High Frequency Board

Abstract

The high frequency substrate (100) includes a ceramic substrate (12) having a surface (12a) on which a semiconductor laser (20) is mounted and formed of a material having heat dissipation properties, and a low dielectric constant substrate (11) having a surface (11a) on which a signal line (13) for transmitting a high frequency signal to the semiconductor laser 20 is provided and formed of a material having a dielectric constant lower than that of the ceramic substrate (12). A side surface (11b) of the low dielectric constant substrate (11) and a side surface (12b) of the ceramic substrate (12) are butt-jointed.

Description

[Technical field]

[0001] The present disclosure relates to high frequency substrates. [Background technology]

[0002] An optical semiconductor module is disclosed in Patent Document 1. In the optical semiconductor module disclosed in Patent Document 1, a semiconductor laser and a signal line for transmitting a high-frequency signal to the semiconductor laser are provided on an AIN substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-76389 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the optical semiconductor module disclosed in Patent Document 1, the signal line for transmitting a high-frequency signal is provided on an AIN substrate with a relatively high dielectric ratio, which deteriorates the pass characteristic of the high-frequency signal transmitted through the signal line, resulting in attenuation of the high-frequency signal.

[0005] In order to solve these problems, it is conceivable to change from the AIN substrate to a low-dielectric substrate made of a material with a low dielectric constant. However, the low-dielectric substrate has a lower thermal conductivity than the AIN substrate, and this may result in a decrease in the heat dissipation from the semiconductor laser.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a high-frequency substrate that can dissipate heat from a semiconductor laser and suppress attenuation of a high-frequency signal transmitted through a signal line. [Means for solving the problem]

[0007] A high-frequency substrate according to the present disclosure includes a first substrate having a first surface on which a semiconductor laser is mounted and formed of a material having heat dissipation properties, and a second substrate having a second surface on which a signal line for transmitting a high-frequency signal to the semiconductor laser is provided and formed of a material having a dielectric constant lower than that of the first substrate; The first surface has a semiconductor laser mounted thereon and a GND formed so as to surround the signal line, and the second substrate is formed so as to be surrounded by the first substrate. It is something. Effect of the Invention

[0008] According to the present disclosure, it is possible to dissipate heat from a semiconductor laser and suppress attenuation of a high-frequency signal transmitted through a signal line. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view of a laser light emitting device to which a high-frequency substrate according to a first embodiment is applied. [Diagram 2] Fig. 2 is a front view showing an example of bonding two substrates. Fig. 2A is a view showing a state before the two substrates are bonded. Fig. 2B is a view showing a state after the two substrates are bonded. Fig. 2C is a view showing a state after a first wire 31 is wire-bonded to the two bonded substrates. [Diagram 3] FIG. 13 is a diagram showing a comparison result of an S21 characteristic simulation when the high-frequency substrate material is aluminum nitride and quartz. [Figure 4] 11 is a perspective view of a laser light emitting device to which a high-frequency substrate according to a second embodiment is applied. FIG. [Diagram 5] 11 is a perspective view of a laser light emitting device to which a high-frequency substrate according to a third embodiment is applied. FIG. [Figure 6] FIG. 11 is a perspective view of a laser beam emitting device to which a high-frequency substrate according to a conventional example is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In order to describe the present disclosure in more detail, embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0011] Embodiment 1 A high-frequency substrate 100 according to the first embodiment will be described with reference to FIGS. 1 to 3 and 6. FIG.

[0012] First, the configuration of a laser light emitting device to which the high-frequency substrate 100 according to the first embodiment is applied will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view of a laser light emitting device to which the high-frequency substrate 100 according to the first embodiment is applied. Fig. 2 is a front view showing an example when two substrates 11 and 12 are bonded together.

[0013] As shown in FIG. 1, the laser light emitting device according to the first embodiment includes a high-frequency substrate 100, signal lines 13 and 14, a GND 15, a terminating resistor 16, a semiconductor laser 20, a first wire 31, and a second wire 32.

[0014] The high-frequency substrate 100 is composed of a low-dielectric-constant substrate 11 and a ceramic substrate 12. The low-dielectric-constant substrate 11 and the ceramic substrate 12 are joined together with their side surfaces 11b, 12b butted against each other. This will be described later.

[0015] The low dielectric constant substrate 11 is formed in a plate shape. The low dielectric constant substrate 11 is formed of a low dielectric constant material having a low dielectric constant. Specifically, the dielectric constant of the low dielectric constant substrate 11 is lower than the dielectric constant of a ceramic substrate 12 described later. The low dielectric constant substrate 11 is formed of, for example, quartz. The low dielectric constant substrate 11 constitutes a second substrate, and a surface 11a thereof constitutes a second surface.

[0016] The ceramic substrate 12 is formed in a plate shape. The ceramic substrate 12 is formed of a material having high thermal conductivity or heat dissipation. Specifically, the thermal conductivity or heat dissipation of the ceramic substrate 12 is higher than that of the low dielectric constant substrate 11. . The ceramic substrate 12 is made of, for example, aluminum nitride. The ceramic substrate 12 constitutes a first substrate, and a surface 12a thereof constitutes a first surface.

[0017] The signal lines 13 and 14 are provided on the surface 11a of the low dielectric constant substrate 11. In this way, the signal lines 13 and 14 are provided on the surface 11a of the low dielectric constant substrate 11, which has a low dielectric constant, and this improves the passing characteristics of high-frequency signals, thereby enabling the high-speed transmission of the high-frequency signals to be achieved. In other words, attenuation of the high-frequency signals passing through the signal lines 13 and 14 is suppressed. The signal lines 13 and 14 are, for example, coplanar lines.

[0018] GND 15 is provided across the surface 11a of the low dielectric constant substrate 11 and the surface 12a of the ceramic substrate 12. GND 15 is composed of GND 15a provided on the surface 11a and GND 15b provided on the surface 12a. GND 15a constitutes the second GND, and GND 15b constitutes the first GND.

[0019] GND 15a is disposed so as to surround signal line 13 disposed at a corner of surface 11a. GND 15a is formed so as to be bent at a substantially right angle toward surface 12a, and the tip of the bent portion is connected to GND 15b. GND 15b is formed in a straight line and is provided on the side of signal line 13 along the longitudinal direction of signal line 13.

[0020] Therefore, GND 15a and 15b are arranged so as to surround the signal line 13. Specifically, GND 15a covers two sides of the signal line 13, and GND 15b covers one side of the signal line 13.

[0021] The terminating resistor 16 is provided on the surface 11a of the low dielectric constant substrate 11. The terminating resistor 16 is electrically connected to the signal line 14. The terminating resistor 16 terminates a modulated signal from a semiconductor laser 20, which will be described later.

[0022] The semiconductor laser 20 is, for example, an EML (Electro-absorption modulator laser). The semiconductor laser 20 is mounted on the GND 15b provided on the surface 12a of the ceramic substrate 12 by, for example, soldering or the like. In this manner, the semiconductor laser 20 is provided on the surface 12a of the ceramic substrate 12, and thus heat generated from the semiconductor laser 20 is released to the ceramic substrate 12.

[0023] The semiconductor laser 20 has a laser light source 21 and a modulation section 22. The laser light source 21 receives power supply to generate laser light. The modulation section 22 modulates and emits the laser light generated by the laser light source 21. An arrow L shown in Fig. 1 indicates the emission direction of the laser light.

[0024] The laser light source 21 is configured, for example, by a distributed feedback laser diode (DFB-LD). The laser light source 21 is formed so that the length in the D1 direction, which is the longitudinal direction of the laser light source 21, is about 500 um.

[0025] The modulation unit 22 modulates the laser light generated by the laser light source 21 based on a modulation signal from a drive circuit (not shown). The modulation unit 22 is disposed forward of the laser light source 21 in the D1 direction. The modulation unit 22 modulates the intensity of the laser light generated by the laser light source 21 based on, for example, a voltage change of the modulation signal from the drive circuit, and emits the modulated laser light in the D1 direction from one end of the ceramic substrate 12 along the surface 12a of the ceramic substrate 12. The modulation unit 22 is formed, for example, by an electro-absorption modulator (EAM). In addition, the modulation unit 22 is formed so that the length in the D1 direction is about 100 um shorter than the length of the laser light source 21 in the D1 direction in order to reduce parasitic capacitance.

[0026] The first wire 31 and the second wire 32 are, for example, conductive metal wires. The first wire 31 electrically connects the signal line 13 and the modulation section 22 of the semiconductor laser 20. One end of the first wire 31 is wire-bonded to the signal line 13. The other end of the first wire 31 is wire-bonded to the modulation section 22 of the semiconductor laser 20. The second wire 32 electrically connects the modulation section 22 of the semiconductor laser 20 and the signal line 14. One end of the second wire 32 is wire-bonded to the modulation section 22 of the semiconductor laser 20. The other end of the second wire 32 is wire-bonded to the signal line 14.

[0027] Therefore, the high-frequency signal is transmitted through the signal line 13, and then through the first wire 31 to the modulation section 22 of the semiconductor laser 20. Then, the high-frequency signal (modulation signal) output from the modulation section 22 of the semiconductor laser 20 is transmitted through the second wire 32 to the signal line 14, and then terminated at the termination resistor 16.

[0028] Here, as shown in Fig. 1, the length of low dielectric constant substrate 11 in the D1 direction is the same as the length of ceramic substrate 12 in the D1 direction. In addition, the thickness of low dielectric constant substrate 11 is the same as the thickness of ceramic substrate 12. As shown in Fig. 2A, low dielectric constant substrate 11 has a side surface 11b extending in the D1 direction. Ceramic substrate 12 has a side surface 12b extending in the D1 direction.

[0029] When the low dielectric constant substrate 11 and the ceramic substrate 12 are butt-joined, the side surface 11b of the low dielectric constant substrate 11 and the side surface 12b of the ceramic substrate 12 are arranged to face each other as shown in Fig. 2A. Then, as shown in Fig. 2B, the side surface 11b and the side surface 12b are butt-joined using solder 41. Next, as shown in Fig. 2C, for example, a first wire 31 is connected to the signal line 13 and between the modulator section 22 of the semiconductor laser 20 and the modulator section 22 by wire bonding.

[0030] In this way, the low dielectric constant substrate 11 and the ceramic substrate 12 are connected to each other to form a single rectangular high frequency substrate 100 as a whole. At this time, the surface 11a of the low dielectric constant substrate 11 and the surface 12a of the ceramic substrate 12 are flush with each other, with no step between them. In addition, the outer peripheral surface of the low dielectric constant substrate 11 and the outer peripheral surface of the ceramic substrate 12 are flush with each other, with no step between them.

[0031] The first wire 31 and the second wire 32 may be joined after the low dielectric constant substrate 11 having the signal lines 13, 14, GND 15a, and the termination resistor 16 provided on the surface 11a and the ceramic substrate 12 having the GND 15b and the semiconductor laser 20 provided on the surface 12a are butt-joined. Alternatively, the low dielectric constant substrate 11 and the ceramic substrate 12 may be butt-joined, the signal lines 13, 14, GND 15a, and the termination resistor 16 are provided on the surface 11a, and the GND 15b and the semiconductor laser 20 are provided on the surface 12a, and then the first wire 31 and the second wire 32 may be joined.

[0032] Next, the effects of the high-frequency substrate 100 according to the first embodiment will be described in comparison with those of a conventional high-frequency substrate.

[0033] Fig. 6 is a perspective view of a laser beam emitting device to which a conventional high-frequency substrate is applied. In Fig. 6, components having the same functions as those described in the above-mentioned embodiment 1 are denoted by the same reference numerals, and the description thereof will be omitted.

[0034] The high-frequency substrate applied to the laser light emitting device shown in Fig. 6 is only the ceramic substrate 12. Signal lines 13, 14, a GND 15, a terminating resistor 16, and a semiconductor laser 20 are provided on a surface 12a of the ceramic substrate 12. A first wire 31 electrically connects the signal line 13 and the modulation section 22 of the semiconductor laser 20. A second wire 32 electrically connects the modulation section 22 of the semiconductor laser 20 and the signal line 14.

[0035] In general, in order to reduce parasitic capacitance, the modulation section 22 is formed so that the length in the D1 direction is about 100 um, which is shorter than the length in the D1 direction of the laser light source 21. In contrast, in order to obtain a high output, the laser light source 21 is formed so that the length in the D1 direction is about 500 um. For this reason, the length in the D1 direction of the signal line 13 needs to be longer than 500 um. However, if the length in the D1 direction of the signal line 13 is made longer than 500 um, the signal line 13 may resonate at high frequencies, degrading the high-frequency characteristics.

[0036] 1, the high-frequency substrate 100 according to the first embodiment provides the signal line 13 on the surface 11a of the low-dielectric substrate 11, thereby shortening the electrical length of the high-frequency signal transmitted through the signal line 13. Therefore, the high-frequency substrate 100 can shift the resonance frequency occurring near the high-frequency substrate 100 to the high-frequency side, thereby improving the high-frequency characteristics. As a result, the high-frequency substrate 100 does not suffer from band limitations due to high-frequency resonance, and a good optical waveform can be obtained in high-Baud rate modulation that requires a band exceeding 60 GHz, such as 100 GBaud PAM4, which is a promising modulation method for next-generation Ethernet.

[0037] Fig. 3 is a diagram showing the comparison results of S21 characteristic simulation when the high-frequency substrate material is aluminum nitride (ε = 8.8) and quartz (ε = 3.8). In Fig. 3, the results when the signal line is provided on the high-frequency substrate made of aluminum nitride are shown by a two-dot chain line, and the results when the signal line is provided on the high-frequency substrate made of quartz are shown by a solid line. It can be confirmed that when the signal line is provided on the high-frequency substrate made of quartz, the electrical length of the high-frequency signal is shortened, suppressing resonance and improving the characteristics of the 3 dB band.

[0038] As described above, the high-frequency substrate 100 according to the first embodiment can dissipate heat from the semiconductor laser 20 and suppress attenuation of the high-frequency signal transmitted through the signal line 13.

[0039] Embodiment 2 The high-frequency substrate 200 according to the second embodiment will be described with reference to Fig. 4. Fig. 4 is a perspective view of a laser light emitting device to which the high-frequency substrate 200 according to the second embodiment is applied. Note that components having the same functions as those described in the first embodiment above are denoted by the same reference numerals, and description thereof will be omitted.

[0040] The high-frequency substrate 100 according to the first embodiment shown in Fig. 1 includes one GND 15 extending across the surface 11a of the low-dielectric substrate 11 and the surface 12a of the ceramic substrate 12. In contrast, the high-frequency substrate 200 according to the second embodiment shown in Fig. 4 electrically connects the GND 15a provided on the surface 11a of the low-dielectric substrate 11 and the GND 15b provided on the surface 12a of the ceramic substrate 12 by a third wire 33. The third wire 33 is, for example, a conductive metal wire.

[0041] For this reason, the high-frequency substrate 200 does not need to have one GND 15 across the surface 11a of the low-dielectric substrate 11 and the surface 12a of the ceramic substrate 12. As a result, the high-frequency substrate 200 can easily electrically connect the GNDs 15a and 15b together regardless of the accuracy of butt-jointing between the low-dielectric substrate 11 and the ceramic substrate 12.

[0042] Embodiment 3 A high-frequency substrate 300 according to the third embodiment will be described with reference to Fig. 5. Fig. 5 is a perspective view of a laser light emitting device to which the high-frequency substrate 300 according to the third embodiment is applied. Note that components having the same functions as those described in the first embodiment above are denoted by the same reference numerals, and description thereof will be omitted.

[0043] The high-frequency substrate 100 according to the first embodiment shown in Fig. 1 includes a signal line 13 on the surface 11a of the low-dielectric substrate 11, and includes one GND 15 extending from the surface 11a of the low-dielectric substrate 11 to the surface 12a of the ceramic substrate 12. In contrast, the high-frequency substrate 300 according to the third embodiment shown in Fig. 5 includes a signal line 13 on the surface 11a of the low-dielectric substrate 11A, and includes one GND 15 extending from the surface 11a of the ceramic substrate 12A to the surface 12a of the ceramic substrate 12A. of Only the surface 12a is provided with a GND 15.

[0044] Therefore, the high-frequency substrate 300 according to the third embodiment can simplify the manufacture of the low dielectric constant substrate 11A and the ceramic substrate 12A.

[0045] In addition, within the scope of the present disclosure, the embodiments may be freely combined, or any of the components in each embodiment may be modified, or any of the components in each embodiment may be omitted. [Industrial Applicability]

[0046] The high-frequency substrate according to the present disclosure comprises a first substrate having heat dissipation properties and a second substrate having a low dielectric constant, and is therefore capable of dissipating heat from a semiconductor laser and suppressing attenuation of high-frequency signals transmitted through signal lines, and is suitable for use as a high-frequency substrate, etc. [Explanation of symbols]

[0047] 11, 11A low dielectric constant substrate, 11a surface, 11b side, 12, 12A ceramic substrate, 12a surface, 12b side, 13, 14 signal line, 15, 15a, 15b GND, 16 termination resistor, 20 semiconductor laser, 21 laser light source, 22 modulation section, 31 first wire, 32 second wire, 33 third wire, 41 solder, 100, 200, 300 high frequency substrate.

Claims

1. A first substrate having a first surface on which a semiconductor laser is mounted, and being made of a heat-dissipating material, The system comprises a second substrate having a second surface on which a signal line for transmitting high-frequency signals to the semiconductor laser is provided, and a second substrate made of a material having a dielectric constant lower than that of the first substrate, The first surface is on which the semiconductor laser is mounted and has a GND formed to surround the signal line. The second substrate is formed so as to be surrounded by the first substrate. A high-frequency substrate characterized by the following features.

2. The first surface has a termination resistor to which the high-frequency signal from the semiconductor laser terminates. The high-frequency substrate according to claim 1, characterized in that it is a high-frequency substrate.

3. The first substrate is a ceramic substrate. A high-frequency substrate according to claim 1 or 2, characterized by its features.

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