Semiconductor module

Abstract

This semiconductor module comprises a substrate, a plurality of semiconductor elements positioned on the substrate, and a control IC positioned on the substrate to control the plurality of semiconductor elements. Further, each of the plurality of semiconductor elements includes a light emitting element. An initial value of a drive current value that differs from one light emitting element to another is set in the control IC in advance.

Description

Semiconductor Module

[0001] The disclosed embodiments relate to a semiconductor module.

[0002] Conventionally, semiconductor modules have been known in which semiconductor elements (hereinafter also referred to as optical elements) that convert electrical signals into optical signals are mounted on a substrate, and in some cases, these semiconductor modules are connected to optical fiber cables that transmit the converted optical signals from the optical elements to the outside (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-9824

[0004] The semiconductor module of the present disclosure includes a substrate, a plurality of semiconductor elements located on the substrate, and a control IC located on the substrate for controlling the plurality of semiconductor elements, each of which has a light-emitting element, and the control IC is preset with a different initial drive current value for each of the light-emitting elements.

[0005] FIG. 1 is a perspective view of a semiconductor module according to an embodiment, as seen obliquely from above. FIG. 2 is a perspective view of a semiconductor module according to an embodiment, as seen obliquely from below. FIG. 3 is a plan view of a semiconductor module according to an embodiment. FIG. 4 is a functional block diagram of a semiconductor module according to an embodiment. FIG. 5 is a diagram for explaining a light emitting operation of a semiconductor module in a reference example. FIG. 6 is a diagram showing an example of the amount of light emitted by each optical element in a reference example. FIG. 7 is a diagram for explaining a light emitting operation of a semiconductor module according to an embodiment. FIG. 8 is a diagram showing an example of the amount of light emitted by each optical element according to an embodiment. FIG. 9 is a plan view of a semiconductor module according to an embodiment. FIG. 10 is a plan view of a semiconductor module according to an embodiment.

[0006] Hereinafter, embodiments of the semiconductor module disclosed herein will be described with reference to the accompanying drawings. Note that the present disclosure is not limited to the embodiments described below. Furthermore, the embodiments can be appropriately combined as long as the processing content is not contradictory. Furthermore, the same components in the following embodiments are designated by the same reference numerals, and redundant explanations will be omitted.

[0007] Furthermore, in the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in the strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision, installation precision, etc.

[0008] In addition, in the drawings referred to below, for ease of understanding, an orthogonal coordinate system may be shown in which the X-axis direction, Y-axis direction, and Z-axis direction, which are perpendicular to each other, are defined, and the positive Z-axis direction is the vertically upward direction.

[0009] Conventionally, semiconductor modules have been known in which semiconductor elements (hereinafter also referred to as optical elements) that convert electrical signals into optical signals are mounted on a substrate. These semiconductor modules may be connected to optical fiber cables that transmit the converted optical signals from the optical elements to the outside.

[0010] However, in the above-mentioned conventional technology, when multiple optical elements are mounted on a semiconductor module, the light emission intensity of each optical element may vary, which may result in variations in the amplitude and median value of the optical signal output from the semiconductor module, resulting in a risk of degrading the signal quality of the optical signal.

[0011] Therefore, there is a need for a technology that can overcome the above-mentioned problems and improve the signal quality of the optical signal output from the semiconductor module.

[0012] <Configuration of Semiconductor Module> First, the configuration of a semiconductor module 1 according to an embodiment will be described with reference to Figures 1 to 3. Figure 1 is a perspective view of the semiconductor module 1 according to an embodiment as seen obliquely from above, and Figure 2 is a perspective view of the semiconductor module 1 according to an embodiment as seen obliquely from below.

[0013] In each of the following embodiments, the semiconductor module 1 will be described as an optical module in which an optical element 3 is mounted on a substrate, but the semiconductor module according to the present disclosure does not necessarily have to be an optical module.

[0014] 1 and 2, a semiconductor module 1 according to the embodiment includes a substrate 2, a plurality of optical elements 3 (optical elements 3a to 3d), and a heat dissipation member 4. The optical elements 3 are an example of semiconductor elements.

[0015] The substrate 2 has, for example, a rectangular plate shape in plan view. In addition to the optical elements 3a to 3d and the heat dissipation member 4, a power supply IC 5, a control IC 6, and a plurality of passive components 7 (all of which are shown in FIG. 3 ) are positioned on a first surface 21 (here, the top surface) of the substrate 2. The passive components 7 include, for example, resistors, capacitors, and coils.

[0016] A connector 25 is located on the second surface 22 (here, the lower surface) of the substrate 2. The substrate 2 is electrically connected to a motherboard via the connector 25.

[0017] The optical elements 3 are semiconductor elements that convert electrical signals into optical signals. Alternatively, the optical elements 3 may convert optical signals into electrical signals. An interface unit 31 is located on the top surface of each optical element 3. The interface unit 31 is connected to an optical connector 33 via a cable group 32A (see FIG. 3 ) that is composed of a plurality of optical fiber cables 32.

[0018] The heat dissipation member 4 is a so-called heat sink, and is located above the plurality of optical elements 3. Note that the heat dissipation member 4 does not necessarily have to cover the entire upper surface of the plurality of optical elements 3. In other words, as shown in FIG. 1 , the upper surfaces of the plurality of optical elements 3 may be partially exposed from the heat dissipation member 4.

[0019] The heat dissipation member 4 is located close to the optical elements 3 and dissipates heat generated from the optical elements 3 to the outside of the semiconductor module 1. The heat dissipation member 4 may be in direct contact with the optical elements 3. Alternatively, the heat dissipation member 4 may be in contact with the optical elements 3 via a thermal interface material (TIM). In other words, the heat dissipation member 4 may be thermally connected to the optical elements 3.

[0020] The heat dissipation member 4 may be made of a metal with a relatively high thermal conductivity, such as aluminum, copper, iron, etc. A TIM is a composite material containing a thermally conductive filler in a resin.

[0021] The heat dissipation member 4 has a plate-shaped portion 41, a plurality of legs 42, and a plurality of heat dissipators 45. The plate-shaped portion 41 is a plate-shaped portion that is disposed opposite the first surface 21 of the substrate 2 with a gap therebetween. The plurality of legs 42 are provided on the plate-shaped portion 41. Specifically, the plurality of legs 42 extend from the plate-shaped portion 41 toward the substrate 2 and come into contact with the substrate 2 (are placed on the substrate 2).

[0022] These legs 42 are shaped so that their thickness increases partially from the plate-shaped portion 41. The legs 42 may be integrated with the plate-shaped portion 41. The multiple legs 42 may be connected to the plate-shaped portion 41 and the substrate 2. The multiple legs 42 extend in a fixed direction (here, the X-axis direction).

[0023] The plurality of heat sinks 45 are located on the surface of the plate-shaped portion 41 opposite to the surface facing the substrate 2. Although Figures 1 and 2 show an example in which the heat sinks 45 have a pin shape (i.e., heat sink pins), the heat sinks 45 may also have a plate shape (i.e., heat sink fins), for example.

[0024] 3 is a plan view of the semiconductor module 1 according to the embodiment. In order to facilitate understanding, the heat dissipation member 4 is shown by a broken line in FIG.

[0025] 3, the optical elements 3a to 3d are arranged in a direction (Y-axis direction) perpendicular to the extension direction (X-axis direction) of the optical fiber cable 32 when viewed along the extension direction of the optical fiber cable 32. Specifically, the optical elements 3a to 3d are arranged in the positive direction of the Y-axis in the order of optical element 3d, optical element 3c, optical element 3b, and optical element 3a.

[0026] Furthermore, the optical elements 3a to 3d are positioned apart from one another. With this configuration, when multiple optical elements 3a to 3d are positioned on the substrate 2, thermal interference between the optical elements 3a to 3d can be reduced.

[0027] 3, among the plurality of optical elements 3a to 3d, optical element 3a and optical element 3b located closest to optical element 3a are misaligned in the extension direction (X-axis direction) of optical fiber cable 32 and in the direction perpendicular to said extension direction (Y-axis direction). Similarly, among the plurality of optical elements 3a to 3d, optical element 3d and optical element 3c located closest to optical element 3d are misaligned in the X-axis direction and Y-axis direction.

[0028] In this way, the plurality of optical elements 3 are arranged with a staggered arrangement, which in this embodiment makes it possible to reduce the size of the substrate 2 while ensuring the distance between adjacent optical elements 3, in other words, while reducing the thermal interference between adjacent optical elements 3.

[0029] Here, an example has been described in which two adjacent optical elements (for example, optical element 3a and optical element 3b) among the plurality of optical elements 3a to 3d are spaced apart in the X-axis direction and the Y-axis direction. However, the present disclosure is not limited to this, and in all of the plurality of optical elements 3a to 3d, the positions of two adjacent semiconductor elements may be shifted in the extension direction of optical fiber cable 32 (X-axis direction) and in a direction perpendicular to this extension direction (Y-axis direction).

[0030] For example, the optical elements 3a to 3d may be arranged alternately, which also reduces the thermal interference between the optical elements 3 and allows the size of the substrate 2 to be reduced.

[0031] A blower (not shown), such as a cooling fan, that blows air toward the semiconductor module 1 may be located on the negative X-axis side of the semiconductor module 1. The blower generates air W that flows in the positive X-axis direction.

[0032] The wind W sent from the blower hits multiple heat sinks 45 (see Figure 1) and flows along the first surface 21 of the substrate 2, passing through the ventilation passage 100 formed between the substrate 2 and the plate-shaped portion 41 of the heat sink member 4.

[0033] In the embodiment, the wind W hits the plurality of optical elements 3 located on the outlet side of the ventilation passage 100, thereby further improving the heat dissipation efficiency of the plurality of optical elements 3.

[0034] Furthermore, in the embodiment, the plurality of optical elements 3 are arranged in a direction (here, the Y-axis direction) that intersects with the flow direction of the wind W, so that the wind W hits all of the optical elements 3 approximately evenly. Therefore, according to the embodiment, the heat dissipation efficiency of the plurality of optical elements 3 can be further improved.

[0035] 3, the control IC 6 may be located below the heat dissipation member 4. The control IC 6 may be thermally connected to the heat dissipation member 4. This allows the heat generated by the control IC 6 to be efficiently dissipated by the heat dissipation member 4.

[0036] For example, a plurality of power supply ICs 5 may be located on the substrate 2. This makes it possible to supply power to the optical element 3 at a plurality of reference voltages.

[0037] Furthermore, when the first surface 21 is viewed in plan, the power supply IC 5 may be located on the opposite side of the control IC 6 with respect to the optical element 3. For example, the control IC 6 may be located on the negative side of the X-axis of the optical element 3, and the power supply IC 5 may be located on the positive side of the X-axis of the optical element 3.

[0038] This reduces interference between the power supply IC 5 and various wirings (not shown) located between the control IC 6 and the optical element 3 on the first surface 21 side of the substrate 2. Therefore, according to the embodiment, it is possible to ensure a degree of freedom in wiring design.

[0039] <Embodiment> Next, details of the operation of the semiconductor module 1 according to the embodiment will be described with reference to Figures 4 to 10. Figure 4 is a functional block diagram of the semiconductor module 1 according to the embodiment.

[0040] 4, the semiconductor module 1 according to the embodiment includes an optical element 3, a control IC 6, a connector 25, and an optical fiber cable 32. The optical element 3 also includes an LD (laser diode) 34, a driver 35, and an optical modulation circuit 36. The LD 34 is an example of a light-emitting element.

[0041] The control IC 6 sets a drive current value for the LD 34 of the optical element 3 based on a preset initial value of the drive current value. The LD 34 emits light with the drive current of the set drive current value. The continuous light generated by the LD 34 is transmitted to the modulated light circuit 36.

[0042] In addition, a pulsed electrical signal is input from an external FPGA (Field-Programmable Gate Array) 200 to a driver 35 of the optical element 3 via a connector 25. This pulsed electrical signal has characteristics that serve as a reference for the optical signal output from the optical element 3.

[0043] The driver 35 generates a drive signal for driving the modulated light circuit 36 ​​based on the electrical signal supplied from the FPGA 200, and supplies the drive signal to the modulated light circuit 36. The driver 35 is also controlled by a control signal supplied from the control IC 6 to turn on / off its operation, modulate the pulse, and so on.

[0044] The modulated light circuit 36 ​​generates pulsed light by modulating the continuous light supplied from the LD 34 based on the drive signal supplied from the driver 35. The pulsed light generated by the modulated light circuit 36 ​​is transmitted to the outside via the optical fiber cable 32.

[0045] 5 is a diagram for explaining the light emitting operation of the semiconductor module 1 in the reference example. As shown in FIG. 5, in the semiconductor module 1, one control IC 6 controls all of the multiple optical elements 3a to 3d.

[0046] In this reference example, the initial values ​​of the drive currents of the LDs 34 (see FIG. 4) located at the respective optical elements 3a to 3d are all the same (drive current value = A). That is, in the reference example, the initial values ​​of the drive currents of the LDs 34, which are preset in the control IC 6, are all the same.

[0047] On the other hand, even if the initial values ​​of the drive current values ​​are all the same, the light emission amounts of the optical elements 3a to 3d will not necessarily be the same. This is because even if the drive current values ​​of the LDs 34 are the same, other factors in the optical elements 3a to 3d are not completely the same, and so the light emission amounts will not necessarily be the same.

[0048] That is, as shown in Fig. 6, there may be variations in the light emission amount B1 of the optical element 3a, the light emission amount B2 of the optical element 3b, the light emission amount B3 of the optical element 3c, and the light emission amount B4 of the optical element 3d. Fig. 6 is a diagram showing an example of the light emission amount of each of the optical elements 3a to 3d in the reference example.

[0049] As a result, in the reference example, the amplitude and median value of the optical signals output from each of the multiple optical connectors 33 (see Figure 1) vary, which could result in a decrease in the signal quality of the optical signal output from the semiconductor module 1.

[0050] 7, the control IC 6 may set different initial drive current values ​​(drive current values ​​= A1 to A4) for each LD 34 (see FIG. 4). That is, in the embodiment, the control IC 6 may be set in advance different initial drive current values ​​for each LD 34.

[0051] For example, a drive current value A1 larger than the drive current value A (see FIG. 5) shown in the reference example is preset as an initial value for the LD 34 of the optical element 3a in the control IC 6. As a result, as shown in FIG. 8, the optical element 3a emits light with an amount of light emission B1' larger than the amount of light emission B1 of the optical element 3a in the reference example.

[0052] 7, a drive current value A2 smaller than the drive current value A shown in the reference example is preset as an initial value for the LD 34 of the optical element 3b in the control IC 6. As a result, as shown in FIG. 8, the optical element 3b emits light with an amount of light emission B2' smaller than the amount of light emission B2 of the optical element 3b in the reference example.

[0053] 7, a drive current value A3 larger than the drive current value A shown in the reference example is preset as an initial value for the LD 34 of the optical element 3c in the control IC 6. As a result, as shown in FIG. 8, the optical element 3c emits light with an amount of light emission B3' larger than the amount of light emission B3 of the optical element 3c in the reference example.

[0054] 7, a drive current value A4 smaller than the drive current value A shown in the reference example is preset as an initial value for the LD 34 of the optical element 3d in the control IC 6. As a result, as shown in FIG. 8, the optical element 3d emits light at an amount of light B4' smaller than the amount of light B4 of the optical element 3d in the reference example.

[0055] 8, it is possible to make the light emission amounts B1' to B4' of all the optical elements 3a to 3d mounted on the semiconductor module 1 uniform. Therefore, according to the embodiment, it is possible to improve the signal quality of the optical signal output from the semiconductor module 1.

[0056] In the embodiment, the initial values ​​of the drive current values ​​in the plurality of LDs 34 may be set according to the light emission amounts of the respective optical elements 3 a to 3 d. For example, in the embodiment, the initial values ​​of the drive current values ​​in the plurality of LDs 34 may be set so that the light emission amounts of the respective optical elements 3 a to 3 d are equal.

[0057] This makes it possible to improve the signal quality of the optical signal output from the semiconductor module 1.

[0058] In the embodiment, for example, after assembling the semiconductor module 1, the amount of light emitted by each optical element 3 when driven to emit light with the same drive current value is measured. Then, based on the measured amount of light emitted by each optical element 3, initial values ​​of the drive current values ​​for the multiple LDs 34 may be set so that the amount of light emitted by all optical elements 3 is uniform. In this way, the initial values ​​of the drive current values ​​for the multiple LDs 34 can be set so that the amount of light emitted by each of the multiple optical elements 3 a to 3 d is uniform.

[0059] In addition, in the embodiment, the initial values ​​of the drive current values ​​in the plurality of LDs 34 may be set by means other than the means described above. Figures 9 and 10 are plan views of the semiconductor module 1 according to the embodiment.

[0060] 9, in the embodiment, the wiring lengths of the wirings C1 to C4 located on the substrate 2 and connecting the connector 25 to the optical elements 3a to 3d may differ from each other. For example, in the example of FIG. 9, the wirings C2 and C3 connecting the connector 25 to the optical elements 3b and 3c, respectively, are longer than the wirings C1 and C4 connecting the connector 25 to the optical elements 3a and 3d, respectively.

[0061] As a result, the electrical signal input from FPGA 200 (see FIG. 4) via connector 25 may be attenuated more by the time it reaches optical elements 3b and 3c than by the time it reaches optical elements 3a and 3d. In this case, the amount of light emitted by optical elements 3b and 3c may be smaller than the amount of light emitted by optical elements 3a and 3d.

[0062] Therefore, in the embodiment, the initial value of the drive current value in the LD 34 of each of the optical elements 3 a to 3 d may be set according to the wiring length between the connector 25 and the optical elements 3 a to 3 d. For example, in the embodiment, the initial value of the drive current value in the LD 34 of each of the optical elements 3 a to 3 d may be set to increase as the wiring length between the connector 25 and the optical elements 3 a to 3 d increases.

[0063] For example, in the example of FIG. 9, the initial values ​​of the drive current values ​​in the LDs 34 of the optical elements 3b and 3c may be set to be larger than the initial values ​​of the drive current values ​​in the LDs 34 of the optical elements 3a and 3d.

[0064] This makes it possible to equalize the amounts of light emitted by the optical elements 3a to 3d, thereby improving the signal quality of the optical signal output from the semiconductor module 1. Furthermore, according to the embodiment, even if the lengths of the wirings C1 to C4 are not the same, the amounts of light emitted by the optical elements 3a to 3d are equalized, thereby ensuring flexibility in wiring design.

[0065] 10, in the embodiment, the lengths of the optical fiber cables 32 connected to the optical elements 3a to 3d may differ. For example, in the example of FIG. 10, the length L1 of the optical fiber cables 32 connected to the optical elements 3a and 3d is longer than the length L2 of the optical fiber cables 32 connected to the optical elements 3b and 3c.

[0066] As a result, the optical signals transmitted from the optical elements 3a and 3d to the optical connector 33 via the optical fiber cable 32 may be attenuated more than the optical signals transmitted from the optical elements 3b and 3c to the optical connector 33 via the optical fiber cable 32.

[0067] In this case, the amplitude and median value of the optical signals transmitted from the optical elements 3a and 3d to the optical connector 33 may be smaller than the amplitude and median value of the optical signals transmitted from the optical elements 3b and 3c to the optical connector 33.

[0068] Therefore, in the embodiment, the initial value of the drive current value in the LD 34 of each of the optical elements 3 a to 3 d may be set according to the length of the optical fiber cable 32 connected to each of the optical elements 3 a to 3 d. For example, in the embodiment, the initial value of the drive current value of the LD 34 may be set to increase as the length of the optical fiber cable 32 connected to the optical elements 3 a to 3 d increases.

[0069] For example, in the example of FIG. 10, the initial values ​​of the drive current values ​​in the LDs 34 of the optical elements 3a and 3d may be set to be larger than the initial values ​​of the drive current values ​​in the LDs 34 of the optical elements 3b and 3c.

[0070] As a result, the amplitude and median value of the optical signals transmitted to all the optical connectors 33 become uniform, and the signal quality of the optical signals output from the semiconductor module 1 can be improved.

[0071] In the embodiment, the control IC 6 may have a correction function for correcting the drive current value of the LD 34 in each of the optical elements 3 a to 3 d based on the light emission amount of the optical elements 3 a to 3 d. The control IC 6 may use a preset initial value of the drive current value (for example, drive current values ​​A1 to A4 (see FIG. 7)) as the initial value of the correction function.

[0072] This allows the amount of correction of the drive current value by the correction function to be smaller than when a uniform drive current value A (see FIG. 5) is used as the initial value of the correction function for all the optical elements 3a to 3d.

[0073] Therefore, according to the embodiment, the configuration of the correction circuit for realizing the functions can be simplified, and the manufacturing cost of the semiconductor module 1 can be reduced.

[0074] Furthermore, according to the embodiment, the configuration of the correction circuit for realizing the function can be simplified, and the correction function can be performed without excessively illuminating the LD 34, thereby reducing the power consumption of the semiconductor module 1.

[0075] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments and various modifications are possible without departing from the spirit thereof. For example, in the above embodiments, an example was shown in which a laser diode was used as the light-emitting element mounted on the optical element 3, but the present disclosure is not limited to such an example and a light-emitting diode (LED) or the like may be mounted as the light-emitting element.

[0076] Further advantages and other aspects may readily occur to those skilled in the art. Therefore, the disclosure in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

[0077] The present technology may also be configured as follows. (1) A semiconductor module comprising: a substrate; a plurality of semiconductor elements located on the substrate; and a control IC located on the substrate and controlling the plurality of semiconductor elements, wherein the plurality of semiconductor elements each have a light-emitting element, and wherein the control IC is preset with a different initial drive current value for each of the light-emitting elements. (2) The semiconductor module described in (1), wherein the initial drive current value for the light-emitting element is set according to the amount of light emitted by the semiconductor element. (3) The semiconductor module described in (2), wherein the initial drive current value for the light-emitting element is set so that the amount of light emitted by each of the plurality of semiconductor elements is uniform. (4) The semiconductor module described in any one of (1) to (3), further comprising: a connector that receives from an external device an electrical signal that serves as a reference for an optical signal output from the light-emitting element, and wherein the initial drive current value for the light-emitting element is set according to the wiring length between the connector and the semiconductor elements. (5) The semiconductor module described in (4), wherein the initial drive current value for the light-emitting element is set so that it increases as the wiring length increases. (6) The semiconductor module according to any one of (1) to (5), further comprising a plurality of optical fiber cables connected to the plurality of semiconductor elements respectively, wherein an initial value of a drive current value of the light-emitting element is set according to the length of the optical fiber cables. (7) The semiconductor module according to (6), wherein the initial value of a drive current value of the light-emitting element is set to increase as the optical fiber cables become longer. (8) The semiconductor module according to any one of (1) to (7), wherein the control IC has a correction function that corrects the drive current value of the light-emitting element based on the amount of light emitted by the semiconductor elements, and the control IC uses a preset initial value of the drive current value as the initial value of the correction function.

[0078] REFERENCE SIGNS LIST 1 semiconductor module 2 substrate 25 connector 3, 3a to 3d optical element (an example of a semiconductor element) 32 optical fiber cable 33 optical connector 34 LD (an example of a light emitting element) 35 driver 36 modulated light circuit 6 control IC

Claims

1. A substrate; a plurality of semiconductor devices located on the substrate; a control IC located on the substrate and controlling the plurality of semiconductor elements; Equipped with Each of the semiconductor elements has a light emitting element, The control IC has a preset initial value of the drive current value, which is different for each of the light-emitting elements. Semiconductor module.

2. The initial value of the drive current value of the light emitting element is set according to the amount of light emitted by the semiconductor element. The semiconductor module according to claim 1 .

3. The initial values ​​of the drive current values ​​of the light emitting elements are set so that the light emission amounts of the plurality of semiconductor elements are uniform. The semiconductor module according to claim 2 .

4. a connector for receiving an electrical signal from an outside source as a reference for the optical signal output from the light emitting element; The initial value of the drive current value of the light emitting element is set according to the wiring length between the connector and the semiconductor element. The semiconductor module according to any one of claims 1 to 3.

5. The initial value of the drive current value of the light emitting element is set to increase as the wiring length increases. The semiconductor module according to claim 4 .

6. a plurality of optical fiber cables respectively connected to the plurality of semiconductor elements; The initial value of the drive current value of the light emitting element is set according to the length of the optical fiber cable. The semiconductor module according to any one of claims 1 to 3.

7. The initial value of the drive current value of the light emitting element is set to increase as the optical fiber cable becomes longer. The semiconductor module according to claim 6 .

8. the control IC has a correction function of correcting a drive current value of the light emitting element based on an amount of light emitted by the semiconductor element, The control IC uses a preset initial value of the drive current value as the initial value of the correction function. The semiconductor module according to any one of claims 1 to 3.