JP6921708B2 - Ceramic substrate - Google Patents

Description

The present invention relates to a ceramic substrate in which a plurality of via conductors are relatively densely arranged on the central side in a plan view of the surface of a substrate body made of ceramic.

Generally, a ceramic substrate is manufactured by printing or filling a conductive paste containing a metal powder on the surfaces of a plurality of ceramic green sheets or through holes provided therein, laminating these green sheets, and further firing them. ing. However, it is known that the obtained ceramic substrate is inadvertently warped due to the difference in the amount of shrinkage between the ceramic and the metal during the firing.
For example, a plurality of wiring portions formed by laminating a plurality of ceramic layers to form an external wiring pattern, an internal wiring pattern, and vias (via conductors) connecting the external wiring patterns, and along the periphery of the wiring portions. It consists of an arranged rectangular frame-shaped non-wiring portion, and by providing a dummy via (dummy via conductor) in the non-wiring portion, it is possible to suppress the occurrence of inadvertent warpage and improve the yield in the mounting process of electronic components. A ceramic multilayer substrate has been proposed (see, for example, Patent Document 1).

By the way, on the central side of the surface of the substrate body made of ceramic, a plurality of pads for mounting electronic components are formed on the surface, and directly below each pad, in the thickness direction of the substrate body. A plurality of via conductors arranged along the line are individually connected. The central side in a plan view between the central side and the peripheral side on the surface of the substrate body in which the plurality of via conductors are relatively densely arranged is due to the difference in the amount of shrinkage in the firing process during manufacturing. The surface of the above-mentioned is further contracted along the thickness direction due to the contraction of the entire plurality of via conductors than the surface on the peripheral side. As a result, when the shrinkage amount of the via conductor is larger than the shrinkage amount of the ceramic, a recess that is convex toward the opposite back surface side is included on the center side of the front surface, and includes the plurality of via conductors in a plan view. It is formed along the mounting area. When the recess is generated, the peripheral portion of the bottom surface of the electronic component mounted on the plurality of pads is in contact with or too close to the inclined surface or the curved surface on the peripheral side of the recess, so that the electronic component is required. It cannot be mounted in the posture and position of, and the electrical connection can become unstable. Further, since the recess is formed of a curved surface, the connection height between the pad on the peripheral side near the end of the recess and the pad on the center side are different. There was a problem that the connection reliability was lowered.

Japanese Unexamined Patent Publication No. 2012-114183 (pages 1 to 13, FIGS. 1 to 5)

The present invention solves the problems described in the background art, and even if a plurality of via conductors are relatively densely arranged on the central side in a plan view on the surface of a substrate body made of ceramic, the plurality of vias are arranged. An object of the present invention is to provide a ceramic substrate capable of accurately and electrically mounting electronic components on the upper side of a conductor.

Means for Solving Problems and Effects of Invention

In order to solve the above problems, the present invention is mounted in a plan view by arranging dummy via conductors along the outside of a mounting region in which a plurality of via conductors are arranged on the surface of a substrate body made of ceramic. It was conceived to form a recess wider than the bottom surface of the electronic component to be formed.
That is, the ceramic substrate (claim 1) of the present invention is made of ceramic and has a rectangular outer shape in a plan view and has a front surface and a back surface facing each other. A ceramic substrate that is located, has a rectangular outer shape in a plan view, and has a mounting region having a plurality of via conductors arranged along the thickness direction of the substrate body, and is provided on the surface of the substrate body. A plurality of dummy via conductors formed along the thickness direction of the substrate main body are arranged along the outside of the mounting region in a plan view, and the mounting region and a plurality of the mounting regions on the surface of the substrate main body in a plan view. The dummy via conductors are included, and have concave portions that are convex on the back surface side of the substrate body in a side view, and the plurality of dummy via conductors are L in a plan view along only the vicinity of the four corners in the mounting region. It is characterized in that it is arranged in a character shape.

According to the ceramic substrate, the following effects (1) and (1') can be obtained.
(1) On the surface of the substrate main body, there is a mounting region in which a plurality of the via conductors are relatively densely arranged on the center side of the surface in a plan view, and a plurality of mounting regions are arranged along the outside of the mounting region. Dummy via conductor is arranged. Therefore, in the firing step at the time of manufacturing, the plurality of dummy via conductors as well as the plurality of via conductors also shrink along their axial directions. A relatively flat recess that includes a plurality of dummy via conductors located on the outside and is convex on the back surface side of the substrate body in a side view and has a larger area than the mounting area of the electronic component to be mounted later is formed. ing. Therefore, when the electronic component is mounted by brazing or the like with respect to the upper end surfaces of the plurality of via conductors or through a plurality of pads joined to the upper end surfaces of the via conductors, the electronic component is used. Can be accurately and easily mounted in a required posture and position, so that it is possible to reliably obtain an electrical connection between each via conductor and the electronic component.
(1') The mounting area has a rectangular (square or rectangular) shape in a plan view, and the outer shapes of the plurality of via conductors arranged in the mounting area are substantially similar to the outer shape of the mounting area in a plan view. It is in shape. Therefore, in the firing process during manufacturing, the via conductors are relatively dense in the vicinity of the four corners of the mounting region, and the region where the via conductor exists (that is, the region where the shrinkage is large) and the via conductor do not exist. It is a boundary with a region (that is, a region with small contraction). As a result, the vicinity of the four corners is relatively less likely to shrink than the other portions, and as described above, the plurality of dummy via conductors are formed into an L shape along only the vicinity of the four corners in the mounting region in a plan view. By disposing of the ceramic substrate, the ceramic substrate has a recess on the surface of the substrate body that is relatively wider than the mounting area of the same electronic component. Therefore, it is possible to achieve the effect (1).

The ceramic is, for example, a high-temperature fired ceramic such as alumina or aluminum nitride, or a low-temperature fired ceramic such as glass-ceramic.
Further, the mounting area has a rectangular shape (square or rectangular shape) in a plan view.
Further, the via conductor is made of tungsten (hereinafter, simply referred to as W) or molybdenum (hereinafter, simply referred to as Mo) when the substrate body is the high temperature co-fired ceramic, and when the substrate body is the high temperature co-fired ceramic, the via conductor is made of molybdenum (hereinafter, simply referred to as Mo). Consists of copper or silver.
Further, the dummy via conductor may be formed for each ceramic layer located at different depths in the same substrate body.
Further, the via conductor may have a pad protruding on the surface of the substrate body bonded to the upper end surface thereof.
Further, the dummy via conductor is made of the same metal as the via conductor or a metal of the same type.
Further, the recess has a flat arc shape or a flat inverted trapezoidal shape when viewed from the side.
In addition, the ceramic substrate may be in the form of a large number of pieces including a product area in which a plurality of the ceramic substrates are arranged vertically and horizontally adjacent to each other in a plan view.

Further, in the present invention, the substrate body is a laminate of a plurality of ceramic layers, and the upper end surface of the dummy via conductor is exposed on the surface of the substrate body (claim 2 ). Is also included.
According to this, since the upper end surfaces of the plurality of dummy via conductors are exposed on the surface of the substrate main body, the surface side of the substrate main body in which the plurality of dummy via conductors are located is included in the firing step at the time of manufacturing. The recess is formed at the position. As a result, the electronic components can be accurately mounted via the conductor balls (for example, solder balls) or through the pads previously joined to each of the upper end surfaces of the plurality of via conductors located in the mounting region. Can be done. Therefore, it is possible to surely achieve the effect (1).
The plurality of dummy via conductors may be those that penetrate the uppermost ceramic layer having the surface of the substrate main body, or the ceramic layer and the ceramic layer of the middle layer adjacent thereto.

The present invention also includes a ceramic substrate (claim 3 ) in which the upper end surface of the dummy via conductor also serves as an alignment mark.
According to this, for example, when the mounting area is rectangular in a plan view, four dummy via conductors whose upper end surface also serves as an alignment mark are arranged at four corners which are extension lines of each of the two diagonal lines in the mounting area. Alternatively, in the outer shape of the mounting area, four dummy via conductors that also serve as alignment marks are arranged on the extension line of each pair of intermediate lines that pass through the intermediate points of the pair of opposing sides at right angles in the vertical and horizontal directions. Is exemplified. As a result, more accurate mounting is possible by confirming the position of each of the dummy via conductors by image processing using a CCD camera or the like at the time of mounting the electronic component to be performed later. Therefore, by using a dummy via conductor that also serves as an alignment mark, the effect (1) can be obtained more prominently, and further mounting by image processing becomes possible (hereinafter, referred to as the effect (2)).
The dummy via conductor that also serves as the alignment mark may be the same as the via conductor, or may have a color added to the upper end surface thereof by plating or painting.

In addition, in the present invention, the substrate body is a laminate of a plurality of ceramic layers, and the dummy via conductor is formed on the middle ceramic layer in the substrate body (claim 4 ). Is also included.
According to this, since the plurality of dummy via conductors are formed in the ceramic layer of the middle layer in the substrate main body, shrinkage during firing is less likely to be alive on the front surface side and the back surface side of the substrate main body. As a result, the ceramic substrate has the recess, which is wider than the mounting region in a plan view and suppresses the inclination of the inclined surface or the steepness of the curved surface located on the peripheral side, on the central side of the surface of the substrate main body. Has been done. Therefore, the ceramic substrate can obtain the effect (1) more reliably.
Further, according to the above-described embodiment, it is possible to reliably prevent a situation in which an electronic component is mounted in an erroneous region by being confused with a mounting pad (hereinafter, referred to as effect (3)).
Further, according to the above-described embodiment, since the via conductor is not exposed to the outside, the amount of nickel film or gold film used by electrolytic plating described later can be reduced (hereinafter, referred to as effect (4)).
The dummy via conductor has, for example, a relatively vertically long form penetrating the ceramic layer of the uppermost layer and the ceramic layer of the middle layer in the vicinity of the four corners of the mounting region, and the middle layer is placed at an intermediate position on each of the four sides of the mounting region. It may be in a relatively short form that penetrates only the ceramic layer.

(A) is a plan view showing a premise and name Ru one reference embodiment of the ceramic substrate of the present invention, (B) is a vertical sectional view taken along the arrow line X-X in (A), (C) an electron A vertical cross-sectional view similar to the above showing a state in which components are mounted. (A) is a partial plan view of the ceramic substrate of the embodiment including the dummy via conductors of different arrangements, and (B) is a partial plan view of the ceramic substrate including the dummy via conductors of the application embodiment. FIG. 3 is a vertical cross-sectional view of the ceramic substrate of the embodiment or reference embodiment comprising dummy via conductors of different forms of arrangement. (A) is a partial plan view of the ceramic substrate including a dummy via conductor of a different reference form, and (B) is a plan view of the ceramic substrate including a dummy via conductor of a further different reference form.

Hereinafter, embodiments for carrying out the present invention will be described.
Figure 1 (A) is a plan view showing assumption and the ceramic substrate 1 one reference embodiment ing of the present invention, FIG. 1 (B), a vertical cross section along the arrow line X-X in (A) It is a figure.
As shown in FIGS. 1 (A) and 1 (B), the ceramic substrate 1 has a substrate main body 2 having a square (rectangular) outer shape in a plan view and having a front surface 3 and a back surface 4 facing each other, and the substrate main body 2. A mounting region 5 having a plurality of via conductors 7 arranged along the thickness direction of the substrate main body 2 and located on the central side in a plan view of the surface 3 of the substrate 3 is provided.
The substrate main body 2 is formed by integrally laminating three (plural) ceramic layers (ceramics) c1 to c3, and the ceramic layers c1 to c3 are mainly made of, for example, alumina.

Further, the mounting area 5 is a virtual area for arranging an electronic component described later to be mounted on the surface 3 of the substrate main body 2, and has substantially the same size as the bottom surface of the electronic component. The upper end surfaces of the plurality of via conductors 7 arranged in a grid pattern in a plan view are exposed on the surface 3 in the mounting region 5. The via conductor 7 is made of W or Mo and penetrates the ceramic layers c1 and c2 of the uppermost layer and the middle layer of the substrate main body 2.
The plurality of via conductors 7 are arranged relatively densely as compared with the peripheral side of the surface 3 of the substrate main body 2 in a plan view. The plurality of via conductors 7 may be arranged in a checkered pattern (staggered pattern) in a plan view.
Further, as shown in FIGS. 1A and 1B, disk-shaped pads 9 projecting on the surface 3 of the substrate main body 2 are individually joined in advance to each of the upper end surfaces of the plurality of via conductors 7. Has been done. The pad 9 is also made of W or Mo, and the surface exposed to the outside is coated with a nickel film and a gold film (neither shown) by electroplating.

An inner layer wiring (not shown) is appropriately formed between the ceramics c1 to c3, and the inner layer wiring is connected to any of the via conductors 7 and penetrates the ceramic layers c2 and c3 of the middle layer and the bottom layer. It is also electrically connected to a plurality of external connection terminals (not shown) formed on the back surface 4 of the substrate main body 2 via a via conductor (not shown). The inner layer wiring, via conductor, and external connection terminal are also made of W or Mo.
Further, as shown in FIGS. 1A and 1B, on the surface 3 of the substrate main body 2, a plurality of dummy via conductors 8 have a rectangular frame shape and substantially along the outside of the mounting region 5 in a plan view. They are evenly spaced. The dummy via conductor 8 is also made of W or Mo, and both penetrate the ceramic layers c1 and c2. At the time of manufacture, the dummy via conductor 8 is conductive, containing W powder or Mo powder filled in each of a plurality of via holes formed in the ceramic green sheet by the same punching process, as in the via conductor 7. It is a baked paste.

In addition, as shown in FIGS. 1A and 1B, the surface 3 of the substrate body 2 has a rectangular shape including the mounting region 5 and the plurality of dummy via conductors 8 in a plan view, and has side surfaces. Visually, it has a recess 10 that is shallowly convex on the back surface 4 side of the substrate body 2. The recess 10 is a shaft of the plurality of via conductors 7 and the plurality of dummy via conductors 8 which were not fired when the three-layer ceramic green sheet laminate serving as the substrate main body 2 was fired. It is formed as a result of contraction along the direction. Depending on the degree of contraction and the like, a smaller and shallow recess (not shown) may be formed substantially line-symmetrically on the central side of the back surface 4 of the substrate main body 2 as well as having a similar figure in plan view. ..

FIG. 1C is a similar vertical cross-sectional view showing a state in which the electronic component 12 is mounted on the mounting region 5 on the surface 3 of the substrate main body 2.
As shown in the drawing, the electronic component 12 having a rectangular parallelepiped as a whole is formed by solder or the like (not shown) above a plurality of pads 9 joined at each upper end of the plurality of via conductors 7 located in the mounting region 5. It is implemented via. Moreover, the recess 10 is also formed in the region of the surface 3 of the substrate main body 2 including the plurality of dummy via conductors 8, and the recess 10 is relatively flat on the central side in a plan view and is on the central side. The peripheral side has a relatively steep curved surface. As a result, as shown in FIG. 1C, the electronic component 12 has a plurality of external surfaces (not shown) provided on the bottom surface of the electronic component 12, while the entire periphery of the bottom surface of the electronic component 12 is located inside the recess 10. The electrodes can be individually conducted with the plurality of via conductors 7 via the solder or the like or the pads 9.
Therefore, according to the ceramic substrate 1 as described above, it becomes easy to mount the electronic component 12 in a predetermined position and orientation with high accuracy (the effect (1)).

FIG. 2A is a partial plan view showing the ceramic substrate 1 of the embodiment including the dummy via conductors 8 having an arrangement different from the above.
As shown in FIG. 2A, a mounting region 5 having a plurality of via conductors 7 arranged in the same manner is located on the central side of the surface 3 of the substrate main body 2 in a plan view, and the mounting region 5 is located. A plurality of dummy via conductors 8 are arranged at substantially equal intervals on the outside of the four corners of the region 5 only in the vicinity thereof. The shrinkage during firing tends to be relatively unlikely to occur in the mounting region 5 having a rectangular shape in a plan view, in the vicinity of the four corners where the two sides are adjacent to each other than the intermediate side in each side of the mounting region 5.
Therefore, the effect (1) can also be obtained by the above-described embodiment in which the plurality of dummy via conductors 8 are arranged only in the vicinity of the four corners outside the mounting region 5.
In FIG. 2A, of the five dummy via conductors 8 at each of the four corners having an L-shaped plan view, the dummy via conductors 8 located at each corner may be omitted.

FIG. 2B is a partial plan view of the ceramic substrate 1 showing an application form of the form shown in FIG. 2A.
As shown in FIG. 2B, a plurality of similar mounting regions 5 are located on the central side of the surface 3 of the substrate main body 2, and a plurality of the same mounting regions 5 are located outside the four corners of the mounting region 5 only in the vicinity. The dummy via conductor 8 is arranged in an L shape in a plan view. Then, among the five dummy via conductors 8 for each of the four corners that exhibit an L-shape in the plan view, the ones located at each corner are combined with the dummy via conductor 8a that also serves as an alignment mark for easy image recognition in the plan view. It was done. Like the other dummy via conductors 8, the dummy via conductor 8a has a form in which the outermost layer of the upper end surface is coated with a gold film by plating, or a coating film having a bright color such as white (both are shown in the figure). It may be coated with (1).
As shown in the figure, the four dummy via conductors 8a are located at positions where two diagonal lines (virtual lines) in the mounting region 5 individually pass through the center of the mounting region 5 in a plan view. Therefore, when the electronic component 12 is mounted on the mounting region 5, the mounting accuracy of the electronic component 12 is achieved by recognizing the positions of the four dummy via conductors 8a in advance by a CCD camera or the like (not shown). Can be increased more remarkably.
Therefore, according to the above-described embodiment, the above-mentioned effects (1) and (2) can be obtained.

FIG. 3 is a vertical cross-sectional view of the ceramic substrate 1 of the embodiment or the reference embodiment including the dummy via conductors 8b having different arrangements.
As shown in FIG. 3, in the present ceramic substrate 1, the same mounting region 5 is located on the central side of the surface 3 of the substrate main body 2 in a plan view, and the middle layer is formed along the outside of the mounting region 5. A plurality of dummy via conductors 8b penetrating only the ceramic layer c2 are arranged. The dummy via conductor 8b, which is not exposed on the front surface 3 and the back surface 4 of the substrate main body 2, may be formed along the entire outer circumference of the mounting region 5 in a plan view, or may be formed only in the vicinity of the four corners of the mounting region 5. It may be arranged.
By using the dummy via conductor 8b, as shown in FIG. 3, the concave portion 10 formed on the surface 3 side of the substrate main body 2 has a more relaxed steepness on the curved surface of the peripheral portion thereof, and thus the above effect (1). ) Can be obtained more reliably.
In addition, the effects (3) and (4) can be combined.

FIG. 4A is a partial plan view of the ceramic substrate 1 including dummy via conductors 8 and 8b having different reference forms.
As shown in FIG. 4A, also in the present ceramic substrate 1, the same mounting region 5 is located on the central side of the surface 3 of the substrate main body 2 in a plan view. A plurality of dummy via conductors 8 are arranged along the outside of the mounting region 5 in a plan view, penetrating the ceramic layers c1 and c2 in the vicinity of each of the four corners, and exposing the upper end surface on the surface 3 of the substrate main body 2. In addition, a plurality of dummy via conductors 8b that penetrate only the ceramic layer c2 and are not exposed on the surface 3 are arranged in the middle of each side of the mounting region 5.

As described above, by disposing the plurality of dummy via conductors 8 in the vicinity of the four corners of the mounting region 5, and disposing the plurality of dummy via conductors 8b in the middle of each side of the mounting region between them. In the shrinking process after firing, a steep curved surface is formed in the vicinity of the four corners of the mounting region 5 at each corner of the recess 10 along the thickness direction of the substrate body 2, and each of the mounting regions 5 is formed. It is possible to form a recess 10 having a relatively gentle curved surface peripheral portion adjacent to each intermediate position of the side.
Therefore, the ceramic substrate 1 of the above-described form also has the above-mentioned effect (1).
In FIG. 4A, the dummy via conductor 8a, which also serves as an alignment mark, may be individually added and arranged near the four corners of the recess 10.

FIG. 4B is a plan view of the ceramic substrate 1 including dummy via conductors 8 and 8a having a different reference form.
As shown in FIG. 4B, also in the present ceramic substrate 1, the same mounting region 5 is located on the central side of the surface 3 of the substrate main body 2 in a plan view. Along the outside of the mounting area 5 in a plan view, a plurality of dummy via conductors 8 are arranged in two rows inside and outside and in a staggered manner in the vicinity of each of the four corners, and each of the mounting areas 5 is located between them. A plurality of dummy via conductors 8 are arranged in a row along the inside of the mounting area 5 in the middle of each side.

Further, as shown in the drawing, one dummy via conductor 8a also serving as an alignment mark is arranged outside each corner portion of the mounting region 5.
According to the above-described form, the ceramic substrate 1 having a recess 10 having a relatively large area on the central side of the surface 3 of the substrate main body 2 in a plan view can be formed, and the effects (1), (1). 2) can be played.
It should be noted that a plurality of dummy via conductors 8 may be arranged in two or more rows inside and outside along the entire outer circumference of the mounting region 5 in a plan view. In this case, the plurality of dummy via conductors 8 are not limited to the staggered shape in a plan view, and may be arranged at each grid-like position.
Further, the dummy via conductor 8a may be replaced with a normal dummy via conductor 8.

The present invention is not limited to each of the forms described above.
For example, the ceramic constituting the substrate main body 2 may be, for example, a high-temperature fired ceramic such as aluminum nitride or mullite, or a low-temperature fired ceramic such as glass-ceramic. In the latter case, copper or silver is applied to the conductors such as the via conductor 7, the dummy via conductors 8, 8a, 8b, and the pad 9.
Further, the substrate main body 2 may be a laminate of two ceramic layers or four or more ceramic layers. For example, in the case of the substrate main body 2 composed of four ceramic layers, the via conductor 7 and the dummy via conductors 8 and 8a are only the uppermost ceramic layer having the surface 3 or adjacent to the uppermost ceramic layer. The dummy via conductor 8b may be formed to penetrate one or both of the two ceramic layers in the middle layer.

Further, the front surface 3 and the back surface 4 of the substrate main body 2 may have a rectangular shape facing each other in a plan view.
Further, a mounting region 5 having a rectangular outer shape in a plan view may be provided on the central side of the surface 3 of the substrate main body 2. In the case of such a form, the dummy via conductor 8 (including the dummy via conductors 8a and 8b) is arranged only along the outside of the pair of short sides facing each other among the sides constituting the rectangular shape. , It is recommended that the pitch arranged along the outside of the pair of short sides be smaller than the pitch arranged along the outside of the pair of long sides facing each other.
Further, the pad 9 may be omitted, and the upper end surface of the via conductor 7 may be exposed on the surface of the substrate main body 2.

Further, the dummy via conductor 8a also serving as the alignment mark is arranged at four locations outside the intermediate position on each side of the mounting region 5 having a rectangular shape in a plan view, or a corner portion of the mounting region 5. The form may be arranged in any three places in each case.
In addition, the recess 10 has a substantially similar shape surrounding the mounting region 5 having a rectangular shape in a plan view, and the middle of each side is gently curved toward the peripheral side or the central side of the surface 3. It may be.

According to the present invention, even if a plurality of via conductors are relatively densely arranged on the central side of the surface of the substrate body made of ceramic, the electronic component can be accurately and accurately arranged above the plurality of via conductors. It is possible to reliably provide a ceramic substrate that can be reliably mounted electrically.

1 ……………… Ceramic substrate 2 ……………… Substrate body 3 ……………… Front side 4 ……………… Back side 5 ……………… Mounting area 7 ……………… Via conductors 8,8a, 8b ... Dummy via conductors 10 ............... Recesses c1 to c3 ... Ceramic layer (ceramic)

Claims (4)

A substrate body made of ceramic, having a rectangular outer shape in a plan view and having opposite front and back surfaces.
It is located on the central side of the surface of the substrate body in a plan view, has a rectangular outer shape in a plan view, and has a mounting region having a plurality of via conductors arranged along the thickness direction of the board body. It ’s a ceramic substrate.
On the surface of the substrate body, a plurality of dummy via conductors formed along the thickness direction of the substrate body are arranged along the outside of the mounting region in a plan view, and also.
It includes the mounting area and a plurality of dummy via conductors on the surface of the substrate body in a plan view, and has a concave portion that is convex on the back surface side of the substrate body in a side view.
The plurality of dummy via conductors are arranged in an L shape in a plan view along only the vicinity of the four corners in the mounting region in a plan view .
A ceramic substrate characterized by that. The substrate main body is obtained by laminating a plurality of ceramic layers, and the upper end surface of the dummy via conductor is exposed on the surface of the substrate main body.
The ceramic substrate according to claim 1. The upper end surface of the dummy via conductor also serves as an alignment mark.
The ceramic substrate according to claim 2. The substrate main body is formed by laminating a plurality of ceramic layers, and the dummy via conductor is formed on a middle ceramic layer in the substrate main body.
The ceramic substrate according to claim 1.

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