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.

Applications Claiming Priority (3)

Publications (2)

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Country Status (7)

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• 1998
  • 1998-06-05 FR FR9807094A patent/FR2779575B1/fr not_active Expired - Fee Related
• 1999
  • 1999-06-01 JP JP2000553223A patent/JP4288002B2/ja not_active Expired - Fee Related
  • 1999-06-01 KR KR1020007013515A patent/KR100577036B1/ko not_active IP Right Cessation
  • 1999-06-01 CN CN998070041A patent/CN1217749C/zh not_active Expired - Fee Related
  • 1999-06-01 WO PCT/FR1999/001284 patent/WO1999064169A1/fr active IP Right Grant
  • 1999-06-01 EP EP99922247A patent/EP1084000B1/de not_active Expired - Lifetime
  • 1999-06-01 US US09/701,560 patent/US6522051B1/en not_active Expired - Lifetime

Non-Patent Citations (1)

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