JPH06176954A - Laminated grain insulating type semiconductor ceramic capacitor - Google Patents

Abstract

PURPOSE:To provide a laminated grain insulating type semiconductor ceramic capacitor including Ni as an internal electrode used for the purpose of protecting semiconductors and electronic instruments from abnormal voltage such as noise, pulses, static electricity produced in the electronic instruments. CONSTITUTION:A Ni internal electrode 2a employs as a starting stock material internal electrode paste yielded by dissolving at least one kind or more among Li, Na, and K atoms of low atomic values in Ni or a compound containing Ni. Such Ni internal electrodes 2a are disposed such that they reach alternately opposing end edges of a molded structure 4. Further, an external electrode 3a yielded by adding and mixing Ti in Ni or a compound containing a Ni atom is provided at opposite ends of the molded structure 4. With such construction, there is ensured a laminated grain insulating type semiconductor ceramic capacitor having excellent performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention normally serves as a capacitor for absorbing low-voltage noise and high-frequency noise, while exhibiting a varistor function when high voltage such as pulse or static electricity enters. The present invention relates to a laminated type grain boundary insulation type semiconductor ceramic capacitor used for the purpose of protecting a semiconductor element and an electronic device from an abnormal voltage.

[0002]

2. Description of the Related Art In recent years, semiconductor devices such as ICs and LSIs have been widely used in electronic equipment in order to realize multi-functionality, lightness, thinness, shortness and size reduction, and the noise resistance of the equipment is decreasing accordingly. Therefore, in order to ensure the noise resistance of such electronic devices, film capacitors, laminated ceramic capacitors, semiconductor ceramic capacitors, etc. are used as bypass capacitors in the power supply lines of various ICs and LSIs. However, although these capacitors have excellent performance in absorbing low-voltage noise and high-frequency noise, these capacitors themselves have the function of absorbing high-voltage pulses and static electricity with the same high voltage. Since it does not have it, when a pulse or static electricity having a high voltage enters, malfunctions of devices, destruction of semiconductor elements, and even destruction of capacitors have become serious problems.

For this purpose, SrTiO 3 is used as a new type capacitor having high pulse resistance and excellent pulse absorption in addition to good noise absorption and stable temperature and frequency. A grain boundary insulation type semiconductor ceramic capacitor (hereinafter referred to as a ceramic capacitor with a varistor function) in which a _3- system semiconductor ceramic capacitor has a varistor function has been developed, and it has already been disclosed in JP-A-57-27001 and 57-35303. It is publicly known from the publications.

The ceramic capacitor with a varistor function normally absorbs low-voltage noise and high-frequency noise as a capacitor, but when a high voltage such as pulse or static electricity enters, it functions as a varistor and the semiconductor element is protected from abnormal voltage. It also has the feature of protecting electronic devices, and its use is expanding more and more.

On the other hand, in the field of electronic parts, lightness, thinness, shortness, miniaturization and high performance have been further advanced, and even with this ceramic capacitor with a varistor function, there is an increasing demand for miniaturization and high performance. However, since the conventional varistor function-equipped ceramic capacitor is a single plate type, miniaturization causes a reduction in the electrode area, resulting in problems such as a decrease in capacitance and a decrease in reliability. Therefore,
As a solution to this, it is expected to develop into a laminated structure that can substantially increase the electrode area.

However, a ceramic capacitor with a varistor function usually has a step of coating an oxide on the surface of a SrTiO ₃ type semiconductor element and insulating the grain boundary layer by thermal diffusion, so that it is generally used BaTiO _{3 type.} It is very difficult to form a multilayer varistor function capacitor (hereinafter referred to as varistor function multilayer ceramic capacitor) by firing the varistor function ceramic capacitor material at the same time as the internal electrode material, as compared with the system type multilayer ceramic capacitor. Was considered.

Therefore, as a method for solving the problem of simultaneous firing of a multilayer ceramic capacitor material with a varistor function and an internal electrode material, JP-A-54-53248 and JP-A-54-53250 are applied, A ceramic paste with a large amount of organic binder is printed on the part corresponding to the internal electrode, and a porous layer is formed on this part during the sintering process.
A method for injecting a conductive metal into the porous layer under appropriate pressure after sintering or a method for forming an internal electrode by a plating method or a melting method to form a laminated ceramic capacitor with a varistor function has been developed and provided. There is. But,
These are considerably difficult in terms of process, and have not yet reached the level for practical use.

Further, in Japanese Patent Laid-Open No. 59-215701, a heat diffusion material capable of insulating a grain boundary layer is mixed on a green sheet made of powder calcined in a non-oxidizing atmosphere. A method in which a conductive paste is printed and sintered in an oxidizing atmosphere, and further, Japanese Patent Laid-Open No. 63-219115 discloses that a powder which has been made into a semiconductor is used as a main component, and oxidation is performed to form an insulating layer on this main component. A method has been reported in which a green sheet mixed with a diffusing agent containing a coloring agent and / or a glass component and a molded body in which internal electrodes are alternately laminated are fired in air or in an oxidizing atmosphere.

However, in these two methods, the firing temperature is relatively low at 1000 to 1200 ° C., and the ceramic is less likely to sinter. Therefore, the crystal grains are less likely to come into surface contact with each other, and the finished element is a completely sintered body. Therefore, there is a problem that the capacitance is low, the voltage non-linear index α which is a typical characteristic of the varistor is small, the varistor voltage is unstable, and the reliability is poor. Furthermore, in the latter Japanese Patent Laid-Open No. 63-219115,
When a glass component is added as an additive, a glass phase is precipitated in a crystal grain boundary, the above electrical characteristics are likely to be deteriorated, and reliability is poor, and this also does not reach a level for practical use. Is.

Therefore, the present inventors have filed Japanese Patent Application No. 1-3675.
As described in Japanese Patent Publication No. 7, etc., Ti-excess SrTiO 3
_The ceramic composition based on the semiconductor component and MnO ₂ —SiO ₂ system as a base material and its manufacturing method are
It has become possible to develop a monolithic ceramic capacitor with varistor function that uses t, Rh, Pd or Ni as internal electrodes. Furthermore, as described in Japanese Patent Application No. 3-152991, an internal electrode composition in which at least one kind of low-valence Li, Na, and K atoms is solid-dissolved in Ni or a compound containing Ni atoms. And its manufacturing method,
The development of a multilayer ceramic capacitor with a varistor function using i as an internal electrode has become possible.

Regarding the laminated varistor, ZnO, Fe have already been disclosed in Japanese Patent Publication No. 58-23921.
A laminated voltage non-linear element using ₂ O ₃ and TiO ₂ system is disclosed. However, since this element has almost no capacitance, it exhibits excellent performance with respect to pulses with a relatively high voltage and absorption of static electricity, but with respect to noise with a low voltage below the varistor voltage and high frequency noise. Had a problem that it showed almost no effect.

[0012]

The above-mentioned Ti-excessive SrT
ceramic composition and a low valence in iO ₃ the semiconductor component and MnO ₂ -SiO ₂ system-based materials Li, Na, or more at least one of the K atoms were solid-dissolved in the compound containing Ni or Ni atoms Although it has become possible to develop a multilayer ceramic capacitor with a varistor function in which Ni is used as the internal electrode depending on the internal electrode composition and the manufacturing method, the external electrode composition has not been studied as deeply as the internal electrode composition. There is a problem that one of the function as a capacitor and the function as a varistor may be deteriorated due to deterioration, or the series equivalent resistance value ESR may be increased.

The present invention solves the above-mentioned problems and normally functions as a capacitor to absorb low-voltage noise and high-frequency noise, while exhibiting a varistor function when high voltage such as pulse or static electricity enters. Regarding a laminated ceramic capacitor with a function, a laminated grain boundary insulation type semiconductor ceramic capacitor containing SrTiO ₃ as a main component and having Ni as an internal electrode and capable of simultaneously firing a ceramic capacitor material and an internal electrode material in a process It is intended to be provided.

[0014]

In order to solve the above problems, the present invention provides an internal electrode in which at least one kind of low valence Li, Na and K atoms is Ni or a compound containing Ni atoms. A solid solution of the internal electrode paste was used as the starting material for the Ni internal electrode, and the external electrode was used as the starting material for the external electrode paste obtained by adding and mixing Ti to Ni or a compound containing Ni atoms. is there.

[0015]

With this structure, the oxidation resistance of the Ni internal electrode can be improved by dissolving at least one kind of low-valence Li, Na, and K atoms in Ni or a compound containing the Ni atom. At the same time, the oxidizability of the crystal grain boundary portion of the ceramic element can be improved. Further, when Ti is formed as an external electrode by adding and mixing it to Ni or a compound containing Ni atoms,
The contact between the Ni internal electrode and the external electrode is improved, the oxidation rate is further reduced, the oxidation of the external electrode can be suppressed as much as possible, and the multilayer ceramic capacitor with a varistor function can be easily provided.

[0016]

EXAMPLES The first example according to the present invention will be specifically described below with reference to examples.

Example 1 First, as shown in FIGS. 3 and 4, SrTiO ₃ (Sr / Ti = 0.97) 97 mol
%, Nb ₂ O ₅ : 0.5 mol%, Ta ₂ O ₅ : 0.5 mo
1%, MnO ₂ : 1.0 mol%, SiO ₂ : 1.0mo
A raw sheet having a composition of 1% and having a thickness of about 30 μm produced by a doctor blade method or the like was cut into a predetermined size, and NiO: 99.
The internal electrode paste 2 having a composition of 5 mol% and Li ₂ CO ₃ : 0.5 mol% was pattern-printed by screen printing according to a predetermined size. As is clear from FIG. 4, the internal electrode paste 2 containing Ni as a main component is not printed on the raw sheets 1a of the uppermost layer and the lowermost layer which are ineffective layers. Also, at this time, the raw sheet 1 to be laminated in the middle
The internal electrode paste 2 containing Ni as a main component printed on the above was printed so as to reach opposite (different) edges alternately as is well known. After that, the green sheets 1a are arranged on the upper and lower sides (normally, a plurality of layers are laminated respectively), while a plurality of layers of the green sheets 1 on which the internal electrode paste 2 is printed are laminated, and pressure and pressure are applied while heating, A molded body 4 was obtained as shown in FIG.

Next, when the average particle size is 0.5 μm or less and the purity is 9
TiO with an average particle size of 0.5 μm or less in 0% or more of NiO
_The powder to which ₂ powders were added was used as a starting material for the external electrode, and this powder was dispersed in a solvent together with an organic binder such as butyral resin to obtain an external electrode paste. Then, as shown in FIG. 1, the external electrode paste containing Ni as a main component is applied to both end surfaces of the molded body 4 in which the internal electrode paste 2 of the molded body is exposed at different edges alternately, and the external electrode paste containing Ni as the main component is applied in air at 1050
Degreasing and calcination were performed in the air at ℃ for 2 hours. afterwards,
Firing was performed at 1250 ° C. for 2 hours in a reducing atmosphere of N ₂ : H ₂ = 99: 1. After this calcination, reoxidation was performed in air at 900 ° C., and further 400 in a reducing atmosphere of N ₂ : H ₂ = 99: 1.
The external electrode 3a was re-reduced at 30 ° C. for 30 minutes. As shown in FIG. 1, the multilayer ceramic capacitor with a varistor function thus formed is provided with a plurality of layers of internal electrodes 2a so that the internal electrodes 2a alternately reach different edges, and The internal electrodes 2a are electrically connected to the external electrodes 3a containing Ni as a main component at both end edges of the molded body 4.

The shape of the multilayer ceramic capacitor with a varistor function in this embodiment is 1.3 (width L × height W × height H of 1.60 × 3.20 × 1.20 mm in FIG. 1).
It is called a type and is formed by laminating 30 layers of ceramic sheets on which the internal electrodes 2a are formed.

Regarding the multilayer ceramic capacitor with varistor function thus obtained, its capacitance, tan
Various electrical characteristics such as δ, varistor voltage, voltage non-linearity index α, and series equivalent resistance value ESR are shown in the following (Table 1). The following measured values are described for various electrical characteristics.

◇ Capacity C is measured voltage 1.0V, frequency 1.
Value at 0 kHz. ◇ The varistor voltage V _0.1mA is the value when the measurement current is 0.1mA.

Voltage non-linearity index α is measured current 0.1 m
From the value at A and 1.0 mA, it was calculated from the formula of α = 1 / log (V _1mA V _0.1mA ).

The series equivalent resistance value ESR is 1.
The resistance value at the resonance point at 0V.

[0024]

[Table 1]

Explaining the above (Table 1), the material numbers marked with * are comparative examples, and are outside the scope of the claims of the present invention. That is, in these sintered body elements, the oxidation of the external electrode 3a occurs violently, and the function of absorbing low voltage noise and high frequency noise of the capacitor,
A varistor does not have both a pulse and a function of absorbing high voltage such as static electricity at the same time, and a series equivalent resistance value ESR is large and a frequency characteristic is not good. Therefore, these samples are not suitable as ceramic capacitors with a varistor function for protecting semiconductors and electronic devices from noise, pulses, static electricity, etc. generated in electronic devices.

On the other hand, in the samples of the present invention indicated by other sample numbers, the capacitance is large, the voltage non-linearity index α is large, and the series equivalent resistance value ESR is small. It has both the function of absorbing high frequency noise and the function of absorbing high voltage such as pulse and static electricity as a varistor at the same time. Furthermore, the capacitance temperature change rate and the varistor voltage temperature coefficient are small, and the reliability and electrical characteristics are It has the characteristic that it is not easily affected by temperature. Therefore, these samples are suitable as ceramic capacitors with a varistor function for protecting semiconductors and electronic devices from noise, pulses, static electricity, etc. generated in electronic devices.

Further, in the multilayer ceramic capacitor with a varistor function, which is produced by adding TiO ₂ to NiO as the material of the external electrode 3a, the external electrode 3a is suppressed from being oxidized, and the tan δ and the series equivalent resistance value ESR value are reduced. confirmed. This is because the added Ti acts as a reducing agent,
It is considered that this is because oxidation of the surface layer of the external electrode 3a is suppressed and the resistance value of the electrode is lowered.

(Embodiment 2) Next, referring to FIG. 2, as a second embodiment of the present invention, a new Ag or Ag-Pd based external electrode 3b is formed on the upper layer portion of the external electrode 3a. Show.

An external electrode paste prepared by adding and mixing TiO ₂ to NiO was applied to both ends of a laminated molded body 4 having the same ceramic material composition as in Example 1 and obtained by using the internal electrode composition, and the mixture was placed in the air. Degreasing and calcination in air at 1050 ° C. for 2 hours. Then, it was fired at 1250 ° C. for 2 hours in a reducing atmosphere of N ₂ : H ₂ = 99: 1. After firing, A
A g-Pd-based (Pd: 10 wt% added) external electrode paste was applied onto the external electrode 3a containing Ni as a main component, and baked in air at 900 ° C. The product thus obtained is provided with a plurality of layers of internal electrodes 2a as shown in a partially cutaway perspective view in FIG. 2 so that the internal electrodes 2a reach the different edges of the molded body 4 alternately. , And these internal electrodes 2a and electrical external electrodes 3a are connected, and Ag
Alternatively, it becomes a monolithic ceramic capacitor with a varistor function 4a provided with an Ag-Pd based external electrode 3b. Also,
FIG. 5 shows the manufacturing process of this embodiment.

Regarding the multilayer ceramic capacitor with a varistor function thus obtained, its capacitance, tan
Various electrical characteristics such as δ, varistor voltage, voltage non-linearity index α, and series equivalent resistance value ESR are described in (Table 2) and (Table 3) below.

[0031]

[Table 2]

[0032]

[Table 3]

Explaining Example 2 above, those in Table 2 and Table 3 marked with an asterisk * are comparative examples, which are outside the scope of the present invention. (Table 2)
Ag shown in (Table 3) is better when the Ag external electrode shown in is formed.
The series equivalent resistance value ESR was slightly lower than that of the sample in which the -Pd-based external electrode was formed. It is considered that this is because the non-resistance value of Pd is slightly higher than the non-resistance value of Ag.

Further, when a multilayer ceramic capacitor with a varistor function was prepared by adding and mixing TiO ₂ to NiO, it was confirmed that tan δ and series equivalent resistance value ESR were lowered. At this time, when Ti was not added, it was observed that a relatively high resistance layer was formed at the boundary between the lower layer external electrode 3a and the upper layer Ag or Ag-Pd based external electrode 3b. It was confirmed that the boundary layer was not formed when Ti was added to the external electrode paste of the lower layer portion. That is, it is considered that Ni and Ag or Ag-Pd form an alloy through Ti. However, this phenomenon is effective only when Ti is added to the external electrode paste of the lower layer portion, and no effect is obtained even when Ti is added to the external electrode paste of the upper layer portion.

As described above, the structure described in Examples 1 and 2 makes it possible to easily manufacture a monolithic ceramic capacitor with a varistor function, and the monolithic ceramic capacitor with a varistor function thus obtained has a large size. Capacitance, large voltage nonlinear index α, small varistor voltage and series equivalent resistance ESR, and excellent temperature characteristics, frequency characteristics, and noise characteristics. It has a varistor function when a high voltage such as pulse or static electricity enters, and exhibits excellent responsiveness to noise, pulse, static electricity, etc. , Is expected to replace semiconductor ceramic capacitors.

Further, since the monolithic ceramic capacitor with varistor function having the internal electrodes 2a of the present invention is small in size and large in capacity and high in performance as compared with the conventional single plate type ceramic capacitor with varistor function. To
Application as a mounting component is also highly expected.
Further, as compared with a monolithic ceramic capacitor with a varistor function that uses a noble metal such as Pd or Ag as an internal electrode, it is expected that the cost of raw materials will be reduced because Ni is used as an internal electrode at a low cost.

[0037]

As described above, the ceramic capacitor with a varistor function according to the present invention has a capacitor function and a varistor function at the same time, and normally functions as a capacitor to absorb low-voltage noise and high-frequency noise, while a pulse When a high voltage such as electricity or static electricity enters, it exhibits a varistor function, so noise, pulses, and
It has a function to protect semiconductors and electronic devices from static electricity, etc., and it has a large capacity and high performance compared to the conventional single-plate type ceramic capacitor with varistor function. As expected, it can be used as a high-density mounting element for video cameras, communication devices, etc., and its effect is extremely large.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing a monolithic ceramic capacitor with a varistor function obtained according to a first embodiment of the present invention.

FIG. 2 is a partially cutaway perspective view showing a laminated ceramic capacitor with a varistor function obtained according to a second embodiment of the present invention.

FIG. 3 is a manufacturing process diagram of a multilayer ceramic capacitor with a varistor function according to the first embodiment of the present invention.

FIG. 4 is an exploded perspective view of a multilayer ceramic capacitor with a varistor function obtained according to a second embodiment of the present invention.

FIG. 5 is a manufacturing process diagram of a multilayer ceramic capacitor with a varistor function according to a second embodiment of the present invention.

[Explanation of symbols]

 1,1a green sheet 2 internal electrode paste 2a internal electrode 3a lower layer external electrode 3b upper layer external electrode 4 molded body

Claims (2)

[Claims] 1. L for Ni or a compound containing a Ni atom
A ceramic green sheet provided with a Ni internal electrode using a paste in which at least one of i, Na, and K atoms is solid-dissolved as a starting material is in contact with different end faces where the Ni internal electrodes are alternately opposed to each other. A plurality of sheets are laminated to form a molded body, and Ti is added to and mixed with a compound containing Ni or Ni atoms so that the Ni internal electrodes are electrically connected to the facing end faces of the molded body. Multilayer grain boundary insulation type semiconductor ceramic capacitor with external electrodes. 2. The laminated grain boundary insulating semiconductor ceramic according to claim 1, wherein the external electrode is a lower layer external electrode, and an Ag or Ag-Pd-based upper layer external electrode is further provided on the lower layer external electrode. Capacitors.