JP2011044456A - Optical transmitter module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic package type optical transmitter module for mounting a monitor PD in a form not affecting a high-frequency electric signal. <P>SOLUTION: In the optical transmitter module 1, a package frame 12 made of ceramic for surrounding sides of an LD 11 is provided on a bottom ceramic substrate 11 for mounting an LD 3, the LD 3 and a PD 4 for monitoring are sealed into a package 2 where a lid 14 having an optical window is mounted onto the package frame 12, and light from a front end face 3a of the LD3 having a light axis in parallel with the bottom ceramic substrate 11 is reflected by a reflecting member and is emitted from the optical window. The package frame 2 includes a signal supply substrate 15 where a signal line 15b to the LD 3 is formed, and steps 16 that oppose each other while sandwiching the signal line 15b at a rear part of the LD 3, and the monitor PD 4 is mounted to a submount 7 mounted to cross-link the opposing steps 16. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a ceramic package type optical transmission module used for optical communication.

  An optical transmission module used for optical communication uses light from a laser diode (LD) as signal light, and there are the following types. For example, there is a CAN package type in which an optical window is provided at a front end portion of a cylindrical metal package that accommodates an LD and lead pins extend from the rear end portion (see, for example, Patent Document 1). In addition, there is a butterfly package type in which an optical window is provided at the front end portion of the rectangular parallelepiped package and lead pins extend from the side portion and / or the rear end portion. For example, see Patent Document 2).

JP-A-5-102617 JP-A-6-318863

  At present, in addition to the above, a smaller and cheaper ceramic package type optical transmission module is considered. FIG. 6 is a perspective view for explaining a ceramic package type optical transmission module, in which the optical transmission module is shown with a cover with an optical window omitted. In the illustrated ceramic package type optical transmission module 100, a package 102 that houses an LD 101 is configured as follows. That is, the package 102 is a ceramic package that surrounds the side of the electronic cooler on the bottom ceramic substrate 111 on which electronic components such as the electronic cooler 103 are mounted and a connection portion with an external electric circuit is provided. A frame 112 is attached, a metal frame 113 is provided thereon, and a metal lid with an optical window (not shown) is attached. The ceramic package shown in the drawing is a stacked package in which the package frame 112 is formed by sequentially stacking rectangular annular ceramic substrates.

In this optical transmission module 100, the LD 101 is mounted so that its optical axis is parallel to the bottom ceramic substrate 111 due to the limitation of mounting space. Then, light from the front end surface 101a of the LD 101 is reflected in a direction perpendicular to the bottom ceramic substrate 111 (X direction in the drawing) by a reflecting member (not shown) and output as signal light to the outside of the package 102 through the optical window. I try to let them.
In the optical transmission module 100, a high-frequency line 114 that supplies an electrical signal to the LD 101 is formed on the signal supply substrate 115 in the rear portion of the LD 101 in the package frame 112.

  Also, in the ceramic package type optical transmission module 100, as in the conventional optical transmission module, monitoring of the light output intensity of the LD 101 is indispensable. Therefore, for monitoring so that light from the rear end face 101b of the LD 101 can be received. The photodiode (PD) is mounted in the package 102. However, depending on the mounting form of the monitor PD, there is a problem that the high-frequency electric signal is affected.

  An object of the present invention is to provide a ceramic package type optical transmission module in which a monitor PD is mounted in a form that does not affect a high-frequency electric signal in view of the above situation.

  In order to solve the above-described problems, the optical transmission module of the present invention is provided with a ceramic package frame that surrounds the side of the laser diode on the bottom ceramic substrate on which the laser diode is mounted, and on which an optical window is provided. A laser diode and a light-receiving element for monitoring are sealed in a package having a lid attached thereto, and light from the front end face of the laser diode having an optical axis parallel to the bottom ceramic substrate is reflected by a reflecting member. The package frame has a signal supply board in which a signal line for the laser diode is formed in a rear portion of the laser diode, and a stepped portion facing each other with the signal line interposed therebetween. And the light receiving element is mounted on a submount that is mounted so as to bridge between opposing stepped portions. And wherein the Rukoto.

  In the submount, it is preferable that the wiring pattern for the light receiving element is formed only on one surface, and the light receiving element is offset upward from the optical axis of the laser diode while the light receiving surface faces downward. It is also preferable to be mounted on.

  According to the optical transmission module of the ceramic package type of the present invention, the sub-mount for the monitor PD is attached so as not to touch the high-frequency line, so that the high-frequency electric signal supplied from the outside is not delayed in the LD. Can be supplied. Further, since the structure for attaching the submount is provided integrally with the package, the cost can be reduced as compared with the case where the structure is prepared as a separate part.

It is a figure explaining an example of the optical transmission module of this invention. FIG. 2 is a partial enlarged cross-sectional view of the optical transmission module of FIG. 1. It is a figure which shows the arrangement | positioning relationship between LD and monitor PD in this invention. It is a figure explaining the relationship between arrangement | positioning relationship of LD of FIG. 3, monitor PD, and monitor current. It is a figure explaining the other example of the optical transmission module of this invention. It is a figure explaining the conventional optical transmission module.

Hereinafter, the outline of the optical transmission module of the present invention will be described with reference to the drawings. 1A is an external view of an example of the optical transmission module of the present invention, and FIG. 1B is a diagram showing an internal structure of the optical transmission module of FIG. 1A. FIG. 2 is a diagram for explaining the arrangement around the monitor PD of the optical transmission module of FIG.
As illustrated by reference numeral 1 in FIG. 1A, an optical transmission module of the present invention (hereinafter referred to as an optical module) is provided with a ceramic package frame 12 on a bottom ceramic substrate 11, and a metal frame thereon. 13 and a package 2 to which a lid 14 with an optical window such as a flat glass 14a is attached. The size (width × depth × height) of the package 2 is, for example, 5.6 × 5.6 × 3.0 mm. As shown in FIG. 1B, the optical transmission module 1 is formed by hermetically sealing an LD 3 and a monitor PD 4 in the package 2.

  For example, an element such as an electronic cooler 5 is mounted on the bottom ceramic substrate 11 of the package 2. The package frame 12 constitutes a side wall surrounding the side portion of the element. For example, the package frame 12 is formed by sequentially laminating ceramic rectangular annular substrates on which wiring patterns and the like are formed. The annular substrate is produced by processing a ceramic sheet. The package frame 12 includes a signal supply board 15 in which a wiring pattern 15a such as a high frequency line 15b is formed in a portion corresponding to the rear of the LD 3, and a pair of step parts 16 having a step on the upper surface side of the signal supply board 15. And.

  The pair of stepped portions 16 are provided so as to face each other with the wiring pattern 15a including the high-frequency line 15b interposed therebetween. A submount 7 on which the monitor PD 4 is mounted is attached so as to bridge between the pair of step portions 16. In addition, the pair of step portions 16 are formed with a wiring pattern 16a that forms a wiring for the anode electrode of the monitor PD4 and a wiring pattern 16b that forms a wiring for the cathode electrode of the monitor PD4. As will be described later, the optical transmission module 1 according to the present invention is characterized in that a pair of stepped portions 16 which are structures for mounting the monitor PD4 are integrally provided on a package frame 12 constituting the package. is there.

  The lid 14 is attached to the package frame 12 via the metal frame 13 so as to hermetically seal the LD 3 and the monitor PD 4. A lid 14 c is formed on a metal flat plate 14 c having an opening 14 b for passing signal light in the center. An optical member 14a such as a lens or flat glass is fixed so as to close the opening 14b. The optical member 14a serves as an optical window that transmits the signal light from the LD 3, and a low-melting glass or the like is used for fixing the optical member 14a so as not to impair the hermeticity of the package.

  The LD 3 is mounted so that its optical axis is parallel to the bottom ceramic substrate 11. In this example, the LD 3 is mounted on the electronic cooler 5 mounted on the bottom ceramic substrate 11 via the submount 6. Mounting on the submount 6 is performed using, for example, Ag paste. The light from the front end surface 3a of the LD 3 is reflected in a direction perpendicular to the bottom ceramic substrate 11 (X direction in the drawing) by a reflecting member (not shown), and is output as signal light to the outside of the package 2 through the optical member 14a. Is done.

The monitor PD4 is for receiving light from the rear end surface 3b of the LD 3, and as shown in FIG. 2, on the lower surface 7a of the submount 7 attached so as to bridge between the pair of step portions 16, The light receiving unit 4a is mounted in a state offset upward from the optical axis P of the LD3.
Mounting of the monitor PD4 on the package 2 and electrical connection between the electrodes of the monitor PD4 and the wiring patterns 16a and 16b (see FIG. 1B) of the package 2 are performed as follows.

  That is, first, the monitor PD 4 is fixed on the mounting pattern (not shown) formed on the lower surface 7a of the submount 7 using a conductive adhesive material such as Ag paste, and the monitor PD 4 is fixed. The cathode electrode on the back surface of the PD 4 is electrically connected to the mounting pattern. Then, the anode electrode on the surface of the monitor PD4 is electrically connected to the wiring pattern constituting the wiring for the anode electrode of the monitor PD4 formed on the lower surface 7a of the submount by wire bonding. Then, the wiring pattern and the mounting pattern on the lower surface 7a of the submount 7 are bonded to the wiring patterns 16a and 16b of the package 2 using a conductive adhesive or the like, so that the submount 7 is paired with the pair of step portions 16. Secure on top. In this way, the monitor PD4 is mounted on the package 2 and the electrodes of the monitor PD4 are electrically connected to the wiring patterns 16a and 16b of the package 2.

  Although illustration is omitted, an electrode pad is formed on the lower end surface of the bottom ceramic substrate 11, and the electrode pad, the high frequency line 15b, the wiring patterns 16a and 16b, and the like are connected to the bottom ceramic substrate 11 and the package frame. 12 is electrically connected through a through hole or the like provided in 12. In the optical transmission module 1, when these electrode pads and an external circuit board are electrically connected using a flexible printed circuit board or the like, a high-frequency electrical signal can be supplied to the LD 3 or an electrical signal from the monitor PD 4 can be taken out. it can.

  As described above, in the optical module 1, the submount 7 for the monitor PD 4 is attached so as to bridge between the pair of stepped portions 16 facing each other with the signal line 15a interposed therebetween. Therefore, the configuration shown by the phantom line in FIG. 6, that is, the configuration in which the submount 105 for the monitor PD 104 made of an insulating substrate such as an alumina substrate is in direct contact with the high frequency line 114 (the submount 105 is in contact with the high frequency line 114). Unlike the case where the impedance changes in this state, the high-frequency electric signal supplied from the outside can be supplied to the LD 3 without deteriorating.

  Furthermore, since the structure for mounting the submount (the pair of stepped portions 16) is integrally provided in the package 2, the cost is lower than in the case of separately preparing components having the same function. In order to form the stepped portion 16 integrally with the package 2, when the package frame 12 is manufactured, a portion that functions as the stepped portion 16 is formed on the first annular substrate 12a on which the signal supply substrate 15 is formed. The second annular substrate 12b thus formed may be laminated.

  Further, in the present optical transmission module 1, the normal line of the light receiving surface of the light receiving portion 4a of the monitor PD4 and the optical axis P of the LD3 are orthogonal to each other. If it is mounted offset in the direction, a sufficient monitor current can be obtained. Hereinafter, this will be described with reference to FIGS.

As shown in FIG. 3, the distance between the upper surface 3c of the LD 3 and the lower surface 4c of the substrate 4b of the monitor PD 4 is X, the distance between the rear end surface 3b of the LD 3 and the front surface 4d of the monitor PD 4 is Y, and ΔX = X−80 μm , The relationship between the distances ΔX, Y and the monitor current Im in the monitor PD 4 with the light receiving portion 4a having a diameter of 240 μm is as shown in FIG. In FIG. 4, the horizontal axis represents the distance ΔX, the vertical axis represents the monitor current value on the monitor PD 4, and each graph shows the distance Y = 100, 150, 200, 250, 300, 350, 400 (μm). It's time.
As shown in FIG. 4, when ΔX = ± 50 μm (X = 80 ± 50 μm) and Y = 150 ± 50 μm, a sufficient monitor current of 100 μA or more can be obtained.

In the above example, the monitor PD4 is mounted so that the normal line of the light receiving surface of the light receiving portion 4a faces downward. As shown in FIG. 5, the light receiving surface of the light receiving portion 4a is the rear end surface of the LD3. It may be mounted to face 3b.
In the case of the example in FIG. 5 as well, in the same way as in the examples in FIGS. 1 to 4, the submount 7 is metalized only on one surface (front surface in FIG. 5) to form a wiring pattern 7b for the monitor PD4. Has been. As described above, the wiring pattern 7b and the wiring patterns 16a and 16b of the package 2 are electrically connected to each other even if metallization is performed only on the front surface of the submount 7 in FIG. can do. That is, when the submount 7 is fixed on the stepped portion 16 of the package 2 with Ag paste, the submount 7 is pressed against the stepped portion 16. At this time, the Ag paste wraps up to the front surface and contacts the wiring pattern 7 b. In this case, an Ag paste may be applied in advance.

As described above, by using the submount 7 in which the metallization is performed only on one surface and the wiring pattern 7b is formed, the optical transmission module is manufactured at a lower cost than in the case of using the submount that performs metallization on a plurality of surfaces. Can do.
In the above example, the package frame 12 is formed by sequentially laminating annular substrates formed by processing ceramic green sheets to form a multilayer structure. However, the package frame 12 is manufactured by placing a ceramic material in a mold for firing. You can also. However, it is cheaper to produce from a ceramic green sheet.

  Further, the metal frame 13 is not an essential constituent element, and the metal lid 3 may be simply attached directly to the upper part of the ceramic package frame 12. As long as the lid 14 is attached so as to seal the space formed by the package frame 12 and the bottom ceramic substrate 11, the attachment structure of the lid 14 may be in any form.

DESCRIPTION OF SYMBOLS 1 ... Optical transmission module, 2 ... Package, 3 ... LD, 4 ... Monitor PD, 5 ... Electronic cooler, 6 ... Submount, 7 ... Submount 11 ... Bottom ceramic substrate, 12 ... Package frame, 13 ... Metal frame, DESCRIPTION OF SYMBOLS 14 ... Cover, 14a ... Flat glass, 14b ... This opening, 15 ... Signal supply board | substrate, 16 ... Step part, 16a ... Wiring pattern.

Claims (3)

A ceramic package frame surrounding a side of the laser diode is provided on a bottom ceramic substrate on which the laser diode is mounted, and a laser-attached lid is attached on the ceramic frame. A light transmission module that seals a light receiving element for monitoring and reflects light from a front end face of the laser diode having an optical axis parallel to the bottom ceramic substrate by a reflecting member and emits the light from the optical window,
The package frame includes a signal supply substrate on which a signal line for the laser diode is formed at a rear portion of the laser diode, and a step portion facing each other with the signal line interposed therebetween,
The optical transmission module, wherein the light receiving element is mounted on a submount attached so as to bridge between the opposed stepped portions.   The optical transmission module according to claim 1, wherein a wiring pattern for the light receiving element is formed on only one surface of the submount.   3. The optical transmission module according to claim 1, wherein the light receiving element is mounted in a state in which a light receiving surface faces downward and is offset upward from an optical axis of the laser diode. 4.

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