JP2014220127A - Conductive paste, method of producing the same and ceramic electronic part using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive paste which produces no defects even when an external electrode of a ceramic electronic part is in a thin-layer form.SOLUTION: A conductive paste comprises a conductive powder, a glass powder and an organic vehicle and has a yield value of 3.2-5.8 Pa at a descending shear rate of 9-4 s, calculated by the Casson approximation. An external electrode which has a clear shape free of defects, e.g. discontinuous parts, in corner parts of a laminate ceramic chip can be obtained by applying the conductive paste onto a laminate ceramic chip and baking.

Description

  The present invention relates to a conductive paste, a manufacturing method thereof, and a ceramic electronic component using the same, and more particularly, for example, a conductive paste used for an external electrode formed on an outer surface of a ceramic body, a manufacturing method thereof, and the same. The present invention relates to ceramic electronic components.

  In recent years, along with miniaturization of electronic devices including mobile phones, there is a demand for miniaturization of mounted ceramic electronic components. Against this background, further thinning is desired for the external electrodes of ceramic electronic components.

  In order to form an external electrode of a ceramic electronic component, a conductive paste is prepared by mixing and dispersing conductive powder, glass powder, and an organic vehicle with a mixer or a roll machine. Then, an external electrode is formed by applying a conductive paste to a ceramic body such as a ceramic substrate or a multilayer ceramic element by using screen printing or a dip method, drying, baking, and plating.

  However, the dispersibility of the conductive powder contained in the conductive paste for forming the external electrode changes with time, the rheological properties of the conductive paste change, the application shape changes, and the conductive paste There is a problem that the denseness of the electrode film formed by coating and baking is lowered. Then, the conductive paste which can solve such a problem is disclosed (refer patent document 1 and patent document 2).

JP 2004-171804 A JP 2004-39267 A

These patent documents disclose a conductive paste using glass powder having a specific surface area measured by the BET method of 3 m ² / g or less. However, when such a glass powder having a small specific surface area is used, the yield value of the conductive paste is lowered. When forming the external electrode on the ceramic body, the conductive paste is applied so as to go around from the end surface of the ceramic body to the side surface, but when the external electrode is thinned using the conductive paste having a low yield value, The coating thickness of the conductive paste at the corner portion of the ceramic body is particularly thin. When the conductive paste is fired in such a state, defects such as discontinuous portions may occur in the external electrodes at the corner portions of the ceramic body due to shrinkage during sintering.

  Therefore, a main object of the present invention is to provide a conductive paste that does not cause defects even when the external electrode of the ceramic electronic component is thinned, a manufacturing method thereof, and a ceramic electronic component using the same.

According to the present invention, in a conductive paste containing conductive powder, glass powder, and organic vehicle, the yield value calculated from the Casson approximation in the range of 9-4 s ^-1 descent rate is 3.2-5. A conductive paste characterized by being in the range of 8 Pa.
By using the conductive paste whose yield value is in the above range, the thickness of the conductive paste applied to the corner portion of the ceramic body can be sufficiently secured. Therefore, it is possible to prevent the external electrode from being defective when the conductive paste applied to the ceramic body is fired.

In such a conductive paste, the specific surface area of the glass powder measured by the BET method is preferably in the range of 7.0 to 10.1 m ² / g.
When the specific surface area of the glass powder is in such a range, a conductive paste having a yield value as described above can be obtained.

The present invention also includes a step of adjusting the specific surface area of the glass powder to 7.0 to 10.1 m ² / g by performing wet or dry media fine grinding, and a glass powder having an adjusted specific surface area, A method for producing a conductive paste, comprising a step of dispersing and mixing a conductive powder and an organic vehicle.
By employing such a manufacturing method, the conductive paste as described above can be obtained.

According to another aspect of the present invention, there is provided a ceramic electronic component having an external electrode formed on the outer surface of the ceramic body, wherein the external electrode is formed using the above-described conductive paste. is there.
By forming the external electrode using the above-described conductive paste, a ceramic electronic component having a thin external electrode without a defect can be obtained.

  According to the present invention, even if the conductive paste is thinly applied to the ceramic body, the application thickness of the conductive paste at the corner portion can be sufficiently ensured. Therefore, even if the conductive paste applied to the ceramic body is sintered, a discontinuous portion or the like does not occur in the electrode, and a ceramic electronic component having a thin external electrode without defects can be obtained.

  The above-described 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.

FIG. 1 is a perspective view showing an example of the ceramic electronic component of the present invention. FIG. 2 is a perspective view of the multilayer ceramic chip used in the embodiment of the present invention. FIG. 3 is an exploded perspective view of the multilayer ceramic chip shown in FIG. FIG. 4 is a photomicrograph showing the portion of the external electrode measured in the example. FIG. 5 is a graph showing the relationship between the specific surface area of the glass powder contained in the conductive paste and the yield value of the conductive paste. FIGS. 6A and 6B are photomicrographs showing the state of the external electrodes formed with conductive pastes having yield values of 5.8 Pa and 3.2 Pa, respectively. FIG. 7 is a photomicrograph showing a state of the external electrode formed of a conductive paste having a yield value of 1.5 Pa. FIGS. 8A and 8B are photomicrographs showing the state of external electrodes formed from conductive pastes having a yield value of 14.8 Pa and 19.6 Pa, respectively.

The electrically conductive paste of this invention contains electrically conductive powder, the glass powder which improved the specific surface area by pulverizing, and the organic vehicle. Here, the conductive paste has a yield value of the conductive paste in the range of 3.2 to 5.8 Pa calculated from the Casson approximation in the range of the descent rate of 4 to 9 s ⁻¹ .

  There is no restriction | limiting in the shape and form of the electroconductive powder used here, The thing of various shapes, such as spherical shape, indefinite shape, and flat shape, can be used. As the organic solvent constituting the organic vehicle, various substances capable of dissolving the polymer substance can be used. For example, aromatic hydrocarbons such as benzene, xylene and toluene, aliphatic hydrocarbons such as hexane and decane, alcohols such as benzyl alcohol and 3-methoxy-3-methyl-1-butanol, terpineol, dihydroterpineol and the like It is possible to use terpenes, polyhydric alcohols such as ethylene glycol monomethyl ether and ethylene glycol monobutyl ether, esters such as butyl lactate, ketones, ethers, acetals, nitrogen-containing compounds, sulfur-containing compounds, etc. it can. These solvents can be used alone or in combination of two or more.

  In addition, as the polymer material constituting the organic vehicle, known synthetic polymer materials and natural polymer materials can be used. Specifically, acrylic resins, vinyl acetate resins, polyester resins, polyolefins can be used. Examples of such resins include fluororesins, fluororesins, polystyrene resins, polyamide resins, alkyd resins, and cellulose resins. These polymer substances can be used alone or in combination of two or more.

Moreover, there is no restriction | limiting in the shape and form of glass powder, The thing of various shapes, forms, such as spherical shape, indefinite shape, and flat shape, can be used. The specific surface area of the glass powder measured by the BET method is preferably in the range of 7.0 to 10.1 m ² / g. As the glass powder, for example, known glass powders such as silica borate glasses and zinc borate glasses can be used alone or in combination of two or more.

In order to obtain this conductive paste, conductive powder, glass powder, and an organic vehicle are prepared. Here, the glass powder is adjusted to have a specific surface area of 7.0 to 10.1 m ² / g by wet or dry media fine grinding. Then, the conductive powder and the glass powder are put into an organic vehicle, and dispersed and mixed using a known method such as dispal mill, ball mill, or roll, whereby a conductive paste can be manufactured.

  A ceramic electronic component 10 as shown in FIG. 1 is manufactured using the conductive paste thus obtained. The ceramic electronic component 10 includes, for example, a rectangular parallelepiped ceramic body 12. As the ceramic body 12, for example, a ceramic body used for a multilayer ceramic capacitor, a chip inductor, or the like can be used. A conductive paste is applied to the outer surface of such a ceramic body 12, dried and fired to form the external electrode 14. The external electrode 14 is plated as necessary.

Since the specific surface area of the glass powder contained in this conductive paste is in the range of 7.0 to 10.1 m ² / g, the yield value calculated from the Casson approximation in the range of the descent rate of 4 to 9 s ⁻¹ is A conductive paste in the range of 3.2 to 5.8 Pa can be obtained. By setting the yield value of the conductive paste in such a range, the thickness of the conductive paste at the corner portion of the ceramic body can be sufficiently ensured. Therefore, even if shrinkage occurs when firing the conductive paste, discontinuous portions do not occur in the external electrodes at the corners of the ceramic body, and good characteristics can be obtained.

  When the yield value of the conductive paste is 2.0 Pa or less, when the conductive paste is applied to the ceramic body by a well-known screen printing or dip method, the thickness of the conductive paste applied at the corner is reduced, and the firing is performed. There is a problem that defects occur when contracted. Further, when the yield value of the conductive paste is significantly higher than 5.8 Pa, for example, when the yield value is 14.8 Pa or more, when the conductive paste is applied to the ceramic body by a known screen printing or dipping method, There is a problem that the leveling deteriorates and the external electrode becomes uneven.

  On the other hand, when the yield value of the conductive paste is in the range of 3.2 to 5.8 Pa, there is no defect in the corner portion of the ceramic body, and a clean external electrode can be obtained.

  As raw materials of the conductive paste, conductive powder (Cu powder) shown in Table 1, glass powder shown in Table 2, and organic vehicle shown in Table 3 were prepared. The glass powder shown in Table 2 has a specific surface area adjusted by wet or dry media fine grinding. Moreover, the average particle diameter of the electroconductive powder of Table 1 and the average particle diameter of the glass powder of Table 2 have shown D50 value of the laser diffraction type particle size distribution measuring method. Furthermore, the specific surface area of the glass powder in Table 2 is a value measured by the BET method.

  Conductive powder, glass powder and an organic vehicle were dispersed and mixed with three rolls to obtain a conductive paste having the composition shown in Table 4.

  Table 5 shows the relationship between the specific surface area of the glass powder contained in the conductive paste in Table 4 and the yield value of the conductive paste.

In Table 5, the yield value of the conductive paste was measured using a rheometer manufactured by TA Instruments, with a cone angle of 0.04 °, a cone diameter of 25 mm, a gap of 0.0559 mm, and a measurement temperature of 25 ° C. The speed was accelerated from ⁰ to 10 s ^{−1 in} 30 seconds and then decelerated from 10 to 0 s ⁻¹ for 30 seconds. The yield value was calculated by applying Casson approximation in the range where the descending shear rate of the flow curve thus obtained was 9 to 4 s ⁻¹ .

  Moreover, in order to form an external electrode using a conductive paste, as shown in FIG. 2, a JIS2012 size (length L: 2.0 mm, height T: 1.2 mm, width W: 1.2 mm) A multilayer ceramic chip 10 was prepared. The multilayer ceramic chip 12 includes a plurality of internal electrodes 16 as shown in FIG. The internal electrode 16 is formed so as to extend from one side in the length direction of the multilayer ceramic chip 12 to the other side. The plurality of internal electrodes 16 are formed so as to overlap each other at the center in the length direction of the multilayer ceramic chip 12. The adjacent internal electrodes 16 are drawn out to different end portions of the multilayer ceramic chip 12 in the length direction. Therefore, the laminated internal electrodes 16 are alternately drawn on both end faces in the length direction of the multilayer ceramic chip 12, and the internal electrodes are not drawn on the side surfaces of the multilayer ceramic chip 12. A conductive paste of Sample Nos. 1 to 5 is applied to the end in the length direction of such a multilayer ceramic chip 12 using a dipping method, and then sintered at 850 ° C. to form a sintered film of the external electrode did.

  For the obtained sintered film, the LT surface including the length direction and the height direction of the ceramic chip is polished, and the surface where the internal electrode is first exposed is the WGap0 polished surface, and the corner portion of the external electrode on this surface The bonding state of was observed with a metallographic microscope. Here, the external electrodes were observed with respect to the end face thickness, the outermost layer thickness, and the corner portion thickness. The end face thickness is the thickness of the external electrode on the end face of the multilayer ceramic chip from which the internal electrode is drawn, as shown in FIG. Further, the outermost layer thickness is the thickness of the external electrode in a portion connected to the internal electrode in the outermost layer, as shown in FIG. Furthermore, the corner portion thickness is the thickness of the external electrode at the corner portion that transitions from the end surface to the side surface of the multilayer ceramic chip, as shown in FIG. Table 6 shows the measured thickness of the external electrode of each part. Table 6 shows target thicknesses in the respective portions of the external electrode.

  The relationship between the specific surface area of the glass powder shown in Table 5 and the yield value of the conductive paste is shown in FIG. 5 as a graph. As can be seen from the semilogarithmic graph of FIG. 5, the yield value of the conductive paste increases exponentially with respect to the specific surface area of the glass powder.

FIGS. 6A and 6B show micrographs of the external electrodes at the corners of the multilayer ceramic chip when the conductive pastes having the yield values of 5.8 Pa and 3.2 Pa are used. 6A and 6B, the yield value of the conductive paste is in the range of 3.2 to 5.8 Pa (the specific surface area of the glass powder is in the range of 7.0 to 10.1 m ² / g). Was able to secure a sufficient thickness of the external electrode at the corner of the multilayer ceramic chip on the WGap0 polished surface, and was in a good state without defects.

  FIG. 7 shows a photomicrograph of the external electrode at the corner portion of the multilayer ceramic chip when a conductive paste having a yield value of 1.5 Pa is used. As can be seen from FIG. 7, when the yield value of the conductive paste is as low as 2.0 Pa or less, the external electrode thickness at the corner portion of the multilayer ceramic chip on the WGap0 polished surface cannot be sufficiently secured, and the external electrode has a discontinuous portion. The defect was seen.

  8A and 8B show micrographs of the external electrodes at the corners of the multilayer ceramic chip when using conductive pastes having yield values of 14.8 Pa and 19.6 Pa. As can be seen from FIGS. 8A and 8B, when the yield value of the conductive paste is remarkably high, coating leveling deteriorates when the conductive paste is applied to the multilayer ceramic chip by a known screen printing or dip method. Thus, the shape of the external electrode at the corner of the multilayer ceramic chip is uneven.

  From this example, it can be seen that by using a conductive paste having a yield value in the range of 3.2 to 5.8 Pa, an external electrode having no defects and having a good shape can be obtained. Therefore, by using such a conductive paste, it is possible to obtain a ceramic electronic component on which a thin external electrode having no defect is formed, which can contribute to the manufacture of a small ceramic electronic component.

Claims (4)

In a conductive paste containing a conductive powder, a glass powder, and an organic vehicle,
A conductive paste having a yield value calculated from Casson approximation in the range of 9-4 s ^-1 of the descent rate in the range of 3.2 to 5.8 Pa. ^2. The conductive paste according to claim 1, wherein a specific surface area of the glass powder measured by a BET method is in a range of 7.0 to 10.1 m ² / g. A step of adjusting the specific surface area of the glass powder to 7.0 to 10.1 m ² / g by performing wet or dry media pulverization, and the glass powder having the adjusted specific surface area, a conductive powder, A method for producing a conductive paste, comprising a step of dispersing and mixing an organic vehicle. In ceramic electronic components in which external electrodes are formed on the outer surface of the ceramic body,
A ceramic electronic component, wherein the external electrode is formed using the conductive paste according to claim 1 or 2.