Batteries: thermoelectric and photoelectric – Thermoelectric – Processes
Reexamination Certificate
2000-08-14
2002-06-25
Gorgos, Kathryn (Department: 1741)
Batteries: thermoelectric and photoelectric
Thermoelectric
Processes
C136S205000, C136S237000
Reexamination Certificate
active
06410840
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermoelectric conversion device having elements constituted of p-type and n-type thermoelectric materials and capable of enabling temperature-difference power generation (thermal power generation) based on the Seebeck effect or electronic cooling and heating based on the Peltier effect and a method of manufacturing.
2. Description of the Related Art
The construction of a conventional thermoelectric conversion device for converting heat into electricity or converting electricity into heat and a method for manufacturing the thermoelectric conversion device will be described with reference to
FIGS. 14
to
16
. The conventional thermoelectric conversion device is constructed in such a manner that, as shown in
FIG. 14
, n-type elements
505
and p-type elements
605
are interposed between a lower substrate
601
having a lower electrode wiring
604
provided on its surface and an upper substrate
501
having an upper electrode wiring
504
provided on its surface. Also, as shown in
FIG. 16
, p-type elements
605
and n-type elements
505
are electrically connected in series to each other to form pn junctions, and are connected to an external electrical circuit by external connection electrodes
608
. Thermoelectric materials ordinarily used at room temperature not exceeding a temperature of about 200° C. are Bi—Te materials. The material of the p-type elements is a chemical compound semiconductor mainly composed of Bi, Te and Sb. The material of the n-type elements is a chemical compound semiconductor mainly composed of Bi, Te and Se.
When, in the above-described thermoelectric conversion device, a direct current is caused to flow through the external connection electrode
608
provided at both end portions of the thermoelectric conversion device, heat absorption or heat development occurs at each of the interface at which the upper electrode wiring
504
contacts the elements
505
and
506
and the interface between at which the lower electrode wiring
604
contacts the elements
505
and
506
, thus creating a temperature difference between the two faces of the thermoelectric conversion device. Conversely, when there is a temperature difference between the upper electrode wiring
504
and the lower electrode wiring
604
, it is possible to extract power from the external connection electrodes
608
.
A method for manufacturing such a thermoelectric conversion device will next be described.
FIG. 15
shows an element joining method in a conventional thermoelectric conversion device manufacturing method in a case where elements formed from thermoelectric materials are monocrystals, or where a sintering process is used. First, on a thermoelectric material processed to have the shape of a plate or rod, a layer of Ni or the like is formed by plating. This layer is formed on the flat surfaces of the thermoelectric member which are to be joined to the substrates. The thermoelectric member is cut into rectangular blocks, and electrode joint layers for soldering are provided on opposite end surfaces. In this manner, p-type elements
605
having electrode joint layers
606
and
607
and n-type elements
505
having electrode joint layers
506
and
507
are made. Then, the completed p-type elements
605
and n-type elements
505
are respectively set in predetermined places on the electrode wirings with a jig or the like, and the elements and the electrode wirings are joined to each other by the electrode joint layers, thus manufacturing a thermoelectric conversion device.
FIG. 16
shows a see-through view of the thermoelectric conversion device manufactured by this process.
Ordinary conventional thermoelectric material forming methods are represented by the above-mentioned method of directly cutting a monocrystal into elements, and the method of pulverizing a monocrystal into a powder, sintering the powder and cutting the sintered material into elements. Sol-gel methods, electroplating methods, flash evaporation methods are presently being studied.
A process based on an electroplating method disclosed in Japanese Patent Laid-Open Publication No. 22533/1998 will be outlined. First, a mask pattern is formed on a plating electrode made of Ti or the like on a plating substrate. This plating substrate is then placed in an acid plating solution together with an opposed electrode and a current is caused to flow therethrough.
When the growth of a plating layer to a certain thickness is attained, the substrate with the plating layer is taken out of the liquid plate and the plating layer is transferred onto an insulating substrate. As a transfer method, a method of physically shaving the plating substrate may be used. In this process, however, a method of stripping from the plating substrate by using the adhesion of an adhesive on the insulating material is used. The step of forming an insulating layer on the stripped off plating layer and transferring another plating layer onto the insulating layer is repeated several ten times to make a laminated block. Internal electrodes for pn junction are directly formed on end surfaces of the block by vacuum deposition or the like.
In the thermoelectric conversion device using monocrystals or sintered members as its elements, however, shorting by contact between the elements or failure of contact of the elements with the electrodes can occur easily due to a move of the elements on solder at the time of joining when the both sides of the elements are soldered to fix the elements. Also, since the elements having the shape of a rectangular block are made by cutting the thermoelectric material in the form of a plate, corner portions of the elements can crack or chip easily and a stress due to heat or an external force is concentrated in corner portions of the elements to increase the possibility of breakage. Therefore, there is a problem of a reduction in the yield or instability of the yield in mass production of the thermoelectric conversion device.
In the thermoelectric conversion device manufacturing method using a monocrystal or a sintered member to form elements, the elements formed from a thermoelectric material is a rectangular block one side of which (one in the direction of thickness and one of the bottom sides) has a length of, at the minimum, several hundred micrometers, depending upon restrictions in terms of machining and ease of handling. To obtain a high electromotive force by using such elements with respect to a small temperature difference, it is necessary to connect several thousand elements in series. However, it is very difficult to manufacture a thermoelectric conversion device in which several thousand worked elements are arrayed one by one on a substrate and connected in series.
Even if it is possible, the size of the thermoelectric conversion device is so large that the device is difficult to mass-produce at a low cost.
In the case of the manufacturing method disclosed in Japanese Patent Laid-Open Publication No. 22533/1998, a sufficiently stable yield cannot be expected with respect to plating transfer. Also, the device using laminated blocks having intermediate layers of an insulating material has a heat flow loss larger than that of the device having air between the elements, and cannot generate sufficient power when the temperature difference is small. Also, according to the method, the internal electrodes for series connection of the elements are joined directly to the elements and, therefore, the electrical resistance and the loss of heat are reduced. In practice, however, there is a need to polish the end surfaces of the blocks, so that it is difficult to manufacture the device at a low cost. Further, positioning marks cannot be used at the time of forming the internal electrodes, and it is difficult to form the internal electrode with sufficiently high reliability.
For these reasons, it is very difficult to manufacture a small, thin, compact thermoelectric conversion device with stability at a low cost by any of the conventional ma
Kishi Matsuo
Nemoto Hirohiko
Sudo Shuzo
Adams & Wilks
Gorgos Kathryn
Parsons Thomas H
Seiko Instruments Inc.
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