WO2011073414A2

WO2011073414A2 - Oscillatory system for an ultrasonic transducer and method for producing the oscillatory system

Info

Publication number: WO2011073414A2
Application number: PCT/EP2010/070128
Authority: WO
Inventors: Franz Rinner
Original assignee: Epcos Ag
Priority date: 2009-12-18
Filing date: 2010-12-17
Publication date: 2011-06-23
Also published as: WO2011073414A3; DE102010010099A1

Abstract

The invention relates to an oscillatory system (1) for an ultrasonic transducer. The system (1) comprises a membrane (4), which is supported on a base (2). The system (1) further comprises a piezoelectrical system (3), which is fastened to the membrane (4) by means of an electrically conductive adhesion promoter (5). Moreover, a method for producing an oscillatory system (1) for an ultrasonic transducer is provided.

Description

description

Oscillating system for an ultrasonic transducer and

Method for producing the oscillatory system

It is specified for an ultrasound transducer ^¬ an oscillatory system. The oscillatory system is used

For example, as an ultrasonic transmitter or ultrasonic ^¬ receiver, by means of which the distance to an obstacle can be determined.

An object to be solved is to provide a vibratory system for an ultrasonic transducer, which is inexpensive to manufacture.

It is specified for an ultrasound transducer ^¬ an oscillatory system. The system has a membrane supported by a pedestal. A piezoelectric element is arranged on the membrane and connected in an electrically conductive manner to the membrane.

For example, the system is used as an ultrasonic transmitter for delivering an ultrasonic signal. For this purpose, the piezoelectric element is electrically excited by applying a voltage and thereby resulting in the element electric field. The piezoelectric element expands or contracts, depending on the direction of the electric field, thereby causing the diaphragm to vibrate. Preferably, the base is formed such that it forms together with the membrane a resonator body, for example, has the shape of a drum, which by the vibrations of the

Membrane is excited in its resonant frequency and thus emits an ultrasonic signal. The system can be used simultaneously or alternatively as an ultrasonic receiver. In this case, an ultrasonic signal, for example after reflection at an obstacle, strikes the membrane, whereupon it is excited to oscillate. This results in a deformation, for example, an expansion or contraction of the piezoelectric

Elements, whereby this generates an electrical signal. From the time interval between the transmission of the ultrasonic signal and the arrival of the ultrasonic signal, the distance to the obstacle can be determined.

Due to the electrically conductive connection of the piezoelectric element with the membrane, an electrical contacting of the element over the membrane is made possible. This allows greater freedom in the arrangement and the

Fixing an electrical contact as one

Attachment of a separate electrical connection element, for. B. a contact wire, directly on an outer side of the piezoelectric element.

Preferably, the membrane and at least the part of the base adjacent to the membrane are electrically conductive and electrically conductively connected to each other. In this case, an electrical contact to an outside of the

piezoelectric element can be made via the base and the membrane.

Preferably, the piezoelectric element is attached to the membrane by means of an electrically conductive adhesive. The adhesive may be disposed in the form of a layer between the piezoelectric element and the membrane. In a preferred embodiment, the adhesive is an electrically conductive adhesive. The adhesive can be used in this case both for electrical contacting and for fixing the piezoelectric element to the membrane. In particular, an electrical contact to the piezoelectric element via the base, the membrane and the electrically conductive

Adhesive are running running. This allows a particularly simple and space-saving electrical

Contacting the piezoelectric element, since the

Production of the electrical contact of the

piezoelectric element, which is passed over the adhesive, already takes place during the attachment and therefore no additional process step is needed.

For example, the membrane and the base are made in one piece. The base and the membrane can as

Main component contain aluminum or consist entirely of aluminum. Preferably, the pedestal with the diaphragm forms a drum which can be excited to vibrate at its resonant frequency.

Preferably, the system has a first electrical

Connection for contacting the piezoelectric element.

In a preferred embodiment, the first one

electrical connection electrically connected to the membrane. Preferably, the membrane is electrically conductively connected to the base, so that a contacting of the piezoelectric element via the base and the membrane can take place.

For example, the first electrical connection is arranged on the base and, preferably, attached to the base. At a Attachment of the first connection is at the base, z. B. compared with a mounting of the first terminal on the piezoelectric element, a relatively large

Mounting surface available. This allows a simple and inexpensive production of the contact.

Preferably, the system also has a second one

electrical connection, so that by means of the first and the second electrical connection, a voltage can be applied to the piezoelectric element.

For example, the second electrical connection is attached to an outer side of the piezoelectric element.

Preferably, the second electrical connection is on

attached to the outside of the piezoelectric element which faces away from the membrane. For example, the piezoelectric element is attached to the membrane with a first outer side, and the second connection is attached to the second outer side opposite the first outer side. The second outer side is preferably facing a cavity bounded by the base and the membrane.

For example, the electrical connections as

Bonding wires formed. The bonding wires may have the same material as the socket. For example, contains at least the first electrical connection as a main ingredient ^¬ aluminum.

The piezoelectric element preferably has the shape of a small plate. The first outside and the second Outside are, for example, the opposite major surfaces of the plate ^¬ .

In one embodiment, on an outside of the

piezoelectric element is an electrically conductive

Contact layer arranged. Preferably, the

Contact layer arranged on the outside, on which the second electrical connection is attached. Especially

Preferably, the second electrical connection is at the

Contact layer attached.

By means of the electrically conductive contact layer, a particularly reliable contacting of the piezoelectric element by the second electrical connection can be achieved. In addition, the contact layer allows a reliable attachment of the second terminal to the piezoelectric element.

For example, the contact layer comprises a

Metallization, the z. B. contains as the main component aluminum. This is particularly advantageous if the second electrical connection is also the main component

Contains aluminum. Particularly preferably, the base, the membrane, the contact layer, the first and the second electrical connection contain the same material as the main component. In this case, a particularly good electrical connection of the individual elements is possible. In addition, both connections can be made of the same material, so that the system can be manufactured inexpensively.

In a preferred embodiment, the

Contact layer over the entire surface of the outside of the piezoelectric element to which the second terminal is attached.

In a full-scale extension covers the

Contact layer this outside as completely as possible.

In particular, the electrically conductive contact layer has as few recesses as possible.

In this way, the piezoelectrically active part of the piezoelectric element can be formed as large as possible. In particular, the entire surface of the first outer side can be used to generate an electric field. This allows compared to contact layers, the one

Have structuring in the form of recesses, so that z. B. two terminals of different polarity at the

the same external side of the piezoelectric element can be mounted, a miniaturization of the system with a piezoactively active part of the same size

piezoelectric element.

Preferably, the outside of the piezoelectric

Element to which the second port is attached

rotationally symmetrical and at the same time full surface of the

Contact layer covered. As a result, both the

Receive and transmit properties of the system

improve .

Preferably, the electrically conductive extends

Adhesive over the entire surface of an outside of the

piezoelectric element. Particularly preferred is a contact layer on the opposite outer side

applied. For example, the piezoelectric element

formed disc-shaped, wherein the first and the second outer side of the element form the main surfaces thereof. In the case that the contact layer and the electrically conductive adhesive in each case over the entire surface of opposite

Main surfaces of the element extend, the piezoelectric active part of the piezoelectric element can be maximized.

In a preferred embodiment, the contact layer is arranged only on an outer side of the piezoelectric element and all other outer sides are free of the material of the contact layer.

In this way, the piezoelectric properties of the piezoelectric element can be improved. In addition, an electrical insulation of the electrically conductive

Adhesive can be reliably produced by the contact layer. Preferably belong to an outside of the

piezoelectric element all outer surfaces of the element, which are oriented in the same direction. For example, the piezoelectric element has two major surfaces located on two opposite sides of the element

and several side surfaces. The contact layer is in this case preferably only on one of

Main surfaces arranged so that the opposite

Main surface and side surfaces free from the material of

Contact layer are.

Furthermore, a method for producing a

oscillatory system for an ultrasonic transducer

specified. In this case, a piezoelectric element and a membrane are provided, which are supported by a pedestal is. In addition, an electrically conductive adhesive

provided. Preferably, the electrically conductive adhesive is applied to at least one of the amount of the membrane and the piezoelectric element. For example, the adhesive may be applied only to the membrane or only to the piezoelectric element. It is also possible to apply the adhesive to both the membrane and the piezoelectric element.

The piezoelectric element is attached to the membrane so that attachment of the element to the membrane is achieved by the electrically conductive adhesive. In this case, the piezoelectric element can be pressed against the membrane so as to achieve a reliable as possible attachment.

In further steps of the method, a first electrical connection and a second electrical connection for applying a voltage to the piezoelectric element can be provided. Preferably, the terminals as a main component contain a material from the amount of silver, aluminum, copper. For example, the terminals are formed as bonding wires.

The first electrical connection is fastened, for example, to the base, so that an electrically conductive connection is made from the connection to the base. The second electrical connection is attached to the piezoelectric element. The attachment of the electrical connections can take place before or after the attachment of the piezoelectric element to the membrane. Preferably, a contact layer on a first

Outside of the piezoelectric element applied. The contact layer is preferably before the step of

Attachment of the piezoelectric element applied to the membrane. The second electrical connection is

preferably attached to the contact layer.

For example, the contact layer is a metallization baked on the piezoelectric element

educated. The material of the metallization can through

Screen printing or applied in a sputtering process. For example, the metallization contains one or more components from the amount containing silver, aluminum and copper.

Preferably, the contact layer is only on one of

Outside of the piezoelectric element applied, so that all other outer sides free of the material

Contact layer are.

Furthermore, an ultrasonic transducer is provided, which is a membrane, which is supported by a socket and a

piezoelectric element which is arranged on the membrane has. The piezoelectric element is electrically connected to the membrane. In particular, the

Ultrasonic transducers have all the features of the oscillatory system described above.

The objects described here are explained in more detail below with reference to schematic and not to scale embodiments. Show it: FIG. 1 is a sectional view of a vibratable system for an ultrasonic transducer;

Figure 2 is a plan view of the back of the oscillatory

System of FIG. 1,

Figure 3 shows a detail of the swingable

System of Figure 1.

FIG. 1 shows a vibratory system 1 which can be used in an ultrasound transducer and in particular an ultrasound sensor. The oscillatory system 1 serves as part of an ultrasonic transmitter or

Ultrasonic receiver.

The oscillatory system 1 has a base 2, on whose upper side 21 a vibratable membrane 4 is arranged. The membrane 4 and the base 2 are made of one piece. For example, the base 2 and the membrane 4 contain aluminum as a main component. The base 2, together with the membrane 4, a drum, in its

Resonant frequency can be excited.

On the membrane 4, a piezoelectric element 3 is attached in the form of a small plate. The piezoelectric element 3 is fixed to an inner side 41 of the membrane 4 and thus arranged within a cavity 24 formed by the base 2 and the membrane 4. The piezoelectric element 3 is fixed to the membrane 4 by means of an electrically conductive adhesive (not shown here).

For applying an electrical voltage between a first 31 and a second outer side 32 of the piezoelectric Elements 3, a first electrical connection 7 and a second electrical connection 6 are provided. The terminals 6, 7 can also be used to detect an applied between the outer sides 31, 32 electrical voltage.

The terminals 6, 7 are formed as bonding wires. The second electrical terminal 6 is fixed to the outer side 31 of the piezoelectric element 3, which faces the cavity 24. The first electrical connection 7 is at

Socket 2 attached. The base 2, the membrane 4 and the

Adhesive for fixing the piezoelectric element 3 are electrically conductive and electrically conductively connected to each other.

When the system 1 to transmit an ultrasonic signal

is used, by means of the terminals 6, 7 a

Voltage between the first 32 and the second outer side 31 applied. The piezoelectric element 3 expands or contracts perpendicular to its main extension plane 34. This leads to a deformation of the membrane 4 and as a result to a vibration of the membrane 4 in a direction 35 perpendicular to the main extension plane 34. The drum is preferably at its resonant frequency

stimulated, for example, at about 50 kHz.

When using the system to receive a

Ultrasound signal is the membrane 4 vibrated by an incoming ultrasonic signal. Due to the resulting bending of the piezoelectric element 3, an electrical voltage between the terminals 6, 7 is generated. From the time difference between sending and receiving an ultrasonic signal, the distance to an obstacle can be determined. FIG. 2 shows a plan view of a rear side 12 (see FIG. 1) of the oscillatable system 1. The base 2 has a tubular shape and has a cavity 24 which is delimited by the membrane 4 at one end. The cavity 24 here has an elliptical circumferential line. Depending on the desired radiation characteristic of the cavity 24 may also have a different shape. On the cavity 24th

facing inside 41 of the membrane 4 is the

attached piezoelectric element 3. The piezoelectric element 3 has the shape of a plate with a

circular circumference.

On an outer side 31 of the piezoelectric element 3, the second terminal 6 is attached in the form of a bonding wire. The first terminal 7 is fixed to the underside 22 of the base 2.

The contact layer 8 is completely on the first

Outside 31 of the piezoelectric element 3 is applied and thus extends over the entire first outer side 31st

FIG. 3 shows in detail the attachment of the piezoelectric element 3 to the membrane 4.

The piezoelectric element 3 is fixed to the membrane 4 by means of the conductive adhesive 5. The adhesive 5 produces a positive and sufficiently rigid attachment of the piezoelectric element 3 to the membrane. The conductive adhesive 5 is disposed between the diaphragm 4 and the piezoelectric element 3 and covers the membrane-facing outside 32 of the piezoelectric

Elements 3, and a part of the inside 41 of the membrane. 4 The electrically conductive adhesive 5 has the shape of a layer and completely covers the outer side 32 of the piezoelectric element 3 facing the membrane. In this way, the piezoelectrically active part of the

formed as large as possible piezoelectric element 3.

In addition, the adhesive 5 also produces an electrical connection between the first outer side 32 and the membrane 4, so that an electrical voltage can be applied between the first 31 and the second outer side 32 via the adhesive 5. Since the base 2, the membrane 4 and the adhesive 5 are electrically conductive, the electrical voltage can be applied by means of a first terminal 7 fixed to the base 2 and one on an outer side 31 of the piezoelectric element 3

attached second terminal 6 are created.

Reference sign list

1 oscillatory system

11 front side

12 back side

2 sockets

21 top

22 bottom

24 cavity

3 piezoelectric element

31 first outside

32 second outside

34 main extension plane

35 direction perpendicular to the main extension plane 36, 37 more outsides

4 membrane

41 inside

5 electrically conductive adhesive

6 second electrical connection

7 first electrical connection

8 contact layer

Claims

claims

An oscillatory system for an ultrasonic transducer having a diaphragm (4) carried by a pedestal (2) and a piezoelectric element (3) disposed on the diaphragm (4) and electrically conductive with the diaphragm (4) ) connected is.

2. oscillatory system according to claim 1,

in which the piezoelectric element (3) is attached to the membrane by means of an electrically conductive adhesive (5).

3. oscillatory system according to one of claims 1 or 2 with a first electrical connection (7) for applying a voltage to the piezoelectric element (3), wherein the first electrical connection (7) is electrically conductively connected to the membrane (2).

4. oscillatory system according to claim 3,

wherein the first electrical connection (7) on the base

(2) is arranged.

An oscillatory system according to any one of claims 1 to 4, comprising a second electrical terminal (6) for applying a voltage to the piezoelectric element (3) on an outer side (31) of the piezoelectric element

(3) is attached.

6. oscillatory system according to claim 5,

in which an electrically conductive contact layer (8) is arranged on the outer side (31).

7. oscillatory system according to claim 6,

wherein the second terminal (6) is attached to the contact layer (8).

8. oscillatory system according to any one of claims 6 or 7, wherein the contact layer (8) over its entire surface over the outer side (31).

9. The oscillatory system according to any one of claims 6 to 8, wherein the contact layer (8) is arranged only on an outer side (31) and all other outer sides (32, 36, 37) of the piezoelectric element (3) free of the material of the contact layer (8) are.

10. An oscillatory system according to any one of claims 1 to 9, wherein the adhesive (5) is formed as an electrically conductive adhesive.

11. An oscillatory system according to any one of claims 1 to 10, wherein the piezoelectric element (3) has the shape of a small plate.

12. A method of manufacturing a vibratable system for an ultrasonic transducer comprising the steps

A) providing a piezoelectric element (3) and a membrane (4) carried by a base (2),

B) providing an electrically conductive

Adhesive (5) and

C) attaching the piezoelectric element (3) to the membrane (4), so that a fastening by the

electrically conductive adhesive (5) is produced. The method of claim 12 with the additional

steps

D) providing a first electrical connection (7) and a second electrical connection (6) to the

Applying a voltage to the piezoelectric element (3),

E) attaching the second electrical connection (6) to the piezoelectric element (3).

F) Attaching the first electrical connection (7) to the base (2).

14. The method according to any one of claims 12 or 13 with the additional step

G) applying a contact layer (8) to a

Outside (31) of the piezoelectric element (3).

Method according to claim 14,

wherein in step G) the contact layer (8) is applied only on an outer side (31) of the piezoelectric element (3) so that all other outer sides (32, 36, 37) of the piezoelectric element (3) are free of the material of the contact layer ( 8).