SAW sensor module

Abstract

The invention relates to a SAW sensor module comprising a cartridge having a sensor chip made of a piezoelectric material and at least one SAW sensor formed thereon, and at least one control and reading device for the at least one SAW sensor. According to the invention, the control and reading device has a device circuit board, on a device circuit board front side of which a device coupling electrode is formed, which is connected to a device connection formed on the device circuit board via an electrical conductor passing through the device circuit board, the device circuit board has a device coupling electrode, and the cartridge has a cartridge coupling electrode which is capacitively coupled to the device coupling electrode on the one hand and to a sensor electrode of the at least one SAW sensor on the other hand, at least one magnetic element being formed on the device circuit board, and the box body is provided with at least one metal and / or magnetic alignment element which is aligned with the at least one magnetic element.

Description

[0001] The present application relates to a SAW sensor module having a cartridge comprising a sensor chip made of a piezoelectric material and at least one SAW sensor formed thereon, and at least one control and readout device for the at least one SAW sensor.

[0002] A surface acoustic wave (SAW) is a type of structural acoustic wave that propagates planarly, i.e. only in two dimensions, on a surface. The SAW wave penetrates only very slightly into the material on which it propagates, the penetration depth being limited to one wavelength. In a SAW sensor, an acoustic surface wave is sent from a transmitting electrode located on the surface of the sensor to a receiving electrode. Between the transmitting electrode and the receiving electrode, a respective selective receptor layer is located on the piezoelectric substrate.

[0003] Preferably, interdigitated comb structures of metal, so-called interdigital transducers (IDTs), are used as transmitter and receiver. An alternating voltage is then applied to one comb structure, while the other comb structure is grounded. Thereby, a periodically varying electric field is generated between the fingers of different charge. Since in the piezoelectric substrate, an externally applied electric field can cause mechanical deformation thereof, the substrate is alternately stretched and contracted.

[0004] In a SAW sensor, two such IDTs are arranged side by side on the sensor substrate. Of these, one IDT serves as a transmitter and the other IDT serves as a receiver. At the transmitter, an alternating voltage signal is converted into an acoustic surface wave and sent into the substrate. The acoustic surface wave causes a charge displacement in the piezoelectric substrate, which generates an alternating voltage signal in the finger structure of the receiver.

[0005] A SAW sensor can be operated as a delay line or as a resonator. In the latter principle, reflector structures are located outside the IDTs, respectively.

[0006] By means of the respective reflectors, a respective radiated radio signal is reflected as an echo. The time interval between the original signal and the echo, as well as the change in amplitude and phase of the respective signals, depend, among other factors, on the speed of sound of the sensor substrate material used, the temperature, and mechanical stresses in the substrate. It has also been shown that, for a SAW sensor based on such reflection, the time interval, the amplitude, and the phase change depending on a receptor layer applied to the sensor substrate and bound to the substrate surface. A resulting mass attachment to the sensor surface causes a change in the surface wave speed. This effect is utilized, for example, in biological or chemical sample analysis in order to be able to determine specific components of a fluid.

[0007] It is the task of the present application to create a practical device for simple analysis of chemical and / or biological fluids based on a SAW sensor.

[0008] According to the application, this task is solved by a SAW sensor module, comprising a housing and at least one control and evaluation device for the at least one SAW sensor, the housing having a sensor chip made of piezoelectric material and at least one SAW sensor formed thereon, wherein the control and evaluation device has a device circuit board, on the device circuit board a device coupling electrode is formed, the device coupling electrode being connected via an electrical conductor which penetrates the device circuit board to a device connection formed on the device circuit board and the housing has a housing coupling electrode which is capacitively coupled on the one hand to the device coupling electrode and on the other hand to a sensor electrode of the at least one SAW sensor, wherein at least one magnetic element is formed on the device circuit board and the housing has at least one metallic and / or magnetic alignment element which is aligned with the at least one magnetic element.

[0009] The SAW sensor module according to the application has a variable and permanently usable control and evaluation device which can be used for a large number of measurements. Furthermore, the SAW sensor module according to the application has a housing which is used in principle only once, i.e. as a disposable part. In the SAW sensor assembly of the housing, measurements of the changes in the generated surface acoustic waves which are related to the sample are carried out. The driving and evaluation of the SAW sensor used is carried out by means of the control and evaluation device.

[0010] In the application, the signal transmission from the control and evaluation device to the housing and back from the housing to the control and evaluation device takes place simply and with low losses by means of the capacitive coupling between the control and evaluation device and the housing. Here, two types of capacitive coupling are used: On the one hand, the device coupling electrodes are arranged opposite one another at a very small distance from the housing coupling electrodes, whereby a simple capacitive coupling can be achieved; on the other hand, the housing coupling electrodes are capacitively coupled to the sensor electrodes by means of the piezoelectric substrate.

[0011] The respective electrodes are arranged directly above one another here. In the application, the alignment of the device coupling electrodes with the housing coupling electrodes is achieved simply by the fact that the housing is aligned automatically on the control and evaluation device as a result of the magnetic attraction between the at least one alignment element and the at least one magnetic element. Therefore, in the application, no complex adjustment and wiring is necessary. Quite the contrary: The housing only has to be placed simply on the control and evaluation device, it is automatically rotated into the correct position and then the evaluation can be started. This alignment works both in the rotational and in the translational direction. After the alignment has been completed, the housing is stably positioned on the control and evaluation device in all axial directions.

[0012] In one mechanically particularly stable embodiment of the application, the cartridge has a carrier circuit board between the sensor chip and the device circuit board, on which carrier circuit board the cartridge coupling electrodes are formed. The carrier circuit board forms a stable base on which the cartridge coupling electrodes can advantageously be formed and, in addition, on which the sensor chip and further configurations of the cartridge, such as its housing, can advantageously be built.

[0013] However, in principle, the sensor electrodes of the sensor chip can also be capacitively coupled directly with the device coupling electrodes of the device circuit board.

[0014] When a fluid frame is built on the SAW sensor assembly, which fluid frame encloses a fluid cell, and a cover is formed on the sensor chip around the fluid frame, a fluid can be particularly easily and safely analyzed by means of the SAW sensor module of the application, wherein the cover and the fluid frame cover the sensor electrodes and the reflectors of at least one SAW sensor. By means of the fluid cell it can be achieved that, when the SAW sensor module has a plurality of SAW sensors, the propagation paths or tracks of all these SAW sensors can be designed to be equal in length, which facilitates differential processing between the signals of these SAW sensors.

[0015] When the fluid frame is a lever structure, which forms a mechanically particularly stable and sealed frame around the fluid cell, which lever structure is suspended in a recess formed on the cover on the one hand and presses on the sensor chip front side of the sensor chip and seals there on the other hand.

[0016] When the fluid frame forms a funnel with a slanted wall on at least one SAW sensor or such a funnel is mounted on the fluid frame, it can be particularly easy to fill the fluid cell with fluid.

[0017] The cover is preferably a plastic injection-molded part, through which at least one alignment element penetrates. Thus, the cartridge can be manufactured with high reproducibility, in high yield and thus inexpensively.

[0018] As long as the SAW sensor module of the application has not yet been used, at least one SAW sensor can be particularly effectively protected from external influences when a cover film is laminated on the fluid frame.

[0019] When the cartridge has a plurality of SAW sensors which are arranged in strips parallel to one another, at least one of these SAW sensors can be used as a reference sensor. This reference sensor can be formed, for example, without a selective receptor layer. In addition, one of these SAW sensors can be used to compensate for environmental or temperature effects.

[0020] It is meaningful for the propagation path sections of the measuring SAW sensor and the reference SAW sensor, which come into contact with the fluid to be analyzed, to be equal in length.

[0021] The SAW sensors are preferably separated from one another by a separating wall located therebetween.

[0022] When the at least two SAW sensors have different propagation paths, they can be electrically connected in parallel or in series and read together via a coupling path. The signals of the sensors can then be separated by means of their propagation times by evaluation electronics.

[0023] In another advantageous embodiment of the application, each SAW sensor is assigned a separate capacitive interface. Thus, the SAW sensors can be measured and evaluated simultaneously, so that measurement errors can be reduced.

[0024] It is particularly advantageous if at least one RFID chip is formed on the sensor chip and / or on the carrier circuit board, which RFID chip is connected to the device connection by means of the at least one capacitive coupling. By means of the RFID chip, the cartridge and the fluid sample determination carried out therein can be uniquely determined and assigned to the recorded measurement values, wherein the data transmission takes place simply by means of the at least one capacitive coupling.

[0025] When a dielectric protective film is arranged between the cartridge and the control and read device, an advantageous protection of the control and read device from, for example, dirt or moisture can be achieved. Such a protective film serves as a dielectric for the capacitive coupling between the control and read device and the cartridge and does not influence it.

[0026] The preferred embodiments of the application and their structure, function and advantages are explained in more detail below with the aid of the drawings, in which:

[0027] Figure 1 a top view of an embodiment of the SAW sensor module of the application is schematically shown;

[0028] Figure 2 a top view of an embodiment of the SAW sensor module of the application is schematically shown; Figure 1 a top view of an embodiment of the SAW sensor module of the application is schematically shown;

[0029] Figure 3 a top view of an embodiment of the SAW sensor module of the application is schematically shown;

[0030] Figure 4 a top view of an embodiment of the SAW sensor module of the application is schematically shown;

[0031] Figure 5 a top view of an embodiment of the SAW sensor module of the application is schematically shown.

[0032] Figure 1A top view of one embodiment of the inventive SAW sensor module 1 is shown schematically. Therein, the hidden structure of the SAW sensor module 1 is shown in grey. In Figure 3 A cut-away side view of one embodiment of the inventive SAW sensor module 1 is shown schematically.

[0033] The SAW sensor module 1 has Figure 3 The control and read-out device 4 is shown schematically in Figure 2 The device circuit board 40 is a non-conductive printed circuit board, on which conductive structures are formed. The device circuit board 40 has on its Figure 2 The device circuit board 40 has on its device front side 41 two device coupling electrodes 43, 44, which are formed as circular rings in the shown embodiment, but can also have other shapes.

[0034] The device coupling electrodes 43, 44 are connected to an electrical device connection 47 on the device back side 42 by electrical conductors 45, 46, which run through the device circuit board 40.

[0035] Furthermore, the device circuit board 40 has two magnetic elements 51, 52, which are accessible through the device front side 41. In other embodiments of the invention, only one or more than two magnetic elements 51, 52 can also be formed on the device front side 41.

[0036] On the control and read-out device 4 a cartridge 2 is placed, which can also be called Cartridge. The control and read-out device 4 is designed for permanent use, while the cartridge 2 is designed for single use, i.e. as a single-use element. Between the control and read-out device 4 and the cartridge 2 a dielectric protection film 8, for example a Kapton tape, is arranged.

[0037] The cartridge 2 has a SAW sensor assembly 3. In the shown embodiment, the SAW sensor assembly 3 has a carrier circuit board 20 and a sensor chip 30 with at least one SAW sensor 33, preferably a plurality of SAW sensors 33, 34, 35, located thereon. In other not shown embodiments of the invention, the SAW sensor assembly 3 can also only have a single substrate, on which the elements of the carrier circuit board 20 and the sensor chip 30 described below are combined.

[0038] The carrier circuit board 20 has back-side cartridge coupling electrodes 23, 24 on its carrier circuit board back side 27, which are opposite the device coupling electrodes 43, 44. In the embodiment shown, the device coupling electrodes 43, 44 have a larger diameter than the back-side cartridge coupling electrodes 23, 24. The device coupling electrodes 43, 44 and the back-side cartridge coupling electrodes 23, 24 formed on the cartridge back side 27 of the cartridge 2 can be concentric with one another, but this is not a requirement.

[0039] Only the dielectric protection film 8 is between the back-side cartridge coupling electrodes 23, 24 and the device coupling electrodes 43, 44. Since the control and reading device 4 must be disinfected regularly, the dielectric protection film 8 can provide advantageous protection against disinfectants and also against dirt and general moisture. The back-side cartridge coupling electrodes 23, 24 and the device coupling electrodes 43, 44 are not connected by electrical conductors, but are capacitively coupled.

[0040] On the carrier circuit board front side 28 of the carrier circuit board 20, there are front-side cartridge coupling electrodes 25, 26, which are electrically conductively connected to the back-side cartridge coupling electrodes 23, 24 by electrical conductors 48, 49 that run through the carrier circuit board 20.

[0041] In the embodiment shown, the carrier circuit board 20 is a printed circuit board made of an electrically non-conductive material, on which electrically conductive structures are formed. The carrier circuit board 20 serves to establish a capacitive coupling between the sensor chip 30 of the cartridge 2 and the control and reading device 4. In addition, the carrier circuit board 20 has a carrier function, i.e. it carries the sensor chip 30. On the carrier circuit board 20, matching elements for power matching, such as coils and / or capacitors, can also be provided.

[0042] The carrier circuit board 20 can also have markings, which can be used to place the sensor chip 30 on the carrier circuit board 20.

[0043] On the carrier circuit board 20, the electrical connections between the electrical contacts or electrodes on the carrier circuit board front side 28 and the carrier circuit board back side 27 can be designed arbitrarily. This creates degrees of freedom in terms of mechanics and electrics.

[0044] The sensor chip 30 is made of a piezoelectric material. The sensor chip 30 has at least one SAW sensor 33 on its sensor chip front side 37. The at least one SAW sensor 33 is operated by means of sensor electrodes 31, 32 also located on the sensor chip front side 37.

[0045] The sensor electrodes 31, 32 are capacitively coupled to the front-side cartridge coupling electrodes 25, 26. Here, the piezoelectric material of the sensor chip 30 constitutes the dielectric of this capacitive coupling arrangement.

[0046] Typically, the sensor chip 30 is bonded to the carrier circuit board 20. The adhesive used then forms part of the dielectric mentioned above.

[0047] The sensor electrodes 31, 32 are thus connected to the device connection 47 of the control and readout device 4 via the front-side case coupling electrodes 25, 26, the back-side case coupling electrodes 23, 24 and the device coupling electrodes 43, 44, so that electrical contact can be made to the at least one SAW sensor 33 and its signal can be read out.

[0048] Above the at least one SAW sensor 33, a fluid cell 70 is formed in the case 2. The fluid cell 70 is laterally delimited by a fluid frame 7.

[0049] The fluid frame 7 can be formed, for example, as shown schematically in Figure 4 Fig. 2, by inclined walls which form a funnel above the at least one SAW sensor 33 on the sensor chip 30. Here, the inclined walls can be formed, as shown in Figure 4 Fig. 3, in the form of levers which are suspended on the one hand in recesses 72 of a cover 71 which surrounds the fluid cell 70 and on the other hand rest on the sensor chip 30 and are sealed against it by a seal 75. The seal 75 can be, for example, an adhesive bead.

[0050] In the embodiment shown, the cover 71 is formed as a plastic injection-moulded part.

[0051] The cover 71, together with the fluid frame 7, covers the sensor electrodes 31, 32 and the reflector of the at least one SAW sensor 33.

[0052] The fluid to be detected can be added to the fluid cell 70. The size of the fluid cell 70 defines the volume of fluid which can be analysed. The molecules of this fluid can bind to the surface of the at least one SAW sensor 33, so that its surface wave conduction properties can be changed, and the corresponding fluid can thus be detected.

[0053] As long as the case 2 is not in use, the fluid cell 70 is covered by a cover film 9. The cover film 9 is tearable.

[0054] In the embodiment shown, at least one RFID chip 10 is arranged on the sensor chip 30. The RFID chip 10 is also capacitively coupled to the case coupling electrodes of the carrier circuit board 2 via the sensor chip 30 and, via them, to the device coupling electrodes of the device circuit board 40. By means of the RFID chip 10, the case 2 and the fluid sample determination carried out in it can be uniquely identified and, as a result, assigned to the recorded measurement values. The RFID chip 10 can also be arranged in other embodiments of the application on the carrier circuit board 20.

[0055] Preferably, the RFID chip 10 is not a SAW-based but a semiconductor- based RFID chip. In the RFID chip 10, for example, it can be recorded which test is currently performed by the SAW sensor module 1. From the RFID chip 10, it can also be read whether the SAW sensor module 1 has already been used. Furthermore, a batch number, an expiration date, etc. can be stored in the RFID chip 10.

[0056] In the shown embodiment, three SAW sensors 33, 34, 35 are formed on the sensor chip 30. The SAW sensors 33, 34, 35 have different propagation paths L1, L2, L3 as schematically shown in Figure 5

[0057] In the shown embodiment, the SAW sensors 33, 34, 35 are SAW sensors of 300 MHz, but can also be SAW sensors based on other frequencies. The SAW sensors 33, 34, 35 are formed in a strip and parallel to each other. Above the middle region of the SAW sensors 33, 34, 35 is the fluid cell 70.

[0058] Between the SAW sensors 33, 34, 35 there are photoetched isolation walls 38. The isolation walls 38 protect the individual regions of the SAW sensors 33, 34, 35 and also their IDTs from each other.

[0059] Furthermore, on the regions of the sensor chip 30 which are not in contact with the fluid to be analyzed, a cover layer is formed. This cover layer is formed by photoetching the layer structure.

[0060] In the shown embodiment, the SAW sensors 33, 34, 35 are connected in series and are contacted only with one pair of common capacitive coupling electrodes. However, this is not necessarily so, for example, the SAW sensors 33, 34, 35 can be driven and read sequentially by a multiplexer. Also a parallel connection of the individual SAW sensors 33, 34, 35 is possible.

[0061] In the shown embodiment, the SAW sensor 33 constitutes one sample channel, i.e. the actual measurement channel, the SAW sensor 34 constitutes one compensation channel for compensating temperature effects, and the SAW sensor 35 constitutes one reference channel, i.e. without a selective receptor layer. Figure 5 In other embodiments of the application, the SAW sensors 33, 34, 35 can also be used for measuring different analytes.

[0062]

[0063] ​​The cartridge 2 passes through a metal or magnetic alignment element 6, which in the shown embodiment is constituted by a metal wire, such as a steel wire. The at least one alignment element 6 advantageously passes through a preformed hole in the cartridge 2, for example at a corner of the cartridge 2. Instead of a steel wire, a magnetic field yoke can also be used as the alignment element 6.

[0064] The end of the alignment element 6 terminates at the back side 27 of the carrier circuit board opposite the magnetic elements 51, 52. By the interaction between the end of the alignment element 6 and the magnetic elements 51, 52, the cartridge 2 is automatically aligned on the device circuit board 40 when it is placed on the device circuit board 40. By this automatic alignment, the cartridge coupling electrodes 23, 24 are automatically positioned on the device coupling electrodes 43, 44.

Claims

1. A SAW sensor module (1) comprising a housing (2) with a sensor chip (30) made of a piezoelectric material and at least one SAW sensor (33, 34, 35) formed on the sensor chip (30) and at least one control and readout device (4) for the at least one SAW sensor (33, 34, 35), characterized in that The control and evaluation device (4) has a device circuit board (40) on the device circuit board front side (41) of which device coupling electrodes (43, 44) are formed which are connected to device connection parts (47) formed on the device circuit board (40) by means of electrical conductors (45, 46) which pass through the device circuit board (40), and the cartridge (2) has cartridge coupling electrodes (23, 24; 25, 26) which are on the one hand capacitively coupled to the device coupling electrodes (43, 44) and on the other hand to sensor electrodes (31, 32) of the at least one SAW sensor (33, 34, 35), wherein at least one magnetic element (51, 52) is formed on the device circuit board (44) and the cartridge (2) has at least one metallic and / or magnetic alignment element (6) which is aligned with the at least one magnetic element (51, 52).

2. The SAW sensor module according to claim 1, characterized in that The cartridge (2) has a carrier circuit board (20) between the sensor chip (30) and the device circuit board (40) on which the cartridge coupling electrodes (23, 24; 25, 26) are formed.

3. The SAW sensor module according to any of the preceding claims, characterized in that, A fluid frame (7) is built on the SAW sensor assembly (3) which surrounds a fluid cell (70), and a cover (71) is formed on the sensor chip (30) around the fluid frame (70), wherein the cover (71) and the fluid frame (70) cover the sensor electrodes (31, 32) and reflectors of the at least one SAW sensor (33, 34, 35).

4. The SAW sensor module according to claim 3, characterized in that The fluid frame (70) is a kind of lever structure which is on the one hand suspended in a recess (72) formed on the cover (71) and on the other hand presses against and seals at a sensor chip front side (37) of the sensor chip (30).

5. SAW sensor module according to claim 3 or 4, characterized in that The fluid frame (70) forms a funnel with an inclined wall (7) on the at least one SAW sensor (33, 34, 35), or such a funnel is mounted on the fluid frame (70).

6. The SAW sensor module according to any one of claims 3 to 5, characterized in that The cover (71) is a plastic injection molding in which the at least one alignment element (6) is passed through.

7. The sensor module according to any one of claims 3 to 6, characterized in that, A cover film (9) is laminated on the fluid frame (70).

8. SAW sensor module according to any of the preceding claims, characterized in that The cartridge (2) has a plurality of strip-shaped, parallelly arranged SAW sensors (33, 34, 35).

9. The SAW sensor module according to claim 8, characterized in that Isolation walls (38) are formed between the SAW sensors (33, 34, 35).

10. The SAW sensor module according to claim 8 or 9, characterized in that At least two of the SAW sensors (33, 34, 35) have different propagation paths (L1, L2, L3).

11. The SAW sensor module according to any one of claims 8 to 10, characterized in that Each of the SAW sensors (33, 34, 35) is assigned a separate capacitive interface.

12. The SAW sensor module according to any one of the preceding claims, characterized in that At least one RFID chip (10) is formed on the sensor chip (30) and / or the carrier circuit board (20) which is connected to the device connection parts (47) by means of at least one capacitive coupling.

13. The SAW sensor module according to any of the preceding claims, characterized in that A dielectric protection film (8) is arranged between the cartridge (2) and the control and reading device (4).

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