JP4595613B2 - Electrode paste and method for producing multilayer ceramic electronic component using the same - Google Patents

Description

  The present invention relates to an electrode paste for forming internal electrodes used when forming a multilayer body of multilayer ceramic electronic components.

  Further, the present invention relates to a method for manufacturing a multilayer ceramic electronic component using this electrode paste.

  With the recent downsizing and higher performance of electronic devices, multilayer ceramic electronic components such as multilayer ceramic capacitors used in many of these devices are becoming more and more compact and ensure the same performance as conventional products. Further, the number of layers is increasing.

  FIG. 1 is a cross-sectional view showing the internal structure of a general multilayer ceramic capacitor 11. At least a pair of opposed internal electrodes 13 across a dielectric layer 12 are external electrodes 14 provided on both end faces of the multilayer ceramic capacitor. Are connected alternately.

  As described above, when the number of layers is increased and the number of dielectric layers 12 and internal electrodes 13 is further increased, the internal electrodes 13 must be thinned together with the dielectric layers 12.

  In such a situation, the dielectric layer 12 and the internal electrode 13 are greatly different in shrinkage behavior in the sintering process of the laminated body, so that an internal structural defect is likely to occur when the multilayered laminated body is fired. Have

  In order to solve this problem, a co-material of the same composition as the dielectric layer is put in the internal electrode to suppress the shrinkage behavior of the internal electrode.

As a prior art document related to the internal electrode paste using such a common material, for example, Patent Document 1 is known.
JP 2001-110233 A

  However, in the multilayer ceramic electronic parts such as multilayer ceramic capacitors, an ultra-small one such as 0.6 mm × 0.3 mm has appeared, and when the number of the multilayers becomes multi-layered, it has been shown in the above patent document. Even when the electrode paste is used, internal structural defects may occur.

  In such a multilayer ceramic electronic component with a large number of layers, it is necessary to more precisely control the firing shrinkage behavior of the dielectric layer and the internal electrode, and the common component contained in the electrode paste that forms the internal electrode. It is also necessary to consider the interaction in the sintering of the material and the dielectric layer.

  Therefore, in view of the above problems, the present invention provides an electrode paste for forming an internal electrode capable of suppressing structural defects even in a multilayer ceramic electronic component having a small size and a large number of layers. An object of the present invention is to provide a multilayer ceramic electronic component that uses an electrode paste to suppress structural defects and is excellent in performance and reliability.

  In order to achieve the above object, the present inventors have conducted extensive research, and as a result, more precise control of the firing shrinkage behavior of the internal electrode and the dielectric layer and the common material contained in the electrode paste forming the internal electrode In order to control the interaction in sintering between the dielectric layer and the dielectric layer, it was found that the activity in the sintering reaction of the co-material contained in the electrode paste is important, and the present invention has been achieved. .

That is, in order to achieve the above object, the present invention provides an electrode paste used for forming an internal electrode in a laminated body in which ceramic sheets and internal electrodes are alternately laminated, and the electrode paste has a predetermined temperature. The ceramic shrinkage behavior of the internal electrode and dielectric layer is more precisely controlled by including ceramic powder with a change rate of specific surface area value by BET method larger than 30% and smaller than 60% before and after heat treatment in As a result of controlling the interaction in sintering of the common material and dielectric layer contained in the electrode paste forming the internal electrode, the internal structural defects are suppressed, and the performance such as capacitance is reduced. It is possible to provide an electrode paste capable of producing an excellent multilayer ceramic electronic component with improved reliability.

  Here, the reason why the heat treatment is performed at a predetermined temperature is to determine the reactivity of the common material used for the electrode paste and the activity such as the surface activity based on the change in the specific surface area value measured by the BET method before and after the heat treatment. The predetermined temperature used for this purpose is preferably 500 ° C to 1000 ° C, more preferably 600 ° C to 1000 ° C.

  When the heat treatment temperature is lower than 500 ° C. or higher than 1000 ° C., the reproducibility of the rate of change of the specific surface area measured by the BET method before and after the heat treatment becomes low, and the value of the rate of change varies.

  Furthermore, empirically, about 900 ° C. ± 100 ° C. is most preferable in terms of the reproducibility of the change rate of the specific surface area value.

Further, the main component is a perovskite type compound having an ABO ₃ type as a co-material, an average particle size before heat treatment at a predetermined temperature is 0.03 μm to 0.10 μm, and a specific surface area value is 15 m ² / g— By using the one having 25 m ² / g, the occurrence of internal structural defects can be further suppressed.

Further, when the ratio of the A site element to the B site element of the ABO ₃ type perovskite type compound is expressed as A / B, the A / B is set to 0.990 or more and 1.010 or less, so It is possible to provide an electrode paste that can produce a multilayer ceramic electronic component that suppresses the influence of the material to the minimum, suppresses internal structural defects, has excellent performance such as capacitance, and has improved reliability.

Here, the ABO ₃ type perovskite type compound is a compound such as BaTiO ₃ , where Ba corresponds to the A site element and Ti corresponds to the B site element.

As the A site element, Ca, Sr, Mg and the like are raised in addition to Ba, and as the B site element, Zr and the like are raised in addition to Ti. For example, in the chemical formula (BaCa) (TiZr) O ₃ The compounds represented also correspond to ABO ₃ type perovskite type compounds.

The electrode paste of the present invention includes a ceramic powder having a rate of change in specific surface area value before and after heat treatment at a predetermined temperature of greater than 30% and less than 60% as a co-material, thereby firing the internal electrode and the dielectric layer. The shrinkage behavior can be controlled more precisely, and the interaction in the sintering of the common material and dielectric layer contained in the electrode paste forming the internal electrode can be controlled, resulting in the suppression of internal structural defects. It is possible to provide an electrode paste that can produce a multilayer ceramic electronic component having excellent performance such as capacitance and improved reliability.

(Embodiment 1)
Hereinafter, an embodiment of the present invention will be described using a multilayer ceramic capacitor as an example with reference to FIG.

  FIG. 1 is a partially cutaway perspective view of a multilayer ceramic capacitor 11 according to the present embodiment. Dielectric layers 12 and internal electrodes 13 are alternately stacked to form a multilayer body, and the internal electrode 13 has an end portion thereof. Are laminated so as to be alternately exposed at opposite end faces of the laminate, and are alternately connected to a pair of external electrodes 14 formed at both end faces of the laminate.

  Regarding the production of such a multilayer ceramic capacitor, first, inorganic powder mainly composed of barium titanate, a binder such as acrylic resin or polyvinyl butyral resin, a plasticizer such as dibutyl phthalate, and a solvent are mixed, and a doctor blade method is used. To produce a ceramic sheet.

  Separately, Ni metal powder with an average particle size of 0.2 μm, barium titanate as a co-material, a resin such as ethyl cellulose, acrylic resin, and polyvinyl butyral resin and an organic solvent are mixed, and a three roll mill or the like is mixed. And kneading to prepare an electrode paste for forming an internal electrode.

Here, as shown in Table 1, the common barium titanate used for the electrode paste has an average particle size of 0.02 to 0.12 μm, and the specific surface area value before heat treatment at 900 ° C. for 15 minutes is 13-27 m < ² > / g and the thing with the change rate of the specific surface area value before and after performing heat processing of 27%-67% were used. Further, the barium titanate having a ratio A / B between the A site element and the B site element of 0.985 to 1.012 was used.

  In addition, about the specific surface area value, it measured by the normal BET method.

  Further, the ratio of the A site element and the B site element of barium titanate was measured by an X-ray diffraction method, and the average particle diameter was measured by using an image analyzer with a scanning electron microscope (SEM).

  Next, an electrode paste is screen-printed on the surface of the ceramic sheet to form internal electrodes.

  Next, the ceramic sheets on which the internal electrodes are formed are alternately laminated so that the internal electrodes face each other with the ceramic sheets sandwiched between them. While heating to a temperature at which the ceramic sheets soften, pressurize at 5 MPa to 20 MPa, integrate and fire. As a result, a multilayer body (not shown) that is an element body of the multilayer ceramic capacitor 11 having a shape of 0.6 mm × 0.3 mm × 0.3 mm is produced.

  Subsequently, after organic substances in the laminate are removed in nitrogen gas, the temperature is raised to 1300 ° C. in a nitrogen-hydrogen mixed gas atmosphere in which Ni serving as an internal electrode is not excessively oxidized, and a sintered body is obtained. .

  Next, the sintered body is chamfered, and the internal electrodes 13 are completely exposed on both end faces. Subsequently, after applying an electrode paste mainly composed of copper to both end faces and end faces of the sintered body, baking is performed in a nitrogen atmosphere at 800 ° C. to form an external electrode 14 on which Ni plating and Sn are formed. Plating is performed to obtain a multilayer ceramic capacitor sample having a shape of 0.6 mm × 0.3 mm × 0.3 mm as shown in FIG.

  Each of the 100 multilayer ceramic capacitor samples was embedded and polished to examine the number of internal structural defects.

  Moreover, as an evaluation of electric characteristics and reliability, the results of a reliability test while applying a measurement of capacitance and a voltage of 12.6 V at 85 ° C. are shown together with (Table 1).

  Here, the capacitance is measured at a temperature of 20 ° C. and 1 kHz under a voltage of 1 Vrms, and the target value of the capacitance is 100 nF (0.1 μF). Those having a capacitance exceeding 10% were determined to be out of the range of the present embodiment.

  As for short-circuit defects, samples having 10 or more shorts out of 30 measured numbers were out of the scope of the present embodiment.

The evaluation of the reliability test is shown by the number of samples in which the insulation resistance value decreased to 10 ³ Ω or less after 1000 hours while applying a voltage of 12.6 V at 85 ° C.

The insulation resistance value of the sample before the start of the reliability test is 10 ⁸ Ω or more. The insulation resistance value was measured by applying a voltage of 6.3 V for 1 minute at a room temperature of 25 ° C.

  As is clear from sample number 18 in (Table 1), the specific surface area value of the co-material contained in the electrode paste before heat treatment at a predetermined temperature (900 ° C. in the case of Embodiment 1) and after the heat treatment When the rate of change from the specific surface area value exceeds 60%, the short-circuit rate of the multilayer ceramic capacitor (sample No. 18) using the electrode paste as an internal electrode is as high as 20 out of 30.

  On the other hand, in sample numbers 1 to 17 produced using internal electrodes containing a co-material having a change rate of the specific surface area value before and after the heat treatment of 60% or less, the short rate is less than 10 out of 30, and the short rate It can be seen that is greatly improved.

  In Sample No. 1 in which the change rate of the specific surface area value before and after the heat treatment is less than 30%, the short-circuit rate is small, but the capacitance is decreased.

  This is because in Sample No. 1, the change rate of the specific surface area value before and after heat treatment of the co-material is small, and therefore the activity in the sintering reaction of the co-material is low. This is thought to be because the control of the interaction at the time became insufficient and the continuity of the internal electrodes was lowered.

The electrode comprising a ceramic powder with an average particle size 0.03μm~0.10μm before the heat treatment at a predetermined temperature, and a specific surface area value does not satisfy the condition of 15m ² / g~25m ² / g to the common material In sample numbers 6 and 14 made of paste, although the short-circuit rate is small, the breakdown voltage is as low as 140V. In particular, Sample No. 14 has an increased number of internal structural defects.

  Further, in the sample number 2 in which the A / B ratio of the ceramic powder as the co-material exceeds 1.010 and the sample number 17 in which the A / B ratio is less than 0.990, the capacitance is 100 nF ± 10 which is the target value. It is not within% and is low.

From these, the rate of change between the specific surface area value of the common material contained in the electrode paste before the heat treatment at a predetermined temperature (900 ° C. in the case of Embodiment 1) and the specific surface area value after the heat treatment is obtained. When it is larger than 30% and smaller than 60% , it becomes possible to more precisely control the firing shrinkage behavior of the internal electrode and the dielectric layer, and the co-material and the dielectric layer included in the electrode paste forming the internal electrode As a result of controlling the interaction in sintering, it is possible to produce a multilayer ceramic electronic component excellent in performance that achieves reduction in capacitance, breakdown voltage, short-circuit rate, and the like.

Furthermore, the main component is a perovskite type compound of ABO ₃ type as a co-material, the average particle size before heat treatment at a predetermined temperature is 0.03 μm to 0.10 μm, and the specific surface area value is 15 m ² / g By using the one having 25 m ² / g, the occurrence of internal structural defects can be further suppressed.

Further, when the ratio of the A site element to the B site element of the ABO ₃ type perovskite type compound is expressed as A / B, A / B is set to 0.990 or more and 1.010 or less, so An electrode paste capable of producing a laminated ceramic electronic component with reduced performance, reduced internal structure defects, excellent electrostatic capacity, and improved reliability is provided. It is.

  In the above embodiment, barium titanate is used as the ceramic powder of the co-material, but it is not limited to barium titanate, and barium titanate and other perovskite type compounds (calcium titanate, titanium) The same effect can be obtained with a compound or mixture of one or more of strontium acid and magnesium titanate.

The electrode paste according to the present invention includes a ceramic powder having a change rate of a specific surface area value before and after heat treatment at a predetermined temperature of more than 30% and less than 60% as a co-material. The firing shrinkage behavior can be controlled more precisely, and the interaction between the sintering of the common material contained in the electrode paste forming the internal electrode and the dielectric layer can be controlled, resulting in suppression of internal structural defects. It has the effect of being able to produce multilayer ceramic electronic components with excellent performance such as capacitance and improved reliability, and internal electrodes for multilayer ceramic electronic components such as multilayer ceramic capacitors, multilayer ceramic filters and multilayer substrates Useful for electrode pastes and the like.

1 is a partially cutaway perspective view of a multilayer ceramic capacitor according to an embodiment of the present invention.

11 Multilayer Ceramic Capacitor 12 Dielectric Layer 13 Internal Electrode 14 External Electrode

Claims (2)

In a laminated body in which ceramic sheets and internal electrodes are alternately laminated, an electrode paste used for forming the internal electrodes, the electrode paste including ceramic powder, and the ceramic powder is heat-treated at a predetermined temperature The change rate of the specific surface area value by the BET method before and after the annealing was larger than 30% and smaller than 60%, and the ceramic powder had an average particle size before heat treatment at the predetermined temperature of 0.03 μm to 0.03 μm. 10μm in it, and a specific surface area value is 15m ² / g~25m ² / g and a electrode paste. A laminating step of alternately laminating ceramic sheets and internal electrodes to produce a laminated body, a firing step of firing the laminated body to obtain a sintered body, and forming external electrodes on both end faces of the sintered body The electrode paste used for forming the internal electrode has a change rate of the specific surface area value by the BET method before and after heat treatment at a predetermined temperature is larger than 30% and smaller than 60%. electrode ceramic powder containing ceramic powder average particle size before the heat treatment at the predetermined temperature is 0.03Myuemu～0.10Myuemu, and the specific surface area is 15m ² / g~25m ² / g A method of manufacturing a multilayer ceramic electronic component using a paste.

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