Prepreg, metal-clad laminate, wiring board, and electronic device

Abstract

To provide a prepreg, a metal-clad laminate, and a wiring board capable of efficiently producing a circuit board that allows suppression of variations in signal transmission speed within a high-frequency band when separated into individual sections, and to provide an electronic device provided with the circuit board.SOLUTION: The prepreg according to the present invention includes a fiber base material composed of a nonwoven fabric and a resin composition impregnated into the fiber base material, wherein when a first test piece of 450 mm square is cut out from the nonwoven fabric, the first test piece is divided equally into 25 portions to prepare 25 second test pieces of 90 mm square, the range R and the average weight A of the weights of the 25 second test pieces are measured, and a ratio R / A of the range R to the average weight A is calculated, the ratio R / A is 12% or less.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a prepreg, a metal-clad laminate, a wiring board, and an electronic device. [Background technology]

[0002] Patent Document 1 discloses a prepreg formed by impregnating a fiber substrate with a resin composition and drying the prepreg, a copper-clad laminate formed by providing copper foil on at least one surface of the prepreg, and a printed wiring board formed by patterning the copper foil.

[0003] In recent years, signals transmitted over printed circuit boards have become increasingly high frequency, and signals in the high frequency band of, for example, 60 GHz or higher are increasingly being used.

[0004] However, high-frequency signals are easily affected by the dielectric properties of the printed wiring board. For example, if the fiber base material of the printed wiring board is glass cloth, the presence or absence of basket holes affects the transmission characteristics.

[0005] Therefore, the use of nonwoven fabric as a fiber substrate has been considered. However, the relationship between the structure of the nonwoven fabric and the dielectric properties of the printed wiring board has not been fully investigated. Therefore, when printed wiring boards are fabricated by cutting multiple pieces from a prepreg roll using nonwoven fabric, there is a problem that the resulting printed wiring boards have large individual differences in dielectric properties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-312751 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a prepreg, a metal-clad laminate, and a wiring board that can be individually separated to efficiently manufacture circuit boards with reduced variation in signal transmission speed in the high-frequency band, as well as an electronic device equipped with the circuit board. [Means for solving the problem]

[0008] These objects can be achieved by the present invention as set forth in (1) to (11) below. (1) A fiber substrate made of a nonwoven fabric; A resin composition impregnated into the fiber substrate; and A first test piece measuring 450 mm square was cut out from the nonwoven fabric. Divide the first test piece into 25 equal parts to cut out 25 second test pieces each 90 mm square. Measure the weight range R and average weight A of 25 of the second test pieces; When the ratio R / A of the range R to the average weight A is calculated, A prepreg characterized in that the ratio R / A is 12% or less.

[0009] (2) The prepreg according to (1) above, wherein the resin composition contains a thermosetting resin.

[0010] (3) The prepreg according to (2) above, wherein the thermosetting resin contains at least one of an epoxy resin, a maleimide compound, a benzoxazine compound, a cyanate compound, a polyphenylene ether compound, and a polyimide compound.

[0011] (4) The prepreg according to any one of (1) to (3) above, wherein the resin composition contains a filler.

[0012] (5) The prepreg according to any one of (1) to (4) above, wherein the nonwoven fabric is an organic nonwoven fabric made of organic fibers.

[0013] (6) The prepreg according to (5) above, wherein the organic fiber is made of a material containing at least one of polyamide resin, polyimide resin, polyamideimide resin, polyolefin resin, polyester resin, fluorine resin, polycycloolefin resin, and polyphenylene ether resin.

[0014] (7) The prepreg according to any one of (1) to (4) above, wherein the nonwoven fabric is a glass nonwoven fabric made of glass fibers.

[0015] (8) The prepreg according to any one of (1) to (7) above, wherein the volume ratio of the fiber base material is 20% by volume or more and 60% by volume or less.

[0016] (9) A cured product of the prepreg according to any one of (1) to (8) above; a metal layer provided on at least one surface of the cured prepreg; A metal-clad laminate comprising:

[0017] (10) A wiring board comprising a plurality of circuit portions formed by patterning the metal layer of the metal-clad laminate described in (9) above.

[0018] (11) A circuit board obtained by dividing the wiring board according to (10) above; an electronic component mounted on the circuit board; An electronic device comprising: [Effects of the Invention]

[0019] According to the present invention, a prepreg, a metal-clad laminate, and a wiring board can be obtained that can be singulated to efficiently produce circuit boards with reduced variations in signal transmission speed in the high-frequency band. Furthermore, according to the present invention, an electronic device including the circuit board can be obtained. [Brief explanation of the drawings]

[0020] [Figure 1]FIG. 1 is a cross-sectional view showing a prepreg according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram illustrating a method for evaluating the weight variation of the fiber base material shown in FIG. [Figure 3] FIG. 2 is a schematic diagram illustrating a method for evaluating the weight variation of the fiber base material shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The prepreg, metal-clad laminate, wiring board, and electronic device of the present invention will be described in detail below with reference to preferred embodiments shown in the accompanying drawings.

[0022] 1. Prepreg Fig. 1 is a cross-sectional view showing a prepreg 10 according to an embodiment. In the following description, the upper side in Fig. 1 will be referred to as "upper" and the lower side as "lower."

[0023] The prepreg 10 shown in FIG. 1 has a flat fiber base material 3 and a resin composition that has been impregnated into the fiber base material 3 and semi-cured. The resin composition impregnated into the fiber base material 3 forms a resin layer 1 on one surface (upper surface) of the fiber base material 3 and a resin layer 2 on the other surface (lower surface). Therefore, the prepreg 10 shown in FIG. 1 has the fiber base material 3, the resin layer 1, and the resin layer 2.

[0024] Such prepreg 10 has excellent dielectric properties, mechanical properties, electrical insulation, and the like. Therefore, the prepreg 10 is used in the manufacture of wiring boards. Specifically, when the prepreg 10 is used in the core layer of a wiring board, for example, two or more sheets of prepreg 10 are stacked, and the resulting laminate is heated to harden the prepreg 10, thereby obtaining an insulating layer for the core layer. This insulating layer is laminated with metal foil during hardening to form a metal-clad laminate. Furthermore, a wiring board is obtained by patterning the metal foil of the metal-clad laminate. When this wiring board is an aggregate substrate comprising multiple circuit sections, it can be cut into individual pieces, allowing multiple circuit boards to be efficiently manufactured. Therefore, the prepreg 10 is a so-called prepreg raw material that is intended to be cut into individual pieces, and is large enough to allow multiple circuit boards to be cut out.

[0025] The fiber base material 3 is made of nonwoven fabric. Nonwoven fabrics have superior in-plane structural uniformity compared to woven fabrics such as glass cloth. In other words, unlike glass cloth, the presence or absence of basket holes is less likely to cause a decrease in in-plane structural uniformity. In particular, the nonwoven fabric used for the fiber base material 3 is a nonwoven fabric whose weight variation is suppressed within a predetermined range when measured using the method described below. When a wiring board is individually divided into multiple circuit boards to produce multiple circuit boards, the fiber base material 3 made of such a nonwoven fabric can suppress variations in dielectric properties between circuit boards. This suppresses variations in signal transmission speed when transmitting high-frequency signals across the circuit board. In other words, by using the prepreg 10 according to this embodiment, wiring boards with excellent in-plane dielectric uniformity can be manufactured, ultimately enabling the efficient production of circuit boards with minimal variations in high-frequency signal transmission speed.

[0026] The configuration of the prepreg 10 will be described in detail below. 1.1. Fiber substrate The fiber base material 3 is a sheet-like member made of nonwoven fabric. Unlike woven fabric, nonwoven fabric does not have basket holes, so it has a high degree of structural uniformity. This allows the effect of the fiber base material 3 on signal transmission speed to be uniform.

[0027] Examples of the fiber base material 3 include organic nonwoven fabrics made of pulp or organic fibers, inorganic nonwoven fabrics made of inorganic fibers, and composite nonwoven fabrics made of both organic and inorganic fibers. Of these, organic nonwoven fabrics are preferred. By using organic nonwoven fabrics, prepregs 10 can be obtained that can be used to manufacture wiring boards including insulating layers with low dielectric constants and good mechanical strength.

[0028] The constituent material of the organic fibers is not particularly limited as long as it is an organic material. Among these, at least one of polyamide-based resins, polyimide-based resins, polyamideimide-based resins, polyolefin-based resins, polyester-based resins, fluorine-based resins, polycycloolefin-based resins, and polyphenylene ether-based resins is preferably used. These have relatively good mechanical strength among organic materials. Therefore, by using these organic materials, it is possible to realize a prepreg 10 suitable for manufacturing a wiring board with excellent mechanical strength. Furthermore, since these organic materials have the property of softening at low temperatures (low softening property), good moldability can be obtained even at low temperatures when the prepreg 10 is pressure-molded. Note that the organic nonwoven fabric may contain two or more types of organic fibers composed of these materials.

[0029] Examples of materials for inorganic fibers include glass and ceramics. Among these, glass is preferably used as the material for inorganic fibers. Glass nonwoven fabrics made of glass fibers have particularly good mechanical strength and heat resistance.

[0030] The size of the fiber base material 3 is 450 mm square or larger. 450 mm square or larger means a size that can encompass a square with one side measuring 450 mm. Using a fiber base material 3 of this size, it is possible to produce prepregs 10 of the size required to cut out multiple commonly used circuit boards.

[0031] The nonwoven fabric constituting the fiber base material 3 is configured so that the weight variation measured as follows falls within a predetermined range.

[0032] 2 and 3 are schematic diagrams illustrating a method for evaluating the weight variation of the fiber base material 3 shown in FIG.

[0033] First, as shown in FIG. 2, a cutout line CL1 is made in the nonwoven fabric 30, and a 450 mm square first test piece 31 is cut out. A 450 mm square means a square with one side measuring 450 mm. The direction in which the cutout line CL1 extends is set to be parallel to the machine direction MD or width direction TD of the nonwoven fabric 30. The machine direction MD is the direction in which the nonwoven fabric 30 is unwound or wound when continuously produced by a machine. The width direction TD is perpendicular to the machine direction MD.

[0034] Next, as shown in Figure 3, a cut-out line CL2 is drawn in the first test piece 31, and the first test piece 31 is divided into 25 equal parts. As a result, 25 90 mm square second test pieces 32 are cut out. A 90 mm square is a square with one side measuring 90 mm. The extension direction of the cut-out line CL2 is set to be parallel to the machine direction MD or the width direction TD of the nonwoven fabric 30.

[0035] Next, the weights of the 25 second test pieces 32 are measured. Then, the range R of the weights of the 25 second test pieces 32 and the average weight A are calculated. The range R is the difference between the maximum weight and the minimum weight. Then, when the ratio R / A of the range R to the average weight A is calculated, this ratio R / A is 12% or less.

[0036] The ratio R / A is an index that quantitatively represents weight variation. The present inventors have found that, as long as the ratio R / A is within the above-mentioned range, it is possible to realize a prepreg 10 that can be singulated to efficiently produce circuit boards with reduced variation in signal transmission speed in the high-frequency band. In other words, by forming the fiber base material 3 using a nonwoven fabric 30 with a ratio R / A within the above-mentioned range, it is possible to realize a prepreg 10 that is suitable for efficiently producing circuit boards with reduced variation in signal transmission speed in the high-frequency band. As a result, circuit boards with stable quality can be produced at low cost.

[0037] The ratio R / A is an index determined from the weight of 25 second test pieces 32 distributed in a matrix. Therefore, this index can be considered to accurately reflect the influence of both the machine direction MD and the width direction TD on the weight. Therefore, when circuit boards are cut out from a wiring substrate containing a nonwoven fabric 30 having a ratio R / A within the above range, circuit boards of stable quality can be efficiently manufactured without strict consideration of the cutting method. Specifically, this can be expected to increase the number of circuit boards produced or to eliminate the need for orientation of the cut-out circuit boards.

[0038] Furthermore, when lines extending in different directions are arranged on a single cut-out circuit board, the difference in signal transmission speed between the lines can be reduced, thereby increasing the degree of freedom in line design.

[0039] In order to produce nonwoven fabric 30 having a ratio R / A within the above range, it is sufficient to adjust the fiber distribution. Specifically, methods include adjusting the distribution of the raw material supply amount, slowing down the raw material supply speed, and slowing down the raw material conveying speed. By performing at least one of these methods, the fiber distribution can be made uniform, and nonwoven fabric 30 having a ratio R / A within the above range can be produced.

[0040] The ratio R / A is preferably 10% or less, and more preferably 8% or less. If the ratio R / A exceeds the upper limit, the signal transmission speed in the high frequency band of the manufactured circuit board will vary greatly. This will increase the individual differences between circuit boards and reduce quality.

[0041] On the other hand, the lower limit of the ratio R / A does not need to be set specifically, but is preferably 1% or more, and more preferably 3% or more, in consideration of the risk of increased manufacturing costs if weight variation is excessively suppressed in the manufacture of nonwoven fabric 30. Within this range, the effect on the signal transmission speed in the high frequency band can be relatively suppressed.

[0042] The diameter of the fibers constituting the nonwoven fabric 30 is not particularly limited, but is preferably 0.01 μm to 30 μm, more preferably 0.5 μm to 20 μm, and even more preferably 1 μm to 10 μm. This configuration allows for a fiber base material 3 with a smaller ratio R / A.

[0043] If the fiber diameter is below the lower limit, the fiber dispersion is reduced, which may cause the ratio R / A to deviate from the range. This may also result in a reduction in the mechanical strength of the wiring board. On the other hand, if the fiber diameter is above the upper limit, the ratio R / A is more likely to be affected by the fiber distribution. This may cause the ratio R / A to deviate from the range.

[0044] Furthermore, the thickness of the fiber base material 3 is not particularly limited, but is preferably 500 μm or less, more preferably 5 μm to 400 μm, even more preferably 10 μm to 150 μm, and particularly preferably 12 μm to 90 μm. If the thickness of the fiber base material 3 is within this range, the mechanical strength of the wiring board can be ensured. Furthermore, if the thickness of the fiber base material 3 is within this range, handling during production of the prepreg 10 is improved.

[0045] If the thickness of the fiber base material 3 is below the lower limit, warping of the prepreg 10, metal-clad laminate, or wiring board may increase, and handling may be impaired when producing the prepreg 10. On the other hand, if the thickness of the fiber base material 3 exceeds the upper limit, the rigidity of the fiber base material 3 increases, and handling may be impaired when producing the prepreg 10.

[0046] The volume ratio of the fiber base material 3 in the prepreg 10 is preferably 20% by volume or more and 60% by volume or less, and more preferably 30% by volume or more and 50% by volume or less. This allows the volume ratio of the fiber base material 3 to be optimized, thereby further improving the pressure moldability of the prepreg 10.

[0047] 1.2.Resin layer The resin layer 1 and the resin layer 2 are composed of a semi-cured resin composition impregnated into the fiber base material 3. The resin composition includes, for example, a thermosetting resin and a filler.

[0048] 1.2.1.Thermosetting resin The thermosetting resin is the main component of the resin composition. The main component refers to the component with the largest mass fraction in the resin composition. By including the thermosetting resin, the heat resistance of the cured product of the prepreg 10 can be further improved.

[0049] The thermosetting resin is not particularly limited, and any resin having thermosetting properties can be used. Among them, at least one of epoxy resin, maleimide compound, benzoxazine compound, cyanate compound, polyphenylene ether compound, and polyimide compound is preferably used. These exhibit good dielectric properties, i.e., low dielectric constant and low dielectric loss tangent, and are therefore useful as a thermosetting resin used in a resin composition.

[0050] 1.2.2.Filling material Examples of fillers include inorganic fillers made of inorganic materials and organic fillers made of organic materials. Adding a filler to the resin composition can reduce the thermal expansion and water absorption of the cured product of the prepreg 10. In addition, the viscosity of the resin composition can be reduced, improving the moldability of the prepreg 10.

[0051] The inorganic filler is not particularly limited as long as it is composed of an inorganic material, but examples thereof include silicates such as talc, calcined clay, uncalcined clay, mica, and glass; oxides such as titanium oxide, alumina, boehmite, silica, and fused silica; carbonates such as calcium carbonate, magnesium carbonate, and hydrotalcite; hydroxides such as aluminum hydroxide, magnesium hydroxide, and calcium hydroxide; sulfates or sulfites such as barium sulfate, calcium sulfate, and calcium sulfite; borates such as zinc borate, barium metaborate, aluminum borate, calcium borate, and sodium borate; nitrides such as aluminum nitride, boron nitride, silicon nitride, and carbon nitride; and titanates such as strontium titanate and barium titanate. These inorganic fillers may be used alone or in combination.

[0052] Among these, at least one selected from the group consisting of talc, alumina, glass, silica, mica, aluminum hydroxide and magnesium hydroxide is preferably used, and silica is more preferably used.

[0053] The organic filler is not particularly limited as long as it is made of an organic material, and examples thereof include polytetrafluoroethylene, polymethylpentene, polyvinyl butyral, acrylonitrile butadiene rubber, cyclic olefin copolymer, polyphenylene ether, pulp, wood flour, etc. As the organic filler, one of these may be used alone, or two or more may be used in combination. The filler may be a combination of an inorganic filler and an organic filler.

[0054] The shape of the filler is not particularly limited, but examples thereof include chunks, scales, spheres, fibers, etc. Among these, the shape of the filler is preferably spherical. This makes it easier for the filler to penetrate all the way to the inside of the fiber base material 3 when the fiber base material 3 is impregnated with the resin composition.

[0055] The average particle size of the filler is not particularly limited, but is preferably 0.01 μm or more, and more preferably 0.05 μm or more. This prevents the viscosity of the resin composition from increasing, improving workability during the production of the prepreg 10. The upper limit of the average particle size of the filler is also not particularly limited, but is preferably 5.0 μm or less, more preferably 2.0 μm or less, and even more preferably 1.0 μm or less. This prevents settling of the filler in the resin composition, allowing for the formation of more uniform resin layers 1 and 2.

[0056] The average particle size of the filler is determined, for example, by measuring the particle size distribution of the particles on a volume basis using a laser diffraction particle size distribution analyzer, and determining the particle size D50 at 50% of the cumulative size.

[0057] The filler content is preferably 40% by mass to 85% by mass, more preferably 45% by mass to 75% by mass, and even more preferably 50% by mass to 65% by mass of the total solid content of the resin composition, which optimizes the viscosity and moldability of the resin composition and reduces the thermal expansion and water absorption of the cured resin layers 1 and 2.

[0058] The resin composition may contain additives such as a thermoplastic resin, a curing agent, a curing accelerator, a polymerization initiator, a crosslinking agent, an elastomer, a coupling agent, a leveling agent, a colorant, a stress reducing agent, an antifoaming agent, an ultraviolet absorber, an antioxidant, an ion scavenger, etc. The resin composition may contain two or more of these additives.

[0059] 2. Prepreg manufacturing method Next, a method for producing the prepreg 10 will be described.

[0060] The prepreg 10 is produced, for example, by impregnating the fiber base material 3 with a resin composition and then semi-curing it.

[0061] The method for impregnating the fiber substrate 3 with the resin composition is not particularly limited, but examples include a method in which the solid content of the resin composition is dissolved in a solvent to prepare a varnish-like resin composition and then the fiber substrate 3 is immersed in the varnish-like resin composition, a method in which the varnish-like resin composition is applied to the fiber substrate 3 using various coaters, a method in which the varnish-like resin composition is sprayed onto the fiber substrate 3 using a sprayer, and a method in which both sides of the fiber substrate 3 are laminated with a resin film made of the resin composition.

[0062] Examples of the solvent include organic solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, mesitylene, ethyl acetate, cyclohexane, heptane, cyclohexane, cyclohexanone, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, ethylene glycol, ethylene glycol ether, cellosolve-based solvents, carbitol-based solvents, anisole, and N-methylpyrrolidone. These may be used alone or in combination of two or more.

[0063] The solid content of the varnish-like resin composition is preferably 30% by mass or more and 80% by mass or less, and more preferably 40% by mass or more and 70% by mass or less, thereby obtaining a resin composition with excellent workability and film-forming properties.

[0064] 3.Metal clad laminate Next, a metal-clad laminate according to an embodiment will be described.

[0065] The metal-clad laminate according to the embodiment includes a cured product of prepreg 10 and a metal layer provided on at least one surface of the cured product. After the metal layer of such a metal-clad laminate is patterned, it is separated into individual pieces, making it possible to efficiently manufacture a plurality of circuit boards with reduced variations in signal transmission speed in the high-frequency band.

[0066] Examples of materials constituting the metal layer include copper, copper-based alloys, aluminum, aluminum-based alloys, silver, silver-based alloys, gold, gold-based alloys, zinc, zinc-based alloys, nickel, nickel-based alloys, tin, tin-based alloys, iron, iron-based alloys, Fe-Ni-based alloys such as Kovar (registered trademark), 42 Alloy, Invar, and Super Invar, W, and Mo.

[0067] Of these, copper or a copper-based alloy is preferably used as the material for the metal layer, as this provides a metal layer that is excellent in conductivity and can be easily patterned by etching.

[0068] The metal layer may be made of a metal foil containing the above-mentioned material, or may be a cured product of a metal paste containing the above-mentioned material.

[0069] The thickness of the metal layer is not particularly limited, but is preferably 0.5 μm or more and 35 μm or less, and more preferably 1.5 μm or more and 18 μm or less.

[0070] The metal-clad laminate is produced, for example, by the following method. First, a metal foil is laminated on both the upper and lower outer surfaces or one surface of the prepreg 10 or two or more laminated prepregs 10 to form a laminate. Next, if necessary, the laminate is pressurized under high vacuum conditions using a vacuum laminator. The laminate is then heated and pressurized to obtain a metal-clad laminate.

[0071] 4. Wiring board Next, a wiring board according to an embodiment will be described.

[0072] The wiring board according to the embodiment includes an assembly of circuit sections formed by patterning the metal layer of a metal-clad laminate. That is, the wiring board includes a cured prepreg 10 and a plurality of circuit sections provided on at least one surface of the cured prepreg 10. By singulating such wiring boards, it becomes possible to efficiently manufacture a plurality of circuit boards with reduced variations in high-frequency band signal transmission speed. This allows multiple circuit boards to be efficiently manufactured simultaneously, and the manufactured circuit boards have little individual variation in characteristics such as high-frequency band signal transmission speed. As a result, high-quality circuit boards can be manufactured at low cost.

[0073] For example, etching and SAP (semi-additive process) are used to pattern metal layers. Examples of etching methods include chemical etching (wet etching) using an etching solution. SAP (semi-additive process) involves applying an electroless metal plating film to a metal foil or insulating layer, protecting non-circuit forming areas with a plating resist, forming an electrolytic metal plating film on the exposed electroless plating film, and then removing the plating resist and patterning the electrolytic metal plating film by flash etching.

[0074] The wiring board is preferably used for signal transmission in high frequency bands such as microwave bands and millimeter wave bands. The frequency of the transmitted signal is, for example, in the range of 1 GHz to 100 GHz, particularly in the range of 30 GHz to 80 GHz.

[0075] 5.Electronic equipment Next, an electronic device according to an embodiment will be described.

[0076] The electronic device according to the embodiment includes a circuit board obtained by singulating a wiring board, and electronic components mounted on the circuit board. This configuration reduces individual variations in the circuit board and reduces costs. This allows for the realization of electronic devices with reduced performance variations and reduced costs. The individual variations refer to, for example, variations in signal transmission speeds in the high-frequency band. Therefore, this embodiment is particularly useful in electronic devices that use high-frequency signals, such as electronic devices equipped with various sensors, antennas, receivers, etc., such as in-vehicle sensors.

[0077] 6. Effects of the above embodiment The prepreg 10 according to the embodiment includes a fiber base material 3 made of a nonwoven fabric 30 and a resin composition impregnated into the fiber base material 3. A first test piece 31 measuring 450 mm square is cut from the nonwoven fabric 30, and the first test piece 31 is divided into 25 equal parts to cut out 25 second test pieces 32 each measuring 90 mm square. The weight range R and average weight A of the 25 second test pieces 32 are measured, and the ratio R / A of the range R to the average weight A is calculated; the ratio R / A is 12% or less.

[0078] According to this configuration, it is possible to realize a prepreg 10 that can be singulated to efficiently manufacture circuit boards with reduced variations in signal transmission speed in the high frequency band.

[0079] In the prepreg 10 according to the embodiment, the resin composition contains a thermosetting resin. With this configuration, the heat resistance of the cured product of the prepreg 10 can be further improved.

[0080] In the prepreg 10 according to the embodiment, the thermosetting resin contains at least one of an epoxy resin, a maleimide compound, a benzoxazine compound, a cyanate compound, a polyphenylene ether compound, and a polyimide compound.

[0081] This configuration makes it possible to realize prepreg 10 suitable for manufacturing a wiring board having excellent mechanical strength. Furthermore, since these organic materials have the property of softening at low temperatures (low softening property), good moldability can be obtained even at low temperatures when prepreg 10 is pressure molded.

[0082] In the prepreg 10 according to the embodiment, the resin composition contains a filler. This configuration can reduce the thermal expansion and water absorption of the cured product of the prepreg 10. In addition, the viscosity of the resin composition can be reduced, thereby improving the moldability of the prepreg 10.

[0083] In the prepreg 10 according to the embodiment, the nonwoven fabric is an organic nonwoven fabric made of organic fibers.

[0084] According to this configuration, a prepreg 10 is obtained that can be used to manufacture a wiring board including an insulating layer having a low relative dielectric constant and good mechanical strength.

[0085] Furthermore, in the prepreg 10 according to the embodiment, the constituent material of the organic fiber includes at least one of polyamide-based resin, polyimide-based resin, polyamideimide-based resin, polyolefin-based resin, polyester-based resin, fluorine-based resin, polycycloolefin-based resin, and polyphenylene ether-based resin.

[0086] This configuration makes it possible to realize prepreg 10 suitable for manufacturing a wiring board having excellent mechanical strength. Furthermore, since these organic materials have the property of softening at low temperatures (low softening property), good moldability can be obtained even at low temperatures when prepreg 10 is pressure molded.

[0087] In the prepreg 10 according to the embodiment, the nonwoven fabric is a glass nonwoven fabric made of glass fibers.

[0088] With this configuration, it is possible to realize a prepreg 10 that can be used to manufacture a wiring board having particularly good mechanical strength and heat resistance.

[0089] In the prepreg 10 according to the embodiment, the volume ratio of the fiber base material 3 is 20% by volume or more and 60% by volume or less.

[0090] According to this configuration, the volume ratio of the fiber base material 3 can be optimized, and therefore the pressure moldability of the prepreg 10 can be further improved.

[0091] The metal-clad laminate according to the embodiment includes a cured product of the prepreg according to the embodiment, and a metal layer provided on at least one surface of the cured product of the prepreg .

[0092] According to this configuration, a metal-clad laminate can be realized that can be singulated to efficiently manufacture circuit boards with reduced variations in signal transmission speed in the high-frequency band.

[0093] Moreover, the wiring board according to the embodiment includes a plurality of circuit portions formed by patterning the metal layer of the metal-clad laminate according to the embodiment.

[0094] According to this configuration, it is possible to realize a wiring board that can be individually divided, allowing efficient production of circuit boards in which variations in signal transmission speed in the high frequency band are suppressed.

[0095] Moreover, the electronic device according to the embodiment includes a circuit board obtained by dividing the wiring board according to the embodiment, and an electronic component mounted on the circuit board.

[0096] This configuration reduces the individual differences in the circuit boards and reduces costs, thereby realizing electronic devices with less variation in performance and at lower costs.

[0097] Although the prepreg, metal-clad laminate, wiring board, and electronic device of the present invention have been described above, the present invention is not limited to these.

[0098] For example, the prepreg, metal-clad laminate, wiring board, and electronic device of the present invention may be such that each configuration of the above-described embodiments is replaced with any configuration that can exert the same function, or any configuration may be added to the above-described embodiments. [Example]

[0099] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples in any way.

[0100] 7. Raw Material Preparation Two types of resin compositions (a PPE-based composition and an epoxy-based composition) were prepared by blending the components shown in Table 1 in the blending ratios shown in Table 1. Details of each component shown in Table 1 are as follows.

[0101] [Table 1]

[0102] 7.1.PPE-based composition Maleimide compound: Biphenylaralkyl-type maleimide compound, "MIR-3000-70MT" manufactured by Nippon Kayaku Co., Ltd. Modified polyphenylene ether copolymer: Methacrylic-terminated polyphenylene ether, "SA9000" manufactured by SABIC Innovative Plastics Crosslinking agent: Triallyl isocyanate, "TAIC" manufactured by Shinryo Corporation Silane coupling agent: "KBM-503" manufactured by Shin-Etsu Silicone Co., Ltd. Polymerization initiator: 1,3-di[(t-butylperoxy)isopropyl]benzene, "Perbutyl P" manufactured by NOF Corporation Filler: Spherical fused silica, "SO-32R" manufactured by Admatechs, average particle size 1 μm

[0103] 7.2. Epoxy-based compositions Epoxy resin: "HP-5000" manufactured by DIC Novolac cyanate resin: "PT-30" manufactured by Arcsada Japan Hardener: 2:2-phenyl-4-methyl-5-hydroxymethylimidazole, "Curesol 2P4MHZ" manufactured by Shikoku Chemicals Corporation Silane coupling agent: "KBM-403" manufactured by Shin-Etsu Silicone Co., Ltd. Filler: Spherical fused silica, "SO-32R" manufactured by Admatechs, average particle size 1 μm

[0104] Furthermore, the fiber base materials shown in Table 2 were prepared. Details of the fiber base materials shown in Table 2 are as follows.

[0105] 7.3. Fibre substrate PP nonwoven fabric: Organic nonwoven fabric made of polypropylene, "Delpore DP1001-27P" manufactured by Delstar, wire diameter 5μm, thickness 330μm HDPE nonwoven fabric: Organic nonwoven fabric made of high-density polyethylene, "Tyvek 1422A" manufactured by DuPont Japan, wire diameter 5 μm, thickness 130 μm Glass nonwoven fabric: "Glass fiber nonwoven fabric Grasper" manufactured by Oji F-Tex, thickness 130 μm Aromatic polyamide cloth: Aramid cloth, thickness 110 μm Glass cloth: NE glass cloth, thickness 44 μm (#1078)

[0106] 8. Prepreg Preparation First, a fiber base material shown in Table 2 was impregnated with a resin composition shown in Table 1 and dried for 5 minutes in a hot air dryer at 150°C. This resulted in a prepreg having the blending ratio of the fiber base material and the resin composition shown in Table 2. Table 2 also shows the ratio R / A of the weight range R to the average weight A of the second test piece, which was measured in advance for the fiber base material used.

[0107] In Table 2, prepregs corresponding to the present invention are designated as "Examples," and prepregs not corresponding to the present invention are designated as "Comparative Examples."

[0108] 9. Evaluation of wiring boards First, copper foil was placed on both sides of the prepreg, and the prepreg was heated and press-molded at a pressure of 3 MPa and a temperature of 225°C for 2 hours. This resulted in a metal-clad laminate with an insulating layer made of the cured prepreg and copper foil (metal layer) on both sides of the insulating layer. An ultra-thin sheet of pure copper with a thickness of 18 μm was used for the copper foil.

[0109] Next, the copper foil of the metal-clad laminate was patterned by etching, thereby obtaining a wiring board provided with a circuit layer including a circuit.

[0110] 9.1. Measurement of relative permittivity and dielectric loss tangent The relative permittivity and dielectric loss tangent (tanδ) of the wiring board at a frequency of 10 GHz were measured using the cavity resonator method in accordance with the method specified in JIS C 2565:1992. The measurement results are shown in Table 2.

[0111] 9.2.Evaluation of signal transmission speed variations between circuit boards The variation in signal transmission speed between circuit boards was evaluated as follows.

[0112] First, multiple circuit boards were cut out from the wiring board. Each circuit board had a ground pattern on one side and a signal pattern on the other side as circuit layers. The ground pattern covered the entire surface, and the signal pattern was a microstrip line pattern including short lines with a line width of 0.2 mm and a line length of 10 mm and long lines with a line width of 0.2 mm and a line length of 20 mm, spaced 30 mm apart. The signal patterns were formed so that the extension direction of the signal patterns was different from the flow direction of the nonwoven fabric. Specifically, five circuit boards (parallel pattern samples) were prepared in which the extension direction of each line constituting the signal pattern was parallel to the flow direction (MD) of the nonwoven fabric, and five circuit boards (orthogonal pattern samples) were prepared in which the extension direction of each line constituting the signal pattern was perpendicular to the flow direction (MD) of the nonwoven fabric.

[0113] Next, the circuit board was connected to a vector network analyzer. High-frequency signals were then input to the signal pattern while changing the frequency, and the signals output from the signal pattern were imported into the vector network analyzer and analyzed. The frequency of the high-frequency signals was changed from 10 to 65 GHz, and when analyzing the output signal, results up to 78 GHz were obtained by extrapolation.

[0114] The output signal was analyzed as follows. First, the phase difference between the signals output from the short line and the long line was calculated. This phase difference corresponds to the transmission speed of the signal transmitted by the signal pattern. Therefore, if the variation in phase difference between circuit boards is small, it can be assumed that the variation in signal transmission speed is small. On the other hand, if the variation in phase difference between circuit boards is large, it can be assumed that the variation in signal transmission speed is large.

[0115] Next, the difference between the maximum and minimum phase difference values ​​(variation in phase difference in the machine direction MD) at a frequency of 76 GHz was calculated for the five parallel pattern samples. Similarly, the difference between the maximum and minimum phase difference values ​​(variation in phase difference in the width direction TD) at a frequency of 76 GHz was calculated for the five orthogonal pattern samples. The calculation results are shown in Table 2.

[0116] 9.3.Evaluation of variations in signal transmission speed between lines with different extension directions The variation in signal transmission speed between lines extending in different directions was evaluated as follows.

[0117] First, the difference between the variation in retardation in the machine direction MD calculated in 9.2 and the variation in retardation in the width direction TD was calculated. The calculation results are shown in Table 2.

[0118] This difference in the variation in phase difference indicates the degree to which the signal transmission speed is affected when the signal transmission direction in the circuit board is changed relative to the nonwoven fabric flow direction (MD). In other words, when the difference in the variation in phase difference is small, the signal transmission speed in the circuit board is less affected by the relationship between the signal transmission direction and the nonwoven fabric flow direction (MD). In this case, there is less need to consider the orientation of the circuit board when cutting out circuit boards from the wiring board, which is useful in that it is easy to increase the number of cutouts and makes the handling of the circuit boards easier after cutting out. On the other hand, when this difference is large, it indicates that the signal transmission speed in the circuit board is more easily affected by the relationship between the signal transmission direction and the nonwoven fabric flow direction (MD). In this case, there is a concern that the need to consider the orientation of the circuit board when cutting out circuit boards from the wiring board increases, which may reduce the number of cutouts and make the handling of the circuit boards more difficult after cutting out.

[0119] [Table 2]

[0120] 9.4. Discussion of evaluation results As shown in Table 2, the circuit boards obtained using the prepregs of each example had smaller variations in retardation than the comparative examples. This result is thought to be due to the use of nonwoven fabrics with reduced weight variations as the fiber base material provided in the prepregs of each example.

[0121] Furthermore, in the circuit boards obtained using the prepregs of each Example, the variation in signal transmission speed between lines with different extension directions was suppressed to a smaller extent than in the comparative examples. This result is thought to indicate that in the circuit boards obtained using the prepregs of each Example, the signal transmission speed is less affected by the relationship between the signal transmission direction and the flow direction MD of the fiber base material. [Explanation of symbols]

[0122] 1 resin layer 2 Resin layer 3. Fiber substrate 10 Prepreg 30 Nonwoven fabric 31 First test piece 32 Second test piece CL1 Cutting line CL2 cutting line MD Flow direction TD width direction

Claims

1. A fiber substrate made of nonwoven fabric; A resin composition impregnated into the fiber substrate; and A first test piece measuring 450 mm square was cut out from the nonwoven fabric. The first test piece was divided into 25 equal parts to cut out 25 second test pieces each 90 mm square. Measure the weight range R and average weight A of 25 of the second test pieces; When the ratio R / A of the range R to the average weight A is calculated, A prepreg characterized in that the ratio R / A is 12% or less.

2. The prepreg according to claim 1 , wherein the resin composition includes a thermosetting resin.

3. 3. The prepreg according to claim 2, wherein the thermosetting resin contains at least one of an epoxy resin, a maleimide compound, a benzoxazine compound, a cyanate compound, a polyphenylene ether compound, and a polyimide compound.

4. The prepreg according to claim 1 , wherein the resin composition contains a filler.

5. 4. The prepreg according to claim 1, wherein the nonwoven fabric is an organic nonwoven fabric made of organic fibers.

6. 6. The prepreg according to claim 5, wherein a constituent material of the organic fibers includes at least one of polyamide-based resin, polyimide-based resin, polyamideimide-based resin, polyolefin-based resin, polyester-based resin, fluorine-based resin, polycycloolefin-based resin, and polyphenylene ether-based resin.

7. 4. The prepreg according to claim 1, wherein the nonwoven fabric is a glass nonwoven fabric made of glass fibers.

8. 4. The prepreg according to claim 1, wherein the volume ratio of the fiber base material is 20% by volume or more and 60% by volume or less.

9. A cured product of the prepreg according to any one of claims 1 to 3; a metal layer provided on at least one surface of the cured prepreg; A metal-clad laminate comprising:

10. A wiring board comprising a plurality of circuit portions formed by patterning the metal layer of the metal-clad laminate according to claim 9.

11. a circuit board obtained by dividing the wiring board according to claim 10; an electronic component mounted on the circuit board; An electronic device comprising:

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