U.S. patent application number 09/760852 was filed with the patent office on 2001-08-30 for thermoelectric device.
This patent application is currently assigned to AISIN SEIKI KABUSHIKI KAISHA. Invention is credited to Ebina, Noburo, Ogawa, Satoru, Sugiura, Hirotsugu, Tauchi, Hitoshi.
Application Number | 20010017151 09/760852 |
Document ID | / |
Family ID | 18536067 |
Filed Date | 2001-08-30 |
United States Patent
Application |
20010017151 |
Kind Code |
A1 |
Tauchi, Hitoshi ; et
al. |
August 30, 2001 |
Thermoelectric device
Abstract
The present invention is a thermoelectric device comprising: a
thermoelectric element composed of principally thermoelectric
material, a counter element adhered to said thermoelectric
material, a solder layer lying between said thermoelectric element
and said counter element and adhering said thermoelectric element
to said counter element, a restraining layer to prevent said
solder's ingredient of said solder layer from spreading into said
thermoelectric element, wherein said restraining layer comprising a
first layer to prevent said solder's ingredient of said solder
layer from spreading into said thermoelectric element and a second
layer composed of material which gets wetter than said first layer
against said solder layer.
Inventors: |
Tauchi, Hitoshi; (Anjo-shi,
JP) ; Ogawa, Satoru; (Okazaki-shi, JP) ;
Sugiura, Hirotsugu; (Hekinan-shi, JP) ; Ebina,
Noburo; (Tokyo, JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
AISIN SEIKI KABUSHIKI
KAISHA
Kariya-shi
JP
|
Family ID: |
18536067 |
Appl. No.: |
09/760852 |
Filed: |
January 17, 2001 |
Current U.S.
Class: |
136/200 ;
136/237 |
Current CPC
Class: |
H01L 35/08 20130101 |
Class at
Publication: |
136/200 ;
136/237 |
International
Class: |
H01L 035/00; H01L
035/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 17, 2000 |
JP |
2000-007701 |
Claims
1. A thermoelectric device comprising: a thermoelectric element
composed of principally thermoelectric material, a counter element
adhered to said thermoelectric material, a solder layer lying
between said thermoelectric element and said counter element and
adhering said thermoelectric element to said counter element, a
restraining layer to prevent solder's ingredient of said solder
layer from spreading into said thermoelectric element, wherein said
restraining layer comprising a first layer to prevent said solder's
ingredient of said solder layer from spreading into said
thermoelectric element and a second layer composed of material
which gets wetter than said first layer against said solder
layer.
2. A thermoelectric device according to claim 1: wherein said first
layer is a non-electrolytic plating layer composed of
nickel-phosphorus series, and said second layer is non-electrolytic
plating layer composed of nickel-boron series.
3. A thermoelectric device according to claim 1: wherein the
average of the thickness of said first layer is thicker than that
of said second layer.
4. A thermoelectric device according to claim 2: wherein the
average of the thickness of said first layer is thicker than that
of said second layer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a thermoelectric device
comprising a thermoelectric element composed of principally
thermoelectric material.
[0003] 2. Discussion of the Background
[0004] The thermoelectric device comprising a thermoelectric
element principally composed of thermoelectric material is well
known in the art.
[0005] The thermoelectric device has two types of usages one is a
cool-heat type which can cool or heat when electricity being
supplied, and the other is a power generation type which can
generate electricity when being cooled or heated.
[0006] A known conventional thermoelectric device is disclosed in
pages 24 to 25 of "thermoelectric transfer system technical general
handbook" published by realize company published date; on June 30,
June, 1995 (heisei 7).
[0007] The nickel plating layer prevents the solder's ingredient of
said solder layer from spreading into the thermoelectric element,
and consists of a single layer. According to the conventional
thermoelectric device, the nickel plating layer prevents the
solder's ingredient of the solder from spreading into said
thermoelectric element. Therefore, the conventional thermoelectric
device has advantages of restrained degradation of thermoelectric
device and maintained characteristic of thermoelectric device for
long term.
[0008] Furthermore, in general, the thermoelectric element composed
of thermoelectric material is hard to be soldered. The nickel
plating layer has an advantage to prevent the solder's ingredient
of the solder layer from spreading into the thermoelectric element,
and improve a soldering characteristic of the thermoelectric
element when the thermoelectric element being assembled.
[0009] In the industry, the higher characteristic of restraining
spread prevention and soldering are requested. However, the single
nickel plating layer needs more improvement in aspect of combining
two higher characteristics of spread prevention and soldering. In
other words, if the nickel plating layer is used for high
characteristic of spread prevention, it has an advantage to prevent
solder's ingredient of the solder layer from spreading into the
inside of the thermoelectric element, but then it has disadvantage
to get insufficient increase wetting property against the solder.
Contrary, if the nickel plating layer is used for the high wetting
property against the solder, it is not sufficient to increase the
increasing of the characteristic of spread prevention.
[0010] An object of the present invention is to solve the
above-mentioned disadvantages, and more specifically, to provide a
thermoelectric device having both improvements for better soldering
property and spread prevention.
SUMMARY OF THE INVENTION
[0011] The present invention is a thermoelectric device comprising:
a thermoelectric element composed of principally thermoelectric
material, a counter element adhered to said thermoelectric
material, a solder layer lying between said thermoelectric element
and said counter element and adhering said thermoelectric element
to said counter element, a restraining layer to prevent said
solder's ingredient of said solder layer from spreading into said
thermoelectric element, wherein said restraining layer composed a
first layer to restrain what said solder's ingredient of said
solder layer spreads into said thermoelectric element and a second
layer composing of material which gets wetter than said first layer
against said solder layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The above and other objects, features and advantages of the
present invention will be more apparent and more readily
appreciated from the following detailed description of preferred
exemplary embodiments of the present invention, taken in connection
with the accompanying drawings, in which:
[0013] FIG. 1 is front view showing an outline structure of a
thermoelectric device according to an embodiment of the present
invention.
[0014] FIG. 2 is a schematic cross sectional view of substantial
part of a thermoelectric device according to the embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] According to the present invention, the thermoelectric
material for the thermoelectric device is at least one of selected
from bismuth-tellurium series, bismuth-selenium series,
antimony-tellurium series, antimony-selenium series,
bismuth-tellurium-antimony series, and bismuth-tellurium-selenium
series. Specifically, it is at least one of selected from
Bi.sub.2Te.sub.3, Bi.sub.2Se.sub.3, Sb.sub.2Te.sub.3,
Sb.sub.2Se.sub.3. Bismuth-tellurium-antimony series is selected for
a thermoelectric device of P-type (positive type).
Bismuth-tellurium series and bismuth-tellurium-selenium series are
selected for a thermoelectric device of N-type (negative type).
[0016] According to the present invention, the counter element
adhered to the thermoelectric element is a substrate having an
electrode. A ceramic substrate may be employed for the substrate. A
ceramic material is selected from alumina series, aluminum nitride
series, beryllia (BeO) series, and silicon carbide series etc. A
solder may be selected from bismuth-tin series, tin-antimony
series, lead-tin series, lead-tin-bismuth series, tin series, and
lead series etc., but the solder is not limited to aforementioned
series.
[0017] According to the present invention, the restraining layer
comprises a first layer to prevent the solder's ingredient of said
solder layer from spreading into the thermoelectric element and a
second layer composed of material which gets wetter against the
solder layer than the first layer. The first layer is
nonelectrolytic plating layer composed of nickel-phosphorus series,
or non-electrolytic plating layer composed of nickel series. The
second layer has preferably both improvements of wetting property
against the solder. A second layer comprised a non-electrolytic
plating layer composing of nickel-boron series. A non-electrolytic
plating layer composed of nickel-boron series is slower in the
plating speed and more expensive in manufacturing than a
non-electrolytic plating layer composed of nickel-phosphorus
series. However, nickel-boron has excellent wetting property
against the solder when soldering, so that the soldering
characteristic of the thermoelectric device is improved.
[0018] A non-electrolytic plating layer composed of
nickel-phosphorus series is a little degradation in the wetting
property, but is faster in the plating speed and cheaper in
manufacturing than a nonelectrolytic plating layer composing of
nickel-boron series.
[0019] A non-electrolytic plating layer composing of
nickel-phosphorus series is produced by the plating bath including,
but not limited to nickel-chloride or hydrosulfate, with sodium
hypophosphite as the reducer. A non-electrolytic plating layer
composing of nickel-boron series is produced by plate bath
including, but not limited to, nickel-chloride or hydrosulfate with
boron hydroxylase as the reducer.
[0020] In some cases, the first layer and the second layer do not
limited by non-electrolytic plating, and these can be produced by
electroplating of nickel metal etc.
[0021] According to the present invention, the average thickness of
the first layer is thicker than that of the second layer to
increase the spread prevention effect at low cost by the short time
process. Though a ratio of the average thickness between the first
layer, and the second layer is varied by consideration of
manufacturing speed or manufacturing cost under usable conditions,
it may be settled for "the average of the first layer: the average
of the second layer=1: (1 to 300)". Preferably, it may be settled
for "the average of the first layer: the average of the second
layer=1: (1 to 100)". More preferably, it may be settled for "the
average of the first layer: the average of the second layer=1: (2
to 10)". However, the present invention is limited by the
aforementioned.
[0022] A ratio of raw value of the average thickness between the
first layer and the second layer is varied by consideration of
manufacturing speed, manufacturing cost under usable conditions, or
material of the first layer or the second layer etc. Accordingly,
in some cases, for example, the average of the first layer is
settled for 0.2 to 50 .mu.m, 0.5 to 20 .mu.m, 1.0 to 15 .mu.m, 1.0
to 10 .mu.m, and 5 to 10 .mu.m etc. The average of the second layer
is settled for 0.04 to 10 .mu.m, 0.8 to 5 .mu.m, 0.1 to 1.0 .mu.m,
and 0.1 to 0.5 .mu.m etc. However, the present invention is not
limited by the aforementioned ratio of them.
EMBODIMENT EXAMPLE
[0023] Preferred embodiments of the present invention will be
described hereinafter in detail with reference to the accompanying
drawings.
[0024] FIG. 1 is a front view showing an outline structure of a
thermoelectric device according to the embodiment of the present
invention. FIG. 2 is schematic cross sectional view of a
thermoelectric device according to the embodiment of the present
invention. As shown in FIG. 1, the thermoelectric device related to
the present invention comprises the thermoelectric modules, which
are the thermoelectric element 1, the counter element 3 countered
each other, and the solder layer 5 to adhere the thermoelectric
element 1 and the counter element 3 each other.
[0025] The counter element 3 comprises a pair of insulative ceramic
substrata (material: alumina) 30, 31 having the planes 30c, 31c for
mounting the elements countered each other and the conductive
electrodes (material: copper) 35 lain between said planes 30c, 31c
and the solder layer 5.
[0026] The solder 5 is composed of conductive, and low melt point
metal. The solder 5 is composed of tin-antimony alloy.
[0027] The thermoelectric material for the thermoelectric element 1
converts electric energy into heat energy, or heat energy into
electric energy, and the material is composed of one of selected
from bismuth-tellurium series, bismuth-selenium series,
antimony-tellurium series, and antimony-selenium series. The
aforementioned thermoelectric material has naturally poor wetting
property against the solder when soldering. Furthermore when used
for the thermoelectric device, the solder's ingredient composed of
the solder layer 5 is apt to spread into the inside of the
thermoelectric element 1 by heat-influences. If the thermoelectric
device is used for long time, the spread brings the degradation of
the thermoelectric element 1 and the conductive defect.
[0028] According to the present invention, in order to improve the
characteristic of soldering and prevent the degradation of the
thermoelectric element 1 due to the spread of the solder's
ingredient, the restraining layer 7 lies between the thermoelectric
element 1 and solder layer 5 as shown in FIG. 2 to prevent the
solder's ingredient consisting the solder layer 5 from spreading
into the inside of the thermoelectric element 1.
[0029] The restraining layer 7 related to the present invention
comprises two-layer composition of the first layer 71 (the average
thickness: 0.5 to 10.0 .mu.m) and the second layer 72 (the average
thickness: 0.1 to 1.0 .mu.m). The first layer 71 has the conductive
characteristic, and a main object of the first layer 71 is to
prevent the solder's ingredient of the solder layer 5 from
spreading into the inside of the thermoelectric element 1.
Furthermore, the first layer 71 lies between the end face 1a of the
thermoelectric element 1 and the second layer 72 so that it
counters directly to the plain end face 1a of the thermoelectric
element 1 which is the physical object to be prevented from the
spreading phenomenon. Specifically, the first layer 71 comprises
the non-electrolytic plating layer composed of nickel-phosphorus
series. The average of the thickness of the first layer 71 is
thicker than that of said second layer 72.
[0030] The second layer 72 has conductive characteristic and an
main object of the second layer 72 is to provide better wetting
property against the solder layer than said first layer 71 when
soldering. Therefore, the second layer 72 lies between the solder 5
and the first layer 71 so that it counters directly to a solder
layer 5. Accordingly, the second layer 72 composed of the better
wetting property than the first layer 71 against the solder.
Specifically, the second layer 72 comprises the non-electrolytic
plating layer composed of nickel-boron series.
[0031] As shown in FIG. 1, the distinction of P-type and N-type of
each thermoelectric element 1 is labeled as "P", and "N". When the
thermoelectric device is used, the electrode 35A (35) of one end
side is connected to a plus pole of a power supply, and the other
end side is connected to a minus pole of power supply through the
plural thermoelectric elements including the electrode 35B (35) is
connected, so that electric power is fed between the plus pole of
and the minus pole of the power supply. Therefore, the substrate 30
of the one side is cooled to be the low temperature side, and the
substrate 31 of the other side is heated to be the high temperature
side due to the thermoelectric effect of the each thermoelectric
element.
[0032] Alternatively, the low temperature and the high temperature
sides are reversed when switching the plus pole and the minus pole
to feed electric power in the revered direction.
EXAMPLE OF EMBODIMENT
[0033] The thermoelectric device shown in FIG. 1 and FIG. 2 was
used for the test piece. The first layer 71 composed of the
non-electrode nickel-phosphorus plate layer (phosphorus is 2 to 8
wt %) was laminated on the both end sides la of the thermoelectric
element 1 by the first non-electrode plating procedure.
Furthermore, the first layer 72 composed of the non-electrode
nickel-boron plate layer (boron is 1 wt %) was laminated on the
first layer 71 by the second nonelectrode plating procedure.
[0034] The three kinds of the first layer 71 were prepared for the
evolution with the thickness of 0.5 to 1.0 .mu.m, 1.0 to 5.0 .mu.m
and 5.0 to 10.0 .mu.m. The two kinds of the second layer 72 were
also prepared with the thickness of 0.1 to 0.5 .mu.m and 0.5 to 1.0
.mu.m.
[0035] In order to evaluate the defect of soldering, the burn-in
test which fed electric current of 2 [A] to each test piece was
performed. After the burn-in test the cool-heat test was performed
to hold the test pieces at the temperature of -40.degree. C., for
15 minutes and at the temperature of 80.degree. C. for 15 minutes.
The variation ratio of inner electrical resistance of the test
pieces were measured before and after the burn-in test and the
cool-heat test. If the alteration ratio of inner electrical
resistance is not more than 0.5%, the test piece is evaluated as an
acceptable product. If the alteration ratio of inner electrical
resistance exceeds 0.5%, the test piece is evaluated as an
acceptable product. 30 test pieces were prepared, and the rate of
occurrence for non-acceptable product among thirty (30) test pieces
were calculated.
[0036] Furthermore, the other test pieces were tested by the high
temperature exposure test to maintain the temperature the test
pieces at 150.degree. C. Accordingly, the variation ratio of inner
electrical resistance of the test pieces were measured before and
after the high temperature exposure test. If the alteration ratio
of inner electrical resistance is not more than 10%, the test piece
is evaluated as an acceptable product. If the alteration ratio of
inner electrical resistance exceeds 10%, the test piece is
evaluated as a non-acceptable product. 22 test pieces were
prepared, and the rate of occurrence for non-acceptable product
among 22 test pieces were calculated.
[0037] Table 1 shows results of the evaluation concerning the
embodiment examples.
[0038] In the same way as the present embodiment example, as the
test piece related to the comparative example 1, the first layer 71
composed of the non-electrode nickel-phosphorus plate was laminated
with the thickness of 1.0 to 5.0 .mu.m on the end side of the
thermoelectric element 1. The thermoelectric device was produced as
the same way as above-mentioned, and was evaluated as the same way
as the above-mentioned test example. As the test piece related to
the comparative example 2, the first layer 71 composed of the
non-electrode nickel-phosphorus plate was laminated with the
thickness of 0.5 to 1.0 .mu.m on the end side of the thermoelectric
element 1. The thermoelectric device was produced as the same way
as above-mentioned, and was evaluated as the same way of as the
above-mentioned test example.
[0039] Regarding the test pieces of the comparative example 1 and
the comparative example 2, the first layer 71 composed of
non-electrode nickel-phosphorus plate was laminated, but the second
layer 72 composed of non-electrode nickel-boron plate was not
laminated.
[0040] Table 1 shows results of the evolution concerning the
comparative example 1 and the comparative example 2.
[0041] Regarding the test piece related to the embodiment example,
the second layer 72 composed of the nonelectrode nickel-boron plate
layer with good wetting property against the solder is laminated on
the first layer 71 composed of the non-electrode nickel-phosphate
plate layer with the high spread prevention property. Therefore,
this embodiment example had the spread property to prevent solder's
ingredient from spreading into the inside of the thermoelectric
element 1, and had improved soldering characteristic for electrode
35 and thermoelectric element 1, and had restrained degradation of
the test piece after each test.
[0042] Consequently, as understood in Table 1, according the test
pieces from the embodiment example, the rate of occurrence of
defective test pieces were zero or extremely low.
[0043] As shown in Table 1, under the aforementioned test
condition, when the thickness of the first layer 71 was 0.5 to 1.0
.mu.m, the rate of occurrence of defective test pieces after the
high temperature exposure test was {fraction (3/22)} (three per
twenty-two). Considering this result, under the aforementioned test
condition, the preferable thickness of the first layer 71 is no
less than 1.0 .mu.m. Furthermore, if the test condition of the
thermoelectric device is loosened, the thickness of the first layer
71 of no more than 1.0.mu. is satisfied as a non-defective test
piece.
[0044] According to the present invention, when the first layer is
a non-electrolytic plating layer composed of nickel-phosphorus
series, and the second layer is non-electrolytic plating layer
composed of nickel-boron series, the present invention is able to
achieve the good effect.
[0045] According to the present invention, when the average
thickness of the first layer is thicker than that of said second
layer, the solder's ingredient is effectively prevented from
spreading into the thermoelectric element. Specially, when the
average thickness of the first layer composed of nickel-phosphorus
series is thicker than that of the second layer composed of
nickel-boron series, the present invention may efficiently achieve
the spread prevention effect, may increase the productivity and may
achieve low cost in manufacturing due to the thin non-electrolytic
plating layer composed of nickel-boron series whose plating speed
is slow and expensive in manufacturing.
1 TABLE 1 Comparative Comparative Embodiment example Example 1
Example 2 Second layer Ni--B Thickness (.mu.m) 0.1.about.0.5
0.5.about.1.0 -- -- First layer Ni--P Thickness (.mu.m) 0.5-1.0
1.0-5.0 5.0-10.0 0.5-1.0 1.0-5.0 5.0-10.0 1.0-5.0 0.5-1.0 Defect
ratio after the burn- 0/30 0/30 0/30 0/30 0/30 0/30 4/30 5/30 in
test and the cool-heat test High temperature exposure 3/22 0/22
0/22 0/22 0/22 0/22 0/22 9/22 test Defect ratio after 30-hours High
temperature exposure 0/22 0/22 0/22 0/22 0/22 0/22 0/22 2/22 test
Defect ratio after 10-hours
* * * * *