Patent Abstract:
The present invention relates to a method for producing a microphone unit, which can be contacted by a plug connector, and a microphone unit, wherein this comprises a housing, a circuit board having a microphone component and contacts, wherein the contacts are embodied on second contact ends as contact pins and wherein the contacts are connected at the first contact ends to the circuit board, wherein a multi-pole plug connector can be connected to the contact pins. The housing is embodied as a one-part injection molded part and the first contact ends are embodied as pressfit contacts.

Full Description:
[0001]    This application claims the benefit under 35 USC §119(a)-(d) of German Application No. 10 2015 108 945.9 filed Jun. 8, 2015, the entirety of which is incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a method for producing a microphone unit which can be contacted by a plug connector and a microphone unit comprising a housing, a circuit board having a microphone component and contacts. 
       BACKGROUND OF THE INVENTION 
       [0003]    DE 10 2013 014 526 A1 discloses a microphone unit that can be contacted by a plug connector. 
       SUMMARY OF THE INVENTION 
       [0004]    It is the object of the present invention to propose a method for producing a microphone unit and also a microphone unit of this type by means of which it is rendered possible to produce a microphone unit in an effective manner. 
         [0005]    The method in accordance with the present invention for producing a microphone unit that can be contacted by means of a plug connector proposes the following mentioned steps: 
         [0006]    bending contacts, which are held in a non-displaceable manner with respect to one another by means of a bridge, in such a manner that contact ends that are part of the contacts and are embodied as pressfit ends include an angle of at least 90° in pairs with respect to contact ends that are part of the contacts and are adjacent to one another and embodied as contact pins, 
         [0007]    insert injection molding a first assembly, which comprises the contacts, with a housing in such a manner that the pressfit ends of the contacts protrude into a first hollow chamber of the housing and that the contact pins of the contacts protrude into a second hollow chamber of the housing, 
         [0008]    providing a second assembly, wherein the assembly is formed by virtue of mounting a microphone unit on a circuit board as a surface-mounted device, 
         [0009]    producing a pressfit connection between the pressfit ends of the contacts and the circuit board that is populated with the microphone unit as the circuit board is inserted into the first hollow chamber in such a manner that in so doing the pressfit ends of the contact pins are pressed into metal-lined through-going bores of the circuit board. 
         [0010]    When using a method of this type during the production of the microphone unit, it is not necessary to mount devices in a multi-part housing but rather the complete microphone unit is assembled in steps quasi from inside outwards and completed by means of the prepared circuit board. As a consequence, it is possible to reduce the costs and improve the quality. 
         [0011]    By virtue of insert injection molding the contacts so as to form the first assembly and by virtue of the associated production of a retaining plate that fixes the contacts, it is possible in a particularly easy manner to handle the first construction unit so as to prepare the insert injection molding process for forming the housing since the rigid retaining plate renders it possible to handle and orient the first construction unit without creating the risk that in so doing the contact pins become bent out of shape. 
         [0012]    It is provided to insert injection mold the contacts in such a manner that the retaining plate is positioned on the contacts in such a manner that the retaining plate encases the contacts between bends, at which the contacts are bent, and the contact ends of the contacts, the contact ends being embodied as contact pins. As a consequence, the retaining plate is oriented with respect to the contact ends of the contact, the contact ends being formed as contact pins, in such a manner that these contact ends pass through the retaining plate without bending. Consequently, the contact ends of the contact that are embodied as contact pins are supported by means of the retaining plate in an optimal manner for plugging on and removing a plug connector. 
         [0013]    It is also provided that the bridge is removed after the retaining plate has been formed and prior to the housing being produced. At this point in time, the first assembly is not yet constructed and can still be handled easily for the removal operation. 
         [0014]    Insofar as the contacts are insert injection molded without first having to insert injection mold a retaining plate with the housing, it is provided to remove the bridge only after the housing has been produced. As a consequence, the contacts can still be handled as one prior to the insert injection molding process with the housing. 
         [0015]    It is also provided to provide the circuit board with a dust protector after the circuit board is assembled in the first hollow chamber of the housing. As a consequence, the microphone component is particularly well protected in the housing. 
         [0016]    Furthermore, it is provided during the production of the housing to embed at least one fastening pin, which is embodied according to a type of a pressfit end, in the housing, in such a manner that the fastening pin protrudes in a parallel manner with respect to the pressfit ends of the contacts in the first hollow chamber. As a consequence, it is possible to connect the fastening pins to the housing during the step in which the contacts or the first construction unit is also connected. 
         [0017]    Finally, the method provides that, as the pressfit connection is produced between the pressfit ends of the contact pins and the circuit board, a pressfit connection is also produced between the pressfit end of the connecting pin or the pressfit ends of the connecting pins. As a consequence, it is possible to fix the circuit board to the housing at other sites during the process of producing the contacts and consequently to retain the circuit board permanently in a reliable manner in the second hollow chamber of the housing. 
         [0018]    In the case of the microphone unit in accordance with the invention, the housing is embodied as a one-part injection molded part and the first contact ends of the contacts are embodied as pressfit contacts. In the case of a microphone unit of this type, it is neither necessary to seal a multi-part housing after the components are assembled nor is it necessary to perform a soldering process so as to connect the contacts to the circuit board. As a consequence, the costs are reduced and the quality improved. 
         [0019]    In the sense of the invention, the term “process of insert injection molding” is understood to mean an injection molding operation according to the so-called “insert molding” method, in which an insert part or insert component or insert parts or insert components are arranged in a hollow chamber of an injection molding mold and then cast with a synthetic material, wherein a one-part component is produced whose individual components are fixedly connected to one another. 
         [0020]    In the sense of the invention, the term “a surface-mounted device” is understood to mean a device such as for example a microphone component that is soldered directly to connection surfaces of a circuit board that are able to receive a soldering mass. In English, such a component is described as a so-called “surface-mount device”, wherein the abbreviation “SMD” is used for this term. 
         [0021]    In the sense of the present invention, the term “a pressfit connection” is understood to mean a connection where pressfit ends that are arranged on components are inserted into metal-lined bore holes of a circuit board in such a manner that the pressfit ends are deformed during the insertion process and thus a permanent and reliable electrical connection is produced between the pressfit ends and the metal-lined bore holes. 
         [0022]    In the sense of the present invention, the term “a pressfit end of a contact” is understood to mean a contact end that is suitable as a result of its shape and its material characteristics to be pressed into a matching metal-lined through-going bore hole of a circuit board so as to form an electrical contact. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    Further details of the invention are described in the drawing with reference to schematically illustrated exemplary embodiments. 
           [0024]      FIG. 1  illustrates a perspective view of a first microphone unit in accordance with the present invention; 
           [0025]      FIG. 2  illustrates a plan view of contacts that are held together by means of a bridge; 
           [0026]      FIG. 3  is a plan view of the contacts illustrated in  FIG. 2  together with a retaining plate injection molded thereon; 
           [0027]      FIG. 4  is an illustration corresponding to  FIG. 3 , wherein the bridge is removed; 
           [0028]      FIG. 5  is an illustration corresponding to  FIG. 4  wherein the contacts are bent; 
           [0029]      FIG. 6  is a further illustration of the microphone unit illustrated in  FIG. 1 ; 
           [0030]      FIG. 7  illustrates a view from below of the microphone unit illustrated in  FIGS. 1 and 6 ; 
           [0031]      FIG. 8  illustrates a second embodiment variant of the microphone unit in the view from below and with the circuit board removed; 
           [0032]      FIG. 9  illustrates a third exemplary variant of the microphone unit in the view from below and with the circuit board removed; and 
           [0033]      FIG. 10  illustrates a transparent, perspective view of the embodiment variant illustrated in  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]      FIG. 1  illustrates a perspective view of a first embodiment variant of a microphone unit  1  in accordance with the invention. The microphone unit  1  comprises four contacts  2 ,  3 ,  4  and  5 , also illustrated in  FIG. 2 , and a housing  6 . The four contacts  2  to  5  pass through the housing  6 . First contact ends  2   a  to  5   a  of the contacts  2  to  5  are in each case embodied as pressfit ends  7  to  10  and second contact ends  2   b  to  5   b  are embodied as contact pins  11  to  14 . The contact pins  11  to  14  protrude—as illustrated in  FIG. 1 —into a second hollow chamber  15  of the housing  6  and together with a frame  16  form a socket  17  into which it is possible to plug a plug connector  501  that is illustrated schematically in  FIG. 1 , so as to incorporate the microphone unit  1  by way of example in a communication system in a vehicle. 
         [0035]      FIGS. 6 and 7  illustrate other views of the microphone unit  1 . Not only is the second hollow chamber  15  visible in  FIG. 7 , which illustrates an oblique view from below of the microphone unit  1 , but rather a first hollow chamber  18  is also evident and the first hollow chamber is already sealed in part by means of a circuit board  19  and a microphone component  20  that is embodied as a so-called SMD component and is indicated schematically by the broken lines is soldered onto an upper face of the circuit board, the upper face being remote from the observer. Four metal-lined through-going bore holes  21  to  24  are formed in the circuit board  19  through which the pressfit ends  7  to  10  of the contacts  2  to  5  that protrude into the first hollow chamber  18  are evident.  FIG. 7  illustrates the circuit board  19  in its final mounted position in which electrical connections between the contacts  2  to  5  and the circuit board  19  are already completely produced so that the contacts  2  to  5  also retain the circuit board  19  in a mechanical manner in the illustrated position. In order to provide an additional fixing arrangement of the circuit board  19 , which together with the microphone component  20  forms a second assembly  25 , the housing  6  also comprises two cast fastening pins  26 ,  27  that pass through further through-going bore holes  28 ,  29  of the circuit board  19  and as the circuit board  19  is pushed into the first hollow chamber  18  to form a friction-type connection with the circuit board. 
         [0036]    However, prior to the contacts  2  to  5  being insert injection molded with the housing  6  in a so-called “insert molding” method, the contacts are insert injection molded in a first step in a preceding “insert molding” method with a retaining plate  30  in such a manner that the retaining plate  30 —as is illustrated in the  FIGS. 3 to 5 —fixes the contacts  2  to  5  to one another. In order to facilitate the placing of the four contacts  2  to  5  in a hollow chamber of an injection molding mold for the first “insert molding” method, the contacts  2  to  5  are initially—as illustrated in the  FIGS. 2 and 3 —connected to one another by means of a bridge  601 . As is evident from the overview of  FIGS. 3 and 4 , the bridge  601  is removed after the retaining plate  30  is formed. An overview of  FIGS. 4 and 5  illustrates that the first contact ends  2   a  to  5   a  of the contacts  2  to  5  are embodied as pressfit ends  7  to  10  and after the bridge  601  is removed so as to prepare for a second “insert molding” method step are bent in such a manner that the individual contacts  2  to  5  include with their first contact ends  2   a  to  5   a  and second contact ends  2   b  to  5   b  in each case a 90° angle α. As is illustrated in  FIG. 5 , the retaining plate  30  is fixed by means of the “insert molding” process to the contacts  2  to  5  between bends B 2  to B 5  of the contacts  2  to  5  and the contact ends  2   b  to  5   b  of the contacts  2  to  5 , the contact ends  2   b  to  5   b  being embodied as contact pins  11  to  15 . According to a first variant of the method, the contacts  2  to  5  are bent prior to the retaining plate  30  being formed. According to a second variant of the method, the contacts  2  to  5  are bent after the retaining plate  30  has been produced. Preparations are accordingly made for a first assembly  31  that is embodied from the bent contacts  2  to  5  and the retaining plate  30  to be placed in a hollow chamber of a second injection molding mold, not illustrated, and to be insert injection molded therein in such a manner that the housing  6  illustrated in  FIGS. 1, 6 and 7  is produced, wherein it is necessary to mount the circuit board  19  on the housing following the insert injection molding process so as to complete the microphone unit  1 . The circuit board  19  (cf.  FIG. 7 ) is mounted in that the circuit board is pressed into the first hollow chamber  18  in the direction in which the pressfit ends  7  to  10  extend and in so doing the electrical contacts are provided between the pressfit ends  7  to  10  and conductor tracks, not illustrated, that are provided on the circuit board  19  are produced. The housing  6  is embodied in such a manner that the first hollow chamber  18  and the second hollow chamber  15  are separated from one another in an air-tight and fluid-tight manner. 
         [0037]      FIG. 8  illustrates a second embodiment variant of a microphone unit  101  in a similar manner to the illustration in  FIG. 7 , wherein a circuit board has not yet been mounted on a housing  106 . Nonetheless, a retaining plate  130  that is cast in the housing  106  is evident in the perspective view and the retaining plate protrudes in part into a first hollow chamber  118 . Furthermore, pressfit ends  107  to  110  are evident and the pressfit ends protrude out of a casting compound GM 106  of the housing  106  into the first hollow chamber  118 . Fastening pins  126 ,  127  are embodied with pressfit ends  126   a,    127   a  so that so as to provide the additional fixing of the circuit board, not illustrated, further pressfit connections are produced, wherein these further pressfit connections do not have an electrical function and are used only to retain the circuit board in a mechanical 
         [0038]    A third embodiment variant of a microphone unit  201  is illustrated in  FIG. 9  in a similar manner to the illustration in  FIG. 7  or  FIG. 8 , wherein a circuit board is not mounted on a housing  206 . In the case of this embodiment variant, the contacts  202  to  205  are insert injection molded with the housing  206  without the contacts having to be first insert injection molded with a retaining plate. Accordingly, the contacts  202  to  205  were still connected by a bridge during production of the housing  206  so as to be able to handle them as one despite the lack of a retaining plate. In other aspects, the third embodiment variant of the microphone unit  201  is comparable to the second embodiment variant of the microphone unit  101 . 
         [0039]    As far as the sockets  117  or  217  are concerned, the second and third microphone unit  101  or  201  are embodied in a corresponding manner to the first microphone unit  1 . The views  7  to  9  illustrate the microphone units  1  or  101  or  201  in such a manner that second contact ends of the contacts are not visible in each case. 
         [0040]    Finally,  FIG. 10  illustrates the second embodiment variant of the microphone unit  101  as a perspective transparent model with visible and concealed edges. It is evident in this view how the contacts  102  to  105  pass through the housing  106  and how the retaining plate  130  is embedded in the housing  106 . A circuit board with a microphone component arranged on the circuit board is not illustrated in  FIG. 10 , the circuit board is however embodied according to the illustration in  FIG. 7 , wherein the circuit board naturally comprises suitable through-going bore holes for the fastening pins  126 ,  127 . 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           1  Microphone unit  1   
           2 - 5  Contact 
           2   a - 5   a  Contact end 
           2   b - 5   b  Contact end 
           6  Housing 
           7 - 10  Pressfit end 
           11 - 4  Contact pin 
           15  Second hollow chamber of  6   
           16  Frame of  17   
           17  Socket 
           18  First hollow chamber 
           19  Circuit board 
           20  Microphone component 
           21 - 24  Metal-lined through-going bore hole 
           25  Second assembly 
           26 ,  27  Fastening pin 
           28 ,  29  Through-going bore hole 
           30  Retaining plate 
           31  First assembly 
         B 2 -B 5  Bend from  2  to  5   
         α Angle between  2   a - 5   a  and  2   b - 5   b    
           101  Microphone unit 
           102 - 105  Contact 
           107 - 110  Pressfit end 
           106  Housing 
           107 - 110  Pressfit end 
           117  Socket 
           118  First hollow chamber 
           126 ,  127  Fastening pin 
           126   a ,  127   a  Pressfit end 
           130  Retaining plate 
         GM 106  Casting compound 
           201  Microphone unit 
           202 - 205  Contact 
           206  Housing 
           217  Socket 
           501  Plug connector 
           601  Bridge

Technology Classification (CPC): 7