JP6015221B2 - Manufacturing method of ceramic electronic component - Google Patents

Description

  The present invention relates to a method for manufacturing a ceramic electronic component such as a multilayer ceramic capacitor.

  In general, the monolithic ceramic capacitor has been miniaturized, and the film thickness of the external electrode has been reduced. For this reason, a denser external electrode has been required.

  However, when the external electrode becomes dense, the carbon component contained in the external electrode conductive paste is gasified and blisters (bubbles) are generated when the external electrode conductive paste is baked.

  Therefore, for example, in the manufacturing method described in Patent Document 1, in the step of baking the conductive paste for external electrodes on the ceramic body, the temperature required to remove the binder resin contained in the conductive paste for external electrodes is increased. A first region for raising the temperature, a second region for raising the temperature to a temperature necessary for sintering the conductive paste for external electrodes, and a second region for lowering the temperature from the temperature raised in the second region to room temperature. In the first region, the pressure in the firing furnace is increased from atmospheric pressure to 0.15 MPa, and the oxygen concentration in the firing furnace is set to 30 to 100 ppm and fired.

  This manufacturing method facilitates the removal of the binder resin and can reduce the amount of residual carbon, so that a fine external electrode film can be formed while suppressing the generation of blisters (bubbles) due to the residual carbon. Can be formed.

JP 2011-238834 A

  However, when the external electrode is Cu, the carbon adsorbed on the Cu powder contained in the external electrode conductive paste is difficult to be combusted and thermally decomposed, and even if the manufacturing method described in Patent Document 1 is used, In the region 1, it is difficult to reduce the amount of residual carbon in a short time. For this reason, for example, in the temperature range of 700 ° C. to 750 ° C., the generation of residual binder gas and the densification of the external electrode occur at the same time, thereby suppressing blistering of the external electrode (a phenomenon in which the electrode film rises) and There was a problem that it was difficult to achieve both.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing a ceramic electronic component that can achieve both suppression and densification of external electrode blisters (a phenomenon in which an electrode film is lifted).

The present invention
Forming a ceramic body containing Ca oxide;
Applying a conductive paste for external electrodes including Cu powder and glass having a viscosity of log η <2 Pa · s at a temperature of 820 ° C. to 870 ° C. on the surface of the ceramic body;
Baking the conductive paste for external electrodes in an inert gas at a temperature not lower than the temperature at which the viscosity of the glass is log η = 2 Pa · s or lower and a baking temperature of 870 ° C. or lower;
A method for manufacturing a ceramic electronic component, comprising:

  In the present invention, a glass having a relatively high softening point is used as the glass of the conductive paste for external electrodes, so that residual carbon adsorbed on the Cu powder of the conductive paste for external electrodes burns to generate a binder gas. In the temperature range (for example, 750 ° C. or lower), the softening flow of the glass is suppressed, and the external electrode film can be kept in a porous state. Therefore, the residual binder gas is easily scattered, and the occurrence of blisters (a phenomenon in which the electrode film is lifted) of the external electrode is suppressed.

  On the other hand, since the ceramic element contains a Ca component, in the temperature range after the binder gas is scattered (for example, 750 ° C. or more), the Ca component contained in the ceramic element diffuses into the glass, thereby reducing the viscosity of the glass. Therefore, the softening flow of the glass proceeds, the gap between the Cu powders is filled, or the Cu powder is sintered, and the external electrode film becomes dense.

  Moreover, this invention is a manufacturing method of the ceramic electronic component characterized by the thickness after baking of the electroconductive paste for external electrodes apply | coated to the surface of the ceramic element | base_body in the range of 10-20 micrometers.

  In order to reduce the thickness of the external electrode, it is necessary to atomize the Cu powder. However, the smaller the particles of Cu powder, the easier it is to oxidize. Therefore, although rust prevention treatment may be performed on Cu powder, such a rust inhibitor is adsorbed on Cu powder. Accordingly, the carbon derived from the rust preventive agent is difficult to gasify in the low temperature region and gasifies in the high temperature region, which causes generation of blisters in the external electrode. Therefore, the present invention is particularly effective when the thickness after baking of the conductive paste for external electrodes applied to the surface of the ceramic body is in the range of 10 to 20 μm.

  Moreover, this invention is a manufacturing method of the ceramic electronic component characterized by the ratio of the fine powder of Cu powder contained in the electroconductive paste for external electrodes, and flat powder being 40% or more of flat powder ratios. is there. Thereby, the film breakage (hereinafter referred to as “Kiretsu”) of the external electrode at the corner portion of the ceramic body is suppressed.

  According to the present invention, it is possible to achieve both suppression and densification of external electrode blisters (a phenomenon in which the electrode film is lifted).

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

It is a perspective view which shows the multilayer capacitor for demonstrating one Embodiment of the manufacturing method of the ceramic electronic component which concerns on this invention. It is AA sectional drawing of the multilayer capacitor shown in FIG.

  An embodiment of a method for producing a ceramic electronic component according to the present invention will be described by taking a multilayer capacitor as an example.

  As shown in FIG. 1, the multilayer capacitor 1 includes a ceramic body 10 and external electrodes 20 and 22 formed on the surface of the ceramic body 10. The ceramic body 10 has a pair of main surfaces 10a and 10b facing each other, a pair of side surfaces 10c and 10d facing each other, and a pair of end surfaces 10e and 10f facing each other.

  The external electrode 20 is formed at the left end portion (left end surface 10 e) of the ceramic body 10 and wraps around the main surfaces 10 a and 10 b and the side surfaces 10 c and 10 d of the ceramic body 10. The external electrode 22 is formed on the right end portion (right end surface 10f) of the ceramic body 10, and wraps around the main surfaces 10a and 10b and the side surfaces 10c and 10d of the ceramic body 10. However, the external electrodes 20 and 22 do not necessarily have to wrap around the side surfaces 10c and 10d. The external electrodes 20 and 22 of the ceramic body 10 are composed of a base layer and a plating layer.

  As shown in FIG. 2, in the ceramic body 10, the internal electrode pattern 2 and the internal electrode pattern 4 are opposed to each other via the dielectric ceramic layer 6 in the thickness direction. Capacitance is formed in a portion where the internal electrode pattern 2 and the internal electrode pattern 4 face each other with the dielectric ceramic layer 6 interposed therebetween.

  The left end portion 2 a of the internal electrode pattern 2 is drawn out to the left end surface 10 e of the ceramic body 10 and is electrically connected to the external electrode 20. The right end portion 4 a of the internal electrode pattern 4 is drawn out to the right end surface 10 f of the ceramic body 10 and is electrically connected to the external electrode 22.

  Next, a method for manufacturing the multilayer capacitor 1 having the above configuration will be described.

First, a ceramic material powder is mixed with an organic binder and an organic solvent to form a slurry. As the ceramic material, for example, a dielectric ceramic containing Ca and containing CaTiO ₃ , CaZrO ₃ or the like as a main component is used. Or what added subcomponents, such as a Mn compound, Fe compound, Cr compound, Co compound, Ni compound, to these main components is used.

  This slurry is formed into a sheet by the doctor blade method and then dried to form a ceramic green sheet. This ceramic green sheet should become the above-mentioned dielectric ceramic layer 6 after firing. The thickness of the ceramic green sheet 6 is preferably 0.5 to 10 μm after firing.

  Next, a conductive paste for internal electrodes is applied on the ceramic green sheet 6 by, for example, a screen printing method to form a predetermined internal electrode pattern 2 (or internal electrode pattern 4). For example, Ni, Cu, Ag, Pd, Ag—Pd alloy, Au, or the like is used as the material of the internal electrode patterns 2 and 4. The thickness of the internal electrode patterns 2 and 4 (thickness of the thickest part after firing) is preferably 0.5 to 2.0 μm.

  Next, after stacking a predetermined number of outer layer ceramic green sheets 6 on which the internal electrode patterns 2 and 4 are not formed, the inner layer ceramic green sheets 6 and the internal electrodes on which the internal electrode pattern 2 is formed are stacked thereon. A predetermined number of ceramic green sheets 6 for the inner layer on which the pattern 4 is formed are alternately stacked. Further, a predetermined number of outer layer ceramic green sheets 6 on which the internal electrode patterns 2 and 4 are not formed are stacked thereon. In this way, a mother laminated body is created.

  Next, the mother laminate is pressed and pressure-bonded in the stacking direction of the ceramic green sheets 6 by an isostatic pressing method or the like.

  Next, the mother laminate is cut into a predetermined product size. The unfired ceramic body 10 cut to the product size is rounded at corners and ridges by barrel polishing or the like.

  Next, the ceramic body 10 is fired. Although the firing temperature depends on the materials of the ceramic green sheet 6 and the internal electrode patterns 2 and 4, it is preferably 900 to 1300 ° C. The ceramic green sheet 6 becomes the dielectric ceramic layer 6 by firing. The thickness of the dielectric ceramic layer 6 is preferably 0.5 to 10 μm.

  Next, the conductive paste for the underlayer of the external electrodes 20 and 22 is applied to both ends of the fired ceramic body 10 by an immersion method and dried. The conductive paste for the underlayer is made by mixing Cu powder and glass together with an organic binder and an organic solvent.

  The Cu powder of the conductive paste for the underlayer is composed of fine powder and flat powder, and the ratio of fine powder and flat powder is preferably a flat powder ratio of 40% or more. The conductive paste for the underlayer applied to the end of the ceramic body 10 has a film thickness at the center of the end faces 10e and 10f of the ceramic body 10 and a corner (for example, the main surface 10a and the main surface 10a). There is a difference in film thickness depending on the location between the film thickness at the ridge line part between the end face 10e and the film. Therefore, as the sintering shrinkage (densification) of the metal component progresses, film breakage (hereinafter referred to as “Kiretsu”) may occur particularly in the corner portion where the film thickness is thin. Therefore, flat powder is added to Cu powder in order to suppress this cracking. By adding the flat powder, sintering shrinkage in the film surface direction can be suppressed even if the film thickness becomes denser. The particle size of the fine powder is 0.45 to 0.66 μm, and the particle size of the flat powder is preferably 3.4 to 3.55 μm.

  As the glass of the conductive paste for the underlayer, borosilicate glass, silica-based glass, or the like having a characteristic that the viscosity becomes log η <2 Pa · s at a temperature of 820 ° C. to 870 ° C. is used in the form of particles. Here, the viscosity of the glass is measured by a glass parallel plate pressure viscometer (GPM-2 manufactured by Opt Corporation) (the glass green compact is 7 mmφ, T = 6 to 8 mm). The measurement condition is that heating is performed from room temperature to 870 ° C. at a rate of temperature increase of 5 ° C./min while applying a weight of 60.14 g. The average particle size of the glass particles is preferably 0.7 to 5 μm.

Next, the ceramic body 10 coated with the conductive paste for the underlayer is placed in the chamber, and the conductive paste for the underlayer combines air, H ₂ , N ₂ , N ₂ + water vapor, and the like. In an atmosphere, the glass is baked at a baking temperature of 870 ° C. or lower and a temperature at which the viscosity of the glass becomes log η = 2 Pa · s or lower.

  For example, the following two processes are mentioned as the baking process. In either process, the reducing atmosphere is finally introduced into the chamber, so that the glass contained in the conductive paste for the base layer is segregated on the surface of the base layer.

<Process 1>
(A) First, binder removal of the conductive paste for underlayer is performed in an acidic / weakly acidic atmosphere, and the conductive paste for underlayer is used as the underlayer.
(B) Next, the acidic / weakly acidic atmosphere is replaced with a reducing atmosphere, and the ceramic body 10 and the base layer are joined in the reducing atmosphere.
(C) Next, the reducing atmosphere is replaced with an acidic / weakly acidic atmosphere, and the underlayer is sintered in the acidic / weakly acidic atmosphere.
(D) Finally, the acidic / weakly acidic atmosphere is replaced with a reducing atmosphere, and the glass is segregated on the surface of the underlayer in the reducing atmosphere.

<Process 2>
(A) First, binder removal of the conductive paste for underlayer is performed in an acidic / weakly acidic atmosphere, and the conductive paste for underlayer is used as the underlayer.
(B) Next, the base layer is sintered in an acidic / weakly acidic atmosphere.
(C) Finally, the acidic / weakly acidic atmosphere is replaced with a reducing atmosphere, and the glass is segregated on the surface of the underlayer in the reducing atmosphere, and the ceramic body 10 and the underlayer are joined. Is called.

  Thus, the base layers of the external electrodes 20 and 22 are formed on both ends of the ceramic body 10, respectively. The thickness of the base layer after baking (the thickness of the thickest part) is preferably in the range of 10 to 20 μm (MAX 20 μm). This is because blisters are likely to occur when the thickness of the underlying layer after baking is greater than 20 μm, and IR defects are likely to occur when the thickness is less than 10 μm.

  In the present embodiment, a method (postfire method) is employed in which after the ceramic body 10 is fired, a base layer conductive paste is applied and baked to form the base layer. However, before firing the ceramic body 10, the base layer conductive paste is applied, and the base layer conductive paste is baked simultaneously with the internal electrode patterns 2, 4 and the ceramic green sheet 6 to form the base layer. A method (cofire method) may be employed.

  Thereafter, in order to improve solderability, moisture resistance, and the like, the plating layers of the external electrodes 20 and 22 are formed on the surface of the base layer by a method such as electrolytic plating. As the material for the plating layer, for example, Ni, Cu, Ag, Pd, Ag—Pd alloy, Au, or the like is used. The plating layer may be composed of a plurality of layers. Preferably, it has a two-layer structure of a Ni plating layer (primary plating layer) and a Sn plating layer (secondary plating layer). It is preferable that the thickness of one plating layer (thickness of the thickest part) is 1-10 micrometers.

  In this way, the multilayer capacitor 1 is obtained.

(Evaluation of blister generation and IR failure of multilayer capacitors)
A manufacturing method according to the above embodiment using a plurality of conductive pastes including Cu powder and glass having a viscosity η of log η ≦ 2 Pa · s at a temperature of 800 ° C. to 900 ° C. Thus, the multilayer capacitor 1 was produced. And the blister generation | occurrence | production and IR defect of the samples 1-16 of the produced multilayer capacitor 1 were evaluated. Table 1 shows the evaluation results.

  The occurrence of blister is the (1/2) LT section obtained by cutting a half position in the width direction of the multilayer capacitor 1 along the length direction, or a half position in the thickness direction of the multilayer capacitor 1. A (1/2) LW cross section cut along the length direction was observed using a digital microscope VHX (magnification: 200 times) manufactured by KEYENCE. The evaluation of blister generation was performed for each of Sample 1 to Sample 16 with respect to the multilayer capacitor 1 having the number of samples n = 300.

  IR failure is caused by the multilayer capacitor 1 (the number of samples n = 100,000) in which the two-layer plating process of the Ni plating layer (primary plating layer) and the Sn plating layer (secondary plating layer) is completed. ) Was measured, and the presence or absence of an IR defective sample in which the IR value decreased to 3σ or less from the average value was confirmed.

  The thickness of the undercoat layer after baking was measured using a digital microscope VHX manufactured by KEYENCE Corp. (1/2) LT cross section obtained by cutting a half position in the width direction of the multilayer capacitor 1 along the length direction. It was done. The measured values shown in Table 1 are used for IR measurement among 200,000 samples of one lot of multilayer capacitors 1 manufactured under the same processing conditions, and n = 10 among the remaining samples. It is an average value (average value obtained by rounding off the decimal point) of samples sampled randomly.

  The distribution of the Ca component of the ceramic body 10 is, for example, a (1/2) LT section obtained by cutting a half position in the width direction of the multilayer capacitor 1 along the length direction. Observed using an analyzer (WDX).

  From Sample 1 and Sample 2 in Table 1, when an underlying layer conductive paste containing glass having a viscosity of log η ≦ 2 Pa · s and having a temperature of 800 ° C. was used, blistering and IR failure were observed.

  Further, from the sample 9 in Table 1, when the conductive paste for the base layer including glass having a viscosity of log η ≦ 2 Pa · s including 900 ° C. is used, the baking temperature of the conductive paste for the base layer is 900 ° C. Thus, the occurrence of blistering and IR failure were recognized.

  Furthermore, even if it is a case where the conductive paste for base layers containing the glass whose glass viscosity is 850 degreeC from the sample 10 of Table 1 is used, the baking temperature of the conductive paste for base layers is used. Was 800 ° C., the viscosity of the glass was log η> 2 Pa · s, and an IR defect was observed.

  On the other hand, using a conductive paste for an underlayer containing Cu powder and glass having a viscosity of log η ≦ 2 Pa · s and a temperature of 820 ° C. to 870 ° C., the viscosity of the glass is log η = 2 Pa · s or less. When the conductive paste for the base layer is baked at a baking temperature of 870 ° C. or lower (in the case of Sample 3 to Sample 8 and Sample 11 to Sample 16), either blister generation or IR failure No tick was observed.

(Evaluation of cracking rate of external electrode)
Using the plurality of conductive pastes in which the ratio of the fine powder of the Cu powder and the flat powder was changed as the conductive paste for the underlayer, the multilayer capacitor 1 was created by the manufacturing method of the above embodiment. The crease generation rate of the external electrodes 20 and 22 of the produced multilayer capacitor 1 (Samples 21 to 24) was evaluated. Table 2 shows the evaluation results.

  The crispness of the external electrodes 20 and 22 was observed on the multilayer capacitor 1 having n = 600 samples using a Nikon stereo microscope (magnification is about 40 to 50 times). As a criterion for determining the sharpness, the case where the length of the sharpness reached 1/3 or more of the length of the corner portion of the ceramic body 10 was determined to be defective.

  From Sample 21 in Table 2, it was confirmed that when the flat powder ratio of the Cu powder was 0%, the generation of cricket was generated at a high rate of 4.0%.

  On the other hand, when the flat powder ratio of Cu powder is 40% or more (in the case of sample 22 to sample 24), the crease generation rate is as low as 0.2 to 0.7%, and almost crease is generated. It was recognized that they did not.

In addition, this invention is not limited to the said embodiment, A various deformation | transformation is carried out within the range of the summary.
For example, the present invention can be applied not only to a two-terminal ceramic electronic component but also to an array type multi-terminal ceramic electronic component. In this case, the external electrode has a belt shape and does not wrap around the side surface. The internal electrode of the ceramic body is not necessarily required.

  In addition to dielectric ceramics, piezoelectric ceramics such as PZT ceramics and semiconductor ceramics such as spinel ceramics can be used as the ceramic green sheet material. When the piezoelectric ceramic is used, the ceramic electronic component functions as a piezoelectric component. When a semiconductor ceramic is used, the ceramic electronic component functions as a thermistor.

1 Multilayer capacitor 2, 4 Internal electrode pattern 6 Ceramic green sheet (dielectric ceramic layer)
10 Ceramic body 20, 22 External electrode

Claims (3)

Forming a ceramic body containing Ca oxide;
Applying a conductive paste for external electrodes including Cu powder and glass having a viscosity of log η <2 Pa · s at a temperature of 820 ° C. to 870 ° C. on the surface of the ceramic body;
Baking the conductive paste for external electrodes in an inert gas at a temperature not lower than the temperature at which the viscosity of the glass is log η = 2 Pa · s or lower and a baking temperature of 870 ° C. or lower;
A method for producing a ceramic electronic component, comprising:   2. The method for manufacturing a ceramic electronic component according to claim 1, wherein a thickness of the external electrode conductive paste applied to the surface of the ceramic body after baking is in a range of 10 to 20 μm.   3. The ceramic electron according to claim 1, wherein the ratio of the fine powder and the flat powder of the Cu powder contained in the external electrode conductive paste is a flat powder ratio of 40% or more. 4. A manufacturing method for parts.

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