JP2001267642A - Manufacturing method of thermoelectric conversion module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bonding method in which the thermal / electrical resistance at the bonding portion is small and the bonding yield is improved when electrically bonding the end faces of a bismuth-tellurium-based thermoelectric element. And a method of manufacturing a thermoelectric conversion module having a high density of thermoelectric conversion performance and low loss. A thermoelectric conversion module (6) having at least one pair of p-type and n-type thermoelectric elements (2, 4) and a thermoelectric conversion module (6) electrically connected by electrode layers (5) at opposite end faces of the thermoelectric elements (2, 4). At the time of manufacture, a step of joining an end face metal layer 3 made of a Cu or Al plate to the end faces of the thermoelectric elements 2 and 4 containing a bismuth-tellurium system as a main component by an ultrasonic welding method is included.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a thermoelectric conversion module using a bismuth-tellurium-based material as a thermoelectric element for converting heat and electricity.

[0002]

2. Description of the Related Art In a thermoelectric conversion element pair having a junction in which p-type and n-type thermoelectric semiconductors are electrically joined, if the junction is heated to a high temperature and the other of the thermoelectric element semiconductors is cooled to a temperature difference, There is a phenomenon in which a thermoelectromotive force is generated, and this is called the Seebeck effect. Also, in the above thermoelectric conversion element pair, when a current flows from one thermoelectric semiconductor to the other thermoelectric semiconductor, there is a phenomenon that one junction absorbs heat and the other generates heat, which is called a Peltier effect. ing. Further, when one of the p-type or n-type thermoelectric semiconductor is heated to a high temperature and the other is cooled to flow a current along a temperature gradient, there is a phenomenon that heat is absorbed or generated inside the semiconductor depending on the direction of the current, This is called the Thomson effect.

A thermoelectric conversion device utilizing such an effect has no moving parts that generate vibration, noise, wear, etc.
The present invention can be a simplified energy direct conversion device having features such as simple structure, high reliability, long life and easy maintenance.

A module portion for performing thermoelectric conversion includes at least one thermoelectric element pair having a configuration in which p-type and n-type thermoelectric semiconductors are electrically joined, and each thermoelectric element pair is electrically connected in series.
In general, it is generally thermally connected in parallel. By applying a temperature difference between both ends of the module, a thermoelectric generator utilizing the Seebeck effect to extract an electromotive force depending on the temperature difference, or by applying a voltage to both ends of the module to generate a temperature difference ,
The present invention can be used for a thermoelectric cooling device utilizing the Peltier effect for cooling one end of a module.

When a module having high thermoelectric conversion efficiency is formed, it is a serious problem to manufacture a module having a small loss at a junction between both ends of a thermoelectric element made of p-type and n-type thermoelectric semiconductors. For example, in a thermoelectric power generation module, a junction between a p-type thermoelectric element and an n-type thermoelectric element,
Alternatively, a junction between each thermoelectric element and an electrode is required to have the following characteristics.

In many cases, thermal energy is transmitted from a heat source through a junction at a high-temperature end of a module to an element portion, so that a small thermal resistance is required at the junction.

Further, the power generated depending on the temperature difference applied to the element portion is taken out through the junction of the element pair electrically connected in series, or the module is generated depending on the power input to the element. Since heat is absorbed and dissipated at both ends, it is required that the electric resistance at the junction be small.

Furthermore, since the junction at the high-temperature end particularly reaches a high temperature, it does not peel off at a high temperature and does not deteriorate the element characteristics due to the progress of the diffusion reaction at the junction.
Excellent heat durability is also required.

In general, a thermoelectric conversion module has a configuration in which several hundred thermoelectric elements are electrically connected in series and thermally in parallel. Therefore, the yield of forming a junction increases the production yield of the module. It depends.

A bismuth-tellurium compound is known as a thermoelectric element material having a high conversion efficiency, and a thermoelectric conversion module using this thermoelectric element has been manufactured. The junction between the electrode and the thermoelectric element is made as follows. I have.

(1) A method of soldering an electrode layer made of a Cu plate to an end face of a thermoelectric element arranged in a desired pattern.

(2) For the purpose of not lowering the electric resistance of the joint, improving the thermal durability of the joint, and improving the wettability of the solder, a nickel plated layer is formed and then a Cu plate is formed. A method of soldering an electrode layer.

(3) A method of forming an electrode layer made of Al by thermal spraying so that adjacent end faces of bismuth-tellurium-based thermoelectric elements arranged in a desired pattern are electrically connected to each other.

[0014]

However, the above (1)
In the prior art, there is a problem that in a thermoelectric conversion module in which hundreds of thermoelectric elements are arranged, it is troublesome to evenly solder the end faces of the thermoelectric elements. In addition, even at one location, if a poor junction between the thermoelectric element end face and the solder has poor wettability, the portion becomes an electric resistance, and thus the thermoelectric conversion performance is degraded. Further, at a joint having a high electric resistance, local heat is generated due to the electric resistance, so that the thermoelectric element is cracked or the solder material is deteriorated, thereby lowering the durability. Furthermore, the smaller the distance between adjacent thermoelectric elements, the higher the performance density of the module can be.However, if solder protrudes from the adjacent thermoelectric element that needs to be insulated from the end face of the thermoelectric element, a few Since a part of the configuration in which one hundred thermoelectric elements are electrically connected in series is short-circuited, the thermoelectric conversion performance is significantly reduced. As a result, there is a problem that the manufacturing yield is reduced. Further, at the time of joining, the molten solder directly contacts the bismuth-tellurium-based element end face, so that tellurium, bismuth, Se, Sb, and other additives, which are constituent elements of the thermoelectric element, are melted into the solder material. . As a result, there is a problem that the durability of the solder portion is reduced, for example, the solder composition is changed, the heat resistance of the solder is reduced, and cracks are easily generated by a thermal shock.

Further, the prior art (2) is characterized in that the end face of the thermoelectric element is nickel-plated to improve the wetting of the Pb-based solder material and to suppress the diffusion reaction between the solder material and the thermoelectric element material. However, there is a problem that the heat resistance of the thermoelectric conversion module is limited by the softening temperature of the Pb-based solder material. Another problem is that the solder contains Pb, which is a harmful substance. In addition, when Pb-less solder is used, there is a problem that the wettability on the nickel plating layer is not always good, and the heat resistance of the thermoelectric conversion module is significantly reduced due to the low melting point of the solder.

Further, the prior art (3) has a feature that the thermoelectric conversion module has high heat resistance because no solder is used, but it is difficult to form electrodes in a pattern with a small gap between thermoelectric elements. Therefore, there is a problem that the thermoelectric conversion performance density is lowered. In addition, in order to form a thick electrode layer by thermal spraying, it is necessary to previously fix the thermoelectric element by inserting and fixing it in an electrically insulating frame, but the electrical insulating property that can withstand the thermal spraying process is required. Since the thermal conductivity of the frame material becomes relatively high, when the heat flow from the high-temperature end to the low-temperature end of the module increases, the ratio of the flow of the frame material other than the thermoelectric element increases. The problem is that the conversion performance is reduced.

[0017]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and solves the above-mentioned problems. The object of the present invention is to provide a joining method in which the thermal / electrical resistance of the element is small and the joining yield is improved, and at the same time, to provide a method of manufacturing a thermoelectric conversion module having a high density of thermoelectric conversion performance and low loss. It is.

[0018]

According to a method of manufacturing a thermoelectric conversion module according to the present invention, a plate-like end face metal layer made of Cu or Al is formed on an end face of a thermoelectric element mainly composed of bismuth-tellurium. It is characterized by joining by a welding method. That is, as described in claim 1, a thermoelectric conversion module having a configuration in which at least one pair or more of p-type and n-type thermoelectric elements are electrically connected by electrode layers on opposite end faces of the thermoelectric elements. Is characterized by including a step of joining an end face metal layer made of a Cu or Al plate to an end face of a thermoelectric element containing a bismuth-tellurium system as a main component by an ultrasonic welding method.

And, as described in claim 2,
A is attached to the end face of the thermoelectric element mainly containing bismuth-tellurium.
After the formation of the intermediate layer made of 1 or Ni, a step of joining the end face metal layer made of the Cu or Al plate by an ultrasonic welding method can be included.

Further, as set forth in claim 3, an end surface metal layer made of a Cu or Al plate having a thickness of 0.1 to 1 mm is provided on the end surface of the thermoelectric element mainly composed of bismuth-tellurium. It can be made to join by a welding method.

Further, as described in claim 4, an intermediate layer made of Al or Ni having a thickness of 0.01 to 0.1 mm is provided on an end face of the thermoelectric element mainly containing bismuth-tellurium. After the formation, an end face metal layer made of a Cu or Al plate having a thickness of 0.1 to 1 mm can be joined by an ultrasonic welding method.

Further, according to a fifth aspect of the present invention, in the method for manufacturing a thermoelectric conversion module, Cu or A
After joining the end face metal layers made of the 1 plate by the ultrasonic welding method, the end face metal layers of the adjacent thermoelectric elements can be electrically connected to each other by a connection or the like.

The step of bonding the end face metal layer to the end face of the thermoelectric element may be performed for each thermoelectric element alone and then arranged in a desired pattern.
It is also possible to join the end faces of the arranged and fixed thermoelectric element group.

The thermoelectric element having the end face metal layer of the present invention joined to the end face can be electrically connected to an adjacent thermoelectric element by, for example, soldering an electrode plate on a Cu plate. In this case, Al or Cu on the thermoelectric element end face is used.
Since the end face metal layer made of the plate is soldered to the electrode metal, poor joining due to poor wettability of the solder is less likely to occur. In addition, it is not necessary to consider the dissolution of components from the thermoelectric element mainly composed of bismuth-tellurium, and it is possible to select a lead-less solder material in view of the solder melting point and the required heat resistance of the thermoelectric conversion module. Become.

Generally, the welding method includes a fusion welding method and an electric resistance welding method other than the ultrasonic welding method, and the metal can be easily joined in the air without requiring a vacuum vessel or atmosphere control in the joining process. Has features. However, there is a problem in that when the joining portion is locally heated and cooled rapidly, joining ceramics or semiconductors having a high melting point and high brittleness cannot be joined or cracks occur.

Then, as a result of earnest research on welding of metal to the end face of the bismuth-tellurium-based thermoelectric element, it was found that the ultrasonic welding method can control the ultrasonic energy to join the bismuth-tellurium-based thermoelectric element. .

In the ultrasonic welding method applied in the present invention, generally known devices used for welding metals or welding plastics can be used. However, it is important to reduce the input of ultrasonic waves as compared with a general ultrasonic device. Here, the input energy of the ultrasonic wave is
The shape and size of the tip of the terminal called the horn anvil, the composition and hardness of the thermoelectric element, Cu and A
Although it largely changes depending on the thickness of the l-plate, when the element end face is 1 to 25 mm ² , 30 J / m
It can be m ² or less is generally well bonded.

The end face metal layer is an Al or Cu plate, and preferably has a thickness of 0.1 to 1 mm. And 0.
If the thickness is less than 1 mm, the end face metal layer is greatly deformed by the unevenness of the terminal (anvil) of the joining device, and the joining tends to be difficult due to cracks in the thermoelectric element. In addition, when it exceeds 1 mm, 30 J /
large ultrasonic energy exceeding ² mm is required,
Cracks tend to occur in the thermoelectric element, making joining difficult. In addition, since the thickness of the junction between the end face of the thermoelectric conversion module and the thermoelectric element increases, the thermal resistance increases and the thermoelectric conversion characteristics tend to decrease.

In the present invention, an intermediate layer made of Al or Ni can be previously formed on the end face of the thermoelectric element by plating, vapor deposition, ion sputtering, or the like. When joining the end face metal layers, it is also possible to insert and join an intermediate layer foil between the end face metal plate and the thermoelectric element. In this case, the thickness of the intermediate layer is 0.01 to 0.1 mm
Is good. And when it is thinner than 0.01mm,
Joining with a smaller joining energy is not preferable because the effect of preventing cracks from being generated in the thermoelectric element is reduced, but the manufacturing process tends to be complicated because the number of steps for forming the intermediate layer increases. Also, 0.1mm
If the thickness is larger, the adjustment of the input of the bonding energy becomes unstable, and the production yield tends to decrease, which is not preferable.

As the thermoelectric element applied in the present invention, a known bismuth-tellurium-based thermoelectric semiconductor can be used.
It can be formed by a melting method, a hot press sintering method, or the like.

[0031]

The method of manufacturing a thermoelectric conversion module according to the present invention has a structure in which at least one or more pairs of p-type and n-type thermoelectric elements are electrically connected to each other at opposite end faces of the thermoelectric element by electrode layers. In manufacturing the thermoelectric conversion module, since the end face of the thermoelectric element having a bismuth-tellurium system as a main component, a step of joining an end face metal layer made of a Cu or Al plate by an ultrasonic welding method was included,
A metal layer can be formed on both end surfaces of the bismuth-tellurium-based thermoelectric element by a simple method. In addition, by using the ultrasonic welding method, the step of removing the oxide on the joining surface of the thermoelectric element and the plate material for the end face metal layer in the joining step can be simplified, so that the joining can be performed easily and stably. The formation can take place. Further, a remarkably excellent effect such as the ability to form a joint having low electrical and thermal resistance can be obtained.

Then, after forming an intermediate layer made of Al or Ni on the end face of the thermoelectric element mainly containing bismuth-tellurium, Cu or A
By including the step of joining the end face metal layer made of the 1 plate by the ultrasonic welding method, it is possible to suppress the occurrence of cracks in the thermoelectric element at the time of joining, and it is possible to improve the production yield. Significant effects are achieved.

[0033] As described in claim 3, the thickness of the thermoelectric element having a thickness of 0.
By joining an end face metal layer made of a Cu or Al plate of 1 to 1 mm by an ultrasonic welding method,
An extremely excellent effect is obtained in that the deformation of the end face metal layer is small, the soldering to the electrode is easy, and the crack generation rate of the bismuth-tellurium-based thermoelectric element can be reduced.

Furthermore, an intermediate layer made of Al or Ni having a thickness of 0.01 to 0.1 mm is formed on the end face of the thermoelectric element containing bismuth-tellurium as a main component. Thereafter, by joining the end face metal layer made of a Cu or Al plate having a thickness of 0.1 to 1 mm by an ultrasonic welding method, it is possible to stably supply ultrasonic energy at the time of joining. Therefore, a remarkably excellent effect that the production yield can be improved is brought about.

According to a fifth aspect of the present invention, in the method for manufacturing a thermoelectric conversion module, the end face of the thermoelectric element containing a bismuth-tellurium system as a main component may be made of Cu or A
After joining the end face metal layers composed of 1 plate by ultrasonic welding, by connecting the end face metal layers of adjacent thermoelectric elements electrically by wire connection or the like, when soldering the electrode metal, A thermoelectric conversion module can be manufactured by selecting a lead-free solder having high heat resistance without considering the reaction with the thermoelectric element and the wettability.
In addition, since the soldering between the end face metal layer and the electrode is a soldering of metal to metal, it is easy to control the soldering conditions and stably perform the soldering. A remarkably excellent effect that the occurrence rate of bonding failure can be reduced is brought about.

[0036]

Hereinafter, embodiments of the present invention will be described.
It goes without saying that the present invention is not limited to only such an embodiment.

Example 1 The composition was Bi ₂ (Te-Se)
_The n-type thermoelectric semiconductor No. 3 was sintered by a hot press sintering method. Then, the end face was 3.5 mm from the sintered plate.
Each of the thermoelectric elements having a height of 3.5 mm and a height of 5 mm was cut. Then, an Al vapor-deposited film or a Ni-plated film was applied to both end surfaces of some of the thermoelectric elements. An Al foil having a thickness of 0.015 mm was prepared for the intermediate layer. Furthermore, a 3 mm × 3 mm Al plate and a Cu plate were prepared as end surface metal layers.

Table 1 summarizes the configuration, bonding conditions, and results of the respective bonding tests.
At this time, the joining result was judged visually,
An example in which good bonding was achieved with good reproducibility will be described. In addition, if the bonding result is △, it can be bonded, but the element is cracked,
An example in which some parts could not be joined and the reproducibility was insufficient will be described.

[0039]

[Table 1]

Then, for Examples of Table 1 in Table 1, Cu wires for lead were stuck on the surfaces of the end metal layers at both ends with silver paste, and the resistance at room temperature was measured from the current-voltage characteristics between the end metal. As a result, while the resistance of the single element is 0.025Ω, the thermoelectric conversion element according to the present invention including the end face metal layer and the junction between the end face metal layer and the thermoelectric element has a resistance of 0.025Ω.
025 ± 0.001Ω. In other words, it indicates that a good junction with an extremely small electric resistance at the junction was formed.

(Embodiment 2) As in Embodiment 1, FIG.
As shown in FIG. 1A, a p-type sintered body 1 having a composition of (Bi-Sb) ₂ Te ₃ is sintered and cut to form a p-type thermoelectric element 2 as shown in FIG. 1B. did. Then, Example 1-2
FIG. 1 shows a p-type thermoelectric element and an n-type thermoelectric element, respectively.
As shown in (c), the Cu plate 3 was joined to form a thermoelectric element with an end face metal layer. Subsequently, as shown in FIG. 1D, four pairs of p-type and n-type thermoelectric elements (2, 4) are alternately arranged, and the adjacent end face metal layers (3, 3) are electrically connected to each other. A Cu electrode 5 having a thickness of 0.2 mm was soldered so as to be serially connected to obtain a thermoelectric conversion module 6 as shown in FIG. At this time, Ag-Sn solder was used as the solder material.

As described above, by including the step of bonding the end face metal layer according to the present invention, it is possible to use a solder which is highly versatile as a Pb-less solder but has poor wettability for a bismuth-tellurium-based element. A thermoelectric conversion module could be manufactured.

[Brief description of the drawings]

FIGS. 1A to 1C show examples of a manufacturing process of a thermoelectric conversion module.
It is a slope explanatory view divided and shown to (e).

[Description of Signs] 1 p-type sintered body 2 p-type thermoelectric element 3 Cu plate 4 n-type thermoelectric element 5 Cu electrode 6 thermoelectric conversion module

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[Procedure amendment]

[Submission date] March 16, 2000 (200.3.1.1)
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005] If the thermoelectric conversion efficiency is to form a high module, at the junction of the thermoelectric elements both end portions consisting of thermoelectric semiconductor of p-type and n-type, to produce a low loss module is an important issue. For example, in a thermoelectric power generation module, a junction between a p-type thermoelectric element and an n-type thermoelectric element,
Alternatively, a junction between each thermoelectric element and an electrode is required to have the following characteristics.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

The thermoelectric element having the end face metal layer of the present invention joined to the end face can be electrically connected to an adjacent thermoelectric element by, for example, soldering a Cu plate- shaped electrode plate. In this case, Al or Cu on the thermoelectric element end face is used.
Since the end face metal layer made of the plate is soldered to the electrode metal, poor joining due to poor wettability of the solder is less likely to occur. In addition, it is not necessary to consider the dissolution of components from the thermoelectric element mainly composed of bismuth-tellurium, and it is possible to select a lead-less solder material in view of the solder melting point and the required heat resistance of the thermoelectric conversion module. Become.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

In the present invention, an intermediate layer made of Al or Ni can be previously formed on the end face of the thermoelectric element by plating, vapor deposition, ion sputtering, or the like. Further, at the time of bonding of the end face metal layers can be joined by inserting a foil intermediate layer between the end surface metal plate and the thermoelectric elements. In this case, the thickness of the intermediate layer is 0.01 to 0.1 mm
Is good. And when it is thinner than 0.01mm,
Joining with a smaller joining energy is not preferable because the effect of preventing cracks from being generated in the thermoelectric element is reduced, but the manufacturing process tends to be complicated because the number of steps for forming the intermediate layer increases. Also, 0.1mm
If the thickness is larger, the input adjustment of the bonding energy becomes unstable, and the production yield tends to decrease, which is not preferable.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 35/32 H01L 35/32 A

Claims (5)

[Claims] At least one pair of p-type and n-type thermoelectric elements and bismuth-tellurium for manufacturing a thermoelectric conversion module having a configuration in which the thermoelectric elements are electrically connected to each other at opposite end surfaces by electrode layers. A method for manufacturing a thermoelectric conversion module, comprising joining an end face metal layer made of a Cu or Al plate to an end face of a thermoelectric element mainly composed of a system by ultrasonic welding. 2. The method for manufacturing a thermoelectric conversion module according to claim 1, wherein an intermediate layer made of Al or Ni is formed on an end face of the thermoelectric element containing bismuth-tellurium as a main component, and then a Cu or Al plate is formed. A method for manufacturing a thermoelectric conversion module, comprising joining an end face metal layer by ultrasonic welding. 3. The method for producing a thermoelectric conversion module according to claim 1, wherein the end face of the thermoelectric element containing bismuth-tellurium as a main component has a thickness of 0.1 to 1 mm.
Alternatively, a method for manufacturing a thermoelectric conversion module, wherein an end face metal layer made of an Al plate is joined by an ultrasonic welding method. 4. The method for manufacturing a thermoelectric conversion module according to claim 2, wherein the thermoelectric element having a bismuth-tellurium system as a main component has an end face made of Al or Ni having a thickness of 0.01 to 0.1 mm. After forming the layer, thickness 0.1 ~
A method for manufacturing a thermoelectric conversion module, comprising joining an end face metal layer made of a 1 mm Cu or Al plate by ultrasonic welding. 5. The method for manufacturing a thermoelectric conversion module according to claim 1, wherein the thermoelectric element mainly composed of bismuth-tellurium is provided with Cu or A
A method for manufacturing a thermoelectric conversion module, comprising: bonding an end face metal layer made of a single plate by ultrasonic welding, and then electrically connecting end face metal layers of adjacent thermoelectric elements.