JPH04357887A - Thermoelectric element - Google Patents

Abstract

PURPOSE:To obtain a small thermoelectric element having a low thermal capacity by connecting in series a positive thermoelectric foot and a negative thermoelectric foot provided on the surface of an insulating base material with a conductive layer provided at a cross-section of the insulating base material. CONSTITUTION:A copper foil laminated polyimide sheet 1 adhering a copper foil 20 at the one surface thereof is prepared and a constant an foil 2n is bonded with pressure to the opposite surface of the copper foil 2p in such a form as sandwiching the polyimide sheet 1 using a polyimide type bonding agent. Thereby, metal foils having positive and negative thermoelectric performances are laminated to the front and rear surfaces of the polyimide sheet 1 to form a double-side polyimide sheet of different metals. Subsequently, the copper foil 2p and constant an foil 2n are patterned to the predetermined shape by photoetching, etc., and through hole plating is conducted to holes 4 of round pattern 21 (21p, 21n). Thereafter, a thermocouple is cut out in the predetermined shape from the sheet to manufacture a thermocouple 10.

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 more particularly to a thermoelectric element with improved thermoelectric conversion efficiency and time response characteristics required for thermoelectric conversion.

0002

[Prior Art] Thermoelectric elements directly receive heat input through the Seebeck effect of the thermoelectric leg with positive thermoelectric power (hereinafter referred to as positive thermoelectric leg) and the thermoelectric leg with negative thermoelectric power (hereinafter referred to as negative thermoelectric leg). This is a conversion element that converts electrical output into electrical output. Such a thermoelectric element is
In addition to being used as an energy conversion element, they are generally used for various temperature measurements as thermocouples whose thermoelectromotive force changes according to temperature differences. Furthermore, since the amount of heat dissipated from the thermoelectric element differs depending on the flow velocity of the fluid surrounding the thermoelectric element and the degree of vacuum of the gas, it is widely used for measuring flow velocity and degree of vacuum. Taking thermocouples for temperature measurement as an example, recently they have been used to measure minute temperature distributions inside integrated circuits, research on the physical properties of new materials, and measure local temperatures of the human body during hyperthermia therapy. For this purpose, there is a need for thermocouples to be smaller, lower in heat capacity, and faster in response than ever before.

[0003] In response to such demands for miniaturization, lower heat capacity, and faster response, ultra-thin bare thermocouple wires and sheathed thermocouples have conventionally been used. For example, the wire diameter is 50
A bare thermocouple made by spot welding a chromel wire and an alumel wire of about μm, or a sheathed thermocouple with an outer diameter of about 250 μm, whose surface is insulated with magnesia or the like and embedded in a stainless steel protective tube. be.

0004

[Problems to be Solved by the Invention] However, according to the above-mentioned prior art, as a result of miniaturization, the mechanical strength of the thermoelectric element is weakened, and it not only lacks durability, but also has difficulty in accurately positioning the thermoelectric element with respect to the object to be measured. It is difficult to measure temperature accurately at delicate locations. Moreover, welding and processing of extremely thin bare thermocouple wires requires a high level of skill, and is generally difficult to use. Further, according to the sheathed thermocouple, stainless steel or magnesia is interposed between the object to be measured and the thermoelectric element, so the heat capacity becomes large and high-speed response is lacking. Moreover, the heat of the object to be measured is wastefully lost to the outside via the stainless steel protection tube or magnesia, resulting in poor thermoelectric conversion efficiency and disturbing the thermal state of the object to be measured, which has a small heat capacity. The problem was that it could not be measured.

[0005]

[Means for Solving the Problems] In view of the problems based on the above-mentioned prior art, the present invention provides a conductive device in which a positive thermoelectric leg and a negative thermoelectric leg are provided on the surface of an insulating base and are provided on a cross section of the insulating base. The present invention aims to solve the above problem by providing a thermoelectric element that is small and has a low heat capacity by connecting layers in series.

[0006]

[Function] According to the structure of the present invention, the insulating base mechanically fixes the positions of the positive thermoelectric leg and the negative thermoelectric leg, and has the function of reinforcing and supporting them. electrically insulated and separated. Further, the conductive layer deposited on the cross section of the insulating base acts to electrically connect both thermoelectric legs in series and output the thermoelectromotive force of both thermoelectric legs at the leg ends of both thermoelectric legs.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Several embodiments of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is an outline drawing showing the configuration of a thermocouple that is a first embodiment of the present invention.
) is a front view with some parts omitted. Also, the same figure (
b) is an enlarged sectional view of the portion indicated by AA' in the figure (a).

The thermocouple 10 has a sheet shape with a length of about 150 mm, a width of about 5 mm, and a thickness of about 50 μm.
A copper foil 2p as a positive thermoelectric leg is patterned on one side of the polyimide sheet 1 as an insulating substrate, and a pattern of constantan foil 2n as a negative thermoelectric leg is formed on the opposite side.

Here, copper foil 2p and constantan foil 2n
The pattern shape will be explained. The copper foil 2p and the constantan foil 2n have round patterns 21 (21p, 2
1n) is formed. An external terminal pattern 22 (22p, 22n) for supplying thermoelectromotive force to the outside is formed at the opposite end of the round pattern 21 (21p, 21n), which is the other end of the thermocouple 10. ing.

Round pattern 21 (21p, 21n)
A hole 4, which forms the cross section of the sheet 1, is formed through the sheet 1 in the center thereof. A copper plating layer 3 as a conductive layer is deposited on the inner wall surface of the hole 4 by so-called through-hole plating.
Copper foil 2 via round pattern 21 (21p, 21n)
p and the constantan foil 2n are electrically connected in series to form a so-called thermocouple contact.

To describe the structure of the above embodiment in more detail, the thickness of the sheet 1 is approximately 25 μm, the thickness of the copper foil 2p is approximately 10 μm, and the thickness of the constantan foil 2n is as follows.
It is approximately 10 μm. Further, these copper foil 2p and constantan foil 2n are patterned with a minimum pattern width of 50 μm. Note that the outer diameter of the round pattern 21 (21p, 21n) with increased pattern width is approximately 0.
3 mm, and the inner diameter of the hole in the center is approximately 0.2 mm.
It is. Note that the thickness of the copper plating layer 3 deposited on the inner wall surface of the hole 4 is approximately 5 μm.

An example of the manufacturing method of the above embodiment will be explained as follows. First, a copper foil laminated polyimide sheet with copper foil pasted on one side is prepared, and a constantan foil is pressure-bonded to the opposite side of the copper foil using a polyimide adhesive with the polyimide sheet sandwiched between them. In this way, metal foils having positive and negative thermoelectric powers are laminated on the front and back sides of the polyimide sheet, respectively, to form a double-sided laminated polyimide sheet of different metals. Next, the copper foil and constantan foil are patterned into a predetermined shape by photo-etching or the like, and through-hole plating is applied to the holes of the round pattern. Thereafter, the thermocouple is manufactured by cutting out the thermocouple in a predetermined outer shape from the sheet.

According to the configuration shown in the first embodiment, the round pattern 21 (21p, 21n) of the thermocouple 10
) in contact with or facing the object to be measured, the heat of the object to be measured is transferred to the round pattern 21 (21p, 21
The heat is transferred to the positive thermoelectric leg 2p and the negative thermoelectric leg 2n via n). At this time, round pattern 2 with a large surface area
1 (21p, 21n) act as a heat transfer surface that effectively transfers and receives heat from the object to be measured, and exhibits a heat collection effect. Moreover, round pattern 21 (21p, 21n)
Since the copper foil 2p and the constantan foil 2n are thin and have a small heat capacity, they follow the object to be measured and reach a thermal equilibrium state in a short time. As a result, even if the thermocouple 10 is brought into contact with the object to be measured, the degree of disturbance in the temperature of the object to be measured is small.

[0014] Moreover, the round pattern 21 (21p,
The copper plating layer 3 on the inner surface of the hole 4 of 21n) acts as a thermocouple contact point that electrically connects the copper foil 2p with positive thermopower and the constantan foil 2n with negative thermopower, and also serves as a thermal contact point. It acts to connect the round patterns 21 (21p, 21n) of the copper foil 2p and the constantan foil 2n. As a result, the heat transferred to and received by the round pattern 21 (21p, 21n) can also move in the thickness direction of the sheet 1 via the copper plating layer 3, reducing the time required for thermal equilibrium and increasing the response speed of the thermocouple 10. There is an effect.

Note that the round pattern 21 (21p, 2
The reason why the conductive layer 3 on the inner surface of the hole 4 in 1n) is formed of a copper plating layer is that the thermoelectromotive force generated by the conductive layer at the contact point can be ignored compared to the thermoelectromotive force of the positive or negative thermoelectric leg. This is to reduce parasitic noise components by suppressing the noise to a small level, and if it is suitable for this purpose, it is also possible to replace the copper plating layer with another metal layer or a conductive material layer. Note that for the above purpose, it is also effective to laminate a metal having positive thermoelectric power and a metal having negative thermoelectric power.

Furthermore, when the object to be measured is a highly fluid gas or liquid, the copper plating layer 3 on the inner surface of the hole 4 can directly contact the gas or liquid and transfer heat. Coupled with the heat collecting effect of the pattern, the copper plating layer 3 also collects heat directly from the object to be measured, which has the effect of further improving the response characteristics.

Note that the round pattern 21 (21p, 2
The thermoelectric leg portions of the copper foil 2p and constantan foil 2n that extend from the round pattern 21 (21p, 22n) to the external terminal pattern 22 (22p, 22n) have a large thermal resistance because they are narrow and thin. Terminal pattern 2
2 (22p, 22n) to substantially suppress the amount of heat escaping by thermal conduction.

Furthermore, the polyimide sheet 1 that mechanically reinforces the copper foil 2p and the constantan foil 2n has excellent mechanical strength at high temperatures and low thermal conductivity, so that the amount of heat escaping via the sheet 1 is kept to a minimum.

As described above, according to this embodiment, the round pattern quickly and efficiently reaches a thermal equilibrium state by receiving and receiving a small amount of heat from the object to be measured. Furthermore, there is less adverse effect such as heat applied to the round pattern conducting and heating the external terminal pattern. As a result, an appropriate temperature difference is generated between the round pattern and the external terminal pattern, and an accurate thermoelectromotive force corresponding to the respective thermoelectric capacities of the copper foil and the constantan foil is generated in the external terminal pattern.

According to the above embodiment, since the thickness of the thermocouple is thin, even if the thermocouple is immersed in a flowing object to be measured, the flowing state is not disturbed and the thermocouple can be immersed in the flowing object. It has the excellent effect of being able to measure the temperature of the object to be measured from moment to moment.

Next, a second embodiment of the present invention will be explained with reference to FIG. FIG. 2 is a front view of the thermocouple with some parts omitted. The configuration of the thermocouple 11 of this second embodiment differs from the configuration of the first embodiment described above in the following points.

First, in this thermocouple 11, four sets of copper vapor deposited films 2p as positive thermoelectric legs and four nickel vapor deposited films 2n as negative thermoelectric legs are patterned. To be more specific, a copper layer and a nickel layer each having a thickness of 0.3 μm are deposited by electron beam on the front and back sides of a polyimide sheet 1 having a thickness of 50 μm, and these deposited films 2p and 2n are as follows. Each positive and negative thermoelectric leg is patterned into a predetermined shape. Second, this thermocouple 11
Here, two contacts are provided in parallel at each end of the pattern of the four pairs of copper vapor deposited films 2p and nickel vapor deposited films 2n on the sheet 1. That is, each thermoelectric leg is electrically connected to the two round patterns 211, 212 and the copper plating layer 3 deposited on the inner surface of the hole 4 (41, 42) in the center of the round patterns 211, 212. They are also thermally redundantly connected. Note that in order to arrange four pairs of copper foils 2p and nickel foils 2n at a predetermined pitch P (in this second embodiment, the pitch is 0.5 mm) on the thermocouple 11, the round patterns 211, 212 The holes 4 are arranged in a houndstooth pattern.

According to the configuration of the second embodiment described above, a plurality of thermocouples are integrally arranged in the thermocouple 11 with accurately determined positions on the sheet 1. As a result, by simply positioning the thermocouple 11 with respect to the object to be measured,
It is possible to accurately measure the temperature and temperature distribution at multiple locations on an object to be measured at the same time.

Furthermore, since the positive and negative thermoelectric legs and the round pattern are formed by the thin metal vapor deposition layer, the heat capacity of the thermocouple can be further reduced and the response characteristics can be increased. Furthermore, the influence of measurement on the object to be measured can be reduced.

Furthermore, since the positive and negative thermoelectric legs are connected in parallel through multiple contacts, the temperature of the round pattern is brought to thermal equilibrium in a short time due to heat conduction via the through holes.
Furthermore, the thermocouple 11 can be made redundant against mechanical damage, and is highly reliable.

Although several embodiments of the present invention have been described above, various modifications can be easily made within the scope of the technical idea of the present invention. For example, in the example above,
Although the contact point is provided inside the edge portion of the insulating substrate, the contact point can also be provided on the edge surface of the insulating substrate. For example, if a contact is formed by a through hole according to the above embodiment and the insulating substrate is cut at the center of the through hole, a semicircular contact will be formed at the edge of the thermocouple formed by the cutting line. It is possible to do so. Alternatively, in the description of the above embodiment, the shape of the hole is a round hole, but it is also possible to use a square hole. Furthermore, instead of through-hole plating, it is also possible to selectively perform end face plating on the edge face of the insulating substrate. According to this, the temperature of the object to be measured can be measured at the edge portion of the thermocouple.

Although not mentioned in the explanation of the above embodiment,
The inside of the hole can also be filled with anaerobic resin or metal. This increases the mechanical strength of the contact, improves heat transfer from the object to be measured, and allows the contact to have a certain heat capacity, suppressing thermal fluctuations during measurement. A stable thermoelectromotive force can be obtained.

It is also possible to increase the diameter of the hole so that the thermocouple can be screwed onto the object to be measured, or to expand the heat receiving area by enlarging the round pattern. Furthermore, laser processing can also be used to process the outer shape of the thermocouple and to form minute holes. In any case, the present invention is not limited to the materials, dimensions, and shapes described in the description of the above embodiments, and the materials may be changed to other insulating materials or thermoelectric materials, or
It is also possible to change the shape of the pattern. Furthermore, the thermocouple can be mechanically, electrically, or chemically protected by coating the surface of the thermoelectric leg with a protective layer or an insulating layer.

According to the present invention, the positive and negative thermoelectric legs attached to the insulating base are connected in series through the conductive layer provided on the cross section of the insulating base, so the entire thermocouple can be made smaller and smaller. This has the remarkable effect of providing a thermocouple that can be made thin and has excellent response characteristics.

[Brief explanation of drawings]

FIG. 1(a) is a front view with some parts omitted of a thermocouple according to a first embodiment, and FIG. 1(b) is a cross-sectional view showing an enlarged configuration of the main parts thereof.

FIG. 2 is a partially omitted front view showing the configuration of a second embodiment.

[Explanation of sign]

1 Insulating substrate 2p positive thermoelectric leg 2n Negative thermoelectric leg, 3 Conductive layer 4 Hole 10, 11 Thermocouple

Claims (1)

[Claims] 1. A thermoelectric element having a positive thermoelectric leg and a negative thermoelectric leg electrically connected in series, the positive thermoelectric leg 2p and the negative thermoelectric leg 2n being attached to the surface of an insulating substrate 1. A thermoelectric element characterized in that these are electrically connected in series by a conductive layer 3 deposited on a cross section of an insulating substrate 1.