Abstract:
An electronic control module for a gear mechanism controller in motor vehicles includes a printed circuit board and an electrical component. The printed circuit board has a mounting side and includes conductor tracks. The electrical component has an electrically conductive connection section. The control module further includes a press contact that is pressed into an opening in the printed circuit board such that it is mechanically fixed to the printed circuit board. The press contact forms an electrical contact with a conductor track of the printed circuit board via an electrically conductive mating connection section of the press contact. The connection section of the electrical component is connected to the mating connection section of the press contact by a welded connection. The connection technique enables soldered connections to be dispensed with and replaced by cold pressing of press contacts and subsequent welding by, for example, a copper/copper laser welding process.

Description:
BACKGROUND INFORMATION 
       [0001]    The present invention relates to an electronic control module, as it may be used in particular for transmission controls in motor vehicles, and a method for producing an electronic control module. 
         [0002]    In motor vehicles, electronic control modules are used in particular for controlling transmissions. In this case, it may be advantageous to arrange a control module at the transmission, for example, inside a transmission housing, in such a way that it comes into contact with the transmission fluid, for example, an aggressive transmission oil. 
         [0003]    The control modules may, for example, include electrical components such as plugs, sensors, actuators, at least one encapsulated control device (ICU, transmission control unit), and, if necessary, additional components. The electrical components may be arranged on a printed circuit board. The printed circuit board may be a conventional printed circuit board, on the surface of which or in the interior of which conducting paths are formed, with the aid of which the electrical components arranged on a placement side of the printed circuit board could be electrically interconnected. For this purpose, each of the electrical components may have electrically conductive terminal sections, for example, in the form of wires routed out of the component, by means of which the component may be brought into electrical contact with one of the conducting paths provided on the printed circuit board. 
         [0004]    An arrangement of the control module in the transmission fluid may pose major challenges for the packaging of the building components on the printed circuit board of the electronic control module, since the electrical connections are, for example, subjected to high temperature change loading and furthermore must be able to withstand the aggressive transmission fluid and possibly metal shavings contained therein. 
         [0005]    Conventionally, the electrical components have typically been soldered via their terminal sections to the conducting paths of the printed circuit board. US 2009/0176402 A1 and US 2008/0144260 A1 demonstrate, for example, plug parts whose terminal elements are soldered into vias of the printed circuit board. 
         [0006]    However, it has been observed that solder connections cannot always ensure long-term reliability which is required, for example, in vehicle production; therefore, malfunctions or failures may occur in electronic control modules for transmission controls. 
       SUMMARY OF THE INVENTION 
       [0007]    Embodiments of the present invention enable an electronic control module which in particular is better able than conventional control modules to meet the high demands arising in the case of use as a transmission control, with respect to a long-term, stable electrical connection between electrical components and conducting paths of a printed circuit board. In particular, embodiments of control modules according to the present invention may be produced in a simple, reliable, and/or economical manner. 
         [0008]    According to a first aspect of the present invention, an electronic control module, in particular for a transmission control, is provided, which includes a printed circuit board and at least one electrical component. The printed circuit board is provided with conducting paths and has a placement side. The electrical component has at least one electrically conductive terminal section. The control module is characterized in that it furthermore includes at least one press contact which is pressed into an opening in the printed circuit board in such a way that it is mechanically fixed to the printed circuit board and forms both a mechanical and an electrical contact with a conducting path of the printed circuit board, via a subarea of an electrically conductive mating terminal section of the press contact pressed into the printed circuit board. Furthermore, a weld connection between the terminal section of the electrical component and the mating terminal section of the press contact is provided. 
         [0009]    According to a second aspect of the present invention, a method for producing an electronic control module, in particular a control module according to the above first aspect of the present invention, is described. In the method, a printed circuit board having a placement side and having conducting paths, and an electrical component having at least one electrically conductive terminal section, are provided. The method is characterized in that a press contact is pressed into an opening in the conducting path in such a way that it is mechanically fixed to the printed circuit board and forms both a mechanical and an electrical contact with a conducting path of the printed circuit board, via a subarea of an electrically conductive mating terminal section of the press contact pressed into the printed circuit board; and the terminal section of the electrical component is welded to the mating terminal section of the press contact. 
         [0010]    Embodiments of the present invention may inter alia be considered to be based on the ideas and thoughts described below. 
         [0011]    As initially stated, in the case of conventional electronic control modules, electrical components have generally been soldered to conducting paths of a printed circuit board. For this purpose, for example, terminal sections of an electrical component have been arranged in through-holes in the printed circuit board and then dipped from an opposite side into a solder bath, so that solder was able to electrically conductively connect the terminal sections to the conducting paths. 
         [0012]    However, it has been observed that solder connections established in such a way may have a certain probability of failure, for example, in the range of 2 ppm; therefore, faults may occur during the operation of the electronic module. This problem has been exacerbated in the last several years, since, according to recent standards, it is generally no longer allowed to use solder containing lead. Therefore, solder connections must be elaborately developed and tested and adapted to particular thermomechanical characteristics of lead-free solder. 
         [0013]    It is therefore provided to replace conventional solder connections in an electronic control module by a new type of electrical connection of electrical components to a printed circuit board, in which solder may be dispensed with. In the case of this connection, first, one or multiple press contacts are pressed into an opening in the printed circuit board. 
         [0014]    Here, a press contact may be understood to mean a small component which is made entirely of electrically conductive material, for example, a metal, or is at least partially provided with an electrically conductive material, for example, on its surface. In this case, the press contact has at least one web, which is sized in such a way that it may be pressed into an opening provided in the printed circuit board under pressure. The structure or the dimensions of the web are designed in such a way that conductive material of the press contact is pressed to conductive material of a conducting path of the printed circuit board in the area of the opening, at least at a subarea of the electrically conductive mating terminal section of the press contact pressed into the printed circuit board, and an electrical connection is thus established. Furthermore, the web of the press contact is sized in such a way that the press contact is kept mechanically stable on the printed circuit board after pressing into the opening. Since pressing in the press contact generally requires no local heating of components to be connected, it is also referred to as cold contacting. 
         [0015]    In addition to the web pressed into the opening, the press contact has an electrically conductive mating terminal section. This mating terminal section is electrically conductively connected to the electrically conductive material at the web of the press contact, so that, after pressing in, an electrical connection between the mating terminal section and the conducting path of the printed circuit board is provided overall. 
         [0016]    After the press contact or the press contacts have been arranged on the printed circuit board, the electrical components may be arranged on the placement side of the printed circuit board, and their terminal sections may then be suitably welded to the mating terminal sections of the press contacts. 
         [0017]    In the described production method or the correspondingly produced electronic control module, soldering of electrical components may be omitted and replaced by the pressing in of press contacts and subsequent welding of the connection and mating terminal sections. As a result, testing and development costs may be significantly reduced in comparison to conventional soldering. For example, solder joints must generally be tested four times longer than weld joints. In addition, it may be assumed that a failure statistic in the case of weld connections is significantly lower than in the case of solder connections. In particular, it is assumed that weld connections exhibit practically no faults during operation, whereas a failure statistic of 2 ppm may be observed in the case of solder connections. In addition, weld connections have a significantly higher mechanical load capacity and temperature resistance in comparison to solder connections. 
         [0018]    As described in greater detail below, under the provided production method, thermally induced mechanical stress within the electronic control module may furthermore be significantly reduced, since, for example, the local, rapid welding of the connection and mating terminal sections results in considerably less heat input than with conventional soldering processes. 
         [0019]    According to one embodiment, the terminal section of the electronic component and the mating terminal section of the press contact may be formed with copper, i.e., made of a material containing copper or made completely of copper. Not only does copper have excellent electrical conductivity, it also has a relatively low melting point, so that it can be welded even at low heat levels. 
         [0020]    In particular, it may be advantageous to weld the terminal section of the electrical component to the mating terminal section of the press contact by means of a laser. Laser welding is well suited to industrial applications and may provide many advantages, for example, high positioning accuracy of the weld, non-contact and thus contamination-free welding, energy efficiency, etc. 
         [0021]    In particular, for the laser welding of copper which is contained, for example, in the terminal section and the mating terminal section, green laser light may be used. For copper-copper welding, considerably smaller and more economical systems may be used than is known, for example, in NiFe—Cu laser welding, which is conventionally often used for other purposes. A laser which is applicable to Cu—Cu welding may, for example, have considerably lower laser power than is the case in conventional lasers used for welding. 
         [0022]    For example, the laser may have a laser light output in the continuous operating mode of less than 500 W, preferably less than 200 W. For Cu—Cu welding, for example, disk lasers may be used, which emit laser light in the green wavelength range in the continuous operating mode and have a maximum laser output of 200 W, and may also have a very high beam quality due to a beam quality factor of constantly less than 1.15. In order to achieve an emission wavelength of, for example, 515 nm, frequency doubling of the disk laser radiation is carried out within a laser resonator. The green laser light thus generated is absorbed by copper materials significantly better than laser radiation in the infrared wavelength range. It has furthermore been observed that in the case of laser welding using green, relatively low-power laser light, essentially no weld spatters occur, thereby considerably simplifying the welding process. 
         [0023]    According to one embodiment of the present invention, the terminal section of the electrical component and the mating terminal section of the press contact may be arranged parallel to the placement side of the printed circuit board. As a result, it may be achieved that the two sections are easily accessible and may be welded to each other from above by means of a laser. 
         [0024]    According to one embodiment of the present invention, the weld connection between the terminal section of the electrical component and the mating terminal section of the press contact may be covered with an electrically insulating material. For example, the entire exposed area of the two connection and mating terminal sections may be covered with electrically insulating material and thus be protected from dirt, moisture, or corrosion. The electrically insulating material may, for example, be provided in the form of a coating or a potting compound, for example, globe top or epoxy. 
         [0025]    According to one embodiment of the present invention, the electronic control module furthermore may include a carrier plate which is arranged on the printed circuit board on a surface opposite to the placement side, wherein the carrier plate is made of plastic. In conventional control modules, a carrier plate made of metal has usually been provided on a printed circuit board. A pure plastic carrier plate would be thermally heavily damaged during conventional soldering, for example, in particular in the pre-heating path; therefore, conventional metal plates are used as carrier plates. In the design provided here, cold-contacting is used; therefore, carrier plates made of plastic may also be used. In addition, a plastic carrier plate may also be closed underneath, thus providing insulation protection with respect to pins which possibly protrude downward. A metal insert is usually required beneath an electronic system in order to be able to dissipate heat losses into the transmission by acting as a cooling surface. 
         [0026]    The carrier plate may have a blind hole which is adjacent to an area of a press contact projecting beyond the carrier plate, which accommodates this area. In other words, the carrier plate may be attached to the surface of the printed circuit board opposite to the placement side and may have correspondingly sized recesses, since portions of the press contacts inserted therein may protrude at this surface in the area of the through-holes in the printed circuit board. These recesses may be formed as blind holes, i.e., not continuous but rather closed on one side, so that the protruding areas of the press contacts are able to be accommodated in the recess of the carrier plate and are protected outwardly from dirt and corrosion. 
         [0027]    By using a carrier plate made of plastic instead of metal, a considerable weight reduction may be achieved for the control module. In addition, a shaving protection cover on the bottom side of the control module may be omitted. As described above, a shaving protection cover on the top side of the printed circuit board may be replaced by providing an electrically insulating material, for example, in the form of a coating or a potting compound. 
         [0028]    By means of the provided production method or with the correspondingly produced electronic control module, a molded housing and a fastening spring for the electronic system may be omitted altogether. 
         [0029]    In addition, no pronounced thermal stresses occur in the module, since all components are connected to the printed circuit board, and the carrier plate is only an electrical insulator and a transport protection if no additional demands, for example, functions in the form of an integrated plug, are made on it. 
         [0030]    It is to be noted that possible features and advantages of embodiments of the present invention are described herein in part with reference to an electronic control module and in part with reference to a method for producing an electronic control module. Those skilled in the art will recognize that the features may be suitably combined, adapted, or exchanged, in order to achieve additional embodiments of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    Embodiments of the present invention will be described with reference to the appended drawings, wherein neither the description nor the drawings are to be interpreted as restricting the present invention. 
           [0032]      FIG. 1  shows a cross section through a conventional transmission control module. 
           [0033]      FIG. 2  shows a cross section through a control module for a transmission control according to one embodiment of the present invention. 
           [0034]      FIG. 3  shows an enlarged cross-sectional view of an electrical connection of an electrical component to a printed circuit board of a control module according to one embodiment of the present invention. 
       
    
    
       [0035]    The figures are merely schematic and are not true to scale. In the figures, identical reference numerals refer to identical or identically acting features. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0036]      FIG. 1  shows a conventional transmission control module  1 , in which multiple electrical components  3  are soldered to a printed circuit board  5 . 
         [0037]    The printed circuit board  5  (PCB) has multiple conducting paths on its surface or integrated into its interior (not depicted separately in  FIG. 1 ). The electrical components  3  may, for example, be arranged as a high-current assembly  7 , rotational speed, position, or displacement sensors  9 , electronic circuits  11 , pressure sensors  13 , and/or plug&#39;s  15 , on a placement side  17  of the printed circuit board  5 . Each of the components  3  is electrically connected to conducting paths of the printed circuit board  5  via associated electrically conductive terminal sections  19 , so that the individual components  3  can be electrically interconnected via the conducting paths. For this purpose, the terminal sections  19  are plugged through through-holes  21  in the printed circuit board  5  and are, for example, soldered to the conducting paths of the printed circuit board  5  from below by dipping in a solder bath. 
         [0038]    In order to protect the terminal sections  19 , for example, from metal shavings which may be contained in ambient transmission oil, shaving protection covers  23  are provided. A carrier plate  25  made of metal is provided on the printed circuit board  5  opposite the placement side  17 . On the one hand, this carrier plate  25  may stabilize the printed circuit board  5 , and on the other hand, ensure good heat transfer from the electrical components to a transmission component  27 , for example, a hydraulic plate, to which the transmission control module  1  is attached. Furthermore, on the bottom side of the printed circuit board  5 , a pressure regulator  29  is provided with a plug which is connected via a contact block or mating plug  31  to the printed circuit board  5 . 
         [0039]      FIG. 2  shows an electronic control module  1  according to one embodiment of the present invention. 
         [0040]    As in a conventional transmission control module  1 , various electrical components  3  are arranged on the placement side  17  of a printed circuit board  5  in the form of various components  7 ,  9 ,  11 ,  13 ,  15 . However, terminal sections  19  of these component parts  3  are not soldered to conducting paths of the printed circuit board  5 . Instead, press contacts  39  are pressed into openings  21  of the printed circuit board, so that on the one hand, they are mechanically fixedly anchored, and on the other hand, form an electrical contact with the conducting paths of the printed circuit board  5 . The terminal section  19  of the electrical component  3  is locally welded to a mating terminal section  20  of a press contact  39 . 
         [0041]    The arrangement and electrical connection of the component  3  to the printed circuit board  5  is shown magnified in  FIG. 3 . The press contact  39  is designed and sized in such a way that it may be pressed into one of the openings  21  in the printed circuit board  5  under pressure. In this case, the press contact  39  may be held in the printed circuit board  5  via a thickened area  45  in such a way that a mechanically stable fixing is provided, and an electrical contact is formed between the mating terminal section  20  of the press contact  39  on the one hand, and conducting paths  16  provided in the printed circuit board  5  on the other hand. In this case, the conducting paths  16  may run in the interior of the printed circuit board  5  and contact a partial area of the mating terminal section  20  in the interior of the opening  20 . For example, the interior of the opening may be provided with a metal layer. 
         [0042]    The press contact  3  may, for example, be made completely of metal, in particular, for example, completely of copper or a copper alloy. If necessary, it may be provided with a surface coating, for example, made of gold or tin. The press contact may be one piece. Furthermore, the press contact may be essentially rectangular, so that a lower leg  47  may be introduced into the opening  21  of the printed circuit board  5 , perpendicular to its plane, and an upper leg  49  is arranged at a right angle to the lower leg  47  and may thus run essentially parallel to the placement side  17  of the printed circuit board  5 . In this case, the press contact  39  may be designed in such a way that it rests against the placement side  17  with its upper leg in the state of being pressed into the printed circuit board  5 . 
         [0043]    A plastic frame  35  which is also provided at the press contact  39  may protect partial areas of the press contact  39  as well as the opening  21  from contamination, in particular due to metal shavings. 
         [0044]    The electrical component  3  arranged on the placement side  17 , for example, in the form of a sensor  9 , has a terminal section  19  which is arranged at least partially overlapping with the mating terminal section  20  of the press contact  39 . Both sections  19 ,  20  thus run parallel to the placement side  17  and may thus be easily connected to each other via a weld  43  by means of a laser irradiated perpendicular to the placement side  17  from above, illustrated by the arrow  41 . 
         [0045]    In the area of the weld  43  and the adjacent partial areas of the connection and mating terminal sections  19 ,  20 , a subsequently applied layer made of electrically insulating material  37 , for example, a globe top, may provide protection from impurities. 
         [0046]    As depicted in  FIG. 2 , the printed circuit board  5  may be connected to the transmission component  27  via a carrier plate  26  made of plastic. A metal plate  24  may be locally integrated into the carrier plate  26 , for example, in the area of an electronic circuit  11 , which generates a great deal of heat during operation, in order to be better able to dissipate heat to the transmission component  27 . 
         [0047]    Adjacent to areas of the press contacts  39 , which project downward over the printed circuit board  5 , a blind hole  33  may be formed in each case in the carrier plate  26 , which is sized sufficiently large so that the areas of the press contact  39  projecting beyond the printed circuit board  5  may be accommodated in it on the one hand, and on the other hand, for example, are protected from contamination, since the blind hole  33  is closed downwardly. 
         [0048]    Finally, an installation sequence within the scope of producing an electronic control module is to be described. 
         [0049]    First, the press contacts  39  are fitted into the openings  21  of the printed circuit board  5 . Bonding surfaces  51  are cleaned if necessary. The electronic circuit  11  is glued in and bonded and sealed by an impervious cover  23 , for example, by means of a glue or a sealing ring. Subsequently, the printed circuit board is populated with all remaining components  3 . Assemblies, for example, sensors  9  and plugs  15 , are glued, or are snapped in place or attached by riveting into the printed circuit board  5  via holes. Subsequently, the plastic carrier plate  26  is prepared, if necessary, having an inserted or extrusion-coated metal plate  24  for cooling the electronic circuit  11 . The populated printed circuit board  5  may be placed on the carrier plate  26  now or at a later point in time, and attached at a few points, for example, by gluing, riveting, or latching. 
         [0050]    The electrical components  3 , for example, the sensors  9 ,  13 , etc., have terminal sections  19  which, after the installation, rest against weld surfaces at the mating terminal sections  20  of the press contacts  39 , having a slight vertical pre-tensioning. All individual parts are able to balance each other until then with respect to their positions. Stresses and warping during installation do not essentially affect the electrical connection of the components  3  to the printed circuit board  5 . The welding of the terminal sections  19  to the mating terminal sections  20  takes place only now, virtually without thermal distortion, due to low melting temperatures of the press contacts  39  which are, for example, made of copper, and minimal heat input on a very small surface (weld point). A green laser light is used as a laser beam  41 , which was developed specifically for copper-copper welds. Subsequently, the electrical connection formed in the area of the connection and mating terminal sections  19 ,  20  may be covered with covers or a coating or potting material made of electrically insulating material, for example, globe top. 
         [0051]    Press contacts are more economical and more reliable than, for example, THT solder joints (through-hole technique). Globe top may also protect the press contacting in a printed circuit board opening  21  from a corrosive attack by the surrounding medium, for example, aggressive transmission oil. The overall population of the printed circuit board  5  may take place by means of a fully automated installation on a very compact system. No large selective or continuous furnace soldering systems and no preheating or cooling sections are required. The press contacts  39  may be pressed in and laser-welded in a controlled manner. As a result, testing procedures, for example, the usual x-raying during soldering, may be omitted. 
         [0052]    The inserted metal plate  24  included in the embodiments described above, which may act as a heat-conducting plate, may be omitted if cooling oil flows past the printed circuit board  5 , for example, in the area of the electronic system, or a plateau-like protuberance of the hydraulic plate acting as a transmission component  27  contacts the printed circuit board  5  directly through the carrier plate  26 . The printed circuit board  5  may furthermore have thermal vias below the electronic system, in order to be able to effectuate better cooling.