JPH05299288A - Manufacture of laminated ceramic capacitor - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a laminated ceramic capacitor small in size and high in quality, where organic binder removable at a low temperature and high in flexibility is used as organic binder which forms conductive paste used for forming ceramic green sheets and inner electrodes in place of plastic organic binder. CONSTITUTION:Ceramic laminates 1 and inner electrodes 2 are laminated to form a laminated ceramic capacitor, where polyether polyurethane resin where -COOM [C: carbon, O: oxygen, M: hydrogen(H), potassium(K), or sodium(Na)] group as a side-chain is contained as high in concentration as 0.01 to 0.95mmmol/gram and whose glass transition temperature (Tg) is lower than 60 deg.C is used as organic bonder of ferroelectric ceramic slurry and conductive paste.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a monolithic ceramic capacitor obtained by laminating, molding and sintering a dielectric ceramic layer and a low resistance metal conductor layer by a green sheet method.

[0002]

2. Description of the Related Art In recent years, with the rapid miniaturization and weight reduction of electronic devices, electronic components are being further miniaturized to meet the demand for miniaturization of electronic circuit components constituting the electronic devices. The capacitor type that can be surface-mounted is becoming the mainstream for the capacitor element. A chip capacitor mounted on a printed wiring board or the like usually has a ferroelectric layer composed of a ferroelectric ceramic powder and an organic binder and an internal electrode layer composed of a conductive fine powder and an organic binder, which are alternately arranged. It is made by stacking and then sintering. Therefore,
Factors that affect the performance of such a monolithic ceramic capacitor are ferroelectric ceramic powder, which is the main raw material,
Alternatively, the characteristics of the conductive fine powder itself are, of course, important, and the characteristics of the organic binder, which is indispensable for forming a coating film of these fine powders, are also very important when manufacturing a chip type multilayer ceramic capacitor.

That is, the main properties required of the organic binder are that it can impart mechanical strength and flexibility sufficient for the lamination process by the green sheet method, and pressure bonding during lamination and press molding. That the binder can be sufficiently imparted, and further that the organic binder is treated as a pre-sintering treatment, that is, the binder can be treated at a low temperature, and the organic binder is a ferroelectric ceramic powder and a conductive material. Conditions such as being completely removed from the fine powder must be met. As a non-aqueous organic binder satisfying these requirements, that is, in a system using an organic solvent as a dispersion medium, conventionally, nitrocellulose, ethyl cellulose,
There are polyvinyl butyral and the like, which have been widely and commonly used by adding various plasticizers together in order to impart flexibility to these organic binders.

[0004]

However, it has been found that these conventional organic binders have various drawbacks in order to further miniaturize and improve the performance of the monolithic ceramic capacitor. That is, first, in order to further reduce the size while ensuring the same performance as a capacitor, it is necessary to improve the powder filling rate of the dielectric layer and the conductor layer. Conventional organic binders such as polyvinyl butyral and the like have weak dispersion characteristics for the ceramic powder and the conductive powder forming the internal electrodes represented by the silver (Ag) -palladium (Pd) mixed powder, and therefore high powder packing is achieved. The rate cannot be expected. Second, conventional organic binders generally have a low glass transition temperature (softening temperature) and are therefore less flexible, and have a high binder removal temperature. Also, in order to make them easy to handle and soft, the amount of plasticizer added must be increased. Is indispensable and has been a cause of deteriorating the filling rate of the dielectric layer and the conductor layer. Therefore, in order to improve the filling rate of the coating film, how to reduce the addition amounts of the organic binder and the plasticizer has been a problem.

[0005]

SUMMARY OF THE INVENTION The present invention overcomes the deficiencies of conventional organic binders and provides a small, high performance laminated ceramic capacitor formed by the green sheet method. The present invention comprises a ferroelectric ceramic powder and an organic binder as main raw materials, a ferroelectric slurry having an organic solvent as a dispersion medium, formed into a film, and dried on a green sheet obtained by drying the metal fine powder and the organic binder. In a multilayer ceramic capacitor obtained by printing a conductive paste containing a binder as a main raw material and an organic solvent as a dispersion medium, laminating, press molding and sintering, the organic binder of the ferroelectric slurry is polyurethane. -COOM [C: carbon, O: oxygen, M: hydrogen (H), potassium (K) or sodium (Na)] on the side chain of the organic binder made of resin.
A method for producing a monolithic ceramic capacitor, which comprises a polyether polyurethane resin having a group and a glass transition temperature (Tg) of 60 ° C. or lower,
Further, the organic binder of the conductive paste forming the internal electrodes also has -COOM [C: carbon, on the side chain of the organic binder made of polyurethane resin as in the case of forming the ferroelectric slurry.
O: oxygen, M: hydrogen (H), potassium (K) or sodium (Na)] group, and has a glass transition temperature (T
g) is formed by using a polyether polyurethane resin having a temperature of 60 ° C. or lower.

In the present invention, the polyether polyurethane resin used to disperse the dielectric fine powder forming the dielectric layer and the conductive fine powder forming the internal electrode is a polyether polyurethane having an ether bond site in the main chain. An ether polyurethane having side chains of -COOM [C: carbon, O:
Oxygen, M: hydrogen (H), potassium (K) or sodium (Na)] group, and a green sheet of a dielectric layer using a polyether polyurethane resin having a glass transition temperature (Tg) of 60 ° C. or less, And forming a conductive paste,
It is a monolithic ceramic capacitor.

That is, the present invention is as follows. Ferroelectric ceramic powder and organic binder as the main raw materials, a ferroelectric slurry with organic solvent as the dispersion medium is formed into a film, and dried to obtain a green sheet on which the fine metal powder and organic binder are the main raw materials. In a multilayer ceramic capacitor obtained by printing a conductive paste having an organic solvent as a dispersion medium, laminating, press molding, and sintering, the ferroelectric slurry and the organic binder of the conductive paste have side chains. -COOM [C: carbon, O: oxygen, M: hydrogen (H), potassium (K) or sodium (Na)] as a group, and the glass transition temperature (T gram) is 60 ° C. or less. It is a method for manufacturing a monolithic ceramic capacitor, which is made of resin. 2. -COOM [C: carbon, O: oxygen, M: hydrogen (H), potassium (K) or sodium (Na) as a side chain contained in the polyether polyurethane resin as the organic binder of the ferroelectric paste and the conductive paste. )] Weight of the base polyether polyurethane resin 1
The method according to claim 1, wherein the concentration per gram is in the range of 0.01 mmol / gram to 0.95 mmol / gram.

[0008]

The action of the -COOM [C: carbon, O: oxygen, M: hydrogen (H), potassium (K) or sodium (Na)] group-containing polyether polyurethane resin in the present invention is as follows. I think so. That is, first, -COOM which forms the side chain of the polyurethane resin.
The [C: carbon, O: oxygen, M: hydrogen (H), potassium (K) or sodium (Na)] group has a hydrophilic surface, and has a ferroelectric ceramic powder and silver (Ag) -palladium ( Since it is directed to the surface of the conductive fine powder represented by Pd), excellent powder dispersion characteristics are obtained, and as a result, the packing density of the green sheet is improved.

Second, the glass transition temperature (Tg) is 60 ° C.
Because of the following, the resin itself has a practically sufficient flexibility at room temperature. Therefore, it is possible to obtain appropriate flexibility and pressure-bonding property during lamination without adding a plasticizer, and it is possible to exclude a plasticizer that is a factor that lowers the coating density, and as a result, the filling density of the coating film improves.

Thirdly, since the main chain has an ether bond site, this site is easily oxidatively decomposed at a relatively low temperature, and as a result, the organic binder removal treatment, that is, the binder removal is promptly performed. Proceed to.

When the glass transition temperature (Tg) of the above-mentioned polyether polyurethane resin exceeds 60 ° C., it is not preferable because imparting flexibility, which is one of the effects of the present invention, cannot be expected without the addition of a plasticizer. -COOM [C: carbon, O: oxygen, M: hydrogen (H), potassium (K) or sodium (Na)] of a polyether polyurethane resin
The concentration of groups is preferably in the range of 0.01 mmol / gram to 0.95 mmol / gram per gram of polyether polyurethane resin. When the concentration is 0.01 mmol / g or less, the improvement of the packing density of the powder, which is one of the effects of the present invention, cannot be expected. On the other hand, when the concentration is 0.95 mmol / g or more, the dielectric fineness is increased. This is not desirable because it causes the slurry of powder or gelation of the conductive paste. In addition, as the element of M constituting the side chain,
In the examples of the present invention, those having hydrogen (H) were used. However, even if potassium (K) or sodium (Na) is bonded instead of hydrogen (H), the effect of the organic solvent is practical. There is no change in terms of aspect. Due to these actions, the polyether polyurethane resin according to the present invention can obtain a green sheet, which is indispensable for downsizing of a monolithic ceramic capacitor, and an improvement in printing density and excellent processability.

[0012]

EXAMPLE An example of a method for manufacturing a monolithic ceramic capacitor according to the present invention will be described. FIG. 1 shows the basic structure of a monolithic ceramic capacitor. A ceramic laminated body 1 made of a dielectric material and an internal electrode 2 made of a conductor laminated between the ceramic laminated bodies are alternately connected and drawn out to the terminal electrodes on both end faces to form a capacitor. As described above, the ferroelectric ceramic powder and the slurry containing the organic binder as the main component are film-dried with a doctor blade or the like, and the low resistance metal fine powder and the conductor containing the organic binder as the main components are formed on the film. The paste is printed, dried, laminated, hot pressed, and sintered to obtain the capacitor element 3 shown in FIG. Further, as shown in FIG. 3, by forming terminal electrodes 4 which are alternately connected to the internal electrodes between the laminated bodies of the dielectrics, the laminated ceramic capacitor of the present invention is obtained. Here, in order to clarify the effect of the present invention, ceramic slurries having different compositions and conductor pastes are prepared in advance, and various characteristics of each are evaluated, and thereafter, the laminated ceramic capacitor of the present invention is prepared and evaluated. did.

[0013]

Example 1 In order to evaluate the characteristics of a ceramic green sheet forming a monolithic ceramic capacitor using a polyether polyurethane resin according to the present invention, the raw materials of the ceramic slurry composition shown in Table 1 were used as a pressure kneader and a sand grinder. To a ceramic slurry with a doctor blade method to form a film with a thickness of 20 μm after drying, and after performing gloss measurement with a gloss meter and flexibility test with a bending test, use a thermobalance method. The binder removal completion temperature was determined. The results obtained are shown in Table 7.

[Table 1]

[0014]

Example 2 In order to evaluate the characteristics of the internal electrode conductors forming the laminated ceramic capacitor using the polyether polyurethane resin according to the present invention, the raw materials of the conductor coating composition shown in Table 2 were used with a pressure kneader and a sand. Conductive paste with a grinder and 5.5m by screen printing
3m in thickness after drying the electrode pattern of mx 4.5mm
It was printed so as to have a thickness of 4 to 4 μm, and the pattern accuracy was observed with a microscope. Further, the same paste was formed by a doctor blade method so that the thickness after drying was 20 μm, glossiness was measured by a gloss meter and flexibility test by a bending test, and then by a thermobalance method. The binder removal completion temperature was determined. The results obtained are shown in Table 7.

[Table 2]

[0015]

COMPARATIVE EXAMPLE 1 Table 3 shows the characteristics of the conventional ceramic green sheet compared with the present invention and evaluated. Table 3
A ceramic slurry having the composition shown in (1) was obtained, and a film was formed by the doctor blade method so that the thickness after drying was 20 μm as in Example 1, and the flexibility test was performed by measuring the glossiness with a gloss meter and the bending test. After that, the binder removal completion temperature was determined by the thermobalance method. The results obtained are shown in Table 7.

[Table 3]

[0016]

Comparative Example 2 A ceramic slurry having a conventional composition shown in Table 4 was obtained, and the thickness after drying was 2 by the doctor blade method.
A film was formed to a thickness of 0 μm, glossiness was measured by a gloss meter, and a flexibility test was performed by a bending test, and then the completion temperature of the binder removal was determined by a thermobalance method. The results obtained are shown in Table 7.

[Table 4]

[0017]

[Comparative Example 3] A conductor paste having the composition shown in Table 5 was obtained under the same conditions as in Example 2. The results obtained are shown in Table 7.

[Table 5]

[0018]

[Comparative Example 4] A conductive paste having the composition shown in Table 6 was obtained under the same conditions as in Example 2. The results obtained are shown in Table 7.

[Table 6]

Table 7 shows the evaluation results of the obtained green sheets.

[Table 7] In the table, the glossiness is an index of the dispersibility of the ferroelectric ceramic powder and the conductor powder, and it can be said that the larger the value, the better the dispersion state. In a laminated ceramic capacitor, it is extremely important to improve the dispersibility of the ferroelectric ceramic powder and the conductor powder. That is, being in an excellent dispersed state makes it possible to improve the filling rate of the ferroelectric ceramic powder and the filling rate of the internal electrodes, and promotes the homogenization of the mixed powder, thereby improving the insulation resistance and the breakdown voltage. As a result, the reliability under high temperature and high humidity can be improved.

In the table, the flexibility is a measure of the flexibility of each green sheet. If the flexibility is insufficient, cracks may occur during the formation of the green sheet,
When multilayering the green sheet, a crimping failure occurs, resulting in a decrease in workability and a failure, which is not preferable.

The pattern accuracy in the table is a measure of the flexibility of the shape of the conductor layer and the thinning and miniaturization of the conductor layer, and is an essential element for downsizing and high performance of the laminated ceramic capacitor. It strongly depends on the dispersion state of the paste. Thus, as can be seen from the characteristics shown in Table 7,
A method for manufacturing a monolithic ceramic capacitor according to the present invention,
It is extremely effective for manufacturing method and quality of laminated ceramic capacitors. Next, a laminated ceramic capacitor was prepared with each composition of the above-mentioned Examples and Comparative Examples, and the characteristics of the laminated ceramic capacitors were compared with those of the capacitors manufactured by the conventional example.

[0022]

Example 3 A lead (Pb) -based ferroelectric ceramic powder having a composite perovskite structure shown in Table 1, a polyether polyurethane resin, and an organic solvent were mixed with a pressure kneader for 5 hours, and then charged into a sand glider. A dielectric slurry was obtained. With the doctor blade method, the ferroelectric slurry
120mm × 160 so that the thickness after drying is 20μm
After forming a film with a size of mm to form a green sheet, the silver (Ag) and palladium (Pd) powders shown in Table 2 are mixed with a polyether polyurethane resin and a solvent by a pressure kneader, and then the mixture is transferred to a sand grinder. The internal electrode paste, which was charged and made into a paste, was printed on the above green sheet by screen printing. Printing is performed so that the thickness after drying is 3 μm to 4 μm, and since positive and negative potentials are applied at the time of production, the overlapping electrode area of the electrodes laminated facing each other is 6.0 mm × 4.3 mm. 2 kinds of electrodes are printed, and a plurality of internal electrodes for 120 mm can be printed by one printing.
Printed within an area of x160 mm. The green sheets were punched out, 14 green sheets were laminated in the mold, 28 green sheets with internal electrodes were printed, and 15 green sheets were further laminated.
A 0 mm × 0.85 mm laminate was obtained. Cut the laminated body into capacitor elements one by one, 450 ℃ ×
After removing the binder for 5 hours and firing in the air at 950 ° C. for 10 hours, both ends of the silver paste connected to the electrodes laminated inside are dip-coated and baked at 700 ° C. for 1 hour. A multilayer ceramic capacitor according to the present invention shown in 8 was obtained. About the multilayer ceramic capacitor,
The insulation resistance and the non-defective rate were investigated, and a high temperature load test was conducted. The results are shown in Table 9.

[Table 8]

[Table 9]

[0023]

COMPARATIVE EXAMPLE 5 As shown in Table 4, the ferroelectric ceramic slurry shown in Comparative Example 2 and the conductive paste shown in Comparative Example 4 were used under the same conditions as in Example 3. A monolithic ceramic capacitor was prepared by using the above, and the results are shown in Table 9. From Table 9, the method for manufacturing a monolithic ceramic capacitor of the present invention improves the yield by almost 8% as compared with the element manufactured by the conventional method, and the failure rate becomes 0% in the high temperature load test using 50 samples. It is understood that the yield and the high temperature load test characteristics are greatly improved by adopting the manufacturing method of the monolithic ceramic capacitor described in 1.

[0024]

As described above, the organic binder in the present invention has a —COOM [C: carbon, O: oxygen, M: hydrogen (H), potassium (K) or sodium (Na)] group as a side chain. In addition, by using a polyether polyurethane resin having a glass transition temperature of 60 ° C. or less, the drawbacks of the prior art can be solved, and a compact, high-performance and highly reliable monolithic ceramic capacitor with improved packing density after firing can be obtained. Offering is now possible. In the configuration of the present invention, the method for forming the ferroelectric ceramic slurry and the conductor paste may be any forming method such as a gravure printing method, a doctor blade method, an extrusion forming method, and an injection forming method. The effect of the present invention does not change at all.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view in which a ceramic laminated body of a laminated ceramic capacitor and internal electrodes are laminated.

FIG. 2 is a cross-sectional view of an end face of a monolithic ceramic capacitor.

FIG. 3 is an external perspective view of a monolithic ceramic capacitor.

[Explanation of symbols]

 1 Ceramic Laminate 2 Internal Electrode 3 Capacitor Element 4 Terminal Electrode

Claims (2)

[Claims] 1. A green sheet obtained by film-forming and drying a ferroelectric slurry containing a ferroelectric ceramic powder and an organic binder as main raw materials and an organic solvent as a dispersion medium. A multilayer ceramic capacitor obtained by printing, laminating, press-molding, and sintering a conductive paste containing a binder as a main raw material and an organic solvent as a dispersion medium, in which a ferroelectric slurry and an organic bond of the conductive paste are formed. The agent has a side chain of -COOM [C: carbon, O: oxygen,
M: hydrogen (H), potassium (K) or sodium (N
a)] group and having a glass transition temperature (Tg) of 60 ° C.
A method for manufacturing a monolithic ceramic capacitor comprising the following polyether polyurethane resin. 2. A ferroelectric slurry, and -COOM [C: carbon, O: oxygen, M: hydrogen (H), potassium (K) as a side chain contained in a polyether polyurethane resin as an organic binder of a conductive paste. ) Or sodium (Na)]
The method for producing a monolithic ceramic capacitor according to claim 1, wherein the concentration of the base polyether polyurethane resin per gram by weight is in the range of 0.01 mmol / gram to 0.95 mmol / gram.