Patent Publication Number: US-6902430-B2

Title: Connector housing retainer

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   The present invention is related to applications Ser. No. 10/064,145 entitled “Electrostatic Discharge Protective Boot For A Connector”, Ser. No. 10/064,146 entitled “Electrical Connector Extraction Tool”, Ser. No. 10/064,147 entitled “Interposer Extraction Tool”, and Ser. No. 10/064,148 entitled “Protective Housing For A High Density Electrical Connector”, filed simultaneously herewith and incorporated by reference herein. 

   BACKGROUND OF INVENTION 
   The present invention relates generally to electrical connectors, and more particularly, to a retaining mechanism for connecting a connector to a circuit board particularly suited for dense circuit boards such as a data acquisition system of a computed tomography system. 
   Electrical connections for various types of systems are commonly located in hard to reach and compact locations. One example of such a device is a computed tomography (CT) device. Computed tomography systems are complex systems that include an X-ray detector made up of a number of detection modules that are electrically coupled to a data acquisition system (DAS). A method for connecting a module to a data acquisition system is via a flex circuit attached to a connector. The connector provides the electrical path between a module and the DAS. During the manufacturing and servicing processes, the connection between the connector and the data acquisition system must be connected and disconnected multiple times. 
   The data acquisition system is a densely populated circuit board and thus has a number of components and a number of traces therein. Due to the large number of connections and limited space available, making reliable, serviceable connections is difficult. Also, detector modules as well as the DAS system are susceptible to damage from electro static discharge (ESD), thus the connector design necessarily needs to incorporate ESD protection to allow safe connections and disconnections. Further, the connection of the detector to the DAS is susceptible to microphonics, leakage and particulate contamination all of which can lead to electrical noise and image quality problems in the case of a CT scanner. Because a number of pins are used to connect the flex connector and the data acquisition system, the removal of the flex connector portion must be performed without bending the interconnection pins. 
   It would therefore be desirable to provide a retaining mechanism for an electrical connector that does not interfere with a densely populated circuit board. 
   SUMMARY OF INVENTION 
   The present invention provides an improved retaining mechanism for retaining a connector to a circuit board. In one aspect of the invention the retainer is positioned between a first carrier board and a second carrier board that is mounted to a circuit board. The retainer body has a middle retainer portion having a hole therethrough. The first retainer side extends from the middle portion. A second retainer side also extends from the middle portion. A first snap is disposed on the first retainer side and a second snap is disposed on the second retainer side. The first snap engages the first carrier board and the second snap engages the second carrier board. 
   The present invention is particularly suitable for retaining a connector on a crowded circuit board. Such connectors are particularly suitable for imaging systems. 
   One advantage of the invention is that the underlying circuit board does not have holes or other direct connections thereto to interfere with circuit trace routing and component placement. Nor is any form of adhesive used to attach a retainer feature to the circuit board, which can promote electrical leakage. 
   Other aspects and advantages of the present invention will become apparent upon the following detailed description and appended claims, and upon reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a perspective view of a data acquisition system circuit board coupled to a plurality of detector module circuits. 
       FIG. 2  is a perspective view of a partially assembled circuit according to the present invention. 
       FIG. 3  is a perspective exploded view of a back shell coupled to a flex circuit relative to an interposer and a circuit carrier according to the present invention. 
       FIG. 4  is a perspective view of a dust shield showing the internal assembly thereof according to the present invention. 
       FIG. 5  is a perspective view of a substrate on a data acquisition system. 
       FIG. 6  is a perspective view of a retaining mechanism according to the present invention. 
       FIG. 7  is a front view of a retaining mechanism according to the present invention. 
       FIG. 8  is a protective boot to be coupled to the back shell according to the present invention. 
       FIG. 9  is a perspective view of a connection extraction tool in use according to the present invention. 
       FIG. 10  is a perspective view of the extraction tool alone. 
       FIG. 11  is an exploded view of the extraction tool according to the present invention. 
       FIG. 12  is an enlarged view of the pin with the extraction tool according to the present invention. 
       FIG. 13  is a perspective view of the interposer extraction tool according to the present invention. 
       FIG. 14  is a perspective view of the interposer extraction tool removing an interposer according to the present invention. 
       FIG. 15  is a cross-sectional view of the interposer extraction tool of  FIGS. 13 and 14 . 
       FIG. 16  is a perspective view of the interposer extraction tool of  FIGS. 13 and 14 . 
       FIG. 17  is a cross-sectional view of the second embodiment of the extraction tool according to the present invention. 
       FIG. 18  is a side view of a first position of the second embodiment of the interposer extraction tool. 
       FIG. 19  is a side view of the second embodiment of the extraction tool in a second position according to the present invention. 
       FIG. 20  is a perspective view of the second embodiment of the extraction tool when the interposer is extracted. 
   

   DETAILED DESCRIPTION 
   In the following figures the same reference numerals will be used to illustrate the same components in the various views. The present invention is described with respect to a computed tomography device. However, those skilled in the art will recognize that the present invention has several applications within the medical imaging field and outside the medical imaging field. That is, the present invention is suitable for applications that employ connections in hard to reach, densely populated circuit boards. The present invention is also suitable for applications in which a connector is to be connected and disconnected often. 
   Referring now to  FIG. 1 , a portion of a CT system  10  is illustrated having a data acquisition system  12  and several detector modules  14  coupled together through a plurality of connector assemblies  16 . Although a CT system  10  is illustrated, the present invention applies equally to other types of systems requiring a connector assembly. 
   Data acquisition system  12  includes a circuit board  18  that has a plurality of electrical components and circuit traces thereon and therein. 
   Each detector module  14  includes a photo diode used for X-ray detection that are electrically coupled to a flex circuit  20 . By providing a flex circuit  20  the data acquisition system  12  and detector modules  14  may be easily connected or disconnected at connector assembly  16 . 
   Connector assembly  16  has a back shell  22  and a housing  24 . Of course, the number of connectors utilized on a data acquisition  12  depends upon the number of detectors and other physical characteristics of the system. 
   Referring now to  FIG. 2 , a housing  24  or first connector portion is shown partially assembled with a second connector portion or back shell  22  with the flex circuit  20  removed for simplicity. As will be further described below, housing  24  is indirectly coupled to circuit board  18 . Because the back shell  22  and housing  24  must be connected and reconnected several times during manufacturing and servicing, shell  22  is easily removed from housing  24 . Also, the CT system may be adversely affected by microphonics, leakage and short circuits resulting from contamination of the connection provided by connector  14 . The circuit is also highly sensitive to electrostatic discharge and charge induced noise, which is called microphonics. Also, the pins within housing  24  are also susceptible to damage if bent due to forces not parallel to the axis of the pin. 
   Housing  24  is illustrated as receiving two back shells  22 . However, one or more than two may also be accommodated in an appropriately sized housing  24 . Housing  24  has longitudinal sides  30  and lateral sides  32 . Preferably, the width of lateral side  32  is about the same size as back shell  22 . 
   Housing  24  has a plurality of guide arms  34  extending from the housing on the longitudinal sides upward or outward from circuit board  18 . As will be further described below, guide arms  34  are used to guide and retain back shell  22 . Arms  34  each have a snap opening  36  for receiving a snap on back shell  22 . Preferably, two guide arms  34  are used for each back shell  22 . Snap opening  36  preferably extends through the thickness of guide arm  34 . Guide arms  34  also include a removal guide  38 . Removal guide  38  as illustrated is a U-shaped indention in the top of each guide arm  34 . Adjacent to each guide arm  34  in housing  24  a plurality of alignment openings are provided for receiving a portion of back shell  22 . As illustrated, two alignment openings  40  are provided on each side of each guide arm  34 . Alignment openings  40  also add flexibility to arms  34  to allow easier engagement and disengagement of the two connector portions. 
   A pair of longitudinal ribs  42  on the inside of longitudinal sides  30  are provided to retain an interposer as will be further described below. Each longitudinal side  30  has a longitudinal rib  42 . Longitudinal rib  42  is positioned beneath alignment opening  40  at the position where the substrate is to be positioned. 
   Referring now to  FIG. 3 , back shell  22  is illustrated with respect to an interposer  48  and a circuit board socket carrier  72 . Interposer  48  is electrically coupled to flex circuit  20  through a back shell socket carrier  50 . 
   Back shell  22  includes a removal grip  52 . As illustrated, two removal grips  52  are integrally molded to back shell  22 . Removal grips  52  are illustrated as slotted cups that are sized to engage a removal tool as will be further described below. A guide channel  54  is provided in each side of back shell  22 . Guide channel  54  receives the guide arms  34  of housing  24 . Each guide channel  54  has a snap  56  therein. Snap  56  is sized to engage snap opening  36  on guide arms  34 . 
   An alignment key  57  may be included adjacent to each side of each arm  34 . Alignment key  57  is sized to be received within a corresponding alignment opening  40 . 
   Back shell  22  includes a rounded end  58  to help bend flex circuit  20  to a desired shape. Thus, rounded end  58  acts as a fixture to bend flex circuit  20  into a proper position without damage thereto. Back shell socket carrier  50  includes a plurality of ball grid array electrical sockets  60  thereon, only one of which is shown for simplicity. Alignment and ground socket  62  may be located at each corner of back shell socket carrier. Alignment and ground socket  62  are larger than socket  60  to provide a guide during assembly. Back shell socket carrier  50  and alignment and ground socket  62  are electrically coupled to flex circuit  20  and to back shell  22  which is formed of an electric charge dissipative material. A connection may be formed through through-holes  64  using a conductive material such as a pin, conductive epoxy, or solder. In one constructive embodiment four through-holes were provided in the top surface of back shell  22 . Interposer  48  has a plurality of pins  68  and a plurality of alignment and guide pins  70 . Alignment and guide pins  70  align with sockets  62  on back shell socket carrier  50  and on the circuit socket carrier as will be described below. Each pin  68  and  70  correspond to a socket on back shell socket carrier  50 . Alignment and ground pin  70  may actually extend into through-holes  64 . In one constructed embodiment,  146  pins  68  are provided on interposer  48 . 
   Socket carrier  72  has sockets  74  which when assembled are electrically connected to pins  68 . Alignment and ground sockets  86  coupled to pins  70 . 
   Referring now to  FIG. 4 , a partially assembled connector assembly  16  is illustrated. In this illustration one interposer  48  is positioned within housing  24 . Preferably, one interposer is provided for each back shell. Interposer  48  connects to a carrier board or circuit board socket carrier  72  that has a plurality of sockets  74  thereon. Pins  68  of interposer  48  are received within socket  74 . An alignment guide  76  formed on lateral side  32  of housing  24  is used to position housing  24  over alignment guide  76 . Circuit board socket carrier  72  has an alignment slot  78  that aligns with alignment guide  76 . Housing  24  is retained on circuit board  18  through a retainer  80  that is positioned beneath cross-member  83  and a fastener  82 . Cross-member is preferably integrally molded into the housing  24 . Fastener  82  extends through cross-member  83  and retainer  80 . 
   Referring now to  FIGS. 5 ,  6 , and  7 , circuit board socket carrier  72  is illustrated positioned on circuit board  80 . Circuit board socket carrier  72  has a plurality of sockets  84  that are electrically coupled to traces on circuit board  18 . Circuit board socket carrier  72  has a plurality of alignment and ground sockets  86 . When the connector is assembled, sockets  84  and  86  are soldered to circuit board  18  in a conventional manner. Retainer  80  is then snapped into place. 
   Retainer  80  has a thread insert  88  received within a hole  90  through a middle retainer portion  92 . The thread insert  88  receives the fastener  82  that is positioned on a cross-member  83  that extends across housing  24 . Middle retainer portion  92  is preferably parallel to circuit board  18 . A snap  94  is provided on a first retainer sidewall  96  and a second retainer sidewall  98 . Snaps  94  prevent the retainer from moving in a vertical direction (outward from circuit board) once inserted into the space between circuit board  18  and socket carrier  72 . A restraint  100  is employed on each sidewall  96 ,  98 . Restraint  100  is formed as a rounded portion extending from the sidewall that engages an alignment slot  102  through circuit board socket carrier  72 . First retainer sidewall  96  and second retainer sidewall  98  may each have flex slots  104  therein. Flex slots  104  allow a portion of the first retainer sidewall  96  and the second retainer sidewall  98  to flex inward to provide clearance for snaps  94  when the retainer  80  is positioned. 
   Referring now to  FIG. 8 , as mentioned above, the detector and data acquisition circuits are sensitive to contamination and electrostatic discharge. To alleviate this problem a connector cap assembly is illustrated relative to a back shell  22 . Once the back shell  22  is disconnected from housing  24 , it may be mechanically coupled to connector cap assembly  110 . Connector cap assembly  110  has a boot housing  112  that has some similar features to that of housing  24 . That is, boot housing  112  has a guide arm  114 , a snap opening  116  that engage guide channel  54  and snap  56  on back shell  22 . Boot housing  112  preferably has a compliant floor  118  that has a plurality of electrical contacts  120  positioned thereon. Compliant floor  118  and boot housing  112  are preferably formed of an electrically dissipative material. Alignment guides  122  that correspond to the alignment guides  76  and restraint  100 . Alignment guides  122  receive alignment slots  78  and  102  on back shell socket carrier  50  allowing boot housing to be a fixture to back shell  22 . Boot housing  112  may also include alignment openings  124  that receive alignment key  57  on each side of guide channel  54 . 
   Boot housing  112  includes a retainer  130  for positioning a ground wire  132  therein. Thus, retainer  130  maintains an electrical contact with ground wire  132  to boot housing  112  to slowly bleed any electrostatic build up on housing. Retainer  130  may include two protrusions  134  that extend from boot housing  112 . A tab  136  is used to hold ground wire  132  between protrusions  134  and housing  112 . Preferably, tab  136  is flexible to allow the ground wire to be easily placed between the tab  136 , protrusions  134 , and boot housing  112 . 
   Referring back to compliant floor  118 , electrical contacts  120  are illustrated as pyramidal shapes. One contact is provided for every four sockets. That is, the pyramid has four sides, each side contacting a respective socket. Electrical contacts  122  may thus dissipate any electrostatic buildup within flex circuit  20  or socket  60  through the boot housing  112  and ultimately through ground wire  132 . 
   In operation, the connector assembly  16  is formed by first mounting the circuit board socket carriers  72  to circuit board  18 . Each of the sockets  84 ,  86  are soldered to the circuit board so that they are fixedly attached thereto. Retainer  80  is then snapped into place so that snaps  94  engage the bottom surface of the substrate of the circuit board socket carrier  72 . The restraints  100  engage alignment slots  102  in the circuit board socket carrier  72  so that horizontal movement of the retainer is prevented. The connector housing  24  is then placed over the circuit board socket carrier  72  so that the alignment guides  76  align with alignment slot  78 . Also, the cross-member  83  is aligned with retainer  80  so that fastener  82  extends into and engages thread insert  88 . 
   The interposer  48  is then placed upon the circuit board socket carrier  72  so that the pins align with the appropriate sockets. 
   Flex circuit  20  is connected to the sockets  60 ,  62  of back shell socket carrier  50 . Conductive material may be placed in through-holes  64  so that alignment and ground socket  62  are electrically coupled to the back shell  22 . The flex circuit  20  and sockets are coupled together in a conventional manner such as by soldering. The sockets of back shell socket carrier  50  along with back shell  22  are then aligned so that guide arms  34  are placed within guide channel  54 . The back shell  22  is then forced in a vertical direction toward circuit board  18  until snap  56  engages snap opening  36 . 
   Referring now to  FIG. 9 , a back shell extraction tool  140  is shown engaged with removal grip  52  of back shell  22 . Extraction tool  140  provides a force perpendicular to the plane of the circuit board to prevent the pins from being damaged. Also, extraction tool  140  provides an outward pressure on guide arms  34  to flex the guide arms outward so that snaps  56  disengage snap openings  36 . 
   Referring now to  FIGS. 10 and 11 , extraction tool  140  includes a piston assembly  141  that includes piston  142  that has a handle  144  attached thereto. Piston  142  also has a channel  146  at the end opposite handle therethrough. Piston assembly  141  includes spring  148  that is received on piston  142 . Piston  142  is inserted within a channel  150  within grip  152 . Piston  142  is slidably received within a sleeve  154  that is also part of the piston assembly  141 . Piston  146  extends through sleeve  154  through a cross-member  156 . Cross-member  156  has two post heads  158  extending therefrom. Post heads  158  are used to engage removal grip  52  on back shell  22 . A pin  160  is received within channel  146  in piston  142 . As will be further described below, pin  160  is preferably angled. Pin  160  is receiving within a slot  162  that extends vertically from the bottom of cross-member  56 . 
   Spring  148  biases handle  144  and thus piston  142  in an upward position so that pin  160  is in the uppermost position of slot  162 . For removal of back shell  22 , pin  160  is placed within removal guide  38 . Pin  160  flexes the guide arms  134  outward so that snap  56  disengages snap opening  36 . The post heads  158  engage the removal grips  52  so that extraction may be made perpendicular to the surface of the circuit board. Extraction is made by overcoming the spring bias and bringing handle  144  closer to grip  152 . Typically the thumb or palm of a hand will engage handle  144  while the first two fingers engage each side of grip  142 . 
   Post heads  158  have a wide diameter cylindrical portion  164  and a mounting post  166 . 
   Referring now to  FIG. 12 , pin  160  is preferably angled or slightly U-shaped. Pin  160  has an angle θ with respect to the horizontal axis or the axis of piston  162 . Angle θ is preferably less than  90  degrees and more preferably 15 degrees. This angle allows pin  160  to provide outward pressure on guide arms  34  so that snap  56  disengages snap opening  36 . 
   Referring now to  FIGS. 13 ,  14 , and  15 , once the back shell  22  is disconnected from housing  24 , the interposer  48  may be removed. It is important to remove the interposer in a manner perpendicular to the circuit board or parallel to the direction of the pins on the interposer. It is also important to capture the interposer so that it does not fall into an undesirable location within the system from which it is removed. 
   An interposer extraction tool  170  has a piston assembly  171  that includes a piston  172  that has a handle  174  thereon. Piston  174  is received within a handle  176  so that they move relative to each other. A pair of springs  178  and  180  bias the piston  172  upward. Handle  176  has a pair of blades  182  attached thereto. Blades  182  have an end portion that are parallel to the plain of the interposer. Blades  182  are normally biased outward so that end portion  184  may be positioned parallel to and beneath the interposer  48 . A cross-member  186  and pair of blocks  188  are fixed to piston  172 . Blocks  188  are used to compress blades  182  to engage the interposer  48 . Spring  180  is connected to a guide block  190  that is coupled to piston  172 . Guide block  190  forms a channel  192  therein. Channel  192  is formed between fingers  194  extending downward from guide block  190 . The fingers  194  and thus channel  192  retain the interposer  48  after extraction. For extraction, two motions result. A downward motion of the piston  188  closes the blades  182  between the bottom of the interposer  48  and the top of board mounted socket carrier  48 . Second, an upward motion of the handle  176  pulls the blades  182  upward forcing the interposer  48  to disengage from the board mounted socket carrier  72  and eventually lock against stop  192 . The wedging of the interposer  48  against the stop  192  captures the interposer within the removal tool. Typically, the handle  174  of piston  172  will rest against the palm while the handle  176  is gripped by two fingers in the same hand. 
   Referring now to  FIGS. 16 ,  17 ,  18 ,  19 , and  20 , a second embodiment of interposer extraction tool  170 ′ is illustrated. Extraction tool  170 ′ has a piston assembly  200  that has a handle  202  on a first end of a plunger  204 . The second end of plunger  204  has a channel  206  coupled thereto. As illustrated, the second end of plunger  204  is threaded in to channel  206 . Thus, as plunger moves, channel  206  moves accordingly. Channel  206  is similar to the channel described above in the previous embodiment. Piston assembly  200  also has a spring  207  thereon. 
   Piston assembly  200  is slidably received within a handle assembly  209  that includes a handle  208 , a sleeve  210 , and a block  212 . Spring  207  is coupled to plunger  204  between handle  202  and handle  208 . Handle  208 , sleeve  210 , and block  212  move together and are guided by guide pins  214 . Handle assembly  209  has blades  216  coupled to each side thereof. Blades  216  have a bump  218  that allows the blade to be biased inward as will be further described below. Blades  216  have a grip portion  220  that is used to grip the interposer therein. 
   Channel  206  has a biasing member  222  fixably attached thereto. Blades  216  are slidably received between channel  206  and biasing member  222 . As bump  218  is positioned adjacent to biasing member  222  by movement of the piston assembly  200 , the grip portion  220  of blades  216  are moved inwardly about the interposer. 
   The plunger assembly  200  is also received within a guide block  224 . Guide block  224  has a channel  226  that slidably receives blade  216 . The channel  206  moves only a predetermined distance since biasing member  222  can only move within opening  228  and stops in a vertically downward position by stop  230 . 
   In operation, the plunger assembly  200  is moved from an upward position ( FIG. 18 ) to a downward position ( FIG. 19 ) so that channel  206  engages the interposer. In  FIG. 20 , the blades position interposer  48  against channel  206 . Blades  218  move inwardly when the bump  218  engages biasing member  222 . The biasing member  222  physically pushes the blades inward. The handle  208  is moved vertically upward so that the interposer is captured between the channel  206  and the grip portion of the blades  220 . Biasing member  222  acts as a compression member to compress the blades inward. Once the interposer is gripped between channel  206  and the blade, the tool may be removed from the system and the interposer may be dislodged from the device. 
   While the invention has been described in connection with one or more embodiments, it should be understood that the invention is not limited to those embodiments. On the contrary, the invention is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the appended claims.