JP3091556B2 - Method and apparatus for measuring conductor thickness - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the thickness of a conductor which can determine the thickness of a plate-like or thin-film conductor in a non-contact manner.

[0002]

2. Description of the Related Art As a method for measuring the thickness of aluminum, copper, silver and other conductors in a non-contact manner, for example, a reflected magnetic field generated when a plate-shaped conductor is excited by an exciting coil depends on the thickness of the conductor. A method of measuring the thickness of the conductor by detecting the reflected magnetic field with a detection coil utilizing this fact is known.

[0003]

However, in the above-mentioned conventional method, the target thickness is limited to several mm, and it is difficult to measure over a wide range of thickness.

The present invention has been made in view of the above background, and has a method for measuring a conductor thickness in a non-contact manner over a wide range from a plate shape to a thin film shape. And an apparatus.

[0005]

In order to solve the above problems BRIEF SUMMARY OF THE INVENTION, thickness measurement method of the conductor according to the present invention, the conductor from the coil and when to close the conductor (1) coil electromagnetic
The distance until the negligible interaction can be ignored (hereinafter referred to as the separation
In the equation representing the difference between the impedances of the coils, the terms representing the resistance component and the reactance component are both expressed as a function of the thickness of the conductor. Based on this function, the resistance and the reactance are calculated. Are taken in rectangular coordinates, and a map showing the relationship between them is created in advance using the thickness as a parameter, and then the coil in the case where the conductor is brought close to the coil and in the case where the conductor is separated from the coil The impedance difference of the conductor is measured, and the thickness of the conductor is obtained from the value of the resistance and the reactance indicating the difference in impedance by the map, and the thickness of the conductor according to the present invention is measured. The equipment is (2)
A coil; impedance measuring means for measuring a resistance component and a reactance component indicating a difference in impedance of the coil between a case where a conductor is brought close to the coil and a case where the conductor is separated from the coil; and Resistance component and reactance component values indicating the difference in impedance
A map that is created in advance, and a term indicating a resistance component and a reactance component in an expression representing a difference in impedance of the coil when a conductor is brought close to the coil and when a conductor is separated from the coil, respectively. Both are represented by a function of the thickness of the conductor, and based on this function, the resistance and the reactance are taken in rectangular coordinates, and the thickness is used as a parameter to be compared with a map showing the relationship between them, and the thickness of the conductor is determined. And an information processing means for performing a process of obtaining the value.

[0006]

In the above configuration (1), on the map, an actual measured value of the resistance and the reactance indicating the impedance difference of the coil when the conductor is close to the coil and when the conductor is separated from the coil is designated. Then
From the value of the parameter curve on which the designated point rides, the thickness of the sample to be measured can be immediately obtained.

Further, according to the configuration (2), it is possible to obtain an apparatus for performing the method of the configuration (1).

[0008]

FIG. 1 is a diagram showing the configuration of an apparatus for carrying out a method for measuring the thickness of a conductor according to one embodiment of the present invention, and FIGS. 2 and 3 are diagrams showing maps prepared for an aluminum sample. 4 is a diagram showing skin depth, FIG. 5 is a diagram showing an optimum film thickness measurement range, and FIGS. 6 and 7 are diagrams showing measured values. Hereinafter, an embodiment will be described in detail with reference to these drawings.

In the apparatus shown in FIG. 1, an aluminum plate or thin film sample 2 is brought close to or away from the circular solenoid coil 1 and the sample 2 comes close to the circular solenoid coil 1 by the LCR meter 3. The thickness difference of the sample 2 is obtained by measuring the impedance difference of the circular solenoid coil 1 when the sample 2 is separated from the coil 1 and inputting the measured value to the computer 4 and performing predetermined arithmetic processing. is there. Here, purely theoretically, "Near
The “contact” is a conductor at which integration is started in [Equation 1] described later.
A point at a distance of 0 is defined as a "separation".
Are thinking about a point at infinity. In actual measurements,
Contacting means that the conductor and coil are as close as possible
It assumes a girder state. On the other hand, in actual measurement
“Separation” means no electromagnetic interaction between the conductor and the coil.
It is to be able to see. In any case, the “proximity” and “separation” in the present invention are purely theoretical “distance 0”.
This is a state where “infinity” is approximated in actual measurement.

Now, let ΔZ be the difference between the impedance of the circular solenoid coil 1 when the sample 2 approaches the circular solenoid coil 1 and when the sample 2 separates from the circular solenoid coil 1, and let ΔR be the resistance, ΔX / ω
Is the reactance component,

(Equation 1) As is apparent from the above equation (1), the resistance ΔR
And the reactance ΔX / ω are functions of the thickness d of the sample 2. Therefore, when the value of d is determined and calculated, ΔR and ΔX / ω at that time can be calculated.

Then, for various values of d, if the corresponding ΔR and ΔX / ω are calculated one after another, d and ΔX
It is possible to obtain a map indicating the correspondence between R and ΔX / ω. This map can be represented, for example, by a graph in which ΔR and ΔX / ω are set on orthogonal coordinate axes and d is a parameter.

FIG. 2 and FIG. 3 show maps prepared by performing the above-mentioned calculations for aluminum as the sample 2. FIG.

2 and 3, the horizontal axis represents resistance ΔR (unit: Ω), and the vertical axis represents reactance ΔX / ω.
(Unit: × 10 ^-5 H). In these figures, the curves shown by solid lines are curves obtained when the impedance measurement frequency by the LCR meter 3 is kept constant and the thickness d is variously changed, and the dotted lines show the frequency when the thickness d is kept constant. It is a curve in the case. In FIG. 2, the thickness d is 0.1 mm,
In each case of 0.2 mm, 0.4 mm, 1 mm, 2 mm and 4 mm (curves indicated by dotted lines in FIG. 2), and in cases where the frequency is 300 Hz, 500 Hz, 1 KHz and 10 KHz (curves indicated by solid lines in FIG. 2) ) Are shown as curves, and in FIG. 3, the thickness is 1 μm, 2 μm, 3 μm.
m, 5 μm, 10 μm, 30 μm, and 60 μm (dotted curve), and frequencies of 10 KHz, 50 KH
The calculated values for each of z, 100 KHz, 300 KHz and 500 KHz (solid curve) are shown as curves. In this case, the constant values in the above equation (1) were as follows.

A (radius of coil 1) = 8 mm φ 1 (ell; length of coil 1) = 49.8 mm N (number of turns of coil 1) = 415 times Z ₁ = 0 Z ₂ = 49.8 σ (of aluminum Conductivity) = 3.65 × 10 ⁷ s / m μ = μ ₀ = 1.256 × 10 ^-6 H / m In this case, if both the radius a, the length l (ell) and the number of turns N of the coil 1 are large, The sensitivity increases as the radius increases. However, if the radius a is too large, the sensitivity is liable to be affected by the size of the conductor. Even if the length l is longer than a certain level, the sensitivity cannot be improved so much (infinite length at 50 mm). In order to increase the number of turns with a fixed coil length, the thickness of the winding must be reduced. However, the strength of a wire thinner than 0.1 mmφ is required. Practically select the above values because Specified. In addition, the coil 1 is placed around the acrylic pipe at 0.1 mm.
It was produced by winding a conductive wire having a thickness of 1 mmφ.

The computer 4 stores the map created in this way, and compares ΔR and ΔX / ω actually measured by the LCR meter 3 with this map to obtain d.
Is performed. Here, the LCR meter 3 is an LCR meter having a four-terminal pair structure (for example, a product name HP sold by Hewlett-Packard Company).
4284A).

From the curves in FIGS. 2 and 3, when the thickness d of the sample becomes larger than a certain value at each frequency,
It can be seen that the impedance change is reduced. This is because the penetration depth of the magnetic field becomes shallow at high frequencies due to the skin effect. That is, assuming that the penetration depth of the magnetic field is δ and the frequency is f, δ = 1 / (πfμ ₀ σ) ^1/2 (2) FIG. 4 shows the results of the determination of the skin depth at each frequency using the equation (2). If the thickness of the sample is greater than the skin depth, the impedance will not change much, so even a small error in the measured value will cause a large error in the thickness reading. Therefore, there is an optimum range for measuring the thickness (film thickness) according to the frequency,
2 and 3, it can be seen that the optimum thickness measurement range is as shown in FIG. Roughly, low frequencies (several hundred H
z) is suitable for measuring a film having a large film thickness (several mm), and a film having a small film thickness (a few μm) at a high frequency (several hundred KHz)
Suitable for measuring.

Next, aluminum plate-like and thin-film samples 2 of various thicknesses are actually prepared, and ΔZ is actually measured for each of these samples by the coil 1 and the LCR meter 3 described above. / Ω
This was compared with the created map to obtain a thickness measurement value. The results are shown in FIGS. 6 and 7, the measured value obtained by the method and apparatus according to the present embodiment and the thickness (true thickness) obtained by other means (micrometer) are shown together, and the percentage of the difference between the two is shown. Shown as error.

The measurement results are plotted in FIG. 2 and FIG. In FIG. 2, the mark が indicates a thickness of about 0.1 mm.
(Accurately, the values shown in FIG. 6).
2 mm, □ is 0.4 mm, ■ is 1 mm, △ is 2 mm, ▲
Is 4 mm. In FIG. 3, the mark ◎ is about 1 μm in thickness.
(Accurately, the value shown in FIG. 7).
m, ●: 3 μm, □: 5 μm, Δ: 10 μm, Δ: 30
μm and ▲ are 60 μm.

According to the embodiment described in detail above, a wide range of thickness can be measured in a non-contact manner, and a map is stored in a computer to perform a series of processing. Measurement is possible.

In the above-described embodiment, the case where a circular solenoid coil is used as the coil has been described as an example, but this may be a coil of another form. Further, in the above-described embodiment, an example in which aluminum is used as the sample 2 has been described, but this is, of course, applicable to other conductive materials.

[0021]

As described above in detail, according to the present invention, the terms representing the resistance component and the reactance component in the equation representing the difference in impedance between the case where the conductor is brought close to the coil and the case where the conductor is placed away from the coil are represented by the terms of the conductor. It is expressed as a function of thickness, this is taken in rectangular coordinates, a map showing the relationship between them is created in advance using the thickness as a parameter, and the resistance and reactance values based on the measured values of the coil impedance differences are mapped. By determining the thickness of the conductor by collating, the thickness of the conductor can be quickly determined in a non-contact manner over a wide range.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an apparatus for carrying out a conductor thickness measuring method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a map created for an aluminum sample.

FIG. 3 is a diagram showing a map created for an aluminum sample.

FIG. 4 is a diagram showing skin depth.

FIG. 5 is a diagram showing an optimum film thickness measurement range.

FIG. 6 is a diagram showing measured values.

FIG. 7 is a diagram showing measured values.

[Explanation of symbols]

1 ... coil, 2 ... conductor sample, 3 ... LCR meter, 4 ... computer.

────────────────────────────────────────────────── ─── Continued on the front page (72) Shuji Yoshizawa, Inventor 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Dowa Mining Co., Ltd. (72) Inventor Hiroshi Nakane 2-183-3, Osawa, Mitaka City, Tokyo ( 56) References JP-A-62-225947 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B ^7/ 00-7/34

Claims (2)

(57) [Claims] 1. A resistance component and a reactance component in an equation representing a difference in impedance of a coil when a conductor is brought close to the coil and when the conductor is separated from the coil until electromagnetic interaction is negligible. The terms shown are both expressed as a function of the thickness of the conductor, and based on this function, the resistance and the reactance are taken in rectangular coordinates, and a map showing the relationship between the thickness and the parameter is created in advance, Next, the difference between the impedance of the coil when a conductor is brought close to the coil and the case where the conductor is separated from the coil is actually measured, and the conductor is determined by the map from the resistance and reactance values indicating the impedance difference. A method for measuring the thickness of a conductor, comprising determining the thickness of a conductor. 2. The method according to claim 1, wherein the coil and the conductor are brought close to each other and the electromagnetic interaction between the coil and the conductor is negligible.
An impedance measuring means for measuring the resistance component and reactance component indicative of a difference in impedance of the coil in the case where is separated until that, the value of the resistance component and reactance component representing the difference impedance measured by the impedance measuring means, advance In the created map, the term indicating the resistance component and the reactance component in the expression representing the difference in impedance of the coil when a conductor is brought close to the coil and when the conductor is separated from the coil, Both are represented by a function of the thickness of the conductor.Based on this function, the resistance and the reactance are taken in rectangular coordinates, and the thickness is compared with a map showing the relationship between them as a parameter, and the thickness of the conductor is determined. Information processing means for performing processing for Thickness measuring device of the body.