JP2842388B2 - Surface mount optical module - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication optical module having a light emitting element and a light receiving element, and more particularly to an optical module having elements mounted on a surface.

[0002]

2. Description of the Related Art Optical communication uses an optical fiber or a semiconductor laser (L).
D), light-emitting diodes (LEDs), photodiodes (PDs), and other optical switches, optical modulators, isolators, optical waveguides, and other passive and active elements with higher performance and higher functionality have expanded their application range. . In recent years, as the demand for transmitting more information has increased, parallel transmission of data between computer terminals, exchanges and large computers in parallel, or advanced information services for general households, etc. Application is considered. In the case of this optical subscriber system, it is indispensable to reduce the price of an optical module in which the optical element is functionally configured as well as the optical element. For this purpose, it is desirable to adopt a module configuration in which a plurality of optical elements are arranged on the same substrate, that is, a module configuration similar to a printed circuit board of electronic components, from a conventional coaxial module configuration in which optical elements are arranged in a block shape in a micro-optic manner. Have been.

FIG. 3 is a diagram showing an example of a flat transmission module including an LD, a PD for monitoring an LD light, and an optical fiber. An end of the optical fiber 23 is fixed to a V-groove 22 provided on the mounting substrate 21, and the laser beam emitted from the LD 24 surface-mounted on the mounting substrate 21 is set so that the laser light is incident from the end face of the optical fiber 23. The light emitting end face optical fiber 23 is mounted on a mounting board so as to face one end face. In order to keep the intensity of the light emitted from the LD 24 constant, the surface light receiving type PD 26 for monitoring the laser light emitted from the opposite end face of the LD 24 has a light receiving surface 26 a on the opposite end face of the LD 24. As opposed to
It is mounted on a PD board 25 provided separately from the mounting board 21.

[0004]

In such a transmission module, since the LD 24 is positioned on the mounting substrate 11 by utilizing image recognition of a positioning marker or the like, an extremely high positional accuracy can be obtained. . Further, the positioning of the optical fiber 23 is performed by the V-groove 22 formed in the mounting substrate 21, so that the optical fiber 23 is positioned with respect to the mounting substrate 21 with high accuracy. On the other hand, PD2 for LD light monitor
6 is a surface light-receiving type, it cannot be surface-mounted on the mounting substrate 21 to receive light emitted from the LD 24. Therefore, the PD 26 needs to be mounted in a state where the light-receiving optical path is converted by about 90 degrees. As shown in the figure, there is a dedicated P which is oriented at an angle of 90 degrees with the mounting board 21.
It is mounted on a D mounting board 25. Therefore, it is necessary to position the PD mounting board 25 with high precision with respect to the mounting board 21, and positioning for that purpose is extremely difficult. Further, two-dimensional wiring for electrically connecting the mounting substrate 21 and the PD mounting substrate 25 is required, and there is also a problem that components and mounting costs increase.

An object of the present invention is to provide a surface-mount type optical module which enables high-accuracy positioning of a PD and its mounting easily, and realizes low cost.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to an optical module having a light receiving element for receiving light transmitted along the surface of a mounting substrate. That the surface is mounted on the mounting board so as to face the mounting board at a position higher than that of the light, and that a reflection bump for reflecting transmitted light is provided on the surface of the mounting board facing the light receiving surface. Features. When the present invention is configured as an optical module for transmission, an edge-emitting light-emitting element and a surface-light-receiving light-receiving element that receives light emitted from the light-emitting element are arranged on the same mounting board, The light receiving surface of the light receiving element is set at a position higher than the emitted light on the mounting substrate, and a reflective bump made of a hemispherical metal bump is formed on the surface of the mounting substrate facing the light receiving surface. And Further, it is preferable that the light emitting element and the light receiving element are fixed to the mounting board by metal bumps.

[0007]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a cross-sectional structure of a transmitting optical module according to a first embodiment of the present invention. A V-groove 12 having a required angle is formed in the silicon mounting substrate 11 by the crystal orientation of the silicon crystal and the anisotropic etching technique, and one end of the optical fiber 13 is fixed to the V-groove 12 in a positioned state. . An electrode (not shown) is formed of a metal thin film on the surface of the mounting substrate 11 facing one end of the optical fiber 13, and an edge emitting LD 14 is surface-mounted using a metal bump 15 such as AuSn on the electrode. Is done. The LD 14 is configured to emit LD light from both end faces, one end face of which is positioned to face the optical fiber 13, and the emission optical axis of the LD light emitted from the end face is located on the surface of the mounting substrate 11. The optical axis of the optical fiber 13 is set to be close to the height position, and the optical axis of the optical fiber 13 coincides with the optical axis of the LD light. In this example, the LD 14
Since the metal bumps 15 need to be mounted on the mounting substrate 11 with a dimensional accuracy of 1 to 2 μm, metal bumps having a height of about 20 μm are used as the metal bumps 15. For this reason, LD1
The optical axis of No. 4 is located at a height of 5 μm from the lower surface of the chip. As a result, the optical axis of LD 14 is at a position of 25 μm from the surface of the mounting substrate 11.

On the other hand, a surface-receiving type PD monitor 16 for LD light monitoring is surface-mounted on the mounting substrate 11 so as to face the opposite end face of the LD 14. When mounting the PD 16, a metal bump 17 using an electrode (not shown) provided on the mounting substrate 11 is used, and at that time, the light receiving surface of the PD 16 faces downward so as to face the surface of the mounting substrate 11. We are implementing for. In this case, PD1
6 only needs to receive a part of the light emitted from the LD 14,
It is sufficient that the positional accuracy is about 5 μm, and a metal bump having a height of about 80 to 100 μm can be used as the metal bump 17. Thereby, PD16
The height position of the light receiving surface 16a is higher than the optical axis position of the light emitted from the LD. And the mounting substrate 11
A non-illustrated electrode is formed at a position directly below the PD 16 on the surface of the PD, that is, a position substantially directly below the light receiving surface 16a, and a hemispherical metal bump having a height of about 50 μm, that is, a reflective bump is formed on the electrode. 18 are formed.

According to this configuration, the LD light emitted from one end face of the LD 14 is transmitted (progressed) along the surface of the mounting substrate 11, is incident on one end face of the optical fiber 13, and passes through the optical fiber 13. Transmitted. The LD light emitted from the other end surface of the LD 14 is transmitted along the surface of the mounting substrate 11 in the direction opposite to the optical fiber 13, and a part of the light is projected on the reflective bump 18 and reflected there. Then, of the reflected LD light, the LD light reflected upward is projected on the light receiving surface 16a of the PD 16 and received here. Thus, the LD light emitted from the LD 14 is monitored by the PD 16, and control of the LD light intensity and the like in the LD 14 is realized by using the monitor output.

As described above, in this embodiment, it is possible to receive the LD light even when the surface light receiving type PD 16 is mounted on the surface with the edge emitting type LD 14 side by side. Therefore,
The PD 16 can be surface-mounted on the mounting substrate 11 in the same manner as the LD 14, so that the mounting operation can be facilitated and mounting with high positional accuracy can be performed. Also,
The positioning of the PD 16 with respect to the reflective bump 18 can be easily performed. Further, the electric wiring for the PD 16 can use the metal wiring pattern (not shown) formed on the mounting board 11 together with the electrodes as it is, and
Since a separate PD mounting board is not required, the number of components can be reduced, wiring work is unnecessary, and cost can be reduced.

The reflection bump 18 is formed of the LD 14 or PD.
A technique similar to the technique of each of the 16 metal bumps 15, 17 can be used, for example, a technique of plating a metal on an electrode, melting the plating, and forming a hemisphere by the surface tension. For this reason, even when compared to the case of performing light reflection as described above using a special microlens or micromirror,
These components become unnecessary, and the mounting work therefor becomes unnecessary, so that further reduction in cost and ease of manufacture can be realized.

FIG. 2 is a view showing a cross-sectional structure of a second embodiment of the present invention, and portions equivalent to those of the first embodiment are denoted by the same reference numerals. In this embodiment, an optical waveguide 19 is used instead of an optical fiber as an optical transmission path, and the LD light emitted from the edge emitting type LD 14 is transmitted to the optical waveguide 19 by being made incident on the optical waveguide 19. Also in this embodiment, the LD emitted from the opposite end face of the LD 14
Since the light is reflected and received by the reflective bumps 18 provided directly below the light receiving surface 16a of the surface light receiving type PD 16, the surface mounting of the PD 16 is enabled, and the PD 16 can be mounted with high precision and ease. it can. Further, a reflection bump 18 made of a metal bump for reflecting the LD light.
, The production can be performed easily and at low cost.

In each of the above embodiments, a silicon substrate is used as a mounting substrate. However, the same applies when an insulating substrate such as alumina is used. Further, other metal such as PbSn can be used as the metal bump.

In each of the above embodiments, the present invention is applied to an optical module for transmission. However, an optical fiber or an optical waveguide is optically coupled to a PD for receiving the light transmitted therethrough. The present invention can be applied to a case where a receiving optical module is configured.

[0015]

As described above, according to the present invention, the light receiving element of the surface light receiving type is surface-mounted, and the reflection bump is formed on the mounting substrate at a position facing the light receiving surface of the light receiving element. The light transmitted along the mounting board can be reflected by the reflective bumps and received on the light receiving surface. For this reason, the light receiving element can be surface-mounted on the mounting substrate to form an optical module, the mounting of the light receiving element can be facilitated, and the wiring to the light receiving element can be simplified to reduce the cost. . Also, by using a metal bump for mounting the light receiving element as the reflective bump, the reflective bump can be formed simultaneously with the mounting of the element, and special optical components such as microlenses and micromirrors are not required. Cost reduction can be further promoted.

[Brief description of the drawings]

FIG. 1 is a sectional configuration diagram of a first embodiment of an optical module of the present invention.

FIG. 2 is a sectional configuration diagram of a second embodiment of the optical module of the present invention.

FIG. 3 is a cross-sectional configuration diagram of an example of a conventional optical module.

[Explanation of symbols]

 Reference Signs List 11 silicon mounting substrate 12 V groove 13 optical fiber 14 LD (laser diode) 15, 17 metal bump 16 PD (photodiode for laser monitor) 18 reflective bump 19 optical waveguide

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02B 6/42 G02B 6/26

Claims (5)

(57) [Claims] 1. An optical module comprising a light receiving element of a surface light receiving type for receiving light transmitted along a surface of a mounting board, wherein the light receiving element has a light receiving surface higher than the transmitted light. A surface mounted on the mounting substrate in a state facing the mounting substrate, and having a reflective bump for reflecting the transmitted light on a surface of the mounting substrate facing the light receiving surface. Mountable optical module. 2. A light emitting element of an edge emitting type and a light receiving element of a surface light receiving type for receiving light emitted from the light emitting element are arranged on the same mounting substrate in a plane, and a light receiving surface of the light receiving element is on the mounting substrate. At a higher position than the emitted light,
A surface-mounted optical module, wherein a reflective bump made of a hemispherical metal bump is formed on a surface of the mounting substrate facing the light-receiving surface. 3. An optical transmission means comprising an optical fiber or an optical waveguide into which light emitted from one end face of the edge emitting optical element is incident, and the light receiving element receives light emitted from the other end face of the light emitting element. The surface mount type optical module according to claim 2. 4. The surface mount type optical module according to claim 3, wherein the light emitting element and the light receiving element are fixed to the mounting board by metal bumps. 5. The surface mount type optical module according to claim 4, wherein the metal bump for mounting the light receiving element has a larger diameter than the metal bump for mounting the light emitting element.