Abstract:
A sensor system includes a sensor device and a cover device. The sensor device includes an external surface on which at least one electrical test contact is arranged. The cover device includes at least partially an electrically insulating material and is mechanically connected to the sensor device. The cover device is configured to cover the at least one electrical test contact of the sensor device so as to prevent contact from being made to the at least one electrical test contact from outside the sensor system.

Description:
[0001]    This application claims priority under 35 U.S.C. §119 to patent application no. DE 10 2012 224 424.7, filed on Dec. 17, 2012 in Germany, the disclosure of which is incorporated herein by reference in its entirety. 
       BACKGROUND 
       [0002]    The present disclosure relates to a sensor system and to a cover device for a sensor system. 
         [0003]    Multichip packages (without dedicated software control) are the current prior art and are integrated e.g. in smartphones. These sensors (multichip packages or individual systems), however, always have electrical contacts to the outside at which the sensors can be tested and calibrated once they have been made (yet before they are fitted in a smartphone). Then the sensors are solder-mounted in the smartphone on these electrical contacts. 
         [0004]    For production reasons, autonomous sensor systems always have electrical contacts for testing and calibration on at least one side of the package. The end user has direct access to these contacts. 
       SUMMARY 
       [0005]    Against this background, the present disclosure presents a sensor system and a cover device for a sensor system according to the description below. The following description contain advantageous embodiments. 
         [0006]    The sensor system according to the disclosure has the advantage that the electrical contacts, which for production reasons for functionality testing during or after finishing a sensor device, cannot be accessed, or contact cannot be made with said contacts, from outside the sensor system. In other words, this means that by providing on a sensor device the cover substrate embodied according to the disclosure, the electrical test contacts of the sensor device, and hence the sensor device or the whole sensor system, are protected from access by the end user in a very simple and cost-effective manner, thereby preventing unauthorized tampering with the whole system. In addition, the cover substrate according to the disclosure also protects the integrated electronics from short-circuits e.g. resulting from moisture (condensation). In the case of energy-autonomous sensor systems, for instance comprising built-in energy harvesters, which constantly produce power, the cover substrate also protects the end-user from potential electric shocks. 
         [0007]    The cover substrate according to the disclosure provides a facility for attaching to an external object, thereby enabling an extremely flexible, cost-effective and compact sensor system. This measure enables standard production of the sensor device, which, for instance, is in the form of a multichip sensor, because the attachment facility for the target application is not defined until the particular separately made cover device is selected, which again further reduces costs of the whole system. 
         [0008]    The sensor system can be an energy-autonomous sensor that can communicate wirelessly with other devices, for instance in a network. The sensor device may be an acceleration sensor, for example for detecting the window position on the window frame, and/or a moisture sensor, for example for detecting mildew behind a cupboard. 
         [0009]    An electrical test contact in the sense of the disclosure is understood to mean an electrical contact by means of which it is possible to test the functionality of the sensor system or the sensor device during, or on completion of, the production process of the sensor device. The sensor device may here be a ready-to-use, tested and, if applicable, delivered sensor. 
         [0010]    In addition, known integrated circuit packaging techniques can preferably be used to connect the cover device mechanically to the sensor device in a cost-effective and compact way. As a field of microelectronics and microsystem engineering, integrated circuit packaging includes all the technologies and design tools that are needed to assemble microelectronic components. The bonding techniques used in integrated circuit packaging include, for example, wire-bonding techniques, TAB (Tape Automated Bonding), flip-chip technology, adhesive bonding, anodic bonding, solder techniques, reflow soldering methods (SMT, Surface Mount Technology) and wave-soldering processes. The assembly techniques used in integrated circuit packaging include, for instance, film technologies, thin-film technologies, techniques for modifying, patterning and removing film layers, laser processes and dicing. 
         [0011]    It is advantageous if the cover device has an internal surface which faces the external surface comprising the at least one test contact, and on which internal surface is arranged at least one first metallization, wherein the first metallization is mechanically connected to at least one of the electrical test contacts. The first metallization can here be configured in the form of a “dummy pad” as a solder bump or formed by conductive adhesive. This measure offers a simple facility for fixing the cover substrate to the sensor device. In addition, the metallization can also be disconnected as the last electrical connection, e.g. for the purpose of making contact with a dual-sided solar cell in order to close the circuit for the sensor system thereby. Furthermore, the metallization can extend into the inside of the cover substrate and be configured in the form of a functional electrical conductor loop, for example as an antenna pattern. The antenna pattern can here be arranged mainly inside the cover substrate and connected to the sensor device only via a relatively small portion arranged on the internal surface of the cover substrate, in order to further reduce the complexity of the sensor system. 
         [0012]    In addition, it is advantageous if in addition at least one electrical connecting contact is arranged on the external surface comprising the at least one test contact, and if the cover device is configured such that electrical contact can be made to at least one of the electrical connecting contacts from outside the sensor system. In this case, the connecting contacts are obviously not test contacts, and therefore it is not possible to use the connecting contacts to perform a functionality test. The cover device can advantageously comprise at least one first opening and/or at least one via that is electrically connected to at least one of the electrical connecting contacts, in order to enable electrical contact to be made from outside the sensor system. This measure makes it possible to provide electrically conducting access paths to which contact can be made from outside the sensor system, which access paths are essential, for instance, in order to charge a battery or to provide an interface for system updates. 
         [0013]    It is also advantageous if the sensor device comprises a sensor substrate which forms the external surface comprising at least one test contact, and if the cover device comprises a cover substrate comprising a first segment that corresponds to the external surface, wherein the first segment of the cover device and the external surface, which comprises the at least one test contact, are connected together at least partially. In this case, a sensor and/or ASIC can be arranged on a substrate comprising metallizations, and can be screened from the environment e.g. by encapsulation or a cap (made of metal or plastic), so that test contacts are arranged only on the substrate external face. The cover substrate can be fabricated, for example, also by means of printed circuit board technology, e.g. from standard materials such as FR4, high Tg FR4 or BT. This can provide a compact, easy-to-make sensor system. 
         [0014]    Moreover, it is advantageous if the cover device comprises a second segment which bounds the first segment and at least partially encloses the sensor device at right angles to the external surface. By means of this measure, the cover device provides lateral protection of the sensor system. 
         [0015]    In addition, it is advantageous if the sensor device and/or the cover device comprise an energy storage unit and/or an energy converter unit, which can be used to supply the sensor device with power. An extremely compact sensor having an in-built power supply can be realized in this way. 
         [0016]    It is also advantageous if the energy converter unit comprises a photovoltaic cell and/or a thermoelectric generator, and the cover device comprises at least one corresponding second opening in order to allow the entry of light rays or heat. This measure enables versatile use of the sensor system, and allows the sensor system to use the light energy or thermal energy from its surroundings to generate power. 
         [0017]    In addition, it is advantageous if a transparent protective layer and/or a thermally conductive material is introduced at least partially in the second opening. The cover device can here be arranged as a square frame having an opening positioned in the center. In the case of a photovoltaic cell, a transparent protective layer can be applied inside the second opening, which protects the photovoltaic cell from mechanical effects (impacts, scratches) and also from environmental influences (moisture). The protective layer can here be in the form of small glass panels, a film or gel, and can be applied by gluing, blade coating or printing. In the case of a thermoelectric generator, a thermally conductive material can be introduced in the second opening in order to increase the efficiency of the thermoelectric generator. In addition, thermal structures can be provided in order to dissipate the heat from the thermoelectric generator, because the efficiency of a thermoelectric generator depends on the temperature difference between the upper face and the lower face. 
         [0018]    It is also advantageous if the sensor device and/or the cover device comprise an integrated circuit, in particular a wireless communications unit for data transmission. This measure enables the sensor system to communicate with other devices, in particular in a network, e.g. via the Internet, and to transmit data, in particular sensor data, to these devices. 
         [0019]    In addition, it is advantageous if the sensor device comprises at least one access aperture, and the cover device comprises at least one third opening that corresponds to the access aperture. This measure makes it possible to enable the entry of fluids and/or radiation and/or sound into the sensor device and hence to configure the sensor system, for example, as a moisture sensor, gas sensor and/or acoustic sensor. 
         [0020]    In addition, it is particularly advantageous if the cover device and/or the sensor device comprise at least one fastening means in order to enable the sensor system to be fitted to another object. The fastening means may then be in the form of a suction pad, adhesive surface, hook-and-loop fastener, electrostatic pad or magnet. Different attachment facilities are thereby provided according to the application, for instance for attaching to windows, radiators, wallpaper, tiles, wooden objects etc. For example, (micro)pads are useful for smooth surfaces such as windows, tiles or radiators, whereas (micro)pins can be used for attaching to wallpaper (mildew detection). Adhesive surfaces are another alternative here for attaching to surfaces, as are magnets, which allow attachment combined with easy means of repositioning, if required, on metal surfaces such as radiators, metal lamps or metal window frames. An electrostatic pad is also possible for particularly small sensor systems. As explained above, the provision according to the disclosure of attachment means on the cover substrate enables an extremely versatile, cost-effective and compact sensor system. This measure allows standard production of the sensor device, for instance in the form of a multichip sensor, because the attachment facility for the target application is not defined until the particular separately made cover device is selected. 
         [0021]    It shall be understood that the abovementioned features and the features still to be described below can be used not just in the stated combinations but also in other combinations or in isolation without departing from the scope of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The disclosure is described and explained in greater detail below with reference to some selected exemplary embodiments in conjunction with the enclosed drawings, in which: 
           [0023]      FIGS. 1   a  and  1   b  show a schematic diagram of a sensor device of the sensor system according to the disclosure without cover device fitted; 
           [0024]      FIGS. 2   a  to  2   c  show an exemplary embodiment of the sensor system according to the disclosure; 
           [0025]      FIGS. 3   a  to  3   c  show a second exemplary embodiment of the sensor system according to the disclosure comprising a metallization; 
           [0026]      FIGS. 4   a  to  4   c  show a further exemplary embodiment according to the disclosure comprising an opening; 
           [0027]      FIGS. 5   a  to  5   c  show a further exemplary embodiment according to the disclosure comprising vias; 
           [0028]      FIGS. 6   a  and  6   b  show a further exemplary embodiment according to the disclosure comprising lateral protection; 
           [0029]      FIGS. 7   a  to  7   c  show a further exemplary embodiment according to the disclosure comprising a photovoltaic cell; 
           [0030]      FIGS. 8   a  and  8   b  show a further exemplary embodiment according to the disclosure comprising a thermoelectric generator; 
           [0031]      FIGS. 9   a  and  9   b  show a further exemplary embodiment according to the disclosure comprising an access aperture; 
           [0032]      FIGS. 10   a  to  10   d  show exemplary embodiments of the cover device according to the disclosure comprising fastening means. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    To improve understanding,  FIGS. 1   a  and  1   b  show a sensor device  12  of the sensor system  10  according to the disclosure without a cover device fitted. The sensor device  12  comprises a sensor substrate  16  having an internal surface  20  and an external surface  28 . A sensor  22  is arranged on the internal face  20  of the sensor substrate  16 . The sensor  22  can here comprise a sensor element, for example in the form of a temperature sensor, load cell or acceleration sensor. In addition, an energy storage unit  24  is arranged on the internal face  20 . The energy storage unit  24  is connected to the sensor  22  via a bond wire  26 . A wireless communications unit  46  can be provided instead of, or in addition to, the energy storage unit  24 , as is described in greater detail below. 
         [0034]    An encapsulation compound  27  is disposed on the internal surface  20  of the sensor substrate and encapsulates the sensor  22 , the bond wire  26  and the energy storage unit  24 , which can be in the form of a battery for example. The encapsulation compound  27  also encapsulates the exposed areas of the internal surface  20  of the sensor substrate  16 . A thickness of the layer of the encapsulation compound  27  can be chosen such that the components  22 ,  24  are completely enclosed by the encapsulation compound  27 . Depending on the embodiment, the encapsulation compound  27  can be in the form of a potting compound or a molding compound or even a cap, for instance made of metal or plastic. The encapsulation compound  27  provides a simple way of forming a package for the components  22 ,  24  or for the sensor device  12 . 
         [0035]    Test contacts  30  are arranged on the external face  28  of the sensor device  12 , which external face is formed by the sensor substrate  16 . In this case, the test contacts  30  are electrically connected via metallizations  18  to the components, i.e. the sensor  22  and the battery  24 , that are arranged on the interior surface  20  of the sensor substrate  16 . As mentioned in the introductory part, the test contacts  30  are used to test the functionality of the sensor device  12  before finishing the sensor system, i.e. before the test contacts  30  are covered by the cover device according to the disclosure that is described below. 
         [0036]    A first exemplary embodiment of a sensor system according to the disclosure is shown in  FIGS. 2   a  to  2   c  and is denoted in its entirety by the reference number  10 . The sensor system  10  here comprises the sensor device  12  shown in  FIGS. 1   a  and  1   b,  and a cover device  14  according to the disclosure.  FIG. 2   a  shows an arrangement in which the sensor device  12  and the cover device  14  are not yet connected together, i.e. before the step of connecting the cover device  14  to the sensor device  12 . 
         [0037]    In the embodiment shown, the cover device  14  comprises a cover substrate  32 . The cover substrate  32  can be made here using printed circuit board technology, where standard materials such as FR4, high Tg FR4 or BT, for example, can be used. It should be mentioned, however, that pre-mold packages, molded interconnected devices (MID) or liquid-crystal polymers (LCP) can also be used for the cover device  14 . The cover substrate  32  further comprises contact receptacles  34 . The contact receptacles  34  are arranged on an internal surface  36  of the cover device  14 , or more specifically of the cover substrate  32 . In addition, the cover device comprises fastening means  38 . The fastening means  38  are arranged on an external surface  40  of the cover device  14 , or more specifically of the cover substrate  32 . It should be pointed out here that the fastening means  38  are not essential to the sensor system  10  according to the disclosure. 
         [0038]      FIG. 2   b  shows the sensor system  10  according to the disclosure in the assembled state, i.e. after testing the sensor device  12  and connecting the cover device  14  to the sensor device  12 . The cover device  14  is here mechanically connected to the sensor device  12  preferably using known integrated circuit packaging techniques. In particular, the external surface  28  of the sensor device  12  is connected to the internal surface  36  of the cover device  14  in the process. As  FIG. 2   b  also shows, the contact receptacles  34  are used to accommodate the test contacts  30  in order to ensure better positioning of the cover device  14  on the sensor device  12 . 
         [0039]      FIG. 2   c  shows the external surface  40  of the cover device  14 , or more specifically of the cover substrate  32 , comprising four fastening means  38 . The cover device  14  here has a square shape. 
         [0040]      FIGS. 3   a  to  3   c  show a further exemplary embodiment of the sensor system  10  according to the disclosure, in which first metallizations  42  are provided instead of the contact receptacles  34 . As  FIG. 3   b  shows, the first metallizations  42  are connected to the test contacts  30  after finishing the sensor system  10 . Thus the first metallizations  42 , in the form of “dummy pads”, act as solder bumps for connecting the cover substrate  14  to the sensor device  12 . In addition, the first metallization  42  can also be configured as one or more electrical connections  43 , which close the circuit for the sensor devices  12  when the cover substrate  14  is connected to the sensor device  12 , in other words the test contacts  30  are connected to the first metallizations  42 . The first metallization  42  can also be configured as a functional electrical line or conductor loop, for example as an antenna pattern or as EMC protection. In this case, the metallization  42  can extend into the interior of the cover substrate  32 . The antenna pattern can be arranged largely inside the cover substrate  32  and connected to the sensor device  12  only via a relatively small portion arranged on the internal surface  36  of the cover substrate  36 . 
         [0041]      FIGS. 4   a  to  4   c  show a further embodiment of the sensor system  10  according to the disclosure. Unlike the exemplary embodiments described above, the sensor device  12  comprises connecting contacts  48 . Like the test contacts  30 , the connecting contacts  48  are arranged on the external surface  28  of the sensor device  12 , or more specifically of the sensor substrate  16 . The connecting contacts  48  are connected via metallizations  18  to the energy storage unit  24  and an additionally provided wireless communications unit  46 . The wireless communications unit  46  is arranged on the interior surface  20  of the sensor substrate  16  and electrically connected to the sensor  22  and the energy storage unit  24 . Since, unlike the test contacts  30 , the connecting contacts  48  can be accessible from outside the sensor system  10 , the cover device  12  comprises a first opening  44 . The first opening  44  thereby enables an electrically conducting access path to the connecting contacts  48 , for example in order to charge the energy storage unit  24  or to provide an interface for updates for the wireless communications unit  46 . 
         [0042]      FIG. 4   c  shows a view from below of the sensor device  10 , from which it is clear that the cover device  12  is in the form of a square frame. 
         [0043]    Similar to the exemplary embodiment shown in  FIGS. 4   a  to  4   c , the exemplary embodiment shown in  FIGS. 5   a  to  5   c  of the sensor system  10  according to the disclosure comprises vias  50  instead of the first opening  44 , which extend from the interior surface  36  of the cover device  14  to the external surface  40  of the cover device  14  and are electrically and mechanically connected to the connecting contacts  48 . This measure likewise enables electrical contact to be made to the connecting contacts  48  from outside the sensor system  10 . 
         [0044]      FIGS. 6   a  and  6   b  show the exemplary embodiment of  FIGS. 3   a  to  3   c  with additional lateral protection provided for the sensor system  10 . In this case, the cover device  14  comprises a first segment  52 , which forms the interior surface  36  of the cover device  14  and is connected to the external surface  28 , or more specifically to the test contacts  30  on the external surface  28 . On the sides of the sensor device  12 , the cover device  14  additionally comprises a second segment  54 . The second segment  54  is arranged such that it bounds the first segment  52  and is in the form of a lateral lip. This forms a sensor device receptacle  55  that is configured to fit the external surface  28  of the sensor device  12 . As  FIG. 6   b  shows, the sensor device  12  is arranged in the sensor device receptacle  55  and is hence mechanically protected by the segment  54 , which preferably completely encloses the sides of the sensor device  12 . 
         [0045]      FIGS. 7   a  to  7   c  show a further exemplary embodiment according to the disclosure of the sensor system  10 , which is configured to be energy autonomous, i.e. comprises an in-built power supply. In this case, the sensor system  10  comprises an energy conversion unit  56  in the form of a photovoltaic cell  58 . The photovoltaic cell  58  here replaces the sensor substrate  16  of the exemplary embodiments described above, so that a more compact system configuration can be achieved. Thus the external surface  28  comprising the test contacts  30  of the sensor device  12  is formed by the photovoltaic cell  58 . As  FIG. 7   b  shows, the sensor  22  and the energy storage unit  24  are arranged on the internal surface  20  of the photovoltaic cell  58 . As can also be seen from the figure, the cover device  14 , or more specifically the cover substrate  32 , comprises a second opening  60 . The opening  60  is used here to allow the passage of light rays onto the photovoltaic cell  58 . In addition, a protective layer  62  is provided in the opening  60  in order to protect the photovoltaic cell  58 . Since this specific exemplary embodiment relates to a photovoltaic cell having dual-sided contacts, the cover device  14  comprises a projection  64 , which extends into the second opening  60 . On the side of the projection  64  that faces the photovoltaic cell  58  is additionally provided a further metallization  42 , which ensures that contact is made with the photovoltaic cell  58  on its photovoltaically active front face and thereby closes the circuit of the sensor device  12 . 
         [0046]      FIGS. 8   a  and  8   b  show a further exemplary embodiment of an energy-autonomous sensor system  10 , wherein the power supply is provided by a thermoelectric generator  68 . In order to increase the efficiency of the thermoelectric generator  68 , in place of the protective layer  62  shown in  FIGS. 7   a  to  7   c , a thermally conductive material  70  is arranged in the second opening  60 . In addition, the sensor device  12  comprises a cooling structure  72 , which is arranged in the encapsulation compound  27  and ensures efficient cooling of the thermoelectric generator  68 . It should be mentioned here, however, that the thermally conductive material  70  can also be arranged in the encapsulation compound  27  and conversely the cooling structure  72  can be provided in the cover device  14  without departing from the scope of the present disclosure. 
         [0047]      FIGS. 9   a  and  9   b  show a further exemplary embodiment according to the disclosure of the sensor system  10 , which can be configured in particular as a moisture sensor, gas sensor and/or acoustic sensor. In order to enable the entry of fluids, radiation and/or sound into the sensor device, a case  74  is provided instead of the encapsulation compound  27 . The case  74  has an internal space  75  in which the sensor  22  is arranged. In order to ensure access into the internal space  75  and hence to the sensor  22 , an access aperture  76  is provided in the sensor device and an opening  78  that corresponds thereto is provided in the cover device  14 . Hence fluids, radiation and/or sound from the surroundings can enter the internal space  75  through the third opening  78  of the cover device  14  and through the access aperture  76  of the sensor device  12 , and can be detected by the sensor  22 . 
         [0048]    Finally,  FIGS. 10   a  to  10   d  show different exemplary embodiments of the cover device  14  according to the disclosure having different fastening means  38 . The cover device  14  shown in  FIG. 10   a  comprises on the external surface  40  thereof fastening means  38  in the form of suction pads  80 . These can obviously also be in the form of micro suction-pads. Such an embodiment of the fastening means  38  is particularly useful for smooth surfaces such as windows, tiles or radiators. In  FIG. 10   b , the fastening means  38  are in the form of pins or micro-pins  38 .  FIG. 10   c  shows a further embodiment of the fastening means  38 . In this case, the fastening means  38  are in the form of an adhesive surface  84 , hook-and-loop fastener  86  or electrostatic pad  88 . The latter embodiment is particularly advantageous for very small sensor systems  10 . In  FIG. 10   d , the fastening means  38  are in the form of magnets  90 . Unlike the fastening means described above, the magnets  90  are not arranged on the external surface  40  of the cover device  14  but integrated inside the cover device  14 , or more specifically inside the cover substrate  32 . By means of this embodiment of the cover device  14 , the sensor system  10  can be attached and, if applicable, repositioned, extremely easily on metallic surfaces such as radiators, metal lamps or metal window frames. 
         [0049]    The exemplary embodiments described and illustrated in the figures are only chosen by way of example. Different exemplary embodiments can be combined with one another either in full or by individual features. Furthermore, features of one exemplary embodiment can be added to another exemplary embodiment. In addition, method steps according to the disclosure can be repeated and can be executed in a different order from that described. If an exemplary embodiment comprises an “and/or” conjunction between a first feature and a second feature, then this shall be interpreted to mean that the exemplary embodiment according to one embodiment includes both the first feature and the second feature, and according to another embodiment comprises either just the first feature or just the second feature.