Soft board structure, TO optical module and optical transmission device

Abstract

The present invention discloses a flexible board structure, a TO optical module and an optical transmission device, wherein the flexible board structure includes a first area connected to a TO optical device and a second area connected to the first area, a high-speed signal hole corresponding to the high-speed signal pin of the TO optical device is formed on the first area, the flexible board structure includes a first covering film, a first metal layer, a substrate and a second metal layer stacked in sequence from top to bottom, the first metal layer is configured to provide a ground plane, the second metal layer is formed with a high-speed signal link, the first covering film is configured to be assembled toward the TO optical device, the first covering film is formed with a through hole adjacent to the high-speed signal hole in the first area, the first metal layer is exposed at the through hole, the through hole is filled with a conductive material connected to the first metal layer, and the conductive material exceeds the first covering film upward. The present invention can be applied to the transmission of high-speed signals, and has a simple manufacturing process and a low manufacturing cost.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to a flexible board structure, a TO optical module and an optical transmission device. Background Art

[0002] Currently, driven by the demand for 5G wireless fronthaul and ultra-large broadband data centers, the speed requirements for its core components, optical transceiver modules, are getting higher and higher. In terms of 5G wireless fronthaul, 25Gbps optical modules have become mainstream, and the market demand is huge. In addition, high-speed optical modules are more widely used in data centers.

[0003] Common packaging forms for optical modules include TO packaging and Box packaging. Figure 1 ) is a mainstream packaging form for optical modules in the past, with simple process and low cost, but it cannot be applied in high-speed and ultra-high-speed optical modules. Box packaging uses ceramic tube holders to assemble optical chips, electrical chips and optical devices, etc., which can achieve high-speed packaging, but its cost is extremely high, which is 5-10 times the price of TO packaging, and the packaging process requirements are extremely high.

[0004] TO packaging has a simple manufacturing process and extremely low cost, but it can only be maturely applied to low-speed optical modules with a rate of 10G or less. The reason is that the special structure of the TO package optical module causes the high-speed link between the internal laser chip and the external circuit driver to be too long and the path is complicated. The entire link routing is located in the PCB hard board, FPC soft board and TO pin (such as Figure 1 ), especially the interface between TO optical devices and FPC soft boards, where high-speed and ultra-high-speed signals will experience severe signal reflection and loss, often resulting in the optical module performance failing to meet index requirements. Figure 2 This is a schematic diagram of a TO optical device. The pins of the TO optical device need to be inserted into the pre-designed pin holes of the FPC soft board. There is a circle of pads around the pin holes. The pins and pads are connected with solder through the welding process, and finally the excess length of the pins is cut off to complete the connection between the FPC soft board and the TO optical device.

[0005] The interface between the FPC soft board and the TO optical device is the most important reason for the deterioration of ultra-high-speed signal transmission. It is mainly manifested in that the transmission modes of high-speed lines on TO optical devices and FPC soft boards are completely different. Even if the design of high-speed lines or ultra-high-speed lines can meet the standard impedance requirements, the conversion of transmission modes at the interface often brings about resonance problems with devastating effects. This is the key technical bottleneck that prevents TO packaging from being applied to high-speed and ultra-high-speed applications. The probability of this problem occurring when the optical module is used at low speed is very small. Summary of the invention

[0006] The object of the present invention is to provide a flexible board structure, which can be suitable for the transmission of high-speed signals when used in a TO optical module.

[0007] Another object of the present invention is to provide a TO optical module that is suitable for transmission of high-speed signals.

[0008] Another object of the present invention is to provide an optical transmission device that can be used for transmission of high-speed signals.

[0009] To achieve the above-mentioned purpose, the present invention provides a flexible board structure for connecting to a TO optical device, the flexible board structure comprising a first area connected to the TO optical device and a second area connected to the first area, a high-speed signal hole corresponding to the high-speed signal pin of the TO optical device is formed on the first area, the flexible board structure comprises a first covering film, a first metal layer, a substrate and a second metal layer stacked in sequence from top to bottom, the first metal layer is configured to provide a ground plane, the second metal layer forms a high-speed signal link, the first covering film is configured to be assembled toward the TO optical device, the first covering film forms a through hole adjacent to the high-speed signal hole in the first area, the first metal layer is exposed at the through hole, the through hole is filled with a conductive material connected to the first metal layer, and the conductive material extends upward beyond the first covering film.

[0010] Preferably, the through hole is a circular hole with a diameter between 0.6 mm and 0.9 mm.

[0011] Preferably, the first covering film is provided with one or more through holes at a position adjacent to each of the high-speed signal holes.

[0012] Preferably, the conductive material is thermally cured in the through hole.

[0013] Preferably, the conductive material is conductive glue or metal solder.

[0014] Preferably, the flexible board structure further includes a second covering film, and the second covering film covers the second metal layer.

[0015] To achieve the above another object, the present invention provides a TO optical module, including a TO optical device and the above mentioned flexible board structure.

[0016] To achieve another objective, the present invention provides an optical transmission device, including the TO optical module and a circuit board as described above, wherein an end of the second area of ​​the flexible board structure away from the first area is connected to the circuit board.

[0017] Compared with the prior art, the soft board structure of the present invention has a through hole formed on the first covering film thereof adjacent to the high-speed signal hole to expose the first metal layer, and the through hole is filled with a conductive material connected to the first metal layer, and the conductive material extends upward beyond the first covering film; when in use, the impedance at the interface between the TO optical device and the soft board structure can be adjusted to near the expected value, thereby improving the impedance matching effect, reducing high-frequency noise, reducing signal loss, and raising the resonant frequency to a higher frequency band, so that the present invention can move the resonant frequency to a frequency band far away from signal transmission, making the present invention suitable for the transmission of high-speed signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a structural schematic diagram of an optical transmission device.

[0019] Figure 2 It is a schematic diagram of the three-dimensional structure of a TO optical device.

[0020] Figure 3 It is a three-dimensional structural schematic diagram of the flexible board structure according to an embodiment of the present invention.

[0021] Figure 4 It is a schematic diagram of the exploded structure of the flexible circuit board structure according to an embodiment of the present invention, in which the conductive material is hidden.

[0022] Figure 5 1 is another schematic diagram of the exploded structure of the flexible circuit board according to an embodiment of the present invention, in which the conductive material is hidden.

[0023] Figure 6 It is a cross-sectional schematic diagram of a local structure of a flexible board structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to explain the technical content and structural features of the present invention in detail, further description will be given below in combination with the implementation modes and the accompanying drawings.

[0025] See also Figures 1 to 6The present invention discloses a flexible board structure 1 for connecting with a TO optical device 7. The flexible board structure 1 includes a first area Z1 connected with the TO optical device 7 and a second area Z2 connected with the first area Z1. A high-speed signal hole 10 corresponding to a high-speed signal pin 71 of the TO optical device 7 is formed on the first area Z1. The flexible board structure 1 includes a first covering film 20, a first metal layer 30, a substrate 40 and a second metal layer 50 stacked in sequence from top to bottom. The first covering film 20 can protect the first metal layer 30 and improve the reliability of the entire package. The first metal layer 30 is configured to provide a ground plane, and the second metal layer 50 forms a high-speed signal link. The first covering film 20 is configured to be assembled toward the TO optical device 7. The first covering film 20 forms a through hole 21 adjacent to the high-speed signal hole 10 in the first area Z1. The first metal layer 30 is exposed at the through hole 21, and the through hole 21 is filled with a conductive material 22 connected to the first metal layer 30, and the conductive material 22 exceeds the first covering film 20 upward. Specifically, the high-speed signal link includes pads 51 and high-speed signal lines 52 formed around the high-speed signal hole 10. In addition, in the specific example, pads 53 and 54 are formed on the second metal layer 50 around the DC signal hole 11 and the ground signal hole 12.

[0026] Since the soft board structure 1 of the present invention can adjust the impedance of the interface between the TO optical device 7 and the soft board structure 1 to near the expected value when in use, the impedance matching effect can be improved, and at the same time, high-frequency noise can be reduced, signal loss can be reduced, and the resonant frequency can be moved to a frequency band far away from signal transmission, thereby making the present invention suitable for high-speed signal transmission, and having a simple manufacturing process and a low manufacturing cost.

[0027] See also Figures 3 to 5 In some embodiments, the through hole 21 is a circular hole with a diameter between 0.6 mm and 0.9 mm. Of course, it is not limited thereto. In other embodiments, the through hole 21 may also be a circular hole with a diameter of other sizes or a non-circular hole.

[0028] See also Figures 3 to 5 In some embodiments, the first cover film 20 is provided with one or more through holes 21 adjacent to each high-speed signal hole 10. That is, for each high-speed signal hole 10, one or more through holes 21 may be provided adjacent to the hole and the through hole 21 may be filled with a conductive material 22 extending upward beyond the first cover film 20 to improve the transmission capability of high-speed signals.

[0029] See also Figure 3 and Figure 6In some embodiments, the conductive material 22 is thermally cured in the through hole 21, and the conductive material is preferably conductive glue or metal solder. Of course, in other embodiments, the conductive material 22 is not limited to the thermally cured conductive material 22.

[0030] See also Figure 2 and Figure 3 In a specific example, the first area Z1 is further formed with a DC signal hole 11 and a ground signal hole 12 corresponding to the DC signal pin 72 and the ground signal pin 73 of the TO optical device 7. The DC signal hole 11 and the ground signal hole 12 are arranged along the longitudinal direction of the flexible board structure 1. The ground signal hole 12 is closer to the second area Z2 than the DC signal hole 11. The first area Z1 is formed with two high-speed signal holes 10. The two high-speed signal holes 10 are located between the DC signal hole 11 and the ground signal hole 12 in the longitudinal direction of the flexible board structure 1, and are located on both sides of the DC signal hole 11 and the ground signal hole 12 in the transverse direction (the direction perpendicular to the longitudinal direction) of the flexible board structure 1. The first area Z1 is formed with through holes 21 on the side of the two high-speed signal holes 10 close to the second area Z2. Of course, this is only a specific embodiment of the present invention. In the case where the flexible board structure 1 has the same arrangement of high-speed signal holes 10, DC signal holes 11 and ground signal holes 12, the through holes 21 can also be arranged on the outside of the through holes 21 or on the side away from the second area Z2. Moreover, it should be noted that the flexible board structure 1 of the present invention is not limited to the TO optical device 7 with a specific number of pins and a specific pin arrangement. As long as the TO optical device 7 has a high-speed signal pin 71, and a high-speed signal hole 10 matching the high-speed signal pin 71 is formed on the flexible board structure 1, the present invention can be applied.

[0031] See also Figures 4 to 6 In some embodiments, the flexible board structure 1 further includes a second covering film 60 , and the second covering film 60 covers the second metal layer 50 .

[0032] Please combine Figures 1 to 3 The present invention also discloses a TO optical module, including a TO optical device 7 and the flexible board structure 1 as described in the above embodiment.

[0033] Please combine Figure 1 The present invention also discloses an optical transmission device, including the TO optical module and the circuit board 8 as described above, wherein the end of the second area Z2 of the flexible board structure 1 away from the first area Z1 is connected to the circuit board 8.

[0034] In summary, since the soft board structure 1 of the present invention has a through hole 21 that exposes the first metal layer 30 at a position adjacent to the high-speed signal hole 10 on the first covering film 20, and the through hole 21 is filled with a conductive material 22 that is connected to the first metal layer 30 and extends upward beyond the first covering film 20, the impedance at the interface between the TO optical device 7 and the soft board structure 1 can be adjusted to a near expected value when in use, thereby improving the impedance matching effect, reducing high-frequency noise, reducing signal loss, and moving the resonant frequency to a frequency band far away from signal transmission, thereby making the present invention applicable to high-speed signal transmission, while having a simple manufacturing process and extremely low manufacturing cost. The present invention can achieve high-quality signal transmission at 25Gbps and higher rates using the TO package structure without the need for high-cost BOX packaging.

[0035] The above disclosure is only a preferred embodiment of the present invention, which cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are all within the scope of the present invention.

Claims

1. A flexible board structure for connecting with TO optical devices. It is characterized in that The flexible board structure includes a first area connected to the TO optical device and a second area connected to the first area, a high-speed signal hole corresponding to the high-speed signal pin of the TO optical device is formed on the first area, the flexible board structure includes a first covering film, a first metal layer, a substrate and a second metal layer stacked in sequence from top to bottom, the first metal layer is configured to provide a ground plane, the second metal layer forms a high-speed signal link, the first covering film is configured to be assembled toward the TO optical device, the first covering film forms a through hole adjacent to the high-speed signal hole in the first area, the through hole is only opened in the first covering film, the first metal layer is exposed at the through hole, the through hole is filled with a conductive material connected to the first metal layer, and the conductive material extends upward beyond the first covering film; the first area also forms a DC signal hole and a ground signal hole corresponding to the DC signal pin and the ground signal pin of the TO optical device.

2. The soft board structure as claimed in claim 1, It is characterized in that The through hole is a circular hole with a diameter between 0.6 mm and 0.9 mm.

3. The soft board structure as claimed in claim 1, It is characterized in that The first covering film is provided with one or more through holes at a position adjacent to each of the high-speed signal holes.

4. The soft board structure according to claim 1, It is characterized in that The conductive material is thermally cured within the through-hole.

5. The soft board structure as claimed in claim 4, It is characterized in that The conductive material is conductive glue or metal solder.

6. The soft board structure according to claim 1, It is characterized in that The invention also includes a second covering film, wherein the second covering film covers the second metal layer.

7. A TO optical module, It is characterized in that It comprises a TO optical device and a flexible board structure as claimed in any one of claims 1 to 6.

8. An optical transmission device, It is characterized in that It comprises the TO optical module and circuit board as claimed in claim 7, wherein an end of the second area of ​​the flexible board structure away from the first area is connected to the circuit board.

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