thickness is less than the said minimum, there exists a possibility that the intensity | strength of the board | substrate 1 cannot fully be improved and generation | occurrence | production of the curvature in the board | substrate 1 cannot be suppressed effectively.

  The upper limit of the ratio of the average thickness of the reinforcing material layer 3 to the average thickness of the portion 2a other than the reinforcing material of the fluororesin layer 2 is preferably 30, more preferably 2, and even more preferably 0.5. On the other hand, the lower limit of the ratio is preferably 0.001, more preferably 0.1, and still more preferably 0.2. When the ratio exceeds the upper limit, sufficient flexibility may not be obtained. When the ratio is less than the lower limit, the occurrence of warpage in the substrate 1 may not be effectively suppressed.

(Modified layer)
The substrate 1 has a modified layer 4 on one surface. The modified layer 4 includes a siloxane bond (Si—O—Si) and a hydrophilic organic functional group. Therefore, the surface of the substrate 1 on the modified layer 4 side is rich in reactivity. Here, “rich in reactivity” includes large physical effects such as adhesiveness. That is, the surface of the modified layer 4 is surface active. In addition, since the modified layer 4 has a siloxane bond structure and is stable over time, the surface modified state (surface active state) is stable. The “hydrophilic functional group” refers to a functional group composed of atoms having a high electronegativity and having hydrophilicity.

  The modified layer 4 is formed by bonding, for example, a modifier (silane coupling agent) having a hydrophilic functional group and generating a siloxane bond to the fluororesin included in the matrix of the fluororesin layer 2. . In this case, in the modified layer 4, for example, hydrophilic functional groups are bonded to Si atoms constituting siloxane bonds. Here, the bond between the fluororesin and the modifier may include a covalent bond, a hydrogen bond, or the like, when it is configured only by a covalent bond.

In the modified layer 4, the Si atom constituting the siloxane bond (hereinafter, this atom is also referred to as “Si atom of siloxane bond”) is, for example, at least one of N atom, C atom, O atom, and S atom. It is covalently bonded to the C atom of the fluororesin through an atom. Specifically, the Si atom of the siloxane bond is, for example, —O—, —S—, —SS—, — (CH ₂ ) _n —, —NH—, — (CH ₂ ) _n —NH—, — It binds to the C atom of the fluororesin through an atomic group such as (CH ₂ ) _n —O— (CH ₂ ) _m — (n and m are integers of 1 or more).

  Examples of the hydrophilic functional group include hydroxyl group, carboxy group, carbonyl group, amino group, amide group, sulfide group, sulfonyl group, sulfo group, sulfonyldioxy group, epoxy group, methacryl group, mercapto group, and combinations thereof. preferable. Among these, a hydrophilic functional group containing an N atom and a hydrophilic functional group containing an S atom are more preferable. These hydrophilic functional groups further improve surface adhesion and adhesion.

  The modified layer 4 may contain two or more of these hydrophilic functional groups. Thus, by imparting hydrophilic functional groups having different properties to the modified layer 4, the surface reactivity and the like can be varied. These hydrophilic functional groups can be bonded directly to Si atoms, which are constituents of siloxane bonds, or via one or more C atoms.

  As the modifier for forming the modified layer 4 having the above characteristics, a silane coupling agent having a hydrophilic functional group in the molecule is preferable, and among them, a compound having a hydrolyzable silicon-containing functional group is more preferable. . Such a silane coupling agent is chemically bonded to the fluororesin included in the matrix of the fluororesin layer 2. The chemical bond between the silane coupling agent and the fluororesin may include a covalent bond, a hydrogen bond, or the like in some cases. Here, the “hydrolyzable silicon-containing functional group” refers to a group that can form a silanol group (Si—OH) by hydrolysis.

  The upper limit of the contact angle with the pure water on the surface of the modified layer 4 is preferably 90 °, more preferably 80 °, and even more preferably 70 °. When the contact angle with the pure water on the surface of the modified layer 4 exceeds the above upper limit, there is a possibility that sufficient adhesion and adhesion cannot be obtained. In addition, the minimum of a contact angle with the pure water of the surface of the modification layer 4 is not specifically limited. The contact angle can be controlled, for example, by adjusting the type and amount of the hydrophilic functional group. The above-mentioned “contact angle with pure water” is a value of a contact angle measured by a JIS-R-3257 (1999) sessile drop method.

The modified layer 4 preferably has the following etching resistance. That is, for an etching process that includes iron chloride, has a specific gravity of 1.33 g / cm ³ , and is immersed in an etching solution (temperature 45 ° C.) having a free hydrochloric acid concentration of 0.2 mol / L for 2 minutes Thus, it is preferable that the modified layer 4 is not removed. Here, “the modified layer is not removed” indicates that the hydrophilicity is not lost, and that the contact angle with pure water does not exceed 90 ° in the portion where the modified layer 4 is provided. When the modified layer 4 has the above-mentioned etching resistance, an etching solution penetrates between the conductive layer and the substrate when the conductive layer of the flexible printed wiring board substrate including the substrate and the conductive layer is etched into a pattern. Therefore, it is possible to maintain good adhesion between the substrate and the conductive layer. The etching resistance can be imparted to the modified layer 4 by using, for example, the preferred silane coupling agent described above. In some cases, the etching treatment may cause a minute portion having hydrophobicity in the region where the modified layer 4 is formed to be patchy. If the entire region is hydrophilic, such a state is hydrophilic. Is maintained.

  Moreover, it is preferable that the modified layer 4 has the etching tolerance with respect to the etching liquid containing a copper chloride. In addition, when the modified layer 4 has etching resistance with respect to the iron chloride-containing etching solution, it is confirmed that the modified layer 4 has etching resistance similar to the above with respect to the etching solution containing copper chloride. ing.

  The upper limit of the average thickness of the modified layer 4 is preferably 200 nm, and more preferably 50 nm. On the other hand, the lower limit of the average thickness is preferably 3 nm, and more preferably 5 nm. When the average thickness exceeds the upper limit, the high frequency characteristics may be insufficient due to the influence of dielectric loss caused by the modified layer 4. Moreover, when the said average thickness is less than the said minimum, surface active effect cannot fully be acquired and there exists a possibility that adhesiveness and adhesiveness cannot fully be acquired. Therefore, by adjusting the average thickness of the modified layer 4, the transmission loss suppressing function and the adhesion improving function can be exhibited in a well-balanced manner. The average thickness of the modified layer 4 can be measured by, for example, X-ray spectroscopy.

  As an upper limit of the average thickness of the substrate 1, 2.7 mm is preferable, 2.5 mm is preferable, and 2.2 mm is more preferable. On the other hand, the lower limit of the average thickness is preferably 1 μm, more preferably 1.5 μm, and even more preferably 2 μm. When the average thickness exceeds the upper limit, sufficient flexibility may not be obtained. Moreover, when the said average thickness is less than the said minimum, handling may become difficult.

  The upper limit of the relative dielectric constant of the substrate 1 at −40 ° C. or more and 125 ° C. or less and 10 GHz is 2.6, preferably 2.55, and more preferably 2.50. When the relative dielectric constant exceeds the upper limit, there is a possibility that the transmission loss cannot be sufficiently reduced or a sufficient transmission speed cannot be obtained.

  The upper limit of the dielectric loss tangent of the substrate 1 at −40 ° C. to 125 ° C. and 10 GHz is 0.004, preferably 0.0037, and more preferably 0.0035. When the dielectric loss tangent exceeds the above upper limit, there is a possibility that the transmission loss cannot be sufficiently reduced and a sufficient transmission speed may not be obtained.

  The upper limit of the change range of the relative dielectric constant at −40 ° C. to 125 ° C. and 10 GHz of the substrate 1 is 0.08, preferably 0.065, and more preferably 0.055. On the other hand, the lower limit of the change range of the relative dielectric constant is 0.0001, preferably 0.0005, and more preferably 0.01. When the change width of the relative dielectric constant exceeds the upper limit, there is a risk of deterioration of electrical characteristics due to temperature change. Moreover, when the change width of the relative dielectric constant is less than the lower limit, the range of material selection may be reduced.

  The upper limit of the variation range of the dielectric loss tangent at −40 ° C. to 125 ° C. of the substrate 1 is 0.002, preferably 0.0018, and more preferably 0.0016. On the other hand, the lower limit of the change width of the dielectric loss tangent is 0.00001, preferably 0.00005, and more preferably 0.0001. When the change width of the dielectric loss tangent exceeds the upper limit, there is a risk of deterioration of electrical characteristics due to temperature change. Moreover, when the variation | change_quantity of the said dielectric loss tangent is less than the said minimum, there exists a possibility that the range of material selection may become narrow.

<Substrate manufacturing method>
Next, the preferable manufacturing method of the above-mentioned board | substrate at the time of using a glass cloth or a resin cloth is demonstrated. Examples of the substrate manufacturing method include the following first substrate manufacturing method and second substrate manufacturing method.

  The manufacturing method of a 1st board | substrate is equipped with the process of impregnating the composition which has a fluororesin as a main component in the surface and the inside of a glass cloth or a resin cloth, and the process of heating the said impregnated said composition.

[Impregnation process]
In the impregnation step, the surface and the inside of the glass cloth or resin cloth are impregnated with a composition containing a fluororesin as a main component. Examples of a method of impregnating the surface of glass cloth or resin cloth with the above composition include, for example, a method of applying the above composition to the surface of glass cloth or resin cloth, and a method of immersing glass cloth or resin cloth in the above composition Etc.

[Heating process]
In the heating step, the impregnated composition is heated. The heating step corresponds to a baking step in which the impregnated composition is dried and cured. After the heating step, a fluororesin layer is formed on the surface of the glass cloth or resin cloth.

  As a minimum of the temperature of a heating process, 150 ° C is preferred and 200 ° C is more preferred. On the other hand, as an upper limit of the temperature of a heating process, 600 degreeC is preferable and 500 degreeC is more preferable. When the temperature of a heating process is less than the said minimum, there exists a possibility that drying and hardening of the said impregnated composition may become inadequate. Moreover, when the temperature of a heating process exceeds the said upper limit, there exists a possibility that the board | substrate obtained may deform | transform.

  In the first substrate manufacturing method, a fluororesin layer may be formed on one surface of a glass cloth or resin cloth, and then a fluororesin layer may be formed on the other surface of the glass cloth or resin cloth. In the first substrate manufacturing method, a fluororesin layer may be simultaneously formed on both surfaces of the glass cloth or the resin cloth.

  In the first substrate manufacturing method, the step of impregnating the surface of the glass cloth or the resin cloth with a composition containing a fluororesin as a main component and the step of heating the impregnated composition may be repeated. For example, by repeatedly applying and heating the composition, a fluororesin layer having a predetermined thickness can be easily formed.

  In the first substrate manufacturing method, a glass cloth or a resin cloth is impregnated with a composition containing a fluororesin as a main component on the surface and inside thereof. For this reason, in the manufacturing method of the first substrate, it is possible to obtain a more integrated substrate as a whole.

  Next, the second substrate manufacturing method includes a step of superposing a resin film mainly composed of a fluororesin on both surfaces of a glass cloth or a resin cloth, and a step of thermocompression bonding the superposed material while vacuum suctioning. Is provided.

[Overlay process]
In the superimposing step, a resin film containing a fluororesin as a main component is superimposed on both surfaces of the glass cloth or the resin cloth.

[Thermo-compression process]
In the thermocompression bonding process, the superposed product obtained in the superimposing process is thermocompression bonded while vacuum suction.

  As an upper limit of the temperature of the said thermocompression bonding, 600 degreeC is preferable and 500 degreeC is more preferable. When the thermocompression bonding temperature exceeds the upper limit, the resulting substrate may be deformed.

  As a minimum of the temperature of the said thermocompression bonding, melting | fusing point of the above-mentioned fluororesin is preferable, and the decomposition start temperature of the above-mentioned fluororesin is more preferable. More specifically, a temperature that is 30 ° C. higher than the melting point of the fluororesin described above is preferable, and a temperature that is 50 ° C. higher than the melting point of the fluororesin described above is more preferable. When the temperature is less than the lower limit, it may be difficult to obtain a more integrated substrate by impregnating the resin of the resin film into a glass cloth or a resin cloth. Here, “decomposition start temperature” refers to the temperature at which the fluororesin begins to thermally decompose, and “decomposition temperature” refers to the temperature at which the mass of the fluororesin decreases by 10% due to thermal decomposition.

  The pressure for the thermocompression bonding is preferably 0.01 MPa or more and 1200 MPa or less. Further, the pressing time for the thermocompression bonding is preferably 5 seconds or more and 10 hours or less.

  The upper limit of the degree of vacuum at the time of vacuum suction is preferably 10 MPa, more preferably 1 MPa, and even more preferably 10 Pa. By setting the degree of vacuum to the upper limit or less, the resin of the resin film can be further infiltrated into the gaps of the glass cloth or the resin cloth, and a substrate that is more integrated as a whole can be obtained. On the other hand, the lower limit of the degree of vacuum is not particularly limited, but is about 0.01 Pa, for example.

  In the second substrate manufacturing method, from the viewpoint of obtaining a more integrated substrate by impregnating the resin of the resin film into a glass cloth or a resin cloth, vacuum suction may be started before the start of the thermocompression bonding. preferable.

<Base material for flexible printed wiring boards>
In FIG. 2, the typical sectional drawing of the base material 10 for flexible printed wiring boards which concerns on one Embodiment of this invention is shown. The substrate for flexible printed wiring board 10 includes a substrate 1 and a conductive layer 5 laminated on one surface side of the substrate 1. The substrate 1 includes a fluororesin layer 2 having a reinforcing material layer 3 in the middle in the thickness direction. The conductive layer 5 may be directly laminated on the substrate 1 or may be laminated on the substrate 1 via another layer. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

(Conductive layer)
Examples of the conductive material constituting the conductive layer 5 include metals such as copper, silver, gold, iron (stainless), aluminum, nickel, ITO (Indium Tin Oxide), and conductive resins that are a mixture of resin and metal. Can be mentioned.

  Among these, copper is preferable as the conductive material from the viewpoints of cost, electrical characteristics, and flexibility. That is, the conductive layer 5 is preferably a copper foil.

  The upper limit of the ten-point average roughness (Rz) of the copper foil is preferably 4 μm, more preferably 1 μm, and even more preferably 0.6 μm. When the ten-point average roughness (Rz) exceeds the above upper limit, the unevenness of the portion where the high-frequency signal is concentrated becomes large due to the skin effect, current flow is hindered, and unintended transmission loss may occur. is there. In addition, although it does not specifically limit as a minimum of the ten-point average roughness (Rz) of the said copper foil, 0.01 micrometer is preferable and 0.1 micrometer is more preferable. Ten-point average roughness (Rz) is a value defined by JIS-B-0601 (1994).

  The upper limit of the average thickness of the conductive layer 5 is preferably 300 μm, more preferably 200 μm, and even more preferably 150 μm. On the other hand, the lower limit of the average thickness is preferably 1 μm, more preferably 5 μm, and even more preferably 10 μm. When the average thickness exceeds the upper limit, application to an electronic device that requires flexibility may be difficult. Moreover, when the said average thickness is less than the said minimum, there exists a possibility that the resistance of the conductive layer 5 may increase.

  The lower limit of the peel strength between the substrate 1 and the conductive layer 5 of the flexible printed wiring board substrate 10 is preferably 10 N / cm, more preferably 12 N / cm, and even more preferably 15 N / cm. When the said peeling strength is less than the said minimum, there exists a possibility that peeling from the board | substrate 1 of the conductive layer 5 cannot be suppressed effectively.

  The upper limit of the heat deformability of the flexible printed wiring board substrate 10 is preferably 0.5%, more preferably 0.3%, and even more preferably 0.2%. When the heat deformability exceeds the upper limit, it may be difficult to reduce the temperature dependence of the electrical characteristics and further improve the dimensional stability.

<Method for producing substrate for flexible printed wiring board>
An example of a preferable manufacturing method of the flexible printed wiring board substrate 10 will be described by using a copper foil as the conductive layer 5 and the above-described substrate 1 as the substrate. First, a primer material containing a silane coupling agent, which is a modifier, alcohol, and water is attached to the copper foil as the conductive layer 5. Next, after removing the alcohol in the primer material adhering to the copper foil by drying and heating as necessary, the substrate 1 is laminated on the side of the primer material of the copper foil so as to sandwich the primer material. And the obtained laminated body is thermocompression-bonded with a press. This thermocompression bonding is preferably performed under reduced pressure in order to prevent bubbles and voids from being formed between the copper foil and the substrate 1. Moreover, in order to suppress oxidation of copper foil, it is preferable to carry out under low oxygen conditions (for example, in nitrogen atmosphere). As a result, a modified layer is formed between the copper foil as the conductive layer 5 and the substrate 1, and the flexible printed wiring board substrate described above is obtained.

  As an upper limit of the temperature of the said thermocompression bonding, 600 degreeC is preferable and 500 degreeC is more preferable. On the other hand, the lower limit of the thermocompression bonding temperature is preferably the melting point of the fluororesin described above, and more preferably the decomposition start temperature of the fluororesin described above. More specifically, a temperature that is 30 ° C. higher than the melting point of the fluororesin that is the main component of the matrix of the substrate 1 is preferable, and a temperature that is 50 ° C. higher than the melting point of the fluororesin is more preferable. When the temperature of the thermocompression bonding exceeds the upper limit, there is a risk of causing unintended deformation during the production. Moreover, when the temperature of the said thermocompression bonding is less than the said minimum, there exists a possibility that sufficient adhesiveness may not be acquired between copper foil and the board | substrate 1. FIG.

  The reason why it is preferable to perform thermocompression bonding at a temperature equal to or higher than the melting point of the fluororesin during the thermocompression bonding is that the fluororesin is not activated at a temperature below the melting point. Moreover, since the C atom of the said fluororesin is radicalized by heating more than the decomposition start temperature of the said fluororesin, the said fluororesin can be further activated. That is, it is considered that the adhesion between the copper foil and the substrate 1 can be further promoted by setting the thermocompression bonding temperature to be equal to or higher than the melting point of the fluororesin (more preferably higher than the decomposition start temperature).

  The pressure for the thermocompression bonding is preferably 0.01 MPa or more and 1000 MPa or less. Further, the pressing time for the thermocompression bonding is preferably 5 seconds or more and 10 hours or less.

  By such thermocompression bonding, the radicalized C atom in the fluororesin is considered to be chemically bonded to the siloxane bond (Si—O—Si) formed by the silane coupling agent via another atom or atomic group. It is done.

<Flexible printed wiring board>
The flexible printed wiring board which concerns on one Embodiment of this invention is a flexible printed wiring board using the above-mentioned base material for flexible wiring boards, and is provided with the said conductive layer in which the pattern was formed. The conductive layer of the flexible printed wiring board is formed by etching into a pattern.

  The etching method is not particularly limited. For example, when a subtractive method is applied as the etching method, a flexible printed wiring board on which wiring is formed can be obtained by performing pattern masking and etching on the conductive layer. Other examples of the etching method include a semi-additive method.

[advantage]
Since the main component of the matrix of the substrate is a fluororesin, transmission loss when used in a high frequency region can be suppressed. Moreover, since the said board | substrate contains a reinforcing material in a matrix, intensity | strength and dimensional stability are securable. Further, since the substrate has a relative dielectric constant and a dielectric loss tangent at −40 ° C. or higher and 125 ° C. or lower and 10 GHz in the above range, the substrate has excellent transmission characteristics. In addition, since the substrate has a relative dielectric constant variation range and a dielectric loss tangent variation range of −40 ° C. or more and 125 ° C. or less and 10 GHz, the temperature dependence of electrical characteristics is small.

  Since the flexible printed wiring board base material includes the substrate, the temperature dependence of electrical characteristics is small and the transmission characteristics are excellent.

  Since the flexible printed wiring board includes the flexible printed wiring board base material, the temperature dependence of electrical characteristics is small and the transmission characteristics are excellent.

  The substrate manufacturing method can easily manufacture a substrate having less temperature dependence of electrical characteristics and excellent transmission characteristics.

[Other Embodiments]
The disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. The

  The substrate including the film-like or cloth-like reinforcing material of the above embodiment has a laminated structure of a layer not containing the reinforcing material and a layer containing the film-like or cloth-like reinforcing material. May be 2 or 4 or more. In addition, the substrate may include two or more film-like or cloth-like reinforcing materials as the reinforcing material. For example, the substrate may be a substrate having a two-layer structure of a reinforcing material layer and a layer not containing a reinforcing material by containing one film-like or cloth-like reinforcing material, or two or more films. It may be a substrate having a laminated structure of three or more layers by containing a reinforcing material in the form of a cross or a cloth.

  The substrate may include a reinforcing material other than a film-like or cloth-like reinforcing material. For example, the substrate may include a granular material such as inorganic particles and organic particles as a reinforcing material.

  The said board | substrate may contain a reinforcing material uniformly in the thickness direction, and may contain a reinforcing material biased in the thickness direction. The part in which the reinforcing material of the substrate containing the reinforcing material in the thickness direction is not particularly limited. The substrate containing the reinforcing material biased in the thickness direction may contain the reinforcing material in the middle of the thickness direction as in the above embodiment, or may contain the reinforcing material biased near the surface.

  The said board | substrate may contain a reinforcing material uniformly in a plane direction, and may contain a reinforcing material biased in a plane direction. That is, the region where the reinforcing material is present in plan view of the substrate may be the entire substrate or a part of the substrate.

  The substrate may have a modified layer on both sides. Further, the substrate does not have to have a modified layer. Further, the substrate may have a modified layer on the entire surface, or may have a modified layer on a part of the surface.

  Moreover, the said base material for flexible printed wiring boards may laminate | stack a conductive layer on one whole surface of a board | substrate, and may laminate | stack a conductive layer on a part of one side | surface of a board | substrate.

  Further, the substrate manufacturing method includes steps other than a step of superposing a resin film mainly composed of a fluororesin on both surfaces of a glass cloth or a resin cloth and a step of thermocompression bonding the superposed product while vacuum suctioning. Also good.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

[Example 1]
(Production of substrate)
The substrate of Example 1 was produced by the following procedure. First, FEP films (average thickness 50 μm) were superimposed on both surfaces of a glass cloth (IPC standard style 1030, average thickness 27 μm) to obtain a laminate. Next, this laminate was subjected to thermocompression bonding under vacuum suction at a temperature of 300 ° C., a pressure of 20 MPa, and a time of 120 minutes to obtain a substrate. This substrate had FEP impregnated inside the glass cloth.

(Preparation of flexible printed wiring board base material)
The base material for flexible printed wiring boards of Example 1 was produced according to the following procedure. First, a primer material was attached to a copper foil (electroless copper foil, average thickness 18 μm, ten-point average roughness Rz 0.6 μm) by an immersion method, then dried and heated at 120 ° C. Thereby, a primer material layer was formed on the copper foil. And the said board | substrate is laminated | stacked on the primer material adhesion side surface of the said copper foil so that this primer material layer may be pinched | interposed, and the obtained laminated body is thermocompression-bonded with a press machine, Between the said copper foil and the said board | substrate. A substrate for a flexible printed wiring board having a modified layer having an average thickness of 30 nm was obtained. The thermocompression bonding conditions were a temperature of 300 ° C., a pressure of 20 MPa, and a time of 120 minutes. As the primer material, a material containing 1% by mass of 3-aminopropyltrimethoxysilane and ethanol was used. Note that water is not added to the primer material. That is, as water, moisture present in the air and moisture as impurities contained in the ethanol were used.

[Example 2]
(Production of substrate)
The substrate of Example 2 was produced by the following procedure. First, PFA dispersion (liquid in which fine particles of PFA were dispersed in water) was applied to glass cloth (IPC standard style 1030, average thickness 27 μm), and the glass cloth was impregnated with PFA dispersion. Next, the glass cloth coated with the PFA dispersion was heated to 330 ° C., and the PFA dispersion was dried and melted. By repeatedly applying and baking a PFA dispersion on such a glass cloth, a substrate having an FEP surface layer having an average thickness of 30 μm on both surfaces of the glass cloth is obtained. It was.

(Preparation of flexible printed wiring board base material)
Using the substrate, a flexible printed wiring board substrate was obtained in the same procedure as in Example 1.

[Comparative Example 1]
A film having an average thickness of 100 μm was produced from ETFE (“EA-2000” manufactured by Asahi Glass Co., Ltd.), and this film was used as a substrate. Glass cloth was not used. Next, using this substrate, a flexible printed wiring board substrate was obtained in the same procedure as in Example 1.

[Comparative Example 2]
A fluororesin impregnated glass cloth (“TETLAS G-103” manufactured by Nippon Polymer Co., Ltd., average thickness of 80 μm, fluororesin: PTFE) was used as a substrate. Next, using this substrate, a flexible printed wiring board substrate was obtained in the same procedure as in Example 1.

[Evaluation]
The following items were evaluated for the substrates of Examples 1 and 2 and Comparative Examples 1 and 2 and the substrate for flexible printed wiring board.

(The relative dielectric constant at −40 ° C. to 125 ° C. and 10 GHz, and the dielectric loss tangent at −40 ° C. to 125 ° C. and 10 GHz)
With respect to the substrates of Examples 1 and 2 and Comparative Examples 1 and 2, the relative dielectric constant at −40 ° C. to 125 ° C. and 10 GHz, and the dielectric loss tangent at −40 ° C. to 125 ° C. and 10 GHz were measured. The measurement was performed under the conditions of a frequency of 10 GHz, a temperature of −40 ° C. to 125 ° C., and a relative humidity of 50% by a cavity resonator perturbation method based on JIS-C-2138 (2007). As a measuring device, a cylindrical cavity resonator was used. The measurement results of relative dielectric constant are shown in Table 1 and FIG. 3, and the measurement results of dielectric loss tangent are shown in Table 2 and FIG.

(Peel strength)
About the base material for flexible printed wiring boards of Examples 1 and 2 and Comparative Examples 1 and 2, JIS-K-6854-2 (1999) "Adhesive-peeling adhesive strength test method-2 part: 180 degree peeling. The peel strength (N / cm) between the substrate and the copper foil was measured by a test method conforming to

(Heat deformation)
Regarding the substrates for flexible printed wiring boards of Examples 1 and 2 and Comparative Examples 1 and 2, the temperature is 150 ° C. and the time is 30 minutes in accordance with “Dimensional stability” of JIS-C-6471 (1995). It was determined by measuring the dimensional change rate of the copper foil before and after heating at. The dimensional change rate was obtained from the following formula.
Dimensional change rate (%) = (absolute value of difference between distance between gauge points after heating and distance between gauge points before heating) / (distance between gauge points before heating) × 100

  As shown in Tables 1 to 3 and FIGS. 3 to 4, in Examples 1 and 2, the relative dielectric constant and the dielectric loss tangent are low and the relative dielectric constant change width and the dielectric loss tangent change width are also small. For this reason, Examples 1 and 2 are excellent in transmission characteristics and have little temperature dependence of electrical characteristics. Further, Comparative Example 1 has a larger variation width of dielectric loss tangent than Examples 1 and 2. For this reason, the comparative example 1 is inferior in the temperature dependence of an electrical characteristic compared with Example 1 and 2. FIG. Further, Comparative Example 2 has a large relative dielectric constant and dielectric loss tangent, and also has a large variation width of relative dielectric constant and dielectric loss tangent. For this reason, the comparative example 2 is inferior in an electrical property, and the electrical property deterioration by the temperature change has arisen. From these results, it can be seen that according to the present invention, the transmission characteristics are excellent and the temperature dependence of the electrical characteristics can be reduced.

  The substrate of the present invention has less temperature dependence of electrical characteristics and excellent transmission characteristics. For this reason, for example, it can be used suitably for portable equipment, such as an in-vehicle millimeter wave radar, a portable information device, and a portable communication terminal.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Fluororesin layer 2a Parts other than the reinforcement material of a fluororesin layer 3 Reinforcement material layer 4 Modification layer 5 Conductive layer 10 Base material for flexible printed wiring boards

Claims (13)

A substrate containing a matrix and a reinforcing material contained in the matrix, the main component of the matrix being a fluororesin,
The relative dielectric constant at −40 ° C. to 125 ° C. and 10 GHz is 2.6 or less, the dielectric loss tangent is 0.004 or less, the variation range of the relative dielectric constant is 0.0001 or more and 0.08 or less, and the variation range of the dielectric loss tangent is 0. A substrate having a thickness of 0.0001 to 0.002.   The substrate according to claim 1, wherein the reinforcing material is a glass cloth or a resin cloth, and is laminated in the middle in the thickness direction.   The said fluororesin contains the tetrafluoroethylene-hexafluoropropylene copolymer (FEP) or the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) 50 mass% or more of Claim 1 or Claim 2. substrate.   4. The substrate according to claim 1, wherein the content of the reinforcing material is 1 volume% or more and 50 volume% or less.   The substrate according to any one of claims 1 to 4, which has a modified layer containing a siloxane bond and a hydrophilic functional group on one surface. A substrate according to any one of claims 1 to 5,
A substrate for a flexible printed wiring board, comprising: a conductive layer laminated on one surface side of the substrate.   The flexible printed wiring board substrate according to claim 6, wherein the conductive layer is a copper foil.   The base material for flexible printed wiring boards according to claim 6 or 7, wherein a peel strength between the substrate and the conductive layer is 10 N / cm or more.   The base material for flexible printed wiring boards according to claim 6, wherein the heat deformability is 0.5% or less.   The flexible printed wiring board using the base material for flexible printed wiring boards of any one of Claims 6-9. A step of superposing a resin film mainly composed of a fluororesin on both sides of a glass cloth or a resin cloth;
A step of thermocompression bonding the superposed material while vacuum suction,
The obtained substrate has a relative permittivity of −40 ° C. or more and 125 ° C. or less and 10 GHz, a dielectric loss tangent of 0.004 or less, a relative dielectric constant variation of 0.0001 or more and 0.08 or less, A manufacturing method of a substrate whose change width is 0.00001 or more and 0.002 or less.   The method for manufacturing a substrate according to claim 11, wherein vacuum suction is started before the thermocompression bonding is started. Impregnating the surface and the inside of a glass cloth or a resin cloth with a composition containing a fluororesin as a main component;
Heating the impregnated composition, and
The obtained substrate has a relative permittivity of −40 ° C. or more and 125 ° C. or less and 10 GHz, a dielectric loss tangent of 0.004 or less, a relative dielectric constant variation of 0.0001 or more and 0.08 or less, A manufacturing method of a substrate whose change width is 0.00001 or more and 0.002 or less.

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