CN113281859B

CN113281859B - Optical module

Info

Publication number: CN113281859B
Application number: CN202110542293.6A
Authority: CN
Inventors: 郭蓉; 叶书华
Original assignee: Hisense Broadband Multimedia Technology Co Ltd
Current assignee: Hisense Broadband Multimedia Technology Co Ltd
Priority date: 2021-05-18
Filing date: 2021-05-18
Publication date: 2022-11-11
Anticipated expiration: 2041-05-18
Also published as: CN113281859A

Abstract

The optical module comprises a circuit board, an optical submodule and a flexible circuit board, wherein the optical submodule comprises an optical chip, the flexible circuit board comprises a first connecting part, a second connecting part and a bending part, the first connecting part is provided with a bonding pad, and the bonding pad is electrically connected with the circuit board; the second connecting part is electrically connected with the optical chip, and two ends of the bending part are connected with the first connecting part and the second connecting part; the number of the wiring layers of the second connecting portion is more than that of the first connecting portion, the high-speed signal wiring and the low-speed signal wiring of the second connecting portion are located on different wiring layers, and the high-speed signal wiring and the low-speed signal wiring of the first connecting portion are located on the same wiring layer. This application adopts the different stacked structure design of walking the line number of piles in flexible circuit board both ends, has reduced the line number of piles of walking of second connecting portion, has reduced the thickness of kink, has guaranteed that high-speed signal transmission is not influenced to both satisfied the constrictive operation demand of structural space, realized the product demand of high speed high performance again simultaneously.

Description

Optical module

Technical Field

The application relates to the technical field of optical fiber communication, in particular to an optical module.

Background

With the development of new services and application modes such as cloud computing, mobile internet, video and the like, the development and progress of the optical communication technology become increasingly important. In the optical communication technology, an optical module is a tool for realizing the interconversion of optical signals and is one of key devices in optical communication equipment, and the transmission rate of the optical module is continuously increased along with the development requirement of the optical communication technology.

The optical module generally includes a circuit board a and an optical subassembly, and the optical subassembly can be directly electrically connected to the circuit board a, or the optical subassembly and the circuit board a are connected by switching through a circuit board B, where the circuit board a is generally a hard circuit board. When the circuit board B is used to connect the circuit board a, the circuit board B is usually bendable to facilitate the connection of the optical sub-module and the circuit board a through the circuit board B, and therefore the circuit board B is usually connected to the optical sub-module and the hard circuit board through the flexible circuit board.

However, the QSFP-DD optical module has a small structural size, a small space exists between the circuit board and the optical sub-module, and it is difficult to satisfy both the bending property and the high-speed performance of the flexible circuit board when the optical sub-module and the circuit board are connected by the flexible circuit board.

Disclosure of Invention

The embodiment of the application provides an optical module to solve the problem that the space is narrow and small between present circuit board and the optics submodule, and the nature of buckling and the high-speed performance of flexible circuit board are hardly satisfied simultaneously.

The application provides an optical module, includes:

a circuit board;

an optical sub-module comprising a photonic chip for emitting or receiving a light beam;

the flexible circuit board comprises a first connecting part, a second connecting part and a bending part, wherein the first connecting part is provided with a welding disc and is electrically connected with the circuit board through the welding disc; the second connecting part is electrically connected with the optical chip, one end of the bending part is connected with the first connecting part, and the other end of the bending part is connected with the second connecting part; the number of the wiring layers of the second connecting portion is more than that of the first connecting portion, the high-speed signal wiring and the low-speed signal wiring of the second connecting portion are located on different wiring layers, and the high-speed signal wiring and the low-speed signal wiring of the first connecting portion are located on the same wiring layer.

The optical module comprises a circuit board, an optical sub-module and a flexible circuit board, wherein the optical sub-module comprises an optical chip used for transmitting or receiving light beams; the flexible circuit board comprises a first connecting part, a second connecting part and a bending part, wherein the first connecting part is provided with a bonding pad and is electrically connected with the circuit board through the bonding pad; the second connecting part is electrically connected with the optical chip, one end of the bending part is connected with the first connecting part, and the other end of the bending part is connected with the second connecting part; the number of the wiring layers of the second connecting portion is more than that of the first connecting portion, the high-speed signal wiring and the low-speed signal wiring of the second connecting portion are located on different wiring layers, and the high-speed signal wiring and the low-speed signal wiring of the first connecting portion are located on the same wiring layer. In the optical module provided by the application, the space between the circuit board and the optical submodule is narrow, and the bending requirement of the bent part of the flexible circuit board is increased, so that the bent part needs to be very thin; in addition, for the 400G optical module, the requirement on high-speed performance is strict, so that the requirement on the high-speed performance of the flexible circuit board is strict; according to the flexible circuit board, the design of a laminated structure with different wiring layers at two ends of the flexible circuit board is adopted, the number of wiring layers of the second connecting part connected with the optical sub-module is larger than that of the first connecting part connected with the circuit board, so that the thickness of a bent part can be reduced, and the flexibility of the flexible circuit board can be improved; meanwhile, the high-speed signal routing and the low-speed signal routing at the second connecting part are positioned on different routing layers, so that high-speed signal transmission is not influenced; the design can meet the operation requirement of narrow structural space and can also realize the product requirements of high speed and high performance.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic diagram of a connection relationship of an optical communication terminal;

FIG. 2 is a schematic diagram of an optical network unit;

fig. 3 is a schematic structural diagram of an optical module according to an embodiment of the present application;

fig. 4 is an exploded structural diagram of an optical module according to an embodiment of the present disclosure;

fig. 5 is an assembly view of a circuit board and an optical receive sub-module in an optical module according to an embodiment of the present disclosure;

fig. 6 is a partial cross-sectional view of an optical module according to an embodiment of the present disclosure;

fig. 7 is a schematic diagram of signal routing design of a flexible circuit board in an optical module according to an embodiment of the present application;

fig. 8 is a schematic laminated view of a flexible circuit board in an optical module according to an embodiment of the present application;

fig. 9 is a schematic diagram of a signal routing relationship of a flexible circuit board in an optical module according to an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

One of the core links of optical fiber communication is the interconversion of optical and electrical signals. The optical fiber communication uses optical signals carrying information to transmit in information transmission equipment such as optical fibers/optical waveguides, and the information transmission with low cost and low loss can be realized by using the passive transmission characteristic of light in the optical fibers/optical waveguides; meanwhile, the information processing device such as a computer uses an electric signal, and in order to establish information connection between the information transmission device such as an optical fiber or an optical waveguide and the information processing device such as a computer, it is necessary to perform interconversion between the electric signal and the optical signal.

The optical module realizes the function of interconversion of optical signals and electrical signals in the technical field of optical fiber communication, and the interconversion of the optical signals and the electrical signals is the core function of the optical module. The optical module is electrically connected with an external upper computer through a golden finger on an internal circuit board of the optical module, and the main electrical connection comprises power supply, I2C signals, data signals, grounding and the like; the electrical connection mode realized by the gold finger has become the mainstream connection mode of the optical module industry, and on the basis of the mainstream connection mode, the definition of the pin on the gold finger forms various industry protocols/specifications.

Fig. 1 is a schematic diagram of connection relationship of an optical communication terminal. As shown in fig. 1, the connection of the optical communication terminal mainly includes the interconnection among the optical network terminal 100, the optical module 200, the optical fiber 101 and the network cable 103;

one end of the optical fiber 101 is connected with a far-end server, one end of the network cable 103 is connected with local information processing equipment, and the connection between the local information processing equipment and the far-end server is completed by the connection between the optical fiber 101 and the network cable 103; and the connection between the optical fiber 101 and the network cable 103 is made by the optical network terminal 100 having the optical module 200.

An optical port of the optical module 200 is externally connected to the optical fiber 101, and establishes bidirectional optical signal connection with the optical fiber 101; an electrical port of the optical module 200 is externally connected to the optical network terminal 100, and establishes bidirectional electrical signal connection with the optical network terminal 100; the optical module realizes the interconversion of optical signals and electric signals, thereby realizing the establishment of information connection between the optical fiber and the optical network terminal; specifically, the optical signal from the optical fiber is converted into an electrical signal by the optical module and then input to the optical network terminal 100, and the electrical signal from the optical network terminal 100 is converted into an optical signal by the optical module and input to the optical fiber.

The optical network terminal is provided with an optical module interface 102, which is used for accessing the optical module 200 and establishing bidirectional electric signal connection with the optical module 200; the optical network terminal is provided with a network cable interface 104, which is used for accessing the network cable 103 and establishing bidirectional electric signal connection with the network cable 103; the optical module 200 is connected to the network cable 103 through the optical network terminal 100, specifically, the optical network terminal transmits a signal from the optical module to the network cable and transmits the signal from the network cable to the optical module, and the optical network terminal serves as an upper computer of the optical module to monitor the operation of the optical module.

At this point, a bidirectional signal transmission channel is established between the remote server and the local information processing device through the optical fiber, the optical module, the optical network terminal and the network cable.

Common information processing apparatuses include routers, switches, electronic computers, and the like; the optical network terminal is an upper computer of the optical module, provides data signals for the optical module, and receives the data signals from the optical module, and the common upper computer of the optical module also comprises an optical line terminal and the like.

Fig. 2 is a schematic diagram of an optical network terminal structure. As shown in fig. 2, the optical network terminal 100 has a circuit board 105, and a cage 106 is disposed on a surface of the circuit board 105; an electric connector is arranged in the cage 106 and used for connecting an electric port of an optical module such as a golden finger; the cage 106 is provided with a heat sink 107, and the heat sink 107 has a projection such as a fin for increasing a heat radiation area.

The optical module 200 is inserted into the optical network terminal, specifically, the electrical port of the optical module is inserted into the electrical connector inside the cage 106, and the optical port of the optical module is connected to the optical fiber 101.

The cage 106 is positioned on the circuit board, and the electrical connector on the circuit board is wrapped in the cage, so that the electrical connector is arranged in the cage; the optical module is inserted into the cage, held by the cage, and the heat generated by the optical module is conducted to the cage 106 and then diffused by the heat sink 107 on the cage.

Fig. 3 is a schematic view of an optical module according to an embodiment of the present disclosure, and fig. 4 is a schematic view of an exploded structure of an optical module according to an embodiment of the present disclosure. As shown in fig. 3 and 4, an optical module 200 provided in the embodiment of the present application includes an upper housing 201, a lower housing 202, an unlocking member 203, a circuit board 300, a tosa 400, and a tosa 500.

The upper shell 201 is covered on the lower shell 202 to form a wrapping cavity with two openings; the outer contour of the wrapping cavity is generally a square body, and specifically, the lower shell comprises a main plate and two side plates which are positioned at two sides of the main plate and are perpendicular to the main plate; the upper shell comprises a third shell, and the third shell covers the two side plates of the upper shell to form a wrapping cavity; the upper shell can also comprise two side walls which are positioned on two sides of the third shell and are vertically arranged with the third shell, and the two side walls are combined with the two side plates to cover the lower shell.

The two openings can be two ends (204, 205) in the same direction, or two openings in different directions; one opening is an electric port 204, and a gold finger of the circuit board extends out of the electric port 204 and is inserted into an upper computer such as an optical network terminal; the other opening is an optical port 205 for external optical fiber access to connect the optical transmitter sub-module 400 and the optical receiver sub-module 500 inside the optical module; the optoelectronic devices such as the circuit board 300, the transmitter sub-assembly 400, the receiver sub-assembly 500, etc. are located in the package cavity.

The assembly mode of combining the upper shell and the lower shell is adopted, so that the circuit board 300, the transmitter sub-module 400, the receiver sub-module 500 and other devices can be conveniently installed in the shells, and the outermost packaging protection shell of the optical module is formed by the upper shell and the lower shell; the upper shell and the lower shell are made of metal materials generally, so that electromagnetic shielding and heat dissipation are facilitated; generally, the housing of the optical module is not made into an integral component, so that when devices such as a circuit board and the like are assembled, a positioning component, a heat dissipation component and an electromagnetic shielding component cannot be installed, and production automation is not facilitated.

The unlocking component 203 is located on the outer wall of the wrapping cavity/lower shell 202, and is used for realizing the fixed connection between the optical module and the upper computer or releasing the fixed connection between the optical module and the upper computer.

The unlocking component 203 is provided with a clamping component matched with the upper computer cage; the end of the unlocking component can be pulled to enable the unlocking component to move relatively on the surface of the outer wall; the optical module is inserted into a cage of the upper computer, and the optical module is fixed in the cage of the upper computer by a clamping component of the unlocking component; by pulling the unlocking component, the clamping component of the unlocking component moves along with the unlocking component, so that the connection relation between the clamping component and the upper computer is changed, the clamping relation between the optical module and the upper computer is released, and the optical module can be drawn out from the cage of the upper computer.

The circuit board 300 is provided with circuit traces, electronic components (such as capacitors, resistors, triodes, and MOS transistors), and chips (such as an MCU, a laser driver chip, a limiting amplifier chip, a clock data recovery CDR, a power management chip, and a data processing chip DSP).

The circuit board connects the electrical appliances in the optical module together according to the circuit design through circuit wiring to realize the functions of power supply, electrical signal transmission, grounding and the like.

The chip on the circuit board 300 may be a multifunctional integrated chip, for example, a laser driver chip and an MCU chip are integrated into one chip, or a laser driver chip, a limiting amplifier chip and an MCU chip are integrated into one chip, and the chip is an integrated circuit, but the function of each circuit does not disappear due to integration, and only the circuit appears and changes in form, and the chip still has the circuit form. Therefore, when the circuit board is provided with three independent chips, namely, the MCU, the laser driver chip and the limiting amplifier chip, the scheme is equivalent to that when the circuit board 300 is provided with a single chip with three functions in one.

The circuit board is generally a hard circuit board, and the hard circuit board can also realize a bearing effect due to the relatively hard material of the hard circuit board, for example, the hard circuit board can stably bear a chip; when the optical transceiver is positioned on the circuit board, the rigid circuit board can also provide stable bearing; the hard circuit board can also be inserted into an electric connector in the upper computer cage, and specifically, a metal pin/golden finger is formed on the surface of the tail end of one side of the hard circuit board and is used for being connected with the electric connector; these are not easily implemented with flexible circuit boards.

A flexible circuit board is also used in a part of the optical module to supplement the rigid circuit board; the flexible circuit board is generally used in combination with a rigid circuit board, for example, the rigid circuit board may be connected to the optical transceiver device by using the flexible circuit board.

Fig. 5 is an assembly schematic diagram of a circuit board 300, a light-receiving sub-assembly 500, and a first flexible circuit board 600 in an optical module provided in an embodiment of the present application, and fig. 6 is a partial assembly cross-sectional view of an optical module provided in the embodiment of the present application. As shown in fig. 5 and fig. 6, the circuit board 300 of the 400G QSFP-DD LR8 (8 × 50g) optical module is connected to the optical receive sub-module 500 through the first flexible circuit board 600, and the optical transmit sub-module 400 is connected to the circuit board 300 through the second flexible circuit board 700 and the third flexible circuit board 800, so that the circuit board 300 is electrically connected to the optical receive sub-module 500 through the first flexible circuit board 600 to receive an optical signal; the second flexible circuit board 700 and the third flexible circuit board 800 are used to electrically connect the circuit board 300 and the tosa 400, so as to transmit the optical signal.

However, the QSFP-DD standard structure has a small size, and the space between the circuit board 300 and the tosa 400 and the rosa 500 is small (the space between the circuit board 300 and the tosa 400 and the rosa 500 is 3-6 mm), for example, the space between the circuit board 300 and the rosa 400 and the rosa 500 is only 4.48mm, and there is not only the first flexible circuit board 600 connected to the rosa 500, but also the second flexible circuit board 700 and the third flexible circuit board 800 connected to the rosa 400, and there are cover plates above and below, so that the space for assembling the first flexible circuit board 600, the second flexible circuit board 700 and the third flexible circuit board 800 is further small.

In order to meet the flexibility of the flexible circuit board, and considering that the manufacturing work of the flexible circuit board is +/-0.1mm, the flexible circuit board needs to be longer than the distance of 4.48mm between the tosa 400 and the tosa 500 and the circuit board 300, so that the extra redundancy of the flexible circuit board can be absorbed during assembly, and the bending requirement of the flexible circuit board is further increased, and the flexible circuit board needs to be thin.

Fig. 7 is a schematic diagram of signal routing design of a first flexible circuit board 600 in an optical module according to an embodiment of the present application. As shown in fig. 7, the light receiving chip on the light receiving sub-module 500 side has 8 pairs of high-speed signal lines, 10 ground isolation lines, 9 low-speed signal lines, and 2 power supply networks, while the high-speed signal lines and the low-speed signal lines are separated by ground between copper layers and copper layers of adjacent layers, and each high-speed signal line of the 400G product has a rate of 500GBPS, which is a strict requirement for high-speed performance, so that the flexible circuit board connected to the light receiving sub-module 500 side can realize the design of network interconnection by using at least 3 layers (the high-speed signal lines, the ground isolation lines, and the low-speed signal lines are respectively located on different wire layers of the flexible circuit board).

The thinnest flexible circuit board formed by the 3 wiring layers is also 0.2mm thick, so that the stress borne by the bending area of the flexible circuit board is overlarge, but when the flexible circuit board on the side of the light receiving submodule 500 is connected with the 2 wiring layers, the high-speed performance on the side of the light receiving submodule 500 cannot be guaranteed.

In order to ensure the high-speed performance and the flexibility of the flexible circuit board, the two ends of the first flexible circuit board 600 are made into the laminated structure with different routing layers, namely, the routing layer number of one end of the first flexible circuit board 600 connected with the light receiving submodule 500 is more than that of the other end of the first flexible circuit board 600 connected with the circuit board 300, so that the thickness of the first flexible circuit board 600 close to one end of the circuit board 300 is reduced, the bending property of the first flexible circuit board 600 can be improved, and the flexible circuit board 600 is suitable for narrow space between the circuit board 300 and the light receiving submodule 500. In the embodiment of the present application, the first flexible circuit board 600 has a stack structure of 3+2, that is, a 3-layer structure for connecting the first flexible circuit board 600 on the light receiving sub-module 500 side and a 2-layer structure for connecting the first flexible circuit board 600 on the circuit board 300 side.

Specifically, the first flexible circuit board 600 includes a first connection portion 610, a second connection portion 620 and a bending portion 630, wherein a pad is disposed at the first connection portion 610 and electrically connected to the circuit board 300 through the pad; the second connection portion 620 is electrically connected to the light receiving chip of the light receiving sub-module 500 through a gold wire; one end of the bending portion 630 is connected to the first connection portion 610, and the other end is connected to the second connection portion 620. In the embodiment of the present application, the first connecting portion 610, the second connecting portion 620 and the bending portion 630 may be an integral structure, that is, the first flexible circuit board 600 is integrally formed; the first connecting portion 610, the second connecting portion 620 and the bending portion 630 may also be separate structures, that is, one end of the bending portion 630 is fixedly connected to the first connecting portion 610, and the other end is fixedly connected to the second connecting portion 620.

After the first connection portion 610 of the first flexible circuit board 600 is electrically connected to the circuit board 300 through the bonding pad and the second connection portion 620 is electrically connected to the light receiving chip through the gold wire, the driving electrical signal on the circuit board 300 can be transmitted to the light receiving chip of the light receiving sub-module 500 through the first flexible circuit board 600 to drive the light receiving chip to receive the light beam transmitted by the external optical fiber; the light receiving chip converts the light beam into an electrical signal, and then the electrical signal is transmitted to the circuit board 300 through the first flexible circuit board 600.

In order to facilitate transmission of the electrical signal output by the light receiving chip to the circuit board 300 through the first flexible circuit board 600, the first flexible circuit board 600 is provided with a high-speed signal trace, a low-speed signal trace and a ground trace. At the second connecting portion 620 of the first flexible circuit board 600, in order to ensure the high-speed transmission performance of the first flexible circuit board 600, the flexible circuit board at the second connecting portion 620 includes three wiring layers, and a high-speed signal wiring, a low-speed signal wiring and a ground wiring are respectively located on different wiring layers, so as to avoid the influence of the low-speed signal wiring, the ground wiring and the like on the signal transmission of the high-speed signal wiring, and ensure that the high-speed performance is not influenced.

At the first connecting portion 610 and the bending portion 630 of the first flexible circuit board 600, in order to ensure the bending property of the bending portion 630 of the first flexible circuit board 600, the flexible circuit board at the first connecting portion 610 and the bending portion 630 includes two wiring layers, the high-speed signal wiring and the low-speed signal wiring are located on the same wiring layer, and the ground signal wiring is located on another wiring layer. Thus, the thickness of the flexible circuit board at the first connecting portion 610 and the bending portion 630 can be reduced, and the stress borne by the bending portion 630 can be reduced, so that the bending property of the bending portion 630 can be improved.

Fig. 8 is a schematic laminated diagram of a first flexible circuit board 600 in an optical module according to an embodiment of the present disclosure. As shown in fig. 8, the second connection portion 620 of the first flexible circuit board 600 includes a first signal layer 640, a second ground layer 650 and a third signal layer 660, the second ground layer 650 is located between the first signal layer 640 and the third signal layer 660, and the first signal layer 640, the second ground layer 650 and the third signal layer 660 are sequentially stacked. In addition, the length dimension of the first signal layer 640 is identical to that of the second ground layer 650, and the length dimension of the third signal layer 660 is smaller than that of the first signal layer 640. That is, the left end surface of the first signal layer 640, the left end surface of the second ground layer 650, and the left end surface of the third signal layer 660 are flush with each other, the right end surface of the first signal layer 640 is flush with the right end surface of the second ground layer 650, and the right end surface of the third signal layer 660 is shorter than the right end surface of the first signal layer 640.

The first connection portion 610 and the bending portion 630 of the first flexible circuit board 600 both include a first signal layer 640 and a second ground layer 650, the first signal layer 640 and the second ground layer 650 are stacked, and the length of the first signal layer 640 is consistent with the length of the second ground layer 650. In the embodiment of the present disclosure, the first signal layer 640 of the first connection portion 610 and the bending portion 630 and the first signal layer 640 of the second connection portion 620 are the same signal layer, and the second ground layer 650 of the first connection portion 610 and the bending portion 630 and the second ground layer 650 of the second connection portion 620 are the same ground layer.

Fig. 9 is a schematic diagram of a signal routing relationship of a first flexible circuit board 600 in an optical module according to an embodiment of the present application. As shown in fig. 9, a high-speed signal trace 6420, a low-speed signal trace 6610 and a ground trace 6510 are disposed on the first flexible circuit board 600, in order to ensure the high-speed transmission performance of the first flexible circuit board 600, the first signal layer 640 is provided with the high-speed signal trace 6420 and a high-speed signal pad 6410, one end of the high-speed signal trace 6420 is electrically connected to the light-receiving chip of the light-receiving sub-module 500, the other end of the high-speed signal trace 6420 is electrically connected to the high-speed signal pad 6410 on the first flexible circuit board 600, and the high-speed signal pad 6410 is electrically connected to the circuit board 300. The present application realizes high-speed signal transmission between the light-receiving chip and the circuit board 300 through the high-speed signal traces 6420 on the first signal layer 640.

After the high-speed signal trace 6420 is disposed in the first signal layer 640, in order to avoid the high-speed signal transmission being affected, the high-speed signal trace 6420 needs to be isolated from the ground, and therefore, the ground trace needs to be accessed. In this embodiment, the second ground layer 650 is provided with a ground trace 6510 and a ground pad, one end of the ground trace 6510 is electrically connected to the optical receiving chip of the rosa 500, and the other end is electrically connected to the ground pad, so as to be used as a ground reference for the high-speed signal trace 6420 on the first signal layer 640.

In addition, the second connection portion 620 of the first flexible circuit board 600 is provided with a plurality of first laser holes 6520 penetrating the first signal layer 640 and the second ground layer 650, and the first laser holes 6520 connect the first signal layer 640 and the second ground layer 650. In this way, the ground trace 6510 disposed on the second ground layer 650 can access the first signal layer 640 through the first laser hole 6520 to access the ground trace 6510.

After the high-speed signal trace 6420 is laid on the first signal layer 640 and the ground trace 6510 is laid on the second ground layer 650, in order to further avoid the influence on the high-speed signal transmission, the low-speed signal trace 6610 is disposed on the third signal layer 660, and one end of the low-speed signal trace 6610 is electrically connected to the optical receiving chip of the optical receiving sub-module 500 to receive the low-speed signal output by the optical receiving chip; the other end of the low-speed signal trace 6610 is electrically connected to the circuit board 300 to transmit the low-speed signal transmitted by the low-speed signal trace to the circuit board 300.

The second connection portion 620 of the first flexible circuit board 600 is provided with a plurality of second laser holes 6530 penetrating through the second ground layer 650 and the third signal layer 660, and the second laser holes 6530 connect the second ground layer 650 and the third signal layer 660. Thus, the ground trace 6510 disposed on the second ground layer 650 and the low-speed signal trace 6610 disposed on the third signal layer 660 are respectively connected to the second laser hole 6530, so as to access the ground trace 6510 on the third signal layer 660.

In the embodiment of the present application, in the second connection portion 620 of the first flexible circuit board 600, the high-speed signal trace 6420 is disposed on the first signal layer 640, the ground trace 6510 is disposed on the second ground layer 650, and the low-speed signal trace 6610 is disposed on the third signal layer 660. The main function of the third signal layer 660 is to space the low-speed signal trace 6610 above the high-speed adjacent layer when it needs to intersect, so as to ensure that the high-speed performance of the first flexible circuit board 600 is not affected.

In this embodiment, the second ground layer 650 is not only disposed with the ground trace 6510, but also disposed with a power pad, and the power pad is electrically connected to the power pad on the circuit board 300 to supply power to the first flexible circuit board 600, so as to ensure the signal transmission function of the first flexible circuit board 600, and realize the signal transmission between the circuit board 300 and the optical receive sub-module 500.

The second connection portion 620 of the first flexible circuit board 600 includes a first signal layer 640, a second ground layer 650 and a third signal layer 660, the first signal layer 640 is provided with a high-speed signal trace 6420, the second ground layer 650 is provided with a ground trace, and the third signal layer 660 is provided with a low-speed signal trace 6610; the first connection portion 610 and the bending portion 630 of the first flexible circuit board 600 only include the first signal layer 640 and the second ground layer 650, the high-speed signal trace 6420 is disposed on the first signal layer 640, and the ground trace 6510 is disposed on the second ground layer 650, so the low-speed signal trace 6610 can only be disposed on the first signal layer 640 or the second ground layer 650, and is located on the same trace layer as the high-speed signal trace 6420 or the ground trace 6510.

In order to dispose the low-speed signal trace 6610 on the first signal layer 640 or the second ground layer 650 of the first connection portion 610 and the bending portion 630, a plurality of through holes 6620 penetrating through the first signal layer 640, the second ground layer 650 and the third signal layer 660 are further disposed on the second connection portion 620 of the first flexible circuit board 600, and the low-speed signal trace 6610 on the third signal layer 660 is disposed on the first signal layer 640 or the second ground layer 650 through the through holes 6620.

In the embodiment of the present application, the low-speed signal trace 6610 on the third signal layer 660 passes through the through hole 6620 and is disposed on the first signal layer 640, and is located on the same routing layer as the high-speed signal trace 6420 disposed on the first signal layer 640, so that the routing density on the first signal layer 640 of the first connection portion 610 is greater than the routing density on the first signal layer 640 of the second connection portion 620; meanwhile, the ground trace 6510 disposed on the second ground layer 650 is connected to the via 6620, so as to form a ground layer above the space between the high-speed signal trace 6420 and the low-speed signal trace 6610, thereby ensuring that the high-speed performance is not affected.

A through hole 6620 penetrating through the first signal layer 640, the second ground layer 650 and the third signal layer 660 is disposed on a side of the third signal layer 660 facing the circuit board 300, so as to conveniently arrange a low-speed signal trace 6610 on the third signal layer 660. In the embodiment of the present application, the length dimension of the third signal layer 660 is not limited, but the smaller the length dimension is, the better the high speed performance is guaranteed.

In this embodiment, not only the two ends of the first flexible circuit board 600 connecting the rosa 500 and the circuit board 300 adopt the stacked structure with different wiring layers, but also the two ends of the second flexible circuit board 700 and the third flexible circuit board 800 connecting the rosa 400 and the circuit board 300 adopt the stacked structure with different wiring layers, so as to reduce the thickness of the bending portions of the first flexible circuit board 600, the second flexible circuit board 700 and the third flexible circuit board 800, and improve the bending property of the flexible circuit board.

The optical module provided by the embodiment of the application comprises a circuit board, an optical sub-module and a flexible circuit board, wherein the optical sub-module comprises an optical chip used for transmitting or receiving light beams; the flexible circuit board comprises a first connecting part, a second connecting part and a bending part, wherein the first connecting part is provided with a bonding pad and is electrically connected with the circuit board through the bonding pad; the second connecting part is electrically connected with the optical chip through a gold thread, one end of the bending part is connected with the first connecting part, and the other end of the bending part is connected with the second connecting part; the second connecting part comprises a first signal layer, a second grounding layer and a third signal layer, the first signal layer, the second grounding layer and the third signal layer are sequentially stacked, high-speed signal routing is arranged on the first signal layer, grounding routing is arranged on the second grounding layer, and low-speed signal routing is arranged on the third signal layer, so that the high-speed signal routing and the low-speed signal routing are positioned on different routing layers and are separated by the grounding layer, the high-speed transmission performance of the flexible circuit board is ensured, and the strict requirement of a 400G product on the high-speed performance is met; the first connecting portion and the bending portion comprise a first signal layer and a second grounding layer, the first signal layer and the second grounding layer are arranged in a stacked mode, the low-speed signal wiring arranged on the third signal layer of the second connecting portion penetrates through the flexible circuit board and is arranged on the first signal layer, the high-speed signal wiring and the low-speed signal wiring are located on the same first signal layer, the thickness size of the first connecting portion and the bending portion is reduced, and the bending performance of the bending portion of the flexible circuit board is met. According to the flexible circuit board, the flexible circuit board for connecting the circuit board and the optical receiving submodule is designed to be of a laminated structure of 3+2, the second connecting portion connected with the optical submodule is of a three-layer laminated structure, the first connecting portion connected with the circuit board is of a two-layer laminated structure, and the bent portion for connecting the first connecting portion and the second connecting portion is of a two-layer laminated structure, so that the thickness size of the first connecting portion and the bent portion is reduced, the stress borne by the flexible circuit board at the bent portion is reduced, the bending property of the flexible circuit board is improved, and therefore the flexible circuit board is effectively suitable for a narrow space between the circuit board and the optical receiving submodule; meanwhile, the high-speed signal routing and the low-speed signal routing at the second connecting part are located on different routing layers and are separated by the grounding layer, so that the high-speed signal transmission is not influenced. Such a design not only meets the operational requirements of narrow structural space, but also meets the product requirements of high speed and high performance.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.

Claims

1. A light module, comprising:

a circuit board;

the flexible circuit board comprises a first connecting part, a second connecting part and a bending part, wherein the first connecting part is provided with a welding disc and is electrically connected with the circuit board through the welding disc; the second connecting part is electrically connected with the optical chip, one end of the bending part is connected with the first connecting part, and the other end of the bending part is connected with the second connecting part; the first connecting portion comprises two wiring layers, the second connecting portion comprises three wiring layers, the high-speed signal wiring and the low-speed signal wiring of the second connecting portion are located on different wiring layers, and the high-speed signal wiring and the low-speed signal wiring of the first connecting portion are located on the same wiring layer.

2. The optical module according to claim 1, wherein the second connection portion includes a first signal layer, a second ground layer, and a third signal layer, and the first signal layer, the second ground layer, and the third signal layer are sequentially stacked;

the first signal layer is provided with a high-speed signal wire, the second grounding layer is provided with a grounding wire, and the third signal layer is provided with a low-speed signal wire.

3. The optical module according to claim 2, wherein a first signal layer length dimension of the second connection portion coincides with a length dimension of the second ground layer, and a length dimension of the third signal layer is smaller than the length dimension of the first signal layer.

4. The optical module according to claim 2, wherein the first connecting portion and the bending portion each include a first signal layer and a second ground layer, and the first signal layer and the second ground layer are stacked; the first signal layer is provided with high-speed signal wiring and low-speed signal wiring, and the second grounding layer is provided with grounding wiring.

5. The optical module according to claim 4, wherein the first signal layer of the second connection portion and the first signal layer of the first connection portion are the same signal layer, and the second ground layer of the second connection portion and the second ground layer of the first connection portion are the same ground layer.

6. The optical module of claim 5, wherein a trace density on the first signal layer of the first connection portion is greater than a trace density on the first signal layer of the second connection portion.

7. The optical module according to claim 2, wherein a first laser hole penetrating through the first signal layer and the second ground layer is disposed on the second connection portion, and the first laser hole connects the first signal layer and the second ground layer.

8. The optical module according to claim 7, wherein a second laser hole penetrating through the second ground layer and the third signal layer is disposed on the second connecting portion, and the ground trace and the low-speed signal trace are respectively connected to the second laser hole.

9. The optical module according to claim 8, wherein the second connecting portion further has a plurality of through holes penetrating through the first signal layer, the second ground layer and the third signal layer, and the low-speed signal trace on the third signal layer is disposed on the first signal layer through the through holes; and the grounding wire on the second grounding layer is connected with the through hole.

10. The optical module of claim 1, wherein a spacing between the optical sub-module and the circuit board is in a range of 3-6mm.