JP2000199831A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reliable and excellent optical module that not only the breakage of an optical fiber and the breakage of sealing structure are prevented as much as possible but also optical connection between the optical fiber and an optical element is precisely executed. SOLUTION: The optical module M houses a V-groove substrate 5 mounting the optical element 18, the optical fiber 7, etc., to be optically connected with this. A good heat conductor pattern 6 precisely positioned to the center axis of a V groove 12 and connected with the element 18 is formed 7 on the lower surface of the substrate 5, a through hole 9 for putting the fiber 7 through is provided on the side part of the housing 1 through which the center axis of the V groove 12 passes, connection pads 3a, 3b,... positioned to the center of the hole 9 are provided on the bottom surface of the housing 1 to connect the lower surface of the substrate 5 and the pads 3a, 3b,..., and the fiber 7 and the hole 9 with soldering 4a, 4b,....

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 for transmitting and receiving optical transmission such as optical fiber communication and optical interconnection.

[0002]

2. Description of the Related Art In recent years, in an optical module used for transmitting and receiving an optical signal, a metal electrode for power supply of an optical semiconductor element or an optical fiber has been proposed in order to reduce the cost by simplifying the component structure and to improve the assemblability. Use mounting substrates in which the fixing V-grooves are precisely formed.

Conventionally, a condensing lens has been used for optical coupling between an optical semiconductor element and an optical fiber in order to obtain a desired coupling efficiency. However, it is necessary to fix both to a precision-processed mounting substrate. Thus, the optical semiconductor element and the optical fiber can be arranged very close to each other, and a desired coupling efficiency can be obtained without using a condenser lens.

For an optical semiconductor device, it is necessary to use an airtight structure filled with an inert gas in order to prevent deterioration in characteristics due to moisture and increase reliability. Since the space consisting of the element, the condenser lens and the optical fiber, that is, the long coupling length, can be secured, a glass window through which the optical signal is passed is provided in the package for mounting and fixing the optical semiconductor element, so that the airtight structure and the optical signal Exchange can be achieved.

In the case of a coupling structure using a mounting substrate, an optical fiber that optically couples with an optical semiconductor element is pulled out of the housing as it is, and the gap between the optical fiber and a hole formed in a package through which the optical fiber is inserted is hermetically sealed by some method. I have no choice.

For example, as in an optical module J shown in FIG. 6, a notch 61 and a pipe groove 55 formed on the upper surface of a package 51 have an optical fiber 62 and a glass pipe 58 partially covered with a protective film 63. And the package 51
Mounting board 60 disposed in a concave portion 54 formed inside
A semiconductor laser 52 is mounted and fixed on the
And the semiconductor laser 52 are optically coupled to each other.
After sealing 5, the powder of the low-melting glass placed in the notch groove 61 is heated and melted to form an airtight structure. In order to heat the low melting point glass, it has been proposed to perform partial heating by means of a CO ₂ (carbon dioxide gas) laser or the like (for example, see Japanese Patent Application Laid-Open No. 7-63957).

[0007]

However, the hermetic structure of the optical module J employs a structure in which the optical fiber 62 and the glass pipe 58 attached thereto are disposed in the package 51. In the package, since a manufacturing method of laminating thin plates is used, the central axes of the notch 61 in which the optical fiber 62 is provided and the pipe groove 55 in which the glass pipe 58 is provided are largely shifted with respect to the package 51.

Further, a semiconductor laser 5 is provided in a package 51.
2 and the mounting substrate 60 on which the optical fiber 62 is mounted, the V-groove 66 formed on the mounting substrate 60 is fixed on the basis of the outer shape by the center axis of the notch 61 with respect to the V-groove 66. And the central axis of the V-groove 66 deviates greatly. That is, a mounting substrate such as silicon is generally formed with a V-groove by etching a wafer of several inches in size,
Dividing into individual substrates is performed by dicing, but it is difficult for such dicing method to process the outer shape with high precision based on the V-groove.

Therefore, when the optical fiber is mounted on the basis of the V-groove, the positional relationship between the cutout of the package, the pipe groove and the V-groove is largely displaced, so that the axis of the optical fiber and the axis of the ferrule attached thereto are linearly aligned. Not fixed. As a result, careless bending, so-called microbending, occurs in the optical fiber, and there is a serious problem that the optical fiber breaks from the bending position due to an environmental change received by the optical module.

In order to prevent the micro-bend, it is conceivable to cut out the optical fiber and the ferrule and precisely position the shaft with respect to the pipe groove. A complicated and sophisticated device for performing surface treatment and positioning the shaft is required. As a result, the assembly of the optical module becomes complicated, which is a problem.

The optical module J is package 5
An optical fiber 62 is arranged in one notch 61, and a low melting point glass 67 is melted into a gap formed by the package 51 and a lid 65 for sealing the package 51 to obtain an airtight structure. No axially symmetric structure is formed in the fixing of. This causes a difference in the amount of thermal contraction or thermal expansion due to the difference in the amount of the sealing material, applies stress in a specific direction of the optical fiber 62, and causes a problem in that the optical fiber 62 is broken.

In such an optical module, the electrical connection between the mounting substrate on which the semiconductor laser is mounted and the package is made by wiring. However, good high-frequency electrical characteristics cannot be obtained by wiring, and a high-speed optical module can be obtained. Not only cannot be provided, but also a serious problem such as breaking of the wiring occurs.

Further, when the package and the lid are made of different materials, since the bonding strength of the sealing material is different, the bonding agent may peel off due to heat shrinkage or thermal expansion and a gap may be formed in the sealing portion. In addition, the sealing structure cannot be maintained for a long time, and as a result, the reliability of the optical semiconductor element cannot be ensured.

Accordingly, the present invention not only prevents the breakage of the optical fiber and the wiring and the breakage of the sealing structure as described above, but also achieves a reliable optical connection between the optical fiber and the optical element. It is an object to provide a high and excellent optical module.

[0015]

In order to solve the above-mentioned problems, an optical module according to the present invention comprises an optical element and a V-groove substrate on which an optical fiber to be optically connected to the optical element is placed in a housing. A good heat conductor pattern positioned with respect to the V-groove central axis is formed on the lower surface of the V-groove substrate, and a through hole for inserting an optical fiber is provided on the side of the housing through which the V-groove central axis passes. A connection pad positioned on the bottom of the housing with respect to the center of the through-hole, and soldered between the good thermal conductor pattern and the connection pad, and between the optical fiber and the through-hole. And Here, it is preferable that the good heat conductor pattern is connected to the optical element because the heat dissipation of the optical element is improved.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic perspective view of an optical module M according to the present invention, FIG. 2 is a schematic plan view of the optical module M, FIG. 3 is a cross-sectional view taken along line AA of FIG. FIG. 4 is a partial perspective view schematically illustrating an example of the electrode structure of the optical module M.

The optical module M includes an optical element 18 which is a light emitting element such as a semiconductor laser, and a V-groove substrate 5 made of silicon or the like on which an optical fiber 7 or the like optically connected thereto is mounted.
It is housed in a housing 1 which is a multilayer ceramic package. On the lower surface of the V-groove substrate 5, a good heat is accurately positioned with respect to the center axis of the V-groove 12 and connected to the optical element 18. A plurality of electrode patterns 6 as conductor patterns are formed, and a through hole 9 through which an optical fiber 7 is inserted is provided on a side portion of the housing 1 through which the central axis of the V groove 12 passes. further,
Provided on the bottom surface of the housing 1 are connection pads 3a, 3b,... Positioned with respect to the center of the through-hole 9, between the plurality of electrode patterns 6 and the connection pads 3a, 3b,. Solder 4a, 4b,... Between fiber 7 and through hole 9
・ It is joined by The optical element 19 disposed on the V-groove substrate 5 is a light receiving element such as a photodiode for monitoring the optical element 18, and monitors light emitted backward from the optical element 18 to monitor the optical element 18. This is for controlling the intensity of light emitted forward.

Hereinafter, the optical module M will be described in more detail. The housing 1 is mainly made of a multilayer ceramic,
This is a multilayer wiring board on which wiring is provided. Lead electrodes 2a, 2 for transmitting and receiving electric signals are provided on the lower surface of the housing 1.
.. are formed. These lead electrodes 2a, 2
are internal wirings 10a, 11a, 10
b, 10c, 11b, 10d, etc. These internal wirings are connected to connection pads 3a, 3b,... Formed on the bottom surface of the housing 1.

The internal wirings 10a, 11a, 10b, 10
For c, 11b, 10d, and the like, high-frequency electric characteristics can be improved by using via holes or internal wiring called microstrip lines in consideration of high-frequency electric characteristics.

The V-groove substrate 5 is formed with an electrode pattern 6 for arranging the optical elements 18 and 19 with high precision and a V-groove 12 for mounting the optical fiber 7. The electrode pattern 6 is accurately positioned and formed with respect to the V-groove 12 in which the optical fiber 7 is mounted by using a photolithography technique or the like.

The connection pad 3a formed on the housing 1 has a V
A through hole 9 is formed in advance so as to match the connection pad 6 formed on the groove substrate 5, and a through hole 9 for drawing out the optical fiber 7 is provided near the center of the side wall of the housing 1. It is manufactured in advance so that the optical fiber 7 to be mounted in the groove 12 is arranged.

Next, the joining of the V-groove substrate 5 and the housing 1 will be described in detail. Optical elements 18 and 19 are arranged and mounted on the V-groove substrate 5 by a passive alignment technique, and are electrically connected to electrode wirings manufactured by photolithography or vapor deposition by wires 13a and 13b using gold or the like. I have.

The optical fiber 7 is accurately positioned with respect to the portion on which the optical element 18 is mounted, mounted on the V-groove 12 precisely manufactured by anisotropic etching, and held down by a holding plate 20 made of quartz or the like. Is mounted and fixed to the V-groove substrate 5 by pressure bonding with an ultraviolet curing adhesive. The optical fiber 7 is bonded and fixed to a ferrule 8 mainly made of ceramic in order to take out an optical signal to the outside.
The ferrule 8 is bonded and fixed to a through hole 9 formed in the multilayer wiring board 1.

As shown in FIG. 4, the V-groove substrate 5 has V-grooves 15 and 16 formed on both main surfaces thereof by anisotropic etching. V-groove 1 formed on the surface on which the optical element is mounted
In 5, a metal film such as gold is formed by patterning by photolithography or the like. Further, an electrode wiring 14 electrically connected to the optical element is formed, and is connected to the electrode pattern 6 deposited on the slope of the V-groove 16 etched from the back surface.

The housing 1 has connection pads on which solder bumps 4 a are formed so as to match the electrode patterns 6 formed on the V-groove substrate 5 for bonding and electrical connection with the V-groove substrate 5. The connection pad 3a is provided in the housing 1 with a via hole 10a, a microstrip line 11a designed in consideration of high-frequency electrical characteristics, and a via hole 10b.
And a lead electrode 2a for transmitting and receiving electric signals to and from the outside.

The V-groove substrate 5 is joined by arranging the electrode pattern 6 of the V-groove substrate 5 on the connection pads 3a,. The solder bumps 4 formed on the pads 3a,... Are melted, and the electrode pattern 6 on the V-groove substrate 5 and the connection pads 3a,.
.. are aligned so that V of the V-groove substrate 5 is
The groove is arranged at the center of the through hole 9 for taking out the optical fiber 7 formed in the housing 1, so that the solder is solidified by cooling, and the optical fiber 7 can be securely fixed and joined.

Here, the metal pads formed on the V-groove substrate 5 and the connection pads and the solder bumps formed on the housing 1 are formed so as to match each other and form a pair. It is good to manufacture it according to the arrangement and the logarithm. Further, the height of the solder bump to be formed may be adjusted and manufactured in advance so that the optical fiber 7 becomes the center of the through hole 9 formed in the housing 1 after melting.

Next, a method for fixing the optical fiber 7 to the through hole 9 formed on the side of the housing 1 will be described in detail with reference to FIGS. The optical fiber 7 is partially preliminarily pre-soldered with ultrasonic solder or the like, and a solder preform 17 is formed in advance. Also, the through holes 9 are previously plated with metal such as gold.

When the housing 1 is heated, the connection pads 3a to 3a
The solder bumps 4a to 4f formed on the optical fiber 7 and the solder preform 17 formed on the optical fiber 7 are heated and melted. The melted solder bumps 4a to 4f are
The metal pads 6a to 6f formed on the housing 1 and the connection pads 3a to 3f formed on the housing 1 are manufactured so as to match in advance. At this time, the solder preform formed on the optical fiber is also melted and filled in the through hole 9 of the housing 1.

Next, by cooling the housing 1, the housing 1, the V-groove substrate 5, and the optical fiber 7 are simultaneously bonded. At this time, since the V-groove substrate 5 and the optical fiber 7 are fixed at the same time, the optical fiber 7 can be fixed to the multilayer wiring board without causing microbending. After the joining, the gap between the ferrule 8 joined to the optical fiber 7 and the housing 1 is filled with, for example, an epoxy-based adhesive and cured to fix the ferrule. Thus, the hermetic sealing structure can be easily and reliably obtained.

[0032]

As described above, according to the optical module of the present invention, it is possible to provide an excellent optical module that can easily and accurately position and fix the V-groove substrate with respect to the housing.

Further, the fixing of the optical fiber in the through-hole formed in the housing and the mounting of the V-groove substrate on the housing can be performed accurately at the same time, and the hermetic sealing structure can be obtained simply and reliably. It is possible to provide an optical module having excellent reliability without breaking the optical fiber.

Further, the electrical connection between the V-groove substrate and the housing can be made without wiring, so that an optical module which can be reduced in size and has excellent high frequency characteristics can be provided.

[Brief description of the drawings]

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

FIG. 2 is a plan view schematically illustrating an embodiment of the optical module according to the present invention.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a partial perspective view schematically illustrating an electrode structure of the optical module according to the present invention.

FIGS. 5A and 5B are cross-sectional views schematically illustrating a mounting process of an optical module according to the present invention.

FIG. 6 is a perspective view for explaining a conventional optical module.

[Explanation of symbols]

1: Housing (package) 2a, 2b: Lead electrode 3a, 3b, 3c, 3d, 3e, 3f: Connection pad 4a, 4b, 4c, 4d, 4e, 4f: Solder bump 5: V-groove substrate 6a, 6b, 6c, 6d, 6e, 6f: Good thermal conductor pattern (electrode pattern) 7: Optical fiber 8: Ferrule 9: Through hole 10a, 10b, 10c, 10d: Via hole 11a, 11b: Microstrip line 12: V groove 13a, 13b: Wire 14: Electrode 15: V-groove 16: V-groove 17: Solder preform 18: Optical element (semiconductor laser) 19: Optical element (photodiode) 20: Holding plate

Claims (2)

[Claims] 1. An optical module comprising a housing and an optical element and a V-groove substrate on which an optical fiber optically connected to the optical element is mounted. Forming a good heat conductor pattern positioned with respect to the first hole, providing a through hole through which the optical fiber is inserted in a side portion of the housing through which the V-groove central axis passes, and forming the through hole in a bottom surface of the housing. Provide a connection pad positioned with respect to the center of, between the good heat conductor pattern and the connection pad,
And an optical module, wherein the optical fiber and the through hole are joined by solder. 2. The optical module according to claim 1, wherein the good thermal conductor pattern is connected to the optical element.