JPH0193179A - Temperature difference detector - Google Patents

Abstract

PURPOSE:To produce an temperature difference detector simple in structure and high in sensitivity by a method wherein electrodes are provided on one surface of a semiconductor ceramic substrate to constitute pairs of hot and cold junctions, locations to serve as thermoelements between the electrodes are connected in series, and slits are provided between neighboring electrodes. CONSTITUTION:On one surface of a semiconductor ceramic substrate 12, a plurality of pairs of electrodes 13a, 13b, ...16a, 16b serving as a hot and cold junctions. A pair of electrodes and a part of the semiconductor ceramic substrate 12 constitute a thermoelement. Neighboring thermoelements are connected in series by conductive channels 19a-19c. In the substrate 12, between neighboring thermoelements, slits 21a-21f are provided. With a plurality of thermoelements being connected in series in one and the same substrate, it is easy to construct a multistage series type thermopile. In addition, slits provided between neighboring electrodes increases resistance in presence between the electrodes, which increases the thermoelement output voltage.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a temperature difference sensing element that utilizes the Seebeck effect, and particularly to a temperature difference sensing element that uses a semiconductor ceramic substrate and has an improved arrangement structure of constituent elements. Regarding elements.

[Prior Art] Japanese Unexamined Patent Publication No. 114090/1983 discloses a heat ray detector using a semiconductor thermoelectric element made of reducible titanium oxide. This heat ray detector, as shown in Figure 2,
An ohmic metal film 2a is formed on one main surface of a plate-shaped reducible titanium oxide semiconductor substrate 1.

2b, one of the junctions between the ohmic metal films 2a and 2b and the semiconductor substrate 1 is a hot junction 3, and the other is a cold junction 4. That is, although three thermoelectric elements 6a to 6C are shown in a plane in FIG. 2, these thermoelectric elements 6a to 6C are connected in series using lead wires 7.8 to form a heat ray detector. structure is disclosed.

Here, it is possible to increase the output voltage by connecting a plurality of thermoelectric elements 6a to 6C in series.

[Problems to be Solved by the Invention] However, the thermoelectric elements 6a to 6C shown in FIG. 2 must be prepared separately. Furthermore, in order to connect a plurality of thermoelectric elements in series, they must be alternately arranged in opposite directions and connected using lead wires 7.8, as shown in FIG. Therefore, the manufacturing process becomes complicated, and especially when the overall size is reduced, such connection work is extremely difficult.

Therefore, an object of the present invention is to provide a highly sensitive temperature difference sensing element having a structure that can be obtained through a simpler process.

[Means for Solving the Problems] The temperature difference sensing element of the present invention has a single substrate made of semiconductor ceramic as a basic component.

That is, a plurality of pairs of electrodes are formed on at least one surface of this substrate to form a hot junction and a cold junction. A plurality of thermoelectric cables are constructed using a single substrate, including a pair of electrodes and a semiconductor ceramic substrate portion between the pair of electrodes. Further, a conductive path is provided to connect the plurality of thermoelectric cables in series. Furthermore, a slit is formed in the substrate portion between the electrodes of at least one adjacent thermoelectric element.

[Operation] Since a plurality of thermoelectric elements are constructed using a single substrate made of semiconductor ceramics, a multi-stage series thermopile can be easily obtained. In addition, since multiple thermoelectric elements connected in series are connected on the board, they can be connected using conductive paste, etc., in the same way as the electrodes for configuring each thermoelectric element, without using lead wires. It can be formed in a process.

Furthermore, since the slit is formed in the substrate portion between the electrodes of at least one adjacent thermoelectric element, the resistance caused by the ceramic semiconductor substrate portion between adjacent cold junction electrodes and between adjacent hot junction electrodes is increased. Therefore, as will be clear from the embodiments described later, the thermoelectric cable output voltage per stage is effectively increased.

[Description of Embodiment] FIG. 1 shows a temperature difference sensing element 11 according to an embodiment of the present invention. This temperature difference sensing element 11 is constructed using a substrate 12 made of semiconductor ceramics. As the semiconductor ceramic constituting the substrate 12, for example, if it is an n-type ceramic semiconductor, it is BaTio treated in a reducing atmosphere.

5rTiO, , CaTl0. BaTio, which has been subjected to valence control by adding rare earth elements such as La, Ce, and Nd.
, 5rTiO=, etc. can be used. In addition, for p-type ceramic semiconductors, Nip, Coo, FeO treated in an oxidizing atmosphere, Ni added with Li2O, etc.
p, Coo, FeO, M n Os or SrO, Ca
LaMn0. , LaFe0. etc. can be used.

On one main surface of the substrate 12, a plurality of electrodes 13a to 16a,
13b to 16b are formed. Of these, electrode 13
a to 16a are formed on one main surface of the substrate 12 so as to be distributed along one longitudinal edge. On the other hand, the electrodes 13b to 16b are on the other edge side of the substrate 12,
They are formed in a dispersed manner so as to face the electrodes 13a to 16a. Here, the electrode 13a and the electrode 13b constitute a pair of electrodes for constructing a hot junction and a cold junction of the present invention. Similarly, electrodes 14a to 16a and electrode 1
4b to 16b each form a pair.

In this embodiment, one thermoelectric element is constituted by the pair of electrodes described above, for example, electrodes 13a and 13b, and the semiconductor ceramic substrate portion between the pair of electrodes 13a and 13b. Therefore, in total, four thermoelectric elements are constructed using a single substrate 12.

One of the electrodes 13a to 16a and the electrodes 13b to 16b is formed to constitute a hot junction, and the other is formed to constitute a cold junction. Either electrode side may be used as a hot junction or a cold junction, but for ease of explanation, here, the electrodes 13a to 16a cooperate with the substrate 12 to constitute the hot junction 17, and the electrodes 13
b to 16b constitute the cold junction 18. Therefore, it can be seen that in this embodiment, four thermoelectric elements are arranged side by side on the rectangular substrate 12 such that the electrodes constituting the respective hot or cold junctions are adjacent to each other.

Each thermoelectric element has a connecting conductive path 1 formed on a substrate 12.
9a to 19c, thus resulting in four thermocouples being connected in series.

The electrodes 13a to 16b described above are made of a metal material that provides ohmic contact, such as nickel, aluminum, gold, or
It can be formed from a metal such as indium or an alloy thereof. As a forming method, various thin film forming methods such as a thick film forming method by printing or vapor deposition or sputtering can be used. Preferably, when the connecting conductive paths 19a to 19c are made of the same material as the electrodes 13a to 16b, they can be formed at the same time as the electrodes 13a to 16b. However, the connection conductive paths 19a to 1
9c may be formed of a conductive material different from the electrode material. Further, as the conductive paths 19a to 19c, a metal material that provides non-ohmic contact with the ceramic semiconductor may be used.

Furthermore, in this embodiment, slits 21a to 21f are formed between adjacent electrodes of the four thermoelectric elements. The slits 21a to 21f are formed by cutting a portion of the substrate 12 inward from the longitudinal edge of the substrate 12. The slits 21a to 21f are provided to increase the electromotive force output voltage of each thermoelectric cable. This will be explained with reference to FIGS. 3 to 5.

As shown in a schematic plan view in FIG. 3, a temperature difference sensing element 31 having no slit described above will be considered as a comparative example. The temperature difference sensing element 31 shown in FIG. 3 is completely similar to the embodiment shown in FIG. 1 except that no slit is formed. Therefore, corresponding parts will be given corresponding reference numbers.

An equivalent circuit of this temperature difference sensing element 31 is shown in FIG.

In FIG. 4, Rr indicates the substrate resistance between a pair of electrodes in one thermoelectric element, and RP indicates the substrate resistance between adjacent thermoelectric elements, that is, between adjacent electrodes on the cold junction side and the hot junction side. Note that the subscript numbers indicate each thermoelectric cable. Therefore, the electrode 33a and the electrode 33b-3
4a, the potential difference e1,2 is e+,2 '' e+
・Rp )/(Rr l+Rr + ). When n semiconductor thermoelectric elements are configured, the total output e1. ．． ．． .

-pe+, 1-1-Σ[ei-R1/(RrI+R
Pl)]ill+. On the other hand, in the embodiment shown in FIG.
Since 1a to 21f are formed, RP has a much larger value than R. Therefore, in the equivalent circuit of the embodiment in FIG. 1, Rp can be ignored as shown in FIG. 5, so the output per one stage thermoelectric element can be increased, and as a result, the overall element output can be It is possible to increase

Note that the above-mentioned slits 21a to 21f do not need to be formed between all the adjacent electrodes of adjacent thermoelectric cables as shown in FIG. 1, but if they are formed between at least one adjacent electrode, the output can be increased. can be done.

Furthermore, the slits 21a to 21f are provided to dramatically increase the resistance between the electrodes of adjacent thermoelectric elements, thereby increasing the output so that the above-mentioned RF can be ignored. Therefore, the slits 21a to 21
This effect does not change even if f is filled with an insulating material.

In this case, by forming the slits 21a to 21f, it is possible to prevent a decrease in substrate strength, and it is also possible to correct the thermal conductivity of the element.

Furthermore, the shape of the slits 21a to 21f is not particularly limited as long as it provides a resistance greater than the substrate resistance between adjacent electrodes; You can also use it as

In the embodiment shown in FIG. 1, pairs of electrodes 13a to 16a and 13b to 16b were formed on one side of the substrate 12, but pairs of electrodes were also formed on the other side of the substrate 12, and the other side A plurality of thermoelectric elements may be configured on the side. In that case, it is preferable to connect the thermoelectric elements formed on both sides in series, thereby making it possible to obtain a thermopile in which thermoelectric elements are connected in more stages using a substrate of the same size.

Regarding the shape of the substrate 12, it is not necessary to use a substantially rectangular shape as shown in FIG. 1, but a circular substrate may also be used. When a circular substrate is used, a plurality of thermoelectric elements can be arranged radially side by side by arranging paired electrodes, for example, in the radial direction.

[Effects of the Invention] In the present invention, a plurality of thermoelectric elements are connected in series using a single semiconductor ceramic substrate. Therefore, there is no need to prepare a plurality of substrates as in the past, and the complicated work of bonding a plurality of substrates together or connecting them using lead wires or the like can be eliminated. moreover,
Connection between each thermoelectric cord is possible by simply forming a conductive path on the substrate. Therefore, the manufacturing process can be dramatically simplified compared to conventional multi-stage series ceramic semiconductor thermopiles.

Furthermore, since a slit is formed in at least one part between the electrodes on the hot junction side or the cold junction side of adjacent thermoelectric elements, the output of the thermoelectric element can be increased in the part where the slit is formed. Therefore, a temperature difference detection element with higher sensitivity can be realized.

It should be pointed out that this invention can be used in various infrared sensors and heat flow sensors.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a schematic plan view for explaining an example of a ceramic semiconductor thermopile used in a conventional heat ray detector, and FIG.
Figure 4 is a plan view showing a temperature difference sensing element without a slit as a comparative example for the embodiment; Figure 4 is an equivalent circuit diagram of the temperature difference sensing element shown in Figure 3; It is an equivalent circuit diagram. In the figure, 11 is a temperature difference detection element, 12 is a substrate made of semiconductor ceramics, 13a to 16b are electrodes, and 19a
-19c are conductive paths for connection, and 21a-21f are slits. Figure 2

Claims (4)

[Claims] (1) A substrate made of semiconductor ceramics, and a plurality of pairs of electrodes formed on at least one surface of the substrate to form a hot junction and a cold junction, the paired electrodes and a semiconductor ceramic substrate portion between the pair of electrodes to form a plurality of thermoelectric elements, further comprising a conductive path for connecting the plurality of thermoelectric elements in series on the substrate, and at least one A temperature difference sensing element with a slit formed in the substrate between the electrodes of adjacent thermoelectric elements. (2) the slit is filled with an insulating material;
A temperature difference sensing element according to claim 1. (3) On both sides of the substrate made of semiconductor ceramics,
The temperature difference sensing element according to claim 1 or 2, wherein the plurality of thermoelectric elements are configured, and the thermoelectric elements configured on both surfaces are connected to each other in series. (4) A plurality of thermoelectric elements are arranged side by side on a substrate so that electrodes for forming hot junctions and cold junctions are adjacent to each other between adjacent thermoelectric elements, and the slits form adjacent hot junctions. The temperature according to any one of claims 1 to 3, which is formed in at least one inter-electrode portion of at least one of the electrodes for forming an adjacent cold junction and the electrodes for forming an adjacent cold junction. Difference sensing element.