JPH09312363A - Package for photo semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the consumption of a valuable Cu-W alloy material, without losing the heat radiation property of a metal bottom plate by using this material for forming a limited part of the bottom plate for mounting photo semiconductor devices. SOLUTION: The photo semiconductor device mounting package has a metal bottom plate 31 composed of a Kovar-made main body 32 and Cu-W alloy-made member 33 for mounting photo semiconductor devices. The main body 32 has through-holes 32a at a part for mounting these devices to assemble inner components and recess 32b at the bottom of the package. The recess 32b has two wall faces 32c in the length direction of the main body 32 but walls in the width direction are removed. A Cu-W alloy plate fit to the recess 32b is prepared as the mounting member 33 and brazed to this recess with Ag braze to ensure the air tightness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device package, and more particularly to an optical semiconductor device package having an improved metal bottom plate.

[0002]

2. Description of the Related Art FIG. 10 shows an example of an optical semiconductor element package used in an optical communication device or the like. Usually, the package 1 for optical semiconductor elements includes a metal frame body 2, a ceramic terminal 3, a metal bottom plate 4, leads 5, a seal ring 6 and a window frame 7 to which an optical fiber is attached, as main constituent members. The metal frame 2 has a role of shaping the outer shape of the optical semiconductor element package 1, storing internal components, and bonding the ceramic terminal 3 and the optical fiber. The metal frame 2 is usually made of an Fe—Ni—Co alloy (commonly called Kovar).

The metal bottom plate 4 functions to shape the bottom of the optical semiconductor element package 1 and efficiently dissipate the heat generated inside the optical semiconductor element package 1 to the outside. This function is extremely important because the characteristics of the mounted optical semiconductor element have a temperature dependence, and it is necessary to maintain the optical semiconductor element at a constant temperature. So, for example,
As shown in FIG. 11, a laser chip 61 during laser driving
The cooling element 63 absorbs the generated heat through the carrier 62, and the heat is radiated to the outside from the heat radiation surface 63a of the cooling element 63 through the metal bottom plate 4. The metal bottom plate 4 is required to have the following two characteristics. First, as described above, high thermal conductivity is required to efficiently cool the laser chip. Secondly, since the package 1 for an optical semiconductor element is assembled by brazing, generally silver brazing, it is possible to obtain the consistency of the coefficient of thermal expansion with other components up to a high temperature (up to 800 ° C.). If the coefficient of thermal expansion is not matched with that of other parts, the metal bottom plate 4 is distorted by brazing. Then, when the board is fixed with screws using the screw holes 8, this distortion is corrected, and the optical axis of the laser chip 61 and the optical fiber (not shown) attached to the window frame 7 are relative to each other. The position is displaced, which leads to a decrease in coupling efficiency of laser light. As a material satisfying the above two characteristics, a copper-tungsten alloy is often adopted as the material of the metal bottom plate 4.

[0004]

However, in addition to the above-mentioned two characteristics, the high thermal conductivity and the matching of the thermal expansion coefficient, the metal bottom plate 4 has severe conditions regarding the shape, and it is highly accurate and various. Need to be processed. However, the copper-tungsten alloy forming the metal bottom plate 4 is an expensive material and is also known as a very difficult-to-cut material, and its processing cost becomes very high. Since the material cost and the processing cost are very high, the metal bottom plate 4 made of copper-tungsten alloy is used.
However, there is a problem that it becomes a great barrier to the cost reduction of the package for optical semiconductor elements.

The conditions of the shape of the metal bottom plate 4 will be described below.
This will be described with reference to FIG. That is, in order to prevent the deviation of the optical axis due to the screw tightening, not only the warpage due to brazing as described in the prior art but also the flatness of 10 to 30 μm on the surface 4a contacting the board at the stage of parts before brazing. Is required. Also, the brazing surface 4b is required to have high flatness for brazing. Further, since the package for optical semiconductor element is generally fixed to a board or the like by screw tightening, it is necessary to process the screw hole 4c for screw tightening.
Further, when the screw is tightened for the purpose of preventing the optical axis shift, distortion is prevented from reaching the entire metal bottom plate 4, so that the screw hole 4c is formed.
In some cases, a step 4d may be formed so that the plate thickness of the part becomes thinner than the other part, or the recessed part 4e or the like may be processed in the part where the optical semiconductor element is mounted.

It is extremely difficult to adopt a material other than the copper-tungsten alloy as the material of the metal bottom plate 4 because the two characteristics as described in the prior art must be satisfied at the same time. For example, when the Kovar used in the metal frame body 2 in FIG. 10 is adopted as the metal bottom plate 4, the thermal expansion coefficient can be matched with that of the metal frame body 2, but the thermal conductivity is low, which causes a problem of heat dissipation. Remains. By the way,
Thermal conductivity near room temperature is 10% Cu-W 180,20
% Cu-W is 200, while Kovar is 16.7 (unit: W / mK), and the thermal conductivity of Kovar is one digit smaller than that of the copper-tungsten alloy. When oxygen-free copper is used for the metal bottom plate 4, high thermal conductivity (398 W / m ·
Because of K), the heat dissipation is sufficiently secured, but the coefficient of thermal expansion does not match with that of the metal frame body 2, and a large strain occurs during brazing.
By the way, the average coefficient of thermal expansion from room temperature to around the brazing temperature of 800 ° C is about 10 × 10 ^-6 / ° C for Kovar and about 20 × 10 ^-6 / ° C for oxygen-free copper. Has an average coefficient of thermal expansion twice that of Kovar.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a package for an optical semiconductor device having a metal bottom plate on which an optical semiconductor device is mounted and a metal frame body, wherein the metal bottom plate is used. Is characterized in that a portion substantially limited to a portion on which an optical semiconductor element is mounted is made of a copper-tungsten alloy.

As described above, when the copper-tungsten alloy is used substantially only in the portion of the metal bottom plate on which the heat-dissipating property of the metal bottom plate is mounted, when the entire metal bottom plate is made of the copper-tungsten alloy material. Compared with the above, the amount of expensive copper-tungsten alloy material used can be reduced and the material cost can be reduced without impairing the heat dissipation of the metal bottom plate. In addition, as compared with the case where the entire metal bottom plate is made of a copper-tungsten alloy material,
Since the degree of processing applied to the tungsten alloy material is reduced, the processing cost is reduced.

In the present invention, the metal bottom plate can be made of the same material as the metal frame, for example, Kovar material, except for the portion where the optical semiconductor element is mounted. Then, since metal injection molding can be applied to the Kovar material, the metal bottom plate can be easily formed by performing simple processing after the near net shape product is manufactured. Further, if the coefficient of thermal expansion of the metal bottom plate and that of the metal frame are made equal, the strain generated at the time of joining them by brazing can be reduced. Furthermore, by utilizing the fact that the metal frame is the same material as the part other than the part where the optical semiconductor element of the metal bottom plate is mounted, a near net shape product in which the kovar part of the metal bottom plate and the metal frame are integrated by metal injection molding is available. It can also be produced. In this case, the brazing step of the metal frame and the portion other than the optical semiconductor element mounting portion of the metal bottom plate can be omitted, and the assembling work is simplified.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory diagram of an embodiment of a metal bottom plate that constitutes a package for optical semiconductor elements according to the present invention. The metal bottom plate 11 includes a bottom plate body 12 made of Kovar and a mounting member 13 for mounting an optical semiconductor element made of a copper-tungsten alloy.
A through hole 12 a is provided in the central portion of the bottom plate body 12, and the through hole 12 a is provided on one side of the bottom plate body 12.
The recess 12b is provided in the region including a. The mounting member 13 has a shape fitted in the recess 12b. The metal bottom plate 11 is formed by fitting the mounting member 13 into the bottom plate body 12 and brazing. At this time, the metal bottom plate 1
The mounting member 13 is fitted into the bottom plate main body 12 so that the surface corresponding to the outside of the optical semiconductor device package No. 1, that is, the bottom plate main body surface 12c and the mounting member surface 13b are flat. Then, the optical semiconductor element is mounted on the mounting member surface 13a in the through hole 12a via, for example, a cooling element.

In this embodiment, the mounting member 13 made of a copper-tungsten alloy occupies only a part of the metal bottom plate 11, and the copper-tungsten used in comparison with the case where the entire metal bottom plate is made of copper-tungsten. The alloy material can be saved. Moreover, the shape of the mounting member 13 is a simple flat plate, and the processing cost of the copper-tungsten alloy, which is a difficult-to-process material, can be reduced.

FIG. 2 is an explanatory view of another embodiment of the metal bottom plate constituting the optical semiconductor device package according to the present invention. This metal bottom plate 21 is composed of a bottom plate body 22 made of Kovar and a mounting member 23 for mounting an optical semiconductor element made of a copper-tungsten alloy. Bottom plate body 2
A through hole is provided in the central portion of 2, and the mounting member 23 is fitted therein. A recess 23a is provided in a portion of the mounting member 23 where the optical semiconductor element is mounted.

In this embodiment, the amount of copper-tungsten used can be reduced as compared with the case where the entire metal bottom plate is made of copper-tungsten. However, the amount of the copper-tungsten material used is increased as compared with the above embodiment. Further, since the mounting member 23 is provided with the recessed portion 23a, the processing cost is higher than that of the above embodiment.

[0014]

【Example】

(Embodiment 1) FIG. 3 is an exploded perspective view of an embodiment of a metal bottom plate constituting a package for optical semiconductor elements according to the present invention. This embodiment corresponds to FIG. 12 used for explaining the conventional technique. The metal bottom plate 31 of this embodiment includes a bottom plate body 32 made of Kovar and a mounting member 33 for mounting an optical semiconductor element made of a copper-tungsten alloy. Here, the copper-tungsten alloy is an alloy containing 10 to 30% of copper in tungsten. The bottom plate main body 32 is formed by metal injection molding. A binder is added to metal powder, injection is performed, and appropriate heat treatment is performed after molding, so that a complicated shape that is difficult to achieve by normal machining can be manufactured at low cost.

The metal bottom plate 31 of this embodiment is formed as follows. That is, an optical semiconductor element is mounted on the bottom plate main body 32, a through hole 32a is provided in a portion for assembling internal parts, and a recessed portion 32b is provided on the bottom surface (upper side in FIG. 3) of the optical semiconductor element package. The recess 32b is
The bottom plate main body 32 has two side wall surfaces 32c in the longitudinal direction, and the wall surface in the width direction is removed. Also, the recess 32
A plate member made of a copper-tungsten alloy having the same shape as b is prepared and plated with Ni to form the mounting member 33. Then, the mounting member 33 is brazed to the recessed portion 32b of the bottom plate body 32 so as to ensure airtightness with silver solder.

When brazing, the bottom surface is pressed against a flat surface such as a brazing jig, and a weight is applied if necessary. In order to secure the thickness of the brazing material, the mounting member 33 is thinner than the depth of the recess 32b by several tens of μm.
Variations in clearance due to processing can be filled by melting the brazing material. By brazing in this way, the bottom plate main body 32 and the mounting member 33 can be joined to each other without forming a step on the surface side of the metal bottom plate 31 which becomes the bottom of the package for optical semiconductor elements.

In the recess 32b of the bottom plate body 32, as shown in FIG. 4, the corner 32d is not a perfect right angle, but is slightly rounded. When the mounting member 33 is fitted in here, there is a possibility that the mounting member 33 does not sink and floats. Therefore, the edge 33a of the mounting member 33 is provided with a C surface as shown by the dotted line in the drawing, or the recess 32b of the bottom plate body 32 is enlarged to such an extent that the corner 32d and the edge 33a do not collide with each other. Avoid floating. 34 is a brazing material.

Further, as shown in FIG. 5, a step 32e is partially provided along the corner 32d of the recess 32b of the bottom plate main body 32 at least to the extent that the mounting member 33 can be supported, and is mounted on the bottom plate main body 32 with R. A method of avoiding the collision of the edge of the member 33 may be adopted. Furthermore, when brazing
The mounting member 33 can be brought into contact with the step 32e to accurately position in the height direction.

(Embodiment 2) FIG. 6 is an exploded perspective view of another embodiment of the metal bottom plate constituting the optical semiconductor element package according to the present invention. In this embodiment, the metal bottom plate 41 includes the bottom plate body 42 and the mounting member 4 made of a copper-tungsten alloy.
Consists of three. The bottom plate body 42 is provided with a recess 42b. Unlike the above embodiment, the recess 42b of the bottom plate body 42 has a right-angled quadrilateral shape surrounded by the four side wall surfaces of the bottom plate body 42. The mounting member 43 is fitted into the recess 42b and brazed.

(Embodiment 3) FIG. 7 is an exploded perspective view of still another embodiment of the metal bottom plate constituting the optical semiconductor device package according to the present invention. In this embodiment, the bottom plate body 52 of the metal bottom plate 51 has a right angle 4 surrounded by the wall surface 52b.
A quadrangular through hole 52a is provided. The mounting member 53 made of a copper-tungsten alloy is made of a copper-tungsten alloy plate material having the same shape as the through hole 52a. The mounting member 53 is fitted into the through hole 52a and brazed. The surface of the metal bottom plate 51 on which the optical semiconductor element is mounted is flat, which is different from the first and second embodiments.

(Embodiment 4) FIG. 8 is an exploded perspective view of still another embodiment of the metal bottom plate constituting the optical semiconductor device package according to the present invention. In this embodiment, the metal bottom plate 61 is constructed by brazing the bottom plate body 62 to both sides of the mounting member 63 made of a copper-tungsten alloy. The surface of the metal bottom plate 61 on which the optical semiconductor element is mounted is flat.

In the third and fourth embodiments, in order to prevent the brazing material from flowing out during brazing, as shown in FIG. 9, the bottom plate bodies 52 and 62 and the mounting members 53 and 63 are provided.
Staggered steps 52b, 62a on the brazed part of
It is preferable to provide 53a and 63a.

Further, the mounting member made of the copper-tungsten alloy has a high strength when the plate thickness is large, but the heat dissipation characteristics deteriorate.
On the contrary, as the thickness is thinner, the heat dissipation characteristics are improved, but the strength is weakened. From the relationship between heat dissipation characteristics and strength, as an example, the preferred plate thickness is 0.3 to 1.0 mm, and the most preferred plate thickness is 0.5 mm.
A value of ˜0.8 mm was obtained.

[0024]

As described above, according to the present invention, in a package for an optical semiconductor element having a metal bottom plate on which an optical semiconductor element is mounted and a metal frame, the metal bottom plate is a portion on which the optical semiconductor element is mounted. Since the portion substantially limited to 1 is made of a copper-tungsten alloy, there is an excellent effect that an inexpensive package for an optical semiconductor element can be manufactured without impairing necessary functions.

[Brief description of drawings]

FIG. 1 is an exploded explanatory view of an embodiment of a metal bottom plate which constitutes a package for an optical semiconductor device according to the present invention.

FIG. 2 is an explanatory view of another embodiment of the metal bottom plate which constitutes the optical semiconductor device package according to the present invention.

FIG. 3 is an exploded perspective view of an embodiment of a metal bottom plate that constitutes a package for an optical semiconductor device according to the present invention.

FIG. 4 is an explanatory view of a joined state of the bottom plate body and the mounting member in the embodiment shown in FIG.

5 is another explanatory view of the joined state of the bottom plate body and the mounting member in the embodiment shown in FIG.

FIG. 6 is an exploded perspective view of still another embodiment of the metal bottom plate constituting the optical semiconductor device package according to the present invention.

FIG. 7 is an exploded perspective view of still another embodiment of the metal bottom plate constituting the optical semiconductor device package according to the present invention.

FIG. 8 is a perspective view of still another embodiment of the metal bottom plate constituting the optical semiconductor device package according to the present invention.

FIG. 9 is an explanatory view of a brazing portion of the bottom plate body and the mounting member in the embodiment shown in FIGS.

FIG. 10 is a perspective view of a conventional optical semiconductor device package.

11 is a partial explanatory view of a portion of the optical semiconductor element package shown in FIG. 10 on which an optical semiconductor element is mounted.

FIG. 12 is a perspective view of a conventional metal bottom plate.

[Explanation of symbols]

 11, 21, 31, 41, 51, 61 Metal bottom plate 12, 22, 32, 42, 52, 62 Bottom plate body 12a, 32a, 52a Through hole 12b, 23a, 32b, 42b Recessed portion 12c Bottom plate body surface 13, 23, 33, 43, 53, 63 mounting member 13a, b mounting member surface 32c, 52b wall surface 32d corner 32e step 33a edge 34 brazing material 52b, 53a, 62a, 63a step

Claims (2)

[Claims] 1. A package for an optical semiconductor element having a metal bottom plate on which an optical semiconductor element is mounted and a metal frame body,
A package for an optical semiconductor element, wherein the metal bottom plate is made of a copper-tungsten alloy in a portion substantially limited to a portion where an optical semiconductor element is mounted. 2. The bottom plate body, wherein the metal bottom plate has a through hole in a portion where the optical semiconductor element is mounted, and a recessed portion in a region including the through hole on a side opposite to a side where the optical semiconductor element is mounted, 2. A package for an optical semiconductor element according to claim 1, further comprising a mounting member that is fitted into and bonded to the recessed portion, and a copper-tungsten alloy is used only for the mounting member.