JP2520747B2 - Method for manufacturing capacitor material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a capacitor material.

(Prior Art) Conventionally, for example, in the case of a semiconductor capacitor, manufacturing of a capacitor material uses a ceramic base material such as BaTiO ₃ , SrTiO ₃ or CaTiO ₃ and Nb for the purpose of controlling valence.
₂ O ₅ , Y ₂ O ₃ , Bi ₂ O _{3 and} other trace additives were blended in a ball mill and dispersed, but this was done because the trace additives have not been sufficiently crushed and dispersed. It was also a cause of variations in the capacitance of the capacitors.

Therefore, a method has been proposed in which only a small amount of additive is crushed by a ball mill and then added and mixed with a base material. Also,
A method of mixing by a bead mill using beads having a diameter of 1 to 2 mm has also been proposed.

(Problems to be Solved by the Invention) However, in the method of crushing only the above-mentioned trace amount additive in a ball mill and then adding and mixing the base material, re-aggregation of the crushed additive occurs, resulting in dispersibility. Was not improved, and the variation in capacitance was not improved.

In addition, in the method of mixing with a bead mill using beads having a diameter of 1 to 2 mm, at the same time as the dispersion of the additive, the base material is crushed and the particle size becomes non-uniform, which causes the capacitance to change. There was a case where there were variations and a molding failure during extrusion molding, and the improvement effect was not obtained.

Therefore, the present invention provides a method for producing a material for a capacitor, which is capable of pulverizing a trace amount of additive and highly dispersing it in a base material, and at that time, preventing pulverization into a base material and non-uniform particle size. It is intended to be provided.

(Means for Solving the Problems) In order to solve the above problems, the present invention relates to a method for producing a capacitor material by mixing a trace amount additive with a ceramic base material, wherein the trace additive total amount and the ceramic base material are used. It is characterized in that 1 to 20 wt% of the total amount of the material is premixed, and after calcination, the premixed material and the remaining amount of the ceramic base material are mixed.

(Operation) In the method for producing the capacitor material according to the present invention, first, the pulverization of the trace additive is promoted by mixing the total amount of the trace additive and a part of the base material. Then, by calcination, the trace amount additive and the base material are reacted to maintain the dispersed state.

Moreover, since the remaining base material is then mixed with the above-mentioned premix, unnecessary pulverization is not performed and the particle size of the base material does not become nonuniform.

(Example) Hereinafter, the Example of this invention is demonstrated with a comparative example and a prior art example, referring an addition drawing.

First, in the description of examples, comparative examples and conventional examples, 995 parts by weight of SrTiO ₃ as a base material and Nb as a trace additive were added.
_The addition of 5 parts by weight of ₂ O ₅ will be described.

Example 1 First, a Nb ₂ O ₅ total amount, 1 wt% of the total amount of SrTiO ₃ and water in an amount twice as much as the total amount of these powders were ball milled.
The mixture was stirred for 15 hours and premixed. Then, the premix was dehydrated and dried to obtain a powder. After the powder thus obtained was calcined at 1200 ° C., the remaining SrTiO ₃ and water in an amount twice as much as the total amount of these powders were added and stirred and mixed in a ball mill for 15 hours.

After dehydrating and drying this mixture, 5 wt% as a binder
Polyvinyl alcohol was added to granulate, and the granulated product was put into a molding machine and pressure-molded into a disk shape at a pressure of 1000 kg / cm ² .

Next, this molded product is placed in a furnace and placed in air for 800
The temperature was raised to 100 ° C. per hour at a rate of 100 ° C., and the binder polyvinyl alcohol was burned. After that, the inside of the furnace was changed to a reducing atmosphere of N ₂ of 97.0 vol% and H ₂ of 3.0 vol%, and the temperature was maintained at 1400 ° C. for 3 hours for firing to obtain semiconductor ceramics.

Further, a paste containing CuO as a component was applied to the disc-shaped semiconductor ceramics, and the temperature was raised at a rate of 100 ° C./hour,
While maintaining the temperature of 200 ° C. for 3 hours, CuO was diffused into the grain boundaries of the semiconductor ceramics to obtain grain boundary insulating dielectric ceramics having a thickness of 0.50 mm and a diameter of 16 mm.

Next, a silver paste was applied to both surfaces of this dielectric ceramic and baked at 800 ° C. to form an electrode having a diameter of 10 mm to obtain a semiconductor capacitor.

Example 2-4 The mixing amounts of SrTiO ₃ in the above premixing were 5 wt% and 10 wt%.
% And 20 wt%, semiconductor capacitors were obtained in the same manner as in Example 1 above, and these were Examples 2 to 4, respectively.

Comparative Examples 1 and 2 The mixing amounts of SrTiO ₃ in the above premixing were 0.5 wt% and 30 w.
t%, and semiconductor capacitors were obtained in the same manner as in Example 1 above, and these were designated as Comparative Examples 1 and 2, respectively.

Conventional Example 1 The whole amount of Nb ₂ O _{5 and the} total amount of SrTiO ₃ were mixed once, and a semiconductor capacitor was obtained in the same manner as in Example 1 after the granulation step.

Next, in the above Examples, Comparative Examples, and Conventional Example, 970 parts by weight of SrTiO ₃ was used as a base material and 5 parts of Nb ₂ O ₅ was added as a trace additive.
The addition of 25 parts by weight of Bi ₂ O ₃ will be described.

Examples 5 to 8 In premixing, 1 wt%, 5 wt%, 10 wt% and 20 wt% of the total amount of Nb ₂ O ₅ and Bi ₂ O ₃ and SrTiO ₃ were mixed and Example 1
Semiconductor capacitors were obtained in the same manner as in, and these were designated as Examples 5 to 8, respectively.

Comparative Examples 3 and 4 In the above premixing, the mixing amount of SrTiO ₃ was 0.5 wt% and 30 w
A semiconductor capacitor was obtained in the same manner as in Example 1 with t% being set as Comparative Examples 3 and 4, respectively.

Conventional Example 2 A total amount of Nb ₂ O ₅ and Bi ₂ O _{3 and an} entire amount of SrTiO ₃ were mixed at once, and a semiconductor capacitor was obtained in the same manner as in Example 1 after the granulation step.

For each of the above Examples 1 to 8, Comparative Examples 1 to 4 and Conventional Examples 1 and 2, 100 semiconductor capacitors were prepared as samples, and the capacitances were measured. Based on the capacitance, the variation in capacitance, that is, the standard deviation was measured. The results are shown in the attached graphs of FIGS. 1 and 2.

Although the above embodiments have been described by taking the case of the material for the semiconductor capacitor as an example, the present invention is not limited to this, and other materials for the ceramic capacitor can be used.

(Effects of the Invention) According to the method for manufacturing a capacitor material of the present invention described above, as can be seen from the graph of the accompanying drawings, it is possible to greatly reduce variations in the capacitance of the capacitor,
Therefore, the yield of capacitor manufacturing is improved and
It is possible to cope with the narrowing of the capacity allowable width.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 are graphs showing the standard deviation of the capacitances of capacitors according to examples of the present invention, comparative examples, and conventional examples.

Claims (1)

(57) [Claims] 1. A method of manufacturing a capacitor material by mixing a trace amount additive with a ceramic base material, wherein 1 to 1 of the total amount of the trace amount additive and the total amount of the ceramic base material is used.
A method for producing a capacitor material, which comprises premixing 20 wt% with calcination and then mixing the premix with the remaining amount of the ceramic base material.