JP2010034508A - Thermoelectric conversion module and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a FeSi2-based thermoelectric conversion module, which facilitates soldering a connection wire to its terminal easily, and to provide a method of manufacturing the same. <P>SOLUTION: Each p-type and n-type FeSi2-based thermoelectric conversion semiconductor raw powder 22', 23' and plate made of predetermined metal or powder 21' and/or 24', which are located at least one edge place thereof, are cast inside a sintering mold 3, and these are sintered and jointed at one step in an electric discharge plasma sintering method. Then, a metal electrode unified thermally and electrically to the FeSi2-based thermoelectric conversion semiconductor can be formed, and connecting wire made of copper and the like can be easily soldered to the electrode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thermoelectric conversion module and a manufacturing method thereof, and more particularly to an iron silicide (FeSi 2) type thermoelectric conversion module and a manufacturing method thereof capable of easily soldering a connecting wire made of a copper wire or the like.

  In general, when a thermoelectric conversion module is mounted on a circuit, it is necessary to connect a lead wire to the module (element). In the thermoelectric conversion module, a thermoelectromotive force is generated in accordance with a temperature change or a temperature difference of the element portion. Therefore, it is desirable that the connection of the lead wire be integrated with the thermoelectric conversion semiconductor element both thermally and electrically.

  However, since the iron silicide (FeSi2) -based thermoelectric conversion semiconductor is made of sintered iron and silicon powder, it has high heat resistance, and solder that normally melts at 160 ° C to 180 ° C does not fit well. Moreover, when it approaches the limit temperature (about 380 ° C) of the soldering operation, the life of the tip itself is shortened due to oxidation, erosion, etc. Connected. In addition, since the FeSi 2 -based thermoelectric conversion semiconductor is hard and brittle, it is impossible to make a screw hole and fix the connection line.

  For this reason, conventionally, a conductive material such as a copper plate is attached with a conductive adhesive made of silver paste, silver double-sided tape or the like, and a connecting wire is soldered to the conductive material (electrode).

JP 2007-324500 A

“Measurement of Seebeck coefficient of FeSi2 based thermoelectric conversion module” Katsuyuki Tanaka et al., The 28th Japan Symposium on Thermophysical Properties. Oct. 24-26. 2007, Sapporo.

  However, in the method of bonding the conductive material with the conductive adhesive, there is a problem that the impedance of the conductive adhesive and the deterioration over time deteriorate the performance of the FeSi2 thermoelectric conversion module.

  In addition, although the method of arc welding or laser welding of the connecting wire is also conceivable, since the heat-resistant temperature of the thermoelectric conversion semiconductor is high, the temperature of the welded portion is excessively increased and the composition having the thermoelectric conversion semiconductor characteristics (β phase) is destroyed. As a result, the characteristics (Seebeck coefficient) as a thermoelectric conversion semiconductor are reduced, and it has been confirmed that this is not an effective connection line connection method.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a FeSi2-based thermoelectric conversion module capable of easily soldering a connecting wire to a terminal portion and a method for manufacturing the same. It is in.

  In order to solve the above-described problems, a method for manufacturing a thermoelectric conversion module according to the first aspect of the present invention includes, in a sintered mold, each thermoelectric conversion semiconductor raw material powder composed of FeSi2 p-type and n-type, and these A plate or powder made of a predetermined metal is put into at least one end of each of them, and these are sintered and joined in one step by a discharge plasma sintering method.

  In the present invention, FeSi2 series is sintered and joined by a discharge plasma sintering method with a predetermined metal interposed at least at one end of each of the thermoelectric conversion semiconductor raw material powders of FeSi2 series p-type and n-type. A metal electrode that is thermally and electrically integrated with the thermoelectric conversion semiconductor can be formed, and a connecting wire made of copper or the like can be easily soldered to the electrode portion. In the present invention, since a predetermined metal is sintered and bonded together with the p-type and n-type raw material powders in one step, the manufacturing cost of the thermoelectric conversion module can be greatly reduced.

  In the second aspect of the present invention, 4.1 mass% chromium (Cr) is mixed in the FeSi2 raw material powder to obtain a p-type thermoelectric conversion semiconductor raw material powder.

  In the third aspect of the present invention, 2.4 mass% cobalt (Co) is mixed into the FeSi2 raw material powder to obtain an n-type thermoelectric conversion semiconductor raw material powder.

  In the fourth aspect of the present invention, the predetermined metal is made of silver (Ag) or a silver-based alloy.

  According to the present invention, silver (Ag) has a low electrical resistance and high thermal conductivity, so it is optimal as an electrode metal for transferring heat and electrical energy, and the melting point of silver (approximately 962 ° C.) is thermoelectric. Since the temperature is somewhat higher than the optimum temperature for sintering the conversion module (that is, FeSi2-based thermoelectric semiconductor raw material powder), the electrode portion can be appropriately sintered and joined to the thermoelectric conversion semiconductor portion.

  In the fifth aspect of the present invention, the predetermined metal is made of nickel (ni), titanium (Ti), or an alloy mainly composed of these.

  Experiments have confirmed that even when nickel (ni), titanium (Ti), or a nickel-based or titanium-based alloy is used as the electrode metal, the electrode portion can be appropriately sintered and bonded to the thermoelectric conversion semiconductor portion.

  In the sixth aspect of the present invention, the sintering and joining are performed at a pressure of 35 MPa to 70 MPa, a temperature of 923 K (650 ° C.) to 1073 K (800 ° C.), and a time of 300 sec to 3.6 ksec.

  This sintering condition basically depends on conditions for obtaining a crystal structure (that is, a β-phase monolayer) exhibiting a high Seebeck coefficient for each sintered body of p-type and n-type thermoelectric conversion semiconductors. However, in the present invention, the sintering conditions are selected within a range in which appropriate bonding characteristics can be obtained mechanically and electrically for the electrode metal.

  The thermoelectric conversion module according to the seventh aspect of the present invention comprises a sintered die, a thermoelectric conversion semiconductor raw material powder composed of FeSi2 p-type and n-type, and a plate made of a predetermined metal at least at one end thereof. Powders are charged, and these are sintered and joined in one step by the discharge plasma sintering method. Thereby, the thermoelectric conversion module which has a high Seebeck coefficient and can easily solder the lead wire can be provided at low cost.

  In an eighth aspect of the present invention, the predetermined metal is made of silver (Ag), nickel (ni), titanium (Ti), or an alloy mainly containing any one of them.

  The thermoelectric conversion module according to the ninth aspect of the present invention comprises a thermoelectric conversion semiconductor raw material powder composed of FeSi2 p-type and n-type in a sintered mold, and p-type and n-type at least at one end thereof. A mixed powder of each thermoelectric conversion semiconductor raw material powder and a predetermined metal powder is charged, then a powder made of a predetermined metal is charged, and these are sintered and combined in one step by a discharge plasma sintering method. Thereby, it is possible to provide a thermoelectric conversion module in which the bonding strength between the thermoelectric conversion semiconductor and the electrode is further strong.

  In a tenth aspect of the present invention, the predetermined metal is made of silver (Ag), nickel (ni), titanium (Ti), or an alloy mainly containing any one of them.

  As described above, according to the present invention, since the connecting wire can be directly soldered to the thermoelectric conversion module, it is extremely effective in terms of manufacturing equipment cost and manufacturing cost of the apparatus using the thermoelectric conversion module.

It is a schematic block diagram of a discharge plasma sintering apparatus. It is a figure explaining the manufacturing method of the thermoelectric conversion module by embodiment. It is a figure explaining the thermoelectric conversion module of Example 1. FIG. It is a figure explaining operation | movement of the thermoelectric conversion module of Example 1. FIG. It is a figure which shows the thermoelectromotive force measurement result of the thermoelectric conversion module of Example 1. FIG. It is a figure explaining the thermoelectric conversion module of Example 2. FIG. It is a figure explaining the thermoelectric conversion module of Example 3. FIG. It is a figure explaining the manufacturing method of the thermoelectric conversion module of Example 4. FIG. It is a perspective view of the thermoelectric conversion module of Example 4. It is a figure explaining the manufacturing method of the thermoelectric conversion module of Example 5. FIG.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Throughout this specification, the same or corresponding parts are denoted by the same reference numerals. FIG. 1 is a schematic configuration diagram of a discharge plasma sintering apparatus used in the present embodiment. The discharge plasma sintering apparatus 1 includes a water-cooled vacuum chamber 2 capable of reducing the pressure in a substantially vacuum state, a ring-shaped graphite sintering die 3 accommodated in a substantially central portion of the vacuum chamber 2, A laminate 4 of various raw material powders put into the through-holes of the sintering mold 3, punches (pressors) 5a and 5b made of a pair of upper and lower columnar graphite for pressurizing the laminate 4, and these A pair of upper and lower punch electrodes 6a and 6b for supplying a current to the punches 5a and 5b is provided.

  Further, outside the vacuum chamber 2, a control unit 9 that performs sintering control of the thermoelectric conversion module according to the present embodiment, and special sintering that allows current to flow through the punch electrodes 6a and 6b under the control of the control unit 9. The control unit 9 controls the power source 7, the pressurizing mechanism unit 8 that applies pressure to the punch electrodes 6a and 6b under the control of the control unit 9, the atmospheric pressure in the vacuum chamber 2, the sintering temperature detected by the thermocouple 3a, and the like. And a measurement unit 10 that feeds back to.

  Next, the manufacturing method of the thermoelectric conversion module by embodiment using such a discharge plasma sintering apparatus 1 is demonstrated in detail. FIG. 2 is a diagram for explaining a method of manufacturing a thermoelectric conversion module according to the embodiment, and shows an enlarged view of a portion related to the sintering mold 3 of FIG. A p-type thermoelectric conversion semiconductor raw material powder is prepared in advance by mixing, for example, 4.1% by mass of chromium (Cr) into an FeSi2 raw material powder having an average particle size of approximately 8 μm, for example, and the FeSi2 raw material powder has, for example, 2.4 An n-type thermoelectric conversion semiconductor raw material powder is prepared by mixing mass% cobalt (Co).

  A punch 5b is inserted into the lower portion of the sintering die 3, and preferably a disc-shaped carbon paper C1 is laid thereon as shown in the inset (a). Further, the carbon paper C2 is arranged in a cylindrical shape on the inner peripheral surface of the sintering mold 3, and the raw material powder is put into the layers in order. For example, the electrode metal powder 24 ′ made of silver (Ag), the n-type thermoelectric conversion semiconductor raw material powder 23 ′, the p-type thermoelectric conversion semiconductor raw material powder 22 ′, and the electrode metal powder 21 ′ made of silver (Ag) Put them in order and place the carbon paper C6 on top of it. And the punch 5a is inserted from the top, and the set of the sintering mold | type 3 is created in this way.

  The set of the sintering mold 3 is set between the punch electrodes 6a and 6b in the discharge plasma sintering apparatus 1, and the atmospheric pressure in the vacuum chamber 2 is reduced to a substantially vacuum (for example, 3 Pa or less). A special sintering current is passed between the punch electrodes 6a and 6b while applying pressure to the upper and lower punch electrodes 6a and 6b, and a discharge plasma sintering method using graphite (graphite) 3, 5a and 5b as a heating element. Each raw material powder is sintered and bonded in one step under the following sintering conditions.

  Preferably, the applied pressure is in the range of 35 MPa to 70 MPa. During sintering and joining, a large pressure is applied to each raw material powder to facilitate the movement of the substance, and the rearrangement of the powder particles is promoted at the initial stage of shrinkage due to sintering, which can be rapidly densified. it can. It was confirmed that when the applied pressure is lower than this range, the sintered body has a low density and mechanical properties are low, and when the pressure is higher than this range, the sintered body has a high density and becomes brittle.

  Preferably, the sintering temperature is in the range of 923K (650 ° C) to 1073K (800 ° C). Even if the sintering temperature is lower or higher than this range, the thermoelectromotive force (Seebeck coefficient) of the thermoelectric conversion semiconductor is reduced.

  Preferably, the sintering time is in the range of 300 sec to 3.6 ksec. It was confirmed that when the sintering time was shorter than this range, the sintered body had a low density and the mechanical properties were low, and when the sintering time was longer than this range, it became dense and brittle.

  After sintering, the inside of the vacuum chamber 2 is cooled to about 523 K (250 ° C.), for example, and the inside is returned to normal pressure (atmospheric pressure), and the cylindrical sintered body thus obtained is taken out. Thereby, an electrode layer made of silver (Ag) is integrally sintered and bonded to both end portions of the thermoelectric conversion module, and a connecting wire made of copper or the like can be easily soldered to the electrode.

  The above sintering conditions basically include a β-phase single-phase crystal structure that exhibits effective thermoelectric conversion characteristics (Seebeck coefficient) for sintered bodies of p-type and n-type thermoelectric semiconductor raw material powders. Although it depends on the conditions to be obtained, in the present embodiment, the range in which an electrode metal such as silver (Ag) is appropriately sintered and bonded to such an FeSi2-based thermoelectric semiconductor is further set. Sintering conditions. For example, the melting point of Ag is 1235 K (approximately 962 ° C.), and the sintering and joining according to the present embodiment are appropriately performed at a lower process temperature.

  In addition to the above soldering, the connection of the connecting wire to the thermoelectric conversion module is a temperature that does not affect the composition (β phase) of the thermoelectric conversion semiconductor, such as electric welding and laser welding by laser irradiation in a short time. If so, it is possible.

  In addition to the above-mentioned silver (Ag), nickel (ni), titanium (Ti), and alloys mainly composed of these can be sintered and bonded satisfactorily for the electrode metal used in the thermoelectric conversion module. confirmed. In this case, the melting point of nickel metal is 1453 ° C. and the melting point of titanium metal is very high, 1680 ° C., and soldering work can be performed around the limit temperature (380 ° C.).

  When a copper (Cu) plate or copper powder was used for the electrode metal, cracks, chips, etc. occurred in the electrode portion of the sintered body, and good sintering / joining could not be obtained.

  Next, examples of the thermoelectric conversion module according to the present invention will be described.

<Example 1>
FIG. 3 is a diagram for explaining the thermoelectric conversion module 20A of the first embodiment, and shows a case where the thermoelectric conversion module is used as a thermoelectric conversion temperature sensor for detecting a temperature change. This thermoelectric conversion module 20A was manufactured by the following method, for example. That is, p-type thermoelectric conversion semiconductor raw material powder is prepared by mixing 4.1% by mass of chromium (Cr) into FeSi2 raw material powder having an average particle size of about 8 μm, and 2.4% by mass of cobalt (Co) is mixed. Thus, an n-type thermoelectric conversion semiconductor raw material powder is prepared. Further, from the bottom of the sintering mold 3, silver (Ag) powder, n-type thermoelectric conversion semiconductor raw material powder, p-type thermoelectric conversion semiconductor raw material powder, and silver (Ag) powder are sequentially added in layers, and these are applied with a pressure of 35 MPa, Sintering and joining were performed in one step by a discharge plasma sintering method under sintering conditions of a sintering temperature of 1023 K (750 ° C.) and a sintering time of 600 seconds. The material having a diameter of 20 mm, the p-type layer, and the n-type layer having a thickness of about 7 mm was 10 g and the diameter was 20 mm, and the Ag metal powder material was 0.2 g, and the thickness was about 1 mm. Ag is in the range of 0.2 g to 2 g when sintered at a diameter of 20 mm. Since the Ag material is expensive, a small amount is preferable, but the amount that can be uniformly sintered over a diameter of 20 mm by experiment is 0.2 g. Note that the Ag amount can be reduced by reducing the diameter of the Ag layer by changing the mold of the Ag layer portion to be sintered. Also, since the melting point of Ag is 962, which is close to the sintering temperature, Ag penetrates into the n-type layer and the p-type layer in the case of a large amount, and an effective Ag layer can be formed by experiments when the diameter is 20 mm. Met.

  FIG. 3A is a front view of the thermoelectric conversion module 20A of the first embodiment, and FIG. 3B is a perspective view thereof. In this thermoelectric conversion module 20A, a silver (Ag) electrode 21, a p-type thermoelectric conversion semiconductor 22, an n-type thermoelectric conversion semiconductor 23, and a silver (Ag) electrode 24 are integrally sintered and bonded. As an example, the diameter of the cylinder is 20 mm, the thicknesses of the p-type layer 22 and the n-type layer 23 are both about 7 mm, and the thicknesses of the Ag electrodes 21 and 24 are about 1 mm. In the thermoelectric conversion module 20A, since the upper and lower electrodes 21 and 24 are both made of silver (Ag), the connecting wires 32a and 32b made of copper (Cu) or the like can be easily soldered. Here, 31a and 31b are solders.

  Next, the operation when the thermoelectric conversion module 20A of the first embodiment is used as a thermoelectric conversion temperature sensor that detects a temperature change will be described with reference to FIG. FIG. 4 shows a front view when the thermoelectric conversion module 20A is placed sideways, and shows a state where the entire thermoelectric conversion module 20A is heated from below. In general, it is known that charged carriers (electrons in a metal, electrons in a semiconductor, holes, etc.) in a substance diffuse according to the thermal gradient when one end of a conductor or semiconductor is at a different temperature. That is, hot carriers (holes, electrons) at the hot end have a property of diffusing toward the cold end where the density of hot carriers is thin.

  Specifically, in the example of FIG. 4, the Ag electrodes 21 and 24 at both ends have high thermal conductivity (that is, a small heat capacity), so that the whole is quickly warmed. On the other hand, the semiconductor junction with which the pn interface is in contact is made of ceramic having a large heat capacity, so that the heat conduction is delayed and the semiconductor junction becomes a relatively cold part. As a result, in the p-type region 22, the heated and active holes move to the cold end (junction surface) side where the energy is low, so that the electrode 21 side becomes a minus pole due to the lack of holes. On the side, the holes gather and become a + pole. Further, in the n-type region 23, the warmed electrons move to the cold end (junction surface) side, so that the electrode 24 side becomes a + pole due to the lack of electrons, and the electrons gather on the junction surface side − Become the pole. In the entire pn junction, these thermoelectric conversion actions are electrically overlapped, so that the electrode 24 side becomes a positive electrode and the electrode 21 side becomes a negative electrode. Even in this case, since the silver (Ag) electrodes 21 and 24 have a small electric resistance, the generated thermoelectromotive force is transmitted to the outside without loss.

  FIG. 5 is a diagram showing the measurement result of the thermoelectromotive force of the thermoelectric conversion temperature sensor 20A of the first embodiment. In the graph, the entire thermoelectric conversion temperature sensor 20A is 30 ° C. higher than room temperature and is introduced into a vertical airflow at a wind speed of 85 cm / sec, and the change in thermoelectromotive force with time is measured. As shown in FIG. 5, the thermoelectromotive force of the thermoelectric conversion temperature sensor 20A reaches a maximum of about 0.97 mV about 30 seconds after the introduction of the hot air current, and after the heat is transferred to the entire sensor, The electromotive force is gradually decreasing. The thermoelectric conversion temperature sensor 20A can estimate the difference in temperature introduced based on the rate of change in the section where the thermoelectromotive force is rising.

<Example 2>
FIG. 6 is a diagram for explaining the thermoelectric conversion module 20B of the second embodiment, and shows another case of connecting a connection line to the thermoelectric conversion module according to the present invention. FIG. 6 (A) shows a front view when the raw material powder is laminated. At the time of manufacturing this thermoelectric conversion module, both electrode powders 21 'and 24' made of Ag and FeSi2-based p-type and n-type thermoelectric semiconductor raw material powders 22 'and 23' are laminated, and then electrode powders 21 'and p A through-hole 33a is made to penetrate partway through the center of the mold raw material powder 22 ', and a through-hole 33b is made partway through the central part of the electrode powder 24' and the n-type raw material powder 23 '. Such through-holes 33a and 33b can be formed by drilling holes or inserting cylindrical rods or the like in the laminated portions of the raw material powders that have been preliminarily pressed and hardened to some extent.

  FIG. 6B is a front view of a state in which the lead terminals are soldered to the electrodes 21 and 24 of the thermoelectric conversion module 20B of the second embodiment. The lead terminals 34a and 34b are made of a conductive material such as copper or brass, and flange portions 35a and 35b are fixed at positions of a predetermined length from the tip portion. This predetermined length corresponds to the depth of the through holes 33a and 33b. The leading end portions of the lead terminals 34a and 34b are inserted into the through holes 33a and 33b of the thermoelectric conversion module 20B, and inserted until the flange portions 35a and 35b come into contact with the surfaces of the Ag electrodes 21 and 24. , 24. The operation of the thermoelectric conversion module 20B of the second embodiment may be the same as that described for the thermoelectric conversion module 20A of the first embodiment cold.

<Example 3>
FIG. 7 is a diagram for explaining the thermoelectric conversion module 20C according to the third embodiment, and shows a case where a pnpn type thermoelectric conversion module is used as a thermoelectric conversion temperature sensor. The manufacturing method of this thermoelectric conversion module 20C will be outlined according to FIG. In this example, Ag24 ′, n-type thermoelectric conversion semiconductor 26 ′, p-type thermoelectric conversion semiconductor 25 ′, n-type thermoelectric conversion semiconductor 23 ′, p-type thermoelectric conversion semiconductor 22 ′, Each raw material powder is put into a layer in the order of Ag21 ′. Preferably, carbon paper is provided on the boundary surface between the upper and lower punches and the powder according to usual conditions, and the sintered mold 3 thus obtained is subjected to a pressure of 35 MPa, a sintering temperature of 1023 K (750 ° C.), and a sintering time of 600 sec. Thus, sintering and joining are performed in one step by the discharge plasma sintering method.

  FIG. 7B is a perspective view of the thermoelectric conversion module 20C of the third embodiment. In the sintered body obtained by the above manufacturing method, the Ag electrode 21, the p-type thermoelectric conversion semiconductor 22, the n-type thermoelectric conversion semiconductor 23, the p-type thermoelectric conversion semiconductor 25, the n-type thermoelectric conversion semiconductor 26, and Ag The electrode 24 is integrally sintered and bonded.

  In Example 3, as shown in FIG. 7B, the lower half of the n-type region 23 and the upper half of the p-type region 25 including the contact surface s3 at the center are further provided for this sintered body. Are cut with a wire cutter or the like, thereby forming a thermoelectric conversion module 20C having a constricted intermediate portion as shown in the figure. As an example, the diameter Φ1 of the cylindrical part is 20 mm, the diameter Φ2 of the small cylinder is 10 mm, the thickness of the p-type layer and the n-type layer are both about 7 mm, the thickness of the central constriction part is about 7 mm, and each Ag electrode The thickness of each is about 1 mm. Further, when used as the thermoelectric conversion temperature sensor 20C, the connection wires 32a and 32b made of copper wire or the like are soldered to the Ag electrodes 21 and 24 on the upper and lower end surfaces by solders 31a and 31b and mounted on a circuit (not shown).

  Next, the thermoelectric conversion operation of such a thermoelectric conversion temperature sensor 20C will be outlined. Note that the Ag electrodes 21 and 24 have a high thermal conductivity and a small thickness, and therefore have a very small heat capacity. For this reason, it is assumed that the Ag electrodes 21 and 24 are not provided for heat conduction.

  When heat is applied from the outside to the entire thermoelectric conversion temperature sensor 20C, in the p-type semiconductor region 22, the temperature rises quickly because the side of the joint surface s1 is close to the outside air, but the side of the joint surface s2 is n-type. Since it is in contact with the semiconductor region 23, the temperature rises slowly with a delay. That is, a relationship of (heat capacity of the joint surface s1) <(heat capacity of the joint surface s2) is established. For this reason, the joint surfaces s1 and s2 temporarily have a relationship of “warm” and “cold”, the joint surface s1 side has a small number of holes and a negative pole, and the joint surface s2 side has many holes and a positive pole. . In the n-type semiconductor region 23, (area of the bonding surface s2)> (area of the bonding surface s3), so that the relationship of (heat capacity of the bonding surface s2)> (heat capacity of the bonding surface s3) is satisfied. For this reason, the bonding surfaces s2 and s3 have a relationship of “cold” and “warm”, the bonding surface s2 side has many electrons and becomes a negative pole, and the bonding surface s3 side has few electrons and has a positive pole.

  Next, in the p-type semiconductor region 25, since (the area of the bonding surface s3) <(the area of the bonding surface s4), the relationship of (heat capacity of the bonding surface s3) <(heat capacity of the bonding surface s4) is satisfied. For this reason, the bonding surfaces s3 and s4 have a relationship of “warm” and “cold”, the bonding surface s3 side has a small number of holes and a negative pole, and the bonding surface s4 side has a large number of holes and a positive pole. Further, in the n-type semiconductor region 26, the temperature rises quickly because the side of the junction surface s5 is close to the outside air, but the temperature rises slowly with a delay because the side of the junction surface s4 is in contact with the p-type semiconductor region 25. That is, a relationship of (heat capacity of bonding surface s5) <(heat capacity of bonding surface s4) is established. For this reason, the bonding surfaces s4 and s5 have a relationship of “cold” and “warm”, the bonding surface s4 side has many electrons and becomes a negative pole, and the bonding surface s5 side has few electrons and becomes a positive pole.

  Thus, in the entire pnpn junction, the thermoelectric conversion action of each layer is electrically overlapped, so that the Ag electrode 21 side becomes a negative electrode and the Ag electrode 24 side becomes a positive electrode. Also in this case, since the silver (Ag) electrodes 21 and 24 have small electric resistance, the thermoelectromotive force is transmitted to the outside without loss.

  In view of the thermoelectric conversion action as described above, the ratio of the area of the bonding surface s2 or s4 and the area of the bonding surface s3 is preferably as large as possible. This is because if this area ratio is increased, a large difference is generated in the heat capacity, a larger temperature difference is easily generated, and a larger thermoelectromotive force can be obtained.

<Example 4>
FIG. 8 is a view for explaining a method of manufacturing the thermoelectric conversion module 20D of the fourth embodiment, and this figure shows an enlarged view of a portion related to the sintering mold 11. FIG. FIG. 8A is a plan sectional view, and FIG. 8B is a side sectional view. The sintering mold 11 has a shape in which a central portion of columnar graphite is hollowed out into a rectangular shape. A box-shaped lower sintering mold 12 a and a lid-shaped upper sintering mold are formed inside the sintering mold 11. 12b, and a pair of rectangular punches 13a and 13b are inserted above and below.

  As the p-type and n-type thermoelectric conversion semiconductor raw material powders 42 ′ and 43 ′, those similar to those described in FIG. 2 can be used. Preferably, carbon paper is provided so as to cover the inner wall surface of the lower sintered mold 12a, carbon paper is laid on the floor surface, and Ag powders 41 'and 44' are charged in layers. Further, the p-type thermoelectric conversion semiconductor raw material powder 42 ′ is filled on the Ag powder 41 ′. Further, the n-type thermoelectric conversion semiconductor raw material powder 43 ′ is filled on the Ag powder 44 ′. Then, carbon paper is laid on the p-type and n-type thermoelectric conversion semiconductor raw material powders 42 ′ and 43 ′, and the upper sintered mold 12 b is mounted thereon. The set of sintering molds 11 thus obtained is set in the discharge plasma sintering apparatus 1, and each raw material powder is sintered and joined in one step under the same sintering conditions as described in FIG.

  FIG. 9 is a perspective view of the thermoelectric conversion module 20D of the fourth embodiment, and shows an application example to a thermoelectric conversion module capable of detecting a temperature difference. In this thermoelectric conversion module 20D, an Ag electrode 41, a p-type thermoelectric conversion semiconductor 42, an n-type thermoelectric conversion semiconductor 43, and an Ag electrode 44 are integrally sintered and bonded. In this example, both end electrodes 41 and 44 of the thermoelectric conversion module are made of metal (Ag), and a lead wire or the like can be easily soldered. Alternatively, the Ag electrodes 41 and 44 may be placed on the printed wiring and soldered directly. Alternatively, these methods can be used as long as the temperature does not affect the thermoelectric conversion semiconductor composition, such as electric welding or laser welding by laser irradiation in a short time.

  Next, the operation when measuring the temperature difference using such a thermoelectric conversion module 20D will be described. As shown in FIG. 9, when this thermoelectric conversion module 20D is heated from above and cooled from below, the holes move to the cold temperature (electrode 41) side in the p-type thermoelectric conversion semiconductor 42, so that the heating side becomes a negative electrode. The cold side becomes the + pole. Further, in the n-type thermoelectric conversion semiconductor 43, electrons move to the cold temperature (electrode 44) side, so that the heating side becomes a positive electrode and the cold temperature side becomes a negative electrode. Then, in the entire thermoelectric conversion module 20D, these thermoelectric conversion actions are electrically overlapped, so that the Ag electrode 41 side becomes a positive electrode and the Ag electrode 44 side becomes a negative electrode. In this case, since each Ag electrode 41, 44 has a small electrical resistance and a high thermal conductivity, it works optimally as an electrode metal that transmits heat and electrical energy.

<Example 5>
FIG. 10 is a diagram for explaining a method of manufacturing the thermoelectric conversion module of Example 5, and shows an enlarged view of a portion related to the sintering mold 3 of FIG. The thermoelectric conversion module of Example 5 includes FeSi2 based p-type and n-type thermoelectric conversion semiconductor raw material powders 22 'and 23', and one end portion thereof and metal powders 21 'and 24' for electrodes. As a raw material for the intermediate layer, a mixed powder 215 ′ of p-type thermoelectric conversion semiconductor raw material powder 22 ′ and metal powder 21 ′ and a mixed powder 235 ′ of n-type thermoelectric conversion semiconductor raw material powder 23 ′ and metal powder 24 ′ are respectively added. Next, metal powders 21 'and 24' made of a predetermined metal are added, and sintered and joined in one step by a discharge plasma sintering method under the conventional sintering conditions. Hereinafter, the intermediate layer between the p-type thermoelectric conversion semiconductor and the electrode is referred to as a p-side intermediate layer, and the intermediate layer between the n-type thermoelectric conversion semiconductor and the electrode is referred to as an n-side intermediate layer. Therefore, the thermoelectric conversion module of Example 5 has a structure in which an electrode, an n-side intermediate layer, an n-type thermoelectric conversion semiconductor, a p-type thermoelectric conversion semiconductor, a p-side intermediate layer, and an electrode are stacked.

  As shown in FIG. 10, a punch 5b is inserted into the lower portion of the sintering die 3, and preferably a disc-shaped carbon paper C1 is laid on the punch 5b as shown in the inset (a). Further, the carbon paper C2 is arranged in a cylindrical shape on the inner peripheral surface of the sintering mold 3, and the raw material powder is put into the layers in order. For example, electrode metal powder 24 ′ made of silver (Ag), mixed powder 235 ′ of metal powder 24 ′ and n-type thermoelectric conversion semiconductor raw material powder 23 ′ prepared above, n-type thermoelectric conversion semiconductor raw material powder 23 ′, and above The produced p-type thermoelectric conversion semiconductor raw material powder 22 ′, the mixed powder 215 ′ of the metal powder 21 ′ for electrode made of silver (Ag) and the p-type thermoelectric conversion semiconductor raw material powder 22 ′, and the metal powder 21 ′ in this order The carbon paper C6 is put into the carbon paper C2 and the carbon paper C6 is placed on the metal powder 21 '. Then, the punch 5a is inserted into the upper part of the sintering mold 3 from above, and thus a set of the sintering mold 3 is created.

  Carbon paper may be disposed between the powder layers. For example, as shown in FIG. 10, carbon paper C3 is disposed between the metal powder 24 'and the mixed powder 235', and carbon paper C8 is disposed between the mixed powder 235 'and the n-type thermoelectric conversion semiconductor raw material powder 23'. Carbon paper C4 is disposed between the n-type thermoelectric conversion semiconductor raw material powder 23 'and the p-type thermoelectric conversion semiconductor raw material powder 22'. Further, carbon paper C7 is disposed between the p-type thermoelectric conversion semiconductor raw material powder 22 'and the mixed powder 215', and carbon paper C5 is disposed between the mixed powder 215 'and the metal powder 21'.

  For example, under the same sintering conditions as described in FIG. 2, the raw material powders of the sintering mold 3 are sintered and joined in one step, and the thermoelectric conversion module of Example 5 is manufactured. The mixed powder 215 'is sintered to form a p-side intermediate layer, and the mixed powder 235' is sintered to form an n-side intermediate layer. That is, an n-side intermediate layer is formed between the electrode formed by sintering the metal powder 24 ′ and the n-type thermoelectric conversion semiconductor formed by sintering the n-type thermoelectric conversion semiconductor raw material powder 23 ′. Is done. A p-side intermediate layer is formed between the p-type thermoelectric conversion semiconductor formed by sintering the p-type thermoelectric conversion semiconductor raw material powder 22 ′ and the electrode formed by sintering the metal powder 21 ′. Is done.

  In the case of the example of the p-type thermoelectric conversion semiconductor powder and the Ag electrode, the p-side intermediate layer was satisfactorily sintered and bonded when the mass ratio of the p-type thermoelectric conversion semiconductor powder and the Ag powder was 3: 1. On the other hand, when the mass ratio of the p-type thermoelectric conversion semiconductor powder and the Ag powder was 1: 1 or 1: 3, cracks and chipping occurred, and good sintering / bonding could not be obtained. This is presumably because sintering and bonding were not sufficiently performed between the p-side intermediate layer and the Ag electrode due to the wettability of Ag when the Ag ratio of the p-side intermediate layer was large.

  In the case of the n-type thermoelectric conversion semiconductor powder and the Ag electrode, the n-side intermediate layer was satisfactorily sintered and bonded when the mass ratio of the n-type thermoelectric conversion semiconductor powder and the Ag powder was 1: 1. On the other hand, when the mass ratio of the n-type thermoelectric conversion semiconductor powder and the Ag powder was 3: 1, cracking and chipping occurred, and good sintering / bonding could not be obtained.

  By forming the p-side intermediate layer and the n-side intermediate layer, the strength between the electrode and the thermoelectric conversion semiconductor is further strengthened, and the strength between the lead wire and the module is such that there is no p-side intermediate layer and no n-side intermediate layer. Experiments have confirmed that it is even stronger.

  In the experiment, 0.4 g of the Ag electrode, 0.8 g of the mixed powder of the n-side intermediate layer, and 21 g of the n-type thermoelectric conversion semiconductor powder were sintered and bonded into a Φ20 mm cylindrical shape and confirmed. Further, 0.4 g of the Ag electrode, 0.8 g of the mixed powder of the p-side intermediate layer, and 17.2 g of the p-type thermoelectric conversion semiconductor powder were sintered and bonded into a Φ20 mm cylindrical shape and confirmed.

  The intermediate layer is preferably one layer. In an experiment in which a two-layer or three-layer intermediate layer in which the mixing ratio of the thermoelectric conversion semiconductor powder and the metal powder was changed, good sintering / joining could not be obtained due to cracking and chipping.

  The thermoelectric conversion module of the present invention having the above-described features is a thermoelectric conversion in hot spring waste heat power generation, biomass heat utilization power generation, power plant waste heat power generation, automobile waste heat power generation, etc. using the Seebeck effect for converting heat into electricity. It can be used as a module, or as a thermoelectric conversion temperature sensor that detects a temperature change in an air conditioner, a plant, a fire alarm facility, or the like. The thermoelectric conversion module of the present invention can also be used as a thermoelectric conversion module in CPU cooling, electronic equipment cooling, road freezing prevention, snow melting countermeasures in winter, non-Freon refrigerator, etc. using the Peltier effect that converts electricity to heat. .

  In the above embodiments, the thermoelectric conversion module including one or two pairs of pn junctions is specifically described. However, a thermoelectric conversion module including three or more pairs of pn junctions can be similarly configured. Further, the present invention can be applied not only to a pn junction but also to an np junction thermoelectric conversion module.

  Moreover, although Ag powder for constituting an electrode part was laminated in layers in each of the above embodiments, the present invention is not limited to this. Various other shapes of electrodes can be formed by changing the laminated shape of Ag powder or the like.

1 Discharge Plasma Sintering Equipment 2 Vacuum Chamber 3 Sintering Mold 3a Thermocouple 4 Raw Material Powder 5 Punch (Presser)
6 Punch Electrode 7 Special Sintering Power Supply 8 Pressurizing Mechanism 9 Control Unit 10 Measuring Unit 11 Sintering Mold 12a Lower Sintering Mold 12b Upper Sintering Mold 13a, 13b Rectangular Punches 20A-20D Thermoelectric Conversion Modules 21, 24, 41, 44 Metal for electrodes (Ag)
22, 25, 42 p-type thermoelectric conversion semiconductors 23, 26, 43 n-type thermoelectric conversion semiconductors 31a, 31b solder 32a, 32b connection wires 34a, 34b lead terminals 35a, 35b flange portion C carbon paper

Claims (10)

Each thermoelectric conversion semiconductor raw material powder made of FeSi2 p-type and n-type and a plate or powder made of a predetermined metal at least one end thereof are put into a sintering mold, and these are discharged by a discharge plasma sintering method. A method for producing a thermoelectric conversion module, characterized by sintering and joining in one step. The method for producing a thermoelectric conversion module according to claim 1, wherein 4.1 mass% of chromium (Cr) is mixed into the FeSi2 raw material powder to obtain a p-type thermoelectric conversion semiconductor raw material powder. 2. The method of manufacturing a thermoelectric conversion module according to claim 1, wherein 2.4 mass% of cobalt (Co) is mixed into the FeSi2 raw material powder to obtain an n-type thermoelectric conversion semiconductor raw material powder. The method of manufacturing a thermoelectric conversion module according to any one of claims 1 to 3, wherein the predetermined metal is made of silver (Ag) or a silver-based alloy. The method of manufacturing a thermoelectric conversion module according to any one of claims 1 to 3, wherein the predetermined metal is made of nickel (Ni), titanium (Ti), or an alloy mainly composed of these. 6. The sintering and bonding are performed at a pressure of 35 MPa to 70 MPa, a temperature of 923 K (650 ° C.) to 1073 K (800 ° C.), and a time of 300 sec to 3.6 ksec. The manufacturing method of the thermoelectric conversion module of description. Each thermoelectric conversion semiconductor raw material powder made of FeSi2 p-type and n-type and a plate or powder made of a predetermined metal at least one end thereof are put into a sintering mold, and these are discharged by a discharge plasma sintering method. Thermoelectric conversion module characterized by sintering and joining in one stage. The thermoelectric conversion module according to claim 7, wherein the predetermined metal is made of silver (Ag), nickel (Ni), titanium (Ti), or an alloy mainly including any one of them. In the sintering mold, FeSi2 type p-type and n-type thermoelectric conversion semiconductor raw material powders, and at least one end of each thermoelectric conversion semiconductor raw material powder consisting of p-type and n-type and a predetermined metal powder A thermoelectric conversion module, wherein powder is charged, and then powder made of the predetermined metal is charged, and these are sintered and bonded in one step by a discharge plasma sintering method. The thermoelectric conversion module according to claim 9, wherein the predetermined metal is made of silver (Ag), nickel (Ni), titanium (Ti), or an alloy mainly including any one of them.

Images