Batteries: thermoelectric and photoelectric – Thermoelectric – Processes
Reexamination Certificate
2000-05-18
2001-08-14
Gorgos, Kathryn (Department: 1741)
Batteries: thermoelectric and photoelectric
Thermoelectric
Processes
C136S203000, C136S242000
Reexamination Certificate
active
06274803
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermoelectric module that is a temperature control device using Peltier effect, and particularly a thermoelectric module with improved heat-transfer efficiency, and a method of manufacturing the thermoelectric module.
2. Disclosure of the Prior Art
As shown in
FIGS. 10A and 10B
, a conventional thermoelectric module
1
P has a structure comprising an arrangement of N-type semiconductor elements
21
P and P-type semiconductor elements
22
P, which are arranged in a matrix manner such that each of the N-type semiconductor elements
21
P is disposed adjacent to the P-type semiconductor element
22
P through a required space, upper electrodes
5
P disposed on a top surface of the arrangement to connect between adjacent semiconductor elements
21
P and
22
P according to a first circuit pattern, lower electrodes
6
P disposed on a bottom surface of the arrangement to connect between adjacent semiconductor elements
21
P and
22
P according to a second circuit pattern different from the first circuit pattern, and ceramic plates
8
P such as sintered alumina plates bonded to the upper and lower electrodes
5
P and
6
P.
For example, when direct current is supplied to the thermoelectric module
1
P, each of the upper electrodes
5
P has the flow of electricity from N-type semiconductor element
21
P to the P-type semiconductor element
22
P, and on the other hand the each of the lower electrodes
6
P has the flow of electricity from the P-type semiconductor element
22
P to the N-type semiconductor element
21
P. At this time, the upper electrodes
5
P absorb heat from the surroundings through the ceramic plate
8
P, and the lower electrodes
6
P radiate heat to the surroundings through the ceramic plate
8
P. Therefore, the thermoelectric module
1
P works as a kind of heat pump for pumping heat from one side to the opposite side thereof, which is usually called Peltier effect. According to this principle, it is possible to use the thermoelectric module
1
P as a temperature control device for electronic parts or circuit boards
As materials for the semiconductor elements
21
P and
22
P, Bi
2
Te
3
and Sb
2
Te
3
are widely used. Since these compounds are brittle materials, cracks or chippings of the semiconductor elements easily occur during a manufacturing process of the thermoelectric module, so that there is a problem that the yields of the semiconductor-element materials are low. This increases the production cost and reduces a degree of reliability of the thermoelectric module. In addition, the ceramic plates
8
P are usually soldered to the upper and lower electrodes
5
P and
6
P by the use of a solder material
9
P to maintain the structural stability of the thermoelectric module
1
P. Since thermal stress occurs according to a difference of thermal expansion coefficient between the semiconductor-element materials and the ceramic-plate material, cracks may be generated in the ceramic plates or the semiconductor elements by the thermal stress.
Japanese Patent Early Publication [KOKAI] No. 10-51039 discloses a thermoelectric module
1
R having flexibility and resistance to thermal stress. In this thermoelectric module
1
R, adjacent semiconductor elements
21
R and
22
R are mechanically connected by a supporting member
3
R such as a silicone-resin adhesive having electrical insulation and flexibility in place of brittle ceramic plates, as shown in FIG.
11
. Due to the flexibility of the supporting member
3
R, the thermoelectric module
1
R can be fitted and bonded to a curved surface. In addition, silicone films
51
R having electrical insulation are formed on upper and lower electrodes
5
R and
6
R of the thermoelectric module
1
R.
On the other hand, Japanese Patent Early Publication [KOKAI] No. 9-293909 discloses a method of manufacturing a thermoelectric module
1
S for the purpose of increasing the yields of semiconductor-element materials. In this method, as shown in
FIG. 12A
, a thermoelectric chip
10
S having exposed surfaces of N-type and P-type semiconductor elements
21
S and
22
S on its top and bottom surfaces
11
S,
12
S is prepared by making a matrix arrangement of the semiconductor elements, and integrally molding the matrix arrangement with an electrical insulation resin
3
S such as epoxy resins. Subsequently, as shown in
FIG. 12B
, metal films
4
S are formed on the exposed surfaces of the semiconductor elements
21
S,
22
S and the insulation resin
3
S to connect between adjacent semiconductor elements according to a first circuit pattern on the top surface and a second circuit pattern on the bottom surface of the thermoelectric chip
10
S. Copper electrodes
5
S are then formed on the metal films
4
S by electroplating, as shown in FIG.
12
C. Since the semiconductor elements
21
S and
22
S are reinforced with the insulation resin
3
S in the thermoelectric chip
10
S, it is possible to reduce the occurrence of cracks or chippings of the semiconductor elements and improve the yields of the semiconductor element materials.
By the way, in order to accurately control the temperature of articles such as electronic parts and circuit boards by the use of the thermoelectric module, it is necessary to improve heat-transfer efficiency between the thermoelectric module and the articles, while maintaining electrical insulation therebetween. The silicone films
51
R formed on the electrodes
5
R,
6
R of the thermoelectric module
1
R shown in
FIG. 11
provide the electrical insulation. However, the heat-transfer efficiency of the silicone film
51
R is much lower than that of conventional ceramic materials. Conventional organic resins are of {fraction (1/50)}th to {fraction (1/200)}th thermal conductivity of alumina ceramic. Therefore, this thermoelectric module is susceptible to improvement from the viewpoint of heat-transfer efficiency.
On the other hand, in the thermoelectric module
1
S of Japanese Patent Early Publication [KOKAI] No. 9-293909, a grease material
51
S having electrical insulation is applied on the top and bottom surfaces
11
S,
12
S of the thermoelectric chip
10
S, as shown in
FIG. 12D
, and then heat-transfer plates
52
S made of a metal material having excellent thermal conductivity such as aluminum or copper are put on the grease material
51
S, as shown in FIG.
12
E. In this case, there are problems that the thermal conductivity of the grease material
51
S is poor, and the structural stability of the thermoelectric module
1
S is low because the heat-transfer plates
52
S are merely put on the thermoelectric chip
10
S through the grease material
51
S. In addition, when the thickness of the grease material
51
S partially becomes small, a short circuit may be caused between the electrodes and the heat-transfer plate. Therefore, it is required to apply the grease material
51
S having poor thermal conductivity on the thermoelectric chip
10
S with a thickness sufficient to maintain the electrical insulation therebetween.
SUMMARY OF THE INVENTION
In view of the above problems, a primary object of the present invention is to provide a thermoelectric module with improved heat-transfer efficiency. That is, the thermoelectric module of the present invention comprises:
a thermoelectric chip with exposed surfaces of first-type and second-type thermoelectric elements on its top and bottom surfaces, in which the thermoelectric telements are arranged in a matrix manner such that each of the first-type thermoelectric elements is disposed adjacent to the second-type thermoelectric element through a space, and the space is filled with a first resin material having electrical insulation;
a metal layer formed on each of the exposed surfaces of the thermoelectric elements on the top and bottom surfaces of the thermoelectric chip; first electrodes formed on the top surface of the thermoelectric chip according to a first circuit pattern, each of which electrically connects between adjacent thermoelectric elements; and
secon
Kamada Kazuo
Kobayashi Kentaro
Urano Yoji
Yoshioka Hirokazu
Gorgos Kathryn
Matsushita Electric & Works Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Parsons Thomas H
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