DE102010010099A1 - Oscillatable system for an ultrasonic transducer and method of manufacturing the oscillatory system - Google Patents

Abstract

An oscillatable system (1) for an ultrasonic transducer is specified. The system (1) has a membrane (4) which is carried by a base (2). In addition, the system (1) has a piezoelectric element (3) which is attached to the membrane (4) by means of an electrically conductive adhesive (5). In addition, a method for producing an oscillatory system (1) for an ultrasonic transducer is specified.

Description

An oscillatory system for an ultrasonic transducer is specified. 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.

An oscillatory system for an ultrasonic transducer is specified. 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 form of a drum, which is excited by the vibrations of the membrane in their resonant frequency and 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 element, 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 attachment of an electrical contact than in a mounting 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 may be made to an outside of the piezoelectric element via the pedestal and the diaphragm.

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, electrical contact may be made with the piezoelectric element via the pedestal, the membrane and the electrically conductive adhesive. This allows a particularly simple and space-saving electrical contacting of the piezoelectric element, since the preparation of the electrical contacting of the piezoelectric element, which is guided 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 may contain aluminum as its main component or may 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 electrical connection is electrically conductively 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. When attaching the first connector to the base is, 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 electrical connection, so that by means of the first and the second electrical After connecting 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 attached to that outer side 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 are formed as bonding wires. The bonding wires may have the same material as the socket. For example, at least the first electrical connection contains aluminum as the main component.

The piezoelectric element preferably has the shape of a small plate. The first outer side and the second outer side are, for example, the opposing major surfaces of the plate.

In one embodiment, an electrically conductive contact layer is arranged on an outer side of the piezoelectric element. Preferably, the contact layer is disposed on the outside, to which the second electrical connection is attached. Particularly preferably, the second electrical connection is attached to the contact layer.

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 also contains aluminum as its main component. 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 extends over the entire surface of the outside of the piezoelectric element to which the second terminal is attached.

In the case of a full-surface extent, the contact layer covers 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 in comparison to contact layers having a structuring in the form of recesses, so that z. B. two terminals of different polarity can be attached to the same outer side of the piezoelectric element, a miniaturization of the system with an equal sized piezoelectric active part of the piezoelectric element.

Preferably, the outer side of the piezoelectric element, to which the second connection is attached, is rotationally symmetrical and at the same time completely covered by the contact layer. This can improve both the reception and transmission characteristics of the system.

Preferably, the electrically conductive adhesive extends over the entire surface over an outer side of the piezoelectric element. Particularly preferably, a contact layer is applied on the opposite outer side.

For example, the piezoelectric element is disc-shaped, with the first and the second outer side of the element forming its main surfaces. In the case that the contact layer and the electrically conductive adhesive each extend over the entire area over opposite major surfaces of the element, the piezoelectrically 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, all outer surfaces of the outer side of the piezoelectric element belong to the Elements oriented in the same direction. For example, the piezoelectric element has two major surfaces located on two opposite sides of the element and a plurality of side surfaces. The contact layer is in this case preferably arranged only on one of the main surfaces, so that the opposite main surface and the side surfaces are free of the material of the contact layer.

Furthermore, a method for producing a vibratory system for an ultrasonic transducer is given. In this case, a piezoelectric element and a membrane are provided, which is supported by a socket. In addition, an electrically conductive adhesive is 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 is applied to a first outer side of the piezoelectric element. The contact layer is preferably applied to the membrane prior to the step of attaching the piezoelectric element. The second electrical connection is preferably fastened to the contact layer.

For example, the contact layer is formed as a burnt-on metallization on the piezoelectric element. The material of the metallization can be applied by screen printing or 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 applied only on one of the outer sides of the piezoelectric element, so that all other outer sides are free of the material of the contact layer.

Further, an ultrasonic transducer is provided which has a diaphragm supported by a pedestal and a piezoelectric element disposed on the diaphragm. The piezoelectric element is electrically connected to the membrane. In particular, the ultrasonic transducer can 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:

1 a sectional view of a vibratory system for an ultrasonic transducer,

2 a view of the back of the oscillatory system 1 .

3 a detail of the oscillatory system 1 ,

1 shows an oscillatory system 1 , which can be used in an ultrasonic transducer and in particular an ultrasonic sensor. The oscillatory system 1 serves as part of an ultrasonic transmitter or ultrasonic receiver.

The oscillatory system 1 has a pedestal 2 on top of it 21 a vibratable membrane 4 is arranged. The membrane 4 and the pedestal 2 are made of one piece. For example, the socket included 2 and the membrane 4 as main component aluminum. The base 2 forms together with the membrane 4 a drum that can be excited at its resonant frequency.

At the membrane 4 is a piezoelectric element 3 attached in the form of a small plate. The piezoelectric element 3 is on an inside 41 the membrane 4 attached and thus within one of the pedestal 2 and the membrane 4 formed cavity 24 arranged. The piezoelectric element 3 is by means of an electrically conductive adhesive (not shown here) on the membrane 4 attached.

For applying an electrical voltage between a first 31 and a second outside 32 of the piezoelectric element 3 are a first electrical connection 7 and a second electrical connection 6 intended. The connections 6 . 7 You can also capture one between the outsides 31 . 32 Serve applied voltage.

The connections 6 . 7 are formed as bonding wires. The second electrical connection 6 is on the outside 31 of the piezoelectric element 3 attached to the cavity 24 is facing. The first electrical connection 7 is on the pedestal 2 attached. The base 2 , the membrane 4 and the adhesive for fixing the piezoelectric element 3 are electrically conductive and electrically connected to each other.

If the system 1 is used to send an ultrasonic signal is by means of the terminals 6 . 7 a tension between the first 32 and the second outside 31 created. The piezoelectric element 3 Expands perpendicular to its main plane of extension 34 out or contract. This leads to a deformation of the membrane 4 and as a result to a vibration of the membrane 4 in one direction 35 perpendicular to the main extension plane 34 , The drum is preferably excited at its resonant frequency, which is for example at about 50 kHz.

When using the system for receiving an ultrasonic signal, the membrane becomes 4 vibrated by an incoming ultrasonic signal. Due to the resulting bending of the piezoelectric element 3 will be an electrical voltage between the terminals 6 . 7 generated. From the time difference between sending and receiving an ultrasonic signal, the distance to an obstacle can be determined.

2 shows a view of a back 12 (please refer 1 ) of the oscillatory system 1 , The base 2 is tubular and has a cavity 24 on, at one end of the membrane 4 is limited. The cavity 24 here has an elliptical circumferential line. Depending on the desired radiation characteristics of the cavity 24 also have a different shape. On the the cavity 24 facing inside 41 the membrane 4 is the piezoelectric element 3 attached. The piezoelectric element 3 has the shape of a small plate with a circular circumference.

On an outside 31 of the piezoelectric element 3 is the second connection 6 attached in the form of a bonding wire. The first connection 7 is at the bottom 22 of the pedestal 2 attached.

The contact layer 8th is completely on the first outside 31 of the piezoelectric element 3 applied and thus extends over the entire first outside 31 ,

3 shows in detail the attachment of the piezoelectric element 3 on the membrane 4 ,

The piezoelectric element 3 is by means of the conductive adhesive 5 on the membrane 4 attached. The adhesive 5 provides a positive and sufficiently rigid attachment of the piezoelectric element 3 on the membrane. The conductive adhesive 5 is between the membrane 4 and the piezoelectric element 3 arranged and covers the membrane facing the outside 32 of the piezoelectric element 3 , as well as a part of the inside 41 the membrane 4 , The electrically conductive adhesive 5 has the shape of a layer and covers the outer side facing the membrane 32 of the piezoelectric element 3 Completely. In this way, the piezoelectrically active part of the piezoelectric element 3 as large as possible.

In addition, the adhesive provides 5 also an electrical connection of the first outside 32 with the membrane 4 forth, so that over the glue 5 an electrical voltage between the first 31 and the second outside 32 can be created. As the pedestal 2 , the membrane 4 and the glue 5 are electrically conductive, the electrical voltage can by means of a sockets 2 attached first connection 7 and one on an outside 31 of the piezoelectric element 3 attached second connection 6 be created.

LIST OF REFERENCE NUMBERS

1

Oscillating system

11

front

12

back

2

base

21

top

22

bottom

24

cavity

3

piezoelectric element

31

first outside

32

second outside

34

Main 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

8th

contact layer

Claims (15)

Oscillatable system for an ultrasonic transducer with a membrane ( 4 ), from a pedestal ( 2 ) and with a piezoelectric element ( 3 ) attached to the membrane ( 4 ) is arranged and electrically conductive with the membrane ( 4 ) connected is. Oscillatable system according to claim 1, wherein the piezoelectric element ( 3 ) by means of an electrically conductive adhesive ( 5 ) is attached to the membrane. Oscillatable 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 ) electrically conductive with the membrane ( 2 ) connected is. Oscillatable system according to claim 3, wherein the first electrical connection ( 7 ) on the base ( 2 ) is arranged. Oscillatable system according to one of claims 1 to 4 with a second electrical connection ( 6 ) for applying a voltage to the piezoelectric element ( 3 ), which on an outside ( 31 ) of the piezoelectric element ( 3 ) is attached. Oscillatable system according to claim 5, wherein on the outside ( 31 ) an electrically conductive contact layer ( 8th ) is arranged. Oscillatable system according to claim 6, in which the second connection ( 6 ) at the contact layer ( 8th ) is attached. Oscillatable system according to one of claims 6 or 7, in which the contact layer ( 8th ) over the entire surface ( 31 ). Oscillatable system according to one of Claims 6 to 8, in which the contact layer ( 8th ) only on one side ( 31 ) and all other outer pages ( 32 . 36 . 37 ) of the piezoelectric element ( 3 ) free of the material of the contact layer ( 8th ) are. An oscillatory system according to any one of claims 1 to 9, wherein the adhesive ( 5 ) is formed as an electrically conductive adhesive. Oscillatable system according to one of claims 1 to 10, in which the piezoelectric element ( 3 ) has the shape of a platelet. Method for producing a vibratory system for an ultrasonic transducer, comprising the steps A) providing a piezoelectric element ( 3 ) and one from a pedestal ( 2 ) supported membrane ( 4 B) providing an electrically conductive adhesive ( 5 ) and C) attaching the piezoelectric element ( 3 ) to the membrane ( 4 ), so that attachment by the electrically conductive adhesive ( 5 ) will be produced. Method according to claim 12 with the additional steps D) providing a first electrical connection ( 7 ) and a second electrical connection ( 6 ) for applying a voltage to the piezoelectric element ( 3 ), E) attaching the second electrical connection ( 6 ) on the piezoelectric element ( 3 ). F) Fastening the first electrical connection ( 7 ) on the base ( 2 ). Method according to one of claims 12 or 13 with the additional step G) applying a contact layer ( 8th ) on an outside ( 31 ) of the piezoelectric element ( 3 ). The method of claim 14, wherein in step G) the contact layer ( 8th ) only on an outside ( 31 ) of the piezoelectric element ( 3 ) is applied, so that all other outer sides ( 32 . 36 . 37 ) of the piezoelectric element ( 3 ) free of the material of the contact layer ( 8th ) are.

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