Abstract:
A process and manufacturing system for manufacturing injection molded parts with integrated flexible printed circuit board ( 9 ), provided with a cover ( 39/47 ) of plastic, fixed in a recess ( 2 ) of a carrier strip ( 1 ) by projecting carrier elements ( 14, 15, 16, 17 ). A circuit board ( 9 ) fixed in the carrier strip ( 1 ) is inserted into the cavity ( 21 ) of first casting mold half ( 20 ) of an injection mold, held in position by the carrier elements ( 14  through  17 ). The cavity ( 21 ) of the first casting mold half is closed by a closing mold part, which has no cavity, including the printed circuit board ( 9 ), and the cavity ( 21 ) is filled with injection molding compound in a first casting operation. The closing mold part ( 35 ) is removed and replaced with a second casting mold half ( 45 ) with a cavity ( 46 ), which is filled with injection molding compound in a second casting operation.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2006 028 816.5 filed Jun. 21, 2006, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a process for manufacturing an injection molded part with integrated flexible printed circuit board. 
       BACKGROUND OF THE INVENTION 
       [0003]    The extrusion coating of flexible printed circuit boards has been known from the state of the art for a long time. Individual flexible printed circuit boards are introduced into a cavity and extrusion coated with a plastic. To accurately define the location of such flexible printed circuit boards in the later finished plastic component or in the cover thereof, it is necessary to introduce corresponding fixing means into the cavity, doing so such that the flexible printed circuit board is not deformed and/or does not change its position unacceptably. 
         [0004]    The processes and procedures known so far, especially in automatic manufacture, are extremely complicated, on the one hand, because additional fixing means must be provided within the cavity, and, on the other hand, because a handling means is to be provided, by means of which the individual flexible printed circuit boards can be fed to the injection molding machine. 
       SUMMARY OF THE INVENTION 
       [0005]    Accordingly, the basic object of the present invention is to provide a process that makes it possible to provide flexible printed circuit boards as finished plastic components with a cover consisting of plastic in a work process taking place as a continuous or stepwise process. 
         [0006]    The object is accomplished according to the present invention by
   a) fixing the flexible printed circuit boards to be provided with a cover consisting of plastic by means of carrier elements projecting at the edge in a recess of a carrier strip with spaces on all sides,   b) inserting one of the printed circuit boards fixed in the carrier strip into the cavity of the casting mold half of an injection mold with spacing on all sides and by holding same by the carrier elements in a predetermined position,   c) closing the cavity of the casting mold half by means of a closing mold part, which has no cavity, including the printed circuit board, and filling the cavity with injection molding compound in a first casting operation and   d) removing the closing mold part and replacing it with a second casting mold half with a cavity, which corresponds to the rest of the cover and which is filled with injection molding compound in a second casting operation.   
 
         [0011]    A flexible printed circuit board can be processed with the process according to the present invention into a finished plastic component in a manufacturing process taking place continuously or stepwise, and it is guaranteed that the printed circuit boards always assume the same predetermined position in the finished plastic parts. With the carrier strip used now, in the cavity of which the printed circuit boards are accommodated, it is also possible in a simple manner to position and hold the printed circuit boards in the respective casting mold. The dimensions of these recesses are adapted to the dimensions of the surface shape of the flexible printed circuit boards and of the casting mold such that the printed circuit board can be completely extrusion-coated. 
         [0012]    To make it possible to fasten the printed circuit boards on the carrier strip in a simple manner and in a secure position, the lateral edges of the printed circuit boards are provided with outwardly projecting carrier elements designed as mounting tabs. To receive the carrier elements, i.e., the mounting tabs, in a position-fixing manner, the components that limit the recesses of the carrier strip and are in the form of longitudinal and cross bands are provided with depressions each. To obtain a rigid and reliable connection to the carrier strip, the mounting tabs are bonded or welded to the longitudinal or cross bands. 
         [0013]    A plurality of flexible printed circuit boards to be extrusion-coated can thus be arranged one after another and fixed in the recesses of the carrier strip, which are present as multiple recesses in rows, so that they can be fed one after another to a correspondingly designed injection mold in a work process taking place stepwise. 
         [0014]    Due to the fact that the printed circuit boards are extrusion-coated with a first cover half one after another on one flat side only in a first casting operation, the risk that the printed circuit board is exposed to strong, destructive compressive forces acting on one side during such an injection operation is extensively avoided by the printed circuit board being able to be in contact with and supported on the flat side located opposite the cavity at a back pressure surface. 
         [0015]    It may be advantageous in this connection if vacuum can be applied to the flat mold part of the injection molding cavity to fix the printed circuit board, so that the flexible printed circuit board is pulled against the wall of this flat mold half of the injection mold cavity. A half of the cover is injected around the flexible printed circuit board during the subsequent injection molding operation. 
         [0016]    A second half of the cover is injected on the top side on the flexible printed circuit board and on the first half of the cover in a second injection molding operation, so that a finished component with integrated flexible printed circuit board is subsequently obtained. 
         [0017]    Based on the carrier strip with the flexible printed circuit boards arranged snugly thereon, the manufacture of a plastic component with integrated printed circuit board can be manufactured in a continuous work operation progressing stepwise. 
         [0018]    The individual process steps of the process according to the present invention will be explained in more detail below as an example on the basis of the drawings. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    In the drawings: 
           [0020]      FIG. 1  is a perspective exploded view of a section of a punched carrier strip together with a flexible printed circuit board; 
           [0021]      FIG. 2  is a perspective view showing the carrier strip section from  FIG. 1  with a plurality of printed circuit boards placed thereon; 
           [0022]      FIG. 3  is a perspective view showing a half of a casting mold with a cavity, which is used to inject a half of a cover on a flexible printed circuit board; 
           [0023]      FIG. 4  is a schematic perspective view showing the half of the casting mold from  FIG. 3  with the attached carrier strip section according to  FIG. 2  and with a closing mold part not yet located in the closing position; 
           [0024]      FIG. 5  is a perspective view of a the carrier strip section from  FIG. 4  with two printed circuit boards injection-coated on the underside offset by a transport step compared to  FIG. 4 ; 
           [0025]      FIG. 6  is a schematic perspective view showing the carrier strip section from  FIG. 5  with a completely injection-coated printed circuit board on the underside and the top side and with a printed circuit board injection-coated on the underside only, which is in a second casting mold part, which is provided with a closing mold part having a cavity for the upper cover; and 
           [0026]      FIG. 7  is a schematic perspective exploded view showing a double injection mold with two printed circuit boards injection-coated on one side. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    Referring to the drawings in particular,  FIG. 1  shows a carrier strip  1 , which may be manufactured, for example, from a paper web, a metal web or another thin, flexible material. This carrier strip  1  could also be manufactured from a plastic band. As is shown in  FIG. 1 , this carrier strip  1  is provided with a plurality of recesses  2 , which have a square surface shape in the present exemplary embodiment. Due to these recesses  2 , the carrier strip  1  forms two longitudinal bands  3  and  4 , which extend in parallel to one another and are connected to one another by a plurality of cross bands  5 . The longitudinal bands  3  are provided with impressed depressions  6  and  7  in the middle between two cross bands  5 . The cross bands  5  have a depression  8  each approximately in the middle between the two longitudinal bands  3  and  4 . 
         [0028]    The recesses  2  are used to receive a flexible printed circuit board  9 , which is provided in this exemplary embodiment with carrier elements each in the form of an outwardly projecting mounting tab  14 ,  15 ,  16  and  17 , respectively, at the edge, i.e., at their lateral edges  10  and  11  as well as  12  and  13  extending longitudinally and crosswise. In addition, the flexible printed circuit board  9  has two holes  18  and  19  within its base between the two mounting tabs  16  and  17 . 
         [0029]    The printed circuit board  9  is present as multiple printed circuit boards corresponding to the number of recesses  2  of the carrier strip  1 , into which [recesses] it is inserted. 
         [0030]    As is apparent from  FIG. 2 , the flexible printed circuit boards  9  are arranged individually in one of the recesses  2  of the carrier strip  1 . It can also be recognized that the lateral edges  10  through  13  have a lateral distance from the longitudinal and cross bands  3 ,  4  and  5  of the carrier strip  1 . 
         [0031]    The mounting tabs  14  and  15  fittingly protrude into the respective associated depressions  6  and  7  of the longitudinal bands  3  and  4 . By contrast, the mounting tabs  16  and  17  protrude fittingly into the depressions  8  of the cross bands  5  in the mounted state, as this is apparent from  FIG. 2 . In this position shown in  FIG. 2 , the printed circuit boards  9  are fixed snugly at the longitudinal bands  3 ,  4  and the cross bands  5  via their mounting tabs  14 ,  15 ,  16  and  17 , for example, by means of a bonded connection or a welded connection or another type of connection that can be established essentially automatically. Thus, the use of a carrier strip  1 , which is provided with recesses  2 , into which a printed circuit board  9  each can be individually inserted, also belongs to the process according to the present invention. The mounting tabs  14 ,  15 ,  16  and  17  made integrally in one piece with the printed circuit boards  9  are used at first to center the printed circuit boards  9  in a recess  2  at an essentially equal distance all around from the longitudinal and cross bands  3 ,  4  and  5 , the mounting tabs  14  through  17 , seated fittingly in the depressions  6 ,  7  and  8  of the carrier strip  1 , being fastened in these depressions  6 ,  7  and  8  by a connection that is preferably a connection in substance, such as bonding or welding. Thus, the carrier strip provided with the printed circuit boards  9  forms an “endless band” of flexible printed circuit boards  9  arranged one after another in rows, so that these printed circuit boards  9  can be extrusion-coated in a machining process taking place continuously stepwise to form a finished component. 
         [0032]      FIG. 3  shows for this, as an example and a schematically simplified form, an embodiment of a lower casting mold half  20 , which has an inner cavity  21 , whose shape corresponds to the outer contour of a half of a later cover half  39 . The casting mold half  20  is provided in this exemplary embodiment with a circumferential [sic-Tr.Ed.] edge web  22  projecting upwardly approximately by the thickness of the carrier strip  1 . The edge web is divided into longitudinally extending sections  23  and  24  as well as into transversely extending sections  25  and  26 . Depressions  28 ,  29 ,  30  and  31  are arranged centrally in these sections  23 ,  24 ,  25  and  26 . These depressions  28 ,  29 ,  30  and  31  are coordinated with the mounting tabs  14  through  17  in terms of both their surface shape and their depth, so that they receive the sections of the mounting tabs  14  through  17  located within the longitudinal and cross bands of the carrier strip with a flush surface and in a laterally fitting manner and they can as a result fix the position of a printed circuit board  9  in the cavity of the casting mold half. 
         [0033]    The recesses  2  are dimensioned such that they can receive the circumferential edge web  22 . The internal dimensions of the cavity  21  and of the circumferential edge web  22  are in turn selected to be such that a sufficient distance, which permits a sufficiently thick-walled extrusion coating of these lateral edges  10  through  13 , is left between their lateral inner surfaces and the lateral edges  10  through  13 . 
         [0034]    To make it possible to close this first lower casting mold half  20  for a first casting operation, by which the underside cover half  39  is produced, a second upper casting mold half  35  is provided, which has a lower, flat limiting surface  36  towards the first casting mold half  20  in this exemplary embodiment. Two cylindrical holes  37 , whose arrangement is congruent to the two holes  18  and  19  of the printed circuit board  9 , are provided in this limiting surface  36  in this exemplary embodiment. 
         [0035]    Thus, after closing the injection mold, consisting of the two casting mold halves  20  and  35 , the printed circuit board  9  is thus flatly in contact on the top side with the flat limiting surface  36  of the upper casting mold half  35 . To ensure during the subsequent injection molding operation that the printed circuit board  9  will come into and remain flatly in contact with this limiting surface  36 , vacuum channels (not shown in the drawing), via which the printed circuit board  9  is suctioned onto the limiting surface  36  during the injection molding operation, may be provided in the upper casting mold half  35 . 
         [0036]    A first lower cover half  38  is injected onto the printed circuit board  9  in this first injection molding operation, as this is apparent especially from  FIGS. 5 and 7 . 
         [0037]      FIG. 5  shows a section of a carrier strip  1  with a total of three printed circuit boards  9  in a position in which the first, underside cover has just been injected onto the middle printed circuit board  9  and the middle of the carrier strip  1  after a first casting operation and the carrier strip  1  is in a state immediately before performing another transport step to take place in the direction of arrow  50 . The left-hand printed circuit board  9  of  FIG. 5  has already been extrusion-coated with the underside cover half  39  before this casting operation and the transport step that had preceded it. 
         [0038]    The right-hand printed circuit board  9  is shown in a state in which it has not yet been extrusion-coated.  FIG. 5  also shows that two upwardly projecting coupling pins  40  and  41  are injected simultaneously during the injection molding operation through the cylindrical holes  37  and  38  provided in the upper casting mold half  35 . Furthermore,  FIG. 5  shows that the mounting tabs  14 ,  15 ,  16  and  17  pass outwardly through the lower cover half  38  and continue to be rigidly connected to the carrier strip  1 . 
         [0039]    After injecting this first cover half  39 , the upper casting mold half  35  is removed and replaced with a second upper casting mold half  45 , which is shown schematically in  FIG. 6 . This second upper casting mold half  45  has a second cavity  46 , which is open towards the printed circuit board  9 , which is located under it and is already provided with the first cover half  39 , the dimensions of the second cavity  46  approximately corresponding to the cavity  21  of the lower casting mold half  20  according to  FIG. 3 . After closing the two casting mold halves  20  and  45 , the upper cover half  47  can now be injected onto the lower cover half  39  and to the printed circuit board  9 . The printed circuit board is now completely enclosed by the two cover halves  39  and  47 , as this can be recognized especially from  FIG. 6  for the front printed circuit board  9  shown in a perspective partial section. An additional connection now becomes established between the two cover halves  39  and  47  via the coupling pins  41 , which can also be recognized from  FIG. 6 . 
         [0040]    After this process step of injecting the second cover half  47 , the mounting tabs  14 ,  15 ,  16  and  17  can again be separated from the carrier strip  1  and removed if they laterally project from the cover  39 / 47 , so that the finished component provided with an integrated printed circuit board  9  is now obtained. 
         [0041]    While it is necessary in the working method just described to carry out the injection of the two cover halves  39 ,  47  in separate casting molds or in casting molds with replaceable upper casting mold halves  35  and  45 ,  FIG. 7  shows a double casting mold, in which the lower cover half  39  and the upper cover half  47  can be prepared in work cycles immediately following each other after an intermediate transport step. This double casting mold has an additional lower casting mold part  20 ′, which has a cavity  39 ′, which can fittingly accommodate the lower cover half  39  injected in the casting mold half  20 , immediately adjacent to the first lower casting mold half  20  in the transport direction indicated by arrow  50 . An upper casting mold half  45  with its cavity  46  can be attached closingly to this additional mold part. While the lower cover half is being formed in the casting mold half  20  with the attached closing mold part  35 , the upper cover half  47  can be produced next to it in the casting mold part  45  at the same time. 
         [0042]    Highly efficient manufacture is thus achieved. 
         [0043]    While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.