JPH0485974A - Thermoelectric device - Google Patents

Abstract

PURPOSE:To maintain excellent characteristic without damage and removal even if a temperature difference between a low temperature section and a high temperature section is large by composing a heat exchanging board of a material having low thermal expansion coefficient. CONSTITUTION:Copper tungsten electrodes 4, 5 are formed on a heat exchanging board formed of a material having 4X10<-6>/ deg.C or below of linear expansion coefficient such as low expansion glass boards (Vycor of 96% quartz) 1, 2 through a nickel metallized layer M by a thick film method, and a thermoelectric element 3 is secured thereto to complete it. Since the boards 1, 2 are formed of the material having low thermal expansion coefficient, even if a temperature difference between a low temperature section and a high temperature section is large, excellent characteristics are maintained, and high reliability is provided.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a thermoelectric device, and particularly relates to a mounting structure for a thermoelectric device that has a large temperature difference between a low-temperature part and a high-temperature part. .

[Conventional technology]

A P-type semiconductor and an N-type semiconductor are bonded via metal to form a P-type semiconductor.
Thermoelectric elements that utilize the so-called Beltier effect, in which N element pairs are formed and one end is heated and the other end is cooled depending on the direction of current flowing through the junction, are small and simple in structure. Therefore, it is expected to be widely used in various devices such as portable coolers.

A thermo module formed by collecting a large number of such thermoelectric elements has first and second heat exchangers made of insulating substrates with good thermal conductivity such as alumina ceramic substrates, as shown in FIG. Substrate 11, . A large number of PN element pairs 1 are connected to each other so as to have good thermal contact between the 12
3 are sandwiched between each other, and each element pair 13 is connected in series by first and second electrodes 14 and 15, respectively.

The first and second electrodes 14.15 are usually made of copper plates so as to withstand large currents, and the heat exchanger substrate 1.
1.12 It is fixed on the conductor layer pattern formed on the surface via a welding layer such as solder.

Furthermore, pairs of P-type thermoelectric elements 1.3a or N-type thermoelectric elements 13b are alternately fixed onto the first and second electrodes via solder layers, thereby forming a PN element pair 13. In addition, each element is connected in series.

By the way, in such a thermoelectric device structure, in order to improve assembly workability when positioning and fixing the electrodes to the heat exchange substrate, the electrodes are constructed with a thick film conductor layer pattern formed on the surface of the heat exchange substrate. is proposed.

According to a thermoelectric device having such a structure, the step of positioning the electrode plate to the conductor pattern on the heat exchange board and the step of fixing it are not necessary, and the process can be greatly simplified, and the connection between the conductor pattern and the electrodes can be greatly simplified. No positional deviation occurs, and reliability can be improved.

By the way, in order to increase the heat exchange efficiency, the heat exchange board must be made of an insulating material with good thermal conductivity, and in order to prevent deterioration due to thermal distortion, it must be made of a material with a small coefficient of thermal expansion. Must.

However, alumina ceramic substrates and beryllia ceramic substrates, which have been conventionally used as heat exchange substrate materials, have a large coefficient of linear expansion of 7×10-'/"C, and a coefficient of linear expansion of 16.5xlCM'/"C. ``Since the copper electrode of C was formed, there was a problem that the thermoelectric semiconductor could be damaged due to thermal stress.

Therefore, in order to alleviate stress, the board has a divided structure,
A method has been proposed in which a skeleton structure consisting only of electrodes without using a substrate is used, but this method has the problem of making the structure complicated.

In addition, while the temperature difference Δt between the high-temperature part and the low-temperature part used to be about 40 to 50°C, recently, the temperature difference Δt between the high-temperature part and the low-temperature part has been increased to 60 to 100°C by using heaters and refrigerants in combination.
A split structure has been proposed, and if it is a split structure, the heat transfer efficiency is poor and it is not possible to increase the heat exchange efficiency, and there are also problems with strength, and conventional materials and structures cannot cope with it. It's coming.

(Problem to be Solved by the Invention) As described above, since the substrate materials and electrodes of conventional thermoelectric devices have a large coefficient of thermal expansion, as the difference between the low temperature side and the high temperature side increases, the thermoelectric semiconductor Damaged or
There was a problem with it falling off.

The present invention has been made in view of the above-mentioned circumstances, and is applicable even when the temperature difference Δt between the high temperature part and the low temperature part is large.
The purpose is to provide a highly reliable thermoelectric device without the thermoelectric semiconductor being damaged or falling off.

[Structure of the invention]

(Means for Solving the Problems) Therefore, in the present invention, the heat exchange substrate has a linear expansion coefficient of 4×10
It is made of materials with a temperature of -6/℃ or less.

Desirably, an electrode material having a small difference in linear expansion coefficient from the heat exchange substrate material is used.

Preferably, the electrodes are made of an electrode pattern made of a material having a linear expansion coefficient of 8×10 −6 /° C. or less and a volume resistivity of 10 −6 Ωel or less.

Preferably, the heat exchange substrate is made of quartz glass, low expansion glass,
It is made of one of the amber alloys.

Further, the electrodes are made of high melting point metals such as amber alloy, molybdenum, tungsten, and tantalum, or alloys of these and copper.

(Function) According to the above configuration, since the heat exchange board is made of a material with a small coefficient of thermal expansion, even if there is a large temperature difference between the low temperature part and the high temperature part, it will not be damaged or fall off. , good characteristics can be maintained.

Furthermore, since a material with a small difference in linear expansion coefficient from that of the heat exchange substrate is used as the electrode material, even if the temperature difference between the upper and lower substrates is large, the thermoelectric semiconductor will not be damaged by thermal stress.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Example 1 As shown in FIG. 1, this thermoelectric device was constructed by forming a film with a thickness of 5 μm on the surface of a low expansion glass substrate (96% quartz Vycor) 1.2.
Copper-tungsten electrodes 4 and 5 with a film thickness of 120 .mu.m are formed by a thick film method via a nickel metallized layer N1, and a thermoelectric element 3 is fixed thereto.

For this thermoelectric device, the operation of setting the high temperature side to 60°C and the low temperature side temperature to 0°C was repeated for 5 minutes on and 15 minutes off.
Table 1 shows the results of measuring the internal resistance change rate after 1000 cycles, 10000 cycles, and 30000 cycles.

Table 1 2.0% 1.5% 3.0% Cycle l　　　　　zoo.

No. N0.1 2. 0% sample no.
21,0% Sample No. 31,5% 3,5% 4,0% 5,5% As is clear from Table 1, according to the thermoelectric device of the present invention, the internal resistance change rate remains constant even after 30,000 cycles. It can be seen that is kept small.

Furthermore, it is extremely reliable with no damage or falling off. In the conventional thermoelectric device shown in FIG. 5, two out of three devices were damaged.

For comparison, Table 2 shows the results of a similar test conducted on the conventional thermoelectric device shown in FIG.

Although copper tungsten is used for the lath and electrodes, the present invention is not limited thereto, and combinations of other materials may be used. Table 3 shows examples of combinations of other materials.

Table 3 Substrate material Silica glass Low-heavy truss Surface insulation amber alloy metallized layer Ni
Cu-W Ni Mn-No Ti Electric HR Amber Alloy Molybdenum Copper Tungsten Alloy Tantalum Table 2 5.5% 3.5% 4.0% Cycle 1000 Sample No. 11.5% Sample No. 22.5% +7 pull NO, 32. 0% 55% A comparison between Tables 1 and 2 shows that according to the present invention, the rate of change in internal resistance can be suppressed significantly.

In the first embodiment, a low-heavy bulge is used as the substrate.Next, a second embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 2, this thermoelectric device uses substrates made of conductive amber alloy as the first and second heat exchange substrates 21 and 22.

After forming a silicon oxide film 26 with a thickness of 100 μm on this heat exchange substrate by plasma spraying, a W metallized layer is formed, and an electrode chip made of an amber alloy is soldered onto this using Pb-5n solder. This is what I did.

The thermoelectric element 3 is similarly fixed to the electrodes 4 and 5 via Pb-5n solder.

For this thermoelectric device, the operation of setting the high temperature side to 60°C and the low temperature side temperature to 0°C was repeated with 5 minutes on and 15 minutes off as in Example 1, and after 1000 cycles at this time, 10000 cycles Table 4 shows the results of measuring the internal resistance change rate after 30,000 cycles.

Table 4 1, 0000 2.8% 1.9% 3.3% Cycle l 1000 Sample No. l 1 Sample No. 0.2 0. 5% size no.
31,2% 0% 3,4% 3,7% 4,2% As is clear from Table 4, according to the thermoelectric device of the present invention, the internal resistance change rate remains small even after 30,000 cycles. I know that there is.

Example 3 Next, a third embodiment of the present invention will be described.

As shown in Fig. 3, this thermal lightning device has first and second
Low expansion glass is used as the heat exchange substrates 31 and 32, and the tank stencil electrode patterns 34' and 35 are formed by a thick film method.

The thermoelectric element 3 is, as shown in an enlarged view in FIG.
A nickel plating layer 37 is formed on both sides of the P-type and N-type B1-Te semiconductors 33a33b.

A Pb-3n solder plating layer 38 is formed.

Further, on the surface of the second heat exchange substrate 32, a film with a thickness of 150 μm is provided.
m tungsten layer 39 and a 10 μm thick Pb-3n layer 39
An electrode pattern 35 having a two-layer structure with a solder plating layer 38 is formed, and a P-type thermoelectric element 33a and an N-type thermoelectric element 33b are fixed thereon. On the other hand, a two-layer electrode pattern is similarly formed on the other side.

Although an enlarged view of the main parts is not shown, the first heat exchange board 31 also has the same structure as the second heat exchange board.

In this way, the adjacent P-type thermoelectric element 33a and N-type thermoelectric element 33 are
b) are connected by the solder melting method to form a PN element pair 33, and these PN element pairs 1 are connected in series with each other, and a first electrode lead 7 and a second electrode lead 7 are connected to electrode patterns located at both ends of the circuit, respectively. Electrode leads 8 are provided.

By energizing the first and second electrode leads, for example, the first heat exchange board side becomes a low temperature part, and the second heat exchange board side becomes a high temperature part.

20 For the thermoelectric device, repeat the operation of setting the high temperature side temperature to 60 °C and the low temperature side temperature to 0 °C with 5 minutes on and 15 minutes off, as in Example 1, and after 1000 cycles at this time, 10000 Table 5 shows the results of measuring the internal resistance change rate after 30,000 cycles.

Number of cycles Sample No. 1 Sample No. 0.2 Sample No. 3 Table 5 1, 1% 3.0% 1.5% 2.2% 0.8% 2.0% 4, 6% 3, 7% 2 , 9% As is clear from Table 5, it can be seen that according to the thermoelectric device of the present invention, the internal resistance change rate is maintained small even after 30,000 cycles.

〔Effect of the invention〕

As explained above, according to the thermoelectric device of the present invention,
Since the heat exchange board is made of a material with a small coefficient of thermal expansion, it maintains good characteristics and is highly reliable even when there is a large temperature difference between the low-temperature part and the high-temperature part.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a thermoelectric device according to a first embodiment of the present invention, FIG. 2 is a diagram showing a thermoelectric device according to a second embodiment of the present invention, and FIG.
4 and 4 are diagrams showing a thermoelectric device according to a third embodiment of the present invention, and FIG. 5 is a diagram showing a conventional thermoelectric device. 1.2... Heat exchange board, 4,5... Copper tungsten electrode, 11.12... Heat exchange board, 13... P type and N type B1-Te semiconductor, 1.4.15-... Copper tungsten electrode, 21.22... Heat exchange substrate, 26... Silicon oxide film, 33a, 33b... P type and N type B1
-Te semiconductor, 34.35-electrode pattern, 37...
Nickel plating layer, 38... Pb-3n solder plating layer, 39... tungsten layer. Figure 2 Figure 5

Claims (5)

[Claims] (1) In a thermoelectric device in which at least one pair of thermoelectric elements is arranged on a heat exchange substrate via electrodes, the heat exchange substrate
A thermoelectric device comprising a material having a linear expansion coefficient of 4×10^-^6/°C or less. (2) The heat exchange board is made of an insulating material, and the electrode is formed on the surface of the heat exchange board via a metallized layer, and has a linear expansion coefficient of 8 x 10^-^6/°C or less; The thermoelectric device according to claim 1, wherein the thermoelectric device is made of a material having a volume resistivity of 10^-^6 Ωcm or less. (3) The heat exchange substrate is made of a conductive material, and the electrodes are formed on an insulating layer covering the entire surface of the heat exchange substrate via a metallized layer, and have a linear expansion coefficient of 8×10^.
Claim No. 1, characterized in that it is made of a material having a volume resistivity of -^6/℃ or less and a volume resistivity of 10^-^6 Ωcm or less.
Thermoelectric device described in ). (4) The thermoelectric device according to any one of claims (1) to (3), wherein the heat exchange substrate is made of quartz glass, low expansion glass, or an amber alloy. (5) The electrode is made of a high melting point metal such as an amber alloy, molybdenum, tungsten, tantalum, or an alloy of these and copper. The thermoelectric device described.