JPH06310765A - Thermionic element and thermionic device - Google Patents

Abstract

PURPOSE:To protect a thermionic semiconductor against damage or falling off by composing the electrode of a thermionic element of a nickel layer and a copper layer or a copper alloy layer of specific or larger thickness. CONSTITUTION:A contact electrode having double structure of a nickel plating layer and a copper plating layer of 10mum thick or thicken formed at the opposite ends of a Bi-Te based thermionic semiconductor 13 is bonded through a solder layer 18 to a copper electrode formed on a heat-exchanging board 11 comprising an insulating board of alumina ceramic, for example. The thick copper plating layer in the contact electrode relaxes concentration of stress and the copper having the properties for reducing the oxide of solder flux also provides high wettability to the solder thus enhancing the reliability. This structure enhances durability against the temperature cycle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric element and a thermoelectric device using the same, and more particularly to an electrode structure thereof.

[0002]

2. Description of the Related Art A p-type semiconductor and an n-type semiconductor are joined to each other through a metal electrode to form a pn element pair, and one end is made to generate heat and the other is made to go by the direction of the current flowing through this joint. Thermoelectric elements that utilize the so-called Peltier effect, whose ends can be cooled, are expected to be widely used in various devices such as portable coolers because of their small size and simple structure.

Conventionally, such a thermoelectric element has, as shown in FIG. 4, a contact electrode 106 having a two-layer structure of a nickel plating layer 106a and a solder layer 106b formed at both ends of a Bi-Te system thermoelectric semiconductor 103, for example. It was formed by fixing to a copper electrode 105 formed on a heat exchange substrate 101 made of an insulating substrate such as an alumina ceramic. In this case, since the contact electrode 106 is formed to be extremely thin, the stress generated due to the difference in coefficient of thermal expansion between the thermoelectric semiconductor 103 and the heat exchange substrate 101 is entirely applied to the solder layer 10.
Since it takes 6b, there is a problem that the durability against the temperature cycle is poor.

A thermomodule formed by collecting a large number of such thermoelectric elements has, for example, as shown in FIG. 5, a first and a second insulating substrates made of an insulating ceramic material such as an alumina ceramic substrate. Second heat exchange substrate 111, 112
A large number of PN element pairs 113 are sandwiched between them so as to have good thermal contact therewith, and each element pair 113 is connected in series by the first and second electrodes 114 and 115, respectively. Is configured.

Then, the first and second electrodes 11
4, 115 are usually made of a copper plate so as to be able to withstand a large current, and are fixed on a conductor layer pattern formed on the surfaces of the heat exchange substrates 111, 112 via a solder layer 116b.

Further, a pair of P-type thermoelectric elements 113a or N-type thermoelectric elements 113b are alternately fixed on the first and second electrodes via a solder layer 116b and a nickel layer 116a, respectively. The pair 113 is formed and each element pair is connected in series.

Since the P-type thermoelectric element 113a and the N-type thermoelectric element 113b have different characteristics such as thermoelectromotive force and electric resistance, it may be necessary to change the size, but it is usually difficult to mount them. Used the same type of thermoelectric element for both P type and N type.

However, when the P-type and N-type thermoelectric elements having different characteristics have the same shape, the P-type thermoelectric element 113 is used.
There is a problem in that the electrical matching (compatibility) cannot be optimized between a and the N-type thermoelectric element 113b, and the performance as a thermoelectric module is deteriorated.

[0009]

As described above, due to the stress concentration due to the difference in the thermal expansion coefficient between the heat exchange substrate material or electrode of the conventional thermoelectric device and the thermoelectric semiconductor body, the temperature difference between the low temperature side and the high temperature side is high. There is a problem that the thermoelectric semiconductor may be damaged or fall out as the temperature becomes larger or the temperature change becomes larger.

In the thermoelectric device, the P-type thermoelectric element 113a is used.
Since the N-type thermoelectric element 113b and the N-type thermoelectric element 113b have different characteristics such as thermoelectromotive force and electric resistance, it may be necessary to change the size, but due to the difficulty of mounting, the thermoelectric elements having the same shape are usually used. , The P-type thermoelectric element 113 has the same shape.
There is a problem in that the electrical matching cannot be optimized between a and the N-type thermoelectric element 113b, and the performance of the thermoelectric module deteriorates.

The present invention has been made in view of the above circumstances, and the shape factor can be selected relatively freely, and the temperature difference ΔT between the high temperature portion and the low temperature portion is large or the temperature change is large. The present invention is also applicable, and an object thereof is to provide a highly reliable thermoelectric device without damaging or dropping the thermoelectric semiconductor.

[0012]

Therefore, in the present invention, the contact electrode formed on the thermoelectric semiconductor of the thermoelectric element is composed of a nickel layer and a copper layer having a thickness of 10 μm or more or an alloy layer containing copper.

According to a second aspect of the present invention, a pair of electrodes formed facing each other at both ends of the thermoelectric semiconductor body is formed.
The thickness of the thermoelectric semiconductor body is 80% or less of the thickness of the thermoelectric element.

Further, in a third aspect of the present invention, there is provided a thermoelectric device in which at least one thermoelectric element pair consisting of an n-type thermoelectric element and a p-type thermoelectric element is provided on a heat exchange substrate via electrodes, wherein the n-type thermoelectric element is provided. A thermoelectric element and a p-type thermoelectric element are formed opposite to each other at both ends of the n-type and p-type thermoelectric element bodies, respectively.
A pair of electrodes, one of the thermoelectric element bodies is thicker than the other thermoelectric element body, and the n-type thermoelectric element and the p-type thermoelectric element have the same total thickness of each electrode. The thickness is adjusted.

[0015]

According to the above structure, the copper layer or the alloy containing copper has good wettability with the solder, and the solder is well adapted to the side surface of the thick copper layer or the alloy layer containing copper. Stress concentration can be relaxed, and durability against temperature cycling can be increased.

According to the second aspect of the present invention, since the thermoelectric element having a thickness 1.2 times or more the thickness of the thermoelectric semiconductor body is formed, the thermoelectric element having a very small thickness can be easily assembled. is there. Further, the L / A (thickness / cross-sectional area) of the element, that is, the form factor can be relatively freely selected, and the maximum current value can be freely selected.

Further, according to the third aspect of the present invention, the p-type thermoelectric element body and the n-type thermoelectric element body can be designed so as to have different lengths in the same cross section, and are optimal even when the electric characteristics are different from each other. It can be designed and is easy to mechanically assemble.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

Example 1 This thermoelectric element has a partially enlarged sectional view as shown in FIG.
The contact electrode is formed by a nickel plating layer 16 and a copper plating layer 17 having a thickness of 15 μm, which is connected to the heat exchange substrate via a solder layer 18.

That is, the nickel plating layers 16 formed on both ends of the Bi-Te system thermoelectric semiconductor 13 and the thickness of 15 μm.
The copper-plated layer 17 and the contact electrode having a two-layer structure are connected to the copper electrode 15 formed on the heat exchange substrate 11 made of an insulating substrate such as alumina ceramic and the solder layer 1
It is formed by fixing via 8.

According to this structure, since the contact electrode includes the thick copper plating layer, stress concentration is relaxed by the copper plating layer, and copper has a property of easily reducing the oxide of the solder flux, and the copper Since the wettability is also good, the connection is highly reliable. Therefore, the durability against temperature cycling is increased.

Example 2 As shown in FIG. 2, this thermoelectric element has a 1.3 mm thick copper plating layer 27 with Ni plating layers 26 at both ends of an ultrathin thermoelectric semiconductor 23 having a thickness of 0.2 mm. Is formed.

That is, the nickel plating layers 26 formed on both ends of the Bi-Te system thermoelectric semiconductor 23 and the thickness of 1.0 mm
A thick contact copper plating layer 27 and a contact electrode having a two-layer structure, which is formed on a heat exchange substrate (not shown) made of an insulating substrate such as alumina ceramic (see FIG. (Not shown) is fixed via a solder layer.

According to this structure, in addition to the effects of the first embodiment, since the thermoelectric element having a thickness of 6 times or more the thickness of the thermoelectric semiconductor body is formed, the thermoelectric element having a very thin thickness can be assembled. It's easy. In addition, L / A of element (thickness / cross-sectional area)
That is, the form factor can be relatively freely selected, and the maximum current value can be freely selected.

Example 3 In this thermoelectric device, as shown in FIG. 3, the p-type thermoelectric element and the n-type thermoelectric element have the same cross-sectional area, and the p-type thermoelectric semiconductor 33a is thinner than the n-type thermoelectric semiconductor 33b. However, this difference is compensated by adjusting the thickness of the copper plating layers 37a and 37b forming the contact electrodes to form thermoelectric element pairs having the same total length.

That is, the p-type (Bi-Te based) thermoelectric semiconductor 33a is made thinner than the p-type (Bi-Te based) thermoelectric semiconductor 33b, and the copper plating layers formed on both ends of the nickel plating layer 36 are interposed therebetween. Fixing the contact electrode having a two-layer structure formed by 37a and 37b to the copper electrode 35 formed on the heat exchange substrates 31 and 32 made of an insulating substrate such as alumina ceramic through the solder layer 38. Is formed by. Here, the copper plating layer 37a of the p-type thermoelectric element is
The p-type thermoelectric semiconductor 33a and the p-type thermoelectric semiconductor 33b are formed to be thicker by a half of the difference in thickness, so that both elements can be satisfactorily connected to the heat exchange substrates 31 and 32.

With this structure, the p-type thermoelectric element body and the n-type thermoelectric element body can be designed to have different lengths in the same cross section, and optimal design can be performed even when the electric characteristics are different from each other. The maximum current value can be made equal. Furthermore, mechanical assembly is easy.

In the above embodiment, an example using a copper plating layer has been described, but other materials such as copper alloy may be used.

[0029]

As described above, according to the present invention, it is possible to obtain a thermoelectric element and a thermoelectric device which have improved durability against temperature cycles, are easy to assemble, and have a high degree of freedom in design.

[Brief description of drawings]

FIG. 1 is a diagram showing a thermoelectric element according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a thermoelectric element according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a thermoelectric device according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a conventional thermoelectric device.

FIG. 5 is a diagram showing a conventional thermoelectric device.

[Explanation of symbols]

 1 Heat Exchange Substrate 31, 32 ... Heat Exchange Substrate 33a P-type Bi-Te Thermoelectric Semiconductor 33b N-type Bi-Te Thermoelectric Semiconductor 35 Electrode 36 Nickel Plating Layer 37a, b Copper Plating Layer 38 Solder Layer

Claims (3)

[Claims] 1. A thermoelectric element body made of a semiconductor material having a Peltier effect, and a thermoelectric element body mounted on opposite ends of the thermoelectric element body so as to face each other.
A thermoelectric element comprising a pair of electrodes, the electrode comprising a nickel layer and a copper layer having a thickness of 10 μm or more or an alloy layer containing copper. 2. A thermoelectric element body comprising a thermoelectric element body made of a semiconductor material having a Peltier effect, and a pair of electrodes formed opposite to each other at both ends of the thermoelectric element body. 80% of the thickness of the thermoelectric element
A thermoelectric element characterized by the following. 3. A thermoelectric device in which at least one thermoelectric element pair consisting of an n-type thermoelectric element and a p-type thermoelectric element is provided on a heat exchange substrate via electrodes, wherein the n-type thermoelectric element and the p-type thermoelectric element are provided. The element is composed of a pair of electrodes formed opposite to each other at both ends of the n-type and p-type thermoelectric element bodies, one thermoelectric element body being thicker than the other thermoelectric element body, and A thermoelectric device characterized in that the thickness of each electrode is adjusted so that the n-type thermoelectric element and the p-type thermoelectric element have the same thickness.