Prepreg, laminate, metal-clad laminate, printed wiring board, semiconductor package, method for manufacturing prepreg, and method for manufacturing metal-clad laminate

Abstract

Provided is a prepreg which is capable of achieving a metal-clad laminate having high thickness accuracy and high insulation reliability even when a fiber base material having a thickness of 40 [mu] m or more is used. Also provided are a laminate, a metal-clad laminate, a printed wiring board, and a semiconductor package, each of which is obtained using the prepreg. Also provided are a method for producing the prepreg and a method for producing the metal-clad laminate. The prepreg contains a fiber base material having a thickness of 40 [mu] m or more and a thermosetting resin composition, the fiber base material has regions impregnated with the thermosetting resin composition and regions not impregnated with the thermosetting resin composition, the regions not impregnated with the thermosetting resin composition are intermittently present, and the surface waviness (Wa) of the prepreg is 5.0 [mu] m or less.

Description

Technical Field

[0001] The present disclosure relates to prepregs, laminates, metal-clad laminates, printed circuit boards, semiconductor packages, and methods for manufacturing prepregs and methods for manufacturing metal-clad laminates. Background Art

[0002] With the recent high density of semiconductor packages and high communication speeds, there is an urgent demand for printed circuit boards with low warpage, high reliability, and improved impedance control. In order to meet this demand, it is necessary to further reduce the thickness variation of copper-clad laminates compared to the past. However, copper-clad laminates manufactured using prepregs obtained by impregnating a fiber substrate with a resin varnish and then drying (for example, see Patent Document 1) tend to have thickness variations.

[0003] On the other hand, there is known a method in which, instead of impregnating a fiber substrate with a resin varnish, a resin film is previously made from a thermosetting resin composition, and the fiber substrate and the resin film are bonded by heating and pressing to manufacture a prepreg (for example, see Patent Document 2). With this method, prepregs with excellent thickness accuracy can be manufactured compared to the method of impregnating a fiber substrate with a resin varnish. However, according to the research by the present inventors, although there is a tendency to obtain excellent thickness accuracy of the prepreg when the thickness of the fiber substrate is small, for example, 35 μm or less, when the thickness of the fiber substrate is greater than this value, the thickness accuracy of the prepreg deteriorates, and furthermore, the thickness accuracy of the copper-clad laminate deteriorates.

[0004] Under such circumstances, there is proposed a prepreg having a fiber substrate formed in layers and a resin layer provided on at least one surface side of the fiber substrate and composed of a resin composition, and in at least a part of the fiber substrate, a void layer in which the resin composition is not impregnated is formed (see Patent Document 3). As described in Figures 1 to 3 paragraphs

[0022] of Patent Document 3, the void layer communicates from one end to the other end, so that air is easily discharged during lamination of the prepreg, and bubbles are not easily generated.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Laid-Open No. 01-272416

[0008] Patent Document 2: Japanese Patent Laid-Open No. 2011-132535

[0009] Patent Document 3: Japanese Patent Laid-Open No. 2013-180406 Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] However, through further research by the present inventors, it has been found that in a metal-clad laminate made of a prepreg having a void layer communicating from one end to the other end as described in Patent Document 3, the insulation reliability may be insufficient.

[0012] Therefore, an object of the present disclosure is to provide a prepreg that can achieve a metal-clad laminate having high thickness accuracy and high insulation reliability even when using a fiber base material with a thickness of 40 μm or more, and to provide a laminate, a metal-clad laminate, a printed wiring board, and a semiconductor package using the prepreg. In addition, a method for manufacturing the prepreg and a method for manufacturing the metal-clad laminate are provided.

[0013] Means for Solving the Problems

[0014] The present inventors have repeatedly conducted in-depth research and as a result, have found that the above object can be achieved by the present disclosure. The present disclosure includes the following embodiments [1] to

[13] .

[0015] [1] A prepreg containing a fiber base material with a thickness of 40 μm or more and a thermosetting resin composition, having an impregnated area and a non-impregnated area of the thermosetting resin composition in the fiber base material, the non-impregnated area existing discontinuously, and the surface waviness (Wa) of the prepreg being 5.0 μm or less.

[0016] [2] The prepreg according to [1] above, wherein the non-impregnated area exists discontinuously in the in-plane direction.

[0017] [3] The prepreg according to [1] or [2] above, wherein the existence ratio of the impregnated area calculated by the following calculation method is 30 to 98%.

[0018] Calculation method: Observe the surface of the prepreg at a magnification of 50 times using an optical microscope to obtain a surface observation image. After converting the obtained surface observation image to black and white mode using image editing software, save it in the BMP (Microsoft Windows Bitmap Image) format. Then, for the surface observation image in black and white mode saved in the BMP format, convert each pixel to RGB (Red, Green, Blue) values using image conversion software and save it in the CSV (comma-separated values) format. Paste the RGB data saved in the CSV format into Microsoft Excel (manufactured by Microsoft Corporation) and calculate the areas of the black part (RGB value = 255) and the white part (RGB value = 0). Based on these values, find the area ratio of the black part to the total of the black part and the white part. Set the area ratio of the black part thus obtained as the presence ratio of the above-mentioned impregnation region.

[0019] [4] The prepreg according to [3] above, wherein the presence ratio of the above-mentioned impregnation region is 50 to 90%.

[0020] [5] The prepreg according to any one of [1] to [4] above, wherein the thickness of the above-mentioned fiber substrate is 70 to 120 μm.

[0021] [6] A laminated board having one or more of the prepregs according to any one of [1] to [5] above.

[0022] [7] A metal-clad laminated board having a metal foil and one or more of the prepregs according to any one of [1] to [5] above.

[0023] [8] A printed circuit board having the laminated board according to [6] above or the metal-clad laminated board according to [7] above.

[0024] [9] A semiconductor package having the printed circuit board according to [8] above and a semiconductor element.

[0025]

[10] A method for manufacturing a prepreg, wherein a prepreg is manufactured by laminating a film of a thermosetting resin composition onto a fiber substrate having a thickness of 40 μm or more, an impregnation region and a non-impregnation region of the thermosetting resin composition are provided in the above-mentioned fiber substrate, and the non-impregnation region exists discontinuously, and the surface waviness (Wa) of the above-mentioned prepreg is 5.0 μm or less.

[0026]

[11] The method for manufacturing a prepreg according to

[10] above, wherein the non-impregnation region exists discontinuously in the in-plane direction.

[0027]

[12] According to the method for manufacturing a prepreg described in

[10] or

[11] above, the existence ratio of the impregnation region obtained by the following calculation method is 30 to 98%.

[0028] Calculation method: Observe the surface of the prepreg with an optical microscope at a magnification of 50 times to obtain a surface observation image. After converting the obtained surface observation image into black and white mode using image editing software, save it in the BMP (Microsoft Windows Bitmap Image) format. Then, for the surface observation image in black and white mode saved in the BMP format, convert each pixel into RGB (Red, Green, Blue) values using image conversion software and save it in the CSV (comma - separated values) format. Paste the RGB data saved in the CSV format into Microsoft Excel (manufactured by Microsoft Corporation) and calculate the areas of the black part (RGB value = 255) and the white part (RGB value = 0). Calculate the area ratio of the black part to the total of the black part and the white part based on these values. Set the area ratio of the black part thus obtained as the existence ratio of the impregnation region.

[0029]

[13] A method for manufacturing a metal - clad laminate, wherein metal foils are provided on both sides of one prepreg obtained by the manufacturing method described in any one of

[10] to

[12] above or on both sides of a laminate of prepregs including at least one or more of the above prepregs, and then press - forming is performed.

[0030] Advantages of the Invention

[0031] According to the present disclosure, it is possible to provide a prepreg that can achieve a metal - clad laminate with high thickness accuracy and high insulation reliability even when using a fiber substrate with a thickness of 40 μm or more, and it is possible to provide a laminate, a metal - clad laminate, a printed wiring board, and a semiconductor package obtained by using the prepreg. In addition, it is possible to provide a method for manufacturing the prepreg and a method for manufacturing the metal - clad laminate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic cross - sectional view showing one mode of the prepreg of the present embodiment.

[0033] Figure 2 It is a schematic cross - sectional view for explaining one mode of the prepreg of the present embodiment.

[0034] Figure 3 It is a schematic cross - sectional view of a prepreg manufactured by a conventional method of impregnating a fiber substrate in a resin varnish and then drying.

[0035] Figure 4 It is a cross-sectional view of the fiber substrate contained in the prepreg of the present embodiment, which is used to illustrate the thickness of the fiber substrate.

[0036] Figure 5 It is a surface observation image obtained by converting to black and white mode the surface observation image used for calculating the existence ratio of the impregnated area in the prepreg produced in Example 1. Detailed Description of the Embodiment

[0037] Hereinafter, an embodiment of the present disclosure will be described in detail. However, the present disclosure is not limited to the embodiment described below.

[0038] In the numerical ranges described in this specification, the lower limit value or the upper limit value of the numerical range can be replaced with the value shown in the examples. In addition, the lower limit value and the upper limit value of the numerical range can be arbitrarily combined with the lower limit value or the upper limit value of other numerical ranges. In the expression of the numerical range "AA to BB", the two end values AA and BB are included in the numerical range as the lower limit value and the upper limit value, respectively. In addition, the expression of the numerical range "greater than CC to DD" means greater than CC and less than or equal to DD.

[0039] In this specification, for example, the description "10 or more" means 10 and a value greater than 10, and the same applies in the case of different numerical values. In addition, for example, the description "10 or less" means 10 and a value less than 10, and the same applies in the case of different numerical values.

[0040] In addition, each component and material exemplified in this specification can be used alone in one kind, or two or more kinds can be used in combination, unless otherwise specified. In this specification, regarding the content of each component in the thermosetting resin composition, when there are a plurality of substances corresponding to each component in the thermosetting resin composition, unless otherwise specified, it means the total amount of the plurality of substances present in the thermosetting resin composition.

[0041] In this specification, the so-called "resin component" means all components other than inorganic compounds such as inorganic fillers, flame retardants, and flame retardant aids among the solid components constituting the thermosetting resin composition.

[0042] In this specification, the so-called "solid component" means components other than the solvent, and a component that is liquid at 25 °C is also regarded as a solid component.

[0043] The expression "containing XX (component)" described in this specification of course has the meaning of simply containing ~~, but also includes containing in a state where the substances described in ~~ have reacted (however, this is limited to the case where they can react).

[0044] A mode obtained by arbitrarily combining the descriptions in this specification is also included in the present disclosure and the present embodiment.

[0045] [Prepreg]

[0046] The prepreg of the present embodiment contains a fiber base material with a thickness of 40 μm or more and a thermosetting resin composition. In the above fiber base material, there are impregnated areas and non-impregnated areas of the above thermosetting resin composition, and the above non-impregnated areas exist intermittently. The surface waviness (Wa) of the prepreg is 5.0 μm or less. It should be noted that having the impregnated areas and non-impregnated areas of the above thermosetting resin composition in the fiber base material ultimately refers to the prepreg, that is, the prepreg in the B-stage state, and does not involve the cured product of the prepreg.

[0047] The surface waviness (Wa) of the present disclosure is the arithmetic mean height (Wa) that can be obtained from the waviness curve in accordance with ISO 4287 (1997). JIS B 0601 (2001) can also be used instead of ISO 4287 (1997). It should be noted that the surface waviness (Wa) of the present disclosure can be measured as follows.

[0048] Using a shape analysis laser microscope "VK-X100" (manufactured by Keyence Corporation), shape measurement is performed by automatic measurement using the observation application program to obtain a waviness curve in accordance with ISO 4287 (1997) or JIS B 0601 (2001). For the obtained waviness curve, surface roughness analysis can be performed using the analysis application program to calculate the surface waviness (Wa). Here, the so-called waviness curve is a curve obtained by removing wavelengths less than 80 μm from the cross-sectional curve by applying a phase compensation type high-pass filter λc (λc = 80 μm) to the cross-sectional curve. In addition, the analysis range is set to 1000 μm × 1000 μm.

[0049] It should be noted that unless otherwise specified, the surface waviness (Wa) of the prepreg of the present disclosure is the surface waviness of both sides of the prepreg. The above-mentioned "surface" is the surface that coincides when multiple prepregs are laminated to produce a metal-clad laminate or the surface on the opposite side.

[0050] In addition, in this specification, when referring to the "surface direction" of the prepreg, this direction is as Figure 2 shown, meaning the direction along the surface of the prepreg on the surface of the prepreg. In addition, in this specification, when referring to the "in-plane direction", this direction is as Figure 2As shown, it means in the direction along the surface of the fiber base material inside the fiber base material. Whether it is "plane direction" or "in-plane direction", it is parallel to the direction approximately perpendicular to one edge of the prepreg and facing the edge opposite to this edge. In this specification, the so-called approximately perpendicular means substantially perpendicular, preferably within the range of 86 to 94°, more preferably within the range of 88 to 92°, and further preferably 90°.

[0051] Although the prepreg of this embodiment uses a "fiber base material with a thickness of 40 μm or more" with a larger surface waviness compared to a thin fiber base material, the surface waviness (Wa) is 5.0 μm or less. This is achieved by adopting a method of "intentionally providing an unimpregnated area of the thermosetting resin composition in the fiber base material of the prepreg". This method is a method that is usually difficult to adopt based on the following conventional technical common sense, that is, by unrestrictedly increasing the impregnation rate of the thermosetting resin composition into the fiber base material during the manufacturing stage of the prepreg to suppress void generation. By using the prepreg of this embodiment, the thickness accuracy of the metal-clad laminate of this embodiment has been successfully improved significantly.

[0052] On the other hand, in the conventional method of impregnating the fiber base material with a resin varnish and then drying it, as Figure 3 shown, since the thermosetting resin composition follows the waviness of the glass cloth, the surface waviness of the prepreg becomes larger. That is, in the prepreg, the fluctuation of the thickness of the resin layer in the plane direction becomes larger. Since the prepreg is pressed in the thickness direction during the manufacturing of the metal-clad laminate, the thermosetting resin composition is likely to flow in the thickness direction. If it does not flow sufficiently in the plane direction, it will cause fluctuations in the thickness of the metal-clad laminate. However, it is technically difficult to control the flow of the thermosetting resin composition in the plane direction to the extent that the fluctuation of the thickness of the above resin layer is reduced or eliminated.

[0053] However, in the prepreg of this embodiment, the resin layer near the surface exists without following the waviness of the glass cloth. Thus, as described above, the surface waviness is small, that is, the thickness fluctuation is small. Therefore, it can be considered that even if there is no flow of the thermosetting resin composition in the plane direction during the manufacturing of the metal-clad laminate, the fluctuation of the thickness of the metal-clad laminate will become smaller.

[0054] In addition, in the prepreg of this embodiment, "the above unimpregnated area is made to exist discontinuously", whereby the insulation reliability of the metal-clad laminate of this embodiment can be further improved, and thus the insulation reliability of the printed circuit board can be improved. It is preferred that the above unimpregnated area exists discontinuously in the in-plane direction of the fiber base material.

[0055] Although the mechanism for achieving success is not certain, it can be considered as follows. As Figure 1 and Figure 2As shown, when impregnating a resin film into a fiber base material, by intentionally providing an area in the fiber base material where the thermosetting resin composition does not impregnate, the layer of the thermosetting resin composition near the surface (hereinafter simply referred to as the resin layer) will exist without following the corrugation of the glass cloth. As a result, the large corrugation of the fiber base material having a thickness of 40 μm or more is not easily reflected on the surface of the prepreg, whereby the surface corrugation (Wa) of the prepreg is 5.0 μm or less. Moreover, by performing press molding using a prepreg having a surface corrugation (Wa) of 5.0 μm or less, due to the small surface corrugation (Wa) of the prepreg, the thickness unevenness of the metal-clad laminate is suppressed, and high thickness accuracy can be achieved.

[0056] Moreover, regarding improving the insulation reliability by intermittently providing the non-impregnated area so as not to communicate from one end to the other end of the prepreg, although the exact reason is not certain, it is speculated that perhaps because when manufacturing the metal-clad laminate, the thermosetting resin composition is also sufficiently impregnated near the part where the density of the fiber base material is high. Use Figure 1 and Figure 2 are used for illustration. For example, in the case of glass cloth, it can be considered that the density of glass fibers becomes high at the part where glass yarns are woven and overlapped, and there is a tendency for voids to easily exist at this part in the prepreg. When the thermosetting resin composition is not sufficiently impregnated into the part where the density of glass fibers is high during the manufacture of the metal-clad laminate, this situation may lead to insulation failure. On the other hand, regarding the prepreg of the present embodiment, it can be considered that the part where the density of glass fibers is high forms a state with few voids or a state without voids, and a state where the thermosetting resin composition is sufficiently impregnated into the part where the density of glass fibers is high is formed in the metal-clad laminate, so the insulation reliability is improved.

[0057] In the case of a prepreg having a void layer communicating from one end to the other end as described in Patent Document 3, it is speculated that since a void layer is also formed at the part where the density of glass fibers is high, the resin is not impregnated, and the thermosetting resin composition is not sufficiently impregnated into the part where the density of glass fibers is high during the manufacture of the metal-clad laminate, which results in poor insulation reliability (refer to Comparative Examples 2 and 3).

[0058] In the present embodiment, although the non-impregnated area of the thermosetting resin composition is intermittently provided in the fiber base material of the prepreg, during the press molding in the manufacture of the metal-clad laminate, the thermosetting resin composition flows in the thickness direction and flows into the above non-impregnated area, thereby sufficiently suppressing the generation of voids in the metal-clad laminate.

[0059] From the above viewpoints, the surface waviness (Wa) of the prepreg of the present embodiment is preferably 5.0 μm or less, more preferably 3.0 μm or less, and still more preferably 1.0 μm or less. The lower limit value of the surface waviness (Wa) of the prepreg of the present embodiment is not particularly limited, and may be 0.01 μm or more, may be 0.1 μm or more, or may be 0.2 μm or more. That is, the surface waviness (Wa) of the prepreg of the present embodiment may be 0.01 to 5.0 μm, may be 0.1 to 3.0 μm, or may be 0.2 to 1.0 μm.

[0060] (Regarding the presence of unimpregnated regions of the thermosetting resin composition in the fiber substrate)

[0061] As described above, the prepreg of the present embodiment is characterized in that it has impregnated regions and unimpregnated regions of the thermosetting resin composition in the above fiber substrate, and in particular, the above unimpregnated regions and the above unimpregnated regions exist intermittently. The presence of the unimpregnated region can be confirmed by determining the presence ratio of the impregnated region of the thermosetting resin composition in the fiber substrate. That is, if the presence ratio of the impregnated region is not 100%, it means that there is an unimpregnated region.

[0062] In the present embodiment, the presence ratio of the impregnated region of the thermosetting resin composition in the above fiber substrate is defined as the value obtained by the following calculation method. From the viewpoint of the thickness accuracy of the metal-clad laminate, the presence ratio of the impregnated region obtained based on the "calculation method" described later is not particularly limited, and may be 30 to 98%, may be 30 to 95%, may be 35 to 95%, may be 40 to 95%, may be 45 to 90%, may be 50 to 90%, may be 55 to 90%, or may be 60 to 85%. When the above presence ratio is 98% or less, the effect of improving the thickness accuracy of the metal-clad laminate tends to increase, and particularly when it is 95% or less, this tendency further increases. In addition, when the above presence ratio is 30% or more, the situation where the thermosetting resin composition falls off from the prepreg in the form of powder particles is suppressed, and thus there is a tendency to obtain a secondary effect of good handleability. It should be noted that if the presence ratio of the impregnated region is 30% or more, the unimpregnated region tends to exist intermittently. From this viewpoint, the presence ratio of the impregnated region is preferably 50% or more.

[0063] - Calculation method -

[0064] The surface of the prepreg is observed with an optical microscope at a magnification of 50 times to obtain a surface observation image. Regarding the observation conditions, from the viewpoint of photographing with an appropriate brightness, the observation conditions described in detail in the examples are adopted.

[0065] After converting the obtained surface observation image into black-and-white mode using image editing software, it is saved in the BMP (Microsoft Windows Bitmap Image) format. Then, for the black-and-white mode surface observation image saved in the BMP format, each pixel is converted into RGB (Red, Green, Blue) values using image conversion software and saved in the CSV (comma-separated values) format. The RGB data saved in the CSV format is pasted into Microsoft Excel (manufactured by Microsoft Corporation), and the areas of the black part (RGB value = 255) and the white part (RGB value = 0) are calculated. Based on these values, the area ratio of the black part to the total of the black part and the white part is obtained. The area ratio of the black part thus obtained is set as the existence ratio of the above-mentioned impregnated area.

[0066] For example, "Microsoft Paint" (manufactured by Microsoft Corporation) etc. can be used as the above-mentioned image editing software. Additionally, for example, "bmp2csv" etc., which is free software, can be used as the above-mentioned image conversion software.

[0067] It should be noted that in the above observation, when converting the surface observation image taken with an appropriate brightness into black-and-white mode, since the surface of the unimpregnated area of the thermosetting resin composition at the lower part of the observation surface is a void part and is prone to reflecting light, it is displayed as "white", and the other surfaces are displayed as "black". Here, when taking the surface observation image, the exposure time during surface shooting is adjusted within the range of 60 to 100 ms, whereby it will be taken with an appropriate brightness that can fully reflect the impregnated area and the unimpregnated area, so it is preferred. Regarding the surface observation image of the prepreg, in order of decreasing color intensity, they are "the area where the glass cloth does not exist in the resin layer", "the area where the thermosetting resin composition is fully impregnated into the glass cloth", and "the area where the impregnation of the thermosetting resin composition into the glass cloth is insufficient". In this embodiment, the above-mentioned "area where the glass cloth does not exist in the resin layer" is also included in the above-mentioned impregnated area. If the surface observation image is too bright, in the black-and-white mode surface observation image, not only is the part where the resin is insufficiently impregnated into the glass cloth prone to being displayed as white, but also the part where the resin is fully impregnated into the glass cloth is prone to being displayed as white. In the case of an even brighter image, the black-and-white mode surface observation image has a tendency to become white as a whole. On the other hand, if the surface observation image is too dark, the black-and-white mode surface observation image becomes black as a whole, and there is a tendency to be difficult to reflect the existence of the unimpregnated area. Therefore, it is preferred to take the image with an appropriate brightness. As an example of converting the surface observation image taken with an appropriate brightness into black-and-white mode, in Figure 5The surface observation image converted to black-and-white mode obtained in Example 1 is shown. Figure 5 In this, the appearance in which the impregnated regions and the non-impregnated regions alternately exist in the in-plane direction can be observed.

[0068] In addition, the area ratio of the white portion to the total of the white portion and the black portion can be easily calculated by using the COUNTIF function of Microsoft Excel (manufactured by Microsoft Corporation).

[0069] (Regarding the non-impregnated region)

[0070] As described above, in the prepreg of the present embodiment, by intermittently providing the above non-impregnated regions, the insulation reliability of the metal-clad laminate is improved. It is considered that by intermittently providing the non-impregnated regions of the thermosetting resin composition in the fiber base material of the prepreg, the thermosetting resin composition exists in a place infinitely close to the portion where it is difficult for the thermosetting resin composition to enter due to the high density of the glass cloth. Therefore, it is considered that during press molding, the thermosetting resin composition rapidly flows into the portion where it is difficult for the thermosetting resin composition to enter due to the high density of the glass cloth, thereby suppressing the generation of minute voids, and thus improving the insulation reliability. On the other hand, it is considered that if the non-impregnated regions of the thermosetting resin composition continuously exist in the fiber base material of the prepreg, the thermosetting resin composition exists in a place away from the portion where it is difficult for the thermosetting resin composition to enter due to the high density of the glass cloth. Therefore, it is considered that although the thermosetting resin composition flows during press molding, it advances to cure before flowing into the portion where it is difficult for the thermosetting resin composition to enter due to the high density of the glass cloth, and thus minute voids remain in the metal-clad laminate.

[0071] (Surface roughness (Ra))

[0072] The prepreg of the present embodiment is not particularly limited, but preferably has a surface roughness (arithmetic mean roughness Ra; hereinafter sometimes simply referred to as "Ra") of 0.1 to 5 μm.

[0073] The surface roughness (Ra) of the present disclosure is the arithmetic mean height (Ra) that can be obtained from a roughness curve in accordance with ISO 4287 (1997). JIS B 0601 (2001) can also be used in place of ISO 4287 (1997). It should be noted that the surface roughness (Ra) of the present disclosure is the surface roughness (Ra) obtained by measuring using a shape analysis laser microscope "VK-X100" (manufactured by Keyence Corporation). Here, the so-called roughness curve measured in this embodiment is a curve obtained by applying a phase compensation type high-pass filter λc (λc = 80 μm) to a cross-sectional curve and removing wavelengths of 80 μm or more from the above cross-sectional curve. In addition, the analysis range is set to 1000 μm × 1000 μm.

[0074] In the prepreg of this embodiment, by setting Ra to 0.1 μm or more, appropriate unevenness is imparted to the surface of the prepreg, whereby the amount of static electricity charged can be reduced, and there is a tendency to become a prepreg with excellent workability. On the other hand, by setting Ra to 5 μm or less, there is a tendency to improve the thickness accuracy of the metal-clad laminate.

[0075] From such a viewpoint, the Ra of the prepreg of this embodiment can be 0.15 to 3 μm, can be 0.2 to 2 μm, can be 0.2 to 1.6 μm, or can be 0.2 to 1.0 μm.

[0076] It should be noted that even if not specifically indicated, the Ra of the prepreg of the present disclosure is the Ra of at least one surface of the prepreg. The so-called "surface" above is the surface that coincides when multiple prepregs are laminated to produce a metal-clad laminate or the surface on the opposite side thereof. It is preferable that the Ra of at least one surface of the prepreg is within the above range, and it is more preferable that the Ra of both surfaces is within the above range.

[0077] <Fiber base material>

[0078] As the fiber base material having a thickness of 40 μm or more contained in the prepreg of this embodiment, well-known fiber base materials used in various laminated boards for electrical insulation materials can be used. As the material of the fiber base material, natural fibers such as paper and cotton linter can be cited; inorganic fibers such as glass fiber and asbestos; organic fibers such as aramid, polyimide, polyvinyl alcohol, polyester, tetrafluoroethylene, and acrylic fiber; mixtures thereof, etc. Among them, from the viewpoint of flame retardancy, inorganic fibers are preferred, and glass fiber is more preferred. In addition, as the glass fiber, glass cloth using E glass, C glass, D glass, S glass, etc. can be cited; glass cloth obtained by bonding short fibers with an organic binder; fibers obtained by co-papering glass fiber and cellulose fiber, etc. Among them, as the glass fiber, glass cloth using E glass is preferably used.

[0079] The shape of the fiber base material is not particularly limited and may be a woven fabric, non-woven fabric, roving, chopped strand mat, surface mat, etc. Among them, when it is a woven fabric, the effects of the present embodiment tend to become more significant. It should be noted that the material and shape can be appropriately selected according to the use and performance of the target molded article. As the fiber base material, one kind can be used alone, or two or more kinds of materials and two or more kinds of shapes can be used in combination as needed.

[0080] The fiber base material may be a fiber base material composed of one layer or a fiber base material composed of multiple layers. It should be noted that the so-called fiber base material composed of one layer means a fiber base material composed only of wound fibers. In the case where there are unwound fiber base materials, it is classified as a fiber base material composed of multiple layers. The materials and shapes of the fiber base materials of two or more layers may be the same or different.

[0081] (Thickness of the fiber base material)

[0082] The thickness of the fiber base material contained in the prepreg of the present embodiment (refer to Figure 4 ) is set to "40 μm or more", which is found to have a tendency for the thickness accuracy of the metal-coated laminate to deteriorate when using the conventional method. The thickness of the fiber base material can be 40 to 120 μm, or 45 to 120 μm, or 50 to 120 μm, or 55 to 120 μm, or 60 to 120 μm, or 70 to 120 μm, or 70 to 100 μm, or 80 to 100 μm. In addition, from the viewpoint of improving the impregnation property of the thermosetting resin composition into the fiber base material and having a tendency to make the heat resistance and insulation reliability of the cured product of the prepreg better, the thickness of the fiber base material is preferably less than 100 μm, or can be 40 μm or more and less than 100 μm, or 40 to 97 μm, or 50 to 97 μm, or 60 to 97 μm, or 70 to 97 μm, or 80 to 95 μm. Since the surface waviness of the fiber base material itself tends to increase as the thickness of the fiber base material increases, the thickness accuracy of the metal-coated laminate decreases in the case of the conventional method. However, in the prepreg of the present embodiment, even if the thickness of the fiber base material is increased as described above, the surface waviness (Wa) of the prepreg can be suppressed to be small. As a result, the thickness accuracy of the metal-coated laminate becomes high.

[0083] It should be noted that in this specification, the thickness of the fiber base material is Figure 4 the thickness of the part shown, and is the average value of the values measured with a micrometer at any five places of the fiber base material.

[0084] (Surface waviness (Wa) of the fiber base material)

[0085] The surface waviness (Wa) of the fiber base material contained in the prepreg of the present embodiment is not particularly limited, but it can be greater than 5.0 μm, can be 6.0 μm or more, can be 7.0 μm or more, can be 10.0 μm or more, and can be 15.0 μm or more. The upper limit value of the surface waviness (Wa) of the fiber base material of the present embodiment is not particularly limited, but it can be 40 μm or less, can be 30 μm or less, and can be 25 μm or less. That is, the surface waviness (Wa) of the above-mentioned fiber base material can be greater than 5.0 to 40 μm, can be 6.0 to 30 μm, can be 7.0 to 30 μm, can be 10 to 25 μm, and can be 15 to 25 μm.

[0086] According to the present embodiment, even if the surface waviness (Wa) of the fiber base material is in the above range, the surface waviness (Wa) of the prepreg can be suppressed within the above range, and the thickness accuracy of the metal-clad laminate can be maintained at a high level.

[0087] <Thermosetting resin composition>

[0088] As described above, the prepreg of the present embodiment is a prepreg containing a fiber base material with a thickness of 40 μm or more and a thermosetting resin composition. The above thermosetting resin composition contains at least a thermosetting resin. As the components contained in the above thermosetting resin composition, there is no particular limitation, but it is preferably further contains at least 1 selected from curing agents, curing accelerators, inorganic fillers, organic fillers, coupling agents, leveling agents, antioxidants, flame retardants, flame retardant aids, thixotropy imparting agents, thickeners, flexibility materials, surfactants, and photoinitiators in addition to the above thermosetting resin.

[0089] Hereinafter, each component contained in the above thermosetting resin composition will be described in turn.

[0090] (Thermosetting resin)

[0091] Examples of the thermosetting resin include epoxy resin, polyimide resin, maleimide resin, modified maleimide resin, phenolic resin, polyphenylene ether resin, bismaleimide triazine resin, cyanate ester resin, isocyanate resin, benzoxazine resin, oxetane resin, amino resin, unsaturated polyester resin, allyl resin, dicyclopentadiene resin, silicone resin, triazine resin, melamine resin, etc. Examples of the above-mentioned modified maleimide resin include reaction products of a maleimide compound having at least two N-substituted maleimide groups and at least one compound selected from monoamine compounds and diamine compounds. Here, the above-mentioned maleimide resin does not include the above-mentioned modified maleimide resin. In addition, as the thermosetting resin, it is not particularly limited to these resins, and known thermosetting resins can be used. The thermosetting resin can be used alone or in combination of two or more.

[0092] Among them, from the viewpoints of formability and electrical insulation, as the thermosetting resin, it is preferably at least one selected from epoxy resin, polyimide resin, maleimide resin, modified maleimide resin, cyanate ester resin, polyphenylene ether resin, and bismaleimide triazine resin, and more preferably at least one selected from epoxy resin, maleimide resin, modified maleimide resin, and cyanate ester resin.

[0093] As the epoxy resin, an epoxy resin having two or more epoxy groups in one molecule is preferred. Here, the epoxy resin can be classified into glycidyl ether type epoxy resin, glycidyl amine type epoxy resin, glycidyl ester type epoxy resin, etc. Among them, glycidyl ether type epoxy resin is preferred.

[0094] Epoxy resins can also be classified into various epoxy resins according to the difference in the main skeleton. For example, among the above-mentioned various types of epoxy resins, it can be further classified into bisphenol type epoxy resin; alicyclic epoxy resin; aliphatic chain type epoxy resin; linear phenolic type epoxy resin; stilbene type epoxy resin; naphthalene skeleton-containing epoxy resin; biphenyl type epoxy resin; benzene dimethylene type epoxy resin; dihydroanthracene type epoxy resin, etc. The epoxy resin can be used alone, and from the viewpoints of insulation reliability and heat resistance, two or more can be used in combination.

[0095] As the epoxy resin, it can be a linear phenolic type epoxy resin or a phenol linear phenolic type epoxy resin.

[0096] The content of the thermosetting resin in the thermosetting resin composition is preferably 10 to 200 parts by mass, more preferably 20 to 150 parts by mass, and still more preferably 20 to 80 parts by mass relative to 100 parts by mass of the total of the thermosetting resin composition.

[0097] (Curing agent)

[0098] As a curing agent, for example, in the case where the thermosetting resin contains an epoxy resin, curing agents for epoxy resins such as phenolic curing agents, cyanate ester curing agents, acid anhydride curing agents, amine curing agents, and compounds containing an active ester group can be cited. In addition, in the case where the thermosetting resin contains a resin other than an epoxy resin, a known curing agent can be used as the curing agent for the thermosetting resin. The curing agent can be used singly or in combination of two or more.

[0099] The phenolic curing agent is not particularly limited, but cresol novolak phenolic resin, biphenyl aralkyl phenolic resin, phenol novolak phenolic resin, naphthyl ether phenolic resin, phenolic resin containing a triazine skeleton, etc. are preferably selected.

[0100] The cyanate ester curing agent is not particularly limited, but bisphenol A dicyanate ester, polyphenol cyanate ester (oligo(3-methylidene-1,5-phenylene cyanate ester)), etc. can be cited.

[0101] The acid anhydride curing agent is not particularly limited, but phthalic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, etc. can be cited.

[0102] The amine curing agent is not particularly limited, but aliphatic amines such as triethylenetetramine and tetraethylenepentamine; aromatic amines such as 4,4'-diaminodiphenylmethane, etc. can be cited.

[0103] In addition, urea-formaldehyde resin, etc. can also be used as the curing agent.

[0104] When the thermosetting resin composition contains a curing agent, its content is preferably 20 to 200 parts by mass, more preferably 20 to 150 parts by mass, and still more preferably 30 to 100 parts by mass relative to 100 parts by mass of the thermosetting resin.

[0105] It should be noted that when the thermosetting resin composition contains a curing agent, its content can also be expressed in terms of functional group equivalent. Specifically, the content of the curing agent is preferably an amount that satisfies the formula (mass of thermosetting resin / functional group equivalent) ≈ (mass of curing agent / functional group equivalent capable of reacting with the thermosetting resin) × constant C. The constant C varies depending on the type of functional group of the curing agent. It is preferably 0.8 to 1.2 when the functional group is a phenolic hydroxyl group, 0.2 to 0.4 when it is an amino group, and 0.3 to 0.6 when it is an active ester group.

[0106] When the thermosetting resin contains an epoxy resin, the above formula is (mass of epoxy resin / epoxy equivalent) ≈ (mass of curing agent / functional group equivalent capable of reacting with the epoxy group) × constant C.

[0107] (Curing accelerator)

[0108] As the curing accelerator, general curing accelerators used in the curing of the above-mentioned thermosetting resins can be used. For example, when the thermosetting resin contains an epoxy resin, as the curing accelerator, imidazole compounds and their derivatives; phosphorus compounds; tertiary amine compounds; quaternary ammonium compounds, etc. can be cited. From the viewpoint of promoting the curing reaction, imidazole compounds and their derivatives are preferred.

[0109] As specific examples of imidazole compounds and their derivatives, imidazole compounds such as 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-phenylimidazole, 1,2-dimethylimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-sym-triazine, etc. can be cited; salts of the above-mentioned imidazole compounds and trimellitic acid such as 1-cyanoethyl-2-phenylimidazolium trimellitate; salts of the above-mentioned imidazole compounds and isocyanuric acid; salts of the above-mentioned imidazole compounds and hydrobromic acid, etc. Imidazole compounds and their derivatives can be used alone or in combination of two or more.

[0110] The curing accelerator can be imidazole compounds and their derivatives, or can be imidazole compounds.

[0111] When the thermosetting resin composition contains a curing accelerator, its content is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the thermosetting resin.

[0112] (Inorganic filler)

[0113] By using an inorganic filler, the thermal expansion rate can be reduced and the film strength can be improved.

[0114] As the inorganic filler, silica, alumina, barium sulfate, talc, mica, kaolin, boehmite, beryllium oxide, barium titanate, potassium titanate, strontium titanate, calcium titanate, aluminum carbonate, magnesium hydroxide, aluminum hydroxide, aluminum borate, aluminum silicate, calcium carbonate, calcium silicate, magnesium silicate, zinc borate, zinc stannate, alumina, zirconia, mullite, magnesium oxide, zinc oxide, titanium oxide, silicon carbide, silicon nitride, boron nitride, clay (such as fired clay, etc.), molybdate compounds such as zinc molybdate, glass short fibers, glass powder, and hollow glass beads, etc. It should be noted that as the glass used as the material for glass short fibers, glass powder, and hollow glass beads, E glass, T glass, D glass, etc. are preferably selected. The inorganic filler can be used alone or in combination of two or more. Among them, from the viewpoints of reducing the thermal expansion rate, reducing the relative dielectric constant and the dielectric loss tangent, silica and alumina are preferred. In addition, from the viewpoint of heat resistance, aluminum hydroxide is preferred. As the inorganic filler, a combination of silica and aluminum hydroxide is more preferably used.

[0115] As the above-mentioned silica, precipitated silica produced by a wet process and having a high water content and dry-process silica produced by a dry process and substantially not containing bound water or the like can be cited. As the dry-process silica, further depending on the difference in the production method, crushed silica, pyrogenic silica, and fused silica (fused spherical silica) can be cited.

[0116] The inorganic filler can be surface-treated with a surface treatment agent such as a silane coupling agent in order to improve moisture resistance, or can be hydrophobized in order to improve dispersibility.

[0117] When the thermosetting resin composition contains an inorganic filler, its content also varies depending on the addition purpose, but is preferably 0.1 to 65% by volume relative to the total of the solid components. If it is 0.1% by volume or more relative to the total of the solid components, there is a tendency to reduce the coefficient of thermal expansion. On the other hand, by being 65% by volume or less by pressing, the viscosity during resin component blending is not too high, and there is a tendency to easily suppress a decrease in workability. From the same viewpoint, the content of the inorganic filler is more preferably 10 to 60% by volume, further preferably 15 to 55% by volume, and particularly preferably 30 to 55% by volume relative to the total of the solid components.

[0118] (Coupling agent)

[0119] By containing a coupling agent, there are effects of improving the dispersibility of the inorganic filler and the organic filler and improving the adhesion to the reinforcing substrate and the metal foil. The coupling agent can be used alone as one kind or two or more kinds can be used in combination.

[0120] As the coupling agent, a titanate coupling agent, a silane coupling agent, etc. can be used.

[0121] (Organic solvent)

[0122] From the viewpoint of facilitating operation, the thermosetting resin composition can further contain an organic solvent. In this specification, the thermosetting resin composition containing an organic solvent is sometimes referred to as a resin varnish.

[0123] As the organic solvent, there is no particular limitation, but alcohol solvents such as methanol, ethanol, methyl cellosolve, butyl cellosolve, and propylene glycol monomethyl ether can be cited; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, butanone, cyclohexanone, and 4-methyl-2-pentanone; ester solvents such as ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, and γ-butyrolactone; ether solvents such as tetrahydrofuran; aromatic solvents such as toluene, xylene, and mesitylene; nitrogen atom-containing solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; sulfur atom-containing solvents such as dimethyl sulfoxide, etc. can be cited.

[0124] The organic solvent may be used alone or in combination of two or more kinds.

[0125] From the viewpoint of easy coatability, for example, the content of the organic solvent may be adjusted so that the concentration of the nonvolatile components of the thermosetting resin composition is preferably 20 to 85% by mass, more preferably 40 to 80% by mass.

[0126] However, although a resin varnish can be prepared using an organic solvent, in the method for manufacturing the prepreg of the present embodiment described below, since the resin film is impregnated into the fiber base material after the resin film is formed to obtain the prepreg, the organic solvent volatilizes during the resin film formation stage. As a result, in the prepreg of the present embodiment, the organic solvent is substantially absent, specifically 5% by mass or less.

[0127] The method for preparing the above thermosetting resin composition is not particularly limited, and a conventionally known preparation method can be adopted.

[0128] For example, after adding a thermosetting resin and other components used as needed to the above organic solvent, mixing and stirring are performed using various mixers, whereby a resin varnish can be prepared. Examples of the mixer include a mixer using an ultrasonic dispersion method, a high-pressure collision dispersion method, a high-speed rotation dispersion method, a bead mill method, a high-speed shear dispersion method, a rotation-revolution type dispersion method, and the like.

[0129] (Thickness of prepreg)

[0130] The thickness of the prepreg of the present embodiment may be appropriately determined according to the thickness of the fiber base material and the like, and may be 50 to 300 μm, may be 50 to 250 μm, may be 55 to 200 μm, may be 60 to 180 μm, may be 60 to 170 μm, or may be 60 to 150 μm. Here, the thickness of the prepreg refers to the thickness of one sheet of prepreg. If the thickness of the prepreg is at least the above lower limit value, there is a tendency to significantly obtain the effect of reducing the surface waviness of the present embodiment. If the thickness of the prepreg is at most the above upper limit value, there is a tendency to suppress the generation of voids after the manufacture of the laminated board in the present embodiment.

[0131] It should be noted that in this specification, the thickness of the prepreg is the average value of the values measured at five arbitrary positions using a digital display indicator.

[0132] [Method for manufacturing prepreg]

[0133] The method for manufacturing the prepreg of the present embodiment is not particularly limited, and from the viewpoint of improving the thickness accuracy, the following manufacturing method is preferred.

[0134] That is, a method for manufacturing a prepreg is preferably employed. The prepreg is manufactured by laminating a film of a thermosetting resin composition onto a fiber substrate having a thickness of 40 μm or more. In the fiber substrate, an impregnation region and a non-impregnation region of the thermosetting resin composition are provided, and the non-impregnation region is intermittently present, whereby the surface waviness (Wa) of the prepreg is 5.0 μm or less. More preferably, the non-impregnation region is intermittently present in the in-plane direction.

[0135] In this manufacturing method, a film of a thermosetting resin composition (hereinafter sometimes referred to as "resin film") is used. It should be noted that in the method of impregnating a fiber substrate with a resin varnish and then drying it, it is difficult to intentionally provide a non-impregnation region in the fiber substrate, and the surface waviness (Wa) also tends to increase (see Figure 3 ), so the above manufacturing method is preferred.

[0136] In the above method for manufacturing a prepreg, the fiber substrate, the thermosetting resin composition, and the surface waviness (Wa) are described as previously mentioned.

[0137] The above resin film can be produced by forming a layer of a thermosetting resin composition (resin layer) on one surface of a release film. For example, by applying the above resin varnish to one surface of the release film and then drying it, the formation of this resin layer can be carried out.

[0138] The method of applying the resin varnish is not particularly limited. For example, it can be carried out using known coating devices such as a comma coater, a rod coater, a kiss coater, a roll coater, an intaglio coater, a die coater, etc. These coating devices are preferably appropriately selected according to the film thickness of the resin layer.

[0139] The drying temperature and drying time vary depending on the amount of organic solvent used, the boiling point of the organic solvent, etc. For example, in the case of a resin varnish containing 30 to 70% by mass of an organic solvent, drying at 50 to 160 °C for 1 to 8 minutes can appropriately form the resin film.

[0140] Sometimes the film thus produced is referred to as a resin film with a release film.

[0141] (Thickness of the resin film)

[0142] The thickness of the resin film may be appropriately determined according to the thickness of the prepreg or the like. For example, when the thickness of the fiber base material is in the range of 40 to 120 μm, the thickness of the resin film is preferably 10 to 100 μm, more preferably 15 to 70 μm, and further preferably 20 to 50 μm. It should be noted that in this specification, the thickness of the resin film is the value measured as follows. First, use a digital indicator to measure the total thickness of the resin-coated film at any 5 locations. After peeling off the resin layer at the measurement site with adhesive tape, use a digital indicator to measure the thickness of the release film, and subtract the thickness of the release film from the total thickness, which is the average value of the obtained values.

[0143] If the thickness of the resin film is equal to or greater than the above lower limit value, there is a tendency to sufficiently ensure the amount of resin for impregnating a thick glass cloth with a thickness of 40 μm or more. If the thickness of the resin film is equal to or less than the above upper limit value, there is a tendency to easily manufacture the resin film.

[0144] (Release film)

[0145] As the release film, organic films such as polyethylene terephthalate (PET), biaxially stretched polypropylene (OPP), polyethylene, polyvinyl fluoride, and polyimide can be cited; metal or alloy films such as copper and aluminum can also be used. These release films can also be subjected to a release treatment with a release agent.

[0146] The thickness of the release film is not limited. From the viewpoints of operability and economy when coating the thermosetting resin composition, it is preferably 10 to 200 μm, more preferably 20 to 100 μm, and further preferably 30 to 70 μm.

[0147] As the release film, commercially available products can be used.

[0148] (Method for impregnating a fiber base material with a resin film)

[0149] Hereinafter, a method for impregnating the above resin film into the above fiber base material by lamination will be described.

[0150] First, the resin film with the release film is arranged on at least one surface of the fiber base material in such a manner that the resin film abuts against the fiber base material. Thereafter, the arranged resin film with the release film and the fiber base material are heated and pressed, whereby the resin film is impregnated into the fiber base material. At this time, in the fiber base material, unimpregnated regions of the thermosetting resin composition are intermittently provided. In this way, the prepreg of the present embodiment with the release film is obtained.

[0151] The heating and pressing here are preferably performed by lamination. As the lamination method, (a) roll lamination, (b) a method of performing lamination under reduced pressure using a vacuum lamination method, etc. can be cited.

[0152] (a) There are no particular limitations on the conditions for roll lamination. However, the heating temperature is preferably 80 to 180°C, and the pressing pressure (linear pressure) is preferably 0.05 to 1.0 MPa / m.

[0153] (b) There are no particular limitations on the conditions for the lamination method under reduced pressure. However, the heating temperature is preferably 50 to 170°C, more preferably 110 to 160°C, the pressing time is preferably 10 to 120 seconds, more preferably 20 to 80 seconds, and the pressing pressure is preferably 0.05 to 1.0 MPa, more preferably 0.1 to 0.6 MPa.

[0154] (Method of intermittently providing an unimpregnated area)

[0155] There are no particular limitations on the method of intermittently providing an unimpregnated area of the above thermosetting resin composition in the fiber substrate. However, for example, a method of adjusting the conditions when heating and pressing the above resin film with a release film and the above fiber substrate can be cited. Specifically, a method of adjusting the above lamination conditions can be cited.

[0156] Here, when the same lamination conditions are set for a thin fiber substrate and a thick fiber substrate, there is a tendency for the resin film to be difficult to impregnate into the thick fiber substrate. Therefore, even if the conditions for laminating the resin film on a thin fiber substrate in the past are of the same level as the lamination conditions of the present embodiment, it is possible to intermittently provide an unimpregnated area of the above thermosetting resin composition in the fiber substrate in the present embodiment.

[0157] As a specific method of adjusting the conditions for heating and pressing, there are no particular limitations. For example, the following method can be cited. First, after producing a prepreg using given heating and given pressing conditions, the existence ratio of the impregnated area of the above thermosetting resin composition in the fiber substrate based on the above calculation method is obtained. As a result, when the impregnated area is 100%, that is, when there is no unimpregnated area, the heating temperature is lowered, the pressing pressure is lowered, or both the heating temperature and the pressing pressure are lowered, and the prepreg is remade, and the existence ratio of the impregnated area is obtained again. This operation is further repeated as needed, whereby the conditions for manufacturing a prepreg having an intermittently (preferably intermittently in the in-plane direction) unimpregnated area can be easily grasped.

[0158] In addition, when it is desired to lower the existence ratio of the unimpregnated area, it is only necessary to remake the prepreg by raising the heating temperature, raising the pressing pressure, or raising both the heating temperature and the pressing pressure.

[0159] As the above-mentioned heating temperature, from the viewpoint of intermittently providing an unimpregnated area of the above-mentioned thermosetting resin composition in the fiber base material, it is preferably 120°C or higher, more preferably 120 to 170°C, and further preferably 130 to 160°C.

[0160] In addition, as the above-mentioned pressing pressure, from the viewpoint of intermittently providing an unimpregnated area of the above-mentioned thermosetting resin composition in the fiber base material, it is preferably 0.2 MPa or higher, more preferably 0.2 to 1.0 MPa, further preferably 0.3 to 0.8 MPa, and particularly preferably 0.3 to 0.6 MPa.

[0161] It should be noted that in the case of laminating under reduced pressure, the existence ratio of the unimpregnated area can also be adjusted by adjusting the degree of vacuum.

[0162] It should be noted that the resin films are preferably laminated with one or more sheets disposed on each of the two sides of the fiber base material. The number of sheets of the resin film is preferably one or two on each side of the fiber base material, and more preferably one sheet.

[0163] After the above-mentioned resin film is impregnated into the above-mentioned fiber base material, it is cooled as needed, and then the release film is peeled off from the obtained prepreg with the release film, whereby a prepreg with a surface waviness (Wa) of 5.0 μm or less can be manufactured.

[0164] [Laminated board, metal-clad laminated board]

[0165] The present disclosure also provides a laminated board having one or more prepregs of the present embodiment. It should be noted that a laminated board provided with a metal foil is specifically called a "metal-clad laminated board". That is, the present disclosure also provides a metal-clad laminated board having a metal foil and one or more prepregs of the present embodiment. The prepregs of the present embodiment can also be used in combination with other prepregs. In the laminated board and the metal-clad laminated board of the present embodiment, as long as there is one or more prepregs of the present embodiment, the number of prepreg sheets can be 1 to 20 sheets, can also be 2 to 20 sheets, can also be 5 to 18 sheets, and can also be 8 to 16 sheets.

[0166] Examples of the metal foil included in the metal-clad laminated board include copper foil, aluminum foil, tin foil, tin-lead alloy (solder) foil, nickel foil, etc. The thickness of the metal foil can be set to the thickness usually used in laminated boards, for example, 1 to 200 μm. In addition to this, a three-layer structure composite foil having nickel, nickel-phosphorus, nickel-tin alloy, nickel-iron alloy, lead, lead-tin alloy, etc. as an intermediate layer and copper layers of 0.5 to 15 μm and 10 to 300 μm provided on both sides thereof, a two-layer structure composite foil obtained by laminating aluminum and copper foil, etc. can also be used.

[0167] It should be noted that when the metal foil is a copper foil, the metal-clad laminated board is called a copper-clad laminated board.

[0168] The laminated board and the metal-clad laminated board of the present embodiment can be manufactured using more than one prepreg, and sometimes include three or more fiber base materials. Since the laminated board and the metal-clad laminated board of the present embodiment have high thickness accuracy, there is no need to perform smoothing processes such as grinding and rolling on the surface of the cured product of the prepreg included in the laminated board and the metal-clad laminated board of the present embodiment, and the productivity is excellent. Therefore, in the metal-clad laminated board including three or more fiber base materials, the outermost fiber base material is not cut by the smoothing process, and the thickness of the outermost fiber base material on at least one surface side of the laminated board or the metal-clad laminated board is in the range of 0.6 to 1.3 times the thickness of the fiber base material adjacent to the fiber base material, preferably in the range of 0.7 to 1.3 times, more preferably in the range of 0.8 to 1.2 times, and further preferably in the range of 0.9 to 1.1 times. It is preferred that the thicknesses of the outermost fiber base materials on both surface sides of the laminated board or the metal-clad laminated board are in the above range relative to the thickness of the adjacent fiber base materials.

[0169] [Manufacturing method of metal-clad laminated board]

[0170] The present disclosure also provides a manufacturing method of a metal-clad laminated board, wherein metal foils are provided on both surfaces of one prepreg of the present embodiment or a laminate of prepregs including at least one or more prepregs of the present embodiment, and then press molding is performed. As a specific method of the above press molding, for example, a method of performing press molding under the conditions that the degree of vacuum is preferably 300 kPa or less, more preferably 100 kPa or less, the temperature is preferably 130 to 350 °C, more preferably 150 to 300 °C, further preferably 170 to 250 °C, and the pressure is preferably 0.5 to 10 MPa, more preferably 1 to 5 MPa, and further preferably 2 to 5 MPa using a vacuum press can be cited. Through this press molding, the thermosetting resin composition flows into the unimpregnated area of the thermosetting resin composition in the above fiber base material, and as a result, the generation of voids is suppressed.

[0171] The above laminate of prepregs is not particularly limited. However, in order to obtain a metal-clad laminated board with high thickness accuracy, it is preferably composed of 10% by mass or more of the prepreg of the present embodiment, more preferably 20% by mass or more, further preferably 50% by mass or more, and may also be entirely composed of the prepreg of the present embodiment. However, even when the prepreg of the present embodiment constitutes less than 10% by mass of the laminate of prepregs, it is helpful to improve the thickness accuracy of the metal-clad laminated board.

[0172] It should be noted that the laminated board of the present embodiment can be obtained by removing the metal foil from the metal-clad laminated board of the present embodiment by etching treatment or the like.

[0173] [Printed Circuit Board]

[0174] The present disclosure also provides a printed circuit board having the laminate of the present embodiment or the metal-clad laminate of the present embodiment. In other words, the present disclosure also provides a printed circuit board obtained by forming a wiring pattern on the laminate of the present embodiment or the metal-clad laminate of the present embodiment.

[0175] The printed circuit board of the present embodiment can be manufactured by forming a wiring pattern on the laminate of the present embodiment or the metal-clad laminate of the present embodiment. As a method for forming the wiring pattern, known methods such as a subtractive method, a full-additive method, a semi-additive method (SAP: Semi Additive Process), and a modified semi-additive method (m-SAP: modified Semi Additive Process) can be cited.

[0176] [Semiconductor Package]

[0177] The present disclosure also provides a semiconductor package having the printed circuit board of the present embodiment and a semiconductor element. The semiconductor package of the present embodiment can be manufactured, for example, by mounting semiconductor elements such as semiconductor chips and memories at given positions on the printed circuit board of the present embodiment by a known method and then sealing the semiconductor elements with a sealing resin or the like.

[0178] Examples

[0179] Hereinafter, the present embodiment will be described in further detail using the following examples, which, however, do not limit the present embodiment.

[0180] It should be noted that the prepregs and copper-clad laminates manufactured in each example were evaluated according to the following methods.

[0181] [1. Surface Waviness (Wa)]

[0182] The surface waviness (Wa) was measured using the prepregs produced in each example. Using a shape analysis laser microscope "VK-X100" (manufactured by Keyence Corporation), shape measurement was performed by automatic measurement using an observation application program to obtain a waviness curve in accordance with ISO 4287 (1997). Surface roughness analysis was performed on the obtained waviness curve using an analysis application program to calculate the surface waviness (Wa). Here, the so-called waviness curve is a curve obtained by removing wavelengths less than 80 μm from the cross-sectional curve by applying a phase compensation type high-pass filter λc (λc = 80 μm) to the cross-sectional curve. The analysis range was set to 1000 μm × 1000 μm.

[0183] It should be noted that the surface waviness (Wa) is measured on both sides of the prepreg, and the larger value is adopted.

[0184] [2. Existence ratio of impregnated area]

[0185] Based on the following calculation method, the existence ratio (%) of the impregnated area of the thermosetting resin composition in the fiber base material is obtained.

[0186] - Calculation method -

[0187] Using an optical microscope (manufactured by Olympus Corporation, trade name: MX61L-F), observe the surface of the prepreg under the following conditions to obtain a surface observation image.

[0188] <Observation conditions>

[0189] · Magnification: 50 times

[0190] · Observation mode: Dark field

[0191] · Sensitivity: ISO400

[0192] · Exposure time during surface shooting: 60 - 100 ms

[0193] · Brightness of the observation environment: Two 35W fluorescent lamps are set 2m above the observation stage.

[0194] After converting the obtained surface observation image to black and white mode using image editing software, save it in the BMP (Microsoft Windows Bitmap Image) format. Then, for the black and white mode surface observation image saved in the BMP format, convert each pixel to RGB (Red, Green, Blue) values using image conversion software and save it in the CSV (comma - separated values) format. Paste the RGB data saved in the CSV format into Microsoft Excel (manufactured by Microsoft Corporation) to calculate the areas of the black part (RGB value = 255) and the white part (RGB value = 0). Calculate the area ratio of the black part to the total of the black part and the white part based on these values. Set the area ratio of the black part obtained in this way as the existence ratio (%) of the impregnated area.

[0195] Here, when shooting the surface observation image, adjust the exposure time during surface shooting between 60 - 100 ms as described above in such a way that the impregnated area and the non - impregnated area can be fully reflected, and thus shoot with an appropriate brightness.

[0196] It should be noted that "Microsoft Paint" (manufactured by Microsoft Corporation) is used as the above-mentioned image editing software. In addition, "bmp2csv", which is free software, is used as the above-mentioned image conversion software.

[0197] [3. Presence or absence of blending of thermosetting resin compositions on the front and back surfaces]

[0198] As shown in Table 1, when prepregs were produced by laminating resin films of different colors on the front and back surfaces of glass cloth, the presence or absence of color blending was observed visually. For example, when observing the prepreg from the front side, if the color of the resin film used on the front side did not change, the blending was evaluated as "none", and if the color changed to a color in which the color of the resin film used on the front side was mixed with the color of the resin film used on the back side, the blending was evaluated as "present". It should be noted that in the case of "present", it was judged that unimpregnated regions intermittently existed, and in the case of "none", it was judged that the presence of unimpregnated regions was not intermittent.

[0199] [4. Fluctuation in the thickness of the copper-clad laminate]

[0200] The thicknesses of 10 points were measured at 50-mm intervals in the width direction from the center in the width direction of the copper-clad laminates obtained in each example, and the thicknesses of 10 points were measured at 50-mm intervals in the length direction starting from each of these 10 points (wherein these 10 points respectively included the above-mentioned starting points. That is, the measurement positions were 10 points × 10 points = a total of 100 points). Specifically, the measurement was performed in 0.001-mm units using a base adjusted to be horizontal and a digital display indicator "ID-C112P" (manufactured by Mitutoyo Corporation). Thereafter, the value obtained by the following formula was set as an index of the thickness fluctuation. Since the smaller the value, the smaller the thickness fluctuation, it indicates excellent thickness accuracy.

[0201] Thickness fluctuation (%) = 100 × (maximum thickness - average thickness) / average thickness

[0202] [5. Insulation reliability]

[0203] After forming vias by drilling the copper-clad laminates obtained in each example such that the via pitch (distance between adjacent hole walls) is 200 μm, the formed vias are subjected to a decontamination treatment, then electroless plating treatment, and then electroplating treatment, thereby producing a test pattern in which the top and bottom of the copper-clad laminate are electrically connected, and this is set as a measurement sample. The insulation resistance of 160 holes is measured over time for each measurement sample. The measurement conditions are carried out at 130 °C and 85% RH atmosphere, applying 5.5 V, and the time until conduction failure occurs is measured. The measurement time is set to up to 200 hours, and if it is greater than 200 hours, it is judged that the insulation reliability is sufficient.

[0204] Reference Example 1

[0205] After measuring the surface waviness (Wa) of the following glass cloths in the same manner as the above [1. Surface waviness (Wa)], the surface waviness (Wa) of glass cloths with different thicknesses is compared. Note that the thickness of each of the following glass cloths is the average value of the values measured at five arbitrary locations using a micrometer "MDC-25MX" (manufactured by Mitutoyo Corporation).

[0206] <Glass cloth with a thickness of 40 μm or more>

[0207] (i) Glass cloth "IPC#2116" (manufactured by Nitto Boseki Co., Ltd., unit area weight: 104 g / m 2 , base material width: 530 mm, thickness: 91 μm)

[0208] (ii) Glass cloth "IPC#3313" (manufactured by Nitto Boseki Co., Ltd., unit area weight: 82 g / m 2 , base material width: 530 mm, thickness: 73 μm)

[0209] (iii) Glass cloth "IPC#1078" (manufactured by Nitto Boseki Co., Ltd., unit area weight: 47 g / m 2 , base material width: 530 mm, thickness: 44 μm)

[0210] <Glass cloth with a thickness less than 40 μm>

[0211] (iv) Glass cloth "IPC#1037" (manufactured by Nitto Boseki Co., Ltd., unit area weight: 24 g / m 2 , base material width: 530 mm, thickness: 24 μm)

[0212] (v) Glass cloth "IPC#1027" (manufactured by Nitto Boseki Co., Ltd., unit area weight: 20 g / m 2 , base material width: 530 mm, thickness: 21 μm)

[0213] The surface waviness (Wa) of the above glass cloths "IPC#2116", "IPC#3313", and "IPC#1078" is 21.9 μm, 13.4 μm, and 7.3 μm respectively.

[0214] In addition, the surface waviness (Wa) of the above glass cloths "IPC#1037" and "IPC#1027" is 4.7 μm and 4.5 μm respectively.

[0215] It can be seen that the surface waviness (Wa) of the glass cloth with a thickness of 40 μm or more is larger than that of the glass cloth with a thickness less than 40 μm.

[0216] Production Example 1

[0217] (1-1. Preparation of Resin Varnish A)

[0218] Add 60 parts by mass of phenol novolac epoxy resin "EPICLON (registered trademark) N-770" (manufactured by DIC Corporation, epoxy equivalent: 188 g / eq), 40 parts by mass of biphenyl aralkyl type phenolic resin (manufactured by UBE Industries, Ltd., trade name: MEH-7700), 17.5 parts by mass of aluminum hydroxide, 86 parts by mass of fused silica, 0.5 parts by mass of 2-methylimidazole, and methyl isobutyl ketone and cyclohexanone as dilution solvents and mix them to prepare Resin Varnish A with a white solid component concentration of 65% by mass (content of aluminum hydroxide: 8% by volume, content of fused silica: 32% by volume).

[0219] (1-2. Preparation of Resin Varnish B)

[0220] Further add 0.3% by mass of Sudan Black (manufactured by Central Synthetic Chemical Co., Ltd., trade name: SUDAN BLACK 141) relative to the total of the solid components to the above Resin Varnish A and stir it to prepare Resin Varnish B with a black solid component concentration of 65% by mass (content of aluminum hydroxide: 8% by volume, content of fused silica: 32% by volume). Resin Varnish B is a substance obtained by simply imparting black color to Resin Varnish A.

[0221] Production Example 2

[0222] (1. Preparation of Modified Maleimide Resin)

[0223] Add 595.8 g of bis(4-maleimidophenyl)methane, 54.2 g of 4,4'-diaminodiphenylmethane, and 350.0 g of propylene glycol monomethyl ether to a 2 L reaction vessel capable of heating and cooling equipped with a thermometer, a stirring device, and a moisture quantifier with a reflux condenser, and react for 5 hours while refluxing to obtain a solution of the modified maleimide resin.

[0224] (2-1. Preparation of Resin Varnish C)

[0225] Add 107 parts by mass of the solution of the above-mentioned modified maleimide resin, 30 parts by mass of 4-functional naphthalene-type epoxy resin "EXA-4710" (manufactured by DIC Corporation), 17.5 parts by mass of aluminum hydroxide, 130 parts by mass of fused silica, 0.5 parts by mass of 2,4-diamino-6-[2'-undecylimidazolyl-(1)']-ethyl-S-triazine, methyl isobutyl ketone and cyclohexanone as dilution solvents and mix them to produce resin varnish C with a brown solid content concentration of 65% by mass (content of aluminum hydroxide: 8% by volume, content of fused silica: 41.5% by volume).

[0226] (2-2. Preparation of Resin Varnish D)

[0227] Further add 0.3% by mass of Sudan Black (manufactured by Central Synthetic Chemical Co., Ltd., trade name: SUDAN BLACK 141) relative to the total solid content to the above resin varnish C and stir it to produce resin varnish D with a black solid content concentration of 65% by mass (content of aluminum hydroxide: 8% by volume, content of fused silica: 41.5% by volume). Resin varnish D is a substance that only imparts black to resin varnish C.

[0228] Example 1

[0229] (1. Preparation of Resin Film)

[0230] Apply the resin varnish A obtained in Production Example 1 to a PET film (manufactured by TOYOBO FILMSOLUTIONS Co., Ltd., thickness: 50 μm, release film, trade name: G2) using a comma-type knife coater. At this time, adjust the coating amount so that the coating width is 530 mm and the thickness after drying is 30 μm. Then, heat and dry at 130 °C for 2 minutes to produce a resin film A with a PET film attached.

[0231] In addition, in the same manner as above, use the resin varnish B obtained in Production Example 1 to produce a resin film B with a PET film attached.

[0232] (2. Preparation of Prepreg)

[0233] Then, on the surface of the glass cloth "IPC#2116" (manufactured by Nitto Boseki Co., Ltd., unit area weight: 104 g / m 2 , base material width: 530 mm, thickness: 91 μm), arrange the resin layer of the above resin film A with a PET film attached so as to be in contact with the glass cloth, and on the back of the above glass cloth "IPC#2116", arrange the resin layer of the above resin film B with a PET film attached so as to be in contact with the glass cloth.

[0234] The laminate of "PET film / resin film A / fiberglass cloth / resin film B / PET film" is heated and pressed under vacuum using a vacuum laminating device. By performing such an operation, a prepreg with a PET film impregnated with a thermosetting resin composition in the fiberglass cloth is obtained. It should be noted that the conditions for vacuum lamination are set as follows: heating plate temperature 130 °C, crimping pressure 0.5 MPa, degree of vacuum 100 kPa or less, and vacuum time 30 seconds. The PET film is peeled off from the obtained prepreg with a PET film to obtain a prepreg 1 with a thickness of 125 μm.

[0235] It should be noted that the thickness of the prepreg 1 is set as the average value of the values measured at any 5 locations using a base adjusted to be horizontal and a digital display indicator (Mitutoyo Corporation).

[0236] In addition, the content ratio of the thermosetting resin composition in the prepreg 1 is calculated as follows. The total mass of the two resin films with PET films used when producing the prepreg 1 is subtracted from the total mass of the two PET films, thereby calculating the mass of the resin film (w r ). Using the mass of the resin film (w r ) and the mass of the prepreg 1 (w p ), the content ratio of the thermosetting resin composition is obtained using the following formula.

[0237] Content ratio of thermosetting resin composition = (w r / w p ) × 100

[0238] In addition, the above evaluations are performed on the obtained prepreg 1. The results are shown in Table 1. In addition, the surface observation image of the prepreg converted to black and white mode used when calculating the existence ratio of the impregnation region is shown in Figure 5 . The observation conditions of the prepreg surface are as described above, however, the exposure time during surface photography is set to 85 ms.

[0239] (3. Fabrication of Copper-Clad Laminate)

[0240] Twelve pieces of the obtained prepreg 1 are overlapped, and copper foils "GTS-12" with a thickness of 12 μm (manufactured by Furukawa Electric Co., Ltd.) are arranged above and below it. Then, pressing is performed under the following conditions to fabricate a copper-clad laminate 1. The above evaluations are performed on the obtained copper-clad laminate 1. The results are shown in Table 1.

[0241] -Pressing Conditions-

[0242] Heating conditions: Heat from 25 °C to 185 °C at a heating rate of 3 °C / minute, hold at 185 °C for 90 minutes, and then cool for 30 minutes.

[0243] Pressure condition (pressure applied to 12 prepregs held by copper foil): 4 MPa (from the start of temperature rise to the end of cooling)

[0244] Example 2

[0245] In the production of the prepreg of Example 1, resin varnish C produced in Production Example 2 was used in place of resin varnish A, and resin varnish D produced in Production Example 2 was used in place of resin varnish B. Otherwise, the same operations as in Example 1 were carried out, whereby prepreg 2 (thickness 125 μm) was produced. Further, in the production of the copper-clad laminate of Example 1, prepreg 2 was used in place of prepreg 1, and the pressing conditions were changed as shown below. Otherwise, the same operations as in Example 1 were carried out, whereby copper-clad laminate 2 was produced. The above evaluation results are shown in Table 1.

[0246] - Pressing conditions -

[0247] Heating condition: Heating from 25°C to 230°C at a rate of 3°C / minute, holding at 230°C for 90 minutes, and then cooling for 30 minutes.

[0248] Pressure condition (pressure applied to 12 prepregs held by copper foil): 4 MPa (from the start of temperature rise to the end of cooling)

[0249] Example 3

[0250] In the production of the prepreg of Example 1, the heating plate temperature of the vacuum lamination was changed to 150°C. Otherwise, the same operations as in Example 1 were carried out, whereby prepreg 3 (thickness 115 μm) was produced. Further, in the production of the copper-clad laminate of Example 1, prepreg 3 was used in place of prepreg 1. Otherwise, the same operations as in Example 1 were carried out, whereby copper-clad laminate 3 was produced. The above evaluation results are shown in Table 1.

[0251] Example 4

[0252] In the production of the prepreg of Example 1, the heating plate temperature of the vacuum lamination was changed to 150°C, and the vacuum time was changed to 60 seconds. Otherwise, the same operations as in Example 1 were carried out, whereby prepreg 4 (thickness 110 μm) was produced. Further, in the production of the copper-clad laminate of Example 1, prepreg 4 was used in place of prepreg 1. Otherwise, the same operations as in Example 1 were carried out, whereby copper-clad laminate 4 was produced. The above evaluation results are shown in Table 1.

[0253] Example 5

[0254] In the production of the resin film of Example 2, the PET film was changed to (manufactured by Toray Industries, Inc., thickness: 50 μm, release film, trade name: LUMIRROR (registered trademark) #50-X44), and in the production of the prepreg, the conditions of vacuum lamination were changed to a hot plate temperature of 140°C and a vacuum time of 40 seconds. Other than that, the same operations as in Example 2 were carried out, and thus prepreg 5 (thickness 125 μm) was produced. Additionally, in the manufacture of the copper-clad laminate of Example 2, prepreg 5 was used instead of prepreg 2. Other than that, the same operations as in Example 2 were carried out, and thus copper-clad laminate 5 was produced. The above evaluation results are shown in Table 1.

[0255] Example 6

[0256] In the production of the prepreg of Example 1, the glass cloth "IPC #2116" was changed to the glass cloth "IPC #3313" (manufactured by Nitto Boseki Co., Ltd., unit area weight: 82 g / m 2 , base material width: 530 mm, thickness: 73 μm). Other than that, the same operations as in Example 1 were carried out, and thus prepreg 6 (thickness 105 μm) was produced. Additionally, in the manufacture of the copper-clad laminate of Example 1, prepreg 6 was used instead of prepreg 1. Other than that, the same operations as in Example 1 were carried out, and thus copper-clad laminate 6 was produced. The above evaluation results are shown in Table 1.

[0257] Example 7

[0258] In the production of the resin film of Example 1, the thickness after drying was changed to 24 μm, and in the production of the prepreg, the glass cloth "IPC #2116" was changed to the glass cloth "IPC #1078" (manufactured by Nitto Boseki Co., Ltd., unit area weight: 47 g / m 2 , base material width: 530 mm, thickness: 44 μm). Other than that, the same operations as in Example 1 were carried out, and thus prepreg 7 (thickness 70 μm) was produced. Additionally, in the manufacture of the copper-clad laminate of Example 1, prepreg 7 was used instead of prepreg 1. Other than that, the same operations as in Example 1 were carried out, and thus copper-clad laminate 7 was produced. The above evaluation results are shown in Table 1.

[0259] Example 8

[0260] In the manufacture of the copper-clad laminate of Example 1, instead of laminating 12 prepregs 1, "2 prepregs 1" and "10 prepregs X manufactured in Comparative Example 1 described below" were laminated. Other than this, the same operations as in Example 1 were carried out, whereby a copper-clad laminate 8 was manufactured. It should be noted that the lamination order of the prepregs was "(1 prepreg 1) / (10 prepregs X) / (1 prepreg 1)". The above evaluation results are shown in Table 1.

[0261] Example 9

[0262] In the manufacture of the copper-clad laminate of Example 2, instead of laminating 12 prepregs 2, "4 prepregs 2" and "8 prepregs X manufactured in Comparative Example 1 described below" were laminated. Other than this, the same operations as in Example 2 were carried out, whereby a copper-clad laminate 9 was manufactured. It should be noted that the lamination order of the prepregs was "(2 prepregs 2) / (8 prepregs X) / (2 prepregs 2)". The above evaluation results are shown in Table 1.

[0263] Comparative Example 1

[0264] The glass cloth "IPC #2116" (manufactured by Nitto Boseki Co., Ltd., unit area weight: 104 g / m 2 , base material width: 530 mm, thickness: 91 μm) was impregnated in the resin varnish A prepared in Production Example 1 and then taken out, and dried by heating at 140°C for 3.5 minutes to obtain prepreg X (thickness 180 μm). Moreover, in the manufacture of the copper-clad laminate of Example 1, prepreg X was used instead of prepreg 1. Other than this, the same operations as in Example 1 were carried out, whereby a copper-clad laminate X was manufactured. The above evaluation results are shown in Table 1.

[0265] It can be seen that prepreg X has a larger surface waviness compared with prepregs 1 to 9 manufactured in the examples, and moreover, the thickness fluctuation of the copper-clad laminate 10 manufactured using this prepreg X is large. It should be noted that since prepreg X has a large surface waviness, in the optical microscope observation, the focal length cannot be focused on the prepreg surface, and the existence ratio of the impregnation region cannot be obtained.

[0266] Comparative Example 2

[0267] In the manufacture of the prepreg of Example 1, the heating plate temperature of the vacuum lamination was changed to 120°C, and the pressing pressure was changed to 0.1 MPa. Other than this, the same operations as in Example 1 were carried out, whereby prepreg 11 (thickness 135 μm) was manufactured. In addition, in the manufacture of the copper-clad laminate of Example 1, prepreg 11 was used instead of prepreg 1. Other than this, the same operations as in Example 1 were carried out, whereby a copper-clad laminate 11 was manufactured. The above evaluation results are shown in Table 1.

[0268] Comparative Example 3

[0269] In the production of the prepreg of Example 7, the temperature of the heating plate for vacuum lamination was changed to 120°C, and the crimping pressure was changed to 0.1 MPa. Otherwise, the same operations as in Example 7 were performed, whereby a prepreg 12 (thickness: 75 μm) was produced. Further, in the production of the copper-clad laminate of Example 7, prepreg 12 was used instead of prepreg 7. Otherwise, the same operations as in Example 7 were performed, whereby a copper-clad laminate 12 was produced. The above evaluation results are shown in Table 1.

[0270] Comparative Example 4

[0271] In the production of the prepreg of Example 1, the temperature of the heating plate for vacuum lamination was changed to 160°C, the crimping pressure was changed to 1.0 MPa, and the vacuum time was changed to 60 seconds. Otherwise, the same operations as in Example 1 were performed, whereby a prepreg 13 (thickness: 110 μm) was produced. Further, in the production of the copper-clad laminate of Example 1, prepreg 13 was used instead of prepreg 1. Otherwise, the same operations as in Example 1 were performed, whereby a copper-clad laminate 13 was produced. The above evaluation results are shown in Table 1.

[0272]

[0273] As is apparent from Table 1, when the prepreg of the present embodiment is used, even if a fiber base material having a large waviness, i.e., a fiber base material having a thickness of 40 μm or more, is used, the thickness accuracy of the copper-clad laminate is high (see Examples 1 to 9). Further, the insulation reliability of the copper-clad laminates of Examples 1 to 9 is also excellent.

[0274] On the other hand, in the prepreg produced by the method of impregnating a glass cloth with a resin varnish and then drying it as shown in Comparative Example 1, the surface waviness (Wa) becomes large, and the thickness fluctuation of the copper-clad laminate becomes large. In Comparative Examples 2 and 3, since the existence ratio of the impregnation region is too small, the existence of the non-impregnated region is not intermittent, and as a result, the insulation reliability is reduced. In Comparative Example 4, since there is no non-impregnated region, the thickness accuracy of the copper-clad laminate becomes low.

Claims

1. A prepreg containing a fiber substrate with a thickness of 40 μm or more and a thermosetting resin composition, having an impregnated area and a non-impregnated area of the thermosetting resin composition in the fiber substrate, and the non-impregnated areas are intermittently present. The surface waviness (Wa) of the prepreg is 5.0 μm or less.

2. The prepreg according to claim 1, wherein the non-impregnated areas are intermittently present in the in-plane direction.

3. The prepreg according to claim 1, wherein the existence ratio of the impregnated area obtained based on the following calculation method is 30% to 98%; Calculation method: Observe the surface of the prepreg with an optical microscope at a magnification of 50 times to obtain a surface observation image; convert the obtained surface observation image to black and white mode using image editing software and save it in the BMP (Microsoft Windows Bitmap Image) format; then, for the black and white mode surface observation image saved in the BMP format, convert each pixel to RGB (Red, Green, Blue) values using image conversion software and save it in the CSV (comma-separated values) format; paste the RGB data saved in the CSV format into Microsoft Excel manufactured by Microsoft Corporation, calculate the areas of the black part and the white part, where the RGB value of the black part = 255 and the RGB value of the white part = 0; calculate the area ratio of the black part to the total of the black part and the white part based on these values; set the area ratio of the black part thus obtained as the existence ratio of the impregnated area.

4. The prepreg according to claim 3, wherein the existence ratio of the impregnated area is 50% to 90%.

5. The prepreg according to claim 1, wherein the thickness of the fiber substrate is 70 μm to 120 μm.

6. A laminated board having one or more prepregs according to claim 1.

7. A metal-clad laminated board having a metal foil and one or more prepregs according to claim 1.

8. A printed wiring board having the laminated board according to claim 6 or the metal-clad laminated board according to claim 7.

9. A semiconductor package having the printed wiring board according to claim 8 and a semiconductor element.

10. A method for manufacturing a prepreg, wherein, A prepreg is manufactured by laminating a film of a thermosetting resin composition to impregnate a fiber substrate with a thickness of 40 μm or more. An impregnated area and a non-impregnated area of the thermosetting resin composition are provided in the fiber substrate, and the non-impregnated areas are made to be intermittently present. The surface waviness (Wa) of the prepreg is 5.0 μm or less.

11. The method for manufacturing the prepreg according to claim 10, wherein the non-impregnated areas are made to be intermittently present in the in-plane direction.

12. The method for manufacturing the prepreg according to claim 10, wherein the existence ratio of the impregnated area obtained based on the following calculation method is 30% to 98%; Calculation method: Observe the surface of the prepreg at a magnification of 50 times using an optical microscope to obtain a surface observation image; after converting the obtained surface observation image into black and white mode using image editing software, save it in the form of BMP, i.e., Microsoft Windows Bitmap Image; then, for the surface observation image in black and white mode saved in BMP form, convert each pixel into RGB, i.e., Red, Green, Blue values using image conversion software, and save it in the form of CSV, i.e., comma - separated values; paste the RGB data saved in CSV form into Microsoft Excel manufactured by Microsoft Corporation, calculate the areas of the black part and the white part, where the RGB value of the black part = 255, and the RGB value of the white part = 0; calculate the area ratio of the black part to the total of the black part and the white part based on these values; set the area ratio of the black part thus obtained as the existence ratio of the impregnation region.

13. A method for manufacturing a metal - clad laminate, wherein, After setting metal foils on both sides of one piece of prepreg obtained by the manufacturing method according to claim 10 or on both sides of a laminate of prepregs including at least one or more pieces of the prepreg, press - forming is performed.

Images