Film for circuit board, circuit board, transmission method, and method for manufacturing film for circuit board

Abstract

A film for a circuit board according to the present disclosure contains an intrinsic microporous polymer. The porosity of the film is, e.g., 15-50%. The average pore diameter of the pores in the film is, e.g., 0.3-6 nm. The thickness of the film is, e.g., 30 μm to 1.0 mm. A circuit board according to the present disclosure comprises an insulating layer containing an intrinsic microporous polymer. A transmission method according to the present disclosure allows transmission of a circuit-board high-frequency signal of the present disclosure. A method for manufacturing the film for a circuit board according to the present disclosure comprises: dissolving the intrinsic microporous polymer in a solvent to prepare a solution; applying the solution to a support to form a coating film; and removing the solvent from the coating film.

Description

Film for circuit board, circuit board, transmission method, and method for manufacturing film for circuit board

[0001] The present disclosure relates to a film for a circuit board, a circuit board, a transmission method, and a method for manufacturing a film for a circuit board.

[0002] Various porous polymer films or membranes have been proposed in which the dielectric constant is controlled by the porosity by making a substrate made of a polymer material porous. For example, Patent Document 1 discloses a film for a millimeter-wave antenna, which has a porosity of 70 vol% or more, an average pore size of 10 μm or less, and is made of a polymer selected from the group consisting of polyimide, polyetherimide, and fluorinated polyimide.

[0003] JP 2018-21171 A

[0004] M. Carta, RM Evans, M. Croad, Y. Rogan, JC Jansen, P. Bernardo, F. Bazzarelli, NB McKeown, “An Efficient Polymer Molecular Sieve for Membrane Gas Separations”, Science, 2013, Vol.339, p.303-307.Baisong Liu, Kok-Giap Haw, Chi Zhang, Guangli Yu, Jialu Li, Panpan Zhang, Shuying Li, Sheng Wu, Jiyang Li, Xiaoqin Zou, “Flexible films derived from PIM-1 with ultralow dielectric constants”, Microporous and Mesoporous Materials, 2020, Vol.294, p.109887.

[0005] The porous polymer film described in Patent Document 1 has a low relative dielectric constant but low mechanical strength.

[0006] The present disclosure provides a film for circuit boards and a circuit board suitable for improving mechanical strength while maintaining a low dielectric constant.

[0007] The circuit board films of the present disclosure comprise an intrinsically microporous polymer.

[0008] The circuit board of the present disclosure includes an insulating layer comprising a polymer of intrinsic microporosity.

[0009] According to the present disclosure, it is possible to provide a film for circuit boards and a circuit board suitable for improving mechanical strength while maintaining a low relative dielectric constant.

[0010] FIG. 1 is a cross-sectional view showing an example of a circuit board including a film for circuit boards according to Embodiment 1. FIG. 2 is a flowchart showing a method for manufacturing a film for circuit boards according to Embodiment 1. FIG. 3A is a cross-sectional view showing an example of a circuit board according to Modification 1. FIG. 3B is a partial enlarged view of FIG. 3A. FIG. 4 is a cross-sectional view showing an example of a circuit board according to Modification 2. FIG. 5 is a cross-sectional view showing an example of a circuit board according to Modification 3. FIG. 6 is a nitrogen gas adsorption isotherm for the polymer of intrinsic microporosity (PIM-1) of Example 1. FIG. 7 is a nitrogen gas adsorption isotherm for the polymer of intrinsic microporosity (PIM-SBI-TB) of Example 2.

[0011] (Knowledge Forming the Basis of the Present Disclosure) Next-generation mobile communication systems using wireless technologies, which are currently being researched and developed with the aim of practical application around 2030, are expected to use millimeter waves or terahertz waves, which have higher frequencies than current microwaves. Millimeter waves refer to radio waves with a wavelength of 1 mm to 10 mm and a frequency of 30 GHz to 300 GHz. Terahertz waves refer to radio waves with a wavelength of 3 mm to 30 μm and a frequency of 100 GHz to 10 THz. The use of high frequencies makes it possible to send high-quality or large-capacity data at high speed and with low power consumption. Next-generation mobile communication systems using high frequencies are expected to be used to cyberize society as a whole using cyber-physical systems (CPS), and to automate industries and services such as unmanned factories and fully autonomous driving using the IoT.

[0012] Conventionally, antennas used in mobile communication systems generally have a structure in which an array of antenna elements is formed on a resin or ceramic circuit board. However, when conventional antennas are used for communication in high-frequency bands such as millimeter waves or terahertz waves, dielectric loss increases and the straightness of radio waves decreases. The dielectric loss of a circuit board is proportional to the square root of the circuit board's relative permittivity, and the straightness of radio waves is proportional to the circuit board's relative permittivity. Therefore, reducing the relative permittivity of the circuit board is effective in suppressing the increase in dielectric loss of the antenna, increasing gain, and extending communication distance.

[0013] As an effective method for reducing the dielectric constant of a circuit board, various porous polymer films or membranes have been proposed, taking advantage of the fact that the dielectric constant of air is approximately 1.0, by making a substrate made of a polymer material porous, thereby controlling the dielectric constant through the porosity. For example, the millimeter-wave antenna film described in Patent Document 1 is a porous polymer film made of a polymer material in which fine pores are dispersed, and the dispersed formation of fine pores achieves a dielectric constant of 2.0 or less. However, the film has a problem of low mechanical strength. Furthermore, polyimide resins are easily hydrolyzed under alkaline conditions, which poses problems in terms of chemical stability, such as chemical resistance and plating processability.

[0014] Known methods for forming pores in substrates made of polymer materials include physical foaming and chemical foaming. Physical foaming involves dispersing a low-boiling solvent, such as a chlorofluorocarbon or hydrocarbon, as a foaming agent in a polymer material, followed by heating to remove the foaming agent, thereby obtaining a porous body. However, physical foaming involves environmental issues, such as the harmfulness of the foaming agent and ozone layer depletion. Furthermore, the pore diameter of the pores in porous bodies obtained by physical foaming is several tens of micrometers or larger. It is difficult to form a fine, uniform pore structure using physical foaming. Chemical foaming involves adding a foaming agent to a polymer material and using the gas generated by thermal decomposition to obtain a porous body. However, chemical foaming involves issues such as residual foaming agent residue after gas generation and contamination by corrosive gases.

[0015] Polymers of intrinsic microporosity (PIM) are known as polymer materials capable of forming porous bodies without using a blowing agent. Intrinsic microporous polymers have a rigid and distorted main chain skeleton, resulting in a large free volume and high gas permeability. Therefore, in recent years, various proposals have been made to apply intrinsic microporous polymers to gas separation membranes. For example, Non-Patent Document 1 describes that gas separation membranes produced using intrinsic microporous polymers exhibit excellent gas permeability. Furthermore, Non-Patent Document 2 describes that membranes of intrinsic microporous polymers produced by spin coating exhibit a low dielectric constant. However, the membrane described in Non-Patent Document 2 cannot be peeled off from the substrate and cannot be used alone. Furthermore, the membrane described in Non-Patent Document 2 leaves room for improvement in terms of achieving both a reduced dielectric constant and mechanical strength.

[0016] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using a film containing a polymer with inherent microporosity as a film for a circuit board, or by using an insulating layer containing a polymer with inherent microporosity as an insulating layer provided on a circuit board, and have arrived at the present invention.

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0018] (Embodiment 1) [Film for Substrate] FIG. 1 shows an example of a circuit board 100 including a film for circuit board according to embodiment 1. The circuit board 100 includes a wiring board 10, an antenna board 20, and a radio-frequency integrated circuit (RFIC) 30. The antenna board 20 is stacked on the wiring board 10. The RFIC 30 processes high-frequency signals. The circuit board 100 can transmit or send high-frequency signals output by the RFIC 30 from the antenna board 20, and can process high-frequency signals received by the antenna board 20 using the RFIC 30. Note that a circuit board 100 in which an antenna and an RFIC are integrated as shown in FIG. 1 is sometimes called an antenna-in-package (AiP). The circuit board 100 is mounted on a motherboard 50, which serves as a base, for use.

[0019] In this specification, "high frequency" means, for example, a frequency of 1 MHz or higher.

[0020] The circuit board 100 is typically an electronic circuit board that is mounted on a motherboard in a computer and on which an antenna element can be arranged. The circuit board 100 may also be a high-frequency circuit board that is intended to use high-frequency signals.

[0021] As shown in FIG. 1 , the wiring board 10 may include a core layer 11 and a wiring laminate 12 laminated on a first surface 11a of the core layer 11. The core layer 11 is an insulating layer. The wiring laminate 12 is disposed between the core layer 11 and the antenna substrate 20. The wiring laminate 12 includes a plurality of conductor layers 121. One or more insulating layers 122 are provided between the plurality of conductor layers 121. The wiring laminate 12 may be a build-up layer formed by alternately laminating the conductor layers 121 and the insulating layers 122 on the first surface 11a of the core layer 11, i.e., by build-up. The core layer 11 includes conductor layers 111 on the first surface 11a and the second surface 11b, and through holes 112 electrically connecting the first surface 11a and the second surface 11b. The conductor layers 121 and 111 are formed of copper foil. The inner surface of the through hole 112 is plated with copper.

[0022] The antenna substrate 20 includes an insulating layer 21 and an antenna element 22. The antenna element 22 is formed of copper foil. The antenna element 22 is provided on a first surface 21a of the insulating layer 21. The first surface 21a is the surface of the insulating layer 21 opposite to the surface (second surface 21b) of the insulating layer 21 facing the wiring stack 12. The antenna element 22 is electrically connected to the wiring substrate 10, for example, via a via hole (not shown) that penetrates the insulating layer 21 in the thickness direction. The antenna element 22 may be electrically connected to the wiring substrate 10 via a connecting portion (not shown). For example, solder, conductive resin, or the like may be used as the connecting portion. As shown in FIG. 1 , the antenna substrate 20 may include a plurality of antenna elements 22. The plurality of antenna elements 22 may form an array.

[0023] 1, the RFIC 30 is embedded in the core layer 11 and is electrically connected to the antenna substrate 20 via the conductor layer 121 of the wiring stack 12. However, the arrangement of the RFIC 30 is not limited to the example shown in FIG.

[0024] 1 , the circuit board 100 may be connected to an upper surface 50a of a motherboard 50 via a connection portion 40 provided on the second surface 11b of the core layer 11. The connection portion 40 electrically connects the circuit board 100 to the motherboard 50 and fixes the circuit board 100 to the motherboard 50. The connection portion 40 may be made of, for example, solder, conductive resin, or the like.

[0025] Although not shown in the figure, the circuit board 100 may further include a bonding film that bonds the core layer 11 and the wiring laminate 12 together, and / or a bonding film that bonds the wiring laminate 12 and the insulating layer 21 of the antenna substrate 20 together.

[0026] The film for circuit boards in the first embodiment can be applied to any of the core layer 11, the insulating layer 122 of the wiring laminated portion 12, the insulating layer 21 of the antenna substrate 20, and the bonding film.

[0027] The film for circuit boards in the first embodiment contains a polymer with intrinsic microporosity. A polymer with intrinsic microporosity has a rigid and distorted main chain skeleton, resulting in a large free volume. Therefore, the film for circuit boards can be a free-standing film with dispersed nanoscale pores. Such a film for circuit boards is suitable for improving mechanical strength while maintaining a low dielectric constant.

[0028] The film for circuit boards in the first embodiment may contain a polymer of intrinsic microporosity as a main component, for example, may consist essentially of a polymer of intrinsic microporosity. Here, "main component" refers to the component that is contained in the film for circuit boards in the largest amount by mass. "Consisting essentially of a polymer of intrinsic microporosity" means excluding other components that alter the essential characteristics of the referenced material. However, the film for circuit boards may contain inevitable impurities in addition to the polymer of intrinsic microporosity.

[0029] The dielectric constant Dk of the film for circuit boards in embodiment 1 is, for example, 2.5 or less at a frequency of 10 GHz and 25°C. The dielectric constant Dk of the film for circuit boards can be 2.4 or less, and even 2.3 or less. The lower limit of the dielectric constant Dk of the film for circuit boards is not particularly limited, and is, for example, 1.5 or more. A method for evaluating the dielectric constant Dk of the film for circuit boards will be described in the Examples section below.

[0030] The mechanical strength of the film for circuit boards in embodiment 1 can be evaluated, for example, based on the Young's modulus E of the film. The larger the Young's modulus E of a film, the higher the mechanical strength of the film can be determined to be. The Young's modulus E of the film for circuit boards is, for example, 110 MPa or more. The Young's modulus E of the film for circuit boards can be 120 MPa or more, or even 130 MPa or more. There is no particular upper limit for the Young's modulus E of the film for circuit boards, and it is, for example, 650 MPa or less. A method for evaluating the Young's modulus E of a film for circuit boards will be explained in the Examples section below.

[0031] The thickness T of the film for circuit boards in embodiment 1 is desirably 30 μm or more and 1.0 mm or less. When the thickness T is 30 μm or more, sufficient mechanical strength of the film is likely to be ensured. Furthermore, for example, when sufficient mechanical strength is ensured, the film formed on the support during the film manufacturing process is easy to peel off, and the film is less likely to be damaged when peeled off. A method for evaluating the thickness T of the film for circuit boards will be explained in the Examples section below.

[0032] The lower limit of the thickness T of the film for circuit boards may be 10 μm or more, 15 μm or more, or even 20 μm or more. The upper limit of the thickness T of the film for circuit boards may be 1.0 mm or less, 0.9 mm or less, or even 0.8 mm or less.

[0033] The porosity P of the film for circuit boards in embodiment 1 is desirably 15% or more and 50% or less. With such a configuration, a low relative dielectric constant of the film is easily achieved. A method for evaluating the porosity P of the film for circuit boards will be described in the Examples section below.

[0034] The lower limit of the porosity P may be 16% or more, 17% or more, or even 18% or more. The upper limit of the porosity P may be 45% or less, 40% or less, 35% or less, or even 30% or less.

[0035] The average pore diameter D of the pores in the film for circuit boards in embodiment 1 is desirably 0.3 nm or more and 6 nm or less. With such a configuration, sufficient mechanical strength of the film can be ensured and the thermal expansion coefficient of the film can be reduced. A film for circuit boards having a low thermal expansion coefficient is particularly suitable for use in the insulating layer 21 of the antenna substrate 20 on whose surface the antenna element 22 is disposed.

[0036] In addition, in order to reduce the thermal expansion coefficient of a film for circuit boards, inorganic fillers with low thermal expansion coefficients are generally mixed into the polymer material. However, because the filler itself has a high relative dielectric constant, mixing the filler raises the relative dielectric constant of the film. Therefore, it is desirable for the thermal expansion coefficient of the film itself to be as low as possible.

[0037] In the film for circuit boards according to the first embodiment, by controlling the average pore diameter D of the pores to be 0.3 nm or more and 6 nm or less, it is possible to achieve both a low relative dielectric constant and mechanical strength, and also to reduce the coefficient of thermal expansion. A method for evaluating the average pore diameter D of the pores in the film for circuit boards will be described in the Examples section below.

[0038] The lower limit of the average pore diameter D of the pores may be 0.5 nm or more, 1 nm or more, 1.5 nm or more, or even 2 nm or more. The upper limit of the average pore diameter D of the pores may be 5.5 nm or less, 5 nm or less, 4.5 nm or less, or even 4 nm or less.

[0039] The thermal expansion coefficient of the film for circuit boards in embodiment 1 is, for example, 40 ppm / °C or less. The thermal expansion coefficient of the film for circuit boards can be 38 ppm / °C or less, and even 35 ppm / °C or less. The lower limit of the thermal expansion coefficient of the film for circuit boards is not particularly limited, and is, for example, 100 ppm / °C or more. A method for evaluating the thermal expansion coefficient of the film for circuit boards will be described in the Examples section below.

[0040] The film for circuit boards in embodiment 1 has excellent heat resistance. The heat resistance of a film for circuit boards can be evaluated, for example, based on the glass transition temperature Tg of the film. The higher the glass transition temperature Tg of a film, the higher the heat resistance of the film can be determined. The glass transition temperature Tg of a film for circuit boards is, for example, 190°C or higher. The glass transition temperature Tg of a film for circuit boards can be 195°C or higher, or even 200°C or higher. The upper limit of the glass transition temperature Tg of a film for circuit boards is not particularly limited, and is, for example, 300°C or lower. A method for evaluating the glass transition temperature Tg of a film for circuit boards will be described in the Examples section below.

[0041] The film for circuit boards in embodiment 1 has excellent chemical stability. The chemical stability of the film for circuit boards can be evaluated, for example, by conducting a chemical resistance test in which the film is immersed in an aqueous hydrochloric acid solution (1 mol / L) and / or an aqueous sodium hydroxide solution (1 mol / L) and determining the weight change rate of the film before and after immersion. In the film for circuit boards in embodiment 1, the weight change rate after the test is, for example, 0.1% or less.

[0042] From the viewpoint of dielectric properties, the pores in the film for circuit boards may be closed pores or connected pores. However, from the viewpoint of substrate processability, it is desirable that the pores in the film for circuit boards be closed pores. For example, when holes are drilled with a drill or laser or the like and then copper plating is performed during the manufacturing process of the antenna substrate 20, if the pores are closed pores, the plating liquid is less likely to penetrate into the interior of the antenna substrate 20, thereby suppressing copper deposition due to the plating liquid. Furthermore, if the pores are closed pores, for example, when a low-dielectric film is bonded to the wiring substrate 10, the closed pores can be prevented from being crushed by heat pressing.

[0043] The polymer of intrinsic microporosity contained in the film for circuit boards in embodiment 1 has a rigid and distorted main chain skeleton. The polymer of intrinsic microporosity desirably has a rigid and twisted three-dimensional structure that can suppress entanglement of the main chain skeleton. Examples of polymers of intrinsic microporosity having such a three-dimensional structure include those containing repeating units having an aromatic ring and a spiro ring. That is, the polymer of intrinsic microporosity may contain repeating units having an aromatic ring and a spiro ring. A film for circuit boards containing such a polymer of intrinsic microporosity is suitable for improving mechanical strength while maintaining a low dielectric constant.

[0044] From the viewpoint of ease of production, it is desirable that the polymer of intrinsic microporosity contained in the film for circuit boards is soluble in a solvent, so that the film for circuit boards can be produced as a coating film by, for example, a drop casting method.

[0045] The repeating unit may be represented by the following formula (1) or (2): In formula (1) and formula (2), R to R 12 each independently contains at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I, and Br.

[0046] The polymer of intrinsic microporosity containing the repeating unit represented by formula (1) or (2) has a rigid main chain structure for forming nanoscale pores and a spiro ring structure that exhibits a twisted three-dimensional structure. The film for circuit board containing the polymer of intrinsic microporosity containing the repeating unit is suitable for improving mechanical strength while maintaining a low dielectric constant.

[0047] The intrinsically microporous polymer containing the repeating unit represented by formula (1) or formula (2) can be formed into a film on a resin support such as a release film or a PET film, or a metal support such as a copper foil, and can form dispersed nanoscale pores by applying a coating solution without using a foaming agent.

[0048] The polymer of intrinsic microporosity may contain a repeating unit represented by formula (1) or formula (2) as a major component, for example, may consist essentially of a repeating unit represented by formula (1) or formula (2). Here, "major component" refers to the component that is contained in the polymer of intrinsic microporosity in the largest amount by mass. "Consisting essentially of a repeating unit represented by formula (1) or formula (2)" means excluding other components that alter the essential characteristics of the referenced material.

[0049] In formulas (1) and (2), R to R 12 may each independently be a hydrogen atom, a halogen atom, an alkyl group, a halogenated alkyl group, an unsaturated hydrocarbon group, a hydroxy group, a carboxy group, an alkoxycarbonyl group, an acyl group, an amide group, a nitrile group, an alkoxy group, an acyloxy group, a thiol group, an alkylthio group, a sulfonic acid group, an acylthio group, an alkylsulfonyl group, a sulfonamide group, a primary amino group, a secondary amino group, a tertiary amino group, or a nitro group. 12 may each independently be a hydrogen atom, a halogen atom, an alkyl group, a halogenated alkyl group, an unsaturated hydrocarbon group, a hydroxy group, a carboxy group, an alkoxycarbonyl group, an acyl group, an amide group, a nitrile group, an alkoxy group, an acyloxy group, a thiol group, an alkylthio group, a sulfonic acid group, an acylthio group, an alkylsulfonyl group, a sulfonamide group, a primary amino group, a secondary amino group, or a nitro group.12 may each independently be a hydrogen atom, a halogen atom, an alkyl group, a halogenated alkyl group, an unsaturated hydrocarbon group, a carboxy group, an alkoxycarbonyl group, an acyl group, an amide group, a nitrile group, an alkoxy group, an acyloxy group, a thiol group, an alkylthio group, a sulfonic acid group, an acylthio group, an alkylsulfonyl group, a sulfonamide group, a primary amino group, a secondary amino group, or a nitro group.

[0050] Examples of halogen atoms include F, Cl, Br, and I.

[0051] The number of carbon atoms in the alkyl group is not particularly limited and is, for example, 1 to 20. From the viewpoint of easily synthesizing the polymer of intrinsic microporosity, the number of carbon atoms in the alkyl group may be 1 to 10 or 1 to 5. The solubility of the polymer of intrinsic microporosity in a solvent can be adjusted by adjusting the number of carbon atoms in the alkyl group. The alkyl group may be linear, branched, or cyclic. At least one hydrogen atom contained in the alkyl group may be substituted with a group containing at least one atom selected from the group consisting of N, O, P, and S. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a 2-methylbutyl group, a pentyl group, a hexyl group, a 2,3-dimethylhexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an eicosyl group, a 2-methoxybutyl group, and a 6-methoxyhexyl group.

[0052] A halogenated alkyl group refers to a group in which at least one hydrogen atom contained in an alkyl group is substituted with a halogen atom. The halogenated alkyl group may be a group in which all hydrogen atoms contained in the alkyl group are substituted with halogen atoms. Examples of the alkyl group include those mentioned above. A specific example of a halogenated alkyl group is —CF3.

[0053] The unsaturated hydrocarbon group contains an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond. The number of unsaturated bonds contained in the unsaturated hydrocarbon group is, for example, 1 to 5. The number of carbon atoms in the unsaturated hydrocarbon group is not particularly limited and is, for example, 2 to 20, or alternatively 2 to 10, or alternatively 2 to 5. The unsaturated hydrocarbon group may be linear, branched, or cyclic. At least one hydrogen atom contained in the unsaturated hydrocarbon group may be substituted with a group containing at least one atom selected from the group consisting of N, O, P, and S. Examples of unsaturated hydrocarbon groups include a vinyl group and an ethynyl group.

[0054] A hydroxy group is represented by -OH, a carboxy group is represented by -COOH, and an alkoxycarbonyl group is represented by -COOR. a The acyl group is represented by -COR b The amide group is represented by -CONR c R d The nitrile group is represented by -CN. The alkoxy group is represented by -OR e The acyloxy group is represented by -OCOR f A thiol group is represented by -SH. An alkylthio group is represented by -SR g A sulfonic acid group is represented by -SO3H. An acylthio group is represented by -SCOR h The alkylsulfonyl group is represented by -SO2R i The sulfonamide group is represented by -SONR j R k A primary amino group is represented by -NH2. A secondary amino group is represented by -NHR l The tertiary amino group is represented by -NR m R n The nitro group is represented by —NO2. a From R n are each independently an alkyl group. Examples of the alkyl group include those mentioned above. However, the R c , R of the amide group d , R of the sulfonamide group j and R of the sulfonamide groupk may be, independently of each other, a hydrogen atom.

[0055] Specific examples of alkoxycarbonyl groups are -COOCH3, -COO(CH2)3CH3, and -COO(CH2)7CH3. Specific examples of acyl groups are -COCH3. Specific examples of amido groups are -CONH2. Specific examples of alkoxy groups are methoxy, ethoxy, 2-methoxyethoxy, butoxy, 2-methylbutoxy, 2-methoxybutoxy, 4-ethylthiobutoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy, tetradecyloxy, pentadecyloxy, hexadecyloxy, heptadecyloxy, octadecyloxy, nonadecyloxy, and eicosyloxy. Specific examples of acyloxy groups are -OCOCH3. A specific example of an alkylthio group is -SCH3. A specific example of an acylthio group is -SCOCH3. A specific example of an alkylsulfonyl group is -SO2CH3. A specific example of a sulfonamide group is -SO2NH2. A specific example of a tertiary amino group is -N(CH3)2.

[0056] The repeating unit may be represented by the following formula (3) or (4):

[0057] A film for circuit boards containing a polymer with intrinsic microporosity that includes a repeating unit represented by formula (1) or formula (2) is suitable for improving mechanical strength while maintaining a low dielectric constant.

[0058] The polymer of intrinsic microporosity composed of repeating units represented by formula (3) is called PIM-1.

[0059] The polymer of intrinsic microporosity composed of repeating units represented by formula (4) is called PIM-SBI-TB.

[0060] The film for circuit boards in Embodiment 1 may further contain an inorganic filler. By mixing an inorganic filler, the thermal expansion coefficient of the film for circuit boards can be reduced.

[0061] The film for circuit boards in the first embodiment can be suitably used for antennas that are expected to use high frequency signals.

[0062] The film for circuit boards in the first embodiment can also be regarded as an insulating layer containing an intrinsic microporous polymer.

[0063] [Method for Manufacturing Film for Circuit Boards] The film for circuit boards in the first embodiment can be manufactured by, for example, the drop casting method described below.

[0064] 2 is a flowchart showing a method for producing a film for circuit boards in Embodiment 1. The method for producing a film for circuit boards includes, for example, dissolving an intrinsic microporous polymer in a solvent to prepare a solution (step S1), applying the solution to a support to form a coating film (step S2), and removing the solvent from the coating film (step S3).

[0065] In step S1, a solution is prepared by dissolving a polymer of intrinsic microporosity in a solvent, such as an organic solvent such as chloroform or toluene. In step S1, an inorganic filler may be further added to the solvent, if necessary.

[0066] In step S2, the solution is applied onto a resin support such as a PET film or a metal support such as a copper foil, and formed into a sheet or film, thereby forming a coating film.

[0067] In step S3, the coating film is heated and dried to remove the solvent from the coating film. The heater temperature for heating the coating film can be set appropriately within a range of, for example, 100° C. to 200° C. The heating time for the coating film can be set appropriately within a range of, for example, 1 hour to 12 hours.

[0068] By peeling the dried coating film from the support, a film for circuit boards having nanoscale pores can be obtained.

[0069] (Embodiment 2) [Circuit Board] Circuit board 100 in embodiment 2 includes an insulating layer containing a polymer of intrinsic microporosity. This insulating layer corresponds to the film for circuit board in embodiment 1, and therefore a detailed description thereof will be omitted. Because circuit board 100 includes an insulating layer containing a polymer of intrinsic microporosity, it is suitable for improving mechanical strength while maintaining a low dielectric constant.

[0070] The insulating layer containing the intrinsic microporous polymer can be applied to any of the core layer 11 provided in the circuit board 100 in embodiment 2, the insulating layer 122 of the wiring stack 12, the insulating layer 21 of the antenna substrate 20, and the bonding film.

[0071] 1, the circuit board 100 may further include an antenna element 22 capable of transmitting high-frequency signals. The circuit board 100 may have a plurality of antenna elements 22. The plurality of antenna elements 22 may form an array. A circuit board having such a configuration is suitable for use in an antenna that is expected to use high-frequency signals.

[0072] A circuit board having an insulating layer containing an intrinsic microporous polymer corresponding to the film for circuit boards of embodiment 1 is not limited to the circuit board 100 shown in FIG. 1 . The film for circuit boards of embodiment 1 is suitable for improving mechanical strength while maintaining a low dielectric constant, and therefore can be suitably used, for example, as an insulating layer for a multilayer printed wiring board. Furthermore, the film for circuit boards of embodiment 1 can be suitably used as an insulating layer for forming wiring portions by plating, for example, as an insulating layer for a multilayer printed wiring board in which wiring portions are formed by plating. Furthermore, the film for circuit boards of embodiment 1 can be suitably used as an insulating layer for forming a build-up layer of a multilayer printed wiring board.

[0073] Modified examples of the circuit board will be described below. In the following, elements common to the circuit board 100 shown in FIG. 1 will be denoted by the same reference numerals and the description thereof will be omitted.

[0074] (Modification 1) Fig. 3A is a cross-sectional view showing an example of a circuit board 200 in Modification 1. Fig. 3B is an enlarged view of part IIIB in Fig. 3A. The circuit board 200 includes an insulating layer containing a polymer with intrinsic microporosity, and is therefore suitable for improving mechanical strength while maintaining a low dielectric constant.

[0075] The circuit board 200 includes a package substrate 15 and a semiconductor chip 35. The semiconductor chip 35 includes active elements such as transistors and diodes. The active elements of the semiconductor chip 35 are connected to the circuitry of the package substrate 15. The package substrate 15 may include a core layer 151 and a pair of buildup layers 152 that sandwich the core layer 151 from above and below. The pair of buildup layers 152 form the first surface 15a and the second surface 15b of the package substrate 15. Each buildup layer 152 includes multiple insulating layers 152a and multiple wiring portions 152b. The core layer 151 has through holes 151a. The circuit board 200 shown in FIG. 3A is sometimes called an FC-BGA (Flip Chip-Ball-Grid Array) substrate. The circuit board 200 is mounted on a motherboard 50, which serves as its base, for use.

[0076] 3A and 3B , the package substrate 15 has a core layer 151 and a pair of buildup layers 152 that sandwich the core layer 151 from above and below. However, the package substrate 15 may be a so-called coreless substrate that does not have the core layer 151. In other words, the package substrate 15 may be composed of only the buildup layers 152.

[0077] As shown in FIG. 3A , the semiconductor chip 35 may be connected to the first surface 15a of the package substrate 15 via a first connection portion 40a provided on the first surface 15a of the package substrate 15. The first connection portion 40a electrically connects the semiconductor chip 35 to the package substrate 15 and fixes the semiconductor chip 35 to the package substrate 15. For example, solder, a conductive resin, or the like may be used as the first connection portion 40a. A first sealing resin 60a may be filled in the gap between the semiconductor chip 35 and the package substrate 15. A second sealing resin 60b may be molded to cover the semiconductor chip 35, further sealing the semiconductor chip 35. For example, a resin composition containing an epoxy resin and a curing agent may be used as the first sealing resin 60a and the second sealing resin 60b.

[0078] 3A , the circuit board 200 may be connected to the upper surface 50a of the motherboard 50 via a second connection portion 40b provided on the second surface 15b of the package substrate 15. The second connection portion 40b electrically connects the circuit board 200 to the motherboard 50 and also fixes the circuit board 200 to the motherboard 50. For example, solder, conductive resin, etc. may be used as the second connection portion 40a.

[0079] The insulating layer containing a polymer of intrinsic microporosity can be applied to the insulating layer 152a of the package substrate 15 included in the circuit board 200 in Modification 1. That is, the insulating layer containing a polymer of intrinsic microporosity may be the insulating layer 152a of the package substrate 15. Since the insulating layer containing a polymer of intrinsic microporosity is suitable for improving mechanical strength while maintaining a low dielectric constant, applying it as the insulating layer 152a of the package substrate 15 can minimize signal attenuation in the circuit board 200. This enables high-speed signal transmission.

[0080] 4 is a cross-sectional view showing an example of a circuit board 300 according to Modification 2. The circuit board 300 includes an insulating layer containing an intrinsic microporous polymer, and is therefore suitable for improving mechanical strength while maintaining a low dielectric constant.

[0081] The circuit board 300 includes two or more semiconductor chips 35 and further includes an intermediate layer 16 between the package substrate 15 and the semiconductor chips 35. Active elements of the two or more semiconductor chips 35 are connected to the circuit of the intermediate layer 16. The intermediate layer 16 is connected to the package substrate 15. The intermediate layer 16 includes an insulating layer 161 and a wiring portion 162 that electrically connects the two or more semiconductor chips 35 to the package substrate 15. Except for these, the circuit board 300 has the same configuration as the circuit board 200 shown in FIG. 3A. For the configuration of the package substrate 15 of the circuit board 300, refer to FIG. 3B. The intermediate layer 16 is sometimes called an organic interposer or an RDL interposer. The circuit board 300 shown in FIG. 4 is sometimes called a 2D or 3D package. The circuit board 300 is mounted on a motherboard 50 as a base for use.

[0082] 4 , two or more semiconductor chips 35 may be connected to the first surface 16a of the intermediate layer 16 via first connection portions 40a provided on the first surface 16a of the intermediate layer 16. The first connection portions 40a electrically connect the semiconductor chips 35 to the intermediate layer 16 and fix the semiconductor chips 35 to the intermediate layer 16. A first sealing resin 60a may be filled in each gap between the two or more semiconductor chips 35 and the intermediate layer 16. A second sealing resin 60b may be molded to cover the two or more semiconductor chips 35, further sealing the two or more semiconductor chips 35.

[0083] 4 , the intermediate layer 16 may be connected to the first surface 15a of the package substrate 15 via a third connection portion 40c provided on the first surface 15a of the package substrate 15. The third connection portion 40c electrically connects the intermediate layer 16 to the package substrate 15 and fixes the intermediate layer 16 to the package substrate 15. For example, solder, a conductive resin, or the like may be used as the third connection portion 40c. The gap between the intermediate layer 16 and the package substrate 15 may be filled with a third sealing resin 60c. For example, the resin compositions described for the first sealing resin 60a and the second sealing resin 60b may be used as the third sealing resin 60c.

[0084] 4 , the circuit board 300 may be connected to the upper surface 50a of the motherboard 50 via a second connection portion 40b provided on the second surface 15b of the package substrate 15. The second connection portion 40b electrically connects the circuit board 200 and the motherboard 50 and also fixes the circuit board 300 to the motherboard 50.

[0085] The insulating layer containing a polymer of intrinsic microporosity can be applied to both the insulating layer 152a of the package substrate 15 and the insulating layer 161 of the intermediate layer 16 included in the circuit board 300 in Modification 2. That is, the insulating layer containing a polymer of intrinsic microporosity may be at least one selected from the group consisting of the insulating layer 152a of the package substrate 15 and the insulating layer 161 of the intermediate layer 16. Since the insulating layer containing a polymer of intrinsic microporosity is suitable for improving mechanical strength while maintaining a low dielectric constant, applying it as the insulating layer 152a of the package substrate 15 and / or the insulating layer 161 of the intermediate layer 16 can minimize signal attenuation in the circuit board 300. This enables high-speed signal transmission.

[0086] 5 is a cross-sectional view showing an example of a circuit board 400 according to Modification 3. The circuit board 400 includes an insulating layer containing an intrinsic microporous polymer, and is therefore suitable for improving mechanical strength while maintaining a low dielectric constant.

[0087] The circuit board 400 includes a redistribution layer 17 and a semiconductor chip 35. Active elements of the semiconductor chip 35 are connected to the circuit of the redistribution layer 17. The redistribution layer 17 includes an insulating layer 171 and a wiring portion 172 that is electrically connected to the semiconductor chip 35. The circuit board 400 shown in FIG. 5 is sometimes called a wafer level package (WLP), a panel level package (PLP), or the like. The circuit board 400 is mounted on a motherboard 50 that serves as a base when in use.

[0088] 5, a second sealing resin 60b may be molded to cover the semiconductor chip 35, thereby sealing the semiconductor chip 35. The semiconductor chip 35 may be fixed to the rewiring layer 17 by the second sealing resin 60b.

[0089] 5 , the circuit board 400 may be connected to the upper surface 50a of the motherboard 50 via second connection portions 40b provided on the second surface 17b of the redistribution layer 17. The second connection portions 40b electrically connect the circuit board 400 and the motherboard 50 and also fix the circuit board 400 to the motherboard 50.

[0090] The insulating layer containing the polymer of intrinsic microporosity can be applied to the insulating layer 171 of the redistribution layer 17 included in the circuit board 400 in Modification 3. That is, the insulating layer containing the polymer of intrinsic microporosity may be the insulating layer 171 of the redistribution layer 17. Since the insulating layer containing the polymer of intrinsic microporosity is suitable for improving mechanical strength while maintaining a low dielectric constant, applying it as the insulating layer 171 of the redistribution layer 17 can minimize signal attenuation in the circuit board 400. This enables high-speed signal transmission.

[0091] [Transmission Method of Circuit Board] The circuit boards 100, 200, 300, and 400 according to the second embodiment satisfy both the low dielectric constant and mechanical strength required for circuit boards used in next-generation mobile communication systems. Therefore, the circuit boards 100, 200, 300, and 400 are suitable for a transmission method that includes transmitting high-frequency signals.

[0092] The transmission method of the circuit boards 100, 200, 300, and 400 includes transmitting a high-frequency signal through the circuit board, which allows the circuit board to transmit a high-frequency signal.

[0093] (Other Embodiments) (Additional Notes) The above description of the embodiments discloses the following techniques.

[0094] (Technology 1) A film for circuit boards, comprising an intrinsically microporous polymer.

[0095] The film for circuit boards of Technology 1 is suitable for improving mechanical strength while maintaining a low relative dielectric constant.

[0096] (Technology 2) The film for circuit boards according to Technology 1, wherein the porosity of the film is 15% or more and 50% or less. With this configuration, a low relative dielectric constant of the film is easily achieved.

[0097] (Technology 3) The film for circuit boards according to Technology 1 or 2, wherein the average pore size of the pores in the film is 0.3 nm or more and 6 nm or less. With this configuration, in addition to achieving both a low relative dielectric constant and mechanical strength, the thermal expansion coefficient can be reduced.

[0098] (Technology 4) The film for circuit boards according to any one of Technologies 1 to 3, wherein the film has a thickness of 30 μm or more and 1.0 mm or less. With this configuration, sufficient mechanical strength of the film is easily ensured.

[0099] (Technology 5) The film for circuit boards according to any one of Technologies 1 to 4, wherein the polymer of intrinsic microporosity contains a repeating unit having an aromatic ring and a spiro ring. A film for circuit boards having such a configuration is suitable for improving mechanical strength while maintaining a low dielectric constant.

[0100] (Technology 6) The film for circuit boards according to any one of Technologies 1 to 5, wherein the repeating unit is represented by the following formula (1) or the following formula (2): A film for circuit boards having such a configuration is suitable for improving mechanical strength while maintaining a low relative dielectric constant. [In formula (1) and formula (2), R to R 12 each independently contains at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I, and Br.

[0101] (Technology 7) The film for circuit boards according to Technology 6, wherein the repeating unit is represented by the following formula (3) or the following formula (4): A film for circuit boards having such a configuration is suitable for improving mechanical strength while maintaining a low relative dielectric constant.

[0102] (Technology 8) The film for circuit boards according to any one of Technologies 1 to 7, further comprising an inorganic filler. With this configuration, the thermal expansion coefficient of the film for circuit boards can be reduced.

[0103] (Technology 9) A circuit board comprising an insulating layer containing an intrinsic microporous polymer.

[0104] The circuit board of Technology 9 is suitable for improving mechanical strength while maintaining a low relative dielectric constant.

[0105] (Technology 10) A circuit board according to Technology 9, comprising a package substrate and a semiconductor chip, wherein the insulating layer is at least one selected from the group consisting of an insulating layer included in the package substrate and an insulating layer included in an intermediate layer located between the semiconductor chip and the package substrate. A circuit board having such a configuration is suitable for improving mechanical strength while maintaining a low dielectric constant.

[0106] (Technology 11) The circuit board according to Technology 9, comprising a redistribution layer and a semiconductor chip, wherein the insulating layer is an insulating layer of the redistribution layer. A circuit board having such a configuration is suitable for improving mechanical strength while maintaining a low dielectric constant.

[0107] (Technology 12) The circuit board according to any one of Technologies 9 to 11, further comprising an antenna element capable of transmitting high-frequency signals. A circuit board having such a configuration is suitably used for an antenna that is expected to use high-frequency signals.

[0108] (Technology 13) A transmission method for transmitting a high frequency signal to the circuit board according to any one of Technologies 9 to 12.

[0109] According to the transmission method of Technology 13, a high frequency signal can be transmitted to a circuit board.

[0110] (Technology 14) A method for producing a film for circuit boards, comprising: dissolving a polymer of intrinsic microporosity in a solvent to prepare a solution; applying the solution to a support to form a coating film; and removing the solvent from the coating film.

[0111] According to the method for producing a film for circuit boards of Technique 14, a film for circuit boards suitable for improving mechanical strength while maintaining a low relative dielectric constant can be produced.

[0112] The present disclosure will be described in detail below using examples and reference examples, but the present invention is not limited to the following examples.

[0113] (Evaluation of Thickness T) The thickness (mm) of the film was measured at 10 randomly selected points, and the average of these measurements was regarded as the thickness T (mm) of the film.

[0114] (Evaluation of Porosity P) The porosity P (%) of the film was evaluated based on the following method. First, the volume Vf (mm) of the film was calculated from the length (mm), width (mm), and thickness T (mm) of the film. 3 Next, the mass Wf (g) of the film was measured. The apparent density Df (g / cm 3 ) of the film was calculated using the following formula (I): 3 Next, the true density Dp (g / cm 3 ) of the film was calculated by the pycnometer method. 3 The porosity P of the film was calculated from the apparent density Df and the true density Dp of the film using the following formula (II): Apparent density Df (g / cm 3 )=Wf / Vf×1000...(I) Porosity P(%)={1-(Df / Dp)}×100...(II)

[0115] (Evaluation of Average Pore Diameter D of Pores) The average pore diameter D of the pores in the film was evaluated by the gas adsorption method using nitrogen gas based on the following method. First, a nitrogen gas adsorption isotherm was obtained for a sample having pores by the gas adsorption method using nitrogen gas. In the adsorption isotherm, the vertical axis represents the amount of nitrogen gas adsorbed (Vs / cm 3 (STP)g -1 The horizontal axis represents the relative pressure (P / P0) obtained by dividing the equilibrium pressure by the saturated vapor pressure. The intrinsic microporous polymer powder before being processed into a film was used as the porous sample. The specific surface area Ap (m2) of the porous sample was calculated by converting the obtained adsorption isotherm using the Brunauer-Emmett-Teller (BET) method. 2 / g) was determined. Next, the total pore volume Vp (mL) was calculated by converting the amount of nitrogen gas adsorbed at saturated vapor pressure (P / P0 = 0.99) in the obtained adsorption isotherm into liquid. The value calculated using the following formula (III) was regarded as the average pore diameter D of the pores in the substrate film. Average pore diameter D (nm) of pores = 4 × Vp / Ap (III)

[0116] (Evaluation of Relative Dielectric Constant Dk) The relative dielectric constant Dk of the film was evaluated by a test in accordance with the provisions of JIS C 2138:2007 under the conditions of a frequency of 10 GHz and a measurement temperature of 25° C. The test was carried out by a cavity resonator method (TE mode) using a network analyzer (Anritsu MS46122B manufactured by AET Corporation).

[0117] (Evaluation of Young's Modulus E) The Young's modulus E (MPa) of the film was evaluated by a tensile test in accordance with the provisions of JIS K 7161:2014 under the conditions of a test piece of 30 mm × 10 mm, a chuck distance of 10 mm, a tensile speed of 10 mm / min, and a measurement temperature of 25° C. A tensile compression tester (SVF-500N manufactured by Imada Seisakusho Co., Ltd.) was used for the tensile test.

[0118] (Evaluation of Thermal Expansion Coefficient and Glass Transition Temperature Tg) The thermal expansion coefficient (ppm / °C) and glass transition temperature Tg (°C) of the film were evaluated based on the following method. By thermomechanical analysis in accordance with the provisions of JIS K 7197:2012, a 20 mm x 4 mm test piece was heated from 25°C to 280°C at a rate of 5°C per minute. The average value of the linear expansion coefficient (ppm / °C) in the in-plane direction from 100°C to 160°C was regarded as the thermal expansion coefficient of the test piece. The glass transition temperature Tg of the test piece was determined from the position of the inflection point in the temperature-displacement graph obtained by the above heating. For the thermomechanical analysis, a thermomechanical analyzer (TMA SS6000 manufactured by SII NanoTechnology Inc.) was used.

[0119] (Evaluation of Chemical Stability) The chemical stability of the film was evaluated based on the following method. A chemical resistance test was conducted by immersing a film having a length of 10 mm and a width of 30 mm in an aqueous hydrochloric acid solution (1 mol / L) and an aqueous sodium hydroxide solution (1 mol / L) at 25°C for 2 hours. For both the aqueous hydrochloric acid solution and the aqueous sodium hydroxide solution, a film whose weight change rate before and after immersion was 1.0% or less was evaluated as good A, and a film whose weight change rate was more than 1.0% was evaluated as poor B.

[0120] Example 1 PIM-1 having a repeating unit represented by formula (3) was used as a polymer having intrinsic microporosity.

[0121] Chloroform was prepared as a solvent. 0.5 g of PIM-1 was added to 9.5 mL of chloroform and stirred at 50°C for 6 hours to dissolve PIM-1 in chloroform. This resulted in a coating solution. The concentration of PIM-I in the coating solution was 5% by mass. The coating solution was applied to a polymer film with a release agent to obtain a coating film. The coating film was heated and dried to remove the solvent from the coating film. This resulted in the film of Example 1 having nanoscale pores.

[0122] Example 2 PIM-SBI-TB having a repeating unit represented by formula (4) was used as a polymer having intrinsic microporosity.

[0123] Toluene was prepared as a solvent. 0.5 g of PIM-SBI-TB was dissolved in 4.5 mL of toluene to obtain a coating solution. The concentration of PIM-SBI-TB in the coating solution was 10 mass %. Except for these, a film of Example 2 having nanoscale pores was obtained by the same method as Example 1.

[0124] Comparative Example 1 A commercially available porous polyimide film (functional film (PF) manufactured by Tokyo Ohka Kogyo Co., Ltd.) was used as the film of Comparative Example 1.

[0125] Comparative Example 2 A substrate made of polyphenylene ether (PPE) was made porous by a physical foaming method. The resulting porous polyphenylene ether film was used as the film of Comparative Example 2.

[0126] The films of the Examples and Comparative Examples were evaluated based on the evaluation methods described above. The evaluation results are shown in Table 1. FIG. 6 shows the nitrogen gas adsorption isotherm of PIM-1 of Example 1. FIG. 7 shows the nitrogen gas adsorption isotherm of PIM-SBI-TB of Example 2. Note that the nitrogen gas adsorption isotherms of the films of Examples 1 and 2 showed similar behavior to the nitrogen gas adsorption isotherm of the polymer of intrinsic microporosity before processing into a film in the high-pressure region, but did not show a complete Type I adsorption isotherm in the low-pressure region because nitrogen gas did not enter the pores. Therefore, in this Example, the average pore diameter of the pores calculated based on the adsorption isotherm of the polymer of intrinsic microporosity was considered to be the average pore diameter D of the pores in the substrate film.

[0127]

[0128] <<Discussion>> As shown in Table 1, the films of Examples 1 and 2 containing the polymer of intrinsic microporosity maintained a low dielectric constant even at high frequencies. Furthermore, the films of Examples 1 and 2 exhibited a higher Young's modulus and improved mechanical strength than the films of Comparative Examples 1 and 2. Thus, the films of Examples 1 and 2 achieved both a low dielectric constant and mechanical strength.

[0129] Furthermore, the films of Examples 1 and 2 had a sufficiently reduced coefficient of thermal expansion, a high glass transition temperature, and excellent chemical stability. The porous polyimide film of Comparative Example 1 was hydrolyzed with alkali, and therefore had low base resistance and poor chemical stability.

[0130] The technology of the present disclosure is useful, for example, in next-generation mobile communication systems that use wireless technology.

Claims

1. Containing a uniquely microporous polymer, Film for circuit boards.

2. The void ratio of the aforementioned film is 15% or more and 50% or less. The circuit board film according to claim 1.

3. The average pore size of the pores in the aforementioned film is 0.3 nm or more and 6 nm or less. A film for a circuit board according to claim 1 or 2.

4. The thickness of the aforementioned film is 30 μm or more and 1.0 mm or less. A film for a circuit board according to claim 1 or 2.

5. The aforementioned microporous polymer includes repeating units having aromatic rings and spiro rings. A film for a circuit board according to claim 1 or 2.

6. The repeating unit is represented by the following formula (1) or formula (2): The circuit board film according to claim 5. 【Chemistry 1】 【Chemistry 2】 [In equations (1) and (2), R 1 From R 12 Each element independently contains at least one atom selected from the group consisting of H, C, N, O, F, P, S, Cl, I, and Br.

7. The repeating unit is represented by the following formula (3) or formula (4): The circuit board film according to claim 5. 【Transformation 3】 【Chemistry 4】

8. Further containing inorganic fillers, A film for a circuit board according to claim 1 or 2.

9. The film for the circuit board is a self-supporting film. The circuit board film according to claim 1.

10. Equipped with an insulating layer containing a uniquely microporous polymer, Circuit board.

11. The package substrate and semiconductor chip are included. The insulating layer is at least one selected from the group consisting of the insulating layer of the package substrate and the insulating layer of the intermediate layer located between the semiconductor chip and the package substrate. The circuit board according to claim 10.

12. A redistribution layer and a semiconductor chip are included. The insulating layer is the insulating layer of the redistribution layer. The circuit board according to claim 10.

13. It is further equipped with an antenna element capable of transmitting high-frequency signals. The circuit board according to claim 10.

14. A circuit board according to any one of claims 10 to 13 transmits a high-frequency signal. Transmission method.

15. Dissolving the microporous polymer in a solvent to prepare a solution, The above solution is applied to a support to form a coating film, Removing the solvent from the coated film, including, A method for manufacturing films for circuit boards.

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