JPH03210468A - Thick film magnetic semiconductor and preparation thereof - Google Patents

Abstract

PURPOSE:To obtain an element having thermistor characteristics and varistor characteristics by forming a thick film on an insulating substrate from a mixture of soft magnetic oxide and resistance paste. CONSTITUTION:For example, a thick film is formed on an insulating substrate 1 composed of alumina, zirconia or titania from a mixture of soft magnetic oxide and resistance paste. Subsequently, an electrode pattern 2 is formed to the upper layer of the thick film. In this case, the soft magnetic oxide is constituted of Mn-Cu-Zn type ferrite and the resistance paste is constituted of a ruthenium compound. By this constitution, the resistance of an element reacts with temp. or gas concn. in spite of one element and the element having both of thermistor characteristics and varistor characteristics can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to thick film magnetic semiconductors (Thlek Film Ma
gnetIc5eslconductor, hereinafter,
The present invention relates to TFMS) and its manufacturing method, and specifically relates to elements having many functions such as moisture-sensitive sensors, gas-sensitive sensors, thermistor characteristics, varistor characteristics, etc.

[Prior Art] The present inventors have so far conducted research on soft magnetic temperature-sensitive ferrite. This temperature-sensitive ferrite becomes paramagnetic at high temperatures, and
By taking advantage of the fact that it exhibits ferromagnetism at low temperatures, it is used in temperature-sensitive sensors and temperature-sensitive switches.

This is because the temperature-sensitive ferrite was used only electrically to function as an inductance.

The present inventors further researched these temperature-sensitive ferrites, and found that, for example, "11th Japanese Society of Applied Magnetics Academic Lecture Abstracts, p. 373, November 1987,
Paper No. 4aE-1” and “Journal of the Institute of Electronics and Communication Engineers C
-II, vo17e -c II, No,
3 + pages 204-209, March 1983, etc., in addition to magnetic changes in temperature-sensitive ferrite, its voltage-current characteristics exhibit a nonlinear electrical conduction phenomenon, and its use as a semiconductor. I found a function.

Specifically, it was revealed that it has gas and humidity detection (sensor) functions and thermistor characteristics. However, these presentations considered temperature-sensitive ferrite produced by powder metallurgy, similar to ferrite traditionally used in communication equipment.

Incidentally, in recent years, electronic devices are required to be more compact and have higher performance.

Therefore, the technical problem of the present invention is to make it possible to provide a thick-film element that is downsized, highly reliable, and low-cost, and that also allows the resistance of even one element to react to temperature and gas concentration. Another object of the present invention is to provide an element having both voltage-current dependent thermistor characteristics and varistor characteristics.

[Means for Solving the Three Problems] According to the present invention, a thick film magnetic semiconductor characterized by forming a thick film of a mixture of a soft magnetic oxide and a resistance paste on an insulating substrate is obtained.

According to the present invention, there is obtained a thick film magnetic semiconductor characterized in that in the thick film magnetic semiconductor, the soft magnetic oxide is Mn-Cu-Zn-based ferrite, and the resistance paste is made of a ruthenium compound. .

According to the present invention, there is obtained a thick film magnetic semiconductor characterized in that a change in resistance value in the semiconductor is temperature sensitive, gas sensitive, and voltage dependent. It will be done.

According to the present invention, a coating film is formed on an insulating substrate such as alumina by a printing method or the like using a mixture of soft magnetic oxide magnetic material powder and resistance paste, and then a drying and firing process is performed. A method for manufacturing a thick film magnetic semiconductor is obtained.

According to the present invention, there is obtained a method for manufacturing a thick film magnetic semiconductor, characterized in that a coating film is formed on an electrode pattern previously formed on the insulating substrate.

According to the present invention, in the method for manufacturing a thick film magnetic semiconductor, after forming the thick film magnetic semiconductor on the insulating substrate,
A method for manufacturing a thick film magnetic semiconductor is obtained, which is characterized in that an electrode pattern is formed on the upper layer of the thick film.

That is, recently, a chip inductor has been proposed in which internal electrodes are formed by forming a film of ferrite slurry by a thick film method, but this only utilizes the magnetism of ferrite.

However, the present invention provides a thick film element (TFMS) that focuses on the function of a semiconductor with electrical characteristics rather than magnetic properties.

[Example〕 Embodiments of the present invention will be described with reference to the drawings.

1 and 2 are diagrams showing the specific structure of the thick film semiconductor of the present invention, with FIG. 1 being a plan view and FIG. 2 being a sectional view.

A conductive lead extraction electrode 3 is formed on an insulating substrate 1 made of alumina (A120.), zirconia (ZrO□), titania (TiO2), etc., and a thick film magnetic semiconductor pattern 2 is further formed by screen printing or the like. (Figure 2 (a)
)) Alternatively, it is also possible to form a structure (FIG. 2(b)) in which the thick film magnetic semiconductor 2 is coated on the substrate 1 and then the patterned lead electrodes 3 are deposited.

Further, the electrode patterns of the thick film magnetic semiconductor shown in FIGS. 1(a), (b), (C), and (d) are merely examples, and do not impose equivalent limitations on the present invention.

These are used depending on the purpose of use and the accuracy of detecting dependence on gas humidity, and are selected depending on the rate of change of thermistor characteristics and varistor characteristics.

In addition, Fig. 1 (a), (b), (c), (d
), the pattern 2 of the thick film magnetic semiconductor was shaped into an S-shape or a comb shape, but there is also one in which the conductor pattern is formed as shown in Figure 1 and the thick film magnetic semiconductor film is coated on the entire surface. It is clear that it falls within the scope of the invention.

Further, it goes without saying that the conductive electrode may be formed by a plating method, a sputtering method, or the like, and the pattern can be formed by a general etching method or the like.

It is a mixture of ferrite powder and resistance paste, and is made into a semiconductor. Ferrite, a soft magnetic oxide, has the chemical formula MO-Fe20s (where M is Mn, Cu, Co,
It is an oxide magnetic material represented by divalent transition metals such as Zn and Mg.

In addition, the resistance paste is a ruthenium compound M2RLJO7
-X (where M is Bi, Pb, Ba, etc.)
a is the substance to be vitrified.

With this configuration, microscopically, magnetic particles and conductor particles are arranged in a complicated manner in the glass matrix.
It is presumed that it constitutes a magnetic material-resistance network.

That is, the magnetic particles and the conductive particles or their secondary grains form one group, and this group of grains also forms a loop. Grain groups with perfect ohmic contact, groups of grains with low contact resistance, or groups of grains with fairly high contact resistance form loops with each other to form a mesh-like conductive network. It can be said that it has become a semiconductor.

Further, embodiments of the present invention will be described in more detail.

<Example 1. > Using an alumina substrate, conductive paste containing Ag-Pd (silver palladium) as the main component (D- manufactured by Shoei Chemical Industry Co., Ltd.)
4344 and the company's solvent thinner T-131),
A required pattern of electrodes was formed by a printing method. that time,
A conductor paste containing Ag--Pd as a main component is used. Silver has low resistance and good solderability, but it tends to cause migration, so Pd is added to improve stability. In addition, if glass bond is used as an inorganic binder and the firing time is extremely long and the temperature is extremely high, or if firing is repeated many times, the glass will migrate to the conductor surface and the solder wettability and adhesive strength will deteriorate. Therefore, caution is required. The applied electrode paste is dried at 130° C. for 10 minutes, and then baked.

For firing, the temperature is raised from room temperature to 850° C. over 30 minutes at a constant temperature gradient, held at this temperature for 10 minutes, and then slowly cooled down to room temperature over 20 minutes.

Next, a thick film magnetic semi-moving body TF was formed on the electrode pattern.
Apply a film of MS. The magnetic semiconductor was composed of a mixture of Mn-Cu-Zn ferrite and resistive paste. M
n -Cu -Z n-type ferrite is manufactured by Tokin Co., Ltd., trade name Thermolite TC45 material (composition is Fe20s
45.3 mol%, Mn0 11.0%, Zn0 30.7 mol%, CuO 13゜0 mol%) obtained by normal powder metallurgy method and physically crushed into powder (powder particles are about 10 microns). was used.

The resistance paste is manufactured by Engelhardt, product name RELY.
-OHM R-4403 ruthenium compound (particle size -200 mesh) was used, and thinner was used as the solvent. The ratio of the above-mentioned ferrite powder and resistance paste was determined to an appropriate value to form a mixed paste, and a thick magnetic semiconductor layer was deposited by a coating film forming method such as screen printing or drawing printing.

There is a screen printing method for producing thick films, and the former is suitable for mass production, while the former is suitable for producing complex patterns.
The latter will be adopted.

After printing, the magnetic semiconductor paste is dried at 130° C. for 10 minutes, and the firing step is divided into three steps: temperature raising, constant temperature holding, and temperature lowering.

The temperature is raised from room temperature to 850° C. over 25 minutes with a constant temperature gradient. In this process, the organic binder in the paste is
It starts to decompose at about 350°C, and when it reaches 500°C, it decomposes completely and becomes a complete gas such as CH4, C2H6, H20 vapor or CO2.

If the temperature is raised too quickly, it may cause voids in the film.

Also, sufficient time and oxygen must be provided for complete combustion of the organic binder.

When there is a lack of oxygen, the organic binder will undergo incomplete combustion,
The inside of the furnace becomes a reducing atmosphere, which causes a decrease in resistance value, TCR fluctuation, etc.

In the next constant temperature holding step, the firing temperature is kept at 850° C. for 10 minutes, and the film and the substrate are bonded together by melting the inorganic binder and reacting the substrate. When the temperature exceeds 600°C, the glass begins to soften and flow, and when the firing temperature is reached, magnetism and metal particles rearrange and sinter, and the glass crystallizes, giving it magnetic and electrical properties. This area is called the firing zone.

This step has a large effect on characteristics such as resistance value and TCR, reproducibility, and reliability, so it is necessary to keep it within ±3%.

The temperature lowering step refers to a step of cooling to room temperature in 25 minutes. In order to remove the strain generated in the film in the previous step, it is desirable to cool the film as slowly as possible, and the temperature is lowered from about 700°C to 300°C at a rate of 50°C to 200°C per minute. This region is called an annealing zone. If the temperature decreases quickly, cracks may occur in the pattern or substrate. Note that in the case of a Pd/Ag-based conductor with a high Pd content, if the cooling time is extremely long, palladium oxide may be formed on the film surface, which may cause poor solderability.

The manufacturing method of the present invention has been described above using one example, but as described above, it is natural that the method is not limited to this example in order to obtain a thick film magnetic semiconductor element. Note that the thick film method allows various patterns to be easily formed, and furthermore, it is easy to reduce the size and weight. Furthermore, compared to conventional sintered bodies, the sintering temperature can be as low as 850°C.

Next, the present invention will be explained in detail from the aspect of a magnetic semiconductor element.

<Example 2> FIG. 3 shows the temperature characteristics of the inductance of TFMS in which a printed coating film was formed on a cylindrical substrate through each process as in Example 1.

However, the component ratio of the ferrite powder and the resistance paste is 1:1 by weight. As shown in FIG. 3, magnetism appears due to the mixing of ferrite powder, and the characteristics of a magnetic material are recognized. In the figure, the number of turns is Ll-37 turns and L
The case of 2-145 turns is shown, but both decrease as the temperature rises and have significant temperature characteristics. In Ll, 0
The inductance is 8.3~ for a temperature change of ~50℃
It decreases to 7.0μH.

The inductance of the thick film magnetic semiconductor according to Example-2 is:
Although it is considerably smaller than conventional sintered temperature-sensitive ferrite, its characteristics are similar and it can be used as a temperature sensor in the same way as temperature-sensitive ferrite.

FIG. 4 is a diagram showing the humidity characteristics of inductance. In this example, the TFMS was installed in a constant temperature bath, the temperature was maintained at 20° C., and the measurement was performed at a frequency of 1 kHz. LX,
It can be seen that L2 maintains a constant value even when the humidity changes from 50 to 90%, and does not depend on humidity at all.

FIG. 5 shows the gas concentration characteristics of the same inductance as used in FIGS. 3 and 4. Although ammonia gas was used as the measurement target, Ll and L2 always maintain constant values even when the concentration changes from 0 to 2000 ppm.

From the above, it was confirmed that the inductance of TFMS depends on temperature but does not depend on humidity or gas concentration. The magnetic permeability of TFMS is extremely large compared to non-magnetic permeability such as water vapor or gas, so these molecules
Even if it adheres to S, the effect on the overall magnetic permeability is so small that it can be ignored.

Therefore, it can be seen that TFMS has excellent characteristics as a temperature sensor.

<Example 3> A sample was prepared and experimented under the same conditions as in Example 2, except that the electrode pattern was different.

The humidity, gas concentration dependence, and voltage-current characteristics of the resistance of the TFMS according to the present invention were investigated.

However, the methods for measuring 1) temperature characteristics, humidity characteristics, 2) gas concentration characteristics, and 3) voltage-current characteristics are as shown below.

1) Temperature and humidity characteristics: Place the sample in a thermostatic chamber and use an LCR meter to constant n1.

2) Gas concentration characteristics: A sample is placed in a sealed container H of a certain size, and liquids such as ammonia, ethanol, methanol, etc. are appropriately poured into this container and completely evaporated. The gas concentration was determined using a gas detection tube. R and C parameters were measured using an LCR meter.

3) 1R piezoelectric current characteristics: A voltage was applied to the sample, and the voltage and current across the sample at that time were measured.

The film thickness of the sample was 60 μm, and the distance between the electrodes was 10 mm.
And so.

FIG. 6 is a diagram showing the temperature characteristics of the resistance of TFMS. In FIG. 6, it can be seen that the resistance R tends to decrease from 570 to 530 Ω with respect to a temperature change of 20 to 80°C.

FIG. 7 shows the humidity dependence of the resistance of TFMS.

As shown by the curve (a) in FIG. 7, the resistance tends to decrease as the humidity increases, showing a significant humidity dependence.

R is 560 to 290Ω for a humidity change of 50 to 80%
The change in resistance ΔR per 1% humidity is 7.7.
Ω, and a sufficient detection amount can be obtained.

In FIG. 7, curve (b) shows the humidity dependence of the temperature-sensitive ferrite sintered body for comparison. As shown in Figure 7, in the sintered body, Δ
R is 1.25Ω, and the rate of change for a humidity of 50 to 85% is 560Ω/290Ω for thick films.
-1.93 times, whereas in the sintered body, it is 225Ω/17
The rate of change is small, 7 kΩ-1.27 times.

FIG. 8 is a diagram showing the dependence of resistance on gas concentration.

In FIG. 8, R shows a sensitive reaction to three types of gases such as ethanol, acetone, and ammonia. In the case of ammonia, when the gas concentration increases from 0 to 2000 ppm,
R decreased from 570 to 450 Ω, and the amount of change ΔR per 1100 pp was 6 Ω, which was the largest amount of change among the three. Ethanol and acetone show an upward trend, contrary to ammonia, and the amount of change is small, but it seems that they can be used satisfactorily as a sensor.

FIG. 9 is a diagram showing the current-voltage characteristics of the TFMS of the present invention.

In FIG. 9, in a region where the voltage is low, only a small amount of current flows, but as the voltage increases, the current increases rapidly, and becomes a substantially constant value at 175 V, resulting in nonlinear characteristics.

When the polarity of the voltage is reversed, the characteristics become symmetrical and exhibit characteristics similar to those of a varistor.

The current-voltage characteristics of bulk ferrite exhibit a conductive switching phenomenon, but TFMS does not exhibit such switching characteristics and exhibits near-nonlinear characteristics at low voltages.

From the above, the thick film magnetic semiconductor (TF) of the present invention
It is clear that MS) is effective as a temperature-sensitive sensor and a gas-sensitive sensor, and also has the function of a varistor.

TFMS is a low-temperature sintered body containing a metal oxide, and has pores and resistance suitable for a temperature sensor, and the detection mechanism uses physical adsorption, which facilitates the absorption and desorption of moisture.

When TFMS is placed in an atmosphere, water vapor enters the pores, water is adsorbed to the microcrystals, and electrical resistance decreases.

Furthermore, since TFMS is used while being exposed to air containing various components in addition to water vapor, if left in high temperature and high humidity for a long period of time, the water adsorption effect will decrease. However,
These surface stains can be returned to their original state by heat treatment.
Restores temperature sensitivity.

In addition, as an electronic component, varistors currently contain StCs Z
Although ceramics such as nO-based ceramics have been put into practical use,
It is used for surge absorption, voltage stabilization, and temperature compensation, and it is thought that TFMS can also be applied to such uses.

<Example-4> The thickness of a film obtained by blending the ferrite powder used in Example-1, ruthenium compound resistance paste powder (A), and ruthenium compound resistance paste (B) in a weight ratio of 1 to 3 was approximately A thick film magnetic semiconductor having a diameter of 40 μm and an inter-electrode distance of 10 mm was manufactured and measured in the same manner as in Example-1 and Example-3.

Table 1 shows the measurement results of inductance and resistance of each sample at room temperature and humidity.

Table T: Below 20°C Margin Figure 10 is a diagram showing the relationship between temperature and resistance value for each sample, Figure 11 is a diagram showing changes in humidity and resistance value,
FIG. 12 shows the results of measuring the resistance value of the same sample with respect to changes in ammonia gas concentration.

The second table summarizes the amount of change for these samples.
It is a table.

Table 2 Changes in weight component ratio [kΩ/℃] ;Δ
From Figure 2, R2 is the amount of change in resistance per humidity of 60 to 70% [kΩ/%; From Figure 3, ΔR2 is the amount of change in resistance when the humidity is 1
Gas concentration xoo in the range of 000 to 2000 ppm
The amount of change in resistance per ppm is [kΩ/1100pp.

The present invention also involves hybridization (or integrated circuitization).
Because of this, you can take advantage of that advantage.

When the thick film magnetic material of the present invention is used as an electronic device such as a sensor, it can be made smaller and lighter, and various electrode patterns can be easily obtained.

Therefore, although the degree of integration of electronic circuits is currently increasing, the present invention can also be smoothly adapted to IC circuits.

In addition, in the conventional sintered ferrite (called bulk) that the present inventors have already researched and published, the resistance value changes depending on the temperature and humidity of the element, and it does not respond to gas concentration. Futa. However, capacitance (0 minutes) changes with temperature, humidity, and gas concentration in the thick film element of the present invention, and the change in capacitance was extremely small. As a result, in the interface for converting an output signal into an electrical signal, the bulk type requires a resistance-capacitance separation circuit, but the thick film element does not require such a separation circuit.

Furthermore, when the thick film magnetic material of the present invention is used together with a magnetic circuit, the bulk type requires winding and a closed magnetic circuit is preferable, but the present invention provides a non-contact magnetic head that does not require winding. It can be read out and can be configured as an element even in a closed magnetic circuit.

In addition, with the thick film magnetic semiconductor of the present invention, changes in resistance, temperature, humidity, and gas concentration are converted into voltage using a bridge circuit, and the output is converted to high frequency using a voltage-frequency inverter, making digital measurement possible. Of course it is possible to do so.

C Effects of the Invention As explained above, according to the thick film magnetic element of the present invention,
It can be used as a temperature sensor, humidity sensor, gas sensor, and can also be applied from various angles as a surge absorption element, constant voltage compensation element, temperature compensation element, etc., and can be said to have extremely great industrial value.

[Brief explanation of drawings]

Figure 1 (a), (b), (C), (d), and Figure 2 (
FIGS. 1A and 2B are diagrams showing a specific example of the structure of the thick film semiconductor of the present invention, with FIG. 1 being a plan view and FIGS. 2A and 2B being a cross-sectional view. Figure 3 shows that after the process as in Example-1,
Figure 5 shows the temperature characteristics of inductance of TFMS with a printed coating film formed on a cylindrical substrate. Figure ff14 shows the humidity characteristics of inductance. Diagram showing gas concentration characteristics,
FIG. 6 is a diagram showing the temperature characteristics of resistance, and FIG. 7 is a diagram showing the humidity dependence of the resistance of TFMS. For comparison, the temperature dependence of a conventional sintered body is also shown. Figure 8 is a diagram showing the dependence of resistance on gas concentration, and Figure 9 is a diagram showing the dependence of resistance on gas concentration.
Figure 10 is a diagram showing the current-voltage characteristics of FMS, Figure 10 is a diagram showing the relationship between temperature and resistance value for each sample, Figure 11 is a diagram showing changes in humidity and resistance value, and Figure 12 is a diagram showing the relationship between temperature and resistance value for each sample. FIGS. 10 and 11 are diagrams showing the results of measuring resistance values of the same sample with respect to changes in ammonia gas concentration. In the figure, 1 is a substrate, 2 is a thick film magnetic semiconductor pattern, and 3 is an electrode. Fig. 2 Fig. 3 Temperature dependence of inductance L Fig. 4 Temperature characteristics of inductor L Fig. 5 Gas 5 of inductor L Fig. 6 Humidity dependence of resistance R Pillar Figure 7 Humidity dependence of resistance R Pillar 8 Figure 8 Concentration characteristics of resistance Figure 9 Current-voltage characteristics of TFMS Figure 10 Humidity dependence of resistance R Fig. 11 Humidity characteristics of 1 steam scale Fig. 12

Claims (6)

[Claims] 1. A thick film magnetic semiconductor characterized by forming a thick film of a mixture of soft magnetic oxide and resistance paste on an insulating substrate. 2. 2. The thick film magnetic semiconductor according to claim 1, wherein the soft magnetic oxide is Mn--Cu--Zn ferrite, and the resistive paste is comprised of a ruthenium compound. 3. The thick film magnetic semiconductor according to claim 1 or 2, wherein a change in resistance value in the semiconductor has humidity sensitivity, gas sensitivity, and voltage dependence. semiconductor. 4. A thick film magnetic semiconductor is produced by forming a coating film on an insulating substrate such as alumina using a printing method or the like using a mixture of soft magnetic oxide magnetic material powder and resistance paste, and then drying and firing the mixture. Production method. 5. 5. The method of manufacturing a thick film magnetic semiconductor according to claim 4, wherein a coating film is formed on an electrode pattern previously formed on the insulating substrate. 6. A method of manufacturing a thick film magnetic semiconductor according to claim 4, wherein after forming the thick film magnetic semiconductor on the insulating substrate, an electrode pattern is formed on the upper layer of the thick film. Production method.