JPH0555609A - Optical module - Google Patents

Abstract

PURPOSE:To improve long-term reliability by reducing the fluctuation of the optical output after mounting, concerning the optical module used for optical communication system. CONSTITUTION:An optical module 1 is provided where main optical parts such as a light emitting element 4, a condensing lens 6, etc., are provided on a stem 2 and are sealed, a recess 15 is made in the mounting face of the stem 2 in the case of mounting the optical module 1 on a printed board.

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 an optical communication system.

In recent years, optical communication systems have become faster, have a large capacity,
With the rapid progress of long distance, optical modules are required to have long-term reliability. Therefore, it is necessary to reduce the fluctuation of the optical output after mounting the optical module.

[0003]

2. Description of the Related Art FIG. 3 is a sectional view showing the structure of a conventional optical module. In FIG. 3, the optical module 1 has a mounting hole 2
The substrate 3 is brazed with silver brazing or the like on the plate-shaped stem 2 having a formed therein. The light emitting element 4 is provided on the substrate 3.
Is provided, a light receiving element 5 for monitoring the light emitting state of the light emitting element 4 is provided behind it, and a holder 7 for supporting the condenser lens 6 is provided at the front. Then, the housing 8 is brazed on the stem 2 with silver solder or the like so as to cover it.

The housing 8 is provided with a support 9, and the support 9 is provided with a glass window 10 to be hermetically sealed. The optical fiber 11 is provided with a ferrule 12,
The optical axis is aligned so that the light emitted from the light emitting element 4 enters the end face of the optical fiber 11 via the condenser lens 6, and the ferrule 12 is fixed to the support 9.

Such an optical module 1 is fixed to a printed circuit board or the like with a mounting hole 2a by a screw.

[0006]

By the way, the stem 2 is attached to the stem 2 by mechanical strain when the substrate 3 or the housing 8 is attached to the stem 2, or by a foreign substance or the like when the optical module 1 is attached to a printed circuit board or the like. Warpage or unevenness occurs. In particular, it becomes particularly noticeable as the stem 2 becomes thinner as the optical module 1 becomes smaller.

If the printed circuit board is tightened and fixed with screws in this state, stress is generated in the solder or the like fixing the main optical components such as the light receiving element 4. As a result, there is a problem in that the optical output such as an optical axis shift fluctuates or a solder creep phenomenon or the like is induced to lower long-term reliability.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide an optical module that reduces fluctuations in optical output after mounting and improves long-term reliability.

[0009]

SUMMARY OF THE INVENTION The above-mentioned problems can be solved by the following: in a housing mounted on a base mounted on a printed circuit board, irradiation light from a light emitting portion provided on the base is passed through an optical waveguide. In an optical module that outputs light as a result, the problem can be solved by forming a recess of a predetermined size on the mounting surface of the base to the printed circuit board.

[0010]

As described above, the recess is formed on the mounting surface of the base. Therefore, even if the base is warped or uneven, only the periphery of the mounting of the base on the printed circuit board is forced to bend, and the portion where the optical components are provided is less likely to bend.

As a result, it is possible to reduce the fluctuation of the optical output after mounting the optical module, and it is possible to improve the long-term reliability without causing solder creep due to deformation.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of an embodiment of the present invention.
The same components as those in FIG. 3 are designated by the same reference numerals.

In FIG. 1, the optical module 1 has a mounting hole 2
On the lower surface of the stem 2 which is the base on which the a is formed, the recess 15 is formed to the maximum in the vicinity of the mounting hole 2a, and the substrate 3 is attached to the upper surface by brazing with silver solder or the like. The stem 2 is formed of a material having good heat dissipation (heat conductivity) such as cobalt, stainless steel, and copper tungsten, and prevents the internal temperature from rising. The recess 15 is preferably formed to be larger than at least a mounting portion of a housing (described later).

A light emitting element 4, which is a light emitting portion, is supported on the substrate 3, and a light receiving portion 5 for monitoring the light emitting state of the light emitting element 4 is provided behind it. A holder 7 having a condenser lens 6 therein is attached to the front of the light emitting element 4 on the substrate 3 by soldering or the like. A housing 8 is attached to the stem 2 by brazing with silver solder or the like so as to cover the substrate 3. The housing 8 is provided with a support 9, and the support 9 is provided with a glass window 10 to be hermetically sealed. A ferrule 12 is provided in the optical fiber 11, and the optical axis is aligned so that the light emitted from the light emitting element 4 enters the terminal of the optical fiber 11 through the condenser lens 6, and the ferrule 12 is supported by the support 9 Fixed to.

Then, the optical module 1 is mounted on the printed board 16 (see FIG. 2), and the optical module 1 is mounted by tightening screws (not shown) through the mounting holes 2a.

Next, FIG. 2 shows a diagram for explaining the stem of FIG. FIG. 2 shows a case where the stem 2 is warped in the + direction (direction of the drawing) by, for example, 50 μm due to attachment of optical components, and FIG. 2 (A) is the case of the present invention, and FIG. Is a conventional case as shown in FIG. The stem 2 has a flatness of ± 50μ in the current manufacturing process.
In many cases, it will warp in m, and in many cases it will warp in the + direction by brazing the housing 8 and the like.

In FIG. 2A, the recess 15 of the stem 2
When the mounting surface on which is formed is placed on the printed circuit board 16, the edge A of the concave portion 15 contacts the printed circuit board 16. Therefore, when the stem 2 is fastened to the printed circuit board 16 with the screw from the mounting hole 2a, the stem 2 causes only the amount of X bending around the mounting hole 2a with the edge A as a fulcrum. This bending does not give stress to the main optical components such as the light emitting element 4 and the condenser lens 6 provided in the housing 8, and does not affect the positional relationship between them. That is, it is possible to prevent the fluctuation of the optical output from the optical fiber 11 without causing the optical axis shift. In this case, the depth of the recess 15 should be set to be larger than the bending amount X.

On the other hand, in FIG. 2B, when the concave portion 15 is not formed, the stem 2 is bent by the amount of Y with the point B at which it abuts the printed circuit board 16 as a fulcrum by tightening the screw in the mounting hole 2a. By occurring throughout the stem. As described above, when the stem 2 is warped by 50 μm, the optical axis is deviated due to the tightening of the screw, and the optical output is not output from the optical fiber 11.

In the above embodiment, the case where the warp of the stem 2 is in the + direction (the drawing direction of FIG. 2) has been described.
Even if it is warped in the direction (the direction opposite to the drawing), the amount of bending of the stem 2 due to the tightening of the screw is the same, and the same effect is obtained.

[0020]

As described above, according to the present invention, by providing the concave portion on the mounting surface of the base to the printed circuit board,
Since the bending of the base at the time of mounting the optical module can be reduced, it is possible to reduce the fluctuation of the optical output after mounting and also to maintain the high reliability for a long time.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram for explaining the stem of FIG.

FIG. 3 is a sectional view showing the configuration of a conventional optical module.

[Explanation of symbols]

 1 Optical Module 2 Stem 2a Mounting Hole 4 Light-Emitting Element 5 Light-Receiving Element 6 Condensing Lens 8 Housing 9 Support 11 Optical Fiber 15 Recess 16 Printed Circuit Board

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 33/00 H 8934-4M

Claims (2)

[Claims] 1. Irradiation from a light emitting part (4) provided on a base (2) in a housing (8) mounted on the base (2) attached to a printed circuit board (16). In an optical module for outputting light through an optical waveguide (11), a recess (15) having a predetermined size is formed on a mounting surface of the base (2) to the printed board (16). Characteristic optical module. 2. The optical module according to claim 1, wherein the recessed portion (15) is formed to be larger than a mounting portion of the housing (8).