KR100916135B1 - Stacked ptc thermistor composition and its manufacturing method - Google Patents

Abstract

The present invention relates to a reduced temperature resistant powder of a PTC thermistor fired in a reducing atmosphere, a method for producing a reduced resistance powder, a method of manufacturing the same, and a laminated PTC thermistor obtained by alternately laminating and co-firing an internal electrode and a semiconductor ceramic layer. The present invention provides a laminated PTC thermistor having low room temperature resistance and high resistivity change rate of the laminated PTC thermistor.

Reduction-resistant powder production method provided by the present invention includes a gas atmosphere around the mixed powder during the calcination process, air, oxygen / nitrogen = 20/80, nitrogen, hydrogen / nitrogen = 5/95, hydrogen / nitrogen = 10/90 To form different nonstoichiometric compositions. In addition, the PTC characteristics of the laminated PTC thermistor manufactured according to the prior art can be obtained by manufacturing a ceramic green sheet in which the composition is a semiconductor ceramic layer, and manufacturing a laminated PTC thermistor obtained by alternately laminating the internal electrodes by combining the respective ceramic green sheets. Improve.

Multilayer PTC Thermistor, Semiconductor Ceramic Layer, Internal Electrode, Calcining Atmosphere

Description

Stacked static thermistor composition and manufacturing method {STACKED PTC THERMISTOR COMPOSITION AND ITS MANUFACTURING METHOD}

The present invention relates to a multilayer semiconductor ceramic device composition used for overcurrent protection, temperature control, and the like, and a multilayer PTC thermistor device comprising the same, in particular, a reduction resistance composition having a low temperature resistance and a resistance-temperature characteristic of a constant temperature coefficient and A manufacturing method and a laminated PTC thermistor are related.

In recent years, as miniaturization, weight reduction, and high functionality of electronic devices are required, the necessity and development of lamination in ceramic parts is gradually increasing. In the case of the conventional single-plate ceramic PTC, it is known that it is difficult to manufacture below 10 Ωcm due to the inherent room temperature resistivity of the ceramic, but recently, a composition development having a room temperature resistivity of less than that has been reported. However, in order to have low resistance at room temperature, the cross-sectional area of the body has to be widened and the thickness of the ceramic body has to be extremely thin, so it is difficult to expect miniaturization of components. Therefore, in order to lower the room temperature resistance, as shown in FIG. 1, the internal electrodes 3 and the semiconductor ceramic layer 2 are alternately stacked, and external electrodes are formed on both ends, thereby reducing the thickness of the semiconductor ceramic layer and the large electrode surface. At the same time, the room temperature can be reduced.

The conventional multilayer PTC thermistor 1 prints the conductive paste, which is the internal electrode 3, on the ceramic green sheet, which becomes the semiconductor ceramic layer 2, and alternately stacks the conductive paste for the internal electrode so as to be drawn out in one section. , The conductive pastes for the external electrodes 4 were formed on both end surfaces thereof, and then connected to the internal electrodes.

However, electrode materials such as Zn, Fe, Sn, and Ni, which are mainly used, show excellent ohmic contact, but in most cases, due to the low melting point or high oxidation characteristics, the room temperature resistance is rapidly increased to degrade the characteristics of the laminated PTC thermistor. I was letting go.

In particular, when Ni is used as the internal electrode material, since the internal electrode and the semiconductor ceramic layer are laminated and co-fired, the Ni electrode having a low melting point is easily oxidized. In order to prevent this, firing is required under a strong reducing atmosphere. However, since this reduces the PTC characteristics of the ceramic PTC element, there is a need for a reduction-resistant semiconductor ceramic layer.

In the present invention, in order to improve the deterioration of the PTC characteristics due to the above problems, additional costs are incurred compared to the conventional method, and the lamination process is complicated, but the low room temperature is prevented by preventing non-ohmic contact due to oxidation of the internal electrode material. By obtaining a resistance and a high resistivity change rate, a high quality laminated PTC thermistor device is to be obtained.

The present invention is a semiconductor ceramic composition comprising a barium titanate added with Ce and containing BN and SiO ₂ , a method for manufacturing the same, and a laminated PTC thermistor element composed of such a composition.

A first invention is a semiconductor ceramic composition comprising barium titanate containing Ce as a main component and containing BN and SiO ₂ , comprising a barium titanate-based semiconductor ceramic layer having a constant resistance temperature characteristic and having a rare earth in place of Ba. Substitution of trivalent Sm, Ce, Ho, Y, La, Dy, Pr, Yb, E, etc., which is an element, is effective, and Zn, Sn, Ni, etc., which have excellent ohmic contact, are used as the metal powder of the conductive paste for internal electrodes. Although it is effective to use the present invention, it is preferable to use a conductive paste containing Ni for the internal electrodes. The main feature here is that the content of Ce, which is a rare earth element, is 0.02 mol%, while BN contains 1.0 to 7.5 mol% and SiO ₂ contains 2 to 3 mol% as a preferred sex fraction. This reducing resistance composition was prepared by first adding a small amount of Ce to barium titanate, and then weighing and mixing the additive BaCO ₃ , MnCO ₃ , BN, SiO ₂ , according to the compositional formula of Example 1 (1), and ethanol and zirconium oxide. It can be obtained by mixing, grinding and drying with a ball for a certain time.

In the second invention, the calcination atmosphere in the calcination step for the composition in which Ce is added to barium titanate is in air, or oxygen / nitrogen = 20/80, or nitrogen, or hydrogen / nitrogen = 5/95, or hydrogen / It is a manufacturing method of obtaining a calcined body using the additive and composition formula of the said 1st invention after obtaining calcining powder with nitrogen = 10/90. The PTC thermistor element thus obtained has room temperature low resistance and high resistivity change rate as shown in Table 2.

A third invention is a multilayer PTC thermistor in which internal electrodes are alternately stacked and both left and right cross-sections are surrounded by external electrodes, which are produced under the first calcination atmosphere of the second invention and have an internal electrode printed on one surface thereof. -1) is laminated on the ceramic layer 12a produced under the second calcination atmosphere, and the ceramic layer 12b-2 formed under the first calcination atmosphere is laminated thereon, and then again the ceramic layer produced under the second calcination atmosphere. The structure in which 12a is laminated is repeated. The completed reduction-resistant laminated PTC thermistor element can be manufactured by forming the external electrodes 14 on both end surfaces of the firing chip in which the semiconductor ceramic layers 12b-1 and 12b-2 and the internal electrodes 13 are alternately stacked. Wherein the first or second calcination atmosphere is one of air or oxygen / nitrogen = 20/80, or nitrogen, or hydrogen / nitrogen = 5/95, or hydrogen / nitrogen = 10/90. It is done. In this case, the first calcining atmosphere and the second calcining atmosphere may be the same or different from each other. The PTC thermistor element thus obtained becomes a high-quality PTC thermistor element having a low room temperature resistance and a high resistivity change rate despite the firing process under a strong reducing atmosphere.

The invention is explained in more detail by way of examples.

A method of synthesizing the laminated PTC thermistor composition of the present invention and a method of manufacturing the same, wherein a powder synthesized in a different heat treatment atmosphere is laminated by a heterogeneous combination of a conductive paste serving as an internal electrode and a ceramic green sheet serving as a semiconductor ceramic layer. Forming a can reduce the room temperature resistance and increase the resistivity change rate.

Hereinafter, embodiments of the present invention for a laminated PTC thermistor will be described in detail.

Example 1

First of all, in order to obtain a reducing-resistant PTC thermistor composition, a composition prepared by adding a small amount of rare earth element Ce to barium titanate, Ba site / Ti site = 0.998, prepared by the hydroxyl method as a starting material, was first prepared, and additives BaCO ₃ and MnCO were added. ₃ , BN and SiO ₂ were weighed and mixed with the following composition formula.

(Ba _{0 .998} Ce _{0 .002} ) TiO ₃ + 0.03 BaCO ₃ + 0.0002MnCO ₃ + xBN + ySiO ₂ ------------- (1)

After weighing and adding as in Formula (1) above, the mixture was pulverized with ethanol and zirconium oxide balls for 24 hours, and dried.

After the mixed powder was molded into a single plate of 10 mm x 1.5 mm, the molded body was calcined at a low temperature of H ₂ / N ₂ = 5% for 2 hours at 970 ° C to 1050 ° C to obtain a fired body. In addition, reoxidation heat treatment was performed for 2 hours at 700 ° C. in air to impart a PTC effect. Below, the characteristic of the PTC thermistor manufactured by the sample obtained by Example 1 was evaluated, and the result is shown in Table 1.

Table 1

 sample B element amount x Si element amount y Room temperature resistivity, 25 ℃ (Ωcm) Resistivity change rate Log (ρ285 / ρ25)  Sinterability One 0.025 0 - - x 2 0.025 0.01 12.5 3.12 ◎ 3 0.025 0.02 8.1 2.82 ◎ 4 0.025 0.03 6.4 2.35 ○ 5 0.025 0.04 - - x 6 0 0.02 9.3 2.4 ◎ 7 0.01 0.02 9.1 2.7 ◎ 8 0.05 0.02 7.9 3.1 ◎ 9 0.075 0.02 6.9 2.97 ○ 10 0.1 0.02 6.0 1.8 ○

Example 2

As a starting material of the present invention, a small amount of Ce, which is a rare earth element, was added to a barium titanate having Ba site / Ti site = 0.998 prepared by the fishery method, and then calcined at 1150 ° C. for 2 hours to synthesize a powder. The calcination atmosphere at this time was performed in air, O ₂ / N ₂ = 20/80, N ₂ , H ₂ / N ₂ = 5/95, and H ₂ / N ₂ = 10/90, respectively. The calcined powder was weighed and added in the following formula (2), mixed with ethanol and zirconium oxide balls for 24 hours, and dried.

(Ba _{0 .998} Ce _{0 .002} ) TiO ₃ + 0.03BaCO ₃ + 0.0002MnCO ₃ + 0.05BN + 0.02SiO ₂ ----------------- (2)

After the mixed powder having the above composition was molded into a single plate of 10 mm x 1.5 mm, the molded body was calcined at a low atmosphere of H ₂ / N ₂ = 5% for 2 hours at 1000 ° C to 1150 ° C to obtain a fired body. In addition, reoxidation heat treatment was performed for 2 hours at 700 ° C. in air to impart a PTC effect.

Below, the characteristic of the PTC thermistor manufactured by the sample obtained by Example 2 was evaluated, and the result is shown in Table 2.

[Table 2]

sample Calcination atmosphere of ceramic layer Room temperature resistivity, 25 ℃ (Ωcm) Resistivity change rate Log (ρ285 / ρ25) 11 air 7.9 3.1 12 Oxygen / nitrogen = 20/80 7.4 2.9 13 nitrogen 6.5 3.27 14 Hydrogen / Nitrogen = 5/95 6.9 3.52 15 Hydrogen / Nitrogen = 10/90 7.9 3.74

Example 3

Each mixed powder prepared in Example 1 was mixed with an organic binder, a dispersant, and a solvent of toluene: ethanol = 60: 40, which is a non-aqueous solvent, for 20 to 50 hours to obtain a ceramic slurry. This ceramic slurry was thick-film-formed in the sheet form by the doctor blade method, and it dried, and obtained the ceramic green sheet.

Next, in order to form the internal electrode layer 13, conductive Ni paste is applied by screen printing on the ceramic green sheets 12b-1 and 12b-2, and the green sheets on which the Ni electrodes are printed are alternately laminated. By cutting, green chips in which internal electrodes are drawn on both end surfaces of the laminate are obtained.

An embodiment of the laminated PTC thermistor of the present invention is shown in Figs. 2 and 3, and the present invention will be described in more detail with reference to the drawings.

2 is a schematic cross-sectional view showing the structure of a stacked PTC thermistor according to an embodiment of the present invention.

Figure 3 is a schematic perspective view showing the stacking order of the green sheet according to an embodiment of the present invention.

As shown in Fig. 3, 12a, 12b-1, and 12b-2 are ceramic green sheets prepared by the respective samples obtained in Example 2, and the green sheets according to each of these samples were combined as shown in Table 3. Laminated.

For example, in the case of Sample 20 shown in Table 3, 12a is N _2. Green sheet prepared by mixing the additive in the powder calcined in the gas and 12b-1 and 12b-2 is a green sheet prepared by calcining in the gas of H ₂ / N ₂ = 5/95.

In the laminated chip of FIG. 2, the Ni electrode paste was simultaneously fired at 950 ° C. to 1050 ° C. for 2 hours under a reducing atmosphere of H ₂ / N ₂ = 5/95, and the resulting firing chip was subjected to barrel polishing by dry drying. The edges were rounded and polished. In addition, as shown in FIG. 2, after applying the Ag electrode paste having ohmic contact characteristics to both end surfaces of the firing chip in which the semiconductor ceramic layers 12a, 12b-1, 12b-2 and the internal electrodes 13 are alternately stacked, The external electrode 14 was formed by simultaneously performing the electrode element portion and the reoxidation heat treatment.

At this time, the reoxidation heat treatment was performed in the air at 600 ° C to 800 ° C for 1 hour.

Below, the characteristic of the laminated PTC thermistor manufactured by Example 3 was evaluated, and the result is shown in Table 3.

Table 3

sample Calcination atmosphere of ceramic layer Room Temperature Resistance, 25 ℃ (Ω) Resistivity change rate Log (ρ285 / ρ25) 12a 12b-1,12b-2 16 Air Air 1.2 2.22 17 N ₂ Air 0.87 2.98 18 N ₂ 20% O ₂ 0.29 2.80 19 N ₂ N ₂ 0.23 3.67 20 N ₂ 5% H ₂ 0.27 3.72 21 N ₂ 10% H ₂ 0.3 3.98 22 10% H ₂ Air 1.01 3.09 23 10% H ₂ 20% O ₂ 0.56 3.11 24 10% H ₂ N ₂ 0.41 4.03 25 10% H ₂ 5% H ₂ 0.52 4.32 26 10% H ₂ 10% H ₂ 0.57 4.3

1 is a schematic cross-sectional view of a laminated PTC thermistor manufactured in the prior art.

2 is a schematic cross-sectional view of a stacked PTC thermistor according to an embodiment of the present invention.

3 is a schematic perspective view before lamination of a laminated PTC thermistor according to an embodiment of the present invention.

<Brief description of the main parts of the drawing>

11: Stacked PTC Thermistor 12a, 12b-1, 12b-2: Semiconductor Ceramic Layer

13: internal electrode material 14: external electrode

Claims (7)

A reduced resistance semiconductor ceramic composition comprising barium titanate containing Ce as a main component and containing BN and SiO ₂ , wherein the BN content is 1.0 to 7.5 mol% and the SiO ₂ content is 2 to 3 mol%. The reduction resistant semiconductor ceramic composition according to claim 1, wherein the content of Ce is 0.02 mol%. delete delete delete In a multilayer PTC thermistor in which internal electrodes and ceramic layers are alternately stacked, and external electrodes are wrapped around both left and right cross sections, a ceramic layer 12b-1, which is generated under a first calcination atmosphere and has an internal electrode printed on one surface thereof, is formed in a second type. The ceramic layer 12a formed under the calcination atmosphere is stacked, and the ceramic layer 12b-2 formed under the first calcination atmosphere is stacked thereon, and then the ceramic layer 12a generated under the second calcination atmosphere is laminated. Structure is repeated, The first calcining atmosphere or the second calcining atmosphere is air, or oxygen / nitrogen = 20/80, or nitrogen, or hydrogen / nitrogen = 5/95, or hydrogen / nitrogen = 10/90, characterized in that Stacked PTC Thermistors. 7. The stacked PTC thermistor of claim 6, wherein the first and second calcination atmospheres have different calcination atmospheres.

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