A high-speed optical module transmitting component with low crosstalk

Abstract

The present invention discloses a high-speed optical module transmitting component with low crosstalk. It includes an ODSP chip, a PCB board, a substrate and transmission lines; the ODSP chip is arranged on the PCB board, the laser chip is arranged on the substrate, a plurality of metal pads and a plurality of BGA pads are arranged on the surface of the PCB board, the laser chip is connected to the corresponding metal pad, the ODSP chip is connected to the corresponding BGA pad, and each metal pad is electrically connected to the corresponding BGA pad to form a corresponding transmission channel; the PCB board includes a first metal layer, a second metal layer, a first insulating layer, a second insulating layer and a third insulating layer, and the metal pads and BGA pads are both arranged on the first metal layer; the signals of adjacent transmission channels alternately pass through the transmission lines of the first metal layer and the transmission lines of the second metal layer, and the transmission channels corresponding to adjacent BGA pads are adjacent transmission channels. In the present invention, the transmission lines in adjacent channels are arranged in different layers of the PCB board, increasing the coupling distance between adjacent channels to achieve the purpose of reducing near-end crosstalk.

Description

Technical Field

[0001] The present invention relates to the technical field of high-speed optical modules, and particularly to a high-speed optical module transmitting component with low crosstalk. Background Art

[0002] With the rapid development of the Internet and big data, video and streaming media services have given rise to a vast amount of personal consumption data; the development of high-tech such as cloud computing, the Internet of Things, and artificial intelligence has generated a vast amount of enterprise data, promoting the continuous evolution of the data center network bandwidth from 40G→100G→400G→800G, the total number of optical modules increasing from 9 * the number of cabinets in the traditional three-layer architecture to 48 * the number of cabinets, and the number of internal channels in a single module increasing from 1→2→4→8. In the context of current high-speed and high-density applications, the high-speed signal integrity design of the module has become extremely important.

[0003] A high-speed signal consists of two parts, one is the signal transmission path and the other is the signal return path. Good high-speed signal integrity design is to optimize the performance of both the transmission path and the return path. This patent focuses on optimizing the crosstalk between high-speed signals inside the optical module. Crosstalk is a kind of interference noise generated between high-speed signals due to the mutual coupling relationship between electromagnetic fields. It is an effect that occurs between the signal path and the return path of one transmission line and the signal path and the return path of another transmission line, including two parts: near-end crosstalk and far-end crosstalk. Reducing crosstalk is to reduce the coupling degree between adjacent channels.

[0004] Specifically, in a high-speed optical module, the transmission link of the transmitting channel includes: an ODSP chip 1, BGA solder balls, a PCB, a metal pad 3, a substrate, and a laser chip 5 (including but not limited to DFB / EML / MZ). Currently, the common practice in the industry is that high-speed modulation signals travel on the surface layer of the PCB and are connected to the substrate through wire bonding with gold wires. Specifically, the signal flow is as follows: the high-speed modulation signal is output from the ODSP chip 1, flows into the PCB through the BGA solder balls, then is transmitted to the metal pad 3 through the surface layer trace, continues to flow into the upper layer of the substrate through the gold wires on the metal pad 3, and finally enters the laser chip 5 bonded to the substrate. However, there are also inherent defects that will increase the crosstalk between channels. The specific defects are as follows:

[0005] ① After the high-speed modulation signal is output from the ODSP chip 1 and passes through the BGA metal pad 3, it all directly travels on the surface layer of the PCB, and each channel is distributed on the same layer. Although such a wiring structure is simple and avoids the via loss generated by the transmission line going through the inner layer, because the coupling distance between adjacent channels is close and the coupling length is long, the mutual inductance and mutual capacitance between channels on the same layer will also be large, and the crosstalk will also be large.

[0006] ② The transmission line is arranged on the surface layer and belongs to a non-uniform strip line. One side is wrapped by solder mask, and the other side is the material of PCB board 2. The thickness and dielectric constant of the two are different. The magnetic field lines will pass through different effective dielectric constants, and their relative capacitive and inductive couplings are different. According to the formula 2 of the far-end crosstalk coefficient, far-end crosstalk will occur. Moreover, the transmission line lacks an upper reference ground layer, and the EMI radiation is also relatively large.

[0007] ③ The ground between the substrate 8 and the PCB board is only interconnected by several GND bonding wires. The return path is long, and there is a defect in the return path directly below the bonding wire gold wire, resulting in energy leakage and causing crosstalk.

[0008] ④ The metal pad 3 is the position where the signal transmission mode changes. The electromagnetic wave changes from the propagation mode of the GSG coplanar waveguide to the propagation along the gold wire S. The signal reflection will increase, and the external radiation will increase. And because the gold wire needs to be bonded at the metal pad 3, the flatness requirement for the metal pad 3 is high. It is impossible to directly drill a GND via on the metal pad 3, and the flatness of the via is poor, resulting in the return path of the signal being pulled far away, the inductive reactance of the signal return path also increases, and the signal quality decreases.

[0009] ⑤ The bonding gold wire is completely exposed in the air, lacking the wrapping of dielectric materials and GND shielding. The radiation is serious, and the magnetic field lines of the signal can directly couple with adjacent channels to generate crosstalk.

[0010] In view of this, how to overcome the defects existing in the prior art and solve the above technical problems is a difficult problem to be solved in the technical field. Summary of the Invention

[0011] One of the purposes of the present invention is to solve the problem of serious crosstalk between adjacent channels of the existing high-speed optical module transmitting component.

[0012] The present invention is implemented as follows:

[0013] The present invention provides a high-speed optical module transmitting component with low crosstalk, including an ODSP chip 1, a PCB board 2, a substrate 4, and a laser chip 5;

[0014] The ODSP chip 1 is arranged on the PCB board 2, and the laser chip 5 is arranged on the substrate 4; a plurality of metal pads 3 and a plurality of BGA pads are arranged on the surface of the PCB board 2. The laser chip 5 is connected to the corresponding metal pad 3, and the ODSP chip 1 is connected to the corresponding BGA pad. Each metal pad 3 is electrically connected to the corresponding BGA pad to form a corresponding transmission channel;

[0015] The PCB board 2 includes, from top to bottom, a first insulating layer 21, a first metal layer 22, a second insulating layer 23, a second metal layer 24, and a third insulating layer 25 in sequence; the metal pad 3 and the BGA pad are both disposed on the first metal layer 22;

[0016] Transmission lines are fabricated on the first metal layer 22 and the second metal layer 24, and the transmission lines connect the metal pad 3 with the corresponding BGA pad;

[0017] The signals of adjacent transmission channels alternately travel on the transmission lines of the first metal layer 22 and the transmission lines of the second metal layer 24, wherein the transmission channels corresponding to adjacent BGA pads are adjacent transmission channels.

[0018] Preferably, when the signal of a transmission channel travels on the transmission line of the second metal layer 24, two second vias are provided for this transmission channel. The two second vias terminate at the second metal layer 24, and the two second vias are filled with a conductive material;

[0019] One of the second vias is disposed on the BGA pad, and the BGA pad is connected to the transmission line in the second metal layer 24 through this second via;

[0020] The other second via is disposed near the metal pad 3, and the transmission line in the second metal layer 24 is connected to the metal pad 3 through this second via.

[0021] Preferably, the first insulating layer 21, the second insulating layer 23, and the third insulating layer 25 have equal dielectric constants.

[0022] Preferably, the first insulating layer 21, the second insulating layer 23, and the third insulating layer 25 have equal thicknesses.

[0023] Preferably, a metal substrate 6 is further included. The substrate 4 is disposed on the metal substrate 6, and the side surface of the metal substrate 6 is butted against the side surface of the PCB board 2;

[0024] The ground signal of the substrate 4 is connected to the ground signal of the metal substrate 6, and the ground signal of the metal substrate 6 is connected to the ground signal of the PCB board 2.

[0025] Preferably, a transition block 7 is further included. The transition block 7 includes an upper layer, an intermediate layer, and a lower layer. The upper layer is a first ground plane layer 71, the intermediate layer is a coplanar waveguide transmission line layer 72, and the lower layer is a second ground plane layer 73. The metal pad 3 is electrically connected to the coplanar waveguide transmission line layer 72 to reduce signal radiation in the channel.

[0026] Preferably, through first vias are respectively provided in the vertical direction of the transition block 7 and the substrate 4. Among them, the second ground plane layer 73 of the transition block 7 is interconnected with the metal substrate 6 through the first via on the substrate 4, and the first via is filled with a conductive material to facilitate enclosing the transmission line 72 within the region formed by the interconnection of the first ground plane layer 71 and the second ground plane layer 73, and to form an interconnected ground plane layer between the second ground plane layer 73 and the metal substrate 6.

[0027] Preferably, a conductive adhesive 8 is provided between the metal substrate 6 and the PCB board 2, and the PCB board 2, the transition block 7, the substrate 4, and the conductive adhesive 8 form a complete ground return path to reduce the radiation of energy outside the transmission channel.

[0028] Preferably, the transition block 7 is a rigid board or an FPC flexible tape.

[0029] Preferably, the first insulating layer 21 is a green oil layer, and a magnetic dielectric material is provided within the first insulating layer 21. The magnetic dielectric material is used to absorb the electromagnetic waves overflowing from the conductor to suppress the reflection of the transmission signal on the transmission line within the first metal layer 22.

[0030] The above technical solutions adopted by the present invention have the following beneficial effects compared with the prior art:

[0031] The PCB board 2 in the embodiment of the present invention is provided with a multi-layer structure. Among them, the PCB board is provided with a first metal layer 22 and a second metal layer 24, and the first metal layer 22 and the second metal layer 24 belong to the second layer and the fourth layer of the PCB board from top to bottom. The signals of adjacent transmission channels alternately pass through the transmission lines of the first metal layer 22 and the transmission lines of the second metal layer 24, increasing the coupling distance between adjacent channels and avoiding the coupling of the transmission lines of adjacent transmission channels on the same layer, so as to achieve the purpose of reducing near-end crosstalk. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 It is a schematic structural diagram of a low-crosstalk high-speed optical module transmitting component provided by an embodiment of the present invention;

[0034] Figure 2 It is a schematic side view structural diagram of the PCB board layering of a low-crosstalk high-speed optical module transmitting component provided by an embodiment of the present invention;

[0035] Figure 3 Schematic diagram of crosstalk between transmission lines corresponding to a first transmission channel and a second transmission channel adjacent to a low-crosstalk high-speed optical module transmitting component provided by an embodiment of the present invention;

[0036] Figure 4 Schematic diagram of the position of a second via hole of a low-crosstalk high-speed optical module transmitting component provided by an embodiment of the present invention;

[0037] Figure 5 Schematic diagram of the position of a second via hole from another perspective of a low-crosstalk high-speed optical module transmitting component provided by an embodiment of the present invention;

[0038] Figure 6 Schematic diagram of the hierarchical structure of a transition block of a low-crosstalk high-speed optical module transmitting component provided by an embodiment of the present invention;

[0039] Figure 7 Schematic diagram of the position setting of a conductive adhesive of a low-crosstalk high-speed optical module transmitting component provided by an embodiment of the present invention;

[0040] Figure 8 Schematic diagram of a defective complete loop of a low-crosstalk high-speed optical module transmitting component provided by an embodiment of the present invention;

[0041] Figure 9 Schematic diagram of a complete ground return loop of a low-crosstalk high-speed optical module transmitting component provided by an embodiment of the present invention;

[0042] Among them, the reference numerals are:

[0043] 1 - ODSP chip; 2 - PCB board; 21 - First insulating layer; 22 - First metal layer; 23 - Second insulating layer; 24 - Second metal layer; 25 - Third insulating layer; 3 - Metal pad; 4 - Substrate; 5 - Laser chip; 6 - Metal substrate; 7 - Transition block; 71 - First ground plane layer; 72 - Coplanar waveguide transmission line layer; 73 - Second ground plane layer; 8 - Conductive adhesive; 9 - Second via hole. Detailed implementation manners

[0044] In the description of the present invention, the orientation or positional relationship indicated by the terms "inner", "outer", "longitudinal", "transverse", "upper", "lower", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention rather than requiring the present invention to be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0045] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0046] Embodiment 1:

[0047] The embodiment of the present invention provides a high-speed optical module transmitting component with low crosstalk, including an ODSP chip 1, a PCB board 2, a substrate 4, and a laser chip 5;

[0048] The ODSP chip 1 is disposed on the PCB board 2, and the laser chip 5 is disposed on the substrate 4; a plurality of metal pads 3 and a plurality of BGA pads are disposed on the surface of the PCB board 2. The laser chip 5 is connected to the corresponding metal pad 3, and the ODSP chip 1 is connected to the corresponding BGA pad. Each metal pad 3 is electrically connected to the corresponding BGA pad to form a corresponding transmission channel;

[0049] The PCB board 2 includes a first insulating layer 21, a first metal layer 22, a second insulating layer 23, a second metal layer 24, and a third insulating layer 25 from top to bottom; the metal pads 3 and the BGA pads are both disposed on the first metal layer 22;

[0050] Transmission lines are fabricated on the first metal layer 22 and the second metal layer 24, and the transmission lines connect the metal pads 3 to the corresponding BGA pads;

[0051] The signals of adjacent transmission channels alternately pass through the transmission lines of the first metal layer 22 and the transmission lines of the second metal layer 24, where the transmission channels corresponding to adjacent BGA pads are adjacent transmission channels.

[0052] As Figure 1 and Figure 2 shown, wherein, in order to more clearly see the setting position of the transmission lines, Figure 1 the first insulating layer 21 and the first metal layer 22 are omitted and not drawn. Since the embodiment of the present invention does not change the connection manner between the ODSP chip 1 and the transmission lines in the prior art, the ODSP chip 1 in the embodiment of the present invention is only Figure 2It is presented in [the relevant figure], and the presentation of the ODSP chip 1 is omitted in other diagrams. The PCB board 2 of the embodiment of the present invention includes at least a five-layer structure, and is laminated in sequence from top to bottom according to the order of the first insulating layer 21, the first metal layer 22, the second insulating layer 23, the second metal layer 24, and the third insulating layer 25; the signals of adjacent transmission channels alternately pass through the transmission lines in the first metal layer 22 and the second metal layer 24, increasing the coupling distance between adjacent channels and avoiding the coupling of transmission lines on the same layer, so as to achieve the purpose of reducing near-end crosstalk. It should be noted that in the embodiment of the present invention, the transmission lines corresponding to the first metal layer 22 and the second metal layer 24 play the role of transmitting signals. In the actual production process of the high-speed optical module transmitting component with low crosstalk of the embodiment of the present invention, there are many transmission channels, but the transmission lines between adjacent transmission channels are alternately and parallelly misaligned in the first metal layer 22 and the second metal layer 24 respectively, which will not be elaborated here.

[0053] To elaborate the complete solution of the embodiment of the present invention, the details of the present invention will be described in detail below. Further, the first insulating layer 21 is a solder mask layer, and a magnetic medium material is provided in the first insulating layer 21. The magnetic medium material is used to absorb the electromagnetic waves overflowing from the conductor, so as to suppress the reflection of the transmission signal on the transmission line in the first metal layer 22.

[0054] Among them, in order to make the crosstalk between adjacent channels of the embodiment of the present invention smaller, in addition to playing the traditional insulating role, the first insulating layer 21 on the uppermost layer of the PCB board 2 of the embodiment of the present invention also needs to add a magnetic medium material in the first insulating layer 21. The magnetic medium material absorbs the electromagnetic waves overflowing during the transmission of the conductor, suppresses the reflection of the surface transmission line, and reduces the crosstalk between channels. In order to make the magnetic medium material evenly distributed in the first insulating layer 21, the first insulating layer 21 usually adopts a solder mask material, mixes the magnetic medium material in the solder mask, and then smears it on the upper surface of the first metal layer 22 as the first insulating layer 21.

[0055] In order to reduce the transmission crosstalk between adjacent transmission channels as much as possible, the dielectric constants of the first insulating layer 21, the second insulating layer 23, and the third insulating layer 25 in the embodiment of the present invention are equal. The thicknesses of the first insulating layer 21, the second insulating layer 23, and the third insulating layer 25 are equal.

[0056] To more clearly elaborate the reasons for setting the dielectric constants and thicknesses of each layer of the PCB board 2 in the embodiment of the present invention. The embodiment of the present invention gives the formulas for the near-end crosstalk coefficient and the far-end crosstalk coefficient, as follows:

[0057]

[0058]

[0059] Among them, NEXT represents the near-end crosstalk coefficient, FEXT represents the far-end crosstalk coefficient, Len represents the coupling length between two lines, RT represents the rising edge time of the signal, v represents the propagation speed of the signal, C mL represents the mutual capacitance per unit length of the upper layer of the transmission line, C L represents the capacitance per unit length of the lower layer of the transmission line, L mL represents the mutual inductance per unit length of the upper layer of the transmission line, L L represents the inductance per unit length of the lower layer of the transmission line, represents the relative capacitive coupling, represents the relative inductive coupling. Among them, the capacitance per unit length and the mutual inductance per unit length are only determined by the thickness and the dielectric constant.

[0060] Such as Figure 3 shown, which represents a schematic diagram of signal crosstalk. Among them, Figure 3 the first transmission channel and the second transmission channel in are adjacent transmission channels. The signal is emitted from end A of the transmission line in the first transmission channel. The C end of the transmission line in the second transmission channel is the near-end crosstalk, and the D end of the transmission line in the second transmission channel is the far-end crosstalk. It can be seen from formula (2) that when the signal line is wrapped by homogeneous materials up and down and the magnetic lines of force pass through the medium with the same effective dielectric constant and the same thickness, the relative capacitive coupling is equal to the relative inductive coupling, and the far-end crosstalk coefficient is zero. At this time, there will be no far-end crosstalk in the structure.

[0061] Next, the connection relationship between the devices of the high-speed optical module transmitting component in the embodiment of the present invention will be described in detail. Such as Figure 4 and Figure 5 shown. Among them, in order to more clearly present the position of the second via 9 and the connection method with the transmission line, Figure 4 the first insulating layer 21 and the first metal layer 22 are omitted, Figure 5The first insulating layer 21, the first metal layer 22, and the second insulating layer 23 are omitted and not shown. The ODSP chip 1 in the embodiment of the present invention is a multi-port chip. The number of ports of the ODSP chip 1 should be greater than or equal to the actual number of transmission channels of the present invention. Each transmission channel corresponds to a transmission line. The ODSP chip 1 is usually electrically connected to the end of the transmission line using BGA solder balls. In the embodiment of the present invention, when the signal of the transmission channel travels on the transmission line of the second metal layer 24, two second vias 9 are provided for this transmission channel. The two second vias 9 terminate at the second metal layer 24, and the two second vias 9 are filled with a conductive material. One of the second vias 9 is provided on the BGA pad, and through this second via 9, the BGA pad is connected to the transmission line in the second metal layer 24. The other second via 9 is provided near the metal pad 3, and through this second via 9, the transmission line in the second metal layer 24 is connected to the metal pad 3. The transmission line of the second metal layer 24 transmits the signal to the corresponding metal pad 3 through the second via 9, and then transmits it to the corresponding laser chip 5 through the transition block 7, so as to facilitate the transmission of the signal within the inner metal layer. It should be noted that the second via 9 in the embodiment of the present invention usually uses BGA solder balls to achieve the electrical interconnection between the ODSP chip 1 and the transmission line in the second metal layer 24. For example, the BGA solder ball is inserted into the second via 9 on the PCB board 2 on the side away from the substrate 4, and the port of the ODSP chip 1 is connected to the BGA solder ball of the corresponding channel using a metal wire to achieve the electrical connection between the ODSP chip 1 and the transmission line. In addition, the second via 9 on the PCB board 2 near the substrate 4 side is usually provided at a preset distance from the metal pad 3 (the preset distance is set according to the actual situation), and then a section of transmission line is used to electrically interconnect the second via 9 and the metal pad 3.

[0062] The substrate 4 in the embodiment of the present invention is mainly used to carry the laser chip 5 and some related devices. After the laser chip 5 is fixed on the substrate 4, the laser chip 5 needs to be fixed so that the laser chip 5 always maintains a fixed state during operation. The present invention also includes a metal substrate 6. The substrate 4 is provided on the metal substrate 6, and the side surface of the metal substrate 6 is butted against the side surface of the PCB board 2. The ground signal of the substrate 4 is connected to the ground signal of the metal substrate 6, and the ground signal of the metal substrate 6 is connected to the ground signal of the PCB board 2. After the substrate 4 is fixed on the metal substrate 6, the metal substrate 6 is usually fixed to the housing of the optical module to ensure that the laser chip 5 always remains in a fixed state during operation.

[0063] Such as Figure 6As shown in the figure, in order to prevent the traditional wire bonding from being exposed to the air, which may cause strong crosstalk between adjacent channels, an embodiment of the present invention further includes a transition block 7. The transition block 7 includes an upper layer, an intermediate layer, and a lower layer. The upper layer is a first ground plane layer 71, the intermediate layer is a coplanar waveguide transmission line layer 72, and the lower layer is a second ground plane layer 73. The metal pad 3 is electrically connected to the coplanar waveguide transmission line layer 72 to reduce signal radiation in the channel.

[0064] Among them, in the embodiment of the present invention, the connection method between the PCB board 2 and the substrate 4 is replaced by the transition block 7 instead of the traditional metal wire bonding. One end of the coplanar waveguide transmission line layer 72 of the transition block 7 is welded or adhered to the metal pad 3 of the high-speed optical module in the embodiment of the present invention, so as to electrically connect the transition block 7 to the metal pad 3 in the corresponding transmission channel on the PCB board 2; and the other end of the coplanar waveguide transmission line layer 72 of the transition block 7 is electrically interconnected with the laser chip. For one transition block 7 corresponding to one transmission channel in the embodiment of the present invention, the transition blocks 7 in the embodiment of the present invention are arranged in a stacked manner. The intermediate layer can be arranged with a GSG coplanar waveguide transmission line. The upper layer and the lower layer are laid with a complete ground plane, and the upper and lower surfaces are interconnected through vias. In the embodiment of the present invention, the transition block 7 is used to replace the traditional metal wire bonding. After the transition block 7 is set in the corresponding position, the signal line of the coplanar waveguide transmission line layer 72 transmitted into the transition block is wrapped in the middle by the surrounding metal materials, playing a role in shielding electromagnetic signals. The electromagnetic signals generated at the coplanar waveguide transmission line layer 72 are firmly bound to the ground plane between the upper layer and the lower layer, so that the intensity of signal external radiation is greatly reduced, and thus the crosstalk problem between channels is significantly optimized. In addition, in the embodiment of the present invention, the transition block 7 is used to replace the gold wire bonding, and the return path of the signal is reduced by drilling vias, reducing the loop inductance, and finally improving the signal quality.

[0065] It should be noted that the transition block in the present invention is actually a five-layer structure. Usually, an insulating layer is provided between the first ground plane layer 71 and the coplanar waveguide transmission line layer 72, and another insulating layer is also provided between the coplanar waveguide transmission line layer 72 and the second ground plane layer 73. The coplanar waveguide transmission line layer 72 is wrapped by the two insulating layers, separating the coplanar waveguide transmission line layer 72 from the first ground plane layer 71 and the second ground plane layer 73, achieving an insulating effect. During the description process, for the convenience of understanding the solution of the present invention, the transition block is simplified into a three-layer structure for description. In addition, during the actual production process, the coplanar waveguide transmission line layer 72 and the metal pad 3 are usually electrically interconnected by means of vias (and the metal pad 3 and the second ground plane layer 73 also need to be separated by an insulating material). For vias, usually an insulating layer is first coated on the inner wall of the via, and then a metal layer is coated, so that the transmission line (or metal pad) forms an electrical connection relationship with the corresponding transmission line while avoiding the ground plane layer. In addition, during the actual implementation of the embodiments of the present invention, a section of transmission line is also provided on the substrate 4. One end of the transmission line is electrically interconnected with the laser chip, and the other end of the transmission line is connected to the coplanar waveguide transmission line layer 72, or the coplanar waveguide transmission line layer 72 can also be directly pulled out to form an electrical interconnection relationship with the laser chip.

[0066] Furthermore, first vias penetrating through are respectively provided in the vertical direction of the transition block 7 and the substrate 4 in the embodiments of the present invention. Among them, the second ground plane layer 73 of the transition block 7 is interconnected with the metal substrate 6 through the first via on the substrate 4, and the first via is filled with a conductive material, so as to facilitate wrapping the coplanar waveguide transmission line layer 72 within the region formed by the interconnection of the first ground plane layer 71 and the second ground plane layer 73, and forming an interconnected ground plane layer between the second ground plane layer 73 and the metal substrate 6. It should be noted that the first via on the substrate 4 in the embodiments of the present invention is usually provided at the connection between the transition block 7 and the substrate 4, and penetrates through the substrate 4 to abut against the substrate, so as to facilitate interconnecting the metal substrate 6 under the substrate 4 and the second ground plane layer 73 through a metal wire to form an interconnected ground plane layer. In addition, the transition block 7 in the embodiments of the present invention is a rigid board or an FPC flexible tape, which is usually selected according to the actual situation.

[0067] In addition, in order to form a complete ground return loop in the embodiments of the present invention, so that the high-speed signals between the PCB board 2 and the substrate 4 are shielded within the ground plane, a conductive adhesive 8 is provided between the metal substrate 6 and the PCB board 2 in the embodiments of the present invention. The PCB board 2, the transition block 7, the substrate 4, and the conductive adhesive 8 form a complete ground return path to reduce the radiation of the energy in the transmission channel to the outside.

[0068] As Figures 7-9 shown, among which, Figure 8Schematic diagram showing the structure where a complete ground return loop cannot be formed when the conductive adhesive 8 is not used. Figure 9 Schematic diagram showing the complete ground return structure formed by using the conductive adhesive 8. Figure 8 and Figure 9 In [the structure shown in] Figure 9 , the related structure of wire bonding is still used. In the embodiment of the present invention, a gap between the PCB board 2 and the substrate 4 is filled with a flowable conductive adhesive 8 to bond the metal substrate 6 under the substrate 4 of the embodiment of the present invention to the PCB board 2, so that the PCB board 2, the wire bonding or the transition block 7, the substrate 4 with the metal substrate 6, and the conductive adhesive 8 form a ground return loop. One end of the wire bonding is connected to the metal pad 3, and the other end is connected to a via on the substrate 4 and is electrically connected to the substrate through the via. One end of the conductive adhesive 8 is connected to the substrate, and the other end is connected to the side of the PCB board 2. Vias are also provided in the PCB board 2 to electrically connect the metal pad 3 and the conductive adhesive 8 through the vias. Then, through grounding, a ground return loop is formed in the embodiment of the present invention, so that the high-speed signal between the PCB board 2 and the substrate 4 has a reference ground plane on the lower layer, and the ground return path is more complete rather than incomplete. The added ground shielding layer below reduces the external radiation of energy, reduces the crosstalk between channels, and improves the signal quality.

[0069] The PCB board 2 in the embodiment of the present invention is arranged as a multi-layer structure. Among them, the PCB board is provided with a first metal layer 22 and a second metal layer 24, and the first metal layer 22 and the second metal layer 24 belong to the second layer and the fourth layer of the PCB board from top to bottom. The signals of adjacent transmission channels alternately pass through the transmission lines of the first metal layer 22 and the transmission lines of the second metal layer 24, increasing the coupling distance between adjacent channels and avoiding the coupling of the transmission lines of adjacent transmission channels on the same layer, so as to achieve the purpose of reducing near-end crosstalk. In the embodiment of the present invention, the transmission lines in each transmission channel are arranged in different layers of the PCB board 2, and the thickness and the dielectric constant between the upper layer and the lower layer of the respective corresponding transmission lines are set to be the same, which can theoretically eliminate the far-end crosstalk in the transmission channel. In addition, in the embodiment of the present invention, a conductive adhesive 8 is provided between the metal substrate 6 under the substrate 4 and the PCB board 2, so that a complete ground return path is formed for the low-crosstalk high-speed optical module transmitting component in the embodiment of the present invention, further reducing the external energy radiation of the transmission lines in the transmission channel of the present invention, reducing the crosstalk between the transmission channels, and improving the signal quality of the present invention.

[0070] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-speed optical module transmitting component with low crosstalk, characterized in that, it includes an ODSP chip (1), a PCB board (2), a substrate (4) and a laser chip (5); the ODSP chip (1) is arranged on the PCB board (2), and the laser chip (5) is arranged on the substrate (4); a plurality of metal pads (3) and a plurality of BGA pads are arranged on the surface of the PCB board (2), the laser chip (5) is connected to the corresponding metal pad (3), the ODSP chip (1) is connected to the corresponding BGA pad, and each metal pad (3) is electrically connected to the corresponding BGA pad to form a corresponding transmission channel; the PCB board (2) sequentially includes a first insulating layer (21), a first metal layer (22), a second insulating layer (23), a second metal layer (24) and a third insulating layer (25) from top to bottom; the metal pads (3) and the BGA pads are both arranged on the first metal layer (22); the dielectric constants of the first insulating layer (21), the second insulating layer (23) and the third insulating layer (25) are equal; transmission lines are made on the first metal layer (22) and the second metal layer (24), and the transmission lines connect the metal pads (3) to the corresponding BGA pads; the signals of adjacent transmission channels alternately pass through the transmission lines on the first metal layer (22) and the transmission lines on the second metal layer (24), wherein, the transmission channels corresponding to adjacent BGA pads are adjacent transmission channels.

2. The high-speed optical module transmitting component with low crosstalk according to claim 1, characterized in that, when the signal of the transmission channel passes through the transmission line on the second metal layer (24); two second vias are provided for this transmission channel, the two second vias terminate at the second metal layer (24), and the two second vias are filled with conductive materials; one of the second vias is arranged on the BGA pad, and the BGA pad is connected to the transmission line in the second metal layer (24) through this second via; the other second via is arranged near the metal pad (3), and the transmission line in the second metal layer (24) is connected to the metal pad (3) through this second via.

3. The high-speed optical module transmitting component with low crosstalk according to claim 1, characterized in that, the first insulating layer (21), the second insulating layer (23) and the third insulating layer (25) have equal thicknesses.

4. The high-speed optical module transmitting component with low crosstalk according to claim 1, characterized in that, it further includes a metal substrate (6), the substrate (4) is arranged on the metal substrate (6), and the side surface of the metal substrate (6) is butted against the side surface of the PCB board (2); the ground signal of the substrate (4) is connected to the ground signal of the metal substrate (6), and the ground signal of the metal substrate (6) is connected to the ground signal of the PCB board (2).

5. The high-speed optical module transmitting component with low crosstalk according to claim 4, characterized in that, It further includes a transition block (7), and the transition block (7) includes an upper layer, a middle layer and a lower layer. The upper layer is a first ground plane layer (71), the middle layer is a coplanar waveguide transmission line layer (72), and the lower layer is a second ground plane layer (73). The metal pad (3) is electrically connected to the coplanar waveguide transmission line layer (72) to reduce signal radiation in the channel.

6. The high-speed optical module transmitting component with low crosstalk according to claim 5, characterized in that through first vias are respectively provided in the vertical direction of the transition block (7) and the substrate (4). Among them, the second ground plane layer (73) of the transition block (7) is interconnected with the metal substrate (6) through the first via on the substrate (4), and the first via is filled with a conductive material, so as to facilitate the coplanar waveguide transmission line layer (72) to be wrapped in the area formed by the interconnection of the first ground plane layer (71) and the second ground plane layer (73), and the second ground plane layer (73) and the metal substrate (6) form an interconnected ground plane layer.

7. The high-speed optical module transmitting component with low crosstalk according to claim 5, characterized in that a conductive adhesive (8) is provided between the metal substrate (6) and the PCB board (2), and the PCB board (2), the transition block (7), the substrate (4) and the conductive adhesive (8) form a complete ground return path to reduce the radiation of energy in the transmission channel to the outside.

8. The high-speed optical module transmitting component with low crosstalk according to claim 5, characterized in that the transition block (7) is a rigid board or an FPC flexible tape.

9. The high-speed optical module transmitting component with low crosstalk according to claim 1, characterized in that the first insulating layer (21) is a green oil layer, and a magnetic medium material is provided in the first insulating layer (21). The magnetic medium material is used to absorb the electromagnetic waves overflowing from the conductor to suppress the reflection of the transmission signal on the transmission line in the first metal layer (22).

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