Ceramic electronic component and manufacturing method therefor

Abstract

A ceramic electronic component includes a ceramic body, baked external electrodes, and plated external electrodes, and glass layers derived from a glass material included in a conductive paste of the baked external electrodes, are provided at interfaces between the baked external electrodes and the ceramic body, such that the glass layers extend from the interfaces between the ceramic body and the baked external electrodes to a surface of the ceramic body that does not contain the baked external electrodes.

Claims

1. A ceramic electronic component comprising: a ceramic body; a baked external electrode including a baked conductive paste including a conductive material and a glass material on the ceramic body; and a plated external electrode plated on a surface of the baked external electrode; wherein a glass layer derived from the glass material included in the conductive paste is provided at an interface between the baked external electrode and the ceramic body; the ceramic body has a first basicity; the glass material included in the conductive paste has a second basicity; a difference between the first basicity and the second basicity has an absolute value of about 0.21 or less; and the glass layer extends from the interface between the ceramic body and the baked external electrode to a surface of the ceramic body that does not contain the baked external electrode.

2. The ceramic electronic component according to claim 1, wherein the glass layer extending on the surface of the ceramic body extends about 10 μm or more from an outer edge of the baked external electrode, and the outer edge of the baked external electrode does not contact with the surface of the ceramic body over an entire periphery.

3. The ceramic electronic component according to claim 1, wherein the conductive material comprises at least one of Cu, an alloy containing Cu, Ag, an alloy containing Ag, Pd, and an alloy containing Pd.

4. The ceramic electronic component according to claim 1, wherein the ceramic electronic component is one of an NTC thermistor and a PTC thermistor.

5. The ceramic electronic component according to claim 1, wherein the plated external electrode includes two plated layers.

6. The ceramic electronic component according to claim 1, wherein the plated external electrode includes a Ni plated external electrode plated on the baked external electrode.

7. The ceramic electronic component according to claim 6, further comprising an Sn plated external electrode plated on the Ni plated external electrode.

8. The ceramic electronic component according to claim 1, wherein the ceramic body includes internal electrodes connected to the plated external electrode.

9. A method for manufacturing a ceramic electronic component, the method comprising the steps of: firing a ceramic body; applying a conductive paste including a conductive material and a glass material to the ceramic body; baking the applied conductive paste to form a baked external electrode on the ceramic body, and forming a glass layer derived from the glass material included in the conductive paste, to extend between an interface between the baked external electrode and the ceramic body, and from the interface to a surface of the ceramic body that does not contain the baked external electrode; and forming a plated external electrode on a surface of the baked external electrode; wherein the ceramic body has a first basicity; the glass material included in the conductive paste has a second basicity; and a difference between the first basicity and the second basicity has an absolute value of about 0.21 or less.

10. The method for manufacturing a ceramic electronic component according to claim 9, wherein the glass layer extending on the surface of the ceramic body extends about 10 μm or more from an outer edge of the baked external electrode, and the outer edge of the baked external electrode is not brought into contact with the surface of the ceramic body over an entire periphery.

11. The method for manufacturing a ceramic electronic component according to claim 9, wherein a temperature of baking the conductive paste is about 30° C. or more higher than a softening point of the glass material included in the conductive paste.

12. The method for manufacturing a ceramic electronic component according to claim 9, wherein the glass layer has a solubility in plating solution of about 3.3% or less after immersion for about 5 hours in a plating solution for use in the step of forming the plated external electrode.

13. The method for manufacturing a ceramic electronic component according to claim 9, wherein the ceramic electronic component is one of an NTC thermistor and a PTC thermistor.

14. The method for manufacturing a ceramic electronic component according to claim 9, wherein the plated external electrode includes two plated layers.

15. The method for manufacturing a ceramic electronic component according to claim 9, wherein the plated external electrode includes a Ni plated external electrode plated on the baked external electrode.

16. The method for manufacturing a ceramic electronic component according to claim 15, further comprising an Sn plated external electrode plated on the Ni plated external electrode.

17. The method for manufacturing a ceramic electronic component according to claim 9, wherein the ceramic body includes internal electrodes connected to the plated external electrode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross-sectional view illustrating a ceramic electronic component 100 according to a first preferred embodiment of the present invention.

(2) FIG. 2 is a scanning electron micrograph (SEM) of the ceramic electronic component 100 from above.

(3) FIGS. 3A to 3C are respectively cross-sectional views illustrating steps that are applied in an example of a method for manufacturing the ceramic electronic component 100.

(4) FIGS. 4D and 4E, following FIGS. 3A-3C, are respectively cross-sectional views illustrating steps that are applied in an example of a method for manufacturing the ceramic electronic component 100.

(5) FIG. 5 is a graph showing two types of baking profiles in a step of baking a conductive paste for baked external electrodes of the ceramic electronic component 100 shown in FIG. 3C.

(6) FIG. 6 is a cross-sectional view illustrating a ceramic electronic component 200 according to a second preferred embodiment of the present invention.

(7) FIGS. 7A to 7G are respectively perspective views illustrating steps that are applied in a method for manufacturing a conventional electronic component 300.

(8) FIGS. 8A to 8G are respectively perspective views illustrating steps that are applied in a method for manufacturing a conventional electronic component 400.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) Preferred embodiments of the present invention will be described below with reference to the drawings.

First Preferred Embodiment

(10) FIG. 1 is a cross-sectional view illustrating a ceramic electronic component 100 according to a first preferred embodiment of the present invention. In addition, FIG. 2 is a scanning electron micrograph of the ceramic electronic component 100 from above. It is to be noted that the appearance configurations of the ceramic electronic components 100 shown in FIGS. 1 and 2 fail to conform with each other, because scales on external electrode portions, etc. are adjusted (exaggeratingly shown) in FIG. 1 for the sake of illustration.

(11) In the present preferred embodiment, the ceramic electronic component 100 is an NTC thermistor, that is, a thermistor with a negative temperature coefficient of resistance. However, the ceramic electronic component 100 is not to be considered limited to any NTC thermistor.

(12) The ceramic electronic component 100 preferably has a size of, for example, 0.5 mm in width, 0.5 mm in height, and 1.0 mm in length.

(13) The ceramic electronic component 100 includes a ceramic body 1. The ceramic electronic component 100 according to the present preferred embodiment includes internal electrodes 2 laminated within the ceramic body 1. It is to be noted that while the ceramic electronic component 100 includes the internal electrodes 2 laminated within the ceramic body 1, the internal electrodes 2 are not essential to the ceramic electronic component 100 according to a preferred embodiment of the present invention, but a ceramic body may be used which includes no internal electrodes 2. In addition, when the internal electrodes 2 are laminated within the ceramic body 1, the number of layers is arbitrary.

(14) A conductive paste for external electrodes is applied to both ends of the ceramic body 1, and baked to form a pair of baked external electrodes 3. The baked external electrodes 3 are each connected to predetermined internal electrodes 2. In connection portions between the internal electrodes 2 and the baked external electrodes 3, a conductive material included in the internal electrodes 2 and a conductive material included in the baked external electrodes 3 diffuse mutually.

(15) Glass layers 4 derived from a glass material (glass frit) contained in the conductive paste for the formation of the bake external electrodes 3 are located at the interfaces between the ceramic body 1 and the baked external electrodes 3.

(16) The glass layers 4 include glass layer extensions 4a that extend from the interfaces between the ceramic body 1 and the baked external electrodes 3 to the surface of the ceramic body 1 that does not contain the baked external electrodes 3. It is to be noted that preferably, the glass layer extensions 4a preferably extend about 10 μm or more from outer edges of the baked external electrodes 4, and the outer edges of the baked external electrodes 3 are not brought into contact with the surface of the ceramic body 1 over the entire periphery. This is because the glass layer extensions 4a ensure the protection of the ceramic body 1 near the outer edges of the baked external electrodes 3 in the formation of Ni plated external electrodes 5 and Sn plated external electrodes 6 as will be described later in this case.

(17) The glass layers 4, which are derived from the glass material contained in the conductive paste used for the formation of the baked external electrodes 3, may contain a glass material (component) contained in, e.g., the ceramic body 1 (the ceramic material used for the formation of the ceramic body 1) in some cases, and the cases also fall within the scope of the present invention.

(18) Ni plated external electrodes 5 are located on the surfaces of the baked external electrodes 3.

(19) Sn plated external electrodes 6 are located on the surfaces of the Ni plated external electrodes 5.

(20) The ceramic electronic component 100 according to the present preferred embodiment, which is structured as described above, is manufactured by a method as shown in, for example, FIGS. 3A through 4E.

(21) First, the ceramic body 1 with the internal electrodes 2 laminated therein is prepared as shown in FIG. 3A.

(22) Specifically, first, predetermined starting raw materials are mixed in predetermined proportions to obtain a raw material.

(23) While the composition of the ceramic constituting the ceramic body 1 prepared is arbitrarily specified, starting raw materials are selected so as to provide a desired ceramic composition, and mixed in predetermined proportions to obtain a raw material.

(24) For example, the compositions (compositional systems) of samples C-1 to C-4 as shown in Table 1 can be adopted as the composition of the ceramic constituting the ceramic body 1.

(25) TABLE-US-00001 TABLE 1 Compositional System and Basicity of Ceramic constituting Ceramic Body Sample Compositional Number System First Basicity B.sub.1 C-1 Mn—Ni—Fe 0.46 C-2 Mn—Ni—Al 0.44 C-3 Mn—Ni—Fe—Ti 0.48 C-4 Mn—Ni—Co—Al 0.38

(26) For example, the sample C-1 refers to a ceramic for Mn—Ni—Fe based NTC thermistor.

(27) In order to obtain the ceramic of the sample C-1 for Mn—Ni—Fe based NTC thermistor, for example, Mn.sub.3O.sub.4, NiO, and Fe.sub.2O.sub.3 can be used for starting raw materials, and mixed in predetermined proportions to obtain the raw material.

(28) Likewise, the samples C-2, C-3, and C-4 refer to a ceramic for Mn—Ni—Al based NTC thermistor, a ceramic for Mn—Ni—Fe—Ti based NTC thermistor, and a ceramic for Mn—Ni—Co—Ti based NTC thermistor, and for each of the ceramics, starting raw materials can be selected, and mixed in predetermined proportions to obtain the raw material.

(29) Each ceramic used to form the ceramic body 1 has a basicity. In the present preferred embodiment, the basicity of the ceramic constituting the fired ceramic body 1 is referred to as a first basicity, and denoted by a symbol B.sub.1.

(30) The ceramics according to the samples C-1 to C-4, subjected to firing, each have the first basicity B.sub.1 as listed in Table 1. For example, for the ceramic according to the sample C-1, mixing the Mn.sub.3O.sub.4, NiO, and Fe.sub.2O.sub.3 in the predetermined proportions has resulted in a first basicity B.sub.1 of about 0.46, for example. Similarly, the ceramic according to the sample C-2 has achieved a first basicity B.sub.1 of about 0.44, for example. The ceramic according to the sample C-3 has achieved a first basicity B.sub.1 of about 0.48, for example. The ceramic according to the sample C-4 has achieved a first basicity B.sub.1 of about 0.38, for example.

(31) Next, the above-described raw materials are subjected to calcination, and subjected to grinding to obtain calcined powders.

(32) Next, the calcined powder and an organic vehicle are mixed in predetermined proportions to obtain ceramic slurry. In this regard, a plasticizer, a dispersant, etc. are also mixed, if necessary.

(33) Next, the ceramic slurry is subjected to sheet forming by a doctor blade method or the like, thus providing ceramic green sheets.

(34) Next, the ceramic green sheets are subjected to punching into rectangular or substantially rectangular plates.

(35) Next, if necessary, a conductive paste for internal electrodes is applied in predetermined shapes to the predetermined ceramic green sheets obtained by the punching, thus forming electrode patterns.

(36) The conductive paste for internal electrodes preferably includes at least one conductive material of, for example, Cu, an alloy containing Cu, Ag, an alloy containing Ag, Pd, an alloy containing Pd, or the like; and an organic vehicle.

(37) Next, the ceramic green sheets with the electrode patterns formed thereon and the ceramic green sheets without any electrode pattern formed thereon are stacked in predetermined order to reach a predetermined number of sheets, and brought into pressurization to obtain an unfired mother laminated body.

(38) Next, the unfired mother laminated body is cut into the form of a chip to obtain an unfired ceramic body.

(39) Next, the unfired ceramic body is subjected to firing in accordance with a predetermined profile to obtain the ceramic body 1. Then, if necessary, the ceramic body 1 is subjected to barrel polishing.

(40) On the other hand, a conductive paste for baked external electrodes is prepared separately from the ceramic body 1.

(41) The conductive paste for baked external electrodes includes a conductive material, glass frit, and an organic vehicle. The conductive paste for baked external electrodes may further include another minute amount of aid, if necessary, and may include unintended impurities.

(42) The conductive material may preferably include at least one of, for example, Cu, an alloy containing Cu, Ag, an alloy containing Ag, Pd, and an alloy containing Pd.

(43) As the glass frit, five types of glass frits according to samples G-1 to G-5 as shown in Tables 2 and 3 were prepared in the present preferred embodiment.

(44) Table 2 shows compositions for each glass frit. Table 3 shows details of alkali metals and alkaline-earth metals in each glass frit. It is to be noted that in Table 2, the amount of BaO is not included in the alkaline-earth metals, because the BaO is listed separately.

(45) TABLE-US-00002 TABLE 2 Composition of Glass Frit ZrO Alkali Alkaline-Earth Sample Al.sub.2O.sub.3 B.sub.2O.sub.3 BaO CuO SiO.sub.2 TiO.sub.2 ZnO (weight Metal Metal* Number (weight %) (weight %) (weight %) (weight %) (weight %) (weight %) (weight %) %) (weight %) (weight %) G-1 6.9 15.1 49.4 6.1 17.7 4.8 G-2 4.1 17 5.7 50.4 2.1 3 6.5 11.2 G-3 5.7 16.3 24.2 4.8 26.6 0.8 13.3 2.1 4.4 1.8 G-4 1.3 42.4 4.8 8.8 2.8 31.6 8.3 G-5 2.5 26.0 32.5 24.3 4.8 9.9 Softening Point ST Solubility in Sample Number (° C.) Plating Solution** (%) Second Basicity B.sub.2 G-1 529 1.1 0.7 G-2 581 0.9 0.4 G-3 583 1.0 0.5 G-4 546 3.3 0.5 G-5 820 10.7 0.4 *The alkaline-earth metals do not include the BaO stated separately. **The solubility in plating solution refers to the solubility in the case of immersion for 5 hours in the Ni plating solution used.

(46) TABLE-US-00003 TABLE 3 Compositional Details of Glass Frit (on Alkali Metals and Alkaline-Earth Metals) Alkali Metal Alkaline-Earth Metal Sample Na.sub.2O K.sub.2O Li.sub.2O Total CaO SrO Total Number (weight %) (weight %) (weight %) (weight %) (weight %) (weight %) (weight %) G-1 0.0 4.5 0.3 4.8 G-2 7.8 3.4 11.2 0.0 G-3 3.1 1.4 4.4 1.84 1.8 G-4 6.4 1.9 8.3 0.0 G-5 4.8 4.8 9.9 9.9

(47) For example, the glass frit according to the sample G-1 contains 6.9 weight % of Al.sub.2O.sub.3, 15.1 weight % of B.sub.2O.sub.3, 49.4 weight % of BaO, 6.1 weight % of SiO.sub.2, 17.7 weight % of ZnO, and 4.8 weight % of alkaline-earth metals, as shown in Table 2. The glass frit according to the sample G-1 contains no alkali metal. The alkaline-earth metals include 4.5 weight % of Ca and 0.3 weight % of SrO as shown in FIG. 3.

(48) Similarly, the glass frits according to the samples G-2 to G-5 are each composed of the composition shown in Tables 2 and 3.

(49) The glass frit according to the samples G-1 to G-5 preferably has a size on the order of about 1.4 μm to about 2.1 μm in average particle size in the form of milled powder.

(50) Each of the glass frit G-1 to G-5 has a softening point (° C.), solubility in plating solution (%), and basicity. It is to be noted that the basicity of the glass frit included in the conductive paste for baked external electrodes is referred to as a second basicity and denoted by a symbol B.sub.2 in the present preferred embodiment. In addition, hereinafter, the softening point (° C.) of the glass frit may be denoted by a symbol ST.

(51) For example, for the glass frit according to the sample G-1, the softening point ST is 529° C., the solubility in plating solution is 1.1%, and the second basicity B.sub.2 has a value of 0.65.

(52) The solubility in plating solution was determined by how much the weight of baked glass was decreased with respect to the initial value, after each glass frit was kneaded with an organic vehicle, applied onto an alumina plate, baked, and immersed for 5 hours in a plating solution for the formation of plated external electrodes (when the plated external electrodes are each composed of multiple layers, a plating solution for the formation of plated external electrodes for first layers; a Ni plating solution in the present preferred embodiment) as will be described later.

(53) For example, the composition shown in Table 4 can be used as the organic vehicle in the conductive paste for external electrodes according to the present preferred embodiment.

(54) TABLE-US-00004 TABLE 4 Composition of Organic Vehicle Resin Acrylic Alkyd Sample Resin Resin Solvent Number (12 × 10.sup.4) (8 × 10.sup.3) Terpineol V-1 15 weight % 5 weight % 80 weight %

(55) For example, this organic vehicle contains: 15 weight % of an acrylic resin with a weight average molecular weight of 12×10.sup.4; 5 weight % of an alkyd resin with a weight average molecular weight of 8×10.sup.3; and 80 weight % of terpineol as a solvent.

(56) The above-mentioned conductive material, glass frit, and organic vehicle are compounded, along with aids, if necessary, so as to provide a predetermined composition. Subsequently, the compounded materials are kneaded and dispersed with a triple roll mill to prepare a conductive paste for baked external electrodes.

(57) Next, as shown in FIG. 3B, a conductive paste 3′ for baked external electrodes is applied to both ends of the ceramic body 1. The application can be achieved by, for example, a dip method.

(58) Next, the applied conductive paste 3′ for baked external electrodes is baked onto the ceramic body 1, for example, in a tunnel furnace subjected to atmosphere control with the use of a mixed gas of N.sub.2—H.sub.2—O.sub.2, for example, in accordance with a profile with a maximum temperature of 830° C. (solid line) or a profile with a maximum temperature of 850° C. (dashed line) as shown in FIG. 5. It is to be noted that hereinafter, the maximum temperature of the baking profile for the conductive paste for baked external electrodes may be denoted by a symbol BT.

(59) As a result, as shown in FIG. 3C, a pair of baked external electrodes 3 is formed on both ends of the ceramic body 1. The baked external electrodes 3 are each connected to predetermined internal electrodes 2. In connection portions between the internal electrodes 2 and the baked external electrodes 3, a conductive material included in the internal electrodes 2 and a conductive material included in the baked external electrodes 3 diffuse mutually.

(60) Furthermore, the glass layers 4 derived from the glass material contained in the conductive paste for the formation of the bake external electrodes 3 are formed at the interfaces between the ceramic body 1 and the baked external electrodes 3.

(61) In addition, the glass layers 4 include the glass layer extensions 4a from the interfaces between the ceramic body 1 and the baked external electrodes 3 to the surface of the ceramic body 1 that does not contain the baked external electrodes 3. The extended lengths of the glass layer extensions 4a are preferably longer in order to protect, from plating solutions, the ceramic body 1 just below outer edges of the baked external electrodes 3. It is to be noted that the extended lengths of the glass layer extensions 4a are affected mainly by the composition of the glass frit contained in the conductive paste for baked external electrodes, the maximum temperature in the case of baking the conductive paste for baked external electrodes, and the period of time for keeping at a temperature equal to or higher than the softening point of the glass frit. When the maximum temperature BT of the baking profile is about 30° C. or more higher than the softening point ST of the glass frit contained in the conductive paste, for example, the extended lengths of the glass layer extensions 4a can be about 10 μm or more in the case of many types of glass frits, for example.

(62) The glass layers 4, which are derived from the glass material contained in the conductive paste for baked external electrodes, may contain a glass material (component) contained in, e.g., the ceramic material used for the formation of the ceramic body 1 in some cases, and the cases also fall within the scope of the present invention.

(63) Next, as shown in FIG. 4D, the Ni plated external electrodes 5 are formed on the surfaces of the baked external electrodes 3 by a method that is used commonly in the process of manufacturing a chip ceramic electronic component. Subsequently, as shown in FIG. 4E, the Sn plated external electrodes 6 are formed on the surfaces of the Ni plated external electrodes 5 similarly by a method that is used commonly in the process of manufacturing a chip ceramic electronic component, thus completing the ceramic electronic component 100 according to the present preferred embodiment. In the formation of the Ni plated external electrodes 5 and Sn plated external electrodes 6, the presence of the glass layer extensions 4a keeps a portion of the ceramic body 1 just below the outer edges of the baked external electrodes 3 from being eroded by plating solutions. In addition, the presence of the glass layer extensions 4a prevents the external electrodes from being short-circuited by any plated film attached on the surface of the ceramic body 1.

Second Preferred Embodiment

(64) FIG. 6 shows a cross-sectional view of a ceramic electronic component 200 according to a second preferred embodiment of the present invention.

(65) The ceramic electronic component 200 differs, as compared with the ceramic electronic component 100 according to the first preferred embodiment as shown in FIG. 1, in that no internal electrode is provided within the ceramic body 11. The other configuration of the ceramic electronic component 200 is the same as the ceramic electronic component 100. It is to be noted that the ceramic body 11 is brought into contact with (electrically connected to) baked external electrodes 3 through portion that form no glass layer (not shown), which are generated in the form of, for example, balls, in glass layers 4 present at the interfaces between both the body and electrodes in the ceramic electronic component 200.

(66) It is to be noted that in order not to form any internal electrode within the ceramic body 11 like the ceramic electronic component 200, only ceramic green sheets without any electrode pattern for defining an internal electrode may be stacked when ceramic green sheets are stacked, and brought into pressurization to prepare an unfired mother laminated body.

(67) The structure of the ceramic electronic component 100 according to the first preferred embodiment, an example of a manufacturing method therefor, and the structure of the ceramic electronic component 200 according to the second preferred embodiment have been described above. However, the present invention is not to be considered limited to the foregoing content, but various changes, modifications, combinations, and variations can be made within the scope of the present invention.

(68) For example, while NTC thermistors have been presented as the ceramic electronic component 100 according to the first preferred embodiment and the ceramic electronic component 200 according to the second preferred embodiment, the types of the ceramic electronic components are not limited to the NTC thermistors, but may be PTC thermistors or other ceramic electronic components.

EXAMPLE

(69) Examples of eleven types of ceramic electronic components (NTC thermistors) according to samples 1 to 11 as shown in Table 5 were produced. The same structure as the ceramic electronic component 100 according to the first preferred embodiment as shown in FIG. 1 was adopted for the structures of the ceramic electronic components according to the samples 1 to 11. In addition, the methods for manufacturing the ceramic electronic components according to the samples 1 to 11 relied on the same manufacturing method as the method for manufacturing the ceramic electronic component 100 according to the first preferred embodiment as shown in FIGS. 3A through 4E. It is to be noted that fifty pieces were produced for each of the ceramic electronic components according to the samples 1 to 11.

(70) TABLE-US-00005 TABLE 5 Composition of Conductive Paste for External Electrode and Composition, Evaluation, etc. of Ceramic Body Composition of Conductive Paste for Baked External Electrode Difference Evaluation Glass Frit Baking between Baked Excess (Second Maximum Maximum Reaction Composition Basicity B.sub.2) Organic Temperature Temperature Presence or Plating between of Ceramic (Softening Point ST) Conductive Vehicle for Baked and Softening Absence of Solution Glass Body (Solubility in Material 70.3 External Temperature |ΔB| Glass Layer Resistance Material and Sample (First Plating Solution) 4.5 volume Electrode of Glass Frit (|B.sub.1 − Extention of Glass Ceramic Number Basicity B.sub.1) 25.2 volume % volume % % (BT) (BT − ST) B.sub.2|) Formed Layer Body 1 C-1 G-1 Cu V-1 830° C. 301° C. 0.19 ◯ ◯ ◯ (0.46) (0.65) (529° C.) (1.1%) 2 C-1 G-2 Cu V-1 830° C. 250° C. 0.06 ◯ ◯ ◯ (0.46) (0.40) (581° C.) (0.9%) 3 C-1 G-3 Cu V-1 830° C. 247° C. 0.01 ◯ ◯ ◯ (0.46) (0.45) (583° C.) (1.0%) 4 C-1 G-4 Cu V-1 830° C. 284° C. 0.01 ◯ ◯ ◯ (0.46) (0.47) (546° C.) (3.3%) 5 C-1 G-5 Cu V-1 830° C.  10° C. 0.11 X Evaluation ◯ (0.46) (0.35) impossible (820° C.) (10.7%) 6 C-2 G-1 Cu V-1 830° C. 301° C. 0.21 ◯ ◯ ◯ (0.44) (0.65) (529° C.) (1.1%) 7 C-3 G-1 Cu V-1 830° C. 301° C. 0.17 ◯ ◯ ◯ (0.48) (0.65) (529° C.) (1.1%) 8 C-4 G-1 Cu V-1 830° C. 301° C. 0.27 ◯ ◯ Δ (0.38) (0.65) (the ceramic (529° C.) may have a (1.1%) crack defect or the like caused) 9 C-1 G-5 Cu V-1 850° C.  30° C. 0.11 ◯ Δ ◯ (0.46) (0.35) (the ceramic (820° C.) body may be (10.7%) eroded just below outer edges of the baked external electrodes) 10 C-1 G-1 Ag V-1 830° C. 301° C. 0.19 ◯ ◯ ◯ (0.46) (0.65) (529° C.) (1.1%) 11 C-1 G-1 Ag/Pd = V-1 830° C. 301° C. 0.19 ◯ ◯ ◯ (0.46) (0.65) 95/5 (529° C.) (1.1%)

(71) For the ceramic bodies, the four types of ceramic bodies were prepared according to the samples C-1 to C-4 as shown in Table 1. The ceramic bodies according to the samples C-1 to C-4 each have the first basicity B.sub.1. Specifically, the first basicity B.sub.1 of the ceramic according to the sample C-1 is about 0.46, for example. The first basicity B.sub.1 of the ceramic according to the sample C-2 is about 0.44, for example. The first basicity B.sub.1 of the ceramic according to the sample C-3 is about 0.48, for example. The first basicity B.sub.1 of the ceramic according to the sample C-4 is about 0.38, for example.

(72) The conductive paste for baked external electrodes includes glass frit, a conductive material, and an organic vehicle. In the present example, the glass frit, the conductive material, and the organic vehicle were compounded respectively in the proportions of about 25.2 volume %, about 4.5 volume %, and about 70.3 volume %.

(73) For the glass frit, the five types of glass frits were prepared according to samples G-1 to G-5 as shown in Tables 2 and 3. Each glass frit according to the samples G-1 to G-5 has a second basicity B.sub.2, a softening point ST, and solubility in plating solution.

(74) For example, the second basicity B.sub.2 of the glass frit according to the sample G-1 is 0.65, the softening point ST thereof is 529° C., and the solubility thereof in plating solution is 1.1%. The glass frits according to the samples G-2 to G-5 have second basicities B.sub.2, softening points ST, and solubility in plating solution as listed in Table 2.

(75) For the conductive material, three types of materials: Cu; Ag; and an alloy of Ag and Pd (Ag is 95 weight %, Pd is 5 weight %) were prepared.

(76) For the organic vehicle, the organic vehicle of sample number V-1 was prepared as shown in Table 4.

(77) The conductive paste for baked external electrodes was baked onto the ceramic body in accordance with either the profile with the maximum temperature BT of 830° C. (solid line) or the profile with the maximum temperature BT of 850° C. (dashed line) as shown in FIG. 5.

(78) The ceramic electronic components according to each of the samples 1 to 11 prepared were evaluated for: “Presence or Absence of Glass Layer Extension Formed”, that is, whether glass layer extensions were formed or not; “Plating Solution Resistance of Glass Layer”, that is, whether the surface of the ceramic body just below outer edges of the baked external electrodes were eroded or not after the formation of the plated external electrodes; and “Excess Reaction between Glass Material and Ceramic Body”, that is, whether the ceramic body was damaged or not in baking the conductive paste for baked external electrodes onto the ceramic body.

(79) The inventors have discovered that the “Presence or Absence of Glass Layer Extension Formed” is affected by the relationship between the maximum temperature BT in the case of baking the conductive paste for baked external electrodes and the softening point ST of the glass material (glass frit) included in the conductive paste for baked external electrodes.

(80) In addition, the inventors have discovered that the “Plating Solution Resistance of Glass Layer” is affected by the solubility in plating solution, of the glass material (glass frit) included in the conductive paste for baked external electrodes.

(81) In addition, the inventors have discovered that the “Excess Reaction between Glass Material and Ceramic Body” is affected by the relationship between the basicity (first basicity B.sub.1) of the ceramic body and the basicity (second basicity B.sub.2) of the glass material (glass frit) included in the conductive paste for baked external electrodes.

(82) Explanations will be given below in order.

(83) First, as for “Presence or Absence of Glass Layer Extension”, a case where glass layer extensions of 10 μm or more in length were formed from the outer edges of the baked external electrodes was regarded as “◯”, whereas a case where no glass layer extension was formed, or glass layers extensions were less than 10 μm, if any, was regarded as “×”. The glass layer extensions were distinguished between the lengths of 10 μm or more and the lengths less than 10 μm, depending on a separately obtained finding that the glass layer extensions protect the surface of the ceramic body just under the outer edges of the baked external electrodes from plating solutions as long as the extensions are 10 μm or more, while the protection is insufficient when the extensions are less than 10 μm.

(84) As can be seen from Table 5, the “Presence or Absence of Glass Layer Extension Formed” was regarded as “◯” in the ceramic electronic components according to samples 1 to 4 and 6 to 11 with a difference (BT−ST) of 30° C. or more between the maximum temperature BT in the case of baking the conductive paste for baked external electrodes and the softening point ST of the glass material included in the conductive paste for baked external electrodes. On the other hand, the “Presence or Absence of Glass Layer Extension Formed” was regarded as “×” in the ceramic electronic component according to a sample 5 with the difference of less than 30° C. (10° C.). From the foregoing, it has been determined that the difference (BT−ST) between the maximum temperature BT in the case of baking the conductive paste for baked external electrodes and the softening point ST of the glass material included in the conductive paste for baked external electrodes is preferably adjusted to about 30° C. or more in order to form glass layer extensions of about 10 μm or more, for example.

(85) As for the “Plating Solution Resistance of Glass Layer”, whether the surface of the ceramic body just below the outer edges of the baked external electrodes was eroded or not was checked after the formation of the plated external electrodes, and for each sample, a case where the pieces (fifty) were not eroded at all was regarded as “◯”, a case where some of the pieces were eroded was regarded as “Δ”, and a case where the pieces were all eroded was regarded as “×”.

(86) As can be seen from Table 5, the “Plating Solution Resistance of Glass Layer” was regarded as “◯” in the ceramic electronic components according to the samples 1 to 4, 6 to 8, 10, and 11 with the solubility in plating solution of 3.3% or less, of the glass material included in the conductive paste for baked external electrodes. The ceramic electronic component according to the sample 5 with the solubility in plating solution of 10.7% failed to form glass layer extensions in the first place, and it was impossible to make an evaluation of “Plating Solution Resistance of Glass Layer”. As for the ceramic electronic component according to the sample 9 with the solubility in plating solution of 10.7%, seventeen pieces were eroded among all the fifty pieces, and the “Plating Solution Resistance of Glass Layer” was thus regarded as “Δ”. It is to be noted that there was no sample with the “Plating Solution Resistance of Glass Layer” regarded as “×”. From the foregoing, it has been determined that the solubility in plating solution, of the glass material (glass frit) included in the conductive paste for baked external electrodes, is preferably adjusted to about 3.3% or less in order to protect, from plating solutions, the ceramic body just below the outer edges of the baked external electrodes.

(87) As for the “Excess Reaction between Glass Material and Ceramic Body”, it was checked whether surfaces of the ceramic body with the glass layers formed were broken or cracked by excess reaction between the glass material and the ceramic body or not, and for each sample, a case where the pieces (fifty) were not broken or cracked at all was regarded as “◯”, a case where some of the pieces were broken or cracked was regarded as “Δ”, and a case where the pieces were all broken or cracked was regarded as “×”.

(88) As can be seen from Table 5, in the ceramic electronic components according to the samples 1 to 7 and 9 to 11 with the absolute value (hereinafter, referred to as |ΔB|) of 0.21 or less for the difference (B.sub.1−B.sub.2) between the basicity (first basicity B.sub.1) of the ceramic body and the basicity (second basicity B.sub.2) of the glass material (glass frit) included in the conductive paste for baked external electrodes, the ceramic bodies were not broken or cracked, thus resulting in the “Excess Reaction between Glass Material and Ceramic Body” regarded as “◯”. As for the ceramic electronic component according to the sample 8 with the absolute value |ΔB| of 0.27, eight ceramic bodies were broken or cracked among all the fifty pieces, and the “Excess Reaction between Glass Material and Ceramic Body” was thus regarded as “Δ”. It is to be noted that there was no sample with the Excess Reaction between Glass Material and Ceramic Body” regarded as “×”.

(89) In this regard, the value B (basicity) will be outlined. The basicity of an oxide melt can be represented by an average oxygen ion activity (conceptual basicity) calculated from the composition of an intended system.

(90) The value B which is a basicity parameter is represented by the following formula (1).
B=Σn.sub.i.Math.B.sub.i  (1)

(91) In the formula (1), n.sub.i represents a cation fraction of a constituent i, and B.sub.i represents an oxygen donation ability of the constituent i. This B.sub.i is obtained from the following formulas (2) to (4).

(92) The M.sub.i-O bonding force of an oxide M.sub.iO can be represented by the attractive force A.sub.i between the cation and the oxygen ion. This A.sub.i is represented by the following formula (2).
A.sub.i=Z.sub.i.Math.Zo.sup.2−/(r.sub.i+ro.sup.2−).sup.2=2Z.sub.i/(r.sub.i+1.4).sup.2  (2)

(93) In this formula, Z.sub.i represents the valence of a cation from the constituent M.sub.i. In addition, r.sub.i represents a cation radius of the constituent M.sub.i, and the unit thereof is the angstrom. Zo.sup.2− represents the valence of an anion, and ro.sup.2− represents an anion radius.

(94) The oxygen donation ability B.sub.i.sup.0 of the oxide M.sub.iO as a single constituent is given by the reciprocal of A.sub.i, and thus represented by the following formula (3).
B.sub.i.sup.0≡1/A.sub.i  (3)

(95) In this regard, in order to deal with the oxygen donation ability B.sub.i.sup.0 ideologically and quantitatively, the obtained value B.sub.i.sup.0 is turned into an indicator. Specifically, the B.sub.i.sup.0 obtained from the above formula (3) is substituted into the following formula (4) for recalculation. This makes it possible to deal with the basicity quantitatively for all oxides. It is to be noted that when the B.sub.i.sup.0 is turned into an indicator, the B.sub.i of CaO and the B.sub.i of SiO.sub.2 are respectively defined as 1.000 (B.sub.i.sup.0=1.43) and 0.000 (B.sub.i.sup.0=0.41).
B.sub.i=(B.sub.i.sup.0−B.sub.SiO2.sup.0)/(B.sub.CaO.sup.0−B.sub.SiO2.sup.0)  (4)

(96) In this regard, when glass and ceramic are together subjected to firing, in general, as the absolute value (|ΔB|) is larger for the difference (B.sub.1−B.sub.2) in value B between the basicity (first basicity B.sub.1) of the ceramic and the basicity (second basicity B.sub.2) of the glass material, the glass is more likely to react with the ceramic, thus making a reaction layer more likely to be formed. Accordingly, it is theoretically possible to control the reactivity by the value of |ΔB|. However, in fact, the stronger reaction between the glass and the ceramic under the influence of the firing condition, etc. may lead to the ceramic altered, which is not theoretical.

(97) As described above, the ceramic body was not broken or cracked by excess reaction between the glass material and the ceramic body in the ceramic electronic component with the |ΔB| of about 0.21 or less, whereas the ceramic body was broken or cracked by excess reaction between the glass material and the ceramic body in the ceramic electronic component with the |ΔB| in excess of about 0.21 (for example, the ceramic electronic component according to the sample 8 with the |ΔB| of 0.27).

(98) Therefore, it has been determined that the |ΔB| is preferably adjusted to about 0.21 or less in order to prevent excess reaction between the glass material and the ceramic body.

(99) While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.