JPH05267004A - Manufacture of chip type thermistor - Google Patents

Abstract

PURPOSE:To obtain a chip type thermistor at a lower cost by firing a chip molded body formed through dry or sheet molding to obtain a chip fired body. CONSTITUTION:Transition metal oxide materials, such as Mn, Ni, Cu and so on, are prepared and weighed according to a desired composition. These materials are mixed in a wet manner, and the resultant mixture is dehydrated and dried. It is then temporarily fired and ground in a wet manner using a ball mill. The ground material is dried, and subsequently, granulated with binder added. The granulated material is then placed in a metal mold, and pressed to form a chip molded body 6. The molded body 6 is chamfered to provide the whole circumference with a roundness 7. The binder is removed, and then the molded body 6 is fired. Conductive paste 8 is applied to part of both ends 1B and both major surfaces 1A of the fired molded body 1. It is then dried and baked to form electrodes 2, obtaining a chip type thermistor 10. This reduces its cost and minimizes the dispersion in its electric characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a chip type thermistor which constitutes an NTC thermistor or the like.

[0002]

2. Description of the Related Art NTC thermistors are transistors and ICs.
It is widely used for temperature compensation of components such as the above, or for temperature sensors, and the demand for chip-shaped ones, that is, chip-type thermistors, has recently been rapidly increasing. As shown in FIG. 4, this chip-type thermistor 36 is
2, 23, etc. are used for surface mounting on the substrate 24. Since the end electrodes 35 can be directly soldered to the pattern 25 of the substrate 24 by eliminating the lead wire, the height dimension becomes small. It has an advantage of contributing to miniaturization and thinning of various electronic devices incorporating the substrate 24.

Next, a conventional method for manufacturing a chip type thermistor will be described in the order of steps with reference to FIG.

First, using a transition metal oxide such as Mn, Ni, or Cu as a raw material, after mixing, drying, calcination, and crushing, it is molded into a block shape by a dry molding method and then calcined. Then, the block fired body 30 is obtained. Alternatively, after the pulverization, a sheet-shaped fired body 31 is obtained as in the step B after forming into a sheet by a wet molding method and then firing.

Next, after the block fired body 30 is cut into a sheet with a cutter such as a wire saw or a slicer,
Apply plane wrapping to adjust the thickness to the desired value, then process C
The sheet fired body 32 is obtained as described above. Similarly, the sheet calcined body 31 is subjected to flat lapping to adjust it to a desired thickness. The shapes of the sheet fired bodies 31 and 32 at this time are different, but they are substantially the same, and the sheet fired body 32 will be described below as a representative.

Next, the sheet fired body 32 is cut into a columnar shape to obtain a rectangular chip-shaped fired body 33 as in step D.
Subsequently, the fired body 33 is chamfered by barrel polishing to form a roundness 34 as in step E. Next, a conductive paste such as an Ag-Pd alloy is applied to both ends and a part of both main surfaces of the fired body 33, and after drying, the chip type thermistor 36 having the end electrodes 35 formed by baking the conductive paste is formed. To manufacture.

[0007]

By the way, in the conventional chip type thermistor manufacturing method, many steps are required as shown in FIG. 3, resulting in an increase in cost, and further in a block shape before being divided into individual chips or Since a block fired body is formed by firing the sheet-shaped molded body as it is, there is a problem in that electrical characteristics of the manufactured chip-type thermistor vary.

That is, if firing is performed on the block-shaped or sheet-shaped molded body as it is, the specific resistance of the entire baked body is not uniform due to the influence of the firing atmosphere, and the specific resistance on the surface of the fired body and in the central portion. Tend to be different. For this reason, when chips are formed in the subsequent process, variations in electrical characteristics among individual chip-type thermistors cannot be avoided.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for manufacturing a chip type thermistor which is capable of reducing the cost and suppressing variations in electrical characteristics. It is a thing.

[0010]

To achieve the above object, the present invention provides a step of molding a chip-shaped molded body from a thermistor material by a dry molding method or a sheet molding method, and firing the chip-shaped molded body. And a step of obtaining a chip-shaped fired body.

[0011]

According to the structure of the present invention, after the chip-shaped molded body molded by the dry molding method or the sheet molding method is fired, electrodes are formed on both ends of the chip-shaped fired body to form the chip. I made a type thermistor,
Since the number of steps is reduced, the cost can be reduced and the variation in the electrical characteristics of the chip type thermistor can be suppressed.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a chip-type thermistor manufactured by the method for manufacturing a chip-type thermistor of the present invention. The chip-type thermistor 10 is a chip-shaped thermistor formed by a dry molding method or a sheet molding method. N
TC thermistor fired body 1 and both ends 1B of this fired body 1
Is provided with an electrode 2 made of an Ag / Pd alloy containing frit, a part of which covers both main surfaces 1A.

Next, a method of manufacturing the chip type thermistor of the present invention will be described in the order of steps with reference to FIG.

First, Mn304, NiO, and CuO, which are transition metal oxides such as Mn, Ni, and Cu, are used as raw materials, weighed so as to have a desired composition, wet-mixed, dehydrated and dried, and dried at 800 to 1000 ° C. After calcination for 2 hours,
Wet grind with a ball mill. After drying, add polyvinyl alcohol as a binder and granulate 2.3 ×
A 1.43 mm die is filled with the material, and a pressure of 3 ton / cm ² is applied to mold the chip-shaped molded body 6 as in step A. That is, the chip-shaped molded body 6 is obtained by the dry molding method. At this time, the thickness of the molded body 6 is 1.
It was 14 mm. In the case of the sheet molding method, a sheet molded body having a desired thickness is formed, and the sheet molded body is cut into chips or punched with a press or the like to form chip shaped bodies.

Next, the chip-shaped molded body 6 is chamfered by green barrel polishing to form a roundness 7 on the entire circumference as in step B. Subsequently, the molded body 6 is debindered in a firing furnace, and then 1200 to 1300
As shown in Structure C, a chip-shaped molded body 1 is obtained by firing at 1 ° C.
To form. Then, a conductive paste 8 made of Ag / Pd alloy containing a frit is applied to both ends 1B of the molded body 1 and a part of both main surfaces 1A as in step D so as to form electrodes.

Next, the fired body 1 is dried at 150 ° C. and baked at 700 to 900 ° C. in a belt furnace to form the electrode 2 as in step E. As a result, the chip type thermistor 10 having the structure shown in FIG. 1 is manufactured.

According to the manufacturing method of the present invention as described above, since the chip-shaped molded body 6 is molded by the dry molding method or the sheet molding method, the chip-shaped molded body 6 is fired to form the chip-shaped baked body 1. It is possible to reduce the number of steps as compared with the conventional manufacturing method. Therefore, the cost can be reduced. Furthermore, as shown in Table 1, it is possible to reduce variations in electrical characteristics.

That is, the following Table 1 shows that electrical characteristics B obtained by applying eight kinds of samples a to h and applying the manufacturing method of the present invention are obtained by the cutting method which is a conventional method. It is shown in comparison with the electrical characteristic A. In addition,
Each electrical characteristic was shown by obtaining the value of the coefficient of variation as shown in the lower part of the table.

[0020]

[Table 1]

As is clear from Table 1, in the electrical characteristics B obtained by the present invention, RC. V and BC. Each of V shows a value smaller than each value in the conventional electrical characteristic A, and it is understood that the variation is small.

The reason for this is that, in the present invention, the block-shaped or sheet-shaped molded body is not fired as it is, but the chip-shaped molded body 6 is fired after firing. Be done. That is, by reducing the shape of the molded body, the specific resistance of the chip-shaped fired body becomes uniform, and as a result, it becomes possible to suppress variations in electrical characteristics.

[0023]

As described above, according to the present invention, since the chip-shaped molded body molded by the dry molding method or the sheet molding method is fired, the chip-shaped fired body is obtained. It is possible to provide a method of manufacturing a chip type thermistor that can reduce the number of steps to reduce the cost and suppress the variation in electrical characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a chip thermistor manufactured by a method of manufacturing a chip thermistor of the present invention.

FIG. 2 is an explanatory view showing a method of manufacturing a chip type thermistor of the present invention in process order.

FIG. 3 is an explanatory view showing a method of manufacturing a conventional chip type thermistor in process order.

FIG. 4 is a cross-sectional view showing an example in which a chip type thermistor is used for surface mounting.

[Explanation of symbols]

 1 Fired Body 2 Electrode 6 Dry Molded Body 10 Chip Type Thermistor

Claims (1)

[Claims] 1. A step of molding a chip-shaped molded body from a thermistor material by a dry molding method or a sheet molding method,
And a step of firing the chip-shaped molded body to obtain a chip-shaped fired body.