High speed optical devices and packaging methods based on flexible circuit boards

Abstract

The application discloses a high-speed optical device based on a flexible circuit board and a packaging method thereof, and relates to the field of optical device packaging. The high-speed optical device based on the flexible circuit board comprises an optical device, a bottom shell and a face shell for packaging the optical device, the optical device comprises an optoelectronic chip, the bottom shell is provided with a sunken fixing groove on a mounting position matched with the optoelectronic chip; a flexible circuit board (FPC) is provided with a rectangular notch matched with the spatial position of the fixing groove; wherein the optoelectronic chip and a chip pad matched with the optoelectronic chip are arranged at the bottom of the fixing groove; the upper surfaces of the optoelectronic chip, the chip pad and the FPC are at the same height in space, and are connected through matched welding groups. The application provides the high-speed optical device based on the flexible circuit board and the packaging method thereof, fully utilizes the advantages of two packaging schemes of conventional COB packaging and C0C packaging, avoids inherent defects of the two schemes in design, reduces the process difficulty, and realizes high-performance and low-cost optoelectronic integrated packaging.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of optical device packaging design.More specifically, the present application relates to a kind of high-speed optical device based on flexible circuit board and packaging method used in high-speed optical device packaging. BACKGROUND

[0002] In the scheme of high-speed optical device packaging, there are usually COB packaging (Chips on Board), COC packaging (Chip On Carrier) and other schemes.

[0003] The packaging scheme of COB is to directly integrate optical chips, driving chips and the like on a PCB board, and the chips are connected to the pads on the PCB through soldered gold wires, which has the advantages of short wire distance, optical and electrical integrated packaging, low cost, etc., but has the following shortcomings:

[0004] 1. The chips are attached to the PCB board, and the material of the PCB board is limited, with low thermal conductivity and poor heat dissipation effect;

[0005] 2. Due to the irregular shape of the components on the circuit board, it is difficult to achieve airtight packaging, and the optical chips that are not airtight and filled with nitrogen are exposed to a high-temperature and oxygen environment, which is prone to oxidation and aging, affecting the reliability and life of the optical device, so it is generally used in short-distance transmission applications;

[0006] The packaging scheme of COC is to package optical chips on a ceramic heat sink, and the ceramic substrate is attached to a metal shell with good thermal conductivity, and the internal electrodes of the packaging shell are connected to the chips through gold wire bonding, which has the advantages of stable packaging structure, good heat dissipation through the ceramic heat sink, and good airtightness, etc., but has the following shortcomings:

[0007] The position of the patch and the position of the wire are limited by the position of the ceramic heat sink and the chip attachment, and the wire distance is usually long, with multiple levels of wire bonding. Due to multiple wire bonding, many gold wire connection nodes are generated, and the signal reflection is enhanced during high-frequency signal transmission, which easily causes the S parameter of the device to deteriorate, resulting in poor device performance. In order to compensate for this loss, special circuit design and simulation of the packaging shell are usually required, which is complex, difficult to process, and high in manufacturing cost. This part is an unavoidable loss in the COC scheme, and usually only through special design of the packaging shell and simulation optimization of the external matching circuit can the impact of this loss be reduced, but it cannot be eliminated and avoided, and can only be downgraded by reducing the index. This is an inherent defect of the COC scheme.

[0008] However, the current optical device packaging cannot integrate the common advantages of the two schemes. SUMMARY

[0009] An object of the present application is to solve at least the above problems and / or drawbacks and to provide at least the advantages later described.

[0010] To achieve these objects and other advantages in accordance with the present application, a flexible circuit board based high-speed optical device is provided, comprising an optical device and a bottom shell and a face shell for packaging the optical device, the optical device comprising an optoelectronic chip, the bottom shell being provided with a sunken fixing groove at a mounting position matched with the optoelectronic chip;

[0011] A flexible circuit board FPC is provided with a rectangular notch matched in space with the fixing groove;

[0012] The optoelectronic chip and the chip pad matched therewith are arranged at the bottom of the fixing groove;

[0013] The optoelectronic chip, the chip pad and the upper surface of the FPC are at the same height in space and are connected through a matched soldering group.

[0014] Preferably, the optoelectronic chip and the chip pad are arranged at the bottom of the mounting groove through a matched aluminum nitride gasket, and are further connected with the bottom shell.

[0015] Preferably, the FPC pad is further provided with a patch capacitor, a magnetic bead and a thermistor.

[0016] Preferably, the extended end of the FPC is connected with an external PCB printed circuit board.

[0017] Preferably, the face shell is provided with a matched limiting groove at the extended end of the FPC.

[0018] Preferably, the soldering group is configured to include:

[0019] A plurality of first soldering points arranged on the chip pad to realize the connection between the optoelectronic chip and the chip pad;

[0020] A third soldering point arranged on the chip pad to realize the connection between the chip pad and each second soldering point on the FPC;

[0021] The FPC is connected with an external device through a plurality of gold wires matched with each second soldering point thereon.

[0022] A packaging method of a high-speed optical device, comprising:

[0023] Arranging the optoelectronic chip and the chip pad matched therewith in the mounting groove and realizing the electrical connection between the optoelectronic chip and the chip pad through the first soldering points;

[0024] Arranging the FPC on the bottom shell and matching the position of the rectangular notch with the outer edge of the fixing groove;

[0025] The optoelectronic chip, the chip pad and the FPC board are configured in the same plane in space to realize the electrical connection between the chip pad and the FPC through the second soldering point and the third soldering point, and then realize the connection with the external PCB board through the wiring on the FPC.

[0026] Preferably, the optoelectronic chip and the chip pad are respectively attached to the aluminum nitride gasket, and then connected to the fixing groove through the aluminum nitride gasket.

[0027] Preferably, the FPC adopts multi-layer wiring to cooperate with each third soldering point on the FPC pad.

[0028] The present application has at least the following advantages: first, the flexible circuit board FPC is introduced into the optical device, and the advantages of the FPC are used to realize the planarization of the pin layout of the optoelectronic chip in the optical device, overcome the defects caused by multi-layer wiring and long wiring distance, and since the wiring is all on the pad of the FPC, the external pins of the metal shell and the internal electrodes of the shell are no longer needed, the manufacturing difficulty and cost of the metal shell are reduced, the structure of the shell is improved little, it is easy to realize, and the air tightness, reliability and life of the device are improved.

[0029] Secondly, the lower layer design of the structure of the bottom shell makes the optoelectronic chip, the chip pad and the FPC in the same plane in space, so that the straight line distance is short, multi-layer or multi-stage wiring is avoided, the distance between the RF pad and the FPC pad is ensured to be the smallest through the design of the rectangular notch on the FPC, the wiring length is shortened, the line loss caused by the long multi-wire is reduced, the aluminum nitride gasket is avoided, the gasket can be in contact with the shell to realize direct conduction of the chip heat to the packaging metal shell, the chip heat dissipation performance is equivalent to the COC process, and the S parameter of the device is optimized.

[0030] Thirdly, the packaging scheme of the present application fully utilizes the advantages of the conventional COB packaging (Chip on Board) and COC packaging (Chip On Carrier) by using the flexible circuit board, and avoids the inherent disadvantages of the two schemes from the design, reduces the process difficulty, and realizes the high-performance and low-cost optoelectronic integrated packaging.

[0031] Other advantages, objects and features of the present application will be embodied in part by the following description, and will be understood by those skilled in the art through research and practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a structure schematic view of a high-speed optical device based on a flexible circuit board in an embodiment of the present application.

[0033] Figure 2 Structure diagram of the bottom shell in another embodiment of the present application;

[0034] Figure 3 Structure diagram of the bottom shell in another embodiment of the present application;

[0035] Figure 4 Structure diagram of the FPC board in another embodiment of the present application;

[0036] Figure 5 Structure diagram of the bottom shell and the optical device after assembly in another embodiment of the present application;

[0037] Figure 6 Structure diagram of the partial enlargement of the cooperation between the optoelectronic chip and the FPC in another embodiment of the present application;

[0038] Figure 7 Structure diagram of the partial enlargement of the cooperation between the optoelectronic chip and the bottom shell in another embodiment of the present application;

[0039] Figure 8 Structure diagram of the cooperation between the optoelectronic chip, the chip pad and the aluminum nitride gasket in another embodiment of the present application. DETAILED DESCRIPTION

[0040] The present application will be further described in detail with reference to the accompanying drawings, so that those skilled in the art can implement the present application according to the description and the drawings.

[0041] It should be understood that the terms such as "have", "contain" and "include" used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0042] It should be noted that in the description of the present application, the terms indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0043] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "provided with", "sleeved / connected", "connected" and the like should be understood in a broad sense, for example, "connected" can be fixedly connected, or detachably connected, or integrally connected, can be mechanically connected, or electrically connected, can be directly connected, or indirectly connected through an intermediate medium, can be internal communication of two elements, and those skilled in the art can understand the specific meaning of the above terms in the present application according to the specific circumstances.

[0044] Figures 1-8 An implementation form of a high-speed optical device based on a flexible circuit board according to the present application is shown, which includes an optical device and a bottom shell 1 and a face shell 2 for packaging the optical device, the optical device includes an optoelectronic chip 3, the bottom shell is provided with a sunken fixing groove 4 on the mounting position matched with the optoelectronic chip, in this structure, the bottom shell in the prior art is improved in structure, so that compared with the prior art, a stepped structure is formed on the bottom shell by specially providing a mounting groove for mounting the optoelectronic chip, so that the mounting space of the device has a height difference, which is beneficial to adaptively limit the corresponding of the component structure space level in actual operation;

[0045] A flexible circuit board FPC 5 is provided with a rectangular notch 6 matched with the spatial position of the fixing groove, in this structure, the FPC has the advantages of thin thickness, easy processing and smooth surface, which is very easy to realize when designing airtight packaging, the overall airtightness of the device is good, it can be directly connected with a PCB circuit board, has good reliability and long service life, the mode of leading out of the optical device is limited, so as to realize the connection between the PCB circuit board and the optoelectronic chip as a bridge, ensure the small volume of the internal structure of the optical device, and the assembly mode is simple and easy to operate, at the same time, by providing a rectangular notch on the FPC, the spatial positions of the optoelectronic chip and the chip pad are designed in a staggered manner, so as to ensure that the distance between the chip (RF) pad and the FPC pad is minimized, the wire length is shortened, the line loss caused by the excessive length of the multi-wire is reduced, and the S parameter of the device is optimized, the full name of S parameter is Scatter parameter, i.e. scattering parameter, S parameter describes the frequency domain characteristics of the transmission channel, when performing serial link SI analysis, obtaining accurate S parameter of the channel is a very important link, through S parameter, we can see almost all the characteristics of the transmission channel. Most of the problems concerned about signal integrity, such as signal reflection, crosstalk and loss, can find useful information from S parameter, the present scheme optimizes the wire position length and the like, and simply speaking, the optimization of S parameter is to reduce the reflection, crosstalk and loss of the loaded signal, so that the optical device can have very good optical signal output;

[0046] The photoelectric chip and the chip pad cooperating with the photoelectric chip are arranged at the bottom of the fixing groove, and in the structure, the photoelectric chip and the chip pad are arranged in the fixing groove, so that the photoelectric chip and the chip pad are in a sunken state in space and can cooperate with the space height after the FPC is mounted, so that the welding stability in the later stage is better.

[0047] The upper surfaces of the photoelectric chip, the chip pad and the FPC are at the same height in space and are connected through the cooperating welding group 11, and in the structure, the height of the three components in space is limited, so that the horizontal degree is better, and the connection between the components is realized through the welding group, and in the scheme, the photoelectric chip and the chip pad can be sunken at the same time through the step design of the metal bottom shell, so that the surface of the FPC pad wire layer and the surface of the chip pad wire layer are on the same horizontal plane, multi-layer or multi-stage wire bonding is avoided, the rectangular notch design ensures that the distance between the RF pad and the FPC pad is minimized, the wire length is shortened, the line loss caused by the excessively long multi-wire length is reduced, the S parameter of the device can be effectively optimized, and the metal shell and the bottom shell only need to be designed as a simple mechanical structure, so that the device is easy to realize.

[0048] As shown in FIG. 1, the photoelectric chip 1 is arranged on the bottom of the fixing groove 2, and the chip pad 3 is arranged on the bottom of the fixing groove 2. Figure 8 In another example, the photoelectric chip and the chip pad are arranged at the bottom of the mounting groove through the cooperating aluminum nitride gasket 8, and then connected with the bottom shell, and in the scheme, the internal chip of the photoelectric integrated package is directly attached to the high-thermal-conductivity aluminum nitride gasket through the COC process, and then integrally attached to the bottom seat of the package shell, and the chip is directly cooled through the aluminum nitride gasket, and the chip cooling performance is equivalent to the COC process.

[0049] As shown in FIG. 1, the photoelectric chip 1 is arranged on the bottom of the fixing groove 2, and the chip pad 3 is arranged on the bottom of the fixing groove 2. Figures 5-6 In another example, the FPC pad is further integrally provided with a patch capacitor, a magnetic bead and a thermistor 9, and in the scheme, the FPC is integrally provided with electronic elements such as a magnetic bead, a thermistor and a capacitor, the number of aluminum nitride gaskets required inside is reduced, the complexity of the internal structure is reduced, the number of wire bonds is reduced, the process difficulty of the device is reduced, and the reliability of the optical device is improved.

[0050] In another example, the extending end of the FPC is connected with an external PCB (not shown), and in the scheme, the FPC is thin in thickness and flat in surface, so that the airtight packaging is easy to realize in design, the airtightness, reliability and long service life of the device are improved, the other end of the FPC is directly connected with the PCB, the connection between the photoelectric chip and the PCB is further realized, compared with the prior art, the FPC is used as a connection bridge between the photoelectric chip and the PCB, and compared with the COB packaging scheme, the airtightness, service life and reliability of the device are effectively improved.

[0051] As shown in FIG. 1, the photoelectric chip 1 is arranged on the bottom of the fixing groove 2, and the chip pad 3 is arranged on the bottom of the fixing groove 2. Figure 2In another example, the face shell is provided with a matching limiting groove 10 at the FPC extension end, in this scheme, the spatial position of the FPC is limited by the limiting groove, and the face shell and / or the bottom shell can be provided with a flexible silica gel layer at the limited position of the FPC, which can release heat and reduce damage to the FPC caused by the device during assembly, use and maintenance, while ensuring the stability between the structural members, that is, by the action of the limiting groove, the FPC and the shell have a small gap, which can realize reliable airtight packaging.

[0052] As Figure 6 In another example, the welding group is configured to include:

[0053] A plurality of first welding points 12 are arranged on the chip pad to realize the connection of the optoelectronic chip and the chip pad;

[0054] A third welding point 14 is arranged on the chip pad to realize the connection of the chip pad and each second welding point 13 on the FPC;

[0055] The FPC is connected with the external device through a plurality of gold wires 15 on the FPC and each second welding point, in this structure, through the reasonable layout of the FPC pad, multi-layer wire bonding is avoided, and because the wire bonding is all on the pad of the FPC, the shell external pin and the shell internal electrode no longer need to be made in the metal shell, which reduces the manufacturing difficulty and cost of the metal shell, and through the limitation of the welding group, the cooperation of the optoelectronic chip and the FPC pad in the spatial plane distribution is realized, all the welding points are reasonably arranged on a plane, thereby ensuring the connection stability of the same layer and the optoelectronic chip, and effectively solving the technical problems of insufficient pads, multi-layer wire bonding, and insulation and wire design of the metal shell in the prior art.

[0056] A packaging method of a high-speed optical device, comprising:

[0057] The optoelectronic chip and the chip pad matched therewith are fixedly arranged in the mounting groove, and the electrical connection of the optoelectronic chip and the chip pad is realized through the first welding point, the bottom of the optical device shell is designed to be sunken, and the components are mounted in the sunken structure, so that the surface of the FPC pad layer and the surface of the chip pad are on the same horizontal plane, high-low step wire bonding is avoided, the wire length is shortened, the wire bonding process is simplified, the device S parameter is optimized, and through the action of the chip pad, the pin distribution of the chip is planarized, so that the metal shell does not need to be insulated and wired during the packaging process;

[0058] The FPC is set on the bottom shell, and the position of the rectangular notch matches the outer edge of the fixing groove. The FPC is a kind of flexible printed circuit board with high reliability and excellent flexibility, which is made of polyimide or polyester film as a base material, has the characteristics of high wiring density, light weight, thin thickness and good bending property, and makes the third welding point on the FPC correspond to the second welding point in space, realizes the correspondence of points on the plane, and solves the technical problem of insufficient pads requiring multi-layer wire bonding.

[0059] The photoelectric chip, chip pad and FPC board are in the same plane in space to realize the electrical connection of the chip pad and the FPC through the second welding point and the third welding point, and then realize the connection with the external PCB board through the wiring on the FPC. In this scheme, based on the advantage of multi-layer wiring of FPC, more pads can be arranged through reasonable layout of FPC pads, avoiding multi-layer wire bonding, solving the technical problem that the original device often needs to design complex multi-layer pad position due to insufficient single-layer pad position, and must be wire-bonded in multiple layers. Since the wire bonding is all on the pads of the FPC, the metal shell no longer needs to be made with external pins and internal electrodes, greatly reducing the manufacturing difficulty and cost of the metal shell. Therefore, the packaging technical difficulty is significantly reduced, and the packaging effect can integrate the common advantages of COB packaging and COC packaging, with the effects of short wire bonding distance, low cost, photoelectric integrated packaging, stable packaging structure, good heat dissipation performance, good airtightness and controllable process difficulty.

[0060] In another example, the photoelectric chip and the chip pad are respectively attached and arranged on the aluminum nitride pad, and then connected with the fixing groove through the aluminum nitride pad. In this scheme, the chip patch part of the photoelectric integrated packaging adopts the same way as the COC packaging, and the high-heat chip in the BOX is attached to the aluminum nitride (aluminum nitride is a kind of insulating high-thermal-conductivity material) pad. The heat of the chip can be well conducted through the aluminum nitride pad to ensure good heat dissipation performance of the chip in the packaging. Specifically, according to the easy processing characteristics of the FPC, a rectangular notch is designed according to the patch position to effectively avoid the aluminum nitride pad, so that the pad can be in contact with the shell to directly conduct the heat of the chip to the packaging metal shell.

[0061] In another example, the FPC adopts multi-layer wiring to match each third welding point on the FPC pad. In this scheme, the layout of the internal gold wire can match each third welding point, and there is no need to additionally set other connection gold wires to realize the connection of the photoelectric chip and the PCB. The reliability and stability of the device packaging are better.

[0062] The foregoing description is only one implementation of the present application. Many modifications and alterations of this design can become apparent to a person skilled in the art, without departing from the spirit and scope of the application.

[0063] The number of devices and the scale of processing illustrated herein are intended to simplify the description of the present application. Applications, modifications and variations of the present application will be apparent to those skilled in the art.

[0064] While the embodiments of the application have been disclosed as above, it is not limited to the applications listed in the specification and the embodiments. It can be applied to various fields suitable for the present application. Further modifications can be easily made by those skilled in the art. Therefore, the present application is not limited to the specific details and the figures shown and described herein. It is intended to cover the general concepts defined by the claims and their equivalents.

Claims

1. A high-speed optical device based on a flexible circuit board, comprising an optical device and a bottom case and a face case which encapsulate the optical device, the optical device comprising an optoelectronic chip, characterized in that, The bottom shell is provided with a sunken fixing groove on the mounting position matched with the optoelectronic chip; A flexible circuit board (FPC) is provided with a rectangular notch matched with the spatial position of the fixing groove; The optoelectronic chip and the chip pad matched therewith are arranged at the bottom of the fixing groove; The upper surfaces of the optoelectronic chip, the chip pad and the FPC are at the same height in space and are connected through the matched welding group; The welding group is configured to include: A plurality of first welding points arranged on the chip pad to realize the connection between the optoelectronic chip and the chip pad; A third welding point arranged on the chip pad to realize the connection between the chip pad and each second welding point on the FPC; The FPC is connected with external equipment through a plurality of gold wires matched with each second welding point thereon; The packaging method of the high-speed optical device includes: The optoelectronic chip and the chip pad matched therewith are fixedly arranged in the mounting groove, and the electrical connection between the optoelectronic chip and the chip pad is realized through the first welding point; The FPC is arranged on the bottom shell, and the position of the rectangular notch is matched with the outer edge of the fixing groove; The optoelectronic chip, the chip pad and the FPC are arranged in the same plane in space to realize the electrical connection between the chip pad and the FPC through the second welding point and the third welding point, and then realize the connection with the external PCB through the wiring on the FPC; The optoelectronic chip and the chip pad are respectively arranged on the aluminum nitride gasket, and then connected with the fixing groove through the aluminum nitride gasket; The FPC adopts multi-layer wiring to match each third welding point on the FPC pad.

2. The flexible circuit board based high speed optical device of claim 1, wherein, The optoelectronic chip and the chip pad are arranged at the bottom of the mounting groove through the matched aluminum nitride gasket, and then connected with the bottom shell.

3. The flexible circuit board based high speed optical device of claim 1, wherein, The FPC pad is further integrated with a patch capacitor, a magnetic bead and a thermistor.

4. The flexible circuit board based high speed optical device of claim 1, wherein, The extending end of the FPC is connected with the external PCB.

5. The flexible circuit board based high speed optical device of claim 1, wherein, The face shell is provided with a matched limiting groove at the extending end of the FPC.

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