JP2000082605A - Temperature compensation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a mounting area by forming an external electrode on both the end faces of an element body where the compound ceramic layer of a Perovskite dielectric and a metal compound oxide NTC thermistor with a specific wt.% each and an internal electrode layer are laminated alternately, and achieving parallel resistance and capacitance with a specific value each. SOLUTION: A compound ceramic element used for a temperature compensation circuit is formed into a mixed powder by mixing and grinding 10-90 wt.% Perovskite dielectric and 90-10 wt.% metal compound oxide NTC thermistor. A conductive material sheet is printed on a green sheet using the mixed powder for forming an internal electrode layer, and the green sheet is piled up on it and the internal electrode layer is printed. The lamination and printing are repeated as a lamination sheet, and the lamination sheet is cut into chips and baked after pressurization, thus forming an external electrode 4 on both the end faces of an element body 3 where the compound ceramic layer 1 and the internal electrode layer 2 are alternately laminated, thus obtaining performance with a parallel resistance of 20 Ω or higher and a parallel capacity of 10 pF or higher at 25 deg.C and at 20-30 MHz.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature compensation circuit comprising a composite ceramic element mounted on a circuit board for temperature compensation of a piezoelectric material such as quartz.

[0002]

2. Description of the Related Art As shown in FIG. 9, a temperature-compensated crystal oscillating circuit includes a crystal oscillator 11, a capacitor 12, a low-temperature compensating circuit 13, a high-temperature compensating circuit 14, and a parallel connection 15 of a capacitor and a variable capacitor connected in series. The circuit configuration is as follows.

Conventionally, when forming a temperature compensation circuit in which a thermistor and a capacitor are arranged in parallel,
A plurality of thermistors and capacitors are individually used and mounted on a substrate by flow or reflow soldering.

As a composite element having a thermistor function and a capacitor function in one chip, a green sheet of a dielectric material is superposed on the plate surface of a plate-like thermistor sintered body, sintered, and then cut to form a chip. And those obtained by superposing a green sheet of a thermistor material on a plate surface of a plate-shaped dielectric sintered body, sintering, and then cutting into a chip shape are disclosed.

[0005]

In order to form a temperature compensation circuit using a plurality of thermistors and capacitors, a large mounting area is required to mount many components on the same substrate. It does not meet the current situation where miniaturization of equipment is required.

It is conceivable to reduce the mounting area by stacking and mounting the components. However, when the components are stacked, the adhesion on the lamination surface is not sufficient.
It has been difficult to obtain desired electrical characteristics.

The present invention solves the above-mentioned conventional problems, and uses a composite ceramic element having both the characteristics as a dielectric and the characteristics as an NTC thermistor, so that the mounting area of the temperature compensation circuit can be reduced. It is a first object to provide a temperature compensation circuit that has been used.

The above-described composite device having the thermistor and capacitor functions is manufactured through a plurality of firing steps and molding steps, and the manufacturing process is complicated.
High cost.

A second object of the present invention is to provide an inexpensive temperature compensation circuit comprising a composite ceramic element.

[0010]

The temperature compensation circuit of the present invention comprises a composite ceramic layer containing 10 to 90% by weight of a perovskite-based dielectric and 90 to 10% by weight of a metal composite oxide NTC thermistor and a layer of an internal electrode. And a composite ceramic element in which external electrodes are formed on both end faces of the element body alternately laminated, the thermistor parallel resistance is 20Ω or more,
Parallel capacitance of 10pF or more (25 ° C, 10-30MHz)
And a temperature compensation element.

This composite ceramic element has both the characteristics as a dielectric and the characteristics as an NTC thermistor, so that the mounting area of the temperature compensation circuit can be reduced.

This composite ceramic preferably contains 10 to 90% by weight of a perovskite-based dielectric and 90 to 10% by weight of a metal composite oxide NTC thermistor. By mixing a perovskite-based dielectric having a high relative dielectric constant and a metal composite oxide NTC thermistor in this manner, a composite ceramic having both characteristics as a dielectric and NTC thermistor can be obtained.

The perovskite dielectric includes barium titanate dielectric, lead titanate dielectric and PL.
One or more selected from the group consisting of ZT can be used.

This composite ceramic has a relative permittivity of 30 or more, a thermistor B constant of 2000 K or more, and a resistivity of 1 to 1.
It is preferably 50,000 Ω · cm.

This composite ceramic element comprises external elements formed on both end faces of a body in which the composite ceramic layers and the internal electrode layers are alternately laminated, and the thermistor parallel resistance is 20 Ω or more. Preferably, the parallel capacitance is 10 pF or more (25 ° C., 10 to 30 MHz).

In particular, the thermistor parallel resistance is 1500
Ω or more and the thermistor B constant is 3500-4500K
And the thermistor parallel resistance is 30 to
150Ω or more and the thermistor B constant is 3500-45
It is preferable to connect a low temperature compensating element of 00K in series.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A composite ceramic element constituting a temperature compensating circuit according to the present invention is an equivalent circuit diagram shown in FIG. 2 composed of a perovskite-based dielectric and a metal composite oxide NTC thermistor. The reason why a perovskite-based dielectric is used as the dielectric is that the dielectric constant is high. When a dielectric having a low relative dielectric constant is used, the dielectric constant of the composite ceramic decreases, and the composite ceramic element does not perform its function.

As the perovskite-based dielectric, a barium titanate-based dielectric, a lead titanate-based dielectric, PLZT, or a mixture thereof can be suitably used. Here, the barium titanate-based dielectric means a dielectric mainly composed of barium titanate, and may contain other elements as long as the properties as the dielectric are not impaired. The same applies to the lead titanate-based dielectric and PLZT.

As the metal composite oxide NTC thermistor, a sintered product in which several kinds of metal oxides among metals such as Fe, Ni, Co, Mn, Zn, Cu and Al are used. The metal composite oxide NTC thermistor
It is composed of a simple substance or a composite of minerals such as spinel and glass. Since these metal composite oxide NTC thermistors have a large thermistor B constant, they can be suitably used for the composite ceramic of the present invention.

This composite ceramic element comprises 10 to 90% by weight of a perovskite dielectric and a metal composite oxide NT
It is preferable that the C thermistor is contained at a ratio of 10 to 90% by weight. If the perovskite-based dielectric in the composite ceramic is 10% by weight or less, the dielectric constant is too low to impair the function of the composite ceramic element as a capacitor.
If it exceeds 0% by weight, the function as a thermistor becomes too small, and in either case, it is not preferable. The preferred compounding ratio is 20 to 80% by weight of a perovskite dielectric and 80 to 20% by weight of a metal composite oxide NTC thermistor.

In order to manufacture this composite ceramic, first, a perovskite-based dielectric and a metal composite oxide NTC thermistor are mixed with raw materials and fired (from 800 to 10%).
00 ° C.), these predetermined amounts are mixed, and 10
Sintering is performed at about 100 to 1200 ° C, particularly about 1050 to 1200 ° C. That is, even if the respective raw materials of the perovskite-based dielectric and the metal composite oxide NTC thermistor are mixed and fired without heat treatment, each of the raw materials reacts non-selectively, and the target perovskite-based dielectric or metal is not heated. The composite oxide NTC thermistor does not form effectively. Therefore, as described above, a perovskite-based dielectric and a metal composite oxide NTC thermistor are prepared in advance, and a mixture in a predetermined ratio thereof is refired to obtain a sintered body.

In view of the fact that the re-firing is performed to obtain a composite ceramic element sintered body, the firing temperature for forming each of the perovskite-based dielectric and the metal composite oxide NTC thermistor is 800 to 1000 ° C., particularly 800 to 1000 ° C. ~ 9
Preferably, the temperature is about 50 ° C.

As the above-mentioned raw materials, besides metal oxides, carbonates, nitrates, acetates and the like which can be converted into oxides by firing can be used.

Since such a composite ceramic for temperature compensation needs to have both properties of a dielectric and a thermistor, it is required to have a high relative dielectric constant and a large thermistor B constant. Furthermore, the electrical conductivity must satisfy the properties of an insulator required when used as a capacitor and the properties of a conductor when used as a thermistor.

From such a viewpoint, it is desired that the above-mentioned composite ceramic has a relative dielectric constant of 30 or more. If the relative dielectric constant is less than 30, sufficient capacity cannot be obtained.

The thermistor B constant of the composite ceramic is desirably 2000K or more. Thermistor B
If the constant is less than 2000K, sufficient thermistor characteristics cannot be obtained.

This composite ceramic has a resistivity of 1 to 500.
It is desired to be 00 Ω · cm. If the resistivity is lower than the above range, it cannot show properties as a dielectric,
Conversely, if it is higher than this range, the properties as a thermistor cannot be exhibited.

This composite ceramic is prepared, for example, by mixing a perovskite-based dielectric prepared by mixing and firing respective materials for a dielectric and a thermistor and a metal composite oxide NTC thermistor at a predetermined ratio, and pulverizing the composite. A powder is obtained, and the composite powder is molded and fired according to a conventional method to form a single-layer composite ceramic body, and electrodes are formed on both end faces of the body to form a composite ceramic element (the equivalent circuit diagram is shown in FIG. 2). As shown in FIG. 1, external electrodes 4 are formed on both end surfaces of a body 3 in which composite ceramic layers 1 and internal electrode layers 2 are alternately laminated and integrated. By using the composite ceramic element described above, higher characteristics can be obtained. In order to manufacture the composite ceramic element of FIG. 1, a dielectric material is mixed and fired to form a perovskite-based dielectric, and a thermistor material is mixed.
Baking to create a thermistor. Next, the dielectric and the thermistor are mixed and pulverized at a predetermined ratio to obtain a mixed powder. An organic solvent and a binder (for example, polyvinyl alcohol, methylcellulose, etc.) are added to the mixed powder and kneaded to form a ceramic paste, which is then formed into a green sheet according to a conventional method. A conductive material paste for forming an internal electrode layer is printed on the green sheet in a predetermined pattern to form an internal electrode layer. A green sheet is superimposed on this and the internal electrode layer is printed. This lamination and printing are repeated a required number of times to form a laminated sheet. The laminated sheet is subjected to a pressure treatment and then cut into chips. After the binder is removed, it is fired at about 1000 to 1200 ° C. to obtain a composite ceramic sintered body chip. After subjecting the chip to a polishing process such as barrel polishing, a terminal electrode is formed on both end surfaces of the chip by a dipping method, a plating method, and the like, and baked if necessary, and the terminal electrode is baked on the chip. And

In the laminated composite ceramic element, the thickness of the composite ceramic layer 1 is preferably about 5 to 50 μm, and the thickness of the internal electrode layer 2 is preferably about 1 to 10 μm. The number of layers is appropriately determined depending on the purpose of use and required characteristics, but is generally 5 to 5.
It is about 50 layers.

In the case of the composite ceramic element having such a laminated structure, the thermistor parallel resistance is 20 Ω or more, and the capacitor parallel capacitance is 10 pF or more (25 ° C., 10 to 30 MH).
The high-performance composite ceramic element of z) is provided, and this element constitutes a small temperature compensation circuit.

In the present invention, in particular, the thermistor parallel resistance is 1500Ω or more and the thermistor B constant is 3500-4.
A high temperature compensating element of 500 K, a thermistor parallel resistance of 30 to 150 Ω or more and a thermistor B constant of 350
It is preferable to connect a low temperature compensating element of 0 to 4500K in series.

[0032]

The present invention will be described more specifically below with reference to examples and comparative examples.

A high-temperature compensating element was manufactured according to the following manufacturing example 1, and a low-temperature compensating element was manufactured according to the manufacturing example 2. These were connected to form a temperature compensating circuit as in the first embodiment.

Production Example 1 (Production of a High-Temperature Compensation Element) MnCO ₃ , CoCO ₃ , and Al ₂ O ₃ were used as starting materials and weighed so that the atomic ratio was Mn: Co: Al = 37: 55: 8. Then, after wet mixing with a ball mill for 10 hours,
This was dried and crushed, and then calcined at 900 ° C. for 10 hours to prepare a thermistor composition.

Separately, PbO, La ₂ O ₃ , ZrO ₂ , Ti
O ₂ , MgO, and WO ₃ are used as starting materials, they are mixed at a predetermined ratio, and the mixture is fired at a temperature of 1160 ° C. for 5 hours to obtain a PLZT-based dielectric composition (Pb _0.92 La _0.08 Zr).
_0.57 Ti _0.25 (Mg _0.5 , W _0.5 ) _0.05 O ₃ ) was prepared.

The thus prepared thermistor composition and the dielectric composition were weighed at a weight ratio of 34:66, wet-mixed with a ball mill for 10 hours, dried and crushed.

Here, an organic solvent and a binder were added and kneaded to 100 parts by weight of the crushed powder to form a ceramic paste, and a green sheet having a thickness of 20 μm was prepared by a slip casting method using the ceramic paste.

A predetermined pattern of silver-palladium paste for electrodes (Ag / Pd weight ratio = 70/30) is printed on a ceramic green sheet, and green sheet lamination and paste printing are alternately repeated to obtain the structure shown in FIG. The laminated body which has was produced. After drying this laminate, it was cut to produce a chip having a length of 1.6 mm, a width of 0.8 mm, and a thickness of 0.8 mm, and then fired at 1100 ° C. After chamfering both ends of the chip by barrel polishing, a silver paste was adhered by a dipping method, followed by Ni plating and solder plating to form terminal electrodes, thereby producing a composite ceramic element for high temperature compensation.

This composite ceramic element for high temperature compensation is formed by laminating 30 layers of a composite ceramic layer 1 having a thickness of 30 μm and an internal electrode layer 2 having a thickness of 2 μm.

The DC resistance of the composite ceramic element for high temperature compensation was measured, and the parallel equivalent resistance Rp and the parallel equivalent capacitance Cp were measured with an impedance analyzer. Rp and Cp were measured in a frequency range of 10 MHz to 30 MHz and a temperature range of -30 ° C to + 100 ° C.

FIG. 5 shows the parallel equivalent resistance R at 12.8 MHz.
6 shows temperature characteristics of p and the parallel equivalent capacitance Cp. FIG. 6 shows the temperature characteristics of the load capacitance Cs of the composite device.

Note that Cs = Cp + 1 / ω ² CpRp ² .

Production Example 2 (Low temperature compensating element) Commercially available MnCO ₃ ,
A ceramic composite device was produced in the same manner as in Production Example 1, except that CoCO ₃ and CuO were used in an atomic ratio of 43:43:14. The characteristics of this ceramic composite device were measured in the same manner as in Production Example 1, and the results are shown in FIGS.

As shown in FIGS. 5 to 8, it can be seen that these composite ceramic elements have excellent dielectric characteristics and thermistor characteristics.

Example 1 The element manufactured in Production Example 1 was used for low-temperature compensation, and the element produced in Production Example 2 was used for high temperature, and these were connected in series as shown in FIG. 9 to form a compensation circuit. FIG. 3 shows the temperature characteristics of the load capacity in this case. Further, this circuit is connected to a crystal oscillator as shown in FIG. 9, and an oscillation frequency deviation (Δf = (ft−f2
When the temperature characteristics of 5) / f25) were measured, the temperature compensation characteristics shown in FIG. 4 were obtained.

As is clear from FIG. 4, by connecting the compensating circuit composed of the above-mentioned composite element, the oscillation frequency becomes ± 2.
It can be seen that compensation is made within ppm.

[0047]

As described above in detail, according to the present invention, a temperature compensating circuit comprising a composite ceramic element having both characteristics as a dielectric and characteristics as an NTC thermistor and excellent in stability of the characteristics. Is provided. In addition, this composite ceramic is easy to manufacture.

In this composite ceramic element, a plurality of electrode layers sandwiching a composite ceramic layer having a thermistor property and a dielectric property are laminated, so that a desired resistance value and capacitance value can be simultaneously obtained. it can. Further, the resistance-temperature characteristics can be controlled by the thermistor material composition.

Further, the composite element constituting the temperature compensation circuit of the present invention has characteristics equivalent to a parallel circuit of a thermistor and a capacitor. Therefore, when applied to a compensation circuit such as a temperature compensated crystal oscillator, the size of the compensation circuit can be reduced. Thus, the number of mounted components can be reduced.

[Brief description of the drawings]

FIG. 1A is a schematic cross-sectional view showing a composite ceramic element used in a temperature compensation circuit of the present invention, and FIG. 1B is an explanatory view of an electrode pattern thereof.

FIG. 2 is an equivalent circuit diagram of the device of FIG.

FIG. 3 is a graph showing a load capacitance of the temperature compensation circuit created in the first embodiment.

FIG. 4 is a graph showing characteristics of the temperature compensation circuit created in the first embodiment.

FIG. 5 is a graph showing temperature characteristics of a parallel equivalent resistance Rp and a parallel equivalent capacitance Cp of the composite ceramic element prepared in Production Example 1.

FIG. 6 is a graph showing the temperature characteristics of the load capacitance of the composite ceramic element prepared in Production Example 1.

FIG. 7 is a graph showing temperature characteristics of a parallel equivalent resistance Rp and a parallel equivalent capacitance Cp of the composite ceramic element prepared in Production Example 2.

FIG. 8 is a graph showing a temperature characteristic of a load capacitance of the composite ceramic element prepared in Production Example 2.

FIG. 9 is a circuit diagram of a temperature compensated crystal oscillator.

[Explanation of symbols]

 Reference Signs List 1 composite ceramic layer 2 internal electrode layer 3 element body 4 external electrode

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Koji Shimoto, Inventor 2270 Yokoze, Yokoze-machi, Chichibu-gun, Saitama Prefecture Inside the Electrotechnical Laboratory, Mitsubishi Materials Corporation (72) Masaki Koshimura, 2270 Yokoze, Yokoze-cho, Yachize-cho, Chichibu-gun, Saitama Address Mitsubishi Electric Materials Co., Ltd.Electronic Technology Research Laboratories (72) Inventor Toshimichi Nakamura 2270 Yokoze, Yokoze-cho, Chichibu-gun, Saitama F-term in Ceramics Factory, Mitsubishi Materials Corporation AA36 AA40 BA06 BA09 CA01 5E034 BA10 BB01 BC01 DA02 DA07 DC01 DD03 DD04 5J079 AA04 BA02 CB02 DB01 FA24

Claims (5)

[Claims] 1. A perovskite-based dielectric of 10 to 90% by weight and a metal composite oxide NTC thermistor of 90 to 10% by weight.
And a composite ceramic element in which external electrodes are formed on both end surfaces of a body in which layers of composite ceramics and layers of internal electrodes are alternately laminated, and the thermistor parallel resistance is 2
0Ω or more, parallel capacitance 10pF or more (25 ° C, 10-3
(0 MHz). 2. The temperature according to claim 1, wherein the perovskite-based dielectric is at least one member selected from the group consisting of barium titanate-based dielectrics, lead titanate-based dielectrics, and PLZT. Compensation circuit. 3. The relative permittivity of the composite ceramic is 30 or more,
Thermistor B constant is 2000K or more, resistivity is 1-50
3. The method according to claim 1, wherein the resistance is 000 Ω · cm.
Temperature compensation circuit. 4. A high-temperature compensator having a thermistor parallel resistance of 1500Ω or more and a thermistor B constant of 3500-4500K, and a low-temperature compensation element having a thermistor parallel resistance of 30-150Ω or more and a thermistor B constant of 3500-4500K. The temperature compensating circuit according to claim 1, wherein the temperature compensating circuit is configured by connecting elements in series. 5. The temperature compensation circuit according to claim 4, wherein a crystal oscillator and a capacitor are connected in series.