JPH03177351A - Preparation of ceramic electronic part - Google Patents

Abstract

PURPOSE:To prevent the rocking-out of granulated powder to improve the productivity of the subject part by disposing a novel secondary mixing process for impregnating and mixing a specific resistance-adjusting agent between a granulation process and a molding process. CONSTITUTION:The method for preparing the objective part comprises a mixing process for wet-mixing a main component with a primary additive, a dehydrating.drying process for dehydrating and drying the mixture, a calcination process for subjecting the dried product to the first calcination, a grinding process for grinding the calcination product, a granulation process for granulating the ground with a binder, the second mixing process for impregnating and mixing the ground product with a specific resistance-adjusting agent, a molding process for press-molding the second mixture in a desired shape and a sintering process for sintering the molded product.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing ceramic electronic components such as barium titanate PTC thermistors used as self-heating elements in electrical circuits.

Conventional technology Traditionally, barium titanate PTC thermistors are the second
It was manufactured by the manufacturing method shown in the figure.

That is, the main components and additives wet-mixed in the mixing step 1 are dried in the dehydration/drying step 2, then first fired in the calcination step 3, and then pulverized in the pulverization step 4 and then granulated. It was manufactured by granulating in Step 5, molding in Step 6, and sintering in Step 7.

Problems to be Solved by the Invention However, in the conventional manufacturing method described above, countermeasures against room-temperature resistivity fluctuations caused by loft-to-loft variations in raw materials were taken before the granulation process. For this reason,
In the granulation process during mass production, when several hundred particles are granulated using large equipment, the room temperature resistivity value of the sintered body obtained by molding and firing the granulated powder is If there was a large difference from the target value, this large amount of granulated powder would be sold out.

Therefore, the present invention solves these problems, and -
The purpose is to improve the productivity of highly granulated powder.

Means for Solving the Problems And in order to achieve this objective, the present invention provides a secondary mixing process in which a resistivity adjuster is newly impregnated and mixed between the granulation process and the molding process. It is characterized by:

According to the above-mentioned means, the normal temperature resistivity value of the sintered body obtained by initially molding and firing a part of the granulated powder that has been granulated at -degrees satisfies the target resistivity value. If not, the specific resistance value can be adjusted by impregnating the granulated powder with Mn, Cu, or the like in a molten acid state such as nitrate or sulfate and uniformly mixing. Therefore, lot-out of a large amount of granulated powder is eliminated.

Example An embodiment of the present invention will be described below.

FIG. 1 shows a flowchart of the steps performed in the present invention.

First, in the mixing step 8, the main component (B
ao7sP bo,=s) T i 03 and further as additives, Nb2O5, S i O=, Mn (NO
3) = in a composition of 0.001 to 0.024 mol each were blended and wet mixed in a ball mill. Next, the mixed powder dried in the dehydration/drying step 9 is subjected to a calcining step 10.
The mixture was calcined at a temperature of 000 to 1100°C, and then wet-pulverized in a pulverizing step 11 using a ball mill until the particle size became 2.0 μm or less. Then, in a granulation step 12, 1Qwt% of P, V, A (polyvinyl alcohol) was added to the dried product based on the raw material to granulate it.

Then, a part of it was sampled and the diameter was 17.5mm.
The material was molded into a disk shape with a thickness of 4.0 cm under a pressure of 1 ton/cnf, and fired in air at 1250° C. to 1300° C. for 1 hour.

On the other hand, in the secondary mixing step 13, a part of the granulated powder was sampled and treated. At this time, M as a resistivity adjuster
Using Mn(NO3)2 solution, Mn(NO3)2 is calculated based on the value obtained by converting the weight of granulated powder to the weight of pulverized powder.
The mixture was diluted with pure water so that the wt% of Mn was 1 to 3%, and the number of moles of Mn was set and added in multiple stages, and secondary mixing was performed (as shown in Table 1 below).

The method of addition is to accurately measure the volume equivalent of the number of moles of the Mn(NO3)2 solution using a whole pipette, drop it dropwise or spray it in the form of a mist only onto the sampled granulated powder. were placed in a polypot, etc., and mixed dry to ensure thorough dispersion and impregnation.

The thus-secondarily mixed powder was molded in a molding step 14 in the same manner as the first sampled powder, and then fired in a firing step 15, after which an ohmic A1 electrode was applied to each powder.

Table 2 below shows the room temperature resistivity values and voltage increase breakdown test results of the samples prepared in the secondary mixing step 13.

Here, the increased voltage breakdown test result indicates the voltage value at which the element was destroyed when the voltage was increased from 100 V in 20 inch steps at 30 second intervals from both ends of the sample electrode surface as the withstand voltage value.

Table 2> As is clear from Table 2 above, in contrast to sample magnet 1 which was not subjected to secondary mixing, samples 2 and 3.4 contained Mn as shown in Table 1.
(No:+): It can be seen that the specific resistance at room temperature increases stepwise as the amount of addition increases. Further, from the withstand voltage value at this time, it can be seen that no deterioration of the element has occurred.

On the other hand, it has been confirmed through experiments that the scope of application of these secondary mixing implementations is similarly applicable to barium titanate-based PTC thermistor granulated powders having compositions other than those in the above examples.

Effects of the Invention As described above, the present invention improves the room temperature resistivity value of the sintered body obtained by molding and firing the granulated powder once it is granulated, to the target resistivity value. In cases where the specific resistance value is not satisfied, the room temperature specific resistance value can be adjusted by impregnating the granulated powder with a solution containing an element that contributes to specific resistance adjustment.

Therefore, the granulated powder that has been granulated twice is not sold out, and productivity can be improved.

[Brief explanation of drawings]

FIG. 1 is a flowchart of an embodiment of the present invention, and FIG. 2 is a flowchart of a conventional example. 13...Second mixing step.

Claims (1)

[Claims] A mixing step of wet-mixing the main component and the primary additive, then a dehydration/drying step of dehydrating and drying the wet-mixed material, and then a calcination step of primary firing of the dehydrated and dried material. a pulverizing step of pulverizing the calcined material, a granulation step of adding a binder to the pulverized material and granulating it, and then adding a resistivity adjuster to the granulated material. A ceramic comprising a secondary mixing step of impregnating and mixing, a molding step of pressing the secondary mixture into a required shape, and a firing step of sintering the molded product. Method of manufacturing electronic components.