Abstract:
A subassembly, intended for use in motor vehicles in particular, consisting of a one-piece or multi-part housing, a plug unit with connecting pins formed integrally with the housing, and a circuit board to accommodate components, wherein the circuit board is configured and arranged in such a way that the connecting pins of the plug unit are guided directly onto or into the circuit board.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a subassembly, intended for use in motor vehicles in particular, consisting of a one-piece or multi-part housing, a plug unit with connecting pins, and a printed circuit board incorporating strip conductors and capable of accommodating components, whereby the plug unit forms an integral part of the one-piece or multi-part housing and the circuit board is arranged in such a way that the plug unit connecting pins are guided directly onto the circuit board. 
     A subassembly of this type, in this case configured as an electrical switching device, is described in publication DE 32 48 715 A1. As a means of achieving a moisture-proof housing which is suitable to accommodate, e.g., ignition systems, fuel injection systems, anti-lock braking systems or transmission control systems in motor vehicles, plug connectors  18  (among other things) are integrated into the housing during the manufacturing process by being cast around with plastic (FIGS. 2,  3 ). In this way, the measures required to seal a separately mounted plug are eliminated. 
     A disadvantage of this design is that the plug terminals must be connected to the electric switching elements  16  by means of a fastening agent  17 , e.g., bonding wires, which necessitates additional work stages. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide a subassembly which does not need any fastening components between the connecting pins and the circuit board. 
     According to the invention, there is a circuit board provided with strip conductors to accommodate components in a one-piece or multi-part housing, with which the plug unit is integrally formed, arranged in such a way that the plug unit connecting pins are guided directly onto the circuit board. 
     The advantages of the invention, in particular, are that, with the integration of the plug unit into one part of the housing, additional sealing is eliminated and no additional manufacturing operations are needed to achieve an electrical connection between the connecting pins and the strip conductors on the circuit board or components arranged thereon. 
     Advantageous embodiments, features and developments of the invention. 
     According to one such feature, contact faces are arranged on the circuit board, while the connecting pins are configured as spring-loaded plug pins. Contact is made by the pressing action of the spring-loaded plug pins onto the contact faces. 
     According to another feature, the plug unit is provided with stiffening devices which prevent the spring-loaded plug pins from spreading or springing back when pressed against the contact faces of the circuit board. 
     According to a further feature, locating and assembly aids are provided on the housing and circuit board which permit machine assembly and achieve the effect of guiding the plug unit connecting pins directly onto the contact faces of the circuit board. The spring-loaded plug pins make contact by the application of pressure at that point. 
     According to another feature, the locating and assembly aids described above are also used as fastening agents between the housing and circuit board or multiple housing components. 
     According to still further feature, so-called soldering bumps are applied to the contact faces of the circuit. 
     According to still another, soldering eyelets are arranged on the circuit board as an alternative, into which the plug unit connecting pins are soldered. 
     According to a particularly advantageous development of the invention contact-making between the connecting pins of the plug unit and the soldering eyelets of the circuit board is achieved in that the connecting pins possess a somewhat larger diameter than the soldering eyelets and are tapered at the tip, so that contact is established when the connecting pins are pressed into the soldering eyelets. 
     According to another feature, one part of the housing is configured as a baseplate with a surrounding groove, which serves to accommodate another part of the housing configured as a lid or cover. This surrounding groove preferably exhibits a conical profile. 
     According to another advantageous embodiment of the subassembly an area is formed in the rim of one part of with the housing by means of a two-component injection process, the said area being composed of a different, softer material, the purpose of which is to seal the subassembly against external (environmental) influences such as moisture or dust. 
     Finally, according to another feature, a number of plug units can also be arranged in one or more components of the subassembly housing. 
     An advantage of the invention is that no rivets, screws or similar are needed to fasten the individual housing components to each other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A first example of an embodiment of the invention is depicted in the drawings and will be described in detail below. A second example of an embodiment will also be explained. The drawings depict the following: 
     FIG. 1 is a perspective representation of a first example of an embodiment of a subassembly complying with the invention, consisting of a baseplate, circuit board and cover with integral plug unit; 
     FIG. 2 is a side view of a fully assembled subassembly; 
     FIG. 3 is a front view of the subassembly depicted in FIG. 2, and 
     FIG. 4 is a sectional drawing of the subassembly depicted in FIG.  2 . 
     FIG. 5 is an elevation showing the relationship between the outer diameter of the pin and the inner diameter of a metallized bore for a solderless press fit connection. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 to  4  depict a first example of an embodiment of a subassembly complying with the invention, consisting of a baseplate  3 , a circuit board  2  and a cover  1 , advantageously composed of a glassfibre reinforced plastic, into which a plug unit  10  is integrated which is made of the same material as the cover  1 . The plug unit  10  contains connecting pins  11  made of a satisfactorily conductive, torsion resistant metal such as a copper alloy, and is provided with a polarising arrangement  13  for the purpose of ensuring that a related plug  15  with a signal lead  16  cannot be installed with the poles reversed. The locating devices  12 , configured as lugs, ensure the precise alignment of the circuit board  2 , so that the connecting pins  11  can be positioned accurately on the contact faces  20  or in soldering eyelets  24 . In combination with the locating devices  32 , configured as sockets in the baseplate  3 , they ensure that the rim of the cover  1  can be fitted without difficulty into a surrounding groove  33  in the baseplate  3  during the assembly process. 
     In conjunction with the sockets  32 , the lugs  12  also serve to secure the housing components  1  and  3  of the subassembly on the completion of the assembly process, in that the ends of the lugs  12  projecting through the socket  32  can first be ultrasonically heated, then pressed flat. To ensure that this does not produce any excrescences on the underside of the baseplate  3 , recesses are provided around the sockets  32  to accommodate the flattened lugs  12  (FIG.  4 ). Fastening holes  34  permit the subassembly to be secured to a designated surface by means of rivets or screws. 
     Contact faces  20  are arranged on the circuit board  2  for contact-making with the connecting pins  11 , the said contact faces mainly being connected to electronic components  25  by means of strip conductors  21 . This being so, three types of contact face  20  offer inherent advantages. 
     In the first type, the contact faces  20  are configured as soldering eyelets  24  which are of a greater diameter than the connecting pins  11 . During assembly, the connecting pins  11  are inserted through the soldering eyelets  24  in a known manner and are soldered. In the second version, so-called soldering bumps  23  are applied to the contact faces  20 . For the purpose of contact-making, the connecting pins  11  are advantageously provided with tapered tips and are configured as spring-loaded plug pins; these are supported against the cover  1  by means of stiffening elements  14  (FIG. 4) and are pressed into the soldering bumps  23 . In the case of the third type of contact face  20 , these are again configured as soldering eyelets  24  which, in contrast to the first version, exhibit a slightly smaller diameter than the connecting pins  11  as shown in FIG.  5 . It is of advantage if the tips of the connecting pins  11 , again configured as spring-loaded plug pins, are tapered. For the purpose of contact-making, the circuit board  2  is pressed onto the connecting pins  11  with the aid of the locating devices  12  and  22 , whereby the stiffening elements  14  (FIG. 4) prevent the connecting pins  11 , configured as spring-loaded plug pins, from spreading or springing aside. When the two elements are pressed together, the circular shape of the soldering eyelets  24  is slightly notched by the hard spring-loaded plug pins  11 . Spacers  31  on the baseplate  3 , and the stiffening elements  14 , prevent the contacts, which provide permanent contact-making with excellent conductivity, from separating after assembly. The method of establishing contact described as the third and most advantageous configuration is also designated as a “solder-free-press-fitting technique”. 
     To provide electromagnetic shielding for the (electronic) components  25  mounted on the circuit board  2 , which can also include an acceleration sensor, three measures are of advantage. In the first of these, contact faces  20  are arranged on the top and underside of the circuit board  2  at those points which come into contact with the baseplate  3  and the cover  1 . As the second measure, the baseplate is made of a mechanically strong, electrically conductive metal, preferably diecast aluminum, and is provided with spacers  31  and a transverse rib  35  at those points which correspond to the contact faces  20  on the circuit board  2 . As the third measure, the cover  1  is provided on the inside with either a vacuum metallized surface of a metallic lining, corresponding in shape to that of the cover  1 , wherein provision must be made to ensure that the metallized surface or the lining is electrically connected to the contact faces  20  of the circuit board  2  after assembly. Together, all three measures ensure the electromagnetic compatibility of the subassembly, in that any radiated electromagnetic waves received are trapped by the metallized surface or lining, directed through the contact faces  20 , the rib  35  and the spacers  31  on the baseplate  3 , and discharged to ground via the screws or rivets which penetrate through the mounting holes  34 . 
     In general, the subassembly described as the first typical embodiment is intended to be used in situations where there is a need for the sensitive components  25  on the circuit board  2  to be protected against moisture and electromagnetic radiation, e.g., when the subassembly is mounted in the engine compartment of a motor vehicle. 
     In a second example of an embodiment of the subassembly complying with the invention, there is a one-piece housing  1  which serves to accommodate and simultaneously to cover a circuit board  2  which is provided with switching devices  25 . 
     By virtue of the fact that the cover is provided with fastening facilities  34 , a baseplate of the type employed in the first typical embodiment is eliminated (FIG.  1 ); the subassembly consisting of a housing  1  and circuit board  2  can be secured, in a suitable place, directly to the interior compartment of the vehicle or a flat part of the vehicle body. The circuit board  2  can then accommodate, e.g., a hazard warning light circuit. 
     In general, the subassembly described as the second typical embodiment can be used in situations where it is not necessary to protect the switching components on the circuit board by a moisture-proof housing or to provide a mechanically strong baseplate.