Patent Publication Number: US-6220876-B1

Title: Electrical interconnect system and method for integrating a bussed electrical distribution center with a printed circuit board

Description:
RELATED APPLICATION 
     The present application is a continuation-in-part of commonly owned U.S. patent application Ser. No. 09/163,138, filed Sep. 29, 1998, entitled “INTERCONNECT SYSTEM FOR INTEGRATING A BUSSED ELECTRICAL DISTRIBUTION CENTER WITH A PRINTED CIRCUIT BOARD,” now U.S. Pat. No. 6,000,952. 
    
    
     TECHNICAL FIELD 
     The present invention relates to bussed electrical distribution centers having bussed circuits and/or various electronic components and to printed circuit boards composed of a dielectric substrate having various side-mounted and stickleaded electronic components, and more particularly to an interconnect system for providing a direct connection therebetween. 
     BACKGROUND OF THE INVENTION 
     A bussed electrical distribution center (hereinafter referred to simply as a “BEDC”) is a stand-alone central junction block assembly which has gained increasing applications in the automotive arts as motor vehicles become ever more electronically sophisticated. BEDC&#39;s package, for example, various fuses, relays and electronic devices in a single central location. BEDCs not only save cost by consolidating electrical interconnections, but also advantageously reduce the number of cut and spliced leads, thereby increasing reliability. 
     A BEDC construction which is considered state of the art is described in U.S. Pat. No. 5,715,135, to Brussalis et al., dated Feb. 3, 1998, which is assigned to the assignee of the present invention, the disclosure of which is hereby incorporated by reference herein. 
     In the BEDC described in U.S. Pat. No. 5,715,135, a two-piece main insulation assembly is provided. Stamped male blade or tuning fork terminals are press-fit between the main insulation assembly, wherein the terminals are provided with a wire slot. The upper half of the main insulation assembly has a top surface provided with a plurality of terminal stations and guide stations that are raised and separated from each other so as to provide a network of channels that provide wire passages. The terminal stations have IDC (insulation displacement) type terminal slots that extend through the upper half of the main insulation assembly and allow a press-fit affixment of the terminals, wherein the wiring slots thereof intersect the wiring passages. The lower half of the main insulation assembly is configured similarly. When a segment of bus wire (preferably solid copper) is routed selectively along the wiring channels, the bus wire segment is pressed through the wire slot of a selected number of the terminals to thereby electrically connect those terminals therewith. 
     A printed circuit board (hereinafter simply referred to as a “PCB”), is a board-like, electrically interfaced package of electronic components which has become ubiquitous in the electrical arts. PCBs typically are in the form of a dielectric substrate (such as for example an organic resin reinforced by fibers) and a predetermined pattern of perforations for making connections with wiring and electrical devices, wherein a conductive path, usually cladded copper, is patterned so as to provide a predetermined electrical routing between the perforations so that the wiring and electrical devices are functionally interconnected. 
     Referring now to FIG. 1, a prior art interconnection system for electrically interfacing a BEDC with a PCB is depicted for an automotive environment of operation. In this automotive environment, a BEDC  10  is connected by a wiring harness  12  to a PCB  14 . At each connection of the wiring harness  12 , a connector  16 ,  18  is required. Further, the connectors  16 ,  18  must be enlarged, or additional connectors must be provided, in order to interface with separate wiring  20 ,  22  that must communicate with various electrical components of the motor vehicle. 
     The prior art interconnection system of FIG. 1 has several disadvantages, among these are: high cost of interface via a wiring harness; lower reliability due to use of numerous connectors; large volume of space allocated for the separate BEDC and PCB; and intensive assembly labor; limited flexibility in configuring the interconnection system; and susceptibility to weakened soldered connections. Accordingly, what remains needed in the art is a connection system for providing an integrated BEDC and PCB that is flexible, resistant t o electrical disconnection, and easy to make at low cost. 
     SUMMARY OF THE INVENTION 
     In accordance with the teachings of the present invention, an interconnect system and method are provided for directly connecting a printed circuit board to a bussed electrical distribution center. The system includes a bussed electrical distribution center having a main assembly and at least one bus wire. Also included is a printed circuit board having a substrate and a conductive path fabricated thereon. An electrical interconnect connects the at least one bus wire on the bussed electrical distribution center with the conductive path on the printed circuit board, and the interconnect has a flexible bend located between the bussed electrical distribution center and printed circuit board to provide a flexible strain relieved interconnection. 
     Accordingly, the interconnect system and method of the present invention provide for the connection of a PCB to a BEDC with enhanced reliability and requires minimal assembly labor. The present invention provides enhanced flexibility in the electrical connection to minimize the likelihood of electrical disconnection due to vibration or other adverse forces. The present invention further obviates the need for wiring harnesses, and provides minimized component volume. 
     These, and additional objects, advantages, features and benefits of the present invention will become apparent from the following specification. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 is a schematic view of a prior art connection system for connecting a PCB to a BEDC; 
     FIGS. 2 a - 2   e  are partly sectional side views illustrating steps for interconnecting a PCB with a BEDC according to the present invention; 
     FIG. 3 is a detail, partly sectional view of an alternative configuration for mounting a PCB with respect to a BEDC according to the present invention; 
     FIG. 4 is an exploded perspective view of a first example of an integrated BEDC and PCB according to the present invention; 
     FIG. 5 is a perspective view of the integrated BEDC and PCB of FIG. 4 in a fully assembled state; 
     FIG. 6 is an exploded perspective view of a second example of an integrated BEDC and PCB according to the present invention; 
     FIG. 7 is a perspective view of an integrated BEDC and PCB electrically connected via an interconnect system according to another embodiment of the present invention; 
     FIG. 8 is an exploded sectional view of one electrical interconnection between the BEDC and PCB shown in FIG. 7; 
     FIG. 9 is a schematic view of a portion of the BEDC and PCB shown in both the L-shape and flat pack configurations; 
     FIG. 10 is a partial cross-sectional view of a BEDC and PCB illustrating a hinged assembly process for forming a flexible strain relief bend in the electrical interconnection according to another embodiment; 
     FIG. 11 is a partial cross-sectional view of the BEDC and PCB shown in FIG. 10, further illustrating the formation of the flexible bend in the electrical interconnection; 
     FIG. 12 is a partial cross-sectional view of the BEDC and PCB showing yet another assembly process for forming a flexible strain relief bend in the electrical interconnection; 
     FIG. 13 is a partial cross-sectional view of the BEDC and PCB shown in FIG. 12, further illustrating the formation of the flexible bend in the electrical interconnection; 
     FIG. 14 is a side view of a portion of the BEDC and PCB illustrating an L-pack electrical interconnection according to a further embodiment of the present invention; and 
     FIG. 15 is a side view of a portion of the BEDC and PCB further illustrating an electrical interconnection having a coined surface according to yet a further embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, FIGS. 2 a - 2   e  depict a series of steps according to the interconnect system  100  of the present invention. In this regard, a bussed electrical distribution center (BEDC) described in U.S. Pat. No. 5,715,135 is utilized herein by way of example. 
     As indicated at FIG. 2 a , an upper half member  102  of a two-piece main insulation assembly  104  (see FIG. 2 e ) is provided with a recess  106  at the inner face  102   b  thereof, wherein the inner face is preferably characterized by side rails and grooved beams in the manner described in U.S. Pat. No. 5,715,135. The recess  106  is located at an end portion of the upper half member  102  and provides seating of an end portion  108  of a substrate  110  of a populated printed circuit board (PCB)  112 , wherein the seating preferably is abutting at the edge of the PCB and is separated by a spacing S adjacent the edge, as shown at FIG. 2 b . The PCB  112  includes a conductive path  114  cladded to the substrate  110  and various electronic components  116  connected with the conductive path  114 . Apertures  130  in the form of holes and/or slots are provided in the PCB  112  at the end portion  108 . 
     As recounted in U.S. Pat. No. 5,715,135, the outer face  102   a  of the upper half member  102  is provided with various raised guides  118  for providing wiring channels  120  for bus wires  122  (shown best at FIGS.  4  and  5 ). As further recounted in U.S. Pat. No. 5,715,135, the upper half member  102  is further provided with apertures  124  in the form of terminal slots for fixedly receiving terminals  126  having wire slots  128  (see FIG. 2 d ). 
     When the end portion  108  is received seatingly into the recess  106 , the apertures  130  align with respective apertures  124 ′ in the form of corresponding holes and/or terminal slots on the BEDC at the recess. 
     Next, the combined assemblage of the PCB  112  and upper half member  102  is placed in a bus wire routing machine where the bussed circuits for the BEDC are created. As shown at FIG. 2 c , the bus wires  122  are laid in the wiring channels  120  in a predetermined pattern. The bus wires  122  are, where appropriate, planted through the apertures  130 ,  124 ′ which are in the form of holes in the PCB  112  and the BEDC, respectively. 
     As shown at FIG. 2 d , the terminals  126  are press-fit into the terminal slots  124  of the upper half member  102 , and, where appropriate, the bus wires  122  are pressed into the wire slots  128  of the terminals  126 . Similarly, where terminals  140  are placed into the apertures  130  of the PCB  112 , where appropriate, the bus wires  122  press-fit into wire slots  142  thereof. 
     The end  122   a  of the planted portion  122   b  of the bus wires  122  are now soldered, via a solder joint  136  to the conductive path  114  of the PCB  112 . Similarly, the planted end  132   a  of the terminals  132  is soldered, via another solder joint  136 , to the electrically conductive path  114 . In this regard, it is preferred to use a fountain wave soldering methodology that is well-known in the soldering arts. 
     As shown in FIG. 2 e , the lower half member  144  of the main insulation assembly  104  is configured similar to the upper half member  102 , including the recess for receiving the PCB in the manner hereinabove described. Terminals  126  are similarly press-fit and bus wires  122  are similarly laid down in the wiring channels of the outer face thereof and press-fit into the wire slots  128  of the terminals. When the inner faces  102   b ,  144   b  of the upper and lower half members  102 ,  144  are brought into abutment to thereby assemble the main insulation assembly  104  of the BEDC, the substrate  110  is in alignment with the interface  146  therebetween and the recess serves to firmly sandwich the edge and afford spacings S adjacent thereto. Finally, the entire assembly is then cold staked to lock the terminals and PCB  112  in position relative to the upper and lower half members  102 ,  144 . In this regard the upper and lower half members afford strain relief to the solder joints  136 . 
     It will be noted that the interconnect system  100  provides simultaneously a mechanical and electrical direct interface between the PCB and the BEDC, wherein external wiring need only be connected through the BEDC. 
     FIG. 3 depicts a variation of the interconnect system, wherein a populated PCB  112 ′ is integrated with a main insulation assembly  104 ′, wherein each of the upper half member  102 ′ and the lower half member  144 ′ are provided with a portion of the recess  106 ′, and wherein the substrate  110 ′ is situated fixedly therein. 
     FIG. 4 depicts an example for carrying out the interconnect system, wherein a BEDC  150  is integrated with the PCB  112 , upper half member  102  and lower half member  144  of FIG. 2 e . The PCB  112  is interfaced at the recess  106  of the upper half member  102 , and the upper half member is interfaced with the lower half member  144  to form the main insulation assembly  104 . The terminals  126 , guides  118 , wiring channels  120  and bus wires  122  are as described hereinabove with respect to FIGS. 2 a  through  2   e . An enclosure  152  provides external electrical connections and environmental protection. 
     FIG. 5 depicts the integrated BEDC unit  150  in a fully assembled state. 
     FIG. 6 depicts a second example for carrying out the interconnect system  100 , wherein a BEDC  150 ′ includes a PCB  112 ″ entirely received by a recess  106 ″ of the lower half member  144 ″ and the electronic components  116 ′ project into an opening  154  formed in the upper half member  102 ″. The terminals  140 ′ are, at least in part, in the form of micro pack terminal pins. The terminals  126 , guides  118 , wiring channels  120  and bus wires  122  are as described hereinabove with respect to FIGS. 2 a - 2   e . An enclosure  152 ′ provides external electrical connections and environmental protection. 
     Some of the distinguishing advantages of the interconnect system  100  are: 
     a) A conventional wiring harness connecting the PCB to the BEDC is eliminated, as are the associated connectors. 
     b) Custom routed bus wiring from the BEDC is solderingly connected to the PCB, thereby greatly enhancing reliability. 
     c) The number of parts and the amount of material is minimized because of a co-location design and a common enclosure. 
     d) Common mounting features and fewer connectors simplifies installation and minimizes connect labor. 
     e) Connection to external electronics is simplified, in that an integrated connector can accommodate BEDC electronics and PCB I/O. 
     f) The PCB may be used to achieve bussing of some low current circuits. 
     g) Solid state devices on the PCB may be used to replace pluggable mechanical relays of the BEDC. 
     Referring to FIG. 7, an interconnect system  200  for electrically interfacing a BEDC  250  with a PCB  212  is depicted according to another embodiment of the present invention. The interconnect system  200  is particularly well-suited, but is not limited, to use in an instrument panel of an automotive vehicle. The interconnect system  200  provides a low cost electrical interface that is flexible to allow for various package configurations such as an L-shaped configuration and a flat configuration. 
     The bussed electrical distribution center (BEDC)  250  is shown having a two-piece main insulation assembly  204  including an upper half member  202  and a lower half member  244  with bus wire  222  routed through wiring channels in the two-piece main insulation assembly  204 . The BEDC  250  houses high-current electronic devices  218  which may include relays, fuses, splices, and other electronic devices. The printed circuit board  212  includes conductive paths  214  cladded to a substrate  210  and contains various low-current electronic components  216 . The printed circuit board  212  is composed of various electronics  216  to drive the relays, communicate via serial data, condition and regulate the power supply, sense feedback from the relay devices, monitor low-current discrete inputs, drive low-current discrete outputs and process inbound or outgoing serial data. Examples of electronic devices  216  may include a processor, serial transceiver/protocol handler, relay driving integrated circuits, discrete parts, and application specific integrated circuits (ASICs). The printed circuit board  212  and BEDC  250  may be configured as described in connection with printed circuit board  112  or  112 ′ and BEDC  150  or  150 ′, respectively, as described above. 
     The BEDC  250  and printed circuit board  212  are electrically interconnected so that certain bus wires  222  are electrically coupled to certain conductive paths  214  to provide electrical signal transmission paths therebetween, while at the same time providing a physical interconnection between BEDC  250  and printed circuit board  212 . With particular reference to FIG. 8, the interconnection between BEDC  250  and printed circuit board  212  is further shown therein. Bus wire  222  is shown extending through a channel in the two-piece main insulation assembly  204  and extends outward from the bottom edge through an aperture in the assembly  204  and into a wire termination aperture formed in the printed circuit board  212 , where it is soldered in place via solder joint  236 . The bus wire  222  has a flexible strain relief bend  260  formed therein, which may be in the shape of a partial or complete loop, that provides a flexible electrical interconnection which may utilize a standard solder process and is achieved at a low cost. According to the present invention, the routed bus wire  222  is bent in such a way as to facilitate its placement into a wire termination aperture formed in printed circuit board  212  and to reduce strain on the solder joint  236 . The geometry of the flexible bend  260  may include a number of embodiments which may depend on the desired end package configuration for the module. 
     According to the embodiment shown in FIGS. 7 and 8, the routed bus wire  222  has a flexible bend  260  configured with reverse “S” geometry. The electrical interconnection is made by placing the bus wire  222  into a prepared through hole in the printed circuit board  212 , and forming a solder joint  236 , which may include a conventional soldering process, to solder the bus wire  222  to a conductive path  214  on printed circuit board  212 . 
     The interconnect system  200  allows for an L-shape package configuration as shown in FIG. 7, and further allows the BEDC  250  to be rotated ninety degrees relative to the printed circuit board  212  to form a flat pack configuration as shown in FIG.  9 . When rotating the BEDC  250  relative to the printed circuit board  212 , the shape of the reverse S-shape flexible bend  260  changes and the flexible bend  260  stretches longitudinally to allow relative movement between the BEDC  250  and printed circuit board  212 . The reverse S-shaped flexible bend  260  advantageously reduces the strain on the solder joint  236 , and thereby reduces the possibility of damaging the solder joint  236 , especially during movement of the BEDC  250  relative to the printed circuit board  212 . According to the flat pack configuration, the interconnected assembly may be easily installed into a housing to complete the module assembly. 
     Referring to FIGS. 10 and 11, the formation of flexible bend  260  in bus wire  222  is illustrated therein for a flat pack configuration. According to this embodiment, the BEDC  250  has a hinged member  262  integrally formed in or connected to BEDC  250  via a reduced thickness hinge  266 . Hinged member  262  lies on top of the printed circuit board  212  above an opening  264  formed therein. With the bus wire  222  inserted through a wire termination aperture  230  in the printed circuit board  212 , a tool  268 , such as a pin, is forcibly actuated upward through opening  264  to contact hinged member  262 , which in turn is forced vertically upward to deform bus wire  222  and form the flexible bend  260  therein. To assist in formation of the flexible bend  260 , a support member  270 , such as a cylindrical anvil, may be employed to hold the bus wire  222  against BEDC  250 . Once the flexible bend  260  is formed, tool  268  may be removed and bus wire  222  is soldered to the printed circuit board  212 . The bus wire  222  preferably extends through and beyond the printed circuit board  212  by a length long enough to allow the flexible bend  260  to be formed thereabove to a desired height and the solder joint to be formed thereafter. 
     Referring to FIGS. 12 and 13, another embodiment is shown for forming the flexible bend  260  in bus wire  222  for a flat pack configuration. The routed bus wire  222  has a rounded ninety degree bend that allows the wire  222  to extend through an aperture  230  in printed circuit board  212 , leaving a sufficient length of wire extending through the aperture  230  and below the printed circuit board  212 . With the bus wire  222  in place, tool  268  is used to form a flexible strain relief loop  260  in wire  222  prior to soldering. The flexible loop  260  is formed by securing the bus wire  222  within an opening in a guide member  272 , engaging a support member  270 , such as a cylindrical anvil, to hold the bus wire  222  down on the BEDC  250 , and applying an upward force on tool  268  that in turn pushes the end of bus wire  222  upward and against support member  270 , thus forming the flexible bend  260 . Once the flexible bend  260  is formed, the interconnection is ready for soldering. 
     Referring to FIG. 14, an electrical interconnection is shown according to yet another embodiment for facilitating the implementation of an L-shaped configuration. The routed bus wire  222  is terminated with a bend  280  and extends through a prepared through hole in printed circuit board  212 . The bus wire  222  then undergoes a traditional solder process to form solder joint  236 . According to this embodiment, the bottom end of bus wire  222  may extend beyond the bottom contact surface of printed circuit board  212  to provide added alignment and stability during the solder and final assembly processes. 
     The routed bus wire  222  may further include a coined section  290  as shown in FIG.  15 . The coined section  290  provides a generally flat section of reduced thickness, preferably formed at the intended location of the bend, to reduce bending force and subsequent strain on the solder joint, particularly during the flat pack bending process as described herein. The reduced thickness may be formed on either the inside or outside of the wire relative to the bend, and is preferably formed on both sides as shown. The coined section  290  may be provided on any of the above electrical interconnections described herein. 
     Accordingly, the present invention provides for a unique electrical interconnection that connects the routed bus wire of a bussed electrical distribution center to a printed circuit board. The present invention advantageously provides for such an electrical interface with enhanced flexibility, that has reduced sensitivity to vibration and other forces, and can be made available at low cost. 
     To those skilled in the art to which this invention appertains, the above described preferred embodiments may be subject to change or modification. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.