Contacting structure and method for contacting a piezo element of an ultrasonic sensor, and ultrasonic sensor
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- VALEO SCHALTER & SENSOREN GMBH
- Filing Date
- 2026-01-29
- Publication Date
- 2026-08-06
Smart Images
Figure EP2026052299_06082026_PF_FP_ABST
Abstract
Description
[0001] 2023PF01393
[0002] 1
[0003] CONTACT STRUCTURE AND METHOD FOR CONTACTING A PIEZOELEMENT OF AN ULTRASONIC SENSOR AND ULTRASONIC SENSOR
[0004] The present invention relates to the field of ultrasonic sensors for motor vehicles and in particular to a contacting structure for contacting a piezoelectric element for vibration excitation of an ultrasonic membrane of an ultrasonic sensor, an ultrasonic sensor with the contacting structure and a method for manufacturing the contacting structure.
[0005] Ultrasonic sensors are known for open or concealed installation on vehicle body panels. These sensors can emit ultrasonic pulses into the vehicle's surroundings and receive reflections of these pulses. By measuring the signal travel time between the emission of an ultrasonic pulse and the reception of the reflection, the distance to an obstacle can be determined. By taking multiple such measurements with different ultrasonic sensors, the obstacle's position can be determined through trilateration.
[0006] Ultrasonic sensors typically consist of an ultrasonic membrane located in an opening of a housing and a piezoelectric element attached to the inside of the ultrasonic membrane. The piezoelectric element is, for example, made of a flat ceramic material coated on its flat sides with a metallization that forms the two electrodes of the piezoelectric element. The piezoelectric element is controlled by the ultrasonic sensor's control circuitry to transmit and receive ultrasonic pulses. One objective is to acoustically decouple the ultrasonic membrane from the ultrasonic sensor housing. For this reason, the piezoelectric element attached to the ultrasonic membrane, which is made of a ceramic material, for example, is connected by a strain-relieved wire to a contact pin fixed in the housing, which in turn is connected to the control electronics.
[0007] 2
[0008] The present invention specifically addresses the question of how the strain-relieved wire can be contacted in a suitable manner with the piezoelectric element of the ultrasound membrane.
[0009] German patent DE 1020130220631 A1 discloses such an ultrasonic sensor for a vehicle, in which electrical conductor elements are connected to the electrodes of the piezoelectric element via soldered connections. However, such a soldered connection has the disadvantage that flux and additional solder are required during soldering. Flux remaining at the solder joint and the additional solder create a significant additional mass on the vibrating ultrasonic membrane and can also contaminate subsequent processes. Therefore, manufacturing variations can be high and the dynamics of the ultrasonic sensor reduced.
[0010] Against this background, DE 102017 109 159 B4 proposes a solder- and flux-free welding contact, which is formed by friction welding or wire bonding.
[0011] US 2019 / 0044298 A1 proposes dipping the contact base of a wire into a conductive adhesive, such as silver adhesive, applied to the top surface of a sensor element and curing the adhesive in a heat treatment step. Alternatively, the same document proposes joining the contact base to the sensor element either by welding, bonding, or thermal compression welding.
[0012] However, welded joints result in a contact point with a very thin cross-section, which is susceptible to mechanical defects.
[0013] Against this background, one object of the present invention is to provide a contacting structure for contacting a piezoelectric element of an ultrasonic sensor with improved properties. 2023PF01393
[0014] 3
[0015] Accordingly, according to a first aspect, a contacting structure for contacting a piezoelectric element for vibration excitation and / or detection of vibrations of an ultrasonic membrane of an ultrasonic sensor is proposed, comprising a contact pin fixed in a housing of the ultrasonic sensor and a wire which is connected at a first end to the contact pin and contacted at a second end to an electrode of the piezoelectric element, wherein at the second end of the wire a hybrid contact point of the wire with the electrode is formed, comprising a welded contact and a soldered contact.
[0016] A hybrid contact point, comprising both a welded and a soldered connection, increases the contact area and thus improves the mechanical robustness of the connection. Furthermore, a simple manufacturing process, requiring no additional solder or flux, can be described for such a hybrid contact point. Consequently, the dynamics of the ultrasonic sensor are hardly affected. The proposed contact structure thus combines the advantages of increased mechanical robustness, ease of manufacture, and improved dynamics of the ultrasonic sensor.
[0017] A "hybrid contact point comprising a welded contact and a soldered contact" is to be understood in particular as a spatially contiguous area in which the wire and the electrode are both welded and soldered, whereby it is sufficient if the wire and the electrode are only welded in one section of the spatially contiguous area and only soldered in another section of the spatially contiguous area, and the two areas are spatially contiguous.
[0018] A piezoelectric element for exciting and / or detecting vibrations of an ultrasonic membrane of an ultrasonic sensor can, in particular, be a piezoelectric element attached to the ultrasonic membrane, for example, glued to it. 2023PF01393
[0019] 4
[0020] An electrode of the piezoelectric element can, in particular, be a metallization layer applied to one side of the piezoelectric element. It is understood that electrodes can be arranged on both sides of the piezoelectric element, with each of the two electrodes being connected to one of two contact pins via a proposed contact structure. For example, an electrode located on the side facing the ultrasound membrane can extend partially to the opposite side, so that both contact structures can be formed on the same side of the piezoelectric element facing away from the ultrasound membrane, thus making both electrodes accessible.
[0021] The contact pin, which is fixed in place within the housing of the ultrasonic sensor, can, for example, be overmolded or encased in the housing.
[0022] In this context, the term "connected" means, in particular, simply that an electrically conductive connection exists between the wire and the contact pin. The wire may be formed integrally with the contact pin, for example, stamped from a sheet of metal. However, the wire may also be attached to the contact pin, for example, by welding or soldering. In contrast, "contacted" in this context means, in particular, that the electrically conductive connection is created by a joining process that includes both soldering and welding.
[0023] The wire can be strain-relieved. For example, the wire can be longer than the direct distance from the point at the first end where the wire is connected to the contact pin to the point at the second end where the wire is contacted with the electrode of the piezoelectric element.
[0024] The phrase "at one end of the wire" encompasses a location at the end of the wire, meaning the end of the wire itself, but also locations near the end of the wire. "Near the end" is to be understood in particular as meaning that the remaining section from the location "at the end of the wire" to the end of the wire is small, preferably 2023PF01393
[0025] 5
[0026] significantly smaller, preferably by at least a factor of 5, particularly preferably by at least a factor of 10, is a section from the point at the end of the wire to an opposite end of the wire.
[0027] According to one embodiment, the solder contact is flux-free.
[0028] This means that, advantageously, no flux remains at or near the hybrid contact point after its production, and contamination of further manufacturing processes by flux and / or an increase in mass due to remaining flux residues can be avoided.
[0029] According to one embodiment, the soldered contact is formed outside the welded contact.
[0030] This means that in the spatial area of the hybrid contact point, the welded contact can be located in the center and an additional soldered contact can be located around the welded contact.
[0031] In particular, the solder contact formed outside the welded contact can be arranged flush with the welded contact outside of it.
[0032] Accordingly, the welding can advantageously be mechanically reinforced by soldering the soldered contact and the contact area can be increased.
[0033] Such a hybrid contact point can be manufactured in a particularly simple manufacturing process in just one step, which is described below.
[0034] According to one embodiment, the second end of the wire extends beyond the hybrid contact point. 2023PF01393
[0035] 6
[0036] Accordingly, during the manufacturing of the contact point, it is advantageously ensured that wire is present throughout the entire area of the hybrid contact point. This helps to minimize manufacturing variations.
[0037] According to one embodiment, the wire has a conductor made of a conductive material, in particular Cu, and a coating made of a fusible conductive material, in particular Sn, and the solder contact is formed from the molten conductive material of the coating of the wire.
[0038] In particular, the preferably solder contact can be formed predominantly or especially preferably exclusively from the molten conductive material of the wire coating.
[0039] Accordingly, the mass increase due to the soldered contact can be advantageously reduced to a minimum. At the same time, when using such a wire, the hybrid contact point can advantageously be produced in a single, simple operation; that is, when welding the coated wire to the electrode of the piezoelectric element, the soldered contact around the welded contact can be formed simultaneously. Therefore, the manufacturing process is advantageously particularly simple.
[0040] The thickness of the tinning can, for example, be between 0% and 25% of the total diameter of the wire, and in preferred embodiments is, for example, 10% or 5% of the total diameter.
[0041] According to a second aspect, an ultrasonic sensor is proposed, comprising a housing, an ultrasonic membrane arranged in an opening of the housing, a piezoelectric element arranged inside the ultrasonic membrane for vibration excitation and / or detection of vibrations of the ultrasonic membrane, a contact pin fixed to the housing, and a wire connected at one end to the contact pin and at the other end to an electrode of the piezoelectric element. 2023PF01393
[0042] 7
[0043] is contacted, with a hybrid contact point of the wire with the electrode being formed at the second end of the wire, comprising a welded contact and a soldered contact.
[0044] In other words, the ultrasonic sensor according to the second aspect has the contact structure according to the first aspect. The embodiments, definitions, features, and advantages described for the contact structure of the first aspect also apply accordingly to the ultrasonic sensor of the second aspect.
[0045] According to a third aspect, a method for contacting a piezoelectric element for vibration excitation and / or detection of vibrations of an ultrasonic membrane of an ultrasonic sensor is proposed, comprising: a) stationary arrangement of a contact pin with a wire having a conductor and a coating and connected at a first end to the contact pin, in a housing of the ultrasonic sensor such that a second end of the wire rests on an electrode of the piezoelectric element; and b) welding a region at the second end of the wire resting on the electrode to the electrode of the piezoelectric element, wherein the conductor of the wire is welded to the electrode and the coating of the wire is melted, so that a hybrid contact point is formed which comprises a welded contact and a soldered contact of the wire to the electrode.
[0046] Accordingly, an advantageous manufacturing process is specified for the advantageous contacting structure of the first aspect and its embodiments and / or the advantageous ultrasonic sensor of the second aspect and its embodiments, in which the hybrid contact point with enlarged contact area, improved dynamics and improved mechanical stability can be produced in just one simple operation.
[0047] According to one embodiment, the welding in step b) includes thermocompression welding. 2023PF01393
[0048] 8
[0049] In particular, during thermocompression welding, a thermode can be placed on the second end of the wire resting on the electrode. The thermode can then be electrically heated. Unlike resistance welding, the advantage here is that the electric current flows only through the thermode (the tool), while no current flows through the elements being welded, especially the electrode or the piezoelectric element. This advantageously prevents damage to the electrically sensitive piezoelectric element from current during welding.
[0050] The thermode can thus advantageously form the welded contact in a gentle manner in one operation, as well as melt the coating of the wire and form the soldered contact from the material of the molten coating.
[0051] According to another embodiment, the solder contact in step b) is formed without the use of additional solder and without the use of flux.
[0052] This means the inventors have recognized that by thermocompression welding a wire coated with a fusible conductive material to the electrode, solder contacts can be formed without the need for additional solder or flux. Accordingly, the contact area of the contact point can be increased while keeping the mass low, thus combining good mechanical durability with good dynamic properties.
[0053] According to another embodiment, the conductor of the wire is made of a conductive material, in particular Cu, and the coating of the wire is made of a fusible conductive material, in particular Sn.
[0054] Such a wire can be easy to obtain or manufacture and can be advantageously used for the proposed method. 2023PF01393
[0055] 9
[0056] The embodiments, definitions, features and advantages described for the contacting structure of the first aspect also apply mutatis mutandis to the manufacturing process of the third aspect and its embodiments.
[0057] Other possible implementations of the invention also include combinations of features or embodiments described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In such cases, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.
[0058] Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the exemplary embodiments of the invention described below. The invention will be explained in more detail below with reference to preferred embodiments and the accompanying figures.
[0059] Fig. 1 shows a schematic structural view of the mechatronics of an ultrasonic sensor according to an exemplary embodiment;
[0060] Fig. 2 shows an enlarged view of a contact point with a welded contact according to a comparative example;
[0061] Fig. 3 shows a greatly enlarged section through the contact point from Fig. 2;
[0062] Fig. 4 shows an enlarged view of a hybrid contact point according to a working example based on the embodiment; and
[0063] Fig. 5 shows a section through the hybrid contact point from Fig. 4.
[0064] Fig. 6 illustrates steps of a method for manufacturing the contacting structure according to the exemplary embodiment;2023PF01393
[0065] 10
[0066] Fig. 7 shows a coated wire according to the exemplary embodiment; and
[0067] Fig. 8 shows a sectional view of the coated wire from Fig. 7;
[0068] In the figures, identical or functionally equivalent elements have been given the same reference symbols, unless otherwise indicated.
[0069] Fig. 1 shows a schematic structural view of the mechatronics of an ultrasonic sensor 1 according to an exemplary embodiment. The ultrasonic sensor 1 comprises a sensor housing 2 and a diaphragm housing 3. Fixed elements, such as a contact pin 13 (described in more detail later) and a circuit board (not shown) with a control circuit, are arranged within the sensor housing 2. The diaphragm housing 3 is essentially cylindrical. An ultrasonic diaphragm 7 is inserted into an opening 6 on an end face of the diaphragm housing 3. A piezoelectric element 8 is arranged, for example, glued, on the inner side of the diaphragm for exciting and detecting vibrations of the ultrasonic diaphragm 7.
[0070] The membrane housing 3 is inserted into an opening 5 of the sensor housing 2 via a decoupling element 4. The decoupling element 4 can be elastic and decouple vibrations of a vibration system formed by the ultrasonic membrane 7, the piezoelectric element 8, and the membrane housing 3 from a system formed by the sensor housing 2 and elements fixed within it. In this way, two acoustically decoupled vibration systems are formed.
[0071] The piezoelectric element 8, located on the inner surface of the ultrasound membrane 7, is made of a solid material, for example ceramic, with a metallization layer applied to each of its two flat surfaces, forming a respective electrode 9, 10. The electrode 10, located on the flat surface of the piezoelectric element facing the ultrasound membrane 7, also extends over an edge of the piezoelectric element 82023PF01393.
[0072] 11
[0073] on the flat side of the piezoelectric element 8 facing away from the ultrasound membrane 7, on which both electrodes 9, 10 are thus accessible.
[0074] The piezoelectric element 8 has the property of converting pressure exerted by the ultrasonic membrane 7 on one of its flat surfaces into a voltage via the piezoelectric effect. This voltage can be detected at electrodes 9 and 10. Thus, when the ultrasonic membrane 7 is set into vibration by an ultrasonic signal from the vicinity of a vehicle (not shown), these vibrations can be detected as a wave-like voltage signal at electrodes 9 and 10. Similarly, the piezoelectric element 8 can convert an externally applied voltage to electrodes 9 and 10 into pressure via the piezoelectric effect, which the piezoelectric element 8 exerts on the ultrasonic membrane 7. Therefore, when a wave-like voltage signal is applied to electrodes 9 and 10, the ultrasonic membrane 7 is excited to vibrate and emits an ultrasonic signal into the vicinity of the vehicle.
[0075] In order to make the described functions of the piezoelectric element 8 attached to the ultrasound membrane 7 accessible to a control unit of the motor vehicle (not shown), it is necessary to electrically contact the piezoelectric element 8 (its electrodes 9, 10).
[0076] A connecting cable 11 leads through a feedthrough 12 in the sensor housing 2 into the interior of the ultrasonic sensor 1 and is connected to a control circuit (not shown). The control circuit receives digital or analog signals from the external control unit and transmits digital or analog signals to the control unit. The control circuit can, for example, be implemented as an ASIC. The control circuit is in turn contacted via a contact structure 100 with the electrodes 9, 10 of the piezoelectric element 8.
[0077] Below, a contacting structure 100 for contacting the electrode 10 is described; however, it is understood that the contacting structure 100 is of a similar type. 2023PF01393
[0078] 12
[0079] Elements such as those illustrated and described below may also be used to contact electrode 9.
[0080] The contacting structure 100 for contacting the electrode 10 of the piezoelectric element 8 has a contact pin 13 that is fixedly arranged in the sensor housing 2. The contact pin 13 is a rigid element and, in the example shown, rests on an inner console 19 of the sensor housing 2. The contact pin 13 can also be overmolded in the sensor housing 2 and thus fixedly arranged, i.e., fixed to the sensor housing 2.
[0081] The contacting structure 100 further comprises a thin wire 14, which is connected at a connection point 15 at one end of the wire 14 to the contact pin 13 and at a contact point 16 at the other end of the wire 14 to the electrode 10 of the piezoelectric element 8. The wire 14 is thin and flexible and longer than the direct line from the connection point 15 to the contact point 16. In this way, the wire 14 is strain-relieved and provides acoustic decoupling between the electrode 10, which is part of the vibration system of the ultrasonic membrane 7 and the membrane housing 3, and the contact pin 13, which is part of the system of the sensor housing 2 and the elements arranged therein.
[0082] Particular attention should be paid to the contact point 16, where the wire 14 is contacted with the electrode 10 of the piezoelectric element 8, when describing the contact structure 100. It is desirable that this contact point 16 has the lowest possible mass to minimize its impact on the dynamics of the ultrasonic membrane 7's vibration system. At the same time, it is desirable that the contact point 16 has the largest possible contact area to avoid manufacturing variations and rejects, and to make the contact point 16 robust against mechanical stress.
[0083] If the wire 14 were soldered to the electrode 10, a relatively large amount of solder would be required, which would impair the dynamics of the vibration system of the ultrasonic membrane 7, and flux would also have to be used to introduce the solder as desired. 2023PF01393
[0084] 13
[0085] to be able to do so. However, the flux could contaminate the piezoelectric element 8. Direct soldering without the use of flux has not been successful so far.
[0086] Fig. 2 shows an enlarged view of a contact point 16' with a welded connection according to a comparative example, and Fig. 3 shows a highly magnified section AA through the contact point 16' from Fig. 2. In the comparative example, the wire 14 is placed on a surface of the electrode 10 and welded to the electrode 10 in the area of the contact point 16'. Resistance welding, for example, can be used for welding. Such a resistance-welded contact point 16' advantageously has a low mass. However, as can be seen in Figs. 2 and 3, the resistance-welded contact point 16' is elongated, but has only a very thin cross-section and thus a small total contact area with the electrode 10, and can therefore be susceptible to damage from mechanical stress.
[0087] According to the exemplary embodiment, however, it is proposed that the contact point 16 (Fig.
[0088] 1) to form a hybrid contact point which includes both a welded contact 21 (Fig.
[0089] 5) - similar to the comparative example from Fig. 2 and Fig. 3 - as well as a soldered contact 22 (Fig. 5) which can give additional mechanical stability to the welded contact and which can be produced in a manufacturing process in which no direct soldering is required and accordingly neither additional solder nor flux needs to be used.
[0090] Fig. 4 shows an enlarged view of a hybrid contact point 16 according to a working example in which the teachings of the embodiment were applied, and Fig. 5 shows a greatly enlarged section along AA through the hybrid contact point 16.
[0091] In the same way as in the comparative example in Fig. 2 and Fig. 3, the wire 14 lies on the electrode 10 in the area of the hybrid contact point 16 and is flattened (see Fig.
[0092] 5) and welded to electrode 10, i.e., a welded contact 21 is formed. However, unlike the comparison example, outside the welded 2023PF01393
[0093] 14
[0094] An additional solder contact 22 is formed at contact point 21, reinforcing the welded contact 21 from the outside. A comparison with the reference example shows that the hybrid contact point 16 has an increased cross-section and thus a larger contact area with the electrode due to the additional solder contact 22. However, only a comparatively small amount of solder has been used (compared to a hypothetical soldered contact without a welded contact). Accordingly, the increase in mass compared to the reference lead example is small, but the mechanical robustness against damage under mechanical stress can be advantageously significantly improved.
[0095] Fig. 6 illustrates steps of a method for producing the contacting structure 100 with the hybrid contact point 16 according to the exemplary embodiment. With reference to Fig. 6 and, if necessary, to Fig. 1, Fig. 4 and Fig. 5, a method for producing the contacting structure 100 with the hybrid contact point 16 will now be described, which can be carried out flux-free and simply.
[0096] In a preparatory step S1, the contact pin 13 with the wire 14 is first manufactured. For example, a first end of the wire 14 is welded to a stamped strip at a predetermined position. The contact pin 13, with the wire 14 welded to it at a contact point 15, is then punched out of the stamped strip. The punched-out contact pin 13 with the attached wire 14 is then placed in a forming tool, and the contact pin 13, and optionally also the wire 14, is given a desired shape. For example, the contact pin 13 can be given the stepped shape with diagonal extension shown in Fig. 1. For example, the wire 14 can be bent for strain relief.
[0097] In this embodiment, the wire 14 is a coated wire. Fig. 7 shows the coated wire 14 according to the embodiment, and Fig. 8 shows a sectional view of the coated wire 14 from Fig. 7. The wire 14 has a conductor 17 made of a conductive material and a coating 18 made of a 2023PF01393
[0098] 15
[0099] The conductor 17 is made of a fusible conductive material. The conductor 17 is particularly preferably made of copper (Cu) and the coating of tin (Sn). To produce the coated wire 14, the conductor 17 can be drawn to the desired diameter and then, for example, electroplated. The coating 18 has a thickness in the range of 0 to 25% of the total diameter of the coated wire 14, and particularly preferably a thickness of 10% or 5% of the total diameter.
[0100] Reference is again made to Figures 6, 1, 4, and 5. In step S2, the contact pin 13 with the associated coated wire 14 is fixedly positioned in the sensor housing 2, for example, by placing it on the console 19 and overmolding it. A portion of the connection point 15 can be left unmolded. Specifically, the contact pin 13 with the associated coated wire 14 is fixedly positioned in the sensor housing 2 such that a portion at the second end 20 (Fig. 4) of the coated wire 14 rests on the electrode 10 of the piezoelectric element 8 in the area of the contact point 16 to be formed.
[0101] Then, in step S3, a section at the second end 20 of the wire 14 resting on the electrode is welded to the electrode 10 of the piezoelectric element 8. Here, on the one hand, similar to the comparative example shown in Figures 2 and 3, a welded contact 21 (Figure 5) is formed at the contact point 16, in which the conductor 17 of the wire 14 is flattened and welded to the electrode 10. On the other hand, the heat generated during welding causes the coating 18 of the wire 14 to melt at the welding position, forming a droplet. Upon cooling, this droplet forms a soldered contact 22 around the welded contact 21, thus reinforcing the welded contact 21. In this way the hybrid contact point 16 is created, which includes both the welded contact 21 and a soldered contact 22 of the wire 14 with the electrode 10.
[0102] In the described process, the use of the coated wire 14 advantageously enables the fusible coating 18 (Fig. 7, 8) to be used as solder to form the 2023PF01393
[0103] 16
[0104] The solder contact 22 is positioned in the area of the hybrid contact point 16 without the need for flux or additional solder for precise placement. In particular, due to the higher heat during welding compared to soldering, the fusible coating 18 (Fig. 7, 8) of the wire 14 forms a droplet of the desired shape even without the use of flux.
[0105] The proposed welding process with the coated wire 14, in which, advantageously, a welded contact 21 of the wire 14 with the electrode 10 and a solder contact 22 formed around the welded contact 21 and reinforcing it are formed simultaneously in one operation, can advantageously be carried out simply if the contact pin 13 with the wire 14 attached to it is already fixedly arranged in the sensor housing 2, i.e. installed.
[0106] In step S3, a thermoelectrode or thermode, which may be made of tungsten, for example, is preferably used as the welding tool. The welding process is particularly preferably thermocompression welding. Here, the thermode is placed on the wire 14 resting on the electrode 10 in a region of the contact point 16 to be formed, and an axial force (force in the direction of the axis of the piezoelectric element 8) is exerted on the wire 14. For a copper wire 14 with a thickness of, for example, 100 pm, an axial force of 10 to 12 N is suitable. The thermode is electrically heated. Advantageously, current flows only through the thermode, but not through the electrode 10 or the piezoelectric element 8.
[0107] Referring to Fig. 4, it can be seen in particular that in the working example, the second end 20 of the wire 14 extends beyond the hybrid contact point 16. In other words, the thermocompression welding in step S3 (Fig. 6) did not take place exactly at the second end 20 of the wire 14, but in a region at or just before the second end 20, which is spaced a certain distance away from it. This ensures that during welding, the wire 14 runs completely from one end of the thermode to the other end of the thermode. (See Figure 2023PF01393.)
[0108] 17
[0109] In this way it can be ensured that when the proposed manufacturing process is carried out repeatedly, manufacturing variation is low and all welded contacts 21 (Fig. 5) are formed with essentially the same dimensions.
[0110] According to the exemplary embodiment and its preferred configurations, a teaching has thus been proposed with which a contact structure 100 with a hybrid contact point 16 of the wire 14 with the electrode 10 of the piezoelectric element 8 can be formed by using a coated wire 14 during thermocompression welding. This contact structure comprises a welded contact 21 and a soldered contact 22. The production of the hybrid contact point 16 is advantageously carried out in a single, simple operation. Only the coating 18 of the wire 14, melted by thermocompression welding, is used as solder for producing the soldered contact 22, and no additional solder or flux is required. In this way, the production of the contact structure 100 is simple, and problems with flux contamination are avoided.Furthermore, the hybrid contact point 16 can have only a slightly increased mass compared to a single welded contact and advantageously hardly impairs the dynamics of the ultrasonic membrane 7. Thanks to the additional solder contact 22, which is formed around and reinforces the welded contact 21, the hybrid contact point 16 can have an enlarged contact area, in particular a larger cross-section, lower manufacturing variations, and higher resistance to mechanical stress than a purely welded contact point 16'.
[0111] Although the present invention has been described with reference to an exemplary embodiment and a working example, it can be modified in many ways.
[0112] Thus, the wire 14 does not need to be coated along its entire length. It is sufficient if the wire 14 is coated in an area near its second end 20 where the welding takes place. In this respect, embodiments are conceivable in which it is no longer visible on the finished contact structure 100 that the conductor 17 was coated during the welding process.
[0113] 18
[0114] The contact structure 100 had a coating 18 during production because all material of the coating 18, which may only have been present in the area at the second end, was melted during welding and used to form the soldered contact 22. Therefore, embodiments of contact structures 100 with a bare wire 14 without a coating are also embodiments according to the invention, provided that at least at the second end of the wire 14 a hybrid contact point 16 with a welded contact 21 and a soldered contact 22 is formed.
[0115] It has been described that the conductor 17 is electroplated with the coating 18 to form the coated wire 14. Alternatively, the conductor 17 can also be hot-dip tinned in a tin bath. Another alternative is chemical tinning via a chemical reaction in a bath, which leaves a tin layer 18 on the conductor 17. Physical deposition of the coating 18 via the vapor phase (so-called sputtering) is also conceivable.
[0116] Tin (Sn) was primarily described as the fusible material for the coating 18, but it would also be conceivable to form the coating 18 from lead (Pb), silver (Ag), zinc (Zn), nickel (Ni), bismuth (Bi) or antimony (Sb) or any combination of the aforementioned elements.
[0117] Likewise, the material of conductor 17 is not limited to copper (Cu), and other conductive and weldable materials, such as aluminium (Al), can be used.
[0118] The description mainly focused on the particularly advantageous thermocompression welding process; however, it would also be conceivable to form the welded contact 21 using a different welding process, such as resistance welding, as long as sufficient heat is generated to melt the coating 18 of the wire 14 and form the soldered contact 22 in the same step. 2023PF01393
[0119] 19
[0120] Fig. 1 shows a membrane housing 3 and an ultrasonic membrane 7 inserted into an opening 6 of the membrane housing 3. However, the teaching of this embodiment is equally applicable when a one-piece hollow cylindrical membrane pot is used. In this case, the entire membrane pot can serve as the ultrasonic membrane 7 and be inserted directly into the opening 5 of the sensor housing 2. 2023PF01393
[0121] 20
[0122] REFERENCE MARK LIST
[0123] 1 ultrasonic sensor
[0124] 2 sensor housings
[0125] 3 membrane housings
[0126] 4 decoupling element
[0127] 5 Opening the sensor housing
[0128] 6 Opening of the membrane housing
[0129] 7 Ultrasound membrane
[0130] 8 Piezoelectric element
[0131] 9 electrode
[0132] 10 electrode
[0133] 11 Connection line
[0134] 12 Implementation
[0135] 13 Contact pin
[0136] 14 wires
[0137] 15 liaison point
[0138] 16 hybrid contact points
[0139] 16' Contact point of the comparison example
[0140] 17 leaders
[0141] 18 coating
[0142] 19 Console of the sensor housing
[0143] 20 second end
[0144] 21 welded contacts
[0145] 21' welded contact of the comparison example 22 solder contact
[0146] S1-S3 process steps
Claims
2023PF01393 21 PATENT CLAIMS 1. Contacting structure (100) for contacting a piezoelectric element (8) for vibration excitation and / or detection of vibrations of an ultrasonic membrane (7) of an ultrasonic sensor (1), comprising a contact pin (13) fixedly arranged in a housing (2) of the ultrasonic sensor (1) and a wire (14) which is connected at a first end to the contact pin (13) and is contacted at a second end (20) to an electrode (10) of the piezoelectric element (8), wherein at the second end (20) of the wire (14) a hybrid contact point (16) of the wire (14) with the electrode (10) is formed, comprising a welded contact (21) and a soldered contact (22).
2. Contacting structure according to claim 1, wherein the solder contacting (22) is flux-free.
3. Contacting structure according to claim 1 or 2, wherein the solder contacting (22) is formed outside the welded contacting (21).
4. Contacting structure according to one of claims 1 to 3, wherein the second end (20) of the wire (14) extends beyond the hybrid contact point (16).
5. Contacting structure according to one of claims 1 to 4, wherein the wire (14) has a conductor (17) made of a conductive material, in particular Cu, and a coating (18) made of a fusible conductive material, in particular Sn, and wherein the solder contact (22) is formed from the molten conductive material of the coating (18) of the wire (14).
6. Ultrasonic sensor (1) comprising a housing (2, 3), an ultrasonic membrane (7) arranged in an opening (6) of the housing (2, 3), a piezoelectric element (8) arranged on the inside of the ultrasonic membrane (7) for excitation of vibration and / or detection of vibrations of the ultrasonic membrane (7), a stationary component attached to the housing (2) 2023PF01393 22 arranged contact pin (13) and a wire (14) which is connected at a first end to the contact pin (13) and is contacted at a second end (20) with an electrode (10) of the piezoelectric element (8), wherein at the second end (20) of the wire (14) a hybrid contact point (16) of the wire (14) with the electrode (10) is formed, comprising a welded contact (21) and a soldered contact (22).
7. Method for contacting a piezoelectric element (8) for vibration excitation and / or detection of vibrations of an ultrasonic membrane (7) of an ultrasonic sensor (1), comprising: a) stationary arrangement (S2) of a contact pin (13) with a wire (14) having a conductor (17) and a coating (18) and connected at a first end to the contact pin (13), in a housing (2) of the ultrasonic sensor (1) such that a second end (20) of the wire (14) rests on an electrode (10) of the piezoelectric element (8); and b) Welding (S3) a region at the second end (20) of the wire (14) resting on the electrode (10) to the electrode (10) of the piezoelectric element (8), wherein the conductor (17) of the wire (14) is welded to the electrode (10) and the coating (18) of the wire is melted, so that a hybrid contact point (16) is formed which comprises a welded contact (21) and a soldered contact (22) of the wire (14) to the electrode (10).
8. Method according to claim 7, wherein the welding (S3) in step b) comprises thermocompression welding.
9. Method according to claim 7 or 8, wherein the solder contact (22) is formed in step b) without the use of additional solder and without the use of flux.
10. Method according to one of claims 7 to 9, wherein the conductor (17) of the wire (14) is made of a conductive material, in particular Cu, and the coating (19)2023PF01393 23 of the wire (14) is made of a fusible conductive material, in particular of Sn.