JP2020109761A - Conductive paste and method for forming conductor film - Google Patents

Abstract

To provide a conductive paste for gravure printing capable of forming continuous suitable thin conductor films in an internal electrode of a small-sized high-capacity MLCC, and a method for forming a conductor film of the same.SOLUTION: A method for forming continuous suitable thin conductor films in an internal electrode of a small-sized high-capacity MLCC that allows a conductive paste to be quickly and uniformly transferred from a plate, allows a paste surface to be smooth immediately after transfer, and facilitates thinning of a film thickness while keeping continuity, in which a ratio of the conductive powder in the conductive paste is 30-60 (%) in a weight ratio, and a viscosity x (Pa s) and a contact angle y(°) to a horizontal test surface subjected to Cr or Ni plating having an arithmetic average roughness Ra of 0.010 (μm) or less satisfy Expression (1): y<17.6x+19.1, Expression (2): y>8.8x+12.4, Expression (3): x≤3.0 and Expression (4): y<40; and accordingly a ceramic green sheet is subjected to gravure printing using the conductive paste.SELECTED DRAWING: Figure 2

Description

The present invention relates to a conductive paste that is preferably used for gravure printing and a method for forming a conductor film that uses a gravure printing method.

For example, when manufacturing a multilayer ceramic capacitor (MLCC) 10 whose sectional structure is schematically shown in FIG. 1, a non-fired ceramic green sheet for forming the dielectric layer 12 has a heat-resistant metal on the surface thereof. Conductive paste containing as a conductive component is applied by printing, a large number of these are laminated and pressure-bonded, and then firing treatment is performed to form the dielectric layer 12 from the green sheet and at the same time form the internal electrode from the conductive paste. The conductor layer 14 is produced. In FIG. 1, reference numeral 16 is an external electrode for energizing the internal electrode (conductor layer 14). A gravure printing method, which is a kind of intaglio printing, is applied to the print formation of such internal electrodes (see, for example, Patent Document 1). The gravure printing method is a continuous printing method in which a conductive paste is filled in a concave portion provided in a plate and the conductive paste is transferred from the plate by pressing the conductive paste against a surface to be printed, and has an advantage of high printing speed.

A screen printing method has been generally used for printing the conductive paste for forming the internal electrodes of the MLCC. However, the screen printing method has a problem in that dimensional accuracy is deteriorated due to plate elongation. Especially in 0603 size (outer dimension 0.6mm×0.3mm×0.3mm) and 0402 size (outer dimension 0.4mm×0.2mm×0.2mm) ultra-compact MLCCs, it becomes more difficult to secure the dimensional accuracy of the printed film. Become. On the other hand, according to the gravure printing method described above, plate elongation does not occur, and thus it is suitable for MLCC applications where such highly accurate printing is required.

JP, 10-199331, A JP, 2003-249121, A JP, 2005-126505, A JP, 06-142579, A

By the way, in the small high-capacity MLCCs such as 0603 size and 0402 size as described above, the thickness dimension of the internal electrodes is required to be 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, which has a high printing speed and a short tact time in the steps of printing and drying, the time from printing to the start of drying is short, and therefore the time for leveling the printed film is also short. Therefore, in order to obtain a printed film having excellent surface smoothness, it is desirable that the printed film having a smooth surface is formed immediately after the transfer by uniformly transferring the conductive paste from the plate.

Heretofore, various proposals have been made to improve the conductive paste used in the gravure printing method. For example, in applying the gravure printing method to MLCC, it has been proposed to use a petroleum-based solvent or an alcohol-based solvent to suppress swelling or redissolution (sheet attack) of the ceramic green sheet due to the solvent (for example, the above-mentioned. See Patent Document 1.). Further, it has been proposed to use a solvent such as 1-P-menthene or P-menthane in consideration of the drying speed of the printed coating film when suppressing the sheet attack (for example, refer to Patent Document 2). ..

Further, when manufacturing a multilayer ceramic component such as MLCC, after printing a conductive paste on a ceramic green sheet, a paste containing a ceramic raw material as a main component is printed on a portion other than a portion where a conductor pattern is formed, so that the ceramic green sheet In the case of flattening the surface, it has been proposed to form a printed film having excellent flexibility by including a terpene resin having a number average molecular weight of 300 to 5,000 in the paste in addition to the ethyl cellulose resin ( For example, see Patent Document 3.). In gravure printing, a conductive paste with low viscosity and suppressed thixotropy is used so that it can be easily transferred from the printing plate to the printing medium, but the printed film generated from such conductive paste is a ceramic paste printing. At times, when the printing plate comes into contact, the conductor pattern is easily damaged or missing. Therefore, it is intended to suppress the damage/missing by increasing the flexibility of the printed film.

Further, for the purpose of improving paste transferability by changing the plate making side, a plate making is proposed in which the inside of the cell groove is covered with a film having a contact angle with water of 50° or more (see, for example, Patent Document 4). ). According to this plate making, since the contact angle with water is increased to 50° or more by covering the cell grooves with a perfluoroalkoxy resin or the like, the wettability between the paste and the plate making is lowered, and the transferability is improved. It is supposed to be.

As described above, from the viewpoint of suppressing the sheet attack and increasing the strength of the print film, various improvements have been proposed for the conductive paste used in the gravure printing method and the plate making. However, these cannot be used for forming a continuous film with a thin film thickness of 1 (μm) or less. In addition, even if a conductive paste is prepared so as to have a similar contact angle, the transferability will be different if the type and particle size of the conductive powder and the composition of the vehicle are different, and it is not always possible to obtain good results. Also, it became clear as a result of the additional test.

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 thin conductive film suitable for an internal electrode of a small high-capacity MLCC, and And a method of forming a conductor film.

In order to achieve such an object, the gist of the first invention is a conductive paste for gravure printing containing a conductive powder, a binder, and an organic solvent, and a shear rate of 40 ( The viscosity at 1/s) is x (Pa·s), and the contact angle when dropping 10 (μL) at 25 (°C) on a horizontal test surface with arithmetic mean roughness Ra of 0.010 (μm) or less is y (° ), x and y satisfy the following expression (1).
y<17.6x+19.1 (however, x≦3.0, y<40)・・・(1)

Further, the gist of the second invention for achieving the above-mentioned object is to prepare a conductive paste containing conductive powder, a binder, and an organic solvent, and to form the conductive paste into a recess for gravure printing platemaking. A method of forming a conductor film, comprising: a printing step of filling the surface of the print surface and transferring the print film to the surface to be printed; and a baking step of forming a conductor film on the surface to be printed by performing a baking treatment on the formed print film, In the step of preparing the conductive paste, the viscosity x (Pa·s) at a shear rate of 40 (1/s) at 25 (° C.) and the same material as the outermost peripheral surface of the gravure printing plate making the same surface state and horizontal It is to prepare the conductive paste so that the contact angle y (°) when 10 (μL) is dropped on the arranged test surface satisfies the expression (1).

According to the first invention, the conductive paste for gravure printing has a viscosity x (Pa·s) and a contact angle y (°) with respect to a test surface having an arithmetic average roughness Ra of 0.010 (μm) or less, Since the equation (1) is satisfied, when the surface to be printed is gravure-printed using this conductive paste, the conductive paste is rapidly and uniformly transferred from the gravure printing plate to the surface to be printed. As a result, the paste surface becomes smooth immediately after transfer, and it is easy to reduce the film thickness while maintaining continuity. Therefore, using this conductive paste is suitable for the internal electrode of a small high-capacity MLCC. It is possible to form a continuous thin conductive film.

According to the second aspect of the invention, in forming the conductive film using the gravure printing method, in the step of preparing the conductive paste, the viscosity x (Pa·s) at 40 (1/s) and the gravure printing plate making The conductive paste is prepared so that the contact angle y (°) when 10 (μL) is dropped on a test surface horizontally arranged with the same material as the outermost peripheral surface and having the same surface condition satisfies the above formula (1). To be done. Therefore, when gravure printing is performed using the conductive paste in the printing process, the conductive paste is quickly and uniformly transferred to the surface to be printed. As a result, since the paste surface becomes a smooth surface immediately after the transfer, it becomes easy to reduce the film thickness while maintaining the continuity, so that the continuous thin film thickness suitable for the internal electrode of the small high capacity MLCC is obtained. A conductor film can be formed. In the present application, the “outermost peripheral surface of plate making” means the surface on the cylindrical surface before forming the printing pattern on the plate making.

Incidentally, conventionally, for the purpose of uniformly transferring from the gravure printing plate to the printing surface, optimization of the organic composition of the conductive paste and optimization of the rheology have been attempted. Attempts have not yielded sufficient results. On the other hand, the present invention was made by finding that not only the wettability of the plate-making and the conductive paste, that is, the size of the contact angle, but also the viscosity of the conductive paste is related to the transferability. By adjusting the viscosity and the contact angle so as to satisfy 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 is uniformly applied from the gravure printing plate to the printing surface. And the film surface becomes smooth immediately after the transfer.

In the first invention, the surface roughness of the test surface is required to have an arithmetic average roughness Ra of 0.010 (μm) or less. The surface roughness of the outermost peripheral surface of the gravure printing plate is generally 0.010 (μm) or less in Ra, therefore, the evaluation using the test surface is an evaluation using the outermost peripheral surface of a general gravure printing plate. You can see it.

Further, in the present application, as the viscosity x (Pa·s), the static viscosity at a shear rate of 40 (1/s) at 25 (° C.) is used. This condition is determined by taking into consideration the room temperature when performing gravure printing, the stress that acts on the conductive paste when the conductive paste is transferred to the printing surface during gravure printing, and this value is used. Thereby, the correlation between the transferability and the viscosity and contact angle of the conductive paste can be stably obtained. The viscosity can be measured using a commercially available viscometer.

Further, in the present application, the contact angle y (°) is a value obtained by measuring 10 (μL) of the liquid droplets dropped on the horizontal surface at 25 (° C.). This condition is determined in consideration of the room temperature at the time of gravure printing, the amount of the conductive paste transferred at the time of forming the internal electrodes of the MLCC, and the like. A stable correlation between viscosity and contact angle and transferability can be obtained. The conductive paste can be dropped using, for example, a micropipette, and the contact angle can be measured using a commercially available contact angle meter.

Further, the equation (1) is satisfied in the range of x≦3.0 and y<40. When the viscosity and the contact angle are above these ranges, good transferability cannot be obtained even if y<17.6x+19.1 is satisfied.

According to the invention of the present application, the viscosity and the contact angle are measured by the above-described method, and the conductive paste is prepared so that the values thereof satisfy the expression (1). Is uniformly transferred from the gravure printing plate to the printing surface, and the film surface is smoothed immediately after the transfer. That is, it is not always possible to obtain good transferability as long as the contact angle has a wettability that is a certain value or more, and it is necessary to reduce the contact angle as the viscosity becomes smaller, that is, to make it easier to wet. become.

Regarding the relationship between the contact angle and the transferability, in Patent Document 4, the larger the contact angle is, the better the transferability is, and it is necessary that the contact angle is 50° or more. It has been shown to be difficult to enter. However, according to the results of research conducted by the present inventors, it is preferable that the contact angle is small in order to obtain good transferability. Moreover, as shown in the formula (1), the conductive paste and the plate making It is necessary to set the angle to 40° or less when measured between. The description of the above-mentioned Patent Document 4 is that "50° or more and not too large" is preferable, but the present inventors obtained the opposite result. Further, in the above-mentioned Patent Document 4, the contact angle is limited by the value with respect to water, but this is indirectly determined by the value of the contact angle with respect to the surface of the cell groove, and is actually used. It is not considered that the appropriate contact angle varies depending on the physical properties of the paste.

Here, it is preferable that the test surface in the first invention, or the outermost peripheral surface and the test surface of the gravure printing plate according to the second invention are both Cr-plated or Ni-plated. .. The gravure printing plate is preferably Cr-plated or Ni-plated in order to improve wettability with the conductive paste. Therefore, it is preferable that the test surface also be plated with Cr or Ni in accordance with this. In order to improve the wettability and reduce the contact angle, it is preferable to perform plating, and the type of plating on the test surface is preferably matched to that of gravure printing plate making. However, even if the types of plating are different, a similar contact angle can be obtained, so it is not essential to match them.

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

Further, preferably, in the formula (1), the range of the contact angle y(°) is 10<y<40. When the contact angle y is 10° or less, the wettability becomes too high, so that good transferability cannot be obtained.

Further, preferably, 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 poorer the handleability, but the lower the viscosity x, the smaller the contact angle y can be tolerated. Therefore, it is preferable to satisfy the above formula (2).

In addition, preferably, the conductive paste is used for forming a conductive film by printing and coating on a ceramic green sheet. Although the use of the conductive paste of the present invention is not limited, it is preferably used when a conductive film is formed on a ceramic insulator. In particular, if the green sheet is applied by printing, it is possible to simultaneously produce the conductor film by firing when the firing process is performed to produce the insulator, which is advantageous in terms of manufacturing cost.

Further, preferably, the conductive paste is used to form the internal electrodes of the MLCC. As described above, the conductive paste of the present invention makes it easy to reduce the film thickness while maintaining continuity, and is therefore suitable for the internal electrode of a small high-capacity MLCC.

Also, preferably, the conductive powder is nickel powder. For example, in the case of using internal electrodes of MLCC, ceramic green sheets printed with a conductive paste are laminated and subjected to a firing treatment to generate a dielectric layer from the ceramic green sheets and at the same time to generate internal electrodes. It is required to have heat resistance. Therefore, as the conductive powder of the conductive paste of the present invention, a metal having heat resistance, for example, Pt, Pd, Ag-Pd, Ag, Ni, Cu and the like are suitable, in terms of manufacturing cost, cheap base metal A material is preferable, and nickel is particularly preferable in terms of heat resistance, conductivity, and cost. The average particle diameter of the conductive powder is appropriately determined within the range in which the desired characteristics of the conductive paste are obtained, but is, for example, 1.0 (μm) or less, preferably 0.01 to 0.50 (μm), and 0.05 to 0.30 (μm). Is more preferable.

Further, preferably, the binder is polyvinyl butyral, polyvinyl alcohol, acrylic resin, epoxy resin, phenol resin, alkyd resin, cellulose polymer, rosin resin, or the like. The binder of the conductive paste of the present invention can be appropriately selected from those generally used in the range that can achieve the desired viscosity and contact angle, but the above is the coating film forming ability (that is, adhesion to the substrate) and It is preferable in terms of decomposability during firing.

Further, the organic solvent is not particularly limited as long as it can suitably dissolve or disperse the components of the conductive powder and the binder resin. Examples include alcohol solvents such as terpineol, terpene solvents such as isobornyl acetate, glycol solvents such as ethylene glycol, glycol ether solvents such as diethylene glycol monobutyl ether (butyl carbitol), ester solvents, toluene, xylene. And other organic solvents having a high boiling point such as mineral spirits. These organic solvents are preferable because they are difficult to dissolve the binder of butyral resin or acrylic resin in the ceramic green sheet and so-called sheet attack hardly occurs.

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

Further, the component ratio of the conductive paste is not particularly limited and may be appropriately determined so as to satisfy the above formulas (1) and (2). For example, the conductive powder may be 30 to 60(%) in terms of mass ratio. A composition containing 1 to 5 (%) of the binder, 35 to 65 (%) of the organic solvent, and 0 to 20 (%) of the common material is preferable. When a common material is included, the range of 1 to 20(%) is preferable.

It is a figure which shows the cross section of MLCC to which the electrically conductive paste of one Example of this invention was applied to the internal electrode. 3 is a graph showing a relationship between a viscosity and a contact angle of a conductive paste according to an example of the present invention.

An embodiment of the present invention will be described in detail below. In addition, in the examples described below, a configuration generally used conventionally can be appropriately used unless otherwise specified.

The conductive paste of the present embodiment is used for forming the conductor layer 14 to be an internal electrode of the MLCC 10 as shown in FIG. 1 by using the gravure printing method. In this embodiment, the thickness of one layer of the dielectric layer 12 is, for example, 10 (μm) or less, for example, within a range of 0.1 to 3 (μm), for example, about 1 (μm), and The thickness dimension of one layer is, for example, 10 (μm) or less, for example, within a range of 0.1 to 3 (μm), for example, about 0.5 (μm).

The conductor layer 14 is made of nickel, for example, and the dielectric layer 12 is made of barium titanate, for example. When manufacturing such an MLCC 10, a conductive powder, a ceramic powder, a binder, and an organic solvent are mixed according to a predetermined mixing specification to prepare a conductive paste, and a dielectric layer 12 separately prepared is prepared. Gravure printing is applied on one surface of the ceramic green sheet for forming. The ceramic green sheets coated with the conductor paste are laminated and pressure-bonded, and then fired to form the dielectric layer 12 from the ceramic green sheets, and at the same time, to form the conductor layer 14 from the conductor paste. The MLCC 10 shown in FIG. 1 is obtained by forming the external electrode 16 by the method described above.

The conductive powder is, for example, an average particle size of 1 (μm) or less, for example, a nickel powder within the range of 0.13 to 0.18 (μm), for example, a ratio of about 30 to 60 (wt%) in the conductive paste. Mixed in. The ceramic powder is, for example, a barium titanate powder having an average particle size of 0.1 (μm) or less, for example, in the range of 10 to 20 (nm), that is, a mixture of barium titanate constituting the dielectric layer 12 It is a material and is mixed into the conductive paste at a nickel ratio of about 10 to 15 (wt %). The binder is, for example, ethyl cellulose or polyvinyl butyral, and the organic solvent is dihydroterpineol, isobornyl acetate, or mentanol propionate as a main solvent. These are used in proportions of about 1 to 5 (%) and 30 to 65 (%), respectively.

In this example, the composition of the conductive paste had the following viscosity (1) and a contact angle when dropped on a test surface prepared by using the same material as the outermost peripheral surface of the gravure printing plate and having the same surface condition. ) Prepare so that the formula (reprinted) is satisfied. The viscosity is, for example, a value measured using a rheometer (Rheosttress 6000 manufactured by HAAKE), and the static viscosity after 1 minute is used under the conditions of 25 (° C.) and a shear rate of 40 (1/s). Further, the contact angle was 25 (° C.), 10 (μL) was dropped on a horizontally arranged test surface using a micropipette, and, for example, with a FACE contact angle meter (CA-DT manufactured by Kyowa Interface Science Co., Ltd.). The measured contact angle is used. The contact angle is, for example, an average value measured 5 times.
y<17.6x+19.1 (however, x≦3.0, y<40)・・・(1)

The test surface is, for example, a Cr plate when the gravure printing plate is a Cr plating plate, and the surface thereof has an extremely high arithmetic smoothness of 0.010 (μm) or less. It is finished in a state. Note that, instead of the Cr plate, a plate plated with Cr as in plate making may be used. In the present embodiment, for example, a gravure printing plate with its surface material peeled off from the non-patterned portion is used. The size of the test flat substrate is, for example, 5 (cm)×3 (cm).

The conductive paste prepared in this manner was applied by printing onto a ceramic green sheet using a gravure printing method. As a result, the formed print film had a dry film thickness of about 0.5 (μm) and a surface roughness Ra of 0.020 (μm). It has the following smooth surface, and a smooth continuous film can be obtained by baking this. By obtaining this level of smoothness, it is possible to further contribute to the improvement of the characteristics and reliability of the capacitor.

Table 1 below summarizes the results of evaluating the printability with various combinations of the viscosity and the contact angle in the printing and applying step of the conductor layer 14 by changing the conductive paste composition variously. In Table 1, "Ni particle size" and "BT particle size" are the average particle size of nickel powder and the average particle size of barium titanate powder, respectively. 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 a rheometer as described above. In addition, “contact angle with Cr plate” and “Cr plating plate Ra” are the evaluation data when performing gravure printing using Cr plating plate. The former is the contact between the conductive paste and the Cr plate. The measured value of the angle, and the latter is the surface roughness after drying of the printing film printed by the Cr plating using the conductive paste. The surface roughness was measured using an interference microscope (Nikon LV150 ECLIPSE) with a magnification of 10 times, a measurement range of 50 (μm)×1000 (μm), and an arithmetic average roughness Ra of 12 measurements. The “contact angle with the Ni plate” and the “Ni-plated plate-making printed material Ra” are evaluation data when performing gravure printing using the Ni-plated plate.

In Table 1 above, prints having a surface roughness Ra of 0.020 (μm) or less have good printability, that is, Examples. FIG. 2 shows a graph of the above evaluation results. In FIG. 2, “◆” is the example and “□” is the comparative example. Examples 1 to 11 are conductive pastes below the formula (1) shown in FIG. 2 and satisfying the formula. Comparative Examples 1 to 8 are conductive pastes of Comparative Examples outside the scope of the present invention, which are on the upper side of the formula (1) or on the right side of the viscosity of 3.0 (Pa·s) and do not satisfy this.

As shown in the above evaluation results, a combination of the viscosity and the contact angle satisfying the above formula (1) in the range of the viscosity of 0.1 to 3.0 (Pa·s) and the contact angle of 14 to 39 (°). As a result, extremely good results with a surface roughness of the printed body of 0.003 to 0.016 (μm) can be obtained. Therefore, when the internal electrodes (conductor layer 14) of the MLCC 10 are formed using such a conductive paste, good transferability from the gravure printing plate to the surface to be printed is obtained, and as a result, a thin and smooth continuous film is obtained. Can be easily obtained, so that the MLCC 10 of small size and high capacity can be obtained with a high manufacturing yield. In addition, in Example 11, the Ni-plated plate-making was also evaluated, and the same favorable result as that of the Cr-plate-made plate was obtained. If the conductive paste is prepared so as to satisfy the formula (1), a thin and smooth surface continuous film can be similarly obtained regardless of whether the Cr-plated plate or the Ni-plated plate is used.

On the other hand, in Comparative Examples 1 to 6, even though the viscosity is in the range of 0.2 to 3.0 (Pa·s), the contact angle is as large as 22 to 72 (°), so that the formula (1) is satisfied. Since the combination of the viscosity and the contact angle is not present, the transferability from the gravure printing plate is poor, and the surface roughness Ra of the printed material becomes a large value of 0.021 to 0.194 (μm). The size of the surface roughness Ra represents the size of the unevenness on the surface of the printed film, but the thickness dimension of the conductor layer 14 is as thin as about 0.5 (μm). Large unevenness means that the continuity of the printed film is not obtained. That is, with the conductive paste of the comparative example, it is difficult to obtain a thin continuous film having a smooth surface.

Further, Comparative Examples 7 and 8 have extremely high viscosities of 5.3 to 6.9 (Pa·s), but have a contact angle of 51 to 61 (°), which is below the formula (1). However, when gravure printing is performed using these, the surface roughness Ra of the printed film becomes a large value of 0.036 to 0.095 (μm), and a continuous film cannot be obtained as in Comparative Examples 1 to 6. Even if it is located on the lower side of the formula (1), if the viscosity exceeds 3.0 (Pa·s), the transferability is poor.

As described above, according to the present embodiment, the conductive paste has a viscosity x (Pa·s) and a contact angle y (°) with respect to the test surface of which the arithmetic average roughness Ra is 0.010 (μm) or less, Since the formula (1) is satisfied, when gravure printing is performed on the ceramic green sheet using this conductive paste, the conductive paste is rapidly and uniformly transferred from the gravure printing plate. As a result, since the paste surface becomes a smooth surface immediately after the transfer, it becomes easy to reduce the film thickness while maintaining the continuity, so that the continuous thin film thickness suitable for the internal electrodes of the small high-capacity MLCC 10 can be obtained. The conductor film 14 can be formed.

The viscosity and contact angle of the conductive paste may be appropriately adjusted by changing the Ni particle size, the BT particle size, the Ni amount, and the BT amount, or by changing the types and amounts of the binder and the organic solvent.

Further, according to the above Table 1 and FIG. 2, the preferable lower limit value of the viscosity is 0.1 (Pa·s). It is difficult to make the conductive paste have a viscosity lower than this. The lower limit of the contact angle is 10 (°). When the contact angle is 10 (°) or less, the wettability becomes too high, so that good transferability cannot be obtained.

Further, it is preferable that the viscosity x and the contact angle y are above the formula (2) in FIG. 2, that is, y>8.8x+12.4 is satisfied. The smaller the contact angle y, the higher the wettability and the poorer the handleability, but the lower the viscosity x, the smaller the contact angle y can be tolerated.

Although the present invention has been described above in detail with reference to the drawings, the present invention can be implemented in other modes and various changes can be made without departing from the spirit of the invention.

10 MLCC
12 dielectric layer 14 conductor layer 16 external electrode

In order to achieve such an object, the gist of the first invention is a conductive paste for gravure printing, which contains a conductive powder, a binder, and an organic solvent, and the conductive powder in the conductive paste. Is 30 to 60 (%) by weight, the viscosity at 25 (°C) at a shear rate of 40 (1/s) is x (Pas), and the arithmetic average roughness Ra is 0.010 (μm) or less. , Y (°) is the contact angle when 10 (μL) is dropped at 25 (°C) on a horizontal test surface plated with Cr, Ni or Ni , x and y are calculated from the following formulas (1) to (4 ) ) .
y<17.6x+19.1 ・・・(1)
y>8.8x+12.4 (2)
x≦3.0 (3)
y<40 ・・・(4)

Further, the gist of a second invention for achieving the above-mentioned object is to prepare a conductive paste containing a conductive powder, a binder, and an organic solvent, and the conductive paste is used as a recess for gravure printing platemaking. A method of forming a conductor film, comprising: a printing step of filling the surface of the print surface with a print film, and a firing step of forming a conductor film on the print surface by subjecting the formed print film to a firing process. The ratio of the conductive powder in the conductive paste is 30 to 60 (%) by weight, and the step of preparing the conductive paste is 25 (° C.) viscosity at shear rate 40 (1/s) x ( Pa·s) and the contact angle y when 10 (μL) is dropped on a Cr-plated or Ni-plated test surface that is horizontally arranged with the same material and the same surface state as the outermost peripheral surface of the gravure printing plate. (°) means that the conductive paste is prepared so as to satisfy the expressions (1) to (4) .

According to the first aspect of the present invention, the conductive paste for gravure printing has a ratio of the conductive powder in the conductive paste of 30 to 60 (%) by weight, a viscosity x (Pa·s), and an arithmetic mean roughness. Since the Ra of 0.010 (μm) or less and the contact angle y (°) with respect to a horizontal Cr-plated or Ni-plated test surface satisfy the above equations (1) to (4) , this conductive paste When the surface to be printed is subjected to gravure printing by using, the conductive paste is rapidly and uniformly transferred from the gravure printing plate to the surface to be printed. As a result, the paste surface becomes smooth immediately after transfer, and it is easy to reduce the film thickness while maintaining continuity. Therefore, using this conductive paste is suitable for the internal electrode of a small high-capacity MLCC. It is possible to form a continuous thin conductive film.

Further, according to the second aspect of the present invention, a step of preparing a conductive paste in which the ratio of the conductive powder in the conductive paste is 30 to 60% by weight when forming the conductive film using the gravure printing method. Then, the viscosity x (Pa·s) at 40 (1/s) and the Cr-plated or Ni-plated test surface horizontally arranged with the same material as the outermost peripheral surface of the gravure printing plate and with the same surface condition The conductive paste is prepared so that the contact angle y (°) when 10 (μL) is dropped satisfies the above expressions (1) to (4) . Therefore, when gravure printing is performed using the conductive paste in the printing process, the conductive paste is quickly and uniformly transferred to the surface to be printed. As a result, since the paste surface becomes a smooth surface immediately after the transfer, it becomes easy to reduce the film thickness while maintaining the continuity, so that the continuous thin film thickness suitable for the internal electrode of the small high capacity MLCC is obtained. A conductor film can be formed. In the present application, the “outermost peripheral surface of plate making” means the surface on the cylindrical surface before forming the printing pattern on the plate making.

In the present example, the composition of the conductive paste has its viscosity and was prepared in the same surface state as the outermost peripheral surface of the gravure printing plate in the same surface state, when dropped on a Cr-plated or Ni-plated test surface. And the contact angle of (2) satisfy the following formula (1) (reprinted). The viscosity is a value measured by using, for example, a rheometer (Rheosttress 6000 manufactured by HAAKE), and the static viscosity after 1 minute is used under the conditions of 25 (° C.) and a shear rate of 40 (1/s). Further, the contact angle was 25 (° C.), 10 (μL) was dropped on a horizontally arranged test surface using a micropipette, and, for example, with a FACE contact angle meter (CA-DT manufactured by Kyowa Interface Science Co., Ltd.). The measured contact angle is used. The contact angle is, for example, an average value measured 5 times.
y<17.6x+19.1 (however, x≦3.0, y<40)・・・(1)

Claims (2)

A conductive paste for gravure printing, containing a conductive powder, a binder, and an organic solvent,
The proportion of the conductive powder in the conductive paste is 30 to 60 (%) by weight,
The viscosity at 25 (°C) at a shear rate of 40 (1/s) is x (Pa·s), the cutoff value is 80 (μm), and the arithmetic mean roughness Ra at an evaluation length of 1.0 (mm) is 0.010 (μm) or less. X, y satisfy the following formulas (1) to (4), where y (°) is the contact angle when 10 (μL) is dropped on a Cr-plated or Ni-plated horizontal test surface. Conductive paste characterized by:
y<17.6x+19.1 (1)
y>8.8x+12.4 (2)
x≦3.0 (3)
y<40 ・・・(4) A step of preparing a conductive paste containing a conductive powder, a binder and an organic solvent, a printing step of filling the conductive paste in a recess of a gravure printing plate and transferring the same to a surface to be printed, and a printed film formed A method of forming a conductor film, which comprises a firing step of forming a conductor film on a surface to be printed by performing a firing treatment on
The proportion of the conductive powder in the conductive paste is 30 to 60 (%) by weight,
The step of preparing the conductive paste,
The viscosity x (Pa·s) at a shear rate of 40 (1/s) at 25 (°C) and the same material as the outermost peripheral surface of the gravure printing plate, the Cr and Ni platings arranged horizontally as the same surface state The contact angle y (°) when 10 (μL) was dropped on the test surface subjected to the test was y<17.6x+19.1...(1), y>8.8x+12.4...(2), x A method of forming a conductor film, characterized in that the conductive paste is prepared so as to satisfy ≦3.0 (3) and y<40 (4).

Images