Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2002-02-12
2004-05-11
Chervinsky, Boris (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S699000, C361S700000, C257S706000, C257S707000, C257S714000, C174S015100, C174S016100, C174S016300, C165S080300, C165S080400, C165S104260
Reexamination Certificate
active
06735077
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermal diffuser for uniformly forming a path for close thermal coupling between a mounted electronic component and a surface of a desired thermal conductor in an electronic equipment and to a radiator for radiating heat generated in this electronic component via the thermal diffuser.
2. Description of the Related Art
In recent years, a ‘tunable OS (optical sender)’ outputting an optical signal with a prescribed wavelength stably and precisely has been in practical use owing to positive application of a technique of precisely controlling operating temperature, and consequently, a WDM (wavelength division multiplexing) transmission method is being positively applied to various transmission systems as well as to relay transmission systems such as submarine optical transmission.
FIG. 9
is a view showing a configuration example of a node in which the tunable OS is mounted.
In
FIG. 9
, the tunable OS
90
is disposed on a printed circuit board
92
constituting a package attachable to and detachable from a predetermined slot of a shelf (a rack is also acceptable)
91
.
FIG. 10
is a view showing the configuration of a radiation system of the tunable OS.
In
FIG. 10
, inside the tunable OS
90
disposed on the aforesaid printed circuit board
92
, provided is a tunable laser diode module (hereinafter, referred to as a ‘TLD module’)
94
which is connected with one end of an optical fiber
93
and has close thermal coupling with a case
90
C of this tunable OS.
An outer wall opposite to an outer wall facing the printed circuit board
92
, out of outer walls of the case
90
C, is bonded to one surface of a plate-shaped flat heat pipe
95
and the other surface of this flat heat pipe
95
is bonded to a bottom surface (supposed to be a specific surface on which no radiation fin is formed for simplification here) of a heat sink
96
.
The TDL module
94
is composed of the following elements.
a case
94
C thermally coupled with the aforesaid case
90
C (supposed to be in close contact with it for simplification here)
a peltier
97
having close thermal coupling with the inner wall of the case
94
C
a laser diode
98
having close thermal coupling with a predetermined place of a surface of this peltier
97
an optical system
99
optically coupled with an emission port of this laser diode
98
and the aforesaid one end of the optical fiber
93
.
In the conventional example having the configuration as described above, a laser beam emitted by the laser diode
98
is led to a not-shown wavelength-division multiplexing part via the optical system
99
and the optical fiber
93
. Note that the present invention does not relate to a wavelength of the above laser beam and processing for wavelength-division multiplexing (may include modulation to be executed for each wavelength) executed by the wavelength-division multiplexing part and therefore, the explanations thereof are omitted here.
Meanwhile, heat generated in the laser diode
98
in the process in which the aforesaid laser beam is emitted is once absorbed by the peltier
97
and transferred to the flat heat pipe
95
via the cases
94
C and
90
C.
Then, the flat heat pipe
95
leads thus transferred heat to each part of the bottom surface of the heat sink
96
via a heat medium (coolant) injected into linear channels which are formed in parallel to each other inside the flat heat pipe
95
as shown by the dotted line in the upper part of FIG.
10
and whose atmospheric pressure is reduced to a predetermined value.
The heat sink
96
radiates thus led heat to an exterior via the radiation fin formed on a predetermined outer wall of the heat sink
96
.
In short, the heat generated in the laser diode
98
is absorbed by the peltier
97
according to power supplied to the peltier
97
and radiated to the exterior via the cases
94
C and
90
C, the flat heat pipe
95
, and the heat sink
96
.
Therefore, the characteristics of the laser diode
98
and the optical system
99
are stably maintained and the aforesaid wavelength of the laser beam is maintained at a prescribed value as long as temperature is controlled properly via the peltier
97
.
Incidentally, in the conventional example described above, the heat generated in the laser diode
98
and transferred to the flat heat pipe
95
via the peltier
97
and the cases
94
C and
90
C is transferred to the bottom surface of the heat sink
96
via the heat medium injected individually into the plural linear channels which are formed in parallel inside the flat heat pipe
95
as described above.
Therefore, most of the above heat is transferred to the heat sink
96
via the heat medium injected only to specific channels having close thermal coupling with the peltier
97
, out of the channels formed inside the flat heat pipe
95
, via the cases
90
C and
94
C.
Consequently, thermal conductivity between the peltier
97
(the laser diode
98
) and each part of the bottom surface of the heat sink
96
is not uniform as shown in FIG.
11
and the most of the heat generated in the laser diode
98
is transferred to this heat sink
96
, for example, via regions of the bottom surface of this heat sink
96
, having close thermal coupling with the peltier
97
.
Incidentally, the above thermal conductivity between the peltier
97
(the laser diode
98
) and each part of the bottom surface of the heat sink
96
can be made uniform, for example, when a single chamber into which a coolant is injected and whose atmospheric pressure is set at a predetermined value is formed to occupy the whole area inside the flat heat pipe
95
.
However, mechanical strength of the flat heat pipe
95
in which this chamber is formed is lowered to a great extent unless the flat heat pipe
95
is formed of a strong material or is formed to have a large thickness. Furthermore, a prescribed value is not always obtained in efficiency of heat exchange achieved by the flat heat pipe
95
since adequate capillary attraction (capillary pressure) for promoting recirculation of the heat medium inside the chamber is not gained.
Moreover, in the conventional example, the flat heat pipe
95
is joined with the surface of the corresponding outer wall of the case
90
C and the bottom surface of the heat sink
96
via adhesive, which requires many man-hours in its assembly and brings about restrictions not only on decrease in thermal conductivity due to applicable adhesive but also on reduction in total thickness, and consequently, a prescribed cooling capacity is not always achieved.
However, improvement in reliability and performance, cost reduction, and downsizing are not only objects of nodes to which the aforesaid wavelength-division multiplexing method is applied but also objects common to various equipments such as the tunable OS
90
whose temperature is to be precisely controlled, and therefore, there has been a strong demand for a technique flexibly applicable to high density assembly of various devices.
Incidentally, a prescribed cooling capacity can be achieved by forming the cases
94
C and
90
C of metallic material having high thermal conductivity such as copper alloy.
However, since such metallic material generally has a large specific gravity and is higher cost compared with aluminum and the like, it has been difficult to be applied in practical use.
Furthermore, the aforesaid decrease in thermal conductivity due to the adhesive is avoidable, for example, when the peltier
97
and the cases
94
C and
90
C have close thermal coupling with the flat heat pipe
95
via a metallic screw or the like.
However, when a hole through which the above screw is to pass (or to be screwed) is formed in the flat heat pipe
95
, the aforesaid channels should be formed not to pass this hole.
Consequently, the channels are prevented from being formed linearly to cause structure complexity, and furthermore, since a place where the threaded hole is to be formed is originally a region which should have close thermal coupling with the channels (the heat medium
Iino Kazuhiro
Shirakami Takashi
Tada Yoshiaki
Yamazaki Naoya
Chervinsky Boris
Fujitsu Limited
Katten Muchin Zavis & Rosenman
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