JPH06137971A - Pressure sensor - Google Patents

Abstract

PURPOSE:To contrive improvement of quality and durability of a sensor by forming a resistor of the sensor into a specified pattern with a method for sputtering a target of a resistor material. CONSTITUTION:A sensor is formed with an insulation layer on the surface of a metal substrate and composed of a circuit for detecting resistor provided on its surface and resistant change. A sputtering method for forming the resistor shows that a resistor material target is irradiated with ions, so that resilient and non-resilient collision are conducted with atoms, a group of the atoms and molecules on the surface of the target, they are evaporated and evaporated target substances are precipitated on a board. The target preferably consists of composite targets composed of a glass component selected from among at least Si2, B2O3 and the like and a conductive crystal component selected from among at least RuO2, Ta2O5 and the like. The glass layer is selected in regard to the insulation layer, which is preferably composed of a non-alkali glass-ceramic from a view point of heat resistance and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor for detecting pressure by a change in electric resistance of a resistor against a change in pressure.

[0002]

2. Description of the Related Art In recent years, a sensor for detecting a load amount and a pressure has been widely used for detecting a stress or a load magnitude generated in each part of a machine, a ship, an automobile or the like. Various sensors of this type have been proposed depending on the type of base material and the type of strain-sensitive material. As a typical example,
(A) A pressure sensor in which a thin film resistor made of Cu-Ni alloy, Ni-Cr alloy or the like is formed by vapor deposition or sputtering on a film made of resin such as polyester, epoxy or polyimide, and (b) Japanese Patent Publication No. 3 No. 20682, a pressure sensor using a glass plate instead of the above resin film, (c) Japanese Patent Application No. 3-
As disclosed in Japanese Patent No. 282663, a metal substrate, a glass layer made of a crystallized glass material formed on the surface thereof, and further formed on the surface of the glass layer, the electric resistance changes when strain is applied. A pressure sensor composed of a resistor has been proposed.

The magnitudes of stress, load and pressure are measured as follows. The pressure of the member generated by an external force or load is transmitted to the resistor via the resin film, the glass plate, and the metal base material. Due to the transmitted pressure, the length and cross-sectional area of the resistor change, and the electric resistance of the resistor changes. By detecting the change in the electric resistance as an electric signal, the magnitude of the pressure can be measured, and the stress applied to the member, the load, and the magnitude of the pressure can be measured from the magnitude of the pressure.

By the way, one of the applications in which the pressure sensor has a large market is a suspension for a vehicle used in an automobile or the like. Hereinafter, the vehicle suspension will be described as an example. For example, a pressure sensor is attached to the surface of the shaft with an adhesive resin or the like, and the load applied to the wheel by the vehicle body is detected by this pressure sensor.

[0005]

However, (a)
When used for a long time under harsh environmental conditions, such as a vehicle suspension, where the temperature range is -50 to 150 ° C and the maximum load reaches 2 tons, the sensor of the There is a problem that the sensor is separated from the member. Particularly, in the pressure sensor of (b), when the glass plate is welded to a member having a curved surface such as a shaft,
Since the glass plate has poor adhesion, strong adhesion is difficult and easy to peel off. However, the pressure sensor of (c) has very strong adhesion because the constituent elements of the metal substrate and the crystallized glass layer and between the crystallized glass layer and the resistor layer are mutually diffused. It is the most suitable sensor to use, but it has not been put to practical use. The reason for this is that resistor paste made of ruthenium oxide, glass powder and vehicle is used as the resistor material, and the particle size distribution and material dispersity of these materials affect the sensor characteristics, causing variations in sensor characteristics. This is because it lacked stability.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a pressure sensor of high quality and excellent in durability.

[0007]

In order to solve the above problems, a pressure sensor according to the present invention comprises a metal base, an insulating layer formed on the surface of the metal base, and a pressure formed on the surface of the insulating layer. Is a pressure sensor including a resistor whose electric resistance changes due to a change in the resistance of the resistor, and a circuit for detecting a resistance change of the resistor, wherein the resistor is formed into a predetermined pattern by sputtering a target of the resistor material. It is characterized by being formed.

[0008]

The conventional resistor is formed by (A) a method of depositing an alloy resistor on a resin film and sputtering, and (B) a method of printing and firing a resistor paste. The method (A) has difficulty in adhesion, and the method (B), as described above, the resistor paste is usually composed of ruthenium oxide, glass powder, and vehicle. The rates are different. The resistor paste used for strain detection is a mixture of materials with large particle size of ruthenium oxide and small particle size of glass powder.
Particle size distribution of a mixture of ruthenium oxide powder and glass powder,
Due to the non-uniform dispersibility, there was a problem in variations in sensor characteristics.

On the other hand, the pressure sensor of the present invention is formed by sputtering a resistor material target. In this sputtering method, by irradiating the resistor material target with ions, atoms and atoms on the target surface are irradiated. It causes elastic or inelastic collision with groups and molecules, and as a result, the atoms, atomic groups, and molecules on the target surface are evaporated, and the evaporated target material is deposited on the substrate.

In the present invention, unlike the method (A), since the material to be measured is directly sputtered, it does not need to be adhered by a resin or the like and has excellent adhesion, and the rate of change in resistance to strain, that is, the gauge factor is also the alloy resistance. On the other hand, in the metal oxide system of the present invention, it can be expected to be 5 times or more. Also, unlike (B), the resistor material has no dispersibility and non-uniformity of particle size distribution, stabilizes the sensor characteristics, and has a resistance value, gauge ratio, TC
Characteristic variations such as R (rate of temperature change of resistance) characteristics are reduced. Therefore, the present invention can provide a strain sensor in which the adhesiveness of the resistor is strong and the characteristic is excellent.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pressure sensor according to an embodiment of the present invention will be specifically described below. (1) Metal Substrate As the metal substrate used in the present invention, various alloy materials such as holo steel, stainless steel, silicon steel, nickel-chromium-iron, nickel-iron, kovar, invar, and clad materials thereof are selected. To be done. Once the material of the metal substrate is determined,
Desired shape processing, hole processing and the like are performed by ordinary mechanical processing, etching processing, laser processing and the like. A cylindrical shape, a plate shape (including a foil shape), or the like is selected as the shape depending on the size of the load applied and the application.

For the purpose of improving the adhesiveness of the insulating layer described below, these metal substrates are degreased on the surface, then sandblasted, plated with nickel, cobalt or the like, or thermally oxidized to form an oxide coating layer. To form.

(2) Insulating Layer The insulating layer formed on the metal substrate of the sensor of the present invention is crystalline.
A fog glass layer is selected. Crystallized glass layer is electrically insulating
From the viewpoint of heat resistance and heat resistance
, For example, MgO-based crystal phase is deposited)
Preferably. Its glass composition, especially MgO
16-50% by weight, SiO₂Is 7 to 30% by weight, B₂O ₃Is 5 to 34 weight
%, BaO 0-50% by weight, La₂O₃Is 0-40% by weight, CaO is 0
~ 20% by weight, P₂O_FiveIs 0-5% by weight, MO₂Is 0-5% by weight
(However, M is at least one element of Zr, Ti, Sn)
Is preferred. Thus, crystallized glass material
One of the reasons for selecting is that the metal substrate and the glass layer are closely packed.
This is for strengthening the wearability. Especially of the above composition
Has very strong adhesion.

As a method for coating the above-mentioned crystallized glass layer on a metal substrate, there are a usual spray method, a powder electrostatic coating method, an electrophoretic electrodeposition method and the like. The electrophoretic electrodeposition method is the most preferable from the viewpoints of the denseness of the coating film, the electric insulating property, and the like. In this method, alcohol and a small amount of water are added to glass, and the mixture is ground and mixed in a ball mill for about 20 hours to make the average particle size of glass about 1 to 5 μm. The obtained slurry is put in an electrolytic cell and the liquid is circulated. Then, the metal substrate is immersed in this slurry and negatively polarized at 100 to 400 V to deposit glass particles on the surface of the metal substrate. After this is dried, it is baked at 850 to 900 ° C. for 10 minutes to 1 hour. As a result, the glass fine particles are melted, and the glass component and the metal material component are sufficiently diffused into each other, so that a strong adhesion between the glass layer and the metal substrate can be obtained.

It should be noted that in the firing, when the temperature is gradually raised from room temperature to reach the above temperature, innumerable fine needle-shaped crystals are deposited, so that the function of the anchor effect described later is further improved, and the adhesion with the resistor is improved. This is preferable because it has an effect on improvement.

(3) Resistor As a material for the resistor, there is used a resistance material such as ruthenium oxide, tantalum oxide, thallium oxide, lead ruthenate, etc., which has a property that electric resistance is changed by various pressure changes. A sputtering method is selected as a method for forming the resistor. As the sputtering method, there are direct current sputtering, high frequency sputtering, magnetron sputtering, ion beam sputtering and the like, but in consideration of mass productivity, magnetron sputtering having a high sputtering speed is preferable. The sputtering gas is usually 4N to 5N of high purity Ar or Ar / Ar depending on the purpose.
O ₂ , Ar / Nr ₂ or the like is used.

As a method of using the spatter, a method of directly depositing a target substance by sputtering and a method of making a target state by an appropriate heat treatment after sputtering can be considered. The former is also applicable to a base material having low heat resistance such as resin. In the latter case, the state of the film can be controlled by selecting the subsequent heat treatment conditions.

Next, a concrete example will be described. (Example 1) A crystallized glass layer having a composition shown in (Table 1) to (Table 5) having a thickness of 100 µm was electrically formed on the surface of a SUS430 substrate (100 mm × 100 mm × 0.5 mm) according to the above-mentioned insulating layer forming step. Electrophoresis electrodeposition, baking at 880 ℃ for 10 minutes, surface roughness of sample,
Various characteristics such as waviness and heat resistance were investigated. The results are shown in (Table 1) to (Table 5) together with the composition.

The surface roughness was measured by a Talysurf surface roughness meter and indicated by the surface center line average roughness Ra, and the waviness was expressed by the difference Rmax between the peak and the valley obtained by the Talysurf surface roughness meter. Regarding the heat resistance, the sample was put in an electric furnace at 850 ° C. for 10 minutes, taken out of the furnace, and allowed to stand for 30 minutes to carry out a spalling test in which a cycle of repeated natural cooling was repeated to examine the state of cracking and peeling of the sample. The cracks were immersed in the red ink, the surface was wiped off, and the presence or absence of the cracks was checked by visual observation. ○, △, × in the table, ○ indicates that no abnormality is observed even after 10 cycles or more, △ is 5
What occurred in ~ 9 cycles, x shows what occurred in 4 cycles or less. For adhesion, a bending test of the substrate is performed,
The case where the glass layer was peeled off to expose the metal part was rated as x, the part where the metal part was exposed was rated as Δ, and the part where the metal part was not exposed was rated as o.

Based on the above evaluation, a comprehensive evaluation was carried out, and the results are shown by ◯, Δ, and ×. Nos. 1 to 8 are the ones in which SiO ₂ and B ₂ O ₃ are changed while keeping other components constant, and Nos. 9 to 15 are
SiO ₂ / B ₂ O ₃ is kept almost constant, the amount of MgO is changed,
Similarly, No16 to 19 have different CaO contents. No20 ~ 24
Is also the BaO amount changed. No. 25 to 29 are the ones with the same La ₂ O ₃ content. No30 to 42 are
It shows the effects of ZrO ₂ , TiO ₂ , SnO ₂ , P ₂ O ₅ , and ZnO.

As is apparent from the table, when SiO ₂ is increased, the heat resistance is improved, but the surface property and the adhesion are deteriorated. On the contrary, if the amount of B ₂ O ₃ is increased, the surface property and the adhesion are certainly improved, but the heat resistance is decreased. Therefore, in the present invention, it is preferable that SiO ₂ is in the range of 7 to 30% by weight and B ₂ O ₃ is in the range of ₅ to 34% by weight.

The amount of MgO has a correlation with the crystallinity, and if it is 16% by weight or less, the precipitation of crystals is insufficient and the heat resistance is poor. On the other hand, if it is 50% by weight or more, crystals tend to precipitate, it is difficult to crystallize when the glass melts, it is difficult to obtain a homogeneous glass, and the surface roughness becomes large.

If the CaO content is 20% by weight or more, the surface properties are deteriorated, which is not preferable. If the amount of BaO is 50% by weight or more, heat resistance and adhesion are deteriorated, which is not preferable. La ₂ O
_{When the} content of ₃ is 40% by weight or more, the heat resistance is deteriorated, which is not preferable.

Other components that can be added are ZrO ₂ , TiO ₂ and Sn.
O ₂ , P ₂ O ₅ , ZnO and the like can be mentioned, but up to 5% by weight can be added.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

[Table 5]

A pressure sensor manufactured by forming a resistor based on the above-described manufacturing method will be described. Diameter 40φ mm,
After performing the degreasing, water washing, pickling, water washing, nickel plating, and water washing steps as a pretreatment on a 100 μm thick disk-shaped metal substrate, it consists of glass particles with the composition shown in No. 7 in (Table 1). By immersing in a slurry and applying a DC voltage between the counter electrode and the metal base material, the surface of the metal base material is coated with glass particles, and the temperature is raised from room temperature to 880 ° C over 2 hours. Baking for 10 minutes was performed to form a 70 μm crystallized glass layer to form an insulating layer. Next, Au was vapor-deposited on the surface of the insulating layer to form an electrode.

Next, SiO₂ー B₂O₃-PbO-Al₂O₃System glass,
Crystalline RuO as a conductive component₂, Ta ₂O_Five, Tl₂O, Pb₂RuO
₆Magnetron spa
By patterning, a predetermined pattern with a thickness of 30 μm
To form a pressure sensor.

(Example 2) The same plate-shaped metal body as in Example 1 was degreased, washed with water, pickled, washed with water, nickel-plated, washed with water, pretreated, and then No7 glass having the composition shown in (Table 1). Immersing in a slurry consisting of particles, applying a DC voltage between the counter electrode and the metal body, coat the glass particles on the metal body, from room temperature
The temperature was raised to 880 ° C. over 2 hours, and the temperature was maintained for 10 minutes, followed by firing to form a crystallized glass layer and form an insulating layer. Next, an Ag-Pd paste was pattern-printed on the surface of the insulating layer by a screen printing method and baked at 850 ° C. to form an electrode.

Next, MmOn-SiO ₂ -B ₂ O ₃ -PbO-Al ₂ O ₃ (MmOn = R
uO ₂ , Ta ₂ O ₅ , Tl ₂ O) glass is used as a single target and magnetron sputtering is performed to obtain a thickness
A 30 μm patterned resist precursor was formed. This was heat-treated at 600 ° C. for 10 minutes to deposit a conductive crystal to form a resistor, which constituted a pressure sensor.

(Example 3) In Example 2, RuO ₂ -SiO
About ₂ -B ₂ O ₃ obtained by sputtering -PbO-Al ₂ O ₃ based glass was varied by 50 ° C. The heat treatment temperature at 600 to 800 ° C..

(Comparative Example 1) As a comparative example, in the same manner as in Example 1, a target constituted by coating a crystallized glass layer, providing an electrode, and a metal base material provided with the electrode and comprising two components of copper and nickel Sputtered to a constantan (45Ni ・ 55Cu
Alloy) was deposited, and a pressure sensor using this as a resistor was produced.

(Comparative Example 2) As a comparative example, a crystallized glass layer was coated in the same manner as in Example 1, electrodes were provided, and a conventional ruthenium oxide and glass frit were used as main components on a metal base material provided with the electrodes. A comparative sample was produced by screen-printing a paste manufactured by Shoei Chemical Co., Ltd. and firing at 830 ° C.

For the samples of Examples 1, 2 and 3 and Comparative Examples 1 and 2, the conductive crystals of the resistors were determined by thin film X-ray diffraction diffraction, and the TCR was measured between 25 ° C and 125 ° C. The resistance change rate between 0 and 2000 mmH ₂ O was measured. The results are shown in Table 6 (Example 1), Table 7 (Example 2), Table 8 (Example 3), and Table 9 (Comparative Examples 1 and 2). The pressure sensor of the present embodiment has a large rate of resistance change as compared with the conventional one and is also excellent in temperature characteristics.

[0038]

[Table 6]

[0039]

[Table 7]

[0040]

[Table 8]

[0041]

[Table 9]

[0042]

As described above, according to the pressure sensor of the present invention, the resistance value is changed by sputtering the resistor material.
It has become possible to provide high-quality sensors with stable characteristics such as gauge ratio and TCR.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiko Yoshida 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A pressure sensor comprising a metal base, an insulating layer formed on the surface of the metal base, and a resistor formed on the surface of the insulating layer and having an electric resistance that changes with deformation. The resistor is formed into a predetermined pattern by sputtering a target of the resistor material. 2. The target is at least SiO ₂ , B ₂ O ₃ ,
At least a glass component selected from PbO and Al ₂ O ₃
It is composed of a composite target composed of two components of a conductive crystal component selected from RuO ₂ , Ta ₂ O ₅ , Tl ₂ O, and Pb ₂ RuO ₆ , and the conductive crystal component is contained in the glass by sputtering. The pressure sensor according to claim 1, wherein the pressure sensor is a dispersed resistor. 3. The target is at least RuO ₂ , Ta
₂ O _5, it consists of a single target composed of glass containing one or more materials selected from the Tl ₂ O, after sputtering, at least RuO ₂ from the glass by heat treatment, Ta ₂ O _5, Tl The pressure sensor according to claim 1, which is a resistor in which one or more kinds of conductive crystal components selected from ₂ O and Pb ₂ RuO ₆ are deposited. 4. The pressure sensor according to claim 1, wherein the insulating layer is a crystallized glass layer. 5. The composition of the crystallized glass layer is such that MgO is 16 to 50.
% By weight, 7-30% by weight of SiO ₂ , 5-34% by weight of B ₂ O ₃ , Ba
O is 0 to 50% by weight, La ₂ O ₃ is 0 to 40% by weight, CaO is 0 to
20% by weight, P ₂ O ₅ 0-5% by weight, MO ₂ 0-5% by weight
The pressure sensor according to claim 4, wherein M is at least one element of Zr, Ti, and Sn.