JP2001015935A - Conductive foil and wiring board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To outstandingly improve shield effect of an electrical conductive foil by laminating a plurality of conductive thin layers with insulation thin layers arranged between the same. SOLUTION: An electrical conductive foil comprises a plurality of conductive thin layers 1A, 1B, and 1C, the conductive thin layer 1B formed inside thereof in a laminated direction functions as an electrical conductive layer, and both the conductive thin layers 1A and 1C formed outside thereof functions as an electrical shield layer against the conductive thin layer 1B. These conductive layers 1A to 1C are laminated with insulation thin layers 2 composed of compound of metal and nonmetal or an organic substance interposed therebetween. This makes it possible to acquire conductive foil capable of high-frequency application and to outstandingly improve shield effect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive foil used as a material film of a circuit pattern of a wiring board and a wiring board using the conductive foil as a circuit pattern.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become smaller, lighter, and more sophisticated, wiring boards have been required to be smaller, lighter, have faster signal processing, and have higher density packaging.
To meet such demands, conventional wiring boards
Techniques such as multi-layering, reduction in the diameter of via holes, and fine circuit technology are required, but it is extremely difficult to satisfy these requirements with the conventional multilayer substrate structure in which electrical connection between layers is made by a through-hole structure. there were. For this reason, wiring boards having a new structure have been developed, and in terms of materials, wiring boards using not only conventional glass substrates but also substrates and films made of organic fibers have been developed.

[0003] As one of the typical examples, there is a wiring board having a complete IVH structure in which interlayer connection is ensured by a conductive paste (for example, Japanese Patent No. 26001128). This wiring board uses a composite material such as aramid-epoxy resin for the insulating layer, and has a low thermal expansion, a low dielectric constant,
Taking advantage of its light weight, it is used in many electronic devices that need to be small and light.

[0004]

However, the structure of the above-mentioned conventional circuit board adapted to miniaturization, weight reduction, high-speed signal processing, and high-density mounting has the following problems. Was. That is, as the degree of integration of the LSI increases, the intersection of high-speed signals becomes more intense, and noise and furthermore, the disturbance of the waveform due to resonance or electromagnetic wave absorption occurs. Therefore, there is a problem that the signal lines must be shielded with higher accuracy in order to prevent waveform disturbance due to these noises.

[0005]

In order to solve the above-mentioned problems, the present invention has a plurality of conductive thin layers, and these conductive thin layers are laminated with an insulating thin layer interposed therebetween to form a conductive foil. Was configured.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is characterized in that it has a plurality of conductive thin layers, and these conductive thin layers are laminated with an insulating thin layer interposed therebetween. This has the following effects. That is, when one of the conductive thin layers stacked and arranged with the insulating thin layer interposed therebetween is used as an electrically conductive layer, the other functions as an electrical shield layer. In addition, since such a shield structure is formed in an extremely thin structure inside the conductive foil, opposition between the conductive thin layer functioning as an electrical shield layer and the conductive thin layer functioning as an electrical conductive layer The interval can be made very narrow. For this reason, the shielding effect is significantly improved as compared with the case where a shielding structure is formed in the wiring board.

According to a second aspect of the present invention, there is provided the conductive foil according to the first aspect, wherein at least one of the conductive thin layers is an electrically conductive layer and the other is an electrically shielded layer. Which has the following effects. In other words, the electrically conductive layer and the electrically shielded layer can be arranged to face each other via the insulating thin layer in an extremely thin structure inside the conductive foil. As a result, the shielding effect is dramatically increased.

[0008] The invention described in claim 3 of the present invention is the invention of claim 2
The conductive foil according to the above, characterized in that a conductive thin layer serving as the electrical shield layer is disposed on one or both sides of the conductive thin layer serving as the electrical conductive layer, whereby the following: It has such an effect. That is, by arranging a conductive thin layer serving as an electric shield layer on one or both surfaces of the conductive thin layer serving as an electrically conductive layer, the shielding effect is further enhanced.

The invention according to claim 4 of the present invention is the conductive foil according to claim 2 or 3, wherein the conductive thin layer serving as the electrically conductive layer is a copper thin layer. This has the following effects. That is, when the conductive thin layer serving as the electrically conductive layer is a copper thin layer, the conductive thin layer can have high conductivity and be inexpensive.

According to a fifth aspect of the present invention, there is provided the conductive foil according to any one of the second to fourth aspects, wherein the conductive thin layer serving as the electrically conductive layer and the electrical shield layer are provided. It is characterized in that the conductive thin layer is made of different conductive materials, and thus has the following effects. That is, for example, the conductive thin layer serving as the electrically conductive layer is formed from a conductive material suitable for the electrical conductive layer, and the conductive thin layer serving as the electrical shield layer is formed from a conductive material suitable for the electrical shield layer This makes it possible to achieve both electrical conduction performance and electrical shielding performance.

According to a sixth aspect of the present invention, in the conductive foil according to the fifth aspect, the conductive thin layer serving as the electrically conductive layer is made to be smaller than the conductive thin layer serving as the electrical shield layer. The conductive foil is characterized by being made of a conductive material that is not easily etched by an etchant used for patterning, and has the following effects. That is, when this conductive foil is used as an electrically conductive layer such as a wiring board, a patterning process is performed on the conductive foil. Furthermore, when this conductive foil is used for an internal circuit pattern of a laminated board, other elements (a conductive thin layer serving as a shield layer, an insulating thin layer) are selected while leaving only a conductive material serving as an electrically conductive layer. Must be removed. In such a case, according to the present invention, only the conductive thin layer serving as the electrically conductive layer is selectively left due to the difference in the etching rate (the degree of difficulty in etching) of both conductive thin layers. This facilitates patterning with high accuracy.

According to a seventh aspect of the present invention, there is provided the conductive foil according to any one of the first to sixth aspects, wherein the insulating thin layer is a compound of a metal and a nonmetal. This has the following effects. That is, the insulating thin layer can be made of not only a general organic material but also a compound of a metal and a nonmetal. In particular, if a metal is used as the conductive thin layer and the surface of the conductive thin layer made of the metal is subjected to oxidation treatment or the like, the insulating thin layer is formed from a compound of the conductive thin layer and a nonmetallic compound. The insulating thin layer can be easily formed.

The invention according to claim 8 of the present invention is the conductive foil according to any one of claims 1 to 7, wherein the conductive foil is used as a material film of a circuit pattern of a wiring board. In addition, the thickness of the insulating thin layer is made smaller than the thickness of the insulating base material constituting the wiring board, thereby having the following effects. In other words, the electrical shield structure is formed in a structure that is extremely thin compared to the thickness of the insulating base material, that is, the inside of the conductive foil, and the facing distance between the two conductive thin layers constituting the shield structure is extremely narrow. It becomes possible. For this reason, the shielding effect is significantly improved as compared with the case where a shielding structure is formed in the wiring board.

If the above-described conductive foils according to claims 1 to 8 are applied to the wiring boards according to claims 9 and 10 of the present invention, the effect becomes remarkable. Furthermore, claim 1
As described in 1, if the thickness of the insulating thin layer provided in the circuit pattern is made thinner than the thickness of the insulating base material, the inside of the conductive foil, which is an extremely thin structure as compared with the thickness of the insulating base material, Since the electric shield structure is formed at the same time, it is possible to make the distance between the two conductive thin layers constituting the shield structure very small. For this reason, the shielding effect is significantly improved as compared with the case where a shielding structure is formed in the wiring board.

Hereinafter, embodiments of the present invention will be described in detail.

FIG. 1 is a sectional view showing the structure of a conductive foil according to an embodiment of the present invention.

This conductive foil has a plurality of conductive thin layers (three layers in this example) 1A, 1B and 1C.
To 1C are laminated with the insulating thin layers 2 and 2 interposed therebetween, whereby the conductive thin layer 1B located on the inner side in the stacking direction becomes suitable for functioning as an electrically conductive layer, The outer conductive thin layers 1A and 1C are suitable for functioning as an electric shield layer for the conductive thin layer 1B.

The conductive thin layers 1A to 1C are suitably made of a metal such as copper, aluminum, nickel, and silver. This is because these metals can be formed by a relatively simple method such as plating or vapor deposition. In the present embodiment, as an example, the conductive thin layers 1A to 1C are formed by plating.

Further, the conductive thin layer 1B is preferably made of the above-mentioned copper. This is because the conductive thin layer 1B having the necessary conductivity as the electrically conductive layer can be easily formed at low cost. Conductive thin layers 1A, 1C
Is preferably made of aluminum. This is because the conductive thin layers 1A and 1C having the necessary electric characteristics as the electric shield layer can be formed at low cost and easily. Further, aluminum has the following characteristics. That is, the etching rate for an etching solution (for example, hydrochloric acid) suitable for use in etching the conductive foil having such a multilayer structure is that copper (conductive thin layer) is higher for aluminum (conductive thin layers 1A and 1C). 1
B) It has a larger (easy to etch) property. Therefore, by selecting the material of the conductive thin layers 1A, 1B, and 1C as described above (conductive thin layers 1A and 1C: aluminum, conductive thin layer 1B: copper), the conductive thin layer 1B becomes the conductive thin layer 1A. A characteristic that etching is harder than that of 1C can be imparted to the conductive foil.

The insulating thin layer 2 is composed of a compound of a metal and a nonmetal (for example, an oxide of the conductive thin layers 1A to 1C) or an organic substance. If the insulating thin layer 2 is composed of an oxide of the conductive thin layers 1A to 1C, the insulating thin layer 2 can be formed only by oxidizing the conductive thin layers 1A to 1C, and therefore, it can be easily formed. Further, the insulating thin layer 2 made of an organic substance can be formed by spray coating.

This conductive foil can form a shield structure for the conductive thin layer 1B by laminating the conductive thin layers 1A to 1C and the insulating thin layer 2. Can be formed in an extremely thin structure inside. Therefore, the opposing distance between the conductive thin layers 1A and 1C functioning as an electric shield layer and the conductive thin layer 1B located inside thereof (which depends on the thickness of the insulating thin layer 2) is extremely small. It becomes possible,
The shielding effect is remarkable.

Next, the structure of a wiring board using the conductive foil as a circuit pattern will be described with reference to FIG. This wiring board is configured by alternately stacking a plurality of sheet-shaped insulating base materials (hereinafter, referred to as insulating base materials) 3 with a circuit pattern 4 interposed therebetween. The circuit pattern 4 is formed by selectively removing unnecessary portions of the conductive foil from the conductive foil shown in FIG. 1 by an existing patterning method using a photolithography method, and thus formed. The circuit pattern 4 is closely attached to the surface of each insulating base material 3 after being positioned.

The wiring board is formed with a through hole 5 penetrating in the thickness direction thereof. Further, the through hole 5 extends from the inner wall surface to the surface of the wiring board near the through hole 5. Plating 6 is formed. The through-hole plating 6 can be formed by a known metal plating method such as gold plating, silver plating, or copper plating. The conductive thin layer 1B (the conductive thin layer located inside) constituting the electrically conductive layer of the circuit pattern 4 is in contact with and electrically connected to the through-hole plating 6 at a necessary portion. On the other hand, the conductive thin layers 1A and 1C constituting the electric shield layer of the circuit pattern 4 are formed as follows. That is, openings 7 having a larger diameter than the through holes are formed in the through-hole forming portions of the conductive thin layers 1A and 1C, whereby the conductive thin layers 1A and 1C are separated from the through-hole 5 forming portions in the plane direction. It is arranged.

As the insulating base material 3, a prepreg in which an insulating base material is impregnated with a thermosetting resin is used. Examples of the insulating base material include a glass cloth material, a glass nonwoven material, an aramid cloth material, an aramid nonwoven material, and a liquid crystal polymer nonwoven material. Further, as the thermosetting resin, a known thermosetting resin such as a phenol resin, a naphthalene resin, a urea resin, an amino resin, an alkyd resin, a silicon resin, a furan resin, an unsaturated polyester resin, an epoxy resin, and a polyurethane resin. The prepreg constituting the insulating base material 3 can be constituted by a combination of these insulating base materials and a thermosetting resin.

The wiring board described with reference to FIG. Next, the configuration of a wiring board connected between layers with a conductive filler using a conductive paste will be described with reference to FIG.

This wiring board is also constructed by alternately laminating a plurality of sheet-like insulating base materials (insulating base materials) 10 with a circuit pattern 11 interposed therebetween. The circuit pattern 11 is formed by selectively removing unnecessary portions of the conductive foil by an existing patterning method using a photolithography method from the conductive foil illustrated in FIG. 1, and thus formed. The circuit pattern 11 is made of each insulating substrate 1
0 and closely attached to each other.

Each insulating substrate 10 has a through hole 12 formed in the thickness direction thereof.
2 is provided with an intermediate connector 13. The intermediate connector 13 is formed by filling the through hole 12 with a conductive paste and subjecting the paste to heating and pressurizing. Here, the following processing is performed on the circuit pattern 11 at the contact position of the intermediate connector 13. That is, of the conductive thin layers 1A to 1C constituting the circuit pattern 11, the outer conductive thin layers 1A and 1C located on the side in contact with the intermediate connector 13, and these conductive thin layers 1A and 1C and the inner conductive thin layer The insulating thin layer 2 located between the layer 1B and the layer 1B has previously been selectively removed by patterning. Thereby, the intermediate connector 1
3, the inner conductive thin layer 1 </ b> B (electrically conductive layer) is exposed, and the conductive thin layer 1 </ b> B is in contact with and electrically connected to the intermediate connector 13.

The conductive paste constituting the intermediate connector 13 is made of at least a conductive powder and a thermosetting resin. Examples of the conductive powder include metal powders such as copper powder, silver powder, nickel powder, and aluminum powder, and powders having a coating layer of the above-described metal, and the form is resin-like, flake-like, spherical, or amorphous. Either form may be used. Thermosetting resins include phenolic resins, naphthalene resins,
Known thermosetting resins such as urea resin, amino resin, alkyd resin, silicon resin, furan resin, unsaturated polyester resin, epoxy resin and polyurethane resin can be used, and these can be appropriately combined. In addition, additives and solvents can be added for adjusting the oxidation stability and viscosity of the conductive paste.

In the above embodiment, the conductive thin layers 1A to 1A
Examples of 1C include metals such as copper, aluminum, nickel, and silver, and examples of the thin insulating layer 2 include compounds of metals and nonmetals, organic substances, and the like. It is needless to say that the present invention is not limited to the configuration of the insulating layer, but includes known metals and compounds.

In the above-described embodiment, the conductive foil of the present invention has three conductive thin layers 1A to 1C, but has two conductive thin layers. A conductive thin layer may be formed, or the present invention may be formed with four or more conductive thin layers. Further, in that case, the electrical conduction layer may be formed from a single conductive thin layer, or the electrical conduction layer may be configured from a plurality of conductive thin layers. Further, the conductive thin layer serving as an electrically conductive layer is preferably disposed inside the conductive foil from the viewpoint of improving the shielding characteristics, but it is needless to say that the conductive thin layer may be disposed on the outermost layer.

[0031]

EXAMPLES In order to facilitate understanding of the present invention, the present invention will be further described with reference to examples of the present invention. However, the present invention is not limited to these examples. Further, FIG. 4 shows a method in an embodiment of the wiring board of the present invention in the embodiment, but the present invention is not limited to one manufactured by such a method.

First, as shown in FIG. 4A, a prepreg base material 20 for an inner layer in which an aromatic polyamide nonwoven fabric is impregnated with a thermosetting epoxy resin is prepared, and a predetermined position of the prepreg base material 20 for the inner layer is prepared. Then, as shown in FIG.
The through holes 21 are formed by using a laser processing method or the like. Then, the conductive paste 22 is filled in the formed through holes 21. As described in the embodiment, while the thermosetting resin 22 is a mixture of the thermosetting resin and the conductive powder, the inner layer conductive foils 25 and 25 to be adhered to the inner layer prepreg base material 20 are prepared. I do. The inner layer conductive foil 25 is formed by separating the two conductive thin layers 23A and 23B and the insulating thin layer 24 from each other.
, And are alternately stacked and arranged. Then, the inner layer conductive foil 25 configured as described above is patterned. In this patterning, a process of patterning the inner layer conductive foil 25 into an arbitrary circuit pattern shape and, at a predetermined position, a conductive thin layer (conductive thin layer 23B in the figure) located on the side in contact with the inner layer prepreg base material 20 are selected. And a patterning process for removing the other conductive thin layer (conductive thin layer 23A in the figure) and the insulating thin layer 24.
Here, the predetermined position refers to a position where the conductive foil 25 for the inner layer contacts the conductive paste 32 of the prepreg base material 30 for the outer layer described later.

At this time, a protective sheet 26 is attached to one surface of the inner layer conductive foil 25 for the purpose of protecting the inner layer conductive foil 25 during operation and preventing the inner layer conductive foil 25 from being separated by patterning. deep. The same applies to the case where the protective sheet 26 is attached to the outer layer conductive foil 35 used in a later step.

Next, as shown in FIG. 4 (c), with the prepreg base material 20 for the inner layer in between, the conductive foils 25 for the patterned inner layer are laminated on both surfaces thereof. At this time, the conductive foil 25 for the inner layer is arranged with the protective sheet 26 on the outside, and the conductive thin layer (conductive thin layer 2 in FIG.
The inner layer conductive foil 25 is arranged so that the pattern forming portion 3B) and the conductive paste 22 are in contact with each other. With this arrangement, the conductive thin layer (conductive thin layer 25B in the figure) located inside and in contact with the conductive paste 22 functions as an electrically conductive layer, and located outside and the conductive paste 22
The conductive thin layer (the conductive thin layer 23A in the figure) not in contact with the layer functions as an electric shield layer. In the prepreg base material 20 for the inner layer located on the inner side, since it is only necessary to prevent mixing of noise from the outside, the electric shield layer (conductive thin layer 23A) is arranged outside the electrically conductive layer (conductive thin layer 35B). I do.
After laminating the inner layer prepreg base material 20 and the inner layer conductive foil 25, the protective sheet 26 is removed.

Under the above-mentioned conditions, the heating temperature of 200 ° C., 5
The inner layer prepreg base material 20 and the inner layer conductive foil 25 are heated and pressed under the conditions of a pressure of 0 kg / cm ² and a processing time of 1 hour. As a result, as shown in FIG.
An inner substrate 29 having an inner circuit pattern 27 (a heat-treated material of the inner-layer conductive foil 25) and an intermediate connector 28 (a heat-treated material of the conductive paste 22) is prepared.

Further, outer layer prepreg base materials 30, 30 made of the same material as the inner layer prepreg base material 20 are prepared, and a predetermined position of the outer layer prepreg base material 30, 30 is applied by a laser processing method or the like. Then, a through hole 31 is formed. Then, the conductive paste 32 is formed in the formed through hole 31.
Fill. Furthermore, both surfaces of the inner layer base material 29 are sandwiched between the outer layer prepreg base materials 30 and 30 filled with the conductive paste 32.

On the other hand, the three conductive thin layers 33A, 33B, 3
After preparing an outer layer conductive foil 35 in which 3C and the insulating thin layers 34A and 34B are alternately stacked, the outer layer conductive foil 35 is patterned. This patterning is a process of patterning the entire outer layer conductive foil 35 into an arbitrary circuit pattern shape, and a conductive thin layer (the conductive thin layer 33C in the figure) located at a predetermined position on the side in contact with the outer layer prepreg base materials 30, 30. ) And this conductive thin layer (33)
C) and a patterning process for selectively removing the insulating thin layer 34B disposed between the conductive thin layer 33B located inside. Here, the predetermined position is the conductive foil 3 for the outer layer.
5 is the conductive paste 32 of the outer layer prepreg base material 30
Refers to the position in contact with

Next, as shown in FIG. 4 (e), the prepreg base material 3 for the outer layer is provided on both surfaces thereof with the inner base material 29 interposed therebetween.
0, 30 are arranged, and the prepreg base material 3 for the outer layer is further provided.
0, 30 on the outer surface of the conductive foil 3 for patterned outer layer
5 are stacked. At this time, the outer layer conductive foil 35 is arranged so that the exposed portion of the conductive thin layer 33B and the conductive paste 32 are in contact with each other. With such an arrangement, the conductive thin layer 35B in contact with the conductive paste 32 functions as an electrical conductive layer, and the conductive thin layers 33A and 33B located on both sides of the conductive thin layer 35B function as an electrical shield layer. I do.
In the outermost prepreg base material 30, 30 located at the outermost layer, noise is apt to be mixed in from the outside in the position, so that the electric shield layers (conductive thin layers 35A, 35A, 35A, 35B) is arranged.

In the above state, the prepreg base material 2 for the inner layer
0 (heating temperature of 200 ° C., 50 kg /
The prepreg base material 30 for the outer layer and the conductive foil 35 for the outer layer (including the inner layer base material 29) are heated and pressed under a pressure of 1 cm ² and a processing time of 1 hour. Thus, as shown in FIG. 4 (f), the outer layer base material including the outer layer circuit pattern 36 (the heat-treated product of the outer layer conductive foil 35) and the intermediate connector 37 (the heat-treated product of the conductive paste 32). Forming the outer layer base materials 38 and 38 and the inner layer base material 29
Are laminated and integrated, thereby obtaining a four-layer wiring board having a structure capable of shielding signal lines.

Using this wiring board, an EMI standard FC
The amount of radiation and the amount of conduction were measured based on C. It was confirmed that the maximum value of both the radiation amount and the conduction amount was 10 dB lower than the level B limit value of the FCC of the EMI standard. EMI standard FCC / DO for radiated and conducted emissions
It was confirmed that the value was within the limit of Class B of C.

[0041]

As described above, according to the present invention, a high-frequency conductive foil having an electrical conductive layer capable of shielding signal lines and a wiring board using this conductive foil are obtained. Can be. Moreover, since such a shield structure is formed in an extremely thin structure inside the conductive foil, the opposing distance between the conductive thin layer functioning as an electrical shield layer and the conductive thin layer located inside the conductive thin layer is reduced. It can be very narrow. For this reason, the shielding effect is significantly improved as compared with the case where a shielding structure is formed in the wiring board.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a conductive foil according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of a wiring board according to one embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a configuration of a wiring board according to another embodiment of the present invention.

FIG. 4 is a view showing a method of manufacturing the wiring board according to one embodiment of the present invention, and is a cross-sectional view showing each step of the manufacturing method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1A, 1C Conductive thin layer (electric shield layer) 1B Conductive thin layer (electrically conductive layer) 2 Insulating thin layer 3 Insulating base material 4 Circuit pattern 5 Through hole 10 Insulating base material 11 Circuit pattern 12 Through hole 13 Intermediate connector Reference Signs List 20 prepreg base material for inner layer 21 through hole 22 conductive paste 23A, 23B conductive thin layer 24 insulating thin layer 25 conductive foil for inner layer 26 protective sheet 27 inner wiring 28 intermediate connector 29 inner base material 30 prepreg base material for outer layer 31 penetration Hole 32 conductive paste 33A to 33C conductive thin layer 34 insulating thin layer 35 conductive foil for outer layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Fumio Echigo 1006 Kazuma Kadoma, Kazuma, Osaka Pref. F-term (reference) in Matsushita Electric Industrial Co., Ltd. CC08 CC16 CC31 CC32 CC58 DD02 DD12 EE02 EE06 EE07 EE09 FF04 FF18 GG15 GG28 HH01

Claims (11)

[Claims] 1. A conductive foil comprising a plurality of conductive thin layers, wherein the conductive thin layers are laminated with an insulating thin layer interposed therebetween. 2. The conductive foil according to claim 1, wherein at least one of the thin conductive layers is an electrically conductive layer, and the other is an electrical shield layer. 3. The conductive foil according to claim 2, wherein a conductive thin layer serving as the electrical shield layer is disposed on one or both surfaces of the conductive thin layer serving as the electrically conductive layer. Conductive foil. 4. The conductive foil according to claim 2, wherein the conductive thin layer serving as the electrically conductive layer is a copper thin layer. 5. The conductive foil according to claim 2, wherein the conductive thin layer serving as the electrically conductive layer and the conductive thin layer serving as the electrical shield layer are formed of different conductive layers. A conductive foil comprising a material. 6. The conductive foil according to claim 5, wherein the conductive thin layer serving as the electrically conductive layer is etched from the conductive thin layer serving as the electrical shield layer when patterning the conductive foil. A conductive foil comprising a conductive material that is not easily etched by a liquid. 7. The conductive foil according to claim 1, wherein the insulating thin layer is a compound of a metal and a nonmetal. 8. The conductive foil according to claim 1, wherein the conductive foil is used as a material film of a circuit pattern of a wiring board, and the thickness of the insulating thin layer is reduced. ,
A conductive thin film, which is thinner than a thickness of an insulating base material constituting the wiring board. 9. A wiring board comprising a circuit pattern formed on a surface of an insulating base material impregnated with a thermosetting resin, wherein the circuit pattern is formed from the conductive foil according to claim 1. A wiring substrate, comprising: 10. The wiring board according to claim 9, wherein the wiring board has a through hole formed in the insulating layer, and an intermediate connector made of a conductive paste filling is provided in the through hole. A wiring substrate, characterized in that: 11. The wiring board according to claim 9, wherein a thickness of the insulating thin layer provided in the circuit pattern is smaller than a thickness of the insulating base material.