Abstract:
A system and method for connecting flexible circuitry in a disk drive system such as that used in computer systems. The system and method allow a large number of traces to be connected in a small area by forming male and female connector portions at an end of a mating pair of traces. the male and female portions are formed using conventional flexible circuit fabrication techniques, making possible very accurate control of very small built-in type connectors. The connection can be uncoupled and re-coupled, and added security of attachment can be achieved through the use of ultra-sonic bonding and use of a mechanical clamp.

Description:
This application is a Continuation of U.S. patent application Ser. No. 09/519,280, Filed Mar. 7, 2000, abandoned. 

   BACKGROUND OF THE INVENTION 
   Field of the Invention 
   The present invention relates to magnetic disk drive storage systems and more particularly to connection of circuitry therein. 
   Magnetic disk drives are used to store and retrieve data for digital electronic apparatuses such as computers. In  FIGS. 1A and 1B , a magnetic disk data storage system  10  of the art is illustrated which includes a sealed enclosure  12  and a plurality of magnetic disks  14 , each of which has an upper surface  16  and a lower surface  18 . The disks are supported for rotation by a spindle  20  of a motor  22 . 
   An actuator  24  includes an E-block  25  having at its distal end a plurality of actuator arms  26 . The actuator also includes a bearing  27 , which mounts the actuator  24  pivotally within the enclosure  12 , and further includes a voice coil  28  at its proximal end. The voice coil is disposed between a pair of magnets  30  which are fixedly connected with respect to the enclosure  12 . Generating an electrical current in the coil  28  induces a magnetic field about the coil. Interaction between the magnetic fields of the coil  28  and the magnets  30  provides a desired, controlled pivotal movement of the actuator about a pivot point  31  of the bearing  27 . 
   With continued reference to  FIGS. 1A and 1B , the actuator arms  26  support a plurality of suspensions  32 , each of which supports at its distal end a slider  34   a ,  34   b . Each suspension holds its corresponding slider  34   a ,  34   b  in close proximity to a surface of one of the disks  14  to facilitate reading and recording data to and from the disk  14 . 
   The motor  22  and spindle  20  cause the disks  14  to rotate. As the disks  14  rotate, the air immediately adjacent the disks moves with the disks as a result of friction and the viscosity of the air. This moving air passes between each of the sliders  34   b ,  34   a  and its adjacent disk surface  16 ,  18  forming an air bearing. This air bearing causes the head to fly a very small distance from the disk surface  16 ,  18 . 
   Each of the sliders  34   b ,  34   a  has embedded within it a read element and a write element (both not shown). As the disk surface  16  or  18  moves past the slider  34   b ,  34   a  the write element generates a magnetic field leaving magnetic data on the passing disk  14 . Such write elements are generally in the form of an electrical coil passing through a magnetic yoke. As a current passes through the coil it induces a magnetic field which in turn generates a magnetic flux in the yoke. A gap in the yoke causes the magnetic flux in the yoke to generate a magnetic field which fringes out from the gap. Since the gap is purposely located adjacent the disk, this magnetic fringing field imparts magnetic data onto the passing magnetic disk  14 . The coil is embedded within a dielectric material which electrically isolates it from the yoke. An insulating layer covers the write element. 
   The read element detects changes in surrounding magnetic fields caused by the disk  14  passing thereby. Several read elements may be used to read such data. An effective read element currently in use is a GMR Spin Valve sensor. Such sensors take advantage of the changing electrical resistance exhibited by some materials when a passing magnetic field affects the magnetic orientation of adjacent magnetic layers. At its most basic level, a GMR spin valve includes a free magnetic layer and a pinned magnetic layer separated by a non-magnetic layer such as copper. The pinned layer has magnetization which is pinned in a pre-selected direction. On the other hand, the free layer has a direction of magnetization which is perpendicular with the pinned layer, but is free to move under the influence of an external magnetic field such as that imparted by a passing magnetic recording medium. As the angle between the magnetic directions of the free and pinned layers changes, the electrical resistance through the sensor changes as well. By sensing this change in electrical resistance, the magnetic signal passing by the read element can be detected. The read sensor is embedded within a dielectric layer, between a shield and the yoke of the write element. 
   With reference now to  FIG. 2 , a head suspension assembly (HSA)  35  is illustrated. Read and write signals from the heads  34  pass through trace circuitry  36  on the suspension  32  to a flexible interconnect adapter (FIA)  38 . The FIA  38  has its own set of trace circuitry  40  ( FIG. 3A ) for conducting the read and write signals to a junction  42  on the E-block  25 . From the junction  42 , the signals are routed through flexible circuitry  44  to a mother chip (not shown). 
   With reference to  FIG. 3A  a head gimbal assembly (HGA)  39  is illustrated. The HGA  39  includes the suspension  32  having a head  34  and FIA  38  attached thereto. Connection of the suspension trace circuitry  36  and the FIA trace circuitry  40  is made at the location of a set of suspension contacts  46 . Connection can be accomplished either by solder reflow techniques or by ultrasonic bonding. The read and write signals pass through a split pre-amp  48  on the FIA  38 . 
   The a real density (bits per unit area of storage surface) of magnetic hard disk drives has been increasing significantly. These increases have been achieved by a combination of increased track density—which is the number of tracks per inch along the radius of the disk—and an increase in linear bit density—which is the number of bits written along one inch of a track. As the storage industry progresses toward increasing the areal density, or the memory capacity, the increase in linear density and data transfer rate is a consequential by-product of the trend. The higher data rates will force up the bandwidth required for transmitting read and write signals between the read/write transducer and the front-end electronics module. The maximum attainable data rate of a magnetic data storage device depends on the components in the recording channel, e.g. electronics, interconnects, head and media. The suspension interconnect becomes less of a limitation as its length is made shorter. This can be accomplished by placing a Read/Write IC or pre-amp  48  as close as practicable to the head  34 . This split preamplifier architecture splits the standard read/write chip mounted on a head stack assembly (HSA) into two or more pieces, including a mother chip and a series of daughter chips mounted on the head gimbal assembly (HGA). 
   As memory capacity and data transfer rates of hard disk drives increase, the signal-to-noise ratios become more critical. One way to improve the signal to noise ratio is to amplify the signal from the head. U.S. Pat. No. 5,055,969 issued to Patnam, for example, discloses an amplifier on the actuator arm of a disk drive. Placement of this amplifier on the actuator arm, close to the head improves the signal to noise ratio before the signal is overwhelmed by noise. 
   With continued reference to  FIG. 3A , the FIA  38  includes a set of test contacts  50 . The test contacts are used to connect with test equipment (not shown) to test the performance of the HGA  39  prior to installation onto the E-block  25 . After the performance of the HGA  39  has been confirmed, the FIA  38  is cut along line  52 , removing the test contacts  50 . The FIA  38  is also bent at 90 degrees along line  54  to allow a set of FIA contacts  56  to join with a similar set of contacts on the E-block  25 . Connection between the FIA contacts  56  and the contacts of the E-block  25  can be made by solder reflow techniques or by ultrasonic bonding. 
   With reference to  FIG. 3B , another way of achieving such higher density has been to record data in much narrower tracks. A very high precision servo would be required to drive the slider and position it over such a narrow data track. One promising approach is a dual-stage servo system, which uses the conventional voice coil motor as a primary (coarse low-bandwidth) actuator, and the piezoelectric micro-actuator  58  as a secondary (fine high-bandwidth) stage. The micro-actuator  58  flexes the suspension slightly laterally, thereby finely adjusting the location of the head  34  in relation to the disk  14  (not shown in  FIG. 3B ). 
   With reference to  FIG. 3B , the use of such a micro-actuator  58  in conjunction with a pre-amp  48  has been limited by the number of traces necessary to accommodate such a combination. Such a combination would necessitate multiple traces leading from the pre-amp to the E-block  25 . The problem arises, not in fitting the trace lines  40  on the FIA  38 , but in connecting the FIA trace circuitry  40  with the circuitry  44  at the junction  42  located on the E-block  25  ( FIG. 2 ). The conventional connection techniques, solder reflow and ultra-sonic bonding, are limited by space restrictions. Solder reflow is problematic because in small spaces the solder flows across contacts causing undesirable electric conduction between them. Ultrasonic bonding is similarly limited by the inability to develop equipment which can efficiently bond individual contacts in a very small area. In addition, the use of mechanical connections, such as conventional machined pin-and-socket connections is limited by the fact that such connectors cannot currently be manufactured with a pitch less than 0.05 inches. 
   Therefore, there remains a need for a connection technique which will allow a first set of trace circuitry, such as on a FIA  38  to be connected with a second set of trace circuitry, such as on an E-block  25  in an extremely small area. Such a connection technique would greatly facilitate the use of a pre-amp  48  in conjunction with micro-actuator  58 , by accommodating connection of an increased number of traces. Such a technique would preferably allow for a connection which can be disconnected and re-connected while reducing wiring errors, increasing impedance control and signal quality and would reduce manufacturing cost by simplifying circuitry. 
   SUMMARY OF THE INVENTION 
   The present invention provides a system and method for connecting trace circuitry in a very small area. Using a photolithographic process familiar to those skilled in the art, a female connector is formed on one end of a first circuit. This is accomplished by first constructing a thick trace line and then selectively etching the trace to form the female connector. The finished copper is thick at interconnect areas and thinner at trace, or flexible, areas. Similarly, a male connector portion is formed at the end of a second trace circuit. Again, the trace line is formed thick and is etched to form the male connector portion and to render the trace line thin and flexible. The male and female connector portions are configured to be force fit one within the other. 
   The present invention allows many connections to be made in a very small area while reducing wiring errors and increasing impedance control and signal quality. The present invention also allows for circuit simplification and higher circuit density while reducing manufacturing cost. 
   The present invention facilitates testing and enhances the assembly process by allowing multiple reworks at the levels of the HGA and HSA. Another benefit of the present invention is that the FIA is readily removable and replaceable to enable rework of HGA and its defective components during the assembly process. Rework may be necessary several times for any of a number of reasons. For example, removing the HGA from a HSA is required to precisely align the heads, assure targeted static attitude and gram load, scrap the electrically defective heads and replace mechanical defective components. Accordingly, the FIA is re-usable a number of times to enable multiple reworks. 
   The system includes an actuator having one or more arms mounted for pivotal movement within an enclosure. Each arm has at its distal end a suspension which holds a magnetic head in close proximity to a surface of a rotating magnetic disk. As the disk turns, the head flies above the disk writing and reading data to and from the disk. 
   Trace circuitry routes data signals from the head to a set of contact pads on an edge of the suspension. A flexible interconnect adapter picks up the signals and routes them through trace circuitry on the flexible interconnect adapter to a junction located on the E-block. At that junction, the traces of the flexible interconnect adapter connect with trace circuitry on the E-block which routes the signals to a mother chip. A pre-amp is provided on the FIA, and a micro-actuator is provided on the suspension. 
   In order to handle the increased number of leads necessary to accommodate the pre-amp and micro-actuator, a set of mechanical connectors is used in the junction at the E-block to join the FIA trace circuitry with the trace circuitry of the E-block. The mechanical connectors achieve a male/female connection which advantageously allows connection in a much smaller area than is possible with prior art ultrasonic bonding and soldering techniques. In addition, the connectors are constructed using a semiconductor patterning process, advantageously allowing them to be constructed much smaller than is possible using existing machining techniques. 
   The patterning process for constructing the connectors includes lithography and etching. The trace circuitry of the FIA is formed relatively thick. The trace circuitry is then etched resulting in a thin trace circuit having a doughnut shaped raised portion at its end. After etching, a cover film is applied and exposed copper traces and raised portion are gold plated. The doughnut shaped raised portion has an inner socket of a predetermined inner dimension. 
   Similarly a male connector portion is formed on the end of the E-block trace circuitry. The trace is formed to be relatively thick, and is then etched to form the male portion which rises from the trace circuitry, having such a diameter that the male portion fits within the socket of the female portion in a force fit relationship. 
   It will be appreciated that the choice of which trace circuitry terminates in a male end and which should terminate in a female end is somewhat arbitrary. For example the circuitry of the E-block could be formed to have the female end, with the FIA trace circuitry having the male end. Furthermore the shape of the male portion and the socket can also be varied, so long as they connect together. These and other advantages of the present invention will become apparent to those skilled in the art upon a reading of the following descriptions of the invention and a study of the several figures of the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, with like reference numerals designating like elements of the background art. 
       FIG. 1A  is a top plan view of a hard disk drive system  1 A; 
       FIG. 1B  is a cross-sectional front elevation view taken along line  1 B— 1 B of  FIG. 1A ; 
       FIG. 2  is a perspective view of a head suspension assembly (HSA) of the prior art; 
       FIG. 3A  is a perspective view of a head gimbal assembly (HGA) of the prior art; 
       FIG. 3B  is a view similar to that of  FIG. 3B  of a (HGA) of the prior art having a micro-actuator; 
       FIG. 4  is a perspective view of a HSA of the present invention; 
       FIG. 4A  is a schematic diagram showing certain of the circuit parts of  FIGS. 5A and 6  in juxtaposition. 
       FIG. 5A  is a plan view of a flexible interconnect adapter of the present invention; 
       FIG. 5B  is a view taken from line  5 B— 5 B of  FIG. 4 ; 
       FIG. 5C  is a view taken from the circle designated  5 C in  FIG. 5A , shown enlarged; 
       FIG. 6  is a view taken from line  6 — 6  of  FIG. 4 , shown enlarged; 
       FIG. 7  is a view taken from line  7 — 7  of  FIG. 9 ; 
       FIG. 8  is a view taken from line  8 — 8  of  FIG. 10 ; 
       FIG. 9  is a view taken from the circle designated  9  in  FIG. 5A  shown enlarged and rotated 90 degrees clockwise; 
       FIG. 10  is a view taken from the circle designated  10  in  FIG. 6  shown enlarged and rotated 90 degrees clockwise; and 
       FIG. 11  is a diagram of a process of manufacturing the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to  FIGS. 1A and 1B , the present invention is embodied in a system  10  for reading and recording data and for use with a computer system or the like. The system  10 , contained within an enclosure  12 , includes a spindle  20  driven by a motor  22 . The spindle  20  supports one or more magnetic disks  14  for rotation within the enclosure  12 . The disks have upper and lower surfaces  16 ,  18  on which data can be stored in the form of magnetic pulses. 
   An actuator  24 , having one or more arms  26  extending from its distal end, is pivotally mounted upon a bearing  27  within the enclosure  12 . The actuator  24  has at its proximal end a voice coil  28  which moves between a pair of magnets  30  fixedly connected with the enclosure  12 . An electrical current in the coil  28  generates a magnetic field which interacts with a magnetic field of the magnets  24  to drive the actuator in a controlled manner. 
   A suspension  32  extends from each arm  26  of the actuator to suspend at its distal end a slider  34   a ,  34   b . The suspension  32  holds the slider  34   b ,  34   a  close to a surface  16 ,  18  of a disk  14 . As the disk  14  turns, air adjacent to the surface  16 ,  18  moves with the disk to flow under the slider  34   b ,  34   a . This creates an air bearing under the slider, causing the slider to fly ever so slightly over the disk surface  16 ,  18 . The slider has a read element and a write element (not shown) embedded therein which read and record magnetic signals to and from the passing disk surface  16 ,  18  and translate those signals into electrical signals. 
     FIG. 4  illustrates a head gimbal assembly (HGA)  400  according to an embodiment of the invention. The suspension  32  includes trace circuitry  402  which transmits the electrical signals from the slider  34  to a flexible interconnect adapter  404 . The flexible interconnect adapter (FIA)  404  includes a pre-amp  406  which should be located as close as practicable to the slider  34 . Trace circuitry  408  on the FIA transmits the electrical signals from the suspension  32  through the pre-amp  406  to a junction on the E-block  25 . Trace circuitry  410  on the E-block  25  transmits the signals to a mother chip  412 . A clamp  414  maintains connection between the FIA  404  and the E-block  25 . 
   With continued reference to  FIG. 4 , the pre-amp  406  improves signal strength and reduces signal noise. In addition, the integration of a peizo-electric micro-actuator  405  improves bandwidth and positioning accuracy. As discussed above in reference to the Background of the Invention, such improvements greatly increase the number of trace circuits which must be routed from the pre-amp  406  to the mother chip  412 . This large number of traces  408  translates to a correspondingly large number of connections between the FIA  404  and the trace circuitry  410  on the E-block  25 . 
   With continued reference to  FIG. 4 , the pre-amp  406  improves signal strength and reduces signal noise. In addition, the integration of a peizo-electric micro-actuator improves bandwidth and positioning accuracy. As discussed above in reference to the Background of the Invention, such improvements greatly increase the number of trace circuits which must be routed from the pre-amp  406  to the mother chip  412 . This large number of traces  408  translates to a correspondingly large number of connections between the FIA  404  and the trace circuitry  410  on the E-block  25 . 
   With reference now to  FIG. 5A , the FIA of the present invention can be more clearly understood. Each FIA trace  408  terminates in a doughnut shaped female connector portion  502  which is formed integrally with the trace  408 , by a conductor patterning process which will be discussed further below. A pair of gold plated pads  504  are provided on the FIA  404  to help hold the FIA to the E-block  25  by welding the gold pads  504  with a matching set of pads  604  ( FIG. 6 ) on the E-block  25 . These pads  504  can be more clearly understood with reference to  FIG. 5C  as having gold plated copper tab portions  505  each surrounded by a window portion  509 . An alignment hole  507  ( FIG. 5A ) mates with an alignment pad  605  ( FIG. 6 ) on the E-block to ensure proper alignment of the FIA  404  on the circuitry  410  of the E-block  25 . In order to attach the FIA  404  to the E-block  25 , the FIA is bent at a bend line  506  to bring a part  500  of the FIA to an angle of 90 degrees. 
   With reference now to  FIG. 5B , a set of pads  508 , located at the distal end of the FIA (indicated at  516  in  FIG. 5A ), for connecting the circuitry  402  of the suspension  32  will be described. These connectors are described in my co-pending application Ser. No. 09/213,472 entitled “INTERCONNECT ADAPTER AND HEAD SUSPENSION ASSEMBLY”, which application is incorporated herein by reference in its entirety.  FIG. 5B  shows a pad set  508  coupled over a set of termination pads (not shown) of the suspension trace circuitry  402 . One termination pad lies directly beneath each pad of the pad set  508 . The placement of the pad set  508  can vary in configuration, as needed, according to the load beam geometry and amplifier chip  406  layout. According to one aspect of the invention, the pad set  508  includes six pads. 
   Each pad  512  includes a frame  514 , and connection tabs  516 . The frame  514  is rectangular in shape, having an inner periphery  518 . The frame surrounds the connection tabs  516 . The connection tabs  516  cantilever, extending from the inner periphery  518 . Traces  520  couple the amplifier chip  406  to the frame  514  of each pad  512 . Each frame  514  electronically couples with the tabs  516 . The use of connection tabs  516  allows the pads  512  to be removed and replaced to facilitate reworks. 
   One tab  516  of each pad  512  ultrasonically bonds to the corresponding termination pads that underlie each pad  512 . Each pad  512  disconnects from the corresponding termination pad when a laser, for example, is used to sever the tab  516  from the frame. The suspension trace circuits  402  are reconnectable to the pad  512  by re-coupling one of the remaining tabs  516  to one of the termination pads. 
   With reference now to  FIG. 6  the doughnut shaped female connectors  502  ( FIG. 5A ) of the FIA  404  are configured to receive a set of male connector portions or pins  602  in a force fit connection. The pins  602  are formed integrally with the trace circuitry  410  ( FIG. 4 ). The male connector portions and trace circuitry are formed by lithography, and etching process in a similar manner to that used to produce the female connectors  502  and trace circuitry  408  of the FIA  404 . A set of gold-plated pads  604  join with the pads  504  of the FIA  404  to hold the FIA to the E-block  25 . The pads  604  and  504  are joined to at least one of the gold-plated copper tabs  505  by ultrasonic welding or the like. 
   With reference to  FIG. 7  the structure of the female connectors  502 , can be more clearly understood. A layer of polyimide film provides a substrate  702  upon which the trace circuitry  408  and connector portion  502  are built. The trace circuitry  408  and female shaped connector  502  are formed of copper and are integral with one another. A layer of gold or nickel-gold (Ni—Au) alloy  704  coats the connector  502  to improve electrical conductivity and prevents corrosion of the connection with the male connector  602  ( FIG. 6 ). A top dielectric layer  706  coats the trace circuitry  408  and substrate  702 , with the connector  502  and its gold coating  704  extending therefrom. The female connector  502  and its gold coating  704  define a socket  708 . 
   With reference to  FIG. 8 , the structure of the male connector portion  602  is similar to that described with reference to  FIG. 7 . A substrate  802  is constructed of a base layer of dielectric material. Upon the substrate the trace circuitry  410  and male connector  602  are integrally formed of copper. A layer of gold coats the male connector  602 . A top dielectric layer  806  covers the substrate  802  and trace circuitry  410 , the male connector portion  602  and its associated gold coating  804  extend from the insulation layer  806 . 
   With reference to  FIG. 9 , the female connector portion  502  of the preferred embodiment is shown with the top dielectric layer  706  removed. As can be seen, the socket  708  has a circular cross section. Similarly with reference to  FIG. 10 , also shown with the top dielectric  806  removed, the male connector portion  602  has a circular cross section. The male connector portion  602  defines a plug having a size and shape to allow the connector  602  to be force fit within the socket  708  of the female connector portion  502 . The pitch (spacing) between adjacent male/female connectors preferably does not exceed about 0.015 inches and more preferably does not exceed about 0.010 inches. Also, the female connector portions preferably do not exceed 0.010 inches in outer diameter and more preferably do not exceed about 0.005 inches in outer diameter. Furthermore, the inner diameter of the female connector portion preferably does not exceed about 0.005 inches and more preferably does not exceed about 0.0025 inches. Similarly, the outer diameter of the male portion preferably does not exceed about 0.005 inches and more preferably about 0.0025 inches. 
   With reference now to  FIG. 11 , a simplified fabrication process  1100  for constructing the trace circuitry  408 , and connectors  502 , of the present invention will be described. However, those skilled in the art will recognize that numerous manufacturing options and material choices are available to produce this specialized FIA connection. While the process will be described in terms of constructing the female connector  502  and trace circuitry  408  associated with the FIA  404 , it should be appreciated that the same process can be used to construct the male connector  602  and trace circuitry  410  associated with the E-block  25 . The process begins with a step  1102  of providing a substrate of polyimide base material. Then, in a step  1104 , a layer of copper foil is added. The copper is applied thicker than would ordinarily be done for a conventional flex circuit. Then, in a step  1105 , the copper is coated with a photoresist at the connector portion  502 . In a step  1106 , a photolithography process is used to image the circuit trace pattern on the copper layer. Thereafter, in a step  1107 , the copper is etched to remove the copper which is not covered by the photoresist, thereby creating the traces. In a step,  1108 , the photoresist is removed, and in a step  1109  a photoresist is coated onto the traces: Then, in a step  1110 , the connector pattern is imaged using photolithography, and in a step  1111  the copper is etched again to form the connector  502  with its associated socket  708 . In a step  1112 , the photoresist is removed. The finished copper conductor has a different thickness at different places, being thin and flexible along the trace lines and thicker at the location of the connector. Thereafter, in a step  1113  the gold, or nickel/gold alloy, layer  704  is plated onto the connector  502 . In a step  1114  the top dielectric layer (overlay) is applied such that the connector  502  extends uncovered therefrom. In a step  1115 , the circuit is cut to form the FIA. 
   Once the FIA  404  has been constructed and the trace circuitry  410  and male connector  602  have been applied to the E-block  25 , the head suspension assembly can be assembled in a manner familiar to those skilled in the art, with the FIA connected to the suspension  32 . Connection between the FIA circuitry  408  and E-block circuitry  410  can be achieved by inserting the male connectors  602  into the female connectors  502 . This can be accomplished simultaneously for all of the connectors of a single FIA  32 , by aligning the connectors  502  of the FIA with the connectors  602  of the E-block  25  and then pressing the FIA against the E-block. To ensure contact, the pad sets  504  and  604  can be ultrasonically welded, however this is an optional step. Once all of the FIAs  32  have been attached to the E-block  25 , the clamp  414  is fastened to the E-block to further ensure secure attachment of the FIAs  32  to the E-block  25 . 
   From the above it can be appreciated that the present invention provides a solution to the problem of connecting a large number of circuits in a limited space. While the invention has been described herein in terms of a preferred embodiment, other embodiments of the invention, including alternatives, modifications, permutations and equivalents of the embodiments described herein, will be apparent to those skilled in the art from consideration of the specification, study of the drawings, and practice of the invention. For example, a virtually unlimited number of shapes are possible for the socket  708  of the female connector as well as for the male connector. For example the connectors could have a square cross section rather than a round one. In addition the female connector  704  could be located on the E-block  25  and the male connector  602  on the FIA  404 . In addition, the fabrication process used to construct the invention could be altered. 
   The embodiments and preferred features described above should be considered exemplary, with the invention being defined by the appended claims, which therefore include all such alternatives, modifications, permutations and equivalents as fall within the true spirit and scope of the present invention.