JP2001066471A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical module capable of being simply and surely sealed hermetically and superior in reliability. SOLUTION: A substrate 2, in which an optical fiber 31 is arranged to be optically connected to an optical semiconductor device 5, is inserted into a through-hole 6 formed on the side wall of a causing 1 for forming the optical semiconductor device 5, in a manner that the substrate 2 and the optical fiber 31 are exposed outside the casing 1; also, a low-melting point sealing member L1 is provided between one or both ends of the through-hole 6 and the optical fiber 31, while a high-melting point sealing member H1 is provided in a gap between the substrate 2 and the through-hole 6; and finally, the through-hole 6 is hermetically sealed to form the optical module M1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module used in the field of optical communication and optical information processing, and more particularly to a hermetically sealed structure of an optical module capable of ensuring high reliability by simple optical connection. .

[0002]

2. Description of the Related Art In recent years, in the field of wired communication, optical fiber communication has been put to practical use mainly from a main transmission system, and the capacity of communication has been increased. Today, optical fiber communication is being introduced to access systems, subscriber systems connecting offices and homes, and furthermore, local area networks (LAs).
N), applications are expanding to the field of CATV, and it is gradually developing as a fundamental system indispensable to society. In order to further develop such optical fiber communication, not only the performance of optical devices used in systems but also the cost of modularizing the optical devices,
Productivity is a challenge.

[0003] In a conventional method of assembling an optical module, a process of mounting and fixing an optical semiconductor element on a package, a step of wire bonding for connecting an optical semiconductor element to wiring inside the package, an optical fiber to the optical semiconductor element, The optical connection between the optical fiber and the optical semiconductor device is performed by manually aligning the optical axis under a microscope and then guiding the light to the optical semiconductor device by connecting the optical fiber and the optical semiconductor device. The light emitted from the optical fiber is monitored by a light receiver, and the position of the optical fiber is finely adjusted so that the light amount becomes maximum.

[0004] However, in such a method, in many cases, connection work by a human requires a very long time, and this is the biggest factor that lowers productivity. In order to solve this problem, a technique for mechanically arranging the relative positions of the optical semiconductor element and the optical fiber and performing optical connection, so-called passive alignment, has been actively studied in recent years.

According to the passive alignment, the relative position between the optical semiconductor element and the optical fiber is determined only by mechanical accuracy, and the optical fiber can be easily positioned. Further, since there is no need to guide light to the optical semiconductor element or the optical fiber, the mass production effect is extremely large. For example, after anisotropically etching a crystal, an optical semiconductor element is accurately positioned using a marker or the like on a Si single crystal substrate (Si submount) on which a V-groove is formed, and is then Au-S
There has been proposed a method in which an optical connection between an optical semiconductor element and an optical fiber is performed with high precision by simply fixing with an n-alloy solder or the like and mounting an optical fiber on the V-groove.

The following method has been used for assembling an optical module using the above passive alignment.

A method in which an optical semiconductor device and an optical fiber are first mounted on a Si submount in order, and then the Si submount is mounted on a package and sealed.

A method in which only an optical semiconductor element is mounted on a Si submount, the Si submount is mounted on a package, and finally, an optical fiber is mounted and sealed.

[0009]

However, in the above method, the mounting of the Si submount on the package is
It is necessary to check the mounting position of the Si submount and the mounting position of the optical fiber so as not to damage the optical semiconductor element and the optical fiber, and the workability is extremely poor, and the sealing part of the package lid In some parts, it is necessary to provide a discontinuous portion for passing the optical fiber, and depending on the element structure, the sealing area is widened, the workability is poor, and the airtightness of the package is easily deteriorated. There is a problem that the semiconductor element is deteriorated and the characteristics of the optical module are deteriorated. Since the Si submount must be fixed to the package at a temperature equal to or lower than the fixing temperature of the optical semiconductor element or the optical fiber, there is a problem that the fixing material is restricted and a problem in reliability.

Further, in the above method, S
The mounting of the i-submount on the package needs to be performed while checking the mounting position of the Si submount so as not to damage the optical semiconductor element, and the workability is extremely poor. In addition, it is necessary to accurately align the fiber sealing hole of the package with the V-groove on the Si submount. However, there is a limit in the accuracy of the package fabrication and the accuracy of mounting the Si submount on the package. Positioning was very difficult.

The present invention has been proposed in view of the above-mentioned conventional problems, and an object of the present invention is to provide an optical module which can perform simple and reliable hermetic sealing and has excellent reliability. And

[0012]

In order to solve the above problems, an optical module according to the present invention comprises an optical fiber for optically connecting an optical semiconductor element to a through hole formed in a side wall of a casing for housing the optical semiconductor element. Is inserted through the substrate so that the substrate and the optical fiber are exposed outside the casing, and a low melting point sealing member is provided between one or both ends of the through hole and the optical fiber, and A high melting point sealing member is provided in a gap between the through hole and the through hole, and the through hole is hermetically sealed.

Further, at least a region of the optical fiber located in the through hole is covered with a protective cover.

[0014] Further, a lower substrate in which an optical fiber to be optically connected to the optical semiconductor element is disposed in a through hole formed in a side wall of a casing accommodating the optical semiconductor element, and a part of the optical fiber is placed on the lower substrate. A plywood body consisting of an upper substrate to cover
A high melting point sealing member is provided between the upper substrate and the lower substrate, and in the gap between the through hole and the outer peripheral portion of the plywood body, while being inserted so that one end thereof is exposed to the outside of the casing. A low melting point sealing member may be provided between the optical fiber and the optical fiber to seal the through hole.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the optical module according to the present invention will be described in detail with reference to the drawings.

In FIG. 1, the positions of a casing 1 which is a box-shaped body before mounting an optical fiber and a coated fiber (hereinafter referred to as an optical fiber (fiber element wire) whose outer peripheral portion is covered with a coating material) 3 are shown. Show the relationship. Further, FIG.
FIG. 2B is a partial cross-sectional top view of an optical module M1 in which an optical fiber 31 and a semiconductor laser diode (hereinafter, referred to as an LD) 5 as an optical semiconductor element are accommodated in a casing 1 shown in FIG. 2 (c) is a front view. In addition, FIG.
In (b), the V-groove forming substrate and the optical semiconductor element are not shown in cross section. The finished product of the optical module M1 is configured so that the upper surface 1a of the casing 1 in FIG.

As shown in FIGS. 1 and 2, the basic structure of the optical module M1 is to insert a LD 5 into a through-hole 6 having a rectangular cross section formed in a side wall (side surface) of the casing 1 accommodating the LD 5.
A part of the substrate (submount) 2 on which the optical fiber 31 to be optically connected to the substrate 5 is disposed and a part of the optical fiber 31 are inserted so as to be exposed to the outside of the casing 1, and one end or both ends of the through hole 6. A low melting point sealing member (sealing material having a melting point lower than 500 ° C.) L1 is provided between the optical fiber 31 and the high melting point sealing member in the gap between the substrate 2 and the through hole 6. By providing H1 (a sealing material having a melting point of 500 ° C. or more), the through hole 6 can be almost completely sealed.

Here, the casing 1 is made of SUS or ceramics in which at least a sealing region is metallized. The substrate 2 is made of single-crystal silicon. For example, a V-groove 4 having a (100) plane as a main surface and a slope of a (111) plane is formed by crystal anisotropic etching.

Next, the substrate 2 is accommodated in the casing 1,
A method for hermetically sealing the space between the casing 1 and the substrate 2 to protect the optical semiconductor element 5 will be described.

First, the optical semiconductor device 5 and the optical fiber 31
Before mounting in the casing 1, the substrate 2 is mounted in the casing 1 in advance. The substrate 2 is inserted into a through hole 6 formed in a side wall of the casing 1, and is mounted in the casing 1 and brazed so that a part of the V-groove 4 is exposed to the outside of the casing 1.

The outer peripheral portion of the substrate 2 in the through hole 6 is formed at the end of a cylindrical guide portion 11 protruding outside the casing 1 at the end of the brazing material drop groove 1 having an enlarged diameter.
Sealing is performed by melting and solidifying the brazing material (for example, gold brazing material) arranged in 2. At this time, the through-hole (fiber through-hole 6a) at the place where the optical fiber 31 is installed is made of a material having low wettability such as glass so that the place where the optical fiber 31 is installed in the through-hole 6 is not blocked by the brazing material. ) Should be protected. Further, as shown in FIG. 3, a second V-groove 14 deeper than the V-groove 4 is formed in the through-hole 6 to protect at least a region of the optical fiber 31 located in the through-hole 6. A cover, for example, a protective pipe 15 made of, for example, metal (for example, a surface of stainless steel plated with gold) may be used. In this case, after the optical fiber 31 at one end or both ends of the through hole 6 is sealed with the high melting point sealing material H1, it is sealed with the low melting point sealing material L1.

By doing so, a high melting point sealing material H1 such as gold brazing can be used as a sealing material between the outer peripheral portion of the substrate 2 and the through hole 6, and the optical semiconductor element 5 and the optical fiber The mounting of 31 is advantageous in terms of reliability because it can be fixed at a relatively high temperature using an Au-Sn alloy or the like.
As the high melting point sealing material H1, silver brazing, alloys thereof, other brazing materials, solder, etc. can be used in addition to gold brazing.

Next, the optical semiconductor element 5 is positioned and fixed on the substrate 2. This alignment can be performed with high precision by optically recognizing images of alignment markers formed in advance on both the substrate 2 and the optical semiconductor element 5. In this case, the connection is made by heating an Au—Sn alloy or the like to about 330 ° C. in a nitrogen atmosphere. In addition, this heating preliminarily covers the entire casing 1 by 100 to 25.
Preheating is performed to about 0 ° C., and pulse heating is performed on the optical semiconductor element 5.

Thereafter, in the pigtail type optical module in which a connector is attached to the end of the optical fiber, the coated fiber 3 is inserted into the fiber through hole 71 provided at the center of the fiber protective cap 7, and then the optical fiber 31 is inserted into the through hole. 6 (fiber through-hole 6a), the tip of which abuts against the end face of the optical semiconductor element 5 along the V-groove 4 or is formed in advance on the substrate 2 by dicing or the like so as to stop near the end face. And mounted on the V-groove 4. The fixing of the optical fiber 31 to the V groove 4
The optical fiber 31 on the V-groove 4 is covered with a Si cover plate 17 having the same width as that of the optical fiber 31, and the substrate 2 and this Si cover plate 17 are joined by solder such as Sn-Pb alloy which is a low melting point sealing material L1. It is done by doing. The low-melting-point sealing material L1 may be provided between the through-hole 6 inside the casing 1 and the optical fiber 31, or may be provided in the through-hole 6 inside and outside the casing 1. The low melting point sealing material L1 is made of Sn-
In addition to the Pb alloy, for example, an Au-Sn alloy or the like can be used.

Next, the space between the through-hole 6 and the optical fiber 31 is completely sealed with an appropriate amount of solder such as Sn-Pb alloy in the solder flow groove 13 formed vertically in the guide portion 11, and a casing is formed. By seam welding the lid 8 to the casing 1, the casing 1 is completely hermetically sealed. Fiber through hole 6a
The diameter of is preferably about 150 to 300 μm where the passage of the fiber 3 on the V-groove 4 is not restricted by the manufacturing accuracy of the casing 1, which is preferable in terms of tolerance of the positional accuracy of the hole and sealing property. That is, since the portion from the through hole 6 to the optical semiconductor element 5 is guided by the V groove 4, the V groove 4 on the substrate 2 is formed.
Gradual accuracy that does not deviate from the through hole 6. Further, the shape of the fiber through-hole 6a may be a shape having good manufacturing accuracy, such as a round shape or a square shape, depending on the material of the casing 1. In this state, the inside of the casing 1 has been almost completely air-tightly sealed. Finally, the fiber protection cap 7 may be attached along the cylindrical guide portion 11 of the casing 1 using a resin adhesive or the like. . Further, by covering the gap of the fiber protective cap 7 at the portion where the coated fiber 3 penetrates with a resin adhesive or the like, the coated fiber 3 can be easily and reliably fixed.

As described above, the optical fiber 3 is connected to the casing 1
After passing through the through-hole 6, no alignment with the V-groove 4 is required, and the mounting of the fiber becomes extremely easy. The mountability of the fiber is much better than the conventional one.

In a receptacle type optical module in which the coated fiber 3 can be detached from the outside of the casing 1 by a connector, airtightness can be obtained in the fiber through hole 6a by using the short optical fiber 31 as in the pigtail type. it can. However, in the receptacle type, when the substrate 2 is mounted on the casing 1, there is no problem that the coating (fiber jacket) of the optical fiber 31 is damaged by the heat treatment. It can be mounted on the casing 1.

Next, an example of application to a receptacle type optical module, which is another embodiment of the present invention, will be described with reference to FIG.

The basic configuration of the optical module M2 is such that an optical fiber 32 for optically connecting to the optical semiconductor element 5 is disposed in a through-hole 16 having a rectangular cross section formed on the side wall of the casing 1 for accommodating the optical semiconductor element 5. The lower substrate 2 and the plywood body 50 on which the upper substrate 21 covering a part of the optical fiber 32 is placed are inserted through the lower substrate 2 such that one end 50a is exposed to the outside of the casing 1, A high melting point sealing member H2 is provided between the upper substrate 21 and the lower substrate 2 and in the gap between the through hole 61 and the outer peripheral portion of the plywood body 50.
2, a low melting point sealing member L2 is provided to seal the through hole 16.

Specifically, first, before mounting the plywood body 50 in the casing 1, the optical fiber 32 is mounted in the V-groove 4 formed on the lower substrate 2 by crystal anisotropic etching.
The optical fiber 32 is fixed by the upper substrate 21 for holding the fiber, which is made of the same material as the lower substrate 2. The upper substrate 21 is provided with a V-groove 41 formed in the same manner as the V-groove 4 in advance, the optical fiber 32 is placed along the V-groove 4, and the lower substrate 2 and the upper substrate 21 are about 30 μm. A brazing material (for example, a gold brazing material) arranged in a brazing material dropping groove 22 having an enlarged diameter at an end of a cylindrical guide portion 21 which is fixed so as to have a very small interval and protrudes outside the casing 1. Is melted and solidified, whereby the gap and the gap between the plywood body 50 and the through hole 16 are completely sealed by the high melting point sealing member H2. The high melting point sealing member H2 is made of the same material as the high melting point sealing member described with reference to FIG. Next, the side surface of the lower substrate 2 on the fiber connection side is polished together with the end surface of the optical fiber 32.

Next, the optical semiconductor element 5 is mounted on the lower substrate 2. As described above, this mounting method can be mounted with high precision by optically recognizing the alignment markers formed on both the lower substrate 2 and the optical semiconductor element 5 in advance.

Thereafter, the optical semiconductor device 5 and the optical fiber 3
2 is die-bonded to the casing 1 through the through hole 16, and finally, the upper substrate 21 and the optical fiber 3 are bonded.
2, a low melting point sealing member L2 is provided to substantially completely seal the through hole 16. The low melting point sealing member L2 is made of the same material as the low melting point sealing member L1 described above.

Since the optical fiber 32 is already connected to the optical semiconductor element 5, the optical fiber 3 is inserted into the through hole 16.
There is no need to perform any alignment while passing through the casing 2, and the casing 1 can be made almost completely airtight by a simple operation of merely inserting the plywood body 50 into the through hole 16 and melting the solder, and mounting the optical semiconductor element. A very advantageous hermetic sealing structure can be provided.

[0034]

As described above, according to the optical module of the present invention, not only high-precision passive alignment between the optical semiconductor element and the optical fiber can be achieved, but also the optical fiber can be easily mounted on the casing. In addition, the space for accommodating the optical semiconductor element can be reliably hermetically sealed. That is, for example, there is no need to mount the optical fiber in the V-groove for mounting the optical fiber while aligning the optical fiber, and insert the optical fiber into the through hole along the V-groove, or the optical fiber is already mounted. By inserting the V-groove substrate into the through-hole and filling the gap, which has been kept to a minimum, with solder, it is possible to perform simple and reliable hermetic sealing, thereby minimizing the deterioration of the characteristics of the optical semiconductor element. It is possible to provide an optical module that can be prevented and has extremely excellent reliability.

The relative positional accuracy between the through-hole formed in the casing and the substrate on which the optical fiber is disposed can be determined by a simple method of die-bonding the substrate to a predetermined position of the casing using the through-hole as a guide. Accuracy is obtained, the tolerance of casing production accuracy becomes large, and the production becomes easy.

Further, in the optical module of the receptacle type, it is possible to provide an optical module which can be used not only for sealing the substrate but also for the receptacle, so that the number of parts can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an embodiment of an optical module according to the present invention.

2A and 2B are diagrams for explaining an embodiment of the optical module according to the present invention, wherein FIG. 2A is a partial cross-sectional view of the top surface of the optical module, FIG.
(C) is a front view of the optical module.

FIGS. 3A and 3B are diagrams illustrating another embodiment that covers an optical fiber in a through hole, and FIGS. 3A and 3B are a partial longitudinal sectional view and a partial transverse sectional view, respectively.

4A and 4B are diagrams for explaining another embodiment of the optical module according to the present invention, wherein FIG. 4A is a partial cross-sectional view of the upper surface of the optical module, FIG.
(C) is a front view of the optical module.

[Explanation of symbols]

 1: Casing 2: Substrate 3: Coated fiber 4: V-groove 5: Optical semiconductor element 6: Through hole 7: Fiber protection cap 11: Guide 12: Brazing filler groove 13: Solder flow groove 14: V-groove 15: Protection pipe (Protective cover) 21: Fiber holding substrate 31, 32: Optical fiber (fiber strand) 41: V groove 50: Plywood 61: Fiber through hole L1, L2: Low melting point sealing member H1, H2: High melting point sealing Member M1, M2: Optical module

Claims (3)

[Claims] A substrate provided with an optical fiber for optically connecting to the optical semiconductor element is provided in a through hole formed in a side wall of a casing accommodating the optical semiconductor element. A low-melting-point sealing member is provided on the optical fiber at one end or both ends of the through-hole, and a high-melting-point sealing member is provided in a gap between the substrate and the through-hole. With
An optical module in which the through hole is hermetically sealed. 2. The optical module according to claim 1, wherein at least a region of the optical fiber located in the through hole is covered with a protective cover. 3. A lower substrate in which an optical fiber to be optically connected to the optical semiconductor element is disposed in a through hole formed in a side wall of a casing for housing the optical semiconductor element, and a part of the optical fiber on the lower substrate. A plywood body, on which an upper substrate that covers the plywood, is inserted so that one end thereof is exposed outside the casing, and between the upper substrate and the lower substrate, and between the through hole and the plywood. An optical module in which a high-melting-point sealing member is provided in a gap with an outer peripheral portion of a body, and a low-melting-point sealing member is provided between the upper substrate and the optical fiber to seal the through hole.