EP0090267B1 - Ultrasonic transducer and method for its manufacture - Google Patents

Abstract

1. An ultrasonic applicator comprising an acoustic head which has finely divided transducer elements (2), a plurality of which are electrically combined to form groups (3) by contact sheets which are placed onto the counter-surfaces (6) of the transducer elements (2), which are opposite the reflecting surfaces (5), characterised in that the contact sheets have the shape of a longitudinal strip (20; 22) which extends in the region between the ends of the transducer elements (2) at right angles to the counter-surfaces (6), that the strip (20; 22) is designed as a comb (7) with a plurality of electrical contact lugs (8) and a plurality of consecutive recesses (9; 21), where the recesses are open at the strip edge which faces away from the counter-surfaces (6) of the transducer elements (2) and where their depth of cut (h, h') in the direction of the counter-surfaces (6) of the transducer elements (2) is smaller than the overall height (H) of the strip (20; 22), that in the region of each recess (9; 21) the strip (20, 22) is provided with at least one slot (12) which extends through the strip ridge (10) from the recess (9; 21) to a gap (14) between two adjacent transducer elements (2), and thereby separates two adjacent transducer elements (2), and that the base width (c) of the recess (9, 21) is essentially greater than the width (s) of the slot (12).

Description

The invention relates to an ultrasound applicator according to the preamble of claim 1. It also relates to a method for producing such an ultrasound applicator.

EP-A-0 040 374 already discloses an ultrasound applicator and a method for producing the same, in which the transducer elements on the transducer are finely divided. Several transducer elements are electrically combined into a finely divided group by the individual contact tongues of a contact sheet cut several times in parallel. A total of two cut-in contact plates are present on the counter surfaces of the transducer elements of a group, one of which is attached along the left edge of the transducer element arrangement and the other along the right edge of the transducer element arrangement. The two contact plates have a triangular shape and are made of foil material. Each triangular contact plate is bent in the uncut area opposite to the direction of radiation of the ultrasound head. Depending on the number of groups used, a plurality of contact plates on the right and an equal number of contact plates on the left are provided along the edges of the transducer element arrangement. A common rod-shaped current conductor runs along the middle of the radiation surfaces of the transformer elements.

The basic principle of the fine division of transducer elements is described in more detail in US-A-4,305,014.

As far as the embodiment of the ultrasonic applicator according to EP-A-0 040 374 is concerned, there is the following disadvantage: according to the manufacturing process described there, the fine structure of the individual transducer elements results from sawing a complete ceramic plate with the external dimensions of the later ultrasonic head. This ceramic plate is already equipped with the respective slotted contact plates on the sides of the later counter surfaces of the converter elements. The sawing must now be carried out so precisely that each sawing step, which is to separate two adjacent groups of finely divided transducer elements, lies exactly where the bases of two adjacent triangular contact plates touch. Only then is the triangular contact plate separated exactly from the neighboring one, and there is a clear electrical contact assignment of such a contact plate to a group of transducer elements. It is easy to see that such a precise sawing step can only be carried out with strict adherence to particularly narrow tolerances. However, the manufacturing process as a whole is very complicated and the amount of reject applicators is correspondingly high.

The object of the present invention is to design an ultrasound applicator of the type mentioned at the outset in such a way that an extremely precise separation of adjacent sections, which are intended to electrically group together a group of finely divided transducer elements, is achieved even without adhering to strict tolerance regulations.

The object is achieved with the characterizing features of claim 1. A method for producing such an ultrasound applicator results according to the invention from the features of claim 9.

According to the invention, the comb of electrical contact plates is roughly pre-structured by the width of the cutouts. This allows large tolerances when sawing the ceramic. Adjacent comb sections, which are to electrically group together a group of finely divided transducer elements, are always separated extremely precisely from one another, even in the event of tolerance fluctuations in the sawing steps. The manufacturing process is overall much easier and the reject rate is extremely low.

Ultrasound applicators with pre-structured comb contact plates are also known per se from US Pat. No. 3,952,387. However, the transducers of these applicators are not finely divided with regard to the transducer elements. Group contact with the problem described above is not necessary from the start.

Advantageous embodiments of the invention result from the subclaims. Claim 4 is of particular importance, since here the tolerance range corresponding to the relatively large width in the area of the greatest incision depth is particularly large. The embodiment of subclaim 6 is also advantageous. Because of the contact plate comb that runs nittily on the counter surfaces of the individual transducer elements, optimal symmetry conditions result. The load on the individual transducer elements does not have an asymmetrical effect and there are optimal forms of vibration for both the transmission and the reception case. The object of the invention allows line soldering instead of surface soldering according to claim 8. This is a particularly simple soldering method which allows relatively thick and thus stable foils to be used as a contact comb even at higher frequencies.

Further advantages and details of the invention result from the following description of exemplary embodiments with reference to the drawing and in conjunction with the remaining subclaims.

• Figur 1 einen Ultraschall-Applikator gemäß der Erfindung
• Figur 2 ein erstes, bevorzugtes Ausführungsbeispiel für eine Kammstruktur in Ausschnittsvergrößerung,
• Figur 3 ein zweites mögliches Ausführungsbeispeil für eine Kammstruktur,
• Figur 4 eine Ausschnittvergrößerung der Figur 2, die den Sägeplan im Detail zeigt,
• Figur 5 bis Figur 8 Darstellungen, die das erfindungsgemäße Herstellungsverfahren zeigen,
• Figur 9 eine erste mögliche Art der Kontaktierung eines Kontaktblechkammes,
• Figur 10 eine zweite mögliche Art der Kontaktierung eines Kontaktblechkammes, und
• Figur 11 eine Modifikation der Art, in der ein Trägerkörper auf der Keramik angebracht ist.

Show it

• 1 shows an ultrasound applicator according to the invention
• Figure 2 shows a first, preferred Exemplary embodiment of a comb structure in enlarged detail,
• FIG. 3 shows a second possible exemplary embodiment for a comb structure,
• FIG. 4 shows an enlarged detail of FIG. 2, which shows the sawing plan in detail,
• 5 to 8 representations showing the manufacturing method according to the invention,
• FIG. 9 shows a first possible way of contacting a contact plate comb,
• Figure 10 shows a second possible way of contacting a contact plate comb, and
• Figure 11 shows a modification of the manner in which a carrier body is attached to the ceramic.

FIG. 1 shows a finely divided single-line array 1. This comprises a large number of finely divided transducer elements 2 arranged one behind the other. The transducer elements are electrically combined into groups 3. In the embodiment of Figure 1, each group 3 comprises e.g. five finely divided transducer elements 2. The total number of all groups along the Vandler array 1 is e.g. 77. Each transducer element 2 consists in the usual way of a rod-shaped piezoceramic body 4 which is coated on the radiation surface 5 and on the counter surface 6. The mesallayer consists e.g. made of evaporated or baked silver.

All finely divided transducer elements 2 arranged one behind the other are provided with a film comb 7 along the middle of their counter surfaces 6. In the manner shown in FIG. 1, the film comb 7 consists of contact tabs 8 with recesses 9 in between. Ag, Cu or a Cu alloy. The depth of cut h of the recesses 9 is less than the total height H of the contact comb 7, as is shown in more detail in FIG. A strip part 10 of height B thus remains on the film edge facing the counter surfaces 6 of the transducer elements 2. Saw slits 11 and 12 protrude from below into this strip part 10. The saw slits 11 originate from the fine sawing of the transducer elements 2. They only partially extend from below into the strip part 10. As indicated in FIG. 2, their total sawing depth through the ceramic material into the strip part 70 is t. The saw slots 72, on the other hand, have a greater depth T. They protrude beyond the strip part 70 into recesses 9 of the foil comb 7. The longer saw slots 12 divide the foil comb 7 into the individual, electrically separated contact tabs 8. The grid width R of the contact tabs 8 along the Comb 7, as is shown again in more detail in FIG. 2, is R-A. It thus corresponds in each case to the group width A of a group 3 of finely divided converter elements 2 which are to be electrically connected together.

The recesses 9, like the recesses 21 of the comb of FIG. 3, can have a purely rectangular shape. However, as shown in FIGS. 1 and 2, it is advisable to make the cutouts 9 less wide at their open upper end (width b) than in the region of the greatest incision depth T (width c). The recess, which is wider in depth (width c), allows large tolerance ranges when sawing the ceramic. In the exemplary embodiment in FIG. 2, the tolerance range corresponds e.g. the width c of the lower widest recess part. The total depth of the group division cuts 12 is indicated by T in FIG. The pitch width for fine division is a. The saw slots for the fine division of the transducer elements in the piezo material are indicated at 13. The saw slots in the transducer elements, which simultaneously divide the groups, are denoted by 14.

In the exemplary embodiment in FIG. 1, the component 15 is a carrier body for the finely divided converter elements 2. The film comb 7 made of contact tabs 8 is embedded in the carrier body 15. The carrier body 13 consists of a material that dampens ultrasonic waves well. E.g. it can consist of epoxy resin with oxidized tungsten powder.

The contact tabs 8 of the foil comb 7 serve as hot connections. Two contact foils 16 and 17 are provided for the ground connection. consist of the same material as the foil comb 9 and which are soldered along the left and right lower edge of the row of transducer elements 2 to the radiation surfaces 5 of the transducer elements 2. The metal foils 16 and 17, which are bent upwards in the opposite direction to the radiation direction of the ultrasound transducer elements, are also slit up to the height of the saw gaps 13 and 14 of the transducer elements 2. However, the slots 18 do not extend to the upper edge of the film; they are only partially cut into the respective film 16, 17.

The component 19 is an adaptation body with which the array 1 of the figure is completed on the application side. This adapter body 19 is e.g. made of epoxy resin.

As shown in FIG. 2, a film strip 20 is used as the base body for the film comb 7, said film strip first comprising self-contained window-shaped recesses 9. By cutting off the upper part of the strip along the section line S-S, a comb is then obtained with recesses 9 which are open at the top in accordance with FIG. 1.

As already mentioned above, the example of FIG. 3 represents an alternative solution to that of FIG. 2, however, which is less advantageous than that of FIG. 2. The only difference from the embodiment of FIG. 2 is that the cutouts 21 in the film strip 22 have a rectangular shape. The width b 'of these rectangular recesses 21 is thus the same over the entire incision depth h'. The tolerance range of the saw cuts for groups falling in this area (saw cuts 14) is smaller with these recesses 21 than with that of FIG. 2.

FIG. 4 shows in detail the sawing plan for the exemplary embodiment in FIGS. 1 and 2. The gap width of the saw slots 13 and 14 is in each case s.

FIGS. 5 to 8 show in an exploded view the manufacturing method according to the invention for an array according to FIG. 1.

As already mentioned above, a ceramic plate 30 with the external dimensions of the later array serves as the base body for the later finely divided converter elements 2. The ceramic plastic 30 is provided on the lower surface 31 (later radiation surface of the transducer elements) and the surface 32 (later counter surface of the transducer elements) with a thin Ag layer. According to the first manufacturing step in FIG. 5, a film strip 20 aligned in the longitudinal direction of the plate 30 with the closed recess windows 9 is soldered onto the ceramic plate 30 in the middle position. An edge 33 of the strip 20 is used for soldering.

Figure 6 shows the second manufacturing step. In this manufacturing step, the not yet slotted contact foils 16 and 17 are soldered along the right and left lower edges of the ceramic plate 30.

In the third manufacturing step in FIG. 7, the ceramic plate 30 and the contact strip 20 are cast around the carrier body 15. FIG. 7 also shows the fourth manufacturing step, which consists of cutting the contact strip 20 along the section line S-S. This cutting creates the actual comb shape with recesses 9 open at the top and the contact tabs 8.

The fifth manufacturing step consists of sawing the entire assembly. This sawing is done from the radiation side, as shown in FIG. 8.

The sixth and last manufacturing step consists in breaking the adaptation layer 79 on the application side. This last manufacturing step is also indicated in FIG.

Of course, individual manufacturing steps can be interchanged. For example, after the second process step (shown in FIG. 6), the ceramic plate 30 can be sawn immediately. Only then is the carrier body 15 applied, or first the adaptation layer 19 and then the carrier body 15 are applied. Other swaps are also conceivable, but not necessarily appropriate.

FIG. 9 shows again in an enlarged manner how the foil comb 7 can be soldered or even welded onto the ceramic body 30 by means of the soldering edge 33. However, soldering or welding without an edge 33 is also possible, as is indicated in FIG. 10 by soldering or welding seams 34.

The exemplary embodiment is explained below with the aid of some numbers for e.g. a 3.5 MHz and a 7 MHz array specified:

3.5 MHz array

Here the fine division grid for the converter elements 2 is e.g. 0.308 mm with a saw gap width in the range 0.07 to 0.1 mm. In this case, a grid width of the contact lugs 8 of R = 1.54 mm is recommended for the film comb 7. The upper width of the recesses 9 is b - 0.4 mm, the lower width is c = 0.8 mm.

7 MHz array

The fine division grid for the converter elements 2 at this frequency is e.g. 0.192 mm for the same saw gap width. The grid width of the contact lugs 8 of the film comb is R - 0 77 mm. The upper width b of the recesses 7 is b = 0.3 mm, the lower width c is c ≈ 0.6 mm.

The exemplary embodiments described are merely exemplary in nature. There are of course any number of modifications. E.g. The damping body 15 can also be applied to the ceramic body 30 in such a way that it also encompasses the edges thereof, see FIG. 11. In this arrangement, undesired radiation of ultrasonic energy at the edge is prevented. When the foil comb 7 is soldered or welded on by means of an edge 33, the cutouts 9 between the foil flags 8 can also be cut to the edge 33. The comb strip part for the saw cuts 12 (optionally also 11) is then formed by the edge 33. This modified embodiment only requires very small sawing depths.

Claims (11)

1. An ultrasonic applicator comprising an acoustic head which has finely divided transducer elements (2), a plurality of which are electrically combined to form groups (3) by contact sheets which are placed onto the counter-surfaces (6) of the transducer elements (2), which are opposite the reflecting surfaces (5), characterised in that the contact sheets have the shape of a longitudinal strip (20; 22) which extends in the region between the ends of the transducer elements (2) at right angles to the counter-surfaces (6), that the strip (20; 22) is designed as a comb (7) with a plurality of electrical contact lugs (8) and a plurality of consecutive recesses (9; 21), where the recesses are open at the strip edge which faces away from the counter-surfaces (6) of the transducer elements (2) and where their depth of cut (h, h') in the direction of the counter-surfaces (6) of the transducer elements (2) is smaller than the overall height (H) of the strip (20; 22), that in the region of each recess (9; 21) the strip (20, 22) is provided with at least one slot (12) which extends through the strip ridge (10) from the recess (9; 21) to a gap (14) between two adjacent transducer elements (2), and thereby separates two adjacent transducer elements (2), and that the base width (c) of the recess (9,21) is essentially greater than the width (s) of the slot (12).

2. An ultrasonic applicator as claimed in claim 1, characterised in that the contact lugs (8) of the comb strip (20,22), whose shape is predetermined as a result of the shape of the recesses (9), have a raster measure (R) which approximately corresponds to the width (A) of a group (3) of electrically contacted, finely divided transducer elements (2).

3. An ultrasonic applicator as claimed in Claim 1 or 2, characterised in that the recesses (21) in the strip (22) are of a rectangular shape.

4. An ultrasonic applicator as claimed in Claim 1 or 2, characterised in that the recesses (9) in the strip (20) have a smaller width (b) at their open upper end than at their base.

5. An ultrasonic applicator as claimed in one of Claims 1 to 4, characterised in that in the region of the separating gaps (13) between the individual finely divided transducer elements (2) each strip component (10) between two continuous slots (12) is respectively provided with serrated slots (11) which, from that edge of the strüip by means of which the strip is secured to the counter-surfaces (6) of the transducer elements, do not extend into the strip component (10) to the level of the recesses (9; 21).

6. An ultrasonic applicator as claimed in one of Claims 1 to 5, characterised in that the comb (7) is arranged so as to approximately extend along the centre of the counter-surfaces (6) of the individual transducer elements (2).

7. An ultrasonic applicator as claimed in one of Claims 1 to 6, characterised in that contact sheets (16, 17) in the form of a comb or in the form of a commonly continuous baffle plate or in a mixed form of the two are arranged and aligned on the reflecting surfaces (5) in such a manner that in accordance with a longitudinal extension of the transducer elements they are parallel to the reflecting surfaces or upwardly bent away from the direction of reflection at an angle.

8. An ultrasonic applicator as claimed in one of Claims 1 to 7, characterised in that the comb (7) is soldered on to the counter-surfaces (6) of the transducer elements (2) so as to be bent over or directly soldered thereon at the front end.

9. A process for the production of an ultrasonic applicator as claimed in one of Claims 1 to 8, characterised by the following process steps:

a) the contact strip (20, 22) comprising the recesses (9, 21) is applied onto the surface (32) of a ceramic plate (30) which has the outer dimensions of the future array and which is provided with a thin metal layer, e.g. a silver layer, on the lower surface (31) and the upper surface (32),

b) strips of contact foil (16,17) are arranged along the right-hand and optionally the left-hand edge of the lower surface (31) of the ceramic plate (30),

c) on the upper surface the ceramic plate (30) is provided with a carrier body (15), into which the contact strip (20,22) is partially embedded,

d) the entire structure is finely serrated from the underside of the ceramic plate (30) in such a manner that finely dividing serrating cuts (11, 13) for the division within one group extend into the structure to a lesser depth than those finely dividing serrating cuts (12, 14) which extend to the recesses (9, 21) in order to divide the individual groups, and

e) a covering layer (19) is applied to the serrated system on the side of the applicator, i.e. on the reflecting surfaces (5) of the finely divided transducer elements (2).

10. A process as claimed in Claim 9, characterised in that the contact strip (20), which is placed onto the ceramic plate (30) in accordance with process step a), initially possesses closed recess windows (9,21), and wherein the individual contact lugs (8) with intermediate open recesses (9, 21) are obtained by cutting the contact strip (20,21) at the top along a cutting line (S-S).

11. A process as claimed in Claim 9 or 10, characterised in that the carrier body (15) is applied to the ceramic plate (30) in such a manner that it includes the edges thereof.

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