DE102008053184B4 - Measuring device for E-field measurement in the near field - Google Patents

Abstract

Measuring device for indirect, non-galvanic contacting measurement and detection of charge distributions and charge shifts within a DUT due to their own inhomogeneities and different distribution of electrically conductive, semiconducting and / or insulating material components, coatings, alloys, mixtures, formations, densifications, deformations and other physical or chemical Treatments of the specimen presenting themselves with adequate physically different relative permittivities in the specimen, the specimen (3) being introduced into a constant, homogeneous electric near-E field generated by means of a frequency generator (2) between two capacitor plates (1) is simultaneously positioned above or below the specimen (3) an indirectly measuring E-field probe (4) or an E-field probe array, consisting of a plurality of individual probes (4) at a defined distance, wherein the at the capacitor plates (2) consist of electrically good conductive material, are designed to be exactly flat and flat and plane-parallel, exactly one above the other, fixed without offset, at a defined distance from each other, with a first thin support plate (10) made of an electrically insulating material very low ...

Description

The The invention relates to the construction of a measuring device an E-field measuring method, for the analysis, measurement and localization of defects, inhomogeneities, cracks, Bubbles, voids etc. within flat or voluminous, conductive, semiconducting or insulating bodies, plates, layers, Coatings, films or the like physical or biological bodies.

in this connection can the examinee either indirectly a constant, homogeneous E-field in the near range exposed or direct, galvanic contacting with a constant current be charged. Analogous to the geometrically distributed in the specimen body Subaddresses, with their corresponding specific Teilpermittivitäten place in an indirectly imprinted homogeneous E-field influence or a directly impressed constant current adequate spatially resolved Field, charge and current distributions with corresponding field density changes one.

Thus, it is an object of the invention, these field density changes spatially resolved on the specimen body indirectly by means of a probe to detect selectively or by means of a probe array as an area, with the aim of a simple, indirect, very inexpensive, for a 100% -supplier test online-enabled, safe, Non-interfering measuring device to provide with a particle detection and resolution up to 0.2 mm, with measuring times <2 sec, for measuring surfaces up to 5 000 mm ² .

Known Method for material analysis, such as X-ray, computed tomography, Ultrasound, eddy current are all non-contacting methods, However, either very expensive, susceptible to interference, or often not online-enabled.

Around To record impedance or admittance values of test objects, areas or volumes with spatial resolution, It is also necessary to distribute them geometrically to contact. That means in a direct measuring process have to depending on grid and area up to 100 springy mechanical contacts simultaneously or consecutively on the test object apply, with a repeat accuracy of 0.0x mm. This requires a very high requirement on service life, mechanics, friction, abrasion and Operational reliability.

Directly contacting procedures as in DE 102 35 124 A1 and DE 10 2006 044 962 A1 meet almost all the above requirements. However, they are not suitable for permanent online operation due to their direct contact with the test object with regard to service life, abrasion, contact reliability, contact failure, friction and risk of short circuits.

In the DE 102 35 124 A1 and DE 10 2006 044 962 A1 In order to detect inhomogeneities and defects in planar or voluminous physical materials by means of direct 4-wire / Kelvin contact, the impedance changes are measured diffe rentiell and represented as 2D and 3D graphics as resistance mountains. A spatially resolved detection of the defects is so possible there. The DE 10 2006 044 962 A1 also mentions the possibility of using different types of measurement and measurement frequencies. However, an indirect measurement or detection of the impedance changes is not described.

In the DE 295 13 955 U1 an indirectly measuring E-field probe device is described which tests a test piece for EMC immunity by means of RF burst generator E field interference pulses in the MHz range, in order to detect conducted and line-bound defects on printed circuit boards and ICs. The measuring device is a point probe for single measurement. The E-field is not homogeneous. The interference frequency is very high (MHz) and pulsed. A measuring area of 5 000 mm ² can not be detected in <2 sec. The measuring device can only be used for laboratory operation and is not online-capable for manufacturing operations.

Another device for measuring surface resistances is in WO 01/90749 A2 and similarly in the WO 01/90730 A2 and the WO 01/19972 A1 specified. In this known device, which is based on an indirect contacting method for the measurement and analysis of surface properties of conductive, semiconducting, physical and chemical surfaces, a contact module assembly of a probe with the usual four Kelvin contacts is indirectly assigned to the measuring surface using a mechanically oscillating capacitor plate whose charge displacement drives an alternating current through the test specimen. The interaction between the capacitor, the test specimen and the air gap results in a contact potential as a measure of the surface resistance, which is further processed in a connected evaluation device. The measuring surface on the test specimen is limited by the small surface of the oscillating probe and can only measure different specimen surfaces one after the other with a time delay. Thus, the measuring surface located on a table which can be moved in the xy direction is moved relative to the contacts of the measuring probe into the individual measuring positions by means of a positioning device controlled by a control device, so that relatively long measuring times result. The proposed measurement principle also makes it difficult to ensure accurate measurement results because the measurements are very sensitive to air gap tolerances, shocks, noise, temperature, humidity, and similar environmental influences.

The DE 198 28 207 A1 shows a device for determining the residual moisture content of the laundry in a tumble dryer by means of a capacitor. In this case, the components of the capacitor by components of the dryer, such as. B. the drum formed. With these measures, only the global state of drying of the laundry in the drum can be detected. On the other hand, no inhomogeneities within a test piece are measurable.

The DE 692 13 301 T2 shows an apparatus for measuring the properties of a multiphase flow in a pipeline across the cross-section of the pipeline, wherein within the conduit a pair of immovable parallel plates are arranged in line with the flow and at least one of the plates has a plurality of segmented electrodes and the other Plate has at least one continuous electrode. In this case, the measurement signal of the plates themselves is evaluated in order to carry out a continuous measurement of the flow pattern velocity. From the capacitance measurement, a dielectric constant of the fluid between the plates is calculated. Even such a measure is insufficient for an accurate spatially resolved detection of charge distributions within a test sample.

In the DE 93 20 446 U1 is a capacitive measuring cell for non-contact measurement of volume, density and composition of materials specified, which is designed as a plate capacitor. Between the plates a Volumenmes solution is made in the chamber formed. Even with such a structure, it is difficult to reliably measure local charge distributions and charge shifts within a sample.

The DE 44 13 840 C2 shows a further device for non-contact measurement in an electric field between electrode surfaces, wherein an alternating voltage is detected on an electrode whose amplitude is characteristic of a guided between the electrodes through measurement object. This device is used to measure the thickness of a job, in particular to determine the moisture contained, wherein it is stated that the position of the substrate between the electrodes is not critical (see column 4, lines 26 to 32). Again, however, it is difficult to determine areal distributed inhomogeneities in a specimen.

Of the Invention is based on the object of providing a measuring device, by means of an indirect, non-contacting measuring method the impedance or admittance gradients and their distribution within of a test object captured and represented.

outgoing from the physical proportionality between the complex electrical Admittance with conductance Gx and the capacity Cx of a medium to the complex relative permittivity This object is achieved with the features of claim 1. in this connection is provided that either by means of a frequency generator a homogeneous E-field (AC or DC) is generated in a plate capacitor, with constant frequency and adjustable from 0 Hz ... 1 MHz, and the examinee is inserted into the homogeneous electric field. According to the distribution of Partial impedances / partial admittances of the device under test arises by the electrical polarization effect a corresponding distribution the field line density partially in the test specimen. Or as a variant for indirect impression an outer E-field can the candidate be impressed by direct contacting a constant current (AC or DC), the produces an identical field line distribution as described above.

These Field distribution can be captured by moving at a defined distance above / below the examinee an E-field probe / E-field array is introduced.

The E-field probe consists of a small miniaturized capacitor the spatially resolved in the x and y direction within the electrode plates geometric can be variably adjusted.

Particularly according to the invention advantageous is a probe arrangement as an E-field probe array, consisting of n × m single-E field probes, depending on the specimen geometry and design changeable designed can be. Here you can Any individual probes / capacitor plates in a grid up to 3 mm and smaller in the array. Every single measuring probe is a separate amplifier assigned. This is a simultaneous, synchronous measurement of a field area of the test piece possible. According to the geometric Arrangement of the individual electrodes is a spatially resolved detection the field strength gradients guaranteed. Each individual measuring probe of the array is connected to an evaluation and amplifier unit and can be read in parallel and / or serially. That's how measuring times are of <2 sec. possible.

Because of the strong sensitivity of e-fields, especially at close range, as well as the low transmission power of the interference field and the very low Measuring voltage of the individual probes shielding is absolutely necessary. Similarly, send and Test leads, as well as the amplifier units to shield and interference-proof perform.

The Invention will now be described with reference to exemplary embodiments with reference closer to the drawings explained. Show it:

1A Plate capacitor with homogeneous E-field with frequency generator,

1B DUT with current line distribution, and directly contacted constant current source,

2 DUT in E-field with charge shift,

3A Overall structure of the measuring arrangement with homogeneous E-field,

3B Overall structure of the measuring arrangement with constant current source,

4 Embodiments of the measuring probe,

5 Embodiments of a Probe Array with Plate Capacitor,

6 and 7 Embodiments of a probe array with coaxial capacitor design.

1A shows a schematic representation of a plate capacitor 1 , which optionally consists of a frequency generator 2 with DC voltage or with an AC voltage, variably adjustable to a constant frequency of 0 Hz ... 1 MHz, is operated. Between the capacitor plates, a homogeneous field is created, with straight and parallel field lines.

1B shows a schematic representation of a test specimen 3 which is directly connected to a constant current source 2 ' connected. The constant current source 2 ' can be operated with direct current or alternating current and with variably adjustable frequency. In the test piece 3 is a distribution of the streamlines indicated.

2 shows a schematic representation of a test specimen 3 placed in the impressed homogeneous E-field of the plate capacitor 1 is inserted. The examinee 3 consists of a material with the relative permittivity ε2 3.2 , In the middle of examinee 3 there is a simulated error with the permittivity ε1 3.1 , As a result of the different permittivities ε1 and ε2, a charge shift corresponding to the local fault location sets in, which causes a change in the constant homogeneous field line distribution at this point.

A shield 6 , such as Faraday cage, causes foreign field influences to be withheld by operators, 50 Hz grid, gauges and others.

3A shows an example of the overall construction of the measuring arrangement, with plate capacitor 1 , Frequency generator 21 , Examinee 3 , Measuring probe 4 , Measuring amplifier with measured value processing, control and interface 5 and shielding housing 6 ,

For the actual measuring unit, the frequency generator 2 and for the measurement gain 5 are separate Faraday cage units 12 . 13 and 14 intended.

Across from 2 here is a single probe 4 , also called a probe array (see 5 . 6 and 7 ) with n × m-arrayed single probes 4 can be led out, in the impressed E-field between the capacitor plate 1 and the examinee 3 brought in. By moving the probe 4 parallel to the test object 3 So the finest local field changes can be measured.

3B shows an example of the overall construction of the measuring arrangement with a constant current source 22 , Examinee 3 , Measuring probe 4 and measuring amplifier with measured value processing, control and interface 5 ,

4 shows possible embodiments of the measuring probe 4 ,

In 4.1 this is shown as a miniaturized plate capacitor. The shield line 7 is to be as close as possible to the capacitor plates in order to shield parasitic conduction capacitances.

4.2 shows a side view of a possible embodiment of the probe 4 as a plate capacitor, shown as a printed circuit board or printed circuit board foil with double-sided copper coating. The electrically effective capacitor plate elements 4.11 and 4.12 are here exactly overlapping each on the top and bottom of the substrate, as etched portions of the copper coating.

4.3 shows the design of a measuring probe 4 as plate capacitor in round design.

In 4.4 is a measuring probe 4 executed in a coaxial design, consisting of a variant with concentric outer annular surface and an inner circular surface.

5.1 and 5.2 show, for example, a probe array, similar 4.2 here, however, as a 4 × 4 matrix in a schematic representation, consisting of 4 × 4 A zelmesssonden 4 , Here are the single probes 4 geometrically to each other, in a defined grid spacing to each other in the x and y direction to the measuring surface, arranged as a probe matrix. With such an arrangement, it is possible to make the specimen contour geometrically so that the entire surface or particularly interesting, critical Surfaces of the test specimen to be detected by individual probes. According to the invention, it is hereby particularly advantageous that all measuring voltages of the individual probes can be detected at the same time. Measuring times of <1 sec can be realized in this way. It is necessary here that each measuring channel has its own measuring amplifier unit. Thus, a parallel query of the 4 × 4 measured values can take place simultaneously.

In 5.1 and 5.2 Such an array arrangement is shown as area / plate capacitor design.

In 6 and 7 Such an arrangement is shown in coaxial design, such as a tube capacitor or similar design.

• 1. Messsondenarray: Es gibt keine Kontakt/Positionsfehler bei jeder Messung, da der Array-Körper massiv, als Einheit mit fest einander zugeordneten Einzelmesselementen ausgeführt ist.
• 2. Die Messsonde oder das Messsondenarray kann etwa mittels Passstifte in definierter Position zum Prüfling 3 fixiert werden. Somit sind reproduzierbare Messungen möglich. Die verschiedenen Prüflinge haben immer die gleichen geometrischen Positionen und können ohne Fehler verglichen werden.
• 3. Prüflinge werden nicht beschädigt oder verletzt durch indirekte berührungslose Messung.
• 4. Es gibt keine Kontaktprobleme, etwa durch Korrosion, Alterung, Beschädigung, Abrieb, Toleranz- und Positionsveränderung, Bruch der Federkontakte, Reibung oder Klemmung. Direkt kontaktierende Messeinheiten besitzen bis zu 50 ... 100 verschiedene federnde Messkontakte.
• 5. Messzeiten von < 1 sec für eine Gesamtfläche oder Teilfläche eines Prüflings sind mit einem erfindungsgemäß aufgebauten Messsonden-Array möglich.
• 6. Partikelerkennung, Fehler- und Inhomogenitäten: eine Partikel- und Risserkennung von 0,1 × 3 mm wurde an Versuchsobjekten nachgewiesen.
• 7. Die Lebensdauer der Messeinrichtung ist sehr hoch und wird durch keine mechanisch bewegten Teile begrenzt, sondern durch die Lebensdauer der elektrischen und elektronischen Bauelemente.
• 8. Ausfall, Störung, Redundanz: Durch Bereitstellung redundant verfügbarer Ersatzmodule ist bei Störung und Ausfall ein Bauteilwechsel in Minuten gewährleistet.
• 9. On-line-Fähigkeit für Fertigungsbetrieb: Infolge der Messfähigkeit zur Erkennung kleinster Risse von 0,1 mm, der extrem kurzen Messzeit von << 1 sec, des nicht störenden, störsicheren und preiswerten Aufbaus ist die Messeinrichtung für einen On-line-Fertigungseinsatz geeignet.

In summary, the invention provides the following advantages:

• 1. Probe array: There are no contact / position errors in each measurement, as the array body is solid, designed as a unit with dedicated single measurement elements.
• 2. The measuring probe or the probe array can be approximately by means of dowel pins in a defined position to the DUT 3 be fixed. Thus, reproducible measurements are possible. The different test pieces always have the same geometric positions and can be compared without errors.
• 3. DUTs are not damaged or injured by indirect non-contact measurement.
• 4. There are no contact problems, such as corrosion, aging, damage, abrasion, tolerance and position change, breakage of the spring contacts, friction or clamping. Direct contacting measuring units have up to 50 ... 100 different spring-loaded measuring contacts.
• 5. Measuring times of <1 sec for a total area or partial area of a test object are possible with a measuring probe array constructed according to the invention.
• 6. Particle detection, error and inhomogeneities: a particle and crack detection of 0.1 × 3 mm was detected on test objects.
• 7. The life of the measuring device is very high and is limited by no mechanical moving parts, but by the life of the electrical and electronic components.
• 8. Failure, malfunction, redundancy: By providing redundantly available replacement modules, a component change in minutes is ensured in the event of failure and failure.
• 9. On-line capability for manufacturing operation: Due to the measuring ability for the detection of smallest cracks of 0.1 mm, the extremely short measuring time of << 1 sec, the non-interfering, interference-free and inexpensive construction, the measuring device for an on-line Suitable for production use.

Claims (6)

Measuring device for indirect, non-galvanic contacting measurement and detection of charge distributions and charge shifts within a DUT due to their own inhomogeneities and different distribution of electrically conductive, semiconducting and / or insulating material components, coatings, alloys, mixtures, formations, densifications, deformations and other physical or chemical Treatments of the device under test that represent adequate physically different relative permittivities in the device under test, whereby the device under test ( 3 ) into a constant, homogeneous electric near-E field, generated by means of a frequency generator ( 2 ), between two capacitor plates ( 1 ) and at the same time above or below the examinee ( 3 ) an indirectly measuring E-field measuring probe ( 4 ) or an E-field probe array consisting of a plurality of individual probes ( 4 ) is arbitrarily positioned at a defined distance, wherein the two capacitor plates ( 2 ) consist of electrically good conductive material, are designed to be exactly flat and flat and plane-parallel, exactly one above the other, without offset, are firmly fixed to each other at a defined distance, with a first thin carrier plate ( 10 ) of an electrically insulating material with very low permittivity, between the capacitor plates ( 2 ) is guided parallel to the plane and at the same distance within the capacitor plates slidably and on which the test specimen ( 3 ) is placed and fixed and wherein a second thin carrier plate ( 11 ), the measuring probe ( 4 ) or the probe array carries with the individual probes, of an electrically insulating material with very low permittivity between upper or lower capacitor plate ( 2 ) and the first carrier plate ( 10 ) is guided plane-parallel and displaceable with the same distance or wherein both support plates are in the case of the probe array insulating, rigidly connected at the same distance from each other. Measuring device for indirect, non-galvanic contacting measurement and detection of charge distributions and charge shifts within a DUT due to their own inhomogeneities and different distribution of electrically conductive, semiconducting and / or insulating material components, coatings, alloys, mixtures, formations, densifications, deformations and other physical or chemical Treatments of the specimen presenting themselves with adequate physically different relative permittivities in the specimen, the specimen being placed on a first thin support plate ( 10 ) from an electrically conductive material with very low permittivity launched and fixed test specimen ( 3 ) with a constant current source ( 2 ' ) directly contacting and simultaneously above or below the test ling ( 3 ) an indirectly measuring E-field measuring probe ( 4 ) or an E-field probe array consisting of a plurality of individual probes ( 4 ), is arbitrarily positioned at a defined distance and wherein a second carrier plate ( 11 ) the measuring probe ( 4 ) or the probe array with the individual probes ( 4 ) carries or contains and the measuring probes ( 4 ) and their test leads are made of a material of very low permittivity. Device according to claim 1 or 2, characterized in that the measuring probe ( 4 ) is designed as a plate capacitor. Device according to one of claims 1 to 3, characterized in that optionally the capacitor plates ( 1 ), the carrier plates ( 10 and 11 ), the examinee ( 3 ) and the measuring probes ( 4 ) into a Faraday cage ( 12 ) are installed. Device according to one of claims 1 to 4, characterized in that the frequency generator ( 21 ) or the constant current source ( 22 ) in a separate Faraday cage ( 13 ) and the amplifier unit ( 5 ) in a separate Faraday cage ( 14 ) is installed. Device according to claims 4 or 5, characterized in that the Faraday cages ( 12 . 13 and 14 ) star-shaped with ground lines ( 9 ) are connected.