JP5251589B2 - Manufacturing method of ceramic capacitor - Google Patents

Description

  The present invention relates to a method for manufacturing a ceramic capacitor.

Some multilayer ceramic capacitors have an internal electrode made of a base metal such as Ni and an external electrode made of a base metal such as Cu. The ceramic material constituting the ceramic body of the multilayer ceramic capacitor is an oxide such as BaTiO ₃ , and when fired in a neutral atmosphere or a reducing atmosphere, the ceramic material may be reduced to deteriorate the characteristics. It is desirable to be baked with.

  In addition, when an external electrode made of a base metal is baked in a reducing atmosphere, the resin component such as a binder contained in the external electrode paste is not sufficiently burned, resulting in the formation of pores in the external electrode, and the reliability of the multilayer ceramic capacitor descend. On the other hand, when the external electrode is baked in an oxidizing atmosphere, the combustion efficiency of the binder (resin component) is increased, and the external electrode is easily sintered. As a result, the external electrode becomes dense, and the water resistance performance and plating solution performance are improved. However, when the external electrode is baked in an oxidizing atmosphere, an oxide film is likely to be formed at the joint between the internal electrode and the external electrode. There is a problem that the equivalent series resistance (ESR) is increased. When a capacitor with a large equivalent series resistance is used for high frequency applications, heat generation abnormalities occur at the junction between the internal electrode and the external electrode. Thus, it is necessary to consider the baking conditions when baking the external electrodes. Thus, for example, Patent Document 1 describes a method of baking external electrodes while switching between an oxidizing atmosphere and a reducing atmosphere.

JP 2003-234257 A

  However, as in Patent Document 1, the method of baking the external electrode while switching between the oxidizing atmosphere and the reducing atmosphere is complicated and cumbersome to manage the baking conditions, and variation in the electrical characteristics of the ceramic capacitor due to variation in atmosphere tends to occur. There was a problem that.

  Therefore, a main object of the present invention is to provide a manufacturing method capable of obtaining a ceramic capacitor having good electrical characteristics such as capacitance and dielectric loss while ensuring water resistance.

  The present invention provides a ceramic body, a first external electrode and a second external electrode provided on the outer surface of the ceramic body, and a first external electrode provided inside the ceramic body and joined to the first external electrode. A ceramic capacitor having a first internal electrode and a second internal electrode joined to the second external electrode, wherein an alternating current is passed between the first external electrode and the second external electrode, A process for removing an oxide film formed at a junction between one external electrode and a first internal electrode and a junction between a second external electrode and a second internal electrode, respectively. Is the method.

  In this invention, by passing an alternating current between a pair of external electrodes, an alternating current flows through the joint between the external electrode and the internal electrode, and the oxide film generated at the joint between the external electrode and the internal electrode is destroyed, Electrical connection between the external electrode and the internal electrode is ensured.

  Further, the present invention is characterized in that the alternating current is a high frequency current of 0.1 mA or more. Thereby, an alternating current sufficiently flows through the junction between the external electrode and the internal electrode, and the oxide film generated at the junction between the external electrode and the internal electrode is reliably destroyed.

  In addition, the present invention is characterized in that the first external electrode and the second external electrode are baked in an oxidizing atmosphere. As a result, the external electrodes can be densely formed, and there is no need to burn the external electrodes while switching between the oxidizing atmosphere and the reducing atmosphere, and the management of the baking conditions becomes simple and easy. Variations in electrical characteristics are less likely to occur.

  Furthermore, the present invention is characterized in that the first external electrode and the second external electrode are made of a base metal. Thereby, even if it is a ceramic capacitor which has the external electrode which consists of a base metal which is easy to oxidize when baking in an oxidizing atmosphere, the outstanding electrical characteristic is acquired.

  According to the present invention, an alternating current flows between the pair of external electrodes and an alternating current flows through the joint between the external electrode and the internal electrode, thereby destroying the oxide film generated at the joint between the external electrode and the internal electrode. It is possible to ensure electrical continuity between the external electrode and the internal electrode. As a result, a ceramic capacitor having good electrical characteristics such as capacitance and dielectric loss can be obtained.

  The above-mentioned object, other objects, features and advantages of the present invention will become more apparent from the following description of embodiments for carrying out the invention with reference to the drawings.

It is an external appearance perspective view for demonstrating one Embodiment of the manufacturing method of the ceramic capacitor which concerns on this invention. It is sectional drawing of the ceramic capacitor shown in FIG. It is a disassembled perspective view of a ceramic body.

  An embodiment of a method for producing a ceramic capacitor according to the present invention will be described. In the following, a case where ceramic capacitors are produced individually will be described as an example. However, in the case of mass production, a mother laminated body including a plurality of ceramic capacitors is manufactured. 1 is an external perspective view of the multilayer ceramic capacitor 10, FIG. 2 is a sectional view thereof, and FIG. 3 is an exploded perspective view of the ceramic body 2. As shown in FIG. The ceramic capacitor 10 includes a ceramic body 2 and a pair of external electrodes 3 and 4 formed on the outer surfaces of both ends of the ceramic body 2.

As shown in FIG. 3, the ceramic body 2 includes ceramic green sheets 20c to 20h having internal electrode patterns 22 and 23 formed on the surface, and ceramic green sheets 20a, 20b, 20i for outer layers on which no electrode pattern is formed. 20j is a laminated body configured by stacking. As a material of the ceramic green sheets 20a to 20j, a material in which a known organic binder or an organic solvent is added to a dielectric ceramic composed of main components such as BaTiO ₃ , CaTiO ₃ , SrTiO ₃ , and CaZrO ₃ is used. Moreover, you may use what added subcomponents, such as a Mn compound, Fe compound, Cr compound, Co compound, Ni compound, to these main components. In particular, in the present embodiment, since a high frequency is applied to the ceramic capacitor 10, it is preferable to use a temperature-compensated ceramic material that generates little heat due to the application of the high frequency. Specifically, ε such as CaTiO ₃ and CaZrO ₃ is used. It is preferable to use a small ceramic. The thickness of the ceramic green sheets 20c to 20h is preferably set so that the thickness of the ceramic layer between the internal electrode patterns 22 and 23 after firing is 0.5 to 10 μm.

  The internal electrode patterns 22 and 23 are formed by applying a conductive paste on the ceramic green sheets 20c to 20h by, for example, screen printing. The internal electrode pattern 22 is exposed on the left side of the ceramic green sheets 20c, 20e, and 20g. The internal electrode pattern 23 is exposed on the right side of the ceramic green sheets 20d, 20f, and 20h. The internal electrode patterns 22 and 23 are arranged so as to face each other with the ceramic green sheets 20c to 20g interposed therebetween in the stacked state. Predetermined electrical characteristics can be obtained by this facing portion. As a material of the internal electrode patterns 22 and 23, for example, Ni, Cu, Ag, Pd, an Ag—Pd alloy, Au, or an alloy mainly containing any one of them is used. The thicknesses of the internal electrode patterns 22 and 23 are preferably set to be 0.3 to 2.0 μm after firing.

  The above ceramic green sheets 20a to 20j are laminated to form a ceramic laminate as shown in FIG. At this time, if necessary, the ceramic laminate may be pressed in the stacking direction by an isostatic press or the like. Next, after cutting the ceramic laminate into a predetermined size, barrel polishing is performed to form roundness at the corners and ridges of the ceramic laminate. Next, the ceramic laminate is fired. The firing temperature depends on the materials of the ceramic green sheets 20a to 20j and the internal electrode patterns 22 and 23, but is preferably 900 to 1300 ° C. Thus, the ceramic body 2 is formed.

  Next, a conductive paste for external electrodes is applied to both ends of the ceramic body 2 by a printing method or the like, and baked at a temperature of 700 to 900 ° C. to form the external electrodes 3 and 4. The external electrode 3 is bonded to one end of the internal electrode pattern 22, and the external electrode 4 is bonded to one end of the internal electrode pattern 23. As a material of the external electrodes 3 and 4, for example, Ni, Cu, or an alloy mainly containing any one of them is used. At this time, the baking atmosphere is an oxidizing atmosphere, the combustion efficiency of the binder (resin component) in the conductive paste for external electrodes is increased, the sintering of the external electrodes 3 and 4 is advanced, and the external electrodes 3 and 4 are densified. The thickness (thickest part) of the external electrodes 3 and 4 is preferably set to be 10 to 50 μm. In addition, before baking a ceramic laminated body, the method of apply | coating the electrically conductive paste for external electrodes to a ceramic laminated body, and baking the external electrodes 3 and 4 simultaneously with baking of a ceramic laminated body may be sufficient.

  Next, an alternating current is passed between the external electrodes 3 and 4 of the ceramic body 2, and the external electrodes 3 and 4 are burned on the joints between the internal electrode patterns 22 and 23 and the external electrodes 3 and 4. The resulting oxide film is removed. At this time, the alternating current is preferably a high-frequency current of 0.1 mA or more. Thereby, an alternating current sufficiently flows through the junction between the external electrodes 3 and 4 and the internal electrode patterns 22 and 23, and the oxide film generated at the junction between the external electrodes 3 and 4 and the internal electrode patterns 22 and 23 is surely obtained. Destroyed. The upper limit of the alternating current is preferably 10 mA. This is because when the alternating current exceeds 10 mA, the capacitor 10 generates abnormal heat, resulting in a short circuit failure.

  Next, the ceramic body 2 on which the external electrodes 3 and 4 are formed is subjected to physical surface treatment such as barrel polishing or chemical surface treatment such as etching, so that the external electrodes 3 and 4 are baked. The oxide film formed on the surface of the external electrodes 3 and 4 is removed. Thereafter, a plating layer is formed on the surfaces of the external electrodes 3 and 4. As a material for the plating layer, for example, Ni, Cu, Ag, Pd, Ag-Pd, Au, or an alloy containing any one of them as a main component is used. The thickness per one plating layer is preferably set to be 1 to 10 μm. Furthermore, a conductive resin layer for stress relaxation may be formed between the external electrodes 3 and 4 and the plating layer.

  According to the manufacturing method of the ceramic capacitor 10 described above, an alternating current flows between the external electrodes 3 and 4 and the internal electrode patterns 22 and 23 by flowing an alternating current between the external electrodes 3 and 4. The oxide film formed at the joint between the external electrodes 3 and 4 and the internal electrode patterns 22 and 23 during the baking of 3 and 4 can be destroyed. Conduction between them can be ensured. As a result, excellent electrical characteristics (capacitance, dielectric loss, etc.) can be obtained even with the ceramic capacitor 10 having the external electrodes 3 and 4 made of base metals that are easily oxidized when baked in an oxidizing atmosphere.

  Moreover, since the external electrodes 3 and 4 are formed by baking in an oxidizing atmosphere, the external electrodes 3 and 4 can be formed densely, and the water resistance performance and the plating solution performance can be improved. Furthermore, it is not necessary to bake the external electrodes 3 and 4 while switching between the oxidizing atmosphere and the reducing atmosphere, management of the baking conditions becomes simple and easy, and variations in the electrical characteristics of the ceramic capacitor 10 due to variations in atmosphere are less likely to occur.

  In addition, this invention is not limited to the said embodiment, In the range of the summary, it changes variously. The ceramic body does not necessarily need to be a laminated body composed of a plurality of ceramic sheets, and may be an integral bulk.

A ceramic capacitor sample was prepared by the following manufacturing method, and the electrical characteristics and the like were evaluated. That is, an internal electrode pattern mainly composed of Ni was formed on a ceramic green sheet having a relative dielectric constant (εr) mainly composed of CaZrO ₃ and a thickness of 20 μm by a printing method. Thereafter, several ceramic green sheets were stacked, and further, ceramic green sheets for outer layers were stacked and pressure-bonded to obtain a ceramic laminate. And after degreasing | defatting this ceramic laminated body at 270 degreeC, it baked at 1250-1350 degreeC and it was set as the ceramic body.

  Next, Cu paste was applied to the fired ceramic body and baked to form external electrodes. At this time, the Cu paste was baked in two types of atmospheres, a reducing atmosphere and an oxidizing atmosphere. Thereafter, a Ni layer and a Sn layer were sequentially formed on the surface of the external electrode by electrolytic plating.

  In the ceramic capacitor thus obtained, the ceramic capacitor in which the external electrode Cu paste was baked in a reducing atmosphere had a capacitance of 1000 pF (Q> 1000) as designed. Q is the reciprocal of tan δ, and the larger the value, the lower the equivalent series resistance at the junction between the external electrode and the internal electrode pattern. However, the ceramic capacitor in which the external electrode Cu paste is baked in an oxidizing atmosphere results in poor electrical connection due to the oxide film formed at the joint between the external electrode and the internal electrode pattern. The electrical characteristics were as follows. The electrical characteristics after applying a high frequency voltage of 630 Vp-p (300 kHz) for 10 hours between a pair of external electrodes of the ceramic capacitor with poor electrical connection are shown in “After high frequency application” in Table 1. From Table 1, it is recognized that by applying a high frequency voltage, all of the three ceramic capacitors have electrical characteristics of a non-defective product level (about 1000 pF, Q> 1000).

  In this embodiment, a high-frequency voltage of 630 Vp-p (300 kHz) is applied between the pair of external electrodes of the ceramic capacitor, but the point of improving the junction between the external electrode and the internal electrode pattern is the alternating current value ( 2πfCV, f: frequency, C: capacitance, V: voltage). Table 2 shows the relationship between the AC current value and the joint improvement property. The alternating current values in Table 2 are current values per ceramic capacitor. From Table 2, it is recognized that the alternating current is preferably a high-frequency current of 0.1 mA or more.

2 Ceramic body 3, 4 External electrode 5, 6 Metal terminal 10 Ceramic capacitor

Claims (3)

A ceramic body, a first external electrode and a second external electrode provided on an outer surface of the ceramic body, and a first body provided in the ceramic body and joined to the first external electrode A method of manufacturing a ceramic capacitor having an internal electrode and a second internal electrode joined to the second external electrode,
A high-frequency alternating current of 0.1 mA or more is allowed to flow between the first external electrode and the second external electrode, and a junction between the first external electrode and the first internal electrode, the second external electrode, A method for producing a ceramic capacitor, comprising a step of removing oxide films respectively formed at joint portions with a second internal electrode. The method of manufacturing a ceramic capacitor according to claim 1, wherein the first external electrode and the second external electrode are baked in an oxidizing atmosphere. The method for manufacturing a ceramic capacitor according to claim 1, wherein the first external electrode and the second external electrode are made of a base metal.

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