# Microwave method of measurement of magneto-dielectric parameters and thickness of spin coatings on surface of metal

FIELD: electrical measurements.

SUBSTANCE: device is proposed for measurement of dielectric and magnetic permeability as well as thickness of spin coatings on surface of metal and can be used in chemical industry for inspecting composition and properties of liquid and solid media. Electro-magnetic field is induced in body of dielectric material to be inspected which material is applied onto dielectric substrate, by means of sequent excitation of slow surface waves: two E-waves are excited at different, but having almost the same value, wavelengths λ_{r1} and λ_{r2} and one H-wave having wavelength of λ_{r3}. Attenuation of field intensity is measured t normal plane in relation to direction of wave propagation by means of receiving vibrators system for different values of base d between them. Normal attenuation factors α_{E1},α_{E2} and α_{H} are found from ratio of E(y)= E_{0 }exp[-α(y) y]. Magnetic and dielectric permeability and thickness of magneto-dielectric coating are found from relations of and where has to be phase coefficient of H-wave.

EFFECT: improved precision of measurement.

1 dwg

The present invention relates to methods for measuring permittivity and permeability, and thickness of spin coating on the metal surface and can be used to control the structure and properties of liquid and solid media in the chemical and other industries.

The known method of determining the thickness of the coating of ferromagnetic material, on the basis of ponderomotive principle (see Instruments for non-destructive testing of materials and products. The guide below. edit VLA. - 2nd ed., revised and enlarged extra - M.: Mashinostroenie, 1986. P.58).

This method has the following disadvantages: does not allow high-speed scanning of large surfaces and insensitive to changes in the dielectric permittivity and magnetic permeability.

There is a method of determining properties of material inspected using a two-electrode or three-electrode capacitive transducers (see Hillocks AV RF capacitive transducers and instruments for quality control. - M.: Mashinostroenie, 1982. P.44). In the General case, the properties of the Converter depends both on the size, configuration and relative location of the electrodes, and the shape, electrical properties of the controlled material and its location relative to the electrodes.

The disadvantages of this method are the two which are: the inability of high-speed scanning of large surfaces, the lack of measurement of magnetic permeability, and the dependence of the accuracy of measurement of the thickness of the dielectric coating on the variation of the dielectric constant.

There is a method of determining the thickness of a dielectric coating on a conductive base (refer to the Devices for non-destructive testing

materials and products. The guide below. edit VLA. - 2nd ed., revised and enlarged extra - M.: Mashinostroenie, 1986. S-125), taken as a prototype, consisting in the creation of eddy currents in the conductive substrate and the subsequent registration of the complex voltage V or the resistance Z eddy current probe as a function of the conductivity of the substrate and the gap between the transducer and the substrate.

The disadvantages of this method are: the dependence of the accuracy of measurement of the thickness of the coating from the gap between the transducer and the substrate, the inability to measure the dielectric permittivity and magnetic permeability of the coating, high sensitivity to changes in parameters of the substrate (conductivity and permeability) and the low speed scanning of large surfaces.

The technical result of the invention is to improve the accuracy of determining the thickness of the coating b, and the extension of functionality (for additional definition of dielectr the character ε and magnetic μ permeabilities).

The invention consists in that in the method of determining the thickness of a dielectric coating on a conductive base, which consists in creating an electromagnetic field in the volume-controlled dielectric material on a conductive substrate and subsequent registration of the change of transducer parameters characterizing the high-frequency field, sequentially excite the slow surface waves: two E-wave on different, but similar wavelengths λ_{G1}that λ_{T2}and one N-wave length λ_{G3}using a system of receiving vibrators with different base values of d between them is measured field strength E_{0}over a dielectric coating on the distance y_{0}and E(y) at distance in the normal plane relative to the direction of wave propagation, calculate the coefficients of the normal attenuation of surface slow waves α_{E1}that α_{E2}that α_{N}from the expression E(y)=E_{0}exp[-a(y)·y] and define magnetic μ and dielectric ε permeability and thickness b magnetodielectrics coverage of the formulas:

where β_{3}=- coefficient phase H - wave./p>

The essence of the proposed method of measurement magnetodielectrics parameters and thickness of spin coating on the metal is illustrated in the following (drawing). Using the device of the slow excitation of surface waves (mouthpiece) 1 along the dielectric coating 3 on a conductive metal substrate 2 sequentially excite the slow surface waves: two S-waves at different but similar wavelengths λ_{G1}that λ_{T2}and one N-wave length λ_{G3}Using a system of receiving vibrators 4 for dierent values of base d=y-y_{0}=Δy between measured field strength E_{0}over a dielectric coating on the distance y_{0}and E(y) at a distance y in the normal plane relative to the direction of propagation for each type of waves. Condition for the neglect of the influence of geometrical and electrical gradient of the studied layer is the measurement with a small base d between the receiving transducer (drawing) and at low altitude in_{0}.

The coefficients of the normal attenuation α_{E1}that α_{E2}that α_{H}calculated from the expression E(y)=e_{0}exp[-α(y)·y], considering α(y)=α=const.

Solve the system of equations:

determine MAGN is tnou permeability μ , dielectric ε and the thickness b magnetodielectrics coverage.

Analytical solution of the system of transcendental equations (1)...(3) provided thatwritten as a system of arithmetic equations:

The solution of system of equations (1)...(3) or (4)...(6)gives the values of the localized values ε, μ and b.

Translate foster vibrators in another point of the surface being examined, taking a step proportional to the gradient value of the attenuation coefficient, and repeat the previous measuring and computing algorithm.

Thus, the proposed method along with the determination of thickness to determine permittivity and magnetic permeability of the coating. As well as measuring the relative and does not depend on the distance of the vibrators from the surface, it does not require special measures the detuning from the gap, which increases accuracy and gives the ability to quickly scan the surface without moving the pathogen surface waves. The result of the measurement does not impact the change in electric conductivity and magnetic permeability of the substrate, since the penetration depth of electromagnetic waves in the depths of the conductive substrate is on the Lee microns (for example, for copper), which significantly (by several orders of magnitude) less than the measured thickness.

Microwave method for measuring magnetodielectrics parameters and thickness of spin coating on the metal, which consists in creating an electromagnetic field in the volume-controlled dielectric material on a conductive base and the subsequent registration of the change of transducer parameters characterizing the high-frequency field, characterized in that sequentially excite the slow surface waves: two S-waves at different but similar wavelengths λ_{G1}that λ_{T2}and one N-wave length λ_{G3}using a system of receiving vibrators with different base values of d between the measured intensity of the field E_{0}over a dielectric coating on the distance y_{0}and E(y) at distance in the normal plane relative to the direction of wave propagation, calculate the coefficients of the normal attenuation of surface slow waves α_{E1}that α_{E2}that α_{N}from the expression E(y)=E_{0}exp[-α(y)·y] and define magnetic μ and dielectric ε permeability and thickness b magnetodielectrics coverage of the formulas:

where - coefficient phase H-wave.

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