JP2004103979A - Method for forming plated through-hole - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a plated through-hole, which enables formation of a suitable plated layer and barely creates problems resulting from remnant plating solution, in the case where a porous film is used as an insulating layer for a circuit board, and to provide a circuit board having the through-hole formed by the method. <P>SOLUTION: The method for forming a plated through-hole comprises processes of; forming a first hole H1 through a stacked plate SP having one or more porous resin layers 12; filling a resin 17 into the first hole H1; forming a second hole H2 through a filler resin 17a; and forming the plating layer at least on the inner peripheral surface of the second hole H2. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for forming a plated through hole for forming a plated through hole in a laminate having a porous layer, and a wiring board in which a wiring layer is conductively connected by the plated through hole.
[0002]
[Prior art]
With the recent increase in the speed of information processing and the increase in the frequency of communication radio waves in information and communication equipment, wiring boards on which electronic components and the like are mounted are required to be capable of handling high frequencies. For example, an insulating layer of a wiring board is required to have a small dielectric constant and a small dielectric loss tangent at high frequencies in order to exhibit excellent high-frequency transmission characteristics.
[0003]
That is, an energy loss in the transmission process called dielectric loss occurs in the circuit of the wiring board, and the dielectric loss is proportional to the product of the signal frequency f, the 1/2 power of the dielectric constant ε, and the dielectric loss tangent tan δ of the material. For this reason, a high-frequency wiring board having a large frequency f requires a material having a small dielectric constant ε and a small dielectric loss tangent tan δ. Further, since the signal transmission speed is inversely proportional to the 1/2 power of the dielectric constant ε, a low dielectric constant ε is desired for high frequency applications from this point as well.
[0004]
Conventionally, as a method of forming such an insulating layer having a low dielectric constant and a low dielectric tangent, a method using a resin material having a low dielectric constant or the like has been generally used. As such a resin material having a low dielectric constant, for example, a fluorine-containing polymer such as polytetrafluoroethylene or a polyimide resin is known.
[0005]
Further, as a method of forming an insulating layer having a lower dielectric constant than the dielectric constant of the material resin itself, there is a technique of forming the insulating layer into a porous structure. For example, a porous insulating material having a porous structure having fine continuous pores and a high heat-resistant resin film having a porosity of 15 to 80% is known. A polyimide porous membrane obtained by forming a polyamic acid porous membrane and then performing imide conversion of the porous membrane is disclosed (for example, see Patent Document 1).
[0006]
On the other hand, a wiring layer such as a double-sided wiring board, a multilayer wiring board, or a core substrate used for the production thereof is conductively connected between two layers or three or more layers. Plated through holes are known.
[0007]
[Patent Document 1]
JP-A-2000-319442 (page 1, FIG. 1)
[0008]
[Problems to be solved by the invention]
However, when the above-described resin porous film is used as an insulating layer of a wiring board, if a through-hole is formed by drilling or laser, the inner peripheral surface of the through-hole has a porous structure. For this reason, when plating the through hole, the plating solution enters and remains inside the resin porous layer, and a problem such as a short circuit due to migration is likely to occur. Further, depending on the pore diameter and porosity of the porous structure, plating itself may not be performed in some cases.
[0009]
Therefore, an object of the present invention is to provide a method for forming a plated through hole, in which a plating layer can be suitably formed when a porous film is used as an insulating layer of a wiring board, and a problem due to a residual plating solution does not easily occur, and the method. It is another object of the present invention to provide a wiring board having a plated through hole formed by the method described above.
[0010]
[Means for Solving the Problems]
The above object can be achieved by the present invention as described below.
That is, the method for forming a plated through hole according to the present invention includes a step of forming a first through hole in a laminate having one or more resin porous layers, a step of filling the first through hole with a resin, and a step of filling the filled resin. And a step of forming a plating layer on at least the inner peripheral surface of the second through hole.
[0011]
In the above, after the step of forming the first through hole is performed using a laminate having a release film disposed on the surface thereof, and the step of filling the resin is performed by applying a resin raw material from the surface side of the release film. Preferably, the method further includes a step of peeling the release film.
[0012]
Further, it is preferable that the laminate has a barrier layer made of an insulator on at least one surface, and a plating layer is also formed on the barrier layer in the step of forming the plating layer.
[0013]
On the other hand, the wiring board of the present invention has one or more resin porous layers and two or more wiring layers, and the wiring layers are conductively connected by plated through holes. A non-porous resin layer or a resin-impregnated resin porous layer is interposed between the hole and the surrounding resin porous layer.
[0014]
Further, another wiring board of the present invention has an inner layer in a wiring board having two or more resin porous layers and three or more wiring layers, and the wiring layers are conductively connected by plated through holes. Is electrically connected to the plated through hole, and the resin porous layer around the plated through hole is impregnated with resin.
[0015]
[Effects]
According to the plating through hole forming method of the present invention, the resin is filled in the first through hole formed in advance, and then the second through hole is formed again in the resin. It becomes a porous resin layer or a resin porous layer impregnated with resin. For this reason, when forming a plating layer on the inner peripheral surface of the second through hole, the plating solution does not easily enter the inside of the resin porous layer, and plating can be suitably performed. As a result, when the porous film is used as the insulating layer of the wiring board, it is possible to provide a method for forming a plated-through hole, in which a plated layer can be suitably formed and a problem due to a residual plating solution hardly occurs.
[0016]
The step of forming the first through-hole is performed by using a laminate having a release film disposed on the surface thereof, and the step of filling the resin is performed by applying a resin material from the surface side of the release film, and further performing In the case where the step of peeling the release film is included, a resin material is applied from the opening of the laminated release film, and the resin is filled only in the first through hole by peeling the release film. As described above, the resin can be suitably filled by the simple process, and the problem due to the remaining of the resin in other portions hardly occurs.
[0017]
In the case where the laminate has a barrier layer made of an insulator on at least one surface and a plating layer is also formed on the barrier layer in the step of forming the plating layer, since the barrier layer is present, the plating solution is made of resin. It is difficult to enter from the surface of the porous layer, and a wiring layer on the surface can be formed on the plating layer formed on the barrier layer, so that a separate step of providing a metal layer on the surface becomes unnecessary.
[0018]
On the other hand, according to the wiring board of the present invention, a non-porous resin layer or a resin-impregnated resin porous layer is interposed between a plated through hole that electrically connects the wiring layers and the surrounding resin porous layer. Because of the interposition, a problem such as a short circuit due to migration due to a residual plating solution that has entered during plating hardly occurs.
[0019]
According to another wiring board of the present invention, the wiring layer located in the inner layer is conductively connected to the plated through hole, and the resin is impregnated in the resin porous layer around the plated through hole. In addition, problems due to the residual plating solution that has entered during plating are less likely to occur. In the method of interposing a non-porous resin layer between the plating through hole and the surrounding resin porous layer, it is difficult to electrically connect the wiring layer located in the inner layer to the plating through hole.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 are process diagrams showing an example of a method for forming a plated through hole according to the present invention.
[0021]
The method for forming a plated through hole according to the present invention includes a step of forming a first through hole H1 in a laminated plate SP having one or more resin porous layers 12, as shown in FIGS. Including. In the present embodiment, a laminated plate SP in which adhesive layers 11 and 13 are further laminated and integrated with metal layers 14 and 15 on the surface of the resin porous layer 12 and a release film 16 is disposed on the surface thereof. Then, an example in which the first through hole H1 is formed will be described.
[0022]
First, the resin porous layer 12 will be described. As a material of the resin porous layer 12, a resin having good heat resistance and mechanical strength is preferable, and polyimide, polyester, polyamide, particularly aromatic polyamide, polyamide imide, polyether imide, polyether sulfone, polyether ether Various resins such as ketones can be employed. Among these resins, polyimide resins are preferable because of their good insulation properties and heat resistance. Further, aromatic polyamides are also preferable because they have good insulation properties and heat resistance and have a low coefficient of linear thermal expansion.
[0023]
The resin porous layer 12 preferably has a porosity of 10 to 90% and an average pore diameter of 0.01 to 3 μm. The thickness of the resin porous layer 12 is preferably 2 to 100 μm, more preferably 5 to 50 μm. As such a resin porous layer 12, a porous film that has been formed in advance by a wet coagulation method, a stretching method, a dry coagulation method, or the like can be used.
[0024]
In the wet coagulation method, in general, a film-forming stock solution (dope) in which a resin and additives are dissolved in a solvent is prepared, and the solution is applied (cast) to a film-forming base material and immersed in the coagulation solution to form a solvent. By substituting the resin, the resin is solidified (gelled), and then the coagulation liquid or the like is dried and removed to obtain a porous film. As the film forming substrate, a resin sheet of polyester or the like is used. However, a resin porous film may be formed and attached to the first adhesive layer 11.
[0025]
As the polyimide-based resin, a resin containing another copolymer component or a blend component may be used as long as it is mainly composed of a repeating unit in which an acid residue and an amine residue are imide-bonded. Preferably, in view of heat resistance, hygroscopicity, and mechanical strength, it is a polyimide having an aromatic group in a main chain, and examples thereof include a polyimide comprising a polymer of a tetracarboxylic acid component and an aromatic diamine component. In particular, 0.55 to 3.00, preferably 0. It is desirable that the polymer has an intrinsic viscosity of 60 to 0.85 (measured value at 30 ° C.). Those having an intrinsic viscosity in the above range, when forming a porous film by a wet coagulation method, have a good solubility in a solvent, a large mechanical strength and a self-supporting porous film.
[0026]
The polyimide resin can use the polymer or its precursor (polyamic acid) for film formation. However, since polyamic acid has higher solubility than polyimide, there is an advantage that there is little restriction on a molecular structure. There is. The polymer is preferably completely imidized, but may be one having an imidation ratio of 70% or more. When a dope having a relatively high imidation ratio is used, it is preferable to use a polymer containing a highly flexible component such as butanetetracarboxylic dianhydride in a repeating unit.
[0027]
The solvent for dissolving the polyimide resin or its precursor is not particularly limited as long as it dissolves them, but N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide Such aprotic polar solvents can be preferably used from the viewpoint of solubility and the speed of solvent replacement with a coagulating solvent when a porous film is formed by a wet coagulation method. Preferred examples include N-methyl-2-pyrrolidone. A solvent such as diethylene glycol dimethyl ether and diethylene glycol diethyl ether may be mixed to adjust the rate of solvent replacement in the wet coagulation method.
[0028]
On the other hand, aromatic polyamides include, in addition to so-called para-type aramids and meta-type aramids, those in which a part of the skeleton is substituted with diphenyl ether, diphenylpropane, diphenylmethane, diphenyl ketone, diphenyl sulfoxide, biphenyl, or the like, or a hydrogen group of an aromatic ring. With a methyl group, a halogen atom or the like.
[0029]
Examples of the para-type aramid include poly-p-phenylene terephthalamide and the like, but an aramid composed of only a rigid component like this polymer needs to be dissolved with a special agent. Therefore, as the aromatic polyamide used for the porous membrane, it is preferable to use at least a part of an aramid or a meta-aramid whose skeleton is partially substituted with a component imparting flexibility. Examples of the component that imparts flexibility include m-phenylene, 2,7-naphthalene, diphenyl ether, 2,2-diphenylpropane, and diphenylmethane. Such a component is used as a dicarboxylic acid monomer or a diamine monomer for copolymerization and is introduced into the skeleton. Generally, the higher the copolymerization ratio of the component, the higher the solubility in a solvent.
[0030]
From the viewpoint of solubility, for example, tetramethylurea, hexamethylphosphoramide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylpiperidone-2, N, N-dimethylethylene urea, N, N, N ', N'-tetramethylalonamide, N-methylcaprolactam, N-acetylpyrrolidine, N, N-diethylacetamide, N-ethylpyrrolidone-2, N, N- Examples thereof include dimethylpropionamide, N, N-dimethylisobutylamide, N-methylformamide, N, N-dimethylpropyleneurea, and a mixed system thereof. Further, aprotic polar solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide and N, N-dimethylformamide can be preferably used in terms of solubility and the speed of solvent replacement with a coagulating solvent. . A particularly preferred example is N-methyl-2-pyrrolidone.
[0031]
Further, a solvent such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, or the like may be mixed to adjust the rate of solvent replacement.
[0032]
The dope in the wet coagulation method is preferably applied in a temperature range of -20 to 40C. Further, as the coagulating liquid, without dissolving the resin to be used, as long as it has compatibility with the above-mentioned solvent, water, methanol, ethanol, alcohols such as isopropyl alcohol and a mixture thereof are used. In particular, water is preferably used. The temperature of the coagulating liquid during immersion is not particularly limited, but is preferably a temperature of 0 to 90 ° C.
[0033]
The polymer concentration of the stock solution is preferably in the range of 5% to 25% by weight, more preferably 7% to 20% by weight. If the concentration is too high, the viscosity becomes too high and handling becomes difficult. If the concentration is too low, a porous film tends to be difficult to form.
[0034]
An inorganic substance such as lithium nitrate and an organic substance such as polyvinylpyrrolidone can be added for controlling the pore shape and pore diameter. The concentration of the additive is preferably from 1% by weight to 10% by weight in the solution. When lithium nitrate is added, the replacement speed between the solvent and the coagulating liquid is high, and a finger void structure (a structure having finger-like voids) can be formed in the sponge structure. By adding an additive such as polyvinylpyrrolidone which slows down the coagulation speed, a porous membrane having a sponge structure uniformly spread can be obtained.
[0035]
The film-forming stock solution is applied to a certain thickness and immersed in a coagulating liquid such as water to coagulate, or left in a steam atmosphere to coagulate, then immersed in water to remove the solvent and form a porous membrane. It becomes. After the formation of the porous membrane, it is taken out of the coagulation liquid and dried. The drying temperature is not particularly limited, but drying at 200 ° C. or lower is desirable.
[0036]
When the precursor (polyamic acid) is used when forming the porous layer of the polyimide-based resin, the precursor (polyamic acid) is finally heat-treated at 200 to 500 ° C., and the precursor (polyamic acid) is heated and closed to form a polyimide. I do.
[0037]
The materials of the adhesive layers 11 and 13 may be the same or different, and examples thereof include an epoxy resin, a phenol resin, a polyimide resin, and a polyamic acid. The thickness of the first adhesive layer 11 and the second adhesive layer 13 is preferably 2 to 50 μm from the viewpoint of securing the adhesiveness with the metal layers 14 and 15 and the resin porous layer 12.
[0038]
The metal layers 14 and 15 are preferably made of copper from the viewpoint of conductivity as a wiring pattern, workability, and the like. The thickness of the metal layers 14 and 15 may be any thickness for forming the wiring layer together with the plating layer, but is preferably 1 to 50 μm. The surface of the metal foil portion may be subjected to various physical or chemical surface treatments such as a roughening treatment and a blackening treatment in order to enhance the adhesion to the adhesive layers 11 and 13.
[0039]
As a method of forming the laminated plate SP, a method of forming each layer in a sheet shape in advance and laminating and integrating them by heat pressing, laminating, or the like, a method of applying and forming an adhesive on both surfaces of a resin porous film, a resin A method using an attached copper foil is exemplified. Therefore, the first adhesive layer 11 and the second adhesive layer 13 may be partially impregnated in the resin porous layer 12 of the laminated plate SP, or may be in a temporarily attached state.
[0040]
The method of arranging the release film 16 on the surface of the laminated plate SP is preferably a method of performing temporary attachment or the like so as not to cause a positional shift, and the temporary attachment is performed using the hot melt type or the adhesive release film 16. And the like. Examples of the release film 16 include those based on polyolefin or polyester.
[0041]
The method of forming the first through holes H1 in the laminated plate SP may be performed by any method such as drilling, punching, and laser irradiation. The hole size (hole diameter) of the first through hole H1 is the same as the second through hole H2 forming the plated through hole, but is preferably slightly larger or smaller. In the present invention, the hole diameter of the second through hole H2 is preferably from 10 to 200 μm.
[0042]
In the present embodiment, an example is shown in which the first through-hole H1 has a slightly larger hole diameter than the second through-hole H2. In this case, there is no gap between the plated through-hole 18a and the resin porous layer 12 around it. The porous resin layer 17b is interposed (see FIG. 2 (f)). Conversely, when the first through-hole H1 is slightly smaller than or has the same diameter as the second through-hole H2, the resin-impregnated resin impregnated between the plated through-hole 18a and the surrounding resin porous layer 12 is formed. The material layer 12a is interposed (see FIG. 5A).
[0043]
The present invention includes a step of filling the first through hole H1 with the resin 17, as shown in FIG. 1 (c). The first through hole H1 may be filled as long as at least the peripheral wall of the first through hole H1 is filled with the resin 17, and it is not necessary to fill the entire first through hole H1.
[0044]
The resin 17 to be filled may be either conductive or insulating. In the case of conductivity, for example, a resin containing conductive fine particles can be used. As the resin, the same resin as used for the adhesive layers 11 and 13 and the resin porous layer 12 can be used, but preferably an epoxy resin or a mixture of an epoxy resin and another resin.
[0045]
The method of filling the resin 17 may be any of various printing methods such as screen printing, a squeeze method, and the like. When the release film 16 is provided, a method of applying a resin material from the surface side of the release film 16 is preferable. . After the application, the resin 17 is solidified by drying, heating, or the like as necessary. The resin 17a filled in the first through hole H1 is preferably partially impregnated in the surrounding resin porous layer 12 from the viewpoint of obtaining sufficient strength when forming the second through hole H2. .
[0046]
The present invention includes, as shown in FIG. 1D, a step of forming a second through hole H2 again in the filled resin 17a. The method of forming the second through hole H2 is the same as that of the first through hole H1. In the present embodiment, the resin layer 17b is formed around the second through hole H2 by this step.
[0047]
Next, as shown in FIG. 2E, the peeling film 16 is physically peeled. This step may be performed prior to the formation of the second through hole H2. Due to the peeling of the peeling film 16, only the resin layer 17b around the second through hole H2 remains.
[0048]
The present invention includes a step of forming a plating layer 18 on at least the inner peripheral surface of the second through hole H2, as shown in FIG. In the present embodiment, an example is shown in which the surfaces of the metal layers 14 and 15 are simultaneously plated. As a result, a plating through hole 18a and a surface plating layer 18b are formed. The metal constituting the plating layer 18 is preferably copper, like the metal layers 14 and 15.
[0049]
When the resin layer 17b is insulative, for example, electroplating may be performed after electroless plating is performed on the surface, but a plating catalyst may be deposited on the surface prior to electroless plating.
[0050]
As the method of electroless plating and electrolytic plating, any conventionally known methods can be used. For example, a plating solution such as copper or tin is usually used for electroless plating. Plating solutions for electroless plating are well known for various metals, and various plating solutions are commercially available. Generally, the liquid composition contains a metal ion source, an alkali source, a reducing agent, a chelating agent, a stabilizer and the like. In general, in electroplating, while a target laminate is immersed in a plating bath, the surface metal is used as a cathode, and a metal ion replenishment source for the metal to be plated is used as an anode to deposit metal on the cathode side by an electrolytic reaction. This is done by letting Note that the thickness of the plating layer 18 is preferably 1 to 50 μm.
[0051]
Next, as shown in FIG. 2G, a pattern is formed on the surface plating layer 18b as necessary. This step is performed by, for example, etching using an etchant. For the etching, an etching solution according to the type of metal is used, and for the pattern etching, a dry film resist or the like can be used. In the present embodiment, since the metal layers 14 and 15 and the plating layer 18 are the same kind of metal, these layers are simultaneously etched to form the wiring layer 19.
[0052]
In the present embodiment, since the adhesive layers 11 and 13 function as barrier layers made of an insulator during etching, it is possible to prevent an etchant from entering. In the present invention, the laminate SP preferably has a barrier layer made of an insulator on at least one surface of the resin porous layer 12, and more preferably has a barrier layer on both surfaces.
[0053]
As shown in FIG. 2 (g), the wiring board of the present invention has one or more resin porous layers 12 and two or more wiring layers 19, and these wiring layers 19 are plated through holes 18a. In the conductively connected wiring board, a non-porous resin layer 17b (or resin-impregnated resin porous layer) is interposed between the plated through hole 18a and the surrounding resin porous layer 12. It is characterized by the following.
[0054]
[Other embodiments]
Hereinafter, another embodiment of the present invention will be described.
[0055]
(1) In the above-described embodiment, an example is shown in which a laminate having a metal layer on both sides is used. However, as shown in FIGS. 3 and 4, in the present invention, the adhesive layer 11 having no metal layer is used. , 13 and the resin porous layer 12 may be used. That is, the laminated plate SP has a barrier layer made of an insulator on at least one surface, and the plating layer 18 is also formed on the barrier layer in the step of forming the plating layer 18.
[0056]
In this embodiment, as shown in FIG. 3C, in the step of filling the first through hole H1 with a resin, a resin porous layer 12a impregnated with resin is formed around the first through hole H1. are doing. In order to impregnate the resin into the resin porous layer 12 around the first through hole H1, the pore diameter of the resin porous layer 12 is made relatively large, the viscosity of the resin raw material is reduced, or a resin having a low melt viscosity is used. You can do it.
[0057]
When a laminate SP having no metal layer is used, it is preferable to attach a catalyst when performing electroless plating on the adhesive layers 11 and 13. Further, in order to enhance the adhesion of the plating layer 18, it is preferable that the surfaces of the adhesive layers 11 and 13 are subjected to a roughening treatment.
[0058]
(2) In the above-described embodiment, an example of a wiring board in which plated through holes are formed in a laminate having one resin porous layer has been described. However, as shown in FIG. The wiring board may be formed by forming a plated through hole 18 a for conductively connecting the wiring layer 19 to a laminate having the resin porous layer 12 and three or more wiring layers 19.
[0059]
In this example, the outer wiring layers 19a and 19d and one inner wiring layer 19b are conductively connected to the plated through hole 18a, and the other inner wiring layer 19c is conductively connected to the plated through hole 18a. Not connected. Such a structure is obtained by making the second through-hole H2 slightly larger or the same diameter as the first through-hole H1, and the resin layer 17b is not interposed around the plated through-hole 18a. Is electrically connected to the wiring layer 19b. In other words, when the second through hole H2 is formed, the wiring layer 19b is exposed on the inner peripheral surface, and the plated through hole 18a is formed on the surface, and the conductive layer is electrically connected. The resin porous layer 12 around the plating through hole 18a is impregnated with resin (resin porous layer 12a). The wiring board before the formation of the plated through holes 18a is formed by laminating and integrating the wiring layers 19b and 19c formed on the surface of the resin porous layer 12 via the adhesive layers 11 and 13 via the prepreg 20. It can be produced by a method or the like.
[0060]
(3) In the above-described embodiment, the example in which the plating layer is formed on the entire surface including the inner peripheral surface of the second through-hole has been described. Alternatively, a plating layer may be formed. In that case, a plating resist having an opening at or around the position where the second through hole is formed may be used.
[Brief description of the drawings]
FIG. 1 is a process diagram showing an example of a method for forming a plated through hole according to the present invention; FIG. 2 is a process diagram showing an example of a method for forming a plated through hole according to the present invention; FIG. FIG. 4 is a process diagram showing another example of the method. FIG. 4 is a process diagram showing another example of the method of forming a plated through hole of the present invention. Explanation of code]
11 first adhesive layer 12 resin porous layer 12a resin porous layer impregnated with resin 13 second adhesive layer 16 release film 17 resin 17a resin 17b resin layer 18 plating layer 18a plating through hole 19 wiring layer H1 1 through hole H2 2nd through hole SP laminated board

Claims (5)

Forming a first through hole in a laminate having one or more resin porous layers, filling the first through hole with a resin, forming a second through hole again in the filled resin, and at least A method for forming a plated through hole, comprising a step of forming a plated layer on an inner peripheral surface of a second through hole. The step of forming the first through-hole is performed using a laminate having a release film disposed on the surface thereof, and the step of filling the resin is performed by applying a resin material from the surface side of the release film, and then further performing the above-described steps. The method for forming a plated through hole according to claim 1, further comprising a step of peeling the peeling film. 3. The formation of the plated-through hole according to claim 1, wherein the laminate has a barrier layer made of an insulator on at least one surface, and a plating layer is also formed on the barrier layer in the step of forming the plating layer. Method. In a wiring board having one or more resin porous layers and two or more wiring layers, and the wiring layers are conductively connected by plated through holes, the plated through hole and the surrounding resin porous layer And a non-porous resin layer or a resin porous layer impregnated with a resin. In a wiring board having two or more resin porous layers and three or more wiring layers, and those wiring layers are conductively connected by plating through holes, the wiring layer located in the inner layer is conductive to the plating through holes. A wiring board which is connected and has a resin impregnated in a resin porous layer around the plated through hole.

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