JPH08325062A - Ceramic green sheet, its production and laminated body thereof - Google Patents

Abstract

PURPOSE: To prevent a sheet attack on a ceramic green sheet by printing paste, to enhance printing precision and laminating precision and to stabilize the characteristics of laminated electronic parts. CONSTITUTION: A ceramic slurry prepd. by dispersing ceramic powder in a binder 5 is applied on a carrier film 3 and dried. At the time of the drying, a formed layer of the slurry is heated in a high concn. atmosphere of vapor of a solvent in the binder 5 with the side corresponding to a face of the resultant ceramic layer 7 to be printed upward and the objective ceramic green sheet in which the dispersion density of the ceramic powder 4 in the binder 5 in a face to be printed is higher than that in a face not to be printed is obtd. A pattern 8 is printed on the face of the green sheet to be printed with printing paste 8 and plural such sheets are laminated to obtain the objective laminated body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic green sheet for producing laminated electronic components such as laminated chip capacitors and laminated chip inductors, and a method for producing the same.

[0002]

2. Description of the Related Art A monolithic ceramic capacitor, which is the most typical example of a monolithic electronic component, has a large number of dielectric ceramic layers each having an internal electrode, which are alternately stacked on an end face of the laminate. Then, external electrodes are formed on the end faces of the stacked body from which these internal electrodes are drawn out.

In the conventional manufacturing method of such a monolithic ceramic capacitor, a ceramic slurry in which a dielectric ceramic powder is dispersed in an organic binder is applied onto a carrier film such as polyethylene terephthalate film by a roll coater or the like, and then applied. A ceramic green sheet consisting of a thin ceramic layer is made by drying the ceramic slurry. Next, an internal electrode pattern is printed on the ceramic green sheet with a conductive paste by a screen printing method or the like. Then, the green sheets printed with the internal electrode patterns are cut into a predetermined size, laminated in a predetermined order, and a plurality of green sheets not printed with the internal electrode patterns are stacked on both sides of the green sheets. The laminate thus obtained is cut into chips so that the internal electrodes are exposed at the end faces, and the chips are fired. As a result, a sintered laminate is obtained. Then, a conductive paste is applied to the end surface of the sintered laminated body where the internal electrodes are exposed, and this is baked to form external electrodes. As a result, the multilayer chip capacitor is completed.

In the manufacturing process of the ceramic green sheet, a ceramic slurry having a viscosity adjusted to about several hundred to 1,000 centipoise is used, which is coated on a carrier film and then dried. In this drying step, a tunnel furnace having a total length of more than 10 m is used, and the carrier film coated with the ceramic slurry is introduced into this tunnel furnace, and heated and dried. To prevent cracks and blister (air bubbles) from being generated on the ceramic green sheet,
The inside of the tunnel furnace is divided into a plurality of zones, the temperature gradually increases as it goes from the entrance to the back, and after reaching the maximum temperature, the temperature is lowered near the exit and then withdrawn. In addition, the tunnel furnace is constantly ventilated in order to promote evaporation of the solvent in the binder and improve drying efficiency, and the vapor concentration of the solvent is suppressed to 20% or less. Then, the heating temperature reaches a maximum of around 120 ° C.

[0005]

While many circuit components are miniaturized, the multilayer electronic components such as the above-mentioned multilayer ceramic capacitors and multilayer ceramic inductors are also required to be miniaturized and have a large capacity. ing. In order to manufacture such a capacitor with high yield, it is necessary to have a technique of printing a pattern on the green sheet with high accuracy and stacking the pattern with high accuracy.

However, when a pattern such as an internal electrode is printed on the above-mentioned ceramic green sheet by using a printing paste such as a conductive paste, the solvent contained in the printing paste is contained in the binder contained in the ceramic green sheet. When the components are melted and the pattern printed on the ceramic green sheet swells and extends, wrinkles are formed or the printed pattern is deformed. Such a phenomenon is called so-called seat attack.

When a laminated body is made by using such a ceramic green sheet, the laminating accuracy is deteriorated, the printed patterns of the upper and lower ceramics are deviated, and the characteristics are varied. For example, in the case of a monolithic ceramic capacitor, variations in capacitance occur, and in the case of monolithic ceramic inductors, variations in inductance occur. In addition, delamination such as delamination of the laminated body is likely to occur. The present invention has been made in view of the above problems in the conventional ceramic green sheet, and an object of the present invention is to provide a ceramic green sheet in which sheet attack due to a printing paste is unlikely to occur and a manufacturing method thereof.

[0008]

That is, according to the present invention,
In order to achieve the above object, the dispersion density of the ceramic powder 4 in the binder 5 on the printing surface side of the ceramic layer 7 constituting the ceramic green sheet is made higher than the dispersion density of the ceramic powder 4 on the non-printing surface side. , The printing surface side of the ceramic green sheet was made hard to be attacked by the solvent of the printing paste. Further, in order to manufacture such a ceramic green sheet, after applying the ceramic slurry on the carrier film 3, the layer of the ceramic slurry is heat-treated in a high-concentration vapor atmosphere of the solvent of the binder.

That is, in the ceramic green sheet according to the present invention, the dispersion density of the ceramic powder 4 on the printing surface side of the ceramic layer 7 constituting the sheet in the binder 5 is higher than the dispersion density of the ceramic powder 4 on the non-printing surface side. It is characterized by For example, the printed surface of the ceramic layer 7 is often the surface on the side opposite to the side in contact with the carrier film 3. In that case, the dispersion density of the ceramic powder 4 on that side is the same as that on the side in contact with the carrier film. Ceramic powder 4
Higher than the dispersion density of.

Further, according to the manufacturing method of the present invention for manufacturing the above-mentioned ceramic green sheet, when the ceramic slurry in which the ceramic powder is dispersed in the binder 5 is applied onto the carrier film 3 and is dried,
After the ceramic slurry is applied on the carrier film 3, the layer of the ceramic slurry is heat-treated in a high-concentration vapor atmosphere of the solvent of the binder 5 with the side to be the printing surface of the ceramic layer 7 facing up. For example,
In a solvent vapor atmosphere with a saturated vapor concentration of 80% or more,
Heat treatment is performed at a temperature of 80 ° C. or higher. A laminate obtained from such a ceramic green sheet is characterized in that a pattern 8 is printed on the printing surface of the ceramic green sheet using a printing paste, and a plurality of the ceramic green sheets are laminated. .

[0011]

In the method of manufacturing a ceramic green sheet according to the present invention, when the ceramic slurry is applied on the carrier film 3 and then the layer of the ceramic slurry is heat-treated in a high-concentration vapor atmosphere of the solvent of the binder 5, the heating temperature is reduced. The solvent contained in the binder 5 hardly evaporates. Therefore, the solvent of the binder 5 is gradually evaporated from the surface of the ceramic slurry, but at the same time, convection occurs in the ceramic slurry coated on the carrier film due to the high temperature. Due to this convection, the ceramic powder 4 uniformly dispersed in the ceramic slurry rises in the layer of the ceramic slurry and collects on the upper surface side of the ceramic layer 7, which is the printing surface. Therefore, the binder 5 of the ceramic powder 4 is formed above the lower side of the layer of the ceramic slurry.
The dispersion density inside becomes high. Then, in this state, the ceramic slurry applied on the carrier film 3 is gradually dried to form the ceramic layer 7 forming the ceramic green sheet. As a result, a ceramic green sheet according to the present invention, that is, a ceramic green sheet in which the dispersion density of the ceramic powder 4 on the printed surface side of the ceramic layer 7 in the binder 5 is higher than the dispersion density of the ceramic powder 4 on the non-printed surface side is obtained.

In such a ceramic green sheet, since the binder 5 on the printed surface side of the ceramic layer 7 is less than that on the non-printed surface side, even if a pattern such as internal electrodes is printed on the printed surface using a printing paste. The erosion of the binder 5 by the solvent of the printing paste is small, and so-called sheet attack hardly occurs. For this reason, the print pattern portion is unlikely to expand, and the print pattern is less likely to be deformed. On the other hand, on the non-printing surface side of the ceramic layer 7, since the concentration of the binder 5 is high, the adhesiveness is improved, delamination and the like when laminated are less likely to occur, and structural defects such as so-called delamination are less likely to occur. Therefore, a laminated body obtained by printing the pattern 8 on the printed surface of the ceramic green sheet using a printing paste and laminating a plurality of the ceramic green sheets has good laminating accuracy and is less likely to cause structural defects such as delamination.

[0013]

Embodiments of the present invention will now be described specifically and in detail with reference to the drawings. As shown in FIG. 1, the ceramic green sheet according to the present invention comprises a carrier film 3 such as a polyethylene terephthalate film.
It consists of a thin ceramic layer 7 formed on top. This ceramic layer 7 is, for example, for manufacturing a monolithic ceramic capacitor, a ceramic powder 4 made of a dielectric material such as barium titanate dispersed in a binder 5, and also for manufacturing a monolithic ceramic inductor. For this purpose, the ceramic powder 4 made of a magnetic material such as ferrite is dispersed in the binder 5.

In FIG. 1 (c), reference numeral 6 is a positioning hole provided at a constant interval in the carrier film 3 for positioning during printing and cutting. On the surface of the ceramic layer 7 constituting such a ceramic green sheet,
Using a printing paste, patterns 8 such as internal electrodes of a plurality of laminated electronic components as shown in FIG. 2A are arranged vertically and horizontally and printed simultaneously. Thereafter, as shown in FIG. 2 (b), the ceramic green sheets are cut into a predetermined shape, further laminated as shown in FIG. 2 (c), and pressure-bonded. After that, this laminated body is cut and divided into laminated chips for individual laminated electronic components. After this laminated chip is fired, a conductive paste for external electrodes is printed on the surfaces of both ends of the laminated chip and baked, for example. As a result, the laminated electronic component is completed.

The monolithic ceramic capacitor, which is a monolithic electronic component manufactured in this manner, has a layer structure as shown in FIG. 3, for example. That is, the dielectric layers 11, 11 ... Having the internal electrodes 15, 16 are stacked in the order shown in FIG. 6, and a plurality of dielectric layers 17, 18 having no internal electrodes are stacked on both sides thereof. Then, an external electrode (not shown) is formed on the exposed end surface of the internal electrodes 15 and 16 of the laminated body. Therefore, it goes without saying that the ceramic green sheets are laminated so as to have such a layer structure in the laminating step of the ceramic green sheets described above.

On the other hand, FIG. 4 is a conceptual diagram showing a laminated structure of a laminated chip inductor. The magnetic layers 21, 21 ...
Circular internal electrodes 35a, 35b, 35c, 35d, 3
5e and 35f. Through holes 32, 32 ... Are provided at positions corresponding to one ends of the internal electrodes 35a, 35b, 35c, 35d, 35e, 35f of the magnetic layers 21, 21, ..., Through hole conductors 33, 33. Has been done.

The magnetic layer 2 having the internal electrodes 35a, 35b, 35c and 35d, depending on the required number of coil turns.
1, 21 ... Are sequentially laminated by an appropriate number of sets. Further, instead of the conductor 35a, internal electrodes 35e and 35f having internal conductor lead portions 25 and 26, respectively, are printed on both sides of the magnetic layers 23, 24 ...
Are stacked. Here, in the state where the magnetic layers 21, 21 ... Are laminated, the end portions of the internal electrodes 35a, 35b, 35c, 35d of the upper and lower magnetic layers 21, 21 ... Are sequentially connected, and a series of conductors connected in a coil shape are formed inside the laminated body. Further, magnetic layers 27 and 28 having no internal electrode are laminated on both sides thereof.

It should be noted that, although the internal electrode patterns and their connection structures are different, a hybrid integrated circuit composed of a composite component such as an LC filter or a resonator in which a capacitor and an inductor are combined, or a multilayer circuit board having a circuit pattern formed therein. Circuits and the like are manufactured in the same manner. FIG. 1A schematically shows the internal structure of the ceramic green sheet according to the present invention for producing such a laminated electronic component. As described above, the ceramic green sheet is composed of the ceramic layer 7 formed by applying the ceramic slurry in which the ceramic powder 4 is dispersed in the binder 5 on the carrier film 3 and drying the applied slurry. As shown in FIG. 1A, the ceramic powder 4 is dispersed in the binder 5 in the ceramic layer 7, but the ceramic powder 4 on the printing surface side of the ceramic layer 7 is dispersed in the binder 5. The density is higher than the dispersion density of the ceramic powder 4 on the non-printing surface side. More specifically, the ceramic layer 7
1 (a), the dispersion density of the ceramic powder 4 on the upper side of the ceramic layer 7 in the binder 5 is equal to that of the carrier film 3 in FIG. 1 (a). It is higher than the dispersion density of the ceramic powder 4 on the lower surface side in contact.

As described above, in such a ceramic green sheet, even if a pattern such as internal electrodes is printed on the printing surface of the ceramic layer 7 using the printing paste, the sheet attack due to the solvent of the printing paste does not easily occur. Therefore, the print pattern portion is unlikely to be stretched, and the print pattern is less likely to be deformed. In addition, delamination of ceramic green sheets is less likely to occur when laminated,
Structural defects such as so-called delamination are less likely to occur.

Such a ceramic green sheet is
It is made as follows. First, finely divided ceramic powder and an organic binder are kneaded to prepare a slurry, which is spread thinly on a base film with a uniform thickness by a roll coater or the like and dried. In this case, immediately after the ceramic slurry is applied onto the carrier film 3, the ceramic slurry is not dried immediately, and the side to be the printed surface of the ceramic layer 7 is faced up in a high-concentration solvent vapor atmosphere of the ceramic slurry. Layer is heat treated. Simultaneously with or after this, the binder solvent is evaporated from the layer of ceramic slurry and dried.

As described above, the ceramic slurry applied on the carrier film 3 is usually dried in a tunnel furnace. For example, the first zone of the tunnel furnace is exposed to a solvent vapor atmosphere having a saturated vapor concentration of 80% or more. , 80
The temperature is set to ℃ or higher, and then the normal drying zone, that is, drying in a low solvent vapor atmosphere is started. Or, by suppressing the ventilation at the entrance and exit of the tunnel furnace as much as possible, the entire zone is dried in a solvent vapor atmosphere having a saturated vapor concentration of 80% or more at a temperature of 80 ° C. or more to dry the ceramic green sheet. May be.

In such a method of manufacturing a ceramic green sheet, the solvent contained in the binder 5 in the ceramic slurry evaporates slowly in spite of the heating temperature because of the high-concentration solvent atmosphere. Therefore, the solvent of the binder 5 is gradually evaporated from the surface of the ceramic slurry. At the same time, convection occurs in the ceramic slurry applied on the carrier film 3 due to the high temperature. By this convection, the ceramic powder 4 uniformly dispersed in the ceramic slurry rises in the layer of the ceramic slurry,
Collected on the upper surface side that is the printing surface of the ceramic layer 7, a concentration gradient of the ceramic powder is formed. After that, the ceramic slurry applied on the carrier film is dried,
Since it becomes the ceramic layer 7 forming the ceramic green sheet, the concentration gradient of the ceramic powder is fixed, and the dispersion density of the ceramic powder 4 on the printing surface side of the ceramic layer 7 is the dispersion density of the ceramic powder 4 on the non-printing surface side. Higher ceramic green sheets are obtained.

When the solvent concentration in the air in the tunnel furnace is set to less than 80% of the saturated solvent concentration, the solvent evaporates quickly from the ceramic slurry applied on the carrier film. In some cases, it may be difficult to generate a concentration gradient of such a ceramic powder. Further, when the heating temperature is lower than 80 ° C., convection in the applied ceramic slurry on the carrier film 3 is less likely to occur, so depending on the solvent concentration in the air in the tunnel furnace,
In some cases, the concentration gradient of the ceramic powder as described above may be difficult to occur. Therefore, it is preferable that at least the first zone of the tunnel furnace is in a solvent vapor atmosphere having a saturated vapor concentration of 80% or more and the heating temperature is 80 ° C. or more.

Next, a specific example of the present invention will be described.
First, a roll coater is used to apply a thin layer of ceramic slurry on a carrier film made of polyethylene terephthalate film with a uniform thickness, then this carrier film is introduced into a tunnel furnace, and the ceramic slurry applied on it is dried to obtain a ceramic green sheet. I made it. The binder solvent used was an organic solvent composed of toluene and alcohol in a ratio of 7: 3.

Here, in the tunnel furnace, the inlet and outlet portions of the ceramic green sheet are narrowed down, the solvent concentration in the entire zone atmosphere is set to 85% of the solvent saturation concentration, and the heating temperature is set to 8
It was set to 0 ° C. The manufactured ceramic green sheets had a thickness of 70 μm, and 10 lots were prepared using the same method and conditions. Using the ceramic green sheet thus obtained, a multilayer ceramic inductor having a standard number of turns of 5 and a standard length and width of 2.1 mm and a length of 2.5 mm was manufactured by the known method as described above.

When the laminated ceramic inductor thus obtained was fractured and its cross section was observed with a microscope, a density gradient of the ceramic powder was observed in each layer of the laminated body. In addition, these multilayer ceramic inductors 500
For each piece, the rate of occurrence of structural defects such as extension of each layer, stacking accuracy, inductance values L and Q values, and delamination was measured. Table 1 shows the results. For comparison, the inlet and outlet portions of the ceramic green sheet in the tunnel furnace were not throttled, the solvent concentration in the first zone atmosphere was 10% or less of the solvent saturation concentration, the heating temperature was 40 ° C, and the maximum heating temperature was A ceramic green sheet was prepared in the same manner as described above except that the ceramic slurry applied to the carrier film was dried at 80 ° C. to prepare a laminated ceramic inductor.

When the laminated ceramic inductor thus obtained was fractured and its cross section was observed with a microscope, no density gradient of the ceramic powder was observed in each layer of the laminated body. In addition, these multilayer ceramic inductors 5
The occurrence rate of structural defects such as extension, stacking accuracy, inductance values L and Q values, and delamination of each of the 00 layers was measured, and the results are shown in Table 1. As is clear from Table 1, in the example of the present invention, the layer elongation and the layering accuracy are smaller than those of the comparative example, and the inductance value L is small.
Also, it can be seen that the variation in Q value is small.
Further, no structural defect has occurred.

[0028]

[Table 1]

Further, in the above-mentioned method for manufacturing a ceramic green sheet, the solvent concentration of the entire zone atmosphere of the tunnel furnace is changed in steps of 70-95% and 5% of the solvent saturation concentration, and at the same time, the heating temperature is 70-120. ℃ and 10 ℃
At the stage of making a ceramic green sheet, and then making a laminated ceramic inductor in the same manner. The cross section of this multilayer ceramic inductor was examined to see if a dispersion density gradient of the ceramic powder was observed in each layer. The solvent concentration in the zone atmosphere was controlled by adjusting dampers at the entrance and exit of the tunnel furnace. As a result, the dispersion density gradient of the ceramic powder is clearly seen in each layer of the cross section of the multilayer ceramic inductor.
Those in which the dispersion density gradient of the ceramic powder is unclear or not observed are shown in Table 2 by x.

[0030]

[Table 2]

As is clear from the results of Table 2, the drying temperature is 7% when the solvent atmosphere concentration in the furnace is 75% of the saturated solvent concentration.
It can be seen that the dispersion density gradient of the ceramic powder of the ceramic green sheet does not occur unless the temperature is as low as 0 ° C. On the other hand, when the heating temperature is 70 ° C., it is understood that the dispersion density gradient of the ceramic powder of the ceramic green sheet does not occur unless the solvent atmosphere concentration in the furnace is increased to 90% or more of the saturated solvent concentration. In these cases, the evaporation of the solvent contained in the ceramic slurry is too slow, resulting in a decrease in productivity. In other words, the solvent vapor atmosphere during drying is set to 80% or more of the saturated vapor concentration and the heating temperature is set to 80%.
It can be said that it is desirable because the dispersion density gradient of the ceramic powder of the ceramic green sheet is stably generated and the drying speed of the solvent of the ceramic slurry is appropriate when the temperature is higher than or equal to ° C.

Although the above is a specific example in the case of manufacturing a laminated ceramic inductor, the same effect can be seen in the case of manufacturing other laminated electronic parts, for example, a laminated ceramic capacitor. That is, when the present invention is applied to the manufacture of a monolithic ceramic capacitor, it is possible to obtain the effect of reducing variations in capacitance value. The conditions of the solvent atmosphere concentration and the heating temperature are the same in the case of manufacturing other laminated electronic components such as a laminated ceramic capacitor.

[0033]

As described above, according to the present invention, when a pattern such as an internal electrode is printed on a ceramic green sheet by using a printing paste, a sheet attack due to the printing paste does not easily occur. The sheet does not stretch. Therefore, a laminated body having a high laminating accuracy can be obtained. Moreover, this laminated body is less likely to cause structural defects such as delamination. This stabilizes the characteristics,
The effect that a laminated electronic component with a low defect rate can be manufactured can be obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a distribution of ceramic powder of a ceramic green sheet according to the present invention, a sectional view of a main part of the ceramic green sheet and a partial perspective view of the ceramic green sheet.

FIG. 2 is a plan view showing a process of manufacturing a laminated body for manufacturing a laminated electronic component using the ceramic green sheet according to the present invention, and a perspective view of the completed laminated body.

FIG. 3 is an exploded perspective view showing a layer structure of a laminated ceramic capacitor manufactured by using the ceramic green sheet according to the present invention.

FIG. 4 is an exploded perspective view showing a layer structure of a laminated ceramic inductor made by using the ceramic green sheet according to the present invention.

[Explanation of symbols]

 3 Carrier Film 4 Ceramic Powder 5 Binder 7 Ceramic Layer 8 Pattern 9 Laminate

Claims (6)

[Claims] 1. A ceramic green sheet comprising a ceramic layer (7) formed by applying a ceramic slurry (4) in which a ceramic powder (4) is dispersed in a binder (5) onto a carrier film (3) and drying. In the ceramic green sheet, the dispersion density of the ceramic powder (4) on the printing surface side of the ceramic layer (7) in the binder (5) is higher than the dispersion density of the ceramic powder (4) on the non-printing surface side. . 2. The ceramic green sheet according to claim 1, wherein the printed surface of the ceramic layer (7) is the surface opposite to the side in contact with the carrier film (3). 3. A ceramic green sheet for forming a ceramic layer (7) by applying a ceramic slurry comprising a binder (5) and ceramic powder (4) dispersed on a carrier film (3) and drying the slurry. In the manufacturing method, after applying the ceramic slurry on the carrier film (3), the side of the ceramic layer (7) to be the printing surface is faced up to form a layer of the ceramic slurry in a high-concentration vapor atmosphere of the solvent of the binder (5). A method for producing a ceramic green sheet, which comprises heat treatment. 4. The method for producing a ceramic green sheet according to claim 3, wherein the high-concentration vapor atmosphere of the binder solvent is 80% or more of the saturated vapor concentration of the solvent. 5. The method for producing a ceramic green sheet according to claim 3, wherein the heat treatment temperature of the layer of the ceramic slurry in a high-concentration vapor atmosphere of the solvent of the binder is 80 ° C. or higher. 6. A printing paste is used on the printing surface of a ceramic green sheet in which the dispersion density of the ceramic powder (4) on the printing surface side in the binder (5) is higher than the dispersion density of the ceramic powder (4) on the non-printing surface side. A pattern (8) is printed by using the above method, and a plurality of the ceramic green sheets are laminated to form a ceramic green sheet laminate.