JPH11207850A - Resin sheet, metal foil clad laminated board and multi-layer printed-wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an insulating substrate layer easy to bore by laser by a method wherein a heat curable resin particle which is solid and cured at room temperature is dispersed among fibers having an organic fiber formed in a nonwoven state with a curable binder resin as an essential ingredient. SOLUTION: A sheet is made from a slurry containing a fiber having an organic fiber as an essential ingredient and a heat curable resin particle, a curable binder resin is applied to the obtained sheet, and then the curable binder rein is cured to a B stage or a C stage by heating to be dried. As the organic fiber to be used, a polyvinyl chloride based fiber such as a polyamide fiber, a polyvinyl chloride fiber, a vinylchloride-ethylene copolymer fiber, etc., polyvinylidene chloride fiber, etc., are given. As for the heat curable resin particle to be used which is solid and uncured at room temperature, particles of an epoxy-based resin, a phenol-based resin, a cyanate-based resin, a polyimide- based resin, or the like are given.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin sheet, a metal-clad laminate, and a multilayer printed wiring board.

[0002]

2. Description of the Related Art In electronic equipment, a printed wiring board is used as a substrate of a board on which circuit elements are mounted. This printed wiring board is made by impregnating and drying a thermosetting resin varnish on a fiber base material, and laminating a required number of prepregs to form a metal clad laminate by heating and pressing. It is obtained by forming a circuit pattern by performing processing such as etching on the metal foil surface of the plate. Copper foil is usually used as the metal foil, and in PCs and industrial electronic equipment, glass woven fabric prepreg using glass woven fabric as the fiber base material is used because of its good reliability. I was In order to increase the wiring density, a multilayer printed wiring board having three or more circuit patterns on one board is used.
Usually, a double-sided printed wiring board on which a circuit is formed is used as an inner layer component, copper foil is used as an outer layer component, and these components are laminated and integrated using a sheet-like adhesive material. As this sheet-like adhesive material, a prepreg using a glass woven fabric as a base material has been used. As described above, the glass substrate was contained in the insulating base material layer in both the multilayer printed wiring board and the double-sided or single-sided printed wiring board.

[0003] Portable communication devices have become more popular and smaller. Printed wiring boards used in such small electronic devices need to be thin, and thin metal-clad laminates or multilayer printed wiring boards have been required. When using a prepreg based on a glass woven fabric, there is a limit to thinning, and thermosetting resin particles that are solid and uncured at room temperature between inorganic fibers formed into a nonwoven fabric by a curable binder resin. It has been proposed to use a non-woven resin sheet obtained by dispersing a prepreg instead of a prepreg (see JP-A-8-109278).

[0004]

With the improvement in wiring board technology and the trend toward weight reduction, multilayer printed wiring boards are becoming more multi-layered and higher in density. In order to increase the density, the wiring circuit of the multilayer printed wiring board has become thinner, and accordingly, the IVH
(Interstitial Via Hole) or S
Holes for interlayer connection such as VH (Surface Via Hole) have also been reduced in diameter. As a result, drilling cannot be used, and a laser drilling method has been used. However, a metal-clad laminate or a multilayer printed wiring board using the above resin sheet in place of a prepreg has a high melting point inorganic fiber in an insulating base material layer. Was difficult.

An object of the present invention is to provide a resin sheet capable of forming an insulating base material layer that is easily drilled by a laser. The resin sheet according to the first aspect is manufactured by forming a sheet using a slurry in which thermosetting resin particles and fibers are dispersed in water.
At this time, the thermosetting resin particles are carried on the fibers to form a resin sheet. However, the thermosetting resin particles easily pass through the gap between the fibers and are hardly fixed in the resin sheet.
Therefore, an object of the present invention is to provide, in addition to the object of the present invention, a resin sheet having good fixation of thermosetting resin particles when manufacturing the resin sheet. I do. Another object of the present invention is to provide a metal-clad laminate having an insulating base material layer that can be easily drilled by a laser. Still another object of the present invention is to provide a multilayer printed wiring board having an insulating base material layer that is easily drilled by a laser.

[0006]

According to the first aspect of the present invention, there is provided an uncured thermosetting solid at room temperature between fibers containing organic fibers formed as a non-woven fabric by a curable binder resin. It is a resin sheet in which conductive resin particles are dispersed.

[0007] The resin sheet of the present invention, as described below,
It is manufactured by forming a slurry containing fibers containing organic fibers as essential components and thermosetting resin particles into a slurry. When only organic fibers are used as the fibers, fixing of the thermosetting resin particles may be deteriorated. In such a case, it is preferable to use glass fibers in combination within a range that does not impair the drilling property by the laser. That is, in the invention according to claim 2, glass fibers having a fiber diameter of 10 μm or less are added to all the fibers in addition to the organic fibers.
The resin sheet according to claim 1, which is contained in an amount of 5 to 70 parts by weight based on parts by weight. Here, the fiber diameter means an average fiber diameter.

Fine glass fibers having a fiber diameter of 10 μm or less serve as a support for the thermosetting resin particles, and can increase the fixing amount of the thermosetting resin particles. As the fiber diameter of the glass fiber increases, the laser processability tends to deteriorate. Therefore, a fiber having a fiber diameter of 10 μm or less, more preferably 6 μm or less, and still more preferably 3 μm or less is suitable. If the fiber diameter is 10 μm or less, glass fibers having different fiber diameters may be used in combination. If the blending amount of glass fiber having a fiber diameter of 10 μm or less is less than 5 parts by weight based on 100 parts by weight of all fibers, the effect of fixing the thermosetting resin particles tends to be too small, and if it exceeds 70 parts by weight, laser processing is performed. It tends to be poor. From this, the blending amount of glass fiber having a fiber diameter of 10 μm or less is 2 parts per 100 parts by weight of all fibers.
More preferably, it is 0 to 60 parts by weight.

[0009] The resin sheet according to the present invention is used as a material for a laminated board and an adhesive material for a multilayer printed wiring board in the same manner as a conventionally known prepreg. That is, the invention according to claim 3 is a metal-clad laminate in which an insulating base material layer is constituted by a cured product of the resin sheet according to claim 1 or 2. According to a fourth aspect of the present invention, there is provided a multilayer printed wiring board formed by laminating and integrating the resin sheet according to the first or second aspect as an adhesive material for a component.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The resin sheet of the present invention is obtained by forming a slurry containing fibers containing organic fibers as essential components and thermosetting resin particles, and applying a curable binder resin to the obtained sheet. Then, it is manufactured by curing by heating and drying the curable binder resin to the B stage or the C stage.

The organic fibers used here include:
(A) a polyamide fiber, (b) a polyvinyl chloride fiber,
Polyvinyl chloride fibers such as vinyl chloride-ethylene copolymer fibers, (c) polyvinylidene chloride fibers, polyvinylidene chloride fibers such as polyvinylidene chloride-ethylene copolymer fibers, (d) polyacrylonitrile fibers, e) polyester fiber, (f) polyurethane fiber, (g)
Polyvinylidene cyanide fiber, (h) polyfluoroethylene fiber, (i) phenolic fiber such as phenol-formaldehyde copolymer fiber, (j) poly (p-benzamide) fiber, poly (p-phenylene terephthalamide) Fiber, poly (2-chloro-p-phenyleneterephthalamide) fiber, poly (p-phenylene-2,6-naphthalene dicarboxylic amide) fiber, poly (2,6-dichloro-p-phenylene-2,6-naphthalene) Dicarboxylic acid amide) fiber, poly (p, p'-phenylene benzamide) fiber, poly (1,5-naphthylene terephthalamide) fiber, regular aromatic copolymer amide fiber (for example, p, p'-diaminobenz) Anilide-terephthalamide copolymer fiber), random aromatic copolymer amide fiber (for example, p-ben Amide-p-phenyleneterephthalamide copolymer fiber), polymetaphenyleneisophthalamide fiber, metaphenyleneisophthalamide-metaphenyleneterephthalamide copolymer fiber, metaphenyleneisophthalamide-paraphenyleneterephthalamide copolymer Wholly aromatic polyamide fibers (aramide) such as coalesced fibers, polyoxabenzolamide fibers, polybenzoxadiazoleamide fibers, polybenzoxazolamide fibers, paraphenylene-3,4'-oxydiphenylene terephthalamide copolymer fibers (K) polybenzimidazole fiber, polythiazole fiber, polythiazole fiber such as polyphenylene triazole fiber, (l) polybisbenzimidado azobenzophenanthroline fiber, (m) polyparaphenylene fiber Fido fibers, poly-p-phenylene oxide fibers, poly (p-
(Phenylenebenzobisoxazole) fiber and the like. These organic fibers may be used alone or in combination of several kinds. Further, these organic fibers need only be capable of being formed into a sheet, and both long fibers and short fibers can be used. Further, the fiber diameter of the organic fiber is 1 to 30.
μm is preferred from the viewpoints of dispersibility, resin sheet formability, laser workability, and embedding of circuit irregularities.

Glass fibers having a fiber diameter of 6 μm or less are known as microfibers, and commercially available products can be used.

The thermosetting resin particles which are solid and uncured at room temperature (hereinafter, simply referred to as thermosetting resin particles) used in the present invention include epoxy resins, phenol resins, cyanate resins, polyimide resins, melamine resins. Particles of a series resin, a urea series resin, a furan series resin, an aniline series resin, a urethane series resin, a polyester series resin, a polyether series resin, and a silicone series resin. These may be used alone or in combination. These can be used in any form synthesized in the form of particles or granulated by grinding.
Each is used with the required curing agent. The particle size of the thermosetting resin particles is preferably 0.01 to 300 μm from the viewpoint of dispersibility and formability of the resin sheet.
More preferably, it is 1 to 100 μm. Particle size 0.0
If it is less than 1 μm, fixing to the resin sheet tends to be difficult, and if it exceeds 300 μm, the surface of the resin sheet tends not to be smooth.

The mixing ratio of the fibers containing organic fibers as essential components and the thermosetting resin particles is in the range of 50 to 10% by weight of fibers containing organic fibers as essential components and 50 to 90% by weight of thermosetting resin particles. Preferably, 30 to 10% by weight of fibers containing organic fibers as essential components, 70 to 90% by weight of thermosetting resin particles
Is more preferable. When the amount of the fiber containing the organic fiber as an essential component exceeds 50% by weight and the amount of the thermosetting resin particles is less than 50% by weight, voids and blurs are easily generated when the resin sheet is cured to form the insulating base material layer. In addition, there is a tendency that the embedding property of the circuit unevenness tends to be poor, the fiber containing organic fiber as an essential component is less than 10% by weight, and the thermosetting resin particles are 9% by weight.
If it exceeds 0% by weight, the strength tends to decrease.

[0015] In addition to the thermosetting resin particles, if necessary,
A paper can also be formed by adding a flame retardant, a thermoplastic resin, a curing accelerator, a colorant, an ultraviolet opaque agent, an antioxidant, a reducing agent, a filler, and the like to the slurry. These are added to the slurry as particles having a particle size similar to the thermosetting resin particles. Further, when these are added in large amounts, the strength of the cured product tends to be reduced. Therefore, it is necessary to determine the range of the added amount in consideration of this point and according to the purpose of addition.

A slurry containing fibers containing organic fibers as essential components, thermosetting resin particles, and a curing agent is formed into a sheet, and the sheet obtained by the forming is impregnated with a curable binder resin, sprayed, or the like. And heat drying to produce a resin sheet. By appropriately setting the papermaking conditions, for example, a resin sheet having a range of 10 to 400 μm can be obtained. The obtained resin sheet is
For example, it is wound by a winding machine and provided to the next step. The curable binder resin is preferably a resin that can be cured to the B stage or the C stage at a temperature at which the thermosetting resin particles do not completely cure (usually appropriately selected in the range of 100 to 180 ° C.). Examples of such a curable binder resin include a thermosetting acrylic emulsion, a phenol resin emulsion, and a water-soluble silicone resin emulsion.

The curable binder resin is used in an amount of 1 to 20 parts by weight based on 100 parts by weight of the thermosetting resin particles and fibers in a dry state in view of the strength and handleability of the resin sheet. Preferably applied, 5 to 1
It is more preferable that the composition is applied so as to be in a range of 0 parts by weight. If the amount of the curable binder resin is less than 1 part by weight, the strength of the resin sheet tends to be weak, and if it exceeds 20 parts by weight, the heat resistance after curing the resin sheet tends to deteriorate.

The resin sheet of the present invention is used for the same applications as known prepregs. For example, a predetermined number of resin sheets are stacked, a metal foil is arranged on one or both sides thereof, and heated and pressed to produce a metal-clad laminate. Also,
A resin sheet is placed between the inner layer constituting material of the multilayer printed wiring board and the metal foil for the outer layer, and heated and pressed to manufacture a multilayer printed wiring board. As the metal foil, mainly copper foil or aluminum foil is used, but it is not limited to this.
Other metal foils can be used. There is also no particular limitation on the thickness of the metal foil, and a metal foil having a thickness of 5 to 200 μm, which is usually used for a laminate, can be used. The conditions for manufacturing a metal-clad laminate or a multilayer printed wiring board, that is, the heating temperature, and the pressure of pressurization differ depending on the thermosetting resin particles used for the resin sheet, and the thermosetting resin particles It is necessary to select an appropriate condition according to the type of.

[0019]

Example 1 A polyimide fiber having a fiber diameter of 15 μm and a fiber length of 5 mm was dispersed in water so that the fiber concentration became 0.4% by weight. Bisphenol A type epoxy resin (Epicoat E5048 (trade name) manufactured by Yuka Shell Epoxy Co., Ltd.) 1
00 parts by weight, 15 parts by weight of a phenol novolak resin (made by Dainippon Ink and Chemicals, Inc., using phenolite TD-2131 (trade name)), and 0.15 parts by weight of 2-phenylimidazole were mixed and pulverized to obtain a granule. 10-90μ in diameter
m, powder was added to water in which the polyimide fiber was dispersed, mixed and dispersed to prepare a slurry. A sheet was formed from this slurry such that the rice tsubo was 80 g / m ² . The ratio of the polyimide fiber and the resin component containing thermosetting resin particles (hereinafter, referred to as thermosetting resin particles) was 2 in the weight ratio of the polyimide fiber 2 and the thermosetting resin component 7 in the sheet formed. .

On this sheet, a thermosetting acrylic resin emulsion (HTR-600L, manufactured by Teikoku Chemical Industry Co., Ltd.)
B (trade name), 10 parts by weight of melamine resin (trade name, Melan X66 (trade name), manufactured by Hitachi Chemical Co., Ltd.), and 0.1 part of p-toluenesulfonic acid.
A curable binder resin blended in a ratio of 3 parts by weight was applied by a spray method so that the weight after drying was 7% by weight, and heated and dried at 120 ° C. for 40 seconds to prepare a resin sheet. The thickness of the resin sheet was 173 μm.

Two sheets of the obtained resin sheet are stacked, and copper foil having a thickness of 18 μm is stacked on both sides thereof at a temperature of 170 ° C. and a pressure of 3 ° C.
Heating and pressing at 90 MPa for 90 minutes, the thickness of the insulating base material layer is 10
A 0 μm double-sided copper-clad laminate was obtained. The copper foil on the surface was removed by etching into a hole shape having a diameter of 0.2 mm, and using the copper foil as a mask, a carbon dioxide laser drilling machine (NLC-1B21 (trade name) manufactured by Hitachi Seiko Co., Ltd.) was used. When laser drilling was performed with a pulse width of 20 μs, a hole having a diameter of 0.2 mm could be drilled through with three shots. A glass cloth base epoxy resin double-sided copper-clad laminate having a thickness of 0.6 mm and a copper foil thickness of 18 μm (manufactured by Hitachi Chemical Co., Ltd., MCL-E-67)
(Using trade name)), the resin sheets obtained above are stacked one by one on both sides of an inner layer constituting material obtained by forming a conductor pattern, and a copper foil having a thickness of 18 μm is arranged on the outside thereof. Then, it was heated and pressed at a temperature of 170 ° C. and a pressure of 3 MPa for 90 minutes to obtain a four-layer printed wiring board. The thickness of the insulating base layer between the conductor pattern of the inner layer component and the copper foil of the surface component is
It was 47 μm. The copper foil on the surface is removed by etching into a hole shape having a diameter of 0.2 mm, and the copper foil is used as a mask, and the pulse width is 10 mm by the same laser drilling machine as described above.
When laser drilling was performed in μs, a hole having a diameter of 0.2 mm was able to be drilled in two shots by penetrating the insulating base material layer on the conductor pattern of the inner layer constituting material.

Example 2 In addition to changing the polyimide fiber to a polyparaphenylene sulfide (PPS) fiber having a fiber diameter of 20 μm and a fiber length of 6 mm, a sheet was formed so that the rice tsubo became 90 g / m ^2. A sheet was formed in the same manner as in Example 1. In the sheet thus produced, the ratio of the PPS fiber to the thermosetting resin was 2 in terms of the weight ratio of the PPS fiber and the thermosetting resin.

The same curable binder resin as in Example 1 was applied to this sheet by a spray method so that the weight after drying was 8% by weight, and heated and dried at 120 ° C. for 43 seconds to prepare a resin sheet. . The thickness of the resin sheet is 186μm
Met.

Thereafter, a double-sided copper-clad laminate having a thickness of 140 μm was obtained in the same manner as in Example 1. This double-sided copper-clad laminate was drilled with the same laser drilling machine as in Example 1 at a pulse width of 30 μs. As a result, a hole having a diameter of 0.2 mm could be drilled through three shots. When a four-layer printed wiring board was produced in the same manner as in Example 1, the thickness of the insulating base layer between the conductor pattern of the inner layer component and the copper foil as the surface component was 65%.
μm. The copper foil on the surface was removed by etching, and the pulse width was 2 using the same laser drilling machine as in Example 1.
When laser drilling was performed at 0 μs, a hole having a diameter of 0.15 mm was able to be drilled in two shots by penetrating the insulating base material layer on the conductor pattern of the inner layer constituting material.

Example 3 An aramid fiber having a fiber diameter of 12 μm and a fiber length of 3 mm and a small-diameter E glass fiber having a fiber diameter of 1.8 μm and a fiber length of 6 mm were mixed by an equal weight, and the concentration of the mixed fiber was 0.4% by weight. And dispersed in water. 100 parts by weight of bisphenol A novolak epoxy resin (Epiclon N-865 (trade name) manufactured by Dainippon Ink and Chemicals, Inc.), modified phenol novolak resin (Phenolite VH-4170 manufactured by Dainippon Ink and Chemicals, Inc.) (Use the product name)
45 parts by weight, 30 parts by weight of tetrabromobisphenol A and 0.3 part by weight of undecylimidazole are mixed and pulverized to obtain a powder having a particle size of 10 to 60 μm. The mixed fiber is added to water, mixed, and dispersed. A slurry was prepared. A sheet was formed from this slurry so that the rice tsubo was 70 g / m ² . The ratio of the mixed fiber and the thermosetting resin in the sheet thus formed was 3 in the mixed fiber and 7 in the thermosetting resin in weight ratio.

The same curable binder resin as in Example 1 was applied to this sheet by a spray method so that the weight after drying was 8% by weight, and was heated and dried at 120 ° C. for 30 seconds to produce a resin sheet. . The thickness of the resin sheet is 168 μm
Met.

Thereafter, a double-sided copper-clad laminate having a thickness of 85 μm was obtained in the same manner as in Example 1. This double-sided copper-clad laminate was drilled with the same laser drilling machine as in Example 1 with a pulse width of 20 μs. As a result, a hole having a diameter of 0.2 mm could be drilled with four shots. When a four-layer printed wiring board was produced in the same manner as in Example 1, the thickness of the insulating base layer between the conductor pattern of the inner layer component and the copper foil as the surface component was 39 μm.
m. The copper foil on the surface is removed by etching,
Pulse width of 20 μm using the same laser drilling machine as in Example 1.
When the laser drilling process was performed in s, a hole having a diameter of 0.10 mm was able to be drilled in two shots by penetrating the insulating base material layer on the conductor pattern of the inner layer constituting material.

Example 4 The mixed fiber was changed to a mixed fiber obtained by mixing equal weights of 20 μm fiber diameter, 10 mm fiber length tetrafluoroethylene fiber and 6 μm fiber diameter, 6 mm small fiber E glass fiber in equal weight. A sheet was formed in the same manner as in Example 3, except that the sheet was formed so that the basis weight was 97 g / m ² . In the sheet, the ratio of the mixed fiber to the thermosetting resin component was 2 by the mixed fiber and the thermosetting resin component was 7 by weight.

The same curable binder resin as in Example 1 was applied to this sheet by a spray method so that the weight after drying was 6% by weight, and was heated and dried at 120 ° C. for 40 seconds to produce a resin sheet. . The thickness of the resin sheet is 200 μm
Met.

Thereafter, a double-sided copper-clad laminate having a thickness of 180 μm was obtained in the same manner as in Example 1. This double-sided copper-clad laminate was drilled with the same laser drilling machine as in Example 1 with a pulse width of 30 μs. As a result, a hole having a diameter of 0.2 mm could be drilled through 8 shots. When a four-layer printed wiring board was manufactured in the same manner as in Example 1, the thickness of the insulating base layer between the conductor pattern of the inner layer component and the copper foil as the surface component was 82%.
μm. The copper foil on the surface was removed by etching, and a pulse width of 3 using the same laser drilling machine as in Example 1.
When laser drilling was performed at 0 μs, a hole having a diameter of 0.10 mm was able to be drilled through three shots through the insulating base material layer on the conductor pattern of the inner layer constituting material.

Comparative Example 1 A polyimide fiber was prepared by mixing a small-diameter E glass fiber having a fiber diameter of 1.8 μm and a fiber length of 6 mm with an E glass fiber having a fiber diameter of 9 μm and a fiber length of 10 mm.
The glass fiber was changed to glass mixed fiber (polyimide fiber 25, glass fiber 75 in weight ratio), and the rice tsubo was 75 g / m ^2.
The sheet was formed in the same manner as in Example 1 except that the sheet was formed in such a manner that The ratio of the mixed fiber and the thermosetting resin particles in the sheet made was 3 by the glass mixed fiber and 7 by the thermosetting resin particles by weight.

The same curable binder resin as in Example 1 was applied to this sheet by a spray method so that the weight after drying was 5% by weight, and heated and dried at 120 ° C. for 40 seconds to prepare a resin sheet. . The thickness of the resin sheet is 220 μm
Met.

Thereafter, a double-sided copper-clad laminate having an insulating substrate layer thickness of 85 μm was obtained in the same manner as in Example 1. For this double-sided copper-clad laminate, drilling was performed with the same laser drilling machine as in Example 1 with a pulse width of 20 μs. However, drilling was not possible with 6 shots, and a glass ball formed by melting glass on the hole wall surface was seen. Was done. When a four-layer printed wiring board was prepared in the same manner as in Example 1, the thickness of the insulating base layer between the conductor pattern of the inner layer component and the copper foil as the surface component was 42 μm. there were. Copper foil on the surface has a diameter of 0.2
The hole was removed by etching into a hole shape of mm, and laser drilling was performed with the same laser drilling machine as in Example 1 using a copper foil as a mask and a pulse width of 20 μs. Glass beads formed by melting were seen.

Comparative Example 2 Bisphenol A epoxy resin (Epicoat E5048 (trade name) manufactured by Yuka Shell Epoxy Co., Ltd.)
100 parts by weight, phenol novolak resin (Denippon Ink and Chemicals, Inc., phenolite TD-2131)
(Using trade name) 15 parts by weight and 0.15 parts by weight of 2-phenylimidazole were mixed with a mixed solvent of methyl ethyl ketone and ethylene glycol monomethyl ether (1 by weight ratio).
0: 1) to prepare a varnish having a resin solid content of 60% by weight. This varnish was applied to a glass cloth (M
(IL type 1080 type) and dried in a dryer at 170 ° C. for 3 minutes to obtain a prepreg having a resin content of 64% by weight. When the thickness of the obtained prepreg was measured, it was 82 μm.
m.

Two sheets of the obtained prepreg were stacked, and copper foil having a thickness of 18 μm was stacked on both sides thereof at a temperature of 170 ° C. and a pressure of 3 ° C.
By heating and pressurizing at 90 MPa for 90 minutes, the thickness of the insulating base material layer becomes 12
A 5 μm double-sided copper-clad laminate was obtained. The copper foil on the surface was removed by etching into a hole shape having a diameter of 0.2 mm, and laser drilling was performed with a pulse width of 50 μs using the copper foil as a mask by the same laser drilling machine as in Example 1. Could not drill. A four-layer printed wiring board was prepared in the same manner as in Example 1, except that the obtained prepreg was used in place of the resin sheet.
The thickness of the insulating base layer between the conductor pattern of the inner layer component and the copper foil as the surface component was 68 μm. The copper foil on the surface was removed by etching, and laser drilling was performed using the same laser drilling machine as in Example 1 with a pulse width of 50 μs. However, drilling was not possible even with 5 shots.

[0036]

The resin sheet according to the first aspect of the present invention is a resin sheet capable of forming an insulating base material layer that is easily drilled by a laser. In addition, the resin sheet according to the second aspect of the present invention is a resin sheet in which the thermosetting resin particles are well fixed when the resin sheet is manufactured. The metal-clad laminate according to the third aspect of the present invention and the multilayer printed wiring board according to the fourth aspect of the present invention can be easily drilled by a laser.

Claims (4)

[Claims] 1. A resin sheet in which uncured thermosetting resin particles which are solid at normal temperature are dispersed between fibers having an organic fiber formed as a nonwoven fabric by a curable binder resin as an essential component. 2. The resin sheet according to claim 1, further comprising 5 to 70 parts by weight of glass fibers having a fiber diameter of 10 μm or less based on 100 parts by weight of the total fibers in addition to the organic fibers. 3. A metal-clad laminate comprising an insulating base material layer made of a cured product of the resin sheet according to claim 1 or 2. 4. A multilayer printed wiring board obtained by laminating and integrating the resin sheet according to claim 1 or 2 as an adhesive material for a constituent material.