JPH11266082A - Multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board with which a through-hole and a via hole are assured of connection reliability in restraining a filler from shrinking on curing. SOLUTION: Interlayer resin insulating layers and conductor layers are alternately laminated on a board provided with a conductor layer, and inner and outer conductor layers are mutually connected through via holes to form a build-up wiring layer for the formation of a multilayer printed wiring board, wherein a through-hole is provided to the board to electrically connect the front and rear of the boards together, a non-conductive filler which contains metal particles is filled into the through-hole, and a conductor layer is formed on the exposed surface of the filler in the through-hole. It is preferable that the filler be composed of metal particles, resin, and inorganic fine powder and has 1 MΩ.cm or above in resistivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board, and more particularly, to a multilayer printed wiring board which suppresses curing shrinkage of a filler to secure connection reliability between a through hole and a via hole.

[0002]

2. Description of the Related Art In recent years, a package substrate on which an IC chip is mounted has been required to have a high density and high reliability by a fine pattern in response to the miniaturization or high speed of electronic equipment accompanying the progress of the electronics industry. I have.

As such a package substrate, for example, Japanese Patent Application Laid-Open No. 5-243728 discloses a package substrate in which a conductive paste is filled in a plated through hole and a conductive layer covering the conductive paste is formed.

[0004]

However, in the above-described package substrate according to the prior art, since a conductive paste is used, it is necessary to cure and shrink the resin to generate conductivity. Therefore, in such a package substrate,
Gap due to curing shrinkage of the filler is likely to occur between the conductive paste and the conductor on the inner wall of the through-hole, and when exposed to high temperature and high humidity conditions, the conductive layer covering the conductive paste may peel off, or the through-hole and the via may be removed. A problem such as disconnection between the holes occurred.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a printed wiring board which suppresses curing shrinkage of a filler and secures connection reliability between a through hole and a via hole.

[0006]

Means for Solving the Problems The inventors of the present invention have intensively studied for realizing the above-mentioned object, and as a result, have arrived at an invention having the following contents as the gist. (1) A multilayer printed wiring board according to the present invention has a build-up wiring layer in which an interlayer resin insulating layer and a conductive layer are alternately laminated on a substrate having a conductive layer and inner and outer conductive layers are connected to each other via holes. In the multilayer printed wiring board in which is formed, the substrate is formed with a through hole for electrically connecting the front surface and the back surface, and the through hole is filled with a non-conductive filler containing metal particles, Furthermore, a conductive layer is formed to cover the exposed surface of the filler from the through hole.

[0007] In the above multilayer printed wiring board,
Via holes are preferably connected to the conductor layer covering the filler, and the filler is preferably made of metal particles, a resin, and an inorganic ultrafine powder having an average particle size of preferably 1 to 1000 nm. The filler has a specific resistance of 1 MΩ · cm or more, more preferably 1 × 10 ⁸ Ω · cm or more, and the metal particles have an average particle diameter of 0.1 to 30 μm.
It is preferred that

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In such a multilayer printed wiring board of the present invention, a filler containing metal particles is used as a material for filling a through hole. Excellent adhesion and non-conductive fillers are used, so there is no need to impart hardening shrinkage to impart conductivity to the fillers containing metal particles. Peeling can be prevented. If such peeling is present, water accumulates under high-temperature and high-humidity conditions, and when the water evaporates, the conductor layer is pushed up and peeled.

Particularly, in the present invention, it is desirable to use, as the filler, a composition comprising metal particles, a resin, and an inorganic ultrafine powder having an average particle size of preferably 1 to 1000 nm (more preferably 2 to 100 nm). The reason is that the network structure formed by the intermolecular force of the inorganic ultrafine powder traps metal particles, and the metal particles do not settle. For this reason, the metal particles protrude from the surface of the filler, and the metal particles and the conductor layer covering the metal particles are integrated to improve the adhesion. This prevents separation between the filler and the through-hole conductor layer, and prevents separation between the filler and the conductor layer covering the filler even under high-temperature and high-humidity conditions.

Here, as the metal particles constituting the filler, copper, gold, silver, aluminum, nickel, titanium, chromium, tin / lead, palladium and the like can be used.
The metal particles may be provided with a metal surface modifier such as a complexing agent on the surface thereof in order to improve the adhesion to the resin. The metal particles preferably have an average particle size of 0.1 to 30 μm. The reason for this is that the adhesiveness with the conductor layer covering the filler can be ensured. Also,
The mixing amount of the metal particles is 30% based on the total solid content of the filler.
It is desirable to set it to 90% by weight. The reason for this is that the adhesiveness and printability can be simultaneously secured.

As the matrix resin constituting the filler, a thermosetting resin or a thermoplastic resin can be used. As the thermosetting resin, at least one resin selected from an epoxy resin, a polyimide resin, and a phenol resin is preferable. As the thermoplastic resin, a fluororesin such as polytetrafluoroethylene (PTFE), tetrafluoroethylene hexafluoropropylene copolymer (FEP), and tetrafluoroethylene perfluoroalkoxy copolymer (PFA), polyethylene terephthalate ( PET),
Polysulfone (PSF), polyphenylene sulfide (PPS), thermoplastic polyphenylene ether (PP
E), polyethersulfone (PES), polyetherimide (PEI), polyphenylene sulfone (PP
ES), polyethylene naphthalate (PEN), polyether ether ketone (PEEK), and at least one selected from polyolefin resins.

In particular, as the optimum resin used for the filler, at least one selected from bisphenol type epoxy resin and novolak type epoxy resin is preferable. The reason for this is that bisphenol type epoxy resin has A
The viscosity can be adjusted without using a diluting solvent by appropriately selecting the resin such as mold and F-type. Novolak-type epoxy resin has high strength, excellent heat resistance and chemical resistance, This is because it does not decompose even in a strongly basic solution such as described above, and does not thermally decompose. As the bisphenol-type epoxy resin, it is desirable to use at least one selected from a bisphenol A-type epoxy resin and a bisphenol F-type epoxy resin. Among them, bisphenol F type epoxy resin is advantageous because it can be used with low viscosity and without solvent. As the novolak type epoxy resin, it is desirable to use at least one selected from a phenol novolak type epoxy resin and a cresol novolak type epoxy resin. When a novolak type epoxy resin and a bisphenol type epoxy resin are blended and used among such resins, the blending ratio is desirably 1/1 to 1/100 by weight. The reason for this is that the sedimentation of metal particles can be prevented while suppressing an increase in viscosity.

It is desirable to use silica, alumina, silicon carbide, or mullite as the inorganic ultrafine particles constituting the filler. Among them, silica is most suitable. The average particle size of the inorganic ultrafine particles is 1 to 1000 nm, more preferably 2 to 1000 nm.
100100 nm. The reason for this is that, since the particle diameter is fine, it is possible to form a network assumed to be a hydrogen bond without impairing the filling property of the through hole and to trap particulate matter. The amount of the inorganic ultrafine powder is 0.1 to 5% by weight based on the total solid content of the filler.
It is desirable that The reason for this is that curing shrinkage can be prevented without impairing the filling property.

The curing agent used in such a resin composition is preferably an imidazole curing agent, an acid anhydride curing agent, or an amine curing agent. This is because curing shrinkage is small. By suppressing the curing shrinkage, the filler can be integrated with the conductor layer covering the filler to improve the adhesion.

The resin composition before curing is as follows:
If necessary, it can be diluted with a solvent. Examples of the solvent include NMP (normal methylpyrrolidone), DMD
G (diethylene glycol dimethyl ether), glycerin, water, 1- or 2- or 3-cyclohexanol, cyclohexanone, methylcellosolve, methylcellosolve acetate, methanol, ethanol, butanol, propanol and the like.

In the present invention, the specific resistance of the filler is set to 10 ⁶ Ω ·
cm or more, more preferably 10 ⁸ Ω · cm or more, and non-conductive. The reason for this is that when the filler is made conductive, when the resin composition is cured and then polished, polishing debris adheres between the conductor circuits and causes a short circuit. Further, the resin composition needs to be cured and shrunk in order to impart conductivity, but it is not preferable that the resin composition is cured and shrunk, since it causes peeling from the conductor layer covering the filler.

In the present invention, the via hole may be connected to the conductor layer covering the through hole and the filler.
The reason for this is that dead space due to through holes can be eliminated.

In the present invention, in order to increase the wiring density,
It is desirable that a conductor layer be formed on the inner layer of the substrate.
At this time, the substrate is formed by alternately laminating conductor layers and prepregs. For example, the substrate is formed by alternately laminating a prepreg made of glass fiber or aramid fiber cloth or non-woven fabric with a resin and impregnating the resin into a B stage with a copper foil or a circuit board, and heat-pressing and integrating them. .

In the present invention, it is preferable that a roughened layer is formed on the inner wall conductor surface of the through hole filled with the filler. The reason for this is that the filler and the through hole are in close contact with each other via the roughened layer, and no gap is generated. If there is a gap between the filler and the through-hole, the conductor layer formed by electrolytic plating directly above it will not be flat, or the air in the gap will thermally expand, causing cracks and peeling. Or cause water to accumulate in the voids, causing migration or cracks.
In this regard, the formation of the roughened layer can prevent such defects from occurring.

In the present invention, it is advantageous that a roughened layer similar to the roughened layer formed on the conductor surface on the inner wall of the through hole is formed on the surface of the conductor layer covering the filler. The reason for this is that the roughened layer can improve the adhesion to the interlayer resin insulating layer and via holes.
In particular, if the roughened layer is formed on the side surface of the conductor layer, cracks generated toward the interlayer resin insulation layer starting from the interface due to insufficient adhesion between the conductor layer side surface and the interlayer resin insulation layer can be suppressed. Can be.

The thickness of the roughened layer formed on the inner wall of the through hole or the surface of the conductor layer is preferably 0.1 to 10 μm.
The reason for this is that if it is too thick, it causes interlayer short-circuit, and if it is too thin, the adhesion to the adherend decreases. The roughened layer is formed by subjecting the conductor on the inner wall of the through hole or the surface of the conductor layer to an oxidation (blackening) -reduction treatment, or a treatment formed with a mixed aqueous solution of an organic acid and a cupric complex. Alternatively, a material formed by plating a copper-nickel-phosphorus needle-like alloy is preferable.

Among these treatments, in the method by oxidation (blackening) -reduction treatment, NaOH (20 g / l), NaClO ₂ (50 g
/ L), Na ₃ PO ₄ (15.0 g / l) in an oxidation bath (blackening bath), Na
OH (2.7 g / l) and NaBH ₄ (1.0 g / l) are used as the reducing bath.

In the treatment using an aqueous solution of an organic acid-cupric acid complex, a metal foil such as copper, which is a conductive circuit, is dissolved under the coexistence conditions of oxygen such as spraying and bubbling as follows. Cu + Cu (II) A _n → 2Cu (I) A _{n / 2} 2Cu (I) A _{n / 2} + n / 4O ₂ + nAH (aeration) → 2Cu (II) A _n + n / 2H ₂ O A is a complexing agent (chelate) N acts as a coordination number.

The cupric complex used in this treatment is preferably an azole cupric complex. The cupric complex of azoles acts as an oxidizing agent for oxidizing metallic copper and the like. As the azoles, diazole, triazole,
Tetrazole is preferred. Among them, imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole and the like are preferable. The content of the cupric complex of azoles is preferably 1 to 15% by weight.
This is because, when it is in this range, solubility and stability are excellent.

The organic acid is added to dissolve copper oxide. Specific examples include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, acrylic acid, crotonic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, benzoic acid, glycolic acid, lactic acid, apple At least one selected from acids and sulfamic acids is preferred. The content of this organic acid is 0.1-30
% By weight is good. This is for maintaining the solubility of the oxidized copper and ensuring the solubility stability. The generated cuprous complex dissolves under the action of an acid and combines with oxygen to form a cupric complex, which again contributes to copper oxidation. Further, in addition to the organic acid, an inorganic acid such as borofluoric acid, hydrochloric acid, and sulfuric acid may be added.

In order to assist the dissolution of copper and the oxidizing action of azoles, a halogen ion, for example, a fluorine ion, a chlorine ion or a bromine ion is added to the etching solution comprising the organic acid-cupric complex. Is also good. The halogen ions can be supplied by adding hydrochloric acid, sodium chloride, or the like. The amount of halogen ions is preferably 0.01 to 20% by weight. This is because if it is within this range, the formed roughened layer has excellent adhesion to the interlayer resin insulating layer.

The etching solution comprising the organic acid-cupric complex is prepared by dissolving a cupric complex of an azole and an organic acid (halogen ion if necessary) in water.

In the plating of a needle-shaped alloy consisting of copper-nickel-phosphorus, copper sulfate 1-40 g / l, nickel sulfate 0.1-6.0 g / l, citric acid 10-20 g / l, hypophosphite 10-100 g / l, boric acid 10-40 g / l, surfactant
It is desirable to use a plating bath having a liquid composition of 0.01 to 10 g / l.

In the present invention, a thermosetting resin, a thermoplastic resin, or a composite of a thermosetting resin and a thermoplastic resin can be used as the interlayer resin insulating layer used in the build-up wiring layer. As the thermosetting resin, an epoxy resin, a polyimide resin, a phenol resin, a thermosetting polyphenylene ether (PPE), or the like can be used.
As the thermoplastic resin, a fluororesin such as polytetrafluoroethylene (PTFE), tetrafluoroethylene hexafluoropropylene copolymer (FEP), and tetrafluoroethylene perfluoroalkoxy copolymer (PFA), polyethylene terephthalate ( PET), polysulfone (PS)
F), polyphenylene sulfide (PPS), thermoplastic polyphenylene ether (PPE), polyether sulfone (PES), polyetherimide (PEI), polyphenylene sulfone (PPES), polyethylene naphthalate (PEN), polyether ether ketone ( PEEK), polyolefin resins, and the like. As a composite of a thermosetting resin and a thermoplastic resin, epoxy resin-PES, epoxy resin-PSF, epoxy resin-PPS, epoxy resin-PPES, or the like can be used.

In the present invention, a glass cloth impregnated resin composite can be used as the interlayer resin insulating layer. As the glass cloth impregnated resin composite, glass cloth impregnated epoxy, glass cloth impregnated bismaleimide triazine,
Glass cloth impregnated PTFE, glass cloth impregnated PPE,
Examples include glass cloth impregnated polyimide.

In the present invention, an adhesive for electroless plating can be used as the interlayer resin insulating layer. As the adhesive for electroless plating, heat-resistant resin particles that are soluble in a cured acid or oxidizing agent are dispersed in an uncured heat-resistant resin that becomes hardly soluble in an acid or an oxidizing agent by the curing treatment. Is best. The reason for this is that by treating with an acid or an oxidizing agent, the heat-resistant resin particles are dissolved and removed, and a roughened surface composed of an octopus pot-shaped anchor can be formed on the surface. The depth of the roughened surface is 0.01
~ 20 µm is preferred. This is to ensure adhesion. Also,
In the semi-additive process, the thickness is preferably 0.1 to 5 μm. This is because the electroless plating film can be removed while ensuring adhesion.

In the above-mentioned adhesive for electroless plating, the heat-resistant resin particles which have been particularly hardened include a heat-resistant resin powder having an average particle diameter of 10 μm or less, and an average particle diameter of 2 μm.
Aggregated particles obtained by aggregating the following heat-resistant resin powder, a mixture of a heat-resistant resin powder having an average particle size of 2 to 10 μm and a heat-resistant resin powder having an average particle size of 2 μm or less, and an average particle size of 2 to 10 μm
m, a pseudo particle obtained by adhering at least one of a heat-resistant resin powder or an inorganic powder having an average particle diameter of 2 μm or less to the surface of the heat-resistant resin powder having an average particle diameter of 0.1 to 0.8 μm.
m heat resistant resin powder and average particle size exceeding 0.8 μm and 2 μm
Mixture with heat-resistant resin powder of less than 0.1, average particle size 0.1 ~
It is desirable to use at least one selected from heat-resistant resin powder of 1.0 μm. This is because they can form more complex anchors. As the heat-resistant resin used in the adhesive for electroless plating, the above-mentioned thermosetting resin, thermoplastic resin, or a composite of the thermosetting resin and the thermoplastic resin can be used.

In the present invention, the conductive layer formed on the substrate (including the one covering the filler filled in the through hole) and the conductive circuit formed on the interlayer resin insulating layer are connected by a via hole. Can be. In this case, the via hole is preferably filled with a plating film or a conductive paste.

Next, the method for producing the multilayer printed wiring board of the present invention will be specifically described by way of an example. The method described below relates to a method of manufacturing a multilayer printed wiring board by a semi-additive method, but the method of manufacturing a multilayer printed wiring board in the present invention employs a full additive method, a multi-lamination method, and a pin lamination method. can do.

(1) First, a through hole is drilled in the substrate with a drill,
Electroless plating is performed on the substrate surface including the inner wall surface of the through hole to form a through hole. As the substrate, a resin substrate such as a glass epoxy substrate, a polyimide substrate, a bismaleimide-triazine resin substrate, a fluororesin substrate, or a copper-clad laminate of these resins, a ceramic substrate, a metal substrate, or the like can be used. In particular, when the dielectric constant is considered, it is preferable to use a double-sided copper-clad fluororesin (polytetrafluoroethylene or the like) substrate. This substrate is obtained by thermocompression bonding copper foil having one surface roughened to a fluororesin substrate. Copper plating is preferred as the electroless plating. For substrates with poor plating coverage, such as fluororesin substrates,
Pretreatment liquid consisting of organic acid, etc. (trade name: Tetra etch)
And surface modification such as plasma treatment.

(2) Next, electrolytic plating is performed for thickening. Copper plating is preferable as the electrolytic plating. Further, a roughening layer may be provided by roughening the inner wall of the through hole and the surface of the electrolytic plating film. The roughened layer may be formed by oxidation (blackening) -reduction treatment, formed by spraying (etching) a mixed aqueous solution of an organic acid and a cupric complex, or a copper-nickel-phosphorus needle-like alloy. Some are by plating.

When a roughened layer is formed by electroless plating in these treatments, the copper ion concentration, nickel ion concentration and hypophosphite ion concentration are each 2.2 × 10 4
^{-2 to} 4.1 × 10 ^-2 mol / l, 2.2 × 10 ^{-3 to} 4.1 × 10 ^-3 mol
/ L, an aqueous plating solution having a composition of 0.20 to 0.25 mol / l is desirably used. This is because the crystal structure of the film deposited in this range has a needle-like structure and is excellent in anchor effect. To this aqueous electroless plating solution, a complexing agent or an additive may be added in addition to the above compounds. In addition, 0.01 to 10 g / l
May be added. Examples of the surfactant include Surfynol 440 and 46 manufactured by Nissin Chemical Industry.
It is desirable to use an acetylene-containing polyoxyethylene surfactant such as 5,485. That is, when a roughened layer is formed by electroless plating, copper sulfate 1 to 40 g / l,
Nickel sulfate 0.1-6.0 g / l, citric acid 10-20 g /
l, hypophosphite 10-100 g / l, boric acid 10-40 g /
It is desirable to use an aqueous plating solution having a solution composition of 0.01 to 10 g / l of a surfactant.

When a roughened layer is formed by oxidation-reduction treatment, NaOH (20 g / l), NaClO ₂ (50 g / l), Na ₃ PO
₄ (15.0 g / l) as oxidation bath, NaOH (2.7 g / l), N
Preferably, aBH ₄ (1.0 g / l) is used as the reducing bath.

In the case where a roughened layer is formed by etching using a mixed aqueous solution of an organic acid and a cupric complex, a CZ8100 solution manufactured by Mec Co., Ltd. is typically used.
The copper surface is made uneven using the oxidizing power of copper.

The roughened layer may be covered with a layer of a metal or a noble metal having an ionization tendency larger than copper and equal to or smaller than titanium. The reason for this is that the metal or noble metal layer covers the roughened layer and prevents local electrode reaction of the conductor circuit when roughening the interlayer insulating layer, thereby preventing the conductor circuit from melting. . The thickness of this layer is preferably 0.01 to 2 μm. Such metals include titanium, aluminum,
There is at least one selected from zinc, iron, indium, thallium, cobalt, nickel, tin, lead and bismuth. The noble metals include gold, silver, platinum and palladium. Among them, tin is advantageous because it can form a thin layer by electroless displacement plating and can follow a roughened layer. In the case of tin, tin borofluoride-thiourea or tin chloride-thiourea solution is used, and the substitution reaction of Cu-Sn is performed.
A Sn layer of about 0.01 to 2 μm is formed. On the other hand, in the case of a noble metal, a method such as sputtering or vapor deposition is adopted.

(3) Next, the filler having the above-described structure is filled in the through holes. Specifically, the filler is placed on a substrate on which a mask having an opening in a through-hole portion is placed.
It is filled in the through hole by applying by a printing method, and after filling, it is dried and cured. The curing conditions are 50
It is desirable that the heating time is 0.5 to 5 hours at 160 ° C.

Further, the filler protruding from the through holes and the roughened layer on the surface of the electrolytic plating film of the substrate are removed by polishing to flatten the substrate surface. This polishing is preferably performed by a belt sander or buff polishing. As a result of this polishing, a part of the metal particles is exposed on the surface, and the metal particles in the exposed portion are integrated with the plating film of the conductor layer, thereby exhibiting good adhesion.

(4) After providing a catalyst nucleus on the surface of the substrate flattened in the above (3), electroless plating is performed to a thickness of 0.1 to 5 mm.
An electroless plating film having a thickness of about μm is formed, and further, if necessary, electrolytic plating is performed to provide an electrolytic plating film having a thickness of 5 to 25 μm. Next, a photosensitive dry film is laminated on the surface of the plating film by a hot press, a photomask film (preferably made of glass) on which a pattern is drawn is placed, exposed, and developed with a developer. An etching resist is provided. Then, the conductor in the portion where the etching resist is not formed is dissolved and removed with an etching solution to form a conductor layer portion covering the conductor circuit portion and the filler. As the etchant, an aqueous solution of sulfuric acid-hydrogen peroxide, an aqueous solution of persulfate such as ammonium persulfate, sodium persulfate, or potassium persulfate, or an aqueous solution of ferric chloride or cupric chloride is preferable.

(5) Then, after the etching resist is peeled off to form independent conductor circuits and conductor layers, a roughened layer is formed on the surfaces of the conductor circuits and conductor layers. If a roughened layer is formed on the surface of the conductor layer covering the conductor circuit and the filler, the conductor has excellent adhesion to the interlayer resin insulation layer, so that the side of the conductor layer covering the conductor circuit and the filler and the resin insulation layer No crack originating from the interface with the metal. On the other hand, the adhesion of the conductor layer covering the filler to via holes that are electrically connected is improved. The method of forming the roughened layer is as described above, and includes a method of forming by oxidation (blackening) -reduction treatment, acicular alloy plating, or etching. Further, after the roughening, a resin may be filled between the conductor circuits, and the surface may be polished and smoothed. In this case, it is desirable to roughen the surface of the conductor circuit after polishing. At this time, the filling resin includes a bisphenol F type epoxy resin, an imidazole curing agent, and an average particle diameter.
A composition comprising inorganic particles of 0.1 to 30 μm is preferred.

(6) An interlayer resin insulating layer is formed on the wiring board thus manufactured. As the interlayer resin insulating layer, a thermosetting resin, a thermoplastic resin, or a composite of a thermosetting resin and a thermoplastic resin can be used. In the present invention, the above-described adhesive for electroless plating can be used as the interlayer resin insulating material. The interlayer resin insulating layer is formed by applying an uncured liquid of these resins using a roll coater or a curtain coater, or by laminating a film-like resin by thermocompression bonding. In this state, the thickness of the interlayer resin insulation layer on the conductor circuit pattern is small, and the thickness of the interlayer resin insulation layer on the conductor circuit having a large area is large, and irregularities are often generated. It is desirable that the surface of the interlayer resin insulating layer be planarized by using a metal plate or a metal roll and pressing while heating.

(7) Next, an opening is provided in the interlayer resin insulating layer in order to secure electrical connection with a lower conductive circuit (through hole) covered by the interlayer resin insulating layer. The opening is formed by exposure and development when the interlayer resin insulating layer is made of a photosensitive resin, and is formed by laser light when the interlayer resin insulating layer is made of a thermosetting resin or a thermoplastic resin. At this time, the laser light used includes a carbon dioxide laser, an ultraviolet laser, an excimer laser, and the like. If holes are formed by laser light, desmearing may be performed. This desmear treatment can be performed using an oxidizing agent composed of an aqueous solution such as chromic acid or permanganate, or may be performed using oxygen plasma, a mixed gas plasma of oxygen and CF ₄ , or the like.

(8) The surface of the interlayer resin insulation layer in which the openings are formed is roughened as necessary. When the above-mentioned adhesive for electroless plating is used as an interlayer resin insulating layer, the surface of the insulating layer is treated with an acid or an oxidizing agent to selectively dissolve or decompose and remove only the heat-resistant resin particles to roughen. I do. As the acid,
There are phosphoric acid, hydrochloric acid, sulfuric acid, and organic acids such as formic acid and acetic acid, and it is particularly preferable to use organic acids. This is because when the roughening treatment is performed, the metal conductor layer exposed from the via hole is hardly corroded. As the oxidizing agent, it is desirable to use chromic acid or permanganate (such as potassium permanganate). Further, even when a thermosetting resin or a thermoplastic resin is used, a surface roughening treatment using an oxidizing agent selected from aqueous solutions such as chromic acid and permanganate is effective. In the case of a resin such as a fluororesin (eg, polytetrafluoroethylene) that is not roughened by an oxidizing agent, the surface is roughened by plasma treatment or tetraetch (metal naphthalene compound manufactured by Junko).

(9) Next, a catalyst nucleus for electroless plating is applied to the roughened surface of the interlayer resin insulating layer. Generally, the catalyst core is
It is a palladium-tin colloid, and the substrate is immersed in this solution, dried, and heat-treated to fix the catalyst core on the resin surface.
Further, a metal nucleus can be used as a catalyst nucleus by being driven into the resin surface by CVD, sputtering, or plasma. In this case, a metal nucleus is embedded in the resin surface, and plating is deposited around the metal nucleus to form a conductor circuit. Therefore, it is difficult to roughen the resin or fluorine resin (polytetrafluoroethylene or the like). Even if the resin has poor adhesion between the resin and the conductor circuit, the adhesion can be ensured. The metal nucleus is preferably at least one selected from palladium, silver, gold, platinum, titanium, copper and nickel.
The amount of metal nuclei is preferably 20 μg / cm ² or less. If the amount exceeds this amount, metal nuclei must be removed.

(10) Next, electroless plating is performed on the roughened surface of the interlayer resin insulating layer, and an electroless plated film is formed on the entire surface. The thickness of this electroless plating film is 0.1 to 5 μm, more preferably 0.5 to 3 μm. The electroless plating is preferably an electroless copper plating. As the plating solution, a conventional plating solution can be used. For example, 29 g / l copper sulfate, 25 g / l sodium carbonate, 140 g / l tartrate, 40 g / l sodium hydroxide, 37% formaldehyde 150 ml, A composition having a pH of 11.5 is preferred.

(11) A plating resist is formed on the electroless plating film formed in (10). As described above, the plating resist is formed by laminating a photosensitive resin film (dry film), exposing and developing.

(12) Further, electrolytic plating is applied to the portion where the plating resist is not formed, and the conductor circuit portion (including the via hole portion) is thickened. Here, it is preferable to use copper plating as the electrolytic plating, and its thickness is 5
3030 μm is preferred. In addition, it is desirable to form a so-called filled via by filling an electrolytic plating film in the via hole. This is because the flatness of the interlayer resin insulating layer can be ensured. Further, the via hole may include:
It may be formed directly above a through hole provided in the substrate. This is for higher density.

(13) After peeling off the plating resist, the electroless plating film under the plating resist is replaced with a mixed aqueous solution of sulfuric acid and hydrogen peroxide, sodium persulfate, ammonium persulfate, sodium persulfate and potassium persulfate. It is dissolved and removed with an etching solution such as a sulfate aqueous solution, an aqueous solution of ferric chloride or cupric chloride to form an independent conductor circuit (including via holes). Further, the palladium catalyst nuclei on the exposed roughened surface are dissolved and removed with chromic acid or the like.

(14) The above steps can be repeated on this substrate to provide a further upper layer conductive circuit.
Hereinafter, description will be made based on embodiments.

[0054]

[Electroless plating aqueous solution]

 EDTA 150 g / l Copper sulfate 20 g / l HCHO 30 ml / l NaOH 40 g / l α, α'-bipyridyl 80 mg / l PEG 0.1 g / l [Electroless plating conditions] 30 minutes at a liquid temperature of 70 ° C.

Then, electrolytic copper plating was performed under the following conditions to form an electrolytic copper plating film having a thickness of 15 μm (FIG. 1 (c)).
reference). [Electroplating aqueous solution] Sulfuric acid 180 g / l Copper sulfate 80 g / l Additive (manufactured by Atotech Japan, trade name: Capparaside GL) 1 ml / l [Electroplating conditions] Current density 1 A / dm ² hours 30 minutes Temperature Room temperature

(2) A substrate having a conductor (including through holes) formed of an electroless copper plating film and an electrolytic copper plating film formed on the entire surface is washed with water, dried, and then subjected to NaOH (20 g / l), NaCl
Redox using O ₂ (50 g / l) and Na ₃ PO ₄ (15.0 g / l) as an oxidation bath (blackening bath), NaOH (2.7 g / l), and NaBH ₄ (1.0 g / l) as a reduction bath A roughening layer 4 was provided on the entire surface of the conductor including the through hole 3 (see FIG. 1 (d)).

[Preparation of Filler for Through-hole] 3.5 parts by weight of cresol novolak type epoxy resin (manufactured by Yuka Shell, Epikote 152) 14.1 parts by weight of bisphenol F type epoxy resin (manufactured by Yuka Shell, Epicoat 807), average particle size 1.0 part by weight of ultrafine silica powder (Aerosil R202) having a diameter of 14 nm is kneaded with three rollers, and further, an imidazole curing agent (2E4MZ-CN, manufactured by Shikoku Chemicals) 1.2 parts by weight, average particle diameter
100 parts by weight of 15 μm copper powder was added and kneaded with three rollers, and the viscosity of the mixture was adjusted to 200 to 1000 Pa · s at 22 ± 1 ° C.
s was adjusted to s.

(3) Fill the prepared filler 5 with the through hole 3
Filled by screen printing into and dried, 80
Curing was carried out by heating for 1 hour at 100 ° C. and 100 ° C., respectively, and further for 1 hour at 150 ° C. Then, the filler 5 protruding from the roughened surface of the conductor upper surface and the through hole 3 is # 40
In order to remove the belt sander by using a belt sanding paper (manufactured by Sankyo Rikagaku Co., Ltd.), and to remove the scratches caused by the belt sanding, buffing is performed with alumina abrasive grains or SiC abrasive grains to flatten the substrate surface. (Fig. 1
(e).)

(4) A palladium catalyst (manufactured by Atotech) is applied to the substrate surface flattened in the above (3), and electroless copper plating is performed under the same conditions as in the above (1).
An electroless copper plating film 6 having a thickness of m was formed (see FIG. 1 (f)).

(5) Next, electrolytic copper plating is performed under the same conditions as in (1) above to form an electrolytic copper plating film 7 having a thickness of 15 μm. A portion serving as a conductor layer (circular through-hole land) 10 covering the filled filler 5 was formed.

(6) A commercially available photosensitive dry film is adhered to both sides of the substrate on which the portions to be the conductor circuits 9 and the conductor layers 10 are formed, a mask is placed, and exposure is performed at 100 mJ / cm ² .
Developed with 0.8% sodium carbonate solution, thickness 15μm
An etching resist 8 was formed (see FIG. 2A).

(7) The plating film in the portion where the etching resist 8 is not formed is dissolved and removed with an etching solution using a mixture of sulfuric acid and hydrogen peroxide, and the etching resist 8 is further stripped and removed with 5% KOH. And independent conductor circuit 9
Then, a conductor layer 10 covering the filler 5 was formed (see FIG. 2B). Further, the surface of the conductor including the side surfaces was subjected to oxidation-reduction treatment and roughened in the same manner as in (2) above.

[Preparation of resin filler] Bisphenol F type epoxy monomer (manufactured by Yuka Shell, molecular weight 310, YL983U) 100 parts by weight, silane coupling agent coated on the surface, average particle size 1.6 μm, Si
O ₂ spherical particles (manufactured by Admatech, CRS 1101-CE, where the maximum particle size is not more than the thickness (15 μm) of the inner layer copper pattern described below) 170 parts by weight, leveling agent (manufactured by San Nopco, Perenol S4) 1.5 The weight of the mixture is kneaded with three rolls and the viscosity of the mixture is 45,000 ~ at 23 ± 1 ° C.
Adjusted to 49,000cps. . Imidazole curing agent (2E4MZ-CN, manufactured by Shikoku Chemicals) 6.5
Parts by weight. These were mixed to prepare a resin filler 12a.

(8) The prepared resin filler 12a is applied to one surface of the substrate by screen printing to fill the space between the conductor circuits 9 or the conductor layers 10 and dried at 70 ° C. for 20 minutes. Similarly, the resin filler 12a was filled between the conductor circuits 9 or the conductor layers 10 and dried at 70 ° C. for 20 minutes. That is, in this step, the resin filler 12a is filled between the inner layer copper patterns.

(9) The surface of the inner copper patterns 9 and 10 is filled with a resin by polishing one side of the substrate after the processing of the above (8) with a belt sander using # 400 belt abrasive paper (manufactured by Sankyo Rikagaku). Polishing was performed so that the agent 12a did not remain, and then buffing was performed to remove scratches caused by the belt sander polishing. Such a series of polishing was similarly performed on the other surface of the substrate. Then, at 100 ° C for 1 hour, 120
C. for 3 hours, 150.degree. C. for 1 hour, and 180.degree. C. for 7 hours to cure the resin filler 12a.

Thus, the conductor circuit 9 or the conductor layer
The resin filler 12a and the conductor circuit 9 or the conductor layer 10 are smoothed by removing the surface layer portion of the resin filler 12a and the roughened layer 11 on the upper surface of the conductor circuit 9 or the conductor layer 10 filled between the resin filler 12a and the conductor filler 9a. A substrate was firmly adhered to the side surface of the substrate through the roughened layer 11. That is, by this step, the surface of the resin filler 12a and the surface of the inner layer copper pattern become flush with each other. Here, the filled resin has a Tg point of 155.6 ° C. and a linear thermal expansion coefficient of 44.5 ° C.
× 10 ^-6 / ° C.

(10) Next, the thickness of the Cu—Ni—P alloy on the surface of the conductor layer 10 covering the surfaces of the conductor circuit 9 and the filler 5
A roughened layer (uneven layer) 11 having a thickness of 2.5 μm was formed, and a Sn layer having a thickness of 0.3 μm was formed on the surface of the roughened layer 11 (FIG. 2).
(See (c), Sn layer not shown). The formation method is as follows. That is, the substrate was acid-degreased and soft-etched, and then treated with a catalyst solution comprising palladium chloride and an organic acid to provide a Pd catalyst. After activating this catalyst, copper sulfate 8 g / l, nickel sulfate 0.6g /
l, citric acid 15 g / l, sodium hypophosphite 29 g /
1, boric acid 31 g / l, surfactant 0.1 g / l, pH = 9
A 2.5μm thick roughened layer made of Cu-Ni-P alloy on the surface of copper conductor circuit
11 formed. Furthermore, 0.1 mol / l tin borofluoride-
In a 1.0 mol / l thiourea solution, an electroless tin displacement plating bath having a pH of 1.2 was immersed for 1 hour at a temperature of 50 ° C. to cause a Cu-Sn displacement reaction, and the surface of the roughened layer had a thickness of 0.3 μm. A layer was provided (the Sn layer is not shown).

(11) Adhesives A and B for electroless plating were prepared as follows. A. Preparation of adhesive for electroless plating for upper layer. 35 parts by weight of a 25% acrylate of a cresol novolac type epoxy resin (manufactured by Nippon Kayaku, molecular weight: 2500), 3.15 parts by weight of a photosensitive monomer (manufactured by Toagosei Co., Aronix M315), an antifoaming agent (manufactured by San Nopco, S-65) 0.5 parts by weight, N
3.6 parts by weight of MP was mixed with stirring. . 12 parts by weight of polyethersulfone (PES), 7.2 parts by weight of an average particle diameter of 1.0 μm of epoxy resin particles (manufactured by Sanyo Chemical Industries, polymer pole), and 3 parts by weight of an average particle diameter of 0.5 μm.
After mixing 9 parts by weight, 30 parts by weight of NMP was further added, and the mixture was stirred and mixed by a bead mill. . 2 parts by weight of imidazole curing agent (2E4MZ-CN, manufactured by Shikoku Chemicals), 2 parts by weight of photoinitiator (benzophenone, manufactured by Kanto Chemical), 0.2 parts by weight of photosensitizer (EAB, manufactured by Hodogaya Chemical), N
1.5 parts by weight of MP was mixed with stirring. These were mixed to obtain an adhesive for electroless plating for the upper layer.

B. Preparation of adhesive for electroless plating for lower layer. 35 parts by weight of a 25% acrylate of a cresol novolac type epoxy resin (manufactured by Nippon Kayaku, molecular weight 2500), 4 parts by weight of a photosensitive monomer (manufactured by Toagosei Co., Aronix M315), an antifoaming agent (manufactured by San Nopco, S-65) 0.5 parts by weight, NM
3.6 parts by weight of P was mixed with stirring. . After mixing 12 parts by weight of polyether sulfone (PES) and 14.49 parts by weight of an epoxy resin particle (manufactured by Sanyo Chemical Industries, polymer pole) having an average particle size of 0.5 μm, further add 30 parts by weight of NMP and stir with a bead mill. Mixed. . 2 parts by weight of an imidazole curing agent (2E4MZ-CN, manufactured by Shikoku Chemicals), a photoinitiator (Irgacure I-, manufactured by Ciba-Geigy)
907) 2 parts by weight, photosensitizer (DETX-S, manufactured by Nippon Kayaku) 0.2
Parts by weight and 1.5 parts by weight of NMP were mixed with stirring. These were mixed to obtain an adhesive for electroless plating for a lower layer.

(12) Adhesive B for electroless plating (viscosity: 1.5 to 3.2 Pa · s) and adhesive A for electroless plating (viscosity: 5 to 20 Pa · s) prepared in (11) above were applied to both sides of the substrate. Then, apply it sequentially using a roll coater, leave it in a horizontal state for 20 minutes, and then dry it at 60 ° C for 30 minutes to obtain a 40 μm thick adhesive layer.
12b (two-layer structure) was formed (see FIG. 2 (d)). Further, a polyethylene terephthalate film was stuck on the adhesive layer 12b via an adhesive.

(13) A photomask film on which a black circle of 85 μmφ was printed was brought into close contact with both surfaces of the substrate on which the adhesive layer 12b was formed, and was exposed at 500 mJ / cm ² using an ultra-high pressure mercury lamp. This was spray-developed with a DMDG solution to form an 85 μmφ via hole in the adhesive layer 12b. Further, the substrate is 3,000
exposed with mJ / cm ^2, 1 hour at 100 ° C., thereafter 0.99 ° C. 5
By performing the heat treatment for a long time, an adhesive layer (interlayer resin insulating layer) 12b having a thickness of 35 μm and having an opening (opening 13 for forming a via hole) having excellent dimensional accuracy corresponding to a photomask film was formed (FIG. 2 (e)). Note that the roughened layer is partially exposed in the opening serving as the via hole.

(14) The substrate on which the via hole forming openings 13 are formed is immersed in chromic acid for 19 minutes to dissolve and remove the epoxy resin particles present on the surface of the adhesive layer, so that the surface of the adhesive layer is roughened. After that, it was immersed in a neutralizing solution (manufactured by Shipley Co., Ltd.) and then washed with water.

(15) By applying a palladium catalyst (manufactured by Atotech) to the substrate that has been subjected to the surface roughening treatment (roughening depth: 3 μm), the surface of the adhesive layer 12 b and the surface of the opening 13 for via hole are formed A nucleus was provided.

(16) This substrate was subjected to electroless copper plating in the same manner as in (1) above to form an electroless copper plating film having a thickness of 0.6 μm on the entire rough surface (see FIG. 3 (a)). . At this time, since the plating film was thin, irregularities were observed on the surface of the electroless plating film.

(17) A commercially available photosensitive resin film (dry film) is stuck on the electroless copper plating film 14, a mask is placed, exposed at 100 mJ / cm ² , developed with 0.8% sodium carbonate, A plating resist 16 having a thickness of 15 μm was provided (see FIG. 3B).

(18) Next, electrolytic copper plating is performed in the same manner as in (1) to form an electrolytic copper plating film 15 having a thickness of 15 μm.
Conductive circuit portions and via hole portions were thickened (see FIG. 3 (c)).

(19) After stripping and removing the plating resist 16 with 5% KOH, the electroless plating film under the plating resist 16
14 is dissolved and removed by etching with a mixed solution of sulfuric acid and hydrogen peroxide, and a 16 μm-thick conductor circuit 9 (including via holes 17) composed of an electroless copper plating film 14 and an electrolytic copper plating film 15
Was formed (see FIG. 3 (d)).

(20) In the above (19), the conductor circuit 9 (via hole)
17 g), copper sulfate 8 g / l, nickel sulfate 0.6 g / l, citric acid 15 g / l, sodium hypophosphite 29 g / l, boric acid 31 g / l, surfactant 0.1 g /
1 was immersed in an electroless plating solution having a pH of 9 to form a roughened layer 11 made of copper-nickel-phosphorus having a thickness of 3 μm on the surface of the conductor circuit. At this time, the roughened layer 11 is
(Fluorescence X-ray analysis) showed that 98 mol% of Cu,
The composition ratio was 1.5 mol% and P 0.5 mol%. Further, the substrate is washed with water, immersed in an electroless tin displacement plating bath composed of 0.1 mol / l tin borofluoride-1.0 mol / l thiourea solution at 50 ° C. for 1 hour, and the surface of the roughened layer 11 is Thickness 0.
A tin-substituted plating layer of 05 μm was formed (however, the tin-substituted plating layer is not shown).

(21) By repeating the above steps (12) to (20), the upper interlayer resin insulating layer 12b and the conductor circuit 9 (including the via hole 17) are further laminated to form a multilayer wiring board. (See FIG. 4 (a)). Here, a roughened layer 11 made of copper-nickel-phosphorus is provided on the surface of the conductor circuit, but no tin-substituted plating layer is formed on the surface of the roughened layer 11.

(22) On the other hand, 60% by weight dissolved in DMDG
Cresol novolak epoxy resin (Nippon Kayaku)
46.67 parts by weight of a photosensitizing oligomer (molecular weight 4000) in which 50% of the epoxy groups of the above were acrylated, and 14.121 parts by weight of a bisphenol A type epoxy resin (manufactured by Yuka Shell, Epicoat 1001) of 80% by weight dissolved in methyl ethyl ketone;
1.6 parts by weight of imidazole curing agent (2E4MZ-CN, manufactured by Shikoku Chemicals), 1.5 parts by weight of polyacrylic monomer (R604, manufactured by Nippon Kayaku) as a photosensitive monomer, and 3.0 parts by weight of polyacrylic monomer (Kyoeisha Chemical, DPE6A) 3.0 Parts by weight, 0.36 parts by weight of a leveling agent composed of an acrylate polymer (manufactured by Kyoeisha Co., Ltd., Polyflow No. 75), 2.0 parts by weight of Irgacure I-907 (manufactured by Ciba Geigy) as a photoinitiator, 0.2 parts by weight of DETX-S (produced by Nippon Kayaku) as a photosensitizer was added, and 1.0 part by weight of DMDG (diethylene glycol dimethyl ether) was added.
A solder resist composition adjusted to 1.4 ± 0.3 Pa · s at ℃ was obtained. The viscosity was measured using a B-type viscometer (Tokyo Keiki,
(DVL-B type), rotor No. 4 at 60 rpm, rotor No. 4 at 6 rpm.

(23) The solder resist composition was applied to both sides of the multilayer wiring board obtained in the above (21) in a thickness of 20 μm. Next, after performing a drying process at 70 ° C. for 20 minutes and a temperature of 70 ° C. for 30 minutes, a thickness 5 in which a circular pattern (mask pattern) of the solder resist opening is drawn by the chromium layer.
A soda lime glass substrate having a thickness of ² mm was exposed to ultraviolet light of 1000 mJ / cm ² with the side on which the chromium layer was formed in close contact with the solder resist layer, and subjected to DMTG development treatment. In addition, at 80 ° C
Heat treatment at 100 ° C for 1 hour, 120 ° C for 1 hour, and 150 ° C for 3 hours to open the pad (opening diameter
(200 μm) A solder resist layer 18 (20 μm in thickness) was formed.

(24) Next, the substrate on which the solder resist layer 18 was formed was treated with a pH of 30 g / l of nickel chloride, 10 g / l of sodium hypophosphite, and 10 g / l of sodium citrate.
= 5 for 20 minutes to form a nickel plating layer 19 having a thickness of 5 µm at the opening. Further, the substrate was placed on an electroless gold plating solution comprising 2 g / l of potassium gold cyanide, 75 g / l of ammonium chloride, 50 g / l of sodium citrate, and 10 g / l of sodium hypophosphite at 93 ° C. for 23 seconds. By dipping, a gold plating layer 20 having a thickness of 0.03 μm was formed on the nickel plating layer 19.

(25) Then, a solder paste is printed in the opening of the solder resist layer 18 and reflowed at 200 ° C. to form a solder bump (solder body) 21, and the multilayer printed wiring board having the solder bump 21 is formed. Was produced (see FIG. 4 (b)). In addition, as a solder, tin-silver, tin-indium, tin-zinc, tin-bismuth, or the like can be used.

(Comparative Example 1) A multilayer printed wiring board having solder bumps was prepared in the same manner as in Example 1 except that a conductive paste (manufactured by Tsuta Electric Co., DD paste XAE1209) was screen-printed and cured in the through holes. Manufactured.

The multilayer printed wiring boards of Example 1 and Comparative Example 1 thus manufactured were subjected to a humidity of 100% and a temperature of 1%.
A PCT (pressure cooker test) test in which the substrate was left at 200 ° C. for 2 hours under conditions of 21 ° C. and 2 atm was performed to confirm the presence or absence of disconnection between the via hole and the through hole. As a result, in the wiring board of Example 1, no disconnection was observed between the conductor layer and the through hole, whereas in the wiring board of Comparative Example 1, the disconnection was observed. This is because when the wiring board of Comparative Example 1 was cross-cut at the through hole and observed with an optical microscope, the conductive paste was cured and contracted, and a gap was generated between the through hole and the cured body of the conductive paste. Then, it is presumed that water accumulates here and becomes a gas by heating to push up the conductor layer on the through-hole, leading to disconnection.

[0086]

As described above, according to the present invention, it is possible to provide a printed wiring board in which the curing reliability of the filler is suppressed and the connection reliability between the through hole and the via hole is ensured.

[Brief description of the drawings]

1 (a) to 1 (f) are views showing a part of a process for manufacturing a multilayer printed wiring board of the present invention.

2 (a) to 2 (e) are views showing a part of a process for manufacturing a multilayer printed wiring board according to the present invention.

FIGS. 3 (a) to 3 (d) are views showing a part of a process of manufacturing a multilayer printed wiring board according to the present invention.

FIGS. 4A and 4B are diagrams showing a part of a process of manufacturing a multilayer printed wiring board according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Copper foil 3 Through hole 4,11 Roughened layer 5 Filler 6,14 Electroless plated film 7,15 Electroplated film 8 Etching resist 9 Conductor circuit 10 Conductive layer 12a Resin filler 12b Interlayer resin insulating layer (adhesion Agent layer) 13 Via hole opening 16 Plating resist 17 Via hole 18 Solder resist layer 19 Nickel plating layer 20 Gold plating layer 21 Solder bump (solder)

Claims (5)

[Claims] 1. A multilayer print in which an interlayer resin insulation layer and a conductor layer are alternately laminated on a substrate having a conductor layer, and a build-up wiring layer is formed by connecting inner and outer conductor layers via via holes. In the wiring board, the substrate is formed with a through hole for electrically connecting the front and back surfaces, the through hole is filled with a non-conductive filler containing metal particles, and the through hole of the filler is further formed. A multilayer printed wiring board, wherein a conductor layer that covers a surface exposed from the substrate is formed. 2. The multilayer printed wiring board according to claim 1, wherein a via hole is connected to the conductor layer covering the filler. 3. The filler according to claim 1, wherein the filler comprises metal particles, a resin and an inorganic ultrafine powder.
2. The multilayer printed wiring board according to item 1. 4. The multilayer printed wiring board according to claim 1, wherein the filler has a specific resistance of 1 MΩ · cm or more. 5. The metal particles have an average particle size of 0.1 to 30 μm.
5. The multilayer printed wiring board according to claim 1, wherein m is m.