Connector with interceptor plate

A connector is provided of the type that has rows of contacts, which minimizes cross talk between adjacent contacts. An interceptor plate (60, FIG. 2) which is grounded or at another controlled potential, extends along each row of contacts (34), the plate lying close to the row to provide better capacitive coupling between each contact and the plate than between contacts of the same or different rows.

BACKGROUND OF THE INVENTION 
As clock speeds of electrical systems increase, attention has to be paid to 
connectors that connect circuit boards to one another or to other 
peripherals, in order to prevent signal degradation at the connectors. 
Cross talk between adjacent contacts can be a problem. Connectors often 
include two parallel rows of contacts. One prior art approach is to embed 
a grounded plate halfway between two rows of contacts in insulation lying 
between the contacts. Such a grounded plate reduces cross talk, but not 
sufficiently for high speed circuits. A connector which greatly reduced 
cross talk between contacts as well as outside interference would be of 
considerable value. 
SUMMARY OF THE INVENTION 
In accordance with one embodiment of the present invention, a connector 
with at least one row of contacts is constructed to greatly isolate the 
contacts from one another to prevent cross talk between adjacent contacts 
as well as to avoid outside interference. In a connector with two rows of 
contacts, wherein each contact has a mounted part held on a mount and an 
elongated leg, and wherein the legs of a row of contacts all lie 
substantially coplanar, an interception plate is provided to minimize 
cross talk The interception plate, which is maintained at a controlled 
constant potential, extends along a plane that is close to and parallel to 
the plane of the contact legs. With two rows of contacts, two interception 
plates are provided that lie outside the space between the two rows of 
contacts. Each interceptor plate is close enough to a contact leg, and 
preferably to a face of a strip shaped contact leg, so there is a large 
area of the contact leg facing the plate, and there is much better 
capacitive coupling between the plate and each contact than between 
adjacent contacts. 
The novel features of the invention are set forth with particularity in the 
appended claims. The invention will be best understood from the following 
description when read in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates a connector 10 which is used to connect conductors such 
as 11A, 11B on first and second circuit boards 12, 14. The connector has a 
housing 16 that includes a support 20 held on the first circuit board 12. 
The housing also includes a board or card end receiver 22 that is held on 
the support and that receives the second circuit board 14 to a final 
position against a rear face of the receiver. The connector includes first 
and second rows of contacts 24, 26 for contacting rows of conductive pads 
30, 32 on the second circuit board. 
As shown in FIG. 2, each contact such as 34 includes a mounted part 36 that 
extends along the front face 20f the support 20 and closely through a hole 
40 in the support. In this system, the mount part has a rearward end 42 
that is electrically connected and fixed to a plated-through hole 44 in 
the first circuit board. Each contact also has an elongated leg 46 that 
extends forwardly, in the direction of arrow F, from the mounted part 36. 
The contact has a substantially 180.degree. loop 50 at the forward end of 
the leg, and has a reverse arm 52 extending largely rearwardly from the 
loop, the reverse arm having a protrusion 54 for contacting a pad on the 
second circuit board. The reverse arm also has a rearward end 56 that 
bears against a side of the receiver 22. Each contact such as 56 of the 
second row is similar, except that its leg 58 is longer. 
In accordance with the present invention, the connector includes a pair of 
interception plates 60, 62 that minimize cross talk between each contact 
and adjacent contacts of the same or other row. The elongated legs such as 
46 of the contacts in a row such as 24 all lie substantially in a common 
imaginary plane 64. The contacts such as 34 are formed from strips of 
metal having a greater width than thickness, and the plane 64 lies at the 
faces of the contact legs that are closest to the interception plate 60. 
The plate 60 has an inner face 66 that lies in an imaginary plane 70 that 
is parallel to the plane 64 of the contact legs. The distance A between 
adjacent faces of the contact legs and interception plate is small, so 
there can be close capacitive coupling of the interception plate with the 
contact leg of each contact of a row of contacts. 
The distance A between the interceptor plate and the contact legs is less 
than the distance B between adjacent rows of contacts when the two rows of 
contacts engage the second circuit board. Also, as shown in FIG. 6, the 
distance A is less than the row spacing distance C by which contacts in 
the row 24 are spaced apart. In fact, the distance A is preferably no more 
than the distance or length D of the gap between adjacent contacts 34A, 
34B. Even if the distances A and D were equal, there would be closer 
coupling between each contact leg 46 and an adjacent interceptor plate 60 
because the adjacent faces of the plate and leg 46 have greater areas than 
the adjacent surfaces of the two contacts 34A, 34B. 
As shown in FIG. 2, the height H of each interception plate such as 62 is 
more than half the height G of the adjacent contact leg 58. The connector 
housing includes an insulator 72 with a location 74 that backs the forward 
end of the contact leg to limit its deflection away from the region 76 
where the second circuit board is received. The interception plate such as 
62 extends slightly below this insulator location 74 so that the space 76 
between each contact leg and interception plate can be substantially 
empty. That is, the space 76 is substantially devoid (at least 90% of the 
space is empty) of solid material including insulation. By providing a 
substantially empty space between the plate and contact leg, applicant 
avoids degradation of capacitive coupling that would result from the 
presence of (solid) material in the space. 
Applicant prefers that the height H of the plate be at least about 75% and 
preferably at least 90% of the height G of the contact leg 58. The fact 
that the contact legs are substantially coplanar allows the relatively 
simple interception plate to lie facewise close to the large areas of all 
contacts of the adjacent row. The interception plates also provide 
shielding against radio frequency interference although this is a 
secondary consideration. 
As shown in FIG. 4, the interception plates 60, 62 are parts of an 
interceptor 82 which is formed of a copper alloy for good electrical 
conduction. Each plate has recesses 83 in its rear edge, through which 
pass the mounted parts 36 of alternated contacts of a row. The interceptor 
includes bridges 84, 86 that connect the plates and that are integral with 
them. The bridges lie facewise adjacent to the upper surface 20f (FIG. 1) 
of the support. The interceptor has pins 90, 92 that pass through holes in 
the support and that engage plated-through holes in the first circuit 
board. The pins 90 are connected to a source of predetermined constant 
potential which may be a ground. Actually, applicant prefers to connect 
the pins and therefore all of the interceptor to a source which has a 
potential at least as low as or lower than the potential on any of the 
contacts that lie adjacent to either of the plates. Thus, in a computer 
system wherein the extreme voltages are +12 volts and -12 volts, and the 
signal pins carry high frequency signals that are between these voltages, 
applicant prefers to maintain the interceptor and its plates 60, 62 at a 
potential of no more than -12 volts, and preferably below that, such as 
-15 volts. By maintaining the interceptor plates at a voltage below that 
of any of the contacts, applicant sets up an appreciable electric field 
between each contact and the interceptor plate. This electric field 
influences adjacent magnetic fields so that magnetic fields around any 
contact carrying a high frequency signal do not extend with appreciable 
intensity to the vicinity of adjacent contacts, to avoid cross talk. In 
FIG. 1, the conductor 11A that connects to the interceptor pin 90, is 
shown as at a voltage below ground. 
FIGS. 7-11 illustrate a connector 100 that is useful for connecting 
conductive pads such as 101 of a pair of circuit boards 102, 104 that lie 
in parallel planes, and which may be any of a variety of boards such as 
where one is a display panel. This connector is of the basic type shown in 
U.S. Pat. No. 4,634,199. In this connector, two rows of contacts 106, 108 
are provided, that lie in parallel planes on opposite sides of a central 
beam 110 on the housing 112. The housing has forward and rearward flanges 
114, 116 at forward and rearward ends of the beam. Each flange forms a row 
of through holes 120, 122 at opposite sides of the beam, and a groove 124, 
126 extending along a face 130, 132 of the flange which faces the other 
flange. Each contact, such as 106, has a pair of opposite mounted parts 
134, 136 passing through a hole 120, 121 in the front and rear flanges, to 
be slideably mounted in the flanges. Each contact also has an elongated 
leg 138 connecting the mounted parts. Each of the contacts is a flat sheet 
metal part and is held adjacent to a side of the housing central beam by a 
pair of retainer strips 140, 142. Each retainer strip has front and rear 
edges 144, 146 lying in the front and rear grooves on one side of the 
central beam, to sandwich a row of contacts between the retainer such as 
142 and a corresponding side 150 of the central beam. 
In accordance with the present invention, each retainer strip such as 140 
includes a strip 152 of dielectric material adjacent to a row of contacts, 
and a strip or thin plate 154 of electrically conductive material forming 
an interception plate. The two strips 152, 154 are preferably bonded 
together. The conductive strip or plate 154 is maintained at a 
predetermined constant potential, and provides close capacitive coupling 
to an adjacent row of contacts. 
Applicant maintains each interception plate such as 154 at a predetermined 
constant potential by forming the plate with a contactor 160 that bears 
directly against a selected one of the contacts of a row of contacts such 
as 106. That particular contact 106 is positioned to touch a pad of one of 
the circuit boards that is at the desired potential such as ground or -12 
volts. FIG. 8 shows the plate contactor 160 as provided by a deformed 
portion of the plate 154 which extends through a hole 162 in the strip 152 
of dielectric material to press directly against the contact 106 which is 
backed by the central beam 110 of the housing. 
In some applications, it is desirable to maintain the portion of the 
interception plate adjacent to one or several of the contacts of a row at 
a different potential than the portion of a plate that lies adjacent to 
other contacts of the same row. The two plate portions are electrically 
isolated. Applicant accomplishes this by interrupting the conductive strip 
or plate 154 so it has different portions that are electrically isolated 
from each other, and with each portion of the plate connected to a 
different contact that is at the selected potential for that plate 
portion. 
Thus, the invention provides a connector with an interception plate which 
lies along the length of a row of contacts adjacent to the contact legs, 
where the legs have faces that all lie substantially in a single plane, to 
isolate each contact from the others to avoid cross talk, especially at 
high speed operation or high rate switching. The interception plate is at 
a controlled potential and lies close to a wide area of the contact legs 
to provide close capacitive coupling of the plate to the contact legs. The 
plate or selected portions thereof are each preferably of a potential 
considerably below that of the dc potential on adjacent contacts. In 
connectors with two rows of contacts, the plates are preferably located so 
two rows of contacts lie between the two plates, and without substantial 
insulation between each plate and an adjacent contact leg. 
Although particular embodiments of the invention have been described and 
illustrated herein, it is recognized that modifications and variations may 
readily occur to those skilled in the art and consequently it is intended 
to cover such modifications and equivalents.