Abstract:
A method of assembling and sealing a circuit board within a housing includes the steps of placing the circuit board within the housing, filling the space above the circuit board or around the circuit board with a potting material, and then exhausting that cavity of gases during a curing process of the potting material. Exhausting of the gases is performed and accommodated by a vent opening. An access opening is in communication with the vent opening and provides for the injection of sealant to block the vent opening.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     The application claims priority to U.S. Provisional Application No. 60/583,265 which was filed on Jun. 24, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     A printed circuit board (PCB) is a delicate device that is susceptible to damage if not adequately protected. PCBs that are utilized in automotive applications are protected by being installed and mounted within a housing. The housing can be fabricated from many different materials based on the location in which the PCB will be located and the application for which the PCB is used.  
         [0003]     Typically, a PCB is placed within a housing and then sealed with a potting material to prevent contamination or moisture from affecting operation. The potting material is typically a liquid plastic material that hardens through a heat curing process. In some instances the potting material may consist of an epoxy that is mixed with a hardening agent. Use of either type of potting material generates heat that can generate gases. The gases must be exhausted to prevent degradation to the potting material. Preferably, gases are exhausted in a controlled manner and not merely allowed to bubble up through the potting material. Accordingly, a housing is typically provided with a vent opening that provides for the exhaust of the generated gases.  
         [0004]     Disadvantageously, the vent opening provides a path for moisture and other contaminants to enter the housing and the cavity within which the PCB is located. The vent opening typically is open to a portion of the housing that will be plugged from contact with the environment, such as for example within a connector housing. In this way, the seal for the connector will also prevent moisture from intruding into the sealed housing. However, in some applications it is desirable to further seal the vent opening. Sealing a vent opening within a connector requires insertion of a tool that can undesirably contact and possibly dislodge electrical connections disposed within the connector.  
         [0005]     Accordingly, it is desirable to develop a venting method and device to provide for exhausting gases that is capable of being sealed without interfering with desired electrical connections.  
       SUMMARY OF THE INVENTION  
       [0006]     An example method and housing according to this invention protects a printed circuit board (PCB) and provides for the exhaust of gases generated during curing. The housing and method of this invention also provides for the sealing of the vent opening.  
         [0007]     An example housing according to this invention includes a vent opening. The vent opening provides for the escape of gases that are generated during the curing process. The housing is provided with a cavity within which a PCB is mounted. A space above the threaded circuit board is filled with a potting material. The potting material is cured to harden and therefore protect the threaded circuit board against contamination, water intrusion, and other outside environmental elements that may affect operation of the printed circuit board. As appreciated, during the heating process heat is generated by the potting material. The heat generating by the potting material creates gases within the housing and specifically within a lower space below the printed circuit board. The housing includes the vent opening to provide a defined path within which the gas may escape. The vent opening is in communication with a protected exterior surface of the housing. In an example, the housing includes a connector pocket. The vent opening opens within the connector pocket. During operation, a connector inserted into the connector pocket includes a seal that provides a seal to the intrusion of moisture and other contaminants. In some applications it is desirable to plug up all paths to the housing cavity. This includes the opening of the vent opening to the connector pocket. However, within the connector pocket is also a terminal. Therefore, to plug the vent opening a tool or other device must be inserted into the connector pocket to inject a sealant into the vent opening. The close proximity that a tool must be placed relative to the terminal is not desirable. In some instances, the tool may cause movement of the terminal that may affect other performance.  
         [0008]     For this reason, the housing assembly according to this invention includes a sealing access opening that is in communication of the vent opening. The sealing access opening is in communication with the vent opening on a first side and an exterior non-protected surface on another side. Once the potting material has fully cured sealant is injected into the sealant access opening to fill the vent opening. This provides an alternate channel and opening to the vent opening within which sealant may be injected. Because the sealant access opening is not within the connector pocket there is substantially no possibility of affecting the terminal position.  
         [0009]     Accordingly, the housing and method according to this invention provides the venting required along with a means of sealing the vent opening without inserting affecting the within the connector pocket.  
         [0010]     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a cross-sectional view of a housing and a connector assembly according to this invention.  
         [0012]      FIG. 2  is a cross-sectional view of the housing and connector assembly according to this invention with the vent opening filled with sealant.  
         [0013]      FIG. 3  is a schematic representation of the housing assembly and method according to this invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]     Referring to  FIG. 1 , a housing assembly  10  includes a housing  12  that defines a cavity  14 . The cavity  14  is formed and configured to accept and protect a printed circuit board  22 . The printed circuit board  22  is disposed and inserted within the cavity  14  and rests on a mounting ledge  19 . The printed circuit board  22  defines an upper space  26  and a lower space  28  when inserted within the cavity  14 .  
         [0015]     The housing  12  includes an integral connector body  18 . The connector body  18  defines a connector pocket  20 . Within the connector pocket  20  is a terminal  16 . In this view a single terminal  16  is shown, however, this housing configuration may include several other terminals that are disposed within the connector pocket  20 . The terminal is provided within the connector pocket  20  in a desired position. This desired position is maintained to allow mating connectors to be electrically connected and communicate with the terminal  16 .  
         [0016]     The printed circuit board  22  within the cavity  14  is filled in the upper space  26  with a potting material  24 . The potting material  24  may be of any composition known to a worker skilled in the art. This may include potting material that is cured with the application of heat or the potting material that is mixed just prior to the filling of the cavity  14  and that hardens due to the mixture of several components. In either case, once the potting material  24  begins curing, heat is generated. Heat generated by the potting material  24  creates gases within the cavity  14 . These gases within the cavity  14  can naturally escape when in the upper space  26 . However, within the lower space  28  the gases are trapped. Escape of the gases is not desirable through the potting material  24 . This is because escape of gases through the potting material would create undesirable air bubbles that can degrade the protection function of the potting material  24 .  
         [0017]     A vent opening  30  is provided to exhaust gases from the lower space  28 . The vent opening  30  communicates between the lower space  28  of the cavity  14  and a protected outer surface  36 . The protected outer surface  36  is disposed within the connector pocket  20 . As appreciated, the connector pocket  20  is not exposed once the housing  12  is inserted and installed within an automobile. This is because a mating connector will include seals that form a barrier to contaminants and moisture. However, in some applications it is desirable to plug the vent opening  30  once the potting material  24  has fully cured. Plugging of the vent opening  30  completes the seal of the cavity  14  and is therefore desirable in many applications. However, the filling of the vent opening  30  requires insertion of a tool into the connector pocket  20 . In some instances, insertion of a tool within the connector pocket  20  is not desirable as it may errantly contact the terminal  16  moving it from its desired location.  
         [0018]     Accordingly, the housing  12  of this invention includes a sealant access opening  32 . This access opening allows for the insertion of sealant into the vent opening  30  without the need for inserting a tool in the connector pocket  20 . The access opening  32  communicates with the vent opening  30  on one side and with a non-protected exterior surface  34  on another side.  
         [0019]     Referring to  FIG. 2 , once the potting material  24  has fully cured and all gases have been allowed to escape from the space below the printed circuit board  22 , a sealant  40  is injected into the access opening  32  to fill the vent opening  30 . The sealant  40  provides a barrier to water intrusion, moisture and other contaminants that may adversely affect operation of the printed circuit board  22 . The sealant  40  may comprise any known compound and can be of any composition or material that will flow naturally within the access opening  32  and then harden or cure such that the vent opening  30  is fully closed.  
         [0020]     Referring to  FIG. 3 , the method according to this invention is shown schematically. The method begins with an initial step of providing a housing  12  that includes a vent opening  30  that communicates from a cavity  14  of the housing  12  to the non-exposed exterior surface  36 . The housing  12  also includes the access opening  32  that communicates between the vent opening  30  and an exposed non-protected exterior surface  34 . The printed circuit board  22  is inserted into the cavity  14  and rested on mounting ledge  19  or other devices that are commonly known to a worker skilled in the art to properly position the printed circuit board  22  within the housing cavity  14 . Once the printed circuit board  22  is mounted as desired within the housing  12 , a potting material  24  is filled over the printed circuit board  22 . The printed circuit board  22  divides the cavity  14  into the upper space  26  and the lower space  28 . The lower space  28  does not receive potting material and therefore is open. The open area is also in communication with the vent opening  30 .  
         [0021]     The potting material  24  is either cured by the application of heat  42  or generates heat on its own due to the chemical reactions required by mixing several components to create a hardened mixture. In any of these potting material configurations curing of the potting material  24  generates heat. This heat in turn generates gases that must be exhausted from the cavity  14 . The further step includes exhausting gases from the cavity  14  through the vent opening  30  and further through the connector pocket  20 . This exhausting of gases is necessary to prevent bubbling up of material through the potting material  24 . Once the potting material  24  has cured to a desirable level and the gases have been exhausted from the cavity  14  the final step in the sealing of the cavity  14  is performed.  
         [0022]     The final step includes injecting sealant material within the access opening  32 . The sealing access opening  32  is disposed and in communication with a non-protected outer surface  34  of the housing  12 . This non-protected outer surface  34  is outside of the connector pocket  20 . Accordingly, insertion of a tool into the sealing access opening  32  or adjacent the access opening  32  does not affect or come in close proximity to terminals  16  within the connector pocket  20 .  
         [0023]     Accordingly, the sealing access opening  32  provides for communication of sealant to the vent opening  30  for the easy and safe sealing of a cavity after curing of potting material without the possibility of disrupting connector components.  
         [0024]     Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.