JPH0829268A - Structure of thermistor for electronic clinical thermometer and its manufacture - Google Patents

Abstract

PURPOSE:To enhance a pressure-resistant insulating property in a thermistor single body and to enhance a static electricity-resistant characteristic and a noise-resistant characteristic when the thermistor single body is incorporated in an electronic clinical thermometer by a method wherein an insulating member has a two-layer structure at the tip part of a thermistor. CONSTITUTION:A thermistor 10 is constituted in such a way that an element part in which lead wires 14, 14' having lead-wire coatings 141, 141' are electromechanically coupled, by solders 13, 13', to an element-material part 11 having electrodes 12, 12' on both faces is covered with an insulating member 151 and, in addition, that the insulating member 151 is covered with an insulating member 152. Then, a thermistor 9 which is obtained in a first dipping process is passed through a second dipping process in which a molten insulating member 15 put into a molten insulating-member tank 15 used in the first dipping process is inserted down to a depth at which its tip part 151' is hidden completely by the insulating member 15 and in which the insulating member is pulled up. After that, the thermistor is put into a drying furnace, the insulating member is hardened, the insulating member 152 as a second layer is formed, and the thermistor 10 is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermistor structure for an electronic thermometer and a method for manufacturing the thermistor.

[0002]

2. Description of the Related Art It is well known that a mercury thermometer is used to measure a body temperature, but in recent years, an electronic thermometer using a temperature sensor has rapidly become popular. A thermistor is generally used for the temperature sensitive element of the electronic thermometer.

A conventional thermistor for electronic thermometer will be described below with reference to the drawings. FIG. 3 is a side sectional view showing the structure of a conventional thermistor for an electronic thermometer. Lead wire coatings 141, 1 on the element material portion 11 having electrodes 12, 12 'on both sides
The lead wires 14 and 14 ′ having 41 ′ are soldered to the solder wires 13 and 13.
It has a structure in which it is electromechanically coupled with ‘′ and covered with an insulating member 151. Here, the element material portion 11 is the element corner portion 11
a, the insulating member 151 has a thin portion 151 ′ and a tip portion 1
51a. Further, 17 is the thermistor outer diameter.

Next, the manufacturing process of the conventional electronic thermometer will be described. 4A and 4B are manufacturing process diagrams of a general thermistor element. FIG. 4A is a top view showing a state immediately after cutting a disc-shaped element, and FIG. 4B is a perspective view of the element. The element material 310 is made by mixing materials such as manganese, cobalt, iron, etc., cut out from an ingot fired at high temperature, and lapped into a disk shape to a thickness defined by the resistance value of the intended element. Then, a member such as palladium or silver is printed on both sides of the disk-shaped element material 310 and baked to form the electrode member 32.
0,320 ', and the electrodes 320,320
The disk-shaped element material 310 with the ‘
Glue with wax or the like. As shown in FIG. 4 (A), this is cut with a dicing saw or the like along a cutting line 6 in the Y direction and a cutting line 7 in the X direction into a size having a predetermined resistance value.
An element 30 as shown in (B) is formed. The size of this element 30 is about 0.7 mmW × 0.7 m for an electronic thermometer.
mL × 0.25 mmT, the resistance value is about 135 kΩ, and the electrodes 12, 12 ′ and the element corner portion 11a are included.

FIG. 5 is a process diagram showing a conventional method for manufacturing a thermistor structure for an electronic thermometer. The lead wires 14 and 14 ′ are soldered to the electrodes 12 and 12 ′ of the element 30 with solder 13 and 1 ′.
After connecting with 3 ', solder flux is washed and the element part 1
Form 10. This element part 110 is connected to the melt insulation member tank 1
In the molten insulating member 15 made of epoxy resin, which is placed in FIG. 6, a depth of about 2 mm (lead wires 14, 14 ′ and lead wire coating 141 is provided from the tip of the element portion 110 opposite to the lead wires 14, 14 ′. , 141 'on the element 11 side is inserted at a depth such that the insulating member 151 completely covers the boundary.
The molten insulating member 15 is held for a second to conform to the entire element portion 110, and then pulled up to complete the dipping process.
Then, the molten insulating member 15 is cured by placing it in a drying oven at about 120 ° C. for about 40 minutes, and the thermistor 9 as shown in FIG.
Get. The thermistor outer diameter 17 of the insulating member 151 is finished to 1.4 mm or less for the reason described later.

Here, FIG. 6 is an enlarged view of the vicinity of the tip portion 151 'shown in FIG. 3 for facilitating understanding of the thin portion 151a. When measuring the body temperature with an electronic thermometer, in order to shorten the measurement time, the thickness of the insulating member 151 at the tip portion 151 ′ of the thermistor 9 is made as thin as possible to reduce the thermal time constant and maintain the insulating property. Although it is manufactured as described above, the tip portion 15 is cured after the melt insulating member 15 is cured due to the variation in the amount of adhesion to the tip portion 151 ′ of the melt insulating member 15.
A thin portion 151a of the insulating member 15 often occurs at 1a.

The thin portion 151a is the insulating member 151 from the element corner portion 11a to the tip portion 151 'of the insulating member 151.
Is a relatively thin portion, but actually the insulating member 1
Not only is the wall thickness of 51 small, but the element corner portion 11a may be exposed to the outside of the insulating member 151.

The reason why the thin portion 151a of the insulating member 151 is generated is that the distance between the lead wire coating 141 and the lead wire coating 141 'is as narrow as about 0.3 mm. ′ Connected element part 1
10 is inserted and held for about 20 seconds and then pulled up, until the melt insulating member 15 is hardened, the melt insulating member 15 is pulled up between the lead wire coatings 141 and 141 'due to the capillary phenomenon, and the tip end thereof is recoiled. The portion 151 ′ is cured in a state in which the amount of the molten insulating member 15 is small, and therefore, from the element corner portion 11 a to the tip portion 151 of the insulating member 151.
It is considered that a thin portion 151a having a relatively thin wall thickness up to ′ is generated.

FIG. 7 is a sectional view showing a state in which the thermistor 9 shown in FIG. 3 is attached to the tip of the thermometer. The metallic sensor cap 50 joined to the distal end of the thermometer exterior 52 is filled with a gel-like element part fixing filler 51, and the thermistor 9 is inserted into the exterior part 54 through the probe inner diameter 53. It is pressed against the inner tip of the sensor cap 50 and then the element portion fixing filler 51 is dried and solidified to fix the thermistor 9 to the inner tip of the sensor cap 50. At this time, the thermistor outer diameter 17 is the probe inner diameter 5
As mentioned above, the standard 1.4
It is less than or equal to mm.

[0010]

However, when the thin portion 151a of the insulating member is generated, the lead wire 1 is subjected to a 500v withstand voltage insulation test in the thermistor alone.
Insulation defects between the end portions 151 ′ of the insulating members 151 and 4 and 14 ′ are increased, which causes deterioration of the yield. The cause of this insulation failure is that the element corner portion 11a is the insulating member 1.
Not only those exposed outside 51 but also lead wire 1
This is because a high voltage of 500 V is applied between the end portions 151 ′ of the insulating members 151 and 4, 14 ′, and the element corners 11 a and the insulating members 151 having a small thickness are also broken down due to insufficient insulation resistance.

Further, even if the thermistor has passed the withstand voltage insulation test, when it is incorporated into the sensor cap 50, it is strongly pressed against the tip of the sensor cap 50 to be assembled in order to improve the thermal response. Therefore, the thin portion 151a of the insulating member 151 is broken or the insulation resistance is insufficient, so that the sensor cap 50 and the element corner portion 11a.
An electrical short circuit is induced between the electrical circuit and the (element which is an electrode or a resistor), and static electricity increases or electrical noise enters the electrical circuit section (not shown) through the element section 110, and the electrical circuit However, there is a drawback in that the phenomenon that IC's are destroyed and the measured values are apt to occur easily occurs.

Further, due to the influence of the surface tension of the lead wire coatings 141 and 141 'on the insulating member 151, the insulating member 15
It is conceivable to adjust the insertion depth of the dipping in order to avoid the phenomenon that the thickness of the tip portion 151 'of No. 1 becomes thin. The insertion depth is reduced to about 1.2 mm, and the insertion is stopped when the melt insulating member 15 covers only the element portion 110 as much as possible, and the surface tension of the melt insulating member 15 is prevented from being applied to the lead wire coatings 141 and 141 '. By pulling up and hardening it before it is affected, the thickness of the tip portion 151 ′ of the insulating member 151 becomes thick to some extent.

However, there occurs a problem that the boundary between the lead wires 14 and 14 'and the lead wire coatings 141 and 141' on the side of the electrodes 12 and 12 'is not completely covered by the insulating member 151. As a result, This results in a thermistor structure in which the insulation between the lead wire and the insulating member is insufficient. Furthermore, in order to prevent this problem, a considerable amount of capital investment is required for lead wire peeling position accuracy, thermistor chip and lead wire soldering position accuracy, dipping device height position accuracy, melt insulation member viscosity control, etc. Therefore, there is a problem that the manufacturing cost increases.

An object of the present invention is to solve the above problems, and a structure of a thermistor having excellent withstand voltage insulation properties of a thermistor unit and excellent electrostatic resistance characteristics and noise resistance characteristics when incorporated in an electronic thermometer, and a manufacturing method thereof. To provide.

[0015]

The gist of the present invention for achieving the above object is characterized by a structure in which the insulating member has two layers at the tip of the thermistor, and a manufacturing method thereof.

Further, the insulating member is characterized in that the two layers are made of the same insulating member.

[0017]

In other words, the structure of the thermistor according to the present invention covers the corners of the element with a sufficient amount of an insulating member having an insulating property, so that the withstand voltage insulation reliability of the thermistor itself is improved, so that when incorporated in a thermometer. The structure is completely unaffected by static electricity and electrical noise.

[0018]

Embodiments of the present invention will be described in detail below with reference to the drawings.
FIG. 1 is a side sectional view of the thermistor for an electronic thermometer according to the present invention. The thermistor 10 has a structure in which the element material portion 11 having the electrodes 12 and 12 'on both sides is covered with lead wire coatings 141 and 141.
The element portion 110 in which the lead wires 14, 14 ′ having ′ ′ are electromechanically coupled with the solder 13, 13 ′ is covered with the insulating member 151, and further covered with the second insulating member 152. is there. The element material portion 11 has an element corner portion 11a, and the second-layer insulating member 152 has a tip portion 152 '.

FIG. 2 is a process drawing showing the second dipping process. A dipping process similar to the conventional one is used as a first dipping process, and the thermistor 9 manufactured in the first dipping process is attached to the melt insulating member 15 contained in the melt insulating member tank 16 used in the first dipping. Depth of about 0.5 mm from the part 151 '(tip 151'
Is completely hidden by the melt insulating member 15), is held for about 10 seconds, and is then pulled up to complete the second dipping step. Then, the molten insulating member 15 is cured by placing it in a drying oven at about 120 ° C. for about 40 minutes to form a second layer insulating member 152 to obtain the thermistor 10 shown in FIG.

The purpose of this second dipping process is to reduce the thickness of the thin portion 151a from the element corner 11a generated in the first dipping process to the tip 151 'of the insulating member 151.
To increase the withstand voltage insulation by increasing the thickness of the insulating member 151 in the vicinity to maintain the thermal response in a good state by reducing the amount as much as possible, and to reduce the thermal time constant. It is intended to be realized at low cost.

Here, in the second dipping step, the thickness of the insulating member with respect to the insertion depth of the dipping,
And the change in the outer diameter of the entire insulating member will be described. When the viscosity of the epoxy resin which is the melt insulating member of the present embodiment is about 3000 to 8000 cps, the insertion depth of the second dipping is the thickness of the second insulating member 152 of the tip portion 152 'and the insulating member 151. The overall outer diameter 17 is affected, and the thickness of the tip portion 152 ′ is insulating, and the insulating member 1
The outer diameter 17 of the entire 51 affects the assembling workability when the thermometer probe portion of the thermistor 10 is inserted.

More specifically, the insertion depth is 0.
In the range of 4 mm or less, the insulating member 152 of the tip portion 152 '
The thickness of the insulating member 151 increases depending on the insertion depth.
The overall outer diameter 17 does not change. This is the lead wire coating 1
41 is not affected by the surface tension due to the distance between the lead wire coating 141 'and the lead wire coating 141', and the surface area of the molten insulating member 15 in contact with the tip portion 151 'is small, and the contact portion has an outer diameter of the insulating member 151. Since it is on the tip end 151 ′ side of the portion that forms 17, the molten insulating member 15 attached to the tip end 151 ′ is pulled in the tip direction by gravity and attaches. Therefore, although the thickness of the insulating member 152 of the second layer of the tip portion 152 'increases according to the insertion depth, the outer diameter 17 of the entire insulating member 151 does not change.

However, when the insertion depth is 0.4 mm or less, the amount of the molten insulating member 15 attached to the tip portion 151 'is small, so that the thickness of the second-layer insulating member 152 at the tip portion 152' is small. Since the thickness is thin, the effect of enhancing the withstand voltage insulation property is small, and a defect may occur in the 500v withstand voltage insulation test.

Next, when the insertion depth is in the range of 0.4 to 0.7 mm, the insulating member 1 of the second layer having sufficient withstand voltage insulation property.
It has been experimentally confirmed that the amount of 52 can be secured and that the outer diameter 17 of the insulating member 151 does not change for the above reason.

Further, in the range where the insertion depth exceeds 0.7 mm, the thickness of the insulating member 152 at the distal end portion 152 'increases, but the outer diameter 17 of the entire insulating member 151 also increases, and the diameter exceeds the standard of 1.4 mm. Begins to occur. This is because the portion where the molten insulating member 15 contacts the insulating member 151 is the tip portion 1.
This is because not only 51 ′ but also the portion forming the outer diameter 17 of the entire insulating member 151 is reached, but although this does not result in any insulation failure, the outer diameter specification failure increases and the yield of the thermistor alone increases. It causes a decrease.

From the above, the insertion depth of the second dipping step is 0. 0, where the outer diameter of the insulating member 151 does not change and the amount of the insulating member 152 of the second layer having sufficient withstand voltage insulation is secured. Although it is in the range of 4 to 0.7 mm, the insertion depth of 0.5 mm was experimentally the best in this example.

[0027]

According to the present invention, therefore, the thermal time constant is minimized by making the amount of the insulating member the necessary minimum amount that can sufficiently insulate and does not slow down the heat transfer rate. In addition, the thermistor structure with excellent insulation resistance has made it possible to realize a thermistor structure with excellent static resistance characteristics and noise resistance characteristics when incorporated in an electronic thermometer.

[Brief description of drawings]

FIG. 1 is a side sectional view of a thermistor structure for an electronic thermometer according to the present invention.

FIG. 2 is a second dipping process diagram of the thermistor structure for an electronic thermometer according to the present invention.

FIG. 3 is a side sectional view of a conventional thermistor structure for an electronic thermometer.

4A and 4B are process diagrams showing a method for manufacturing an element of a general thermistor for an electronic thermometer, where FIG. 4A is a top view showing a state immediately after cutting a disc-shaped element, and FIG. 4B is a perspective view of the element. It is a figure.

FIG. 5 is a process drawing showing a method of manufacturing a conventional thermistor structure for an electronic thermometer.

FIG. 6 is an enlarged cross-sectional view of a tip portion of a conventional thermistor for electronic thermometer.

FIG. 7 is a cross-sectional view of a conventional electronic thermometer thermistor mounted on the electronic thermometer.

[Explanation of symbols]

 11 Element Material Part 11a Element Corner Part 110 Element Part 12, 12 'Electrode 13, 13' Solder 14, 14 'Lead Wire 141, 141' Lead Wire Covering 15 Melt Insulating Member 151 Insulating Member 151 ', 152' Tip Part 151a Insulation Thin part of member 152 Second layer insulation member 16 Melt insulation member tank 17 Thermistor outer diameter 30 Element 310 Element material 320, 320 'Electrode member 50 Sensor cap 51 Element part fixing filler 52 Thermometer exterior 53 Probe inner diameter 54 Exterior 6 Y-direction cutting line 7 X-direction cutting line 8 Cutting substrate 9, 10 Thermistor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshihiko Nakayama 6-12 Hommachi, Tanashi City, Tokyo Citizen Watch Co., Ltd. Tanashi Factory (72) Inventor Shinji Nakayama 4107 Miyota, Miyota-cho, Kitasaku-gun, Nagano Prefecture Ground 5 Within Simeo Precision Co., Ltd.

Claims (3)

[Claims] 1. A thermistor for an electronic thermometer, which has a lead wire and is covered with an insulating member, wherein the insulating member is covered in two layers at the tip of the thermistor. . 2. The structure of the thermistor for an electronic thermometer according to claim 1, wherein the insulating members coated in two layers are the same member. 3. An electronic clinical thermometer having a lead wire and covered with an insulating member, comprising: a first dipping step and a hardening step thereof; and a second dipping step and a hardening step thereof. For manufacturing a thermistor for automobiles.