Embedded flexible photoelectric interconnection circuit board and laminated packaging method

Abstract

The invention discloses an embedded flexible photoelectric interconnection circuit board and a lamination packaging method, and belongs to the technical field of circuit boards, a circuit board body comprises a top substrate and a bottom substrate, an optical communication layer is arranged between the top substrate and the bottom substrate, and an optical transmitting module and an optical receiving module are arranged in the optical communication layer. The optical transmitting module converts electric signals into optical signals under regulation and control of the driving chip, the optical transmitting module transmits the optical signals to the optical receiving module through the optical path assembly, and the optical receiving module converts the optical signals into electric signals and transmits the electric signals to the receiving chip. And the light emitting module and the light receiving module are fixed on the upper surface of the middle substrate in a laminated manner and are positioned in the insulating encapsulation layer, so that the influence of heat generated during operation on the chip is effectively reduced. The light emitting module and the light receiving module are embedded in the circuit board body, so that signal loss is effectively avoided, and photoelectric interconnection between chips or modules is easier to realize.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit boards, and in particular to an embedded flexible optoelectronic interconnection circuit board and a stacking packaging method. Background Art

[0002] With the rapid development of the microelectronics industry, traditional optoelectronic interconnection methods have become a bottleneck for high-speed communication electronic products. The future direction is flexible optoelectronic circuit boards that combine electronic and photonic signals to transmit information through optoelectronic interconnection. Therefore, combining traditional flexible circuits with optical interconnection technology offers the advantages of flexibility, high speed, low power consumption, and immunity to electromagnetic interference, resolving the conflict between high speed and high density.

[0003] Currently, optical transceiver modules are often integrated into the surface of optoelectronic integrated circuit boards using surface mount technology. Optoelectronic components are connected to the motherboard via gold wire ball bonding or lead-chip bonding. While this method is flexible, it takes up a lot of space, hindering the design of thinner and lighter circuit boards. Summary of the Invention

[0004] The purpose of the present invention is to provide an embedded flexible optoelectronic interconnection circuit board and a stacking packaging method to solve the above technical problems.

[0005] To achieve the above-mentioned objectives, the present invention provides an embedded flexible optoelectronic interconnection circuit board, including a circuit board body, the circuit board body including a top substrate and a bottom substrate, a chip is arranged on the top substrate, the chip includes a driving chip and a receiving chip, an optical communication layer is arranged between the top substrate and the bottom substrate, an optical transmitting module and an optical receiving module are arranged in the optical communication layer, the optical transmitting module converts an electrical signal into an optical signal under the control of the driving chip, the optical transmitting module transmits the optical signal to the optical receiving module through an optical path component, the optical receiving module converts the optical signal into an electrical signal and transmits it to the receiving chip, the optical path component includes two mirrored reflectors, the two reflectors are respectively arranged opposite to the optical transmitting module and the optical receiving module, and an optical transmission component is arranged between the two reflectors.

[0006] Preferably, the optical communication layer is provided with an optical transmission layer, an intermediate substrate and an insulating potting layer in sequence from bottom to top, the optical transmitting module and the optical receiving module are both fixed on the upper surface of the intermediate substrate and are located in the insulating potting layer, and the insulating potting layer is provided below the top substrate;

[0007] The light transmission layer adopts a cladding made of PI polyimide material with a thickness of 0.3mm. An optical channel is set in the middle of the cladding. The optical transmission component is set in the optical channel, and the two ends of the optical channel are set opposite to the reflector.

[0008] Preferably, the optical transmission component is an optical waveguide or an optical fiber, the reflector has an inclination angle of 45°, the optical transmission component and the reflector are both arranged in the cladding, the outer side of the optical fiber is arranged in a sawtooth shape, and the thickness of the optical fiber is 0.15 mm.

[0009] Preferably, the intermediate substrate, the top substrate and the bottom substrate are all made of glass fiber epoxy resin, the top substrate is provided with an electrical blind hole, and the upper surface of the bottom substrate is provided with a metal conductive layer.

[0010] Preferably, the intermediate substrate is provided with a light-transmitting channel for light to pass through.

[0011] A stacking packaging method based on the above-mentioned embedded flexible optoelectronic interconnection circuit board, the specific steps are as follows:

[0012] Step S1: preparing an optical communication layer;

[0013] Step S11: opening a light-transmitting through hole in the intermediate substrate and arranging a pad array;

[0014] Step S12: pressing the intermediate substrate onto the light transmission layer, with the light-transmitting through hole and the reflector arranged opposite to each other;

[0015] Step S13: thinning the optical transmitter module and the optical receiver module, and mounting the optical transmitter module and the optical receiver module on the intermediate substrate using a surface mounting process;

[0016] Step S14: encapsulating the optical transmitting module and the optical receiving module with a potting compound;

[0017] Step S2: attaching the metal conductive layer and the bottom substrate below the optical communication layer;

[0018] Step S3: Mounting the top substrate with the electrical blind vias on top of the potting compound;

[0019] Step S4: The driving chip and the receiving chip are fixed on the upper surface of the top substrate by reflow soldering. The driving chip and the receiving chip are respectively arranged opposite to and parallel to the optical transmitting module and the optical receiving module.

[0020] A communication system based on the above-mentioned embedded flexible optoelectronic interconnection circuit board includes an optical transmitter module, an optical path component, and an optical receiver module embedded in the embedded flexible optoelectronic interconnection circuit board;

[0021] An optical transmitter module is used to convert the electrical signal of the driver chip into an optical signal. The optical transmitter module includes a modulator connected to a signal source and a laser.

[0022] An optical path component, wherein the transmission component inside the optical path component transmits the optical signal emitted by the modulator to the optical receiving module; the optical transmission component in the optical path component is connected to an optical amplifier, which is connected to a dispersion compensation component;

[0023] The optical receiving module is used to receive the optical signal transmitted by the optical path component and convert the optical signal into an electrical signal. The optical receiving module includes an optical filter and a detector connected to the optical filter. The detector is connected to the electrical filter, and the electrical filter is connected to the 3R generator.

[0024] Therefore, the present invention adopts the above-mentioned embedded flexible optoelectronic interconnection circuit board and stacking packaging method, which has the following beneficial effects:

[0025] (1) Both the optical transmitter module and the optical receiver module are fixed to the upper surface of the intermediate substrate in a stacked manner and are located within the insulating potting layer. When the intermediate substrate is in operation, the stress and strain of the chips, optical transmitter module, and optical receiver module on the top substrate caused by heat generation are effectively reduced, thereby increasing the service life of the intermediate substrate. The optical transmitter module and the optical receiver module are embedded within the circuit board body. When the circuit board body is in operation, signal loss can be effectively avoided, making it easier to achieve optoelectronic interconnection between chips or modules.

[0026] (2) Optical transmission components use optical fibers or optical waveguides to replace the original copper wires, and a sawtooth structure is engraved on the optical fiber to improve transmission performance.

[0027] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic structural diagram of the embedded flexible optoelectronic interconnection circuit board of the present invention;

[0029] Figure 2 Schematic diagram of light propagation in optical fiber;

[0030] Figure 3 This is a schematic diagram of the structure of a traditional surface mount optoelectronic interconnection circuit board;

[0031] Figure 4 Schematic diagram of the traditional stacked package structure;

[0032] Figure 5 This is a flow chart of a stacking packaging method for an embedded flexible optoelectronic interconnection circuit board according to the present invention;

[0033] Figure 6 Schematic diagram for comparing results of thermal analysis physical field settings;

[0034] Figure 7 A schematic diagram showing the comparison of transient thermal analysis results;

[0035] Figure 8 This is a schematic diagram for comparing the total deformation analysis results;

[0036] Figure 9This is a schematic diagram of the structure of a communication system based on an embedded flexible optoelectronic interconnection circuit board according to the present invention;

[0037] Figure 10 This is a schematic diagram of the structure of the optoelectronic communication system with a 10G optical waveguide according to the present invention;

[0038] Figure 11 Output eye diagram for the optoelectronic communication system of the present invention.

[0039] Reference numerals

[0040] 1. Chip; 2. Optical transmitter module; 3. Optical receiver module; 4. Top substrate; 5. Insulation potting layer; 6. Middle substrate; 7. Optical transmission layer; 8. Metal conduction layer; 9. Bottom substrate; 10. Optical fiber; 11. Reflector; 12. Light-transmitting channel; 13. Electrical blind via; 101. Conductive layer, 102. Bottom glass fiber layer. DETAILED DESCRIPTION

[0041] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships in which the inventive product is usually placed when in use. These are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention. In the description of the present invention, it should also be noted that, unless otherwise expressly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be a communication between the internal parts of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0043] Example 1

[0044] like Figure 1The figure shows an embedded flexible optoelectronic interconnect circuit board, comprising a circuit board body comprising a top substrate 4 and a bottom substrate 9. An optical communication layer is disposed between the top and bottom substrates 4 and 9 using a laminated packaging technique. The optical communication layer comprises, from bottom to top, an optical transmission layer 7, an intermediate substrate 6, and an insulating potting layer 5. Both the optical transmitter module 2 and the optical receiver module 3 are laminated and affixed to the upper surface of the intermediate substrate 6 and within the insulating potting layer 5. When the intermediate substrate 6 is in operation, the heat generated by the chip 1, optical transmitter module 2, and optical receiver module 3 on the top substrate 4 is effectively reduced, thus increasing the service life of the intermediate substrate 6. Embedding the optical transmitter module 2 and optical receiver module 3 within the circuit board body effectively prevents signal loss during operation, making optoelectronic interconnection between chips 1 or modules easier.

[0045] An insulating encapsulation layer 5 is positioned beneath the top substrate 4. The optical transmitter module 2, under the control of the driver chip on the top substrate 4, converts electrical signals into optical signals. This optical signal is coupled via an optical path component and transmitted to the optical receiver module 3. The optical receiver module 3 then converts the optical signal into an electrical signal and transmits it to the receiving chip on the top substrate 4. The receiving chip receives and amplifies the optical signal, converting it back into an electrical signal. The optical path component includes two mirror-image reflectors 11, positioned opposite the optical transmitter module 2 and the optical receiver module 3, respectively. An optical transmission element is positioned between the two reflectors 11. The optical transmission layer 7 utilizes a 0.3mm thick polyimide cladding with a low refractive index, ensuring that the optical signal does not leak during transmission through the optical transmission element. An optical channel is positioned in the center of the cladding, with the optical transmission element positioned within the channel, and its ends facing the reflectors 11. The intermediate substrate 6 and the optical transmission layer 7 define a 0.15mm diameter light-transmitting channel 12 for light to pass through. The function of the cladding is to limit light propagation, protect optical transmission components and improve transmission efficiency.

[0046] The optical transmission component of this embodiment is an optical fiber 10. The optical fiber 10 will produce various effects when heated, causing signal attenuation. In a high temperature environment, the absorption loss of the optical fiber 10 will increase; the transmission quality will decrease, and high temperature will also cause the scattering loss of the optical fiber 10 to increase, which is mainly due to the impurities inside the optical fiber 10 and the hydrogen loss in a high temperature environment; the mechanical properties will change. In a high temperature environment, the optical fiber 10 material will expand, which may cause problems such as twisting and stretching inside the optical fiber 10, affecting the stability of signal transmission. The influencing factors are that the top layer of the optoelectronic printing includes a high-power heat source chip 1 as the main heat source, and also includes an optical transmitter module 2 and an optical receiver module 3 as secondary heat sources. The reflector 11 has an inclination angle of 45°. The optical transmission component and the reflector 11 are both arranged in the cladding, and the outer side of the optical fiber 10 is set to a sawtooth shape, such as Figure 2As shown, the thickness of the optical fiber 10 is 0.15 mm. First, the zigzag structure enhances the light coupling efficiency. The more zigzags there are, the better the coupling effect. The zigzag structure can effectively couple the light in the optical fiber 10 into the cladding, making the transmission of light inside the optical fiber 10 more efficient and reducing light leakage and loss. Secondly, the quality of optical signal transmission can be improved. Through multiple, dense zigzag structures, the transmission path of light can be optimized, and the scattering and reflection of light inside the optical fiber 10 can be reduced, thereby improving the transmission quality of the optical signal. In addition, the zigzag structure also helps to reduce mode dispersion, so that the optical signal maintains better consistency and stability during transmission. The sensing performance of the optical fiber 10 can be enhanced. Engraving a zigzag structure on the sensing optical fiber 10 can enable the optical fiber 10 to have better sensing performance while transmitting the optical signal. This structure enables the optical fiber 10 to respond more sensitively to changes in the external environment. As Figure 3 As shown, the prior art places the optical transmitter module 2 and the optical receiver module 3 on the top substrate 4, which is provided with a conductive layer 101 and a bottom glass fiber layer 102. The technical solution of this embodiment places the optical transmitter module 2 and the optical receiver module 3 in the circuit board body using a stacked packaging technology. The optical transmission component used in this embodiment is an optical fiber 10 instead of the existing traditional copper wire. Figure 4 As shown, in the traditional stacked packaging structure, the chip 1 is embedded in the substrate as a packaging component for multi-layer stacking. The technical solution of this embodiment embeds the optical transmitting module 2 and the optical receiving module 3 inside the circuit board body. When the substrate is working, the signal loss can be effectively avoided, and the optoelectronic interconnection between the chips 1 or modules can be more easily realized.

[0047] The optical transmission component can also be an optical waveguide, which is used to realize the transmission of optical signals. The optical waveguide is a structure or medium that can guide the propagation of light waves in it. Its principle is to use the refractive index difference of the medium to make the light waves propagate within a specific path. By setting a cladding with a lower refractive index around the waveguide material, the light waves are confined to propagate in the core layer with a higher refractive index, thereby realizing the transmission and control of optical signals.

[0048] The intermediate substrate 6, top substrate 4, and bottom substrate 9 are all made of glass fiber epoxy resin. Glass fiber epoxy resin has the advantages of high strength, corrosion resistance, light weight, high strength, easy processing, and excellent electrical insulation, which effectively protects the operation of the circuit board. The intermediate substrate 6, top substrate 4, and bottom substrate 9 are all 0.15mm wide. The top substrate 4 is provided with electrical blind vias 13, which facilitate the optoelectronic interconnection between the driver chip and receiving chip on the top substrate 4 and the optical transmitter module 2 and optical receiver module 3. By connecting the surface layer and the inner layer circuit of the circuit board, it saves board space, improves layout density and reliability, and reduces the number of through holes, reduces the risk of short circuits, and enhances electromagnetic compatibility. It also improves heat dissipation performance. The upper surface of the bottom substrate 9 is provided with a metal conductive layer 8. In this embodiment, the metal conductive layer 8 is made of copper foil with a thickness of 0.02mm.

[0049] The thickness of the driving chip and the receiving chip is 0.1 mm. The driving chip and the receiving chip control the optical transmitting module 2 to modulate the signal and the optical receiving module 3 to detect the signal respectively.

[0050] like Figure 5 As shown, a stacking packaging method based on the above-mentioned embedded flexible optoelectronic interconnection circuit board has the following specific steps:

[0051] Step S1: preparing an optical communication layer;

[0052] Step S11: opening a light-transmitting through hole in the intermediate substrate 6 and arranging a pad array;

[0053] Step S12: pressing the intermediate substrate 6 onto the light transmission layer 7, with the light-transmitting through hole and the reflector 11 arranged opposite to each other;

[0054] Step S13: thinning the optical transmitter module 2 and the optical receiver module 3, and mounting the optical transmitter module 2 and the optical receiver module 3 on the intermediate substrate 1 using a surface mounting process;

[0055] Step S14: encapsulating the optical transmitting module 2 and the optical receiving module 3 with a potting compound;

[0056] Step S2: Mounting the metal conductive layer 8 and the bottom substrate 9 below the optical communication layer;

[0057] Step S3: Mounting the top substrate 4 with the electrical blind vias 13 on top of the potting compound;

[0058] Step S4: The driving chip and the receiving chip are fixed on the upper surface of the top substrate 4 by reflow soldering. The driving chip and the receiving chip are respectively arranged opposite to and parallel to the optical transmitting module 2 and the optical receiving module 3 .

[0059] In order to verify the superiority of the technical solution of this embodiment, a simulation test was carried out, and the control group was a surface mount circuit board.

[0060] (1) Thermal analysis physical field setting structure

[0061] The control group and embedded flexible optoelectronic interconnection circuit board models were established and meshed, and the boundary conditions of thermal analysis were set: heat flux, which means the amount of heat transferred through a unit heat transfer area per unit time; heat flow, which means the heat dissipation power of the chip applied to points, edges, and surfaces; and internal heat generation, which means the heat applied to the volume. The heat flux or internal heat generation is converted according to whether the area or volume is used in the analysis. When the heat flux is 1500W / m 2 ; Heat convection is 50W / m 2 ×℃; when the room temperature is 25℃, calculate the internal heat generation of the chip and optical transceiver module. Figure 6 (a) is a surface mount device, (b) is the circuit board structure used in this embodiment, and the chip heat dissipation power in (a) is 50 W. In (b), the heat dissipation power of the control optical transmitter module 2 is 25 W, and the heat dissipation power of the control optical receiver module 3 is 20 W.

[0062] (2) Transient thermal analysis

[0063] Transient heat mainly includes the heat generated by the chip and optical transceiver module (optical transmitter module 2 and optical receiver module 3) during operation, so it is necessary to set the corresponding heat source in the model. The size and distribution of the heat source should be determined according to the actual power consumption and heat generation characteristics of the chip. Figure 7 In the figure, (a) and (b) are the transient thermal analysis results of the control group and this embodiment respectively. The results show that the temperature of the control group's packaging substrate is 66.5℃-77.7℃, and the temperature of the stacked packaging substrate of the technical solution of this embodiment is 44.5℃-66.9℃. The comparison shows that the maximum temperature after optimization is lower and the temperature difference is larger, and the heat dissipation effect is better through the optimized structure.

[0064] (3) Total deformation analysis

[0065] like Figure 8As shown, a total deformation analysis was performed on the circuit board bodies of the control group and this embodiment. Using indirect thermal-structural coupling analysis, we explored how the temperature field affects key physical properties of the structure, such as stress, strain, and displacement. Based on the acquired temperature field data, it was introduced as a volume load into the structural analysis process, with the bottom surface of the substrate determined to be a fixed support. The stress distribution characteristics of the structure under thermal effects were then solved. The simulation clearly shows that the optimized stacked package substrate is 3.5 times smaller than the surface mount substrate before optimization. The stacked package is less affected by the temperature of the chip and optical transceiver module during operation, resulting in a smaller magnitude of total structural deformation.

[0066] like Figure 9 As shown, a communication system of the above-mentioned embedded flexible optoelectronic interconnection circuit board includes an optical transmitting module 2, an optical path component and an optical receiving module 3 embedded in the embedded flexible optoelectronic interconnection circuit board.

[0067] The optical transmission module 1 is used to convert the electrical signal of the driver chip into an optical signal. The optical transmission module includes a modulator connected to a signal source and a laser.

[0068] The optical path component, the transmission component inside the optical path component transmits the optical signal emitted by the modulator to the optical receiving module 3; the optical transmission component in the optical path component is connected to an optical amplifier, and the optical amplifier is connected to a dispersion compensation component.

[0069] The optical receiving module 3 is used to receive the optical signal transmitted by the optical path component and convert the optical signal into an electrical signal. The optical receiving module includes an optical filter and a detector connected to the optical filter. The detector is connected to the electrical filter, and the electrical filter is connected to the 3R generator.

[0070] like Figure 10-11 As shown, a 10G optical waveguide signal is used, with a modulation bit rate of 10 GHz, a sample constant of 25 bits, a laser center wavelength of 193.1 THz, and an optical signal power of -20 dBm. The optical output wavelength after the modulator is 1552.52 nm, and the optical power is -23 dBm. Comparing the electrical and optical signal diagrams, the optical signal is converted to an electrical signal without catastrophic changes. The optical waveguide channel is divided into three parts: optical fiber, optical amplifier, and dispersion compensation. Negative dispersion is used here, and when offset, no signal mutation occurs. After compensation, the optical power is checked to be -13.5 dBm. The optical receiving module uses a filter to remove noise optical signals, and the detector uses a PIN diode. An electrical filter is then connected to filter out the noise introduced by the diode, and finally a 3R generator is connected to adjust the signal output. Analysis of the entire simulation results shows that the eye diagram is open and closed in good condition, and the minimum bit error rate measured is approximately 4.4×10 -18, 10G optical waveguide can meet the communication requirements, so the embedded flexible optoelectronic interconnection circuit board of this embodiment can adopt the form of stacked packaging.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An embedded flexible optoelectronic interconnect circuit board, comprising a circuit board body, the circuit board body comprising a top substrate and a bottom substrate, a chip disposed on the top substrate, the chip comprising a driver chip and a receiver chip, characterized in that: An optical communication layer is arranged between the top substrate and the bottom substrate. An optical transmitting module and an optical receiving module are arranged in the optical communication layer. The optical transmitting module converts the electrical signal into an optical signal under the control of the driving chip. The optical transmitting module transmits the optical signal to the optical receiving module through the optical path component. The optical receiving module converts the optical signal into an electrical signal and transmits it to the receiving chip. The optical path component includes two mirrored reflectors. The two reflectors are respectively arranged opposite to the optical transmitting module and the optical receiving module. An optical transmission component is arranged between the two reflectors.

2. The embedded flexible optoelectronic interconnection circuit board according to claim 1, characterized in that: The optical communication layer is provided with an optical transmission layer, an intermediate substrate and an insulating potting layer from bottom to top. The optical transmitting module and the optical receiving module are both fixed on the upper surface of the intermediate substrate and are located in the insulating potting layer. The insulating potting layer is provided below the top substrate. The light transmission layer adopts a cladding made of PI polyimide material with a thickness of 0.3mm. An optical channel is set in the middle of the cladding. The optical transmission component is set in the optical channel, and the two ends of the optical channel are set opposite to the reflector.

3. The embedded flexible optoelectronic interconnection circuit board according to claim 2, characterized in that: The optical transmission component is an optical waveguide or optical fiber, the reflector has an inclination angle of 45°, the optical transmission component and the reflector are both arranged in the cladding, the outer side of the optical fiber is set to a sawtooth shape, and the optical fiber thickness is 0.15mm.

4. The embedded flexible optoelectronic interconnection circuit board according to claim 3, characterized in that: The materials of the middle substrate, top substrate and bottom substrate are all glass fiber epoxy resin. The top substrate is provided with electrical blind holes, and the upper surface of the bottom substrate is provided with a metal conductive layer.

5. The embedded flexible optoelectronic interconnection circuit board according to claim 4, characterized in that: The middle substrate is provided with a light-transmitting channel for light to pass through.

6. A stacking packaging method for an embedded flexible optoelectronic interconnection circuit board according to claim 5, characterized in that: The specific steps are as follows: Step S1: preparing an optical communication layer; Step S11: opening a light-transmitting through hole in the intermediate substrate and arranging a pad array; Step S12: pressing the intermediate substrate onto the light transmission layer, with the light-transmitting through hole and the reflector arranged opposite to each other; Step S13: thinning the optical transmitter module and the optical receiver module, and mounting the optical transmitter module and the optical receiver module on the intermediate substrate using a surface mounting process; Step S14: encapsulating the optical transmitting module and the optical receiving module with a potting compound; Step S2: attaching the metal conductive layer and the bottom substrate below the optical communication layer; Step S3: Mounting the top substrate with the electrical blind vias on top of the potting compound; Step S4: The driving chip and the receiving chip are fixed on the upper surface of the top substrate by reflow soldering. The driving chip and the receiving chip are respectively arranged opposite to and parallel to the optical transmitting module and the optical receiving module.

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