JPH08330638A - Thermoelectric conversion device - Google Patents

Abstract

PURPOSE: To provide a thermoelectric conversion device which has a high thermoelectric conversion efficiency and a long useful life. CONSTITUTION: An oxide insulating film which comprises many slender holes 5 is formed at least on one face of a metal substrate. A pore 5 is not sealed but filled with bonding metal 6. The surface of the oxide insulating film is endowed with a conductive property, and an electrode 4 is bonded onto the oxide insulating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric conversion device such as an electronic cooling device or a thermoelectric generator, and more particularly to a substrate and an electrode for supporting the electrode thereof.

[0002]

2. Description of the Related Art FIG. 9 is a partially enlarged sectional view of a conventional electronic cooling device. Heat-radiating side insulating substrate 1 made of alumina, etc.
On the heat radiation side, the heat radiation side electrode 102 is placed on the heat radiation side electrode 102 via the solder layer 101, and the P-type semiconductor layer 10
3 and the N-type semiconductor layer 104 are arranged respectively. A heat absorption side electrode 105 is provided so as to connect the P type semiconductor layer 103 and the N type semiconductor layer 104, and a heat absorption side insulating substrate 107 is further disposed on the heat absorption side electrode 105 via a solder layer 106.

The P-type semiconductor layer 103 and the N-type semiconductor layer 1
Reference numeral 04 is a pair, and the heat radiation side electrode 102 and the heat absorption side electrode 105
A large number of them are connected in parallel, and electrically connected in series and thermally connected in parallel to form an electronic cooling element group.

By supplying a predetermined current to the electronic cooling element group, the heat absorbing side insulating substrate 107 side absorbs heat and the surrounding area is cooled. The heat taken away by the heat absorption is radiated on the heat radiating side insulating substrate 100 side and is radiated to the outside by a heat radiating fin or a fan (not shown), so that heat is transferred.

[0005]

By the way, the conventional thermoelectric conversion device does not have a sufficient service life, and during repeated use, the thermoelectric conversion efficiency such as cooling efficiency deteriorates, and constant power is supplied. In comparison, the temperature on the cooling side did not drop, and sufficient power could not be obtained despite the temperature difference.

As a result of diligent studies on this problem, the present inventors have found that there is a problem in the structure of the thermoelectric conversion device. That is, in the conventional thermoelectric conversion device, the insulating substrates 100 and 107 made of ceramic such as alumina are integrally joined to the metal electrodes 102 and 105 by the solder layers 101 and 106.

An insulating substrate 100 made of this ceramic,
107 and solder layers 101 and 106 made of metal (electrode 1
02, 105, and semiconductor layers 103, 104) differ greatly in thermal expansion (contraction) coefficient, so that if the thermoelectric conversion device is repeatedly used (that is, if the temperature history of cold and warm is repeated), the insulating substrate Deformation such as warpage occurs in 100 and 107. Then, a fatigue phenomenon occurs at the boundaries between the solder layers 101 and 106 and the electrodes 102 and 105 and the P-type semiconductor layer 103 and the N-type semiconductor layer 104, resulting in a large thermal resistance, resulting in poor connection and disconnection. This has been a factor in shortening the useful life of the thermoelectric conversion device.

The insulating substrate 10 made of ceramics
Nos. 0 and 107 themselves also have large thermal resistance, and deformation such as warpage occurs even when they are molded or sintered, so that the adhesion with the heat conducting member including the fins is poor and the thermal resistance during that time becomes large.

Further, the insulating substrate 10 made of ceramics
Since 0 and 107 are mechanically fragile, they have defects such as chipping and cracking during handling in the manufacturing process and poor yield.

Conventionally, a method of manufacturing a thermoelectric conversion device as described in Japanese Patent Publication No. 40-11577 has been proposed. In this method, a metal heat conductor such as aluminum is immersed in an electrolytic solution such as oxalic acid to form an anodized film on the surface. Then, this oxide film is sealed with boiling water or steam for a short time (within 2 minutes), and an electrode is formed on the sealed oxide film by electroplating.

However, the substrate obtained by sealing the anodic oxide film has a weak bonding strength with the electrode formed thereon, so that the electrode often peels from the substrate.
Not practical.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a thermoelectric conversion device having a good thermoelectric conversion efficiency and a long service life.

[0013]

In order to achieve the above object, the first aspect of the present invention is based on, for example, alumite having a large number of pores formed on at least one surface of a metal base material such as aluminum by, for example, anodization. The oxide insulating film is formed by filling the pores with a binding metal such as nickel or copper without sealing the pores to give conductivity to the surface of the oxide insulating film. It is characterized in that an electrode made of, for example, nickel, copper, or the like is bonded to the top.

In order to achieve the above object, the second aspect of the present invention is to form an electric insulating layer made of, for example, alumina or aluminum nitride on one surface of an electrode body made of, for example, copper by means such as thermal spraying. A P-type semiconductor layer and an N-type semiconductor layer are joined to the electrode body by using a laminated electrode in which a solder joining metal layer made of, for example, copper is laminated on the electrically insulating layer by means of, for example, thermal spraying. It is characterized in that a heat conductor is bonded to the solder bonding metal layer.

[0015]

According to the first aspect of the invention, unlike the conventional case, an insulating substrate made of ceramic such as alumina is not used,
Since the metal base material on which the insulating film is formed is used, the thermal resistance of the substrate itself can be reduced.

Since this metal base material has little difference from the coefficient of thermal expansion (contraction) of the solder layer, the electrode, the semiconductor layer, etc., the substrate is deformed even when the thermoelectric conversion device is repeatedly used, and the solder layer, the electrode, etc. No fatigue phenomenon occurs, the thermal resistance can be kept low, and the service life of the thermoelectric conversion device can be extended.

Further, in the case of an insulating substrate made of ceramics, deformation such as warpage occurs when it is molded or sintered, and thus the adhesion with the heat conductor deteriorates. However, in the substrate of the present invention mainly composed of a metal base material. This is not the case, and the close contact with the heat conductor is always good.

Further, since the pores in the insulating film are not sealed, the bonding metal is filled in the pores, and the electrodes are bonded on the pores, so that the bonding strength between the substrate and the electrodes is high. Can be increased.

According to the second aspect of the present invention, since the relatively thick insulating substrate made of ceramic is not used but the laminated electrode having the thin insulating layer is used, the thermal resistance can be greatly reduced. It is also possible to reduce the total height of the thermoelectric conversion device.

[0020]

Embodiments of the present invention will now be described with reference to the drawings. (First Example) An aluminum substrate was immersed in an electrolytic solution containing an oxalic acid solution of 0.5% by weight and anodized at a bath temperature of 20 ° C. and a constant voltage of 100 V for 5 minutes.
As shown in (a), a film thickness of about 10 is formed on the aluminum substrate 1.
An insulating film 2 having a thickness of μm is formed.

Then, the aluminum substrate 1 is added to 5% by weight.
The pore diameter of the fine pores formed in the insulating film 2 is expanded by immersing in the phosphoric acid solution (solution temperature 30 ° C.) for a certain time.

The expanded aluminum substrate 1 is dipped in a hydrochloric acid tin chloride solution for 1 to 10 minutes, washed with water, and then allowed to stand in distilled water for 10 to 30 minutes to complete the sensitization treatment. Next, it is immersed in a lead chloride solution for 5 minutes, then washed with water, and allowed to stand in distilled water for 10 to 30 minutes to complete the activation treatment.

After the sensitizing treatment and the pretreatment for the activating treatment are carried out in this manner, they are immersed in an electroless plating bath having the following composition. NiSO ₄ · 6H ₂ O 2.5 _{wt% NaPH 2 O 2 · H 2} O 5.0 _{wt% Na 4 P 2 O 7 ·} 10H 2 O 2.5 wt% pH value of 11 (adjusted with aqueous ammonia) Bath Temperature By the electroless plating at 40 ° C. in this manner, nickel is deposited and filled in the fine pores in the insulating coating 2 to impart conductivity to the surface of the insulating coating 2.

Next, as shown in FIG. 1B, a copper conductive film 3 having a thickness of about 0.3 to 50 μm is formed by electroplating on the insulating film 2 having conductivity on its surface by a conventional method. After the formation, the unnecessary portion of the conductive film 3 is removed by a method such as photolithography and patterned as shown in FIG.

In the case of a thermoelectric conversion device in which a small current is passed during driving, the patterned conductive film 3 can be used as an electrode as it is, and the P and N semiconductor layers can be placed on it. In the case of the device, the thickness is about 2 on the patterned conductive film 3 as shown in FIG.
The electrodes 4 having a relatively large thickness of 00 to 1000 μm are joined by soldering.

FIG. 2 is an enlarged cross-sectional view of the X portion in FIG. 1 (d), in which the pores 5 formed in the insulating film 2 are filled with a binding metal (Ni in this embodiment) 6. As a result, it is in close contact with the peripheral wall surface of the uneven pores 5 and also with the conductive film 3 to enhance the bonding strength between the substrate 1 and the conductive film 3.

(Embodiment 2) FIG. 3 is a cross-sectional view of an aluminum substrate 1 according to Embodiment 2, in which a substrate 1a made of inexpensive aluminum or aluminum alloy having a relatively low purity (eg, 97% purity) is inexpensive. , A thin layer for anodization 1 made of high-purity aluminum (for example, 99.99% purity)
b is joined by means such as clad or thermal spraying. The thickness of the thin layer 1b for anodization is 0.3 mm, which corresponds to 10% of the total thickness of the substrate 1 of 3 mm.
Is enough.

On the thin layer 1b for anodic oxidation, an insulating film 2 is formed by anodic oxidation in the same manner as in Example 1, and a conductive film 3 and an electrode 4 which are patterned are provided.

(Embodiment 3) FIGS. 4 (a) and 4 (b) are views for explaining the embodiment 3, and as shown in FIG. 4 (a), the purity is relatively low (eg, purity 97%). Aluminum particles 7 of high purity (for example, 99.99% purity) are provided on a base material 1a made of inexpensive aluminum or aluminum alloy to a predetermined thickness (for example, about 0.2 to 1 mm) by a plasma sintering method or the like. And sintered to form a sintered layer 8 having innumerable irregularities on the surface and innumerable grain boundaries inside.

Then, as shown in FIG. 1B, an insulating film 2 is formed by anodic oxidation on the sintered layer 8 in the same manner as in the first embodiment. Although not shown, the insulating film 2 is formed. A patterned conductive film 3 and an electrode 4 are sequentially formed on the top.

(Embodiment 4) FIGS. 5 (a) and 5 (b) are views for explaining Embodiment 4, and as shown in FIG. 5 (a), the surface of the base material 1a made of aluminum is sandblasted, for example. The rough surface 9 is formed by a mechanical method such as a method or a chemical method such as etching. Then, as shown in FIG. 2B, the insulating film 2 by anodic oxidation is formed on the side of the rough surface 9 having a myriad of fine irregularities as shown in FIG.
Although not shown, a patterned conductive film 3 and an electrode 4 are sequentially formed on the insulating film 2.

(Embodiment 5) FIGS. 6 (a) to 6 (d) are views for explaining Embodiment 5, in which the surface of a substrate 1a made of aluminum is heated as shown in FIG. 6 (a). In the softened state, hard particles 10 made of, for example, alumina or aluminum nitride having a particle size of about 50 to 150 μm are embedded in the vicinity of the surface by applying a high pressure. By embedding the hard particles 10, the surface of the base material 1a is slightly raised.

Next, as shown in FIG. 3B, the surface of the base material 1a is roughened by eluting only the hard particles 10 from the base material 1a without eroding the base material 1a. As shown in FIG. 7, the insulating film 2 by anodic oxidation is formed on the rough surface 9 in the same manner as in the first embodiment.

Thereafter, as shown in FIG. 3D, a layer of the bonding metal 6 is formed on the insulating film 2 by electroless plating, and the bonding metal 6 (Ni) is formed in the pores in the insulating film 2. ) Is filled in, and the patterned conductive film 3 and electrode 4 are sequentially formed on the bonding metal 6 (not shown).

(Sixth Embodiment) FIGS. 7 and 8 show a sixth embodiment.
7 is an enlarged sectional view of an electrode according to this embodiment, and FIG. 8 is a partial sectional view of an electronic refrigerator using the electrode.

The electrodes of the conventional thermoelectric conversion device are composed only of a metal such as copper or nickel, which is soldered to an insulating substrate made of alumina or the like. This insulating substrate had a thickness of about 0.64 mm, and therefore had a large thermal resistance and the efficiency of the device was not so good.

In order to improve this, in the present embodiment, as shown in FIG. 7, for example, the electrode body 11 (2 mm long, 5 mm wide, 0.5 m thick) made of a good conductor metal such as copper or nickel.
The insulating layer 12 having a thickness of 100 μm is formed on one surface of m) by spraying alumina, aluminum nitride or the like. Further, a metal having good compatibility with solder, such as copper or nickel, is sprayed on the insulating layer 12 to form a solder bonding metal layer 13 having a thickness of 100 μm to form a laminated electrode 14 having a three-layer structure. There is. Therefore, the electrode body 11 functions as a support when the insulating layer 12 and the solder-bonding metal layer 13 are sprayed, and the electrode body 11 and the solder-bonding metal layer 13 are electrically interposed by the insulating layer 12. Is completely insulated.

FIG. 8 is a view showing a usage example of this electrode, in which the metal layer 13a for solder bonding of the heat absorption side laminated electrode 14a is directly soldered to the outer surface of the cooling side heat conductor 15 such as an inner box of a refrigerator. The solder joint metal layer 13b of the heat dissipation side laminated electrode 14b is directly soldered to the surface of the heat dissipation side heat conductor 16 provided with a heat dissipation fin (not shown). The cooling side heat conductor 15 and / or the heat radiation side heat conductor 1
If 6 is not so well compatible with the solder metal, it is necessary to plate the surface with a metal having good compatibility with the solder such as copper or nickel in advance.

A large number of P-type semiconductor layers 17 and N-type semiconductor layers 18 are arranged in parallel between the heat absorption side laminated electrode 14a and the heat radiation side laminated electrode 14b, and the electrode body 11a of the heat absorption side laminated electrode 14a and the heat radiation side laminated layer are formed. The electrodes 14b and the electrode body 11b are electrically connected in series.

Although the oxalic acid method was used as the anodizing method in Examples 1 to 5, the present invention is not limited to this, and other methods such as a sulfuric acid method, a hard anodizing method, and a chromic acid method are used. It is also possible to apply an anodic oxidation method.

In the above-mentioned embodiment, the case of the electronic cooling device has been described, but the present invention is also applicable to a thermoelectric generator.

[0042]

According to the first aspect of the present invention, since the conventional insulating substrate made of ceramic such as alumina is not used, the metal base material having the insulating film is used. The thermal resistance of the substrate itself can be reduced.

Since this metal base material does not differ much from the coefficient of thermal expansion (contraction) of the solder layer, electrode, semiconductor layer, etc., the substrate is deformed even when the thermoelectric conversion device is repeatedly used, and the solder layer, electrode, etc. No fatigue phenomenon occurs, the thermal resistance can be kept low, and the service life of the thermoelectric conversion device can be extended.

Further, in the case of an insulating substrate made of ceramic, deformation such as warpage occurs when it is molded or sintered, and the adhesion with the heat conductor deteriorates. However, in the substrate of the present invention mainly composed of a metal base material. This is not the case, and the close contact with the heat conductor is always good.

Further, since the pores in the insulating film are not sealed, the bonding metal is filled in the pores, and the electrodes are bonded onto the pores, so that the bonding strength between the substrate and the electrodes is high. Can be increased.

Further, as described in claim 2, when the surface of the oxide insulating film has fine irregularities and the directions of the pores in the oxide insulating film are not uniform (see Examples 3 to 5), The bonding strength between the base material and the bonding metal is increased, and therefore the service life can be extended.

Further, as described in claim 3, the oxide insulating film contains a high-purity metal containing almost no impurities (for example, a purity of 9).
9.99% by weight) oxide film,
Even if it is extremely thin, high electrical insulation can be obtained and reliability can be improved.

According to the second aspect of the present invention, a relatively thick insulating substrate made of ceramic is not used,
Since the laminated electrode having the thin insulating layer is used, the thermal resistance can be significantly reduced, and the total height of the thermoelectric conversion device can be reduced.

From the above, it is possible to provide a thermoelectric conversion device having a good thermoelectric conversion efficiency and a long service life.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of a substrate according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of an X portion in FIG. 1 (d).

FIG. 3 is a cross-sectional view of a substrate used in Example 2 of the present invention.

FIG. 4 is a cross-sectional view showing a manufacturing process of a substrate according to a third embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a manufacturing process of a substrate according to a fourth embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a manufacturing process of a substrate according to a fifth embodiment of the present invention.

FIG. 7 is an enlarged cross-sectional view of an electrode used in Example 6 of the present invention.

FIG. 8 is a partial cross-sectional view of an electronic refrigerator using the electrode.

FIG. 9 is a partially enlarged sectional view of a conventional electronic cooling device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Aluminum substrate 1a Base material 1b Thin layer for anodic oxidation 2 Insulating film 3 Conductive film 4 Electrode 5 Pore 6 Metal for bonding 7 Aluminum particle 8 Sintered layer 9 Rough surface 10 Hard particle 11 Electrode body 12 Insulating layer 13 For soldering Metal layer 14 Laminated electrode 14a Heat absorption side laminated electrode 14b Radiation side laminated electrode 15 Cooling side heat conductor 16 Radiation side heat conductor 17 P-type semiconductor layer 18 N-type semiconductor layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mitsutoshi Ogasawara 3-20-11 Higashimachi, Muroran-shi, Hokkaido (72) Inventor Tsuyoshi Higashimatsu 3-16-1 Kashiwagicho, Noboribetsu-shi, Hokkaido

Claims (4)

[Claims] 1. A surface of an oxide insulating film formed by forming an oxide insulating film having a large number of pores on at least one surface of a metal substrate, and filling the pores with a binding metal without sealing the pores. A thermoelectric conversion device characterized in that conductivity is imparted to an electrode and an electrode is bonded onto the oxide insulating film. 2. The thermoelectric device according to claim 1, wherein an oxide insulating film is formed on the surface of the metal layer having fine irregularities on the surface, and the orientation of the pores in the oxide insulating film is uneven. Converter. 3. The thermoelectric conversion device according to claim 1, wherein the oxide insulating film is composed of an oxide film of a high-purity metal containing almost no impurities. 4. A P-type semiconductor layer and an N-type semiconductor layer are joined to the electrode body by using a laminated electrode in which a solder joining metal layer is laminated on one surface of the electrode body through an electrically insulating layer, and the solder joint is formed. A thermoelectric converter characterized in that a heat conductor is joined to a metal layer for use.