Laminate and method for manufacturing same, printed wiring board, and semiconductor device

Abstract

Provided are: a laminate having a low dielectric constant and high reliability when used as an interlayer insulating film; a method for manufacturing the same; a printed wiring board in which the laminate is used; and a semiconductor device. A laminate is provided with a thermosetting resin layer (2) containing at least a resin and hollow inorganic particles (1) and having a dielectric constant of less than 2.6 at a frequency of 10 GHz, and satisfies at least one of conditions (1) and (2). Condition (1): A substrate (3) disposed in contact with a first surface (2A) of the thermosetting resin layer (2) is provided, and the number of voids (4) that are present at the interface between the substrate (3) and the thermosetting resin layer (2) and that have a cross-sectional area of 500 µm2 or more is 10 voids / mm2 or less. Condition (2): A protection film (5) disposed in contact with a second surface (2B) of the thermosetting resin layer (2) opposite to the first surface (2A) is provided, and the number of voids (6) that are present at the interface between the thermosetting resin layer (2) and the protection film (5) and that have a cross-sectional area of 50 µm2 or more is 10 voids / mm2 or less.

Description

Laminate and method for manufacturing the same, printed circuit board and semiconductor device

[0001] This disclosure relates to laminates, methods for manufacturing the same, printed circuit boards, and semiconductor devices.

[0002] To achieve low semiconductor loss, interlayer insulating films (build-up films: BUFs) used in printed circuit boards and the like are required to have low transmission loss performance. One known means of achieving low transmission loss is to lower the dielectric constant of the interlayer insulating film. Patent Document 1 discloses an insulating film composed of a resin composition using a filler containing a specific amount of hollow silica in order to achieve a low dielectric constant.

[0003] Japanese Patent Publication No. 2013-173841

[0004] Interlayer insulating films containing hollow inorganic particles such as hollow silica can lower the dielectric constant, but printed circuit boards made using these films tend to have a higher rate of circuit breakage. Furthermore, when using interlayer insulating films, the rate of unfilled gaps in circuit patterns tends to be high. Therefore, in addition to a low dielectric constant, interlayer insulating films are required to have good embedding properties in circuit patterns and high reliability, such as not causing circuit breakage.

[0005] This disclosure has been made in view of the above-mentioned problems, and aims to provide a laminate that is highly reliable and has a low dielectric constant when used as an interlayer insulating film, a method for manufacturing the same, a printed circuit board, and a semiconductor device using the laminate.

[0006] The laminate, its manufacturing method, printed circuit board, and semiconductor device relating to this disclosure are as shown in [1] to

[14] below. [1] A laminate having a thermosetting resin layer comprising at least a resin and hollow inorganic particles, having a dielectric constant of less than 2.6 at a frequency of 10 GHz, and satisfying at least one of the following conditions (1) and (2): (1) Having a substrate disposed in contact with the first surface of the thermosetting resin layer, wherein the cross-sectional area at the interface between the substrate and the thermosetting resin layer is 500 μm ２ The number of voids above this is 10 / mm ２The following applies: (2) A protective film is provided which is in contact with the second surface of the thermosetting resin layer facing the first surface, and the cross-sectional area at the interface between the thermosetting resin layer and the protective film is 50 μm ２ The number of voids above this is 10 / mm ２ The following: [2] The laminate according to [1], wherein the weight loss rate when the thermosetting resin layer peeled from the substrate is heated at 150°C for 1 hour is 1.7 to 3.8%, satisfying condition (1) above. [3] The laminate according to [1], wherein the curvature in the sheet flow direction is 0.01 or less, satisfying condition (2) above. [4] The laminate according to any one of [1] to [3], wherein the average particle diameter of the hollow inorganic particles is 0.1 to 10.0 μm. [5] The laminate according to any one of [1] to [4], wherein the porosity of the hollow inorganic particles is 5 volume% or more. [6] The specific gravity of the hollow inorganic particles is 1.0 g / cm³. ３ The laminate according to any one of [1] to [5], which is as follows: [7] The laminate according to any one of [1] to [6], wherein the uniformity of the hollow inorganic particles is 1.7 to 3.4. [8] The laminate according to any one of [1] to [7], wherein the thermosetting resin layer comprises a thermosetting resin, a thermoplastic elastomer and a thermoplastic elastomer. [9] The laminate according to any one of [1] to [8], wherein the thickness of the thermosetting resin layer is 10 to 125 μm.

[10] The laminate according to any one of [1] to [9], wherein the substrate comprises a polyester stretched film having a glass transition temperature of 105°C or higher.

[11] The laminate according to any one of [1] to

[10] , which is a thermosetting resin sheet.

[12] A method for manufacturing the laminate according to any one of [1] to

[10] , comprising the step of drying the undried thermosetting resin layer from the first surface side of the thermosetting resin layer. A printed circuit board comprising a cured product of the thermosetting resin layer in the laminate according to any one of [1] to

[11] . A semiconductor device comprising the printed circuit board according to

[13] .

[0007] This disclosure provides a laminate that is highly reliable and has a low dielectric constant when used as an interlayer insulating film, a method for manufacturing the same, a printed circuit board using the laminate, and a semiconductor device.

[0008] (It is) a schematic cross-sectional view showing an example of the layered product (first layered product) according to the first embodiment. (It is) a schematic cross-sectional view showing an example of the layered product (second layered product) according to the second embodiment. (It is) a schematic cross-sectional view showing an example of the layered product (third layered product) according to the third embodiment. (It is) a diagram for explaining the method for measuring the curvature of the layered product according to the present embodiment in the sheet flow direction. (It is) a diagram for explaining voids present at the interface between the base material and the thermosetting resin layer in the layered product. (It is) a diagram for explaining voids present at the interface between the thermosetting resin layer and the protective film in the layered product.

[0009] In the present specification, in a numerical range indicated by "to", the numerical values stated before and after "to" are included as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in the present specification, the upper limit value or lower limit value described in one numerical range may be replaced with the upper limit value or lower limit value of another stepwise described numerical range. Further, in the numerical ranges described in the present specification, the upper limit value or lower limit value of the numerical range may be replaced with the values shown in the examples. Furthermore, the (semi-)curing described in the present specification is a general term for semi-curing and (full) curing, and indicates that either state is acceptable. A (fully) cured product does not undergo further curing reaction even when more temperature is applied, and its hardness does not change. On the other hand, semi-curing may include all states other than (full) curing, and a semi-cured product may have a change in hardness due to storage and / or temperature change. Whether a target object (for example, a resin composition) is (fully) cured or semi-cured is determined as follows. That is, when the calorific value of the target object is measured using a differential scanning calorimeter (DSC), an object that does not have an exothermic peak based on the polymerization reaction is judged to be in a fully cured state. On the other hand, when the calorific value of the target object is measured, an object that has a remaining exothermic peak, in other words, an object that has an exothermic peak, is judged to be in a semi-cured state. Therefore, the semi-cured product may contain uncured components. Unless otherwise specified, curing means full curing, and a cured product means a fully cured product.

[0010] As explained in the section [Problems to be Solved by the Invention], the dielectric constant and / or dielectric loss tangent can be reduced by using an interlayer insulating film (build-up film: BUF) containing a specific amount of hollow inorganic particles such as hollow silica, as described in Patent Document 1. Here, the conventional build-up process is as follows: A resin composition is coated onto a substrate (for example, having a release layer to facilitate later peeling) to form a resin composition layer (thermosetting resin layer), which is dried and / or heated to a semi-cured state, a protective film is bonded to the surface of the resin composition layer opposite the substrate, and if necessary, it is wound up to form a thermosetting resin sheet (thermosetting resin laminate). When manufacturing a printed circuit board or the like, the protective film of the obtained thermosetting resin sheet is peeled off, and it is laminated onto a metal-clad laminate such as a copper-clad laminate, and a curing treatment is performed to fully cure the resin composition layer to form a cured layer, after which the substrate is peeled off from the cured layer. Finally, circuit processing is performed on the substrate peeled surface of the cured layer.

[0011] However, when using the resin composition containing a specific amount of hollow inorganic particles as described in Patent Document 1, the following phenomena I and II may occur. When circuit processing is applied to the substrate peel surface of the cured layer containing a specific amount of hollow inorganic particles, the frequency of wire breakage during wiring formation may be higher compared to cases where hollow inorganic particles are not included (Phenomenon I). In addition, the surface of the resin composition layer containing a specific amount of hollow inorganic particles has low adhesion to the protective film, and there may be uneven areas where the resin is partially exposed and / or where fillers such as hollow inorganic particles are exposed. Furthermore, when using a thermosetting resin sheet containing a semi-cured layer of the resin composition layer containing a specific amount of hollow inorganic particles, compared to a thermosetting resin sheet that does not contain hollow inorganic particles, unfilled areas may occur during embedding into the circuit pattern, resulting in poor embedding of the circuit (Phenomenon II).

[0012] The present inventors first presumed that Phenomenon I occurs for the following reason. During the drying process of a particle dispersion system, a pressure flow directed from the interior toward the surface is generated, and it is considered that the particles move along the flow from the interior to the surface (in the laminate according to the present disclosure, the surface (second surface) opposite to the base material-side surface (first surface) of the thermosetting resin layer). As a result, in the laminate according to the present disclosure, it is considered that a particle-rich layer, in which more particles are present on the second surface side than in other portions, is formed (see Yamamura et al., Seikei-Kakou, Vol. 22, No. 8, 2010, "Diffusion, Drying Phenomena and Coating Film Formation"). Further, in the build-up process, when the resin composition layer containing hollow inorganic particles is dried before laminating the protective film, the hollow inorganic particles having a lower specific gravity than solid particles are considered to be more likely to be unevenly distributed on the surface side (second surface side, air surface side) of the resin composition layer to which the protective film is laminated. As a result, as shown in Figure 1, a rich layer of hollow inorganic particles 1, in which more hollow inorganic particles 1 are present in the outermost layer portion on the second surface 2B side of the thermosetting resin layer 2 than in other portions, is considered to be easily formed. It is also considered that the solvent is drawn up by capillary action due to the gaps between the particles, so that the resin contained in the thermosetting resin layer 2 is also likely to be unevenly distributed on the second surface 2B side. As a result, it is considered that the resin present on the first surface 2A side decreases, and voids 4 may be generated at the interface between the base material 3 and the thermosetting resin layer 2. Then, it is presumed that disconnection of the circuit (Phenomenon I) may occur due to the existence ratio such as the size and number of the voids 4.

[0013] As a result of extensive studies, the present inventors have found that a laminate having a thermosetting resin layer 2 containing a resin and hollow inorganic particles 1 has a specific dielectric constant, and the number of voids 4 of a specific size present at the interface between the base material 3 and the thermosetting resin layer 2 is equal to or less than a specific amount (satisfies condition (1) described later), whereby the occurrence of Phenomenon I can be suppressed, and a laminate having high reliability and a low dielectric constant when used as an interlayer insulating film can be obtained.

[0014] Furthermore, when a protective film 5 is laminated to the second surface 2B of a thermosetting resin layer 2 in a state where the hollow inorganic particles 1 are unevenly distributed on the second surface 2B side (a state in which the hollow inorganic particles 1 in the dense layer of hollow inorganic particles 1 are exposed on the surface), there were cases where parts of the protective film 5 that were in close contact with the protective film 5 and parts that were not were mixed together. In such cases, it becomes necessary to apply pressure and temperature to cause the resin of the thermosetting resin layer 2 to seep out to the second surface 2B side, thereby ensuring close contact between the protective film 5 and the thermosetting resin layer 2. At this time, the presence of the dense layer of hollow inorganic particles 1 creates significant resistance when the resin seeps out to the second surface 2B side, and as shown in Figure 2, there were cases where areas where the resin did not seep out completely remained as voids 6. It is also conceivable to improve the adhesion between the protective film 5 and the thermosetting resin layer 2 by increasing the lamination temperature to improve the flow of the resin, but when the temperature is increased, the laminate may bend (curl), making it difficult to handle. Thus, when a sheet (laminated structure) with uneven adhesion to the protective film 5 and low adhesion to the protective film 5 is used, voids 6 may remain on the second surface 2B side. Depending on the size and number of voids 6, it is presumed that when the sheet is laminated to a metal-clad laminate, unfilled areas may occur during embedding into the circuit pattern, resulting in a faulty embedding of the circuit pattern (Phenomenon II).

[0015] As a result of diligent research, the present inventors have found that a laminate having a thermosetting resin layer 2 containing resin and hollow inorganic particles 1 has a specific dielectric constant, and the amount of voids 6 of a specific size at the interface between the thermosetting resin layer 2 and the protective film 5 is less than or equal to a specific amount (satisfying condition (2) described later), thereby suppressing the occurrence of phenomenon II and obtaining a laminate that is highly reliable and has a low dielectric constant when used as an interlayer insulating film.

[0016] Hereinafter, embodiments of the laminate according to the present disclosure (hereinafter also referred to as the present laminate) will be described in detail, but the present disclosure is not limited to these embodiments. The present composition may be in a state before curing (solidification), a state after semi-curing, or a state after (full) curing. That is, the present laminate may include laminates in all curing processes before and after curing. Therefore, the thermosetting resin layer included in the present laminate may include any of a pre-cured layer, a semi-cured layer, and a fully cured layer. Further, arbitrary design modifications can be made without departing from the gist of the present disclosure.

[0017] <Laminate> The present laminate has a thermosetting resin layer containing at least a resin and hollow inorganic particles and having a dielectric constant of less than 2.6 at a frequency of 10 GHz, and satisfies at least one of the following conditions (1) and (2). That is, the present laminate may satisfy only condition (1), may satisfy only condition (2), or may satisfy both condition (1) and condition (2). (1) The laminate has a base material disposed in contact with the first surface of the thermosetting resin layer, and the cross-sectional area existing at the interface between the base material and the thermosetting resin layer is 500 μm ２ or more is 10 pieces / mm ２ or less. (2) The laminate has a protective film disposed in contact with the second surface of the thermosetting resin layer facing the first surface, and the cross-sectional area existing at the interface between the thermosetting resin layer and the protective film is 50 μm ２ or more is 10 pieces / mm ２ or less.

[0018] Hereinafter, the laminate according to the first embodiment that satisfies only condition (1) is also referred to as the first laminate, the laminate according to the second embodiment that satisfies only condition (2) is also referred to as the second laminate, and the laminate according to the third embodiment that satisfies both condition (1) and (2) is also referred to as the third laminate. From the viewpoint of obtaining an interlayer insulating film with higher reliability, the present laminate preferably satisfies both conditions (1) and (2). FIGS. 1 to 3 show schematic cross-sectional views each illustrating an example of the first laminate, the second laminate, and the third laminate.

[0019] As shown in Figure 1, condition (1) is satisfied (the cross-sectional area at the interface between the substrate 3 and the thermosetting resin layer 2 is 500 μm²). ２ There are 10 of the above gaps 4 per mm. ２ The first laminate (described below), when used as an interlayer insulating film, can suppress the frequency of circuit disconnections, enabling the production of a highly reliable printed circuit board with a low dielectric constant. From a similar viewpoint, the number of voids 4 is preferably 8 voids / mm². ２ More specifically, 6 pieces / mm ２ More preferably 4 pieces / mm ２ The following is particularly preferable: 2 pieces / mm ２ Below, the most preferred is 0 pieces / mm ２ Therefore, it is preferable to have fewer voids (4).

[0020] In the first laminate that satisfies condition (1), the weight loss rate when the thermosetting resin layer 2 peeled from the substrate 3 is heated at 150°C for 1 hour is preferably 1.7 to 3.8%. Since the weight loss is considered to be low molecular weight material, if the weight loss rate is 1.7% or more, the thermosetting resin layer can be expected to act like a plasticizer. Therefore, when cutting the laminate from a roll into a sheet, resin chipping (commonly known as chipping) can be easily suppressed. From a similar viewpoint, the weight loss rate is more preferably 2.0% or more. Furthermore, if the weight loss rate is 3.8% or less, the increase in dielectric constant due to the gradual incorporation and accumulation of low molecular weight material, which is the weight loss, into the shells of hollow inorganic particles during storage can be easily suppressed. From a similar viewpoint, the weight loss rate is more preferably 3.0% or less. The method for measuring the weight loss rate will be described later.

[0021] As shown in Figure 2, condition (2) is satisfied (the cross-sectional area at the interface between the thermosetting resin layer 2 and the protective film 5 is 50 μm). ２ There are 10 of the above-mentioned gaps 6 per mm. ２ The second laminate (described below) can suppress embedding defects in the circuit pattern and can suppress bending when bonding with the protective film. From a similar viewpoint, the number of voids 6 is preferably 8 / mm ２ More specifically, 6 pieces / mm ２ More preferably 4 pieces / mm ２The following is particularly preferable: 2 pieces / mm ２ Below, the most preferred is 0 pieces / mm ２ Therefore, fewer voids 6 are preferable. The methods for measuring the cross-sectional area and number of voids in conditions (1) and (2) will be described later.

[0022] In the second laminate that satisfies condition (2), from the viewpoint of workability, the curvature in the sheet flow direction is preferably 0.01 or less, and more preferably 0.008 or less. The method for measuring the curvature in the sheet flow direction will be described later.

[0023] The laminate that satisfies condition (1) comprises a thermosetting resin layer 2 and a base material 3 disposed on the first surface 2A of the thermosetting resin layer 2. The laminate that satisfies condition (2) comprises a thermosetting resin layer 2 and a protective film 5 disposed on the second surface 2B of the thermosetting resin layer 2. The laminate that satisfies conditions (1) and (2) comprises a thermosetting resin layer 2, a base material 3 disposed on the first surface 2A of the thermosetting resin layer 2 and a protective film 5 disposed on the second surface 2B of the thermosetting resin layer. These laminates may have one or more other layers as needed.

[0024] Here, the substrate can have a single-layer structure consisting only of a base made of resin or the like, or a laminated structure including other layers in addition to the base. For example, from the viewpoint of ease of peeling, the substrate may have a laminated structure including a release layer, which will be described later, in addition to the base. When the substrate has a laminated structure, "interface between the substrate and the thermosetting resin layer" means the interface between the outermost layer on the thermosetting resin layer side of the substrate and the thermosetting resin layer.

[0025] Similarly, protective films can have a single-layer structure or a multi-layer laminated structure. When a protective film has a laminated structure, the "interface between the thermosetting resin layer and the protective film" means the interface between the thermosetting resin layer and the outermost layer of the protective film on the thermosetting resin layer side.

[0026] This laminate can be used as a thermosetting resin sheet. When this laminate, including the protective film, is used in printed circuit boards and semiconductor devices, the protective film side can be positioned on the circuit board side.

[0027] (Thermosetting resin layer) The thermosetting resin layer 2 of this laminate contains at least resin and hollow inorganic particles, and may contain one or more other optional components as needed. Each component is described below.

[0028] [Hollow Inorganic Particles] The inclusion of hollow inorganic particles 1 in the thermosetting resin layer 2 results in improved electrical properties such as dielectric constant Dk and dielectric loss tangent Df. The hollow inorganic particles 1 contain one or more inorganic materials. Examples of inorganic materials included in the hollow inorganic particles 1 include metal oxides (e.g., silicon oxide (silica), beryllium oxide, cerium oxide, aluminum oxide (alumina), soda-alumina, magnesium oxide, zinc oxide, titanium oxide, lead oxide, nickel oxide, cobalt oxide, copper oxide, zirconium oxide, iron oxide, lithium oxide, barium oxide, potassium oxide, calcium oxide, boron oxide, and sodium oxide), boron nitride, and magnesium metasilicate (steatite). Among these, from the viewpoint of electrical properties, inorganic oxides containing one or more metal elements selected from the group consisting of aluminum, magnesium, silicon, titanium, and zinc are preferred, and silica is particularly preferred. For example, the laminate may be implemented by replacing "hollow inorganic particles" in this specification with "hollow silica particles". Furthermore, the hollow inorganic particles may be composed of a composite inorganic oxide containing multiple inorganic oxides. One type of hollow inorganic particle may be used alone, or multiple types may be used in combination. When multiple types of hollow inorganic particles are used, it is preferable that all hollow inorganic particles satisfy the preferred embodiments described below.

[0029] Silica (SiO₂) in a total amount of 100% by mass of hollow inorganic particles 1 ２ The content of ) can be, for example, 70% by mass or more, 75% by mass or more, or 80% by mass or more, and the hollow inorganic particles may consist only of silica. Also, the silica content in 100% by mass of the total amount of hollow inorganic particles 1 can be, for example, 99% by mass or less, 95% by mass or less, 90% by mass or less, or 85% by mass or less.

[0030] Furthermore, the hollow inorganic particles 1 may contain one or more of the following inorganic materials as alternatives or in addition to the above-mentioned inorganic materials: glass, cordierite, barium sulfate, barium carbonate, talc, clay, mica powder, hydrotalcite, boehmite, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, aluminum nitride, manganese nitride, aluminum borate, strontium carbonate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, barium titanate, barium zirconate titanate, barium zirconate, calcium zirconate, zirconium phosphate, zirconium tungstate phosphate, and aluminosilicate, etc.

[0031] From the viewpoint of electrical properties, the shape of the hollow inorganic particle 1 is preferably spherical, and particularly preferably perfectly spherical.

[0032] The porosity of the hollow inorganic particles 1 is not particularly limited, but is preferably 5 vol% or more, 10 vol% or more, 15 vol% or more, 20 vol% or more, 25 vol% or more, 30 vol% or more, 40 vol% or more, or 50 vol% or more. If the porosity of the hollow inorganic particles 1 is 5 vol% or more, the hollow inorganic particles 1 contain sufficient pores, and the dielectric constant tends to decrease further. Alternatively, the porosity of the hollow inorganic particles 1 is preferably 90 vol% or less, 85 vol% or less, or 80 vol% or less. If the porosity of the hollow inorganic particles is 90 vol% or less, the strength of the shell of the hollow inorganic particles becomes higher and they become less prone to breakage.

[0033] The porosity of a hollow inorganic particle 1 represents the volume percentage of the hollow portion within the hollow inorganic particle 1. This porosity is calculated from the density of the hollow inorganic particle 1. Specifically, the density of the hollow inorganic particle 1 to be measured is measured using a true density analyzer. More specifically, nitrogen is used as the measuring gas, and as the true density analyzer, for example, the ULTRAPYCNOMETER 1000 (product name) manufactured by QUANTACH ROME is used. Then, using the measured density and the material density of the inorganic material constituting the hollow inorganic particle 1, the porosity is calculated according to the following formula 1. (Formula 1) Porosity (volume %) = {1 - (measured density [g / cm³]) ３ ] / Material density of inorganic materials [g / cm³]３ ])} × 100

[0034] The average particle diameter of the hollow inorganic particles 1 is not particularly limited and can be, for example, 0.01 μm or more, 0.05 μm or more, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.4 μm or more, or 0.5 μm or more. Alternatively, the average particle diameter of the hollow inorganic particles 1 can be, for example, 10 μm or less, 5.0 μm or less, 4.0 μm or less, 3.0 μm or less, 2.5 μm or less, 2.0 μm or less, 1.6 μm or less, or 1.0 μm or less. From the viewpoint of electrical properties, the average particle diameter of the hollow inorganic particles 1 is preferably, for example, 0.1 μm or more and 10.0 μm or less.

[0035] In this specification, the average particle diameter of hollow inorganic particles 1 refers to the 50% particle diameter (D50). The 50% particle diameter (D50) can be determined using a laser diffraction particle size distribution analyzer (e.g., Microtrac-Bell Co., Ltd., product name "MT3300EXII"), or a particle size distribution analyzer using an electrical detection method (Coulter counter method) (e.g., Beckman Coulter, product name "Multisizer4e").

[0036] The BET specific surface area of ​​hollow inorganic particle 1 is 30 m². ２ Preferably less than / g, and 28m ２ More preferably less than / g, and 25m ２ A value of less than or equal to / g is even more preferable. The BET specific surface area of ​​the hollow inorganic particle 1 is 30 m². ２ If the amount is less than / g, the adsorption of resin and / or solvent to the hollow inorganic particles 1 can be easily adjusted to an appropriate range, dispersion becomes easier, and the dispersion containing it can be easily coated. Also, the BET specific surface area of ​​the hollow inorganic particles 1 is 3 m². ２ Preferably 5 m ２ A value of 3 / g or more is more preferable. The BET specific surface area of ​​the hollow inorganic particle 1 is 3 m². ２ If the concentration is greater than or equal to g / g, the resin components in the thermosetting resin layer 2 are appropriately adsorbed onto the surface of the inorganic particles, and when a concentrated layer of hollow inorganic particles 1 is formed during drying, these resin components can act as a repulsive force. As a result, the distance between particles increases and the capillary force decreases, which can easily prevent the formation of a concentrated layer.

[0037] The BET specific surface area of ​​hollow inorganic particles 1 can be measured, for example, using a specific surface area measuring device "Tristar II 3020" (product name) manufactured by Shimadzu Corporation. This can be done by pretreatment by drying the particles at 230°C until they reach 50 mTorr, followed by measurement using a multi-point method with liquid nitrogen.

[0038] The specific gravity of hollow inorganic particle 1 is 1.0 g / cm³. ３ Preferably, the specific gravity of the hollow inorganic particles 1 is 1.0 g / cm³. ３ If the specific gravity is as follows, the specific gravity will be closer to that of the resin component, which will improve dispersibility and make it easier to lower the dielectric constant. From a similar perspective, the specific gravity of hollow inorganic particle 1 is 0.9 g / cm³. ３ The following is more preferable: 0.8 g / cm³ ３ The following is even more preferable. Furthermore, the specific gravity of the hollow inorganic particles 1 is 0.2 g / cm³. ３ Preferably, the above conditions are met. The specific gravity of the hollow inorganic particles 1 is 0.2 g / cm³. ３ If the above conditions are met, excessive migration to the surface during coating and drying of the substrate can be easily suppressed. From a similar viewpoint, the specific gravity of the hollow inorganic particles 1 is 0.3 g / cm³. ３ The above is more preferable, 0.4 g / cm³ ３ The above is even more preferable. The method for measuring the specific gravity of the hollow inorganic particles 1 will be described later.

[0039] The uniformity of the hollow inorganic particles 1 is preferably 1.7 to 3.4. If the uniformity of the hollow inorganic particles is within the above range, the size of the hollow inorganic particles will vary appropriately, so even if a dense layer of hollow inorganic particles is formed on the air surface side, the particles are less likely to be densely arranged, the capillary forces between particles are easily weakened, and the generation of voids is easily suppressed.

[0040] The details of the method for measuring the uniformity of hollow inorganic particles 1 will be described later, but it is defined by the D60 / D10 ratio when measuring the particle size distribution. Furthermore, a uniformity value greater than 1 for hollow inorganic particles 1 means that the particle size distribution is wide, and a uniformity value closer to 1 means that the particle size distribution is narrow.

[0041] The shell thickness of the hollow inorganic particle 1 is preferably 0.01 to 0.3, more preferably 0.02 to 0.2, and even more preferably 0.03 to 0.1, relative to the size (diameter) (1) of the (primary) particle. If the shell thickness of the hollow inorganic particle 1 is 0.01 or more relative to the particle size (1), the hollow inorganic particle 1 can easily have good strength. Furthermore, if this ratio is 0.3 or less, the size of the internal voids can be easily adjusted to an appropriate size, and the properties due to the hollow shape can be easily exhibited. Here, the shell thickness can be determined by measuring the shell thickness of individual particles by TEM (transmission electron microscope) observation.

[0042] The sphericity of the hollow inorganic particles 1 is preferably 0.75 or higher. When the sphericity is 0.75 or higher, it is easier to adjust the contact area between the hollow inorganic particles in the thermosetting resin layer and the member they are in contact with to an appropriate range, and it is easy to prevent a decrease in peel strength. From a similar viewpoint, the sphericity of the hollow inorganic particles 1 is more preferably 0.80 or higher, even more preferably 0.82 or higher, even more preferably 0.83 or higher, even more preferably 0.85 or higher, particularly preferably 0.87 or higher, and most preferably 0.90 or higher.

[0043] The sphericity of a hollow inorganic particle 1 is expressed as the average value of the ratio of the minimum diameter (DS / DL) to the maximum diameter (DL) when measuring the maximum diameter (DL) and the minimum diameter (DS) perpendicular to it for any 100 particles in a photographic projection obtained by taking a picture with a scanning electron microscope (SEM).

[0044] [Resin] The thermosetting resin layer 2 of this laminate contains one or more resins, including one or more thermosetting resins. The thermosetting resin can be any resin conventionally known in the field of printed circuit boards, etc., and is not particularly limited. Examples of thermosetting resins include phenolic resins, aromatic polyether resins (e.g., polyphenylene ether resins), epoxy resins, polyfunctional cyanate ester resins, maleimide resins (e.g., aromatic maleimide, polyfunctional maleimide, and polyfunctional maleimide-cyanate ester resins, etc.), vinyl group-containing resins (e.g., ortho-divinylbenzene resins, etc.), unsaturated polyester resins, diallyl phthalate resins, urea resins, melamine resins, guanamine resins, and melamine-urea cocondensation resins. Among these, one or more thermosetting resins selected from the group consisting of aromatic polyether resins, epoxy resins, vinyl group-containing resins, and maleimide resins are preferred.

[0045] The resin contained in the thermosetting resin layer 2 may include, in addition to the thermosetting resin, one or more thermoplastic elastomers conventionally known in fields such as printed circuit boards. From the viewpoint of embedding into circuit patterns, it is preferable that the thermosetting resin layer 2 contains a thermoplastic elastomer. Examples of thermoplastic elastomers include polystyrene elastomers, polyolefin elastomers, vinyl chloride elastomers, polyurethane elastomers, polyester elastomers, and polyamide elastomers. Among these, polystyrene elastomers are preferred. Examples of polystyrene elastomers include polystyrene-polyethylene block copolymer, polystyrene-polybutadiene block copolymer, and polystyrene-polyisoprene block copolymer. Examples of polyolefin elastomers include 1,2-polybutadiene, 1,4-polybutadiene, maleic acid-modified polybutadiene, acrylic acid-modified polybutadiene, and epoxy-modified polybutadiene. The content of thermoplastic elastomers in the thermosetting resin layer (total amount if there are multiple types) can be, for example, 5 to 10% by mass.

[0046] The resin content in 100% by mass of the solids content of the thermosetting resin layer is not particularly limited and can be set by referring to the prior art. The resin content in the thermosetting resin layer (total amount in the case of multiple types) relative to 100% by volume of the solids content of the thermosetting resin layer can be, for example, 30 to 70% by mass.

[0047] [Other Materials] In addition to the resin and hollow inorganic particles, the thermosetting resin layer 2 may contain one or more additives such as other inorganic materials, crosslinking agents (curing agents), flame retardants, radical initiators, and silane coupling agents. The content of each additive is not particularly limited.

[0048] Other inorganic material shapes include, for example, particulate, needle-shaped, fibrous, flaky, layered, plate-shaped, leaf-shaped, almond-shaped, columnar (e.g., prismatic), comb-shaped, equiaxed, leaf-shaped, mica-like, block-shaped, wedge-shaped, rosette-shaped, and network-shaped. From the viewpoint of electrical properties, particulate shapes are preferred for other inorganic materials, more preferably spherical, and particularly preferably perfectly spherical. Other inorganic materials include, for example, inorganic particles other than hollow inorganic particles, with solid inorganic particles being preferred.

[0049] Other inorganic materials that can be used include silica other than hollow silica particles. Specific examples include flake silica, fumed silica, solid spherical silica (solid silica particles), and crushed silica. Among these, solid spherical silica is preferred because it allows for easier adjustment of complex viscosity. The average particle size of solid spherical silica is not particularly limited, but is preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less. The lower limit is not particularly limited, but is preferably 0.01 μm. It is thought that hollow inorganic particles, which have a specific gravity lighter than the resin, are the main contributors to the formation of the particle density layer during drying.

[0050] The content of solid inorganic particles in the thermosetting resin layer relative to 100 volume percent of the solid content of the thermosetting resin layer (total amount in the case of multiple types) is not particularly limited and can be, for example, 5 to 35 volume percent. The content of solid inorganic particles in this composition (solid content) can be measured by known analysis such as thermogravimetric analysis (TGA). Furthermore, the total content of hollow inorganic particles 1 and solid inorganic particles in the thermosetting resin layer relative to 100 volume percent of the solid content of the thermosetting resin layer can be, for example, 80 volume percent or less, 70 volume percent or less, or 60 volume percent or less. Furthermore, the total content of hollow inorganic particles 1 and solid inorganic particles in the thermosetting resin layer can be, for example, 15 volume percent or more, 25 volume percent or more, 30 volume percent or more, or 45 volume percent or more. Furthermore, when the total volume of hollow inorganic particles 1 and solid inorganic particles in the thermosetting resin layer (solid content) is set to 100 volume%, the volume occupied by hollow inorganic particles 1 is preferably 65 volume% or more, and more preferably 70 volume% or more. Setting the volume of hollow inorganic particles 1 to 65 volume% or more makes it easier to adjust the dielectric constant within a predetermined range. Furthermore, the volume occupied by hollow inorganic particles 1 is preferably 90 volume% or less, and more preferably 85 volume% or less. Setting the volume occupied by hollow inorganic particles 1 to 90 volume% or less makes it easier to lower the coefficient of linear expansion of the thermosetting resin layer 2.

[0051] Examples of crosslinking agents include polyfunctional vinyl compounds such as divinylbenzene, divinylnaphthalene, and divinylbiphenyl; vinylbenzyl ether compounds synthesized from the reaction of phenol and vinylbenzyl chloride; allyl ether compounds synthesized from the reaction of styrene, phenol, and allyl chloride; polyfunctional acrylic compounds having two or more (meth)acryloyl groups in one molecule; and trialkenyl isocyanurates such as triallyl isocyanurate (TAIC) and triallyl cyanurate (TAC).

[0052] Examples of flame retardants include phosphorus-based flame retardants containing one or more compounds selected from the group consisting of phosphate esters such as condensed phosphate esters and cyclic phosphate esters, and phosphonate metal salts such as cyclic phosphazene compounds and aluminum dialkylphosphinate; and halogen-based flame retardants such as bromine-based flame retardants.

[0053] Examples of radical initiators include α,α'-bis(t-butylperoxy-m-isopropyl)benzene (also known as 1,3-bis(butylperoxyisopropyl)benzene), 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexine, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, benzoyl peroxide, 3,3',5,5'-tetramethyl-1,4-diphenoquinone, chloranil, 2,4,6-tri-t-butylphenoxyl, t-butylperoxyisopropyl monocarbonate, and azobisisobutyronitrile.

[0054] Examples of silane coupling agents include 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-isocyanatetopropyltriethoxysilane.

[0055] [Dielectric Constant] The dielectric constant Dk of the thermosetting resin layer (cured product) of this laminate at a frequency of 10 GHz is less than 2.6 from the viewpoint of application to high-speed communication. From the same viewpoint, the dielectric constant Dk is more preferably 2.5 or less, even more preferably 2.4 or less, and particularly preferably 2.3 or less. The method for measuring the dielectric constant will be described later.

[0056] [Dielectric Loss Tangent] The dielectric loss tangent Df of the thermosetting resin layer (cured product) of this laminate at a frequency of 10 GHz is preferably 0.008 or less, more preferably 0.004 or less, even more preferably 0.003 or less, even more preferably 0.0025 or less, and particularly preferably 0.002 or less, from the viewpoint of application to high-speed communication. The method for measuring the dielectric loss tangent will be described later.

[0057] [Thickness] In this laminate, the thickness of the thermosetting resin layer (cured product) is preferably 10 μm or more, more preferably 12 μm or more, even more preferably 15 μm or more, and most preferably 20 μm or more, from the viewpoint of practical application and interlayer insulation. Furthermore, if the thickness of the thermosetting resin layer is 10 μm or more, the effect of solvent absorption due to capillary action is mitigated, and as a result, the generation of voids on the first surface side is suppressed. On the other hand, from the viewpoint of thinning, the thickness of the thermosetting resin layer is preferably 125 μm or less, more preferably 100 μm or less, even more preferably 60 μm or less, most preferably 40 μm or less, and most preferably 30 μm or less.

[0058] (Base Material) The laminate may have a base material 3 that is in contact with the first surface 2A of the thermosetting resin layer 2. As described above, the base material 3 may have a single-layer structure or a laminated structure including a release layer, etc. The base material 3 can be any conventionally known material and is not particularly limited; for example, a thermoplastic resin film, a metal foil, or a release paper can be used. Among these, a thermoplastic resin film or a metal foil is preferred as the base material 3.

[0059] When a thermoplastic resin film is used as the base material 3, examples of thermoplastic resins include polyester (e.g., polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), etc.), polycarbonate (PC), acrylic resin (e.g., polymethyl methacrylate (PMMA), etc.), cyclic polyolefin, triacetylcellulose (TAC), polyethersulfone (PES), polyetherketone, and polyimide. Among these, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are preferred, and inexpensive polyethylene terephthalate (PET) is particularly preferred. As the polyester film, a stretched polyester film is preferred. From the viewpoint of suppressing curling after the protective film is applied, the stretched polyester film is preferably 105°C or higher in glass transition temperature.

[0060] When using a metal foil as the base material 3, examples of metal foils include copper foil and aluminum foil, with copper foil being preferred. As for the copper foil, foil made of pure copper may be used, or foil made of an alloy of copper with one or more other metals (for example, tin, chromium, silver, magnesium, nickel, zirconium, silicon, and titanium, etc.) may be used.

[0061] The substrate 3 may have surface treatments such as matte treatment, corona treatment, and antistatic treatment applied to the surface on which the thermosetting resin layer 2 is placed (for example, the surface to be joined). Alternatively, as described above, a substrate with a release layer may be used for the substrate 3, which has a release layer on the surface on which the thermosetting resin layer 2 is placed. Examples of release agents used for the release layer include one or more release agents selected from the group consisting of non-silicone materials such as alkyd resins, polyolefin resins, and urethane resins; and silicone materials (silicone resins). The substrate with a release layer may be a commercially available product (for example, PET films having a release layer mainly composed of an alkyd resin-based release agent, such as Film Vina manufactured by Fujimori Industries, Ltd., AL-5 manufactured by Lintec Corporation, and Therapiel manufactured by Toray Industries, Ltd. (all are product names)).

[0062] The total thickness of the substrate 3 is not particularly limited, but is preferably 5 to 75 μm, and more preferably 10 to 60 μm.

[0063] When a metal foil is used as the base material 3, a metal foil with a support substrate, which is formed by laminating a peelable support substrate onto a thin metal foil, may be used. In one embodiment, the metal foil with a support substrate may include a support substrate, a release layer provided on the support substrate, and a metal foil provided on the release layer. When a metal foil with a support substrate is used as the base material 3, the thermosetting resin layer is provided on the metal foil.

[0064] In a metal foil with a support substrate, the material of the support substrate is not particularly limited and includes, for example, copper foil, aluminum foil, stainless steel foil, titanium foil, and copper alloy foil. The copper foil may be electrolytic copper foil or rolled copper foil. The release layer is not particularly limited as long as it can be peeled off the metal foil from the support substrate and includes, for example, an alloy layer containing an alloy of metal elements selected from the group consisting of Cr, Ni, Co, Fe, Mo, Ti, W, and P, and an organic coating. In a metal foil with a support substrate, copper foil and copper alloy foil are preferred as the metal foil. In a metal foil with a support substrate, the thickness of the support substrate is not particularly limited and is preferably 10 to 150 μm, and more preferably 10 to 100 μm. The thickness of the metal foil may be, for example, 0.1 to 10 μm.

[0065] (Protective Film) The protective film 5 can be any conventionally known film and is not particularly limited. The thickness of the protective film 5 is not particularly limited, for example, 1 to 40 μm. By laminating the protective film 5 onto the second surface 2B of the thermosetting resin layer 2, the adhesion of foreign matter such as dust and / or scratches on the surface of the thermosetting resin layer 2 can be easily suppressed. This laminate may further include one or more arbitrary layers as needed.

[0066] <Method for Manufacturing Laminates> The method for manufacturing laminates according to this disclosure is a method for manufacturing the laminates described above (the first laminate, the second laminate, or the third laminate), characterized in that drying is performed from the first surface 2A side (the substrate 3 side) of the undried thermosetting resin layer 2. By drying the undried thermosetting resin layer 2 from the substrate 3 side before the protective film 5 is attached and the substrate 3 is peeled off, convection occurs within the thermosetting resin layer 2, resulting in easier dispersion of the filler containing hollow inorganic particles 1 and making it difficult for a particle-dense layer to form.

[0067] Methods for drying the undried thermosetting resin layer 2 include, for example, a method of drying by blowing air on it and allowing the solvent to evaporate through retention, and a method of directly heating the resin varnish, described later, with radiant heat such as infrared rays to evaporate the solvent. Methods for drying by blowing air include a parallel flow method in which air is sent parallel to the direction of travel of the substrate coated with the resin varnish, a counterflow method in which air is sent opposite to the direction of travel of the substrate, a two-dimensional nozzle method in which a jet of air is applied perpendicular to the substrate and directly to the coating film, and a method in which air is applied from the opposite side of the substrate from the coating film. From the viewpoint of avoiding the movement of hollow inorganic particles 1 to the second surface 2B and the formation of a particle density layer, a method of applying hot air from the substrate 3 side (first surface 2A) of the thermosetting resin layer 2, or a method of applying infrared radiation from the bottom surface is preferred. In addition, the film during drying may be in contact with a roll on the first surface 2A for transport. In that case, heating the roll is preferred from the viewpoint of promoting drying from the first surface 2A.

[0068] The drying temperature of the undried thermosetting resin layer 2 is preferably 30°C or higher than the boiling point of the solvent used, and more preferably 20°C or higher. By setting the drying temperature to 30°C or higher, excess solvent residue can be avoided, and sufficient drying can be achieved in a shorter time. Alternatively, the drying temperature is preferably 20°C or lower than the boiling point of the solvent used, and more preferably 10°C or lower. By setting the drying temperature to 20°C or lower than the boiling point, excessive drying can be avoided, making chipping and cracking less likely in subsequent processes, and improving handling.

[0069] It is preferable to control the wind speed during drying to between 1 m / s and 8 m / s. If the wind speed is 1 m / s or higher, the solvent dries more easily. If the wind speed is 8 m / s or lower, the phenomenon of the solvent being blown away by the wind is suppressed more easily. The drying speed is affected by the heat transfer coefficient of the boundary film between the coating and the air in the drying oven, and the wet-bulb temperature, which is related to the solvent vapor concentration in the atmosphere. The heat transfer coefficient of the boundary film is related to the wind speed acting on the coating, and drying is easier as the wind speed increases. On the other hand, if the wind speed is increased, the coating is blown away by the wind during drying, so uneven film thickness is likely to occur. Therefore, by adjusting the solvent contained in the thermosetting resin composition and using a solvent with low latent heat of vaporization as a second solvent in addition to the main solvent (first solvent), the drying speed can be easily adjusted while reducing the influence of drying temperature and drying wind speed.

[0070] The manufacturing method for this laminate is described in detail below. The first laminate can be manufactured by coating a thermosetting resin composition (resin varnish) containing at least resin and hollow inorganic particles 1 onto a substrate 3 to a desired thickness, and drying the undried thermosetting resin composition layer from the substrate 3 side (first surface side). The dielectric constant of the thermosetting resin layer 2 (cured product) of the final obtained first laminate at a frequency of 10 GHz is less than 2.6, and the number of specific voids 4 at the interface between the substrate 3 and the thermosetting resin layer 2 is 10 voids / mm ２ The following applies:

[0071] The second laminate can be manufactured by laminating a protective film 5 to the side of the thermosetting resin layer 2 opposite to the substrate 3 (second surface 2B) and winding it up as needed. The dielectric constant of the thermosetting resin layer 2 (cured product) of the final second laminate at a frequency of 10 GHz is less than 2.6, and the number of specific voids 6 at the interface between the thermosetting resin layer 2 and the protective film 5 is 10 voids / mm². ２ The following applies:

[0072] The protective film 5 can be laminated on the second surface 2B of the thermosetting resin layer 2, for example, using a continuous lamination apparatus having a pair of heatable rolls. The lamination temperature of the protective film 5 is preferably below the glass transition temperature of the base film 3 + 30°C, and more preferably below the glass transition temperature of the base film 3 + 20°C. Within this temperature range, curling after lamination can be easily suppressed. The material of the pair of heatable rolls can be metal, rubber, or a combination thereof, and from the viewpoint of uniformity of pressure in the plane and uniformity of temperature, a metal-rubber or rubber-rubber combination is preferred.

[0073] The curvature in the sheet flow direction of the laminate when the protective film 5 is laminated can be measured by the following method. Figure 4 is a diagram illustrating the method for measuring the curvature in the sheet flow direction of the laminate according to this embodiment. Three pieces of film, 4 mm wide and 80 mm long, are cut from the roll after the protective film 5 has been laminated, parallel to the flow direction. Next, a length of 30 mm from the root in the flow direction of the cut film is fixed, and 50 mm (let's call it X) is left free and placed on a flat surface. The height (let's call it Y) of the tip of the curled film from the flat surface is measured. The curvature is calculated according to the following equation 2. (Equation 2) Curvature = 2 × Y ２ / (X ２ +Y ２ The curvature of the laminate in the sheet flow direction is preferably 0.010 or less, and more preferably 0.008 or less. If the curvature in the sheet flow direction is 0.010 or less, the handling of the film in the cutting process is improved.

[0074] The third laminate can be manufactured by laminating a protective film 5 onto the side (second surface 2B) of the thermosetting resin layer 2 of the first laminate that is opposite to the substrate 3, and then winding it up as needed. The dielectric constant and voids of the final obtained third laminate satisfy the same conditions as those of the first and second laminates.

[0075] The resin varnish used in manufacturing this laminate may be a resin varnish comprising this composition containing one or more solvents (dispersion media), or a resin varnish comprising this composition and one or more solvents (dispersion media), and may be a dispersion containing resin and hollow inorganic particles, and further containing one or more solvents (dispersion media).

[0076] [Solvent] Conventional known solvents can be used as the solvent for resin varnish. One type of solvent may be used alone, or multiple types may be used in combination. By using a mixed solvent, the drying rate (film shrinkage rate) can be easily controlled. Due to compatibility with other components such as hollow inorganic particles, the mixed solvent preferably contains toluene as the main solvent (first solvent), and further contains a second solvent, and may also contain a third solvent. From the viewpoint of adjusting the drying rate and ensuring suitable wettability to the substrate, the second solvent is preferably ketone-based, ester-based, acetate-based, or a combination thereof.

[0077] The surface tension of the second solvent is preferably 20 mN / m to 40 mN / m, and more preferably 22 mN / m to 35 mN / m. If the surface tension is within this range, it is possible to easily ensure wettability to the substrate while maintaining good solubility or dispersibility of components other than the solvent.

[0078] The amount of the second solvent used may be, for example, 5 to 49 parts by mass, or 10 to 40 parts by mass, per 100 parts by mass of the main solvent (first solvent).

[0079] When butyl acetate is used as the baseline (1.0), the relative evaporation rate of the second solvent is preferably 0.5 to 5.0, and more preferably 1.0 to 4.5. By keeping the relative evaporation rate of the second solvent within this range, it is easier to adjust the drying rate to an appropriate range. The relative evaporation rate of the mixed solvent of the main solvent (first solvent) and the second solvent is preferably 1.0 to 4.5, and more preferably 1.5 to 4.0. The relative evaporation rate of the mixed solvent refers to the value obtained by averaging the relative evaporation rates of each solvent by mass ratio. Furthermore, relative evaporation rate refers to the relative evaporation rate when the evaporation rate of n-butyl acetate is set to 1.0, as described in J. Ramsbotham: Prog. Org. Coatings, 8, 113 (1980). The relative evaporation rates of the main solvents are shown below. Toluene: 2.0, Butyl acetate: 1.0, Isopropyl acetate: 3.5, Xylene: 0.76.

[0080] The dispersion can be prepared using conventionally known methods. Specifically, dispersion can be carried out using dispersion devices such as homodispersers, homogenizers, ultrasonic dispersers, ball mills, and bead mills. Among these, dispersion is preferably carried out using a ball mill or bead mill from the viewpoint of preventing the hollow inorganic particles from breaking.

[0081] When using a ball mill, a predetermined mass of resin varnish and balls called media are placed in a container, and the container is rotated to crush hollow inorganic particles and prepare a dispersion. Examples of ball materials include glass, zirconia, silicon nitride, and agate, but zirconia balls are preferred because they crush hollow inorganic particles well and the balls themselves wear down little.

[0082] The ball diameter is preferably 1,000 to 10,000 times the primary particle diameter of the hollow inorganic particles contained in the resin varnish. For example, when dispersing hollow inorganic particles with an average particle diameter of 1 μm, the ball diameter is preferably 1 mm to 10 mm. If the ball diameter is 1,000 times or more the diameter of the hollow inorganic particles, the disintegration of the hollow inorganic particles proceeds easily, and if it is 10,000 times or less, the hollow inorganic particles can be easily dispersed without breaking their shells.

[0083] This laminate is obtained by coating a resin varnish onto a substrate 3 using a single-wafer or continuous method (e.g., roll-to-roll method) and then drying it. Various existing coating methods can be used, such as gravure coating, bar coating, die coating, comma coating, roll coating, and lip coating. Among these, die coating is particularly preferred from the viewpoint of uniformity of thickness and prevention of varnish drying.

[0084] The die-coating method involves using a quantitative pump to dispense resin varnish, which is then fed through slits in the die and applied to the substrate. Quantitative pumps include gear pumps, mono pumps (registered trademark), and diaphragm pumps. Mono pumps are preferred due to their low pulsation and suppression of hollow inorganic particle crushing. For the stator of the mono pump, a rubber material is preferred from the viewpoint of being able to pump the liquid without crushing the hollow inorganic particles.

[0085] The manifold, which is the liquid reservoir inside the die, is preferably semicircular in plan view, and its diameter is preferably between 10 mm and 40 mm. If the diameter is within this range, hollow inorganic particles are less likely to accumulate inside the manifold. In addition, the lip opening of the die is preferably between 2 and 10 times the wet thickness during coating.

[0086] <Printed Wiring Board> The printed wiring board according to this disclosure includes a cured product of the thermosetting resin layer 2 in the laminate. An example of a method for manufacturing a printed wiring board will be described below. If the laminate has a protective film 5 on the second surface 2B side of the thermosetting resin layer 2, the protective film 5 should be removed in advance. Prepare a substrate (for example, a prepreg made by impregnating a fibrous substrate such as glass cloth with resin; a metal-clad laminate or circuit board having a metal layer or wiring layer formed on at least one surface of the prepreg; a glass plate, etc.). A metal-clad laminate or circuit board is preferred as the substrate. If necessary, preheat the thermosetting resin layer 2 and / or the substrate (preferably a metal-clad laminate or circuit board).

[0087] The second surface 2B of the thermosetting resin layer 2 of this laminate is placed on a substrate (preferably a metal-clad laminate or circuit board), and these are heat-compressed (pressurized and heated) by a lamination method. Vacuum lamination, which is performed under reduced pressure, is preferred. The lamination conditions are not particularly limited. For example, the compression temperature (lamination temperature) is preferably 70 to 140°C, and the compression pressure is preferably 1 to 11 kgf / cm². ２ (9.8 x 10 ４ ~107.9 x 10 ４ N / m ２ The atmosphere is preferably a reduced pressure atmosphere with an air pressure of 20 mmHg (26.7 hPa) or less. The lamination method may be single-wafer or continuous (for example, roll-to-roll). Vacuum lamination can be performed using a commercially available vacuum laminator. Examples of commercially available vacuum laminators include the vacuum applicator manufactured by Nichigo Morton Co., Ltd., the vacuum pressure laminator manufactured by Meiki Seisakusho Co., Ltd., the roll-type dry coater manufactured by Hitachi Industries, Ltd., and the vacuum laminator manufactured by Hitachi AIC Co., Ltd. After that, the substrate on the first surface 2A side of the thermosetting resin layer 2 is peeled off. Furthermore, if necessary, a circuit is formed on at least one side of the obtained laminate (for example, the substrate peeled side) by a known method. A printed circuit board is obtained in this manner.

[0088] <Semiconductor Device> The semiconductor device according to this disclosure includes a printed circuit board according to this disclosure. Other components can be those that are conventionally known. For example, a semiconductor device can be manufactured by mounting semiconductor elements on the connection electrode portion of a multilayer printed circuit board. The method of mounting semiconductor elements is not particularly limited and includes, for example, wire bonding mounting, flip-chip mounting, and mounting using an anisotropic conductive film (ACF) or non-conductive film (NCF).

[0089] The present disclosure will be further illustrated below with several examples, but the present disclosure is not limited to these examples. Examples 3 to 13 are embodiments relating to the present disclosure, while Examples 1 to 2 and 14 are comparative examples.

[0090] <Preparation of Hollow Inorganic Particles> (Preparation of Hollow Silica Particles A1) - Preparation of Emulsion 2 g of EO-PO-EO block copolymer (manufactured by ADEKA Corporation, trade name: Pluronic® F68) was added to 1250 g of pure water and stirred until dissolved to obtain an aqueous solution. 42 g of n-decane in which 2 g of sorbitanic acid monooleate (manufactured by Sanyo Chemical Industries, trade name: Ionet® S-80) was dissolved was added to this aqueous solution, and the mixture was stirred using an IKA homogenizer until the entire liquid was homogenized to prepare a crude emulsion. This crude emulsion was emulsified at a pressure of 50 bar using a high-pressure emulsifier (manufactured by SMT Corporation, trade name: LAB1000) to prepare an emulsion with a dispersed particle size of 2 μm.

[0091] The emulsion obtained from aging was left to stand at 40°C for 12 hours.

[0092] - After the first shell layer has formed and allowed to stand, add a diluted sodium silicate aqueous solution (SiO₂) to 1300g of the emulsion so that the pH is 2. ２ Concentration 10.4% by volume, Na ２ 23 g of 3.6 vol. % O concentration and 2 M hydrochloric acid were added, and the mixture was stirred while maintaining the temperature at 30°C to obtain a mixture. Next, while stirring the mixture, 1 M aqueous sodium hydroxide solution was slowly added dropwise until the pH reached 6 to obtain an oil core-silica shell particle dispersion. The obtained oil core-silica shell particle dispersion was held and allowed to mature.

[0093] The second shell layer-forming oil core-silica shell particle dispersion was heated to 70°C, and a 1M sodium hydroxide aqueous solution was slowly added while stirring to adjust the pH to 9. Next, the diluted sodium silicate aqueous solution (SiO2) was added. ２ Concentration 10.4% by volume, Na ２ 330 g of 3.6 vol. % O was gradually added with 0.5 M hydrochloric acid to a pH of 9. This suspension was kept at 80°C for 1 day, then cooled to room temperature (25°C) to obtain a dispersion of hollow silica particle precursors.

[0094] - Filtration, Washing, Drying, and Calcination The entire dispersion of hollow silica particle precursor was neutralized to pH 2 with 2M hydrochloric acid, and then filtered using quantitative filter paper 5C. Afterward, 350 ml of ion-exchanged water at 80°C was added and the mixture was pressure filtered again to wash the hollow silica particle precursor cake. The filtered cake was dried under a nitrogen atmosphere at 100°C for 1 hour, followed by 400°C for 2 hours (heating rate 10°C / min) to remove organic matter and obtain hollow silica particle precursors. The obtained hollow silica particle precursors were calcined at 1050°C for 1 hour (heating rate 10°C / min) to solidify the shells and obtain hollow silica particles A1. The average particle size was 2.2 μm, the uniformity was 1.3, and the true density (specific gravity) was 0.48 g / cm³. ３ That was the case.

[0095] (Preparation of Hollow Silica Particles A2) The amount of EO-PO-EO block copolymer (manufactured by ADEKA Corporation, trade name: Pluronic® F68) added was changed to 1 g. Also, the amount of sorbitanic acid monooleate (manufactured by Sanyo Chemical Industries, Ltd., trade name: Ionet S-80) added was changed to 1 g. Other than these, hollow silica particles A2 were obtained under the same conditions as hollow silica particles A1. SiO2 relative to the total amount of hollow silica particles A2 ２ The content is 99.9% by mass, the average particle size of hollow silica particles A2 is 0.5 μm, the uniformity is 1.3, and the true density (specific gravity) is 0.67 g / cm³. ３ That was the case.

[0096] (Preparation of hollow silica particles A3) The amount of EO-PO-EO block copolymer (manufactured by ADEKA Corporation, trade name: Pluronic® F68) added was changed to 5 g. In addition, the amount of sorbitanic acid monooleate (manufactured by Sanyo Chemical Industries, Ltd., trade name: Ionet S-80) added was changed to 5 g. Hollow silica particles A3 were obtained under the same conditions as hollow silica particles A1, except for these changes. SiO2 to the total amount of hollow silica particles A3 ２ The content is 99.9% by mass, the average particle size of hollow silica particles A3 is 4.2 μm, the uniformity is 1.2, and the true density (specific gravity) is 0.51 g / cm³. ３ That was the case.

[0097] (Preparation of hollow silica particles A4) Hollow silica particles A1 and hollow silica particles A2 were placed in a container in a mass ratio of 3:1 and mixed for 30 minutes using a pot blender PBS-MINI (product name, manufactured by Makino Sangyo Co., Ltd.). The resulting hollow silica particles A4 had an average particle size of 1.8 μm, a uniformity of 1.7, and a true density (specific gravity) of 0.54 g / cm³. ３ That was the case.

[0098] (Preparation of Hollow Silica Particles A5) Hollow silica particles A1, A2, and A3 were mixed for 30 minutes in a pot blender PBS-MINI (product name, manufactured by Makino Sangyo Co., Ltd.) in a mass ratio of 3:0.8:0.8. The resulting hollow silica particles A5 had an average particle size of 2.5 μm, a uniformity of 3.4, and a true density (specific gravity) of 0.57 g / cm³. ３ That was the case.

[0099] (Preparation of Hollow Silica Particles A6) Hollow silica particles A1, A2, and A3 were mixed in a mass ratio of 3:1:1 using a pot blender PBS-MINI (product name, manufactured by Makino Sangyo Co., Ltd.) for 30 minutes. The average particle size of the resulting hollow silica particles A6 was 2.6 μm, the uniformity was 4.0, and the true density (specific gravity) was 0.64 g / cm³. ３ That was the case.

[0100] (Preparation of hollow silica particles A7) Hollow silica particles A1 and hollow silica particles A2 were placed in a container in a mass ratio of 1:4 and mixed for 30 minutes using a pot blender PBS-MINI (product name, manufactured by Makino Sangyo Co., Ltd.). The resulting hollow silica particles A7 had an average particle size of 0.7 μm, a uniformity of 1.7, and a true density (specific gravity) of 0.69 g / cm³. ３ That was the case.

[0101] (Surface Treatment) 200 g of each hollow silica particle was placed in a 3.5 L planetary mixer (product name: Hibismix 3L-5, manufactured by PRIMIX). In addition, 1.4 g of silane coupling agent (manufactured by Dow-Toray, product name: OFS-6030) and hexane were added, and the mixture was stirred with a magnetic stirrer for 5 minutes to prepare a solution. The prepared solution was added to the planetary mixer containing the hollow silica particles, and nitrogen was flowed through it for 10 minutes while stirring at 60 rpm. Furthermore, the temperature was raised to 80°C at a rate of 2°C / min while flowing nitrogen, and the mixture was held at 80°C for 1 hour. After that, it was allowed to cool to 50°C and removed to the air to obtain surface-treated hollow silica. The hollow silica particles A1 to A7 described above were surface-treated according to this procedure.

[0102] <Uniformity> For each example of hollow silica particle powder, the particle size distribution was measured using a dry method with a laser diffraction / scattering particle size distribution analyzer, product name: LA-920 (manufactured by Horiba, Ltd.). The particle size D10 (10% cumulative volume-based particle size) and particle size D60 (60% cumulative volume-based particle size) were measured. The uniformity of the hollow silica particles in each example was calculated by calculating D60 / D10. The measurement was performed by placing 5 mL of hollow silica particle powder into a dry flow cell and measuring in transmittance mode at room temperature (25°C).

[0103] [Example 1] The following materials were added to 60 parts by mass of toluene and 20 parts by mass of methyl ethyl ketone, which are solvents, and the mixture was stirred until it became a clear liquid. - Thermosetting resin (SABIC, product name: Noryl SA9000) 14 parts by mass, - SEBS elastomer (styrene-based thermoplastic elastomer) (Kraton, product name: MD1623) 7 parts by mass, - Crosslinking agent 1 (Hantzman, product name: ARALDITE MT35610) 10 parts by mass, - Crosslinking agent 2 (Regina electronics, BVPE (bis(4-vinylphenyl)ethane)) 3.5 parts by mass, - Phosphorus-based flame retardant (Otsuka Chemical Co., Ltd., product name: SPV-100) 20 parts by mass, - Radical initiator (United Initiator, product name: CUROX CC-DC) 1 part by mass, - Silane coupling agent (Manufactured by Toray Dow, product name: OFS-6030) 0.5 parts by mass.

[0104] Subsequently, 17 parts by mass of hollow silica particles A1 and 27 parts by mass of solid silica particles (manufactured by Sibelco, product name: SS-15V) were added to the mixture, and the mixture was further stirred with a high-speed rotary mixer to produce a thermosetting resin composition (resin varnish). The specific gravity of the resin composition was 1.0, the relative evaporation rate of the mixed solvent was 1.8, and the solid content of the resin composition was 55% by mass. The content of solid inorganic particles in the thermosetting resin layer (solid content) was 12% by volume, the total content of the aforementioned hollow inorganic particles 1 and solid inorganic particles in the thermosetting resin layer (solid content) was 47% by volume, and the ratio of hollow inorganic particles 1 to solid inorganic particles in the thermosetting resin layer (solid content) was such that, when the total volume of these particles was taken as 100% by volume, the volume occupied by hollow inorganic particles 1 was 74% by volume.

[0105] The obtained thermosetting resin composition was transported by a Mono pump (manufactured by Hyoshin Equipment Co., Ltd.) and coated onto a substrate (a 38 μm thick PET film (Lintec Corporation, product name: 6501)) using a roll-to-roll die coating method. The die lip opening was 250 μm, the coating width was 500 mm, and the wet film thickness was 100 μm. The substrate is a stretched polyester film with a glass transition temperature of 105°C or higher. The film was passed through a drying oven on a roll support and dried by blowing air directly from the top of the coated surface (the second surface 2B side of the thermosetting resin layer) using a two-dimensional nozzle. The set temperature was 100°C and the drying time was 6 minutes. The obtained film thickness was 30 μm. After passing through the drying oven, a protective film OPP (Toray Industries, Inc., product name: Trefan #30-2500H) was continuously laminated onto the film. The surface temperature of the lamination roll was 100°C and the linear pressure was 100 N / cm. Subsequently, the material was continuously wound onto a 3-inch core to obtain a laminate.

[0106] [Examples 2-9, 11-14] As shown in Tables 1 and 2, the laminates for each example were manufactured in the same manner as in Example 1, except that the various materials and conditions for manufacturing the laminates were changed. In Table 2, "1st S" refers to the "first surface side" and "2nd S" refers to the "second surface side". The drying direction being the first surface 2A side of the thermosetting resin layer means that in the drying oven of the roll support, the coated surface (the second surface 2B side of the thermosetting resin layer) is not directly exposed to drying air, but heat is applied only from a near-infrared heater on the substrate side, and the roll in contact with the substrate side on the bottom is heated to dry it. The set temperature and drying time were as shown in Table 2.

[0107] [Example 10] A laminate was manufactured in the same manner as in Example 1, except that the composition of the thermosetting resin composition was changed as follows. 60 parts by mass of toluene and 20 parts by mass of butyl acetate were added to the following materials, and the mixture was further stirred with a high-speed rotary mixer to prepare a resin composition (resin varnish). The solid content of the resin composition was 55% by mass. - Biphenyl aralkyl epoxy resin (manufactured by Nippon Kayaku Co., Ltd., product name "NC-3000H") 5 parts by mass, - Naphthalene epoxy resin (manufactured by DIC Corporation, product name "HP4032SS") 5 parts by mass, - Bisphenol A type epoxy resin and bisphenol F type epoxy mixture (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name "ZX1059") 31 parts by mass, - Curing agent: Active ester-based curing agent (manufactured by DIC Corporation, product name "HPC-8150-62T") 5 parts by mass, Phenolic curing agent having a triazine skeleton and novolac structure (manufactured by DIC Corporation, product name "LA-3018-50P") 5 parts by mass, - Phenoxy resin (manufactured by Mitsubishi Chemical Corporation, product name "YX7553BH30") 5 parts by mass, - Hollow silica particles A4 17 parts by mass - Solid silica particles (manufactured by Sibelco, product name: SS-15V) 27 parts by mass.

[0108] The following describes the measurement and evaluation methods for various physical properties obtained in the laminates in each example.

[0109] <Weight Loss Rate> The weight loss rate of each laminate was measured as follows. A 10 cm square was cut from each laminate, and the protective film was removed. Next, the laminate was folded into quarters along with the substrate, and the exposed thermosetting resin sheets were stuck together. The substrate was then peeled off to prepare a 2.5 cm square sample. Next, the weight was measured. After that, it was dried for 1 hour in a hot air circulation oven (Yamato Scientific Co., Ltd. DKN303) heated to 150°C, removed, allowed to return to room temperature, and the weight was measured again. The value calculated using the following formula was defined as the weight loss rate (residual solvent rate). Weight loss rate (%) = (Weight before drying - Weight after drying) / (Weight before drying) × 100

[0110] <Measurement of voids at the interface between the substrate and the thermosetting resin layer> Voids at the interface between the substrate and the thermosetting resin layer were detected by the following method. Specifically, the laminates obtained in each example were observed with a laser microscope from the substrate side under the following conditions, focusing on the interface between the substrate and the thermosetting resin layer. Ten images were taken of an area of ​​644 μm × 647 μm, ensuring no overlap, and the white areas shown in Figure 5 were detected as voids. Figure 5 is a diagram illustrating the voids present at the interface between the substrate and the thermosetting resin layer in the laminate. Equipment: Laser microscope LEXT OLS4100 (product name, Olympus Corporation), objective lens magnification 20x. The cross-sectional area of ​​the void was calculated by approximating it as a circle with the major axis of the detected white area as the diameter. Cross-sectional area of ​​500 μm ２ The number of voids was measured and calculated as the number per 1 mm square.

[0111] <Measurement of Dielectric Constant and Dielectric Loss Tangent> In each example, the protective film was peeled off the thermosetting resin layer of the laminate. The exposed thermosetting resin surface was then superimposed on a 10 cm square polyimide film (Toray DuPont, product name: Kapton H 50 μm) and laminated using a vacuum laminator (Japan Steel Works, product name: MVLP300). During this process, the hot plate temperature was reduced for 30 seconds at 110°C, then increased to 1 MPa over 30 seconds, and held at 1 MPa for 30 seconds. This was repeated three times to create a 90 μm thick coating film with three layers. Subsequently, the resin composition layer was heat-cured at 185°C for 60 minutes using a (Yamato Scientific Co., Ltd., product name: DN610I). Further heat curing was performed in the same oven at 230°C for 120 minutes. The dielectric constant (Dk) and dielectric loss tangent (Df) at a frequency of 10 GHz were measured at room temperature (25°C) using a vector network analyzer (Agilent Technologies, "E8361C" (product name)) by the SPDR method. For each example, Dk was evaluated based on the following evaluation criteria, and the evaluation results are shown in Table 2. • Evaluation Criteria A: Dk is 2.5 or less. B: Dk is greater than 2.5 and less than 2.6. C: Dk is 2.6 or greater.

[0112] <Wiring Disconnection Rate (Frequency of Disconnection)> After removing the protective film from the laminates obtained in each example, the exposed thermosetting resin surface was placed on a 10 cm square glass plate and laminated using a vacuum laminator (manufactured by Japan Steel Works, product name: MVLP300). At that time, the hot plate temperature was reduced for 30 seconds at 110°C, then increased to 1 MPa over 30 seconds, and held at 1 MPa for 30 seconds. After lamination of the laminates (thermosetting resin sheets) with the protective film removed, the resin composition layer was heat-cured in an inert oven (manufactured by Yamato Scientific Co., Ltd., DN610I) filled with nitrogen at 185°C for 60 minutes. After that, the substrate was peeled off.

[0113] The resulting thermosetting resin layer was treated with a swelling solution (Atotec Japan Co., Ltd., product name "Swelling Dip Securigant P", an aqueous sodium hydroxide solution containing diethylene glycol monobutyl ether) at 60°C for 10 minutes, and then with a roughening solution (Atotec Japan Co., Ltd., product name "Concentrate Compact P", KMnO４ The substrate was immersed in an aqueous solution of 60 g / L of sodium sulfate and 40 g / L of NaOH at 80°C for 20 minutes, and finally in a neutralizing solution (Atotec Japan Co., Ltd., product name "Reduction Solution Securigant P", sulfuric acid aqueous solution) at 40°C for 5 minutes. After that, it was dried at 80°C for 30 minutes. The resulting substrate is referred to as "Evaluation Substrate 1".

[0114] A conductive layer was formed on the evaluation substrate 1 using a semi-additive method. Specifically, the evaluation substrate 1 was formed using a PdCl ２ The substrate was immersed in an electroless plating solution containing [material name missing] at 40°C for 5 minutes, then immersed in an electroless copper plating solution at 25°C for 20 minutes. After annealing by heating at 150°C for 30 minutes, an etching resist was formed, and a pattern was created by etching 500 lines with a width of 10 μm, a pitch of 100 μm, and a length of 8 cm to connect the vias. After this, copper sulfate electroplating was performed to form a conductive layer with a thickness of 10 μm. After removing the mask pattern, the unnecessary plating seed layer was removed by etching with a copper etching solution: SAC manufactured by JCU Corporation, and the conductive pattern was formed. The obtained substrate was annealed by heating at 190°C for 60 minutes. As a result, 500 lines with a length of 8 cm and a width of 10 μm, a pitch of 100 μm, were formed, and 50 μm pads were formed at both ends.

[0115] Terminals were placed on both ends of 500 pads, the resistance was checked, and the number of non-conducting wires was counted. The wire breakage rate was evaluated according to the following criteria, and the evaluation results for each example are recorded in Table 2. • Evaluation Criteria A: 0 wires B: 1 wire C: 2 or more wires

[0116] <Chipping during cutting> The laminate obtained in each example was cut to its full width using a rotary cutter (OLFA, LL type 136B), and the chipping at the cut edge was visually checked. If chipping was observed, its width was measured with a ruler and evaluated based on the following criteria, and the evaluation results are recorded in Table 2. ・Evaluation criteria A: No chipping was observed, or chipping of 0.5 mm or less was observed. B: Chipping exceeding 0.5 mm was observed. C: The film cracked and peeled off the film during cutting.

[0117] <Changes in Df after storage> The laminates of each example were stored in a freezer at -20°C for two weeks, and then Df was measured in the same manner as above and evaluated based on the following evaluation criteria. The change in Df and evaluation results for each example are listed in Table 2. ・Evaluation criteria A: Change in Df is 0.0001 or less. B: Change in Df is greater than 0.0001 and 0.0002 or less. C: Change in Df is greater than 0.0002.

[0118] <Measurement of voids at the interface between the thermosetting resin layer and the protective film> Voids at the interface between the thermosetting resin layer and the protective film were detected by the following method. Specifically, the laminates obtained in each example were observed with a laser microscope from the protective film side under the following conditions, focusing on the interface between the thermosetting resin layer and the protective film. 100 images with an area of ​​130 μm × 129 μm were observed without overlap, and the white areas seen in Figure 6 were detected as voids. Figure 6 is a diagram illustrating the voids present at the interface between the thermosetting resin layer and the protective film in the laminate. Equipment: Laser microscope LEXT OLS4100 (product name, Olympus Corporation), objective lens magnification 100x. The cross-sectional area of ​​the void was calculated by approximating it as a circle with the major axis of the detected white area as the diameter. Cross-sectional area 50 μm ２ The number of voids was measured and calculated as the number per 1 mm square.

[0119] <Wiring Embedding Ability> On a 2-inch diameter silicon wafer, 100 circuits with a wiring width of 20 μm, a wiring depth of 20 μm, and a groove width of 20 μm between wirings were formed in parallel by dry etching. Subsequently, the laminates (thermosetting resin sheets) obtained in each example were stacked on the silicon wafer and laminated using a vacuum laminator (manufactured by Japan Steel Works, product name: MVLP300). During this process, the hot plate temperature was set to 110°C and the pressure was reduced for 30 seconds, then the pressure was increased to 1 MPa over 30 seconds and held at 1 MPa for 30 seconds. After that, a cross-section of the removed laminate was obtained by ion milling and observed with an electron microscope, and evaluated based on the following evaluation criteria. The evaluation results for each example are shown in Table 2. ・Evaluation Criteria A: The resin was embedded in the width of the grooves, and no gaps were observed at the silicon-sheet interface. B: The resin was embedded in the width of the grooves, and no gaps were observed at the silicon-sheet interface, but an interface was observed in the resin. C: The groove width was filled with resin, but a gap was observed at the interface between the silicone and the sheet.

[0120] <Measurement of Curl Curvature> The curvature (curl curvature) of the laminate in the sheet flow direction was measured by the following method. Three sheets of film, 4 mm wide and 80 mm long, were cut from the roll after the protective film was laminated, parallel to the flow direction. Next, 30 mm from the base of each cut film in the flow direction was fixed to a flat surface, and 50 mm (let's call it X) was left free and placed on the flat surface. The height (let's call it Y) of the tip of the curled film from the flat surface was measured. The curvature was calculated using the following formula and evaluated based on the following evaluation criteria. The curvature and evaluation results for each example are shown in Table 2. Curvature = 2 × Y ２ / (X ２ +Y ２ ) ・Evaluation criteria A: Curvature is 0.01 or less B: Curvature is greater than 0.01

[0121] The evaluation results for each example are shown below.

[0122] From the above results, it can be seen that this laminate, which includes a thermosetting resin layer containing resin and hollow inorganic particles and having a specific dielectric constant, can achieve high reliability, low dielectric constant, and low dielectric loss tangent when used as an interlayer insulating film. Furthermore, it can be seen that printed circuit boards and semiconductor devices with excellent electrical properties can be provided by using this laminate.

[0123] This disclosure is not limited to the embodiments described above, and design modifications can be made without departing from the spirit of this disclosure. This disclosure may also be implemented in combination with the embodiments described above and / or examples thereof.

[0124] This application claims priority based on Japanese Patent Application No. 2025-068173, filed on 17 April 2025, and incorporates all of its disclosures herein.

[0125] 1 Hollow inorganic particles 2 Thermosetting resin layer 2A First surface 2B Second surface 3 Base material 4 Void 5 Protective film 6 Void

Claims

1. A laminate having a thermosetting resin layer comprising at least a resin and hollow inorganic particles, with a dielectric constant of less than 2.6 at a frequency of 10 GHz, and satisfying at least one of the following conditions (1) and (2): (1) Having a substrate disposed in contact with the first surface of the thermosetting resin layer, wherein the cross-sectional area at the interface between the substrate and the thermosetting resin layer is 500 μm² ２ The number of voids above this is 10 / mm ２ The following applies: (2) A protective film is provided which is in contact with the second surface of the thermosetting resin layer facing the first surface, and the cross-sectional area at the interface between the thermosetting resin layer and the protective film is 50 μm ２ The number of voids above this is 10 / mm ２ The following applies:

2. The laminate according to claim 1, wherein the above condition (1) is met, and the weight loss rate when the thermosetting resin layer peeled from the substrate is heated at 150°C for 1 hour is 1.7 to 3.8%.

3. The laminate according to claim 1, which satisfies condition (2) above and has a curvature in the sheet flow direction of 0.01 or less.

4. The laminate according to any one of claims 1 to 3, wherein the average particle size of the hollow inorganic particles is 0.1 to 10.0 μm.

5. The laminate according to any one of claims 1 to 3, wherein the porosity of the hollow inorganic particles is 5 volume percent or more.

6. The specific gravity of the hollow inorganic particles is 1.0 g / cm³. ３ The laminate according to any one of claims 1 to 3, which is as follows:

7. The laminate according to any one of claims 1 to 3, wherein the uniformity of the hollow inorganic particles is 1.7 to 3.

4.

8. The laminate according to any one of claims 1 to 3, wherein the thermosetting resin layer comprises a thermosetting resin and a thermoplastic elastomer.

9. The laminate according to any one of claims 1 to 3, wherein the thickness of the thermosetting resin layer is 10 to 125 μm.

10. The laminate according to claim 1 or 2, wherein the substrate comprises a stretched polyester film having a glass transition temperature of 105°C or higher.

11. A laminate according to any one of claims 1 to 3, wherein the laminate is a thermosetting resin sheet.

12. A method for manufacturing a laminate according to any one of claims 1 to 3, comprising the step of drying the undried thermosetting resin layer from the first surface side of the thermosetting resin layer.

13. A printed circuit board comprising a cured product of the thermosetting resin layer in the laminate according to any one of claims 1 to 3.

14. A semiconductor device comprising a printed circuit board as described in claim 13.

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