WO2014118383A2

WO2014118383A2 - Method for contacting an ultrasonic transducer; ultrasonic transducer component with contacted ultrasonic transducer for use in an ultrasonic test probe; ultrasonic test probe and device for the non-destructive testing of a test object by ultrasound

Info

Publication number: WO2014118383A2
Application number: PCT/EP2014/052091
Authority: WO
Inventors: York Oberdoerfer; Matthias Schulz; Marek Parusel
Original assignee: Ge Sensing & Inspection Technologies Gmbh
Priority date: 2013-02-04
Filing date: 2014-02-04
Publication date: 2014-08-07
Also published as: WO2014118383A3; DE102013101097A1

Abstract

The invention relates to a method for contacting an ultrasonic transducer (10; 10'; 10") for the non-destructive testing of a test object with a great material thickness by means of ultrasound. In this case, an ultrasonic transducer (10; 10'; 10") is provided that is divided into a plurality of individually activatable transducer segments (11; 11'; 11"; 11"'), wherein these transducer segments (11; 11'; 11"; 11'") are formed as concentric circles or rings, or sections thereof, and several groups of transducer segments (11; 11'; 11"; 11'") can be selectively chosen in such a way that a parallel activation of these transducer segments (11; 11'; 11"; 11'") in each case results in a circular active surface of the ultrasonic transducer (10; 10'; 10"). Furthermore, a printed circuit board (20) is provided on which several conductor paths run (21) that respectively extend between two sides (22; 23) of the printed circuit board (21). In order to form a damping body, the printed circuit board (21) is inserted into this damping body (40) in such a way that first conductor path (21) ends (24; 24',..., 24ⁿ) are exposed on one side (22) of the damping body (40), while associated second ends (25; 25',..., 25ⁿ) are exposed on the other side (23) of the damping body (40). Thus, the ultrasonic transducer (10; 10'; 10") can be connected to the damping body (40) in an orientation in which the printed circuit board (20) extends at an angle α to the ultrasonic transducer (10; 10'; 10") surface to be contacted, which is unequal to 0°, and at least a part of the first conductor path (21) ends (24; 24',...,24ⁿ) is contacted to the transducer segments (11; 11'; 11"; 11"') of the ultrasonic transducer (10; 10'; 10"), and at least a part of the second ends (25; 25',...,25ⁿ) is contacted to means for activating the ultrasonic transducer (10; 10'; 10") via the contacted conductor paths (21).

Description

METHOD FOR CONTACTING AN ULTRASONIC TRANSDUCER;

ULTRASONIC TRANSDUCER COMPONENT WITH CONTACTED ULTRASONIC TRANSDUCER FOR USE IN AN ULTRASONIC TEST PROBE; ULTRASONIC TEST PROBE AND DEVICE FOR THE NON-DESTRUCTIVE

TESTING OF A TEST OBJECT BY ULTRASOUND

The present disclosure concerns a method for contacting an ultrasonic transducer for the non-destructive testing of a test object with a great material thickness by means of ultrasound. The disclosure moreover relates to an ultrasonic transducer component for use in an ultrasonic test probe, wherein the ultrasonic transducer installed therein was contacted by means of the method according to the disclosure. An associated ultrasonic test probe and a device for the non-destructive testing of a test object with such a test probe are also disclosed.

A variety of methods for the non-destructive testing of a test object by means o ultrasound are known from the field of material testing. In pulse-echo methods, a short ultrasonic pulse generated by an ultrasonic transducer acting as a transmitter is suitably insonified into a test object so that it propagates in the test object. If the pulse hits a flaw in the test object (e.g. a discontinuity) or a geometric structure, the pulse is reflected at least partially by it. The reflected pulse is detected by means of an ultrasonic transducer. In this case, an ultrasonic transducer is frequently used both as a transmitter as well as a receiver. The position of the discontinuity in the test object can be deduced from the travel time between the insonifi cation of the pulse into the test object and the arrival of the reflected pulse at the receiver. The amplitude of the reflected pulse can be used to obtain information on the size of the discontinuity.

In standardized manual ultrasonic testing, two methods for assessing the size of a discontinuity have become established globally, i.e. the reference body method (DAC method, "distance-amplitude correction") and the DGS method ("distance-gain-(flaw) size"). Both methods are different as regards their mode of application, but not with respect to the fundamental physics of sound propagation and sound reflection on which they are based. In both methods, the tester determines the size (diameter) of a model reflector (cylindrical reflector in the DAC method, circular disk in the DGS method). The size thus determined is, in principle, not identical with the actual flaw size; it is therefore referred to as equivalent circular disk or cross hole diameter. If circular disk reflectors are used, the shorter term "equivalent reflector size" (ERS) has become established. That the actual flaw size does not correspond to the equivalent reflector size is due to the fact that the portions of the sound reflected by a natural flaw are additionally affected by the shape, orientation and surface properties of the flaw. Because further examinations in this respect are difficult and not very practicable in manual ultrasonic testing, the criteria for recording faults are tied to a certain equivalent reflector size in most specifications and guidelines for ultrasonic testing. This means that the tester determines in practice whether a detected fault reaches or exceeds the equivalent reflector size specified as a threshold value (registration threshold) in the documentation. In addition, he generally will have to carry out further inspections, for example with regard to the registration length, echo dynamics, etc. Even though the above-mentioned pulse-echo methods have been well-established methods in the field of material testing for years, their application to the testing of test objects with a great material thickness, e.g. in the case of thick- walled pressure or safety tanks with a great wall thickness, still requires a lot of effort today. This results in the necessity, when testing test objects with a great material thickness, of using test probes with a large transducer diameter D when testing sectors having a large distance from the coupling location, i.e. for the detection of deep flaws. In turn, however, they are not suitable for detecting near-surface defects. In practice, a plurality of different test probes is therefore always used in the testing of test objects with a great material thickness, such as, for example thick-walled cast containers or of long shafts. If a flaw is identified, an ultrasonic test probe is specifically selected for a quantitative flaw determination whose near-field length is approximately in the range of the distance between the coupling location and the flaw position. A consequence of this is that, on the one hand, a plurality of different test probes has to be kept in storage, which increases the technical expenditure; on the other hand, a change of the test probe increases the testing expenditure, which leads to cost disadvantages. Therefore, the applicant has developed, for test objects with a great material thickness, a method which, in its simplest form, is based on providing an ultrasonic test probe that is basically known from the prior art and which comprises an ultrasonic transducer that is in turn divided into a plurality of individually activatable transducer segments. In this case, the transducer segments form concentric circles or rings, or constitute sections of concentric circles or rings. In the prior art, such a transducer is referred to as "annular array" or "ring array".

For the improved method, at least one group of transducer segments of the ultrasonic transducer is activated in parallel in such a manner that the result is a circular active surface of the ultrasonic transducer that can function as an ultrasound transmitter and receiver. An ultrasonic inspection of the test object is then carried out with this circular "effective" ultrasonic transducer. The test can be carried out, for example, in accordance with the pulse-echo methods known from the prior art.

This method permits controlling the sound field generated by an ultrasonic test probe with an annular array and thus adapting it to the specific testing task by controlling the diameter of the active surface of the ultrasonic transducer. In this case, the active surface is considered to be the surface of the ultrasonic transducer that participates as a transmitter in generating the ultrasound when the transducer is activated, or which participates as a receiver in generating the signal when the transducer is activated. In the process, only a partial set of the transducer elements is activated, with the activation taking place in a phase-locked manner, in particular without a phase shift between the transducer elements. Accordingly, the beam is controlled through changing the diameter of the active surface of the ultrasonic transducer. Therefore, this method permits carrying out standardized inspection methods, such as in accordance with EN 583-2, which do not provide for the use of phased array test probes, with only a single ultrasonic test probe even on test objects with a great material thickness, for which a plurality of different test probes had to be used so far.

Consequently, the method requires the specific activation of individual transducer elements of a test probe, so that they also have to be contacted individually in order to be capable of being activated in parallel. In the context of contacting individual transducer segments it is known, for example from the field of linear test probes, that a flexible printed circuit board (PCB) in the form of a sheet is used, this PCB sheet extending parallel to the ultrasonic transducer surface to be contacted. The required conductor paths are applied to the sheet and contacted at the appropriate points to the segmented ultrasonic transducer.

In addition, it is known, for example in the case of test probes with 2D arrays, to contact a printed circuit board in the form of a flexible PCB sheet perpendicularly to the individual transducer elements. In this case, several sheets with conductor paths are provided, which sheets are separated from each other by means of individual damping bodies on the back having the same thickness.

Based on this prior art, it is desireable to provide a method for contacting a segmented ultrasonic transducer, with the individual transducer segments of the ultrasonic transducer being contacted to conductor paths of a printed circuit board in such a way that they can be activated selectively and in parallel. Furthermore, it is desirable to provide an associated ultrasonic transducer component for use in an ultrasonic test probe, wherein the ultrasonic transducer installed therein can be contacted by means of the method according to the invention.

Accordingly, the present invention provides a method according to the independent claim 1. Advantageous embodiments of the method are apparent from the dependent claims 2-13. Furthermore, the present invention provides an ultrasonic transducer component according to the independent claim 14. An advantageous embodiment of this component is apparent from claim 15. Claim 16 seeks protection for an associated ultrasonic test probe, while claim 17 seeks protection for a device for the ultrasonic testing with such a test probe. The method according to the invention serves for contacting an ultrasonic transducer for the non-destructive testing of a test object with a great material thickness by means of ultrasound and comprises at least the following steps: Providing an ultrasonic transducer divided into a plurality of individually activatable transducer segments, a) Providing a printed circuit board on which several conductor paths run; b) Forming a damping body into which the printed circuit board is inserted in such a way that first conductor path ends are exposed on one side of the damping body, while associated second ends are exposed on the other side of the damping body; c) Connecting the ultrasonic transducer to the damping body in an orientation in which the printed circuit board extends at an angle a to the ultrasonic transducer surface to be contacted, which is unequal to 0°, and, in the process, d) Contacting at least a part of the first conductor path ends to the transducer segments of the ultrasonic transducer and contacting at least a part of the second ends to means for activating the ultrasonic transducer via the contacted conductor paths.

Specific advantages arc obtained particularly if the transducer segments are formed as concentric circles or rings, or sections thereof, and if several groups of transducer segments can be selectively chosen in such a way that a parallel activation of these transducer segments results in a circular active surface of the ultrasonic transducer.

In alternative embodiments, the individual transducer segments have a different geometry and/or arrangement in the form of an array. The method according to the invention is also particularly advantageous in connection with the contacting of transducer arrays of the "sparse array" type, which comprise individually activatable transducer segments disposed in a surface in accordance with predefined statistical principles. The statistical principle takes into account the mechanisms of imaging and permits the reduction of the number of individually activatable transmitting and receiving transducer segments in an ultrasonic array without any relevant quality loss occurring in the generated image. Sparse arrays can be built, for example, from reguiarly shaped (e.g. rectangular) transducer segments that can be, for example, part of a regularly shaped (e.g. rectangular) 2D array, with only a partial set of the transducer segments comprised by the array (chosen in accordance with the aforementioned statistical principle) actually being used for sound generation or echo detection.

In the manner according to the invention, the individual segments of a segmented ultrasonic transducer can be contacted in a simple manner, with various advantages resulting from the printed circuit board extending at an angle unequal to zero relative to the transducer, and thus from the conductor paths extending correspondingly. In this case, the printed circuit board extends, relative to the contacted ultrasonic transducer surface, at an angle a that is greater than 0° and amounts to up to 90°. In this case, the angle is preferably between 45° and 90°, in particular approximately 90°, so that the printed circuit board, and thus also the conductor paths in the contact region, are perpendicular to the ultrasonic transducer.

In the case of a solution in which the conductor paths are applied to a printed circuit board disposed parallel to the ultrasonic transducer surface to be contacted, they have to have a particular arrangement so that each transducer segment can be reached and contacted. This arrangement is tree-shaped with a plurality of branches, and its complexity increases significantly as the number of transducer segments to be contacted increases. This requires such a printed circuit board or PCB sheet to be useable only for a certain type of transducer. The method according to the invention, however, is able to use a standard printed circuit board, for example with parallel and even equidistant conductor paths, for various types of transducers. Such a printed circuit board is simple to manufacture, and the adaptation to various types of transducers is not effected through a change of the path of the conductor paths on the printed circuit board, but through an adapted arrangement of the otherwise unchanged printed circuit board vis-a-vis the ultrasonic transducer. Thus, the method according to the invention enables a simpler contacting with less expenditure as regards production and cost.

The printed circuit board can be flat and straight, if all of the segments can thus be reached with the conductor paths. However, it can also be curved, bent, undulating or even spiral-shaped in order to route the conductor path ends to be contacted to the desired points on the transducer. In particular, a printed circuit board wound in a spiral shape has proven advantageous in order to correspond to and follow, as it were, the circular structure of the ultrasonic transducer. In a preferred embodiment of the invention, the printed circuit board is therefore wound in a spiral shape transverse to the conductor paths, with no contact existing between the conductor paths. In this case, the printed circuit board is preferably perpendicular to the ultrasonic transducer, so that the conductor paths also run towards the transducer segments in a perpendicular manner and the exposed conductor path ends are disposed on a spiral- shaped line. Given different segmentations of an ultrasonic transducer to be contacted, the same printed circuit board can always be used in this case, with only the profile of the printed circuit board and/or the choice of conductor paths that are actually contacted having to be adapted. Then the conductor paths can be disposed on the printed circuit board independently from the type of transducer to be contacted. Furthermore, printed circuit boards that are disposed parallel to the surface of the segmented ultrasonic transducer are disadvantageous in that, acoustically, they constitute an additional boundary surface that can become a source of unwanted noise. The attachment of the printed circuit board at an angle to the surface of the segmented ultrasonic transducer, and in particular at an angle of approximately 90°, avoids such a boundary surface, so that the noise is reduced compared with the aforementioned parallel solutions.

In this case, the printed circuit board is inserted into a damping body which is typically positioned on the back of an ultrasonic transducer, whereas a leading body, through which the transducer is able to transmit and receive, is attached to the other side. Thus, due to the damping body, the contacting is protected well against damage and environmental influence such as moisture, dirt etc.

Preferably, the first ends and the second ends of the conductor paths are located on opposite sides of the damping body. In this way, the second ends on the back of the damping body can be connected easily with an activating unit. However, the second ends can also exit at any other point from the printed circuit board if this is expedient for contacting or for other reasons.

The damping body with the printed circuit board inserted therein can be formed in various ways, it having proved advantageous to ovcrmold the printed circuit board with the damping body material, whereby the printed circuit board is embedded into the damping body. The printed circuit board is thus embedded in a firm and air-tight manner in the damping body, wherein the shape of the printed circuit board can be variable up to a certain degree prior to casting because imprecisions can be compensated by the overmolded damping body material. It would also be possible to prefabricate a damping body into which a cut-out is inserted and formed in such a way that the printed circuit board can then be inserted into this cut-out with a certain profile. In this case, the damping body can also consist of several assembled parts, with a single-piece configuration being preferred.

In order to improve the contacting of the conductor paths to the ultrasonic transducer, the side of the damping body with the exposed first conductor path ends can be provided, after the damping body has been formed, with a conductive layer which is then removed again in some regions. Thus, the exposed first conductor path ends are in contact with conductive material that was not removed, and via which the transducer segments are contacted. Given an appropriate structure, this conductive layer is advantageous in that the contact surface of the conductor path can be increased and/or that the conductor paths can also be extended parallel to the ultrasonic transducer surface if this is necessary for reaching the transducer segment.

The printed circuit board can be formed in different ways, wherein it can be, in particular, rigid or flexible. A printed circuit board can easily be made to have a certain profile before it is inserted into the damping body in method step c). Thus, a flexible standard printed circuit board can be made to have various shapes. In contrast, a rigid printed circuit board is advantageous in that it is dimcnsionally more stable and less susceptible to displacements/deformations until it is inserted into the damping body. In a preferred embodiment of the invention, the printed circuit board is therefore wound in a spiral shape transverse to the conductor paths, with no contact existing between the conductor paths, in order to avoid short circuits. In the case of a rigid printed circuit board, this spiral shape can, for example, be generated in a previous production step, so that the printed circuit board is already spiral-shaped prior to being inserted into the damping body. In contrast, it may be provided in the case of a flexible printed circuit board that it is brought into the desired spiral shape not until just before insertion into the damping body.

In order to embed the printed circuit board into the damping body, the former can be inserted, prior to the method step c), into a molding tool which is at least partially filled with the damping body material. In this case, the advantages of overmolding the printed circuit board already mentioned come to have an effect, with the external shape of the subsequent damping body being determined by the molding tool.

In order to make the flexible printed circuit board have a certain profile and/or keep a rigid printed circuit board in a profile already obtained, a shaping body with a shaping receptacle can be provided. In that case, the printed circuit board can be inserted, prior to the method step c), into this receptacle, which determines the profile of the printed circuit board and retains the printed circuit board therein. For example, the shaping receptacle can be a groove on a surface of the shaping body into which, prior to the method step c), the printed circuit board is partially inserted with one side towards which the conductor paths run. Thus, one part of the printed circuit board is located in the groove that forces the printed circuit board into a certain profile and also keeps it in it. For a spiral-shaped circuit board, for example, the shaping receptacle is therefore also spiral-shaped. However, the larger part of the printed circuit board protrudes from the groove and can be overmolded by the damping body material.

Together with the shaping body, the printed circuit board can then be inserted, prior to the method step c), into the molding tool which is at least partially filled with the damping body material.

At least the shaping body together with the part of the printed circuit board inserted therein is then preferably removed, after overmolding the printed circuit board with the damping body material, to such an extent that first conductor path ends are again exposed on that side. This separation can take place, for example, by milling. The shaping body thus merely serves for fixating the printed circuit board, but preferably does not become part of the damping body. Those materials that are easy to process, in particular plastics such as PVC or the like, have proved to be advantageous as materials for the shaping body.

The damping body typically consists of a material mix of epoxy resin and fillers. The material mix is selected such that the acoustic impedance is adapted to that of the oscillator. In this case, the impedance can be set by the type and quantity o the fillers, with fine-grain powders such as aluminum oxide, lead oxide or more granular materials such as, for example, silicone or abraded rubber being used as fillers. In addition, both the absorption as well as the scattering o sound are optimized by means of the fillers. Another advantage of the above-described material mix is that it is relatively easy to process mechanically and to bring into shape. Using the profile of the printed circuit board and the conductor paths located thereon, it is possible to cause at least one conductor path, which can be connected to the activating unit on the other side, to lead to each transducer segment. In particular if very standardized printed circuit boards are used, which are to be capable of being used for several types of transducers, it may happen that a conductor path ends at the boundary line of two transducers, so that it would have an electrical contact with two transducer segments at the same time. Moreover, several conductor paths may end in the region of a single transducer segment, for example if it is very large. If all of these conductor paths were contacted, this would lead to short circuits that must be prevented. Therefore, it can be provided that not all first exposed conductor path ends are contacted to transducer segments. Furthermore, it can be provided that, even in the case where a first exposed end of a conductor path is contacted, the associated other end is not connected to the activating unit. Thus, there may be used and unused conductor paths. The invention moreover includes an ultrasonic transducer component for an ultrasonic test probe for the non-destructive testing of a test object with great material thickness by means of ultrasound, comprising at least the following components: an ultrasonic transducer divided into a plurality of individually activatable transducer segments; a damping body in connection with the ultrasonic transducer, into which a printed circuit board with several conductor paths is inserted in such a way that first conductor path ends on one side of the damping body are contacted to the transducer segments of the ultrasonic transducer, while associated second ends on the other side of the damping body can be contacted to means for activating the ultrasonic transducer, with the contacting of the conductor paths enabling a parallel activation of transducer segments of the different groups o transducer segments, and the ultrasonic transducer and the damping body are situated in an orientation in which the printed circuit board extends at an angle a to the contacted ultrasonic transducer surface which is unequal to 0°.

This ultrasonic transducer component can be installed in an ultrasonic test probe, it being capable of being integrated into other components or being connected thereto. Preferably, this is an ultrasonic transducer component manufactured in accordance with an embodiment of the above-described method, so that the features of the method according to the invention can also be used for the ultrasonic transducer component manufactured therewith and th advantages of the method according to the invention can be exploited.

In an advantageous embodiment, the transducer segments are formed as concentric circles or rings, or sections thereof, and several groups of transducer segments can be selectively chosen in such a way that a parallel activation of these transducer segments results in a circular active surface of the ultrasonic transducer.

In another advantageous embodiment, the transducer segments are arranged as a sparse array. The invention moreover includes an associated ultrasonic test probe comprising such an ultrasonic transducer component, and a device for the non-destructive testing of a test object by means of ultrasound comprising at least one such ultrasonic test probe.

Other features and advantages of the invention are apparent from the dependent claims as well as from the exemplary embodiments described below. It is noted that the features of the subject matters o the dependent claims as well as the features of the exemplary embodiments can be freely combined with one another within the context of what is technically possible and viable. Moreover, it is noted that the exemplary embodiments are not to be understood to be limiting, but are to serve for illustrating the present invention.

In the drawings:

Fig. 1 shows a schematic top view of an ultrasonic transducer to be contacted according to a first preferred embodiment;

Fig. 2 shows a schematic top view of an ultrasonic transducer to be contacted according to a second preferred embodiment;

Fig. 3 shows a schematic top view of an ultrasonic transducer to be contacted according to a third preferred embodiment;

Fig. 4 shows a representation of the profile of a spiral-shaped printed circuit board on a segmented ultrasonic transducer; Fig. 5a shows a schematic top view of a shaping body with a spiral-shaped shaping receptacle;

Fig. 5b shows a schematic side view of a shaping body according to Fig. 5a with an inserted printed circuit board;

Fig. 5c shows a schematic three-dimensional view of a shaping body according to Fig. 5a with an inserted printed circuit board; Fig. 6a shows a schematic view of a molding tool with an inserted and overmolded printed circuit board;

Fig. 6b shows a schematic view of a printed circuit board overmolded to form a damping body according to Fig. 6a after removal from the molding tool and separation of the shaping body;

Fig. 6c shows a schematic view of the connection of a damping body according to Fig. 6b to an ultrasonic transducer;

Fig. 7 shows an unwound view of a printed circuit board; and

Fig. 8 shows an unwound view of the contacting of a printed circuit board. An ultrasonic test probe for use in a device for the non-destructive testing o a test object by means of ultrasound usually comprises an ultrasonic transducer disposed on a suitable leading body which is provided to be placed upon a surface of the test object. Hereinafter, this surface is referred to as the coupling surface. The leading body serves as a protection against wear and for acoustically coupling the ultrasonic transducer to the test object; it can consist, for example, of Plexiglass®. In this case, the ultrasonic test probe can be configured in such a way that it is manually guided by a tester over the coupling surface of the test object so as to obtain information on structures in the material of the test object in the process. According to the invention, the ultrasonic transducer is in this case divided into a plurality of transducer segments, which are either circular or annular, or constitute sections of circular or annular transducer elements.

By way of example, Fig. 1 shows such a segmented ultrasonic transducer 10 of an ultrasonic test probe, whose structure is basically known from the prior art, but which has proved to be particularly suitable for use within the context of the method developed by the applicant for ultrasonic testing of test objects with a great material thickness. The three outer transducer segments 11 , 1 and 1 1 " of the ultrasonic transducer 10 according to Fig. 1 are in this case configured to be annular, whereas the central transducer segment 1 " is circular. The radius r of the central transducer segment 1 " in this case matches the ring width S of the subsequent transducer segments 1 1 ", 1 and 1 1. All transducer segments 1 1 , I V, 1 1 ", 1 1 "' are electrically insulated from one another and separately activatable. Different groups of transducer segments can thus be jointly activated, so that the result in each case is an ultrasonic transducer with a circular active transducer surface having a certain diameter. The surface of the circular insulating areas situated between the transducer segments 1 1 , 1 , 1 1 ", 1 ", which electrically insulate the different transducer segments from each other, are in this case configured so as to be negligibly small relative to the surface of the individual transducer segments 1 1 , 1 1 ', 1 1", 1 1 "' themselves. The ultrasonic transducer 10 can consist, for example, of a plate-shaped piezo-electric material which is provided with a metallic electrode on the top and the bottom. In order to form the independently activatable transducer segments 1 1 , 1 Γ, 1 1 ", 1 Γ", this electrode can be patterned at least on one of the two covering surfaces of the plate- shaped transducer material in order to form electrode areas that are electrically insulated from one another.

An associated activating unit is in that case configured to select from the set of the transducer segments 1 1 , I V, 1 1 ", 1 1 "' a group whose parallel activation results in a circular active surface of the ultrasonic transducer. In the exemplary embodiment shown here, the first group consists, for example, of the central transducer segment 1 1 '", the second group consists of the transducer segments 1 " and 1 1 ", the third group of the transducer segments 1 ", 1 1 " and 1 1 ', and the fourth group of all transducer segments 1 1 , 1 Γ, 1 1" and 1 1 "'.

I the diameter D l of the central transducer segment 1 V" with the surface F l is D 1 = 2 x r, then the diameter D2 of the active circular surface F2 is D2 - 4 r, the diameter D3 of the active surface F3 is D3 =6 x r, and the diameter D4 of the circular active surface F4 is D4 8 x r. In that case, various values for the near- field length N of the emerging "effective ultrasonic transducers" are obtained for the ultrasonic transducer 10, given a certain ultrasound frequency of, for example, 2 MHz and a sound velocity in the test object of 5920 m/s. After the activating unit has selected a first group of transducer segments, it activates exclusively that group of transducer segments. The activated transducer segments then generate a sequence of short ultrasonic pulses that propagate through the leading body and enter the material o the test object via the coupling surface. If the ultrasonic pulses hit, for example, a discontinuity or a back face of the test object in the material of the test object, they are reflected back and return to the test probe. Its ultrasonic transducer then acts as a receiver, records the reflected pulses as pulse echoes, converts them into electrical signals and transmits them to the activating unit. In the activating unit the received echo signals are processed, for example amplified and filtered, and displayed on a display device.

By a specific variation of the diameter of the acoustically active surface of the ultrasonic transducer, the method then permits varying the near-field length N of the ultrasonic test probe so that different sectors of the test object can be specifically tested under optimum conditions. The transducer configuration with annular transducer segments of a constant ring width S shown in Fig. 1 in this cases substantially serves for illustrating the basic principle of the ultrasonic transducer to be contacted in accordance with the invention. Another criterion which must be taken into account when designing the ultrasonic transducer is that the sound field generated by the segmented ultrasonic transducer must be substantially identical to the sound field which would be generated by a single-part circular ultrasonic transducer with the same surface. In the case of a segmented ultrasonic transducer, this can be achieved by all transducer segments oscillating with the same amplitude during sound generation. It was now found that the aforementioned condition is satisfied if all transducer segments have substantially the same electrical capacitance. As a rule, the transducer segments form electrical capacitors with a certain capacitance. In a plate-shaped configuration of the ultrasonic transducer, the above-mentioned condition is generally satisfied if the different transducer segments have the same surface.

Fig. 2 therefore shows another exemplary embodiment of an ultrasonic transducer 1 ()' whose individual transducer segments have a ring thickness that decreases in an outward direction, so that the surfaces of the transducer segments are substantially identical. This particular ring configuration is also known from the field of optics as a "zone plate" and has the particular advantage that all the transducer segments transmit with the same amplitude if activated in parallel. If, on the other hand, it is intended that the thickness of the sectors that can be tested with the ultrasonic transducer is substantially constant, then it has to be ensured that the near-field length increases in a linear manner when transitioning from any effective ultrasonic transducer formed by a first group of transducer segments to the effective ultrasonic transducer formed by a second group of transducer segments. This, however, causes the annular transducer segments thus determined not to have the same surface. Therefore, the further criterion that the capacitance of the individual transducer segments is supposed to be substantially the same is not satisfied in this case. However, this criterion can be satisfied by the individual circular or annular transducer segments being again subdivided into smaller, individually activatable transducer elements, all of which in that case have substantially the same surface and thus the same capacitance. Such an ultrasonic transducer 1 0" in accordance with a third exemplary embodiment is shown schematically in Fig. 3. In practice, a subdivision of the individual transducer segments into significantly smaller transducer elements can be necessary in order to be able to satisfy the additional criterion of identical surfaces of the transducer elements with sufficient accuracy.

If the individual transducer segments of a segmented ultrasonic transducer according to one of the embodiments of the Figures 1 to 3 are to be activatable selectively and in a parallel manner, a connection between them and an activating unit must be established by means of suitable contacting. This can be accomplished with the method according to the invention, wherein Fig. 4, by way of example, shows a top view of another circular ultrasonic transducer 10'" with several transducer segments, of which only some individual transducer segments 1 1 , 1 1 ', 1 1 ", I V" are provided with reference numerals in an exemplary fashion. All of the transducer segments must be contacted, so that a connection has to be established from all of them to an activating unit. According to the invention, a printed circuit board 20 (PCB) is used for this purpose which is inserted into a damping body that is attached to the back of the ultrasonic transducer.

A plurality of conductor paths that can be used for contacting is formed on the printed circuit board. In this case, the printed circuit board can consist, for example, of a solid or flexible plastic on which the conductor paths were formed by known methods. In a preferred embodiment of the invention, the printed circuit board is a flexible sheet (PCB sheet), because that can be brought in to any shape in order to realize a certain profile of the printed circuit board on the ultrasonic transducer surface to be contacted. However, rigid printed circuit boards can also be used if they can be brought into a desired shape.

Polyimide, for example, can be selected as the material for the printed circuit board, with any material known from the prior art, in principle, being capable of being used that is suitable for manufacturing PCBs and has sufficient flexibility. The conductor paths can be formed from a conductive material, such as gold, copper, etc. An exemplary profile of a printed circuit board is shown in the top view of Fig. 4 by a spiral-shaped printed circuit board 20. The printed circuit board 20 is wound in a spiral shape, with the conductor paths attached thereto having no contact to one another. Thus, there is always a certain minimum distance between the individual regions of the wound printed circuit board 20 in order to prevent contact of the conductor paths attached thereto to one another. Preferably, the printed circuit board 20 stands perpendicularly on the ultrasonic transducer surface so that it is spiral- shaped in a top view. However, the spiral need not be regular, but may also be slightly irregular and angular.

The conductor path extend transverse to this winding, so that they also run towards the ultrasonic transducer 10"' perpendicularly. This enables all of the transducer segments to be contacted to a conductor path in the region of the respective transducer segment. In this case, the conductor paths can substantially extend parallel to one another and have the same distance from one another. They need not be disposed in any special way because the routing of the conductor path ends to the correct transducer segments takes place via the shape of the printed circuit board. In Fig. 4, the associated contact points are marked, by way of example, by thickened points and the reference numeral 26.

In this case, the printed circuit board 20 in the desire profile is inserted into a block- shaped damping body that can be positioned on the back of the ultrasonic transducer. In that case, first conductor path ends that can be contacted to the transducer segments of the ultrasonic transducer are then situated on the one side of the damping body, whereas the associated second ends are situated on another side of the damping body. In this case, these are preferably opposite sides of the damping body, so that the conductor paths extend from one surface of the damping body to an opposite side. However, it would also be conceivable that the conductor path extend from one side of the damping body to another side adjacent thereto. The second ends can then be connected to an activating unit on the corresponding side of the damping body.

In order to insert the printed circuit board into a damping body or to form a damping body with the printed circuit board inserted therein, it has proved advantageous to ovcrmold the printed circuit board with the damping body material. For this purpose, the printed circuit board can be inserted in the desired position into a molding tool, which is then at least partially filled with the damping body material. Then, the material hardens and can be removed from the molding tool so that a damping body with a printed circuit board embedded therein is manufactured. Before and during the casting process, the printed circuit board should remain within the molding tool in the desired shape, if possible, which can be problematic particularly in the case of flexible printed circuit boards consisting of a sheet, because they can move and/or be deformed during the casting process. However, rigid printed circuit boards can also slip during casting, for example, which may affect or even render impossible the accurate contacting of the associated conductor paths. In one exemplary embodiment of the method according to the invention, an additional shaping body is therefore used which comprises a shaping receptacle into which the printed circuit board is inserted and retained during the casting process. Thus, the receptacle defines the shape and position of the printed circuit board within the damping body to be manufactured, with the receptacle being intended to ensure that the first conductor path ends are situated at the correct locations on the side of the damping body facing towards the ultrasonic transducer.

Fig. 5a shows an exemplary top view of such a shaping body 30. The shaping body is preferably circular, like the damping body to be manufactured, and a spiral-shaped groove 3 1 is inserted into its surface. The profile of the groove 31 corresponds to the desired profile of the printed circuit board, and the printed circuit board can be plugged with one side into the groove 31 from above. In this case, the printed circuit board can have a certain rigidity and can have been brought into the approximate desired spiral shape, so that it already fits into the groove 31 and the latter only prevents the profile of the printed circuit board from changing during the casting of the damping body. However, as a PCB sheet, the printed circuit board can also be very flexible and be forced into the desired profile only by the shaping groove 31 , by the sheet being wound in a spiral shape not until it is inserted into the spiral shape of the groove 31. Fig. 5b shows a printed circuit board 20 with several conductor paths 21 inserted into the shaping groove 31 of the shaping body 30 in a schematic section along the line A- A in Fig. 5a. In this case, the printed circuit board 20 protrudes from the shaping body substantially perpendicularly, at an angle a of approximately 90°. The groove 31 has a certain depth T, which is, for example, half of the thickness o the shape 30. The thickness d of the shape in this case is typically in an order of magnitude of 5 to 20 millimeters. Since the shape has to be removed from the damping body after the casting process, the thickness d of the shaping body should not be too great, if possible. In this case, the groove is selected to be so deep that the printed circuit board 20 is retained well in it, so that the play between the printed circuit board 20 and the groove 31 should be as small as possible. In principle, the thickness is dependent on the volume of the damping body or on the shrinkage during hardening. Preferably, the depth is to be selected in such a way that the shrinkage does not warp the board. Given a damping body with a diameter of approx. 60 mm and a height of approx. 40 mm, a board with a thickness of approx. 10 mm would typically be selected. Preferably, the depth of the groove should at least be 1 mm. Fig. 5c schematically shows a three-dimensional view of a printed circuit board 20 in the shaping groove of a shaping body 30. The printed circuit board 20 comprises several conductor paths which are indicated in the Figure only by means of dashed lines and marked in an exemplary fashion with a reference numeral 21 . Preferably, all of the conductor paths 21 run perpendicularly towards the surface of the shape 30, wherein they can run parallel with the same distance between each other. However, the distance can also vary, and the conductor paths 21 can also run towards the surface of the shape 30 at an angle different from 90°. On the opposite side, the conductor paths 21 change their otherwise parallel course and are brought together preferably at one point. At this point, a connection of the conductor paths 21 to a terminal point can be realized.

After the insertion o the printed circuit board 20 into the shaping receptacle 31 of the shaping body 30, the shaping body 30, together with the printed circuit board 20, can be inserted into a molding tool 60 and positioned at the bottom thereof, or the shaping body 30, together with a side wall 61 that extends peripherally in a circle, forms the molding tool, with the shape 30 forming the bottom of the molding tool 60, as in the exemplary embodiment of Fig. 6a. In order to support the printed circuit board 20 also in an upper area and fixate its position, a bracket 32 can be provided in that area. After the printed circuit board 22 has been positioned, the molding tool 60 is filled up to a certain level with the material 41 of the damping body. In the process, the shaping body 30 and the printed circuit board 20 are embedded into the damping body material, wherein the conductor path 20 does not have to be overmolded completely but may also protrude at the top from the damping body that is to be manufactured in this way. Preferably, the level is below the bracket 32, so that that is not also overmolded. However, the bracket 32 also can be overmolded, with it having to be detachable from the molding tool 60 after the casting process. It can also be provided that the shaping body 30 is not overmolded by material 41 of the damping body but gets into contact with it only on its upper side if the shaping body 30, for example, forms the bottom of the molding tool 60. After the material 41 has hardened, the damping body can be separated from the molding tool 60, wherein this is not yet the final damping body but also may be a blank that is subjected to further processing steps in order to form a damping body.

In particular, at least the shaping body 30, together with the part of the printed circuit board 20 that was stuck in the groove 31 , is separated at a dividing line 33 as is schematically shown in Fig. 6b. This results in first ends 24, 24', 24", 24" of the conductor paths 21 being exposed on one side 22 of the damping body 40 thus created. In that case, associated second ends 25, 25', 25", 25" are exposed on the opposite side 23 of the damping body 40. Depending on the level to which the molding tool 60 was filled, the printed circuit board 20 in this case protrudes to a certain extent from this side 23 of the damping body 40. The removal of the material can take place, for example, by milling.

In order to contact these first ends 24, 24', 24", 24" of the conductor paths 21 to an ultrasonic transducer, the corresponding side 22 of the damping body 40 can then be provided with a conductive layer. After its application, this layer is in contact with all exposed free ends of the conductor path 21. The layer is preferably formed as a gold layer. However, other materials are also conceivable that, on the one hand, are conductive and, on the other hand, can be applied to a surface by typical processes such as, for example, vapor deposition, screen printing, wet-chemical deposition or the like. Apart from gold, copper, chromium, platinum and similar metals have proved their value. In this case, the thickness of the layer is selected in such a way that a continuous conductive surface is formed on a processed surface with a given surface roughness. This is typically done with a few μιη up to a few 10 μηι. In this case, the preferred layer thickness is at least 2 μιη, in particular at least 10 μη , and particularly preferably at least 20 μιη.

This conductive layer is finally given a structure, which can be done, for example, mechanically and/or chemically. By means o the structure, further conductor paths can be formed on the associated surface of the damping body 40 which extend the conductor paths 21 protruding perpendicularly from the surface 22 parallel to this surface into precisely the region in which they are to contact a particular transducer segment. However, the structure may also only cause the contact surface in the region of the exposed conductor path ends to be enlarged, so that they can be better contacted to the transducer segments. For example, contact regions can be formed for this purpose with a surface area that is greater than the cross-sectional surface area of the conductor paths 21 .

Fig. 6c shows the connection of the damping body 40 thus formed and of an ultrasonic transducer 1 ()"' via the correspondingly structured conductive layer 50. Preferably, the printed circuit board 20 is in this case at an angle a of approximately 90° to the ultrasonic transducer surface, so that the conductor paths 21 also come up against the transducer segments to be contacted at this angle. However, this angle can also be changed, provided it is unequal to 0°. The damping body 40 and the ultrasonic transducer 1 ()"' together form an ultrasonic transducer component 12 which can be installed as a component in an ultrasonic test probe that is not shown. For this purpose, a leading body, through which the transducer segments of the ultrasonic transducer 10"' transmit sound, is typically provided on the side of the ultrasonic transducer 10"' opposite to the damping body 40.

Fig. 7 again shows the printed circuit board 20 inserted into the shaping groove 1 of the shaping body 30 prior to being molded into the damping body, with the bracket 32 also being already attached to the printed circuit board 20. This is a view in which the printed circuit board 20 is shown unwound so as to be flat. The conductor paths 21 , which at first extend in an equidistant and parallel manner relative to one another, and which on the first side 22 preferably extend at a fixed distance x from each other before they come together on the opposite side 23 to form a terminal point, are apparent from this view. However, this terminal point can also be fonned at a side of the printed circuit board 20 that is adjacent to the lower contact side 22.

Since the material of the printed circuit board 20, in the region located within the groove 31 of the shaping body 30, is removed together with the shape 30 after the casting process in order to form the damping body, it can be provided that the conductor paths 21 of the originally inserted conductor paths 20 do not reach up to the lower edge of the printed circuit board and thus, to the bottom of the groove 31 , but end already before reaching this edge. This embodiment is selected in Fig. 7, this being advantageous particularly in that no valuable conductor path material is wasted or has to be treated in a complex process during the removal of the shaping body 30, for example by milling. In this case, the length of the conductor paths 21 and the depth T of the groove are preferably matched in such a way that the conductor paths 21 end a short distance behind the dividing line 33 at which the shaping body 30 is removed. It is thus ensured that the conductor path ends are subsequently exposed at the lower side of the damping body and can be coated with the conductive layer 50 and contacted. In order to simplify the illustration, Fig. 8 again shows an unwound view of the contacting of a printed circuit board 20 with the transducer segments 1 1 , 1 Γ, 1 1 ", 1 ", 1 1" of an ultrasonic transducer 10. Due to the preferably constant distance x between the conductor paths 21 and the concentric arrangement of the transducer segments with different ring widths S, it may happen that some conductor paths are clearly in the area of only a single transducer segment, whereas other conductor paths end in the boundary area between two transducer segments. Moreover, it may happen that more than one conductor path ends in the area of a transducer segment. In the schematic representation of Fig. 8, the conductor paths are made very broad for illustrative purposes in order to show that, for example, a conductor path 2 Γ ends both in the area of the transducer segment 1 1 ' as well as in the area of the transducer segment 1 1 ". Furthermore, the two conductor paths 21 and 2 end at the transducer segment 1 Γ, and the two conductor paths 2 Γ and 21 " at the transducer segment 11". This also applies to other areas.

In order to uniquely contact the transducer segments to only a single conductor path, it can therefore be provided that the conductor paths are not all contacted to the ultrasonic transducer 10. In particular, this can be achieved by giving the conductive layer between the damping body 40 and the ultrasonic transducer 10 a corresponding structure. In order for conductor path ends that are not be contacted not to have any contact to the transducer segments, cut-outs in the conductive layer can be provided in these regions, or the conductive layer remains only in the regions of the conductor paths to be contacted. The non-contacted conductor paths are marked with a cross in Fig. 8, so that there are used and unused conductor paths in the printed circuit board 20.

It can also be provided that all conductor paths are contacted to the ultrasonic transducer 10, so that a transducer segment can be connected with several conductor paths. However, some individual conductor paths are in that case not connected to the terminal point on the other side, so that they remain unused. Used and unused conductor paths can also be realized in this manner, with the structuring of the conductive layer requiring less effort. However, in order to prevent short circuits due to conductor paths in this case, such as the one with the reference numeral 21 ", which are in contact with two transducer segments 1 Γ and 11" at the same time, a structuring of the conductive layer may additionally be required, in order to prevent at least this special situation. In contrast, it is largely unproblematic if several conductor paths lead into a transducer segment and only one of these conductor paths is contacted at the terminal point. This is the case, for example, for the transducer segment 1 1 The patter for conductor paths to be connected and not to be connected can be predefined for different transducer types, so that a different pattern is to be used for a transducer with a higher number of transducer segments than for a transducer with fewer transducer segments. The size of the segments can also have an influence on the connecting pattern, but a standard printed circuit board can always be used. Whilst exemplary and preferred embodiments of the invention have been described herein, the skilled person will appreciate that other embodiments are possible and contemplated. The invention is intended to encompass all such embodiments that fall within the scope of the appended claims.

Claims

CLAIMS:

1. A method for contacting an ultrasonic transducer (10; 10'; 10") for the nondestructive testing of a test object with a great material thickness by means of ultrasound, comprising at least the following steps: a) providing an ultrasonic transducer (10; 10'; 10") divided into a plurality of individually activatable transducer segments (1 1 ; 1 1';1 1"; 1 1 "'), b) providing a printed circuit board (20) on which several conductor paths run (21 ) that respectively extend between two sides (22;23) of the printed circuit board

(21); c) forming a damping body (40) into which the printed circuit board (21 ) is inserted in such a way that first conductor path (21 ) ends (24;24',...,24ⁿ) are exposed on one side (22) of the damping body (40), while associated second ends (25;25',...,25ⁿ) are exposed on the other side (23) of the damping body (40); d) connecting the ultrasonic transducer (10; 10'; 10") to the damping body (40) in an orientation in which the printed circuit board (20) extends at an angle a to the ultrasonic transducer ( 10; 10'; 10") surface to be contacted, which is unequal to 0°, and, in the process, e) contacting at least a part of the first conductor path (21) ends (24;24',...,24ⁿ) to the transducer segments (1 1 ; 1 ; 1 1 ";1 Γ") of the ultrasonic transducer (10; 10'; 10") and contacting at least a part of the second ends (25;25',...,25ⁿ) to means for activating the ultrasonic transducer (10; 10'; 10") via the contacted conductor paths (21 ).

2. The method according to claim 1, wherein the first ends (24;24',...,24ⁿ) and the second ends (25;25',...,25ⁿ) of the conductor paths (21 ) are located on opposite sides (22;23 ) of the damping body (40).

3. The method according to claim 1 or claim 2, wherein the printed circuit board (20) extends, relative to the contacted ultrasonic transducer (10; 10'; 10") surface, at an angle a that is greater than 0° and amounts to up to 90°.

4. The method according to any one of claims 1 to 3, wherein the damping body (40) is formed by the printed circuit board (20) being overmolded by the damping body (40) material, whereby the printed circuit board (20) is embedded into the damping body (40).

5. The method according to any one of claims 1 to 4, wherein the side (22) of the damping body (40) with the exposed first conductor path (21 ) ends (24;24',.··,24^η) is coated, after the damping body (40) has been formed, with a conductive layer (50) which is then removed again in some regions, whereby the exposed first conductor path (21 ) ends (24;24',...,24ⁿ) are in contact with conductive material (50) that was not removed, via which the transducer segments (1 1 ; 1 ; 1 1 "; 1 ") are contacted.

6. The method according to any one of claims 1 to 5, wherein the printed circuit board (21 ) is flexible prior to embedding into the damping body (40) in method step c).

7. The method according to any one of the claims 1 to 6, wherein the printed circuit board (21 ) is wound in a spiral shape transverse to the conductor paths (21), with no contact existing between the conductor paths (21).

8. The method according to any one or more of the claims 4 to 7, wherein the printed circuit board (21 ) is inserted, prior to the method step c), into a molding tool (60) which is at least partially filled with the damping body (40) material.

9. The method according to any one of claims 4 to 8, wherein a shaping body

(30) with a shaping receptacle (31 ) is provided, and the printed circuit board (21) is inserted, prior to the method step c), into the receptacle (31).

10. The method according to claim 9, wherein the shaping receptacle is a groove

(3 1 ) on a surface of the shaping body (30) into which, prior to the method step c), the printed circuit board (20) is partially inserted with one side (22) towards which the conductor paths (21) run, and that at least the shaping body (30), together with the part of the printed circuit board (20) inserted therein, is removed, after overmolding the printed circuit board (20) with the damping body (40) material, to such an extent that first conductor path (21 ) ends (24;24',...,24ⁿ) are again exposed on that side (22).

11. The method according to claim 9 or claim 10, wherein the shaping receptacle (21 ) is spiral-shaped.

12. The method according to any one of claims 8 to 1 1 , wherein the printed circuit board (20), together with the shaping body (30), is inserted, prior to the method step c), into the molding tool (60) which is at least partially filled with the damping body (40) material.

13. The method according to any one of claims 1 to 12, wherein not all first exposed conductor path (21) ends (24;24',...,24ⁿ) are contacted to transducer segments (11 ;11';1 Γ;1 Γ').

14. The method according to any one of claims 1 to 13, wherein the transducer segments (1 1 ; 1 Γ; 1 Γ'; 1 Γ") are formed as concentric circles or rings, or sections thereof, and several groups of transducer segments ( 1 1 ; 1 1'; 1 1 "; 1 ") can be selectively chosen in such a way that a parallel activation of these transducer segments ( 1 1 ; 1 1 ^*; 1 1 "; 1 ") in each case results in a circular active surface of the ultrasonic transducer ( 10; 10'; 10").

15. An ultrasonic transducer component (12) for an ultrasonic test probe for the non-destructive testing of a test object with great material thickness by means of ultrasound, comprising at least the following components: an ultrasonic transducer ( 10; 10'; 10") divided into a plurality of individually activatable transducer segments (11 ; 11 '; 11 "; 11 "'), a damping body (40) in connection with the ultrasonic transducer (10; 10'; 10"), into which a printed circuit board (20) with several conductor paths (21 ) is inserted in such a way that first conductor path (21 ) ends (24;24',...,24ⁿ) on one side (22) of the damping body (40) are contacted to the transducer segments (1 1 ; 1 Γ; 1 1 "; 1 ") of the ultrasonic transducer (10; 10'; 10"), while associated second ends (25;25',...,25ⁿ) on the other side (23) of the damping body (40) can be contacted to means for activating the ultrasonic transducer (10; 10'; 10"), with the contacting of the conductor paths (21) enabling a parallel activation of transducer segments (11;1 ;11";1 ") of the different groups of transducer segments (11 ; 1 Γ; 11 "; 11 '"), and the ultrasonic transducer (10; 10'; 10") and the damping body (40) arc situated in an orientation relative to each other in which the printed circuit board (20) extends at an angle a to the contacted ultrasonic transducer (10; 10'; 10") surface which is unequal to 0°.

16. The ultrasonic transducer component (12) according to claim 15, wherein the transducer segments (11;1 ;11";1 ") are formed as concentric circles or rings, or sections thereof, and several groups of transducer segments (11;1 ;11";1 Γ") can be selectively chosen in such a way that a parallel activation of these transducer segments (11;1 ;1 ';1 Γ") results in a circular active surface of the ultrasonic transducer (10; 10'; 10").

17. The ultrasonic transducer component according to claim 15 or claim 16, wherein it was manufactured in accordance with a method according to any one or more of the claims 1 to 14.

18. An ultrasonic test probe comprisng an ultrasonic transducer component (12) according to claim 15.

19. A device for the non-destructive inspection of a test object by means of ultrasound comprising at least one ultrasonic test probe according to claim 18.