KR100190907B1 - Ptc chip thermistor - Google Patents

Abstract

The invention BaTiO ₃ and Y ₂ O ₃ as a basic composition, and the auxiliary component as SrTiO _3, CaTiO _3, MnO ₂ PbO, surface-mount containing SiO ₂ PTC chip thermistor for producing BaTiO ₃ type ceramic composition, the composition 1310 The present invention relates to a surface-mounted PTC thermistor manufactured by sintering at an optimum sintering temperature of ˜1390 ° C., having a low temperature resistance, a breakdown voltage characteristic, and a PTC effect, which is precisely controlled in a wide range of curie temperatures, and which can be used for surface mounting. . The BaTiO _3- based PTC chip thermistor of the present invention realizes the low temperature resistance and PTC effect that can be used for controlling the Curie temperature and surface mount than the conventional BaTIO ₃ -type PTC thermistor, and can operate at low voltage due to the low temperature resistance. As the driving voltage is lowered, the applicability of SMD has been greatly expanded. By changing the SrTiO ₃ content, Curie temperature (Tc) can be precisely controlled, and the precise controllability of Tc is used for SMD in various fields. It is possible and has a wide range of Tc, increasing its applicability in switching devices.

Description

Surface-Mount PTC Chip Thermistors

The present invention relates to a surface mount PTC chip thermistor. More specifically, the present invention is BaTiO ₃ and the Y ₂ O ₃ as a, and auxiliary component to the basic composition SrTiO _3, CaTiO _3, MnO _2, PbO, for manufacturing surface mount PTC chip thermistor containing SiO ₂ BaTiO ₃ based ceramic Composition, the surface-mounted PTC chip thermistor which is produced by sintering the composition at the optimum sintering temperature, has a low temperature resistance, withstand voltage characteristics, and PTC effect, which is precisely controlled in a wide range of Curie temperatures and can be used for surface mounting, and a method for manufacturing It is about.

Surface mount technology (SMT) is a general term for joining technology that is applied when a circuit is configured to be electrically connected by bonding electronic components on one or both surfaces of a substrate. Unlike that, it is possible to mount many parts on both sides of the board. The surface mount device (SMD) fabricated by such SMT is small in size by 50 to 70% in one size, but can be up to 10 times smaller in size and lighter in mounting density. Therefore, the use of SMT enables the realization of ultra-compact devices, and has a structure without leads, thereby shortening the circuit connection and reducing unnecessary instant stray capacitance, thereby improving the high frequency characteristics.

On the other hand, barium titanate (BaTiO ₃ ) having a perovskite crystal structure is one of the representative ferroelectric materials, and is widely used as a capacitor material by utilizing high dielectric constant and high stability characteristics. In 1955, Haayman, Netherlands Etc., PTC (positive temperature coefficient) in which the resistance value rapidly rises above the Curie temperature when semiconductors are added to BaTiO ₃ having such characteristics by adding a small amount (0.1 to 0.3 atm%) of rare earth, niobium, and antimony. Phenomena). Since then, research has been actively conducted in the identification and application of this unusual phenomenon, and is now widely used in various heating elements, switching elements, sensors, and the like.

In addition to these as the material that can exhibit a PTC characteristic BaTiO ₃ based materials, a number of materials such as carbon particles dispersed organic PTC materials, V ₂ O ₃ based material, PbTiO ₃ -TiO ₂ based materials, BaTiO ₃ in an organic-based resin material, Although it is known, BaTiO ₃ materials have been used most widely since they are superior in terms of performance stability, mass productivity, price, and the like, and have various characteristics as follows. That is, the BaTiO ₃ -based material,

1. It shows PTC effect (resistance increase of resistance value) according to crystal deformation, resistance largely changes to 7 digits, and resistance temperature coefficient is 3-20% / degreeC normally;

2. The resistance value and switching temperature can be adjusted according to the use within a relatively wide range; And,

3. It has high withstand voltage and withstand power characteristics.

On the other hand, PTC chip thermistors include resistance and temperature characteristics, voltage and current characteristics, and current and time characteristics as basic characteristics, and these three basic characteristics are used for many applications. Its main uses include temperature compensation using resistance and temperature characteristics, temperature sensors, constant temperature heating elements using constant power heating by self-heating of conduction current, hot air heaters, and self-heating by conduction current. Used for current limiting. As described above, in order to apply PTC chip thermistors applied to various applications to SMT, it is known to have low room temperature resistance and good withstand voltage characteristics. In addition, it is known that the microstructure of PTC chip thermistor should be in the form of polycrystals, and in order to improve properties, the crystal grains should be thin, uniform, small pores, and dense materials.

On the other hand, BaTiO _3- based PTC chip thermistor generally has a chemical composition as shown in Table 1, it is known that such a composition can have a great effect on the microstructure with the process conditions for manufacturing the ceramic.

In the composition of the electric BaTiO ₃ -based PTC chip thermistor, Mn, Fe, Na, etc. have a great influence on the characteristics of the thermistor even at a very small amount, and one of the difficulties in manufacturing the PTC thermistor is how to control these elements. You can also As an example, when Fe is mixed as an impurity, the resistance value is increased, and even at 0.001% level, it shows a large influence. Therefore, in manufacturing PTC chip thermistors, it is necessary to pay attention to such impurities that may be contained in raw materials such as TiO 2 and BaCO ₃ , and to take sufficient measures against the incorporation of impurities in each process from mixing to firing during ceramic manufacturing. Do.

As such a composition for BaTiO ₃ -based PTC chip thermistors, a barium titanate-based semiconductor ceramic composition containing BaTiO ₃ , SrTiO ₃ , CaTiO ₃ , Y ₂ O ₃ , MnO _2, and SiO ₂ as a base composition and containing PbTiO ₃ for curie temperature control is used. Reported in US Pat. No. 4,483,933; Japanese Patent Laid-Open No. 58-1483; US 54-27555; And (SO) 53-29234]. However, this composition has a disadvantage in that the Curie temperature is controlled in a high temperature range because the Curie temperature is controlled using PbTiO ₃ having a Curie temperature of about 495 ° C.

Yamamoto et al. Also studied the effect of Ca particle size changes and room temperature on the resistivity of room temperature and the effects of SiO _{2 as} a sintering aid in PTC thermistors based on BaTiO ₃ and Nb ₂ O ₅ . : Yamamoto Heavy Industries Co., Ltd. and Toshishige Yamamoto, Development of Low Resistance PTC Thermistors, 住友 金, Vol. 45, 2, pp. 63-72 (1993). However, such a barium titanate-based PTC thermometer uses Nb ₂ O ₅ as a semiconductor element, and therefore, there is a problem that low normal temperature resistance, which is essential for use in surface mounting, is not obtained.

Thus, the present inventors have BaTiO ₃ based surface result of intensive studies about the mount PTC chip thermistor, BaTiO ₃ and Y ₂ O ₃ the SrTiO ₃ of adjusting the Curie temperature as a, and auxiliary component as a basic composition and the, CaTiO _3, MnO ₂ and BaTiO ₃ -based ceramic compositions containing PbO and SiO ₂ as sintering agents are sintered at an optimum sintering temperature of 1,310 to 1,390 ° C., so that the Curie temperature can be precisely controlled in a wide temperature range, and low ambient temperature available for surface mounting It was confirmed that the surface mount type PTC chip thermistor having resistance, withstand voltage characteristics, and PTC effect can be manufactured, and thus, the present invention has been completed.

As a result, the main object of the present invention is to provide a BaTiO _3- based ceramic composition for manufacturing a surface-mounted PTC chip thermistor which can control the Curie temperature accurately in a wide temperature range and has low temperature resistance, voltage resistance, and PTC effect available for surface mounting. To provide.

Another object of the present invention is to provide a method of manufacturing a surface-mounted PTC chip thermistor by molding the electrical BaTiO ₃ -based ceramic composition and sintering at an optimum sintering temperature.

It is still another object of the present invention to provide a surface mount type PTC chip thermistor manufactured by a method for producing an electrical surface mount type PTC chip thermistor.

1 is a photograph showing a change in particle size according to the content of SrTiO ₃ of the surface mount type PTC chip thermistor of the present invention.

2 is a graph showing a change in Curie temperature according to the content of SrTiO ₃ in the surface mount type PTC chip thermistor of the present invention.

3 is a graph showing a change in resistance-temperature characteristics according to the content of SrTIO ₃ of the surface mount type PTC chip thermistor of the present invention.

The BaTiO3-based ceramic composition for preparing a surface-mounted PTC chip thermistor for achieving the object of the present invention has a composition represented by the following general formula;

Ba _{1- (a + b + c)} SraCao, ₁ TiO ₃ + bY ₂ O ₃ + cMnO ₂ + 1.02wt% PbO + 0.142wt% SiO ₂

In the electric formula,

a is between 0 and 0.195;

b is 0.001-0.0015; And,

c is 0.004-0.0008.

Further, the manufacturing method of the surface mount PTC chip thermistor of the present invention, BaTiO _3, SrTiO _3, CaTiO _3, Y ₂ O _3, MnO _2, PbO and SiO to the _second powder blend to the basis weight in an amount satisfying the following formula fair;

Ba _{1- (a + b + c)} SraCao, 1TiO ₃ + bY ₂ O ₃ + cMnO ₂ + 1.02wt% PbO + 0.142wt% SiO ₂

In the electric formula,

a is between 0 and 0.195;

b is 0.001-0.0015; And,

c is 0.004-0.0008.

Adding a binder to the mixture obtained in the previous step and drying;

Granulating and molding the dried mixed powder; And,

The molding obtained in the former is sintered at sintering temperature of 1,310-1,390 degreeC, and it cools to 900 degreeC in 1 step, and includes the process of obtaining a sintered compact.

In the manufacturing method of the surface-mounted PTC chip thermistor of the present invention, as the binder, a binder commonly used in the art, for example, polyvinyl alcohol (PVA), may be used, and the molding may be, for example, 1 ton / cm 2. Press molding can be performed under the pressure of. Sintering is particularly important because it has a large effect on the room temperature resistance, it is carried out according to the sintering conditions to sinter for about 1 hour at 1,310 ~ 1,390 ℃, preferably 1,330 ℃, and cooled to 900 ℃ in one step.

The surface-mounted PTC chip thermistor manufactured by the method of manufacturing the surface-mounted PTC thermistor of the present invention has a low room temperature resistance of about 3.9 to 6.5 Ω, a room temperature specific resistance of about 190 to 316Ω, to be.

In addition, the surface mounted PTC thermistor of the present invention has a Curie temperature Tc which is precisely controlled according to the following general formula.

Y = 0.30041X + 37.53957

In the electric formula,

Y is the content of SrTiO ₃ (mol%); And,

X is the Curie temperature.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited to these examples.

(Example)

In Examples 1 to 4, the following raw materials were used.

BaTiO ₃ powder: HPBT-1 BaTiO ₃ powder from Fuji Titanium;

SrTiO ₃ powder: Purity 99.8% SrTiO ₃ powder of Fuji Titanium Corporation; And

CaTiO ₃ , Y ₂ O ₃ , MnO ₂ , PbO, SiO ₂ powders: powders with a purity of at least 99.9%.

(Example 1)

This embodiment is to investigate the effect of Curie temperature according to the content of SrTiO _{3 in} the surface-mount PTC chip thermistor. Accurately weigh each raw material powder in the amount shown in Table 2 below, and then mix using a ball mill, and then, in a small amount of polyvinyl alcohol as an aqueous solution at a concentration of 2 (w / v)% as a binder. (15 ml) was added and dried in an electric oven at 90 ° C. for about 12 hours. The dried powder was granulated and then press molded at a pressure of 1 ton / cm 2. Thereafter, a sintered body having a thickness of 1.5 mm and a diameter of 10 mm was manufactured by sintering at 1,330 ° C. for 1 hour and cooled to 900 ° C. in one step. An In—Ga electrode was attached to the obtained disk-shaped sintered body for ohmic contact, and room temperature resistance was measured using a multimeter. The multimeter, thermometer, and computer were then interconnected to measure the resistance-temperature relationship. The results were as shown in Table 2 below.

From Table 2, it can be seen that as the content of SrTiO ₃ increases by 2.5 mol%, the Curie temperature increases by about 8 ° C. This is because the Curie temperature of SrTiO ₃ is about −170 ° C., which is much lower than the Curie temperature of BaTiO ₃ about 120 ° C. In addition, the particle size was found to decrease with increasing content of SrTiO ₃ (see FIG. 1). The change in Curie temperature (Tc) according to the content of SrTiO ₃ is as shown in Figure 2, from Figure 2 was able to derive the relationship between the SrTiO ₃ content and the Curie temperature as follows.

Y = -0.30041X + 37.53957

In the electric formula,

Y represents the content of SrTiO ₃ ; And,

X represents the Curie temperature.

Therefore, it can be seen that the surface mount type PTC chip thermistor of the present invention can accurately control the Curie temperature according to the content of SrTiO ₃ from the electric formula.

(Example 2)

This embodiment is to investigate the change in room temperature resistance according to the content of Y ₂ O ₃ and MnO ₂ . Except for exactly weighing each raw material powder in the amounts shown in Table 3 below, except that the raw material powder was sintered at 1,310 ° C, the same procedure as in Example 1 was carried out to produce a disk-shaped sintered body having a thickness of 1.5 mm and a diameter of 10 mm. Same as 1, the room temperature resistance was measured using a multimeter. The results were as shown in Table 3 below.

It can be seen from Table 3 that Y ₂ O ₃ and MnO ₂ have the lowest room temperature resistance when the contents are 0.15 mol% and 0.04 mol%, respectively. Effect of these changes in content of MnO ₂ is expected to the MnO ₂ which is added with a jumper (jumper) the PTC effect due to accompany an increase in resistance at room temperature, with increase of the PTC effect. Since low room temperature resistance is required for use in surface mount, from these results, the Y ₂ O ₃ content is fixed at 0.15 mol%, and it is low to reduce the MnO ₂ content to 4 mol% even with the effect of reducing the PTC effect. It can be seen that it is preferable for room temperature resistance.

(Example 3)

This embodiment is to investigate the change in room temperature resistance according to the sintering temperature. Accurately weigh each raw material powder in the amount shown in Table 4 below, and then mix each raw material powder using a ball mill, and then concentrate 2 (w / v)% of polyvinyl alcohol as a binder. A small amount (15 ml) was added in the form of an aqueous solution of, and dried in an electric oven at 90 ° C. for about 12 hours. The granulated powder was granulated and then press-molded at a pressure of 1 ton / cm 2 to obtain four moldings. Thereafter, each molded product was sintered at sintering temperatures of 1,310 ° C, 1,330 ° C, 1,350 ° C, and 1,370 ° C for 1 hour, and the disc having a thickness of 1.5 mm and a diameter of 10 mm was sintered under cooling to 900 ° C in one step. Four shaped sintered bodies were manufactured. Curie temperature and room temperature resistance were measured for each sintered body. The results were as shown in Table 4 below.

From Table 4, it can be seen that a sintered body exhibiting the smallest room temperature resistance is obtained at a sintering temperature of 1,330 ° C to 1,370 ° C, particularly 1,330 ° C. From these results it can be seen that the sintering temperature of the sintered body having a room temperature resistance suitable for use in surface mounting is 1,330 ℃ to 1,370 ℃, preferably 1,330 ℃.

(Example 4)

This embodiment is to investigate the change in the Curie temperature according to the content of Sr. As shown in Table 5 below, the amounts of the other components were constant, and each raw powder was precisely weighed by changing both sides of Sr, and then mixing the respective raw powders using a ball mill, followed by a binder. A small amount (15 ml) of polyvinyl alcohol was added as an aqueous solution at a concentration of 2 (w / v)%, and dried in an electric oven at 90 ° C for about 12 hours. After the granulated powder was granulated, six moldings were obtained under pressure molding at a pressure of 1 ton / cm 2. Thereafter, each molded product was sintered at a sintering temperature of 1,330 ° C. for 1 hour, and six disk-shaped sintered bodies having a thickness of 1.5 mm and a diameter of 10 mm were produced under the sintering conditions of cooling to 900 ° C. in one step. Curie temperature and room temperature resistance were measured for each sintered body. The results were as shown in Table 5 below, and the resistance-temperature characteristics for this composition are shown in FIG.

From Tables 5 and 3 above, the Curie temperature was found to be 124 ° C in a composition of 0.015, b 0.0015, and 0.0004, but the Curie temperature decreased by 10 ° C as a increased by 0.03. Can be. In addition, by sintering the molded product at 1,330 ° C, it was possible to obtain low room temperature resistance and relatively good PTC effect available for surface mounting.

As described and demonstrated in detail above, the BaTiO3-based PTC thermistor of the present invention realizes a lower temperature resistance and PTC effect that can be used for more precise Curie temperature control and surface mounting than the conventional BaTiO3-based PTC thermistor. There is this.

1. Low temperature resistance allows driving with low voltage.

2. As the driving voltage is lowered, the applicability of SMD is greatly expanded.

3. Tc can be controlled precisely by changing SrTiO3 content.

4. Accurate controllability of Tc makes it available for SMD in various fields where temperature changes.

5. Because of the wide range of Tc, its applicability in switching devices has increased.

Claims (4)

BaTiO _3- based ceramic composition for producing a surface-mounted PTC chip thermistor represented by the following general formula. Ba _{1- (a + b + c)} Sra Cao. ₁ TiO ₃ + bY ₂ O ₃ + cMnO ₂ + 1.02wt% PbO + 0.412wt% SiO ₂ In electric a is between 0 and 0.195; b is 0.001-0.0015; And, c is 0.0004-0.0008. BaTiO3, SrTiO3, CaTiO3, Y2O3, MnO2, PbO and SiO2 powder to be weighed and mixed in an amount satisfying the following general formula; Ba _{1- (a + b + c)} Sra Cao. ₁ TiO ₃ + bY ₂ O ₃ + cMnO ₂ + 1.02wt% PbO + 0.412wt% SiO ₂ [In electric a is between 0 and 0.195; b is 0.001-0.0015; And, c is 0.0004 to 0.0008.] Adding and drying a binder to the mixture obtained in the foregoing; Granulating the dried powder to press molding; And, A method for producing a surface-mounted PTC chip thermistor comprising the step of sintering a molded product obtained in the past at a sintering temperature of 1310 to 1390 ° C. and cooling to 900 ° C. in one step. A surface-mounted PTC chip thermistor manufactured by molding a BaTiO3-based PTC thermistor composition represented by the following general formula, sintering at 1310 to 1390 ° C, and cooling to 900 ° C in one step. Ba _{1- (a + b + c)} Sra Cao. ₁ TiO ₃ + bY ₂ O ₃ + cMnO ₂ + 1.02wt% PbO + 0.412wt% SiO ₂ In electric a is between 0 and 0.195; b is 0.001-0.0015; And, c is 0.0004-0.0008. The method of claim 3, Room temperature resistance is 3.9 ~ 6.5Ω, Room temperature specific resistance is 190 ~ 361Ωmm, = 8.6 to 16.6, and the following general formula Y = -0.30041X + 37.53957 [In electric Y is the content of SrTiO ₃ (mol%); And, X is the Curie temperature] Surface-mounted PTC chip thermistor characterized by having a Curie temperature (Tc) controlled in accordance with.