Wiring Substrate and Electronic Device

Abstract

This wiring substrate comprises: an insulating substrate which has a first surface; a mounting part which is on the first surface and upon which one electronic element is mounted; a first signal line and a second signal line which are positioned on the first surface in parallel to each other; and a recessed part which is positioned on the first surface. The recessed part is positioned in the vicinity of a first end part which is one end part of the first signal line and a second end part which is one end part of the second signal line. In a plan view, the first end part, the second end part, and at least a portion of the recessed part overlap with the mounting part.

Description

Technical Field

[0001] The present disclosure relates to a wiring board and an electronic device.

Background Art

[0002] An electrode on a wiring board may be electrically connected while facing an electrode on the lower surface of an electronic element (for example, flip chip mounting in Japanese Patent Application Laid-Open No. 2002-575113).

Summary of the Invention

Means for Solving the Problems

[0003] The wiring board according to the present disclosure includes an insulating substrate having a first surface, a mounting portion on the first surface on which one electronic element is mounted, a first signal line and a second signal line that are parallel to each other and located on the first surface, a recess located on the first surface, and is provided with the recess is located around a first end of the first signal line and a second end of the second signal line, in a plan view, at least a part of the recess, the first end, and the second end overlap the mounting portion.

[0004] The electronic device according to the present disclosure includes the above wiring board, and an electronic element mounted on the mounting portion. and is provided with

Brief Description of the Drawings

[0005]

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 3

Figure 4A

Figure 4B

Figure 4C

Figure 4D

Figure 4E

Figure 5A

Figure 5B

Figure 5C

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0006] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0007] FIG. 1 is a perspective view showing a wiring board according to Embodiment 1 of the present disclosure. FIGS. 2A to 2C show the wiring board of Embodiment 1, where FIG. 2A is a plan view of the first surface, FIG. 2B is a plan view of the first conductor layer, and FIG. 2C is a cross-sectional view taken along line C-C of FIG. 2B. In FIG. 2B, the structure above the first conductor layer is shown by a phantom line. FIG. 3 is an enlarged plan view of one transmission line in the wiring board of Embodiment 1.

[0008] The wiring board 1 according to Embodiment 1 includes an insulating substrate 2 having a first surface S1, a first signal line 11 and a second signal line 12 located on the first surface S1, a recess 20 located on the first surface S1, and a mounting portion H1 on which an electronic element is mounted. The wiring board 1 may further include a first ground line 31, a second ground line 32, and a third ground line 33 located on the first surface S1, a ground film conductor 35 located in the first conductor layer Ly1 of the insulating substrate 2, and a plurality of ground via conductors 36 and one or more side ground conductors 37 extending between the first conductor layer Ly1 and the first surface S1 of the insulating substrate 2.

[0009] The first signal line 11 and the second signal line 12 may be parallel to each other. Parallel means that one line extends in the direction along the other line, and both lines are arranged side by side in the short direction of each line. The first signal line 11 and the second signal line 12 may be a pair of signal lines for transmitting differential signals.

[0010] The first ground line 31 to the third ground line 33 may be parallel to the first signal line 11 and the second signal line 12. The first ground line 31 may be located between the first signal line 11 and the second signal line 12. The second ground line 32 may be located on the opposite side of the second signal line 12 across the first signal line 11. The third ground line 33 may be located on the opposite side of the first signal line 11 across the second signal line 12.

[0011] When the first signal line 11, the second signal line 12, the recess 20, and the first to third ground lines 31 to 33 are referred to as a set of transmission lines 6, the wiring board 1 may have a plurality of sets of transmission lines 6. The plurality of sets of transmission lines 6 may be arranged in parallel. When having a plurality of sets of transmission lines 6, the second ground line 32 of one of the pair of adjacent transmission lines 6 and the third ground line 33 of the other transmission line 6 may be shared.

[0012] On the first surface S1, the first end portion 11e, which is one end portion of the first signal line 11, may be located. The first end portion 11e may be an electrode portion that is electrically connected to the electrode of the electronic element. Similarly, on the first surface S1, the second end portion 12e, which is one end portion of the second signal line 12, may be located. The second end portion 12e may be an electrode portion that is electrically connected to the electrode of the electronic element. The electrode positions p1 and p2 in FIG. 2A indicate positions connected to the electrodes of the electronic element via connection members such as copper pillars.

[0013] The recess 20 may be located around the first end portion 11e and the second end portion 12e. The inside of the recess 20 may be a space. Alternatively, an insulating material having a relative permittivity lower than that of the insulating substrate 2 may be located inside the recess 20. The depth of the recess 20 may be the depth at which the ground film conductor 35 is located, may be shallower than the depth (for example, 1 / 2, 1 / 3, etc. of the depth), or may be deeper than the depth.

[0014] That the recess 20 is located around a certain object means that the distance between the recess 20 and the object is equal to or less than twice the line width w1 (see FIG. 3) of the first signal line 11. The line width w1 of the first signal line 11 and the line width w2 of the second signal line 12 may be the same. When the line width of the first signal line 11 is not constant, the line width w1 of the first signal line 11 means the line width that coincides in a range of at least half in the longitudinal direction. The line width means the width of the signal line in the short direction. Since the recess 20 is located around the first end 11e and the second end 12e, the recess 20 can affect the impedance of the transmission line in the vicinity of the first end 11e and the second end 12e. The distance between the recess 20 and the first end 11e and the second end 12e may be equal to or less than the line width w1. In this case, the effect of the recess 20 on the impedance of the transmission line can be enhanced.

[0015] In plan view, at least a part of the recess 20 and the first end 11e and the second end 12e may overlap the mounting portion H1. Plan view means viewing from a direction perpendicular to the first surface S1. Planar perspective means perspective from a direction perpendicular to the first surface S1.

[0016] The shape of the recess 20 is not particularly limited and may be an oval, circular, elliptical, rectangular shape, or a composite shape of an oval, circular, elliptical, rectangular shape, etc., and a shape suitable for the design conditions may be adopted as appropriate.

[0017] FIGS. 4A to 4E are plan views showing Modification Examples 1 to 5 of the recess 20, respectively. As shown in FIGS. 4A to 4E, the recess 20 may be located anywhere on the first surface S1 as long as at least a part thereof overlaps the mounting portion H1 and is located around both the first end 11e and the second end 12e.

[0018] Specifically, as shown in FIG. 4A, the recess 20 corresponding to the first end portion 11e may be a recess 20a located on the extension line of the first signal line 11 (in other words, on the opposite side of the first signal line 11 across the first end portion 11e). Further, as shown in FIGS. 4B and 4C, the recess 20 corresponding to the first end portion 11e may be a recess 20b or a recess 20c located laterally of the first end portion 11e (in other words, in a direction along the first surface S1 and orthogonal to the longitudinal direction of the first signal line 11). Further, as shown in FIGS. 4D and 4E, the recess 20 corresponding to the first end portion 11e may be recesses 20d and 20e located in an oblique direction from the first end portion 11e (in other words, in a direction between the longitudinal direction and the short-side direction of the first signal line 11).

[0019] Furthermore, the recess 20 corresponding to the first end portion 11e may be a combination of a plurality of the above-described recesses 20a to 20e. Further, in the case of a configuration in which a plurality of the recesses 20a to 20e are combined, the plurality of recesses may be connected or separated.

[0020] Similarly, as shown in FIG. 4A, the recess 20 corresponding to the second end portion 12e may be a recess 20a-1 located on the extension line of the second signal line 12 (in other words, on the opposite side of the second signal line 12 across the second end portion 12e). Further, as shown in FIGS. 4B and 4C, the recess 20 corresponding to the second end portion 12e may be recesses 20b-1 and 20c located laterally of the second end portion 12e (in other words, in a direction along the first surface S1 and orthogonal to the longitudinal direction of the second signal line 12). Further, as shown in FIGS. 4D and 4E, the recess 20 corresponding to the second end portion 12e may be recesses 20d-1 and 20e located in an oblique direction from the second end portion 12e (in other words, in a direction between the longitudinal direction and the short-side direction of the second signal line 12).

[0021] Furthermore, the recess 20 corresponding to the second end portion 12e may be a combination of a plurality of the above-described recesses 20a-1 to 20e. Further, in the case of a configuration in which a plurality of the recesses 20a-1 to 20e are combined, the plurality of recesses may be connected or separated.

[0022] Furthermore, the recess 20 located around the first end portion 11e and the recess 20 located around the second end portion 12e may be connected or may be separated. Furthermore, the recess 20 located around the first end portion 11e and the recess 20 located around the second end portion 12e may have a symmetric shape or an asymmetric shape with respect to a plane that partitions between the first end portion 11e and the second end portion 12e. The above-mentioned plane is a plane having a normal line in the direction of a line segment connecting the center of the first end portion 11e and the center of the second end portion 12e, and corresponds to a plane located at an equal distance from the center of the first end portion 11e and the center of the second end portion 12e.

[0023] <Function> Since the first end portion 11e and the second end portion 12e overlap with the mounting portion H1, when an electronic element is mounted (for example, flip chip mounting), it can be adopted as a configuration in which two electrodes on the lower surface of the electronic element face each other and are electrically connected to the two electrodes. Furthermore, the electronic element can transmit a differential signal via the first signal line 11 and the second signal line 12.

[0024] On the other hand, in the transmission path of the differential signal having the first signal line 11 and the second signal line 12, by positioning one dielectric (for example, an electronic element) so as to span between them above the first end portion 11e and the second end portion 12e, the capacitance component between the two signal lines of the differential signal increases, and it acts in the direction of reducing the characteristic impedance of the transmission path. On the other hand, by positioning the recess 20 around the first end portion 11e and the second end portion 12e, the capacitance component around the recess 20 is reduced, and it acts in the direction of increasing the characteristic impedance of the transmission path. Therefore, the recess 20 can reduce the effect of reducing the characteristic impedance of the transmission path due to the position of the electronic element. Therefore, the characteristic impedance of the transmission path of the differential signal is also matched below the electronic element, and the transmission characteristics of the differential signal can be improved in a wide band.

[0025] <Details of the transmission path> The wiring board 1 may further have the following conditions.

[0026] As shown in FIG. 3, at least a part of the recess 20 may be located between the first end portion 11e and the second end portion 12e. With this configuration, the capacitance component between the first end portion 11e and the second end portion 12e can be efficiently reduced. Therefore, the increase in the capacitance component caused by a dielectric (for example, an electronic element) located above the first end portion 11e and the second end portion 12e and spanning between them can be efficiently reduced. Therefore, the characteristic impedance matching in the transmission line overlapping the mounting portion H1 can be improved.

[0027] As shown in FIG. 3, at least a part of the recess 20 may be located on the extension line of the first signal line 11 on the first end portion 11e side and on the extension line of the second signal line 12 on the second end portion 12e side. With this configuration, the action of increasing the capacitance component at the termination of the first signal line 11 and the capacitance component at the termination of the second signal line 12 by a dielectric (for example, an electronic element) on the mounting portion H1 can be efficiently reduced. Therefore, the characteristic impedance matching at the termination of the transmission line overlapping the mounting portion H1 can be improved.

[0028] As shown in FIG. 3, the recess 20 may have a configuration including a T-shaped portion where the portion between the first end portion 11e and the second end portion 12e is connected to the portions on the extension lines of the first signal line 11 and the second signal line 12. In addition to the T-shaped portion, other shaped portions (for example, a cross, etc.) may be added. According to this configuration, the capacitance component between the termination and the signal line in the differential signal transmission line overlapping the mounting portion H1 can be reduced, and the characteristic impedance matching in the transmission line can be improved.

[0029] The recess 20 may not be connected to the first signal line 11. In other words, a gap may be located between the closest part of the recess 20 and the first signal line 11. Similarly, the recess 20 may not be connected to the second signal line 12. In other words, a gap may be located between the closest part of the recess 20 and the second signal line 12. According to this configuration, when the wiring board 1 is manufactured, the possibility that the materials of the first signal line 11 and the second signal line 12 drip into the recess 20 is reduced. Therefore, the occurrence of deviation of characteristic impedance due to such dripping can be reduced.

[0030] As shown in FIG. 2B, the ground film conductor 35 located in the first conductor layer Ly1 of the insulating substrate 2 may have a non-ground region D in a region R1 that overlaps the first end 11e and a region R2 (shown hatched in the figure) that overlaps the second end 12e in a plan view. The non-ground region D means a part where the ground film conductor 35 is not formed. The non-ground region D does not necessarily need to be formed by cutting out the ground film conductor 35, and the ground film conductor 35 may be formed except for the part of the non-ground region D. The ground film conductor 35 may have a plurality of non-ground regions D that are separated from each other, and the non-ground region D in the region R1 and the non-ground region D in the region R2 may be separated.

[0031] At the connection parts of the first end 11e and the second end 12e with a dielectric (for example, an electronic element), the impedance may decrease. However, due to the non-ground regions D in the regions R1 and R2 (see FIGS. 2B and 2C), the capacitance components between the first end 11e and the ground film conductor 35 and between the second end 12e and the ground film conductor 35 can be reduced. Therefore, the action of increasing the capacitance component of the transmission line by the dielectric (for example, an electronic element) on the mounting part H1 can be reduced, and the characteristic impedance matching in the transmission line overlapping the mounting part H1 can be improved.

[0032] As shown in FIG. 2B, the ground film conductor 35 may have a non-ground region D in a region R3 (shown hatched in the figure) that overlaps a part of the recess 20 in a plan view. A part of the recess 20 corresponds to a portion located between the first end portion 11e and the second end portion 12e. The non-ground region D in the region R3 and the non-ground regions D in the regions R1 and R2 may be integrated or may be separated from each other.

[0033] The non-ground region D in the region R3 can enhance the effect of reducing the capacitance component between the first end portion 11e and the second end portion 12e by the recess 20. Therefore, the matching of the characteristic impedance can be improved in the transmission line overlapping the mounting portion H1.

[0034] The recess 20 has a connection portion 22 connected to the first ground line 31, and may have a side ground conductor 37 (see FIGS. 1, 2A, 2C, and 3) extending in the thickness direction of the insulating substrate 2 from the connection portion 22 on the inner surface of the recess 20. According to this configuration, the possibility of the first ground line 31 becoming a stub can be reduced by the side ground conductor 37, and the matching of the characteristic impedance can be improved in the transmission line under the mounting portion H1. Therefore, the transmission characteristics of the transmission line can be improved for differential signals in a wide band.

[0035] The side ground conductor 37 may be a part of a via conductor 38 located at the connection portion 22. The via conductor 38 corresponds to a conductor filled in a through hole extending between the first surface S1 of the insulating substrate 2 and the first conductor layer Ly1. The via conductor 38 may have a different thickness or shape from other ground via conductors 36 connected to the first ground line 31 to the third ground line 33, or may be manufactured in a separate process from the plurality of ground via conductors 36. The via conductor 38 may be, for example, in an oblong hole shape. In the manufacturing process of the wiring substrate 1, after the through hole for the via conductor 38 is filled with a conductor, the recess 20 is formed so that the through hole and the recess 20 partially overlap, thereby exposing a part of the via conductor 38 on the inner surface of the recess 20, and the exposed portion may be used as the side ground conductor 37. According to this manufacturing method, the side ground conductor 37 located on the inner surface of the recess 20 can be easily manufactured.

[0036] Note that the via conductor 38 connected to the recess 20 may be a via conductor (so-called castellation) in which the conductor is located on the inner surface and the central portion penetrates from the first surface S1 to the first conductor layer Ly1. When such a configuration is adopted, the ground of the transmission line can be strengthened, and the high-frequency characteristics can be made more stable.

[0037] As shown in FIG. 3, the second ground line 32 may have a protruding portion 32a that protrudes from the first signal line 11 in the longitudinal direction of the first signal line 11 and bends toward the first signal line 11 in a plan view. Due to the protruding portion 32a, the first end portion 11e is surrounded by the conductor at the ground potential also from an oblique direction, and the range in which the first signal line 11 is surrounded by the second ground line 32 can be expanded. Therefore, the action of the ground on the first signal line 11 is strengthened, and the transmission characteristics of the transmission line can be improved.

[0038] Similarly, the third ground line 33 may have a protruding portion 33a that protrudes from the second signal line 12 in the longitudinal direction of the second signal line 12 and bends toward the second signal line 12 in a plan view. Due to the protruding portion 33a, the second end portion 12e is surrounded by the conductor at the ground potential also from an oblique direction, and the range in which the second signal line 12 is surrounded by the third ground line 33 can be expanded. Therefore, the action of the ground on the second signal line 12 is strengthened, and the transmission characteristics of the transmission line can be improved.

[0039] The first signal line 11 may have a width-reduced portion 11a (see FIG. 3) near the first end 11e. The width-reduced portion in the signal line corresponds to a portion where the line width of the signal line is smaller than that before and after. The vicinity of the first end 11e means a range within twice or less the line width w1 (see FIG. 3) of the first signal line 11 from the first end 11e. In plan view, a part of the width-reduced portion 11a may overlap with the mounting portion H1. According to the above configuration, the inductance component of the first signal line 11 can be increased by the width-reduced portion 11a. Then, the increase in the inductance component acts in a direction to cancel out the capacitance component added by the dielectric (for example, an electronic element) on the mounting portion H1, and the characteristic impedance matching in the transmission line overlapping with the mounting portion H1 can be improved. Therefore, the transmission characteristics of the transmission line can be improved for differential signals in a wide band.

[0040] Similarly, the second signal line 12 may have a width-reduced portion 12a (see FIG. 3) near the second end 12e. The vicinity of the second end 12e means a range within twice or less the line width w2 (see FIG. 3) of the second signal line 12 from the second end 12e. In plan view, a part of the width-reduced portion 12a may overlap with the mounting portion H1. According to the above configuration, the inductance component of the second signal line 12 can be increased by the width-reduced portion 12a. Then, the increase in the inductance component acts in a direction to cancel out the capacitance component added by the dielectric (for example, an electronic element) on the mounting portion H1, and the characteristic impedance matching in the transmission line overlapping with the mounting portion H1 can be improved. Therefore, the transmission characteristics of the transmission line can be improved for differential signals in a wide band.

[0041] As shown in FIG. 3, the shortest distance L1 between the first signal line 11 and the recess 20 may be shorter than the shortest distance L2 between the first signal line 11 and the second ground line 32. According to this configuration, since the recess 20 is located near the first signal line 11, the effect of the recess 20 on the characteristic impedance of the transmission line can be enhanced. Therefore, the characteristic impedance matching in the transmission line overlapping with the mounting portion H1 can be further improved.

[0042] Similarly, the shortest distance L3 between the second signal line 12 and the recess 20 may be shorter than the shortest distance L4 between the second signal line 12 and the third ground line 33. According to this configuration, since the recess 20 is located near the second signal line 12, the effect of the recess 20 on the characteristic impedance of the transmission line can be enhanced. Therefore, the matching of the characteristic impedance in the transmission line overlapping with the mounting portion H1 can be further improved.

[0043] Of the recess 20, the width w21 of the portion located between the first signal line 11 and the second signal line 12 may be larger than the line width w31 of the first ground line 31. The width w21 may mean the maximum width when the width of the portion of the recess 20 is not constant. According to this configuration, compared with the case where the width w21 is less than or equal to the line width w31, the recess 20 becomes larger and the distances between the recess 20 and the first signal line 11 and between the recess 20 and the second signal line 12 become narrower. Therefore, the effect of the recess 20 on the characteristic impedance of the transmission line is enhanced, and the matching of the characteristic impedance in the transmission line overlapping with the mounting portion H1 can be further improved. Thus, the transmission characteristics can be further improved for wide-band differential signals.

[0044] <Simulation Results> Figs. 5A to 5C are graphs showing the frequency characteristics of the wiring boards of Embodiments 1 to 3 and the wiring board of the comparative example. Fig. 5A shows the reflection characteristics, Fig. 5B shows the transmission characteristics, and Fig. 5C shows the results of TDR measurement. Fig. 6 is a plan view showing the wiring board of Embodiment 2. Fig. 7 is a plan view showing the wiring board of Embodiment 3. In the simulation, a configuration in which an electronic element is flip-chip mounted on the wiring board 1 was adopted as a condition, and the relative dielectric constant εr of the electronic element was set to 12.

[0045] The wiring board 1 of Embodiment 1 has the configuration shown in FIGS. 1 to 3. That is, as shown in FIGS. 1 to 3, the recess 20 is located on the extension lines of the first signal line 11 and the second signal line 12 and between the first signal line 11 and the second signal line 12, and has a side surface ground conductor 37.

[0046] The wiring board 1A of Embodiment 2 is the same as the wiring board 1 of Embodiment 1 except that the shape of the recess 20A is different. The recess 20A of Embodiment 2 is located between the first end portion 11e and the second end portion 12e, while the recess 20A is not located on the extension line of the first signal line 11 and the extension line of the second signal line 12. The recess 20A has a side surface ground conductor 37.

[0047] The wiring board 1B of Embodiment 3 is the same as the wiring board 1 of Embodiment 1 except that the recess 20B does not have a side surface ground conductor 37 (in other words, there is no via conductor 38). The shape of the recess 20B is the same as that of the recess 20 of Embodiment 1.

[0048] The comparative example is the same as the wiring board 1 of Embodiment 1 except that it does not have a recess 20 (that is, the portion of the recess 20 is filled with the material constituting the insulating substrate).

[0049] The wiring boards 1, 1A, and 1B of Embodiments 1 to 3 have a smaller reflection coefficient in a wide band (see Fig. 5A) and a larger transmission coefficient in a wide band (see Fig. 5B) compared with the comparative example. Therefore, according to the wiring boards 1, 1A, and 1B of Embodiments 1 to 3, good signal transmission can be realized in a wide band. In the TDR measurement result of Fig. 5C, the time domain Z1 represents the characteristic impedance of the region overlapping with the electronic element in the transmission line. The result of Fig. 5C shows that by having the recesses 20, 20A, and 20B, the impedance matching of the wiring boards 1, 1A, and 1B of Embodiments 1 to 3 is improved below the electronic element.

[0050] Embodiment 1 has a smaller reflection coefficient in a wider band (see Fig. 5A), a larger transmission coefficient in a band of 40 GHz or more (see Fig. 5B), and improved impedance matching in the region overlapping with the electronic device (see Fig. 5C) compared with Embodiment 2. Therefore, by positioning the recess 20 on the extension line of the first signal line 11 and the extension line of the second signal line 12, better signal transmission characteristics can be obtained.

[0051] Embodiment 1 has a smaller reflection coefficient in the frequency band of 55 GHz to 90 GHz (see FIG. 5A) and a larger transmission coefficient in the frequency band of 80 GHz or higher (see FIG. 5B) compared with Embodiment 3. Therefore, by having the side ground conductor 37, better signal transmission characteristics can be obtained.

[0052] (Embodiment 4) FIG. 8 is a plan view showing a wiring board according to Embodiment 4. The wiring board 1C according to Embodiment 4 is the same as Embodiment 1 except that the structure of the connection portion between the second ground line 32 and the recess 20 and the structure of the connection portion between the third ground line 33 and the recess 20 are different from those of Embodiment 1. The same components as those in Embodiment 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

[0053] The second ground line 32 may have a protruding portion 32aC that protrudes from the first signal line 11 in the longitudinal direction of the first signal line 11 and bends toward the first signal line 11 in a plan view. The protruding portion 32aC may bend at a right angle or may bend at various angles. The protruding portion 32aC may be connected to the recess 20 via a connection portion 22C1. The connection portion 22C1 may be located at a portion of the recess 20 that is on the extension line of the first signal line 11. The connection portion 22C1 may have a side ground conductor 37C1 on the inner surface that extends in the thickness direction of the insulating substrate 2 from the connection portion 22C1. The side ground conductor 37C1 may be a part of a via conductor 38C located at the connection portion 22C1. The via conductor 38C may correspond to a conductor filled in a through hole extending between the first surface S1 of the insulating substrate 2 and the first conductor layer Ly1. Alternatively, the via conductor 38C may be a via conductor (so-called castellated via) having a conductor located on the inner surface and a central portion penetrating from the first surface S1 to the first conductor layer Ly1. In the case of such a configuration, the conductor located on the inner surface of the via conductor 38C may correspond to the side ground conductor 37C1. The configuration having the connection portion 22C1 between the recess 20 and the second ground line 32 and the configuration having the side ground conductor 37C1 enhance the action of the ground of the transmission line and can further improve the transmission characteristics.

[0054] The second ground line 32 may also have a similar configuration (protruding portion 32bC, connecting portion 22C3, side ground conductor 37C3, via conductor 38C) with respect to the recess 20 in the adjacent transmission line 6 (see FIG. 1).

[0055] Similarly, the third ground line 33 may have a protruding portion 33aC that protrudes beyond the second signal line 12 in the longitudinal direction of the second signal line 12 and bends toward the second signal line 12 in plan view. The protruding portion 33aC may bend at a right angle or at various angles. The protruding portion 33aC may be connected to the recess 20 via the connecting portion 22C2. The connecting portion 22C2 may be located at a portion of the recess 20 that lies on the extension line of the second signal line 12. The connecting portion 22C2 may have a side ground conductor 37C2 on its inner surface that extends in the thickness direction of the insulating substrate 2 from the connecting portion 22C2. The side ground conductor 37C2 may be part of a via conductor 38C located at the connecting portion 22C2. The via conductor 38C may correspond to a conductor filled in a through hole extending between the first surface S1 of the insulating substrate 2 and the first conductor layer Ly1. Alternatively, the via conductor 38C may be a via conductor (so-called casterlation) having a conductor on its inner surface and a central portion that penetrates from the first surface S1 to the first conductor layer Ly1. In the case of such a configuration, the conductor located on the inner surface of the via conductor 38C may correspond to the side ground conductor 37C2. The configuration having the connecting portion 22C2 between the recess 20 and the third ground line 33, and the configuration having the side ground conductor 37C2 enhance the action of the ground of the transmission line and can improve the transmission characteristics.

[0056] The third ground line 33 may also have a similar configuration (for example, protruding portion 33bC, connecting portion 22C4, side ground conductor 37C4, and via conductor 38C) with respect to the recess 20 in the adjacent transmission line 6 (see FIG. 1).

[0057] (Electronic device) FIG. 9 is a side view showing an electronic device according to an embodiment of the present disclosure. The electronic device 100 of the present embodiment includes a wiring board 1 and an electronic element 80 mounted on a mounting portion H1 of the wiring board 1. The wiring board 1 may be replaced with the wiring boards 1A to 1C of Embodiments 2 to 4. The electronic element 80 has electrodes 81a and 81b on its lower surface, and the electrodes 81a and 81b may be connected (for example, flip chip mounting) to a first end 11e of a first signal line 11 and a second end 12e of a second signal line 12 of the wiring board 1 via a bonding material U such as a copper pillar. Further, the electronic element 80 has ground electrodes 82a and 82b on its lower surface, and the ground electrodes 82a and 82b may be connected to a second ground line 32 and a third ground line 33 via a bonding material U such as a copper pillar, respectively. The electronic element 80 may be configured to input, output, or perform both differential signals via the electrodes 81a and 81b. The electronic element 80 may be an element having a substrate with a relative dielectric constant larger than that of the SiO2 film, such as a silicon substrate or an InP (indium phosphide) substrate.

[0058] According to the electronic device 100 of the present embodiment, by providing the wiring board 1, good signal transmission characteristics can be obtained in a wide band.

[0059] As described above, each embodiment of the present disclosure has been described. However, the wiring board and the electronic device of the present disclosure are not limited to the above embodiments. For example, in the above embodiment, the first signal line 11 and the second signal line 12 are described as being configured to transmit differential signals, but each of the first signal line and the second signal line may be configured to transmit single-ended signals. Further, the first signal line and the second signal line may be configured to transmit digital signals or may be configured to transmit analog signals.

[0060] Note that various combinations of the characteristic parts in each embodiment and each modification example are not limited to the examples of the above embodiments. Also, combinations of each embodiment and each modification example are possible.

Industrial Applicability

[0061] The present disclosure can be used for a wiring board and an electronic device.

Explanation of Signs

[0062] 1, 1A, 1B, 1C Wiring board 2 Insulating substrate 6 Transmission line 11 First signal line 11a Narrowed portion 11e First end 12 Second signal line 12a Narrowed portion 12e Second end 20, 20a~20e, 20a-1, 20b-1, 20d-1, 20A, 20B Recessed portion 22, 22C1~22C4 Connection portion 31 First ground line 32 Second ground line 32a, 32aC Protruding portion 33 Third ground line 33a, 33aC Protruding portion 35 Ground film conductor 36 Ground via conductor 37, 37C1~37C4 Side ground conductor 38, 38C Via conductor L1~L4 Shortest distance H1 Mounting portion Ly1 First conductor layer S1 First surface w1, w2, w31 Line width w21 Width 80 Electronic element 100 Electronic device

Claims

1. An insulating substrate having a first surface; A mounting portion on the first surface on which one electronic element is mounted; A first signal line and a second signal line that are parallel to each other and located on the first surface; A recess located on the first surface; comprising: The recess is located around a first end of the first signal line and a second end of the second signal line; In a plan view, at least a part of the recess, the first end, and the second end overlap the mounting portion; A wiring substrate.

2. At least a part of the recess is located between the first end and the second end; The wiring substrate according to claim 1.

3. At least a part of the recess is located on an extension line of the first signal line on the first end side or an extension line of the second signal line on the second end side; The wiring substrate according to claim 1 or claim 2.

4. The first signal line and the recess are not connected; The second signal line and the recess are not connected; The wiring substrate according to claim 1 or claim 2.

5. The insulating substrate has a first conductor layer where a ground film conductor is located; The ground film conductor has a non-ground region; In a plan view, the non-ground region overlaps the first end and the second end; The wiring substrate according to claim 1 or claim 2.

6. In a plan view, the non-ground region overlaps the recess located between the first end and the second end; The wiring substrate according to claim 5.

7. Further comprising a first ground line located between the first signal line and the second signal line, The recess has a connection portion to which the first ground line is connected, On the inner surface of the recess, a side ground conductor extending in the thickness direction of the insulating substrate from the connection portion is located, The wiring board according to claim 1 or claim 2.

8. Further comprising a second ground line parallel to the second signal line on the opposite side of the first signal line, The second ground line has a protruding portion that protrudes from the first signal line in the longitudinal direction of the first signal line and bends toward the first signal line in a plan view, The wiring board according to claim 1 or claim 2.

9. The protruding portion is connected to the recess, The wiring board according to claim 8.

10. Having a side ground conductor extending in the thickness direction of the insulating substrate from the connection portion between the protruding portion and the recess, The wiring board according to claim 9.

11. The first signal line has a width-reducing portion near the first end, The wiring board according to claim 1 or claim 2.

12. Comprising a second ground line parallel to the second signal line on the opposite side of the first signal line, The shortest distance between the first signal line and the recess is smaller than the shortest distance between the first signal line and the second ground line, The wiring board according to claim 1 or claim 2.

13. Comprising a first ground line located between the first signal line and the second signal line, The width of the recess located between the first signal line and the second signal line is larger than the line width of the first ground line, The wiring board according to claim 1 or claim 2.

14. A wiring board according to claim 1 or claim 2, and an electronic component mounted on the mounting portion, An electronic device comprising the same.

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