Flat receptacle contact for extremely high density mounting

High contact density post and blade electrical receptacles for edge-mount semiconductor packages or like substrate carried circuits comprise an insulator housing retaining a plurality of contacts having substantially planar construction and providing redundant electrical connections with the mating post or blade.

BACKGROUND AND BRIEF SUMMARY OF THE INVENTION 
A 0.100" contact spacing within a single row is considered the present 
practical limit for standard spacing in existing miniature electrical 
connectors. 
Recently designers have been increasing number of functions per electronic 
package; this, together with space and speed requirements of many 
applications, has forced into existence connectors with higher density 
contact spacing, such as 0.050" within a single row. 
However, severe physical constraints of such spacing have made it difficult 
to produce reliable and economic connectors. 
The object of this invention is to achieve the contact reliability, 
mechanical integrity, and economy of standard spacing connectors, such as 
0.100", in higher density spacing connectors, such as 0.050", 0.0375", or 
even less, to which this invention specifically but not exclusively 
relates. 
Two rows of contacts having mating means on 0.050" pitch within each row 
can be further interlaced to provide an effective edge spacing of 0.025". 
This invention provides high contact density receptacle connectors for 
mating with blade contacts, which can be utilized for disengageably 
connecting substrate-mounted electronic devices to a printed wiring board. 
The term "substrate" as used in this specification, broadly encompasses 
ceramic substrates, printed circuit boards, flexible circuits or cables or 
any panel member provided with electrical conductors in either wired or 
printed form. 
The term "blade contact" encompasses square and rectangular posts and thin 
metal flat or formed blades. 
Another object of this invention is to provide a simple and versatile 
resilent coupling contact means which can be mounted on an extremely small 
pitch and adapted to numerous applications by providing suitable 
extensions to the mating means. 
One such extension to the blade contact is a solder or a pressfit and 
solderless wrap tail, and for the receptacle contact a cantilever tab 
terminal means for resilently receiving a module package board. 
A basically planar construction of the receptacle contacts, characterized 
by lack of severe forming operations between the blank stage and the final 
stage in a progressive contact-forming die, affords an efficient stock to 
scrap ratio and good tolerance control since the functional dimensions are 
blank dimensions and only minor forming operations are required to convert 
the blank to a finished part. 
The lack of severe forming operations such as right angle folds, permits 
use of highest strength contact spring materials since the strip temper 
does not have to be compromised by elongation requirements. 
The planar construction of receptacle contacts is particularily suitable 
for mounting on a small pitch. 
In addition, an efficient space utilization along the pitch is effected by 
mutually offsetting the free end noses of the cantilever mating means 
including the contact areas on their apexes, (called load points 
throughout this specification), horizontally side by side, or vertically 
to different levels and correspondingly profiling the surrounding 
insulator partitions. The offsetting of the load points of the resilent 
cantilever mating means also permits using a very thin metal mating blade 
and contact preload since the limitations associated with ordinary post 
receptacles having mutually opposing cantilever load points are absent. 
While in the ordinary contact a minimum gap has to exist for plating and 
cleaning requirements and is difficult to control as a result of folds, 
the planar contacts with offset cantilevers afford a negative effective 
gap whose magnitude can be precisely controlled. 
A still further object of this invention is to provide high module board 
retention force by permanently but replaceably driving the substrate 
between two rows of metal cantilever tabs extending upwardly from the 
receptacle means and outwardly above the insulator housing. This effects 
high pressure registrations on the substrate pads and permits infra-red 
reflow-soldering, visual inspection of registration, and on-duty contact 
probing. 
One cantilever tab of each common pair makes electrical contact with the 
pad on the component side of the package substrate, the other tab 
providing back-up means and, if desired, serving as a jumper to the other 
side of the substrate. 
The tails of successive contacts can be alternately rotated in the housing 
180 degrees to plug into an offset hole pattern in the circuit board. 
Similarly, the substrate receiving cantilever tabs can be made to project 
by uneven distances to further stratify the connections in order to 
improve registration and relax tolerancing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows the preferred embodiment of a high contact density connector 
employing receptacle contacts 21, each having resilent, fully independent 
cantilevers 22 and 23 with vertically offset free end noses 24 and 25, 
having load points on their convex sides for making a two-sided 
disengageable connection with a mating blade contact 26. 
The contacts are side loaded into insulator housing 27, from side 28 into 
apertures 29. Side wall 30 is added to fully enclose contacts 21 and 
retain the contacts from their shank portion 31 to its adjacent legs. 
The minimum pitch at which contacts 21 are installable is determined by the 
width requirement of aperture 29 and the minimum successfully moldable 
wall thickness of partition 32. The width of aperture 29 which is required 
to house mated contact pairs is minimized by routing cantilever leg 22 
adjacent a nonmating side of the engaging blade 26 contact rather than in 
the conventional manner, i.e., adjacent to its mating side. Only the free 
end nose 24 of cantilever leg 22, including its load point, is brought to 
the side of the mating blade passageway just above its protective lead-in 
33, but it is vertically offset from the free end portion 25 of the other 
cantilever leg 23 so that it does not increase the aperture width 
requirement. 
Stated otherwise, by offsetting the mating portions of the cantilever legs 
vertically, i.e., in the direction of mating, the contact can be made 
substantially flatter in its horizontal dimension (i.e., parallel to the 
directions in which the mating surfaces face and flex), for the same 
electrical and mechanical characteristics, than if the mating portions 
were aligned vertically. 
The partition wall 32 between adjacent contacts is profiled to surround the 
contacts with minimum operating clearance and is stepped at 34 
corresponding to the vertically offset cantilever free end portions, thus 
optimizing space utilization in the direction of contact mounting pitch. 
The free end portion 24 of cantilever leg 22 is also shown stepped at 35 to 
reduce its space requirement and to increase the lead-in engagement 
between the lead-in portion of cantilever leg 22 and its mating blade. 
FIG. 2 shows an application of the principle of the contact of FIG. 1 to an 
edge-mount receptacle connector. 
Contacts 36 are side-loaded into a center insulator 37 and the thus 
obtained sub-assembly is inserted into an outer insulator 38 and retained 
therein. 
The two rows of identical contacts 36 are oppositely oriented so that the 
substrate edge receiving means, which extend upwardly from shank portions 
31, interlace centrally in the connector, yielding spacing equal to 
one-half of a single row contact pitch. For example, if the contacts 
within each row are on a 0.050" pitch, the substrate receiving means will 
be on a 0.025" pitch. 
The two common substrate receiving cantilever tabs of each contact project 
upwardly by uneven distances so that when the successive contacts are 
alternately rotated 180 degrees, tabs 39 and 40 of successive contacts on 
the circuit side of the substrate will correspondingly and alternately 
register on different level pads 41 and 42 deposited on substrate 43. 
FIG. 3 shows an alternative planar receptacle contact which is derived from 
receptacle contact 21 of FIG. 1 by the addition of resilent strap 22'. 
FIG. 4 shows a perspective view of an alternative receptacle contact 44 
having vertically offset resilient mating means 45. A portion of a tail 46 
and a stabilizing tab 47 are shown projecting from a bridging strap 48. 
In FIG. 5 there is shown a solder-tab printed circuit board connector 
comprising plurality of contacts 44 side entered into apertures 49 of 
insulator 50, alternately rotated 180 degrees, and retained therein by a 
side wall 51 which is bonded to a side 52 of insulator 50. 
FIG. 6 shows an alternative construction of a planar receptacle contact 53 
in resilent two-sided engagement with a blade contact 54. 
The two resilent cantilevers 55, having substantially similar spring 
parameters, are separated by a bifurcation slot 56 centrally located in 
the wide or planar side of contact 53 and are offset from the plane of 
shank 57 in mutually opposite directions, defining a passageway for the 
mating blade which is situated below shank 57 in the same vertical plane. 
Prior to engagement, the resilent cantilever noses 59 protrude into the 
mating blade's passageway, the amount of protrusion determining the amount 
of resilent deflection imposed by the mating blade 54. 
If in their free state the engaging noses protrude beyond the connection 
symmetry plane, a negative gap condition results, whereby the total 
resilent deflection created by the mating blade is greater than the 
blade's thickness. 
The contact of FIG. 6 can be adapted to various applications by suitably 
extending shank 57 and end 60 of mating blade 54. One such application is 
an edge-mount receptacle connector depicted in FIG. 7 in which shank 57 is 
extended into cantilever tabs 61 for resilently receiving a circuit 
substrate. 
The blade contact has a solderable or solderless wrap tail 62 which is 
offset relative to the mating blade in order to achieve a staggered tail 
pattern. 
In order to fully realize the highest possible contact density, contacts 53 
are mounted into insulator 63 its wide, or planar, side, transversely to 
the insulator's longitudinal axis. 
Furthermore, cantilevers 55 of receptacle contact 53 are confined in 
corresponding aperture pockets 64 which are conformally asymmetrically 
configured and mutually transversely spaced by a distance equal to the 
width of bifurcation slot 56 less the operating clearance, thus creating 
the ability to use a stepped insulating partition 65 between adjacent 
apertures and permitting placing the adjacent apertures in close 
longitudinal proximity or mutual overlap. 
A damage-proof entry opening is achieved without using protective 
insulation in front of the cantilever's free end noses 59 since the 
entering blade is prevented from deviating from proper mating position by 
the restrictive passageway between each two aperture pockets 64. 
Contact retention bars 57a forcibly engage the insulator, providing 
retention, and contact centering is assured by restrictive chamfers 66. 
FIG. 8 shows an alternative configuration of receptacle contact 67 in which 
a center resilent cantilever leg 68 makes connection to one side of mating 
pin 54 and two side cantilever legs 69 make connections to the other side 
of mating pin 54. 
To balance the contact forces on both sides of the mating pin, the width of 
center cantilever leg 68 can be made twice the width of each side 
cantilever leg 69. 
Each slot 70 could be made as wide as the bifurcation slot in the contact 
53 (FIG. 6) if a high contact mounting density similar to that illustrated 
in the FIG. 7 is to be employed. 
In FIGS. 9 and 10, which provide a bottom view of the receptacle of FIG. 7, 
planar contacts of the types shown in FIGS. 8 and 6, respectively, are 
shown in alternative high contact density engagement with very thin mating 
blades 71 and 72. 
In this case, slots 56 and 70 must only minimally functionally separate the 
adjacent cantilevers and may be extended only where this separation is not 
achieved by offset 58, namely, on the distance by which resilent 
cantilever noses mutually interlace. 
The interlacing overlap of resilent cantilever noses, corresponding to a 
negative gap condition, makes the planar contacts particularily suitable 
for engagement with very thin mating blades, thus resulting in a decreased 
minimum mounting pitch requirement for the mated contact means. 
Mating blades 71 and 72 are reinforced by stiffening forms 73, configured 
not to demand increased pitch space but rather to fully utilize the 
available insulator aperture space 74 to the side of the resilent 
cantilevers, and also to enable a damage proof entry without protective 
insulation. 
In FIG. 9, a blade contact having a C-shaped cross-sectional profile 
cooperates with a "C"-shaped outline of the insulator aperture to provide 
a damage-proof entry and so that upon engagement, stiffening forms 73 
occupy spaces 74 adjacent the sides of resilent cantilever leg 68. 
The load point 75 of leg 68 is shown preloaded against the aperture wall it 
faces. 
In FIG. 10, the blade contact's cross-sectional profile is "J"-shaped and 
cooperates with a "J" or "L"-shaped insulator aperture to provide a damage 
proof entry and so that upon engagement, the blade's stiffening extension 
73 occupies space 74, adjacent the side of resilent cantilever 55. 
Cantilever leg 55 is shown preloaded against the insulator's aperture wall 
at 75'. 
A second stiffening extension (not shown) can be added to blade 72, 
assymmetrically to the existing one, so that the blade's cross-sectional 
profile would be "S"-shaped and the cooperating insulator aperture would 
be substantially rectangular. 
In FIG. 11 there is shown a planar receptacle contact 76 used in an 
edge-mount connector embodiment similar to that of FIG. 2. 
The contacts 76 are forcibly installed in one piece insulator housing 77 
from its top side as seen in FIG. 11, the two rows oppositely oriented so 
that the substrate edge receiving means interlace centrally in the 
connector, yielding spacing equal to one-half of the contact spacing 
within each row. 
The receptacle contact 76 has resilent cantilevers 78 and 79 which extend 
downwardly and co-planarly, side by side, from an offset shank portion 80 
and provide two one-sided connections to the engaging side of mating blade 
81. 
The redundancy is further assured by making the resilent cantilevers 78 and 
79 of unequal width, thus differentiating their natural frequency response 
in vibration environments. 
If a relatively thin blade is used, the resilent cantilever load points 82 
can be preloaded against the aperture wall 83 they face and the blade 
contact's lead-in chamfer can be made more generous on the blade contact's 
mating side 84. 
In FIG. 12 there is shown still another embodiment of the connector of FIG. 
2. 
A tuning fork type mating means are employed in the planar contact 85, 
which is forcibly installed in one piece insulator housing 86 from its top 
side as seen in FIG. 12, and retained therein by retention barbs 87 
extending sideways from contact shank 88. 
The resilent mating cantilevers 89 are shown in engagement with blade 
contact 90, which is received from the connector's bottom side through a 
protective lead-in opening 91. 
While I have illustrated and described this invention with respect to 
several embodiments, they cannot be exhaustive because of the multitude of 
connector applications to which a basic pair of contact mating means can 
be adapted. A basic pair of mating contacts should be understood to 
encompass a receptacle contact's resilent mating means up to its 
sustaining shank and the blade contact's mating portion, not including 
extensions thereof.