Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2001-07-19
2003-05-13
Thompson, Gregory (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C165S080400, C174S015100, C257S714000
Reexamination Certificate
active
06563709
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a liquid-cooled heat sink and a manufacturing method thereof which is connected to a semiconductor device through a ceramic substrate, and discharges a coolant after the coolant has absorbed the heat emitted by the semiconductor device.
2. Description of the Related Art
As shown in
FIGS. 5 and 6
, a conventional example of this type of heat sink is a liquid-cooled heat sink
1
in which a flat bar formed from a malleable material made of aluminum or aluminum alloy is cut to a prescribed length, flat block
2
is fabricated by milling in which a meandering groove
2
a
is formed, cover
3
is fabricated by cutting a bar formed from a malleable material made of aluminum or aluminum alloy to a prescribed length, and this cover
3
is placed over the above flat block
2
so as to form passage
4
in which coolant passes through the above grooves
2
a.
The above liquid-cooled heat sink
1
has the problem of having an extremely large number of machining steps which increases the production cost.
In order to solve this problem, the present invention provides a liquid-cooled heat ink in which the above flat block and cover are formed by aluminum die casting. In this heat sink, since the grooves and so forth can be formed with good precision by cast extraction, the number of machining steps can be reduced considerably.
However, in contrast to the thermal conductivity of a malleable material made of aluminum or aluminum alloy being about 180 to 230 W/m.° C., the thermal conductivity of the aluminum material for die casting (ADC
12
) in the above liquid-cooled heat sink formed by aluminum die casting of the prior art is about 50% of the above malleable material at about 92 W/m.° C., thereby resulting in the problem of inferior heat radiation efficiency.
In addition, when a heat sink is fabricated by aluminum die casting, solidification and shrinkage causes cracks as well as voids depending on the shape of the heat sink, thereby resulting in the risk of leakage of coolant.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a liquid-cooled heat sink and a manufacturing method thereof that is able to obtain high thermal conductivity as well as satisfactory moldability and corrosion resistance by using a malleable material made of aluminum or aluminum alloy, while also being able to prevent leakage of coolant by preventing the occurrence of cracks and so forth.
A second object of the present invention is to provide a liquid-cooled heat sink and a manufacturing method thereof that is able to improve the heat radiation efficiency of the heat sink by increasing the amount of heat absorbed from the casing and fins by coolant passing through a passage as a result of increasing the contact surface area with the coolant, snaking the passage, or allowing heat to rapidly transfer to the fins from upper and lower walls of the casing.
A third object of the present invention is to provide a liquid-cooled heat sink and a manufacturing method thereof that is able to inhibit increases in production cost by forming through holes by extrusion molding to reduce the number of machining steps, or by unitarily forming the fins and covers with the casing in a single step.
As shown in
FIG. 1
, the invention as claimed in claim 1 is an improvement of a liquid-cooled heat sink having a passage
23
in which coolant is able to pass and which is joined to a ceramic substrate.
Its characteristic constitution is comprised of: a casing
12
of which both ends are open and in which a plurality of through holes
12
a
extending from one end to the other end are formed by a plurality of dividing walls
13
-
15
, notches
16
formed in one or both ends of the plurality of dividing walls
13
-
15
, a corrugated fin
17
inserted into each of the plurality of through holes
12
a
which demarcates each of the through holes
12
a
into a plurality of slots
12
b
extending from one end to the other end of casing
12
, a pair of covers
18
,
19
that close both ends of casing
12
, and an inlet
18
a
and outlet
18
b
of the coolant formed in casing
12
or covers
18
,
19
; wherein, passage
23
is formed by communication of notches
16
and slots
12
b,
and inlet
18
a
and outlet
18
b
are composed so as to be positioned on both ends of passage
23
.
In this liquid-cooled heat sink according to claim 1, since fin
17
is inserted into each through hole
12
a,
the contact surface area between heat sink
11
and coolant increases, thereby making it possible to improve the heat radiation efficiency of heat sink
11
.
The invention as claimed in claim 2 is the invention as claimed in 1 wherein, as shown in
FIG. 1
, notches
16
are composed of first notches
16
a
formed in one end of very other plurality of dividing walls
13
-
15
, and a second notch
16
b
formed in the other end of dividing wall
14
in which said first notches
16
a
are not formed, and passage
23
is composed so as to snake by communicating with said first notches
16
a,
second notch
16
b
and slots
12
b.
In this liquid-cooled heat sink according to claim 2, since passage
23
snakes, the amount of heat absorbed from casing
12
and fins
17
by coolant that passes through this passage
23
increases, thereby making it possible to improve the heat radiation efficiency of heat sink
11
.
As shown in
FIGS. 1 and 3
, the invention as claimed in claim 3 is a production method of a liquid-cooled heat sink comprising: a step in which a casing
12
, of which both ends are open and in which a plurality of through holes
12
a
extending from one end to the other end are formed by a plurality of dividing walls
13
-
15
, is fabricated by extrusion molding of a malleable material made of aluminum or aluminum alloy, a step in which notches
16
are formed by milling in one or both ends of the plurality of dividing walls
13
-
15
, a step in which each of the through holes
12
a
is demarcated into a plurality of slots
12
b
extending from one end to the other end of casing
12
by inserting a corrugated fin
17
into each of the plurality of through holes
12
a,
and a step in which a passage
23
is formed that is composed of notches
16
and slots
12
b
by closing both ends of casing
12
with a pair of covers
18
,
19
.
In this production method of a liquid-cooled heat sink according to claim 3, since heat sink
11
is formed using a malleable material made of aluminum or aluminum alloy, a heat sink
11
can be obtained having high thermal conductivity as well as satisfactory moldability and corrosion resistance. In addition, since through holes
12
a
serving as passage
23
can be formed by extrusion molding, the number of machining steps can be reduced as compared with heat sinks of the prior art, thereby making it possible to inhibit increases in production costs.
As shown in
FIGS. 1 and 3
, the invention as claimed in claim 4 is the invention as claimed in claim 3 wherein, notches
16
are composed of first notches
16
a
formed by milling in one end of every other plurality of dividing walls
13
-
15
, and a second notch
16
b
formed by milling in the other end of dividing wall
14
in which first notches
16
a
are not formed, and passage
23
, which snakes by communicating with first notches
16
a,
second notch
16
b
and slots
12
b,
is formed by closing both ends of casing
12
with covers
18
,
19
.
In this production method of a liquid-cooled heat sink according to claim 4, heat sink
11
of the above claim 2 can be fabricated by snaking passage
23
with only a slight increase in production cost.
As shown in
FIGS. 1 through 3
, the invention as claimed in claim 5 is the invention as claimed in claim 3 or 4 wherein, after forming fins
17
and covers
18
,
19
from a brazing sheet in which a 4000 series Al—Si alloy brazing material is coated by cladding onto the surface of a malleable material made of aluminum or aluminum alloy, and assembling fins
17
and covers
18
,
19
in casing
12
, fins
17
and covers
18
,
19
are br
Nagase Toshiyuki
Nagatomo Yoshiyuki
Negishi Takeshi
Shimamura Shoichi
Tokiwa Asao
Mitsubishi Materials Corporation
Rader & Fishman & Grauer, PLLC
Thompson Gregory
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