Patent Application
20250210265
The present invention relates to a multilayer ceramic electronic device.
Patent Document 1 discloses a multilayer ceramic electronic component having a structure in which, for example, a segregation phase containing Mg is formed in at least a part of an electrode missing portion. Having this structure, the multilayer ceramic electronic component with a high relative permittivity, less dielectric loss, and high reliability despite having a thin dielectric layer can be provided.
It is an object of the present invention to provide a multilayer ceramic electronic device with high moisture resistance.
To achieve the above object, a multilayer ceramic electronic device according to the present invention is
The dielectric layer may contain 0.40 mol or more and 0.80 mol or less Si oxide in terms of SiO2 with respect to 100 mol of the main component.
A segregate containing Mg and Si may be provided at an interface between the electrode layer and the dielectric layer and in a region comprised of the dielectric layer; and a coverage ratio of the electrode layer may be 80% or more and 100% or less.
The present invention is described below with reference to an embodiment illustrated in the drawings.
As shown in
The capacitor element body 10 may have any shape but normally has a rectangular parallelepiped shape as shown in
The dielectric layers 2 contain a main component represented by a formula ABO3 (A includes only Ba or includes Ba and at least one selected from the group consisting of Ca and Sr; and B includes only Ti or includes Ti and at least one selected from the group consisting of Zr and Hf) and further contain a Mn oxide, a Mg oxide, an R oxide, and a Zr oxide. The dielectric layers 2 further contain V. The dielectric layers 2 may further contain a Si oxide.
In the present embodiment, oxides include complex oxides. For example, Mn oxides include a complex oxide of Mn and another element. The Mn oxide, the Mg oxide, the R oxide, and the Si oxide may each be a simple oxide (oxide of a single metal element).
The dielectric layers 2 preferably contain barium titanate as a main component. Barium titanate is represented by a composition formula BamTiO2+m, where m satisfies 0.995≤m≤1.010. The following description is provided on the premise that the dielectric layers 2 contain barium titanate as a main component.
The Mn oxide content is 0.05 mol or more and 0.25 mol or less in terms of MnO with respect to 100 mol of the main component. In a situation where the dielectric layers 2 have too low a Mn oxide content, segregates containing Mg and Si described later are less readily generated, and a coverage ratio described later is readily decreased. Consequently, the multilayer ceramic capacitor 1 has lower moisture resistance. In a situation where the dielectric layers 2 have too high a Mn oxide content, the multilayer ceramic capacitor 1 has lower moisture resistance.
The Mg oxide content is 1.00 mol or more and 2.50 mol or less in terms of MgO with respect to 100 mol of the main component. The Mg oxide content may be 1.50 mol or more and 2.00 mol or less. In a situation where the dielectric layers 2 have too low or too high a Mg oxide content, the multilayer ceramic capacitor 1 has lower moisture resistance. In particular, a Mg oxide content of less than 1.50 mol readily impairs sintering stability of the dielectric layers 2. A Mg oxide content of above 2.00 mol readily decreases relative permittivity of the dielectric layers 2.
The R oxide content is 0.50 mol or more and 1.50 mol or less in terms of R2O3 with respect to 100 mol of the main component. The R oxide content may be 0.60 mol or more and 1.20 mol or less. In a situation where the dielectric layers 2 have too low or too high an R oxide content, the multilayer ceramic capacitor 1 has lower moisture resistance. An R oxide content of less than 0.60 mol readily decreases reliability of the multilayer ceramic capacitor 1. An R oxide content of above 1.20 mol readily decreases insulation resistance of the dielectric layers 2.
R includes at least one selected from the group consisting of Y, Gd, Tb, Dy, Ho, Yb, and Lu. R preferably includes at least one selected from the group consisting of Y, Dy, and Ho or more preferably includes Y or Dy.
The Zr oxide content is 0.05 mol or more and 0.45 mol or less in terms of ZrO2 with respect to 100 mol of the main component. The Zr oxide content may be 0.20 mol or more and 0.40 mol or less. In a situation where the dielectric layers 2 have too low or too high a Zr oxide content, the multilayer ceramic capacitor 1 has lower moisture resistance. Moreover, the lower the Zr oxide content, the less readily the segregates containing Mg and Si described later are generated.
The V content is not limited. The V content may be, for example, in terms of V2O5, 0.004 mol or more and 0.10 mol or less with respect to 100 mol of the main component. How the dielectric layers 2 contain V is also not limited. The dielectric layers 2 may contain V as, for example, a V oxide.
The Si oxide content is not limited. The Si oxide content may be, for example, in terms of SiO2, 0.30 mol or more and 1.00 mol or less, or 0.40 mol or more and 0.80 mol or less, with respect to 100 mol of the main component. In particular, a Si oxide content of 0.40 mol or more and 0.80 mol or less more readily enhances an effect of improving wettability described later. Consequently, an effect of efficiently and readily removing pores of the dielectric layers 2 outside the dielectric layers 2 at the time of sintering is enhanced. This more readily improves the sintering density of the capacitor element body 10. Thus, moisture resistance of the multilayer ceramic capacitor 1 is more readily improved.
Depending on intended properties, the dielectric layers 2 may further contain other components, i.e., components other than the main component, the Mn oxide, the Mg oxide, the R oxide, the Zr oxide, the Si oxide, and V. The content of the other components is not limited and may be within the extent that performance of the multilayer ceramic capacitor 1 is not significantly affected. The content of the other components may be, for example, 5 wt % or less in total with respect to the dielectric layers 2.
Preferably, the dielectric layers 2 substantially do not contain Al. Specifically, the Al content is preferably 0.1 mol or less (including 0 mol) in terms of Al2O3.
The dielectric layers 2 have a Zr/V ratio of 2.0 or more and 4.0 or less in atomic ratio. In a situation where the Zr/V ratio is outside the above range, the multilayer ceramic capacitor 1 has lower moisture resistance. Moreover, in a situation where the Zr/V ratio is too small, the segregates containing Mg and Si described later are not readily generated in the dielectric layers 2.
The dielectric layers 2 may have any thickness. In the present embodiment, 0.30≤t1≤2.0 may be satisfied, where t1 [μm] denotes the thickness (inter-layer thickness) of the dielectric layers 2. 0.35≤t1≤1.8 is preferably satisfied, or 0.40≤t1≤1.5 is more preferably satisfied. Having t1 being within the above range, the multilayer ceramic capacitor 1 readily has less withstand voltage failures or less short circuits and has larger capacitance.
The number of the dielectric layers 2 is not limited. In the present embodiment, the number of the dielectric layers 2 is preferably 20 or more, is more preferably 50 or more, or is most preferably 100 or more.
A reason why the above content ranges of the components of the dielectric layers 2 improve moisture resistance of the multilayer ceramic capacitor 1 is as follows. The above content ranges of the components of the dielectric layers 2 readily improve wettability of the various oxides other than the main component with respect to the main component at an initial stage of firing. Consequently, the pores of the dielectric layers 2 are efficiently and readily removed outside the dielectric layers 2 at the time of sintering, and the sintering density of the capacitor element body 10 is more readily improved. Because the sintering density of the capacitor element body 10 is improved, it becomes difficult for moisture to enter the capacitor element body 10 from outside. It is assumed that moisture resistance is thus improved and that even a long-time moisture resistance test less readily decreases electrical properties and less readily causes structural defects.
The internal electrode layers 3 may contain any conductive material. Because a constituent material of the dielectric layers 2 has resistance to reduction, as the conductive material, a relatively inexpensive base metal material can be used. As a base metal material used as the conductive material, Ni or a Ni alloy is preferred. The Ni alloy is preferably an alloy of Ni and at least one element selected from the group consisting of Mn, Cr, Co, Cu, Sn, and Al. The Ni alloy has a Ni content of preferably 95 wt % or more. Note that the base metal material may contain approximately 0.1 wt % or less each of various trace components, such as P.
The internal electrode layers 3 may have any thickness. In the present embodiment, 0.30≤t2≤1.0 may be satisfied, where t2 [μm] denotes the thickness of the internal electrode layers 3. 0.30≤t2≤0.80 is preferably satisfied, or 0.30≤t2≤0.60 is more preferably satisfied. Having t2 being within the above range, the capacitor element body 10 readily has a smaller size, particularly a smaller height. Further, the coverage ratio described later is readily improved, and the multilayer ceramic capacitor 1 readily has larger capacitance.
As shown in
Note that,
In the section shown in
In the section shown in
In the present embodiment, the coverage ratio may be 80% or more and 100% or less. The coverage ratio is preferably 85% or more and 100% or less, more preferably 90% or more and 100% or less, or most preferably 95% or more and 100% or less. The higher the coverage ratio, the fewer the electrode discontinuous portions 3a. Thus, particularly in a process of manufacturing the multilayer ceramic capacitor 1, water or a plating solution less readily enters the dielectric layers 2. Consequently, the multilayer ceramic capacitor 1 readily has improved moisture resistance. Note that, when the coverage ratio is 100%, there are no electrode discontinuous portions 3a.
The higher the coverage ratio and the fewer the electrode discontinuous portions 3a, the larger the electrode area of the multilayer ceramic capacitor 1 and the larger the capacitance of the multilayer ceramic capacitor 1. From that point as well, a high coverage ratio is preferred.
Segregation phases 5 are phases having a composition different from that of the dielectric layers 2 having barium titanate as their main component or the internal electrode layers 3. The multilayer ceramic capacitor 1 according to the present embodiment may include no segregation phases 5; however, as shown in
Each segregation phase 5 containing Mg and Si may include an interface between one of the dielectric layers 2 and one of the internal electrode layers 3 or may entirely circumferentially be covered by one of the dielectric layers 2. The segregation phases 5 containing Mg and Si may contain elements other than Mg and Si. The multilayer ceramic capacitor 1 according to the present embodiment may include segregation phases 5 that do not contain Mg and/or Si. The segregation phases 5 containing Mg and Si may have any Mg content and any Si content. For example, segregation phases 5 having a Mg content higher than that of the dielectric layers 2 by 10 at % or more and a Si content higher than that of the dielectric layers 2 by 10 at % or more may be deemed to be the segregation phases 5 containing Mg and Si.
In a situation where the multilayer ceramic capacitor 1 according to the present embodiment includes the segregation phases 5 containing Mg and Si (which may hereinafter be simply referred to as Mg—Si segregates), the Mg—Si segregates are preferably generated at interfaces between the internal electrode layers 3 and the dielectric layers 2 and in regions comprised of the dielectric layers 2. That is, the Mg—Si segregates are preferably generated in the dielectric layers 2 and/or at the interfaces between the internal electrode layers 3 and the dielectric layers 2.
By contrast, it may be that no Mg—Si segregates are generated at the electrode discontinuous portions 3a. Also, when the coverage ratio is 90% or more and 100% or less, the Mg—Si segregates are less readily generated at the electrode discontinuous portions 3a.
The third internal electrode layer 3 counted from the top has two electrode discontinuous portions 3a, partly at which the respective Mg—Si segregates are generated.
One dielectric layer 2 between the second and third internal electrode layers 3 counted from the top in
The other Mg—Si segregates in
The multilayer ceramic capacitor 1 has particularly improved moisture resistance when satisfying both of the following: the Mg—Si segregates are generated at the interfaces between the internal electrode layers 3 and the dielectric layers 2 and in the regions comprised of the dielectric layers 2; and the coverage ratio is 90% or more and 100% or less. Also, the Mg—Si segregates are more preferably generated both in the dielectric layers 2 and at the above-mentioned interfaces.
The dielectric layers 2 include dielectric grains mainly containing the main component and a grain boundary between the dielectric grains. Mg and Si are readily contained in the grain boundary. When the Mg—Si segregates are generated, Mg and Si moves in the grain boundary. When the Mg—Si segregates are generated, at the same time, pores in the vicinity of the grain boundary readily move and are readily removed outside the dielectric layers 2. Consequently, the sintering density of the capacitor element body 10 is improved. Moreover, when the coverage ratio is 90% or more and 100% or less, the internal electrode layers 3 are less missing. Thus, diffusion of moisture into the internal electrode layers 3 is prevented or mitigated, which readily prevents or mitigates decrease in the electrical properties or occurrence of structural defects.
Mg and Si are readily contained in the grain boundary. The presence of Mg and Si in the grain boundary suitably controls the sintering starting temperature during sintering to readily give a dense sintered body. However, abundant Mg and Si in the grain boundary readily increase the area of paraelectric regions in the dielectric layers 2 to decrease relative permittivity. Providing Mg and Si as the Mg—Si segregates at the interfaces between the internal electrode layers 3 and the dielectric layers 2 and in the regions comprised of the dielectric layers 2 decreases the area of paraelectric regions in the dielectric layers 2. Note that, no Mg—Si segregates are preferably generated at the electrode discontinuous portions 3a.
Therefore, the multilayer ceramic capacitor 1 can have improved moisture resistance while suitably maintaining magnetic properties, particularly relative permittivity of the dielectric layers 2, when satisfying both of the following: the Mg—Si segregates are generated at the interfaces between the internal electrode layers 3 and the dielectric layers 2 and in the regions comprised of the dielectric layers 2; and the coverage ratio is 90% or more and 100% or less.
The external electrodes 4 may contain any conductive material. As a conductive material contained in the external electrodes 4, for example, Ni, Cu, a Ni alloy, or a Cu alloy, which are known, can be used. The external electrodes 4 may have any thickness; and the thickness is appropriately determined according to usage or the like. Normally, the external electrodes 4 have a thickness of preferably about 5 μm to about 50 μm.
The multilayer ceramic capacitor 1 of the present embodiment is manufactured using a method similar to a method of manufacturing a conventional multilayer ceramic capacitor. Specifically, green chips are first prepared using a normal method involving a paste (e.g., a printing method or a sheet method). Then, the green chips are fired. To the fired green chips, external electrodes are printed or transferred; and then the external electrodes are baked. This completes the manufacture. This manufacturing method is specifically described below.
First, dielectric raw materials for forming the dielectric layers 2 are prepared. The prepared dielectric raw materials are turned into paint to give a dielectric layer paste. The dielectric layer paste may be organic paint or aqueous paint.
As the dielectric raw materials, a raw material of barium titanate, a raw material of the Mn oxide, a raw material of the Mg oxide, a raw material of the R oxide, a raw material of the Zr oxide, and a raw material of the V oxide are prepared. To have the dielectric layers 2 contain the Si oxide, a raw material of the Si oxide is prepared as well. Examples of these raw materials can include, for example, a simple oxide of each element, a complex oxide of each element, or a mixture of them. Alternatively, the raw materials can be appropriately selected from various compounds (e.g., carbonates, oxalates, nitrates, hydroxides, and organic metal compounds of the elements) that become the above-mentioned simple oxide or complex oxide by firing, and the selected compounds can be mixed for use.
Note that, as the raw material of barium titanate, a raw material manufactured by various methods, such as a so-called solid phase method or a liquid phase method (e.g., an oxalate method, a hydrothermal synthesis method, an alkoxide method, or a sol-gel method) can be used.
In the present embodiment, the raw material of barium titanate has a BET specific surface area of preferably 6.0 m2/g or more in order to meet demand for thinner dielectric layers 2.
In a situation where the dielectric layers 2 are thinned, the dielectric grains need to be disposed in between the internal electrode layers 3 in order to ensure sufficient reliability. To have the dielectric grains disposed in between the internal electrode layers 3, the dielectric grains are required to have a smaller average grain size. One way to decrease the average grain size of the dielectric grains may be decreasing the average particle size of the raw material of barium titanate. The average particle size of the raw material of barium titanate is in reciprocal proportion to the specific surface area of the raw material of barium titanate. Thus, the raw material of barium titanate has a BET specific surface area of preferably 6.0 m2/g or more.
In a situation where the dielectric layers 2 contain components other than the above components, raw materials of such components are prepared. Similarly to the above components, as the raw materials of such components, simple oxides of such components, complex oxides of such components, or a mixture of them can be used. Alternatively, various compounds that become the above simple oxides or complex oxides by firing can be used.
The amount of each compound in the dielectric raw materials is determined so that, after firing, the dielectric layers 2 have the composition described above. Before being turned into paint, the dielectric raw materials normally have an average particle size of about 0.05 μm to about 1 μm.
When the dielectric layer paste is to be organic paint, the dielectric raw materials and an organic vehicle are kneaded to give the organic paint. The organic vehicle is a mixture of an organic solvent and a binder dissolved therein. The binder may be of any type. The binder is appropriately selected from various binders (e.g., ethyl cellulose and polyvinyl butyral) normally used in this technical field. The organic solvent may be of any type. The organic solvent is appropriately selected from various organic solvents (e.g., terpineol, butyl carbitol, acetone, and toluene) according to a method of manufacturing the green chips.
When the dielectric layer paste is to be aqueous paint, the dielectric raw materials and an aqueous vehicle are kneaded to give the aqueous paint. The aqueous vehicle is a mixture of water and a water-soluble binder, dispersant, or the like dissolved therein. The water-soluble binder may be of any type. The water-soluble binder is appropriately selected from various water-soluble binders (e.g., polyvinyl alcohol, cellulose, and water-soluble acrylic resin) normally used in this technical field.
The following description is provided on the premise that the dielectric layer paste is organic paint.
Various conductive materials described above or various oxides, organic metal compounds, resinate, or the like that become the various conductive materials after firing and the organic vehicle described above are kneaded to give an internal electrode layer paste. The internal electrode layer paste may include an inhibitor. The inhibitor may be of any type. The inhibitor preferably has a composition similar to that of the main component.
An external electrode paste is prepared using a method similar to the method of forming the internal electrode layer paste.
Each of the pastes described above may have any organic vehicle content. The organic vehicle content is a normal content in this technical field. For example, each paste has a binder content of about 1 wt % to about 5 wt % and a solvent content of about 10 wt % to about 50 wt %. Each paste may further contain additives selected from various dispersants, plasticizers, dielectrics, insulators, and the like as necessary. Each paste has a total additive content of preferably 10 wt % or less.
When a printing method is used to give the green chips, the green chips are given by printing and laminating the dielectric layer paste and the internal electrode layer paste on substrates (e.g., PET), cutting the resultant product into a predetermined shape, and peeling the cut pieces off from the substrates.
When a sheet method is used to give the green chips, first, green sheets are formed with the dielectric layer paste, and the internal electrode layer paste is printed on the green sheets. Then, the green sheets having the internal electrode layer paste printed are laminated, and this laminate is cut into a predetermined shape to give the green chips.
Before firing described later, the green chips are subject to a binder removal treatment. Conditions of the binder removal treatment are not limited. The heating rate is preferably 5° C./hour to 300° C./hour. The holding temperature is preferably 180° C. to 400° C. The temperature holding time is preferably 0.5 hours to 24 hours. The binder removal atmosphere is preferably air or a reducing atmosphere.
The firing atmosphere for the green chips is preferably a reducing atmosphere. As an ambient gas for the reducing atmosphere, for example, a humidified mixed gas of N2 and H2 can be used. The oxygen partial pressure during firing can be appropriately determined according to the type of the conductive material in the internal electrode layer paste. When a base metal (e.g., Ni or a Ni alloy) is used as the conductive material in the internal electrode layer paste, the oxygen partial pressure is preferably 10−11 MPa to 10−8 MPa, and the heating rate is preferably 600° C./hour to 8000° C./hour or is more preferably 800° C./hour to 8000° C./hour.
Other conditions are preferably as follows. The holding temperature during firing is preferably 1300° C. or less or is more preferably 1000° C. to 1300° C. The temperature holding time during firing is preferably 0.2 hours to 8 hours or is more preferably 0.2 hours to 3 hours. In particular, the holding temperature during firing being within the above range prevents electrode disconnection due to abnormal sintering of the internal electrode layers 3 or a decrease in dielectric properties due to excessive grain growth of the dielectric grains while sufficiently readily densifying the dielectric layers 2. The cooling rate after firing is preferably 50° C./hour to 8000° C./hour.
After firing in the reducing atmosphere, the capacitor element bodies 10 are preferably subject to annealing. Annealing is a treatment for reoxidizing the dielectric layers 2. Annealing can remarkably extend the high-temperature load life of the multilayer ceramic capacitor 1.
The oxygen partial pressure of the annealing atmosphere is preferably 10−9 MPa to 10−5 MPa. The oxygen partial pressure within the above range prevents oxidation of the internal electrode layers 3 while sufficiently readily reoxidizing the dielectric layers 2.
The holding temperature during annealing is preferably 1100° C. or less or is more preferably 900° C. to 1100° C. The holding temperature during annealing being within the above range prevents oxidation of the internal electrode layers 3 while sufficiently readily reoxidizing the dielectric layers 2. Consequently, the multilayer ceramic capacitor 1 readily has suitable insulation resistance (IR), suitable high-temperature load life, and suitable capacitance.
Note that, while annealing normally includes a heating process, a temperature holding process, and a cooling process, annealing may include only the heating process and the cooling process. That is, the temperature holding time may be 0. In this situation, the holding temperature is equivalent to a maximum temperature.
Conditions of annealing other than the holding temperature are as follows. The temperature holding time during annealing is preferably 0 hours to 30 hours or is more preferably 1 hour to 25 hours. The cooling rate during annealing is preferably 50° C./hour to 500° C./hour or is more preferably 100° C./hour to 300° C./hour. The ambient gas for annealing is preferably, for example, a humidified N2 gas.
In the binder removal treatment, firing, and annealing described above, any method of humidifying the N2 gas, the mixed gas, or the like may be used. For example, a wetter is used for humidification. When a wetter or the like is used, the water temperature is preferably about 5° C. to about 75° C.
The binder removal treatment, firing, and annealing may be carried out continuously or independently.
End surfaces of the capacitor element bodies 10 given as above are polished, and the external electrode paste is applied there and is baked to form the external electrodes 4. Any method of polishing the end surfaces may be used. Examples of such methods include barrel polishing and sandblasting. Further, surfaces of the external electrodes 4 may be provided with a coating layer by plating or the like as necessary.
The multilayer ceramic capacitor 1 of the present embodiment manufactured in such a manner is mounted on a printed circuit board or the like by soldering or the like and is included in various electronics. In particular, the multilayer ceramic capacitor 1 is suitably included in on-board electronics or the like, which are required to have a small size, high performance, high reliability, and high moisture resistance.
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be variously modified without departing from the gist of the present invention.
In the above embodiment, the multilayer ceramic capacitor 1 exemplifies a multilayer ceramic electronic device according to the present invention; however, the multilayer ceramic electronic device according to the present invention is not limited to the multilayer ceramic capacitor 1 and may be any other electronic device having the structure described above.
Hereinafter, the present invention is described based on further detailed examples; however, the present invention is not limited to these examples.
A barium titanate powder (BaTiO3 powder) having a BET specific surface area of 8.0 m2/g was prepared as a raw material of a main component. A MnO powder, a MgO powder, a Dy2O3 powder, a ZrO2 powder, a V2O5 powder, and a SiO2 powder were prepared as raw materials of subcomponents. In the present examples, R included Dy.
Then, the BaTiO3 powder and the raw materials of the subcomponents prepared above were wet-pulverized in a ball mill for 15 hours and were dried to give a dielectric raw material. Note that, the amount of each subcomponent was controlled so that the subcomponent content of dielectric layers after firing was as shown in Table 1 with respect to 100 mol BaTiO3 (main component).
Then, the resultant dielectric raw material (100 parts by weight), polyvinyl butyral resin (10 parts by weight), dioctyl phthalate (DOP) as a plasticizer (5 parts by weight), and alcohol as a solvent (100 parts by weight) were mixed in a ball mill and were turned into a paste to give a dielectric layer paste.
Separately from the dielectric layer paste, a Ni powder (44.6 parts by weight), terpineol (52 parts by weight), ethyl cellulose (3 parts by weight), and benzotriazole (0.4 parts by weight) were kneaded in a triple-roll mill and were turned into slurry to give an internal electrode layer paste.
Using the dielectric layer paste prepared using the method described above, green sheets were formed on PET films. Then, using the internal electrode layer paste, electrode layers, which eventually became internal electrode layers, were printed in a predetermined pattern on the green sheets. After the electrode layers were printed, the green sheets were peeled off from the PET films to give green sheets with the electrode layers. Then, the green sheets with the electrode layers were laminated and were adhered with pressure to give a green laminated body. This green laminated body was further cut into predetermined size to give green chips.
Then, the resultant green chips were subject to a binder removal treatment, firing, and annealing under the following conditions to give capacitor element bodies (sintered bodies).
As for the conditions of the binder removal treatment, the heating rate was 25° C./hour; the holding temperature was 260° C.; the temperature holding time was 8 hours; and the atmosphere was air.
As for the firing conditions, the heating rate was 800° C./hour; the holding temperature was 1100° C. to 1300° C.; and the temperature holding time was 1 hour. The cooling rate was 800° C./hour. The ambient gas was a humidified N2+H2 mixed gas (oxygen partial pressure was 10−10 MPa).
As for the annealing conditions, the heating rate was 200° C./hour; the holding temperature was 1000° C.; the temperature holding time was 2 hours; the cooling rate was 200° C./hour; and the ambient gas was a humidified N2 gas (oxygen partial pressure was 10−7 MPa).
To humidify the ambient gases used in firing and annealing, a wetter was used.
Then, end surfaces of the resultant capacitor element bodies were polished by sandblasting. After that, Cu was applied as external electrodes to give multilayer ceramic capacitor samples shown in
Observation of segregation phases of the resultant capacitor samples and measurement of a coverage ratio, relative permittivity, dielectric loss (tan δ), and moisture resistance thereof were carried out as follows.
First, the capacitor samples were cut in a plane perpendicular to the dielectric layers. Then, this section was observed with a SEM and was subject to a STEM-EDX analysis. From results of Mg element mapping and Si element mapping, the presence or absence of Mg—Si segregates in the dielectric layers, at interfaces between the dielectric layers and the internal electrode layers, and at electrode discontinuous portions was checked. Specifically, the presence of a Mg—Si segregate entirely circumferentially covered by one of the dielectric layers was deemed to be the presence of a Mg—Si segregate in the dielectric layer. The presence of a Mg—Si segregate partially overlapping an interface between one of the dielectric layers and one of the internal electrode layers was deemed to be the presence of a Mg—Si segregate at the interface between the dielectric layer and the internal electrode layer. The presence of a Mg—Si segregate partially or entirely overlapping one of the electrode discontinuous portions was deemed to be the presence of a Mg—Si segregate at the electrode discontinuous portion. Table 1 shows the results. Note that, in the capacitor samples that did not include the Mg—Si segregates in the dielectric layers, at the interfaces between the dielectric layers and the internal electrode layers, or at the electrode discontinuous portions, no Mg—Si segregates were included in other portions of such capacitor samples.
The section described above was observed with a SEM, and the coverage ratio was calculated from the resultant SEM picture. Specifically, the ratio of the total of line lengths of regions actually provided with the electrode layers to the total of line lengths of regions where the electrode layers should have been provided on the supposition that there were no electrode discontinuous portions in the internal electrode layers was calculated and was defined as the coverage ratio. A coverage ratio of 80% or more and 100% or less was deemed good. A coverage ratio of 90% or more and 100% or less was deemed better. Table 1 shows the results.
Three hundred capacitor samples were manufactured and were classified into three groups, each including one hundred capacitor samples. To each of the capacitor samples, a direct voltage was applied at a temperature of 85° C., a relative humidity of 85%, and 20 V/μm.
The direct voltage was applied to a first group of capacitor samples for 2000 hours, a second group of capacitor samples for 3000 hours, and a third group of capacitor samples for 4000 hours. After the direct voltage was applied, the temperature of each capacitor sample was set to room temperature (25° C.), and its insulation resistance was measured. The capacitor samples having an insulation resistance of above 1 MΩ were deemed to be good products. The capacitor samples having an insulation resistance of 1 MΩ or less were deemed to be defective products. Table 1 shows the number of defective products in each group.
As for the first group, the number of defective products being 0 was deemed good. That is, a defective percentage of less than 1% was deemed good. As for the second group, the number of defective products being less than 20 was deemed good; the number of defective products being less than 9 was deemed better; and the number of defective products being less than 5 was deemed best. That is, a defective percentage of less than 20% was deemed good; a defective percentage of less than 9% was deemed better; and a defective percentage of less than 5% was deemed best. As for the third group, the number of defective products being less than 30 was deemed good; the number of defective products being less than 17 was deemed better; and the number of defective products being less than 10 was deemed best. That is, a defective percentage of less than 30% was deemed good; a defective percentage of less than 17% was deemed better; and a defective percentage of less than 10% was deemed best.
According to Table 1, when all the subcomponent contents were within predetermined ranges (e.g., the Mn oxide content was 0.05 mol or more and 0.25 mol or less in terms of MnO) and the Zr/V ratio was within a predetermined range, the Mg—Si segregates were generated; the coverage ratio was high; and the results of the moisture resistance test were good. By contrast, in Sample No. 1, in which the Mn oxide content was too low, no Mg—Si segregates were generated. Consequently, the results of the moisture resistance test were inferior to those of each Example. In Sample No. 8, in which the Mn oxide content was too high, the results of the moisture resistance test were inferior to those of each Example.
Experiment 2 was conducted as in Sample No. 3 of Experiment 1 except that the Mg oxide content was changed. Table 2 shows the results.
According to Table 2, when all the subcomponent contents were within the predetermined ranges (e.g., the Mg oxide content was 1.00 mol or more and 2.50 mol or less in terms of MgO) and the Zr/V ratio was within the predetermined range, the Mg—Si segregates were generated; the coverage ratio was high; and the results of the moisture resistance test were good. By contrast, in both Sample No. 9, in which the Mg oxide content was too low, and Sample No. 16, in which the Mg oxide content was too high, the results of the moisture resistance test were inferior to those of each Example.
Experiment 3 was conducted as in Sample No. 3 of Experiment 1 except that the R (Dy) oxide content was changed. Table 3 shows the results.
According to Table 3, when all the subcomponent contents were within the predetermined ranges (e.g., the R (Dy) oxide content was 0.50 mol or more and 1.50 mol or less in terms of R2O3) and the Zr/V ratio was within the predetermined range, the Mg—Si segregates were generated; the coverage ratio was high; and the results of the moisture resistance test were good. By contrast, in both Sample No. 17, in which the R oxide content was too low, and Sample No. 22, in which the R oxide content was too high, the results of the moisture resistance test were inferior to those of each Example.
Capacitor samples of Sample Nos. 23 to 28 were manufactured as in Sample No. 3 of Experiment 1 except that the Zr oxide content and the V oxide content were changed. All the samples had the same Zr/V ratio. Table 4 shows the results.
According to Table 4, in Sample Nos. 24 to 27, in which all the subcomponent contents were within the predetermined ranges and the Zr/V ratio was within the predetermined range, the Mg—Si segregates were generated; the coverage ratio was high; and the results of the moisture resistance test were good. By contrast, in Sample No. 23, in which the Zr oxide content was too low, no Mg—Si segregates were generated, and the results of the moisture resistance test were inferior to those of each Example. In Sample No. 28, in which the Zr oxide content was too high, the results of the moisture resistance test were inferior to those of each Example.
Capacitor samples of Sample Nos. 29 to 35 were manufactured as in Sample No. 3 of Experiment 1 except that the Zr oxide content was changed as shown in Table 5. Table 5 shows the results.
According to Table 5, in Sample Nos. 30 to 34, in which all the subcomponent contents were within the predetermined ranges and the Zr/V ratio was within the predetermined range, the Mg—Si segregates were generated; the coverage ratio was high; and the results of the moisture resistance test were good. By contrast, in Sample No. 29, in which all the subcomponent contents were within the predetermined ranges but the Zr/V ratio was too small, no Mg—Si segregates were generated, and the results of the moisture resistance test were inferior to those of each Example. In Sample No. 35, in which all the subcomponent contents were within the predetermined ranges but the Zr/V ratio was too large, the results of the moisture resistance test were inferior to those of each Example.
Capacitor samples of Sample Nos. 36 to 40 were manufactured as in Sample No. 3 of Experiment 1 except that the Si oxide content was changed as shown in Table 6. Table 6 shows the results.
According to Table 6, in Sample Nos. 36 to 40, in which all the subcomponent contents were within the predetermined ranges and the Zr/V ratio was within the predetermined range, the Mg—Si segregates were generated; the coverage ratio was high; and the results of the moisture resistance test were good. Moreover, in Sample Nos. 37 to 40, in which the Si oxide content was 0.40 mol or more and 0.80 mol or less in terms of SiO2, the results of the moisture resistance test were better than those of Sample Nos. 3 and 36, which were carried out as in Sample Nos. 37 to 40 except that the Si oxide content was less than 0.40 mol or above 0.80 mol.
Capacitor samples of Sample Nos. 39a to 39c and 41 to 45 were manufactured as in Sample No. 39 of Experiment 6 except that the coverage ratio was changed by changing the thickness t2 of the internal electrode layers by changing the electrode printing thickness. Table 7 shows the results.
According to Table 7, in Sample Nos. 39, 39c, and 41 to 45, in which the coverage ratio was 85% or more and 100% or less, the results of the moisture resistance test were better than those of Sample Nos. 39a and 39b, in which the coverage ratio was 80% or more and less than 85%. Moreover, in Sample Nos. 41 to 45, in which the coverage ratio was 90% or more and 100% or less and no Mg—Si segregates were generated at the electrode discontinuous portions, the results of the moisture resistance test were still better than those of Sample Nos. 39 and 39a to 39c, in which the coverage ratio was 80% or more and less than 90%.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-219742 | Dec 2023 | JP | national |
| 2024-144477 | Aug 2024 | JP | national |
