Wiring board and electronic module

Abstract

This wiring board, which introduces a high-frequency signal from a module substrate and transmits the high-frequency signal along a signal path, comprises: a substrate which has insulating properties and includes a first surface that faces the module substrate; an electrode which is positioned on the first surface and introduces a signal; a plurality of via conductors which are continuous on one straight line that intersects the electrode inside the substrate, and which transmit the signal; and a film-shaped first connection conductor which is positioned between a first via conductor and a second via conductor adjacent to each other among the plurality of via conductors, and which is connected to the first via conductor and the second via conductor. In a perspective plan view, the width of the electrode is greater than the width of the plurality of via conductors, and the width of the first connection conductor is greater than the width of the electrode.

Description

Wiring board and electronic module

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

[0002] Japanese Patent Laid-Open Publication No. 2012-248797 discloses a wiring board including a base on which a plurality of insulating layers are stacked, an electrode located on the underside of the base, and a plurality of through conductors located in each of the insulating layers. The plurality of through conductors are aligned in a straight line on one electrode, and the through conductor in each insulating layer is connected to the through conductor in the adjacent insulating layer via a circular film-shaped connecting conductor.

[0003] The wiring board of the present disclosure is a wiring board that introduces a high-frequency signal from a module substrate and transmits it along a signal path, and comprises: an insulating base including a first surface facing the module substrate; an electrode located on the first surface and introducing the signal; a plurality of via conductors that are connected on a single straight line inside the base intersecting the electrode and transmit the signal; and a film-like first connecting conductor that is located between adjacent first and second via conductors among the plurality of via conductors and is connected to the first and second via conductors, wherein, in a planar perspective view, the width of the electrode is greater than the width of the plurality of via conductors, and the width of the first connecting conductor is greater than the width of the electrode.

[0004] The electronic module of the present disclosure comprises: a module substrate; a wiring board according to claim 1 mounted on a substrate surface of the module substrate so that the first surface faces the substrate surface; and an electronic element mounted on the wiring board.

[0005] FIG. 1 is a cross-sectional view showing a wiring board and an electronic module according to a first embodiment of the present disclosure. FIG. 2 is a perspective perspective view showing a portion of the wiring board of the first embodiment, showing a configuration in which ideal positional accuracy is achieved. FIG. 3 is a perspective perspective view showing a portion of the wiring board of the first embodiment, showing a configuration including misalignment. FIG. 4 is a configuration diagram showing signal vertical conductors in the wiring board of the first embodiment. FIG. 5 is a graph showing the reflection loss of the wiring board of the first embodiment. FIG. 6 is a graph showing the insertion loss of the wiring board of the first embodiment. FIG. 7 is a configuration diagram showing signal vertical conductors in the wiring board of Comparative Example 1. FIG. 8 is a graph showing the reflection loss of the wiring board of Comparative Example 1. FIG. 9 is a graph showing the insertion loss of the wiring board of Comparative Example 1. FIG. 10 is a configuration diagram showing signal vertical conductors in the wiring board of Comparative Example 2. FIG. 11 is a graph showing the reflection loss of the wiring board of Comparative Example 2. FIG. 12 is a graph showing the insertion loss of the wiring board of Comparative Example 2. FIG. 13 is a configuration diagram showing signal vertical conductors in the wiring board of the second embodiment. FIG. 14 is a graph showing the reflection loss of the wiring board of the second embodiment. FIG. 15 is a graph showing the insertion loss of the wiring board of the second embodiment. FIG. 16 is a configuration diagram showing signal vertical conductors in the wiring board of the third embodiment. FIG. 17 is a graph showing the reflection loss of the wiring board of the third embodiment. 10 is a graph showing the insertion loss of the wiring board of embodiment 3. FIG. 11 is a configuration diagram showing signal vertical conductors in the wiring board of embodiment 4. FIG. 12 is a graph showing the reflection loss of the wiring board of embodiment 4. FIG. 13 is a graph showing the insertion loss of the wiring board of embodiment 4. FIG. 14 is a configuration diagram showing signal vertical conductors in the wiring board of embodiment 5. FIG. 15 is a graph showing the reflection loss of the wiring board of embodiment 5. FIG. 16 is a graph showing the insertion loss of the wiring board of embodiment 5. FIG. 17 is a configuration diagram showing signal vertical conductors in the wiring board of comparative example 3. FIG. 18 is a graph showing the reflection loss of the wiring board of comparative example 3. FIG. 19 is a graph showing the insertion loss of the wiring board of comparative example 3. FIG. 19 is a configuration diagram showing signal vertical conductors in the wiring board of comparative example 4. FIG. 19 is a graph showing the reflection loss of the wiring board of comparative example 4. FIG. 19 is a graph showing the insertion loss of the wiring board of comparative example 4.

[0006] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following description, planar perspective refers to a perspective view from a direction perpendicular to the first surface S11a. Furthermore, width refers to the smallest distance between two parallel lines when an object is sandwiched between the parallel lines in various orientations in planar perspective. When the object is circular in planar perspective, width refers to the diameter. Furthermore, the effective wavelength of a signal refers to the effective wavelength at the maximum frequency in the frequency band of the signal.

[0007] 1 is a cross-sectional view showing a wiring board 10 and an electronic module 100 according to a first embodiment of the present disclosure. Figures 2A and 2B are perspective views showing a portion of the wiring board 10 according to the first embodiment, with Figure 2A showing a configuration in which ideal positional accuracy is achieved and Figure 2B showing a configuration in which misalignment occurs.

[0008] The wiring board 10 of the first embodiment may be a submount on which the electronic element 110 is mounted, or may be a substrate mounted on the module substrate 120. The wiring board 10 may be a substrate that introduces a high-frequency signal from the module substrate 120 and transmits the signal to the electronic element 110. The high frequency refers to any band between 10 GHz and 300 GHz, more specifically, between 50 GHz and 200 GHz. In the wiring board 10 of the present embodiment, the band between 0 Hz and 80 GHz is set as the band for transmission signals.

[0009] The wiring substrate 10 includes a base 11 having a first surface S11a and an electrode 12 located on the first surface S11a. The first surface S11a may be a surface facing the substrate surface S120 of the module substrate 120. The electrode 12 may be electrically connected to a signal conductor 131 of the module substrate 120 and configured to introduce a signal from the module substrate 120. The signal transmission path is indicated by arrows in FIG. 1. The electrode 12 is pad-shaped and may be referred to as an electrode pad. The electrode 12 may be film-shaped extending along the first surface S11a and may be circular in planar perspective. Note that the electrode 12 may also have other shapes, such as a rectangular or polygonal shape, in planar perspective.

[0010] The wiring board 10 may further have a second surface S11b located on the opposite side to the first surface S11a, a signal conductor 15 located on the second surface S11b, and a mounting portion 16 for the electronic element 110 located on the second surface S11b. A portion of the signal conductor 15 may be electrically connected to the electronic element 110 at the mounting portion 16. The signal conductor 15 may be configured to transmit a signal in a direction along the second surface S11b. Note that a portion or all of the signal conductor 15 may be located within the base 11, rather than on the second surface S11b. Alternatively, the signal conductor 15 that transmits a signal in a direction along the second surface S11b may be omitted, and the signal may be transmitted directly to the electronic element 110 from a signal vertical conductor 18 (described later).

[0011] The wiring board 10 may further include, within the base 11, a plurality of via conductors 13 arranged in a line intersecting (e.g., perpendicular to) the electrodes 12, and connection conductors 14 located between the plurality of via conductors 13. The linearly arranged electrodes 12, the plurality of via conductors 13, and the plurality of connection conductors 14 are referred to as signal vertical conductors 18. One end of the plurality of via conductors 13 may be connected to the electrode 12, and the other end of the plurality of via conductors 13 may be connected to the signal conductor 15. The continuous plurality of via conductors 13 may be configured to transmit a signal introduced from the electrode 12 to the signal conductor 15. The via conductors 13 are cylindrical, but may also be rectangular or polygonal. The connection conductors 14 are circular in plan view, but may also be other shapes, such as rectangular or polygonal.

[0012] The wiring board 10 may further include a ground electrode 22 located on the first surface S11a, a ground via conductor 23, a ground connection conductor 24 (see FIG. 2A), and a ground solid conductor 24a located within the base 11, and a ground conductor 25 (see FIG. 2A) located on the second surface S11b. The ground electrode 22, the ground via conductor 23, the ground connection conductor 24, the ground solid conductor 24a, and the ground conductor 25 may be electrically connected to one another, and the ground electrode 22 may be electrically connected to a ground conductor of the module substrate 120. The ground via conductor 23 is cylindrical, but may also be rectangular. The ground connection conductor 24, the ground solid conductor 24a, and the ground conductor 25 may be configured to extend in a direction along the first surface S11a or the second surface S11b. A solid conductor refers to a conductor that extends over a large area.

[0013] 2, the ground electrode 22, the ground via conductor 23, and the ground connection conductor 24 may include a combination in which they are connected in a straight line. This combination is called a ground vertical conductor 28. The ground vertical conductors 28 may be located on both sides of the signal vertical conductor 18.

[0014] The base 11 may be configured by stacking multiple insulating layers 11a. The via conductors 13 and the ground via conductors 23 may be conductors that penetrate from one surface of one insulating layer 11a to the other. The connection conductors 14 and the ground solid conductors 24a may be film-like conductors that are located between a pair of adjacent insulating layers 11a and extend along the surface between the pair of insulating layers 11a.

[0015] The base 11 may be made of aluminum nitride (AlN) ceramics. This material allows heat generated by the electronic element 110 to be dissipated to a heat dissipation section such as the module substrate 120 with high thermal conductivity. The base 11 may be configured by stacking and firing multiple ceramic green sheets. The multiple insulating layers 11a may correspond to the multiple ceramic green sheets before firing. The multiple via conductors 13, the multiple connection conductors 14, the multiple ground via conductors 23, the multiple ground connection conductors 24, and the multiple ground solid conductors 24a may be conductors containing a high-melting point metal such as tungsten, and may be configured by firing simultaneously with the ceramic green sheets.

[0016] The electrode 12 and the ground electrode 22 located on the first surface S11a, and the signal conductor 15 and the ground conductor 25 (see FIG. 2A) located on the second surface S11b may be conductors formed after firing the base 11. The conductors may be thin films formed by a thin film formation technique such as vapor deposition using photolithography, or may be thin films plated.

[0017] Since shrinkage and the like occur during the firing process of the base 11, the positional accuracy of the conductors inside the base 11 is relatively low. On the other hand, the electrodes 12 and the ground electrodes 22 on the first surface S11a are formed at predetermined positions with high positional accuracy. Therefore, as shown in FIG. 2B , eccentricity (i.e., misalignment of the center points in a planar perspective view) may occur between the via conductors 13 located inside the base 11 and the electrodes 12 located on the first surface S11a.

[0018] The electronic element 110 may be a light-emitting element that generates heat. The electronic module 100 may be a module that transmits an electrical signal in a wide band from a low frequency band to a high frequency band (e.g., 0 Hz to 80 GHz) to the electronic element 110 via the wiring substrate 10.

[0019] The module substrate 120 may be a printed wiring board. The module substrate 120 may have a signal conductor 131 and a ground conductor 132 exposed on a board surface S120 on which the wiring substrate 10 is mounted, and the electrode 12 and the ground electrode 22 of the wiring substrate 10 may be connected to the signal conductor 131 and the ground conductor 132, respectively, via a conductive bonding material 31 such as solder.

[0020] <Details of the Signal Vertical Conductor> Figures 3A to 3C are a configuration diagram, a return loss graph, and an insertion loss graph showing the signal vertical conductor 18 in the wiring board 10 of embodiment 1, respectively. In the return loss graph, a smaller value indicates a smaller return loss, and in the insertion loss graph, a value closer to zero indicates a smaller insertion loss. The horizontal axis of both graphs indicates frequency from 0 Hz. The same applies to the return loss graphs of Figures 4B to 11B and the insertion loss graphs of Figures 4C to 11C.

[0021] The reflection loss graph of Fig. 3B and the insertion loss graph of Fig. 3C were obtained by simulation. In the simulation, the width φ12 of the electrode 12 was 200 μm, the width φ13 of the via conductor 13 was 75 μm, the width of the small connecting conductor 14 was 120 μm, the width φ14A of the large first connecting conductor 14A was 235 μm, the thickness T of the base 11 was 0.5 mm, the distance L1 from the electrode 12 to the first connecting conductor 14A was 0.25 mm, and the relative dielectric constant εr of the base 11 was 8.6.

[0022] 3A , in the signal vertical conductor 18, the width φ12 of the electrode 12 may be larger than the width φ13 of the via conductor 13. That is, the following condition may be satisfied: φ12 > φ13 (1) With this configuration, even if a positional deviation occurs between the center of the electrode 12 and the center of the via conductor 13 during manufacturing, it is possible to reduce the variation in the connection area between the electrode 12 and the via conductor 13.

[0023] 3A, the width φ12 of the electrode 12 may be equal to or greater than twice the width φ13 of the via conductor 13. That is, the following condition may be satisfied: φ12 > 2 × φ13 (2) According to this configuration, even if a positional deviation occurs between the center of the electrode 12 and the center of the via conductor 13 during manufacturing, the variation in the connection area between the electrode 12 and the via conductor 13 can be further reduced.

[0024] Furthermore, as shown in FIG. 3A , the signal vertical conductor 18 may include a first connecting conductor 14A among the multiple connecting conductors 14, the first connecting conductor 14 having a width greater than the width of the other connecting conductors 14. The first connecting conductor 14A is located between the adjacent first via conductor 13A and second via conductor 13B among the multiple via conductors 13, and is connected to the first via conductor 13A and second via conductor 13B. The width φ14A of the first connecting conductor 14A may be greater than the width φ12 of the electrode 12, as shown in the following equation: φ14A > φ12 (3) With this configuration, as shown in FIGS. 3B and 3C , excellent signal transmission characteristics can be achieved from low to high frequency bands. The width φ14A of the first connecting conductor 14A may be less than twice the width φ12 of the electrode 12.

[0025] Next, a comparison is made with Comparative Examples 1 and 2, which do not satisfy any of the conditions of the above formulas (1) to (3). Fig. 4A is a diagram showing the signal vertical conductors of the wiring board of Comparative Example 1. Fig. 5A is a diagram showing the signal vertical conductors of the wiring board of Comparative Example 2. In wiring board 81 of Comparative Example 1, the width φ12 of the electrodes 12 is less than twice the width φ13 of the via conductors 13, and all of the connecting conductors 14 have small widths. In wiring board 82 of Comparative Example 2, the width φ12 of the electrodes 12 is about twice the width φ13 of the via conductors 13, but the widths of all of the connecting conductors 14 are small.

[0026] 4B and 5B are reflection loss graphs for wiring board 81 of Comparative Example 1 and wiring board 82 of Comparative Example 2, and FIGS. 4C and 5C are insertion loss graphs for wiring board 81 of Comparative Example 1 and wiring board 82 of Comparative Example 2. These graphs were obtained by simulation. In the simulation of Comparative Example 1, the width φ12 of electrode 12 was 155 μm, the width φ13 of via conductor 13 was 75 μm, the width of small connecting conductor 14 was 120 μm, the thickness T of base 11 was 0.5 mm, and the relative dielectric constant εr of base 11 was 8.6. In the simulation of Comparative Example 2, the width φ12 of electrode 12 was 200 μm, and the other parameters were the same as in Comparative Example 1.

[0027] 4B and 4C, the wiring board 81 of Comparative Example 1 has small reflection loss and insertion loss from low to high frequency bands. On the other hand, in Comparative Example 1, the width of the electrode 12 is small, so misalignment occurs between the center of the electrode 12 and the center of the via conductor 13 during manufacturing. This causes the via conductor 13 to protrude from the electrode 12 in a planar perspective view, which tends to reduce the connection area between the two. When this connection area becomes small, reflection loss increases in the high frequency band, and the good characteristics shown in FIGS. 4B and 4C cannot be obtained.

[0028] In the wiring board 82 of Comparative Example 2, the width φ12 of the electrode 12 is large, so even if misalignment occurs between the center of the electrode 12 and the center of the via conductor 13 during manufacturing, the variation in the connection area between the via conductor 13 and the electrode 12 can be reduced. On the other hand, as shown in Figures 5B and 5C, the large width φ12 of the electrode 12 results in relatively large reflection loss in the mid-high frequency band. The increase in reflection loss is caused by a portion of the electric field component of the signal that is blocked by the large electrode 12 being attracted toward the module substrate 120 due to the dielectric properties of the module substrate 120.

[0029] On the other hand, according to the wiring board 10 of the first embodiment, by having the first connecting conductor 14A that satisfies the formula (3), a large capacitance component is formed between the first connecting conductor 14A and the electrode 12. Then, the electric field component of the signal that is held up by the large electrode 12 is subjected to mutually opposite attracting actions: attracting it toward the module substrate 120 side and attracting it toward the above-mentioned capacitance component on the wiring board 10 side. As a result, the attraction toward the module substrate 120 side is reduced. Therefore, the increase in reflection loss that is present in the characteristics of Comparative Example 2 is suppressed, and good characteristics are obtained as shown in FIGS. 3B and 3C .

[0030] (Embodiments 2-5) FIGS. 6A to 9A are configuration diagrams showing the signal vertical conductors 18 in the wiring boards 10A to 10D of embodiments 2 to 5, respectively. FIGS. 6B to 9B are reflection loss graphs for the wiring boards 10A to 10D of embodiments 2 to 5, respectively. FIGS. 6C to 9C are insertion loss graphs for the wiring boards 10A to 10D of embodiments 2 to 5, respectively. The configuration diagrams in FIGS. 6A to 9A show cross sections passing through the centers of the via conductors 13. The wiring board 10A of embodiment 2-5 has a thickness (i.e., the distance from the first surface S11a to the second surface S11b) greater than that of embodiment 1, and the height position of the first connecting conductor 14A is varied, but the other configurations may be the same as embodiment 1.

[0031] The above graphs for Examples 2 to 5 were obtained by simulation. In the simulation for Example 2, the width φ12 of the electrode 12 was 200 μm, the width φ13 of the via conductor 13 was 75 μm, the width of the small connecting conductor 14 was 120 μm, the width φ14A of the large first connecting conductor 14A was 235 μm, the thickness T of the base 11 was 0.8 mm, the distance L2 from the electrode 12 to the first connecting conductor 14A was 0.25 mm, and the relative dielectric constant εr of the base 11 was 8.6. In the simulation for Examples 3 to 5, the distances L from the electrode 12 to the first connecting conductor 14A were L3 = 0.55 mm, L4 = 0.4 mm, and L5 = 0.1 mm, respectively, and the other parameters were the same as in Example 2.

[0032] The wiring boards 10A to 10D of embodiments 2 to 5 also satisfy the conditions of the above-described formulas (1) to (3), as in embodiment 1. Because the width φ12 of the electrode 12 is large due to the conditions of formulas (1) and (2), even if misalignment occurs between the center of the electrode 12 and the center of the via conductor 13 during manufacturing, it is possible to reduce variation in the connection area between the via conductor 13 and the electrode 12. Furthermore, by having the first connecting conductor 14A with a large width φ14A, it is possible to form a capacitance component between the first connecting conductor 14A and the electrode 12, which suppresses an increase in reflection characteristics caused by the electrode 12 with a large width φ12 and contributes to good frequency characteristics.

[0033] Next, the contribution of Embodiments 2-5 to good frequency characteristics will be specifically described in comparison with Comparative Examples 3 and 4. FIGS. 10A and 11A are diagrams showing the vertical signal conductors 18 in the wiring boards 83 and 84 of Comparative Examples 3 and 4, respectively. FIGS. 10B and 11B are graphs showing the reflection loss in the wiring boards 83 and 84 of Comparative Examples 3 and 4, respectively. FIGS. 10C and 11C are graphs showing the insertion loss in the wiring boards 83 and 84 of Comparative Examples 3 and 4, respectively. The diagrams in FIGS. 10A and 11A show cross sections passing through the centers of the via conductors 13. The graphs above were obtained by simulation. In the simulation of Comparative Example 3, the width φ12 of the electrode 12 was 155 μm, the width φ13 of the via conductor 13 was 75 μm, the width of the small connecting conductor 14 was 120 μm, the thickness T of the base 11 was 0.8 mm, and the relative dielectric constant εr of the base 11 was 8.6. In the simulation of Comparative Example 4, the width φ12 of the electrode 12 was set to 200 μm, and the other parameters were set to the same as those of Comparative Example 1.

[0034] The wiring boards 83 and 84 of Comparative Examples 3 and 4 have the same substrate thickness T as the wiring boards 10A to 10D of Embodiments 2 to 5. In the wiring board 83 of Comparative Example 3, as shown in FIG. 10A, the width φ12 of the electrode 12 is not large, and the deterioration of the frequency characteristics caused by increasing the width φ12 is small, resulting in ideal frequency characteristics as shown in FIGS. 10B and 10C. However, in Comparative Example 3, because the width of the electrode 12 is small, misalignment occurs between the center of the electrode 12 and the center of the via conductor 13 during manufacturing, causing the via conductor 13 to protrude beyond the electrode 12 in a planar perspective view, making it difficult to obtain the good characteristics shown in FIGS. 10B and 10C.

[0035] 11A, in wiring board 84 of Comparative Example 4, because width φ12 of electrode 12 is large, even if there is misalignment during manufacturing, it is possible to reduce variation in the connection area between electrode 12 and via conductor 13. However, in Comparative Example 4, as shown in FIG. 11B, part of the electric field component of the signal that is blocked by electrode 12 with large width φ12 is attracted toward module substrate 120, thereby increasing reflection loss across the entire frequency band.

[0036] On the other hand, as shown in Fig. 6A, the wiring board 10A of the second embodiment includes a first connecting conductor 14A having a width φ14A larger than the width φ12 of the electrode 12. This configuration suppresses the increase in reflection loss in the fourth comparative example, and as shown in Fig. 6B, reflection loss is reduced in the high frequency band of 40 GHz to 80 GHz or higher.

[0037] In the wiring boards 10B and 10C of Embodiments 3 and 4, as shown in FIGS. 7A and 8A, the distances L3 and L4 between the electrode 12 and the first connecting conductor 14A are greater than the distance L2 in Embodiment 2. Even in this configuration, the increase in reflection loss in Comparative Example 4 is suppressed by the action of the first connecting conductor 14A. For example, in the wiring board 10B of Embodiment 3, as shown in FIG. 7B, the reflection loss is reduced in the range of 30 GHz to 50 Hz. Furthermore, in the wiring board 10C of Embodiment 4, as shown in FIG. 8B, the reflection loss is reduced in the range of 30 GHz to 65 GHz. In the wiring boards 10B and 10C of Embodiments 3 and 4, the capacitance component formed by the electrode 12 and the first connecting conductor 14A is smaller due to the greater distances L3 and L4, and the effect of reducing reflection loss is smaller compared to the wiring board 10A of Embodiment 2.

[0038] In the wiring board 10D of the fifth embodiment, the distance L5 between the electrode 12 and the first connecting conductor 14A is smaller than the distance L2 in the second embodiment. Even in this configuration, the increase in reflection loss in the fourth comparative example can be suppressed by the action of the first connecting conductor 14A. In the graph of FIG. 9B , the reflection loss is larger than that in the fourth comparative example. However, depending on the values ​​of other parameters, such as the distance between the wiring board 10D and the module substrate 120 (specifically, the thickness of the conductive bonding material 31), the relative dielectric constant of the base 11, and the relative dielectric constant of the module substrate 120, even with the distance L5, reflection loss can be reduced more than in the fourth comparative example in at least some frequency bands. In the wiring board 10D of the fifth embodiment, the first connecting conductor 14A exerts a similar effect to the electrode 12 to a greater extent due to the shorter distance L5. Therefore, the reflection loss reduction effect is smaller compared to the wiring board 10A of the second embodiment.

[0039] <Distance L from Electrode 12 to First Connecting Conductor 14A> If the distance L from the electrode 12 to the first connecting conductor 14A approaches zero, the electrode 12 and the first connecting conductor 14A are positioned at approximately the same height, which is equivalent to a configuration in which the width φ12 of the electrode 12 is increased. In this case, it is presumed that the effect of increasing reflection loss due to the wide electrode 12 will be significant. Furthermore, if the distance L from the electrode 12 to the first connecting conductor 14A is significantly increased, the capacitance component formed between the first connecting conductor 14A and the electrode 12 will be smaller, and it is presumed that the effect of suppressing the reduction of reflection loss due to the large electrode 12 will be reduced. Therefore, the distance L from the electrode 12 to the first connecting conductor 14A affects the effect of reducing reflection loss, and there exists a distance L at which a significant reduction effect can be obtained.

[0040] The distance L from the electrode 12 to the first connecting conductor 14A may be equal to or less than 0.4 times the effective wavelength λg of the signal, as shown in the following formula (4): L ≦ 0.4 × λg (4) By satisfying the condition of formula (4), the capacitance component formed between the first connecting conductor 14A and the electrode 12 becomes large, and the effect of suppressing the reduction in reflection loss caused by the large electrode 12 can be sufficiently obtained.

[0041] In the first to fifth embodiments, the signal frequency band is assumed to be 0 to 80 GHz, and in the simulation parameters, 0.4 times the effective wavelength λg is approximately 0.5 mm. Among the first to fifth embodiments, the wiring board 10B of the third embodiment has a distance L greater than 0.5 mm and closest to 0.5 mm, L3 = 0.55 mm. Among the first to fifth embodiments, the wiring board 10C of the fourth embodiment has a distance L equal to or less than 0.5 mm and closest to 0.5 mm, L4 = 0.4 mm. Comparing the reflection characteristics of the third embodiment (see FIG. 7B ) with the reflection characteristics of the fourth embodiment (see FIG. 8B ), the reflection loss in the 0 Hz to 65 GHz frequency band is -15 dB or less, achieving lower reflection loss. This indicates that satisfying the condition of formula (4) sufficiently suppresses the reduction in reflection loss due to the large electrode 12.

[0042] The distance L from the electrode 12 to the first connecting conductor 14A may be 0.17 to 0.22 times the effective wavelength λg of the signal, as shown in the following equation (5): 0.17×λg≦L ≦0.22×λg (5) Satisfying the condition of equation (5) increases the capacitance component formed between the first connecting conductor 14A and the electrode 12, and increasing the distance between the module substrate 120 and the first connecting conductor 14A reduces the first connecting conductor 14A from acting in the same way as the electrode 12. Therefore, the reflection loss caused by the large electrode 12 can be further reduced.

[0043] In the first to fifth embodiments, the signal frequency band is assumed to be 0 to 80 GHz, and in the simulation parameters for the first to fifth embodiments, 0.17×λg to 0.22×λg are approximately 0.22 mm to 0.28 mm. Among the first to fifth embodiments, the wiring board 10 of the first embodiment, where L1 = 0.25 mm, and the wiring board 10A of the second embodiment, where L2 = 0.25 mm, satisfy the condition of formula (5). The reflection characteristics of the first embodiment (see FIG. 3B ) and the second embodiment (see FIG. 6B ) achieve a reflection loss of −15 dB or less across the entire signal frequency band (i.e., 0 Hz to 80 GHz), achieving low reflection loss. This indicates that satisfying the condition of formula (5) further reduces reflection loss due to the large electrodes 12.

[0044] <Frequency Characteristics of Return Loss> In the wiring board 10 of the first embodiment, as shown in FIG. 3B, the frequency characteristics of return loss may have a minimum value of return loss at a frequency ω1 that is higher than half the frequency band of the signal (i.e., 0 Hz to 80 GHz). This minimum value may be the lowest minimum value excluding the minimum value of return loss in the low-frequency region (e.g., 0 Hz). By having such frequency characteristics, lower return loss can be achieved throughout the entire frequency band of the signal.

[0045] As in the first embodiment, the wiring boards 10A and 10C of the second and fourth embodiments also have minimum values ​​of return loss at frequencies ω2 and ω3, which are higher than half the frequency band of the signal (i.e., 0 Hz to 80 GHz). These minimum values ​​are the lowest, excluding the minimum value of return loss in the low-frequency region (e.g., 0 Hz). By having these frequency characteristics, the second and fourth embodiments also achieve lower return loss throughout the entire frequency band of the signal.

[0046] 1 , the electronic module 100 of the present embodiment may include a module substrate 120, a wiring substrate 10 mounted with its first surface S11a facing a substrate surface S120 of the module substrate 120, and an electronic element 110 mounted on the wiring substrate 10. The wiring substrate 10 may be replaced with the wiring substrates 10A to 10D of the second to fifth embodiments.

[0047] The module substrate 120 may be a printed wiring board having a larger dielectric constant than air. The electronic element 110 may be a light-emitting element (e.g., a semiconductor laser) that generates heat as it emits light. The base 11 of the wiring substrate 10 may be made of aluminum nitride ceramics, as described above. The module substrate 120 may be mounted with one or more electronic elements, one or more electric elements, etc., in addition to the wiring substrate 10 including the electronic element 110.

[0048] The electrode 12 and the ground electrode 22 of the wiring board 10 may be joined to the signal conductor 131 and the ground conductor 132 of the module substrate 120 via a conductive bonding material 31 such as solder, respectively. The electronic element 110 may be joined to the signal conductor 15 and the ground conductor 25 of the wiring board 10 via a conductive bonding material 31 such as solder.

[0049] According to the electronic module 100 of this embodiment, the electronic element 110 is mounted on the module substrate 120 via the wiring board 10, so that the high heat generated by the electronic element 110 can be widely dissipated and then dissipated to the module substrate 120. Furthermore, compared to when the electronic element 110 is mounted directly on the module substrate 120, stress generated in the mounting portion of the electronic element 110 due to thermal expansion can be reduced.

[0050] Furthermore, according to the electronic module 100 of this embodiment, the wiring board 10 of the first embodiment described above is employed as the wiring board 10 interposed between the electronic element 110 and the module substrate 120. Therefore, signals in a high frequency band can be transmitted with good characteristics from the module substrate 120 to the electronic element 110 via the wiring board 10.

[0051] Although the embodiments of the present disclosure have been described above, the wiring board and electronic module of the present disclosure are not limited to the above embodiments, and the details shown in the embodiments can be modified as appropriate without departing from the spirit of the invention.

[0052] An embodiment of the present disclosure is described below. In one embodiment, (1) a wiring board is a wiring board that introduces a high-frequency signal from a module substrate and transmits the signal along a signal path, comprising: an insulating base including a first surface facing the module substrate, an electrode located on the first surface and introducing the signal, a plurality of via conductors arranged inside the base on a straight line intersecting the electrode and transmitting the signal, and a film-like first connecting conductor located between adjacent first and second via conductors among the plurality of via conductors and connected to the first and second via conductors, wherein, in a planar perspective view, the width of the electrode is larger than that of the plurality of via conductors, and the width of the first connecting conductor is larger than that of the electrode.

[0053] (2) In the wiring board of (1) above, the width of the electrode is at least twice the width of the via conductor in the planar perspective view.

[0054] (3) In the wiring board of (1) or (2) above, the distance from the electrode to the first connection conductor is 0.4 times or less the effective wavelength of the signal.

[0055] (4) In the wiring board of (3) above, the distance from the electrode to the first connection conductor is 0.17 to 0.22 times the effective wavelength of the signal.

[0056] (5) In the wiring board according to any one of (1) to (4) above, the base is made of aluminum nitride ceramics.

[0057] (6) Any one of the wiring boards (1) to (5) above has a minimum value of return loss at a frequency higher than half the frequency band of the signal.

[0058] In one embodiment, (7) an electronic module comprises: a module substrate; a wiring substrate according to any one of (1) to (6) above, mounted so that the first surface faces a substrate surface of the module substrate; and an electronic element mounted on the wiring substrate.

[0059] (8) In the electronic module of (7), the module substrate is a printed wiring board.

[0060] (9) In the electronic module of (7) or (8), the electronic element is a light-emitting element.

[0061] (10) In the electronic module of any one of (7) to (9) above, the substrate is made of aluminum nitride ceramics.

[0062] The present disclosure can be used in wiring boards and electronic modules.

[0063] 10, 10A to 10D Wiring board 11 Base 11a Insulating layer S11a First surface 12 Electrode 13 Via conductor 13A First via conductor 13B Second via conductor 14 Connection conductor 14A First connection conductor 15 Signal conductor 16 Mounting portion 18 Signal vertical conductor 22 Ground electrode 23 Ground via conductor 24 Ground connection conductor 24a Ground solid conductor 25 Ground conductor 28 Ground vertical conductor 100 Electronic module 110 Electronic element 120 Module substrate S120 Substrate surface 131 Signal conductor 132 Ground conductor φ12, φ13, φ14A Width L, L1 to L5 Distance ω1, ω2, ω3 Frequency having minimum value

Claims

1. A wiring board that introduces a high-frequency signal from a module substrate and transmits it along a signal path, comprising: an insulating base including a first surface facing the module substrate; an electrode located on the first surface and introducing the signal; a plurality of via conductors that are connected on a straight line inside the base intersecting the electrode and transmit the signal; and a film-like first connecting conductor that is located between adjacent first and second via conductors among the plurality of via conductors and is connected to the first and second via conductors, wherein, in a planar perspective view, the width of the electrode is greater than the width of the plurality of via conductors, and the width of the first connecting conductor is greater than the width of the electrode.

2. The wiring board according to claim 1, wherein the width of said electrode is at least twice the width of said via conductor in said planar perspective view.

3. The wiring board according to claim 1 or 2, wherein the distance from the electrode to the first connection conductor is 0.4 times or less the effective wavelength of the signal.

4. The wiring board according to claim 3, wherein the distance from said electrode to said first connection conductor is 0.17 to 0.22 times the effective wavelength of said signal.

5. The wiring board according to any one of claims 1 to 4, wherein the base is made of aluminum nitride ceramics.

6. The wiring board according to any one of claims 1 to 5, wherein the wiring board has a minimum value of return loss at a frequency higher than half the frequency band of the signal.

7. An electronic module comprising: a module substrate; a wiring board according to any one of claims 1 to 6 mounted so that the first surface faces the substrate surface of the module substrate; and an electronic element mounted on the wiring board.

8. The electronic module of claim 7, wherein the module substrate is a printed wiring board.

9. The electronic module according to claim 7 or claim 8, wherein the electronic element is a light-emitting element.

10. An electronic module according to any one of claims 7 to 9, wherein the substrate is made of aluminum nitride ceramics.

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