WO2014034834A1

WO2014034834A1 - Heater

Info

Publication number: WO2014034834A1
Application number: PCT/JP2013/073266
Authority: WO
Inventors: 神谷　哲
Original assignee: 京セラ株式会社
Priority date: 2012-08-31
Filing date: 2013-08-30
Publication date: 2014-03-06
Also published as: JPWO2014034834A1; JP5748918B2

Abstract

This heater is provided with an insulating base body, and a resistor embedded in the insulating base body, and the resistor contains first conductor particles having tungsten as a main component, and second conductor particles having molybdenum as a main component, said first conductor particles having the main component of the second conductor particles as an accessory component, and said second conductor particles having the main component of the first conductor particles as an accessory component.

Description

heater

The present invention relates to a heater used in a hair iron, a water heater, an oxygen sensor, an air-fuel ratio sensor, a glow plug, a semiconductor manufacturing apparatus, or the like.

As the heater, for example, a heater in which a resistor made of a high melting point metal such as tungsten (W) and molybdenum (Mo) is embedded in a ceramic substrate mainly composed of alumina is used. Such a heater is disclosed in Japanese Patent Laid-Open No. 2001-57284.

In recent years, for example, electronic components are often arranged around a heater such as an oxygen sensor. In the future, when the integration of electronic parts is further advanced, conductive noise generated when the heater is energized is released as radioactive noise when flowing through the resistor and is arranged around the heater. It is expected to affect the electronic components and cause malfunctions.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a heater capable of reducing the generation of radioactive noise.

The heater of the present invention is a heater including an insulating base and a resistor embedded in the insulating base, wherein the resistor is mainly composed of first conductive particles mainly composed of tungsten and molybdenum. The second conductor particles include the second conductor particles, the first conductor particles have the main component of the second conductor particles as a subcomponent, and the second conductor particles have the main component of the first conductor particles as a subcomponent. It has as.

(A) is a partially transparent perspective view schematically showing an embodiment of the heater of the present invention, and (b) is an enlarged view of a resistor showing an example of a main part of the present invention. It is an enlarged view of the resistor which shows the other example of the principal part of this invention. It is an enlarged view of the resistor which shows the other example of the principal part of this invention.

Hereinafter, an embodiment of the heater of the present invention will be described in detail with reference to the drawings.

FIG. 1A is a partially transparent perspective view schematically showing one embodiment of the heater of the present invention. FIG.1 (b) is an enlarged view of the resistor 2 which shows an example of the principal part of this invention.

The heater according to the present embodiment is a heater including an insulating base 1 and a resistor 2 embedded in the insulating base 1. The resistor 2 includes first conductive particles 21 mainly containing tungsten (W) and second conductive particles 22 mainly containing molybdenum (Mo). The first conductor particle 21 has the main component of the second conductor particle 22 as the subcomponent 210, and the second conductor particle 22 has the main component of the first conductor particle 21 as the subcomponent 220. That is, the first conductor particles 21 containing W as the main component have Mo as the subcomponent 210, and the second conductor particles 22 containing Mo as the main component have W as the subcomponent 220.

The insulating substrate 1 is made of ceramics having insulating properties such as oxide ceramics, nitride ceramics or carbide ceramics. Specifically, alumina ceramics, silicon nitride ceramics, aluminum nitride ceramics, silicon carbide ceramics, or the like can be used as such ceramics. In the heater of this embodiment, the insulating substrate 1 is made of alumina ceramics. Thereby, the oxidation resistance of the heater can be improved.

The insulating substrate 1 is a rod-shaped member. The insulating base 1 is formed by providing a ceramic layer 12 around the outer periphery of a cylindrical ceramic core 11. When the insulating substrate 1 is rod-shaped, particularly cylindrical, the outer diameter can be set to 1 to 30 mm, for example, and the length in the longitudinal direction can be set to 5 to 200 mm, for example. Further, the insulating substrate 1 may be a plate-like member. When the insulating substrate 1 is plate-shaped, the size of the main surface can be set to 5 to 200 mm square, for example, and the thickness can be set to 1 to 30 mm, for example.

Further, a resistor 2 is embedded in the insulating substrate 1. The resistor 2 is provided in a predetermined area between the ceramic core 11 and the ceramic layer 12 in a plate shape or a line shape. When the resistor 2 is linear, the resistor 2 is formed in, for example, a meander shape, a spiral shape, or a wave shape. The line width of the resistor 2 is, for example, 0.1 to 5 mm, and the thickness is 0.01 to 1 mm.

The resistor 2 includes first conductor particles 21 mainly composed of W and second conductor particles 22 mainly composed of Mo. The first conductor particle 21 has the main component of the second conductor particle 22 as the subcomponent 210, and the second conductor particle 22 has the main component of the first conductor particle 21 as the subcomponent 220. The average particle diameters of the first conductor particles 21 and the second conductor particles 22 are, for example, 0.1 to 4 μm, respectively.

The first conductor particle 21 has the main component of the second conductor particle 22 as the subcomponent 210 and the second conductor particle 22 has the main component of the first conductor particle 21 as the subcomponent 220. It means that a relatively large component and a small component are present in one conductor particle. This can be observed by analyzing the cut cross-sectional structure with an electron beam microanalyzer (EPMA).

According to this configuration, it is possible to reduce variation in resistance value of each conductor particle as compared with the case where the W conductor particles and the Mo conductor particles exist independently. As a result, the current can flow smoothly. Therefore, radioactive noise generated from the heater can be attenuated. As a result, it is possible to reduce the influence on the surrounding electronic components due to radioactive noise. In addition, the structure described above makes it difficult for slipping between atoms to occur, so that the strength of the resistor 2 can be improved.

As a result, the occurrence of cracks between the conductor particles can be reduced. Thereby, the possibility that the resistor 2 is disconnected can be reduced. As a result, the durability of the heater can be improved.

Further, as shown in FIG. 2, it is preferable that glass 25 is included between the first conductor particles 21 and the second conductor particles 22. Examples of the glass 25 include glass containing silicon dioxide as a main component and containing magnesium oxide or calcium oxide as a subcomponent. Since the thermal expansion coefficient of the glass 25 is smaller than the thermal expansion coefficient of the resistor 2, the glass 25 does not remove the conductive particles even when a force is applied to peel off the conductive particles from the insulating substrate 1 at a high temperature. By pulling, the generation of cracks between the conductor particles can be reduced. As a result, the possibility that the resistor 2 is disconnected can be reduced. Thereby, durability of a heater can be improved.

Further, in the heater shown in FIG. 3, the

subcomponents

210 and 220 contained in the respective conductor particles of the first conductor particle 21 and the second conductor particle 22 are largely present in the surface layer portion including the surface of each conductor particle. Distributed. In general, conductive noise propagates in a large amount on the surface layer of conductive particles. Therefore, by distributing a large amount of the subcomponent metal in the surface layer portion of the conductor particles, it is possible to reduce the variation in resistance value in a portion where a lot of conductive noise is transmitted. Therefore, since conductive noise is transmitted more smoothly, generation | occurrence | production of the radioactive noise in the resistor 2 can be reduced. As a result, it is possible to reduce the influence on the surrounding electronic components due to the radioactive noise.

The surface layer means a region within 10% of the particle diameter from the surface of the conductor particles. It can be observed by using an electron beam microanalyzer (EPMA) that many subcomponents are distributed in the surface layer portion of the conductor particles.

The heater has an electrode pad 3 and a power supply wiring 4 as shown in FIG. The electrode pad 3 is formed on the surface of the insulating base 1 and is electrically connected to the resistor 2. The electrode pad 3 is made of W, for example. The power supply wiring 4 is electrically connected to the electrode pad 3. The power supply wiring 4 is provided on the electrode pad 3. The electrode pad 3 and the power supply wiring 4 are members for supplying electric power to the resistor 2 from an external electrode (not shown).

Next, a method for manufacturing the heater according to the present embodiment will be described.

First, in order to produce the insulating substrate 1, a sintering aid such as SiO ₂ , CaO, MgO or ZrO _{2 is} added to a ceramic component such as alumina ceramic, silicon nitride ceramic, aluminum nitride ceramic or silicon carbide ceramic. A ceramic slurry prepared by containing the above is prepared. This ceramic slurry is formed into a sheet to produce a ceramic green sheet. Or the said component is mixed and a plate-shaped or rod-shaped molded object is produced by press molding or extrusion molding.

The pattern of the conductive paste that becomes the resistor 2 is formed on one main surface of the ceramic green sheet or the molded body that becomes the insulating substrate 1 by using a method such as screen printing. As the material of the resistor 2, a material mainly composed of W and Mo that can be manufactured by simultaneous firing with the insulating substrate 1 is used.

More specifically, as the conductor material of the resistor 2, for example, W main particles, W fine particles, Mo main particles, and Mo fine particles are used. The W main particles and the Mo main particles have, for example, an average particle size of about 2 to 3 μm. The W fine particles and the Mo fine particles have, for example, an average particle diameter of about 0.1 to 0.5 μm. Further, the surfaces of the W fine particles and the Mo fine particles are oxidized. Specifically, for the W fine particles, the surface of the W fine particles can be oxidized by putting W fine powder in a vacuum furnace and heating at 500 ° C. while flowing a certain amount of oxygen and nitrogen. it can. Regarding the Mo fine particles, the surface of the Mo fine particles can be oxidized by putting the powder of the Mo fine particles in a vacuum furnace and heating at 400 ° C. while flowing a certain amount of oxygen and nitrogen. Here, the weight ratio between the W main particles and Mo main particles and the W fine particles and Mo fine particles can be set to about 10: 1.

The reactivity with the main particles can be improved by adding fine particles with oxidized surfaces to the conductor material. As a result, in the firing step described later, the surface activity of the fine particles increases even at a low temperature below the melting point, so that the fine particles easily enter the main particles.

Therefore, the first conductor particle 21 has the main component of the second conductor particle 22 as the subcomponent 210, and the second conductor particle 22 has the main component of the first conductor particle 21 as the subcomponent 220. can do.

Particularly, it is assumed that the ease of entering the main particles can be improved by oxidizing the surface of the fine particles for the following reason. Specifically, by oxidizing the surface of the fine particles, it becomes easy to get wet with the liquid sintering aid surrounding the main particles, so that the fine particles are likely to enter the sintering aid. Since the main particles before sintering are surrounded by the sintering aid, the possibility of the fine particles coming into contact with the main particles is improved by facilitating the entry of the fine particles into the sintering aid. As a result, the possibility that the fine particles enter the main particles is improved.

Further, in order to obtain a configuration in which the glass 25 is included in the grain boundaries of the first conductor particles 21 and the second conductor particles 22, glass powder may be added when the conductor material is prepared. For example, the glass powder may be added at a ratio of 0.001 to 0.1 mass% with respect to the total of W main particles, W fine particles, Mo main particles, and Mo fine particles.

Also, the conductive paste can be produced by appropriately mixing and kneading ceramic raw materials, binders or organic solvents with these high melting point metals.

At this time, the heating position and the resistance value of the resistor 2 are changed by changing the length of the conductive paste pattern, the distance and interval of the folded pattern, and the line width of the pattern depending on the use of the heater. Is set to the desired value.

Then, a ceramic green sheet or molded body of the same material is further laminated and adhered to the ceramic green sheet or molded body on which this pattern is formed. At this time, a pattern to be the electrode pad 3 is provided on the back surface of the ceramic green sheet on which the pattern to be the resistor 2 is formed, and is electrically connected to the pattern to be the resistor 2. As described above, a rod-like or plate-like molded body that becomes the insulating substrate 1 having the resistor 2 inside is obtained.

Next, the obtained molded body is fired at about 1500 to 1600 ° C. Firing is performed in a non-oxidizing gas atmosphere such as hydrogen gas. At this time, in order to obtain a configuration in which the

subcomponents

210 and 220 contained in the respective conductor particles of the first conductor particle 21 and the second conductor particle 22 are distributed in a large amount in the surface layer portion of each conductor particle. The firing time may be set short. Specifically, for example, baking may be performed for 18 hours to rise from room temperature to 1500 ° C., 3 hours at 1500 ° C., and then for 15 hours to fall from 1500 ° C. to 50 ° C. As described above, by setting the time of 1500 to 1600 ° C. during which the diffusion of the fine particles of W and Mo proceeds to be short, a configuration in which a large amount of subcomponents are distributed in the surface layer portion of the conductor particles can be obtained.

Further, a Ni plating film is provided on the electrode pad 3 on the main surface of the insulating substrate 1 by electrolytic plating. Further, the power supply wiring 4 is joined to the Ni plating film. For joining the power supply wiring 4, for example, Ag row can be used.

As described above, a heater can be manufactured.

An example of the heater of the present invention was produced as follows.

First, a ceramic green sheet having Al ₂ O ₃ as a main component and adjusted so that SiO ₂ , CaO, MgO and ZrO ₂ were within 10 mass% in total was produced.

And, W powder having an average particle diameter of 2 μm as W main particles, W powder having an average particle diameter of 0.1 μm as W fine particles, Mo powder having an average particle diameter of 2 μm as Mo main particles, and average as Mo fine particles Mo powder having a particle size of 0.1 μm was prepared. The weight ratio between the W main particles and Mo main particles and the W fine particles and Mo fine particles was set to about 10: 1.

These particle sizes were measured by the Fischer sub-sieve sizer method. Further, with respect to the W fine particles and the Mo fine particles, these powders were put in a vacuum furnace and heated while flowing a certain amount of oxygen and nitrogen to oxidize the surfaces of the W fine particles and the Mo fine particles. Next, a conductive paste was prepared by mixing W main particles, W fine particles, Mo main particles, and Mo fine particles together with a binder.

And the conductive paste which has Mo and W as a main component used as the resistor 2 and the electrode pad 3 on the surface of this ceramic green sheet was printed on each pattern by the screen printing method. The ceramic green sheet on which these are printed and the rod-shaped molded body produced by extrusion molding of the same material as the ceramic green sheet are applied and laminated by applying a laminated liquid in which ceramics of the same composition are dispersed. A laminate was obtained.

The rod-like laminate thus obtained was fired in a reducing atmosphere (nitrogen atmosphere) at 1500 to 1600 ° C.

Next, a Ni plating film having a thickness of 2 to 4 μm was provided on the electrode pad 3 on the main surface of the insulating substrate by electrolytic plating. Furthermore, the electrode pad 3 and the power supply wiring 4 were joined by Ag brazing. As the power supply wiring, one made of nickel (Ni), having a diameter of 0.8 mm and a length of 50 mm was used.

In this way, a heater for Sample 1 was produced.

Also, a conductive paste was prepared without oxidizing the surface of the W fine particles and the Mo fine particles, and a heater of Sample 2 was prepared. Regarding conditions other than the presence or absence of surface oxidation, the preparation conditions of Sample 1 and the preparation conditions of Sample 2 are the same.

Further, a heater of Sample 3 was fabricated using W fine particles having an average particle diameter of 0.3 μm and Mo fine particles having an average particle diameter of 0.3 μm. Regarding conditions other than the particle diameter of the W fine particles and the particle diameter of the Mo fine particles, the preparation conditions of the sample 1 and the preparation conditions of the sample 3 are the same.

Further, a heater of Sample 4 was fabricated using W fine particles having an average particle diameter of 1.5 μm and Mo fine particles having an average particle diameter of 1.5 μm. Regarding conditions other than the particle diameter of the W fine particles and the particle diameter of the Mo fine particles, the preparation conditions of the sample 1 and the preparation conditions of the sample 4 are the same.

Further, a heater of Sample 5 was manufactured using W main particles having an average particle diameter of 1 μm and Mo main particles having an average particle diameter of 1 μm. Regarding conditions other than the particle size of the W main particles and the Mo main particles, the preparation conditions of the sample 1 and the preparation conditions of the sample 5 are the same.

Further, a heater of Sample 6 was fabricated using W main particles having an average particle diameter of 3 μm and Mo main particles having an average particle diameter of 3 μm. Regarding the conditions other than the particle size of the W main particles and the particle size of the Mo main particles, the preparation conditions of the sample 1 and the preparation conditions of the sample 6 are the same.

Further, while using W main particles having an average particle diameter of 5 μm and Mo main particles having an average particle diameter of 5 μm, a heater of Sample 7 was produced without using W fine particles and Mo fine particles. Regarding the conditions other than the particle diameters of the W main particles, the Mo main particles, the presence or absence of the W fine particles, and the presence or absence of the Mo fine particles, the preparation conditions of the sample 1 and the preparation conditions of the sample 7 are the same.

The main parts of the preparation conditions for Samples 1 to 7 are summarized in Table 1.

The obtained heaters of Samples 1 to 7 were cut and polished in the region including the resistor 2, and then analyzed by an electron beam microanalyzer (EPMA). As a result, as shown in Table 2, with respect to

Samples

1, 3, 5, and 6, the state in which the fine particles of Mo are contained in the main particles of W and the fine particles of W are contained in the main particles of Mo. I was able to confirm. That is, it was confirmed that

Samples

1, 3, 5, and 6 have the configuration of the present invention. For

Samples

2, 4, and 7, it was not possible to confirm that the fine particles of Mo were contained in the main particles of W and the fine particles of W were contained in the main particles of Mo.

Especially, it was found from the comparison between Sample 1 and Sample 2 that the surface of the fine particles needs to be oxidized in order for the fine particles to enter. Further, from comparison of samples 1 to 4, it was found that the entry of fine particles does not occur even when the respective fine particles are too large.

In addition, a direct current was applied to Samples 1 to 7, and a pulse waveform and radioactive noise flowing through the heater were confirmed using an oscilloscope. As a result, for

samples

1, 3, 5, and 6, the pulse waveform became steep at the same time as energization, and conductive noise was confirmed, but no radioactive noise was observed. On the other hand, for

samples

2, 4, and 7, the pulse waveform became steep at the same time as energization, and conductive noise was confirmed. Furthermore, at the same time, radioactive noise that was thought to be caused by the conduction noise transmitted through the resistor 2 was observed.

Here, the reason why noise was not observed for

Samples

1, 3, 5, and 6 is that the conductive particles of W and the conductive particles of Mo are present independently of each other. It seems that the variation in resistance value can be reduced and the conductive noise can be transmitted smoothly.

1: Insulating substrate 11: Ceramic core 12: Ceramic layer 2: Resistor 21: First conductor particle 210: Subcomponent 22: Second conductor particle 220: Subcomponent 25: Glass

Claims

A heater comprising an insulating substrate and a resistor embedded in the insulating substrate, wherein the resistor includes first conductor particles mainly composed of tungsten and second conductor particles mainly composed of molybdenum. And a heater in which the first conductor particles have the main component of the second conductor particles as a subcomponent, and the second conductor particles have the main component of the first conductor particles as a subcomponent.
2. The heater according to claim 1, wherein a large amount of subcomponents contained in each of the first conductive particles and the second conductive particles are distributed in a surface layer portion of each of the conductive particles.