JPH04150002A - Thermistor element - Google Patents

Abstract

PURPOSE:To finely adjust a resistance value by a method wherein a plurality of kinds of resistor layers whose thermistor constant are different and electrodes are formed between oxide ceramic layers and one part of the resistor layers is formed by a thick-film method. CONSTITUTION:A resistor layer 12 whose thermistor constant is high and a resistor layer 14 whose thermistor constant is low are formed between insulating ceramic layers 20a to 20d. A paste, for thick film use, which is matched to a required resistant value is used as a resistor material for the resistor layer 14; it is printed in a prescribed area. Then, a conductive paste is printed on both end parts of it to form internal electrodes 18a, 18b. Then, this assembly is baked collectively. In addition, external electrodes 24a, 24b by a conductive paste are baked at the external face. Thereby, it is possible to easily manufacture a thermistor element which ensures a required characteristic and whose reliability is high.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a thermistor element used, for example, as a temperature-sensitive element.

(b) Conventional technology A thermistor used as a temperature-sensitive element uses oxides such as MnNi, Mn-Ni-Co, or Mn-Ni-Co, which can be used at around room temperature, and can be used at temperatures up to 800°C. Zr-y type oxides are used because they can be used both before and after. Thermistors made of these materials have advantages such as a large temperature coefficient, a large degree of freedom in design of shape and resistance value, and low cost.

These negative characteristic thermistors utilize semiconductor characteristics, and their resistance temperature characteristics are expressed by the following equation.

R1=R2exp ((1/Tl-1/T2)BIT
l, T2: Temperature [k] R1: Resistance value R2 at temperature T1; Resistance value B at temperature T2; Thermistor constant Ck) fc) Problems to be solved by the invention As described above, in the conventional negative characteristic thermistor, the resistance temperature characteristic is not linear, so when used as a temperature sensor, it was necessary to perform so-called linearization unless correction was made on the circuit side. The principle of linearization will be explained based on the resistance temperature characteristics shown in FIG.

First, consider two resistors with different thermistor constants whose resistance values are equal at a certain predetermined temperature.

At this time, the resistance value of the resistor with a large thermistor constant becomes small on the higher temperature side than the predetermined temperature, and the resistance value of the resistor with a small thermistor constant becomes small on the low temperature side.Therefore, if these two resistors are connected in parallel, In the combined resistance value, the resistance value of the resistor with a large thermistor constant becomes dominant on the high temperature side of a predetermined temperature, and the resistance value of the resistor with a small thermistor constant becomes dominant on the low temperature side. This is exactly the intermediate region.By selecting the combination of the two thermistor constants and resistance values in this way, linearized characteristics can be obtained in the intermediate region.Also, the linearized temperature range is
Adjustment is possible by shifting the temperature at which the resistance values of the two resistors become equal. That is, by changing the resistance values of both resistors, it is possible to adjust the point at which the resistance values become equal.

Conventionally, linearization has been performed by combining several types of negative characteristic thermistors and several types of constant resistors.

In addition, a laminated thermistor element in which two types of resistors with different thermistor constants are combined using a sheet molding method has been proposed as a single linearized temperature sensor. Diffusion occurs, resulting in variations in resistance and thermistor constant.

Furthermore, the purpose of this invention was to create a highly reliable linearizer that can secure the necessary characteristics even by integral firing. The object of the present invention is to provide a thermistor element that has been improved.

(61 Means for Solving Problems) The thermistor element of the present invention includes a plurality of resistor layers having different thermistor constants forming internal electrodes, and a structure in which these resistor layers are bonded together with the internal electrodes between a plurality of oxide ceramic layers. It is characterized in that the resistor layers are laminated in a state in which they are interposed, an external electrode is formed on the outer surface of the oxide ceramic layer, and the internal electrodes of each resistor layer are commonly connected to each other and connected to the external electrode.

te1 Effect In the thermistor element of the present invention, a plurality of types of resistor layers having different thermistor constants are integrally laminated with being interposed between a plurality of oxide ceramic layers. Therefore, mutual diffusion does not occur between adjacent resistor layers, and the resistance value and thermistor constant remain stable even after integral firing. In addition, the oxide ceramic layer has a high melting point (it is chemically stable), so it can be used at high temperatures and in harsh atmospheres.

Furthermore, an internal electrode is formed in each resistor layer, which is laminated together with the resistor layer between the oxide ceramic layers, the internal electrodes of each resistor layer are commonly connected, and the internal electrode is formed on the outer surface of the oxide ceramic. Since each resistor layer is electrically connected to the external electrode, each resistor layer is connected in parallel, thereby forming a linearized thermistor element. Moreover, a new mounting method is also possible in which this linearized thermistor element is directly mounted on a circuit board using external electrodes.

(fl Embodiment) The structure of a thermistor element which is an embodiment of the present invention is shown in FIG. 1 as a cross-sectional view. In FIG.
is a resistor layer with a small thermistor constant made of MnO, -CaO system.

20 is an insulating oxide ceramic with a high melting point made of AlzOx, ZrO□, etc., and 20a, 20b, 2
It consists of four layers: 0c and 20d. These resistor layers and insulator layers are laminated and sintered into an integral layer. Resistor layer 1
2 and both ends of the resistor layer 14, p
Internal electrodes 16a, 16b, 18a, 18 consisting of
It forms b. 22a and 22b are electrodes filled in the through holes, and the electrode 22a is the internal electrode 18 of the resistor layer.
The electrode 22b electrically connects the internal electrodes 18b and 16b. Also, 24
a and 24b are external electrodes made of PT or the like formed on the outer surface of the insulating oxide ceramic 20;
, 22b, respectively.

As described above, a laminated thermistor element is constructed in which the resistor layers 12 and 14 are connected in parallel between the external electrodes 24a and 24b. In addition, to linearize a thermistor for boat fishing, the resistance value of each resistor used is
The values must be approximately the same around the temperature range for linearization.

However, in this example, the Mn-Ni oxide system used as the resistor layer 12 and the Mn0z-CaO system used as the resistor layer 14 have a resistance value of 2 at around room temperature.
There is a difference of several orders of magnitude. Therefore, in order to eliminate this difference, the resistor layer 14 was formed by a thick film method and its resistance value was adjusted.

Next, an example of a method for manufacturing the thermistor element shown in FIG. 1 will be described.

First, Mn CO3, N i C○, and Al2O,
After mixing a predetermined amount, the mixture is calcined at 900°C for 2 hours, and the calcined product is thoroughly kneaded with a binder, a plasticizer, and pure water to form a slurry. This slurry was tape cast using a doctor blade method to create a green tape with a thickness of 0.030 and a high thermistor constant. A through-hole is formed at a predetermined position in this clean tape, and filled with pt-<-st as the IJ-do part of the electrode (the part indicated by the broken line in FIG. 1).

Next, after mixing a predetermined amount of MnOz Ca○ and glass frit according to the required sheet resistance value, a binder, plasticizer and pure water are added and thoroughly kneaded with a Miki roller to form a resistor with a low thermistor constant. Create a material for thick film paste.

A slurry is prepared by adding an organic binder, a solvent, a plasticizer, and a dispersant to the A7!203 powder. Using this slurry, green sheets having a thickness of 0.02 mm are prepared, and four green sheets shown as 20a, 20b, 20C, and 20d in FIG. Then, through holes are formed at predetermined positions corresponding to the internal electrodes 18a and 18b, filled with PT paste, and dried. This conductive paste becomes electrodes 22a and 22b shown in FIG. Furthermore, a predetermined area of thick film paste, which is a resistance material with a low thermistor constant, is printed on the surface of the green sheet 20b to form the resistor layer 14. Further, Pt paste is printed on both ends thereof to form internal electrodes 18a and 18b.

Green sheet 20 that becomes these oxide ceramic layers
A, 20b, 20c, and 20d as well as the green sheet 12, which serves as a resistor with a high thermistor constant, are aligned and laminated, and thermocompression bonded for 1 minute at 60° C. and 5 ton/cm 2 . Thereafter, the laminate is integrally fired at 1200 to 1300°C.
FIG. 2 shows the resistance-temperature characteristics of the laminated thermistor element obtained in the above manner by baking the external electrodes 24a and 24b using T-paste. In FIG. 2, A is the resistance temperature characteristic of the laminated thermistor element.

In this way, linearity is exhibited within the measurement range (0 to 50°). Note that B is the resistance-temperature characteristic of the resistor layer 12 with a high thermistor constant, and C is the resistance-temperature characteristic of the resistor layer 14 with a low thermistor constant. In addition, the thermistor element according to the above embodiment showed only a change in resistance value over time of within +:3% even in a high temperature storage test at 500° for 1000 hours.
Chemically stable properties were also obtained.

(g) Effects of the Invention According to the present invention, since mutual diffusion during the lamination manufacturing process of multiple resistor layers having different thermistor constants is prevented, the initial resistance value and thermistor constant are maintained, and each resistor layer is interposed between the oxide ceramic layers, the environmental resistance is also improved. Therefore, it is possible to obtain a thermistor element having predetermined resistance-temperature characteristics with extremely small variations in resistance value and S'-mister constant.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a thermistor element according to an embodiment of the present invention, FIG. 2 is a diagram showing the resistance temperature characteristics of the thermistor element, and FIG. 3 is a diagram for explaining the principle of linearization. 12 - Resistor layer with Misk constant, 14 - Resistor layer with low thermistor constant, 16a, i6b, 18a, 18b internal electrode, 20 - Oxide ceramic layer, 22a, 22b - Through electrode, 24a, 24b - External electrode.

Claims (1)

[Claims] (1) Multiple types of resistor layers with different thermistor constants forming internal electrodes are laminated and integrated with these resistor layers interposed between multiple oxide ceramic layers together with the internal electrodes to form an oxide ceramic. 1. A thermistor element characterized in that an external electrode is formed on the outer surface of the layer, and the internal electrodes of each resistor layer are commonly connected to each other and also connected to the external electrode.