JP7274749B2 - Thermoelectric conversion module and thermoelectric conversion module manufacturing method - Google Patents

Description

The present invention relates to a thermoelectric conversion module and a thermoelectric conversion module manufacturing method.

For example, Patent Document 1 discloses a P-type or N-type thermoelectric element, an electrode joined to the P-type or N-type thermoelectric element, and a thermoelectric element provided between the P-type or N-type thermoelectric element and the electrode. and an intermediate layer formed on the electrode, wherein the intermediate layer is provided between the titanium layer or titanium alloy layer formed on the electrode and the titanium layer or titanium alloy layer and the thermoelectric element. A thermoelectric module is disclosed, characterized in that it comprises an aluminum or aluminum alloy layer coated with a

Further, Patent Document 2 describes a pair of substrates, plate-like electrodes formed on the surfaces of the pair of substrates facing each other, a thermoelectric element joined between the plate-like electrodes, and an external thermoelectric element. an external wiring portion that is a post electrode or a lead wire for electrically connecting to a circuit; a bonding layer that is a sintered body of paste containing metal particles and that bonds the plate-like electrode and the external wiring portion; A thermoelectric conversion module is disclosed in which a bonding strength improving layer for improving bonding strength with a bonding target is formed at the interface of the bonding layer.

JP-A-2006-49736 JP 2015-18986 A

An object of the present invention is to provide a thermoelectric conversion module joined while ensuring electrical conductivity.

A thermoelectric conversion module according to the present invention includes a thermoelectric element, an electrode, and a conductive multilayer film disposed between the thermoelectric element and the electrode, wherein the multilayer film is mainly composed of palladium. Including layers.

Preferably, the thermoelectric element is made of a porous thermoelectric material, and the multilayer film further includes a nickel layer mainly containing nickel between the thermoelectric element and the palladium layer.

Preferably, the thermoelectric element is made of a thermoelectric material containing magnesium, and the nickel layer has a thickness of 500 nm to 1000 nm.

Preferably, the multilayer film is joined to the electrode via a solder layer, and the multilayer film further includes a gold layer mainly composed of gold between the palladium layer and the solder layer.

Preferably, the multilayer film is composed only of a gold layer containing gold as a main component, the nickel layer, the palladium layer, and the gold layer.

Further, a method for manufacturing a thermoelectric conversion module according to the present invention includes a multilayer film formation step of forming a multilayer film on the surface of a thermoelectric element by sputtering, and a bonding step of soldering the formed multilayer film and an electrode. and the step of forming a multilayer film includes the step of forming a palladium layer mainly composed of palladium.

ADVANTAGE OF THE INVENTION According to this invention, it can join, ensuring electrical conductivity.

1 is a cross-sectional view illustrating the configuration of a thermoelectric conversion module 1 in this embodiment; FIG. 3 is a diagram illustrating in detail the configuration of a multilayer film 20; FIG. 4 is a flow chart explaining a method (S10) for manufacturing the thermoelectric conversion module 1 in this embodiment.

First, the background of the present invention will be described.
A thermoelectric conversion module is an assembly in which a large number of thermoelectric conversion elements are connected in series. When connecting thermoelectric conversion elements in series, the thermoelectric conversion elements and electrodes are often joined together with solder. In the case of soldering, it is difficult to directly contact the thermoelectric conversion element with the solder to join the thermoelectric conversion element.
However, when a magnesium-containing porous thermoelectric conversion material is plated, the thermoelectric conversion material deteriorates, making surface treatment difficult.
Methods other than plating include a method of using a paste containing conductive particles, and a technique of combining a layer containing aluminum and silicon with tungsten, titanium, nickel, palladium, molybdenum, etc., but the electric resistance increases. I was worried that I would lose it.
Therefore, the embodiment of the present invention has been created with the above circumstances as a point of focus. According to the embodiments of the present invention, it is possible to join the thermoelectric conversion material and the electrodes while ensuring electrical conductivity. Hereinafter, such embodiments of the present invention will be described with reference to the drawings.

The configuration of a thermoelectric conversion module 1 according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG.
FIG. 1 is a cross-sectional view illustrating the configuration of a thermoelectric conversion module 1 according to this embodiment.
FIG. 2 is a diagram illustrating in detail the configuration of the multilayer film 20. As shown in FIG.
As illustrated in FIG. 1 , the thermoelectric conversion module 1 has a thermoelectric element 10 , a multilayer film 20 , electrodes 30 , a substrate 40 and a bonding layer 50 . The electrodes 20 and the thermoelectric elements 30 are electrically connected via the multilayer film 40 .

The thermoelectric element 10 is an element made of a material that mutually converts heat and electric energy. The thermoelectric element 10 is formed in the shape of a cylinder or prism, and in this example, it has the shape of a quadrangular prism. Also, the thermoelectric element 10 is composed of a porous thermoelectric material. The thermoelectric material forming the thermoelectric element 10 includes, for example, a silicide-based thermoelectric material. A silicide-based thermoelectric material is specifically a magnesium silicide (Mg ₂ Si)-based thermoelectric material, and more specifically a thermoelectric material mainly composed of an MgSiSn alloy or an Mg ₂ Si alloy (so-called porous magnesium silicide-based thermoelectric material). That is, the thermoelectric element 10 is made of a thermoelectric material containing magnesium. This thermoelectric material includes a matrix composed of Mg ₂ Si and MgO, holes formed in the matrix, and a silicon layer containing silicon as a main component attached to the walls of the holes. The parent phase has two Si-rich phases (referred to as a first Si-rich phase and a second Si-rich phase) having different chemical compositions in the MgSiSn alloy. The first Sn-rich phase has a higher Sn composition ratio than the second Si-rich phase, and the second Si-rich phase has a higher Si composition ratio than the first Sn-rich phase. Also, the thermoelectric material contains 1.0 wt % or more and 20.0 wt % or less of MgO with respect to the weight of the thermoelectric material. Further, the silicon layer constituting the thermoelectric material is composed of amorphous Si, or amorphous Si and microcrystalline Si. Moreover, the porosity of the thermoelectric element 10 is 5% or more and 50% or less.

The multilayer film 20 is a conductive thin film disposed between the thermoelectric element 10 and the electrode 30 . The multilayer film 20 is joined to the electrode 30 via the solder layer 50 . The multilayer film 20 has a multilayer film 20A and a multilayer film 20B. For convenience of explanation, the multilayer film 20A will be mainly described, but the multilayer film 20A and the multilayer film 20B have substantially the same configuration. Moreover, the multilayer film 20A and the multilayer film 20B may be simply referred to as the multilayer film 20 when there is no particular need to distinguish between them. As illustrated in FIG. 2, the multilayer film 20A includes a first gold layer 200, a nickel layer 202, a palladium layer 204, and a second gold layer 206, and in the direction from the thermoelectric element 10 to the substrate 40, the A first gold layer 200, a nickel layer 202, a palladium layer 204, and a second gold layer 206 are laminated in this order. Note that the multilayer film 20A of this example consists of the first gold layer 200, the nickel layer 202, the palladium layer 204, and the second gold layer 206 only.

The first gold layer 200 is a gold layer mainly containing gold. The first gold layer 200 diffuses onto the surface of the thermoelectric element 10 to provide adhesion. The first gold layer 200 has a thickness of 50 nm or more and 500 nm or less, preferably 50 nm or more and 200 nm or less. Note that the first gold layer 200 in this example has a thickness of 100 nm. When the thickness of the first gold layer 200 is less than 50 nm, it diffuses completely and does not play a role as an adhesion layer. Moreover, when the thickness of the first gold layer 200 is thicker than 500 nm, the resistance of the first gold layer 200 becomes high. Further, when the thickness of the first gold layer 200 is 50 nm or more and 200 nm or less, the resistance of gold can be almost ignored.
Also, the first gold layer 20 is formed using a method such as sputtering, vacuum deposition, ion beam deposition, laser film formation, thermal spraying, plating, or spray coating. Sputtering was used in this example.

The nickel layer 202 is a nickel layer mainly containing nickel. Nickel layer 202 is located between thermoelectric element 10 and palladium layer 204 . By covering the surface of the thermoelectric element 10 , the nickel layer 202 prevents diffusion of magnesium, which is a constituent element of the thermoelectric element 10 , generated from the thermoelectric element 10 . The nickel layer 202 has a thickness of 200 nm or more and 2000 nm or less, preferably 500 nm or more and 1000 nm or less. Note that the nickel layer 202 has a thickness of 500 nm. Although the diffusion of magnesium can be prevented even when the thickness of the nickel layer 202 is 200 nm or more, the diffusion prevention effect is large when the thickness is about 500 nm. Also, when the thickness of the nickel layer 202 is thicker than 2000 nm, the resistance of the nickel portion increases, and when the thickness is 1000 nm or less, the resistance value can be reduced. Therefore, it is desirable that the thickness of the nickel layer 202 is 500 nm or more and 1000 nm or less.
Also, the nickel layer 202 is formed using a technique such as sputtering, vacuum deposition, ion beam deposition, laser film formation, thermal spraying, plating, or spray coating. Sputtering was used in this example.

The palladium layer 204 is a palladium layer mainly containing palladium. The palladium layer 204 is located between the nickel layer 202 and the solder layer 50 and functions to prevent the nickel layer 202 and the solder layer 50 from being repelled. The palladium layer 204 has a thickness of 50 nm or more and 500 nm or less, and a thickness of 150 nm in this example. If the thickness of the palladium layer 204 is less than 50 nm, diffusion of the nickel layer 202 cannot be suppressed. Moreover, when the thickness of the palladium layer 204 is thicker than 500 nm, the resistance of the palladium layer 204 increases. Therefore, it is desirable that the thickness of the palladium layer 204 is 50 nm or more and 500 nm or less.
Also, the palladium layer 204 is formed using a technique such as sputtering, vacuum deposition, ion beam deposition, laser film formation, thermal spraying, plating, or spray coating. Sputtering was used in this example. Thus, the multilayer film 20 is a thin film including the palladium layer 204 .

The second gold layer 206 is a gold layer mainly containing gold. A second gold layer 206 is located between the palladium layer 204 and the solder layer 50 . The second gold layer 206 functions as an antioxidant for the palladium layer 204 . The second gold layer 206 has a thickness of 50 nm or more and 500 nm or less, preferably 50 nm or more and 200 nm or less. Note that the second gold layer 206 in this example has a thickness of 100 nm. If the thickness of the second gold layer 206 is less than 50 nm, the surface of the palladium layer 204 cannot be covered. Moreover, when the thickness of the second gold layer 206 is thicker than 500 nm, the resistance of the first gold layer 200 becomes high. On the other hand, when the thickness of the second gold layer 206 is 200 nm or less, the resistance of gold is almost negligible. Therefore, it is desirable that the thickness of the second gold layer 206 is 200 nm or less.
Also, the second gold layer 206 is formed using a technique such as sputtering, vacuum deposition, ion beam deposition, laser film formation, thermal spraying, plating, or spray coating. Sputtering was used in this example.

The electrode 30 is a thin plate of conductive metal. The electrodes 30 can be made of materials such as alumina, alumite, stainless steel, nickel-iron alloys, copper-nickel alloys, phosphor bronze, and copper-iron alloys. In addition, the electrode 30 of this embodiment is a copper thin plate. Electrode 30 is located between substrate 40 and solder layer 50 . The electrodes 30 may be plated for better solderability.

The substrate 40 is a flat plate having an insulating film on one surface. The insulating film provided on one surface of the substrate 40 is a film that electrically disconnects the electrodes 30 and the substrate 40 . The substrate 40 can be manufactured using metal, insulating ceramics, a composite of insulating material such as metal and synthetic resin, or synthetic resin as a base material, and it is preferable to use a material with high thermal conductivity. Specifically, when the substrate 40 is manufactured using a metal base material, it can be manufactured from aluminum, copper, or an alloy containing these. Also, when the substrate 40 is manufactured using an insulating ceramic substrate, it can be manufactured from alumina or aluminum nitride. Further, when the substrate 40 is manufactured using a composite of metal and insulating material such as synthetic resin, it can be manufactured from a base material of copper or aluminum coated with a thin film of insulating resin. Moreover, when manufacturing the board|substrate 40 using a base material made from a synthetic resin, it can manufacture from glass epoxy resin.

The solder layer 50 is located between the multilayer film 20 and the electrode 30 and is a layer made of a conductive bonding material that bonds the multilayer film 20 and the electrode 30 . That is, the solder layer 50 is a bonding layer made of a bonding material that bonds the multilayer film 20 and the electrode 30 . For the solder used to form the solder layer 50, for example, Pb--Sn-based, Sn--Ag--Cu-based, Sn--Cu-based, Sn--Sb-based, or Sn--Bi-based solder can be used. In this example, Sn--Ag--Cu solder was used. In addition to solder, for example, a conductive adhesive or brazing material can be used as the bonding material.

Next, a method for manufacturing the thermoelectric conversion module 1 according to this embodiment will be described with reference to FIG.
FIG. 3 is a flow chart for explaining the manufacturing method (S10) of the thermoelectric module conversion module 1 in this embodiment.
As illustrated in FIG. 3 , in step 100 ( S100 ), first, the manufacturer removes the oxide of the thermoelectric element 10 before forming the first gold layer 200 . If there is a thin film of magnesium oxide or the like between the thermoelectric element 10 and the first gold layer 200, the resistance increases, so it is removed. Methods such as acid cleaning, reverse sputtering, and polishing are used as means for removing these oxides. In this example, the oxide is removed by polishing.
Next, the manufacturer forms the multilayer film 20 on the surface of each bottom surface (in other words, surfaces other than the side surfaces) of the thermoelectric element 10 formed in the shape of a quadrangular prism using a sputtering apparatus. That is, the multilayer film 20 is formed on the surface of the thermoelectric element 10 using the sputtering phenomenon.
Specifically, the manufacturer uses a metal mainly composed of gold to form a thin film of gold mainly composed of gold on the surface of the thermoelectric element 10 to a thickness of 100 nm (so-called first gold layer 200 formation). Next, after the formation of the first gold layer 200, the manufacturer forms a thin film of nickel, mainly nickel, on the first gold layer 200 to a thickness of 500 nm (so-called formation of the nickel layer 202). ). Next, after forming the nickel layer 202, the manufacturer forms a thin film of palladium, mainly palladium, on the nickel layer 202 to a thickness of 150 nm (formation of a so-called palladium layer 204). Next, after forming the palladium layer 204, the manufacturer forms a gold thin film mainly composed of gold over the palladium layer 204 to a thickness of 100 nm (formation of a so-called second gold layer 206). Thus, the manufacturer forms the multilayer film 20 having a four-layer structure on the surface of the thermoelectric element 10 .

In step 101 (S101), the manufacturer forms the multilayer film 20 on the surface of the thermoelectric element 10 and then performs diffusion treatment by heat treatment. The heat treatment temperature is desirably 200° C. or higher and 800° C. or lower. If the heat treatment temperature is 200° C. or less, diffusion between metal layers does not occur. Also, if the heat treatment temperature is 800° C. or higher, the thermoelectric element 10 deteriorates. Therefore, the heat treatment temperature is desirably 200° C. or higher and 800° C. or lower. Also, in this example, the case where the heat treatment is performed after the formation of the multilayer film 20 will be described, but it may be performed at the same time as the formation of the multilayer film 20 .

In step 102 (S102), the manufacturer solders the multilayer film 20 formed on the thermoelectric element 10 and the electrode 30 formed to a predetermined size. That is, a solder layer 50 is formed between the multilayer film 20 and the electrode 30 .

In step 104 (S104), the manufacturer bonds the electrode 30 and the substrate 40 with an adhesive so that the thermoelectric element 10 and the electrode 30 on which the multilayer film 20 is formed are sandwiched between the pair of substrates 40 . Then, the manufacturer seals between the two substrates 40 with a sealing material.
Thus, the manufacturer can manufacture the thermoelectric conversion module 1 .

As described above, according to the thermoelectric conversion module 1 of the present embodiment, by forming the multilayer film 20 on the thermoelectric element 10 made of a porous magnesium silicide-based thermoelectric material, the electrodes 30 are formed through the solder layer 50 . can be joined with As a result, the thermoelectric elements 10 and the electrodes 30 can be joined together with the electrical resistance kept low.

REFERENCE SIGNS LIST 1 thermoelectric conversion module 10 thermoelectric element 20 multilayer film 200 first gold layer 202 nickel layer 204 palladium layer 206 second gold layer 30 electrode 40 substrate 50 solder layer

Claims (4)

a thermoelectric element;
an electrode;
Having a conductive multilayer film disposed between the thermoelectric element and the electrode,
The multilayer film includes a palladium layer mainly composed of palladium,
The thermoelectric element is composed of a porous thermoelectric material containing magnesium,
The multilayer film further includes a nickel layer mainly composed of nickel between the thermoelectric element and the palladium layer,
The nickel layer has a thickness of 500 nm to 1000 nm
Thermoelectric conversion module. The multilayer film is joined to the electrode via a solder layer,
The thermoelectric conversion module according to claim 1 , wherein the multilayer film further includes a gold layer mainly containing gold between the palladium layer and the solder layer. 3. The thermoelectric conversion module according to claim 2 , wherein the multilayer film comprises only a gold layer mainly containing gold, the nickel layer, the palladium layer, and the gold layer. a multilayer film forming step of forming a multilayer film by sputtering on the surface of the thermoelectric element;
a bonding step of soldering the formed multilayer film and the electrode,
The step of forming a multilayer film includes the steps of: forming a palladium layer mainly containing palladium; and forming a nickel layer mainly containing nickel between the thermoelectric element and the palladium layer. .

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