JPH0850062A - Temperature detector - Google Patents

Abstract

PURPOSE:To provide a detector having an excellent thermal response even though it has a good corrosion resistance and a high breakdown voltage are provided by penetrating a polyimide-based or polyamide-based tube, wherein a temperature detecting element is inserted, in the inverted U-shape into holes made in an insulating substrate. CONSTITUTION:A thermistor 1 is inserted into a polyimide tube 3 in a state that silicone grease 2 is applied around a thermistor element part 6. Heading lead wires 4 are protruding from both ends of the tube 3 in this state. The silicone grease 2 blocks the leaking current flowing through the lead wires 4 through the surface of the thermistor 1 owing to moisture during the stoppage of use and during storage. Then, the tube 3, wherein the thermistor 1 is inserted, is curved in the inverted U-shape. Under the state, wherein the element part of the thermistor 1 is separated from a substrate by twice or more of the radius of curvature of the arc, the tube is made to penetrate into holes 8 in the substrate 7 made of heat resisting insulating resin. The gap part of the hole 8 is filled with the insulating resin 9, the resin is thermally set, the thermistor 1 is fixed, and the tube 3 is sealed. The lead wire 4 is connected to a pin terminal 10 provided at the substrate 7 by welding and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature detector used in a high temperature, high humidity, corrosive gas atmosphere such as exhaust temperature detection of a microwave oven.

[0002]

2. Description of the Related Art Temperature detection is an important element in heating equipment, and temperature detectors are being widely used. However, exhaust temperature detectors installed in exhaust ducts of microwave ovens are
Since it is used in an atmosphere of high humidity and corrosive gas, there are many problems in its corrosion resistance, withstand voltage, adhesion strength of the insulation coating, etc. Conventionally, such a temperature detector has a thermistor 12 welded to the tip of a pin terminal 10 standing upright on an insulating substrate 11 as shown in FIG. 4, and the pin terminal and the thermistor as a whole are made of heat resistant insulation such as Teflon or polyimide. Resin 1
It is covered with 3. Incidentally, such a temperature detector is installed from the outside of the hole formed in the exhaust duct, and only the tip (thermistor side) from the surface of the insulating substrate is exposed to the bad environment.

[0003]

However, the above-mentioned conventional structure has the following problems. The temperature sensor with such a structure is extremely difficult to eliminate pinholes even if it is thickly coated with Teflon or polyimide,
Moisture and corrosive gas will infiltrate through the pinholes, so that leakage current will be observed in a few hundred hours in a practical state. Further, a thick insulating coating can be obtained by multiple coating of coatings, but it has a drawback that it is easily peeled off due to weak adhesion to the base material, the response time is delayed and precise temperature detection cannot be performed. Further, since the thermistor element part is arranged in the vicinity of the substrate, it is easily affected by heat from the substrate and the lead wire is directly connected to the substrate,
Since the heat from the substrate is transmitted to the thermistor element section via the lead wire, there is also a drawback that precise temperature detection cannot be performed. The present invention has been made to solve such conventional drawbacks, and an object of the present invention is to provide a temperature detector excellent in thermal response while having corrosion resistance and withstand voltage. is there.

[0004]

In order to solve the above-mentioned problems, a temperature detector according to the present invention has a reverse U-shaped polyimide or polyamide tube having a temperature detecting element inserted in a hole formed in an insulating substrate. The temperature sensing element located at the apex of the inverted U-shape is separated from the substrate by at least twice the radius of this arc, and the void of the hole is fixed by insulating resin. It is characterized by being sealed.

Examples of the polyimide include general polyimides such as polypyromellitic imide, polyester imide, polyamide imide, polyether imide,
Polyimides containing other components such as fluorinated polyimides are also effective. Examples of the polyamide include heat-resistant non-thermoplastic aromatic polyesteramides and wholly aromatic polyamides. Teflon tubes other than polyimide-based or polyamide-based tubes, such as Teflon tubes, have excellent heat-resistant insulation, but are thermoplastic, and lose rigidity at high temperatures, and are deformed even by the weak rigidity of the heading lead wire of the temperature sensing element. It causes instability factors such as causing or biting into the tube, and at the same time, it is extremely difficult to adhere to the substrate.

The tube in which the temperature detecting element is inserted is bent in an inverted U shape so as to draw an arc, and the thermistor element is mounted in a state in which it is separated from the substrate by at least twice the radius of this arc. If the right and left sides are bent at a right angle without forming the inverted U-shape, the tube is likely to tear and corrosion resistance and voltage resistance deteriorate. Further, if the distance between the element portion of the thermistor and the substrate is shorter than twice the radius of the circular arc, it is easily affected by the heat from the heated substrate, and accurate temperature detection cannot be performed.

The insulating resin is preferably a thermosetting resin that does not lose its rigidity even at high temperatures, such as polyimide resin.

[0008]

In the temperature detector of the present invention having the above structure, the portion installed in the exhaust duct is integrally covered with a pinhole-free polyimide-based or polyamide-based tube, and adheres to the insulation-covered pinhole. The problem of strength is eliminated and extremely high corrosion resistance and withstand voltage can be obtained even in a bad environment, and since the tube is thin, the response time is fast and precise temperature detection is possible. further,
Since the element portion of the temperature detecting element is separated from the substrate by more than twice the radius of the arc, it is less susceptible to the heat from the substrate, and the tube is connected to the substrate through the insulating resin. It is difficult for heat to be transferred to the lead wires, which enables accurate temperature detection.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to the drawings. FIG. 1 is a partially cutaway view showing an embodiment of a temperature detector according to the present invention, partially cut away. FIG. 2 is a cross-sectional view of a polyimide tube in which a thermistor that constitutes the temperature detector of FIG. 1 is inserted.

As shown in FIG. 2, the thermistor 1 has an inner diameter of 1.2 mm and a thickness of 0.05 mm when the thermistor element portion 6 is coated with silicone grease 2.
The polyimide tube 3 is inserted into the polyimide tube 3, and the heading lead wires 4 are left on both ends of the polyimide tube 3.

The reason for using silicone grease is that the diameter of the thermistor element portion 6 is as small as about 1 mm, and both ends of the polyimide tube are open, so that moisture is passed through the thermistor surface during use and storage. This is to prevent a leak current flowing between the lead wires, and is a commonly used means. Depending on the operating temperature, not only silicone grease but also silicone resin or silicone rubber is effective. Further, by applying the silicone grease coating treatment as described above, the heat conduction between the thermistor element portion 6 and the inner wall of the polyimide tube 3 is increased, and the response time can be shortened.

The thermistor used in this embodiment is shown in FIG.
As shown in FIG. 3, the thermistor chip 5 having electrode layers formed on both sides is thermocompression bonded by a pair of heading lead wires 4 and, at the same time, the glass tube is melted to form a thermistor element part 6. The diameter of the portion 6 is about 1 mm and the diameter of the lead wire is 0.2 mm.

Next, the polyimide tube in which the thermistor shown in FIG. 2 is inserted is curved in an inverted U shape so that the radius of the arc is 12 mm, and the element portion of the thermistor is 26 mm which is twice or more the radius of the arc. In a state of being separated from the substrate, as shown in FIG. 1, it penetrates into a hole 8 formed in a substrate 7 made of PPS which is a heat resistant insulating resin, and the void portion of this hole is filled with an insulating resin 9 and thermoset. Fix and seal. The heading lead wire 4 is connected to the pin terminal 10 provided on the substrate 7 by welding or the like.

In order to examine the corrosion resistance and withstand voltage of the temperature detector according to the present invention prepared as described above, JIS-C-7021 "Environmental test method and durability of individual semiconductor device" is applied with a voltage of DC5V applied. After performing a salt spray test prescribed in "Surability test method" for 500 hours, the tip portion from the surface of the substrate 7 made of PPS is immersed in water, and the insulation resistance is measured at DC 5V between the water and the heading lead wire 4 of the thermistor. The result was 100 MΩ or more.

For comparison, a conventional temperature sensor as shown in FIG. 4 having a coating layer having a thickness of 0.3 mm is obtained by applying a polyimide resin, which is a heat-resistant insulating resin, three times to the entire pin terminal and the thermistor. Prepared. When a test similar to the above is performed using this conventional product, it is in a short state,
It is clear that there is a pinhole leak. Further, when the response time in air at 25 to 200 ° C. is measured, the one according to the present invention has a 90% response for 25 seconds, and the conventional one under the same conditions is 1 min 4
It was 5 seconds.

As described above, according to the present invention, the insulation property, the corrosion resistance, and the withstand voltage properties are remarkably improved, and at the same time, the response time is extremely fast and accurate temperature detection can be performed. Although a thermistor is used as the temperature detecting element in the present embodiment, the same applies when a thermocouple or a micro platinum temperature measuring element is used.

[0017]

As described above in detail, according to the present invention, the portion inserted into the exhaust duct of a microwave oven in a high temperature, high humidity and corrosive gas atmosphere is covered with a polyimide or polyamide tube. Since the problem of pinholes and adhesion strength of the insulation coating is eliminated, it is possible to obtain extremely excellent insulation, corrosion resistance, and withstand voltage.
Since the tube is thin, the response time can be remarkably shortened to enable precise temperature detection. Furthermore, the element portion of the temperature detecting element that actually performs detection has a radius of 2 arcs.
Since it is more than twice as far away from the board, it is less likely to be affected by heat from the board, and because the tube is connected to the board via an insulating resin, heat from the board is less likely to be transferred to the lead wires and accurate temperature detection is possible. Is possible.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention and is a partially cutaway view.

FIG. 2 is a view showing an embodiment of the present invention and is a cross-sectional view of a tube with a thermistor inserted.

FIG. 3 is a partial cutaway view of a thermistor used in an example of the present invention.

FIG. 4 is a diagram showing a conventional example and an explanatory diagram showing a temperature detector.

[Explanation of symbols]

 1 ... Thermistor 2 ... Silicone grease 3 ... Polyimide tube 4 ... Heading lead wire 5 ... Thermistor chip 6 ... Thermistor element part 7 ... Substrate 8 ... Hole 9 ... Insulating resin 10 ... Pin terminal

Claims (1)

[Claims] 1. A temperature at which a polyimide-based or polyamide-based tube having a temperature sensing element inserted in a hole formed in an insulating substrate is penetrated in an inverted U-shaped state and located at an apex of the inverted U-shaped. A temperature detector characterized in that the element portion of the detection element is separated from the substrate by at least twice the radius of this arc and the void portion of the hole is fixed and sealed by an insulating resin.