JP2007333912A - Optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module that has a CAN packaging structure and that enables mounting by a passive alignment method. <P>SOLUTION: The optical module includes a sleeve for guiding a ferrule of an optical connector, a stub 5 for optical coupling to the ferrule, a stem 3 for mounting a PD 6 and a TIA 7, and a cap for sealing the PD6 and the TIA 7. The stub 5 is connected to the stem 3 in a hermetically sealable structure, making the PD6 mounted on a face opposite from the ferrule side of the stub 5. On the side for mounting an optical device of the stub 5, there is provided a marking M for mounting the optical device by metallization. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical module that is mounted by a passive alignment method and can be hermetically sealed.

  Conventionally, an active alignment method and a passive alignment method are known as alignment methods for optical coupling between an optical fiber and a semiconductor optical device. In the former active alignment method, in order to determine the optimum positional relationship between the optical device and the optical fiber, alignment is performed while monitoring the output. The core diameter of the semiconductor laser, photodiode, planar waveguide, etc. is 9 μm. It is suitable for optically coupling optical fibers of the order of magnitude on the order of microns and submicrons. However, it takes a considerable amount of time to detect the maximum output and coupling, and the alignment device is also required to be expensive with high accuracy. In addition, after fixing the optical coupling, position fixing adhesion and welding are performed, but it is necessary to satisfy the requirements of ensuring the mechanical strength and precision fixing. It was.

  On the other hand, the latter passive alignment method performs alignment by mechanical positioning without monitoring the output, and is easy to automate. This passive alignment method can be mounted in a shorter time than the active alignment method.

  In an optical module that optically couples an optical device and an optical fiber, it is required to reduce the manufacturing cost and the manufacturing equipment cost and to assemble efficiently. For this reason, the passive alignment method is becoming the mainstream as an alignment method for optical coupling instead of the active alignment method.

  However, in an optical module using a general passive alignment method, a bench (silicon bench or glass bench) having a V-shaped groove for positioning an optical fiber, or a package (ceramics) for ensuring the airtightness of an optical device. Parts). Compared with a CAN package (coaxial package) that is frequently used in an optical module that employs an active alignment method, these components have a problem of an increase in cost of a single component.

  In order to ensure the airtightness of the optical device, the existing sealing technology (sealing method by projection welding of the metal package) is established for the CAN package, but the seam welding of the lid part to the box-shaped package is performed for the ceramic package. Although methods such as sealing by resin, sealing by resin bonding (adhesive) of ceramic parts, and resin sealing by transfer mold are being studied, all have advantages and disadvantages, and a structure that can achieve both manufacturability and airtightness has not been achieved. .

  As an example of a conventional optical module using passive alignment, for example, in Patent Document 1, an optical device and an optical fiber are positioned by a substrate and a lid, which are ceramic packages, and hermetic sealing is performed by a thermoplastic resin. An optical assembly is described and the positioning of the optical device and the optical fiber is performed on the substrate.

  Patent Document 2 describes an optical module formed by setting a semiconductor substrate on which a semiconductor laser (optical device) is mounted on an end face of a metal ferrule on which an optical fiber is mounted.

Patent Document 3 describes an optical module in which a rear portion of a capillary on which an optical fiber is mounted is cut and a photodiode (optical device) is mounted on that portion.
JP-A-8-166523 JP 2004-101996 A JP 2004-191794 A

  However, in the structure described in Patent Document 1, the work of mounting the optical device on the substrate and the work of setting the optical fiber on the substrate are necessary, so the mounting workability in passive alignment is poor. Further, since the hermetic sealing of the optical module with respect to the optical device is performed by the resin, there is a problem in long-term reliability.

  Further, in the structure described in Patent Document 2, it is difficult to ensure the airtightness of the optical device, and it is necessary to form a groove on the side surface of the metal ferrule that serves as a main package for forming the optical module and to attach an electrode wire. And manufacturability is poor. In consideration of use as a light receiving module, it is desirable to mount a TIA (Trans Impedance Amplifier), which is a device component, in the vicinity of the light receiving element, but this package structure makes it difficult.

  Further, with the structure described in Patent Document 3, it is difficult to ensure the airtightness of the optical device. Further, when considering the coupling between the optical module and the optical fiber, the outer diameter of the capillary is preferably equal to the outer diameter of the ferrule of the optical connector, which is φ1.25 mm or φ2.50 mm. It is necessary to process the back part of the capillary and form an electrode for such a part, which is also inferior in manufacturability.

  As described above, the conventional techniques including the above-mentioned Patent Documents 1 to 3 cannot achieve both the manufacturability and airtightness of the optical module using passive alignment.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical module having a CAN package structure and capable of being mounted by a passive alignment method.

  An optical module according to the present invention is an optical module for receiving an optical connector having an optical fiber and a ferrule attached to the tip of the optical fiber, the optical device optically coupled to the optical fiber, and the ferrule. A sleeve; a stub that is optically aligned with the ferrule and optically coupled to the optical fiber at one end; a stem on which the optical device is mounted; and a cap that seals the optical device in a space between the stem. The stub penetrates the stem while hermetically sealing the space, and mounts the optical device on the surface opposite to one end of the stub. Moreover, marking for mounting an optical device may be metallized on the optical device mounting surface side of the stub.

According to the present invention, since the CAN package structure is provided and mounting by the passive alignment method is possible, the existing technology, projection welding, can be used to secure the airtightness of the optical device. An optical module can be manufactured using the equipment.
In addition, alignment (that is, active alignment method) while monitoring the optical power becomes unnecessary, and an optical module can be manufactured by a semiconductor mounting machine.

  Hereinafter, preferred embodiments of an optical module according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a perspective view showing an example of a stem assembly provided in the optical module of the present invention, and FIGS. 2A and 2B are sectional views of the stem assembly. In the figure, 1 is an optical fiber, 2a is a stub sealing glass, 2b is a lead sealing glass, 3 is a stem, 4a is a case lead, 4b is an isolated lead, and 5 is a stub. Hereinafter, the case lead 4 a and the isolated lead 4 b are collectively referred to as a lead 4.

  As shown in FIGS. 1 and 2, the optical module according to the present invention is configured by a CAN package, and includes optical devices such as LD (Laser Diode) and PD (Photo Diode), LDD (Laser Diode Driver) and TIA. A lead 4 for electrical connection and a stub 5 for optical connection are mounted on a stem 3 having a space for mounting device components.

  Since the lead 4 needs to be electrically insulated from the stem 3, the lead 4 is glass-sealed with lead-sealing glass 2b. The stub 5 is mounted on the stem 3 with the optical fiber 1 at the center. Since the connection between the stub 5 and the stem 3 only needs to ensure airtightness, in addition to the connection by glass sealing with the stub sealing glass 2a, for example, connection by resin adhesion or connection by solder glass or the like is also possible.

  Each component of the stem 3 and the lead 4 is made of, for example, an iron-based alloy because electrical connection is required. The stem 3 and the lead 4 are sealed with a glass material for hermetic sealing, but it is necessary to select an appropriate material in order to prevent the hermetic sealing from being broken due to a difference in the linear expansion coefficient of the material. . In the existing technology, there are a matched seal using a low linear expansion material such as KOVAR, and a compression seal using a normal iron-based material such as SPC. Each metal part is plated with Au in order to eliminate the influence of oxidation or the like. By wire plating with Au, wire bondability is also improved.

  Since the stub 5 is fitted with an optical connector (not shown), the resistance (hardness) of the end face on the optical connector side is important. Therefore, it is desirable to use the same zirconia or crystallized glass as the ferrule of the optical connector. In addition to this, it is also possible to use a glass ferrule such as a ferrule made of Ni or borosilicate glass.

  FIG. 3 is a diagram illustrating an example of a state in which the optical device component is mounted on the stem assembly. 3A is a perspective view, and FIG. 3B is a top view. In the figure, 6 is a PD (photodiode), 7 is a TIA, and M is a marking for mounting an optical device.

  As shown in FIG. 3, the PD 6 as an optical device and the TIA 7 as a device part are mounted on the stub 5, and wire bonding connection is used for each electrical connection. Device parts such as TIA 7 are mounted on the outer peripheral side of the stem 3, and are mounted on the stem 3 with a solder material.

  Optical device components such as PD6 are mounted by a passive alignment method by matching the position of an optical fiber (not shown) in stub 5 with the position of the light receiving surface of PD6. As a mounting method, for example, a marking M by metallization may be performed on the mounting side end surface of the stub 5 in advance, and positioning may be performed by self-alignment with a solder material used for mounting the PD 6. Alternatively, the optical fiber and the light receiving surface of the PD 6 may be positioned by image recognition and then fixed with a thermosetting resin, an ultraviolet curable resin, or the like.

  In this way, the optical fiber and the PD 6 in the stub 5 are aligned by the passive alignment method, and the PD 6 is hermetically sealed by projection welding the stem 3 and a cap shown in FIG. 4 described later. .

  In consideration of optical coupling with the optical fiber, it is desirable that the mounted PD 6 has a smaller distance between the end face of the optical fiber and the PD light receiving surface. In this case, the back side light receiving type PD is mounted with the back side facing the stub 5. However, the surface light receiving type may be used by taking into consideration the spread of light from the end face of the optical fiber (aperture index), the refractive index of the substance that propagates the light, the PD die size (thickness), and the PD light receiving diameter.

  FIG. 4 is a diagram illustrating an example of a state after the hermetic sealing of the optical module of the present invention. 4A is a perspective view, and FIG. 4B is a partial cross-sectional perspective view. In the figure, 8 indicates a cap. As a method of hermetic sealing of the optical device components, the cap 8 may be fixed to the stem 3 by using projection welding adopted in the CAN package. In this way, since the optical module has a CAN package structure, projection welding, which is an existing technology, can be used. Therefore, it is not necessary to newly prepare a sealing facility in accordance with the structural change of the optical module.

  FIG. 5 is a view showing an example of a state in which a sleeve is mounted and an optical fiber ferrule guide is provided. 5A is a side view, and FIG. 5B is a cross-sectional view. In the figure, 9 indicates a sleeve. The sleeve 9 shown here is an integral sleeve formed by metal cutting, but may be other sleeves, such as a zirconia split sleeve, a zirconia or crystallized glass precision sleeve, or the like. It may be used.

  As shown in FIG. 5, the optical module according to the present invention receives an optical connector having an optical fiber and a ferrule attached to the tip of the optical fiber, and an optical device optically coupled to the optical fiber. , A sleeve 9 for receiving the ferrule of the optical connector, a stub 5 optically aligned with the ferrule and optically coupled to the optical fiber at one end, a stem 3 for mounting an optical device or device component, an optical device, And a cap 8 for sealing the device component in the space between the stem 3. The stub 5 penetrates the stem 3 while hermetically sealing the space, and an optical device is mounted on a surface opposite to the one end (ferrule side) of the stub 5.

  FIG. 6 is a diagram illustrating an example of a connection state with an FPC board when used as an optical module. 6A is a side view and FIG. 6B is a perspective view. In the figure, 10 indicates a solder connection and 11 indicates an FPC. The optical module of the present invention can be connected to the FPC 11 made of an easily handled polyimide film or the like by the solder connection 10.

As described above, according to the present invention, since the CAN package structure is provided and mounting by the passive alignment method is possible, the projection welding which is the existing technology can be used to ensure the airtightness of the optical device, and the reliability is improved. And an optical module can be manufactured using existing equipment.
In addition, alignment (that is, active alignment method) while monitoring the optical power becomes unnecessary, and an optical module can be manufactured by a semiconductor mounting machine.

It is a perspective view which shows an example of the stem assembly with which the optical module of this invention is provided. FIG. 6 is a cross-sectional view of a stem assembly. It is a figure which shows an example of the state which mounted the optical device component in the stem assembly. It is a figure which shows an example of the state after airtight sealing of the optical module of this invention. It is a figure which shows an example in which the sleeve is mounted and the ferrule guide of the optical fiber is provided. It is a figure which shows an example of a connection state with the FPC board | substrate when using as an optical module.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical fiber, 2a ... Stub sealing glass, 2b ... Lead sealing glass, 3 ... Stem, 4a ... Case lead, 4b ... Isolated lead, 5 ... Stub, 6 ... PD, 7 ... TIA, 8 ... Cap, 9 ... Sleeve, 10 ... Solder connection, 11 ... FPC.

Claims (2)

An optical module for receiving an optical connector having an optical fiber and a ferrule attached to the tip of the optical fiber,
An optical device optically coupled to the optical fiber;
A sleeve for receiving the ferrule;
A stub optically aligned with the ferrule and optically coupled to the optical fiber at one end;
A stem on which the optical device is mounted;
A cap for sealing the optical device in a space between the stem and
The stub penetrates the stem while hermetically sealing the space, and the optical device is mounted on a surface opposite to the one end of the stub.   2. The optical module according to claim 1, wherein a marking for mounting an optical device is metallized on the opposite surface of the stub.

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