Rotating contact ZIF connector

A two-piece rotating contact zero insertion force connector is used to interconnect printed circuit boards (daughter boards) to backplanes (mother boards), cables to panels or cables to cables. This is accomplished by rotating one-half of the mating contacts relative to the other half to complete the necessary electrical connection. A number of different rotating contact designs are included which could be utilized to implement the overall concept.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to printed wiring board connectors and more 
particularly to a connector arrangement that utilizes rotating contacts of 
unique design to provide a zero insertion force type of connector. 
2. Background Information 
Zero insertion force connectors have been available in the marketplace for 
well over a decade. Their acceptance by the user community has been sparse 
and slow largely due to the relative high cost per contact compared to 
conventional printed circuit board connectors. 
Conventional zero insertion force connectors consist of a molded plastic 
body equipped with two rows of contacts located along both sides of a 
narrow slot into which a printed circuit board is inserted. At this point 
no electrical contact is made between the connector contacts and the 
printed circuit board. Typically, a lever-actuated cam internal to the 
connector body prevents the contact engagement from occurring. When the 
lever is then actuated the cam surfaces cause the connector contacts to 
translate and make electrical contacts with the printed circuit board 
tabs. This procedure is reversed prior to removing the printed circuit 
board from the zero insertion force connector. 
Connector blocks of this type have been disclosed in U.S. Pat. No. 
3,526,869, a connector disclosed therein also requires a large number of 
parts and is expensive to manufacture in terms of the cost, parts and 
labor to assemble the parts. Further, of course, as with any zero 
insertion force connector arrangement such as this, after the daughter 
board has been inserted it then becomes necessary as a separate step to 
actuate the cam means to form the electrical connections. Frequently the 
electrical connections achieved by the conventional zero force type 
connector do not include the wiping action between the terminal and 
circuit board pad so that it is possible that there may be an undesirably 
high contact resistance developed between the terminal and the daughter 
board. Contact wiping action has long been recognized as a good method of 
breaking through oxides and other insulating films that occur on contact 
interfaces. It is also well known that a contact wiping action will also 
push particulant matter, which can cause electrical opens, away from the 
point of electrical contact. 
Thus, it is obvious from the foregoing that contact wiping action will tend 
to promote low and stable contact resistance. Another disadvantage to 
current zero insertion force connectors is their means of actuation. This 
actuation mechanism is generally located at one end of the connector body 
where actuation has occurred by rotating a lever through a 90 degree angle 
or applying a push pull force to a straight rod. In many card files, as 
utilized in telephone central office switching systems and in some 
computers, the connectors are located in the backplane at the back of the 
file and cannot be accessed from the front to perform the necessary zero 
insertion force actuation sequence. Since cards are inserted and extracted 
from the front of the card file, the use of zero insertion force 
connectors at the back of the file is very cumbersome at best. This 
"volumetric" approach to packaging of printed circuit boards and 
backplanes however has found wide usage throughout the electronic 
industry. 
A "planar" approach to printed circuit board packaging is being explored 
and pursued by some manufacturers. Instead of mounting the printed circuit 
boards perpendicular to the backplane, they are mounted parallel to it. 
Such an arrangement is also suggested in U.S. Pat. No. 3,701,071 and U.S. 
Pat. No. 4,273,401. In the present application, the particular 
implementation proposed is substantially different than that taught in the 
prior art. 
SUMMARY OF THE INVENTION 
In the present invention planar mounted daughter boards are employed. That 
is to say that both mother and daughter boards in ultimate position or 
usage lie in parallel planes. While such an arrangement has obvious 
advantages in terms of packaging, it has been found to be somewhat 
difficult to connecterize. Accordingly, the two piece zero insertion force 
connector described in the present application has been designed 
particularly for use with planar mounted printed circuit boards. The 
particular construction of the printed circuit board is not necessarily 
part of the present invention and they may be manufactured of any typical 
material now in use, such as ceramic, glass reinforced epoxy or of 
insulated metal core construction. In the arrangement taught in the 
present invention, one half of the two piece zero insertion force 
connector is mounted on the mother board and the other half mounted on the 
daughter board. Initially, the two halves are mated with the daughter 
board being placed perpendicular to the mother board. This card 
orientation, during the mating operation, simplifies the printed circuit 
board mounting. Due to the design of the contacts employed, the initial 
engagement force is zero. After this the daughter board and its connector 
half is rotated through an angle to a position parallel to the mother 
board. The pivot point is established by pivot pins and pivot slots 
located on the ends of both connector halves. It is during this rotation 
that the contact forces and contact wiping action is generated. A number 
of different contact designs have been employed for use in the present 
invention that satisfy the requirements of rotation through an angle for 
actuation. It should be pointed out, however, that the angle of rotation 
is not necessarily critical in all designs and might have a tolerance as 
high as 90 degrees plus or minus 45 degrees. 
Inasmuch as the rotation is not critical, another degree of freedom is 
afforded to the engineer when working in the planar mode. That is, full 
rotation through an angle of 90 degrees would occupy a particular amount 
of space on the associated mother board. However, it is also possible to 
only rotate the card 45 degrees and latch it in this position, therefore 
the space required on the associated mother board would be less than three 
quarters of that of a fully rotated card. While in this arrangement the 
component height off of the mother board would be increased, space below 
the card could be used to mount other components. It is also possible by 
virtue of the teachings of the present invention to place circuit board 
components on the underneath side of the daughter board rather than on the 
top side of the daughter board by merely extending the mounting portions 
of the associated plastic housing of the connector. 
In referring to the contacts in the preferred design, a similar contact is 
used in both halves of the connector, each includes an embossed section 
which causes a depression on one side of the contact and a raised portion 
on the other. During zero force engagement, the raised side of the emboss 
of one contact is nested in the recessed side of the emboss on the other. 
Thus, when the contacts are rotated at 90 degrees to each other, the 
embossed portions interfere with each other and the resulting 
interferences causes the contacts being forced apart. It is this force 
that generates the contact force to create a reliable two point electrical 
connection as well as a desirable wiping action.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1, a two piece zero insertion force connector in 
accordance with the present invention is shown in perspective form. As may 
be seen in FIG. 1, a mother board 11, having a plurality of circuit 
conductors such as 13 has a lower portion of the connector mounted 
thereon. The lower portion of the connector consists of a u-shaped plastic 
or other insulated material base unit 14, having upstanding earlike 
projections on either end thereof designated 15A and 15B located on each 
of the end projections and projecting portions are pivot pins 16A and 16B, 
respectively. Included in the base 14A are a plurality of contacts like 
19A which pass through the base portion of lower connector section 14 and 
make electrical contact with the circuit connector conductors such as 13. 
Shown in an upright or vertical position prior to joining the upper and 
lower connector sections is daughter board 12 on which is mounted at 
either end thereof the other portion of the zero insertion force connector 
in accordance with the present invention consisting of circuit board 
supports 17A and 17B each including a pivot receiving slot such as 18A and 
18B respectively. Also included are a plurality of circuit contacts such 
as 19B which are electrically connected to the components mounted on 
daughter board 12. Initially the two halves of the connector are mated 
with the daughter board 12 perpendicular to mother board 11. As may be 
seen from the drawing of FIG. 1, the embosses on contacts 19A and 19B 
directly engage with each other as the daughter board is brought down with 
the pivot slots 18A and 18B engaging the pivots 16A and 16B. Because of 
the design of the contacts, this initial engagement force is zero. The 
contacts are engaged and the pivots rest in the pivot slots, the daughter 
board is rotated 90 degrees to the location shown in FIG. 2. It is during 
this rotation that the contact forces and contact wiping action are 
generated. A further understanding may also be had by to reference to FIG. 
3A and 3B wherein again the daughter board 32 is shown in the vertical 
position relative to the mother board 31, but with the pivot slots in the 
pivot pins and then as seen in FIG. 3B with the daughter board rotated 90 
degrees to establish the connections. As may be seen in FIGS. 3A and 3B, a 
daughter board combined support and lock 35 as shown in FIG. 3A or 35 and 
39 shown in FIG. 3B is included as a portion of the lower part of the 
connector. As can be readily seen in FIG. 3B the daughter board 32 once in 
the parallel or horizontal position relative to mother board 31 is 
supported and locked into position by support 39 and adjacent daughter 
board such as 36 would be supported and engaged by support 35, etc. 
Because the angle of rotation is not critical, substantial freedom of 
design is afforded by means of the present arrangement when working in the 
planar mode. As may be readily seen if the support members such as 39 and 
35 were made much taller, the connectors such as 33 and 37 (FIG. 3B) could 
be placed closer together and the card might be rotated something less 
than a full 90 degrees such as, for example, 45 degrees. In this case the 
projected area on the mother board occupied by the resultant assembly 
would be less than three quarters of the space occupied by a fully rotated 
card. In another arrangement, component height off the mother board could 
be increased and the space below the card could be used to mount other 
components. Such an arrangement is shown in FIGS. 4A and 4B whereby 
placing the connector half on the underside of the card as may be seen in 
FIG. 4B, the profile of components could be then mounted on the mother 
board underneath the daughter board. 
As may be seen in FIGS. 3A, 3B, 4A and 4B, when an array of printed wiring 
boards are mounted on a mother board, the spring latch for one card may be 
part of the molded plastic housing of an adjacent connector. Such an 
arrangement clearly minimizes the amount of additional mounting hardware 
required. 
Referring now to FIG. 5A, shown in perspective form is an embossed blade 
contact, which may be considered a preferred design for use in the 
connector of the present invention. Both contacts 51 and 52 are identical 
as used in the two halves of the connector of the present invention. 
During zero force engagement, the raised side 54 of the emboss of one 
contact is nested in the recessed side 53 of the emboss on the other 
contact 51. The top view of both contacts prior to engagement is shown in 
FIG. 5D taken along lines 5D and 5D' shown in FIG. 5B, wherein it can be 
readily seen how contacts 51 and 52 have their raised and depressed 
portions of the embosses nesting in each other. Because of the design of 
the embosses, zero force engagement takes place. 
When the contacts are rotated 90 degrees to each other as shown in FIG. 5C, 
the embosses then interfere with each other and the resulting interference 
causes the contacts to be forced apart as can be seen in FIG. 5E, which is 
taken along section lines 5E and 5E prime of FIG. 5C. It is this force 
that generates the contact force to create a reliable two point electrical 
contact. Both contacts may be plated with a noble medal, such as gold, 
which is typical practice for electrical contacts of this nature. 
In practice, these contacts would be arranged in their connector bodies 
with every other contact of emboss facing one way, with the remaining 
contacts facing in the opposite direction. By doing this, the contact 
forces generated during 90 degree rotation cancel each other out thereby 
eliminating any side thrust forces between mating connector halves. Pivot 
pins and locking pivot slots located at the ends of the connectors act as 
the pivot points during rotation and also prevent the connector halves 
from disengaging during and after rotation as may be seen again by 
referring to FIGS. 1 and 2. 
Contact sequencing (make first, break last, etc.) can be accomplished by 
changing the relative sizes of the two embosses and selectively loading 
them in the connector body during manufacture. When the recess side of the 
emboss is wider than the raised emboss on the mating contact, the point at 
which electrical contact is established, occurs at a different angle 
during the rotation than when both embosses are the same size and width. 
Thus, by varying the relative sizes of the embosses, such as 53 and 54, as 
seen in FIG. 5A, it can be readily seen that normal make first and make 
last contact types can be created and employed within the same connector 
body. It should also be noted that since this contact system is 
hermaphroditic in nature, it is possible to double the useful life (that 
is the number of mating and unmating cycles) if initially the near sides 
of the contacts are mated and then they are repositioned within the 
connector so as to engage the far sides. This duality of electrical 
contact surfaces could be used to double the longevity of the connector 
system in accordance with the present invention when utilized in the 
field. 
An additional feature of the present contact system is that rotation of the 
contact is not necessary to develop the contact forces to create a 
reliable connection. Straight translation along the axis of the emboss 
will also create contact. If the length L2 of the recessed emboss as seen 
in FIG. 5A is much smaller than the length L1 of the raised emboss, 
contact engagement will occur when the depth of insertion is equal to L2. 
If full depth insertion is equal to L1, then the point of electrical 
contact will occur on a line equal in length to L1-L2. By using this 
emboss blade contact in both the rotating and translating modes, it is 
possible to double the number of input and output connections on a given 
daughter board/mother board combination. That is, additional connectors 
could be placed on the end of daughter boards at the end opposite to those 
previously described; with direct non-rotating contact being established 
as outlined above. 
FIG. 6A shows in perspective a split blade contact design wherein a groove 
passes through the center of the embossed section. Mating occurs as shown 
initially in FIG. 6B and 6D where the embosses nest within each other and 
then upon rotation as shown in FIG. 6C contact is established as shown in 
FIG. 6E. 
FIG. 7A shows in perspective another contact design, utilizing embossed 
blade and fork arrangement, wherein the embossed or projection section 
placed within the fork and falls within the fork as shown in FIG. 7B and 
falls within the opening of the fork as shown in FIG. 7D. Upon rotation, 
the raised or embossed portion forces the edges of the fork to deflect and 
to provide a firm contact as shown in FIG. 7E. 
FIG. 8A shows in perspective form a rotating wedge and fork zero insertion 
force contact design wherein the rotating wedge is inserted within the 
fork and then on rotation as shown in FIG. 8C establishes contact with the 
fork edges as shown in FIG. 8E. Such an arrangement has all the attributes 
of the arrangement shown in FIG. 7, except that the method of generating 
the contact forces between the wedge and the fork is different. In the 
arrangement shown in FIG. 8A, the wedge is shaped like an elipse where 
dimension a, as may be seen in FIG. 8B, is larger than dimension b. The 
width of the slot c is larger than b and smaller than a. During engagement 
dimension b being smaller than dimension c, permits zero insertion force 
operation. When the two are rotated 90 degrees to each other, as can be 
seen in FIG. 8C, the wedge is caused to spread the tines of the fork due 
to the interference created by dimension a of the wedge and dimension c of 
the fork. Two points of contact having a force f are created on the inside 
surface of the fork as shown in detail in FIG. 8C and also as may be seen 
in the side view taken along the section lines 8E and 8F, as shown in FIG. 
8E. 
FIG. 9A shows in perspective a levered wedge and fork arrangement of zero 
force contact design. Rotation is required to actuate the contacts but the 
angle of rotation is much less than 90 degrees, the pivot point no longer 
at the point of contact as it was in the previously described designs. In 
this case, the wedge in the upper portion appears as a cylinder having a 
diameter equal to d1. The lower portion, or fork, has a slot width, as may 
be seen in FIG. 9B, equal to d2. Diameter of d1 is greater than diameter 
d2 by a prescribed amount. When the wedge and fork assembly are engaged, 
as shown in FIG. 9C, and rotated through an angle about the pivot point, 
as can be seen in FIG. 9D, the wedge is forced into the fork slot with an 
interference fit. It is this interference fit that generates the necessary 
contact force F against contact point B. 
A final contact arrangement is shown in perspective form in FIG. 10A in 
which a narrow slot effectively is placed through the center of embossed 
blade contacts, as may be seen in FIG. 10A and 10B. This so-called 
bifurcated arrangement increase the probability of maintaining electrical 
contact in an environment containing insulating particulate matter. In 
this case, both of the mating contacts are bifurcated, the result is 
quadruplicated electrical points of contact wherein nomal bifurcated 
contacts result in only two points of contact rather than four. Very few 
contact systems arrange for four points of contact because of the high 
cost normally associated therewith. In the present arrangement the 
embossed blade system provides the necessary four points of electrical 
contact at little or no extra cost. 
As noted above, while the unique rotating contact zero insertion force 
connector of the present design can employ any of the contact arrangements 
set forth above, that shown FIGS. 5A, 5B, 5C is preferred. 
While a number of embodiments of the present invention are shown, it will 
be obvious to those skilled in the art that numerous modifications can be 
made without departing from the spirit of the present invention which 
shall be limited only by the scope of the claims appended hereto.