Multi-channel optical chip packaging method and multi-channel optical module

Abstract

The present invention relates to the field of optical communication technology, and provides a multi-channel optical chip packaging method, comprising the following steps: preparing a plurality of EML chips and a ceramic substrate having a plurality of metal conductive channels; covering the ceramic substrate on the EML chip, and electrically connecting each of the metal conductive channels in the ceramic substrate to each EML chip; mounting each EML chip on a COC substrate and communicating with the COC substrate; setting a gold finger area of ​​a PCB board, electrically connecting the ceramic substrate to the gold finger of the PCB board, and communicating with the COC substrate to the gold finger of the PCB board. A multi-channel optical module is also included, and the EML chip is packaged using the above-mentioned multi-channel optical chip packaging method. The present invention supplies power to semiconductor laser chips of each channel or wavelength through the design of multiple conductive channels inside the ceramic substrate, thereby reducing the metal wire bonding steps under the multi-channel semiconductor laser COB packaging in the conventional mode and reducing the risk of gold wire breakage.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to a multi-channel optical chip packaging method and a multi-channel optical module. Background Art

[0002] With the increasing demand for cloud computing, AI computing power, 5G transmission, and other needs, the demand for infrastructure construction such as data centers and base stations is also increasing. The optical communication market represented by 400G / 800G and higher speeds has also entered a period of rapid development. In order to increase the transmission rate of a single optical module and meet the needs of high-density computing power and transmission, multiple semiconductor laser chips (EML chips) will be placed in an optical module, and the optical module will be miniaturized and packaged through multi-channel or multi-wavelength parallel solutions to reduce the cost of a single optical module and meet the functions of high-density, high-speed transmission and data exchange in different scenarios. As the core component with the highest cost and the most important performance in optical modules, semiconductor laser chips have always been the focus of major communication equipment manufacturers and network operators.

[0003] The traditional multi-channel or multi-wavelength parallel solution has a relatively simple packaging, which is to place the semiconductor laser chips of each channel or wavelength on the PCB board, and then use metal wire bonding to electrically connect the electrode area of ​​each semiconductor laser chip with the functional areas of the gold finger area of ​​the PCB board, so that each semiconductor laser chip works independently without affecting each other. Under this solution, as the number of channels or wavelengths increases, the space in the optical module required to place the semiconductor laser chip will also be larger, and because each semiconductor laser chip needs to be electrically connected to the gold finger area of ​​the PCB board by wire bonding, the number of wire bonding will also increase, and the space required for wire bonding will also increase. As time goes by, or the risks of movement and shaking of the optical module arise, once one or some gold wires break or collapse, it will cause short circuit or open circuit of some components in the optical module, and the optical module will therefore have the reliability risk of failure, causing immeasurable economic losses to equipment manufacturers or network operators. In the traditional multi-channel optical module packaging solution, multiple independent semiconductor laser chips are generally placed on the corresponding COC substrate, and then multiple COC substrates with semiconductor laser chips are placed on the PCB. The two placements take a lot of time, and there will be slight mechanical errors in the final positions, which creates great difficulties for the subsequent optical path coupling. Secondly, the relatively sealed space in the optical module is not conducive to the heat dissipation of multiple semiconductor laser chips working at the same time. The increase in ambient temperature will reduce the light output efficiency of the chip. Under this condition, in order to ensure the stable operation of each semiconductor laser chip and the unchanged output power, it is necessary to increase the injection current, thereby increasing the power consumption of the entire optical module. Summary of the invention

[0004] The object of the present invention is to provide a multi-channel optical chip packaging method and a multi-channel optical module, which can at least solve some of the defects in the prior art.

[0005] To achieve the above object, the embodiment of the present invention provides the following technical solution: a multi-channel optical chip packaging method, comprising the following steps:

[0006] preparing a plurality of EML chips and a ceramic substrate having a plurality of metal conductive channels;

[0007] Covering the ceramic substrate on the EML chip, and electrically connecting each of the metal conductive paths in the ceramic substrate to each of the EML chips;

[0008] Mounting each of the EML chips on a COC substrate and communicating with the COC substrate;

[0009] A PCB board is provided, so that the ceramic substrate is electrically connected to the gold finger area of ​​the PCB board, and the COC substrate is communicatively connected to the gold finger area of ​​the PCB board.

[0010] Furthermore, a whole chip array is taken out from the wafer, wherein the chip array includes each of the EML chips.

[0011] Furthermore, the COC substrate is a whole substrate.

[0012] Furthermore, each of the metal conductive channels corresponds to each of the EML chips one by one, and each of the metal conductive channels is electrically connected to the corresponding EML chip.

[0013] Furthermore, each of the EML chips has a light-emitting bar, and the metal conductive channel covers the light-emitting bar.

[0014] Furthermore, the EML chips are identical, and the light-emitting bars are arranged side by side in parallel, and the intervals between two adjacent light-emitting bars are equal.

[0015] Furthermore, a current injection electrode is provided on the surface of the ceramic substrate facing away from the EML chip, and the current input by the current injection electrode enters each of the metal conductive channels, and the current also flows to the gold finger area of ​​the PCB board.

[0016] Furthermore, a high-frequency signal channel is provided on the COC substrate, and the gold finger area of ​​the PCB board is communicatively connected with the EML chip through the high-frequency signal channel.

[0017] Furthermore, there are multiple high-frequency signal channels, and the electrodes of the EA part of each EML chip are communicatively connected to one of the high-frequency signal channels. The other parts on the COC substrate are GND, which is in contact with the negative electrode of the EML chip and is electrically isolated from each high-frequency signal channel.

[0018] An embodiment of the present invention provides another technical solution: a multi-channel optical module, comprising an EML chip, and the EML chip is packaged using the multi-channel optical chip packaging method described above.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: through the design of multiple conductive paths inside a ceramic substrate, power is supplied to semiconductor laser chips of each path or wavelength at the same time, reducing the need for multiple metal wire bonding steps under the conventional mode of multi-channel semiconductor laser COB packaging, reducing the risk of gold wire breakage, and due to the setting of the conductive path in the ceramic substrate, the thickness of the metal layer on the light-emitting bar is equivalently increased in the longitudinal direction, and the injected current is evenly distributed along the light-emitting bar of each semiconductor laser chip, increasing the heat dissipation area, thereby improving the electro-optical conversion efficiency of the semiconductor laser chip, and making the current density on a single semiconductor laser chip evenly distributed, reducing the probability of kink occurring in the LI output curve, thereby reducing the reliability risk of the semiconductor laser chip and making the semiconductor laser work more stably. At the same time, the packaging solution has a high degree of integration. The DFB part on the EML chip is no longer connected to the corresponding gold wire separately, so there is no need to set the corresponding gold wire welding points, so that multiple semiconductor laser chips can be designed and manufactured with a smaller size, and multiple EMLs can be placed closer and more compactly, thereby reducing the volume of the entire optical module, which is conducive to the miniaturization of a single optical module. At the wafer level of the semiconductor laser, the required number of semiconductor laser chips can be directly cut off at one time according to demand, thereby simplifying the manufacturing process of semiconductor laser chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of a traditional multi-channel optical module;

[0021] Figure 2 A schematic diagram of a chip array of a multi-channel optical module provided by an embodiment of the present invention;

[0022] Figure 3 A schematic diagram of electrical connections of a COC substrate and a chip array of a multi-channel optical module provided by an embodiment of the present invention;

[0023] Figure 4 A schematic diagram of a top view of a ceramic substrate of a multi-channel optical module provided by an embodiment of the present invention;

[0024] Figure 5A schematic diagram of a side view of a ceramic substrate of a multi-channel optical module provided by an embodiment of the present invention;

[0025] Figure 6 A schematic diagram of a ceramic substrate of a multi-channel optical module provided by an embodiment of the present invention when viewed from above;

[0026] Figure 7 A schematic diagram of electrical connection between a ceramic substrate and a chip array of a multi-channel optical module provided by an embodiment of the present invention (top view);

[0027] Figure 8 A schematic diagram of electrical connection between a ceramic substrate and a chip array of a multi-channel optical module provided by an embodiment of the present invention (side view);

[0028] Fig. 9 A schematic diagram of a multi-channel optical module provided by an embodiment of the present invention;

[0029] In the figure markings: 1-gold finger area of ​​PCB board; 2-gold finger at hot plug end; 3-gold finger at wire bonding end; 4-GND electrode of traditional COC substrate; 5-high frequency signal channel of traditional COC substrate; 6-traditional COC substrate; 7-DFB part of EML chip; 8-electrode of DFB part; 9-EA part of EML chip; 10-electrode of EA part; 11-light bar; 12-chip array; 13-COC substrate; 14-high frequency signal channel; 15-ceramic substrate; 16-current injection electrode; 17-metal conductive channel; 18-PCB board. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] See also Figures 2 to 9 The embodiment of the present invention provides a multi-channel optical chip packaging method, comprising the following steps: preparing a plurality of EML chips and a ceramic substrate 15 having a plurality of metal conductive channels 17; covering the ceramic substrate 15 on the EML chip, and electrically connecting each of the metal conductive channels 17 in the ceramic substrate 15 with the DFB portion of each of the EML chips; installing each of the EML chips on a COC substrate 13 and communicating with the COC substrate 13; setting a PCB board 18, electrically connecting the ceramic substrate 15 with the gold finger area 1 of the PCB board, and communicating with the COC substrate 13 with the gold finger area 1 of the PCB board. Figure 1 As shown, it is a traditional package, which involves a lot of wire bonding, is very complicated, and the size of the optical module is very large. In this embodiment, by introducing a ceramic substrate 15, the DFB parts of multiple EML chips are powered respectively through a plurality of metal conductive channels 17 of the ceramic substrate 15. The EML chip is an electro-absorption modulated laser chip, referred to as a laser chip. In this way, the metal wire bonding steps in the traditional package are reduced, and the volume of the optical module can be made smaller and smaller, which is conducive to the miniaturization of the optical module. The direction of the current and signal in this packaging method is: ceramic substrate 15, EML chip, COC substrate 13 and the gold finger area 1 of the PCB board. COC is the abbreviation of Chip on Carrier, which means that the chip is mounted on a carrier.

[0032] As an optimization solution of the embodiment of the present invention, please refer to Figures 2 to 9, a whole chip array 12 is taken from the wafer, and the chip array 12 includes each of the EML chips. In this embodiment, a chip array 12 can be cut from the wafer, and the chip array 12 can include a number of EML chips. The number of EML chips required can be selected for cutting according to the needs, so that an optical module with a certain number of channels can be obtained. For example, eight channels correspond to eight EML chips, eight metal conductive channels 17, and eight high-frequency signal channels 14, with high integration, and the more channels there are, the more obvious the advantages compared with the traditional solution. As shown in this embodiment, a four-channel optical module can be cut from the wafer containing a chip array 12 of four EML chips, which is more flexible, so that the chip array 12 can be placed on a COC substrate 13 as a whole, and then the COC substrate 13 is placed on the PCB board 18, so there are only two steps of placement, which reduces a lot of packaging process flow compared with the traditional solution, and the final position can almost be free of mechanical errors, which provides great convenience for subsequent optical path coupling. In addition, the COC substrate 13 can also be a whole substrate. Compared with the existing single multiple EML chips and single multiple COC substrates 13, the traditional multi-channel optical module packaging solution generally has multiple independent semiconductor laser chips each bonded and placed on the corresponding COC substrate 13, and then the multiple COC substrates 13 with semiconductor laser chips are bonded and placed on the PCB board 18. The two bonding and placement takes a lot of time, and there will be slight mechanical errors in the final positions, which causes great difficulties for the subsequent optical path coupling. Secondly, the relatively sealed space in the optical module is not conducive to the heat dissipation of multiple semiconductor laser chips working at the same time. The increase in ambient temperature will reduce the light output efficiency of the chip. Under this condition, if each semiconductor laser chip is to ensure stable operation and unchanged output power, it is necessary to increase the injection current, thereby increasing the power consumption of the entire optical module. The above defects can be completely solved by adopting the whole block structure of this embodiment. In addition, by adopting a whole ceramic substrate 15, the heat generated by the operation of the semiconductor laser chip can be transferred to the ceramic substrate 15, and a large area of ​​heat dissipation is performed, and the heat dissipation effect is better. In this way, the injected current can remain unchanged, the operation is more stable, and the power consumption of the entire optical module will not be increased. According to the actual number of channels required, a corresponding number of chips are directly cut from the wafer, formed into an array, and placed together on the entire COC substrate 13 and the PCB board 18, ensuring the accuracy of the position after placement, with almost no mechanical error, which greatly facilitates the subsequent optical path coupling.

[0033] As an optimization solution of the embodiment of the present invention, please refer to Figures 2 to 9, each of the metal conductive channels 17 corresponds to each of the EML chips one by one, and each of the metal conductive channels 17 is electrically connected to the DFB part of the EML chip corresponding to it. In this embodiment, the number of metal conductive channels 17 and the number of EML chips can be designed to be the same. For example, when four EML chips are used, four metal conductive channels 17 can be designed, each channel is a 100Gbps EML chip, and the four metal conductive channels 17 respectively supply power to the DFB parts of the four EML chips. The metal conductive channels 17 at the bottom of the ceramic substrate 15 are attached to and electrically connected to the light-emitting strips 11 of the DFB part at the top of the chip array 12.

[0034] As an optimization solution of the embodiment of the present invention, please refer to Figures 2 to 9, each of the EML chips has a light bar 11, and the metal conductive channel 17 covers the light bar 11. The EML chips are the same, and the light bars 11 are arranged side by side in parallel, and the spacing between two adjacent light bars 11 is equal. In this embodiment, the core part of the semiconductor laser chip is the light bar 11. Using this solution, there is no need to make electrodes for each chip (such as the existing electrodes 8 that require the DFB part), which can greatly shorten the size of each semiconductor laser chip, and achieve more chips on the same size wafer. In this way, the area occupied by the same multiple semiconductor laser chips is reduced, and each channel chip can be placed more compactly, which can make the entire optical module more compact, so that more optical modules can be inserted on the same switching device to meet the needs of high-density data transmission and exchange. At the same time, without the electrode 8 of the DFB part, it is not necessary to provide a current injection channel for the DFB part of each chip, which reduces the way of electrode bonding for electrical connection, reduces the risk of gold wire breakage, and improves the reliability of the entire optical module. In addition, since the chip array 12 is obtained by directly cutting along the crystal phase direction on the wafer, the spacing between the light strips 11 of each EML chip is completely equal, which greatly facilitates the optical path coupling after the light is emitted. In addition, the metal conductive channel 17 is covered on the light strip 11, and the metal conductive channel 17 inside the ceramic substrate 15 is directly bonded and electrically connected to the light strip 11 of the DFB part of each semiconductor laser chip. In principle, the thickness of the metal layer of the light strip 11 is equivalent to increasing, so that the heat dissipation effect of the semiconductor laser chip is better when working, so that the electro-optical conversion efficiency is higher, and the working current under the same power is reduced compared with the previous traditional solution, which greatly reduces the overall power consumption of the optical module. The same amount of current is injected and the optical power emitted is greater. If such a large optical power is not required, the size of the injected current can be reduced, thereby greatly reducing the power consumption of the entire optical module. Preferably, a large current injection electrode 16 is provided on the top of the ceramic substrate 15, and four metal conductive channels 17 are designed in the middle layer. The spacing between each metal conductive channel 17 is equal to the spacing between the light-emitting bars 11 of each EML chip, and the length and width dimensions of each metal conductive channel 17 are designed to be consistent with the length and width dimensions of the light-emitting bars 11 of the DFB part 7 of each EML chip.

[0035] As an optimization solution of the embodiment of the present invention, please refer to Figures 2 to 9, a current injection electrode 16 is provided on the surface of the ceramic substrate 15 facing away from the EML chip, and the current input by the current injection electrode 16 enters each of the metal conductive channels 17, and the current also flows to the gold finger area 1 of the PCB board. In this embodiment, the electrode on the top of the ceramic substrate 15 is used as the only current injection channel, and the number of gold fingers used to inject current on the gold finger area 1 of the PCB board can also be reduced, thereby optimizing the design of the gold finger area 1 of the PCB board and the PCB board 18. The current is injected by the current injection electrode 16 on the top of the ceramic substrate 15, and the current is evenly distributed to the four metal conductive channels 17 inside the ceramic substrate 15, and the same amount of current is injected into the corresponding light-emitting strips 11 of the DFB part of the EML chip. The EA part 9 of each EML chip is independent of each other and can be modulated separately to obtain the modulation effect required for each channel.

[0036] As an optimization solution of the embodiment of the present invention, please refer to Figures 2 to 9 , a high-frequency signal channel 14 is provided on the COC substrate 13, and the gold finger area 1 of the PCB board is connected to the EML chip through the high-frequency signal channel 14. Preferably, there are multiple high-frequency signal channels 14, and the electrodes of the EA part 9 of each EML chip are connected to one of the high-frequency signal channels 14, and the other parts on the COC substrate 13 are GND, which is connected to the negative electrode of the EML chip and is electrically isolated from each high-frequency signal channel 14. In this embodiment, four high-frequency signal channels 14 can be designed on the COC substrate 13, which are connected to four EML chips respectively.

[0037] See also Figures 2 to 9 The embodiment of the present invention provides a multi-channel optical module, including a PCB board 1 and a plurality of laser chips, and also includes a ceramic substrate 15 having a plurality of metal conductive channels 17, wherein the ceramic substrate 15 covers each of the laser chips, and each of the metal conductive channels 17 is electrically connected to the laser chip, and the signal of each of the laser chips is output to the gold finger area 1 of the PCB board. In this embodiment, the ceramic substrate 15 is introduced, and then the DFB part of the EML chip is powered through the plurality of metal conductive channels 17 of the ceramic substrate 15. The EML chip is an electro-absorption modulated laser chip, referred to as a laser chip. In this way, the DFB part of the EML chip no longer requires metal bonding in traditional packaging, and the volume of the optical module can also be made smaller and smaller, which is conducive to the miniaturization of the optical module. The multi-channel optical module is encapsulated and manufactured using the above method.

[0038] As an optimization solution of the embodiment of the present invention, please refer to Figures 2 to 9Each of the laser chips is integrated on the chip array 12, that is, a whole chip array 12 is used, which can be directly removed from the wafer. The number of laser chips is selected according to needs. The laser chip here is the above-mentioned EML chip.

[0039] As an optimization solution of the embodiment of the present invention, please refer to Figures 2 to 9 , the ceramic substrate 15 is electrically connected to the gold finger area 1 of the PCB. In this embodiment, the PCB 1 can also supply power to the ceramic substrate 15. Specifically, the power can be supplied through the current injection electrode 16 thereof.

[0040] As an optimization solution of the embodiment of the present invention, please refer to Figures 2 to 9 Each of the metal conductive channels 17 is built into the ceramic substrate 15, and the current injection electrode 16 is disposed on the surface of the ceramic substrate 15 away from the EML chip. For example, there are four metal channels connected through the current injection electrode 16.

[0041] As an optimization solution of the embodiment of the present invention, please refer to Figures 2 to 9 The laser chip includes an EA part 9 of the EML chip and a DFB part 7 of the EML chip. A hot-swap end gold finger 2 and a bonding end gold finger 3 are provided on the gold finger area 1 of the PCB board, one of the bonding end gold fingers 3 is electrically connected to the current injection electrode 16, and the other bonding end gold fingers 3 are electrically connected to each high-frequency signal channel 14. The high-frequency signal channel 14 is electrically connected to the electrode 10 of the EA part.

[0042] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A multi-channel optical chip packaging method, characterized in that: The steps include: preparing a plurality of EML chips and a ceramic substrate having a plurality of metal conductive channels; The ceramic substrate is covered on the EML chip, and each of the metal conductive channels in the ceramic substrate is electrically connected to each of the EML chips; each of the EML chips has a light-emitting bar, and the metal conductive channel is covered on the light-emitting bar, and is directly bonded and electrically connected to the light-emitting bar of the DFB part of each semiconductor laser chip through the metal conductive channel inside the ceramic substrate; Mounting each of the EML chips on a COC substrate and communicating with the COC substrate; Setting a gold finger area of ​​the PCB board so that the ceramic substrate is electrically connected to the gold finger of the PCB board, and the COC substrate is communicatively connected to the gold finger area of ​​the PCB board; Only one current injection electrode is provided on the surface of the ceramic substrate away from the EML chip, and the current input by the current injection electrode enters each of the metal conductive channels respectively, and the current also flows to the gold finger area of ​​the PCB board; The COC substrate is provided with a high-frequency signal channel, and the gold finger area of ​​the PCB board is connected to the EML chip through the high-frequency signal channel. There are multiple high-frequency signal channels, and the electrode of the EA part of each EML chip is connected to one of the high-frequency signal channels. The other parts on the COC substrate are GND, which is connected to the negative electrode of the EML chip and is electrically isolated from each high-frequency signal channel; the DFB part of the EML chip does not require metal bonding; A plurality of EML chips form a chip array; the chip array as a whole is bonded and placed on a COC substrate, and the COC substrate is then bonded and placed on a PCB board.

2. The multi-channel optical chip packaging method according to claim 1, characterized in that: A whole chip array is taken out from the wafer, wherein the chip array includes each of the EML chips.

3. The multi-channel optical chip packaging method according to claim 1, characterized in that: The COC substrate is a whole substrate.

4. The multi-channel optical chip packaging method according to claim 1, characterized in that: Each of the metal conductive channels corresponds to each of the EML chips one by one, and each of the metal conductive channels is electrically connected to the corresponding EML chip.

5. The multi-channel optical chip packaging method according to claim 1, characterized in that: The EML chips are identical, and the light-emitting bars are arranged side by side in parallel, and the spacing between two adjacent light-emitting bars is equal.

6. A multi-channel optical module, comprising an EML chip, characterized in that: The EML chip is packaged using the multi-channel optical chip packaging method as described in any one of claims 1 to 5.

Images