TW201729221A - Conductive paste and method for forming conductor membrane suitable for internal electrodes of a small-sized high-capacity MLCC - Google Patents

Abstract

To provide a conductive paste for gravure printing which can form a continuous thin conductor membrane suitable for internal electrodes of a small-sized high-capacity MLCC, and a method for forming the conductor membrane. In the conductive paste, viscosity x(Pa.s) and a contact angle y for a test surface having an arithmetic average roughness Ra of 0.010 ([mu]m) or less satisfy y < 17.6x+19.1 (where x ≤ 3.0 and y < 40); therefore, when gravure printing is performed on a ceramic green sheet using this conductive paste, the conductive paste is transferred promptly and uniformly from a gravure printing plate. Accordingly, the paste surface becomes smooth immediately after the transfer to make it easy for the film thickness to be thinned while maintaining continuity. Thus, it becomes possible to form a continuous conductor membrane having a thin film thickness suitable for internal electrodes of a small-sized high-capacity MLCC.

Description

Method for forming conductive paste and conductor film

FIELD OF THE INVENTION The present invention relates to a conductive paste which can be suitably used in gravure printing, and a method of forming a conductor film by gravure printing.

BACKGROUND OF THE INVENTION For example, when a multilayer ceramic capacitor (MLCC) 10 having a cross-sectional structure is schematically shown in Fig. 1, a conductive paste containing a metal having heat resistance as a conductive component is printed and coated to form a dielectric layer thereof. 12 uncalcined ceramic green sheet surface, and after laminating a large number and pressure-bonding, by performing a calcination treatment, the dielectric layer 12 is formed from the green sheet, and a conductive paste is formed. Conductor layer 14 of internal electrodes. Further, in Fig. 1, 16 is an external electrode for energizing the internal electrode (conductor layer 14). In the printing formation of such an internal electrode, a gravure printing method in which gravure printing can be applied (for example, refer to Patent Document 1). The gravure printing method is a method in which a conductive paste is filled into a concave portion provided in a plate making, and a conductive paste is transferred from the plate-making by pressurizing it to contact the surface to be printed, which has an advantage of a printing speed being fast.

A conductive paste for forming an internal electrode or the like of an MLCC has been conventionally used in a conventional screen printing method, but the screen printing method has a problem in that the dimensional accuracy of the plate extension is lowered. In particular, in an ultra-small MLCC such as 0603 size (outer size 0.6 mm × 0.3 mm × 0.3 mm) and 0402 size (outer size 0.4 mm × 0.2 mm × 0.2 mm), it is further difficult to ensure the dimensional accuracy of the printed film. On the other hand, when the above-described gravure printing method is used, since the plate extension is not generated, it is suitable for the MLCC application requiring such high-precision printing. Prior Technical Literature Patent Literature

Patent Document 1: Japanese Laid-Open Patent Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. Bulletin

Disclosure of the Invention Problems to be Solved by the Invention In the small-sized high-capacity MLCC such as the 0603 size and the 0402 size described above, it is required to set the thickness of the internal electrode to 1 (μm) or less. In order to obtain a continuous film with such a thin film thickness, it is necessary to form a printed film having a smooth surface. In the gravure printing method in which the printing speed is relatively fast and the tact time of the printing and drying steps is short, the time from the printing to the drying is shortened, and the time for leveling the printing film is also shortened. Therefore, in order to obtain a printing film having excellent surface smoothness, it is preferable to uniformly transfer from a plate by a conductive paste, and a film having a smooth surface immediately after the transfer is formed.

In the past, various proposals have been made to improve the conductive paste in the gravure printing method. For example, when the gravure printing method is applied to the MLCC, it has been proposed to use a petroleum solvent or an alcohol solvent to suppress swelling and redissolution of the ceramic green sheet by the solvent (see, for example, Patent Document 1). In addition, when suppressing the etch of the sheet, it is proposed to use a solvent such as 1-p-menthene or p-menthane in consideration of the drying speed of the printing coating film (for example, refer to Patent Document 2). ).

In the case of producing a laminated ceramic component such as MLCC, the conductive paste is printed on the ceramic green sheet, and the paste containing the ceramic raw material as a main component is printed on a portion other than the portion where the conductor pattern is formed, thereby making the ceramic green sheet. When the surface is flattened, it is proposed to form a printed film having excellent flexibility by using a terpene resin having a number average molecular weight of 300 to 5,000 in addition to the ethyl cellulose resin in the paste (for example, reference) Patent Document 3). In gravure printing, a low-viscosity and thixotropy-resistant conductive paste is used to easily transfer it from a printing plate to a to-be-printed body, but a printed film formed from such a conductive paste is printed in a ceramic paste. When the printing plate is in contact, the conductor pattern is likely to be damaged or peeled off. Therefore, it is desirable to suppress the damage and fall off by improving the flexibility of the printed film.

In addition, it is proposed to improve the paste transfer property by the change of the plate-making side, and it is proposed to use a film having a contact angle of 50 Å or more in water to cover the groove (for example, see Patent Document 4). . According to the plate making, since the groove is covered with a perfluoroalkoxy resin or the like, the contact angle with water is increased to 50 Å or more, and it is considered that the wettability of the paste and the plate is lowered and the transfer property is improved.

As described above, various proposals for improvement of the conductive paste by the gravure printing method and improvement of the plate making have been made from the viewpoints of suppressing the etching of the sheet and improving the strength of the printed film. However, these cannot be used to form a continuous film with a thin film thickness of 1 (μm) or less. In addition, when the conductive paste is prepared so as to have the same contact angle, the type of the conductive powder, the particle diameter, and the like, and the composition of the vehicle or the like is different, the transfer property is different, and it is not always possible to obtain good results. The results were also clearly understood again.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a conductive paste for gravure printing capable of forming a continuous and thin conductor film suitable for an internal electrode of a small-sized high-capacity MLCC, and a method of forming the conductor film.

In order to achieve such an object, the conductive paste for gravure printing containing a conductive powder, an adhesive, and an organic solvent is at 25 (° C.) and a shear rate of 40 (1/s). The contact angle at which the viscosity is set to x (Pa·s) and the arithmetic mean roughness Ra is 0.010 (μm) or less is set to y (∘) at a drop rate of 10 (μL) at 25 (° C.), at this time, x y satisfies the following formula (1). y<17.6x+19.1 (however, x≦3.0, y<40)・(・)

In order to achieve the above object, a second aspect of the invention provides a method for forming a conductor film comprising the steps of: preparing a conductive paste containing a conductive powder, an adhesive, and an organic solvent; and filling the conductive paste with a step of printing a concave portion of the gravure printing plate and transferring it to the surface to be printed; and a calcining step of forming a conductor film on the printed surface by performing a calcination treatment on the formed printing film; wherein the step of preparing the conductive paste The above-mentioned conductive paste is prepared by the following: the viscosity x (Pa·s) at 25 (° C.) and the shear rate of 40 (1/s) is the same as the outermost peripheral surface of the gravure printing plate. The contact angle y (∘) at the time of the test surface in which the material is horizontally disposed in the same surface state, and x and y satisfy the above formula (1). Effect of the invention

According to the first aspect of the invention, the contact angle y (∘) of the test surface with respect to the arithmetic mean roughness Ra of 0.010 (μm) or less is satisfied by the above-mentioned (1) because the viscosity of the conductive paste for gravure printing is (Pa·s). Therefore, when the conductive paste is used to perform gravure printing on the surface to be printed, the conductive paste is quickly and uniformly transferred from the gravure plate to the to-be-printed surface. In this way, since the surface of the paste immediately after the transfer becomes a smooth surface, it is easy to reduce the film thickness while maintaining the continuity. Therefore, when the conductive paste is used, an internal electrode suitable for a small-sized high-capacity MLCC can be formed. A continuous and thin film thickness of the conductor film.

Further, according to the second invention, when the conductor film is formed by the gravure printing method, the step of preparing the conductive paste is performed by adjusting the conductive paste under the following conditions: viscosity at 40 (1/s) x (Pa) s), using the same material as the outermost peripheral surface of the gravure printing plate and dropping the contact angle y (∘) at 10 (μL) on the test surface horizontally arranged to have the same surface state, the x, y satisfying the above ( 1). Therefore, in the printing step, when the conductive paste is used for gravure printing, the conductive paste is quickly and uniformly transferred to the surface to be printed. As a result, since the surface of the paste becomes a smooth surface immediately after the transfer, it is easy to reduce the film thickness while maintaining the continuity. Therefore, it is possible to form a continuous and thin film suitable for the internal electrodes of the small-sized high-capacity MLCC. Thick conductor film. Further, in the present case, "the outermost surface of the plate making" means the surface on the cylindrical surface before the printing pattern is formed.

By the way, in order to uniformly transfer the gravure printing plate to the surface to be printed, the organic composition of the conductive paste has been optimized, and the rheology has been optimized, but as described above, The attempt did not yield sufficient results. On the other hand, the invention of the present application found that not only the wettability of the plate-making and the conductive paste, that is, the contact angle, but also the viscosity of the conductive paste is related to the transfer property. The viscosity is adjusted by the contact angle system satisfying the above formula (1), that is, by setting the contact angle to a certain value or less in relation to the viscosity, the conductive paste can be uniformly transferred from the gravure printing plate to The surface to be printed is smoothed from the surface of the film immediately after transfer.

Further, in the first invention, the surface roughness of the test surface is required to be equal to or less than 0.015 (μm) in arithmetic mean roughness Ra. Since the surface roughness of the outermost peripheral surface of the gravure printing plate is usually Ra of 0.010 (μm) or less, evaluation using the above test surface can be considered as evaluation using the outermost peripheral surface of a usual gravure printing plate.

Further, in the present case, the viscosity x (Pa·s) is a static viscosity at 25 (° C.) and a shear rate of 40 (1/s). This condition is determined by considering the room temperature at the time of gravure printing and the stress acting on the conductive paste when the conductive paste is transferred to the surface to be printed during gravure printing. Therefore, the viscosity of the conductive paste is used by using the crucible. And the correlation between the contact angle and the transfer property can be stably obtained. Further, the viscosity measurement can be carried out using a commercially available viscometer.

Further, in the present case, the contact angle y (∘) is measured by measuring the enthalpy measured by dropping 10 (μL) to the liquid level at 25 (°C). Since this condition is determined by considering the room temperature at the time of gravure printing and the amount of the conductive paste transferred at the time of formation of the internal electrode of the MLCC, the viscosity and contact angle of the conductive paste and the transfer are used by using the crucible. The correlation between sexes can be obtained stably. Further, the dropping of the conductive paste can be performed, for example, using a micropipette, and the contact angle can be measured using a commercially available contact angle meter.

Further, the above formula (1) is established in the range of x≦3.0 and y<40. When it is larger than the range of the viscosity and the contact angle of the above range, good transferability cannot be obtained even if y<17.6x+19.1 is satisfied.

According to the invention of the present application, the conductive paste is prepared by using the method specified above, and the conductive paste is prepared in such a manner that the above formula (1) is satisfied, and the conductive paste can be uniformly obtained from the gravure printing plate as described above. Transferred to the surface to be printed and smoothed from the surface of the film immediately after transfer. That is, when the wettability of the contact angle is not more than 値, it is not always possible to obtain good transferability, and the smaller the viscosity, the smaller the contact angle must be, that is, it must be easily wetted.

Further, in the relationship between the contact angle and the transfer property, Patent Document 4 discloses that the transfer angle is large and the transfer property is good and must be 50 Å or more. However, when it is too large, the paste does not easily enter the groove. situation. However, according to the results of studies by the inventors of the present invention, in order to obtain good transferability, the contact angle is preferably smaller, and as shown in the above formula (1), when measured between the conductive paste and the plate making, it is necessary to measure Become 40 ∘ or less. In the above-described Patent Document 4, it is preferable to use "50 Å or more and not too large". However, according to the present inventors, the result is reversed. Further, although in the above Patent Document 4, the contact angle is limited by the enthalpy of water, this is indirectly restricting the surface state of the groove by the contact angle with water, without considering the actual system. The appropriate contact angle differs depending on the physical properties of the paste used.

Here, it is preferable that either the test surface of the first invention or the outermost peripheral surface of the gravure printing plate of the second invention and the test surface are plated with Cr or Ni plating. In order to improve the wettability with the conductive paste, it is preferred that the gravure printing plate is subjected to Cr plating or Ni plating. Therefore, it is preferable to use Cr or Ni plating on the test surface in the same manner. Moreover, in order to improve the wettability and reduce the contact angle, it is preferable to perform plating, and the type of plating of the test surface is preferably the same as the type of plating of the gravure printing plate. However, since the same contact angle can be obtained even if there is a difference in the type of plating, it is not necessary to match the types of plating.

Further, in the above formula (1), the viscosity x (Pa·s) is preferably in the range of 0.1 ≦ x ≦ 3.0. As shown in the above formula (1), the lower the viscosity, the lower the upper limit 値 of the allowable contact angle y, so that it becomes difficult to prepare the conductive paste which satisfies the formula (1). Therefore, the viscosity is preferably 0.1 (Pa·s) or more.

Further, in the above formula (1), the range of the contact angle y (∘) is preferably 10 < y < 40. When the contact angle y is 10 Å or less, the wettability becomes too high, and on the contrary, good transferability cannot be obtained.

Further, it is preferable that the viscosity x and the contact angle y satisfy y>8.8x+12.4 (2). The smaller the contact angle y, the higher the wettability and the lower the workability. However, since the viscosity x is lower, the value of y can be allowed to be smaller, so that the above formula (2) is preferably satisfied.

Further, it is preferable that the conductive paste is used for printing and coating a ceramic green sheet to form a conductor film. The conductive paste of the present invention is not limited by use, but can be suitably used in the case where a conductor film is formed on a ceramic insulator. In particular, when printing is applied to a green sheet, when a firing treatment is performed to form an insulator, a conductor film can be simultaneously formed by firing, which is advantageous in terms of production cost.

Further, it is preferable that the conductive paste is used to form an internal electrode of the MLCC. As described above, when the conductive paste of the present invention is used, since the film thickness can be easily reduced while maintaining continuity, it is suitable for an internal electrode of a small-sized high-capacity MLCC.

Further, it is preferable that the conductive powder is nickel powder. For example, in the internal electrode application of the MLCC, a ceramic green sheet printed with a conductive paste is laminated and subjected to a calcination treatment, since an internal electrode is formed while a dielectric layer is formed from the ceramic green sheet, the conductive powder is It is required to have heat resistance. Therefore, the conductive powder of the conductive paste of the present invention is preferably a metal having heat resistance such as Pt, Pd, Ag-Pd, Ag, Ni, Cu, etc., but is inexpensive in terms of manufacturing cost. The base metal material is preferred, and in terms of heat resistance, electrical conductivity, and price, nickel is particularly preferred. The average particle diameter of the conductive powder can be appropriately determined in the range of characteristics required for obtaining the conductive paste, and is, for example, 1.0 (μm) or less, preferably 0.01 to 0.50 (μm), and 0.05 to 0.30 (μm). The range is better.

Further, the adhesive is preferably polyvinyl butyral, polyvinyl alcohol, acrylic resin, epoxy resin, phenol resin, alkyd resin, cellulose polymer, rosin resin or the like. The adhesive for the conductive paste of the present invention can be suitably selected from those which are usually in a range capable of achieving a desired viscosity and contact angle, but in terms of coating film forming ability (i.e., adhesion to a substrate) and at the time of calcination In terms of decomposability, it is preferred to use the above substances.

Moreover, it is preferable that the organic solvent is not particularly limited as long as it can be suitably dissolved or dispersed in the conductive powder and the adhesive resin component. Examples of the solvent include an alcohol solvent such as terpineol, a terpene solvent such as isodecyl acetate, a glycol solvent such as ethylene glycol, and diethylene glycol monobutylate. A glycol ether solvent such as ether (butyl carbitol), an ester solvent, a hydrocarbon solvent such as toluene or xylene, or an organic solvent having a high boiling point such as other mineral spirits. Since these organic solvents do not easily dissolve the butyral resin and the acrylic resin adhesive in the ceramic green sheet, it is preferable that so-called sheet etching is likely to occur.

Further, it is preferable that the conductive paste contains a constituent component (common material) of a ceramic green sheet to which the conductive paste is applied as usual. For example, when the dielectric layer of MLCC is composed of barium titanate, it is preferred to contain barium titanate powder. Since the conductive paste of the present invention can easily form a thin internal electrode, the average particle diameter of the shared material is preferably small, for example, 0.5 (μm) or less, and 0.005 to 0.2 (μm) is Preferably, the range of 0.01 to 0.1 (μm) is more preferable.

In addition, the component ratio of the conductive paste is not particularly limited, and can be appropriately determined so as to satisfy the above formulas (1) and (2). For example, the mass ratio is 30 to 60% by weight. The composition of the conductive powder, 1 to 5 (%) of the above-mentioned adhesive, 35 to 65 (%) of the organic solvent, and 0 to 20 (%) of the common material is preferable. Moreover, when a shared material is contained, it is preferable that it is the range of 1-20 (%).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail. Further, in the embodiments described below, it is possible to appropriately use a configuration that has been conventionally employed as long as it is not specifically notified in advance.

The conductive paste of the present embodiment was produced as shown in Fig. 1 described above in order to form the conductor layer 14 as an internal electrode by the gravure printing method when the MLCC 10 was produced. In the present embodiment, the thickness dimension of one layer of the dielectric layer 12 is, for example, 10 (μm) or less, for example, 0.1 to 3 (μm), for example, about 1 (μm), and the thickness of one layer of the conductor layer 14 is For example, it is 10 (μm) or less, for example, in the range of 0.1 to 3 (μm), for example, about 0.5 (μm).

The conductor layer 14 described above is formed, for example, of nickel, and the dielectric layer 12 described above is formed, for example, of barium titanate. When the MLCC 10 is produced, the conductive powder, the ceramic powder, the adhesive, and the organic solvent are mixed in accordance with a predetermined mixing method to prepare a conductive paste, which is printed and coated by gravure printing to form a separate medium. One side of the ceramic green sheet of the electric layer 12. After laminating and bonding the ceramic green sheets coated with the conductor paste, the dielectric layer 12 formed of the ceramic green sheets is formed by the calcination treatment, and the conductor layer 14 is formed from the conductor paste, and then borrowed. The external electrode 16 is formed by a method such as immersion to obtain the MLCC 10 shown in Fig. 1 described above.

The conductive powder is, for example, a nickel powder having an average particle diameter of 1 (μm) or less, for example, 0.13 to 0.18 (μm), for example, mixed in a conductive paste at a ratio of about 30 to 60 (wt%). . Further, the ceramic powder is, for example, a barium titanate powder having an average particle diameter of 0.1 (μm) or less, for example, 10 to 20 (nm), that is, a common material of barium titanate constituting the dielectric layer 12. For example, it is mixed in a conductive paste at a ratio of a nickel ratio of about 10 to 15 (wt%). Further, the above-mentioned adhesive is, for example, ethyl cellulose or polyvinyl butyral, and the above organic solvent is dihydroterpineol, isodecyl acetate or menthone propionate as a main solvent. Each of these systems uses a ratio of about 1 to 5 (%) and 30 to 65 (%).

In the present embodiment, the composition of the conductive paste is such that the contact angle thereof is such that the viscosity thereof and the test surface which is dropped to the same surface as the outermost peripheral surface of the intaglio printing plate and are prepared to have the same surface state satisfy the above (1). Mode (re-disclosed) mode modulation. The viscosity is a static viscosity measured by using, for example, a rheometer (Rheostress 6000 manufactured by HAAKE) and using a condition of 25 (° C.) and a shear rate of 40 (1/s) for 1 minute. Further, the contact angle was dropped by 10 (μL) to the horizontally arranged test surface at 25 (° C.) using a micropipette, and was measured, for example, using a FACE contact angle meter (CA-DT manufactured by Kyowa Interface Chemical Co., Ltd.). Contact angle. The contact angle is, for example, an average of five measurements. y<17.6x+19.1 (however, x≦3.0, y<40)・(・)

In addition, when the test surface is, for example, a gravure printing plate is a Cr plated plate, for example, a Cr plate has a surface which is finished to have a state in which the arithmetic mean roughness Ra is 0.010 (μm) or less and the smoothness is extremely high. Further, it is also possible to use a Cr-plated plate instead of the Cr plate in the same manner as the plate making. In the present embodiment, the surface material is peeled off, for example, from the unpatterned portion of the gravure printing plate. The size of the test planar substrate is, for example, 5 (cm) × 3 (cm).

The conductive paste prepared in this manner is printed and applied on the ceramic green sheet by gravure printing, and the formed film has a dry film thickness of about 0.5 (μm) and a surface roughness Ra of 0.020 (μm) or less. The smooth surface is obtained by calcining it to obtain a smooth continuous film. By obtaining the smoothness of the level, it is possible to further improve the capacitor characteristics and reliability.

In the printing and coating step of the conductor layer 14 described above, the conductive paste composition was variously changed, and the results of evaluating the printability by various combinations of the viscosity and the contact angle were summarized. In Table 1, "Ni particle diameter" and "BT particle diameter" are each an average particle diameter of a nickel powder and an average particle diameter of a barium titanate powder. Further, the "BT amount" is a mass ratio of barium titanate powder to Ni. Further, "MC" is a mass ratio of nickel powder to the entire paste. "40 (1/s) viscosity" is the static viscosity measured by the rheometer described above. In addition, the "contact angle with the Cr plate" and the "Cr-plated plate-printing body Ra" are evaluation data when gravure printing is performed using a Cr-plated plate. The former is a measurement of the contact angle between the conductive paste and the Cr plate, and the latter is The surface roughness of the printed film formed by plating with Cr was printed and applied using the conductive paste. The surface roughness was a dry average microscope (Nikon LV150 ECLIPSE) and the arithmetic mean roughness Ra measured at a magnification of 10 times, a measurement range of 50 (μm) × 1000 (μm), and a measurement number of 12. In addition, the "contact angle with the Ni plate" and the "Ni plated printing plate Ra" are evaluation data when gravure printing is performed using a Ni plate.

[Table 1]

In the above Table 1, the surface roughness Ra of the printed material is not more than 0.020 (μm), which is a good printability, that is, an embodiment. In Fig. 2, a graph showing the above evaluation results is shown. In Fig. 2, "◆" is an example, and "mouth" is a comparative example. Examples 1 to 11 are located on the lower side than the formula (1) shown in Fig. 2, and are conductive pastes satisfying the same. In Comparative Examples 1 to 8, the conductive paste was placed on the upper side of the formula (1) or on the right side of the viscosity of 3.0 (Pa·s), and was a conductive paste of a comparative example which did not satisfy the range of the present invention.

As shown in the above evaluation results, the surface roughness of the printed body can be obtained by satisfying the viscosity and contact angle of the above formula (1) at a viscosity of 0.1 to 3.0 (Pa·s) and a contact angle of 14 to 39 (∘). Very good results from 0.003 to 0.016 (μm). Therefore, when the internal electrode (conductor layer 14) of the MLCC 10 is formed by using such a conductive paste, it is possible to obtain good transferability from the gravure printing plate to the printed surface, and as a result, it is possible to easily obtain a thinner and smooth surface. The continuous film allows a small, high-capacity MLCC10 to be obtained at a high manufacturing yield. Further, in Example 11, the Ni-plated plate was also evaluated, and good results were obtained in the same degree as in the case of Cr-plating. When the conductive paste is prepared in such a manner as to satisfy the formula (1), any of the Cr-plated plate and the Ni-plated plate can be similarly obtained as a continuous film having a thin surface and a smooth surface.

On the other hand, in Comparative Examples 1 to 6, even in the range of 0.2 to 3.0 (Pa·s), the contact angle is 22 to 72 (∘), because the viscosity of the above formula (1) is not satisfied. Since it is combined with the contact angle, the transfer property from the gravure printing plate is inferior and the surface roughness Ra of the printed body is larger than 0.021 to 0.194 (μm). The size of the surface roughness Ra indicates the size of the unevenness on the surface of the printed film. Since the thickness of the conductor layer 14 is very thin and is about 0.5 (μm), the large unevenness as described above means that the printed film cannot be printed. Get continuity. That is, it is difficult to obtain a continuous film having a thin surface and a smooth surface in the conductive paste of the comparative example.

Further, the viscosity of Comparative Examples 7 and 8 was very high, and was 5.3 to 6.9 (Pa·s), and the contact angle was 51 to 61 (∘) and was located on the lower side of the above formula (1). However, when gravure printing was performed using these, the surface roughness Ra of the printing film was large, and it was 0.036 to 0.095 (μm), and a continuous film could not be obtained similarly to the comparative examples 1 to 6. Even when it is located on the lower side of the type (1), the transferability is poor when the viscosity is more than 3.0 (Pa·s).

As described above, according to the present embodiment, the contact angle y(∘) of the test surface of the conductive paste is 0 (Pa·s) and the arithmetic mean roughness Ra is 0.010 (μm) or less to satisfy the above (1). In the formula, when the conductive paste is used to perform gravure printing on the ceramic green sheet, the conductive paste can be quickly and uniformly transferred from the gravure printing plate. With this, since the surface of the paste immediately after the transfer becomes a smooth surface and the film thickness is easily thinned while maintaining the continuity, it is possible to form a continuous and thin inner electrode suitable for the small-sized high-capacity MLCC 10. The film thickness 14 of the conductor film.

In addition, the viscosity and the contact angle of the conductive paste may be appropriately adjusted by changing the Ni particle diameter, the BT particle diameter, the Ni amount, the BT amount, or the type and amount of the adhesive and the organic solvent.

Further, according to Table 1 and Figure 2 above, the lower limit 较佳 of the preferred viscosity is 0.1 (Pa·s). It is difficult to make the conductive paste a lower viscosity than the conductive paste. Further, the lower limit 接触 of the contact angle is 10 (∘). When the contact angle is 10 (∘) or less, the wettability becomes too high, and on the contrary, good transferability cannot be obtained.

Further, the viscosity x and the contact angle y are preferably higher than the formula (2) of Fig. 2, that is, y > 8.8 x + 12.4. The smaller the contact angle y, the higher the wettability and the worse the workability, and the lower the viscosity x, the allowable contact angle y to a small value.

The present invention has been described in detail with reference to the drawings. However, the present invention can be further modified and various modifications can be made without departing from the spirit and scope of the invention.

10‧‧‧MLCC
12‧‧‧ dielectric layer
14‧‧‧Conductor layer
16‧‧‧External electrode

Fig. 1 is a view showing a cross section of an MLCC in which an electroconductive paste is applied to an internal electrode according to an embodiment of the present invention. Fig. 2 is a graph showing the relationship between the viscosity of the conductive paste and the contact angle in an embodiment of the present invention.

Claims (4)

The conductive paste is a conductive paste for gravure printing containing a conductive powder, an adhesive, and an organic solvent, and has a viscosity of 25 (° C.) and a shear rate of 40 (1/s) as x (Pa· s), the contact angle at which the arithmetic mean roughness Ra of the length 1.0 (mm) is equal to or less than 0.010 (μm) is 10 (μL) at a level of 80 (μm), and the contact angle is set to y (∘), At this time, x and y satisfy the following formula, y<17.6x+19.1 (however, x≦3.0, y<40). The conductive paste of claim 1, wherein the test surface is subjected to Cr plating or Ni plating. A method for forming a conductor film, comprising the steps of: preparing a conductive paste containing a conductive powder, an adhesive, and an organic solvent; filling the conductive paste in a recess of the gravure printing plate and transferring it to be printed a printing step of forming a conductive film on the surface to be printed by performing a calcination treatment on the formed printing film; wherein the step of preparing the conductive paste is carried out under the following conditions: Modulation: a viscosity x (Pa·s) at a shear rate of 40 (1/s) at 25 (° C.), using the same material as the outermost peripheral surface of the gravure printing plate, and horizontally arranged to have the same surface state. The contact angle y (∘) at 10 (μL) of the test surface was dropped, and x and y satisfy y<17.6x+19.1 (however, x≦3.0, y<40). The method for forming a conductor film according to claim 3, wherein the outermost peripheral surface of the gravure printing plate and the test surface are subjected to Cr plating or Ni plating.