U.S. patent application number 09/752693 was filed with the patent office on 2001-05-31 for method of fabricating thermoelectric device.
Invention is credited to Hiraishi, Hisato, Watanabe, Shigeru.
Application Number | 20010001960 09/752693 |
Document ID | / |
Family ID | 17937982 |
Filed Date | 2001-05-31 |
United States Patent
Application |
20010001960 |
Kind Code |
A1 |
Hiraishi, Hisato ; et
al. |
May 31, 2001 |
Method of fabricating thermoelectric device
Abstract
The invention provides a method of fabricating a thermoelectric
device, whereby a grooved block (11) composed of n-type
thermoelectric semiconductor and a grooved block (21) composed of
p-type thermoelectric semiconductor, provided with a plurality of
grooves (16, 26) formed therein, respectively, at a same pitch and
parallel with each other, are formed such that a depthwise portion
of respective grooved blocks is left intact, and then, an
integrated block (3) is formed by fitting and adhering together the
grooved blocks (11, 21) composed of the n-type and p-type
thermoelectric semiconductors, respectively, filling up gaps in
fitting parts with adhesive insulation members. After removing
portions of the integrated block (3), other than the fitting parts
where the n-type and p-type thermoelectric semiconductors are
fitted to each other, n-type and p-type thermoelectric
semiconductor pieces are exposed, and by forming electrodes for
connecting the pieces to each other alternately and in series, the
thermoelectric device is completed. Further, it is preferable to
apply a process of exposing the thermoelectric semiconductor pieces
and a process of forming the electrodes after applying a process of
forming grooves to the integrated block (3) such that a plurality
of grooves are formed in the -direction crossing the direction in
which the grooves (16, 26) have been formed, leaving a depthwise
portion of the integrated block (3) intact, and insulation members
filling up the grooves thus formed are solidified.
Inventors: |
Hiraishi, Hisato; (Tokyo,
JP) ; Watanabe, Shigeru; (Tokorozawa-shi,
JP) |
Correspondence
Address: |
ARMSTRONG,WESTERMAN, HATTORI,
MCLELAND & NAUGHTON, LLP
1725 K STREET, NW, SUITE 1000
WASHINGTON
DC
20006
US
|
Family ID: |
17937982 |
Appl. No.: |
09/752693 |
Filed: |
January 3, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09752693 |
Jan 3, 2001 |
|
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09101700 |
Jul 15, 1998 |
|
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09101700 |
Jul 15, 1998 |
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PCT/JP97/04115 |
Nov 12, 1997 |
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Current U.S.
Class: |
136/201 |
Current CPC
Class: |
H01L 35/34 20130101;
H01L 35/32 20130101 |
Class at
Publication: |
136/201 |
International
Class: |
H01L 035/34; H01L
037/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 15, 1996 |
JP |
8-304846 |
Claims
What is claimed is:
1. A method of fabricating a thermoelectric device comprising: a
grooved block fabrication process of forming grooved blocks
composed of an n-type thermoelectric semiconductor and p-type
thermoelectric semiconductor, respectively, each provided with a
plurality of grooves formed at a same pitch and parallel with each
other, leaving a depthwise portion of respective grooved blocks
intact; a fitting process of fitting the grooved blocks composed of
the n-type thermoelectric semiconductor and p-type thermoelectric
semiconductor formed, respectively, by said grooved block
fabrication process to each other such that surfaces of the
respective grooved blocks, with the grooves formed thereon, face
each other; an adhesion process of forming an integrated block by
adhering the grooved block composed of the n-type thermoelectric
semiconductor and the grooved block composed of the p-type
thermoelectric semiconductor, fitted to each other by said fitting
process, to each other after filling up gaps in fitting parts
between the respective grooved blocks with an adhesive insulation
member; and a thermoelectric semiconductor pieces exposure process
of exposing n-type and p-type thermoelectric semiconductor pieces
by removing all portions of the integrated block formed by said
adhesion process, other than the fitting parts where the grooved
block composed of the n-type thermoelectric semiconductor and the
grooved block composed of the p-type thermoelectric semiconductor
are fitted to each other.
2. A method of fabricating a thermoelectric device comprising: a
grooved block fabrication process of forming grooved blocks
composed of an n-type thermoelectric semiconductor and p-type
thermoelectric semiconductor, respectively, each provided with a
plurality of grooves formed at a same pitch and parallel with each
other, leaving a depthwise portion of respective grooved blocks
intact; a fitting process of fitting the grooved blocks composed of
the n-type thermoelectric semiconductor and p-type thermoelectric
semiconductor formed, respectively, by said grooved block
fabrication process to each other such that surfaces of the
respective grooved blocks, with the grooves formed thereon, face
each other; an adhesion process of forming an integrated block by
adhering the grooved block composed of the n-type thermoelectric
semiconductor and the grooved block composed of the p-type
thermoelectric semiconductor, fitted to each other by said fitting
process, to each other after filling up gaps in fitting parts
between the respective grooved blocks with an adhesive insulation
member; a second grooving process of forming a plurality of grooves
in the integrated block formed by said adhesion process, in the
direction crossing the direction of the grooves formed by said
grooved block fabrication process, leaving a depthwise portion of
the integrated block intact; a solidification process of filling up
the grooves formed by said second grooving process with an adhesive
insulation member and solidifying the same; and a thermoelectric
semiconductor pieces exposure process of exposing n-type and p-type
thermoelectric semiconductor pieces by removing all portions of the
integrated block wherein the adhesive insulation member filling up
the grooves is solidified in said solidification process, other
than the fitting parts where the grooved block composed of the
n-type thermoelectric semiconductor and the grooved block composed
of the p-type thermoelectric semiconductor are fitted to each
other.
3. A method of fabricating a thermoelectric device comprising: a
grooved block fabrication process of forming two pairs of grooved
blocks composed of an n-type thermoelectric semiconductor and
p-type thermoelectric semiconductor, respectively, provided with a
plurality of grooves formed at a same pitch and parallel with each
other, respectively, leaving a depthwise portion of respective
grooved blocks intact; a first fitting process of fitting each pair
of the grooved blocks composed of the n-type thermoelectric
semiconductor and the grooved block of the p-type thermoelectric
semiconductor, formed by said grooved block fabrication process, to
each other such that surfaces with the grooves formed thereon face
each other; a first adhesion process of forming two integrated
blocks by filling up gaps in fitting parts between each pair of the
grooved blocks composed of the n-type thermoelectric semiconductor
and the p-type thermoelectric semiconductor, respectively, fitted
to each other by said first fitting process, with adhesive
insulation members; and solidifying the same; a grooving process of
forming two grooved integrated blocks by forming in each of the two
integrated blocks a plurality of grooves at a same pitch and in the
direction crossing the direction of the grooves formed by said
grooved block fabrication process, leaving a depthwise portion of
respective integrated blocks intact; a second fitting process of
fitting the two grooved integrated blocks to each other such that
surfaces with the grooves thus formed thereon face each other; a
second adhesion process of forming a second integrated block by
filling gaps in fitting parts between the two grooved integrated
blocks fitted to each other by said fitting process with adhesive
insulation members, and solidifying the same; and a thermoelectric
semiconductor pieces exposure process of exposing n-type and p-type
thermoelectric semiconductor pieces by removing all depthwise
portions of the second integrated block, other than the fitting
parts.
4. A method of fabricating a thermoelectric device according to one
of claims 1 to 3, wherein the grooved block fabrication process is
a process of forming the grooved block of the n-type thermoelectric
semiconductor and grooved block of the p-type thermoelectric
semiconductor by applying a grooving process to an n-type
thermoelectric semiconductor block and p-type thermoelectric
semiconductor block, respectively, such that a plurality of grooves
are formed at a same pitch and parallel with each other, leaving a
depthwise portion of said respective blocks intact.
5. A method of fabricating a thermoelectric device according to one
of claims 1 to 3, wherein the grooved block fabrication process is
a process of forming the grooved block of the n-type thermoelectric
semiconductor and grooved block of the p-type thermoelectric
semiconductor by forming a molded n-type thermoelectric
semiconductor material and molded p-type thermoelectric
semiconductor material by use of a mold for the grooved block,
respectively, and sintering the same.
6. A method of fabricating a thermoelectric device according to one
of claims 1 to 5, further comprising an electrode forming process
of forming electrodes for connecting the n-type and p-type
thermoelectric semiconductor pieces exposed with each other
alternately and in series after the thermoelectric semiconductor
pieces exposure process.
7. A method of fabricating a thermoelectric device comprising: a
first grooving process applied to an n-type thermoelectric
semiconductor composite block prepared by bonding an n-type
thermoelectric semiconductor block to a base and a p-type
thermoelectric semiconductor composite block prepared by bonding a
p-type thermoelectric semiconductor block to a base, for forming a
plurality of grooves in the n- type thermoelectric semiconductor
block and the p-type thermoelectric semiconductor block,
respectively, at a same pitch, and to a depth close to the
interface between the respective thermoelectric semiconductor
blocks and the base thereof; a fitting process of fitting the
n-type thermoelectric semiconductor composite block and p-type
thermoelectric semiconductor composite block, with the grooves
formed by said first grooving process, respectively, to each other
such that respective grooved surfaces face each other; an adhesion
process of forming an integrated block by filling gaps in fitting
parts between the n-type thermoelectric semiconductor composite
block and p-type thermoelectric semiconductor composite block,
fitted to each other by said fitting process, with adhesive
insulation members so as to adhere the n-type thermoelectric
semiconductor composite block and p-type thermoelectric
semiconductor composite block to each other; a second grooving
process of forming a plurality of grooves in the direction crossing
the direction of the grooves formed by said first grooving process,
and to a depth close to the interface between the respective
thermoelectric semiconductor blocks and the base thereof in the
integrated block formed by said adhesion process; a solidification
process of filling up the grooves formed by said second grooving
process with insulation members, and solidifying the same; and a
thermoelectric semiconductor pieces exposure process of exposing
n-type and p-type thermoelectric semiconductor pieces by removing
the respective bases of the integrated blocks wherein the grooves
are filled with the insulation member and the insulation member is
then solidified in said solidification process.
8. A method of fabricating a thermoelectric device according to
claim 7, characterized in that the bases of the n-type
thermoelectric semiconductor composite block and the p-type
thermoelectric semiconductor composite block, respectively, have a
surface area larger than an area of a bonded portion of the surface
of the respective thermoelectric semiconductor blocks, and in the
fitting process, spacers are interposed between portions of the
bases of the n-type thermoelectric semiconductor composite block
and the p-type thermoelectric semiconductor composite block,
respectively, where the respective thermoelectric semiconductor
blocks do not exist, so that a spacing between the bases is
controlled to be substantially equivalent to thicknesses of the
respective thermoelectric semiconductor blocks.
9. A method of fabricating a thermoelectric device comprising: a
first grooving process applied to two n-type thermoelectric
semiconductor composite blocks prepared by bonding an n-type
thermoelectric semiconductor block to a base, respectively, and two
p-type thermoelectric semiconductor composite blocks prepared by
bonding a p-type thermoelectric semiconductor block to a base,
respectively, for forming a plurality of grooves at a same pitch,
and to a depth close to the interface between the respective
thermoelectric semiconductor blocks and the base thereof, in the
n-type thermoelectric semiconductor block and the p- type
thermoelectric semiconductor block, respectively; a first fitting
process of fitting the two pairs of the n-type thermoelectric
semiconductor composite block and p-type thermoelectric
semiconductor composite block, with the grooves formed therein,
respectively, by said first grooving process to each other,
respectively, such that respective grooved surfaces face each
other; a first adhesion process of forming two integrated blocks by
adhering the two pairs of the n-type thermoelectric semiconductor
composite blocks and p-type thermoelectric semiconductor composite
blocks to each other, respectively, by filling gaps in fitting
parts between the respective n-type thermoelectric semiconductor
composite blocks and p-type thermoelectric semiconductor composite
blocks, fitted to each other by said first fitting process, with
adhesive insulation members; a second grooving process of forming
two grooved integrated blocks by forming a plurality of grooves at
a same pitch in the two integrated blocks formed, respectively, by
said first adhesion process, in the direction crossing the
direction of the grooves formed by said first grooving process, and
to a depth close to an interface between the respective
thermoelectric semiconductor blocks and the base thereof; a second
fitting process of fitting the two grooved integrated blocks to
each other such that respective grooved surfaces face each other; a
second adhesion process of forming a second integrated block by
adhering the two grooved integrated blocks, fitted to each other by
said second fitting process, to each other by filling gaps in
fitting parts between the two grooved integrated blocks with
adhesive insulation members; and a thermoelectric semiconductor
pieces exposure process of exposing n-type and p-type
thermoelectric semiconductor pieces by removing the respective
bases of the second integrated block.
10. A method of fabricating a thermoelectric device according to
claim 9, characterized in that bases having a surface area larger
than an area of a bonded portion of the surface of the respective
thermoelectric semiconductor blocks are used for the base of the
n-type thermoelectric semiconductor composite block and the p-type
thermoelectric semiconductor composite block, respectively, and
spacers are interposed between portions of the respective bases of
the n-type thermoelectric semiconductor composite block and the
p-type thermoelectric semiconductor composite block to be fitted to
each other, where the respective thermoelectric semiconductor
blocks do not exist, controlling a spacing between the bases to be
substantially equivalent to thicknesses of the respective
thermoelectric semiconductor blocks in the first fitting process,
spacers being further interposed between portions of the respective
bases of the two integrated grooved blocks to be fitted to each
other, where the respective thermoelectric semiconductor blocks do
not exist, controlling a spacing between the bases to be
substantially equivalent to the thickness of the respective
thermoelectric semiconductor blocks in the second fitting
process.
11. A method of fabricating a thermoelectric device according to
one of claims 7 to 10, further comprising an electrode forming
process of forming electrodes for connecting the exposed n-type and
p-type thermoelectric semiconductor pieces to each other
alternately and in series, applied after the thermoelectric
semiconductor pieces exposure process.
12. A method of fabricating a thermoelectric device according to
one of claims 1, 2 or 7, characterized in that an insulation film
is formed on at least one of plural fitting surfaces of a pair of
thermoelectric semiconductor blocks to be fitted to each other in
the fitting process.
13. A method of fabricating a thermoelectric device according to
one of claims 1, 2 or 7, characterized in that the insulation
member for filling up the gaps in the fitting parts in the adhesion
process is an adhesive insulation member with insulating spacers
dispersed therein.
14. A method of fabricating a thermoelectric device according to
claim 3 or 9, characterized in that an insulation film is formed on
at least one of plural fitting surfaces of a pair of thermoelectric
semiconductor blocks to be fitted to each other in at least either
of the first fitting process or the second fitting process.
15. A method of fabricating a thermoelectric device according to
claim 3 or 9, characterized in that the insulation member for
filling up the gaps in the fitting parts in at least either of the
first adhesion process or the second adhesion process is an
adhesive insulation member with insulating spacers dispersed
therein.
16. A method of fabricating a thermoelectric device according to
one of claims 7 to 10, characterized in that before the n-type Fat
thermoelectric semiconductor block and the p-type thermoelectric
semiconductor block are bonded to the bases, respectively, a metal
coated layer is formed on the surface of the respective
thermoelectric semiconductor blocks, bonded to the respective
bases, and on the surface thereof on the opposite side.
17. A method of fabricating a thermoelectric device according to
claim 16, further comprising an electrode formation process of
forming electrodes for connecting the exposed n-type and p-type
thermoelectric semiconductor pieces to each other alternately and
in series by use of an electrically conductive paste applied on the
metal coated layer after the thermoelectric semiconductor pieces
exposure process.
18. A method of fabricating a thermoelectric device according to
one of claims 1, 2, 3, 7, or 9, further comprising a metal layer
formation process of forming metal layers on respective surfaces of
the exposed n-type and p-type thermoelectric semiconductor pieces,
where the electrodes are formed, and an electrode formation process
of forming the electrodes for connecting the exposed n-type and
p-type thermoelectric semiconductor pieces to each other
alternately and in series over the metal layers, said processes
being applied after the thermoelectric semiconductor pieces
exposure process.
19. A method of fabricating a thermoelectric device according to
claim 18, characterized in that the electrodes are formed by use of
an electrically conductive paste in the electrode formation
process.
20. A method of fabricating a thermoelectric device according to
claim 1, characterized in that provisional fixture layers as
insulation members for filling up the gaps in the fitting parts are
formed using a material removable by heating or by use of a solvent
in the adhesion process; said method further comprising an
electrode formation process of forming electrodes for connecting
the exposed n-type and p-type thermoelectric semiconductor pieces
to each other alternately and in series after the thermoelectric
semiconductor pieces exposure process, fabricating a provisional
thermoelectric device, and thereafter performing a process of
fixedly attaching a heat radiation plate to one of the surfaces of
the provisional thermoelectric device, where the electrodes are
formed, and a heat absorption plate to the other via an insulating
fixture layers, respectively, and a process of removing the
provisional fixture layers either by heating or by use of a solvent
after said preceding process.
21. A method of fabricating a thermoelectric device according to
claim 2 or 7, characterized in that provisional fixture layers are
formed using a material removable by heating or by use of a solvent
as at least either of the insulation members for filling up the
gaps in the fitting parts in the adhesion process or the insulation
members for filling up the grooves in the solidification process;
said method further comprising an electrode formation process of
forming electrodes for connecting the exposed n-type and p-type
thermoelectric semiconductor pieces to each other alternately and
in series after the thermoelectric semiconductor pieces exposure
process, fabricating a provisional thermoelectric device, and
thereafter performing a process of fixedly attaching a heat
radiation plate to one of the surfaces of the provisional
thermoelectric device, where the electrodes are formed, and a heat
absorption plate to the other via an insulating fixture layers,
respectively, and a process of removing the provisional fixture
layers either by heating or by use of a solvent after said
preceding process.
22. A method of fabricating a thermoelectric device according to
claim 3 or 9, characterized in that provisional fixture layers as
insulation members for filling up the gaps in the fitting parts are
formed using a material removable by heating or by use of a solvent
in the first adhesion process or the second adhesion process; said
method further comprising an electrode formation process of forming
electrodes for connecting the exposed n-type and p-type
thermoelectric semiconductor pieces to each other alternately and
in series after the thermoelectric semiconductor pieces exposure
process, fabricating a provisional thermoelectric device, and
thereafter performing a process of fixedly attaching a heat
radiation plate to one of the surfaces of the provisional
thermoelectric device, where the electrodes are formed, and a heat
absorption plate to the other via an insulating fixture layers,
respectively, and a process of removing the provisional fixture
layers either by heating or by use of a solvent after said
preceding process.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method of fabricating a
thermoelectric device for use in a thermoelectric power generator
taking advantage of the Seebeck effect, or a cooler taking
advantage of the Peltier effect, and more particularly, to a method
of fabricating a small sized thermoelectric device incorporating a
plurality of thermocouples.
BACKGROUND TECHNOLOGY
[0002] In each of the thermocouples making up a thermoelectric
device, a voltage is developed by providing a difference in
temperature between the opposite ends thereof. This is due to the
effect of the Seebeck effect, and a device designed to extract the
voltage as electric energy is a thermoelectric power generator. The
thermoelectric power generator wherein heat energy can be converted
directly into electric energy has attracted much attention as
effective means of utilizing heat energy, as represented by the
case of waste heat utilization.
[0003] Meanwhile, the flow of a current caused to occur through a
thermocouple results in generation of heat at one end thereof, and
absorption of heat at the other end thereof. This is due to the
Peltier effect, and a cooler can be manufactured by taking
advantage of such phenomenon of heat absorption. This type of
cooler which does not comprise mechanical components and can be
reduced in size has an application as a portable refrigerator, or a
localized cooler for lasers, integrated circuits, and the like.
[0004] Thus, the thermoelectric power generator or cooler made up
of the thermoelectric device is simple in construction, and is in a
more favorable condition for miniaturization as compared with other
types of power generators or coolers, offering high usefulness. For
example, with the thermoelectric device for use in the
thermoelectric power generator, there will not arise a problem of
leakage or depletion of electrolyte as with the case of a redox
cell, and the thermoelectric device has therefore promising
prospects for application to portable electronic devices such as an
electronic wrist watch.
[0005] The general construction of a conventional thermoelectric
device, and a conventional method of fabricating the same, have
been disclosed in, for example, Japanese Patent Laid-open
Publication No. 63-20880 or Japanese Patent Laid-open Publication
No. 8-43555. The description disclosed therein are concerned with a
thermoelectric device for use in generation of power. However, the
basic construction thereof is the same as that of a thermoelectric
device for use in cooling. Hence, the thermoelectric device for use
only in generation of power is described hereinafter to avoid
complexity in explanation.
[0006] In the conventional thermoelectric device disclosed in the
publications described above, p-type and n-type thermoelectric
semiconductors are alternately and regularly arranged so that a
multitude of thermocouples are formed on a horizontal plane, and
the thermocouples thus formed are electrically connected to each
other in series.
[0007] The thermoelectric device is formed in a sheet-like shape by
disposing the thermocouples on a plane, and the upper surface and
under surface of the thermoelectric device become faces on which
hot junctions and cold junctions of the thermocouples are located,
respectively. Generation of electric power in the thermoelectric
device is caused to occur by a difference in temperature between
the upper surface and the under surface of the device having a
sheet-like shape.
[0008] Meanwhile, an output voltage of a thermocouple using a
BiTe-based material, said to have the highest figure of merit of
thermoelectric power generation at present, is about 400 .mu.V
/.degree.C. per couple.
[0009] When such thermocouples as described above are employed in a
portable electronic device for use at around room temperature, for
example, in an electronic watch, a satisfactory difference in
temperature can not be expected to be developed inside the device.
For example, in the case of a wrist watch, the temperature
difference in a wrist watch developed between body temperature and
the ambient temperature will be 2.degree. C. at most.
[0010] It follows that not less than about 2000 couples of
BiTe-based thermocouples are required to obtain a voltage not lower
than 1.5V, necessary for driving an electronic watch.
[0011] Furthermore, in the case of an electronic wrist watch,
wherein mechanical components and electric circuit components need
to be encased therein in spite of a small internal volume thereof
in the first place, it is required that a thermoelectric device for
power generation, very small in size, be used.
[0012] The conventional method of fabricating a thermoelectric
device small in size and composed of a multitude of thermocouples
has been disclosed in Japanese Patent Laid-open Publication No.
63-20880.
[0013] In the method disclosed, a multi-layered body is formed by
stacking p-type and n-type thermoelectric semiconductors, in a thin
sheet-like shape, on top of each other in layers while interposing
a heat insulating material between respective layers, and then by
bonding them together. Subsequently, grooves are formed at a given
spacing in the multi-layered body, whereupon the grooves are filled
up with a heat insulating material, and connecting portions of
individual thermoelectric semiconductors are removed, thereby
forming n-type and p-type thermocouples, surrounded by the heat
insulating material and isolated from each other. By electrically
connecting the thermocouples with each other in series, a
thermoelectric device is completed.
[0014] Then, in the method disclosed in Japanese Patent Laid-open
Publication No. 8-43555, p-type and n-type thermoelectric
semiconductors, each having a plate-like shape, are first bonded to
separate substrates, and thereafter, a grooving process of forming
a multitude of grooves at very small spacings in the longitudinal
and transverse directions is applied to respective thermoelectric
semiconductors.
[0015] As a result of the grooving process described above, a
multitude of thermoelectric semiconductors, each columnar in shape,
and upstanding regularly on top of the respective substrates,
resembling a kenzan (a needle-point flower holder for flower
arrangement), are formed. The kenzan-like bodies composed of the
n-type and p-type thermoelectric semiconductors, respectively, are
thus prepared, and joined together such that the respective
thermoelectric semiconductors, columnar in shape, are mated with
each other. Thereafter, an insulating material is filled between
the respective thermoelectric semiconductors.
[0016] In the final step of processing, the substrates are removed,
and a thermoelectric device is completed by electrically connecting
thermocouples with each other in series.
[0017] However, with the methods of fabricating the thermoelectric
device as described in the foregoing, there will arise a problem
that the material used for the thermoelectric semiconductors is
prone to breakage during the process of forming the thermoelectric
semiconductors into a sheet-like shape, during the grooving process
of forming the kenzan-like bodies, and the like, because of the
fragile nature of the material itself for the thermoelectric
semiconductors.
[0018] In particular, for forming as many as not less than 2000
couples of thermocouples in an ultra-small sized thermoelectric
device which can be encased in a wrist watch, it is required that
the thickness of the respective sheet-like thermoelectric
semiconductors or the diameter of the respective columnar
thermoelectric semiconductors be set to on the order of 100 .mu.m
or less, and consequently, the problem of fragility described above
will become quite serious.
[0019] Hence, the present invention has been developed in order to
solve such problems as encountered with the conventional methods of
fabricating the thermoelectric device, and an object of the
invention is therefore to provide a method of fabricating with ease
and efficiently a thermoelectric device small in size, but
incorporating a multitude of thermocouples so as to be able to
output a high voltage.
DISCLOSURE OF THE INVENTION
[0020] To this end, a method of fabricating a thermoelectric device
according to the invention comprises:
[0021] a grooved block fabrication process of forming grooved
blocks composed of an n-type thermoelectric semiconductor and
p-type thermoelectric semiconductor, respectively, each provided
with a plurality of grooves formed at a same pitch and parallel
with each other, leaving a depthwise portion of respective grooved
blocks intact;
[0022] a fitting process of fitting the grooved blocks composed of
the n-type thermoelectric semiconductor and p-type thermoelectric
semiconductor formed, respectively, by said grooved block
fabrication process to each other such that surfaces of the
respective grooved blocks, with the grooves formed thereon, face
each other;
[0023] an adhesion process of forming an integrated block by
adhering the grooved block composed of the n-type thermoelectric
semiconductor and the grooved block composed of p-type
thermoelectric semiconductor, fitted to each other by said fitting
process, to each other after filling up gaps in fitting parts
between the respective grooved blocks with an adhesive insulation
member; and
[0024] a thermoelectric semiconductor pieces exposure process of
exposing n-type and p-type thermoelectric semiconductor pieces by
removing all portions of the integrated block formed by said
adhesion process, other than the fitting parts where the grooved
block composed of the n-type thermoelectric semiconductor and the
grooved block composed of p-type thermoelectric semiconductor are
fitted to each other.
[0025] When fabricating the thermoelectric device by the method
comprising the process described above, thermoelectric
semiconductor material having a problem of fragility is always
handled in the form of a unit (block). Hence, delicate processing
can be applied to the thermoelectric semiconductor material without
causing breakage thereof, enabling the thermoelectric device made
up of a plurality of thermocouples composed of a plurality of
thermoelectric semiconductor pieces very small in size to be
efficiently fabricated with ease.
[0026] Further, it is preferable that the method according to the
invention further comprises a second grooving process of forming a
plurality of grooves in the integrated block formed by the adhesion
process, in the direction crossing the direction of the grooves
formed by said grooved block fabrication process, leaving a
depthwise portion of the integrated block intact; a solidification
process of filling the grooves formed by the second grooving
process with adhesive insulation members and solidifying the same;
and, a thermoelectric semiconductor pieces exposure process, to be
applied thereafter, of exposing n-type and p-type thermoelectric
semiconductor pieces by removing all portions of the integrated
block wherein the adhesive insulation members filling up the
grooves are solidified in the solidification process, other than
the fitting parts where the grooved blocks composed of the n-type
thermoelectric semiconductor and p-type thermoelectric
semiconductor, respectively, are fitted to each other.
[0027] This will result in a considerable increase in the number of
thermocouples making up a thermoelectric device of a same size, and
the output voltage of the thermoelectric device when used for
generation of power can be raised.
[0028] It is yet further preferable that the method according to
the invention further comprises a grooving process of forming two
grooved integrated blocks by forming a plurality of grooves at a
same pitch and in the direction crossing the direction of the
grooves formed by the grooved block fabrication process, leaving a
depthwise portion of respective integrated blocks intact, in each
of the two integrated blocks fabricated by means of the grooved
block fabrication process, fitting process, and adhesion process
described in the foregoing; a second fitting process of fitting the
two grooved integrated blocks to each other such that surfaces
thereof with the grooves formed thereon face each other; a second
adhesion process of forming a second integrated block by filling up
gaps in fitting parts between the two grooved integrated blocks
fitted to each other by the fitting process with adhesive
insulation members, and solidifying the same; and a thermoelectric
semiconductor pieces exposure process, to be applied thereafter, of
exposing n-type and p-type thermoelectric semiconductor pieces by
removing all depthwise portions of the second integrated block,
other than the fitting parts.
[0029] This will result in a further considerable increase in the
number of thermocouples making up a thermoelectric device of a same
size, and the output voltage of the thermoelectric device when used
for generation of power can be additionally increased.
[0030] In the methods of fabricating the thermoelectric device
described, the process of forming the grooved block of the n-type
thermoelectric semiconductor and grooved block of the p-type
thermoelectric semiconductor by applying a grooving process to an
n-type thermoelectric semiconductor block and p-type thermoelectric
semiconductor block, respectively, such that a plurality of grooves
are formed at a same pitch and in parallel with each other, leaving
a depthwise portion of the respective blocks intact may be adopted
for the grooved block fabrication process described above.
[0031] Otherwise, a process of forming the grooved block of the
n-type thermoelectric semiconductor and grooved block of the p-type
thermoelectric semiconductor by molding n-type thermoelectric
semiconductor material and p-type thermoelectric semiconductor
material by use of a mold for the grooved block, respectively, and
sintering the same, may be adopted for the grooved block
fabrication process described above.
[0032] In the methods of fabricating the thermoelectric device
described, the thermoelectric device can be completed by applying a
process of forming electrodes for connecting the exposed n-type and
p-type thermoelectric semiconductor pieces to each other
alternately and in series after the thermoelectric semiconductor
pieces exposure process.
[0033] The method of fabricating the thermoelectric device may also
comprise a grooving process applied to an n-type thermoelectric
semiconductor composite block, prepared by bonding an n-type
thermoelectric semiconductor block to a base, and a p-type
thermoelectric semiconductor composite block, prepared by bonding a
p-type thermoelectric semiconductor block to a base, for forming a
plurality of grooves in the n-type thermoelectric semiconductor
block and the p-type thermoelectric semiconductor block,
respectively, at a same pitch, and to a depth close to the
interface between the respective thermoelectric semiconductor
blocks and the base thereof; forming an n-type thermoelectric
semiconductor composite block and p-type thermoelectric
semiconductor composite block, with the grooves formed therein,
respectively; and, the fitting process, adhesion process, second
grooving process, solidification process, and the like, applied to
a pair of thermoelectric semiconductor composite blocks, with the
grooves formed therein, forming an integrated block. Or by means of
these processes, two integrated blocks may be formed, and fitted to
each other after the second grooving process is applied thereto,
forming a second integrated block. Thereafter, the thermoelectric
semiconductor pieces exposure process of exposing the n-type and
p-type thermoelectric semiconductor pieces by removing the
respective bases may be applied.
[0034] By adopting the processes described above, the
thermoelectric semiconductor material can be fully utilized without
wastage.
[0035] It may be preferable to use bases having a surface area
larger than an area of the bonded surface of the respective
thermoelectric semiconductor blocks and to interpose spacers
between portions of the bases of the n-type thermoelectric
semiconductor composite block and the p-type thermoelectric
semiconductor composite block, respectively, where the respective
thermoelectric semiconductor blocks do not exist, and in the
fitting process, controlling a spacing between the bases to be
substantially equivalent to the thicknesses of the respective
thermoelectric semiconductor blocks.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIGS. 1 to 6 are perspective views of respective processes
illustrating a first embodiment of a method of fabricating a
thermoelectric device according to the invention;
[0037] FIGS. 7 and 8 are expanded views of the portion A of an
integrated block 3, shown by the imaginary lines in FIG. 3,
illustrating variations of the adhesion process;
[0038] FIG. 9 is a plan view of a completed thermoelectric device
according to the first embodiment for explaining the construction
of electrodes;
[0039] FIGS. 10 to 14 are perspective views of respective processes
illustrating a second embodiment of a method of fabricating a
thermoelectric device according to the invention;
[0040] FIGS. 15 to 17 are perspective views showing the latter
parts of fabrication processes illustrating a third embodiment of a
method of fabricating a thermoelectric device according to the
invention;
[0041] FIG. 18 is plan view of a completed thermoelectric device
according to the third embodiment for explaining the construction
of electrodes;
[0042] FIGS. 19 to 21 are perspective views showing parts of
fabrication processes illustrating a fourth embodiment of a method
of fabricating a thermoelectric device according to the
invention;
[0043] FIGS. 22 to 24 are perspective views showing the first half
of fabrication processes illustrating a fifth embodiment of a
method of fabricating a thermoelectric device according to the
invention;
[0044] FIGS. 25 to 26 are perspective views showing parts of
fabrication processes illustrating a sixth embodiment of a method
of fabricating a thermoelectric device according to the
invention;
[0045] FIGS. 27 to 29 are sectional views showing parts of
fabrication processes illustrating a seventh embodiment of a method
of fabricating a thermoelectric device according to the
invention;
[0046] FIGS. 30 and 31 are sectional views showing parts of
fabrication processes illustrating an eighth embodiment of a method
of fabricating a thermoelectric device according to the
invention;
[0047] FIGS. 32 and 33 are sectional views showing parts of
fabrication processes illustrating a ninth embodiment of a method
of fabricating a thermoelectric device according to the invention;
and
[0048] FIG. 34 is a sectional view showing an example of a mold
used in forming a grooved block of thermoelectric semiconductor by
means of injection molding.
BEST MODE FOR CARRYING OUT THE INVENTION
[0049] Embodiments of the method of fabricating a thermoelectric
device in carrying out the invention in the best mode are described
hereinafter.
[0050] First Embodiment: FIGS. 1 to 9
[0051] Firstly, a first embodiment of the method of fabricating a
thermoelectric device according to the invention is described with
reference to FIGS. 1 to 9.
[0052] In the first embodiment of the invention, as shown in FIG.
1, an n-type thermoelectric semiconductor block 1 and a p-type
thermoelectric semiconductor block 2 are prepared. It is desirable
that the both blocks 1 and 2 be identical in all dimensions
including the thickness thereof. For ease in identification of the
respective blocks, all the surfaces of the n-type thermoelectric
semiconductor block 1 are shown by the diagonally shaded areas. The
same applies to all other figures shown hereinafter.
[0053] Subsequently, as shown in FIG. 2, a first grooving process
of fabricating a grooved block is applied, whereby a plurality of
longitudinal grooves 16 at a given pitch are formed parallel with
each other in the n-type thermoelectric semiconductor block I to a
depth such that a thicknesswise portion 15 thereof is left intact,
completing an n-type grooved block 11 provided with longitudinal
partition walls 17 formed thereon at a predetermined spacing.
Similarly, a plurality of longitudinal grooves 26 at a given pitch
are formed parallel with each other in the p-type thermoelectric
semiconductor block 2 as well to a depth such that a thicknesswise
portion 25 thereof is left intact, completing the p-type grooved
block 21 provided with longitudinal partition walls 27 formed
thereon at a predetermined spacing.
[0054] In this instance, the longitudinal partition walls 17 of the
n-type grooved block 11 and the longitudinal partition walls 27 of
the p-type grooved block 21 are formed in a shape resembling the
teeth of a comb, respectively, to enable the grooved blocks 11, 21
to snugly fit to each other, and while the longitudinal grooves 16,
26 are formed at a same pitch, the width of the respective
longitudinal grooves 16, 26 is rendered slightly wider than that of
the respective longitudinal partition walls 17, 27, to provide room
for adhesion. Further, it is desirable to equalize the depth of the
respective longitudinal grooves 16 to that of the respective
longitudinal grooves 26.
[0055] The first grooving process of forming the longitudinal
grooves 16, 26 is applied to the n-type thermoelectric
semiconductor block 1 and p-type thermoelectric semiconductor block
2, respectively, by, for example, polishing with the use of a wire
saw, or by grinding with the use of a dicing saw.
[0056] In the first embodiment of the invention, a BiTeSe sintered
body is used as the n-type thermoelectric semiconductor block 1 and
a BiTeSb sintered body is used as the p-type thermoelectric
semiconductor block 2, the dimensions of the both blocks being set
at 12 mm.times.12 mm.times.4 mm. The longitudinal grooves 16, 26,
each 70 .mu.m wide, are formed at a pitch of 120 .mu.m in the
grooved blocks 11 and 21, respectively, to a depth of 3 mm against
4 mm in the thickness of the respective grooved blocks.
Accordingly, the width of the respective longitudinal partition
walls 17, 27 becomes 50 .mu.m.
[0057] The method of fabricating the grooved blocks 11 and 21,
composed of thermoelectric semiconductors, is not limited to the
method of fine grooving by machining as described above. The same
may be fabricated by a molding method such as an injection molding
method, or the like, an example of which will be described
later.
[0058] Subsequently, as shown in FIG. 3, a fitting process and
adhesion process are applied, whereby the n-type grooved block 11
and p-type grooved block 21 are fitted to each other such that the
longitudinal partition walls 27, 17 of the respective blocks are
inserted into the longitudinal grooves 16, 26 of the respective
opposite blocks, and both blocks are fitted to each other by
filling up gaps in fitting parts therebetween with an adhesive
insulating material, forming an integrated block 3.
[0059] In these processes of forming the integrated block 3,
wherein the n-type grooved block 11 and p-type grooved block 21 are
fitted to each other, and adhered together with the insulating
material, adhesive layers formed thereby need to have the function
of ensuring electrical insulation between the n-type grooved block
11 and p-type grooved block 21 besides the function of bonding the
two blocks together.
[0060] For example, in the case where the inner walls of the
longitudinal grooves 16, 26 are finished to have very smooth
surfaces by polishing with the use of a wire saw, such electrical
insulation can be ensured by simply immersing portions of the
integrated block 3 in an adhesive of high fluidity prior to the
adhesion process such that gaps between the longitudinal grooves
16, 26 and the longitudinal partition walls 27, 17, respectively,
are filled up with the adhesive due to the capillary effect.
[0061] On the other hand, in the case where the inner walls of the
longitudinal grooves 16, 26 are finished up into somewhat rough
surfaces, maintenance of electrical insulation is ensured by
applying a method as illustrated in FIG. 7 or 8 showing an enlarged
view of the part A of the integrated block 3, as indicated by the
imaginary lines in FIG. 3.
[0062] In the method shown in FIG. 7, an insulation film 31 is
formed on the surfaces of both the longitudinal partition walls 17
and the longitudinal grooves 16 of the n-type grooved block 11, and
the p-type grooved block 21 is fitted onto the insulation film 31
so that gaps between the insulation film 31 and the longitudinal
partition walls 27 as well as the longitudinal grooves 26 thereof
are filled up with the adhesive taking advantage of the capillary
effect as described in the foregoing, forming an adhesive layer 32
after the adhesive is cured. The integrated block 3 is thus
completed.
[0063] For the insulation film 31, either an inorganic film
composed of silicon oxide, aluminum oxide, silicon nitride or the
like, or an organic film composed of polyimide or the like may be
used.
[0064] The insulation film 31 may be alternatively formed on the
surfaces of the longitudinal partition walls 27 as well as the
longitudinal grooves 26 of the p-type grooved block 21. Further,
electrical insulation is additionally ensured by forming the
insulation film 31 on the surfaces of both the n-type grooved block
11 and p-type grooved block 21, to be fitted with each other.
[0065] In the method shown in FIG. 8, the integrated block 3 is
fabricated by use of an adhesive with insulating spacers 33
dispersed therein. For example, 5 wt % of glass beads spherical in
shape, 8 .mu.m in average grain size, are added as the insulating
spacers 33 to an epoxy adhesive. This will cause the glass beads to
be dispersed substantially evenly in the adhesive layer 32 such
that the n-type grooved block 11 and p-type grooved block 21 are
forced to be isolated spatially from each other by the insulating
spacers 33 composed of the glass beads, ensuring electrical
insulation therebetween.
[0066] As shown in FIG. 4, a second grooving process is applied to
the integrated block 3 shown in FIG. 3, completed by applying the
fitting process and adhesion process as described hereinbefore,
thereby forming transverse grooves 46. The block shown in FIG. 4,
completed by forming the transverse grooves 46 in the integrated
block 3, is referred to as a grooved integrated block 4
hereinafter.
[0067] In the process of forming the transverse grooves 46, a
plurality of the transverse grooves 46 are formed at a given pitch
in the direction crossing the direction in which the longitudinal
grooves have been formed in the first grooving process as described
in FIG. 3, leaving a thicknesswise portion 45 of the grooved
integrated block 4 intact so that transverse partition walls 47 are
formed at a predetermined spacing. In this process, the transverse
grooves 46 may be formed so as to cross the longitudinal grooves
16, 26 formed in the first grooving process at optional angles.
However, they most preferably cross at right angles as shown in
FIG. 4.
[0068] Further, in this embodiment, the transverse grooves 46 are
formed in the integrated block 3 from the side of the p-type
grooved block 21 as shown in FIG. 4. However, the same may be
formed therein conversely from the side of the n-type grooved block
11. Otherwise, the same may be formed in the fitting parts from the
front face side or from the rear face side of the integrated block
3 shown in FIG. 3.
[0069] The transverse grooves 46 are preferably formed in the
integrated block 3 to a depth such that the fitting parts between
the n-type grooved block 11 and the p-type grooved block 21 are
severed thereby.
[0070] As opposed to the case of the longitudinal grooves 16, 26,
it is preferable that the width of the respective transverse
grooves 46 be rendered as narrow as possible- This is because it is
the transverse partition walls 47 that contribute to the capacity
of power generation of the thermoelectric device as is shown from
subsequent steps of processing, and consequently, from the
viewpoint of performance of the thermoelectric device, the regions
for the transverse grooves 46 should be reduced in size as much as
possible.
[0071] Accordingly, in the first embodiment of the invention, the
transverse grooves 46, 40 .mu.m in width and 4 mm in depth, are
formed at a pitch of 120 .mu.m. Incidentally, the width 40 .mu.m of
the respective transverse grooves 46 represents a substantial limit
size for the width of a groove formed by processing with the use of
a wire saw.
[0072] Subsequently to the foregoing step of processing, a
solidification process as shown in FIG. 5 is applied. That is, the
respective transverse grooves 46 of the grooved integrated block 4
shown in FIG. 4 are filled up with insulating resin (insulation
member), forming insulating resin layers 54 after the insulation
member is cured. A block solidified with the insulating resin
layers 54 is referred to as a grooved integrated block 4'
hereinafter.
[0073] Thereafter, a process of exposing thermoelectric
semiconductor pieces is applied to the grooved integrated block 4'
solidified with the insulating resin layers 54, whereby portions
(portions having thickness denoted by a, b, respectively, in FIG.
5) of the grooved integrated block 4' which have been left intact
without the grooving process applied thereto during the first and
second grooving processes described in the foregoing are removed by
polishing, or grinding the upper and under surfaces of the grooved
integrated block 4', and the remainder is finished up such that
only the fitting parts shown in FIG. 3, wherein the longitudinal
grooves 16, 26, composed of the n-type thermoelectric
semiconductor, and p-type thermoelectric semiconductor,
respectively, are fitted to the longitudinal partition walls 27,
17, composed of the p-type thermoelectric semiconductor, and n-type
thermoelectric semiconductor, respectively, and a portion wherein
the transverse grooves 46 are formed, is left intact. A
thermoelectric device block 5 shown in FIG. 6 is thus obtained.
[0074] In the thermoelectric device block 5, a multitude of n-type
thermoelectric semiconductor pieces 51, and p-type thermoelectric
semiconductor pieces 52 are insulated from each other via the
insulating resin layers 54, and integrally adhered to each other
while the upper as well as under surfaces thereof are exposed.
[0075] In the final step of processing, a process of forming
electrodes is applied to both the upper and under surfaces of the
thermoelectric device block 5 shown in FIG. 6 such that the n-type
thermoelectric semiconductor pieces 51 and p-type thermoelectric
semiconductor pieces 52 are connected with each other, alternately
and electrically in series, thereby obtaining a thermoelectric
device 6 shown in FIG. 9.
[0076] FIG. 9 is a plan view of the thermoelectric device 6, as
seen from directly above, illustrating various electrodes formed on
the upper as well as under surfaces thereof.
[0077] In the figure, upper surface electrodes 61a circular in
shape as indicated by the solid lines and under surface electrodes
62a circular in shape as indicated by the broken lines are
electrodes for connecting together the n-type thermoelectric
semiconductor pieces 51 and p-type thermoelectric semiconductor
pieces 52 adjacent to each other, electrically in series, forming a
multitude of thermocouples. Upper surface electrodes 61b and under
surface electrodes 62b, resembling the letter L in shape, are
electrodes required in the periphery region of the thermoelectric
device 6 for connecting the n-type or p-type thermoelectric
semiconductor pieces in parallel although it is deemed unusable.
The respective thermoelectric semiconductor pieces 51, 52 are
insulated from each other by means of the adhesive layers 32 and
the insulating resin layers 54. Further, under surface electrodes
63, 64, in the shape of a small circle indicated by the broken
lines are electrodes for outputting voltage externally.
[0078] Each of the electrodes described above is formed by
depositing a gold (Au) film on both the upper and under surfaces of
the thermoelectric device block 5 shown in FIG. 6 by means of the
vacuum coating method, sputtering method, electroless plating
method, or the like, and then, by patterning on the gold film by
the photolithographic technique and etching technique.
[0079] In the case where the upper and under surfaces of the
thermoelectric device block 5, on which the electrodes are to be
formed, are likely to cause a problem of surface roughness when
finished by only grinding as described hereinbefore, it is
desirable to render the surfaces smoother by lapping, or the like
as this will prevent occurrence of faults with the electrodes (such
as breakage) thereof.
[0080] For the electrodes, use can be made of not only the gold
film but also other metal film, for example, a Cu film, Al film, Ni
film, Fe film, or a multi-layer film (for example, Al / Ni film)
composed of the aforesaid films combined together. Further, in
forming the electrodes, use may be made of the printing method,
masked vapor deposition method, or a method whereby the electrodes
are patterned beforehand on an insulating sheet-like material made
of glass or ceramic, and the sheet-like material as a whole is
pasted on the surfaces.
[0081] In the method according to the first embodiment of the
invention, the longitudinal partition walls 17, 27 and the
transverse partition walls 47, composed of the thermoelectric
semiconductor materials, and very thin, are formed in the first and
second grooving processes as shown in FIGS. 2 and 4. Although these
partition walls, individually, are very thin and fragile, the same
together constitute an integrated block, and processing operations
can be performed on respective blocks as a whole without need of
performing delicate operations such as holding individual partition
walls for transfer and stacking the same, and the like. Hence, in
comparison with the conventional method disclosed in Japanese
Patent Laid-open Publication No. 63-20880, it is possible to
fabricate a thermoelectric device incorporating a multitude of
small sized thermocouples efficiently with ease, overcoming the
problem of fragility.
[0082] In the case of another conventional method disclosed in
Japanese Patent Laid-open Publication No. 8-43555, integrated
blocks are used. However, thermoelectric semiconductors are bonded
to separate base members, and processed so as to form a multitude
of columnar shapes. As a result, extreme difficulties are still
encountered in fabrication of a product due to the serious problem
of fragility. As opposed to such a method, the method according to
the first embodiment of the invention is a method of fabrication
whereby thermoelectric semiconductors are always processed when the
same are in the form of an integrated block, thus enabling fine
structural processing and assembling of thermoelectric
semiconductor material, which is a very fragile material, to be
carried out with ease. Consequently, it is possible to efficiently
fabricate with ease a thermoelectric device provided with a
multitude of thermocouples in order to enhance the output voltage
thereof, although same is small in size.
[0083] However, the process of exposing thermoelectric
semiconductor pieces may be applied straight to the integrated
block 3 shown in FIG. 3 by omitting the second grooving process,
and the solidification process whereby grooved parts (the
transverse grooves 47 in FIG. 4) are filled up with the insulation
member, which is then solidified, forming the insulating resin
layers 54 shown in FIG. 5, as applied in carrying out the first
embodiment. Such omission, however, will result in a decrease in
the number of thermocouples making up the thermoelectric
device.
[0084] In this case, the grinding process, and the like are applied
to the upper as well as under surfaces of the integrated block 3
fabricated by means of the fitting process and adhesion process as
shown in FIG. 3, and by removing portions of the integrated block
3, other than parts where the longitudinal partition walls 17, 27
of the n-type grooved block 11 and p-type grooved block 21,
respectively, are fitted to the longitudinal grooves 16, 26, the
thermoelectric device block with the n-type and p-type
thermoelectric semiconductor pieces exposed can be fabricated.
[0085] Thereafter, the process of forming the electrodes is applied
thereto, whereby electrodes for connecting the exposed n-type and
p-type thermoelectric semiconductor pieces (that is, the
longitudinal partition walls 17 of the n-type groove block 11 and
the longitudinal partition walls 27 of the p-type groove block 21)
alternately to each other and in series are formed on the upper as
well as under surfaces of the thermoelectric device block, thus
fabricating the thermoelectric device.
[0086] Second Embodiment: FIGS. 10 to 14
[0087] Next, a second embodiment of the method of fabricating a
thermoelectric device according to the invention is described
hereinafter with reference to FIGS. 10 to 14. In these figures,
parts corresponding to those previously described with reference to
the first embodiment shown in FIGS. 1 to 5 are denoted by the same
reference numerals.
[0088] In the second embodiment, as shown in FIG. 10, an n-type
thermoelectric semiconductor composite block 12 formed by bonding
an n-type thermoelectric semiconductor block 1 to a base 10, and a
p-type thermoelectric semiconductor composite block 22 formed by
bonding a p-type thermoelectric semiconductor block 2 to a base 20
are first prepared. It is desirable that the n-type thermoelectric
semiconductor block 1 and the p-type thermoelectric semiconductor
block 2 be identical in all dimensions including the thickness
thereof.
[0089] The thermoelectric semiconductor blocks 1, 2 are bonded to
the bases 10, 20, respectively, with an adhesive or was. Further,
for the bases 10, 20, use can be made of various materials having a
given hardness such as glass, ceramic, plastic, metal, and the
like.
[0090] Subsequently, a grooving process, the same as applied in the
first grooving process in the first embodiment is applied to the
respective thermoelectric semiconductor blocks 1, 2 of the
thermoelectric semiconductor composite blocks 12, 22, respectively,
and as shown in FIG. 11, longitudinal grooves 16, 26 as well as
longitudinal partition walls 17, 27, resembling the teeth of a comb
in shape, are formed, fabricating an n-type grooved composite block
13 and a p-type grooved composite block 23. The pitch and width of
the longitudinal grooves 16, 26 are the same as in the case of the
first embodiment, however, the depth thereof is set to be
substantially close to the interface between the thermoelectric
semiconductor block 1, or 2 and the base 10 or 20, respectively.
More specifically, the depth is selected from among slightly short
of the interface, down to just the interface, or below the
interface, cutting slightly into the base 10 or 20, depending on
the circumstance.
[0091] Thereafter, a fitting process whereby the n-type grooved
composite block 13 and p-type grooved composite block 23 are fitted
to each other such that respective grooved surfaces face each other
is applied, and then, an adhesion process whereby gaps in fitting
parts between the n-type grooved composite block 13 and p-type
grooved composite block 23 which are fitted to each other are
filled up with an adhesive insulation member so that the n-type
grooved composite block 13 and p-type grooved composite block 23
are adhered to each other is applied, thereby fabricating an
integrated block 3' shown in FIG. 12.
[0092] Subsequently, a grooving process, the same as applied in the
second grooving process in the first embodiment, as shown in FIG.
4, is applied to the integrated block 3' as shown in FIG. 13,
whereby transverse grooves 46 and transverse partition walls 47 are
formed, fabricating a grooved integrated block 14. In this
instance, the transverse grooves 46 are cut into one of the grooved
composite blocks to a depth close to the interface thereof with the
base 10 or 20 of the other grooved composite block and in such a
direction as to cross (at right angles,. in this embodiment) the
longitudinal grooves 16, 26, and the longitudinal partition walls
17, 27, formed in the first grooving process.
[0093] Then, as shown in FIG. 14, a solidification process is
applied whereby grooved parts, that is, the transverse grooves 46,
are filled up with insulating resin (insulation member), and the
insulating resin is then solidified, forming insulating resin
layers 54. A block solidified with the insulating resin layers 54
is referred to hereafter as a grooved integrated block 14'.
[0094] Thereafter, a process of exposing thermoelectric
semiconductor pieces is applied to the grooved integrated block 14'
shown in FIG. 14, whereby the bases 10 and 20, that is, bottom and
top portions of the grooved integrated block 14', are removed,
obtaining a thermoelectric device block 5, the same as shown in
FIG. 6 in the case of the first embodiment. The base on the side
where the grooving process is applied (the base 20 in the example
shown in FIG. 13) may be removed prior to forming the transverse
grooves 46.
[0095] Further, by applying a process of forming electrodes for
forming the electrodes on the upper and under surfaces of the
thermoelectric device block 5 such that n-type thermoelectric
semiconductor pieces 51 and p-type thermoelectric semiconductor
pieces 52 are connected to each other alternately and electrically
in series, a thermoelectric device 6, the same as shown in FIG. 9,
can be fabricated.
[0096] In the method according to the second embodiment, the bases
10, 20 are employed to integrally support the longitudinal
partition walls 17, 27, and the transverse partition walls 47 in
place of portions left intact without the grooving process applied
thereto (the portions 15, 25 shown in FIG. 2) of the thermoelectric
semiconductor blocks 1 and 2, respectively, which will be
eventually removed by grinding as in the aforesaid first
embodiment. Consequently, effective use can be made of portions of
the thermoelectric semiconductor material, in regions close to the
upper and under surfaces thereof, reducing unusable portions
thereof. Therefore, the method has an advantage of remarkably
improving the utilization efficiency of the material.
[0097] Other merits of operation according to this embodiment are
the same as for the first embodiment.
[0098] Third Embodiment: FIGS. 15 to 18
[0099] Now, a third embodiment of the method of fabricating a
thermoelectric device according to the invention is described
hereinafter with reference to FIGS. 15 to 18. The first half of a
process applied in carrying out the third embodiment is the same as
for the first embodiment described with reference to FIGS. 1 to 3,
and accordingly, will only be briefly described referring to these
figures.
[0100] In the third embodiment, two each of the n-type
thermoelectric semiconductor blocks 1 and p-type thermoelectric
semiconductor blocks 2 as shown in FIG. 1 are prepared.
Subsequently, a first grooving process as shown in FIG. 2 is
applied to the respective thermoelectric semiconductor blocks,
whereby a plurality of longitudinal grooves 16, 26, and
longitudinal partition walls 17, 27 are formed at a same pitch, and
parallel with each other such that the depth of the former is equal
to the height of the latter, fabricating two pairs of n-type
grooved blocks 11, and p-type grooved blocks 21.
[0101] In this case as well, the two pairs of the n-type grooved
blocks 11, and p-pe grooved blocks 21 may be fabricated by a
process of fabricating grooved blocks using a molding method, which
will be described later.
[0102] Subsequently, by applying a fitting process as shown in FIG.
3, whereby the respective n-type grooved blocks 11 and p-type
grooved blocks 21 are fitted to each other, and a first adhesion
process of forming integrated blocks, whereby the grooved blocks
fitted are adhered to each other by filling up gaps in fitting
parts thereof with an adhesive insulating material, two integrated
blocks 3 are fabricated.
[0103] Thereafter, a second grooving process is applied to one of
the two integrated blocks 3 from the side of the p-type grooved
block 21 shown in FIG. 3, and to the other from the side of the
n-type grooved block 11, whereby a plurality of grooves parallel
with each other are formed at a same pitch in the direction
crossing the direction in which the first grooving process has been
applied, (at right angles, in this embodiment), fabricating a pair
of grooved integrated blocks 43A, 43B, wherein a plurality of
transverse grooves 46 and transverse partition a walls 47 are
formed as shown in FIG. 15, the depth of the former being equal to
the height of the latter.
[0104] In this case, the dimensions of the transverse grooves 46
and transverse partition walls 47 are rendered similar to those of
the longitudinal grooves 16, 26, and longitudinal partition walls
17, 27, described in the first embodiment with reference to FIG. 2,
so that the transverse grooves 46 in one of the grooved integrated
blocks, and the transverse partition walls 47 in the other of the
grooved integrated blocks can be fitted to each other. That is, in
the grooved integrated blocks 43A, 43B, shown in FIG. 15, the
transverse grooves 46 are formed at a same pitch, and the width of
the respective transverse grooves 46 is rendered wider than that of
the respective transverse partition walls 47.
[0105] Subsequently, as shown in FIG. 16, by applying a second
fitting process whereby the pair of grooved integrated blocks 43A,
43B are combined with each other by fitting the respective
transverse partition walls 47 into the respective transverse
grooves 46, and further, by applying a second adhesion process
whereby the grooved integrated blocks fitted together are
integrally adhered to each other by filling up gaps between fitting
parts with an adhesive insulating material, the pair of the grooved
integrated blocks are integrally joined together, forming a doubly
integrated block 44.
[0106] Further, for fitting and adhering together the grooved
integrated blocks 43A with 43B, the methods previously described in
the first embodiment with reference to FIGS. 3, 7, and 8 are
applied.
[0107] Thereafter, a process of exposing thermoelectric
semiconductor pieces is applied to the doubly integrated block 44.
That is, portions of the doubly integrated block 44, other than a
depthwise portion denoted by d in FIG. 16, are removed by polishing
or grinding the upper as well as under surfaces thereof so that the
remainder is finished up, leaving intact regions where the
longitudinal grooves 16, 26, the transverse grooves 46, the
longitudinal partition walls 27, 17, and the transverse partition
walls 47, composed of either of the n-type thermoelectric
semiconductor and p-type thermoelectric semiconductor, are all
fitted to each other. Thus, as shown in FIG. 17, a thermoelectric
device block 50 wherein n-type thermoelectric semiconductor pieces
51 and p-type thermoelectric semiconductor pieces 52 are
alternately arranged is fabricated.
[0108] In integrally joining the grooved integrated blocks 43A with
43B in carrying out this embodiment, preferable fabrication
conditions require that the n-type thermoelectric semiconductor
pieces 51 and p-type thermoelectric semiconductor pieces 52 be
arranged regularly like a checkerboard as shown in FIG. 17.
Accordingly, respective positions thereof need to be aligned, which
may be accomplished by providing a benchmark face on the periphery
of each of the grooved integrated blocks, and joining the same
together based on the benchmark face using a jig.
[0109] Such alignment in positioning will facilitate wiring work in
a process of electrode wiring described hereinafter because of
standardized and simplified shapes and layout of the electrodes as
shown in FIG. 18. Furthermore, this will contribute to improvement
in the utilization efficiency of the thermoelectric semiconductors
because the thermoelectric semiconductor pieces located in the edge
portions on the opposite sides in FIG. 9, not contributing to
electrical connection in series, can be eliminated in this way.
[0110] Then, a process of forming electrodes is applied to the
upper as well as under surfaces of the thermoelectric device block
50 such that the n-type thermoelectric semiconductor pieces 51 and
p-type thermoelectric semiconductor pieces 52 are alternately and
electrically connected with each other in series, thereby
fabricating a thermoelectric device 60 shown in FIG. 18.
[0111] FIG. 18 is a plan view of the thermoelectric device 60, as
seen directly from above, and respective electrodes are formed on
both the upper surface and the under surface thereof.
[0112] Upper surface electrodes 61 circular in shape as indicated
by the solid lines, formed on the upper surface of the
thermoelectric device block 50 and under surface electrodes 62
circular in shape as indicated by the broken lines, formed on the
under surface thereof are electrodes for connecting together the
n-type thermoelectric semiconductor pieces 51 and p-type
thermoelectric semiconductor pieces 52, adjacent to each other, in
series, forming a plurality of thermocouples. Further, under
surface electrodes 63, 64 are electrodes for outputting voltage
externally.
[0113] Each of the electrodes denoted by 61 to 64 is formed by
depositing a gold (Au) film on both the upper and under surfaces of
the thermoelectric device block 50 shown in FIG. 17 by means of the
vacuum coating method, sputtering method, electroless plating
method, or the like, and then, by patterning on the gold film by
use of the photolithographic technique and etching technique.
Further, as a material for the electrodes, use can be made of not
only gold film but also various other materials cited in the first
embodiment described in the foregoing.
[0114] In the case where surface roughness of the upper and under
surfaces of the thermoelectric device block 50, on which the
electrodes 61 to 64 are formed, is likely to cause a problem as
with the case of the first embodiment, it is desirable to render
the surfaces smoother by lapping, or the like, as occurrence of
faults with the electrodes (such as breakage) thereof is inhibited
in this way.
[0115] Accordingly, the method according to the third embodiment of
the invention has an advantage in that the upper surface electrodes
61b and under surface electrodes 62b formed in the shape resembling
the letter L as shown in FIG. 9, which are required in the first
and second embodiments, can be dispensed with, facilitating the
wiring process and enabling effective use of the thermoelectric
semiconductor material.
[0116] Further, with the thermoelectric device according to the
third embodiment, the number of thermoelectric semiconductor pieces
incorporated therein per unit volume thereof can be substantially
doubled over that in the case of the first embodiment or the second
embodiment so that a thermoelectric device smaller in size, but
capable of outputting a higher voltage, will be obtained.
[0117] With the method according to the third embodiment, the side
of the integrated block 3 shown in FIG. 3, on which the grooving
process is applied, may be ground beforehand prior to forming the
transverse grooves 46 as shown in FIG. 15 such that fitting parts
between the longitudinal grooves 16, 26, and the longitudinal
partition walls 17, 27, composed of the n-type thermoelectric
semiconductor and p-type thermoelectric semiconductor,
respectively, are exposed.
[0118] If the transverse grooves 46 are formed subsequently, all of
the longitudinal grooves 16, 26, the transverse grooves 46, the
longitudinal partition walls 17, 27, and the transverse partition
walls 47, composed of the n-type thermoelectric semiconductor, and
p-type thermoelectric semiconductor, respectively, are fitted
together in their entirety when the second fitting process shown in
FIG. 16 is applied. As a result, in the process of exposing the
thermoelectric semiconductor pieces, the thermoelectric
semiconductor pieces can be formed by leaving intact a portion of
thermoelectric semiconductor material, corresponding to the full
height of the longitudinal partition walls 17, 27 with the result
that the utilization efficiency of the thermoelectric semiconductor
material is enhanced.
[0119] Fourth Embodiment: FIGS. 19 to 21
[0120] A fourth embodiment of a method of fabricating a
thermoelectric device according to the invention is described
hereinafter with reference to FIGS. 19 to 21. The first half of a
process applied in carrying out the fourth embodiment is the same
as for the second embodiment described with reference to FIGS. 10
to 12, and accordingly, will only be briefly described referring to
these figures.
[0121] In the fourth embodiment, two each of n-type thermoelectric
semiconductor composite blocks 12 formed by bonding the n-type
thermoelectric semiconductor block 1 to the base 10, shown in FIG.
10, and p-type thermoelectric semiconductor composite blocks 22
formed by bonding the p-type thermoelectric semiconductor block 2
to the base 20, shown in FIG. 10, are prepared.
[0122] Then, a first grooving process is applied to the respective
thermoelectric semiconductor composite blocks 12, 22, whereby a
plurality of grooves at a same pitch are formed in the n-type
thermoelectric semiconductor block 1, and the p-type thermoelectric
semiconductor block 2, respectively, to a depth close to the
interface between the thermoelectric semiconductor block 1, or 2
and the base 10 or 20 as shown in FIG. 11 such that longitudinal
grooves 16, 26 as well as longitudinal partition walls 17, 27 are
formed in a shape resembling the teeth of a comb. Thus, two pairs
of n-type grooved composite blocks 13 and p-type grooved composite
blocks 23 are fabricated- The positions of the respective
longitudinal grooves 16 of the n-type grooved composite block 13
are preferably deviated from those of the corresponding
longitudinal grooves 26 of the p-type grooved composite block 23 by
a half of the pitch.
[0123] Subsequently, a first fitting process is applied to the two
pairs of the n-type thermoelectric semiconductor composite blocks
13 and p-type thermoelectric semiconductor composite blocks 23, to
which the grooving process described above has been applied,
respectively, whereby respective grooved n-type thermoelectric
semiconductor composite blocks 13 and respective grooved p-type
thermoelectric semiconductor composite blocks 23 are fitted to each
other such that grooved surfaces of each pair face each other, and
then a first adhesion process is applied to the two pairs of the
grooved n-type thermoelectric semiconductor composite blocks 13 and
grooved p-type thermoelectric semiconductor composite blocks 23,
fitted to each other through the first fitting process, whereby
both blocks in each pair are adhered to each other by filling up
gaps in fitting parts therebetween with an adhesive insulation
member, thereby fabricating two integrated blocks 3' as shown in
FIG. 12.
[0124] With one of the two integrated blocks 3', the base 20 on the
side of the p-type thermoelectric semiconductor block is removed
while with the other, the base 10 on the side of the n-type
thermoelectric semiconductor block is removed, obtaining a pair of
integrated blocks 142A, 142B, with the longitudinal partition walls
17 of the n-type thermoelectric semiconductor and the longitudinal
partition walls 27 of the p-type thermoelectric semiconductor,
exposed on either the upper surface or under surface thereof,
respectively, as shown in FIG. 19.
[0125] Subsequently, a process, the same as the second grooving
process described in the second embodiment described hereinbefore
with reference to FIG. 13, is applied to the pair of the integrated
blocks 142A, 142B, from the side where the base 10 or the base 20
is removed, whereby a plurality of grooves at a same pitch are
formed in the direction crossing the direction in which the first
grooving process has been applied (at right angles, in this
embodiment) to a depth close to the interface between the
respective thermoelectric semiconductor blocks and the base 20 or
the base 10 which has not been removed, thereby fabricating two
grooved integrated blocks 143A, 143B, with a plurality of
transverse grooves 46 and transverse partition walls 47 formed
therein. In this connection, it is preferable that the transverse
grooves 46 in one of the grooved integrated blocks, e.g. 143A, are
formed such that the positions thereof are deviated by a half of
the pitch from those of the transverse grooves 46 formed in the
other of the grooved integrated blocks, e.g. 143B.
[0126] Subsequently, by applying a second fitting process whereby
the two grooved integrated blocks 143A, 143B are fitted to each
other such that respective grooved surfaces face each other, and
then a second adhesion process, whereby the two grooved integrated
blocks 143A, 143B, thus fitted to each other, are adhered together
by filling up gaps in fitting parts therebetween with an adhesive
insulation member, a doubly integrated block 144 shown in FIG. 21
is fabricated.
[0127] In this case, similarly to the case of the third embodiment,
the relative position of the n-type thermoelectric semiconductor
pieces 51 and p-type thermoelectric semiconductor pieces 52 need to
be controlled so as to be arranged like a checkerboard as shown in
FIG. 17 when fitting the two grooved integrated blocks 143A, 143B
to each other.
[0128] As described in the third embodiment, alignment of
respective positions can be accomplished by providing a benchmark
face on the periphery of each of the grooved integrated blocks.
Further, in the fourth embodiment, precision alignment of the
respective positions may be attained through direct observation of
the respective n-type thermoelectric semiconductor pieces 51 and
respective p-type thermoelectric semiconductor pieces 52 by use of
a microscope if a transparent member such as glass, or the like is
used for the bases 10 and 20.
[0129] Then, by removing the bases 10 and 20 from the doubly
integrated block 144, a thermoelectric device block, the same as
the thermoelectric device block 50 shown in FIG. 17 with reference
to the third embodiment, is obtained. Subsequently, by providing
electrodes as same as the electrodes 61 to 64 illustrated in FIG.
18, a thermoelectric device, the same as the thermoelectric device
60 shown in FIG. 18, is fabricated.
[0130] In this embodiment, before the second grooving process is
applied to the two integrated blocks 3', the base 20 or 10 on the
side where the process of forming the transverse grooves 46 are
applied is removed from the respective integrated blocks 3' so that
when the pair of the grooved integrated blocks 143A and 143B, with
the transverse grooves 46 formed therein, are fitted to each other,
the thermoelectric semiconductors as a whole can be fitted to each
other, enabling all thermoelectric semiconductors left intact to be
put to use for the thermoelectric semiconductor pieces without any
wastage thereof.
[0131] However, since such a step of processing is not essential,
the base 10 or the base 20 may be removed after the second grooving
process (formation of the transverse grooves) has been applied
instead of first removing the base 10 or the base 20.
[0132] Fifth Embodiment: FIGS. 22 to 24
[0133] A fifth embodiment of a method of fabricating a
thermoelectric device according to the invention is described
hereinafter with reference to FIGS. 22 to 24.
[0134] In the method according to the fifth embodiment, an n-type
thermoelectric semiconductor block 1 and a p-type thermoelectric
semiconductor block 2 are bonded, respectively, to each of two
large bases 110, 120 (hereinafter referred to as large bases),
similarly to the case of the second embodiment, fabricating a pair
of an n-type thermoelectric semiconductor composite block 91 and
p-type thermoelectric semiconductor composite block 92.
[0135] More specifically, the large bases 110, 120 employed in
carrying out this embodiment have a surface area larger than a
bonded surface area of the respective thermoelectric semiconductor
blocks 1, 2.
[0136] Similarly to the case of the second embodiment, longitudinal
grooves 16, 26, and longitudinal partition walls 17, 27 are formed
in the thermoelectric semiconductor blocks 1 and 2, respectively,
by applying a first grooving process thereto, fabricating an n-type
grooved composite block 181, and p-type grooved composite block 182
shown in FIG. 23. In this instance, the longitudinal grooves 16, 26
are preferably formed to a depth cutting into a portion of the
large bases 110, 120, respectively. The reason for this is to make
the most of the effect of spacers 190 in a fitting process
described hereinafter with reference to FIG. 24 such that n-type as
well as p-type thermoelectric semiconductors can be put to use
efficiently.
[0137] Then, as shown in FIG. 24, a first fitting process is
applied, whereby the n-type grooved composite block 181 and p-type
grooved composite block 182, shown in FIG. 23, are combined to be
fitted to each other. In this instance, by interposing the spacers
190 between the large bases 110 and 120, a spacing D between the
two large bases 110 and 120 is controlled (restrained) accurately
to match the height of the longitudinal partition walls 17, 27,
composed of a thermoelectric semiconductor, corresponding to the
thickness of the respective thermoelectric semiconductor blocks 1,
2.
[0138] For example, by equalizing the thickness of the n-type
thermoelectric semiconductor block 1, p-type thermoelectric
semiconductor block 2, and spacers 190, respectively, the spacing D
between the two large bases 110 and 120 can be maintained at a
given distance, enabling the longitudinal partition walls 17, 27,
composed of the n-type and p-type thermoelectric semiconductors,
respectively, to be arranged without unevenness in thickness.
[0139] That is, even in case there is no uniformity in the depth of
the longitudinal grooves 16, 26, respectively, the n-type and
p-type thermoelectric semiconductors can be arranged so as to have
no unevenness in thickness with respect to each other by use of the
spacers 190 with the result that wasteful polishing or grinding of
the n-type and p-type thermoelectric semiconductors can be avoided,
enabling improvement in utilization efficiency thereof.
[0140] After the first fitting process with the use of the spacers
190, the n-type grooved composite block 181 and p-type grooved
composite block 182 are adhered to each other by filling up gaps in
fitting parts therebetween with an adhesive insulation member,
obtaining an integrated composite block 193 shown in FIG. 24.
[0141] Subsequently, a second grooving process is applied,
fabricating a grooved integrated composite block with transverse
grooves and transverse partition walls formed therein, similar to
the grooved integrated block 14 shown in FIG. 13 with reference to
the second embodiment, and insulating resin layers, the same as the
insulating resin layers 54 shown in FIG. 14, are formed by filling
up the respective transverse grooves with insulating resin, and by
curing the insulating resin. Thereafter, by removing the large
bases 110, 120, a thermoelectric device block, the same as the
thermoelectric device block shown in FIG. 6, is obtained. Further,
as shown in FIG. 9, by forming various electrodes on the upper as
well as under surfaces of the thermoelectric device block, and
connecting the respective thermoelectric semiconductor pieces with
each other, alternately and in series, the thermoelectric device 6
can be fabricated.
[0142] Sixth Embodiment: FIGS. 25 and 26
[0143] Next, a sixth embodiment of the method of fabricating a
thermoelectric device according to the invention using the
integrated composite blocks described in carrying out the fifth
embodiment is described hereinafter with reference to FIGS. 25 and
26.
[0144] In the method according to the sixth embodiment, two
integrated composite blocks 193 are fabricated by means of
processes, the same as the respective processes described in the
fifth embodiment with reference to FIGS. 22 to 24.
[0145] Subsequently, a second grooving process (formation of
transverse grooves) is applied to the two integrated composite
blocks 193, respectively, whereby a large base 110 or 120, on the
side where the second grooving process is applied, is removed in a
manner similar to the process as applied in the fourth embodiment
described with reference to FIG. 19, fabricating a pair of grooved
integrated composite blocks 203A, 203B as shown in FIG. 25,
provided with a plurality of transverse grooves 46 as well as
transverse partition walls 47 formed therein, respectively, so as
to be fitted to each other.
[0146] Thereafter, the pair of grooved integrated composite blocks
203A and 203B are fitted to each other while maintaining a spacing
between the large bases 110 and 120 at a given distance (a value
equivalent to the height of the thermoelectric semiconductors left
intact) with the use of spacers 190, and gaps in fitting parts
therebetween are filled up with an adhesive insulation member,
fabricating a doubly integrated block 213, as shown in FIG. 26.
[0147] Then, n-type and p-type thermoelectric semiconductor pieces
51, and 52 are exposed by removing the large bases 110, and 120 of
the doubly integrated block 213, thereby obtaining a thermoelectric
device block, the same as the thermoelectric device block shown in
FIG. 17 with reference to the third embodiment.
[0148] Further, by forming electrodes 81 to 84 on the upper as well
as under surfaces of the thermoelectric device block as shown in
FIG. 18, and connecting respective thermoelectric semiconductor
pieces 51, 52 with each other, alternately and in series, the
thermoelectric device 60 can be fabricated.
[0149] Provided that the thermoelectric device 60 fabricated in the
third, fourth, or sixth embodiment has dimensions of 10 mm.times.10
mm.times.2 mm after removing the peripheral region of the
thermoelectric device block, 12 mm square, about 3400 couples of
thermocouples can be integrated therein.
[0150] When a temperature difference of 1.5.degree. C. was applied
to the thermoelectric device 60, an output voltage at 2.0 V was
obtained.
[0151] Thus, as the thermoelectric device 60 is small enough to be
encased in a small portable electronic device such as a wrist watch
and yet has an open circuit output voltage at a level high enough
to drive a wrist watch, it is possible to drive various portable
electronic devices with the thermoelectric device 60 in combination
with a booster circuit.
[0152] Seventh Embodiment: FIGS. 27 to 29
[0153] Next, a seventh embodiment of the method of fabricating a
thermoelectric device according to the invention is described
hereinafter with reference to FIGS. 27 to 29.
[0154] In the method according to the seventh embodiment of the
invention, an n-type thermoelectric semiconductor block 1 and a
p-type thermoelectric semiconductor block 2 as shown in FIG. 1 with
reference to the first embodiment are first prepared, and as shown
in FIG. 27, a metal coated layer 223 is formed on the surfaces of
the respective thermoelectric semiconductor blocks 1, 2, that is,
at least the surface bonded to a base, and the surface on the
opposite side thereof (the surface on which electrodes are formed
in a process of forming electrodes applied later on) by means of
plating, vapor deposition, sputtering, or the like. Thus, a coated
n-type thermoelectric semiconductor block 221, and coated p-type
thermoelectric semiconductor block 222 are obtained.
[0155] The metal coated layer 223 is either a single layer composed
of nickel (Ni), copper (Cu), gold (Au), or the like, or a composite
layer composed of single layers stacked up. The metal coated layer
223 is provided in order to improve electrical connection between
various wiring electrodes described hereinafter and thermoelectric
semiconductors. It is desirable therefore to ensure ohmic contact
between the metal coated layer 223 and the n-type thermoelectric
semiconductor block 1, as well as the p-type thermoelectric
semiconductor block 2, by applying proper heat treatment to the
metal coated layer 223 when or after being formed.
[0156] The thickness of the metal coated layers 223 may be in the
range of about 0.1 to 50 .mu.m. However, in view of the possibility
that the height of the coated n-type thermoelectric semiconductor
block 221, and coated p-type thermoelectric semiconductor block
222, respectively, is made even by slightly removing portions of
the surfaces of the metal coated layers 223 through a polishing
process, or the like in a later step of processing, there will
arise problems that if the metal coated layers 223 are excessively
thin, it becomes difficult to apply treatment thereto due to too
little allowance for polishing while if the same are excessively
thick, this is prone to cause a stress-related problem.
Accordingly, the thickness of the metal coated layers 223 is
preferably in the range of 2 to 10 .mu.m, and an electrolytic or
electroless plating method is most suitable for forming a film in a
thickness on this order.
[0157] In this embodiment, for the metal coated layer 223, a
multi-layered film composed of the Ni layer and Au layer, 5 .mu.m
in total thickness, is formed by the electrolytic plating
method.
[0158] For the process shown in FIG. 27 and ones thereafter, any
selected from the processes adopted in the second, fourth, fifth,
and sixth embodiments can be applied. The seventh embodiment will
be described on the assumption processes substantially similar to
those applied in the fifth embodiment are adopted.
[0159] Accordingly, FIG. 28 corresponds to FIG. 23. That is, an
n-type thermoelectric semiconductor composite block formed by
bonding the coated n-type thermoelectric semiconductor block 221 to
a large base 110, and a p-type thermoelectric semiconductor
composite block formed by bonding the coated p-type thermoelectric
semiconductor block 222 to a large base 120 are prepared, and
longitudinal grooves 16, 26, and longitudinal partition walls 17,
27 are formed in the coated n-type and p-type thermoelectric
semiconductor blocks, respectively, by means of the grinding
process using a dicing saw, or the polishing process using a wire
saw. As a result, a coated n-type grooved composite block 231, and
coated p-type grooved composite block 232 are fabricated. In this
instance, portions of the respective metal coated layers 223, at
the upper or lower ends of the longitudinal partition walls 17, 27,
are left intact as metal layers 233.
[0160] The coated n-type thermoelectric semiconductor block 221 and
coated p-type thermoelectric semiconductor block 222 are bonded to
the large base 110 and large base 120, respectively, by use of an
adhesive or wax. Further, for the large bases 110 and 120, any
material having a hardness to a given degree such as glass,
ceramic, plastics, metal, or the like, may be employed.
[0161] The pitch at which the longitudinal grooves 16, 26 are
formed, and the width and depth of the longitudinal grooves 16, 26
are substantially as described with reference to FIG. 23, except
that the depth thereof somewhat differs. In this embodiment, the
longitudinal grooves 16, 26 are formed to a depth either of the
interface between the coated n-type thermoelectric semiconductor
block 221 and the large base 110 or between the coated p-type
thermoelectric semiconductor block 222 and the large base 120, or
so as to be cut into the large base 110 or 120.
[0162] The reason for this is that in carrying out a process of
combining the coated n-type grooved composite block 231 with the
coated p-type grooved composite block 232, the surfaces of the
metal layers 233 of the respective coated grooved composite blocks
are rendered to be flush with each other.
[0163] Subsequently, as described in the fifth embodiment with
reference to FIG. 24, the coated n-type grooved composite block 231
and coated p-type grooved composite block 232 are combined to be
fitted to each other, and gaps in fitting parts therebetween are
filled with adhesive insulation members, forming adhesion layers 32
shown in FIG. 29, so that an integrated composite block is
fabricated through adhesion of the coated grooved composite blocks
with each other.
[0164] Thereafter, a second grooving process is applied to the
integrated composite block, whereby a grooved integrated composite
block with transverse grooves as well as transverse partition walls
formed therein is formed, and by filling up the respective
transverse grooves with insulating resin and curing the same,
insulating resin layers, the same as the insulating resin layers 54
shown in FIG. 5, are formed.
[0165] After removing the large bases 110, 120, a thermoelectric
device block 5 as shown in FIG. 6 is obtained. Further, by forming
respective electrodes 81, 82, as shown in FIG. 29, on both the
upper and under surfaces of the thermoelectric device block, and
connecting n-type thermoelectric semiconductor pieces 51 and p-type
thermoelectric semiconductor pieces 52 to each other, alternately
and in series, a thermoelectric device 80 can be fabricated.
[0166] FIG. 29 illustrates the sectional shape of the
thermoelectric device 80 according to the seventh embodiment of the
invention, corresponding to the plan view shown in FIGS. 9 and 18,
respectively. In this connection, for forming the upper surface
electrode 81 and the under surface electrode 82, the vapor
deposition film described hereinbefore is normally used. However,
the method according to this embodiment may be characterized by use
of an electrically conductive paste such as silver paste.
[0167] Electrical connection between the electrically conductive
paste and such semiconductor as used in the method of the invention
is generally prone to create a problem due to high contact
resistance. Therefore, with the construction according to the
invention, the electrically conductive paste is not suitable for
use for wiring electrodes. However, by providing the metal layer
233 shown in the seventh embodiment, the contact resistance
described can be reduced to a negligible level. Consequently, the
electrically conductive paste can be used for the upper surface
electrode 81 and the under surface electrode 82.
[0168] The method according to this embodiment has an advantage in
that productivity is remarkably improved because with the use of
the electrically conductive paste, the electrodes can be formed
through patterning by use of a screen printing method.
[0169] Eighth Embodiment: FIGS. 30 and 31
[0170] Next, an eighth embodiment of the method of fabricating a
thermoelectric device according to the invention is described
hereinafter with reference to FIGS. 30 and 31.
[0171] The method according to the eighth embodiment is described
starting from the stage of a thermoelectric device block (for
example, the same as the thermoelectric device block a shown in
FIG. 6) prior to the wiring process described in the first to the
fifth embodiments. That is, respective processes applied up to this
stage in this embodiment are the same as those in the case of the
respective embodiments described above.
[0172] After the formation of the thermoelectric device block
described above, metal layers 233, the same as in the case of the
seventh embodiment, are formed on at least the surfaces of n-type
thermoelectric semiconductor pieces 51 and p-type thermoelectric
semiconductor pieces 52, where wiring electrodes are to be
formed.
[0173] As a result, a thermoelectric device block 253 shown in FIG.
30 illustrating the sectional view thereof is fabricated.
[0174] In this embodiment, the metal layers 233 are preferably
deposited by a plating method whereby a single-layered film
composed of Ni, Au, Cu, or the like, or a multi-layered film
composed of the aforesaid films, is formed. In particular, an
electroless plating is most suitable whereby selective plating can
be applied to exposed surfaces of the thermoelectric semiconductor
pieces 51, 52, taking advantage of selectivity in the condensation
coefficient of Pd (palladium) acting as a catalyst on the surfaces
of the thermoelectric semiconductor pieces 51, 52, adhesive layers
32, and insulating resin layers 54.
[0175] Further, it is preferable not to form the metal layer 233 on
the side faces of the thermoelectric semiconductor pieces on the
periphery of the thermoelectric device block (for example, the
thermoelectric device block 5 shown in FIG. 6) prior to the wiring
process being applied thereto, which is the starting point of
description of this embodiment. Hence, in this embodiment, a coated
layer 254 composed of the same material as is used for the adhesive
layers 32, or the insulating resin layers 54, is formed on the
peripheral face (the side face) of the thermoelectric device
block.
[0176] FIG. 31 shows a thermoelectric device 80, completed by
forming upper surface electrodes 81 and under surface electrodes 82
on the thermoelectric device block 253 shown in FIG. 30 by use of
the electrically =conductive paste as described in the seventh
embodiment.
[0177] The method according to this embodiment, whereby the metal
layers 233 are formed at a later stage of processing, has still an
advantage in that productivity is remarkably improved because the
electrically conductive paste can be used as in the case of the
seventh embodiment, and the electrodes can be formed through
patterning by use of the screen printing method.
[0178] Ninth Embodiment: FIGS. 32 and 33
[0179] Next, a ninth embodiment of the method of fabricating a
thermoelectric device according to the invention is described
hereinafter with reference to FIGS. 32 and 33.
[0180] FIG. 32 shows a provisional thermoelectric device 270
fabricated according to the ninth embodiment, which is
substantially the same as the thermoelectric device 6, 60, or 80
described in the respective embodiments described in the foregoing
and fabricated by substantially the same processes except that in
place of the adhesive layers 32, and the insulating resin layers
54, provisional fixture layers 271 are provided therein.
[0181] As opposed to the embodiments described in the foregoing,
wherein the adhesive layers 32 and the insulating resin layers 54
are among the components of the thermoelectric device in the final
form, the insulating resin layers 54 are not included in the
components of the thermoelectric device in the final form in the
case of the method according to the ninth embodiment.
[0182] Accordingly, in place of the adhesive layers 32 and the
insulating resin layers 54, the provisional fixture layers 271 are
formed for provisionally securing the n-type thermoelectric
semiconductor pieces 51 and p-type thermoelectric semiconductor
pieces 52, and are removed later on. The provisional fixture layers
271 are formed by filling up gaps in the fitting parts after the
fitting process is applied to the pair of the grooved blocks or by
filling up the transverse grooves 47 after being formed as shown in
FIGS. 4, 13, and the like, with a provisional fixture material in
the same way as for the formation of the adhesive layers 32, and
the insulating resin layers 54. For the provisional fixture
material, an adhesive material removable by heating or by use of a
solvent such as wax is employed.
[0183] In the method of fabrication according to the ninth
embodiment, an adhesive resin such as epoxy resin is applied as
shown in FIG. 33 to the entire upper as well as under surfaces of
the provisional thermoelectric device 270 shown in FIG. 32, thereby
forming insulating fixture layers 284. The provisional
thermoelectric device 270 is then sandwiched between a heat
radiation plate 281 and a heat absorption plate 282, and fixedly
attached thereto via the insulating fixture layers 284 integrally
formed.
[0184] For the heat radiation plate 281 and heat absorption pate
282, a material having high thermal conductivity, that is, a metal
or ceramic, is used.
[0185] Particularly in the case of a metal being selected for this
purpose, a treatment to form an insulating oxide film may
preferably be applied to the surface of the metal because of the
risk of an accidental short circuit occurring between upper surface
electrodes 81 and the heat radiation plate 281, or between under
surface electrodes 82 and the heat absorption plate 282 if the
insulating fixture layers 284 is rendered too thin.
[0186] Thereafter, as shown in FIG. 33, after securing the
provisional thermoelectric device 270 onto the heat radiation plate
281 and heat absorption plate 282, the provisional fixture layers
271 are removed by use of heat or a solvent, thereby fabricating a
thermoelectric device 280 provided with voids 283 created in
regions vacated as above.
[0187] With the construction of the thermoelectric device 280
according to this embodiment, heat conduction by materials other
than the thermoelectric semiconductors between the heat radiation
plate 281 and the heat absorption plate 282 is largely inhibited
because of the very low thermal conductivity of the air in the
voids 283, enhancing the performance of the thermoelectric
device.
[0188] In the aforesaid embodiment, in place of both the adhesive
layers 32 provided in the fitting parts between the n-type and
p-type thermoelectric semiconductor grooved blocks and the
insulating resin layers 54 provided in the transverse grooves
formed after the pair of the grooved blocks are integrated, the
provisional fixture layers 271 are provided. However, only either
of the adhesive layers or the insulating resin layers may be
substituted by the provisional fixture layers 271, and after
sandwiching the provisional thermoelectric device 270 between the
heat radiation plate 281 and heat absorption plate 282 so as to be
integrally secured by the insulating fixture layers 284, the
provisional fixture layers 271 may be removed so that either the
adhesive layers 32 or the insulating resin layers 54 are left
intact.
[0189] This will enable the thermoelectric device to maintain
sufficient strength while enhancing the performance thereof.
[0190] With the thermoelectric device 280 shown in FIG. 33, when
used for generation of power, the heat absorption plate 282 is
positioned on the lower temperature side.
[0191] Another Embodiment of a Process of Fabricating a
Thermoelectric Semiconductor Grooved Block: FIG. 34
[0192] Now, another embodiment of a process of fabricating a
thermoelectric semiconductor grooved block according to the
invention is described hereinafter with reference to FIG. 34.
[0193] With the first embodiment or the third embodiment described
hereinbefore, in the process of fabricating the n-type and p-type
thermoelectric semiconductor grooved blocks, the plurality of
grooves parallel with each other are formed in the n-type and
p-type thermoelectric semiconductor blocks 1 and 2, respectively,
by machining using the wire saw or the like, thereby fabricating
the n-type thermoelectric semiconductor grooved block 11 and p-type
thermoelectric semiconductor grooved block 21.
[0194] However, the n-type thermoelectric semiconductor grooved
block 11 and p-type thermoelectric semiconductor grooved block 21
can also be fabricated by molding n-type thermoelectric
semiconductor material and p-type thermoelectric semiconductor
material separately into a mold (metal mold) for the grooved block,
and then sintering the molded materials.
[0195] In such a process of fabricating the grooved blocks as
described above, a compound used for injection molding is produced
by adding a mixture as an organic binder, consisting of, for
example, ethylene-vinyl-acetate - polybutylmethacrylate -
polystyrene copolymer, atactic polypropylene, paraffin wax, and
dibutyl phthalate to pulverized powders of a thermoelectric
semiconductor material (for example, in the case of the p-type
thermoelectric semiconductor material, pulverized powders of BiTeSb
crystals as in the case of the first embodiment) on the order of 1
.mu.m in average grain size, and kneading the same with the use of
a pressurized kneader. A suitable mixing ratio of the pulverized
powders to the organic binder is 5 to 15 wt parts of the organic
binder against 100 wt parts of the pulverized powders.
[0196] The compound for injection molding thus produced is molded
by use of an injection molding machine, and FIG. 34 is a sectional
view of a metal mold with which molding is performed.
[0197] In this case, the compound for injection molding is
pressurized and filled from a nozzle 304 into a molding cavity 308
formed in the shape of the grooved block inside a movable mold 301
via a sprue 306 of a fixed mold 303 and a gate 307 of an
intermediate mold 302.
[0198] A molded body formed in the molding cavity 308 as described
above is pushed out by ejector pins 305, and taken out after the
movable block 301 is shifted and separated from the intermediate
mold 302. The molding cavity 308 is designed to have dimensions
about 20% larger than those of the grooved block to allow for
shrinkage occurring to the molded body during the sintering
thereof.
[0199] The molded bodies are then placed side by side on a flat
plate made of alumina in a vacuum furnace at 400.degree. C. for a
retention time of 1 hour, obtaining provisional sintered bodies
with organic binders substantially removed. In the final step, the
provisional sintered bodies are again placed side by side on the
flat plate made of alumina, and subjected to a sintering process at
470.degree. C. for a duration of 3 hours in an electric furnace in
a hydrogen-flow atmosphere, obtaining sintered bodies composed of
the n-type or p-type thermoelectric semiconductors, respectively.
The sintered bodies are the n-type grooved block 11, and p-type
grooved block 21, respectively.
[0200] Supplementary Explanation
[0201] Various embodiments of the method of fabricating the
thermoelectric device according to the invention have been
described in the foregoing, and every one of the embodiments is
based on the construction wherein the thermoelectric semiconductor
pieces 51, 52 are all arranged in a matrix fashion. That is, all
the embodiments have made a point of applying the process of
forming the transverse grooves after the process of forming the
longitudinal grooves, then the process of exposing the
thermoelectric semiconductor pieces, and further, the process of
forming the electrodes for wiring and the like, thus completing the
fabrication of the thermoelectric device.
[0202] However, in the case where the thermocouples, even though
small in number, can be effectively utilized, the thermoelectric
device may be completed in the respective embodiments described
hereinbefore by applying the process of exposing the thermoelectric
semiconductor pieces without applying the process of forming the
transverse grooves, and then, by forming the electrodes for wiring
and the like.
[0203] In the case of adopting such steps of processing, the
finished product will be the thermoelectric device of a
construction wherein thin layers composed of n-type and p-type
thermoelectric semiconductors, respectively, are alternately
arranged and connected to each other in series.
[0204] It is obvious that the method of fabricating the
thermoelectric device according to the invention is sufficiently
effective for fabrication of the thermoelectric device having the
construction described above.
[0205] As described in each of the aforesaid embodiments, the
longitudinal grooves as well as the transverse grooves are formed
by use of the wire saw or the dicing saw, and in the case that the
grooving process is applied by a grinding method using the wire
saw, the bottom surfaces of the longitudinal grooves as well as the
transverse grooves become a circular arc in actual shape.
[0206] Although the longitudinal grooves have arc-shaped bottom
surfaces while the longitudinal partition walls have rectangular
top ends, there will arise no particular problem when the n-type
grooved block is combined with the p-type grooved block to be
fitted to each other because gaps formed are filled up with the
adhesive.
[0207] Further, when the transverse grooves are formed by use of
the wire saw after the integrated block has been formed, the bottom
surfaces of the transverse grooves become a circular arc in shape.
However, there will arise no problem in this case either, because
the transverse grooves are filled up with the insulating resin.
[0208] As is evident from the foregoing description, in the method
of fabricating the thermoelectric device according to the
invention, the grooved blocks composed of the n-type and p-type
thermoelectric semiconductors, respectively, are fabricated by
applying a precision machining process to thermoelectric
semiconductor members, or by applying a precision molding process
to thermoelectric semiconductor material, and then, by applying an
integration process of combining the grooved blocks so as to be
fitted to each other, the thermoelectric semiconductor members can
always be handled in the form of a unit (block). Hence, the
thermoelectric device incorporating the thermocouples composed of a
multitude of thermoelectric semiconductor pieces can be fabricated
without applying processes such as a process of forming
thermoelectric semiconductors into a thin sheet-like shape, a
process of forming thermoelectric semiconductors into a kenzan-like
shape by applying a fine grooving process, and the like wherein the
thermoelectric semiconductor materials are susceptible to undergo
breakage.
[0209] Accordingly, an ultra small thermoelectric device capable of
outputting a high voltage can be fabricated easily and efficiently,
making it possible to utilize power generated by temperature
differences occurring in a portable electronic device such as a
wrist watch.
INDUSTRIAL APPLICABILITY
[0210] With the method of fabricating a thermoelectric device
according to the invention, a thermoelectric device small in size,
incorporating a multitude of thermocouples formed therein, and
capable of outputting a high voltage can be fabricated easily and
efficiently. As a high output voltage can be produced by putting
the thermoelectric device to use as a small thermoelectric
generator, the thermoelectric device installed in a portable
miniature electronic device such as a wrist watch and the like can
be used as a power supply for electric power generated by
temperature differences.
[0211] The thermoelectric device can also be used in fabrication of
a high performance cooling system of small size, which is quite
useful as a portable refrigerator, or a localized cooler for
lasers, integrated circuits, and the like.
* * * * *