ELECTRONIC MODULE AND METHOD FOR THE PRODUCTION THEREOF

Description

Technical area

[0001] The invention relates to an electronic module, such as, by way of example but not as a limitation, it can serve as a component of a driver assistance system in a vehicle. Furthermore, the invention relates to a method for manufacturing an electronic module according to the invention. State of the art

[0002] From DE 10 2009 001 932 A1 of the applicant, an electronic module in the form of a chip module with the features of the preamble of claim 1 is known, which is essentially characterized by a carrier film on which electrically conductive structures are formed. Chips, which may be configured, inter alia, as pressure sensors, are connected to the carrier film. The carrier film is (completely) covered on the side facing the chips by a protective material in the form of a molding compound. The known chips acting as pressure sensors constitute separate components from the pressure sensors, and no details regarding the exact structure of the pressure sensors are disclosed.

[0003] Furthermore, DE 10 2007 011 472 A1 discloses a pressure sensor with an elastically deformable diaphragm clamped at its lower and upper surfaces by means of an annular housing part, which are aligned with each other. An effective area of ​​the diaphragm located in the central region of the housing parts has an electrically conductive structure whose electrical resistance changes depending on the deformation of the effective area. The diaphragm also has connection elements outside the housing parts for contacting, for example, an electronic circuit. WO2018 / 235087A1 also discloses a pressure sensor with an elastically deformable diaphragm, an electronic circuit, and a protective compound. Disclosure of the invention

[0004] The electronic module according to the invention, with the features of claim 1, has the advantage that it enables the cost-effective integration and manufacture of sensors, in particular pressure sensors, on a carrier film, wherein the carrier film simultaneously serves as the substrate for an electronic circuit that is at least partially covered by a protective compound to protect against external influences. In particular, the electronic module makes it possible to dispense with sensors or pressure sensors designed as separate components. Instead, a portion of the carrier film forms an elastically deformable membrane of the sensor or pressure sensor, or a sensing area, and the protective compound or fixing element provided for protection against external influences simultaneously enables the membrane to be clamped in a particularly simple manner, thus defining the geometric boundaries or forming the sensing area.

[0005] Against this background, the teaching of the invention proposes that the sensor has an elastically deformable detection area formed by a partial area of ​​the carrier film and additionally by a detection film with a microstructure connected to the carrier film, wherein the detection film is made of silicon to achieve contact of the detection film protected against mechanical stresses and media, that means for detecting the deformation of the detection area are provided, and that the protective mass or a fixing element has a recess within which the carrier film and the detection film are exposed, wherein the recess limits the detection area at its edges, so that the protective mass or the fixing element fixes the detection area relative to the carrier film, wherein the wall of the recess is slightly inclined, so that the diameter of the recess increases with increasing distance from the carrier film.

[0006] Advantageous further developments of the electronic module according to the invention are listed in the dependent claims.

[0007] In order to form the means for detecting the deformation of the detection area, it is provided that the means are formed by the detection film, in particular such that an electrical resistance of the detection film changes depending on the deformation of the detection area.

[0008] To either increase the sensitivity or accuracy of the pressure sensor, or to allow a pressure to be detected to act on or be measured on both sides of the membrane, it is proposed that the carrier film on the side opposite the detection area has an additional detection area aligned with the detection area, wherein the size of the additional detection area corresponds at most to the size of the detection area.

[0009] Further developing the previous proposal, it is envisaged that the side of the carrier film containing the additional detection area will be free of protective material. This simplifies the manufacturing of the electronic module, as the protective material, usually in the form of a molding compound, only needs to be applied to one side of the carrier film.

[0010] A design for the advantageous contacting of the detection film involves electrically connecting the detection film to the electrically conductive structure of the carrier film via wire bonds, with the area of ​​the wire bonds being covered by the protective compound. In the contact area, the detection film has a thin silicon layer. This ensures that the contact of the detection film is protected against mechanical stress and various media.

[0011] In a further advantageous embodiment of the electronic module, it is provided that the means for detecting the deformation of the detection area includes evaluation electronics that are covered by the protective mass.

[0012] The invention further comprises a method for manufacturing a module according to the invention as described above, wherein the method includes at least the following steps: First, a carrier film having an electrically conductive structure is provided. Next, a detection film capable of detecting deformation is connected to the carrier film. Then, an electronic circuit is at least partially formed by populating the electrically conductive structures with electronic components. In an immediately subsequent or later step, the carrier film is partially covered with a protective compound or a fixing element, leaving the detection area exposed. Finally, additional electronic components may be placed in areas of the carrier film where no protective compound is present.

[0013] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings.

[0014] Brief description of the drawings Fig. 1 shows a non-inventive electronic module in a longitudinal section, in which a carrier film for forming a pressure sensor is structured in certain areas, Fig. 2 a opposite Fig. 1 Modified electronic module according to the invention using a detection film connected to the carrier film as part of a pressure sensor, Fig. 3 a simplified representation of a tool for manufacturing an electronic module in a longitudinal section and Fig. 4 a flowchart to illustrate the essential steps for manufacturing the electrical modules according to the Fig. 1 und Fig. 2 . Embodiments of the invention

[0015] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0016] In the Fig. 1 An electronic module 10 not according to the invention is shown, such as it can serve, for example, as a component of an assistance system or a safety device in a motor vehicle. For example, the module 10 can be configured as a component of an airbag triggering system.

[0017] Module 10 comprises a carrier film 12 made of a polymer, the thickness of which is, for example, between 2 µm and 100 µm, preferably between 5 µm and 50 µm. The carrier film 12 serves as a component or carrier for an electronic circuit 14. The electronic circuit 14 includes, for example, electrically conductive structures 18 in the form of conductor tracks 20 formed on a top surface 16 of the carrier film 12. Furthermore, the electronic circuit 14 includes, for example, an antenna array 22 on the top surface 16. On the underside 24 of the carrier film 12, for example, electronic components, in particular SMD components 26, and a connector 28 for electrical contacting the module 10 are arranged. The components mentioned are also part of the electronic circuit 14, for which the carrier film 12 also has electrically conductive structures 18 or conductor tracks 20 on the underside 24.

[0018] Additionally, module 10 includes a sensor in the form of a pressure sensor 30, which serves to detect an (elastic) deformation of the carrier film 12 in the area of ​​the pressure sensor 30 or a detection area 32 of the pressure sensor 30. The detection area 32, which is particularly circular, is characterized by the fact that a structure 34 is provided or formed on the underside 24 of the carrier film 12 in this area, the electrical resistance of which changes when the detection area 32 is deformed. The structure 34 can, for example, be in the form of a resistor structure or a Wheatstone bridge. For evaluation or acquisition of the detection of the detection area 32, the structure 34 is connected, for example, to evaluation ICs 36, 38. This is done either by connecting the structure 34 via conductor tracks 20 or by separate elements, for example, wire bonds or similar.(not shown) is connected to the evaluation ICs 36, 38.

[0019] Alternatively or in addition to the structure 34 provided on the underside 24 of the carrier film 12, an additional detection area 42 with an additional structure 44 may also be provided or formed on the upper side 16 of the carrier film 12. In the case where corresponding detection areas 32, 42 or structures 34, 44 are provided on both the underside 24 and the upper side 16 (as shown in the Fig. 1 (as shown), the corresponding detection areas 32, 42 are preferably arranged in mutual overlap or aligned with each other, wherein the additional detection area 42 preferably has a maximum size equal to that of the detection area 32.

[0020] Essential for ensuring the function of the detection area 32, 42 with regard to elastic deformation or the correct detection of the deformation of the carrier film 12 is that the detection area 32, 42 is precisely defined in terms of its size or clamped at its edge. For this purpose, in the embodiment according to the Fig. 1 It is provided that the underside 24 of the carrier film 12 is partially surrounded by a protective compound 45 in the form of a molding compound 46. For example, the molding compound 46 is arranged in the area of ​​the evaluation ICs 36 and 38, or covers them. Crucially, no molding compound 46 is provided in the area of ​​the detection area 32 or 42. For this purpose, the molding compound 46 forms, for example, a round recess 48 with a slightly inclined wall in the area of ​​the (lower) structure 34. The detection area 32 or the structure 34 is arranged within the recess 48. Because the molding compound 46 is connected to the carrier film 12 in the area of ​​the underside 24, it forms a circumferential clamping structure for the structure 34 or the detection area 32. Likewise, the structure 44 is also clamped to the top surface 16 of the carrier film 12, even if no molding compound 46 is provided in this area, i.e., on the top surface 16.Here, the connection of the molding compound 46 to the underside 24 is sufficient to cause a corresponding stiffening or clamping of the structure 44 on the top side 16 of the carrier film 12.

[0021] Finally, module 10 also includes vias 50, 52 as part of the electronic circuit 14, which electrically connects or contacts the electrically conductive structures 18 on the top 16 with those on the bottom 24, as is known from the prior art.

[0022] In the Fig. 2 is opposite to Fig. 1 The modified module 10a according to the invention is shown, which is essentially distinguished by a different configuration of the pressure sensor 30a. In the pressure sensor 30a, the carrier film 12 in the area of ​​the pressure sensor 30a is not modified on its surface compared to the other areas or with the structure 34. Instead, in the detection area 32a, a detection film 54, consisting of silicon with a microstructure, is provided instead of the structure 34. This detection film 54 also serves to detect the deformation of the carrier film 12 in the detection area 32a. The preferably circular detection film 54 is also preferably fully bonded to the carrier film 12 by techniques known from the prior art, so that a deformation of the carrier film 12 is directly transferred to the detection film 54. Furthermore, it can be seen in the Fig. 2 Wire bonds 56, 58 connect the detection film 54 to the electrical circuit 14 or the evaluation ICs 36, 38. Generally, wire bonds 56 are useful or necessary where the detection film 54 is made of silicon. The protective compound 45 or molding compound 46 completely covers the wire bonds 56, 58 to protect against mechanical stress and media, and simultaneously forms the necessary clamping of the detection area 32a or the detection film 54 by covering the edges of the detection film 54.

[0023] In the Fig. 3 In a highly simplified form, a tool 100 for manufacturing the non-inventive module 10 according to Figur 1 or of the module 10a according to the invention Figur 2 The tool 100 comprises a lower tool part 101 and an upper tool part 102, which are arranged or designed to be movable relative to each other. For example, the lower tool part 101 is fixed in position, and the upper tool part 102 is adjustable relative to the lower tool part 101 in the direction of arrow 103. To manufacture the module 10a, the carrier film 12 with its electrically conductive structures 18 on the top 16 and the bottom 24 is attached to the upper tool part 102. Furthermore, the structures 28, 44 or the detection film 54, as well as at least some of the electronic components that are to be surrounded by the molding compound 46, are also pre-mounted on the carrier film 12. In the area of ​​the lower part of the tool 101, a sealing rib 104 can be seen, which is arranged in the area where no molding compound 46 is provided, i.e. in particular also in the detection area 32, 32a.

[0024] The upper surface of the lower mold part 101 is covered by a non-stick coated film 105. Molding compound 46 is already arranged in the area of ​​two receiving chambers 106, 107 of the lower mold part 101, which are separated from each other by the sealing rib 104. Furthermore, two compression cylinders 108, 109 are provided at the base of the lower mold part 101. These cylinders are adjustable towards the receiving chambers 106, 107 to allow the molding compound 46 to be compressed in the receiving chambers 106, 107 when the mold 100 is closed. The interior of the mold 100 is also sealed from the external environment by means of seals 110 and can be evacuated by a vacuum source (not shown), as indicated by the arrows 112.

[0025] For the arrangement or application of the molding compound 46 to the carrier film 12, the tool 100 is taken from the one in the Fig. 3 The tool is moved from the position shown to a position in which it is closed. For this purpose, the upper tool part 102 is moved towards the lower tool part 101. This brings the areas of the carrier film 12 on the underside 24 into contact with the molding compound 46, in which the molding compound 46 is to be arranged, at the latest when the compression cylinders 108, 109 are moved towards the receptacles 106, 107, at which point additional compression of the molding compound 46 can take place.

[0026] After the initially liquefied or warm molding compound 46 has hardened, the upper part of the tool 102 is moved back into a raised position to allow the module 10, 10a to be removed from the tool 100. Subsequently, further electronic components are assembled on the module 10, 10a, for example, the connector 28 or at the points where no molding compound 46 is provided.

[0027] It is also mentioned that, for clamping the carrier film 12 or for defining the detection area 32, 32a, it is also conceivable to use a pre-fabricated (ring-shaped) body instead of a molding compound 46, which is connected to the carrier film 12 and fixes or clamps the detection area 32, 32a at the edge (not shown).

[0028] In the Fig. 4The essential manufacturing steps of module 10, 10a are illustrated by way of example in the form of a flowchart. In a first step 201, the carrier film 12 is provided, wherein the carrier film 12 has the electrically conductive structures 18. Optionally, electronic components of the electronic circuit 14 can also be mounted (particularly on the side of the carrier film 12 where no molding compound 46 is provided). Subsequently, in a second step 202, which is not according to the invention, the structure 34 is formed in the detection area 32 if the structure 34 is formed directly on the carrier film 12. Alternatively, instead of the second step 202, a second step 202a according to the invention can be provided, in which the detection film 54 in the detection area 32a is connected to the carrier film 12 by suitable techniques.

[0029] Subsequently, in a third step 203, the module 10, 10a can be further populated with electronic components. This population includes, in particular, connecting the structure 34 or the detection film 54 with the evaluation ICs 36, 38, if this has not already been done. Then, in a fourth step 204, the carrier film 12 is partially remolded with the molding compound 46, as already explained above in connection with the tool 100. It is essential that the detection area 32, 32a is free of molding compound 46. Finally, in a fifth step 205, further components can be placed on the module 10, 10a.

[0030] The module 10a described so far can be modified or adapted in various ways without deviating from the idea of ​​the invention as defined in the claims. For example, it is conceivable to connect the detection film 54 to the carrier film 12 simultaneously with or before the formation of the electrically conductive structures 18. It is further mentioned that the present invention has been explained using a pressure sensor 30a as an example. However, the invention is also intended to be applicable to other sensors where it is necessary to detect a deformation of an (elastic) membrane or an elastically deformable detection area 32, 32a. A flow sensor is one example.

Claims

1. Electronic module (10; 10a), comprising a carrier film (12), wherein at least one electrically conductive structure (18) and electronic components (26, 28) connected to the electrically conductive structure (18) as part of an electronic circuit (14) are arranged on the carrier film (12), wherein the electronic circuit (14) is connected to a sensor, in particular a pressure sensor (30; 30a), and wherein the carrier film (12) is at least regionally covered by a protective compound (45) at a top side (16) or an underside (24), wherein the sensor, in particular the pressure sensor (30; 30a), has an elastically deformable sensing region (32; 32a), characterized in that the sensing region (32, 32a) is formed by a partial region of the carrier film (12) and additionally by a detection film (54) connected to the carrier film (12) and having a micro-structuring, wherein the detection film (54) consists of silicon, in order to achieve a contacting of the detection film (54) that is protected against mechanical loads and media, in that means for sensing the deformation of the sensing region (32; 32a) are provided, and in that the protective compound (45) or a fixing body has a cutout (48) within which the carrier film (12) and the detection film (54) are exposed, wherein the cutout (48) marginally delimits the sensing region (32; 32a), such that the protective compound (45) or the fixing body fixes the sensing region (32; 32a) with respect to the carrier film (12), wherein the wall of the cutout (48) extends slightly obliquely, such that the diameter of the cutout (48) increases with increasing distance from the carrier film.

2. Electronic module according to Claim 1, characterized in that the means for sensing the deformation of the sensing region (32; 32a) are formed by the detection film (54), in particular in such a way that an electrical resistance of the detection film (54) changes depending on the deformation of the sensing region (32; 32a).

3. Electronic module according to either of Claims 1 and 2, characterized in that the carrier film (12) has on the opposite side relative to the sensing region (32) an additional sensing region (42) aligned with the sensing region (32), wherein the size of the additional sensing region (42) corresponds at most to the size of the sensing region (32).

4. Electronic module according to Claim 3, characterized in that the side of the carrier film (12) on which the further sensing region (42) is situated is free of protective compound (45).

5. Electronic module according to any of Claims 1 to 4, characterized in that the detection film (54) is electrically connected to the electrically conductive structure (18) of the carrier film (12) by means of wire bonding connections (56, 58), and in that the region of the wire bonding connections (56, 58) is covered by the protective compound (45).

6. Electronic module according to any of Claims 1 to 5, characterized in that the means for sensing the deformation of the sensing region (32; 32a) comprise evaluation electronics (36, 38), covered by the protective compound (45).

7. Electronic module according to any of Claims 1 to 6, characterized in that the protective compound (45) is formed by a mold compound (46).

8. Method for producing an electronic module (10; 10a) configured according to any of Claims 1 to 7, comprising at least the following steps: - providing a carrier film (12) having at least one electrically conductive structure (18) - connecting to the carrier film (12) a detection film (54) that senses a deformation of a sensing region (32a) of the carrier film (12) - at least partially forming an electronic circuit (14) by equipping the electrically conductive structure (18) with electronic components - partially covering the carrier film (12) with a protective compound (45) or attaching a fixing body to the carrier film (12) while leaving the sensing region (32; 32a) free - optionally equipping the carrier film (12) in regions in which no protective compound (45) is arranged.

9. Method according to Claim 8, characterized in that the detection film (54) is connected to the electrically conductive structure (18) by means of wire bonding connections (56, 58) before the process of covering the carrier film (12) with the protective compound (45), and in that the wire bonding connections (56, 58) are covered by the protective compound (45).