Abstract:
In order to secure wired components of large mass or non-uniform mass distribution safely on a circuit board, without the components needing, as currently usual, to be glued onto the circuit board or held on the circuit board with snap-in holders, integrated into a connection bore for receiving a connection wire, or pin, of an electronic component a holding mechanism for secured holding of the connection wire, or pin. The holding mechanism represents a narrowing in the connection bore to a diameter smaller than that of the connection wire, or pin. The holding mechanism can be implemented, for example, by a connection bore embodied in the form of a bore drilled from one side of the circuit board, not completely through the circuit board. In such case, edge remains as a narrowing, which securely seizes the connection pin of the relevant component and holds the component fixed to the circuit board.

Description:
FIELD OF THE INVENTION 
     The invention relates to a circuit board having a holding mechanism for holding electronic components, a method for manufacturing such a circuit board, and their use in a soldering oven. 
     BACKGROUND OF THE INVENTION 
     Various methods and devices are known, by way of which wired electronic components can be so affixed on circuit boards, that they do not slip or otherwise change their position during populating or during transport of the circuit boards, with the components populated thereon, to a soldering facility. 
     The term “wired components” is meant here to include all components having at least one connection wire or connection pin, which is stuck through, or into, as the case may be, a corresponding, ordinary connection bore, or hole, of the circuit board and soldered to, or with, as the case may be, a desired contact location, in order to provide electric contacting of the component. Wired components, in this sense, can, therefore, also include row sockets, connection wires or litz wires, and even transformers and other active, or passive, electronic components. 
     Especially in the case of components of large mass or components with non-uniform mass distribution, simple sticking-in, or sticking-through, of the connection wires or connection pins is not sufficient to assure a safe mechanical securement for the components in the case of a transport to, or through, an automatic soldering facility. It has been found that wired components of the described kind on jolting or jerking conveyor belts can shake out of the circuit board on the way to, or through, an automatic soldering facility. There have even been instances where these components were pressed out of the circuit board by the soldering wave of a wave soldering facility. Even when the components do not fall completely out of the circuit board under these unfavorable conditions, it can still happen, that they assume an undesired location or position on the circuit board. In order to attempt to overcome these problems, the components in question have been, for example, glued onto the circuit board, or held on the circuit board with snap-in holders. These methods are, however, complicated and associated with additional costs, since they require an extra working step for these special components. 
     SUMMARY OF THE INVENTION 
     An object of the invention is, therefore, to create a circuit board, which has a holding mechanism for secure holding of the connection wires, or pins, of components and, in such manner, avoids the above-described disadvantages, without requiring that the components under consideration be secured by gluing or by holding elements additionally placed on the circuit board. 
     This object is achieved by a circuit board having at least one connection bore for receiving a connection wire, or pin, of an electronic component of predetermined wire, or pin, diameter, wherein, for secure holding of the connection wire, or pin, a holding mechanism is provided, in the form of a narrowing in the cross section of part of the connection bore to a diameter smaller than the diameter of the connection wire, or pin. 
     In a special form of embodiment of the circuit board of the invention, the narrowing is provided by a foil, which, in a special further development of the invention, is arranged on a surface of the circuit board. 
     Another form of embodiment of the circuit board of the invention concerns a multi-ply circuit board, wherein the foil narrowing the cross section of the connection bore is an inner ply of the circuit board. 
     In another form of embodiment of the circuit board, the foil is slit or provided with a hole in the area of the connection bore. 
     In a further form of embodiment of the circuit board of the invention, the narrowing is brought about by a unilateral, not completely continuous bore. 
     Yet a further form of embodiment of the circuit board of the invention concerns a narrowing brought about by a beaker-shaped insert having a restriction and inserted into a continuous, connection bore. 
     Other forms of embodiment of the circuit board of the invention include two bores which cooperate to bring about the narrowing, wherein, in special further developments of this circuit board of the invention, there are provided: Two equally directed bores of different diameters; or two bores running toward one another; or two bores running toward, and shifted with respect to, one another. 
     The above-described object is, furthermore, achieved by a method of the invention for manufacture of a circuit board with at least one connection bore for receiving a connection wire or pin of an electronic component having a predetermined wire, or pin, as the case may be, diameter, wherein in such method:
         after the manufacture of at least one ply, or layer, of the circuit board and the drilling of the connection bore, a foil is applied onto a surface of the circuit board, with the foil covering the connection bore;   the foil is opened in the area of the connection bore in such a manner that a narrowing in cross section of a part of the connection bore is formed, the narrowing being smaller that the wire, or pin, diameter of the electronic component and providing a holding mechanism for secure holding of the connection wire, or pin.       

     Further developments of the method of the invention provide, that the foil is slit or provided with a hole in the area of the connection bore, wherein this can be done also by means of laser. 
     In another form of embodiment of the method of the invention for manufacturing a circuit board having at least one connection bore for receiving a connection wire, or pin, of an electronic component with a predetermined wire, or pin, diameter:
         the circuit board is manufactured with at least one ply, or layer;   drilling is performed from a surface of the circuit board, into the circuit board, with a drilling tool of a nominal diameter, in such a manner, that the drilling tool does not completely go through the circuit board and, therefore, the connection bore has a region where its cross section has a diameter which is smaller than the wire, or pin, diameter of the electronic component, in order that cross sectional narrowing of the connection bore brought about in this way forms a holding mechanism for secure holding of the connection wire, or pin.       

     In yet another form of embodiment of the method of the invention for manufacturing a circuit board with at least one connection bore for receiving a connection wire, or pin, of an electronic component of predetermined wire, or pin, diameter:
         the circuit board is manufactured with at least one ply, or layer;   the circuit board is completely drilled-through at the location desired for the connection bore;   a tubular insert is inserted into the connection bore;   the tubular insert has a restriction in its cross section of a diameter, which is smaller than the wire, or pin, diameter of the electronic component;   the restriction represents a holding mechanism for secure holding of the connection wire, or pin.       

     A further form of embodiment of the method of the invention for manufacturing a circuit board having at least one connection bore for receiving a connection wire, or pin, of an electronic component of predetermined wire, or pin, diameter provides that:
         the circuit board is manufactured with at least one ply, or layer;   at a location desired for the connection bore, a blind hole is drilled with a drilling tool of a desired diameter into the circuit board;   then the floor of the blind hole is drilled-through with a drilling tool having a diameter smaller than the wire, or pin, diameter, so that, by the narrowing of the cross section of a part of the connection bore created thereby, a holding mechanism is formed for secure holding of the connection wire, or pin.       

     In yet another form of embodiment of the method of the invention for manufacture of a circuit board having at least one connection bore for receiving a connection wire, or pin, of an electronic component of predetermined wire, or pin, diameter:
         the circuit board is manufactured with at least one ply, or layer;   at a location desired for the connection bore, a first blind hole is drilled from a first surface of the circuit board, into the circuit board, with a drilling tool of a desired diameter;   from a second surface of the circuit board, a second blind hole is drilled into the circuit board;   the second blind hole is slightly offset with respect to the first blind hole and meets the first blind hole, so that, by the offset of the two blind holes with respect to one another, a restriction is formed, which represents a holding mechanism for secure holding of the connection wire, or pin.       

     Yet a further method of the invention for manufacture of a circuit board having at least one connection bore for receiving a connection wire, or pin, of an electronic component with a predetermined wire, or pin, diameter provides that:
         the circuit board is manufactured with at least one ply, or layer;   at the location desired for the connection bore, a first blind hole is drilled into the circuit board from a first surface of the circuit board with a drilling tool having a desired diameter;   from a second surface of the circuit board, a second blind hole is drilled into the circuit board, with the second blind hole being arranged essentially axially parallel and aligned with the first blind hole and meeting the first blind hole, but not passing completely into it, so that, in a portion of the connection bore, where the two blind holes meet, a restriction is formed, which represents a holding mechanism for secure holding of the connection wire, or pin.       

     A special advantage of the invention is that it avoids previously usual holding elements, which had to be applied extra to the wired components or on the circuit board, elements such as e.g. gluing dots, snap-in holders, etc., for the securing of critical, wired components. Such extra holding elements always mean one or even several additional working steps, as well as additional costs, during the populating and even during the soldering of the circuit board. The invention offers, in contrast, a solution which affects only the circuit board itself and which, additionally, achieves its goal without extra appurtenances on the surface of the circuit board. The foils of the invention are, like the connection bores of the invention, parts of the circuit boards and not items added separately on, or to, the circuit boards. Easy pressing of a connection pin into a connection bore of a circuit board of the invention and against the resistance of the narrowing provided in the connection bore is sufficient to secure the involved component mechanically safely on the circuit board. The circuit board of the invention is especially suited for automatic soldering facilities, especially for wave soldering facilities and reflow soldering ovens. Especially in the case of the latter, it provides the assurance that, even in the case of the new, so-called “upside-down soldering”, also called the “backside-reflow” method, thermally critical, wired components hanging upside-down and beneath the circuit board in the reflow soldering oven do not fall out of the connection bores. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be explained in greater detail on the basis of various examples of embodiments presented in the appended drawing, the figures of which show as follows: 
         FIG. 1  a schematic, cross sectional representation of a first example of a circuit board of the invention; 
         FIG. 2  a schematic, cross sectional representation of a second example of a circuit board of the invention; 
         FIG. 3  a schematic, plan view of a third example of a circuit board of the invention; 
         FIG. 4  a schematic, plan view of a fourth example of a circuit board of the invention; 
         FIG. 5  a schematic, plan view of a fifth example of a circuit board of the invention; 
         FIG. 6  a schematic, cross sectional representation of a sixth example of a circuit board of the invention; 
         FIG. 7  a schematic, cross sectional representation of a seventh example of a circuit board of the invention; 
         FIG. 8  a schematic, cross sectional representation of a eighth example of a circuit board of the invention; 
         FIG. 9  a schematic, cross sectional representation of a ninth example of a circuit board of the invention; 
         FIG. 10  a schematic, cross sectional representation of a tenth example of a circuit board of the invention; 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For simplifying the drawings, equal elements or assemblies of the different examples of embodiments are given equal reference characters. 
       FIG. 1  shows a portion of a circuit board  10  having a traversing connection bore  11  for receiving a connection pin  111  of a wired electrical, or electronic, component  110 . Until now, it has been usual to drill a diameter  12  of the connection bore  11  slightly larger than the diameter of the connection pin  111 . This allows, it is true, easy insertion of the connection pin  111  into the connection bore  11 , but does lead in the case of vibrations or shaking to the falling-out of component  110 , when it is not secured to the circuit board  10  by additional measures. 
     In order to avoid this, the example of an embodiment shown here includes, according to the invention, a foil  13 , which is, for example, applied on a surface of the circuit board  10 . Foil  13 , which, according to the invention, is applied onto a circuit board finished as regards its layers and already provided with the connection bore  11 . The foil  13  at first covers and seals connection bore  11 . The foil is applied permanently on circuit board  10  in usual manner, for example by lamination. 
     Then, foil  13  is opened in the area of the connection bore  11 , with the opening  14  being formed in such a manner that it represents a narrowing  15  of the cross section of a part of the connection bore  11 . The material and thickness of foil  13 , as well as the size and shape of its opening  14 , are expediently so selected, that the relevant connection pin  111  of the component  110  under consideration can be pushed through without great effort. Since the narrowing  15  is smaller than the diameter  112  of the connection pin  111  of component  110 , connection pin  111  is securely seized and the component  110  secured against falling out. 
     In the case of the example of the invention illustrated in  FIG. 1 , the foil  13 , by means of which the narrowing  15  is implemented, is arranged on the populating side of the circuit board  10 . Of course, it is also possible to place the foil  13  on the other side of the circuit board. 
       FIG. 2  shows another example of the circuit board  20  of the invention; only a portion of the board is shown here. 
     A connection bore  21 , which does, in itself, traverse the board, for receiving the connection pin  111  of the wired component  110  is narrowed about halfway through the circuit board  20  by a foil  23  arranged as an intermediate ply in the circuit board  20 . An opening  24  provided in the foil  23  has a diameter which is smaller than the diameter  112  of the relevant connection pin  111  of the wired component  110 . A narrowing  25  of the connection bore  21  formed thereby holds the connection pin  111  of the component  110  inserted into the connection bore  21  and seizes it. 
     It makes sense to provide the two parts of the circuit board  20  separated by the foil  23  first with the connection bore  21 . After laying the foil  23  between the two parts of the circuit board or after the applying of the foil  23  on one part of the circuit board  20 , the parts are joined together to provide the arrangement shown in  FIG. 2 . 
       FIG. 3  illustrates a further example of an embodiment of a circuit board of the invention. A portion of the circuit board  30  is shown here in a plan view. Similarly to the circuit board shown in  FIG. 1 , here, likewise, a foil  33  is applied on a side of the circuit board  30 . An opening  34  in the foil  33  has a smaller diameter than the connection bore  11  (shown by the dashed line) covered by the foil  33 . The foil  33 , as shown in  FIG. 3 , can be a copper lamination in the sense of a conductive path, so that it provides a narrowing  35  for securing the connection pin  111  of component  110  (see in this respect  FIGS. 1 and 2 ) directly there, where the connection pin  111  is also then soldered. 
     For the sake of simplicity, component  110  with the connection pin  111  to be inserted into the relevant connection bore is not shown in  FIGS. 3 to 5 . Reference is made, in this respect, to  FIGS. 1 and 2 , or to  FIGS. 6 to 8  discussed below. 
       FIG. 4  shows yet another example of an embodiment of a circuit board of the invention. A circuit board  40  is illustrated here. Again, a foil  43  is applied to a side of the circuit board  40 . An opening  44  in the foil  43  is formed in this example of an embodiment by mutually crossing slits and provides a narrowing  45  of the connection bore  11 , which is indicated here by an outer, dashed line. Foil  43  is, in this example of an embodiment, a minimal, dot-shaped covering of the connection bore  11 . 
       FIG. 5  is yet another example of an embodiment of a circuit board of the invention presented as a circuit board portion in a plan view, similarly to the illustrations in  FIGS. 3 and 4 . Here, there is applied on the circuit board  50  a foil  53  of an electrically conducting material, as in the example of an embodiment of the circuit board  30  of  FIG. 3 . In contrast to the hole-like opening  34  of the foil  33  in the case of the circuit board  30  of  FIG. 3  and the slitted opening  44  of the foil  43  of  FIG. 4 , in the case of the foil  53  shown in  FIG. 5  an opening  54  formed of a plurality of overlapping holes is provided. By the corners formed thereby at their edges and projecting into the opening  54 , also here a narrowing  55  is achieved for the securing of the connection pins  111  of the component  110  (see, in this connection,  FIGS. 1 and 2 ) in the connection bore  11 . 
     The foil  13 ;  23 ;  33 ;  43  appearing in  FIGS. 1-5  can be of electrically conductive or non-conducting material. It can be conductive material for soldering points, for example. Another option, however, is to provide the foil, not as a finished product, but, instead, as a film of a suitable material applied onto the circuit board, where it then cures to become a foil. 
     The openings  14 ,  24 ,  34 ,  44  and  54  are manufactured, for example, by punching, or by cutting with a laser beam. 
       FIG. 6  shows a circuit board  60  of the invention, in the case of which the connection bore  11  is embodied as a unilateral bore  16  not completely drilled through the circuit board  60 . As shown in  FIG. 6 , a edge remains in this case as a narrowing  65  relative to the diameter  12  of the connection bore. Such edge is smaller than the diameter  112  of the connection pin  111  of the relevant component  110 . In this way, the connection pin  111  and the component  110  under consideration are held safely in the connection bore  11  and, thus, on the circuit board  60 . 
       FIG. 7  shows another example of an embodiment of the circuit board  60  of the invention. Similarly to the circuit board  60  in  FIG. 6  and in contrast to the circuit boards  10  to  50 , the circuit board here has no foil for forming a narrowing of the inner diameter of the connection bore. In the case of circuit board  70 , a desired narrowing  106  is achieved by a beaker-shaped, very thin-walled shell  101 , which is inserted into the connection bore  11 . Shell  101  is so embodied, that its inner diameter  102  is slightly greater than the diameter  112  of the connection pin  111  of the relevant component  110 . In order that shell  101  not be pushed through the connection bore  11  during the inserting of the connection pin, shell  101  has a collar  103 , which bears against the circuit board  70  and guards against slipping of the shell through the connection bore. On its floor, the beaker-shaped shell  101  has an opening  104 , whose diameter is smaller than the diameter  112  of the connection pin  111  of the component  110  under consideration. During insertion of the connection pin  111 , the such moves through the opening  104  against the resistance of the deforming shell  101 . Shell  101  is deformed and seizes the relevant connection pin  111  securely in the connection bore  11 . 
     In contrast with the examples of embodiments of the circuit board of the invention presented until now in  FIGS. 1 to 7 , wherein connection bores involve a single drilled hole, the examples of embodiments of the circuit board of the invention to be presented now are concerned with a connection bore formed from two separately drilled holes. 
     Thus, in  FIG. 8 , another example of an embodiment of the circuit board  60  is presented, in which the connection bore  11  is formed of two oppositely drilled bores  17  and  36 , which are slightly offset with respect to one another. At the location, where the two bores  17  and  36  meet, the offset results in a narrowing  75 . Each of the bores  17  and  36  has a diameter greater than the diameter  112  of the connection pin  111  of the considered component  110 . The narrowing  75  formed by the offset of the bores  17  and  36  seizes the connection pin  111  securely and cares for a safe seating of the component  110  on the circuit board  60 . 
       FIG. 9  shows yet another example of an embodiment of the circuit board  60 , in the case of which the connection bore  11  is formed from two bores  27  and  46 . In contrast to the circuit board of  FIG. 8 , involved here are two aligned bores  27  and  46 , which can be drilled in opposition to one another from different sides of the circuit board  60  or else, in effect, one on top of the other, from a single, predetermined side of the circuit board  60 . Important is only that one of the bores, in this case bore  27 , has a smaller diameter than the other bore, with the greater diameter corresponding to the diameter of the connection bores  11  already described above, i.e. slightly greater than the diameter  112  of the connection pin  111  of the relevant component  110  (see, in this connection,  FIGS. 6-8 ) and the smaller diameter of the bore  27  being smaller than the diameter  112  of the connection pin  111  of the relevant component  110 . The transition from a greater diameter to a smaller diameter in the connection bore  11  provides the narrowing  85 , which seizes the connection pin  111  of the relevant component  110  (see, in this regard,  FIGS. 6-8 ) and enables a safe seating of component  110  on the circuit board  60 . 
       FIG. 10  presents yet another example of an embodiment of the circuit board  60 , in the case of which the connection bore  111  is formed from two holes  37  and  56  drilled from opposite sides of the board. Here, holes  37  and  56  are mutually aligned and have the same diameter  12 . The hole, for example hole  37 , which is drilled first, is done as a blind hole-thus, it does not extend completely through the circuit board  60 . The other hole, in the case treated here, hole  56 , which is placed in alignment with the first hole  37 , penetrates into the first drilled hole  37  only incompletely in the floor thereof, so that, as shown in  FIG. 10 , there then remains in the connection bore  11  a collar directed internally into the connection bore  11 . This collar forms a narrowing  95  of the connection bore  11 . With the help of this narrowing  95 , the connection pin  111  of the considered component  110  (see, for this,  FIGS. 6-8 ) becomes seized securely, and component  110  is held safely on the circuit board  60 .