Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Metallic housing or support
Reexamination Certificate
1999-04-06
2002-03-12
Picardat, Kevin M. (Department: 2822)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Metallic housing or support
C438S025000, C438S026000, C438S029000
Reexamination Certificate
active
06355505
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat sink which integrally carries a semiconductor laser chip as part of a semiconductor laser device, and a method of manufacturing such a heat sink.
2. Description of the Related Art
Semiconductor laser devices (hereinafter referred to as “LD”) have heretofore widely been used in various fields including electricity, electronics, communications, etc.
As shown in
FIG. 27
of the accompanying drawings, an LD
1
comprises a heat sink
2
and a semiconductor laser chip (hereinafter referred to as “LD chip”)
3
disposed on and integrally coupled to the heat sink
2
. A laser beam is emitted from ends of the heat sink
2
and the LD chip
3
where they lie flush with each other.
The LD chip
3
is bonded to the heat sink
2
which is highly thermally conductive in order to prevent the LD chip
3
from being destroyed due to its own heat buildup developed when the LD chip
3
emits a laser beam. The heat sink
2
is made of a copper-based material of good thermal conductivity for efficiently absorbing the heat of the LD chip
3
and allowing the LD chip
3
to emit a laser beam highly efficiently.
In order to radiate the heat from the LD chip
3
reliably, the LD chip
3
and the heat sink
2
need to be held in close contact with each other over their entire contact surfaces. The surface of the heat sink
2
to which the LD chip
3
is bonded is required to have an ultra-accurate level of surface roughness and surface flatness in its entirety up to their edges. Specifically, the heat sink
2
should preferably be a heat sink
2
a
(see
FIG. 28
of the accompanying drawings) whose cross-sectional shape exhibits an ultra-accurate level of surface roughness and surface flatness. A heat sink
2
b
(see
FIG. 29
of the accompanying drawings) having a large level of surface roughness and a poor level of surface flatness, and a heat sink
2
c
(see
FIG. 30
of the accompanying drawings) with a burr
4
on an edge thereof are not suitable for use with an LD chip.
It is necessary that the end of the heat sink
2
be free of any burrs at its edge close to the LD chip
3
so as not to obstruct the laser beam emitted from the LD chip
3
. More specifically, as shown in
FIG. 31
of the accompanying drawings, if the heat sink
2
a
having an ultra-accurate level of surface roughness and surface flatness and free of any burrs at its edges is used, then it can efficiently absorb the heat of the LD chip
3
and allow the LD chip
3
to radiate the emitted laser beam highly efficiently. However, as shown in
FIG. 32
of the accompanying drawings, if a heat sink
2
d
with a large drooping surface
5
present on an edge thereof is used, then the ends of the LD chip
3
and the heat sink
2
d
from which a laser beam is emitted are not held in intimate contact with each other, but spaced from each other by a clearance
6
. Therefore, the LD chip
3
suffers poor heat radiation, and may be broken due to its own heat buildup. As shown in
FIG. 33
of the accompanying drawings, if a heat sink
2
c
with a burr
4
present on an edge thereof is used, then the burr
4
blocks the laser beam emitted from the LD chip
3
, and hence causes a lack of laser beam output power.
To meet the strict requirements for the heat sink
2
, it has been the conventional practice to manufacture the heat sink
2
as follows: The surface of a panel of heat sink stock on which the LD chip
3
is to be mounted is machined by precision grinding, lapping, or the like, and then a heat sink
2
of desired shape is blanked out of the panel of heat sink stock by a press or cut off the panel of heat sink stock by a cutting machine. According to the lapping process, the surface of the panel of heat sink stock is polished by an abrasive material.
However, the above conventional manufacturing process fails to produce heat sinks having an ultrahigh level of surface finish accuracy (surface roughness and surface flatness) at a stable rate, and tends to result in large burrs and drooping surfaces on edges of produced heat sinks.
Furthermore, the conventional manufacturing process requires large investments to be made in the purchase of mechanical facilities for machining heat sinks. As a consequence, the cost of heat sinks produced by the conventional manufacturing process is relatively high.
Recent years have seen demands for more efficient absorption of an increased heat buildup in high-power LDs.
SUMMARY OF THE INVENTION
It is a main object of the present invention to provide a heat sink which has a desired ultrahigh level of surface finish accuracy over an entire surface thereof up to its edges and which can be manufactured relatively inexpensively, and a method of manufacturing such a heat sink.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.
REFERENCES:
patent: 5500077 (1996-03-01), Nishibayashi et al.
patent: 5943553 (1999-08-01), Spaeth
patent: 6025213 (2000-02-01), Nemoto et al.
Fujisawa Mamoru
Hanada Yoshikazu
Maeda Hiroshi
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