METHOD OF MANUFACTURING A MEMS PRINTED CIRCUIT BOARD MODULE AND/OR SOUND TRANSDUCER ASSEMBLY

Abstract

A method of manufacturing a MEMS printed circuit board module and/or a sound transducer assembly includes the step of forming a multi-layer printed circuit board by connecting a metallic conductive layer to a plurality of printed circuit board support layers that are laminated together. The method includes the step of forming a multi-layer piezoelectric structure that includes an anchoring area. The method includes the step of turning the anchoring area of the multi-layer piezoelectric structure toward the multi-layer printed circuit board. The method includes the step of laminating the multi-layer printed circuit board directly and firmly to the anchoring area of the multi-layer piezoelectric structure.

Claims

1. A method of manufacturing a MEMS printed circuit board module and/or a sound transducer assembly, the method comprising the following steps: forming a multi-layer printed circuit board by connecting a metallic conductive layer to a plurality of printed circuit board support layers that are laminated together; forming a multi-layer piezoelectric structure that includes an anchoring area; turning the anchoring area of the multi-layer piezoelectric structure toward the multi-layer printed circuit board; and laminating the multi-layer printed circuit board directly and firmly to the anchoring area of the multi-layer piezoelectric structure.

2. The method of claim 1, wherein each of the plurality of printed circuit board support layers is made of fiber composite material.

3. The method of claim 1, wherein the multi-layer piezoelectric structure defines a first side and a second side disposed spaced apart from the first side, and wherein the step of laminating the printed circuit board directly and firmly to the anchoring area of the multi-layer piezoelectric structure includes embedding the multi-layer piezoelectric structure into the printed circuit board so that the printed circuit board is connected to the first side and the second side of the multi-layer piezoelectric structure.

4. The method of claim 1, wherein the step of laminating the printed circuit board directly and firmly to the anchoring area of the multi-layer piezoelectric structure includes gluing the anchoring area of the multi-layer piezoelectric structure to the printed circuit board.

5. The method of claim 1, wherein the printed circuit board is a laminated multi-layer printed circuit board.

6. The method of claim 1, wherein the step of turning an anchoring area of the multi-layer piezoelectric structure toward a printed circuit board includes disposing the multi-layer piezoelectric structure into a recess that extends completely through the printed circuit board.

7. The method of claim 1, wherein the step of forming a multi-layer piezoelectric structure includes using the metallic conductive layer of the multi-layer printed circuit board to form a support layer of the multi-layer piezoelectric structure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further advantages of the invention are described in the following embodiments. The following is shown:

[0035] FIG. 1 a MEMS printed circuit board module in a side view,

[0036] FIG. 2 a detailed section of the MEMS printed circuit board module according to FIG. 1 in the connection area between a piezoelectric structure and a printed circuit board,

[0037] FIG. 3 an additional embodiment of the MEMS printed circuit board module in a detailed section,

[0038] FIG. 4 a schematic detailed view of a piezoelectric structure,

[0039] FIG. 5 a second embodiment of a piezoelectric structure in a schematic detailed view,

[0040] FIG. 6 a sound transducer assembly in a sectional view,

[0041] FIG. 7 a second embodiment of a sound transducer assembly in a sectional view,

[0042] FIG. 8 a third embodiment of a piezoelectric structure with an actuator/sensor area in a top view.

[0043] In the following description of the figures, in order to define the relationships between the various elements, with reference to the locations of objects shown in the figures, relative terms, such as above, below, up, down, over, left, right, vertical or horizontal are used. It is self-evident that such a term may change in the event of a deviation from the location of the devices and/or elements shown in the figures. Accordingly, for example, in the case of an orientation of a device and/or an element shown inverted with reference to the figures, a characteristic that has been specified as above in the following description of the figures would now be arranged below. Thus, the relative terms are used solely for a more simple description of the relative relationships between the individual devices and/or elements described below.

DETAILED DESCRIPTION

[0044] FIG. 1 shows a MEMS printed circuit board module 1 in a sectional view. The MEMS circuit board module 1 is provided for a sound transducer assembly 2 (see FIGS. 6 and 7) for generating and/or detecting sound waves in the audible wavelength spectrum. The MEMS printed circuit board module 1 essentially comprises a printed circuit board 4 and a multi-layer structure 5, in particular a piezoelectric structure 5. The printed circuit board 4 is a multi-layer composite fiber component with at least one electrical conductive layer 8 made of metal. The printed circuit board 4 comprises an ASIC 27 (FIG. 1) and/or passive electronic additional components 28 (FIG. 2), which are completely integrated into the printed circuit board 4. Thus, the ASIC 27 and/or the passive electronic additional components 28 are completely encapsulated by the printed circuit board 4.

[0045] As shown in FIGS. 1 and 2, the printed circuit board 4 defines a recess 17 with a first opening 18 and a second opening 19 opposite the first opening 18. Thus, the recess 17 extends completely through the printed circuit board 4 from the first opening 18 to the second opening 19. The recess 17 is a through-hole, such that the printed circuit board 4 is formed as a circumferentially closed frame, in particular as a support frame 15. In addition to the ASIC 27 and the additional components 28, the structure 5, in particular in an anchoring area 21, is also integrated into such support frame 15.

[0046] The structure 5 is connected directly to the printed circuit board 4 in the interior of the recess 17. Accordingly, the printed circuit board 4 forms a structural support, which supports the piezoelectric structure 5 and with respect to which the structure 5 can be deflected. The piezoelectric structure 5 features a support layer 7 and a piezoelectric functional region 9. In its outer area, the structure 5 features the anchoring area 21. In such anchoring area 21 facing towards the printed circuit board 4, the structure 5 is firmly connected to the printed circuit board 4, in particular the conductive layer 8. At this, the conductive layer 8 essentially forms the support layer 7 of the piezoelectric structure 5, which is integrated into the printed circuit board 4 in this manner.

[0047] In addition, the structure 5 includes a central region 22, which is substantially arranged centrally in the interior of the recess 17. In this central region 22, the structure 5 is connected to a coupling element 23 through at least one flexible connecting element 26. The coupling element 23 and the printed circuit board 4 are preferably made of the same material, in particular a fiber composite material. The structure 5 can deflect the coupling element 23 relative to the printed circuit board 4 in the z-direction or along the lifting axis from the neutral position shown in FIG. 1.

[0048] The recess 17 at least partially forms a cavity 20 of the sound transducer assembly 2, which is shown in full in FIGS. 6 and 7. The printed circuit board 4 also includes an external contact 29 for the electrical connection to an external device, which is not shown here.

[0049] FIG. 2 shows a detailed section of the MEMS printed circuit board module 1 according to FIG. 1 in cross-section, in particular in the connection area between the printed circuit board 4 and the piezoelectric structure 5. The multi-layer printed circuit board 4 is a laminated fiber composite component, which features at least a first conductive layer 8 and a second conductive layer 34. The two conductive layers 8, 34 are electrically decoupled from each other through printed circuit board support layers 14. The structure 5 is connected to the printed circuit board 4 in its anchoring area 21. At this, the first conductive layer 8 of the printed circuit board 4 forms the support layer 7 of the structure 5. The piezoelectric functional region 9 (see FIGS. 4 and 5) is supported by the support layer 7.

[0050] The support layer 7 is laminated in the printed circuit board 4 and thus directly connected to it. The functional area 9 is firmly connected to the printed circuit board 4 by means of the support layer 7. The functional layer 9 can be laminated on the support layer 7.

[0051] External devices can be connected to the sound transducer assembly 2 through an external contact 29, which is arranged on one side of the printed circuit board 4. For this purpose, the printed circuit board 4 in the area of the second conductive layer 34 includes the additional components 28 or the ASIC 27 (see FIG. 3), as the case may be, which are indicated only schematically in FIG. 2.

[0052] FIG. 3 shows an additional embodiment of the MEMS printed circuit board module 1, whereas the following essentially addresses the differences with respect to the embodiment already described. Thus, with the following description, the additional embodiments for the same characteristics use the same reference signs. To the extent that these are not explained once again in detail, their design and mode of action correspond to the characteristics described above. The differences described below can be combined with the characteristics of the respective preceding and subsequent embodiments.

[0053] FIG. 3 shows the MEMS printed circuit board module 1 in a detailed section, whereas the piezoelectric structure 5 is arranged not inside the recess 17, but in the area of the second opening 19. At this, the first conductive layer 8 is connected directly to the support layer 7. It would also be conceivable to connect the piezoelectric structure 5 to the printed circuit board 4 in the area of the first opening 18. The functional area 9 is at least partially embedded in the printed circuit board 4 and is supported by the support layer 7 in the area of the second opening 19. Accordingly, the printed circuit board 4 forms a structural support, which supports the piezoelectric structure 5 and with respect to which the piezoelectric structure 5 can be deflected.

[0054] The second conductive layer 34 shown in FIG. 3 is connected to the ASIC 27. The ASIC 27 constitutes an encapsulated control unit, which is electrically connected to the second conductive layer 34. In the illustrated embodiment, the ASIC 27 is encapsulated in a hollow space of the printed circuit board 4. However, alternatively or in addition, the ASIC 27 may also be coated or cast with synthetic resin. Like the ASIC 27, the additional electrical component 28 may be coupled to one of the conductive layers 8, 34.

[0055] FIG. 4 shows a detailed view of the piezoelectric structure 5. The structure 5 features the support layer 7 and the functional area 9. The functional area 9 comprises a piezoelectric layer 10, which preferably consists of lead zirconate titanate (PZT) and/or aluminum nitride (ALN). In order to be able to detect an electrical signal upon a deflection of the piezoelectric layer 10 and/or to be able to actively deflect the piezoelectric layer 10 through the application of voltage, the piezoelectric layer 10 is embedded between an upper electrode layer 12 and a lower electrode layer 13. At this, the support layer 7 of the printed circuit board 4 forms the lower electrode layer 13, whereas the piezoelectric structure 5 is embedded or integrated directly into the printed circuit board 4 through this configuration.

[0056] FIG. 5 shows an additional embodiment of the piezoelectric structure 5. According to the piezoelectric structure 5 illustrated in FIG. 4, this embodiment includes a piezoelectric layer 10 that is sandwiched between two electrode layers 12, 13. This three-layer combination constitutes the basis for the embodiment described below. With the following description of this embodiment, the same reference signs are used for the same features in comparison with the embodiment shown in FIG. 4. Unless they are once again explained, their design and mode of action corresponds to the features already described above.

[0057] According to the embodiment illustrated in FIG. 5, the piezoelectric structure 5 includes, in addition to the two electrode layers 12, 13 and the piezoelectric layer 10, an insulating layer 11, which is formed in particular from silicon oxide. In this embodiment, the lower electrode layer 13 is not formed by the support layer 7 of the printed circuit board 4 itself, but by an additional layer in the functional area 9. Through the insulating layer 11, the lower electrode layer 13 is electrically decoupled from the support layer 7.

[0058] FIG. 6 shows a first embodiment of the sound transducer assembly 2 in a sectional view. The sound transducer assembly 2 comprises the MEMS printed circuit board module 1, the membrane 6 and the membrane frame 16. The membrane 6 has a region that is free to move in the z-direction or along the lifting axis in an oscillating manner with respect to the membrane frame 16. The membrane 6 and the membrane frame 16 essentially form a membrane module 3. In its outer frame area, the printed circuit board 4 is connected to an outer connection area 33 of the membrane module 3, in particular to the membrane frame 16. An inner connection area 32 is formed between the membrane 6 and the coupling element 23. Thus, the membrane 6 spans the membrane frame 16 and is stiffened in its central area where the interconnection area 32 is defined.

[0059] The recess 17 shown in FIG. 6 at least partially forms a cavity 20 of the sound transducer assembly 2. The cavity 20 is closed by a housing part 30 on the side of the MEMS printed circuit board module 1 facing away from the membrane frame 16. The housing part 30 is formed from metal or plastic and defines in the interior of the housing part 30 a housing hollow space 35, which combines with the recess 17 to form the cavity 20. The size of the housing housing space 35 can be selected depending on the sound pressure to be generated.

[0060] The piezoelectric structure 5 is arranged below the membrane 6 and/or substantially parallel to it. The support layer 7 of the piezoelectric structure 5 is directly connected to one of the conductive layers 8, 34 of the printed circuit board 4, and can be deflected relative to the printed circuit board 4 in the z-direction. The piezoelectric layer 10 is designed to produce a uni-directional or bidirectional lifting movement of the piezoelectric structure 5 for the deflection of the membrane 6. Accordingly, the piezoelectric layer 10 works together with the membrane 6 in order to convert electrical signals into acoustically perceptible sound waves. Alternatively, the acoustically perceptible sound waves can be converted into electrical signals.

[0061] The structure 5 is connected to the ASIC 27 by means of contacts not shown in the figures. Thus, the sound transducer assembly 2 can be controlled or operated via the ASIC 27, such that, for example through the piezoelectric structure 5, the membrane 6 can be set into oscillation relative to the membrane frame 16 in order to produce sound energy.

[0062] FIG. 7 shows an additional embodiment of the sound transducer assembly 2, whereas the following essentially addresses the differences with respect to the embodiment already described. Thus, with the following description, the additional embodiments for the same characteristics use the same reference signs. Unless they are once again explained in detail, their design and mode of action corresponds to the features already described above. The differences described below can be combined with the features of the respective preceding and following embodiments.

[0063] A reinforcing element 31, which itself is not connected to the membrane frame 16, is arranged on a bottom surface of the membrane 6, in particular in its middle area. Thus, the reinforcing element 31 can oscillate together with the membrane 6 with respect to the membrane frame 16 in the z-direction. In addition, the inner connection area 32 of the membrane 6 is stiffened in this manner. In this embodiment, the membrane frame 16 is formed from the printed circuit board 4 itself and therefore of the same material. Thus, the membrane frame 16 and the printed circuit board 4 are formed in one piece.

[0064] According to FIG. 7, the sound transducer assembly 2 does not feature any separate housing parts 30. Here, the cavity 20 is formed and closed by the printed circuit board 4 itself. However, a design of the membrane frame 16 according to the first embodiment of the sound transducer assembly 2 is likewise conceivable.

[0065] FIG. 8 shows a third embodiment of a piezoelectric structure 5 in a top view. The piezoelectric structure 5, which is designed in particular as a cantilever, includes at least one actuator region 24 and one sensor region 25. The actuator/sensor region 24, 25 is arranged between the anchoring area 21 and the central area 22. The connection to the central area 22 takes place by means of at least one flexible connecting element 26. At this, the sensor region 25 is preferably designed as a position sensor in order to provide the ASIC 27 with a sensor signal that is dependent on the membrane deflection. In doing so, the elastic oscillation properties of the connecting element 26 are taken into account. The voltage generated via the piezoelectric effect, which is approximately proportional to the deflection of the region structure 5, is tapped and evaluated via the electrode layers 12, 13 (compare FIGS. 4 and 5). Based on the control signal, the region structure 5 can be driven in a controlled manner by the ASIC 27.

[0066] The sensor region 25 and the actuator region 24 are formed by a common piezoelectric layer 10. At this, at least one area is a sensor region 25, by means of which two actuator regions 24 are spaced apart from each other. The actuator regions 24 are electrically isolated from each other. The two regions 24, 25 may be formed from material different from each other, in particular from lead zirconate titanate or aluminum nitride.

[0067] This invention is not limited to the illustrated and described embodiments. Variations within the scope of the claims, just as the combination of characteristics, are possible, even if they are illustrated and described in different embodiments.

LIST OF REFERENCE SIGNS

[0068] 1 1 MEMS printed circuit board module [0069] 2 Sound transducer assembly [0070] 3 Membrane module [0071] 4 Circuit board [0072] 5 Structure [0073] 6 Membrane [0074] 7 Support layer [0075] 8 First conductive layer [0076] 9 Functional region [0077] 10 Piezoelectric layer [0078] 11 Insulating layer [0079] 12 Upper electrode layer [0080] 13 Lower electrode layer [0081] 14 Printed circuit board support layers [0082] 15 Support frame [0083] 16 Membrane frame [0084] 17 Recess [0085] 18 First opening [0086] 19 Second opening [0087] 20 Cavity [0088] 21 Anchoring area [0089] 22 Central region [0090] 23 Coupling element [0091] 24 Actuator region [0092] 25 Sensor region [0093] 26 Connecting element [0094] 27 ASIC [0095] 28 Additional components [0096] 29 External contact [0097] 30 Housing part [0098] 31 Reinforcing element [0099] 32 Inner connection area [0100] 33 Outer connection area [0101] 34 Second conductive layer [0102] 35 Housing hollow space