JPH0816660B2 - Thick film magnetic semiconductor and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a thick film magnetic semiconductor.
emicondactor (hereinafter referred to as TFMS) and its manufacturing method, and more particularly to a humidity sensor, a gas sensor, or an element having many functions such as thermistor characteristics and varistor characteristics.

[Prior Art] The inventors have studied soft magnetic temperature-sensitive ferrite so far. By utilizing the fact that this temperature-sensitive ferrite exhibits paramagnetism at high temperatures and ferromagnetism at low temperatures, with the Curie temperature peculiar to the temperature-sensitive ferrite material as the boundary,
It is used for temperature sensors and temperature switches. This is because the use of this temperature-sensitive ferrite is, electrically, the use of the function of the inductance component.

When the present inventors further studied these temperature-sensitive ferrites, they found that, for example, “The 11th Japan Society for Applied Magnetics Academic Lectures, pp. 373, November 1987, Paper No. 4a.
E-1 "and" Journal of the Institute of Electronics, Information and Communication Engineers C-II, vol J72-
c-II, No. 3, pp. 204-209, March 1989 ”, etc.,
As already announced, in addition to the magnetic change of temperature-sensitive ferrite, it showed a non-linear electric conduction phenomenon in voltage-current characteristics, and found its function as a semiconductor.

Specifically, the function to detect gas and humidity (sensor),
It was clarified that it has thermistor characteristics. However, in these presentations, the temperature-sensitive ferrite produced by the powder metallurgy method was examined in the same manner as the ferrite conventionally used for communication devices and the like.

By the way, in recent years, electronic devices have been required to be smaller and have higher performance.

Therefore, technical problems of the present invention include miniaturization, high reliability,
Alternatively, it is possible to provide a thick film element that leads to cost reduction, and even with a single element, the element resistance reacts with temperature and gas concentration, and also has thermistor characteristics and varistor characteristics due to voltage-current dependence. To provide.

[Means for Solving the Problems] According to the present invention, a mixture of an oxide magnetic material having soft magnetism formed on an insulating substrate, a substance to be vitrified, and a resistance paste containing a resistance material is formed into a thick film. In the thick film magnetic semiconductor formed, the thick film is formed such that particles of the oxide magnetic material and particles of the resistance material are complexly connected in a glass matrix, and the glass matrix is formed on the insulating substrate. A thick-film magnetic semiconductor characterized by being bound by the constituent glass material is obtained.

According to the invention, in the thick film magnetic semiconductor, the soft magnetic oxide is Mn-Cu-Zn ferrite,
A thick film magnetic semiconductor is obtained in which the resistance paste is composed of a ruthenium compound.

Further, according to the present invention, in any one of the thick film magnetic semiconductors, a change in resistance value in the semiconductor has humidity sensitivity, gas sensitivity, and voltage dependence. A film magnetic semiconductor is obtained.

Further, according to the present invention, a mixture of powder of an oxide magnetic material having soft magnetism and a resistance paste containing a substance to be vitrified and a resistance material is formed on an insulating substrate such as alumina by a printing method or the like. A method of manufacturing a thick-film magnetic semiconductor is obtained, which is characterized by undergoing drying and firing steps.

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

On the other hand, according to the present invention, in the method for manufacturing a thick film magnetic semiconductor, after forming the thick film magnetic semiconductor layer on the insulating substrate, an electrode pattern is formed on an upper layer portion of the thick film magnetic semiconductor layer. A method of manufacturing a thick film magnetic semiconductor is obtained.

That is, recently, a chip inductor or the like in which a ferrite slurry (slurry) is formed into a film by a thick film method to form an internal electrode has been proposed, but this utilizes only the magnetism of ferrite.

However, the present invention provides a thick film element (TFMS) focusing on the function of a semiconductor having electric characteristics rather than magnetism.

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

1 and 2 are views showing a specific structure of the thick film semiconductor of the present invention. FIG. 1 is a plan view and FIG. 2 is a sectional view.

A conductive lead extraction electrode 3 is formed on an insulating substrate 1 made of alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), titania (TiO ₂ ) or the like, and further, a thick film magnetic semiconductor pattern 2 is formed by screen printing or the like. (FIG. 2 (a)) or a structure in which the patterned lead electrodes 3 are deposited after the thick magnetic semiconductor 2 is applied to the substrate 1 (FIG. 2 (b)). It is possible to

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

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

1 (a), (b), (c), and (d), the pattern 2 of the thick film magnetic semiconductor has an S shape or a comb shape, but the conductor pattern is as shown in FIG. It is obvious that the present invention also includes a thick magnetic semiconductor film formed on the entire surface to form a coating film.

Needless to say, the conductive electrode may be formed by a plating method, a sputtering method, or the like, and the pattern may be formed by a general etching method or the like.

It is a mixture of ferrite powder and resistance paste,
Although it is a semiconductor, the soft magnetic oxide ferrite has the magnetic properties of the oxide represented by the chemical formula MO ・ Fe ₂ O ₃ (where M is a divalent transition metal such as Mn, Cu, Co, Zn, and Mg). It is a material.

The resistance paste is a ruthenium compound M ₂ RuO _7-x (where M is Bi, Pb, Ba, etc.), and Bi, Pb, Ba are vitrified substances.

Microscopically, it is presumed that such a structure forms a magnetic substance-resistive network by complexly connecting magnetic substance particles and conductor particles in the glass matrix.

That is, the magnetic particles and the conductive particles or the grains that are the secondary particles form one group, and this group of grains also forms a loop. A group of grains having a perfect ohmic contact, a group of grains having a low contact resistance, or a group of grains having a considerably high contact resistance form a loop with each other to form a mesh-shaped conductive network. Therefore, it can be said that it has become a semiconductor.

 Further, examples of the present invention will be described more specifically.

<Example 1.> A conductive paste containing Ag / Pd (silver-palladium) as a main component using an alumina substrate (D-4344 manufactured by Shoei Chemical Industry Co., Ltd.)
And a solvent thinner T-131 manufactured by the same company were used to form the required pattern electrodes by the printing method. At that time, a conductive paste containing Ag / Pd as a main component is used, and silver has low resistance and good solder wettability, but migration is likely to occur.
To improve stability. Further, when a glass bond is used as an inorganic binder and the firing time is extremely long and the temperature is extremely high, or when a number of firings are repeated, the glass migrates to the conductor surface and the wettability of the solder and the adhesive strength deteriorate. So be careful. The applied electrode paste is dried at 130 ° C. for 10 minutes and then fired.

Firing is performed by raising the temperature from room temperature to 850 ° C. in a constant temperature gradient in 30 minutes, maintaining this temperature for 10 minutes, and then gradually cooling to room temperature over 20 minutes.

Next, the thick film magnetic semiconductor TF is formed on the electrode pattern.
Apply MS. The magnetic semiconductor was composed of a mixture of Mn-Cu-Zn ferrite and resistance paste. Mn-Cu-Zn ferrite is manufactured by Tokin Co., Ltd., trade name Thermolite TC45
Material (composition: Fe ₂ O ₃ 45.3 mol%, MnO 11.0%, ZnO 30.7 mol%, CuO 13.0 mol%) obtained by ordinary powder metallurgy, and physically pulverized into powder (powder Particle is about 10 microns)
Was used.

The resistance paste is manufactured by Engel Heart Co., Ltd. under the trade name RELY-
A ruthenium compound of R-4403 of OHM was used (particle size: 200 mesh), and a solvent was thinner. The ratio of the above ferrite powder to the resistance paste was set to an appropriate value to form a mixed paste, and a thick magnetic semiconductor layer was deposited by a film forming method such as screen printing or drawing printing.

The thick film manufacturing method includes a screen printing method and a drawing printing method. The former is suitable for mass production, and the latter is used for manufacturing a complicated pattern.

After printing, the magnetic semiconductor paste is dried at 130 ° C. for 10 minutes, and the firing process of moving to the firing process is divided into three steps: temperature increase, constant temperature maintenance, and temperature decrease.

The temperature is raised from room temperature to 850 ° C. over 25 minutes with a constant temperature gradient. In this step, the organic binder in the paste is about
Decomposition starts at 350 ℃, complete decomposition when reaching 500 ℃,
CH _4, becomes C ₂ H _6, H ₂ O vapor or complete gas such as CO _2.

If the temperature rise is too fast, it will cause voids in the film. Also, sufficient time and oxygen must be provided for the organic binder to completely burn. If the oxygen is insufficient, the organic binder will be incompletely burned and the furnace will be in a reducing atmosphere, resulting in a decrease in resistance value and TCR fluctuation.

In the next constant temperature holding step, the firing temperature of 850 ° C. is maintained for 10 minutes, and the film and the substrate are bonded by melting the inorganic binder and reacting the substrate. When the temperature exceeds 600 ° C, the glass begins to soften and begins to flow, and when it reaches the firing temperature, magnetic properties and metal particles are rearranged / sintered, glass crystallization, and other phenomena impart magnetic and electrical characteristics. This area is called the firing zone.

It is necessary to keep this step within ± 3% because it greatly affects the characteristics such as resistance value and TCR, reproducibility and reliability.

The temperature lowering step is 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 gradually cool as much as possible, and the temperature is lowered between about 700 ° C and 300 ° C at 50 ° C to 200 ° C per minute. This area is called an annealing zone. If the cooling rate is high, the pattern or the substrate may be cracked. In the case of an Ag / Pd-based conductor having a high Pd content, if the temperature-falling time is extremely long, palladium oxide may be formed on the film surface, which may cause poor solder wettability.

Although the manufacturing method of the present invention has been described with reference to the embodiment, it is needless to say that the invention is not limited to this embodiment in order to obtain the thick film magnetic semiconductor element as described above. In the thick film method, various patterns can be easily formed and the size and weight can be easily reduced. Further, compared with the conventional sintered body, the sintering temperature can be considerably low at 850 ° C.

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

<Example-2> The temperature characteristics of the inductance of TFMS in which a printed coating film was formed on a cylindrical substrate through the respective steps as in Example-1 are shown in FIG.

However, the component ratio of ferrite powder and resistance paste is
The weight ratio is 1: 1. As shown in FIG. 3, magnetism appears due to the inclusion of the ferrite powder, and the characteristics as a magnetic material are recognized. In the figure, the number of turns is L1 = 37 turns and L2 = 14 turns.
The case of 5 turns is shown, but both have a remarkable temperature characteristic that decreases with an increase in temperature. In L1, the inductance decreases to 8.3 to 7.0 μH with respect to the temperature change of 0 to 50 ° C.

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

FIG. 4 is a diagram showing the humidity characteristic of the inductance.
In this example, TFMS was installed in a constant temperature bath, the temperature was kept at 20 ° C, and measurement was performed at a frequency of 1 kHz. L1, L2 is 50-9
It can be seen that a constant value is maintained for a humidity change of 0% and it does not depend on the humidity at all.

FIG. 5 shows the gas concentration characteristic of the same inductance as that used in FIGS. 3 and 4. Ammonia gas was used as the measurement target, but L1 and L2 always hold constant values with respect to the concentration change of 0 to 2000 ppm.

From the above, it was confirmed that the inductance of TFMS depends on temperature but not on humidity or gas concentration. Since the magnetic permeability of TFMS is much higher than that of non-magnetic permeability of water vapor or gas, even if these molecules adhere to TFMS, the effect on the overall magnetic permeability is negligibly small.

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

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

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

However, 1) temperature characteristics, humidity characteristics, 2) gas concentration characteristics,
And 3) The method for measuring the voltage-current characteristics is as follows.

1) Temperature and humidity characteristics: Place the sample in a constant temperature bath and measure with an LCR meter.

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

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

The sample had a thickness of 60 μm and the distance between the electrodes was 10 mm.

FIG. 6 is a diagram showing temperature characteristics of the resistance of TFMS. Sixth
In the figure, the resistance R is 570-5 for temperature changes of 20-80 ° C.
There is a tendency to decrease to 30 kΩ.

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

As shown by the curve (a) in FIG. 7, the resistance tends to decrease with an increase in humidity, and shows a remarkable humidity dependency. R changes to 560 to 290 kΩ with respect to a humidity change of 50 to 80%, and the change amount ΔR of resistance per 1% of humidity is 7.7 kΩ, and a sufficient detection amount can be obtained.

In FIG. 7, the curve (b) is a summary of the humidity dependence of the temperature-sensitive ferrite sintered body for comparison. As shown in Fig. 7, in the sintered body, Δ
R is 1.25 kΩ, and the change rate for humidity 50 to 85% is 560 kΩ / 290 kΩ = 1.93 times for thick film,
In the sintered body, the rate of change is small at 225 kΩ / 177 kΩ = 1.27 times.

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

In FIG. 8, R shows a sensitive reaction to three kinds of gases such as ethanol, acetone, and ammonia. In the case of ammonia, R is 5 for the gas concentration increase of 0 to 2000 ppm
It falls to 70-450kΩ and the amount of change ΔR per 100ppm is 6k
Ω, which is the largest change among the three. Contrary to ammonia, ethanol and acetone show a rising tendency and the amount of change is small, but it seems that they can be sufficiently used as sensors.

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

In FIG. 9, in the low voltage region, a small amount of current flows, but when the voltage becomes high, it rapidly increases and becomes a substantially constant value at 175 V, which is a non-linear characteristic.

When the polarity of the voltage is reversed, the characteristic becomes symmetrical and exhibits a characteristic similar to that of a varistor.

The current-voltage characteristics of bulk ferrite show a conductive switching phenomenon, but such switching characteristics are not observed in TFMS, which is a near-linear characteristic near low voltage.

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

TFMS is a low temperature sintered body containing a metal oxide, has proper pores and resistance as a temperature sensor, and uses physical adsorption that easily adsorbs and desorbs water as a detection mechanism. TF
When MS is placed in the atmosphere, water vapor enters the pores, water is adsorbed on the microcrystals, and the electrical resistance decreases.

In addition, TFMS is exposed not only to water vapor but also to air containing various components, and is used. Therefore, if it is left in high temperature and high humidity for a long time, the water adsorption effect decreases. However, the stains on these surfaces return to their original state when heated, and the humidity sensitivity is restored.

Also, as electronic components, ceramics such as SiC and ZnO are currently in practical use for varistor, but they are used for surge absorption, voltage stabilization, and temperature compensation, and TFMS can also be applied to such applications. It is considered to be a thing.

<Example-4> The thickness of the film obtained by mixing the ferrite powder used in Example-1, the resistance paste powder (A) of the ruthenium compound and the resistance paste (B) of the ruthenium compound in a weight ratio of 1 to 3 was about. Example of thick film magnetic semiconductor with 40 μm and electrode distance of 10 mm −
It manufactured and measured like 1 and Example-3.

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

FIG. 10 is a diagram showing the relationship between temperature and resistance value for each sample, and FIG. 11 is a diagram showing changes in humidity and resistance value.
Figure 12 shows the results of measuring the resistance of the same sample against changes in the ammonia gas concentration.

Table 2 summarizes the changes in these samples.

In this table, ΔR ₁ is the amount of change in resistance per temperature 1 ° C [kΩ / ° C] in the temperature range of 40 to 60 ° C from Fig. 1; ΔR ₂ is from 60 to 70% of humidity from Fig. 2 Amount of change in resistance [kΩ /%];
ΔR ₂ is the amount of change in resistance per gas concentration of 100ppm in the gas concentration range of 1000 to 2000ppm "kΩ / 100pp from Fig. 3.
m].

The present invention can also take advantage of the fact that it is hybridized (or integrated circuit).

When the thick film magnetic material of the present invention is used as an electronic element such as a cesar, it is possible to reduce the size and weight, and it is possible to easily obtain various electrode patterns.

Therefore, although the degree of integration of electronic circuits is being improved today, the present invention can be smoothly adapted to IC circuits.

Further, in the conventional sintered body (referred to as bulk) ferrite that the present inventors have already researched and announced, the resistance value changes with temperature and humidity as an element and does not respond to gas concentration. It was However, the capacitance (C) changes with temperature and humidity and with the thick film element of the present invention with respect to temperature, humidity and gas concentration, and the change in capacitance is extremely small. As a result, in the interface for converting an output signal to an electric signal, a resistance-capacitance separation circuit is required in the bulk type, but it can be said that the separation circuit is unnecessary in the thick film element.

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

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

[Effects of the Invention] As described above, according to the thick film magnetic element of the present invention, it can be used as a temperature sensor, a humidity sensor, a gas sensor, and also as a surge absorbing element, a constant voltage compensating element, a temperature compensating element and the like. It can be applied from various angles, and it can be easily configured without complicated manufacturing processes, and it can be said that its industrial utility value is extremely large.

[Brief description of drawings]

FIGS. 1 (a), (b), (C), (d), and FIGS. 2 (a), (b) are diagrams showing a concrete configuration example of the thick film semiconductor of the present invention. Is a plan view, and FIGS. 2A and 2B are cross-sectional views. FIG. 3 is a diagram showing temperature characteristics of inductance of TFMS in which a printed coating film is formed on a cylindrical substrate through steps as in Example-1, and FIG. 4 is a diagram showing humidity characteristics of inductance. The figure shows a gas concentration characteristic of the same inductance as that used in FIGS. 3 and 4, and FIG.
The figure shows the temperature dependence of resistance, and FIG. 7 shows the humidity dependence of resistance of TFMS. The temperature dependence of the conventional sintered body is also shown for comparison. FIG. 8 shows the gas concentration dependence of resistance, FIG. 9 shows the current-voltage characteristics of TFMS, and FIG. 10 shows the relationship between temperature and resistance for each sample. FIG. 11 is a diagram showing changes in humidity and resistance value, FIG. 12 is a diagram showing measurement results of resistance values of the same sample with respect to changes in concentration of ammonia gas. In the figure, 1 is a substrate, 2 is a thick film magnetic semiconductor pattern, and 3 is an electrode.

Continuation of the front page (56) References JP-A-58-168950 (JP, A) JP-A-59-60348 (JP, A)

Claims (6)

[Claims] 1. A thick film magnetic semiconductor in which a mixture of an oxide magnetic material having soft magnetism formed on an insulating substrate and a resistance paste containing a substance to be vitrified and a resistance material is formed into a thick film. The thick film is formed by forming particles of the oxide magnetic material and particles of the resistance material in a complicated manner in a glass matrix and binding them to the insulating substrate by a glass substance forming the glass matrix. A thick-film magnetic semiconductor characterized by the above. 2. The thick-film magnetic semiconductor according to claim 1,
A thick film magnetic semiconductor characterized in that the soft magnetic oxide is Mn-Cu-Zn ferrite and the resistance paste is composed of a ruthenium compound. 3. The thick-film magnetic semiconductor according to claim 1, wherein a change in resistance value of the semiconductor is humidity-sensitive,
A thick-film magnetic semiconductor characterized by having gas sensitivity and voltage dependence. 4. A mixture of powder of an oxide magnetic material having soft magnetism and a resistance paste containing a substance to be vitrified and a resistance material is formed on an insulating substrate such as alumina by a printing method or the like, dried and dried. A method for manufacturing a thick-film magnetic semiconductor, characterized by comprising a firing step. 5. The method of manufacturing a thick film magnetic semiconductor according to claim 4, wherein the thick film magnetic semiconductor is applied and formed on an electrode pattern previously formed on the insulating substrate. 6. The method of manufacturing a thick film magnetic semiconductor according to claim 4, wherein after forming the thick film magnetic semiconductor layer on the insulating substrate, an electrode pattern is formed on an upper layer portion of the thick film magnetic semiconductor layer. A method for manufacturing a thick-film magnetic semiconductor having the characteristics.