JP2001345525A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board which has a through-hole conductor of an inside and outside double structure where inductance of the whole inside of a through-hole can be reduced effectively and electrical characteristics can be improved, in an insulating board, and to provide the manufacturing method of the wiring board. SOLUTION: This wiring board 1 is provided with the insulating board 2 having a front 3 and a back 4, an outside through-hole conductor 6 which penetrates a part between the surface 3 and the back 4 of the insulating board 2, and an inside through-hole conductor 10 which is formed in the inside of the outside through-hole conductor 6 via an insulating material 8, and the sectional shape of the inside through hole conductor 10 is an ellipse shape having a long axis L and a short axis S. Since mutual inductance at the position of shortest distance x between the inside and the outside through-hole conductors 10, 6 becomes large, the inductance of the overall through-hole where the mutual inductance subtracted from the total value of self inductances of the conductors 10, 6 can be reduced to be as small as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board having wiring layers on the front surface and the back surface of an insulating substrate, and the wiring layers are electrically connected to each other.

[0002]

2. Description of the Related Art In recent years, in response to demands for higher density and higher performance of wiring boards, a plurality of wiring layers on the front and back surfaces of an insulating substrate are individually connected to each other. It is known to form inner and outer double through-hole conductors coaxially. For example, in the multilayer wiring board 50 shown in FIGS. 6A and 6B, inner copper foil layers 54 and 55 for a ground circuit are formed on both front and back surfaces of an insulating substrate 52, and
Is formed in a through hole 53 penetrating through the inner copper foil layers 54 and 55. Outer copper foil layers 58, 59 are formed on the inner copper foil layers 54, 55 via a prepreg 57, and signal patterns 61, 62 extending at right angles to each other are formed thereon. Inside the conductor 56, a through-hole conductor 64 coaxial with the conductor 56 penetrates through the filling resin 63, and electrically connects the outer copper foil layers 58, 59 and the signal patterns 61, 62 individually ( JP-A-4-62894).

In the wiring board 50 described above, a characteristic impedance corresponding to the distance between the shield conductor 56 and the through-hole conductor 64 arranged coaxially is obtained. The reflection can be eliminated. For this reason, even when the rise time of the signal is short, it is possible to avoid malfunction in the system caused by the signal reflection.
(See the above publication). Meanwhile general, when energized in the same direction of current to the parallel conductors of the two, because the addition both the mutual inductance (2 × M) is the self-inductance L _1, L ₂ of each lead, large overall inductance L _T Is known to be.

In the case of the wiring substrate 50, the insulating substrate 52
In particular, when a pair of through-hole conductors (56, 64) coaxially arranged inside and outside in the through-hole 53 are connected to a power source and the other is connected to a ground (ground), power is supplied. Mutual inductance M occurs in both the conductors together with the self-inductances L ₁ and L ₂ . in this case,
A current flows in opposite directions to each other, the whole inductance L _T is a value obtained by subtracting both the mutual inductance (2 × M) from the total value of the self-inductance L _1, L ₂ of each conductor. Therefore, in the wiring board 50, it is possible to suppress the overall inductance L _T by the shielding conductor 56 and through-hole conductors 64. However, in the conductor 56, 64 is arranged in the coaxially, because it is insufficient to reduce the overall inductance L _T, hardly contribute to the improvement of electrical characteristics, for example, the occurrence of simultaneous switching and radiation noise There was a problem that it could not be prevented effectively.

[0005]

SUMMARY OF THE INVENTION The present invention solves the problems of the prior art described above, and can effectively reduce the entire inductance in the through hole and improve the electrical characteristics. An object of the present invention is to provide a wiring board having a double-layered through-hole conductor in an insulating substrate.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an inner / outer double through-hole conductor,
The present invention has been conceived to have a cross-sectional shape having a long axis and a short axis. That is, the wiring board of the present invention is an insulating substrate having a front surface and a back surface, and an outer through-hole conductor penetrating between the front surface and the back surface of the insulating substrate,
An inner through-hole conductor formed inside the outer through-hole conductor via an insulating material, wherein at least one of the cross-sectional shapes of the outer through-hole conductor and the inner through-hole conductor has a long axis and a short axis. Having a shape,
It is characterized by the following.

[0007] According to this, the inner / outer through-hole conductor is more reliably approached than other parts at a position on the extension of the long axis of the inner through-hole conductor or the extension of the short axis of the outer through-hole conductor, for example. However, the mutual inductance (2 × M) at the above position increases. For this reason, such mutual inductance is used as the self-inductance L ₁ ,
Total inductance L _T subtracted from the total value of L ₂
Can be reduced as much as possible. Therefore, a wiring board with improved electrical characteristics such as reduced simultaneous switching noise and radiation noise can be obtained. In the cross section of the inner / outer through-hole conductor, for example, when the cross section is a circle such as an ellipse or an oval, the long axis and the short axis are the longest diameter and the shortest diameter. Refers to things that are almost orthogonal to each other. When the cross section is a rectangle such as a rectangle, the longer one of the perpendicular bisectors between the opposing sides is the longer axis, and the shorter one is the end axis.

[0008] The present invention also includes a wiring board in which at least one of the outer through-hole conductor and the inner through-hole conductor has a cross-sectional shape of one of an ellipse, an oval, and a rectangle. According to this, a through-hole conductor having a cross-sectional shape having the long axis and the short axis can be easily and accurately set. In this specification, an oval or a rectangle also has a major axis, a minor axis, and one central axis. Further, a wiring board in which the center axis (z1) of the outer through-hole conductor is shifted from the center axis (z2) of the inner through-hole conductor is also included. According to this, the distance of the closest part between the inner and outer through-hole conductors can be further reduced, and the entire inductance in the through-hole can be further reduced.
The center axis also includes the position where the long axis and the short axis intersect in the cross section of the inner / outer through-hole conductor.

[0009] The present invention also includes a wiring board in which the shortest distance between the outer through-hole conductor and the inner through-hole conductor is 10 μm. According to this, since a proper interval is provided in a portion where the inner and outer through-hole conductors are closest to each other, the mutual inductance between the two conductors can be effectively increased. The distance (x)
Is less than 10 μm, this range is excluded because they are too close to each other and unfavorable from the viewpoint of temperature / humidity / bias voltage acceleration test (HAST), that is, insulation degradation or failure due to migration occurs. . The distance (x) is more desirably 20 μm or more.

A step of forming an outer through-hole penetrating between the front and back surfaces of the insulating substrate, a step of forming an outer through-hole conductor on the inner peripheral surface of the through-hole, A step of filling the hollow portion penetrating along the axial direction with an insulating material, a step of forming an inner through hole penetrating along the axial direction in the filled insulating material, and Forming an inner through-hole conductor on the inner peripheral surface, wherein the cross-sectional shape of at least one of the outer through-hole conductor and the inner through-hole conductor is a shape having a long axis and a short axis. The manufacturing method of the wiring board described above may also be included. In this case, it is possible to reliably provide a wiring board having the above-described cross-sectional shape and having inner / outer through-hole conductors having a double structure.

The inner and outer through-hole conductors having the above-mentioned cross-sectional shape are formed with a through-hole having substantially the same cross-sectional shape as the inner and outer through-hole conductors by using a drill or laser irradiation on an insulating substrate or an insulating material. The through hole is formed by plating the inner peripheral surface with metal. For the above laser irradiation, long pulse by CO ₂ laser or cycle mode method of high power laser (circular shot)
Is preferable for forming a through hole with good shape accuracy. Note that a through-hole having a cross-sectional shape of an ellipse or the like may be formed by performing trepanning (boring a hole) by a burst mode method (continuous shots) or laser scanning. On the other hand, in the case of drilling with a drill, the cross-sectional shape can be formed by repeatedly performing normal drilling along one direction.

Further, the ratio of the major axis to the minor axis of the outer through-hole conductor or the inner through-hole conductor is more than 1: 1.
The wiring board may be in the range of 2: 1. According to this, the mutual position of the inner and outer through-hole conductors and the shortest distance (x) of the closest part between the two can be accurately and effectively set. If the above ratio is larger than 2: 1, the shortest contact distance between the inner and outer through-hole conductors is too small and the conductors are too close to each other. Further, the wiring board may be configured such that one of the outer through-hole conductor and the inner through-hole conductor is connected to a power supply circuit, and the other is connected to a ground (ground) circuit. According to this, it is possible to particularly effectively reduce simultaneous switching noise and radiation noise.

[0013]

Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1A shows a cross section of a main part of a wiring board 1 of the present invention. As shown in the figure, a wiring board 1 is made of a bismaleimide-triazine (BT) resin having a thickness of about 0.8 mm, and a plurality of Cu substrates symmetrically arranged on the upper surface 3 and the lower surface 4 thereof. Wiring layer 1
2, 14, 20, 21, 28, 29 and an insulating layer 16, 17, 22, 23, 26, 27 made of an epoxy resin.
And In FIG. 1A, the uppermost insulating layer (solder resist layer) 26 has a plurality of flip-chip bumps made of solder projecting therefrom and projecting from the wiring layer 28 to the first main surface 30. (IC connection terminal) 32 protrudes. Each bump 32 is individually connected to a terminal of an IC chip (not shown) mounted on the first main surface 30.

In the opening 31 provided in the lowermost insulating layer (solder resist layer) 27, a connection terminal 33, which is a part of the wiring layer 29, is exposed on the second main surface 34 side. The surface of the terminal 33 is coated with an Au / Ni plating film and connected to a motherboard (not shown). In FIG. 1A, the wiring layers 12, 20, and 28 are connected via via conductors 18 and 24, respectively.
The wiring layers 14, 21, 29 are electrically connected to each other via via conductors 19, 25. On the other hand, as shown in FIG.
An outer through hole 5 having a diameter of about 0.35 mm penetrates between the front and back surfaces 3 and 4 of the insulating substrate 2, and an inner through surface of the through hole 5 has a cylindrical outer through hole having a thickness of about 15 μm. The conductor 6 is formed. The conductor 6 conducts between the wiring layers 12 and 14 above and below the front and back surfaces 3 and 4 of the insulating substrate 2.

Further, the inside of the outer through-hole conductor 6 is filled with an insulating material 8 such as a resin, and as shown in FIG. In the position, the major axis L is about 0.2 mm and the minor axis S is about 0.1 mm
An inner through hole 9 having an elliptical cross section is formed. An inner through-hole conductor 10 having an elliptical cross section and a thickness of about 15 μm is formed on the inner peripheral surface of the hole 9, and an insulative or conductive filler resin having an elliptical column shape is formed inside the conductor 10. 11 are formed. At the upper and lower ends of the conductor 10, a part of the wiring layers 20, 21 is formed.
The outer through-hole conductor 6 and the wiring layers 12 and 14 conducting therewith form, for example, a ground (grounding) circuit, and the inner through-hole conductor 10 and the wiring layers 20 and 21 conducting therethrough, for example, A power supply circuit is formed.

As shown in FIG. 1B, the inner through hole
The conductor 10 has a major axis L orthogonal to each other at an outer diameter of about 0.2.
mm and the minor axis S has an elliptical cross section of about 0.1 mm.
As shown in the figure, the inner and outer
Shortest distance x between the side through-hole conductors 10 and 6 (approximately
60 μm). By the way, on the extension of the short axis S
The distance between the conductors 10 and 6 is about 110 μm, the shortest distance
It is about twice x. At the position of the shortest distance x, the conventional
Compared to the case where the inner and outer through-hole conductors are concentric,
Mutual inductance (2 × M) between the bodies 10 and 6 becomes large.
You. Therefore, when currents flow in opposite directions,
Self inductance L of both₁, L ₂From the sum of
Overall inductance minus mutual inductance
L_TCan be made as small as possible. For example, in
· Overall inductance in the outer through holes 9 and 5
L_TIs the self-injection of the inner and outer through-hole conductors 10, 6.
L is the inductance₂, L₁Is expressed by the following equation 1.
Is done. Incidentally, the inner and outer through-hole conductors in FIG. 1 (B)
When the shortest distance x is set to 60 μm,
As in FIG. 6B, the inner and outer through-hole conductors (56,
64) is arranged in a concentric circle.
Lactance L_TWas reduced by about 20%.

[0017]

L _T = (L ₁ + L ₂ ) −2 × M

Also, as shown in FIG.
The center axis z2 of the hole conductor 10 is set to the outside through-hole conductor.
6 along the long axis L of the conductor 10 with respect to the central axis z1 of
By shifting the distance by 0 μm, the shortest distance x is 20 to 30 μm
Can be reduced. In this case, the inner and outer through hoes
Temperature / humidity due to too close
/ Bias voltage acceleration test (HAST) is inconvenient
And the mutual inductance between the conductors 10 and 6
In order to effectively increase (2 × M), the shortest distance x is 1
It should not be less than 0 μm. As a result,
Dactance L _TCan be further reduced.
The ratio between the major axis L and the minor axis S of the inner through-hole conductor 10 is shown.
Is preferably in the range of more than 1: 1 to 2: 1. This
As a result, the shortest distance between the inner and outer through-hole conductors 10 and 6
The closest part having the distance x can be formed, and the shortest distance
The separation x can be less likely to be less than 10 μm.

FIGS. 2 to 3 relate to main manufacturing steps of the wiring board 1. FIG. 2A shows a BT having a thickness of about 0.8 mm.
1 shows an insulating substrate 2 made of resin and having a copper foil (not shown) adhered to front and rear surfaces 3 and 4. First, an outer through hole 5 having a diameter of about 0.35 mm penetrating between the front and back surfaces 3 and 4 of the insulating substrate 2 is drilled by a drill (not shown). Next, electroless and electrolytic copper plating was performed on the inner peripheral surface of the hole 5 and the copper foil on the front and back surfaces 3 and 4 of the substrate 2, as shown in FIG.
As shown in FIG. 1A, plating layers 3a and 4a including an outer through-hole conductor 6 having a thickness of about 15 μm are formed.

Next, a resin paste is printed and filled in the outer through-holes 5 in which the outer through-hole conductors 6 are formed, and the resin paste is hardened. As shown in (B), the insulating material 8 is filled in the outer through-hole 5. Further, the plating layers 3a,
As shown in FIG. 2B, an etching resist having a predetermined pattern is formed above and below 4a, and unnecessary portions of the plating layers 3a and 4a on the front and back surfaces 3 and 4 are removed by etching. The wiring layers 12 and 14 having a predetermined pattern are formed on the front and rear surfaces 3 and 4 of the second semiconductor device.

Further, as shown in FIG.
Insulating layers 16, 1 made of epoxy resin on the upper and lower sides of 2, 14
7 is formed, a predetermined position in the insulating layers 16 and 17 and the insulating material 8 is applied to a laser Y from a not-shown emission source.
Is irradiated. Among them, the laser Y on the insulating material 8 includes:
A long pulse by a CO ₂ laser or a high-power laser by a cycle mode method is applied, so that the inner through hole 9 with good shape accuracy can be formed. Also, by laser processing,
As shown in (D), via holes 13 are formed in predetermined positions of the insulating layers 16 and 17. Further, the insulating layer 16,
At a predetermined position penetrating the insulating material 17 and the insulating material 8, FIG.
As shown in FIG. 5, an inner through hole 9 having a major axis L of about 0.2 mm and a minor axis S of about 0.1 mm and an elliptical cross section is formed. As shown, the inner through-hole 6 has the central axis at the same position as the central axis of the outer through-hole 5, and the ratio of the major axis L to the minor axis S is about 2: 1.

Next, electroless and electrolytic copper plating is applied to the inner peripheral surface of the inner through hole 9, the upper and lower portions of the insulating layers 16 and 17, and the inside of each via hole 13. The conditions of the plating solution used for this were Cu: concentration 18 g / liter, H ₂ SO ₄ : 18.
0 g / liter, Cl ^- ion: 48 g / liter, leveler (inhibitor): 0.3 g / liter, current density: 1 A / dm ² . As a result, as shown in FIG. 3B, plating layers 15 including the inner through-hole conductors 10 having a thickness of about 15 μm, a major axis of about 0.2 mm, and a minor axis of about 0.1 mm are formed at the above-described locations.
The plating layer 15 in each via hole 13 is a via conductor 18, 1.
It becomes 9. Further, a resin paste is printed and filled into the inside through-hole 9 in which the inside through-hole conductor 10 is formed via a metal mask (not shown) having an opening for filling a hole according to the cross-sectional shape of the hole 9. I do. As the paste, a mixture obtained by adding an inorganic filler and an imidazole-based curing agent to a bisphenol-type epoxy resin and mixing them is used. The filled resin paste is semi-cured by heating, the upper and lower portions are polished and flattened, and then re-heated and cured.

As a result, as shown in FIG. 3 (C), an insulative elliptic column-shaped filling resin 11 is formed in the inner through-hole conductor 10. In addition, by filling a resin paste in which a large amount of metal powder is kneaded, the conductive filler resin 11 is filled.
Can also be formed. Further, an etching resist (not shown) having a predetermined pattern is formed on the plating layers 15 on both the front and back sides in FIG. 3B, and unnecessary portions of the plating layer 15 are removed by etching, thereby obtaining FIG. As shown in (C), wiring layers 20 and 21 having predetermined patterns and via conductors 18 and 19 are formed on the insulating layers 16 and 17. At this time, the upper and lower ends of the inner through-hole conductor 10 are
Part of 0,21 is formed. As a result, the wiring layers 20,
21 are electrically connected to each other via the inner through-hole conductor 10.

The insulating layers 16 and 17 and the wiring layer 2
The insulating layers 22, 23, 26, 27, the wiring layers 28, 29,
Via conductors 24 and 25 and flip chip bump 3
Form 2 and so on. Thus, the wiring board 1 shown in FIGS. 1A and 1B can be obtained. FIG. 2A to FIG.
According to the method of manufacturing the wiring board 1 shown in FIG. 3C, the inner through hole 9 is formed in addition to the normal manufacturing process. The inner through-hole conductor 10 having a cross section can be formed, and the portion having the shortest distance x can be easily and reliably formed between the inner and outer through-hole conductors 10 and 6.

FIG. 4A is a cross-sectional view similar to FIG. 1B, in which the insulating substrate 2 has an outer through hole 5a having an elliptical cross section.
And an outer through-hole conductor 36 having a similar shape along its inner peripheral surface and having an elliptical cross section having a major axis L and a minor axis S,
3 shows a state in which the insulating substrate 2 is formed so as to penetrate between the front and back surfaces 3 and 4. Inside the outer through-hole conductor 36, through the insulating material 8, an inner through-hole 9a concentric with the center axis and having a circular cross section and an inner through-hole conductor 38 having a circular cross section along the inner peripheral surface are formed. The filling resin 11 is formed inside the inside through-hole conductor 38.
The outer through hole 36 is formed by drilling or trepanning of a CO ₂ laser (Y).

For this reason, a pair of upper and lower shortest distances x between the inner and outer through-hole conductors 38, 36 along the short axis S.
And a mutual inductance (2 × M) between the conductors 38 and 36 increases at such a position. Thus, when currents flow in the conductors 38 and 36 in opposite directions, the self-inductance L of the two conductors 38 and 36 is reduced.
_1, the overall inductance L _T from the total value obtained by subtracting the mutual inductance L _2, can be reduced as much as possible. As shown in FIG. 4B, the center axis z of the inner through-hole conductor 38 is shifted upward along the short axis S with respect to the center axis z1 of the outer Inner and outer through-hole conductors 38,
36, the closest part can be formed, and the shortest distance x can be further reduced. Thus, when currents flow in the conductors 38 and 36 in opposite directions, the inner and outer through-hole conductors 3
8,36 the overall inductance _{L T} can be further reduced.

FIG. 4C is a cross-sectional view similar to FIG. 1B, in which the insulating substrate 2 has an outer through hole 5a having an elliptical cross section.
And an outer through-hole conductor 36 having a similar shape along the inner peripheral surface and having a long axis L and a short axis S are formed so as to penetrate between the front and back surfaces 3 and 4 of the insulating substrate 2. . Inside the outer through-hole conductor 36, via an insulating material 8, an inner through-hole 9 having an elliptical cross-section concentric with the center axis thereof, and having an elliptical cross-section along the inner peripheral surface and having a short axis L and a short axis L An inner through-hole conductor 10 having an axis S is formed. The major axes L of the conductors 36 and 10 and the minor axis S
Are formed so as to be orthogonal to each other.
Filled resin 11 is formed inside the inside through-hole conductor 10.

Therefore, in FIG. 4C, the short axis S of the outer through-hole conductor 36 and the inner through-hole conductor 10
Along the long axis L of the inner and outer through-hole conductors 10,
Between 36, a closest part having a pair of shortest distances x can be formed. At such a portion, the mutual inductance between the two conductors 10 and 36 increases, so that the conductors 10 and 3
If 6 current flows in opposite directions, both self-inductance L _1, from the sum of L ₂ of the total minus the mutual inductance inductance L _T, it can be as small as possible. As shown in FIG. 4D, the center axis z2 of the inner through-hole conductor 10 is shifted upward in the figure with respect to the center axis z1 of the outer through-hole conductor 36.
As a result, a portion closest to the left-right symmetric position can be formed between the inner and outer through-hole conductors 38 and 36, and the shortest distance x can be further reduced. Therefore, if the current conductors 38 and 36 flows in opposite directions, it is possible to reduce the inductance L _T of the entire inner and outer through-hole conductors 38, 36.

FIG. 5A shows an insulating substrate 2 in which an outer through-hole 5 having a circular cross section and an outer through-hole conductor 6 along the inner peripheral surface thereof are provided between the front and back surfaces 3 and 4 of the insulating substrate 2. This shows a penetrated state. As shown in FIG. 5A, inside the outer through-hole conductor 6, an inner through-hole 40 having an oval cross-section and concentric with the center axis of the conductor 6 via an insulating material 8.
An inner through-hole conductor 42 having an oblong cross section having a major axis L and a minor axis S along its inner peripheral surface is formed. The inside of the inside through-hole conductor 42 has a filling resin 11
Are formed. For this reason, in FIG. 5 (A), along the long axis L of the inner through-hole conductor 42 in the left-right direction, a pair of shortest distances x between the inner and outer through-hole conductors 42, 6 having the shortest distance x on the left and right sides. Can be formed. The inner through hole 40 having an oval cross section is formed by trepanning the CO ₂ laser Y.

At such a position, the mutual inductance between the conductors 42 and 6 becomes large. Therefore, when currents flow in the conductors 42 and 6 in opposite directions to each other, the above-mentioned values are obtained from the sum of the self inductances L ₁ and L ₂ of the _two. it is possible to reduce the overall inductance L _T by subtracting the mutual inductance as possible. As shown in FIG. 5B, the center axis z2 of the inner through-hole conductor 42 is shifted rightward in the drawing along the long axis L thereof with respect to the center axis z1 of the outer Can be formed between the inner and outer through-hole conductors 42, 6 so that the shortest distance x can be further reduced. Thus, if the conductor 42,6 current flows in opposite directions, the inductance L _T of the entire inner and outer through-hole conductors 42,6 can be further reduced.

FIG. 5 (C) shows an outer through-hole 44 having an oblong cross section in the insulating substrate 2 and an outer through hole 44 having a similar shape along the inner peripheral surface and having a long axis L and a short axis S. The through hole conductor 46 is shown penetrating between the front and back surfaces 3 and 4 of the insulating substrate 2. The outer through-hole 44 having an elliptical cross section is formed by an extremely fine drill or the laser Y scanning. As shown in FIG.
Inside the outer through-hole conductor 46, an insulating material 8 is interposed, and an inner through-hole 9 having a circular cross section concentric with the center axis thereof is provided.
a and an inner through-hole conductor 38 having a circular cross section along the inner peripheral surface thereof, and inside the conductor 38,
The filling resin 11 is formed.

For this reason, an approaching portion having a pair of upper and lower shortest distances x can be formed between the inner and outer through-hole conductors 38, 46 along the short axis S. At such a portion, the mutual inductance between the conductors 38 and 46 increases.
Thus, current conductors 38, 46 may flow in opposite directions to each other, to both the self-inductance L _1, from the sum of L ₂ of the total minus the mutual inductance inductance L _T as small as possible be able to. As shown in FIG. 5D, the center axis z2 of the inner through-hole conductor 38 is equal to the center axis z2 of the outer through-hole conductor 46.
Is shifted downward along the short axis S in the figure, a portion closest to the lower and inner through-hole conductors 38 and 46 can be formed, and the shortest distance x can be further reduced. Thus, if the current conductors 38, 46 are reversed to each other, the inductance L _T of the entire inner and outer through-hole conductors 38, 46 can be further reduced.

The present invention is not limited to the embodiments described above. The outer through-hole conductor may be connected to a power supply circuit, and the inner through-hole conductor may be connected to a ground circuit. Also, when the outer through-hole conductor is connected to the ground circuit and the inner through-hole conductor is used as the signal circuit wiring, if the currents flowing in both directions are opposite to each other, the inner and outer through-hole conductors The overall inductance can be reduced. Further, an arbitrary number of the inner / outer through-hole conductors 10, 6 and the like are formed at predetermined positions on the insulating substrate 2 in any of the above-described embodiments. The material of the insulating substrate 2 and the like is, in addition to the BT resin, a glass-epoxy resin composite material, a glass woven fabric having the same heat resistance, mechanical strength, flexibility, workability, and the like, a glass woven fabric, and the like. A glass fiber-resin material which is a composite material of the above glass fiber and a resin such as an epoxy resin, a polyimide resin, or a BT resin may be used. Alternatively, a composite material of an organic fiber and a resin such as a polyimide fiber or a resin-resin composite material in which a resin such as an epoxy resin is impregnated with a fluorine resin having a three-dimensional network structure such as PTFE having continuous pores may be used. It is possible.

Further, the inner and outer through-hole conductors 1
The material such as 0, 6 or the wiring layers 12, 14 may be Ni, Ni-Au, or the like in addition to Cu, or a conductive resin may be applied without using such a metal plating film. May be formed by the above method. Further, the via conductor 18 and the like are not limited to a conical shape following the via hole 13,
A filled via that fills the via hole 13 may be used. Further, the material of the insulating layers 16 and 17 is not limited to the epoxy resin as a main component, but also polyimide resin, BT resin, P
A resin-resin composite material in which a resin such as an epoxy resin is impregnated with a fluorine resin having a three-dimensional network structure such as PE resin or PTFE having continuous pores can also be used. For the formation of the insulating layer, a method of thermocompression bonding of an insulating film can be used in addition to a method of applying a liquid resin by a roll coater.

[0035]

According to the wiring board of the present invention described above, for example, the inner and outer through-holes are positioned on the extension of the major axis of the inner through-hole conductor or on the extension of the minor axis of the outer through-hole conductor. The conductor is more reliably approached than other parts, and the mutual inductance at the position is increased. Therefore, the total inductance obtained by subtracting the mutual inductance from the total value of the self-inductances of the two can be reduced as much as possible. Therefore, a wiring board with improved electrical characteristics such as reduced simultaneous switching noise and radiation noise can be obtained. According to the wiring board of the third aspect, the distance of the closest part between the inner and outer through-hole conductors can be further reduced, and the inductance of the entire through-hole can be further reduced. Furthermore, according to the wiring board of claim 4,
Since the closest distance between the inner and outer through-hole conductors can be appropriately set, the mutual inductance between the two conductors can be effectively increased, and the overall inductance can be minimized.

[Brief description of the drawings]

FIG. 1A is a sectional view showing a main part of a wiring board of the present invention,
(B) is a sectional view taken along line BB in (A), and (C) is a sectional view showing a modification of (B).

2 (A) to 2 (D) are cross-sectional views showing respective manufacturing steps for obtaining the wiring board of FIG. 1 (A).

FIG. 3A is a cross-sectional view taken along line AA in FIG. 2D.
(B), (C) is sectional drawing which shows each subsequent manufacturing process.

4A is a cross-sectional view at a position similar to FIG. 1B including an outer through-hole conductor having a different form, FIG. 4B is a cross-sectional view showing a modified form of FIG. 1A, and FIG. FIG. 9D is a similar cross-sectional view including inner and outer through-hole conductors of the embodiment, and FIG.

FIG. 5A is a cross-sectional view at a position similar to FIG. 1B including an inner through-hole conductor having a further different form, and FIG.
(A) is a cross-sectional view showing a modified embodiment, (C) is a similar cross-sectional view including a different form of an outer through-hole conductor, (D) is (C)
Sectional drawing which shows the modification of FIG.

FIG. 6A is a cross-sectional view illustrating a main part of a conventional wiring board.
(B) is a sectional view taken along line BB in (A).

[Explanation of symbols]

 1 Wiring substrate 2 Insulating substrate 3 Front surface 4 Back surface 5, 5a, 44 Outside through hole 6, 36, 46 ... outside through-hole conductor 8 ... insulation material 9, 9a, 40 ... inside through-hole 10, 38, 42 ... inside through-hole conductor L ... long-axis S ... short axis z1, z2 ... central axis x ... shortest distance

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Ritsuhiro Matsushima 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi F-term in Japan Special Ceramics Co., Ltd. 5E317 AA24 AA25 BB01 BB11 CC31 CD21 CD23 CD25 CD27 CD32 GG11 5E346 AA02 AA06 AA41 BB01 BB16 CC09 CC31 CC40 DD01 DD22 EE31 FF15 GG15 GG17 HH06

Claims (4)

[Claims] 1. An insulating substrate having a front surface and a back surface, an outer through-hole conductor penetrating between the front surface and the back surface of the insulating substrate, and an inner surface formed inside the outer through-hole conductor through an insulating material. And a through hole conductor, wherein a cross-sectional shape of at least one of the outer through hole conductor and the inner through hole conductor is a shape having a major axis and a minor axis. 2. A sectional shape of at least one of said outer through-hole conductor and said inner through-hole conductor is elliptical.
The wiring board according to claim 1, wherein the wiring board is one of an oval and a rectangle. 3. The wiring board according to claim 1, wherein a center axis of the outer through-hole conductor is shifted from a center axis of the inner through-hole conductor. 4. The wiring board according to claim 1, wherein a shortest distance between the outer through-hole conductor and the inner through-hole conductor is 10 μm.