WO2015076005A1

WO2015076005A1 - Method for sintering ceramics and method for producing multilayer ceramic electronic component

Info

Publication number: WO2015076005A1
Application number: PCT/JP2014/074469
Authority: WO
Inventors: 清水　尚
Original assignee: 株式会社村田製作所
Priority date: 2013-11-20
Filing date: 2014-09-17
Publication date: 2015-05-28
Also published as: JPWO2015076005A1; JP6217760B2

Abstract

Provided is a method for producing a multilayer ceramic electronic component which can suppress occurrences of delamination defects in a laminated body and coverage defects of an internal electrode layer. Each time a ceramic sheet (21) on which is formed a conductive paste film (22) having a relatively high light absorption rate is laminated, light (24) from a heating light source (23) such as a Xenon lamp is applied onto the conductive paste film (22). The conductive paste film (22) is heated by absorbing the light (24) and as a result, metal particles in the conductive paste film (22) are sintered and ceramic particles in the ceramic sheet (21) are sintered by the heat transferred from the heated conductive paste film (22) to the ceramic sheet (21). A laminated body obtained by laminating a plurality of the ceramic sheets (21) is further sintered thereafter.

Description

Ceramic firing method and multilayer ceramic electronic component manufacturing method

The present invention relates to a method for firing a ceramic and a method for producing a multilayer ceramic electronic component carried out using this firing method.

As a technique of interest to the present invention, a method for manufacturing a multilayer ceramic electronic component is described in various documents such as International Publication No. 2004/075216 (Patent Document 1). According to the manufacturing method described in these prior art documents, the multilayer ceramic electronic component is manufactured through the following steps.

First, a conductive paste film having a pattern corresponding to a desired electrode pattern is printed on a ceramic green sheet formed on a film substrate, and then a plurality of ceramic green sheets are laminated to obtain a raw laminate. . The film substrate is peeled off before the ceramic green sheets are laminated, or is peeled off every time the ceramic green sheets are laminated while performing the lamination process.

Next, the raw laminate is cut into an appropriate size as necessary, and then fired. In the firing step, the resin component in the raw laminate is removed (degreasing), and the ceramic particles in the ceramic green sheet and the metal particles in the conductive paste film are sintered. As a result, a laminated body in which ceramic layers and electrode layers are alternately laminated having desired electrical characteristics can be obtained. Thereafter, for example, the external electrode is formed by baking a conductive paste.

In the above baking process, a batch furnace or a tunnel furnace is applied. The atmosphere in the furnace is heated to a temperature at which the ceramic is sintered (about 1300 ° C.) at a temperature rising rate of several to several tens of degrees per minute, and the electrode layer and the ceramic layer are sintered. At this time, since the melting point of the metal particles contained in the electrode layer is lower than the melting point of the ceramic particles contained in the ceramic layer, the metal particles start sintering earlier than the ceramic particles. Therefore, in the firing process, there is a stage where only the electrode layer shrinks and shrinks, and in such a stage where only the electrode layer shrinks, a relatively large stress is generated at the interface between the electrode layer and the ceramic layer. As a result, defects such as delamination between layers (delamination defects) and defects in which the electrode layer contracts into a network and the electrode coverage decreases (coverage defects) occur. The poor coverage causes a problem that desired electrical characteristics cannot be obtained in the obtained multilayer ceramic electronic component.

In order to suppress such defects as described above, as a means for delaying the sintering of the electrode layer, it is generally performed to mix ceramic particles into a conductive paste for electrode layer formation. It was not enough.

International Publication No. 2004/075216 Pamphlet

Therefore, an object of the present invention is to provide a method for manufacturing a multilayer ceramic electronic component capable of suppressing the occurrence of the above-mentioned delamination failure and coverage failure.

Another object of the present invention is to provide a ceramic firing method that does not depend on atmosphere firing in a batch furnace or a tunnel furnace that may cause the above-mentioned problems of delamination and coverage. .

This invention is first directed to a ceramic firing method. The present invention is characterized in that firing using a heating light source capable of instantaneous and rapid heating is applied instead of atmosphere firing such as a batch furnace or a tunnel furnace. However, many ceramic sheets, such as dielectric ceramic sheets, have a white color or a color tone close to white, and thus are difficult to absorb light and thus are not easily heated. Therefore, a light absorption film having a light absorption rate higher than that of the ceramic sheet is formed on the ceramic sheet. In this state, the light absorption film is irradiated with light from the heating light source.

That is, in the ceramic firing method according to the present invention, a step of preparing a ceramic sheet containing ceramic particles and a light absorption film having a light absorption rate higher than that of the ceramic sheet are formed on the ceramic sheet. And a light irradiation step of irradiating light from the heating light source toward the light absorption film. In this light irradiation step, the light absorption film is heated and heated by absorbing light. The ceramic particles are sintered by heat transferred from the absorption film to the ceramic sheet.

When the light absorption film is formed of a film that remains on the ceramic sheet even after the light irradiation step, as in the case of, for example, a conductive paste containing metal particles, As in the case of a paste containing a dark organic pigment, at least a part thereof may be a film that disappears in the light irradiation step.

The present invention is also directed to a method for manufacturing a multilayer ceramic electronic component that is carried out by applying the ceramic firing method described above.

A method for manufacturing a multilayer ceramic electronic component according to the present invention includes a step of preparing a plurality of ceramic sheets containing ceramic particles, a step of stacking a plurality of ceramic sheets, thereby obtaining a laminate, and a laminate A main firing step of firing.

And as a characteristic configuration, the method of manufacturing a multilayer ceramic electronic component according to the present invention includes a step of forming a light absorption film having a light absorption rate higher than that of the ceramic sheet on the ceramic sheet, and heating. A light irradiation step of irradiating the light from the light source toward the light absorption film. At least a part of the light absorption film is provided by a conductive paste film made of a conductive paste containing metal particles. Further, in the light irradiation step, the light absorption film is heated by absorbing light, and as a result, the metal particles are sintered and the ceramic particles are heated by the heat transferred from the heated light absorption film to the ceramic sheet. Is characterized by sintering.

It can be said that the light irradiation process is a preliminary baking process performed prior to the above-described main baking process.

The particle size of the ceramic particles is preferably smaller than the particle size of the metal particles described above. This makes it possible to sinter ceramic particles faster than metal particles, and as a result, it is possible to realize a unique phenomenon that cannot occur in conventional atmosphere firing, in which the ceramic sheet shrinks before the conductive paste film. . This is considered to be effective in suppressing the occurrence of delamination failure and coverage failure.

Also in this method of manufacturing a multilayer ceramic electronic component, a xenon lamp is preferably used as the heating light source. According to the xenon lamp, as described above, a large irradiation energy can be obtained. Therefore, the temperature of the light absorption film can be instantaneously increased, and accordingly, the ceramic sheet can be brought to a high temperature in a short time. Therefore, the sintering of the ceramic particles contained in the ceramic sheet and the sintering of the metal particles contained in the conductive paste film can be started almost simultaneously, and the occurrence of defective delamination and coverage can be more reliably suppressed. The production yield of the multilayer ceramic electronic component can be improved.

In order to achieve the above advantages more reliably, it is preferable that the xenon lamp has a higher irradiation energy such that the irradiation energy is 0.5 kW / cm ² or more.

Further, when a xenon lamp is used as the heating light source, it is preferable that the visible light absorption rate of the light absorption film is 21% or more. This is because the light absorption film is more efficiently heated by the light from the heating light source, and accordingly, the ceramic particles contained in the ceramic sheet can be sintered more rapidly.

In the method for manufacturing a multilayer ceramic electronic component according to the present invention, there are typically the following two types of timing for performing the light irradiation step and the lamination step. 1stly, in a lamination process, a light irradiation process is implemented whenever it laminates | stacks the ceramic sheet in which the light absorption film was formed. Second, in the laminating step, the ceramic sheets that have finished the light irradiation step are laminated.

When a xenon lamp is used as the heating light source, it is preferable that the light irradiation step is performed every time the ceramic sheets on which the light absorption film is formed are stacked in the stacking step as in the former case. In this case, in order not to reduce the efficiency of the laminating process, it is preferable that the irradiation time per pulse of the xenon lamp is 10 milliseconds or less so that it is shorter.

In the method for manufacturing a multilayer ceramic electronic component according to the present invention, the thickness of the ceramic sheet is preferably 0.1 to 10 μm. This is because the ceramic particles contained in the ceramic sheet are sufficiently sintered.

As described above, according to the ceramic firing method of the present invention, even if the ceramic sheet cannot sufficiently absorb light, the ceramic particles are formed by the light from the heating light source by forming the light absorbing film. Can be sintered. In addition, the firing by light can achieve the sintering of the ceramic particles more rapidly than the atmosphere firing using a batch furnace or a tunnel furnace.

Further, according to the method of manufacturing a multilayer ceramic electronic component according to the present invention, since each of the ceramic particles and the metal particles is pre-sintered in the stage of the main firing step, the ceramic layer provided by the ceramic sheet and the conductivity The stress at the interface between the two due to the difference in contraction behavior between the electrode layer and the electrode layer provided by the paste film can be reduced, and therefore, the occurrence of delamination failure and coverage failure can be suppressed.

Further, since at least a part of the light absorption film is provided by the conductive paste film, the conductive paste film also serves as at least a part of the light absorption film, and an electrode layer to be provided in the obtained multilayer ceramic electronic component is provided. It can be provided by at least part of the light absorbing film.

It is sectional drawing which shows the laminated ceramic capacitor as an example of the laminated ceramic electronic component to which this invention is applied. It is a figure for demonstrating the state which is for demonstrating the manufacturing method by 1st Embodiment of this invention, and the light irradiation process is implemented. It is for demonstrating the manufacturing method by 2nd Embodiment of this invention, and is a figure which shows the state which is implementing the light irradiation process schematically. It is a figure for demonstrating the state which is for demonstrating the manufacturing method by 3rd Embodiment of this invention, and is implementing the light irradiation process. It is for demonstrating the manufacturing method by 4th Embodiment of this invention, and is a figure which shows the state which is implementing the light irradiation process schematically. It is for demonstrating the manufacturing method by 5th Embodiment of this invention, and is a figure which shows the state which is implementing the light irradiation process schematically. It is a figure which shows the absorption spectrum of visible light about four types from which the light absorption rate investigated in Experimental example 2 mutually differs.

First, the structure of a multilayer ceramic capacitor 1 as an example of a multilayer ceramic electronic component to which the present invention is applied will be described with reference to FIG.

A multilayer ceramic capacitor 1 includes a multilayer body 5 including a plurality of laminated ceramic layers 2 and first and second

internal electrode layers

3 and 4 disposed along a plurality of interfaces between the ceramic layers 2. It has. The first internal electrode layer 3 and the second internal electrode layer 4 are opposed to each other in a part of each, and are alternately arranged as viewed in the stacking direction. The ceramic layer 2 is made of, for example, a BaTiO ₃ based dielectric ceramic, and the

internal electrode layers

3 and 4 are mainly made of nickel, for example.

The laminate 5 includes first and second main surfaces 6 and 7 facing each other, first and second side surfaces facing each other (a surface parallel to a paper surface not shown), and first and second end surfaces facing each other. It has a substantially rectangular parallelepiped shape with 8 and 9.

Each end of the first internal electrode layer 3 is exposed at the first end face 8 of the multilayer body 5. A first external electrode 10 is formed on the first end face 8 of the multilayer body 5 so as to be electrically connected to each end of the first internal electrode layer 3.

Each end of the second internal electrode layer 4 is exposed at the second end face 9 of the multilayer body 5. A second external electrode 11 is formed on the second end face 9 of the multilayer body 5 so as to be electrically connected to each end of the second internal electrode layer 4.

External electrodes

10 and 11 are formed, for example, by applying a conductive paste containing copper or silver as a conductive component on end faces 8 and 9 of laminate 5 and heat-treating (baking) it. On the

external electrodes

10 and 11, plating

films

12 and 13 are formed as necessary. The plating

films

12 and 13 include, for example, a nickel plating layer 14 mainly composed of nickel and a tin plating layer 15 mainly composed of tin formed thereon.

Hereinafter, a method for manufacturing the multilayer ceramic capacitor 1 will be described.

First, a raw ceramic sheet 21 (see FIG. 2) to be the ceramic layer 2 is prepared. The ceramic sheet 21 is obtained by forming a ceramic slurry containing ceramic particles, a resin and a dispersant into a sheet shape on a film substrate.

On the other hand, a conductive paste for forming the

internal electrode layers

3 and 4 is prepared. The conductive paste includes, for example, metal particles made of nickel, a resin, and an organic solvent. The conductive paste is printed with a predetermined pattern on the above-described ceramic sheet 21, thereby forming the conductive paste film 22 (see FIG. 2) to be the

internal electrode layers

3 and 4 on the ceramic sheet 21. . If the metal particles contained in the conductive paste have a nano-level particle size, the conductive paste film 22 usually looks blackish. That is, the conductive paste film 22 has a light absorption rate higher than that of the whitish ceramic sheet 21. Therefore, in this embodiment, the conductive paste film 22 itself serves as a light absorption film.

Next, a plurality of ceramic sheets 21 including the ceramic sheet 21 on which the conductive paste film 22 is formed are peeled off from a film base material (not shown), and then laminated to form a raw laminate. can get. This lamination process is shown in FIG.

Referring to FIG. 2, first, a plurality of ceramic sheets 21 that are not formed with a conductive paste film and that are outer layer portions on one side in the stacking direction of the stacked body 5 are stacked.

Next, a plurality of ceramic sheets 21 on which the conductive paste film 22 is formed are laminated. At this time, each time the ceramic sheets 21 are laminated, a light irradiation process is performed in which the light 24 from the heating light source 23 is irradiated toward the conductive paste film 22 as a light absorption film. As the heating light source 23, a light source capable of irradiating a strong light 24 of preferably 0.5 kW / cm ² or more, more preferably 1 kW / cm ² or more is used. For example, a xenon lamp is advantageously used.

For example, a halogen lamp other than a xenon lamp can be used as the heating light source 23. In this case, in order to further increase the irradiation energy, a condensing optical system including a lens and a mirror may be combined.

When a xenon lamp is used as the heating light source 23, pulsed light 24 in the order of microseconds to milliseconds is irradiated. At this time, the dark conductive paste film 22 absorbs the light 24 and is heated, and at the same time, the heat is transmitted to the ceramic sheet 21 immediately below the conductive paste film 22. Here, since the conductive paste film 22 is usually as thin as several μm, it can be considered that the conductive paste film 22 and the ceramic sheet 21 are heated almost simultaneously.

When the energy of the irradiation light 24 is sufficiently large (for example, when it is 1 kW / cm ² or more for each thickness of 1 μm of the conductive paste film 22 and the ceramic sheet 21; that is, when it is about 10,000 times or more of sunlight) ), The conductive paste film 22 and the ceramic sheet 21 are instantaneously heated to 1000 ° C. or higher, and the metal contained in the conductive paste film 22 for a short time (˜several milliseconds) until the temperature starts to drop. Both the particles and the ceramic particles contained in the ceramic sheet 21 are sintered.

As described above, in the light irradiation process, the conductive paste film 22 is heated by absorbing the light 24, and as a result, the metal particles contained in the conductive paste film 22 are sintered and the heated conductive paste is heated. The ceramic particles contained in the ceramic sheet 21 are sintered by the heat transferred from the film 22 to the ceramic sheet 21.

In the case of conventional atmosphere firing, since the firing object is gradually heated, the sintering proceeds in the order of metal particles and ceramic particles, whereas in the case of the so-called light firing described above, the firing object is instantaneously Therefore, the sintering of the metal particles and the sintering of the ceramic particles start almost simultaneously.

In general, particle sintering occurs from the point of contact necking between particles, and the speed is known to be inversely proportional to the particle size (written by Tsuneo Ishida, “Sintered Materials Engineering”, Morikita Publishing Co., Ltd.) , March 1997, pp. 77-82). Therefore, as described above, the sintering of the metal particles and the sintering of the ceramic particles start almost simultaneously. However, when the ceramic particles are smaller than the metal particles, more precisely, the ceramic particles are more than the metal particles. Sinters as soon as possible. Therefore, it is possible to realize a specific phenomenon that cannot occur in the conventional atmosphere firing, in which the ceramic sheet 21 contracts before the conductive paste film 22. This is considered to be effective in suppressing the occurrence of delamination failure and coverage failure.

Photo-firing is a short-time pre-firing process and is intended for necking of ceramic particles. Therefore, the sintering of the metal particles and the full-scale sintering (densification) of the ceramic particles are performed using a conventional atmospheric furnace in the main firing step described later. At this time, since the ceramic particles are preliminarily contracted, the stress at the interface between the conductive paste film 22 and the ceramic sheet 21 in the process of sintering the metal particles and the ceramic particles in this order can be reduced. As a result, it is possible to reduce defects such as delamination and electrode coverage and improve yield.

Thus, after repeating the light irradiation process for light baking every time it laminates | stacks the ceramic sheet 21 in which the electrically conductive paste film | membrane 22 was formed in a lamination process, again, the laminated body 5 A plurality of ceramic sheets 21 on which the conductive paste film is not formed, which is the outer layer portion on the other side in the laminating direction, are laminated.

The laminated body obtained as described above is pressed in the laminating direction. In addition to the press at the final stage, a preliminary press may be further performed for each stacking of the ceramic sheets 21 at a stage in the middle of the above-described lamination process.

In the light irradiation process described above, the conductive paste film 22 that absorbs more light serves as a main heat source and the ceramic sheet 21 is heated. Therefore, the ceramic particles are sintered immediately below the conductive paste film 22. There is a high possibility that the ceramic particles are not sintered in the periphery of the ceramic sheet 21, for example, in the peripheral portion. Therefore, there is a high possibility that the resin component as the binder remains in the peripheral portion of the ceramic sheet 21. However, this resin component advantageously acts to further improve the adhesion between the ceramic sheets 21 in the laminated body after pressing.

Next, a cutting step is performed as necessary in order to obtain a laminated body before the main firing for the individual multilayer ceramic capacitors 1 shown in FIG. And the main baking process by atmospheric baking using a batch furnace, a tunnel furnace, etc. is implemented, and the laminated body 5 sintered is obtained.

Next, a conductive paste is applied on the end faces 8 and 9 of the laminate 5 and baked, whereby

external electrodes

10 and 11 are formed. Furthermore, plating

films

12 and 13 are formed on the

external electrodes

10 and 11 as necessary, and the multilayer ceramic capacitor 1 is completed.

The manufacturing method according to the present invention is not limited to the multilayer ceramic capacitor as described above, and can be applied to other multilayer ceramic electronic components such as a positive temperature coefficient thermistor, varistor, and inductor. .

FIG. 3 is a view for explaining a manufacturing method according to the second embodiment of the present invention. 3, elements corresponding to those shown in FIG. 2 are denoted by the same reference numerals, and redundant description is omitted. This embodiment is characterized in that the ceramic sheets that have undergone the light irradiation step are laminated in the lamination step.

FIG. 3 shows a long ceramic sheet 21 lined with a film substrate 25. While the ceramic sheet 21 is intermittently conveyed in the direction of the arrow 26 by a roll-to-roll method (not shown), the conductive paste film 22 is printed at the printing station 27, and then the heater heating and drying station 28 is moved. After that, in the light irradiation station 29, the light 24 from the heating light source 23 is irradiated toward the conductive paste film 22. In this light irradiation station 29, the conductive paste film 22 is heated by absorbing the light 24, the metal particles are sintered, and the heat transferred from the heated conductive paste film 22 to the ceramic sheet 21 The ceramic particles sinter.

After that, the ceramic sheet 21 is cut along the cutting line 30 and then subjected to a lamination process (not shown). In the stacking step, the same steps as those described with reference to FIG. 2 are performed except that the light irradiation step is not performed.

FIG. 4 is a view for explaining a manufacturing method according to the third embodiment of the present invention. 4, elements corresponding to those shown in FIG. 2 are denoted by the same reference numerals, and redundant description is omitted. This embodiment is characterized in that not only the conductive paste film remaining on the ceramic sheet after the light irradiation process but also a film that disappears in the light irradiation process is provided as the light absorption film.

Referring to FIG. 4, a conductive paste film 22 is formed on the ceramic sheet 21 with a predetermined pattern. Further, in the region where the conductive paste film 22 is not formed on the ceramic sheet 21, a erasable film 31 made of a paste containing carbon or a dark organic pigment is formed, for example, which disappears in the light irradiation process. Note that the order of forming the conductive paste film 22 and the erasable film 31 is not limited.

In the above state, when the light 24 from the heating light source 23 is irradiated toward the conductive paste film 22 and the erasable film 31 as the light absorption film, the conductive paste film 22 and the erasable film 31 are lighted. 24 is absorbed and heated, and at the same time, the heat is transmitted to the ceramic sheet 21 immediately below the conductive paste film 22 and the erasable film 31. As a result, the metal particles in the conductive paste film 22 are sintered and the ceramic particles in the ceramic sheet 21 are sintered. Further, the erasable film 31 disappears by heat generated by absorbing the light 24 itself. The disappearance of the lossable film 31 is accompanied by phenomena such as evaporation and combustion.

In this embodiment, sintering of the ceramic particles can be achieved over the entire region in the main surface direction of the ceramic sheet 21.

FIG. 5 illustrates a manufacturing method according to the fourth embodiment of the present invention. In FIG. 5, elements corresponding to those shown in FIG. 2 or 4 are denoted by the same reference numerals, and redundant description is omitted. As in the case of the third embodiment, this embodiment includes not only a conductive paste film remaining on the ceramic sheet after the light irradiation process but also a film that disappears in the light irradiation process as the light absorption film. It is characterized by that. Further, this embodiment is the same as the third embodiment in that the sintering of the ceramic particles can be achieved over the entire region in the main surface direction of the ceramic sheet.

Referring to FIG. 5, a conductive paste film 22 is formed on the ceramic sheet 21 with a predetermined pattern. Further, the erasable film 31 that disappears in the light irradiation process is formed in the entire region in the main surface direction of the ceramic sheet 21 including the region where the conductive paste film 22 is formed on the ceramic sheet 21. The

In this embodiment, in forming the erasable film 31, alignment with the conductive paste film 22 is not necessary. Therefore, not only printing but also application by spraying, for example, can be applied.

Also in this embodiment, the conductive paste film 22 and the erasable film 31 as the light absorption film are heated by the light 24 from the heating light source 23, and at the same time, the heat is transferred to the conductive paste film 22 and the erasable film. It is transmitted to the ceramic sheet 21 immediately below 31. As a result, the metal particles in the conductive paste film 22 are sintered and the ceramic particles in the ceramic sheet 21 are sintered. Further, the erasable film 31 disappears by heat generated by absorbing the light 24 itself.

In the above-described third and fourth embodiments, as shown in FIG. 2, in the laminating step, when the light irradiation step is performed every time the ceramic sheets 21 are laminated, as shown in FIG. The present invention can also be applied to the case where the ceramic sheets 21 that have been processed are laminated.

FIG. 6 illustrates a manufacturing method according to the fifth embodiment of the present invention. In FIG. 6, elements corresponding to the elements shown in FIG. 4 are denoted by the same reference numerals, and redundant description is omitted. This embodiment is characterized in that only a film that disappears in the light irradiation step is provided as the light absorption film. Also in this embodiment, the sintering of the ceramic particles can be achieved over the entire region in the main surface direction of the ceramic sheet.

Referring to FIG. 6, a erasable film 31 that disappears in the light irradiation process is formed in the entire region in the main surface direction of the ceramic sheet 21. For the formation of the lossable film 31, for example, application by printing or spraying is applied.

In this embodiment, the light 24 from the heating light source 23 heats the erasable film 31 as a light absorption film, and at the same time, the heat is transmitted to the ceramic sheet 21 immediately below the erasable film 31. As a result, the ceramic particles in the ceramic sheet 21 are sintered, and the erasable film 31 disappears by heat generated by absorbing the light 24 itself.

Next, experimental examples carried out according to the present invention will be described.

[Experiment 1]
In this experimental example, a multilayer ceramic capacitor was produced as a sample.

First, BaCO ₃ and TiO ₂ powders were prepared and prepared so that the composition of BaTiO ₃ was obtained.

Next, pure water was added to the blended powder, mixed and pulverized with zirconia balls for 10 hours, dried, calcined at a temperature of 1000 ° C. for 2 hours, and then pulverized to obtain a calcined powder. .

Next, a resin, a dispersant, and water were added to the calcined powder and mixed with zirconia balls for several hours to obtain a ceramic slurry containing the calcined powder as ceramic particles having an average particle diameter of 50 nm.

Next, the ceramic slurry was formed into a sheet shape by a doctor blade method on a film substrate and dried to obtain a ceramic sheet having a thickness of 2 μm.

Next, a conductive paste containing nickel powder having an average particle diameter of 200 nm, a resin, and an organic solvent is prepared, and a conductive paste having a thickness of 1.0 μm serving as an internal electrode layer is formed on a predetermined ceramic sheet by a screen printing method. A film was formed. Here, it is noted that the particle size of the ceramic particles described above is smaller than the particle size of the nickel powder as the metal powder.

Next, after laminating an appropriate number of outer-layer ceramic sheets on which no conductive paste film is formed, the conductive paste film is placed on the ceramic sheet so that the conductive paste film faces the ceramic sheet. A plurality of ceramic sheets formed with the above were laminated. In this laminating process, each time one ceramic sheet is stacked, light (wavelength 300 to 1200 nm) from a mercury xenon lamp is directed toward the conductive paste film as “irradiation light power” and “irradiation” shown in Table 1. The laser sheet was pre-fired by irradiating 1 pulse with time. Further, an appropriate number of outer layer ceramic sheets on which a conductive paste film is not formed are laminated and pressure-bonded, and then cut into dimensions of 2.2 mm in length and 2.75 mm in width, and 1.2 mm in thickness. A raw laminate was obtained.

Next, the raw laminate was degreased at a temperature of 400 ° C. and then baked at a temperature of 1250 ° C. for 20 minutes for main baking. As a result, a sintered laminate was obtained in which the ceramic layer was provided by the ceramic sheet and the internal electrode layer was provided by the conductive paste film.

Next, the sintered laminate was mixed with a cobblestone having a diameter of 1 mm containing Si and Al, and a predetermined amount of water was added to perform barrel polishing.

Next, an external electrode is formed by applying and baking a conductive paste containing Cu as a conductive component on both end faces of the laminate, and then, on the external electrode, an Ni layer and Sn as a plating film are further formed. Layers were sequentially formed by electroplating.

Thus, a multilayer ceramic capacitor according to each sample was obtained. A multilayer ceramic capacitor as a comparative sample was produced under the same conditions except that the preliminary firing with the mercury xenon lamp was not performed. These samples were evaluated for delamination incidence and room temperature resistance. The results are shown in Table 1. In Table 1, “◯” is displayed for samples in which the delamination occurrence rate is reduced and the room temperature resistance is maintained at the same level as the comparative sample, and the delamination occurrence rate is not reduced or the room temperature resistance is high. “×” was displayed for the samples that were lost.

As can be seen from Table 1, when the “irradiation light power” is small or the “irradiation time” is short, the delamination occurrence rate is not reduced as compared with the comparative sample. This is presumably because the sintering of the ceramic particles did not proceed sufficiently in the preliminary firing with the mercury xenon lamp.

On the other hand, when the “irradiation light power” and “irradiation time” were appropriate, the delamination occurrence rate was reduced while maintaining the room temperature resistance as compared with the comparative sample. This is because the ceramic particles were sufficiently sintered by pre-firing with a mercury xenon lamp, and the stress caused by the difference in sintering shrinkage behavior between the internal electrode layer and the ceramic layer in the main firing stage was alleviated. Guessed.

Note that when the “irradiation light power” was excessive or the “irradiation time” was inappropriately long, a defect in which the room temperature resistance was higher than that of the comparative sample occurred. This is presumably because the metal particles in the conductive paste film were excessively sintered and contracted, defects were generated in the internal electrode layer, and the coverage of the internal electrode layer was reduced.

The appropriate range of “irradiation light power” is considered to vary depending on the composition, particle size, film thickness, and the like of the ceramic material. However, in this experimental example, it was demonstrated that the ceramic particles can be sufficiently sintered by pre-firing with a mercury xenon lamp at least if the “irradiation light power” is 0.5 kW / cm ² or more.

Further, when pre-firing with a mercury xenon lamp is performed every time the ceramic sheets on which the conductive paste film functioning as a light absorption film is formed are laminated, in order to efficiently produce a multilayer laminate, 1 The light irradiation time per ceramic sheet of the layer is preferably shorter. In this experimental example, good results were obtained when the “irradiation time” was in the range of 0.5 to 10 milliseconds. Usually, the time required for laminating one ceramic sheet is about several hundred milliseconds to several seconds. Compared with this, the “irradiation time” at which the above-mentioned good results were obtained is sufficiently short. Therefore, it is possible to introduce a preliminary baking step using light without reducing the efficiency of the conventional lamination step.

[Experiment 2]
In this experimental example, in order to investigate the performance of each of a plurality of types of light absorption films having different light absorption rates, the above-mentioned types of light absorption films are formed on each of a plurality of types of ceramic sheets having different thicknesses, and mercury Light from a xenon lamp (wavelength 300 to 1200 nm) was irradiated toward the light absorption film, and the possibility of sintering of the ceramic particles contained in the ceramic sheet was investigated.

FIG. 7 shows an absorption spectrum of visible light (wavelength: 400 nm to 800 nm) for the light absorption film investigated in this experimental example. The light absorption rate was measured using an ultraviolet-visible spectrophotometer (Shimadzu Corporation).

In the figure, “nickel” is a light absorbing film formed by printing and applying a conductive paste containing nickel powder used in Experimental Example 1 onto the ceramic sheet used in Experimental Example 1.

"Copper" uses a copper powder having an average particle size of 200 nm, and a conductive paste produced by the same manufacturing method as that of the conductive paste containing the nickel powder is printed on the ceramic sheet used in Experimental Example 1. It is the formed light absorption film.

“Silver foil” is a light absorbing film formed on the ceramic sheet used in Experimental Example 1 by sputtering so that the silver foil has a thickness of 200 nm.

“None (ceramic)” is the ceramic sheet itself used in Experimental Example 1 in which no light absorption film was formed.

Table 2 shows whether or not each sample shown in FIG. 7 is irradiated with light and the ceramic particles contained in the ceramic sheet can be sintered.

In Table 2, the case where the ceramic particles are sintered is indicated by “◯”, and the case where the ceramic particles are not sintered is indicated by “X”.

As shown in FIG. 7, “nickel” had an average light absorption rate of 63%, and “copper” had an average light absorption rate of 21%. When these “nickel” and “copper” were used as the light absorbing film, the ceramic particles were sintered. On the other hand, “silver foil” had an average light absorptivity of 0.7%, which was lower than “none (ceramic)”. When “silver foil” was used as the light absorbing film, the ceramic particles were not sintered. Of course, the ceramic particles were not sintered even in “None (ceramic)”.

From these facts, it was found that when a ceramic is fired by a light firing technique, it is necessary to use a light absorption film made of a material having a light absorption rate higher than that of the ceramic sheet. In addition, the light absorption film preferably has a higher light absorption rate. More specifically, the average absorption rate of visible light (wavelength 400 to 800 nm) is preferably 21% or more, more preferably 63% or more. I found out.

In this experimental example, a non-volatile and non-combustible material called a metal material was used in the light absorption film. However, a volatile material represented by an organic dye or a combustible material represented by carbon was used. It is understood that the same effect can be obtained even when used in a light absorbing film.

It was also found that if the thickness of the ceramic sheet is excessively large, the ceramic particles cannot be sufficiently sintered. That is, it was found that the thickness of the ceramic sheet as the object of photo-fired is preferably 0.1 to 10 μm, more preferably 0.1 to 3 μm.

1 Multilayer ceramic capacitors (multilayer ceramic electronic components)
2

Ceramic layer

3, 4 Internal electrode layer 5 Laminate 21 Ceramic sheet 22 Conductive paste film 23 Heating light source 24 Light 29 Light irradiation station 30 Cutting line 31 Erasable film

Claims

Preparing a ceramic sheet containing ceramic particles;
Forming a light absorption film having a light absorption rate higher than the light absorption rate of the ceramic sheet on the ceramic sheet;
Irradiating light from a light source for heating toward the light absorbing film;
With
In the light irradiation step, the light absorption film is heated by absorbing the light, and the ceramic particles are sintered by the heat transferred from the heated light absorption film to the ceramic sheet.
Ceramic firing method.
The ceramic firing method according to claim 1, wherein a xenon lamp is used as the heating light source.
3. The ceramic firing method according to claim 1, wherein at least a part of the light absorbing film is made of a film remaining on the ceramic sheet after the light irradiation step.
The ceramic firing method according to claim 1 or 2, wherein at least a part of the light absorbing film is formed of a film that disappears in the light irradiation step.
Preparing a plurality of ceramic sheets containing ceramic particles;
Laminating a plurality of the ceramic sheets, thereby obtaining a laminate, and a laminating step;
A main firing step of firing the laminate;
A method for producing a multilayer ceramic electronic component comprising:
Forming a light absorption film having a light absorption rate higher than the light absorption rate of the ceramic sheet on the ceramic sheet;
Irradiating light from a light source for heating toward the light absorbing film;
Further comprising
At least a part of the light absorption film is provided by a conductive paste film made of a conductive paste containing metal particles,
In the light irradiation step, the light absorption film is heated by absorbing the light, and as a result, the metal particles are sintered, and by heat transferred from the heated light absorption film to the ceramic sheet. The ceramic particles are sintered;
Manufacturing method of multilayer ceramic electronic component.
The method for manufacturing a multilayer ceramic electronic component according to claim 5, wherein the ceramic particles have a particle size smaller than that of the metal particles.
The method for producing a multilayer ceramic electronic component according to claim 5 or 6, wherein a xenon lamp is used as the heating light source.
The manufacturing method of the multilayer ceramic electronic component of Claim 7 whose irradiation energy of the said xenon lamp is 0.5 kW / cm < 2 > or more.
The method for producing a multilayer ceramic electronic component according to claim 7 or 8, wherein the visible light absorption rate of the light absorption film is 21% or more.
10. The method of manufacturing a multilayer ceramic electronic component according to claim 7, wherein in the stacking step, the light irradiation step is performed every time the ceramic sheet on which the light absorption film is formed is stacked.
The method for producing a multilayer ceramic electronic component according to claim 10, wherein the irradiation time per pulse of the xenon lamp is 10 milliseconds or less.
The method for producing a multilayer ceramic electronic component according to claim 5, wherein the ceramic sheet that has finished the light irradiation step is stacked in the stacking step.
13. The method for producing a multilayer ceramic electronic component according to claim 5, wherein the ceramic sheet has a thickness of 0.1 to 10 μm.