JP2017120826A - Substrate and base material for printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate and a base material for a printed wiring board, each having a superior transmission property of which the temperature dependence is small.SOLUTION: A substrate according to an embodiment of the present invention comprises: a first resin layer including a matrix having a liquid crystal polymer as a primary component; and a second resin layer laminated on at least one face of the first resin layer, and including a fluorine resin as a primary component. The substrate is 4.0 or less in relative permittivity at 30-120°C and 10 GHz, 0.0001-0.04 in the width of change in the relative permittivity, and 0.01 or less in dielectric dissipation factor. The fluorine resin may include a tetra fluoroethylene-hexafluoropropylene copolymer, a tetrafluoroethylene-perfluoro alkylvinylether copolymer or a combination thereof by 50 mass% or more. The substrate further comprises: a porous sheet in a lamellar region including opposing faces of the first and second resin layers. The porous sheet may include a liquid crystal polymer as a primary component.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a substrate and a printed wiring board substrate.

  In recent years, the amount of information communication has been increasing, and in order to meet this demand, communication in a high-frequency region such as microwaves and millimeter waves has become popular in devices such as IC cards, mobile phone terminals, and in-vehicle sensors.

  In a general printed wiring board, the transmission speed V and the transmission loss αd satisfy the following relationship (formula (a) and formula (b)) with the relative dielectric constant εr, the frequency f, and the 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 transmission characteristics with a substrate, it is necessary to suppress variations in relative dielectric constant and the like. However, it cannot be said that the conventional substrate described above can sufficiently control the relative dielectric constant and the like. .

  Furthermore, in communications in the high-frequency region, there is a need for a substrate with low temperature dependence of transmission characteristics for applications that use millimeter waves in mobile devices such as in-vehicle millimeter wave radars, portable information devices, and portable communication terminals. However, the conventional substrate using the fluororesin is not sufficient in this respect.

  The present invention has been made based on the above-described circumstances, and an object of the present invention is to provide a substrate and a substrate for a printed wiring board that have less temperature dependency of transmission characteristics and excellent transmission characteristics.

  In order to solve the above problems, a substrate according to one embodiment of the present invention is formed by laminating a first resin layer containing a matrix mainly composed of a liquid crystal polymer and at least one surface side of the first resin layer. And a second resin layer mainly composed of a fluororesin, wherein the relative dielectric constant at 30 to 120 ° C. and 10 GHz is 4.0 or less, and the variation range of the relative dielectric constant is 0.0001 to 0. 0.04 or less and dielectric loss tangent is 0.01 or less.

  A printed wiring board base material according to another aspect of the present invention, which has been made to solve the above problems, is laminated on the substrate and the surface of the substrate opposite to the first resin layer of the second resin layer. A conductive layer.

  The substrate and printed wiring board substrate of the present invention are excellent in 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 board | substrate of embodiment different from FIG. It is a typical sectional view showing the substrate for printed wiring boards of one embodiment of the present invention.

[Description of Embodiment of the Present Invention]
A substrate according to one embodiment of the present invention includes a first resin layer containing a matrix mainly composed of a liquid crystal polymer, and a first resin layer laminated on at least one surface side of the first resin layer, the fluororesin being a main component. A substrate having two resin layers, the relative dielectric constant at 30 to 120 ° C. and 10 GHz is 4.0 or less, the variation range of the relative dielectric constant is 0.0001 to 0.04, and the dielectric loss tangent is 0.2. 01 or less.

  Since the matrix includes the first resin layer whose main component is a liquid crystal polymer and the second resin layer whose main component is a fluororesin, the first resin layer reduces the temperature dependence of transmission characteristics, The second resin layer can reduce transmission loss when used for communication in a high frequency region. Further, the substrate has excellent transmission characteristics because the relative dielectric constant and dielectric loss tangent at 30 to 120 ° C. and 10 GHz are in the above ranges. Furthermore, since the change width of the relative permittivity is in the above range, the substrate has less temperature dependence of transmission characteristics.

  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 according to JIS-C-2138 (2007). is there. “Change width” means a difference obtained by subtracting the minimum value from the maximum value at 30 ° C. or more and 120 ° C. or less.

  The fluororesin preferably contains 50% by mass or more of tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), or a combination thereof. By including FEP or PFA as the main component of the second resin layer in this manner, it is possible to reduce the temperature dependence of the transmission characteristics while obtaining better transmission characteristics. This is presumably because FEP and PFA have a small degree of crystallinity and a small change in transmission characteristics due to a change in crystal structure.

  A porous sheet is preferably provided in a layered region including the opposing surfaces of the first resin layer and the second resin layer, and the main component of the porous sheet is preferably a liquid crystal polymer. Thus, by providing the porous sheet which has a liquid crystal polymer as a main component between a 1st resin layer and a 2nd resin layer, while maintaining a transmission characteristic favorable, it is the 1st resin layer and a 2nd resin layer. Bonding strength can be increased.

  The first resin layer may further contain a reinforcing material included in the matrix. Thus, intensity | strength and dimensional stability can be improved because a 1st resin layer contains a reinforcing material.

  The peel strength between the first resin layer and the second resin layer is preferably 5 N / cm or more. By setting the peel strength to the above lower limit or more, the bonding strength between the first resin layer and the second resin layer can be more reliably increased. Here, “peel strength” means peel strength obtained by a test method based on “Adhesive—Peel Adhesive Strength Test Method—Part 2: 180 ° Peel” of JIS-K-6854-2 (1999). Point to.

  The printed wiring board according to another aspect of the present invention includes the substrate and a conductive layer laminated on the surface of the substrate opposite to the first resin layer of the second resin layer. Since the printed wiring board base material includes the substrate, the temperature dependence of the transmission characteristics is small, and the conductive layer is laminated on the second resin layer side, so that 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.

[Details of the embodiment of the present invention]
Hereinafter, the board | substrate and printed wiring board base material which concern on this invention are demonstrated, referring drawings.

[First Embodiment of Substrate]
A substrate 1 shown in FIG. 1 includes a first resin layer 2 containing a matrix mainly composed of a liquid crystal polymer, and a first resin layer 2 laminated on at least one surface side of the first resin layer 2 and mainly composed of a fluororesin. 2 resin layers 3. The substrate 1 has a relative permittivity of 30 ° C. or more and 120 ° C. or less and a relative permittivity at 10 GHz of 4.0 or less, a change range of the relative permittivity of 0.0001 or more and 0.04 or less, and a dielectric tangent of 0.01 or less. Further, the substrate 1 includes a porous sheet 4 in a layered region including the opposing surfaces of the first resin layer 2 and the second resin layer 3.

  The substrate 1 can reduce the transmission loss when used for communication in the high frequency region by the second resin layer 3 while reducing the temperature dependence of the transmission characteristics by the first resin layer 2. Further, the substrate 1 has excellent transmission characteristics because the relative dielectric constant at 30 GHz to 120 ° C. and 10 GHz is in the above range. Further, since the substrate 1 has a change range of the relative dielectric constant in the above range, the temperature dependence of the transmission characteristics is small.

<First resin layer>
The matrix of the 1st resin layer 2 has a liquid crystal polymer (LCP) as a main component. The liquid crystal polymer includes a thermotropic type exhibiting liquid crystallinity in a molten state and a lyotropic type exhibiting liquid crystallinity in a solution state. In the present invention, it is preferable to use a thermotropic liquid crystal polymer.

  The liquid crystal polymer is, for example, an aromatic polyester obtained by synthesizing an aromatic dicarboxylic acid and a monomer such as an aromatic diol or an aromatic hydroxycarboxylic acid. A typical example is a polymer having structural units of the following formulas (1), (2) and (3) synthesized from parahydroxybenzoic acid (PHB), terephthalic acid and 4,4′-biphenol. A polymer having structural units of the following formulas (3) and (4) synthesized from PHB, terephthalic acid and ethylene glycol; a formula (2) synthesized from PHB and 2,6-hydroxynaphthoic acid; Examples thereof include polymers having the structural units (3) and (5).

  The liquid crystal polymer is not particularly limited as long as it exhibits liquid crystallinity, and the above-mentioned polymers are the main components (in the liquid crystal polymer, 50 mol% or more), and other polymers or monomers may be copolymerized. . The liquid crystal polymer may be a liquid crystal polyester amide, a liquid crystal polyester ether, a liquid crystal polyester carbonate, or a liquid crystal polyester imide.

  The liquid crystal polyester amide is a liquid crystal polyester having an amide bond, and examples thereof include a polymer having structural units of the following formula (6) and the above formulas (2) and (4).

  The liquid crystal polymer is preferably produced by melt polymerization of raw material monomers corresponding to the constituent units constituting the liquid crystal polymer, and solid-phase polymerization of the obtained polymer (prepolymer). Thereby, a high molecular weight liquid crystal polymer having high heat resistance, strength, rigidity and the like can be produced with good operability. Melt polymerization may be carried out in the presence of a catalyst. Examples of this catalyst include metal compounds such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide, And nitrogen-containing heterocyclic compounds such as 4- (dimethylamino) pyridine and 1-methylimidazole, and nitrogen-containing heterocyclic compounds are preferably used.

  The lower limit of the flow start temperature of the liquid crystal polymer is usually 250 ° C, more preferably 260 ° C. On the other hand, the upper limit of the flow start temperature of the liquid crystal polymer is preferably 350 ° C., more preferably 330 ° C. As the flow start temperature is higher, the heat resistance, strength, rigidity, etc. are more likely to be improved. However, if the flow start temperature is too high, the resin viscosity before molding is increased and the moldability may be lowered.

The flow start temperature is also called flow temperature or flow temperature, and the liquid crystal polymer is heated using a capillary rheometer at a rate of 4 ° C./min under a load of 9.8 MPa (100 kg / cm ² ). It is a temperature that shows a viscosity of 4800 Pa · s (48000 poise) when melted and extruded from a nozzle having an inner diameter of 1 mm and a length of 10 mm, and is a measure of the molecular weight of the liquid crystal polymer (Naoyuki Koide, “Liquid Crystal Polymer” -See "Synthesis / Molding / Application-", CMC Corporation, June 5, 1987, p. 95).

  The first resin layer 2 may contain components (arbitrary components) other than the liquid crystal polymer. Examples of the optional component include resins other than liquid crystal polymers, flame retardants, flame retardant aids, pigments, antioxidants, reflection imparting agents, masking agents, lubricants, processing stabilizers, plasticizers, and foaming agents. In this case, as an upper limit of content of the arbitrary component in the 1st resin layer 2, 20 mass% is preferable and 10 mass% is more preferable.

  The lower limit of the average thickness of the first resin layer 2 is preferably 1 μm and more preferably 10 μm. On the other hand, the upper limit of the average thickness of the first resin layer 2 is preferably 500 μm, and more preferably 100 μm. If the average thickness of the first resin layer 2 is smaller than the lower limit, the temperature dependency suppressing effect may be insufficient. Conversely, if the average thickness of the first resin layer 2 exceeds the above upper limit, the transmission loss reduction effect of the substrate 1 may be insufficient, or the thickness may be unnecessarily increased.

  The upper limit of the relative dielectric constant of the first resin layer 2 at 30 ° C. and 10 GHz is preferably 10, and more preferably 3.6. On the other hand, the lower limit of the relative dielectric constant is preferably 1.6, more preferably 2.5. 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. Moreover, when the said dielectric constant is less than the said minimum, there exists a possibility that the cost of the 1st resin layer 2 may become high unnecessarily.

<Second resin layer>
The 2nd resin layer 3 has a fluororesin as a main component. 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, hexafluoropropylene And thermoplastic fluororesin (THV) formed with three types of monomers, vinylidene fluoride, and fluoroelastomer. Moreover, the mixture and copolymer containing these compounds can also be used as the said fluororesin.

  Among these, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) is preferable as the fluororesin. Since these fluororesins are materials having a relatively low relative dielectric constant and low temperature dependence, the fluororesin of the second resin layer 3 should contain 50% by mass or more of FEP, PFA or a combination thereof. Thus, transmission loss can be further suppressed.

  More specifically, PTFE has a specific change in crystal structure at 19 ° C. and 30 ° C., resulting in a change in linear expansion coefficient and specific gravity, and a large change in electrical characteristics (for example, “Fluorine Resin Handbook” (Nikkan Kogyo Shimbun, 1990). Issue). 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. For this reason, it is estimated that PFA and FEP have little influence on changes in transmission characteristics and the like even if a specific change in crystal structure occurs. For this reason, compared with PTFE, PFA and FEP have a smaller variation width of transmission characteristics due to temperature changes, and the transmission characteristics are stable. That is, PFA and FEP have better temperature dependence of transmission characteristics than PTFE.

  The second resin layer 3 may contain components (arbitrary components) other than the fluororesin. As this optional component, for example, resins other than the above fluororesins, dielectric property imparting agents such as barium titanate and potassium titanate, thermal conductivity imparting agent, linear expansion coefficient suppressing agent, flame retardant, flame retardant aid, pigment, Antioxidants, reflection-imparting agents, masking agents, lubricants, processing stabilizers, plasticizers, foaming agents and the like can be mentioned. In particular, titanium compounds such as barium titanate, potassium titanate, and titanium dioxide are useful for controlling the dielectric constant and keeping the dielectric loss tangent at 0.01 or lower. In this case, as an upper limit of content of the arbitrary component in the 2nd resin layer 3, 50 mass% is preferable and 20 mass% is more preferable.

  The second resin layer 3 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 lower limit of the average thickness of the second resin layer 3 is preferably 1 μm and more preferably 5 μm. On the other hand, the upper limit of the average thickness of the second resin layer 3 is preferably 500 μm, and more preferably 200 μm. When the average thickness of the 2nd resin layer 3 is smaller than the said minimum, there exists a possibility that the reduction effect of a transmission loss may become inadequate. On the contrary, when the average thickness of the second resin layer 3 exceeds the upper limit, the temperature dependence of the transmission characteristics of the substrate 1 may be increased, and the thickness may be unnecessarily increased.

  The upper limit of the relative dielectric constant of the second resin layer 3 at 30 ° C. and 10 GHz is preferably 5.0 and more preferably 3.6. On the other hand, the lower limit of the relative dielectric constant is preferably 1.4, and more preferably 1.8. 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, there is a possibility that the circuit width cannot be sufficiently reduced when the circuit is provided by etching the substrate 1 on which the conductive layer is laminated in a pattern, and the strength may be lowered. .

<Porous sheet>
The porous sheet 4 is disposed in a layered region including the opposing surfaces of the first resin layer 2 and the second resin layer 3, and the main component is a liquid crystal polymer. That is, the surface of the first resin layer 2 on the second resin layer 3 side and the surface of the second resin layer 3 on the first resin layer 2 side are both present in the porous sheet 4. The substrate 1 is thus provided with the porous sheet 4 mainly composed of a liquid crystal polymer between the first resin layer 2 and the second resin layer 3, so that the first resin layer 2 and the second resin layer 3 are provided. The joint strength can be increased.

  As the liquid crystal polymer used for the main component of the porous sheet 4, the same liquid crystal polymer as that used for the matrix of the first resin layer 2 can be used. In particular, from the viewpoint of bonding strength and the like, the main components of the porous sheet 4 and the matrix of the first resin layer 2 are preferably the same type of resin.

  Further, at least a part of the first resin layer 2 and the second resin layer 3 may be impregnated in the porous sheet 4, and these layers may be in contact with each other inside the porous sheet 4. By setting it as such a structure, the reduction effect of a transmission loss and the improvement effect of joining strength can be accelerated | stimulated. In this case, the layered region in which the porous sheet 4 is disposed includes the interface between the first resin layer 2 and the second resin layer 3.

  When the main component of the matrix of the first resin layer 2 and the main component of the porous sheet 4 are the same, the first resin layer 2 may be integrated with the porous sheet 4 by impregnation and fusion. In this case, the porous sheet 4 includes a non-porous region in part (impregnated portion of the first resin layer 2).

  The porous sheet 4 is not particularly limited as long as the first resin layer 2 and the second resin layer 3 can be impregnated, but from the viewpoint of realizing a uniform bonding strength in the plane direction, a woven fabric (cloth), a knitted fabric, Nonwoven fabric is preferred.

  The lower limit of the average thickness of the porous sheet 4 is preferably 0.1 μm and more preferably 2 μm. On the other hand, the upper limit of the average thickness of the porous sheet 4 is preferably 100 μm, and more preferably 30 μm. If the average thickness of the porous sheet 4 is smaller than the lower limit, the bonding strength between the first resin layer 2 and the second resin layer 3 may not be sufficiently improved. Conversely, if the average thickness of the porous sheet 4 exceeds the above upper limit, the transmission loss reduction effect of the substrate 1 may be insufficient, or the thickness may be unnecessarily increased.

  As a minimum of the porosity of porous sheet 4, 1% is preferred and 20% is more preferred. On the other hand, the upper limit of the porosity of the porous sheet 4 is preferably 95% and more preferably 80%. If the porosity of the porous sheet 4 is smaller than the lower limit, the bonding strength between the first resin layer 2 and the second resin layer 3 may not be sufficiently improved. Conversely, even if the porosity of the porous sheet 4 exceeds the above upper limit, the bonding strength between the first resin layer 2 and the second resin layer 3 may not be sufficiently improved. The “porosity” means the ratio of the area occupied by the voids in the cross section in any direction of the porous sheet.

<Modified layer>
The substrate 1 may have a modified layer containing a siloxane bond (Si—O—Si) and a hydrophilic organic functional group on one surface (one surface of the second resin layer 3). Due to the modified layer, the surface of the substrate 1 on the modified layer side is rich in reactivity. Here, “rich in reactivity” includes large physical effects such as adhesiveness. That is, the surface of the modified layer is surface active. Moreover, since the modified layer 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 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 second resin layer 3. In this case, in the modified layer, 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, 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 atom of N atom, C atom, O atom, and S atom. And covalently bonded to the C atom of the fluororesin. 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.

  Further, the modified layer may contain two or more of these hydrophilic functional groups. Thus, by imparting hydrophilic functional groups having different properties to the modified layer, 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 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 second resin layer 3. The chemical bond between the silane coupling agent and the fluororesin may include a covalent bond, a hydrogen bond, or the like when it is constituted only by a covalent bond. 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 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 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 on the surface of a modified layer is not specifically limited. The contact angle can be controlled, for example, by adjusting the type and amount of the hydrophilic functional group. Here, the “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 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 is not removed. Here, “the modified layer is not removed” means 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 is provided. When the modified layer has the above-mentioned etching resistance, an etching solution penetrates between the conductive layer and the substrate 1 when the conductive layer of the printed wiring board substrate including the substrate 1 and the conductive layer is etched into a pattern. Therefore, it is possible to maintain good adhesion between the substrate 1 and the conductive layer. The etching resistance can be imparted to the modified layer by using, for example, the preferred silane coupling agent described above. In addition, the etching treatment may cause a microscopic portion showing hydrophobicity in the region where the modified layer is formed, but when the entire region has hydrophilicity, such a state is hydrophilic. It shall be maintained.

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

  The upper limit of the average thickness of the modified layer 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. 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, the transmission loss reducing function and the adhesion improving function can be exhibited in a balanced manner. The average thickness of the modified layer can be measured by, for example, X-ray spectroscopy.

<Properties of substrate>
The upper limit of the average thickness of the substrate 1 is preferably 2.7 mm, preferably 2.5 mm, and more preferably 2.2 mm. 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 30 ° C. to 120 ° C. and 10 GHz is 4.0, preferably 3.5, and more preferably 2.8. 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 30 ° C. to 120 ° C. and 10 GHz is 0.01, preferably 0.005, and more preferably 0.004. 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 30 GHz to 120 ° C. and 10 GHz of the substrate 1 is 0.04, 0.035 is preferable, and 0.03 is more preferable. 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. If the change width of the relative permittivity exceeds the upper limit, there is a risk of deterioration of transmission characteristics due to temperature changes. 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 30 GHz to 120 ° C. and 10 GHz of the substrate 1 is preferably 0.01, more preferably 0.005, and further preferably 0.0016. On the other hand, the lower limit of the change width of the dielectric loss tangent is preferably 0.00001, more preferably 0.00005, and further preferably 0.0001. When the variation width of the dielectric loss tangent exceeds the upper limit, there is a possibility that transmission characteristics are deteriorated due to a 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.

  The lower limit of the peel strength between the first resin layer 2 and the second resin layer 3 of the substrate 1 is preferably 5 N / cm, more preferably 10 N / cm, and even more preferably 12 N / cm. When the peeling strength is less than the lower limit, the bonding strength between the first resin layer 2 and the second resin layer 3 may not be sufficiently increased.

<Substrate manufacturing method>
The substrate 1 includes, for example, a first superimposing step of superposing a resin film mainly composed of a liquid crystal polymer on one surface of a porous sheet mainly composed of a liquid crystal polymer, and fluorine on the other surface of the porous sheet. It can be obtained by a production method comprising a second superposing step of superposing resin films mainly composed of a resin, and a step of thermocompression bonding the superposed material while vacuum suction.

(First overlay process)
In the first superimposing step, a first resin film containing a liquid crystal polymer as a main component is superposed on one surface of the porous sheet.

(Second overlay process)
In the second overlapping step, a second resin film containing a fluororesin as a main component is superimposed on the other surface of the porous sheet (the surface opposite to the overlapping surface of the first resin film). In addition, the order of a 1st superimposition process and a 2nd superimposition process is not ask | required.

(Thermo-compression process)
In the thermocompression bonding process, the superposed product obtained in the first superimposing process and the second 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 the lower limit of the thermocompression bonding temperature, the higher one of the flow start temperature of the liquid crystal polymer of the first resin layer and the melting point of the fluororesin of the second resin layer is preferable, and the flow start temperature of the liquid crystal polymer of the first resin layer and The higher one of the decomposition start temperatures of the fluororesin of the second resin layer is more preferable. More specifically, a temperature 30 ° C. higher than the flow start temperature of the liquid crystal polymer of the first resin layer and the melting point of the fluororesin of the second resin layer is preferable, and the flow start temperature of the liquid crystal polymer of the first resin layer and the second A temperature higher by 50 ° C. than the melting point of the fluororesin of the resin layer is more preferable. When the said temperature is less than the said minimum, there exists a possibility that a liquid crystal polymer and a fluororesin may not impregnate a porous sheet. Here, the “decomposition start temperature” refers to a temperature at which the fluororesin starts to thermally decompose.

  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 kPa, more preferably 1 kPa, and even more preferably 10 Pa. By setting the degree of vacuum to the upper limit or less, the first resin film and the second resin film can surely enter the voids of the porous sheet, 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.

  From the viewpoint of obtaining a more integrated substrate as a whole, it is preferable to start vacuum suction before the start of the thermocompression bonding.

[Second Embodiment of Substrate]
A substrate 11 shown in FIG. 2 includes a first resin layer 12 containing a matrix mainly composed of a liquid crystal polymer, and a first resin layer 12 laminated on at least one surface side of the first resin layer 12 and mainly composed of a fluororesin. 2 resin layers 3 and a porous sheet 4 disposed in a layered region including the opposing surfaces of the first resin layer 12 and the second resin layer 3. The substrate 11 has a relative dielectric constant of 2.6 or less and a relative dielectric constant variation of 0.0001 or more and 0.04 or less at 30 GHz to 120 ° C. and 10 GHz.

  Since the 2nd resin layer 3 and the porous sheet 4 of the said board | substrate 11 are the same as that of the board | substrate 1 of said 1st embodiment, description is abbreviate | omitted.

<First resin layer>
The 1st resin layer 12 contains the matrix which has a liquid crystal polymer as a main component, and the reinforcing material contained in this matrix. Specifically, the first resin layer 12 includes a pair of liquid crystal polymer layers 12a that do not contain a reinforcing material, and a reinforcing material layer 12b that is laminated between the pair of liquid crystal polymer layers 12a and contains a reinforcing material and a matrix. Have

  Since the first resin layer 12 contains a reinforcing material in the matrix, the substrate 11 can ensure strength and dimensional stability.

(Liquid crystal polymer layer)
The material of the liquid crystal polymer layer 12a can be the same as that of the first resin layer 2 of the first embodiment.

(Reinforcement layer)
The reinforcing material layer 12b is a layer including a matrix mainly composed of a liquid crystal polymer and 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 liquid crystal polymer layer 12a. However, the insulating property, the flow start temperature of the liquid crystal polymer, and the fluororesin of the second resin layer 3 are not limited. It is desirable to have heat resistance that does not melt and flow at the melting point, tensile strength equal to or higher than that of the liquid crystal polymer, and corrosion resistance. As such a reinforcing material, for example, a glass cloth formed of a glass cloth, a liquid crystal polymer-containing glass cloth in which such a glass cloth is impregnated with a liquid crystal polymer, a fluorine in which a glass cloth is impregnated with a fluororesin such as PFA Resin-containing glass cloth, metal cloth, ceramic cloth, polytetrafluoroethylene, polyetheretherketone, polyimide resin, resin cloth containing heat-resistant fibers formed of aramid, polytetrafluoroethylene, liquid crystal polymer, polyimide, polyamideimide, polybenzimidazole , Polyether ether ketone, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, thermosetting resin, heat-resistant film mainly composed of cross-linked resin, and the like can be used. As a weaving method of the resin cloth, a plain weave is preferable to make the first resin layer 12 thin, but a twill weave and a satin weave are preferable to make the first resin layer 12 bendable. In addition, a known weaving method can be applied.

  When the reinforcing material is a liquid crystal polymer-containing glass cloth, the liquid crystal polymer impregnated in the glass cloth may be a matrix of the first resin layer 12.

  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.

  As an upper limit of content of the reinforcing material in the 1st resin layer 12, 50 volume% is preferable with respect to the whole volume of the 1st resin layer 12, 40 volume% is more preferable, and 30 volume% is further more preferable. 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 said content exceeds the said upper limit, there exists a possibility of producing deterioration of a transmission characteristic with 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 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 the cost of a reinforcing material 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 the cost of a reinforcing material may become high. The linear expansion coefficient is a value measured according to JIS-K-7197 (2012).

  The upper limit of the ratio of the linear expansion coefficient of the reinforcing material to the linear expansion coefficient of the liquid crystal polymer in the reinforcing material layer 12b 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 upper limit, the occurrence of warpage on the substrate 11 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 12b is preferably 50 μm, more preferably 40 μm, and even 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 said board | substrate 11 cannot fully be improved or generation | occurrence | production of the curvature in the said board | substrate 11 cannot be suppressed effectively.

  The upper limit of the ratio of the average thickness of the reinforcing material layer 12b to the average thickness of one layer of the liquid crystal polymer layer 12a 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 11 may not be effectively suppressed.

  The pair of liquid crystal polymer layers 12a preferably have substantially the same thickness. If the thicknesses of the pair of liquid crystal polymer layers 12a are greatly different, the first resin layer 12 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 one liquid crystal polymer layer 12a 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 11 becomes large, and there is a possibility that the transmission loss cannot be sufficiently reduced or a sufficient transmission speed cannot be obtained.

  The first resin layer 12 is, for example, a manufacturing method comprising a step of impregnating a composition mainly composed of a liquid crystal polymer on the surface and inside of a glass cloth or a resin cloth, and a step of heating the impregnated composition, It can be obtained by a production method comprising a step of superposing a resin film containing a liquid crystal polymer as a main component on both surfaces of a glass cloth or a resin cloth and a step of thermocompression bonding the superposed product while vacuum suction. In the case of a manufacturing method for thermocompression bonding, the thermocompression bonding step can be made common with the above-described substrate manufacturing method.

[Substrates for printed wiring boards]
A printed wiring board substrate 10 shown in FIG. 3 includes a substrate 1 and a conductive layer 5 laminated on the surface of the second resin layer 3 of the substrate 1 opposite to the first resin layer 2. The conductive layer 5 may be directly laminated on the substrate 1 or may be laminated on the substrate 1 via another layer. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  Since the printed wiring board base material 10 includes the substrate 1, the temperature dependence of the transmission characteristics is small, and the conductive layer 5 is laminated on the second resin layer 3 side, so that the transmission characteristics are excellent. In addition, the said base material 10 for printed wiring boards can be used for the flexible printed wiring board which has flexibility, or the rigid (hard) printed wiring board which does not have flexibility.

(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, transmission 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 further 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 upper limit of the heat deformability of the printed wiring board substrate is preferably 0.5%, more preferably 0.3%, and still more preferably 0.2%. When the heat deformability exceeds the upper limit, it may be difficult to further reduce the temperature dependence of the transmission characteristics and further improve the dimensional stability. “Heat deformation” refers to 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). It is a value obtained by measuring. 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

<Method for producing substrate for printed wiring board>
An example of a preferable method for producing the printed wiring board substrate will be described by using a copper foil as the conductive layer 5. 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). Thereby, a modified layer is formed between the copper foil as the conductive layer 5 and the substrate 1, and the above-described substrate for a printed wiring board 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 second resin layer 3 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.

[Printed wiring board]
A printed wiring board according to an embodiment of the present invention is formed by etching the conductive layer into a pattern using the above-described substrate for printed wiring board.

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

[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 may include a plurality of second resin layers. For example, the board | substrate can be used as a base material for double-sided printed wiring boards by laminating | stacking a 2nd resin layer on both surfaces of one 1st resin layer.

  Moreover, the said board | substrate does not necessarily need to provide a porous sheet between the 1st resin layer and the 2nd resin layer, if the above-mentioned relative dielectric constant and its change width are realizable. Moreover, you may laminate | stack a 1st resin layer and a 2nd resin layer through sheets other than a porous sheet. Furthermore, you may use the porous sheet which has resin other than a liquid crystal polymer as a main component.

  Further, in the printed wiring board substrate, a conductive layer may be laminated on the entire one surface of the substrate, or a conductive layer may be laminated on a part of one surface of the substrate.

  In the substrate, when the first resin layer includes a film-like or cloth-like reinforcing material, the number of layers in the laminated structure of the layer not containing the reinforcing material and the layer containing the film-like or cloth-like reinforcing material is two. It may be 4 or more. In addition, the substrate may include two or more film-like or cloth-like reinforcing materials as the reinforcing material.

  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.

  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, a liquid crystal polymer non-woven fabric (Kuraray Co., Ltd. “Vecruz”, basis weight 9 g / m ² , average thickness after pressing 9 μm) is superimposed on both sides of a liquid crystal polymer film (average thickness 65 μm). In addition, a five-layer laminate in which FEP films (average thickness: 50 μm) were superimposed on the outer surfaces of the pair of porous sheets was obtained. Next, the laminate is subjected to thermocompression bonding under vacuum suction at a temperature of 320 ° C., a pressure of 100 MPa, and a time of 60 minutes, and a pair of porous sheets and a pair of second resin layers are provided on both surfaces of the first resin layer. A substrate was obtained. In this substrate, the porous sheet was impregnated with the liquid crystal polymer and FEP, and these were in contact with each other inside.

(Preparation of printed wiring board substrate)
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 copper foil is laminated | stacked so that this primer material layer may contact | abut on both surfaces (each surface of a pair of 2nd resin layer) of the board | substrate of Example 1, and the obtained laminated body is thermocompression-bonded with a press. Thereby, the base material for flexible printed wiring boards which has a modified layer with an average thickness of 30 nm between the said copper foil and the said board | substrate 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]
As a first resin layer, a pair of liquid crystal polymer films having an average thickness of 20 μm are superimposed on both sides of a glass cloth (IPC standard style 1030, average thickness 27 μm), and the outer surface of the liquid crystal polymer film is also coated with the weight of Example 1. A substrate was obtained in the same manner as in Example 1 except that a pair of different liquid crystal polymer nonwoven fabrics (weight per unit area: 14 g / m ² , average thickness after pressing: 14 μm) were superposed. Using this substrate, a flexible printed wiring board substrate was obtained in the same procedure as in Example 1.

[Example 3]
The average thickness of the pair of liquid crystal polymer films superimposed on both surfaces of the glass cloth inside the first resin layer was 40 μm. The average thickness of the second resin layer was 12 μm. Except this, a substrate was obtained in the same manner as in Example 2. Using this substrate, a flexible printed wiring board substrate was obtained in the same procedure as in Example 1.

[Example 4]
As the glass cloth inside the first resin layer, a glass cloth impregnated with PFA and barium titanate was used. Specifically, 5 mass% of barium titanate was mixed in a dispersion of PFA (“AD2CR” manufactured by Daikin), impregnated with glass cloth (IPC standard style 1030, average thickness 27 μm), and fired. A substrate was obtained in the same manner as in Example 3 except for this. Using this substrate, a substrate for a printed wiring board (a substrate for a buildup substrate for a multilayer board) was obtained in the same procedure as in Example 1.

[Comparative Example 1]
A three-layer laminate in which a pair of the FEP films were laminated on both surfaces of the liquid crystal polymer nonwoven fabric was thermocompression bonded under the same conditions as in Example 1 to obtain a substrate. Using this substrate, a flexible printed wiring board substrate was obtained in the same procedure as in Example 1.

[Comparative Example 2]
A three-layer laminate in which a pair of the FEP films were superimposed on both surfaces of the glass cloth was thermocompression bonded under the same conditions as in Example 1 to obtain a substrate. Using this substrate, a flexible printed wiring board substrate was obtained in the same procedure as in Example 1.

[Comparative Example 3]
Using the liquid crystal polymer film alone as a substrate, a flexible printed wiring board substrate was obtained using the substrate in the same procedure as in Example 1.

[Comparative Example 4]
A three-layer laminate in which a pair of the FEP films were superimposed on both surfaces of the liquid crystal polymer film was thermocompression bonded under the same conditions as in Example 1 to obtain a substrate. Using this substrate, a flexible printed wiring board substrate was obtained in the same procedure as in Example 1.

[Evaluation]
About the board | substrate of Examples 1-4 and Comparative Examples 1-4 and the base material for printed wiring boards, the following item was evaluated.

(Relative permittivity at 30 GHz to 120 ° C. and 10 GHz)
The relative dielectric constant of each substrate was measured under the conditions of a frequency of 10 GHz, a temperature of 30 ° C. to 120 ° C., and a relative humidity of 50% by a cavity resonator perturbation method based on JIS-C-2138 (2007). A cylindrical cavity resonator was used as the measuring device. The measurement results are shown in Table 1.

(Peel strength)
The first resin of the substrate of each flexible printed wiring board substrate by a test method in accordance with JIS-K-6854-2 (1999) "Adhesive-Peeling adhesive strength test method-2 parts: 180 degree peeling" The peel strength (N / cm) between the layer and the second resin layer was measured. The measurement results are shown in Table 1.

  As shown in Table 1, in Examples 1 to 4, the relative dielectric constants at 30 ° C. and 120 ° C. are both 4.0 or less, and the change width of the relative dielectric constant between these temperatures is 0.04 or less. Furthermore, the dielectric loss tangent at 30 ° C. and 120 ° C. is 0.01 or less. From these results, it is estimated that in Examples 1 to 4, the relative dielectric constant at 30 ° C. or higher and 120 ° C. or lower is 4.0 or lower, the relative dielectric constant variation is 0.04 or lower, and the dielectric loss tangent is 0.01 or lower. The Such Examples 1-4 are excellent in transmission characteristics, and have little temperature dependence of transmission characteristics.

  The substrate of the present invention has less temperature dependence of transmission 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, 11 Substrate 2, 12 1st resin layer 3 2nd resin layer 4 Porous sheet 5 Conductive layer 12a Liquid crystal polymer layer 12b Reinforcement material layer

Claims (7)

A first resin layer containing a matrix mainly composed of a liquid crystal polymer;
A substrate that is laminated on at least one surface side of the first resin layer and includes a second resin layer mainly composed of a fluororesin,
A substrate having a relative dielectric constant of not more than 4.0 at 30 ° C. or more and 120 ° C. or less, a relative dielectric constant of 0.0001 or more and 0.04 or less, and a dielectric loss tangent of 0.01 or less.   The said fluororesin contains the tetrafluoroethylene-hexafluoropropylene copolymer (FEP), the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), or these combination 50 mass% or more. substrate.   The substrate according to claim 1 or 2, wherein a porous sheet is provided in a layered region including the opposing surfaces of the first resin layer and the second resin layer, and a main component of the porous sheet is a liquid crystal polymer.   The substrate according to claim 1, wherein the first resin layer further contains a reinforcing material contained in the matrix.   The substrate according to any one of claims 1 to 4, wherein a peel strength between the first resin layer and the second resin layer is 5 N / cm or more. A substrate according to claim 1;
A printed wiring board substrate comprising: a conductive layer laminated on a surface of the substrate opposite to the first resin layer of the second resin layer.   The printed wiring board substrate according to claim 6, wherein the conductive layer is a copper foil.

Images