EP2027430A1 - Method for determining the layer thickness of an electrically conductive coating on an electrically conductive substrate - Google Patents
Method for determining the layer thickness of an electrically conductive coating on an electrically conductive substrateInfo
- Publication number
- EP2027430A1 EP2027430A1 EP07729503A EP07729503A EP2027430A1 EP 2027430 A1 EP2027430 A1 EP 2027430A1 EP 07729503 A EP07729503 A EP 07729503A EP 07729503 A EP07729503 A EP 07729503A EP 2027430 A1 EP2027430 A1 EP 2027430A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- current sensor
- eddy current
- voltage
- induced voltage
- air
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
- G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
- G01B7/10—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using magnetic means, e.g. by measuring change of reluctance
- G01B7/105—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using magnetic means, e.g. by measuring change of reluctance for measuring thickness of coating
Definitions
- the invention relates to a method for determining the layer thickness of an electrically conductive coating which is applied to an electrically conductive substrate of a test object.
- Non -destructive methods are required for numerous material tests .
- the surfaces of metal parts are often exposed to an environment that causes corrosion, oxidation, diffusion, and other aging processes.
- the surfaces of such a substrate are provided with one or more protective layers.
- the protective layers are also, albeit to a lesser extent, exposed to external influences. But internal influences can also trigger aging processes. In the boundary layers between the
- Substrate and the coating take place physical and chemical ⁇ cal reactions, such as diffusion and oxidation, through which the quality of the coating changes.
- US Pat. No. 6,377,039 B1 discloses a system for determining properties of a coated substrate.
- the test object is exposed to an electromagnetic alternating field with adjustable frequency.
- eddy currents are induced in the test object.
- the result of the eddy currents sired electromagnetic field and its induced voltage clamping ⁇ is detected.
- the frequency spectrum of the induced voltage is determined.
- the layer thickness is made available to the user as a function of the measurable variables, so that the layer thickness can be determined indirectly.
- the data set with the impedances or material-induced stresses in the eddy current probe is expanded depending on the frequency, layer thickness and electrical and magnetic properties of the layers.
- the impedances or voltages are represented in the complex plane as so-called lattice structures.
- the lattice structures arise from two approximately vertically intersecting groups of curves.
- a curve is created by the variation of a first parameter with fixed values for all other parameters.
- the family of curves by another value of a second Para ⁇ meters.
- the grid now arises by connecting the impedances for a given value of the first parameter and a variable value of the second parameter.
- the method according to the invention comprises the following steps: a) detecting the induced voltage in an eddy current sensor in air as a function of the frequency of a field of excitation, b) providing a plurality of coated reference objects, each comprising a substrate and a Beschich ⁇ tion of the same Materials such as the substrate and the coating of the test article, wherein the reference articles have different known layer thicknesses, c) detecting a reference voltage as a function of the frequency of the exciter field for each reference object with the eddy current sensor, d) determining a material-induced voltage from the reference voltage and the induced voltage of the eddy current sensor in air as a function of the frequency for each reference object, e) forming a normalized amplitude of the material-induced voltage as a function of the frequency for each reference object, f) establishing a calibration curve representing the no rmtechnisch Ampli amplitude ⁇ the material-induced voltage as a function of the layer thickness of the coating is, g tand)
- the essence of the invention is that, on the one hand, by detecting the reference voltage in step c) and, on the other hand, by normalizing the material-induced voltage in step e), those properties which depend, for example, on the properties of the eddy current sensor or on the exciting current are eliminated.
- This allows the use of a structurally simple measuring device. It can be used eddy current sensors, which are constructed of commercially available components.
- the material-induced voltage is the difference vector in the complex voltage plane between the vector of the reference voltage and the vector of the induced voltage of the eddy current sensor in air.
- the amplitude and / or the phase of the complex materialindu ⁇ ed voltage can be determined.
- At least one uncoated reference object is provided, from which a further reference voltage is detected as a function of the frequency of the exciter field with the eddy current sensor. This can compensate for influences that are due to the substrate.
- a further material-induced voltage from the further reference voltage and the induced voltage of the eddy current sensor in the air is determined by the uncoated reference object.
- the material-induced voltage of the uncoated reference article of the Diffe ⁇ ence vector in the complex voltage level between the vector of the further reference voltage and the vector of the induced voltage of the eddy current sensor to the air is provided. Since ⁇ with is used for the uncoated reference object, the moving ⁇ che measuring methods as reference coated objects.
- step a) it is further determined in step a) at which frequency or at which frequencies in the eddy current sensor a resonance or resonances occur.
- the calibration curve is created for such a frequency at which no resonances occur in the eddy current sensor. This will ensure that the
- Eddy current sensor behaves linearly with respect to the relevant variables.
- the eddy current sensor used comprises a flexible sheet and at least one coil. Due to the flexible patch, the eddy current sensor can be connected to the
- the eddy-current sensor used has at least one coil which is used both as an exciter coil and as a detector coil. This is a particularly simple and inexpensive construction.
- the eddy current sensor used may have at least one separate exciter coil and at least one separate detector coil. The influence of the excitation ⁇ stream is less on the measurement.
- the employed eddy current sensor having a coil is formed as a flat conductor track at least the up on the flexible face piece ⁇ is introduced.
- the eddy current sensor can be adapted to the structure of the surface of the test object with high accuracy.
- the conductor track of the coil is formed spirally. This can generate a particularly strong magnetic field.
- the conductor track of the coil may also have a meandering shape.
- the connection terminals may be arranged outside the coil is ⁇ so that between the coil and the coating is no disturbing part.
- the substrate of the Referenzge ⁇ genstands with the substrate of the test object is identical. This reduces the influence of the substrate. Gleichzei ⁇ tig characterized the influence of the coating increases on the measurement.
- FIG. 1 is a schematic plan view of a first exporting ⁇ approximate shape of an eddy current sensor for the process according OF INVENTION ⁇ dung
- FIG. 2 is a schematic plan view of a second exporting ⁇ approximate shape of the eddy current sensor for the process according OF INVENTION ⁇ dung
- FIG. 1 is a schematic plan view of a first exporting ⁇ approximate shape of an eddy current sensor for the process according OF INVENTION ⁇ dung
- FIG. 2 is a schematic plan view of a second exporting ⁇ approximate shape of the eddy current sensor for the process according OF INVENTION ⁇ dung
- FIG. 3 is a schematic plan view of a third exporting ⁇ approximate shape of the eddy current sensor for the inventions dung modern methods
- FIG. 4 is a schematic plan view of a fourth exporting ⁇ approximate shape of the eddy current sensor for the process according OF INVENTION ⁇ dung,
- FIG. 5 is a diagram of the phase of a complex voltage as a function of frequency
- FIG. 6 is a schematic representation of differential vectors in the plane of the complex voltage
- FIG. 7 is a graph of normalized amplitude of a material-induced voltage versus frequency
- FIG. 8 is a graph of a calibration curve, which represents the amplitude, normalized with respect to the material-induced voltage as a function of the layer thickness
- FIG. 9 shows the diagram of the calibration curve from FIG. 8, in which a measured value is plotted and from this the layer thickness is determined graphically, and
- FIG. 10 is an equivalent circuit diagram and a schematic sectional ⁇ intention of the eddy current sensor and theticians ⁇ tands.
- FIG. 1 shows a schematic plan view of a first guide From ⁇ form an eddy current sensor, the extension for the proper OF INVENTION ⁇ method is usable.
- the eddy current sensor comprises a flexible sheet 10, on which a coil 12 is applied.
- the coil 12 is formed as a spiral conductor ⁇ path.
- On the sheet 10 is located au ⁇ ßerrenz the coil 12 at one end of the conductor track, a first terminal 14 within the coil 12 is located at the other end of the strip conductor, a second connection terminal 16.
- the coil 12 is provided as an excitation coil and also as a detector coil.
- FIG. 2 is a schematic plan view of a second embodiment of the eddy current sensor.
- the second embodiment of the eddy current sensor comprises a flexible sheet 10, on which a coil 18 is applied.
- the coil 18 is alsobil ⁇ det as a meandering conductor.
- the first connection terminal 14 and the second connection terminal 16 are located in each case at the two ends of the meander-shaped conductor track of the coil 18.
- the connection terminals 14 and 16 are spaced apart from the turns of the coil 18. This has the advantage that the eddy current sensor can be arranged on a test object so that the terminals 14 and 16 have no contact with the test object.
- the coil 18 is provided both as an excitation coil and as a Detek ⁇ torspule.
- the constructive effort is low, because only one coil erforder ⁇ is Lich, who holds two functions, namely as excitation coil and a detection coil.
- FIG. 3 shows a schematic plan view of a third embodiment of the eddy current sensor for the method according to the invention.
- the third embodiment of the eddy current sensor also includes a flexible face piece 10.
- On the FLAE ⁇ chen Culture 10 is an excitation coil 20 and a detection coil 22 is applied.
- the exciter coil 20 and the detector coil 22 are formed as helical conductor tracks.
- the Detek ⁇ torspule 22 is located inside the excitation coil 20.
- At the two ends of the conductor track of the excitation coil 20 are the first connecting terminal 14 and the second connection 16.
- At the ends of the track of the detector coil 22 are a third terminal 24 and a fourth terminal 26th
- FIG. 4 is a schematic plan view of a fourth embodiment of the eddy-current sensor.
- the fourth embodiment of the eddy current sensor comprises a flexible sheet 10.
- an excitation coil 28 and a detector coil 30 is applied on the sheet 10.
- the excitation coil 28 and the detector coil 30 are formed as meandering conductor tracks.
- the excitation coil 30 is located within the detector coil 28.
- At the two ends of the trace of the exciter coil 28 are the first terminal 14 and the second terminal 16.
- At the ends of the trace of the detector coil 30 are the third terminal 24 and the fourth terminal 26th
- the terminals 14, 16, 24 and 26 are spaced from the turns of the coils 28 and 30.
- the vortex ⁇ current sensor can be arranged on the test object so that the terminals 14, 16, 24 and 26 have no contact with the test object.
- eddy current sensors are preferably formed as planar coils.
- the patch 10 is flexible in all four embodiments so that the eddy current sensors are geometrically adaptable to the surface of the test article.
- the conductor tracks of the coils 12, 18, 20, 22, 28 and 30 are preferably made of copper.
- the patch 10 is made of Kapton foil, for example.
- an eddy-current sensor is selected which is suitable for a test object.
- the voltage U (air, ⁇ ) on the coil 12 or 18 or on the detector coil 22 or 30 is detected as a function of the frequency ⁇ , when the eddy current sensor is in the air. It also determines those frequencies at which resonances occur. These frequencies are not used in the later analysis since the eddy current sensor does not behave linearly at these frequencies.
- FIG. Figure 5 is a graph showing the phase of the detected complex voltage as a function of frequency.
- the function value corresponds to the tangent function of the phase.
- a first characteristic 32 relates to a measurement in which the eddy current sensor is in the air.
- a second characteristic 34 relates to a measurement in which the eddy current sensor is arranged on a special alloy.
- a third characteristic 36 represents a measurement in which the eddy current sensor is located on an aluminum sample. In this example resonances occur in two places. The frequency range between 4 MHz and 6 MHz, however, is free of resonances, so that this frequency range is particularly suitable.
- the reference articles each have a coating with different layer thicknesses.
- the layer thicknesses can be measured optically, for example, and are thus known.
- At least one reference item is uncoated.
- the coating of the reference Jacobs ⁇ tände is made of the same material as the Be ⁇ coating of the test object.
- the eddy current sensor detects a reference voltage U (x, ⁇ ) as a function of the frequency. Between the reference voltage U (x, ⁇ ) and the voltage U (air, ⁇ ) at which the eddy current sensor is in the air, the difference vector in the plane of the complex voltage is determined. This difference vector corresponds to a complex material-induced voltage U mat (x).
- FIG. 6 is a schematic representation of the relevant voltage vectors in the complex voltage plane.
- the two Cartesian coordinates correspond to the real part or the imaginary part of the voltage.
- a vector U (air, ⁇ ) corresponds to the voltage at which the vortex ⁇ current sensor is in the air.
- the reference voltage U (x, ⁇ ) is also shown as a vector.
- the differential ⁇ vector of the above two vectors corresponds to the material mat induced voltage U (x).
- the normalized amplitude for the material-induced voltage is formed.
- FIG. 7 shows the normalized amplitude
- Each characteristic corresponds to a specific layer thickness of the coating of the reference object.
- the lowest characteristic ⁇ line corresponds to the uncoated reference object.
- one or more calibration curves are created.
- the calibration curves represent the normalized amplitudes for the material-induced voltage as a function of the layer thickness.
- the calibration curves are calculated from the characteristic field according to FIG. 7 determined. For this purpose, a bestimm ⁇ te frequency is selected, which is outside the resonance range. The function values at this frequency are assigned to the known layer thicknesses.
- FIG. 8 is an example of the calibration curve Darge ⁇ represents. This calibration curve is shown in FIG. 7, if the Function values can be used for 4 MHz.
- FIG. 8 verdeut ⁇ light that is a linear relationship between the normalized amplitude and the layer thickness.
- both the substrate 50 and the coating are made of the same materials as in the reference counter ⁇ facts.
- the measurement is analogous to the measurements of the reference objects. It is first measured with the same vortex ⁇ current sensor, the complex voltage and then determines the difference vector. The difference vector corresponds to the material-induced voltage. Of these, the amplitude is formed and with respect to the amplitude
- FIG. 9 shows the calibration curve according to FIG. 8, which additionally has a determined numerical value 40 of the normalized amplitude for the test object 50.
- the test article 50 has a coating 52 of unknown layer thickness.
- the numerical value 40 for the normalized amplitude is about 1.017.
- the layer thickness of the coating 52 can be determined graphically therefrom. In this specific example, the layer thickness is 123 ⁇ m.
- the calibration curve and the underlying measured values can be stored in a computer system, so that the layer thickness can be calculated and output after input of the amplitude by means of a suitable EDP program.
- the equivalent circuit diagram comprises an inductance L 0 , an AC voltage source U 0 and a resistor R 0 , which are connected in series and form an exciter circuit.
- the electrically conductive coating 52 is characterized by a Ri and an inductance Li representable, which are connected in Rei ⁇ hey.
- the substrate 50 is formed by a reflection ⁇ stand Rb and an inductance L b be displayed, which are connected in series.
- Mi is the mutual inductance in the coating 52
- M 2 is the mutual inductance in the coated substrate 50
- Ii is the current in the coating 52
- I 2 is the current in the substrate 50.
- IW (X) I err (Mi ⁇ ) 2 / (j ⁇ Li + Ri) + I err (M 2 CO) 2 / (j ⁇ > L b + R b ). (Ia)
- IW (X) I err (C0 2 Mi 2 / Ri + C ⁇ W / R f a).
- IW (b) IerrC0 2 M 3 2 / R b, (3)
- M 3 strat the mutual inductance in the uncoated Sub ⁇ is fiftieth Since the uncoated substrate 50 from the surfaces moving ⁇ material as the uncoated substrate 50, The material-dependent variables L b and R b can also be used. The mutual inductance M 3 of the uncoated Sub ⁇ strats 50 is different from the mutual inductance M 2 of the coated substrate 50 due to the different spacings between the substrate 50 and the eddy current sensor.
- the mutual inductances Mi, M 2 and M 3 depend on the distance between the eddy current circuit and the eddy current sensor. Therefore, the ratios between the mutual inductances in Equation (4) are not equal to one.
- the Jacobin- hang inductances of the technical data of the coils so that the calibration curve and the actual measurement with the sel ⁇ ben eddy current sensor must be carried out.
- the process according to the invention is a particularly simple and rapid method.
- the design effort for imple ⁇ ren of the inventive method is relatively ring ge ⁇ .
- Prototypes of modified substrates 50 and / or coatings can be tested within a short time. It is not necessary for company-internal information to be passed on in advance to external companies, so that special software and / or hardware can be provided. Thus, the manufacturer or developer of the test article is able to perform the inventive method within the company, so that no confidential information must be given to external companies.
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE102006025356A DE102006025356A1 (en) | 2006-05-31 | 2006-05-31 | Method for determining the layer thickness of an electrically conductive coating on an electrically conductive substrate |
PCT/EP2007/055074 WO2007137997A1 (en) | 2006-05-31 | 2007-05-25 | Method for determining the layer thickness of an electrically conductive coating on an electrically conductive substrate |
Publications (1)
Publication Number | Publication Date |
---|---|
EP2027430A1 true EP2027430A1 (en) | 2009-02-25 |
Family
ID=38328278
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP07729503A Withdrawn EP2027430A1 (en) | 2006-05-31 | 2007-05-25 | Method for determining the layer thickness of an electrically conductive coating on an electrically conductive substrate |
Country Status (7)
Country | Link |
---|---|
US (1) | US20090251137A1 (en) |
EP (1) | EP2027430A1 (en) |
JP (1) | JP2009539086A (en) |
CN (1) | CN101460808A (en) |
DE (1) | DE102006025356A1 (en) |
RU (1) | RU2008152770A (en) |
WO (1) | WO2007137997A1 (en) |
Families Citing this family (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8106651B2 (en) * | 2008-04-17 | 2012-01-31 | Novellus Systems, Inc. | Methods and apparatuses for determining thickness of a conductive layer |
GB0820930D0 (en) * | 2008-11-17 | 2008-12-24 | Dvs Techology Ltd | Coating thickness measurement |
WO2010105668A1 (en) | 2009-03-17 | 2010-09-23 | Abb Ab | A method and an apparatus for measuring the thickness of a metal layer provided on a metal object |
JP5730747B2 (en) * | 2010-12-10 | 2015-06-10 | 株式会社荏原製作所 | Eddy current sensor and polishing method and apparatus |
CN102080949B (en) * | 2009-12-01 | 2013-11-06 | 无锡华润上华半导体有限公司 | Silicon epitaxial film thickness measuring method and device |
US9194687B1 (en) * | 2010-02-04 | 2015-11-24 | Textron Innovations Inc. | System and method for measuring non-conductive coating thickness using eddy currents |
FR2981741B1 (en) * | 2011-10-20 | 2013-11-29 | Messier Bugatti Dowty | METHOD FOR MEASURING THE THICKNESS OF A COATING LAYER BY INDUCING MAGNETIC FIELDS |
CN102735152B (en) * | 2012-06-06 | 2014-08-27 | 电子科技大学 | Calibrating and measuring method of microwave absorbing coating thickness measuring instrument |
CN103852000B (en) * | 2014-03-24 | 2016-05-25 | 电子科技大学 | The eddy current detection method of multilayer conductive coating layer thickness and device |
DE102016205495B4 (en) * | 2016-04-04 | 2022-06-09 | Volkswagen Aktiengesellschaft | Measuring device and method for determining layer thickness and associated reference body and calibration body |
CN109580771B (en) * | 2018-12-19 | 2022-10-18 | 四川沐迪圣科技有限公司 | Double square excitation flexible eddy current array sensor |
DE102021001964A1 (en) * | 2021-04-14 | 2022-10-20 | Giesecke+Devrient Mobile Security Gmbh | Process for quality control of a metallic foil of a card body |
CN114076795B (en) * | 2021-11-16 | 2023-09-01 | 中国人民解放军空军工程大学 | Alternating induction type flexible vortex array sensor and crack monitoring method thereof |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5017869A (en) * | 1989-12-14 | 1991-05-21 | General Electric Company | Swept frequency eddy current system for measuring coating thickness |
US5416411A (en) * | 1993-01-08 | 1995-05-16 | Lockheed Fort Worth Company | System and method for measuring the thickness of a ferromagnetic layer |
JP2000502189A (en) * | 1995-12-22 | 2000-02-22 | シーメンス アクチエンゲゼルシヤフト | Method and apparatus for determining thickness of conductive film |
DE19652750C2 (en) * | 1996-12-18 | 1999-12-02 | Bosch Gmbh Robert | Method for determining a thickness of a layer of electrically conductive material |
US6377039B1 (en) * | 1997-11-14 | 2002-04-23 | Jentek Sensors, Incorporated | Method for characterizing coating and substrates |
-
2006
- 2006-05-31 DE DE102006025356A patent/DE102006025356A1/en not_active Ceased
-
2007
- 2007-05-25 EP EP07729503A patent/EP2027430A1/en not_active Withdrawn
- 2007-05-25 US US12/227,527 patent/US20090251137A1/en not_active Abandoned
- 2007-05-25 JP JP2009512555A patent/JP2009539086A/en not_active Abandoned
- 2007-05-25 WO PCT/EP2007/055074 patent/WO2007137997A1/en active Application Filing
- 2007-05-25 RU RU2008152770/28A patent/RU2008152770A/en not_active Application Discontinuation
- 2007-05-25 CN CNA2007800201899A patent/CN101460808A/en active Pending
Non-Patent Citations (1)
Title |
---|
See references of WO2007137997A1 * |
Also Published As
Publication number | Publication date |
---|---|
DE102006025356A1 (en) | 2007-12-06 |
CN101460808A (en) | 2009-06-17 |
US20090251137A1 (en) | 2009-10-08 |
JP2009539086A (en) | 2009-11-12 |
WO2007137997A1 (en) | 2007-12-06 |
RU2008152770A (en) | 2010-07-10 |
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