JP2858352B2 - Thin film thermistor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat-resistant thin-film thermistor used as a temperature sensor for cooking appliances such as electric ovens and gas ovens, and combustion appliances such as oil fan heaters.

2. Description of the Related Art Various mounting structures of a thin-film thermistor have been considered in order to protect a thermistor element having a pair of thick-film electrode films and a temperature-sensitive resistor formed on an alumina substrate from a use environment.

For example, according to Nagai et al., Electronics and Ceramics, May '85, May, Special Issue on Thin Film Electronic Materials, page 16, as shown in FIG. 5, the thin film thermistor hermetically seals the thermistor element 4 inside the glass tube 15. Then, the Pt internal lead wire 7 from the thermistor element 4 is welded to the Kovar wire (external lead wire) 5 and taken out of the glass tube 15. Then, the holding base 16 and the protective cover 17 are attached to complete the process.

Problems to be Solved by the Invention The above-mentioned conventional thin film thermistor has a usable temperature of
The temperature is up to 350 ° C. If the temperature is higher than 350 ° C, the characteristics are greatly affected by the external environment due to the following problems, and it cannot be used.

A first problem is that a large amount of water vapor generated in a cooking cabinet, a combustor, or the like is exposed to an external environment.
It easily adheres to an external lead wire, a thermistor element, a holding base, and the like, and the adhesion of water vapor causes electrical conduction, which tends to reduce electrical insulation. For this measure,
For example, a conventional thin-film thermistor that coats a polytetrafluoroethylene resin and prevents dew condensation by using water repellency is used.However, the heat resistance of this resin is 350 ° C. Is deteriorated, the water repellency is reduced, and accordingly, the electrical insulation is reduced, and the temperature cannot be measured correctly.

The second problem is that the glass tube that protects the thin-film thermistor element from the external environment is sealed with a Kovar external lead wire through a chemical bonding layer at the interface. Due to the difference in thermal expansion characteristics, when a large temperature difference is generated, a large strain is generated and the glass tube is damaged and deteriorated. This means that as a result of studying materials of various chemical compositions as a glass material having a glass thermal expansion coefficient close to the Kovar external lead wire, a conventional thin film thermistor selected borosilicate and glass,
This is because it has been confirmed that there is no practical problem if the operating temperature is up to 350 ° C. Therefore, there has been a problem that it cannot be used at 350 ° C. or higher where a large temperature difference easily occurs.

Means for Solving the Problems To solve the above problems, the present invention provides an element support for fixing a thin film thermistor element main body via a glass coating film,
The thin-film thermistor element and a pair of external leads for fixing the element support while providing electrical continuity through the internal leads, a protective container for accommodating the element support, and insulating the external leads. Having a pair of through-holes for fixing the protective container and a separator fixed thereto, and storing and fixing the thin-film thermistor element body in a concave recess provided in the element support, An external lead wire was inserted into a through-hole provided in the element support, folded, and fixed to each other at a through-hole provided at another position to form a thin-film thermistor.

With the above-described configuration, the thin-film thermistor of the present invention is configured such that the thin-film thermistor element main body and the inner lead wire and the outer lead wire are housed in a protective container to be shielded from the external environment, and the thin-film thermistor element main body is connected to the element support member. Secured to each other with external lead wires and protective container. Therefore, there is no decrease in electrical insulation due to the adhesion of water vapor, and the temperature can be accurately measured even in an atmosphere in which a large amount of water vapor is easily condensed. Further, since the protective container has no sealing with materials having different thermal expansion coefficients, there is no generation of distortion due to thermal shock, and there is no damage of the protective container even when the temperature is rapidly dropped from high temperature to room temperature. Therefore, the thin-film thermistor element body and the lead wires are shielded from the external environment for a long time, and the temperature can be accurately measured at a high temperature for a long time.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is an external view of a thin film thermistor element body of the present invention. A pair of thick electrode films 2 and a temperature-sensitive resistor 3 are formed on a salamic substrate 1. The ceramic substrate 1 uses an alumina substrate in consideration of practicality, and has a surface roughness of 2 to 2.
It was 3 μm.

On the other hand, the temperature-sensitive resistor 3 includes metal oxide, silicon carbide (hereinafter referred to as SiC), etc., but it has a high sensitivity and can be measured over a wide temperature range. Thin film (thickness of about 6μ)
m) was formed.

The thick-film electrode film 2 is an Au-Pt film, a Pt film, an Au film, or the like.
FIG. 2 is an external view of a thin film thermistor according to one embodiment of the present invention, obtained by printing, drying, and firing a paste on an alumina substrate 1 using a highly reliable Au-Pt film.

The thin-film thermistor element body 4 is fixed on a ceramic element support 6 to which a pair of heat-resistant metal external leads 5 are fixed, and the pair of thick-film electrode films 2 and the pair of external leads 5 are heat-resistant. Each is electrically connected by a metal internal lead wire 7. Thereafter, the element support 6 is housed in a heat-resistant metal protective container 8, and the pair of external lead wires is inserted through the through-hole 10 of the ceramic separator 9 fitted with the protective container 8 using a jig 18. 5 is insulated and fixed, and at least one is separated from the protective container 9.

The material of the heat-resistant metal external lead wire 5 and the heat-resistant metal protection container 8 is stainless steel such as SUS304 or SUS430, or copper.

The material of the ceramic element support 6 and the ceramic separator 10 is at least one selected from the group consisting of alumina, calcium oxide, silicon oxide, magnesium oxide, zirconium oxide, and titanium oxide.

The heat-resistant metal inner lead wire 7 is a platinum wire, a nickel wire,
Kovar line or the like.

FIG. 3 is an external view of an element support in the thin film thermistor according to one embodiment of the present invention.

The thin film thermistor element main body 4 is fixed to the element support 6 via a glass coating layer 11. In addition, external lead wire 5
Are inserted into a through-hole 12 provided in the element support 6 and folded, and are fixed to each other by welding at a through-hole 13 provided at another position. The internal lead wires 7 drawn out from the film thickness electrode film 2 of the thin film thermistor element main body 4 are electrically connected to the external lead wires 5.

FIG. 4 is a sectional view taken along the line AA 'of the element support shown in FIG.

The thin film thermistor element main body 4 is stored in a concave recess 14 provided in the element support 6 and is fixed via a glass coating film 11. With this configuration, the element support 6
Fixing the thin film thermistor element body 4 via the glass coating layer 11 can be performed in a short time without causing displacement. Further, the concave recess 14 is provided with a through hole 15 and has an effect of preventing the generation of bubbles when the glass coating film 11 is formed by heating.

The effect of the present invention was determined based on the embodiment shown in FIGS. First, the manufacturing method will be described.

Au: Pt = 3: 7 thick electrode film (thickness: about 12μm) is formed in a comb shape on an alumina substrate (1.8mm x 6.5mm x 0.5mm). A body film was formed with a thickness of about 6 μm to obtain a thin film thermistor element.

The thin-film thermistor element is fixed to a pair of thick-film electrode films by electrically connecting an internal lead wire made of platinum using a welding method, and then using glass on an alumina-made element support.

The glass is mainly composed of SiO ₂ , BaO, and CaO, and has a thermal expansion coefficient substantially equal to that of the alumina substrate of the thin-film thermistor element and the alumina substrate of the element support. In addition,
The thin film thermistor element was housed in a concave recess provided on the element support, and then covered with glass.

Next, SUS430 external lead wire (1.2Wmm × 100Lmm × 1.
3tmm) was inserted into a through-hole provided in the alumina element support, folded, and fixed to each other by a welding method at a through-hole provided at another position. Thus, the element support and the external lead wires were fixed.

The external leads were inserted into through holes of the ceramic separator, and fixed by twisting both ends.

Thereafter, the element support is housed in a stainless steel protective container (pipe structure closed at one end) having an inner diameter of 6.7 mm and an outer diameter of 7.2 mm, and the protective container and the above-described separator are fitted using a jig. It was fixed by joining to make a finished product.

In addition, the external lead wire separates at least one from the protective container.

 The various reliability results are described below.

A load of 1000 V DC was applied to this thin-film thermistor to check its insulation. As a result, it showed a resistance of 1000 MΩ or more, and showed electrical insulation that was not problematic in practical use.

When the thin film thermistor was left in a furnace maintained at 200 ° C. and taken out in an atmosphere at room temperature, the temperature difference between the two was determined.
When the time required to reach a resistance value corresponding to a temperature of 63% (hereinafter, this time is referred to as a thermal time constant) was measured,
Seconds. For reference, when the thermal time constant of another structure was measured, it was 50 seconds without the protective container and 75 seconds for the structure of the conventional example (Fig. 5). It had almost the same thermal time constant, and there was no practical problem in response.

When the thin-film thermistor is left in a high-temperature atmosphere (500 ° C) for 1000 hours, or (Leave in air at room temperature for 15 minutes → 500 ° C
When this thermal shock was repeated 2,000 times with one cycle of “leave in air for 15 minutes → leave in room temperature air for 15 minutes”, the resistance value change rate was ± 3% or less in each case.

Furthermore, the resistance value change rate was within ± 3% when both were left for 1000 hours in a high-humidity atmosphere (temperature 70 ° C., relative humidity 95% or more) or when they were left in boiling water for 8 hours.

The thin film thermistor has a vibration close to a sine wave (frequency 300 to 360
0Hz, amplitude 0.2 ~ 3.2mm, acceleration 1 ~ 3G) were applied in X, Y, Z directions for 2 hours each, but there was no change in temperature-resistance characteristics and it was strong against mechanical vibration. Was also confirmed.

Effect of the Invention As described above, the thin film thermistor of the present invention has a thin film thermistor element main body and an internal lead wire and an external lead wire housed in a heat-resistant metal protective container, and the thin film thermistor element main body is connected to the element support body and the outside. (1) Since the thin-film thermistor element is shielded from the external environment, chemical chemistry of the element due to harmful environmental factors such as organic substances, moisture, corrosive gas, etc. Deterioration can be prevented, and high reliability can be maintained for a long time.

(2) Not only thin-film thermistor elements but also internal lead wires
Since the external lead wires are also shielded from the external environment, there is no decrease in electrical insulation due to adhesion of water vapor. Therefore, the temperature can be measured accurately even in an atmosphere where a large amount of water vapor is likely to be condensed.

(3) Since the protective container that shields the thin-film thermistor element from the external environment has no sealing with materials having different coefficients of thermal expansion,
No distortion due to thermal shock. Therefore, even if the temperature drops rapidly from high temperature to room temperature, there is no damage of the protective container,
The thin-film thermistor element is shielded from the external environment for a long time, and the temperature can be accurately measured at a high temperature for a long time.

On the other hand, the thin-film thermistor element body is covered with glass after being stored in the concave recess provided in the element support, and furthermore, the element support is fixed to the external lead wire through the through-hole and the through-hole, so that it is firmly fixed. Structure and resistant to mechanical vibration.

(4) Since the main body of the thin film thermistor element is housed in the concave recess provided in the element support, the total volume of the element support is reduced by the concave recess, and the heat capacity of the element support is reduced accordingly, resulting in quick response. Become.

Further, when fixing the thin film thermistor element body to the element support using glass, the fixing positioning is accurate due to the concave depression, and the operation is completed in a short time. Further, when a through-hole is provided in the concave depression, bubbles generated during firing accompanying the glass coating can be removed more efficiently than the through-hole, and a glass coating film with few bubbles can be obtained. Therefore, a correspondingly strong and non-porous glass coating film is obtained, and a thin film thermistor with even higher reliability is obtained.

(5) The structure is such that the external lead wires are inserted into the through-holes provided in the element support, bent, and fixed to each other by the through-holes provided at other positions, so that they are firmly fixed. Further, since the element support has a pair of through-holes and through-holes, the total volume thereof is further reduced, and the heat capacity is correspondingly reduced and the response is quickened.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an external perspective view of a thin film thermistor element according to an embodiment of the present invention, FIG. 2 is a partially cutaway perspective view of the thin film thermistor, and FIG. FIG. 4 is a sectional view taken along the line AA 'of FIG. 3, and FIG. 5 is a partially cutaway perspective view of a conventional thin film thermistor element. DESCRIPTION OF SYMBOLS 1 ... Ceramic substrate, 2 ... Thick film electrode film, 3 ... Temperature sensitive resistor, 4 ... Thin film thermistor element, 5 ... External lead wire, 6 ... Element support, 7 ... Internal lead wire, 8: Protective container, 9: Separator, 10: Through hole of separator, 11:
Glass coating film, 12: through-hole of element support, 13: through-hole of element support, 14: concave recess of element support.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Ito 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-63-41002 (JP, A) JP-A-1- 270202 (JP, A) JP-A-59-218928 (JP, A) JP-A-55-166902 (JP, A) JP-A-2-275602 (JP, A) JP-A-2-305406 (JP, A) (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01C 7/02-7/22

Claims (1)

(57) [Claims] An element support for fixing a thin-film thermistor element body via a glass coating film, and a pair of elements for electrically connecting the thin-film thermistor element body and internal leads via internal leads and fixing the element support. An external lead wire, a protective container for accommodating the element support, and a separator fixed to the protective container having a pair of through holes for insulating and fixing the external lead wire. The thin film thermistor element main body is stored and fixed in a concave recess provided in the support, and the external lead wires are inserted into through holes provided in the element support and folded, so that the external lead wires are provided at other positions. Thin film thermistor fixed to.