Abstract:
A method for producing a composite window pane, particularly a motor vehicle windscreen, includes mounting guide pins and electronic components on traces of a printed circuit board and inserting the printed circuit board between a first and a second glass plate. The guide pins are inserted in passthroughs in the first glass plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to German Patent Application No. 10 2016 002 636.7, filed Mar. 3, 2016, which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present disclosure pertains to a composite window pane, particularly a window pane for a motor vehicle with an integrated electronic circuit, and a method for producing such a composite window pane. 
       BACKGROUND 
       [0003]    A composite window pane with integrated electronic circuit is described in the previously unpublished German patent application DE 10 2015 013 469.8. In the production of this window pane, a printed circuit board with mounted circuit components is connected between two glass plates of the composite window pane and contacted via wires that extend through passthroughs in one of the glass plates. The wires may be inserted in the passthroughs before the glass plates and the printed circuit board are joined together, or they may be inserted in the passthroughs after the plates and the circuit board have been assembled. 
         [0004]    Errors that occur while the printed circuit board is being placed can make it impossible for the contacting to take place, but they are difficult to correct because they only become apparent after the printed circuit board is placed in position, and in order to correct them the flexible printed circuit board would have to be lifted off the glass plate and then spread out over it again without any creases or bubbles. 
       SUMMARY 
       [0005]    The present disclosure provides a method for producing a composite window pane, which makes it possible to avoid errors when placing the printed circuit board before they occur. According to one variant of the present disclosure, a method includes mounting guide pins and electronic components on a printed circuit board, and inserting the printed circuit board between a first and a second glass plate. The guide pins are inserted in passthroughs in the first glass plate. 
         [0006]    Since the guide pins are already in position on the printed circuit board when the printed circuit board and the first glass plate are joined together, they prevent the two from coming into contact, unless they engage in the passthroughs of the first glass plate. This makes it impossible for the printed circuit board to be placed in a position in which it cannot be contacted. 
         [0007]    If the guide pins themselves are metallic, the traces may be contacted via the guide pins themselves. However, it is also conceivable to use guide pins that are not electrically conductive, but which simply ensure the contact pin which is inserted in the passthrough after the composite window pane has been put together by engaging in a passthrough that conductive will come into contact with the trace that is marked by the guide pin. 
         [0008]    Metallic guide pins can be assembled on the printed circuit board together with the electronic components of the circuit in the same soldering step. 
         [0009]    However, another variant is conceivable in which, in a soldering step for mounting the electronic components on the printed circuit board, initially only creating soldering pads for the guide pins on the printed circuit board, and then soldering the guide pins as they are placed on the soldering pads while hot. This particularly makes it possible to mount guide pins which are difficult to assemble in a wave soldering operation because of their dimensions. 
         [0010]    In step b), the printed circuit board should first be positioned on the first glass plate and then covered with the second glass plate. If the printed circuit board were to be positioned on the second glass plate first, any inaccuracy occurring in this step would make it impossible for the glass plates to be positioned congruently against one another. 
         [0011]    The guide pins should be introduced into the passthroughs even before the printed circuit board comes into contact with the first glass plate itself for the first time. This ensures that the printed circuit board is orientated correctly even before the first contact. After emerging from the passthroughs, the printed circuit board may then be spread out over the first glass plate without creases or bubbles. 
         [0012]    A layer of composite plastic which is essential for keeping the composite window pane together even after a notional breakage of the glass plate should be inserted between the printed circuit board and the second glass plate. This ensures that it does not obstruct the positioning of the printed circuit board on the first glass plate and in particular does not prevent the guide pins from protruding into the passthroughs in the first glass plate. 
         [0013]    The printed circuit board is preferably covered by the plastic composite layer when the glass plates are joined with each other. The placement of the plastic composite layer is made considerably easier if a window has not been cut out of it to accommodate the printed circuit board, and which would require attention to ensure the correct positioning thereof. Furthermore, the printed circuit board is protected effectively from ambient moisture by the plastic composite layer, particularly if the circuit board does not extend as far as the edge of the composite window pane and instead is stuck to the first glass plate by the plastic composite layer extending around the border of the printed circuit board. 
         [0014]    In order to stabilize the guide pins after the glass plates have been joined, in a further method step c) the cavities that remain after the guide pins have been inserted in the passthroughs may be filled in. The filling material may be solder, which is able to penetrate the cavities spontaneously due to capillary forces. 
         [0015]    The present disclosure also provides a method to create a composite glass window pane that can be produced simply and reliably. 
         [0016]    According to one variant of the present disclosure, a composite window pane, particularly a window pane for a motor vehicle, includes two glass plates and a printed circuit board with electronic components and guide pins mounted thereon and embedded between the glass plates, in which the guide pins have a flat frontal face which bears on the printed circuit board and are secured on the printed circuit board by solder. 
         [0017]    The frontal face should be large enough to anchor to the guide pin firmly on the printed circuit board and particularly to prevent the guide pin from becoming misaligned when it is inserted in the associated passthrough. Therefore, the contact pins should have head facing toward the frontal face, on which said frontal face is located, and a shaft which faces away from the printed circuit board and which is thinner than the head. 
         [0018]    To ensure that a guide pin is not pulled out of its passthrough subsequently or to guarantee that the solder contact with the printed circuit board cannot be damaged by a force acting on the shaft of the guide pin, the cross section of the head of a contact pin may be larger than the cross section of the passthrough that accommodates the shaft of the contact pin. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements. 
           [0020]      FIG. 1  is a schematic view of a composite window pane according to the present disclosure, fitted in a motor vehicle; 
           [0021]      FIG. 2  is a cross section through the lower edge area of the composite window pane according to a first variation of the present disclosure; 
           [0022]      FIGS. 3 a - c    shows a method for producing the composite window pane; and 
           [0023]      FIGS. 4 a - d    show further the method. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description. 
         [0025]      FIG. 1  shows a schematic view of a front windscreen  1  in the form of a composite window pane according to the present disclosure and below it the dashboard  2  of a motor vehicle from the viewpoint of a driver. Rows  3 ,  4 ,  5  of LEDs  6  are embedded in front windscreen  1 , as will be explained in greater detail. LEDs  6  are part of a parking assistant, which is described to the extent necessary for helping to understand the structure of composite window pane  1 . The parking assistant includes an environmental sensor, for example a radar sensor that is capable of detecting the distance and dimensions of obstructions close to the motor vehicle, and of actuating the LEDs  6  depending on the result of such detection that the LEDs activated on this basis are positioned in front of the detected obstruction from the point of view of the driver, thereby indicating clearly the direction from which danger threatens, and to show the driver the distance from the obstruction depending on which of rows  3 ,  4 ,  5  the activated LEDs belong to, and/or the colour of the activated LEDs. This also enables the driver to reliably avoid obstacles that are not visible from his perspective when parking, for example because they are hidden by the car bonnet. 
         [0026]    Of course, other windows of the motor vehicle as well as the front windscreen  1  may be designed in the form of composite window panes with embedded LEDs, for example, rows  3 ,  4 ,  5  of LEDs  6  in front windscreen  1  may also be extended into the adjacent side windows  7  on the right and left, and may possibly even include LEDs on A-pillars  8  between them, or a rear window of the motor vehicle may be equipped with LEDs that are able to warn the driver of any obstructions when the driver is reversing as well. 
         [0027]      FIG. 2  shows a schematic cross section through a lower edge area of front windscreen  1  according to one variant of the present disclosure. Front windscreen  1  includes two glass plates, an outer glass plate  9  facing outwards and an inner glass plate  10  facing towards the passenger compartment, and between them a composite layer  11  made from a durable plastic such as polyvinyl butyral (PVB) for example, to which the glass plates  9 ,  10  are attached by surface adhesion and which serves to hold the fragments together in the event that one of the glass plates  9 ,  10  shatters. A flexible printed circuit board  12 —on which rows  3 ,  4 ,  5  of LEDs  6  extend transversely to the sectional plane—is embedded between composite layer  11  and inner glass plate  10  and extends over a part of the area thereof. 
         [0028]    Printed circuit board  12  does not extend far enough to come into direct contact with a lower edge  14  of front windscreen  1 , which is framed by a flexible seal  13 . Consequently, printed circuit board  12  is protected from any precipitation that might penetrate a gap  15  between lower edge  14  and seal  13  by composite layer  11  which extends as far as edge  14  and completely fills in the cavity there between the glass plates  9 ,  10 . 
         [0029]    Printed circuit board  12  is furnished with a plurality of guide pins  17 , which engage in passthroughs  16  in inner glass plate  10 . Guide pins  17  are made of metal and are each connected in electrically conductive manner to a trace on printed circuit board  12 . One of these guide pins  17  is shown in cross section in  FIG. 2 . In order to ensure contact with it, a metal plate  18  is biased by a spring  19  towards the tip of guide pin  17  that protrudes from the composite window pane into the interior of the motor vehicle. 
         [0030]      FIG. 3 a    shows a schematic cross section through printed circuit board  12 . Printed circuit board  12  has a flexible substrate  20 , on a polyimide base for example, on which traces  21  are mounted, in one plane as shown in the figure, or in several planes if required. An insulating foil  22  covers traces  21 . Foil  22  is furnished with apertures at sites  23  where a light emitting diode  6  is to be connected to traces  21 —at the stage shown in  FIG. 3 a    this is only attached adhesively—and at sites  24  where a solder pad is to be created. 
         [0031]      FIG. 3 b    shows printed circuit board  12  after it has passed through a solder bath. Solder  25  sticks to the sites  23  and  24  of traces  21  that are not covered by foil  22 . At sites  23  it contacts light emitting diode  6 , at site  24  it forms a solder pad  26  on which in the next step a guide pin  17  is mounted, as shown in  FIG. 3   c.    
         [0032]    In this example guide pin  17  is shaped like a drawing pin, with a flat head  27  and a shaft  28 . It is mounted by pressing against solder pad  26  while it is still hot, and so melts solder  25 . Alternatively, like light emitting diode  6 , guide pin  27  may be placed on substrate  20  and fixed temporarily with adhesive  29  before it passes through the solder bath, to be attached permanently afterwards with solder that penetrates between trace  21  and head  27 . 
         [0033]    The finished printed circuit board  12  is then placed on the inner glass plate  10  in such a way that the tips of guide pins  17  are positioned opposite the passthroughs  16  in the inner glass plate  10 . In order to make it easier to align guide pins  17  with passthroughs  16 , passthroughs  16  may be flared conically, as shown in  FIG. 3   c.    
         [0034]    Since the surface of inner glass plate  10 , on which printed circuit board  12  is to be mounted has a convex curvature, it is a simple matter to introduce the tips of guide pins  17  into passthroughs  16  before the printed circuit board  12  and the glass plate  10  come into contact with each other elsewhere. 
         [0035]    As soon as the first contact is made between the flexible printed circuit board  12  and glass plate  10 , printed circuit board  12  tends to cling closely to glass plate  10  and to stick to it adhesively. In order to prevent creases from forming when approaching with printed circuit board  12 , the first contact between printed circuit board  12  and glass plate  10  is made in the immediate vicinity of guide pins  17 , as shown in  FIG. 4   a.    
         [0036]    Here, printed circuit board  12  is in the form of a strip due to the arrangement of light emitting diodes  6  in elongated rows  3 ,  4 ,  5 , and guide pins  17  are arranged at one end of the strip. Therefore, printed circuit board  12  is brought into contact with glass plate  10  progressively starting from this end, as it unrolls, for example. 
         [0037]    In this context, the light emitting surfaces of light emitting diodes  6  come to bear on the outer side of glass plate  10  as shown in  FIG. 4 b   . Head  27  of guide pin  17  comes into contact with the outside of glass plate  10  all around passthrough  16 . 
         [0038]    In order to stabilize guide pin  17  in passthrough  16 , passthrough  16  may be filled in, with solder  25  for example, after guide pin  17  has been inserted. 
         [0039]    As shown in  FIG. 4 c   , the composite window pane is produced by spreading composite layer  11  between glass plate  9  on one side and glass plate  10  and printed circuit board  12  on the other side, and then bringing the two glass plates  9 ,  10  together, wherein composite layer  11  clings to glass plates  9 ,  10  and printed circuit board  12 . The composite obtained in this way (see  FIG. 4 d   ) is first placed under vacuum to remove any residual air in the cavity between the glass plates  9 ,  10 , and finally heated under pressure to partially melt composite layer  11  and cause it to adhere to the glass plates  9 ,  10  and printed circuit board  12 . 
         [0040]    The prominences  30  on the exposed surface of substrate  20  (see  FIG. 4 b   ) caused by the inclusion of the light emitting diodes  6  and guide pins  17  are not as high as the thickness of composite layer  11 . As composite layer  11  yields locally to the pressure of these prominences  30  during the partial melting, a full-surface contact is achieved between printed circuit board  12  and composite layer  11 . 
         [0041]    While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.