EP1084000A1 - Multielement sound probe comprising a composite electrically conducting coating and method for making same - Google Patents

Multielement sound probe comprising a composite electrically conducting coating and method for making same

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Publication number
EP1084000A1
EP1084000A1 EP99922247A EP99922247A EP1084000A1 EP 1084000 A1 EP1084000 A1 EP 1084000A1 EP 99922247 A EP99922247 A EP 99922247A EP 99922247 A EP99922247 A EP 99922247A EP 1084000 A1 EP1084000 A1 EP 1084000A1
Authority
EP
European Patent Office
Prior art keywords
film
acoustic
elementary
piezoelectric
composite material
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.)
Granted
Application number
EP99922247A
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German (de)
French (fr)
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EP1084000B1 (en
Inventor
Ngoc-Tuan Thomson-CSF NGUYEN
Nicolas Thomson-CSF SERES
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Thales SA
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Thomson CSF SA
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Publication of EP1084000A1 publication Critical patent/EP1084000A1/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B06B1/0607—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using multiple elements
    • B06B1/0622—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using multiple elements on one surface
    • B06B1/0629—Square array

Definitions

  • the field of the invention is that of acoustic transducers which can be used in particular in medical or underwater imaging, or in non-destructive testing.
  • an acoustic probe comprises a set of piezoelectric transducers connected to a control electrode device via an interconnection network.
  • piezoelectric transducers emit acoustic waves which, after reflection in a given medium, provide information concerning said medium.
  • the acoustic probes are composed of numerous piezoelectric elements which can be excited independently.
  • the method for producing such probes has been described by the applicant in several documents, in particular for one-dimensional probes in European patent 0 190 948 or for three-dimensional probes in French patent 9302586. This method consists in cutting an assembly made up of strips of acoustic adaptation of a piezoelectric ceramic plate, of an electrical circuit comprising metal tracks generally located on the surface of an acoustic support known by the Anglo-Saxon term of "backing".
  • each transducer is connected to a track of the electrical circuit (polyimide film with metallized tracks or tracks cut from a metal sheet) to allow electrical excitation.
  • the elementary transducers are sub-cut into several piezoelectric sub-elements, thus mechanically separated but connected to the same electrical point.
  • the sub-cuts are obtained by cutting beyond the metal tracks as illustrated in FIG. 1 which shows a sectional view of an example of a unidirectional multi-element probe.
  • a backing 1 supports an electrical circuit 2 with conductive tracks pil, elementary transducers til, themselves comprising tilk sub-elements.
  • the width of the pil tracks is of the order of 100 ⁇ m, which limits the number of piezoelectric sub-elements.
  • the cut tracks are fragile and poorly withstand electrical and mechanical stresses.
  • the piezoelectric elements also include acoustic adaptation elements with different impedance L1i1k and L2i1k, the L2i1k elements being able to be metallized on the underside to allow mass recovery.
  • Mass recovery can also be achieved by inserting a thin metallic film between the blade L2i1k and the ceramic or by using, in the case of one-dimensional probes, blades L1i1k and L2i1k of dimensions smaller than those of the ceramic, thus making the accessible earth electrode on the ends of the ceramic. In the latter case, the mass is recovered by welding or gluing a metal film on the "exposed" ends of the ceramic.
  • the present invention provides an acoustic probe comprising a film of conductive composite material.
  • the subject of the invention is an acoustic probe comprising elementary piezoelectric transducers and an electrical circuit comprising metal tracks, so as to connect at least one metal track to at least one elementary transducer, each elementary transducer consisting of mechanically separated piezoelectric elements connected to the same track, characterized in that it further comprises a film of conductive composite material located between the electrical circuit and the elementary transducers, the piezoelectric sub-elements of the same elementary transducer being separated mechanically by interstices extending into said film.
  • the electrical circuit of the acoustic probe according to the invention is affixed to a backing of impedance adjusted to serve as an acoustic support.
  • Such a probe has the following advantages in particular: - the interstices defining the piezoelectric sub-elements stopping in the film of conductive material, the tracks of the electrical circuits are no longer "undercut” and therefore weakened;
  • the film of conductive composite material makes it possible to electrically connect the piezoelectric elements and the electrical circuit without passing through vias as described in particular in French patent 9302586;
  • the film of conductive composite material which may have an intermediate thermal expansion between that of the piezoelectric material and that of the material constituting the “backing”, makes it possible to absorb the deformations due to the thermal stresses of the assembly produced conventionally, at high temperature ;
  • the tracks of the electrical circuit no longer have to be sized as a function of the number of piezoelectric sub-elements that it is desired to obtain, because the interstices stop in the film of conductive composite material.
  • the film of conductive composite material can comprise an organic material of epoxy resin type, which can in particular be loaded with conductive metal particles of the silver, copper, nickel type.
  • the subject of the invention is also a method of manufacturing an acoustic probe according to the invention and further comprising the following steps:
  • the cutting and subcutting steps can be carried out with a diamond saw in one and the same step.
  • FIG. 1 illustrates a section of an example of unidirectional acoustic probe according to the known art
  • FIG. 2 illustrates a first variant of the invention relating to a one-dimensional probe
  • FIG. 3 illustrates a second variant of the invention relating to a bidirectional probe.
  • the acoustic probe according to the invention comprises elementary piezoelectric transducers Tij, connected via a film of conductive composite material to metal tracks located on the surface of an electrical circuit located on a backing.
  • one or two acoustic adaptation blades of the quarter-wave type are fixed to the surface of the piezoelectric transducers to improve energy transfer.
  • These adaptation blades can be of the polymer type loaded with mineral particles, the proportions of which are adjusted to obtain the desired acoustic properties.
  • these blades are shaped by molding or machining and then assembled by gluing on one of the faces of the piezoelectric transducers.
  • each elementary piezoelectric transducer must be connected on one side to ground and on the other side to a positive contact (also called hot spot).
  • the mass is located towards the propagation medium, that is to say that it must be on the side of the acoustic adaptation elements.
  • the ground electrode can be a metallic layer, its position can depend on the nature of the probe, that is to say if it is a unidirectional or bidirectional probe.
  • the layer of piezoelectric material is assembled to said backing via conductive film 3 which by its nature allows the adhesion of the whole.
  • the film of conductive composite material can be composed of a mixture of epoxy resin and metallic particles (silver, copper, nickel ...) with a charge rate of between 50% and 80%, by volume depending on the acoustic properties. wanted.
  • the film has no influence on the acoustic properties of the probe because its impedance is close to that of the backing and its thickness (of the order of 20 to 100 ⁇ m) remains low compared to the ultrasonic wavelength generated by the piezoelectric material.
  • the acoustic adaptation blades are glued to the surface of the layer of piezoelectric material using an epoxy type adhesive, for example.
  • the sub-cuts stop in the thickness of the film of composite material, thereby allowing to maintain the electrical connection between the different sub - Tilk piezoelectric elements, of the same Ti1 element surmounted by these acoustic adaptation elements L1i1k and L2i1k.
  • the lower acoustic adaptation blade can be metallized at its lower face so as to provide mass recovery at the periphery of the probe.
  • the assembly of the backing comprising the electrical circuit, of the conductive composite film and of the layer of piezoelectric material can typically be identical to that previously cited in the case of a unidirectional probe.
  • a ground plane in this type of probe one can proceed as in the method described by the applicant in the French patent application published under No. 2,756,447, or by integrating a ground plane between the transducer elements. and the acoustic adaptation blades.
  • the cuts and sub-cuts are carried out so as to define the elements Tij and Tijk using a diamond saw along two perpendicular axes.
  • the assembly thus formed is covered by an electrode of conductive mass M, affixed then glued, it can typically be a metal sheet or a film of metallized polymer.
  • this cutting operation can be carried out by laser.
  • the laser used can be, for example, an infrared laser of the CO2 type or a UV laser of the Excimer type or of the tripled or quadrupled YAG type.

Abstract

The invention concerns a multielement sound probe comprising a backing (1), an electrical circuit (2) with strip conductors (Pi1) connected to elementary piezoelectric transducers (Ti1). The probe further comprises, a composite material electrically conducting coating located between the piezoelectric transducers (Ti1k) and the strip conductors (Pi1). In standard fashion, the piezoelectric transducers are cut out into sub-elements to obtain elements acoustically uncoupled and electrically coupled. The presence of the composite material electrically conducting coating (3) enables the strip conductors to be dimensioned with respect to the sub-elements and constitutes an intermediate element relative to the thermal expansion variations between the backing (1) and the piezoelectric transducers.

Description

SONDE ACOUSTIQUE MULTIELEMENTS COMPRENANT UN FILM COMPOSITE CONDUCTEUR ET PROCEDE DE FABRICATION MULTIPLE ELEMENT ACOUSTIC PROBE COMPRISING A CONDUCTIVE COMPOSITE FILM AND MANUFACTURING METHOD
Le domaine de l'invention est celui des transducteurs acoustiques pouvant être utilisés notamment en imagerie médicale ou sous-marine, ou en contrôle non destructif.The field of the invention is that of acoustic transducers which can be used in particular in medical or underwater imaging, or in non-destructive testing.
De manière générale, une sonde acoustique comprend un ensemble de transducteurs piézoélectriques reliés à un dispositif d'électrode de commande par l'intermédiaire d'un réseau d'interconnexion.Generally, an acoustic probe comprises a set of piezoelectric transducers connected to a control electrode device via an interconnection network.
Ces transducteurs piézoélectriques émettent des ondes acoustiques qui après réflexion dans un milieu donné, fournissent des informations concernant ledit milieu. Typiquement, dans le domaine de l'imagerie médicale, les sondes acoustiques sont composées de nombreux éléments piézoélectriques qui peuvent être excités indépendamment. La méthode de réalisation de telles sondes a été décrite par la demanderesse dans plusieurs documents notamment pour les sondes unidimensionnelles dans le brevet européen 0 190 948 ou pour les sondes tridimensionnelles dans le brevet français 9302586. Cette méthode consiste à découper un assemblage constitué de lames d'adaptation acoustique, d'une lame de céramique piézoélectrique, d'un circuit électrique comportant des pistes métalliques situé généralement à la surface d'un support acoustique connu sous le terme anglo-saxon de « backing ». La découpe permet ainsi de définir des transducteurs élémentaires qui peuvent être excités indépendamment. En effet, chaque transducteur est relié à une piste du circuit électrique (film polyimide avec des pistes métallisées ou pistes découpées dans une feuille métallique) pour permettre l'excitation électrique. Pour éviter les modes de vibration parasites, notamment le mode transverse, les transducteurs élémentaires sont sous-découpés en plusieurs sous-éléments piézoélectriques, ainsi séparés mécaniquement mais reliés au même point électrique. Les sous-découpes sont obtenues en découpant au-delà des pistes métalliques comme illustré en figure 1 qui montre une vue en coupe d'un exemple de sonde multiéléments unidirectionnelle. Selon cette configuration, un backing 1 supporte un circuit électrique 2 avec des pistes conductrices pil, des transducteurs élémentaires til, comportant eux- mêmes des sous-éléments tilk. Typiquement, la largeur des pistes pil est de l'ordre de 100 μm, ce qui limite le nombre de sous-éléments piézoélectriques. De plus, les pistes découpées sont fragiles et supportent mal les sollicitations électriques et mécaniques.These piezoelectric transducers emit acoustic waves which, after reflection in a given medium, provide information concerning said medium. Typically, in the field of medical imaging, the acoustic probes are composed of numerous piezoelectric elements which can be excited independently. The method for producing such probes has been described by the applicant in several documents, in particular for one-dimensional probes in European patent 0 190 948 or for three-dimensional probes in French patent 9302586. This method consists in cutting an assembly made up of strips of acoustic adaptation of a piezoelectric ceramic plate, of an electrical circuit comprising metal tracks generally located on the surface of an acoustic support known by the Anglo-Saxon term of "backing". The cutting thus makes it possible to define elementary transducers which can be excited independently. Indeed, each transducer is connected to a track of the electrical circuit (polyimide film with metallized tracks or tracks cut from a metal sheet) to allow electrical excitation. To avoid parasitic vibration modes, in particular transverse mode, the elementary transducers are sub-cut into several piezoelectric sub-elements, thus mechanically separated but connected to the same electrical point. The sub-cuts are obtained by cutting beyond the metal tracks as illustrated in FIG. 1 which shows a sectional view of an example of a unidirectional multi-element probe. According to this configuration, a backing 1 supports an electrical circuit 2 with conductive tracks pil, elementary transducers til, themselves comprising tilk sub-elements. Typically, the width of the pil tracks is of the order of 100 μm, which limits the number of piezoelectric sub-elements. In addition, the cut tracks are fragile and poorly withstand electrical and mechanical stresses.
Les éléments piézoélectriques comportent également des éléments d'adaptation acoustique d'impédance différents L1i1k et L2i1k, les éléments L2i1k pouvant être métallisés en face inférieure pour permettre une reprise de masse.The piezoelectric elements also include acoustic adaptation elements with different impedance L1i1k and L2i1k, the L2i1k elements being able to be metallized on the underside to allow mass recovery.
La reprise de masse peut être aussi réalisée en intercalant entre la lame L2i1k et la céramique un film mince métallique ou en utilisant, dans le cas des sondes unidimensionnelles, des lames L1i1k et L2i1k de dimensions plus petites que celles de la céramique rendant ainsi accessible l'électrode de masse sur les extrémités de la céramique. Dans ce dernier cas, la masse est récupérée en soudant ou en collant un film métallique sur les extrémités « dégagées » de la céramique. Pour pallier les inconvénients précités, la présente invention propose une sonde acoustique comprenant un film de matériau composite conducteur.Mass recovery can also be achieved by inserting a thin metallic film between the blade L2i1k and the ceramic or by using, in the case of one-dimensional probes, blades L1i1k and L2i1k of dimensions smaller than those of the ceramic, thus making the accessible earth electrode on the ends of the ceramic. In the latter case, the mass is recovered by welding or gluing a metal film on the "exposed" ends of the ceramic. To overcome the aforementioned drawbacks, the present invention provides an acoustic probe comprising a film of conductive composite material.
Plus précisément, l'invention a pour objet une sonde acoustique comprenant des transducteurs piézoélectriques élémentaires et un circuit électrique comportant des pistes métalliques, de manière à connecter au moins une piste métallique à au moins un transducteur élémentaire, chaque transducteur élémentaire étant constitué de sous-éléments piézoélectriques séparés mécaniquement et reliés à une même piste, caractérisée en ce qu'elle comprend en outre, un film de matériau composite conducteur situé entre le circuit électrique et les transducteurs élémentaires, les sous- éléments piézoélectriques d'un même transducteur élémentaire étant séparés mécaniquement par des interstices se prolongeant jusque dans ledit film.More specifically, the subject of the invention is an acoustic probe comprising elementary piezoelectric transducers and an electrical circuit comprising metal tracks, so as to connect at least one metal track to at least one elementary transducer, each elementary transducer consisting of mechanically separated piezoelectric elements connected to the same track, characterized in that it further comprises a film of conductive composite material located between the electrical circuit and the elementary transducers, the piezoelectric sub-elements of the same elementary transducer being separated mechanically by interstices extending into said film.
De manière classique, le circuit électrique de la sonde acoustique selon l'invention est apposé sur un backing d'impédance ajustée pour servir de support acoustique.Conventionally, the electrical circuit of the acoustic probe according to the invention is affixed to a backing of impedance adjusted to serve as an acoustic support.
Une telle sonde présente notamment les avantages suivants : - les interstices définissant les sous-éléments piézoélectriques s'arrêtant dans le film de matériau conducteur, les pistes du circuit électrique ne sont plus « sous-découpées » et donc fragilisées ;Such a probe has the following advantages in particular: - the interstices defining the piezoelectric sub-elements stopping in the film of conductive material, the tracks of the electrical circuits are no longer "undercut" and therefore weakened;
- le film de matériau composite conducteur permet de relier électriquement les éléments piézoélectriques et le circuit électrique sans passer par des vias comme décrits notamment dans le brevet français 9302586 ;the film of conductive composite material makes it possible to electrically connect the piezoelectric elements and the electrical circuit without passing through vias as described in particular in French patent 9302586;
- le film de matériau composite conducteur pouvant avoir une dilatation thermique intermédiaire entre celle du matériau piézoélectrique et celle du matériau constitutif du « backing », permet d'absorber les déformations dues aux contraintes thermiques de l'assemblage réalisé de manière classique, à haute température ;the film of conductive composite material which may have an intermediate thermal expansion between that of the piezoelectric material and that of the material constituting the “backing”, makes it possible to absorb the deformations due to the thermal stresses of the assembly produced conventionally, at high temperature ;
- les pistes du circuit électrique n'ont plus à être dimensionnées en fonction du nombre de sous-éléments piézoélectriques que l'on veut obtenir, car les interstices s'arrêtent dans le film de matériau composite conducteur.- The tracks of the electrical circuit no longer have to be sized as a function of the number of piezoelectric sub-elements that it is desired to obtain, because the interstices stop in the film of conductive composite material.
Avantageusement, le film de matériau composite conducteur peut comprendre un matériau organique de type résine époxy, pouvant notamment être chargée avec des particules conductrices en métal du type argent, cuivre, nickel.Advantageously, the film of conductive composite material can comprise an organic material of epoxy resin type, which can in particular be loaded with conductive metal particles of the silver, copper, nickel type.
L'invention a encore pour objet un procédé de fabrication d'une sonde acoustique selon l'invention et comprenant en outre les étapes suivantes :The subject of the invention is also a method of manufacturing an acoustic probe according to the invention and further comprising the following steps:
- l'assemblage d'au moins, une couche de matériau piézoélectrique, un film de matériau composite conducteur et un circuit électrique comportant des pistes métalliques ;- The assembly of at least one layer of piezoelectric material, a film of conductive composite material and an electrical circuit comprising metal tracks;
- la découpe de la couche de matériau piézoélectrique et du film de matériau à composite conducteur de manière à définir des transducteurs piézoélectriques élémentaires séparés électriquement ;- Cutting the layer of piezoelectric material and the film of conductive composite material so as to define elementary electrically separated piezoelectric transducers;
- la sous-découpe des transducteurs élémentaires et d'une partie du film de matériau composite de manière à définir des sous-éléments piézoélectriques séparés mécaniquement et connectés électriquement. Selon une variante du procédé de l'invention, les étapes de découpe et de sous-découpe peuvent être réalisées avec une scie diamantée et ce en une même étape.- the sub-cutting of the elementary transducers and of a part of the film of composite material so as to define piezoelectric sub-elements separated mechanically and electrically connected. According to a variant of the method of the invention, the cutting and subcutting steps can be carried out with a diamond saw in one and the same step.
L'invention sera mieux comprise et d'autres avantages apparaîtront à la lecture de la description qui va suivre donnée à titre non limitatif et grâce aux figures annexées parmi lesquelles :The invention will be better understood and other advantages will appear on reading the description which follows given without limitation and thanks to the appended figures among which:
- la figure 1 illustre une coupe d'un exemple de sonde acoustique unidirectionnelle selon l'art connu ;- Figure 1 illustrates a section of an example of unidirectional acoustic probe according to the known art;
- la figure 2 illustre une première variante de l'invention concernant une sonde unidimensionnelle ;- Figure 2 illustrates a first variant of the invention relating to a one-dimensional probe;
- la figure 3 illustre une seconde variante de l'invention concernant une sonde bidirectionnelle.- Figure 3 illustrates a second variant of the invention relating to a bidirectional probe.
De manière générale, la sonde acoustique selon l'invention comprend des transducteurs élémentaires piézoélectriques Tij, connectés par l'intermédiaire d'un film de matériau composite conducteur à des pistes métalliques situées à la surface d'un circuit électrique situé sur un backing.In general, the acoustic probe according to the invention comprises elementary piezoelectric transducers Tij, connected via a film of conductive composite material to metal tracks located on the surface of an electrical circuit located on a backing.
Généralement, pour réaliser ce type de sonde, on fixe à la surface des transducteurs piézoélectriques une ou deux lames d'adaptation acoustique de type quart d'onde par exemple, pour améliorer le transfert d'énergie.Generally, to make this type of probe, one or two acoustic adaptation blades of the quarter-wave type, for example, are fixed to the surface of the piezoelectric transducers to improve energy transfer.
Le matériau de ces lames d'adaptation peut être de type polymère chargé de particules minérales dont on ajuste les proportions pour obtenir les propriétés acoustiques désirées. En général, ces lames sont mises en forme par moulage ou usinage puis assemblées par collage sur une des faces des transducteurs piézoélectriques.The material of these adaptation blades can be of the polymer type loaded with mineral particles, the proportions of which are adjusted to obtain the desired acoustic properties. In general, these blades are shaped by molding or machining and then assembled by gluing on one of the faces of the piezoelectric transducers.
Plus précisément, dans le cas de sondes possédant un ensemble de transducteurs élémentaires, on cherche à séparer mécaniquement les transducteurs piézoélectriques. Il est important de procéder à la découpe des lames d'adaptation acoustique pour éviter tout couplage acoustique entre transducteurs élémentaires.More specifically, in the case of probes having a set of elementary transducers, it is sought to mechanically separate the piezoelectric transducers. It is important to cut the acoustic adaptation blades to avoid any acoustic coupling between elementary transducers.
Par ailleurs, dans ce type de sonde multiéléments, chaque transducteur piézoélectrique élémentaire doit être relié d'un côté à la masse et de l'autre côté à un contact positif (encore appelé point chaud).Furthermore, in this type of phased array probe, each elementary piezoelectric transducer must be connected on one side to ground and on the other side to a positive contact (also called hot spot).
Généralement la masse est située vers le milieu de propagation, c'est-à-dire qu'elle doit être du côté des éléments d'adaptation acoustique. De manière classique, l'électrode de masse peut être une couche métallique, sa position peut dépendre de la nature de la sonde, c'est-à-dire s'il s'agit d'une sonde unidirectionnelle ou bidirectionnelle.Generally the mass is located towards the propagation medium, that is to say that it must be on the side of the acoustic adaptation elements. So conventional, the ground electrode can be a metallic layer, its position can depend on the nature of the probe, that is to say if it is a unidirectional or bidirectional probe.
Exemple de sonde unidirectionnelleExample of a unidirectional probe
Pour réaliser ce type de sonde, on peut procéder de la manière suivante :To make this type of probe, you can proceed as follows:
On réalise par collage l'assemblage suivant : A la surface du circuit électrique comprenant des pistes émergeantes par exemple collé à un backing à l'aide d'une colle de type époxy, on assemble la couche de matériau piézoélectrique audit backing par l'intermédiaire du film conducteur 3 qui de part sa nature permet l'adhérence de l'ensemble. Le film de matériau composite conducteur peut être composé d'un mélange de résine époxy et de particules métalliques (argent, cuivre, nickel ...) avec un taux de charges compris entre 50 % et 80 %, en volume en fonction des propriétés acoustiques recherchées. Le film n'a pas d'influence sur les propriétés acoustiques de la sonde car son impédance est proche de celle du backing et son épaisseur (de l'ordre de 20 à 100 μm) reste faible devant la longueur d'onde ultrasonore générée par le matériau piézoélectrique.The following assembly is carried out by bonding: On the surface of the electrical circuit comprising emerging tracks, for example bonded to a backing using an epoxy type adhesive, the layer of piezoelectric material is assembled to said backing via conductive film 3 which by its nature allows the adhesion of the whole. The film of conductive composite material can be composed of a mixture of epoxy resin and metallic particles (silver, copper, nickel ...) with a charge rate of between 50% and 80%, by volume depending on the acoustic properties. wanted. The film has no influence on the acoustic properties of the probe because its impedance is close to that of the backing and its thickness (of the order of 20 to 100 μm) remains low compared to the ultrasonic wavelength generated by the piezoelectric material.
Dans un second temps, les lames d'adaptation acoustique sont collées à la surface de la couche de matériau piézoélectrique à l'aide d'une colle de type époxy par exemple. On procède alors à la découpe par une scie diamantée de l'assemblage préalablement réalisé, pour obtenir les transducteurs élémentaires Ti1 avec une largeur de l'ordre de 100 à 150 microns. On peut réaliser dans la même opération les sous-découpes permettant de définir les sous-éléments piézoélectriques Tilk, dont la largeur est de l'ordre de 40 à 75 microns. Comme l'illustre la figure 2, alors que les découpes s'arrêtent dans le backing, les sous-découpes s'arrêtent dans l'épaisseur du film de matériau composite, permettant par là-même de conserver la connexion électrique entre les différents sous-éléments piézoélectriques Tilk, d'un même élément Ti1 surmonté de ces éléments d'adaptation acoustique L1i1k et L2i1k. La lame d'adaptation acoustique inférieure peut être métallisée au niveau de sa face inférieure de manière à assurer une reprise de masse en périphérie de la sonde.In a second step, the acoustic adaptation blades are glued to the surface of the layer of piezoelectric material using an epoxy type adhesive, for example. We then proceed to the cutting by a diamond saw of the assembly previously made, to obtain the elementary transducers Ti1 with a width of the order of 100 to 150 microns. It is possible in the same operation to make the sub-cuts allowing the Tilk piezoelectric sub-elements to be defined, the width of which is around 40 to 75 microns. As illustrated in Figure 2, while the cuts stop in the backing, the sub-cuts stop in the thickness of the film of composite material, thereby allowing to maintain the electrical connection between the different sub - Tilk piezoelectric elements, of the same Ti1 element surmounted by these acoustic adaptation elements L1i1k and L2i1k. The lower acoustic adaptation blade can be metallized at its lower face so as to provide mass recovery at the periphery of the probe.
Exemple de sonde bidirectionnelleExample of a bidirectional probe
L'assemblage du backing comportant le circuit électrique, du film composite conducteur et de la couche de matériau piézoélectrique peut typiquement être identique à celui précédemment cité dans le cas d'une sonde unidirectionnelle. Pour réaliser un plan de masse dans ce type de sonde, on peut procéder tel que dans le procédé décrit par la demanderesse dans la demande de brevet français publiée sous le n° 2 756 447, ou en intégrant un plan de masse entre les éléments transducteurs et les lames d'adaptation acoustique. Plus précisément, dans le cadre de l'invention, après avoir réalisé l'assemblage backing/film composite conducteur/couche piézoélectrique, on procède aux découpes et sous-découpes de manière à définir les éléments Tij et Tijk à l'aide d'une scie diamantée selon deux axes perpendiculaires. L'ensemble ainsi constitué est recouvert par une électrode de masse conductrice M, apposée puis collée, il peut typiquement s'agir d'une feuille métallique ou d'un film de polymère métallisé.The assembly of the backing comprising the electrical circuit, of the conductive composite film and of the layer of piezoelectric material can typically be identical to that previously cited in the case of a unidirectional probe. To make a ground plane in this type of probe, one can proceed as in the method described by the applicant in the French patent application published under No. 2,756,447, or by integrating a ground plane between the transducer elements. and the acoustic adaptation blades. More specifically, in the context of the invention, after having carried out the backing / conductive composite film / piezoelectric layer assembly, the cuts and sub-cuts are carried out so as to define the elements Tij and Tijk using a diamond saw along two perpendicular axes. The assembly thus formed is covered by an electrode of conductive mass M, affixed then glued, it can typically be a metal sheet or a film of metallized polymer.
On peut alors procéder au collage de deux lames de matériau d'adaptation acoustique L1 et L2 ; la première lame présentant une forte impédance de l'ordre de 5 à 12 MégaRayleigh, la deuxième lame présentant une plus faible impédance de l'ordre de 2 à 4 MégaRayleigh. On procède alors à la découpe des lames d'adaptation acoustique, sans découper l'électrode de masse M.It is then possible to bond two blades of acoustic adaptation material L1 and L2; the first blade having a high impedance of the order of 5 to 12 MegaRayleigh, the second blade having a lower impedance of the order of 2 to 4 MegaRayleigh. The acoustic adaptation blades are then cut, without cutting the mass electrode M.
Pour obtenir ce résultat, cette opération de découpe peut être effectuée par laser. Le laser utilisé peut être par exemple un laser infrarouge de type CO2 ou un laser UV de type Excimère ou de type YAG triplé ou quadruplé. On obtient alors une sonde bidirectionnelle comme illustrée en figure 3. To obtain this result, this cutting operation can be carried out by laser. The laser used can be, for example, an infrared laser of the CO2 type or a UV laser of the Excimer type or of the tripled or quadrupled YAG type. We then obtain a bidirectional probe as illustrated in Figure 3.

Claims

REVENDICATIONS
1. Sonde acoustique comprenant des transducteurs piézoélectriques élémentaires (Tij) et un circuit électrique comportant des pistes métalliques (Pij), de manière à connecter au moins une piste métallique à au moins un transducteur élémentaire, chaque transducteur élémentaire étant constitué de sous-éléments piézoélectriques (Tijk) séparés mécaniquement et reliés à une même piste, caractérisée en ce qu'elle comprend en outre, un film de matériau composite conducteur situé entre le circuit électrique et les transducteurs élémentaires, les sous- éléments piézoélectriques (Tijk) d'un même transducteur élémentaire (Tij) étant séparés mécaniquement par des interstices se prolongeant jusque dans ledit film.1. Acoustic probe comprising elementary piezoelectric transducers (Tij) and an electrical circuit comprising metal tracks (Pij), so as to connect at least one metal track to at least one elementary transducer, each elementary transducer being made up of piezoelectric sub-elements (Tijk) mechanically separated and connected to the same track, characterized in that it further comprises a film of conductive composite material located between the electrical circuit and the elementary transducers, the piezoelectric sub-elements (Tijk) of the same elementary transducer (Tij) being mechanically separated by interstices extending into said film.
2. Sonde acoustique selon la revendication 1 , caractérisée en ce qu'elle comprend un support acoustique dénommé « backing », le film de matériau composite possédant des propriétés acoustiques voisines de celles du backing.2. Acoustic probe according to claim 1, characterized in that it comprises an acoustic support called “backing”, the film of composite material having acoustic properties close to those of backing.
3. Sonde acoustique selon l'une des revendications 1 ou 2, caractérisée en ce que le film de matériau composite comprend des particules conductrices dont la taille est très inférieure à la longueur d'onde ultrasonore générée par la sonde. 3. acoustic probe according to one of claims 1 or 2, characterized in that the film of composite material comprises conductive particles whose size is much less than the ultrasonic wavelength generated by the probe.
4. Sonde acoustique selon l'une des revendications 1 à 3, caractérisée en ce que le film composite conducteur est un film de matériau organique de type résine époxy ou polyimide comportant des particules conductrices.4. Acoustic probe according to one of claims 1 to 3, characterized in that the conductive composite film is a film of organic material of the epoxy or polyimide resin type comprising conductive particles.
5. Sonde acoustique selon la revendication 4, caractérisée en ce que les particules conductrices sont des particules de métal de type argent, cuivre, nickel.5. Acoustic probe according to claim 4, characterized in that the conductive particles are metal particles of the silver, copper, nickel type.
6. Sonde acoustique selon l'une des revendications 1 à 5, caractérisée en ce que le film de matériau composite comporte un taux de charges conductrices compris entre 50 % et 80 % en volume. 6. Acoustic probe according to one of claims 1 to 5, characterized in that the film of composite material comprises a rate of conductive charges between 50% and 80% by volume.
7. Sonde acoustique selon l'une des revendications 1 à 6, caractérisée en ce que l'épaisseur du film de matériau composite est de l'ordre de plusieurs dizaines de microns.7. Acoustic probe according to one of claims 1 to 6, characterized in that the thickness of the film of composite material is of the order of several tens of microns.
8. Sonde acoustique selon l'une des revendications 1 à 7, caractérisée en ce que les transducteurs élémentaires (Tij) sont séparés électriquement par des interstices se prolongeant jusque dans le circuit électrique.8. Acoustic probe according to one of claims 1 to 7, characterized in that the elementary transducers (Tij) are separate electrically through gaps extending into the electrical circuit.
9. Procédé de fabrication d'une sonde acoustique selon l'une des revendications 1 à 7, caractérisé en ce qu'il comprend en outre les étapes suivantes :9. Method for manufacturing an acoustic probe according to one of claims 1 to 7, characterized in that it further comprises the following steps:
- l'assemblage d'au moins, une lame de matériau piézoélectrique, un film de matériau composite conducteur et un circuit électrique comportant des pistes métalliques ;- The assembly of at least one blade of piezoelectric material, a film of conductive composite material and an electrical circuit comprising metal tracks;
- la découpe de la lame de matériau piézoélectrique et du film de matériau composite conducteur de manière à définir des transducteurs piézoélectriques élémentaires (Tij) séparés électriquement ;- Cutting the blade of piezoelectric material and the film of conductive composite material so as to define elementary piezoelectric transducers (Tij) electrically separated;
- la sous-découpe des transducteurs élémentaires (Tij) et d'une partie du film de matériau composite de manière à définir des sous-éléments piézoélectriques (Tijk), séparés mécaniquement et connectés électriquement.- the sub-cutting of the elementary transducers (Tij) and of a part of the film of composite material so as to define piezoelectric sub-elements (Tijk), mechanically separated and electrically connected.
10. Procédé de fabrication d'une sonde acoustique selon la revendication 9, caractérisé en ce que les étapes de découpe et de sous- découpe sont effectuées avec une scie diamantée. 10. A method of manufacturing an acoustic probe according to claim 9, characterized in that the cutting and sub-cutting steps are carried out with a diamond saw.
11. Procédé de fabrication d'une sonde acoustique selon l'une des revendications 9 ou 10, caractérisé en ce que les étapes de découpe et de sous-découpe sont effectuées simultanément.11. Method for manufacturing an acoustic probe according to one of claims 9 or 10, characterized in that the cutting and subcutting steps are carried out simultaneously.
12. Procédé de fabrication selon l'une des revendications 9 à 10, caractérisé en ce que le circuit électrique est situé à la surface d'un support acoustique, la découpe pour définir les transducteurs piézoélectriques élémentaires étant effectuée jusque dans ledit support acoustique. 12. The manufacturing method according to one of claims 9 to 10, characterized in that the electrical circuit is located on the surface of an acoustic support, the cutting to define the elementary piezoelectric transducers being carried out into said acoustic support.
EP99922247A 1998-06-05 1999-06-01 Multielement sound probe comprising a composite electrically conducting coating and method for making same Expired - Lifetime EP1084000B1 (en)

Applications Claiming Priority (3)

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FR9807094 1998-06-05
FR9807094A FR2779575B1 (en) 1998-06-05 1998-06-05 MULTI-PIECE ACOUSTIC PROBE COMPRISING A CONDUCTIVE COMPOSITE FILM AND MANUFACTURING METHOD
PCT/FR1999/001284 WO1999064169A1 (en) 1998-06-05 1999-06-01 Multielement sound probe comprising a composite electrically conducting coating and method for making same

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EP1084000B1 EP1084000B1 (en) 2004-10-13

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EP (1) EP1084000B1 (en)
JP (1) JP4288002B2 (en)
KR (1) KR100577036B1 (en)
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US6522051B1 (en) 2003-02-18
KR20010043944A (en) 2001-05-25
FR2779575A1 (en) 1999-12-10
CN1304340A (en) 2001-07-18
WO1999064169A1 (en) 1999-12-16
KR100577036B1 (en) 2006-05-08
CN1217749C (en) 2005-09-07
EP1084000B1 (en) 2004-10-13
JP4288002B2 (en) 2009-07-01
FR2779575B1 (en) 2003-05-30
JP2002517310A (en) 2002-06-18

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