KR20010000039A - Architecture of a free-space optical interconnection module - Google Patents

Abstract

PURPOSE: A structure of a free-space optical interconnection module is provided to improve a heat emission characteristic in a free-space optical interconnection module. CONSTITUTION: A structure of a free-space optical interconnection module comprises an optical transmission module(10) and an optical reception module(20). The optical transmission module(10) comprises the first copper substrate(11), a surface emission laser array(12), a laser array drive circuit(13), the first interconnection wiring(14), and the second interconnection wiring(15). The optical reception module(20) comprises the second copper substrate(21), an optical detection array(22), an optical receiving circuit(23), the third interconnection circuit(24), and the fourth interconnection circuit(25).

Description

ARCHITECTURE OF A FREE-SPACE OPTICAL INTERCONNECTION MODULE}

The present invention relates to a structure of a free space optical connection module, and more particularly, to a structure of a free space optical connection module which can be manufactured at low cost and has excellent heat emission characteristics.

In general, the optical connection method uses an optical fiber ribbon, an optical waveguide, a free space, or the like in the channel part according to its application. Of these, free-space optical connections are used for short-range connections between chips or boards, and the packaging cost of modules takes up a large portion of the costs for manufacturing such optical connection modules. Therefore, in order to reduce the manufacturing cost of the optical connection module, it is essential to reduce the cost of the optical packaging.

On the other hand, as the optical alignment method in the above-described optical packaging process, there are an active alignment method and a passive alignment method. First, an active alignment method for aligning while driving a laser has an advantage of performing precise optical alignment, but the packaging module Its size is relatively large, and it takes a lot of time to align the light, which is accompanied by an excessive cost. On the other hand, manual alignment is a method of performing optical alignment without driving an optical element, which simplifies the assembly process and improves the processing speed, thereby reducing the module price. The disadvantage is that it is difficult.

Therefore, various optical or mechanical methods are currently being developed for such optical alignment, in which the mechanical tension of the surface of the solder bump arrays using precision micromachining or solder bumps is used to precisely fit each piece. There is a way to ensure that the correct position by. On the other hand, the alignment using the optical method uses an alignment mark as a similar method to aligning the photomask in a lithography process, which requires an expensive and precise stage for alignment.

Comparing the two methods described above, the mechanical alignment method does not require expensive optical components or stages for precise alignment because the precision depends on the precise manufacture of each device to be aligned. On the contrary, the optical alignment method has an advantage that precision is determined by the optical component or the stage of the alignment device and does not require precise manufacturing of each device. Therefore, a key requirement for reducing the manufacturing cost of optical modules is the low cost optical axis alignment technology with precision.

On the other hand, when fabricating an optical connection module, this method is mainly used because the current method of combining the respective optical components and circuit chips in a hybrid has an advantage over monolithic integration in terms of price performance. . Factors that determine the performance of the fabricated optical coupling module vary, but in particular, the laser diode light source, etc., heat generation has a great influence on the performance. Currently, mount materials such as diamond and alumina are used as optical devices, and a separate TEC (ThermoElectric cooler) for heat dissipation and temperature stabilization is provided.

When fabricating a free space optical connection module in a hybrid manner, in the conventional method, an optical device chip is bonded to a substrate, and a circuit chip is bonded to another substrate, and then the connection between the two devices is connected by a bonding wire or on the same substrate. After the two chips are bonded, they are connected by bonding wires. In this case, the height of each chip is different so that the bonding wire is disturbed when the transmitting module and the receiving module are packaged in close proximity. In addition, when using a microlens to collect the beam from the transmission module, because of this bonding wire, a separate lens support must be provided to fix and fix the microlens at an appropriate distance.

In addition, a sufficient ground area must be secured for stable operation of devices entering the transmitting and receiving modules, and sufficient space for grounding must be secured on the substrate.

As a result, the most important factors to consider when fabricating free-space optical interconnect modules are the light alignment and heat dissipation issues. And, when optical devices are used to replace or additionally use existing electronic devices, the problem is price rather than performance. Therefore, to reduce the cost of light alignment and heat dissipation, there is a need for a solution to both of these problems.

Therefore, the present invention has been made to solve the above problems of the prior art, the lower substrate of the transmission and reception module of the free-space optical connection device is a copper substrate processed instead of the alumina (diamond) or diamond substrate which is mainly used conventionally By using a substrate coated with DLC (Diamond- Like Carbon), the object is to provide a free space optical connection module structure with excellent heat dissipation and grounding properties.

The present invention for achieving the above object, in the free space optical connection module structure, a first copper substrate for forming an optical element, a surface emitting laser array formed on the first copper substrate, and formed on the first copper substrate And a laser array driving circuit for driving the surface emitting laser array, a first connection wiring for interconnecting the surface emitting laser array and the laser driving circuit, and a second connection for external input / output of the laser array driving circuit. An optical transmission module composed of wiring; A second copper substrate for forming an optical element, a photodetecting array formed on the second copper substrate, for detecting light output from the surface emitting laser array of the optical transmission module, and formed on the second copper substrate; An optical receiving module comprising an optical receiving circuit for receiving the detected light, a third connecting wiring for interconnecting the light detecting array and the optical receiving circuit, and a fourth connecting wiring for external input / output of the optical receiving circuit It provides a free space optical connection module structure comprising a.

1 is a cross-sectional view of a free space optical connection module according to an embodiment of the present invention;

2 is a view illustrating a process of forming each connection wiring of the optical connection module shown in FIG. 1 by using a flat metal thin film;

3 is a view illustrating an optical transmitting module or an optical receiving module in which each connection wiring is formed using wire bonding;

4 is a view showing the structure of a light transmitting module or a light receiving module for a two-dimensional array;

FIG. 5 illustrates a microlens array of the optical coupling module shown in FIG. 1. FIG.

<Explanation of symbols for main parts of drawing>

11, 21: copper substrate 12: surface emitting laser array

13: laser array drive circuit 14, 24: first connection wiring

15, 25: second connection wiring 22: light detection array

23: optical receiving circuit 26: micro lens array

The above and other objects and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings.

First, the core technical aspect of the present invention is to solve the problem of heat dissipation of the optical component, in general, using an expensive diamond substrate or an alumina substrate, and additionally using a TEC (thermoelectric cooler) In contrast, by coating DLC (Diamond-Like Carbon) with an insulating film on a copper substrate and using it as a substrate of the optical transmission and reception module, it is possible to use the excellent heat dissipation characteristics of copper and at the same time can be manufactured at low cost.

In addition, it is important to sufficiently secure the ground area in order to reduce the noise characteristics of the optical connection module. To this end, in the present invention, the entire substrate can be used as the ground by using a copper substrate, and a connection wiring for inter-device or external input / output is provided. The use of wire bonding or metal deposition facilitates packaging and light alignment. In addition, the optical transmission and reception module can be optically aligned by a manual alignment method for free space optical connection, thereby reducing the time and cost required for optical alignment.

On the other hand, in connection with the present invention, the general thermal conductivity of copper is 0.94 cal / cm-sec- ° C, about 1/5 of diamond and about 20 times of alumina. Therefore, when utilizing such a copper as a substrate it is possible to obtain a high heat dissipation effect at low cost.

In addition, the DLC provides excellent adhesion to the copper substrate and can be coated by a simple process, so that the DLC is used as an insulating film on the upper copper substrate. The thermal conductivity of this DLC coating is also very good at about 0.9 cal / cm-sec- ° C. Therefore, the structure using the copper coated with DLC as a substrate can provide excellent thermal characteristics to the optical transmission / reception module in which heat emission problem is an important factor.

In addition, one of the other important electrical characteristics in the optical transmission and reception module is the problem of how successful grounding, this can also be efficiently solved by using the material and composition proposed in the present invention. In addition, since the lower substrate material copper itself is a conductive material, the entire substrate can be used as a ground.

Therefore, in the present invention, by using a DLC coated copper substrate which is only about 1/5 of diamond, but can be manufactured at low cost, it is possible to obtain very excellent heat dissipation characteristics by using the high thermal conductivity of copper.

In addition, in the present invention, the low processability of ceramic substrates such as alumina can be used as an optical alignment substrate for manual alignment of the transmission / reception module by using copper, which is a metal material that can be easily processed, and the surface is flattened by processing the copper substrate. In order to facilitate the packaging of the transmitting module and the receiving module in close proximity, a free space optical connection module using the same is provided.

Hereinafter, a free space optical connection module structure according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of a structure of a free space optical connection module according to a preferred embodiment of the present invention, wherein a copper substrate 11, a surface emitting laser array 12, a laser array driving circuit 13, The optical transmission module 10 including the first connection wiring 14 and the second connection wiring 15, the copper substrate 21, the light detection array 22, the light receiving circuit 23, and the first connection wiring 24. ), A light receiving module 20 composed of a second connection wiring 25, and a micro lens array 26.

Each of the copper substrates 11 and 21 provided in the optical transmission module 10 and the optical reception module 20 shown in FIG. 1 is used to fabricate the optical transmission module 10 and the optical reception module 20 in a hybrid manner. As a substrate, a conventional copper substrate is processed and then produced by coating DLC (Damond-Like Carbon) with an insulating film.

First, referring to FIG. 1, a manufacturing process of an optical transceiver module substrate in a free space optical connection module according to the present invention will be described. A groove is formed on a conventional copper substrate and a DLC is coated for insulation. The insulating film is coated only on the remaining part except the part to be grounded. The surface emitting laser array 12 and the laser array driving circuit 13 are mounted on the light transmitting module 10, and the light receiving module 20 is mounted with the light detecting array 22 and the light receiving circuit 23. Make it flat.

Then, between the surface emitting laser array 12 and the laser array driving circuit 13 of the light transmitting module 10 shown in FIG. 1, and the light detecting array 22 and the light receiving circuit of the light receiving module 20. Each of the first connection wires 14 and 24 between the two lines 23 is formed, and each of the second connection wires 15 and 25 is connected to the laser array driving circuit 13 and the light receiving circuit 23 for external input / output. In this case, each of the first connection wirings 14 and 24 and each of the second connection wirings 15 and 25 are formed using wire bonding or metal deposition.

2 is a view illustrating a structure of an optical transmission module (or receiving module) in which each connection wiring is formed using a flat metal thin film. The optical transmission module 10 and the optical receiving module 20 according to the present invention are Since their structures are the same, only one module is shown below as an example.

Referring to FIG. 2, first, each of the copper substrates 11 and 21 is machined for metal deposition, and the copper substrates 11 are flattened to have a constant height when optical devices are mounted, and each copper substrate 11 coated with an DLC with an insulating film. And the surface emitting laser array 12 and the laser array driving circuit 13 and the photodetecting array 22 and the light receiving circuit 23 are respectively formed in the first and second connection wirings 14 by metal deposition. , 24) and second connection wirings 15 and 25 are formed.

3 is a diagram illustrating an optical transmission module or an optical reception module in which the first connection wirings 14 and 24 and the second connection wirings 15 and 25 are formed using wire bonding. Referring to FIG. The process of forming each connection wiring using wire bonding is as follows.

First, each of the second connection wirings 15 and 25 for external input / output is deposited on the processed copper substrates 11 and 21 coated with DLC as an insulating film in the light transmitting module 10 or the light receiving module 20. . And wire bonding each of the first connection wires 14 and 24 for connecting the surface emitting laser array 12 and the laser array driving circuit 13 or between the photodetecting array 22 and the light receiving circuit 23. Next, a pad connection wiring 31 for connecting the pad portion of each of the second connection wirings 15 and 25 to the pad portion of the laser array driving circuit 13 and the light receiving circuit is formed by wire bonding. .

On the other hand, Figure 4 is a view showing the structure of a light transmitting module or a light receiving module for a two-dimensional array.

Referring to FIG. 4, an N × N surface emitting laser array 12 in the case of an optical transmission module 10 on a DLC coated processed copper substrate 11 and 21 as a structure using an N × N two-dimensional light source or a photodetector array. And a 1 × M laser array driving circuit 13, and in the case of the optical receiving module 20, the N × N light detecting array 22 and the 1 × M optical receiving circuit 23 are connected to the respective copper substrates 11, Bond to the groove of 21). In addition, the method of forming each of the connection wires 14, 24, 15, and 25 illustrated in the same drawing may be formed using the method using the metal thin film shown in FIGS. 2 and 3 or the wire bonding.

On the other hand, the microlens array 26 shown in FIG. 1 is used for efficient optical coupling between the light transmitting module 10 and the light receiving module 20. FIG. 5 shows the microlens array 26 shown in FIG. ) Shows the structure of a 1xN microlens array 26 composed of N microlenses 25-1, 25-2, ..., 25-n. At this time, the pitch distance of the micro lens array 26 is configured to be the same as the pitch of the surface emission laser array 12.

Since the optical transmission module 10 and the optical reception module 20 configured as described above are capable of optical transmission and reception between each other only by precise alignment, the optical transmission module 10 and the optical reception module 20 are aligned. The process for making it necessary is necessary, and the manual alignment process of the optical transmission module 10 and the optical reception module 20 will be described as follows.

First, the surface emitting laser array 12 and the laser array driving circuit 13 are mounted on the optical transmission module 10, and the optical detection array 22 and the optical receiving circuit 23 are mounted on the optical receiving module 20. After processing to ensure that the height of the surface of each device and the upper surface of the substrate is the same, and then forming the alignment mark for manual alignment in the process of depositing each connection wiring (14, 24, 15, 25) at the same time.

In addition, in order to align the micro lens array 26, first, an alignment mark for aligning the lenses of the micro lens array 26 to the light transmitting module 10 and the light receiving module 20 is formed together with the connection wiring deposition. . Then, the micro lens array 26 is aligned with the optical transmission module 10 and then fixed, thereby fixing the entire module by aligning the alignment marks engraved on the optical transmission module 10 and the optical reception module 25 to each other. .

As a result, in the optical connection module structure according to the present invention, by using the substrates 11 and 21 coated with DLC on the processed copper substrate to form a free space optical connection module, the heat dissipation characteristics and the grounding characteristics can be improved. Can be.

As described above, according to the present invention, unlike the conventional method using an expensive diamond substrate or an alumina substrate and using TEC to solve the heat dissipation problem of the optical component, the substrate by coating the DLC with an insulating film on the copper substrate By using it, there is an effect that can use the excellent heat dissipation characteristics, there is an effect that can significantly reduce the manufacturing cost. In addition, there is an effect to secure a sufficient ground area to reduce the noise characteristics of the optical connection module, the packaging and optical alignment by using a bonding wire (bonding wire) or metal deposition between the devices or for external input and output This has an easy effect. In addition, it is possible to reduce the time and cost required for optical alignment by additionally enabling the optical alignment of the transmission and reception modules for a free space optical connection by a manual alignment method.

Claims (4)

In the free space optical connection module structure, A first copper substrate for forming an optical device, a surface emitting laser array formed on the first copper substrate, a laser array driving circuit formed on the first copper substrate and driving the surface emitting laser array, and the surface emitting An optical transmission module comprising a first connection wiring for interconnecting a laser array and the laser driving circuit, and a second connection wiring for external input / output of the laser array driving circuit; A second copper substrate for forming an optical element, a photodetecting array formed on the second copper substrate, for detecting light output from the surface emitting laser array of the optical transmission module, and formed on the second copper substrate; An optical receiving module comprising an optical receiving circuit for receiving the detected light, a third connecting wiring for interconnecting the light detecting array and the optical receiving circuit, and a fourth connecting wiring for external input / output of the optical receiving circuit Free space optical connection module structure comprising a. The free space optical connection module structure of claim 1, wherein the free space optical connection module structure includes a micro lens array disposed between the surface emitting laser array and the light detection array to increase optical coupling efficiency. The free space optical connection module structure of claim 1, wherein the first, second, third, and fourth connection wirings are formed by metal deposition. The method of claim 1, wherein the first and second copper substrates are coated with a diamond-like carbon (DLC) insulating film, and each optical device is bonded to each other, and a hole is formed in a portion of the DLC insulating film to form the copper substrate as a grounding means. Free space optical connection module structure, characterized in that.