JPH03125935A - Thermopile - Google Patents

Abstract

PURPOSE:To improve the efficiency of a temperature rise in the warm contact portion of a thermocouple pattern with respect to an incident infrared ray power by forming an elastic resin coating layer coated with the thermocouple pattern thereon an insulating substrate. CONSTITUTION:An elastic resin (usually polyimide resin is used) coating layer 3 is formed on the surface of an insulating substrate 1 on which a thermocouple pattern 2 is formed. The thickness of the elastic resin coating layer 3 is smaller than that of the substrate 1 and usually set to 5mum or less. The coating layer 3 has a heat conductivity of the same order as that of the substrate 1. The layer 3 is formed by a spin coating method. The surface of the pattern 2 is processed to be insulated by the layer 3. Thus, the infrared ray absorbing layer 4 of gold black can be formed on a circular region with a radius larger than that of a circle on which a warm contact 20 is arranged approximately by a clearance (k). Thus, heat is applied to the warm contact 20 from the peripheral portion of the absorbing layer 4 directly via the layer 3. This improves the efficiency of a temperature rise in the pattern 2 coupled with the fact that the thickness of the layer 3 is small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermopile that detects infrared rays used for human body detection or various types of non-contact temperature detection.

[Prior Art] The configuration of a conventional thermopile is shown in FIG. 2. A thermocouple pattern 2, which is a combination of thermoelectric materials 2a and 2b arranged in series, is formed on an insulating substrate 1 by means such as vapor deposition. B1-8b, B1-T as thermoelectric materials
A material with high thermoelectric power such as e is selected. Hot junctions 20 are arranged inside the thermocouple pattern 2, and cold junctions 21 are arranged outside.

The insulating substrate 1 is fixed on the heat sink 5 so as to include the cold junction 21 on its upper surface.

In the inner part of the hot junction 20 of the thermocouple pattern 2.

The infrared absorbing layer 4 is formed with a clearance d (d is approximately 50 to 100 μm). For the infrared absorbing layer 4, goldfish, which has the highest infrared absorption rate, is usually used.

The principle by which a thermopile detects infrared rays is as follows. Infrared rays generated from an object to be detected (such as a human body) are absorbed by the infrared absorbing layer 4, and the temperature of the infrared absorbing layer 4 increases. Heat due to this temperature rise is transferred over the substrate 1 through the section of clearance d, and the hot junction 2 of the thermocouple pattern 2
0 to raise the temperature. Since the temperature of the cold junction 21 is maintained approximately at the temperature of the heat sink 5 (equal to room temperature), a temperature difference ΔT occurs between the hot junction 20 and the cold junction 21. The output voltage V is based on this ΔT. are output terminals 5a, 6
Occurs between b.

Furthermore, the output voltage V. is (thermal conductivity α (μV/”C) due to thermoelectric materials 2a and 2b)X (logarithm of thermocouple).

Since the infrared absorbing layer 4 exhibits a low specific resistance almost equal to that of a metal, if it comes into direct contact with the hot junction of the thermocouple pattern, it will significantly reduce the output voltage of the thermocouple. Therefore,
The infrared absorbing layer 4 must be formed inside the hot junction 20 with a clearance d. Although it is preferable for the size of the clearance d to be as small as possible from the viewpoint of heat transfer, in reality it has to be set to a value of about 50 to 100 μm when considering the yield in mass production. Therefore, between the temperature of the peripheral part of the infrared absorbing layer 4 and the hot junction 20.

A temperature difference corresponding to the clearance d will occur.

Therefore, the thermal efficiency with respect to the temperature rise of the hot junction 20 with respect to the infrared incident power is low.

As shown in Figure 3, one way to improve the above drawbacks is to
There is a method of providing an infrared absorbing layer 4 on the surface of the insulating substrate 1 on which the thermocouple 2 is formed and the surface opposite to that surface. Note that the size of the infrared absorbing layer 4 is such that it completely includes the hot junction 20.

[Problem to be solved by the invention] However, in this case as well, the insulating substrate usually has a density of 20 to 50
Since it is an organic film with μ earthquakes, the heat distribution in this thickness cannot be ignored. That is, the thermal efficiency of increasing the temperature of the hot junction with respect to the incident infrared power is low. Moreover, since the surface of the thermocouple and the heat sink (usually made of metal such as aluminum) face each other, the insulation process between the thermocouple and the heat sink and the process for drawing out the external terminals are complicated, which complicates the manufacturing process. It has the disadvantage of becoming

The technical problem of the present invention is to improve the conventional drawbacks.

It is an object of the present invention to provide a thermopile which improves the efficiency of temperature rise of a hot junction part of a thermocouple pattern with respect to infrared incident power, and which is easy to assemble and suitable for mass production.

[Means for Solving the Problems] According to the present invention, an insulating substrate, a thermocouple pattern having a hot junction and a cold junction formed on the insulating substrate, and an infrared ray to heat the hot junction are provided. In the thermopile having an infrared absorbing layer, the insulating substrate has an elastic resin coating layer covering the thermocouple pattern.

[Example] FIG. 1 shows an embodiment of a thermopile according to the present invention.

Reference numeral 1 denotes an insulating substrate, which is a film having a thickness of 25 to 50 μm and made of mica, polyimide, polyethylene, or the like. On the insulating substrate 1, a thermocouple pattern 2 made of a combination of a first thermoelectric material 2a and a second thermoelectric material 2b is formed by vapor deposition, sputtering, or the like.

The heat sink 5 is made of a material having a large thermal conductivity, such as aluminum, in a ring shape. The inner diameter of the heat sink 5 is set midway between the hot junction 20 and the cold junction 21 of the thermocouple pattern 2. The insulating substrate 1 is closely fixed on the heat sink 5, and as a result, the cold junction 21 is maintained at approximately the temperature of the heat sink 5.

As shown in the figure, an elastic resin coating layer 3 is formed on the surface of the insulating substrate 1 on which the thermocouple pattern 2 is formed. The thickness of the coating layer 3 is smaller than the thickness of the insulating substrate 1, and is usually set to 5 μm or less.

Polyimide resin is usually used as the material for the resin coating layer 3, and its thermal conductivity is 0.0015 to 0.0020W.
/cm deg, and has a thermal conductivity of approximately the same order as that of the insulating substrate 2.

Especially as a method for forming the resin coating layer 3.

The spin coating method is used because it is easy to mass produce and allows for thinner and more uniform film thickness.

The surface of the thermocouple pattern is insulated by the resin coating layer 3, thereby forming an infrared absorbing layer 4 of completely black or the like in a portion corresponding to an area outside the diameter of the arranged hot junctions 20 by about a clearance. It becomes possible to do so. The size of k is usually selected to be about 100 to 200 μm, and the outer diameter of the infrared absorbing layer 4 is selected to be about 1.2 to 1.5 μm.

Regarding the formation of the resin coating layer 3.

Only the output terminals 6a and 6b of the thermocouple pattern 2 are
Consideration is taken to prevent the formation of a resin coating layer by means such as masking.

Here, the thermopile according to the present invention is superior to the conventional one in the following points.

■ Since insulation treatment is performed using the resin coating layer 3, the outer periphery of the infrared absorbing layer 4 (specific resistance is on the same level as metal), which is completely black, is expanded to approximately the hot junction 20 of the thermocouple pattern 2. It is now possible to do so. Heat is applied directly to the hot junction 20 from the periphery of the infrared absorbing layer 4 through the resin coating layer 3, and the thickness of the resin coating layer 3 is made thinner than 5 μm, which is different from the conventional method shown in FIGS. The efficiency of temperature rise of the thermocouple pattern 20 with respect to infrared incident power is significantly improved compared to the thermopile of FIG. 3.

(2) Compared to the conventional structure shown in FIG. 3, the surface of the thermocouple pattern 2 can be placed on the upper side. Therefore, regarding the bonding with the heat sink 5, the insulation treatment between the thermocouple pattern 2 and the heat sink 5 is shared by the insulating substrate 1, so there is no need for a new insulation treatment material 7 like the conventional one shown in FIG. 2. Easy to assemble.

Note that in the present invention, a material with elasticity is selected for the resin coating layer 3. Therefore.

Even if the insulating substrate 1 is bent due to bending stress during manufacturing and assembly, the resin coating layer 3 can sufficiently cope with the bending in terms of shape, and no cracks will occur.

No defects occur at all.

[Effects of the Invention] According to the present invention, the efficiency of temperature rise of the thermocouple pattern hot junction with respect to infrared incident power is improved compared to the conventional method.
We can provide thermopiles that are easy to assemble and suitable for mass production.

External radiation absorption layer, 5, 5... Heat sink, 6a, 6b.

6a, 6b...output terminal, 7...insulation treatment material.

[Brief explanation of the drawing]

FIG. 1(a) is a plan view of a thermopile according to an embodiment of the present invention, a sectional view of the thermopile taken along line B-B in FIG. 1(b), and FIG. 2(a) is a diagram of a conventional thermopile. The plan view, FIG. 2(b) is a sectional view of the thermopile taken along line BB in FIG. 2(a), and FIG. 3 is a sectional view of another conventional thermopile. 1.1... Insulating substrate, 2.2... Thermocouple pattern. 2a, 2a... first thermoelectric material, 2b, 2b... second thermoelectric material, 20.20... hot junction, 21.21.
...Cold junction, 3...Resin coating, 4,4.4.
...Red Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1) An insulating substrate, a thermocouple pattern having a hot junction and a cold junction formed on the insulating substrate, and an infrared absorption layer that absorbs infrared rays to heat the hot junction. 1. A thermopile comprising: the insulating substrate having an elastic resin coating layer covering the thermocouple pattern. 2) The thermopile according to claim 1, wherein the insulating substrate is made of mica, polyimide, polyethylene, or the like. 3) The thermopile according to claim 1, wherein the resin coating layer is formed by a spin coating method. 4) The thermopile according to claim 1, wherein the thickness of the resin coating layer is equal to or less than the thickness of the insulating substrate.