Metal working – Piezoelectric device making
Patent
1997-07-02
2000-04-04
Hall, Carl E.
Metal working
Piezoelectric device making
29848, 310334, 310365, H01L 4122
Patent
active
060445335
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The field of the invention is that of acoustic transducers which can be used in particular in medical or underwater imaging.
DISCUSSION OF THE BACKGROUND
In general, an acoustic probe comprises a set of piezoelectric transducers connected to an electronic control device via an interconnection system. These piezoelectric transducers emit acoustic waves which, after reflection off a given medium, deliver information relating to the said medium. Acoustic waves emitted not towards the external medium to be analysed, but in the opposite direction, disturb the response of the medium and make it essential to interpose, between the piezoelectric transducers and the electronic device, a medium which absorbs the acoustic waves. The presence of this intermediate element makes the interconnection of all the transducers even more complicated.
This interconnection problem is one of the main problems currently encountered in the manufacture of acoustic imaging probes. This is because the miniaturization and the number of piezoelectric elements, combined with the space limitation constraints encountered in echograph probes designed to be used in intracavity mode, require increasingly integrated technologies.
However, when a two-dimensional matrix of transducers is envisaged, it is necessary to produce a surface-type system for connecting the elements, this being complicated by the presence of the acoustically absorbent layer.
Currently, several solutions have been envisaged.
Thus, the Applicant Company in its patent application published under U.S. Pat. No. 2,702,309 describes a process for producing a surface-type connection system which uses an intermediate polymer film sufficiently thin not to disturb the acoustic operation of the transducers, through which film conducting tracks brought into contact with the acoustic transducers are produced. Nevertheless, the interconnection of a two-dimensional matrix having a large number of elements may require the production of a multilayer structure, which means limitations in terms of manufacturing cost and of acoustic "transparency".
Another problem, related to the problem of multiplicity of the connections, is that of the electronics for the transducers. This is because electronic circuits are necessary to manage both the emission and reception of the elements of the transducer. In the case of medical imaging where ergonomics of the probe are essential, these circuits are presently transferred to the echograph, which constitutes the unit for controlling and processing the signal. This configuration requires the use of coaxial cables (one per transducer element) between the probe and the echograph, causing problems in the case of a large number of elements. There is therefore a strong motivation to integrate as close as possible to the transducer some of this electronic circuitry, such as, for example, preamplification integrated circuits.
SUMMARY OF THE INVENTION
In order to respond to these various problems, the subject of the invention is an acoustic probe comprising a matrix of M piezoelectric transducers in a direction D.sub.y and of N piezoelectric transducers in a direction D.sub.x orthogonal to D.sub.y, these being distributed on the surface of an acoustically absorbent material, and an interconnection system connecting the acoustic transducers to an electronic device, characterized in that the interconnection system comprises: contact with the M.times.N piezoelectric transducers and are distributed with a spacing P.sub.N in the direction D.sub.x and with a spacing P.sub.M in the direction D.sub.y, within the acoustically absorbent material; over M dielectric substrates separated by a spacing P'.sub.M each comprising N tracks distributed with a spacing P'.sub.N.
According to one variant of the invention, the dielectric substrates are flexible printed circuits. Advantageously, they may comprise components connected as input to the N conducting rows and as output to N.sub.S conducting rows, N.sub.S being less than N.
In one variant of t
Bernard Fran.cedilla.ois
Bureau Jean-Marc
Calisti Serge
"Thomson-CSF"
Hall Carl E.
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