JP2736197B2 - Package for optical semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a package for an optical semiconductor device such as a semiconductor laser device, and more particularly to a package useful for an optical pickup such as an optical disk player.

[0002]

2. Description of the Related Art As a conventional package for an optical semiconductor device, there is, for example, a package for a semiconductor laser as shown in plan views and side views of FIGS. 5 (a) and 5 (b). The package of the semiconductor laser element 51 is formed by mounting a semiconductor laser chip 5 on a metal block (heat sink) 52 in the package.
3 is die-bonded, and a metal cap 55 provided with a window glass 54 for laser irradiation so as to cover them is electrically welded to a metal stem 57 provided with a reference surface 56 to shut off the outside atmosphere and the inside of the cap 55. doing. The semiconductor laser chip 53 is electrically connected by wire bonding to the electrode pins 58, 58 which penetrate the stem 57 and are drawn out of the package while hermetically sealing the inside of the cap 55 by a hermetic seal.

Generally, a semiconductor laser device is not used alone, but is used in combination with an optical component such as a lens. For example, when used in an optical disk pickup as shown in the schematic diagram of FIG. 6, the light emitting point position of the semiconductor laser element 51 as a light source is determined by the design value such as the f-number of the lens 59. As described above, the position of the semiconductor laser chip 53 in the package cannot be directly measured. Therefore, in order to guarantee the positional relationship between a certain position on the outer surface of the package and the semiconductor laser chip 53, the package is provided with the reference surface 56 as described above.

That is, FIG. 5 shows an example in which a TO-18 package is used.
Is provided, and the semiconductor laser chip 5 from above the reference plane 56 is provided.
The light emitting point position of No. 3 and the center of the outer diameter of the reference surface 56 and the light emitting point position are guaranteed with a certain tolerance. Therefore, as shown in FIG. 6, by attaching the semiconductor laser element 51 to the housing 60 of the optical pickup, the optical position with respect to the lens 59 and the like can be easily determined.

[0005]

However, since the conventional semiconductor laser package uses the metal stem 57, it is necessary to electrically insulate the electrode pins 58, 58 by a hermetic seal. This insulating part is an obstacle when miniaturizing the package. In particular, not only a light emitting element such as a semiconductor laser chip, but also a package containing an OEIC combined with an optical element and an integrated circuit (IC), or a hologram laser containing a semiconductor laser chip and a photodiode for reading a signal from an optical disk in one package. In the unit, the number of electrode pins increases, the package becomes large, and it becomes an obstacle to a thin and lightweight optical pickup or the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been made to reduce the size of an optical semiconductor device package, reduce the thickness and weight of an optical pickup by using ceramic as a stem material, and attach a metal plate as a reference surface of the package. Accordingly, it is an object of the present invention to provide an optical semiconductor element package that can easily align an optical element.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a package for an optical semiconductor device which has a built-in optical semiconductor device chip and which is shielded from the outside atmosphere. The package has a stem made of a ceramic material having metallized wiring electrodes. In addition, a metal plate serving as a reference surface of the package is attached to the back surface of the stem.

[0008]

As described above, in the package of the present invention, the stem itself is used as an electrically insulating material having good heat dissipation properties of the ceramic in the stem for fixing the optical semiconductor chip such as the semiconductor laser chip by die bonding. Since fine plating wiring can be performed and an insulating portion in a conventional metal package is not required, the size of the package can be reduced. Further, the ceramic shrinks due to the firing step, and has a larger tolerance than a metal stem, and is not suitable as a reference surface forming portion. For this reason, in the present invention, the metal plate as the reference surface is attached, thereby increasing the positional accuracy of the semiconductor laser chip and easily aligning the semiconductor laser chip with other optical elements.

[0009]

1 shows an embodiment of a hologram laser unit using an optical semiconductor device package according to the present invention. FIG. 1 (a) is a perspective view from above and FIG. 1 (b) is a perspective view from below. It is. FIG. 2 is a sectional view showing the internal structure.

The package includes a ceramic stem 1 and a metal plate 2 for a reference surface. The reference surface metal plate 2 is fixed to the back surface of the ceramic stem 1 by brazing material or the like.

On the ceramic stem 1, a metal block (heat sink) 3 is fixed with a brazing material, for example, AuSi or the like, and the semiconductor laser chip 4, the PIN diode 5 for monitoring the laser emission light, and the optical disk from the optical disk. The signal reading photodiodes 6 for receiving return light are die-bonded. Each of the optical semiconductor chips 4, 5, 6 is electrically connected to a surface electrode 8 formed on the ceramic stem 1 by a wire bond 7. The surface electrode 8 is provided by metallization, and an electrode with a fine pitch can be formed. The ceramic stem 1 has a lead frame 10 formed with a through hole 9 connected to the front surface electrode 8 and brazed at the through hole 9 on the back surface. , 6 are led out of the package by these.

The ceramic cap 11 is provided with a window glass 12 for emitting laser light, and is bonded to the ceramic stem 1 with an epoxy resin material so that each of the optical semiconductor chips 4,
5 and 6 are covered to shield the outside atmosphere from the inside of the cap 11. The hologram element 13 for light diffraction is adjusted and fixed on the cap 11, thereby constituting a hologram laser unit.

FIG. 3 shows a case where an optical pickup is assembled using the above-mentioned hologram laser unit. A metal plate 2 fixed to a ceramic stem 1 by a brazing material or the like includes a semiconductor laser chip 4 (FIG. 1, FIG. 2)
Function as a reference plane 15 indicating the light emitting point position of the semiconductor laser chip 4 in the unit 14
And the optical components such as the collimating lens 16 can be easily aligned. Also, as clearly shown in FIG.
Since the semiconductor laser chip 4 is die-bonded so that the outer diameter center “0” of the metal plate 2 matches the light emitting point position of the semiconductor laser chip 4, the hologram laser unit 14
When the optical pickup is incorporated into an optical pickup, the rotation can be easily adjusted.

In the optical pickup shown in FIG. 3, after the laser beam passes through the hologram element 13 and the collimating lens 16,
The light is guided toward the disk 18 by the mirror 17 and the spot is narrowed by the objective lens 19. The return light from the disk 18 passes through the above-described reverse path and passes through the signal reading photodiode 6 in the hologram laser unit 14 (FIGS. 1 and 2).
And the signal is read.

FIG. 4 is a perspective view of a main part showing another embodiment. In this embodiment, a block 20 made of an electrically insulating material having excellent thermal conductivity such as AlN is used instead of the metal block 3 fixed on the ceramic stem 1 shown in FIGS.

A surface wiring 20 is provided on an electric insulating block 20 of AlN or the like, and a semiconductor laser chip 4 and a signal reading photodiode 6 are die-bonded and wire-bonded to the electric wiring 20 to be electrically connected thereto. Further, the block 20 is fixed to the ceramic stem 1 by a brazing material, and the electrode terminals of each optical semiconductor element are connected to the outside of the unit through the surface electrodes 8, the through holes 9 and the lead frame 10 (see FIG. 2) as in the previous embodiment. Is derived. This example has the advantage that the wiring inside the unit can be performed by the insulating block itself and the steps such as wire bonding can be simplified.

[0017]

As described above, according to the present invention, in a package for an optical semiconductor device accommodating a semiconductor laser chip or the like, a conventional metal stem portion is formed of a ceramic material, and fine pitch electrodes are formed by metallization. This enables a compact design for a package that requires a large number of electrode pins, and a metal plate attached to the back surface acts as a reference surface, allowing the optical semiconductor device chip such as a semiconductor laser chip in the package to The positional accuracy with respect to a housing for accommodating a package such as a pickup and other optical components can be easily increased.

[Brief description of the drawings]

FIG. 1 is a perspective view (a) from above and a perspective view (b) from below showing a package according to an embodiment of the present invention.

FIG. 2 is a sectional view of the same.

FIG. 3 is a cross-sectional view showing a case where the optical pickup is incorporated as an optical pickup.

FIG. 4 is a perspective view of a main part showing another embodiment.

5A and 5B are a plan view and a side view showing a conventional example.

FIG. 6 is a sectional view showing a case where the optical pickup is incorporated as a conventional optical pickup.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic stem 2 Metal plate for reference surfaces 4 Semiconductor laser chip 6 Photodiode for signal reading 8 Surface electrode 9 Through hole 10 Lead frame

Claims (1)

(57) [Claims] 1. An optical semiconductor device package having an optical semiconductor device chip built therein for shielding an external atmosphere from a surrounding atmosphere. The optical semiconductor device package has a stem made of a ceramic material on which wiring electrodes are formed by metallization. A package for an optical semiconductor device, comprising a metal plate attached thereto.