U.S. patent application number 10/523409 was filed with the patent office on 2005-07-21 for heat-dissipating member and joined structure.
Invention is credited to Azuma, Kenichi, Hasegawa, Atsushi, Hyodo, Shunji.
Application Number | 20050155751 10/523409 |
Document ID | / |
Family ID | 31719873 |
Filed Date | 2005-07-21 |
United States Patent
Application |
20050155751 |
Kind Code |
A1 |
Azuma, Kenichi ; et
al. |
July 21, 2005 |
Heat-dissipating member and joined structure
Abstract
It is an object of the present invention to provide a
heat-dissipating member, which has an excellent handling property
at room temperature and can tightly adhere to a heat generating
element and a heat sink by being interposed between the heat
generating element and the heat sink and by having high flexibility
to efficiently conduct heat generated from the heat generating
element to the heat sink and can keep the state of adherence even
in increasing in temperature, and a joined structure obtainable by
joining a heat sink to a heat generating element with the
heat-dissipating member. The present invention relates to a
heat-dissipating member, which comprises a thermoplastic resin
composition containing a thermoplastic resin and a thermally
conductive fine particle and not containing a compound having a
melting temperature in the range of 40 to 80.degree. C., at
23.degree. C., a storage modulus at 0.1 Hz is 50,000 Pa or larger
and the member remains finite in shape, and in the range of 50 to
80.degree. C., a storage modulus at 0.1 Hz being 400 to 50,000 Pa
and the member being indefinite in shape, and at 100.degree. C., a
storage modulus at 0.1 Hz being 5,000 Pa or smaller and the member
being indefinite in shape.
Inventors: |
Azuma, Kenichi; (Osaka,
JP) ; Hasegawa, Atsushi; (Osaka, JP) ; Hyodo,
Shunji; (Saitama, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Family ID: |
31719873 |
Appl. No.: |
10/523409 |
Filed: |
April 4, 2005 |
PCT Filed: |
August 8, 2003 |
PCT NO: |
PCT/JP03/10112 |
Current U.S.
Class: |
165/185 ;
257/E23.084; 257/E23.107 |
Current CPC
Class: |
C08K 3/00 20130101; H01L
23/4006 20130101; H01L 23/3737 20130101; H01L 2924/0002 20130101;
H01L 2924/0002 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
165/185 |
International
Class: |
F28F 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 9, 2002 |
JP |
2002233597 |
Mar 20, 2003 |
JP |
200378203 |
Claims
1. A heat-dissipating member, which comprises a thermoplastic resin
composition containing a thermoplastic resin and a thermally
conductive fine particle and not containing a compound having a
melting temperature in the range of 40 to 80.degree. C., at
23.degree. C., a storage modulus at 0.1 Hz being 50,000 Pa or
larger and the member remains finite in shape, and in the range of
50 to 80.degree. C., a storage modulus at 0.1 Hz being 400 to
50,000 Pa and the member being indefinite in shape, and at
100.degree. C., a storage modulus at 0.1 Hz being 5,000 Pa or
smaller and the member being indefinite in shape.
2. The heat-dissipating member according to claim 1, wherein the
thermoplastic resin is a styrene block copolymer and/or a
butyl-rubber resin.
3. The heat-dissipating member according to claim 2, wherein the
styrene block copolymer is a styrene-isoprene-styrene block
copolymer having the proportion of diblock of styrene-isoprene
being 50% by weight or larger and the content of styrene being 25%
by weight or smaller.
4. The heat-dissipating member according to claim 1, wherein the
thermoplastic resin composition mainly contains an aromatic
thermoplastic resin being solid at 23.degree. C. and further
contains a xylene resin having viscosity at 23.degree. C.
5. A joined structure obtainable by joining a heat sink to a heat
generating element with the heat-dissipating member according to
claim 1, wherein thickness of the heat-dissipating member may be
reduced by heat generation of the heat generating element compared
with thickness of the member before the heat generation.
6. A joined structure obtainable by joining a heat sink to a heat
generating element with the heat-dissipating member according to
claim 1, wherein thickness of the heat-dissipating member has
already been reduced by heat generation of the heat generating
element compared with thickness of the member before the heat
generation.
7. The heat-dissipating member according to claim 2, wherein the
thermoplastic resin composition mainly contains an aromatic
thermoplastic resin being solid at 23.degree. C. and further
contains a xylene resin having viscosity at 23.degree. C.
8. The heat-dissipating member according to claim 3, wherein the
thermoplastic resin composition mainly contains an aromatic
thermoplastic resin being solid at 23.degree. C. and further
contains a xylene resin having viscosity at 23.degree. C.
9. A joined structure obtainable by joining a heat sink to a heat
generating element with the heat-dissipating member according to
claim 2, wherein thickness of the heat-dissipating member may be
reduced by heat generation of the heat generating element compared
with thickness of the member before the heat generation.
10. A joined structure obtainable by joining a heat sink to a heat
generating element with the heat-dissipating member according to
claim 3, wherein thickness of the heat-dissipating member may be
reduced by heat generation of the heat generating element compared
with thickness of the member before the heat generation.
11. A joined structure obtainable by joining a heat sink to a heat
generating element with the heat-dissipating member according to
claim 4, wherein thickness of the heat-dissipating member may be
reduced by heat generation of the heat generating element compared
with thickness of the member before the heat generation.
12. A joined structure obtainable by joining a heat sink to a heat
generating element with the heat-dissipating member according to
claim 2, wherein thickness of the heat-dissipating member has
already been reduced by heat generation of the heat generating
element compared with thickness of the member before the heat
generation.
13. A joined structure obtainable by joining a heat sink to a heat
generating element with the heat-dissipating member according to
claim 3, wherein thickness of the heat-dissipating member has
already been reduced by heat generation of the heat generating
element compared with thickness of the member before the heat
generation.
14. A joined structure obtainable by joining a heat sink to a heat
generating element with the heat-dissipating member according to
claim 4, wherein thickness of the heat-dissipating member has
already been reduced by heat generation of the heat generating
element compared with thickness of the member before the heat
generation.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a heat-dissipating member,
which has an excellent handling property at room temperature and
can tightly adhere to a heat generating element and a heat sink by
being interposed between the heat generating element and the heat
sink and by having high flexibility to efficiently conduct heat
generated from the heat generating element to the heat sink and can
keep the state of adherence even in increasing in temperature, and
a joined structure obtainable by joining a heat sink to a heat
generating element with the heat-dissipating member.
BACKGROUND ART
[0002] Heat-dissipating members such as heat-dissipating sheets are
employed for the purpose of dissipating heat generated from a heat
generating element by interposing them between a heat generating
element and a heat sink of electric or electronic devices and the
like. But, since not only heat generating elements and heat sinks
of electric or electronic devices but also many heat generating
elements and heat sinks have surfaces which are not smooth,
heat-dissipating members cannot tightly adhere to the heat
generating elements and the heat sinks and contact areas between
heat generating elements or heat sinks and heat-dissipating members
are reduced, and therefore efficiency of heat transfer from a heat
generating element to a heat sink decreases and the heat
dissipation performance of heat-dissipating members cannot be
adequately exerted.
[0003] Resistance between the heat generating element and the heat
sink with respect to heat transfer is referred to as thermal
resistance, and when the thermal resistance is smaller, the heat
transfer from the heat generating element to the heat sink is more
excellent and a higher effect of heat dissipation can be attained.
Hence, high flexibility is required for the heat-dissipating member
in order to reduce the thermal resistance. Thus conventionally,
there have been used heat-dissipating grease containing thermally
conductive fine particles, heat-dissipating sheet obtainable by
dispersing thermally conductive fine particles in a resin, which is
flexible and has rebounding capability such as silicon rubber and
acrylate resin, and the like.
[0004] As the heat-dissipating grease, there is disclosed a grease,
which is silicon-based and contains thermally conductive fine
particles such as zinc oxide, alumina, aluminum nitride and the
like, for example in Japanese Kokoku Publication Hei-6-39591. Since
such a heat-dissipating grease is a material having fluidity and
viscosity, when the grease is interposed between the heat
generating element and the heat sink, it can obtain a large contact
area with them and therefore develop excellent thermal resistance
performance. However, there were problems that in applying grease
to the heat generating element and the heat sink, their workability
was low due to occurrences of soil on the periphery and there was a
high probability that the thermal resistance performance might vary
due to occurrences of variations in work.
[0005] As the heat-dissipating sheet, there is disclosed a
thermally conductive tape, obtainable by dispersing thermally
conductive fine particles randomly in an acrylate resin, for
example in Japanese Kokai Publication Hei-6-88061. Since such a
heat-dissipating sheet is a sheet of finite shape, it can be easily
affixed to the heat generating element and the heat sink and can
keep the space between the heat generating element and the heat
sink constant in being interposed between the heat generating
element and the heat sink, and therefore it can develop stable
thermal resistance performance. However, since the heat-dissipating
sheet did not have fluidity, it was impossible to attain as high
flexibility as the heat-dissipating grease and it was difficult to
develop high thermal resistance performance.
[0006] On the other hand, there is disclosed a heat-dissipating
member, obtainable by mixing a compound such as an alpha-olefinic
thermoplastic component having a melting temperature in the range
of about 50 to 60.degree. C. or a paraffinic wax component having a
melting temperature of about 60 to 70.degree. C. into an acrylic
pressure sensitive viscous component, for example in Japanese Kohyo
Publication No. 2000-509209. These heat-dissipating members soften
rapidly when by applying voltage, a temperature of a heat
generating element rises and reaches the melting temperature of the
alpha-olefinic thermoplastic component or the paraffinic wax
component mixed and improve in the flexibility and therefore in the
thermal resistance performance.
[0007] However, since the compounds having such melting
temperatures are solid matter not having viscosity at a temperature
around 23.degree. C. at which the work of affixing the
heat-dissipating member to the heat generating element and the heat
sink is carried out, the viscosity of the acrylic pressure
sensitive viscous component containing this compound is inhibited
and the workability of affixing is deteriorated. Further, in the
case where a temperature of the heat generating element rises and
exceeds the melting temperature, the temperature of the heat
generating element rises rapidly once because it takes some time
before the entire compound melts. And, when the compound having a
melting temperature is melted, the flexibility of the
heat-dissipating member improves and the heat generating element
and the heat sink tightly adhere to each other, a heat transfer
coefficient improves, and then the temperature of the heat
generating element drops rapidly. Therefore, there was a problem
that a temperature load was put, but for short time, on the heat
generating element. Further, there was also a problem that even if
the compound was melted through an increase in temperature of the
heat generating element and the flexibility of the heat-dissipating
member improved, and the heat generating element and the heat sink
tightly adhered to each other and a heat transfer coefficient
improved, in the case where heat addition was continued, the melted
compound having low viscosity runs away from the heat-dissipating
member, and consequently the adhesion was impaired and the heat
transfer coefficient was also deteriorated, and a temperature of
the heat generating element might rise.
SUMMARY OF THE INVENTION
[0008] In view of the state of the art, it is an object of the
present invention to provide a heat-dissipating member, which has
an excellent handling property at room temperature and can tightly
adhere to a heat generating element and a heat sink by being
interposed between the heat generating element and the heat sink
and by having high flexibility to efficiently conduct heat
generated from the heat generating element to the heat sink and can
keep the state of adherence even in increasing in temperature, and
a joined structure obtainable by joining a heat sink to a heat
generating element with the heat-dissipating member.
[0009] The present invention pertains to a heat-dissipating member
which comprises a thermoplastic resin composition containing a
thermoplastic resin and a thermally conductive fine particle and
not containing a compound having a melting temperature in the range
of 40 to 80.degree. C., at 23.degree. C., a storage modulus at 0.1
Hz being 50,000 Pa or larger and the member remains finite in
shape, and in the range of 50 to 80.degree. C., a storage modulus
at 0.1 Hz being 400 to 50,000 Pa and the member being indefinite in
shape, and at 100.degree. C., a storage modulus at 0.1 Hz being
5,000 Pa or smaller and the member being indefinite in shape.
[0010] The thermoplastic resin is preferably a styrene block
copolymer and/or a butyl-rubber resin. The styrene block copolymer
is more preferably a styrene-isoprene-styrene block copolymer
having the proportion of diblock of styrene-isoprene being 50% by
weight or larger and the content of styrene being 25% by weight or
smaller. And, preferably, the thermoplastic resin composition
mainly contains an aromatic thermoplastic resin being solid at
23.degree. C. and further contains a xylene resin having viscosity
at 23.degree. C.
[0011] A joined structure obtainable by joining a heat sink to a
heat generating element with the heat-dissipating member of the
present invention, wherein thickness of the heat-dissipating member
can be reduced by heat generation of the heat generating element
compared with thickness of the member before the heat generation,
also constitutes the present invention.
[0012] A joined structure obtainable by joining a heat sink to a
heat generating element with the heat-dissipating member of the
present invention, wherein thickness of the heat-dissipating member
has already been reduced by heat generation of the heat generating
element compared with thickness of the member before the heat
generation, also constitutes the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic view showing a measuring apparatus
used for measuring thermal resistance of a heat-dissipating
member.
[0014] FIG. 2 is a schematic view illustrating a method of
evaluating high temperature fluidity in Examples.
[0015] In drawing, reference numerals 1, 2, 3, 4 and 5 denote a
cooler, a heat-dissipating member, a bolt, a thermostatic water
tank and an aluminum block, respectively.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Hereinafter, the present invention will be described in
detail.
[0017] The heat-dissipating member of the present invention has a
storage modulus of 50,000 Pa or larger at 0.1 Hz and remains finite
in shape at 23.degree. C. Accordingly, this member can be used in
the form of a sheet of finite shape at a temperature around
23.degree. C. at which the work of affixing the member to the heat
generating element and the heat sink is carried out, and exhibits
excellent workability of affixing. When the storage modulus at 0.1
Hz at 23.degree. C. is smaller than 50,000 Pa, the member is too
soft and hard to handle, and the work of affixing is hard to carry
out.
[0018] The heat-dissipating member of the present invention has a
storage modulus of 400 to 50,000 Pa at 0.1 Hz and is indefinite in
shape in the range of 50 to 80.degree. C. Accordingly, when a
temperature of a heat generating element rises by applying voltage,
the heat-dissipating member softens rapidly, and when the member
reaches a temperature of 50 to 80.degree. C., it improves in the
flexibility and hence its contact area with the heat generating
element and the heat sink is enhanced, and therefore it develops an
excellent thermal resistance performance. When the storage modulus
at 0.1 Hz in the range of 50 to 80.degree. C. is smaller than 400
Pa, the heat-dissipating member runs away from the heat generating
element and the heat sink due to being too soft, and when it is
larger than 50,000 Pa, the heat-dissipating member cannot tightly
adhere to the heat generating element and the heat sink due to its
low flexibility and therefore sufficient thermal resistance
performance cannot be attained.
[0019] The heat-dissipating member of the present invention has a
storage modulus of 5,000 Pa or smaller at 0.1 Hz and is indefinite
in shape at 100.degree. C. When the storage modulus at 0.1 Hz at
100.degree. C. is more than 5,000 Pa, it is difficult to process
the member in sheet form.
[0020] Incidentally, the storage modulus can be measured using a
dynamic viscoelasticity measuring apparatus such as Dynamic
Analyzer RDA II manufactured by Rheometric Scientific, Inc.
[0021] In the heat-dissipating member of the present invention, a
phenomenon of phase transition does not occur in the range of 40 to
80.degree. C. since the member does not contain a compound having a
melting temperature in this range. In the present invention, since
such a rapid change in the storage modulus occurs without involving
the phenomenon of phase transition between 40.degree. C. and
60.degree. C., the heat-dissipating member increasingly adheres to
the heat generating element and the heat sink in conformity with an
increase in the temperature of heat generating element and there is
not the time delay between the instant of an increase in the
temperature of heat generating element and the instant that the
heat-dissipating member softens and its contact area with the heat
generating element and the heat sink is enhanced and therefore it
develops an excellent thermal resistance performance. Therefore,
the temperature of the heat generating element does not rise
rapidly and a temperature load is not put on the heat generating
element. And, in the case of a thermoplastic resin composition not
involving a phenomenon of phase transition, generally, the resin
composition can become soft by only heating slightly higher than
room temperature or viscosity can occur on the surface of a resin
and therefore it is often hard to handle as a heat-dissipating
member, but the heat-dissipating member of the present invention
has an excellent handling property since it can remain finite in
shape at low temperature.
[0022] In a temperature of above 60.degree. C., since a decrease in
the storage modulus of the heat-dissipating member of the present
invention becomes mild, the heat-dissipating member does not run
away from the heat generating element and the heat sink due to
being too soft and it can continue to tightly adhere to the heat
generating element and the heat sink and to efficiently conduct
heat generated from the heat generating element to the heat
sink.
[0023] Preferably, the heat-dissipating member of the present
invention has the adhesion of 0.5 N/cm.sup.2 or larger to aluminum
at 23.degree. C. Thereby, it has high adhesion to the heat
generating element and the heat sink and the workability of
affixing in affixing the heat-dissipating member to the heat
generating element and the heat sink is improved.
[0024] The heat-dissipating member of the present invention is not
particularly limited but it is preferred to process the member in
sheet form for use. By processing the member in sheet form, the
workability of affixing it is significantly improved.
[0025] When the heat-dissipating member of the present invention is
in sheet form, the thickness of the sheet is preferably 20 to 400
.mu.m. When the thickness is smaller than 20 .mu.m, a handling
property is deteriorated and in addition to this it may become
difficult to adequately fill a gap when the heat-dissipating member
is interposed between the heat generating element and the heat
sink, and when it is larger than 400 .mu.m, the thermal resistance
performance tends to decrease.
[0026] The heat-dissipating member of the present invention
comprises a thermoplastic resin composition containing a
thermoplastic resin and thermally conductive fine particles.
[0027] As the thermoplastic resin, there are given (meth)acrylate
copolymers; styrene block copolymers such as
styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene
block copolymer and the like; ethylene-vinyl acetate resin,
butadiene resins, isobutylene resins, olefine resins, urethane
resins, epoxy resins, vinyl acetate resins, styrene resins, butyral
resin, polyvinyl alcohol resins, silicon resins; and modified
resins thereof. These resins may be used alone or in combination of
two or more species. Among others, acrylate copolymers, styrene
block copolymers, and butyl-rubber resins are suitable in that
design which can realize the storage modulus is relatively
easy.
[0028] However, the thermoplastic resin is preferably not a
substance having a melting point in the vicinity of a higher
operating limit temperature in heat generating elements such as
electronic devices like IC. Also, in the case of resins having a
temperature of glass transition, it is preferred that a temperature
of glass transition measured with a differential calorimeter is not
present in the vicinity of a higher maximum proper operating
temperature in heat generating elements such as electronic devices
like IC. The absorption of latent heat in melting and a phenomenon
of glass transition of these resins may also cause a time delay
before the heat generating element or heat sink and the
heat-dissipating member tightly adhere to each other.
[0029] When an acrylate copolymer is used as the thermoplastic
resin, an acrylate copolymer having a weight average molecular
weight of 5,000 to 200,000 is preferably used. When the acrylate
copolymer having a weight average molecular weight within this
range is used, it is possible to easily develop the storage
modulus.
[0030] When a styrene block copolymer is used as the thermoplastic
resin, it is preferred to use a styrene-isoprene-styrene block
copolymer in which the proportion of diblock of styrene-isoprene is
50% by weight or larger and the content of styrene is 25% by weight
or smaller. In styrene-isoprene-styrene block copolymer, a change
in elastic modulus in the range of 23.degree. C. to 50.degree. C.
can be controlled by adjusting the proportion of diblock and the
content of styrene and by selecting the range like this, it is
possible to develop the storage modulus.
[0031] And, when an aromatic thermoplastic resin, being solid at
23.degree. C., such as styrene block copolymer is used as the
thermoplastic resin, preferably, the thermoplastic resin
composition further contains a xylene resin having viscosity at
23.degree. C. By adding such a xylene resin, a rapid change occurs
in the behavior of the storage modulus between 23.degree. C. and
50.degree. C. and further a mild change in the storage modulus can
be realized at 50.degree. C. or more. It is considered that the
reason for this is that when an aromatic thermoplastic resin being
solid at 23.degree. C. and a xylene resin having viscosity at
23.degree. C. are mixed and used, the mixture retains a solid state
by an interaction between aromatic rings of respective resins at
23.degree. C., but when a resin temperature is increased, the
interaction is gradually weakened and rapidly weakened and it
softens without involving a phenomenon of phase transition in a
certain temperature region, and on the other hand even when the
mixture reaches a given temperature, a interaction between aromatic
rings like pseudo crosslinking remains and therefore a further
fluidization is suppressed. And, since the xylene resin also acts
as a tackifier, the workability in affixing the heat-dissipating
member of the present invention to the heat generating element
and-the heat sink is improved by blending the xylene resin.
However, since when an amount of the thermally conductive fine
particles to be blended is increased, some kinds of particles has a
tendency in which an elastic modulus at elevated temperature is
reduced, it is necessary to appropriately adjust the species and
the amount to be blended of thermoplastic resin and xylene resin to
control the behavior of the elastic modulus of the heat-dissipating
member of the present invention.
[0032] An amount of the xylene resin to be blended in the
thermoplastic resin composition is preferably 10 to 90% by volume.
When it is less than 10% by volume, the heat-dissipating member has
low flexibility and cannot tightly adhere to the heat generating
element and the heat sink and sufficient thermal resistance
performance may not be attained, and when it is more than 90% by
volume, it may become difficult to obtain a sheet of finite shape
at 23.degree. C.
[0033] As the thermally conductive fine particles, a substance
comprising at least one species selected from the group consisting
of, for example, boron nitride, aluminum nitride, alumina,
aluminum, silicon carbide, zinc oxide, copper, metal hydroxide,
graphite, magnesium oxide and silica is suitable.
[0034] As the metal hydroxide, there are given, for example,
magnesium hydroxide, aluminum hydroxide and the like.
[0035] The thermally conductive fine particles are preferably
surface treated in such a way that they can be homogeneously mixed
with the thermoplastic resin in a high proportion.
[0036] An amount of the thermally conductive fine particles to be
blended in the thermoplastic resin composition is preferably 10 to
90% by volume. When it is less than 10% by volume, a sufficient
heat transfer coefficient may not be attained, and when it is more
than 90% by volume, the adhesion to aluminum of the
heat-dissipating member to be obtained is reduced and the
workability of affixing it may be deteriorated.
[0037] The thermoplastic resin composition may contain
fire-retarding material such as halogen compounds, phosphate
compounds, metal hydroxides, titanium oxides, etc.; a coloring
agent such as carbon black, white carbon, etc.; a powder-surface
modifying agent such as silane coupling agent, titanate coupling
agent, etc.; a dispersant of glycerol fatty acids; an antioxidant
such as bisphenols and hindered phenols; a tackifier such as
chroman resin, terpene phenol resin, phenol resin, rosin, terpene
resin, aliphatic hydrocarbons and alicyclic hydrocarbon to such an
extent that does not impair the desired elastic modulus and
adhesion to aluminum as required.
[0038] A method of producing the heat-dissipating member of the
present invention is not particularly limited and includes, for
example, a method in which predetermined amounts of the
thermoplastic resin and the thermally conductive fine particles are
mixed using 2-roll mill, 3-roll mill, plasto mill, a kneader, a
planetary mixer and Banbury mixer, and the resulting mixture was
formed in the form of sheet having desired thickness by coating
forming, extrusion and press molding.
[0039] The heat-dissipating member of the present invention is
finite in shape at room temperature in the vicinity of 23.degree.
C. and extremely superior in a handling property, and therefore it
can produce a joined structure obtainable by joining the heat sink
to the heat generating element with efficiency. When a temperature
of a heat generating element of this joined structure is elevated,
it rapidly softens without involving the phenomenon of phase
transition involving the absorption of latent heat such as a
phenomenon of glass transition and melting at the instant when the
temperature is a given temperature or higher and its contact area
with the heat generating element and the heat sink is enhanced and
further thereby, thickness of the heat-dissipating member is
reduced, and therefore it can develop an excellent thermal
resistance performance. In addition, since such a change of the
heat-dissipating member is rapid and occurs before the temperature
of the heat generating element reaches a temperature which puts
load on the heat generating element, the temperature load is not
put on the heat generating element. Even when the temperature is
further increased, the heat-dissipating member of the present
invention continues to tightly adhere to the heat generating
element and the heat sink without being further fluidized and the
temperature load is not put on the heat generating element.
[0040] A joined structure obtainable by joining a heat sink to a
heat generating element with the heat-dissipating member of the
present invention, wherein thickness of the heat-dissipating member
can be reduced by heat generation of the heat generating element
compared with thickness of the member before the heat generation,
also constitutes the present invention.
[0041] A joined structure obtainable by joining a heat sink to a
heat generating element with the heat-dissipating member of the
present invention, wherein thickness of the heat-dissipating member
has already been reduced by heat generation of the heat generating
element compared with thickness of the member before the heat
generation, also constitutes the present invention.
BEST MODES FOR CARRYING OUT THE INVENTION
[0042] Hereinafter, the present invention will be described in
further detail by way of examples, but the present invention is not
limited to these examples.
EXAMPLE 1
[0043] 20 parts by weight of styrene-isoprene block copolymer in
which the content of styrene was 22% by weight and the proportion
of diblock was 66% by weight, 80 parts by weight of xylene resin
(produced by MITSUBISHI GAS CHEMICAL COMPANY, INC., trade name
"NIKANOL KL-05"), and 140 parts by weight of aluminum nitride
(produced by TOKUYAMA CORP., trade name "GRADE F") were mixed with
a plasto mill and a substance in slurry was obtained. A volume
ratio of the aluminum nitride was 30% with respect to this
substance in slurry.
[0044] Next, a release PET film was laid on a press plate and on
this, a metal frame with thickness of 100 .mu.m was placed and the
resulting substance in slurry was poured within the metal frame.
Then, on this, a release PET film was placed to form a sample and
this sample was sandwiched from above and below with press plates
and press molding was conducted at room temperature. Thereby, a
heat-dissipating member of 100 .mu.m in thickness in sheet form, to
which the release PET films were attached on both sides, was
obtained.
EXAMPLE 2
[0045] 20 parts by weight of styrene-isoprene block copolymer in
which the content of styrene was 22% by weight and the proportion
of diblock was 66% by weight, 80 parts by weight of xylene resin
(produced by MITSUBISHI GAS CHEMICAL COMPANY, INC., trade name
"NIKANOL KL-05"), and 330 parts by weight of aluminum nitride
(produced by TOKUYAMA CORP., trade name "GRADE F") were mixed with
a plasto mill and a substance in slurry was obtained. A volume
ratio of the aluminum nitride was 50% with respect to this
substance in slurry.
[0046] By using this substance in slurry and following the same
procedure as in Example 1, a heat-dissipating member of 100 .mu.m
in thickness in sheet form, to which the release PET films were
attached on both sides, was obtained.
EXAMPLE 3
[0047] 20 parts by weight of styrene-isoprene-styrene block
copolymer in which the content of styrene was 22% by weight and the
proportion of diblock was 66% by weight, 40 parts by weight of
xylene resin (produced by MITSUBISHI GAS CHEMICAL COMPANY, INC.,
trade name "NIKANOL KL-05"), 25 parts by weight of xylene resin
(produced by MITSUBISHI GAS CHEMICAL COMPANY, INC., trade name
"NIKANOL LL"), 15 parts by weight of liquid polyisoprene (produced
by KURARAY Co., Ltd., trade name "LIR30"), and 400 parts by weight
of alumina (produced by SHOWA DENKO K.K., trade name "CB-A20S") and
200 parts by weight of alumina (produced by SHOWA DENKO K.K., trade
name "CB-A05S") were mixed with a plasto mill and a substance in
slurry was obtained. A volume ratio of aluminum nitride was 60%
with respect to this substance in slurry.
[0048] By using this substance in slurry and following the same
procedure as in Example 1, a heat-dissipating member of 100 .mu.m
in thickness in sheet form, to which the release PET films were
attached on both sides, was obtained.
EXAMPLE 4
[0049] 10 parts by weight of styrene-isoprene-styrene block
copolymer in which the content of styrene was 55% by weight and the
proportion of diblock was 16% by weight, 10 parts by weight of
styrene-isoprene-styrene block copolymer in which the content of
styrene was 22% by weight and the proportion of diblock was 66% by
weight, 65 parts by weight of xylene resin (produced by MITSUBISHI
GAS CHEMICAL COMPANY, INC., trade name "NIKANOL KL-05"), 15 parts
by weight of liquid polyisoprene (produced by KURARAY Co., Ltd.,
trade name "LIR403"), and 400 parts by weight of alumina (produced
by SHOWA DENKO K.K., trade name "CB-A20S") and 200 parts by weight
of alumina (produced by SHOWA DENKO K.K., trade name "CB-A05S")
were mixed with a plasto mill and a substance in slurry was
obtained. A volume ratio of aluminum nitride was 60% with respect
to this substance in slurry.
[0050] By using this substance in slurry and following the same
procedure as in Example 1, a heat-dissipating member of 100 .mu.m
in thickness in sheet form, to which the release PET films were
attached on both sides, was obtained.
COMPARATIVE EXAMPLE 1
[0051] 30 parts by weight of styrene-isoprene block copolymer in
which the content of styrene was 22% by weight and the proportion
of diblock was 66% by weight, 70 parts by weight of dodecylbenzene,
and 760 parts by weight of aluminum nitride (produced by TOKUYAMA
CORP., trade name "GRADE F") were mixed with a plasto mill and a
substance in slurry was obtained. A volume ratio of the aluminum
nitride was 70% with respect to this substance in slurry.
[0052] By using this substance in slurry and following the same
procedure as in Example 1, a heat-dissipating member of 100 .mu.m
in thickness in sheet form, to which the release PET films were
attached on both sides, was obtained.
COMPARATIVE EXAMPLE 2
[0053] 50 parts by weight of styrene-isoprene block copolymer in
which the content of styrene was 22% by weight and the proportion
of diblock was 66% by weight, 50 parts by weight of dodecylbenzene,
and 226 parts by weight of boron nitride (produced by DENKI KAGAKU
KOGYO K.K., trade name "GRADE SGP") were mixed with a plasto mill
and a substance in slurry was obtained. A volume ratio of the boron
nitride was 50% with respect to this substance in slurry.
[0054] By using this substance in slurry and following the same
procedure as in Example 1, a heat-dissipating member of 100 .mu.m
in thickness in sheet form, to which the release PET films were
attached on both sides, was obtained.
COMPARATIVE EXAMPLE 3
[0055] A heat-dissipating member of 100 .mu.m in thickness in sheet
form, to which the release PET films were attached on both sides,
was obtained by following the same procedure as in Example 1 except
for employing 100 parts by weight of acrylate copolymer (produced
by Negami Chemical Industrial Co., Ltd., trade name "S-2022 Rev.2":
weight average molecular weight 270,000) in place of 20 parts by
weight of styrene-isoprene block copolymer in which the content of
styrene was 22% by weight and the proportion of diblock was 66% by
weight, and 226 parts by weight of boron nitride (produced by DENKI
KAGAKU KOGYO K.K., trade name "GRADE SGP") in place of 140 parts by
weight of aluminum nitride (produced by TOKUYAMA CORP., trade name
"GRADE F").
COMPARATIVE EXAMPLE 4
[0056] 20 parts by weight of styrene-isoprene block copolymer in
which the content of styrene was 22% by weight and the proportion
of diblock was 66% by weight, 80 parts by weight of dodecylbenzene,
and 400 parts by weight of alumina (produced by SHOWA DENKO K.K.,
trade name "CB-A20S") and 200 parts by weight of alumina (produced
by SHOWA DENKO K.K., trade name "CB-A05S") were mixed with a plasto
mill and a substance in slurry was obtained. A volume ratio of the
aluminum nitride was 60% with respect to this substance in
slurry.
[0057] By using this substance in slurry and following the same
procedure as in Example 1, a heat-dissipating member of 100 .mu.m
in thickness in sheet form, to which the release PET films were
attached on both sides, was obtained.
COMPARATIVE EXAMPLE 5
[0058] 22 parts by weight of styrene-isoprene block copolymer in
which the content of styrene was 22% by weight and the proportion
of diblock was 66% by weight, 8 parts by weight of styrene-isoprene
block copolymer in which the content of styrene was 30% by weight
and the proportion of diblock was 30% by weight, 45 parts by weight
of xylene resin (produced by MITSUBISHI GAS CHEMICAL COMPANY, INC.,
trade name "NIKANOL KL-05"), 25 parts by weight of liquid
polyisoprene block copolymer (produced by KURARAY Co., Ltd., trade
name "KL230"), and 400 parts by weight of alumina (produced by
SHOWA DENKO K.K., trade name "CB-A20S") and 200 parts by weight of
alumina (produced by SHOWA DENKO K.K., trade name "CB-A05S") were
mixed with a plasto mill and a substance in slurry was obtained. A
volume ratio of aluminum nitride was 60% with respect to this
substance in slurry. By using this substance in slurry and
following the same procedure as in Example 1, a heat-dissipating
member of 100 .mu.m in thickness in sheet form, to which the
release PET films were attached on both sides, was obtained.
COMPARATIVE EXAMPLE 6
[0059] A commercially available silicon grease (produced by Dow
Corning Corporation, trade name "#340") was used. In evaluating
thermal resistance, a PET film with thickness of 50 .mu.m, a
central portion of which was cut away in a size of 35 mm.times.35
mm, was placed on a heat sink and the silicon grease was poured
within the hollow central portion and a layer of silicon grease,
having a thickness of 50 .mu.m, was formed by scraping excessive
silicon grease off with a spatula.
[0060] <Evaluation>
[0061] On each of the heat-dissipating members obtained in Examples
1 to 4 and Comparative Examples 1 to 6, thermal resistance, a
storage modulus and high-temperature fluidity were evaluated
according to the following methods.
[0062] (Measurement of Thermal Resistance) The thermal resistance
was measured with a measuring apparatus shown in FIG. 1. That is,
the heat-dissipating member 2, from which both release PET films
were peeled off, was affixed on a cooler 1 made of aluminum, and
further an IC to be a heat source was stacked thereon and it was
secured with bolts 3 with a tightening torque of 1 N.multidot.m
being applied.
[0063] The power to an IC was turned on and 80 W/h of power was
supplied to it, and an IC's temperature T1 and a temperature T2 in
the vicinity of the heat-dissipating member on the cooler 1 were
measured after 60 minutes. Here, the cooler 1 is constructed in
such a way that water from a thermostatic water tank 4 was supplied
to the inside of the cooler in a temperature of 23.degree. C. and
went in cycles. The thermal resistance was determined from the
results of measurement using the following equation. Thermal
resistance (.degree. C./W)=(T1-T2)/amount of power supplied to an
IC=(T1-T2)/80
[0064] (Measurement of Storage Modulus)
[0065] Using Dynamic Analyzer RDA II (manufactured by Rheometric
Scientific, Inc.), the storage moduli of each heat-dissipating
member at 23.degree. C., 50.degree. C., 80.degree. C. and
100.degree. C. were measured in a condition of 0.1 Hz.
[0066] (Evaluation of High-Temperature Fluidity)
[0067] As shown in FIG. 2, each heat-dissipating member, from which
one side of the release PET films was peeled off, was affixed to a
side of a block of a regular hexahedron comprising aluminum. This
aluminum block was kept in a thermostatic chamber of 80.degree. C.
and after a lapse of a week, the presence or absence of running
down of the heat-dissipating member was visually observed.
1 TABLE 1 Thermal Storage modulus (Pa) High-temperature resistance
(.degree. C./W) 23.degree. C. 50.degree. C. 80.degree. C.
100.degree. C. fluidity (running down) Example 1 0.118 207000 2380
906 710 none Example 2 0.098 487000 4560 1050 910 none Example 3
0.104 87000 2570 684 655 none Example 4 0.120 97000 2810 1440 362
none Comparative 0.115 26200 5600 110 85 present Example 1
Comparative 0.135 37500 12500 200 156 present Example 2 Comparative
0.365 123400 56800 5900 3280 none Example 3 Comparative 0.092 14200
321 6 1 present Example 4 Comparative 0.321 1560000 266000 30500
19000 none Example 5 Comparative 0.090 8500 3700 4020 3990 none
Example 6
[0068] Industrial Applicability
[0069] In accordance with the present invention, it is possible to
provide the heat-dissipating member, which has an excellent
handling property at room temperature and can tightly adhere to a
heat generating element and a heat sink by being interposed between
the heat generating element and the heat sink and by having high
flexibility to efficiently conduct heat generated from the heat
generating element to the heat sink and can keep the state of
adherence even in increasing in temperature, and the joined
structure obtainable by joining a heat sink to a heat generating
element with the heat-dissipating member.
* * * * *