Multilayer substrate

A multilayer substrate includes a laminate, signal conductors, and external connection conductors. The signal conductors are at different positions in a lamination direction of the laminate. The external connection conductors are provided on a back surface of the laminate. A first signal conductor is connected at one end to one of the external connection conductors by a first wiring conductor. A second signal conductor is connected at one end to one of the external connection conductors by a second wiring conductor. The first signal conductor is closer to the back surface than the second signal conductor. The first wiring conductor includes wiring adjusting conductors each having a length corresponding to a distance difference in the lamination direction between the first and second signal conductors.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multilayer substrate including a laminate provided by laminating a plurality of insulating base materials, and a plurality of signal conductors disposed in the laminate.

2. Description of the Related Art

Japanese Unexamined Utility Model Publication No. H3-044307 discloses a transmission line including a plurality of signal conductors. The transmission line disclosed in Japanese Unexamined Utility Model Publication No. H3-044307 includes a laminate provided by laminating a plurality of dielectrics. The plurality of signal conductors is disposed at respective positions different in a lamination direction.

This kind of conventional transmission line requires wiring portions for connecting respective end portions of each of the signal conductors to respective external connection conductors provided on the front surface or the back surface of the laminate. Thus, the conventional transmission line uses an interlayer-connection conductor extending in the lamination direction as each of the wiring portions.

Unfortunately, the conventional transmission line is configured such that the plurality of signal conductors is different in position in the lamination direction. This causes the interlayer-connection conductor connected to each of the signal conductor to be different in length, so that impedance of each of the wiring portions is different for each of the signal conductors.

As a result, the wiring portions connecting the corresponding plurality of signal conductors and the corresponding external connection conductors are different in impedance. For example, when the wiring conductor connected to one signal conductor is provided to have an impedance of 50Ω, the wiring conductor connected to the other signal conductor has an impedance deviating from 50Ω. Thus, a transmission line portion different in impedance causes loss.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide multilayer substrates provided with a plurality of transmission lines including a plurality of signal conductors, each of the transmission lines including a wiring portion with the same impedance.

A multilayer substrate according to a preferred embodiment of the present invention includes a laminate, a first signal conductor, a second signal conductor, a first external connection conductor, a second external connection conductor, a first wiring conductor, and a second wiring conductor. The laminate is provided by laminating a plurality of dielectric layers. The first signal conductor and the second signal conductor are disposed at respective positions different in a lamination direction of the laminate. The first external connection conductor and the second external connection conductor are provided on a first surface perpendicular or substantially perpendicular to the lamination direction of the laminate. The first wiring conductor connects an end of the first signal conductor to the first external connection conductor. The second wiring conductor connects an end of the second signal conductor to the second external connection conductor. The first signal conductor is disposed at a position closer to the first surface than the second signal conductor. The first wiring conductor includes a wiring adjusting portion having a length corresponding to a distance difference between the first signal conductor and the second signal conductor in the lamination direction.

This structure causes the wiring adjusting portion to reduce a difference in impedance due to a difference between a connection distance between the first signal conductor and the first external connection conductor, and a connection distance between the second signal conductor and the second external connection conductor.

In a multilayer substrate according to a preferred embodiment of the present invention, the wiring adjusting portion may have a shape bypassing a placement position of the second wiring conductor in a plane parallel or substantially parallel to the first surface as viewed in the lamination direction.

This structure causes only a conductor pattern in one plane to reduce a difference in impedance. This enhances connection reliability of the wiring adjusting portion.

In a multilayer substrate according to a preferred embodiment of the present invention, the wiring adjusting portion may include a portion extending from a position where the first signal conductor is disposed toward a position where the second signal conductor is disposed in the lamination direction.

This structure causes a difference in impedance to be reduced by using a conductor pattern extending in the lamination direction. This enables the wiring adjusting portion to be reduced in size in plan view.

In a multilayer substrate according to a preferred embodiment of the present invention, it is preferable that an intermediate ground conductor for a wiring conductor is provided between the first wiring conductor and the second wiring conductor.

This structure increases isolation between the first wiring conductor and the second wiring conductor.

In a multilayer substrate according to a preferred embodiment of the present invention, it is preferable to provide a planar intermediate ground conductor for a signal conductor, disposed between the first signal conductor and the second signal conductor in the lamination direction.

This structure increases isolation between the first signal conductor and the second signal conductor.

In a multilayer substrate according to a preferred embodiment of the present invention, it is preferable that the wiring adjusting portion includes a planar conductor, and the planar conductor is narrower than a line width of the first signal conductor.

This structure enables a first inductance (an inductance component of the first wiring conductor) to be increased without excessively increasing a line length of the wiring adjusting portion.

In a multilayer substrate according to a preferred embodiment of the present invention, it is preferable that the laminate includes a wiring portion, and a connection portion wider than the wiring portion, and that the wiring adjusting portion is provided in a plane parallel or substantially parallel to the first surface and is disposed in the connection portion in the laminate while having a winding shape as viewed in the lamination direction.

This structure enhances stability of the multilayer substrate disposed on a front surface of a circuit board or the like, and enables mountability of the multilayer substrate to be enhanced. This structure also enables a connector or the like to be easily mounted on the connection portion even when the multilayer substrate has an elongated shape.

This structure enables the wiring portion of the multilayer substrate to be led into a limited narrow space (a position avoiding other surface-mount components and structures), so that the multilayer substrate is capable of being disposed in a narrow space. In addition, this structure causes a wiring adjusting conductor in a winding shape to be disposed on the connection portion having a relatively large width, so that a line width of the wiring adjusting conductor is able to be increased. This enables an inductance component to be increased while reducing or preventing an increase in conductor loss of the first wiring conductor, as compared with the case where the wiring adjusting conductor is narrowed in line width.

Preferred embodiments of the present invention enable fabricating a multilayer substrate provided with a plurality of transmission lines including a plurality of signal conductors, each of the transmission lines including a wiring portion with the same impedance.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a plurality of aspects for practicing the present invention will be described with reference to the drawings and several specific examples. In the respective drawings, identical reference numerals identify the same elements or portions. In consideration of description of main points or easy understanding, while the preferred embodiments are separately described for convenience, structures described in different preferred embodiments can be partially substituted or combined. In the second and subsequent preferred embodiments, descriptions of matters common to those of the first preferred embodiment are eliminated, and only different points will be described. In particular, a similar operation effect caused by a similar structure will not sequentially refer to each preferred embodiment.

First Preferred Embodiment

A multilayer substrate according to a first preferred embodiment of the present invention will be described with reference to the accompanying drawings.FIG. 1is an exploded perspective view of the multilayer substrate according to the first preferred embodiment of the present invention.FIG. 2is an external perspective view of the multilayer substrate according to the first preferred embodiment of the present invention.FIG. 3is an enlarged exploded perspective view of a second end portion of the multilayer substrate according to the first preferred embodiment of the present invention.FIG. 4is an enlarged sectional view of the second end portion of the multilayer substrate according to the first preferred embodiment of the present invention.FIG. 4illustrates a section taken along line A-A illustrated inFIG. 3.

As illustrated inFIG. 2, the laminate20has a rectangular or substantially rectangular shape in plan view. The laminate20has a shape long in X direction that is a main signal transmission direction, and short in Y direction perpendicular or substantially perpendicular to the X direction.

The ground conductor41and the external connection conductors611,612,621, and622are provided on a back surface of the laminate20. The ground conductor42is provided on the entire or substantially the entire front surface of the laminate20.

As illustrated inFIG. 1, the laminate20is provided by laminating a plurality of dielectric layers21,22,23,24, and25. The plurality of dielectric layers21,22,23,24, and25are disposed in this order from the back surface of the laminate20. Each of the plurality of dielectric layers21,22,23,24, and25is made of a flexible base material, which includes a liquid crystal polymer as a main component, for example. The back surface of the laminate20corresponds to the “first surface”.

The ground conductor41and the external connection conductors611,612,621, and622are provided on the back surface of the dielectric layer21(the back surface of the laminate20). The ground conductor41is provided on the entire or substantially the entire back surface of the laminate20. The external connection conductors611,612,621, and622are separated from the ground conductor41by a conductor non-provided portion.

The external connection conductors611and621are provided in a vicinity of a first end ED1of the laminate20in the X direction. The external connection conductor611is disposed closer to the first end ED1than the external connection conductor621. The external connection conductors612and622are provided in a vicinity of a second end ED2of the laminate20in the X direction. The external connection conductor612is disposed closer to the second end ED2than the external connection conductor622. The external connection conductors611and612each correspond to the “first external connection conductor”. The external connection conductors621and622each correspond to the “second external connection conductor”.

The dielectric layer22is provided on its front surface (its surface on a dielectric layer23side) with the signal conductor31, wiring adjusting conductors311and312, and interlayer-connection auxiliary conductors321,322,331, and332. The signal conductor31is a linear conductor extending in the X direction. The signal conductor31is provided at or substantially at the center of the dielectric layer22in the Y direction. The signal conductor31corresponds to the “first signal conductor”.

The wiring adjusting conductor311, and the interlayer-connection auxiliary conductors321and331, are provided on a first end ED1side of the signal conductor31. The interlayer-connection auxiliary conductors321and331are provided at or substantially at the center of the dielectric layer22in the Y direction together with the signal conductor31. The interlayer-connection auxiliary conductor331is provided closer to the first end ED1than the interlayer-connection auxiliary conductor321.

The wiring adjusting conductor311is provided on a front surface of the dielectric layer22so as to bypass a formation region of the interlayer-connection auxiliary conductors321and331. The wiring adjusting conductor311has one end in its extending direction connected to the signal conductor31, and the other end in the extending direction disposed between the first end ED1and the interlayer-connection auxiliary conductor331.

The wiring adjusting conductor312, and the interlayer-connection auxiliary conductors322and332, are provided on a second end ED2side of the signal conductor31. The interlayer-connection auxiliary conductors322and332are provided at or substantially at the center of the dielectric layer22in the Y direction together with the signal conductor31. The interlayer-connection auxiliary conductor332is provided closer to the second end ED2than the interlayer-connection auxiliary conductor322.

The wiring adjusting conductor312is provided on a front surface of the dielectric layer22so as to bypass a formation region of the interlayer-connection auxiliary conductors322and332. The wiring adjusting conductor312has one end in its extending direction connected to the signal conductor31, and the other end in the extending direction disposed between the second end ED2and the interlayer-connection auxiliary conductor331.

More specifically, the wiring adjusting conductor312includes a plurality of conductor patterns3121,3122, and3123as illustrated inFIG. 3. The conductor patterns3121and3123each have a shape extending in the Y direction, and the conductor pattern3122has a shape extending in the X direction. The conductor pattern3121is connected at one end in its extending direction to the signal conductor31, and at the other end to one end of the conductor pattern3122. The conductor pattern3122partially overlaps with the formation region of the interlayer-connection auxiliary conductors322and332in the X direction, and is separated from the formation region of the interlayer-connection auxiliary conductors322and332in the Y direction. The conductor pattern3122is connected at the other end to one end of the conductor pattern3123. The other end of the conductor pattern3123corresponds to the other end of the wiring adjusting conductor312. As described above, the wiring adjusting conductor312is provided in a shape that surrounds half or substantially half of the formation region of the interlayer-connection auxiliary conductors322and332when the dielectric layer22is viewed in Z direction. While description is eliminated, a specific shape of the wiring adjusting conductor311described above is also similar to that of the wiring adjusting conductor312.

The dielectric layer23is provided on its front surface (its surface on a dielectric layer24side) with a ground conductor51, and interlayer-connection auxiliary conductors521and522. The ground conductor51corresponds to the “intermediate ground conductor for a signal conductor”. The ground conductor51is provided on the entire or substantially the entire front surface of the dielectric layer23. The interlayer-connection auxiliary conductors521and522are separated from the ground conductor51by a conductor non-provided portion. The interlayer-connection auxiliary conductor521is provided in the vicinity of the first end ED1of the dielectric layer23in the X direction. The interlayer-connection auxiliary conductor521overlaps with the interlayer-connection auxiliary conductor321in plan view from the lamination direction. The interlayer-connection auxiliary conductor522is provided in the vicinity of the second end ED2of the dielectric layer23in the X direction. The interlayer-connection auxiliary conductor522overlaps with the interlayer-connection auxiliary conductor322in plan view from the lamination direction.

The dielectric layer24is provided on its front surface (its surface on a dielectric layer25side) with a signal conductor32, and interlayer-connection auxiliary conductors333and334. The signal conductor32is a linear conductor extending in the X direction. The signal conductor32is provided at or substantially at the center of the dielectric layer24in the Y direction. The signal conductor32corresponds to the “second signal conductor”.

The signal conductor32has one end on a first end ED1side that overlaps with the interlayer-connection auxiliary conductor521in plan view from the lamination direction. The signal conductor32has the other end on a second end ED2side that overlaps with the interlayer-connection auxiliary conductor522in plan view from the lamination direction.

The interlayer-connection auxiliary conductor333is provided between the signal conductor32and the first end ED1on the dielectric layer24in the X direction. The interlayer-connection auxiliary conductor333overlaps with the interlayer-connection auxiliary conductor331in the laminate20.

The interlayer-connection auxiliary conductor334is provided between the signal conductor32and the second end ED2on the dielectric layer24in the X direction. The interlayer-connection auxiliary conductor334overlaps with the interlayer-connection auxiliary conductor332in the laminate20.

The dielectric layer25is provided entirely or substantially entirely on its front surface (the front surface of the laminate20) with the ground conductor42.

As illustrated inFIG. 1, the laminate20is provided with interlayer-connection conductors711,712,721,722,801, and802. The interlayer-connection conductors711,712,721,722,801, and802are fabricated by providing through holes in predetermined dielectric layers, filling the through holes with conductive paste, and curing the conductive paste.

The interlayer-connection conductor711connects the external connection conductor611and the other end of the wiring adjusting conductor311. The interlayer-connection conductor712connects the external connection conductor612and the other end of the wiring adjusting conductor312, as illustrated inFIG. 4.

The interlayer-connection conductor721connects the external connection conductor621and one end of the signal conductor32via the interlayer-connection auxiliary conductors321and521. The interlayer-connection conductor722connects the external connection conductor622and the other end of the signal conductor32via the interlayer-connection auxiliary conductors322and522, as illustrated inFIG. 4.

The interlayer-connection conductor801connects the ground conductor41, the ground conductor51, and the ground conductor42via the interlayer-connection auxiliary conductors331and333. The interlayer-connection conductor802connects the ground conductor41, the ground conductor51, and the ground conductor42via the interlayer-connection auxiliary conductors332and334, as illustrated inFIG. 4.

The structure as described above causes the multilayer substrate10to include the two signal conductors31and32at respective positions different in the Z direction (lamination direction) in the laminate20. The signal conductor31is sandwiched between the ground conductors41and51in the Z direction. This structure defines a first transmission line. The signal conductor32is sandwiched between the ground conductors42and51in the Z direction. This structure defines a second transmission line. This causes the multilayer substrate10to include the first transmission line and the second transmission line at respective positions different in the Z direction of the laminate20.

The signal conductor31is connected at one end on a first end ED1side to the external connection conductor611via the wiring adjusting conductor311and the interlayer-connection conductor711. The wiring adjusting conductor311and the interlayer-connection conductor711define a conductor portion that corresponds to the “first wiring conductor”. The signal conductor31is connected at the other end on a second end ED2side to the external connection conductor612via the wiring adjusting conductor312and the interlayer-connection conductor712. The wiring adjusting conductor312and the interlayer-connection conductor712define a conductor portion that corresponds to the “first wiring conductor”.

The signal conductor32is connected at one end on a first end ED1side to the external connection conductor621via the interlayer-connection conductor721. The interlayer-connection conductor721defines a conductor portion that corresponds to the “second wiring conductor”. The signal conductor32is connected at the other end on a second end ED2side to the external connection conductor622via the interlayer-connection conductor722. The interlayer-connection conductor722defines a conductor portion that corresponds to the “second wiring conductor”.

Here, the wiring adjusting conductors311and312are appropriately adjusted for length. Specifically, a distance between the signal conductor31and the back surface of the laminate20is indicated as D1, and a distance between the signal conductor32and the back surface of the laminate20is indicated as D2.

The signal conductor32is farther from the back surface of the laminate20than the signal conductor31, so that D1is smaller than D2. Thus, the first wiring conductor provided by simply connecting the signal conductor31and the external connection conductors611and612with a conductor extending in the Z direction (e.g., one interlayer-connection conductor) has an inductance component (first inductance) that is smaller than an inductance component (second inductance) of the second wiring conductor provided by simply connecting the signal conductor32and the external connection conductors621and622with a conductor extending in the Z direction (e.g., one interlayer-connection conductor). Here, impedance of a conductor is proportional to a multiplied value of frequency and inductance of a transmission signal. Thus, a first impedance caused by the first inductance is smaller than a second impedance caused by the second inductance. This causes a difference between the first impedance and the second impedance. In particular, the impedance increases as the frequency of the transmission signal increases, so that a transmission signal with a high frequency causes an increase in the difference in impedance.

Because of this, the wiring adjusting conductors311and312are provided to define a portion functioning as an inductor between each of the ends of the signal conductor31and the corresponding one of the external connection conductors611and612. The portion defining and functioning as an inductor increases the first impedance, and thus achieves a shape reducing the difference in impedance. In other words, the wiring adjusting conductors311and312are each provided with a length that reduces the difference between the first impedance and the second impedance. In particular, when the transmission signal is a high frequency signal, an effect of reducing the impedance difference increases.

As a result, the impedance of the first transmission line including the signal conductor31with respect to the outside and the impedance of the second transmission line having the signal conductor32with respect to the outside are substantially the same. Thus, when a circuit with the first transmission line connected and a circuit with the second transmission line connected each have the same impedance, the first transmission line and the second transmission line is able to similarly transmit a high-frequency signal with low loss.

The multilayer substrate10according to the first preferred embodiment further includes the planar ground conductor51disposed between the signal conductor31and the signal conductor32, so that isolation between the signal conductor31and the signal conductor32is able to be increased. In addition, the planar ground conductor51is also disposed between the wiring adjusting conductors311and312, and the signal conductor32. This enables isolation between the wiring adjusting conductors311and312, and the signal conductor32, to be increased.

The multilayer substrate10according to the first preferred embodiment includes the interlayer-connection auxiliary conductor331connected to the ground conductors41,42, and51, being disposed between the interlayer-connection auxiliary conductor321connected to the signal conductor32and the other end of the wiring adjusting conductor311connected to the signal conductor31. This enables isolation between the interlayer-connection auxiliary conductor321and the wiring adjusting conductor311to be increased in the vicinity of the first end ED1of the laminate20, so that isolation between the signal conductor32and the signal conductor31is able to be increased. Likewise, the multilayer substrate10according to this preferred embodiment includes the interlayer-connection auxiliary conductors332connected to the ground conductors41,42, and51, being disposed between the interlayer-connection auxiliary conductor322connected to the signal conductor32and the other end of the wiring adjusting conductor312connected to the signal conductor31. This enables isolation between the interlayer-connection auxiliary conductor322and the wiring adjusting conductor312to be increased in the vicinity of the second end ED2of the laminate20, so that the isolation between the signal conductor32and the signal conductor31is able to be increased.

The multilayer substrate10of the first preferred embodiment includes the wiring adjusting conductors311and312that are provided on one surface, so that an individual dielectric layer for defining the wiring adjusting conductors311and312does not need to be separately provided. This enables the multilayer substrate10to be reduced in dimension (thickness) in the Z direction. In addition, the structure of the multilayer substrate10enables the number of interlayer-connection conductors used for a wiring adjusting portion to be reduced, so that the wiring adjusting portion is improved in connection reliability. Further, conductor loss is less likely to occur in planar conductors than in interlayer-connection conductors, so that conductor loss in the wiring adjusting portion is less likely to increase in the structure of the multilayer substrate10.

While the multilayer substrate10of the first preferred embodiment preferably has a structure in which the wiring adjusting conductors311and312are provided so as to bypass the corresponding placement positions of the second wiring conductors (the interlayer-connection auxiliary conductors321and322, etc.), the present invention is not limited to this structure. The second wiring conductor may be provided so as to bypass the placement position of the first wiring conductor or the ground conductor. That is, a wiring adjusting conductor may be provided in the second wiring conductor. In that case, to enhance symmetry in wiring length between the first wiring conductor and the second wiring conductor, it is preferable that a wiring adjusting conductor on a first wiring conductor side is provided so as to further bypass a wiring adjusting conductor on a second wiring conductor side as viewed in the lamination direction (Z direction).

Second Preferred Embodiment

Next, a multilayer substrate according to a second preferred embodiment of the present invention will be described with reference to the accompanying drawings.FIG. 5is an exploded perspective view of the multilayer substrate according to the second preferred embodiment of the present invention.

A multilayer substrate10A according to the second preferred embodiment is different from the multilayer substrate10according to the first preferred embodiment in structure of portions in signal conductors31and32in the X direction, near a first end ED1and a second end ED2. Hereinafter, differences therebetween will be described in detail.

The multilayer substrate10A includes a laminate20, and the laminate20includes dielectric layers21,22,23,24, and25.

The ground conductor41and the external connection conductors611,612,621, and622are provided on the back surface of the dielectric layer21(the back surface of the laminate20). The ground conductor41is provided on the entire or substantially the entire back surface of the laminate20. The external connection conductors611,612,621, and622are separated from the ground conductor41by a conductor non-provided portion.

The external connection conductors611and621are provided in the vicinity of a first end ED1of the laminate20in the X direction. The external connection conductors611and621are disposed side by side in the Y direction. The external connection conductors612and622are provided in the vicinity of a second end ED2of the laminate20in the X direction. The external connection conductors612and622are disposed side by side in the Y direction. The external connection conductors611and612each correspond to the “first external connection conductor”. The external connection conductors621and622each correspond to the “second external connection conductor”.

The dielectric layer22is provided on its front surface (its surface on a dielectric layer23side) with the signal conductor31, end conductors351and352, and interlayer connection auxiliary conductors321A,322A,341,342,914, and924. The signal conductor31is a linear conductor extending in the X direction. The signal conductor31is provided at or substantially at the center of the dielectric layer22in the Y direction. The signal conductor31corresponds to the “first signal conductor”.

The end conductor351is connected to an end of the signal conductor31on its first end ED1side. The end conductor351has a bent shape having a portion extending in the Y direction and a portion extending in the X direction. The portion extending in the Y direction of the end conductor351is connected to the signal conductor31. The end conductor351is bent toward the external connection conductor611in the Y direction.

The interlayer-connection auxiliary conductor914is provided between the portion extending in the X direction of the end conductor351and the first end ED1in the X direction. In the Y direction, the interlayer-connection auxiliary conductor914and the portion extending in the X direction of the end conductor351are provided at or substantially at the same position. The interlayer-connection auxiliary conductor914overlaps with the external connection conductor611in plan view from the lamination direction.

The interlayer-connection auxiliary conductor341is provided between the signal conductor31and the first end ED1in the X direction. The interlayer-connection auxiliary conductor341has a shape extending in the X direction, and is positioned in the X direction so as to overlap with a part of the portion extending in the X direction of the end conductor351and the interlayer-connection auxiliary conductor914.

The interlayer-connection auxiliary conductor321A is provided at or substantially at the same position as the interlayer-connection auxiliary conductor914in the X direction. The interlayer-connection auxiliary conductor321A is provided opposite to the interlayer-connection auxiliary conductor914across the interlayer-connection auxiliary conductor341in the Y direction. The interlayer-connection auxiliary conductor321A overlaps with the external connection conductor621in plan view from the lamination direction.

The end conductor352is connected to an end of the signal conductor31on its second end ED2side. The end conductor352has a bent shape having a portion extending in the Y direction and a portion extending in the X direction. The portion extending in the Y direction of the end conductor352is connected to the signal conductor32. The end conductor352is bent toward the external connection conductor612in the Y direction.

The interlayer-connection auxiliary conductor924is provided between the portion extending in the X direction of the end conductor352and the first end ED1in the X direction. In the Y direction, the interlayer-connection auxiliary conductor924and the portion extending in the X direction of the end conductor352are provided at or substantially at the same position. The interlayer-connection auxiliary conductor924overlaps with the external connection conductor612in plan view from the lamination direction.

The interlayer-connection auxiliary conductor342is provided between the signal conductor31and the second end ED2in the X direction. The interlayer-connection auxiliary conductor342has a shape extending in the X direction, and is positioned in the X direction so as to overlap with a part of the portion extending in the X direction of the end conductor352and the interlayer-connection auxiliary conductor924.

The interlayer-connection auxiliary conductor322A is provided at or substantially at the same position as the interlayer-connection auxiliary conductor924in the X direction. The interlayer-connection auxiliary conductor322A is provided opposite to the interlayer-connection auxiliary conductor924across the interlayer-connection auxiliary conductor342in the Y direction. The interlayer-connection auxiliary conductor322A overlaps with the external connection conductor622in plan view from the lamination direction.

The dielectric layer23is provided on its front surface (its surface on a dielectric layer24side) with a ground conductor51A, auxiliary ground conductors511A and512A, and interlayer-connection auxiliary conductors521A,522A,911, and921. The ground conductor51A is provided on the entire or substantially the entire front surface of the dielectric layer23except for the vicinity of each of the first end ED1and the second end ED2. The auxiliary ground conductors511A and512A, and the interlayer-connection conductors801A and802A, each correspond to the “intermediate conductor for a wiring conductor”.

The auxiliary ground conductor511A is provided on a first end ED1side of the ground conductor51A, and has a dimension in the Y direction, smaller than a dimension of the ground conductor51A in the Y direction. The auxiliary ground conductor511A is provided at or substantially at the center of the dielectric layer23in the Y direction. The auxiliary ground conductor511A is connected to the ground conductor51A.

The interlayer-connection auxiliary conductor521A is provided between the ground conductor51A and the first end ED1in the X direction. The interlayer-connection auxiliary conductor521A is provided at an interval from the auxiliary ground conductor511A in the Y direction. The interlayer-connection auxiliary conductor521A has one end overlapping with the interlayer-connection auxiliary conductor321A and the external connection conductor621in plan view from the lamination direction. The interlayer-connection auxiliary conductor521A, the interlayer-connection auxiliary conductor321A, and the external connection conductor621are connected by an interlayer-connection conductor7212A.

The interlayer-connection auxiliary conductor911is provided between the ground conductor51A and the first end ED1in the X direction. The interlayer-connection auxiliary conductor911is provided at an interval from the auxiliary ground conductor511A in the Y direction. The interlayer-connection auxiliary conductor911is provided opposite to the interlayer-connection auxiliary conductor521A in the Y direction with respect to the auxiliary ground conductor511A.

The interlayer-connection auxiliary conductor911has one end overlapping with the interlayer-connection auxiliary conductor914and the external connection conductor611in plan view from the lamination direction. The interlayer-connection auxiliary conductor911, the interlayer-connection auxiliary conductor914, and the external connection conductor611are connected by the interlayer-connection conductor913. The interlayer-connection auxiliary conductor911has the other end overlapping with the end conductor351in plan view from the lamination direction. The interlayer-connection auxiliary conductor911and the end conductor351are connected by an interlayer-connection conductor912.

The auxiliary ground conductor512A is provided on a second end ED2side of the ground conductor51A, and has a dimension in the Y direction, smaller than a dimension of the ground conductor51A in the Y direction. The auxiliary ground conductor512A is provided at or substantially at the center of the dielectric layer23in the Y direction. The auxiliary ground conductor512A is connected to the ground conductor51A.

The interlayer-connection auxiliary conductor522A is provided between the ground conductor51A and the second end ED2in the X direction. The interlayer-connection auxiliary conductor522A is provided at an interval from the auxiliary ground conductor512A in the Y direction. The interlayer-connection auxiliary conductor522A has one end overlapping with the interlayer-connection auxiliary conductor322A and the external connection conductor622in plan view from the lamination direction. The interlayer-connection auxiliary conductor522A, the interlayer-connection auxiliary conductor322A, and the external connection conductor622are connected by an interlayer-connection conductor7222A.

The interlayer-connection auxiliary conductor921is provided between the ground conductor51A and the second end ED2in the X direction. The interlayer-connection auxiliary conductor921is provided at an interval from the auxiliary ground conductor512A in the Y direction. The interlayer-connection auxiliary conductor921is provided opposite to the interlayer-connection auxiliary conductor522A in the Y direction with respect to the auxiliary ground conductor512A.

The interlayer-connection auxiliary conductor921has one end overlapping with the interlayer-connection auxiliary conductor924and the external connection conductor612in plan view from the lamination direction. The interlayer-connection auxiliary conductor921, the interlayer-connection auxiliary conductor924, and the external connection conductor612are connected by the interlayer-connection conductor923. The interlayer-connection auxiliary conductor921has the other end overlapping with the end conductor352in plan view from the lamination direction. The interlayer-connection auxiliary conductor921and the end conductor352are connected by an interlayer-connection conductor922.

The dielectric layer24is provided on its front surface (its surface on a dielectric layer25side) with a signal conductor32, end conductors3512and3522, and interlayer-connection auxiliary conductors323and324. The signal conductor32is a linear conductor extending in the X direction. The signal conductor32is provided at or substantially at the center of the dielectric layer24in the Y direction. The signal conductor32corresponds to the “second signal conductor”.

The end conductor3512is connected to an end of the signal conductor32on its first end ED1side. The end conductor3512has a bent shape having a portion extending in the Y direction and a portion extending in the X direction. The portion extending in the Y direction of the end conductor3512is connected to the signal conductor32. The end conductor3512is bent toward the external connection conductor621in the Y direction. The portion extending in the X direction of the end conductor3512has an end overlapping with the other end of the interlayer-connection auxiliary conductor521A in plan view from the lamination direction. The end conductor3512and the interlayer-connection auxiliary conductor521A are connected by an interlayer-connection conductor7211A.

The interlayer-connection auxiliary conductor323is provided between the signal conductor32and the first end ED1in the X direction. The interlayer-connection auxiliary conductor323has a shape extending in the X direction, and is positioned in the X direction so as to overlap with a part of the portion extending in the X direction of the end conductor3512.

The end conductor3522is connected to an end of the signal conductor32on its second end ED2side. The end conductor3522has a bent shape having a portion extending in the Y direction and a portion extending in the X direction. The portion extending in the Y direction of the end conductor3522is connected to the signal conductor32. The end conductor352is bent toward the external connection conductor621in the Y direction. The portion extending in the X direction of the end conductor3522has an end overlapping with the other end of the interlayer-connection auxiliary conductor522A in plan view from the lamination direction. The end conductor3522and the interlayer-connection auxiliary conductor522A are connected by an interlayer-connection conductor7221A.

The interlayer-connection auxiliary conductor324is provided between the signal conductor32and the second end ED2in the X direction. The interlayer-connection auxiliary conductor324has a shape extending in the X direction, and is positioned in the X direction so as to overlap with a part of the portion extending in the X direction of the end conductor3522.

The dielectric layer25is provided on an entirety or substantially an entirety of its front surface (the front surface of the laminate20) with the ground conductor42.

The interlayer-connection conductor801A connects the ground conductor41, the interlayer-connection auxiliary conductor341, the auxiliary ground conductor511A, the interlayer-connection auxiliary conductor323, and the ground conductor42. A plurality of the interlayer-connection conductors801A is provided at intervals along the X direction.

The interlayer-connection conductor802A connects the ground conductor41, the interlayer-connection auxiliary conductor342, the auxiliary ground conductor512A, the interlayer-connection auxiliary conductor324, and the ground conductor42. A plurality of the interlayer-connection conductors802A is provided at intervals along the X direction.

This structure causes a conductor portion where the interlayer-connection conductor912, the interlayer-connection auxiliary conductor911, and the interlayer-connection conductor913are connected, to define and function as a wiring adjusting conductor on a first end ED1side. In addition, a conductor portion where the interlayer-connection conductor922, the interlayer-connection auxiliary conductor921, and the interlayer-connection conductor923are connected, defines and functions as a wiring adjusting conductor on a second end ED2side.

As described above, the multilayer substrate10A according to the second preferred embodiment includes the wiring adjusting conductors each having a shape bending from the position of the signal conductor31toward the position of the signal conductor32in the Z direction. As in the first preferred embodiment, these wiring adjusting conductors are each set to a shape that reduces a difference in impedance between a wiring portion for the signal conductor31and a wiring portion for the signal conductor32. As a result, as in the first preferred embodiment, the impedance of the first transmission line having the signal conductor31with respect to the outside and the impedance of the second transmission line having the signal conductor32with respect to the outside are substantially the same. Thus, when a circuit with the first transmission line connected and a circuit with the second transmission line connected each have the same impedance, the first transmission line and the second transmission line are able to similarly transmit a high-frequency signal with low loss.

Using the structure of the multilayer substrate10A enables the wiring adjusting conductor to be reduced in length for a portion extending in the Y direction. This enables the multilayer substrate10A to be reduced in dimension (length in width direction) in the Y direction. This also enables inductance components to be set equally in interlayer-connection conductors each have the same line length, so that design of a shape to reduce a difference in impedance is able to be facilitated. In addition, an inductance component is able to be increased without increasing a dimension of the wiring adjusting conductor in the Y direction, so that a wiring adjusting portion for the signal conductor31and the interlayer-connection conductors7212A and7222A for the signal conductor32are able to be prevented from joining with each other by using the auxiliary ground conductor511A and512A, the interlayer-connection conductors801A and802A. This causes isolation between the first transmission line and the second transmission line to be easily increased.

In addition, using the structure of the multilayer substrate10A causes a portion of the wiring adjusting conductor to be provided on the same surface as the ground conductor51A. As a result, an individual layer to define a wiring adjusting conductor does not need to be provided, so that the multilayer substrate10A is able to be reduced in dimension in the Z direction (length (thickness) in the lamination direction).

The multilayer substrate10A has the structure in which the signal conductor31and the signal conductor32have respective bent portions that are bent opposite to each other in the Y direction. This enables increase in isolation between the wiring portion for the signal conductor31and the wiring portion for the signal conductor32. The bent portions provided in the respective signal conductors improve design flexibility of the wiring portions, so that design flexibility in shape of the wiring adjusting conductor is improved. This causes a structure to reduce a difference in impedance to be easily achieved.

The multilayer substrate10A has the structure in which the auxiliary ground conductors511A and512A, and the interlayer-connection auxiliary conductors323,324,341, and342, are disposed between the wiring portion for the signal conductor31and the wiring portion for the signal conductor32. The auxiliary ground conductors511A and512A, and the interlayer-connection auxiliary conductors323,324,341, and342, are connected to the ground conductors41,42, and51A by the corresponding interlayer-connection conductors801A and802A extending in the Z direction. This enables achieving high isolation between the wiring portion for the signal conductor31and the wiring portion for the signal conductor32in the Y direction and the Z direction. In addition, the auxiliary ground conductors511A and512A, and the interlayer-connection auxiliary conductors323,324,341, and342, each have a shape extending in the X direction, so that higher isolation is able to be achieved.

The multilayer substrate10A includes the plurality of dielectric layers21,22,23, and24each of which has the same thickness. As a result, the interlayer-connection conductors (interlayer-connection conductors922and923) of the first wiring conductor are identical in wiring length to the interlayer-connection conductors (interlayer-connection conductors7221A and7222A) of the second wiring conductor. This structure enables the first wiring conductor and the second wiring conductor to be equal or substantially equal in wiring length, so that symmetry between the first wiring conductor and the second wiring conductor is able to be enhanced.

The interlayer-connection auxiliary conductors521A and522A each may be used as a wiring adjusting conductor for the signal conductor32. This enables both of the signal conductor31and the signal conductor32to be connected to the respective wiring adjusting conductors, so that a difference in impedance is able to be reduced more accurately within a wide impedance range.

Third Preferred Embodiment

Next, a multilayer substrate according to a third preferred embodiment of the present invention will be described with reference to the accompanying drawings.FIG. 6is an enlarged exploded perspective view of a second end portion of a multilayer substrate10B according to the third preferred embodiment of the present invention.FIG. 7is an enlarged sectional view of the second end portion of the multilayer substrate10B according to the third preferred embodiment.

The multilayer substrate10B according to the third preferred embodiment is different from the multilayer substrate10according to the first preferred embodiment in structure of a wiring adjusting conductor312A. Other structures are the same as those of the multilayer substrate10. Hereinafter, differences therebetween will be described in detail.

In the third preferred embodiment, the wiring adjusting portion includes a planar conductor. Specifically, the wiring adjusting conductor312A includes planar conductors of a plurality of conductor patterns3121,3122, and3123, as illustrated inFIG. 6. In the third preferred embodiment, the wiring adjusting conductor312A (the plurality of conductor patterns3121,3122, and3123) has a line width narrower than that of the signal conductor31. While description is eliminated, a specific structure of a wiring adjusting conductor on a first end side (corresponding to the wiring adjusting conductor311illustrated inFIG. 1) is also similar to that of the wiring adjusting conductor312A.

This structure enables a first inductance (an inductance component of a first wiring conductor) to be increased without excessively increasing a line length of the wiring adjusting conductor312A.

It is conceivable to increase an interlayer-connection conductor712in length (or reduce the interlayer-connection conductor712in diameter) to increase an inductance component. However, when the interlayer-connection conductor712is increased in length (or when the interlayer-connection conductor712is reduced in diameter), conductor loss of the first wiring conductor increases. Thus, it is preferable to increase a first inductance by narrowing a line width of the wiring adjusting conductor312A that is a planar conductor, as shown in the third preferred embodiment.

Fourth Preferred Embodiment

Next, a multilayer substrate according to a fourth preferred embodiment of the present invention will be described with reference to the accompanying drawings.FIG. 8is an enlarged exploded perspective view of a second end portion of a multilayer substrate10C according to the fourth preferred embodiment of the present invention.

The multilayer substrate10C according to the fourth preferred embodiment is different from the multilayer substrate10A according to the second preferred embodiment in structure of a wiring adjusting conductor. Other structures are the same as those of the multilayer substrate10A. Hereinafter, differences therebetween will be described in detail.

As illustrated inFIG. 8, the fourth preferred embodiment shows that interlayer-connection auxiliary conductors522A and921each are a planar conductor and have a line width narrower than that of each of signal conductors31and32, being a plane conductor. While specific description is eliminated, a specific structure of each of interlayer-connection auxiliary conductors on a first end side (corresponding to the interlayer-connection auxiliary conductor521A and911illustrated inFIG. 5) is also similar to that of the corresponding one of the interlayer-connection auxiliary conductors522A and921.

This structure enables a first inductance to be increased without excessively increasing a line length of the wiring adjusting conductor including an interlayer-connection conductor922, the interlayer-connection auxiliary conductor921, and an interlayer-connection conductor923.

This structure also enables a second inductance component (an inductance component of a second wiring conductor) to be increased without excessively increasing a line length of the second wiring conductor. Thus, adjusting both the first inductance and the second inductance enables an effect of reducing a difference between the first impedance and the second impedance to be enhanced.

It is conceivable to increase interlayer-connection conductors922,923,7221A, and7222A in length (or reduce the interlayer-connection conductor922,923,7221A, and7222A in diameter) to increase an inductance component of the first or second wiring conductor. However, when the interlayer-connection conductors922,923,7221A, and7222A are increased in length (or when the interlayer-connection conductors922,923,7221A, and7222A are reduced in diameter), conductor loss increases. Thus, it is preferable to increase an inductance component by narrowing a line width of each of the interlayer-connection auxiliary conductors522A and921, being a planar conductor, as shown in the fourth preferred embodiment.

Fifth Preferred Embodiment

Next, a multilayer substrate according to a fifth preferred embodiment of the present invention will be described with reference to the accompanying drawings.FIG. 9is an external perspective view of a multilayer substrate10D according to the fifth preferred embodiment of the present invention.FIG. 10is an enlarged exploded perspective view of a second end portion of the multilayer substrate10D according to the fifth preferred embodiment of the present invention.

The multilayer substrate10D according to the fifth preferred embodiment is different from the multilayer substrate10according to the first preferred embodiment in shape of a laminate. The multilayer substrate10D is also different from the multilayer substrate10in shape of a wiring adjusting conductor. Other structures are substantially the same as those of the multilayer substrate10. Hereinafter, differences therebetween will be described in detail.

The multilayer substrate10D includes a laminate20A, and the laminate20A includes dielectric layers21,22,23,24, and25.

The dielectric layer21is provided on its back surface (a back surface of the laminate20A) with a ground conductor41, and external connection conductors611,612,621, and622. The ground conductor41is provided on the entire or substantially the entire back surface of the laminate20A. The external connection conductors611,612,621, and622are separated from the ground conductor41by a conductor non-provided portion.

The external connection conductors611and621are provided in the vicinity of a first end ED1of the laminate20A in the X direction. The external connection conductors611and621are disposed side by side in the Y direction. The external connection conductors612and622are provided in the vicinity of a second end ED2of the laminate20A in the X direction. The external connection conductors612and622are disposed side by side in the Y direction. The external connection conductors611and612each correspond to the “first external connection conductor”. The external connection conductors621and622each correspond to the “second external connection conductor”.

The dielectric layer22is provided on its front surface (its surface on a dielectric layer23side) with the signal conductor31, a wiring adjusting conductor312B, interlayer-connection auxiliary conductors322and342, an end conductor352, and the like. The signal conductor31is a linear conductor extending in the X direction. The signal conductor31is provided at or substantially at the center of the dielectric layer22in the Y direction. The signal conductor31corresponds to the “first signal conductor”.

The wiring adjusting conductor312B, the interlayer-connection auxiliary conductors322and342, and the end conductor352are provided on a second end ED2side of the signal conductor31. The interlayer connection auxiliary conductor342is provided at or substantially at the center of the dielectric layer22in the Y direction together with the signal conductor31.

The wiring adjusting conductor312B is connected to an end of the signal conductor31on its second end ED2side. The wiring adjusting conductor312B has a meander shape having a portion extending in the Y direction and a portion extending in the X direction. In addition, the wiring adjusting conductor may have a looped winding shape of a spiral shape, a loop shape, or the like. The portion extending in the Y direction of the wiring adjusting conductor312B is connected to the signal conductor31. A part of the wiring adjusting conductor312B overlaps with the external connection conductor612in plan view from the lamination direction. The wiring adjusting conductor312B and the external connection conductor612are connected by the interlayer-connection conductor712. While description is eliminated, a wiring adjusting conductor and an interlayer-connection auxiliary conductor, similar to the above, are provided in an end portion on a first end ED1side.

The dielectric layer23is provided on its front surface (its surface on a dielectric layer24side) with a ground conductor51, an interlayer connection auxiliary conductor522, and the like. The ground conductor51is provided on the entire or substantially the entire front surface of the dielectric layer23. The interlayer-connection auxiliary conductor522is provided in the vicinity of the second end ED2of the dielectric layer23in the X direction. The interlayer connection auxiliary conductor522is separated from the ground conductor51by an electrode non-provided portion. While description is eliminated, an interlayer-connection auxiliary conductor similar to the above is provided in the vicinity of the first end ED1.

The dielectric layer24is provided on its front surface (its surface on a dielectric layer25side) with a signal conductor32, an end conductor3522, an interlayer-connection auxiliary conductor324A, and the like. The signal conductor32is a linear conductor extending in the X direction. The signal conductor32is provided at or substantially at the center of the dielectric layer24in the Y direction. The signal conductor32corresponds to the “second signal conductor”.

The end conductor3522is connected to a second end of the signal conductor32. The end conductor3522has a bent shape having a portion extending in the Y direction and a portion extending in the X direction. The portion extending in the Y direction of the end conductor3522is connected to the signal conductor32. The portion extending in the X direction of the end conductor3522has an end overlapping with the interlayer-connection auxiliary conductor522in plan view from the lamination direction. The end conductor3522, the interlayer-connection auxiliary conductors322and522, and the external connection conductor622are connected by an interlayer-connection conductor722. While description is eliminated, an end conductor similar to the above is provided in the vicinity of the first end ED1.

The dielectric layer25is provided on entirety or substantially an entirety of its front surface (the front surface of the laminate20A) with the ground conductor42.

The interlayer-connection conductor802B connects the ground conductor42, the interlayer-connection auxiliary conductor324A, the ground conductor51, and the interlayer-connection auxiliary conductor342. The interlayer-connection conductor832connects the ground conductor51, the end conductor352, and the ground conductor41. The interlayer-connection conductor812B connects the interlayer-connection auxiliary conductor342and the ground conductor41. A plurality of the interlayer-connection conductors812B is provided at intervals along the X direction.

As illustrated inFIG. 9, the laminate20A includes a wiring portion CA, a first connection portion CN1, and a second connection portion CN2. The first connection portion CN1and the second connection portion CN2are each a rectangular or substantially rectangular portion for connection to another circuit. The wiring portion CA extends in the Y direction to connect the first connection portion CN1and the second connection portion CN2to each other.

In addition, as illustrated inFIG. 9, the first connection portion CN1and the second connection portion CN2are wider in the X direction than the wiring portion CA.

Next, a state where the multilayer substrate10D is mounted on a circuit board or the like will be described with reference to the drawings.FIG. 11is an external perspective view illustrating a main portion of an electronic device201according to the fifth preferred embodiment.

The electronic device201includes the multilayer substrate10D, a circuit board101, a plurality of surface mount components2, and the like. The circuit board101is a printed wiring board, for example. The surface mount component2is a chip component (a chip inductor, a chip capacitor, or the like), an IC, or the like, for example.

As illustrated inFIG. 11, the circuit board101is provided on its front surface with the plurality of surface mount components2mounted. The multilayer substrate10D is mounted on the front surface of the circuit board101so as to avoid the plurality of surface components2. Specifically, the multilayer substrate10D is bonded to the front surface of the circuit board101with a conductive bonding material such as solder. That is, the fifth preferred embodiment shows that the external connection conductors (611,612,621, and622) of the first connection portion CN1and the second connection portion CN2are bonded to the corresponding conductors provided on the front surface of the circuit board101.

The electronic device201according to the fifth preferred embodiment achieves the following effects.

The fifth preferred embodiment shows that the multilayer substrate10D according to the fifth preferred embodiment includes the first connection portion CN1and the second connection portion CN2that are wider than the wiring portion CA. This structure increases a connection area of the multilayer substrate10D to increase connection strength to the circuit board101and the like. In addition, even when the multilayer substrate10D having an elongated shape is disposed on the front surface of the circuit board101or the like, this structure enables the multilayer substrate10D not to easily fall over. That is, this structure enhances stability of the multilayer substrate10D disposed on the front surface of the circuit board101or the like, and enables mountability of the multilayer substrate10D to be enhanced. This structure also enables a connector or the like to be easily mounted on each of the first connection portion CN1and the second connection portion CN2even when the multilayer substrate10D has an elongated shape.

In addition, the fifth preferred embodiment shows that the wiring portion CA is narrower than each of the first connection portion CN1and the second connection portion CN2. As illustrated inFIG. 11, this structure enables the wiring portion CA of the multilayer substrate10D to be led into a limited narrow space (a position avoiding other surface mount components and structures), so that the multilayer substrate10D is able to be disposed in a narrow space.

The multilayer substrate10D according to the fifth preferred embodiment includes the wiring adjusting conductor312B in a winding shape that is disposed in the connection portion (second connection portion). This structure causes a wiring adjusting conductor in a winding shape to be disposed on the connection portion having a relatively large width, so that a line width of the wiring adjusting conductor can be increased. This enables an inductance component to be increased while reducing or preventing an increase in conductor loss of the first wiring conductor, as compared with the case where the wiring adjusting conductor is narrowed in line width. Disposing wiring adjusting conductors at respective connection portions (the first connection portion CA1and the second connection portion CA2) each having a relatively large width enables the wiring portion CA to be led into a limited narrow space, so that the multilayer substrate10D with the first inductance increased is able to be achieved.

The fifth preferred embodiment includes the multilayer substrate10D that is bonded to the circuit board101with a conductive bonding material. That is, the multilayer substrate is connected to the circuit board or the like without using a connector or a receptacle, so that transmission loss is reduced as compared with the case where a multilayer substrate is connected to a circuit board or the like using a connector and a receptacle.

The fifth preferred embodiment shows that a portion of the wiring adjusting conductor is not provided on the same surface as the ground conductor51, as in the multilayer substrate10A according to the second preferred embodiment. This increases an area of the ground conductor51as compared with the case where a portion of the wiring adjusting conductor is provided on the same surface as the ground conductor51, so that a ground potential is stabilized. In addition, the multilayer substrate10D according to the fifth preferred embodiment includes the planar ground conductor51disposed between the end conductor3522and the wiring adjusting conductor312B, so that isolation between the first wiring conductor and the second wiring conductor is able to be increased.

Other Preferred Embodiments

The multilayer substrates10,10A,10B,10C, and10D according to the preferred embodiments of the present invention described above each may be configured or structured to cause the laminate20to branch between a wiring portion for the signal conductor31and a wiring portion for the signal conductor32.

Each of the preferred embodiments of the present invention described above shows that the two signal conductors31and32are provided. However, the structure of the wiring portions described above is also able to be applied to a structure in which three or more signal conductors are disposed in the Z direction.

Each of the preferred embodiments described above shows that the ground conductors51and51A are disposed between the two signal conductors31and32. However, when the two signal conductors31and32are used for transmission of a differential signal, the ground conductor between the two signal conductors31and32, and the ground conductor between the wiring portion of the signal conductor31and the wiring portion of the signal conductor32, are eliminated. Even for such a multilayer substrate that transmits a differential signal, the structure to reduce a difference in impedance, described above, can be applied. In this case, a wiring adjusting conductor or the like is provided such that an electric length to the wiring portion of the signal conductor31therefrom is the same as an electric length to the wiring portion of the signal conductor32therefrom.

While each of the preferred embodiments of the present invention described above shows that the conductors are exposed on the front and back surfaces of the laminates20and20A, an insulating resist film may be provided in a region other than the external connection conductors611,612,621, and622on the front and back surfaces thereof.

While each of the preferred embodiments of the present invention described above shows that a portion for adjusting impedance is provided using a wiring adjusting conductor, a mounting type inductor may be connected to the wiring adjusting conductor. In addition, the portion to adjust impedance may be a capacitor, or an inductor and a capacitor may be used therefor.