JPH0653008A - Multilayered thermistor - Google Patents

Abstract

PURPOSE:To reduce the iregularlity of resistance value of a multilayered ceramic thermistor, by making one of the facing areas of a first and a second inner electrode layers and a third inner electrode layer large and making the other small. CONSTITUTION:A first and a second inner electrodes 2 and 3 are arranged at a first position in a thermistor resistor 1. A third inner electrode layer 4 is arranged at a second position in the resistor 1. The third inner electrode 4 is made to face the first and the second inner electrode layers 2, 3. A first and a second outer electrodes 5 and 6 are connected with the first and the second inner lectrodes 2 and 3, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated thermistor for use in temperature compensation, current control, temperature detection, etc. in electronic equipment.

[0002]

2. Description of the Related Art Most of the ceramic thermistors currently in use have a structure in which electrodes are provided at both ends of a prism or a square plate. If the resistor is thinly formed in order to reduce the resistance value of thermist of this type of typical structure, the mechanical strength and the dielectric strength are lowered. to solve this problem,
It is known, for example, from Japanese Examined Patent Publication No. 50-11585 to make a thermistor a multilayer type like a monolithic ceramic capacitor.

[0003]

By the way, in the case of a laminated ceramic thermistor, the deviation of the pair of electrode layers due to the deviation of the lamination of a plurality of ceramic green sheets (green sheets) provided with the electrode layers causes the resistance value to change. It will vary. Therefore, an object of the present invention is to provide a laminated type thermistor capable of reducing the variation in resistance value.

[0004]

According to the present invention for achieving the above object, a resistor whose resistance value changes in response to a temperature change and a first virtual plane in the resistor are respectively provided. The first and second internal electrode layers, and the second internal electrode layers arranged in a second virtual plane parallel to the first virtual plane in the resistor and facing the first and second internal electrode layers. A third internal electrode layer formed so as to have a portion, a first external electrode connected to the first internal electrode layer and provided on an outer peripheral surface of the resistor, and a second internal electrode The present invention relates to a laminated thermistor including a second external electrode connected to an electrode layer and provided on the outer peripheral surface of the resistor.

[0005]

In the laminated thermistor according to the present invention, the resistance between the first and second internal electrode layers and the third internal electrode layer is mainly used. First and second
The resistance value between the internal electrode layers is as follows: the facing area S1 between the first internal electrode layer and the third internal electrode layer;
Depends on the sum S1 + S2 of the area S2 facing the internal electrode layer. When the facing region of the third internal electrode layer with respect to the first and second internal electrode layers is misaligned, two facing areas between the first and second internal electrode layers and the third internal electrode layer are provided. One of S1 and S2 becomes large and the other becomes small. As a result, the sum S1 + S of the two facing areas S1 and S2
2 hardly changes. Therefore, it is possible to provide a laminated type thermistor in which variations in resistance are less likely to occur.

[0006]

[First Embodiment] Next, a laminated type thermistor according to a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, this laminated type thermistor includes a ceramic resistor 1 made of an NTC thermistor material having temperature dependence, first, second and third internal electrode layers 2, 3, 4 and
It is composed of first and second outer electrodes 5 and 6.

The first and second internal electrode layers 2 and 3 are arranged on a first imaginary plane at a first position in the thickness direction of the resistor 1 indicated by P1, and one ends of the first and second inner electrode layers are on different side surfaces. First and second external electrodes 5 and 6 exposed and provided on each side surface
It is connected to the. The third internal electrode layer 4 which is not connected to the first and second external electrodes 5 and 6 is arranged in the second virtual plane at the second position indicated by P2 in the thickness direction in the resistor 1. It has a portion facing the first and second internal electrode layers 2 and 3 with the resistance layer 7 which is a part of the resistor 1 interposed therebetween. The resistor 1 is a rectangular parallelepiped (a hexahedron), and the first and second
Internal electrode layers 2 and 3 are provided in a first virtual plane parallel to one main surface (upper surface) of the resistor 1, and the third internal electrode layer 4 is a second virtual plane parallel to the first virtual plane. It is provided on a virtual plane.

As is apparent from FIG. 2, the third inner electrode layer 4 has a width W2 slightly smaller than the width W1 of the first and second inner electrode layers 2 and 3, and is the first as viewed from above. The inner edges of the third internal electrode layer 4 are arranged so as to be included in the first and second internal electrode layers 2 and 3. Further, the third internal electrode layer 4 has a length L, and the lengths b1 and b2 in this
Part faces the first and second internal electrode layers 2 and 3. Therefore, the facing areas S1 and S2 of the third inner electrode layer 4 with respect to the first and second inner electrodes 2 and 3 are b1 x W2 and b2 x W2. In this embodiment, b1 = b2
It is made with the goal.

Next, a method of manufacturing the laminated thermistor shown in FIG. 1 will be described with reference to FIGS. First, a valence control agent and a sintering aid are added to a predetermined amount of manganese oxide and cobalt oxide, stirred in a wet ball mill, dehydrated and dried, calcined, and again stirred in a wet ball mill and dehydrated. Then, the powder was dried to obtain a powder of ceramic / NTC thermistor material. Next, a predetermined amount of a polyvinyl butyral-based organic binder, a plasticizer, and a toluene-based solvent were added to this powder, and the mixture was stirred with a wet ball mill, and then defoamed to obtain a slurry. Next, using this slurry, ceramic green sheets (green sheets) 1a to 1e having a thickness of 50 μm were obtained by a doctor blade method.

Next, Ag-Pd based conductive paste layers 2a, 3a having a pattern for obtaining a large number of first and second internal electrode layers 2, 3 are formed on the first green sheet 1a by screen printing. Ag− for forming a large number of third internal electrode layers 4 on the second green sheet 1b.
The Pd-based conductive paste layer 4a was formed. Next, the first and second green sheets 1a, 1b and the third, fourth and fifth sheets 1c, 1d, 1e without electrode layers are shown in FIG.
As shown in FIG. 5, they are laminated and pressure-bonded to each other and cut at positions indicated by broken lines in FIG. 4 to obtain a large number of unfired molded bodies 11 shown in FIG. Four
After heat treatment at 00 ℃ for 2 hours, 120 in the atmosphere
The ceramic resistor 1 shown in FIGS. 1 and 6 was obtained by firing at 0 ° C. for 2 hours. Next, the first and second external electrodes 5 and 6 shown in FIGS. 1 and 6 were formed by applying an Ag—Pd based conductive paste on both end faces of the resistor 1 and baking it.

Next, the average initial resistance value of 1000 thermistors having the structure shown in FIG. 6 was 9.8 kΩ, and the standard deviation of the resistance value was 2.4%.

For comparison, as shown in FIG. 7, the first and second internal electrode layers 2 and 3 are arranged so as to face each other with the resistance layer 7 which is a part of the resistor 1 interposed therebetween. 2 is half the sum of the two facing areas (S1 + S2), and the thickness of the resistance layer 7 is double that of FIG. When 1,000 pieces were made and the average value of these resistance values was calculated, it was 10.1 kΩ, and the standard deviation was 7%. As is clear from the comparison between the comparative example and the example, the present invention greatly improves the standard deviation, that is, the variation.

The reduction of standard deviations or variations in accordance with the present invention will now be theoretically explained. The current paths between the first and second internal electrode layers 2 and 3 in FIG. 1 are the first internal electrode layer 2, the resistor layer 7, the third electrode layer 4, the resistor layer 7, and the second internal layer. It can be considered to be the electrode layer 3.
Now, if the resistivity of the resistor layer 7 is ρ and the thickness is D1, the resistance value R1 between the first and second internal electrode layers 2 and 3 can be expressed by the following equation. R1 = .rho.D1 / S1 + .rho.D1 / S2 = .rho.D1 / b1 W2 + .rho.D1 / b2 W2 = K1 / b1 + K1 / b2 where K1 is a constant indicating .rho.D1 / W2. Now, Figure 1
Assuming that the third internal electrode layer 4 is displaced to the left by α, the resistance value R1 is expressed by the following equation. R1 = K1 / (b1 + .alpha.) + K1 / (b2-.alpha.) As is clear from this equation, when the value of the first term increases, the value of the second term decreases on the contrary, and the third internal electrode layer 4
The resistance value does not change so much despite the deviation.

On the other hand, the resistance value R2 between the first and second internal electrode layers 2 and 3 of the conventional structure shown in FIG. 7 is expressed by the following equation. R2 = .rho.D2 / S3 = .rho.D2 / aW2 = K2 / a where K2 is a constant indicating .rho.D2 / W2. This Figure 7
In, the resistance value R2 when the second internal electrode layer 3 is displaced to the left by α is expressed by the following equation. R2 = K2 / (a + α) As is clear from this equation, in the structure of FIG. 7, there is no component that cancels the change in the resistance value due to the shift α. Therefore,
When the shift α is the same in FIGS. 1 and 7, the change in the resistance value in FIG. 1 is significantly smaller than that in FIG. 7. In FIG. 2, even if the third internal electrode layer 4 is displaced relative to the first and second internal electrode layers 2 and 3 in the vertical direction, W1>
Since it is set to W2, the facing areas S1 and S2 do not change.

Now, in the thermistor of FIGS. 1 and 7, b1
= B2 = a and 2D1 = D2 are satisfied, the resistance values of the first and second internal electrode layers 2 and 3 are the same. So, in this condition,
In FIG. 1, the third internal electrode layer 4 is shifted to the left by 1/10 of a, and in FIG. 7, the second internal electrode layer 3 is shifted to the left by 1/1 of a.
Next, the change in resistance value when there is a shift of 0 is calculated.

In the case of FIG. 1, the following values are obtained. R1 = K1 / (a + 0.1a) + K1 / (a-0.1a) = K1 {2a / (a2-0.01a2)} = (2K1 / a) / (1-0.01) = (2K1 / a ) /0.99 resistance value R1 when there is no deviation (when b1 = b2)
Is 2K1 / a, the third internal electrode layer 4 is 10%
It is shown that the resistance value R1 changes only about 1% even if it is deviated.

On the other hand, in the conventional thermistor shown in FIG.
If the second internal electrode layer 3 is displaced to the left by 1/10 of a, the resistance value R2 between the first and second internal electrode layers 2 and 3 is as follows. R2 = 2K1 / (a + 0.1a) = (2K1 / a) /1.1 Since the resistance value before shifting is (2K1 / a) as in FIG. 1, the resistance value changes by about 10%.

[0018]

[Second Embodiment] Next, a thermistor of a second embodiment will be described with reference to FIG. However, FIG. 8 and FIGS.
11, the same parts as those in FIGS. 1 to 3 are designated by the same reference numerals and the description thereof will be omitted.

Since the basic structure of the thermistor of the second embodiment is the same as that of the first embodiment, the whole illustration is omitted, and only the portion corresponding to FIG. 3 is shown in FIG.
In FIG. 8, the third internal electrode layer 4 has first, second and third portions 41, 42, 43, and the first and second portions 41, 42,
42 is formed so as to be included in the first and second internal electrode layers 2 and 3 shown by broken lines when viewed from above, and the narrow third portion 43 is formed into the first and second internal electrode layers 2 and 3. It is located between. According to this structure, when the third internal electrode layer 4 is displaced in the left-right direction relative to the first and second internal electrode layers 2 and 3, the third internal electrode layer 4 is more than the first and second portions 41 and 42. Since only the facing area in the narrow third portion 43 changes, the change in the facing area due to the displacement of the third internal electrode layer 4 becomes extremely small, and as a result, the change in the resistance value also becomes small. Since the thermistor of FIG. 8 has the same basic structure as that of FIG. 1, it has the same effects as those of FIG.

[0020]

[Third Embodiment] The thermistor of the third embodiment is a modification of the pattern of the first, second and third internal electrode layers 2, 3 and 4 of the thermistor of the first embodiment as shown in FIG. Other than that, the configuration is the same as that of the first embodiment. In this embodiment, the first internal electrode layer 2 is the first, second and third parts 2
1, 22, 23, the second internal electrode layer 3 also has first, second and third portions 31, 32, 33. The respective second portions 22, 32 are formed narrower than the respective first and third portions 21, 31 and 23, 33,
When viewed from above, the left and right ends of the third internal electrode layer 4 are formed so as to be included in the third portions 22 and 32. As a result, even if the third internal electrode layer 4 shifts in the left-right direction, the change in the facing area is extremely small. Since the thermistor of FIG. 9 has the same basic structure as that of FIG. 1, it also has the same effects as those of FIG.

[0021]

[Fourth Embodiment] FIG. 10 shows the thermistor of the fourth embodiment in the same manner as in FIG. In this embodiment, two first and second internal electrode layers 2 and 3 are provided, respectively, and a third internal electrode layer 4 is arranged between them. That is, it has a structure in which a sheet corresponding to the green sheet 1a is additionally laminated between the green sheets 1b and 1e in FIG. The current between the first and second external electrodes 5, 6 flows through the two first internal electrode layers 2 and the common third internal electrode layer 4 and the two second internal electrode layers 3. In FIG. 10, the two resistors are first
Since the second external electrodes 5 and 6 are connected in parallel, a low resistance value can be easily obtained. In addition,
Since the basic structure of FIG. 18 is the same as that of FIG. 1, the same effect as the first embodiment can be obtained.

[0022]

[Fifth Embodiment] In the thermistor of the fifth embodiment shown in FIG. 11, two first and second internal electrode layers 2 and 3 and three third internal electrode layers 4 are provided. ing.
As a result, four resistors are connected in parallel between the first and second external electrodes 5 and 6, and the resistance value can be further reduced. Note that FIG. 11 shows the basic structure of FIG.
Since it is the same as, it also has the same effect.

[Brief description of drawings]

FIG. 1 is a central longitudinal sectional view showing a laminated thermistor of a first embodiment.

FIG. 2 is a plan view showing patterns of first and second internal electrode layers at a P1 position in FIG.

FIG. 3 is a plan view showing a pattern of a third internal electrode layer at a P2 position in FIG.

4 is a front view showing an arrangement of green sheets when manufacturing the thermistor of FIG. 1. FIG.

5 is a front view showing a molded body before firing for forming the thermistor of FIG. 1. FIG.

6 is a perspective view of the thermistor of FIG. 1. FIG.

FIG. 7 is a cross-sectional view showing a laminated type thermistor of a comparative example.

FIG. 8 is a plan view showing a pattern of a third internal electrode layer of the thermistor of the second embodiment.

FIG. 9 is a plan view showing patterns of first and second internal electrode layers of the thermistor of the third embodiment.

FIG. 10 is a sectional view showing a thermistor of a fourth embodiment.

FIG. 11 is a sectional view showing a thermistor of a fifth embodiment.

[Explanation of symbols]

 1 Resistor 2,3 First and Second Internal Electrode Layers 4 Third Internal Electrode Layers

Claims (1)

[Claims] 1. A resistor whose resistance value changes in response to a temperature change, and a first resistor disposed on a first virtual plane in the resistor.
And a second internal electrode layer, and a portion of the resistor which is arranged on a second virtual plane parallel to the first virtual plane and which faces the first and second internal electrode layers. A third internal electrode layer formed so as to have; a first external electrode connected to the first internal electrode layer and provided on an outer peripheral surface of the resistor; and a second internal electrode layer A laminated type thermistor comprising: a second external electrode connected to and provided on the outer peripheral surface of the resistor.