Circuit board and optical module

Abstract

The embodiment of the utility model discloses a circuit board and an optical module, the circuit board is provided with a first module and a second module, and a first differential signal terminal of the first module is connected with a second differential signal terminal of the second module through a differential signal line pair comprising a positive electrode connecting line and a negative electrode connecting line; the circuit board comprises a first signal transmission layer and a second signal transmission layer; the positive electrode connecting line comprises a first positive electrode connecting line of the first signal transmission layer and a second positive electrode connecting line of the second signal transmission layer, and the negative electrode connecting line comprises a first negative electrode connecting line of the first signal transmission layer and a second negative electrode connecting line of the second signal transmission layer; on a plane perpendicular to the thickness direction of the circuit board, the projection of the second positive electrode connecting line and the projection of the first negative electrode connecting line intersect, and the projection of the first positive electrode connecting line and the projection of the second negative electrode connecting line do not intersect. Or the projections of the first anode connecting line and the second cathode connecting line intersect, and the projections of the second anode connecting line and the first cathode connecting line do not intersect.

Description

Technical Field

[0001] The present application relates to the technical field of circuit boards and optical modules, and in particular to a circuit board and an optical module. Background Art

[0002] Mainstream optical modules currently use high-speed digital signal processors (DSPs) in their circuit modules to achieve high-speed, high-modulation signal recovery and transmission. While DSPs offer strong signal recovery capabilities, their drawbacks include high cost, high latency, high power consumption, and significant heat generation. To address this, linear drive optical modules utilize a DSP-free design. Compared to traditional DSP-equipped optical modules, this design reduces costs, power consumption, and latency.

[0003] However, because linear drive technology lacks a DSP, its performance in high-speed signal transmission, such as system bit error rate and transmission distance, is inferior to that of optical modules with DSP. This places higher demands on the performance of the high-speed signal transmission lines on the circuit board (e.g., transmission line bandwidth). Furthermore, during circuit board routing design, some functional modules selected on the board, such as transimpedance amplifiers (TIAs) and drivers, connect to the high-speed signal lines of the gold fingers. Due to the polarity arrangement between the signal terminals, this can lead to crossover of the positive and negative polarity of the differential signal lines. If the polarity arrangement of the two gold fingers of a differential signal pair is opposite to the polarity arrangement of the two terminals of the differential signal pair on a chip such as a transimpedance amplifier or driver, the two signal transmission lines connecting the gold fingers to the two terminals of the differential signal pair on the chip will cross. This crossover of signal transmission lines can easily cause impedance jumps and other problems, resulting in reduced high-frequency performance. Utility Model Content

[0004] The embodiments of the present application provide a circuit board and an optical module to solve the problem of impedance mutation and poor transmission performance when differential signal lines on the circuit board are crossed in the prior art.

[0005] In order to solve the above technical problems, the embodiments of the present application disclose the following technical solutions:

[0006] According to a first aspect of the present application, a circuit board is provided, the circuit board having a first surface, a first module and a second module being arranged on the first surface, the first module having a plurality of pairs of first differential signal terminals, the second module having a plurality of pairs of second differential signal terminals; each pair of first differential signal terminals is connected to a corresponding pair of second differential signal terminals via a pair of differential signal line pairs, the differential signal line pairs comprising a positive connection line and a negative connection line; wherein the positive and negative polarity positions of at least one pair of first differential signal terminals are opposite to the positive and negative polarity positions of the connected second differential signal terminals; the circuit board comprises a plurality of metal layers spaced apart in a thickness direction, the plurality of metal layers comprising a first signal transmission layer and a second signal transmission layer; the positive connection line comprises a first positive connection line located in the first signal transmission layer and a second positive connection line located in the second signal transmission layer, the first positive connection line The first and second positive electrode connection lines are connected through a first conductive via, and the negative electrode connection lines include a first negative electrode connection line located in the first signal transmission layer and a second negative electrode connection line located in the second signal transmission layer. The first negative electrode connection line and the second negative electrode connection line are connected through a second conductive via, and the distance between the first conductive via and the first module is not equal to the distance between the second conductive via and the first module; on a plane perpendicular to the thickness direction of the circuit board, the second positive electrode connection line intersects with the projection of the first negative electrode connection line, and the projection of the first positive electrode connection line does not intersect with the projection of the second negative electrode connection line; or, the first positive electrode connection line intersects with the projection of the second negative electrode connection line, and the second positive electrode connection line does not intersect with the projection of the first negative electrode connection line, so as to connect the first differential signal terminal and the second differential signal terminal with opposite positive and negative polarity positions.

[0007] Furthermore, the first positive electrode connection line includes a first lead-out segment connected to the first conductive via, the second positive electrode connection line includes a second lead-out segment connected to the first conductive via, and the line width of the first lead-out segment and the second lead-out segment is smaller than the line width of the remaining parts of the positive electrode connection line except the first lead-out segment and the second lead-out segment; the first negative electrode connection line includes a third lead-out segment connected to the second conductive via, the second negative electrode connection line includes a fourth lead-out segment connected to the second conductive via, and the line width of the third lead-out segment and the fourth lead-out segment is smaller than the line width of the remaining parts of the negative electrode connection line except the third lead-out segment and the fourth lead-out segment.

[0008] Furthermore, in the thickness direction of the circuit board, the projections of the first lead-out section and the second lead-out section overlap, and are inclined at an angle to the projections of the first positive electrode connection line and the second positive electrode connection line; the projections of the third lead-out section and the fourth lead-out section overlap, and are inclined at an angle to the projections of the first negative electrode connection line and the second negative electrode connection line; the first conductive via and the second conductive via are located on the same side of the differential signal line pair, and are at the same distance from the differential signal line pair.

[0009] Furthermore, there is a preset spacing distance between the positive electrode connection line and the negative electrode connection line, and the preset spacing distance is 1 to 3 times the width of the differential signal line.

[0010] Furthermore, at least one first ground layer is provided on the upper and lower sides of the first signal transmission layer and / or the second signal transmission layer, and the first ground layer is used for the ground return of the differential signal line pair; wherein, the first signal transmission layer, the second signal transmission layer and the first ground layer are all metal layers, and there is a dielectric layer between adjacent metal layers.

[0011] Furthermore, the first conductive via and the second conductive via pass through all first ground layers between the first signal transmission layer and the second signal transmission layer; an anti-pad area surrounding the first conductive via and the second conductive via is provided on the first ground layer.

[0012] Furthermore, there are at least two first ground layers between the first signal transmission layer and the second signal transmission layer, and each of the first ground layers is provided with the anti-pad area.

[0013] Furthermore, the anti-pad area includes a supplementary area, wherein the supplementary area is a conductive plate, the conductive plate is connected to the ground layer in which it is located, and in the thickness direction, the supplementary area is between the second negative electrode connection line and the first negative electrode connection line, and between the first positive electrode connection line and the second positive electrode connection line.

[0014] Furthermore, the circuit board also includes an upper surface layer and a lower surface layer, the first surface is the outer side surface of the upper surface layer or the lower surface layer; the first signal transmission layer, the second signal transmission layer and the first ground layer are spaced apart between the upper surface layer and the lower surface layer.

[0015] Further, on the side of the first signal transmission layer facing away from the second signal transmission layer, at least one second ground layer is arranged between the first signal transmission layer and a first ground layer closest to the first signal transmission layer, wherein a portion of the second ground layer corresponding to the projection of the differential signal line pair on the first signal transmission layer on the second ground layer is hollowed out, so that the differential signal line pair of the first signal transmission layer uses the first ground layer as a reference ground; and / or, on the side of the second signal transmission layer facing away from the first signal transmission layer, at least one second ground layer is arranged between the second signal transmission layer and a first ground layer closest to the second signal transmission layer, wherein a portion of the second ground layer corresponding to the projection of the differential signal line pair on the second signal transmission layer on the second ground layer is hollowed out, so that the differential signal line pair of the second signal transmission layer uses the first ground layer as a reference ground.

[0016] According to a second aspect of the present application, an optical module is provided, comprising a housing, an optical component and a circuit board as described in any one of the first aspects above, the housing being provided with an electrical interface and an optical interface, one end of the optical component being electrically connected to the circuit board, and the other end being optically connected to the optical interface for realizing the reception and transmission of optical signals; a plurality of functional modules are provided on the circuit board, the plurality of functional modules comprising a first module and a second module, the first module being a transimpedance amplifier and / or a driver, the second module being a signal transmission interface, the transimpedance amplifier and the driver being electrically connected to the signal transmission interface through the differential signal line pair; the signal transmission interface extending through the electrical interface, the optical module being connected to external communication through the signal transmission interface.

[0017] One of the above technical solutions has the following advantages or beneficial effects:

[0018] The present application performs via layer switching of a differential signal line pair by providing a first conductive via and a second conductive via, and realizes polarity cross routing by exchanging the relative positions of the signal transmission lines during the via layer switching process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The following detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings will make the technical solutions and other beneficial effects of the present application apparent.

[0020] Figure 1 This is a schematic diagram of the connection relationship between the first module and the second module on a circuit board provided according to an embodiment of the present application;

[0021] Figure 2 This is a partial top view of a circuit board provided according to an embodiment of the present application;

[0022] Figure 3 According to an embodiment of the present application, Figure 2 Schematic diagram of the local section in the AA' direction;

[0023] Figure 4 According to another embodiment of the present application, Figure 2 Schematic diagram of the local section in the AA' direction;

[0024] Figure 5 According to another embodiment of the present application, Figure 2 Schematic diagram of the local section in the AA' direction;

[0025] Figure 6 is a schematic diagram of a differential signal line pair provided according to an embodiment of the present application;

[0026] Figure 7 is a schematic diagram of an anti-pad area provided according to an embodiment of the present application;

[0027] The meanings of the figure marks are as follows: 10-circuit board; 10a-first surface; 20-first signal transmission layer; 30-second signal transmission layer; 40-first ground layer; 50-second ground layer; 11-first module; 12-second module; 110-positive electrode connection line; 120-negative electrode connection line; 115-first positive terminal; 116-first negative terminal; 125-second positive terminal; 126-second negative terminal; 111-first positive electrode connection line; 112-second positive electrode connection line; 300-first conductive via; 400-second conductive via; 121-first negative electrode connection line; 122-second negative electrode connection line; 113-first lead-out section; 114-second lead-out section; 123-third lead-out section; 124-fourth lead-out section; 500-anti-pad area; 510-supplementary area. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and beneficial effects of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and specific implementation methods. It should be understood that the specific implementation methods described in this specification are only for the purpose of explaining this application and are not intended to limit this application.

[0029] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present application, the meaning of "multiple" refers to two or more, unless otherwise clearly and specifically defined.

[0030] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, direct connections, or indirect connections through an intermediate medium; they can refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0031] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0032] In response to the problem of impedance mutation and poor transmission performance when the differential signal line pair 100 on the circuit board 10 of the optical module in the prior art crosses, the present application provides an optical module, which includes a shell, an optical component and a circuit board 10 arranged in the shell. The shell is provided with an electrical interface and an optical interface. One end of the optical component is electrically connected to the circuit board 10, and the other end is optically connected to the optical interface to realize the transmission and reception of optical signals.

[0033] like Figure 1As shown, the circuit board 10 in the optical module has a first surface 10 a , on which a plurality of functional modules are arranged, including a first module 11 and a second module 12 .

[0034] Figure 1 , the connection relationship between the first module 11 and the second module 12 is shown. The first module 11 has multiple pairs of first differential signal terminals, which include a first positive terminal 115 and a first negative terminal 116. The first positive terminal 115 and the first negative terminal 116 are configured to transmit a set of differential signals with different polarities. The second module 12 has multiple pairs of second differential signal terminals, which include a second positive terminal 125 and a second negative terminal 126. The second positive terminal 125 and the second negative terminal 126 are configured to transmit a set of differential signals with different polarities.

[0035] Each pair of first differential signal terminals is connected to a corresponding pair of second differential signal terminals via a pair of differential signal lines 100. Exemplarily, the differential signal line pair 100 includes a positive connection line 110 and a negative connection line 120. The first positive terminal 115 is connected to the corresponding second positive terminal 125 via the positive connection line 110, and the first negative terminal 116 is connected to the corresponding second negative terminal 126 via the negative connection line 120.

[0036] In the actual routing of the circuit board 10, due to the differential coupling relationship between the positive connection line 110 and the negative connection line 120, there is a preset spacing distance between the positive connection line 110 and the negative connection line 120. The preset spacing distance is in the range of 1 to 3 times the width of the differential signal line to control its differential impedance and electromagnetic interference, that is, the preset spacing distance is determined based on the width of the differential signal line. When the width of the differential signal line is w, the preset spacing distance is in the range of w-3w.

[0037] The positive and negative polarity positions of at least one pair of differential signal terminals among the multiple pairs of first differential signal terminals are opposite to the positive and negative polarity positions of the connected second differential signal terminals. Therefore, the positive connection line 110 and the negative connection line 120 connected between the first differential signal terminal and the second differential signal terminal with opposite positive and negative polarity positions need to be swapped in the middle of the wiring. This application provides a wiring method for swapping the relative positions of the positive connection line 110 and the negative connection line 120.

[0038] Specifically, if Figure 2 and Figure 3As shown, the circuit board 10 includes a plurality of metal layers spaced apart in the thickness direction, the plurality of metal layers including a first signal transmission layer 20 and a second signal transmission layer 30, the positive electrode connection line 110 includes a first positive electrode connection line 111 located in the first signal transmission layer 20 and a second positive electrode connection line 112 located in the second signal transmission layer 30, the first positive electrode connection line 111 and the second positive electrode connection line 112 are connected through a first conductive via 300, the negative electrode connection line 120 includes a first negative electrode connection line 121 located in the first signal transmission layer 20 and a second negative electrode connection line 122 located in the second signal transmission layer 30, the first negative electrode connection line 121 and the second negative electrode connection line 122 are connected through a second conductive via 400, and the distance between the first conductive via 300 and the first module 11 is not equal to the distance between the second conductive via 400 and the first module 11.

[0039] Figure 2 It is a partial top view through the circuit board 10, as shown in FIG. Figure 2 As shown, on a plane perpendicular to the thickness direction of circuit board 10, the projections of second positive connecting line 112 and first negative connecting line 121 intersect, while the projections of first positive connecting line 111 and second negative connecting line 122 do not intersect. In other embodiments, the projections of first positive connecting line 111 and second negative connecting line 122 may intersect, while the projections of second positive connecting line 112 and first negative connecting line 121 may not intersect.

[0040] Specifically, the positive and negative connecting wires 110 and 120 respectively switch layers through the first and second conductive vias 300 and 400, swapping their relative positions during the layer swapping process. This positions the positive and negative connecting wires 110 and 120 of the differential signal line pair 100 side by side on the first signal transmission layer 20 opposite to their side-by-side relative positions on the second signal transmission layer 30, thereby connecting the first and second differential signal terminals, which have opposite positive and negative polarity positions. The distance between the first and second conductive vias 300 and 400 affects the impedance curve of the differential signal. Therefore, simulation is required to determine a reasonable hole spacing to reduce impedance abruptness and smooth the impedance curve.

[0041] Figure 3 An embodiment of the present application provides Figure 2 A partial cross-sectional diagram in the AA' direction shows the hierarchical distribution of the positive connecting line 110 and the negative connecting line 120 on the circuit board 10. Since the positive connecting line 110 and the negative connecting line 120 are a pair of differential signal line pairs 100 maintaining a preset spacing distance, the hierarchical distribution of the two on the circuit board 10 remains consistent.

[0042] In some embodiments, the first signal transmission layer 20 can be the upper surface layer of the circuit board 10 having the first surface 10a or be set in the internal layer of the circuit board 10, and the second signal transmission layer 30 can be the lower surface layer of the circuit board 10 or be set in the internal layer of the circuit board 10. Figure 3 The figure shows the arrangement of the first signal transmission layer 20 and the second signal transmission layer 30 when they are arranged in the inner layer of the circuit board 10 (the upper surface layer, the lower surface layer and the conductive vias are not drawn). The differential signal line pair 100 extending from the first module 11 located on the first surface 10a of the circuit board 10 is introduced into the first signal transmission layer 20 through the conductive vias arranged between the upper surface layer and the first signal transmission layer 20, and then the differential signal line pair 100 is led back from the second signal transmission layer 30 to the upper surface layer through the conductive vias arranged between the upper surface layer and the second signal transmission layer 30 and connected to the second module 12.

[0043] Figure 4 According to another embodiment of the present application, Figure 2 The local cross-section diagram in the AA' direction is as follows: Figure 3 or Figure 4 As shown, at least one first ground layer 40 is provided on both the upper and lower sides of the first signal transmission layer 20 and / or the second signal transmission layer 30, wherein Figure 3 The figure shows a situation where two first ground layers 40 are provided between the first signal transmission layer 20 and the second signal transmission layer 30. Figure 4 The diagram shows a situation where the first signal transmission layer 20 and the second signal transmission layer 30 share a first ground layer 40 .

[0044] The first ground layer 40 is used for ground return of the differential signal line pair 100. The first signal transmission layer 20 and the second signal transmission layer 30 serve as signal transmission layers, and the first ground layer 40 serves as a ground layer. High-speed signal traces laid on the signal transmission layers are returned through the adjacent ground layers, serving as a return path for high-speed signals. The first signal transmission layer 20, the second signal transmission layer 30, and the first ground layer 40 are all metal layers, with a dielectric layer between adjacent metal layers.

[0045] In some embodiments, the differential signal lines laid on the signal transmission layer can also be refluxed through the adjacent ground layer as a return path for high-speed signals. Figure 5As shown, on the side of the first signal transmission layer 20 facing away from the second signal transmission layer 30, at least one second ground layer 50 is arranged between the first signal transmission layer 20 and a first ground layer 40 closest to the first signal transmission layer 20, wherein a portion of the second ground layer 50 corresponding to the projection of the differential signal line pair 100 of the first signal transmission layer 20 on the second ground layer 50 is hollowed out, that is, this portion of the second ground layer 50 is hollowed out, so that the differential signal line pair of the first signal transmission layer 20 uses the first ground layer 40 as a reference ground.

[0046] In other embodiments, at least one second ground layer 50 may be provided on a side of the second signal transmission layer 30 facing away from the first signal transmission layer 20, between the second signal transmission layer 30 and the first ground layer 40 closest to the second signal transmission layer 30. The portion of the second ground layer 50 corresponding to the projection of the differential signal line pair 100 on the second signal transmission layer 30 on the second ground layer 50 is hollowed out, i.e., this portion of the second ground layer 50 is hollowed out, so that the differential signal line pair of the second signal transmission layer 30 uses the first ground layer 40 as a reference ground. This allows the positive connection line 110 and the negative connection line 120 in the differential signal line pair 100 to be designed with a wider line width to improve signal transmission capability.

[0047] In some embodiments, circuit board 10 includes an upper surface layer and a lower surface layer, with first surface 10a being the outer side of the upper surface layer or the lower surface layer. First signal transmission layer 20, second signal transmission layer 30, and first ground layer 40 are spaced apart between the upper surface layer and the lower surface layer. That is, first signal transmission layer 20, second signal transmission layer 30, and all associated first ground layers 40 are located within circuit board 10. Placing the signal transmission layer and its associated ground layers within circuit board 10 can reduce electromagnetic interference and improve high-frequency performance.

[0048] Specifically, if Figure 4 In the embodiment shown, when the first signal transmission layer 20 and the second signal transmission layer 30 share a first ground layer 40, the circuit board 10 needs to be provided with at least 7 metal layers, namely, the upper surface layer, the first ground layer 40, the first signal transmission layer 20, the first ground layer 40, the second signal transmission layer 30, the first ground layer 40 and the lower surface layer, wherein there is an insulating dielectric layer between each adjacent metal layer.

[0049] like Figure 3 In the embodiment shown, when two first ground layers 40 are included between the first signal transmission layer 20 and the second signal transmission layer 30, the circuit board 10 needs to be provided with at least 8 metal layers, that is, respective first ground layers 40 are provided on the upper and lower sides of the signal transmission layer to provide a ground return path for the high-speed signal, thereby further optimizing the high-speed performance.

[0050] Or as Figure 5 In the illustrated embodiment, circuit board 10 also requires at least eight metal layers, namely, an upper surface layer, a first ground layer, a first signal transmission layer, a first ground layer 40, a second signal transmission layer, a second ground layer, a first ground layer, and a lower surface layer. Alternatively, the layers may be upper surface layer, a first ground layer, a second ground layer, a first signal transmission layer, a first ground layer, a second signal transmission layer, a first ground layer, and a lower surface layer. Of course, circuit board 10 may also be designed with more metal layers based on actual wiring requirements.

[0051] In some embodiments, as Figure 6 As shown, the first positive electrode connection line 111 includes a first lead-out segment 113 connected to the first conductive via 300, and the second positive electrode connection line 112 includes a second lead-out segment 114 connected to the first conductive via 300. The line width of the first lead-out segment 113 and the second lead-out segment 114 is smaller than the line width of the remaining parts of the positive electrode connection line 110 except the first lead-out segment 113 and the second lead-out segment 114.

[0052] First negative electrode connection line 121 includes a third lead segment 123 connected to second conductive via 400. Second negative electrode connection line 122 includes a fourth lead segment 124 connected to second conductive via 400. The widths of third lead segment 123 and fourth lead segment 124 are smaller than the width of the remaining portion of negative electrode connection line 120 excluding third lead segment 123 and fourth lead segment 124. This embodiment reduces the width of the lead segments close to the conductive vias, thereby improving the signal impedance of the differential line pair when the vias cross and switch lines, thereby optimizing the impedance curve.

[0053] In some embodiments, as Figure 6As shown, on a plane perpendicular to the thickness direction of circuit board 10, the projections of first lead section 113 and second lead section 114 overlap and form an oblique angle with the projections of first positive electrode connecting line 111 and second positive electrode connecting line 112. The projections of third lead section 123 and fourth lead section 124 overlap and form an oblique angle with the projections of first negative electrode connecting line 121 and second negative electrode connecting line 122. In other words, the extension direction of first lead section 113 and second lead section 114 is different from the extension direction of first positive electrode connecting line 111, second positive electrode connecting line 112, first negative electrode connecting line 121, and second negative electrode connecting line 122. First conductive via 300 and second conductive via 400 are located beside first positive electrode connecting line 111 and first negative electrode connecting line 121, not in their extension direction. In this embodiment, the first conductive via 300 and the second conductive via 400 are located on the same side of the differential signal line pair and are at the same distance from the differential signal line pair. This ensures that the total length of the positive and negative connecting lines 110 and 120 are the same, resulting in a minimal impedance difference. The overlapping lead-out sections located on different signal transmission layers ensure that the vias are centered and symmetrical relative to the two signal lines of the differential signal line pair 100. This symmetrical design helps improve the transmission quality of differential signals.

[0054] In some embodiments, as Figure 7As shown, the first conductive via 300 and the second conductive via 400 penetrate at least one first ground layer 40 between the first signal transmission layer 20 and the second signal transmission layer 30. The first ground layer 40 is provided with an anti-pad region 500 surrounding the first conductive via 300 and the second conductive via 400. The anti-pad region 500 is an isolated region directly connected to the conductive via. The number of the anti-pad regions 500 is consistent with the number of the first conductive vias 300 and the second conductive via 400 penetrating the first ground layer 40. The distance between the boundary of the anti-pad region 500 and the first conductive via 300 or the second conductive via 400 is greater than a first preset value, which is determined based on the material, number of layers, thickness of the circuit board 10, and wiring space of the circuit board 10. The anti-pad region 500 includes a supplementary region 510, which is a conductive pad connected to the ground layer in which it resides. In the thickness direction, the supplementary region 510 is located between the second negative connection line 122 and the first negative connection line 121, and between the first positive connection line 111 and the second positive connection line 112. The supplementary region 510 is integrated with the anti-pad region 500 through which the via passes. As part of the reference layer for the differential signal line pair 100, the supplementary region 510 can reduce the ground return path while ensuring a safe distance between the supplementary region 510 and the differential signal line pair 100 to prevent short circuits. Specifically, when the spacing between the first and second conductive vias 300 and 400 and the size of the anti-pad region 500 are limited, the line width of the lead-out section can be reduced and the supplementary region added to the anti-pad region 500 can ensure the integrity of the signal return path and minimize impedance jumps. Specifically, to simplify the process, the material of the supplementary area can be consistent with the material of the ground layer, that is, a portion of copper foil is added to the anti-pad area 500 as the supplementary area to optimize high-speed performance.

[0055] Specifically, signal integrity analysis can be performed on the vias during layer switching. Combined with the actual line distribution and PCB board area, the distance between the positive connecting line 110 and the negative connecting line 120 (preset distance), the distance between the first conductive via 300 and the second conductive via 400, the distance between the boundary of the anti-pad area 500 and the first conductive via 300 or the second conductive via 400, and the position and area of ​​the supplementary area 510 and other parameters can be optimized through simulation, thereby smoothing the impedance curve at the via and reducing reflections, thereby improving the performance of the signal transmission line and the link bandwidth.

[0056] The present application also provides an optical module, including a housing, an optical component and the above-mentioned circuit board 10, the housing is provided with an electrical interface and an optical interface, one end of the optical component is electrically connected to the circuit board 10, and the other end is optically connected to the optical interface to realize the transmission and reception of optical signals. A plurality of functional modules are provided on the circuit board 10, and the plurality of functional modules include a first module 11 and a second module 12, the first module 11 is a transimpedance amplifier or a driver, and the second module 12 is a signal transmission interface, and the transimpedance amplifier and the driver are electrically connected to the signal transmission interface through a differential signal line pair 100. The signal transmission interface extends through the electrical interface to realize the communication connection between the optical module and the outside world.

[0057] In this embodiment, the first module 11 includes two components, namely a transimpedance amplifier (TIA) and a driver. The second module 12 is the electrical connection end of the circuit board 10. In this embodiment, the electrical connection end of the circuit board 10 is a gold finger. That is, the circuit board 10 of the optical module is provided with a TIA and a driver. There is no DSP chip between the TIA and / or the driver and the gold finger of the circuit board 10. One end of the TIA and the driver is electrically connected to the photodetector and the laser, respectively, and the other end of the TIA and / or the driver is electrically connected to the gold finger of the circuit board 10 via multiple pairs of differential signal lines 100. Therefore, higher high-frequency performance requirements are placed on the differential signal line pairs 100.

[0058] In this optical module, the positive and negative polarity positions of some of the differential signal terminals of the TIA and driver are opposite to the positive and negative polarity positions of the corresponding differential signal terminals at the gold finger end. Therefore, the polarity of the differential signal line pair 100 connected to the gold finger may be crossed. The optical module of the present application uses the above-mentioned circuit board 10 to achieve the electrical connection between the TIA and driver and the gold finger, and can effectively improve the high-frequency performance of the signal transmission between the TIA, driver and gold finger, meeting the higher requirements of the linear direct drive solution that omits the DSP for the signal transmission line, thereby solving the problems of system bit error rate and transmission distance degradation caused by omitting the DSP.

[0059] The above embodiments are only intended to help understand the structure and core concept of the present application. Those skilled in the art may make improvements and modifications to the present application without departing from the principles of the present application, and such improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A circuit board, characterized in that: The circuit board has a first surface, a first module and a second module are arranged on the first surface, the first module has a plurality of pairs of first differential signal terminals, and the second module has a plurality of pairs of second differential signal terminals; Each pair of first differential signal terminals is connected to a corresponding pair of second differential signal terminals via a pair of differential signal lines, wherein the differential signal line pair includes a positive connection line and a negative connection line; wherein the positive and negative polarity positions of at least one pair of first differential signal terminals are opposite to the positive and negative polarity positions of the connected second differential signal terminals; The circuit board includes a plurality of metal layers spaced apart in a thickness direction, the plurality of metal layers including a first signal transmission layer and a second signal transmission layer; the positive electrode connection line includes a first positive electrode connection line located in the first signal transmission layer and a second positive electrode connection line located in the second signal transmission layer, the first positive electrode connection line and the second positive electrode connection line are connected through a first conductive via, the negative electrode connection line includes a first negative electrode connection line located in the first signal transmission layer and a second negative electrode connection line located in the second signal transmission layer, the first negative electrode connection line and the second negative electrode connection line are connected through a second conductive via, and a distance between the first conductive via and the first module is unequal to a distance between the second conductive via and the first module; On a plane perpendicular to the thickness direction of the circuit board, the projection of the second positive connecting line intersects with the projection of the first negative connecting line, and the projection of the first positive connecting line does not intersect with the projection of the second negative connecting line; or, the projection of the first positive connecting line intersects with the projection of the second negative connecting line, and the projection of the second positive connecting line does not intersect with the projection of the first negative connecting line, so as to connect the first differential signal terminal and the second differential signal terminal with opposite positive and negative polarity positions.

2. The circuit board according to claim 1, wherein: The first positive electrode connection line includes a first lead segment connected to the first conductive via, and the second positive electrode connection line includes a second lead segment connected to the first conductive via, wherein the line width of the first lead segment and the second lead segment is smaller than the line width of the remaining portion of the positive electrode connection line except the first lead segment and the second lead segment; The first negative electrode connecting line includes a third lead segment connected to the second conductive via, and the second negative electrode connecting line includes a fourth lead segment connected to the second conductive via, and the line width of the third lead segment and the fourth lead segment is smaller than the line width of the remaining parts of the negative electrode connecting line except the third lead segment and the fourth lead segment.

3. The circuit board according to claim 2, wherein: In the thickness direction of the circuit board, the projections of the first lead section and the second lead section overlap and form an inclined angle with the projections of the first positive electrode connecting line and the second positive electrode connecting line; the projections of the third lead section and the fourth lead section overlap and form an inclined angle with the projections of the first negative electrode connecting line and the second negative electrode connecting line; The first conductive via and the second conductive via are located on the same side of the differential signal line pair and are at the same distance from the differential signal line pair.

4. The circuit board according to claim 1, wherein: There is a preset spacing distance between the positive electrode connection line and the negative electrode connection line, and the preset spacing distance is 1 to 3 times the width of the differential signal line.

5. The circuit board according to claim 1, wherein: At least one first ground layer is provided on the upper and lower sides of the first signal transmission layer and / or the second signal transmission layer, and the first ground layer is used for the ground return of the differential signal line pair; wherein, the first signal transmission layer, the second signal transmission layer and the first ground layer are all metal layers, and there is a dielectric layer between adjacent metal layers.

6. The circuit board according to claim 5, wherein: The first conductive via and the second conductive via penetrate all first ground layers between the first signal transmission layer and the second signal transmission layer; An anti-pad region surrounding the first conductive via and the second conductive via is provided on the first ground layer.

7. The circuit board according to claim 6, wherein: There are at least two first ground layers between the first signal transmission layer and the second signal transmission layer, and each of the first ground layers is provided with the anti-pad area.

8. The circuit board according to claim 6, wherein: The anti-pad area includes a supplementary area, wherein the supplementary area is a conductive pad, the conductive pad is connected to the ground layer in which it is located, and in the thickness direction, the supplementary area is between the second negative electrode connection line and the first negative electrode connection line, and between the first positive electrode connection line and the second positive electrode connection line.

9. The circuit board according to claim 5, wherein: The circuit board also includes an upper surface layer and a lower surface layer, the first surface is the outer side surface of the upper surface layer or the lower surface layer; the first signal transmission layer, the second signal transmission layer and the first ground layer are spaced apart and arranged between the upper surface layer and the lower surface layer.

10. The circuit board according to claim 5, wherein: On a side of the first signal transmission layer facing away from the second signal transmission layer, at least one second ground layer is provided between the first signal transmission layer and a first ground layer closest to the first signal transmission layer, wherein a portion of the second ground layer corresponding to a projection of the differential signal line pair on the first signal transmission layer on the second ground layer is hollowed out, so that the differential signal line pair on the first signal transmission layer uses the first ground layer as a reference ground; and / or, On the side of the second signal transmission layer facing away from the first signal transmission layer, at least one second ground layer is arranged between the second signal transmission layer and a first ground layer closest to the second signal transmission layer, wherein a portion of the second ground layer corresponding to a projection of the differential signal line pair on the second signal transmission layer on the second ground layer is hollowed out, so that the differential signal line pair of the second signal transmission layer uses the first ground layer as a reference ground.

11. An optical module, characterized in that: A device comprising a housing, an optical assembly, and a circuit board according to any one of claims 1 to 10, wherein the housing is provided with an electrical interface and an optical interface, one end of the optical assembly is electrically connected to the circuit board, and the other end is optically connected to the optical interface, so as to realize the transmission and reception of optical signals; The circuit board is provided with a plurality of functional modules, the plurality of functional modules including a first module and a second module, the first module being a transimpedance amplifier and / or a driver, the second module being a signal transmission interface, the transimpedance amplifier and the driver being electrically connected to the signal transmission interface via the differential signal line pair; The signal transmission interface extends through the electrical interface, and the optical module is connected to the outside world through the signal transmission interface.

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