Abstract:
The invention concerns an electronic component that comprises a printed circuit board stack with multiple printed circuit boards arranged one on top of the other and that is used, in particular, for model aircraft or commercially utilized unmanned aircraft. The printed circuit boards are held at a distance from one another by spacers. The fastening elements that are provided here are electrically conductive in design, and the printed circuit boards are connected to one another in an electrically conductive manner and also mechanically by these fastening elements.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention concerns an electronic component that comprises a printed circuit board stack with multiple printed circuit boards arranged one on top of the other and that is used, in particular, for model aircraft or commercially utilized unmanned aircraft. 
         [0002]    Aeromodelling is currently experiencing enormous surges in development, on the one hand, because of an increase in the performance of propeller motors, and, on the other hand, because of the availability of increased electrical storage capacity. This makes a quadcopter style possible for drones. These multi-motor quadcopters are equipped with three to eight motors, for example. The electric power for these motors is provided by lithium polymer rechargeable batteries. This drive type makes possible high performance of the quadcopter with small size. 
         [0003]    Especially in the field of quadcopters, electronic speed controllers with high power consumption in a range up to a few hundred amperes are used. One controller is used for each motor, and adapts the power supply and thus the speed to the various needs, for example, ascent, horizontal alignment, initiation of course changes, and the like. At the same time, these electronic control units must be designed to be compact, weight-saving, robust, and easy to assemble. 
         [0004]    It is known to construct electronic components from multiple printed circuit boards. However, if multiple layers of printed circuit boards are used, firstly, they must be mechanically connected to one another in the component or module and, secondly, plug and cable connections are used for the power supply. Suitable soldered connections between the connectors and the printed circuit boards are required for this purpose. Such connections disadvantageously represent a risk element with regard to operational reliability of the model aircraft, because these connections are subjected to a tremendous stress caused by vibrations of the aircraft, shock, and large temperature differences. Thus, hairline cracks that endanger operational dependability can occur at the soldered points, especially in the event of unforeseen impacts or severe shocks. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The object of the present invention is to provide a compact, weight-saving yet also robust, and easy-to-assemble electronic component that satisfies, in particular, stringent demands with regard to vibrations, shock and temperature differences such as occur with model aircraft or commercially utilized unmanned aircraft. 
         [0006]    This object is attained by an electronic component with the features of claim  1 . Advantageous embodiments are described by the dependent claims. 
         [0007]    The novel electronic component comprises a printed circuit board stack with at least two printed circuit boards arranged one on top of the other, preferably with more than two printed circuit boards, and printed circuit board stacks with four or six printed circuit boards arranged one on top of the other are especially preferred. In a known fashion, the printed circuit boards carry electronic components that are supplied with the appropriate electric power through electrically conductive connections in the form of conductive traces. Electrical connections are also provided between the different printed circuit boards. However, these are not plug and cable connections that are soldered to the individual printed circuit boards. In the novel electronic component, electrically conductive fastening elements are used that mechanically connect the printed circuit boards to one another, on the one hand, and, on the other hand, also permit an electrical connection between the printed circuit boards and the power supply. 
         [0008]    The printed circuit boards in the printed circuit board stack preferably are arranged parallel to one another and are held at a desired distance from one another by spacers. The shape of the printed circuit boards can be selected freely. The printed circuit board shape may be round, oval or polygonal. Rectangular or square printed circuit boards are preferred, wherein printed circuit boards of the same size or also of different sizes can be arranged in a printed circuit board stack. A printed circuit board stack with printed circuit boards of the same size and shape is preferred. 
         [0009]    The fastening elements that ensure the electrically conductive connection and the mechanical connection are preferably provided at the edge on the printed circuit boards, and, in the case of printed circuit boards with a polygonal shape, preferably are provided at the corners of the printed circuit boards. For this purpose, the printed circuit boards have openings at these intended connection points in the manner of drilled holes for the fastening elements, through which the fastening elements reach. The conductive traces provided on the printed circuit boards extend to the joints with the fastening elements, which is to say to these openings. For especially good contact of the electrically conductive fastening element with the conductive traces of the printed circuit boards, the fastening element preferably has a region that overlaps the opening in the printed circuit board, at least in some areas. In the simplest manner, such a fastening element can be a bolt-and-nut connection, wherein the shank of the bolt passes through the opening in the printed circuit board, the bolt head rests against one side of the printed circuit board, and the nut rests against the opposite side of the printed circuit board in the region of the opening in the printed circuit board. In this design, contact can take place in the simplest manner both through the nut and through the bolt head, and takes place with sufficient contact pressure owing to the mechanical threaded connection. 
         [0010]    Moreover, in a different embodiment, the shank of the electrically conductive fastening means can also contact a conductive trace extending into the opening. 
         [0011]    In order to connect multiple printed circuit boards into a printed circuit board stack, each printed circuit board has appropriate openings for the fastening elements, which results in a stacked arrangement when identical printed circuit board sizes and shapes are provided, in which the openings in the individual printed circuit boards arranged one on top of the other are aligned and form a through passage for the fastening elements. For a sturdy mechanical connection of these printed circuit boards in the printed circuit board stack, at least three openings are provided in each printed circuit board, which produce three through passages in the printed circuit board stack when the printed circuit boards are arranged one on top of the other. For the mechanical connection, one fastening element can be provided for each through passage, for example in the form of a bolt or threaded rod, that is inserted into the individual openings of the through passage and coupled to a nut at the end. In this design, the distances between each of the individual printed circuit boards are achieved through spacers. These can be threaded nuts or metallic spacer rings that are pushed onto the shank of the fastening element and are retained in this way. A robust mechanical connection of the printed circuit boards in the printed circuit board stack is ensured by the threaded connection. Because the fastening element provided is designed to be electrically conductive and the conductive traces of the printed circuit boards extend to the openings, which is to say to the fastening elements, the fastening elements simultaneously serve as electrical connectors to supply the electrical and electronic components provided on the printed circuit boards with the necessary electric power. 
         [0012]    In another embodiment, multiple fastening elements can be provided for each through channel, wherein each individual fastening element passes through only one opening, and after that is connected mechanically and in an electrically conductive manner to the next fastening element. 
         [0013]    In the printed circuit board stack, individual fastening elements, for example the fastening element or elements of one through passage, or all fastening elements may be intended for the electrical supply. If only one fastening element is to serve as the electrical connection, then the other fastening elements serve only for mechanically connecting the printed circuit boards in the printed circuit board stack. If multiple fastening elements, or all fastening elements, are intended for the electrical connection, then preferably only one fastening element establishes an electrical connection with the power supply. 
         [0014]    In a special embodiment, a specially designed base plate and/or cover plate is provided for structural reinforcement of the printed circuit board stack. This base plate and/or cover plate can itself carry electronic components and be a printed circuit board, or can only have conductive traces in order to achieve the electrical connection between the fastening element supplied with electric power from outside and the other fasting elements of the printed circuit board stack. 
         [0015]    This novel electronic component represents a compact design of a printed circuit board stack, which, owing to the elimination of plug connections and soldered points, ensures high operational reliability, even in the case of vibrations, shocks and temperature differences, and furthermore is robust and compact in design. In addition, weight is advantageously saved due to the elimination of electrical connectors. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0016]    The invention is explained below with exemplary embodiments with the aid of the drawings. Shown are: 
           [0017]      FIG. 1  a perspective view of an electronic component according to the invention; 
           [0018]      FIG. 2  a simplified perspective representation of another electronic component; 
           [0019]      FIG. 3 a    fastening elements for an electronic component; 
           [0020]      FIG. 3 b    another fastening element for an electronic component; 
           [0021]      FIG. 3 c    another fastening element for an electronic component. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    Shown in  FIG. 1  is an electronic component, namely a printed circuit board stack  1  with four printed circuit boards  10 . Each printed circuit board is equipped with multiple electronic components  11  that are supplied with electric power through electrically conductive connections. These conductive traces  12  are arranged substantially on the underside in this embodiment shown in  FIG. 1 . Each printed circuit board  10  here consists of a square, insulating support that carries the electronic components  11 . Provided at each corner of the printed circuit board stack  1  is a fastening element  20  for electrically conductive and mechanical connection, namely, a bolt shown in  FIG. 3 b   , which bolts are inserted from below through openings  13 ,  14 ,  15 ,  16  in the printed circuit boards  10 , which are more clearly visible in  FIG. 2 , and are coupled to nuts  26  at the top to form a sturdy threaded connection. For a multi-layer printed circuit board stack  1  of this nature, spacers  25  are arranged between the individual printed circuit boards  10 . These spacers are advantageously connected to the fastening element  20 . In this case, they are nuts that are screwed onto the shank  21 , which has a thread  24 . The fastening element  20 , which includes the spacers  25 , advantageously ensures a mechanical fastening and a simultaneous carrying of current from one printed circuit board  10  to the next printed circuit board  10 . As is evident from  FIG. 1 , the printed circuit board stack  1  is a compact, extremely robust unit that does not permit any deformation, even in the event of a crash of a model aircraft. 
         [0023]    Additional fastening elements  20  that can be used in the exemplary embodiment from  FIG. 1  are shown in  FIG. 3 a    and  FIG. 3 c   . The fastening element  20  in  FIG. 3 c    is a bolt that has a thread  24  only in the lower region, namely, for connection with the terminating nut  26 . In this case, the ring-shaped spacers  25  are merely pushed onto the shaft  21  of the fastening element  20 . However, they are firmly pressed against the individual printed circuit boards by the threaded connection with the nut  26 , and exert an adequate contact pressure on the conductive traces  12  that extend to the opening  13 ,  14 ,  15 ,  16 , thereby ensuring a good electrical connection. 
         [0024]    According to  FIG. 3 a   , fastening is also possible by means of multiple bolt-like fastening elements  20  that can be screwed into one another. Each bolt element  20  has a shank  21  with a thread  24  and a bolt head  22 . The thread  24  is not shown in  FIG. 2 . In the example from  FIG. 2 , the shank  21  is inserted from below into an opening  13 ,  14 ,  15 ,  16  until the head  22  rests against the underside of the printed circuit board  10 . The bolt head  22  can be flat in design in the bottom-most fastening element  20  in order to achieve a space-saving, compact unit. In the rest of the fastening elements  20 , the bolt head  22  represents the spacer  25 . After it is inserted through the first opening  13 ,  14 ,  15 ,  16 , the shank  21  of the bottom-most fastening element  20  is connected to the next bolt-like fastening element  20  located above it. For this purpose, the fastening element  20  preferably has a threaded receptacle in the bolt thread  22 . This fastening element  20  is inserted through the next opening  13 ,  14 ,  15 ,  16  in the same manner and connected to the next fastening element  20 . In this way, the bottom-most base plate  17  is connected to the printed circuit board  10  located above it, and correspondingly to the other identically designed square printed circuit boards  10 , which have openings  13 ,  14 ,  15 ,  16  at the same points, namely, in the corners. Above the cover plate, the top-most fastening elements  20  are each coupled to a nut  26 , and, in this way, a sturdy mechanical connection is achieved. In advantageous fashion, the openings  13 ,  14 ,  15 ,  16  are provided at the same point in all printed circuit boards  10  of the same size and shape so that when the printed circuit boards are arranged one on top of the other prior to assembly, these openings align and form a through channel for the fastening elements  20 . 
         [0025]    For the electrical supply to this printed circuit board stack  1  in this exemplary embodiment from  FIG. 2 , solely one fastening element  20 ′ is used, which in this case has a longer shank  21 , thereby allowing a connection with the structure of the aircraft. The electrical connection to the power supply is ensured by means of this fastening element  20 ′. The fastening element  20 ′—which is electrically conductive in design—reaches through the opening  14  and is mechanically and electrically connected to another fastening element  20 . This fastening element  20  has a bolt head  22  that is larger than the diameter of the opening  14  and can in this way make contact by means of its electrically conductive head  22  with the conductive traces  12  on the base plate  17 , which leads to the opening  13  as shown. In the same manner, it is also possible to provide, on this base plate  17 , conductive traces  12  to the other fastening elements  20  that reach through the openings  13 ,  15 ,  16 , in order to supply electrical energy through all fastening elements  20 . For reasons of better clarity, the electrical and electronic components  11  are omitted on the other printed circuit boards  10  in  FIG. 2 . Owing to the mechanical connection of the base plate  17  to the printed circuit boards  10  located above it, an electrical connection to the conductive traces  12  located on these printed circuit boards  10  is also achieved, these conductive traces in this case extending up to the openings  13 ,  14 . In the event that the base plate  17  has conductive traces  12  which also contact the fastening elements  20  that reach through the openings  15 ,  16 , then the electrical connection with the other printed circuit boards  10  can also be ensured through these fastening elements  20 . 
         [0026]    In addition, it is evident from  FIG. 2  that the heads  22  of the fastening elements  20  advantageously serve as spacers  25 . Serving in each case as a terminating fastener is a nut  26 , which is provided above the top-most printed circuit board  10 . The bottom-most plate, the base plate  17 , is reinforced to make for a sturdy unit and, in this example from  FIG. 2 , has only the conductive traces  12 . The printed circuit board stack  1  is mechanically connected to the aircraft body and electrically connected to the power supply by this reinforced base plate  17  and the fastening element  20 ′. However, a reinforced printed circuit board  10  can also be provided as the base plate  17 , as shown in  FIG. 1 . 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           1  component, printed circuit board stack 
           10  printed circuit board 
           11  electrical components 
           12  conductive traces 
           13  opening 
           14  opening 
           15  opening 
           16  opening 
           17  base plate 
           20 ,  20 ′ fastening element 
           21  shank 
           22  bolt head 
           24  thread 
           25  spacer 
           26  nut