JPH0774006A - Chip-type ceramic thermistor - Google Patents

Abstract

PURPOSE:To adjust the initial resistance value at a normal temperature and easily provide a desired resistance value by providing a trimming conductor layer on the surface of a thermistor base by separating from electrodes and trimming the layer. CONSTITUTION:A thermistor base 2 has a pair of inner electrodes 3 and 4 which are provided at an interval D. On the side and top planes of the thermistor base 2, Ag-Pd conductive paste is printed and baked and a pair of external electrodes 5 and 6 and a trimming conductor layer 7 are formed. The pair of external electrodes 5 and 6 are connected with the pair of inner electrodes 3 and 4. The trimming conductor layer 7 is not electrically connected with the pair of inner electrodes 3 and 4 nor the pair of external electrodes 5 and 6, and is formed in the shape of island with a length L. When the characteristics of the completed thermistor are checked and a resistance value between the pair of external electrodes 5 and 6 is detected not within a desired range, a trimming groove is formed on the trimming conductor layer 7 by laser beams or a part of the layer or the whole layer is removed so as to adjust the resistance value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to temperature compensation of electronic equipment,
The present invention relates to a chip-type ceramic thermistor for use in current control, temperature detection, etc.

[0002]

2. Description of the Related Art For example, a pair of internal electrodes and a pair of external electrodes are provided on a Mg-Co ceramic thermistor substrate containing manganese oxide and cobalt oxide as main components, and the overall shape is similar to that of a multilayer capacitor. Chip-type ceramic thermistors are known.

[0003]

By the way, the laminated ceramic thermistor has an advantage that the resistance can be lowered, but on the other hand, there is a problem that the resistance value varies due to the deviation of the electrode pattern. The problem of resistance variation of this kind also occurs in a chip-type ceramic thermistor of a type having no internal electrode.

Therefore, an object of the present invention is to provide a chip type ceramic thermistor which can easily obtain a desired resistance value.

[0005]

The present invention for achieving the above object provides a chip-type ceramic thermistor comprising a ceramic thermistor substrate and a pair of electrodes provided on the thermistor substrate, on the surface of the thermistor substrate. Further, the present invention relates to a chip-type ceramic thermistor characterized in that a trimming conductor layer is provided separately from the pair of electrodes.

[0006]

Since the trimming conductor layer according to the present invention is provided on the surface of the thermistor substrate,
By trimming this, the initial resistance value at room temperature can be adjusted, and a chip-type ceramic thermistor having desired characteristics can be easily obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An NTC chip type ceramic thermistor according to an embodiment of the present invention will be described with reference to FIGS. The chip-type ceramic thermistor 1 includes a thermistor substrate 2, a pair of internal electrodes 3 and 4, a pair of external electrodes 5 and 6, and a trimming conductor layer 7.

When the thermistor 1 is manufactured, a valence control agent and a sintering aid are added to predetermined amounts of manganese oxide and cobalt oxide, and the mixture is stirred in a wet ball mill and then dehydrated, dried and calcined. After again stirring with a wet ball mill, dehydration and drying were performed to obtain a powder of ceramic / NTC thermistor material. Next, a predetermined amount of a polyvinyl butyral binder, a plasticizer, and a toluene solvent are added to this material powder, the mixture is stirred with a wet ball mill, and then defoamed to obtain a slurry. Using this slurry, a doctor blade method is used. A 50 μm thick green sheet was prepared. Next, a Pd-based conductive paste for the internal electrodes 3 and 4 is printed on this green sheet by screen printing, and green sheets having no conductive layer are stacked on the upper and lower sides of this sheet and pressure-bonded, and cut to a predetermined size. Then, this is subjected to heat treatment at 400 ° C. for 2 hours to remove the binder, and thereafter, it is fired at 1200 ° C. for 2 hours in the air to form a pair of internal electrodes 3 and 4 facing each other with a distance D therebetween. The thermistor substrate 2 having the above was obtained. Next, on the pair of side surfaces and the upper surface of the thermistor base 2,
A g-Pd-based conductive paste was printed and baked to form a pair of external electrodes 5 and 6 and a trimming conductor layer 7 as shown in FIGS. In FIG. 1, the external electrodes 5 and 6 and the trimming conductor layer 7 are schematically illustrated by omitting the thickness.

The pair of outer electrodes 5, 6 are connected to the pair of inner electrodes 3, 4. The trimming conductor layer 7 is not electrically connected to the pair of internal electrodes 3 and 4 and the pair of external electrodes 5 and 6, but is formed in an island shape having a length L and a width W.

Check the characteristics of the completed thermistor,
When the resistance value between the pair of external electrodes 5 and 6 is out of the desired range, a trimming groove is formed in the trimming conductor layer 7 with a laser beam, or a part or all of this is removed to adjust the resistance value. . In this embodiment, the initial resistance value is set lower than the desired range on the premise of trimming. Therefore, the resistance value is increased by trimming the conductor layer 7 to fall within the desired range. The pair of external electrodes 5 and 6
The resistance between them is the resistance of the path directly from the one internal electrode 3 to the other internal electrode 4, and the resistance of the path from the one internal electrode 3 to the other internal electrode 4 via the conductor layer 7. ,
It can be considered as a combined value of resistances connected in parallel in the path from one external electrode 5 to the other external electrode 6 via the conductor layer 7.

In the conventional ceramic thermistor in which the conductor layer 7 for trimming is not provided, a deviation of about 2.0 to 4.0% occurs with respect to the target resistance value, but the conductor layer 7 is formed as in this embodiment. If provided and trimmed, the deviation from the target value can be set to about 0.5 to 1.0%.

[0012]

MODIFICATION The present invention is not limited to the above-mentioned embodiments, and the following modifications are possible. (1) As shown in FIG. 4, an insulating coating layer 8 may be formed by applying a glass paste on the surface of the thermistor substrate 2 and the trimming conductor layer 7. When trimming is performed with a laser beam after the coating layer 8 is formed, a trimming groove is formed in the conductor layer 7 through the coating layer 8 and the groove is covered with the glass of the coating layer 8. The coating layer 8 may be provided only on this in order to protect the conductor layer 7. (2) In FIGS. 1 to 3, the facing distance D between the pair of internal electrodes 3 and 4 is smaller than the length L of the conductor layer 7, but it can be increased conversely as shown in FIG. Although the width W of the conductor layer 7 is larger than the width Y of the internal electrodes 3 and 4 in FIG. (3) The conductor layer 7 of FIGS. 1 to 3 is divided into a plurality of conductor layers 7a and 7b in a direction parallel to the pair of external electrodes 5 and 6 as shown in FIG. 5, or As shown in FIG. 6, a plurality of conductor layers 7a and 7b can be divided in a direction perpendicular to the pair of external electrodes 5 and 6. Further, a plurality of conductor layers having different shapes can be provided on the surface of the thermistor substrate 2 and these can be used for trimming. (4) More electrodes corresponding to the internal electrodes 3 and 4 may be provided. That is, a plurality of pairs of internal electrodes can be provided. Further, the number of internal electrodes connected to one external electrode 5 and the number of internal electrodes connected to the other external electrode 6 can be set to different values. In addition, the internal electrodes 3, 4
Can be arranged so as to overlap each other when seen in a plan view, similarly to the multilayer capacitor. (5) The present invention can be applied to a thermistor which does not have the pair of internal electrodes 3 and 4.

[Brief description of drawings]

FIG. 1 is a perspective view showing a chip-type ceramic thermistor according to an embodiment of the present invention.

FIG. 2 is a plan view of the thermistor of FIG.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a cross-sectional view showing a modified thermistor.

FIG. 5 is a plan view showing a thermistor of another modified example.

FIG. 6 is a plan view showing a thermistor of another modification.

[Explanation of symbols]

 2 Thermistor base 3, 4 Internal electrode 5, 6 External electrode 7 Trimming conductor layer

Claims (1)

[Claims] 1. A chip-type ceramic thermistor comprising a ceramic thermistor base and a pair of electrodes provided on the thermistor base, wherein a trimming conductor is provided on the surface of the thermistor base with a distance from the pair of electrodes. A chip-type ceramic thermistor characterized in that layers are provided.