KR100361310B1 - Negative Temperature Coefficient Thermistor Device using Spinel Ferrite - Google Patents

Abstract

The protective layer of the negative temperature coefficient thermistor is manufactured using a ferrite composition to provide a negative temperature thermistor element having excellent corrosion resistance. In addition, the present invention provides a single plate negative temperature coefficient thermistor having improved thermal stability with excellent corrosion resistance by using a ferrite-based composition, and a multifunctional negative temperature coefficient device using a ferrite sheet as an intermediate insulating layer or an intermediate protective layer. .

Description

Negative Temperature Coefficient Thermistor Device using Spinel Ferrite

The present invention relates to a negative temperature coefficient (NTC) thermistor device, and more particularly to a negative temperature coefficient thermistor device using a spinel-based ferrite composition as a protective layer.

NTC thermistor materials are semiconducting ceramics whose electrical resistance decreases with increasing temperature. Recently, they are widely used as temperature sensors, circuit compensating elements, and liquid level sensors as electronic products become more versatile. .

The part temperature coefficient thermistor element is generally having manganese oxide of Mn ₃ O ₄ with a spinel structure of the base and where the Ni, Co, Fe, Cu, Al, La , and other minor components of the composition are added. From an atomic point of view, 75 to 100 mol% is composed of two or more composite oxides of Mn, Ni, Fe, Co, Cu, Al, Cr. 0 to 25 mol% is added as one or more components of V, B, Ba, Bi, Ca, La, Sb, Sr, Ti, Zr to form an oxide. That is, in the chemical formula, elements such as Fe, Co, Cu Al, and La are added to the basic structure of Ni _x Mn _3-x O ₄ , and also V, B, Ba, Bi, Ca, La, Sb, Sr. , Ti, Zr and the like is added as a small amount of additives. Therefore, the composition for the negative temperature coefficient thermistor element refers to a ceramic material based on Ni _x Mn _3-x O ₄ .

In general, the negative temperature coefficient thermistor element uses a powder synthesized by mixing the oxide form of the raw material in a desired blending ratio and heat-processing at a high temperature. Related properties such as electrical resistance and temperature characteristics of the material change depending on the composition and the sintering temperature of the material, the sintering temperature is carried out in the range of 950 ℃ to 1,400 ℃ depending on the composition, the density of the sintered body is about 5.2g / cc.

Hereinafter, a method of manufacturing a conventional surface mount type negative temperature coefficient thermistor element will be described with reference to FIGS. 1 and 2.

1 illustrates a method of manufacturing a general stacked NTC device.

Mix two or more composite oxides of Mn, Ni, Fe, Co, Cu, Al, Cr, and a composite oxide to which Ni, Co, Fe, Cu, Al, La, and other trace components are added as additives so as to have a predetermined composition. (Step 1), disintegrate (Step 2) and calcinate (Step 3).

The powder thus formed is regrind to form a powder (step 4), and then mixed with a solvent to make a slurry (step 5), and then formed into a sheet using a tape casting method. (Step 6)

An electrode shape is formed on the sheet by a transfer method or a screen printing method, then laminated, and integrated by applying temperature and pressure (step 7). The electrical characteristics of the device will be determined according to the characteristics of the structure of the internal electrodes formed at this stage.

The integrated laminate is cut to the size of a unit device (step 8), and then sintered at 1,000 ° C to 1,400 ° C (step 9). Thereafter, the sintered body is polished to perform barrel polishing to round corners (step 10).

After that, a side electrode is formed, which is usually performed by baking a conductive paste on the side (step 11). Next, the Sn / Pb is plated on the side electrode (12 steps) to facilitate soldering to the actual circuit, and the final product is completed.

2 shows the structure of a conventional stacked negative temperature coefficient device.

The completed negative temperature coefficient thermistor element has a state in which the internal electrode 22 is contained in the negative temperature coefficient ceramic material 21, and the external connection electrode 23 is formed at both ends of the ceramic material. . The protective layer 24 is formed on the outside of the external connection electrode, and the side electrode 25 is formed on the side of the device.

The ceramic material 21 for the negative temperature coefficient thermistor provides a property that the resistance decreases with a constant temperature increase, and thus, the development of the material in the direction of reducing the characteristic change with the linearity and the time elapsed in the constant temperature range has been studied. .

The internal electrode 22 plays a role of controlling final resistance when used in an electronic component, and usually silver (Ag) or the like is designed in the device by a transfer method or a screen printing method.

The outer protective layer 24 serves to protect the internal electrode from the outside and to adjust the thickness of the device. The outer protective layer 24 is usually formed of a ceramic material for negative temperature coefficient thermistor (Ni _x Mn _3-x O _{4 type} ). However, since the outer protective layer only plays a role in controlling the thickness of the product and does not affect the characteristics of the product, it can be said that it does not have to be precisely controlled.

The external connection electrode 23 and the side electrode 25 serve to connect the resistance of the device to the outside when the device is mounted in the electronic device.

The most common manganese-based composition for negative temperature coefficient thermistors (Ni _x Mn _3-x O ₄ series) is semiconducting ceramics, which have some electrical conductivity. Can be. In many cases, the sintered body is eroded by the plating liquid during the plating process. For this reason, the selection of plating conditions is very difficult, and plating may be performed while the device is protected by forming a non-conductive protective layer. In actual products, expensive side electrode materials such as Ag / Pd, which can express solderability without plating, are mainly used.

As described above, the conventional negative temperature coefficient thermistor element has been described with reference to FIGS. 1 and 2, but it can be seen that the following problems exist in the conventional element.

First, although the protective layer is conventionally formed of a negative temperature coefficient thermistor material (Ni _x Mn _3-x O _{4 type} ), as described above, the outer protective layer serves to control the thickness of the product, but the characteristics of the product. There is a problem that the product price is expensive due to the use of expensive negative temperature coefficient ceramic because it does not affect.

Second, the manganese-based composition for negative temperature coefficient thermistors has semiconducting ceramics, which have some electrical conductivity, and thus are unstable in the external environment, and have a disadvantage that the ceramic sintered body is eroded in a plating process. This may be a fatal drawback for electronic components that must ensure stability in various environments. Of course, a protective layer is additionally formed on the outside of the final product, but this is not a solution to the underlying problem but also has an adverse effect of raising the price of the product.

The present inventors solved the above problems and completed the present invention by using a spinel-based ferrite composition as a protective layer of the thermistor element.

It is an object of the present invention to improve the protective layer of a negative temperature coefficient thermistor element and to provide a negative temperature coefficient thermistor element of a novel configuration at a low price while having a particularly stable corrosion resistance of the device according to external environmental changes.

Another object of the present invention is to provide a single plate type negative temperature coefficient thermistor device having improved thermal stability with excellent corrosion resistance using a ferrite-based composition.

Still another object of the present invention is to provide a multifunctional negative temperature coefficient thermistor element using a ferrite sheet as an intermediate insulating layer or an intermediate protective layer.

1 is a method of manufacturing a stacked negative temperature coefficient thermistor device.

Figure 2a is a side view of the structure of a conventional stacked negative temperature coefficient thermistor element,

2B is a front view of the structure of a conventional stacked negative temperature coefficient thermistor element.

3 is a structure of a negative temperature coefficient thermistor element using a ferrite composition as a top and bottom protective layer according to the present invention,

4 is a green sheet stacked form of the negative temperature coefficient thermistor device of FIG.

5 is a structure of a single plate type negative temperature coefficient thermistor element whose upper and lower protective layers are made of a ferrite composition, according to the present invention;

6 is a structure of a three-terminal negative temperature coefficient thermistor element using a ferrite composition as an upper and lower protective layer according to the present invention,

FIG. 7 illustrates a form in which the green sheets are aligned before being stacked in the three-terminal negative temperature coefficient thermistor of FIG. 6.

<Description of the symbols for the main parts of the drawings>

21, 31, 51, 77: negative temperature coefficient thermistor material

22, 32: internal electrode

23, 33: electrode for external connection

24, 34: outer protective layer

25, 35, 53: side electrode

62, 72: first thermistor laminate for negative temperature coefficient

63, 73: Thermistor second laminate for negative temperature coefficient

65, 75: internal electrode connected to the center terminal

66, 76: internal electrode connected to the side electrode

64, 74: ferritic intermediate insulating layer or intermediate protective layer

78: upper electrode

79: lower electrode

The present invention, in order to achieve the above object, the thermistor laminate; Internal electrodes formed in the stack; An external connection electrode connecting the laminate to the outside; Side electrodes electrically connected to the external connection electrodes and formed on both sides of the stack; And an outer protective layer laminated on upper and lower surfaces of the laminate and containing spinel-based ferrite having soft magnetic properties.

In detail, the internal structure of the negative temperature coefficient thermistor element is dualized, and the internal composition affecting the characteristics of the element is based on the Ni-Mn-based spinel structure based on the existing Ni _x Mn _3-x O ₄ system. The protective layer, which is used as it is and does not affect the characteristics of the device, has a spinel structure whose structure is similar to that of the negative temperature coefficient thermistor device, and uses a spinel-based ferrite composition having soft magnetic properties.

Through the improvement of the protective layer, it is possible to obtain an improved negative temperature coefficient thermistor device having stability of the device according to the external environment change, especially excellent corrosion resistance, and using the spinel ferrite composition which is inexpensive in terms of price. A temperature coefficient thermistor element can be obtained.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

First, the protective layer to be improved in the present invention should also have the following conditions. Here, the protective layer means that it covers the outer protective layer and the inner insulating layer.

First, the crystal structure of the negative temperature coefficient thermistor element of the present application Ni _x Mn _3-x O ₄ should be similar, and second, it should be chemically and electrically stable, and third, the raw material should be available at a low price.

In search of a ceramic material having the above conditions, the inventors of the present invention found that iron oxide powder and spinel-based ferrite powder based thereon are suitable as the object of the present invention.

Hereinafter, iron oxide and spinel ferrite will be described.

Iron oxide powder (Fe ₂ O ₃ ) is a by-product of the iron ore industry and is a material rich in resources and capable of cheaply obtaining high purity raw materials. These iron oxides are used as magnetolumbite-based permanent magnets and spinel-based soft magnetic materials.

Magneto plumbite-based ferrite is generally used as a material for permanent magnets and is represented as SrO, 6Fe ₂ O ₃ or BaO, 6Fe ₂ O ₃ depending on the element bonded with iron oxide. Spinel-based ferrite, which is a main component in the present invention, refers to a soft magnetic material, and is represented by MnFe ₂ O ₄ , NiFe ₂ O ₄ , CuFe ₂ O _4, or the like depending on the element to be bonded.

Of course, iron oxide (Fe ₂ O ₃ ) itself is added as an additive to the negative temperature coefficient thermistor element.

To further explain the soft magnetic material of the spinel structure, which is the object of the present invention, MnFe ₂ O ₄ , NiFe ₂ O ₄ , CuFe ₂ O _4, etc., having a spinel structure, are each widely used as main components of the magnetic material. In addition, when the nonmagnetic component ZnFe ₂ O ₄ is incorporated therein, M _1-x Zn _x Fe ₂ O ₄ forms a solid solution, and the soft magnetic material Mn- whose magnetic properties are changed in proportion to the amount injected. Zn-based ferrites, Cu-Zn-based ferrites, and Ni-Zn-based ferrites.

In general, spinel-based ferrites and soft-magnetic ferrites refer to the above-described Mn-Zn-based, Ni-Zn-based and Cu-Zn-based ferrites rather than single-phase spinel structures.

Trace components such as Al, Ca, Co, Cr, Cu, In, La, Pb, Si, V may be added singly or in combination to control permeability, other magnetic and electrical properties, and sintering temperature. For example, Mn-Zn-based ferrite can increase the electrical resistance by adding a small amount of Ca, Si and the like. This composition has a sintered density of about 5.3, the sintering temperature varies from 850 ℃ to 1,350 ℃ depending on the composition of the material, the magnetic properties are also greatly changed, it is very easy to implement a function suitable for the application field.

On the other hand, Ni-Zn-based ferrite and Cu-Zn-based ferrite, etc. also has the advantage of excellent electrical insulation compared to the negative temperature coefficient thermistor material.

As described above, it can be seen that the spinel-based ferrite composition satisfies the basic conditions of the outer protective layer pursued by the present invention. In addition, the negative temperature coefficient thermistor material and the spinel ferrite composition have very similar physical properties such as crystal structure, sintering density, and sintering conditions.

Therefore, in the present invention, in order to integrate the above two materials having different compositions into one component, the material of the protective layer, which is a relatively insignificant part of the negative temperature coefficient thermistor having a built-in electrode As an insulating ceramic of spinel-based ferrite and the inherent negative temperature characteristic, a structure using a conventional negative temperature coefficient device can be proposed.

Therefore, if the negative temperature coefficient thermistor component using the spinel ferrite as a protective layer is implemented, the following advantages are obtained.

First, the spinel-based ferrite is a low-cost powder that can be easily obtained, and can reduce the raw material cost by more than 80% compared to the composition for the negative temperature coefficient thermistor.

Second, it is easy to find a composition meeting the process conditions of the negative temperature coefficient thermistor as the base material.

Third, as an electrically insulating material, it is stable to the external environment and serves as a very stable protective layer in a plating process.

In addition, as will be described later, the spinel-based ferrite may be used as an internal blocking layer as well as a protective layer, and by using the blocking layer, various internal structures may be easily implemented to implement a plurality of functions or a complex function.

Ferritic raw materials can be easily obtained as a by-product of the steel industry. In particular, the composition used to realize the integrated single part can be recycled by using a poor quality insoluble product from a soft magnetic material manufacturer, Raw materials can also be purchased at a price as low as 20% compared to materials for negative temperature coefficient thermistors.

In general, in order to increase the uniformity of the composition of the ceramic raw material and to stabilize the sintered material, the raw material prepared at a desired composition ratio is mixed and then reacted at a high temperature. However, the raw materials obtained as described above are already synthesized similar to the desired composition, and in addition to the addition of some minor additives in some cases, a raw material synthesis process such as a high temperature reaction is not necessary.

The present invention will be described in more detail with reference to the following Examples.

<Example 1>

It demonstrates with reference to FIG. 3 and FIG. Figure 3 shows a manufacturing method of Example 1, Figure 4 shows the structure of the negative temperature coefficient thermistor element according to the first embodiment.

The nickel-zinc-based spinel ferrite (Ni-Zn ferrite) material was obtained from the ferrite magnet manufacturer for EMI noise removal, and then pulverized to prepare a ferrite green sheet 34 for the outer protective layer by tape casting. The composition of the nickel-zinc ferrite used consists of a composition ratio of 66% Fe ₂ O ₃ , 16% NiO, 14% ZnO, 4% CuO and 0.5% other trace components. This ferrite green sheet 34 corresponds to the protective layer 24 of FIG. 2, but is a common configuration of the prior art and the present invention, but the composition itself is different.

Then, using a powder synthesized with a composition ratio of 63% Mn ₂ O ₃ , 15% NiO, 20% Co ₃ O _{4 and} 2% other components (Fe ₂ O ₃ , Al ₂ O ₃ , CuO, La ₂ O ₃ ) A green sheet 31 for negative temperature coefficient thermistor was prepared. This corresponds to the negative temperature coefficient ceramic material 21 of FIG. The powder was prepared by mixing a high purity raw material weighed at a predetermined composition ratio, heat treatment at high temperature (900 ° C.), and coarsely pulverized and pulverized. However, the ferritic powder for the protective layer was prepared only by coarse and fine grinding processes.

Prepare a laminate in which the internal electrode 32 and the external connection electrode 33 are formed on the negative temperature coefficient thermistor green sheet 31, and a total of nine layers are laminated together with the outer protective layer ferrite green sheet 34. It was integrated by pressurizing it at 80 degrees C or less. The laminate was fired in an oxidizing atmosphere at 1,130 ° C., and side electrodes 35 were formed to manufacture devices as shown in FIG. 4.

The device of FIG. 4 is similar in appearance to the conventional stacked negative temperature coefficient device disclosed in FIG. 2, except that the outer protective layer is made of a ferrite-based composition.

Comparative Example 1

In order to compare with Example 1, the device which used the conventional negative temperature coefficient material as an outer protective layer was manufactured.

In Example 1, the characteristics of the device using the ferritic material as the outer protective layer and the device using the conventional negative thermometer material of Comparative Example 1 as the outer protective layer were measured and compared as follows.

First, in order to examine the adhesion between the ferrite-based outer protective layer and the negative temperature coefficient device, the prepared device was placed in a barrel grinder and polished for 30 minutes. Experimental results showed that the edge of the device was very abrasive, but there was no separation at the interface. In other words, it can be seen that the adhesive strength of the interface between the negative temperature coefficient thermistor material and the ferrite protective layer has a value large enough not to be affected by the process.

Second, the same material as the protective layer and the ferrite material as a protective layer for the material having the same internal electrode structure was prepared as described above and then connected to the external electrode and the electrical properties were measured. As a result of the measurement, no differences in thermistor properties were found between the two devices. That is, it was confirmed that the ferrite protective layer did not affect the physical properties of the thermistor.

Third, in order to investigate the corrosion resistance of the negative temperature coefficient device, it was immersed in a nickel plating bath of pH 5 for 18 hours. Experimental results showed that the negative temperature coefficient device using the ferrite protective layer did not change, but the erosion occurred in the thermistor device using the negative temperature coefficient material as the external protective layer.

The above result was put together in Table 1. As shown in Table 1, the results of the present invention according to Example 1, the mechanical adhesion and electrical properties were the same as the conventional negative temperature coefficient device, it can be seen that excellent in corrosion resistance.

Item (characteristic value) Exam conditions Example 1 Comparative Example 1 Polishing test 12 hours barrel polishing No peeling phenomenon No peeling phenomenon Electrical characteristics R ₂₅ B _25/85 ~ 1KΩcm3600K ~ 1KΩcm3600K Erosion Resistance Test 18 hours nickel plating solution No corrosion Some corrosion Thermal Stability ΔR / R ₀ 110 ℃, 1000 hours -0.5% -0.5%

<Example 2>

A negative temperature coefficient device was fabricated using Mn-Zn ferrite as an outer protective layer. The preparation method is the same as in Example 1, the composition used was replaced with Mn-Zn-based ferrite from Ni-Zn-based ferrite.

The characteristics of the negative temperature coefficient device using the Mn-Zn-based ferrite material prepared in Example 2 as the external protective layer and the device using the conventional negative temperature coefficient material of Comparative Example 1 as the external protective layer were measured and compared. Indicated.

Item (characteristic value) Exam conditions Example 2 Comparative Example 1 Polishing test 12 hours barrel polishing No peeling phenomenon No peeling phenomenon Electrical characteristics R ₂₅ B _25/85 ~ 1KΩcm3600K ~ 1KΩcm3600K Erosion Resistance Test 18 hours nickel plating solution No corrosion Some corrosion Thermal Stability ΔR / R ₀ 110 ℃, 1000 hours -0.5% -0.5%

Thus, it can be seen that the device using the Mn-Zn-based ferrite material as the outer protective layer has almost no difference from the device using the Ni-Zn-based ferrite material as the outer protective layer.

That is, regardless of the type of spinel ferrite, when the outer protective layer is replaced by the spinel ferrite, it can be seen that the corrosion resistance is greatly improved without decreasing the electrical characteristics of the negative temperature coefficient thermistor element.

In addition, in Examples 1 and 2, manganese-zinc and nickel-zinc spinel-based ferrites were used as protective layers, but manganese-zinc and nickel-zinc ferrites were similar in physical properties, and at least one of them was mixed. Even the same effect could be obtained.

<Example 3>

A Ni-Zn-based ferrite powder and a negative temperature coefficient thermistor element powder were mixed and then made into a sheet to prepare a negative temperature coefficient element used as an outer protective layer.

That is, in Example 1 and Example 2, the spinel-based ferrite powder was made of a sheet form alone, and then used as the outer protective layer, but in Example 3, the spinel-based ferrite powder and the negative temperature coefficient thermistor element powder were used at a predetermined ratio. After mixing to prepare a sheet form, using this as an outer protective layer to produce a negative temperature coefficient thermistor element is shown.

Here, the mixing ratio is represented by the weight ratio of the ferrite powder to the weight ratio of the negative temperature coefficient thermistor element powder. For example, a mixing ratio of 100 means that the outer protective layer is made of a sheet using only spinel-based ferrite powder, and 0 means that the outer protective layer is made of a sheet using only powder for negative temperature coefficient thermistor.

Table 3 shows the characteristics of the device using the outer protective layer as a mixed material according to Example 3, and measured the results.

Mixing ratio (% by weight) 100 90 80 70 60 50 40 30 20 10 0 Polishing test (with or without peeling phenomenon) radish radish radish radish radish radish radish radish radish radish radish Electrical Characteristics R ₂₅ (kΩcm) B _25/85 (K) -13600 -13600 -13600 -13600 -13600 -13600 -13600 -13600 -13600 -13600 -13600 Erosion resistance test (18 hours nickel plating solution) No corrosion No corrosion No corrosion Some corrosion Some corrosion Some corrosion Some corrosion Some corrosion Some corrosion Some corrosion Some corrosion Thermal stability (110 ° C, 1000 hours, ΔR / R ₀ ,%) -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5

Looking at the results of the polishing test it can be seen that the peeling phenomenon does not change depending on the material of the outer protective layer. In other words, the polishing test is a measure of the degree of bonding between the outer protective layer formed on both ends of the negative temperature coefficient element and the element, and both the spinel ferrite and the powder for the negative temperature coefficient element are negative temperature coefficient elements and crystal lattice. It can be seen that since the size and physical properties of do not differ greatly, they are in good contact with the device.

Even in the case of electrical characteristics, it does not change greatly depending on the material. The factors influencing the electrical properties of the negative temperature coefficient are influenced by the chemical composition of the internal negative temperature coefficient element and the size and shape of the electrodes designed therein.

However, in the case of erosion resistance, as the content of the negative temperature coefficient thermistor element powder used as the outer protective layer increases, its properties decrease. That is, in the case of erosion resistance, when the ratio of (Spinel ferrite) / (Negative temperature coefficient thermistor element powder) is 70% or less, the phenomenon that corrosion occurs on the outside of the element can be seen.

Therefore, even if any one of the spinel-based ferrite is selected as the outer protective layer, the desired corrosion resistance improvement effect can be obtained. When the protective layer sheet is formed by mixing the spinel-based ferrite and the negative temperature coefficient device, the spinel-based ferrite It can be seen that it is preferable to include the content of 70 to 100 parts by weight, the content of the negative temperature coefficient material 0 to 30 parts by weight.

Forming an outer protective layer by mixing spinel ferrite and negative temperature coefficient material is of great economic and environmental protection in terms of recycling the negative temperature coefficient material that must be disposed of in the actual process. There is.

As described above, a novel method of fabricating a negative temperature coefficient thermistor device having good corrosion resistance by using a soft magnetic spinel-based ferrite composition as an outer protective layer has been proposed.

Next, the production of single-plate and three-terminal negative temperature coefficient thermistor elements using the soft magnetic spinel-based ferrite will be described.

Example 4

FIG. 5 shows a surface mount type negative temperature coefficient thermistor device having a single plate structure manufactured by using one composition for a negative temperature coefficient thermistor and one type of spinel ferrite composition at an auxiliary part.

A negative temperature coefficient thermistor material 51 is formed in the center of the device, and ferrite-based compositions 52 having a high resistance value are formed on the upper and lower portions thereof, and side electrodes 53 are formed on both sides thereof. Consists of. It should be noted that the internal electrode is not constructed as compared with the ordinary negative temperature coefficient thermistor element.

In the case of using the spinel ferrite sheet as the outer protective layer in the single plate type negative temperature coefficient thermistor device as shown in FIG. 5, the thermal stability of the negative temperature coefficient thermistor device is improved in addition to the improvement of corrosion resistance as confirmed in Examples 1, 2, and 3. You can also get the effect.

Table 4 shows a single-plate negative temperature coefficient thermistor element (Example 4) consisting of a Mn-Ni-based negative temperature coefficient material as a thermistor layer and a protective layer as a Zn-Cu-based spinel ferrite layer. It shows the characteristics of the single plate type negative temperature coefficient thermistor element (Comparative Example 2). At this time, in Example 4, a device based on a negative temperature coefficient material having a specific resistance of 4 _Pa · cm and a B _25/85 constant of 4,150 K was compared.

Item (characteristic value) Exam conditions Example 4 Comparative Example 2 Polishing test 12 hours barrel polishing No peeling phenomenon No peeling phenomenon Electrical characteristics R ₂₅ B _25/85 4 KΩcm 4150 K 4 KΩcm 4150 K Erosion Resistance Test 18 hours nickel plating solution No corrosion Some corrosion Thermal Stability ΔR / R ₀ 110 ℃, 1000 hours -0.5% -2%

As shown in Table 4, the single plate type negative temperature coefficient thermistor element using ferrite as an outer protective layer was significantly improved in corrosion resistance and thermal stability was much more stable than the case in which ferrite was not used.

Of course, the general laminated negative temperature coefficient device has a resistance change rate of about 0.5%, so the internal characteristics of the device are not improved. However, when the necessity of manufacturing a single plate negative temperature coefficient device is necessary, thermal The significance of the present invention is that the phenomenon of deterioration in stability is remarkably improved by adopting a ferrite protective layer.

In addition, the thermistor implemented in the above configuration, it is easy to implement a device having a high resistance by using a material for the negative temperature coefficient thermistor having a low specific resistance, but by forming both ends of the device as a spinel-based ferrite protective layer There is this. That is, as a device having a stacked structure in which electrodes are formed therein, it is possible to implement a negative temperature coefficient thermistor element in a range of 2.2 DEG C to 10 DEG resistance of 25 DEG C. However, if the single plate type structure shown in the present invention is used, A device of 100 Hz was also possible.

In particular, the high-resistance material formed at the upper and lower portions is composed of (Ni, Zn) -Cu-based ferrite as a main component, and the negative temperature coefficient thermistor base material component may be used while changing its content as a filler. The negative temperature coefficient thermistor material with low specific resistance is based on the material, and the outside is properly mixed with the materials for ferrite and negative temperature coefficient thermistor. As a result, the negative temperature coefficient thermistor element can be realized in a variety of ways from low resistance element to high resistance element. have. In this case, the negative temperature coefficient material used as the filler may be pulverized by about 3 μm using a simple process of coarse pulverization by mixing the byproduct accumulated during the production of the laminated negative temperature coefficient device product, and then mixed with the ferrite component.

Example 5

Example 5 relates to a three-terminal negative temperature coefficient device.

For the temperature compensated crystal oscillator (TCXO), two low resistance thermistors for low temperature and two high resistance thermistors for high temperature are used.

In the past, it was common to form one module using two respective low-temperature and high-temperature thermistors. However, there is a problem of a cost increase in the manufacture of a module by mounting each of the two elements, and the manufacturing process also has a disadvantage of long.

In the present invention by using a spinel-based ferrite composition in the auxiliary part, that is, by using two compositions for the negative temperature coefficient thermistor in the functional part, two kinds of ferrite composition in the auxiliary part to implement the two thermistors in one three-terminal form saw. This is shown in FIGS. 6 and 7.

The basic configuration is that the low resistance element implemented by the electrode formed on the lower side is connected to the outside using the middle terminal and the right terminal, the high resistance element implemented by the electrode formed on the upper side using the middle terminal and the left terminal It is connected to the outside. Specific implementation method is as follows.

As a ferrite material, a powder prepared using a composition ratio of 5% CuO, 19% ZnO, 66% Fe ₂ O ₃ , and 0.5% other trace components was prepared, and a green sheet was prepared using the powder. This serves as the outer protective layers 61 and 71.

As a ferrite material for the intermediate protective layers (64, 74), a powder prepared at a composition ratio of 6% CuO, 19% ZnO, 65% Fe ₂ O ₃ , and 0.5% other trace components was prepared, and a green sheet was prepared using the powder. .

A green sheet was prepared using powders synthesized with a composition of 65% Mn ₂ O ₃ , NiO 15%, Co ₃ O ₄ and other trace components as the first laminates 62 and 72 for the negative temperature coefficient thermistor. The green sheets were prepared using powders synthesized with 50% Mn ₂ O ₃ , NiO 20%, Fe ₂ O _3, and other trace components as second laminates 63 and 73 for negative temperature coefficient thermistors.

Internal electrodes 65 and 75 and external connection electrodes 66 and 76 were formed between the first and second laminates for the negative temperature coefficient thermistor.

Side resistance 77 is formed at both ends, and the electrical resistance of the final product is in the range of 50 to 500 kV by the lower electrode 79 and 5 to 45 kV by the upper electrode 78 as shown in FIG. It was designed to have.

The green sheets without the internal electrodes formed, the green sheets with the internal electrodes formed thereon, and the green sheets of the ferrite material were aligned and then integrated using a process of thermal pressure and co-firing.

Meanwhile, the optimum sintering temperatures of the first laminates 62 and 72 for the negative temperature coefficient thermistor and the second laminates 63 and 73 for the negative temperature coefficient thermistor were 1,100 ° C. and 1,130 ° C., respectively. 61,71 and the sintering temperatures of the material for the intermediate protective layers 64,74 were 1,100 ° C and 1,050 ° C, respectively. The temperature of the simultaneous firing of all the laminates was 1,100 ° C.

As a result of measuring the characteristic after connecting the external terminal to one of the manufactured products, the electrical resistance of 25 ℃ was easily implemented at 100 에서 at the bottom, 10 에서 at the top.

As mentioned above, in order to use the function of a thermistor material complex, for example, a linear signal, in order to use, the element which has a different physical property is used in series, parallel, or a mixture of series and parallel in many cases. Appropriate utilization of the composition of the present invention makes it possible to integrate such a composite function into one device.

It should be borne in mind that the implementation of such a composite function negative temperature coefficient thermistor element was basically possible from the conversion of the idea of using the high-resistance spinel-based ferrite-based composition pursued by the present invention as an outer protective layer or an intermediate insulating layer. will be.

As described above, the present invention uses the material for the negative temperature coefficient thermistor in a part expressing the main function of the device in the manufacture of the surface-mounted negative temperature coefficient thermistor using the similarity of the material, and requires an auxiliary function such as a protective layer. The negative temperature coefficient thermistor constituting a single unit integrated using a ferritic material was provided.

Therefore, the present invention using the ferrite-based composition has the following advantages.

First, a negative temperature coefficient (NTC) thermistor element whose protective layer is manufactured using a ferrite-based composition has excellent corrosion resistance.

Second, the single plate negative temperature coefficient thermistor using the ferrite-based composition has improved thermal stability along with excellent corrosion resistance.

Third, a multifunctional negative temperature coefficient device can be manufactured using a ferrite sheet as an intermediate insulating layer or an intermediate protective layer.

Fourth, the negative temperature coefficient material, which was left as waste, was mixed with ferrite to form an external protective layer, thereby producing a negative temperature coefficient thermistor device having excellent corrosion resistance, and also an environmental protection effect was obtained.

Finally, the lower cost of the product can be achieved by adopting an inexpensive ferrite protective layer.

Claims (9)

Thermistor laminate; Internal electrodes formed in the stack; An external connection electrode connecting the laminate to the outside; Side electrodes electrically connected to the external connection electrodes and formed on both sides of the stack; And A negative temperature coefficient thermistor element which is laminated on the upper and lower surfaces of the laminate and includes an outer protective layer containing a spinel ferrite having soft magnetic properties. Negative temperature coefficient thermistor layer; An outer protective layer stacked on the upper and lower surfaces of the thermistor layer and containing a spinel ferrite having soft magnetic properties; And a side electrode formed to cover both ends of the thermistor layer and the outer protective layer. The negative temperature coefficient thermistor element of claim 1 or 2, wherein the spinel ferrite is any one of nickel-zinc ferrite, manganese-zinc ferrite, copper-zinc ferrite, and mixed ferrites thereof. . The negative temperature coefficient thermistor element of claim 1 or 2, wherein the outer protective layer is formed of a mixture of a negative temperature coefficient thermistor material and a spinel ferrite material. The negative temperature coefficient thermistor element of claim 4, wherein the mixture is made of 70-100 wt% of a spinel ferrite material and 0-30 wt% of a negative temperature coefficient thermistor material. First and second thermistor stacks; An intermediate protective layer of spinel-based ferrite having soft magnetic properties positioned between the first and second thermistor stacks; Internal electrodes formed in the first and second thermistor stacks, respectively; An external connection electrode formed in the first and second thermistor stacks to be spaced apart from the internal electrode to transfer resistance of the device to the outside; An outer protective layer containing spinel-based ferrite having soft magnetic properties stacked on an upper surface of the first thermistor stack and a lower surface of the second thermistor stack; And And a side electrode electrically connected to each of the external connection electrodes and formed to cover both ends of the first and second thermistor stacks and the external protective layer. The negative temperature coefficient thermistor element of claim 6, wherein the spinel ferrite is any one of nickel-zinc ferrite, manganese-zinc ferrite, copper-zinc ferrite, and mixed ferrites thereof. 7. The negative temperature coefficient thermistor element of claim 6, wherein the outer protective layer and the intermediate protective layer are made of a mixture of a spinel ferrite material and a Mn-Ni negative temperature coefficient thermistor material. 7. The three-terminal negative temperature coefficient thermistor element of claim 6, wherein the mixture is made of 70-100 wt% of a spinel ferrite material and 0-30 wt% of a negative temperature coefficient thermistor material.