Photosensitive resin composition, photosensitive resin film, multilayer printed circuit board and semiconductor package, and method for manufacturing multilayer printed circuit board.

Abstract

This invention provides a photosensitive resin composition containing an inorganic filler material as solid particles with a true density of (X) of 1500 kg / m³ or less. Furthermore, it provides a photosensitive resin film formed using the photosensitive resin composition. It also provides a multilayer printed circuit board comprising an interlayer insulating layer formed using the photosensitive resin composition or the photosensitive resin film, and a method for manufacturing the multilayer printed circuit board. Finally, it provides a semiconductor package comprising the multilayer printed circuit board and a semiconductor element.

Description

Photosensitive Resin Composition, Photosensitive Resin Film, Multilayer Printed Wiring Board and Semiconductor Package, and Method for Manufacturing Multilayer Printed Wiring Board The present invention relates to a photosensitive resin composition, a photosensitive resin film, a multilayer printed wiring board and a semiconductor package, and a method for manufacturing a multilayer printed wiring board. In recent years, the miniaturization and high performance of electronic devices have continued to progress, and multilayer printed wiring boards have continued to be densified by increasing the number of circuit layers and miniaturizing the circuits. The densification of semiconductor package substrates such as BGA (Ball Grid Array) and CSP (Chip-scale package) equipped with semiconductor chips is particularly remarkable. In addition to miniaturizing the circuits, thinning of the insulating layer and further reduction of vias (also called through holes) for interlayer connection are also sought. As a method for manufacturing a printed wiring board that has been conventionally adopted, a method for manufacturing a multilayer printed wiring board can be cited, which is formed by a build-up method (for example, refer to Patent Document 1), and this build-up method is formed by sequentially laminating an interlayer insulating layer and a conductor circuit layer. For multilayer printed wiring boards, with the miniaturization of circuits, the semi-additive method is becoming the mainstream, and circuits can be formed by plating. The conventional semi-additive method, for example, has the following steps: (1) After laminating a thermosetting resin film on a conductor circuit, the thermosetting resin film is hardened by heating to form an "interlayer insulating layer"; (2) Subsequently, after forming a via for interlayer connection by laser processing, desmearing treatment and roughening treatment are performed by alkaline permanganate treatment or the like; (3) After that, electroless copper plating treatment is performed on the substrate, and then a pattern is formed using a resist, and then electrolytic copper plating is performed to form a copper circuit layer; (4) Subsequently, after peeling off the resist, flash etching of the electroless layer is performed to form a copper circuit. As described above, as a method for forming vias in the interlayer insulating layer formed by hardening a thermosetting resin film, laser processing is the mainstream, but the reduction of the via diameter by laser irradiation using a laser processing machine has reached its limit. Further, when generating vias by a laser processing machine, each through hole needs to be formed one by one, and when a large number of vias need to be provided due to densification, a large amount of time is required to form the vias, so there is a problem of poor manufacturing efficiency. Under such circumstances, as a method capable of forming a plurality of through-holes at one time, the following method has been proposed. It uses a photosensitive resin composition and forms a plurality of through-holes with small apertures at one time by photolithography. The photosensitive resin composition contains an acid-modified vinyl epoxy resin, a photopolymerizable compound, a photoinitiator, an inorganic filler, and a silane compound, and the content of the inorganic filler is 10 to 80% by mass (for example, refer to Patent Document 2). In Patent Document 2, reducing the decrease in adhesion to copper plating is one of the problems to be solved, and further, the resolution of the through-holes and the adhesion to a silicon substrate and chip components are set as problems to be solved and then solved. The decrease in adhesion to copper plating is due to the use of a photosensitive resin composition instead of the conventional thermosetting resin composition as a material for the interlayer insulating layer or the surface protective layer. In recent years, substrate materials are required to be applied to fifth-generation mobile communication systems (5G) antennas using radio waves in high-frequency bands and further to millimeter-wave radars using radio waves in high-frequency bands. To achieve such applications, it is necessary to develop a resin composition. As one of its goals, it is to further improve the relative dielectric constant in the "10 GHz band". However, the technology of Patent Document 2 still has room for improvement in terms of the relative dielectric constant in the 10 GHz band. [Prior Art Documents] (Patent Documents) Patent Document 1: Japanese Patent Application Laid-Open No. 7-304931. Patent Document 2: Japanese Patent Application Laid-Open No. 2017-116652. [Problems to be Solved by the Invention] In order to reduce the relative dielectric constant in the 10 GHz band, the inventors studied the case where a photosensitive resin composition contains polytetrafluoroethylene (hereinafter referred to as PTFE) particles having a very low relative dielectric constant. However, if only PTFE is contained in the photosensitive resin composition, the relative dielectric constant can indeed be reduced, but there will be a problem of a decrease in the adhesion strength to copper plating, and it is judged that it is difficult to have both the relative dielectric constant in the 10 GHz band and the adhesion strength to copper plating. Therefore, an object of the present invention is to provide a photosensitive resin composition, a photosensitive resin film formed using the photosensitive resin composition, which can exhibit excellent relative dielectric constant in the 10 GHz band and high adhesion strength to copper plating, and to provide a multilayer printed wiring board, its manufacturing method, and a semiconductor package. [Technical Means for Solving the Problem] As a result of the inventors' dedicated research, it was found that the foregoing object can be achieved by the present invention. The present invention includes the following embodiments [1] to

[18] . [1] A photosensitive resin composition containing (X) a true density of 1500 kg / m 3The following inorganic filler as a solid particle. [2] The photosensitive resin composition as described in [1] above, wherein the volume average particle diameter of the foregoing (X) component is 0.3 to 3 μm. [3] The photosensitive resin composition as described in [1] or [2] above, wherein the content of the foregoing (X) component is 1 to 45% by volume based on the total solid content of the photosensitive resin composition. [4] The photosensitive resin composition as described in any one of [1] to [3] above, further comprising (A) a photopolymerizable compound having an ethylenically unsaturated group and an acidic substituent and (B) a thermosetting resin. [5] The photosensitive resin composition as described in [4] above, wherein the foregoing (A) component contains an alicyclic skeleton represented by the following general formula (A-1), In the general formula (A-1), R A1 represents an alkyl group having 1 to 12 carbon atoms and may be substituted at any position in the foregoing alicyclic skeleton, m 1is an integer from 0 to 6, and * is a bonding site with other structures. [6] The photosensitive resin composition as described in [4] or [5] above, wherein the equivalent ratio of the acidic substituent of the foregoing component (A) to the epoxy group of the foregoing component (B), that is, epoxy group / acidic substituent, is 0.5 to 6.0. [7] The photosensitive resin composition as described in any one of [1] to [6] above, further comprising (C) a crosslinking agent. [8] The photosensitive resin composition as described in any one of [1] to [7] above, further comprising (D) an elastomer. [9] The photosensitive resin composition as described in any one of [1] to [8] above, further comprising (E) an organic filler.

[10] The photosensitive resin composition as described in [9] above, wherein the foregoing component (E) comprises resin particles formed of at least one selected from the group consisting of a resin having a fluorine atom, polyethylene, polypropylene, polystyrene, polyphenylene ether, and silicone.

[11] The photosensitive resin composition as described in [9] or

[10] above, wherein the content of the foregoing component (E) is 1 to 45% by volume based on the total solid content of the photosensitive resin composition.

[12] The photosensitive resin composition as described in any one of [1] to

[11] above, further comprising (H) a photoinitiator.

[13] The photosensitive resin composition as described in

[12] above, containing two or more of the foregoing components (H).

[14] A photosensitive resin composition for forming a via hole, which is composed of the photosensitive resin composition as described in any one of [1] to

[13] above.

[15] A photosensitive resin film, which is formed using the photosensitive resin composition as described in any one of [1] to

[13] above.

[16] A multilayer printed wiring board, which contains an interlayer insulating layer, and the interlayer insulating layer is formed using the photosensitive resin composition as described in any one of [1] to

[13] above or the photosensitive resin film as described in

[15] above.

[17] A semiconductor package, which includes the multilayer printed wiring board as described in

[16] above and a semiconductor element.

[18] A method for manufacturing a multilayer printed wiring board, which includes the following steps (1), (2), and (4): Step (1), laminating the photosensitive resin film as described in

[15] above on one or both sides of a circuit board; Step (2), exposing and developing the photosensitive resin film laminated in the foregoing step (1) to thereby form an interlayer insulating layer having a via hole; and Step (4), forming a circuit pattern on the foregoing interlayer insulating layer. [Advantages of the Invention] According to the present invention, it is possible to provide a photosensitive resin composition that can exhibit excellent relative dielectric constant in the 10 GHz frequency band and high adhesion strength to copper plating. In addition, it is possible to provide a photosensitive resin film formed using the photosensitive resin composition. Further, it is possible to provide a multilayer printed wiring board containing an interlayer insulating layer formed using the photosensitive resin composition or the photosensitive resin film, and it is also possible to provide a method for manufacturing the multilayer printed wiring board. In addition, it is possible to provide a semiconductor package including the multilayer printed wiring board and a semiconductor element. Regarding the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range can be replaced with the numerical values shown in the examples. Also, the lower limit value and the upper limit value of the numerical range can be arbitrarily combined with the lower limit value or the upper limit value of other numerical ranges. For a numerical range indicated as "AA to BB", the two end values AA and BB are included in the numerical range as the lower limit value and the upper limit value, respectively. In this specification, for example, a description such as "10 or more" means 10 and numerical values exceeding 10, and the same applies when the numerical values are different. Also, for example, a description such as "10 or less" means 10 and numerical values less than 10, and the same applies when the numerical values are different. In this specification, the content of each component in the photosensitive resin composition, when there are plural substances corresponding to each component, unless otherwise specified, means the total content of the plural substances present in the photosensitive resin composition. The so-called "ring-forming carbon number" in this specification is the number of carbon atoms required to form a ring and does not include the carbon atoms on the substituents of the ring. For example, the ring-forming carbon number of a cyclohexane skeleton and a methylcyclohexane skeleton is both 6. The term "(meth)acrylic XX" means either one or both of acrylic XX and the corresponding methacrylic XX. Also, "(meth)acryloyl" means either one or both of acryloyl and methacryloyl. In this specification, unless otherwise specified, the "relative dielectric constant" is the relative dielectric constant in the 10 GHz frequency band. In addition, aspects arbitrarily combined from the matters described in this specification are also included in this embodiment. [Photosensitive Resin Composition] The photosensitive resin composition according to an embodiment of the present invention (hereinafter, sometimes simply referred to as this embodiment) contains (X) a true density of 1500 kg / m 3The following photosensitive resin composition with an inorganic filler as solid particles. Herein, in this specification, the above components may sometimes be abbreviated as "(X) component", and other components may sometimes be referred to in the same abbreviated manner. Furthermore, in this specification, the so-called "resin component" refers to the following (A) component, (B) component, etc., and also includes other components that may be contained as needed (for example, (C), (D), (E), (F), (G), (H), and (I) components, etc.), but does not include the (X) component, other inorganic fillers, and inorganic compounds such as pigments. In addition, the so-called "solid content" means: the non-volatile components after removing the water and the diluent described below contained in the photosensitive resin composition, and also includes those that are liquid, syrup-like, and wax-like at room temperature of about 25°C. The photosensitive resin composition of this embodiment has excellent relative dielectric constant in the 10 GHz frequency band and is also suitable for forming vias (also known as optical vias) by lithography, and thus is suitable for forming one or more selected from the group consisting of optical vias and interlayer insulating layers. Herein, in this specification, for example, when marked as "layer" such as an interlayer insulating layer, etc., except for the aspect of a base layer, aspects such as at least a part being island-like, having openings, and having an unclear interface with an adjacent layer that do not belong to the base layer are also included in the "layer". Furthermore, the aforementioned base layer means a thin film-like layer that has not been particularly processed. Furthermore, the photosensitive resin composition of this embodiment is suitable for a negative photosensitive resin composition. Hereinafter, after the (X) component is described in detail, the other components that the photosensitive resin composition of this embodiment may contain will be described in detail. <(X) True density is 1500 kg / m 3 The following inorganic filler as solid particles> The photosensitive resin composition of this embodiment, by containing a true density of 1500 kg / m 3The following inorganic filler material as a solid particle, as the (X) component, can exhibit excellent relative dielectric constant in the 10 GHz frequency band and high adhesion strength to copper plating. Here, the true density of the (X) component is the value measured by a dry automatic densitometer "AccuPycII 1340" (manufactured by Shimadzu Corporation), and more specifically, the value measured according to the method described in the examples. In addition, in this specification, the so-called "solid particle" means a particle with a hollowness of 60% or less (including 0%, that is, 0 to 60%) obtained based on the true density measured by a dry automatic densitometer (specifically, the method described in the examples). When the hollowness measured by this method exceeds 60%, it is called a "hollow particle". Therefore, for example, even if the particle is porous inside, as long as the aforementioned hollowness is 60% or less, it is included in the solid particles. From the viewpoints of relative dielectric constant and adhesion strength to copper plating, the hollowness in the solid particles is preferably 55% or less, more preferably 50% or less, further preferably 45% or less, and particularly preferably 43% or less. The lower limit value of the aforementioned hollowness is not particularly limited, and it can be 0% or more, 5% or more, 15% or more, 25% or more, 30% or more, 32% or more, 34% or more, or 37% or more. Furthermore, the method for obtaining the aforementioned hollowness is as described in the examples. The exact mechanism for exhibiting excellent relative dielectric constant and high adhesion strength to copper plating is still unclear, but it is speculated as follows: Due to the true density of 1500 kg / m 3 Hereinafter, the space at the molecular level of the inorganic filler material of the solid particles will become larger, which may contribute to the reduction of the relative dielectric constant. In addition, since the (X) component is an inorganic filler material, it is considered that the situation where the adhesion strength to copper plating is greatly reduced like PTFE will not occur, and thus it is possible to achieve both a reduction in relative dielectric constant and high adhesion strength to copper plating. However, the scope of the photosensitive resin composition of this embodiment is not limited by this speculation. (X) component's true density, from the viewpoints of relative dielectric constant and adhesion strength to copper plating, is preferably 1000 - 1500 kg / m 3 , more preferably 1100 - 1500 kg / m 3 , further preferably 1200 - 1500 kg / m 3 , particularly preferably 1250 - 1450 kg / m 3 , most preferably 1250 - 1400 kg / m 3 . Examples of the (X) component include: silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), titanium oxide (TiO 2 ), tantalum oxide (Ta 2 O 5 ), zirconium oxide (ZrO 2 ), silicon nitride (Si 3 N 4 ), barium titanate (BaO.TiO 2 ), barium carbonate (BaCO 3 ), magnesium carbonate (MgCO 3 ), aluminum hydroxide (Al(OH) 3 ), magnesium hydroxide (Mg(OH) 2 ), lead titanate (PbO.TiO 2 ), lead zirconate titanate (PZT), lanthanum lead zirconate titanate (PLZT), gallium oxide (Ga 2 O 3 ), spinel (MgO.Al 2 O 3 ), mullite (3Al 2 O 3 .2SiO 2 ), cordierite (2MgO.2Al 2 O 3 / 5SiO 2 ), talc (3MgO.4SiO 2 .H2O), aluminum titanate (TiO2.Al 2 O 3 ) Yttria-stabilized zirconia (Y 2 O 3 . ZrO 2 ) Barium silicate (BaO·8SiO 2 ), boron nitride (BN), calcium carbonate (CaCO 3 ), barium sulfate (BaSO 4 ), calcium sulfate (CaSO 4 ), zinc oxide (ZnO), magnesium titanate (MgO·TiO 2 ), hydrotalcite, mica, calcined kaolin, carbon (C), etc. Among these, from the viewpoints of heat resistance, low thermal expansion, and relative dielectric constant, silica is preferred. As the (X) component, commercially available products can be used. For example, as silica as solid particles with a true density of 1500 kg / m 3 or less, examples include "BQQ-0710SCB" (manufactured by T.A.T Co., Ltd.) and "BQQ-0310SCB" (manufactured by T.A.T Co., Ltd.). Silica as solid particles with a true density of 1500 kg / m 3 or less is not particularly limited, but it is preferably silica having Si-R x bonds (R x represents an organic group) in addition to Si-O bonds. (X) component, from the viewpoint of improving the dispersibility in the photosensitive resin composition, may be one surface-treated with a coupling agent or one not surface-treated with a coupling agent, but preferably one surface-treated with a coupling agent. Examples of the coupling agent include the following silane coupling agents: amino-silane coupling agent, epoxy-silane coupling agent, phenyl-silane coupling agent, alkyl-silane coupling agent, alkenyl-silane coupling agent, alkynyl-silane coupling agent, haloalkyl-silane coupling agent, siloxane coupling agent, hydrosilane coupling agent, silazane coupling agent, alkoxysilane coupling agent, chlorosilane coupling agent, (meth)acrylic group-silane coupling agent, isocyanurate-based silane coupling agent, ureido-silane coupling agent, mercapto-silane coupling agent, sulfide-silane coupling agent, isocyanate-based silane coupling agent, etc. (X) component preferably has a volume average particle diameter of 0.3 to 3 μm, more preferably 0.3 to 2.5 μm, still more preferably 0.3 to 2.0 μm, particularly preferably 0.3 to 1.7 μm, and may be 0.3 to 1.2 μm or 1.2 to 2.0 μm. As long as the volume average particle diameter of (X) component is not less than the aforementioned lower limit value, there is a tendency for excellent low thermal expansibility, and as long as it is not more than the aforementioned upper limit value, there is a tendency for excellent resolution of through holes. Furthermore, if the volume average particle diameter of (X) component is 2.5 μm or less, the resolution of through holes tends to become very good. As (X) component, from the viewpoints of improving the adhesion to copper plating and the resolution of through holes, two or more inorganic fillers having different volume average particle diameters may be used in combination. Here, the volume average particle diameter can be obtained by the following method: using a submicron particles analyzer (manufactured by Beckman Coulter, Inc.; trade name: N5), and measuring the particles dispersed in a solvent at a refractive index of 1.38 in accordance with the international standard ISO13321, and then setting it as the particle diameter corresponding to the cumulative value of 50% (volume basis) in the particle size distribution. In the photosensitive resin composition of this embodiment, the content of (X) component is not particularly limited, but based on the total solid content of the photosensitive resin composition, it is preferably 1 to 45% by volume, more preferably 3 to 40% by volume, still more preferably 5 to 40% by volume, and may be 5 to 25% by volume or 25 to 40% by volume. If the content of (X) component is not less than the aforementioned lower limit value, there is a tendency to obtain a lower relative dielectric constant and thermal expansion coefficient, and if it is not more than the aforementioned upper limit value, there is a tendency to obtain more excellent adhesion strength to copper plating and resolution of through holes. The photosensitive resin composition of this embodiment preferably further contains (A) a photopolymerizable compound having an ethylenically unsaturated group and an acidic substituent and (B) a thermosetting resin. Hereinafter, the component (A) and the component (B) will be described in detail in sequence, and other components will also be described in detail later. <(A) Photopolymerizable Compound Having an Ethylenically Unsaturated Group and an Acidic Substituent> The component (A) is a photopolymerizable compound having an ethylenically unsaturated group and an acidic substituent. One kind of the component (A) can be used alone, or two or more kinds can be used in combination. Since the component (A) has an ethylenically unsaturated group, it is a compound that can exhibit photopolymerizability, particularly free radical polymerizability. Examples of the ethylenically unsaturated group possessed by the component (A) include the following functional groups that can exhibit photopolymerizability: vinyl group, allyl group, propargyl group, butenyl group, ethynyl group, phenylacetylene group, maleimide group, naphthalimide group, (meth)acryloyl group, etc. Among these, from the viewpoints of reactivity and via hole resolvability, (meth)acryloyl group is preferred. From the viewpoint of alkaline developability, the component (A) has an acidic substituent. Examples of the acidic substituent possessed by the component (A) include, for example, carboxyl group, sulfonic acid group, phenolic hydroxyl group, etc. Among these, from the viewpoint of via hole resolvability, carboxyl group is preferred. The acid value of the component (A) is preferably 20 to 200 mgKOH / g, more preferably 40 to 180 mgKOH / g, still more preferably 70 to 150 mgKOH / g, particularly preferably 90 to 120 mgKOH / g. If the acid value of the component (A) is at least the aforementioned lower limit value, the photosensitive resin film tends to have excellent solubility in dilute alkali solution, and if it is at most the aforementioned upper limit value, the relative dielectric constant tends to be excellent. The acid value of the component (A) can be measured by the method described in the examples. Furthermore, two or more kinds of the component (A) having different acid values can be used in combination. In this case, preferably, the weighted average acid value of the two or more kinds of the component (A) is within any of the aforementioned ranges. The weight average molecular weight (Mw) of the component (A) is preferably 600 to 30000, more preferably 800 to 25000, still more preferably 1000 to 18000, still more preferably 1000 to 8000, particularly preferably 1200 to 5000, and most preferably 1200 to 3500. If the weight average molecular weight (Mw) of the component (A) is within the aforementioned range, the adhesion strength to copper plating, heat resistance, and insulation reliability tend to be excellent. Here, in this specification, the weight molecular weight is a value obtained by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent and converted to standard polystyrene. More specifically, it is a value measured according to the method described in the examples. From the viewpoint of relative dielectric constant, component (A) preferably contains an alicyclic skeleton. As the alicyclic skeleton of component (A), from the viewpoints of via hole resolvability, adhesion strength with copper plating, and electrical insulation reliability, an alicyclic skeleton having 5 to 20 ring carbon atoms is preferred, an alicyclic skeleton having 5 to 18 ring carbon atoms is more preferred, an alicyclic skeleton having 6 to 18 ring carbon atoms is further preferred, an alicyclic skeleton having 8 to 14 ring carbon atoms is particularly preferred, and an alicyclic skeleton having 8 to 12 ring carbon atoms is most preferred. Further, the aforementioned alicyclic skeleton, from the viewpoints of via hole resolvability, adhesion strength with copper plating, and electrical insulation reliability, is preferably composed of 2 or more rings, more preferably composed of 2 to 4 rings, and further preferably composed of 3 rings. As the alicyclic skeleton of 2 or more rings, examples include: norbornane skeleton, decahydronaphthalene skeleton, bicycloundecane skeleton, saturated dicyclopentadiene skeleton, etc. Among these, from the viewpoints of via hole resolvability, adhesion strength with copper plating, and electrical insulation reliability, a saturated dicyclopentadiene skeleton is preferred. From the same viewpoint, component (A) preferably contains an alicyclic skeleton represented by the following general formula (A-1). In general formula (A-1), R A1 represents an alkyl group having 1 to 12 carbon atoms and can be substituted at any position in the aforementioned alicyclic skeleton, and m 1 is an integer from 0 to 6, and * is a bonding site with other structures. In the aforementioned general formula (A-1), as R A1 the alkyl group having 1 to 12 carbon atoms represented, examples include: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, etc. As the alkyl group, an alkyl group having 1 to 6 carbon atoms is preferred, an alkyl group having 1 to 3 carbon atoms is more preferred, and methyl is further preferred. m 1 is an integer from 0 to 6, preferably an integer from 0 to 2, and more preferably 0. When m 1 is an integer from 2 to 6, the plural R A1 can be the same or different from each other. Further, the plural R A1 can be substituted on the same carbon atom within the possible range, or can be substituted on different carbon atoms. * is a bonding site with other structures and can be bonded to any carbon atom on the alicyclic skeleton, but is preferably bonded to the carbon atoms of the site represented by 1 or 2 and the carbon atoms of the site represented by either 3 or 4 in the following general formula (A-1’). In general formula (A-1’), R A1, m 1 and * are the same as R in the above general formula (A-1). A1 , m 1 and * are the same. (A) component, from the viewpoints of the resolution of the through hole and the adhesion strength to copper plating, is preferably an acid-modified vinyl-containing epoxy resin, which is a compound obtained by reacting (a3) a polybasic acid anhydride containing a saturated or unsaturated group with (a1) an epoxy resin modified with (a2) an ethylenically unsaturated group-containing organic acid [hereinafter, sometimes referred to as (A') component]. Here, in the acid-modified vinyl-containing epoxy resin, "acid-modified" means having an acidic substituent, "vinyl" means an ethylenically unsaturated group, and "epoxy resin" means using an epoxy resin as a raw material. Therefore, the acid-modified vinyl-containing epoxy resin does not necessarily have to have an epoxy group and may not have an epoxy group. Hereinafter, the appropriate aspects of the (A) component obtained from (a1) an epoxy resin, (a2) an ethylenically unsaturated group-containing organic acid, and (a3) a polybasic acid anhydride containing a saturated or unsaturated group will be described. ((a1) epoxy resin) As the (a1) epoxy resin, an epoxy resin having two or more epoxy groups is preferred. The (a1) epoxy resin can be used alone or in combination of two or more. The (a1) epoxy resin can be classified into: glycidyl ether type epoxy resin, glycidyl amine type epoxy resin, glycidyl ester type epoxy resin, etc. Among these, glycidyl ether type epoxy resin is preferred. (a1) epoxy resin can be classified into various epoxy resins based on different main skeletons, and can be classified into epoxy resins having an alicyclic skeleton, novolak type epoxy resins, bisphenol type epoxy resins, aralkyl type epoxy resins, other epoxy resins, etc. Among these, epoxy resins having an alicyclic skeleton and novolak type epoxy resins are preferred. - Epoxy resin having an alicyclic skeleton - Regarding the alicyclic skeleton of the epoxy resin having an alicyclic skeleton, the same description as the alicyclic skeleton of the aforementioned (A) component can be made, and the preferred aspects are also the same. As the epoxy resin having an alicyclic skeleton, an epoxy resin represented by the following general formula (A-2) is preferred. In the general formula (A-2), R A1 represents an alkyl group having 1 to 12 carbon atoms and can be substituted at any position in the aforementioned alicyclic skeleton. R A2 represents an alkyl group having 1 to 12 carbon atoms. m 1 is an integer from 0 to 6. m 2is an integer from 0 to 3. n is a number from 0 to 50. In the general formula (A-2), R A1 is the same as R in the general formula (A-1), and the preferred embodiments are also the same. As R in the general formula (A-2) A1 the alkyl group having 1 to 12 carbon atoms represented thereby, examples include: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tertiary butyl, n-pentyl and the like. As the alkyl group, preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, still more preferably methyl. m in the general formula (A-2) A2 is the same as m in the general formula (A-1), and the preferred embodiments are also the same. m in the general formula (A-2) 1 is the same as m in the general formula (A-1), and the preferred embodiments are also the same. m in the general formula (A-2) 1 is an integer from 0 to 3, preferably 0 or 1, more preferably 0. n in the general formula (A-2) represents the repeating number of the structural unit in the parentheses and is a number from 0 to 50. Epoxy resins are usually mixtures of those having different repeating numbers of the structural unit in the parentheses. Therefore, in such a case, n represents the average value of the mixture. As n, preferably a number from 0 to 30. 2 As the epoxy resin having an alicyclic skeleton, commercially available products can be used. Examples of the commercially available products include: XD-1000 (manufactured by Nippon Kayaku Co., Ltd., trade name), EPICLON (registered trademark) HP-7200 (manufactured by DIC Corporation, trade name), etc. -Novolac type epoxy resin- As the novolac type epoxy resin, examples include: bisphenol A novolac type epoxy resin, bisphenol F novolac type epoxy resin, bisphenol S novolac type epoxy resin and other bisphenol novolac type epoxy resins; phenol novolac type epoxy resin, cresol novolac type epoxy resin, biphenol novolac type epoxy resin, naphthol novolac type epoxy resin and the like. As the novolac type epoxy resin, preferably an epoxy resin having a structural unit represented by the following general formula (A-3). In the general formula (A-3), R represents a hydrogen atom or a methyl group, and Y A3 each independently represents a hydrogen atom or a glycidyl group. The two Rs A1 may be the same or different. At least one of the two Ys A3 represents a glycidyl group. A1 ​From the viewpoints of the resolution of the through-hole and the adhesion strength to copper plating, R A3 is preferably all hydrogen atoms. From the same viewpoint, Y A1 is preferably all glycidyl groups. The number of structural units of the structural unit in the (a1) epoxy resin having a structural unit represented by the general formula (A-3) is a number of 1 or more, preferably a number of 10 to 100, more preferably a number of 15 to 80, and still more preferably a number of 15 to 70. If the number of structural units is within the above range, there is a tendency to improve the adhesion strength to copper plating, heat resistance, and insulation reliability. Regarding the general formula (A-3), it is possible to commercially purchase EXA-7376 series (trade name, manufactured by DIC Corporation) in which R A3 are all hydrogen atoms and Y A1 are all glycidyl groups. In addition, it is possible to commercially purchase EPON SU8 series (trade name, manufactured by Mitsubishi Chemical Corporation) in which R A3 are all methyl groups and Y A1 are all glycidyl groups. Examples of the bisphenol type epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, 3,3',5,5'-tetramethyl-4,4'-diglycidyloxy diphenylmethane, etc. Examples of the aralkyl type epoxy resin include phenol aralkyl type epoxy resin, biphenyl aralkyl type epoxy resin, naphthol aralkyl type epoxy resin, etc. Examples of other epoxy resins include styrene type epoxy resin, naphthalene skeleton-containing epoxy resin, biphenyl type epoxy resin, dihydroanthracene type epoxy resin, cyclohexanedimethanol type epoxy resin, trimethylol type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, heterocyclic epoxy resin, spiro ring-containing epoxy resin, rubber-modified epoxy resin, etc. ((a2) ethylenically unsaturated group-containing organic acid) As the (a2) ethylenically unsaturated group-containing organic acid, an ethylenically unsaturated group-containing monocarboxylic acid is preferred. Examples of the ethylenically unsaturated group possessed by the (a2) component are the same as those exemplified as the ethylenically unsaturated group possessed by the (A) component. Examples of the (a2) component include acrylic acid, dimers of acrylic acid, methacrylic acid, β-furfurylacrylic acid, β-styrylacrylic acid, cinnamic acid, crotonic acid, α-cyanocinnamic acid and other acrylic acid derivatives; reaction products of hydroxy acrylate and dianhydride, i.e., half-ester compounds; reaction products of vinyl monoglycidyl ether or vinyl monoglycidyl ester and dianhydride, i.e., half-ester compounds, etc. The (a2) component can be used alone or in combination of two or more. The aforementioned half-ester compound can be obtained by reacting a vinyl group-containing compound with a dicarboxylic anhydride. The vinyl group-containing compound is one or more selected from the group consisting of hydroxy acrylate, vinyl mono-glycidyl ether, and vinyl mono-glycidyl ester. Preferably, the reaction is carried out by reacting the ethylenically unsaturated group-containing compound with the dicarboxylic anhydride in an equimolar manner. Examples of the hydroxy acrylate used in the synthesis of the aforementioned half-ester compound include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, polyethylene glycol mono-(meth)acrylate, trimethylolpropane di-(meth)acrylate, pentaerythritol tri-(meth)acrylate, dipentaerythritol penta-(meth)acrylate, etc. Examples of the vinyl mono-glycidyl ether include glycidyl (meth)acrylate, etc. The dicarboxylic anhydride used in the synthesis of the aforementioned half-ester compound may contain a saturated group or an unsaturated group. Examples of the dicarboxylic anhydride include: succinic anhydride, maleic anhydride, tetrahydrophthalic anhydride, phthalic anhydride, methyltetrahydrophthalic anhydride, ethyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, ethylhexahydrophthalic anhydride, itaconic anhydride, etc. In the reaction of the component (a1) and the component (a2), the usage amount of the component (a2) is preferably 0.6 to 1.05 equivalents, more preferably 0.7 to 1.02 equivalents, and further preferably 0.8 to 1.0 equivalents relative to 1 equivalent of the epoxy group of the component (a1). By reacting the component (a1) and the component (a2) at the aforementioned ratio, the photopolymerizability of the component (A) tends to increase and the via hole resolution of the obtained photosensitive resin composition tends to increase. Preferably, the component (a1) and the component (a2) are dissolved in an organic solvent for reaction. Examples of the organic solvent include: ketones such as methyl ethyl ketone, cyclohexanone; aromatic hydrocarbons such as toluene, xylene, mesitylene; glycol ether compounds such as methyl cellosolve, butyl cellosolve, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol diethyl ether, triethylene glycol monoethyl ether; esters such as ethyl acetate, butyl acetate, butyl cellosolve acetate, carbitol acetate; aliphatic hydrocarbons such as octane, decane; petroleum-based solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, solvent naphtha, etc. The organic solvent can be used alone or in combination of two or more. In the reaction of component (a1) and component (a2), it is preferable to use a catalyst for promoting the reaction. Examples of such catalysts include amine-based catalysts such as triethylamine and benzylmethylamine; quaternary ammonium salt catalysts such as methyltriethylammonium chloride, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, and benzyltrimethylammonium iodide; phosphine-based catalysts such as triphenylphosphine, etc. Among these, phosphine-based catalysts are preferred, and triphenylphosphine is more preferred. The catalyst can be used alone as one kind, or two or more kinds can be used in combination. When using a catalyst, from the viewpoint of obtaining an appropriate reaction rate, the amount used is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and even more preferably 0.1 to 2 parts by mass, based on 100 parts by mass in total of component (a1) and component (a2). In the reaction of component (a1) and component (a2), for the purpose of preventing polymerization during the reaction, it is preferable to use a polymerization inhibitor. Examples of polymerization inhibitors include hydroquinone, methylhydroquinone, methylhydroquinone monomethyl ether, catechol, pyrogallol, etc. The polymerization inhibitor can be used alone as one kind, or two or more kinds can be used in combination. When using a polymerization inhibitor, the amount used is preferably 0.01 to 1 part by mass, more preferably 0.02 to 0.8 part by mass, and even more preferably 0.1 to 0.5 part by mass, based on 100 parts by mass in total of component (a1) and component (a2). From the viewpoint of obtaining sufficient reactivity and enabling the reaction to proceed homogeneously, the reaction temperature of component (a1) and component (a2) is preferably 60 to 150 °C, more preferably 80 to 120 °C, and even more preferably 90 to 110 °C. As described above, when component (a2) contains a vinyl monocarboxylic acid, the (A') component formed by reacting component (a1) and component (a2) will have a hydroxyl group, and this hydroxyl group is formed by the ring-opening addition reaction of the epoxy group of component (a1) and the carboxyl group of component (a2). Subsequently, by reacting component (a3) with this (A') component, an acid-modified vinyl epoxy resin can be obtained, which is semi-esterified by the hydroxyl group of the (A') component (including the hydroxyl group originally present in component (a1)) and the acid anhydride group of component (a3). ((a3) polyacid anhydride) As component (a3), it can be one containing a saturated group or one containing an unsaturated group. Examples of component (a3) include succinic anhydride, maleic anhydride, tetrahydrophthalic anhydride, phthalic anhydride, methyltetrahydrophthalic anhydride, ethyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, ethylhexahydrophthalic anhydride, itaconic anhydride, etc. Among these, from the viewpoint of via resolvability, tetrahydrophthalic anhydride is preferred. Component (a3) can be used alone as one kind, or two or more kinds can be used in combination. In the reaction of the component (A’) and the component (a3), for example, the acid value of the acid-modified vinyl epoxy resin can be adjusted in such a way that 0.1 to 1.0 equivalents of the component (a3) reacts with the hydroxyl groups in 1 equivalent of the component (A’). From the viewpoint of obtaining sufficient reactivity and enabling the reaction to proceed homogeneously, the reaction temperature of the component (A’) and the component (a3) is preferably 50 to 150 °C, more preferably 60 to 120 °C, and still more preferably 70 to 100 °C. The content of the component (A) in the photosensitive resin composition of the present embodiment is not particularly limited. However, from the viewpoints of heat resistance, relative dielectric constant, and chemical resistance, based on the total amount of the resin components of the photosensitive resin composition, it is preferably 10 to 80% by mass, more preferably 10 to 60% by mass, still more preferably 15 to 45% by mass, particularly preferably 15 to 35% by mass, and most preferably 20 to 35% by mass. <(B) Thermosetting resin> The component (B) is a thermosetting resin. The component (B) does not contain the aforementioned component (A). By containing the (B) thermosetting resin, the photosensitive resin composition of the present embodiment tends to have improved heat resistance in addition to improved adhesion strength to copper plating and insulation reliability. Examples of the thermosetting resin include: epoxy resins, phenol resins, unsaturated imide resins, cyanate ester resins, isocyanate resins, benzoxazine resins, oxetane resins, amino resins, unsaturated polyester resins, allyl resins, dicyclopentadiene resins, silicone resins, triazine resins, melamine resins, etc. In addition, there are no particular restrictions on these, and known thermosetting resins can be used. Among these, from the viewpoints of adhesion strength to copper plating, insulation reliability, and heat resistance, an epoxy resin is preferred. The component (B) can be used alone or in combination of two or more. As the epoxy resin, an epoxy resin having two or more epoxy groups in one molecule is preferred. Here, epoxy resins can be classified into: glycidyl ether type epoxy resins, glycidyl amine type epoxy resins, glycidyl ester type epoxy resins, etc. Among these, glycidyl ether type epoxy resins are preferred. In addition, epoxy resins can be classified into various types according to the differences in the main skeleton, and for the aforementioned different types of epoxy resins, they can be further classified into the following categories. Specifically, they can be classified into: bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins and other bisphenol-based epoxy resins; bisphenol A novolak type epoxy resins, bisphenol F novolak type epoxy resins and other bisphenol-based novolak type epoxy resins; phenol novolak type epoxy resins, cresol novolak type epoxy resins, biphenyl novolak type epoxy resins and other novolak type epoxy resins other than the aforementioned bisphenol-based novolak type epoxy resins; phenol aralkyl type epoxy resins; stilbene type epoxy resins; naphthol novolak type epoxy resins, naphthol type epoxy resins, naphthol aralkyl type epoxy resins, naphthalene ether type epoxy resins and other naphthalene skeleton-containing type epoxy resins; biphenyl type epoxy resins; biphenyl aralkyl type epoxy resins; xylylene type epoxy resins; dihydroanthracene type epoxy resins; saturated dicyclopentadiene type epoxy resins and other alicyclic epoxy resins; heterocyclic epoxy resins; spiro ring-containing epoxy resins; cyclohexanedimethanol type epoxy resins; trimethylol type epoxy resins; aliphatic chain epoxy resins; rubber-modified epoxy resins and the like. Among these, epoxy resins are preferably at least one selected from the group consisting of bisphenol-based epoxy resins, naphthalene skeleton-containing type epoxy resins, and biphenyl aralkyl type epoxy resins, and more preferably at least one selected from the group consisting of naphthalene skeleton-containing type epoxy resins and biphenyl aralkyl type epoxy resins, particularly from the viewpoints of heat resistance, electrical insulation reliability, developability, and adhesion strength to copper plating. The equivalent ratio of the acidic substituent of the component (A) to the epoxy group of the component (B) [epoxy group / acidic substituent] in the photosensitive resin composition of this embodiment is not particularly limited, but from the viewpoints of insulation reliability, relative dielectric constant, heat resistance, and adhesion strength to copper plating, it is preferably 0.5 to 6.0, more preferably 0.7 to 4.0, further preferably 0.8 to 2.0, and particularly preferably 0.9 to 1.8. The content of the component (B) in the photosensitive resin composition of this embodiment is not particularly limited, but from the viewpoints of insulation reliability, relative dielectric constant, heat resistance, and adhesion strength to copper plating, based on the total amount of the resin components of the photosensitive resin composition, it is preferably 1 to 50% by mass, more preferably 5 to 30% by mass, and further preferably 10 to 25% by mass. <(C) Crosslinking Agent> The photosensitive resin composition of this embodiment preferably further contains a crosslinking agent as the (C) component. As the crosslinking agent, a crosslinking agent having two or more ethylenically unsaturated groups and no acidic substituents is preferred. By reacting with the ethylenically unsaturated groups possessed by the (A) component, the crosslinking density of the photosensitive resin film after curing is increased. Thus, the photosensitive resin composition of this embodiment tends to further improve in heat resistance and relative dielectric constant by containing a crosslinking agent. The (C) component may be used alone or in combination of two or more. Examples of the (C) component include bifunctional monomers having two ethylenically unsaturated groups and polyfunctional monomers having three or more ethylenically unsaturated groups. The (C) component preferably contains the aforementioned polyfunctional monomers. Examples of the ethylenically unsaturated groups possessed by the (C) component are the same as those possessed by the (A) component, and the preferred ones are also the same. Examples of the aforementioned bifunctional monomers include aliphatic di(meth)acrylates such as trimethylolpropane di(meth)acrylate, polypropylene glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate; (meth)acrylates having an alicyclic skeleton such as dicyclopentadiene di(meth)acrylate and tricyclodecane dimethanol di(meth)acrylate; and aromatic di(meth)acrylates such as 2,2-bis(4-(meth)acryloxypolyethoxypolypropoxyphenyl)propane and bisphenol A diglycidyl ether di(meth)acrylate. Among these, from the viewpoint of obtaining a lower relative dielectric constant, (meth)acrylates having an alicyclic skeleton are preferred, and tricyclodecane dimethanol di(meth)acrylate is more preferred. Examples of the polyfunctional monomer include (meth)acrylate compounds having a skeleton derived from trimethylolpropane such as trimethylolpropane tri(meth)acrylate; (meth)acrylate compounds having a skeleton derived from tetramethylolmethane such as tetramethylolmethane tri(meth)acrylate and tetramethylolmethane tetra(meth)acrylate; (meth)acrylate compounds having a skeleton derived from pentaerythritol such as pentaerythritol tri(meth)acrylate and pentaerythritol tetra(meth)acrylate; (meth)acrylate compounds having a skeleton derived from dipentaerythritol such as dipentaerythritol penta(meth)acrylate and dipentaerythritol hexa(meth)acrylate; (meth)acrylate compounds having a skeleton derived from ditrimethylolpropane such as ditrimethylolpropane tetra(meth)acrylate; (meth)acrylate compounds having a skeleton derived from diglycerol, and the like. Among these, from the viewpoints of resolution of vias and adhesion strength to copper plating, (meth)acrylate compounds having a skeleton derived from trimethylolpropane are preferred, and trimethylolpropane tri(meth)acrylate is more preferred. Here, the so-called "(meth)acrylate compound having a skeleton derived from XXX" (where XXX is a compound name) means an ester compound of XXX and (meth)acrylic acid, and the ester compound also includes a compound modified with an alkyleneoxy group. When the photosensitive resin composition of the present embodiment contains (C) a crosslinking agent, the content of (C) the crosslinking agent is not particularly limited, but from the viewpoints of heat resistance and relative dielectric constant, it is preferably 10 to 85 parts by mass, more preferably 25 to 80 parts by mass, still more preferably 35 to 75 parts by mass, and particularly preferably 35 to 60 parts by mass with respect to 100 parts by mass of the component (A). <(D) Elastomer> The photosensitive resin composition of the present embodiment preferably further contains an elastomer as the component (D). By containing the (D) elastomer, the adhesion strength to copper plating of the photosensitive resin composition of the present embodiment tends to be further improved. In addition, by containing the (D) elastomer, the photosensitive resin composition of the present embodiment tends to obtain an effect of suppressing "reduction in flexibility and adhesion strength to copper plating" caused by deformation (internal stress) that may occur due to the curing shrinkage of the component (A). The (D) elastomer may be used alone or in combination of two or more. (D) An elastomer, which may have reactive functional groups at the molecular ends or in the molecular chains. Examples of such reactive functional groups include: acid anhydride groups, epoxy groups, hydroxyl groups, carboxyl groups, amino groups, amide groups, isocyanate groups, acrylic groups, methacrylic groups, vinyl groups, etc. Among these, from the viewpoints of through-hole resolvability and adhesion strength to copper plating, acid anhydride groups, epoxy groups, hydroxyl groups, carboxyl groups, amino groups, and amide groups are preferred, acid anhydride groups, epoxy groups are more preferred, and acid anhydride groups are even more preferred. As the acid anhydride group, an acid anhydride group derived from the following acid anhydrides is preferred: phthalic anhydride, maleic anhydride, trimellitic anhydride, pyromellitic dianhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyl nadic anhydride, nadic anhydride, glutaric anhydride, dimethyl glutaric anhydride, diethyl glutaric anhydride, succinic anhydride, methyl hexahydrophthalic anhydride, methyl tetrahydrophthalic anhydride; an acid anhydride group derived from maleic anhydride is more preferred. When the (D) elastomer has an acid anhydride group, from the viewpoints of through-hole resolvability and relative dielectric constant, the number of acid anhydride groups in one molecule is preferably 1 to 10, more preferably 3 to 10, and even more preferably 6 to 10. The photosensitive resin composition of this embodiment preferably contains an elastomer having an ethylenically unsaturated group and an acidic substituent as the (D) elastomer. Examples of the acidic substituent and the ethylenically unsaturated group are the same as those of the (A) component. Among these, the (D) elastomer preferably has the aforementioned acid anhydride group as the acidic substituent and the following 1,2-vinyl group as the ethylenically unsaturated group. Examples of the (D) elastomer include: polybutadiene-based elastomers, polyester-based elastomers, styrene-based elastomers, olefin-based elastomers, polyurethane-based elastomers, polyamide-based elastomers, acrylic-based elastomers, silicone-based elastomers, derivatives of these elastomers, etc. Among these, from the viewpoint of improving the adhesion strength to copper plating and further from the viewpoints of improving the compatibility and solubility with the resin component, polybutadiene-based elastomers are preferred. Examples of the polybutadiene-based elastomer include those containing 1,2-vinyl and having structural units of 1,4-trans and 1,4-cis. As described above, from the viewpoint of the resolvability of the through-holes, the polybutadiene-based elastomer is preferably a polybutadiene-based elastomer modified with an acid anhydride and having an acid anhydride group, and more preferably a polybutadiene-based elastomer having an acid anhydride group derived from maleic anhydride. The polybutadiene-based elastomer can be purchased as a commercial product. Specific examples thereof include "POLYVEST (registered trademark) MA75" and "POLYVEST (registered trademark) EP MA120" (manufactured by Evonik Industries AG, trade names); "Ricon (registered trademark) 100", "Ricon (registered trademark) 130MA8", "Ricon (registered trademark) 131MA5", "Ricon (registered trademark) 131MA17", "Ricon (registered trademark) 184MA6" (manufactured by Cray Valley, trade names), etc. The polybutadiene-based elastomer may be an epoxy group-containing polybutadiene [hereinafter sometimes referred to as epoxidized polybutadiene] from the viewpoint of the adhesion strength to copper plating. The epoxidized polybutadiene is preferably an epoxidized polybutadiene represented by the following general formula (D-1) from the viewpoints of the adhesion strength to copper plating and flexibility. In the general formula (D-1), a, b, and c respectively represent the ratios of the structural units in the parentheses, where a is 0.05 to 0.40, b is 0.02 to 0.30, c is 0.30 to 0.80, and further a + b + c = 1.00 and (a + c) > b are satisfied. y represents the number of structural units in the brackets and is an integer of 10 to 250. In the foregoing general formula (D-1), the bonding order of each structural unit within the square brackets is immaterial as to sequence. That is to say, the structural unit shown on the left side, the structural unit shown in the middle, and the structural unit shown on the right side may be out of sequence. If they are represented by (a), (b), and (c) respectively, the following various bonding orders are possible: -[(a)-(b)-(c)]-, -[(a)-(b)-(c)-]-, -[(a)-(c)-(b)]-, -[(a)-(c)-(b)-]-, -[(b)-(a)-(c)]-, -[(b)-(a)-(c)-]-, -[(a)-(b)-(c)]-, -[(c)-(b)-(a)-]-, -[(a)-(b)-(a)]-, -[(c)-(b)-(c)-]-, -[(c)-(b)-(c)]-, -[(b)-(a)-(a)-]-, etc. From the viewpoints of the adhesion strength to copper plating and flexibility, a is preferably from 0.10 to 0.30, b is preferably from 0.10 to 0.30, and c is preferably from 0.40 to 0.80. Further, from the same viewpoints, y is preferably an integer from 30 to 180. Examples of the polyester-based elastomer include those obtained by polycondensing a dicarboxylic acid or its derivative with a diol compound or its derivative. Examples of the dicarboxylic acid include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid, and aromatic dicarboxylic acids in which the hydrogen atoms of these aromatic nuclei are substituted with a methyl group, an ethyl group, a phenyl group, etc.; aliphatic dicarboxylic acids having 2 to 20 carbon atoms such as adipic acid, sebacic acid, and dodecanedicarboxylic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, etc. Examples of the diol compound include aliphatic diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, and 1,10-decanediol; alicyclic diols such as 1,4-cyclohexanediol; aromatic diols such as bisphenol A, bis-(4-hydroxyphenyl)methane, bis-(4-hydroxy-3-methylphenyl)propane, and resorcinol, etc. Further, as the polyester-based elastomer, a multiblock copolymer is preferably exemplified, which has an aromatic polyester (for example, polybutylene terephthalate) part as a hard segment part and an aliphatic polyester (for example, polybutylene glycol) part as a soft segment part. As the multiblock copolymer, there are various grades of multiblock copolymers depending on the types, ratios, and molecular weight differences of the hard segment and the soft segment. (D) The number average molecular weight of the elastomer is not particularly limited, preferably from 10,000 to 80,000, may be from 20,000 to 70,000, may be from 30,000 to 65,000, or may be from 40,000 to 60,000. The number average molecular weight of (D) the elastomer can be determined by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent and in terms of standard polystyrene conversion. When the photosensitive resin composition of the present embodiment contains the (D) elastomer, the content of the (D) elastomer is not particularly limited. From the viewpoints of heat resistance and adhesion strength to copper plating, based on the total amount of the resin components of the photosensitive resin composition, it is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass, still more preferably 1 to 8% by mass, and particularly preferably 3 to 8% by mass. <(E) Organic filler> The photosensitive resin composition of the present embodiment may further contain an organic filler as the (E) component. By containing the (E) organic filler, the photosensitive resin composition and the photosensitive resin film tend to have a low specific gravity, and in addition, there is a tendency for the relative dielectric constant to be further reduced depending on the material. The (E) component preferably includes resin particles formed of at least one selected from the group consisting of resins having a fluorine atom, polyethylene, polypropylene, polystyrene, polyphenylene ether, and silicone. Among these, from the viewpoint of the effect of reducing the relative dielectric constant, the (E) component preferably includes resin particles formed of a resin having a fluorine atom, and more preferably includes resin particles formed of polytetrafluoroethylene (PTFE) resin. The volume average particle diameter of the aforementioned resin particles is not particularly limited, preferably 20 to 1000 nm, more preferably 30 to 800 nm, still more preferably 50 to 500 nm, and particularly preferably 100 to 300 nm. The method for measuring the volume average particle diameter is as described above. When the photosensitive resin composition of the present embodiment contains (E) an organic filler, the content of the (E) organic filler is not particularly limited. Based on the total amount of the resin components of the photosensitive resin composition, it is preferably 1 to 45% by mass, more preferably 3 to 40% by mass, still more preferably 5 to 30% by mass, and particularly preferably 10 to 30% by mass. If the content of the (E) organic filler is at least the aforementioned lower limit value based on the total amount of the resin components of the photosensitive resin composition, there is a tendency to further reduce the relative dielectric constant. If it is below the aforementioned upper limit value, there is a tendency to suppress the decrease in the adhesion strength to copper plating. From the same viewpoint, in particular, the content of the resin having a fluorine atom is preferably 1 to 45% by mass, more preferably 3 to 40% by mass, still more preferably 5 to 30% by mass, and particularly preferably 10 to 30% by mass based on the total amount of the resin components of the photosensitive resin composition. In particular, when the (E) organic filler contains resin particles formed from a resin having a fluorine atom, the total amount of the (X) component and the (E) component is preferably 50% by volume or less, more preferably 45% by volume or less, still more preferably 40% by volume or less based on the total amount of the resin components of the photosensitive resin composition from the viewpoint of the adhesion strength to copper plating. The lower limit value of the total amount of the (X) component and the (E) component is not particularly limited, but from the viewpoint of reducing the relative dielectric constant, it is preferably 2% by volume or more, more preferably 10% by volume or more, still more preferably 20% by volume or more, and particularly preferably 30% by volume or more. <(F) Hardener> The photosensitive resin composition of the present embodiment preferably further contains a hardener as the (F) component. By containing the (F) hardener, the photosensitive resin composition of the present embodiment tends to further improve heat resistance, relative dielectric constant, etc. The (F) hardener can be used alone as one kind, or two or more kinds can be used in combination. As the (F) curing agent, the curing agent for the aforementioned (B) thermosetting resin may be used. For example, when the aforementioned (B) thermosetting resin is an epoxy resin, it is preferable to use an epoxy resin curing agent. Examples of the epoxy resin curing agent include guanamines such as acetoguanamine and benzoguanamine; polyamines such as diaminodiphenylmethane, m-phenylenediamine, m-xylenediamine, diaminodiphenyl sulfone, dicyandiamide, urea, urea derivatives, melamine, and polyacid hydrazides; organic acid salts and / or epoxy adducts of these components; amine complexes of boron trifluoride; triazine derivatives such as ethylenediamine-S-triazine, 2,4-diamino-S-triazine, and 2,4-diamino-6-dimethylphenyl-S-triazine; polyphenols such as polyvinylphenol, brominated polyvinylphenol, phenol novolac, alkylphenol novolac, and triazine ring-containing phenol novolac resin. The aforementioned polyphenol may be, for example, a modified polyphenol modified with melamine, benzoguanamine, or the like. The hydroxyl equivalent of the aforementioned polyphenol is not particularly limited, and is preferably 40 to 300 g / eq, may be 40 to 250 g / eq, may be 60 to 200 g / eq, may be 80 to 160 g / eq, or may be 100 to 140 g / eq. Here, the hydroxyl equivalent (g / eq) can be determined by titration using an acetylation method with acetic anhydride. When the photosensitive resin composition of the present embodiment contains the (F) curing agent, the content of the (F) curing agent is not particularly limited. From the viewpoint of further improving heat resistance and relative dielectric constant, based on the total amount of the resin components of the photosensitive resin composition, it is preferably 0.01 to 10% by mass, more preferably 0.05 to 5% by mass, and still more preferably 0.1 to 1% by mass. <(G) Curing accelerator> The photosensitive resin composition of the present embodiment preferably further contains a curing accelerator as the (G) component. By containing the (G) curing accelerator, the photosensitive resin composition of the present embodiment tends to further improve heat resistance and relative dielectric constant. The (G) curing accelerator may be used alone or in combination of two or more. Examples of the (G) curing accelerator include imidazole compounds such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-phenylimidazole, 2-phenyl-1-benzyl-1H-imidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and isocyanate-blocked imidazole (an addition reaction product of hexamethylene diisocyanate resin and 2-ethyl-4-methylimidazole); tertiary amines such as trimethylamine, N,N-dimethyloctylamine, N-benzyldimethylamine, pyridine, N-methylmorpholine, hexakis(N-methyl)melamine, 2,4,6-tris(dimethylaminophenol), tetramethylguanidine, and m-aminophenol; organic phosphines such as tributylphosphine, triphenylphosphine, and tris(2-cyanoethyl)phosphine; phosphonium salts such as tributyl(2,5-dihydroxyphenyl)phosphonium bromide and cetyltributylphosphonium chloride; quaternary ammonium salts such as benzyltrimethylammonium chloride and phenyltributylammonium chloride; the aforementioned polycarboxylic anhydrides; diphenyliodonium tetrafluoroborate, triphenylsulfonium hexafluoroantimonate, 2,4,6-triphenylthiophenium hexafluorophosphate, and the like. Among these, from the viewpoint of obtaining excellent curing effects, imidazole compounds are preferred. When the photosensitive resin composition of the present embodiment contains the (G) curing accelerator, the content of the (G) curing accelerator is not particularly limited. From the viewpoint of further improving heat resistance and relative dielectric constant, based on the total amount of the resin components of the photosensitive resin composition, it is preferably 0.01 to 10% by mass, more preferably 0.05 to 5% by mass, and even more preferably 0.1 to 2% by mass. <(H) Photoinitiator> The photosensitive resin composition of the present embodiment preferably further contains a photoinitiator as the (H) component. By containing the (H) photoinitiator, the photosensitivity of the through holes tends to be further improved. The (H) photoinitiator can be used alone or in combination of two or more. From the viewpoint of the photosensitivity of the through holes, the photosensitive resin composition of the present embodiment preferably contains two or more (H) components. As the (H) photoinitiator, any compound that can cause the photopolymerization of ethylenically unsaturated groups can be used without particular limitation, and it can be appropriately selected from commonly used photoinitiators. Examples of the (H) photoinitiator include benzoin-based compounds such as benzoin, benzoin methyl ether, and benzoin isopropyl ether; acetophenone-based compounds such as acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, 2-[4-(methylthio)benzoyl]-2-(4-morpholino)propane, and N,N-dimethylaminoacetophenone; anthraquinone-based compounds such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, 2-pentylanthraquinone, and 2-aminoanthraquinone; ketal-based compounds such as acetophenone dimethyl ketal and benzyl dimethyl ketal; acridine-based compounds such as 9-phenylacridine and 1,7-bis(9,9'-acridinyl)heptane; acylphosphine oxide-based compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide; oxime ester-based compounds such as 1,2-octanedione-1-[4-(phenylthio)phenyl-2-(O-benzoyloxime)], 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone-1-(O-acetyl oxime), and 1-phenyl-1,2-propanedione-2-[O-(ethoxycarbonyl)oxime], etc. Among these, oxime ester-based compounds and acylphosphine oxide-based compounds are preferred, and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone-1-(O-acetyl oxime) and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide are more preferred. Oxime ester-based compounds have the advantage of improving the photocuring property, and acylphosphine oxide-based compounds have the advantage of improving the hardness at the bottom of the cured product obtained by curing the photosensitive resin film and suppressing undercutting. By using an oxime ester-based compound and an acylphosphine oxide-based compound in combination, there is a tendency to further improve the resolution of the through hole. When the photosensitive resin composition of the present embodiment contains the (H) photoinitiator, the content of the (H) photoinitiator is not particularly limited. Based on the total amount of the resin components of the photosensitive resin composition, it is preferably 0.01 to 20% by mass, more preferably 0.05 to 10% by mass, further preferably 0.05 to 3% by mass, and particularly preferably 0.05 to 1.0% by mass. If the content of the (H) photoinitiator is at least the aforementioned lower limit value, there is a tendency to reduce the dissolution of the exposed part during development, and if it is at most the aforementioned upper limit value, there is a tendency to improve the heat resistance. <(I) Photosensitizer> The photosensitive resin composition of this embodiment may contain a photosensitizer as component (I) as needed. One type of (I) photosensitizer can be used alone, or two or more types can be used in combination. From the perspective of via resolution, the photosensitive resin composition of this embodiment may contain two or more types of component (I). Examples of the (I) photosensitizer include thioxanthone compounds such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, and 2,4-diisopropylthioxanthone; tertiary amines such as trialkylamine and triethanolamine; alkyl esters of dialkylaminobenzoic acid such as ethyl N,N-dimethylaminobenzoate and pentyl N,N-dimethylaminobenzoate; bis(dialkylamino)benzophenones such as 4,4'-bis(dimethylamino)benzophenone and 4,4'-bis(diethylamino)benzophenone; phosphine compounds such as triphenylphosphine; toluidine compounds such as N,N-dimethyltoluidine; anthracene compounds such as 9,10-dimethoxyanthracene, 2-ethyl-9,10-dimethoxyanthracene, and 2-ethyl-9,10-diethoxyanthracene; perylene compounds; coumarin compounds, etc. As the (I) photosensitizer, from the viewpoints of via resolution and improvement of via shape, bis(dialkylamino)benzophenones are preferred, and 4,4'-bis(diethylamino)benzophenone is more preferred. When the photosensitive resin composition of this embodiment contains the (I) photosensitizer, the content of the (I) photosensitizer is not particularly limited. Based on the total amount of the resin components of the photosensitive resin composition, it is preferably 0.01 to 5% by mass, more preferably 0.05 to 3% by mass, further preferably 0.1 to 1.5% by mass, and particularly preferably 0.1 to 1.0% by mass. If the content of the (I) photosensitizer is at least the aforementioned lower limit value, the hardness of the bottom of the cured product obtained by curing the photosensitive resin film tends to increase sufficiently. If it is below the aforementioned upper limit value, the hardness of the bottom of the cured product tends to decrease to an appropriate level. <(J) Additives> The photosensitive resin composition of this embodiment may further contain the following various conventional and commonly used additives as needed: inorganic filler materials other than the aforementioned component (X); pigments such as phthalocyanine blue, phthalocyanine green, iodine green, diazo yellow, crystal violet, titanium oxide, carbon black, and naphthol black; adhesion aids such as melamine; defoaming agents such as silicone; polymerization inhibitors; tackifiers; flame retardants, etc. The content of these (J) additives can be appropriately adjusted according to their respective purposes. Based on the total amount of the resin components of the photosensitive resin composition, it is preferably 0.01 to 5% by mass respectively, more preferably 0.05 to 3% by mass, and further preferably 0.1 to 1% by mass. <Diluent> The photosensitive resin composition of this embodiment may contain a diluent as needed. Organic solvents and the like can be used as the diluent. Examples of the organic solvent include: ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; glycol ether compounds such as methyl cellosolve, butyl cellosolve, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol diethyl ether, and triethylene glycol monoethyl ether; esters such as ethyl acetate, butyl acetate, propylene glycol monoethyl ether acetate, butyl cellosolve acetate, and carbitol acetate; aliphatic hydrocarbons such as octane and decane; petroleum-based solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha. The diluent can be used alone or in combination of two or more. When the photosensitive resin composition of this embodiment contains a diluent, the content of the diluent can be appropriately selected according to the purpose to be adjusted. Preferably, the concentration of the total solid content in the photosensitive resin composition is adjusted to the range of 40 to 90% by mass, more preferably 50 to 85% by mass, and further preferably 60 to 80% by mass. By adjusting the amount of the diluent used within the above range, the coatability of the photosensitive resin composition is improved and a finer pattern can be formed. The photosensitive resin composition of this embodiment can be obtained by kneading and mixing each component using a roll mill, bead mill, etc. Here, the photosensitive resin composition of this embodiment can be used in a liquid state (liquid form) or in a film state (film form). When used in a liquid state (liquid form), the coating method of the photosensitive resin composition of this embodiment is not particularly limited, and examples include: printing method, spin coating method, spraying method, nozzle dispensing method, inkjet method, dip coating method, and other various coating methods. Among these, from the viewpoint of more easily forming a photosensitive layer, the printing method and the spin coating method are preferred. In addition, when used in a film form, for example, the form of the photosensitive resin film described later can be used. At this time, a laminator or the like can be used to form a photosensitive layer with a desired thickness by laminating on a carrier film. Furthermore, the method of using in a film form has a higher manufacturing efficiency for a multilayer printed circuit board, so it is preferred. The photosensitive resin composition of this embodiment is suitable for forming a through hole (also referred to as a via hole) by photolithography. Therefore, the present invention also provides a photosensitive resin composition for forming a via hole, which is composed of the photosensitive resin composition of this embodiment. [Photosensitive Resin Film] The photosensitive resin film of this embodiment is formed using the photosensitive resin composition of this embodiment. The photosensitive resin film helps to form a photosensitive layer for forming an interlayer insulating layer. The photosensitive resin film of this embodiment can be in a state of being provided on a carrier film. The photosensitive resin film of the present embodiment can be obtained, for example, by coating the photosensitive resin composition of the present embodiment with a conventional coating device and drying it on a carrier film. Examples of the coating device include a comma coater, a bar coater, a kiss coater, a roller coater, a gravure coater, a die coater, and the like. Examples of the carrier film include polyester films such as polyethylene terephthalate films and polybutylene terephthalate films; polyolefin films such as polypropylene films and polyethylene films. The thickness of the carrier film is preferably 5 to 100 μm, more preferably 10 to 60 μm, and even more preferably 15 to 45 μm. In addition, a protective film can be provided on the surface opposite to the surface in contact with the carrier film of the photosensitive resin film of the present embodiment. As the protective film, a polymer film such as polyethylene or polypropylene can be used. In addition, the same polymer film as the aforementioned carrier film can be used, or a different polymer film can be used. For the drying of the coating film formed by coating the photosensitive resin composition, a dryer using hot air drying, far-infrared rays or near-infrared rays can be used. As the drying temperature, it is preferably 60 to 150 °C, more preferably 70 to 120 °C, and even more preferably 80 to 110 °C. Also, as the drying time, it is preferably 1 to 60 minutes, more preferably 2 to 30 minutes, and even more preferably 5 to 20 minutes. From the viewpoint of avoiding the diffusion of the diluent in the manufacturing process of the multilayer printed wiring board, the content of the residual diluent in the dried photosensitive resin film is preferably 3% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less. The thickness (thickness after drying) of the photosensitive resin film (photosensitive layer) is not particularly limited, but from the viewpoint of thinning the multilayer printed wiring board, it is preferably 1 to 100 μm, more preferably 3 to 50 μm, and even more preferably 5 to 40 μm. The photosensitive resin film of the present embodiment is excellent in terms of the resolution of through holes and the adhesion strength to copper plating, and is therefore suitable for forming an interlayer insulating layer of a multilayer printed wiring board. [Multilayer Printed Circuit Board and Method for Manufacturing the Same] The multilayer printed circuit board of this embodiment contains an interlayer insulating layer, and the interlayer insulating layer is formed using the photosensitive resin composition or the photosensitive resin film of this embodiment described above. Here, the term "containing an interlayer insulating layer" includes: the case of directly containing it in the state of the interlayer insulating layer; and the case of containing it in the state after various treatments such as processing for forming vias, roughening treatment, etc. on the interlayer insulating layer and forming circuits, etc. The manufacturing method of the multilayer printed circuit board of this embodiment only needs to have a step of forming the interlayer insulating layer using the photosensitive resin composition or the photosensitive resin film of this embodiment, and there is no particular limitation. For example, it can be easily manufactured by the manufacturing method of the multilayer printed circuit board of this embodiment described below. A method for manufacturing a multilayer printed circuit board using the photosensitive resin film of this embodiment will be described while appropriately referring to FIG. 1. The multilayer printed circuit board 100A can be manufactured, for example, by a manufacturing method including the following steps (1) to (4) [however, step (3) is optional]. Step (1) is a step of laminating the photosensitive resin film of this embodiment on one or both sides of a circuit substrate (hereinafter referred to as "laminating step (1)"); Step (2) is a step of exposing and developing the photosensitive resin film laminated in step (1) to form an interlayer insulating layer having vias (hereinafter referred to as "photo via formation step (2)"); Step (3) is a step of roughening the aforementioned vias and the aforementioned interlayer insulating layer (hereinafter referred to as "roughening treatment step (3)"); Step (4) is a step of forming a circuit pattern on the aforementioned interlayer insulating layer (hereinafter referred to as "circuit pattern formation step (4)"). Here, as described above in this specification, for convenience, a specific operation may sometimes be referred to as "XX step", but the XX step is not limited to the specific forms described in this specification. (Laminating Step (1)) Laminating step (1) is the following step: using a vacuum laminator, laminating the photosensitive resin film of this embodiment on one or both sides of a circuit substrate (substrate 101 having a circuit pattern 102). Examples of the vacuum laminator include: a vacuum coater manufactured by Nichigo-Morton Co., Ltd., a vacuum pressure laminator manufactured by Meiki Seisakusho Co., Ltd., a roll-type dry coater manufactured by Hitachi, Ltd., a vacuum laminator manufactured by Showa Denko Materials & Electric Co., Ltd., etc. When a protective film is provided on the photosensitive resin film, after peeling or removing the protective film, it is possible to laminate while pressing and heating the circuit board in a state where the photosensitive resin film is in contact with the circuit board. For example, this lamination can be carried out under the conditions of a pressing temperature of 70 to 130 °C, a pressing pressure of 0.1 to 1.0 MPa, and a reduced pressure of an air pressure of 20 mmHg (26.7 hPa) or less after preheating the photosensitive resin film and the circuit board as needed, but it is not particularly limited to these conditions. In addition, the lamination method can be a batch type or a continuous type using rollers. Finally, the photosensitive resin film laminated on the circuit board is cooled to around room temperature to form the interlayer insulating layer 103. When the photosensitive resin film has a carrier film, the carrier film can be peeled off at this time, or it can be peeled off after exposure as described later. (Via hole forming step (2)) In the via hole forming step (2), at least a part of the photosensitive resin film laminated on the circuit board is exposed and then developed. By exposure, the irradiated part of the active light is photocured to form a pattern. There is no particular limitation on the exposure method. For example, a method of irradiating the active light in an image shape through a negative or positive mask pattern called artwork (photomask exposure method) can be used, or a method of irradiating the active light in an image shape by direct drawing exposure method, which is an LDI (Laser Direct Imaging) exposure method, a DLP (Digital Light Processing) exposure method, etc. As the light source of the active light, a known light source can be used. Specifically, examples of the light source include gas lasers such as carbon arc lamps, mercury vapor arc lamps, high-pressure mercury lamps, xenon lamps, and argon lasers; solid lasers such as YAG lasers; semiconductor lasers that can effectively emit ultraviolet rays or visible light, etc. The exposure amount can be appropriately selected according to the light source used, the thickness of the photosensitive layer, etc. For example, when irradiating ultraviolet rays from a high-pressure mercury lamp, when the thickness of the photosensitive layer is 1 to 100 μm, it is usually preferably 10 to 1000 mJ / cm 2 or so, more preferably 50 to 700 mJ / cm 2 or so, even more preferably 150 to 550 mJ / cm 2 or so, particularly preferably 250 to 500 mJ / cm 2 . During development, the uncured portion of the photosensitive layer is removed from the substrate, and thus the photo-cured portion is formed as an interlayer insulating layer on the substrate. When there is a carrier film on the photosensitive layer, the removal (development) of the unexposed portion is performed after removing the carrier film. As the development method, wet development and dry development can both be used, but wet development has been widely used, and wet development can also be used in this embodiment. During wet development, a developer corresponding to the photosensitive resin composition is used and development is performed by a known development method. As the development method, examples include dipping, paddle, spraying, brushing, slapping, scrapping, rocking dipping, and other methods. Among these, from the viewpoint of improving the resolution of the through holes, spraying is preferred, and among spraying methods, high-pressure spraying is more preferred. Development can be performed using only one method, but two or more methods can also be combined. The composition of the developer can be appropriately selected according to the composition of the photosensitive resin composition. Examples include alkaline aqueous solutions, aqueous developers, organic solvent-based developers, etc. Among these, an alkaline aqueous solution is preferred. In the optical via formation step (2), after exposure and development, post UV-cure with an exposure amount of 0.2 to 10 J / cm 2 or so (preferably 0.5 to 5 J / cm 2 ) and post thermal cure at a temperature of about 60 to 250 °C (preferably 120 to 200 °C) can be performed as needed to further cure the interlayer insulating layer, and it is preferably further cured. By the above method, an interlayer insulating layer having through holes 104 can be formed. The shape of the through holes is not particularly limited. When described by the cross-sectional shape, examples include a square, an inverted trapezoid (the upper side is longer than the lower side), etc. When described by the shape observed from the front (the direction in which the bottom of the through hole can be seen), examples include a circle, a quadrilateral, etc. In this embodiment, the through holes formed by photolithography can form through holes having an inverted trapezoidal cross-sectional shape (the upper side is longer than the lower side). At this time, the uniform plating property of copper plating on the through hole wall surface becomes higher, which is thus preferred. The size (diameter) of the through holes 104 formed by this step can be made less than 40 μm, and further can be 35 μm or less or 30 μm or less. Compared with the size of the through holes fabricated by laser processing, the diameter can be further reduced. The lower limit value of the size (diameter) of the through holes formed by this step is not particularly limited and can be 15 μm or more or 20 μm or more. However, the size (diameter) of the through holes 104 formed by this step is not limited to less than 40 μm. For example, it can be arbitrarily selected within the range of 15 to 300 μm. (Roughening treatment step (3)) As needed, the roughening treatment step (3) can be carried out by roughening the surfaces of the through holes and the interlayer insulating layer using a roughening solution. Furthermore, when smears are generated in the aforementioned light through hole forming step (2), the smears can be removed using the aforementioned roughening solution. The roughening treatment and smear removal (desmearing) can be carried out simultaneously. Examples of the aforementioned roughening solution include: chromium / sulfuric acid roughening solution, alkaline permanganic acid roughening solution (such as sodium permanganate roughening solution, etc.), sodium fluoride / chromium / sulfuric acid roughening solution, etc. By the roughening treatment, uneven anchors can be formed on the surfaces of the through holes and the interlayer insulating layer. (Circuit pattern forming step (4)) The circuit pattern forming step (4) is a step of forming a circuit pattern on the aforementioned interlayer insulating layer after the aforementioned roughening treatment step (3). From the viewpoint of forming fine lines by forming the circuit pattern, it is preferably to implement the semi-additive method. By the semi-additive method, a circuit pattern can be formed and the through holes can be made conductive. In the semi-additive method, first, electroless copper plating treatment is carried out on the bottom of the through hole, the wall surface of the through hole, and the entire surface of the interlayer insulating layer after the aforementioned roughening treatment step (3) using a palladium catalyst or the like to form a seed layer 105. The seed layer 105 is used to form a feeding layer for implementing electrolytic copper plating, and it is preferably formed with a thickness of about 0.1 to 2.0 μm. As long as the thickness of the seed layer 105 is 0.1 μm or more, there is a tendency to suppress the reduction of connection reliability during electrolytic copper plating. As long as it is 2.0 μm or less, when flash etching the seed layer between the lines, there is no need to increase the etching amount, and there is a tendency to suppress damage to the lines during etching. The aforementioned electroless copper plating treatment is carried out by the reaction of copper ions and a reducing agent, causing metallic copper to precipitate on the surfaces of the through holes and the interlayer insulating layer. The aforementioned electroless plating treatment method and the aforementioned electrolytic plating treatment method can be applied using known methods and are not particularly limited. As the electroless copper plating solution, commercially available products can be used. Examples of commercially available products include: "MSK-DK" manufactured by Atotech Japan Co., Ltd., "THRU-CUP (registered trademark PEA)" series manufactured by Uemura Corporation, etc. After performing the electroless copper plating treatment described above, a dry film resist is thermocompression bonded to the electroless copper plating in a roll laminator. The thickness of the dry film resist needs to be higher than the height of the circuit after electrolytic copper plating. From this viewpoint, a dry film resist with a thickness of 5 to 30 μm is preferably used. As the dry film resist, the "PHOTEC (registered trademark)" series manufactured by Showa Denko Materials Co., Ltd. etc. can be used. After the dry film resist is thermocompression bonded, for example, the dry film resist can be exposed through a mask depicting a desired circuit pattern. The exposure can use the same device and light source that can be used when forming through holes in the aforementioned photosensitive resin film. After exposure, an alkaline aqueous solution is used to develop the dry film resist and remove the unexposed portion, thereby forming a resist pattern 106. Thereafter, if necessary, operations such as using plasma to remove the development residues of the dry film resist can be performed. After development, an electrolytic copper plating is performed to form a copper circuit layer (circuit pattern) 107 and perform via filling. After electrolytic copper plating, an alkaline aqueous solution or an amine-based stripping solution is used to strip the dry film resist. After stripping the dry film resist, the seed layer (flash etching) between the circuits is removed. Flash etching is performed using an acidic solution such as sulfuric acid and hydrogen peroxide and an oxidizing solution. After flash etching, if necessary, palladium etc. attached to the portion between the circuits is removed. The removal of palladium can preferably be performed using an acidic solution such as nitric acid and hydrochloric acid. After stripping the aforementioned dry film resist or after the flash etching step, it is preferably to perform a post bake treatment. The post bake treatment can fully thermoset the unreacted thermosetting components, and further thereby tends to improve the insulation reliability, hardening characteristics, and adhesion strength to copper plating. The thermosetting conditions vary depending on the type of the resin composition etc., but the preferred conditions are: a hardening temperature of 150 to 240 °C and a hardening time of 15 to 100 minutes. By the post bake treatment, the manufacturing steps of the multilayer printed wiring board 100A based on the general photo via method can be completed, but the substrate can still be manufactured by repeating this step according to the number of required interlayer insulation layers. And, it is preferably to form a solder resist layer 108 on the outermost layer. As described above, a method for manufacturing a multilayer printed wiring board has been described, which uses the photosensitive resin composition of the present embodiment to form through holes. However, since the photosensitive resin composition of the present embodiment has excellent pattern resolution, it is also suitable for forming cavities for built-in chips or passive components, for example. The cavity can be suitably formed in the following form: in the description of the aforementioned multilayer printed wiring board, when exposing the photosensitive resin film to form a pattern, the depicted pattern at this time can be formed into a desired cavity. In addition, the photosensitive resin composition of the present embodiment is also helpful for making solder resist applications. [Semiconductor Package] This specification also provides a semiconductor package, which includes the multilayer printed wiring board and semiconductor element of this embodiment. The semiconductor package of this embodiment can be manufactured by the following method: assembling semiconductor elements such as semiconductor wafers and memories at specific positions on the multilayer printed wiring board of this embodiment, and sealing the semiconductor elements with a sealing resin or the like. [Examples] Hereinafter, this embodiment will be described in further detail by way of examples. However, the present invention is not limited to these examples. Furthermore, the acid value and weight average molecular weight of component (A) are measured according to the following method, and the true densities of component (X), component (X'), and component (E) are measured according to the following method. In addition, the photosensitive resin compositions obtained from each example are evaluated for their properties by the methods shown below. <Method for Measuring Acid Value> The acid value of component (A) is calculated from the amount of potassium hydroxide aqueous solution required to neutralize component (A). <Method for Measuring Weight Average Molecular Weight> The weight average molecular weight of component (A) is measured using the following GPC measuring device and measuring conditions, and is converted using the calibration curve of standard polystyrene. Then, the converted value is set as the weight average molecular weight. In addition, a 5-sample kit ("PStQuick MP-H" and "PStQuick B", manufactured by Tosoh Corporation) was used as the standard polystyrene for preparing the calibration curve. (GPC Measuring Device) Device: High-speed GPC device "HCL-8320GPC", the detector is a differential refractive index detector or a UV detector, manufactured by Tosoh Corporation. Column: Column TSKgel SuperMultipore HZ-H (column length: 15 cm; column inner diameter: 4.6 mm), manufactured by Tosoh Corporation. (Measuring Conditions) Solvent: Tetrahydrofuran (THF). Measuring temperature: 40°C. Flow rate: 0.35 mL / minute. Sample concentration: 10 mg / THF 5 mL. Injection volume: 20 μL. <Method for Measuring True Density and Method for Calculating Void Ratio> (True Density) First, component (X) or component (X') is placed in a mortar and ground with a pestle to obtain component (X) or component (X') with a particle size of 0.1 μm or less. In a dry-type automatic density meter "AccuPycII 1340" (manufactured by Shimadzu Corporation) 1 cm 3In the sample cell used, fill the ground (X) component or (X’) component to 80% full. Measure the weight of the sample cell filled with the aforementioned component, and then subtract the weight of only the sample cell to obtain the weight of the component filled in the sample cell. Subsequently, install the sample cell filled with the aforementioned component on the aforementioned dry-type automatic densitometer, and then input the weight of the component. With the sample cell installed, after leaving it for 1 hour at normal temperature and in a nitrogen atmosphere, conduct 10 measurements to obtain the average value. Set this average value as the true density. (Void ratio) Different from the measurement of the above true density, measure the apparent density (specific gravity) of the (X) component or (X’) component using the aforementioned dry-type automatic densitometer. The measurement of the apparent density (specific gravity) is carried out according to the following operation. In the dry-type automatic densitometer “AccuPycII 1340” (manufactured by Shimadzu Corporation) 1 cm 3 In the sample cell used, fill the (X) component or (X’) component (both in their original state without being ground) to 80% full. Measure the weight of the sample cell filled with the aforementioned component, and then subtract the weight of only the sample cell to obtain the weight of the component filled in the sample cell. Subsequently, install the sample cell filled with the aforementioned component on the aforementioned dry-type automatic densitometer, and then input the weight of the component. With the sample cell installed, after leaving it for 1 hour at normal temperature and in a nitrogen atmosphere, conduct 10 measurements to obtain the average value. Set this average value as the apparent density (specific gravity). Using the apparent density (specific gravity) obtained by the above operation and the aforementioned true density, calculate the void ratio according to the following formula. Void ratio (%) = 100 × {1 - (apparent density) / (true density)} [1. Evaluation of relative dielectric constant (Dk)] Stick two photosensitive resin films from which the protective films have been removed, in a state of having a carrier film with both sides, and irradiate using a UV transmission type exposure machine under the condition of 2 J / cm 2 (wavelength 365 nm). Conduct heat treatment at 170 °C for 1 hour using a hot air circulation type dryer, and then cut the heat-treated product into a size of 7 cm × 10 cm to obtain the evaluation sample. After drying the obtained evaluation sample at 105 °C for 10 minutes using a hot air circulation type dryer, measure the relative dielectric constant (Dk) in the 10 GHz frequency band using the split post dielectric resonator (SPDR) method. [Evaluation of the adhesion strength with copper plating and evaluation of whether plating peeling occurs] Peel the protective film from the "photosensitive resin film laminated with a carrier film and a protective film" produced in each example and comparative example. At the same time, use a pressure-type vacuum laminator (manufactured by Meiki Seisakusho Co., Ltd., trade name "MVLP-500"), and laminate it on a copper-clad laminate substrate with a thickness of 1.0 mm under the following lamination conditions to obtain a laminate. The lamination conditions are: crimping pressure 0.4 MPa, temperature of the pressure heating plate 80 °C, vacuum suction time 25 seconds, lamination pressing time 25 seconds, air pressure 4 kPa or less. For the obtained laminate, use a parallel light exposure machine (manufactured by Oak Seisakusho Co., Ltd., trade name "EXM-1201") with an ultra-high pressure mercury lamp as the light source, and expose the entire surface under the condition of 400 mJ / cm 2 (wavelength 365 nm). Subsequently, use an ultraviolet exposure device to expose it with an exposure dose of 2000 mJ / cm 2 (wavelength 365 nm), and then obtain an "evaluation laminate" with a hardened product formed on the copper-clad laminate substrate by heating at 170 °C for 1 hour. Subsequently, first prepare an aqueous solution of "200 ml / L of diethylene glycol monobutyl ether and 5 g / L of sodium hydroxide" as a swelling solution, then heat it to 70 °C, and immerse the evaluation laminate for 10 minutes. Then, prepare an aqueous solution of 60 g / L of potassium permanganate and 40 g / L of sodium hydroxide as a roughening solution, then heat it to 70 °C, and immerse the evaluation laminate for 15 minutes. Next, prepare a neutralizing solution (tin chloride (SnCl 2) An aqueous solution with a concentration of 30 g / L and 300 ml / L of hydrogen chloride was heated to 40 °C, and then the evaluation laminate was immersed for 5 minutes to reduce potassium permanganate. Through the above operations, the surface of the hardened product of the evaluation laminate was subjected to desmear treatment. Subsequently, the surface of the hardened product of the evaluation laminate after desmear treatment was treated with an alkaline cleaning solution "Cleanse Secretant 902" (manufactured by Atotech Japan Co., Ltd., trade name) at 60 °C for 5 minutes, followed by degreasing and washing. After washing, the hardened product after desmear treatment was treated with a pre-dip solution "Pre-Dip Neo Gantt B" (manufactured by Atotech Japan Co., Ltd., trade name) at 23 °C for 1 minute. Thereafter, the aforementioned hardened product was treated with an activation solution "Activator Neo Gantt 834" (manufactured by Atotech Japan Co., Ltd., trade name) at 35 °C for 5 minutes, and then the hardened product was treated with a reducing solution "Reducer Neo Gantt WA" (manufactured by Atotech Japan Co., Ltd., trade name) at 30 °C for 5 minutes. The evaluation laminate obtained through the above operations was immersed in electroless plating solutions "Basic Print Gantt MSK-DK", "Copper Print Gantt MSK", "Stabilizer Print Gantt MSK" (all manufactured by Atotech Japan Co., Ltd., trade names) to perform electroless plating until the plating thickness reached approximately 0.5 μm. After this electroless plating, in order to remove the remaining hydrogen, a tempering treatment was performed at a temperature of 120 °C for 30 minutes. Thereafter, copper sulfate electrolytic plating was performed, and a tempering treatment was performed at 180 °C for 60 minutes to form a conductor layer with a thickness of 25 μm. Regarding the evaluation laminate with a conductor layer formed by the aforementioned method, in accordance with Japanese Industrial Standard JIS C6481 (1996), the vertical peel strength was measured at 23 °C, and the evaluation was carried out according to the following evaluation criteria. A: The adhesion strength to copper plating is 0.40 kN / m or more. B: The adhesion strength to copper plating is 0.30 kN / m or more and less than 0.4 kN / m. C: The adhesion strength to copper plating exceeds 0.1 kN / m and is less than 0.3 kN / m. D: The adhesion strength to copper plating is 0.1 kN / m or less. In addition, the surface of the evaluation laminate after the aforementioned tempering treatment was visually observed to confirm whether plating peeling occurred. When plating peeling occurred, unevenness would be generated on the plating surface, and when plating peeling did not occur, a flat plating surface would be presented. [Preparation of Photosensitive Resin Composition] Examples 1 to 5, Comparative Examples 1 to 3 (1) Manufacture of Photosensitive Resin Composition After preparing the composition according to the formulation shown in Table 1 (the unit of the values in the table is parts by mass, and when it is a solution, it is the solid content conversion amount), knead it using a three-roll mixer. Then, add methyl ethyl ketone so that the solid content concentration becomes 65% by mass to obtain a photosensitive resin composition. (2) Manufacture of Photosensitive Resin Film Use a polyethylene terephthalate film with a thickness of 16 μm (manufactured by Teijin Limited, trade name "G2-16") as the carrier film. Adjust and coat the photosensitive resin composition prepared in each example on this carrier film so that the thickness after drying becomes 25 μm, and then dry it in a hot air convection dryer at 100 °C for 10 minutes to form a photosensitive resin film (photosensitive layer). Subsequently, laminate a polyethylene film (manufactured by Tamapoly Co., Ltd., trade name "NF-15") on the surface of the photosensitive resin film (photosensitive layer) opposite to the side in contact with the carrier film as a protective film to obtain a photosensitive resin film with the carrier film and the protective film laminated thereon. Perform each evaluation using the prepared photosensitive resin film according to the aforementioned method. The results are shown in Table 1. [Table 1] ‧ The unit of the content is parts by mass, and when it is a solution or dispersion, it is equivalent to the solid content conversion amount. ‧ The content described in parentheses is "volume%" based on the total amount of the solid content. Each component used in Table 1 is as described below. [(A) Photopolymerizable Compound with Ethylenically Unsaturated Group and Acidic Substituent] ‧ A1: "ZXR-1935H" (manufactured by Nippon Kayaku Co., Ltd., acid value: 110 mg KOH / g, weight average molecular weight: 2000). [(B) Thermosetting Resin] ‧ B1: "Epototo (registered trademark) ESN-475V" (manufactured by Nippon Steel Chemical & Material Co., Ltd., naphthol type epoxy resin, epoxy equivalent: 325 g / eq). ‧ B2: "NC-3000L" (manufactured by Nippon Kayaku Co., Ltd., biphenyl aralkyl type epoxy resin, epoxy equivalent: 272 g / eq). [(C) Crosslinking Agent] ‧ C1: "TMPTA" (trimethylolpropane triacrylate). [(D) Elastomer] ‧ D1: "Ricon (registered trademark) 131MA17" (manufactured by Cray Valley, maleic acid modified polybutadiene, number average molecular weight 54000 (catalog value). ‧ D2: "Ricon (registered trademark) 100" (manufactured by Cray Valley, butadiene-styrene block copolymer, number average molecular weight 45000 (catalog value). [(X) The following inorganic filler materials as solid particles] ‧ X1: True density is 1350 kg / m 3 Silane coupling agent treated product of spherical fused silica (volume average particle diameter: 0.7 μm) as solid particles, hollow ratio = 39%. ‧ X2: True density is 1350 kg / m 3 Silane coupling agent treated product of spherical fused silica (volume average particle diameter: 1.5 μm) as solid particles, hollow ratio = 39%. ‧ X3: True density is 1350 kg / m 3 Silane coupling agent treated product of spherical fused silica (volume average particle diameter: 3.0 μm) as solid particles, hollow ratio = 39%. 3 Silane coupling agent treated product of spherical fused silica (volume average particle diameter: 3.0 μm) as solid particles, hollow ratio = 39%. [(X’) Inorganic filler materials other than the components in (X)] (True density exceeds 1500 kg / m 3 The following inorganic filler materials as solid particles) ‧ X’1: True density is 2210 kg / m 3 Silane coupling agent treated product of spherical fused silica (volume average particle diameter: 0.5 μm) as solid particles, hollow ratio = 0%. (True density is 1500 kg / m 3 The following inorganic filler materials as hollow particles) ‧ X’2: True density is 620 kg / m 3 Silane coupling agent treated product of spherical fused silica (volume average particle diameter: 0.7 μm) as hollow particles, hollow ratio = 72%. [(E) Organic filler material] ‧ PTFE: "M-7226EX" (manufactured by Morimura Chemical Co., Ltd., volume average particle diameter: 200 nm). [(F) Hardener] ‧F1: "PHENOLITE (registered trademark) LA7052" (manufactured by DIC Corporation, a phenolic varnish type phenol resin modified with melamine and benzoguanamine, hydroxyl equivalent: 120 g / eq). [(G) Curing accelerator] ‧G1: 2-phenyl-1-benzyl-1H-imidazole (imidazole compound) [(H) Photoinitiator] ‧H1: 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone-1-(O-acetyl oxime) (oxime ester compound). ‧H2: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (acylphosphine oxide compound). [(I) Photosensitizer] ‧I1: 4,4'-bis(diethylamino)benzophenone [(J) Additive] ‧4-tert-butylcatechol: Polymerization inhibitor. ‧"SH-193" (manufactured by Dow Toray Co., Ltd., silicone-based foam control agent). As can be seen from Table 1, compared with the photosensitive resin composition of Comparative Example 1 using an inorganic filler with a true density of 2210 kg / m 3 The photosensitive resin compositions of Examples 1 to 5 of this embodiment can reduce the relative dielectric constant while maintaining a relatively high adhesion strength to copper plating. Furthermore, it can be seen that the photosensitive resin composition of Comparative Example 2 containing a large amount of PTFE for the purpose of significantly reducing the relative dielectric constant, although achieving its purpose, has a significantly reduced adhesion strength to copper plating and is prone to plating peeling. In addition, even when the true density is 1500 kg / m 3 Hereinafter, when it is a hollow particle, the adhesion strength to copper plating will still be significantly reduced and plating peeling will occur. 100A: Multilayer printed circuit board 101: Substrate 102: Circuit pattern 103: Interlayer insulation layer 104: Through hole (perforation) 105: Seed layer 106: Resist pattern 107: Copper circuit layer 108: Solder resist layer Figure 1 is a schematic diagram showing an aspect of the manufacturing steps of a multilayer printed circuit board using the photosensitive resin film of this embodiment as a material for at least one of the surface protection layer and the interlayer insulation layer. Domestic deposit information (please note in the order of deposit institution, date, number) None Foreign deposit information (please note in the order of deposit country, institution, date, number) None 100A: Multilayer printed circuit board 101: Substrate 102: Circuit pattern 103: Interlayer insulating layer 104: Through hole (via hole) 105: Seed layer 106: Resist pattern 107: Copper circuit layer 108: Solder mask layer

Claims

1. A photosensitive resin composition comprising (X) an inorganic filler material having a true density of 1000-1500 kg / m³, wherein the inorganic filler material is a solid particle having a hollow fraction of 60% or less, determined by measuring the true density using a dry automatic densitometer; (A) a photopolymerizable compound having an ethylene unsaturated group and an acidic substituent; and (B) a thermosetting resin; wherein the content of the aforementioned component (X) is 1-45% by volume based on the total solid content of the photosensitive resin composition; and the aforementioned thermosetting resin (B) comprises an epoxy resin.

2. The photosensitive resin composition as described in claim 1, wherein, The volume average particle size of the aforementioned component (X) is 0.3–3 μm.

3. The photosensitive resin composition as described in claim 1, wherein, The aforementioned component (A) comprises an alicyclic skeleton represented by the following general formula (A-1), in which RA1 represents an alkyl group having 1 to 12 carbon atoms and may substitute for any position in the aforementioned alicyclic skeleton, m1 is an integer from 0 to 6, and * is a bonding site with other structures.

4. The photosensitive resin composition as described in claim 3, wherein, The equivalent ratio of the acidic substituent of component (A) to the epoxy group of component (B), i.e., the epoxy group / acidic substituent ratio, is 0.5 to 6.

0.

5. The photosensitive resin composition as described in any one of claims 1 to 4, wherein, It further contains (C) crosslinking agent.

6. The photosensitive resin composition as described in any one of claims 1 to 4, wherein, It further contains (D) elastomer.

7. The photosensitive resin composition as described in any one of claims 1 to 4, wherein, It further contains (E) organic filler material.

8. The photosensitive resin composition as described in claim 7, wherein, The aforementioned component (E) comprises resin particles formed from at least one of the group consisting of resins having fluorine atoms, polyethylene, polypropylene, polystyrene, polyphenylene ether and silicone.

9. The photosensitive resin composition as described in claim 7, wherein, The content of the aforementioned component (E) is 1 to 45% by volume, based on the total solid content of the photosensitive resin composition.

10. The photosensitive resin composition as described in any one of claims 1 to 4, wherein, It further contains (H) photopolymerization initiator.

11. The photosensitive resin composition as described in claim 10, wherein, It contains two or more of the aforementioned (H) components.

12. A photosensitive resin composition for forming a light aperture, comprising the photosensitive resin composition described in any one of claims 1 to 11.

13. A photosensitive resin film formed using any one of the photosensitive resin compositions described in claims 1 to 11.

14. A multilayer printed circuit board comprising an interlayer insulating layer, the interlayer insulating layer being formed using a photosensitive resin composition described in any one of claims 1 to 11 or a photosensitive resin film described in claim 13.

15. A semiconductor package comprising the multilayer printed circuit board and semiconductor element described in claim 14.

16. A method for manufacturing a multilayer printed circuit board, comprising the following steps (1), (2) and (4): Step (1), wherein a photosensitive resin film as described in claim 13 is laminated on one or both sides of a circuit substrate; Step (2), wherein the photosensitive resin film laminated in step (1) is exposed and developed to form an interlayer insulating layer having through holes; and Step (4), wherein a circuit pattern is formed on the interlayer insulating layer.

Images