JP2659716B2 - Alloy having low temperature coefficient of electric resistance and low melting point, method for producing the same, and highly stable electric resistor or eddy current displacement sensor using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a gold-cobalt-iron-based electric resistance alloy. More specifically, the present invention has a feature that the temperature coefficient of electric resistance is small and the melting point is low. The present invention relates to a highly stable resistor or a gold-cobalt-iron-based electric resistance alloy for an eddy current displacement sensor.

(Prior Art) In recent years, components of electronics-related devices, such as electric resistors or eddy current type displacement sensors, have been used to reduce the size, performance, and environmental resistance. There is a strong demand for the development of a material for an electric resistance alloy having excellent stability.

In other words, the necessary conditions required for the electric resistance alloy are that the electric resistance has an appropriate value, the temperature coefficient of the electric resistance is small, the melting point is low, and the material is soft. Less change over time, excellent brazing properties, easy processing,
It is also important that they are chemically stable, have good compatibility with insulators, have low cost, and the like.

Conventionally, silver (Ag), copper (C
Pure metals such as u) and gold (Au) are conceivable, but all have extremely large temperature coefficients of electric resistance of 4000 ppm / ° C. or more, and it is difficult to apply them to the parts for this purpose.

Here the temperature coefficient C _f of the electrical resistance is defined by the formula _{C f = ΔR / ΔT / R} , its unit is [10 ^-6 / ° C.) or (ppm / ° C.].

(Problems to be Solved by the Invention) By the way, the addition of a small amount of nickel (Ni), manganese (Mn), cobalt (Co) or chromium (Cr) to these elements does not significantly improve the electrical characteristics. It has already been reported ("Progress of Measurement Materials", edited by the Materials Research Group of the Measurement Society of Japan, Corona, 1959, p.157). Also disclosed separately therefrom is a palladium-silver alloy previously invented by the present inventors (JP-A-55-1212).
Nos. 2839, 60-204846 and 60-204847) and copper-nickel-gold alloys (JP-A-59-6345). Each of these materials has a negative temperature coefficient of electric resistance or a very small value of 100 ppm / ° C. or less, so that when applied to parts, the alloy can sufficiently exhibit excellent properties. However, on the other hand, individual alloys have many disadvantages, such as high melting point, hard and inflexible materials, lack of chemical stability, or the electrical resistance may change with time due to thermal aging. There are many problems such as difficulty in winding work in the above.

(Means for Solving the Problems) In order to respond to the urgent demands of the related industries, the present inventors have conducted various studies and have found that the temperature coefficient of electric resistance is small, the melting point is low, and the material is excellent. It is an object of the present invention to provide an electric resistance alloy having characteristics, and a highly stable resistor or an eddy current displacement sensor using the alloy.

That is, the present inventors have focused on gold (Au), a noble metal that has a low specific electric resistance, a low melting point, and is chemically stable,
A study was conducted on an alloy containing a small amount of cobalt (Co) and iron (Fe). Regarding the electrical properties of Au-Co binary alloys, see the above-mentioned specialized book “Progress of Measurement Materials” (No. 14).
According to pages 9 to 157), it is described that the temperature coefficient of electrical resistance shows a negative value in cold working by cold working and in low-temperature annealing at 140 ° C. However, since the structure of this alloy is in an unstable state between the solid solution of Au and the eutectic phase, the above-mentioned treatment not only makes it difficult to sufficiently obtain the stability of the electrical characteristics, but also changes the electrical resistance with time due to the influence of precipitation. There are also things to consider. Furthermore, in the above treatment, the alloy material is hard and good flexibility cannot be obtained.

The present invention solves the above-mentioned problems and has excellent characteristics.
It is an object of the present invention to provide an Au-Co-Fe-based electric resistance alloy, a method for producing the same, and a highly stable resistor or an eddy current displacement sensor using the alloy of the present invention.

It is an object of the present invention that the weight percentage of cobalt is 0.01 to 0.01%.
10% iron 0.01-8% and the balance substantially gold,
Consists of a small amount of impurities, the temperature coefficient of specific electrical resistance is 1000pp
An object of the present invention is to provide a method for producing an electric resistance alloy, which has a m / ° C or lower and a melting point of 1055 ° C or lower.

Another object of the present invention is to obtain cobalt by weight of 0.1%.
01-10%, iron 0.01-8%, the balance is substantially gold, and the desired shape selected from wire or plate by hot working or cold working after casting and forging an alloy consisting of a small amount of impurities It is another object of the present invention to provide a method for producing an electric resistance alloy, which comprises heating at 200 to 800 ° C. for 2 seconds to 100 hours in a non-oxidizing atmosphere or vacuum.

Still another object of the present invention is to provide an electric resistance alloy material consisting of 0.01 to 10% by weight of cobalt, 0.01 to 8% of iron and the balance being substantially gold and a small amount of impurities by weight. Shape or a toroidal shape, and fixing the same as it is to an inorganic or organic electrical insulator or embedding it in the insulator, the change in electrical resistance with respect to temperature is small, Temperature coefficient of electric resistance is less than 1000ppm / ℃ and melting point is 1055 ℃
An object of the present invention is to provide a method for manufacturing an eddy current type displacement sensor characterized by obtaining the following highly stable electric resistor.

Still another object of the present invention is to provide an electric resistance alloy consisting of 0.01 to 10% by weight of cobalt, 0.01 to 8% of iron and the balance being substantially gold and a small amount of impurities, by weight percent. After being deposited on the body surface as a thin film by any of the methods of electrodeposition, vapor deposition or sputtering, a desired pattern is formed by etching punching or trimming processing, and this is fixed to another electrical insulator, or is placed in the insulator. By embedding or applying or coating an insulator on the surface of the alloy thin film and loading it in an insulator case, the change in electrical resistance with respect to temperature is small, the temperature coefficient of specific electrical resistance is 1000 ppm / ° C or less and the melting point Is 1055
An object of the present invention is to provide a method for manufacturing an eddy current type displacement sensor characterized by obtaining a highly stable resistor having a temperature of not more than ° C.

It is a further object of the present invention to provide a method of manufacturing a semiconductor device comprising 0.01 to 10% by weight of cobalt, 0.01 to 8% of iron and the balance substantially consisting of gold and a small amount of impurities, and the temperature coefficient of specific electric resistance. An object of the present invention is to provide an eddy current type displacement sensor using an electric resistance alloy having a melting point of 1000 ppm / ° C. or less and a melting point of 1055 ° C. or less.

(Structure and Function of the Invention) Hereinafter, a method for producing the alloy of the present invention will be specifically described.

In the present invention, firstly, 0.01 to 10% of cobalt and 0.01 to 8% of iron.
% And the balance of gold are melted in air or vacuum, preferably in a non-oxidizing atmosphere, using a suitable melting furnace, and then sufficiently stirred to produce a homogeneous molten alloy. In this case, if a gold-iron mother alloy or a gold-cobalt mother alloy prepared in advance is used, the adjustment of the alloy composition becomes extremely easy. In addition, since the melting point of the alloy of the present invention is 1055 ° C. or less, an ordinary wire-type electric furnace or a city gas furnace can be used in the melting operation, so that the handling is very easy. Next, the molten alloy is poured into a mold having an appropriate shape and size to obtain a sound ingot. Thereafter, it is processed as it is or at a high temperature of 800 ° C. or less to produce a rod having an appropriate shape, for example, a rod or a plate. Swaging this further,
Cold working is performed by a method such as drawing, rolling or crushing to obtain a target shape, for example, a thin wire or a thin plate. Finally, in order to stabilize and soften the electrical characteristics, heat and maintain at a temperature of 200 to 800 ° C for 2 seconds to 100 hours in a non-oxidizing atmosphere or vacuum, and then cool at a rate of 5 to 300 ° C / h. Perform annealing. This annealing treatment not only improves the weldability, brazing properties and wettability to insulators because the inner gas and surface dirt of the alloy material escape, and also improves the flexibility by softening the material. It is extremely effective in application.

When the alloy material obtained by the above-described method is used for a highly stable resistor or an eddy current type displacement sensor, various methods are conceivable for applying an electric insulating material. explain.

(A) The alloy material of the present invention, such as a wire or a plate, is directly wound around an insulator, and the surface thereof is coated with an inorganic or organic electrical insulator and dried, or the alloy material is formed into a desired shape, for example, It is formed into a spiral or toroidal shape and embedded in the insulator as it is, or is directly attached to the insulator with an adhesive, or is fixed by a method such as being sandwiched between two insulators.

(B) After forming the alloy of the present invention on a surface of an electric insulator in the form of a thin film by an appropriate method such as electrodeposition, vapor deposition, plating, or sputtering, a desired pattern is formed by punching, trimming, or the like into a desired pattern. If necessary, this is fixed to another insulator as it is, embedded in the insulator, or the insulator is applied or coated on the surface of the alloy thin film.

The product manufactured by the above process may be used as it is, but if necessary, if the above-mentioned annealing treatment is performed again for stabilization of the product, the same stability as the alloy of the present invention itself is exhibited. It becomes possible to manufacture a resistor or an eddy current displacement sensor.

(Example) Next, an example of the present invention will be described.

Example 1 Alloy No. GCF-10 (alloy composition Au = 95%, Co = 2.5%, F
e = 2.5%) As raw materials, gold with a purity of 99.99% or more, cobalt with a purity of 99.8% or more, and iron with a purity of 99.9% or more were used. To prepare a sample, a 10g gold material was added to a high-purity alumina crucible (SSA-
H, # 2) and melted by a Tamman furnace while blowing high-purity argon gas to prevent oxidation, and stirred well to obtain a homogeneous molten alloy. Next, at a temperature of 1080 ° C., which is about 100 ° C. higher than the melting point, a round rod was quickly drawn into a silica pipe having an inner diameter of 3.5 mmφ. Thereafter, the area reduction rate is determined by a swaging machine and a wire drawing machine [(A'-A) / A) × 100.
Was cold-worked in the range of 10 to 99% to obtain a fine wire having a wire diameter of 0.5 mmφ. Here, A 'and A are the cross-sectional areas after and before processing, respectively. Cut to a length of 105 mm from this fine wire, and as it is cold-worked or heated at various temperatures of 200 to 800 ° C for various times of 2 seconds to 100 hours and gradually cooled down to room temperature, annealing for electrical resistance measurement A sample was used. Separately, two types of ribbon-like thin plates having a thickness of 0.28 mm and a thickness of 0.22 mm were prepared from a fine wire having a wire diameter of 0.5 mm by a precision cold rolling mill. Next, these ribbon-shaped thin plates having different thicknesses were stacked and wound in a toroidal shape 20 to 50 times, and then heated at 350 to 400 ° C., which was slightly higher than the recrystallization temperature, for 30 minutes to give a habit. Then, the ribbon-shaped coil with a thickness of 0.22 mm was pulled out, and the other 0.28 mm-thick toroidal sensor coil was immersed in polyimide resin, dried and fixed, and then the resin on the sensor coil surface was further ground. Smooth and none,
The eddy current type displacement sensor was manufactured by mounting in a ceramic case and then soldering a coaxial cable to the electrodes.
First, the above-mentioned measurement of the electric resistance was performed continuously at a heating and cooling rate of 180 ° C./h in a vacuum in a temperature range from room temperature to 800 ° C. FIG. 1 shows the measurement results of the alloy of the present invention. As can be seen from the figure, the specific electrical resistance ρ in the annealed state
Is smaller than that of the processing state, and the change with respect to the temperature T is small. In the case of [rho-T characteristic curve of the annealed condition, but it follows the same curve even after repeated heating and cooling, in the case of machining state [rho decreases reaching a point when cooling from the temperature T ₁ of the middle heating. And again it matches the curve of the machining state at temperature T ₂ higher than T ₁ not follow the original path be heated from a point. However, the above-mentioned unstable phenomenon is stabilized by reducing ρ by maintaining the medium at a medium temperature of 200 ° C. or more for several tens of hours to several days. However, even in the case of a material in a processed state, at a relatively low temperature of 100 ° C. or less, the above-mentioned unstable phenomenon is hardly observed, but it cannot be used for application due to a large ρ.

FIG. 2 shows the specific electric resistance ρ _{0 at} 0 ° C. and the average temperature coefficient of the specific electric resistance obtained from the ρ-T characteristic curve between 0 and 100 ° C. in FIG. And the relationship between the temperature and the annealing temperature. As can be seen, both ρ ₀ and C _f decrease with increasing annealing temperature. Therefore, it shows that the characteristics in the case of performing the annealing treatment are better than those in the case of the cold working. The specific electrical resistance at 0 ° C of the alloy sample heated at 800 ° C for 1 hour and then slowly cooled was 63.0μΩ · cm, the average temperature coefficient of the specific electrical resistance between 0 and 100 ° C was 140ppm / ° C, the melting point was 1025 ° C and Vickers. Hardness was 50. Also, for the eddy current displacement sensor using the alloy of the present invention, the temperature coefficient of the coil impedance and the temperature coefficient of the electrical resistance of the alloy are almost offset by the coil diameter slightly changing with the temperature, and the excellent characteristics of the alloy of the present invention Was fully demonstrated.

Example 2 Alloy No. GCF-6 (alloy composition Au = 98.0%, Fe = 2.0
%) As the production raw materials, the same annealed gold and iron as in Example 1 were used. The sample was manufactured in the same steps as in Example 1. Separately, an appropriate amount of the raw materials, for example, 5 g and 1 g of gold and iron, respectively, are put into an alumina crucible for each raw material, and the composition of the alloy of the present invention is mixed with a thin alumina substrate surface by an ion plating method in a vacuum of 10 ^-6 Torr. The thin film was deposited by controlling so as to be as follows. Thereafter, the surface of the coating film was subjected to laser trimming in a grid shape, and was made into a size of about 5 × 10 mm and baked at 800 ° C. for 1 hour in a vacuum. Next, two electrodes were attached thereto, and the whole was molded with resin to produce a resistor element. FIG. 3 shows the ρ-T characteristic curve of the alloy sample of the present invention. The result is similar to that of the first embodiment, but the specific electric resistance is about 40 μΩ · cm, which is smaller than that of the first embodiment by 25 μΩ · cm or more. Also, ρ-T in FIG.
FIG. 4 shows the relationship between ρ ₀ or C _f obtained from the characteristic curve and the annealing temperature. Changes in the [rho ₀ As seen in FIG Example 1
However, the change of C _f is different from that of the first embodiment, and increases as the annealing temperature increases.
It is a constant value of 0 ppm / ° C. The specific electrical resistance at 0 ° C. when heated at 800 ° C. for 1 hour and then slowly cooled was 37.5 μΩ · cm,
The average temperature coefficient of the specific electrical resistance between 100 ° C. was 294 ppm / ° C., the melting point was 1055 ° C., and the Vickers hardness was 55. The electrical resistance of the resistor element was 1 kΩ, and other electrical characteristics were almost the same as those of the alloy composition.

Example 3 Alloy No. GCF-4 (alloy composition Au = 98.5%, cobalt =
1.5%) As production materials, gold and cobalt having the same purity as in Example 1 were used. The sample was manufactured in the same steps as in Example 1. Relationship between [rho-T characteristic curve and [rho ₀ or C _f of the sample and the annealing temperature is FIG. 5 and FIG. 6 respectively. ρ
It can be seen that the -T characteristic curve is quite different from that of FIG. 1 or FIG. That is, at the temperature of about 300 ° C. or more in the processed state and about 400 ° C. or more in the annealed state, the minimum and the hysteresis of the heating and cooling curves are observed, respectively. Next, in FIG. 6, ρ ₀ has a minimum value of 11 μΩ · cm at a lower temperature of 500 ° C. than in the case of FIG.
_f shows a negative value at a temperature of about 120 ° C. or less. Ie 20
It can be seen that at an annealing temperature of 0 ° C. or higher, ρ ₀ is small and excellent characteristics of C _{f of} 400 ppm / ° C. or lower can be obtained.

FIG. 7 shows Au-0 to 15 which were slowly cooled after heating at 800 ° C. for 1 hour.
% For Co-0% Fe @ 3-way alloy equality curves of the mean temperature coefficient C _f of the electrical resistance are shown. The alloy composition having a C _f of 1000 ppm / ° C. or less is indicated by a point A (Au: Co: Fe = 99.19: 0.
8: 0.01), point B (Au: Co: Fe = 99.19: 0.01: 0.8), point C
(Au: Co: Fe = 91.99: 0.01: 8), point D (Au: Co: Fe = 86: 6:
8), point E (Au: Co: Fe = 86: 10: 4) and point F (Au: Co: Fe)
= 89.99: 10.0: 0.01).

The C _f is 200 ppm / ° C. The following values are the points A ', B', C ' ,
The composition within the range of D ', E' and F ', that is, Au is 9
0.4-97.5%, Co 0.1-5.6% and Fe 0.1-5.
It can be seen that a 3% alloy is obtained. FIG. 8 shows an equivalent curve of the specific electric resistance ρ ₀ of the Au—Co—Fe ternary alloy subjected to the same treatment as in FIG. Further in FIG. 9 shows a melting point T _m of a Au-Co-Fe3 binary alloy having the same composition range as the FIGS. 7 and 8. Further, FIG. 10 shows that the composition ratio of the Au—Co—Fe ternary alloy, C _f , FIG. 8 ρ _0, and T _m of FIG. Is shown. From this figure, it can be seen that in a wide composition range where the [Co + Fe] amount is 2 to 13.7%.
C _f is 1000 ppm / ° C or less, ρ ₀ is 92 μΩ · cm or less, and T _m is
It can be seen that a value of 1055 ° C. or less is obtained.

Experiments were also conducted on a number of alloys in addition to the examples described above. Table 1 shows the electrical properties, melting points, Vickers hardness and flexibility of typical alloy samples.

As can be seen from Examples 1 to 3 and Table 1, the alloy composed of 0.01 to 10% of Co, 0.01 to 8% of Fe and the balance of Au and a small amount of impurities has a temperature coefficient of electric resistance of 1000 ppm /
℃ or less, melting point 1055 ℃ or less has excellent properties,
Further, as shown in FIGS. 7 and 10, there is a feature that a small temperature coefficient of electric resistance of 200 ppm / ° C. or less can be obtained over a wide composition range. Also, since the Vickers hardness of the alloy of the present invention is 100 or less and the flexibility is extremely good, it is extremely easy to manufacture a high-stability resistor and an eddy current type displacement sensor to which the alloy is applied. The change in characteristics is small, and the excellent characteristics of the alloy of the present invention can be sufficiently exhibited.

Next, the reasons for limiting the composition and heat treatment temperature of the alloy of the present invention will be described.

First, for the composition range of the alloy of the present invention, cobalt is 0.01 to
The reason why 10% and iron were limited to 0.01 to 8% is that, as is clear from each embodiment, FIGS. 7, 9 and 10, the temperature coefficient of electric resistance is 1000 ppm / ° C. or less and the melting point is
Although it shows characteristics of 1055 ° C or less, if the composition exceeds this range, it will be larger than the above value, and it will be unsuitable as a highly stable electric resistor or an alloy for eddy current type displacement sensors which is the object of the present invention. It is. The reason for limiting the temperature range of the heat treatment of the alloy of the present invention to 200 to 800 ° C. is that within this temperature range, the heating time is set to 2 seconds to 100 for all the compositions of the alloy of the present invention.
The temperature coefficient of electric resistance is 1000 ppm / ° C or less by slow cooling after holding for a time, and as can be seen from Examples 1 to 3, change in electric resistance with time even if heating and cooling are repeated. Not only stabilizes, but also the alloy material is softened and the flexibility is improved. However, when the temperature is lower than 200 ° C, the electrical resistance becomes thermally unstable, and the flexibility due to work hardening is poor. When the temperature is higher than 800 ° C, fusion occurs due to contact between alloy materials and deformation due to extreme softening occurs. This is because this method is unsuitable as a method for manufacturing a stable resistor or an alloy for an eddy current displacement sensor.

(Effects of the Invention) As described above in Examples 1 to 3, the alloy of the present invention has a very small change in electric resistance with respect to temperature in each case. Particularly, the temperature coefficient of electric resistance of the alloy number GCF-10 of Example 1 is 140 ppm / ° C., which is about 1/30 of that of pure metals such as Cu, Ag and Au, and about 1/3 of that of Cu-10% Ni alloy. The thermal stability of the electric resistor or the eddy current displacement sensor is improved and the change over time is reduced, making the winding process relatively easy. Can be expected. The melting point of the alloy of the present invention is pure Au or Cu-10% Ni.
Since it is lower than alloys, there is no need to use special melting equipment, and there is an energy saving effect.

In short, the Au-Co-Fe alloy of the present invention has not only the excellent temperature coefficient of electric resistance of 1000 ppm / ° C or less and the melting point of 1055 ° C or less, but also the flexibility of the alloy material as compared with that of pure Au. The superior properties of the alloy of the present invention are not inferior, for example, not only as a substitute material of pure Cu and pure Ag that has been conventionally used for eddy current displacement sensor coils, but also as a lead wire and bonding wire for electronic equipment. Has a great industrial advantage that can be further exerted.

[Brief description of the drawings]

1, 3 and 5 show the alloy numbers GCF-10, GCF-6 and GCF-
2, 4 and 6 show the electrical resistance-temperature curves of No. 4, respectively, and show the alloy numbers GCF-10 and GCF-6 when annealed after heating at various temperatures for 1 hour.
FIG. 7 is a characteristic diagram showing the relationship between the specific electric resistance or the temperature coefficient of specific electric resistance of GCF-4 and the annealing temperature, and FIG. 7 shows a gold-cobalt-iron ternary alloy annealed at 800 ° C. at 0 to 100 ° C. FIG. 8 is a characteristic diagram showing an average temperature coefficient of electric resistance, FIG. 8 is a characteristic diagram showing a specific electric resistance at 0 ° C. of a gold-cobalt-iron ternary alloy annealed at 800 ° C., and FIG. 9 is gold-cobalt-iron. FIG. 10 is a characteristic diagram of the melting point of the ternary alloy, and FIG. 10 is a composition ratio of Fe: Co = FIG. 7, FIG. 8 and FIG.
FIG. 3 is a characteristic diagram showing the relationship between the average temperature coefficient, the specific electric resistance, and the melting point of each electric resistance at 1: 1 and the amount of [Co + Fe].

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Claims (6)

(57) [Claims] (1) Cobalt 0.01 to 10% by weight, iron 0.01 to 10% by weight
An electric resistance alloy comprising 8% and a balance substantially composed of gold and a small amount of impurities, having a temperature coefficient of specific electric resistance of 1000 ppm / ° C. or less and a melting point of 1055 ° C. or less. 2. Cobalt 0.1-5.6% by weight, iron 0.1-% by weight%
2. The electric resistance alloy according to claim 1, wherein 5.3% and the balance substantially consist of gold and a small amount of impurities, and have a temperature coefficient of specific electric resistance of 200 ppm / ° C. or less and a melting point of 1050 ° C. or less. 3. Cobalt 0.01 to 10% by weight, iron 0.01 to 10% by weight
8% and a balance substantially consisting of gold, and casting and forging an alloy consisting of a small amount of impurities into a desired shape selected from a wire or a sheet by hot working or cold working;
2 at 200-800 ° C in non-oxidizing atmosphere or vacuum
A method for producing an electric resistance alloy, comprising heating for at least one second and at most 100 hours. 4. Cobalt 0.01 to 10% by weight, iron 0.01 to 10% by weight
An electric resistance alloy material having a composition of 8% and the balance substantially consisting of gold and a small amount of impurities is formed into a desired shape selected from a spiral shape or a toroidal shape, and the material is formed into an inorganic or organic material as it is. By fixing to an electrical insulator or embedded in the insulator, the change in electrical resistance with respect to temperature is small, and the temperature coefficient of specific electrical resistance is 1000
A method for manufacturing an eddy current displacement sensor, characterized in that a highly stable electric resistor having a ppm / ° C or lower and a melting point of 1055 ° C or lower is obtained. 5. Cobalt 0.01 to 10% by weight and iron 0.01 to 10% by weight.
An electric resistance alloy consisting of 8% and the balance substantially consisting of gold and a small amount of impurities is applied as a thin film on the surface of an electric insulator by electrodeposition, vapor deposition or sputtering, followed by etching blanking or A desired pattern is formed by trimming, and this is fixed to another electrical insulator, embedded in the insulator, or the insulator is applied or coated on the surface of the alloy thin film, and is loaded into the insulator case. By doing so, the change in electrical resistance with temperature is small, and the temperature coefficient of specific electrical resistance is 10
A method for manufacturing an eddy current displacement sensor, characterized by obtaining a highly stable resistor having a melting point of not more than 00 ppm / ° C and a melting point of not more than 1055 ° C. 6. Cobalt 0.01 to 10% by weight, iron 0.01 to 10% by weight.
An eddy current type displacement sensor using an electric resistance alloy having a temperature coefficient of specific electric resistance of 1000 ppm / ° C. or less and a melting point of 1055 ° C. or less, which is composed of 8% and the balance substantially composed of gold and a small amount of impurities.