Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With reflector – opaque mask – or optical element integral...
Reexamination Certificate
2002-01-28
2004-11-02
Pert, Evan (Department: 2827)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With reflector, opaque mask, or optical element integral...
C257S079000, C257S080000, C257S100000, C257S666000
Reexamination Certificate
active
06812501
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to semiconductor laser packages and a fabrication method thereof. Here, “semiconductor laser package” includes a laser diode (referred to as “laser chip” herein after) and predetermined light receiving means. The semiconductor laser package is a component with the required lines led out. This is employed as a light source in the optical pickup apparatus of an optical disc system.
2. Description of the Background Art
A conventional semiconductor laser package is disclosed in, for example, Japanese Patent Laying-Open No. 11-233808 in
FIG. 2
(referred to as “first prior art”). The semiconductor laser package will be described with reference to
FIGS. 7 and 8
reflecting the design concept of first prior art
1
. Although the details in the structure of
FIGS. 7 and 8
differ from those of first prior art
1
due to the difference in the specification of the semiconductor laser package of interest, the basical design concept follows that of first prior art
1
. In the description, the reference of “up” and “down” is based on the orientation with the output direction of the laser beam of the semiconductor laser package in a vertical upward direction.
As shown in
FIG. 7
, the conventional semiconductor laser package is formed of a combination of an island member
51
and resin members
55
a
and
55
b
. Island member
51
is a metal member constituting the base where a laser chip
3
and a light receiving element
4
are mounted. Island unit
51
is formed by cold forging. A plurality of leads
6
are embedded in resin members
55
a
and
55
b
. The upper end of lead
6
is exposed above respective resin members
55
a
and
55
b
for the connection with laser chip
3
and light receiving element
4
. Resin members
55
a
and
55
b
are assembled with island member
51
therebetween to be joined integrally by ultrasonic welding.
The main part in an assembled state is shown in FIG.
8
. Although not shown in
FIG. 8
, laser chip
3
and light receiving element
4
are wire-bonded with the upper end of lead
6
in practice. Lead
6
also extends below island member
51
.
In the conventional semiconductor laser package, laser chip
3
and light receiving element
4
are both secured to a block member
57
of island member
51
, as shown in FIG.
8
. Specifically, laser chip
3
is disposed at a side plane of block member
57
whereas light receiving element
4
is disposed at the top plane of block member
57
. Island member
51
has a base plane
2
facing upwards. It is desired that laser chip
3
and light receiving element
4
are secured to have a predetermined position relationship with respect to base plane
2
. Specifically, assuming that the height of the radiation plane of laser chip
3
from base plane
2
is Zl and the height of the light receiving plane of light receiving element
4
from the radiation plane of laser chip
3
is Zd, it is desired that Zl and Zd are set to respective design values.
Fine adjustment of the attaching position of laser chip
3
is allowed since laser chip
3
is disposed at the side plane of block member
57
. Zl can be made to approximate the design value. However, the height of the top plane of block member
57
from base plane
2
is greatly variable since island member
57
is formed by cold forging. Therefore, Zd cannot be ensured to be set to the exact design value even if Zl approximates the design value. Rather, Zd will often be deviated from the design value if the accuracy of Zl is sought. Although the light emitting point of the laser beam should match the focal point of the lens in an ideal situation when incorporated into an optical pickup apparatus, deviation of Zd from the design value will result in misalignment between the light emitting point of the laser beam and the focal point of the lens, or between the light receiving plane of light receiving element
4
and the focal point of the lens to mar the balance of the focus signal.
The portion of resin members
55
a
and
55
b
holding lead
6
is apt to be thin due to the structure of holding respective leads
6
. This thin region of resin members
55
a
and
55
b
will result in a weaker hold on lead
6
. It is to be noted that a ultrasonic wave is applied to the wire in the process of wire bonding, whereby lead
6
is rubbed. If the hold on lead
6
is weak, lead
6
will move, resulting in the degradation of the connection accuracy between the wire and lead
6
. This is particularly noticeable in a thin type semiconductor laser package in which resin members
55
a
and
55
b
are thin.
Also, since island member
51
is formed of metal and integrally, an insulator must be sandwiched between laser chip
3
or light receiving element
4
and island member
51
to electrically insulate laser chip
3
from light receiving element
4
.
SUMMARY OF THE INVENTION
In view of the forgoing, an object of the present invention is to provide a semiconductor laser package and fabrication method thereof that allows approximation of both Zl and Zd to the design values, having sufficient hold of the lead, and dispensable of the aforementioned insulator.
Another object of the present invention is to provide an optical pickup apparatus.
According to an aspect of the present invention, a semiconductor laser package includes an island member formed of metal, having a base plane and a block member protruding substantially perpendicularly to the base plane, a lead, a resin member molded integrally with the island member and the lead so as to fix the relative position relationship between the island member and the lead, a laser chip fixed at the block member to allow a laser beam to be emitted in a direction substantially perpendicular to the base plane, and a light receiving unit directly fixed at the resin member. By employing such a structure, the laser chip is fixed to the block member of the island member whereas the light receiving unit is directly fixed at the resin member. Therefore, the position of the laser chip and the position of the light receiving element can be adjusted and determined independent of each other. Thus, a semiconductor laser package having the relative position between the laser chip and the light receiving unit set closer to the design value is provided.
Preferably, the resin member includes a light receiving unit attaching plane that is substantially parallel to the base plane. The light receiving unit is mounted at the light receiving unit attaching plane. By employing such a structure, the distance between the light receiving plane of the light receiving unit and the base plane can be set more accurately while fixation of the light receiving unit is facilitated.
Preferably, a heat radiator is fixed at the block member. The laser chip is fixed to the block member so as to come into contact with the heat radiator. Since the laser chip and the heat radiator are brought into contact by the above structure, the heat generated from the laser chip can be promptly discharged by the heat radiator. A semiconductor laser package of stable operation can be achieved.
Preferably, the heat radiator includes light receiving means. The reflected light can be monitored by the light receiving means.
Preferably, a hologram element is arranged to be located on an optical path of the laser beam emitted from the laser chip. By employing such a structure, the emitted light passing through the hologram element as well as reflected light can be subjected to a desired process such as dispersion.
Preferably, a cover is provided so as to enclose the laser chip and the light receiving unit. Accordingly, intrusion of foreign objects around the laser chip and light receiving unit can be prevented. A stable semiconductor laser package can be provided.
A fabrication method of a semiconductor laser package according to the present invention includes a resin molding step of molding integrally with resin an island member formed of metal including a base plane and a block member protruding from the base plane substantia
Hamaoka Osamu
Ishiguro Takahide
Mitchell James
Morrison & Foerster / LLP
Pert Evan
Sharp Kabushiki Kaisha
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