Electrical connector assembly

An electrical connector assembly for facilitating connection between interchangeable input/output cables and a high-density arrangement of traces on a circuit board inside a mainframe computer. The assembly comprises a collection of individual connector/terminal assemblies and individual flexible conductive elements, such assemblies and elements being specially formed and relationally positioned so as to optimize serviceability, high frequency performance, systematic routing capability and densifying capability.

BACKGROUND OF THE INVENTION 
The present invention relates to an electrical connector and, more 
particularly, to an electrical connector assembly especially useful for 
detachably engaging electrically with a high-density arrangement of 
interchangeable conductors and for systematically routing the resulting 
current to an even higher-density arrangement of indexed conductors. 
Such an electrical connector assembly finds particular application in the 
area of computer mainframe connections where, for example, the indexed 
conductors represent a row(s) of conductive traces on a circuit board of a 
mainframe computer and where the interchangeable conductors represent 
coaxial or twisted wire cables leading to respective control panels, 
monitors, printing devices, or other input/output devices. In this type of 
exemplary environment, the critical features of an electrical connector 
array include its serviceability, its high frequency capability, its 
systematic routing capability, and its densifying capability. These 
features, in view of existing devices, will now be examined in turn. 
At the detachably engaging end of the connector assembly is a contact array 
including discrete contacts typically requiring periodic serviceability. 
Such contacts may be forks, for example, each having a pair of tines that 
mechanically engages a respective pin-like terminal, as shown, for 
example, in Cacolici U.S. Pat. No. 4,094,564, Webster U.S. Pat. No. 
4,310,208, and Sitzler U.S. Pat. No. 4,327,956. Such pin-like terminals 
may extend from a terminator block into which individual interchangeable 
conductors have been terminated. Such terminator blocks can be designed 
for separate insertion in, or removal from, the back of an insulative 
block contained inside the frame of a mating connector assembly as shown, 
for example, in Tengler et al., U.S. Pat. No. 4,484,792. 
Occasionally, a connect/disconnect operation between a particular fork-like 
contact and a pin-like terminal of a particular terminator block will 
break or bend the fork or cause insulative material to be scraped from the 
separate insulative block surrounding all of the forks. This impairs the 
quality of the resulting electrical connection and makes connector 
serviceability down to the contact level highly desirable. 
Ever increasing computer processing speeds have made the high frequency 
properties of the connector assembly critical. At increasing frequencies 
the conductors of the assembly function as antennaes and therefore they 
must be isolated from externally generated signals as well as from 
adjacent signal lines that would otherwise cause cross-talk. In addition, 
the electrical lengths associated with different contacts in the assembly 
cannot be so diverse as to cause significant delays among the 
high-frequency signals carried by the contact array. 
The systematic routing capability of the electrical connector assembly is 
important because of the high number of signal lines associated with a 
mainframe computer. If a particular contact, in a particular position at 
the engaging end of the contact array, is always associated with a 
specific signal trace on a board inside the computer, then this prevents 
misconnection of external equipment. For example, there may be three 
discrete contacts that are unengaged but the user will be able to tell, by 
the respective positions of the unengaged contacts, which contact he 
should mate his desired interchangeable conductor with. Of course the user 
could test the computer output at each engaging contact to determine which 
contact he wants, but this requires much more time. 
The densifying capability of the electrical connector array is especially 
important so that current may be routed from a high-density environment of 
the interchangeable conductors to an even higher-density environment of 
the indexed signal traces on the computer board. Although large scale 
integration (LSI) has vastly increased the computing power-to-size ratio 
of computer mainframes, the dimensioning capability of present day 
electrical connectors has not kept pace with this scale reduction in 
circuit technology, and the improved power-to-size ratio, to some extent, 
has been wasted. 
Although attempts have been made to improve the densifying capability of 
electrical connectors, each attempt has lead to a commensurate, and 
unacceptable, reduction in serviceability, high frequency performance or 
systematic routing capability of the electrical connector. The first 
difficulty arises at the detachably engaging end of the contacts where the 
width of the mechanical tines on each discrete contact, although necessary 
to make each contact detachably engageable, sets a limit on how closely 
the contacts may be spaced together. When the widths of each tine are 
summed together the resulting sum is the maximum contact "footprint" 
measurable, for example, if the contacts were placed on a level surface, 
side-by-side, touching each other. Generally, from each discrete contact 
extends a terminal, such terminal including a neck portion and a lead 
portion, whereupon the lead portions of all of the terminals together form 
a coplanar layer. The primary difficulty arises in minimizing the spacing 
between respective leads and minimizing total contact footprint without 
degrading high frequency performance. For example, the required lead 
spacing may be achieved solely by the use of bends in the terminal necks, 
but this does nothing to reduce the maximum contact footprint. Such an 
approach also results in each adjacent contact/neck/lead assembly having 
its own unique physical shape and electrical length, thereby greatly 
increasing manufacturer tooling costs and degrading high frequency 
performance. By vertically overlapping adjacent contacts one may reduce 
the total contact footprint, and decrease the lead spacing as well, but 
each assembly still has a unique physical shape and electrical length. 
Furthermore, at high frequencies, the wide conductive surfaces of the 
contacts will tend to capacitively couple thereby inducing cross-talk 
between adjacent signal conducting contacts. A conventional approach, that 
does improve densifying capability, while also addressing high tooling 
cost and degraded high frequency performance, is a division of the 
contacts into a top and bottom group, where a straight neck portion 
extending upwardly from a bottom contact is followed by a straight neck 
portion, of equal length, extending downwardly from a top contact and vice 
versa. Each contact/neck/lead assembly may then have the same physical 
shape and electrical length, greatly decreasing tooling costs and 
improving high frequency performance, Additionally, capacitive coupling 
will be improved over the vertically overlapping aproach because, given a 
lead spacing equalling half the connector width, for example, the flat 
surfaces of the contacts will be arranged in side-by-side, rather than in 
overlapping, relationship. With this approach, however, the contact 
footprint will approach, but never be less than, half the maximum contact 
footprint. Additionally, if the necks are bent to further reduce lead 
spacing (otherwise the use of straight necks sets the minimum lead spacing 
at one-half the width of each contact) then the contact/neck/lead 
combinations will no longer have equal physical shape thereby 
reestablishing increased tooling costs. 
In addition to the limiting factors just discussed, the minimum lead 
spacing obtainable will be determined by the size of the leads themselves 
and by cross-talk requirements. If the widths of the leads are reduced, 
without reducing the spacing between each respective lead, this reduces 
cross-talk between adjacent signal conducting leads but makes each 
individual lead susceptible to breakage or to being bent out of position 
(thus destroying systematic routing capability or creating signal shorts). 
Although the dimensional gap, between the narrow semirigid leads and the 
even narrower indexed conductors, may be made using thin insulative wires 
(that are less susceptible to breakage because of the cushioning effect of 
the insulation) such discrete wires are easily mispositioned 
(non-systematically routed) therefore creating excessive assembly errors. 
Another possible means of bridging the dimensional gap is to use ribbon 
cable. This eliminates systematic routing problems because of the ordered 
arrangement of the ribbon conductors. However, the ribbon conductors may 
only be made so thin before problems are encountered, such as breakage of 
the conductors when the ribbon cable is stripped or such as breakage of 
the conductors when the ribbon conductor-to-lead connection is moved 
slightly due to connector insertion forces. 
SUMMARY OF THE PRESENT INVENTION 
Accordingly, an object of the present invention is to provide a detachably 
engageable connector array that compatibly features serviceability, 
systematic routing capability, high frequency capability and an enhanced 
densifying capability particularly in regard to the minimization of 
contact footprint and the minimization of lead spacing. 
A further object of the present invention is to provide a means of bridging 
the dimensional gap between a dense arrangement of coplanar, substantially 
nondeformable leads and a dense arrangement of narrower indexed conductors 
such as found on a circuit board utilizing large scale integration (LSI) 
technology. 
A first aspect of the present invention is an arrangement of 
contact/terminal assemblies where the contacts are not only divided into 
top and bottom groups but they also each occupy a unique vertical 
position. As contrasted with an arrangement relying solely on top/bottom 
groups, this approach permits the total contact foorprint to be reduced 
below half the maximum contact footprint and the minimum lead spacing may 
be brought well below one-half the width of each contact (even where 
straight neck portions are used for minimum tooling). Additionally, 
reduced high frequency coupling will occur between closely adjacent signal 
conducting contacts. As contrasted with an approach relying solely on 
vertical overlapping of contacts, this approach permits improved high 
frequency performance where assembly pairs having equal electrical length 
are used or where twice the lead distance is provided, for a given lead 
spacing, between closely overlapped signal conducting contacts. 
A second aspect of the present invention relates to an arrangement of 
contact/terminal assemblies utilizing not only top/bottom groups and 
vertical offsets but also symmetry considerations. Specifically, by 
arranging the contacts (keeping in mind footprint minimization as well as 
cross-talk minimization or impedance normalization) so that for each 
contact /terminal assembly above the coplanar leads there is a symmetrical 
contact/terminal assembly below the coplanar leads, assembly pairs having 
equivalent physical shape and electrical length are obtained, thereby 
reducing tooling costs and equalizing high frequency delay times among 
pairs. Uniform spacing between terminal leads, and use of L-shaped 
structures, then permits either minimization of cross-talk levels, where 
each terminal is signal conducting, of normalization of impedance 
characteristics, where alternate terminals are signal conducting and the 
remaining terminals maintain reference potential. Alternatively, or in 
conjunction, each assembly may be adjusted in length so as to equalize 
high frequency delay times among all of the assemblies. Large connector 
insertion forces are provided for through equally sized tines on each 
contact that distribute the applied pressure evenly and by resilient 
latching tangs on each contact that hold a group of forks in a respective 
insulator block despite the opposing pressure. In turn, this prevents 
large-scale movement of flex circuit conductors connectable to the 
terminals as described hereafter. 
A third aspect of the present invention combines the use of vertical 
offsets and electrical length compensation for contact/terminal assemblies 
not necessarily symmetrical with each other but that do each share the 
same minimum contact width. Permitting each contact only enough width for 
reliable detachable engagement results in minimum contact footprint and 
capacitive coupling. To compensate for electrical lengths, the greater the 
vertical displacement required from each contact to its respective lead 
the less the horizontal displacement provided from that same contact to 
that same lead. This optimizes high frequency performance and further 
permits minimization of the contact footprint when the contacts are placed 
in overlapping relationship. The faces of two contacts that are associated 
with two adjacent signal conducting leads may be directed away from each 
other to minimize capacitive coupling. A refinement of this is to employ 
top/bottom groups where the two contacts vertically closest to the leads 
are the contacts that are oppositely directed. An important feature is the 
prescription of a specified ordering sequence where the top contacts, in 
sequence,.are followed by the bottom contacts, in sequence (as opposed to 
the top sequence being interposed with the bottom sequence) that enables 
the smallest achieveable lead spacing for the specified structure. 
A fourth aspect of the present invention is utilization of a flex circuit 
that is specially configured for bridging the dimensional gap between the 
dense arrangement of coplanar leads and the dense arrangement of narrower 
indexed conductors. Specifically, the flex circuit is relatively rigid to 
permit small-scale movements (for example, when the contact array is 
engaged) but at the same time to protect against large-scale movements 
that might break the very thin flex conductors residing in the flex 
circuit. To prevent breakage at the second end of the flex circuit, where 
the flex conductors actually attach to the coplanar leads, the flex 
conductors are made relatively thick relative to their thickness at the 
first end of the flex circuit, where they attach to the narrower indexed 
conductors. 
To prevent breakage at the first end of the flex circuit, where the flex 
conductors are very thin wires attaching to a dense arrangement of very 
narrow indexed conductors, the invention relies on the cushioning effect 
of the insulation surrounding the conductors, as well as on a semi-rigid 
supporting base (preferably a conductive sheet) that is fixed relative to 
the indexed conductors (through reference lead ends). This semi-rigid 
supportive base prevents small-scale physical movements, at the coplanar 
lead end, from being transmitted to the indexed conductor end. The base 
may also be a conductive sheet thus establishing well-defined electrical 
regions around each flex conductor. Not only can the flex conductors be 
varied in dimension along their length, but the lead spacing between these 
conductors can be very precisely controlled by using a photolithographic 
process to etch the flex conductors. As was true with the terminal leads, 
uniform spacing between the flex conductors promotes either cross-talk 
minimization or impedance normalization. Similarly, the controlled order 
of the flex conductors facilitates a rapid simultaneous connection step at 
both ends thereof without the need for expensive indexing equipment. 
A fifth aspect of the present invention is the manner in which it resolves 
the requirement of periodic connector serviceability with the requirement 
of systematic routing by providing a modular assembly of disposable flex 
circuits. Specifically, at least two individual flex circuits are 
positioned in face-to-face relationship, releasably adjoined at one end, 
and vertically separated at the other end for eventual connection to at 
least two vertically separated groups of coplanar leads contained in one 
or more insulator blocks. Each group of coplanar leads preferably carries 
a group of related signals. When the user detects signal errors for a 
particular group of coplanar leads, the related flex circuit may then be 
released from the other flex circuits and disposed of, along with the 
accompanying engageable contacts and, in some cases, a suspect insulator 
block. A specific embodiment of the invention uses back-to-back conductive 
sheets to prevent flex conductor breakage and to provide well-defined 
electrical regions having controlled impedances. At the ends of the flex 
circuits, cross-talk between adjacent signal bearing flex conductors is 
minimized by either alternating each top flex conductor with a bottom flex 
conductor or by extending the top conductive shield beyond the ends of all 
the bottom flex conductors as more specifically described hereafter. The 
latter approach has the further advantage of doubling the densifying 
capability of the contact array. 
A sixth aspect of the present invention is similar to the fifth aspect 
except that individual flex circuits are horizontally separated at their 
separated ends. These separated ends are electrically routed through to at 
least two horizontally separated insulator blocks. In particular, a 
specific embodiment is disclosed that is routable to any number of 
horizontally separated insulator blocks with the use of only three 
manufacturable varieties of flexible circuits, thereby promoting 
exchangeability of the flexible circuits. Further features of the 
invention include an overlapping relationship between releasably adjoined 
flexible circuits, so as to ensure minimum flex conductor spacing, and a 
designation system where flexible conductors designated for signal 
connection are separated by flexible conductors designated for reference 
connection, thereby largely minimizing cross-talk between adjacent 
flexible conductors. 
The foregoing and other objectives, features and advantages of the present 
invention will be more readily understood upon consideration of the 
following detailed description of the invention taken in conjunction with 
the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
FIGS. 1 and 3a show an exemplary electrical connector assembly 10 
constructed in accordance with the present invention and suitable for 
establishing connection between a printed circuit board inside a mainframe 
computer and individual input/output lines that route to individual 
input/output devices. Specifically, electrical assembly 10 is comprised of 
at least one flexible conductive element 55, a contact array 20, at least 
one insulator block 25, and preferably a frame 30. Referring to FIG. 8, 
the electrical connector assembly 10 may be made detachably engageable 
with a mating multiconductor assembly 15. Engagement may occur when the 
frame 40 of the mating multiconductor assembly is slid over the frame 30 
of the electrical assembly thereby bringing the insulator block 35 for the 
mating assembly into contact with the insulator block 25 for the 
electrical connector assembly. The insulator block 25 for the electrical 
connector assembly may be held to the frame 30 due to the wedging action 
of an outside keeper 33 and a central keeper 34 which are screwed to the 
connector frame 30. In a similar way, the insulator block 35 for the 
mating assembly may be held to the frame 40 by outside keeper 43 and a 
central keeper. 
Again referring to FIGS. 1 and 3a, the interchangeable conductor 50 feeding 
to a particular input/output device is represented by a twisted wire pair 
that connects with a pair of terminator blocks 45 from which extend a pair 
of pin-like terminals 46. When the electrical assembly 10 and mating 
connector assembly 15 are engaged, that is, when an insulator block 25 of 
the electrical connector assembly and an insulator block 35 of the mating 
assembly are brought together, the pair of pin-like terminals 46 will 
slide between the opposed tines 14 of a pair of contacts 1A and 1B, each 
contact being of a fork-like structure. As shown in FIG. 1, each cavity 28 
of an insulator block 25 is provided with inwardly converging beveled 
walls 29 at the second side 27 of the insulator block to facilitate 
passage of a pin-like terminal into that respective cavity and into a 
respective pair of opposed tines. The detachably engageable portion 5 of 
the contact 1 lays along the middle of the fork-like structure where the 
pin-like terminal actually establishes electrical connection with the 
contact. More generally, the detachably engageable portion of a contact 
envisioned by the present invention need not be limited to a fork-like 
structure, as shown in the drawings, but may be a socket, an optical 
fiber, or any other device capable of communicating electromagnetically 
with a detachably engageable mating terminal. 
In FIG. 1, the electrical contact array 20 is comprised of 16 individual 
contact/terminal assemblies. One type of such individual contact terminal 
is shown in FIG. 2a. The contact portion 1A of the assembly includes a 
detachably engageable portion 5 and a coupling portion 6. The terminal 
portion 2A of the assembly includes a neck portion 8 and a lead portion 7 
with a juncture 9 being shared between the neck and lead portions. Refer 
also to FIG. 2c. It will be recognized that to be detachably engageable 
the contact must have a certain dimension from side-to-side. For example, 
with the specific embodiment shown, unless the opposed tines 14 are of a 
certain width, they will break upon insertion of the pin and the contact 
will not be detachably engageable. Of course, the width of the contact 
cannot be made too great, or else it will be impossible to achieve the 
very high-density packing required of the electrical connector assembly. 
The appropriate predetermined maximum dimension 3, using pin-like 
terminals of 10 mil across, has been found to be about 60 mil. The 
terminal portion 2A of the contact/terminal assembly may be made about 10 
mil across while still retaining the rigidity needed to maintain its 
relative placement without bending or breaking thereby preserving the 
systematic routing capability of the electrical connector assembly. During 
manufacture, each individual contact/terminal assembly may be etched, or 
stamped, from a sheet of beryllium copper having a thickness of 10 mils. 
The individual pieces may be formed, and plated with nickle, using a 
simultaneous method employing a carrier strip processing technique as is 
conventionally known in the art. If desired, the detachably engageable 
portion may be gold plated to a thickness of at least 0.05 mil. 
During operation, each individual contact/terminal assembly is held in a 
cavity 28 of the insulator block 25 by a resilient latching tang 24. As 
best depicted in FIG. 1, when an individual contact 1A or 1B is inserted 
from the first side 26 of the insulator block into a respective cavity 28, 
the resilient latching tang 24 will be depressed until the interior 
shoulder 32 of the cavity is encountered, at which time the resilient 
latching tang 24 will extend upward and rest against the interior 
shoulder. A stop portion 13 on the individual contact/terminal assembly 
prevents the contact from moving further into the cavity. See also FIGS. 
2a and 2b. Delatch channels 31 are provided in the cavities 28 of the 
insulator block 25 so that an insertion tool may be extended into the 
cavity containing the assembly, whereupon the resilient latching tang may 
be depressed to a flattened position that is level with the contact 
surface and the individual contact/terminal assembly removed from the 
insulator block 25. Similarly, terminator blocks 45 may each be provided 
with a latching tang 47 that releasably locks to interior shoulder 48 of 
insulator block 35 that is part of mating assembly 15. See FIG. 3a. The 
latching tangs serve to counteract the insertion forces present when a 
group of pins are inserted into a group of contacts. 
An important inventive aspect of the electrical assembly 10 is the 
electrical contact array 20 and, in particular,.the special configuration 
of the individual contact/terminal assemblies with respect to one another. 
Referring to FIG. 2c it will be recognized that the contact/terminal 
assemblies are arranged to form coplanar contact lead groups along 
imaginary line 11. In the particular embodiment shown in FIGS. 1 2c each 
insulator block 25 has a first series 18 and a second series 19 of such 
coplanar contact lead groups. The number of coplanar contact lead groups 
may be increased pursuant to design requirements and commensurate with an 
increase in the number of flexible conductive elements 55. See FIG. 1. The 
specific r embodiment shown in FIG. 2c reveals how a basic set of 
contact/terminal assemblies, in this instance having four individual 
assemblies per set, is repeated at uniform intervals to provide a coplanar 
contact lead group. Within each basic set, each of the contacts occupies a 
unique vertical position with two (half) of the contacts being positioned 
above the coplanar lead group and two (half) of the contacts being 
positioned below the coplanar contact lead group. These techniques, of 
unique vertical contact positioning and of equally divided top/bottom 
contact grouping, operate together to facilitate closer spacing between 
individual lead portions 7 than would be possible with either technique 
alone. In particular, the lead spacing 4, here 20 mil, can be made smaller 
than the predetermined maximum dimension 3, here about 60 mil, required to 
make each connector detachably engageable. While the same lead and 
vertical contact spacing, with the same predetermined maximum dimension, 
can be obtained for a basic set by using unique vertical positioning 
alone, such technique used alone would degrade high frequency performance, 
because of increased electrical length disparity among assemblies and 
because of increased cross-talk when each flat contact is signal 
conducting. Depending on where the neek portions are attached, some 
reduction in cross-talk is achievable with vertical overlapping, but an 
increase in total contact footprint 21 for the basic set would then 
result, thereby reducing overall densifying capability. Using top/bottom 
grouping alone, the closest achieveable lead spacing would be 30 mil 
assuming the use of assemblies having straight neck portions 8 and given 
the 60 mil value for the predetermined maximum dimension. Whether four 
assemblies are used per basic set, or greater than four assemblies are 
used per basic set, the two aforementioned techniques, in combination, 
enhance the densifying capability of the electrical connector without 
undue reduction in high frequency capability. 
In FIG. 2c, the ordering of assemblies shown is one where the two top 
assemblies are followed by the two bottom assemblies. An alternative 
ordering is possible, however, where a top assembly is followed by bottom 
assembly in turn followed by a top assembly and thereafter a bottom 
assembly. For example, the two assemblies having contacts 1B, which extend 
closest to the coplanar leads 11, may be imagined as shifted across each 
other so that their lead portions 7 are exchanged in position. The 
illustrated ordering is preferable, however, for the particular shape of 
assemblies shown in FIG. 2c, because, for the given lead spacing 4, an 
alternating order would increase the total contact footprint 21. More 
generally, the minimum total contact footprint, for a given lead spacing, 
will be provided by this ordering arrangement if the contact/terminal 
assemblies are symmetrical, if partial compensation is made for electrical 
length (as explained hereafter), and if all the contacts have identical 
widths 3 and all the assemblies are L-shaped structures having no 
overlapping portions (such as the stop portion 13 shown in FIG. 2a). 
In FIG. 2c it will be seen that lead spacing 4 is uniform between each pair 
of lead portions 7. This ensures, for a given available total lead 
spacing, either cross-talk minimization among signal conducting leads or 
impedance normalization where the leads alternately provide signal or 
reference potential. For the specific embodiment described herein, the 
lead spacing 4 is about 20 mil. In FIG. 2c it will also be seen that the 
vertical spacing between closely adjacent contacts is kept substantially 
uniform thereby decreasing cross-talk, where each contact is signal 
conducting, or normalizing impedance, where the contacts alternate between 
signal and reference potential. For the embodiment described, this 
vertical spacing ranges from 25 mil to 30 mil. Although the assemblies 
depicted are substantially L-shaped, the invention encompasses the use of 
assemblies that are T-shaped, which have slanting or curved terminals 2, 
or which have curved contacts 1. Whatever shape is utilized, however, it 
is advantageous to symmetrically arrange the assemblies to acquire the top 
and bottom groups. For example, the basic set of four assemblies shown in 
FIG. 2c utilizes only two types of assembly: a first type of 
contact/terminal assembly shown in FIG. 2a and a second type of 
contact/terminal assembly shown in FIG. 2b. Each assembly comprises a 
contact, 1A or 1B, and a terminal 2A or 2B. From FIG. 2c, it will be seen 
that the individual assemblies comprising the bottom group are equivalent 
to the individual assemblies comprising the top group, being only in 
translated position about a predetermined axis of rotation 12 through the 
imaginary line 11 defined by the coplanar lead groups. Use of symmetrical 
assemblies reduces tooling costs, electrical length disparity and 
eliminates orientation considerations at assembly. In the embodiment shown 
in FIG. 2c, if the first type of assembly is used exclusively for signal 
lines and the second type of assembly is used exclusively for ground 
lines, high frequency delay times among the signals will be equalized. 
More generally, the idea of symmetrical assemblies may be expanded to 
encompass any number of types of assemblies. The symmetrical assemblies 
are preferably provided with straight terminals 2A and 2B, and flat 
contacts 1A and 1B, for this minimizes cross-talk among signal conducting 
assemblies and minimizes precision bending during manufacture. Such design 
provides the assemblies with their characteristic L-shape when viewed from 
behind as in FIG. 2c. It is preferable, although not required to practice 
this aspect of the invention, that the width 3 for each symmetrically 
different type of contact, 1A or 1B in this instance, be made uniformly 
small so as to ensure minimum capacitive coupling between each type when 
each contact is signal conducting. 
Recognizing that the distance between the detachably engageable portion 5 
of the contact and the juncture 9 of the terminal establishes the 
electrical length of the assembly, partial compensation may be made for 
the varying electrical lengths between different types of assemblies. For 
example, although the first type of assembly shown in FIG. 2a, in contrast 
to the second type of assembly shown in FIG. 2b, has a greater vertical 
distance (first offset) between its detachably engageable portion 5 and 
juncture 9, it also has a lesser horizontal distance (second offset) 
between its detachably engageable portion 5 and juncture 9. Refer to FIG. 
2c. Such an approach reduces delay times among signals at high 
frequencies. A further refinement is to decrease high frequency capacitive 
coupling, among contacts that belong to an adjacent pair of assemblies, by 
horizontally extending the first respective contact 1, of the pair, from 
its juncture 7, in a direction opposite to the horizontal extension of the 
second respective contact 1, of the pair, from its juncture 7. This 
configuration is illustrated in FIG. 2c, between that pair of assemblies 
being both of the second type (FIG. 2 b). This pair also has their 
contacts extending in opposite vertical directions from each other but, 
more generally, it is ufficient to fall within the ambit of the present 
invention that the connectors extend in opposite directions only 
horizontally. 
In addition to the special configuration of the electrical contact array 
20, a further important aspect of the present invention is the deployment 
of flexible conductive elements 55 to bridge the gap between the 
high-density coplanar lead groups and the high-density, but narrower, 
coplanar conductive traces 65 on the planar dielectric circuit board 66 
mountable inside a mainframe computer. Refer to FIG. 3a. In FIG. 5a, the 
flexible conductive elements 55A, 55B and 55C are representative of a 
flexible conductive element 55 in accord with the present invention. As 
stated above, the lead portions 7 of the contact/terminal assemblies may 
be made 10 mil across and still retain their systematic routing 
capability. Also, as stated above, the spacing 4 between adjacent leads 
may be made 20 mil across. Connection to such high-density coplanar leads 
is accomplished by a high-density arrangement of planar conductive strips 
58 as shown on the conductive element 55A of FIG. 5. Each conductive strip 
58 has a flexible lead end 69 extending from the first end 67 of the 
conductive element and a flexible lead end 70 extending from the second 
end 68 of the flexible conductive element. To facilitate connection with 
the narrow indexed conductors 65 on the dielectric board 66 the flexible 
lead ends 69 may each be designed to have a width of 4 mil across and a 
spacing between each other of about 20 mil. This narrow width of the 
flexible lead ends 69 further ensures cross-talk minimization among the 
conductive strips 58 when they are each signal conducting and ensures room 
for the reference lead ends 71 which periodically extend from a semi-rigid 
supporting sheet 63 having a function described below. At the second end 
68 of the flexible conductive element 55A the flexible lead ends 70 are 
made relatively wider, for example about 10 mil, to prevent breakage of 
such ends during small-scale movement of the coplanar lead groups. The 
spacing between the flexible lead ends 70 should correspond to the spacing 
between the lead portions 7 of a coplanar lead group 11, for example may 
be made 20 mil across. The conductive strips 58 are encased within a 
flexible insulative covering 60 and bonded to a semi-rigid supporting 
sheet 63. 
During manufacture, the conductive strips are etched from a sheet of 
Elecrical Tough Pitch (ETP) copper so that the thickness of the leads at 
the first end 67 are approximately 1.5 mil while the thickness of the 
leads at the other end 68 are approximately 3 mil. It is highly desirable, 
when etching the conductive strips 58, to leave a pair of carrier strips 
remaining, so that one strip remains connected to all of the flexible 
leads 69 and another strip remains connected to all of the flexible leads 
70. This preserves the uniform spacing between the conductive strips as 
the strips are being encased in a flexible insulated covering 60 and being 
mounted on a semi-rigid supporting sheet 63. As was true with the lead 
portion 7 of the contact/terminal assemblies, uniform spacing between the 
conductive strips 58 either minimizes cross-talk or normalizes impedance 
in the system. Referring to FIG. 6a, which shows a pair of flexible 
conductive elements 55C and 55B in back-to-back relationship, it will be 
recognized that the flexible insulative covering 60 is comprised of two 
planar insulative sheets 60A and 60B, each sheet having grooves 62 formed 
therein, between which the conductive strips 58 are placed. These planar 
insulative sheets may be made of 3 mil thick polyimide (KAPTON.TM.) 
plastic film that are bonded to one another, to the conductive strips 58, 
and to the semi-rigid supporting sheet 63, by a chemical adhesive. The 
semi-rigid supporting sheet 63 is preferably a conductive sheet. This 
conductive sheet may be made of electrical tough pitch (ETP) copper having 
a thickness of 1.4 mil. After the flexible conductive element 55 has been 
constructed in the manner indicated, the pair of carrier strips that are 
connected to either set of flexible leads may be removed. 
The function of the semi-rigid conductive sheet 63, having reference lead 
ends 71, is best appreciated upon consideration of the flexible conductive 
element 55 in operation between a high-density group of coplanar leads and 
a high-density arrangement of narrower indexed conductors 65. Refer to 
FIG. 3a. Without a supporting sheet 63 it is likely that the imposition of 
transverse forces on the flexible conductive element 55 (caused, for 
example, by dropped external objects or user mishandling) would break the 
very thin (1.4 mil) conductive strips contained in the flexible conductive 
element. Refer to FIGS. 5. Adding a semi-rigid conductive sheet 63 to the 
flexible conductive element 55 prevents this type of damage. In addition 
to these large-scale transverse forces, however, there are also 
small-scale longitudinal forces transmitted from the coplanar lead groups 
as the electrical assembly connector 10 is mated to the mating connector 
assembly 15. The semi-rigid supporting sheet 63 should curve slightly to 
accommodate these forces rather than directly transmitting these forces to 
the very thin flexible lead ends 69 extending from the second end 67 of 
each flexible conductive element 55. To further prevent transmission of 
such forces to the narrow flexible lead ends 69, the semi-rigid conductive 
sheet 63 includes reference lead ends 71 that are interposed between the 
narrow flexible lead ends (see FIGS. 5). Referring to FIG. 3b, these 
reference lead ends 71 fix the position of the semi-rigid conductive sheet 
63 in relation to the coplanar conductive traces 65 so that the conductive 
sheet 63 serves as a cantilevered supporting base for the narrow 
conductive strips 58. In a preferred embodiment of the invention, the 
reference lead ends 71 of the conductive sheet 63, being nominally 
connected to ground potential, further provide a well-defined 
electromagnetic region (characteristic impedance) surrounding the 
conductive strips 58. 
As best illustrated by FIGS. 4 and 8, a particular electrical connector 
assembly 10 may include a number of insulator blocks 25 that are arranged 
in vertical columns and horizontal rows. Referring to FIG. 4, any 
particular insulator block may have one or more coplanar lead groups 11. 
In FIG. 3a, a specific embodiment is illustrated where connection is made 
with a double row of conductive traces 65 on either side of a dielectric 
board 66 through deployment of four flexible conductive elements 55 
electrically connected to four coplanar lead groups, with every two 
coplanar lead groups associated with one individual insulator block 25. To 
achieve vertical adjoining of the flexible conductive elements 55, each 
flexible conductive element is provided with an adjoining end portion 72 
and a separated end portion 73, each separated end portion containing 
conductive strips 58 that connect with a particular coplanar connector 
lead group 11 as indicated by FIG. 4. 
Referring to FIGS. 5a, 5b and 5c, the adjoining end portion 72 of each 
flexible conductive element is provided with forward alignment holes 74A 
and rearward alignment holes 74B. Where attachment to a double row of 
coplanar conductive traces 65 is desired, it is preferable to align the 
two holes, with the use of a pin-like dowel, so that the rearward 
alignment holes 74B of the top flexible conductive element are positioned 
over the forward alignment holes 74A of the bottom flexible conductive 
element, thereby resulting in a long/short relationship between the 
top/bottom pair of conductive elements as shown in FIG. 3b. This 
long/short relationship is also depicted in FIG. 7 between two flexible 
conductive elements adjoined in side-by-side relationship as well as 
top/bottom relationship. Once the respective flexible lead ends 69 of the 
adjoined elements 55 are soldered to the appropriate row of coplanar 
conductive traces 65, proper alignment will be preserved between these 
elements upon removal of the dowels. 
When the flexible conductive elements 55 are adjoined in a long/short 
relationship, the conductive strips 58 and flexible lead ends 69 of the 
top element 55 may oppose and extend beyond the conductive strips 58 and 
flexible lead ends 69 of the bottom element 55. See FIGS. 3b and 6a. For 
the specific embodiment shown in FIGS. 3b and 6a, by having the conductive 
sheet 63 of the top element extending over the flexible lead ends 69 and 
reference leads 71 of the bottom element, cross-talk between the 
respective flexible lead ends is prevented. An alternative embodiment of 
the invention could utilize flexible conductive elements where the forward 
alignment holes 74A of the top element are aligned with the forward 
alignment holes 74A of the bottom element. Here, to prevent cross-talk 
among the respective flexible lead ends, the conductive strips 58 and 
flexible lead ends 69 of the top element may be placed in nonoverlapping 
relationship with the conductive strips 58 and flexible lead ends 69 of 
the bottom element, as indicated by FIG. 6b. With such an approach, the 
adjoining pair of top and bottom elements would have their respective 
flexible lead ends converging to a single row of coplanar conductive 
traces 65 in contrast to the long/short approach which terminates in a 
double row of coplanar conductive traces. 
The individual flexible conductive elements 55 are releasably adjoinable. 
Referring to FIG. 4, if signal transmission errors are detected, along 
lines associated with a particular coplanar lead group 11, then the 
corresponding flexible conductive element 55 may be conveniently removed 
by cutting through its flexible lead ends 70 at its second end 68 and by 
desoldering its flexible lead ends 69 at its first end 67 from the 
coplanar traces on the board. The contact/terminal assemblies of that 
particular coplanar lead group 11 are then removed from the appropriate 
insulator block 25 and are disposed of along with the spent flexible 
conductive element 55. Referring to FIG. 8, if the insulator block 25 also 
needs servicing, then the appropriate outside keeper 33 and center keeper 
34 are unscrewed from frame 30 of the connector assembly 10 so that the 
spent insulator block 25, along with its related contact/terminal 
assemblies, may be removed from the assembly and disposed of. A new 
insulator block 25 is then inserted into the frame 30, new 
connector/terminal assemblies are inserted into the cavities of the 
insulator block, and a new flexible element 55 is adjoined against the 
other elements in the manner described above. As shown in FIG. 3a, after 
reassembly is complete, the new element lies connected between a coplanar 
row of traces 65 on a computer board and a coplanar series, 18 or 19, of 
terminal leads. To facilitate serviceability of the insulator blocks, no 
single flexible conductive element is routed to more than one insulator 
block. 
From FIG. 4, it will be seen that the flexible conductive elements may be 
adjoined horizontally as well as vertically. A preferred embodiment of the 
invention relies on flexible conductive elements of three different types: 
a center type 55A, a left-hand type 55B and a right-hand type 55C. See 
FIG. 5. Although the specific embodiment shown in FIG. 4 utilizes only one 
center type element 55A per horizontal row, it will be recognized that any 
number of center type elements may be employed depending on the particular 
requirements. FIG. 4 further illustrates that the conductive strips 58 of 
the two end type of elements, 55B and 55C, converge toward the conductive 
strips 58 of the center type of conductive element 55A. This provides 
closer spacing of the respective flexible lead ends 69 so that such ends 
are connectable to the closely spaced coplanar conductive traces on a 
single circuit board. To further ensure minimum spacing between the 
respective flexible lead ends, it will be seen that the adjoining end 
portions 72 of adjacent flexible conductive elements 55 are positioned in 
slightly overlapping relationship as shown in FIG. 4. In relation to the 
serviceability aspect of the invention, any of the three types of flexible 
conductive elements, 55A, 55B or 55C, may either be used as a top element, 
or turned over and used as a bottom element. Indeed, as may be seen from 
FIG. 4, a series of top elements may be turned over to provide a series of 
bottom elements. This reduces the expenses associated with the manufacture 
of the flexible conductive elements and ensures an appropriate unit price 
for this disposable item. As shown in FIGS. 6a and 6b, adjacent conductive 
strips 58 may be designated for either signal line use 58A, or reference 
line use, 58B, where the lines designated for signal use alternate with 
the lines designated for reference use, thereby minimizing cross-talk at 
high frequencies. 
It will therefore be appreciated that the aforementioned and other 
desirable objects have been achieved; however, it should be emphasized 
that the particular embodiment of the invention, which is shown and 
described herein, is intended as merely illustrative and not as a 
restrictive of the invention. 
The terms and expressions which have been employed in the foregoing 
specification are used therein as terms of description and not of 
limitation, and there is no intention, in the use of such terms and 
expressions, of excluding equivalents of the features shown and described 
or portions thereof, it being recognized that the scope of the invention 
is defined and limited only by the claims which follow.