JP2012182260A - Thermistor element and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermistor element capable of being manufactured in a simple manufacturing step, avoiding direct thermal influence of laser welding even in a thin electrode film, and obtaining desired thermistor characteristics, and to provide a manufacturing method thereof.SOLUTION: A thermistor element includes: a metal oxide sintered body 2 for chip-like thermistors; a pair of terminal electrodes 3 formed on both ends of the metal oxide sintered body 2 for the chip-like thermistors; and a pair of lead wires 4 bonded to the pair of the terminal electrode 3. An insulator part 5 is bonded to the metal oxide sintered body 2 for the chip-like thermistors and the pair of the terminal electrodes 3 is formed extending to the insulator part 5. The lead wires 4 are laser-welded to a part just above the insulator part 5 of the terminal electrodes 3.

Description

  The present invention relates to a thermistor element used for temperature measurement such as in automobiles and a method for manufacturing the thermistor element.

  Generally, a thermistor temperature sensor is employed as a temperature sensor for measuring the catalyst temperature around the automobile engine, the exhaust system temperature, and the like. The thermistor element used in this thermistor temperature sensor is, for example, used as a temperature sensor for the above-mentioned automobile-related technology, information equipment, communication equipment, medical equipment, housing equipment, etc., and is an oxide semiconductor having a large negative temperature coefficient. A sintered element is used.

  In recent years, there has been an increasing demand for a wide range thermistor element capable of measuring in a wide temperature range from low temperature to high temperature. As a general form of such a thermistor element, a terminal electrode is applied and formed on a thermistor wafer, the wafer is cut into a flake element, and then a lead wire is joined to the pair of terminal electrodes, and the thermistor chip portion is formed as an insulating coating layer. A thermistor element is used.

  In joining to the lead wire which is an electrode wire, fixing with an electrode paste is the mainstream, and there is a problem that the fixing strength is weak. On the other hand, laser welding is a candidate as an alternative joining technology that can improve the bonding strength, but when joining the lead wire and the thermistor with terminal electrode directly using laser welding, an electrode film is simply formed on the thermistor flake. When the lead wire is joined as the terminal electrode, the thermistor part may be melted. In this case, the thermistor characteristics may change.

  As a technique for avoiding this, a method has been proposed in which a lead wire is joined to a portion other than the thermistor using laser welding. For example, Patent Document 1 proposes a thin film temperature sensor in which a bump is formed on an electrode film and a lead wire (lead wire) is laser-welded to the bump. Patent Document 2 proposes a thin film temperature sensor in which a lead wire is laser-welded halfway through a thick Ni plating layer.

JP 2008-241666 A JP 2010-197163 A

The following problems remain in the conventional technology.
That is, when the thin film thermistor technology is used, it is necessary to form a thermistor thin film or an electrode pattern, and there is a disadvantage that the manufacturing process becomes complicated. While measures such as simply increasing the thickness of the electrode layer to avoid thermal effects are effective, if the electrodes are uniformly thickened to avoid thermal effects, they may be processed into flake elements. In addition, there is a possibility that the electrode may be peeled off during the cutting process, which may reduce the yield.

  The present invention has been made in view of the above-mentioned problems, and can be manufactured by a simple manufacturing process and can avoid the direct thermal effect of laser welding even with a thin electrode, and can obtain desired thermistor characteristics. An object is to provide an element and a method for manufacturing the element.

  The present invention employs the following configuration in order to solve the above problems. That is, the thermistor element of the first invention is a chip-like metal oxide sintered body for a thermistor, a pair of terminal electrodes formed at both ends of the metal oxide sintered body for the thermistor, and a pair of the terminal electrodes. A pair of lead wires joined to each other, an insulator portion joined to the metal oxide sintered body for the thermistor, and the pair of terminal electrodes extending to the insulator portion. The lead wire is laser-welded at a portion directly above the insulator portion of the terminal electrode.

  In this thermistor element, the insulator part is joined to the metal oxide sintered body for the thermistor, and a pair of terminal electrodes are formed to extend over the insulator part, and the lead wires are insulated from the terminal electrodes. Since the laser welding is performed directly above the body part, the laser welding point is directly above the insulator part, which is a dummy part shifted from directly above the metal oxide sintered body for the thermistor. However, the direct thermal influence on the metal oxide sintered body for the thermistor can be avoided. In addition, since the terminal electrodes are formed on the chip-like metal oxide sintered body for thermistor and the insulator portion joined to each other, a plurality of pattern forming steps as in the thin film thermistor technique are unnecessary.

The thermistor element of the second invention is characterized in that, in the first invention, the insulator part is formed of an insulating oxide contained in the metal oxide sintered body for the thermistor. .
That is, in this thermistor element, since the insulator portion is formed of an insulating oxide contained in the metal oxide sintered body for the thermistor, the metal oxide sintered body for the thermistor and the insulator portion are mutually connected. Good jointability can be obtained by containing a common insulating oxide.

Furthermore, in the thermistor element of the third invention, in the second invention, the metal oxide sintered body for the thermistor has the general formula: (1-z) (Y _1-y La _y ) (Cr _1-x Mn _x ) O ₃ + zY ₂ O ₃ (where 0.0 ≦ x ≦ 1.0, 0.0 ≦ y ≦ 1.0, 0 <z ≦ 0.8), and the insulator portion Is made of Y ₂ O ₃ .
In this thermistor element, the metal oxide sintered body for the thermistor has the general formula: (1-z) (Y _1-y La _y ) (Cr _1-x Mn _x ) O ₃ + zY ₂ O ₃ 0 ≦ x ≦ 1.0, 0.0 ≦ y ≦ 1.0, 0 <z ≦ 0.8), so that La is arranged at the A site as a Cr, Mn-based perovskite oxide. In addition, the entry / exit of oxygen to / from the perovskite oxide, which is a factor affecting the change in resistance value, is reduced, and the rate of change in resistance value can be suppressed by Y ₂ O ₃ added as an insulator material.

  A method for producing a thermistor element according to a fourth invention is a method for producing the thermistor element according to any one of the first to third inventions, and comprises a thermistor raw material powder that becomes the metal oxide sintered body for the thermistor. Forming the first green sheet, laminating the second green sheet with a slurry containing an insulating raw material powder serving as the insulator, and laminating the first green sheet and the second green sheet. A laminated green sheet, a step of firing the laminated green sheet to form a laminated sintered plate comprising a thermistor layer and an insulator layer, and cutting the laminated sintered plate into strips A step of forming a strip-shaped laminate, a step of forming an electrode layer serving as a terminal electrode on a cut surface of the strip-shaped laminate, and the terminal electrode is formed at both ends by cutting the strip-shaped stack. A step of forming a chip-like laminate, and a lead wire and the terminal by irradiating the lead wire with a laser beam in a state where the lead wire is arranged in a portion directly above the insulator layer among the terminal electrodes of the chip-like laminate. And a step of joining the electrodes by laser welding.

  That is, in this method of manufacturing the thermistor element, a lead wire is irradiated on the lead wire in a state where the lead wire is disposed immediately above the insulator layer in the terminal electrode of the chip-shaped laminate, and the lead wire and the terminal electrode are connected. Since it is joined by laser welding, even if the terminal electrode is thin, the direct thermal effect of laser welding extends only to the insulator part directly under the welding location, and avoids the thermal effect on the metal oxide sintered body for the thermistor. be able to. In addition, the first green sheet as the metal oxide sintered body for the thermistor and the second green sheet as the insulator are laminated and adhered to form a laminated green sheet, which is fired. The bonded body and the insulator portion can be easily laminated and bonded, and the thickness of each can be controlled with high accuracy, so that high productivity can be obtained.

The present invention has the following effects.
That is, according to the thermistor element and the manufacturing method thereof according to the present invention, the insulator part is joined to the metal oxide sintered body for the thermistor, and the pair of terminal electrodes extend to the insulator part. Because the lead wire is laser welded at the portion directly above the insulator portion of the terminal electrode, even if the electrode is thin, the direct thermal effect on the metal oxide sintered body for the thermistor can be avoided, and the desired Thermistor characteristics can be obtained.

It is sectional drawing which shows one Embodiment of the thermistor element which concerns on this invention, and its manufacturing method. In this embodiment, it is a perspective view which shows the manufacturing method of the thermistor element in order of a process.

  Hereinafter, an embodiment of a thermistor element and a manufacturing method thereof according to the present invention will be described with reference to FIGS. In the drawings used for the following description, the scale is appropriately changed to make each member recognizable or easily recognizable.

As shown in FIG. 1, the thermistor element 1 of the present embodiment includes a chip-like metal oxide sintered body 2 for the thermistor and a pair of terminal electrodes formed on both ends of the metal oxide sintered body 2 for the thermistor. 3 and a pair of lead wires 4 joined to the pair of terminal electrodes 3, an insulator portion 5 is joined to the metal oxide sintered body 2 for the thermistor, and the pair of terminal electrodes 3 is an insulator. It extends to the top of the part 5.
Further, in the thermistor element 1, the lead wire 4 is laser-welded at a portion directly above the insulator portion 5 in the terminal electrode 3.

The metal oxide sintered body 2 for the thermistor is La (Cr, Mn) O ₃ + Y ₂ O ₃ , and has a general formula: (1-z) (Y _1-y La _y ) (Cr _1-x Mn _x ) O ₃ + zY ₂ O ₃ (where 0.0 ≦ x ≦ 1.0, 0.0 ≦ y ≦ 1.0, 0 <z ≦ 0.8) is employed. For example, the metal oxide sintered body 2 for the thermistor is obtained by mixing and sintering 50 mol% of La (Cr _0.5 Mn _0.5 ) O ₃ and 50 mol% of Y ₂ O ₃ .

The insulator portion 5 is made of Y ₂ O ₃ . That is, the insulator 5 is formed of an insulating oxide contained in the thermistor metal oxide sintered body 2. This insulator portion 5 is formed of an insulating material having a sufficiently large resistance value as compared with the metal oxide sintered body 2 for the thermistor.
The metal oxide sintered body 2 for the thermistor 2 and the insulator 5 constitute a chip-like laminate 6 as a flake type thermistor chip. This chip-shaped laminate 6 is formed into a chip shape having six surfaces (a chip shape includes a block shape).

The metal oxide sintered body 2 for the thermistor has a general formula: (1-z) (Y _1-y La _y ) (Cr _1-x Mn _x ) O ₃ + zY ₂ O ₃ (however, 0.0 ≦ x.ltoreq.1.0, 0.0.ltoreq.y.ltoreq.1.0, 0 <z.ltoreq.0.8), La is arranged at the A site as a Cr, Mn-based perovskite oxide, and the resistance. Oxygen entry / exit into the perovskite oxide, which is a factor affecting the value change, is reduced, and the resistance change rate can be suppressed by Y ₂ O ₃ added as an insulator material.

The B constant, which is a parameter indicating the electrical characteristics of the thermistor element 1, is represented by the general formula: (1-z) (Y _1-y La _y ) (Cr _1-x Mn _x ) O ₃ + zY ₂ O ₃ x, Adjust by changing the amount of y and z. However, for example, as the B constant decreases, the resistance value also decreases. Therefore, if the resistance cannot be adjusted by changing the shape, it is necessary to mix and sinter the insulator material to increase the resistance value. In this embodiment, the insulator material is Y ₂ O ₃ , but this may be changed to another insulator material, for example, ZrO ₂ , MgO, Al ₂ O ₃ , or CeO ₂ . In that case, it is preferable to change the insulator material which comprises the insulator part 5 to the same material.

The lead wire 4 is an electrode wire, and a jumet wire (copper-coated nickel steel wire), a Pt wire, a wire containing Rh in Pt, a wire containing Ir in Pt, or the like is adopted.
As the terminal electrode 3, for example, an Ag electrode is employed.
The surface of the thermistor metal oxide sintered body 2 and the insulator portion 5 where the terminal electrode 3 is not formed is preferably covered with a protective glass film 7. Further, the periphery of the chip-shaped laminate 6 is covered with an insulating coating material 8 such as glass.

  Next, the manufacturing method of the thermistor element 1 of this embodiment is demonstrated with reference to FIG.

  As shown in FIG. 2, the method for manufacturing the thermistor element 1 of the present embodiment includes a step of forming the first green sheet 11 with a slurry containing a thermistor raw material powder that becomes the thermistor metal oxide sintered body 2, and an insulator. A step of forming the second green sheet 12 with a slurry containing an insulating raw material powder to be part 5, and a step of stacking and adhering the first green sheet 11 and the second green sheet 12 to produce the laminated green sheet 13. The step of firing the laminated green sheet 13 to form a laminated sintered plate 16 comprising the thermistor layer 14 and the insulator layer 15 and the step of cutting the laminated sintered plate 16 into a strip-like laminate 17 A step of forming an electrode layer 18 to be the terminal electrode 3 on the cut surface of the strip-shaped laminate 17, and a chip-shaped laminate 6 in which the strip-shaped laminate 17 is cut and the terminal electrodes 3 are formed at both ends; The lead wire 4 and the terminal electrode by irradiating the lead wire 4 with the laser beam L in a state where the lead wire 4 is arranged in the portion directly above the insulator layer 15 of the terminal electrode 3 of the chip-like laminate 6. 3 is joined by laser welding.

This production method will be described more specifically below. First, as the thermistor raw material powder, for example, La ₂ O ₃ , Y ₂ O ₃ , Cr ₂ O ₃ , and MnO ₂ powder are weighed at a molar ratio of 25: 25: 12.5: 12.5 and then put into a ball mill. Then, an appropriate amount of Zr balls and pure water are added and mixed for about 24 hours. After drying removed, it was fired at 5hr at 1300 ° _C., to obtain a _{La (Cr 0.5 Mn 0.5) O} 3 + Y 2 O 3 calcined powder.

Thereafter, La (Cr _0.5 Mn _0.5 ) O ₃ + Y ₂ O ₃ calcined powder is pulverized using Zr balls and pure water and then dried. PVB, a solvent, a dispersant, and a plasticizer are added to the mixed raw material powder obtained in this way, and mixed with a ball mill to prepare a slurry. This slurry is formed into a first green sheet 11 having a thickness of 300 μm by the doctor blade method as shown in FIG. Further, the second green sheet 12 is formed by using Y ₂ O ₃ powder as a raw material for the insulator layer 15 which is a dummy layer in the same manner as described above.

  Next, as shown in FIG. 2 (b), the first green sheet 11 and the second green sheet 12 are laminated by a thermocompression press and brought into close contact with each other, and then processed by an ISP (hot isostatic press). Thus, the laminated green sheet 13 is obtained. Further, this laminated green sheet 13 was cut into 50 × 50 mm squares, subjected to binder removal treatment, and then fired at 1600 ° C. for 5 hours to obtain a laminated sintered plate 16 composed of the thermistor layer 14 and the insulator layer 15. Form. Thereafter, both surfaces of the laminated sintered plate 16 are polished by about 100 μm and processed flat.

  Thereafter, as shown in FIG. 2C, the protective glass film 7 is formed by printing the protective glass on both surfaces of the laminated sintered plate 16 and drying it, followed by baking at 850 ° C. Further, the laminated sintered plate 16 having a width of 0.3 mm is cut into a strip shape by a dicing machine to produce a strip-shaped laminate 17. Next, as shown in FIG. 2 (d), the Ag paste is applied to the two surfaces where the metal oxide sintered body 2 for the thermistor and the insulator portion 5 are exposed, which are cut surfaces of the strip-shaped laminate 17. The electrode layer 18 which becomes the terminal electrode 3 is formed by applying and drying and baking at 850 ° C.

Next, the strip-like laminate 17 is cut by a dicing machine perpendicular to the direction cut earlier, and a chip-like laminate 6 which is a flake-type thermistor chip is produced as shown in FIG.
In order to connect the lead wire 4 to the chip-like laminate 6, first, the lead wire 4 which is a dumet wire is disposed immediately above the insulator portion 5, temporarily fixed using Au paste, and dried.

In this state, the central portion of the insulator 5, the lead wire 4, and the laser beam L to be irradiated are arranged in a straight line, and laser welding is performed as shown in FIG. In this way, the lead wire 4 is welded to the chip-like laminate 6. In order to further improve the environmental resistance, the thermistor element 1 is manufactured by covering the periphery with an insulating coating material 8 such as glass.
In the fabricated thermistor element 1, the bonding between the terminal electrode 3 and the lead wire 4 remains strong, and as indicated by the two-dot chain line in FIG. 1, the thermal effect due to laser irradiation does not affect the thermistor characteristics. Since the thermistor metal oxide sintered body 2 is generated only in the insulator portion 5 and is not directly affected, a stable and high yield element can be obtained without changing the thermistor characteristics.

As described above, in the thermistor element 1 of the present embodiment, the insulator portion 5 is joined to the thermistor metal oxide sintered body 2 and the pair of terminal electrodes 3 extends to the insulator portion 5. In addition, since the lead wire 4 is laser welded at a portion of the terminal electrode 3 immediately above the insulator portion 5, the insulation is a dummy portion in which the laser welding location is shifted from directly above the metal oxide sintered body 2 for the thermistor. By being directly above the body part 5, even if the terminal electrode 3 is thin, it is possible to avoid a direct thermal effect on the metal oxide sintered body 2 for the thermistor.
That is, at the time of manufacture, the lead wire 4 is irradiated with the laser beam L on the lead wire 4 in a state where the lead wire 4 is arranged on the portion of the terminal electrode 3 of the chip-like laminate 6 immediately above the insulator layer 15 and the lead wire 4 and the terminal. Since the electrode 3 and the electrode 3 are joined by laser welding, the direct thermal influence of the laser welding extends only to the insulator portion 5 immediately below the welded portion, and the thermal influence on the metal oxide sintered body 2 for the thermistor can be avoided. .

Further, since the terminal electrode 3 is formed on the chip-like metal oxide sintered body 2 for the thermistor and the insulator portion 5 that are joined to each other, a plurality of pattern forming steps as in the thin film thermistor technique are unnecessary.
Moreover, since the insulator part 5 is formed of the insulating oxide contained in the thermistor metal oxide sintered body 2, the thermistor metal oxide sintered body 2 and the insulator part 5 are common to each other. It is possible to obtain good bondability by containing an insulating oxide.

  Furthermore, at the time of manufacture, the first green sheet 11 that becomes the metal oxide sintered body 2 for the thermistor and the second green sheet 12 that becomes the insulator portion 5 are laminated and adhered to form a laminated green sheet 13 that is fired. Therefore, the metal oxide sintered body 2 for the thermistor and the insulator portion 5 can be easily laminated and joined, and the thicknesses of each can be controlled with high accuracy, and high productivity can be obtained. .

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Thermistor element, 2 ... Metal oxide sintered compact for thermistors, 3 ... Terminal electrode, 4 ... Lead wire, 5 ... Insulator part, 6 ... Chip-shaped laminated body, 11 ... 1st green sheet, 12 ... 2nd Green sheet, 13 ... laminated green sheet, 14 ... thermistor layer, 15 ... insulator layer, 16 ... laminated sintered plate, 17 ... strip-like laminated body, 18 ... electrode layer, L ... laser beam

Claims (4)

Chip-shaped metal oxide sintered body for thermistor, and
A pair of terminal electrodes formed at both ends of the metal oxide sintered body for the thermistor;
A pair of lead wires joined to the pair of terminal electrodes,
The insulator part is joined to the metal oxide sintered body for the thermistor, and the pair of terminal electrodes are formed to extend onto the insulator part,
The thermistor element, wherein the lead wire is laser welded at a portion of the terminal electrode directly above the insulator portion. The thermistor element according to claim 1,
The thermistor element, wherein the insulator part is formed of an insulating oxide contained in the metal oxide sintered body for the thermistor. The thermistor element according to claim 2,
The metal oxide sintered body for the thermistor has a general formula: (1-z) (Y _1-y La _y ) (Cr _1-x Mn _x ) O ₃ + zY ₂ O ₃ (where 0.0 ≦ x ≦ 1.0, 0.0 ≦ y ≦ 1.0, 0 <z ≦ 0.8),
The thermistor element, wherein the insulator part is made of Y ₂ O ₃ . It is a manufacturing method of the thermistor element according to any one of claims 1 to 3,
Forming a first green sheet with a slurry containing a thermistor raw material powder that becomes the metal oxide sintered body for the thermistor;
Forming a second green sheet with a slurry containing an insulating raw material powder to be the insulator part;
Laminating and adhering the first green sheet and the second green sheet to produce a laminated green sheet;
Firing the laminated green sheet to form a laminated sintered plate comprising a thermistor layer and an insulator layer;
Cutting the laminated sintered plate into strips to form strip-like laminates;
Forming an electrode layer serving as a terminal electrode on the cut surface of the strip-shaped laminate; and
Cutting the strip-shaped laminate to form a chip-like laminate in which the terminal electrodes are formed at both ends; and
A step of irradiating the lead wire with a laser beam in a state in which the lead wire is arranged in the portion directly above the insulator layer among the terminal electrodes of the chip-shaped laminate, and joining the lead wire and the terminal electrode by laser welding. And a thermistor element manufacturing method.

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