JPH02117118A - Green sheet for laminated ceramic capacitor - Google Patents

Abstract

PURPOSE:To decrease substantially the number of pin holes and to provide a very flat surface on which electrodes are printed, by putting a pair of base films together such that dielectric layers formed thereon are faced to each other and then transferring one of the dielectric layer to the other by thermocompression bonding. CONSTITUTION:A pair of base films are put together such that dielectric layers 11a and 11b formed thereon are faced to each other. A transfer roller 13 is applied to the base film 10a of one of the green sheets so that the dielectric layer 11a on the base film 10a is transferred to and integrated with the other dielectric layer 11b by thermocompression bonding. Then, the base film 10a is peeled off from the sheet so that inner electrodes are printed on the peeled surface 14 of the dielectric layer. According to such method, since flatness of the base film can be utilized as it is, the inner electrodes can be formed on the very flat surface. Accordingly, even if an inner electrode layer 17 is thin, it can be formed uniformly without disconnection due to unevenness of the sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to dielectric green sheets used in the manufacture of multilayer ceramic capacitors.

Background of the Invention In recent years, with the development of ultra-compact, thin, and lightweight electronic devices such as radios, microcassette recorders, tuners, and video cameras, capacitors used as circuit elements have become smaller and smaller.
There is now a strong demand for higher capacity. A multilayer ceramic capacitor is known as a component that satisfies these requirements.

As shown in Fig. 3, the method for manufacturing a multilayer ceramic capacitor is to first deposit a dielectric layer several tens of micrometers thick on a base film 1 using a doctor blade method using a slurry consisting of dielectric powder, a binder, a plasticizer, and an organic solvent. A dielectric green sheet 3 on which a layer 2 is formed is produced. Next, a plurality of green sheets 3 with all internal electrodes 4 printed thereon are stacked in a mold die 6, and a laminate molded body is produced by pressure bonding, and then cut into chips and fired.

It is generally manufactured by forming an external electrode e. (
"Insulating/Dielectric Ceramics J" Published by CMC, supervised by Tadashi Shiozaki, completed p. 211-22, published in 1962] On the other hand, in order to achieve even higher capacity, it is desirable to make the dielectric layer thinner, but in the doctor blade method, the dielectric layer 2
Since there is a limit to the thickness of the slurry, thin sheets have recently been proposed that are made by using a reverse roll method with an even lower slurry viscosity.

Problems to be Solved by the Invention By the way, the internal electrode 4 used in this multilayer quench capacitor is a so-called noble metal powder such as platinum, palladium, silver-palladium, etc. Therefore, it is desirable to make the electrode thickness as thin as possible in terms of cost. However, the surface of the dielectric green sheet 3 produced by the above-mentioned doctor blade method or reverse roll method is quite uneven as shown in Fig. 4, so even if an attempt is made to print a thin electrode layer, the electrode layer will crack. This causes problems such as the area of the electrode that actually works effectively as a capacitor becomes smaller. In addition, if the sheet surface has large irregularities, even if electrode paste is printed on the sheet surface, the dielectric layer 2
A space tends to exist between the inner electrode and the four internal electrode layers. Therefore, air tends to remain in the laminated product formed by laminating a plurality of sheets on which the electrode 4 is printed, and even if this is fired, a peeling phenomenon occurs between the dielectric layer 2 and the electrode 4 layer, resulting in a poor yield. There are problems such as becoming a thing.

In view of the above-mentioned problems, the present invention aims to provide a green sheet for a multilayer ceramic capacitor, in which even a thin electrode layer can be formed uniformly and with good adhesion to the dielectric layer of the green sheet.

Means for Solving the Problems The sheet of the present invention for solving the above problems is as follows. That is, after the dielectric layers of the base film each having a dielectric layer provided on its upper surface are superimposed on each other, one dielectric layer and the other dielectric layer are integrated by thermocompression bonding.

Operation In the present invention, as shown in FIG.
, 11b are stacked so that they face each other, and then the dielectric layer 111L'i on the base film surface 1QIL is bonded by thermocompression using the transfer roller 13 from either one of the base film surfaces 102L side. It is transferred and integrated with the body layer 11b. After that, base film 10! L'(i7) The peeled surface is used as the surface 14 on which internal electrodes are printed.

As a result, the smoothness of the base film surface can be used as is, so the surface on which the internal electrodes are formed is extremely flat, as shown in Figure 2, and even the 17th layer of thin internal electrodes can be formed uniformly without cutting due to unevenness of the sheet. It becomes possible.

In addition, a dielectric layer 2 is coated on one side of the base film using the conventional doctor blade method or reverse roll method shown in FIG.
In the green sheet 3 that is still formed, if the sheet 3 is left at room temperature, the solvent contained in the sheet 3 will evaporate, and the composition in the thickness direction of the sheet 3 will shift slightly, resulting in variations in properties. For this reason, it was difficult to store the sheets for long periods of time, and they had to be stored under special environments. However, as in the present invention, if two or more dielectric layers 11a, 11b'j (after thermocompression bonding, the base films 101L, 10bi are left bonded together until just before use), the dielectric layers 111L, 11b are attached to the base film 101. It has the advantage that it is sandwiched between the .10b planes, prevents the evaporation of the solvent, and does not cause composition shifts even if left for a long time.In addition, in the case of thin sheets,
Pinholes sometimes occur in the sheet, causing short circuits between the internal electrodes 17 and deteriorating the yield. However, in the present invention, the dielectric layer 11a
.

Due to the stacked structure of 11b, it is possible to significantly reduce the incidence of pinholes, and an improvement in productivity can be expected.

Example Examples of the present invention will be described in detail below.

22 parts by weight of polyvinyl butyral resin and 2 parts by weight of dioctyl heptalate were blended with 100 parts by weight of dielectric powder mainly composed of BaTi0, and after cooling, the mixture was kneaded for 20 hours in a ball mill using tetrahydrofuran as a solvent.
A slurry having a viscosity of Cps was prepared. After degassing this slurry, it was rolled to a thickness of 60 μm using the reverse roll method.
A sheet was produced by forming a 16 μm thick dielectric layer on a 16 μm thick polyester film. Using two such sheets, after stacking them so that the dielectric layers of each sheet face each other, thermocompression bonding was performed from the base film side of one of them to produce a sheet with a thickness of 30 μm,
This was used as a green sheet for laminated ceramic capacitors.

The thermocompression bonding conditions were a temperature of 180° C. and a pressure of 200 kg 10 IL” using a thermo roll.

After peeling off the base film surface of the green sheet, a 3.5×1. An electrode having a shape of 0 mm was formed.

Next, BaTi0 prepared by the doctor blade method
After superimposing a green sheet on which the above-mentioned electrodes were printed on a dielectric green sheet with a thickness of 200 μm consisting of powder particles mainly composed of and polyvinyl butyral resin,
This green sheet was heat-pressed from the base film side for 2 seconds at a temperature of 130° C. and a pressure of 200 kg/crt using a hot roll to transfer the dielectric layer of the green sheet. After that, the base film of the green sheet was peeled off. Next, another green sheet with electrodes printed on the transferred dielectric layer was heated and pressed onto a hot roll under the same conditions as before, and then the base film was peeled off. The overlapping portion of the internal electrodes, that is, the area of the electrodes that effectively function as a multilayer ceramic capacitor, is 1.4 x 1. Om
It was laminated and molded so that it became m. After repeating this process 10 times, the dielectric green sheets prepared by the doctor blade method and having a thickness of 200 μm described above were superimposed on each other. Next, this laminate was further heated to 500K at 80℃ using a mold press.
The pressure bonding was carried out under the conditions of g/af. After that, 2.4 x 1
．． After cutting into a 6 mm chip shape, the chip molded body fZr
Bake at 1300℃ for 1 hour while sprinkling in O2 powder. Furthermore, the temperature is increased.

The temperature decreasing rate was 200'Q/hr, and the temperature was maintained at 380° C. for 10 hours to remove the binder during the process.

The capacitance of the capacitor thus produced was measured by a conventional method, and the presence or absence of delamination G7 was confirmed by observing the fine structure of the sintered body with a scanning electron microscope. The number of samples to be measured was 100. Table 1 below shows the average capacity and delamination incidence for n=100. For comparison, as a conventional method, BaTi0. A green sheet with a thickness of 30 μm consisting of dielectric powder as the main component? Table 1 also shows the capacitance and delamination incidence of a multilayer ceramic capacitor manufactured using the doctor blade method and according to the manufacturing process shown in FIG. Here, the type, shape, number of laminated layers, firing conditions, etc. of the electrodes were all the same.

Furthermore, the surface roughness of the printed surface of the green sheet and the printed surface of the sheet produced by the conventional method, that is, the doctor blade method, was measured using a surface roughness meter. The results are also listed in Table 1. Furthermore, in order to measure the incidence of pinholes in the sheets of the present invention and the conventional method, the number of pinholes within a sheet area of 10×10af was visually measured. The results are also shown in Table 1.

As is clear from the results in Table 1, the multilayer ceramic capacitor manufactured using the green sheet according to the present invention has a smooth surface on which the internal electrodes are printed, so even if the internal electrodes are thin, the electrodes do not break. The effective electrode area that actually works as a capacitor is important. Therefore, a larger capacity can be obtained compared to the conventional method. Since the surface of the matrix sheet is smooth, the adhesion between the sheets during lamination is good, and uniform lamination is possible, making it possible to suppress the occurrence of delamination. Furthermore, the green sheet according to the present invention has fewer pinholes than the conventional 7-sheet, and its reliability is significantly improved.

In the examples, dielectric powder whose main component is BaTiO3 is used, and i is 5rTi03-based, MgTi03-GaT.
There is no problem in using all ceramic powders having any dielectric properties such as i03 series. Further, although a hot roll was used when transferring the dielectric layer, the same effect can be obtained by moving a hot plate containing a heater up and down for thermocompression bonding. Further, in this embodiment, two hot stamp sheets were used, but a thinner hot stamp sheet t1 may be prepared and a plurality of green sheets laminated until the desired thickness is obtained may be used.

Effects of the Invention As mentioned above, the green sheet according to the present invention has the following advantages:
A structure in which a dielectric layer is provided on the upper surface of each base film, and the dielectric layers are laminated on each other, and then one dielectric layer is laminated on the other dielectric layer by thermocompression bonding. Therefore, the number of pinholes is greatly reduced, and the electrode printing surface is extremely smooth because the peeling surface of the base film is used. Therefore, the internal electrode layer and the sheet surface are formed uniformly and with good adhesion, so a multilayer S-type capacitor using this can reduce internal electrode breakage and suppress the occurrence of delamination.
Its industrial value is extremely great, as it makes it possible to improve productivity.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the manufacturing process of a green sheet according to the present invention, Figure 2 is a cross-sectional view when electrodes are formed on the green sheet according to the present invention, and Figure 3 is a diagram explaining the manufacturing process of a conventional multilayer ceramic capacitor. FIG. 4 is a cross-sectional view of a conventional method in which electrodes are formed on a green sheet. 10! L, 10b・---・Base film, 1
1a. 11b... Dielectric layer, 14... Surface on which internal electrodes are printed. Name of agent: Patent attorney Shigetaka Awano and 1 other person No. 3
figure

Claims (1)

[Claims] After the dielectric layers of the first and second base films each having a dielectric layer on their upper surfaces are stacked so as to face each other, the dielectric layer is bonded by thermocompression from the side of one of the base films. A green sheet for multilayer ceramic capacitors in which the body layer is transferred and integrated with other dielectric layers.