Patent Publication Number: US-2007111566-A1

Title: Elastomeric connector assembly

Description:
BACKGROUND OF THE INVENTION  
      The invention relates generally to electrical connectors and, more particularly, to an elastomeric connector assembly for connecting an electronic module to a circuit board.  
     BRIEF DESCRIPTION OF THE INVENTION  
      Electrical connectors are commonly used to interconnect circuit boards or to interconnect a circuit board with an electrical device. Traditional connector solutions utilize stamped and formed terminal contact designs that are soldered or press fit into the circuit boards. The size and shape of these traditional solutions is limited by the available technologies for forming the stamped and formed terminals. The increasing complexity of electronic assemblies combined with progressively smaller electronic packages has generated a need for smaller connector designs. Many electronic devices include add-on modules having their own circuit boards that are connected to a circuit board in the electronic device. However, some electronic modules, such as cameras, fingerprint recognition modules, speakers, and microphones, and the like, are sensitive to and would be damaged by the heat associated with soldering processes.  
      The aforementioned concerns have led to the increasing use of elastomeric connectors in electronic devices. One type of elastomeric connector includes alternating layers of a conductive and non-conductive elastomeric material such as silicon rubber, with the conductive layers formed with layers of silicon material impregnated with electrically conductive material such as carbon, gold, or silver, and the like. The non-conductive or dielectric elastomer layers are sandwiched between the conductive layers and are of sufficient thickness to insulate the conductive layers from one another. The elastomeric connector is compressively held between the circuit board and module to electrically interconnect conductive traces on the board and module.  
      Notwithstanding the opportunities associated with the use of elastomeric connectors, it remains a challenge to provide a low cost connector solution that is easily customized, with reduced tooling costs, thereby lowering manufacturing costs.  
     BRIEF DESCRIPTION OF THE INVENTION  
      In one aspect, an electrical connector assembly is provided. The assembly includes an elastomeric member including a plurality of conductive elements that extend between first and second contact surfaces. The conductive elements form patterns on the first and second contact surfaces. One of the contact surfaces is configured to mate with an electronic module and the other of the contact surfaces is configured to mate with a circuit board. A holder is configured to be attached to the circuit board. The holder receives the elastomeric member, and is configured to receive and hold the electronic module securely against the elastomeric member to establish an electrical connection between the circuit board and the electronic module.  
      Optionally, the holder includes side walls having slots formed therein to form deflectable sections. The deflectable sections include a clip on an interior portion of the side wall to retain the module. Each conductive element includes a plurality of conductive layers and nonconductive layers in an alternating arrangement. The conductive and nonconductive layers extend between the first and second contact surfaces and are substantially perpendicular to the first and second contact surfaces. The electrical connection between the circuit board and the electronic module is established through the conductive elements. The elastomeric member further includes insulating sections extending between the first and second contact surfaces. An adhesive is applied only to the insulating sections at one of the contact surfaces to bond the elastomeric member to one of the circuit board and the electronic module.  
      In another aspect, an electronic assembly is provided. The assembly includes an electronic module having a mating surface. The mating surface includes a plurality of contact elements arranged in a pattern. An elastomeric member including a plurality of conductive elements extends between first and second contact surfaces. The conductive elements form patterns on the first and second contact surfaces. One of the contact surfaces is configured to mate with the electronic module and the other of the contact surfaces is configured to mate with a circuit board. A holder is configured to be attached to the circuit board. The holder receives the elastomeric member, and is configured to receive and hold the electronic module securely against the elastomeric member to establish an electrical connection between the circuit board and the electronic module. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an exploded view of an electronic assembly including a connector assembly formed in accordance with an exemplary embodiment of the present invention.  
       FIG. 2  is a perspective view of a circuit board of an electronic device.  
       FIG. 3  is a bottom perspective view of an electronic module with the elastomeric connector removed.  
       FIG. 4  is a perspective view of an elastomeric connector formed in accordance with an exemplary embodiment of the present invention.  
       FIG. 5  is a cross sectional view of one row of the connector shown in  FIG. 4  along the line  5 - 5 .  
       FIG. 6  is a perspective view of the electronic assembly shown in  FIG. 1  in an assembled condition.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIG. 1  is an exploded view of an electronic assembly  100  including a connector assembly  110  formed in accordance with an exemplary embodiment of the present invention. The electronic assembly includes a circuit board  114 , the connector assembly  110 , and an electronic module  118 . The connector assembly  110  includes a holder  120  and an elastomeric connector  122  that, in  FIG. 1 , is attached to the electronic module  118 . The electronic module  118  shown in  FIG. 1  depicts a camera module that may be used in an electronic device such as a cellular phone and the invention will be described with reference to such a module. It is to be understood however that such description is for illustration purposes only and that the connector assembly  110  may be used with, and the benefits derived are applicable to, other types of electronic modules including, but not limited to, speakers, microphones, fingerprint recognition sensors, and the like.  
       FIG. 2  is a perspective view of the circuit board  114 . The circuit board  114  includes a number of footprints  130  that are provided for the holder  120 , and a number of electrical contact padsl 32  that form a contact pattern on the circuit board  114 . The footprints  130  surround the contact pads  132  such that when the holder  120  is attached to the circuit board  114 , the contact pads  132  will lie within a perimeter of the holder  120 . In the embodiment shown in  FIG. 2 , the contact pads  132  are rectangular in shape and are of a uniform size wherein each contact pad  132  has a length L 1  and a width W 1 . In other embodiments, the contact pads  132  may be non-uniform and may include a mix of differing sizes and shapes. The illustrated contact pads  132  are arranged in rows R 1 , R 2 , and R 3  and within each row, the pads  132  are uniformly spaced a distance D 1  apart. Rows R 1  and R 2  are spaced a distance D 2  apart and rows R 2  and R 3  are spaced apart a distance D 3  which may be the same or different from the distance D 2 . Row R 2  is offset a distance D 4  from rows R 1  and R 3 .  
      Returning to  FIG. 1 , the holder  120  includes a number of feet  140  that are placed on the footprints  130  on the circuit board  114 . The holder  120  includes side walls  144  that form a holder perimeter P. The holder  120  is positioned on the circuit board  114  such that the contact pads  132  are surrounded by and lie within the perimeter P of the holder  120 . In an exemplary embodiment, the holder  120  is stamped and formed from a metallic material and is attached to the circuit board  114  by reflow soldering to become an integral part of the circuit board  114 . In alternative embodiments, the holder may be formed from other materials such as plastic (e.g. injection molded plastic) and attached to the circuit board  114  using known processes for the attachment of plastic materials. In addition, the holder  120  may provide shielding, if required, for the electronic module  118  from other components in the electronic device.  
      Each of the side walls  144  of the holder  120  include a pair of slots  150  that extend vertically from an upper edge  152  of the side walls  144  toward, but not completely to a bottom edge  154  of the side walls  144 . The pairs of slots define a deflectable section  160  therebetween in each side wall  144 . The deflectable sections  160  include a snap clip  164  formed therein. The snap clips  164  extend toward an interior of the holder  120  and engage the electronic module  118  when the electronic module  118  is inserted onto the holder  120  as will be described. The holder  120  is mechanically attached to the circuit board  114 , but does not form a conductive part of the electrical circuits on either the circuit board  114  or the electronic module  118 . The holder  120  is attached to the main circuit  114  board prior to receiving the electronic module  118  or the elastomeric connector  122  so that the electronic module  118  is not subjected to the heat associated with the reflow solder process when the holder  120  is soldered to the circuit board  114 .  
      The electronic module  118  includes a device  170 , such as a camera module, that is to be connected to the circuit board  114 . In an exemplary embodiment, the electronic module  118  may itself also include a circuit board  174  to which the elastomeric connector  122  is adhered, such that the elastomeric connector  122  forms an integral part of the electronic module  118 . The electronic module  118 , including the elastomeric connector  122 , is received in the holder  120 . The electronic module  118  includes an upper surface  178 . In one embodiment, the upper surface  178  includes engagement areas  180  that engage the snap clips  164  when the electronic module  118  is received in the holder  120 . The holder  118  holds the electronic module  118  securely against, and in a conductive relation with, the elastomeric connector  122 .  
       FIG. 3  is a bottom perspective view of an electronic module  118  with the elastomeric connector  122  removed. The circuit board  174  includes a lower mating surface  186  that includes a plurality of electrical contact pads  190 . The contact pads  190  are arranged in a pattern that is a mirror image of the contact pattern formed on the circuit board  114 . That is, the contact pads  190  are rectangular in shape and are of a uniform size wherein each contact pad  190  has a length L 1  and a width W 1  as with the contact pads  132  on the circuit board  114  ( FIG. 2 ). In other embodiments, the contact pads  190  may be non-uniform and may include a mix of differing sizes and shapes as required to maintain the mirror image relationship with the contact pads  132  on the circuit board  114 . The illustrated contact pads  190  are arranged in rows R 4 , R 5 , and R 6  and within each row, the pads  190  are uniformly spaced a distance D 1  apart. Rows R 4  and R 5  are spaced a distance D 2  apart and rows R 5  and R 6  are spaced apart a distance D 3  with the distances D 2  and D 3  determined by the row spacing on the circuit board  114 . Row R 5  is offset a distance D 4  from rows R 4  and R 6 .  
       FIG. 4  is a perspective view of the elastomeric connector  122 . The elastomeric connector  122  has a first or upper contact surface  200  and a second or lower contact surface  202  that is opposite the first contact surface  200 . The elastomeric connector  122  is substantially rectangular in shape, although it is to be appreciated that other shapes may be formed in other embodiments. The elastomeric connector  122  includes a plurality of conductive elements  210  together with a plurality of insulation sections  212 . In the illustrated embodiment, the elastomeric connector  122  includes three conductive elements  210  that are positioned to overlay the rows R 4 , R 5 , and R 6  of contact pads  190  on the mating surface  186  of the electronic module  118  as shown in  FIG. 3 .  
      When positioned and aligned between the circuit board  114  and the electronic module  118 , the elastomeric connector  122  establishes current flow paths between the corresponding contact pads  132  and  190  on the circuit board  114  and the electronic module  118 , respectively. The illustrated conductive elements  210  are rectangular in shape and are spaced distances D 2  and D 3  apart. The areas spanned by the distances D 2  and D 3  are filled with insulating sections  212 . The distances D 2  and D 3  are determined by the row spacing on the circuit board  114  and the electronic module  118 . In addition, insulating sections such as sections  212 A may be added as appropriate to give the elastomeric connector  122  a nonconductive perimeter. Each conductive element has a longitudinal axis such as the axis  216 .  
       FIG. 5  is a cross sectional view taken along the line  5 - 5  in  FIG. 4  through a conductive element  210 . Each conductive element  210  includes alternating conductive layers  220  and nonconductive layers  222  that extend generally parallel to one another between the upper contact surface  200  and the lower contact surface  202 . The conductive layers  220  and nonconductive layers  222  extend generally perpendicular to the upper and lower contact surfaces  200  and  202 , respectively, and are oriented substantially perpendicular to the longitudinal axis  216 . In an alternative embodiment, however, the conductive layers  220  and nonconductive layers  222  may extend parallel to, or at an angle with respect to the longitudinal axis  216 .  
      The nonconductive layers  222  separate the conductive layers  220 , so that discrete current paths are formed through the individual conductive layers  220  between the upper and lower contact surfaces  200  and  202  enabling current flow therebetween while the nonconductive layers  222  preventing current leakage between the conductive layers  220 . In an exemplary embodiment, the nonconductive layers  222  are fabricated from a known dielectric or insulating material, such as silicone rubber, and the conductive layers  200  are fabricated from a known particle filled or impregnated silicone elastomer. The conductive elements  210  may include any number of conductive layers  220  and nonconductive layers  222  as called for in a given application. Further, each conductive layer  220  may include sublayers of conductive material, and each nonconductive layer  222  may include sublayers of nonconductive material. In alternative embodiments, the conductive layers and nonconductive layers  220  and  222  may be formed into the same or different thicknesses from one another.  
       FIG. 6  is a perspective view of the electronic assembly shown in  FIG. 1  in an assembled condition. The holder  120  and the elastomeric connector  122  are supplied to the manufacturer separately. The holder  120  is placed on and attached to the circuit board  114  before insertion of the electronic module  118  or the elastomeric connector  122 . In an exemplary embodiment, the elastomeric connector  122  is aligned with the pad pattern on the electronic module  118  and bonded to the electronic module  118 . More specifically, the upper contact surface  200  of the elastomeric connector is bonded to the electronic module  118  by applying the bonding agent only to the nonconductive or insulating sections  212  of the elastomeric connector  122 . After bonding to the electronic module  118 , the elastomeric connector  122  becomes an integral part of the electronic module  118 .  
      The assembled electronic module  118  and elastomeric connector  122  are inserted into the holder  120  with the circuit board  174  on the electronic module  118  deflecting the deflectable sections  160  of the side walls  144  until the electronic module  118  passes the snap clips  164 . The snap clips  164  engage the engagement areas  180  to retain the electronic module  118  in the holder  120 . When the electronic module  118  is received in the holder  120 , the elastomeric connector  122  is sandwiched between the electronic module  118  and the circuit board  114  and is not visible. In pressing the electronic module  118  into the holder  120  sufficiently to engage the snap clips  164 , the elastomeric connector  122  is compressed and establishes an electrical connection between the circuit board  114  and the electronic module  118 . Spreading the deflectable sections  160  of the side walls  144  allows for the separation and removal of the electronic module  118  from the holder  120 .  
      The embodiments thus described provide a low cost connector assembly  110  for making component connections such as an electronic module  118  in an electronic assembly  100 . The connector assembly  110  includes a holder  120  that can be reflow soldered to a circuit board  114  and an elastomeric connector  122  that has conductive elements  210  arranged in a pattern that is a mirror image to pad patterns on the circuit board  114  and the electronic module  118 . The elastomeric connector is bonded to the electronic module  118  and sandwiched between the electronic module  118  and the circuit board  114  and establishes an electrical connection between the circuit board  114  and the electronic module  118 . The connector assembly  110  can be easily customized with reduced tooling costs, thereby lowering manufacturing costs.  
      While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.