JP2004063585A - Electrode material for thermoelectric element and thermoelectric element using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce thermal fatigue of a thermoelectric semiconductor and other constitution members by reducing the thermal stress due to a metal electrode of the thermoelectric element and to suppress decrease in element function and element break due to thermal fatigue by using such an electrode material. <P>SOLUTION: The thermoelectric element 1 is characterized in that an n-type thermoelectric semiconductor and a p-type thermoelectric conductor which are arrayed alternately on a support member 2 are connected in series, by a heat-radiation side electrode 6 and a heat-absorption side electrode 7 joined with their ends across solder layers 8 and 9, respectively. The heat-radiation side electrode 6 and heat-absorption side electrode 7 are each formed of a clad electrode material 13 obtained by cladding the surface of a core material 11 made of a low-thermal-expansion metal material with a low-resistant metal material layer 12. The difference in coefficient of thermal expansion of the clad electrode material 13 from the thermoelectric semiconductor is -30 to +10%. <P>COPYRIGHT: (C)2004,JPO

Description

【００４３】
【発明の効果】
以上説明したように、本発明の熱電素子用電極材によれば、熱電素子の金属電極に起因する熱応力が低減されるため、熱電半導体や他の構成部材の熱疲労を軽減することができる。そして、このような電極材を用いた本発明の熱電素子によれば、熱疲労による素子機能の低下や素子破壊の発生を大幅に抑制することが可能となる。すなわち、長期信頼性に優れた熱電素子を提供することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態による熱電素子の概略構造を示す断面図である。
【図２】図１に示す熱電素子の要部を拡大して示す断面図である。
【図３】本発明の熱電素子に使用されるクラッド電極材の一構成例を示す断面図である。
【図４】本発明の熱電素子に使用されるクラッド電極材の他の構成例を示す断面図である。
【図５】本発明の熱電素子に使用されるクラッド電極材のさらに他の構成例を示す断面図である。
【図６】本発明の熱電素子の変形例の構造を示す断面図である。
【図７】本発明の実施例で作製した熱疲労試験用試験体（熱電素子）の構成を示す図である。
【図８】本発明の実施例１で作製した熱電素子構造の各試験体の疲労寿命を電極と熱電半導体との熱膨張差に基づいてプロットした図である。
【符号の説明】
１……熱電素子、２……下部支持部材、３……上部支持部材、４……Ｎ型熱電半導体、５……Ｐ型熱電半導体、６……放電側電極、７……吸熱側電極、１０……直流電源、１１……低熱膨張コア材、１２……低抵抗金属材料層、１３……クラッド電極板[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrode material used for a thermoelectric element using a thermoelectric semiconductor and a thermoelectric element using the same.
[0002]
[Prior art]
A thermoelectric semiconductor such as bismuth (Bi) -tellurium (Te), iron (Fe) -silicide (Si), or cobalt (Co) -antimony (Sb) is used, and a thermoelectric device utilizing its Peltier effect or Seebeck effect is used. The element is used as a cooling or heating device. For example, thermoelectric elements are small and thin and can be cooled without using a heat medium such as liquid or gas (refrigerant). It has been used as a cooling device and a heating device in various fields, and has recently begun to attract attention as a cooling device for a CPU of a personal computer. Further, the thermoelectric element is also used as a power generation element based on a temperature difference between thermoelectric semiconductors, that is, a power generation element using the Seebeck effect.
[0003]
Such a thermoelectric element includes, for example, a plurality of N-type thermoelectric semiconductors and a plurality of P-type thermoelectric semiconductors alternately arranged, and the plurality of thermoelectric semiconductors is arranged on one end side with a heat absorbing side electrode and the other end. It has a structure in which it is connected in series with a heat radiation side electrode arranged on the side of the unit. In such a thermoelectric element, when a direct current is applied to the N-type thermoelectric semiconductor and the P-type thermoelectric semiconductor which are alternately arranged, an electrode (heat-absorbing-side electrode) side on which a current flows from the N-type thermoelectric semiconductor to the P-type thermoelectric semiconductor In this case, heat absorption occurs due to the Peltier effect, and heat dissipation (heat generation) occurs on the electrode (radiation side electrode) side where current flows from the P-type thermoelectric semiconductor to the N-type thermoelectric semiconductor. Therefore, a member to be cooled or a device is arranged on the heat absorption side. By doing so, cooling can be performed.
[0004]
As a specific structure of the thermoelectric element, for example, the following π-type structure is known (for example, JP-A-7-321379, JP-A-11-340527, JP-A-2001-168402, JP 2001-352107 A). That is, a support member such as a ceramic substrate on which the first metal electrode group is formed is prepared, and a plurality of N-type thermoelectric semiconductors and P-type thermoelectric semiconductors are alternately arranged on the first metal electrode group. A second metal electrode group is arranged on the upper end side of the N-type thermoelectric semiconductor and the P-type thermoelectric semiconductor, and each metal electrode is connected to the N-type thermoelectric semiconductor so that all the thermoelectric semiconductors are finally electrically connected in series. And a P-type thermoelectric semiconductor. In such a thermoelectric element, a copper plate or the like having a small electric resistance is applied to each metal electrode so as to withstand a large current, and a relatively thick plate is used.
[0005]
By the way, at the time of the operation of the π-type thermoelectric element as described above, each component (a support member, a metal electrode, a thermoelectric semiconductor, etc.) repeatedly undergoes a cooling / heating cycle. Since there is a difference in thermal expansion between the constituent materials of the thermoelectric element, thermal stress is generated when a cooling cycle is applied. Further, since the thermoelectric element has different thermal expansion (elongation) on the heat absorbing side and the heat radiating side, the entire thermoelectric element bends. The thermoelectric element undergoes thermal fatigue during operation due to the thermal stress caused by the difference in thermal expansion between these constituent materials and the bending of the entire element.The thermal fatigue causes cracks in the thermoelectric semiconductor, peeling of the bonding interface, and soldering. Cracks in the material cause deterioration of element performance such as an increase in resistance value, and further cause element breakage.
[0006]
[Problems to be solved by the invention]
As described above, in the conventional thermoelectric element, various problems occur due to thermal fatigue accompanying the application of the cooling / heating cycle. Specifically, among the constituent materials of the thermoelectric element, a metal electrode made of a copper plate or the like has a larger coefficient of thermal expansion than other constituent materials (support members such as a thermoelectric semiconductor or a ceramic substrate). A large thermal stress is generated at the joint between the metal substrate and the metal electrode and the ceramic substrate.
[0007]
In particular, since the thermoelectric semiconductor is a brittle material and has low mechanical strength, there is a problem that a fatigue crack or the like is easily generated in the thermoelectric semiconductor due to a thermal stress based on a difference in thermal expansion between the thermoelectric semiconductor and the metal electrode. In addition, since the solder layer forming the joint between the metal electrode and the thermoelectric semiconductor also has low fatigue strength, cracks and peeling are likely to occur on the solder layer itself and the joint interface. Similarly, cracks and peeling occur at the joint interface between the metal electrodes and the ceramic substrate due to thermal stress based on the thermal expansion difference.
[0008]
Since the thermoelectric element is constructed by connecting a plurality of thermoelectric semiconductors in series, cracks and peeling may occur even at one place, such as at the thermoelectric semiconductor itself bonded to the metal electrode or at the bonding interface between the metal electrode and other constituent materials. Occurs, the element function of the thermoelectric element is impaired, for example, the resistance value of the entire element increases. For these reasons, there is a strong demand for reducing the thermal stress caused by the metal electrode, thereby suppressing the performance deterioration and the element destruction of the thermoelectric element.
[0009]
The present invention has been made to address such a problem, and by reducing thermal stress caused by metal electrodes of a thermoelectric element, it is possible to reduce thermal fatigue of thermoelectric semiconductors and other components. An object of the present invention is to provide a thermoelectric element for a thermoelectric element, and a thermoelectric element capable of suppressing the deterioration of the element function and the occurrence of element destruction due to thermal fatigue by using such an electrode material.
[0010]
[Means for Solving the Problems]
The electrode material for a thermoelectric element according to the present invention is, as described in claim 1, an electrode material used for a thermoelectric element using a thermoelectric semiconductor, wherein the core material is made of a low thermal expansion metal material, and the surface of the core material is formed. And a low-resistance metal material layer clad with the metal layer. The thermoelectric element electrode material of the present invention is further characterized in that the difference with respect to the coefficient of thermal expansion of the thermoelectric semiconductor is -30% or more and + 10% or less.
[0011]
Further, the thermoelectric element of the present invention has a thermoelectric semiconductor group having an N-type thermoelectric semiconductor and a P-type thermoelectric semiconductor arranged alternately, and one end of the thermoelectric semiconductor group. A thermoelectric element comprising: a joined heat-absorbing electrode; and a heat-dissipating electrode joined to the other end of the thermoelectric semiconductor group so that the N-type thermoelectric semiconductor and the P-type thermoelectric semiconductor are connected in series. Wherein at least one of the heat-absorbing electrode and the heat-radiating electrode is made of the thermoelectric element electrode material of the present invention described above.
[0012]
In the present invention, a low thermal expansion metal material is used as a core material, and an electrode material (clad electrode material) in which a low resistance metal material layer is clad on the surface of the core material is applied to at least one of the heat absorption side electrode and the heat radiation side electrode. ing. According to such a clad electrode material, the coefficient of thermal expansion of the electrode material can be reduced based on the low thermal expansion metal material as the core material. In other words, it is possible to reduce the difference in the coefficient of thermal expansion between the heat-absorbing electrode or the heat-dissipating electrode and the thermoelectric semiconductor or another component. This alleviates the thermal stress applied to the thermoelectric semiconductor, etc., and suppresses cracks due to thermal fatigue of the thermoelectric semiconductor and other components, as well as cracks and delaminations at the bonding interface, thereby deteriorating the function of the thermoelectric element due to thermal cycles. And device destruction can be suppressed.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments for carrying out the present invention will be described.
FIG. 1 is a sectional view showing a schematic structure of a thermoelectric element according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view showing a main part thereof. The thermoelectric element 1 shown in these figures has upper and lower support members 2 and 3, and the lower support member 2 and the upper support member 3 are arranged to face each other. In the thermoelectric element 1 of this embodiment, the lower support member 2 side is a heat dissipation surface, and the upper support member 3 side is a heat absorption surface. That is, the lower support member 2 is a heat dissipation side support member, and the upper support member 3 is a heat absorption side support member.
[0014]
The lower support member (radiation side support member) 2 functions as a structural support for the thermoelectric element 1, and it is preferable to use an insulating ceramic substrate such as an alumina substrate, an aluminum nitride substrate, or a silicon nitride substrate. A ceramic substrate, which is an insulating substrate, may be used for the upper support member 3 (heat absorbing side support member) as in the case of the lower support member 2. If the lower support member 2 can support the entire element structure, the upper support member 3 may be used. The member 3 may be formed of an insulating resin substrate, an insulating resin film, or the like. Note that the upper support member 3 may be formed of an insulating ceramic substrate, and the lower support member 2 may be formed of an insulating resin substrate or an insulating resin film. At this time, the lower support member 2 can be omitted.
[0015]
A plurality of N-type thermoelectric semiconductors 4 and P-type thermoelectric semiconductors 5 are alternately arranged between the lower support member 2 and the upper support member 3 described above, and these are arranged in a matrix as a whole element. To form a thermoelectric semiconductor group. In other words, the thermoelectric semiconductor groups are alternately arranged along one main surface of the lower support member 2. Various known materials can be used for the thermoelectric semiconductors 4 and 5, and a typical example thereof is a Bi-Te-based thermoelectric semiconductor. The Bi-Te-based thermoelectric semiconductor includes at least one element selected from Bi and Sb and at least one element selected from Te and Se as essential elements, and further includes I, Cl, Br, and Compound semiconductors containing additional elements such as Hg, Au, and Cu are known. The thermoelectric semiconductors 4 and 5 are not limited to Bi-Te-based thermoelectric semiconductors, and various types of thermoelectric semiconductors such as Fe-Si-based and Co-Sb-based can be used.
[0016]
The plurality of N-type thermoelectric semiconductors 4 and P-type thermoelectric semiconductors 5 are arranged in a direction from the N-type thermoelectric semiconductor 4 to the P-type thermoelectric semiconductor 5, that is, the N-type thermoelectric semiconductor 4, the P-type thermoelectric semiconductor 5, the N-type thermoelectric semiconductor 4, P Are electrically connected in series by a heat radiation side electrode 6 provided on the lower support member 2 and a heat absorption side electrode 7 provided on the upper support member 3 so that a direct current flows in the order of the mold thermoelectric semiconductors 5. I have. Each of the heat radiation side electrode 6 and the heat absorption side electrode 7 constitutes an electrode group by a plurality.
[0017]
That is, a plurality of heat radiation side electrodes 6 are provided on the surface of the lower support member 2. On the other hand, a plurality of endothermic electrodes 7 are arranged on the upper support member 3 side. The heat absorbing side electrode 7 has a shape for electrically connecting the adjacent N-type thermoelectric semiconductors 4 and P-type thermoelectric semiconductors 5 in this order. Endothermic occurs in the side electrode 7. On the other hand, the heat radiation side electrode 6 has a shape for electrically connecting the adjacent P-type thermoelectric semiconductors 5 and N-type thermoelectric semiconductors 4 in this order except for the electrodes (lead extraction electrodes) at both ends. Heat radiation (heat generation) occurs at the heat radiation side electrode 6 based on the connection order of the thermoelectric semiconductors 5 and 4.
[0018]
Lower ends (radiation-side ends) of the N-type thermoelectric semiconductor 4 and the P-type thermoelectric semiconductor 5 are respectively joined to the radiation-side electrodes 6 via the solder layers 8. The upper ends (heat-absorbing end / cooling surface) of the N-type thermoelectric semiconductor 4 and the P-type thermoelectric semiconductor 5 are similarly joined to the heat-absorbing electrode 7 via the solder layer 9. As described above, the adjacent N-type thermoelectric semiconductor 4 and P-type thermoelectric semiconductor 5 are connected in order by the radiation-side electrode 6 and the heat-absorption-side electrode 7, respectively, so that a plurality of thermoelectric elements 1 can be seen. An N-type thermoelectric semiconductor 4 and a plurality of P-type thermoelectric semiconductors 5 are alternately connected in series.
[0019]
When a DC current is passed from the DC power supply 10 to the thermoelectric semiconductors 4 and 5 to the thermoelectric element 1 having the π-type structure, heat is absorbed at the upper ends of the thermoelectric semiconductors 4 and 5 and heat is released at the lower ends by the Peltier effect. . That is, heat absorption occurs at the heat absorbing side electrode 7 through which a DC current flows from the adjacent N-type thermoelectric semiconductor 4 to the P-type thermoelectric semiconductor 5, and heat dissipation at which a DC current flows from the P-type thermoelectric semiconductor 5 to the N-type thermoelectric semiconductor 4. Heat is generated in the side electrode 6. Therefore, by bringing the object to be cooled (a member, a component, a device, or the like to be cooled) into contact with the upper support member 3 corresponding to the heat absorbing side of the thermoelectric element 1, cooling is performed by removing heat from the object to be cooled. The heat taken from the object to be cooled is radiated from the lower support member 2 corresponding to the heat radiation side of the thermoelectric element 1.
[0020]
In the thermoelectric element 1 having such a structure, the heat radiation side electrode 6 and the heat absorption side electrode 7 are provided with a low resistance metal material layer 12 on the surface of a core material 11 made of a low thermal expansion metal material as shown in FIGS. It is composed of a clad (laminated / integrated) electrode material 13. As a typical structure of the clad electrode material 13, as shown in FIG. 3, a sandwich structure in which a low-resistance metal material layer 12 is clad on both surfaces of a core material 11 is exemplified. However, in the case of a general sandwich structure, the thermal conductivity in the thickness direction is reduced. For example, a structure in which the core material 11 at the end is removed as shown in FIG. 4 and a hole 11a as shown in FIG. Alternatively, a structure in which the low resistance metal material layer 12 is filled in the hole portion 11a using the core material 11 having the following may be applied. Each of these clad materials can be manufactured by a general hot rolling method, an explosion bonding method, a casting method, or the like.
[0021]
In the low-resistance metal material layer 12 constituting the electrode material 13 made of the clad metal as described above, a metal material having high conductivity in maintaining the function as the electrodes 6 and 7 of the thermoelectric element 1, specifically, 3 × 10 resistivity ^-8 Use a metal material of Ω · m or less. Examples of such a low-resistance (high-conductivity) metal material include Cu or a Cu alloy, Ag or an Ag alloy, and Al or an Al alloy. Here, the coefficient of thermal expansion of the constituent material of the low-resistance metal material layer 12 is, for example, 17 × 10 ^-6 / ° C, Ag 19 × 10 ^-6 / ° C, Al is 23 × 10 ^-6 / ° C, which is larger than thermoelectric semiconductors 4, 5 and ceramic substrates.
[0022]
When the electrodes 6 and 7 are made of a low-resistance metal material having a high coefficient of thermal expansion alone, based on a difference in thermal expansion between the thermoelectric semiconductors 4 and 5 and a supporting member (for example, the lower supporting member 2) formed of a ceramic substrate, A large thermal stress acts on the thermoelectric semiconductors 4, 5 and the ceramic substrate when the thermoelectric elements are energized to perform a cooling operation. In particular, in the thermoelectric element, the heat absorption side and the heat radiation side have different amounts of thermal expansion (elongation), and a large stress is applied to the heat radiation side in the substrate surface direction. Such thermal stress causes fatigue cracks in the thermoelectric semiconductors 4 and 5 and the solder layers 8 and 9, and further causes the bonding interface between the thermoelectric semiconductors 4 and 5 and the solder layers 8 and 9 and the electrodes 6 and 7 to the ceramic substrate. Cracks, peeling, etc. occur at the bonding interface of These cracks and interfacial separation cause an increase in the resistance value of the thermoelectric element, which leads to a decrease in element performance, and further cracks destroy the thermoelectric element itself.
[0023]
Therefore, in the thermoelectric element 1 of this embodiment, the electrode material (clad material) 13 in which the low-resistance metal material layer 12 as described above is clad on the surface of the core material 11 made of the low thermal expansion metal material is used. And the heat absorbing side electrode 7. The core material 11 lowers the coefficient of thermal expansion of the electrodes 6 and 7 having the low-resistance metal material layer 12 as described above as a whole of the electrode material 13 made of the clad metal. The coefficient of thermal expansion can be approximated to the coefficient of thermal expansion of a support member made of the thermoelectric semiconductors 4, 5 or a ceramic substrate.
[0024]
For this reason, the core material 11 has an average linear expansion coefficient (25 to 100 ° C.) of 10 × 10 ^-6 It is preferable to use a metal material having a low thermal expansion of not more than / ° C. If the average linear expansion coefficient of the core material 11 is too large, the thermal expansion coefficient of the electrode material (cladding material) 13 can be sufficiently increased depending on the volume ratio (plate thickness ratio) of the low-resistance metal material layer 12 and the core material 11. At the same time, the resistivity cannot be reduced, the resistivity increases, and the thermal conductivity in the thickness direction decreases. As a specific example of the low thermal expansion metal material, W (average linear expansion coefficient: 4.5 × 10 ^-6 / ° C), Mo (average coefficient of linear expansion: 5.1 × 10) ^-6 / ° C), Ta (average coefficient of linear expansion: 6.5 × 10) ^-6 / ° C), Zr (average coefficient of linear expansion: 5.0 x 10) ^-6 / ° C), Nb (average coefficient of linear expansion: 7.2 x 10) ^-6 / ° C), V (average coefficient of linear expansion: 8.3 × 10) ^-6 / ° C) and a low thermal expansion Fe-based alloy.
[0025]
Among the low thermal expansion metal materials described above, the low thermal expansion Fe-based alloy is particularly excellent in the cladding property with the low resistance metal material layer 12 made of Cu, Ag, Al or the like. It is suitable. As the low thermal expansion Fe-based alloy, an Invar alloy (for example, Fe-36 mass% Ni / average linear expansion coefficient: 1.2 × 10 ^-6 / ° C), Super Invar alloy (for example, Fe-31% by mass Ni-5% by mass Co / average coefficient of linear expansion: 0.5 × 10 ^-6 / ° C), Kovar alloy (for example, Fe-29% by mass Ni-17% by mass Co / average coefficient of linear expansion: 4.8 × 10 ^-6 / Alloy), 42 alloy (Fe-42 mass% Ni / average coefficient of linear expansion: 5.3 x 10) ^-6 / ° C).
[0026]
Further, the thermal expansion coefficient of the clad electrode material 13 itself is preferably within a range from -30% to + 10% with respect to the thermal expansion coefficients of the thermoelectric semiconductors 4 and 5. Here, the difference α between the thermal expansion coefficients of the clad electrode material 13 and the thermoelectric semiconductors 4 and 5 is represented by α ₁ , The coefficient of thermal expansion of the thermoelectric semiconductors 4, 5 is α ₂ And the equation: α = [(α ₁ −α ₂ ) / Α ₂ × 100 (%)]. If the thermal expansion difference α between the clad electrode material 13 and the thermoelectric semiconductors 4 and 5 is out of the above range, the thermal stress generated when the thermoelectric element 1 is energized to perform the cooling operation cannot be sufficiently reduced. In other words, by setting the thermal expansion difference α within 30%, the thermal stress generated in the thermoelectric semiconductors 4, 5 and the like during the cooling operation of the thermoelectric element 1 is effectively suppressed, and the thermoelectric semiconductors 4, 5, the solder layer 8, 9. It is possible to reduce thermal fatigue of a ceramic substrate or the like. The thermal expansion difference α is more preferably in the range of −20% to + 10%.
[0027]
The coefficient of thermal expansion of the clad electrode material 13 is a weighted average of the coefficients of thermal expansion of the core material 11 and the low-resistance metal material layer 12 at respective volume ratios. Therefore, the thermal expansion difference α between the clad electrode material 13 and the thermoelectric semiconductors 4 and 5 is set in the above-described range in consideration of the thermal expansion coefficients of the electrode constituent materials and the thermoelectric semiconductors 4 and 5. It is preferable to appropriately select the thickness ratio of the core material 11 and the low-resistance metal material layer 12. However, if the thickness of the low-resistance metal material layer 12 is too small, the electrical characteristics (such as conductivity) of the electrodes 6 and 7 are reduced. Is preferably 30% or more. The upper limit of the thickness ratio of the low-resistance metal material layer 12 is appropriately set according to the target thermal expansion difference α. Generally, the total thickness of the clad electrode material 13 is suitably about 0.15 to 0.5 mm.
[0028]
In the thermoelectric element 1 of this embodiment, the heat radiation side electrode 6 and the heat absorption side electrode 7 are constituted by the clad electrode material 13 having the low thermal expansion core material 11 and the low resistance metal material layer 12, so that the respective electrodes 6, 7 And a thermal expansion difference between the thermoelectric semiconductors 4 and 5 and a support member made of a ceramic substrate. This reduces the thermal stress when the above-described thermoelectric element 1 is energized to perform a cooling operation, so that the thermoelectric semiconductors 4 and 5 and the fatigue cracks of the solder layers 8 and 9 due to the thermal stress and the thermoelectric semiconductor 4 The generation of cracks, peeling, and the like at the bonding interface between the solder layers 8 and 9 and the bonding interface between the thermoelectric semiconductors 4 and 5 and the ceramic substrate can be effectively suppressed. As a result, it is possible to prevent the thermoelectric element 1 from deteriorating its function due to a thermal cycle, breaking the element, and the like. That is, the long-term reliability of the thermoelectric element 1, particularly the long-term reliability of the thermoelectric element 1 used under a condition in which a cooling cycle is frequently added, can be greatly improved.
[0029]
In the embodiment described above, the case where the clad electrode material 13 is applied to both the heat radiation side electrode 6 and the heat absorption side electrode 7 has been described. However, the present invention is not limited to this, and the heat radiation side electrode 6 and the heat absorption side It is also possible to adopt a structure in which the clad electrode material 13 is applied to one of the electrodes 7. In such an element structure, although the effect of reducing thermal fatigue is slightly reduced, thermal fatigue and the occurrence of cracks associated therewith can be reduced as compared with the case where a single electrode of Cu is used for both electrodes. The clad electrode material 13 is preferably applied to at least the heat radiation side electrode 6 having a large thermal expansion.
[0030]
The thermoelectric element 1 having the above-described configuration includes a cold storage and a temperature control device of a semiconductor manufacturing apparatus, and a cooling device for a high heat generation semiconductor component such as an ultra-high integrated circuit element and a laser element such as a CPU of a computer. It is suitably used for cooling devices in various fields. In actual use, the heat-absorbing surface (upper support member 3 corresponding to the heat-absorbing side) of the thermoelectric element 1 and the object to be cooled (various members, parts, devices) are directly or silicone grease while maintaining an insulated state. By contacting through the intermediary, it can function as a cooling device or the like.
[0031]
In the above-described embodiment, the structure in which the support members 2 and 3 of the thermoelectric element 1 are arranged on the upper and lower surfaces of the thermoelectric semiconductors 4 and 5 has been described. However, the present invention is not limited to such a structure. As shown in FIG. 6, a thermoelectric element 1 in which a structural support member 14 (corresponding to the lower support member 2 in FIG. 1) for holding the element structure is arranged at an intermediate position between the N-type thermoelectric semiconductor 4 and the P-type thermoelectric semiconductor 5 It is also possible to apply to. In this case, insulating members 15 and 16 made of an insulating resin substrate, an insulating resin film or the like are arranged on both upper and lower surfaces of the thermoelectric semiconductors 4 and 5.
[0032]
【Example】
Next, specific examples of the present invention will be described.
[0033]
Example 1
First, as a low thermal expansion core material, Super Invar alloy plates of various thicknesses (average coefficient of linear expansion: 0.5 × 10 ^-6 / ° C). Electro-copper plates of various thicknesses (average coefficient of linear expansion: 17 × 10 4) as low-resistance metal material layers on both surfaces of such a Super Invar alloy plate (core material). ^-6 / ° C) by a hot rolling method to produce a plurality of clad electrode plates (sandwich structure) having a final plate thickness of 5 mm.
[0034]
Next, as shown in FIG. 7, the alumina ceramic substrate 21 having a size of 10 mm × 20 mm × 1.5 mm and each of the above-mentioned clad electrode plates (shape: 5 mm × 5 mm × thickness 0.5 mm) were respectively subjected to the DBC method ( Heating to a temperature equal to or higher than the eutectic temperature of copper and copper oxide and equal to or lower than the melting point of copper, and directly bonding without using a brazing material). On the alumina ceramic substrate 21, two clad electrode plates 22a and 22b having the same clad structure were joined.
[0035]
Each of the clad electrode plates 22a and 22b bonded to the alumina ceramic substrate 21 and the clad electrode plate (shape: 5 mm × 5 mm × thickness 0.5 mm) 23 having the same structure were processed into a 3 mm square cube. Bi ₂ Te ₃ The alloys (thermoelectric semiconductors) 24 and 25 were joined so as to sandwich them, and test specimens 26 were produced. Each clad electrode plate 22, 23 and Bi ₂ Te ₃ The alloys 24 and 25 were joined by solder (the thickness of the solder layer 27 was 0.01 mm). Each test piece was provided with a lead wire 28 for energization and evaluation.
[0036]
Next, the test specimens 26 described above were alternately placed in a bath of an inert solvent maintained at 0 ° C. and 80 ° C. to perform a thermal fatigue test. The progress of fatigue was evaluated by measuring the change in resistance between the clad electrode plates 22a and 22b on the ceramic substrate 21 side, and the time when the resistance became 70% of the initial value was defined as the fatigue life. FIG. 8 shows the measurement results of the fatigue life. FIG. 8 shows each clad electrode plate 22, 23 and Bi ₂ Te ₃ The horizontal axis indicates the thermal expansion difference α of the alloys 24 and 25 (calculated by the above-described formula), and the vertical axis indicates the fatigue life of each specimen 26.
[0037]
As shown in FIG. ₂ Te ₃ By using the clad electrode plates 22 and 23 having a thermal expansion difference α of −30% or more and + 10% or less with the alloys 24 and 25, the fatigue life of the test specimen (corresponding to a thermoelectric element) 26 can be greatly improved. It becomes. In FIG. 8, the test piece having a thermal expansion difference α of + 28% is not a clad electrode plate but a single copper plate used as an electrode. This thermal expansion difference α is a value obtained by the equation [(16.6-12.96) /12.95×100=+28%]. In addition, as a low-resistance metal material layer of the above-mentioned clad electrode plates 22 and 23, a clad electrode plate using an Ag plate and an Al plate instead of an electrolytic copper plate was produced, and a similar thermal fatigue test was performed. ₂ Te ₃ It was also confirmed that good results were obtained by using a clad electrode plate having a thermal expansion difference α between alloys 24 and 25 of −30% or more and + 10% or less.
[0038]
Example 2, Comparative Examples 1-2
In the test piece 26 described above, Bi ₂ Te ₃ Instead of the alloy, Bi28at. % -Te57at. % -Sb12at. % -Se3at. % N-type thermoelectric semiconductor 24 and Bi10 at. % -Te57at. % -Sb10at. % -Se3at. Using the P-type thermoelectric semiconductor 25 having a composition of 25%, a test thermoelectric element was actually manufactured. For each of the electrodes 22 and 23, a clad electrode plate having a thermal expansion difference α of −29% from that of the Bi—Te-based thermoelectric semiconductor was used. The specific configuration of this clad electrode plate is such that the total plate thickness is 0.3 mm, the plate thickness of the core material in the clad material is 0.18 mm, and the plate thicknesses of the copper layers on both sides thereof are 0.06 mm, Thermal expansion coefficient as cladding material is 9.2 × 10 ^-6 / ° C.
[0039]
As a comparative example with the present invention, a thermoelectric element using a clad electrode plate having a thermal expansion difference α of −37% between a thermoelectric element using a single electrode plate of copper (Comparative Example 1) and a Bi—Te-based thermoelectric semiconductor was used. Each of the devices (Comparative Example 2) was manufactured. The element structure other than the electrode plate was the same as in Example 2.
[0040]
Each of the test thermoelectric elements of Example 2 and Comparative Examples 1 and 2 thus obtained was subjected to a thermal fatigue test by repeating current supply. The specific conditions of the thermal fatigue test are as follows. In the test thermoelectric element, the ceramic substrate 21 side was the heat radiation side, and a water-cooled copper block was pressed and forcedly cooled to always 25 ° C. In this state, a current was applied to perform a thermal fatigue test between room temperature and -40 ° C. As a result, in the test thermoelectric element of Example 2, the resistance change was 3% or less of the initial value even after 1000 or more thermal cycles (energization cycle), whereas in Comparative Example 1, the change was 50 times. The energization failure (life) was caused by the application of the thermal cycle, and in Comparative Example 2, the energization failure (life) was caused by the application of the 231 heat cycles.
[0041]
Examples 3 to 10
A test thermoelectric element was produced in the same manner as in Example 2 except that each clad electrode material shown in Table 1 was used. For each of these test thermoelectric elements, a thermal fatigue test was performed in the same manner as in Example 2. The results are shown in Table 1. As is clear from Table 1, each of the test thermoelectric elements exhibited good life characteristics.
[0042]
[Table 1]

[0043]
【The invention's effect】
As described above, according to the thermoelectric element electrode material of the present invention, the thermal stress caused by the metal electrode of the thermoelectric element is reduced, so that the thermal fatigue of the thermoelectric semiconductor and other components can be reduced. . According to the thermoelectric element of the present invention using such an electrode material, it is possible to significantly suppress the deterioration of the element function and the occurrence of element destruction due to thermal fatigue. That is, a thermoelectric element having excellent long-term reliability can be provided.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a schematic structure of a thermoelectric element according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view showing a main part of the thermoelectric element shown in FIG.
FIG. 3 is a cross-sectional view showing one configuration example of a clad electrode material used in the thermoelectric element of the present invention.
FIG. 4 is a cross-sectional view showing another configuration example of the clad electrode material used in the thermoelectric element of the present invention.
FIG. 5 is a cross-sectional view showing still another configuration example of the clad electrode material used in the thermoelectric element of the present invention.
FIG. 6 is a sectional view showing a structure of a modification of the thermoelectric element of the present invention.
FIG. 7 is a diagram showing a configuration of a test body (thermoelectric element) for a thermal fatigue test manufactured in an example of the present invention.
FIG. 8 is a diagram in which the fatigue life of each test piece of the thermoelectric element structure manufactured in Example 1 of the present invention is plotted based on the thermal expansion difference between the electrode and the thermoelectric semiconductor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... thermoelectric element, 2 ... lower support member, 3 ... upper support member, 4 ... N-type thermoelectric semiconductor, 5 ... P-type thermoelectric semiconductor, 6 ... discharge side electrode, 7 ... heat absorption side electrode, 10 DC power supply 11 Low thermal expansion core material 12 Low resistance metal material layer 13 Clad electrode plate

Claims (3)

An electrode material used for a thermoelectric element using a thermoelectric semiconductor, comprising: a core material made of a low thermal expansion metal material; and a low resistance metal material layer clad on a surface of the core material. Electrode material for device. The electrode material for a thermoelectric element according to claim 1,
The electrode material for a thermoelectric element, wherein a difference between a coefficient of thermal expansion of the electrode material and a coefficient of thermal expansion of the thermoelectric semiconductor is −30% or more and + 10% or less. A thermoelectric semiconductor group having an N-type thermoelectric semiconductor and a P-type thermoelectric semiconductor arranged alternately; a heat-absorbing electrode joined to one end of the thermoelectric semiconductor group; the N-type thermoelectric semiconductor and the P-type thermoelectric semiconductor Are connected in series, in a thermoelectric element including a heat-radiation-side electrode bonded to the other end of the thermoelectric semiconductor group,
3. A thermoelectric element, wherein at least one of the heat absorption side electrode and the heat radiation side electrode is made of the thermoelectric element electrode material according to claim 1.

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