JP3536759B2 - Thermoelectric module - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric module used for thermoelectric power generation or thermoelectric cooling, and more particularly to a thermoelectric module in which the amount of distortion generated by warpage of a substrate due to thermal stress is reduced.

[0002]

2. Description of the Related Art When two materials of different types are joined to form a circuit having two joints, one of the joints is heated to a high temperature and the other is cooled to a low temperature. An electromotive force is generated based on the difference. This phenomenon is called the Seebeck effect.

[0003] When a direct current is applied to two materials joined in the same manner, heat is absorbed at one joint and heat is generated at the other joint. This phenomenon is called the Peltier effect.

Further, when a temperature gradient is provided in a homogeneous substance and an electric current is applied in a direction having the temperature gradient, heat is absorbed or generated in the substance. This phenomenon is called the Thomson effect.

[0005] These Seebeck effect, Peltier effect and Thomson effect are reversible reactions called thermoelectric effects.
Contrast with irreversible phenomena such as Joule effect and heat conduction.
A combination of these reversible and irreversible processes is used for electronic cooling and heating.

FIG. 2 is a schematic top view showing a conventional thermoelectric module. In a conventional thermoelectric module, a plurality of thin plate-shaped rectangular lower electrodes (not shown) are soldered on a metallized layer on a heat-radiation-side insulating substrate (not shown) made of, for example, alumina or the like. Or a heat-resistant adhesive (not shown) or a thermocompression bonding method. Further, the lower electrode may be formed directly on the metallized layer by a plating method. On each lower electrode, a pair of p-type thermoelectric elements 11a and n-type thermoelectric elements 11b having a square cross section are joined by a solder layer (not shown). The upper end of the p-type thermoelectric element 11a is connected to the n-type thermoelectric element 11b disposed on the adjacent lower electrode by joining the upper electrode 12 with a solder layer (not shown), and the n-type thermoelectric element 11b Is connected to the p-type thermoelectric element 11a disposed on another adjacent lower electrode by joining the upper electrode 12 with a solder layer. The p-type thermoelectric element 11a and the n-type thermoelectric element 1 are formed by the lower electrode and the upper electrode 12.
1b are alternately connected in series. Thus, the p-type thermoelectric element 11a, the n-type thermoelectric element 11b, the upper electrode 12, and the lower electrode constitute a thermoelectric element.

A heat-absorbing insulating substrate 13 also made of alumina is provided on the upper electrode 12. A metallized layer is formed on the heat absorbing side insulating substrate 13 on the side to be bonded to the upper electrode 12, and the metallized layer and the upper electrode 12 are soldered, bonded with a heat resistant adhesive, or thermocompressed. It is joined by the method. Further, a metallized layer is formed on the heat absorption side substrate 13 and the upper electrode 1 is formed thereon.
2 may be formed by a direct plating method, and then the upper electrode 12 and the p-type thermoelectric element 11a and the n-type thermoelectric element 11b may be joined by a solder layer. Further, lead wires (not shown) are connected to the upper electrode 12 or the lower electrode arranged at both ends of the series connection body of the thermoelectric element. As the heat-radiating-side insulating substrate and the heat-absorbing-side insulating substrate 13, in addition to the alumina plate, aluminum nitride or an aluminum plate subjected to alumite treatment is used.

Although the p-type thermoelectric element and the n-type thermoelectric element usually have a square cross section, a circular thermoelectric element may be used in some cases.

In the conventional thermoelectric module configured as described above, when a current is applied to the lead wire from a predetermined direction, heat is generated at the lower electrode, and the heat is absorbed at the upper electrode 12. Thereby, the space or the object in contact with the outer surface of the heat absorbing side insulating substrate 13 is cooled, and the space or the object in contact with the outer surface of the heat absorbing side insulating substrate is heated.

[0010]

However, when the above-described conventional thermoelectric module is used, the thermoelectric module is deformed due to thermal stress, and peeling occurs at a joint between the electrode and the thermoelectric element. There are points. Generally, the heat-dissipating insulating substrate (high-temperature side) expands and the heat-absorbing insulating substrate 13
(Low temperature side) shrinks. This causes thermal stress,
There is a possibility that peeling may occur at the joint between the electrode and the thermoelectric element, or the thermoelectric element may be cracked.

In particular, in the case of a substrate having a rectangular shape and one direction being long,
When there is a temperature difference between the substrate on the high temperature side and the substrate on the low temperature side of the thermoelectric module, that is, when a current is repeatedly turned on and off, a large thermal stress is generated, and the substrate is warped and disconnected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in view of the above-mentioned problems. And to provide a highly reliable thermoelectric module.

[0013]

The thermoelectric module according to the present invention comprises a rectangular substrate, a plurality of lower electrodes provided on the substrate, and a pair of p-type electrodes formed on each of the lower electrodes. In a thermoelectric module having a thermoelectric element and an n-type thermoelectric element, and a plurality of upper electrodes connecting the upper ends of the p-type thermoelectric element and the n-type thermoelectric element on the adjacent lower electrode,
A cross section of the thermoelectric element is rectangular or elliptical, and a longitudinal direction or a long axis direction of the thermoelectric element crosses the longitudinal direction of the substrate.

In the present invention, the thermoelectric elements are rectangular or elliptical, and are arranged so that the longitudinal direction or long axis direction in the cross section thereof and the longitudinal direction of the substrate intersect.
The length of one side of the element cross section in the longitudinal direction of the substrate is shorter than that of a conventional device having a thermoelectric element having a square or circular cross section, so that even if the longitudinal direction of the substrate is warped due to thermal stress during use of the thermoelectric module. In addition, the amount of distortion for each thermoelectric element can be reduced.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the thermoelectric module of the present invention will be described more specifically. The inventors of the present application have conducted intensive studies to solve the above-described problems, and as a result, in the case of a substrate having a long one-way direction such as a rectangle, on / off of a temperature difference,
That is, the inventors found that the occurrence of a large thermal stress during the repetition of the on / off of the current causes disconnection due to the magnitude of the warpage in the longitudinal direction of the substrate. And a method for reducing the amount of strain generated in the thermoelectric element and the strain generated in the thermoelectric element. That is, by using a thermoelectric element in which the cross-sectional shape of the thermoelectric element disposed on the substrate is not a square but a rectangle or an ellipse and has a longitudinal direction or a long axis direction in a direction intersecting the longitudinal direction of the substrate, Has been found to be able to reduce the strain caused by the warpage in the longitudinal direction. That is, if the length in the longitudinal direction of the cross section of the thermoelectric element is shortened with respect to the longitudinal direction of the substrate, the stress generated by the warpage of the substrate at the interface between the substrate and the electrode is reduced, and the thermoelectric element generated by the warpage of the substrate It was also found that the smaller the length of the contact between the substrate and the thermoelectric element in the longitudinal direction, the smaller the internal stress.

FIG. 1 is a schematic top view showing a thermoelectric module of the present invention. As shown in FIG. 1, in the thermoelectric module of the present embodiment, as in the above-described conventional thermoelectric module, a plurality of thin plate-shaped insulating substrates (not shown) made of, for example, alumina or the like are provided. Whether a rectangular lower electrode (not shown) is soldered on the metallized layer or bonded by a heat-resistant adhesive (not shown),
Alternatively, they are arranged by being joined by a thermocompression bonding method. Also,
The lower electrode may be formed directly on the metallized layer by a plating method. A pair of p-type thermoelectric elements 1a and n-type thermoelectric elements 1b are provided on each lower electrode with a solder layer (not shown).
Are joined. The p-type and n-type thermoelectric elements of the present embodiment have a rectangular cross section, and are arranged so that the longitudinal direction is orthogonal to the longitudinal direction of the insulating substrate.

The upper end of the p-type thermoelectric element 1a is connected to the n-type thermoelectric element 1b arranged on the adjacent lower electrode by joining the upper electrode 2 with a solder layer (not shown), and the n-type thermoelectric element 1b is connected to the n-type thermoelectric element 1b. The upper end of the thermoelectric element 1b is connected to the p-type thermoelectric element 1a arranged on another adjacent lower electrode by joining the upper electrode 2 with a solder layer. The p-type thermoelectric element 1a and the n-type thermoelectric element 1b are alternately connected in series by the lower electrode and the upper electrode 2. Thus, the p-type thermoelectric element 1a, the n-type thermoelectric element 1b, and the upper electrode 2
And a lower electrode constitutes a thermoelectric element.

Further, on the upper electrode 2, a heat absorbing side insulating substrate 3 also made of alumina is arranged. A metallized layer is formed on the heat absorbing side insulating substrate 3 on the side to be bonded to the upper electrode 2, and the metallized layer and the upper electrode 2 are soldered, bonded with a heat-resistant adhesive, or thermocompressed. It is joined by the method. Further, a metallized layer is formed on the heat-absorbing side substrate 3, and the upper electrode 2 is formed thereon by direct plating, and thereafter, the upper electrode 2 and the p-type thermoelectric element 1a and the n-type thermoelectric element 1b are connected by a solder layer. You may join. Further, a lead wire (not shown) is connected to the upper electrode 2 or the lower electrode disposed at both ends of the series connection body of the thermoelectric element. When a current is applied to this lead wire from a predetermined direction, heat is generated at the lower electrode and the upper electrode 2
The heat is absorbed. Thereby, the space or the object in contact with the outer surface of the heat absorbing side insulating substrate 3 is cooled, and the space or the object in contact with the outer surface of the heat radiating side insulating substrate is heated.

As the heat-radiating-side insulating substrate and the heat-absorbing-side insulating substrate 3, aluminum nitride or anodized aluminum plate can be used in addition to the alumina plate.

In the thermoelectric module of the present embodiment thus configured, the thermoelectric elements are arranged in the longitudinal direction of the substrate by arranging the thermoelectric elements so that the longitudinal direction of the cross section is perpendicular to the longitudinal direction of the substrate. It is possible to relieve the thermal stress that can easily occur. That is, since the thermoelectric element of the present invention has a shorter cross-sectional area of the thermoelectric element in the longitudinal direction of the substrate than the conventional thermoelectric element having the same cross-sectional area and a square shape, the substrate is larger in the longitudinal direction. Even when warped, the distortion generated in each thermoelectric element is small. Therefore, it is possible to reduce distortion generated by warpage in the longitudinal direction of the substrate caused by a temperature difference during use of the thermoelectric module, and to obtain a highly reliable thermoelectric module.

The thermoelectric elements are preferably arranged so that the longitudinal direction in the cross section thereof is orthogonal to the longitudinal direction of the insulating substrate. However, the thermoelectric elements can be arranged not only orthogonally but also intersecting. By arranging them so as to intersect, the cross section of the thermoelectric element becomes shorter than the case where the cross section of the thermoelectric element is arranged to be parallel to the longitudinal direction of the substrate. Longitudinal distortion can be reduced. Alternatively, the thermoelectric element may be elliptical, and may be arranged so that the major axis direction in the cross section thereof intersects the longitudinal direction of the substrate.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the effects of the embodiments of the thermoelectric module according to the present invention will be described in comparison with comparative examples which are out of the scope of the present invention. Thermoelectric modules having the structures of the example and the comparative example shown in FIGS. 1 and 2, respectively, were prepared. 96% by mass
Was used, and the thickness of the substrate was 0.5 mm. The upper electrode and the lower electrode were formed directly on the insulating substrate by plating. The thickness of these electrodes was 0.1 mm. The thermoelectric element had a height of 1 mm. Table 1 below shows the substrate size, the thermoelectric element size, and the logarithm of the n-type and p-type thermoelectric elements formed on the substrate. The chip width 1 and the chip width 2 of the thermoelectric element size are the widths in the direction parallel to the substrate longitudinal direction and the direction perpendicular to the substrate longitudinal direction, respectively, in the cross section of the thermoelectric element. The shapes of the p-type and n-type thermoelectric elements are the same.

A test was conducted on these thermoelectric modules to evaluate the reliability of the thermoelectric modules. In the test, the temperature of the substrate on the heat radiation side (high temperature side) of the thermoelectric module is always kept at 80 ° C., the maximum drive current is Imax, the on time is 1.5 minutes, the off time is 4.5 minutes, and the energization is on. -The operation of turning off was repeated, and the number of times when power supply became impossible was measured as the endurance number. Maximum current Imax
Table 1 below shows the durability count.

In Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3, the chip width was 1
Since the other conditions are the same except for the value of the chip width 2 and the chip width 2, the total chip area of the thermoelectric element is also the same. Therefore, module characteristics such as the maximum temperature difference ΔTmax between the heat dissipation side substrate and the heat absorption side substrate of the thermoelectric module and the maximum heat absorption Qmax of the thermoelectric module are the same.

[0025]

[Table 1]

As shown in Table 1, in the first to third embodiments, although the module characteristics are the same as those of the first to third comparative examples, the longitudinal direction of the substrate and the longitudinal direction of the cross section of the thermoelectric element are orthogonal to each other. , The endurance times of Examples 1 to 3 were increased. Chip width 2 for thermoelectric element chip width 1
The greater the length ratio, the higher the rate of increase in endurance times,
The number of times of durability in Example 2 was increased to three times the number of times of durability in Comparative Example 2.

[0027]

As described in detail above, according to the present invention,
Since the cross-sectional shape of the thermoelectric element formed on the insulating substrate is rectangular or elliptical, and arranged so as to intersect the longitudinal direction of the insulating substrate and the longitudinal direction or long-axis direction of the cross-section of the thermoelectric element,
The amount of distortion between the substrate and the thermoelectric element and the amount of distortion inside the thermoelectric element caused by warpage of the substrate due to thermal stress in the longitudinal direction when the thermoelectric module is used can be reduced, and extremely high reliability can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view showing a thermoelectric module according to an embodiment of the present invention.

FIG. 2 is a plan view showing a conventional thermoelectric module.

[Explanation of symbols]

1a; p-type thermoelectric element 1b; n-type thermoelectric element 2: Upper electrode 3: Heat absorbing side insulating substrate

Claims (1)

(57) [Claims] 1. A rectangular substrate, a plurality of lower electrodes provided on the substrate, a pair of p-type thermoelectric elements and a pair of n-type thermoelectric elements formed on each of the lower electrodes, and In a thermoelectric module having a plurality of upper electrodes connecting the upper ends of a p-type thermoelectric element and an n-type thermoelectric element on a lower electrode, a cross section of the thermoelectric element is rectangular or elliptical,
A thermoelectric module, wherein a longitudinal direction or a long axis direction of the thermoelectric element crosses a longitudinal direction of the substrate.