U.S. patent application number 17/090950 was filed with the patent office on 2021-05-13 for heat conduction member.
The applicant listed for this patent is Chaun-Choung Technology Corporation, Nidec Corporation. Invention is credited to Masaaki HANANO, Toshihiko KOSEKI, Takeru OMURA, Kiyoshi TADA, Masashi TAKAO.
Application Number | 20210140718 17/090950 |
Document ID | / |
Family ID | 1000005241066 |
Filed Date | 2021-05-13 |
![](/patent/app/20210140718/US20210140718A1-20210513\US20210140718A1-2021051)
United States Patent
Application |
20210140718 |
Kind Code |
A1 |
OMURA; Takeru ; et
al. |
May 13, 2021 |
HEAT CONDUCTION MEMBER
Abstract
A heat conduction member includes a housing including a space
therein, a wick structure located in the space, and a working fluid
enclosed in the space. The housing includes one or more metal
plates and a joint structure that connects the one or more metal
plates. The joint structure includes two stacked metal plate layers
and a boundary portion between the two metal plate layers. The
boundary portion includes a first region including crystal grains
straddling the two metal plate layers.
Inventors: |
OMURA; Takeru; (Kyoto,
JP) ; TADA; Kiyoshi; (Kyoto, JP) ; TAKAO;
Masashi; (Kyoto, JP) ; HANANO; Masaaki;
(Kyoto, JP) ; KOSEKI; Toshihiko; (Kyoto,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nidec Corporation
Chaun-Choung Technology Corporation |
Kyoto
New Taipei City |
|
JP
TW |
|
|
Family ID: |
1000005241066 |
Appl. No.: |
17/090950 |
Filed: |
November 6, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F28D 15/0275
20130101 |
International
Class: |
F28D 15/02 20060101
F28D015/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 8, 2019 |
JP |
2019-203145 |
Claims
1. A heat conduction member comprising: a housing including a space
therein; a wick structure located in the space; and a working fluid
enclosed in the space; wherein the housing includes one or more
metal plates and a joint structure that connects the one or more
metal plates; the joint structure includes two stacked metal plate
layers and a boundary portion between the two metal plate layers;
and the boundary portion includes a first region includes crystal
grains straddling the two metal plate layers.
2. The heat conduction member according to claim 1, wherein the
boundary portion includes a second region including an interface
between the two metal plate layers.
3. The heat conduction member according to claim 2, wherein when a
cross section of an approximately 1 mm range of the boundary
portion is observed at 10 locations randomly selected from the
joint structure, the first region and the second region exist
alternately in all the boundary portions.
4. The heat conduction member according to claim 2, wherein the
boundary portion has a sea-island structure including the first
region that is a discontinuous phase and the second region that is
a continuous phase in plan view.
5. The heat conduction member according to claim 1, wherein when a
cross section of an approximately 1 mm range of the boundary
portion is observed at 10 locations randomly selected from the
joint structure, a mean value of a number of the first regions
included in the boundary portion is about 10.0 or more and about
20.0 or less.
6. The heat conduction member according to claim 1, wherein when a
cross section of an approximately 1 mm range of the boundary
portion is observed at 10 locations randomly selected from the
joint structure, a mean value of a total length of the first
regions included in the boundary portion is about 0.05 mm or more
and about 0.95 mm or less.
7. The heat conduction member according to claim 1, wherein the
housing has a tubular shape; and the heat conduction member defines
a heat pipe.
8. The heat conduction member according to claim 1, wherein the
housing includes the two metal plates facing each other; and the
heat conduction member defines a vapor chamber.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority under 35 U.S.C.
.sctn. 119 to Japanese Application No. 2019-203145 filed on Nov. 8,
2019 the entire contents of which are hereby incorporated herein by
reference.
Field of the Invention
[0002] The present disclosure relates to a heat conduction
member.
Background
[0003] Conventionally, a vapor chamber and a heat pipe, for
example, have been known as heat conduction members using a working
fluid. A conventional vapor chamber includes a container in which a
cavity is formed by one plate-shaped body and another plate-shaped
body facing the one plate-shaped body, a working fluid enclosed in
the cavity, and a wick structure including glass fiber housed in
the cavity.
[0004] A conventional heat pipe includes a long container in which
a working fluid is enclosed, a first wick that is in contact with
an inner wall of the container and faces a vapor flow path, and a
second wick that includes therein a space extending in the
longitudinal direction of the container.
[0005] The conventional vapor chamber and heat pipe include a
housing in which a closed space is formed. Such a housing is
usually formed by connecting one or more metal plates (e.g., copper
plates) by diffusion joining or brazing. Here, diffusion joining or
brazing requires special equipment and requires treatment at high
temperature and high pressure for a long period of time, which may
cause an increase in manufacturing cost. For this reason, the
manufacturing cost of a heat conduction member including a housing
formed by diffusion joining or brazing may increase.
SUMMARY
[0006] A heat conduction member according to an example embodiment
of the present disclosure includes a housing with a space therein,
a wick structure located in the space, and a working fluid enclosed
in the space. The housing includes one or more metal plates and a
joint structure that connects the one or more metal plates. The
joint structure includes two stacked metal plate layers and a
boundary portion between the two metal plate layers. The boundary
portion includes a first region including crystal grains straddling
the two metal plate layers.
[0007] The above and other elements, features, steps,
characteristics and advantages of the present disclosure will
become more apparent from the following detailed description of the
example embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic diagram of an example of a heat
conduction member according to an example embodiment of the present
disclosure.
[0009] FIG. 2 is a sectional view taken along section line II-II of
FIG. 1.
[0010] FIG. 3 is a schematic diagram showing two metal plate layers
that are not joined together.
[0011] FIG. 4 is a schematic diagram showing a joint structure
formed by brazing.
[0012] FIG. 5 is a schematic diagram showing a joint structure
formed by diffusion joining.
[0013] FIG. 6 is a schematic diagram showing a planar structure of
a boundary portion of FIG. 2.
[0014] FIG. 7 is a schematic diagram of a modification of a heat
conduction member according to an example embodiment of the present
disclosure.
[0015] FIG. 8 is a schematic diagram showing a test performed in an
example.
DETAILED DESCRIPTION
[0016] Hereinafter, example embodiments of the present disclosure
will be described while referring to the drawings as appropriate.
Note that in the drawings, the same or corresponding elements or
features will be denoted by the same reference symbols and
description thereof will not be repeated. The size relationships
among the dimensions, shapes, and elements in the drawings are not
necessarily the same as the size relationships among the actual
dimensions, shapes, and elements. In particular, the thickness and
curvature of a housing and wick structure in a drawing may be
greatly different from the thickness and curvature of an actual
housing and wick structure.
[0017] A heat conduction member according to an example embodiment
of the present disclosure includes a housing having a space formed
therein, a wick structure arranged in the space, and a working
fluid enclosed in the space. The housing has one or more metal
plates and a joint structure that connects the metal plates. The
joint structure has two stacked metal plate layers and a boundary
portion between the two metal plate layers. The boundary portion
has a first region configured of crystal grains straddling the two
metal plate layers.
[0018] The heat conduction member according to the present example
embodiment conducts heat according to the following principle.
First, when a part of the housing of the heat conduction member
according to the present example embodiment is heated, the working
fluid evaporates at the heated portion (heating portion). At this
time, the heating portion is cooled by absorbing the latent heat of
vaporization. Next, the vapor generated by the evaporation of the
working fluid moves at high speed in the housing and aggregates at
a relatively low temperature portion (low temperature portion). At
this time, the low temperature portion is heated by releasing the
latent heat of vaporization. Next, the aggregated working fluid is
adsorbed by the wick structure having a capillary structure. Next,
the working fluid adsorbed on the wick structure is returned to the
heating portion by capillarity. Then, the working fluid evaporates
again in the heating portion. By repeating the above cycle, the
heat conduction member according to the present example embodiment
conducts heat from the heating portion to a cooling portion.
[0019] The heat conduction member according to the present example
embodiment can conduct heat more efficiently than an ordinary metal
plate or metal wire. Additionally, the heat conduction member
according to the present example embodiment has a high degree of
freedom in shape. For this reason, the heat conduction member
according to the present example embodiment can be used as a heat
radiating member of an electronic device (particularly, small
electronic device represented by smartphone and tablet terminal),
for example.
[0020] The heat conduction member according to the present example
embodiment does not require brazing or diffusion joining in forming
the housing. Specifically, the housing of the heat conduction
member according to the present example embodiment can be formed by
heating and pressurizing under a mild condition described later.
For this reason, the heat conduction member according to the
present example embodiment can be manufactured at low cost.
[0021] It is preferable that the boundary portion further have a
second region configured of an interface between two metal plate
layers. The boundary portion having the second region can be formed
by heating and pressurizing under a milder condition. For this
reason, by forming the housing under the condition for forming the
second region in the boundary portion, the heat conduction member
according to the present example embodiment can be manufactured at
a lower cost.
[0022] Hereinafter, details of the heat conduction member according
to the present example embodiment will be described with reference
to the drawings. FIG. 1 is a schematic diagram of a heat conduction
member 1 which is an example of the heat conduction member
according to the present example embodiment. The heat conduction
member 1 includes a housing 2 having a closed space 2a formed
therein, a wick structure 3 arranged in the closed space 2a, and a
working fluid (not shown) enclosed in the closed space 2a. The
housing 2 is configured of two metal plates 4 facing each other.
The housing 2 has the two metal plates 4 and a joint structure 5
that connects the metal plates 4. The heat conduction member 1 is
suitably used as a vapor chamber.
[0023] The planar shape of the heat conduction member 1 is not
particularly limited, and a planar shape (e.g., strip shape and
square shape) according to the application can be adopted. The
thickness of the heat conduction member 1 is not particularly
limited, and may be 100 .mu.m or more and 1000 .mu.m or less, for
example. The width of the heat conduction member 1 is not
particularly limited, and may be 5 mm or more and 500 mm or less,
for example.
[0024] FIG. 2 is a sectional view taken along section line II-II of
FIG. 1. As shown in FIG. 2, the joint structure 5 has two stacked
metal plate layers 5a and a boundary portion 5b between the two
metal plate layers 5a. The two metal plate layers 5a are layers
corresponding to the two metal plates 4, respectively. The boundary
portion 5b has a first region A1 configured of crystal grains CP
straddling the two metal plate layers 5a. In FIG. 2, at least 10
first regions A1 exist. The boundary portion 5b further has a
second region A2 configured of an interface S (surface where
displacement of metallographic structure is confirmed) between the
two metal plate layers 5a. In FIG. 2, there are 11 second regions
A2.
[0025] The difference between the joint structure 5 shown in FIG. 2
and a joint structure of a housing of a known heat conduction
member will be described. The housing of a known heat conduction
member has a joint structure formed by brazing or diffusion
joining, for example. FIG. 3 is a schematic diagram showing two
metal plate layers C1 and C2 that are not joined together. FIG. 4
shows a joint structure formed by brazing. In the joint structure
shown in FIG. 4, a brazing material layer B made of a brazing
material is formed between the metal plate layers C1 and C2.
Therefore, in the joint structure shown in FIG. 4, the two metal
plate layers C1 and C2 are not directly stacked on top of one
another. Additionally, FIG. 5 shows a joint structure formed by
diffusion joining. In the joint structure shown in FIG. 5, one
metal plate layer C is formed by completely integrating the metal
plate layers C1 and C2. For this reason, in the joint structure
shown in FIG. 5, no clear boundary portion is confirmed. As
described above, the joint structure 5 shown in FIG. 2 is different
from the joint structure of the housing of the known heat
conduction member in that the two metal plate layers 5a are
directly stacked on top of one another, and that the boundary
portion 5b exists between the two metal plate layers 5a.
[0026] The joint structure 5 is formed by the following method.
First, heat and pressure treatment is performed with the two metal
plates 4 that are materials of the housing 2 stacked on top of one
another. As a result, the metallographic structure is gradually
reconstructed at the contact point between the two metal plate
layers 5a. If all of the temperature, pressure, and processing time
are set to a certain value or more in the heat and pressure
treatment, the two metal plate layers 5a are completely integrated.
In this case, the joint structure shown in FIG. 5 (joint structure
formed by diffusion joining) is formed. However, in the formation
of the joint structure 5, at least one of the temperature, pressure
and processing time is intentionally adjusted to a certain level or
less in the heat and pressure treatment, so that the two metal
plate layers 5a are not completely integrated. As a result, in the
formation of the joint structure 5, the two metal plate layers 5a
are partially integrated in the heat and pressure treatment. As a
result, the boundary portion 5b is formed between the two metal
plate layers 5a, the boundary portion 5b having the first region A1
which is a region where the metallographic structure is
reconfigured and the crystal grains CP are newly formed, and the
second region A2 which is a region where the metallographic
structure is not reconfigured and the interface S remains. As
described above, the joint structure 5 is formed by the heat and
pressure treatment under milder conditions than diffusion
joining.
[0027] The present inventors have discovered that the housing 2
having the joint structure 5 has a high hermeticity even though the
two metal plate layers 5a are not completely integrated at the
boundary portion 5b. This is presumed to be due to the following
reasons. First, in the first region A1 of the boundary portion 5b,
since the two metal plate layers 5a are completely integrated (two
metal plate layers 5a are joined by strong metallic bond),
naturally, permeation of fluid (e.g., working fluid and vapor of
working fluid) is curbed to a great extent. Additionally, the
boundary portion 5b is formed by the heat and pressure treatment
that is performed with enough intensity to form the first region
A1. For this reason, in the second region A2 of the boundary
portion 5b, although the interface S exists between the two metal
plate layers 5a, the two metal plate layers 5a are not completely
separated. Specifically, in the second region A2 of the boundary
portion 5b, the two metal plate layers 5a are joined together by a
weak metallic bond. Hence, the second region A2 of the boundary
portion 5b curbs permeation of fluid to some extent. Specifically,
in the second region A2 of the boundary portion 5b, the joint
between the two metal plate layers 5a is close to a metallic bond,
which has an effect of sufficiently curbing permeation of water and
high-temperature steam. As described above, in the boundary portion
5b, fluid permeation is curbed to a great extent in the first
region A1, and fluid permeation is also curbed to some extent in
the second region A2. For this reason, the housing 2 has a high
hermeticity as a whole.
[0028] When the cross section of a 1 mm range of the boundary
portion 5b is observed at 10 locations randomly selected from the
joint structure 5, it is preferable that the first region A1 and
the second region A2 exist alternately as shown in FIG. 2 in all
the boundary portions 5b. Since the first region A1 and the second
region A2 are thus mixed at the micro level in the joint structure
5, the hermeticity of the housing 2 is further improved.
[0029] The boundary portion 5b preferably has a sea-island
structure including the first region A1 existing as a discontinuous
phase and the second region A2 existing as a continuous phase in
plan view. Hereinafter, such a sea-island structure will be
described with reference to FIG. 6. FIG. 6 shows a planar structure
of the boundary portion 5b. In FIG. 6, the right side shows the
closed space 2a side of the housing 2, and the left side shows the
outside of the housing 2. In FIG. 6, in the boundary portion 5b,
multiple first regions A1 are irregularly scattered in the second
region A2. In FIG. 6, reference symbol X represents a fluid (e.g.,
working fluid and vapor of working fluid). The arrow indicates the
moving direction of the fluid X. In FIG. 6, the fluid X can pass
through the boundary portion 5b at the shortest distance when it
goes straight to the left. Hereinafter, the shortest movement
direction for the fluid X to move from the closed space 2a of the
housing 2 to the outside of the housing 2 may be referred to as a
first direction. The fluid X tries to move as straight as possible
in the first direction in the second region A2. However, as
described above, the first region A1 curbs permeation of the fluid
X to a great extent. That is, the fluid X is substantially
prevented from passing through the first region A1. For this
reason, when the fluid X tries to pass through the boundary portion
5b, the fluid X needs to pass through the second region A2 while
avoiding the first region A1. Specifically, when the fluid X moving
in the first direction comes to the first region A1, the fluid X is
forced to moves in a second direction (vertical direction in FIG.
6) orthogonal to the first direction in order to avoid the first
region A1. Then, the fluid X avoids the first region A1 by moving
in the second direction. Then, the fluid X moves in the first
direction again. Repeating the above, the fluid X does not go
straight in the boundary portion 5b but moves in a bending manner.
As a result, when the fluid X passes through the boundary portion
5b, the fluid X is forced to move for a long distance as if moving
in a maze. Hence, the fluid X is hindered from passing through the
boundary portion 5b. As described above, since the boundary portion
5b has the above-described sea-island structure, the housing 2 can
exhibit high hermeticity even if the ratio of the first region A1
in the boundary portion 5b is relatively low.
[0030] When the cross section of a 1 mm range of the boundary
portion 5b is observed at 10 locations randomly selected from the
joint structure 5, it is preferable that the mean value of the
number of first regions A1 included in the boundary portion 5b be
10.0 or more and 20.0 or less. When the mean value described above
is 10.0 or more and 20.0 or less, the hermeticity of the housing 2
is further improved.
[0031] When the cross section of a 1 mm range of the boundary
portion 5b is observed at 10 locations randomly selected from the
joint structure 5, it is preferable that the mean value of the
total length of the first regions A1 included in the boundary
portion 5b be 0.05 mm or more and 0.95 mm or less. The mean value
described above indicates the ratio of the first region A1 in the
boundary portion 5b of the joint structure 5. As the mean value
described above approaches 1.00 mm, the structure resembles the
joint structure formed by diffusion joining. When the average value
described above is 0.05 mm or more, the hermeticity of the housing
2 is further improved. The joint structure 5 having the above
average value of 0.95 mm or less is easy to manufacture.
[0032] The housing 2 has the two metal plates 4 and the joint
structure 5 that connects the two metal plates 4. One of the two
metal plates 4 has a flat structure. The other metal plate 4 has a
central portion recessed in a direction separating from the one
metal plate 4. The joint structure 5 joins together the outer edge
portions of the two metal plates 4. The housing 2 has the closed
space 2a formed by disposing such two metal plates 4 facing each
other. The closed space 2a is surrounded by an inner surface of the
metal plate 4 and the joint structure 5.
[0033] The closed space 2a is preferably in a depressurized state
(state in which pressure is lower than atmospheric pressure). Such
a depressurized state of the closed space 2a promotes evaporation
of the working fluid.
[0034] The metal plate 4 is a plate-shaped member whose main
component is metal. Examples of the metal contained in the metal
plate 4 include copper, iron, aluminum, zinc, silver, gold,
magnesium, manganese, titanium, and alloys containing these metals
(e.g., brass, stainless steel, and duralumin). The thickness of the
metal plate 4 is 10 .mu.m or more and 1000 .mu.m or less, for
example. When the metal plate 4 contains copper (i.e., when metal
plate 4 is copper plate), the content ratio of copper in the metal
plate 4 is preferably 60 mass % or more, more preferably 90 mass %
or more, even more preferably 99 mass % or more. By setting the
content ratio of copper in the metal plate 4 to 60 mass % or more,
the joint structure 5 can be formed easily.
[0035] The housing 2 may have a columnar structure (not shown) that
supports the closed space 2a from the inside so that the closed
space 2a is not crushed. The columnar structure of the housing 2
increases the strength of the housing 2. The columnar structure may
be unevenness formed on the metal plate 4. Alternatively, the
columnar structure may be a member separate from the metal plate 4
and the wick structure 3. Additionally, the housing 2 may have a
partition wall (not shown) that separates the working fluid and the
vapor of the working fluid in the closed space 2a.
[0036] The working fluid is enclosed in the closed space 2a of the
housing 2. The working fluid is not particularly limited as long as
it is a liquid that evaporates and aggregates in the use
environment of the heat conduction member 1. Examples of the
working fluid include water, alcohol compounds (e.g., methanol and
ethanol), CFC substitutes, hydrocarbon compounds, fluorinated
hydrocarbon compounds, and glycol compounds (e.g., ethylene
glycol). Water is preferably used as the working fluid.
[0037] The wick structure 3 is arranged in the closed space 2a of
the housing 2. The wick structure 3 is not particularly limited as
long as it is a member having a capillary structure. Here, a
capillary structure refers to a structure capable of moving the
working fluid by capillary pressure. Examples of a capillary
structure include a porous structure, a fiber structure, a groove
structure, and a mesh structure.
[0038] Examples of the wick structure 3 include a wire, a mesh, a
nonwoven fabric, and a porous body (e.g., a sintered body).
Examples of the material of the wick structure 3 include copper,
aluminum, nickel, iron, titanium, and alloys of these materials
(e.g., copper alloy, aluminum alloy, nickel alloy, stainless steel
and titanium alloy), carbon fiber, and ceramics. Copper is
preferably used as the material of the wick structure 3.
Additionally, in FIG. 1, the wick structure 3 and the metal plate
are depicted as separate members. However, in the heat conduction
member according to the present example embodiment, the wick
structure and the metal plate may be integrated. For example, in
the present example embodiment, the wick structure may be a groove
or an uneven structure formed on the metal plate.
[0039] The thickness of the wick structure 3 is not particularly
limited, and can be 5 .mu.m or more and 200 .mu.m or less, for
example. In plan view, the wick structure 3 is preferably arranged
in the entire area of the closed space 2a. Note, however, that in
plan view, the wick structure 3 may be arranged only in a part of
the closed space 2a.
[0040] Next, a heat conduction member 11 according to a
modification of the heat conduction member 1 will be described with
reference to FIG. 7. The heat conduction member 11 includes a
housing 12 having a closed space 12a formed therein, two wick
structures 13 arranged in the closed space 12a, and a working fluid
(not shown) enclosed in the closed space 12a. The housing 12 has a
tubular shape. The housing 12 has two metal plates 14 and a joint
structure 15 that connects the metal plates 14. The heat conduction
member 11 is preferably used as a heat pipe. The joint structure 15
is the same as the joint structure 5 shown in FIG. 2.
[0041] The heat conduction member according to the present example
embodiment has been described above with reference to the drawings.
However, the heat conduction member according to the present
example embodiment is not limited to the heat conduction member 1
of FIG. 1 and the heat conduction member 11 of FIG. 7.
[0042] For example, the number of metal plates forming the housing
may be one, or three or more. Additionally, the shape of the
housing of the heat conduction member according to the present
example embodiment is not limited to the sheet shape like the heat
conduction member 1 shown in FIG. 1 and the cylindrical shape like
the heat conduction member 11 shown in FIG. 7, and other shapes
(e.g., rectangular tube shape and semi-cylindrical shape) may be
used. Moreover, the heat conduction member according to the present
example embodiment may further include a member other than the
housing, the wick structure, and the working fluid (e.g., radiation
fin).
[0043] Hereinafter, a method of manufacturing a heat conduction
member according to the present example embodiment will be
exemplified. In the method of manufacturing a heat conduction
member, first, one or more metal plates are formed in a
predetermined shape and arranged to form a temporary housing having
a space formed therein. The temporary housing is different from the
housing included in the heat conduction member according to the
present example embodiment in that it does not have a joint
structure. Next, the metal plate of the temporary housing is
subjected to heat and pressure treatment to form a joint structure
(first heat and pressure treatment). Note, however, that in the
first heat and pressure treatment, an opening is left in at least
one part of the temporary housing. Next, a wick structure is
arranged in the space described above through the opening described
above, and the working fluid is poured into the space described
above. Next, the joint structure is formed by performing heat and
pressure treatment on the above-mentioned opening (second heat and
pressure treatment). The heat conduction member according to the
present example embodiment is obtained in the manner described
above. Note that in the method of manufacturing the heat conduction
member, the wick structure may be arranged in advance in the space
inside the temporary housing before the first heat and pressure
treatment.
[0044] In the method of manufacturing the heat conduction member,
during the second heat and pressure treatment, the working fluid
may be partially evaporated by heating. As a result, air in the
space inside the temporary housing can be expelled by the vapor of
the working fluid. Consequently, the closed space formed in the
housing of the heat conduction member can depressurized.
[0045] The heating temperature in the first heat and pressure
treatment and the second heat and pressure treatment is preferably
500.degree. C. or higher and 1000.degree. C. or lower, and more
preferably 500.degree. C. or higher and 800.degree. C. or lower. By
setting the heating temperature described above to 500.degree. C.
or higher, it becomes easy to form a joint structure that satisfies
the characteristics described above. By setting the temperature
described above to 1000.degree. C. or lower, the manufacturing cost
can be further reduced.
[0046] The rate of temperature increase during heating in the first
heat and pressure treatment and the second heat and pressure
treatment is preferably 5.degree. C./sec or more and 50.degree.
C./sec or less, and more preferably 10.degree. C./sec or more and
30.degree. C./sec or less. By setting the rate of temperature
increase to 5.degree. C./sec or more and 50.degree. C./sec or less,
it becomes easy to form a joint structure that satisfies the
characteristics described above.
[0047] The pressure in the first heat and pressure treatment and
the second heat and pressure treatment is preferably 30.0 MPa or
more and 300.0 MPa or less, and more preferably 45.0 MPa or more
and 230.0 MPa or less. By setting the pressure described above to
30.0 MPa or more, it becomes easy to form a joint structure
satisfying the characteristics described above. By setting the
pressure described above to 300.0 MPa or less, the manufacturing
cost can be further reduced.
[0048] In this example, conditions for forming the joint structure
described in the example embodiment when the metal plate of the
housing is a copper plate were examined.
[0049] As shown in FIG. 8, two cylindrical copper plates P having a
diameter of 8 mm and a height of 4 mm were prepared. One of the two
copper plates P was arranged below, and the other was arranged
above. Additionally, a thermocouple T was set between the two
copper plates P. Next, the two copper plates P were subjected to
heat and pressure treatment using a hot working device.
Specifically, a downward load L was applied to the copper plate P
arranged above while heating at a predetermined rate of temperature
increase (10.degree. C./sec, 20.degree. C./sec, or 30.degree.
C./sec). During the heat and pressure treatment, the temperature of
the two copper plates P was measured by the thermocouple T. The
heating was performed until the temperature measured by the
thermocouple T reached a predetermined temperature (500.degree. C.
or 600.degree. C.). As a result, the copper plate P arranged above
was pressed against the copper plate P arranged below. The two
copper plates P were integrated by the heat and pressure treatment
described above. The heat and pressure treatment was performed
until the total height of the two copper plates P contracted by 3.2
mm (strain: 2%) or 6.4 mm (strain: 4%). For samples with a strain
of 2%, the pressure was recorded when the strain reached 2%.
Additionally, for the sample with a strain of 4%, the pressure was
recorded when the strain reached 4%.
[0050] Next, an attempt was made to separate the integrated two
copper plates P with pliers. When the two integrated copper plates
P could be peeled off with pliers, it was determined that the two
copper plates P were not joined together sufficiently. In this
case, it is determined that the joint structure of the two copper
plates P cannot exhibit sufficient hermeticity. On the other hand,
when the two integrated copper plates P could not be peeled off
with pliers, it was determined that the two copper plates P were
joined together sufficiently. In this case, it is determined that
the joint structure of the two copper plates P can exhibit
sufficient hermeticity.
[0051] Note that if two copper plates P are to be diffusion-joined,
it is necessary to perform heat and pressure treatment at
600.degree. C. to 800.degree. C. for several hours to several tens
of hours. Hence, it is determined that diffusion joining is not
performed under the conditions of the test described above.
[0052] In Table 1 below, reference symbol "A" indicates that the
two integrated copper plates P could not be peeled off with pliers.
Reference symbol "B" indicates that the two integrated copper
plates P could be peeled off with pliers. The pressure in the
parenthesis indicates the pressure recorded during the heat and
pressure treatment. Reference symbol "-" indicates that the test
was not performed under the corresponding conditions.
TABLE-US-00001 TABLE 1 STRAIN RATE OF TEMPERATURE 2% 4% INCREASE
10.degree. C./SEC 20.degree. C./SEC 30.degree. C./SEC 20.degree.
C./SEC HEATING 500.degree. C. -- B (66.6 MPa) -- A (197.8 MPa)
TEMPERATURE 600.degree. C. A (44.2 MPa) A (30.6 MPa) A (73.4 MPa) A
(139.5 MPa)
[0053] As is clear from Table 1, it is determined that the two
copper plates P can be joined together sufficiently when the
heating temperature is 600.degree. C. or higher, the rate of
temperature increase is 10.degree. C./sec or more, and the load is
45 MPa or more.
[0054] Cross sections of the samples of Table 1 were observed with
an electron microscope. The joint structure of the sample whose
evaluation was A in Table 1 had two stacked copper plate layers and
a boundary portion between the two copper plate layers. The
boundary portion had the first region and the second region
described in the example embodiment. Specifically, in the sample
whose evaluation was A, when the cross section of a 1 mm range of
the boundary portion was observed at 10 locations randomly selected
from the joint structure, the first region and the second region
existed in all the boundary portions. On the other hand, in the
joint structure of the sample whose evaluation was B, no region
corresponding to the second region was observed.
[0055] The present disclosure is suitably used as a heat conduction
member for heat radiation of electronic components and the like,
for example.
[0056] Features of the above-described preferred example
embodiments and the modifications thereof may be combined
appropriately as long as no conflict arises.
[0057] While example embodiments of the present disclosure have
been described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing from the scope and spirit of the present disclosure. The
scope of the present disclosure, therefore, is to be determined
solely by the following claims.
* * * * *