JP2001007530A - Circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a via from expanding or shrinking by an insulating layer so as to improve wiring layers in connection reliability between them by a method wherein two or more wiring layers are insulated from each other by an insulating layer, and the specific sites of the wiring layers are electrically connected together with a via which is non-circular in cross section penetrating through the insulating layer. SOLUTION: A composite material sheet of aramid epoxy prepreg is used as an insulating layer 2 provided in a double-sided circuit board. A through-hole (viahole) is bored in the prepreg 2 at required positions respectively with a YAG laser, the through-holes are each filled up with conductive composition 5 formed of epoxy resin composition which contains copper powder and a curing agent, and an electrolytic copper foil 6 is superposed on each primary surface of the prepreg 2. The components are hot-pressed to cure the conductive composition 5 into vias 3, the prepreg 2 and the copper foil 6 are bonded into one piece for the formation of a laminate. The vias 3 are each non-circular in cross section and have a longer circumference than a circle, and the insulating layer 2 residing around the vias 3 restrains the vias 3 from expanding or shrinking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a circuit board,
In particular, the present invention relates to a circuit board configured to improve connection reliability between wiring layers.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become smaller and lighter and have higher functions and higher performance, semiconductor chips such as LSIs can be mounted at a high density not only in industrial devices but also in consumer devices. There is a strong demand to supply a circuit board having a multilayer wiring structure at a low cost, and in this kind of multilayer circuit board, the connection reliability between a plurality of wiring patterns formed with a fine wiring pitch has been improved. It is important to be able to make the above electrical connections. In order to meet such a demand, a conventional multi-layer circuit board, that is, an all-layer IVH structure employing an inner via connection method instead of a circuit board employing an interlayer connection method using through holes is conventionally used. Resin multilayer substrate, for example,
The use of a circuit board disclosed in Japanese Unexamined Patent Publication No. 268345/1990 has been performed.

[0003] That is, this all-layer IVH structure resin multilayer circuit board has a via formed by filling a conductive composition in an inner via hole formed through an insulating layer that electrically insulates between wiring layers. In addition, the wiring layer has a structure capable of connecting predetermined positions of the respective wiring layers, and can realize a reduction in the size of the substrate and an increase in the density. Also, there is a build-up multilayer wiring board as a circuit board of another configuration, and in this build-up multilayer wiring board, each of the wiring layer and the insulating layer is sequentially arranged on the outermost layer of the circuit board employing a through-hole connection method. 2. Description of the Related Art Electrical connection is made between wiring layers by blind via holes that are stacked and copper plated on the inner surface.

[0004]

By the way, in any of the above circuit boards, vias connecting predetermined positions of the wiring layers have physical property values different from those of the insulating layer, that is, such as thermal expansion coefficient and humidity expansion coefficient. It is generally manufactured after using a material whose physical property value is different from the constituent material of the insulating layer. As long as such a structure is used, stress tends to concentrate on the interface between different kinds of materials due to temperature and humidity cycles, and the interface between different kinds of materials may be destroyed if excessive stress is applied. At present, it is difficult to ensure high connection reliability.

[0005] In spite of this situation, in the conventional interlayer connection technology for circuit boards, the cross-sectional shape of a via or the like is changed to a circular shape or the like along the direction in which the wiring layer extends.
That is, a circular or elliptical shape having a geometrical minimum peripheral length with respect to a required cross-sectional area is performed. However, when the cross section of a via or the like is circular or the like, heat is applied when mounting the semiconductor chip on the circuit board, and the via or the like may expand and contract along the thickness direction of the circuit board. Even if it occurs, the insulating layer on which the side surfaces such as vias are in close contact does not exert sufficient suppressing force to suppress expansion and contraction,
There is a disadvantage that the connection reliability is further degraded.

On the other hand, a circuit board provided with an insulating layer made of a composite material composed of a reinforcing fiber and a synthetic resin, for example,
In the circuit board disclosed in Japanese Patent Application Laid-Open No. 7-170046, the reinforcing fiber is inserted from the side wall surface of the via hole based on the fact that the processing rate of the laser at the time of forming the via hole is different between the reinforcing fiber and the synthetic resin. A structure in which the via and the insulating layer are adhered to each other by using a so-called anchor effect by protruding in the direction and supporting the conductive composition filled in the via hole with the protruding reinforcing fiber is shown. ing. With such a structure, not only can the deterioration of the connection reliability be suppressed, but also the connection reliability can be improved.

However, this interlayer connection technique can be applied only when the insulating layer for electrically insulating the wiring layers is made of a composite material composed of a plurality of insulating materials having different processing rates. Form a via hole in an insulating layer made of a homogeneous insulating material or an insulating layer made of an insulating material with a substantially equal processing rate, and not only when filling with a conductive composition, but also plating on the inner surface of the via hole. It cannot be applied to cases such as applying.

The present invention has been made in view of such circumstances, and has an interlayer connection technique capable of ensuring high connection reliability while effectively preventing deterioration of connection reliability between wiring layers. The purpose of the present invention is to provide a circuit board manufactured by applying the method.

[0009]

A circuit board according to the present invention comprises two or more wiring layers, an insulating layer for electrically insulating the wiring layers, and a predetermined position of the wiring layer penetrating the insulating layer. Electrically connected vias, wherein each of the vias has a non-circular cross section. According to the above configuration, the same connection resistance is ensured by assuming that the via having a non-circular cross-section has substantially the same cross-sectional area as the via having the conventional circular cross-section. Since the perimeter of the via having a cross section is longer than the perimeter of a via having a circular cross section, the contact area between the side surface of the via and the insulating layer becomes geometrically larger than before, resulting in a via The suppression force acting from the insulating layer when expands and contracts along the thickness direction is increased.

[0010]

A circuit board according to a first aspect of the present invention has at least two wiring layers, an insulating layer for electrically insulating the wiring layers, and a predetermined position of the wiring layer penetrating the insulating layer. And vias for electrically connecting the vias, wherein each of the vias has a non-circular cross section. According to the present invention, the suppressing force acting from the insulating layer on the side surface of the via that expands and contracts in the thickness direction, that is, the insulating layer existing around the via tries to suppress the expansion and contraction of the via. Since the force is geometrically increased based on the long perimeter of the via, the advantage that the connection reliability between the wiring layers is enhanced is secured.

According to a second aspect of the present invention, there is provided a circuit board according to the first aspect, wherein a via having a non-circular cross section has a polygonal cross section. A circuit board according to a third aspect of the present invention is the circuit board according to the second aspect, wherein at least one interior angle of the polygons has an angle of 180 ° or more. According to a fourth aspect of the present invention, there is provided a circuit board according to the first aspect, wherein a cross-sectional shape of the via having a non-circular cross-section is a shape provided with an inwardly projecting protrusion. I do. A circuit board according to a fifth aspect of the present invention is the circuit board according to the first aspect, wherein a cross-sectional shape of the via having a non-circular cross-section is a shape provided with an inwardly protruding acute angle portion. I have. According to these inventions, not only the above-mentioned advantages, but also the interior angles of the polygonal shape cut into the insulating layer, and the insulating layer cuts into the protrusions and the sharp corners, so that the geometrical shape Therefore, the advantage that the connection reliability between the wiring layers is further enhanced is secured.

According to a sixth aspect of the present invention, there is provided a circuit board comprising:
A plurality of wiring layers, an insulating layer that electrically insulates the wiring layers, and a via that penetrates the insulating layer and electrically connects predetermined positions of the wiring layer, wherein the via is It is characterized by being divided into a plurality. A circuit board according to claim 7 of the present invention is the circuit board according to claim 6, wherein at least one of the plurality of divided vias includes:
It has a non-circular cross section. Each of these inventions is characterized in that a cross-sectional area of a via described in claim 1 to claim 5, that is, a plurality of vias that divide and carry a connection resistance is provided. Even when adopted, the suppression force acting from the insulating layer on the side of each via that expands and contracts in the thickness direction is generally increased, so the advantage that the connection reliability between the wiring layers is improved. Secured.

A circuit board according to claim 8 of the present invention is the circuit board according to any one of claims 1 to 7, wherein the via is made of gold, silver, copper, nickel, indium, tin,
It was formed using a conductive composition comprising one or more metal powders, alloy powders, coat powders or mixed powders selected from lead and zinc, and a thermosetting resin or a thermoplastic resin. Characterized in that: A circuit board according to a ninth aspect of the present invention is the circuit board according to any one of the first to seventh aspects, wherein the via is formed of one of gold, silver, copper, nickel, indium, tin, lead, and zinc. It is characterized by being made of one or more selected metals or alloys. According to these inventions,
The advantage is that the connection reliability between the wiring layers can be improved while the connection resistance of the via is reduced.

A circuit board according to a tenth aspect of the present invention is the circuit board according to any one of the first to ninth aspects, wherein the insulating layer is an organic material sheet or an organic material film. A circuit board according to an eleventh aspect of the present invention is the circuit substrate according to the tenth aspect, wherein the organic material sheet or the organic material film is manufactured using polyimide. According to these inventions, a light-weight circuit board having high heat resistance can be formed.

According to a twelfth aspect of the present invention, there is provided a circuit board according to any one of the first to ninth aspects, wherein the insulating layer is thermosetting with respect to an organic or inorganic woven or nonwoven fabric. It is a composite sheet or a composite film impregnated with a resin or a thermoplastic resin. The circuit board according to claim 13 of the present invention is claim 12.
Wherein the composite material sheet or the composite material film is an aramid epoxy prepreg obtained by impregnating an aramid nonwoven fabric with an epoxy resin. According to these inventions, the advantage is obtained that a circuit board having high strength and high heat resistance can be formed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 is a process sectional view showing a manufacturing procedure when a circuit board according to Embodiment 1 is a double-sided circuit board, and FIG. 2 is a manufacturing procedure when a circuit board is a multilayer circuit board. FIG. 3 is an explanatory view exemplifying a specific cross-sectional shape of the via. In these figures, reference numeral 1 denotes a wiring layer, 2 denotes an insulating layer, and 3 denotes a via. The application scope of the present invention is not limited to the circuit board having the structure described below and the circuit board manufactured by using the manufacturing method, and adopts a more general manufacturing method, or Of course, a circuit board manufactured using a general constituent material may be used, and in particular, in this embodiment, the insulating layer included in the circuit board is assumed to be aramid epoxy prepreg. Needless to say, the insulating layer may be an organic sheet or an organic film made of polyimide.

The circuit board according to the present embodiment is shown in FIG.
As shown in FIG. 2C and FIG. 2B, two or more wiring layers 1 and an insulating layer 2 for electrically insulating the wiring layers 1 from each other.
At a predetermined position of the wiring layer 1 through the insulating layer 2, for example,
And vias 3 that electrically connect predetermined positions such as lands to each other.
Non-circular cross-sections as illustrated in FIGS. 3A to 3D, that is, the cross-sectional area along the spreading direction of the wiring layer 1 is substantially the same as a conventional general circular cross-section, but the circumference is circular. It has a non-circular cross section longer than the cross section. That is, each of the vias 3 having a non-circular cross section has a cross-sectional area as compared with the via 4 having a conventional circular cross section as shown in FIG. As a result, the peripheral length is longer. For example, the cross-sectional area of the via 3 having a non-circular cross-section is S, the peripheral length is L, and the circular cross-section has the same cross-sectional area S. Assuming that the peripheral length of the via 4 is r, the via 3 has a sectional shape satisfying r <L.

When the circuit board according to the present embodiment is a double-sided circuit board, the manufacturing procedure shown in FIGS. When the substrate is used, a manufacturing procedure as shown in FIGS. 2A and 2B is adopted. Hereinafter, a method for manufacturing a circuit board will be described with reference to these drawings.

First, in manufacturing a double-sided circuit board, as shown in FIG. 1A, an aramid epoxy prepreg, which is a composite material sheet or a composite material film in which an aramid nonwoven fabric is impregnated with an epoxy resin, is prepared as an insulating layer 2. In addition, a through hole, that is, a through hole called a via hole is formed at each required position of the prepreg 2 by using a YAG laser. That is, in this case, a mask is arranged between the light source of the YAG laser and the prepreg 2 which is a processing object, and the YAG laser light is focused on the prepreg 2 to form an image shown in FIG.
A via hole having a cross-sectional shape as illustrated in each of (a) to (d) is formed.

Subsequently, a conductive composition 5 comprising 90% by weight of copper powder and 10% by weight of an epoxy resin composition containing a curing agent is prepared, and the conductive composition 5 is converted into a prepreg 2 by employing a printing method. After that, an electrolytic copper foil 6 having a thickness of 18 μm is overlapped on both main surfaces of the prepreg 2. Further, they are placed in a vacuum and pressurized (50 ° C.) at a temperature of 200 ° C. for about 1 hour.
kg / cm ² ), that is, when hot pressed,
As shown in (b), the conductive composition 5 filled in the via hole is cured to form the via 3, and a laminate in which the prepreg 2 and the copper foil 6 are integrally bonded is obtained. In this case, each of the vias 3 electrically connects predetermined positions of a wiring layer 1 to be described later.

Next, when the copper foil 6 located on the outermost layer of the obtained laminate is patterned by photolithography, a circuit wiring pattern as the wiring layer 1 is formed. Note that, specifically, a dry film is stuck to both surfaces of the laminate with a hot roll, and only a required portion of the copper foil 6 is cured by ultraviolet exposure of the pattern, and then the uncured portion is subjected to a development treatment. After removing
A circuit pattern is formed by etching in a copper chloride solution and peeling off the dry film. As a result, a double-sided circuit board as shown in FIG. 1C is completed.

On the other hand, when manufacturing a multilayer circuit board, for example, a four-layer circuit board, as shown in FIG. 2A, a double-sided circuit board manufactured according to the above procedure is prepared as a core layer, and According to the same procedure as described above, the prepreg 2 in which the vias 3 have been formed is overlaid on both surfaces of the double-sided circuit board serving as the core layer, and the copper foil 6 is further overlaid and hot pressed. Is done. Then, when the copper foil 6 located on the outermost layer of the obtained laminate is patterned by photolithography, FIG.
A four-layer circuit board as shown in FIG.

Further, each of the vias 3 in the completed double-sided circuit board and the four-layer circuit board, that is, the cross-sectional area along the spreading direction of the wiring layer 1 is substantially the same as the circular cross-section, but the circumference is circular. According to an investigation of the connection reliability of each of the vias 3 illustrated in FIGS. 3A to 3D as having a longer non-circular cross section, the via 3 expands and contracts in the thickness direction. The suppression force acting on the side surface from the insulating layer 2, that is, the force of the insulating layer 2 present around the via 3 to suppress the expansion and contraction of the via 3 is based on the fact that the peripheral length of the via 3 is long. It has been confirmed that the connection reliability between the wiring layers 1 is higher than that of the via 4 having a circular cross section.

In the present embodiment, the specific sectional shape of the via 3 provided in the circuit board is shown in FIG.
It is assumed that the shape is exemplified by (a) to (d),
The present invention is not limited to such a shape alone, and it is considered that the same operation as that of the present embodiment can be ensured as long as it has a non-circular cross-section even if it has another cross-sectional shape. Therefore,
Based on the explanatory diagrams showing the modified examples of FIGS.
A description will be given of a modification of the cross-sectional shape possessed by. That is, FIG.
In (a) to (j), the cross-sectional shape of the via 3 having a non-circular cross-section is a polygonal shape such as a triangular shape or a quadrangular shape,
5A to 5D exemplify a via 3 having a non-circular cross section, in which at least one interior angle of a polygon has an angle of 180 ° or more. .

In the via 3 illustrated in FIGS. 6A to 6D, the cross-sectional shape of the via 3 having a non-circular cross-section is a shape having the protrusion 3a protruding inward.
(A) to (e) illustrate a via 3 having a non-circular cross-sectional shape provided with an inwardly protruding acute angle portion 3b. When the via 3 having such a cross-sectional shape is provided, the connection reliability between the wiring layers 1 is increased for the same reason as the via 3 illustrated in FIGS. 3A to 3D. In addition to the above, anchors based on a geometric shape due to the fact that each interior corner of the polygonal shape cuts into the insulating layer 2 and the insulating layer 2 cuts into the protrusion 3a and the acute angled portion 3b. It has been confirmed by the inventors of the present invention that as a result of the effect, the connection reliability between the wiring layers 1 is further enhanced.

(Embodiment 2) FIG. 8 is a cross-sectional view showing a structure in a case where a circuit board according to Embodiment 2 is a double-sided circuit board. Since it is only different from the first embodiment of FIG.
In FIG. 7, the same reference numerals are given to the same parts as those in FIG. 1, and the detailed description is omitted here. Here, although the circuit board is a double-sided circuit board, it is needless to say that the circuit board is not limited to a double-sided circuit board and may be a multilayer circuit board such as a four-layer circuit board.

FIG. 8 shows a circuit board according to the second embodiment.
As shown by, two or more wiring layers 1, an insulating layer 2 for electrically insulating between these wiring layers 1, a predetermined position of the wiring layer 1 penetrating the insulating layer 2, for example, a land or the like. And a via 8 for electrically connecting predetermined positions to each other. The via 8 is formed by dividing the single via 3 described in the first embodiment into a plurality of, for example, three, and arranging them in parallel with each other. It has become. Thus, each of the three divided vias 8 divides and bears the connection resistance of the single via 3. Note that the via 8 is not limited to the one divided into three, and it is needless to say that the via 8 may be divided into at least two or more.

That is, in the present embodiment, three vias 8 instead of vias 3 provided in the circuit board according to the first embodiment, that is, vias 8 having substantially the same cross-sectional area as via 3 are used. Above, electrical connection between predetermined positions of the wiring layer 1 is performed. Then, with the adoption of such a configuration, the perimeter of each of the combined vias 8 is longer than the perimeter of the via 4 having a circular cross section, so that the expansion and expansion along the thickness direction occur. Since the suppressing force acting from the insulating layer 2 on each side surface of the shrinking via 8 is generally higher than that of the via 4 having a circular cross section, the connection reliability between the wiring layers 1 is higher than before. Benefits will be secured. In addition, at least one of these three vias 8 may have a non-circular cross section, and in such a configuration, higher connection reliability can be secured.

As described above, the circuit board according to the present invention comprises two or more wiring layers 1, an insulating layer 2 for electrically insulating between the wiring layers 1, and a wiring layer penetrating the insulating layer 2. 1 and a via 3 (8) for electrically connecting predetermined positions to each other, but the manufacturing method and constituent materials are limited to those described in the first and second embodiments. Therefore, various modifications of the manufacturing procedure and the constituent materials will be collectively described below.

(A) The method of forming a via hole is not limited to the YAG laser processing method, and any other method may be employed as long as it can form a via hole conforming to the cross-sectional shape of the via in the present invention. it can. For example, there are a machining method using a puncher and a drill, a laser processing method such as carbon dioxide gas and excimer, a plasma method and a photolithography method. Further, when a via hole having a finer cross-sectional shape is required, a dry etching method or the like can be used.

The above-described YAG laser processing method, mechanical processing method using a puncher, excimer laser processing method, plasma method, and photolithography method are preferable in that a via hole having a relatively free cross-sectional shape can be processed. If an insulating layer made of a composite material having a different processing rate is processed after adopting the laser processing method, a structure in which a material having a lower processing rate protrudes from the inner surface of the via hole can be obtained. Higher connection reliability can be realized by a synergistic effect.

(B) As the insulating layer provided on the circuit board,
In addition to the aramid epoxy base material described in the embodiment, for example, a glass epoxy base material or a paper phenol base material, and PBO (polyparaphenylenebenzobisoxazole) fiber, PBI (polybenzimidazole) fiber, aramid fiber, PTFE (polytetrafluoroethylene)
For a woven or non-woven fabric made of organic fibers such as fibers, PBZT (polyparaphenylene benzobisthiazole) fibers or wholly aromatic polyester fibers or inorganic fibers such as glass fibers, epoxy resin, polyimide resin, phenol resin, fluorine resin, Unsaturated polyester resin, PPE
It is possible to use a composite material sheet or a composite material film impregnated with a thermosetting resin or a thermoplastic resin such as a (polyphenylene ether) resin or a cyanate ester resin. Further, an organic sheet or film made of a synthetic resin such as polyimide, BCB (benzocyclobutene), PTFE, aramid, PBO or wholly aromatic polyester, or an inorganic material such as a ceramic substrate or silicon oxide. Insulating materials can also be used.

When an organic material sheet, an organic material film, or an inorganic insulating material is used as the insulating layer, an adhesive is applied to both surfaces of the organic material sheet or the like as necessary. When the via hole is formed by a photolithography method, for example, a photosensitive synthetic resin sheet or film such as photosensitive polyimide can be used as the insulating layer. In this case, a via hole is formed in the photosensitive sheet or film using a photolithography method, and a via is formed by filling a conductive composition or filling a metal. Is done. It is also possible to form an insulating layer by applying a liquid synthetic resin or a synthetic resin varnished with a solvent or the like and curing the resin, or by forming a desired via by a photolithography method and then curing the same.

(C) The wiring layer is not limited only to those made of electrolytic copper foil, and any metal such as rolled copper foil or aluminum foil may be used as long as it is a conductor capable of forming wiring layers. Although foil may be used, it is preferable to use electrolytic copper foil from the viewpoint of cost.
Electrolytic copper foils of about 3 μm to about 3 μm are used.
Further, it is a matter of course that the wiring layer may be formed by employing a wet film forming method such as electroplating or electroless plating, or a vacuum film forming method such as PVD or CVD. In addition,
According to the wet film forming method, a wiring layer with good accuracy can be manufactured, and thus it is considered preferable when a finer wiring pattern is required. Further, when a finer wiring pattern is required or when a wet process cannot be used, a wiring layer is formed by a vacuum film forming method.

(D) The conductive composition filled in the via hole is not limited to one composed of copper powder and epoxy resin.
For example, gold, silver, copper, nickel, indium, tin, lead,
One or two or more metal powders, alloy powders, coat powders or mixed powders selected from zinc, and a thermosetting resin or a thermoplastic resin such as an epoxy resin or a polyimide resin in a three-roll, hoover. It is needless to say that the paste may be formed by a kneading device such as a marler, a Simpson mill, or a planetary mixer. Note that a conductive composition comprising copper powder, silver powder, silver-coated copper powder, silver-copper alloy powder, and an epoxy resin has low connection resistance and is economical. It can be said that the composition is preferable because it can be filled in the via hole by a printing method or the like.

The conductive composition is not limited to gold, silver, copper, nickel, indium,
It is also possible to use one or more metals or alloys selected from tin, lead, and zinc, and these metals and the like can be obtained by wet plating such as electroplating or electroless plating, sputtering, or the like. The via hole is filled after adopting a vacuum evaporation method such as evaporation or CVD or the like. It should be noted that among these methods, vias having low connection resistance can be formed, and moreover, it is considered that electrolytic copper plating or electroless copper plating is preferable in terms of cost.

[0038]

In the circuit board according to the present invention, by setting the cross-sectional area of the via having a non-circular cross-section to be substantially the same as that of the via having the circular cross-section, the same level of connection resistance is secured, while the non-circular cross-section is ensured. Since the peripheral length of the via having a cross-section is longer than the peripheral length of the via having a circular cross-section, the contact area between the side surface of the via and the insulating layer is geometrically increased, and the via extends in the thickness direction. The restraining force acting from the insulating layer as it expands and contracts along is increasing.
As a result, an effect is obtained that high connection reliability can be ensured while effectively preventing the connection reliability between the wiring layers from deteriorating.

[Brief description of the drawings]

FIG. 1 is a process cross-sectional view showing a manufacturing procedure when a circuit board according to a first embodiment is a double-sided circuit board.

FIG. 2 is a process cross-sectional view showing a manufacturing procedure when the circuit board according to the first embodiment is a multilayer circuit board;

FIG. 3 is an explanatory diagram illustrating a specific cross-sectional shape of a via included in the circuit board according to the first embodiment;

FIG. 4 is an explanatory diagram illustrating a first modification of the cross-sectional shape of the via included in the circuit board according to the first embodiment;

FIG. 5 is an explanatory diagram illustrating a second modification of the cross-sectional shape of the via included in the circuit board according to the first embodiment;

FIG. 6 is an explanatory diagram illustrating a third modification of the cross-sectional shape of the via included in the circuit board according to the first embodiment;

FIG. 7 is an explanatory diagram illustrating a fourth modification of the cross-sectional shape of the via included in the circuit board according to the first embodiment;

FIG. 8 is a cross-sectional view showing a structure when the circuit board according to the second embodiment is a double-sided circuit board.

[Explanation of symbols]

 Reference Signs List 1 wiring layer 2 insulating layer 3 via 8 via

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Satoru Torugawa 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 5E317 AA21 AA24 BB02 BB03 BB12 BB13 BB14 BB15 BB18 CC25 CC31 CC51 CD27 CD32 GG11 5E346 AA43 CC05 CC09 CC10 CC32 CC37 CC38 CC39 CC40 FF07 FF09 FF10 FF13 FF14 FF17 FF24 GG15 HH07 5F044 KK07 KK11

Claims (13)

[Claims] 1. A circuit comprising two or more wiring layers, an insulating layer for electrically insulating the wiring layers, and a via penetrating the insulating layer and electrically connecting predetermined positions of the wiring layers. A circuit board, wherein each of the vias has a non-circular cross-section. 2. The circuit board according to claim 1, wherein the via having a non-circular cross section has a polygonal cross section. 3. The circuit board according to claim 2, wherein at least one interior angle of the polygon is 18
A circuit board having an angle of 0 ° or more. 4. The circuit board according to claim 1, wherein the cross-sectional shape of the via having a non-circular cross-section is a shape provided with a protrusion projecting inward. 5. The circuit board according to claim 1, wherein the cross-sectional shape of the via having a non-circular cross-section is a shape provided with an inwardly protruding acute angle portion. 6. A circuit comprising two or more wiring layers, an insulating layer for electrically insulating the wiring layers, and a via penetrating the insulating layer to electrically connect predetermined positions of the wiring layers. A circuit board, wherein the via is divided into a plurality of pieces. 7. The circuit board according to claim 6, wherein at least one of the plurality of divided vias has a non-circular cross section. 8. The circuit board according to claim 1, wherein the via is made of gold, silver, copper, nickel, indium, tin, lead,
One formed from a conductive composition comprising one or more metal powders, alloy powders, coat powders or mixed powders selected from zinc, and a thermosetting resin or a thermoplastic resin. A circuit board, comprising: 9. The circuit board according to claim 1, wherein the via is made of gold, silver, copper, nickel, indium, tin, lead,
A circuit board comprising one or more metals or alloys selected from zinc. 10. The circuit board according to claim 1, wherein the insulating layer is an organic material sheet or an organic material film. 11. The circuit board according to claim 10, wherein the organic sheet or the organic film is made of polyimide. 12. The circuit board according to claim 1, wherein the insulating layer is formed by impregnating an organic or inorganic woven or nonwoven fabric with a thermosetting resin or a thermoplastic resin. A circuit board, which is a composite sheet or a composite film. 13. The circuit board according to claim 12, wherein the composite material sheet or the composite material film is an aramid epoxy prepreg obtained by impregnating an aramid nonwoven fabric with an epoxy resin.