Metal working – Piezoelectric device making
Patent
1995-08-29
1998-07-07
Hall, Carl E.
Metal working
Piezoelectric device making
310336, H01L 4122
Patent
active
057749604
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to manufacturing processes which can be used to obtain acoustic probes comprising a set of transmitter and/or receiver elements obtained by cutting from a large-sized transducer block. It essentially relates to the means which can be used to make the electrical connections between these elements and the electronic devices which are connected to them. It makes it possible to facilitate the manufacture of transducers which include a large number of elements arranged in a two-dimensional arrangement. It also applies to one-dimensional arrangements, since these are easier to produce than the two-dimensional arrangements.
In order to obtain a beam of acoustic waves, that is directed and focused as required, from an electroacoustic transducer equipping an echograph probe, this transducer is generally divided into a set of elements supplied by signals suitably phase-shifted or staggered over time. This set of elements is generally obtained by cutting a block of transducer material, and the electrical signals applied to these elements are brought in via a set of connections made by various means. The most widely-used probes comprise a set of elements placed in a one-dimensional alignment. The connections to these elements are then taken off, either laterally or in the top and bottom planes of the block of piezoelectric ceramic from which the elements have been cut. A description of such a probe will, for example, be found in the French patent filed on 28 Nov., 1986 under No. 86/16660 and published on 3 Jun., 1988 under No. 2,607,590. Since these planes are continuous, it is only necessary to establish a single connection and the available area is large.
Such a one-dimensional arrangement has major limitations in the use of the probe and with regard to the images obtained. It has therefore been sought to make two-dimensional arrangements in which the transducer elements are arranged as the cells of a lattice, these being square for example. In this case, the number of elementary transducers to be connected is much greater and it is possible to take off, via a lateral access, only the connections for the elements along the edges of the lattice. It is therefore absolutely essential to make contact in the top and bottom planes of the set of transducers, which are, in this case, subdivided into a relatively large number of separate areas. It is therefore necessary to use a connection method which limits the overall size due to the connections themselves, so as not to increase the size of the probe excessively, and which does not disturb, in an excessive manner, the acoustic properties of the transducers and therefore of the probe.
Technologies are known which can be used to obtain a two-dimensional array of electrical connections, for example by reflowing indium balls. These technologies generally use rigid substrates which disturb the acoustic operation of the transducers. Furthermore, the problem of routing the connections to the outside is not solved thereby.
In order to solve these problems, the invention provides a process for manufacturing a multi-element acoustic probe, especially an echograph probe, in which a piezoelectric plate is divided into a set of elementary transducers that are subsequently equipped with connections, principally characterized in that this plate is firstly fixed to one face of a first polymer film, in that this film is drilled at the points where the connections with the said elementary transducers are to be established, by means of an etching process making it possible to attack the polymer film without attacking the piezoelectric plate, in that conducting tracks are deposited on the other face of the polymer film, which conducting tracks will be connected to the elements via the holes thus drilled in the film, and in that the cuts are then made which allow the elementary transducers to be individualized.
Other features and advantages of the invention will appear clearly in the following description, given by way of non-limiting example with regard to the a
REFERENCES:
patent: 4747192 (1988-05-01), Rokurota
patent: 5091893 (1992-02-01), Smith et al.
Bureau Jean-Marc
de Fraguier Sixte
Gelly Jean-Fran.cedilla.ois
"Thomson-CSF"
Hall Carl E.
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