JP2018125360A - Thermoelectric conversion module and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoelectric conversion module which is high in bond strength of a bonding layer that bonds between a thermoelectric conversion element and an electrode member, and which is also excellent in electrical conductivity and thermal conductivity, and a method of manufacturing the same.SOLUTION: In a thermoelectric conversion module, a nickel-containing layer is provided on a surface of a thermoelectric conversion element and/or an electrode member; a conductive bonding layer bonding between the thermoelectric conversion element and the electrode member is a sintered body of a composite silver nanoparticle that has an organic coating layer comprising one or more of a 1-12C alcohol molecule derivative, an alcohol molecule residue, or an alcohol molecule, around silver nuclei comprising an aggregate of silver atoms and having an average particle size in the range of 1-20 nm; and bonding strength by the bonding layer is 20 MPa or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a structure of a thermoelectric conversion module that converts thermal energy into electric energy, and in particular, a thermoelectric element in which a conductive bonding layer for bonding a thermoelectric conversion element and an electrode member is composed of a sintered body of composite silver nanoparticles. The present invention relates to a conversion module and a manufacturing method thereof.

  In recent years, thermoelectric power generation that can directly convert exhaust heat into electrical energy is known as one of the methods for reducing environmental problems such as depletion of energy resources and global warming.

  Thermoelectric conversion materials used for thermoelectric power generation are known as materials that can directly convert heat into electricity. For example, when one end of the thermoelectric conversion material is set to a high temperature and the other end is set to a low temperature, an electromotive force is generated between the end portions according to a temperature difference between the high temperature portion and the low temperature portion. The electromotive force generated between the end portions of this material is called thermoelectromotive force, and such an effect is called Seebeck effect. In the Seebeck effect, the direction of the current is reversed by increasing or decreasing the temperature of the bonding layer of the thermoelectric conversion element. In addition, when a current is passed from the other end of the thermoelectric conversion material, a phenomenon in which a temperature difference occurs between both ends is called a Peltier effect, and an element having these effects is called a thermoelectric conversion element. Thermoelectric conversion materials are generally known as n-type semiconductors in which carriers excited by heat are electrons and p-type semiconductors in holes. These thermoelectric conversion elements are alternately joined via electrodes. Thus, a configuration of a π-type thermoelectric conversion module is well known. The π-type thermoelectric conversion module is configured by joining one end of a p-type semiconductor and one end of an n-type semiconductor with an electrode, and when the joining layer is at a high temperature and the other end of the p-type semiconductor and the n-type semiconductor is at a low temperature. The electromotive force generated between the end portions of the p-type semiconductor and the n-type semiconductor can be efficiently extracted according to the temperature difference between the high temperature portion and the low temperature portion.

The thermoelectric conversion module as described above has features such as no drive unit, simple structure, and maintenance-free characteristics. For example, it has been studied for use in industrial furnaces such as blast furnaces and incinerators, automobile-related products, etc. And when it attaches to these products, it is assumed that a thermoelectric conversion module generates electric power in a 300-600 degreeC high temperature environment.
However, in the high-temperature environment, stress is generated in the bonding layer that joins the thermoelectric conversion element and the electrode member due to a difference in thermal expansion between the thermoelectric conversion element and the electrode member in the thermoelectric conversion module, and the bonding layer is broken. There is concern about being done. In addition, the stress generated in the bonding layer tends to increase as the operating environment temperature increases, or as the linear expansion coefficient difference between the thermoelectric conversion element, the bonding material, and the electrode increases. There is also a concern that vibration and impact are added to the thermal stress generated in the module to promote the destruction of the bonding layer.
Therefore, it is necessary that the bonding layer has high bonding strength (bonding reliability) and does not adversely affect the conductivity and thermal conductivity even in the high temperature environment of 300 to 600 ° C.

Regarding the configuration of the bonding layer, for example, cream solder is applied to the electrode surface by screen printing, and the electrode and the thermoelectric conversion element are bonded with the cream solder (Patent Document 1). A method of forming a conductive film (such as an electroless Ni plating layer) and soldering the electrode to the electrode through this conductive film (Patent Document 2) is described.
However, the soldering described in Patent Documents 1 and 2 cannot satisfy the heat resistance required for the thermoelectric conversion module using a high-temperature heat source, and as a result, the bonding between the thermoelectric conversion element and the electrode. There is a concern that the bonding reliability and the like of the layer may decrease.
Further, metal brazing materials such as silver brazing are known as materials constituting the bonding layer. Silver, which is the main component of silver solder, has the property of being excellent in electrical conductivity and thermal conductivity. On the other hand, it is necessary to heat to a high temperature exceeding 780 ° C. in the joining process. There is a concern that it may be damaged.

In addition to silver brazing, an active metal containing as a main component a two-element alloy of Ag and Cu, and containing 0.1 to 10% by mass of at least one active metal selected from the group consisting of Ti, Zr and Hf Brazing material (patent document 3), containing silver and copper as main components, at least one element A selected from indium, zinc and tin, and at least one selected from titanium, zirconium, hafnium and niobium The content of the copper is 35% by mass or more and 50% by mass in 100% by mass of all the components including the element B and at least one element C selected from molybdenum, osmium, rhenium, and tungsten, and constituting the bonding layer. % Or less brazing material (Patent Document 4) is also known.
Although these brazing materials can keep the processing temperature at the time of bonding lower than in the case of silver brazing, they are conductive because they use materials that have lower conductivity and thermal conductivity than silver. There is a concern that it is inferior in terms of heat conductivity.

In addition, it is known that the thermoelectric conversion element and the electrode member are provided with a metal coating on the surface in order to enhance durability, and among them, the nickel coating containing nickel is excellent in protection and conductivity. It is known.
However, the bonding strength of silver to nickel is low. For example, even if a bonding layer can be formed between the thermoelectric conversion element having the nickel coating on the surface and the electrode member using silver brazing, if a light impact is applied. There was a problem that the bonding layer was damaged.

  Thus, in the thermoelectric conversion module, as a bonding layer provided between the thermoelectric conversion element having a nickel-containing layer on the surface and the electrode member, when the constituent material contains silver, the bonding strength is high, and It has not yet been achieved to obtain a thermoelectric conversion module excellent in conductivity and thermal conductivity.

JP 2001-168402 A JP 2001-352107 A JP 2006-157749 A JP 2012-119379 A

  An object of the present invention is to provide a thermoelectric conversion module having a high bonding strength of a bonding layer for bonding a thermoelectric conversion element and an electrode member, and having excellent conductivity and thermal conductivity, and a method for manufacturing the same.

  As a result of intensive studies to achieve the above object, the inventors of the present invention have gathered silver atoms as a bonding layer for bonding between a thermoelectric conversion element having a nickel-containing layer on the surface and an electrode member. Composite silver having an organic coating layer composed of one or more alcohol molecule derivatives, alcohol molecule residues, or alcohol molecules having 1 to 12 carbon atoms around a silver nucleus having an average particle diameter of 1 to 20 nm. When a nanoparticle sintered body is used and the sintering temperature is adjusted to a range of 350 to 450 ° C., the bonding strength to the nickel-containing layer provided on the surface of the thermoelectric conversion element and / or electrode member is significantly improved. As a result, the present inventors have found the phenomenon to be performed for the first time and have completed the present invention.

That is, the gist of the present invention is as follows.
(1) a thermoelectric conversion element for converting a temperature difference into electric power;
An electrode member for taking out the electric power converted by the thermoelectric conversion element;
A thermoelectric conversion module having a conductive bonding layer for bonding the thermoelectric conversion element and the electrode member,
A nickel-containing layer is provided on the surface of the thermoelectric conversion element and / or the electrode member in contact with the bonding layer;
The bonding layer is a kind of alcohol molecule derivative, alcohol molecule residue, or alcohol molecule having 1 to 12 carbon atoms around a silver nucleus having an average particle diameter of 1 to 20 nm made of an aggregate of silver atoms. It is a sintered body of composite silver nanoparticles having an organic coating layer composed of the above,
A thermoelectric conversion module characterized in that the bonding strength by the bonding layer is 20 MPa or more,
(2) a thermoelectric conversion element for converting a temperature difference into electric power;
An electrode member for taking out the electric power converted by the thermoelectric conversion element;
A method of manufacturing a thermoelectric conversion module, comprising: a conductive bonding layer that bonds the thermoelectric conversion element and the electrode member;
Between the thermoelectric conversion element and the electrode member, after applying a nano silver paste composed of composite silver nanoparticles and a volatile solvent, having a step of sintering at 350 to 450 ° C.,
A nickel-containing layer is provided on the surface of the thermoelectric conversion element and / or the electrode member in contact with the bonding layer;
The composite silver nanoparticles are an alcohol molecule derivative having 1 to 12 carbon atoms, an alcohol molecule residue, or an alcohol molecule around a silver nucleus having an average particle size of 1 to 20 nm composed of an aggregate of silver atoms. A method for producing a thermoelectric conversion module, which is a composite silver nanoparticle having an organic coating layer composed of one or more of the following:
About.

  According to the thermoelectric conversion module of the present invention, the joining layer joining the thermoelectric conversion element having the nickel-containing layer and the electrode member on the surface has high joining strength, and has excellent conductivity and thermal conductivity. Therefore, it can be installed in various members such as industrial furnaces such as blast furnaces and incinerators, automobile-related products, etc., and the exhaust heat discharged from the members can be efficiently converted into electricity.

It is sectional drawing which shows typically the structure of the thermoelectric conversion module 1 by one Embodiment of this invention. 5 is a graph showing the measurement results of bonding strength of an adhesive layer, which was performed in Test Example 1.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, although embodiment of this invention is described based on drawing below, those drawings are provided for illustration and this invention is not limited to those drawings.

  FIG. 1 is a cross-sectional view showing the structure of a thermoelectric conversion module according to an embodiment of the present invention. The thermoelectric conversion module 1 shown in the figure has a plurality of p-type thermoelectric conversion elements 2 and a plurality of n-type thermoelectric conversion elements 3. These p-type thermoelectric conversion elements 2 and n-type thermoelectric conversion elements 3 are alternately arranged on the same plane, and the entire module is arranged in a matrix to constitute a thermoelectric conversion element group. An n-type thermoelectric conversion element 3 is adjacent to one p-type thermoelectric conversion element 2.

The p-type thermoelectric conversion element 2 and the n-type thermoelectric conversion element 3 can convert a temperature difference into electric power. There are various materials for the thermoelectric conversion element, and silicide-based materials, oxide-based materials, skutterudites (intermetallic compounds of transition metals and pnictogens), half-Whistlers, and the like can be used. Among them, silicide materials such as MnSi _1.73 and Mg ₂ Si, oxide materials such as zinc oxide (ZnO), strontium titanate (SrTiO ₃ ), and sodium cobaltate (NaCo ₂ O ₄ ) are 300 to 600 ° C. High thermoelectric performance can be exhibited even under high temperature conditions.

  A first electrode member 4 that connects the p-type thermoelectric conversion elements 2 and one n-type thermoelectric conversion element 3 adjacent to the p-type thermoelectric conversion elements 2 is disposed. On the other hand, a second electrode member 5 for connecting these elements is disposed below one p-type thermoelectric conversion element 2 and one n-type thermoelectric conversion element 3 adjacent thereto. Moreover, the 1st electrode member 4 and the 2nd electrode member 5 are arrange | positioned in the state which shifted | deviated by one element, By making such arrangement | positioning, p-type thermoelectric conversion element 2, n-type thermoelectric conversion A direct current flows in the order of the element 3, the p-type thermoelectric conversion element 2, the n-type thermoelectric conversion element 3.

  The material constituting the first and second electrode members 4 and 5 is preferably a metal material containing at least one selected from Cu, Ag, Fe and Ni as a main component. When these metal materials are bonded to the thermoelectric conversion elements 2 and 3, the metal materials exhibit a function of relieving thermal stress, thereby bonding the first and second electrode members 4 and 5 and the thermoelectric conversion elements 2 and 3. It is possible to improve the reliability against thermal stress of the part, for example, thermal cycle characteristics, and further, since the metal material mainly composed of Cu, Ag, Fe, Ni is excellent in conductivity, for example, the thermoelectric conversion module 1 generates power. Can be taken out efficiently.

  The p-type and n-type thermoelectric conversion elements 2 and 3 and the first and second electrode members 4 and 5 are joined via a joining layer 6, respectively. For this reason, the p-type and n-type thermoelectric conversion elements 2 and 3 are electrically and mechanically connected to the first and second electrode members 4 and 5 via the bonding layer 6.

A nickel-containing layer 7 is provided on the surfaces of the thermoelectric conversion elements 2 and 3 and / or the electrode members 4 and 5 that are in contact with the bonding layer 6. As shown in FIG. 1, the nickel-containing layer 7 may be provided on all the surfaces of the thermoelectric conversion elements 2 and 3 and the electrode members 4 and 5. It may be provided on any of the surfaces of the electrode members 4 and 5.
Examples of the material constituting the nickel-containing layer 7 include nickel, Ni—P alloy, Ni—B alloy, Ni—W alloy, and Ni—Fe alloy.
The nickel-containing layer 7 can be provided by performing a so-called plating process on the surfaces of the thermoelectric conversion elements 2 and 3 or the surfaces of the electrode members 4 and 5.
The plating method may be a known method and is not particularly limited.
Further, when nickel is contained in the surface of the thermoelectric conversion elements 2, 3 or the electrode members 4, 5, the surface is also included in the nickel-containing layer 7.

  The bonding layer 6 includes an alcohol molecule derivative, an alcohol molecule residue, or an alcohol molecule having 1 to 12 carbon atoms around a silver nucleus having an average particle diameter of 1 to 20 nm composed of an aggregate of silver atoms. It is composed of a sintered body of composite silver nanoparticles having one or more organic coating layers. With this configuration, the bonding strength of the bonding layer 6 is increased, and excellent conductivity and thermal conductivity are provided.

  The silver particle diameter of the composite silver nanoparticles is 1 to 20 nm, and the particle diameter of the composite silver nanoparticles themselves increases by the thickness of the alcohol organic coating layer, but the number of carbons is limited to 1-12. Its thickness is not so large. The smaller the number of carbon atoms, the smaller the thickness, and at the same time, the silver nucleus weight ratio increases and the bonding strength increases.

  The silver core particle diameter of the composite silver nanoparticles can be confirmed by observing the composite silver nanoparticles with a high-resolution transmission electron microscope. For example, in the composite silver nanoparticles described in International Publication No. 2009/090846, the composite silver nanoparticles are in a monodispersed state when photographed with a transmission electron microscope JEM-2000FX with an acceleration voltage of 200 kV installed at Kyoto University. A lattice image is confirmed in the silver nuclei, and the diameter of the silver nuclei is in the range of 1 to 20 nm, the lattice spacing is 0.24 nm, and it is confirmed that it matches the spacing of the (111) plane of bulk silver. From this result, it is known that the silver nucleus is not polycrystalline but is a single crystal of silver or a state close to a single crystal. Therefore, composite silver nanoparticles whose silver nuclei are coated with alcohol-derived substances are so crystalline that the lattice image is observed, and as a result, there are almost no grain boundaries inside the silver nuclei. And has high electrical conductivity and high thermal conductivity.

The composite silver nanoparticles have an organic coating layer around the silver core, and the organic coating layer is composed of alcohol having 1 to 12 carbon atoms (C number). In comparison, the alcohol molecular weight is relatively smaller than that of the prior art, and since the amount of exhaust gas during firing is small, the amount of voids generated is reduced, the bonding strength is high, and the silver nucleus weight ratio increases. Since the organic coating layer is composed of an alcohol-derived component, it is safe even if it adheres to the skin of the hand, and is extremely safe and effective for environmental conservation because only CO ₂ and H ₂ O are diffused by firing. is there. Alcohol molecule derivatives are all alcohol derivatives derived from alcohol molecules and include carboxylic acids, carboxylic acid groups, alkoxides, alkoxide groups, and the like. An alcohol molecule residue is a residue from which some components of an alcohol molecule are separated, including alkoxides and alkoxide groups, and other cleavage residues. The alcohol molecule is the alcohol molecule itself.

In the organic coating layer, when the molecular formula of the alcohol is C _n H _{2n + 1} OH, the alkoxide group is C _n H _{2n + 1} O, and even a lower alkoxide group corresponds to the alkoxide group. The alkoxide group may be called an alcohol molecule residue, but may be called an alcohol molecule derivative. When the molecular formula of the alcohol is C _n H _{2n + 1} OH, the carboxylic acid group is C _n-1 H _2n-1 COO, but it may be a lower carboxylic acid group. This carboxylic acid group is contained in the alcohol molecule derivative.
When the organic coating layer contains a carboxylic acid group or an alkoxide group, the composite silver nanoparticles are extremely safe. Moreover, the organic coating layer after production | generation changes with time, may become a carboxylic acid group, may become an alkoxide group, or may change into those mixed layers. C _n H _{2n + 1} O is an alkoxide group in a narrow sense, but in the present invention, it is used in a broad sense when referred to as an alkoxide-coated composite silver nanoparticle, and the composite silver nanoparticle having the alcohol-derived organic coating layer is referred to as “Cn H _{2n + 1} O”. means. Since the organic coating layer materials are all derived from alcohol, and the safety of alcohol is extremely high compared to other organic substances, the composite silver nanoparticles used in the present invention are safe, environmentally safe and easy to handle. Guaranteed.

The composite silver nanoparticles can be produced by the method described in WO2009 / 090846.
For example, silver salt fine particles are mixed in an alcohol solvent having 1 to 12 carbon atoms to prepare an alcohol solution, and the alcohol solution is heated in a reaction chamber at a predetermined generation temperature PT for a predetermined generation time, so that the alcohol The silver salt fine particles are reduced with a solvent to form silver nuclei having an average particle size of 1 to 20 nm, and around the silver nuclei from one or more of alcohol molecule derivatives, alcohol molecule residues, or alcohol molecules of the alcohol solvent. A method for producing composite silver nanoparticles forming an organic coating layer is provided.

As the silver salt, an inorganic silver salt and an organic silver salt can be used. Examples of the inorganic silver salt include silver carbonate, silver chloride, silver nitrate, silver phosphate, silver sulfate, silver borate, and silver fluoride. Salts include fatty acid salts such as silver formate and silver acetate, sulfonates, and silver salts of hydroxy, thiol, and enol groups. Among these, a silver salt composed of C, H, O and Ag or a silver salt composed of C, O and Ag is preferable, and silver carbonate (Ag ₂ CO ₃ ) is preferable.
Since alcohol is used as a solvent, the composite silver nanoparticles of the present invention can be produced at a relatively low temperature, whether an inorganic silver salt or an organic silver salt, by the reducing power of the alcohol. Inorganic silver salts are sparingly soluble in alcohol, while organic silver salts are soluble in alcohol and sparingly soluble. There are very few alcohol-soluble organic silver salts such as silver abitienate, and inorganic silver salts and many organic silver salts may be considered to be hardly soluble in alcohol.

The alcohol solution is a mixed solution of silver salt and alcohol. If the amount of alcohol is increased so that the generated composite silver nanoparticles are in a state of floating in the alcohol, the probability of mutual collision is reduced and the composite solution is reduced. Aggregation of silver nanoparticles can be prevented. Further, a large amount of alcohol molecules are adsorbed on the surface of the silver salt fine particles to promote the surface reaction. The general formula of alcohol is R _n OH (R _n is a hydrocarbon group), R _n is a hydrophobic group, and OH is a hydrophilic group, so if you change the way of thinking, alcohol is a surfactant with a surfactant action is there. Most of the silver salts are hardly soluble in alcohol, but the surface of the silver salt fine particles has a property that the OH group of the alcohol is easily bonded. Therefore, it can be said that the silver salt fine particles are surrounded by alcohol and become a stable monodispersed colloid when the particle diameter of the silver salt fine particles is reduced. When the particle diameter of the silver salt fine particles is increased, the alcohol may precipitate, but when the mixture is stirred and dispersed for a certain period of time, the reaction may be completed during that time.
In addition, alcohol itself has a reducing action, but alcohol easily changes to an aldehyde even at a production temperature of 200 ° C. or lower, and this aldehyde has a strong reducing action. That is, alcohol and / or aldehyde act on the surface of the silver salt fine particles to gradually precipitate silver, and finally the entire region of the silver salt fine particles is reduced and converted into silver nuclei. Around this silver nucleus, an organic coating layer composed of one or more of alcohol molecule derivatives, alcohol molecule residues, or alcohol molecules derived from alcohol is formed to produce composite silver nanoparticles. If the generation temperature PT is set to 200 ° C. or less, for example, composite silver nanoparticles having a low metallization temperature T3 can be generated. In the present invention, the production temperature PT is set lower than the metallization temperature T3 (≦ 200 ° C.) to produce composite silver nanoparticles for low-temperature firing. Although the average particle diameter of the silver nuclei is 1 to 20 nm, composite silver nanoparticles having a smaller particle diameter can be produced if the silver salt fine particles are thoroughly refined.

  The composite silver nanoparticles are also expressed as CnAgAL. Corresponding to n = 1 to 12, there are C1AgAL, C2AgAL, C3AgAL, C4AgAL, C5AgAL, C6AgAL, C7AgAL, C8AgAL, C9AgAL, C10AgAL, C11AgAL, and C12AgAL. The meaning is a composite silver nanoparticle produced | generated from C1-C12 alcohol. Therefore, C1 is methanol, C2 is ethanol, C3 is propanol, C4 is butanol, C5 is pentanol, C6 is hexanol, C7 is heptanol, C8 is octanol, C9 is nonanol, C10 is decanol, C11 is undecanol, C12 is dodecanol Means. Since n = even alcohol is a natural plant-derived alcohol, while n = odd is a chemically synthesized alcohol, n = even alcohol is relatively inexpensive and can provide inexpensive composite silver nanoparticles. Further, as the carbon number n decreases, the weight ratio of silver nuclei increases, and composite silver nanoparticles with a large amount of silver can be provided.

  In addition to the method described in International Publication No. 2009/0908446, the composite silver nanoparticles include composites prepared according to the production methods described in International Publication No. 2009/116136 and International Publication No. 2009/116185. Silver nanoparticles can also be suitably used.

  In the present invention, the sintered body of the composite silver nanoparticles refers to a material obtained by sintering the composite silver nanoparticles at a temperature of 350 to 450 ° C. For example, in the sintered body of composite silver nanoparticles, a nanosilver paste composed of composite silver nanoparticles and a volatile solvent is applied on the electrode members 4 and 5, and thermoelectric conversion elements 2 and 3 are further disposed thereon. Thereafter, these are heat-treated in a vacuum or in an inert atmosphere to melt the silver super-particles in the composite silver nanoparticles into an integrated metal state (metallization), and then cooled to By forming a sintered body between the thermoelectric conversion elements 2 and 3 and the electrode members 4 and 5, the thermoelectric conversion elements 2 and 3 and the electrode members 4 and 5 are electrically and mechanically joined. It becomes possible to do.

As the sintering process, it is preferable to perform a sintering process of heating to 350 to 450 ° C. from the viewpoint that the bonding strength of the bonding layer 6 is remarkably increased.
What is necessary is just to heat the said sintering process for a fixed time in the temperature range of 350-450 degreeC finally. For example, the temperature may be raised from a temperature lower than 350 ° C., and the sintering process may be performed while maintaining the temperature in the range of 350 to 450 ° C.

  Moreover, in the said sintering process, you may apply a pressure at the time of a heating from a viewpoint of improving joining strength. The pressure to be applied may be in the range of 0.1 to 40.0 MPa.

Examples of the volatile solvent used in the nano silver paste include hydrophobic non-aqueous solvents such as petroleum hydrocarbons such as toluene, xylene, kerosene, and cyclohexane, and terpenes such as terpine oil and terpineol. There are organic solvents. As hydrophilic non-aqueous solvents, alcohols such as methanol and ethanol, ketones such as acetone and the like are often used.
Furthermore, the volatile solvent used in the present invention may be the hydrophobic non-aqueous solvent or the hydrophilic non-aqueous solvent.

  In the present invention, water is excluded as a volatile solvent. For example, when water enters composite silver nanoparticles, a metal part containing silver atoms is oxidized and transformed into a metal oxide when it comes into contact with air. For these reasons, water is excluded as a volatile solvent in the present invention.

The nano silver paste may contain a viscosity imparting agent. The viscosity-imparting agent is a material that imparts a viscosity that can be easily applied by adding to the solution. Alcohol that is solid at room temperature of C14 or higher can be used. Examples of terpene derivatives include 1,8-terpine monoacetate and 1,8-terpin diacetate. IBCH is rosin-like, glycerin is syrup-like, and alcohols of C14 or higher have a solid-liquid change property, and are non-flowing at 10 ° C. or less. If the composite silver nanoparticles of the present invention are mixed and dispersed in the non-flowable viscosity imparting agent to form a non-flowable paste, the composite silver nanoparticles are fixed in a dispersed state at a low temperature of 10 ° C. or lower. Aggregation of nanoparticles does not occur. If the non-flowable paste is heated immediately before use, it can be fluidized and applied as a paste, and the function as a paste can be exhibited. Further, if a solvent is added to the non-flowable paste immediately before use, it becomes a flowable paste without heating, and can function as a paste.
The nanosilver paste may contain other metal fine particles as long as the properties of the composite silver nanoparticles are not adversely affected.

  In the sintered body of the composite silver nanoparticles, the volatile solvent is volatilized to become a metallized material having silver as a main component, and it must be heated to 960 ° C. or higher, which is the melting temperature of silver. Since it does not melt, the bonding layer 6 is very excellent in heat resistance.

The bonding strength by the bonding layer 6 made of the sintered body of the composite silver nanoparticles is 20 MPa or more, and more preferably 40 MPa or more.
In the present invention, the bonding strength of the bonding layer 6 can be represented by a shear strength measured according to “JIS Z 3198-5” using a φ5 mm copper joint test piece. Specifically, the bonding strength (shear strength) can be measured by the method described in Examples described later.

  In the thermoelectric conversion module 1 including the bonding layer 6 having the above-described configuration, the thermoelectric conversion elements 2 and 3 can be firmly bonded to the bonding portion 6 and thus to the electrode members 4 and 5, so that it can be electrically and thermally conductive. It becomes possible to connect well, and heat (temperature difference) for obtaining electric power is reduced based on reduction of thermal resistance and electrical contact resistance between the thermoelectric conversion elements 2 and 3 and the electrode members 4 and 5. It can be efficiently transmitted to the thermoelectric conversion elements 2 and 3. By these, it becomes possible to improve the thermoelectric conversion efficiency of the thermoelectric conversion module 1.

  Moreover, the thermoelectric conversion module 1 having the above-described configuration may be used as it is as a skeleton type, or only one of the electrode members 4 and 5 on the high temperature side or the low temperature side is fixed to the insulating heat conducting plate. A skeleton type or a thermoelectric conversion module of a type in which both sides of the electrode members 4 and 5 are fixed to an insulating heat conducting plate or the like as shown in FIG.

  For example, the thermoelectric conversion module of the type shown in FIG. 1 is common to these electrode members 4 on the outer side of the first electrode member 4 (the surface opposite to the surface bonded to the thermoelectric conversion elements 2 and 3). A joined upper insulating heat conducting plate 8 is disposed. On the other hand, a lower insulating heat conducting plate 9 joined in common to these electrode members 5 is also arranged outside the second electrode member 5. That is, the first and second electrode members 4 and 5 are supported by the insulating heat conducting plates 8 and 9, respectively, thereby maintaining the module structure.

  The insulating heat conducting plates 8 and 9 are preferably made of insulating ceramic plates. For example, the insulating heat conducting plates 8 and 9 are made of a ceramic plate made of a sintered body whose main component is at least one selected from aluminum nitride, silicon nitride, silicon carbide, alumina, and magnesia, which are excellent in thermal conductivity. Is desirable.

  The first and second electrode members 4, 5 are joined to the upper and lower insulating heat conducting plates 8, 9 via the joint 10, respectively. For bonding the insulating heat conductive plates 8 and 9 and the electrode members 4 and 5, a heat conductive bonding material may be used. However, if the composite silver nanoparticle sintered body is used, the electrode member 4 may be used. 5 and the insulating heat conducting plates 8 and 9 can be increased in bonding strength and bonding reliability, and at the same time, the thermal resistance can be reduced. These also contribute to the improvement of the module performance of the thermoelectric conversion module 10.

  In the thermoelectric conversion module 1 shown in FIG. 1, the upper insulating heat conducting plate 8 is disposed on the low temperature side (L) so as to give a temperature difference between the upper and lower insulating heat conducting plates 8 and 9, for example, and the lower insulating heat conducting plate 1 The heat conducting plate 9 is used by being arranged on the high temperature side (H). Based on this temperature difference, a potential difference is generated between the first electrode member 4 and the second electrode member 5, and electric power can be taken out by connecting a load to the end of the electrode. Thus, the thermoelectric conversion module 1 is effectively used as a power generation module. At this time, since it can be used at a high temperature of 300 to 600 ° C. and has high thermoelectric conversion performance, it is possible to realize a high-efficiency power generator using a high-temperature heat source.

  The thermoelectric conversion module 1 is not limited to a power generation application that converts heat into electric power, but can also be used for heating or cooling applications that convert electricity into heat. That is, when a direct current is passed through the p-type thermoelectric conversion element 2 and the n-type thermoelectric conversion element 3 connected in series, heat is radiated on one insulating heat conducting plate side and heat is absorbed on the other insulating heat conducting plate side. Occur. Therefore, a to-be-processed object can be heated by arrange | positioning a to-be-processed object on the insulating heat conducting plate by the side of heat radiation. Or by arrange | positioning a to-be-processed object on the heat-insulating insulating heat-conducting plate, it can cool by taking away heat from a to-be-processed object. For example, the semiconductor manufacturing apparatus performs temperature control of the semiconductor wafer, and the thermoelectric conversion module 1 can be applied to such temperature control.

Next, a method for manufacturing the thermoelectric conversion module 1 shown in FIG. 1 will be described.
First, thermoelectric conversion elements 2 and 3 and electrode members 4 and 5 having a nickel coating on the surface are prepared.
Next, an appropriate amount of nano silver paste (6) is applied to the surface of the electrode member 5 where the thermoelectric conversion elements 2 and 3 are to be joined.
The amount of the nano silver paste (6) is preferably 15 μm or more, and more preferably 20 μm to 50 μm, as the thickness of the silver adhesive layer metallized by the sintering treatment with heating at 350 to 450 ° C.

  Next, one each of the p-type and n-type thermoelectric conversion elements 2 and 3 are arranged on the application surface of the nano silver paste (6) for each one of the electrode members 5 at a certain interval.

  The electrode member 5 and the p-type and n-type thermoelectric conversion elements 2 and 3 integrated with the nanosilver paste (6) are placed in an electric furnace and subjected to a sintering process with heating at 350 to 450 ° C. Metalize the paste. The sintering treatment time may be a time until the sintering of the composite silver nanoparticles in the nanosilver paste is completed. From the viewpoint of suppressing the influence of heat on the electrode member 5 and the thermoelectric conversion elements 2 and 3. 10 to 60 minutes is preferable.

  Next, the p-type and n-type thermoelectric conversion elements 2 and 3 and the electrode member 5 which are firmly fixed and integrated by the adhesive layer 6 obtained by metallizing the nano silver paste in the above-described process are combined with the shape of the thermoelectric conversion module. As shown in FIG. 1, the nano silver paste (6) is applied on each of the p-type and n-type thermoelectric conversion elements 2 and 3 in a constant direction and at a constant interval. The amount of nano silver paste is the same as in the above step.

  Thereafter, an electrode member is placed on the nanosilver paste (6) applied to the thermoelectric conversion element so that the p-type thermoelectric conversion element 2 and the n-type thermoelectric conversion element 3 which are the final forms of the thermoelectric conversion module are alternately connected in series. 4 is installed.

  Next, the p-type thermoelectric conversion element 2 and the n-type thermoelectric conversion element 3 are alternately fixed by the electrode member 4 via the nano silver paste (6), and the integrated one is put into an electric furnace, and 350 to 450 The thermoelectric conversion module 1 is obtained by performing a sintering process with heating at 0 ° C., metallizing the nano silver paste (6), and firmly fixing the thermoelectric conversion elements 2 and 3 to the electrode member 4. As a characteristic of the nano silver paste, the metallizing temperature is much lower than the melting point of the sintered body obtained by heat-treating the nano silver paste, and this sintering treatment adversely affects the bonding layer 6 previously fixed. Not give.

  Next, the nano silver paste is dropped or applied on the surface of the electrode members 4 and 5 on the side not joined to the thermoelectric conversion elements 2 and 3, and the insulating heat conductive plates 8 and 9 are applied to the surface of the applied nano silver paste. 1 is formed, and the nanosilver paste is metallized by dry solidification and sintering in the same manner as described above to form the joint 10, and the thermoelectric conversion module 1 shown in FIG. 1 can be manufactured.

  In the embodiment described above, the electrode members are heat-bonded one by one, but both surfaces can be heat-bonded simultaneously.

  Next, an embodiment of a heat exchanger provided with the thermoelectric ring module 1 of the present invention will be described. The heat exchanger includes the thermoelectric conversion module 1 according to the above-described embodiment. The heat exchanger basically has a structure in which a heating surface (heat absorption surface) is disposed on one side of the thermoelectric conversion module 1 and a cooling surface (heat radiation surface) is disposed on the opposite side. For example, the endothermic surface has a passage through which a high-heat medium from a heat source passes, and the opposite heat radiation surface has a passage through which a low-temperature heat medium such as cooling water or air passes. A fin, a baffle plate, or the like may be disposed in the passage through which the heat medium passes or outside thereof. Instead of the water passage or the gas passage, a heat radiating plate, a fin, a heat absorbing plate or the like may be used.

In the heat exchanger, a gas passage is disposed so as to contact one surface of the thermoelectric conversion module 1, and a water flow path is disposed so as to contact the opposite surface. For example, high-temperature exhaust gas from a waste incinerator is introduced into the gas passage. On the other hand, cooling water is introduced into the water flow path. One side of the thermoelectric conversion module 1 becomes a high temperature side due to high temperature exhaust gas flowing in the gas passage, and the other side becomes a low temperature side due to cooling water flowing in the water flow path.
Thus, electric power is taken out from the thermoelectric conversion module 1 which comprises a heat exchanger by producing a temperature difference in the both ends of the thermoelectric conversion module 1. FIG. The endothermic surface is not limited to the high temperature exhaust gas from the combustion furnace, but can be applied to, for example, an exhaust gas of an automobile engine, a water pipe in a boiler, or the like, and may be a combustion section itself for burning various fuels.

(Test Example 1: Measurement of bonding strength of adhesive layer)
A test piece using the same metal composition as the thermoelectric conversion module shown in FIG. 1 was prepared, and a nano silver paste (Arconano (registered trademark) silver paste) containing composite silver nanoparticles described in International Publication No. 2009/090846 was prepared. The shear strength was measured according to JIS Z 3198-5 using the joined test piece obtained.

The material of the test piece was as follows.
Copper test piece (φ10mm, t = 5mm)
Nickel test piece (φ5mm, t = 2mm)
Nano silver paste (trade name “ANP-4”: manufactured by Nippon Superior Co., Ltd.)

Test piece production conditions are as follows.
Using a stencil, a nano silver paste is applied on a φ10 mm copper test piece to a thickness of 50 μm.
Next, the copper test piece coated with the nano silver paste was subjected to a sintering process according to the following procedure and conditions to obtain a test piece.

Prior to the sintering treatment, the test piece was preheated at 130 ° C. for 1 minute, and then heated up to a predetermined temperature while applying pressure at 10 MPa under a nitrogen atmosphere, and then maintained at that temperature for 3 minutes. Sintering was performed. The predetermined temperature was adjusted to four points of 300 ° C, 350 ° C, 400 ° C, and 450 ° C.
The obtained shear strength results are shown in FIG. Four test pieces were prepared and the average value was used as the result.

As shown in FIG. 2, the shear strength was around 11 MPa in the sintering process at 300 ° C., but increased to around 51 MPa in the sintering process at 350 ° C., and 90 MPa and 450 ° C. in the sintering process at 400 ° C. In the sintering process, the strength exceeded the measurement limit.
The shear strength was measured with a Tensilon universal testing machine manufactured by A & D.
Further, in the test piece thermoelectric conversion module, if the bonding layer provided between the p-type or n-type thermoelectric conversion element and the electrode member has a bonding strength exceeding 20 MPa, it is various for using the exhaust heat. Even if it is installed on a simple member, it has a sufficient bonding strength and is expected to correspond to an acceptable product. Therefore, it is understood that a thermoelectric conversion module having a sufficiently high bond strength of the bonding layer can be obtained by performing a sintering process at 350 to 450 ° C.

1 Thermoelectric conversion module 2 Thermoelectric conversion element (p-type)
3 Thermoelectric conversion element (n-type)
4, 5 Electrode member 6 Joining layer 7 Nickel-containing layer 8, 9 Insulating heat conducting plate 10 Joining portion

Claims (2)

A thermoelectric conversion element for converting the temperature difference into electric power;
An electrode member for taking out the electric power converted by the thermoelectric conversion element;
A thermoelectric conversion module having a conductive bonding layer for bonding the thermoelectric conversion element and the electrode member,
A nickel-containing layer is provided on the surface of the thermoelectric conversion element and / or the electrode member in contact with the bonding layer;
The bonding layer is a kind of alcohol molecule derivative, alcohol molecule residue, or alcohol molecule having 1 to 12 carbon atoms around a silver nucleus having an average particle diameter of 1 to 20 nm made of an aggregate of silver atoms. It is a sintered body of composite silver nanoparticles having an organic coating layer composed of the above,
A thermoelectric conversion module characterized in that the bonding strength of the bonding layer is 20 MPa or more. A thermoelectric conversion element for converting the temperature difference into electric power;
An electrode member for taking out the electric power converted by the thermoelectric conversion element;
A method of manufacturing a thermoelectric conversion module, comprising: a conductive bonding layer that bonds the thermoelectric conversion element and the electrode member;
Between the thermoelectric conversion element and the electrode member, after applying a nano silver paste composed of composite silver nanoparticles and a volatile solvent, having a step of sintering at 350 to 450 ° C.,
A nickel-containing layer is provided on the surface of the thermoelectric conversion element and / or the electrode member in contact with the bonding layer;
The composite silver nanoparticles are an alcohol molecule derivative having 1 to 12 carbon atoms, an alcohol molecule residue, or an alcohol molecule around a silver nucleus having an average particle size of 1 to 20 nm composed of an aggregate of silver atoms. A method for producing a thermoelectric conversion module, which is a composite silver nanoparticle having an organic coating layer composed of one or more of the following.

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